JP2014237238A - Release film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film which has excellent heat resistance to injection resins and shows stable releasability after molding orientation.SOLUTION: A release film is a laminate film having a release layer on at least one side of a substrate film, and the resins constituting the release layer contains 50 mass% or more of a melamine resin, relative to the amount of all the resins constituting the release layer. The release film has an average length RSm of roughness curve elements of 10-80 μm.

Description

  The present invention relates to a release film having excellent release stability and heat resistance, and more particularly to a release film exhibiting good and stable release after molding.

  Polyester films represented by polyethylene terephthalate and polyethylene naphthalate have properties such as mechanical strength, dimensional stability, flatness, heat resistance, chemical resistance, optical properties, etc. Is used for various purposes. However, as the applications diversify, the film processing conditions and usage conditions tend to diversify. As an example, there is a release film for molded simultaneous transfer foil. The structure of the transfer foil using the release film is generally provided with a release layer on one side of a polyester film as a base film, and a transfer layer such as a design printing layer and an adhesive layer in order on the release layer. It consists of the structure which laminated | stacked. Depending on the purpose, a hard coat layer, a metal vapor deposition layer or the like is laminated on the transfer layer. Further, a functional agent such as an antistatic agent or an antibacterial agent is added to the release layer or the transfer layer to give a function as a transfer foil.

  In the transfer foil transfer method using the release film described above, the transfer foil is set in a mold for injection molding, and at the same time as molding a resin molded product, the transfer foil sheet is integrated and bonded to the surface. A molding simultaneous transfer method in which a design is transferred to a resin molded product and decorated is widely known.

  Such a transfer method is a method in which a plurality of laminated transfer foils including an adhesive layer are used on the surface of a polyester film as a base film, and transferred to an object to be transferred via the adhesive layer. It is used in a wide range of applications for the purpose of surface treatment such as decoration and surface protection on the surface of various resin molded products such as electric products, automobile parts, cosmetic containers and toys.

  When a conventional release film is used for molding simultaneous transfer applications, when the injected high-temperature resin touches the transfer foil sheet, the release layer or the base film softens, and printing misalignment due to ink flow or injection resin There is a problem that an appearance defect occurs due to transfer of the flow trace.

  For this problem, a release film having a specific roughness or peelable surface (Patent Document 1), a release film having a melting point and a plane orientation coefficient of the base film in a specific range (Patent Document 2), etc. are proposed. Has been. Further, a release film (Patent Document 3) having a release layer with few defects even at 100% elongation has been proposed.

JP 2010-194905 A JP 2010-247423 A JP 2000-255006 A

  However, the film obtained by the method of Patent Document 1 has insufficient heat resistance, and there is a problem that ink flow occurs due to high-temperature resin injection. In addition, the film obtained by the method of Patent Document 2 has a problem that the dimensional stability of the film is insufficient, and the film shrinks greatly when the release coat is dried. In addition, the film described in Patent Document 3 has a thick release layer in order to enhance heat resistance, and therefore the release layer cannot follow during molding stretching, and the peeling becomes unstable due to tearing. There was a problem to do.

  An object of the present invention is to provide a thin film release film that is made in the background of the above-mentioned problems of the prior art, has excellent peeling stability and heat resistance, and exhibits stable peeling after molding and stretching. is there.

That is, the present invention has the following features.
(1) A release film having a release layer on at least one side of a base film, wherein the release film surface has a roughness curve element having an average length RSm of 10 μm or more and 80 μm or less.
(2) The release film according to (1), wherein the resin constituting the release layer contains 50% by mass or more of melamine resin with respect to the entire resin constituting the release layer.
(3) The release film according to (1) or (2), wherein the release layer surface has a skewness RSk of 0.9 or more.
(4) The average of the skewness RSk of the release layer surface after extending twice in the longitudinal direction and the skewness RSk of the release layer surface after extending twice in the width direction is 0.9 or more. The release film according to any one of (3).
(5) The release film according to any one of (1) to (4), wherein the release layer has a thickness of 0.02 μm or more and less than 0.1 μm.
(6) The release film according to any one of (1) to (5), wherein the static friction coefficient of the release layer surface is 1.2 or less.
(7) The release film according to any one of (1) to (6), wherein the stress in the longitudinal direction and the width direction at the time of double elongation at 150 ° C. is 5 to 75 MPa or less.
(8) The release film according to any one of (1) to (7), which is used for molding simultaneous transfer applications.

  According to the present invention, it is possible to obtain a thin film release film that is excellent in heat resistance and peel stability, and exhibits good and stable peelability even after molding.

A representative surface roughness curve is shown.

  Hereinafter, the present invention will be described in detail.

  The release film of the present invention is a laminated film having a release layer on at least one side of a base film. The present inventors have found the present invention as a result of intensive studies on a base film and a release layer constituting the release film.

(I) Base film As the resin constituting the base film used in the present invention, polyester, polyarylate, polyethylene, polypropylene, polyamide, polyimide, polymethylpentene, polyvinyl chloride, polystyrene, polymethyl methacrylate, polycarbonate, Polyether ether ketone, polysulfone, polyether sulfone, fluororesin, polyetherimide, polyphenylene sulfide, polyurethane, cyclic olefin resin, and the like can be used. In the present invention, the base film is preferably composed of a resin mainly composed of polyester from the viewpoint of heat resistance, strength, and productivity. In the present invention, “having polyester as a main component” means that 50% by mass or more of the resin constituting the base film is polyester. Among these, a biaxially oriented polyester film is most preferable in terms of heat resistance, strength, and productivity.

  The polyester used for the base film of the release film of the present invention is a general term for polymers having an ester bond as the main bond in the main chain, and usually a polycondensation reaction between a dicarboxylic acid component and a glycol component. Can be obtained.

  Examples of the dicarboxylic acid component used here include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, and 5-sodiumsulfonedicarboxylic acid. Aromatic dicarboxylic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, 1,4-cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids, paraoxybenzoic acid Each component such as oxycarboxylic acid can be exemplified. Further, as dicarboxylic acid ester derivative components, esterified products of the above dicarboxylic acid compounds, such as dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl terephthalate, dimethyl 2,6-naphthalenedicarboxylate, dimethyl isophthalate, adipic acid Examples of the components include dimethyl, diethyl maleate, and dimethyl dimer. In the polyester resin constituting the base film of the present invention, the ratio of terephthalic acid and / or naphthalenedicarboxylic acid in the total dicarboxylic acid component is preferably 95 mol% or more, more preferably 98 mol% or more. It is preferable from the viewpoint of heat resistance and productivity.

  Examples of the glycol component include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexane. Diol, aliphatic dihydroxy compounds such as 2,2-dimethyl-1,3-propanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polyoxyalkylene glycol such as polytetramethylene glycol, 1,4-cyclohexanedimethanol, spiroglycol Each component includes aromatic dihydroxy compounds such as alicyclic dihydroxy compounds such as bisphenol A and bisphenol S. Of these, ethylene glycol, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, and 1,4-cyclohexanedimethanol are preferably used in terms of moldability and handleability. In the polyester resin constituting the base film of the present invention, it is preferable from the viewpoint of heat resistance and productivity that the proportion of ethylene glycol in all diol components is 65 mol% or more.

  Two or more of these dicarboxylic acid components and glycol components may be used in combination.

  From the viewpoint of moldability and dimensional stability, in the polyester resin constituting the base film, the proportion of terephthalic acid in the total dicarboxylic acid component in the polyester is 95 mol% or more, and the proportion of ethylene glycol in the total glycol component Is 65 to 95 mol%, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, and the total proportion of 1,4-cyclohexanedimethanol is preferably 5 to 35 mol%. More preferably, the total proportion of ethylene glycol is 75 to 95 mol%, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, and 1,4-cyclohexanedimethanol is 5 to 25. More preferably, the proportion of ethylene glycol is 80 to 95 mol%, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol 5 to 20 mol%.

