Adhesive sheet with release film

Abstract

To provide a pressure sensitive adhesive sheet with a release film, in which a pressure sensitive adhesive sheet has excellent ultraviolet cutting properties, with excellent detachability from a release film.SOLUTION: A pressure sensitive adhesive sheet with a release film (1) includes: a pressure sensitive adhesive sheet (50) of a photocurable type having a first principal plane and a second principal plane; and a first release film (10) temporarily adhered to the first principal plane of the pressure sensitive adhesive sheet. The first release film includes a release layer (15) on a surface of a film base material (11). The release layer (15) and the pressure sensitive adhesive sheet (50) are abutting with each other. The pressure sensitive adhesive sheet (50) includes a photocurable type acrylic polymer and an ultraviolet absorber. The release layer (15) is a silicone release layer and has an Si atom content of 0.02-0.07 g / m.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure sensitive adhesive sheet having a release film temporarily attached thereto. To Regarding. [Background technology]

[0002] Transparent adhesive sheets are used for bonding optical members in display devices such as liquid crystal displays and organic EL displays, and display input devices such as touch panels. Transparent adhesive sheets are generally provided as adhesive sheets with release films attached to both sides. When using the adhesive sheet, first, one release film (light release film) is peeled off to expose one side of the adhesive sheet, which is then bonded to a first adherend, and the other release film (heavy release film) is peeled off to bond a second adherend to the other side of the adhesive sheet.

[0003] Optical members used in display devices, input devices, etc., may be required to have ultraviolet ray blocking properties in order to prevent deterioration of elements caused by ultraviolet ray. For example, in an organic EL display, ultraviolet ray blocking of organic molecules constituting the light-emitting layer, etc., has a significant effect on the display characteristics, so optical members arranged in front of the element are required to have high ultraviolet ray blocking properties. Also, polarizing plates used in liquid crystal displays and organic EL displays require ultraviolet ray blocking properties for optical members arranged in front of the polarizer to prevent deterioration of the polarizer caused by ultraviolet ray (e.g., iodine fading).

[0004] As a method for imparting ultraviolet ray blocking properties to an adhesive sheet, a method of adding an ultraviolet ray absorber to an adhesive composition is known. For example, Patent Document 1 describes that an adhesive composition obtained by adding an ultraviolet ray absorber to a thermally polymerizable acrylic adhesive solution is applied in a film form, and then heated and dried to obtain an adhesive sheet having ultraviolet ray blocking properties. Patent Document 2 describes that a photocurable acrylic adhesive composition containing a photocurable acrylic composition, a photopolymerization initiator, and an ultraviolet ray absorber is applied in a layer form on a release film substrate, and another release film is superimposed thereon to block contact with air, and photocuring is performed to obtain a photocurable adhesive sheet having ultraviolet ray blocking properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-75978 A [Patent Document 2] JP 2016-155981 A Summary of the Invention [Problem to be solved by the invention]

[0006] As described in Patent Document 2, if a photocurable adhesive is used, a solvent is not required to form the adhesive sheet, and therefore it is easy to increase the thickness of the adhesive sheet. In addition, by performing photocuring in a state where release sheets are in contact with both sides of the sheet-shaped photocurable adhesive composition, there is an advantage that the smoothness of the adhesive sheet can be improved.

[0007] However, according to the study by the present inventors, it was found that when a photocurable adhesive composition containing an ultraviolet absorber is photocured by irradiating it with ultraviolet light through a release film, the peel strength between the release film on the light irradiated surface and the photocured adhesive sheet increases significantly, and peeling of the release film may become difficult when the adhesive sheet is attached to an adherend. In view of such a problem, the present invention aims to provide an adhesive sheet with a release film that has ultraviolet blocking properties and good peelability from the release film. [Means for solving the problem]

[0008] The adhesive sheet with release film of the present invention comprises a photocurable adhesive sheet having a first main surface and a second main surface, and a first release film temporarily attached to the first main surface of the adhesive sheet. The first release film comprises a release layer on a film substrate, and the release layer and the adhesive sheet are in contact with each other. The adhesive sheet contains a photocurable acrylic polymer and an ultraviolet absorber. The adhesive sheet with release film may comprise a second release film temporarily attached to the second main surface of the adhesive sheet.

[0009] The first main surface of the pressure-sensitive adhesive sheet is the surface irradiated with light when the photocurable pressure-sensitive adhesive composition is photocured. That is, the photocurable pressure-sensitive adhesive sheet is formed by irradiating the photocurable pressure-sensitive adhesive composition with light through a first release film. By using a release film having a predetermined silicone-based release layer as the first release film attached to the side of the surface irradiated with light to the photocurable pressure-sensitive adhesive composition, an excessive increase in peel force can be suppressed even when the pressure-sensitive adhesive contains an ultraviolet absorber. The silicone-based release layer of the first release film has a Si atom content of 0.02 to 0.07 g / m 2 It is preferable that:

[0010] The pressure-sensitive adhesive sheet preferably has a light transmittance of 10% or less at a wavelength of 380 nm. The pressure-sensitive adhesive sheet preferably contains 0.1 to 10 parts by weight of an ultraviolet absorbing agent relative to 100 parts by weight of the acrylic polymer. For example, a triazine-based ultraviolet absorbing agent is used as the ultraviolet absorbing agent. The acrylic polymer of the pressure-sensitive adhesive sheet may contain, as a monomer component, a polyfunctional monomer component having two or more polymerizable functional groups in one molecule.

[0011] With the first release film attached to the first main surface of the photocurable adhesive composition layer, the photocurable adhesive composition is irradiated with light through the first release film to obtain an adhesive sheet with a release film. The photocurable adhesive composition contains an acrylic material, an ultraviolet absorber, and a photopolymerization initiator. Examples of the acrylic material contained in the photocurable adhesive composition include an acrylic monomer and a partial polymer of the acrylic monomer. The acrylic material may contain both an acrylic monomer and a partial polymer of the acrylic monomer.

