Sheet-shaped photocurable composition, photocurable composition solution, method for producing sheet-shaped photocurable composition, and laminate

Abstract

To provide a photocurable composition that achieves improvement in the peel adhesive strength of to a resin substrate, which has been difficult conventionally, under both normal temperature and high temperature environments, and a method for producing the same.SOLUTION: A photocurable composition includes following components (A) to (D) and is in a sheet shape at 25°C in a pre-curing state. Component (A): a (meth)acrylic triblock copolymer, Component (B): a (meth)acrylate oligomer (excluding the component (A)), Component (C): a monomer having a (meth)acryloyl group, represented by Formula 1, and Component (D): photoinitiator. (In the Formula 1, R1 is a hydrogen atom or a methyl group, R2 is a monovalent organic group having an oxygen atom).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photocurable composition that is in the form of a sheet at 25°C. [Background technology]

[0002] Adhesives used in assembling display devices such as organic electroluminescence (EL) displays are required to have good adhesive properties over a wide temperature range. To improve such properties, it has been proposed to use a triblock copolymer elastomer having a hard segment with a high glass transition temperature and a soft segment with a low glass transition temperature in a photocurable composition.

[0003] For example, Japanese Patent Application Laid-Open No. 2017-036368 proposes a photocurable pressure-sensitive adhesive composition (adhesive composition) containing a (meth)acrylate triblock copolymer elastomer as a main component and having removability. However, the photocurable pressure-sensitive adhesive composition disclosed in this document is intended for use as an adhesive (i.e., it is removably attached and remains semi-solid and viscous during use), and is therefore unsuitable for use as an adhesive (i.e., it is not removably attached to an adherend in a solid state). Specifically, when the photocurable pressure-sensitive adhesive composition disclosed in the above document is left in a high-temperature atmosphere, it often peels off from the adherend (substrate) in a reliability test due to reasons such as a decrease in strength. Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, conventional photocurable compositions using (meth)acrylate triblock copolymers for optical applications have been proposed. However, peeling from adherends (substrates) has been problematic both at room temperature and in high-temperature environments (e.g., in 25°C and 85°C atmospheres). Furthermore, when (meth)acrylic resin plates, polyethylene terephthalate (PET) films, etc. are used as adherends (substrates), it has been particularly difficult to improve the peel adhesive strength (adhesion) of these adherends (substrates).

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a means for improving the peel adhesive strength of a photocurable composition to a resin substrate, for which it is difficult to improve the peel adhesive strength, both at room temperature and in a high-temperature environment. [Means for solving the problem]

[0006] As a result of intensive research aimed at achieving the above object, the present inventors have found that a sheet-shaped photocurable composition, which will be described in detail below, can improve the peel adhesion strength to resin substrates, for which it is difficult to improve the peel adhesion strength, both at room temperature and at high temperatures, and have thus completed the present invention.

[0007] In order to achieve at least one of the above-mentioned objects, one aspect of the present invention provides a sheet-shaped photocurable composition comprising the following components (A) to (D), which is in the form of a sheet at 25°C before curing: Component (A): (meth)acrylic triblock copolymer Component (B): (meth)acrylate oligomer (excluding component (A)) Component (C): a compound represented by the following formula 1

[0008] [ka]

[0009] (In the above formula 1, R 1is a hydrogen atom or a methyl group, and R 2 is a monovalent organic group containing an oxygen atom) (D) Component: Photoinitiator.

[0010] The present inventors have also found that the above problems can be solved by the following photocurable composition solution, and have thus completed the present invention.

[0011] In order to achieve at least one of the above-mentioned objects, a photocurable composition solution according to one aspect of the present invention comprises the following components (A) to (D) and a solvent: Component (A): (meth)acrylic triblock copolymer Component (B): (meth)acrylate oligomer (excluding component (A)) Component (C): a compound represented by the above formula 1 (D) Component: Photoinitiator. DETAILED DESCRIPTION OF THE INVENTION

[0012] The following describes embodiments of the present invention. However, the present disclosure is not limited to the following embodiments. In this specification, "X to Y" means a range including the numerical values ​​(X and Y) before and after it as the lower and upper limits, respectively, and means "X or more and Y or less." Furthermore, unless otherwise specified, concentrations and % represent mass concentration and mass %, respectively, and ratios are mass ratios unless otherwise specified. Furthermore, unless otherwise specified, operations and measurements of physical properties, etc. are performed under conditions of room temperature (20 to 25°C) and relative humidity 40 to 55% RH. Furthermore, "A and / or B" means A and B, respectively, and combinations thereof.

[0013] [Sheet-shaped photocurable composition] A sheet-shaped photocurable composition according to one embodiment of the present invention (hereinafter also referred to as "sheet-shaped photocurable composition" or simply "composition") contains the following components (A) to (D) and is in the form of a sheet at 25°C before curing: Component (A): (meth)acrylic triblock copolymer Component (B): (meth)acrylate oligomer (excluding component (A)) Component (C): a compound represented by the following formula 1

[0014] [ka]

[0015] (In the above formula 1, R 1 is a hydrogen atom or a methyl group, and R 2 is a monovalent organic group containing an oxygen atom) (D) Component: Photoinitiator.

[0016] The sheet-shaped photocurable composition according to one embodiment of the present invention can improve peel adhesion strength to resin substrates such as polyethylene terephthalate (PET) films, (meth)acrylic resin plates, and triacetyl cellulose (TAC) films under both room temperature and high temperature environments (e.g., 25°C atmosphere and 85°C atmosphere), i.e., from room temperature environments of about 25°C to high temperature environments of about 85°C.

[0017] Conventionally, these resin substrates have hydrophobic surfaces, making it difficult to adhere them using adhesives, and the adhesion of compositions containing (meth)acrylate triblock copolymers to these resin substrates has been insufficient.

[0018] Furthermore, when a triblock copolymer (a triblock copolymer having a hard segment and a soft segment) such as the one described above is added to a composition in order to obtain an adhesive that can be used over a wide temperature range, segments (blocks) having similar structures aggregate together to form a microphase-separated structure, which poses a problem in that it is difficult to improve adhesion to substrates.

[0019] However, it is presumed that the sheet-shaped photocurable composition of the present invention, which contains the compound contained as component (C), exhibits good adhesion even to resin substrates for which it has been difficult to improve peel adhesion strength in the past. Therefore, the sheet-shaped photocurable composition of the present invention can achieve good adhesion to resin substrates even when a (meth)acrylate triblock copolymer is used. Furthermore, the use of a (meth)acrylate triblock copolymer allows for excellent adhesion over a wide temperature range.

[0020] The above mechanism is based on speculation, and the correctness of the mechanism does not affect the technical scope of the present invention.

[0021] The sheet-shaped photocurable composition according to the present invention is in a sheet form at 25°C before curing. Here, "sheet-shaped" means a shape that has a two-dimensional surface and has a front surface and a back surface that face each other across a distance equal to the thickness of the composition. The thickness is not particularly limited, but is preferably 5 to 300 μm, and particularly preferably 10 to 200 μm, for example. When the thickness of the sheet-shaped photocurable composition is within the above range, the solvent used during production can be sufficiently volatilized, effectively suppressing the occurrence of pinholes and voids.

[0022] In this specification, a photocurable composition before curing and formed into a sheet is referred to as a "sheet-shaped photocurable composition." A composition before curing that has not been processed into a sheet is also simply referred to as a "photocurable composition." Furthermore, a "photocurable composition solution" refers to a composition that contains a solvent in addition to the components contained in the sheet-shaped photocurable composition. Furthermore, a "cured product" refers to a sheet-shaped photocurable composition that has been polymerized by light irradiation in a solvent-free state.

[0023] Components contained in the sheet-shaped photocurable composition according to one embodiment of the present invention will be described below.

[0024] <Component (A)> Component (A) contained in the sheet-shaped photocurable composition according to the present invention is a (meth)acrylate triblock copolymer (also referred to herein as a "(meth)acrylic triblock copolymer" or simply a "triblock copolymer"). In this specification, "(meth)acrylate" refers to a compound having a (meth)acryloyl group. The term "(meth)acryloyl" encompasses both acryloyl and methacryloyl. Thus, for example, the term "(meth)acryloyl group" encompasses both an acryloyl group (HC=CH-C(=O)-) and a methacryloyl group (HC=C(CH)-C(=O)-). Similarly, the term "(meth)acrylate" encompasses both acrylate and methacrylate, and the term "(meth)acrylic" encompasses both acrylic and methacrylic. The (meth)acryloyl group may be contained in the component in the form of a (meth)acryloyloxy group.

