Release film, release film with adhesive layer, and film laminate

Abstract

To provide a release film that can suppress irregularity on a surface of an adhesive layer to smoothen and has an excellent light detachability.SOLUTION: A release film, which comprises a release layer on one side of a substrate film, with the elastic modulus of the release layer being 1.4 MPa or less, is press-processed under the pressure of 1 MPa for 1 hour, and then the release layer is attached with an acrylic adhesive tape, cut into a 50 mm×300 mm size, heat-held for 1 hour in a hot-wind oven at 100°C (setting temperature), and settled for 1 hour at 23°C with 50%RH. As a result, 180-degree peel force under a tension rate of 300 mm / min is 15 mN / cm or less.

Description

[Technical Field]

[0001] The present invention relates to a release film, a release film with an adhesive layer, and a film laminate. [Background technology]

[0002] One example of a method for manufacturing a liquid crystal display device used as an image display device such as a liquid crystal television, computer display, mobile phone, or digital camera is to use a release film with an adhesive layer, i.e., a release film with an adhesive layer formed by laminating a base film on one side of an adhesive layer via a release layer, and then attaching the adhesive layer to a polarizing plate to produce a polarizing plate with an adhesive layer.When attaching the polarizing plate to a liquid crystal cell, the base film (release film) with the release layer is peeled off and the adhesive layer and the glass substrate of the liquid crystal cell are attached to each other.

[0003] In recent years, as displays have become larger, the dimensions of optical components such as polarizing plates and release films have also increased, and the release films used in the manufacture of the above-mentioned liquid crystal display devices are now required to have the property of being easily peelable even when the peeling area is large. Silicone is a material with excellent peelability (also known as "easy peelability"), due to the flexibility of the siloxane skeleton and the low surface energy of methyl group substitution. For this reason, release films with a release layer formed by curing a heat-curable / UV-curable silicone-based release agent whose main component is silicone resin have been attracting attention as release films for protecting adhesives used to bond components that make up optical components, such as liquid crystal displays.

[0004] Regarding release films having a release layer containing silicone as a main component resin, for example, Patent Document 1 discloses a release film that has easy peeling properties, excellent retention during storage, and excellent resistance to atmospheric exposure and non-migration. The release film is a polyester film coated on at least one side with a paint containing curable silicone as a main component resin, and the paint contains solvent-curable silicone, solventless curable silicone, and a reactive heavy release adjuster as main components, and the ratio of SiH groups to vinyl groups in the paint is within a specific range.

[0005] Patent Document 2 discloses a release film characterized by having a silicone-based release layer formed on one side of a polyester film from a coating liquid containing a reactive silicone resin having hexenyl groups, vinyl groups, phenyl groups, and hydrosilyl groups as functional groups, a non-reactive silicone resin having a mass average molecular weight of 50,000 to 100,000, and a platinum-based catalyst.

[0006] Patent Document 3 discloses a release film having a release layer on at least one side of a polyester film, characterized in that the composition forming the release layer contains a curable silicone (A) having a number average molecular weight of 50,000 or more and a curable silicone (B) having a number average molecular weight of 30,000 or less, the curable silicone (B) having a T unit structure, and the content of T unit structures in the polysiloxane chain of the curable silicone (B) is 3 mol % or more in siloxane units.

[0007] Optical components such as polarizing plates and touch sensors are sometimes distributed in a laminated state of an adhesive layer and a release film. For example, an optical component may be distributed in a state in which a protective film is releasably laminated on one side thereof via a light adhesive layer, and a release film with an adhesive layer is laminated on the other side thereof, i.e., in a state of release film / adhesive layer / optical film / light adhesive layer / protective film. In this case, if the peeling force when peeling the release film from the adhesive layer is greater than the adhesion force between the optical component and the light adhesive layer, the protective film may peel off first, which is known as the "sad separation phenomenon." Therefore, release films with adhesive layers used for optical applications are required to have excellent light peeling properties, so that they can be peeled off with even less force.

[0008] Furthermore, in the past, even if the adhesive layer surface (also simply referred to as the "adhesive layer surface") of a release film with an adhesive layer had some unevenness on the side not in contact with the release film, i.e., the side opposite the release film, this was not a problem because the adhesive layer surface was bonded to the optical component. However, in recent years, as components have become thinner and quality requirements regarding optical properties have increased, the unevenness of the adhesive layer surface of release films with an adhesive layer has become an issue. In other words, if the adhesive layer surface is uneven, distortion occurs at the interface between the adhesive layer and the optical component when the film is bonded to the optical component, and this distortion can cause light scattering, which can interfere with accurate optical inspection. Therefore, with respect to a release film with an adhesive layer, the surface of the adhesive layer on the side not in contact with the release film is required to be smooth with few irregularities. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-214359 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-188265 [Patent Document 3] Japanese Patent Application Publication No. 2020-108937 Summary of the Invention [Problem to be solved by the invention]

[0010] The present inventors have investigated the causes of unevenness on the surface of the adhesive layer on the side not in contact with the release film, i.e., the side opposite the release film, of a release film with an adhesive layer, and have found that the unevenness is formed on the surface of the adhesive layer mainly for two reasons due to the interaction between the release layer and the adhesive layer. That is, the inventors have found that if the surface of the release layer is uneven, this can affect the unevenness on the surface of the adhesive layer, and that if an incompatible component elutes from the release layer to the adhesive layer side, repelling can occur when the adhesive layer composition is applied, or the incompatible component can penetrate into the adhesive layer to form a phase-separated structure, resulting in unevenness on the surface of the adhesive layer.

[0011] Therefore, the present invention relates to a release film and a release film with an adhesive layer, and aims to provide a new release film that can suppress unevenness on the adhesive layer surface to make it smooth, while also having excellent easy peelability, as well as a new release film with an adhesive layer and a film laminate using the same. [Means for solving the problem]

[0012] The present invention provides a release film having a release layer on one side of a base film, The release film proposed has an elastic modulus of 1.4 MPa or less, and after the release film is pressed under a pressure of 1 MPa for 1 hour, an acrylic adhesive tape is attached to the release layer, the tape is cut to a size of 50 mm x 300 mm, and the tape is heated and held at 100°C (set temperature) for 1 hour in a hot air oven, and then allowed to stand at 23°C and 50% RH for 1 hour. The 180° peel force is 15 mN / cm or less at a tensile speed of 300 mm / min.

[0013] The present invention also proposes a release film having a release layer formed on one side of a substrate film by curing a release layer composition. In this case, the release layer composition proposed is a release layer composition whose main component is a curable silicone resin having a number average molecular weight (Mn) of 20,000 or more and 350,000 or less, or a release layer composition containing 0.01 to 5.0 mol% of phenyl groups relative to the total siloxane components.

[0014] The present invention also proposes a release film with an adhesive layer, which has a configuration in which an adhesive layer is laminated on the release layer of the release film.

[0015] The present invention further proposes a film laminate having a configuration in which an optical member is bonded to the surface of the adhesive layer of the release film with an adhesive layer. [Effects of the Invention]

[0016] The release film, adhesive layer-attached release film, and film laminate proposed by the present invention not only have excellent light releasability, but also suppress unevenness on the adhesive layer surface to obtain excellent smoothness. Therefore, the release film, adhesive layer-attached release film, and film laminate proposed by the present invention can be suitably used particularly for optical applications. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a graph obtained by plotting the relationship between the elastic modulus of the release surface of the release films (sample films) obtained in Reference Examples 1 to 3 and the coating thickness (after drying) and fitting the relationship using logarithmic transformation and power approximation of linear regression. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, an example of an embodiment of the present invention will be described, but the present invention is not limited to the embodiment described below.

[0019] <<<This release film>>> A release film according to one embodiment of the present invention (referred to as "this release film") is a release film having a release layer (referred to as "this release layer") on at least one side of a base film (referred to as "this base film").

[0020] The present release film only needs to have the present release layer on one side of the present base film, and as will be described later, may have other layers between the present base film and the present release layer.

[0021] <<This base film>> The material of the present substrate film is not particularly limited as long as it is in the form of a film. For example, it may be made of paper, resin, metal, etc. Among these, resin is preferred from the viewpoint of mechanical strength and flexibility.

[0022] Examples of the resin substrate film include films formed from polymers such as polyethylene, polypropylene, polyester, polystyrene, polycarbonate, polyethersulfone, polyamide, polyimide, etc. Furthermore, as long as they can be formed into a film, mixtures of these materials (polymer blends) or composites of structural units (copolymers) may also be used.

