JP6741232B2 - Release film and adhesive sheet - Google Patents

Description

The present invention relates to a release film and a pressure sensitive adhesive sheet.

The pressure-sensitive adhesive used for laminating optical films such as a polarizing film (polarizing plate) and a retardation film is usually attached to the pressure-sensitive adhesive layer and the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer for easy handling. It is composed of a release film. When a film or sheet having such an adhesive layer is produced or processed, external stress may cause dents such as deformation, unevenness, and distortion on the surface of the adhesive layer. If a pressure-sensitive adhesive layer with dents is used for an optical film, it may impair the optical properties of the optical film, and air bubbles may be mixed when it is attached to a liquid crystal panel, so it is possible to prevent dents on the pressure-sensitive adhesive layer. It has been demanded.

It is known that increasing the thickness of the polyester film used for the release film is effective as a measure against dents on the pressure-sensitive adhesive layer. Particularly in touch panel applications, a polyester film having a thickness of 50 to 125 μm is used as a base material of a release film (for example, Patent Document 1).

In addition, a quick-reacting curing agent is used as a curing agent for the pressure-sensitive adhesive, or peroxide is added to the pressure-sensitive adhesive composition to crosslink the peroxide (for example, Patent Document 2). A technique is also known in which the plasticity of the pressure-sensitive adhesive is reduced by adding metal-containing nanoparticles (for example, Patent Document 3) to reduce dents.

JP 2012-184327 A Patent No. 3863151 JP, 2013-216725, A

However, the above-mentioned method of reducing the plasticity of the pressure-sensitive adhesive to reduce the dents cannot sufficiently reduce the dents generated in the pressure-sensitive adhesive layer.

Further, in optical films such as polarizing plates, even if defects such as foreign matters and scratches are minute, they appear as visible bright spots in the display, so the inspection standards for defects are strict and the inspection accuracy is improved. Is important.
For example, the defect inspection of a polarizing plate is generally performed by emphasizing the defect by the crossed Nicol method. In the crossed Nicols method, when two polarizing plates are overlapped so that their principal axes of alignment are orthogonal to each other and put into the extinction state, if there is a defect, that defect will appear as a bright spot, so inspection can be performed even for a minute defect. That is.

The polarizing plate is usually inspected by the above-mentioned crossed Nicol method with the release film attached. Therefore, as the base material of the release film, a film having a small inclination (orientation angle) of the orientation main axis is used so as not to hinder the inspection by the crossed Nicols method. Generally, the thicker the film, the larger the orientation angle tends to be. Therefore, for polarizing plate applications, it is difficult to increase the thickness of the base material of the release film as in Patent Document 1.

The present invention has been made in view of such circumstances, a peeling film that is less likely to cause a dent in the pressure-sensitive adhesive layer formed on the peeling film, and has excellent inspection properties by the crossed Nicols method, and a pressure-sensitive adhesive sheet. The purpose is to provide.

The present inventors have conducted extensive studies to solve the above problems, as a base material of the release film, the first biaxially stretched polyester film, and the second biaxially stretched polyester film, the adhesive layer It has been found that the above-mentioned problems can be solved by using a substrate laminated via the above and setting the inclination of the orientation main axis of the release film within a specific range.
The present invention has been completed based on such findings.

That is, the present invention provides the following [1] to [7].
[1] A base material in which a first biaxially stretched polyester film and a second biaxially stretched polyester film are laminated via an adhesive layer, and a release layer provided on the base material. And the inclination of the orientation main axis is −12 degrees or more and 12 degrees or less.
[2] The release film according to the above [1], wherein both the thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film are 25 to 50 μm.
[3] The release film according to the above [1] or [2], wherein both the first biaxially stretched polyester film and the second biaxially stretched polyester film are polyethylene terephthalate films.
[4] The release film according to any one of the above [1] to [3], wherein the release layer is a layer formed of a silicone resin.
[5] The release film according to any one of the above [1] to [4], wherein the release layer has a thickness of 40 nm to 1 μm.
[6] The release film as described in any of [1] to [5] above, which has a haze value of 25% or less.
[7] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on the release layer of the release film according to any one of [1] to [6] above.

According to the present invention, it is possible to provide a release film and a pressure-sensitive adhesive sheet that are less likely to cause dents in the pressure-sensitive adhesive layer formed on the release film and have excellent inspection properties by the crossed Nicols method.

It is sectional drawing which shows one Embodiment of the peeling film of this invention. It is sectional drawing which shows one Embodiment of the adhesive sheet of this invention.

[Peeling film]
The release film of the present invention is a base material in which a first biaxially stretched polyester film and a second biaxially stretched polyester film are laminated via an adhesive layer, and a release material provided on the base material. A layer, and the inclination of the orientation main axis is not less than −12 degrees and not more than 12 degrees.
Here, the adhesive is used as a broad concept including a pressure-sensitive adhesive in the present specification.

