Film-form adhesive and method for manufacturing optical laminate

Abstract

To provide a film-form adhesive suitably used in manufacturing an optical laminate, and a method for manufacturing an optical laminate using the film-form adhesive.SOLUTION: A film-form adhesive curable by active energy rays contains a compound having a cyclic ether group. The film-form adhesive forms a cured film whose creep strain when a shear stress of 1 kPa is applied at 50°C for 300 seconds after curing is 5% or less. The film-form adhesive is used when joining an optical rigid member and an optical resin film. Also provided is a method for manufacturing an optical laminate using the film-form adhesive.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a film-like adhesive and a method for producing an optical laminate. [Background technology]

[0002] BACKGROUND ART In the past, in the manufacturing process of optical devices such as display devices and light-emitting devices, acrylic pressure-sensitive adhesive sheets have sometimes been used to adhere or fix various members from the viewpoint of transparency. For example, Patent Document 1 describes a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition containing a specific (meth)acrylic acid ester polymer, and also describes that the pressure-sensitive adhesive sheet is suitable for use in displays. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-172536 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 describes a laminate having a layer structure of glass plate / cured pressure-sensitive adhesive layer / polycarbonate resin plate. However, according to the inventors' investigations, in a laminate having an adhesive layer or pressure-sensitive adhesive layer sandwiched between such a hard member (glass plate) and a resin film, if the adhesive or pressure-sensitive adhesive is prone to deformation, when the ambient temperature changes and the resin film expands or contracts, the optical path of the light passing through the laminate changes, and there is a risk of blurring or unevenness occurring in the displayed image. Therefore, there has been a demand for adhesives and pressure-sensitive adhesives that can be suitably used when producing optical laminates.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a film-like adhesive that is suitable for use when producing an optical laminate, and a method for producing an optical laminate using this film-like adhesive. [Means for solving the problem]

[0006] In order to solve the above problems, the present inventors have conducted extensive research into film-like adhesives. As a result, it was found that active energy ray-curable film adhesives containing a compound having a cyclic ether group tend to form cured films with excellent shape retention after irradiation with active energy rays, which led to the completion of the present invention. That is, according to the present invention, the following film-like adhesives [1] to [4] and a method for producing an optical laminate [5] are provided.

[0007] [1] An active energy ray-curable film-like adhesive containing a compound having a cyclic ether group, which, after curing, forms a cured film having a creep strain of 5% or less, which is the amount of strain when a shear stress of 1 kPa is applied at 50°C for 300 seconds, and which is used when bonding optical hard components and optical resin films. [2] The film-like adhesive according to [1], which becomes a cured film having a gel fraction of 80% or more after curing. [3] The film-like adhesive according to [1], wherein the optical hard member is a glass plate. [4] The film-like adhesive according to [1] or [2], wherein the optical resin film is a polyester resin film. [5] A method for producing an optical laminate, comprising: step 1 of bonding an optical hard member and an optical resin film together using an active energy ray-curable film adhesive containing a compound having a cyclic ether group, the film adhesive being such that, after curing, the film adhesive forms a cured film with a creep strain of 5% or less, which is the strain amount when a shear stress of 1 kPa is applied at 50°C for 300 seconds; and step 2, after step 1, of irradiating the film adhesive with active energy rays to cure the film adhesive. [Effects of the Invention]

[0008] According to the present invention, there are provided a film-like adhesive that is suitably used when producing an optical laminate, and a method for producing an optical laminate that uses this film-like adhesive. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present invention, for preferred numerical ranges (e.g., ranges of content, etc.), the lower and upper limits described in stages can be independently combined. For example, the description "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferable upper limit (60)" to form "10 to 60."

[0010] The present invention will be described in detail below, divided into the sections of 1) a film-like adhesive and 2) a method for producing an optical laminate.

[0011] 1) Film adhesive The film-like adhesive of the present invention is an active energy ray-curable film-like adhesive containing a compound having a cyclic ether group. The film-like adhesive of the present invention forms a cured film having a creep strain of 5% or less after curing, and is used when bonding an optical hard member and an optical resin film. In the present invention, the creep strain refers to the amount of strain when a shear stress of 1 kPa is applied to a test piece at 50° C. for 300 seconds. A film-like adhesive is an adhesive formed into a film that is non-fluid at room temperature (23°C, the same applies hereinafter). The film-like adhesive of the present invention may be in the form of a strip or a long strip (strip).

[0012] [Compounds having a cyclic ether group] In the present invention, a compound having a cyclic ether group refers to a compound having at least one cyclic ether group in the molecule. However, among compounds that may be considered phenoxy resins, those with a weight average molecular weight (Mw) of 5,000 or less are considered "compounds having a cyclic ether group," and those with a weight average molecular weight (Mw) of more than 5,000 are considered "phenoxy resins."

[0013] When the film-like adhesive of the present invention is irradiated with active energy rays, the compound having a cyclic ether group reacts, and the film-like adhesive becomes a cured film. By using a compound having a cyclic ether group as a reactive component, the creep strain of the cured film can be easily reduced. Examples of the cyclic ether group include an oxirane group (epoxy group), an oxetane group (oxetanyl group), a tetrahydrofuryl group, and a tetrahydropyranyl group.

[0014] As the compound having a cyclic ether group, a compound having an oxirane group or an oxetane group is preferred, and a compound having two or more oxirane groups or oxetane groups in the molecule is more preferred, since a cured film having a smaller creep strain amount is more likely to be obtained.

[0015] The compound having an oxirane group in the molecule is preferably an epoxy compound, including aliphatic epoxy compounds (excluding alicyclic epoxy compounds), aromatic epoxy compounds, and alicyclic epoxy compounds.

