Adhesive composition, adhesive sheet, optical laminate and image display device

Abstract

Provided is an adhesive composition which contains a sufficient amount of an isocyanate-based crosslinking agent and which is suitable for producing an adhesive sheet having improved reworkability. This adhesive composition contains: a (meth) acrylic polymer (A); an isocyanate crosslinking agent in an amount of 2 parts by weight or more per 100 parts by weight of the (meth) acrylic polymer (A); a polyhydroxyalkylamine compound; and a polyether compound.

Description

Technical Field

[0001] The present invention relates to an adhesive composition, an adhesive sheet, an optical laminate, and an image display device. Background Art

[0002] In recent years, image display devices typified by liquid crystal display devices and electroluminescent (EL) display devices (for example, organic EL display devices, inorganic EL display devices) have been rapidly spreading. The above-described various image display devices generally have a laminated structure of an image forming layer such as a liquid crystal layer and an EL light emitting layer and an optical laminate, and the optical laminate includes an optical film and an adhesive sheet. The adhesive sheet is mainly used for bonding between films contained in the optical laminate and for bonding between the image forming layer and the optical laminate. Examples of the optical film include a polarizing film, a retardation film, and a polarizing film with a retardation film in which a polarizing film and a retardation film are integrated.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-096734 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] Excessive change in the size of the optical film with temperature change causes light leakage and color unevenness in the image display device. In particular, image display devices with a narrow bezel design (narrow bezeled) are becoming popular, and suppression of size change is becoming increasingly important. In order to suppress the change in size, increasing the elastic modulus of the adhesive sheet contained in the optical laminate has been considered. As a method of increasing the elastic modulus of the adhesive sheet, a method of increasing the blending amount of a crosslinking agent in the adhesive composition used for producing the adhesive sheet can be cited. For example, Patent Document 1 discloses an adhesive composition using a sufficient amount of an isocyanate-based crosslinking agent.

[0008] However, according to the research of the present inventors, when producing an adhesive sheet using an adhesive composition containing a sufficient amount of an isocyanate-based crosslinking agent, if an optical laminate is adhered to an adherend such as an image forming layer via the adhesive sheet, there is a tendency that the adhesive force between the optical laminate and the adherend increases excessively over time. In particular, the adhesive force between the optical laminate and the adherend is likely to increase excessively in a high-temperature environment. If the adhesive force between the optical laminate and the adherend increases excessively, it becomes difficult to peel the optical laminate from the adherend, and its reworkability decreases. In particular, in the case of an optical laminate where the film adjacent to the adhesive sheet (e.g., a retardation film) is thin, when attempting to peel the optical laminate from the adherend, stress concentrates near the film, and interlayer peeling is likely to occur within the optical laminate. If interlayer peeling occurs within the optical laminate, a part of the optical laminate remains on the adherend.

[0009] Therefore, an object of the present invention is to provide an adhesive composition containing a sufficient amount of an isocyanate-based crosslinking agent and suitable for producing an adhesive sheet with improved reworkability.

[0010] Means for Solving the Problem

[0011] The present inventors conducted in-depth research and as a result, newly found that by combining a polyhydroxyalkylamine compound with a polyether compound, the reworkability of the adhesive sheet is improved, thereby completing the present invention.

[0012] The present invention provides an adhesive composition comprising:

[0013] (meth)acrylic polymer (A),

[0014] an isocyanate-based crosslinking agent in an amount of 2 parts by weight or more relative to 100 parts by weight of the above-mentioned (meth)acrylic polymer (A),

[0015] a polyhydroxyalkylamine compound, and

[0016] a polyether compound.

[0017] Furthermore, the present invention provides an adhesive sheet formed from the above-mentioned adhesive composition.

[0018] Furthermore, the present invention provides an optical laminate comprising the above-mentioned adhesive sheet and an optical film.

[0019] Furthermore, the present invention provides an image display device including the above-mentioned optical laminate.

[0020] Effects of the Invention

[0021] According to the present invention, an adhesive composition can be provided which contains a sufficient amount of an isocyanate crosslinking agent and is suitable for producing an adhesive sheet with improved reworkability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a cross-sectional view schematically showing an example of the adhesive sheet of the present invention.

[0023] Figure 2 It is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0024] Figure 3 It is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0025] Figure 4 It is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0026] Figure 5 It is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0027] Figure 6 It is a cross-sectional view schematically showing an example of the optical laminate of the present invention.

[0028] Figure 7 It is a cross-sectional view schematically showing an example of the image display device of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] The adhesive composition of the first aspect of the present invention contains:

[0030] (Meth)acrylic polymer (A),

[0031] an isocyanate crosslinking agent in an amount of 2 parts by weight or more relative to 100 parts by weight of the above (meth)acrylic polymer (A),

[0032] a polyhydroxyalkylamine compound, and

[0033] a polyether compound.

[0034] In the second aspect of the present invention, for example, in the adhesive composition of the first aspect, the above polyether compound further has a silicon atom and a hydroxyl group and / or a hydrolyzable group bonded to the silicon atom.

[0035] In the third aspect of the present invention, for example, in the adhesive composition of the first or second aspect, the amount of the above polyether compound is 0.1 to 5 parts by weight relative to 100 parts by weight of the above (meth)acrylic polymer (A).

[0036] In the fourth aspect of the present invention, for example, in the adhesive composition of any one of the first to third aspects, the molecular weight of the above polyhydroxyalkylamine compound is 1500 or less.

[0037] In the fifth aspect of the present invention, for example, in the adhesive composition of any one of the first to fourth aspects, with respect to 100 parts by weight of the above (meth)acrylic polymer (A), the blending amount of the above polyhydroxyalkylamine compound is 0.01 to 5 parts by weight.

[0038] In the sixth aspect of the present invention, for example, in the adhesive composition of any one of the first to fifth aspects, with respect to 100 parts by weight of the above (meth)acrylic polymer (A), the blending amount of the above isocyanate crosslinking agent is 13 parts by weight or less.

[0039] In the seventh aspect of the present invention, for example, in the adhesive composition of any one of the first to sixth aspects, the above (meth)acrylic polymer (A) has a structural unit derived from a carboxyl group-containing monomer.

[0040] In the eighth aspect of the present invention, for example, in the adhesive composition of the seventh aspect, in the above (meth)acrylic polymer (A), the content rate of the above structural unit derived from the carboxyl group-containing monomer is 3% by weight or more.

[0041] In the ninth aspect of the present invention, for example, in the adhesive composition of any one of the first to eighth aspects, the above (meth)acrylic polymer (A) has a structural unit derived from an aromatic ring-containing monomer.

[0042] In the tenth aspect of the present invention, for example, in the adhesive composition of any one of the first to ninth aspects, the weight average molecular weight of the above (meth)acrylic polymer (A) is 1,000,000 or more.

[0043] In the eleventh aspect of the present invention, for example, in the adhesive composition of any one of the first to tenth aspects, the above isocyanate crosslinking agent is a toluene diisocyanate crosslinking agent.

[0044] In the twelfth aspect of the present invention, for example, the adhesive composition of any one of the first to eleventh aspects further contains a silane coupling agent.

[0045] The adhesive sheet of the thirteenth aspect of the present invention is formed from the adhesive composition of any one of the first to twelfth aspects.

[0046] The optical laminate of the fourteenth aspect of the present invention has the adhesive sheet of the thirteenth aspect and an optical film.

[0047] In the 15th aspect of the present invention, for example, the optical laminate of the 14th aspect has a polarizing film, a first retardation film, and a second retardation film as the above-mentioned optical films.

[0048] In the 16th aspect of the present invention, for example, in the optical laminate of the 15th aspect, the adhesive sheet is in contact with the second retardation film, and the thickness of the second retardation film is 5 μm or less.

[0049] The image display device of the 17th aspect of the present invention includes the optical laminate of any one of the 14th to 16th aspects.

[0050] Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be arbitrarily modified and implemented within the scope not departing from the gist of the present invention.

[0051] (Embodiments of the adhesive composition)

[0052] The adhesive composition of the present embodiment contains: (meth)acrylic polymer (A), an isocyanate crosslinking agent in an amount of 2 parts by weight or more based on 100 parts by weight of the (meth)acrylic polymer (A), a polyhydroxyalkylamine compound, and a polyether compound. An adhesive sheet can be made from the adhesive composition.

[0053] [(Meth)acrylic polymer (A)]

[0054] (Meth)acrylic polymer (A) can function as a base polymer of an acrylic adhesive. Acrylic adhesives tend to have excellent optical transparency, appropriate wetting properties, cohesive properties, adhesive properties, etc., and excellent weather resistance, heat resistance, etc. (Meth)acrylic polymer (A) contains, for example, a structural unit derived from an alkyl (meth)acrylate as a main component. In the present specification, “(meth)acrylate” means acrylate and / or methacrylate. “Main component” means the structural unit that is contained in the largest amount by weight among all the structural units constituting the polymer.

[0055] The number of carbon atoms of the alkyl group contained in the (meth)acrylic acid alkyl ester that forms the main skeleton of the (meth)acrylic polymer (A) is not particularly limited, and is, for example, 1 to 30. The alkyl group may be linear, branched, or cyclic. Examples of the alkyl group include, for example: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, decyl, isodecyl, dodecyl, isomyristyl, lauryl, tridecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, etc. The (meth)acrylic acid alkyl ester may be used alone or in combination, and the average number of carbon atoms of the alkyl group is preferably 3 to 9. The (meth)acrylic acid alkyl ester is preferably butyl acrylate.

[0056] From the viewpoint of improving the adhesiveness of the adhesive sheet, in the (meth)acrylic polymer (A), the content of the structural unit derived from the (meth)acrylic acid alkyl ester is, for example, 50% by weight or more, preferably 60% by weight or more, more preferably 70% by weight or more, and further preferably 80% by weight or more.

[0057] As the monomer constituting the (meth)acrylic polymer (A), in addition to the (meth)acrylic acid alkyl ester, at least one comonomer selected from an aromatic ring-containing monomer, an amide group-containing monomer, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer can be cited. The comonomer may be used alone or in combination.

[0058] (Meth)acrylic polymer (A) preferably contains a structural unit derived from a carboxyl group-containing monomer. The carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and contains a polymerizable unsaturated double bond such as (meth)acryloyl or vinyl. Examples of the carboxyl group-containing monomer include, for example: (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, etc. Among these, from the viewpoints of copolymerizability, price, and improving the adhesive properties of the adhesive sheet, acrylic acid is preferred.

[0059] By making the (meth)acrylic polymer (A) have structural units derived from carboxyl group-containing monomers, especially acrylic acid, for example, the self-polymerization property of the isocyanate crosslinking agent can be improved. Specifically, the (meth)acrylic polymer (A) containing structural units derived from carboxyl group-containing monomers has a tendency to promote the reaction between isocyanate crosslinking agents by introducing water molecules in the surrounding atmosphere. The improvement of the self-polymerization property of the isocyanate crosslinking agent is particularly helpful for suppressing the peeling of the adhesive sheet in a humid environment and for stabilizing the physical properties of the adhesive sheet in a system with a high content of the isocyanate crosslinking agent. In addition, in the (meth)acrylic polymer (A) having structural units derived from carboxyl group-containing monomers, the crosslinking reaction with the crosslinking agent tends to proceed rapidly through curing. This (meth)acrylic polymer (A) is suitable for improving the reworkability of the adhesive sheet.

[0060] (Meth)acrylic polymer (A) preferably contains structural units derived from aromatic ring-containing monomers. An aromatic ring-containing monomer is a compound having an aromatic ring structure in its structure and containing polymerizable unsaturated double bonds such as (meth)acryloyl group and vinyl group. As the aromatic ring, for example, a benzene ring, a naphthalene ring, a biphenyl ring, etc. can be cited. The aromatic ring-containing monomer is preferably an aromatic ring-containing (meth)acrylate.

[0061] As the aromatic ring-containing (meth)acrylate, for example, benzyl (meth)acrylate, phenyl (meth)acrylate, o-phenylphenol (meth)acrylate, phenoxymethyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, ethylene oxide-modified cresol (meth)acrylate, phenol ethylene oxide-modified (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, methoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, tolyl (meth)acrylate, styryl (meth)acrylate, etc. (meth)acrylates having a benzene ring; hydroxyethylated β-naphthol acrylate, 2-naphthyl ethyl (meth)acrylate, 2-naphthoxyethyl acrylate, 2-(4-methoxy-1-naphthyloxy)ethyl (meth)acrylate, etc. (meth)acrylates having a naphthalene ring; biphenyl (meth)acrylate, etc. aromatic ring-containing (meth)acrylates having a biphenyl ring. Among these, from the viewpoint of improving the adhesive properties and durability of the adhesive sheet, benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are preferred, and benzyl acrylate is more preferred.

