Photocurable composition

Abstract

To provide a photocurable composition in a film state at 25°C before curing, capable of keeping a high 180 degree peeling strength to an untreated PET as adherend in lamination at normal temperature.SOLUTION: A photocurable composition in a film state at 25°C before curing including the following components (A) to (C), with a component (B) content of 1 to 45 pts.mass relative to 100 pts.mass of the component (A), has a temperature of 30 to 60°C at tan δ=1 before curing, and a storage elastic modulus of 10.0×105 Pa or less at 25°C after curing. Component (A): urethane-modified (meth)acrylate oligomer, component (B): film forming agent, component (C): photoinitiator.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] It is important for the adhesive film to maintain its dimensions. Furthermore, the number of adherends that have curved surfaces rather than flat surfaces is increasing, and there are cases where flat adherends, like laminators, cannot be used. Therefore, there is a demand for a device that can transfer at 20-30°C (room temperature) using pressure alone. Patent Document 1 also forms an adhesive sheet from an adhesive component and a release film. However, it does not contain components for film formation and is equivalent to a pressure-sensitive adhesive, so when pressure is applied, it is crushed, its thickness changes, and the adhesive component is extruded from the edge. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-024785 Summary of the Invention [Problem to be solved by the invention]

[0004] Previously, it was difficult for photocurable compositions that were film-like at 25°C before curing to maintain a high 180-degree peel strength when bonded to untreated PET at room temperature. Generally, plastic films have low surface tension, which often leads to problems such as poor adhesion during printing and coating. Surface treatments such as corona treatment significantly improve the surface tension of the substrate, improving adhesion. The term "untreated" in "untreated PET" refers to the lack of surface treatment. [Means for solving the problem]

[0005] As a result of extensive research to achieve the above object, the present inventors have discovered a method for producing a photocurable composition that is in the form of a film at 25° C. before curing, and have thus completed the present invention.

[0006] The gist of the present invention will now be described.

[0007] A first embodiment of the present invention comprises the following components (A) to (C), containing 1 to 45 parts by mass of component (B) per 100 parts by mass of component (A), and having a storage modulus of 10.0 × 10 at a temperature of 30 to 60°C where tan δ = 1 before curing and at 25°C after curing. 5 The photocurable composition is in the form of a film at 25°C before curing, and has a viscosity of 100 Pa or less. Component (A): urethane-modified (meth)acrylate oligomer (B) Component: Film-forming agent Component (C): Photoinitiator A second embodiment of the present invention is the photocurable composition in the form of a film at 25°C before curing according to the first embodiment, wherein the component (B) is a phenoxy resin that is solid at 25°C and has no (meth)acrylic group in the molecule.

[0008] A third embodiment of the present invention is a photocurable composition in a film form at 25°C in an uncured state according to either the first or second embodiment, further comprising a (meth)acrylate monomer (excluding the component (A)) as the component (D), and comprising 0.1 to 10 parts by mass of the component (D) per 100 parts by mass of the component (A).

[0009] A fourth embodiment of the present invention is a photocurable composition in the form of a film at 25°C before curing according to any one of the first to third embodiments, further comprising a coupling agent as component (E).

[0010] In a fifth embodiment of the present invention, the temperature at which tan δ=1 is 30 to 50°C before curing, and the storage modulus at 25°C after curing is 1.0 × 10 5 ~10.0×10 5The photocurable composition according to any one of the first to fourth embodiments, which is in the form of a film at 25°C before curing, has a viscosity of 1000 Pa.

[0011] A sixth embodiment of the present invention is a photocurable composition in the form of a film at 25°C before curing according to any one of the first to fifth embodiments, wherein the weight average molecular weight of the component (A) is 20,000 to 40,000 and the (meth)acrylic group equivalent is 15,000 to 25,000 g / eq.

[0012] A seventh embodiment of the present invention is a photocurable composition in the form of a film at 25°C in an uncured state according to any one of the first to sixth embodiments, comprising 20 to 40 parts by mass of the component (B) per 100 parts by mass of the component (A).

[0013] An eighth embodiment of the present invention is a photocurable composition in the form of a film at 25°C before curing according to any one of the first to seventh embodiments, which can be transferred to an adherend at 20 to 30°C.

[0014] A ninth embodiment of the present invention is obtained by curing the film-like photocurable composition according to any one of the first to eighth embodiments at 25°C in an uncured state, and has a storage modulus at 25°C of 10.0 x 10 5 The hardened product has a compressive strength of 0.05 Pa or less.

[0015] In a tenth embodiment of the present invention, the storage modulus is 1.0 × 10 5 ~10.0×10 5 Pa.

[0016] An eleventh embodiment of the present invention is a method for laminating two adherends, comprising transferring a film-like photocurable composition described in any one of the first to eighth embodiments at 25°C in a pre-cured state to one adherend in an atmosphere of 20 to 30°C, and then transferring the composition to the other adherend.