FIG. 1 is a sectional view showing an embodiment of a release film of the present invention. The release film 10 of FIG. 1 includes a base material 4 in which a second biaxially stretched polyester film 3 is laminated on a first biaxially stretched polyester film 1 with an adhesive layer 2 interposed between the base material 4 and the base material 4. The peeling layer 5 is provided.

In the release film of the present invention, the inclination of the orientation main axis is −12 degrees or more and 12 degrees or less.
Here, the “inclination of the principal axis of orientation” is also referred to as an orientation angle, and is the inclination of the principal axis with respect to the film width direction or the longitudinal direction. When the inclination of the orientation main axis is less than -12 degrees or more than 12 degrees, light leakage becomes large at the time of inspection by the crossed Nicols method, and there is a risk of impeding the detection of defects such as foreign matters and scratches.
The inclination of the orientation main axis is preferably −10 degrees or more and 10 degrees or less, more preferably −8 degrees or more and 8 degrees or less.

Hereinafter, each layer constituting the release film of the present invention will be specifically described.
(Base material)
The base material used in the release film of the present invention is formed by laminating a first biaxially stretched polyester film and a second biaxially stretched polyester film with an adhesive layer in between. By laminating the two biaxially stretched polyester films in this way, it is possible to increase the thickness of the substrate even if the thickness of each biaxially stretched polyester film is reduced. Therefore, when a pressure-sensitive adhesive layer is formed on the release film of the present invention, it is possible to make dents less likely to occur on the pressure-sensitive adhesive layer.

As for the inclination (orientation angle) of the orientation main axis of the first biaxially oriented polyester film and the second biaxially oriented polyester film, the inclination of the orientation main axis (orientation angle) of the release film of the present invention is within a desired range. To adjust.
In the present invention, the orientation angle is defined as 0 degree when it is parallel to the film width direction, and the clockwise inclination with respect to the film width direction is defined as + and the counterclockwise inclination is defined as −. When the orientation angle of the first biaxially oriented polyester film and the second biaxially oriented polyester film are both +, the orientation angle of the first biaxially oriented polyester film and the second biaxially oriented polyester film is , Both preferably 0 degrees or more and 12 degrees or less, more preferably 0 degrees or more and 10 degrees or less, further preferably 0 degrees or more and 8 degrees or less, and the first biaxially stretched polyester film and the second biaxial When the orientation angles of the stretched polyester film are both −, the orientation angles of the first biaxially stretched polyester film and the second biaxially stretched polyester film are both preferably −12 degrees or more and 0 degrees or less, more preferably Is -10 degrees or more and 0 degrees or less, more preferably -8 degrees or more and 0 degrees or less. Further, when the sign of the orientation angle of the first biaxially oriented polyester film, and the second biaxially oriented polyester film is different, the orientation angle is not particularly limited, for example, the orientation angle of the first biaxially oriented polyester film. Is preferably in the range of -40 degrees to 0 degrees, and the orientation angle of the second biaxially stretched polyester film is preferably in the range of 0 degrees to 40 degrees.

The thickness of the first biaxially stretched polyester film and the thickness of the second biaxially stretched polyester film are both 25 to 50 μm, from the viewpoint of improving the dent resistance and the inspection property by the crossed Nicols method. Is preferred. Further, from the viewpoint of improving the inspection property by the crossed Nicols method, it is more preferable that the thickness of at least one of the biaxially stretched polyester films is 25 to 40 μm, and it is further preferable that both thicknesses are 25 to 40 μm.

The haze of each of the first biaxially stretched polyester film and the second biaxially stretched polyester film is preferably 12% or less, and more preferably 10% or less. By setting it to 12% or less, the haze of the release film can be adjusted to a desired value or less.
The haze can be measured using a haze meter (NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd.) by a method according to JIS K-7136.

Examples of the first biaxially stretched polyester film and the second biaxially stretched polyester film used as the substrate include polyethylene terephthalate film, polybutylene terephthalate film, and polyethylene naphthalate film.
The first biaxially stretched polyester film and the second biaxially stretched polyester film may be the same film or different films. Among them, from the viewpoint of optical characteristics and quality, it is preferable that both the first biaxially stretched polyester film and the second biaxially stretched polyester film are polyethylene terephthalate films.

As a method of biaxially stretching the polyester film, for example, a method of stretching in the longitudinal direction and then in the width direction, a method of stretching in the width direction and then in the longitudinal direction, stretching in the longitudinal direction, and stretching in the width direction are plural. Known methods such as a method of performing a combination of two times and a method called simultaneous biaxial stretching in which simultaneous stretching is performed can be used.