[0023] Among the films exemplified above, polyester films are particularly preferred because they have excellent physical properties such as heat resistance, flatness, optical properties, and strength. The polyester film may be a single layer or a multilayer film (laminated film) having two or more layers with different properties. The polyester film may be a non-stretched film (sheet) or a stretched film. Among these, a uniaxially or biaxially stretched film is preferred. Among these, a biaxially stretched film is more preferred from the viewpoints of balance of mechanical properties and flatness.

[0024] The polyester that is the main component resin of the polyester film may be either a homopolyester or a copolymer polyester. The term "main component resin" refers to the resin with the largest mass proportion among the resins constituting the polyester film, and is expected to account for 50 mass% or more, 75 mass% or more, 90 mass% or more, or 100 mass% of the resins constituting the polyester film.

[0025] The homopolyester is preferably one obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol, such as terephthalic acid or 2,6-naphthalenedicarboxylic acid, and such as ethylene glycol, diethylene glycol, 1,4-butanediol, or 1,4-cyclohexanedimethanol, as the aromatic dicarboxylic acid and such as terephthalic acid or 2,6-naphthalenedicarboxylic acid, as the aliphatic glycol. Representative examples of homopolyester include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT).

[0026] On the other hand, when the polyester is a copolymer polyester, it is preferable that the copolymer contains 30 mol % or less of a third component. Examples of the dicarboxylic acid component of the copolymer polyester include one or more of isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, etc. On the other hand, examples of the glycol component of the copolymer polyester include one or more of ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, etc.

[0027] Among these, polyethylene terephthalate containing ethylene terephthalate units at 60 mol % or more, preferably 80 mol % or more, is preferred for the present substrate film.

[0028] The present substrate film may contain particles, mainly for the purposes of imparting easy slipperiness and preventing scratches during each process. When particles are blended, the type of particles to be blended is not particularly limited as long as they are particles that can impart lubricity, and examples thereof include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenolic resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

[0029] The shape of the particles is not particularly limited. For example, it may be spherical, lumpy, rod-like, flat, or the like. Furthermore, there are no particular limitations on the hardness, specific gravity, color, and the like of the particles. Furthermore, two or more types of particles with different physical properties may be used in combination, as needed.

[0030] The average particle size of the particles is preferably 0.1 μm to 5 μm, more preferably 0.5 μm to 4 μm, and even more preferably 1 μm to 4 μm. By using particles with such an average particle size, an appropriate surface roughness can be imparted to the film, ensuring good slipperiness and smoothness.

[0031] Regarding the particle content in the present base film, if there are no particles or if there are only a few particles, the film will have high transparency but may have insufficient slipperiness. On the other hand, if the particle content is too high, the film may have insufficient transparency. From this perspective, the particle content in the present base film is preferably 5% by mass or less, and more preferably 0.1% by mass or more or 3% by mass or less. In applications requiring a high level of inspection, the transfer of convex shapes resulting from particles present on the surface of the substrate film to the adhesive layer can be a problem. Therefore, to prevent the particles from interfering with the inspection, it may be preferable to configure at least one or both surfaces of the substrate film to be particle-free. Alternatively, the amount of particles on the surface in contact with the adhesive layer can be reduced or the particle diameter can be reduced to smooth that surface, while the surface roughness of the opposite surface can be increased, thereby creating a configuration in which the amount or diameter of particles on the front and back surfaces are different from each other.

[0032] <<Main release layer>> This release layer is a layer formed by curing a release layer composition (referred to as "this release layer composition") whose main component resin is a curable silicone resin ("this curable silicone resin"), and is arranged on at least one side of this substrate film. The present release layer can also be said to be a release layer containing a cured product obtained by curing the present release layer composition.

[0033] <This release layer composition> The release layer composition may be any composition containing a curable silicone resin as a main component resin. The release layer composition may contain components other than the curable silicone resin, and may contain, as necessary, for example, catalysts, reaction control agents, crosslinking agents, polymerization initiators, particles, diluents, and other additives.

[0034] In addition, the above-mentioned "main component resin" means the resin with the largest mass proportion among the resins constituting the present release layer composition, and is expected to account for 50 mass% or more, 75 mass% or more, 90 mass% or more, or 100 mass% of the resins constituting the present release layer composition.

[0035] The release layer composition or the release layer preferably contains 0.01 to 5.0 mol % of phenyl groups relative to the total amount of siloxane components, that is, the total amount of siloxane components contained in the release layer composition or the release layer. By containing a predetermined amount of phenyl groups, the release layer composition or the release layer can cover alkenyl groups (e.g., vinyl groups, hexenyl groups) or Si-H groups that may remain on the surface of the release layer, thereby reducing the interaction between the release layer and the adhesive layer and expected to provide an even easier peeling effect. From this viewpoint, it is preferable that the present release layer composition or the present release layer contains 0.01 to 5.0 mol% of phenyl groups relative to the total amount of siloxane components, and more preferably, 0.05 mol% or more or 4.0 mol% or less, of which 0.1 mol% or more or 3.0 mol% or less, and of which 0.2 mol% or more or 2.0 mol% or less of phenyl groups.

[0036] To ensure that the release layer composition or the release layer contains phenyl groups in the above proportion, a curable silicone resin containing a predetermined proportion of phenyl groups may be used. However, this method is not limited to this. For example, a compound containing phenyl groups, such as a non-curable silicone resin or a silane compound having phenyl groups, may be added.

[0037] Furthermore, if the amount of alkenyl groups, i.e., residual functional groups with double bonds such as hexenyl groups and vinyl groups, is small relative to the total amount of siloxane components, the release layer may not cure sufficiently, while if the amount of alkenyl groups is excessive, the peel strength after exposure to air tends to be strong. For this reason, the release layer composition and the release layer preferably contain 0.4 to 1.0 mol% of alkenyl groups relative to the total amount of siloxane components, and particularly preferably contain 0.5 mol% or more or 0.9 mol% or less, and even more preferably 0.6 mol% or more or 0.8 mol% or less of alkenyl groups. Furthermore, if the amount of Si-H groups in the release layer composition or the release layer is too small relative to the total amount of siloxane components, the release layer will not cure sufficiently, while if the amount of Si-H groups is too large, the remaining Si-H groups may react with the adhesive layer, affecting the release film's peel strength. For this reason, the release layer composition or the release layer preferably contains 0.8 to 2.2 mol% of Si-H groups relative to the total amount of siloxane components, and particularly preferably contains 1.2 mol% or more or 2.1 mol% or less, and particularly preferably 1.4 mol% or more or 2.0 mol% or less of Si-H groups.

[0038] The total siloxane content in the release layer composition or the release layer can be measured, for example, by 1H-NMR from the integral ratio of the main chain dimethylsiloxane unit to other units, and the phenyl group content, alkenyl group content, and Si-H group content can also be evaluated, for example, by measuring 1H-NMR, although the methods are not limited to these.

[0039] <Fully cured silicone resin> In the present invention, the term "curable silicone resin" refers to a silicone resin that has the property of being able to be cured. This also includes silicone resins that can be cured by mixing a crosslinking agent in advance. The curing method of the curable silicone resin is optional, and may be, for example, a resin that cures by a condensation reaction in response to moisture in the air, a resin that cures by an addition reaction caused by heating, or a resin that cures by addition polymerization or radical polymerization caused by light. Among these, thermosetting silicone resins that cure by an addition reaction caused by heating are preferred, since they do not produce by-products in the curing reaction and the physical properties of the cured film are stable. When the present curable silicone resin is a thermosetting type, it is preferable that an alkenyl group such as a vinyl group (Vi group) or a hexenyl group is introduced into the side chain and / or terminal of the main chain consisting of siloxane bonds in the structure.

[0040] The present curable silicone resin may be any polymer having a main chain of siloxane bonds consisting of silicon and oxygen. Examples of the present curable silicone resin include those in which various substituents have been introduced into the side chains or terminals of the main chain consisting of siloxane bonds, such as methyl groups, phenyl groups, polyethers, epoxy groups, amines, carboxyl groups, aralkyl groups, and the like, or combinations of two or more of these groups.

[0041] As an example of a method for ensuring that the present release layer composition or the present release layer contains phenyl groups in a predetermined proportion, an example can be given of using a present curable silicone resin containing 0.01 to 5.0 mol% of phenyl groups, particularly 0.05 mol% or more or 4.0 mol% or less, of which 0.1 mol% or more or 3.0 mol% or less, and of which 0.2 mol% or more or 2.0 mol% or less of phenyl groups. In this case, the molar ratio of phenyl groups to methyl groups (phenyl / methyl) in the present curable silicone resin is more preferably 0.0001 to 0.05, and more preferably 0.0005 or more or 0.04 or less, more preferably 0.001 or more or 0.03 or less, and even more preferably 0.02 or more or 0.02 or less.