[0025] The (meth)acrylate triblock copolymer as component (A) is a triblock copolymer obtained or obtainable by polymerizing (meth)acrylate monomers (ester compounds having one or more (meth)acryloyl groups). By including such component (A), the sheet-shaped photocurable composition according to the present invention exhibits excellent peel strength at room temperature and in high-temperature environments (e.g., in a 25°C atmosphere and in an 85°C atmosphere). Furthermore, the (meth)acrylate triblock copolymer has good compatibility with (meth)acrylate oligomers, and particularly with component (B), which will be described in detail below. Such good compatibility with component (B) results in high transparency, enabling the production of a sheet-shaped photocurable composition suitable for display devices and optical applications.

[0026] Component (A) is preferably an elastomer that does not contain a reactive functional group. The tensile elongation of component (A) is preferably 100 to 600%, more preferably 110 to 580%, and particularly preferably 130 to 400%. A tensile elongation of 100% or more improves the flexibility of the sheet-shaped photocurable composition, making it easier to conform to uneven or curved surfaces, thereby providing excellent adhesion to surfaces of various shapes. On the other hand, a tensile elongation of 600% or less prevents the sheet-shaped photocurable composition from becoming too soft, improving workability and providing excellent peel strength. Furthermore, the photocurable composition is easier to mold into a sheet. The above tensile elongation is a value measured in accordance with ISO 37:2017.

[0027] Examples of triblock copolymers that can be used as component (A) include an XYZ type (a structure having three different types of units) composed of segment X, segment Y, and segment Z, and an XYX type (a structure in which one different type of unit is sandwiched between two identical units) composed of segment X and segment Y. Each of the segments may be composed of a single monomer or two or more types of monomers. Methods for preparing such triblock copolymers include, but are not limited to, living polymerization of known (meth)acrylate monomers that constitute each segment (block). Examples of living polymerization techniques include anionic polymerization using an organic alkali metal compound as a polymerization initiator and polymerization using an organic rare earth metal complex as a polymerization initiator. Furthermore, known (meth)acrylate monomers that constitute each segment (block) can be polymerized using a polyvalent radical polymerization initiator or a polyvalent radical chain transfer agent.

[0028] In particular, the triblock copolymer as component (A) is preferably an XYX type. By using component (A) with such a structure, peel adhesion strength at room temperature and in high temperature environments is further improved, and transparency is also improved due to good compatibility with component (B), which will be described in detail below.

[0029] Furthermore, the triblock copolymer as component (A) is preferably an XYX triblock copolymer, for example, consisting of a hard segment X with a high glass transition temperature and a soft segment Y with a low glass transition temperature. Here, "glass transition temperature" refers to the glass transition temperature (Tg) of the polymer of the monomers that make up the segment. In this specification, the glass transition temperature (Tg) is determined by thermal analysis of the polymer at a heating rate of 20°C / min in accordance with JIS K 7121:1987.

[0030] The glass transition temperature of the segment X is preferably 80 to 250° C., more preferably 90 to 200° C., and particularly preferably 100 to 150° C. When the glass transition temperature of the segment X is within the above range, the adhesive strength when cured is excellent.

[0031] The glass transition temperature of the segment Y is preferably −150 to 0° C., more preferably −100 to −15° C., and particularly preferably −70 to −30° C. When the glass transition temperature of the segment Y is within the above range, the peel adhesive strength to resin substrates, such as PET films, which have a difficult adhesive strength to improve, is further improved under normal temperature and high temperature environments.

[0032] Component (A) is preferably an XYX type (meth)acrylate triblock copolymer composed of segment X having a glass transition temperature of 100 to 150°C and segment Y having a glass transition temperature of -70 to -30°C. Component (A) is further preferably an XYX type (meth)acrylate triblock copolymer composed of segment X and segment Y each having a glass transition temperature within the above-mentioned preferred range. Use of such a triblock copolymer further improves the desired peel adhesive strength.

[0033] The monomer constituting segment X is preferably a methacrylate having a linear or branched alkyl group with 1 to 5 carbon atoms, more preferably a methacrylate having a linear or branched alkyl group with 1 to 3 carbon atoms, and particularly preferably methyl methacrylate. That is, component (A) is preferably a triblock copolymer composed of a PMMA (polymethyl methacrylate) block and a (other) block other than PMMA. Use of a triblock copolymer having such a structure further improves the desired peel adhesive strength.

[0034] Furthermore, the monomer constituting segment Y is preferably an acrylate having a linear or branched alkyl group having 1 to 20 carbon atoms, more preferably an acrylate having a linear or branched alkyl group having 2 to 15 carbon atoms, even more preferably an acrylate having a linear or branched alkyl group having 3 to 8 carbon atoms, and particularly preferably n-butyl acrylate. That is, component (A) preferably contains a PnBA (poly n-butyl acrylate) block. Use of a triblock copolymer having such a structure further improves the desired peel adhesive strength.

[0035] According to a preferred embodiment of the present invention, it is preferred that segment X of component (A) is a polymer of methacrylate having an alkyl group with 1 to 3 carbon atoms, and segment Y is a polymer of acrylate having an alkyl group with 3 to 8 carbon atoms. By using a triblock copolymer having such a structure, the desired peel adhesive strength is further improved. Furthermore, it is more preferred that component (A) is an XYX type (meth)acrylate triblock copolymer in which segment X is a PMMA block and segment Y is a PnBA block.

[0036] In component (A), the content of segment X, when the entire triblock copolymer is taken as 100% by mass, is preferably 5% by mass or more, more preferably 15% by mass or more, and particularly preferably 25% by mass or more. Meanwhile, the upper limit is preferably 60% by mass or less, more preferably 50% by mass or less, and particularly preferably 45% by mass or less. In this case, segment X is preferably a PMMA block. This configuration facilitates a tensile elongation of component (A) of 100% or more, thereby improving the flexibility of the sheet-shaped photocurable composition. As a result, the sheet-shaped photocurable composition can easily conform to uneven or curved surfaces, thereby exhibiting excellent adhesion to surfaces of various shapes.

[0037] On the other hand, in the component (A), when the entire triblock copolymer is taken as 100% by mass, the content of segment Y is preferably 40% by mass or more, more preferably 50% by mass or more, and particularly preferably 55% by mass or more. On the other hand, the upper limit is preferably 95% by mass or less, more preferably 85% by mass or less, and particularly preferably 75% by mass or less. When the content of each segment is within the above range, the expected peel adhesive strength is further improved.

[0038] Furthermore, in component (A), when the entire triblock copolymer is taken as 100% by mass, it is preferable that the content of segment X is 5 to 60% by mass and the content of segment Y is 40 to 95% by mass. In this embodiment, it is further preferable that the content of segment X and segment Y are each within one of the above-mentioned preferred ranges.

[0039] The weight-average molecular weight (Mw) of component (A) is not particularly limited, but is preferably 10,000 to 500,000, more preferably 30,000 to 200,000, even more preferably 40,000 to 150,000, and particularly preferably 50,000 to 100,000. A weight-average molecular weight of 10,000 or more improves curability. Furthermore, a weight-average molecular weight of 500,000 or less reduces viscosity, improving interface compatibility when bonding to an adherend, thereby further improving the desired peel adhesive strength. Note that, in this specification, the weight-average molecular weight is the weight-average molecular weight in terms of polystyrene measured by GPC (gel permeation chromatography).

[0040] As the component (A), either a synthetic product or a commercially available product can be used.

[0041] Specific examples of commercially available products of component (A) include the Kuraray Co., Ltd. Kuraryt (registered trademark, hereinafter the same) LA series, which uses methyl methacrylate and n-butyl acrylate, and the Kuraryt LK series, which uses methyl methacrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. Specific examples of these include Kuraray Co., Ltd. Kuraryt LA2270, LA2250, LA2140, LA2330, and LA3320, but are not limited to these.

[0042] The component (A) may be used alone or in combination of two or more. When two or more types are used in combination, the content of the component (A) refers to the total amount.

[0043] The content of component (A) is not particularly limited, but is preferably 40 to 90 parts by mass, more preferably 50 to 80 parts by mass, and particularly preferably 60 to 70 parts by mass, per 100 parts by mass of the total of components (A) to (D). By keeping the content of component (A) within the above range, the desired peel adhesive strength is further improved.

[0044] The content of component (A) is preferably 40 to 90 mass %, more preferably 50 to 80 mass %, and particularly preferably 60 to 70 mass %, relative to the total mass of the sheet-shaped photocurable composition (excluding volatile components such as solvents).