  Further, the resin constituting the base film of the present invention is arbitrarily selected from so-called internal particles that precipitate due to catalyst residues added during the polymerization reaction, and external particles such as inorganic particles and / or organic particles Particles can be included. When particles are contained in the resin constituting the base film, it is possible to improve the slipperiness of the film and to improve the handleability during production. In applications where low gloss is required on the film surface, by incorporating particles in the base film, the particles can reduce the smoothness of the film surface and adjust the gloss to the desired value. It becomes possible. The average particle diameter of the particles contained in the resin constituting the base film is preferably 0.01 to 10 μm, more preferably 0.5 to 8 μm, and still more preferably 1 to 5 μm. If particles having an average particle diameter exceeding 10 μm are contained, defects may occur in the base film, which is not preferable. Examples of the particles include wet and / or dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, hydroxyapatite, inorganic particles such as styrene, silicone, and acrylic acid. Organic particles having a component obtained by polymerizing methacrylic acid, ester, divinylbenzene or the like can be used. Of these, inorganic particles such as wet and / or dry silica and alumina, and organic particles obtained by polymerizing styrene, silicone, acrylic acid, methacrylic acid, ester, divinylbenzene and the like are preferably used. As the particles, two or more types of internal particles, inorganic particles, and organic particles may be used, or two or more types of internal particles, inorganic particles, and organic particles may be used in combination. Moreover, it is preferable that content of particle | grains is the range of 0.01-5 mass% with respect to the whole resin composition which comprises a base film. More preferably, it is 0.03 to 3 mass%. When the amount is less than 0.01% by mass, film winding may be difficult. When the amount exceeds 5% by mass, there is a possibility that glossiness decreases due to coarse protrusions, transparency and film-forming property deteriorate. Moreover, the average particle diameter said here is a volume average particle diameter.

  The base film of the present invention is preferably a biaxially oriented film from the viewpoints of heat resistance and dimensional stability. Examples of the biaxial orientation method include a sequential biaxial stretching method and a simultaneous biaxial stretching method. From the viewpoint of productivity, the sequential biaxial stretching method is more preferably used.

  The stretching ratio of the biaxial stretching is preferably 3.0 to 4.2 times, more preferably 3.1 to 4.0 times, and further preferably 3 in the longitudinal direction and the width direction. .3 to 3.8 times. In this case, either of the stretching ratios in the longitudinal direction and the width direction may be increased or the same.

  The stretching speed is preferably 1,000% / min to 200,000% / min. More preferably, it is 1,500% / min to 50,000% / min, and more preferably 2,000% / min to 30,000% / min. By setting the stretching speed in the above range, the productivity is improved and the orientation can be easily controlled.

  In the case of the sequential biaxial stretching method in which stretching is performed in the width direction after stretching in the longitudinal direction, stretching is preferably performed under the following conditions because a difference in physical properties between the longitudinal direction and the width direction can be reduced. The stretching ratio is 3 to 4.2 times in the longitudinal direction, 3 to 4.2 times in the width direction, preferably 3.3 to 3.8 times in the longitudinal direction, and the width direction. The stretching ratio is 3.3 to 3.8 times, and the difference between the stretching ratios in the longitudinal direction and the width direction is 0.5 or less, more preferably 0.2 or less. In addition, the preheating temperature for stretching in the longitudinal direction (hereinafter sometimes referred to as longitudinal stretching) is preferably 80 to 100 ° C, more preferably 85 to 95 ° C. The longitudinal stretching temperature is preferably from 80 ° C. to 110 ° C., more preferably from 85 ° C. to 100 ° C., and most preferably from 85 ° C. to 95 ° C. The preheating temperature for the stretching in the width direction (hereinafter sometimes referred to as transverse stretching) is preferably 70 to 120 ° C, more preferably 75 to 110 ° C. The transverse stretching temperature is preferably 80 ° C. or higher and 165 ° C. or lower, more preferably 80 ° C. or higher and 150 ° C. or lower, and most preferably 80 ° C. or higher and 145 ° C. or lower. When the preheating temperature is equal to or higher than the above temperature range, thermal crystallization of the amorphous part in the film proceeds, and tearing may easily occur during stretching. Moreover, when preheating temperature is below the said temperature range, it becomes cold-temperature extending | stretching and thickness unevenness becomes large, and mechanical strength may deteriorate by the orientation degree of a film falling. When the stretching temperature exceeds the above range, process troubles such as roll adhesion and clip adhesion may occur. Moreover, when extending | stretching temperature is less than the said range, extending | stretching tension | tensile_strength raises rapidly, and a tear, clip peeling, etc. may arise, and productivity may fall significantly.

  The base film of the present invention is preferably obtained by performing a heat treatment after biaxially stretching an unstretched sheet. This heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. The heat treatment can be performed at an arbitrary temperature such that the temperature of the film is 120 ° C. or higher and 240 ° C. or lower, but is preferably 200 to 240 ° C. More preferably, it is 225 degreeC-240 degreeC. The heat treatment time can be any time, but preferably 1 to 60 seconds. More preferably, it is 1 to 30 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. Furthermore, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

  The base film of the present invention may be a single layer film or a laminated film having two or more layers. In the case of a three-layer structure, it is preferable that the compositions of both surface layers are the same from the viewpoint of productivity. Furthermore, in order to improve productivity, it is preferable to make the lamination | stacking thickness of both surface layers equal.

(II) Release layer The release layer of the present invention preferably contains 50% by mass or more of melamine resin with respect to the entire resin constituting the release layer. By containing 50% by mass or more of the melamine resin, self-condensation of the melamine resin proceeds during heating, and the heat resistance is greatly improved. When the concentration of the melamine resin is less than 50% by mass, the crosslinking reaction may be insufficient, and sufficient heat resistance may not be exhibited, or it may be difficult to make the surface structure of the release layer within a specific range. . Preferably, it is 70 mass% or more and 90 mass% or less.

  Examples of the melamine resins include melamine formaldehyde resins, methylated melamine formaldehyde resins, butylated melamine formaldehyde resins, etherified melamine formaldehyde resins, melamine formaldehyde resins such as epoxy-modified melamine formaldehyde resins, urea melamine resins, and acrylic melamine resins. Melamine formaldehyde resin is preferable, and methylated melamine formaldehyde resin is particularly preferably used because it has an appropriate release property.

  When the release layer of the present invention contains a binder resin, the adhesion to the base film is improved, and the peeling force from the object to be peeled can be adjusted, or the stretch following property at the time of molding in molding simultaneous transfer. Can be made favorable. Specific examples of the binder resin include polyester resins, acrylic resins, urethane resins, polyvinyls, polyalkylene glycols, polyalkyleneimines, celluloses, starches, etc., but stretch followability, release force at the time of release, and An acrylic resin is most preferably used from the viewpoint of peeling stability.

  Examples of the acrylic resin include a homopolymer or copolymer of (meth) acrylic acid alkyl ester, and a (meth) acrylic acid ester copolymer having a curable functional group at the side chain and / or main chain terminal. Examples of the functional group include a hydroxyl group, a carboxyl group, an epoxy group, and an amino group. Among them, an acrylic monomer copolymer obtained by copolymerizing an acrylic monomer and an acrylic ester having a curable functional group at the side chain and / or main chain terminal is preferable.

  Moreover, it is preferable that the release layer of the present invention contains a release agent as long as the target heat resistance and molding stretchability are not impaired. When the release agent is uniformly dispersed on the surface of the release layer, the adhesion and release properties with the release layer that is laminated and peeled on the release layer can be adjusted to an appropriate range. Examples of the mold release agent include fluorine compounds, long-chain alkyl compounds, and waxes. These release agents may be used alone or in combination.

  The fluorine compound in the present invention is a compound containing a fluorine atom in the compound. Examples thereof include perfluoroalkyl group-containing compounds, polymers of fluorine-containing olefin compounds, and aromatic fluorine compounds such as fluorobenzene. When the release film of the present invention is used for molding simultaneous transfer foil applications and the like, a high heat load is applied at the time of transfer. Therefore, considering heat resistance and contamination, the fluorine compound is preferably a polymer compound.