[0012] In one embodiment, a laminate having a photocurable pressure-sensitive adhesive composition layer sandwiched between a first release film and a second release film is irradiated with light from the first release film side to photocure the photocurable pressure-sensitive adhesive composition, thereby obtaining a pressure-sensitive adhesive sheet having release films temporarily attached to both sides. In the pressure-sensitive adhesive sheet having release films temporarily attached to both sides, the peel force between the first release film and the pressure-sensitive adhesive sheet may be greater than the peel force between the second release film and the pressure-sensitive adhesive sheet. Effect of the Invention

[0013] The adhesive sheet having high visible light transmittance and ultraviolet ray blocking property is preferably used as an optical adhesive sheet for display devices and input devices for displays that require ultraviolet ray blocking property. The adhesive sheet with release film of the present invention has excellent workability in peeling the release film from the adhesive sheet and bonding the adhesive sheet to the adherend, since an excessive increase in the peeling force between the adhesive sheet and the first release film is suppressed. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a cross-sectional view showing a laminated structure of a pressure-sensitive adhesive sheet with a release film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The pressure-sensitive adhesive sheet with a release film of the present invention comprises a release film temporarily attached to at least one surface of the pressure-sensitive adhesive sheet. "Temporarily attached" means a state in which the film is attached in a peelable manner. The pressure-sensitive adhesive sheet with a release film may have the release films temporarily attached to both surfaces of the pressure-sensitive adhesive sheet.

[0016] FIG. 1 is a cross-sectional view of an adhesive sheet 1 with release films, in which release films 10, 20 are temporarily attached to both sides of an adhesive sheet 50. The adhesive sheet 50 is a sheet of adhesive. The adhesive sheet 50 is transparent and has low optical absorption of visible light. The total light transmittance of the adhesive sheet 50 is preferably 85% or more, and more preferably 90% or more. The haze of the adhesive sheet is preferably 2% or less, and more preferably 1% or less. The total light transmittance and haze are measured using a haze meter in accordance with JIS K7136.

[0017] The adhesive sheet 50 is an acrylic adhesive containing a photocurable acrylic polymer, and contains an ultraviolet absorber in addition to the acrylic polymer. The acrylic adhesive sheet is made of a photocurable adhesive obtained by applying a photocurable adhesive composition containing a partial polymer (prepolymer) of an acrylic monomer and / or an acrylic polymer, an ultraviolet absorber, and a photopolymerization initiator in a layer form and photocuring the composition. In this specification, a "photocurable" adhesive refers to an adhesive that contains a compound containing a photopolymerizable functional group such as a vinyl group or a (meth)acryloyl group and is photocurable, and a "photocured" adhesive refers to an adhesive after photocuring of a photocurable adhesive. In the case where a part of the photopolymerizable compound remains unreacted in the adhesive after polymerization of the photocurable adhesive, the adhesive may be both photocured and photocurable.

[0018] [Photocurable adhesive composition] The photocurable pressure-sensitive adhesive composition contains a photopolymerizable acrylic material, an ultraviolet absorber, and a photopolymerization initiator.

[0019] <Photopolymerizable acrylic material> Examples of the photopolymerizable acrylic material contained in the photocurable pressure-sensitive adhesive composition include acrylic monomers and partial polymers (prepolymers) thereof.

[0020] (Monomer component) As the acrylic monomer, a (meth)acrylic acid alkyl ester having an alkyl group with 1 to 20 carbon atoms is preferably used. The (meth)acrylic acid alkyl ester may have a branched alkyl group. The content of the (meth)acrylic acid alkyl ester is preferably 40% by weight or more, more preferably 50% by weight or more, and even more preferably 60% by weight or more, based on the total amount of monomer components of the acrylic material.

[0021] The monomer component may contain, in addition to the (meth)acrylic acid alkyl ester, a highly polar monomer such as a hydroxyl group-containing monomer or a nitrogen-containing monomer. When the acrylic polymer contains a highly polar monomer unit, the cohesive strength of the adhesive is improved, thereby enhancing the adhesiveness of the adhesive sheet to the adherend, and the opacity of the adhesive in a high-temperature and high-humidity environment is suppressed, tending to improve the transparency of the adhesive sheet.

[0022] Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)-methyl acrylate, etc. The content of the hydroxy group-containing monomer is preferably 1 to 40% by weight, more preferably 3 to 30% by weight, and even more preferably 5 to 20% by weight, based on the total amount of the monomer components.

[0023] Examples of the nitrogen-containing monomer include vinyl monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinylcarboxylic acid amides, and N-vinylcaprolactam, and cyanoacrylate monomers such as acrylonitrile and methacrylonitrile. The nitrogen-containing monomer is preferably one having a cyclic structure containing a nitrogen atom, and among them, lactam vinyl monomers such as N-vinylpyrrolidone are preferred. The content of the nitrogen-containing monomer is preferably 0.5 to 50% by weight, more preferably 1 to 40% by weight, and even more preferably 3 to 30% by weight, based on the total amount of the monomer components.

[0024] The monomer component may contain monomers other than those mentioned above, such as a carboxyl group-containing monomer, a cyclic ether group-containing monomer, and a silane-based monomer.

[0025] The monomer component may contain a polyfunctional polymerizable compound having two or more polymerizable functional groups in one molecule. Examples of the polyfunctional polymerizable compound include a compound having two or more C=C bonds in one molecule, and a compound having one C=C bond and a polymerizable functional group such as epoxy, aziridine, oxazoline, hydrazine, or methylol. Among them, a polyfunctional polymerizable compound having two or more C=C bonds in one molecule is preferable. The polyfunctional polymerizable compound may be present in the pressure-sensitive adhesive composition as a monomer or oligomer, and may be bonded to a functional group such as a hydroxyl group of the prepolymer component.

[0026] Examples of polyfunctional polymerizable compounds having two or more C=C bonds in one molecule include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate. Examples of the polyfunctional monomer include polyfunctional acrylates (ester compounds of polyhydric alcohols and (meth)acrylic acid) such as 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and tetramethylolmethane tri(meth)acrylate; allyl(meth)acrylate, vinyl(meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. Among these, polyfunctional acrylates are preferred, and trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate are preferably used as the polyfunctional monomer.