[0016] Examples of aliphatic epoxy compounds include 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, triglycidyl ether of glycerin, triglycidyl ether of trimethylolpropane, tetraglycidyl ether of sorbitol, hexaglycidyl ether of dipentaerythritol, diglycidyl ether of polyethylene glycol, and diglycidyl ether of polypropylene glycol.

[0017] Examples of aromatic epoxy compounds include glycidyl ethers of bisphenol A, bisphenol F, or compounds obtained by further adding alkylene oxide to these compounds; novolac epoxy resins; glycidyl ethers of aromatic compounds having two or more phenolic hydroxyl groups on one aromatic ring, such as resorcinol, hydroquinone, and catechol; glycidyl ethers of aromatic compounds having two or more alcoholic hydroxyl groups in the molecule, such as phenyldimethanol, phenyldiethanol, and phenyldibutanol; and glycidyl esters of polybasic aromatic compounds having two or more carboxylic acids in the molecule, such as phthalic acid, terephthalic acid, and trimellitic acid.

[0018] Examples of alicyclic epoxy compounds include glycidyl ethers of polyhydric alcohols having at least one alicyclic structure, such as dicyclopentadiene dimethanol diglycidyl ether and hydrogenated bisphenol A; and cycloalkene oxide compounds, such as cyclohexene oxide-containing compounds and cyclopentene oxide-containing compounds obtained by epoxidizing a cyclohexene ring-containing compound or a cyclopentene ring-containing compound with an oxidizing agent.

[0019] Furthermore, epoxy compounds having an oxyalkylene structure are preferred as epoxy compounds. Epoxy compounds having an oxyalkylene structure tend to give cured products with a relatively low glass transition temperature (Tg). When the Tg of the cured product is low, the curing reaction of the epoxy compound progresses, and even when the epoxy compound becomes part of the cured product, it retains sufficient molecular mobility. Therefore, when the film adhesive contains an epoxy compound having an oxyalkylene structure, it can be sufficiently cured by light irradiation alone, without heat treatment.

[0020] From the viewpoint of obtaining the effect of maintaining sufficient molecular mobility even when the curing reaction of the epoxy compound progresses and the epoxy compound becomes part of the cured product, the epoxy compound is preferably an epoxy compound that gives a cured product with a Tg of 25° C. or less, more preferably an epoxy compound that gives a cured product with a Tg of −5° C. or less, and even more preferably an epoxy compound that gives a cured product with a Tg of −20° C. or less. The conditions for forming such a cured product are not particularly limited, but a cured product for measurement can be obtained, for example, by the following method. (Preparation of measurement samples) To 100 parts by mass of epoxy compound (converted to solid content, the same applies throughout this measurement), 0.5 parts by mass of a thermal cationic polymerization initiator (manufactured by Sanshin Chemical Industry Co., Ltd., product name: SI-B3A) is added. The resulting mixture is poured into a 1 mm thick, 20 mm x 20 mm releasable mold and cured by heating at 100°C for 60 minutes to obtain a cured product (measurement sample). (Differential Scanning Calorimetry) Differential scanning calorimetry is performed using a differential scanning calorimeter according to the following method, and the glass transition temperature is then determined. Specifically, 5 mg of the sample is crushed, placed in an aluminum pan, sealed with a lid, and held at 120°C for 5 minutes before being cooled. Measurements are then performed from -100°C to +120°C at a heating rate of 10°C / min. The glass transition temperature (Tg) is determined as the temperature at the intersection of a straight line extending the low-temperature baseline of the obtained curve toward the high-temperature side and a tangent drawn at the point where the gradient of the curve in the stepwise change portion of the glass transition is at its maximum. An example of a releasable mold is a mold made of polytetrafluoroethylene, and an example of a differential scanning calorimeter is a product name: DSCQ2000 manufactured by TA Instruments.

[0021] Compounds having an oxetane group in the molecule include 3,7-bis(3-oxetanyl)-5-oxa-nonane, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, 1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane, 1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, triethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, tetraethylene glycol bis( and bifunctional oxetane compounds such as 3-ethyl-3-oxetanylmethyl ether, 1,4-bis(3-ethyl-3-oxetanylmethoxy)butane, and 1,6-bis(3-ethyl-3-oxetanylmethoxy)hexane; and monofunctional oxetane compounds such as 3-ethyl-3-[(phenoxy)methyl]oxetane, 3-ethyl-3-(hexyloxymethyl)oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(hydroxymethyl)oxetane, and 3-ethyl-3-(chloromethyl)oxetane.

[0022] The compound having a cyclic ether group can be used alone or in combination of two or more.

[0023] The weight average molecular weight (Mw) of the compound having a cyclic ether group is preferably 100 to 5,000, and more preferably 200 to 4,000. The weight-average molecular weight (Mw) of a compound having a cyclic ether group can be determined as a value converted into standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0024] The cyclic ether equivalent of the compound having a cyclic ether group is preferably 100 to 500 g / eq, more preferably 115 to 300 g / eq. When the cyclic ether equivalent of the compound having a cyclic ether group is within the above range, it becomes easier to obtain a film adhesive that forms a cured film with a smaller creep strain. The cyclic ether equivalent in the present invention means a value obtained by dividing the molecular weight by the number of cyclic ether groups.

[0025] The compound having a cyclic ether group is preferably liquid at 23°C. "Liquid at 23°C" means that the compound has fluidity at 23°C. The viscosity of the compound having a cyclic ether group is preferably 2 to 10,000 mPa·s. This viscosity is measured using an E-type viscometer at 23°C and 1.0 rpm. Film adhesives containing a compound having a cyclic ether group that is liquid at 23°C tend to have a low modulus of elasticity at room temperature. Such film adhesives have excellent adhesion at room temperature, so there is no need to heat the film adhesive to soften it during the application process.

