Optical laminated film with adhesive layer and image display device

Abstract

The optical laminate film with an adhesive layer according to the present application has a protective film, an optical film, an adhesive layer, and a separator laminated in this order, wherein 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 elastic modulus of the protective film is 1 GPa or more. According to the optical laminate film with an adhesive layer according to the present application, the degree of depression that can occur during storage can be suppressed.

Description

[0001] This application is a divisional application of the application filed on January 21, 2020, with application number 202080006681.6 and invention title "Optical laminated film with adhesive layer and image display device". Technical Field

[0002] This invention relates to an optical laminate with an adhesive layer and an image display device. Background Technology

[0003] Thin image display devices such as liquid crystal displays (LCDs) and organic EL displays typically have a laminated structure comprising an image forming layer, including a liquid crystal layer, an organic EL light-emitting layer, and one or more optical films. When bonding the layers constituting the image display device, an adhesive layer is generally used. A widely adopted method is to manufacture the image display device by bonding an optical film with an adhesive layer on at least one side to the image forming layer (see Patent Document 1). Furthermore, when supplying an optical film with an adhesive layer, it is sometimes supplied in the form of an optical laminated film with an adhesive layer, which further includes a diaphragm protecting the adhesive layer and / or a protective film protecting the optical film. It should be noted that when using the optical laminated film, for example, when bonding it to the image forming layer, the diaphragm is peeled off.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-28573 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] For optical laminates with adhesive layers, they are typically stored in a rolled state or as monolithic sheets before being combined with image forming layers and the like to manufacture an image display device. However, research by the inventors has revealed that such storage tends to cause minute depressions in the adhesive layer, and this tendency is amplified when the optical film is thinned. These depressions can become optical defects. Furthermore, similar depressions can occur during the storage of the image display device after manufacturing. These aspects were not considered in Patent Document 1.

[0009] The purpose of this invention is to provide an optical laminate with an adhesive layer that can suppress the degree of dents that may occur during storage.

[0010] Problem Solving Methods

[0011] This invention provides an optical laminated film with an adhesive layer, which comprises a protective film, an optical film, an adhesive layer, and a separator, stacked sequentially.

[0012] The thickness of the aforementioned optical film is less than 80 μm.

[0013] The thickness of the aforementioned protective film is 30 μm or more, and the tensile elastic modulus of the aforementioned protective film is 1 GPa or more.

[0014] In another aspect, the present invention provides an image display device having a portion of the optical laminate with an adhesive layer of the present invention other than the aforementioned diaphragm.

[0015] The effects of the invention

[0016] The optical laminate with adhesive layer of the present invention has a thinned optical film with a thickness of 80 μm or less, and both the thickness of the protective film and the tensile modulus of elasticity are set to a given value or higher. This allows for the dispersion of pressure caused by embedded foreign objects, suppressing the formation of depressions in the adhesive layer that may result from such foreign object intrusion. Therefore, the optical laminate with adhesive layer of the present invention can suppress the degree of depressions that may occur during storage. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view schematically illustrating an example of an optical laminated film with an adhesive layer according to the present invention.

[0018] Figure 2A This is a schematic diagram illustrating the method for determining the creep ΔCr of the adhesive layer.

[0019] Figure 2B This is a schematic diagram illustrating the method for determining the creep ΔCr of the adhesive layer.

[0020] Figure 3 This is a cross-sectional view schematically illustrating an example of the image display device of the present invention.

[0021] Figure 4 This is a schematic diagram illustrating the fabrication method of the λ / 4 waveplate and λ / 2 waveplate used in the embodiments. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

[0023] An example of the optical laminate with an adhesive layer of the present invention is shown below. Figure 1 . Figure 1The optical laminate 1 with an adhesive layer comprises: a protective film 2, an optical film 3, an adhesive layer 4, and a separator 5, wherein the protective film 2, the optical film 3, the adhesive layer 4, and the separator 5 are sequentially laminated together. The thickness of the optical film 3 is 80 μm or less, and the thickness of the protective film 2 is 30 μm or more. Furthermore, the tensile modulus of elasticity of the protective film 2 is 1 GPa or more. It should be noted that the tensile modulus of elasticity of the protective film 2 is a value at room temperature (23°C).

[0024] [Optical film]

[0025] Optical film 3 is, for example, a polarizing film or a phase retardation film. Optical film 3 can be a laminate or optical laminate containing a polarizing film and / or a phase retardation film, but optical film 3 is not limited to the above examples, and optical film 3 can also contain a glass film.

[0026] The thickness of the optical film 3 is 80 μm or less. According to the research of the inventors, when the optical laminate 1 has a thinned optical film 3 with a thickness of 80 μm or less, there is a tendency for the adhesive layer 4 to become more prone to depressions during storage. However, for the optical laminate 1, even with the aforementioned thinned optical film 3, the degree of depression of the adhesive layer 4 that may occur during storage can be suppressed. The thickness of the optical film 3 can also be 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, and more preferably 35 μm or less. The lower limit of the thickness of the optical film 3 is, for example, 1 μm or more.