[0017] A twelfth embodiment of the present invention is the laminating method according to the eleventh embodiment, wherein the laminate transferred to the two adherends is vacuum heated.

[0018] A thirteenth embodiment of the present invention is the laminating method according to the twelfth embodiment, wherein the temperature in the vacuum heating is 30 to 60°C.

[0019] A fourteenth embodiment of the present invention is a concentrate comprising components (A) to (C) and a solvent, and containing 1 to 45 parts by mass of component (B) per 100 parts by mass of component (A).

[0020] A fifteenth embodiment of the present invention is a method for producing a photocurable composition in a film form at 25°C in an uncured state, wherein the photocurable composition in a film form at 25°C is obtained by volatilizing the solvent of the stock solution described in the fourteenth embodiment.

[0021] A sixteenth embodiment of the present invention is a concentrate comprising a photocurable composition in the form of a film at 25° C. before curing and a solvent. [Effects of the Invention]

[0022] The present invention provides a photocurable composition in the form of a film at 25°C before curing, and when laminated at room temperature, it is possible to maintain a high 180-degree peel strength against untreated PET as an adherend. DETAILED DESCRIPTION OF THE INVENTION

[0023] One embodiment of the present invention comprises the following components (A) to (C), containing 1 to 45 parts by mass of component (B) per 100 parts by mass of component (A), wherein the temperature at which tan δ=1 is achieved before curing is 30 to 60°C, and the storage modulus at 25°C after curing is 10.0 × 10 5 The photocurable composition is in the form of a film at 25°C before curing, and has a viscosity of 100 Pa or less. Component (A): urethane-modified (meth)acrylate oligomer (B) Component: Film-forming agent Component (C): Photoinitiator.

[0024] The present invention provides a photocurable composition in the form of a film at 25°C before curing, and when laminated at room temperature, it is possible to maintain a high 180-degree peel strength against untreated PET as an adherend.

[0025] The photocurable composition refers to the state before photocuring, and is a composition that exhibits adhesiveness or whose adhesiveness is improved by photocuring.

[0026] The present invention will be described in detail below. The component (A) that can be used in the present invention is a urethane-modified (meth)acrylate oligomer, which exhibits excellent adhesion to the glass or plastic of the protective panel. The oligomer is synthesized, for example, from a reaction product of a polyol compound (main skeleton) having two or more hydroxyl groups in its molecule, a compound having two or more isocyanate groups in its molecule, and a (meth)acrylate containing at least one hydroxyl group in its molecule. Examples of compounds having two or more isocyanate groups in their molecule include aromatic polyisocyanates, alicyclic polyisocyanates, and aliphatic polyisocyanates. Among 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. In this specification, acrylate is also referred to as acryloyl, methacrylate as methacryloyl, acrylate and methacrylate are collectively referred to as (meth)acrylate, and acryloyl and methacryloyl are collectively referred to as (meth)acryloyl. Furthermore, a numerical range indicated by "~" indicates a range that includes the upper and lower limits.

[0027] The weight-average molecular weight of component (A) is preferably 20,000 to 60,000, and more preferably 20,000 to 40,000. A weight-average molecular weight of 20,000 or more results in good curability, while a weight-average molecular weight of 60,000 or less results in low viscosity and good compatibility at the interface when bonded to an adherend. Herein, the term "weight-average molecular weight" refers to the weight-average molecular weight in terms of polystyrene measured by gel permeation chromatography. The (meth)acrylic group equivalent of component (A) is preferably 5,000 to 25,000 g / eq, and more preferably 15,000 to 25,000 g / eq. A molecular weight of 5,000 g / eq or more results in good curability, while a molecular weight of 25,000 g / eq or less results in good compatibility at the interface when bonded to an adherend. Herein, the (meth)acrylic group equivalent is expressed as molecular weight / number of functional groups, and refers to the molecular weight per (meth)acrylic group.

[0028] 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 does not become cloudy under high-temperature and high-humidity conditions. These compounds may be used alone or in combination.

[0029] Compounds having two or more isocyanate groups in the molecule include aromatic polyisocyanates and aliphatic polyisocyanates. 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-diisocyanate, 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, diisocyanates such as isophorone diisocyanate and hexamethylene diisocyanate are preferred.

[0030] Examples of (meth)acrylates containing at least one hydroxyl group 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.

[0031] The synthesis method for the urethane-modified (meth)acrylate oligomer is not particularly limited, and known methods can be used. For example, the following method can be used: 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.) at a molar ratio (polyol compound:isocyanate compound) of preferably 3:1 to 1:3, more preferably 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 at least one hydroxyl group in the molecule in an amount sufficient to react with the isocyanate groups to synthesize a urethane (meth)acrylate oligomer.

[0032] Examples of catalysts used in the 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 products with excellent transparency. These catalysts are preferably used in an amount of 0.0001 to 10 parts by weight per 100 parts by weight of the total reactants. The reaction temperature is typically 10 to 100°C, and preferably 30 to 90°C. The urethane-modified (meth)acrylate oligomer may be diluted with a solvent or the following monomer (component (D)) at the raw material stage before use.