[0042] An example of the present curable silicone resin is a silicone resin in which one or more of a phenyl group, a Si-H group (also simply referred to as an "H group"), and an alkenyl group have been introduced into a side chain or terminal of a linear main chain consisting of siloxane bonds. In this case, the phenyl group content in the present curable silicone resin is preferably 0.01 to 5.0 mol%, more preferably 0.05 mol% or more or 4.0 mol% or less, even more preferably 0.1 mol% or more or 3.0 mol% or less, and even more preferably 0.2 mol% or more or 2.0 mol% or less. In this case, the Si-H group content in the present curable silicone resin is preferably 0.8 to 2.2 mol %, more preferably 1.2 mol % or more or 2.1 mol % or less, and even more preferably 1.4 mol % or more or 2.0 mol % or less. Similarly, in this case, the vinyl group content in the present curable silicone resin is preferably 0.4 to 1.0 mol %, more preferably 0.4 mol % or more or 1.0 mol % or less, and even more preferably 0.6 mol % or more or 0.9 mol % or less.

[0043] The present curable silicone resin may be a combination of two or more curable silicone resins. In this case, the content of each of the above-mentioned functional groups is preferably within the above-mentioned range, on average, for the two or more curable silicone resins.

[0044] The number average molecular weight (Mn) of the present curable silicone resin is preferably 20,000 or more and 350,000 or less. If the number-average molecular weight (Mn) of the curable silicone resin is too low, when an adhesive layer is laminated on the release film, a large amount of the low-molecular-weight silicone resin will leach out or migrate into the adhesive layer, which is undesirable. Even if the release layer is applied thickly, the release layer tends to have a poor release-light effect. On the other hand, if the number-average molecular weight (Mn) of the curable silicone resin is too high, the viscosity increases, reducing the fluidity of the release layer composition. This results in streaky coating unevenness when the release layer composition is applied, making it difficult to smooth the surface of the release layer, which is undesirable. From this perspective, the number average molecular weight (Mn) of the present curable silicone resin is preferably 20,000 or more, more preferably 50,000 or more, even more preferably 100,000 or more, and even more preferably 150,000 or more. On the other hand, it is preferably 350,000 or less, even more preferably 300,000 or less, and even more preferably 250,000 or less.

[0045] From the same viewpoint, the mass average molecular weight (Mw) of the present curable silicone resin is preferably 35,000 to 600,000, more preferably 50,000 or more or 500,000 or less, even more preferably 100,000 or more or 450,000 or less, and even more preferably 120,000 or more.

[0046] The curable silicone resin preferably has a ratio (Mw / Mn) of the mass average molecular weight (Mw) to the number average molecular weight (Mn) of 1.7 to 2.7, more preferably 1.9 or more or 2.5 or less. By satisfying this range, it is expected that the crosslinking reaction will proceed efficiently.

[0047] The present curable silicone resin may be a combination of two or more types of curable silicone resins, in which case it is preferable that the average molecular weight of the two or more types of curable silicone resins is within the above range.

[0048] The present curable silicone resin preferably has a viscosity of 10 to 400 mcps at 25° C. when diluted with n-heptane solvent to adjust the content to 15 mass %. If the viscosity of the present curable silicone resin is 10 mcps or more, the appropriate viscosity of the coating solution suppresses repelling and provides a good coating appearance, which is preferable. On the other hand, if the viscosity is 400 mcps or less, the fluidity of the present release layer composition can be maintained, the occurrence of streaky coating unevenness can be suppressed when the present release layer composition is applied, and the surface of the present release layer can be made smooth, which is preferable. From this perspective, the viscosity of the present curable silicone resin is more preferably 40 mcps or more, more preferably 80 mcps or more, and more preferably 300 mcps or less, more preferably 200 mcps or less.

[0049] The present curable silicone resin may be either a solventless curable silicone or a solvent curable silicone, or a combination of both. Here, "solventless curable silicone" refers to a silicone with a viscosity that allows it to be applied without diluting it with a solvent, and is made up of short polysiloxane chains and has a relatively low molecular weight. On the other hand, "solvent-curable silicone" is a silicone that is so viscous that it cannot be applied without being diluted with a solvent, and has a relatively high molecular weight compared to solventless-curable silicone. In particular, it is preferable that the present curable silicone resin has a medium number average molecular weight (Mn) and a medium viscosity, as described above, and furthermore, it is preferable that it is a solvent-type curable silicone, from the viewpoints of providing good adhesion to the present substrate film, good coating appearance (evenness), and ease of adjusting the film thickness of the present release layer.

[0050] <Other ingredients> As described above, in addition to the present curable silicone resin, the present release layer composition may contain, as necessary, for example, a curing catalyst, particles, a diluting solvent, a reaction control agent, a crosslinking agent, a polymerization initiator, an adhesion promoter, and other additives. For example, one example of the release layer composition of the present invention is a composition containing the present curable silicone resin, a crosslinking agent having a hydrosilyl group (SiH group) on the side chain and / or end of a main chain consisting of a siloxane bond, a catalyst containing platinum (Pt), and a solvent.

[0051] (catalyst) The release layer composition may optionally contain a curing catalyst, i.e., a catalyst for promoting the hydrosilylation addition reaction between the alkenyl group bonded to the silicon atom of the curable silicone and the hydrogen silane (SiH) group of the silicone crosslinker. Examples of the curing catalyst include, but are not limited to, platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid with monohydric alcohols, complexes of chloroplatinic acid with olefins, platinum-based catalysts such as platinum bisacetoacetate, palladium-based catalysts, and rhodium-based catalysts.

[0052] The content of the curing catalyst in the present release layer composition is preferably 0.5 to 500 ppm by mass, in terms of metal, relative to the present curable silicone, and more preferably 5 ppm by mass or more or 300 ppm by mass or less, and even more preferably 10 ppm by mass or more or 200 ppm by mass or less.

[0053] (Crosslinking agent) The crosslinking agent is preferably a crosslinking agent having a siloxane bond (also referred to as a "silicone crosslinking agent"). Among these, those having silicon-bonded hydrogen atoms (SiH groups) on the side chains and / or terminals of the main chain consisting of siloxane bonds are preferred.

[0054] For example, examples include those represented by the following general formula (1) having at least two, preferably three or more (usually about 3 to 200), more preferably 3 to 100, and particularly 3 to 50 silicon-bonded hydrogen atoms (SiH groups) in one molecule.

[0055] R b H c SiO (4-b-c) / 2 (1)

[0056] In formula (1), R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, b is 0.7 to 2.1, particularly 0.8 to 2.0, c is 0.001 to 1.0, and b+c is a positive number that satisfies the range of 0.8 to 3.0, particularly 1.0 to 2.5.

[0057] Here, examples of R include the same groups as R in the alkenyl group-containing organopolysiloxane, but preferably those that do not have an aliphatic unsaturated bond such as an alkenyl group.

[0058] The silicon-bonded hydrogen atoms may be bonded to silicon atoms at the ends of the molecular chain, or to silicon atoms in the middle of the molecular chain (non-ends of the molecular chain), or to both.

[0059] The molecular structure of the silicone crosslinking agent may be any of a linear, cyclic, branched, and three-dimensional network structure. Furthermore, the number of silicon atoms (or degree of polymerization) in one molecule is preferably 2 to 1,000, more preferably 3 or more and 500 or less, even more preferably 3 or more and 300 or less, and even more preferably 4 or more and 150 or less.

[0060] Examples of silicone crosslinking agents include tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, methylhydrogenpolysiloxane capped at both ends with trimethylsiloxy groups, and dimethylsiloxane-methylhydrogensiloxane capped at both ends with trimethylsiloxy groups. copolymer, dimethylpolysiloxane capped at both ends with dimethylhydrogensiloxy groups, methylhydrogenpolysiloxane capped at both ends with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both ends with dimethylhydrogensiloxy groups, methylhydrogensiloxane-diphenylsiloxane copolymer capped at both ends with trimethylsiloxy groups, methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymer capped at both ends with trimethylsiloxy groups, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 A copolymer consisting of (CH3)2HSiO units 1 / 2 Units and SiO 4 / 2 Units and (C6H5)SiO 3 / 2 and copolymers consisting of these exemplified compounds in which some or all of the methyl groups have been substituted with other alkyl groups such as ethyl groups or propyl groups, or aryl groups such as phenyl groups, but are not limited to these.

