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

Abstract

To provide a release film that can make an adhesive layer surface smooth by suppressing irregularity of an adhesive layer surface, and, is excellent also in light release property.SOLUTION: A release film having a structure provided with a mold releasing layer on one side of a base film, in which the adhesion energy of the releasing layer is 35 mJ / m2 or larger and 39 mJ / m2 or smaller, and after an acrylic adhesive tape is adhered to the releasing layer, is cut into a size of 50 mm×300 mm, in this state, heating and holding for 1 hour at 100°C (preset temperature) in a hot air oven, after leaving to stand for 1 hour at 23°C and 50%RH, 180° peeling force under condition of tensile speed 300 mm / minute is 15 mN / cm or smaller.

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 an adhesive-layered release film on the side not in contact with the release film had some unevenness, 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 in adhesive-layered release films has become an issue. In other words, if the adhesive layer surface has unevenness, 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 with an adhesive layer, and have found that the interaction between the release layer and the adhesive layer causes unevenness on the surface of the adhesive layer mainly for two reasons: if the surface of the release layer is uneven, this can affect the surface of the adhesive layer, and if an incompatible component elutes from the release layer to the adhesive layer, repelling can occur when the adhesive layer composition is applied, or the incompatible component penetrates 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 relates to a release film having a structure in which a release layer is provided on one side of a base film, and the adhesive energy of the release layer is 35 mJ / m 2 More than 39mJ / m 2 The release film proposed has a 180° peel strength of 15 mN / cm or less at a tensile speed of 300 mm / min after 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 in this state 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.

[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] An adhesive layer was formed on the release layer surface (also referred to as the "release surface") of the release film (sample film) obtained in Example 1 as described below, and the adhesive layer surface was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Co., Ltd., and the image data (5x magnification) are shown. [Figure 2] An adhesive layer was formed on the release surface of the release film (sample film) obtained in Example 2 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Co., Ltd., and the image data (5x magnification) are shown. [Figure 3] An adhesive layer was formed on the release surface of the release film (sample film) obtained in Example 3 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Co., Ltd., and the image data (5x magnification) are shown. [Figure 4]An adhesive layer was formed on the release surface of the release film (sample film) obtained in Comparative Example 1 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Ltd. This is image data (5x magnification). [Figure 5] An adhesive layer was formed on the release surface of the release film (sample film) obtained in Comparative Example 2 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Ltd. This is image data (5x magnification). [Figure 6] An adhesive layer was formed on the release surface of the release film (sample film) obtained in Comparative Example 3 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Ltd. This is image data (5x magnification). [Figure 7] An adhesive layer was formed on the release surface of the release film (sample film) obtained in Comparative Example 4 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Ltd. This is image data (5x magnification). [Figure 8] An adhesive layer was formed on the release surface of the release film (sample film) obtained in Comparative Example 5 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Ltd. This is image data (5x magnification). [Figure 9] An adhesive layer was formed on the release surface of the release film (sample film) obtained in Comparative Example 6 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Ltd. This is image data (5x magnification). [Figure 10] An adhesive layer was formed on the release surface of the release film (sample film) obtained in Comparative Example 7 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Co., Ltd., and the image data (5x magnification) are shown. [Figure 11]An adhesive layer was formed on the release surface of the release film (sample film) obtained in Comparative Example 8 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Co., Ltd. This is image data (5x magnification). [Figure 12] An adhesive layer was formed on the release surface of the release film (sample film) obtained in Comparative Example 9 as described below, and the surface of the adhesive layer was measured over an area of ​​928 x 1235 μm using a ContourGT manufactured by Bruker Japan Co., Ltd. This is image data (5x magnification). 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 viewpoints 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 or size of particles on the surface in contact with the adhesive layer 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 size 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 the 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 is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.10 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 10 μm or less, more preferably 5.0 μm or less, even more preferably 2.0 μm or less, even more preferably 1.0 μm or less, and even more preferably 0.50 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, but are not limited to, an anchor coat layer for increasing the adhesion between the substrate film and the release layer, an oligomer sealing layer for sealing the bleed-out (bleeding, plate-out) of compounds or oligomers onto the film surface, and an antistatic layer having antistatic properties.

[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] <Adhesion energy> The adhesive energy of the release layer of this release film is 35 mJ / m 2 More than 39mJ / m 2 Preferably it is less than 36 mJ / m 2 or more than 39mJ / m 2 It is more preferable that the value is 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.