[0026] The content of the compound having a cyclic ether group in the film-like adhesive of the present invention is preferably 20 to 75 mass %, more preferably 25 to 70 mass %, based on the total mass of the film-like adhesive. Film-like adhesives containing a compound having a cyclic ether group in an amount of 20% by mass or more relative to the total amount of the film-like adhesive tend to produce cured films with smaller creep strain amounts. Film-like adhesives containing a compound having a cyclic ether group in an amount of 75% by mass or less relative to the total amount of the film-like adhesive tend to have excellent shape retention in an uncured state.

[0027] [Binder resin] The film adhesive of the present invention may contain a binder resin. In the present invention, the term "binder resin" refers to a polymer component that improves the shape retention and flexibility of the film adhesive. If the compound having a cyclic ether group contained in the film adhesive is liquid at 23°C, the uncured film adhesive may not be able to maintain its shape under high temperature conditions, but a film adhesive containing a binder resin tends to maintain a certain shape even under high temperature conditions.

[0028] The glass transition temperature (Tg) of the binder resin is preferably 50° C. or higher, more preferably 60° C. or higher. There is no particular upper limit, but it is usually 200° C. or lower, preferably 130° C. or lower, and more preferably 100° C. or lower.

[0029] The glass transition temperature (Tg) of the binder resin can be measured in accordance with JIS K 7121 using a differential scanning calorimeter.

[0030] The weight average molecular weight (Mw) of the binder resin is preferably 10,000 to 300,000, and more preferably 30,000 to 200,000. The weight average molecular weight (Mw) of the binder resin can be determined as a value converted into standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0031] Examples of binder resins include polyolefin resins, polystyrene resins (for example, styrene-isoprene-styrene block copolymers, styrene-butadiene-styrene block copolymers), acrylic resins, polyester resins, polyvinyl alcohol resins, polyvinyl acetal resins, polyvinyl chloride resins, phenoxy resins, polyamide resins, cellulose resins, polyvinyl ether resins, and polyimide resins. The binder resins can be used alone or in combination of two or more.

[0032] Among these, phenoxy resin is preferred as the binder resin. Phenoxy resin is a polymer whose main chain is a polyaddition structure of aromatic diol and aromatic diglycidyl ether. Phenoxy resin generally corresponds to a high molecular weight epoxy resin, with a degree of polymerization of about 100 or more.

[0033] Some phenoxy resins have a high glass transition temperature (Tg), and film adhesives containing such phenoxy resins have excellent shape retention. The glass transition temperature (Tg) of the phenoxy resin is preferably 50° C. or higher, more preferably 60° C. or higher. There is no particular upper limit, but it is usually 200° C. or lower, preferably 130° C. or lower, more preferably 100° C. or lower.

[0034] The epoxy equivalent of the phenoxy resin is preferably 5,000 g / eq or more, more preferably 7,000 g / eq or more. The epoxy equivalent value can be measured in accordance with JIS K7236.

[0035] Examples of phenoxy resins include bisphenol A type phenoxy resins, bisphenol F type phenoxy resins, bisphenol S type phenoxy resins, bisphenol A and bisphenol F copolymer type phenoxy resins, bisphenol E type phenoxy resins, naphthalene type phenoxy resins, novolac type phenoxy resins, biphenyl type phenoxy resins, and cyclopentadiene type phenoxy resins. These phenoxy resins can be used alone or in combination of two or more.

[0036] Phenoxy resins can be obtained by reacting a bifunctional phenol with an epihalohydrin to a high molecular weight, or by subjecting a bifunctional epoxy resin to a polyaddition reaction with a bifunctional phenol. For example, phenoxy resins can be obtained by reacting a bifunctional phenol with an epihalohydrin in the presence of an alkali metal hydroxide in an inert solvent at a temperature of 40 to 120° C. Alternatively, phenoxy resins can be obtained by polyaddition reaction of a bifunctional epoxy resin with a bifunctional phenol in the presence of a catalyst such as an alkali metal compound, an organophosphorus compound, or a cyclic amine compound in an organic solvent having a boiling point of 120° C. or higher, such as an amide solvent, an ether solvent, a ketone solvent, a lactone solvent, or an alcohol solvent, at a temperature of 50 to 200° C.

[0037] The bifunctional phenol is not particularly limited as long as it is a compound having two phenolic hydroxyl groups. Examples thereof include monocyclic bifunctional phenols such as hydroquinone, 2-bromohydroquinone, resorcinol, and catechol; bisphenols such as bisphenol A, bisphenol F, bisphenol AD, and bisphenol S; dihydroxybiphenyls such as 4,4'-dihydroxybiphenyl; dihydroxyphenyl ethers such as bis(4-hydroxyphenyl)ether; compounds in which a linear alkyl group, a branched alkyl group, an aryl group, a methylol group, an allyl group, a cyclic aliphatic group, a halogen atom, a nitro group, or the like is introduced into the aromatic ring of these compounds; and compounds in which a linear alkyl group, a branched alkyl group, an allyl group, a cyclic aliphatic group, an alkoxycarbonyl group, or the like is introduced into the carbon atom at the center of the skeleton of the bisphenols.

[0038] Examples of epihalohydrin include epichlorohydrin, epibromohydrin, and epiiodohydrin.

[0039] In the present invention, commercially available phenoxy resins can also be used, such as YX7200 (glass transition temperature (Tg): 150°C) and YX6954 (phenoxy resin containing a bisphenolacetophenone skeleton, glass transition temperature (Tg): 130°C) manufactured by Mitsubishi Chemical Corporation, and YP70 (glass transition temperature (Tg): 70°C) manufactured by Nippon Steel Chemical & Material Co., Ltd.