  The long-chain alkyl compound in the present invention is a compound having a linear or branched alkyl group having 6 or more, particularly preferably 8 or more carbon atoms. Specific examples include, but are not limited to, long-chain alkyl group-containing polyvinyl resins, long-chain alkyl group-containing acrylic resins, long-chain alkyl group-containing polyester resins, long-chain alkyl group-containing amine compounds, long-chain alkyl groups. And an ether compound, a long-chain alkyl group-containing quaternary ammonium salt, and the like. It is preferable that the long-chain alkyl compound is a polymer compound because the component derived from the release layer on the surface of the counterpart substrate that is bonded when the release film is peeled can be suppressed.

  The wax in the present invention is a wax selected from natural waxes, synthetic waxes, and blended waxes. Natural waxes are plant waxes, animal waxes, mineral waxes, and petroleum waxes. Examples of plant waxes include candelilla wax, carnauba wax, rice wax, wood wax, and jojoba oil. Animal waxes include beeswax, lanolin, and whale wax. Examples of the mineral wax include montan wax, ozokerite, and ceresin. Examples of petroleum wax include paraffin wax, microcrystalline wax, and petrolatum. Synthetic waxes include synthetic hydrocarbons, modified waxes, hydrogenated waxes, fatty acids, acid amides, amines, imides, esters, and ketones. As synthetic hydrocarbons, Fischer-Tropsch wax (also known as Sazoir wax) and polyethylene wax are well known, but in addition to these, low molecular weight polymers (specifically, polymers having a viscosity average molecular weight of 500 to 20000) are used. The following polymers are also included. That is, there are polypropylene, ethylene / acrylic acid copolymer, polyethylene glycol, polypropylene glycol, polyethylene glycol and polypropylene glycol block or graft conjugate. Examples of the modified wax include montan wax derivatives, paraffin wax derivatives, and microcrystalline wax derivatives. The derivative herein is a compound obtained by any of purification, oxidation, esterification, saponification treatment, or a combination thereof. Hydrogenated waxes include hardened castor oil and hardened castor oil derivatives.

  By uniformly dispersing these release agents on the surface of the release layer, the adhesion and release force with the release layer laminated and peeled on the release layer can be within an appropriate range. As the mold release agent, a long-chain alkyl compound is preferably used for the purpose of the present invention because the peel force can be adjusted over a wide range.

  Further, the resin constituting the release layer of the present invention may contain inert particles for the purpose of improving the adhesion and slipperiness of the release layer. Specific examples of the inert particles include silica, alumina, kaolin, calcium carbonate, titanium oxide, and organic particles.

  Furthermore, as long as it does not impair the gist of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, etc. May be contained.

  In this invention, it is preferable to provide the resin composition containing a melamine compound (A) on at least one side of a base film, and to heat it after that, and to form a release layer on a base film. In particular, it is preferable to set the heating temperature in the range of 200 ° C. or more and 240 ° C. or less to two or more steps having different temperatures because a release layer having a specific surface shape can be efficiently formed. Thereby, it is possible to obtain a release film having excellent release properties, release stability, and heat resistance.

  When providing the resin composition containing a melamine compound on a base film, a solvent may be used. That is, the melamine compound may be dissolved or dispersed in a solvent to form a coating solution, which may be applied to the base film. After application, the solvent is dried and heated to obtain a film having a release layer laminated thereon. In the present invention, an aqueous solvent is preferably used as the solvent. By using an aqueous solvent, rapid evaporation of the solvent in the heating step can be suppressed, and a uniform release layer can be formed, which is excellent in terms of environmental load.

  Here, the aqueous solvent is soluble in water such as water or water and alcohols such as methanol, ethanol, isopropyl alcohol and butanol, ketones such as acetone and methyl ethyl ketone, and glycols such as ethylene glycol, diethylene glycol and propylene glycol. A certain organic solvent is mixed at an arbitrary ratio.

  As a method for applying the resin composition to the base film, either an in-line coating method or an off-coating method can be used, but an in-line coating method is preferable. The in-line coating method is a method of applying in the process of manufacturing a polyester film. Specifically, it refers to a method of coating at any stage from melt extrusion of the resin constituting the base film to heat treatment after biaxial stretching, and usually obtained by rapid cooling after melt extrusion. A substantially amorphous unstretched (unoriented) film, a uniaxially stretched (uniaxially oriented) film stretched in the longitudinal direction, or a biaxially stretched (biaxially oriented before heat treatment) stretched further in the width direction. ) Apply to any film.

  In the present invention, the resin composition is applied to any of the unoriented film and the uniaxially oriented film before the crystal orientation is completed, the solvent is evaporated, and then the base film is uniaxially or biaxially. It is preferable to employ a method of stretching and heating to complete the crystal orientation of the base film and providing a release layer. According to this method, the production of the base film, the application of the resin composition, the drying of the solvent, and the heating (that is, the formation of the release layer) can be performed at the same time. . Further, it is easy to reduce the thickness of the release layer in order to perform stretching after coating.

  Among them, a method in which the resin composition is applied to a film uniaxially stretched in the longitudinal direction, the solvent is dried, and then stretched in the width direction and heated is preferable. Compared to the method of biaxial stretching after coating on an unstretched film, the stretching process is less than once, so that the occurrence of defects and cracks in the release layer due to stretching can be suppressed.

  On the other hand, the off-line coating method refers to a film-forming process on a film after stretching the unstretched film uniaxially or biaxially and performing a heat treatment to complete the crystal orientation of the base film, or an unstretched film. Is a method of applying the resin composition in a separate step. In this invention, it is preferable to provide by the in-line coating method from the various advantages mentioned above.

  Therefore, the best method for forming a release layer in the present invention is to form a resin composition using an aqueous solvent by applying the resin film on a substrate film using an in-line coating method, drying the aqueous solvent, and heating. It is a method to do.

  When preparing the coating liquid containing a resin composition, it is preferable to use an aqueous solvent as a solvent. The coating liquid containing the resin composition can be prepared by mixing and stirring a water-dispersed or water-soluble melamine compound and an aqueous solvent in any order at a desired weight ratio as necessary. Then, if necessary, various additives such as lubricants, inorganic particles, organic particles, surfactants, antioxidants, thermal initiators and the like are arbitrarily selected within the range not deteriorating the properties of the release layer formed by the resin composition. In this order, they can be mixed and stirred. The mixing and stirring methods can be performed by shaking the container by hand, using a magnetic stirrer or stirring blade, irradiating ultrasonic waves, vibrating and dispersing.

  As a method for applying the resin composition to the base film, any known method such as a bar coating method, a reverse coating method, a gravure coating method, a die coating method, or a blade coating method can be used.

  The method for producing a release film of the present invention will be described with reference to an example in which a polyethylene terephthalate (hereinafter referred to as PET) film is used as a base film. First, the PET pellets, to which pigments, dyes, organic or inorganic particles are added as necessary, are sufficiently dried in vacuum, then supplied to an extruder, melted and extruded into a sheet at about 280 ° C., cooled and solidified, and left undissolved. A stretched (unoriented) PET film is prepared. This film is stretched 3 to 4.2 times in the longitudinal direction with a roll heated to 80 to 120 ° C. to obtain a uniaxially oriented PET film. A coating solution having a resin composition containing a melamine compound, prepared at a predetermined concentration, is applied to one side of the film. At this time, surface treatment such as corona discharge treatment may be performed on the coated surface of the PET film before coating. By performing surface treatment such as corona discharge treatment, the coating property of the resin composition on the PET film is improved, so that the wettability is improved, the repelling of the resin composition is prevented, and a uniform coating thickness is achieved. be able to.

