KR102706835B1 - Heteromorphic film - Google Patents

Abstract

A release film having a resin layer (A) on one side of a base film and a resin layer (B) on the other side, wherein the resin layer (A) contains a silicone resin release agent and has a thickness of 0.2 to 2.0 µm, and the resin layer (B) contains a non-silicon resin release agent.
It is possible to provide a release film and a film laminate which realize ultra-light peeling properties for various adhesives and in which the peeling characteristics of the release layer are not easily changed by blocking.

Description

Heteromorphic film

The present invention relates to a release film, an adhesive sheet, and a method of using the adhesive sheet.

Conventionally, release films using polyester films as a substrate have excellent properties such as mechanical strength, dimensional stability, chemical resistance, and optical properties, and have excellent cost performance, and are therefore used in various applications. For example, they are used for the production of polarizing plates and phase difference plates for liquid crystal displays (hereinafter abbreviated as LCD), for the production of plasma display panel (hereinafter abbreviated as PDP) component parts, for the production of organic electroluminescence (hereinafter abbreviated as organic EL) component parts, for the production of various display component parts, and for various optical applications.

Recently, in applications using adhesive layers, there are cases where durability is required more than before. For example, when using an adhesive layer for bonding components of a touch panel installed inside an automobile, since the application is outdoors, it is necessary for the components to be firmly bonded to each other even when exposed to a high temperature environment in summer or a low temperature environment in winter. Therefore, as the durability of the adhesive layer itself has improved, the adhesive force of the adhesive layer itself has tended to become stronger than before. Therefore, in the past, a release film of a light peeling type that was generally used sometimes became difficult to peel when peeled from the adhesive layer, and further light peeling has been demanded.

In addition, as a recent trend in adhesives, low-elasticity adhesive layers tend to be preferred because step absorption is getting better. In the case of low-elasticity adhesive layers, the adhesive layer surface is easily deformed when the release film is peeled, and thread-pulling phenomenon may occur. Therefore, the release film needs to be further lightly peeled, so-called ultra-lightly peeled.

As a countermeasure for ultra-light peeling of a release film, there is a method of increasing the thickness of the release layer to achieve light peeling. However, with this method, depending on the type of release agent used, the transfer component derived from the release layer may be transferred to the surface of the adhesive layer, making it difficult to obtain the desired adhesive strength.

On the other hand, in the case where a release agent with low migration properties is used to suppress migration from the release layer, the deposition of the migration component on the surface of the adhesive layer is reduced, but when the release layer is applied thickly, the sliding properties of the surface of the release layer are poor, and when the film is wound in a roll shape, the films block each other, so that the peeling force of the release layer becomes heavy at the lower winding portion of the roll where pressure is applied by the film, or the appearance of the surface of the release layer deteriorates. In order to solve this problem, a method of preventing blocking of the release film by including fine particles in the release layer has been examined (Patent Documents 1 and 2).

In addition, as another review, a proposal has been made to provide a resin layer containing particles on the surface opposite to the surface on which the release layer of the film is provided (Patent Document 3).

Japanese Patent Publication No. 2004-255704 Japanese Patent Publication No. 2017-61081 Japanese Patent Publication No. 2016-165825

However, while blocking can be prevented by including fine particles in the release layer, it is difficult to stably have the fine particles exist on the surface of the release layer, and the release layer itself may become loose, and the release characteristics of the release layer may change due to particle shedding, etc., making it difficult to obtain stable release force.

In addition, when a resin layer containing particles is provided on a surface opposite to the surface on which the release layer is provided, blocking can be prevented, but depending on the degree of unevenness formation, the unevenness of the particles contained in the resin layer is transferred to the release layer when forming the film roll, and the release characteristics of the release layer change, making it difficult to obtain a stable release force in some cases.

The present invention has been made in consideration of the above-mentioned circumstances, and the problem to be solved is to provide a release film and a film laminate which realize ultra-light peeling properties for various types of adhesives, while making it difficult for the peeling characteristics of the release layer to change due to blocking.

The inventors of the present invention, taking the above facts into consideration, have conducted careful examination and have found that the above problems can be solved by using a heteromorphic film having a specific configuration, thereby completing the present invention. That is, the present invention provides the following [1] to [28].

[1] A release film having a resin layer (A) on one side of a substrate film and a resin layer (B) on the other side, wherein the resin layer (A) contains a silicone resin release agent and has a thickness of 0.2 to 2.0 µm, and the resin layer (B) contains a non-silicon resin release agent.

[2] A release film having a resin layer (A) on at least one side of a base film, wherein the resin layer (A) is a cured product of a resin layer composition containing a curable silicone resin and a light-release agent, and the light-release agent has a dimethylsiloxane skeleton (DM) represented by the following formula (I) and a methylphenylsiloxane skeleton (MP) represented by the following formula (II), and has a thickness of 0.2 to 1.5 µm.

[Chemical formula 1]

[Chemical formula 2]

[3] A release film as described in [2], wherein the maximum cross-sectional height (Rt) of the film surface opposite to the surface on which the resin layer (A) is provided is 2.0 ㎛ or less.

[4] A release film as described in [2] or [3], wherein the side opposite to the side on which the resin layer (A) of the above-mentioned base film is provided has a polyester layer containing 0.4 to 1.0 mass% of particles having an average particle size of 1 to 6 ㎛.

[5] A release film as described in any one of [2] to [4] above, wherein the mass average molecular weight of the light-release agent is 10,000 or more and 100,000 or less.

[6] A release film according to any one of [1] to [5], wherein the elastic modulus of the resin layer (A) at 25°C is 500 MPa or less as measured using a nanoindenter device.

[7] A release film as described in [1] or [6], wherein the non-silicone resin release agent is at least one selected from the group consisting of wax, long-chain alkyl group-containing compound, and fluorine compound.

[8] A release film according to [1], [6] or [7], wherein the content of the release agent among the nonvolatile components of the resin layer (B) is 10 to 70 mass%.

[9] A release film according to any one of [1] and [6] to [8], wherein the resin layer (B) substantially does not contain particles.

[10] A release film according to any one of [1] to [9] above, wherein the normal peel strength of the resin layer (A) is 5 g/25 mm or less as measured by the evaluation method below.

<Evaluation method>

After attaching an acrylic adhesive tape ("No. 7475" manufactured by Tesa) to the resin layer (A) surface of the above-mentioned release film, cut it to a size of 25 mm x 150 mm, and leave it at room temperature for 1 hour. The peeling force is performed at 180° under the condition of a tensile speed of 0.3 m/min.

[11] A release film as described in any one of [1] and [6] to [10], comprising an undercoating layer between at least one of the resin layer (A) or the resin layer (B) and the base film.

[12] A release film as described in [11], wherein the undercoating layer is an antistatic layer.

[13] A release film as described in [11] or [12], wherein the undercoating layer contains the following compounds (A) to (C).

(A) A polymer doped with another anionic compound in a compound comprising thiophene or a thiophene derivative, or a polymer self-doped with an anionic group in a compound comprising thiophene or a thiophene derivative.

(B) Polyhydroxy compound

(C) At least one compound selected from the group consisting of polyurethane resin, polyester resin, and acrylic resin.

[14] A release film according to any one of [1] and [6] to [13], wherein the surface resistivity of at least one surface of the resin layer (A) or the resin layer (B) is 1×10 ¹² Ω/□ or less.

[15] A release film as described in any one of [1] to [14], wherein the above-mentioned film is a polyester film.

[16] A release film as described in [15], wherein the polyester film has a three-layer configuration.

[17] A release film as described in any one of [1] to [16] above, wherein the post-press peeling rate of the resin layer (A) evaluated by the following method is 100% or less.

<Evaluation method>

After attaching an acrylic adhesive tape ("No. 7475" manufactured by Tesa) to the surface of the above resin layer (A), cut it to a size of 25 mm x 150 mm, and leave it at room temperature for 1 hour. The peeling force at 180° under the condition of a tensile speed of 0.3 m/min is referred to as (F1).

Next, the resin layer (A) surface is laminated so as to come into contact with each other, and a press treatment is performed at a temperature of 40°C, a humidity of 90%RH, and a load of 1 MPa for 20 hours. After the treatment, an acrylic adhesive tape ("No. 7475" manufactured by Tesa) is attached to the resin layer (A) surface, and then cut to a size of 25 mm x 150 mm, and left at room temperature for 1 hour. The peeling force at 180° peeling under the condition of a tensile speed of 0.3 m/min is referred to as (F2).

The post-press peeling rate is calculated by the following equation.

After pressing, peeling rate (%) = (F2-F1)/F1×100

[18] A release film according to any one of [1] to [17], wherein the center line average roughness (Ra(A)) of the surface of the resin layer (A) is 30 nm or less.

[19] A release film according to any one of [1] or [6] to [18], wherein the center line average roughness (Ra(B)) of the surface of the resin layer (B) is 60 nm or less.

[20] An adhesive sheet comprising a release film as described in any one of the above [1] to [19] and another release film with an adhesive layer interposed therebetween.

[21] An adhesive sheet as described in [20], wherein the adhesive layer is formed from an acrylic adhesive composition.

[22] An adhesive sheet according to [20] or [21], wherein the elastic modulus (25°C) of the adhesive layer is 6.0 MPa or less.

[23] An adhesive sheet according to any one of [20] to [22], wherein the adhesive layer comprises 2-ethylhexylacrylate and/or butylacrylate.

[24] An adhesive sheet for optical transparent adhesive sheets, as described in any one of [20] to [23] above.

[25] A heteromorphic film for display purposes, described in any one of [1] to [19] above.

[26] A heteromorphic film as described in any one of [1] to [19] for a foldable display.

[27] A method of using an adhesive sheet, wherein, in the adhesive sheet described in any one of [20] to [23] above, after peeling off the other release film, the exposed adhesive layer surface is bonded to an optical member.

[28] A method of using the adhesive sheet described in [27], wherein the optical member is a polarizing plate or a touch sensor.

According to the release film of the present invention, it is possible to provide a release film and a film laminate which realize ultra-light peeling properties for various types of adhesives, while making it difficult for the peeling characteristics of the release layer to change due to blocking.

Hereinafter, an example of an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiment described below, and can be implemented by arbitrarily modifying it without departing from the gist of the present invention.

<<<Lee Hyung Film>>>

A release film related to an example of an embodiment of the present invention (hereinafter, sometimes referred to as “the present release film”) is a release film having a resin layer (A) on one surface of a base film and a resin layer (B) on the other surface. The release film is preferably formed as a release film in a wound roll shape (release film roll), and is stored, etc., in the form of a release film roll. In that case, the release layer (A) may be arranged on either the inner or outer side of the roll.

In the present release film, the resin layer (A) on one surface is characterized by containing a silicone resin-based release agent. The thickness of the resin layer (A) is 0.2 to 2.0 µm, and the elastic modulus of the resin layer (A) at 25° C., as measured using a nanoindenter device, is preferably 500 MPa or less. In addition, the resin layer (B) on the other film surface is characterized by containing a non-silicone resin-based release agent.

The above-described heteromorphic film, when formed into a roll shape, covers the surface of the resin layer (A) with the surface of the resin layer (B), but at that time, damage caused by adhesion to the surface of the resin layer (A) by the resin layer (B) is reduced, blocking is suppressed, and peeling of the resin layer (A) and deterioration of the surface appearance at the lower winding portion of the roll where more pressure is applied to the film can be prevented. In addition, the resin layer (A) realizes ultra-light peelability, and since it substantially does not contain particles, the adhesion to the base film is also good, and furthermore, since there is no particle shedding, the transferability to an adhesive tape or the like can be reduced.

<<Reference Film>>

The base film in this heteromorphic film is not particularly limited in its material as long as it has a film shape. For example, it may be made of paper, resin, metal, etc. Among these, from the viewpoint of mechanical strength and flexibility, it is preferable to be made of resin.

As a resin-based base film, examples thereof include films formed in the form of membranes using polymers such as polyethylene, polypropylene, polyester, polystyrene, polycarbonate, polyethersulfone, polyamide, and polyimide. In addition, as long as film formation is possible, a mixture of these materials (polymer blend) or a composite of their constituent units (copolymer) may be used.

Among the films exemplified above, polyester film is particularly preferable in that it has excellent physical properties such as heat resistance, flatness, optical properties, and strength.

<Polyester film>

The polyester film constituting the laminated film of the present invention may have a single-layer configuration or a multilayer configuration, and in addition to a two-layer or three-layer configuration, it may also have a four-layer or more multilayer configuration as long as it does not exceed the gist of the present invention, and there are no particular limitations. In the present invention, it is preferable that it is a polyester film having at least a three-layer configuration. Furthermore, as the polyester film, a biaxially oriented polyester film is preferable in terms of thin film formation and dimensional stability.

The polyester used in the present invention may be either a homopolyester or a copolymerized polyester. When composed of a homopolyester, it is preferable that it is obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, 1,4-cyclohexanedimethanol, and the like. Representative examples of the polyester include polyethylene terephthalate. Meanwhile, as a dicarboxylic acid component of the copolyester, one or more types, such as isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), can be mentioned, and as a glycol component, one or more types, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, and neopentyl glycol can be mentioned.

When composed of a copolyester, examples thereof include those obtained by condensation of a dicarboxylic acid component and a glycol component. Examples of the dicarboxylic acid component include one or more types of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), and examples of the glycol component include one or more types of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, and neopentyl glycol. It is preferable that the copolyester be a copolymer containing a third component of 30 mol% or less with respect to the total of the dicarboxylic acid component and the glycol component.

In addition, the main component resin means a resin having the largest mass ratio among the resins constituting the polyester film, and is a case where it accounts for 50 mass% or more, or 75 mass% or more, or 90 mass% or more, or 100 mass% of the resin constituting the polyester film.

There is no particular limitation as the polymerization catalyst of the above polyester film, and a conventionally known compound can be used, and examples thereof include antimony compounds, titanium compounds, germanium compounds, manganese compounds, aluminum compounds, magnesium compounds, calcium compounds, etc. Among these, titanium compounds or germanium compounds are preferable because they have high catalytic activity, enable polymerization in a small amount, and reduce the amount of metal remaining in the film, thereby increasing the brightness of the film. In addition, since germanium compounds are expensive, titanium compounds are more preferable.

In the case of polyester using a titanium compound, the titanium element content is preferably 50 ppm or less, more preferably 1 to 20 ppm, and even more preferably 2 to 10 ppm. If the content of the titanium compound is too high, deterioration of the polyester may be accelerated in the process of melt extruding the polyester, resulting in a film with a strong yellow color. In addition, if the content is too low, the polymerization efficiency may be poor, resulting in an increase in cost or inability to obtain a film with sufficient strength.

In addition, when using polyester by titanium compound, it is preferable to use a phosphorus compound to lower the activity of the titanium compound for the purpose of suppressing deterioration in the melt extrusion process. As the phosphorus compound, considering the productivity and thermal stability of polyester, orthophosphoric acid is preferable. The phosphorus element content is preferably in the range of 1 to 300 mass ppm, more preferably 3 to 200 mass ppm, and even more preferably 5 to 100 mass ppm, based on the amount of polyester to be melt extruded. When the content of the phosphorus compound is equal to or less than the above upper limit, gelation or foreign matter will not occur, and when it is equal to or more than the above lower limit, the activity of the titanium compound can be sufficiently lowered and coloring can be suppressed, so that the film will not become yellow.

In order to suppress the precipitation amount of the oligomer component, a film may be manufactured using a polyester having a low content of the oligomer component as a raw material. Various known methods can be used as a method for manufacturing a polyester having a low content of the oligomer component, and examples thereof include a method of solid-phase polymerization after manufacturing the polyester.

In addition, by forming a polyester film with a composition of three or more layers and forming the outermost layer of the polyester film with a layer using a polyester raw material having a low content of oligomer components, the amount of precipitation of oligomer components can be suppressed. In addition, polyester can be obtained by subjecting the polyester film to esterification or ester exchange reaction, and then dissolving and condensing the polyester film under reduced pressure at a higher reaction temperature.

Among polyester films, it is also possible to include an ultraviolet absorber to improve the weather resistance of the film and prevent deterioration of the adherend (e.g., liquid crystal). The ultraviolet absorber is a compound that absorbs ultraviolet rays, and is not particularly limited as long as it can withstand the heat added during the manufacturing process of the polyester film.

As ultraviolet absorbers, there are organic ultraviolet absorbers and inorganic ultraviolet absorbers, but from the viewpoint of transparency, organic ultraviolet absorbers are preferable. As organic ultraviolet absorbers, there are no particular limitations, but examples thereof include cyclic iminoesters, benzotriazoles, and benzophenones. From the viewpoint of durability, cyclic iminoesters and benzotriazoles are more preferable. In addition, it is also possible to use two or more types of ultraviolet absorbers in combination.