[0062] The aromatic ring-containing monomer will improve the compatibility of the (meth)acrylic polymer (A) with the polymer (B) having structural units derived from the isocyanate crosslinking agent described later as the main component, and thus is suitable for maintaining the transparency of the adhesive sheet. In addition, the aromatic ring-containing monomer is also suitable for adjusting the reworkability and adhesiveness of the adhesive sheet.

[0063] (Meth)acrylic polymer (A) may contain structural units derived from amide group-containing monomers. The amide group-containing monomers are compounds containing an amide group in their structure and having a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the amide group-containing monomers include: acrylamide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethyl-N-propyl(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, and mercaptoethyl(meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; lactam monomers containing an N-vinyl group such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam. Among these, from the viewpoint of improving the durability of the adhesive sheet, lactam monomers containing an N-vinyl group are preferably contained.

[0064] (Meth)acrylic polymer (A) may contain structural units derived from hydroxyl group-containing monomers. The hydroxyl group-containing monomers are compounds containing a hydroxyl group in their structure and having a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the hydroxyl group-containing monomers include: hydroxyl group-containing (meth)acrylic acid alkyl esters such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxydodecyl (meth)acrylate; hydroxyl group-containing (meth)acrylic acid cycloalkyl esters such as methyl (4-hydroxymethylcyclohexyl) acrylate. Among these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred.

[0065] In (meth)acrylic polymer (A), the content ratio of the structural units derived from the comonomers is not particularly limited, and is, for example, 0 to 40% by weight, may be 0.1 to 30% by weight, or may be 0.1 to 20% by weight.

[0066] In (meth)acrylic polymer (A), the content ratio of the structural units derived from the carboxyl group-containing monomers is not particularly limited, and is, for example, 0.1% by weight or more, preferably 1% by weight or more, 2% by weight or more, 3% by weight or more, and more preferably 4% by weight or more. The content ratio is, for example, 25% by weight or less, may be 20% by weight or less, and further may be 10% by weight or less.

[0067] In the (meth)acrylic polymer (A), the content of the structural unit derived from the aromatic ring-containing monomer is not particularly limited, and is, for example, 3 to 25% by weight, more preferably 22% by weight or less, and still more preferably 20% by weight or less. The content is more preferably 8% by weight or more, and still more preferably 12% by weight or more.

[0068] In the (meth)acrylic polymer (A), the content of the structural unit derived from the amide group-containing monomer is not particularly limited, and is, for example, 0.1 to 10% by weight, more preferably 0.2 to 8% by weight, and still more preferably 0.6 to 6% by weight.

[0069] It should be noted that in the (meth)acrylic polymer (A), it is preferable that the content of the structural unit derived from a copolymerizable monomer having an active hydrogen with high reactivity with an isocyanate crosslinking agent, such as a hydroxyl group-containing monomer, is low. In the (meth)acrylic polymer (A), the content of the structural unit derived from the hydroxyl group-containing monomer is, for example, 1% by weight or less, more preferably 0.5% by weight or less, and still more preferably 0.1% by weight or less. The (meth)acrylic polymer (A) may substantially not contain the structural unit derived from the hydroxyl group-containing monomer.

[0070] For the purpose of improving the adhesiveness and heat resistance of the adhesive sheet, as monomer components, in addition to the (meth)acrylic acid alkyl ester and the above-mentioned copolymerizable monomers, other copolymerizable monomers having a polymerizable functional group containing an unsaturated double bond such as (meth)acryloyl or vinyl may be used. The other copolymerizable monomers may be used alone or in combination.

[0071] As other comonomers, for example, the following can be cited: acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, (meth)acrylic acid sulfopropyl ester, etc.; phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate, etc.; (meth)acrylic acid alkylaminoalkyl esters such as (meth)acrylic acid aminoethyl ester, (meth)acrylic acid N,N-dimethylaminoethyl ester, (meth)acrylic acid tert-butylaminoethyl ester, etc.; (meth)acrylic acid alkoxyalkyl esters such as (meth)acrylic acid methoxyethyl ester, (meth)acrylic acid ethoxyethyl ester, etc.; succinimide monomers such as N-(meth)acryloxymethylene succinimide, N-(meth)acryloyl-6-oxohexamethylene succinimide, N-(meth)acryloyl-8-oxooctamethylene succinimide, etc.; maleimide monomers such as N-cyclohexyl maleimide, N-isopropyl maleimide, N-dodecyl maleimide, N-phenyl maleimide, etc.; itaconimide monomers such as N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, N-2-ethylhexyl itaconimide, N-cyclohexyl itaconimide, N-dodecyl itaconimide, etc.; vinyl monomers such as vinyl acetate, vinyl propionate, etc.; cyanoacrylate monomers such as acrylonitrile, methacrylonitrile, etc.; epoxy group-containing (meth)acrylates such as (meth)acrylic acid glycidyl ester; diol (meth)acrylates such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, etc.; (meth)acrylate monomers such as (meth)acrylic acid tetrahydrofurfuryl ester, fluorine-containing (meth)acrylate, polysiloxane (meth)acrylate, 2-methoxyethyl acrylate, etc.; silane monomers containing silicon atoms such as 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, 10-acryloyloxydecyltriethoxysilane, etc.

[0072] In addition, as other comonomers, for example, the following can be cited: polyfunctional monomers having two or more unsaturated double bonds such as tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0073] When using other comonomers as monomer components, in the (meth)acrylic polymer (A), the content of the structural unit derived from the other comonomer is preferably 10% by weight or less, more preferably 7% by weight or less, and still more preferably 5% by weight or less.

[0074] The weight-average molecular weight of the (meth)acrylic polymer (A) is generally 300,000 to 4,000,000. From the viewpoint of durability, the weight-average molecular weight of the (meth)acrylic polymer (A) is preferably 1,000,000 or more, and may also be 1,500,000 or more. The weight-average molecular weight of the (meth)acrylic polymer (A) can be 3,000,000 or less, and can also be 2,000,000 or less. From the aspect of heat resistance, a weight-average molecular weight of 300,000 or more is preferred. When the weight-average molecular weight is 4,000,000 or less, there is a tendency that the adhesive sheet is not easily hardened and peeling is not likely to occur. The weight-average molecular weight (Mw) / number-average molecular weight (Mn) representing the molecular weight distribution is preferably 1.8 to 10, more preferably 1.8 to 7, and still more preferably 1.8 to 5. From the aspect of durability, a molecular weight distribution (Mw / Mn) of 10 or less is preferred. The weight-average molecular weight and the molecular weight distribution (Mw / Mn) are determined by GPC (gel permeation chromatography) and calculated by conversion to polystyrene.

[0075] The (meth)acrylic polymer (A) can be produced by various known polymerization methods such as solution polymerization, radiation polymerization such as electron beam and UV, bulk polymerization, and emulsion polymerization. The obtained (meth)acrylic polymer (A) can be any copolymer such as a random copolymer, a block copolymer, and a graft copolymer.

[0076] In solution polymerization, as the polymerization solvent, for example, ethyl acetate, toluene, etc. can be used. For example, a polymerization initiator is added under a stream of an inert gas such as nitrogen, and solution polymerization is usually carried out under reaction conditions of about 50 to 70 °C for about 5 to 30 hours.

[0077] There are no particular restrictions on polymerization initiators, chain transfer agents, emulsifiers, etc. used in radical polymerization, and they can be appropriately selected and used. The weight-average molecular weight of the (meth)acrylic polymer (A) can be controlled according to the amounts of the polymerization initiator and chain transfer agent, reaction conditions, etc. Therefore, regarding the polymerization initiator and chain transfer agent, their amounts can be appropriately adjusted according to their compositions.

[0078] Examples of the polymerization initiator include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethylisobutyramidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057); persulfates such as potassium persulfate and ammonium persulfate; peroxides such as di(2-ethylhexyl) peroxydicarbonate, di(4-tert-butylcyclohexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-hexyl peroxy pivalate, tert-butyl peroxy pivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxy 2-ethylhexanoate, bis(4-methylbenzoyl) peroxide, benzoyl peroxide, tert-butyl peroxyisobutyrate, 1,1-di-tert-hexylperoxycyclohexane, tert-butyl hydroperoxide, hydrogen peroxide; redox initiators combining peroxides and reducing agents such as a combination of persulfate and sodium bisulfite, and a combination of peroxide and sodium ascorbate, etc., but not limited thereto.

[0079] The polymerization initiator can be used alone or in combination, and its total amount is preferably about 0.005 to 1 part by weight, more preferably about 0.02 to 0.5 part by weight, relative to 100 parts by weight of the monomer component.

[0080] Examples of the chain transfer agent include dodecyl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, etc. The chain transfer agent can be used alone or two or more thereof can be mixed, and its total amount is preferably about 0.1 part by weight or less relative to 100 parts by weight of the monomer component.

[0081] As an emulsifier used in emulsion polymerization, for example, the following can be cited: anionic emulsifiers such as sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium dodecylbenzenesulfonate, ammonium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate; nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene-polyoxypropylene block polymer, etc. The emulsifier can be used alone or in combination.

[0082] As a reactive emulsifier, an emulsifier having a radically polymerizable functional group such as an allyl group or an allyl ether group introduced therein can be cited. Specific examples of such an emulsifier include AQUALON HS-10, HS-20, KH-10, BC-05, BC-10, BC-20 (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), ADEKA REASOAP SE10N (manufactured by ADEKA Corporation), etc. The reactive emulsifier enters the polymer chain after polymerization, improving water resistance, and is therefore preferred. The amount of the emulsifier is preferably 0.3 to 5 parts by weight, more preferably 0.5 to 1 part by weight, based on 100 parts by weight of the total amount of the monomer components, considering polymerization stability and mechanical stability.

[0083] In radiation polymerization, a (meth)acrylic polymer (A) is produced by irradiating a monomer component with radiation such as an electron beam or UV to effect polymerization. In the case of radiation polymerization by an electron beam, it is not particularly necessary to contain a photoinitiator in the monomer component. In the case of radiation polymerization by UV, considering advantages such as shortening the polymerization time, a photoinitiator can be contained in the monomer component. The photoinitiator can be used alone or in combination.

[0084] As the photoinitiator, as long as it is a photoinitiator that initiates photopolymerization, there is no particular limitation, and commonly used photoinitiators can be used. As the photoinitiator, for example, the following can be used: benzoin ethers, acetophenones, α-hydroxy ketones, photoactive oximes, benzoins, benzils, benzophenones, ketals, thioxanthones, etc. The amount of the photoinitiator is 0.05 to 1.5 parts by weight, preferably 0.1 to 1 part by weight, based on 100 parts by weight of the monomer component. The photoinitiator can be used alone or in combination.

[0085] [Isocyanate crosslinking agent]

[0086] As the isocyanate crosslinking agent, a compound having at least two isocyanate groups (isocyanate compound) can be used. The number of isocyanate groups contained in the isocyanate compound is preferably 3 or more. The upper limit value of the number of isocyanate groups is not particularly limited, for example, it is 5. As the isocyanate compound, aromatic isocyanate compounds, alicyclic isocyanate compounds, aliphatic isocyanate compounds, etc. can be mentioned. The isocyanate crosslinking agent preferably can undergo self-polymerization by reacting with water.

[0087] As the aromatic isocyanate compound, for example, the following can be mentioned: phenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-biphenyl diisocyanate, 1,5-naphthalene diisocyanate, phenyl dimethyl diisocyanate, etc.

[0088] As the alicyclic isocyanate compound, for example, the following can be mentioned: 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated phenyl dimethyl diisocyanate, hydrogenated toluene diisocyanate, hydrogenated tetramethylphenyl dimethyl diisocyanate, etc.

[0089] As the aliphatic isocyanate compound, the following can be mentioned: trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, etc.

[0090] As the isocyanate crosslinking agent, polymers (dimers, trimers, pentamers, etc.) of the above isocyanate compounds, adducts obtained by adding with polyols such as trimethylolpropane, urea modified products, biuret modified products, urethane modified products, isocyanurate modified products, carbodiimide modified products, urethane prepolymers obtained by adding with polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc. can also be mentioned.

[0091] The isocyanate crosslinking agent is preferably an aromatic isocyanate compound and its derivatives, more preferably toluene diisocyanate and its derivatives, that is, toluene diisocyanate-based (TDI-based) crosslinking agents. From the perspective of reactivity, the TDI-based crosslinking agent is more suitable for the adhesive composition of the present embodiment than xylylene diisocyanate and its derivatives, that is, xylylene diisocyanate-based (XDI-based) crosslinking agents. The isocyanate crosslinking agent may contain an adduct of polyol and toluene diisocyanate as the TDI-based crosslinking agent. As a specific example of the adduct, a trimethylolpropane / toluene diisocyanate trimer adduct can be cited.