  After coating, the edge of the PET film is held with a clip and guided to a preheating zone of 80 to 130 ° C., and the solvent of the coating solution is dried. After drying, the film is stretched 3 to 4.2 times in the width direction at a temperature of 100C to 160C. Subsequently, the first stage heat treatment is conducted for 1 to 30 seconds, and then the second stage heat treatment is performed at a temperature higher than the first stage heat treatment temperature and in the range of 200 to 240 ° C. Perform for ˜30 seconds to complete the crystal orientation and complete the formation of the release layer. In this heating step (heat treatment step), 3 to 15% relaxation treatment may be performed in the width direction or the longitudinal direction as necessary.

In the present invention, the average length (RSm) of the roughness curve element on the surface of the release layer needs to be 10 μm or more and 80 μm or less. RSm here is obtained according to JIS B 0601 (2001), and represents the average length between roughness curve elements in the reference length. That is, when the number of peaks in the roughness curve is m and the distance between each peak is W ₁ , W ₂ , W ₃ ... W _m in the reference length (Lr) in FIG. RSm can be obtained by dividing the sum of the lengths of W _{1 to} W _m by the number m of peaks of the roughness curve as shown in FIG. When RSm is 10 μm or more and 80 μm or less, the releasability and releasability can be improved remarkably. About this effect, the present inventors are estimating as follows. RSm represents the interval between the irregularities on the surface of the release layer, and the larger the value, the greater the distance between the irregularities, so that the average slope of the surface becomes gentler. On the other hand, when the value is small, the pitch of the surface irregularities becomes small, the average inclination of the surface becomes steep, and the number of grooves per unit area increases. When RSm is larger than 80 μm, the slope of the release layer surface becomes excessively gentle, and the adhesion between the layer laminated on the release layer and the release layer surface becomes insufficient. On the other hand, when RSm is less than 10 μm, the average inclination of the surface becomes steep, and the number of grooves per unit area increases, making it difficult to obtain stable releasability. By setting RSm to 10 μm or more and 80 μm or less, it is considered that irregularities are arranged on the surface of the release layer at appropriate intervals, and form an optimum height gradient from the viewpoint of release properties and release stability. . RSm is preferably 20 μm or more and 75 μm or less, and most preferably 30 μm or more and 70 μm or less.

Examples of a method for setting the properties of the release film within the above range include formation under the following conditions.
-After applying a coating liquid of a resin composition containing 50% by mass or more of melamine resin to the entire resin composition constituting the release layer on at least one side of the base film, the solvent is evaporated in the drying step. Then, in the method of forming the release layer in the heat treatment step, (i) to (iii) should be satisfied.
(I) The temperature of the heat treatment step is 200 to 240 ° C.
(Ii) The temperature difference between processes or between processes should be within 80 ° C. between the drying process and the heat treatment process.
(Iii) The thickness of the release layer should be 0.02 μm or more and less than 0.1 μm.

  By setting the content of the melamine resin in the resin composition constituting the release layer of the present invention within the above range, the release layer surface becomes excessively rough even when heat treatment is performed at a high temperature satisfying (i). It is possible to adjust RSm to an appropriate range without any problem. When the content of the melamine resin is less than 50% by mass, when the heat treatment is performed at a high temperature of 200 ° C. or higher, the smoothness of the release layer surface is reduced and RSm exceeds 80 μm, and the heat resistance of the release layer surface is reduced. There is a case. The content of the melamine resin in the resin composition constituting the release layer is preferably 60% by mass or more and 90% by mass or less, and more preferably 70% by mass or more and 85% by mass or less.

  By performing the above heat treatment temperature at a high temperature of 200 ° C. or more and 240 ° C. or less, the self-condensation reaction between melamine resins or the crosslinking reaction between the melamine resin and the binder proceeds, and the heat resistance of the release layer is improved. it can. Preferably it is 225 degreeC-240 degreeC. In addition, since the self-condensation reaction between melamine resins or the crosslinking reaction between melamine resin and binder resin proceeds, the stretchability of the release layer is improved. Is less likely to occur, and RSm can be within a preferable range.

  In the process of forming the release layer, the temperature difference between processes or between processes is within 80 ° C. between the drying process and the heat treatment process. Dispersion occurs and the crosslinking reaction and self-condensation reaction proceed to a high degree, thereby forming a dense coating surface and increasing the heat resistance of the release layer surface. Furthermore, even in a melamine resin addition system with high smoothness, the temperature difference between processes or between processes is within 80 ° C., so that the binder resin covers the surface and the surface smoothness does not increase too much. A preferable range can be set. In particular, when the content of the melamine resin in the resin composition constituting the release layer is large, if the self-condensation between the melamine resins proceeds too much, the surface may become too smooth and the RSm may be lowered. For example, in the step of forming a release layer, if the heat treatment is performed at a temperature exceeding 200 ° C. after the stretching step is performed at 120 ° C., surface concentration and self-condensation of the melamine resin added at a high concentration occurs, and the surface becomes It may be difficult to make the RSm within the target range by smoothing excessively. By setting the temperature difference between processes or between processes to be within 80 ° C., the cross-linking reaction between the melamine resin and the binder resin and the self-condensation reaction between the melamine resins can be appropriately advanced, and RSm is the target range. It becomes possible.

  In addition, when the thickness of the release layer is 0.1 μm or more, the stretchable followability at the time of molding is reduced and cracks are likely to occur in the release layer, and thus RSm may increase on the surface of the release layer, Peeling may become unstable. Moreover, when the thickness of the release layer is less than 0.02 μm, it is difficult to obtain a coating film having a uniform RSm, and peeling may become unstable. The thickness of the release layer is preferably 0.025 μm or more and 0.08 μm, and most preferably 0.03 μm or more and 0.6 μm. The thickness of the release layer can be measured by observing the cross section of the release film with a scanning electron microscope, transmission electron microscope, optical microscope or the like at a magnification of 500 to 10,000 times.

  An example of a method for producing a release film that satisfies the above three requirements simply and economically is an in-line coating method in which a release layer is provided in the film production process. The in-line coating method as used herein refers to a film obtained by dispersing a release layer composition in water on at least a uniaxially stretched film, uniformly applied using a metalling bar, gravure roll, etc. This is a method of drying the coating agent. In this process, the heat treatment temperature of the film is set to 200 ° C. or more and 240 ° C. or less, and the maximum temperature of the drawing process, which is the previous process, is set to a temperature within 80 ° C. from the heat treatment temperature. The condition can be achieved. Further, by performing a stretching treatment after the release layer composition is applied, the release layer can be thinned. At this time, the heat treatment time is preferably 5 seconds or more and less than 25 seconds from the viewpoint of promoting the crosslinking reaction with the melamine resin of the release layer. When the heat treatment time is less than 5 seconds, the crosslinking reaction of the release layer does not proceed sufficiently, and the desired heat resistance is not exhibited. On the other hand, if the heat treatment time is longer than 25 seconds, thermal crystallization of the base film proceeds and becomes brittle, which causes a handling problem such as notching during trimming. Specifically describing the temperature requirements in the above production, for example, by setting the transverse stretching temperature to 150 ° C. and the heat treatment temperature to 230 ° C., the temperature change between the steps is set to 80 ° C., and the heat treatment at a high temperature is realized. The

  The release layer of the present invention preferably has a release layer surface skewness RSk of 0.9 or more and 4.0 or less. The skewness RSk here is obtained in accordance with JIS B 0601 (2001) and represents the shape of the uneven portion on the surface. When the RSk is positively large, it indicates that the surface shape is constituted by a sharp acute convex portion and a round concave portion. On the other hand, when RSk is negatively large, it indicates that the surface shape is composed of a rounded convex portion and a sharp acute-angle concave portion. When RSk is less than 0.9, since the concave portion on the surface of the release layer has an excessively acute angle, the anchor effect on the layer to be peeled becomes too strong, so that the release layer is significantly peeled off. On the other hand, by setting RSk to 0.9 or more and 4.0 or less, a surface structure showing an appropriate degree of anchor effect is obtained, and the retention of the surface structure when the release film is stretched is also good. . On the other hand, when RSk is larger than 4.0, the release layer is lightly peeled off, the scratch resistance is lowered, and the film surface may be easily scratched. Preferably, it is 1.0 or more and 2.5 or less.