[0027] The amount of the polyfunctional monomer used varies depending on the molecular weight, the number of functional groups, etc., but is preferably 5% by weight or less, more preferably 3% by weight or less, and even more preferably 2% by weight or less, based on the total amount of the monomer components. The amount of the polyfunctional monomer used may be 0.001 parts by weight or more, 0.01 parts by weight or more, or 0.05 parts by weight or more, based on the total amount of the monomer components.

[0028] In the photocurable pressure-sensitive adhesive composition, the above-mentioned monomer components may be present as a partially polymerized product (prepolymer). A prepolymer is a product obtained by partially polymerizing a monomer component. By having the monomer components present as prepolymers, the viscosity of the photocurable pressure-sensitive adhesive composition can be adjusted to a range suitable for application onto a supporting substrate.

[0029] The prepolymer can be prepared, for example, by partially polymerizing a prepolymer-forming composition obtained by mixing a monomer component and a polymerization initiator. The prepolymer-forming composition may contain all monomer components constituting the acrylic polymer, or may contain only a part of the monomers constituting the acrylic polymer. When the monomer components constituting the acrylic polymer contain a monofunctional monomer and a polyfunctional monomer, the adhesive composition may be prepared by adding a polyfunctional monomer to a prepolymer composition in which only the monofunctional monomer has been partially polymerized. By adding a polyfunctional monomer to a prepolymer composition in which only the monofunctional monomer has been partially polymerized and performing post-polymerization, crosslinking points due to the polyfunctional monomer can be uniformly introduced into the polymer. A part of the polyfunctional monomer components constituting the acrylic polymer may be contained in the prepolymer-forming composition, and the remainder of the polyfunctional monomer components may be added after polymerization of the prepolymer to perform post-polymerization.

[0030] The prepolymer may be prepared by polymerization in two or more stages or three or more stages. For example, after prepolymerization of only monofunctional monomers, a polyfunctional monomer is added to carry out partial polymerization to prepare a prepolymer composition, and further monomer components and the like may be added as necessary to carry out postpolymerization.

[0031] The polymerization method of the prepolymer is not particularly limited. From the viewpoint of adjusting the reaction time to set the molecular weight (polymerization rate) of the prepolymer in a desired range, photopolymerization by irradiation with active light such as ultraviolet light is preferred. When photopolymerization is performed, it is preferred that the prepolymer composition contains a photopolymerization initiator. Specific examples of the photopolymerization initiator will be described later.

[0032] The prepolymer forming composition may contain a chain transfer agent or the like as necessary in addition to the monomer components and the polymerization initiator. The chain transfer agent receives radicals from the growing polymer chain to terminate the elongation of the polymer, and the chain transfer agent that has received the radical attacks the monomer to start polymerization again. By using the chain transfer agent, excessive increase in molecular weight can be suppressed without decreasing the radical concentration in the reaction system. As the chain transfer agent, thiols such as α-thioglycerol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol are preferably used.

[0033] The polymerization rate of the prepolymer is not particularly limited, but is preferably 3 to 50%, more preferably 5 to 40%, from the viewpoint of obtaining a viscosity suitable for application on a substrate. The polymerization rate of the prepolymer can be adjusted to a desired range by adjusting the type and amount of photopolymerization initiator, the irradiation intensity and irradiation time of active light such as ultraviolet light, etc. The polymerization rate is calculated from the weights before and after heating (drying) when the prepolymer composition is heated at 130°C for 3 hours according to the following formula. When partial polymerization is performed by solution polymerization, the polymerization rate is calculated by subtracting the amount of the solvent from the total weight of the prepolymer composition as the weight before heating in the following formula. Polymer conversion rate (%) = 100 × (weight after heating / weight before heating)

[0034] <Preparation of Photocurable Pressure-Sensitive Adhesive Composition>

[0035] The photocurable adhesive composition is obtained by mixing the remaining monomer components, an ultraviolet absorber, a photopolymerization initiator, and other additives with the above-mentioned photopolymerizable acrylic material (monomer and / or its partial polymer).

[0036] <Ultraviolet absorbing agent> Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, triazine-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, and cyanoacrylate-based ultraviolet absorbers. Triazine-based ultraviolet absorbers are preferred because they have high ultraviolet absorption and excellent compatibility with acrylic polymers, and are easy to obtain highly transparent acrylic adhesive sheets. Among them, triazine-based ultraviolet absorbers containing hydroxyl groups are preferred, and hydroxyphenyltriazine-based ultraviolet absorbers are particularly preferred. The number of hydroxyl groups in the triazine-based ultraviolet absorber is preferably 2 or less.

[0037] As the ultraviolet absorbing agent, a commercially available product may be used. Commercially available triazine-based UV absorbers include the reaction product of 2-(4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl)-5-hydroxyphenyl with [(alkyloxy)methyl]oxirane (BASF's "TINUVIN 400"), the reaction product of 2-(2,4-dihydroxyphenyl)-4,6-bis-(2,4-dimethylphenyl)-1,3,5-triazine with (2-ethylhexyl)-glycidic acid ester (BASF's "TINUVIN 405"), (2,4-bis[2-hydroxy-4-butoxyphenyl]-6-(2,4-dibutoxyphenyl)-1,3,5-triazine (BASF's "TINUVIN 460"), and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol (BASF's "TINUVIN 577"), 2-(2-hydroxy-4-[1-octyloxycarbonylethoxy]phenyl)-4,6-bis(4-phenylphenyl)-1,3,5-triazine ("TINUVIN 479" manufactured by BASF), and the like.

[0038] The content of the ultraviolet absorber in the photocurable adhesive composition is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 7 parts by weight, and even more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the monomer component. By setting the content of the ultraviolet absorber within the above range, it is possible to improve the ultraviolet cutoff property of the adhesive sheet while suppressing a decrease in transparency due to bleed-out of the ultraviolet absorber, etc. Furthermore, if the content of the ultraviolet absorber is within the above range, it is possible to suppress a decrease in the polymerization rate of the adhesive composition.

[0039] <Photopolymerization initiator> The photocurable pressure-sensitive adhesive composition contains a photopolymerization initiator, which is a photoradical generator that generates radicals when exposed to visible light or ultraviolet light having a wavelength shorter than 450 nm.