[0040] When the film adhesive of the present invention contains a binder resin, the content thereof is preferably 25 to 80 mass %, more preferably 30 to 75 mass %, based on the total mass of the film adhesive. Film adhesives with a binder resin content of 25% by mass or more relative to the total film adhesive tend to have excellent shape retention in an uncured state. Film adhesives with a binder resin content of 80% by mass or less relative to the total film adhesive tend to produce cured films with smaller creep strains due to a higher content of compounds having cyclic ether groups.

[0041] [Photocationic Polymerization Initiator] The film-like adhesive of the present invention may contain a cationic photopolymerization initiator. A cationic photopolymerization initiator is a compound composed of a cationic moiety that absorbs active energy rays such as ultraviolet rays and an anionic moiety that serves as an acid generating source. The cationic photopolymerization initiator absorbs active energy rays and generates acid while decomposing. The generated acid initiates the curing reaction of the cationic curable compound. A film-like adhesive containing a photocationic polymerization initiator tends to undergo a curing reaction efficiently.

[0042] Examples of the photocationic polymerization initiator include sulfonium salt compounds, iodonium salt compounds, phosphonium salt compounds, ammonium salt compounds, diazonium salt compounds, selenium salt compounds, oxonium salt compounds, etc. Among these, sulfonium salt compounds are preferred because of their excellent compatibility with other components, and aromatic sulfonium salt compounds having an aromatic group are more preferred.

[0043] The sulfonium salt compounds include triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, 4,4'-bis[diphenylsulfonio]diphenylsulfide-bishexafluorophosphate, 4,4'-bis[di(β-hydroxyethoxy)phenylsulfonio]diphenylsulfide-bishexafluoroantimonate, 7-[di(p- 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluorophosphate, 7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthone hexafluoroantimonate, 7-[di(p-toluyl)sulfonio]-2-isopropyltetrakis(pentafluorophenyl)borate, phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide-hexafluorophosphate, phenylcarbonyl-4'-diphenylsulfonio-diphenyl bis(4-fluorophenyl)sulfonium hexafluoroantimonate, 4-tert-butylphenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide-hexafluorophosphate, 4-tert-butylphenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide-hexafluoroantimonate, 4-tert-butylphenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide-tetrakis(pentafluorophenyl)borate, 4-(phenylthio)phenyldiphenylsulfonium hexafluoroantimonate, 4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate, 4-{4-(2-chlorobenzoyl)phenylthio}phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate, thiophenyldiphenylsulfonium hexafluoroantimonate, 4,4',4''-tri(β-hydroxyethoxyphenyl)sulfonium hexafluoroantimonate, 4,Examples include 4'-bis[diphenylsulfonio]diphenylsulfide-bishexafluoroantimonate, diphenyl[4-(phenylthio)phenyl]sulfonium trifluorotrispentafluoroethylphosphate, tris[4-(4-acetylphenylsulfanyl)phenyl]sulfonium tris[(trifluoromethyl)sulfonyl]methanide, and salts in which the cation moiety is 4-(phenylthio)phenyldiphenylsulfonium and the anion moiety is a phosphorus-based anion to which fluorine and a perfluoroalkyl group are added.

[0044] Examples of iodonium salt compounds include diphenyliodonium tetrakis(pentafluorophenyl)borate, diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, di(4-nonylphenyl)iodonium hexafluorophosphate, and (tricumyl)iodonium tetrakis(pentafluorophenyl)borate.

[0045] Examples of the phosphonium salt compound include tri-n-butyl(2,5-dihydroxyphenyl)phosphonium bromide and hexadecyltributylphosphonium chloride.

[0046] Examples of the ammonium salt compounds include benzyltrimethylammonium chloride, phenyltributylammonium chloride, and benzyltrimethylammonium bromide.

[0047] The cationic photopolymerization initiators can be used alone or in combination of two or more.

[0048] When the film adhesive of the present invention contains a cationic photopolymerization initiator, the content thereof is preferably 0.01 to 1 mass %, more preferably 0.05 to 0.5 mass %, based on the total mass of the film adhesive.

[0049] [Crosslinking agent] The film adhesive of the present invention may contain a crosslinking agent. The crosslinking agent is a compound having two or more crosslinkable groups in the molecule that can react with functional groups in the components contained in the film-like adhesive of the present invention. Film-like adhesives containing a crosslinking agent tend to form cured films with smaller creep strains.

[0050] Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, and a metal chelate-based crosslinking agent.

[0051] The isocyanate-based crosslinking agent is a compound having an isocyanate group as a crosslinkable group. Examples of the isocyanate crosslinking agent include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate; alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate; and biuret, isocyanurate, or adduct forms of these compounds (reaction products of the isocyanate compounds with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil).

[0052] The epoxy-based crosslinking agent is a compound having an epoxy group as a crosslinkable group. Examples of epoxy crosslinking agents include 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, and diglycidylamine.

[0053] The aziridine crosslinking agent is a compound having an aziridine group as a crosslinkable group. Examples of the aziridine crosslinking agent include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinylpropionate, toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine), tris-1-(2-methylaziridine)phosphine, and trimethylolpropane tri-β-(2-methylaziridine)propionate.

[0054] Examples of metal chelate crosslinking agents include chelate compounds in which the metal atom is aluminum, zirconium, titanium, zinc, iron, tin, etc. Among these, aluminum chelate compounds are preferred. Examples of aluminum chelate compounds include diisopropoxyaluminum monooleyl acetoacetate, monoisopropoxyaluminum bisoleyl acetoacetate, monoisopropoxyaluminum monooleate monoethyl acetoacetate, diisopropoxyaluminum monolauryl acetoacetate, diisopropoxyaluminum monostearyl acetoacetate, and diisopropoxyaluminum monoisostearyl acetoacetate.