  The above characteristic range is achieved, for example, by satisfying the above three requirements.

  The release film of the present invention is used for molding simultaneous transfer applications and hot press molding applications. In particular, when used in a mold having a deep shape for simultaneous molding transfer, it is required that the mold release film has mold releasability after being molded and simultaneously transferred, that is, in a stretched state. However, when the release layer of the release film cannot follow the elongation, a minute crack may be generated on the surface of the release layer, and RSk is lowered. Therefore, in the release film of the present invention, the average of the skewness RSk on the surface of the release layer after extending twice in the longitudinal direction and the skewness RSk on the surface of the release layer after extending twice in the width direction are 0.9. If it is 4.0 or less, it is preferable since it is excellent in releasability and excellent in mold release stability even after being molded into a deep mold. The average of the skewness RSk of the release layer surface after extending twice in the longitudinal direction and the skewness RSk of the release layer surface after extending twice in the width direction is preferably 1.0 or more and 2.5 or less. is there. If the average of the skewness RSk of the release layer surface after extending twice in the longitudinal direction and the skewness RSk of the release layer surface after extending twice in the width direction is less than 0.9, stretching during molding, etc. In some cases, the surface of the release layer may have fine cracks, and the release stability may be inferior, or the release layer may be transferred to the layer to be peeled during peeling.

  Specifically, RSk is obtained by the following method. In the reference length (Lr) in FIG. 1, when the height of the roughness curve is represented by z = Z (x), the cube of Z (x) is expressed as x as shown in the following formula (2). It is obtained by dividing the value obtained by integrating from = 0 to Lr by the cube of Rq. Here, Rq is a parameter of surface roughness obtained according to JIS B 0601 (2001), and is a value obtained as an average value of the square of Z (x). That is, when the range from x = 0 to Lr is measured, the value obtained by integrating the square of Z (x) from x = 0 to Lr is divided by Lr as shown in the following formula (3). Rq is obtained as the square root of.

  In the release film of the present invention, as a method for setting the RSk of the release layer surface in the above preferable range, for example, in the method of forming a release layer, the conditions satisfying (1) to (3) are satisfied, and the release is performed. The content of the melamine resin in the resin composition constituting the layer may be 80% by mass or less based on the entire resin composition constituting the release layer. When the concentration of the melamine resin is larger than 80% by mass, the stretchable followability of the surface of the release layer is lowered, and the RSk may be lowered by cracking the surface during elongation.

  Moreover, in the release film of the present invention, as a method for setting the RSk of the release layer surface after extending twice in an arbitrary direction to the above preferable range, an acrylic monomer copolymer resin is used as a binder resin, and it is not stretched. This is achieved by setting the hour RSk to 0.9 or more. As content of acrylic monomer copolymer resin, it is preferable that it is 70 mass% or more with respect to structural components other than the melamine resin in a mold release layer, More preferably, it is 80 mass% or more. By using the acrylic monomer copolymer resin as the binder resin, the stretchable followability of the release layer is improved, and the occurrence of cracks on the surface is suppressed even when the film is stretched.

  The release film of the present invention is used for molding simultaneous transfer applications and hot press molding applications. For example, when used for molding simultaneous transfer applications, the molded resin may flow smoothly on the surface of the release film. Desired. If the fluidity of the injected resin is poor, the ink flow is deteriorated, the transferability is deteriorated, and the releasability is deteriorated. This problem is likely to occur particularly when simultaneous molding transfer is performed using a deep mold. Therefore, the release film of the present invention preferably has a static friction coefficient of 1.2 or less on the surface of the release layer. By setting the static friction coefficient of the surface of the release layer of the release film to 1.2 or less, the fluidity of the resin is improved, and good transferability and release properties can be obtained even when a deep mold is used. . Preferably it is 0.8 or less, and it is the most preferable in it being 0.6 or less. As a method of setting the static friction coefficient on the surface of the release layer to 1.2 or less, in addition to making the release layer have the above-described configuration, 0.001% by mass or more of particles are added to the resin constituting the surface layer of the base film. The method of adding 0.5 mass% or less etc. is mentioned. If the addition amount is less than 0.001% by mass, the effect is insufficient. If the addition amount is more than 0.5% by mass, the film surface may have a low gloss, which may affect the appearance after transfer.

  The release layer of the present invention can be laminated on one side or both sides of the base film. When laminated on one side, an antistatic layer may be laminated on the surface opposite to the release layer. The antistatic layer can contain, for example, an antistatic agent such as carbon black, tin oxide, tin oxide antimony dope, polythiophene and polyaniline. In consideration of transparency, a tin oxide antistatic agent is preferred.

(III) Release Film The release film of the present invention has a longitudinal stress and a stress in the width direction (hereinafter referred to as “longitudinal stress”) when stretched twice at 150 ° C. from the viewpoint of moldability to a deep shape when used for molding simultaneous transfer. each may be called _F100 MD, _{F100 TD)} it is preferable that both a 5～75MPa. If either the F100 _MD value or the F100 _TD value is less than 5 MPa, the stress at the time of molding is too low, the dimensional stability is lowered, the film is stretched in the preheating process at the time of molding, and molding unevenness occurs. There is a case. Further, if either the F100 _MD value or the F100 _TD value is greater than 75 MPa, a deep shape may be difficult to form due to high stress during molding. From the viewpoint of dimensional stability and moldability, the F100 _MD value and the F100 _TD value are more preferably 10 to 45 MPa, and particularly preferably 10 to 35 MPa. Here, the F100 _MD value and the F100 _TD value refer to a tensile test at a strain rate of 300 mm / min after preheating for 60 seconds in a thermostat set to 190 ° C. on a film sample cut into a rectangular shape having a test length of 50 mm. It is the stress at the time of 100% elongation when performed in the longitudinal direction and the width direction, respectively.

As a preferable means for setting the F100 _MD value and F100 _TD value of the release film in the present invention in the above ranges, the release film is composed of a base film and a release layer. 1) Use a biaxially oriented polyester film having the characteristics as described in “Base film”, and simultaneously apply a release layer having characteristics as described in “(2) Release layer” to “ (2) Release layer ”is used under the coating / drying conditions.

  Since the release film of the present invention has high heat resistance of the release layer, it is suitable for applications including high-temperature processing steps such as simultaneous molding transfer applications and hot press processes. When the release film of the present invention is used for molding simultaneous transfer, it is preferable because the ink flow due to the injection resin is suppressed and the peeling force at the time of transfer is stabilized. Further, even after the release film is stretched, stable peeling force and heat resistance are exhibited, so that when used for simultaneous molding transfer, deeper simultaneous molding transfer becomes possible. The thickness of the release film of the present invention is preferably 10 to 300 μm, more preferably 15 to 200 μm, and particularly preferably 20 to 100 μm in terms of moldability and processability.

  Hereinafter, the present invention will be described in detail by way of examples. Various characteristics were measured and evaluated by the following methods.

1. Stress in longitudinal direction and width direction at 2 times elongation at 150 ° C. (F100 _MD value, F100 _TD value)
Using a tensile tester (Tensilon UCT-100 manufactured by Orientec Co., Ltd.), a sample film having a width of 10 mm cut in the longitudinal direction and the width direction is set so that the length between chucks is 50 mm (initial sample length), and the temperature is 150. After preheating for 60 seconds in a constant temperature layer set at a temperature of 65 ° C. and a humidity of 65% RH, a tensile test was performed at a tensile speed of 300 mm / min, and the stress at double expansion was defined as an F100 _MD value and an F100 _TD value, respectively. The number of measurements (hereinafter referred to as N) was N = 5 in the longitudinal direction and the width direction, respectively, and the average value was defined as the stress during double expansion.