The adhesive used for the adhesive layer is not particularly limited, and examples thereof include thermoplastic adhesives such as polyamide adhesives, acrylic adhesives, vinyl acetate adhesives, thermosetting urethane adhesives, and epoxies. Examples of the adhesive include curable resin adhesives such as base resins and two-component curing type polyurethane adhesives containing isocyanate as a curing agent, which have no pressure-sensitive adhesive property at room temperature. Examples of the adhesive having pressure-sensitive adhesiveness at room temperature include acrylics, polyesters, urethanes, and silicones.

The thickness (when dried) of the adhesive layer is not particularly limited, but from the viewpoint of durability, coatability, etc., it is preferably 1 to 50 μm, more preferably 2 to 30 μm, and further preferably 5 to 20 μm.

(Peeling layer)
The release layer has a function of imparting releasability to the release film of the present invention. The release layer is formed of, for example, a cured product of a release layer-forming composition containing a release agent.
The release agent is not particularly limited, and examples thereof include a silicone resin, an alkyd resin, an acrylic resin, and a long-chain alkyl resin, but it is preferable to use a silicone resin.

Examples of the silicone resin include silicone resins having dimethylpolysiloxane as a basic skeleton. The silicone resin includes addition reaction type, condensation reaction type, ultraviolet curing type, electron beam curing type and the like. Among them, the addition reaction type silicone resin is preferably used because it has high reactivity and excellent productivity, and has advantages such as a small change in peeling force after production and no curing shrinkage as compared with the condensation reaction type.

Specific examples of the addition reaction type silicone resin include an organo group having two or more alkenyl groups having 2 to 10 carbon atoms such as vinyl group, allyl group, propenyl group and hexenyl group at the terminal and/or side chain of the molecule. Examples include polysiloxane. When using such an addition reaction type silicone resin, it is preferable to use a crosslinking agent and a catalyst together.

Examples of the cross-linking agent include organopolysiloxanes having at least two hydrogen atoms bonded to silicon atoms in one molecule, specifically, a dimethylhydrogensiloxy group end-capped dimethylsiloxane-methylhydrogensiloxane copolymer. , Trimethylsiloxy group-endblocked dimethylsiloxane-methylhydrogensiloxane copolymer, trimethylsiloxy group-endblocked methylhydrogenpolysiloxane, poly(hydrogensilsesquioxane), and the like.

Examples of the catalyst include fine particle platinum, fine particle platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complex of chloroplatinic acid, palladium, and white metal metal compounds such as rhodium. Can be mentioned. By using such a catalyst, the curing reaction of the release layer-forming composition can be more efficiently progressed.

When a silicone resin is used as a release agent, it is preferable to add a release control agent such as MQ resin.
Moreover, you may mix|blend an additive suitably with the composition for peeling layer formation. Examples of the additives include dyes and dispersants. Further, the release layer-forming composition may appropriately contain a dispersion medium or a solvent in order to adjust the viscosity at the time of coating to an appropriate range.
Examples of the dispersion medium or solvent include aromatic hydrocarbons such as toluene, fatty acid esters such as ethyl acetate, ketones such as methyl ethyl ketone, and organic solvents such as aliphatic hydrocarbons such as hexane and heptane.

The content of the release agent contained in the release layer-forming composition is not particularly limited, but is preferably 0.3 to 10% by mass.

Examples of the coating method include a gravure coating method, a bar coating method, a spray coating method, a spin coating method, an air knife coating method, a roll coating method, a blade coating method, a gate roll coating method, and a die coating method. Among these, the gravure coating method and the bar coating method are preferable, and the bar coating method is more preferable.
Moreover, as a heating/drying method of the composition for forming a release layer, for example, a method of thermally drying in a hot air drying oven or the like can be mentioned. The drying temperature is, for example, 50° C. or higher and 150° C. or lower. The drying time is preferably 10 seconds to 5 minutes, for example.

The thickness (when dried) of the release layer is preferably 40 nm to 1 μm, more preferably 50 nm to 0.5 μm, and further preferably 60 nm to 0.3 μm. When the thickness is 40 nm or more, variation in the peeling force due to fluctuation of the coating amount can be suppressed, and when the thickness is 1 μm or less, blocking can be suppressed.

The haze of the release film of the present invention is preferably 25% or less, more preferably 20% or less, still more preferably 10% or less. The haze can be measured by a method according to JIS K-7136 using a haze meter (NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd.).

The thickness of the release film of the present invention is preferably 50 to 150 μm, more preferably 50 to 125 μm, and further preferably 50 to 100 μm.