[0055] The crosslinking agent can be used alone or in combination of two or more.

[0056] When the film-like adhesive of the present invention contains a crosslinking agent, the content thereof is preferably an amount such that the crosslinkable group of the crosslinking agent (in the case of a metal chelate-based crosslinking agent, the metal chelate-based crosslinking agent) is 0.1 to 5 equivalents relative to the functional group in the compound contained in the film-like adhesive, and more preferably an amount such that 0.2 to 3 equivalents.

[0057] [Crosslinking catalyst] The film adhesive of the present invention may contain a crosslinking catalyst. The crosslinking catalyst is a catalyst for the crosslinking reaction of the crosslinking agent. Film adhesives containing a crosslinking catalyst tend to result in cured films with smaller creep strains.

[0058] For example, crosslinking catalysts for the crosslinking reaction of isocyanate-based crosslinking agents include iron chelate compounds such as iron tris(acetylacetonato) and iron tris(hexane-2,4-dionato); aluminum chelate compounds such as aluminum tris(acetylacetonato) and aluminum tris(hexane-2,4-dionato); titanium chelate compounds such as titanium tris(acetylacetonato) and titanium tris(hexane-2,4-dionato); zirconium chelate compounds such as zirconium tetrakis(acetylacetonato) and zirconium tetrakis(hexane-2,4-dionato); and the like.

[0059] The crosslinking catalysts can be used alone or in combination of two or more.

[0060] When the film adhesive of the present invention contains a crosslinking catalyst, the content thereof is usually preferably 3 to 30 parts by mass, more preferably 5 to 20 parts by mass, per 100 parts by mass of the crosslinking agent.

[0061] [Other ingredients] The film adhesive of the present invention may contain other components as long as the effects of the present invention are not impaired. Other components include additives such as silane coupling agents, ultraviolet absorbers, antistatic agents, light stabilizers, antioxidants, resin stabilizers, fillers, pigments, extenders, and softeners. These may be used alone or in combination of two or more. When the film adhesive of the present invention contains these additives, the content thereof can be appropriately determined depending on the purpose.

[0062] [Film adhesive] The thickness of the film-like adhesive of the present invention is usually 1 to 50 μm, preferably 1 to 40 μm, and more preferably 2 to 30 μm. The thickness of the film-like adhesive can be measured using a known thickness meter in accordance with JIS K 7130 (1999). In addition, when the film-like adhesive has a release film as described below, the thickness of the film-like adhesive does not include the thickness of the release film.

[0063] From the viewpoint of protection from the external environment, the film-like adhesive of the present invention preferably has a release film on at least one surface, but the film-like adhesive of the present invention may also have release films on both surfaces.

[0064] It should be noted that the film-like adhesive of the present invention having a release film represents the state before use, and when using the film-like adhesive of the present invention, the release film is usually peeled off and removed. When the film-like adhesive has release films on both sides, the release film with a small release strength (light release type release film) is usually peeled off and removed first, followed by the release film with a large release strength (heavy release type release film).

[0065] As the release film, a resin film can usually be used. Examples of the resin component of the resin film include polyimide, polyamide, polyamideimide, polyphenylene ether, polyether ketone, polyether ether ketone, polyolefin, polyester, polycarbonate, polysulfone, polyether sulfone, polyphenylene sulfide, polyarylate, acrylic resin, cycloolefin polymer, aromatic polymer, polyurethane polymer, etc. Among these, polyester resin is preferred.

[0066] When the release film has a release agent layer, examples of the release agent include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins, long-chain alkyl resins, alkyd resins, and fluorine-based resins.

[0067] The thickness of the release film is usually 10 to 300 μm, preferably 10 to 200 μm, and more preferably 15 to 100 μm.

[0068] The method for producing the film adhesive of the present invention is not particularly limited, and it can be produced, for example, by a casting method.

[0069] The method for producing a film-like adhesive by the casting method involves applying the adhesive composition, which is the raw material, to a release film using a known method, and drying the resulting coating to obtain a film-like adhesive with a release film.

[0070] The adhesive composition contains the compound having a cyclic ether group and, if necessary, other components. The adhesive composition may further contain a solvent. Examples of the solvent include aromatic hydrocarbon solvents such as benzene and toluene; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as n-pentane, n-hexane and n-heptane; and alicyclic hydrocarbon solvents such as cyclopentane, cyclohexane and methylcyclohexane. These solvents can be used alone or in combination of two or more. When the adhesive composition contains a solvent, the content of the solvent can be appropriately determined taking into consideration the coatability and the like. The adhesive composition can be prepared by appropriately mixing and stirring the components according to a conventional method.

[0071] The release film used in the production of the film adhesive functions as a support during the production process of the film adhesive, and also functions as a release film for the film adhesive described above until the film adhesive is used.

[0072] Examples of methods for applying the adhesive composition include spin coating, spray coating, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0073] Methods for drying the coating of the adhesive composition include conventionally known drying methods such as hot air drying, hot roll drying, and infrared irradiation. The conditions for drying the coating film are, for example, 80 to 150°C for 30 seconds to 5 minutes.

[0074] The film-like adhesive of the present invention is curable with active energy rays, such as ultraviolet rays, electron beams, laser beams such as semiconductor lasers, argon lasers, and He—Cd lasers, and ionizing radiation such as α-rays, β-rays, γ-rays, neutron beams, X-rays, and accelerated electron beams. Among these, ultraviolet light and electron beams are preferred as active energy rays, with ultraviolet light being more preferred, since they can be generated using a relatively simple device.