[0033] The component (B) that can be used in the present invention is a film-forming agent, and contains 1 to 45 parts by weight, and particularly preferably 20 to 40 parts by weight, of component (B) per 100 parts by weight of component (A). This allows lamination at room temperature. Components other than component (B) are often liquid at 25°C, and component (B), which is solid or liquid at 25°C but lacks fluidity, is added to form the photocurable composition into a film at 25°C. Unlike compositions that are liquid at 25°C, component (B) forms a film that lacks fluidity at 25°C, preventing the composition from spilling over the edges of the adherend when used to bond plate-like adherends.

[0034] A particularly preferred component (B) is a phenoxy resin. Phenoxy resins are polymers obtained by polymerizing multifunctional epoxy resins, such as bisphenol-type epoxy resins, and have residual epoxy groups at their terminals. The weight-average molecular weight is preferably 10,000 to 100,000, and more preferably 30,000 to 80,000. Specific examples of phenoxy resins include bisphenol-type phenoxy resins, novolac-type phenoxy resins, naphthalene-type phenoxy resins, and biphenyl-type phenoxy resins. These may be used alone or in combination. Bisphenol-type phenoxy resins that are solid at 25°C are preferred. Among these, phenoxy resins obtained by polymerizing only bisphenol A-type epoxy resins, phenoxy resins obtained by polymerizing only bisphenol F-type epoxy resins, phenoxy resins obtained by copolymerizing bisphenol A-type epoxy resins and bisphenol F-type epoxy resins, and mixtures thereof are more preferred due to their good compatibility with the component (A) of the present invention. In addition, phenoxy resins that do not have side chains such as (meth)acrylic groups in the molecule are preferred so that they do not immediately become fluid when heated. These may be used alone or in combination. In one preferred embodiment, component (B) is a phenoxy resin that is solid at 25°C and does not have a (meth)acrylic group in the molecule.

[0035] The phenoxy resin of component (B) can be a commercially available product, and specific examples include, but are not limited to, the Pheno Tohto series manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., such as YP-50, YP-50S, YP-55, YP-70, ZX-1356-2, and FX-316; the jER series manufactured by Mitsubishi Chemical Corporation, such as 1256, 4250, and 4275; and the PKHB, PKHC, PKHH, PKHJ, and PKFE manufactured by Tomoe Engineering Co., Ltd. Component (B) may be diluted with a solvent at the raw material stage before use.

[0036] The amount of component (B) added in the present invention is preferably 1 to 45 parts by mass, more preferably 20 to 40 parts by mass, per 100 parts by mass of component (A). When component (B) is 1 part by mass or more, film-forming properties are exhibited, and the photocurable composition becomes less or no sticky, making it easy to peel off release films, etc. On the other hand, when component (B) is 45 parts by mass or less, lamination at room temperature is possible.

[0037] The component (C) used in the present invention is a photoinitiator, which is a compound that decomposes upon irradiation with active energy rays such as ultraviolet light or visible light to generate radical species, cation species, or anion species.

[0038] Examples of component (C) 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. When an acylphosphine oxide-based photoinitiator that is easily cured by energy rays in the visible light region is added to the composition, the composition itself tends to turn yellow, but it is preferable to include an acylphosphine oxide-based photoinitiator because this improves photocurability.

[0039] 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.

[0040] 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.

[0041] Examples of benzophenone-based photoinitiators include, but are not limited to, benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3',4,4'-tetra(t-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.

[0042] 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.

[0043] Examples of the acylphosphine oxide photoinitiator include, but are not limited to, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide.

[0044] The amount of component (C) added is preferably 0.1 to 5.0 parts by mass per 100 parts by mass of component (A). If the amount is 0.1 part by mass or more, photocurability is exhibited, and if the amount is 5.0 parts by mass or less, the composition is less likely to become colored.

[0045] The photocurable composition of the present invention preferably further contains a (meth)acrylate monomer (excluding the component (A)) as a component (D). By further containing the component (D), the tan δ can be lowered.

[0046] (Meth)acrylate monomers (excluding component (A)) that can be used as component (D) of the present invention include monofunctional, bifunctional, trifunctional, tetrafunctional or higher polyfunctional monomers. From the viewpoint of improving adhesive strength, bifunctional (meth)acrylate monomers are preferred as component (D). In order to reduce the viscosity of the composition, the molecular weight of the monomer is preferably 10,000 or less, more preferably 5,000 or less, and most preferably 1,000 or less.

[0047] 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, phenoxytetraethylene glycol (meth)acrylate, and nonylphenoxyethyl (meth)acrylate. 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, morpholino (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyoxytetramethylene glycol mono(meth)acrylate, and the like.

[0048] 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 di(meth)acrylate, di(meth)acryloyl isocyanurate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polyoxytetramethylene glycol di(meth)acrylate.