The release film of the present invention is less likely to cause dents on the pressure-sensitive adhesive layer formed on the release film and has excellent inspection properties by the crossed Nicols method, and thus can be suitably used for optical films such as polarizing plates.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer on the release layer of the release film described above.
FIG. 2 is a cross-sectional view showing an embodiment of the adhesive sheet of the present invention. The pressure-sensitive adhesive sheet 20 of FIG. 2 includes a base material 14 in which a second biaxially stretched polyester film 13 is laminated on a first biaxially stretched polyester film 11 via an adhesive layer 12, and a base material 14 on the base material 14. The release layer 15 is provided, and the pressure-sensitive adhesive layer 16 is provided on the release layer 15.
Since the pressure-sensitive adhesive sheet of the present invention uses the above-mentioned release film, it is possible to make dents less likely to occur in the pressure-sensitive adhesive layer formed on the release film.

(Adhesive layer)
The pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive. Examples of the adhesive include acrylics, rubbers, polyesters, urethanes and silicones. In the present invention, it is particularly preferable to include an acrylic pressure-sensitive adhesive as the pressure-sensitive adhesive, and it is preferable to include a (meth)acrylic acid ester copolymer from the viewpoint of adhesion durability.
Examples of the form of the pressure-sensitive adhesive include solvent type, emulsion type, solventless type and the like.

When the pressure-sensitive adhesive is a solvent-type or emulsion-type acrylic pressure-sensitive adhesive, the pressure-sensitive adhesive is a main monomer component that imparts tackiness, a comonomer component that imparts adhesiveness or cohesive force, a cross-linking point or an adhesive property improving adhesiveness. It may be composed of a polymer or copolymer mainly containing a functional group-containing monomer component. By including each of these components, the cohesive force and adhesive force of the obtained pressure-sensitive adhesive layer can be improved.

Examples of the main monomer component include butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, cyclohexyl acrylate, benzyl acrylate, methoxyethyl acrylate, etc. Examples thereof include alkyl acrylates, butyl methacrylates, 2-ethylhexyl methacrylates, cyclohexyl methacrylates, benzyl methacrylates, and the like, in which the alkyl group has 1 to 20 carbon atoms.

Examples of the comonomer component include methyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acetate, styrene, acrylonitrile and the like.

The functional group-containing monomer component preferably contains at least one of a hydroxyl group, a carboxyl group, and an amino group as a functional group, and specific examples thereof include 2-hydroxyethyl (meth)acrylate and 2-methacrylate acrylic acid. (Meth)acrylic acid hydroxyalkyl ester such as hydroxypropyl; (meth)acrylic acid monomethylaminoethyl, (meth)acrylic acid monoethylaminoethyl, etc. (meth)acrylic acid monoalkylaminoalkyl; acrylic acid, methacrylic acid, Examples thereof include ethylenically unsaturated carboxylic acids such as maleic acid.

The (meth)acrylic acid ester copolymer is not particularly limited in its copolymerization form, and may be a random, block or graft copolymer.

As the (meth)acrylic acid ester copolymer, it is preferable to use one having a mass average molecular weight of 300,000 or more, more preferably 400,000 to 2,000,000, and 500,000 to 1,800,000. Is more preferably used. As a result, the adhesion and adhesion durability to the adherend become sufficient, and the occurrence of floating, peeling, etc. can be prevented more effectively.

In addition, in this specification, a mass average molecular weight is the value of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

In the (meth)acrylic acid ester copolymer, the content of units derived from the functional group-containing monomer component is preferably 0.01% by mass or more and 10% by mass or less, and 0.05% by mass or more and 7.0% by mass. The content is more preferably not more than mass%, further preferably not less than 0.2 mass% and not more than 6.0 mass%. When the content is within the above range, crosslinking will be sufficient due to the reaction with the crosslinking agent described later. As a result, the pressure-sensitive adhesive layer becomes more excellent in flexibility and adhesion durability.

In addition, such a (meth)acrylic acid ester copolymer may be used individually by 1 type, and may be used in combination of 2 or more type.

Examples of the organic solvent used for preparing the solvent-type acrylic pressure-sensitive adhesive composition include toluene, xylene, t-butanol, acetone, methyl ethyl ketone, tetrahydrofuran, ethyl acetate and the like.

The solvent-type acrylic pressure-sensitive adhesive composition may be either a crosslinked type which is subjected to a crosslinking treatment or a non-crosslinked type which is not subjected to a crosslinking treatment, but a crosslinked type is preferable. When the composition is a cross-linking type pressure-sensitive adhesive layer-forming composition, a pressure-sensitive adhesive layer having more excellent cohesive force can be formed.