[0061] (particle) The release layer composition may contain particles as needed to adjust the release force or to prevent blocking. In this case, the type of particle is not particularly limited as long as it is a particle that can impart the above-mentioned properties, and examples thereof include inorganic particles such as silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, and titanium oxide, and organic particles such as silicone resin, acrylic resin, styrene resin, urea resin, phenolic resin, epoxy resin, and benzoguanamine resin. Among these, it is preferable that the particles are made of silicone resin because of its good compatibility with the silicone resin that is the binder resin component.

[0062] The shape of the particles is not particularly limited, and may be, for example, spherical, blocky, rod-like, flat, or the like. Furthermore, there are no particular limitations on the hardness, specific gravity, color, etc. of the particles. Two or more types of these particles may be used in combination as needed.

[0063] (dilution solvent) The release layer composition may optionally contain a diluent solvent. Examples of the dilution solvent include aromatic hydrocarbons such as toluene, aliphatic hydrocarbons such as hexane, heptane, isooctane, esters such as ethyl acetate, butyl acetate, ketones such as ethyl methyl ketone (MEK), isobutyl methyl ketone, alcohols such as ethanol, 2-propanol, ethers such as diisopropyl ether, dibutyl ether, etc. These are preferably used alone or in combination, taking into consideration solubility, coatability, boiling point, etc.

[0064] (Reaction inhibitor) The release layer composition may optionally contain a reaction inhibitor. The reaction inhibitor may be, for example, acetylene alcohol. The reaction inhibitor may be used alone or in combination of two or more types, if necessary. The content of the reaction inhibitor is preferably 0.001 to 5.0 parts by mass per 100 parts by mass of the total amount of the release layer composition, and more preferably 0.01 part by mass or more or 1.0 part by mass or less, and even more preferably 0.05 part by mass or more or 0.5 part by mass or less.

[0065] <Release layer thickness> The thickness of the release layer is not particularly limited. A larger thickness of the release layer is preferable because it reduces the influence of the substrate film, for example, the hardness of the substrate film, on the release surface of the release film. From this perspective, the thickness of the release layer (after drying) is preferably 0.25 μm or more, more preferably 0.30 μm or more, and even more preferably 0.35 μm or more. On the other hand, if the thickness of the release layer is too thick, blocking may occur, the coating appearance may deteriorate, and so the thickness is preferably 2.0 μm or less, more preferably 1.5 μm or less, even more preferably 1.0 μm or less, and even more preferably 0.8 μm or less.

[0066] <<Other layers>> The present release film may have "another layer" between the present base film and the present release layer. Examples of the "other layer" include an anchor coat layer for increasing the adhesion between the substrate film and the release layer, as well as cured resin layers having various functions. The cured resin layer is a layer mainly composed of a cured resin, in other words, a resin having a crosslinked structure, and examples thereof include an oligomer sealing layer that seals out the bleed (or plate-out) of compounds or oligomers onto the film surface, and an antistatic layer that has antistatic properties, but is not limited to these.

[0067] <<Manufacturing method of this release film>> The present release film can be produced by forming a coating layer such as an antistatic layer or an oligomer sealing layer, as needed, on one or both sides of the present base film, and then applying the present release layer composition to these surfaces, drying, and curing the resulting film.

[0068] The release layer composition can be applied by any conventional coating method, such as multi-roll coating, reverse gravure coating, direct gravure coating, bar coating, die coating, etc. Examples of coating methods are described in "Coating Methods" (published by Maki Shoten, written by Harasaki Yuji in 1979).

[0069] Before applying the release layer composition, the polyester film may be subjected to a surface treatment such as a corona treatment or a plasma treatment.

[0070] The coating amount of the release layer composition, i.e., the thickness (after drying) of the release layer, is preferably thin from the viewpoint of preventing blocking and suppressing an increase in migration (i.e., the property of the release agent component migrating to the adhesive tape, etc.), while it is preferably thick from the viewpoint of maintaining easy releasability (low peel force). In consideration of this, the coating amount of the release layer composition, i.e., the thickness of the release layer (after drying) is 0.1 to 5.0 g / m 2 It is preferable that the density is 0.2 g / m 2 or more than 3.0g / m 2 Below, 0.3g / m 2 or more than 2.0g / m 2 More preferably, it is:

[0071] When the release layer composition is cured by heating, it may be heated using a conventionally known heat treatment device. Examples include a heating oven, a hot plate, a hot air dryer, a near-infrared lamp, and an air dryer. The heat treatment temperature is preferably 35 to 220°C, more preferably 40°C or higher or 200°C or lower, and even more preferably 50°C or higher or 180°C or lower. Furthermore, the heat treatment time is preferably 3 seconds to 3 minutes, more preferably 5 seconds or more or 2 minutes or less, and even more preferably 5 seconds or more or 1 minute or less.

[0072] On the other hand, when the release layer composition is cured by ultraviolet irradiation, the ultraviolet irradiation can be performed using a conventionally known ultraviolet irradiation device, and in this case, the light source can be, for example, a fusion (H) lamp, a metal halide lamp, a high-pressure mercury lamp (ozone-generating type or ozone-less type), a UV-LED, or the like.

[0073] The amount of ultraviolet light irradiation is not particularly limited. The amount of ultraviolet light irradiation is 10 to 3000 (mJ / cm) in terms of the cumulative light amount. 2 ), and above all, 50 (mJ / cm 2 ) or more than 2000 (mJ / cm 2 ) or less, and among them, 100 (mJ / cm 2 ) or more than 1500 (mJ / cm 2 ) or less is particularly preferred.

[0074] <<Physical properties of this release film>> The release film may have the following physical properties:

[0075] <Elastic modulus> The release layer in the release film preferably has an elastic modulus of 1.4 MPa or less. If the modulus of elasticity of the release layer is 1.4 MPa or less, the smoothness of the surface of the adhesive layer formed on the release layer can be improved. From this viewpoint, the elastic modulus of the release layer is preferably 1.4 MPa or less, more preferably 1.3 MPa or less, and even more preferably 1.1 MPa or less. On the other hand, with regard to the lower limit, from the viewpoint of the film strength of the release layer, it is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, more preferably 0.3 MPa or more, even more preferably 0.4 MPa or more, and particularly preferably 0.5 MPa or more.

[0076] <Adhesion energy> The adhesive energy of the release layer of this release film is 25 mJ / m 2 More than 39mJ / m 2 It is preferable that the value is less than 30 mJ / m 2 or more than 39mJ / m 2 It is more preferable that the concentration is 35 mJ / m or less, and especially 35 mJ / m 2 or more than 39mJ / m 2 It is more preferable that the value is 36 mJ / m or less, and more preferably 36 mJ / m or less. 2 or more than 38mJ / m 2 More preferably, it is: When the adhesion energy of this release layer satisfies the above range, the release layer forms a surface with moderate wettability, and even when an adhesive layer is formed on this release layer, incompatible components dissolve from the release layer to the adhesive layer side, thereby achieving easy peelability while suppressing the occurrence of repelling when applying the adhesive layer composition or the incompatible components penetrating into the adhesive layer to form a phase separation structure.

[0077] The adhesion energy and elastic modulus of this release layer can be calculated in accordance with the JKR two-point method based on the force curve obtained by attaching a silicon probe (manufactured by team nanotec, LRCH, radius of curvature: 250 nm, spring constant: 0.2 N / m) to an atomic force microscope (product name: SPM-9700HT, manufactured by Shimadzu Corporation) and tapping at 600 m / s.

[0078] <Heating peel strength (after pressing)> This release film preferably satisfies that the 180° peel strength (referred to as "peel strength after pressing (after heating)") under the condition of a tensile speed of 300 mm / min, which is measured using a tensile tester, for example, "EZgraph" manufactured by Shimadzu Corporation, is 15 mN / cm or less after the release film is press-treated under a pressure of 1 MPa for 1 hour, then one side of an acrylic adhesive tape, for example, No. 502 manufactured by Nitto Denko Corporation, is attached to the surface of the release layer of the release film, cut into a size of 50 mm × 300 mm, heated and held at 100 °C (set temperature) for 1 hour in a hot air oven, left standing at 23 °C and 50% RH for 1 hour, and then measured. Among these, it is more preferable to satisfy 14 mN / cm or less, and among these, 11 mN / cm or less is even more preferable. The above peel strength can be measured using, for example, a tensile tester ((株) Shimadzu Corporation "EZgraph"). However, it is not limited to such a tester.