[0040] When the photocurable pressure-sensitive adhesive composition contains an ultraviolet absorber, a part of the irradiated light for photocuring is absorbed by the ultraviolet absorber. From the viewpoint of promoting the generation of radicals by the cleavage of the photopolymerization initiator and improving the polymerization rate, it is preferable to use a photopolymerization initiator that has sensitivity in a wavelength region where absorption by the ultraviolet absorber is small. Specifically, the photopolymerization initiator is preferably one that has sensitivity to wavelengths longer than 380 nm, and more preferably one that has sensitivity to wavelengths longer than 400 nm. The extinction coefficient at a wavelength of 405 nm is 1×10 2 [mLg -1 cm -1 It is preferable to use a photopolymerization initiator having a sensitivity to light of a long wavelength. The photopolymerization initiator having sensitivity to light of a wavelength of 400 nm or less may be used.

[0041] Specific examples of photopolymerization initiators having a photosensitivity of 400 nm or more include 2,4,6-trimethylbenzoyldiphenylphosphine oxide (BASF's "Lucirin TPO"), 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide (BASF's "Lucirin acylphosphine oxides such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1 (BASF's "Irgacure 369"), aminoketones such as bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BASF's "Irgacure 819"), 2,2-dimethoxy-1,2-diphenylethan-1-one (BASF's "Irgacure 651"), bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide (BASF's "CGI403"), and the like.

[0042] As the photopolymerization initiator, there are two types: one with long wavelength light sensitivity and one without long wavelength light sensitivity (for example, a photopolymerization initiator with an absorption coefficient of 1×10 at a wavelength of 405 nm). 2 [mLg -1 cm -1 ] or less).

[0043] Examples of photopolymerization initiators that do not have sensitivity to long-wavelength light include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, and titanocene-based photopolymerization initiators.

[0044] The content of the photopolymerization initiator in the photocurable pressure-sensitive adhesive composition is preferably 0.02 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the total of the monomer components and prepolymer components constituting the acrylic polymer. If the amount of the photopolymerization initiator is too small, the polymerization rate may be insufficient, and if the amount of the photopolymerization initiator is too large, the molecular weight of the polymer may be low, resulting in insufficient adhesive strength of the pressure-sensitive adhesive.

[0045] As described above, a photopolymerization initiator can also be used in the preparation of the prepolymer (partial polymerization). The photopolymerization initiator used in the partial polymerization may be the same as or different from the photopolymerization initiator added to the photocurable adhesive composition. When the prepolymer forming composition does not contain an ultraviolet absorber and an ultraviolet absorber is added after partial polymerization, the photopolymerization initiator used in the partial polymerization does not need to have sensitivity to long wavelength light. The unreacted product of the photopolymerization initiator used in the partial polymerization may be used as it is as the photopolymerization initiator in the photopolymerizable adhesive composition.

[0046] From the viewpoint of the utilization efficiency of the irradiated light, it is preferable to add an ultraviolet absorber to the prepolymer composition after partial polymerization without adding an ultraviolet absorber to the prepolymer forming composition. For example, it is preferable to carry out partial polymerization using a photopolymerization initiator having no sensitivity to long wavelength light as a pre-addition polymerization initiator, add an ultraviolet absorber and a photopolymerization initiator having sensitivity to long wavelength light as a post-addition polymerization initiator to the composition after partial polymerization to prepare a photocurable pressure-sensitive adhesive composition, apply the photocurable pressure-sensitive adhesive composition in a layer on a substrate, and then carry out post-polymerization.

[0047] <Other ingredients> The photocurable adhesive composition may contain a chain transfer agent. The chain transfer agent contained in the photocurable adhesive composition is not particularly limited, and the above-mentioned chain transfer agents may be used, for example. The adhesive composition may contain a silane coupling agent, a crosslinking agent, a tackifier, a plasticizer, a softener, etc. for the purpose of adjusting the adhesive strength, etc. In addition, the adhesive composition may contain additives such as deterioration inhibitors, fillers, colorants, antioxidants, surfactants, and antistatic agents within a range that does not impair the properties of the adhesive.

[0048] The photocurable pressure-sensitive adhesive composition preferably has a viscosity (e.g., about 5 to 100 poise) suitable for application onto a substrate. The viscosity of the pressure-sensitive adhesive composition can be adjusted, for example, by adding various polymers such as thickening additives or polyfunctional monomers, or by the polymerization rate of the prepolymer. The photocurable pressure-sensitive adhesive composition preferably contains 50% by weight or more of an acrylic monomer component (acrylic monomer and partial polymer of acrylic monomer), more preferably 70% by weight or more, and even more preferably 80% by weight or more.

[0049] [Formation of adhesive sheet] The photocurable adhesive composition is applied onto a supporting substrate and photocured to obtain an adhesive sheet. Examples of methods for applying the adhesive composition onto a substrate include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. Since photoradical polymerization is inhibited by oxygen in the air, it is preferable to provide a cover sheet on the coating layer of the photocurable adhesive composition to block oxygen. The photocurable adhesive composition may be applied so as to be sandwiched between two sheets (supporting substrate and cover sheet).

[0050] The coating thickness of the photocurable adhesive composition (thickness of the adhesive sheet 50) is not particularly limited, but is, for example, about 10 to 500 μm. From the viewpoint of enhancing the ultraviolet absorbing property of the adhesive sheet, the thickness of the adhesive sheet is preferably 50 μm or more, more preferably 100 μm or more, and even more preferably 150 μm or more. The light transmittance of the adhesive sheet 50 at a wavelength of 380 nm is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less.

[0051] A laminate having a photocurable acrylic pressure-sensitive adhesive composition layer on a supporting substrate is irradiated with ultraviolet light and / or short-wavelength visible light to photocure, thereby obtaining a pressure-sensitive adhesive sheet. When photocuring is performed by irradiating a laminate having a photocurable pressure-sensitive adhesive composition layer sandwiched between a supporting substrate and a cover sheet, light irradiation may be performed from either the supporting substrate side or the cover sheet side, or from both sides. As described in detail later, in the present invention, a release film 10 having a predetermined release layer 15 is used as the supporting substrate or the cover sheet attached to the light-irradiated side of the pressure-sensitive adhesive sheet.