[0045] <(B) component> Component (B) contained in the sheet-shaped photocurable composition according to the present invention is a (meth)acrylate oligomer (excluding component (A) above). The (meth)acrylate oligomer refers to an oligomer having one or more (meth)acryloyl groups. The term "oligomer" refers to a polymer in which two to several tens of monomer units (including monomer units other than (meth)acrylate monomers) are repeated. A polymer having three segments (blocks) each composed of a structural unit derived from a (meth)acrylate monomer is considered to be included in component (A), but not in component (B).

[0046] Component (B) preferably has 2 to 5 (meth)acryloyl groups per molecule (di- to penta-functional (meth)acrylate oligomer), and more preferably has 2 (difunctional (meth)acrylate oligomer). Furthermore, the (meth)acryloyl groups contained in component (B) are preferably acryloyl groups.

[0047] The weight-average molecular weight of component (B) is preferably 1,000 to 50,000, more preferably 1,000 to 30,000, even more preferably 3,000 to 10,000, and particularly preferably 4,000 or more and less than 10,000. A weight-average molecular weight of 1,000 or more provides good curability, while a weight-average molecular weight of 50,000 or less provides lower viscosity and good compatibility at the interface when attached to an adherend, resulting in an improvement in the desired peel adhesive strength.

[0048] The glass transition temperature of component (B) is preferably 25°C or lower, more preferably 0°C or lower, and particularly preferably -30°C or lower. Having the glass transition temperature of component (B) within the above range can contribute to improving peel adhesive strength. On the other hand, there is no particular lower limit, but a temperature of -100°C or higher is preferred.

[0049] Examples of the component (B) include an epoxy-modified (meth)acrylate oligomer, a urethane-modified (meth)acrylate oligomer, an oligomer having a main skeleton formed by polymerizing a (meth)acrylic monomer and having a (meth)acryloyl group at the end of the main skeleton, etc. Among these, the component (B) is preferably a urethane-modified (meth)acrylate oligomer because of its good adhesion to glass and plastics used in the protective panel.

[0050] Examples of epoxy-modified (meth)acrylate oligomers include, but are not limited to, epoxy-modified (meth)acrylic oligomers obtained by adding (meth)acrylic acid to bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, phenol novolac resin, or the like.

[0051] In this specification, the urethane-modified (meth)acrylate oligomer refers to an oligomer having one or more urethane bonds and one or more (meth)acryloyl groups. The preferred number of (meth)acryloyl groups contained per molecule of the urethane-modified (meth)acrylate oligomer and the weight-average molecular weight are the same as those described above for the (meth)acrylate oligomer.

[0052] Both synthetic and commercially available products can be used as component (B). A preferred form of component (B) is a urethane-modified (meth)acrylate oligomer, which is synthesized by reacting, for example, a polyol compound (main skeleton) having two or more hydroxyl groups in the molecule, a compound having two or more isocyanate groups in the molecule, and a (meth)acrylate having one or more hydroxyl groups in the molecule.

[0053] Examples of polyol compounds having two or more hydroxyl groups in the molecule include polyether polyols, polyester polyols, caprolactone diols, bisphenol polyols, polyisoprene polyols, hydrogenated polyisoprene polyols, polybutadiene polyols, hydrogenated polybutadiene polyols, castor oil polyols, and polycarbonate diols. Among these, polycarbonate diols, polybutadiene polyols, and hydrogenated polybutadiene polyols are preferred because of their excellent transparency and durability, and polycarbonate diols are particularly preferred because the cured product is less likely to become cloudy under high-temperature and high-humidity conditions. These compounds may be used alone or in combination.

[0054] Examples of compounds having two or more isocyanate groups in the molecule include aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. Of these, aliphatic polyisocyanates and alicyclic polyisocyanates are preferred from the viewpoint of obtaining a flexible cured product. These may be used alone or in combination. From the viewpoint of improving the desired peel adhesive strength, component (B) is preferably an aliphatic urethane-modified (meth)acrylate oligomer synthesized using an aliphatic polyisocyanate.

[0055] Examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, tetramethylxylylene diisocyanate, diphenylmethane diisocyanate, naphthalene-1,5-disocyanate, and triphenylmethane triisocyanate. Examples of alicyclic polyisocyanates include isophorone diisocyanate, bis(4-isocyanatocyclohexyl)methane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, norbornane diisocyanate, and bicycloheptane triisocyanate. Examples of aliphatic polyisocyanates include hexamethylene diisocyanate, 1,3,6-hexamethylene triisocyanate, and 1,6,11-undeca triisocyanate. Among these, alicyclic or aliphatic diisocyanates such as isophorone diisocyanate and hexamethylene diisocyanate are preferred, and aliphatic diisocyanates are particularly preferred.

[0056] Examples of (meth)acrylates containing one or more hydroxyl groups in the molecule include mono(meth)acrylates of dihydric alcohols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and polyethylene glycol; and mono(meth)acrylates or di(meth)acrylates of trihydric alcohols such as trimethylolethane, trimethylolpropane, and glycerin. Among these, mono(meth)acrylates of dihydric alcohols are preferred, and mono(meth)acrylates of ethylene glycol are more preferred, from the viewpoint of obtaining a cured product with excellent flexibility. These may be used alone or in combination.

[0057] The synthesis method of the urethane-modified (meth)acrylate oligomer is not particularly limited, and known methods can be used. The urethane-modified (meth)acrylate oligomer can be synthesized, for example, by a reaction using the above-mentioned compounds as raw materials, and more specifically, can be synthesized by the following method.

[0058] A polyol compound having two or more hydroxyl groups in the molecule and an isocyanate compound having two or more isocyanate groups in the molecule are reacted in a diluent (e.g., methyl ethyl ketone, methoxyphenol, etc.) preferably in a molar ratio of 3:1 to 1:3 (polyol compound:isocyanate compound), more preferably in a molar ratio of 2:1 to 1:2, to obtain a urethane prepolymer. The remaining isocyanate groups in the obtained urethane prepolymer are then reacted with a (meth)acrylate containing one or more hydroxyl groups in the molecule in an amount sufficient to react with the isocyanate groups, thereby synthesizing a urethane-modified (meth)acrylate oligomer.

[0059] Examples of catalysts used during synthesis include lead oleate, tetrabutyltin, antimony trichloride, triphenylaluminum, trioctylaluminum, dibutyltin dilaurate, copper naphthenate, zinc naphthenate, zinc octylate, zinc octenate, zirconium naphthenate, cobalt naphthenate, tetra-n-butyl-1,3-diacetyloxydistannoxane, triethylamine, 1,4-diaza[2,2,2]bicyclooctane, and N-ethylmorpholine. Among these, dibutyltin dilaurate, zinc naphthenate, zinc octylate, and zinc octenate are preferred because of their high activity and the resulting cured product with excellent transparency. These catalysts are preferably used in an amount of 0.0001 to 10 parts by mass per 100 parts by mass of the total amount of reactants. The reaction temperature is typically 10 to 100°C, with 30 to 90°C being particularly preferred. The urethane-modified (meth)acrylate oligomer may be diluted with a solvent or a monomer having a (meth)acryloyl group, which will be described later, at the raw material stage before use.

[0060] Specific examples of commercially available products of component (B) include, but are not limited to, UN-1255, UN-9200A, and UN-9000PEP from Negami Chemical Industrial Co., Ltd., U-200PA and UA-160TM from Shin-Nakamura Chemical Co., Ltd., Shikoh series UV-3000B and UV-3700B from Mitsubishi Chemical Corporation, TEAI-1000 from Nippon Soda Co., Ltd., and EBECRYL (registered trademark) series 230, 270, 4858, 8402, 8804, 8807, 9270, 4513, 8311, 9260, 8701, 4265, 4587, 8210, 1290, 5129, 8310R, 210, and 220 from Daicel-Allnex Corporation.

[0061] The component (B) may be used alone or in combination of two or more. When two or more components are used in combination, the content of the component (B) refers to the total amount.

[0062] The content of component (B) is not particularly limited, but is preferably 10 to 80 parts by mass, more preferably 20 to 60 parts by mass, and particularly preferably 30 to 50 parts by mass, per 100 parts by mass of component (A). When the content of component (B) is 10 parts by mass or more per 100 parts by mass of component (A), peel adhesive strength can be improved both at room temperature and in high-temperature environments (25°C atmosphere and 85°C atmosphere). On the other hand, when the content of component (B) is 80 parts by mass or less, the flow initiation temperature during lamination can be lowered, thereby reducing thermal damage to the adherend.