Among the polyester layers of the polyester film, it is also possible to blend particles for the main purpose of imparting lubricity and preventing scratches in each process. When blending particles, the type of particles to be blended is not particularly limited as long as they are particles capable of imparting lubricity, and specific examples thereof include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, zirconium oxide, and titanium oxide; and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. In addition, precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed can be used during the polyester manufacturing process. Among these, silica particles and calcium carbonate particles are particularly preferable because they are easy to be effective in small quantities.

In addition, the average particle diameter of the particles is preferably in the range of 0.01 to 5 ㎛, more preferably in the range of 0.03 to 4 ㎛, and even more preferably in the range of 0.05 to 3.0 ㎛. When the average particle diameter is equal to or less than the upper limit, the haze of the film is suppressed to a low level, and the film has sliding properties.

In addition, the particle content in the polyester layer of the polyester film is preferably 5 mass% or less, more preferably 0.001 to 3 mass%, still more preferably 0.01 to 1 mass%, and particularly preferably 0.05 to 0.5 mass%. When there are no particles or when there are few particles, the transparency of the film increases and it becomes a good film, but in order to prevent the sliding property from deteriorating, there are cases where it is necessary to study how to improve the sliding property, such as by adding particles to the coating layer. In addition, when the particle content is equal to or less than the upper limit, the haze does not increase, and sufficient transparency of the film can be secured.

There is no particular limitation on the shape of the particles to be used, and any shape such as spherical, blocky, rod-shaped, or flat may be used, and there are no particular limitations on their hardness, specific gravity, color, etc. These series of particles may be used in combination of two or more types as needed.

There is no particular limitation on the method for adding particles to the polyester layer, and a conventionally known method can be adopted. For example, addition can be made at any stage of manufacturing the polyester constituting each layer, but it is preferable to add the particles after the esterification or ester exchange reaction is completed.

The polyester film may have a multilayer structure of two or more layers, but a polyester film having a three-layer structure is preferable. If it has a three-layer structure, as described later, the polyester layers (surface layers) on both surfaces contain particles, and the middle layer does not need to contain particles. Therefore, while improving the sliding properties and blocking resistance, it is also possible to improve the transparency of the polyester film. In addition, the polyester constituting each layer is as described above.

In addition, when the polyester film has a multilayer configuration of two or more layers, the average particle size of the particles used in the polyester layer (typically, the polyester layer on the side where the release layer is not provided) on the side opposite to the side on which the release layer is provided (semi-release side) is preferably 1 to 6 µm, more preferably 2 to 5 µm, and particularly preferably 3 to 5 µm. In addition, the content of the particles in the polyester layer is, for example, 0.03 to 1.0 mass%, preferably 0.3 to 1.0 mass%, more preferably 0.4 to 1.0 mass%, and particularly preferably 0.4 to 0.8 mass%. By simultaneously satisfying the above average particle size and the amount added, the semi-release side has a large maximum cross-sectional height (Rt) and an appropriate uneven shape, so that the release film can achieve both anti-blocking properties and release properties.

In addition, even in the case where the polyester film is composed of a single layer, the single polyester layer preferably contains particles from the viewpoint of anti-blocking properties and releasability, and the range of the average particle diameter and the amount of particles added may be as described above.

In a polyester film having two or more layers, the polyester layer (surface layer) on the side on which the release layer is provided may or may not contain particles, but from the viewpoint of sliding properties, etc., it is preferable to contain particles. The particle content (mass%) in the polyester layer (surface layer) on the side on which the release layer is provided is preferably less than the particle content (mass%) in the polyester layer on the side opposite to the side on which the release layer is provided (semi-release side). Specifically, the particle content (mass%) in the polyester layer on the side on which the release layer is provided is preferably in the range of 0.001 to 0.8 mass%, more preferably 0.01 to 0.5 mass%, and even more preferably 0.02 to 0.2 mass%.

In addition, in the polyester film of the present invention, in addition to the particles described above, conventionally known ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, lubricants, dyes, pigments, etc. may be added as needed.

The thickness of the polyester film in the present invention is not particularly limited as long as it is within a range that can be formed into a film, but is preferably 10 to 300 µm, more preferably 15 to 200 µm, still more preferably 25 to 125 µm, and most preferably 38 to 75 µm.

<Method for manufacturing polyester film>

Hereinafter, a specific description will be given of examples of manufacturing polyester films, but the present invention is not limited to the following examples. For example, when manufacturing a biaxially oriented polyester film, first, the polyester raw material described above is melt-extruded from a die using an extruder, and the molten sheet is cooled and solidified by a cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotating cooling drum, and an electrostatically applied adhesion method or a liquid coating adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in one direction by a roll or tenter-type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, in a direction orthogonal to the first-stage stretching direction, stretching is performed at a temperature of usually 70 to 170°C, with a stretching ratio of usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, a heat treatment is performed at a temperature of 180 to 270°C under tension or under relaxation of 30% or less, thereby obtaining a biaxially oriented film. In the above stretching, a method of performing stretching in one direction in two or more stages may be adopted. In that case, it is preferable that the stretching ratios in the two directions are finally performed so as to fall within the above ranges, respectively.

In addition, with regard to the production of polyester films, a simultaneous biaxial stretching method can also be adopted. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is simultaneously stretched in the machine direction and the width direction under temperature control at usually 70 to 120°C, preferably 80 to 110°C, and is oriented, and the stretching ratio is usually 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Then, heat treatment is performed at a temperature of 170 to 270°C under tension or under relaxation of 30% or less to obtain a stretched and oriented film. With regard to the simultaneous biaxial stretching device that adopts the above-mentioned stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear drive method can be adopted.

<<Resin layer (A)>>

Next, the formation of the resin layer (A) constituting the heteromorphic film in the present invention will be described.

The resin layer (A) is a layer formed by curing a resin layer (A) composition containing a curable silicone resin as a main component resin, and is arranged on at least one side of the above-described base film. The resin layer (A) layer can also be referred to as a release layer containing a cured product formed by curing the resin layer (A) composition.

In addition, the above "main component resin" means a resin having the largest mass ratio among the resins constituting the present resin layer (A) composition, and it is assumed that it accounts for 50 mass% or more, or 75 mass% or more, or 90 mass% or more, or 100 mass% of the resin constituting the present resin layer (A) composition.

In the present invention, it is preferable that the resin layer (A) contains a curable silicone resin.

As the curable silicone resin, a resin containing a curable silicone resin as a main component may be used, or a modified silicone, etc., may be used through graft polymerization with an organic resin such as an acrylic resin, a urethane resin, an epoxy resin, or an alkyd resin. In addition, when the adhesive layer is a silicone adhesive, etc., it is preferable to contain a fluorosilicone resin, etc.

As for the type of curable silicone resin, any of the existing curing reaction types, such as thermal curing types such as addition type and condensation type, or electron beam curing types such as ultraviolet curing type, can be used, and also, multiple types of curable silicone resins can be used in combination. In addition, there is no particular limitation on the coating form of the curable silicone resin when forming the resin layer (A), and any of the forms may be dissolved in an organic solvent, solvent-free, or aqueous emulsion.

The non-solvent curable silicone is a silicone with a viscosity that allows coating without dilution with a solvent, and is a silicone resin with a relatively low molecular weight as it is composed of short polysiloxane chains.

Meanwhile, solvent-based curable silicone is a silicone resin with a viscosity so high that it cannot be coated without being diluted in a solvent, and is a silicone with a relatively high molecular weight compared to solvent-free curable silicone.

From the viewpoints of improved adhesion to the substrate film, uniform coating appearance without coating unevenness, and easy adjustment of the thickness of the resin layer (A), a solvent-based curable silicone is preferable.

There is no limitation on the type of silicone resin used in the present invention, but from the viewpoint of excellent release properties such as peelability, use of a curable silicone resin containing an alkenyl group is preferable in the present invention. The curable silicone resin containing an alkenyl group is exemplified by a diorganopolysiloxane represented by the following general formula (1).

_{R ( 3 - a ) ​}

In the general formula (1), R is a monovalent hydrocarbon group having 1 to 10 carbon atoms, and X is an organic group containing an alkenyl group. a is an integer from 0 to 3, preferably 1, and m is 0 or greater, but when a = 0, m is 2 or greater, and m and n are numbers that each satisfy 100≤m+n≤20000, and further, the above formula does not mean a block copolymer. R is a monovalent hydrocarbon group having 1 to 10 carbon atoms, and specifically, examples thereof include alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group, cycloalkyl groups such as a cyclohexyl group, and aryl groups such as a phenyl group and a tolyl group, but a methyl group and a phenyl group are particularly preferable. X is an organic group containing an alkenyl group, preferably having 2 to 10 carbon atoms, and specifically, examples thereof include a vinyl group, an allyl group, a hexenyl group, an octenyl group, an acryloylpropyl group, an acryloylmethyl group, a methacryloylpropyl group, a cyclohexenylethyl group, a vinyloxypropyl group, and the like, but a vinyl group, a hexenyl group, and the like are particularly preferable. Specific examples thereof include a dimethylsiloxane/methylhexenylsiloxane copolymer having trimethylsiloxy groups capped at both molecular terminals (96 mol% of dimethylsiloxane units, 4 mol% of methylhexenylsiloxane units), a dimethylsiloxane/methylhexenylsiloxane copolymer having dimethylvinylsiloxy groups capped at both molecular terminals (97 mol% of dimethylsiloxane units, 3 mol% of methylhexenylsiloxane units), and a dimethylsiloxane/methylhexenylsiloxane copolymer having dimethylhexenylsiloxy groups capped at both molecular terminals (95 mol% of dimethylsiloxane units, 5 mol% of methylhexenylsiloxane units).

Next, as the polyorganosiloxane containing a SiH group, which is necessary for forming a more rigid silicone release layer by reacting with a curable silicone resin containing an alkenyl group, an organohydrogenpolysiloxane having at least 2, preferably 3 or more hydrogen atoms bonded to silicon atoms per molecule, linear, branched, cyclic, etc. can be used, and examples thereof include compounds represented by the following general formula (2), but are not limited thereto.

HbR ¹ _(3-b) SiO-(HR ¹ SiO) _x -(R ¹ ₂ SiO) _y -SiR ¹ _(3-b) H _b ···(2)

In general formula (2), R ¹ is a monovalent hydrocarbon group having 1 to 6 carbon atoms and not containing an aliphatic unsaturated bond. b is an integer of 0 to 3, and x and y are each integers. Specific examples thereof include a methylhydrogenpolysiloxane having trimethylsiloxy groups capped at both molecular terminals, a dimethylsiloxane/methylhydrogensiloxane copolymer having trimethylsiloxy groups capped at both molecular terminals, a methylhydrogenpolysiloxane having dimethylhydrogensiloxy groups capped at both molecular terminals, and a dimethylsiloxane/methylhydrogensiloxane copolymer having dimethylhydrogensiloxy groups capped at both molecular terminals.

Next, specific examples of various types of commercially available silicone resins that can be used in the present invention include those manufactured by Shin-Etsu Chemical Co., Ltd., such as KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461, X-62-1387, X-62-5039, X-62-5040, KNS-3051, X-62-1496, KNS320A, KNS316, X-62-1574A/B, X-62-7052, X-62-7028A/B, X-62-7619, X-62-7213, X-41-3035, and those manufactured by Momentive Performance Materials. YSR-3022, TPR-6700, TPR-6720, TPR-6721, TPR6500, TPR6501, UV9300, UV9425, XS56-A2775, XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605, Made by Toray and Dow Corning Co., Ltd., SRX357, SRX211, SD7220, SD7292, LTC750A, LTC760A, LTC303E, SP7259, BY24-468C, SP7248S, BY24-452, DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, Among the DEHESIVE series manufactured by Asahi Kasei Wacker Silicone Co., Ltd., examples thereof include, but are not limited to, DEHESIVE 636, 919, 920, 921, 924, and 929.

It is preferable that the resin layer (A) utilizes a platinum-based catalyst that promotes the addition reaction. Examples of this component include platinum-based compounds such as chloroplatinic acid, an alcohol solution of chloroplatinic acid, a complex of chloroplatinic acid and an olefin, a complex of chloroplatinic acid and an alkenylsiloxane, platinum black, platinum-supported silica, and platinum-supported activated carbon.

The content of the curing catalyst in the resin layer (A) is preferably 0.5 to 500 mass ppm in terms of metal relative to the curable silicone resin, more preferably 5 mass ppm or more, more preferably 10 mass ppm or more, further preferably 300 mass ppm or less, and still more preferably 200 mass ppm or less. When the content of the platinum-based catalyst in the release layer is equal to or greater than the lower limit above, sufficient peeling force is obtained, the curing reaction progresses sufficiently, and problems such as deterioration of the shape of the coating surface do not occur. On the other hand, when the content of the platinum-based catalyst in the resin layer (A) is equal to or less than the upper limit above, in addition to being advantageous in terms of cost, the reactivity is increased, and problems such as generation of gel foreign substances do not occur in the process.

In addition, since the addition reaction is highly reactive, in some cases, acetylene alcohol is added as a reaction inhibitor. The component is an organic compound having a carbon-carbon triple bond and a hydroxyl group, but is preferably a compound selected from the group consisting of 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, and phenylbutynol.

The content of the reaction control agent is preferably 0.001 to 5.0 parts by mass, more preferably 0.01 to 2.0 parts by mass, further preferably 0.05 to 1.5 parts by mass, and most preferably 0.1 to 0.5 parts by mass, per 100 parts by mass of the total amount of the resin layer (A) composition (based on nonvolatile components). By setting it within the above range, the curable silicone resin is not subject to curing inhibition without lowering the reaction activity, and the light peelability of the release film can be ensured.

In the resin layer (A) constituting the heteromorphic film, it is possible to use a catalyst in combination for the purpose of promoting a hydrolysis/condensation reaction. Specific examples of the catalyst include organic acids such as acetic acid, butyric acid, maleic acid, and citric acid; inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid; basic compounds such as triethylamine; organometallic salts such as tetrabutyl titanate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctate, dibutyltin dioleate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutylbis(triethoxysiloxy)tin, and dibutyltin benzyl maleate; and fluorine element-containing compounds such as KF, NH ₄ F. The above catalyst may be used alone or in combination of two or more. Among them, organometallic salts are particularly preferable in that the durability of the coating film becomes good.

In order to adjust the peelability of the resin layer (A), various peel control agents may be used in combination. In the case of increasing the peeling strength, the content of organopolysiloxane resin, silica particles, silicone species with medium peeling strength, etc. is generally adjusted appropriately in the resin layer (A) to obtain the desired peeling strength.

Specific examples of commercially available heavy-duty peeling agents include KS-3800 and X-92-183 manufactured by Shin-Etsu Chemical Co., Ltd., and SD7292, BY24-843 and BY24-4980 manufactured by Toray Dow Corning Co., Ltd.

In the case of making the peeling force light, various low-molecular-weight siloxanes are selected, and the content in the resin layer (A) is adjusted appropriately so that the siloxane migration component exhibits release performance. Examples of the low-molecular-weight siloxane compounds include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, etc. In addition, as other compounds of these low-molecular-weight cyclic siloxanes, there are dimethylsiloxane oligomers having trimethylsiloxy groups capped at both molecular chain terminals; dimethylsiloxane oligomers having dimethylhydroxysiloxy groups capped at both molecular chain terminals, etc., and these compounds may be used in mixtures as necessary.

As described above, the resin layer (A) composition may contain a light-releasing agent as needed, and is preferably a silicone oil having a dimethylsiloxane skeleton (DM) represented by the following formula (3) and a methylphenylsiloxane skeleton (MP) represented by the following formula (4). Since the light-releasing agent has a dimethylsiloxane skeleton (DM) and a methylphenylsiloxane skeleton (MP), even when transferred to the adhesive layer to be bonded, it is possible to penetrate into the adhesive layer, thereby reducing the decrease in adhesive strength. The ratio (DM:MP) of the dimethylsiloxane skeleton (DM) represented by the following formula (3) and the methylphenylsiloxane skeleton (MP) represented by the following formula (4) is preferably in the range of 98:2 to 70:30 in terms of molar ratio, more preferably in the range of 95:5 to 80:20, and particularly preferably in the range of 92:8 to 85:15. By setting DM:PM within the above range, the peelability of this heteromorphic film can be ensured.

In addition, it is preferable that the mass average molecular weight of the light peeling agent is less than 10,000. If the mass average molecular weight of the light peeling agent is less than 10,000, it is advantageous in terms of mobility and light peeling properties.