[0027] The polarizing film includes a polarizer. A protective film for the polarizer may be bonded to at least one side of the polarizer. Any adhesive or bonding agent can be used to bond the polarizer and the protective film. The polarizer is typically a polyvinyl alcohol (PVA) film obtained by stretching to orient iodine through stretching in a gas atmosphere (dry stretching) or in a boric acid aqueous solution.

[0028] A retardation film is a film that exhibits birefringence in the in-plane direction and / or the thickness direction. Examples of retardation films include stretched resin films and films obtained by aligning and immobilizing liquid crystal materials.

[0029] Examples of retardation films include λ / 4 waveplates, λ / 2 waveplates, anti-reflection retardation films (see, for example, paragraphs 0221, 0222, and 0228 of Japanese Patent Application Publication No. 2012-133303), viewing angle compensation retardation films (see, for example, paragraphs 0225 and 0226 of Japanese Patent Application Publication No. 2012-133303), and tilt-oriented retardation films for viewing angle compensation (see, for example, paragraph 0227 of Japanese Patent Application Publication No. 2012-13303). 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 no limitations on the phase difference value, arrangement angle, three-dimensional birefringence, or whether it is a single layer or multiple layers. Known films can be used as retardation films.

[0030] The thickness of the phase retardation film is, for example, less than 50 μm.

[0031] The optical film 3 can be a single-layer film or a multilayer film composed of two or more layers.

[0032] [Protective film]

[0033] The protective film 2 functions to protect the optical film 3 during the circulation and storage of the optical laminate 1, and also during the process of introducing the optical laminate 1 into the image display device. When introduced into the image display device, the protective film 2 can function as a window to the outside space. The protective film 2 is typically a resin film. The resin constituting the protective film 2 is, for example, polyester such as polyethylene terephthalate (PET), polyolefins such as polyethylene and polypropylene, acrylics, cyclic olefins, polyimide, and polyamide, preferably polyester. In other words, the protective film 2 can be a polyester film. However, the protective film 2 is not limited to the above examples. The protective film can also be a film containing glass, or a laminate of glass films. Surface treatments such as anti-glare, anti-reflection, and antistatic treatments can be applied to the protective film 2.

[0034] The thickness of the protective film 2 is 30 μm or more. The thickness of the protective film 2 can also 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.

[0035] The tensile modulus of elasticity of the protective film 2 is 1 GPa or higher. The tensile modulus of elasticity of the protective film 2 can also be 2 GPa or higher, 3 GPa or higher, or even 4 GPa or higher. The upper limit of the tensile modulus of elasticity of the protective film 2 is, for example, 100 GPa or lower.

[0036] The protective film 2 can be bonded to the optical film 3 by any adhesive layer. The adhesive layer bonding the protective film 2 to the optical film 3 can have the configuration described in the following description of the adhesive layer 4.

[0037] [Adhesive layer]

[0038] Adhesive layer 4 is composed of various adhesive compositions, such as acrylic adhesives, rubber adhesives, vinyl alkyl ether adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, fluorinated adhesives, epoxy adhesives, and polyether adhesives. Due to its excellent optical transparency, processability, durability, and adhesion, adhesive layer 4 is preferably composed of an acrylic adhesive composition containing a (meth)acrylic polymer. It should be noted that in this specification, "(meth)acrylic acid" refers to acrylic acid and methacrylic acid. Furthermore, "(meth)acrylate" refers to acrylate and methacrylate.

[0039] The type of adhesive composition constituting the adhesive layer 4 can be, for example, emulsion type, solvent type (solution type), active energy ray curing type, or hot-melt type. Among these, solvent type or active energy ray curing type adhesive compositions are preferred. From the viewpoint of easily forming an adhesive layer 4 with a productive thickness, active energy ray curing type adhesive compositions are preferred, but the type of adhesive composition is not limited to the above examples.

[0040] The acrylic adhesive composition that can form adhesive layer 4 will be described below.

[0041] [(Meth)acrylic polymers]

[0042] Preferably, the (meth)acrylic polymer has a structural unit derived from a (meth)acrylic monomer (A) with an alkyl side chain having 1 to 30 carbon atoms as the main unit. The alkyl group can be linear or branched. The (meth)acrylic polymer may have one or more structural units derived from the (meth)acrylic monomer (A). (Meth)acrylate monomers (A) include, for example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, isohexyl methacrylate, isoheptyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, n-dodecyl methacrylate (laurate methacrylate), n-tridecyl methacrylate, and n-tetradecyl methacrylate. It should be noted that the term "main unit" in the specification refers to a unit that occupies, for example, 50% or more by mass, preferably 80% or more by mass, more preferably 90% or more by mass, and even more preferably 94% or more by mass of all structural units possessed by the polymer.

[0043] (Meth)acrylic polymers can have structural units derived from (meth)acrylic monomers (A) with long-chain alkyl groups on their side chains. For example, this structural unit is dodecyl (meth)acrylate (lauryl methacrylate). It should be noted that, in this specification, "long-chain alkyl" refers to an alkyl group having 6 to 30 carbon atoms.

[0044] (Meth)acrylic polymers can have structural units derived from (meth)acrylic monomers (A) whose glass transition temperature (Tg) is in the range of -70 to -20°C when forming homopolymers. For example, 2-ethylhexyl acrylate is a structural unit.