Examples of the cross-linking agent used in the cross-linkable acrylic pressure-sensitive adhesive composition include isocyanate compounds, epoxy compounds, metal chelate compounds, metal alkoxides, metal salts, amine compounds, hydrazine compounds, and aldehyde compounds.

Further, when the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present invention is formed of a solvent-free acrylic pressure-sensitive adhesive, it has a (meth)acrylic acid ester having a radically polymerizable unsaturated double bond group in the side chain. For forming a pressure-sensitive adhesive layer containing at least one selected from a polymer (A1), a (meth)acrylate oligomer (A2), and a (meth)acrylic acid ester monomer (A3), and a photopolymerization initiator (B). Composition (i) can also be used.

The number of radically polymerizable unsaturated double bond groups contained in the (meth)acrylic acid ester polymer (A1) and the (meth)acrylate oligomer (A2) is from the viewpoint of enhancing the strength and cohesive force of the pressure-sensitive adhesive layer. It is preferable that the number is two or more.

The polymer (A1) of (meth)acrylic acid ester means a polymer having a polymer structure of (meth)acrylic acid ester and having a radically polymerizable unsaturated double bond in the side chain of the polymer structure. Specifically, a copolymer of the main monomer component disclosed in the solvent-type acrylic pressure-sensitive adhesive composition, the comonomer component disclosed in the solvent-type acrylic pressure-sensitive adhesive composition, and a monomer having a functional group having active hydrogen. A functional group having a radically polymerizable unsaturated double bond introduced into the above-mentioned functional group having active hydrogen is preferably used.

Examples of the monomer having a functional group having active hydrogen include a monomer having a functional group such as a hydroxyl group, an amino group and a carboxyl group. Specific examples thereof include the compounds exemplified in the section of the functional group-containing monomer disclosed in the solvent-type acrylic pressure-sensitive adhesive composition.

A copolymer is obtained by polymerizing each of the above monomers by a conventional method. The (meth)acrylic acid ester copolymers may be used alone or in combination of two or more.

Introduction of a radical-polymerizable unsaturated double bond group to a functional group having active hydrogen in the above-mentioned copolymer, for example, addition of a compound having both a radical-polymerizable unsaturated double bond and an active hydrogen-reactive group It can be carried out by reacting. Examples of the active hydrogen-reactive group include an isocyanate group and a glycidyl group.

Examples of the compound having both a radical polymerizable unsaturated double bond and an active hydrogen reactive group, specifically, acryloyloxyethyl isocyanate, acryloyloxypropyl isocyanate, methacryloyloxyethyl isocyanate, methacryloyloxypropyl isocyanate, allyl isocyanate, Glycidyl (meth)acrylate and the like are preferable.

The above addition reaction is preferably carried out, for example, at a temperature of 25 to 60° C. for about 6 to 48 hours. In addition, in the above addition reaction, if necessary, it is also preferable to use an organotin compound such as dibutyltin dilaurate or a substituted amine compound as a catalyst.

Examples of the (meth)acrylate oligomer (A2) include urethane (meth)acrylate oligomer, epoxy (meth)acrylate oligomer, polyester (meth)acrylate oligomer, and polyether (meth)acrylate oligomer. Oligomer etc. are mentioned. Among them, urethane (meth)acrylate oligomer can be preferably used. The urethane (meth)acrylate oligomer can be obtained, for example, by esterifying a polyurethane oligomer obtained by reacting a polyether polyol or polyester polyol with a polyisocyanate by a reaction with (meth)acrylic acid.
As the (meth)acrylate oligomer (A2), one type may be used alone, or two or more types may be used in combination. Further, the polymer (A1) of (meth)acrylic acid ester and the (meth)acrylate oligomer (A2) can be used in combination.

The weight average molecular weights of the (meth)acrylic acid ester polymer (A1) and the (meth)acrylate oligomer (A2) are each 20,000 or more, preferably 25,000 to 80,000, and more preferably Is 30,000 to 60,000.
The weight average molecular weight is a polystyrene equivalent value measured by a gel permeation chromatography (GPC) method.

The (meth)acrylic acid ester monomer (A3) has two or more reactive sites such as a monomer constituting the polymer (A1) of the (meth)acrylic acid ester described above and a carbon-carbon double bond. Preferable examples include polyfunctional acrylates.

Specific examples of the polyfunctional acrylate include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, and ethylene oxide-modified Difunctional type such as phosphoric acid di(meth)acrylate; Trifunctional type such as trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate; Diglycerin tetra(meth)acrylate, pentaerythritol tetra(meth) 4-functional type such as acrylate; 5-functional type such as propionic acid-modified dipentaerythritol penta(meth)acrylate; 6-functional type such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate Can be mentioned.