[0079] <Peel strength after heating (without pressing)> This release film preferably satisfies that the peel strength when peeled at 180° under the condition of a tensile speed of 300 mm / min (referred to as "peel strength after heating (without pressing)"), which is estimated using a tensile tester, for example, "EZgraph" manufactured by Shimadzu Corporation, is 15 mN / cm or less after one side of an acrylic double-sided adhesive tape, for example, "No. 502" manufactured by Nitto Denko Corporation, is attached to the surface of the release layer of the release film, cut into a size of 50 mm × 300 mm, heated and held at 100 °C (set temperature) for 1 hour in this state in a hot air oven, then left standing at 23 °C and 50% RH for 1 hour. Among these, it is more preferable to satisfy 14 mN / cm or less, and among these, 11 mN / cm or less is even more preferable.

[0080] <Peel strength after heating of TESA7475 tape> The present release film is prepared by attaching an acrylic adhesive tape, such as "TESA7475" manufactured by Tesa, to the release layer surface of the release film, cutting it to a size of 25 mm x 300 mm, heating and holding it in this state at 100°C (set temperature) in a hot air oven for 1 hour, and then leaving it to stand at 23°C and 50% RH for 1 hour. Thereafter, the side of the sample opposite the release layer is fixed to a SUS plate with double-sided tape, and the peel force (referred to as "TESA7475 tape heat peel force") estimated using a tensile tester, such as "EZgraph" manufactured by Shimadzu Corporation, when peeled at 180° under conditions of a tensile speed of 300 mm / min is preferably 30 mN / cm or less, more preferably 25 mN / cm or less, and even more preferably 20 mN / cm or less.

[0081] The release film can be made even easier to peel by satisfying the above-mentioned heat peel force (after pressing) within the above range, and also satisfying the heat peel force (without pressing) or the TESA 7475 tape heat peel force, or both.

[0082] <Arithmetic mean height of surface (Sa)> In the present release film, there are no particular restrictions on the calculated average roughness (Sa, ISO 25178 surface quality) of the surface of the present release layer, the surface of the film not provided with the present release layer, or both of these surfaces, but from the viewpoint of the blocking resistance of the silicone layer in the present invention, the effects of the present invention are significantly achieved when the arithmetic average roughness Sa is 30 nm or less. It is known that as the calculated average roughness of the surface of the present release layer, the surface of the film not provided with the present release layer, or both of these surfaces decreases, blocking becomes more likely to occur, resulting in heavy peeling of the release layer and the generation of peel electrification when the rolled film is unwound. On the other hand, from the standpoint of transferring the uneven shape to the adhesive layer formed on the surface of this release layer and inspectability for optical applications, it is preferable if the calculated average roughness (Sa) of the surface of this release layer or the surface of a film on which this release layer is not provided is 30 nm or less, since the surface of the release layer is smooth. From this perspective, it is preferable that the calculated average roughness (Sa) of the surface of the release layer, or the surface of the film not having the release layer, or both of these surfaces, is 30 nm or less, more preferably 25 nm or less, and even more preferably 20 nm or less. The calculated average roughness (Sa) of the surface of the release layer or the surface of a film not provided with the release layer can be adjusted to the above range by adjusting the average particle size of the polyester film surface layer, the amount of particles added, the coating thickness of the release layer, etc. However, the present invention is not limited to such methods.

[0083] <<<Release film with adhesive layer>>> Using this release film, a release film with an adhesive layer (referred to as "the release film with the adhesive layer") can be produced, which has an adhesive layer (the "adhesive layer") on the release layer of the release film.

[0084] <<Main adhesive layer>> The present adhesive layer can be formed by applying an adhesive composition (hereinafter referred to as "the present adhesive composition") onto the present release film and curing it.

[0085] <Present Pressure-Sensitive Adhesive Composition> The present pressure-sensitive adhesive composition may be an acrylic pressure-sensitive adhesive composition containing an acrylic resin as the main component resin, a rubber-based pressure-sensitive adhesive composition containing rubber as the main component, a urethane-based pressure-sensitive adhesive composition containing a urethane resin as the main component, or a silicone-based pressure-sensitive adhesive composition containing a silicone resin as the main component. Among these, acrylic pressure-sensitive adhesive compositions containing an acrylic resin as the main component are preferred, as they allow the adhesive strength and peel strength to be adjusted in a well-balanced manner and are inexpensive.

[0086] The "main component resin" refers to the resin with the highest mass percentage among the resins constituting the present pressure-sensitive adhesive composition. For example, it refers to a component that accounts for 50 mass% or more, preferably 60 mass% or more, and more preferably 70 mass% or more of the total amount of resins constituting the present pressure-sensitive adhesive composition. The upper limit is usually 99.99 mass%.

[0087] In addition to the above-mentioned main components, the present pressure-sensitive adhesive composition may contain, as necessary, a crosslinking agent as described below, as well as conventionally known additives such as a silane coupling agent, an antistatic agent, other acrylic pressure-sensitive adhesives, other pressure-sensitive adhesives, tackifiers such as urethane resins, rosin, rosin esters, hydrogenated rosin esters, phenolic resins, aromatic-modified terpene resins, aliphatic petroleum resins, alicyclic petroleum resins, styrene-based resins, and xylene-based resins, colorants, fillers, antioxidants, ultraviolet absorbers, and functional dyes, as well as additives such as compounds that change color or undergo color development when exposed to ultraviolet light or radiation. The amount of these additives blended is preferably 10% by mass or less of the total pressure-sensitive adhesive composition, more preferably 5% by mass or less, and even more preferably 5% by mass or less, and it is preferable that the additives contain as few low-molecular-weight components with a molecular weight of less than 10,000 as possible, in terms of excellent durability.

[0088] (acrylic resin) The acrylic resin that is the main component resin of the present pressure-sensitive adhesive composition may be a (meth)acrylic polymer.

[0089] The (meth)acrylic polymer is a polymer whose main structural unit is a (meth)acrylic acid alkyl ester. Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl and n-hexyl (meth)acrylate, isobornyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentaenyl (meth)acrylate, and adamantyl (meth)acrylate. These may be used alone or in combination of two or more. Among these, methyl (meth)acrylate is preferred from the viewpoints of the compatibility of the (meth)acrylic polymer with the (meth)acrylate and heat resistance. The (meth)acrylic polymer may have a radically polymerizable double bond.

[0090] The (meth)acrylic polymer can be copolymerized with (meth)acrylic acid esters other than (meth)acrylic acid alkyl esters, (meth)acrylic acid, or other compounds having a vinyl group, for the purpose of improving the glass transition temperature, mechanical properties, compatibility, etc. Examples of the (meth)acrylic acid esters other than (meth)acrylic acid alkyl esters include hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate, alkoxyalkyl (meth)acrylates such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, and ethoxyethyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, glycidyl (meth)acrylate, and γ-butyrolactone (meth)acrylate. Examples of the compound having a vinyl group include acrylamide compounds such as dimethylacrylamide, hydroxyethylacrylamide, and dimethylaminopropylacrylamide; styrene compounds such as styrene, α-methylstyrene, and p-methoxystyrene; and maleic anhydride.

[0091] The glass transition temperature (Tg) can be calculated from the type and mass fraction of the monomers that form the (meth)acrylic polymer using the following Fox formula. 1 / Tg=Σ(Wi / Tgi)In this formula, Tg is the glass transition temperature (unit: K) of the (meth)acrylic polymer, Wi is the mass fraction of the monomer units derived from monomer i that constitute the (meth)acrylic polymer, and Tgi is the glass transition temperature (unit: K) of the homopolymer of monomer i. The value of Tgi can be the value described in POLYMERHANDBOOK Volume 1 (WILEY-INTERSCIENCE).

[0092] In the present invention, the copolymerization component may contain an acrylic monomer (a1) which serves as a reaction site with the crosslinking agent described below.

[0093] The acrylic monomer (a1) serves as a reactive site for the crosslinking structure when copolymerized with other copolymerization components to form an acrylic resin. A monomer containing a functional group capable of reacting with the functional group contained in the crosslinking agent (B) described below may be used. Examples of such acrylic monomers (a1) include hydroxyl-containing monomers, amino-containing monomers, acetoacetyl-containing monomers, isocyanate-containing monomers, and glycidyl-containing monomers. Among these, hydroxyl-containing monomers are preferred because they can efficiently crosslink with the crosslinking agent. The acrylic monomers (a1) may be used singly or in combination of two or more.