[0045] (Meth)acrylic polymers may also have structural units other than those derived from the (meth)acrylic monomer (A). These structural units are derived from monomer (B) that can copolymerize with the (meth)acrylic monomer (A). (Meth)acrylic polymers may have one or more of these structural units.

[0046] Monomer (B) is, for example, a (meth)acrylic monomer (C) having a hydroxyl group. Examples of (meth)acrylic monomers (C) include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and other hydroxyalkyl (meth)acrylates, as well as methyl (4-hydroxymethylcyclohexyl)acrylate. Since it can improve the durability and adhesion of adhesive layer 4, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred (meth)acrylic monomers (C).

[0047] Monomer (B) can also be a carboxyl-containing monomer, an amino-containing monomer, or an amide-containing monomer. Using these monomers (B) can improve the adhesion of adhesive layer 4. Examples of carboxyl-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylic acid, carboxypentyl (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and butenoic acid. Examples of amino-containing monomers include N,N-dimethylaminoethyl (meth)acrylic acid and N,N-dimethylaminopropyl (meth)acrylic acid. Amide-containing monomers include, for example, (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, mercaptoethyl(meth)acrylamide, and other acrylamide monomers; N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, and other N-acryloyl heterocyclic monomers; and N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and other N-vinyl lactam monomers.

[0048] Monomer (B) can be a multifunctional monomer. By using multifunctional monomers, the gel fraction and cohesiveness of the adhesive layer 4 can be adjusted. Examples of multifunctional monomers include hexanediol di(meth)acrylate (1,6-hexanediol di(meth)acrylate), butanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene 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 methacrylate, vinyl methacrylate, epoxy acrylate, polyester acrylate, urethane acrylate, and divinylbenzene. Preferred multifunctional acrylates are 1,6-hexanediol diacrylate and dipentaerythritol hexa(meth)acrylate.

[0049] Other monomers (B) besides those mentioned above include, for example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, methoxytriethylene glycol acrylate, 3-methoxypropyl acrylate, 3-ethoxypropyl acrylate, 4-methoxybutyl acrylate, 4-ethoxybutyl acrylate, and other alkoxyalkyl esters of methacrylate; glycidyl acrylate, methyl glycidyl acrylate, and other epoxy-containing monomers; sodium vinyl sulfonate and other sulfonic acid-containing monomers; and phosphorus-containing monomers. Acid monomers; (meth)acrylates with alicyclic hydrocarbon groups, such as cyclopentyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate; (meth)acrylates with aromatic hydrocarbon groups, such as phenyl methacrylate, phenoxyethyl methacrylate, and benzyl methacrylate; 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, and isobutylene; vinyl ethers such as vinyl alkyl ethers; vinyl chloride.

[0050] The total content of structural units derived from hydroxyl-containing (meth)acrylic acid monomers (C), carboxyl-containing monomers, amino-containing monomers, amide-containing monomers, and polyfunctional monomers in (meth)acrylic acid polymers is preferably 20% by mass or less, more preferably 10% by mass or less, further preferably 8% by mass or less, and particularly preferably 5% by mass or less. When the (meth)acrylic acid polymer has this structural unit, the total content of this structural unit is, for example, 0.01% by mass or more, or possibly 0.05% by mass or more.

[0051] The total content of structural units derived from other monomers (B) in (meth)acrylic polymers is, for example, 30% by mass or less, or 10% by mass or less, and preferably 0% by mass (excluding the structural unit).

[0052] (Meth)acrylic acid polymers can be formed by polymerizing one or more of the aforementioned monomers using known methods. Alternatively, monomers can be polymerized with a portion of the monomer polymer. Polymerization can be carried out, for example, by solution polymerization, emulsion polymerization, bulk polymerization, thermal polymerization, or active energy radiation polymerization. Solution polymerization and active energy radiation polymerization are preferred because they can form an adhesive layer 4 with excellent optical transparency. Polymerization is preferably carried out while avoiding contact between the monomers and / or a portion of the polymer and oxygen; therefore, polymerization can be performed, for example, in an inert gas atmosphere such as nitrogen, or in a state where oxygen is blocked using a resin film or the like. The (meth)acrylic acid polymer to be formed can be any form of random copolymer, block copolymer, graft copolymer, etc.

[0053] Polymerization systems that form (meth)acrylic acid polymers may contain one or more polymerization initiators. The type of polymerization initiator can be selected according to the polymerization reaction; for example, it can be a photopolymerization initiator or a thermal polymerization initiator.

[0054] Solvents used in solution polymerization include, for example, 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, but the solvent is not limited to the above examples. The solvent can be a mixture of two or more solvents.

[0055] The polymerization initiators used in solution polymerization are, for example, azo polymerization initiators, peroxide polymerization initiators, and redox polymerization initiators. Examples of peroxide polymerization initiators include benzoyl peroxide and tert-butyl maleate peroxide. Among these, the azo polymerization initiator disclosed in Japanese Patent Application Publication No. 2002-69411 is preferred. Examples of such azo polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylbutyronitrile), dimethyl 2,2'-azobis(2-methylpropionic acid), and 4,4'-azobis(4-cyanopentanoic acid), but the polymerization initiator is not limited to the examples mentioned above. The amount of azo polymerization initiator used relative to 100 parts by weight of the total monomer is, for example, 0.05 to 0.5 parts by weight, or possibly 0.1 to 0.3 parts by weight.