Further, when the polymer (A1) of (meth)acrylic acid ester or the (meth)acrylate oligomer (A2) is used as a main raw material and the pressure-sensitive adhesive layer-forming composition (i) has a high viscosity, the above ( The (meth)acrylic acid ester monomer (A3) may be added to reduce the viscosity of the pressure-sensitive adhesive layer-forming composition (i) and improve the coatability. The (meth)acrylic acid ester monomers (A3) may be (meth)acrylic acid ester monomers (A3) that are irradiated with ultraviolet light, or the above (meth)acrylic acid ester polymer (A1) and/or the above (meth)acrylate oligomer ( Since a crosslinked structure is formed with A2), the cohesive force of the obtained pressure-sensitive adhesive layer can be increased and problems such as bleeding can be effectively prevented.

By containing the photopolymerization initiator (B), the composition (i) for forming a pressure-sensitive adhesive layer can efficiently cure the ultraviolet curable component in the composition (i) for forming a pressure-sensitive adhesive layer. Moreover, the polymerization and curing time and the irradiation amount of ultraviolet rays can be reduced.

Examples of the photopolymerization initiator (B) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, Benzophenone, p-phenylbenzophenone, 4,4′-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, benzyldimethylketal, acetophenonedimethylketal, p-dimethylamino. Examples thereof include benzoic acid ester and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide. These may be used alone or in combination of two or more.

The content of the photopolymerization initiator (B) contained in the pressure-sensitive adhesive layer-forming composition (i) is (meth)acrylic acid ester polymer (A1), (meth)acrylate oligomer (A2) and (meth). It is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and 0.2 to 2 parts by mass based on 100 parts by mass of the total amount of the acrylic acid ester monomer (A3). Is more preferable.

In addition, the composition for forming a pressure-sensitive adhesive layer is, if desired, various additives usually used for pressure-sensitive adhesives, such as a silane coupling agent, an antistatic agent, a tackifier, an antioxidant, an ultraviolet absorber, and a light stabilizer. An agent, a softening agent, a filler, a refractive index adjusting agent, a coloring agent and the like may be contained.

The thickness of the pressure-sensitive adhesive layer is preferably 1 to 250 μm, more preferably 5 to 200 μm, and further preferably 10 to 175 μm from the viewpoint of productivity and cost.

In addition, it is preferable that the surface of the pressure-sensitive adhesive layer is free from scratched skin (a plurality of fine irregularities) from the viewpoint of applying the pressure-sensitive adhesive sheet of the present invention to an optical film. From such a point of view, it is preferable that the surface of the pressure-sensitive adhesive layer has an unevenness outside the range of ±0.2 μm from the reference surface of 20% or less. When the content is within the above range, it is possible to more effectively prevent the appearance defect from occurring when the pressure-sensitive adhesive layer is attached to the adherend.

The ratio of the unevenness outside the range of ±0.2 μm from the reference surface on the surface of the pressure-sensitive adhesive layer can be calculated using, for example, an optical interference type surface shape observation device. Specifically, using an optical interference type surface shape observation device, stitching was performed at a magnification of 2.5 in the VSI mode, and based on the obtained surface shape image in the range of 4×4 mm, ±0 from the reference plane. The image is binarized by a portion outside the range of 0.2 μm and a portion within the range of ±0.2 μm. Thereby, it can be obtained by calculating the area ratio of the unevenness in the portion outside the range of ±0.2 μm from the reference surface.

The pressure-sensitive adhesive sheet of the present invention may have a functional layer such as a hard coat layer, an antiglare layer, a reflective layer, a transparent conductive film, and a colored layer provided on the base material of the release film.
In the pressure-sensitive adhesive sheet of the present invention, an optical member is provided on the pressure-sensitive adhesive layer. Examples of the optical member include a polarizing plate (polarizing film), a polarizer, a retardation film (retardation film), a viewing angle compensation film, a brightness enhancement film, a contrast enhancement film, a liquid crystal polymer film, a diffusion film, a semi-transmissive reflection film. Etc.

(Production method of adhesive sheet)
The method for producing the pressure-sensitive adhesive sheet is not particularly limited, for example, when the solvent-based pressure-sensitive adhesive composition described above is used, the pressure-sensitive adhesive composition is applied onto the release layer of the release film by a known method. The pressure-sensitive adhesive layer can be formed by forming a coating film by heating and drying the coating film. Further, when using the solvent-free pressure-sensitive adhesive composition described above, on the release layer of the release film, to form a coating film by applying the pressure-sensitive adhesive composition by a known method, ultraviolet light to the coating film, The pressure-sensitive adhesive layer can be formed by irradiating an active energy ray such as an electron beam.
Examples of the method for applying the pressure-sensitive adhesive composition include spin coating, spray coating, bar coating, knife coating, roll coating, roll knife coating, blade coating, die coating, gravure coating, etc. Is mentioned.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited to the form described in the embodiments.