[0049] Examples of trifunctional monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, epichlorohydrin-modified trimethylolpropane tri(meth)acrylate, and epichlorohydrin-modified glycerol tri(meth)acrylate.

[0050] Examples of polyfunctional monomers include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0051] These (meth)acrylate monomers can be used alone or in combination of two or more.

[0052] As component (D), a (meth)acrylate containing an ether bond and a (meth)acryloyl group is preferred, and a polyether monomer having 8 to 30 repeating ether bond units per molecule is most preferred. When the repeating ether bond unit is 8 or more, the polyether monomer separates from moisture that permeates into the cured product from the outside in a high-temperature, high-humidity atmosphere, and does not or is unlikely to become cloudy. On the other hand, when the repeating ether bond unit is 30 or less, the monomers do not crystallize, and the cured product does or is unlikely to become cloudy. These may be used alone or in combination.

[0053] Examples of (meth)acrylates containing an ether bond and a (meth)acryloyl group 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. Among these, bifunctional (meth)acrylates containing an ether bond and a (meth)acryloyl group are preferred, with polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polyoxytetramethylene glycol di(meth)acrylate being preferred, and polyethylene glycol di(meth)acrylate being more preferred. The molecular weight of the (meth)acrylate containing an ether bond and a (meth)acryloyl group is preferably in the range of 200 to 5,000, more preferably 250 to 3,000. Specific examples include, but are not limited to, 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 130MA, 130A, 14EG, and 14EG-A as part of the Light Ester series manufactured by Kyoeisha Chemical Co., Ltd.

[0054] To reduce the viscosity of the composition and improve its handleability, the amount of component (D) added is preferably 0.1 to 50 parts by mass, more preferably 0.1 to 30 parts by mass, and even more preferably 0.1 to 10 parts by mass per 100 parts by mass of component (A).

[0055] The photocurable composition of the present invention preferably further comprises a coupling agent (component (E)), which improves adhesive strength.

[0056] The component (E) that can be used in the present invention is, for example, a silane coupling agent. Specific examples of component (E) include glycidyl group-containing silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane; vinyl group-containing silane coupling agents such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, and vinyltrimethoxysilane; (meth)acryloyl group-containing silane coupling agents such as γ-methacryloxypropyltrimethoxysilane (3-methacryloxypropyltrimethoxysilane); amino group-containing silane coupling agents such as N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and N-phenyl-γ-aminopropyltrimethoxysilane; and others such as γ-mercaptopropyltrimethoxysilane and γ-chloropropyltrimethoxysilane. These may be used alone or in combination of two or more. Among these, from the viewpoint that further improvement in adhesion can be expected, a silane coupling agent containing an epoxy group or a (meth)acryloyl group is preferably used, and a silane coupling agent containing a (meth)acryloyl group is more preferably used.

[0057] From the viewpoint of adhesiveness, the amount of component (E) added is preferably 0.1 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of component (A).

[0058] Furthermore, as other components, additives such as fillers such as inorganic fillers and organic fillers, storage stabilizers, antioxidants, light stabilizers, ultraviolet absorbers, adhesion aids, plasticizers, dyes, pigments, flame retardants, sensitizers, thermal initiators, heavy metal deactivators, ion trapping agents, emulsifiers, water dispersion stabilizers, antifoaming agents, release agents, leveling agents, waxes, rheology control agents, and surfactants may be blended within the scope of the present invention.

[0059] 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, metal powder, etc. Furthermore, examples of fumed silica powder include those whose surfaces have been chemically modified (hydrophobized) with organochlorosilanes, polyorganosiloxane, hexamethyldisilazane, etc., and examples thereof include commercially available products such as R974, R972, R972V, R972CF, R805, R812, R812S, R816, R8200, RY200, RX200, RY200S, and R202 as part of the Aerosil series manufactured by Nippon Aerosil Co., Ltd. For the purposes of improving flowability and the mechanical strength of the cured product, the amount of inorganic filler added is preferably about 0.1 to 100 parts by mass per 100 parts by mass of the total of components (A) to (C).

[0060] 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 ultraviolet absorbers include ADK STAB 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.

[0061] The photocurable composition of the present invention contains components (A) to (C) (and optionally components (D) to (E) and other components) and a solvent, and can be obtained by volatilizing the solvent from a stock solution containing 1 to 45 parts by mass of component (B) per 100 parts by mass of component (A). Adding a solvent in this way can reduce the viscosity.

[0062] Examples of solvents include alcohols such as methanol and ethanol, chlorinated solvents such as dichloroethane and trichloroethane, fluorinated solvents such as trichlorofluoroethane, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ester solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate, ethers such as dimethyl ether and methyl ethyl ether, hydrocarbon solvents such as pentane, hexane, heptane, and cyclohexane, and aromatic solvents such as benzene, toluene, and xylene. Ketone solvents are preferred in consideration of compatibility with components (A) to (C) (and further component (D)) of the present invention. The amount of solvent added is preferably 50 to 200 parts by mass per 100 parts by mass of components (A) to (C), and within this range, a thickness of 200 μm or less can be achieved when formed into a sheet.