[0092] Examples of commercially available products of the isocyanate crosslinking agent include: products named "Millionate MT", "Millionate MTL", "Millionate MR-200", "Millionate MR-400", "Coronate L", "Coronate HL", "Coronate HX" manufactured by Tosoh Corporation; products named "Takenate D-101E", "Takenate D-110N", "Takenate D-120N", "Takenate D-140N", "Takenate D-160N", "Takenate D-165N", "Takenate D-170HN", "Takenate D-178N", "Takenate 500", "Takenate 600" manufactured by Mitsui Chemicals, Inc., etc. Among them, Takenate D-101E is preferred.

[0093] As the isocyanate crosslinking agent, one of the above isocyanate crosslinking agents can be used alone, or two or more can be used in combination. With respect to 100 parts by weight of the (meth)acrylic polymer (A), the compounding amount of the isocyanate crosslinking agent is 2 parts by weight or more, preferably 3 parts by weight or more, more preferably 5 parts by weight or more, further preferably 8 parts by weight or more, particularly preferably 10 parts by weight or more, and can also be 11 parts by weight or more. With respect to 100 parts by weight of the (meth)acrylic polymer (A), the compounding amount of the isocyanate crosslinking agent is, for example, 20 parts by weight or less, and can be 15 parts by weight or less, 14 parts by weight or less, 13 parts by weight or less, and further can be 12 parts by weight or less.

[0094] In the adhesive composition, when the blending amount of the isocyanate crosslinking agent relative to 100 parts by weight of the (meth)acrylic polymer (A) is about 2 parts by weight or more, when producing the adhesive sheet, the isocyanate crosslinking agents sometimes react with each other to form a polymer (B) containing structural units derived from the isocyanate crosslinking agent as the main component. The polymer (B) is suitable for suppressing dimensional changes of the adhesive sheet by imparting sufficient cohesion to the adhesive sheet. That is, the polymer (B) is suitable for suppressing display unevenness and light leakage in the image display device. In addition, the combination of the (meth)acrylic polymer (A) and the polymer (B) is suitable for improving the durability of the adhesive sheet in a high-temperature and high-humidity environment or the like. It should be noted that in the adhesive composition of the present embodiment, by adjusting the blending amount of the isocyanate crosslinking agent relative to 100 parts by weight of the (meth)acrylic polymer (A) to, for example, 20 parts by weight or less (preferably 13 parts by weight or less), there is a tendency to be able to suppress an excessive increase in the elastic modulus of the adhesive sheet. According to the adhesive sheet formed from this adhesive composition, it is possible to suppress breakage of members in the optical laminate due to stress concentration near the adhesive sheet during re-operation.

[0095] [Polyhydroxyalkylamine compound]

[0096] As the polyhydroxyalkylamine compound, an amine compound (C) having at least 2 hydroxyl groups can be used. The number of hydroxyl groups in the amine compound (C) can be 3 or more. The upper limit value of the number of hydroxyl groups is not particularly limited, and is, for example, 5.

[0097] The number of nitrogen atoms (specifically, amino groups) contained in the amine compound (C) can be 1 or more, and can also be 2 or more. The upper limit value of the number of nitrogen atoms is not particularly limited, and is, for example, 5.

[0098] Examples of the amine compound (C) having 1 nitrogen atom include: diol amines such as diethanolamine, dipropanolamine, diisopropanolamine, N-methyldiethanolamine, N-methyldiisopropanolamine, N-ethyldiethanolamine, N-ethyldiisopropanolamine, N-butyldiethanolamine, and N-butyldiisopropanolamine; triol amines such as triethanolamine, tripropanolamine, and triisopropanolamine.

[0099] Examples of the amine compound (C) having 2 nitrogen atoms include the compound represented by the following formula (1).

[0100] [Chemical formula 1]

[0101]

[0102] In formula (1), R 1 、R 2 、R 3 and R 4Each independently represents a hydrogen atom or a general formula -(R 5 O) m (R 6 O) n -H. In the above general formula, R 5 and R 6 each independently represent an alkylene group. Among them, the alkylene group of R 5 is different from the alkylene group of R 6 . m and n are each independently integers of 0 or more. Among them, at least one of m and n is an integer of 1 or more. At least two of R 1 , R 2 , R 3 and R 4 are of the general formula -(R 5 O) m (R 6 O) n -H, and R 1 , R 2 , R 3 and R 4 can each be of the general formula -(R 5 O) m (R 6 O) n -H. X represents a divalent hydrocarbon group, and p represents an integer of 1 or more.

[0103] Among R 5 and R 6 , as the alkylene group, for example, there can be mentioned: alkylene groups having about 2 to 6 carbon atoms such as ethylene, propylene, trimethylene, tetramethylene, ethyl ethylene, pentamethylene, hexamethylene, etc. (preferably alkylene groups having 2 to 4 carbon atoms, more preferably alkylene groups having 2 or 3 carbon atoms). The alkylene group can have any of a linear or branched form. As the alkylene group, ethylene and propylene can be suitably used. m and n are, for example, 0 to 20, preferably 1 to 10. It can be that one of m and n is 0 and the other is an integer of 1 or more (especially 1).

[0104] In X, the divalent hydrocarbon group can be in any form of saturated or unsaturated. As the divalent hydrocarbon group, for example, there can be mentioned: alkylene groups, cycloalkylene groups, arylene groups, etc. The alkylene group can have any of a linear or branched form. As the alkylene group, for example, there can be mentioned: alkylene groups having about 1 to 6 carbon atoms such as methylene, ethylene, propylene, trimethylene, tetramethylene, etc. (preferably alkylene groups having 1 to 4 carbon atoms, more preferably alkylene groups having 2 or 3 carbon atoms), etc. As the cycloalkylene group, for example, there can be mentioned: cycloalkylene groups having about 5 to 12 members such as 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, etc. As the arylene group, for example, 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, etc. can be used.

[0105] In formula (1), p is not particularly limited as long as it is an integer of 1 or more, for example, it is an integer of 1 to 10, preferably an integer of 1 to 6, and more preferably an integer of 1 to 4.

[0106] Examples of the amine compound (C) represented by formula (1) include: N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, N,N,N',N'-tetrakis(2-hydroxyethyl)trimethylenediamine, N,N,N',N'-tetrakis(2-hydroxypropyl)trimethylenediamine, etc. Other examples of the amine compound (C) represented by formula (1) include polyoxyethylene condensates of ethylenediamine, polyoxypropylene condensates of ethylenediamine, polyoxyethylene-polyoxypropylene condensates of ethylenediamine, and other polyoxyalkylene condensates of alkylenediamines. As the amine compound (C) represented by formula (1), for example, commercially available products such as the trade name "EDP-300", the trade name "EDP-450", the trade name "EDP-1100", and the trade name "Pluronic" (all manufactured by ADEKA Corporation) can be used.

[0107] The polyhydroxyalkylamine compound can be used alone or in combination of two or more.

[0108] The molecular weight of the polyhydroxyalkylamine compound is, for example, 1500 or less, and can be 1000 or less, 800 or less, 500 or less, 400 or less, and further can be 300 or less. The smaller the molecular weight of the polyhydroxyalkylamine compound, the easier it is to improve the reworkability of the adhesive sheet with a small amount of addition. The lower limit of the molecular weight of the polyhydroxyalkylamine compound is not particularly limited, and can be 100 or more, can be 200 or more, can be 400 or more depending on the situation, and can be 1000 or more. When the molecular weight of the polyhydroxyalkylamine compound is large, there is a tendency to improve the pot life of the adhesive composition.

[0109] With respect to 100 parts by weight of the (meth)acrylic polymer (A), the amount of the polyhydroxyalkylamine compound is, for example, 0.01 to 5 parts by weight, and can be 0.1 part by weight or more. This amount can be 3.5 parts by weight or less, can be 3 parts by weight or less, 2 parts by weight or less, 1.5 parts by weight or less, 1 part by weight or less, and further can be 0.5 part by weight or less. When the amount of the polyhydroxyalkylamine compound is small, there is a tendency to improve the pot life of the adhesive composition.

[0110] [Polyether compound]

[0111] Polyether compounds are compounds having a polyether backbone. When a pressure-sensitive adhesive sheet formed from an adhesive composition is adhered to an adherend such as an alkali-free glass, the polyether compound has a tendency to reduce the adhesive force between the pressure-sensitive adhesive sheet and the adherend (for example, the adhesive force P0 described later) due to segregation on the surface of the adherend. According to the research of the present inventors, in the pressure-sensitive adhesive sheet formed from the adhesive composition of the present embodiment, the polyhydroxyalkylamine compound has a tendency to promote the segregation of the polyether compound. By promoting the segregation of the polyether compound, the adhesive force between the pressure-sensitive adhesive sheet and the adherend can be sufficiently reduced, thereby improving the reworkability of the pressure-sensitive adhesive sheet.

[0112] The polyether compound may contain a silicon atom and may further contain a hydroxyl group and / or a hydrolyzable group bonded to the silicon atom. Preferably, the polyether compound has a reactive silyl group represented by the general formula -SiR a M 3-a at at least one terminal. In the above general formula, R is independently a monovalent organic group having 1 to 20 carbon atoms which may optionally have a substituent. M is independently a hydroxyl group or a hydrolyzable group. a is an integer of 0 to 3, may be an integer of 0 to 2, or may be an integer of 1 to 3.

[0113] For example, the polyether compound has at least one reactive silyl group at its terminal per molecule on average. When the polyether compound is linear, the polyether compound may have one or two reactive silyl groups at its terminal, preferably two reactive silyl groups. When the polyether compound is branched, the polyether compound has at least one reactive silyl group at the main chain terminal or the side chain terminal. The number of reactive silyl groups can be appropriately adjusted according to the number of terminals of the polyether compound, preferably two or more, and may be three or more.

[0114] Preferably, the polyether compound has a reactive silyl group at at least a part of its molecular terminal and has at least one, preferably 1.1 to 5, more preferably 1.1 to 3 reactive silyl groups in its molecule.

[0115] In the above general formula, R is preferably a linear or branched alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group, more preferably an alkyl group having 1 to 6 carbon atoms, and particularly preferably a methyl group. When there are a plurality of R in the polyether compound, the plurality of R may be the same or different.

[0116] In M of the above general formula, the hydrolyzable group can be bonded to the silicon atom to form a siloxane bond through a hydrolysis reaction and / or a condensation reaction. Examples of the hydrolyzable group include a halogen atom, an alkoxy group, an acyloxy group, an alkenyloxy group, a carbamoyl group, an amino group, an aminoxy group, a ketoxime group, etc. When the hydrolyzable group has a carbon atom, the number of carbon atoms is preferably 6 or less, more preferably 4 or less. In particular, an alkoxy group or an alkenyloxy group having 4 or less carbon atoms is preferred, and a methoxy group or an ethoxy group is particularly preferred. When there are a plurality of M in the polyether compound, the plurality of M may be the same or different.

[0117] The reactive silyl group is preferably an alkoxysilyl group represented by the following formula (2) or an alkoxysilyl group represented by the following formula (3).

[0118] [Chemical formula 2]

[0119]

[0120] In formulas (2) and (3), R 7 , R 8 and R 9 are each independently a monovalent hydrocarbon group having 1 to 6 carbon atoms, and examples thereof include a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkenyl group having 2 to 6 carbon atoms, a cycloalkyl group having 5 to 6 carbon atoms, a phenyl group, etc. As -OR 7 , -OR 8 and -OR 9 in the formula, specific examples include a methoxy group, an ethoxy group, a propoxy group, an allyloxy group, a phenoxy group, etc., and a methoxy group and an ethoxy group are preferred, and a methoxy group is particularly preferred.

[0121] Preferably, the polyether skeleton of the polyether compound has a repeating unit of a linear or branched oxyalkylene having 1 to 10 carbon atoms. The number of carbon atoms of the oxyalkylene is preferably 2 to 6, more preferably 3. In the polyether skeleton, the repeating unit of the oxyalkylene may be one kind or two or more kinds. When the polyether skeleton contains two or more repeating units, the repeating units may be arranged in a block form or in a random form. Specific examples of the oxyalkylene include oxyethylene, oxypropylene, oxybutylene, etc. From the viewpoints of ease of material production, material stability, etc., the oxyalkylene is preferably oxypropylene (especially -CH2CH(CH3)O-).

[0122] Preferably, in the polyether compound, except for the reactive silyl group, the main chain is substantially composed of a polyether backbone. However, it should be noted that the main chain of the polyether compound may also contain a small amount of other chemical structures. As the other chemical structures, for example, the chemical structure derived from the initiator of the repeating unit for forming the oxyalkylene, and the linking group between the polyether backbone and the reactive silyl group, etc. are exemplified. The content rate of the repeating unit of the oxyalkylene in the polyether compound is preferably 50% by weight or more, more preferably 80% by weight or more.

[0123] The polyether compound may be a compound represented by the following formula (4).