[0052] To improve the curing speed, the light irradiation intensity was set to 5 mW / cm 2 From the viewpoint of sufficiently increasing the molecular weight of the acrylic polymer after photocuring and ensuring its retention at high temperatures, the light irradiation intensity is preferably 20 mW / cm or more. 2 The following is preferred:

[0053] The cumulative light intensity of the irradiation light is 100 to 5000 mJ / cm 2 The light source for light irradiation is not particularly limited as long as it can irradiate light within a wavelength range to which the photopolymerization initiator contained in the pressure-sensitive adhesive composition has sensitivity, and preferably used are an LED light source, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a xenon lamp, etc.

[0054] Most of the ultraviolet light irradiated to the photocurable adhesive composition containing an ultraviolet absorber is absorbed by the ultraviolet absorber. From the viewpoint of suppressing the molecular weight reduction caused by temperature rise and improving the utilization efficiency and curing speed of the irradiated light, it is preferable to irradiate light in a wavelength region where the light absorption by the ultraviolet absorber is small. It is preferable to use an LED light source because it is possible to irradiate light with small heat dissipation from the light source and narrow wavelength width. When using an LED light source, the emission peak wavelength is preferably 350 nm or more, more preferably 380 nm or more, and even more preferably 400 nm or more.

[0055] The final polymerization rate of the monomer component in the photocured pressure-sensitive adhesive sheet is preferably 90% or more, more preferably 95% or more, and even more preferably 98% or more. The gel fraction of the pressure-sensitive adhesive sheet is preferably 50% or more, more preferably 75% or more, and even more preferably 85% or more.

[0056] [Release film] As the support substrate for applying the adhesive composition and the cover sheet attached to the surface of the applied layer of the adhesive composition, a release film having a release layer on the contact surface with the applied layer (adhesive sheet) is preferably used. In the present invention, photocuring is performed in a state where a release film (first release film) 11 having a predetermined silicone-based release layer 15 is attached to the light irradiated surface side of the photocurable adhesive composition layer 55.

[0057] <Base material> As the substrates 11 and 21 of the release films 10 and 20, various resin films having transparency are used. Examples of the resin material include polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, polyarylate-based resins, and polyphenylene sulfide-based resins. Among these, polyester-based resins such as polyethylene terephthalate are particularly preferred. The thickness of the substrates 11 and 21 is preferably 10 to 200 μm, more preferably 25 to 150 μm.

[0058] <Release layer> Examples of materials for the release layer include silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, silica powder, etc. As the release film 20, one having a silicone-based release layer 25 formed from a silicone-based release agent on the surface of the film substrate 21 is preferably used, since it is possible to achieve both adhesion to the acrylic adhesive sheet and releasability.

[0059] The release film 10 attached to the light irradiated surface side of the photocurable pressure-sensitive adhesive composition layer 55 includes a silicone-based release layer 15. The silicone-based release layer 15 has a Si atom content per unit area of ​​0.02 to 0.07 g / m 2 The silicon atom content of the silicone-based release layer 15 is 0.025 to 0.06 g / m 2 is preferably 0.03 to 0.055 g / m 2 is more preferred.

[0060] The silicone-based release layer 15 of the release film 10 contains a curable silicone resin. The silicone-based resin may be a type that is mainly composed of itself, or may be a silicone-modified resin in which reactive silicone is introduced into an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin by graft polymerization or the like. As the silicone resin, various types of curing reaction types such as addition type, condensation type, ultraviolet curing type, electron beam curing type, and solventless type can be used. In particular, a type of silicone resin that is cured by an addition reaction caused by heat to form a peelable coating is preferably used, since it has excellent adhesion to the film substrate and can achieve both appropriate adhesion and peelability to the acrylic adhesive sheet.

[0061] Silicone-based materials that cure by addition reactions include polyorganosiloxanes having vinyl or alkenyl groups in the molecule. Examples of alkenyl groups include 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl, and 11-dodecenyl groups. Examples of polyorganosiloxanes include polyalkylalkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane; polyalkylarylsiloxanes; poly(dimethylsiloxane-diethylsiloxane); ) and copolymers in which multiple types of Si atom-containing monomer components such as those mentioned above are used. Among these, polydimethylsiloxane is preferred.

[0062] As the silicone resin, a commercially available composition containing a curable silicone resin may be used. Commercially available products of the curable silicone-based release agent include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, and X-62-2461 manufactured by Shin-Etsu Chemical Co., Ltd.; YSR-3022, TPR-6700, TPR-6720, and TPR-6721 manufactured by Toshiba Silicone; LTC300B, LTC303E, LT303E manufactured by Toray Dow Corning Co., Ltd. C310, LTC314, SRX357, BY24-749, SD7333, BY24-179, BY24-840, BY24-842, BY24-850, SP7015, SP7259, SD7220, SD7226, and SD7229; DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, etc. manufactured by Dow Corning Asia.

[0063] The curable silicone-based release agent composition may contain an additive (release control agent) for the purpose of adjusting the release property of the release layer. The addition type silicone-based release agent composition may contain a curing catalyst. The curing catalyst is preferably a platinum-based catalyst. Examples of the platinum-based catalyst include chloroplatinic acid, platinum olefin complexes, and chloroplatinic acid olefin complexes. The amount of the platinum-based catalyst used is about 10 to 1000 ppm in terms of platinum based on the total solid content of the silicone-based release agent composition.

[0064] The silicone-based release agent composition may contain an organic solvent. Examples of the organic solvent include hydrocarbon solvents such as cyclohexane, n-hexane, and n-heptane; aromatic solvents such as toluene and xylene; ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and alcohol solvents such as methanol, ethanol, and butanol. etc. The organic solvent may be a mixed solvent. The amount of the organic solvent used is preferably about 80 to 99.9% by mass in the silicone-based release agent composition.

[0065] The silicone-based release agent composition may contain various additives, such as a filler, an antistatic agent, an antioxidant, a plasticizer, and a colorant, as necessary.