[0056] The active energy rays used in active energy radiation polymerization include ionizing rays such as alpha rays, beta rays, gamma rays, neutron rays, and electron rays, as well as ultraviolet rays. Ultraviolet rays are preferred. Polymerization using ultraviolet irradiation is also called photopolymerization. The polymerization system of active energy radiation polymerization typically includes a photoinitiator. The polymerization conditions for active energy polymerization are not limited as long as they allow the formation of (meth)acrylic acid polymers.

[0057] Photopolymerization initiators include, for example, benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators, α-ol ketone photopolymerization initiators, aromatic sulfonyl chloride photopolymerization initiators, photoactive oxime photopolymerization initiators, benzoin photopolymerization initiators, benzoyl photopolymerization initiators, ketal photopolymerization initiators, and thioxanone photopolymerization initiators, but photopolymerization initiators are not limited to the above examples.

[0058] 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-diphenylethane-1-one, and anisole methyl ether. Examples of acetophenone-based photopolymerization initiators include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 4-phenoxydichloroacetophenone, and 4-(tert-butyl)dichloroacetophenone. Examples of α-olone-based photopolymerization initiators include 2-methyl-2-hydroxyphenylacetone and 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropane-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalenesulfonyl chloride. Photoactive oxime photopolymerization initiators include, for example, 1-phenyl-1,1-propanedione-2-(O-ethoxycarbonyl oxime). Benzoin photopolymerization initiators include, for example, benzoin. Benzoyl photopolymerization initiators include, for example, benzoyl. Benzophenone photopolymerization initiators include, for example, benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexylphenyl ketone. Ketal photopolymerization initiators include, for example, benzoyldimethyl ketal. Thioxanone photopolymerization initiators include, for example, thioxanone, 2-chlorothioxanone, 2-methylthioxanone, 2,4-dimethylthioxanone, isopropylthioxanone, 2,4-diisopropylthioxanone, and dodecylthioxanone.

[0059] The amount of photopolymerization initiator relative to the total amount of monomers (100 parts by weight) is, for example, 0.01 to 1 part by weight, or 0.05 to 0.5 parts by weight.

[0060] It should be noted that multifunctional monomers (such as multifunctional acrylates) as monomers (B) can also be used in any type of adhesive composition, including solvent-based and active energy ray-cured adhesive compositions. However, when using both multifunctional monomers and photopolymerization initiators in solvent-based adhesive compositions, the adhesive composition can be cured by irradiation with active energy rays after the solvent is removed by heat drying.

[0061] The weight-average molecular weight (Mw) of the (meth)acrylic acid polymers is, for example, 1,000,000 to 2,500,000, and preferably 1,200,000 to 2,000,000, more preferably 1,400,000 to 1,800,000, from the viewpoint of the durability and heat resistance of the adhesive layer 4. It should be noted that the weight-average molecular weight (Mw) of the polymers and oligomers in this specification is a value determined based on GPC (gel permeation chromatography) (converted from polystyrene).

[0062] The content of (meth)acrylic polymer in the acrylic adhesive composition, in terms of solids content, is, for example, 50% by mass or more, or 60% by mass or more, or even 70% by mass or more.

[0063] (Meth)acrylic acid oligomers

[0064] The acrylic adhesive composition may further contain (meth)acrylic oligomers. By containing (meth)acrylic oligomers, the entanglement between the molecular chains of the (meth)acrylic polymers is reduced, thereby improving the stress relaxation of the adhesive layer 4.

[0065] (Meth)acrylic acid oligomers, except for differences in weight-average molecular weight (Mw), can have the same composition as the aforementioned (meth)acrylic acid polymers. The weight-average molecular weight (Mw) of the (meth)acrylic acid oligomers is, for example, 1000 or more, or 2000 or more, 3000 or more, or even 4000 or more. The upper limit of the weight-average molecular weight (Mw) of the (meth)acrylic acid oligomers is, for example, 30000 or less, or 15000 or less, 10000 or less, or even 7000 or less. Using (meth)acrylic acid oligomers with weight-average molecular weight (Mw) within the above-mentioned range can further improve the stress relaxation properties of the adhesive layer 4.

[0066] (Meth)acrylate oligomers, for example, have 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, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, propyl (meth)acrylate, etc. Isooctyl acrylate, nonyl acrylate, isononyl acrylate, decyl acrylate, isodecyl acrylate, undecyl acrylate, dodecyl acrylate, etc. (meth)acrylate alkyl esters; esters formed by (meth)acrylate and alicyclic alcohols, such as cyclohexyl acrylate, isobornyl acrylate, dicyclopentyl acrylate; aryl esters of (meth)acrylate, such as phenyl acrylate, benzyl acrylate; and (meth)acrylates obtained from terpene compound derivative alcohols.