[0063] <(C) component> Component (C) contained in the sheet-shaped photocurable composition of the present invention is a compound represented by the following formula 1. The compound represented by the following formula 1 is a monomer having a (meth)acryloyl group, that is, a (meth)acrylamide monomer. By containing such component (C), the sheet-shaped photocurable composition of the present invention has excellent adhesion to resin substrates, despite containing a (meth)acrylate triblock copolymer (component (A)).

[0064] [ka]

[0065] In formula 1, R 1 is a hydrogen atom or a methyl group, and R 2 is a monovalent organic group containing an oxygen atom. Specific examples of the monovalent organic group containing an oxygen atom include, but are not limited to, monovalent organic groups having a hydroxyl group and / or an ether bond. 2 When R contains an ether bond, the ether bond is preferably contained as an alkoxy group. 2 Preferably, contains a hydroxyl group and / or an alkoxy group.

[0066] From the viewpoint of promoting curing by light irradiation, R in the above formula 1 1is preferably a hydrogen atom. That is, the component (C) is preferably an acrylamide compound. In a more preferred embodiment, the compound as the component (C) is 1 is a hydrogen atom, and R 2 contains a hydroxyl group and / or an ether bond. 2 More preferably, contains a hydroxyl group and / or an alkoxy group.

[0067] Furthermore, R in Eq. 2 is preferably a monovalent organic group represented by the following formula 2:

[0068] [ka]

[0069] In formula 2, R' is a linear or branched alkylene group having 1 to 5 carbon atoms, A is a hydrogen atom or a linear or branched alkyl group having 1 to 5 carbon atoms, and "*" is the point of attachment to the nitrogen atom in formula 1.

[0070] Examples of the linear or branched alkylene group having 1 to 5 carbon atoms represented by R' include a methylene group, an ethylene group, a trimethylene group, a propylene group, an n-butylene group, a 1-methylpropylene group, a 2-methylpropylene group, a dimethylethylene group, and an ethylethylene group.

[0071] Examples of the linear or branched alkyl group having 1 to 5 carbon atoms as A include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a tert-pentyl group, and a neopentyl group.

[0072] More preferably, the component (C) is a compound represented by the formula 1 above, R 1 is a hydrogen atom, and R 2is a monovalent organic group represented by the above formula 2, in which R' is a linear or branched alkylene group having 1 to 3 carbon atoms, and A is a hydrogen atom or a linear alkyl group having 2 to 5 carbon atoms. Furthermore, in the above embodiment, it is particularly preferable that A is a hydrogen atom.

[0073] Specific examples of the component (C) include hydroxyethyl(meth)acrylamide and Nn-butoxymethyl(meth)acrylamide, which may be used alone or in combination.

[0074] Specific examples of commercially available products of component (C) include HEAA (registered trademark) from KJ Chemicals Co., Ltd. and NBMA from Shinryo Corporation, but are not limited to these.

[0075] The component (C) may be used alone or in combination of two or more. When two or more components are used in combination, the content of the component (C) refers to the total amount.

[0076] The content of component (C) is not particularly limited, but is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 10 parts by mass, even more preferably 1 to 9 parts by mass, particularly preferably 3 to 8 parts by mass, and most preferably 5 to 8 parts by mass, per 100 parts by mass of component (A). When the content of component (C) is 0.1 parts by mass or more per 100 parts by mass of component (A), adhesion is further improved, and peel strength to resin substrates such as (meth)acrylic resin plates, TAC films, and PET films can be further improved. On the other hand, when the content of component (C) is 30 parts by mass or less, the flow initiation temperature can be lowered, reducing thermal damage to the adherend.

[0077] Furthermore, the content of component (C) is preferably 1 to 50 parts by mass, more preferably 5 to 30 parts by mass, even more preferably 10 to 20 parts by mass, and particularly preferably 12 to 18 parts by mass, per 100 parts by mass of component (B). When the content of component (C) is 1 part by mass or more per 100 parts by mass of component (B), adhesiveness is further improved, and the peel adhesive strength to the resin substrate can be further improved. On the other hand, when the content of component (C) is 50 parts by mass or less, the flow initiation temperature can be lowered, thereby reducing thermal damage to the adherend.

[0078] <(D) component> The component (D) contained in the sheet-shaped photocurable composition according to the present invention is a photoinitiator (photopolymerization initiator). A photoinitiator is a compound that decomposes upon irradiation with active energy rays such as ultraviolet light, visible light, or an electron beam to generate radical species, cation species, or anion species.

[0079] Examples of component (D) include acetophenone-based photoinitiators, benzoin-based photoinitiators, benzophenone-based photoinitiators, thioxanthone-based photoinitiators, and acylphosphine oxide-based photoinitiators. These may be used alone or in combination of two or more. Among these, component (D) preferably contains an acylphosphine oxide-based photoinitiator. Compositions containing an acylphosphine oxide photoinitiator may turn the composition yellow, but they are easily cured by active energy rays in the visible light range, improving photocurability.

[0080] Examples of acetophenone-based photoinitiators include, but are not limited to, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, and 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer.

[0081] Examples of benzoin-based photoinitiators include, but are not limited to, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

[0082] Examples of benzophenone-based photoinitiators include, but are not limited to, benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, and (4-benzoylbenzyl)trimethylammonium chloride.

[0083] Examples of thioxanthone photoinitiators include, but are not limited to, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one mesochloride.

[0084] Examples of the acylphosphine oxide photoinitiator include, but are not limited to, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, and 2,4,6-trimethylbenzoyl-phenylethoxy-phosphine oxide.

[0085] Specific examples of commercially available products of component (D) include, but are not limited to, Omnirad (registered trademark) series TPO from IGM Resins BV.

[0086] The component (D) may be used alone or in combination of two or more. When two or more types are used in combination, the content of the component (D) refers to the total amount.

[0087] The content (amount added) of component (D) is not particularly limited, but is preferably 0.1 to 5.0 parts by mass, more preferably 0.1 to 3.0 parts by mass, and particularly preferably 0.3 to 1.0 parts by mass, per 100 parts by mass of component (A). When the content of component (D) is 0.1 part by mass or more per 100 parts by mass of component (A), a photocurable composition with excellent photocurability can be obtained, and when it is 5.0 parts by mass or less, coloration of the cured product can be effectively prevented.

[0088] Furthermore, the content (amount added) of component (D) is preferably 0.1 to 5.0 parts by mass, and more preferably 0.5 to 3.0 parts by mass, per 100 parts by mass of component (B). In another preferred embodiment, the content (amount added) of component (D) is 0.1 to 1.0 part by mass, per 100 parts by mass of component (B). When the content of component (D) is 0.1 part by mass or more, a photocurable composition with excellent photocurability can be obtained, and when it is 5.0 parts by mass or less, coloration of the cured product can be effectively prevented.

[0089] <(E) component> In addition to the above components (A) to (D), the sheet-shaped photocurable composition of the present invention preferably further contains a coupling agent as component (E) from the viewpoint of improving adhesive strength at the interface.

[0090] The component (E) that can be contained in the sheet-shaped photocurable composition according to the present invention is preferably a silane coupling agent having an alkoxysilyl group.

[0091] Specific examples of silane coupling agents having an alkoxysilyl group include glycidyl group-containing silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane; and vinyl group-containing silanes such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and vinyltrimethoxysilane. Coupling agents include (meth)acryloyl group-containing silane coupling agents such as 3-methacryloyloxypropyltrimethoxysilane (γ-methacryloyloxypropyltrimethoxysilane); amino group-containing silane coupling agents such as N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; and other examples include γ-mercaptopropyltrimethoxysilane and γ-chloropropyltrimethoxysilane. These may be used alone or in combination of two or more. Among these, silane coupling agents containing an epoxy group (glycidyl group) or a (meth)acryloyl group in addition to an alkoxysilyl group are preferred from the viewpoint of being able to expect improved adhesion to resin substrates, and silane coupling agents containing a methacryloyl group are most preferred.

[0092] The component (E) may be used alone or in combination of two or more. When two or more components are used in combination, the content of the component (E) refers to the total amount.

[0093] The content (addition amount) of component (E) is not particularly limited, but is preferably 0.05 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, and particularly preferably 0.8 to 5 parts by mass, per 100 parts by mass of component (A). When the content of component (E) is 0.05 part by mass or more per 100 parts by mass of component (A), it contributes to further improvement of peel adhesive strength, and when it is 15 parts by mass or less, it is effective in reducing outgassing.

[0094] Furthermore, the amount of component (E) added per 100 parts by mass of component (B) is preferably 0.1 to 20 parts by mass, and more preferably 3 to 15 parts by mass. When the content of component (E) per 100 parts by mass of component (B) is 0.1 part by mass or more, it contributes to further improvement of peel adhesive strength, and when it is 20 parts by mass or less, it is effective in reducing outgassing.