[Chemical Formula 3]

[Chemical Formula 4]

These low molecular weight siloxane compounds can achieve the desired peeling property by containing them as a transition component in the silicone resin, usually at 0.1 to 15.0 mass%, preferably at 0.5 to 10.0 mass%, more preferably at 0.5 to 5.0 mass%. When the content is 0.1 mass% or more, the transition component is sufficient, so that the release property is sufficiently exhibited, and when the content of the low molecular weight siloxane is 15.0 mass% or less, the transition component does not precipitate excessively, so there is no concern about process contamination.

The resin layer (A) composition may contain a diluting solvent, if necessary. Examples of the diluting solvent include aromatic hydrocarbons such as toluene, aliphatic hydrocarbons such as hexane, heptane, and isooctane, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone (MEK) and isobutyl methyl ketone, alcohols such as ethanol and 2-propanol, ethers such as diisopropyl ether and dibutyl ether, etc. It is preferable to use these alone or in combination of two or more, taking into consideration solubility, coatability, boiling point, etc.

In addition, in order to improve the adhesion of the coating to the film, it is preferable to use an organic silicon compound represented by the following general formula (5) in the resin layer (A).

Si(X) _d (Y) _e (R ¹ ) _f ···(5)

[In the above formula, X is an organic group having at least one selected from an epoxy group, a mercapto group, a (meth)acryloyl group, an alkenyl group, a haloalkyl group, and an amino group, R ¹ is a monovalent hydrocarbon group and further has 1 to 10 carbon atoms, Y is a hydrolyzable group, d is an integer of 1 or 2, e is an integer of 2 or 3, f is an integer of 0 or 1, and d+e+f=4]

The organic silicon compound represented by the above general formula (5) can be used as one having two (D unit) or three (T unit) hydrolyzable groups Y capable of forming a siloxane bond by a hydrolysis/condensation reaction.

In general formula (5), the monovalent hydrocarbon group R ¹ has 1 to 10 carbon atoms, and is particularly preferably a methyl group, an ethyl group, or a propyl group.

In general formula (5), examples of the hydrolyzable group Y include the following. Namely, a methoxy group, an ethoxy group, a butoxy group, an isopropenoxy group, an acetoxy group, a butanoxime group, and an amino group. These hydrolyzable groups may be used singly or in combination. When a methoxy group or an ethoxy group is used, it is particularly preferable because it can impart good preservation stability to the coating material and also has appropriate hydrolyzability.

Specific examples of the organosilicon compound contained in the resin layer (A) include vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, 5-hexenyltrimethoxysilane, p-styryltrimethoxysilane, trifluoropropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiisopropenoxysilane, and the like.

It is preferable that the resin layer (A) substantially does not contain particles. By substantially not containing particles in the resin layer (A), the peeling characteristics can be stabilized while the migration property can be lowered. In addition, substantially not containing means that the resin layer (A) may contain particles as long as the amount is small enough not to impede the effect of the present invention, and for example, particles that are inevitably mixed may be included. The content of particles in the specific resin layer (A) (A layer) is, for example, less than 0.05 mass%, preferably less than 0.01 mass%, more preferably less than 0.0001 mass%, based on the nonvolatile component. In addition, the range of the content of particles in the resin layer (A) composition based on the nonvolatile component is also the same as the content of the particles.

In addition, within a range that does not impair the spirit of the present invention, the resin layer (A) composition may contain, as necessary, an antifoaming agent, a coating improving agent, a thickener, an organic lubricant, an antistatic agent, a conductive agent, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, a pigment, and the like.

The number average molecular weight (Mn) of the curable silicone resin is preferably 9,000 or more and 350,000 or less. When the number average molecular weight (Mn) of the curable silicone resin is equal to or greater than the lower limit above, when an adhesive layer is laminated on a release film, the amount of low-molecular-weight silicone resin that is eluted or transferred into the adhesive layer can be reduced, and further, by applying the resin layer (A) thickly, it becomes easy to obtain a light-peeling effect. On the other hand, when the number average molecular weight (Mn) of the curable silicone resin is equal to or less than the upper limit above, the viscosity increases, preventing the fluidity of the resin layer (A) composition from decreasing. Therefore, when the resin layer (A) composition is applied, it is possible to prevent uneven coating in the shape of stripes from occurring, and it becomes easy to smooth the surface of the resin layer (A).

From this viewpoint, the number average molecular weight (Mn) of the curable silicone resin is preferably 9000 or more, more preferably 10000 or more, more preferably 20000 or more, and most preferably 30000 or more. On the other hand, it is preferably 350000 or less, more preferably 50000 or less, and most preferably 40000 or less.

The mass average molecular weight (Mw) of the curable silicone resin is preferably 10,000 to 500,000 from the same viewpoint as the number average molecular weight, more preferably 20,000 or more, more preferably 50,000 or more, and most preferably 80,000 or more, and more preferably 250,000 or less, and most preferably 100,000 or less.

The ratio (Mw/Mn) of the mass average molecular weight (Mw) to the number average molecular weight (Mn) of the curable silicone resin is preferably 1.7 to 3.5, more preferably 1.9 to 3.0, and most preferably 2.0 to 3.0. By satisfying this range, it can be expected that the crosslinking reaction will proceed efficiently.

In addition, the number average molecular weight (Mn) and the mass average molecular weight (Mw) are values obtained by gel permeation chromatography (GPC) measurement using polystyrene as a standard, and a specific measurement method is to use a GPC measuring apparatus to measure a chromatogram, and obtain the number average molecular weight (Mn) and the mass average molecular weight (Mw) based on a calibration curve using standard polystyrene. Specifically, 4 mg of the sample for measurement was dissolved in 4 mL of THF to prepare a measurement solution, and 100 μL of the measurement solution was injected into the GPC measuring apparatus for measurement. Tetrahydrofuran (THF) was used as the eluent. For the analysis, "Ecosec8320" manufactured by Tosoh Corporation was used, and four "TSKgel guardcolumn HXL-L" manufactured by Tosoh Corporation was used as the guard column, and "TSKgel GMHXL" manufactured by Tosoh Corporation was used as the column in connections. In addition, the analysis was performed under the conditions of oven temperature of 40℃ and THF flow rate of 1.0 mL/min, and RI was used for detection.

The curable silicone resin may be formed by a combination of two or more types of curable silicone resins, and in this case, it is preferable that the average of the number average molecular weight (Mn) and the mass average molecular weight (Mw) of the two or more types of curable silicone resins be within the above range. In addition, the average referred to here is a weighted average that is weighted by the mass of each resin. In addition, when a main agent and a silicone crosslinking agent are used as the curable silicone resin, the mass average molecular weight (Mn), number average molecular weight (Mw) of the main agent, and Mw/Mn may be within the above range.

The viscosity of the curable silicone resin at 25°C when adjusted to 15 mass% by dilution with n-heptane solvent is preferably 1 to 400 mcps, more preferably 5 to 300 mcps, and even more preferably 10 to 200 mcps.

When the viscosity of the curable silicone resin is 1 mcps or more, cissing is suppressed by the appropriate viscosity of the coating solution, so that a uniform coating appearance with high visibility is obtained, which is preferable. When the viscosity is 400 mcps or less, the fluidity of the resin layer (A) composition can be maintained, and when the resin layer (A) composition is applied, the occurrence of striped coating unevenness can be suppressed, so that the surface of the resin layer (A) can be made smooth.

Viscosity was measured by diluting the curable silicone resin with n-heptane to 15 mass%, and measuring the viscosity of the solution at 25°C using an E-type viscometer (“TVE-22L” manufactured by Tokisangyo Co., Ltd.).

When the curable silicone resin has an alkenyl group in the silicone resin, the content of the alkenyl group is preferably 0.4 to 2.5 mol%, more preferably 0.5 to 2.0 mol%, and even more preferably 0.5 to 1.5 mol%, based on the total amount of the siloxane component. By satisfying this range, since a certain amount or more of the alkenyl group is contained, the release layer is sufficiently cured, and on the other hand, since the amount of the alkenyl group is not excessive, the peeling force after exposure to air can be prevented from becoming heavy.

When the curable silicone resin has a Si-H group in the silicone resin, the content of the Si-H group is preferably 0.8 to 2.5 mol%, more preferably 0.8 to 2.0 mol%, and even more preferably 1.0 to 2.0 mol%, based on the total amount of the siloxane component. By satisfying this range, since a certain amount or more of the Si-H group is contained, the release layer is sufficiently cured, and on the other hand, since the amount of the Si-H group is not excessive, reaction with the adhesive layer is prevented, and heavy peeling of the release film can be suppressed.

The curable silicone resin may contain an alkenyl group and a Si-H group (also simply referred to as “H group”) in the side chain and/or terminal of the main chain formed by a siloxane bond in the same structure. In that case, it is preferable that the content of the alkenyl group and the Si-H group is within the above range.

The content of the total siloxane component in the present heterolayer composition can be measured, for example, from the integral ratio of the dimethylsiloxane unit of the main chain to the other units in ¹ H-NMR. In addition, the content of vinyl groups and Si-H groups represents the ratio to the total amount of functional groups bonded to the siloxane chain, and can be evaluated by measuring ¹ H-NMR. However, this method is not limited thereto.

The thickness of the resin layer (A) is preferably in the range of 0.2 to 2.0 µm, more preferably 0.4 to 1.5 µm, further preferably 0.4 to 1.2 µm, and most preferably 0.4 to 1.0 µm, from the viewpoints of ultra-light peeling, prevention of blocking, and suppression of increased migration properties. If the thickness of the resin layer (A) is less than 0.2 µm, it is difficult to easily peel the resin layer (A) even if the elastic modulus of the resin layer (A) is within a predetermined range, as described later. In addition, if it is made thicker than 2.0 µm, there are cases where the migration properties of the resin layer (A) component to an adhesive tape or the like increase, or blocking cannot be sufficiently prevented.

The elastic modulus of the resin layer (A) at 25°C is preferably 500 MPa or less, more preferably 65 to 400 MPa, and even more preferably 80 to 300 MPa. By satisfying these ranges, good peelability can be exhibited with respect to the adhesive layer. In addition, the elastic modulus of the resin layer (A) can be adjusted by the type of silicone resin used, the thickness of the resin layer (A), etc., and for example, when the resin layer (A) becomes thin, the elastic modulus tends to increase. In addition, the elastic modulus referred to here is a value measured by a nanoindenter.

The state-of-the-art peeling strength of the resin layer (A) is preferably 5 g/25 mm or less, more preferably 0.1 to 4 g/25 mm, and even more preferably 0.5 to 3 g/25 mm. When the state-of-the-art peeling strength is 5 g/25 mm or less, good peeling properties can be exhibited even for the adhesive layer whose elasticity has decreased due to the enlargement and thinning of the optical member. On the other hand, when the state-of-the-art peeling strength exceeds 5 g/25 mm, peeling from the adhesive layer may become difficult, and the adhesive layer may be transferred to the release film side due to deformation or breakage of the adhesive layer.

The residual adhesion rate of the resin layer (A) is an index of the transferability of the transition component derived from the resin layer (A) to the adhesive tape to be bonded. In the case of a resin layer (A) with high transferability, since a large amount of the transition component is attached to the coated evaluation film, the peeling force of the adhesive tape bonded to the evaluation film decreases, and the residual adhesion rate (%) also decreases. Therefore, the residual adhesion rate (%) is preferably high, and is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. If the residual adhesion rate is 80% or more, it can be considered that there is no problem in actual use.

The post-press peeling rate of the resin layer (A) is preferably 100% or less, more preferably 50% or less, and even more preferably 20% or less. If the post-press peeling rate is 100% or less, when the release film is wound into a roll shape, the peeling of the resin layer (A) at the lower winding portion of the roll to which pressure is applied by the film is greatly suppressed, and thus no problem due to the peeling occurs. The method for calculating the post-press peeling rate is as described in the Examples.

Regarding the formation of the resin layer (A), it may be provided by inline coating, which treats the film surface during the film forming process, or by offline coating, which is applied externally on a film once manufactured. However, it is more preferably formed by offline coating.

As a method for providing a resin layer (A) on a film, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, or curtain coating can be used.

The film constituting the release film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

There are no particular limitations on the curing conditions when forming the resin layer (A), and when the resin layer (A) is prepared by offline coating, it is usually preferable to perform heat treatment at 80°C or higher for 10 seconds or longer, preferably at 100 to 200°C for 3 to 40 seconds, more preferably at 120 to 190°C for 3 to 40 seconds, and even more preferably at 150 to 180°C for 3 to 40 seconds.

In addition, heat treatment and active energy ray irradiation such as ultraviolet ray irradiation may be used in combination as needed. In addition, as an energy source for curing by active energy ray irradiation, a known device or energy source can be used. For example, as a light source, a fusion (H) lamp, a metal halide lamp, a high-pressure mercury lamp (ozone generating type, ozone-less type), UV-LED, etc. are exemplified.

There is no particular limitation on the active energy ray irradiation, but in the case of ultraviolet irradiation, the range is 10 to 3000 mJ/cm2, preferably 50 to 2000 mJ/cm2, and more preferably 100 to 1000 mJ/cm2 in terms of the accumulated light dose. By setting the accumulated light dose of ultraviolet irradiation to be within the above range, the curing of the resin layer (A) is promoted, and on the other hand, by not irradiating excessively, the resin layer (A) is not destroyed, which prevents the peeling force after the irradiation from becoming heavy.

In the release film of the present invention, it is preferable that the surface resistivity of at least one surface of the resin layer (A) or the resin layer (B) is 1×10 ¹² Ω/□ or less. The lower the surface resistivity of the resin layer (A) or the resin layer (B), the better the antistatic property, and the charging of the film can be suppressed during the process, thereby preventing the attachment of foreign substances, etc.

The centerline average roughness (Ra(A)) of the surface of the above resin layer (A) is preferably 30 nm or less. Since ultra-thin peeling becomes possible when the centerline average roughness (Ra(A)) is 30 nm or less, it is preferable. Regarding (Ra(A)), it is more preferably 25 nm or less, and particularly preferably 20 nm or less. On the other hand, regarding the lower limit, from the viewpoint of film handleability, it is preferably 5 nm or more.

<<Resin layer (B)>>

Regarding the resin layer (B) in the present invention, it is described below.

The resin layer (B) constituting the release film in the present invention is provided on a surface opposite to the surface on which the resin layer (A) of the base film is provided, and may be a resin layer (B) containing a non-silicon-based release agent, and more preferably, it is a resin layer (B) containing a non-silicon-based release agent and having antistatic properties.

There are no particular restrictions on the non-silicon release agent used in the resin layer (B) as long as it is a release agent other than a silicone compound, and any conventionally known release agent can be used, and examples thereof include long-chain alkyl group-containing compounds, fluorine compounds, waxes, etc.

Among these, long-chain alkyl compounds or waxes are preferable in that they have less contamination and excellent blocking reduction, and long-chain alkyl compounds are more preferable in particular in that they reduce blocking. These release agents may be used alone or in combination.

A silicone compound is a compound having a siloxane bond in the molecule, and includes those having various functional groups on the side chain and/or terminal of the main chain composed of the siloxane bond. Examples thereof include an ether group, a hydroxyl group, an amino group, an epoxy group, a carboxylic acid group, a halogen group such as fluorine, a perfluoroalkyl group, a hydrocarbon group (an alkyl group, an alkenyl group, an aryl group, various aromatic groups, etc.). When the resin layer (B) contains a silicone compound, it strongly blocks the resin layer (A), deforming the surface of the resin layer (A), and the peeling characteristics of the resin layer (A) deteriorate, so it is difficult to use it in the present release film.

A long-chain alkyl group-containing compound is a compound having a straight-chain or branched alkyl group having usually 6 or more, preferably 8 or more, and more preferably 12 or more carbon atoms. Examples of the alkyl group include a hexyl group, an octyl group, a decyl group, a lauryl group, an octadecyl group, a behenyl group, and the like. Examples of the compound having an alkyl group include various long-chain alkyl group-containing polymer compounds, long-chain alkyl group-containing amine compounds, long-chain alkyl group-containing ether compounds, long-chain alkyl group-containing quaternary ammonium salts, and the like. Considering heat resistance and contamination resistance, it is preferable that it is a polymer compound. Furthermore, from the viewpoint of effectively obtaining releasability, it is more preferable that it is a polymer compound having a long-chain alkyl group in a side chain.

A polymer compound having a long-chain alkyl group in the side chain can be obtained by reacting a polymer having a reactive group with a compound having an alkyl group capable of reacting with the reactive group. Examples of the reactive group include a hydroxyl group, an amino group, a carboxyl group, an acid anhydride, and the like. Examples of the compound having such a reactive group include polyvinyl alcohol, polyethyleneimine, polyethyleneamine, a polyester resin containing a reactive group, and a poly(meth)acrylic resin containing a reactive group. Among these, polyvinyl alcohol is preferable in consideration of releasability and ease of handling.