[0067] Preferably, the (meth)acrylic oligomer has structural units derived from acrylic monomers with relatively large bulk structures. In this case, the adhesion of the adhesive layer 4 can be further improved. The acrylic monomer is, for example, an alkyl (meth)acrylic ester with a branched alkyl group, such as isobutyl (meth)acrylic acid or tert-butyl (meth)acrylic acid; an ester formed from (meth)acrylic acid and an alicyclic alcohol, such as cyclohexyl (meth)acrylic acid, isobornyl (meth)acrylic acid, or dicyclopentyl (meth)acrylic acid; or an aryl (meth)acrylic acid ester, such as phenyl (meth)acrylic acid or benzyl (meth)acrylic acid. Preferably, the acrylic monomer has a cyclic structure, more preferably two or more cyclic structures. Furthermore, since ultraviolet irradiation during the polymerization of the (meth)acrylic oligomer and / or the formation of the adhesive layer 4 does not easily hinder the polymerization and / or formation, it is preferable that the acrylic monomer does not have unsaturated bonds. For example, an alkyl (meth)acrylic acid ester with a branched alkyl group or an ester formed from (meth)acrylic acid and an alicyclic alcohol can be used.

[0068] Specific examples of (meth)acrylic oligomers are butyl acrylate, copolymers of methyl acrylate and acrylic acid, copolymers of cyclohexyl methacrylate and isobutyl methacrylate, copolymers of cyclohexyl methacrylate and isobornyl methacrylate, copolymers of cyclohexyl methacrylate and acrylmorpholine, copolymers of cyclohexyl methacrylate and diethylacrylamide, copolymers of 1-adamantane acrylate and methyl methacrylate, copolymers of dicyclopentyl methacrylate and isobornyl methacrylate, homopolymers of dicyclopentyl acrylate, homopolymers of 1-adamantane methacrylate, and homopolymers of 1-adamantane acrylate.

[0069] The polymerization method for (meth)acrylic acid oligomers can be the same as the polymerization method for (meth)acrylic acid polymers described above.

[0070] When the adhesive composition contains an (meth)acrylic oligomer, the amount incorporated relative to 100 parts by weight of the (meth)acrylic polymer is, for example, 70 parts by weight or less, or 50 parts by weight or less, or more preferably 40 parts by weight or less. The lower limit of the amount incorporated relative to 100 parts by weight of the (meth)acrylic polymer is, for example, 1 part by weight or more, or 2 parts by weight or more, or more preferably 3 parts by weight or more.

[0071] (Meth)acrylic acid oligomers can also be used in any type of adhesive composition, including solvent-based and active energy ray-cured adhesive compositions. However, in the case of adhesive compositions used in active energy ray-cured adhesive compositions, where the (meth)acrylic acid oligomer is dissolved in a solvent, the mixture containing the (meth)acrylic acid oligomer can be cured by irradiation with active energy rays, for example, after the solvent is removed by heat drying.

[0072] [Cross-linking agent]

[0073] The acrylic adhesive composition may further contain a crosslinking agent. By using a crosslinking agent, the cohesiveness of adhesive layer 4 is improved.

[0074] Crosslinking agents include, for example, organic crosslinking agents and multifunctional metal chelates. Organic crosslinking agents include, for example, isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, and imine crosslinking agents. Multifunctional metal chelates have structures obtained by covalent or coordination bonding of multivalent metals with organic compounds. Multivalent metals include, for example, Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. The atoms in the organic compounds obtained by covalent or coordination bonding of multivalent metals are typically oxygen atoms. Organic compounds include, for example, alkyl esters, alcohols, carboxylic acids, ethers, and ketones. It should be noted that organic crosslinking agents and multifunctional metal chelates can also be used in any type of adhesive composition, including solvent-based and active energy radiation-cured adhesives.

[0075] When the 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. It should be noted that peroxide-based crosslinking agents enable crosslinking between the side chains of (meth)acrylic polymers. Therefore, compared to crosslinking using isocyanate-based crosslinking agents, the crosslinked molecular chains have a higher degree of freedom. This improves the cohesiveness of the adhesive layer 4 and more reliably ensures stress relaxation. On the other hand, crosslinking using isocyanate-based crosslinking agents improves the durability of the adhesive layer 4 compared to crosslinking using peroxide-based crosslinking agents. However, in crosslinking using difunctional isocyanate crosslinking agents, a two-dimensional crosslinked structure is formed. Therefore, although not as effective as crosslinking using peroxide-based crosslinking agents, stress relaxation of the adhesive layer 4 can be more reliably ensured. When using isocyanate-based crosslinking agents, by combining a trifunctional crosslinking agent that forms a strong three-dimensional crosslinked structure with the aforementioned difunctional crosslinking agent, a balanced improvement in durability and stress relaxation can be achieved. Furthermore, to further improve this balance, peroxide-based crosslinking agents can be used in combination with isocyanate-based crosslinking agents. It should be noted that multifunctional monomers, such as monomer (B) mentioned above, can be used in combination with crosslinking agents.

[0076] When the adhesive composition contains a crosslinking agent, the amount of the agent relative to 100 parts by weight of the (meth)acrylic polymer can be, for example, 0.1 to 10 parts by weight, 0.2 to 5 parts by weight, or even 0.3 to 3 parts by weight.