[0095] <Optional ingredients> The sheet-shaped photocurable composition according to the present invention may further contain additives such as a solvent, a monomer having a (meth)acryloyl group other than the component (C), a filler such as an inorganic filler or an organic filler, a storage stabilizer, an antioxidant, a light stabilizer, an ultraviolet absorber, a plasticizer, a dye, a pigment, a flame retardant, a sensitizer, a thermal initiator, a heavy metal deactivator, an ion trapping agent, an emulsifier, a water dispersion stabilizer, an antifoaming agent, a release agent, a leveling agent, a wax, a rheology control agent, and a surfactant, provided that the object of the present invention is not impaired.

[0096] (Monomers having a (meth)acryloyl group other than component (C)) Examples of the monomer having a (meth)acryloyl group other than the component (C) include monofunctional, bifunctional, trifunctional, tetrafunctional or higher polyfunctional monomers. (Meth)acrylate monomers are preferred, and monofunctional or bifunctional (meth)acrylate monomers are particularly preferred. To reduce the viscosity of the photocurable composition, the monomer having a (meth)acryloyl group other than the component (C) preferably has a molecular weight of 1,000 or less. The molecular weight of such compounds (low molecular weight compounds) can be measured by known methods such as gas chromatography-mass spectrometry (GC-MS).

[0097] Examples of monofunctional monomers include lauryl (meth)acrylate, stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, and phenoxytetate. Examples of the acrylates include ethylene glycol (meth)acrylate, nonylphenoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, glycerol (meth)acrylate, modified butyl (meth)acrylate, epichlorohydrin-modified phenoxy (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and morpholino (meth)acrylate.

[0098] Examples of bifunctional monomers include neopentyl glycol di(meth)acrylate, bisphenol A di(meth)acrylate, epichlorohydrin-modified bisphenol A di(meth)acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, dicyclopentenyl diacrylate, and di(meth)acryloyl isocyanurate.

[0099] Examples of trifunctional monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, epichlorohydrin-modified trimethylolpropane tri(meth)acrylate, epichlorohydrin-modified glycerol tri(meth)acrylate, and tris(acryloyloxyethyl)isocyanurate.

[0100] Examples of polyfunctional monomers include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol pentaacrylate, dipentaerythritol hexa(meth)acrylate, etc. These polymerizable monomers can be used alone or in combination of two or more.

[0101] In another preferred embodiment, the monomer having a (meth)acryloyl group other than component (C) is a (meth)acrylate containing one or more ether bonds and one or more (meth)acryloyl groups. The (meth)acrylate is preferably a polyether monomer (polyether(meth)acrylate) having 8 to 30 repeating ether bond units per molecule. When the number of repeating ether bond units is 8 or more, clouding due to separation between the polyether monomer and moisture that permeates into the cured product from the outside under a high-temperature, high-humidity atmosphere is further suppressed. On the other hand, polyether monomers having 30 or fewer repeating ether bond units are less likely to crystallize with each other, further suppressing clouding of the cured product. These monomers may be used alone or in combination.

[0102] Examples of (meth)acrylates containing an ether bond and a (meth)acryloyl group (polyether (meth)acrylates) include polyethylene glycol mono(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol mono(meth)acrylate, polypropylene glycol di(meth)acrylate, polyoxytetramethylene glycol mono(meth)acrylate, and polyoxytetramethylene glycol di(meth)acrylate.

[0103] The molecular weight of the polyether (meth)acrylate is preferably in the range of 200 to 5,000, more preferably 250 to 3,000.

[0104] Specific examples of commercially available polyether (meth)acrylates include M-90G, AM-130G, M-230G, A-400, A-600, APG-700, A-1000, 9G, 14G, 23G, and 1206PE manufactured by Shin-Nakamura Chemical Co., Ltd.; PDE-600, PDP-700, and ADE-600 manufactured by NOF Corporation; and Light Ester Series 130MA, 130A, 14EG, and 14EG-A manufactured by Kyoeisha Chemical Co., Ltd., but are not limited to these.

[0105] (inorganic filler) Specific examples of inorganic fillers include glass powder, fumed silica powder, silica powder, alumina powder, mica powder, silicone rubber powder, calcium carbonate powder, aluminum nitride powder, carbon powder, kaolin clay powder, dried clay mineral powder, dried diatomaceous earth powder, and metal powder. Fumed silica powders include those whose surfaces have been chemically modified (hydrophobized) with organochlorosilanes, polyorganosiloxanes, hexamethyldisilazane, etc., but are not limited thereto. Specific examples of commercially available inorganic fillers include the Aerosil (registered trademark) series R974, R972, R972V, R972CF, R805, R812, R812S, R816, R8200, RY200, RX200, RY200S, and R202 from Nippon Aerosil Co., Ltd. For the purpose of improving the flowability and the mechanical strength of the cured product, the content (blending amount) of the inorganic filler is preferably about 0.1 to 100 parts by mass per 100 parts by mass of the total of the above components (A) to (D).

[0106] (ultraviolet absorber) Examples of ultraviolet absorbers include, but are not limited to, 2-(5-chloro-2-benzotriazolyl)-6-tert-butyl-p-cresol, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(3,5-di-tert-amyl-2-hydroxyphenyl)benzotriazole, 1,2,3,4-butanetetracarboxylic acid tetrakis(1,2,2,6,6-pentamethylpiperidin-4-yl), bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, and bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate. Specific examples of commercially available ultraviolet absorbers include ADK STAB (registered trademark) LA-52, LA-57, LA-63P, LA-68, LA-72, LA-77Y, and LA-77G manufactured by ADEKA CORPORATION, and JF-90 and JF-95 manufactured by Johoku Chemical Industry Co., Ltd., but are not limited to these.

[0107] <Flow start temperature> The sheet-shaped photocurable composition according to the present invention preferably has a temperature of 60 to 120°C at which tan δ = 1 before curing. When the temperature is within this range, the photocurable composition can be easily processed into a film and can be easily laminated at room temperature. The temperature at which tan δ = 1 can be measured using a rheometer. Tan δ is calculated from the storage modulus (G') and loss modulus (G"), and has the relationship tan δ = G" / G', where "tan δ = 1" means the temperature at the boundary between solid and liquid.

[0108] <Storage modulus> Furthermore, the sheet-shaped photocurable composition according to the present invention has a storage modulus at 25°C of 0.1 × 10 7 ~10.0×10 7 Pa is preferably 0.1×10 7 ~5.0×10 7It is more preferable that the storage modulus is Pa. The storage modulus can be measured at various frequencies by DMA (dynamic viscoelasticity measurement). For example, the value at a frequency of 1 Hz can be used.

[0109] [Photocurable composition solution] In the present invention, a solvent can be used to process the photocurable composition in a state before being cured by light irradiation (uncured state) into a sheet and to mix the components contained in the sheet-shaped photocurable composition. That is, another embodiment of the present invention is a photocurable composition solution containing the following components (A) to (D) and a solvent: Component (A): (meth)acrylic triblock copolymer Component (B): (meth)acrylate oligomer (excluding component (A)) Component (C): a compound represented by the above formula 1 (D) Component: Photoinitiator.

[0110] <Solvent> Examples of the solvent include alcohols such as methanol and ethanol; chlorine-based solvents such as dichloroethane and trichloroethane; fluorine-based solvents such as trichlorofluoroethane; ketone-based solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ethers such as dimethyl ether and methyl ethyl ether; hydrocarbon-based solvents such as pentane, hexane, heptane, and cyclohexane; and aromatic solvents such as benzene, toluene, and xylene. Among these, ketone-based solvents are preferred in view of compatibility with components (A) to (C).

[0111] The content of the solvent in the photocurable composition solution is not particularly limited, but is preferably 30 to 200 parts by mass, and more preferably 50 to 100 parts by mass, per 100 parts by mass of the total mass of components (A) to (D). Within this range, it becomes easier to form the photocurable composition into a sheet with a thickness of 300 μm or less, or even 200 μm or less.

[0112] [Method for producing photocurable composition solution / sheet-shaped photocurable composition] <Method for producing photocurable composition solution> The photocurable composition solution of the present invention can be prepared by mixing the above-described components and solvent using a known mixing method. While the order of addition of the components is not particularly limited, it is preferable to first add component (A) and the solvent to a stirring vessel and stir, followed by the addition of the other components and stirring. If the solvent evaporates during mixing, it is preferable to replenish the evaporated solvent. While the preparation conditions are not particularly limited, it is preferable to perform the preparation under light-shielded conditions to prevent the viscosity from increasing. Furthermore, the mixing conditions are also not particularly limited. The mixing temperature is preferably 10 to 70°C, more preferably 20 to 50°C, and particularly preferably room temperature (25°C). The mixing time (total time when performed in two stages) is preferably 0.1 to 5 hours, more preferably 30 minutes to 3 hours.