[0094] Examples of hydroxyl group-containing monomers include hydroxyalkyl acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate and polyethylene glycol (meth)acrylate; and primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl 2-hydroxyethyl phthalate and N-methylol (meth)acrylamide; secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro 2-hydroxypropyl (meth)acrylate; and tertiary hydroxyl group-containing monomers such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate.

[0095] Among the above hydroxyl group-containing monomers, primary hydroxyl group-containing monomers are preferred because of their excellent reactivity with crosslinking agents, and furthermore, the use of 2-hydroxyethyl acrylate is particularly preferred because it contains less impurities such as di(meth)acrylates and is easy to produce.

[0096] The hydroxyl group-containing monomer used in the present invention preferably contains 0.5% or less of di(meth)acrylate as an impurity, more preferably 0.2% or less, and even more preferably 0.1% or less. Specific examples of the hydroxyl group-containing monomer include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate, which are preferred because they have low molecular weights and are therefore easy to purify.

[0097] Examples of amino group-containing monomers include t-butylaminoethyl (meth)acrylate, ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate.

[0098] Examples of the acetoacetyl group-containing monomer include 2-(acetoacetoxy)ethyl (meth)acrylate and allyl acetoacetate.

[0099] Examples of the isocyanate group-containing monomer include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts thereof.

[0100] Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate and allyl glycidyl (meth)acrylate.

[0101] The content of the acrylic monomer (a1) in the copolymerization components is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, and even more preferably 0.2 to 3% by mass. If the amount of acrylic monomer (a1) is too small, the number of crosslinking points will be too small during crosslinking, and the cohesive strength after crosslinking will tend to be insufficient, whereas if the amount is too large, the adhesive strength will tend to be too low.

[0102] If necessary, a copolymerizable monomer (a2) other than (a1) may also be contained as a copolymerization component. Examples of the copolymerizable monomer (a2) include (meth)acrylic acid alkyl ester monomers such as methyl methacrylate, ethyl (meth)acrylate, n-butyl methacrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, ethoxylated o-phenylphenyl (meth)acrylate, and phenoxyethyl (meth)acrylate. Examples of suitable monomers include aromatic ring-containing monomers such as diethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and styrene; amide monomers such as (meth)acryloylmorpholine, dimethyl (meth)acrylamide, diethyl (meth)acrylamide, and (meth)acrylamide; acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ethers, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, dialkyl itaconate esters, dialkyl fumarate esters, allyl alcohol, acrylic chloride, methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyl trimethylammonium chloride, and dimethyl allyl vinyl ketone.

[0103] The content of the copolymerizable monomer (a2) in the copolymerization components is preferably 0 to 20 mass%, more preferably 1 to 15 mass%, and particularly 2 to 10 mass%. If the amount of the copolymerizable monomer (a2) is too large, the adhesive properties tend to be reduced.

[0104] (Crosslinking agent) The present pressure-sensitive adhesive composition may contain a crosslinking agent as needed depending on the curing method. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, a melamine-based crosslinking agent, an aldehyde-based crosslinking agent, an amine-based crosslinking agent, etc. Among these, an isocyanate-based crosslinking agent is preferably used in terms of improving adhesion to the substrate or reactivity with the acrylic resin. The crosslinking agents may be used alone or in combination of two or more.

[0105] The content of the crosslinking agent is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the main component resin. If the content of the crosslinking agent is within the above range, the cohesive strength will not be insufficient and the desired durability can be obtained, while a decrease in flexibility and adhesive strength can be prevented.

[0106] Regarding the curing reaction, when photocuring by irradiation with active energy rays is used, it is preferable to blend a polyfunctional (meth)acrylate as a crosslinking agent into the pressure-sensitive adhesive composition. Examples of such polyfunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and glycerin polyglycidyl ether poly(meth)acrylate.

[0107] <Adhesive layer thickness> The thickness of the adhesive layer is not particularly limited. For example, from the viewpoint of providing sufficient adhesive strength and filling unevenness or steps in the substrate to which the adhesive is attached, it is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1 μm or more. On the other hand, from the viewpoint of material use efficiency, permeability, and outgassing, it is preferably 10,000 μm or less, more preferably 3,000 μm or less, and even more preferably 1,000 μm or less.

[0108] <<<This film laminate>>> A film laminate (referred to as "the present film laminate") having a configuration in which an optical member is bonded to the surface of the present adhesive layer of the present release film with an adhesive layer can be produced.

[0109] Examples of the optical member include a polarizing plate, a touch sensor, etc. The optical member may also be an optical member for use in an automobile, such as a touch panel mounted on an automobile.

[0110] (polarizing plate) The polarizing plate may be made of any material and have any configuration. For example, a polarizing plate of this type is widely used in practice, which is made by laminating a TAC (triacetyl cellulose) film as a protective film on a stretched polyvinyl alcohol film using iodine as an alignment dye. The polarizing plate may have a layer structure on the surface thereof that has a hard coat having substantially no retardation, anti-glare, low reflection, anti-static, or other functions.

[0111] (touch sensor) The touch sensor is a component that detects the touch point when a user touches an image displayed on a screen with a finger or a touch pen, and examples of sensor technologies include a capacitance type, a resistive film type, and a surface wave type using infrared rays or ultrasonic waves. Touch sensors are generally installed in display devices such as liquid crystal display panels and organic EL displays. Furthermore, in recent years, there has been a trend toward using substrate films as an alternative to glass substrates, focusing on their flexibility. Touch sensor films typically include a patterned transparent conductive layer to perform the function of the sensing electrodes.

[0112] <<<Explanation of terms etc.>>> In the present invention, the term "film" includes the term "sheet", and the term "sheet" includes the term "film". Furthermore, when the term "panel" is used, such as an image display panel or a protective panel, it encompasses a plate, a sheet, and a film.

[0113] In the present invention, when it is stated that "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less", and also means "preferably larger than X" or "preferably smaller than Y". Furthermore, when it is stated that the amount is "X or more" (X is any number), it also means that the amount is "preferably greater than X" unless otherwise specified, and when it is stated that the amount is "Y or less" (Y is any number), it also means that the amount is "preferably smaller than Y" unless otherwise specified. [Example]

[0114] The present invention will now be described in more detail with reference to examples, although the present invention is not limited to the examples described below.

[0115] <Evaluation method> In the following, measurements and evaluations of various physical properties were carried out as follows.

[0116] (1) Viscosity of curable silicone resin The curable silicone resin was diluted with n-heptane to 15% by mass, and the viscosity of this solution at 25° C. was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., "TVE-22L").

[0117] (2) Molecular weight measurement of curable silicone resin The chromatogram was measured using a GPC measurement system, and the number-average molecular weight (Mn) and weight-average molecular weight (Mw) were determined based on a calibration curve using standard polystyrene. These are shown in Table 2. Specifically, 4 mg of the sample to be measured was dissolved in 4 mL of THF to prepare a measurement solution, and 100 μL of the measurement solution was injected into the GPC measurement system for measurement. Tetrahydrofuran (THF) was used as the eluent. The analysis was performed using an Ecosec 8320 (manufactured by Tosoh Corporation), a TSKgel guard column HXL-L (manufactured by Tosoh Corporation), and four TSKgel GMHXL columns (manufactured by Tosoh Corporation) connected together. The oven temperature was 40°C, and the THF flow rate was 1.0 mL / min. RI was used for detection.

[0118] (3) Release layer thickness measurement To suppress reflection from the backside, black tape (Vinyl Tape VT-50, manufactured by Nichiban Co., Ltd.) was applied to the backside of the sample film beforehand. Measurements were performed using a spectrophotometer (UV-Visible Spectrophotometer V-670, manufactured by JASCO Corporation) to measure absolute reflectance in the wavelength range of 300 to 800 nm under the following conditions: synchronous mode, incident angle of 5°, N polarization, response fast, data acquisition interval of 1.0 nm, bandwidth of 10 nm, and scanning speed of 1000 m / min. The film thickness of the release layer was determined by comparing the data obtained from this measurement with data calculated assuming a refractive index of silicone of 1.43.

[0119] (4) Heat peeling force (without pressing) One side of an acrylic double-sided adhesive tape (Nitto Denko Corporation's "No. 502") was attached to the surface of the release layer of the sample film, and the sample was cut to a size of 50 mm x 300 mm. In this state, the sample was heated and held at 100°C (set temperature) in a hot air oven for 1 hour, and then left to stand at 23°C and 50% RH for 1 hour. After that, the 180° peel force was measured using a tensile tester (Shimadzu Corporation's "EZgraph") at a tensile speed of 300 mm / min.