[0077] When using peroxide-based crosslinking agents alone, the amount of the agent is, for example, 0.2 to 5 parts by weight, or 1 to 3 parts by weight, relative to 100 parts by weight of (meth)acrylic polymer.

[0078] 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, more preferably 1.5 or more, and even more preferably 3 or more. Furthermore, the upper limit of the weight ratio is, for example, 500 or less, or 300 or less, and even more preferably 200 or less.

[0079] [additive]

[0080] Acrylic adhesive compositions may also contain other additives. Examples of additives include silane coupling agents, polyether compounds (such as polyalkylene glycols, represented by polypropylene glycol), colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (such as alkali metal salts, ionic liquids, and ionic solids as ionic compounds), inorganic fillers, organic fillers, and powders, particles, or foils such as metal powders.

[0081] [Formation of adhesive layer 4]

[0082] The adhesive layer 4, composed of an acrylic adhesive composition, can be formed as described below. If the adhesive composition is solvent-based, for example, a mixture of a (meth)acrylic polymer and solvent, and as needed, a (meth)acrylic oligomer, crosslinking agent, additives, etc., is applied to a substrate film and dried to form the adhesive layer 4. If the adhesive composition is an active energy ray curing type, for example, a mixture of monomers (groups) polymerized to become (meth)acrylic polymers, and as needed, a portion of the monomers (groups), a polymerization initiator, (meth)acrylic oligomers, crosslinking agent, additives, solvents, etc., is applied to a substrate film. After the solvent is removed by drying as needed, the film is irradiated with active energy rays to form the adhesive layer 4. The substrate film can be a film with a surface stripping treatment. The adhesive layer 4 formed on the substrate film can be transferred to any layer. Alternatively, the substrate film can be an optical film; in this case, an optical laminate with an adhesive layer 4 is obtained by further configuring a protective film 2 and a separator 5. Alternatively, the substrate film can be a diaphragm 5. In this case, an optical laminate with an adhesive layer 4 is obtained by further configuring the optical film 3 and the protective film 2.

[0083] The above mixture can be coated onto the substrate film using known methods. Coating can be carried out by roller coating, licking coating, gravure coating, reverse coating, roller brush coating, spraying, dip-roll coating, bar coating, doctor blade coating, air knife coating, curtain coating, die lip coating, and extrusion coating using a die coating machine, etc.

[0084] The mixture applied to the substrate film preferably has a viscosity suitable for handling and application. Therefore, in the case of an adhesive composition that is an active energy ray curable type, the mixture preferably contains a portion of the polymer of the monomer(s).

[0085] Release films that can be used on substrate films are, for example, resin films whose surfaces have been treated with silicone compounds for release.

[0086] The drying temperature of the mixture is, for example, 40~200℃, or 50~180℃, or even 70~170℃. The drying time of the mixture is, for example, 5 seconds~20 minutes, or 5 seconds~10 minutes, or even 10 seconds~5 minutes.

[0087] When the adhesive layer 4 has a thickness of 25 μm or more, there is a tendency for an increased degree of the aforementioned depressions that may occur when stored in the form of an optical laminate 1. Therefore, the effects of the present invention become more significant when the adhesive layer 4 has a thickness of 25 μm or more. The thickness of the adhesive layer 4 may also be 30 μm or more, 40 μm or more, or even 50 μm or more. The upper limit of the thickness of the adhesive layer 4 is, for example, 150 μm or less. However, the thickness of the adhesive layer 4 is not limited to the above examples, and may also be 1 to 200 μm, 5 to 150 μm, or even 10 to 100 μm.

[0088] The gel fraction of the adhesive layer 4 is preferably 60% or more, or 65% or more, or even 70% or more. The upper limit of the gel fraction of the adhesive layer 4 is, for example, 95% or less, or 90% or less. When the gel fraction of the adhesive layer 4 is within the above-mentioned range, the effect of suppressing the aforementioned degree of depression can be more effectively achieved.

[0089] The weight-average molecular weight (Mw) of the sol portion in the adhesive layer 4 is, for example, 50,000 or more, or 80,000 or more, 100,000 or more, 150,000 or more, and further, 200,000 or more. The upper limit of the weight-average molecular weight (Mw) of the sol portion is, for example, 1,200,000 or less. When the weight-average molecular weight (Mw) of the sol portion in the adhesive layer 4 is within the above-mentioned range, preferably 150,000 or more, the effect of suppressing the degree of the aforementioned depressions can be obtained more effectively.

[0090] The indentation hardness of adhesive layer 4 is 3.0 × 10⁻⁶. 4 When the pressure is below Pa, there is a tendency for an increase in the degree of the aforementioned depressions that may occur when stored as optical laminate 1. Therefore, the indentation hardness of adhesive layer 4 is 3.0 × 10⁻⁶. 4 The effects of this invention become more significant when the pressure is below Pa. The indentation hardness of the adhesive layer 4 can also be 1.4 × 10⁻⁶. 4 Below Pa, 1.2×10 4 Below Pa, 1.0×10 4 Below Pa, 8×10 3 Pa or less, and further up to 5×10 3 Below Pa. The lower limit of indentation hardness is, for example, 1 × 10⁻⁶. 2 Pa or above.