Examples of the compound having an alkyl group capable of reacting with the above reactive group include long-chain alkyl group-containing isocyanates such as hexyl isocyanate, octyl isocyanate, decyl isocyanate, lauryl isocyanate, octadecyl isocyanate, and behenyl isocyanate; long-chain alkyl group-containing acid chlorides such as hexyl chloride, octyl chloride, decyl chloride, lauryl chloride, octadecyl chloride, and behenyl chloride; long-chain alkyl group-containing amines; and long-chain alkyl group-containing alcohols. Among these, considering releasability and ease of handling, long-chain alkyl group-containing isocyanates are preferable, and octadecyl isocyanate is particularly preferable.

In addition, a polymer compound having a long-chain alkyl group in the side chain can also be obtained by polymerization of a long-chain alkyl (meth)acrylate or copolymerization of a long-chain alkyl (meth)acrylate with another vinyl group-containing monomer. Examples of long-chain alkyl (meth)acrylates include hexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, and behenyl (meth)acrylate.

Wax is a wax selected from natural wax, synthetic wax, and a mixture of them. Natural waxes include plant wax, animal wax, mineral wax, and petroleum wax. Examples of plant waxes include candelilla wax, carnauba wax, rice wax, rose wax, and jojoba oil. Examples of animal waxes include beeswax, lanolin, and whale wax. Examples of mineral waxes include montan wax, ozokerite, and ceresin. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and petrolatum. Examples of synthetic waxes include synthetic hydrocarbons, modified waxes, hydrogenated waxes, fatty acids, acid amides, amines, imides, esters, and ketones. Examples of synthetic hydrocarbons include Fischer-Tropsch wax (also known as Sasol wax) and polyethylene wax, and in addition, low-molecular-weight polymers (specifically, polymers having a viscosity number-average molecular weight of 500 to 20,000) include the following polymers: polypropylene, ethylene-acrylic acid copolymers, polyethylene glycol, polypropylene glycol, and block or graft bonds of polyethylene glycol and polypropylene glycol. Examples of modified waxes include montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives. The derivatives herein are compounds obtained by any of refining, oxidation, esterification, and saponification treatments, or a combination thereof. Examples of hydrogenated waxes include hydrogenated castor oil and hydrogenated castor oil derivatives.

Among the above waxes, from the viewpoint of stable properties, synthetic wax is preferable, among them, polyethylene wax is more preferable, and oxidized polyethylene wax is even more preferable. As for the number average molecular weight (Mn) of the synthetic wax, from the viewpoint of stability of properties such as blocking and handleability, it is preferably in the range of 500 to 30,000, more preferably 1,000 to 15,000, and even more preferably 2,000 to 8,000.

Fluorine compounds are compounds containing fluorine atoms in the compound. From the viewpoint of the appearance of the coating by inline coating, organic fluorine compounds are suitably used, and examples thereof include compounds containing perfluoroalkyl groups, polymers of olefin compounds containing fluorine atoms, and aromatic fluorine compounds such as fluorobenzene. From the viewpoint of releasability, compounds containing perfluoroalkyl groups are preferable. In addition, compounds containing long-chain alkyl compounds, as described below, can also be used as fluorine compounds.

Examples of the compound having a perfluoroalkyl group include perfluoroalkyl group-containing (meth)acrylates, perfluoroalkylmethyl (meth)acrylate, 2-perfluoroalkylethyl (meth)acrylate, 3-perfluoroalkylpropyl (meth)acrylate, 3-perfluoroalkyl-1-methylpropyl (meth)acrylate, 3-perfluoroalkyl-2-propenyl (meth)acrylate, and other perfluoroalkyl group-containing (meth)acrylates or polymers thereof; perfluoroalkyl group-containing vinyl ethers, such as perfluoroalkyl methyl vinyl ether, 2-perfluoroalkyl ethyl vinyl ether, 3-perfluoropropyl vinyl ether, 3-perfluoroalkyl-1-methylpropyl vinyl ether, and 3-perfluoroalkyl-2-propenyl vinyl ether, and polymers thereof. Considering heat resistance and contamination resistance, a polymer is preferable. The polymer may be a single compound or a polymer of multiple compounds. In addition, from the viewpoint of heteromorphism, it is preferable that the perfluoroalkyl group has 3 to 11 carbon atoms. Additionally, it may be a polymer with a compound containing a long-chain alkyl compound as described later. In addition, from the viewpoint of adhesion to the substrate, it is also preferable that it is a polymer with vinyl chloride.

In forming the resin layer (B), from the viewpoint of preventing adhesion of foreign substances, etc., it is preferable to contain an antistatic agent, and for example, a polymer doped with another anionic compound in a compound composed of thiophene or a thiophene derivative, a polymer self-doped with an anionic group in a compound composed of thiophene or a thiophene derivative, or a polymer containing a monomer having an alkylsulfonic acid ion as a counter ion as a component, etc. can be used. Among these, from the viewpoint of obtaining excellent antistatic performance, it is more preferable to contain a compound composed of thiophene or a thiophene derivative.

As a compound comprising thiophene or a thiophene derivative, a polymer doped with another anionic compound of a compound comprising thiophene or a thiophene derivative, or a polymer self-doped with an anionic group in a compound comprising thiophene or a thiophene derivative, for example, a compound of the following formula (6) or the following formula (7) is exemplified, obtained by polymerizing in the presence of a polyanion.

[Chemical Formula 5]

In the above formula (6), R ¹ and R ² each independently represent a hydrogen atom or an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, etc. having 1 to 20 carbon atoms.

[Chemical formula 6]

In the above equation (7), n represents an integer from 1 to 4.

Examples of polyanions used in polymerization include poly(meth)acrylic acid, polymaleic acid, polystyrene sulfonic acid, and polyvinyl sulfonic acid. As a method for producing such polymers, a method such as that disclosed in Japanese Patent Application Laid-Open No. 7-90060 can be adopted.

In the present invention, a compound of the above formula (7) in which n is 2 and polystyrene sulfonic acid is used as the polyanion is suitably used.

In addition, if these polyanions are acidic, some or all of them may be neutralized. Ammonia, organic amines, and alkali metal hydroxides are preferable as bases used for neutralization.

As a specific example of a polymer containing a monomer having an alkylsulfonic acid ion as a counter ion as a component, there may be mentioned, for example, a polymer having a component represented by the following formula (8) as a repeating unit. Such a homopolymer or a copolymer, or even a copolymer of multiple other components, may be used. From the viewpoint of improving antistatic properties, a homopolymer is preferable.

[Chemical formula 7]

As the structure of the polymer, for example, in the formula above, the substituent R ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is -O- or -NH-, R ³ is an alkylene group having 1 to 6 carbon atoms, or another structure capable of forming the structure of formula (8), at least one of R ⁴ , R ⁵ , and R ⁶ is a hydrogen atom, and the other substituent is an alkyl group having 1 to 3 carbon atoms, or a hydroxyalkyl group having 2 to 3 carbon atoms in the alkyl group, and X ^- is an alkylsulfonic acid ion having an alkyl group having 1 to 4 carbon atoms.

In forming the resin layer (B), it is preferable to include a polyhydroxy compound for the purpose of improving the coating appearance and antistatic performance. As the polyhydroxy compound, it is preferable to use one or more compounds selected from polyglycerin and alkylene oxide adducts to polyglycerin, or derivatives thereof. Polyglycerin is a compound represented by the following general formula (9).

[Chemical formula 8]

In the above formula (9), n is 2 or more, and in the present invention, n in the formula is usually in the range of 2 to 20, preferably 3 to 15, and more preferably 3 to 12.

An alkylene oxide adduct to polyglycerin has a structure in which an alkylene oxide is added to the hydroxyl group of polyglycerin represented by the general formula (9).

Here, the structure of the alkylene oxide added to each hydroxyl group of the polyglycerin skeleton may be different. In addition, it is sufficient that it is added to at least one hydroxyl group of the molecules, and it is not necessary for the alkylene oxide or its derivative to be added to all the hydroxyl groups.

As the alkylene oxide added to polyglycerin, ethylene oxide or propylene oxide is preferable. If the alkylene chain of the alkylene oxide becomes too long, the hydrophobicity becomes strong, the dispersibility in the coating solution deteriorates, and the antistatic property and transparency of the resin layer (B) tend to deteriorate. Ethylene oxide is particularly preferable. In addition, the number of additions is preferably in the range of 200 to 2000, more preferably in the range of 300 to 1000, and even more preferably in the range of 400 to 900, as a number average molecular weight (Mn) of the final compound.

The above polyglycerin or alkylene oxide adduct to polyglycerin may be used alone or in combination of two or more types.

In forming the resin layer (B), from the viewpoint of improving the coating appearance or transparency, various conventionally known polymers can be used in combination as a binder component, and specific examples of the polymer include polyester resin, urethane resin, acrylic resin, polyvinyl alcohol, vinyl chloride acetate copolymer, etc. From the viewpoint of making the resin layer (B) stronger and reducing blocking, it is preferable to use polyester resin or urethane resin.

As polyester resins, examples thereof include those composed of polycarboxylic acids and polyhydroxy compounds as main components, such as the following. That is, as polycarboxylic acids, terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt, and their ester-forming derivatives can be used. Examples of polyhydroxy compounds that can be used include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylol ethyl sulfonate, and potassium dimethylolpropionate.

Polyester resin is a polycondensation product of polycarboxylic acid and polyhydroxy compound. From the above compounds, one or more polycarboxylic acid and one or more polyhydroxy compound are appropriately selected, and a polyester resin is synthesized by a polycondensation reaction of a conventional method. In addition, the polyester resin may be in the form of an aqueous dispersion, and in that case, a hydrophilic functional group or the like may be appropriately introduced into the polyester resin.

Urethane resin is a polymer compound having urethane bonds in the molecule. Urethane resin is usually produced by the reaction of polyol and isocyanate. Examples of polyols include polycarbonate polyols, polyester polyols, polyether polyols, polyolefin polyols, and acrylic polyols. These compounds may be used alone or in combination. Urethane resin may be an aqueous dispersion, and in that case, for example, a hydrophilic functional group may be introduced appropriately into the polyol.

Polycarbonate polyols are obtained from polyhydric alcohols and carbonate compounds by a dealcoholization reaction. Examples of the polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, etc. Examples of carbonate compounds include dimethyl carbonate, diethyl carbonate, diphenyl carbonate, and ethylene carbonate, and examples of polycarbonate polyols obtained from reactions thereof include poly(1,6-hexylene) carbonate, poly(3-methyl-1,5-pentylene) carbonate, and the like.

Polyester polyols include polycarboxylic acids (malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, fumaric acid, maleic acid, terephthalic acid, isophthalic acid, etc.) or their acid anhydrides and polyhydric alcohols (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 1,8-octanediol, Examples thereof include those obtained from the reaction of 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2,5-dimethyl-2,5-hexanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butyl-2-hexyl-1,3-propanediol, cyclohexanediol, bishydroxymethylcyclohexane, dimethanolbenzene, bishydroxyethoxybenzene, alkyldialkanolamines, lactone diol, etc.

Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol.

In order to improve adhesion with various functional layers, among the above polyols, polycarbonate polyols and polyester polyols are more suitably used.

As polyisocyanate compounds used to obtain urethane resins, aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolidine diisocyanate; aliphatic diisocyanates having an aromatic ring such as α,α,α',α'-tetramethylxylylene diisocyanate; aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, and hexamethylene diisocyanate; alicyclic diisocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and isopropylidenedicyclohexyl diisocyanate. Diisocyanates are examples. These can be used alone or in combination.

When synthesizing a urethane resin, a chain extender may be used. There are no particular restrictions on the chain extender as long as it has two or more active groups that react with isocyanate groups. In general, chain extenders having two hydroxyl groups or amino groups can be mainly used.

Examples of chain extenders having two hydroxyl groups include aliphatic glycols such as ethylene glycol, propylene glycol, and butanediol; aromatic glycols such as xylylene glycol and bishydroxyethoxybenzene; and ester glycols such as neopentyl glycol hydroxypivalate. In addition, as chain extenders having two amino groups, examples thereof include aromatic diamines such as tolylenediamine, xylylenediamine, and diphenylmethanediamine; aliphatic diamines such as ethylenediamine, propylenediamine, hexanediamine, 2,2-dimethyl-1,3-propanediamine, 2-methyl-1,5-pentanediamine, trimethylhexanediamine, 2-butyl-2-ethyl-1,5-pentanediamine, 1,8-octanediamine, 1,9-nonanediamine, and 1,10-decanediamine; and alicyclic diamines such as 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, dicyclohexylmethanediamine, isopropylidenecyclohexyl-4,4'-diamine, 1,4-diaminocyclohexane, and 1,3-bisaminomethylcyclohexane.

The urethane resin in the present invention may be a medium using a solvent, and preferably uses water as a medium. In order to disperse or dissolve the urethane resin in water, there are forced emulsification types using an emulsifier, self-emulsification types introducing hydrophilic groups into the urethane resin, or water-soluble types. In particular, a self-emulsification type in which an ionic group is introduced into the structure of the urethane resin to form an ionomer is preferable because of its excellent storage stability as a liquid and the water resistance, transparency, and adhesion of the resulting coating layer.

Also, as the ionic group to be introduced, various things such as a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, and a quaternary ammonium salt can be mentioned, but a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken during each stage of the polymerization reaction. For example, during prepolymer synthesis, there is a method of using a resin having a carboxyl group as a copolymerization component, or a method of using a component having a carboxyl group as one component such as a polyol, polyisocyanate, or a chain extender. In particular, a method of using a carboxyl group-containing diol and introducing a desired amount of carboxyl groups according to the amount of this component introduced is preferable. For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis-(2-hydroxyethyl)propionic acid, bis-(2-hydroxyethyl)butanoic acid, etc. can be copolymerized with respect to the diol used for polymerization of a urethane resin. In addition, it is preferable that this carboxyl group be in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali, etc. Particularly preferable are ammonia, trimethylamine, and triethylamine. In such a polyurethane resin, the carboxyl group from which the neutralizing agent is removed can be used as a crosslinking reaction site by another crosslinking agent in the drying process after coating. As a result, in addition to excellent stability in the liquid state before coating, it becomes possible to further improve the durability, solvent resistance, water resistance, blocking resistance, etc. of the obtained coating layer.

Acrylic resins are polymers made of polymerizable monomers including acrylic and methacrylic monomers. These may be homopolymers, copolymers, or further copolymers with polymerizable monomers other than acrylic and methacrylic monomers. Furthermore, copolymers of these polymers with other polymers (e.g., polyester, polyurethane, etc.) are also included. Examples thereof include block copolymers and graft copolymers. That is, the acrylic resin may be an acrylic-modified polyester resin or an acrylic-modified polyurethane resin. Furthermore, a polymer (or in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (or in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer in a polyurethane solution or a polyurethane dispersion is also included. Likewise, polymers (and in some cases polymer mixtures) obtained by polymerizing a polymerizable monomer in other polymer solutions or dispersions are also included, and these are also referred to herein as acrylic modified polyester resins or acrylic modified polyurethane resins. In addition, the polyester and polyurethane used in the acrylic resin can be appropriately selected and used from those exemplified as the polyester and polyurethane as the binder component.

Additionally, the acrylic resin may contain a hydroxyl group or an amino group to further improve adhesion to the substrate film.

As the above polymerizable monomer, there is no particular limitation, and representative compounds include, for example, various carboxyl group-containing monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, and citraconic acid, and salts thereof; various hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, monobutyl hydroxyfumarate, and monobutyl hydroxyitaconate; various (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and lauryl (meth)acrylate; Examples thereof include various nitrogen-containing compounds such as (meth)acrylamide, diacetone acrylamide, N-methylolacrylamide, and (meth)acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, and vinyltoluene; various vinyl esters such as vinyl propionate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; phosphorus-containing vinyl monomers; various halogenated vinyls such as vinyl chloride and vinylidene chloride; and various conjugated dienes such as butadiene.

In order to improve the strength of the resin layer (B), it is also possible to use a crosslinking agent in combination. The crosslinking agent may be a conventionally known material, and examples thereof include oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds, carbodiimide compounds, and organic silicon compounds. From the viewpoint of improving the strength of the resin layer (B), a melamine compound is more preferable. In addition, it is also possible to use two or more types of crosslinking agents in combination.

The resin layer (B) in the present release film may contain particles for the purpose of improving the film's activity, but a more preferable form is one in which particles are substantially absent. By containing substantially no particles in the resin layer (B), the release properties can be stabilized while reducing the transferability of the release component.