[0066] A silicone-based release agent composition is applied onto the substrate 11 and dried by heating to form a silicone-based release layer. Examples of the application method include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. Examples of the heat drying method include hot air drying. The conditions for hot air drying vary depending on the heat resistance of the substrate, but are usually about 80 to 150°C and about 10 seconds to 10 minutes. If necessary, a heat treatment may be used in combination with irradiation with active energy rays such as ultraviolet irradiation in order to promote the addition reaction of silicone.

[0067] The amount of silicone resin in the silicone release agent composition to be applied is 0.03 to 1 g / m 2 The thickness of the silicone-based release layer 15 is, for example, 10 to 500 nm. The coating amount of the silicone-based release agent composition and the thickness of the silicone-based release layer 15 may be adjusted so that the Si atom content of the silicone-based release layer 15 falls within the above-mentioned range.

[0068] [Removability of release film and adhesive sheet] In a pressure-sensitive adhesive sheet with release films, in which release films are temporarily attached to both sides of the pressure-sensitive adhesive sheet, the peeling force between the pressure-sensitive adhesive sheet and one of the release films is generally 1 / 2 the peeling force between the pressure-sensitive adhesive sheet and the other release film. of It is relatively small compared to the peel strength. When using the adhesive sheet, the release film with low peel strength (light release film) is peeled off from the adhesive sheet to attach it to the first adherend, and then the release film with relatively high peel strength (heavy release film) is peeled off to attach it to the second adherend. By providing a difference in peel strength between the release films temporarily attached to the front and back of the adhesive sheet, the light release film can be selectively peeled off when attaching it to the first adherend, improving the workability of attachment.

[0069] In the photocurable adhesive sheet, the adhesive strength of the adhesive is different before and after photocuring, so the adhesive properties of the adhesive sheet after photocuring are considered, and the adhesiveness (peeling property) of the light release film and the heavy release film to each adhesive sheet is adjusted. When the adhesive composition does not contain an ultraviolet absorber, the magnitude relationship of the peeling force between one release film and the other release film does not change before and after photocuring. On the other hand, when the photocurable adhesive composition contains an ultraviolet absorber, the increase in the peeling force of the first release film on the light irradiation side tends to be significantly larger than the increase in the peeling force of the second release film arranged on the opposite side.

[0070] Therefore, in the pressure-sensitive adhesive sheet with release film of the present invention, it is preferable that the first release film 10 on the light irradiated surface is a heavy release film and the second release film 20 on the opposite surface is a light release film. In other words, it is preferable that the peel force between the first release film 10 and the pressure-sensitive adhesive sheet 50 is greater than the peel force between the second release film 20 and the pressure-sensitive adhesive sheet 50.

[0071] If the peeling force between the first release film 10 (heavy release film) and the adhesive sheet 50 is excessively large, when the first release film 10 is peeled from the surface of the adhesive sheet 50 in a state where the adhesive sheet 50 is attached to the first adherend, problems such as deformation of the adhesive sheet or peeling of the adhesive sheet from the adherend may occur. The peeling force between the adhesive sheet 50 and the first release film 10 after photocuring is preferably 0.1 to 1.1 N / 50 mm, more preferably 0.2 to 0.8 N / 50 mm, and even more preferably 0.3 to 0.7 N / 50 mm. The peeling force between the release film and the adhesive sheet is a measurement value obtained by a 180° peel test at a tensile speed of 0.3 m / min. In the present invention, by setting the Si atom content in the release layer 15 of the first release film 10 to the above-mentioned range, an excessive increase in the peeling force between the adhesive sheet and the first release film after photocuring can be suppressed.

[0072] It is not clear why the peel strength of the first release film increases when the photocurable adhesive composition contains an ultraviolet absorber, and why adjusting the Si content of the release layer can suppress an excessive increase in the peel strength after photocuring of the adhesive composition; however, it is presumed that this is related to a reaction between unreacted thermally reactive functional groups in the release layer and compounds in the adhesive composition.

[0073] As described above, most of the ultraviolet light irradiated to the photocurable adhesive composition containing an ultraviolet absorber is absorbed by the ultraviolet absorber. Even if the sensitivity wavelength of the photopolymerization initiator and the wavelength of the irradiated light are shifted to the long wavelength side (for example, 400 nm or more), it is difficult to completely suppress the light absorption by the ultraviolet absorber. When the ultraviolet absorber absorbs light, the light energy is converted into heat energy and the temperature rises. In particular, in the vicinity of the interface between the release layer 15 on the light irradiation side and the adhesive composition layer 55, the amount of light absorbed by the ultraviolet absorber is large, so the temperature is likely to rise. When the temperature rises under light irradiation, in addition to the photocuring reaction, the heat curing reaction is likely to proceed. Therefore, the unreacted heat-reactive functional groups (vinyl group, alkenyl group, alkoxysilyl group, silanol group, hydrosilyl group, etc.) in the release layer 15 are easily absorbed. And viscosity It is believed that the adhesive strength (peel strength) increases as a result of a reaction with the compounds in the adhesive composition.

[0074] By reducing the Si atom content per unit area of ​​the silicone-based release layer 15, the amount of unreacted thermally reactive functional groups in the release layer 15 is reduced. Therefore, in the present invention, it is believed that the amount of remaining reactive functional groups in the release layer 15 that can react with the compound in the pressure-sensitive adhesive composition layer 15 is small, and an excessive increase in the peel force between the pressure-sensitive adhesive sheet 50 and the release film 10 after photocuring can be suppressed.

[0075] As described above, the pressure-sensitive adhesive composition may be irradiated with light from either the supporting substrate side or the cover sheet side, or may be irradiated with light from both sides. When irradiating with light from the supporting substrate side, the release film 10 having the above-mentioned silicone-based release layer 15 may be used as the supporting substrate to which the pressure-sensitive adhesive composition is applied. When irradiating with light from the cover sheet side, the release film 10 having the above-mentioned silicone-based release layer 15 may be used as the cover sheet to be attached on the pressure-sensitive adhesive composition layer 55.

[0076] When light is irradiated from both sides, the release film may be used on either the supporting substrate or the cover sheet. The release film may be used on both sides of the supporting substrate or the cover sheet. As described in JP 2014-65754 A, when light is irradiated on both sides while conveying through a return path line that reverses the conveying direction, it is preferable to use the release film on the side that is first irradiated with light.