[0075] Examples of ultraviolet light sources include ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arc lamps, black light fluorescent lamps, metal halide lamps, etc. The wavelength of the ultraviolet light to be irradiated may be in the range of 190 to 380 nm. The type of ultraviolet light, the amount of irradiation, the irradiation time, etc. can be appropriately determined depending on the constituent components of the film-like adhesive to be irradiated and the content of each constituent component. The irradiation intensity is 20 to 1,000 mW / cm 2 , light intensity 50~3,000mJ / cm 2 The degree is preferable.

[0076] The film-like adhesive of the present invention becomes a cured film having a creep strain of 5% or less after curing. The creep strain of the cured film is preferably 3% or less, and more preferably 1% or less. The creep strain can be measured using a viscoelasticity measuring device. Specifically, a measurement sample is prepared by the method described in the Examples, and the creep strain can be measured using the measurement sample. A cured film with a creep strain of 5% or less is a film that is difficult to deform. Therefore, in an optical laminate having a structure of optical hard member / cured film with a creep strain of 5% or less / optical resin film, the optical resin film is fixed by a cured film with a creep strain of 5% or less, so expansion and contraction of the optical resin film is suppressed even when the ambient temperature changes. In this way, by using the film-like adhesive of the present invention, an optical laminate with excellent dimensional stability can be obtained.

[0077] The film adhesive of the present invention preferably becomes a cured film having a gel fraction of 80% or more after curing, and more preferably becomes a cured film having a gel fraction of 85% or more. The gel fraction can be measured by preparing a measurement sample by the method described in the Examples and using the measurement sample. In cured films with a gel fraction of 80% or more, the curing reaction has progressed sufficiently to form a crosslinked structure. Therefore, cured films with a gel fraction of 80% or more tend to have creep strains of 5% or less.

[0078] The total light transmittance of the cured film of the film-like adhesive of the present invention is preferably 90% or more, and more preferably 95% or more. The total light transmittance of the cured film of the film-like adhesive can be measured in accordance with JIS K7361-1:1997.

[0079] The film-like adhesive of the present invention preferably has an adhesive strength of 20 N / 25 mm or more when laminated on a 50 μm-thick polyethylene terephthalate film and the surface opposite to the surface facing the polyethylene terephthalate film is attached to glass. Having an adhesive strength of 20 N / 25 mm or more can prevent peeling of the film-like adhesive from the hard support due to shrinkage of the resin film in an optical laminate in which an optical hard member and an optical resin film are bonded with the film-like adhesive of the present invention. The adhesive strength is more preferably 25 N / 25 mm or more, and even more preferably 30 N / 25 mm or more. Such adhesive strength is measured by the method described in the Examples below. The upper limit of the adhesive strength is, for example, about 70 N / 25 mm or less, preferably 60 mN / 25 mm or less.

[0080] The film-like adhesive of the present invention is used when bonding an optical hard member and an optical resin film. In optical laminates obtained by bonding an optical hard member and an optical resin film using a conventional adhesive, there was a risk that the optical path of light passing through the laminate would fluctuate if the resin film expanded or contracted due to changes in the ambient temperature. On the other hand, when the film-like adhesive of the present invention is used, an optical laminate having excellent dimensional stability can be obtained as described above, and therefore the optical path of light passing through the laminate is less likely to fluctuate.

[0081] Examples of optical hard members include glass plates. Glass plates have low visible light reflection and absorption, are chemically stable, and have excellent gas barrier properties, making them suitable as members of optical laminates. Examples of such glass plates include glass plates for liquid crystal displays, such as glass for supporting transparent electrodes or cover glass.

[0082] As the resin film for optical use, a polyester resin film is preferred because of its excellent transparency and smoothness. Among the polyester resin films, a polyester resin film obtained by polycondensation of an aliphatic diol and a divalent aromatic carboxylic acid is preferred. Specific examples of polyester resins include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate, with polyethylene terephthalate or polyethylene naphthalate being preferred. Polyester resin films are generally manufactured through a biaxial stretching process, so they are prone to thermal deformation, expanding at high temperatures and then shrinking more than their initial state when they return to room temperature. This tendency is particularly pronounced in polyester resin films with a high Young's modulus. In optical laminates, it is necessary to suppress thermal deformation of such polyester resin films in order to maintain a constant optical path, and the film-like adhesive of the present invention is suitably used as an adhesive when producing optical laminates.

[0083] 2) Method for producing optical laminate The method for producing an optical laminate of the present invention includes the steps of: (1) bonding an optical hard member and an optical resin film together using an active energy ray-curable film adhesive containing a compound having a cyclic ether group, the film adhesive forming a cured film having a creep strain of 5% or less after curing, the creep strain being the amount of strain when a shear stress of 1 kPa is applied at 50°C for 300 seconds; Step 2, after step 1, of irradiating the film-like adhesive with active energy rays to cure the film-like adhesive; It has.

[0084] Step 1 is a step of bonding an optical hard member and an optical resin film together using the film adhesive of the present invention. Examples of the optical hard member and the optical resin film include those described above.

[0085] The optical hard member and the optical resin film can be bonded together, for example, by stacking the optical hard member, the film-like adhesive of the present invention, and the optical resin film in this order and then pressing them together.

[0086] Step 2 is a step following step 1 in which the film-like adhesive is irradiated with active energy rays to cure the film-like adhesive. The irradiation of active energy rays may be performed from the optical hard member side or the optical resin film side, and in this case, it is preferable to perform the irradiation of active energy rays from the side of the optical hard member or the optical resin film, whichever is less likely to diffuse or block the active energy rays.

[0087] Examples of active energy rays include ultraviolet rays; electron beams; laser light such as semiconductor lasers, argon lasers, and He—Cd lasers; and ionizing radiation such as α rays, β rays, γ rays, neutron rays, X-rays, and accelerated electron beams. Among these, ultraviolet light and electron beams are preferred as active energy rays, with ultraviolet light being more preferred, since they can be generated using a relatively simple device. The ultraviolet light source and ultraviolet light irradiation conditions can be the same as those explained in the film adhesive invention.