[0091] The indentation hardness of adhesive layer 4 can be determined by an indentation test based on nanoindentation. Specifically, the adhesive layer 4, to be evaluated, is cut into pieces approximately 1 cm × 1 cm in size. The cut adhesive layer 4 is then fixed to the surface of a support as a test specimen. The support has a smooth surface for fixing the adhesive layer 4 and is made of a material with sufficient hardness that will not affect the test results; typically, it is made of glass or metal. For example, a plate can be used as the support. Next, the test specimen is placed in a nanoindentation apparatus. Using a spherical indenter with a radius of curvature of 10 μm, the indenter is pressed into the adhesive layer 4 at a certain speed at room temperature to a depth of 5000 nm to perform the indentation test. The indentation speed is set to 1000 nm / s. The indentation hardness of the adhesive layer 4 can be determined by dividing the maximum load obtained at this point by the projected area, where the projected area is the portion of the indenter in contact with the test specimen at the point of maximum load.

[0092] The creep ΔCr of the adhesive layer 4 at 70°C, determined by the following tests, is for example 65 μm or less, or it can 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 ΔCr is, for example, 0.5 μm.

[0093] Test: For an adhesive layer bonded to a stainless steel test plate with a 20mm x 20mm joint surface, a load of 500gf was applied vertically downwards while the test plate was fixed. The creep (offset) of the adhesive layer relative to the test plate was measured at 100 seconds and 3600 seconds after the load was applied, denoted as Cr. 100 and Cr 3600 Based on the measured Cr 100 and Cr 3600 And through the formula ΔCr=Cr 3600 -Cr 100 Find the creep variable ΔCr.

[0094] When the creep ΔCr of the adhesive layer 4 at 70°C is within the above-mentioned range, the effect of suppressing the degree of the above-mentioned depressions can be more effectively achieved.

[0095] The creep variation ΔCr of adhesive layer 4 can be evaluated as follows (refer to...). Figure 2A and Figure 2BA strip measuring 20mm × 30mm is cut from the laminate of adhesive layer 4 and support film 51, which is to be evaluated, to serve as a test piece 52. The purpose of the support film 51 is to suppress the deformation of the applied portion of the adhesive layer 4 under load during the test, thereby determining the creep variable ΔCr with better accuracy. The support film 51 can be, for example, a resin film such as polyethylene terephthalate (PET) film. In an image display device, the support film 51 can be an optical film to be bonded to the adhesive layer 4 (after bonding). The thickness of the support film 51 is only required to prevent deformation due to the aforementioned load, for example, 20~200μm. The support film 51 can be an optical film 3, or a laminate containing an optical film 3. The laminate is, for example, a laminate of optical film 3 and protective film 2. Next, as Figure 2A and Figure 2B As shown, the test piece 52 is bonded to the surface of the stainless steel test plate 53 with a joint surface of 20mm in length and 20mm in width using adhesive layer 4. It should be noted that... Figure 2B yes Figure 2A The cross section BB. The bonding of test piece 52 to test plate 53 is carried out in a manner that prevents air bubbles from entering between test plate 53 and adhesive layer 4. In addition, after bonding by hand, it is placed in an autoclave at 50°C and 5 atmospheres (absolute pressure) for 15 minutes to bond test plate 53 and adhesive layer 4. Then, it is placed in an atmosphere at 60°C and atmospheric pressure for 2 hours to complete aging. Next, test plate 53 and test piece 52 are held vertically with test plate 53 facing up. After being placed in an atmosphere at 70°C for at least 5 minutes, with test plate 53 fixed, a 500g weight is fixed at the center of the lower end of test piece 52, and a load 54 of 500gf is applied vertically downward. The creep (offset) of adhesive layer 4 relative to test plate 53 is measured at each time point 100 seconds and 3600 seconds after the start of load 54. This is taken as the amount of weight falling at each time point and is denoted as Cr. 100 and Cr 3600 It can be based on the measured Cr 100 and Cr 3600 And through the formula ΔCr=Cr 3600 -Cr 100 Calculate the creep deformation ΔCr. The amount of weight falling can be measured using a laser displacement meter. It should be noted that when calculating the creep deformation ΔCr, Cr should be... 100 The reason for using this as a benchmark is that, immediately after applying a load of 54, even for the same test piece, the deviation in the amount of weight falling is large. In the initial stage, the influence caused by this unavoidable deviation should be eliminated as much as possible to improve the accuracy of the measurement.

[0096] To control the creep ΔCr of adhesive layer 4 at 70°C, the following methods can be used alone or in combination. For more effective control of the creep ΔCr of adhesive layer 4 at 70°C, a combination of the following methods is preferred. However, the control methods are not limited to the examples shown below.

[0097] Method 1

[0098] The composition of the (meth)acrylic monomers contained in the adhesive composition is controlled. For example, when the (meth)acrylic monomers have structural units derived from (meth)acrylic monomers (C) having hydroxyl groups, and / or when they have structural units derived from monomers (B) as crosslinking monomers, the creep ΔCr of the adhesive layer 4 at 70°C generally shows a tendency to decrease.