[0077] [Uses of adhesive sheets] The photocurable adhesive sheet has high visible light transmittance and ultraviolet ray blocking properties, and is therefore suitable for use as an optical adhesive for display devices and display input devices that require ultraviolet ray blocking properties. Examples of the display device include liquid crystal display devices, organic EL (electroluminescence) display devices, PDP (plasma display panel), and electronic paper. Examples of the input device include touch panels. The photocurable adhesive sheet can also be used for bonding a display device and an input device, or bonding a transparent plate disposed on the surface of a display device or input device.

[0078] When using an adhesive sheet with release films temporarily attached to both sides, first, the light release film (second release film 20) is peeled off to expose the second main surface of the adhesive sheet 50, and the sheet is bonded to the first adherend. Thereafter, the heavy release film (first release film 10) is peeled off to expose the first main surface of the adhesive sheet 50, and the sheet is bonded to the second adherend. The sheet may be bonded to the adherend after peeling off the release films on both sides. If the adhesive sheet has photocuring properties, the adhesive sheet may be further irradiated with light after being bonded to the adherend. By further photocuring the adhesive sheet after being bonded to the adherend, the adhesive reliability with the adherend may be improved in some cases. EXAMPLES

[0079] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0080] [Preparation of photocurable adhesive composition] <Adhesive composition A> To a monomer mixture consisting of 78 parts by weight of 2-ethylhexyl acrylate (2EHA), 18 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 4 parts by weight of 2-hydroxyethyl acrylate (HEA), 0.035 parts by weight of 1-hydroxycyclohexyl phenyl ketone (BASF's "Irgacure 184") and 0.035 parts by weight of 2,2-dimethoxy-1,2-diphenylethan-1-one (BASF's "Irgacure 651") were added as photopolymerization initiators (pre-added photopolymerization initiators). This composition was irradiated with ultraviolet light and prepolymerized until the viscosity at room temperature reached approximately 20 Pa·s, and the polymerization rate reached approximately 8. %of A prepolymer was obtained.

[0081] To 100 parts by weight of the prepolymer, 0.15 parts by weight of hexanediol diacrylate (HDDA), 0.3 parts by weight of a silane coupling agent ("KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.), 4.7 parts by weight of a 15% by weight solution of ultraviolet absorber (2,4-bis-[{4-(4-ethylhexyloxy)-4-hydroxy}-phenyl]-6-(4-methoxyphenyl)-1,3,5-triazine; "Tinosorb S" manufactured by BASF) in butyl acrylate (BA) (ultraviolet absorber: 0.7 parts by weight), and 0.15 parts by weight of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide ("Irgacure 819" manufactured by BASF) were added as a post-addition polymerization initiator, to obtain an ultraviolet-curable acrylic adhesive composition A.

[0082] <Adhesive composition B> An adhesive composition B was obtained in the same manner as in the preparation of adhesive composition 1, except that the amount of the post-added polymerization initiator was changed from 0.15 parts by weight to 0.1 parts by weight.

[0083] <Adhesive composition C> In the preparation of the prepolymer composition, the composition of the monomer mixture was changed to 2EHA: 30.5 parts by weight, isostearyl acrylate (ISTA): 30.5 parts by weight, isobornyl acrylate (IBXA): 19 parts by weight, and 4-hydroxybutyl acrylate (4HBA): 20 parts by weight, and the amount of the photopolymerization initiator added was changed to 1-hydroxycyclohexyl phenyl ketone: 0.05 parts by weight, and 2,2-dimethoxy-1,2-diphenylethan-1-one: 0.05 parts by weight. Except for these changes, the preparation of the adhesive composition 1 was carried out in the same manner to obtain the adhesive composition C.

[0084] [Preparation of silicone release agent solution] <Release agent solution A> A 30% toluene solution of hexenyl-containing addition type silicone (addition type silicone-based release agent containing polyorganosiloxane having hexenyl groups in the molecule and polyorganosiloxane crosslinking agent having hydrosilyl groups in the molecule) (Toray Dow Corning "LTC761"): 30 parts by weight, silicone dispersion (Toray Dow Corning "BY 24-850"): 0.9 parts by weight, and silicone curing platinum catalyst (Toray Dow Corning "SRX 212"): 2 parts by weight were diluted with a mixed solvent of toluene and hexane in a volume ratio of 1:1 to a predetermined concentration shown in Table 1, to prepare a release agent solution A.

[0085] <Release agent solution B> 30% toluene solution of vinyl group-containing addition type silicone ("KS-847T" manufactured by Shin-Etsu Chemical) 100 Parts by weight of 1 part by weight of a platinum catalyst for silicone curing ("CAT-PL-50T" manufactured by Shin-Etsu Chemical Co., Ltd.) were diluted with a mixed solvent of toluene and hexane in a volume ratio of 1:1 to a predetermined concentration shown in Table 1 to prepare release agent solution B.

[0086] [Example 1] <Preparation of release film for substrate> Release agent solution B, which had been prepared so that the silicone solid content was 1.25% by weight, was applied to one side of a 75 μm-thick biaxially oriented polyester film ("Lumirror XD500P" manufactured by Toray Advanced Materials Korea Co., Ltd.) using a wire bar (#15), and the film was heated in a hot air dryer at 130° C. for 1 minute to form a release layer.

[0087] <Preparation of cover release film> Release agent solution A, which had been prepared so that the silicone solid content was 0.7% by weight, was applied to one side of a 75 μm-thick biaxially oriented polyester film ("Lumirror XD500P" manufactured by Toray Advanced Materials Korea Co., Ltd.) using a wire bar (#9), and the film was heated in a hot air dryer at 130° C. for 1 minute to form a release layer.

[0088] <Preparation of adhesive sheet with release film> The pressure-sensitive adhesive composition A was applied to the release layer-forming surface of the above-mentioned coating substrate release film to a thickness of 150 μm to form a coating layer, and a cover release film was attached to the surface of the coating layer to obtain a laminate. This laminate was then subjected to illuminance of 6.5 mW / cm from the cover release film side. 2 , Accumulated light intensity: 1500mJ / cm 2 The coating layer was photocured by irradiating it with ultraviolet light under the above conditions to obtain a pressure-sensitive adhesive sheet having release films on both sides of the photocurable pressure-sensitive adhesive layer.