[0113] <Method for producing sheet-shaped photocurable composition> Known techniques can be used to process a photocurable composition into a sheet (a method for producing a sheet-shaped photocurable composition). For example, a solvent is added to each component of the photocurable composition to intentionally reduce the viscosity of the stock solution (photocurable composition solution), and the stock solution is applied to a release paper or film (hereinafter also referred to as "release film, etc.") whose surface has been previously subjected to a release treatment (coating step). The solvent is then dried off (drying step) to produce a sheet-shaped photocurable composition. This results in a photocurable composition that is in a sheet form at 25°C before curing. In other words, yet another aspect of the present invention is a method for producing a photocurable composition that is in a sheet form at 25°C before curing, which method includes volatilizing the solvent contained in the photocurable composition solution. In this case, it is preferable to volatilize the solvent on the release paper or film.

[0114] The coating step can be carried out using a known coating method, specific examples of which include, but are not limited to, flow coating, roll coating, gravure roll coating, wire bar coating, lip die coating, etc. The thickness (film thickness) of the original solution (photocurable composition solution) during coating is not particularly limited, but is preferably 50 to 300 μm.

[0115] In addition, a known drying method can be used for the drying step. The drying device used here is not particularly limited, but examples thereof include a hot air drying oven and an IR oven. In addition, a conveyor for transporting the release film coated with the stock solution may be provided in the hot air drying oven.

[0116] The temperature in the drying step is not particularly limited as long as it is a temperature at which the solvent contained in the raw solution is sufficiently volatilized, but is preferably, for example, 40 to 150°C, and more preferably 60 to 120°C. The drying time is also not particularly limited, but is, for example, preferably 1 to 20 minutes, and more preferably 3 to 10 minutes. Furthermore, the drying step may be carried out in multiple stages by changing the drying temperature.

[0117] The sheet-shaped photocurable composition thus formed has a configuration in which it is formed on a release film or the like as described above (a configuration in which a release film or the like is laminated to one side of the sheet-shaped photocurable composition). The sheet-shaped photocurable composition may also have a release film or the like laminated to both sides. Furthermore, when a release film or the like is not used during the coating process or when a release film or the like other than that used during the coating process is used, a separate release film or the like may be laminated to one or both sides of the sheet-shaped photocurable composition.

[0118] The release paper is not particularly limited, but examples include paper such as fine paper, kraft paper, or glassine paper, on at least one side of which is provided a coating layer made of a filler such as clay, polyethylene, or polypropylene, and on which is coated a silicone-based, fluorine-based, or alkyd-based release agent.

[0119] Examples of materials for the release film include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, as well as cloth and nonwoven fabric. Among these, plastic films are preferred from the viewpoint of releasability. The thickness of the release film is preferably 5 to 300 μm, more preferably 25 to 200 μm. Furthermore, the release film is preferably one that has been subjected to a release treatment using a fluorine-based compound, a silicone-based compound, a long-chain alkyl compound, or the like.

[0120] [Cured product and method for producing the same] The sheet-shaped photocurable composition according to the present invention can be cured by irradiation with light (active energy rays such as ultraviolet light and visible light). That is, yet another aspect of the present invention is a cured product obtained by curing the sheet-shaped photocurable composition. The term "light" as used herein refers to light in a broad sense, including radiation such as α-rays and β-rays, electromagnetic waves such as γ-rays and X-rays, electron beams (EB), and irradiation light with a wavelength of 150 to 750 nm. In particular, the irradiation light is preferably in the wavelength range of 150 to 750 nm, and ultraviolet light with a wavelength of about 150 to 400 nm or visible light with a wavelength of about 400 to 750 nm is preferred.

[0121] The light source used to cure the sheet-shaped photocurable composition is not particularly limited, and examples thereof include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, metal halide lamps, and LED lamps. Furthermore, an irradiation device having the above-mentioned light source (such as a high-pressure mercury lamp or an LED lamp) can be used as a device for curing the sheet-shaped photocurable composition of the present invention by light irradiation (active energy ray irradiation). Specific examples of such devices include, but are not limited to, a belt conveyor-type irradiator and a spot irradiator.

[0122] The range of the cumulative light amount is not particularly limited, but using the above light source, it is 1 to 100 kJ / m 2 It is preferable that the curing is carried out with an integrated light amount of 5 to 70 kJ / m 2 and particularly preferably 10 to 50 kJ / m 2 is.

[0123] [Laminate] As described above, a photocurable composition solution (stock solution) is prepared by adding a solvent to each component contained in the sheet-like photocurable composition according to the present invention, and the stock solution is then applied to an adherend, followed by volatilizing (evaporating) the solvent, thereby forming a laminate of the photocurable composition in a sheet form at 25° C. and the adherend. That is, yet another aspect of the present invention is a laminate having a configuration in which a first adherend, a sheet-like photocurable composition, and a second adherend are bonded (laminated) in this order, and the sheet-like photocurable composition is formed by volatilizing the solvent contained in the photocurable composition solution on the first adherend and / or the second adherend.

[0124] A preferred embodiment of the method for producing the laminate is to first apply a photocurable composition solution (stock solution) onto a first adherend (or a second adherend), then volatilize (dry) the solvent contained in the stock solution to form a sheet-shaped photocurable composition, and then laminate the second adherend (or the first adherend) onto the sheet-shaped photocurable composition.

[0125] Furthermore, the sheet-shaped photocurable composition contained in the thus obtained laminate (a laminate consisting of a first adherend, a sheet-shaped photocurable composition, and a second adherend laminated in this order) can be cured by irradiating it with active energy rays, thereby bonding the first adherend and the second adherend. Therefore, yet another aspect of the present invention is a bonding method comprising the steps of applying a photocurable composition solution (stock solution) to a first adherend, volatilizing (drying) the solvent contained in the stock solution to form a sheet-shaped photocurable composition, laminating a second adherend on the sheet-shaped photocurable composition, and curing the sheet-shaped photocurable composition by irradiating it with active energy rays. The drying and curing conditions are not particularly limited, but are similar to the drying conditions described above in the section <Method for producing a sheet-shaped photocurable composition> and the curing conditions described above in the section [Cured product and method for producing the same].

[0126] Furthermore, as described above, in a preferred embodiment, the sheet-shaped photocurable composition according to the present invention can also be obtained by volatilizing the solvent contained in the photocurable composition solution on a release film or the like, and has a configuration in which a release film or the like is attached to one side of the sheet-shaped photocurable composition.

[0127] Therefore, another preferred embodiment of the method for adhering a first adherend and a second adherend (adhesion method) includes a step of adhering two transparent adherends (adhesion step) using a sheet-shaped photocurable composition having a release film or the like attached to one side thereof. The adhesion step preferably includes a lamination step and a curing step.

[0128] In the lamination step, the surface (exposed surface) of the sheet-shaped photocurable composition that is not covered with the release film is preferably attached to one adherend (first adherend) and then laminated together using a laminator while applying pressure and heat. The release film is then removed, and the other adherend (second adherend) is laminated in the same manner using the laminator. The lamination pressure is not particularly limited, but is preferably, for example, 0.1 to 3 MPa. The lamination temperature is also not particularly limited, but is preferably, for example, 15 to 100°C.

[0129] As an apparatus used for lamination, a vacuum press machine, a vacuum laminator, an autoclave, or the like that can perform lamination in a vacuum or under a reduced pressure atmosphere may be used instead of a laminator.

[0130] In the curing step, the laminate (a laminate consisting of a first adherend, a sheet-shaped photocurable composition, and a second adherend) is irradiated with active energy rays to cure the sheet-shaped photocurable composition, thereby bonding the two adherends. The curing conditions are not particularly limited, but are the same as those described in the above section [Cured product and method for producing the same].

[0131] [Application] The sheet-shaped photocurable composition according to the present invention can be used for assembling display devices such as liquid crystal displays and organic EL displays. Specifically, it is suitable for assembling display elements, cover panels, touch panels, etc. into display devices, and for assembling organic EL elements themselves.

[0132] Although the embodiments of the present invention have been described in detail, it is clear that this is by way of illustration and example only and not of limitation, and that the scope of the present invention should be interpreted by the appended claims.

[0133] The present invention encompasses the following aspects and configurations.