1. Scratch resistance Acrylic adhesive (manufactured by Lintec Co., Ltd., trade name: P274PP) was applied to the release films prepared in Examples and Comparative Examples with an applicator so that the film thickness after drying would be 20 μm, and then with a dryer. After drying, it was attached to a polarizing plate (Sumitomo Chemical Co., Ltd., trade name: SRW062) and aged at 23° C. and 50% RH for 1 week. The obtained polarizing plate with an adhesive was cut into 20 cm×20 cm.
Next, about 50 pieces of black metal powder (foreign matter) having a size of about 50 μm were scattered on the glass, and the pressure-sensitive adhesive-attached polarizing plate prepared as described above was contacted with the foreign matter on the release film side. Placed and passed through laminator. Then, the release film was peeled off from the polarizing plate, and the pressure-sensitive adhesive surface was visually observed. In addition, after the pressure-sensitive adhesive surface of the above polarizing plate was attached to glass using a laminator, it was visually observed from the glass side. In addition, the following criteria evaluated.
<Evaluation criteria>
⊚: Deformation (scratch) of the pressure-sensitive adhesive was not visually confirmed, and no bubbles at a visually observable level were observed even when the adhesive was attached to glass.
○: There was no obvious deformation (dent) of the adhesive, and no bubbles at a level that could be visually confirmed when stuck to the glass were found ×: Definite deformation (dent) of the adhesive was confirmed, Bubbles of a level that can be visually confirmed when stuck to glass were confirmed.

2. Cross Nicol Inspection Property The polarizing plate with the adhesive (20 cm×20 cm) prepared above and another polarizing plate were prepared. A flat illuminator (manufactured by Dentsu Sangyo Co., Ltd., trade name: HF-SL-A312LC, illuminance: 26,000 Lux, brightness: 10, so that the polarizing axes of the polarizing plate with an adhesive and another polarizing plate are orthogonal to each other. 000 cd) and visually evaluated according to the following criteria.
<Evaluation criteria>
◯: Crossed nicols (dark field) were sufficient, and the inspection level was sufficient. △: Light was slightly leaked during crossed nicols, but the inspection level was sufficient. ×: Crossed nicols were insufficient ( (Light is leaking), so the inspection level was insufficient.

3. Foreign matter inspection property About 50 pieces of black metal powder (foreign matter) having a size of about 20 μm between the release film of the polarizing plate with adhesive (20 cm×20 cm) prepared above and the adhesive layer Mixed in. The pressure-sensitive adhesive-attached polarizing plate mixed with the foreign matter thus obtained was visually observed from the release film side, and the detection condition of the mixed foreign matter was evaluated according to the following criteria.
<Evaluation criteria>
⊚: High transparency and very good recognition of foreign matter ○: Good recognition of foreign matter, which was sufficient as an inspection level for optical applications ×: No foreign matter could be confirmed, which was not suitable for optical applications It was an appropriate inspection level

4. Inclination of orientation axis (orientation angle)
The orientation of the biaxially stretched polyethylene terephthalate (PET) film used in Examples and Comparative Examples was observed using a phase difference measuring device (KOBRA-WR manufactured by Oji Scientific Instruments Co., Ltd.), and the main orientation axis in the PET film plane was observed. The orientation angle was measured by measuring how many times the direction inclined with respect to the width direction of the PET film. The orientation angle is 0 degree when it is parallel to the film width direction, and the clockwise inclination with respect to the film width direction is +, and the counterclockwise inclination is −.

5. Haze The haze of the biaxially stretched polyethylene terephthalate (PET) film used in Examples and Comparative Examples, and the release film produced in Examples and Comparative Examples was measured using a haze meter (NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd.). It measured by the method based on JIS K-7136.

(Example 1)
1. Preparation of composition for forming release layer Silicone resin solution containing organopolysiloxane having vinyl group and organopolysiloxane having hydrosilyl group (manufactured by Toray Dow Corning, trade name: BY24-561, solid content 30 mass) %) and 30 parts by mass in terms of solid content, and 15 parts by mass of MQ resin having vinyl group (manufactured by Toray Dow Corning, trade name: SD7292, solid content 71% by mass) in terms of solid content. The mixture was diluted and mixed with a solvent so that the solid content concentration was 1.0% by mass. To this solution, 2 parts by mass of a platinum catalyst (trade name: SRX-212, manufactured by Toray Dow Corning Co., Ltd., solid content: 100% by mass) was added to prepare a composition for forming a peeling layer.