[0089] [Examples 2 to 6 and Comparative Examples 1 to 3] The type and concentration of the release agent solution, the wire diameter (count) of the wire bar, and the type of adhesive composition used when preparing the cover release film were changed as shown in Table 1. Apart from these changes, a photocurable adhesive sheet having release films on both sides was prepared in the same manner as in Example 1.

[0090] [evaluation] <Si atom content in release layer> The amount of Si atoms per unit area (mg / m) was determined by X-ray fluorescence analysis (XRF) of the release layer surface of the cover release film. 2 For the XRF analysis, a scanning X-ray fluorescence analyzer (Rigaku "ZSX100e") equipped with a vertical rhodium tube was used as the X-ray source, and measurements were performed under the following conditions: analysis area: 30 mmφ, analysis element: Si, analyzing crystal: RX4, output: 50 kV, 70 mA.

[0091] <Release film peel strength> The adhesive sheet with release film was cut to a width of 50 mm, and a 180° peel test was performed at a pulling speed of 0.3 m / min using a tensile tester in an environment of 23°C to measure the peel force when peeling the substrate release film and the cover release film from the adhesive sheet.

[0092] [Evaluation Results] Table 1 shows the configuration of the release layer in the cover release films of the examples and comparative examples (type of release agent solution, silicone concentration, thickness, and Si amount), type of adhesive, and evaluation results of peel strength.

[0093] [Table 1]

[0094] In all of Examples 1 to 6 and Comparative Examples 1 to 3, the peeling force of the base release film was about 0.2 N / 50 mm, and no significant difference was observed. In Comparative Example 3, in which the same release agent was used for the base release film and the cover release film, the peeling force of the cover release film after photocuring of the adhesive sheet was 10 times or more that of the base release film, and peeling was difficult. In Comparative Example 1, in which the type of silicone release agent of the cover release film and the composition of the adhesive were changed, the peeling force of the cover release film was also significantly increased as in Comparative Example 3. From these results, it can be seen that when photocuring is performed by irradiating light to a laminate in which a photocurable adhesive sheet containing an ultraviolet absorber is sandwiched between two release films, the peeling force of the release sheet on the light irradiated surface becomes large.

[0095] In Comparative Example 2, in which the concentration of the release agent solution and the coating thickness were greater than those in Comparative Example 1 when preparing the cover release film, the amount of Si per unit area of ​​the release layer was greater and the peel force of the cover release film after the adhesive sheet was photocured was even greater than in Comparative Example 1.

[0096] In Examples 1, 4, and 5, in which the amount of Si per unit area was reduced by adjusting the concentration and coating thickness of the release agent solution when preparing the cover release film, the peeling force of the cover release film after the adhesive sheet was photocured was reduced to less than 1 N / 50 mm, making it difficult for defects such as deformation of the adhesive sheet to occur during peeling. From the results of Examples 1, 4, and 5 and Comparative Examples 1 and 2, it can be seen that by reducing the amount of Si per unit area of ​​the release layer, the peeling force of the cover release film after the adhesive sheet was photocured is reduced.

[0097] In Examples 2 and 3, in which the same cover release film as in Example 1 was used but the adhesive composition was changed, the peeling force of the cover release film was equivalent to that of Example 1. In Example 6, in which the same adhesive sheet as in Example 2 was used, the peeling property of the cover release film after the adhesive sheet was photocured was also good.

[0098] From the above results, it can be seen that by attaching a release sheet having a release layer with a Si atomic weight per unit area in a predetermined range to a photocurable adhesive sheet containing an ultraviolet absorber, it is possible to suppress excessive increase in the peel strength of the release film after photocuring of the adhesive sheet. [Explanation of symbols]

[0099] 1: Adhesive sheet with release film 50: Adhesive sheet 10,20: Release film 11,21: Base material 15,25: Release layer 5: Laminate 55: Photocurable adhesive composition layer

Claims

1. A pressure-sensitive adhesive sheet with a release film, comprising: a photocurable pressure-sensitive adhesive sheet having a first main surface and a second main surface; and a first release film temporarily attached to the first main surface of the pressure-sensitive adhesive sheet, The first release film comprises a release layer on a film substrate, the release layer and the pressure-sensitive adhesive sheet are in contact with each other, The pressure-sensitive adhesive sheet contains a photocurable acrylic polymer and an ultraviolet absorber, The release layer is a silicone-based release layer containing a thermoset product of a polyorganosiloxane having an alkenyl group selected from a 3-butenyl group, a 4-pentenyl group, a 5-hexenyl group, a 6-heptenyl group, a 7-octenyl group, an 8-nonenyl group, a 9-decenyl group, a 10-undecenyl group, and an 11-dodecenyl group in the molecule, and has a Si atom content of 0.02 to 0.07 g / m ２ It is an adhesive sheet with a release film.

2. The pressure-sensitive adhesive sheet with a release film according to claim 1 , further comprising a second release film temporarily attached to a second main surface of the pressure-sensitive adhesive sheet.

3. The adhesive sheet with a release film according to claim 2 , wherein a peel strength between the first release film and the adhesive sheet is greater than a peel strength between the second release film and the adhesive sheet.

4. The pressure-sensitive adhesive sheet with a release film according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive sheet has a light transmittance of 10% or less at a wavelength of 380 nm.

5. The pressure-sensitive adhesive sheet with a release film according to any one of claims 1 to 4, wherein the acrylic polymer contains, as a monomer component, a polyfunctional monomer component having two or more polymerizable functional groups in one molecule.

6. The pressure-sensitive adhesive sheet with a release film according to any one of claims 1 to 5, wherein the ultraviolet absorber is a triazine-based ultraviolet absorber.

7. 7. The pressure-sensitive adhesive sheet with a release film according to claim 1, wherein the pressure-sensitive adhesive sheet contains 0.1 to 10 parts by weight of the ultraviolet absorbing agent per 100 parts by weight of the acrylic polymer.

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