In addition, substantially not containing means that the resin layer (B) may contain particles as long as the amount is small enough not to impede the effect of the present invention, and for example, particles that are inevitably mixed may be contained. The content of particles in a specific resin layer (B) is, for example, less than 0.05 mass%, preferably less than 0.01 mass%, more preferably less than 0.0001 mass%, based on nonvolatile components. In addition, the range of the content of particles in the resin layer (B) based on nonvolatile components is also the same as the content of the particles.

Additionally, within a range that does not impair the spirit of the present invention, the resin layer (B) may contain, as necessary, an antifoaming agent, a coating improving agent, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, a pigment, or the like.

In the resin layer (B), the content of the release agent among the nonvolatile components is preferably 10 to 70 mass%. When the content of the release agent is 10 mass% or more, good anti-blocking performance is obtained.

In the case where a long-chain alkyl group-containing compound is used as a non-silicone-based release agent in the resin layer (B), the proportion of the long-chain alkyl group-containing compound in the total nonvolatile components in the resin layer (B) composition is preferably in the range of 5 to 90 mass%, more preferably 10 to 70 mass%, further preferably 20 to 60 mass%, and most preferably 20 to 40 mass%. When the proportion of the long-chain alkyl group-containing compound is in the above range, good anti-blocking performance is obtained, and by reducing changes in the peeling characteristics of the release layer due to blocking, it is possible to significantly suppress heavy peeling of the release layer in the lower winding portion of the roll where more pressure is applied to the film.

In the resin layer (B), when using wax as a non-silicone release agent, the proportion of the wax in the total nonvolatile components in the resin layer (B) is preferably in the range of 5 to 90 mass%, more preferably 10 to 80 mass%, and even more preferably 25 to 70 mass%. When the proportion of the wax is in the above range, good anti-blocking performance is obtained, and by reducing the change in the peeling characteristics of the release layer due to blocking, the peeling of the release layer in the lower winding portion of the roll where pressure is applied to the film can be significantly suppressed. In addition, when used in combination with a melamine compound, the peeling may progress. Therefore, when using a wax, care must be taken in combining it with a crosslinking agent, etc. On the other hand, a long-chain alkyl group-containing compound does not have the following problems, and can be said to be more preferable.

As combinations of preferred compositions, combinations of a long-chain alkyl group-containing compound and a melamine compound, a long-chain alkyl group-containing compound and an oxazoline compound, a long-chain alkyl group-containing compound and a melamine compound and an oxazoline compound, and a wax and a melamine compound and an oxazoline compound are exemplified.

As a non-silicon release agent, the factors (estimations) that increase the peeling rate when combined with a cross-linking agent, rather than a long-chain alkyl group-containing compound, can be considered as follows.

In addition to being water-repellent, wax also has oil-repellent properties. As a result, it has poor compatibility with the melamine compound it is combined with, making it easier for the melamine compound to be repelled.

Meanwhile, the evaluation of the peeling rate of the present invention is that since the pressing process is performed under high temperature (40°C) and high humidity (90%RH) with moisture present, it is presumed that the surface of the resin layer (B) combining the wax and melamine compound is prone to forming aggregates, which improves the adhesion to the silicone release layer on the opposite surface, resulting in an increased peeling rate.

As described above, the present invention is characterized in that it selects a release agent by focusing on the oil-repelling effect, which was not noticed in conventional non-silicon release agents, and configures a release film having a resin layer (B).

In the case where a compound comprising thiophene or a thiophene derivative is used as an antistatic agent in the resin layer (B), the proportion of the compound comprising thiophene or a thiophene derivative in the total nonvolatile components of the resin layer (B) is preferably in the range of 5 to 50 mass%, more preferably 5 to 40 mass%, and even more preferably 5 to 30 mass%. In the above range, good antistatic properties can be obtained.

In the resin layer (B), the polyhydroxy compound is preferably in the range of 10 to 80 mass%, more preferably 20 to 70 mass%, and even more preferably 30 to 65 mass% in terms of the proportion of the total nonvolatile components of the resin layer (B). Within the above range, good antistatic properties can be obtained.

As a proportion of the total nonvolatile components of the resin layer (B), the binder component is preferably in the range of 5 to 50 mass%, more preferably 5 to 40 mass%, and even more preferably 5 to 30 mass%. When the proportion of the binder component is in the above range, the strength of the resin layer (B) is improved, and blocking can be reduced.

The proportion of the crosslinking agent in the total nonvolatile components of the resin layer (B) is preferably in the range of 5 to 70 mass%, preferably 10 to 60 mass%, and more preferably 15 to 50 mass%. When the proportion of the crosslinking agent is in the above range, the strength of the resin layer (B) is improved, and blocking can be reduced.

<Characteristics of the resin layer (B)>

The resin layer (B) in the present invention can have the following characteristics.

In the present release film, the surface roughness (Ra(B)) of the resin layer (B) is preferably 20 nm or more, more preferably 25 to 60 nm, more preferably 30 to 55 nm, and even more preferably 38 to 50 nm. When it is 20 nm or more, blocking is less likely to occur in the roll state after the release layer is provided. On the other hand, when the surface roughness is 60 nm or less, when the present release film is wound into a roll shape, the unevenness of the film is not transferred to the release layer, and the peeling characteristics of the release layer are maintained.

The thickness of the resin layer (B) is preferably 0.005 to 0.25 µm, more preferably 0.008 to 0.15 µm, and even more preferably 0.01 to 0.10 µm. By setting the thickness of the resin layer (B) to 0.25 µm or less, when the release film is wound into a roll shape, the non-silicone release agent component in the resin layer (B) can be suppressed from migrating to the release layer, and when the thickness of the resin layer (B) is 0.005 µm or more, good anti-blocking properties can be imparted. In addition, it can be presumed that unreacted products of various compounds, compounds after reaction, or mixtures thereof are present in the resin layer (B).

The surface resistivity of the resin layer (B) surface is preferably 1×10 ¹² Ω/□ or less, more preferably 1×10 ¹⁰ Ω/□ or less, even more preferably 1×10 ⁸ Ω/□ or less, and most preferably 1×10 ⁶ Ω/□ or less. There is no particular lower limit of the surface resistivity, but considering the cost of the antistatic agent, it is preferably 1×10 ⁴ Ω/□ or more. The lower the surface resistivity of the resin layer (B), the better the antistatic property, which suppresses charging of the film during the process and prevents adhesion of foreign substances, etc.

The state peeling strength of the resin layer (B) is preferably 400 to 2000 g/25 mm, more preferably 400 to 1500 g/25 mm, and even more preferably 400 to 1000 g/25 mm. By setting the state peeling strength of the resin layer (B) to 2000 g/25 mm or less, good anti-blocking properties can be provided, and when the release film is wound into a roll shape, peeling of the resin layer (A) at the lower winding portion of the roll to which pressure is applied by the film can be suppressed.

The surface free energy of the resin layer (B) is preferably 50 mN/m or less, more preferably 40 mN/m or less, and even more preferably 30 mN/m or less. By setting the surface free energy of the resin layer to 50 mN/m or less, good anti-blocking properties can be imparted, and when the release film is wound into a roll shape, peeling of the release layer (A) at the lower winding portion of the roll to which pressure is applied by the film can be suppressed. Details of the surface free energy are as described in the Examples.

The elastic modulus of the resin layer (B) at 25°C is preferably 500 MPa or more. The elastic modulus referred to here is a value measured by a nanoindenter. If the elastic modulus is 500 MPa or more, when the release film is wound into a roll shape, the resin layer (A) does not delaminate even at the lower winding portion of the roll where pressure is applied by the film.

<Undercoating layer>

It is preferable that the present heteromorphic film has an undercoat layer between at least one of the resin layer (A) or the resin layer (B) and the substrate film. The undercoat layer may be provided between the resin layer (A) and the substrate film, or between the resin layer (B) and the substrate film, or may be provided on both sides.

The undercoat layer is used not only for the purpose of improving the adhesion between the film and the resin layer (A) or the resin layer (B), but also for the purpose of imparting various functions to the release film. Examples of the undercoat layer include antistatic performance for suppressing peeling electrification in the process of peeling a functional layer such as an adhesive layer provided on the resin layer (A) and preventing adhesion of foreign substances, and oligomer sealing performance for sealing the precipitation of oligomers from the polyester film when heat treatment is performed at high temperature for a long time. In the present release film, it is preferable that it is an undercoat layer having antistatic performance. In addition, the undercoat layer may be a single layer or a configuration of two or more layers.

In an undercoating layer having antistatic performance, as an antistatic agent, for example, a polymer doped with another anionic compound in a compound comprising the above thiophene or a thiophene derivative, or a polymer self-doped with an anionic group in a compound comprising thiophene or a thiophene derivative, or a polymer containing as a component a monomer having an alkylsulfonic acid ion as a counter ion can be used.

In addition, in the present heteromorphic film, from the viewpoint of having good antistatic performance, it is more preferable that the undercoating layer contain a compound composed of thiophene or a thiophene derivative.

In forming an undercoating layer having antistatic properties, it is preferable to use at least one compound or derivative thereof selected from polyglycerin represented by the general formula (9) and an alkylene oxide adduct to polyglycerin, for the purpose of improving the antistatic properties.

The undercoating layer having antistatic properties may contain a binder component. As the binder, various conventionally known polymers, such as polyester resin, acrylic resin, urethane resin, and polyvinyl alcohol resin, can be used. From the viewpoint of improving the transparency and antistatic properties of the undercoating layer, urethane resin is preferable.

In order to improve the strength of the undercoating layer, it is also possible to use a crosslinking agent in combination. The crosslinking agent may be a conventionally known material, and examples thereof include oxazoline compounds, epoxy compounds, melamine compounds, isocyanate compounds, carbodiimide compounds, and organic silicon compounds. From the viewpoint of improving the strength of the undercoating layer, a melamine compound is more preferable. It is also possible to use two or more types of crosslinking agents in combination.

In the case where a compound comprising thiophene or a thiophene derivative is used as an antistatic agent in the undercoating layer, the proportion of the compound comprising thiophene or a thiophene derivative in the total nonvolatile components of the undercoating layer is preferably in the range of 5 to 50 mass%, more preferably 5 to 40 mass%, and even more preferably 5 to 30 mass%. In the above range, good antistatic properties can be obtained.

In the undercoating layer, the proportion of at least one compound or derivative thereof selected from polyglycerin and alkylene oxide adducts to polyglycerin in the total nonvolatile components of the undercoating layer is preferably in the range of 10 to 80 mass%, more preferably 20 to 70 mass%, and even more preferably 30 to 65 mass%. Within the above range, good antistatic properties can be obtained.

As a proportion of the total nonvolatile components of the undercoating layer, the binder component is preferably in the range of 5 to 50 mass%, more preferably 5 to 40 mass%, and even more preferably 5 to 30 mass%. When the proportion of the binder component is in the above range, the strength of the undercoating layer becomes good, and the antistatic property can be improved.

The proportion of the cross-linking agent in the total nonvolatile components of the undercoating layer is preferably in the range of 5 to 70 mass%, preferably 10 to 60 mass%, and more preferably 15 to 50 mass%. When the proportion of the cross-linking agent is in the above range, the strength of the undercoating layer becomes good, and blocking can be reduced.

In the undercoating layer having oligomer sealing performance, an undercoating layer having oligomer sealing performance containing an organic compound including one or more metal elements selected from aluminum, titanium, and zirconium may be provided.

The undercoating layer having oligomeric sealing properties may be provided directly on the base film or on the undercoating layer having the antistatic properties.

In addition, it can be assumed that unreacted substances of various compounds of the resin composition, compounds after reaction, or mixtures thereof exist in the undercoating layer.

<Characteristics of the undercoating layer>

The thickness of the undercoating layer having antistatic properties is preferably 0.005 ㎛ or more and 0.25 ㎛ or less, more preferably 0.008 ㎛ or more and 0.15 ㎛ or less, and even more preferably 0.01 ㎛ or more and 0.10 ㎛ or less. When the thickness of the undercoating layer is within the above range, good antistatic properties can be imparted.

The surface resistivity of the undercoating layer surface having antistatic performance is preferably 1×10 ¹² Ω/□ or less, more preferably 1×10 ¹⁰ Ω/□ or less, even more preferably 1×10 ⁸ Ω/□ or less, and most preferably 1×10 ⁶ Ω/□ or less. There is no particular lower limit of the surface resistivity, but considering the cost of the antistatic agent, it is preferably 1×10 ⁴ Ω/□ or more. The lower the surface resistivity of the resin layer (B), the better the antistatic performance, which suppresses charging of the film during the process and prevents adhesion of foreign substances, etc.

<Method for forming resin layer (B) and undercoating layer>

Next, the method of forming the resin layer (B) and the undercoating layer is described.

The formation of the resin layer (B) and the undercoat layer is provided by coating the coating solution on the film, and may be provided by inline coating performed within the film manufacturing process, or may be applied externally on the film once it has been manufactured, so-called offline coating. Inline coating is more preferable.

Inline coating is a method of performing coating within the process of manufacturing polyester film, and specifically, it is a method of performing coating at any stage from melting and extruding polyester to stretching, heat setting, and winding. Usually, coating is performed on any of the following: an unstretched sheet obtained by melting and rapid cooling, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, and a film after heat setting and before winding.

Although not limited thereto, for example, in sequential biaxial stretching, a method of coating a uniaxially stretched film stretched in the longitudinal direction (vertical direction) and then stretching in the transverse direction is excellent. According to this method, since film forming and formation of a resin layer (B) can be performed simultaneously, there is an advantage in manufacturing cost, and furthermore, since stretching is performed after coating, the thickness of the resin layer (B) can be changed by the stretching ratio, so that thin film coating can be performed more easily compared to an offline coating film. Furthermore, by providing a resin layer (B) on the film before stretching, the resin layer (B) can be stretched together with the polyester film, and thereby the resin layer (B) can be firmly adhered to the polyester film.

In addition, in the production of a biaxially oriented polyester film, the film can be restrained in the vertical and horizontal directions by stretching while holding the film ends with clips or the like, so that in the heat-setting process, high temperatures can be applied while maintaining flatness without wrinkles or the like occurring. Therefore, since the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, curing of the resin layer (B) and the undercoat layer progresses further compared to offline coating, so that a stronger coating film can be produced.

In the case where the resin layer (B) is prepared by inline coating, it is preferable to manufacture the base film by applying the resin layer (B) composition, in which the above-described series of compounds are prepared in the form of an aqueous solution or aqueous dispersion and the solid content concentration (total nonvolatile components) is adjusted to be about 0.1 to 50 mass%, onto a polyester film.

As a method for applying the resin layer (B) composition or the undercoat layer composition to the film, for example, a conventionally known coating method such as air doctor coating, blade coating, rod coating, bar coating, knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss roll coating, cast coating, spray coating, curtain coating, calendar coating, or extrusion coating can be used.

There are no particular limitations on the drying and curing conditions when forming the resin layer (B) and the undercoating layer on the film, and when the resin layer (B) is provided by inline coating, it is preferable to perform heat treatment at 70 to 270°C for 3 to 200 seconds, more preferably at 100 to 260°C, and even more preferably at 110 to 250°C for 10 to 100 seconds.

Meanwhile, for example, when preparing a resin layer (B) by offline coating, it is preferable to perform heat treatment at 80 to 200°C for 3 to 40 seconds, more preferably at 100 to 180°C for 3 to 40 seconds.

Regardless of whether offline coating or in-line coating is used, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as needed. The film constituting the release film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

<<Laminated composition of heteromorphic film>>

The release film in the present invention may have a laminated configuration, and as a preferable form, there is provided a form in which an adhesive layer is laminated on the surface on the resin layer (A) side of the release film. As a more preferable form, there is provided a form in which the release film is used as a first release film, an adhesive layer is formed on the resin layer (A) side of the release film, and a release film having a different peeling force from the release film is formed on the other surface of the adhesive layer to which the resin layer (A) of the release film is laminated, as a second release film, and they are laminated together. As a more preferable form, there is provided a form in which the adhesive layer is an optically transparent adhesive sheet (OCA), and the release film is used and laminated as a release film having a light peeling force. In addition, the adhesive layer may be a single layer or a structure of two or more layers.

In addition, the above "release film having a different peeling strength from that of the present release film" means that the peeling strength of the release film evaluated by the measurement method described in the examples is different from the peeling strength of the resin layer (A) side of the present release film. In addition, the release film having a different peeling strength from that of the present release film is preferably one having a peeling strength greater than that of the resin layer (A) of the present release film, and specifically, the peeling strength is preferably 1.5 to 10 times, more preferably 1.5 to 8 times, and still more preferably about 1.5 to 6 times. By satisfying the above peeling strength, the problem of the resin layer (A) of the present release film being peeled in a scene where peeling is not originally necessary can be reduced.