[0063] Known techniques can be used to process the stock solution into a film (sheet). For example, a solvent is added to each component of the photocurable composition to intentionally reduce the viscosity of the stock solution. The stock solution is then coated onto a release film whose surface has been previously treated for release, and the solvent is then dried (volatilized) to form a film. That is, the present invention also provides a method for producing a film-like photocurable composition formed by volatilizing the solvent from the stock solution, which is at 25°C before curing. This results in a film-like photocurable composition at 25°C before curing. A release film may also be attached to one or both sides of the film-like photocurable composition. Specific examples of coating methods include flow coating, roll coating, gravure roll coating, wire bar coating, and lip die coating. Furthermore, a hot air drying oven or an IR oven can be used as a drying device in the drying step. Examples of materials for the release film include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film, as well as paper, cloth, and nonwoven fabric. Plastic films are preferred from the standpoint of releasability. The thickness of the release film is preferably 5 to 300 μm, more preferably 25 to 200 μm.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-based compound, or the like.

[0064] The thickness of the photocurable composition in film form at 25° C. is, for example, 200 μm or less, or preferably 10 to 200 μm, or more preferably 30 to 150 μm.

[0065] In the present invention, a solvent can be used to process the photocurable composition into a sheet. Examples of solvents include alcohols such as methanol and ethanol; chlorinated solvents such as dichloroethane and trichloroethane; fluorinated solvents such as trichlorofluoroethane; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ethers such as dimethyl ether and methyl ethyl ether; hydrocarbon solvents such as pentane, hexane, heptane, and cyclohexane; and aromatic solvents such as benzene, toluene, and xylene. Ketone solvents are preferred in view of compatibility with components (A) to (D) of the present invention. The amount of solvent added is preferably 50 to 200 parts by mass per 100 parts by mass of components (A) to (D) combined. This range ensures a film thickness of 200 μm or less when formed into a sheet.

[0066] Before curing, the photocurable composition of the present invention has a temperature at which tan δ=1 is 30 to 60°C, and more preferably 30 to 50°C. 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 G'' / G'=tan δ. The temperature at which tan δ=1 represents the temperature at the boundary between solid and liquid.

[0067] In the present invention, the term "film-like" refers to a flat plate-like state having a certain thickness. As described above, when the temperature at which tan δ = 1 is 30°C or higher, the photocurable composition can be made into a film. When the temperature at which tan δ = 1 is 60°C or lower, the composition can be laminated at room temperature.

[0068] The temperature at which tan δ=1 can be adjusted appropriately by selecting the molecular weights and structures of component (A), component (B), and optionally component (D).

[0069] After curing, the photocurable composition of the present invention has a storage modulus at 25°C of 10.0 x 10 5Pa or less, and more preferably 1.0×10 5 ~10.0×10 5 That is, the storage modulus at 25°C of the cured product obtained by curing the film-like photocurable composition at 25°C is 10.0 × 10 5 Pa or less, and 1.0 × 10 5 ~10.0×10 5 The storage modulus at 25°C can be measured at each frequency by DMA (dynamic viscoelasticity measurement). The storage modulus at 25°C of the cured photocurable composition is preferably 10.0 x 10 Pa. 5 The peel strength is improved by ensuring that the storage modulus is not more than Pa. The storage modulus at 25°C of the cured photocurable composition can be adjusted appropriately by, for example, selecting the component (A).

[0070] The photocurable composition of the present invention can be cured by irradiation with energy rays such as ultraviolet light and visible light. Irradiation light in the wavelength range of 150 to 750 nm is preferred, and the irradiation light has an intensity of 1 to 100 kJ / m using a low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, xenon lamp, metal halide lamp, or LED lamp. 2 The curing can be performed with an integrated light amount of 5 to 70 kJ / m 2 is the cumulative amount of light.

[0071] The photocurable composition of the present invention can be used in the assembly of display devices such as liquid crystal displays and organic electroluminescence (EL) displays. Specifically, it is suitable for assembling display elements, cover panels, touch panels, etc. into display devices, as well as for assembling organic EL elements themselves. Various components are used in combination as components for assembling these. Examples of components that can be used include untreated PET (not subjected to surface treatment such as corona treatment), treated PET, glass plates, acrylic plates, and polycarbonate plates, and various combinations of these can be bonded together.

[0072] The following describes a process for bonding two (transparent) adherends using a film-like photocurable composition with a release film attached to one side. The bonding process consists of a laminating step and a curing step.