[0076] <Elastic modulus> The modulus of elasticity of the release layer in the release film is 0.1 MPa or more, preferably 0.2 MPa or more, and particularly 0.5 MPa or more, while the upper limit is preferably 8.0 MPa or less, more preferably 6.0 MPa or less, and particularly 5.0 MPa or less. When the release layer satisfies the above ranges for both adhesion energy and modulus of elasticity, the surface of the adhesive layer formed on the release layer can maintain smoothness.

[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] <Heat peeling force> This release film is prepared by laminating an acrylic adhesive tape, such as Nitto Denko No. 502, cutting it to a size of 50 mm x 300 mm, heating and holding it in this state at 100°C (set temperature) for 1 hour in a hot air oven, and then leaving it to stand at 23°C and 50% RH for 1 hour. After that, the 180° peel strength at a pulling rate of 300 mm / min, i.e., the peel strength when the acrylic adhesive tape is peeled at 180° at a pulling rate of 300 mm / min, is preferably 15 mN / cm or less, more preferably 14 mN / cm or less, and even more preferably 11 mN / cm or less. The peel force can be measured using, for example, a tensile tester ("EZgraph" manufactured by Shimadzu Corporation), but is not limited to such a tester.

[0079] <<<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.

[0080] <Smoothness of the adhesive layer surface (image clarity)> The release film with the adhesive layer can have an image clarity value of 70 or more on the surface of the adhesive layer, i.e., the surface of the adhesive layer on the side not in contact with the release film, and more preferably 75 or more. Satisfying such an image clarity value indicates that the surface of the adhesive layer is extremely smooth.

[0081] In order for the surface of the adhesive layer in the release film with the adhesive layer to satisfy the above-mentioned image clarity value, as described above, by adjusting the number average molecular weight (Mn) of the curable silicone resin forming the release layer within a predetermined range and adjusting the phenyl group content in the release layer composition or the release layer within a predetermined range, it is possible to suppress unevenness on the surface of the release layer and to suppress the leaching of incompatible components onto the adhesive layer side, thereby suppressing unevenness on the surface of the adhesive layer and making it smooth.

[0082] <Arithmetic mean height of adhesive layer surface (Sa)> The adhesive layer-attached release film can have an arithmetic mean height (Sa, ISO 25178 surface quality) of the adhesive layer surface, i.e., the surface of the adhesive layer not in contact with the release film, of 53 nm or less, preferably 35 nm or less, more preferably 30 nm or less, and even more preferably 25 nm or less.

[0083] The arithmetic mean height (Sa, ISO25178 surface texture) is a parameter that expands the arithmetic mean roughness Ra into three dimensions, and is a numerical value that represents the average of the absolute values ​​of the height differences at each point relative to the average plane of the surface.

[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 to be 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 in terms of the compatibility of the (meth)acrylic polymer with the (meth)acrylate and the heat resistance of the cured resin layer. 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 element is bonded to the surface of the 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 over a 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 strength 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) Adhesion energy 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 adhesion energy. 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.

[0121] (6) Measurement of the elastic modulus of the release layer Based on the force curve obtained by the same device / method as in the adhesion energy measurement, the elastic modulus was calculated in accordance with the JKR two-point method.

[0122] (7) 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 curing 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 using each of the methods (7-1) to (7-3) described below.

[0123] <<Adhesive Composition>> Main agent (acrylic resin): 100 parts by weight of AT352 (manufactured by Saiden Chemical Co., Ltd.) 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

[0124] (7-1) Visual inspection An adhesive layer was formed on the release surface of the sample film as described above, and the unevenness of the adhesive layer surface on the side not in contact with the release surface was visually observed and judged according to the following criteria. 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.

[0125] (7-2) Measurement of the arithmetic mean height (Sa) of the adhesive layer surface An adhesive layer was formed on the release surface of the sample film as described above, and the arithmetic mean height (Sa) of the adhesive layer surface on the side not in contact with the release surface was measured in an area of ​​928 × 1235 μm using a Contour GT manufactured by Bruker Japan Co., Ltd. in accordance with ISO 25178. The measured arithmetic mean heights (Sa) are shown in Table 2.