2. Preparation of Release Film A biaxially oriented polyethylene terephthalate (PET) film (A) having a thickness of 38 μm, an orientation angle of 6 degrees and a haze of 10% was prepared.
Next, the release layer-forming composition obtained above was applied to one surface of the biaxially stretched PET film (A) with a bar coater so that the thickness after drying would be 0.1 μm, and 120 A peeling layer was formed by drying at 1° C. for 1 minute to obtain a laminate A.

A biaxially stretched polyethylene terephthalate (PET) film (B) having a thickness of 38 μm, an orientation angle of 6 degrees and a haze of 10% was prepared. An acrylic pressure-sensitive adhesive was applied as an adhesive to the biaxially stretched PET film (B) so that the thickness after drying was 15 μm, and dried at 90° C. for 1 minute to form an adhesive layer, which was laminated. Body B is obtained. Next, the surface of the laminate B on the adhesive layer side and the surface of the laminate A on the biaxially stretched PET film (A) side were bonded together to obtain a release film.

(Example 2)
A laminate A was obtained in the same manner as in Example 1. Then, a urethane adhesive is applied as an adhesive to the above-mentioned biaxially stretched PET film (B) so that the thickness after drying becomes 5 μm, and dried at 90° C. for 1 minute to form an adhesive layer. Then, a laminated body B was obtained. Then, the surface of the laminate B on the adhesive layer side and the surface of the laminate A on the biaxially stretched PET film (A) side were laminated by a dry lamination method to obtain a release film.

(Example 3)
A release film was obtained in the same manner as in Example 1 except that the thickness of the biaxially stretched PET film (A) was 50 μm.

(Example 4)
A release film was obtained in the same manner as in Example 1 except that the biaxially stretched PET film (A) had a thickness of 25 μm and the biaxially stretched PET film (B) had a thickness of 50 μm.

(Example 5)
A release film was obtained in the same manner as in Example 1 except that the haze of each of the biaxially stretched PET film (A) and the biaxially stretched PET film (B) was 3%.

(Example 6)
A release film was obtained in the same manner as in Example 1 except that the biaxially stretched PET film (A) had an orientation angle of 12 degrees and the biaxially stretched PET film (B) had an orientation angle of 0 degree.

(Example 7)
A release film was obtained in the same manner as in Example 1 except that the orientation angles of the biaxially stretched PET film (A) and the biaxially stretched PET film (B) were both 0 degrees.

(Example 8)
A release film was obtained in the same manner as in Example 1 except that the biaxially stretched PET film (A) had an orientation angle of 36 degrees and the biaxially stretched PET film (B) had an orientation angle of -12 degrees.

(Comparative Example 1)
A release film was obtained in the same manner as in Example 1 except that the biaxially oriented PET film (A) had an orientation angle of -12 degrees and the biaxially oriented PET film (B) had an orientation angle of -18 degrees.

(Comparative example 2)
A release film was obtained in the same manner as in Example 1 except that the orientation angles of the biaxially stretched PET film (A) and the biaxially stretched PET film (B) were both 15 degrees.

(Comparative example 3)
A biaxially stretched polyethylene terephthalate (PET) film (A) having a thickness of 38 μm, an orientation angle of 6 degrees and a haze of 10% was prepared.
Next, the release layer-forming composition prepared in Example 1 was applied to one surface of the biaxially stretched PET film (A) with a bar coater so that the thickness after drying was 0.1 μm, It was dried at 120° C. for 1 minute to form a release layer to obtain a release film.

(Summary of results)
In each of Examples 1 to 8 using the release film of the present invention, all of them were excellent in dent resistance, and also excellent in cross Nicol inspection property and foreign substance inspection property.

10 Release Film 20 Adhesive Sheet 1, 11 First Biaxially Stretched Polyester Film 2, 12 Adhesive Layer 3, 13 Second Biaxially Stretched Polyester Film 4, 14 Base Material 5, 15 Release Layer 16 Adhesive Layer

Claims (6)

A first biaxially stretched polyester film and a second biaxially stretched polyester film, a base material laminated via an adhesive layer,
A release layer provided on the substrate,
Inclination -12 degrees 12 degrees der following orientation main axis is,
Wherein a thickness of the first biaxially oriented polyester film, the thickness of the second biaxially oriented polyester film are both Ru 25~50μm der release film. The release film according to claim 1 , wherein both the first biaxially stretched polyester film and the second biaxially stretched polyester film are polyethylene terephthalate films. The release film according to claim 1 or 2 , wherein the release layer is a layer formed of a silicone resin. Release film of a thickness of said release layer is a 40Nm～1myuemu, according to any one of claims 1-3. Haze value of 25% or less, the release film according to any one of claims 1-4. Having an adhesive layer on the release layer of the release film according to any one of claims 1 to 5 pressure-sensitive adhesive sheet.