[0073] In the laminating step, a film-like photocurable composition is transferred to one of the adherends at 25°C in an atmosphere of 20 to 30°C. For example, the side of the film-like photocurable composition not covered by the release film is attached to one of the adherends, and the two are then bonded together using a laminator while applying pressure and, optionally, heat. The release film is then removed, and the other adherend is similarly bonded using the laminator. The laminate thus obtained, in which the composition has been transferred to the two adherends, may be subjected to vacuum heating. By performing vacuum heating, bubbles are prevented or are less likely to remain inside the laminate during bonding. The temperature during vacuum heating is preferably 30 to 60°C, as this more easily achieves the above-mentioned effects. Examples of methods for vacuum heating include using an autoclave.

[0074] Finally, the film-like photocurable composition is cured by irradiating it with energy rays, thereby bonding the two adherends. Instead of a laminator, a vacuum press, a vacuum laminator, or an autoclave, which can bond the two adherends in a vacuum or reduced pressure atmosphere, may be used. The bonding process is not limited to these. [Example]

[0075] 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 in the form of a film at 25°C before curing, obtained by drying the solvent, will be referred to simply as a film-like composition, and a stock solution containing the components constituting the photocurable composition and the solvent will be referred to simply as a stock solution.

[0076] [Examples 1 to 4, Comparative Examples 1 to 3] The following ingredients were prepared to prepare the stock solution: Component (A): urethane-modified (meth)acrylate oligomer A urethane acrylate with a weight average molecular weight of 30,000, a (meth)acrylic group equivalent of 19,000 g / eq, and a polycarbonate main skeleton (hereinafter referred to as Oligomer 1). A urethane acrylate with a weight average molecular weight of 30,000, a (meth)acrylic group equivalent of 14,000 g / eq, and a polycarbonate main skeleton (hereinafter referred to as Oligomer 2). A urethane acrylate with a weight average molecular weight of 30,000, a (meth)acrylic group equivalent weight of 9,600 g / eq, and a polycarbonate main skeleton (hereinafter referred to as Oligomer 3). A urethane acrylate with a weight average molecular weight of 50,000, a (meth)acrylic group equivalent weight of 9,600 g / eq, and a polycarbonate main skeleton (hereinafter referred to as Oligomer 4). (B) Component: Film-forming agent Weight average molecular weight: 60,000, bisphenol A epoxy resin / bisphenol F mixed type (solid content 100%) (jER4250, manufactured by Mitsubishi Chemical Corporation) Component (C): Photoinitiator 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (IRGACURE TPO manufactured by BASF) Component (D): (meth)acrylate monomer (excluding component (A)) Polyethylene glycol #1000 dimethacrylate (ethylene glycol repeating units: n=23) (NK Ester 23G, manufactured by Shin-Nakamura Chemical Co., Ltd.) Polyethylene glycol #600 dimethacrylate (ethylene glycol repeating units: n=14) (NK Ester 14G, manufactured by Shin-Nakamura Chemical Co., Ltd.) Component (E): Coupling agent 3-Methacryloxypropyltrimethoxysilane (KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) solvent Methyl ethyl ketone (reagent) Components (A) to (E) and the solvent are weighed into a mixing vessel and stirred for 1 hour in an atmosphere at 25°C. If the methyl ethyl ketone has decreased due to evaporation from the total weight before stirring, the amount of methyl ethyl ketone that has evaporated is replaced. Detailed amounts are shown in Table 1, and all values are expressed in parts by mass.

[0077] The stock solutions of Examples 1 to 4 and Comparative Examples 1 to 3 were each coated onto a release film with a 100 μm clearance using a belt conveyor-type coater. The composition was then dried at a speed of 500 mm / min through two drying lines: a 1.5 m long drying line in an 80°C atmosphere and a 1.5 m long drying line in a 100°C atmosphere, forming a film. Another release film was then attached to create a film composition with two release films. The film thickness, including the release film, was measured with a thickness gauge, and the thickness of the two release films was subtracted to obtain a film composition thickness of 50 μm. During drying to volatilize the solvent, the solvent dries from the surface, making it difficult for the solvent inside to volatilize. Therefore, since a thicker film thickness leaves air bubbles inside the coating, a clearance of 300 μm or less is preferred.

[0078] [Table 1]

[0079] Rheometer measurements (before curing), total light transmittance measurements (after curing), haze measurements (after curing), peel strength measurements (after curing), and dynamic viscoelasticity measurements were carried out using film compositions formed from the stock solutions of Examples 1 to 4 and Comparative Examples 1 to 3. The stock solution numbers in Table 1 are shown in Table 2.

[0080] [Rheometer measurement (before curing)] The film composition was peeled from the release film, and multiple sheets were stacked to a thickness of 700 μm, and degassed using a vacuum laminator. Viscoelasticity measurements were performed using a HAAKE MARSIII from Thermo Fishers in the temperature range of 0°C to 100°C. The temperature at which tan δ = 1 was defined as the "flow initiation temperature (°C)." In the present invention, a flow initiation temperature of 30 to 60°C allows lamination at room temperature, and a temperature of 30 to 50°C is more preferable. The results are shown in Table 1. In Table 1, the flow initiation temperature is expressed in °C.