[0126] (7-3) Evaluation of image clarity on adhesive layer surface An adhesive layer was formed on the release surface of the sample film as described above, and the unevenness of the adhesive layer surface on the side not in contact with the release surface was measured three times in each of the vertical direction (direction in which the silicone release layer and adhesive layer were applied) and horizontal direction of the film using an image clarity measuring device (ICM-1DP, manufactured by Suga Test Instruments Co., Ltd.) under conditions of an optical axis of 0° (transmission mode) and an optical comb width of 0.125 mm, and the average values ​​of these measurements were used for evaluation. The larger the image clarity value, the less distortion there is in the image projected onto the surface of the adhesive layer, indicating that a clearer image can be obtained.

[0127] [Raw materials] The following raw materials were used in the examples and comparative examples.

[0128] <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)

[0129] (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.

[0130] [Table 1]

[0131] 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.)

[0132] [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 0.23 μm, thereby obtaining a release film (sample film).

[0133] <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.

[0134] [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.

[0135] [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.

[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 Comparative 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 0.14 μm. A release film (sample film) was obtained by manufacturing in the same manner as in Comparative Example 1.

[0139] Comparative Example 3 In Comparative 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 0.07 μm. A release film (sample film) was obtained by manufacturing in the same manner as in Comparative Example 1.

[0140] Comparative Example 4 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.

[0141] <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.

[0142] Comparative Example 5 In Comparative Example 4, a release film (sample film) was obtained by manufacturing in the same manner as in Comparative Example 4, except that 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 0.16 μm.

[0143] Comparative Example 6 In Comparative Example 4, a release film (sample film) was obtained by manufacturing in the same manner as in Comparative Example 4, except that 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.

[0144] Comparative Example 7 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.

[0145] <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.

[0146] [Comparative Example 8] In Comparative Example 7, a release film (sample film) was obtained by manufacturing in the same manner as in Comparative Example 7, except that 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 0.22 μm.

[0147] Comparative Example 9 In Comparative Example 7, a release film (sample film) was obtained by manufacturing in the same manner as in Comparative Example 7, except that 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 0.11 μm.

[0148] The properties of each release film (sample film) obtained in the above examples and comparative examples are summarized in Table 2.

[0149] [Table 2]

[0150] <Consideration> From the above examples and the results of tests conducted by the inventors, 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, not only can easy releasability be achieved, but also unevenness on the adhesive layer surface can be suppressed and made smooth. In this case, it can be considered that the suppression of unevenness on the adhesive layer surface is the result of the release layer surface having appropriate wettability and the suppression of elution or migration of low molecular weight silicone resin, i.e., incompatible components, to the adhesive layer side.

[0151] In particular, a release film having a release layer formed by applying and curing a release layer composition containing, as a main component resin, a curable silicone having a moderate number average molecular weight (Mn) of 20,000 or more and 350,000 or less, said release layer is coated with a curable silicone having a number average molecular weight (Mn) of 0.1 g / m 2 It was found that even when the adhesive was applied thickly (thickness after drying: 0.18 μm or more), good easy peelability and a highly smooth adhesive layer surface could be obtained. 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. In the release layers of the examples, the adhesive energy hardly changed even when the film thickness was increased, suggesting stable film formation. On the other hand, in all of the comparative examples, it was confirmed that the adhesive energy tended to decrease as the thickness of the release layer increased.

[0152] 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 configuration in which a release layer is provided on one side of a base film, The adhesive energy of the release layer is 35 mJ / m ２ Larger than 39 mJ / m ２ is as follows: The release layer is a release film obtained by curing a release layer composition in which 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 a curable silicone resin as a main component resin, the curable silicone resin having a number average molecular weight (Mn) of 20,000 or more and 176,000 or less, and a viscosity of 10 to 400 mcps at 25° C. when diluted with n-heptane solvent to 15% by mass, 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. 2. The release film according to claim 1, wherein the thickness of the release layer (after drying) is 0.05 μm to 2.0 μm.

3. The release film according to claim 1 or 2, wherein the base film is a polyester film.

4. A release film with an adhesive layer, comprising the release film according to any one of claims 1 to 3, and an adhesive layer laminated on the release layer.

5. 5. The release film with an adhesive layer according to claim 4, wherein the surface of the adhesive layer opposite the release film (referred to as the "adhesive layer surface") has an arithmetic mean height (Sa, ISO 25178 surface quality) of 53 nm or less.

6. 6. The release film with an adhesive layer according to claim 4, wherein the image clarity value of the surface of the adhesive layer is 70 or more.

7. 7. The release film with an adhesive layer according to claim 4, wherein the adhesive layer is a layer made of an acrylic adhesive.

8. 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 according to any one of claims 4 to 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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