<Adhesive layer>

Regarding the adhesive layer, it is explained below.

The adhesive layer is a layer formed of an adhesive composition, and may be an acrylic adhesive composition having an acrylic resin as a main component, a rubber adhesive composition having rubber as a main component, a urethane adhesive composition having a urethane resin as a main component, or a silicone adhesive composition having a silicone resin as a main component. Among these, an acrylic adhesive composition having an acrylic resin as a main component is preferable because the adhesive composition can adjust the adhesive force and the peeling force in a good balance, and is also inexpensive.

In addition, the above "main component resin" means a resin having the highest mass ratio among the resins constituting the adhesive composition. For example, it means a component accounting for 50 mass% or more, preferably 60 mass% or more, and more preferably 70 mass% or more of the total amount of resins constituting the adhesive composition. In addition, the upper limit is 100 mass%, but is usually 99.99 mass%.

(Acrylic resin)

As an acrylic resin which is the main component resin of the adhesive composition, a (meth)acrylic polymer can be mentioned.

(Meth)acrylic polymers are polymers whose main structural unit is (meth)acrylic acid alkyl ester. Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, isobornyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and adamantyl (meth)acrylate. These may be used alone or in combination of two or more. Among these, methyl (meth)acrylate is preferable in terms of compatibility with other (meth)acrylates constituting the (meth)acrylic polymer and the heat resistance of the cured resin layer (B). The content of the (meth)acrylic acid alkyl ester in the monomers forming the (meth)acrylic polymer is, for example, 50 mass% or more, preferably 60 to 99.99 mass%, more preferably 75 to 98.9 mass%, and even more preferably 87 to 97.8 mass%. Furthermore, the (meth)acrylic polymer may have a radically polymerizable double bond.

(Meth)acrylic polymers can be copolymerized with (meth)acrylic acid esters other than (meth)acrylic acid alkyl esters, (meth)acrylic acid, and other vinyl group-containing compounds for the purpose of improving glass transition temperature, mechanical properties, compatibility, etc.

Examples of (meth)acrylic acid esters other than the above-mentioned (meth)acrylic acid alkyl esters that can be used as a copolymerization component include (meth)acrylic acid hydroxyalkyl, (meth)acrylic acid methoxymethyl, (meth)acrylic acid methoxyethyl, (meth)acrylic acid ethoxymethyl, (meth)acrylic acid ethoxyethyl, etc. (meth)acrylic acid alkoxyalkyl esters, (meth)acrylic acid phenyl, (meth)acrylic acid benzyl, (meth)acrylic acid glycidyl, (meth)acrylic acid γ-butyrolactone, etc., which will be described later.

Examples of the compounds having the above vinyl group include acrylamide compounds such as dimethylacrylamide, hydroxyethylacrylamide, and dimethylaminopropylacrylamide; styrene compounds such as styrene, α-methylstyrene, and p-methoxystyrene; and maleic anhydride.

In addition, other components (a1) and (a2) described later may also be used appropriately.

In the present invention, the monomer constituting the (meth)acrylic polymer may contain, in addition to the (meth)acrylic acid alkyl ester, an acrylic monomer (a1) as a copolymerization component, since it serves as a reaction site with a crosslinking agent described later.

The acrylic monomer (a1) becomes a reaction site of a crosslinked structure when copolymerized with other copolymerization components to form an acrylic resin, and a monomer containing a functional group capable of reacting with a functional group contained in a crosslinking agent described later may be used. Examples of such acrylic monomers (a1) include a hydroxyl group-containing monomer, an amino group-containing monomer, an acetoacetyl group-containing monomer, an isocyanate group-containing monomer, a glycidyl group-containing monomer, and the like. Among these, a hydroxyl group-containing monomer is preferably used because it can efficiently undergo a crosslinking reaction with a crosslinking agent. The acrylic monomer (a1) may be used alone or in combination of two or more.

As the hydroxyl group-containing monomer, for example, acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl 2-hydroxyethyl phthalic acid and N-methylol (meth)acrylamide; Examples of the monomers include secondary hydroxyl groups, such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro 2-hydroxypropyl (meth)acrylate; and tertiary hydroxyl group-containing monomers, such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate.

Among the above hydroxyl group-containing monomers, a first-class hydroxyl group-containing monomer is preferable because of its excellent reactivity with a crosslinking agent, and furthermore, use of 2-hydroxyethyl acrylate is particularly preferable because it contains less impurities such as di(meth)acrylate and is easy to manufacture.

In addition, as the hydroxyl group-containing monomer used in the present invention, it is preferable to use one having a content ratio of di(meth)acrylate, which is an impurity, of 0.5 mass% or less, more preferably 0.2 mass% or less, particularly preferably 0.1 mass% or less. Specifically, as the hydroxyl group-containing monomer, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutylacrylate, etc. are particularly preferable, and these are preferable in that they are easy to purify because they have low molecular weights.

Examples of amino group-containing monomers include t-butylaminoethyl (meth)acrylate, ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate.

Examples of acetoacetyl group-containing monomers include 2-(acetoacetoxy)ethyl(meth)acrylate and allyl acetoacetate.

Examples of the isocyanate group-containing monomers include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

Examples of glycidyl group-containing monomers include (meth)acrylic acid glycidyl, (meth)acrylic acid allyl glycidyl, etc.

The content of the acrylic monomer (a1) among the monomers constituting the (meth)acrylic polymer is preferably 0.01 to 20 mass%, more preferably 0.1 to 10 mass%, and particularly 0.2 to 3 mass%. When the acrylic monomer (a1) is equal to or more than the lower limit above, the crosslinking point at the time of crosslinking becomes appropriate, so that the cohesive force after crosslinking becomes good. Furthermore, when it is equal to or less than the upper limit above, the adhesive force can be prevented from decreasing due to the (a1) component.

In addition, the monomer constituting the (meth)acrylic polymer may contain, in addition to the (meth)acrylic acid alkyl ester or the (meth)acrylic acid alkyl ester and the (a1) component, a copolymerizable monomer (a2) other than (a1) as a copolymerizable component, if necessary.

As the copolymerizable monomer (a2), for example, aromatic ring-containing monomers such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, ethoxylated o-phenylphenyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and styrene, amide monomers such as (meth)acryloylmorpholine, dimethyl (meth)acrylamide, diethyl (meth)acrylamide, and (meth)acrylamide, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyltoluene, vinylpyridine, vinylpyrrolidone, itaconic acid dialkyl ester, Examples thereof include fumaric acid dialkyl ester, allyl alcohol, acrylic chloride, methyl vinyl ketone, N-acrylamide methyltrimethylammonium chloride, allyl trimethylammonium chloride, and dimethylallyl vinyl ketone.

The content ratio of the copolymerizable monomer (a2) among the monomers forming the (meth)acrylic polymer is preferably 0 to 20 mass%, more preferably 1 to 15 mass%, and particularly 2 to 10 mass%, and when the content of the copolymerizable monomer (a2) is within the above range, it is possible to prevent the adhesive properties from being deteriorated due to the (a2) component.

In the present invention, considering application to a foldable display, it is preferable to include 2-ethylhexylacrylate and/or butylacrylate from the viewpoint of providing flexibility to the adhesive layer.

In addition to the above main component resin, the adhesive composition may contain, if necessary, a crosslinking agent and other resins (other than the main component resin and the crosslinking agent) that constitute the adhesive component (e.g., acrylic resin, rubber, silicone resin, urethane resin).

(Bridger)

The adhesive composition may contain a crosslinking agent depending on its curing method.

Examples of crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, and amine crosslinking agents. Among them, isocyanate crosslinking agents are suitably used in terms of improved adhesion to a substrate or reactivity with acrylic resin. The crosslinking agent may be used alone or in combination of two or more.

The content of the crosslinking agent is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and particularly 0.1 to 3 parts by mass, per 100 parts by mass of the main component resin. When the content of the crosslinking agent is within the above range, the cohesive force is not insufficient, and the desired durability can be obtained, while the flexibility and adhesive force can be prevented from deteriorating.

In addition, with regard to the curing reaction, in the case of photocuring by irradiating an active energy ray, it is preferable to blend a polyfunctional (meth)acrylate as a crosslinking agent into the adhesive composition. Examples of such polyfunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerin polyglycidyl ether poly(meth)acrylate, and the like.

(Resin constituting other adhesive components)

The adhesive composition may, in addition to the main component resin and the crosslinking agent, contain, if necessary, a resin constituting the adhesive component other than the main component resin and the crosslinking agent (e.g., acrylic resin, rubber, silicone resin, urethane resin).

For example, it is possible to blend additives such as conventionally known additives such as tackifiers, silane coupling agents, antistatic agents, colorants, fillers, anti-aging agents, ultraviolet absorbers, functional pigments, etc., or additives such as compounds that cause coloration or discoloration by ultraviolet or radiation irradiation.

The blending amount of these additives is preferably 10 mass% or less of the entire adhesive composition (based on nonvolatile components), more preferably 5 mass% or less, and it is preferable to not include low-molecular-weight components having a molecular weight of less than 10,000 as additives as possible from the viewpoint of excellent durability.

<Method of forming adhesive layer>

The method for forming the adhesive layer is not particularly limited, and may be formed by applying the adhesive composition onto the resin layer (A) of the release film, drying appropriately, curing, etc. In addition, the adhesive composition may be formed by applying the adhesive composition onto a base film or a release film having a different peeling strength from that of the release film, drying appropriately, curing, etc., and then bonding the release layer (layer A) of the release film to the side opposite to the side having the release film having a different peeling strength from that of the release film.

The adhesive composition may be cured depending on the crosslinking agent or the main component resin, and may be cured by heating or by light irradiation such as ultraviolet rays. In addition, the adhesive composition may be appropriately diluted with an organic solvent or the like and then applied onto a release layer or the like.

<Adhesive layer characteristics>

(Thickness of adhesive layer)

The thickness of this adhesive layer is not particularly limited. For example, in terms of providing sufficient adhesive strength or filling in unevenness or steps of a substrate to which the adhesive is bonded, it is preferably 0.1 ㎛ or more, more preferably 0.5 ㎛ or more, and more preferably 1 ㎛ or more. On the other hand, in terms of material usage efficiency, permeability, and outgassing, it is preferably 10,000 ㎛ or less, more preferably 3,000 ㎛ or less, and more preferably 1,000 ㎛ or less.

(Elasticity of adhesive layer)

In the present invention, the adhesive layer preferably has an elastic modulus of 6.0 MPa or less at 25°C. The elastic modulus referred to here is a value measured by a nanoindenter. When the elastic modulus is 6.0 MPa or less, the adhesive layer has good deformation followability, and can be applied to foldable display applications. From this viewpoint, the elastic modulus of the adhesive layer is more preferably 5.0 MPa or less, further preferably 4.0 MPa or less, and particularly preferably 3.0 MPa or less. Furthermore, from the viewpoint of adhesive layer formability, the elastic modulus of the adhesive layer at 25°C is preferably 0.5 MPa or more, more preferably 1.0 MPa or more, and further preferably 1.5 MPa or more.

(Glass transition temperature (Tg) of the adhesive layer)

The glass transition temperature is derived from Fox's equation below.

Tg: Glass transition temperature of the copolymer (K)

Tga: Glass transition temperature (K) of the homopolymer of monomer A

Wa: Weight fraction of monomer A

Tgb: Glass transition temperature (K) of the homopolymer of monomer B

Wb: Weight fraction of monomer B

Tgn: Glass transition temperature (K) of the homopolymer of monomer N

Wn: Weight fraction of monomer N

(Wa+Wb+···+Wn=1)

In the present invention, considering application to a foldable display, Tg is preferably in the range of -55°C to -70°C, and more preferably in the range of -58°C to -68°C.

By satisfying the above range, an adhesive layer having good follow-up properties to deformation, such as bending, can be obtained.

<<How to use the film laminate>>

The present film laminate can be used in various laminate configurations. For example, the release film having the adhesive layer may be a film laminate in which an optical member is bonded to the surface of the adhesive layer. Such a film laminate can be created by peeling off the release film and bonding the optical member to the adherend using the exposed adhesive layer. Examples of the optical member include a polarizing plate, a touch sensor, and the like. In addition, it may be an optical member for vehicle use, such as a touch panel mounted on an automobile.

(polarizing plate)

The material and composition of the polarizing plate are arbitrary, and for example, a polarizing plate of this type is widely used, in which a TAC (triacetyl cellulose) film is laminated as a protective film on a stretched polyvinyl alcohol film using iodine as an orientation pigment. In addition, the polarizing plate may have a layer composition having functions such as a hard coating having virtually no phase difference on the surface, and an anti-glare, low-reflection, and anti-static properties.

(Touch sensor)

A touch sensor is a component that detects a touch point by reacting to the contact when a user touches an image displayed on a screen with a finger or a touch pen, and examples of sensor technologies include electrostatic capacitance, resistive film, and surface wave methods using infrared or ultrasonic waves.

Typically, touch sensors are mounted on display devices such as liquid crystal display panels and organic EL displays.

In addition, recently, as a replacement for a glass substrate, there is a tendency to use a substrate film with an emphasis on flexibility, so it is desirable to use a touch sensor film. A touch sensor film generally provides a patterned transparent conductive layer to perform the function of a sensing electrode.

In addition, the film laminate may have a layer structure including a release film having the adhesive layer and another release film, and in which the release film having the adhesive layer is bonded to the other release film with the adhesive layer interposed therebetween. The film laminate having such a layer structure is composed of the release film/adhesive layer/another release film, and can be used as a double-sided adhesive sheet.

Other release films have a release layer formed on the surface of a substrate such as a resin film, and the surface on which the release layer is formed is bonded to the adhesive layer. The release layer of other release films may be used other than the release layer described above.

The film laminate having the above structure preferably has a ratio (MB/MA) of the elastic modulus (MA) of the release layer of the present release film to the elastic modulus (MB) of the release layer of another release film in a range of 4 to 30, more preferably in a range of 4 to 25. By satisfying the above range of elastic moduli, in the film laminate, the problem of the present release film being peeled off in a scene where peeling is not originally necessary can be reduced.

The film laminate in which the above-mentioned different release films are bonded can be used by peeling off the release film and bonding the exposed adhesive layer surface of the release film having the remaining adhesive layer to an optical member. Then, another release film can be peeled off from the adhesive layer of the release film having the adhesive layer. In addition, the release film can be re-bonded on the adhesive layer bonded to the optical member. In this way, since the release film of the present invention has ultra-light peeling properties and low transferability, so-called re-peelable use of the release film is also possible.

In addition, the other release film has a state peel strength measured at 180° peeling at a peeling speed of 0.3 m/min that is greater than the state peel strength of the present release film, and specifically, it is preferably about 2 to 10 times the state peel strength of the present release film, and more preferably, it is 2 to 6 times. By satisfying the above peeling force ratio, the problem of the present release film being peeled in a scene where peeling is not originally necessary can be reduced.

The above-mentioned release film and film laminate are preferably used for vehicle applications. When used for vehicle applications, in order to maintain high adhesiveness even when exposed to a high temperature environment in summer or a low temperature environment in winter, it is necessary to increase the adhesiveness of the adhesive layer. Since the release film can realize ultra-light peeling properties, even if the adhesiveness of the adhesive layer is high, the peeling performance is good.

<<<Explanation of phrases, etc.>>>

In the present invention, even when referring to a “film,” it is considered to include a “sheet,” and even when referring to a “sheet,” it is considered to include a “film.”

In addition, when expressed as a “panel,” such as a display panel, a protective panel, a touch panel, etc., it includes a plate, sheet, and film.

In the present invention, when it is described as “X∼Y” (X, Y are arbitrary numbers), unless specifically stated otherwise, it includes the meaning of “more than X and less than Y,” as well as the meaning of “preferably greater than X” or “preferably less than Y.”

In addition, when it is written as “X or more” (X is any number), it includes the meaning of “preferably greater than X” unless otherwise stated, and when it is written as “Y or less” (Y is any number), it also includes the meaning of “preferably less than Y” unless otherwise stated.

Example

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it goes beyond the gist thereof. In addition, the evaluation methods in the examples and comparative examples are as follows.

(1) Method for measuring the ultimate viscosity of polyester

1 g of polyester from which other polymer components and pigments that are incompatible with polyester have been removed was weighed, 100 ml of a mixed solvent of phenol/tetrachloroethane = 50/50 (mass ratio) was added, dissolved, and measured at 30°C.

(2) Method for measuring average particle size (d50:㎛)

The average particle size was determined by taking the value at 50% of the accumulated (mass basis) value in the equivalent spherical distribution measured using a centrifugal sedimentation particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation).