[0081] Test pieces for the total light transmittance and haze measurements are prepared as follows: One of the release films is peeled off from the film-like composition, which is then attached to an alkali-free glass plate measuring 0.7 mm thick x 100 mm wide x 100 mm long, and transferred using a hot roll laminator with the roll temperature set to 25°C. The other release film is then peeled off, and the alkali-free glass plate is attached. The lamination is then completed by degassing for 120 seconds in a 50°C atmosphere using a vacuum laminator. The laminate is then subjected to a cumulative light dose of 30 kJ / m using a belt conveyor-type ultraviolet irradiator equipped with a high-pressure mercury lamp. 2 The film-like composition was irradiated with ultraviolet light of 1000 kJ / cm 2 and bonded to alkali-free glass to prepare a test piece.

[0082] [Total light transmittance measurement (after curing)] Using a test piece with a film-like composition thickness of 50 μm, the total light transmittance was measured using a spectroscopic haze meter SH7000 manufactured by Nippon Denshoku Industries Co., Ltd. The light transmittance was measured at wavelengths ranging from 780 nm to 380 nm, and the number of tests was n=3. The average value was calculated, and the result was recorded as "total light transmittance (%)" according to the following evaluation criteria. Details are in accordance with JIS K 7361-1:1997. For optical applications, a total light transmittance of 90% or more is preferred. The results are shown in Table 1. In Table 1, the unit of total light transmittance is %.

[0083] [White turbidity (haze) measurement (after curing)] The test piece was used with 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 opacity was calculated in accordance with JIS K 7136:2000. Three tests were conducted, and the average value was calculated. The result was designated as "opacity (unitless)" and is shown in Table 1. To achieve colorless transparency, it is preferable that the opacity be 1.0 or less.

[0084] [Peel strength measurement (after curing)] The 180-degree peel strength was measured for the following three combinations: untreated PET film manufactured by Toyobo Film Solutions Co., Ltd., 100mm long x 25mm wide x 38μm thick; alkali-free glass plate, 100mm long x 25mm wide x 2mm thick; acrylic plate manufactured by Asahi B-Techno Co., Ltd., 100mm long x 25mm wide x 2mm thick; and polycarbonate plate manufactured by Asahi B-Techno Co., Ltd., 100mm long x 25mm wide x 2mm thick.

[0085] Test piece 1: Glass plate / untreated PET film Test piece 2: Acrylic plate / untreated PET film Test piece 3: Polycarbonate plate / untreated PET film The test pieces were processed as follows: each plate was laminated with a film-like composition in an area measuring 70 mm long and 25 mm wide, and then passed through a hot roll laminator at a roll temperature of 25°C and a pressure of 0.2 MPa. The release film was then peeled off, and untreated PET was placed on top, and the laminator was run again under the same conditions. The plate was then left in an autoclave for 20 minutes at a pressure of 0.5 MPa and an atmosphere of 50°C. After confirming that the test pieces had cooled to room temperature, a belt conveyor-type ultraviolet irradiator was used to irradiate the plate with an integrated light dose of 30 kJ / m. 2The test piece is irradiated with ultraviolet light of 1000 kN / m. The average strength value, "peel strength (kN / m)," is measured at a speed of 60 mm / min using a precision universal testing machine (Autograph AGX-V series) manufactured by Shimadzu Corporation. The results are shown in Table 1. In Table 1, the unit of peel strength is kN / m. It is preferable that all of the three combinations of adherends (test pieces 1 to 3) have a peel strength of 1.0 kN / m or more.

[0086] [Dynamic Mechanical Analysis (DMA)] A film-like composition measuring 60 mm in length, 10 mm in width, and 0.7 mm in thickness was applied to a belt conveyor-type ultraviolet irradiator with an integrated light dose of 30 kJ / m 2 Test pieces are prepared by irradiating ultraviolet light of 1000 kJ / cm². Measurements are carried out at a temperature range of -50 to 100°C at a frequency of 1 Hz using a Hitachi High-Tech Science (DMS6100) instrument. The storage modulus (×10) at 25°C is measured at a frequency of 1 Hz. 5 The results are shown in Table 1. In Table 1, the unit of storage modulus is Pa. The storage modulus is 1.0 x 10 5 ~10.0×10 5 Pa is preferred.

[0087] [Table 2]

[0088] In terms of peel strength, Examples 1 to 4 exhibited higher strengths for Test Pieces 1 to 3, respectively, compared to Comparative Examples 1 to 3. This indicates that transfer is possible at 20 to 30°C (room temperature), and transfer requires only pressure on the adherend, with no need for heating. Ultimately, it is clear that stable adhesive strength is exhibited even with untreated PET, a material that is difficult to adhere to. Examples 1 to 4 contain 1 to 45 parts by mass of component (B) per 100 parts by mass of component (A), and by being in this range, the temperature at which tanδ=1 is 30 to 60°C before curing and the storage modulus at 25°C after curing is 10.0 x 10 5This is presumably due to the fact that it satisfies the parameter of less than 100 Pa. In addition, it has high total light transmittance and low opacity, making it suitable for optical applications. [Industrial Applicability]

[0089] While it is generally difficult to maintain a high 180-degree peel strength against untreated PET as an adherend, this film can be transferred to untreated PET at room temperature and has high adhesion, making it suitable for assembling display devices such as liquid crystal displays and organic electroluminescence (EL) displays. Specifically, it is suitable for assembling display elements, cover panels, touch panels, VR goggles, etc. into display devices, as well as for assembling organic EL elements themselves. Because heat transfer is not required, it can be used on curved rather than flat adherends.