[0120] (5) Post-press heat peeling force (after pressing) The sample pieces, each measuring 210 mm x 297 mm (A4 size), were stacked so that the release layer surface and the surface opposite the release layer surface faced each other. Five sheets of 38 μm thick PET film "T100-38" manufactured by Mitsubishi Chemical Corporation were placed on top and bottom of the stacked sample, and pressed under a pressure of 1 MPa for 1 hour. One side of an acrylic double-sided adhesive tape ("No. 502" manufactured by Nitto Denko Corporation) was then attached to the surface of the release layer of the sample film, and the peel force was then measured in the same manner as in "Heated peel force (without pressing)." Pressing began within 15 minutes of sample preparation. In Table 2, "-" means that the item has not been evaluated.

[0121] (6) TESA7475 tape heat peel strength One side of an acrylic adhesive tape (TESA7475 manufactured by Tesa) was attached to the release layer surface of the sample film, and the tape was cut to a size of 25 mm x 300 mm. In this state, the tape was heated and held in a hot air oven at 100°C (set temperature) for 1 hour, and then left to stand at 23°C and 50% RH for 1 hour. Thereafter, the side of the sample opposite the release layer was fixed to a SUS plate with double-sided tape, and the 180° peel force was measured using a tensile tester (EZgraph manufactured by Shimadzu Corporation) at a tensile speed of 300 mm / min. In Table 2, "-" means that the item has not been evaluated.

[0122] (7) Measurement of the elastic modulus of the release layer The surface of the release layer of the sample film was observed with an atomic force microscope, and the obtained image was analyzed to calculate the elastic modulus. In this case, a silicon probe (manufactured by team nanotec, LRCH, radius of curvature: 250 nm, spring constant: 0.2 N / m) was attached to an atomic force microscope (product name: SPM-9700HT, manufactured by Shimadzu Corporation), and calculations were made in accordance with the JKR two-point method based on the force curve obtained by tapping at 600 m / s. The elastic modulus in Examples 1 to 4 is a calculated value based on the data of Reference Examples 1 to 3, in which the coating thickness and elastic modulus are known.

[0123] (8) Evaluation of the roughness of the adhesive layer surface The adhesive composition described below was applied to the surface of the release layer (release surface) of the sample film so that the film thickness in a wet state was 2 mil, and the adhesive layer was formed by hardening it by heat treatment at 150°C for 3 minutes. The unevenness of the adhesive layer surface on the side not in contact with the release surface was evaluated by visual inspection as described below.

[0124] <<Adhesive Composition>> Main agent (acrylic resin): AT352 (manufactured by Saiden Chemical) 100 parts by weight Hardener: AL (manufactured by Saiden Chemical) 0.25 parts by mass Additive: X-301-375SK (manufactured by Saiden Chemical) 0.25 parts by mass Additive: X-301-352S (manufactured by Saiden Chemical) 0.25 parts by mass Toluene: 40 parts by mass

[0125] (Visual inspection) An adhesive layer was formed on the release surface of the sample film as described above, and the coating appearance of the adhesive layer surface on the side not in contact with the release surface, i.e., the unevenness of the adhesive layer surface, was visually observed and judged according to the following criteria, and the results are shown in Table 2. (Judgment criteria) ◯ (good): The surface is so good that the surface irregularities are not recognizable, or the surface irregularities are very slight. △ (poor): Surface irregularities can be recognized. × (very poor): Surface irregularities are clearly recognizable.

[0126] [Raw materials] The following raw materials were used in the examples and comparative examples.

[0127] <Release Layer Composition> a1: Curable silicone resin composition (a mixture (viscosity: 95 mcps) containing a curable silicone resin (number average molecular weight: 176,000) in which vinyl groups have been introduced into the side chains and / or ends of the main chain consisting of siloxane bonds, and a crosslinker in which Si-H groups have been introduced into the side chains and / or ends of the main chain consisting of siloxane bonds) a2: Curable silicone resin composition (a curable silicone resin in which vinyl groups have been introduced into the side chains and / or terminals of the main chain consisting of siloxane bonds, number average molecular weight: 10600, viscosity: 1.7mcps) a3: Curable silicone resin composition (a mixture (viscosity: 410 mcps) containing a curable silicone resin (number average molecular weight: 364,000) in which vinyl groups have been introduced into the side chains and / or ends of the main chain consisting of siloxane bonds, and a crosslinker in which Si-H groups have been introduced into the side chains and / or ends of the main chain consisting of siloxane bonds) a4: Curable silicone resin composition (a mixture (viscosity: 430 mcps) containing a curable silicone resin (number average molecular weight: 399,000) in which hexenyl groups have been introduced into the side chains and / or ends of the main chain consisting of siloxane bonds, and a crosslinker in which Si-H groups have been introduced into the side chains and / or ends of the main chain consisting of siloxane bonds)

[0128] (Composition analysis of curable silicone resin) The composition of the curable silicone resins used in the examples and comparative examples was analyzed using a 400 MHz-NMR (Bruker Avance400M). The results are shown in Table 1. The 1H-NMR measurement was carried out at a temperature of 30°C using CDCl3 as a solvent and using the peak derived from the methyl group of dimethylsiloxane as the chemical shift reference. Table 1 below shows the content (mol %) of each functional group in the curable silicone resin.

[0129] [Table 1]

[0130] b1: Crosslinking agent (CL750: manufactured by Momentive Performance Materials) c1: Addition type platinum catalyst (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) c2: Addition platinum catalyst (CM678: manufactured by Momentive Performance Materials) c3: Addition type platinum catalyst (SRX212: manufactured by Dow Toray Co., Ltd.)

[0131] [Example 1] A release layer composition consisting of the release agent composition A described below was applied by bar coating to one side of a 38 μm thick PET film "T100-38" manufactured by Mitsubishi Chemical Corporation, and the composition was cured by heat treatment at 150°C for 15 seconds to form a release layer having a thickness (after drying) of 0.30 μm, thereby obtaining a release film (sample film).

[0132] <Release agent composition-A> Curable silicone resin composition a1: 98% by mass Addition type platinum catalyst c1: 2 mass% The release layer composition was diluted with n-heptane to adjust the solid content concentration to 5.4% by mass.

[0133] [Example 2] In Example 1, the solid content concentration of the release layer composition was changed to 3.7 mass % so that the thickness of the release layer (after drying) was 0.38 μm. A release film (sample film) was obtained by manufacturing in the same manner as in Example 1.

[0134] [Example 3] In Example 1, the solid content concentration of the release layer composition was changed to 1.9 mass % so that the thickness of the release layer (after drying) was 0.48 μm. A release film (sample film) was obtained by manufacturing in the same manner as in Example 1.

[0135] [Example 4] In Example 1, the solid content concentration of the release layer composition was changed to 1.9 mass % so that the thickness of the release layer (after drying) was 0.59 μm. A release film (sample film) was obtained by manufacturing in the same manner as in Example 1.

[0136] [Comparative Example 1] In Example 1, except that the release layer composition was changed to the release agent composition-B below, the same procedure as in Example 1 was repeated to obtain a release film (sample film) having a release layer with a thickness (after drying) of 0.23 μm.

[0137] <Release agent composition-B> Curing silicone resin composition a2: 91% by mass Crosslinking agent b1: 3% by mass Addition type platinum catalyst c2: 6 mass% The release layer composition was diluted with n-heptane to adjust the solid content concentration to 5.4% by mass.

[0138] Comparative Example 2 In Example 1, except that the release layer composition was changed to the release agent composition-C below, the same procedure as in Example 1 was repeated to obtain a release film (sample film) having a release layer with a thickness (after drying) of 0.24 μm.

[0139] <Release agent composition-C> Curable silicone resin composition a3: 99% by mass Addition type platinum catalyst c1: 1 mass% The release layer composition was diluted with n-heptane to adjust the solid content concentration to 5.4% by mass.

[0140] Comparative Example 3 In Example 1, except that the release layer composition was changed to the release agent composition-D below, the same procedure as in Example 1 was repeated to obtain a release film (sample film) having a release layer with a thickness (after drying) of 0.28 μm.

[0141] <Release agent composition-D> Curable silicone resin composition a4: 99% by mass Addition type platinum catalyst c3: 1 mass% The release layer composition was diluted with n-heptane to adjust the solid content concentration to 5.4% by mass.