[0088] The optical laminate of the present invention is one in which a hard member and a resin film are laminated together with an adhesive, and even when the temperature changes, the expansion and contraction of the optical resin film is suppressed, thereby maintaining a constant optical path. Therefore, the optical laminate of the present invention is suitable for use in displays that have a large area and require high resolution of the object viewed through the optical laminate. Furthermore, among displays, the optical laminate is preferably used as an optical laminate in which a glass plate or the like used in a liquid crystal display is used as the hard member. That is, the optical laminate of the present invention is preferably a laminate for a display, and more preferably a laminate for a liquid crystal display. A liquid crystal display including the optical laminate of the present invention has excellent dimensional stability of the optical laminate, so that the optical path of light passing through the laminate is less likely to fluctuate, resulting in excellent image visibility. [Example]

[0089] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0090] [Compounds used in the Examples and Comparative Examples] Epoxy resin (A): Epoxy resin containing oxyalkylene groups (liquid at 23°C) [Mitsubishi Chemical Corporation, product name: YX7400, epoxy equivalent: 440 g / eq] UV-curable resin: ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: A-9300-1CL, trifunctional UV-curable compound) Binder resin (B): Phenoxy resin (manufactured by Nippon Steel Chemical & Material Co., Ltd., product name: YP70, glass transition temperature (Tg): 70°C, Mw: 55,000) Acrylic resin (1): Acrylic resin synthesized in Manufacturing Example 1 Acrylic resin (2): Acrylic resin synthesized in Production Example 2 Photocationic polymerization initiator (C): 4-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate (manufactured by San-Apro Co., Ltd., product name: CPI-100P) Radical polymerization initiator: A mixture of benzophenone and 1-hydroxycyclohexyl phenyl ketone in a 1:1 mass ratio (manufactured by IGM Resins, trade name: Omnirad 500) Crosslinking agent (D): Isocyanurate-modified hexamethylene diisocyanate (HDI) [manufactured by Tosoh Corporation, product name: Coronate HX] Crosslinking catalyst (E): Zirconium (Zr) chelate compound [Kusumoto Chemicals Co., Ltd., product name: K-KAT-4205]

[0091] The parts by mass of each component in the following Production Examples, Examples, and Comparative Examples are calculated as active ingredients excluding solvents.

[0092] [Production Example 1] An acrylic resin (1) having a weight average molecular weight (Mw) of 500,000 was synthesized by copolymerizing 60 parts by mass of 2-ethylhexyl acrylate, 1 part by mass of 4-acryloylmorpholine, 20 parts by mass of isobornyl acrylate, and 19 parts by mass of 2-hydroxyethyl acrylate by solution polymerization.

[0093] [Production Example 2] An acrylic resin (2) having a weight average molecular weight (Mw) of 800,000 was synthesized by copolymerizing 25 parts by mass of 2-ethylhexyl acrylate, 25 parts by mass of butyl acrylate, 5 parts by mass of 4-acryloylmorpholine, 10 parts by mass of isobornyl acrylate, and 35 parts by mass of 2-hydroxyethyl acrylate by a solution polymerization method.

[0094] Example 1 Adhesive composition (1) was prepared by adding methyl ethyl ketone to 60 parts by mass of epoxy resin (A), 100 parts by mass of binder resin (B), 0.2 parts by mass of photocationic polymerization initiator (C), 2.0 parts by mass of crosslinking agent (D), and 0.2 parts by mass of crosslinking catalyst (E) so that the concentration of the active ingredients was 50% by mass. Note that the number of parts blended is the amount converted into solid content (non-volatile components), and the same applies hereinafter. This adhesive composition (1) was applied to the release-treated surface of a release film (manufactured by Lintec Corporation, product name: SP-PET752150, equivalent to a heavy-release type release film), and the resulting coating was dried at 100°C for 2 minutes to form a film-like adhesive 25 µm thick. The release-treated surface of another release film (manufactured by Lintec Corporation, product name: SP-PET381031, equivalent to a light-release type release film) was attached to the film-like adhesive to produce a film-like adhesive (1) with a release film.

[0095] [Examples 2 and 3] Film-like adhesives (2) and (3) with release films were prepared in the same manner as in Example 1, except that the types and amounts of the components were changed to those shown in Table 1.

[0096] Comparative Example 1 7.0 parts by mass of an ultraviolet-curable resin, 100 parts by mass of the acrylic resin (1) obtained in Production Example 1, 0.7 parts by mass of a radical polymerization initiator, and 0.2 parts by mass of a crosslinking agent (D) were mixed, thoroughly stirred, and diluted with methyl ethyl ketone to prepare an adhesive composition (4).

[0097] The adhesive composition (4) was applied to the release-treated surface of a release film (manufactured by Lintec Corporation, trade name: SP-PET752150, equivalent to a heavy-release release film), and the resulting coating was dried at 90°C for 2 minutes to form a coating layer 25 μm thick. The release-treated surface of another release film (manufactured by Lintec Corporation, trade name: SP-PET381031, equivalent to a light-release release film) was laminated onto this coating layer, and the resulting film was aged at 23°C and a relative humidity (RH) of 50% for 7 days to produce a film-like adhesive (4) with a release film.

[0098] Comparative Example 2 A film-like adhesive (5) with a release film was prepared in the same manner as in Comparative Example 1, except that the types and amounts of the components were changed to those shown in Table 1.

[0099] The following measurements were carried out on the film-like adhesives (1) to (5) with release films obtained in Examples 1 to 3 and Comparative Examples 1 and 2. The results are shown in Table 1.