[0090] This application is based on Japanese Patent Application No. 2020-084884, filed on May 14, 2020, the disclosure of which is incorporated by reference in its entirety.

Claims

1. The cured composition contains the following components (A) to (D), and contains 1 to 45 parts by mass of component (B) per 100 parts by mass of component (A), and contains 0.1 to 10 parts by mass of component (D) per 100 parts by mass of component (A). The cured composition has a storage modulus of 10.0×10 at a temperature of 30 to 60°C where tan δ=1 before curing and at 25°C after curing. ５ The photocurable composition is in the form of a film at 25°C before curing, and has a viscosity of 100 Pa or less. Component (A): a urethane-modified (meth)acrylate oligomer having a weight average molecular weight of 20,000 to 40,000 and a (meth)acrylic group equivalent of 15,000 to 25,000 g / eq. Component (B): a film-forming agent that is a phenoxy resin that is solid at 25°C and does not have a (meth)acrylic group in the molecule Component (C): Photoinitiator Component (D): (meth)acrylate monomer (excluding component (A))

2. The photocurable composition according to claim 1 , which is in the form of a film at 25° C. before curing, further comprising a coupling agent as component (E).

3. Before curing, the temperature when tan δ = 1 is 30 to 50°C, and after curing, the storage modulus at 25°C is 1.0 x 10 ５ ~10.0 x 10 ５ The photocurable composition according to claim 1 or 2, which is in the form of a film at 25°C before curing.

4. 4. The photocurable composition according to claim 1, which is in the form of a film at 25° C. before curing, and contains 20 to 40 parts by mass of the component (B) per 100 parts by mass of the component (A).

5. The photocurable composition according to any one of claims 1 to 4, which is in the form of a film at 25°C before curing and can be transferred to an adherend at 20 to 30°C.

6. The curable composition according to any one of claims 1 to 5 is obtained by curing the film-like photocurable composition at 25°C in an uncured state, and has a storage modulus at 25°C of 10.0 x 10 ５ The hardened product has a viscosity of 0.05 Pa or less.

7. The storage modulus is 1.0 × 10 ５ ~10.0 x 10 ５ The cured product according to claim 6, wherein the cured product is Pa.

8. A method for laminating two adherends, comprising transferring the film-like photocurable composition according to any one of claims 1 to 5 in a pre-cured state at 25°C to one adherend in an atmosphere of 20 to 30°C, and then transferring the composition to the other adherend.

9. The laminating method according to claim 8, wherein the laminate transferred to the two adherends is subjected to vacuum heating.

10. A method for bonding two adherends, comprising: This lamination method involves transferring a film-like photocurable composition to one adherend at 25°C in the pre-cured state described below in an atmosphere of 20 to 30°C, then transferring it to the other adherend, and vacuum heating the laminate that has been transferred to the two adherends. A photocurable composition in the form of a film at 25°C before curing, which contains the following components (A) to (C), containing 1 to 45 parts by mass of component (B) per 100 parts by mass of component (A), and which has a storage modulus at 25°C after curing of 10.0 x 105 Pa or less at a temperature of 30 to 60°C at tan δ = 1 before curing; Component (A): urethane-modified (meth)acrylate oligomer Component (B): a film-forming agent that is a phenoxy resin that is solid at 25°C and does not have a (meth)acrylic group in the molecule Component (C): Photoinitiator

11. The laminating method according to any one of claims 8 to 10, wherein the temperature in the vacuum heating is 30 to 60°C.

12. A stock solution comprising the following components (A) to (D) and a solvent, wherein the stock solution contains 1 to 45 parts by mass of component (B) per 100 parts by mass of component (A), and 0.1 to 10 parts by mass of component (D) per 100 parts by mass of component (A). Component (A): a urethane-modified (meth)acrylate oligomer having a weight average molecular weight of 20,000 to 40,000 and a (meth)acrylic group equivalent of 15,000 to 25,000 g / eq. Component (B): a film-forming agent that is a phenoxy resin that is solid at 25°C and does not have a (meth)acrylic group in the molecule Component (C): Photoinitiator Component (D): (meth)acrylate monomer (excluding component (A))

13. A method for producing a photocurable composition in the form of a film at 25°C in an uncured state, comprising volatilizing the solvent of the concentrate according to claim 12 to obtain a photocurable composition in the form of a film at 25°C.

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