[0134] 1. A sheet-shaped photocurable composition comprising the following components (A) to (D), which is in the form of a sheet at 25°C before curing: Component (A): (meth)acrylic triblock copolymer Component (B): (meth)acrylate oligomer (excluding component (A)) Component (C): a compound represented by the following formula 1

[0135] [ka]

[0136] (In the above formula 1, R 1 is a hydrogen atom or a methyl group, and R 2 is a monovalent organic group containing an oxygen atom) (D) Component: Photoinitiator.

[0137] 2. The sheet-shaped photocurable composition according to 1 above, which contains 0.1 to 10 parts by mass of the component (C) per 100 parts by mass of the component (A).

[0138] 3. The sheet-shaped photocurable composition according to 1. or 2. above, which contains 10 to 80 parts by mass of the component (B) per 100 parts by mass of the component (A).

[0139] 4. R in the above formula 1 1 is a hydrogen atom, and R 2 The sheet-shaped photocurable composition according to any one of 1. to 3. above, wherein contains a hydroxyl group and / or an ether bond.

[0140] 5. The sheet-shaped photocurable composition according to any one of the above 1. to 4., wherein the component (B) is a urethane-modified (meth)acrylate oligomer.

[0141] 6. The sheet-shaped photocurable composition according to any one of 1. to 5. above, further comprising a coupling agent as component (E).

[0142] 7. A photocurable composition solution comprising the following components (A) to (D) and a solvent: Component (A): (meth)acrylic triblock copolymer Component (B): (meth)acrylate oligomer (excluding component (A)) Component (C): a compound represented by the above formula 1 (D) Component: Photoinitiator.

[0143] 8. A method for producing a photocurable composition that is in a sheet form at 25°C before curing, the method comprising volatilizing the solvent contained in the photocurable composition solution described in 7 above.

[0144] 9. The method for producing a sheet-shaped photocurable composition according to 8 above, wherein the solvent is evaporated on a release paper or a release film.

[0145] 10. A laminate having a configuration in which a first adherend, a sheet-shaped photocurable composition, and a second adherend are laminated together in this order, wherein the sheet-shaped photocurable composition is formed by volatilizing the solvent contained in the photocurable composition solution described in 7 above on the first and / or second adherend. [Example]

[0146] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Hereinafter, a photocurable composition containing a solvent (i.e., a photocurable composition solution) may be simply referred to as a "stock solution." Furthermore, a photocurable composition that is obtained by volatilizing the solvent from the "stock solution" and is in a sheet form at 25°C before curing may be simply referred to as a "sheet-like composition." Unless otherwise specified, operations and tests were carried out in an environment of 25°C and 55% RH.

[0147] <Preparation of Photocurable Composition Solution (Stock Solution)> [Examples 1 to 13 and Comparative Examples 1 to 11] (1) The following components were prepared to prepare the stock solution.

[0148] <Component (A): (Meth)acrylic triblock copolymer> (Meth)acrylic triblock copolymer (PMMA-PnBA-PMMA triblock copolymer containing approximately 40% by mass of PMMA (polymethyl methacrylate: glass transition temperature 105°C) and approximately 60% by mass of PnBA (poly-n-butyl acrylate: glass transition temperature -54°C)) (tensile elongation: 149%) (Kuraray Co., Ltd., Kuralyte (registered trademark, the same applies hereinafter) LA2270) (Meth)acrylic triblock copolymer (PMMA-PnBA-PMMA triblock copolymer containing approximately 30% by mass of PMMA and approximately 70% by mass of PnBA, with a weight-average molecular weight of approximately 60,000) (tensile elongation: 380%) (Kuraray Co., Ltd., Clarity LA2250) (Meth)acrylic triblock copolymer (PMMA-PnBA-PMMA triblock copolymer containing approximately 20% by mass of PMMA and approximately 80% by mass of PnBA) (tensile elongation: 570%) (Kuraray Co., Ltd., Clarity LA2140) (Meth)acrylic triblock copolymer (a PMMA-PnBA-PMMA triblock copolymer containing approximately 20% by mass of PMMA and approximately 80% by mass of PnBA, with a weight-average molecular weight of approximately 110,000) (tensile elongation: 490%) (Kuraray Co., Ltd., Clarity LA2330) (Meth)acrylic triblock copolymer (PMMA-PnBA-PMMA triblock copolymer containing approximately 15% by mass of PMMA and approximately 85% by mass of PnBA) (tensile elongation: 540%) (Kuraray Co., Ltd., Clarity LA3320) The tensile elongation value of the component (A) is a value measured in accordance with ISO37:2017.

[0149] <<Component (B): (Meth)acrylate Oligomer>> Aliphatic urethane-modified diacrylate (number of functional groups: 2, weight average molecular weight (Mw): 5,000, glass transition temperature: -55°C) (EBECRYL (registered trademark) 230, manufactured by Daicel-Allnex Corporation).

[0150] Component (C): (meth)acrylate monomer represented by the above formula 1 HEAA (hydroxyethyl acrylamide) (HEAA (registered trademark) manufactured by KJ Chemicals Co., Ltd.) NBMA (Nn-butoxymethylacrylamide) (manufactured by Shinryo Corporation).

[0151] Component (C'): Monomer Other Than Component (C) Ethoxylated (9) trimethylolpropane triacrylate (SR502 manufactured by Sartomer) Polyethylene glycol #600 dimethacrylate (NK Ester 14G, manufactured by Shin-Nakamura Chemical Co., Ltd.) 2-Hydroxyethyl methacrylate acid phosphate (JPA-514 manufactured by Johoku Chemical Industry Co., Ltd.) Mono(2-hydroxyethyl methacrylate) phosphate (JAMP-514, manufactured by Johoku Chemical Industry Co., Ltd.) Dimethylacrylamide (DMAA (registered trademark) manufactured by KJ Chemicals Co., Ltd.) Acryloylmorpholine (ACMO (registered trademark) manufactured by KJ Chemicals Co., Ltd.) Dimethylaminopropylacrylamide (DMPAA® manufactured by KJ Chemicals Co., Ltd.) Diethylacrylamide (DEAA (registered trademark) manufactured by KJ Chemicals Co., Ltd.).

[0152] Component (D): Photoinitiator 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Omnirad® TPO, manufactured by IGM Resins BV).

[0153] <Component (E): Coupling Agent> 3-Methacryloyloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0154] "solvent" Methyl ethyl ketone (reagent).

[0155] (2) The components were mixed and stirred according to the following procedure to obtain a stock solution.

[0156] Component (A) and solvent (methyl ethyl ketone) were weighed and stirred in a stirring vessel under an atmosphere of 25°C for 1 hour. If any solvent had evaporated from the total weight before stirring, the evaporated amount was replaced with the new solvent. Then, components (B), (C) (or (C')), (D), and (E) were weighed and added to the stirring vessel, and stirred for 30 minutes in the dark. The content (prepared amount) of each component in each stock solution is shown in Table 1. All values ​​in Table 1 are given in parts by mass. Blank spaces indicate that the corresponding component was not added.

[0157] [Table 1-1]

[0158] [Table 1-2]

[0159] <Evaluation> Sheet compositions were prepared using the stock solutions of Examples 1 to 13 and Comparative Examples 1 to 11 by the manufacturing method described below. Then, using the sheet compositions, rheometer measurements (before curing), peel adhesion strength measurements (after curing), turbidity (haze) measurements (after curing), and dynamic viscoelasticity measurements (DMA) (after curing) were performed. The results of these evaluations (tests) for each sheet composition are shown in Table 2 below. In Table 2, the numbers for each sheet composition are expressed by directly reflecting the numbers for the stock solutions listed in Table 1.

[0160] [Method of manufacturing a sheet-shaped composition] Using a coating machine, the stock solutions of Examples 1 to 13 and Comparative Examples 1 to 11 were each coated onto a release film with a clearance of 200 μm. The stock solutions were then dried at a speed of 500 mm / min through a 1.5 m long drying line in an 80°C atmosphere and a 1.5 m long drying line in an 100°C atmosphere, forming the stock solutions into sheets. This procedure yielded sheet compositions.

[0161] Then, a different release film was attached to the above to produce a sheet with two types of release film. For each sheet obtained in this way, the film thickness including the two types of release film was measured with a thickness gauge, and the thickness of the two types of release film was subtracted to determine the film thickness of the sheet (after drying), which was 100 μm in all cases. In the drying process to volatilize the solvent, the solvent dries from the surface of the original solution, and the solvent inside is difficult to volatilize. Therefore, if the film thickness is made thick, air bubbles may remain inside the coating film, so the clearance during the above coating is preferably 300 μm or less (lower limit: more than 0 μm).