(3) Method for measuring film thickness of resin layer (A)

In order to suppress reflection from the back, black tape ("Vinyl Tape VT-50" manufactured by Nichiban Co., Ltd.) was attached to the measurement back side of the sample film in advance. For the measurement, a spectrophotometer (UV-Visible Spectrophotometer "V-670" manufactured by Nippon Associativity Co., Ltd.) was used to measure the absolute reflectance in the wavelength range of 300 to 800 nm under the conditions of synchronous mode, 5° incident angle, N polarization, Fast response, 1.0 nm data acquisition interval, 10 nm bandwidth, and 1000 m/min scanning speed. The film thickness was obtained by comparing the data obtained by this measurement with data calculated assuming the refractive index of silicon to be 1.43.

(4) Method for measuring film thickness of resin layer (B) and undercoating layer

The surface of the cured resin layer (B) was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, a section prepared by an ultrathin sectioning method was dyed with RuO ₄ , and the cross-section of the coating layer was measured using TEM (H-7650, Hitachi High-Technologies Co., Ltd., acceleration voltage 100 kV).

(5) Measurement of surface resistivity

Using a low resistivity meter (Mitsubishi Chemical Co., Ltd., “Loresta GP MCP-T600”), the surface resistivity was measured after regulating the humidity of the sample for 30 minutes in a measurement atmosphere of 23°C and 50% relative humidity, and the value after 1 minute was taken as the surface resistivity. If the resistance value exceeded the upper limit of the measurable range, the measurement was considered impossible.

(6) Measurement of average surface roughness

The arithmetic mean roughness (Ra) of the resin layer (B) was measured using a surface roughness meter (two-dimensional roughness meter "surfcorder SE3500" manufactured by Kosaka Laboratory Co., Ltd.) compliant with JIS B 0601-2001. In addition, the maximum cross-sectional height (Rt) of the semi-circular surface was measured. Rt can be obtained as the sum of the maximum value of the peak height (Rp) and the maximum value of the valley depth (Rv) of the roughness curve in the evaluation length.

(7) Measurement of molecular weight of curable silicone resin

Using a GPC measuring device, a chromatogram was measured, and the number-average molecular weight (Mn) and the mass-average molecular weight (Mw) were obtained based on a calibration curve using standard polystyrene, and are shown in Table 2. Specifically, 4 mg of the sample for measurement was dissolved in 4 mL of THF to make a measurement solution, and 100 μL of the measurement solution was injected into the GPC measuring device for measurement. Tetrahydrofuran (THF) was used as the eluent. For the analysis, "Ecosec8320" manufactured by Tosoh Corporation was used, and the guard column was "TSKgel guardcolumn HXL-L" manufactured by Tosoh Corporation, and four "TSKgel GMHXL" manufactured by Tosoh Corporation were connected and used as the column. In addition, the analysis was performed under the conditions of an oven temperature of 40°C and a THF flow rate of 1.0 mL/min, and RI was used for detection.

(8) Composition analysis of curable silicone resin

The composition analysis of the curable silicone resin used in the examples and comparative examples was performed using 400MHz-NMR (Bruker Avance400M). For the ^1H -NMR measurement, CDCl ₃ was used as a solvent, and the peak derived from the methyl group of dimethylsiloxane was used as the chemical shift standard, and was performed at a temperature of 30°C.

(9) Measurement of peel strength of resin layer (A)

The resin layer (A) surface of the sample film was pressed (twice) with a rubber roller (2 kg), and an adhesive tape ("No. 7475" manufactured by Tesa) was attached. The film was then cut to a size of 25 mm x 300 mm, and the peeling force was measured after leaving it at room temperature (23°C) for 1 hour. The peeling force was measured using "Intesco Model 2001" manufactured by Intesco Co., Ltd., and the sample film was peeled at 180° under the condition of a tensile speed of 0.3 m/min.

(10) Measurement of residual adhesion of resin layer (A) (evaluation of transferability)

The sample film was cut into A4 size (210 mm × 297 mm), and a 75 μm biaxially oriented PET film (Mitsubishi Chemical Co., Ltd.: Diafoil T100-75) was placed on the release layer (A layer) surface, and pressed for 2 hours under conditions of a temperature of 23°C and a pressure of 1 MPa. Then, the “75 μm biaxially oriented PET film” alone was used as the evaluation film.

Meanwhile, the same "75 ㎛ biaxially oriented PET film" as described above was applied to an untreated base film that did not have a resin layer (A) and pressed under the same conditions as described above, and the "75 ㎛ biaxially oriented PET film" alone was used as a reference film.

An adhesive tape ("No. 31B" manufactured by Nitto Denko Co., Ltd.) was attached to the contact surface (resin layer (A) (A layer)) of the above evaluation film with the sample film and the contact surface with the base film of the above reference film by pressing (twice reciprocating) with a rubber roller (2 kg), and then cut to a size of 50 mm x 300 mm. The peeling strength was measured after leaving it at room temperature for 1 hour.

The peeling strength was measured using “Intesco Model 2001” manufactured by Intesco Co., Ltd., and was performed by peeling the evaluation film and the reference film at 180° under the condition of a tensile speed of 0.3 m/min.

Then, the peeling force of the measured evaluation film and the peeling force of the reference film were substituted into the following equation to obtain the residual adhesion rate (%). In addition, this is a value that has not been subjected to any heat treatment or the like.

Residual adhesion rate (%) = (peel strength of evaluation film/peel strength of reference film) × 100

In films with high transferability, since a lot of silicone is attached to the film, the peeling force of the adhesive tape decreases and the residual adhesion rate (%) also decreases. Therefore, the transferability of the resin layer (A) of the release film was evaluated as follows based on the value of the residual adhesion rate.

(11) Post-press peeling rate of resin layer (A) (alternative evaluation of blocking properties)

After attaching an acrylic adhesive tape ("No. 7475" manufactured by Tesa) to the resin layer (A) surface of the release film of Examples and Comparative Examples, cut it to a size of 25 mm x 150 mm, and leave it at room temperature for 1 hour. The peeling force at 180° peeling under the condition of a tensile speed of 0.3 m/min is defined as (F1).

Next, the other side (in the present invention, the resin layer (B) side) of the release film of the examples and comparative examples is placed so as to face the resin layer (A) side, and a press treatment is performed at a temperature of 40°C, a humidity of 90%RH, and a load of 1 MPa for 20 hours. After the treatment, an acrylic adhesive tape ("No. 7475" manufactured by Tesa) is attached to the resin layer (A) side, and then the tape is cut to a size of 25 mm × 150 mm and left at room temperature for 1 hour. The peeling force at 180° under the condition of a tensile speed of 0.3 m/min is defined as (F2).

The peeling rate after pressing was calculated by the following equation, and the peeling rate at that time was used as an indicator of blocking resistance. In addition, the blocking resistance is judged to be better the smaller the peeling rate.

After pressing, peeling rate (%) = (F2-F1)/F1×100

(12) Blocking performance evaluation

The release layer surface and the semi-release surface of the release films of the examples and comparative examples were arranged so that they faced each other, and pressurized with a press machine under an atmosphere of 10 kg/cm2, 40°C, and 80%RH for 20 hours to prepare a measurement sample for evaluating blocking resistance. Thereafter, using a peeling device ("AGI" manufactured by Shimadzu Corporation), the peeling force was measured under the conditions of a tensile speed of 300 mm/min and 180° peeling, and the peeling force at this time was taken as an indicator of blocking resistance. It is also judged that the blocking resistance is better the smaller the peeling force.

"metewand"

A(good): Peeling force is less than 20g/25mm and can be peeled without any problem.

B(poor): Peeling force exceeds 20g/25mm, blocking occurs.

(13) Adhesion between the substrate film and the resin layer (A)

In a constant temperature and humidity chamber, the sample film was left for 4 weeks under an atmosphere of 60°C and 80%RH, and then the sample film was taken out. Thereafter, the resin layer (A) side of the sample film was rubbed 5 times with a tentacle, and the adhesion was evaluated according to the following evaluation criteria based on the degree of peeling off of the release layer.

"metewand"

○: The coating did not turn white and no peeling was observed.

×: The coating has turned white or has fallen off.

(14) Measurement of peel strength of resin layer (B)

An acrylic adhesive tape ("No. 7475" manufactured by Tesa) was attached to the resin layer (B) of the sample film by pressing (2 round trips) with a rubber roller (2 kg), then cut to a size of 25 mm x 150 mm, and the peeling force after leaving it at room temperature (23°C) for 1 hour was measured. The peeling force was measured using "Intesco Model 2001" manufactured by Intesco Co., Ltd., by peeling the sample film at 180° under the condition of a tensile speed of 0.3 m/min.

(15) Measurement of surface free energy of resin layer

In a measurement atmosphere of 23℃, 50RH%, a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DMo-501") was used to create droplets of ion-exchange water and diiodomethane on the resin layer of the sample film, and the contact angles were measured. The contact angle was measured 60 seconds after each liquid was dropped on a laminated polyester film. Regarding the contact angle data of ion-exchange water and diiodomethane obtained by this method, the surface free energy of the antireflection layer surface was calculated by the Owens-Wendt theoretical formula using the surface tension component values of each solvent (Table 1).

(16) Measurement of elastic modulus of resin layer (A)

The elastic modulus of the resin layer (A) was measured at room temperature (25°C) and at an indentation depth of 50 nm using a nanoindenter (TI 950 TriboIndenter) from Hysitron.

(17) Measurement of elastic modulus of adhesive layer

Using a nanoindenter (TI 950 TriboIndenter) from Hysitron, the elastic modulus of the adhesive layer was measured at a point with an indentation depth of 500 nm at room temperature (25°C) using an indenter (conical: spherical, radius of curvature: 10 μm).

(18) Adhesive peel strength

The adhesive composition described in Table 8 was applied to the release layer surface of the sample film so that the film thickness in a wet state was 2 mil, and the film was cured by heat treatment at 150°C for 3 minutes to form an adhesive layer (thickness (after drying) 20 μm).

Thereafter, another release film was laminated on the adhesive layer to obtain a film laminate composed of sample film/adhesive layer/another release film. In addition, as the other release film, the release films produced in Comparative Examples 1 to 4 described below were used. In the obtained film laminate, the peeling force when the sample film was peeled off from the adhesive layer was measured. The measurement of the peeling force was performed using “Intesco Model 2001” manufactured by Intesco Co., Ltd., under the condition of a tensile speed of 0.3 m/min, with 180° peeling.

The polyester used in the examples and comparative examples was prepared as follows.

<Method for producing polyester (A)>

Using 100 parts by mass of dimethyl terephthalate and 60 parts by mass of ethylene glycol as starting materials and 0.09 parts by mass of magnesium acetate tetrahydrate as a catalyst, the reaction initiation temperature was set to 150°C, and the reaction temperature was gradually increased along with distillation of methanol, and reached 230°C after 3 hours. After 4 hours, the ester exchange reaction was substantially completed. To this reaction mixture, 0.04 parts by mass of ethyl acid phosphate was added, and then 0.04 parts by mass of antimony trioxide was added, and a polycondensation reaction was performed for 4 hours. That is, the temperature was gradually increased from 230°C to 280°C. Meanwhile, the pressure was gradually decreased from normal pressure and finally reached 0.3 mmHg. After the start of the reaction, the reaction was stopped at a point corresponding to an intrinsic viscosity of 0.65 by changing the stirring power of the reaction tank, and the polymer was discharged under nitrogen pressurization to obtain a polyester (A) having an intrinsic viscosity of 0.65.

<Method for producing polyester (B)>

In the method for producing polyester (A), 0.04 part by mass of ethyl acid phosphate was added, 0.2 part by mass of silica particles dispersed in ethylene glycol having an average particle size of 2.3 ㎛ and 0.04 part by mass of antimony trioxide were added, and the polycondensation reaction was stopped at a point corresponding to an intrinsic viscosity of 0.65, thereby obtaining polyester (B) using the same method as the method for producing polyester (A). The intrinsic viscosity of the obtained polyester (B) was 0.65.

Example 1-1

A mixed raw material in which polyester (A) and (B) were mixed in a ratio of 90 mass% and 10 mass%, respectively, was used as a raw material for the outermost layer (surface layer), and polyester (A) was used as a raw material for the middle layer. Each was supplied to two extruders, respectively, and after each was melted at 290°C, it was co-extruded in a layer configuration of 2 types and 3 layers (output amount of surface layer/middle layer/surface layer = 1:18:1) on a cooling roll set to 25°C, and then cooled and solidified to obtain an unstretched sheet. Next, using a roll speed difference, the film was stretched 3.4 times in the vertical direction at a film temperature of 85°C, and then the coating solution 1 of the resin layer (B) shown in Table 4 was applied to one side of the vertically stretched film, and the undercoat layer composition below was applied to the other side, and then guided into a tenter, stretched 4.5 times in the horizontal direction at 120°C, heat-treated at 225°C, and then relaxed by 2% in the horizontal direction, to obtain a biaxially stretched polyester film having a resin layer (B) thickness (after drying) of 0.05 μm and an undercoat layer thickness (after drying) of 0.05 μm and a thickness of 50 μm.

Subsequently, on the undercoating layer surface of the obtained polyester film, as a resin layer (A), the coating solution 1 of the resin layer (A) shown in Table 3 was applied by the bar coating method using a No. 4 bar so that the thickness of the coating amount (after drying) became 1.0 ㎛, and then dried at 150°C for 30 seconds to obtain a release film.

Examples 1-2 to 1-12:

A release film was obtained by manufacturing in the same manner as in Example 1-1, except that the coating solutions 2 to 12 of the resin layer (B) shown in Table 4 were applied to one side of the vertically stretched film.

As shown in Table 4, the obtained release film had a thin resin layer (A) and an elastic modulus of 500 MPa or less, while the resin layer (B) contained a non-silicone-based release agent, thereby realizing ultra-light peeling with a peeling force (state peeling force) of 5 g/25 mm or less, while also achieving blocking resistance with a post-press heavy peeling rate of 100% or less. In addition, the adhesion to the substrate was good and the transferability was low.

Examples 1-13 to 1-28

A mixed raw material in which polyester (A) and (B) were mixed in a ratio of 97 mass% and 3 mass%, respectively, was used as a raw material for the outermost layer (surface layer), and polyester (A) was used as a raw material for the middle layer. Each was supplied to two extruders, respectively, and after each was melted at 290°C, it was co-extruded in a layer configuration of 2 types and 3 layers (output amount of surface layer/middle layer/surface layer = 1:18:1) on a cooling roll set to 25°C, and then cooled and solidified to obtain an unstretched sheet. Next, using a roll speed difference, the film was stretched 3.4 times in the vertical direction at a film temperature of 85°C, and then the coating solution of the resin layer (B) shown in Table 4 was applied to one side of the vertically stretched film, and the undercoat layer composition below was applied to the other side, and then guided into a tenter, stretched 4.5 times in the horizontal direction at 120°C, heat-treated at 225°C, and then relaxed by 2% in the horizontal direction, to obtain a biaxially stretched polyester film having a resin layer (B) thickness (after drying) of 0.05 μm and an undercoat layer thickness (after drying) of 0.05 μm and a thickness of 50 μm.

Subsequently, on the undercoating layer surface of the obtained polyester film, as a resin layer (A), the coating solution 1 of the resin layer (A) shown in Table 3 was applied by the bar coating method using a No. 4 bar so that the thickness of the coating amount (after drying) became 1.0 ㎛, and then dried at 150°C for 30 seconds to obtain a release film.

As shown in Table 5, the obtained release film had a thin resin layer (A) and an elastic modulus of 500 MPa or less, while the resin layer (B) contained a non-silicone-based release agent, thereby realizing ultra-light peeling with a peeling force (state peeling force) of 5 g/25 mm or less, while also achieving blocking resistance with a post-press heavy peeling rate of 100% or less. In addition, the adhesion to the substrate was good and the transferability was low.

Comparative Example 1-1

A release film was obtained by manufacturing in the same manner as in Example 1-1, except that the resin layer (B) and the undercoating layer were not provided on the vertically stretched film.

Comparative Example 1-2

A release film was obtained by manufacturing in the same manner as in Example 1-1, except that the resin layer (B) was not provided on the vertically stretched film.

As shown in Table 5, the release films of Comparative Examples 1-1 to 1-2 obtained did not have a resin layer (B) containing a non-silicon release agent, so the rate of peeling after pressing was high, and there was concern about blocking occurring.

Comparative Example 1-3

In Example 1-1, a release film was obtained by manufacturing in the same manner as in Example 1, except that the resin layer (B) composition was changed to a coating solution 13 that did not contain a non-silicone-based release agent.

As shown in Table 5, the obtained release film did not contain a non-silicon release agent in the resin layer (B), so there was concern that the rate of peeling after pressing would be high and blocking would occur.