[0124] R a M 3-a Si-X-Y-(AO) n -Z(4)

[0125] In formula (4), R is independently a monovalent organic group having 1 to 20 carbon atoms which may optionally have a substituent. M is independently a hydroxyl group or a hydrolyzable group. a is an integer of 0 to 3, may be an integer of 0 to 2, or may be an integer of 1 to 3. AO is a linear or branched oxyalkylene having 1 to 10 carbon atoms. n represents the average addition mole number of the oxyalkylene and is 1 to 1700. X is a linear or branched alkylene having 1 to 20 carbon atoms. Y is an ether bond, an ester bond, a urethane bond, or a carbonate bond. Z is a hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, a group represented by the following formula (5) or a group represented by the following formula (6).

[0126] -Y1-X-SiR a M 3-a (5)

[0127] -Q{-(OA) n -Y-X-SiR a M 3-a} m (6)

[0128] In formula (5), R, M, X and a are the same as in formula (4). Y1 is a single bond, a -CO- bond, a -CONH- bond or a -COO- bond. In formula (6), R, M, X, Y and n are the same as in formula (4). OA is the same as AO in formula (4). Q is a divalent or higher valent hydrocarbon group having 1 to 10 carbon atoms. m is a value obtained by subtracting 1 from the valence of the hydrocarbon group of Q.

[0129] X in formula (4) is a linear or branched alkylene having 1 to 20 carbon atoms. The number of carbon atoms of the alkylene is preferably 2 to 10, more preferably 3.

[0130] In formula (4), Y is a bond formed by the reaction of an oxyalkylene at the end of the polyether backbone with a hydroxyl group, preferably an ether bond or a urethane bond, more preferably a urethane bond.

[0131] Z is, for example, derived from an initiator (hydroxyl compound) in the synthesis of an alkylene oxide polymer, which is the polymer used in the production of the polyether compound represented by formula (4). When the polyether compound represented by formula (4) has one reactive silyl group at its end, Z can be a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. It should be noted that when Z is a hydrogen atom, it is equivalent to the case where a compound having the same structure as the structural unit contained in the alkylene oxide polymer is used as the hydroxyl compound. The case where Z is a monovalent hydrocarbon group having 1 to 10 carbon atoms is equivalent to the case where a hydroxyl compound having one hydroxyl group is used.

[0132] On the other hand, when the polyether compound represented by formula (4) has multiple reactive silyl groups at its end, Z can be a group represented by formula (5) or a group represented by formula (6). It should be noted that when Z is represented by formula (5), it is equivalent to the case where a compound having the same structure as the structural unit contained in the alkylene oxide polymer is used as the hydroxyl compound. When Z is represented by formula (6), it is equivalent to the case where a hydroxyl compound having a structure different from the structural unit contained in the alkylene oxide polymer and having two hydroxyl groups is used. It should be noted that Y1 in formula (5) is, like Y in formula (4), a bond formed by the reaction of an oxyalkylene at the end of the polyether backbone with a hydroxyl group.

[0133] From the aspect of re - operability, it is preferred that the polyether compound is represented by the following formula (7), formula (8) or formula (9).

[0134] Z 0 -A 2 -O-(A 1 O) n -Z 1 (7)

[0135] Z 0 -A 2 -NHCOO-(A 1 O) n -Z 2 (8)

[0136] Z 3 -O-(A 1 O) n -CH{-CH2-(A 1 O) n -Z 3}2(9)

[0137] In formulas (7) to (9), Z 0 is an alkoxysilyl group represented by formula (2) or formula (3). A 1 O is an oxyalkylene group having 2 to 6 carbon atoms, preferably oxypropylene group. A 1 The oxyalkylene group of O can be linear or branched. n represents the average number of moles of addition of A 1 O, and is 1 to 1700. In formulas (7) and (8), A 2 is an alkylene group having 2 to 6 carbon atoms, preferably propylene group. A 2 The alkylene group can be linear or branched. In formula (7), Z 1 is a hydrogen atom or -A 2 -Z 0 . In formula (8), Z 2 is a hydrogen atom or -CONH-A 2 -Z 0 . In formula (9), Z 3 is a hydrogen atom or -A 2 -Z 0 , and at least one Z 3 is -A 2 -Z 0 .

[0138] As the compound represented by formula (8), preferably a compound represented by the following formula (10).

[0139] [Chemical formula 3]

[0140]

[0141] In formula (10), R 7 , R 8 and R 9 are each independently a monovalent hydrocarbon group having 1 to 6 carbon atoms. n represents the average number of moles of addition of oxypropylene group, 1 to 1700. Z 21 is a hydrogen atom, or a trialkoxysilyl group represented by the following formula (11).

[0142] [Chemical formula 4]

[0143]

[0144] In formula (11), R 7 , R 8 and R 9 are the same as those in formula (10).

[0145] From the viewpoint of reworkability, the number average molecular weight of the polyether compound is preferably 300 to 100,000. The number average molecular weight is preferably 500 or more, 1000 or more, 2000 or more, 3000 or more, 4000 or more, more preferably 5000 or more, and preferably 50,000 or less, 40,000 or less, 30,000 or less, 20,000 or less, more preferably 10,000 or less. The n (average addition mole number of oxyalkylene in the polyether skeleton) in the above formulas (4), (7) to (10) is appropriately adjusted so that the number average molecular weight of the polyether compound falls within the above range. When the number average molecular weight of the polyether compound is 1000 or more, the above n is usually 10 to 1700.

[0146] The Mw (weight average molecular weight) / Mn (number average molecular weight) of the polyether compound is preferably 3.0 or less, more preferably 1.6 or less, and particularly preferably 1.5 or less. In order to obtain a polyether compound with a small Mw / Mn, it is preferable to use an alkylene oxide polymer obtained by polymerizing a cyclic ether using the following double metal cyanide complex as a catalyst in the presence of an initiator, and particularly preferably a method of modifying the terminal of the alkylene oxide polymer to introduce a reactive silyl group.

[0147] The polyether compound represented by the formulas (4), (7) to (10) can be produced, for example, by using an alkylene oxide polymer having a functional group at the molecular terminal as a raw material and bonding a reactive silyl group to the molecular terminal via an organic group such as an alkylene group. As the alkylene oxide polymer used as the raw material, a polymer having a hydroxyl terminal obtained by ring-opening polymerization of a cyclic ether in the presence of a catalyst and an initiator is preferable.

[0148] As the above initiator, a compound having one or more active hydrogen atoms per molecule can be used, such as a hydroxyl compound having one or more hydroxyl groups per molecule. Examples of the initiator include: hydroxyl compounds such as ethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, hexamethylene glycol, hydrogenated bisphenol A, neopentyl glycol, polybutadiene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, allyl alcohol, methallyl alcohol, glycerin, trimethylolmethane, trimethylolpropane, pentaerythritol, and their alkylene oxide adducts. The initiator can be one kind or two or more kinds.

[0149] When ring-opening polymerization of a cyclic ether is carried out in the presence of an initiator, a polymerization catalyst can be used. Examples of the polymerization catalyst include: alkali metal compounds such as potassium hydroxide and potassium methoxide, cesium compounds such as cesium hydroxide; double metal cyanide complexes; metal porphyrin complexes; compounds having a P=N bond, etc.

[0150] The polyether backbone (polyoxyalkylene chain) in the polyether compounds represented by formulas (4), (7) to (10) is preferably composed of repeating units of oxyalkylene formed by ring-opening polymerization of an alkylene oxide having 2 to 6 carbon atoms, more preferably composed of repeating units of oxyalkylene formed by ring-opening polymerization of at least one alkylene oxide selected from ethylene oxide, propylene oxide, and butylene oxide, and particularly preferably composed of repeating units of oxyalkylene formed by ring-opening polymerization of propylene oxide. When the polyoxyalkylene chain is composed of repeating units of two or more oxyalkylenes, the arrangement of the repeating units of two or more oxyalkylenes may be block-like or random-like.

[0151] The polyether compound represented by the above formula (8) can be obtained, for example, by subjecting a polymer having a polyoxyalkylene chain and a hydroxyl group to a urethanization reaction using a compound having a reactive silyl group and an isocyanate group. The polyether compound can also be obtained by the following method: adding a hydrosilane or a mercapto silane to an unsaturated group of an alkylene oxide polymer having an unsaturated group, for example, an allyl-terminated polyoxypropylene monoalcohol obtained by polymerizing an alkylene oxide using allyl alcohol as an initiator, thereby introducing a reactive silyl group to the molecular end.

[0152] The method for introducing a reactive silyl group to the terminal group of a hydroxyl-terminated alkylene oxide polymer obtained by subjecting a cyclic ether to ring-opening polymerization in the presence of an initiator is not particularly limited, and the following methods (a) to (c) in which the reactive silyl group is preferably linked to the terminal group via an organic group are preferred.

[0153] (a) A method in which a reactive silyl group is bonded to the unsaturated group after introducing an unsaturated group to the terminal of an alkylene oxide polymer having a hydroxyl group.

[0154] As this method, the following two methods (a-1) and (a-2) can be further exemplified.

[0155] (a-1) A method using a so-called hydrosilylation reaction, which is a method of reacting a hydrosilane compound with the above unsaturated group in the presence of a catalyst such as a platinum compound.

[0156] (a-2) A method of reacting a mercapto silane compound with an unsaturated group.

[0157] Examples of the mercapto silane compound for (a-2) include: 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltriisopropenyloxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmonomethoxysilane, 3-mercaptopropylmethyldiethoxysilane, etc.

[0158] When reacting an unsaturated group with a mercapto group, compounds such as radical generators that can be used as radical polymerization initiators can be used. If desired, the reaction can also be carried out by radiation or heat without using a radical polymerization initiator. Examples of radical polymerization initiators include peroxide-based, azo-based, and redox-based polymerization initiators, as well as metal compound catalysts. Specific examples include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, benzoyl peroxide, tertiary alkyl peroxide esters, acetyl peroxide, and diisopropyl peroxydicarbonate. When using a radical polymerization initiator to react an unsaturated group with a mercapto group, the reaction conditions vary depending on the decomposition temperature (half-life temperature) of the polymerization initiator. For example, the reaction is preferably carried out at a reaction temperature of 20 to 200 °C, more preferably 50 to 150 °C, for several hours to several tens of hours.

[0159] As a method for introducing an unsaturated group to the end of an alkylene oxide polymer, a method of reacting a reactant having a functional group capable of linking to the terminal hydroxyl group of the alkylene oxide polymer through an ether bond, an ester bond, a urethane bond, or a carbonate bond and an unsaturated group with the alkylene oxide polymer can be cited. When polymerizing a cyclic ether in the presence of an initiator, a method of introducing an unsaturated group into at least a part of the end of the alkylene oxide polymer by copolymerizing an epoxy compound containing an unsaturated group such as allyl glycidyl ether can also be used.

[0160] The hydrosilylation reaction is preferably carried out at a temperature of 60 to 120 °C. Generally, within a reaction time of several hours, the hydrosilylation reaction proceeds sufficiently.

[0161] (b) A method of reacting an alkylene oxide polymer having a hydroxyl group at the end with an isocyanate silane compound having a reactive silyl group.

[0162] Examples of the isocyanate silane compound include isocyanate silane compounds such as 1-isocyanatomethyltrimethoxysilane, 1-isocyanatomethyltriethoxysilane, 1-isocyanatopropyltrimethoxysilane, 1-isocyanatopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 1-isocyanatomethylmethyldimethoxysilane, 1-isocyanatomethyldimethylmonomethoxysilane, 1-isocyanatomethylmethyldiethoxysilane, 1-isocyanatopropylmethyldimethoxysilane, 1-isocyanatopropyldimethylmonomethoxysilane, 1-isocyanatopropylmethyldiethoxysilane, 3-isocyanatopropylmethyldimethoxysilane, 3-isocyanatopropyldimethylmonomethoxysilane, and 3-isocyanatopropylmethyldiethoxysilane. Among them, 3-isocyanatopropyltrimethoxysilane and 1-isocyanatomethylmethyldimethoxysilane are more preferably used, and 3-isocyanatopropyltrimethoxysilane is particularly preferably used.

[0163] The reaction of the alkylene oxide polymer with the isocyanate silane compound is preferably carried out in such a manner that the molar ratio of the isocyanate group (NCO) of the isocyanate silane compound to the hydroxyl group (OH) of the alkylene oxide polymer reaches NCO / OH = 0.80 to 1.05. Since this method has fewer manufacturing process steps, the process time can be significantly shortened, and there are also fewer impurities generated as by-products during the manufacturing process. Therefore, complicated operations such as purification are not required. The more preferred molar ratio of the NCO group to the OH group is NCO / OH = 0.85 to 1.00. When the ratio of NCO is low, reactions such as the reaction of the remaining OH group with the reactive silyl group may occur, and thus the storage stability may sometimes decrease. In this case, it is preferable to react again with the isocyanate silane compound or the monoisocyanate compound to consume the excess OH group, thereby adjusting to a given silylation rate.

[0164] When reacting the hydroxyl group of the alkylene oxide polymer with the above-mentioned isocyanate silane compound, a known urethanization reaction catalyst can be used. The reaction temperature and the reaction time required until the reaction is completed vary depending on whether a urethanization reaction catalyst is used and the amount used. The reaction of the alkylene oxide polymer with the isocyanate silane compound is preferably carried out at a temperature of 20 to 200°C, preferably 50 to 150°C, for several hours.

[0165] (c) A method of reacting a polyisocyanate compound with an alkylene oxide polymer having a hydroxyl group at the molecular end under conditions where the isocyanate group is in excess to produce an alkylene oxide polymer having an isocyanate group at at least a part of the end, and further reacting a silicon compound having a functional group with the isocyanate group.

[0166] The functional group of the silicon compound is at least one group containing active hydrogen selected from the group consisting of a hydroxyl group, a carboxyl group, a mercapto group, a primary amino group, and a secondary amino group. Examples of the silicon compound include amino-silane compounds such as N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane; mercapto-silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane. When reacting an alkylene oxide polymer with the above silicon compound, a known urethanization reaction catalyst can be used. The reaction temperature and the reaction time required until the reaction is completed vary depending on whether a urethanization reaction catalyst is used and the amount used. The above reaction is preferably carried out at a temperature of 20 to 200 °C, preferably 50 to 150 °C for several hours.

[0167] Specific examples of the polyether compound include MS polymers S203, S303, S810 manufactured by KANEKA Corporation; SILYL EST250, EST280; SAT10, SAT200, SAT220, SAT350, SAT400; EXCESTAR S2410, S2420, S3430 manufactured by AGC Inc.

[0168] With respect to 100 parts by weight of the (meth)acrylic polymer (A), the compounding amount of the polyether compound is, for example, 0.1 to 5 parts by weight, can be 0.3 parts by weight or more, and further can be 0.5 parts by weight or more. This compounding amount can be 4 parts by weight or less, can also be 3 parts by weight or less, 2 parts by weight or less, and further can be 1 part by weight or less.

[0169] [Other components]

[0170] The adhesive composition may also contain other crosslinking agents in addition to the isocyanate crosslinking agent. Examples of other crosslinking agents include peroxide crosslinking agents, epoxy crosslinking agents, imine crosslinking agents, polyfunctional metal chelates, etc. With respect to 100 parts by weight of the (meth)acrylic polymer (A), the compounding amount of other crosslinking agents is preferably 2 parts by weight or less, more preferably 1 part by weight or less. From the viewpoint of the durability of the adhesive sheet, the adhesive composition may substantially not contain other crosslinking agents, particularly epoxy crosslinking agents.

[0171] The adhesive composition may further contain a (meth)acrylic oligomer.

[0172] The (meth)acrylic oligomer may have the same composition as the above-described (meth)acrylic polymer (A), except for the difference in the weight-average molecular weight (Mw). The weight-average molecular weight (Mw) of the (meth)acrylic oligomer is, for example, 1,000 or more, and may be 2,000 or more, 3,000 or more, and further 4,000 or more. The upper limit of the weight-average molecular weight (Mw) of the (meth)acrylic oligomer is, for example, 30,000 or less, and may be 15,000 or less, 10,000 or less, and further 7,000 or less.

[0173] The (meth)acrylic oligomer has, for example, one or two or more structural units derived from the following monomers: (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentyl (meth)acrylate; (meth)acrylic acid esters containing an aromatic ring such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylic acid esters obtained from terpene compound-derived alcohols.

[0174] Preferably, the (meth)acrylic oligomer has a structural unit derived from a (meth)acrylic monomer having a relatively large structure. In this case, the adhesiveness of the adhesive sheet can be further improved. Examples of the (meth)acrylic monomer include (meth)acrylic acid alkyl esters containing a branched alkyl group such as isobutyl (meth)acrylate and tert-butyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentyl (meth)acrylate; and (meth)acrylic acid esters containing an aromatic ring such as phenyl (meth)acrylate and benzyl (meth)acrylate. Preferably, the monomer has a cyclic structure, and more preferably has two or more cyclic structures. In addition, from the viewpoint of not easily hindering the polymerization and / or formation when ultraviolet rays are irradiated during the polymerization of the (meth)acrylic oligomer and / or the formation of the adhesive sheet, it is preferable that the above monomer does not have an unsaturated bond. For example, (meth)acrylic acid alkyl esters containing a branched alkyl group and esters of (meth)acrylic acid and alicyclic alcohols can be used.

[0175] Specific examples of the (meth)acrylic oligomer include copolymers of butyl acrylate, methyl acrylate and acrylic acid; copolymers of cyclohexyl methacrylate and isobutyl methacrylate; copolymers of cyclohexyl methacrylate and isobornyl methacrylate; copolymers of cyclohexyl methacrylate and acryloylmorpholine; copolymers of cyclohexyl methacrylate and diethylacrylamide; copolymers of 1-adamantyl acrylate and methyl methacrylate; copolymers of dicyclopentyl methacrylate and isobornyl methacrylate; copolymers of at least one selected from dicyclopentyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate and cyclopentyl methacrylate and methyl methacrylate; homopolymers of dicyclopentyl acrylate; homopolymers of 1-adamantyl methacrylate; and homopolymers of 1-adamantyl acrylate.

[0176] The polymerization of the (meth)acrylic oligomer can be carried out by the polymerization method of the above-mentioned (meth)acrylic polymer (A).

[0177] When the adhesive composition contains the (meth)acrylic oligomer, the blending amount thereof is, for example, 70 parts by weight or less, preferably 50 parts by weight or less, and more preferably 40 parts by weight or less, based on 100 parts by weight of the (meth)acrylic polymer (A). The lower limit of the blending amount is, for example, 1 part by weight or more, preferably 2 parts by weight or more, and more preferably 3 parts by weight or more, based on 100 parts by weight of the (meth)acrylic polymer (A). The adhesive composition may not contain the (meth)acrylic oligomer.

[0178] The adhesive composition may further contain known additives. Examples of the additives include: reoperation improvers other than polyether compounds, silane coupling agents, solvents, coloring agents, powders such as pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, foils, etc. In addition, redox types containing a reducing agent can also be used within a controllable range. From the viewpoint of improving the durability of the adhesive sheet, the adhesive composition preferably contains a silane coupling agent as an additive. These additives can be used, for example, in an amount of 10 parts by weight or less, preferably 5 parts by weight or less, and more preferably 1 part by weight or less, based on 100 parts by weight of the (meth)acrylic polymer (A).

[0179] Specific examples of the silane coupling agent include, for example: epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, etc.; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutyl)propylamine, N-phenyl-γ-aminopropyltrimethoxysilane, etc.; (meth)acrylic acid group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, etc.; isocyanate group-containing silane coupling agents such as 3-isocyanatopropyltriethoxysilane, etc.

[0180] When the adhesive composition contains a silane coupling agent, with respect to 100 parts by weight of the (meth)acrylic polymer (A), its blending amount is, for example, 5 parts by weight or less, and may also be 3 parts by weight or less, 1 part by weight or less, 0.5 part by weight or less, 0.4 part by weight or less, 0.2 part by weight or less, 0.1 part by weight or less, and further may be 0.05 part by weight or less. The lower limit of this blending amount is not particularly limited, and is, for example, 0.02 part by weight or more. It should be noted that the adhesive composition may also not contain a silane coupling agent.

[0181] The type of the adhesive composition is, for example, emulsion type, solvent type (solution type), active energy ray curable type (photo curable type), hot melt type (hot melt type). From the viewpoint of being able to form an adhesive sheet with excellent durability, the adhesive composition can be solvent type. The solvent type adhesive composition may substantially not contain a photo curable agent such as an ultraviolet curable agent.

[0182] (Embodiment of the adhesive sheet)

[0183] An example of the adhesive sheet of the present embodiment is shown in Figure 1 . The adhesive sheet 1 of the present embodiment is formed from the above-mentioned adhesive composition. The adhesive sheet 1 contains, for example, a crosslinked product of the (meth)acrylic polymer (A) and a polymer (B) containing a structural unit derived from an isocyanate crosslinking agent as a main component. In the polymer (B), the content rate of the structural unit derived from the isocyanate crosslinking agent is, for example, 70% by weight or more, preferably 90% by weight or more. The polymer (B) is formed, for example, substantially only from the structural unit derived from the isocyanate crosslinking agent. In the adhesive sheet 1, the crosslinked product of the (meth)acrylic polymer (A) and the polymer (B) may form an interpenetrating network (IPN) structure. This IPN structure is suitable for increasing the elastic modulus of the adhesive sheet 1 and improving the durability.

[0184] The thickness of the adhesive sheet 1 is not particularly limited, and is, for example, about 1 to 100 μm, preferably 2 to 50 μm, more preferably 2 to 40 μm, and further preferably 5 to 35 μm.

[0185] The method for producing the adhesive sheet 1 includes, for example: a step of applying the above-described adhesive composition onto a substrate to form a coating film, and a step of drying the obtained coating film.

[0186] As the substrate, a release film can be used, for example. The adhesive sheet 1 formed on the release film can be transferred onto an optical film or the like, and the substrate can be an optical film. In this case, an optical laminate can be obtained by forming the adhesive sheet 1.

[0187] The release film can be used as a release liner until the adhesive sheet 1 is actually used after transferring the adhesive sheet 1 onto the optical film, thereby enabling simplification of the process.

[0188] Examples of the constituent material of the release film include: plastic films, paper, cloth, porous materials such as non-woven fabrics, nets, foamed sheets, metal foils, and appropriate thin sheet materials such as laminates thereof. From the viewpoint of excellent surface smoothness, a plastic film is preferably used.

[0189] The plastic film is not particularly limited, and examples thereof include: polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate copolymer film, and the like.

[0190] The thickness of the release film is usually 5 to 200 μm, preferably about 5 to 100 μm. The release film is subjected to a release treatment such as a silicone type, a fluorine type, or a long-chain alkyl type. The release film can be subjected to a release and antifouling treatment using a release agent such as fatty acid amide and silica powder, and an antistatic treatment such as a coating type, a mixing type, or a vapor deposition type.

[0191] A solution containing the adhesive composition (adhesive solution) can be applied to the substrate. The solid content concentration of the adhesive solution is, for example, 5 to 50% by weight, preferably 10 to 40% by weight. It should be noted that the adhesive solution can be prepared by appropriately adding the same solvent or a different solvent as the polymerization solvent to the adhesive composition according to the polymerization method of the (meth)acrylic polymer (A).

[0192] As a method for applying the adhesive composition to a substrate, various methods can be used. For example, there can be mentioned: roll coating method, roll kiss coating method, gravure coating method, reverse coating method, roll brush method, spraying method, dip roll coating method, bar coating method, knife coating method, air knife coating method, curtain coating method, die lip coating method, extrusion coating method using a die coater, etc. The coating amount of the adhesive composition can be appropriately adjusted according to the thickness of the target adhesive sheet 1.

[0193] The adhesive sheet 1 is formed by drying the coating film so that the coating film cures. The drying temperature of the coating film is not particularly limited. For example, it is 130°C or lower, preferably 125°C or lower, more preferably 120°C or lower, further preferably 110°C or lower, and particularly preferably 100°C or lower. The drying temperature of the coating film can be 60°C or higher, and can also be 80°C or higher. When the drying temperature is 60°C or higher, for example, the reaction of the isocyanate crosslinking agent proceeds smoothly, and there is a tendency to improve the cohesion of the adhesive sheet 1 and reduce the display unevenness of the image display device. When the drying temperature is 130°C or lower, for example, the reaction rate of the isocyanate crosslinking agent can be appropriately adjusted, and there is a tendency to maintain the compatibility between the (meth)acrylic polymer (A) and the polymer (B) well and ensure transparency.

[0194] The drying time of the coating film can be appropriately adjusted according to the composition of the adhesive composition, and is preferably 30 seconds to 300 seconds, further preferably 40 seconds to 240 seconds, and particularly preferably 60 seconds to 180 seconds.

[0195] [Properties of the Adhesive Sheet]

[0196] Preferably, the adhesive sheet 1 has high transparency. For example, the haze of the adhesive sheet 1 when the thickness of the adhesive sheet 1 is 75 μm is 1% or less (or less than 1%), preferably 0.8% or less, and more preferably 0.6% or less.

[0197] The storage modulus G' of the adhesive sheet 1 at 25°C is not particularly limited. For example, it is 0.4 MPa or higher, and can also be 0.5 MPa or higher, 0.8 MPa or higher, 1.0 MPa or higher, and further can be 1.2 MPa or higher. The upper limit value of the storage modulus G' of the adhesive sheet 1 at 25°C is not particularly limited. For example, it is 5.0 MPa. The adhesive sheet 1 having a high elastic modulus within the above range is suitable for suppressing the dimensional change of the optical film.

[0198] The storage modulus G' of the adhesive sheet 1 at 25°C can be specified by the following method. First, prepare a measurement sample formed of the material constituting the adhesive sheet 1. The shape of the measurement sample is disc-shaped, the diameter of the bottom surface of the measurement sample is 8 mm, and the thickness is 2 mm. The measurement sample can be obtained by punching a laminate in which a plurality of adhesive sheets 1 are laminated into a disc shape. Next, perform dynamic viscoelasticity measurement on the measurement sample. For example, "ARES-G2" manufactured by TA Instruments can be used for the dynamic viscoelasticity measurement. Based on the results of the dynamic viscoelasticity measurement, the storage modulus G' of the adhesive sheet 1 at 25°C can be specified. It should be noted that the conditions for the dynamic viscoelasticity measurement are as described below.

[0199] · Measurement conditions

[0200] Frequency: 1 Hz

[0201] Deformation mode: Torsion

[0202] Measurement temperature: -70°C to 150°C

[0203] Heating rate: 5°C / min

[0204] In the adhesive sheet 1, the gel fraction is not particularly limited and is, for example, 60% to 99%. The gel fraction of the adhesive sheet 1 is preferably 80% or more, more preferably 90% or more, further preferably 94% or more, and particularly preferably 95% or more. The gel fraction of the adhesive sheet 1 can be evaluated, for example, by the following method. First, scrape a part of the adhesive sheet 1 to obtain a small piece. Next, wrap the obtained small piece with a stretched porous film of polytetrafluoroethylene and tie it with a kite string to obtain a test piece. Next, measure the total weight (weight A) of the small piece of the adhesive sheet 1, the stretched porous film, and the kite string. It should be noted that the total of the stretched porous film and the kite string used is defined as weight B. Next, immerse the test piece in a container filled with ethyl acetate and leave it standing at 23°C for 1 week. After standing, take out the test piece from the container, dry it in a dryer set at 130°C for 2 hours, and then measure the weight C of the test piece. Based on the following formula, the gel fraction of the adhesive sheet 1 can be calculated from weight A, weight B, and weight C.

[0205] Gel fraction (wt%) = (C - B) / (A - B) × 100

[0206] (Embodiment of the optical laminate)

[0207] An example of the optical laminate of this embodiment is shown in Figure 2 , Figure 2The optical laminate 10A includes an adhesive sheet 1 and an optical film 2, and the adhesive sheet 1 and the optical film 2 are laminated together. The optical laminate 10A can be used in the form of an optical film with an adhesive sheet.

[0208] Examples of the optical film 2 are a polarizing film, a retardation film, and a laminated film including a polarizing film and / or a retardation film. However, the optical film 2 is not limited to the above examples, and the optical film 2 may also include a glass film.

[0209] The polarizing film is, for example, a laminate including a polarizer and a protective film (transparent protective film). The transparent protective film is, for example, disposed in contact with the main surface (the surface having the largest area) of the layered polarizer, and the polarizer can be disposed between two transparent protective films.

[0210] The polarizer is not particularly limited, and various polarizers can be used. As the polarizer, for example, a film obtained by adsorbing a dichroic substance such as iodine or a dichroic dye on a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or a partially saponified ethylene-vinyl acetate copolymer film and performing unidirectional stretching; a polyene-oriented film such as a dehydrated product of polyvinyl alcohol or a dehydrochlorinated product of polyvinyl chloride. Among these, a polarizer formed from a polyvinyl alcohol film and a dichroic substance such as iodine is preferred, and an iodine-based polarizer containing iodine and / or iodide ions is more preferred. The thickness of the polarizer is not particularly limited, and is usually about 5 to 80 μm.

[0211] A polarizer formed by dyeing a polyvinyl alcohol film with iodine and performing unidirectional stretching can be produced, for example, by immersing the polyvinyl alcohol in an aqueous solution of iodine for dyeing and stretching it to 3 to 7 times its original length. If necessary, the polyvinyl alcohol can be immersed in an aqueous solution of potassium iodide containing boric acid, zinc sulfate, zinc chloride, etc. Further, if necessary, the polyvinyl alcohol film can be immersed in water for washing before dyeing. By washing the polyvinyl alcohol film, in addition to removing dirt and anti-blocking agents on the surface of the polyvinyl alcohol film, it also has the effect of swelling the polyvinyl alcohol film to suppress the occurrence of uneven dyeing. The stretching of the polyvinyl alcohol film can be performed after dyeing with iodine, while dyeing, or before dyeing with iodine. The stretching can be performed in an aqueous solution of boric acid, potassium iodide, etc., or in a water bath.

[0212] As the polarizer, a thin polarizer with a thickness of 10 μm or less can also be used. From the viewpoint of thinning, the thickness of the polarizer is preferably 1 to 7 μm. Such a thin polarizer has less thickness unevenness, excellent visual recognition, and less dimensional change, so it has excellent durability, and further can achieve the thinning of the polarizing film, and is preferred from these aspects.

[0213] As a representative thin polarizer, thin polarizers described in Japanese Patent Laid-Open No. 51-069644, Japanese Patent Laid-Open No. 2000-338329, International Publication No. 2010 / 100917, Japanese Patent No. 4751481, and Japanese Patent Laid-Open No. 2012-073563 can be cited. These thin polarizers can be obtained by a production method including a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA) layer and a stretching resin substrate in a laminated state, and a step of performing dyeing. If it is this production method, the PVA-based resin layer is supported by the stretching resin substrate. Therefore, even if the PVA-based resin layer is thin, it is possible to suppress defects such as breakage caused by stretching.

[0214] In a production method including a step of stretching in a laminated state and a step of performing dyeing, from the viewpoint of being able to stretch at a high magnification to improve polarization performance, a production method including a step of stretching in an aqueous boric acid solution described in International Publication No. 2010 / 100917, Japanese Patent No. 4751481, and Japanese Patent Laid-Open No. 2012-073563 is preferred, and a production method including a step of stretching in a gas atmosphere subsidiarily before stretching in an aqueous boric acid solution described in Japanese Patent No. 4751481 and Japanese Patent Laid-Open No. 2012-073563 is particularly preferred.

[0215] As a material for forming a transparent protective film provided on one or both surfaces of a polarizer, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. can be used. Specific examples of such thermoplastic resins include cellulose resins such as cellulose triacetate, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic olefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material of the transparent protective film may be a thermosetting resin such as (meth)acrylic, urethane, acrylic urethane, epoxy, silicone, or an ultraviolet curable resin. When the polarizing film has two transparent protective films, the materials of the two transparent protective films may be the same or different. For example, a transparent protective film made of a thermoplastic resin can be adhered to one main surface of the polarizer with an adhesive, and a transparent protective film made of a thermosetting resin or an ultraviolet curable resin can be adhered to the other main surface of the polarizer. The transparent protective film may contain one or more arbitrary additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, coloring agents, etc. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, further preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or more, there is a tendency to sufficiently exhibit the high transparency and the like originally possessed by the thermoplastic resin.

[0216] The thickness of the transparent protective film can be appropriately determined. Generally, considering operability such as strength and processability, and film properties, etc., it is about 10 to 200 μm.

[0217] The polarizer and the transparent protective film are usually bonded together via an aqueous adhesive or the like. Examples of the aqueous adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, aqueous polyurethanes, aqueous polyesters, etc. Examples of other adhesives other than the above adhesives include ultraviolet curable adhesives, electron beam curable adhesives, etc. The electron beam curable adhesive for polarizing films exhibits suitable adhesiveness to various transparent protective films. The adhesive may also contain a metal compound filler.

[0218] In the polarizing film, a retardation film or the like may be formed on the polarizer instead of the transparent protective film, and another transparent protective film, a retardation film, etc. may be further provided on the transparent protective film.

[0219] For a transparent protective film, a hard coat can be provided on the surface of the transparent protective film opposite to the surface to which the polarizer is adhered, or a treatment for antireflection, anti-adhesion, diffusion, antiglare, etc. can be applied thereto.

[0220] The polarizing film can be a circularly polarizing film.

[0221] As the retardation film, a film obtained by stretching a polymer film, a film obtained by aligning and immobilizing a liquid crystal material can be used. The retardation film has, for example, birefringence in the in-plane and / or thickness direction.

[0222] Examples of the retardation film include a retardation film for antireflection (see Japanese Patent Application Laid-Open No. 2012-133303

[0221] ,

[0222] ,

[0228] ), a retardation film for viewing angle compensation (see Japanese Patent Application Laid-Open No. 2012-133303

[0225] ,

[0226] ), an inclined alignment retardation film for viewing angle compensation (see Japanese Patent Application Laid-Open No. 2012-133303

[0227] ), etc.

[0223] As the retardation film, as long as it substantially has the above functions, there is no particular limitation on, for example, the retardation value, the arrangement angle, the three-dimensional birefringence, single layer or multiple layers, etc., and a known retardation film can be used.

[0224] The thickness of the retardation film is, for example, 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, further preferably 1 to 9 μm, and particularly preferably 3 to 8 μm.

[0225] Another example of the optical laminate of the present embodiment is shown in Figure 3 , Figure 3 The optical laminate 10B has a laminated structure in which an optical film 2, an adhesive sheet 1, and a release liner 3 are laminated in this order. The optical laminate 10B can be used in the form of an optical film with an adhesive sheet by peeling the release liner 3.

[0226] Examples of the constituent material of the release liner 3 include: plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films, porous materials such as paper, cloth, and non-woven fabrics, nets, foamed sheets, metal foils, and appropriate thin sheet materials such as their laminates. From the viewpoint of excellent surface smoothness, a plastic film is preferably used.

[0227] As the plastic film, as long as it can protect the adhesive sheet 1, there is no particular limitation, and examples thereof include: polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate copolymer film, etc.

[0228] The thickness of the release liner 3 is generally 5 to 200 μm, preferably about 5 to 100 μm. As needed, the release liner 3 can be subjected to release and antifouling treatments using silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based release agents, silica powder, etc., and antistatic treatments such as coating type, mixing type, evaporation coating type, etc. In particular, by appropriately performing release treatments such as silicone treatment, long-chain alkyl treatment, fluorine treatment, etc. on the surface of the release liner 3, the peelability from the adhesive sheet 1 can be further improved.

[0229] It should be noted that, as described above, the release film used in the production of the adhesive sheet 1 can be used as the release liner 3.

[0230] Another example of the optical laminate of the present embodiment is shown in Figure 4 , Figure 4 The optical laminate 10C has a laminated structure in which a polarizing film 2A, an interlayer adhesive 4, a retardation film 2B, an adhesive sheet 1, and a release liner 3 are laminated in sequence. The optical laminate 10C can be used, for example, by attaching it to an image forming layer after peeling off the release liner 3.

[0231] As the interlayer adhesive 4, a known adhesive can be used, or the adhesive sheet 1 can be used as the interlayer adhesive 4.

[0232] Another example of the optical laminate of the present embodiment is shown in Figure 5 , Figure 5 The optical laminate 10D has a polarizing film 2A, a first retardation film 2B, and a second retardation film 2C as the optical film 2. Specifically, the optical laminate 10D has a laminated structure in which a polarizing film 2A, an interlayer adhesive 4A, a first retardation film 2B, an interlayer adhesive 4B, a second retardation film 2C, an adhesive sheet 1, and a release liner 3 are laminated in sequence. The optical laminate 10D can be used, for example, by attaching it to an image forming layer after peeling off the release liner 3.

[0233] As the interlayer adhesives 4A and 4B, known adhesives can be used. The adhesive sheet 1 can also be used as the interlayer adhesives 4A and 4B.

[0234] In the optical laminate 10D, the first retardation film 2B is, for example, a half-wave plate formed by orienting and immobilizing a liquid crystal material. The thickness of the first retardation film 2B is, for example, 5 μm or less, can be 1 μm or less, and further can be 0.5 μm or less.

[0235] The second retardation film 2C is, for example, a quarter-wave plate formed by orienting and immobilizing a liquid crystal material. The thickness of the second retardation film 2C is, for example, 5 μm or less, can be 1 μm or less, and further can be 0.5 μm or less.

[0236] In the optical laminate 10D, the adhesive sheet 1 is in contact with the second retardation film 2C. According to the research of the present inventors, when the thickness of the second retardation film 2C in contact with the adhesive sheet 1 is as thin as about 5 μm or less, when the optical laminate 10D is peeled off from an adherend such as an image forming layer, there is a tendency for stress to concentrate near the second retardation film 2C. In the present embodiment, since the adhesive sheet 1 can be easily peeled off from the adherend, there is a tendency that even if stress concentrates near the second retardation film 2C, delamination (for example, delamination between the interlayer adhesive 4B and the second retardation film 2C) is not likely to occur.

[0237] Another example of the optical laminate of the present embodiment is shown in Figure 6 , Figure 6 The optical laminate 10E has a laminated structure in which a protective film 5, a polarizing film 2A, an interlayer adhesive 4A, a first retardation film 2B, an interlayer adhesive 4B, a second retardation film 2C, an adhesive sheet 1, and a release liner 3 are laminated in this order. The optical laminate 10E can be used by attaching it to, for example, an image forming layer after peeling off the release liner 3.

[0238] The protective film 5 has a function of protecting the outermost optical film 2 (polarizing film 2A) during the circulation and storage of the optical laminate 10E and in the state where the optical laminate 10E is introduced into an image display device. In addition, in the state of being introduced into the image display device, the protective film 5 can function as a window to the external space. The protective film 5 is typically a resin film. The resin constituting the protective film 5 is, for example, a polyester such as PET, a polyolefin such as polyethylene and polypropylene, acrylic acid, cycloolefin, polyimide, and polyamide, and preferably a polyester. However, the protective film 5 is not limited to the above examples, and the protective film 5 can be a glass film or a laminated film including a glass film. Surface treatments such as antiglare, antireflection, and antistatic can be applied to the protective film 5.

[0239] The protective film 5 can be joined to the optical film 2 via an arbitrary adhesive, or can be joined using the adhesive sheet 1.

[0240] The optical laminate of the present embodiment can be circulated and stored, for example, in the form of a wound body obtained by winding a strip-shaped optical laminate or in the form of a single-sheet optical laminate.

[0241] The optical laminate of the present embodiment is typically used in an image display device. The image display device is, for example, an EL display such as a liquid crystal display, an organic EL display, and an inorganic EL display.

[0242] [Characteristics of the optical laminate]

[0243] The adhesive sheet 1 included in the optical laminate according to the present embodiment has a tendency to be easily peeled from the adherend. As an example, the adhesive force P0 obtained by the following Test 1 for the optical laminate is preferably 10.0 N / 25 mm or less.

[0244] Test 1: The optical laminate was pasted on the non-alkali glass via the adhesive sheet 1 after 7 days from production. The optical laminate was peeled from the non-alkali glass at a peeling speed of 300 mm / min and a peeling angle of 90°. The force (adhesive force P0) required at this time was measured.

[0245] Specifically, Test 1 was carried out by the following method. First, a strip of 150 mm in length and 25 mm in width was cut out from the optical laminate having the adhesive sheet 1 after 7 days from production as a test piece. Next, the test piece was pasted on the non-alkali glass via the adhesive sheet 1. The non-alkali glass is a glass that substantially does not contain an alkali component (alkali metal oxide). Specifically, the weight ratio of the alkali component in the glass is, for example, 1000 ppm or less, and further 500 ppm or less. The non-alkali glass is, for example, plate-shaped and has a thickness of 0.5 mm or more.

[0246] The pasting of the test piece to the non-alkali glass was carried out, for example, using a rubber roller so as not to allow air bubbles to be mixed between the non-alkali glass and the adhesive sheet 1. After pasting the test piece, it was left at room temperature (25 °C) for 15 minutes to allow the adhesive sheet 1 to be closely attached to the non-alkali glass. Next, the test piece was peeled from the non-alkali glass at a peeling speed of 300 mm / min and a peeling angle of 90° (measurement length: 80 mm). At this time, the force required to peel the test piece from the non-alkali glass was measured at intervals of 1 time / 0.5 s. The average value of the obtained measured values was determined as the adhesive force P0.

[0247] The adhesive force P0 is preferably 8.0 N / 25 mm or less, and may also be 7.0 N / 25 mm or less, 6.0 N / 25 mm or less, 5.0 N / 25 mm or less, 4.0 N / 25 mm or less, 3.0 N / 25 mm or less, and further may be 2.0 N / 25 mm or less. The lower limit of the adhesive force P0 is, for example, 0.5 N / 25 mm or more, and may be 1.0 N / 25 mm or more.

[0248] In addition, the adhesive force P1 obtained by the following Test 2 for the optical laminate is preferably 10.0 N / 25 mm or less.

[0249] Test 2: The optical laminate was pasted on the non-alkali glass via the adhesive sheet 1 after 7 days from production and left in an environment of 60 °C for 2 hours. The optical laminate was peeled from the non-alkali glass at a peeling speed of 300 mm / min and a peeling angle of 90°. The force (adhesive force P1) required at this time was measured.

[0250] Test 2 can be carried out in the same manner as Test 1, except that the test piece is adhered to the E-glass and left at room temperature for 15 minutes and then further left in an environment of 60°C for 2 hours.

[0251] The adhesive force P1 is preferably 9.0 N / 25 mm or less, and may also be 8.0 N / 25 mm or less, 7.0 N / 25 mm or less, 6.0 N / 25 mm or less, and further may be 5.0 N / 25 mm or less. The lower limit of the adhesive force P1 is, for example, 1.0 N / 25 mm or more, and may be 3.0 N / 25 mm or more.

[0252] The value (P1 - P0) obtained by subtracting the adhesive force P0 from the adhesive force P1 is, for example, 5.0 N / 25 mm or less, and may be 4.0 N / 25 mm or less, and further may be 3.0 N / 25 mm or less. The lower limit of the value (P1 - P0) is not particularly limited, and is, for example, 0.5 N / 25 mm or more.

[0253] (Embodiment of the image display device)

[0254] An example of the image display device of the present embodiment is shown in Figure 7 , Figure 7 The image display device 11 has a laminated structure in which a protective film 5, a polarizing film 2A, an interlayer adhesive 4A, a first retardation film 2B, an interlayer adhesive 4B, a second retardation film 2C, an adhesive sheet 1, an image forming layer (for example, an organic EL layer or a liquid crystal layer) 6, and a substrate 7 are laminated in this order. The image display device 11 has Figures 3 - 6 the optical laminates 10B, 10C, 10D, 10E (excluding the release liner 3). The substrate 7 and the image forming layer 6 may have the same configurations as the substrate and the image forming layer provided in a known image display device, respectively.

[0255] Figure 7 The image display device 11 may be an organic EL display or a liquid crystal display. However, the image display device 11 is not limited to this example, and the image display device 11 may be an electroluminescent (EL) display, a plasma display (PD), a field emission display (FED: Field Emission Display), etc. The image display device 11 can be used for home appliance applications, in-vehicle applications, public information display (PID) applications, etc.

[0256] The image display device of the present embodiment may have any configuration as long as it includes the optical laminate of the present embodiment.

[0257] Examples

[0258] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the examples shown below.

[0259] <Fabrication of Polarizing Film>

[0260] [Fabrication of Polarizer]

[0261] A long strip of polyvinyl alcohol (PVA) - based resin film (manufactured by Kuraray, product name "PE3000", thickness 30 μm) was unidirectionally stretched along the length direction (total stretching ratio 5.9 times) using a roller stretching machine, and at the same time, the above - mentioned resin film was successively subjected to swelling, dyeing, cross - linking, cleaning, and drying treatments to fabricate a polarizer with a thickness of 12 μm. In the swelling treatment, the above - mentioned resin film was treated in pure water at 20°C while being stretched 2.2 times. In the dyeing treatment, the above - mentioned resin film was treated in an aqueous solution at 30°C containing iodine and potassium iodide in a weight ratio of 1:7 while being stretched 1.4 times. The iodine concentration in the aqueous solution was adjusted so that the monomer transmittance of the fabricated polarizer reached 45.0%. The cross - linking treatment was a two - stage treatment. In the first - stage cross - linking treatment, the above - mentioned resin film was treated in an aqueous solution at 40°C in which boric acid and potassium iodide were dissolved while being stretched 1.2 times. The content rate of boric acid in the aqueous solution used in the first - stage cross - linking treatment was 5.0% by weight, and the content rate of potassium iodide was set to 3.0% by weight. In the second - stage cross - linking treatment, the above - mentioned resin film was treated in an aqueous solution at 65°C in which boric acid and potassium iodide were dissolved while being stretched 1.6 times. The content rate of boric acid in the aqueous solution used in the second - stage cross - linking treatment was 4.3% by weight, and the content rate of potassium iodide was set to 5.0% by weight. In the cleaning treatment, an aqueous solution of potassium iodide at 20°C was used, and the content rate of potassium iodide in the aqueous solution used in the cleaning treatment was set to 2.6% by weight. The drying treatment was carried out under drying conditions of 70°C and 5 minutes.

[0262] [Fabrication of Polarizing Film]

[0263] Using a polyvinyl alcohol - based adhesive, triacetyl cellulose (TAC) films (manufactured by Konica Minolta, product name "KC2UA", thickness 25 μm) were respectively adhered to each main surface of the above - fabricated polarizer. Among them, a hard coat (thickness 7 μm) was formed on the main surface of the TAC film adhered to one main surface, on the side opposite to the polarizer side. In this way, a polarizing film having a structure of protective layer (with hard coat) / polarizer / protective layer (without hard coat) was obtained.

[0264] <Fabrication of First - Order Retardation Film>

[0265] As a liquid crystal compound, a polymerizable liquid crystal material (manufactured by BASF, Paliocolor LC242) showing a nematic liquid crystal phase was prepared. 10 g of the above polymerizable liquid crystal material and 3 g of a corresponding photoinitiator (manufactured by BASF, IRGACURE 907) were dissolved in 40 g of toluene to prepare a liquid crystal composition as a coating solution. Next, the coating solution was applied to the surface of a PET film which was a substrate film obtained by subjecting the surface to an alignment treatment, and dried by heating at 90 °C for 2 minutes, thereby forming a liquid crystal layer. Next, the formed liquid crystal layer was irradiated with light of 1 mJ / cm 2 to cure the liquid crystal layer, thereby forming a first retardation film as a liquid crystal alignment fixing layer. The thickness of the first retardation film was 2 μm, and the in-plane retardation Re(550) was 280 nm, that is, the formed first retardation film was a λ / 2 wave plate.

[0266] <Fabrication of the second retardation film>

[0267] A liquid crystal alignment fixing layer with a thickness of 1 μm was formed by adjusting the coating amount of the coating solution, and the second retardation film was formed in the same manner as the fabrication of the first retardation film except for this. The in-plane retardation Re(550) of the second retardation film was 140 nm, that is, the formed second retardation film was a λ / 4 wave plate.

[0268] <Fabrication of the circularly polarizing film>

[0269] [Fabrication of the ultraviolet curable adhesive composition α]

[0270] 29.2 parts by weight of hydroxyethyl acrylamide (HEAA), 16.7 parts by weight of 2-acetoacetoxyethyl methacrylate (AAEM), 33.3 parts by weight of acryloylmorpholine (ACMO), 20.8 parts by weight of tripropylene glycol diacrylate (manufactured by Toagosei Co., Ltd., ARONIX M-220) as a crosslinking agent, 3 parts by weight of 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one (manufactured by BASF, IRGACURE 907) as a photoinitiator, and 3 parts by weight of diethyl thioxanthone (manufactured by Nippon Kayaku Co., Ltd., KAYACURE DETX-S) as a radical polymerization initiator were mixed and stirred for 1 hour, thereby fabricating the ultraviolet curable adhesive composition α.

[0271] [Fabrication of the interlayer adhesive]

[0272] In a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a condenser, a monomer mixture containing 79.9 parts by weight of butyl acrylate, 15 parts by weight of benzyl acrylate, 5 parts by weight of acrylic acid, and 0.1 part by weight of 4-hydroxybutyl acrylate was added. Next, 0.1 part by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was added together with ethyl acetate relative to 100 parts by weight of the monomer mixture. After replacing the nitrogen in the flask by introducing nitrogen while slowly stirring, the liquid temperature in the flask was maintained at around 55 °C, and a polymerization reaction was carried out for 7 hours. Next, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30% by weight, and a solution of a (meth)acrylic polymer for an interlayer adhesive was obtained. The weight-average molecular weight of the obtained polymer was 2.2 million.

[0273] Next, in the obtained solution of the (meth)acrylic polymer, 0.5 part by weight of trimethylolpropane / toluene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), 0.1 part by weight of benzoyl peroxide as a peroxide crosslinking agent, 0.2 part by weight of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403"), and 0.5 part by weight of a polyether compound having a reactive silyl group (manufactured by Kaneka Corporation, Silyl SAT10) were mixed relative to 100 parts by weight of the solid content of the solution, and an adhesive composition for an interlayer adhesive was obtained. The prepared adhesive composition was applied to the release surface of a 38-μm-thick polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Polyester Film, MRF38) which was subjected to a silicone treatment as a release surface so that the thickness of the dried layer reached 12 μm, and a drying treatment was carried out at 155 °C for 1 minute to form an interlayer adhesive.

[0274] [Production of circularly polarizing film]

[0275] The first retardation film (λ / 2 wave plate) was adhered to the exposed surface of the protective layer (without hard coat) in the polarizing film using an ultraviolet curable adhesive composition α. The adhesion was carried out as follows. First, the adhesive composition α was applied to the above-mentioned exposed surface of the polarizing film with a coating thickness of 0.5 μm by an MCD coater (manufactured by Fuji Machine Co., Ltd.). Next, after the first retardation film was placed on the coated film, ultraviolet rays were irradiated from both sides to cure the adhesive composition α. The first retardation film was placed so that the λ / 2 wave plate was in contact with the coated film. Using a metal halide lamp, the peak illuminance was 1600 mW / cm 2 and the cumulative irradiation dose was 1000 / mJ / cm 2Ultraviolet rays were irradiated under the condition of (wavelength 380 to 440 nm). After the irradiation of ultraviolet rays was completed, hot air drying was carried out at 70 °C for 3 minutes. Next, the base film used for the production of this film was peeled off from the first retardation film, and an interlayer adhesive was bonded to the peeled surface. Next, the film used for the production of this adhesive was peeled off from the interlayer adhesive, and the second retardation film (quarter-wave plate) was bonded to the peeled surface. Thus, a circularly polarized film having a polarizing film, a first retardation film, and a second retardation film was obtained.

[0276] <Production of (meth)acrylic polymer A1>

[0277] A monomer mixture containing 81.9 parts by weight of butyl acrylate (BA), 4.8 parts by weight of acrylic acid (AA), 0.1 part by weight of 4-hydroxybutyl acrylate (HBA), and 13.2 parts by weight of benzyl acrylate (BzA) was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a condenser. Further, 0.1 part by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added together with ethyl acetate relative to 100 parts by weight of the monomer mixture. After nitrogen substitution was carried out by introducing nitrogen while slowly stirring, the liquid temperature in the flask was maintained at around 55 °C, and a polymerization reaction was carried out for 7 hours. Then, ethyl acetate was added to the obtained reaction solution to adjust the solid content concentration to 30%, and a solution of (meth)acrylic polymer A1 was obtained.

[0278] <Production of (meth)acrylic polymers A2 to A3>

[0279] The monomers and polymerization initiators used were changed as shown in Table 1. Except for this, solutions of (meth)acrylic polymers A2 to A3 were respectively prepared by the same method as (meth)acrylic polymer A1.

[0280] [Table 1]

[0281]

[0282] The abbreviations in Table 1 are as follows.

[0283] BA: n-Butyl acrylate

[0284] AA: Acrylic acid

[0285] HBA: 4-Hydroxybutyl acrylate

[0286] BzA: Benzyl acrylate

[0287] AIBN: Azide polymerization initiator, 2,2'-azobisisobutyronitrile (manufactured by Kishida Chemical Co., Ltd.)

[0288] (Example 1)

[0289] [Preparation of Adhesive Composition]

[0290] A solvent-based adhesive composition was obtained by mixing a (meth)acrylic polymer, an isocyanate crosslinking agent, a polyhydroxyalkylamine compound, a polyether compound, etc. so as to have the composition shown in Table 2 below.

[0291] [Preparation of Adhesive Sheet]

[0292] The adhesive composition was coated on the surface of a PET film as a base film (release liner) so that the thickness of the dried adhesive sheet reached 20 μm. A jet coater was used for coating the adhesive composition. The obtained coated film was dried in an air-circulation type constant temperature oven at 95°C for 1 minute, thereby forming an adhesive sheet.

[0293] [Preparation of Optical Laminate]

[0294] The produced adhesive sheet was transferred from the release film and pasted onto the second retardation film in the above-mentioned circularly polarized film, thereby obtaining an optical laminate. This optical laminate has the same structure as Figure 5 the optical laminate 10D.

[0295] (Examples 2 to 26 and Comparative Examples 1 to 23)

[0296] The composition of the adhesive composition was changed as shown in Tables 2 to 4. Except for this, adhesive compositions, adhesive sheets, and optical laminates were respectively produced for Examples 2 to 26 and Comparative Examples 1 to 23 by the same method as in Example 1.

[0297] [Evaluation]

[0298] <Weight-average Molecular Weight (Mw) of (Meth)acrylic Polymer>

[0299] The weight-average molecular weight (Mw) of the obtained (meth)acrylic polymer was measured by GPC (gel permeation chromatography).

[0300] · Analytical apparatus: HLC-8120GPC manufactured by Tosoh Corporation

[0301] · Column: G7000H manufactured by Tosoh Corporation XL +GMH XL +GMH XL

[0302] · Column size: Each Total 90 cm

[0303] · Column temperature: 40°C

[0304] · Flow rate: 0.8 ml / min

[0305] · Injection volume: 100 μl

[0306] · Eluent: Tetrahydrofuran

[0307] · Detector: Differential refractometer (RI)

[0308] · Standard sample: Polystyrene

[0309] <Adhesive force>

[0310] The adhesive forces P0 and P1 were measured by conducting the above Tests 1 and 2 on the optical laminates of the examples and comparative examples. In Tests 1 and 2, an alkali-free glass (manufactured by Corning Incorporated, trade name “Eagle XG”) with a thickness of 0.7 mm was used. The operation of peeling the test piece from the alkali-free glass was carried out using a tensile testing machine (manufactured by Shimadzu Corporation, Autograph SHIMAZU AG-X).

[0311] <Reusability>

[0312] The above Test 2 was conducted on the optical laminates of the examples and comparative examples, and the reusability was evaluated according to the following criteria.

[0313] (Evaluation criteria)

[0314] A: The optical laminate can be easily peeled off from the alkali-free glass.

[0315] B: The surface of the optical laminate after peeling off from the alkali-free glass is rough, but there is no problem in actual use.

[0316] C: Interlayer peeling occurs in the optical laminate, and a part of the optical laminate remains on the alkali-free glass.

[0317] <Durability>

[0318] The optical laminates of the examples and comparative examples were fixed to the surface of an alkali-free glass (manufactured by Corning Incorporated, trade name “Eagle XG”) with a thickness of 0.7 mm via an adhesive sheet. The fixing of the optical laminate was carried out in an atmosphere of 23°C and 50% RH. Next, after being treated in an autoclave at 50°C and 5 atmospheres (absolute pressure) for 15 minutes and left to cool to 23°C until the bonding of the optical laminate to the alkali-free glass was stabilized, it was placed in a heated and humidified atmosphere of 60°C and 95% RH for 500 hours. After the placement, it was returned to an atmosphere of 23°C and 50% RH, and it was visually observed to confirm whether the optical laminate peeled off from the alkali-free glass and whether foaming occurred between the alkali-free glass and the optical laminate, and the durability was evaluated according to the following criteria.

[0319] (Evaluation Criteria)

[0320] A: No visible changes in appearance such as foaming or peeling were observed.

[0321] B: Slight peeling or foaming was observed at the ends, but within the range where there are no problems in actual use.

[0322] C: Obvious peeling or foaming was observed at the ends, which causes problems in actual use.

[0323] <Whitening>

[0324] The degree of whitening of the adhesive sheets prepared in the examples and comparative examples was evaluated based on haze. Based on JIS K7136:1981, the haze of the adhesive sheets was measured using a haze meter HZ-V3 manufactured by SUGA Test Instruments in an atmosphere of 25°C. The measurement was carried out in a state where 4 layers of the adhesive sheet to be evaluated were laminated on a glass slide S012140 (thickness 1.3 mm) manufactured by Matsunami Glass Industry Co., Ltd. (total thickness 80 μm). The measured value V at this time was converted to a value equivalent to a total thickness of 75 μm by the formula: V × 75 / 80.

[0325] (Evaluation Criteria)

[0326] A: The measured haze is less than 1%.

[0327] B: The measured haze is 1% or more.

[0328] <Pot Life>

[0329] The adhesive compositions prepared in the examples and comparative examples were placed in an environment of 30°C for 6 hours. The viscosity of the adhesive composition was measured immediately after preparation and after standing, and the pot life was evaluated according to the following criteria.

[0330] (Evaluation Criteria)

[0331] A: The viscosity of the adhesive composition hardly increases.

[0332] B: The increase in the viscosity of the adhesive composition is less than 20 P, and there are no problems in actual use.

[0333] C: The increase in the viscosity of the adhesive composition is 20 P or more.

[0334] <Curing>

[0335] The adhesive force P2 of the optical laminates of the examples and comparative examples was determined by the following Test 3. The adhesive force P0 and the adhesive force P2 were compared, and the progress rate of the crosslinking reaction in the cured adhesive sheet was evaluated according to the following criteria. Note that Test 3 was the same as Test 1 except that an adhesive sheet 14 days after production was used instead of an adhesive sheet 7 days after production.

[0336] Test 3: An optical laminate was adhered to a non-alkali glass via an adhesive sheet 14 days after production. The optical laminate was peeled from the non-alkali glass at a peeling speed of 300 mm / min and a peeling angle of 90°. The force (adhesive force P2) required at this time was measured.

[0337] (Evaluation criteria)

[0338] A: The value of the adhesive force P2 was substantially the same as the adhesive force P0, and the crosslinking reaction in the cured adhesive sheet was fast enough.

[0339] B: The value of the adhesive force P2 was significantly different from the adhesive force P0, and the crosslinking reaction in the cured adhesive sheet was slow.

[0340]

[0341]

[0342]

[0343] The abbreviations in Tables 2 to 4 are as follows.

[0344] D101E: Trimethylolpropane / Toluene diisocyanate trimer adduct (manufactured by Mitsui Chemicals, Inc., trade name “Takenate D-101E”)

[0345] EDP-300: N,N,N',N’-tetrakis(2-hydroxypropyl)ethylenediamine (manufactured by ADEKA Corporation, trade name “EDP-300”)

[0346] EDP-450: Polyoxypropylene condensate of ethylenediamine (manufactured by ADEKA Corporation, trade name “EDP-450”, molecular weight 450)

[0347] EDP-1100: Polyoxypropylene condensate of ethylenediamine (manufactured by ADEKA Corporation, trade name “EDP-1100”, molecular weight 1100)

[0348] SAT10: Polyether compound having an alkoxysilyl group (manufactured by KANEKA CORPORATION, trade name “SilylSAT10”)

[0349] KBM403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM-403")

[0350] As can be seen from Tables 2 to 4, compared with the comparative examples, the optical laminates of the examples having the adhesive sheet formed from the adhesive composition of the present embodiment gave good results in terms of reworkability. From these results, it can be considered that the adhesive composition of the present embodiment is suitable for producing an adhesive sheet with improved reworkability. It should be noted that in all of the optical laminates of the comparative examples, interlayer peeling occurred between the interlayer adhesive and the second retardation film during Test 2.

[0351] Industrial Applicability

[0352] The adhesive composition of the present invention can be suitably used for producing an adhesive sheet for an image display device such as an EL display or a liquid crystal display.

Claims

1. An adhesive composition comprising: (Meth)acrylic polymer (A), An isocyanate crosslinking agent in an amount of 2 parts by weight or more based on 100 parts by weight of the (meth)acrylic polymer (A), A polyhydroxyalkylamine compound, and A polyether compound.

2. The adhesive composition according to claim 1, wherein, The polyether compound further has a silicon atom, and a hydroxyl group and / or a hydrolyzable group bonded to the silicon atom.

3. The adhesive composition according to claim 1, wherein, The compounding amount of the polyether compound is 0.1 to 5 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer (A).

4. The adhesive composition according to claim 1, wherein, The molecular weight of the polyhydroxyalkylamine compound is 1500 or less.

5. The adhesive composition according to claim 1, wherein, The compounding amount of the polyhydroxyalkylamine compound is 0.01 to 5 parts by weight with respect to 100 parts by weight of the (meth)acrylic polymer (A).

6. The adhesive composition according to claim 1, wherein, The compounding amount of the isocyanate crosslinking agent is 13 parts by weight or less with respect to 100 parts by weight of the (meth)acrylic polymer (A).

7. The adhesive composition according to claim 1, wherein, The (meth)acrylic polymer (A) has a structural unit derived from a carboxyl group-containing monomer.

8. The adhesive composition according to claim 7, wherein, In the (meth)acrylic polymer (A), the content of the structural unit derived from the carboxyl group-containing monomer is 3% by weight or more.

9. The adhesive composition according to claim 1, wherein, The (meth)acrylic polymer (A) has a structural unit derived from an aromatic ring-containing monomer.

10. The adhesive composition according to claim 1, wherein, The weight average molecular weight of the (meth)acrylic polymer (A) is 1,000,000 or more.

11. The adhesive composition according to claim 1, wherein, The isocyanate crosslinking agent is a toluene diisocyanate crosslinking agent.

12. The adhesive composition according to claim 1, further comprising a silane coupling agent.

13. An adhesive sheet formed from the adhesive composition according to any one of claims 1 to 12.

14. An optical laminate having: The adhesive sheet according to claim 13, and An optical film.

15. The optical laminate according to claim 14, having a polarizing film, a first retardation film, and a second retardation film as the optical films.

16. The optical laminate according to claim 15, wherein, The adhesive sheet is in contact with the second retardation film. The thickness of the second retardation film is 5 μm or less.

17. An image display device including the optical laminate according to claim 14.

Images