  When the longitudinal direction and the width direction of the film are not known, the direction having the maximum refractive index in the film is regarded as the longitudinal direction, and the direction perpendicular to the longitudinal direction is regarded as the width direction. In addition, the direction of the maximum refractive index in the film may be obtained by measuring the refractive index in all directions of the film with an Abbe refractometer, for example, by using a phase difference measuring device (birefringence measuring device) or the like. You may obtain | require by determining an axial direction.

2. Coefficient of static friction The coefficient of static friction was measured using a slip tester according to ASTM D1894B (1963).

3. RSm, RSk, RSk at double expansion
Measurement was performed using a non-contact surface / layer cross-sectional shape measurement system, VertScan 2.0, manufactured by Ryoka System. The measurement conditions are as follows. Measurement is performed on five samples, and the average values are defined as RSm and RSk.
Measurement length (Lr: reference length): 1252 μm
Lens: For RSk when stretched 10 times and 2 times, using a tensile tester (Tensilon UCT-100 manufactured by Orientec Co., Ltd.), a sample film having a width of 10 mm cut in the longitudinal direction and the width direction has a length between chucks of 50 mm ( The sample was stretched by a factor of 300 mm / min after preheating for 60 seconds in a constant temperature layer set at a temperature of 150 ° C. and a humidity of 65% RH. The measurement was performed in the same manner as the RSk measurement method for the unstretched sample. With respect to the sample obtained by extending the sample film cut in the longitudinal direction by 2 times and the sample obtained by extending the sample film cut in the width direction by 2 times, RSk was measured for 5 samples, respectively, and the average value of 10 samples was doubled. It was RSk at the time of extension.

4). Formability, releasability, heat resistance On the release layer, a topcoat layer, an ink layer, and an adhesive layer were sequentially coated to prepare a transfer foil. UV curable acrylic resin (“LAROMER” (registered trademark) LR8983, manufactured by BASF Japan Ltd.) (thickness 60 μm) as the top coat layer, polyurethane resin gravure ink (manufactured by Dainichi Seika Kogyo Co., Ltd.) as the ink layer "Hylamic", main solvent: toluene / methyl ethyl ketone / isopropyl alcohol, ink: 723B yellow / 701R white) (thickness 70 μm), and further, as an adhesive layer, an acrylonitrile-butadiene-styrene (ABS) copolymer resin film (Okamoto) An ABS film “Hiflex” manufactured by Co., Ltd., having a thickness of 100 μm was applied. Aging was performed at 40 ° C. for 72 hours in order to cure the ink layer. Next, it was set in a cylindrical mold having a diameter of 50 mm and a drawing ratio (depth / bottom diameter) of 0.2, and reduced pressure molding was performed at 120 ° C., and ABS resin (Toyolac Co., Ltd., ABS resin “Toyolac”) ”(Registered trademark) 930) was injection-molded to produce a cylindrical molded product.

(1) Formability S: The corner on the bottom side of the cylindrical molded product is formed sharply.
A: Although the corner on the bottom side of the cylindrical molded product is rounded, it is molded.
B: Although formed, there is a whitened portion.
C: Not molded.
A or higher was accepted.

(2) Releasability Further, in order to cure the top coat layer with the transfer foil attached thereto, the top coat layer was irradiated with 2000 mJ / cm ² of ultraviolet light having a wavelength of 365 nm, and then the molded transfer laminated film on the outer surface was peeled off. A box-shaped molded product made of ABS resin in which the ink layer was visible was prepared. Ten of these were prepared for each level and used for evaluation.
S: All 10 pieces could be peeled without problems.
A: Although there was some resistance, all 10 pieces could be peeled off.
B: Some were peeled off before UV curing.
C: There was something that could not be peeled off.
A or higher was accepted.

(3) Heat resistance S: No trace of resin flow is observed in both the transfer foil and the molded body.
A: A slight resin trace is seen on the transfer foil, but not on the molded body.
B: A trace of a slight resin flow is seen on the molded body.
C: A clear trace of resin flow is seen in the molded body.
A or higher was accepted.

5. Melamine resin content in the release layer 0.1 g of the resin constituting the release layer was dissolved in hexafluoroisopropanol (HFIP), and the resin composed of the melamine skeleton using ¹ H-NMR and ¹³ C-NMR. The content was quantified. In addition, the content of the melamine resin is specified by conducting ¹ H-NMR and ¹³ C-NMR measurements after isolating the constituent polymer by performing a preparative operation using GPC (HLC-8020 manufactured by Tosoh Corporation) as necessary. did.

6). Film thickness Using a dot-type film thickness meter (Anritsu, K402B), the thickness is measured at 50 arbitrary locations in the film width direction and 50 arbitrary locations in the longitudinal direction near the center of the film width, and the number of all 100 locations. The average value was taken as the film thickness.

7). Release Layer Thickness The release layer thickness was determined by electron microscope observation of a sample cut out of a cross section using a microtome. That is, using a transmission electron microscope HU-12 (manufactured by Hitachi, Ltd.), the cross section of the film was magnified 3000 to 200000 times, a cross-sectional photograph was taken, and the thickness of the release layer was determined from the cross-sectional photograph. It was measured. Incidentally, it performed stained with RuO ₄ staining in order to clarify the layer structure were Somewake different resin layers. For the film of the present invention, the coating volume A (cm ³ / m ² ) per square meter on the film surface is calculated from the solid content concentration of the coating agent with the specific gravity of the resin being 1 g / cm ³ , and this A is applied. The thickness (μm) was used.

(Polyester chip α)
To a mixture of 100 parts by weight of dimethyl terephthalate and 70 parts by weight of ethylene glycol, 0.09 parts by weight of magnesium acetate and 0.03 parts by weight of antimony trioxide are added, the temperature is gradually raised, and finally Conducted transesterification while distilling methanol at 220 ° C. Subsequently, 0.020 parts by mass of an aqueous solution of 85% by mass of phosphoric acid was added to the transesterification reaction product, and then transferred to a polycondensation reaction kettle. The reaction system is gradually depressurized while heating in the polymerization kettle, and the polycondensation reaction is performed at 290 ° C. under a reduced pressure of 1 hPa. The inherent viscosity is 0.65, and the by-produced diethylene glycol component is converted into the glycol component in the resin. On the other hand, a polyethylene terephthalate resin copolymerized with 2 mol% was obtained.

(Polyester chip β)
Copolyester in which 1,4-cyclohexanedimethanol component was copolymerized with 33 mol% with respect to the glycol component of polyethylene terephthalate was used.

(Particle Master M)
When the polyester chip α is produced, a polycondensation reaction is performed after adding an ethylene glycol slurry of aggregated silica particles having an average particle size of 2.2 μm after the transesterification reaction, and a particle master having a particle concentration of 2 mass% in the polymer is obtained. Produced.