[0100] [Gel fraction measurement] The film-like adhesives with release films obtained in the Examples and Comparative Examples were irradiated with ultraviolet (UV) rays through the release film under the following conditions to cure the film-like adhesives. <Ultraviolet irradiation conditions> -High pressure mercury lamp used ·Illuminance 200mW / cm 2 , light intensity 1,000mJ / cm 2 The UV illuminance and light intensity meter used is the "UVPF-A1" manufactured by Eye Graphics.

[0101] After the curing treatment, the film-like adhesive with release film was cut to a size of 80 mm x 80 mm, and the film-like adhesive (with the release film removed) was wrapped in a polyester mesh (mesh size 200) and its mass was weighed on a precision balance. The mass of the film-like adhesive alone, calculated by subtracting the mass of the mesh alone, was designated M1. Next, the film adhesive wrapped in the mesh was immersed in ethyl acetate at room temperature (23°C) for 72 hours. Thereafter, the film adhesive wrapped in the mesh was removed and air-dried for 24 hours in an environment of 23°C and 50% relative humidity, and then dried in an oven at 80°C for 12 hours. After drying, its mass was weighed using a precision balance. The mass of the film adhesive alone, calculated by subtracting the mass of the mesh alone, was designated M2. Using the obtained M1 and M2, the gel fraction (%) was calculated by (M2 / M1)×100.

[0102] [Creep strain measurement] The creep strain was measured by a torsional shear method using a viscoelasticity measuring device (manufactured by Anton Paar, product name: MCR302). The details of the measurement method are shown below. (Preparation of measurement samples) After peeling off the release film from the film-like adhesive with release film obtained in the Examples and Comparative Examples, the film-like adhesive was stacked to obtain a film-like adhesive laminate with a thickness of 0.5 mm. The obtained film-like adhesive laminate was irradiated with UV light to cure the film-like adhesive laminate. After UV irradiation, the laminate was left to stand at 23°C for 24 hours to obtain a cured film-like adhesive laminate. The UV irradiation conditions were the same as those for measuring the gel fraction. The cured laminate of the film-like adhesive was punched out into a cylindrical body with a diameter of 8 mm (height of 0.5 mm) and used as a measurement sample. (Creep strain measurement) Using the obtained measurement sample, a shear stress of 1 kPa was continuously applied under the condition of no vibration and a constant temperature of 50°C, and the amount of strain (amount of creep strain) was measured 300 seconds after the start of the measurement.

[0103] (Total light transmittance measurement) The light release film was peeled off from the film-like adhesive with release film obtained in the Examples and Comparative Examples, and the exposed film-like adhesive was stuck to glass. Next, after peeling off the heavy release film, the film-like adhesive was irradiated with UV light to harden the film-like adhesive and obtain a measurement sample. The UV irradiation conditions were the same as those for measuring the gel fraction. After background measurement was performed using glass, the total light transmittance was measured using the obtained measurement sample in accordance with JIS K7361-1:1997.

[0104] (Adhesion measurement) To compare the adhesive strength of film-like adhesives containing epoxy compounds, measurements were only performed for Examples 1 to 3. The light release release sheet was peeled off from the film-like adhesive with release film obtained in the Examples, and the exposed film-like adhesive was attached to the easy-adhesion layer of a polyethylene terephthalate (PET) film (manufactured by Toyobo Co., Ltd., product name "PET50 A4360", thickness: 50 μm) having an easy-adhesion layer, to obtain a heavy release release sheet / film-like adhesive / PET film laminate. The resulting laminate was cut to a width of 25 mm and a length of 100 mm.

[0105] The heavy-release release sheet was peeled from the laminate in an environment of 23°C and 50% RH, and the exposed film-like adhesive was attached to soda-lime glass (manufactured by Nippon Sheet Glass Co., Ltd.). The film-like adhesive was then irradiated with UV light to cure. The adhesive strength (initial adhesive strength (P1); N / 25 mm) was measured using a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon") at a peel rate of 300 mm / min and a peel angle of 180°. Measurements were conducted under conditions other than those described here in accordance with JIS Z0237:2009. The load applied to the film-like adhesive when attaching it to soda-lime glass was also in accordance with JIS Z0237:2009, and the UV irradiation conditions were the same as those for measuring the gel fraction.

[0106] [Table 1]

[0107] The following can be seen from Table 1: The cured films of the film-like adhesives (1) to (3) with release film of Examples 1 to 3 all had high gel fractions, small creep strains, and high total light transmittances, making these film-like adhesives suitable for use as adhesive layers in optical laminates. On the other hand, the cured films of the film-like adhesives with release film (4) and (5) of Comparative Examples 1 and 2 had high total light transmittance but low gel fraction and large creep strain, making it difficult to sufficiently suppress the expansion and contraction of optical resin films due to temperature changes.

Claims

1. An active energy ray-curable film-like adhesive containing a compound having a cyclic ether group, the film-like adhesive, after curing, forms a cured film having a creep strain of 5% or less, which is the strain amount when a shear stress of 1 kPa is applied at 50°C for 300 seconds; A film-like adhesive used to bond optical hard materials and optical resin films.

2. 2. The film-like adhesive according to claim 1, which becomes a cured film having a gel fraction of 80% or more after curing.

3. The film-like adhesive according to claim 1 , wherein the optical hard member is a glass plate.

4. The film-like adhesive according to claim 1 , wherein the optical resin film is a polyester resin film.

5. a step 1 of bonding an optical hard member and an optical resin film together using an active energy ray-curable film-like adhesive containing a compound having a cyclic ether group, the film-like adhesive being capable of forming a cured film having a creep strain of 5% or less when a shear stress of 1 kPa is applied at 50°C for 300 seconds; Step 2, after step 1, of irradiating the film-like adhesive with active energy rays to cure the film-like adhesive; The method for producing an optical laminate comprising the steps of:

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