[0142] [Reference example 1] In Example 1, the solid content concentration of the release layer composition was changed to 5.4 mass % so that the thickness of the release layer (after drying) was 0.23 μm. A release film (sample film) was obtained by manufacturing in the same manner as in Example 1.

[0143] [Reference example 2] In Example 1, the solid content concentration of the release layer composition was changed to 3.7 mass % so that the thickness of the release layer (after drying) was 0.18 μm. A release film (sample film) was obtained by manufacturing in the same manner as in Example 1.

[0144] [Reference example 3] In Example 1, the solid content concentration of the release layer composition was changed to 1.9 mass % so that the thickness of the release layer (after drying) was 0.09 μm. A release film (sample film) was obtained by manufacturing in the same manner as in Example 1.

[0145] The properties of each release film (sample film) obtained in the above Examples and Comparative Examples are summarized in Table 2, and the properties of each release film (sample film) obtained in the Reference Examples are summarized in Table 3.

[0146] [Table 2]

[0147] The "heat peel strength (after pressing)" was evaluated from the perspective of how stable and smooth the peeling could be under more severe conditions by first recreating a condition in which the release surface and the adhesive layer surface were intentionally tightly adhered together through a pressing process. It was found that in Examples 1 to 4, the peel strength did not change significantly before and after the press treatment and was stable. On the other hand, when Comparative Examples 1 to 3 were evaluated for "heat peel force (no press)" without pressing, it was confirmed that the peel force values ​​were already about 60 to 70% higher than those of Examples 1 to 4, indicating that it would be difficult to achieve ultra-light peeling. Furthermore, it was found that the "TESA7475 heat peeling force" exhibits a large change in peeling force depending on the thickness of the release layer, and responds sensitively to the thickness of the release layer, making it easy to see the effect of light peeling.

[0148] [Table 3]

[0149] It was found that in the region where the coating thickness (after drying) of the release layer is less than 0.25 μm, the elastic modulus of the release layer is 1.5 MPa or more, and therefore the releasability to acrylic adhesive tape does not become dramatically easier. On the other hand, when the elastic modulus of the release layer is 1.4 MPa or less, it is not surprising that the peel force value increases due to the press treatment, even though the press treatment has been performed in advance. However, it was found that the peel force value was about 30% lighter at the lightest. Therefore, it can be seen that the release films of the present invention (including the examples) achieve an ultra-light release property that is difficult to achieve at the level of the reference examples (conventional examples).

[0150] The sample films obtained in Examples 1 to 4 are considered to have a release layer thickness of 0.25 μm or more and an elastic modulus of 1.4 MPa or less. It is known that when the elastic modulus of the release layer is 1.4 MPa or less, the possibility of blocking and heavy release due to blocking occurring increases. Therefore, in the present invention, it was found that the above problem can be solved by using a curable silicone resin with a medium viscosity, specifically, a viscosity of 10 to 400 mcps at 25°C when diluted with n-heptane solvent to adjust to 15% by mass. More preferably, the curable silicone resin has a phenyl structure, which is also thought to contribute to solving the above problems. On the other hand, the sample films obtained in Examples 1 to 4 did not show a heavy peeling force after pressing, and it was found that the peeling force after pressing was actually lighter.

[0151] From the above examples and the results of tests conducted by the inventors, it has been found that if the elastic modulus of the release layer is 1.4 MPa or less and the 180° peel strength at 23°C is 15 mN / cm or less, not only will the release layer have excellent light peelability, but it will also be possible to suppress unevenness on the adhesive layer surface and achieve excellent smoothness.

[0152] Furthermore, from the above examples and the results of tests conducted by the inventors to date, it has been found that by using a curable silicone having a moderate number average molecular weight (Mn) of 20,000 or more and 350,000 or less as the main component resin of the release layer composition, it is possible to obtain a release film with very light release properties that does not experience heavy release due to blocking, even when the dry thickness of the release layer is 0.30 μm or more and the elastic modulus of the release layer is 1.4 MPa or less. Therefore, it has been found that by setting the dry thickness of the release layer to 0.25 μm or more and 2.0 μm or less, more preferably 0.30 μm or more and 1.5 μm or less, and even more preferably 0.35 μm or more and 1.0 μm or less, and by setting the elastic modulus of the release layer to 1.4 MPa or less, 0.10 MPa or more, more preferably 1.3 MPa or less, 0.20 MPa or more, and even more preferably 1.0 MPa or less and 0.30 MPa or more, an excellent release film can be obtained, particularly in applications where ultra-light releasability is required.

[0153] Furthermore, it was found that by using a curable silicone having a moderate number average molecular weight (Mn) of 20,000 or more and 350,000 or less as the main component resin of the release layer composition and adjusting the release layer composition to contain a predetermined amount of phenyl groups, it is possible to further improve the easy peelability and further suppress the unevenness of the adhesive layer surface. In this case, it can be considered that the reason the unevenness of the adhesive layer surface can be suppressed is because the release layer surface has appropriate wettability and it is possible to suppress the elution or migration of the low molecular weight silicone resin, i.e., the incompatible component, to the adhesive layer side.

[0154] In particular, it was found that a release film having a release layer formed by applying and curing a release layer composition containing, as the main component resin, a curable silicone having a moderate number average molecular weight (Mn) of 20,000 or more and 350,000 or less can obtain good easy peelability and a highly smooth adhesive layer surface even when the release layer is applied thickly (thickness after drying) to a thickness of 0.30 μm or more. Furthermore, it was found that a release layer composition having a curable silicone resin with a moderate molecular weight as the main component resin as described above can maintain the viscosity of the coating liquid within an appropriate range even when the coating liquid is prepared at a high concentration to increase the thickness of the release layer in order to achieve light release, and can produce a release film with a good coating appearance (no coating unevenness such as streaks) and stable release properties with reduced variation in peel force values ​​within the surface of the release film.

[0155] Furthermore, from the above examples and the results of tests conducted by the inventors to date, it has been found that when an adhesive layer is formed on a release layer, the presence of phenyl groups in the release layer enables easier peeling while suppressing the unevenness of the adhesive layer surface. At present, the detailed mechanism is unknown, but it is speculated that in release layer compositions (such as release layer compositions a3 and a4) whose main component is a typical high-molecular-weight curable silicone resin, the unreacted reactive groups (alkenyl groups, Si-H groups) that increase as the molecular weight increases to medium levels are hidden from the adhesive by the phenyl groups (interaction between the phenyl groups and the alkenyl groups and Si-H groups). Furthermore, from the above examples and the results of tests conducted by the inventors, it has been found that the release layer preferably contains 0.01 to 5.0 mol % of phenyl groups relative to the total amount of siloxane components.

Claims

1. A release film having a release layer on one side of a base film, The release layer has an elastic modulus of 1.4 MPa or less and a thickness (after drying) of 0.25 μm to 2.0 μm; The release layer is a release film obtained by curing a release layer composition in which any one or more of a phenyl group, an Si—H group, and an alkenyl group are introduced into a side chain or an end of a linear main chain composed of siloxane bonds, the release layer having as its main component a curable silicone resin (excluding a curable silicone resin having a number average molecular weight (Mn) of 200,000 which has a methyl group, a hexenyl group, and a phenyl group) having a number average molecular weight (Mn) of 20,000 or more and 176,000 or less and having a viscosity of 10 to 400 mcps at 25° C. when diluted to 15% by mass with n-heptane solvent, the release layer containing a crosslinker having a siloxane bond, and the release layer composition containing 0.01 to 5.0 mol % of phenyl groups, 0.4 to 1.0 mol % of alkenyl groups, and 0.8 to 2.2 mol % of Si—H groups, based on the total siloxane components.

2. The release film according to claim 1 , further comprising a cured resin layer between the release layer and the substrate film.

3. The release film of claim 2 , wherein the cured resin layer is an antistatic layer or an oligomer sealing layer.

4. 4. The release film according to claim 1, wherein the calculated average roughness (Sa) of the release layer surface or the film surface on which no release layer is provided is 30 nm or less.

5. The release film according to any one of claims 1 to 4, wherein the base film is a polyester film.

6. A release film with an adhesive layer, comprising the release film according to any one of claims 1 to 5, and an adhesive layer laminated on the release layer.

7. 7. The release film with an adhesive layer according to claim 6, wherein the adhesive layer is a layer made of an acrylic adhesive composition containing an acrylic resin as a main component.

8. A film laminate comprising an optical member bonded to a surface of the adhesive layer of the release film with an adhesive layer according to claim 6 or 7.

9. The film laminate according to claim 8 , wherein the optical component is a polarizing plate or a touch sensor.

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