(Release layer forming solution)
The following crosslinking agent: binder resin: release agent: particles were mixed at a mass ratio shown in the table, respectively, and adjusted by diluting with pure water so that the solid content was 1%.
-Crosslinking agent I: Methylated melamine / urea copolymer crosslinked resin (manufactured by Sanwa Chemical Co., Ltd. "Nicalak" (registered trademark) "MW12LF")
Cross-linking agent II: Butylated melamine / urea copolymer cross-linked resin (“Beccamin” (registered trademark): “J101” manufactured by Dainippon Ink & Chemicals, Inc.)
-Binder resin I: Acrylic monomer copolymer (Nippon Carbide)
-Binder resin II: 25 mol% of terephthalic acid, 24 mol% of isophthalic acid, 1 mol% of 5-Na sulfoisophthalic acid, 25 mol% of ethylene glycol and 25 mol% of neopentyl glycol are mixed with 25% by mass of water. Diluted dispersion.
Release agent I: 200 parts of xylene and 600 parts of octadecyl isocyanate were added to a four-necked flask and heated with stirring. From the time when 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 over a period of about 2 hours. After the addition of polyvinyl alcohol, the reaction was completed by further refluxing for 2 hours. When the reaction mixture was cooled to about 80 ° C. and added to methanol, the reaction product was precipitated as a white precipitate. This precipitate was filtered off, added with 140 parts of xylene, and heated to dissolve completely. Then, after repeating the operation of adding methanol again for precipitation several times, the precipitate was washed with methanol, dried and pulverized, and a dispersion obtained by diluting with water to 8.6% by mass was obtained.
Release agent II: 300 g of oxidized polyethylene wax having a melting point of 105 ° C., an acid value of 16 mg KOH / g, a density of 0.93 g / mL, and an average molecular weight of 5000 in an emulsification facility having an internal volume of 1.5 L equipped with a stirrer, a thermometer and a temperature controller After adding 650 g of ion-exchanged water and 50 g of decaglycerin monooleate surfactant and 10 g of 48% potassium hydroxide aqueous solution and replacing with nitrogen, it was sealed, stirred at 150 ° C. for 1 hour at high speed, cooled to 130 ° C., and a high-pressure homogenizer A wax emulsion obtained by passing the solution under a pressure of 400 atm and cooling to 40 ° C.
Release agent III: CF ₃ (CF ₂ ) _n CH ₂ CH ₂ OCOCH═CH ₂ (n = 5 to 11, n average = 9) 80 which is a perfluoroalkyl group-containing acrylate in a glass reaction vessel 0.0 g, acetoacetoxyethyl methacrylate 20.0 g, dodecyl mercaptan 0.8 g, deoxygenated pure water 354.7 g, acetone 40.0 g, C ₁₆ H ₃₃ N (CH ₃ ) ₃ Cl 1.0 g and C ₈ H ₁₇ C Add 3.0 g of ₆ H ₄ O (CH ₂ CH ₂ O) _n H (n = 8), add 0.5 g of azobisisobutylamidine dihydrochloride, and stir in a nitrogen atmosphere at 60 ° C. for 10 hours. A copolymer emulsion obtained by polymerization reaction.
Particles: Obtained by diluting silica particles having a number average particle diameter of 170 nm (“Snowtex” (registered trademark) MP2040 manufactured by Nissan Chemical Industries, Ltd.) with pure water so that the solid content concentration becomes 40% by weight. Water dispersion.

Example 1
The base film was a three-layer laminated film (B layer / A layer / B layer).
The polyester chip α, polyester chip β and particle master M were each dried in a vacuum dryer at 180 ° C. for 4 hours to sufficiently remove moisture. Thereafter, the layer B is made of the raw material at a mass ratio of polyester chip α: polyester chip β: particle master M = 88: 10: 2 so that the A layer has a mass ratio of polyester chip α: polyester chip β = 60: 40. Blended. Each was supplied to a separate single-screw extruder, melted at 275 ° C., passed through a filter and a gear pump through separate paths, removed foreign matter, and leveled the extrusion amount. After that, in a feed block installed on the top of the T die, the layers are laminated so that the thickness ratio of B layer / A layer / B layer becomes 1/8/1, and the temperature is controlled to 25 ° C. from the T die. Were discharged into a sheet. At that time, a wire-like electrode having a diameter of 0.1 mm was applied electrostatically and adhered to the cooling drum to obtain an unstretched film. Next, before stretching in the longitudinal direction, the film temperature was raised with a heating roll, the preheating temperature was 90 ° C., the stretching temperature was 95 ° C., and the metal was stretched 3.3 times in the longitudinal direction and immediately temperature controlled to 40 ° C. Cooled with a roll. Thereafter, a corona discharge treatment was performed, and a release layer forming solution (aqueous dispersion) having the composition shown in the table was applied using a metalling bar so that the wet thickness was 13.5 μm. Next, the film was stretched 3.5 times in the width direction at a pre-heating first half temperature (lateral stretching preheating temperature 1) of 100 ° C., a preheating second half temperature (lateral stretching preheating temperature 2) of 130 ° C. and a stretching temperature of 150 ° C. Heat treatment was performed for 8 hours at 230 ° C. while relaxing 4% in the width direction in the tenter to obtain a release film having a film thickness of 50 μm.

  This release film had a release layer surface RSm of 67 μm, high peel stability and heat resistance, and excellent moldability. Therefore, the release film had characteristics particularly suitable for simultaneous molding applications.

(Example 2)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 1.

  This release film had an RSm of 68 μm on the surface of the release layer, exhibited high release stability and heat resistance, and was excellent in moldability, and thus had characteristics particularly suitable for use in simultaneous molding transfer.

Example 3
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 1.

  This release film had an RSm of 75 μm on the surface of the release layer, and exhibited high heat resistance due to the increased melamine resin concentration, but the RSk at the time of 2-fold elongation was reduced to 0.61. However, the film had sufficient characteristics as a release film.

Example 4
A release film was obtained in the same manner as in Example 1 except that the film forming conditions were as shown in Table 1.

  The release film had an RSm of 50 μm on the surface of the release layer, and a decrease in heat resistance and a decrease in RSk were observed due to the lower heat treatment temperature. However, the release film had sufficient characteristics as a release film. Indicated. In addition, since the release film is also excellent in moldability, it has characteristics particularly suitable for use in simultaneous molding and transfer.

(Example 5)
A release film was obtained in the same manner as in Example 1 except that the film forming conditions were as shown in Table 1.

  This release film had an RSm of 70 μm on the surface of the release layer, and exhibited high heat resistance by increasing the heat treatment temperature. In addition, since the release film is also excellent in moldability, it has characteristics particularly suitable for use in simultaneous molding and transfer.

(Example 6)
A release film was obtained in the same manner as in Example 1 except that the thickness of the release layer was as shown in Table 1.

  This release film had an RSm of 75 μm on the surface of the release layer, and a decrease in heat resistance due to a decrease in the thickness of the release layer was observed. However, the release film exhibited sufficient characteristics as a release film. . In addition, since the release film is also excellent in moldability, it has characteristics particularly suitable for use in simultaneous molding and transfer.

(Example 7)
A release film was obtained in the same manner as in Example 1 except that the thickness of the release layer was as shown in Table 1.

  This release film had an RSm of 77 μm on the surface of the release layer, and exhibited high heat resistance due to the increased thickness of the release layer. In addition, since the release film is also excellent in moldability, it has characteristics particularly suitable for use in simultaneous molding and transfer.

(Example 8)
A release film was obtained in the same manner as in Example 1 except that the thickness of the release layer was as shown in Table 1.

  This release film had an RSm of 73 μm on the surface of the release layer, exhibited high peel stability and heat resistance, and was excellent in moldability, and therefore had characteristics particularly suitable for simultaneous molding transfer applications.

Example 9
A release film was obtained in the same manner as in Example 1 except that the film forming conditions were as shown in Table 1.

  The release film had an RSm of 50 μm on the surface of the release layer, and it was confirmed that the release film was embrittled by extending the heat treatment time. However, since the film is excellent in releasability and heat resistance and exhibits high moldability, it has characteristics particularly suitable for simultaneous molding applications.

(Example 10)
A release film was obtained in the same manner as in Example 1 except that the film forming conditions were as shown in Table 1.

  This release film had an RSm of 55 μm on the surface of the release layer, and whitening due to a longer heat treatment time was confirmed. However, since the film is excellent in releasability and heat resistance and exhibits high moldability, it has characteristics particularly suitable for simultaneous molding applications.

(Example 11)
A release film was obtained in the same manner as in Example 1 except that the film forming conditions were as shown in Table 1.

  This release film had an RSm of 52 μm on the surface of the release layer, was excellent in heat resistance and release properties, and had characteristics suitable as a release film. However, an increase in molding stress due to shortening of the heat treatment time was confirmed.

(Example 12)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 2.

  This release film had an RSm of 52 μm on the surface of the release layer, was excellent in heat resistance and release properties, and had characteristics suitable as a release film. However, due to the decrease in RSk due to the addition of particles to the release layer and the RSk at the time of 2-fold elongation, the releasability after molding and stretching was lowered.

(Example 13)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the base film and the release layer forming solution was as shown in Table 2.