Comparative Example 1-4

In Example 1-1, a release film was obtained by manufacturing in the same manner as in Example 1, except that the coating solution 2 of the resin layer (A) was changed.

As shown in Table 5, the obtained heteromorphic film had a thin resin layer (A) and a high elastic modulus, so the peeling force (state peeling force) was about three times higher than that of Examples 1-1 to 1-12, making it impossible to achieve ultra-light peeling. In addition, the adhesion to the substrate was also poor.

Reference Example 1

In Example 1, a release film was obtained by manufacturing in the same manner as in Example 1, except that the coating solution 3 (particle content: 0.19 mass%) of the resin layer (A) was changed.

As shown in Table 5, the obtained heteromorphic film had poor adhesion to the substrate due to the presence of particles, which caused the resin layer (A) to recede, and also had relatively high transferability due to particle detachment. In addition, the rate of peeling after pressing was high, and there was concern about the occurrence of blocking.

Examples of compounds constituting the resin layer (A) are as follows.

a1: Curable silicone resin (silicone resin having a vinyl group introduced into the side chain and/or terminal of the main chain formed by siloxane bonds, number average molecular weight: 10600, viscosity at 25°C when adjusted to 15 mass% by dilution with n-heptane solvent: 1.7 mcps)

a2: A mixture containing a curable silicone resin (a silicone resin having a vinyl group introduced into a side chain and/or terminal of a main chain composed of siloxane bonds, number average molecular weight: 364,000) and a silicone crosslinker (a silicone resin having a Si-H group introduced into a side chain and/or terminal of a main chain composed of siloxane bonds) (viscosity at 25°C when adjusted to 15 mass% by dilution with n-heptane solvent: 410 mcps)

The content ratio (mol%) of each functional group in the curable silicone resin is as follows.

b1: Silicone crosslinker (CL750: Momentive Performance Materials)

c1: Additional platinum catalyst (CM678: Momentive Performance Materials)

c2: Additive platinum catalyst (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.)

d1: Particle (Tospul 120: Momentive Performance Materials)

The coating solution constituting the resin layer (A) is as follows.

Examples of compounds constituting the resin layer (B) and the undercoating layer are as follows.

(Lee Brother)

AI: Long-chain alkyl group-containing compound

A four-necked flask was charged with 200 parts of xylene and 600 parts of octadecyl isocyanate, and the mixture was heated with stirring. From the time when the xylene began to reflux, 100 parts of polyvinyl alcohol having an average degree of polymerization of 500 and a degree of saponification of 88 mol% was added in small portions at 10-minute intervals over a period of about 2 hours. After the polyvinyl alcohol was added to the end, reflux was performed for an additional 2 hours to terminate the reaction. The reaction mixture was cooled to about 80°C and then added into methanol, whereupon the reaction product precipitated as a white precipitate. Therefore, the precipitate was filtered and separated, 140 parts of xylene was added, and after heating to completely dissolve, methanol was added again to precipitate, and this operation of repeating several times, and then the precipitate was washed with methanol, dried, and pulverized to obtain.

AII: Wax

A wax emulsion obtained by adding 300 g of oxidized polyethylene wax having a melting point of 105°C, an acid value of 16 mgKOH/g, a density of 0.93 g/mL, and an average molecular weight of 5000, 650 g of ion-exchanged water, 50 g of decaglycerin monooleate surfactant, and 10 g of 48% potassium hydroxide aqueous solution to a 1.5 L emulsifying facility equipped with a stirrer, a thermometer, and a temperature controller, replacing the mixture with nitrogen, sealing, stirring at high speed at 150°C for 1 hour, cooling to 130°C, and passing the mixture through a high-pressure homogenizer at 400 atm to cool to 40°C.

(anti-warfare agent)

BI: A conductive agent composed of polyethylenedioxythiophene and polystyrene sulfonic acid (Orgacon ICP1010 manufactured by Agphagebat) neutralized with concentrated ammonia water to pH=9, nonvolatile component; 1.2 mass%, solvent; water

(polyhydroxy compounds)

CI: Polyglycerin with an average of n=4 in the above formula (9)

CII: A compound in which an average of 4 molecules of polyethylene oxide are added to a polyglycerin skeleton having an average of n=2 in the above formula (9).

(bookbinder)

DI: A water dispersion of a polyester resin copolymerized with the following composition

Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid/5-sodium sulfoisophthalic acid//(diol component) ethylene glycol/diethylene glycol = 92/8//80/20 (mol%)

DII: Polyurethane resin aqueous dispersion polymerized with the following composition

When a polyester polyol comprising 282 parts by mass of terephthalic acid, 282 parts by mass of isophthalic acid, 62 parts by mass of ethylene glycol, and 250 parts by mass of neopentyl glycol is referred to as (C1a), a polyester polyurethane comprising 876 parts by mass of (C1a), 244 parts by mass of tolylene diisocyanate, 81 parts by mass of ethylene glycol, and 67 parts by mass of dimethylol propionic acid as components is dispersed in water by neutralizing it with ammonia (concentration 20%, viscosity 50 mPa s at 25°C)

(Bridger)

EI: Hexamethoxymethylolmelamine

EII: Acrylic polymer having oxazoline group and polyalkylene oxide chain

Epocross (oxazoline group amount = 4.5 mmol/g, Nippon Shokubai Co., Ltd.)

(surfactant)

FI: A nonionic surfactant having a structure having polyethylene oxide in the side chain, as shown in the following formula.

[Chemical formula 9]

In the above formula, m and n are integers representing the number of moles of ethylene oxide added, and in this case, the average of m+n was used to be 10.

The coating solution constituting the resin layer (B) is as follows. Table 4 also shows the amount based on nonvolatile components.

<Undercoating layer composition>

The coating solution that constitutes the undercoating layer is as follows.

(BI)/(CII)/(DII)/(FI)=10 mass%/35 mass%/50 mass%/5 mass%

<Method for producing polyester (1)>

Using 100 parts by mass of dimethyl terephthalate and 55 parts by mass of ethylene glycol as starting materials and 0.04 parts by mass of magnesium acetate tetrahydrate as a catalyst, the reaction initiation temperature was set to 150°C, and the reaction temperature was gradually increased along with distillation of methanol, and reached 230°C after 3 hours. After 4 hours, the ester exchange reaction was substantially completed. To this reaction mixture, 0.02 parts by mass of ethyl acid phosphate was added, and then 0.04 parts by mass of antimony trioxide was added, and a polycondensation reaction was performed for 4 hours. That is, the temperature was gradually increased from 230°C to 280°C. Meanwhile, the pressure was gradually decreased from normal pressure and finally reached 0.3 mmHg. After the start of the reaction, the reaction was stopped at a point corresponding to an intrinsic viscosity of 0.59 dl/g by changing the stirring power of the reaction tank, and the polymer was discharged under nitrogen pressurization to obtain a polyester (1) having an intrinsic viscosity of 0.59 dl/g.

<Method for producing polyester (2)>

Using 100 parts by mass of dimethyl terephthalate and 45 parts by mass of ethylene glycol as starting materials and 0.06 parts by mass of magnesium acetate tetrahydrate as a catalyst, the reaction initiation temperature was set to 150°C, and the reaction temperature was gradually increased along with distillation of methanol, and reached 230°C after 3 hours. After 4 hours, the ester exchange reaction was substantially completed. After adding 0.03 parts by mass of ethyl acid phosphate to the reaction mixture, 0.3 parts by mass of silica particles having an average particle size of 2.7 μm dispersed in ethylene glycol and 0.03 parts by mass of antimony trioxide were added, and a polycondensation reaction was performed for 4 hours. That is, the temperature was gradually increased from 230°C to 280°C. Meanwhile, the pressure was gradually decreased from normal pressure and finally reached 0.3 mmHg. After the start of the reaction, the reaction was stopped at a point corresponding to an intrinsic viscosity of 0.59 dl/g by changing the stirring power of the reaction tank, and the polymer was discharged under nitrogen pressurization to obtain polyester (2) having an intrinsic viscosity of 0.59 dl/g.

<Method for producing polyester (3)>

In polyester (2), 10 parts by mass of organic particles (styrenedivinylbenzene: styrene resin) having an average particle size of 4.5 μm were added instead of silica particles, and a polyester (3) having an intrinsic viscosity of 0.60 dl/g was obtained by producing the same as polyester (2).

<Method for manufacturing polyester film>

[PET-A]

A blend of polyester (1) and polyester (2) in a mass ratio of 80/20 was used as the raw material for the A layer, and a blend of polyester (1) and polyester (3) in a mass ratio of 95.5/4.5 was used as the raw material for the B layer. Each was supplied to an extruder for the C layer, heated and melted at 285°C, and in a layer configuration of three types of three layers (A (A layer)/B (B layer)/C (C layer)) with the A and C layers as the outermost layers (surface layers) and the B layer as the middle layer, co-extruded so that the thickness composition ratio under the extrusion conditions was A/B/C = 5/90/5, and cooled and solidified while being placed in close contact with a hard cooling drum having a surface temperature of 40 to 50°C, to produce an unstretched polyethylene terephthalate film. This film was stretched 3.0 times in the longitudinal direction while passing through a heated roll group at 85°C to obtain a uniaxially oriented film. For this uniaxially oriented film, the cured resin layer composition shown below was applied to both surfaces, and then this film was guided to a tenter stretching machine, stretched 4.1 times in the width direction at 100°C, and further heat-treated at 235°C, and then relaxation treatment was performed by 2% in the width direction to obtain a biaxially oriented polyester film having a thickness of 50 μm and having a cured resin layer having a film thickness (after drying) of 0.05 μm on both surfaces.

(Curing resin layer composition)

(A): Thiophene-based antistatic agent

A challenge agent consisting of polyethylenedioxythiophene and polystyrene sulfonic acid, "Orgacon ICP1010" manufactured by Agphagebat, was neutralized with concentrated ammonia water to pH = 9.

(B) Polyhydroxy compound

Polyglycerin with an average polymerization degree of 4

(C) A water dispersion of a polyester resin having a condensed polycyclic structure copolymerized with the following composition:

Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid/5-sodium sulfoisophthalic acid//(diol component) ethylene glycol/diethylene glycol = 92/8//80/20 (mol%)

A/B/C=7/10/83(mass%)

<Heteromorphic layer composition>

a1: Curable silicone resin (silicone resin having a vinyl group introduced into the side chain and/or terminal of the main chain formed by siloxane bonds, number average molecular weight: 10600, viscosity at 25°C when adjusted to 15 mass% by dilution with n-heptane solvent: 1.7 mcps)

(Composition analysis of curable silicone resin)

The composition analysis of the curable silicone resin used in the examples and comparative examples was performed using 400MHz-NMR (Bruker Avance400M), and the results are shown in Table 6. For the ^1H -NMR measurement, CDCl ₃ was used as a solvent, and the peak derived from the methyl group of dimethylsiloxane was used as the chemical shift standard, and was performed at a temperature of 30°C. Table 6 below shows the content ratio (mol%) of each functional group in the curable silicone resin.

b1: Crosslinking agent (CL750: Momentive Performance Materials)

c1: Additional platinum catalyst (CM678: Momentive Performance Materials)

e1: Light peeling agent (methyl phenyl silicone oil, Mw: less than 10,000, phenyl group content ratio; DM:MP = 91:9 (mol%))

e2: Light peeling agent (methyl phenyl silicone oil, Mw: 21000, phenyl group content ratio; DM: MP = 91: 9 (mol%))

e3: Light peeling agent (methyl phenyl silicone oil, Mw: 71000, phenyl group content ratio; DM: MP = 90: 10 (mol%))

e4: Light-peel agent BY24-850 (Toray/Dow) (polydimethylsiloxane, Mw: 100,000 or more, phenyl group content ratio; DM:MP = 100:0 (mol%))

[Example 2-1]

The following release layer composition was applied to the flat surface of the A layer side of PET-A so that the coating amount (after drying) was 1 g/㎡ in thickness, and then dried at 150°C for 30 seconds to obtain a release film (sample film).

(heterogeneous layer composition)

Subject: a1; 100 mass parts

Crosslinker: b1; 3 parts by mass

Catalyst: c1; 3 parts by mass

Light peeling agent: e1; 1 mass part

Solvent: Toluene; 1000 parts by mass

MEK; 9000 mass parts

[Examples 2-2 to 2-5]

Regarding the heterolayer composition, a film laminate was obtained by manufacturing in the same manner as in Example 2-1, except that the type and amount of the peeling agent were changed as shown in Table 7 below.

[Comparative Example 2-1]

In the heterolayer composition, a film laminate was obtained by manufacturing in the same manner as in Example 2-1, except that no peeling agent was added.

[Comparative Example 2-2]

In Example 2-1, a release film (sample film) was obtained by manufacturing in the same manner as in Example 2-1, except that the composition of the release layer was changed to the following release layer composition.

(heterogeneous layer composition)

Subject: a1; 100 mass parts

Crosslinker: b1; 3 parts by mass

Catalyst: c1; 3 parts by mass

Light peeling agent: e4; 1 part by mass

Solvent: Toluene; 1000 parts by mass

MEK; 9000 mass parts

From the results of this example, it was confirmed that by making the release layer containing the curable silicone resin relatively thick, using a light-release agent having a specific configuration in combination, and further setting the elastic modulus to 500 MPa or less, while setting the maximum cross-sectional height (Rt) of the semi-release surface to a predetermined range, a release film having not only light peeling force, but also low transferability, being difficult to block, and nevertheless having good adhesion to a substrate can be obtained.

In addition, when comparing Comparative Example 2-1 and each example in terms of peeling strength (state peeling strength) by adhesive tape, in the lightest type, it was possible to achieve light peeling up to about 60% of that of Comparative Example 2-1, thereby realizing ultra-light peeling.

In comparison, Comparative Example 2-1 was found to have a high peeling force for the adhesive layer at the level of a conventional product (light peeling type). Comparative Example 2-2 contained a light peeling agent with a large molecular weight in the release layer, resulting in an insufficient light peeling effect.

Example 3-1

Regarding the release layer used in Example 1-1, the peelability was evaluated using the adhesive described below. The results are shown in Table 8.

Adhesive A: 2EHA/BA/HEA=36/59/5 mass% (elasticity: 2.9 MPa, Tg: -59.0℃)

Adhesive B: 2EHA/HEA/AAc=92.8/7/0.2 mass% (elasticity: 2.7 MPa, Tg: -66.7℃)

2EHA; 2-ethylhexyl acrylate

BA; Butylacrylate

HEA; Hydroxyethyl acrylate

AAc; Acrylic acid

Example 3-2

In Example 3-1, the evaluation was conducted in the same manner as in Example 3-1, except that the heteromorphic layer used in Example 2-1 was used as the heteromorphic layer. The results are shown in Table 8.

It was found that all of the resin layers used in the examples were more easily peeled than the reference example (prior art).

Industrial applicability

According to the release film of the present invention, a release film which realizes ultra-light peelability and is difficult to change in the peeling characteristics of the release layer due to blocking can be provided, and therefore its industrial value is high. In addition, the release film of the present invention and a film laminate comprising the release film have the characteristics of both ultra-light peelability and blocking resistance, and therefore are suitable for applications that avoid changes in the peeling characteristics of the release layer and deterioration in the appearance of the surface of the resin layer (A), and for various applications in which an adhesive layer is interposed and bonded, such as for manufacturing a touch panel of an electrostatic capacitance type, for manufacturing optical members (polarizing plates, phase difference plates, prism sheets, conductive films, resin films, glass substrates, etc.) used in liquid crystal displays, for manufacturing organic electroluminescence component members, and for various adhesive layer protection applications. In particular, application to a foldable display application having a flexible adhesive layer that is easy to follow deformation due to bending is also possible.

Claims (28)

A resin layer (A) is provided on at least one side of the substrate film,
A release film wherein the resin layer (A) is a cured product of a resin layer composition containing a curable silicone resin and a light-release agent, and the light-release agent has a dimethylsiloxane skeleton (DM) represented by the following formula (I) and a methylphenylsiloxane skeleton (MP) represented by the following formula (II), and has a thickness of 0.2 to 1.5 µm.

In paragraph 1,
A release film having a maximum cross-sectional height (Rt) of the film surface opposite to the surface on which the resin layer (A) is provided, of 2.0 ㎛ or less. In claim 1 or 2,
A release film, wherein the surface opposite to the surface on which the resin layer (A) of the above-mentioned base film is provided has a polyester layer containing 0.4 to 1.0 mass% of particles having an average particle diameter of 1 to 6 ㎛. In claim 1 or 2,
A release film having a mass average molecular weight of the above-mentioned light-release agent of 10,000 to 100,000. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete