Optical laminate film with pressure-sensitive adhesive layer and image display device

Abstract

To provide an optical laminated film with a pressure-sensitive adhesive layer capable of suppressing the degree of a recess which may occur during storage.SOLUTION: In the optical laminated film with the adhesive layer, the thickness of the optical film is 80 μm or less, the thickness of the protective film is 30 μm or more, and the tensile modulus of the protective film is 1GPa or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical laminate film with a pressure-sensitive adhesive layer and an image display device. [Background technology]

[0002] Various thin image display devices, such as liquid crystal displays and organic EL displays, typically have a laminated structure including an image-forming layer, such as a liquid crystal layer or an organic EL light-emitting layer, and one or more optical films. A pressure-sensitive adhesive layer is generally used to bond the various layers constituting the image display device, and a widely used method for manufacturing an image display device involves attaching an optical film with a pressure-sensitive adhesive layer, which has a pressure-sensitive adhesive layer on at least one side, to the image-forming layer (see Patent Document 1). Furthermore, when supplying an optical film with a pressure-sensitive adhesive layer, the optical film may also be supplied as a pressure-sensitive adhesive layer-attached optical laminate film further provided with a separator to protect the pressure-sensitive adhesive layer and / or a protective film to protect the optical film. The separator is peeled off when the optical laminate film is used, for example, when it is attached to the image-forming layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-28573 Summary of the Invention [Problem to be solved by the invention]

[0004] Prior to combining an optical laminate film with a pressure-sensitive adhesive layer with an image-forming layer or the like to manufacture an image display device, the optical laminate film is typically stored in a rolled state or laminated as sheets. However, the inventors' investigations have revealed that the storage tends to cause minute depressions in the pressure-sensitive adhesive layer, and that this tendency is exacerbated when a thin optical film is used. These depressions can become optical defects. Furthermore, similar depressions can occur during storage of the image display device after its manufacture. Patent Document 1 does not take these points into consideration.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive layer-attached optical laminate film that can suppress the degree of depression that may occur during storage. [Means for solving the problem]

[0006] The present invention provides A pressure-sensitive adhesive layer-attached optical laminate film in which a protective film, an optical film, a pressure-sensitive adhesive layer, and a separator are laminated in this order, The optical film has a thickness of 80 μm or less, a pressure-sensitive adhesive layer-attached optical laminate film, wherein the protective film has a thickness of 30 μm or more and a tensile modulus of elasticity of 1 GPa or more; to provide.

[0007] In another aspect, the present invention provides a method for producing a composition comprising: an image display device comprising the pressure-sensitive adhesive layer-attached optical laminate film of the present invention except for the separator; to provide. [Effects of the Invention]

[0008] In the optical laminated film with a pressure-sensitive adhesive layer according to the present invention, a thin optical film having a thickness of 80 μm or less can be obtained. By setting both the thickness and tensile modulus of the protective film to a predetermined value or more while providing the optical film, the pressure generated by the trapped foreign matter can be dispersed, and the progression of depressions that may occur in the pressure-sensitive adhesive layer due to the trapped foreign matter can be suppressed. Therefore, the optical laminate film with a pressure-sensitive adhesive layer according to the present invention can suppress the degree of depressions that may occur during storage. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of a pressure-sensitive adhesive layer-attached optical laminate film of the present invention. [Figure 2A] FIG. 2A is a schematic diagram illustrating a method for measuring the creep amount ΔCr for a pressure-sensitive adhesive layer. [Figure 2B] FIG. 2B is a schematic diagram for explaining a method for measuring the creep amount ΔCr for the pressure-sensitive adhesive layer. [Figure 3] FIG. 3 is a cross-sectional view schematically showing an example of an image display device of the present invention. [Figure 4] FIG. 4 is a schematic diagram for explaining the method of producing the λ / 4 plate and the λ / 2 plate used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings, but is not limited to the following embodiments.

[0011] An example of the pressure-sensitive adhesive layer-attached optical laminate film of the present invention is shown in Figure 1. The pressure-sensitive adhesive layer-attached optical laminate film 1 of Figure 1 comprises a protective film 2, an optical film 3, a pressure-sensitive adhesive layer 4, and a separator 5. The protective film 2, the optical film 3, the pressure-sensitive adhesive layer 4, and the separator 5 are laminated in this order. The thickness of the optical film 3 is 80 µm or less. The thickness of the protective film 2 is 30 µm or more. The tensile modulus of the protective film 2 is 1 GPa or more. The tensile modulus of the protective film 2 is a value at room temperature (23°C).

[0012] [Optical film] The optical film 3 is, for example, a polarizing film or a retardation film. The optical film 3 may be a laminated film or an optical laminate including a polarizing film and / or a retardation film. However, the optical film 3 is not limited to the above examples. The optical film 3 may include a glass film.

[0013] The thickness of the optical film 3 is 80 μm or less. According to the investigations of the present inventors, when the optical laminate film 1 includes a thinned optical film 3 having a thickness of 80 μm or less, the degree of depression that may occur in the pressure-sensitive adhesive layer 4 during storage tends to increase. However, the optical laminate film 1 includes the thinned optical film 3, and yet can suppress the degree of depression that may occur in the pressure-sensitive adhesive layer 4 during storage. The thickness of the optical film 3 may be 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, or even 35 μm or less. The lower limit of the thickness of the optical film 3 is, for example, 1 μm or more.

[0014] The polarizing film includes a polarizer. A polarizer protective film may be bonded to at least one surface of the polarizer. Any pressure-sensitive adhesive or adhesive can be used to bond the polarizer and the polarizer protective film. The polarizer is typically a polyvinyl alcohol (PVA) film in which iodine has been oriented by stretching, such as in-air stretching (dry stretching) or stretching in boric acid water.

[0015] A retardation film is a film having birefringence in the in-plane direction and / or the thickness direction, and is, for example, a stretched resin film or a film in which a liquid crystal material is oriented and fixed.

[0016] Examples of retardation films include λ / 4 plates, λ / 2 plates, anti-reflection retardation films (see, for example, paragraphs 0221, 0222, and 0228 of JP 2012-133303 A), viewing angle compensation retardation films (see, for example, paragraphs 0225 and 0226 of JP 2012-133303 A), and tilted orientation retardation films for viewing angle compensation (see, for example, paragraph 0227 of JP 2012-133303 A). However, the retardation film is not limited to the above examples as long as it has birefringence in the in-plane direction and / or the thickness direction. There are also no limitations on the retardation value, arrangement angle, three-dimensional birefringence, whether the retardation film is single-layer or multi-layer, etc. of the retardation film. Known films can be used as the retardation film.

[0017] The thickness of the retardation film is, for example, 50 μm or less.

[0018] The optical film 3 may be a single-layer film or a multi-layer film composed of two or more layers.

[0019] [Protection film] The protective film 2 has a function of protecting the optical film 2 during distribution and storage of the optical laminate film 1 and when the optical laminate film 1 is incorporated into an image display device. The protective film 2 may be a film that functions as a window to the external space when incorporated into an image display device. The protective film 2 is typically a resin film. Examples of resins constituting the protective film 2 include polyesters such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, acrylics, cycloolefins, polyimides, and polyamides, with polyester being preferred. In other words, the protective film 2 may be a polyester film. However, the protective film 2 is not limited to the above examples. The protective film may be a glass film or a laminate film including a glass film. The protective film 2 may be subjected to surface treatments such as anti-glare, anti-reflection, and anti-static.

[0020] The thickness of the protective film 2 is 30 μm or more. The thickness of the protective film 2 may be 35 μm or more, 40 μm or more, 45 μm or more, or even 50 μm or more. The upper limit of the thickness of the protective film 2 is, for example, 100 μm or less.

[0021] The tensile modulus of the protective film 2 is 1 GPa or more. The tensile modulus of the protective film 2 may be 2 GPa or more, 3 GPa or more, or even 4 GPa or more. The upper limit of the tensile modulus of the protective film 2 is, for example, 100 GPa or less.

[0022] The protective film 2 may be bonded to the optical film 3 by an optional pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer bonding the protective film 2 and the optical film 3 may have a structure described in the description of the pressure-sensitive adhesive layer 4 below.

[0023] [Adhesive layer] The pressure-sensitive adhesive layer 4 is composed of various pressure-sensitive adhesive compositions, such as acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, vinyl alkyl ether pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, polyamide pressure-sensitive adhesives, urethane pressure-sensitive adhesives, fluorine-based pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, and polyether pressure-sensitive adhesives. Because of its excellent properties such as optical transparency, processability, durability, and adhesion, the pressure-sensitive adhesive layer 4 is preferably composed of an acrylic pressure-sensitive adhesive composition containing a (meth)acrylic polymer. In this specification, "(meth)acrylic" refers to acrylic and methacrylic. Furthermore, "(meth)acrylate" refers to acrylate and methacrylate.

[0024] The type of the adhesive composition constituting the adhesive layer 4 may be, for example, an emulsion type, a solvent type (a solution type), or the like. ), active energy ray curable type, and hot melt type (hot melt type). Among them, a solvent-type or active energy ray curable pressure-sensitive adhesive composition is preferred, and an active energy ray curable pressure-sensitive adhesive composition is preferred from the viewpoints of productivity and ease of forming a thick pressure-sensitive adhesive layer 4. However, the type of pressure-sensitive adhesive composition is not limited to the above examples.

[0025] The acrylic pressure-sensitive adhesive composition that can constitute the pressure-sensitive adhesive layer 4 will now be described.

[0026] [(Meth)acrylic polymer] The (meth)acrylic polymer preferably has, as a main unit, a structural unit derived from a (meth)acrylic monomer (A) having an alkyl group having 1 to 30 carbon atoms on the side chain. The alkyl group may be linear or branched. The (meth)acrylic polymer may have one or more structural units derived from the (meth)acrylic monomer (A). Examples of the (meth)acrylic monomer (A) include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, and isoheptyl (meth)acrylate. acrylate, 2-ethylhexyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, n-nonyl(meth)acrylate, isononyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, n-dodecyl(meth)acrylate (lauryl(meth)acrylate), n-tridecyl(meth)acrylate, and n-tetradecyl(meth)acrylate. In this specification, the term "main unit" refers to a unit that accounts for, for example, 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 94% by mass or more of all the structural units contained in the polymer.

[0027] The (meth)acrylic polymer may have a structural unit derived from a (meth)acrylic monomer (A) having a long-chain alkyl group on the side chain. An example of such a structural unit is n-dodecyl (meth)acrylate (lauryl (meth)acrylate). In this specification, the term "long-chain alkyl group" refers to an alkyl group having 6 to 30 carbon atoms.

[0028] The (meth)acrylic polymer may have a structural unit derived from a (meth)acrylic monomer (A) that, when made into a homopolymer, has a glass transition temperature (Tg) in the range of −70 to −20° C. An example of such a structural unit is 2-ethylhexyl acrylate.

[0029] The (meth)acrylic polymer may have a structural unit other than the structural unit derived from the (meth)acrylic monomer (A). The structural unit is derived from a monomer (B) copolymerizable with the (meth)acrylic monomer (A). The (meth)acrylic polymer may have one or more types of such structural units.

[0030] The monomer (B) is, for example, a (meth)acrylic monomer (C) having a hydroxy group. The (meth)acrylic monomer (C) is, for example, a hydroxyalkyl (meth)acrylate 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, or 12-hydroxylauryl (meth)acrylate, or (4-hydroxymethylcyclohexyl)-methyl acrylate. The durability of the pressure-sensitive adhesive layer 4 is improved. The (meth)acrylic monomer (C) is preferably 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate, since these can improve the properties and adhesion.

[0031] The monomer (B) may be a carboxyl group-containing monomer, an amino group-containing monomer, or an amide group-containing monomer. Use of these monomers (B) can improve the adhesion of the pressure-sensitive adhesive layer 4. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Examples of the amino group-containing monomer include N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate. Examples of the amide group-containing monomer include acrylamide-based 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-methylol(meth)acrylamide, N-methylol-N-propane(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; and N-vinyl group-containing lactam-based monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam.

[0032] The monomer (B) may be a polyfunctional monomer. By using a polyfunctional monomer, the gel fraction of the pressure-sensitive adhesive layer 4 and the cohesive strength can be adjusted. Examples of polyfunctional monomers include polyfunctional acrylates such as hexanediol di(meth)acrylate (1,6-hexanediol di(meth)acrylate), butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate; and divinylbenzene. Polyfunctional acrylates are preferably 1,6-hexanediol diacrylate and dipentaerythritol hexa(meth)acrylate.

[0033] Examples of the other monomer (B) other than those mentioned above include (meth)acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate; epoxy group-containing monomers such as glycidyl (meth)acrylate and methylglycidyl (meth)acrylate; sulfonic acid group-containing monomers such as sodium vinyl sulfonate; phosphoric acid group-containing monomers; (meth)acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate; p) (meth)acrylic acid esters having an alicyclic hydrocarbon group such as cyclopentyl acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc.; (meth)acrylic acid esters having an aromatic hydrocarbon group such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, etc.; vinyl esters such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene and vinyltoluene; olefins or dienes such as ethylene, propylene, butadiene, isoprene, isobutylene, etc.; vinyl ethers such as vinyl alkyl ether; and vinyl chloride.

[0034] the total content of structural units derived from the (meth)acrylic monomer (C) having a hydroxy group, the carboxyl group-containing monomer, the amino group-containing monomer, the amide group-containing monomer, and the polyfunctional monomer in the (meth)acrylic polymer is preferably 20 mass% or less, It is more preferably 10% by mass or less, even more preferably 8% by mass or less, and particularly preferably 5% by mass or less. When the (meth)acrylic polymer has such structural units, the total content of the structural units is, for example, 0.01% by mass or more, and may be 0.05% by mass or more.

[0035] The total content of the structural units derived from the other monomer (B) in the (meth)acrylic polymer is, for example, 30% by mass or less, may be 10% by mass or less, and is preferably 0% by mass (no such structural units are included).

[0036] The (meth)acrylic polymer can be formed by polymerizing one or more of the above-mentioned monomers by a known method. A monomer and a partial polymer of the monomer may also be polymerized. The polymerization can be carried out, for example, by solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, or active energy ray polymerization. Solution polymerization and active energy ray polymerization are preferred because they allow the formation of a pressure-sensitive adhesive layer 4 with excellent optical transparency. The polymerization is preferably carried out while avoiding contact between the monomer and / or the partial polymer and oxygen. For this purpose, for example, polymerization can be carried out in an inert gas atmosphere such as nitrogen, or polymerization in a state where oxygen is blocked by a resin film or the like. The (meth)acrylic polymer formed may be in any form, such as a random copolymer, a block copolymer, or a graft copolymer.

[0037] The polymerization system for forming the (meth)acrylic polymer may contain one or more polymerization initiators. The type of polymerization initiator can be selected depending on the polymerization reaction, and may be, for example, a photopolymerization initiator or a thermal polymerization initiator.

[0038] Examples of solvents used in solution polymerization include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. However, the solvent is not limited to the above examples. The solvent may be a mixed solvent of two or more solvents.

[0039] Examples of polymerization initiators used in solution polymerization include azo polymerization initiators, peroxide polymerization initiators, and redox polymerization initiators. Examples of peroxide polymerization initiators include dibenzoyl peroxide and t-butyl permaleate. Among these, the azo polymerization initiators disclosed in JP-A-2002-69411 are preferred. Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionate)dimethyl, and 4,4'-azobis-4-cyanovaleric acid. However, the polymerization initiator is not limited to the above examples. The amount of the azo polymerization initiator used is, for example, 0.05 to 0.5 parts by weight, or may be 0.1 to 0.3 parts by weight, per 100 parts by weight of the total amount of monomers.

[0040] The active energy rays used in the active energy ray polymerization include, for example, ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron beams, as well as ultraviolet rays. The active energy ray is preferably ultraviolet rays. Polymerization by irradiation with ultraviolet rays is also called photopolymerization. The polymerization system for the active energy ray polymerization typically contains a photopolymerization initiator. The polymerization conditions for the active energy polymerization are not limited as long as a (meth)acrylic polymer is formed.

[0041] Examples of the photopolymerization initiator include a benzoin ether-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, an α-ketol-based photopolymerization initiator, an aromatic sulfonyl chloride-based photopolymerization initiator, a photoactive oxime-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzyl-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, a ketal-based photopolymerization initiator, and a thioxanthone-based photopolymerization initiator, although the photopolymerization initiator is not limited to the above examples.

[0042] Examples of benzoin ether-based photopolymerization initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one, and anisole methyl ether. Examples of acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4-(t-butyl)dichloroacetophenone. Examples of α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. An example of a photoactive oxime-based photopolymerization initiator is 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. An example of a benzoin-based photopolymerization initiator is benzoin. An example of a benzyl-based photopolymerization initiator is benzil. An example of a benzophenone-based photopolymerization initiator is benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, or α-hydroxycyclohexyl phenyl ketone. An example of a ketal-based photopolymerization initiator is benzil dimethyl ketal. An example of a thioxanthone-based photopolymerization initiator is thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, or dodecylthioxanthone.

[0043] The amount of the photopolymerization initiator used is, for example, 0.01 to 1 part by weight, and may be 0.05 to 0.5 parts by weight, relative to 100 parts by weight of the total amount of the monomers.

[0044] The polyfunctional monomer (such as a polyfunctional acrylate) as the monomer (B) can be used in both solvent-based and active energy ray-curable pressure-sensitive adhesive compositions. When both the polyfunctional monomer and the photopolymerization initiator are used in a solvent-based pressure-sensitive adhesive composition, for example, the solvent may be removed by thermal drying, and then the pressure-sensitive adhesive composition may be cured by irradiation with active energy rays.

[0045] The weight average molecular weight (Mw) of the (meth)acrylic polymer is, for example, 1,000,000 to 2,500,000, and preferably 1,200,000 to 2,000,000, and more preferably 1,400,000 to 1,800,000, from the viewpoint of the durability and heat resistance of the pressure-sensitive adhesive layer 4. The weight average molecular weight (Mw) of the polymer and oligomer in this specification is a value (polystyrene equivalent) based on measurement by GPC (gel permeation chromatography).

[0046] The content of the (meth)acrylic polymer in the acrylic pressure-sensitive adhesive composition may be, for example, 50% by mass or more, 60% by mass or more, or even 70% by mass or more, in terms of solid content.

[0047] [(Meth)acrylic oligomer] The acrylic pressure-sensitive adhesive composition may further contain a (meth)acrylic oligomer. The inclusion of the (meth)acrylic oligomer reduces entanglement between molecular chains of the (meth)acrylic polymer, thereby improving the stress relaxation properties of the pressure-sensitive adhesive layer 4.

[0048] The (meth)acrylic oligomer may have the same composition as the above-mentioned (meth)acrylic polymer, except for the weight-average molecular weight (Mw). The weight-average molecular weight (Mw) of the (meth)acrylic oligomer may be, for example, 1,000 or more, 2,000 or more, 3,000 or more, or even 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, 15,000 or less, 10,000 or less, or 20,000 or less. It may be not more than 7000, or even not more than 7000. A (meth)acrylic oligomer having a weight average molecular weight (Mw) within these ranges can further enhance the stress relaxation properties of the pressure-sensitive adhesive layer 4.

[0049] The (meth)acrylic oligomer has, for example, one or more structural units derived from the following monomers: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, and isooctyl Alkyl (meth)acrylates such as (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 dicyclopentanyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates obtained from terpene compound derivative alcohols.

[0050] The (meth)acrylic oligomer preferably has a structural unit derived from an acrylic monomer having a relatively bulky structure. In this case, the adhesiveness of the pressure-sensitive adhesive layer 4 can be further improved. Examples of the acrylic monomer include alkyl (meth)acrylates having an alkyl group with a branched structure, such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohol, such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; and aryl (meth)acrylates, such as phenyl (meth)acrylate and benzyl (meth)acrylate. The acrylic monomer preferably has a cyclic structure, and more preferably has two or more cyclic structures. Furthermore, when ultraviolet irradiation is carried out during polymerization of the (meth)acrylic oligomer and / or during formation of the pressure-sensitive adhesive layer 4, it is preferable that the acrylic monomer does not have an unsaturated bond, since this makes it less likely that the progress of the polymerization and / or formation will be hindered. For example, an alkyl (meth)acrylate having an alkyl group with a branched structure, or an ester of (meth)acrylic acid and an alicyclic alcohol can be used.

[0051] Specific examples of the (meth)acrylic oligomer include a copolymer of butyl acrylate, methyl acrylate, and acrylic acid, a copolymer of cyclohexyl methacrylate and isobutyl methacrylate, a copolymer of cyclohexyl methacrylate and isobornyl methacrylate, a copolymer of cyclohexyl methacrylate and acryloylmorpholine, a copolymer of cyclohexyl methacrylate and diethylacrylamide, a copolymer of 1-adamantyl acrylate and methyl methacrylate, a copolymer of dicyclopentanyl methacrylate and isobornyl methacrylate, a copolymer of methyl methacrylate and at least one selected from dicyclopentanyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate, and cyclopentanyl methacrylate, a homopolymer of dicyclopentanyl acrylate, a homopolymer of 1-adamantyl methacrylate, and a homopolymer of 1-adamantyl acrylate.

[0052] The polymerization method for the (meth)acrylic oligomer can be the same as the polymerization method for the (meth)acrylic polymer described above.

[0053] When the pressure-sensitive adhesive composition contains a (meth)acrylic oligomer, the blending amount thereof is, for example, 70 parts by weight or less, and 50 parts by weight or less, relative to 100 parts by weight of the (meth)acrylic polymer. The lower limit of the blending amount may be, for example, 1 part by weight or more, 2 parts by weight or more, or even 3 parts by weight or more, relative to 100 parts by weight of the (meth)acrylic polymer.

[0054] The (meth)acrylic oligomer can be used in both solvent-based and active energy ray-curable pressure-sensitive adhesive compositions. However, when the (meth)acrylic oligomer is dissolved in a solvent and used in an active energy ray-curable pressure-sensitive adhesive composition, the solvent may be removed from the mixture containing the (meth)acrylic oligomer by, for example, heat drying, and then curing may be promoted by irradiation with active energy rays.

[0055] [Crosslinking agent] The acrylic pressure-sensitive adhesive composition may further contain a crosslinking agent. The use of a crosslinking agent improves the cohesive strength of the pressure-sensitive adhesive layer 4.

[0056] Examples of the crosslinking agent include organic crosslinking agents and polyfunctional metal chelates. Examples of the organic crosslinking agent include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, and imine crosslinking agents. The polyfunctional metal chelate has a structure in which a polyvalent metal and an organic compound are covalently or coordinately bonded. Examples of the polyvalent metal include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. The atom in the organic compound to which the polyvalent metal is covalently or coordinately bonded is typically an oxygen atom. Examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds. The organic crosslinking agents and polyfunctional metal chelates can be used in both solvent-based and active energy ray-curable pressure-sensitive adhesive compositions.

[0057] When the pressure-sensitive adhesive composition is solvent-based, the crosslinking agent is preferably a peroxide-based crosslinking agent or an isocyanate-based crosslinking agent, more preferably a peroxide-based crosslinking agent. Because peroxide-based crosslinking agents promote crosslinking between side chains of the (meth)acrylic polymer, crosslinking with a peroxide-based crosslinking agent increases the degree of freedom of the molecular chain after crosslinking compared to crosslinking with an isocyanate-based crosslinking agent. This allows the pressure-sensitive adhesive layer 4 to have a higher cohesive strength while still ensuring stress relaxation properties. On the other hand, crosslinking with an isocyanate-based crosslinking agent can improve the durability of the pressure-sensitive adhesive layer 4 compared to crosslinking with a peroxide-based crosslinking agent. However, crosslinking with a bifunctional isocyanate crosslinking agent forms a two-dimensional crosslinked structure, so that the stress relaxation properties of the pressure-sensitive adhesive layer 4 can be more reliably ensured, although not as reliably as with crosslinking with a peroxide-based crosslinking agent. When using an isocyanate-based crosslinking agent, a trifunctional crosslinking agent that forms a strong three-dimensional crosslinked structure may be used in combination with the bifunctional crosslinking agent to improve the balance between durability and stress relaxation properties. To further improve the balance, a peroxide-based crosslinking agent and an isocyanate-based crosslinking agent may be used in combination. The polyfunctional monomer (B) may also be used in combination with a crosslinking agent.

[0058] When the pressure-sensitive adhesive composition contains a crosslinking agent, the amount thereof is, for example, 0.1 to 10 parts by weight, or may be 0.2 to 5 parts by weight, or even 0.3 to 3 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer.

[0059] When the peroxide-based crosslinking agent is used alone, the amount thereof is, for example, 0.2 to 5 parts by weight, or may be 1 to 3 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer.

[0060] When a peroxide-based crosslinking agent and an isocyanate-based crosslinking agent are used in combination, the weight ratio of the peroxide-based crosslinking agent to the isocyanate-based crosslinking agent is preferably 1.2 or more, and more preferably The weight ratio is preferably 1.5 or more, more preferably 3 or more. The upper limit of the weight ratio is, for example, 500 or less. and may be 300 or less, or even 200 or less.

[0061] [Additives] The acrylic pressure-sensitive adhesive composition may contain other additives, such as silane coupling agents, polyether compounds (such as polyalkylene glycols including polypropylene glycol), colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, antiaging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (such as alkali metal salts, ionic liquids, and ionic solids, which are ionic compounds), inorganic fillers, organic fillers, and powders, particles, and foils such as metal powders.

[0062] [Formation of Pressure-Sensitive Adhesive Layer 4] The pressure-sensitive adhesive layer 4 composed of an acrylic pressure-sensitive adhesive composition can be formed as follows. When the pressure-sensitive adhesive composition is solvent-based, for example, a mixture of a (meth)acrylic polymer and a solvent, and optionally a (meth)acrylic oligomer, a crosslinking agent, additives, etc., is applied to a substrate film and dried to form the pressure-sensitive adhesive layer 4. When the pressure-sensitive adhesive composition is active energy ray-curable, for example, a mixture of a monomer(s) that will become a (meth)acrylic polymer upon polymerization, and optionally a partial polymer of the monomer(s), a polymerization initiator, a (meth)acrylic oligomer, a crosslinking agent, additives, a solvent, etc., is applied to a substrate film, and the solvent is removed by drying as necessary, followed by irradiating with active energy rays to form the pressure-sensitive adhesive layer 4. The substrate film may be a film whose surface has been treated for release. The pressure-sensitive adhesive layer 4 formed on the substrate film can be transferred to any layer. The substrate film may also be an optical film. In this case, a pressure-sensitive adhesive layer-attached optical laminate film including the pressure-sensitive adhesive layer 4 can be obtained by further arranging a protective film 2 and a separator 5. The base film may also be a separator 5, in which case an optical laminate film with a pressure-sensitive adhesive layer, which includes a pressure-sensitive adhesive layer 4, can be obtained by further arranging an optical film 3 and a protective film 2 thereon.

[0063] The mixture can be applied to the substrate film by a known method, such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, or extrusion coating using a die coater.

[0064] The mixture to be applied to the substrate film preferably has a viscosity suitable for handling and coating. For this reason, when the pressure-sensitive adhesive composition is an active energy ray-curable type, the mixture preferably contains a partial polymer of the monomer(s).

[0065] The release film that can be used for the base film is, for example, a resin film whose surface has been subjected to release treatment with a silicone compound.

[0066] The temperature for drying the mixture is, for example, 40 to 200° C., and may be 50 to 180° C., or even 70 to 170° C. The time for drying the mixture is, for example, 5 seconds to 20 minutes, and may be 5 seconds to 10 minutes, or even 10 seconds to 5 minutes.

[0067] When the pressure-sensitive adhesive layer 4 has a thickness of 25 μm or more, the degree of the above-mentioned depressions that may occur during storage of the optical laminate film 1 tends to increase. Therefore, when the pressure-sensitive adhesive layer 4 has a thickness of 25 μm or more, the effects of the present invention become more pronounced. The thickness of the pressure-sensitive adhesive layer 4 may be 30 μm or more, 40 μm or more, or even 50 μm or more. The upper limit of the thickness of the pressure-sensitive adhesive layer 4 is, for example, 150 μm or less. However, the thickness of the pressure-sensitive adhesive layer 4 is not limited to the above examples, and may be 1 to 200 μm, 5 to 150 μm, or even 10 to 100 μm.

[0068] The gel fraction of the pressure-sensitive adhesive layer 4 is preferably 60% or more, and may be 65% or more, or even 70% or more. The upper limit of the gel fraction of the pressure-sensitive adhesive layer 4 is, for example, 95% or less, and may be 90% or less. When the gel fraction of the pressure-sensitive adhesive layer 4 is within this range, the effect of suppressing the degree of depression can be more reliably obtained.

[0069] The weight-average molecular weight (Mw) of the sol content in the pressure-sensitive adhesive layer 4 is, for example, 50,000 or more, and may be 80,000 or more, 100,000 or more, 150,000 or more, or even 200,000 or more. The upper limit of the weight-average molecular weight (Mw) of the sol content is, for example, 1,200,000 or less. When the weight-average molecular weight (Mw) of the sol content in the pressure-sensitive adhesive layer 4 is within this range, and preferably 150,000 or more, the effect of suppressing the degree of depression can be more reliably obtained.

[0070] The indentation hardness of the adhesive layer 4 is 3.0×10 4 Pa or less, the optical laminate film 1 Therefore, the degree of the depression that may occur during storage tends to increase. 4 When the viscosity is less than 100 Pa, the effect of the present invention becomes more remarkable. The indentation hardness of adhesive layer 4 is 1.4 x 10 4 Pa or less, 1.2×10 4 Pa or less, 1.0×10 4 Pa or less, 8×10 3 Pa or less, even 5 × 10 3 It may be less than Pa. The lower limit of the size is, for example, 1 × 10 2 Pa or more.

[0071] The indentation hardness of the pressure-sensitive adhesive layer 4 can be measured by an indentation test based on the nanoindentation method. Specifically, the test is performed as follows: The pressure-sensitive adhesive layer 4 to be evaluated is cut into a piece measuring approximately 1 cm × 1 cm, and the cut-out pressure-sensitive adhesive layer 4 is fixed to the surface of a support to prepare a measurement sample. The support has a smooth surface for fixing the pressure-sensitive adhesive layer 4 and is made of a material, typically glass or metal, that has sufficient hardness so as not to affect the measurement results. The support is, for example, a plate. Next, the measurement sample is placed in a nanoindentation device, and an indentation test is performed using a spherical indenter with a curvature radius of 10 μm at room temperature, in which the indenter is pressed at a constant speed to a depth of 5000 nm from the surface of the pressure-sensitive adhesive layer 4. The indentation speed of the indenter is 1000 nm / sec. The indentation hardness of the pressure-sensitive adhesive layer 4 can be determined by dividing the maximum load obtained at this time by the projected area of ​​the indenter in contact with the measurement sample at the time the maximum load was obtained.

[0072] The creep amount ΔCr of the pressure-sensitive adhesive layer 4 at 70°C determined by the following test is, for example, 65 μm or less, and may be 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or even 15 μm or less. The lower limit of the creep amount ΔCr is, for example, 0.5 μm. Test: A pressure-sensitive adhesive layer is attached to a stainless steel test plate at a joint surface of 20 mm long x 20 mm wide. With the test plate fixed, a load of 500 gf is applied vertically downward. The creep amount (amount of displacement) of the pressure-sensitive adhesive layer relative to the test plate is measured at 100 seconds and 3600 seconds after the start of load application, and the Cr 100and Cr 3600 The measured Cr 100 and Cr 3600 From the formula ΔCr=Cr 3600 -Cr 100 The creep amount ΔCr is calculated by the following.

[0073] When the creep amount ΔCr of the pressure-sensitive adhesive layer 4 at 70° C. is within these ranges, the effect of suppressing the degree of the above-mentioned depression can be more reliably obtained.

[0074] The creep amount ΔCr of the adhesive layer 4 can be evaluated as follows (see Figures 2A and 2B). A laminate of the adhesive layer 4 to be evaluated and a support film 51 is cut into a 20mm x 30mm strip to be used as a test piece 52. The support film 51 is placed to suppress deformation of the part of the adhesive layer 4 to which the load is applied during the test, thereby enabling more accurate measurement of the creep amount ΔCr. For example, a resin film such as a polyethylene terephthalate (PET) film can be used as the support film 51. The support film 51 may be an optical film that is bonded (bonded) to the adhesive layer 4 in the image display device. The thickness of the support film 51 may be any thickness that does not deform itself under the above load, for example, 20 to 200 μm. The support film 51 may be an optical film 3 or a laminated film including the optical film 3. The laminated film is, for example, a laminate of the optical film 3 and the protective film 2. Next, as shown in FIGS. 2A and 2B, the test piece 52 is attached to the surface of a stainless steel test plate 53 with the adhesive layer 4 at the bonding surface measuring 20 mm long x 20 mm wide. Note that FIG. 2B is a cross section BB of FIG. 2A. The test piece 52 is attached to the test plate 53 so that no air bubbles are trapped between the test plate 53 and the adhesive layer 4. After being attached by hand, the test plate 53 was placed in an autoclave at 50°C and 5 atmospheres (absolute pressure) for 15 minutes to homogenize the bond between the test plate 53 and the adhesive layer 4, and then left in an atmospheric pressure atmosphere at 60°C for 2 hours to complete the aging process. Next, the test plate 53 and test piece 52 were held vertically with the test plate 53 facing upward and left in an atmosphere at 70°C for at least 5 minutes, and then, with the test plate 53 still fixed, a 500g weight was fixed to the center of the lower end of the test piece 52, and a load 54 of 500gf was applied vertically downward. The amount of creep (shift) of the adhesive layer 4 relative to the test plate 53 was measured as the drop distance of the weight at each time point, 100 seconds and 3600 seconds after the start of application of the load 54, and the Cr 100 and Cr 3600 The measured Cr 100 and Cr 3600 From the formula ΔCr=Cr 3600 -Cr 100 The creep amount ΔCr can be calculated by the following equation. A laser displacement meter can be used to measure the falling distance of the weight. 100 The reason for using this as a reference is that a load of 54 is applied. The amount of fall of the weight immediately after being lifted varies greatly even for the same test piece, and this is done to eliminate as much as possible the influence of this unavoidable variation in the initial stage and improve the accuracy of the measurement.

[0075] To control the creep amount ΔCr of the pressure-sensitive adhesive layer 4 at 70° C., for example, the following methods can be used alone or in combination. To more reliably control the creep amount ΔCr of the pressure-sensitive adhesive layer 4 at 70° C., it is preferable to combine the following methods. However, the control methods are not limited to the examples shown below. ·Method 1 The composition of the (meth)acrylic monomer contained in the pressure-sensitive adhesive composition is controlled. For example, when the (meth)acrylic monomer has a structural unit derived from a (meth)acrylic monomer (C) having a hydroxy group and / or a structural unit derived from a crosslinkable monomer (B), the creep amount ΔCr of the pressure-sensitive adhesive layer 4 at 70°C usually tends to decrease. ·Method 2 The type and amount of crosslinking agent added to the pressure-sensitive adhesive composition are controlled. Increasing the amount of crosslinking agent typically tends to decrease the creep amount ΔCr of the pressure-sensitive adhesive layer 4 at 70°C. Because this tendency differs depending on the type of crosslinking agent, combining different types of crosslinking agents allows for more precise control of the creep amount ΔCr of the pressure-sensitive adhesive layer 4 at 70°C. For example, when the pressure-sensitive adhesive composition is solvent-based, peroxide-based crosslinking agents are more likely to reduce the creep amount ΔCr at 70°C than trifunctional crosslinking agents, while suppressing an increase in the elastic modulus of the pressure-sensitive adhesive layer 4 and maintaining stress relaxation properties. Furthermore, active energy ray-curable pressure-sensitive adhesive compositions that are cured using a photopolymerization initiator and a polyfunctional monomer are more likely to reduce the creep amount ΔCr at 70°C than solvent-based pressure-sensitive adhesive compositions, thereby more reliably suppressing the degree of depression. ·Method 3 When a (meth)acrylic oligomer is added to the pressure-sensitive adhesive composition, the creep amount ΔCr of the pressure-sensitive adhesive layer 4 at 70° C. usually tends to increase by adding a (meth)acrylic oligomer.

[0076] [Separator] The separator 5 is typically a resin film. Examples of resins constituting the separator 5 include polyesters such as PET, polyolefins such as polyethylene and polypropylene, polycarbonate, acrylic, polystyrene, polyamide, and polyimide. The surface of the separator 5 that comes into contact with the pressure-sensitive adhesive layer 4 may be subjected to a release treatment. The release treatment can be performed using, for example, a silicone compound. However, the separator 5 is not limited to the above examples. The separator 5 is peeled off when the optical laminate film 1 is used, for example, when it is attached to the image-forming layer.

[0077] The thickness of the separator 5 is, for example, 20 μm or more, and may be 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, or even 75 μm or more. When the thickness of the separator 5 is 45 μm or more, particularly 75 μm or more, the degree of the above-mentioned depression that may occur in the pressure-sensitive adhesive layer 4 during storage of the optical laminate film 1 can be more reliably suppressed. This is because the thickness of the separator 5 can disperse the pressure generated by trapped foreign matter.

[0078] The pressure-sensitive adhesive optical laminate film of the present invention may have layers other than those described above.

[0079] The pressure-sensitive adhesive layer-attached optical laminate film 1 can be distributed and stored, for example, as a rolled body in which the strip-shaped film 1 is rolled up, or as a laminate of the sheet-shaped film 1.

[0080] The pressure-sensitive adhesive layer-attached optical laminate film 1 is typically used in an image display device. The image display device is, for example, a liquid crystal display or an organic EL display. The type and configuration of the image display device are not limited.

[0081] [Image display device] An example of the image display device of the present invention is shown in Figure 3. The image display device 6 shown in Figure 3 has an optical laminate in which a substrate 8, an image forming layer (e.g., an organic EL layer) 7, a pressure-sensitive adhesive layer 4, an optical film 3, and a protective film 2 are laminated in this order. The image display device 6 has the optical laminate film 1 except for the separator 5. The substrate 8 and the image forming layer 7 may have the same configurations as the substrate and the image forming layer, respectively, of known image display devices. The image display device 6 has advantages such as high reliability and few optical defects because the degree of the above-mentioned depressions that may occur in the pressure-sensitive adhesive layer 4 is suppressed.

[0082] 3 is an organic EL display, but the type and configuration of the image display device 6 are not limited.

[0083] The image display device of the present invention may have any configuration as long as it includes the pressure-sensitive adhesive layer-attached optical laminate film 1 except for the separator 5 . [Example]

[0084] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples shown below.

[0085] First, the evaluation methods for the optical laminate films and pressure-sensitive adhesive layers produced in the examples and comparative examples will be described.

[0086] [Weight average molecular weight (Mw)] The weight average molecular weight (Mw) of the (meth)acrylic polymer and (meth)acrylic oligomer was measured by GPC under the following measurement conditions. Analytical equipment: Waters, Acquity APC Column: Tosoh G7000HXL+GMHXL+GMHXL Column temperature: 40℃ Eluent: tetrahydrofuran (acid added) ·Flow rate: 0.8mL / min ·Injection volume: 100μL Detector: Differential refractometer (RI) Standard sample: Agilent, polystyrene (PS)

[0087] [Creep amount ΔCr at 70℃] The creep amount ΔCr of the prepared pressure-sensitive adhesive layer at 70°C was evaluated using the method described above. The separator used in preparing the optical laminate film was used as the support film 51. A SUS304 plate (30 mm x 75 mm, 2.5 mm thick) was used as the test plate 53. Keyence LK-H057 / LK-HD500 laser displacement meter was used. In addition, the test plate 53 was left in a 70°C atmosphere for 5 minutes between holding the test plate 53 vertically with the top facing up and starting the test.

[0088] [Gel fraction] The gel fraction of the prepared pressure-sensitive adhesive layer was evaluated as follows. First, approximately 0.2 g was scraped off from the prepared pressure-sensitive adhesive layer to obtain a small piece. Next, the obtained small piece was wrapped in a stretched porous polytetrafluoroethylene film (NTF1122 manufactured by Nitto Denko, average pore size 0.2 μm) and tied with kite string to obtain a test piece. Next, the weight A of the obtained test piece was measured. Weight A is the total weight of the pressure-sensitive adhesive layer piece, the stretched porous film, and the kite string. Note that the total weight B of the stretched porous film and kite string used was measured in advance. Next, the test piece was immersed in a 50 mL container filled with ethyl acetate and allowed to stand at 23°C for one week. After standing, the test piece was removed from the container and dried in a dryer set at 130°C for two hours, and then the weight C of the test piece was measured. Then, the gel fraction of the pressure-sensitive adhesive layer was calculated from the measured weights A, B, and C using the formula: gel fraction (wt %)=(CB) / (AB)×100(%).

[0089] [Weight average molecular weight (Mw) of the sol content in the adhesive layer] The pressure-sensitive adhesive layer was dissolved in tetrahydrofuran to prepare a solution with a concentration of 0.2 wt%, which was left at room temperature for 20 hours. The solution was then filtered through a membrane filter with a filtration accuracy of 0.45 μm, and the weight-average molecular weight (Mw) of the obtained filtrate was measured by GPC. The obtained value was used as the weight-average molecular weight (Mw) of the sol content of the pressure-sensitive adhesive layer. The GPC measurement conditions were the same as those used to measure the weight-average molecular weight (Mw) of the (meth)acrylic polymer and (meth)acrylic oligomer.

[0090] Tensile modulus The tensile modulus of the protective film was evaluated by a tensile test using a tensile tester (Shimadzu AG-IS). The sample shape was a strip with a width of 15 mm and a length of 50 mm, and the initial chuck distance was 30 mm and the tensile speed was 20 mm / min. The measurement was performed at 23°C.

[0091] [Dent amount] The degree of dents that may occur in the adhesive layer of the produced optical laminate film was evaluated as "dent amount" as follows: A digital thickness gauge with a measurement stage (Digital Upright Gauge DG-205 manufactured by Ozaki Manufacturing Co., Ltd.) was prepared, and a 5.5 mm diameter iron ball was fixed to the tip of the gauge head via double-sided adhesive tape (No. 500 manufactured by Nitto Denko Corporation). Next, the thickness gauge was operated to move the gauge head up and down, and the iron ball fixed to the tip of the gauge head was pressed against the measurement stage and released, this operation was repeated 10 times, and then the gauge head was lowered and the iron ball was pressed against the measurement stage with a constant load of 100 gf for 3 minutes. This sufficiently compressed the double-sided adhesive tape in the thickness direction and stabilized the fixed state between the gauge head and the iron ball, allowing for highly accurate measurements. Next, the position where the iron ball and the measurement stage came into contact after the above treatment was set as the zero point. Next, the prepared optical laminate film was placed on the measurement stage so that the protective film was the exposed surface. Next, the thickness gauge was activated, and the measuring probe was lowered to press the iron ball against the protective film with a constant load of 100 gf. The pressure applied to the protective film by pressing the iron ball was approximately 2 MPa. The thickness gauge measured the displacement of the iron ball from the zero point at the time when the iron ball contacted the protective film (0 seconds after pressing) and the displacement of the iron ball from the zero point at the time 60 seconds had elapsed from that time (60 seconds after pressing), and the absolute value of the difference was taken as the indentation amount, which is the amount of indentation in the thickness direction of the pressure-sensitive adhesive layer. The zero point was set and the indentation amount was evaluated at 23°C.

[0092] Next, the method for producing each pressure-sensitive adhesive layer of the Examples and Comparative Examples will be described.

[0093] The correspondence between the abbreviations or names shown in the following explanation and the compounds is as follows: BA: n-butyl acrylate LA: Lauryl acrylate MA: methyl acrylate NVP: N-vinylpyrrolidone AA: acrylic acid HBA: 4-hydroxybutyl acrylate DCPMA: dicyclopentanyl methacrylate (Hitachi Chemical, FA-513M) HEA: 2-hydroxyethyl acrylate 2EHA: 2-ethylhexyl acrylate MMA: Methyl methacrylate AIBN: 2,2'-azobisisobutyronitrile Omnirad651: 2,2-dimethoxy-2-phenylacetophenone (manufactured by IGM Resins BV) Omnirad184: 1-hydroxycyclohexyl phenyl ketone (manufactured by IGM Resins BV) D110N: Trimethylolpropane / xylylene diisocyanate adduct (Takenate D110N manufactured by Mitsui Chemicals) C / L: Trimethylolpropane / tolylene diisocyanate (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.) A-HD-N: Hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) Peroxide: Benzoyl peroxide (Niper BMT, manufactured by Nippon Oil & Fats) Irganox 1010: Pentaerythritol tetrakis(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate) (BASF)

[0094] [Preparation of (meth)acrylic polymer] (Synthesis Example 1) A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 99 parts by weight of BA and 1 part by weight of HBA. Next, 0.1 parts by weight of AIBN as a polymerization initiator was added to 100 parts by weight of the BA and HBA mixture. Nitrogen gas was introduced with gentle stirring to replace the atmosphere in the flask with nitrogen. The liquid temperature in the flask was maintained at around 55°C, and the polymerization reaction was allowed to proceed for 7 hours. Ethyl acetate was then added to the resulting reaction solution to adjust the solids concentration to 30% by weight, yielding a solution of (meth)acrylic polymer A1. The weight-average molecular weight (Mw) of (meth)acrylic polymer A1 was 1.6 million.

[0095] (Synthesis Examples 2 and 3) (Meth)acrylic polymers A2 and A3 were obtained in the same manner as in Synthesis Example 1, except that the types and amounts of monomers and polymerization initiators shown in Table 1 below were charged into the flask.

[0096] [Preparation of (meth)acrylic monomer syrup] (Synthesis Example 4) A four-neck flask equipped with a nitrogen gas inlet tube and a spindle connected to a Brookfield viscometer (rotational viscometer) was charged with 40 parts by weight of 2EHA, 50 parts by weight of LA, 9 parts by weight of NVP, 1 part by weight of HBA, and 0.05 parts by weight each of the photopolymerization initiators Omnirad 651 and Omnirad 184. Next, nitrogen gas was introduced into the flask while rotating the spindle, and the atmosphere was replaced with nitrogen. Photopolymerization was then carried out by irradiating with ultraviolet light until the viscosity of the polymerization system measured by the viscometer reached approximately 15 Pa·s, yielding (meth)acrylic monomer syrup A4 containing a partial polymer of the monomer groups. The viscometer used was a Toki Sangyo BH model, with the spindle (rotor No. 5) rotating at 10 rpm. The liquid temperature in the flask was maintained at 30°C.

[0097] (Synthesis Example 5) A (meth)acrylic monomer syrup A5 was obtained in the same manner as in Synthesis Example 4, except that the types and amounts of monomers and photopolymerization initiators shown in Table 1 below were charged into the flask.

[0098] [Preparation of (meth)acrylic oligomer] (Synthesis Example 6) A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 95 parts by weight of BA, 3 parts by weight of MA, 2 parts by weight of AA, 0.1 parts by weight of AIBN as a polymerization initiator, and 140 parts by weight of toluene. Nitrogen gas was then introduced into the flask with gentle stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was maintained at around 70°C, and the polymerization reaction was allowed to proceed for 8 hours, yielding a solution of (meth)acrylic oligomer B1. The weight-average molecular weight of (meth)acrylic oligomer B1 was 4,500.

[0099] (Synthesis Example 7) 60 parts by weight of DCPMA and 40 parts by weight of MMA as monomer components, 3.5 parts by weight of α-thioglycerol as a chain transfer agent, and 100 parts by weight of toluene as a polymerization solvent were mixed and stirred at 70°C for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by weight of AIBN as a thermal polymerization initiator was added, and the mixture was reacted at 70°C for 2 hours, then heated to 80°C and reacted for 2 hours. The reaction solution was then heated to 130°C, and the toluene, chain transfer agent, and unreacted monomers were dried and removed to obtain (meth)acrylic oligomer B2.

[0100] The compositions (monomer charging ratios) and weight average molecular weights (Mw) of the (meth)acrylic polymers, (meth)acrylic monomer syrups, and (meth)acrylic oligomers prepared in each synthesis example are shown in Table 1 below.

[0101] [Table 1]

[0102] [Preparation of adhesive layer] (Manufacturing Examples 1 to 8, 11) A solvent-based pressure-sensitive adhesive composition was obtained by mixing a (meth)acrylic polymer, a (meth)acrylic oligomer, a crosslinking agent, and additives to obtain the composition shown in Table 2. Next, the pressure-sensitive adhesive composition obtained was applied to the surface of a PET film (thickness: 38 μm, 50 μm, or 75 μm) serving as a separator, and then dried for 2 minutes in an air-circulating constant-temperature oven set at 155°C to form pressure-sensitive adhesive layers (thickness: 50 μm) for Production Examples 1 to 8 and 11. A fountain coater was used to apply the pressure-sensitive adhesive composition.

[0103] (Examples 9 and 10) A mixture was obtained by mixing a (meth)acrylic monomer syrup, a crosslinking agent, and additives to obtain the composition shown in Table 2 below. Next, the mixture was applied to the surface of a PET film (thickness 38 μm) serving as a separator, and then another PET film was placed on top of the mixture coating, and the coating film was sandwiched between the pair of PET films. Next, an illuminance of 4 mW / cm was applied. 2 and light intensity 1200mJ / cm 2 The coating film is hardened by irradiating it with ultraviolet light under the irradiation conditions of After the pressure-sensitive adhesive layer was formed, the additional PET film was peeled off to expose the pressure-sensitive adhesive layer.

[0104] [Table 2]

[0105] The evaluation results for each of the pressure-sensitive adhesive layers prepared in Production Examples 1 to 11 are shown in Table 3 below.

[0106] [Table 3]

[0107] [Production of optical laminated film] The separators and pressure-sensitive adhesive layers prepared in Production Examples 1 to 11, optical films, and protective films were laminated in this order based on the combinations shown in Table 4 below to obtain optical laminate films for Examples 1 to 12 and Comparative Examples 1 to 3. However, in Comparative Example 1, no protective film was used. A 31-μm-thick polarizing plate was used for the optical film, which was composed of a polarizer protective film (20 μm thick), a polarizer (5 μm thick), a λ / 2 plate (½ wavelength plate, 3 μm thick), and a λ / 4 plate (¼ wavelength plate, 3 μm thick) laminated in this order from the side to be bonded to the protective film. For Examples 1 to 12 and Comparative Example 3, a PET film (25 μm, 38 μm, or 50 μm thick) was used as the protective film, and for Comparative Example 2, a polyethylene film (30 μm thick) was used. The protective film was bonded to the optical film via an acrylic pressure-sensitive adhesive layer (10 μm thick). The layers constituting the optical film and the optical film were prepared as follows.

[0108] (λ / 4 plate and λ / 2 plate) The retardation film, a laminate of a λ / 4 plate (quarter-wave plate) and a λ / 2 plate (half-wave plate), was fabricated using a polymerizable liquid crystal material (BASF, Paliocolor LC242) that exhibits a nematic liquid crystal phase after the formation of an alignment layer. Specifically, the polymerizable liquid crystal material and a photopolymerization initiator (BASF, Irgacure 907) were dissolved in toluene, and then a fluorine-based surfactant (DIC, Megafac) was added at 0.1 to 0.5 wt % depending on the liquid crystal thickness to improve coating properties, to prepare coating liquid L. The solids concentration of coating liquid L was set to 25 wt %.

[0109] Next, a retardation film manufacturing apparatus 200 shown in FIG. 4 was prepared. The manufacturing apparatus 200 includes a supply reel 221 for supplying a strip-shaped PET substrate 214, pressure rollers 224 and 234, shaping rollers 230 and 240, peeling rollers 226 and 236, a conveying roller 231, dies 222, 229, 232 and 239, and ultraviolet irradiation devices 225, 227, 235 and 237 for irradiating ultraviolet rays from a high-pressure mercury lamp. Next, a solution 210 of ultraviolet curable resin was applied to one side of the PET substrate 214 unwound from the supply reel 221 by the die 222. Next, the pressure roller 224 brings the coating film into contact with the shaping roller 230, and the PET substrate 214 is conveyed along the shaping roller 230 while they are in contact with each other, and The coating film was cured by irradiating ultraviolet rays from the PET substrate 214 side using an ultraviolet irradiation device 225. On the conveyance surface of the PET substrate 214 on the shaping roller 230, linear irregularities (extending in a direction at an angle of 75° to the MD direction of the PET substrate) were formed, which would form a λ / 4 plate when an alignment film of the polymerizable liquid crystal material was further formed. The curing resulted in the formation of a cured film of UV-curable resin, the exposed surface of which had a shape corresponding to the irregularities. Next, the PET substrate 214 on which the cured film had been formed was peeled from the shaping roller 230 using a peeling roller 226. Then, a coating liquid L was applied to the exposed surface of the cured film using a die 229, and UV rays were irradiated using an ultraviolet irradiation device 227 to align and cure the coating film. In this way, a λ / 4 plate (3 μm thick) consisting of a cured film of UV-curable resin and an alignment and cured film of the polymerizable liquid crystal material was formed on the PET substrate 214.

[0110] Next, the PET substrate 214 on which the λ / 4 plate had been formed was transported by transport rollers 231, and further, the ultraviolet-curable resin solution 212 was applied to the exposed surface of the λ / 4 plate by a die 232 to form a coating film. Next, the pressure roller 234 brought the coating film into contact with the shaping roller 240, and while they were in contact, the PET substrate 214 was transported along the shaping roller 240, and ultraviolet light was irradiated from the side of the PET substrate 214 by an ultraviolet irradiation device 235 to harden the coating film. On the transport surface of the PET substrate 214 on the shaping roller 240, linear irregularities (extending in a direction at an angle of 15° to the MD direction of the PET substrate) were formed, which would form the λ / 2 plate when an alignment film of the polymerizable liquid crystal material was further formed, and the curing resulted in the formation of a cured film of the ultraviolet-curable resin having a shape corresponding to the irregularities on the exposed surface. Next, the PET substrate 214 on which the cured film was formed was peeled off from the shaping roller 240 by a peeling roller 236, and then the coating liquid L was applied to the exposed surface of the cured film by a die 239, and the coating film was aligned and cured by irradiating it with ultraviolet light by an ultraviolet irradiation device 237. In this way, a λ / 2 plate (thickness 3 μm) consisting of a cured film of an ultraviolet curable resin and an aligned and cured film of a polymerizable liquid crystal material was further formed on the λ / 4 plate of the PET substrate 214, to obtain a laminate (b).

[0111] (polarizing film) A polarizing film, which is a laminate of a polarizer and a polarizer protective film, was prepared as follows.

[0112] As a thermoplastic resin substrate, an amorphous IPA copolymerized PET film (thickness 100 μm) containing 7 mol% of isophthalic acid (IPA) units was prepared, and its surface was subjected to corona treatment (58 W / m 2 Separately, acetoacetyl-modified PVA (Nippon Synthetic Chemical Co., Ltd.) was used. PVA (polymerization degree 4200, saponification degree 99.2%) containing 1% by weight of Gohsefimer Z200 (manufactured by Gakko Kogyo Co., Ltd., average polymerization degree 1200, saponification degree 98.5 mol%, acetoacetylation degree 5 mol%) was dissolved in water to obtain a PVA coating solution with a concentration of 5.5% by weight. The above PVA coating solution was applied to the corona-treated surface of the polymerized PET film so that the film thickness after drying would be 12 μm, and the coating film was dried by hot air drying at 60°C for 10 minutes to obtain a laminate consisting of the substrate and a PVA layer on the substrate.

[0113] The resulting laminate was then free-end stretched (in-air auxiliary stretching) in air at a stretch ratio of 1.8 times at 130°C to obtain a stretched laminate. The stretched laminate was then immersed in a boric acid insolubilizing aqueous solution at 30°C for 30 seconds to insolubilize the PVA layer. The boric acid content in the boric acid insolubilizing aqueous solution was 3 parts by weight per 100 parts by weight of water. The stretched laminate with the insolubilized PVA layer was then dyed to obtain a colored laminate. The dyeing was performed by immersing the stretched laminate in a dye solution containing iodine and potassium iodide at a liquid temperature of 30°C. In the dyeing, the PVA layer included in the stretched laminate was dyed with iodine. The dyeing time was adjusted so that the single transmittance of the PVA layer constituting the final polarizer was in the range of 40 to 44%. An aqueous solution with an iodine concentration of 0.1 to 0.4 wt % and a potassium iodide concentration of 0.7 to 2.8 wt % was used as the dye solution. The ratio of potassium iodide concentration to iodine concentration in the staining solution was set to 7. The color laminate was immersed in a boric acid crosslinking solution at 30°C for 60 seconds to form a crosslinked structure between PVA molecules in the iodine-adsorbed PVA layer. The boric acid content and potassium iodide content in the boric acid crosslinking solution were both 3 parts by weight per 100 parts by weight of water.

[0114] Next, the crosslinked dyed laminate was stretched in a boric acid aqueous solution at a stretching temperature of 70°C and a stretching ratio of 3.05 (stretching in boric acid water) to obtain a stretched laminate with a final stretching ratio of 5.50. The stretching direction in the boric acid aqueous solution was the same as the stretching direction of the initial in-air auxiliary stretching. Next, the stretched laminate was removed from the boric acid aqueous solution, and the boric acid adhering to the surface of the PVA layer was washed with a potassium iodide solution (potassium iodide content: 4 parts by weight per 100 parts by weight of water). Next, the washed stretched laminate was dried with hot air at 60°C to obtain a laminate consisting of the substrate and a polarizer (5 μm thick) formed on the substrate.

[0115] Next, a stretched film of a methacrylic resin having a glutarimide ring unit (thickness: 20 μm, moisture permeability: 160 g / m) was used as a polarizer protective film. 2 Next, the above-prepared stack was The prepared polarizer protective film was bonded to the exposed surface of the polarizer in the laminate to obtain a laminate (c) of the substrate and the polarizing film having the polarizer and polarizer protective film. A known acrylic adhesive was used to bond the polarizer and the polarizer protective film.

[0116] Next, an optical film was produced using the laminate (b) and laminate (c) produced above as follows. First, the substrate was peeled off from the laminate (c) to expose the polarizer. Next, the exposed polarizer and the λ / 2 plate of the laminate (b) were bonded together with a known acrylic adhesive to obtain an optical film. Note that the bonding between the optical film and the pressure-sensitive adhesive layer was performed by peeling off the PET substrate 214 from the laminate (b) to expose the λ / 4 plate.

[0117] Table 4 below shows the configuration of each optical laminate film of Examples and Comparative Examples and the evaluation results thereof.

[0118] [Table 4]

[0119] As shown in Table 4, the amount of depression was reduced in the optical laminate films of the examples. [Industrial Applicability]

[0120] The pressure-sensitive adhesive layer-attached optical laminate film of the present invention can be used in the production of image display devices. [Explanation of symbols]

[0121] 1. Optical laminated film with adhesive layer 2 Protective Film 3 Optical Film 4 Adhesive layer 5 Separator 6 Image display devices 7 Image forming layer (organic EL layer) 8 PCB

Claims

1. An optical laminated film with a pressure-sensitive adhesive layer, in which a protective film, an optical film, a pressure-sensitive adhesive layer, and a separator are laminated in this order, The thickness of the optical film is 35 μm or less, The thickness of the protective film is 30 μm or more, and the tensile modulus of the protective film is 1 GPa or more, The thickness of the pressure-sensitive adhesive layer is 40 μm or more, the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer formed from an acrylic pressure-sensitive adhesive composition, The thickness of the separator is 30 μm or more, the separator is made of polyethylene terephthalate, The optical film is a polarizing film in which a polarizer protective film, a polarizer, and a retardation film are bonded in this order, or a polarizing film in which polarizer protective films are bonded to both sides of a polarizer, and is an optical laminate film with a pressure-sensitive adhesive layer.

2. The pressure-sensitive adhesive layer-attached optical laminate film according to claim 1 , wherein the protective film is a polyester film.

3. 3. The pressure-sensitive adhesive layer-attached optical laminate film according to claim 1, wherein the separator has a thickness of 45 μm or more.

4. The pressure-sensitive adhesive layer-attached optical laminate film according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive layer has a gel fraction of 60% or more.

5. 5. The pressure-sensitive adhesive layer-attached optical laminate film according to claim 1, wherein the weight average molecular weight (Mw) of the sol component in the pressure-sensitive adhesive layer is 50,000 or more.

6. 6. The pressure-sensitive adhesive layer-attached optical laminate film according to claim 1, wherein the pressure-sensitive adhesive layer has a creep amount ΔCr of 50 μm or less at 70° C. as determined by the following test. Test: A pressure-sensitive adhesive layer is attached to a stainless steel test plate at a bonding surface of 20 mm long x 20 mm wide. With the test plate fixed, a load of 500 gf is applied vertically downward. The creep amount (displacement amount) of the pressure-sensitive adhesive layer relative to the test plate is measured at 100 seconds and 3600 seconds after the start of load application, and the Cr 100 and Cr 3600 The measured Cr 100 and Cr 3600 From the formula ΔCr = Cr 3600 -Cr 100 The creep amount ΔCr is calculated by the following equation.

7. An image display device comprising a portion of the pressure-sensitive adhesive layer-attached optical laminate film according to any one of claims 1 to 6 excluding the separator.

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