[0162] [Rheometer measurement (before curing)] The sheet composition obtained by the above procedure was peeled from the release film, and seven sheets were stacked so that the total thickness was 700 μm, and degassed using a vacuum laminator. Viscoelasticity measurements were performed in the temperature range of 0 to 130°C using a HAAKE MARS III from Thermo Fisher. The temperature at which tan δ = 1 was defined as the "flow initiation temperature (°C)," and this value is shown in Table 2. In the present invention, a flow initiation temperature of 60 to 120°C indicates that lamination at room temperature is possible.

[0163] [Peel adhesion strength measurement (after curing)] A test piece was prepared by combining a 100 mm long x 25 mm wide x 50 μm thick Cosmoshine (registered trademark) A4300 (PET film) manufactured by Toyobo Film Solutions Co., Ltd. with a 100 mm long x 25 mm wide x 2 mm thick acrylic resin plate manufactured by Asahi B-Techno Co., Ltd., and the 180° peel adhesive strength was measured in accordance with JIS K 6854-2:1999. The test piece was prepared under the following conditions: First, a sheet-like composition having a release film attached to the side opposite the PET film was placed over the PET film in an area of ​​70 mm long x 25 mm wide, and the sheet was passed through a hot roll laminator at a roll temperature of 25°C and a pressure of 0.2 MPa. Next, the release film was peeled off, and the acrylic resin plate was placed over the sheet and passed through the laminator again under the same conditions. The sheet was then left in an autoclave at 70°C under a pressure of 0.5 MPa for 20 minutes. After confirming that the temperature of the test piece had dropped to room temperature, the integrated light intensity was increased to 30 kJ / m using a belt conveyor type ultraviolet irradiator. 2The sheet-shaped composition was cured by irradiating it with ultraviolet light (light source: high-pressure mercury lamp) until the peel strength reached 100 kN / m. The strength was measured by pulling at a speed of 60 mm / min using a precision universal testing machine (Autograph AGX-V series) manufactured by Shimadzu Corporation, and the average value was recorded as "peel adhesion strength (kN / m)." The peel adhesion strengths at 25°C and 85°C were referred to as "peel adhesion strength 1" and "peel adhesion strength 2," respectively, and the values ​​are shown in Table 2. The "peel adhesion strength 1" is preferably 1.0 kN / m or more, and the "peel adhesion strength 2" is preferably 0.3 kN / m or more. While there are no particular upper limits, it is preferable that peel adhesion strength 1 be 3.0 kN / m or less, and peel adhesion strength 2 be 2.0 kN / m or less. The peel adhesion strength at 85°C was measured as follows. First, the thermostatic chamber attached to the precision universal testing machine was set to 85°C, and the thermostatic chamber was slid from the rear side of the precision universal testing machine so that the chuck and the test piece (the test piece clamped between the upper and lower chucks) were entirely covered by the thermostatic chamber. After that, the chuck and the test piece were kept in the thermostatic chamber for 10 minutes, and then the strength was measured as described above.

[0164] [White turbidity (haze) measurement (after curing)] One of the release films was peeled off, and the sheet-like composition was then attached to an alkali-free glass plate measuring 0.7 mm thick x 100 mm wide x 100 mm long, and the image was transferred using a hot roll laminator with the roll temperature set to 25°C. The other release film was then peeled off, and the same alkali-free glass plate as above was attached. The test piece was then placed in a diaphragm-type vacuum laminator, degassed for 120 seconds, and then pressurized at a pressure of 0.1 MPa for 180 seconds, set to the flow initiation temperature of each sheet-like composition. Finally, a belt conveyor-type ultraviolet irradiator was used to apply an integrated light dose of 30 kJ / m 2A test piece was prepared by bonding alkali-free glass to the cured sheet-like composition using ultraviolet light (light source: high-pressure mercury lamp) so that the cured sheet-like composition was irradiated with ultraviolet light so that the haze was 0.01. The test piece was subjected to haze measurement using a spectroscopic haze meter SH7000 manufactured by Nippon Denshoku Industries Co., Ltd. The light transmittance was measured over a wavelength range of 780 nm to 380 nm, and the haze was calculated according to JIS K 7136:2000. Three tests were conducted, and the average value was calculated. The results are shown in Table 2 as "haze (unitless)." For optical applications, the haze is preferably 0.50 or less, and more preferably 0.30 or less. While the lower limit is not particularly limited, it is generally about 0.01.

[0165] [Dynamic mechanical properties measurement (DMA) (after curing)] For a sheet-shaped composition measuring 60 mm in length, 10 mm in width, and 0.7 mm in thickness, a belt conveyor-type ultraviolet irradiator was used to irradiate the sheet with an integrated light dose of 30 kJ / m 2 The cured product was prepared by irradiating it with ultraviolet light (light source: high-pressure mercury lamp) so that the temperature range was -50 to 100°C at a frequency of 1 Hz using a dynamic viscoelasticity measuring device DMS6100 manufactured by Hitachi High-Tech Science Corporation. The storage modulus (×10) at 25°C was measured at a frequency of 1 Hz. 7 The values ​​are shown in Table 2. In Table 2, the unit is "×10 7 The storage modulus was reported as 0.1 × 10 7 ~10.0×10 7 Pa is preferred.

[0166] [Table 2]

[0167] In peel strength tests using PET film, which is typically difficult to improve, as the adherend (substrate), Examples 1 to 13 demonstrated high peel strengths of 1.0 kN / m or more in a 25°C atmosphere and 0.3 kN / m or more even in an 85°C atmosphere. While the exact reason is unclear, it is presumed that the use of the compound represented by Formula 1 as component (C) provides the sheet-shaped composition with a moderate affinity for the PET film surface, resulting in high peel strength. Furthermore, for example, Comparative Examples 2 to 4 were able to reduce the storage modulus of the cured product, but compositions not containing the component (C) of the present invention exhibited low peel strength 1, suggesting that delamination occurred at the interface between the cured product and the adherend. Furthermore, the examples and comparative examples reveal that the flow initiation temperature varies depending on the type of component (A). It is believed that the degree of cloudiness can be reduced by performing the lamination operation at the flow initiation temperature of each sheet-shaped composition. [Industrial Applicability]

[0168] The present invention can be used for assembling display devices such as liquid crystal displays and organic EL displays. Specifically, the present invention is suitable for assembling display elements, cover panels, touch panels, VR goggles, etc. as display devices, as well as for assembling organic EL elements themselves, and can be applied even when the adherend is not flat but curved.

[0169] This application is based on Japanese Patent Application No. 2020-205609, filed on December 11, 2020, the disclosure of which is incorporated by reference in its entirety.

Claims

1. A sheet-shaped photocurable composition comprising the following components (A) to (D), which is in the form of a sheet at 25°C before curing: Component (A): (meth)acrylic triblock copolymer Component (B): (meth)acrylate oligomer (excluding the component (A)) Component (C): hydroxyethyl(meth)acrylamide and / or N-n-butoxymethyl(meth)acrylamide Component (D): Photoinitiator.

2. 2. The sheet-shaped photocurable composition according to claim 1, wherein the component (C) is contained in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the component (A).

3. 3. The sheet-shaped photocurable composition according to claim 1, wherein the component (B) is contained in an amount of 10 to 80 parts by mass per 100 parts by mass of the component (A).

4. 4. The sheet-shaped photocurable composition according to claim 1, wherein the component (B) is a urethane-modified (meth)acrylate oligomer.

5. The sheet-shaped photocurable composition according to any one of claims 1 to 4, further comprising a coupling agent as component (E).

6. A photocurable composition solution comprising the following components (A) to (D) and a solvent: Component (A): (meth)acrylic triblock copolymer Component (B): (meth)acrylate oligomer (excluding the component (A)) Component (C): hydroxyethyl(meth)acrylamide and / or N-n-butoxymethyl(meth)acrylamide Component (D): Photoinitiator.

7. 1. A method for producing a photocurable composition that is in a sheet form at 25°C before curing, comprising: A method for producing a sheet-shaped photocurable composition, comprising volatilizing the solvent contained in the photocurable composition solution according to claim 6 .

8. The method for producing a sheet-shaped photocurable composition according to claim 7 , wherein the solvent is evaporated on a release paper or a release film.

9. A laminate having a configuration in which a first adherend, a sheet-shaped photocurable composition, and a second adherend are bonded together in this order, The sheet-shaped photocurable composition is a laminate formed by volatilizing the solvent contained in the photocurable composition solution described in claim 6 on the first adherend and / or the second adherend.

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