  This release film had an RSm of 66 μm on the surface of the release layer, was excellent in heat resistance and release properties, and had characteristics suitable as a release film. However, due to the decrease in RSk due to the addition of particles to the release layer and the RSk at the time of 2-fold elongation, the release property after molding and stretching was slightly lowered, but the film was useful as a release film.

(Example 14)
A release film was obtained in the same manner as in Example 1 except that the composition of the base film was as shown in Table 2.

  This release film had an RSm of 72 μm on the surface of the release layer, exhibited high peel stability and heat resistance, and was excellent in moldability, and thus had characteristics particularly suitable for use in simultaneous molding transfer.

(Example 15)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 2.

  This release film had an RSm of 68 μm on the surface of the release layer, exhibited high peel stability, and was excellent in moldability, and thus had characteristics particularly suitable for molding simultaneous transfer applications.

(Example 16)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 2.

  This release film had an RSm of 54 μm on the surface of the release layer, exhibited high peel stability and excellent moldability, and therefore had characteristics particularly suitable for molding simultaneous transfer applications.

(Example 17)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 2.

  This release film had an RSm of 45 μm on the surface of the release layer, high peel stability, and excellent moldability. Therefore, the release film had characteristics particularly suitable for molding simultaneous transfer applications.

(Example 18)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 2.

  This release film had an RSm of 45 μm on the surface of the release layer, high peel stability, and excellent moldability. Therefore, the release film had characteristics particularly suitable for molding simultaneous transfer applications.

(Example 19)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 2.

  This release film had an RSm of 73 μm on the surface of the release layer, and exhibited high heat resistance due to the high glass transition temperature of the binder polymer. Moreover, since it was excellent in moldability, it had characteristics suitable for use in simultaneous molding and transfer.

(Example 20)
A release film was obtained in the same manner as in Example 1 except that the composition of the base film was as shown in Table 2.

  This release film had an RSm of 78 μm on the surface of the release layer, and had sufficient characteristics as a release film.

(Example 21)
The base film was a single layer film (configuration only of the A layer).

  The polyester chip α and the particle master M were each dried at 180 ° C. for 4 hours in a vacuum dryer to sufficiently remove moisture. Thereafter, layer A was blended at a mass ratio of polyester chip α: particle master M = 50: 50. This blended raw material is supplied to a single screw extruder, melted at 275 ° C, passed through a filter and gear pump, removed foreign matter, and the amount of extrusion was leveled. Were discharged into a sheet. At that time, a wire-like electrode having a diameter of 0.1 mm was applied electrostatically and adhered to the cooling drum to obtain an unstretched film. Thereafter, a release film was obtained in the same manner as in Example 1.

  This release film had an RSm of 44 μm on the surface of the release layer, exhibited high release properties and heat resistance, and had sufficient characteristics as a release film. However, since the molding stress is high, it is somewhat unsuitable for applications in which molding is simultaneously transferred to a deep mold.

(Comparative Example 1)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 3.

  This release film has an RSm of 72 μm on the surface of the release layer. However, since the release layer has a low melamine resin concentration, the release film has insufficient heat resistance and is not suitable for use in a release film requiring heat resistance. It was.

(Comparative Example 2)
A release film was obtained in the same manner as in Example 1 except that the composition of the solid content in the release layer forming solution was as shown in Table 3.

  This release film has an RSm of 77 μm on the surface of the release layer, but since the melamine resin concentration in the release layer is low, the heat resistance and the release properties are not sufficient, and the release film requires heat resistance. It was unsuitable for.

(Comparative Example 3)
A release film was obtained in the same manner as in Example 1 except that the film forming conditions were as shown in Table 3.

  This release film has a large RSm of 130 μm on the surface of the release layer, has insufficient heat resistance and release properties, and is not suitable for use as a release film requiring heat resistance.

(Comparative Example 4)
A release film was obtained in the same manner as in Example 1 except that the film forming conditions were as shown in Table 3.

  This release film had a large RSm of 112 μm on the surface of the release layer, and was not suitable for use as a release film requiring heat resistance.

(Comparative Example 5)
A release film was obtained in the same manner as in Example 1 except that the film forming conditions were as shown in Table 3.

  This release film has a large RSm of 91 μm on the surface of the release layer, has insufficient release properties, and is not suitable for use as a release film.

(Comparative Example 6)
A release film was obtained in the same manner as in Example 1 except that the thickness of the release layer was as shown in Table 3.

  This release film had a large RSm of 108 μm on the surface of the release layer, had insufficient release properties, and was unsuitable for use as a release film.

(Comparative Example 7)
A release film was obtained in the same manner as in Example 1 except that the thickness of the release layer was as shown in Table 3.

  This release film had an RSm of 78 μm on the surface of the release layer and a thickness of the release layer as small as 0.012 μm, resulting in variations in release properties and was unsuitable for use as a release film.

(Comparative Example 8)
The base film was a three-layer laminated film (B layer / A layer / B layer).
Polyester chip α, polyester chip β and particle master M are each dried in a vacuum dryer at 180 ° C. for 4 hours, and after sufficiently removing water, layer A has a mass ratio of polyester chip α: polyester chip β = 60: 40 The B layer is blended at a mass ratio of polyester chip α: polyester chip β: particle master M = 88: 10: 2, fed to separate single-screw extruders, melted at 275 ° C., and separately. After removing the foreign matter and leveling the amount of extrusion through the filter and gear pump, the B / A / B thickness ratio is 1/8 in the feed block installed on the top of the T-die. After being laminated so as to be / 1, the sheet was discharged from a T-die onto a cooling drum whose temperature was controlled at 25 ° C. At that time, a wire-like electrode having a diameter of 0.1 mm was applied electrostatically and adhered to the cooling drum to obtain an unstretched film. Next, the film was stretched 3.5 times in the width direction at a preheating temperature of 80 ° C. and a stretching temperature of 90 ° C. with a tenter-type transverse stretching machine, and the temperature was maintained at 230 ° C. for 5 seconds while relaxing 4% in the width direction. Heat treatment was performed to obtain a biaxially oriented polyester film having a film thickness of 50 μm as a base film.
The release layer composition shown in Table 3 was applied to the drum surface of the base film by a gravure coating method and dried in an oven at 180 ° C. for 20 seconds to obtain a release film. The release film had a large RSm of 144 μm, and both heat resistance and releasability were insufficient, and the flatness was greatly deteriorated, so that it was not suitable for use as a release film.

Abbreviations in the table are as follows.
α: Polyester chip α
β: Polyester chip β
M: Particle master M
Binder I: Binder resin I
Binder II: Binder resin II

  The release film of the present invention has a high heat resistance of the release layer, and is therefore suitable for applications requiring high-temperature processing such as simultaneous molding transfer applications and hot press processes. Further, even after the release film is stretched, stable peeling force and heat resistance are exhibited, so that when used for simultaneous molding transfer, deeper simultaneous molding transfer becomes possible.

1: Roughness curve

Claims (8)

A release film having a release layer on at least one surface of a base film, wherein an average length RSm of roughness curve elements on the surface of the release layer is 10 μm or more and 80 μm or less. The release film according to claim 1, wherein the resin constituting the release layer contains 50% by mass or more of the melamine resin with respect to the entire resin constituting the release layer. The release film according to claim 1 or 2, wherein a skewness RSk of the release layer surface is 0.9 or more and 4.0 or less. The release film according to any one of claims 1 to 3, wherein an average of the skewness RSk after being stretched twice is 0.9 or more and 4.0 or less. The release film in any one of Claims 1-4 whose thickness of a release layer is 0.02 micrometer or more and less than 0.1 micrometer. The release film according to any one of claims 1 to 5, wherein a static friction coefficient on the surface of the release layer is 1.2 or less. The release film according to any one of claims 1 to 6, wherein a stress in a longitudinal direction and a width direction at 2 times elongation at 150 ° C is 5 to 75 MPa. The release film according to any one of claims 1 to 7, which is used for molding simultaneous transfer applications.

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