[0099] Method 2

[0100] The type and amount of crosslinking agent added to the adhesive composition are controlled. Increasing the amount of crosslinking agent generally tends to reduce the creep ΔCr of the adhesive layer 4 at 70°C. Furthermore, this tendency varies depending on the crosslinking agent system; therefore, by combining crosslinking agents with different systems, the creep ΔCr of the adhesive layer 4 at 70°C can be controlled more precisely. For example, in the case of a solvent-based adhesive composition, using a peroxide-based crosslinking agent, compared to a trifunctional crosslinking agent, more easily suppresses the increase in the elastic modulus of the adhesive layer 4, maintains stress relaxation, and easily reduces the creep ΔCr at 70°C. Additionally, using an active energy ray-cured adhesive composition cured by photopolymerization initiator and multifunctional monomers, compared to a solvent-based adhesive composition, more easily reduces the creep ΔCr at 70°C, and can more effectively suppress the aforementioned indentation.

[0101] Method 3

[0102] Adding (meth)acrylic oligomers to the adhesive composition. By incorporating (meth)acrylic oligomers, the creep ΔCr of adhesive layer 4 at 70°C generally shows an increasing tendency.

[0103] [Septum]

[0104] The diaphragm 5 is typically a resin film. The resin constituting the diaphragm 5 is, for example, polyester such as PET, polyolefins such as polyethylene and polypropylene, polycarbonate, acrylics, polystyrene, polyamide, or polyimide. A peeling process can be performed on the side of the diaphragm 5 that is in contact with the adhesive layer 4. The peeling process can be performed, for example, using an organosilicon compound. However, the diaphragm 5 is not limited to the above examples. The diaphragm 5 can be peeled off when using the optical laminate 1, for example, when it is adhered to the image forming layer.

[0105] The thickness of the diaphragm 5 can be, for example, 20 μm or more, or 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, and further, 75 μm or more. When the thickness of the diaphragm 5 is 45 μm or more, and especially 75 μm or more, the degree of the aforementioned depressions that may occur in the adhesive layer 4 when storing the optical laminate 1 can be more effectively suppressed. This is because the pressure generated by the foreign matter that has been infiltrated can be dispersed by the thickness of the diaphragm 5.

[0106] The adhesive-coated optical laminate of the present invention may have other layers besides those described above.

[0107] The optical laminate 1 with adhesive layer can be circulated and stored, for example, in the form of a roll formed by winding the strip of the film 1, or in the form of a laminate of the film 1 in the form of a single sheet.

[0108] Optical laminates with adhesive layers are typically used in image display devices. Image display devices include, for example, liquid crystal displays (LCDs) and organic EL displays (OLEDs). There are no limitations on the types and configurations of image display devices.

[0109] [Image display device]

[0110] An example of the image display device of the present invention is shown in Figure 3 . Figure 3 The image display device 6 shown has an optical laminate comprising, in sequence: a substrate 8, an image forming layer (e.g., an organic EL layer) 7, an adhesive layer 4, an optical film 3, and a protective film 2. The image display device 6 includes all portions of the optical laminate 1 except for the separator 5. The substrate 8 and the image forming layer 7 can have the same configuration as those of substrates and image forming layers in known image display devices. The image display device 6 suppresses the degree of depressions that may occur in the adhesive layer 4, thus exhibiting advantages such as high reliability and fewer optical defects.

[0111] Figure 3 The image display device 6 is an organic EL display. However, the type and composition of the image display device 6 are not limited.

[0112] The image display device of the present invention can have any configuration as long as it includes the portion of the optical laminate 1 with adhesive layer other than the diaphragm 5.

[0113] Example

[0114] The present invention will be described in more detail below through embodiments, but the present invention is not limited to the embodiments shown below.

[0115] First, the evaluation methods for optical laminates and adhesive layers produced in the examples and comparative examples are shown.

[0116] [Weight-average molecular weight (Mw)]

[0117] The weight-average molecular weight (Mw) of (meth)acrylic acid polymers and (meth)acrylic acid oligomers was determined by GPC under the following conditions.

[0118] • Analytical apparatus: Waters, Acquity APC

[0119] • Pillar: East Bureau System, G7000HXL+GMHXL+GMHXL

[0120] • Column temperature: 40℃

[0121] • Eluent: Tetrahydrofuran (with added acid)

[0122] • Flow rate: 0.8 mL / min

[0123] • Injection volume: 100μL

[0124] • Detector: Differential refractometer (RI)

[0125] • Standard sample: Agilent polystyrene (PS)

[0126] [Creep strain ΔCr at 70℃]

[0127] The creep ΔCr of the fabricated adhesive layer at 70°C was evaluated using the method described above. The support film 51 used was the diaphragm used in the fabrication of the optical laminate. The test plate 53 was a SUS304 plate (30mm × 75mm, 2.5mm thick). The laser displacement meter used was a Keyence LK-H057 / LK-HD500. Furthermore, the test plate 53 was placed in a 70°C atmosphere for 5 minutes from the time it was held vertically with the test plate 53 facing upwards until the start of the test.

[0128] [Gel score]

[0129] The evaluation of the gel fraction of the prepared adhesive layer was performed as follows. First, approximately 0.2 g of the prepared adhesive layer was scraped off to obtain a small piece. Next, the obtained small piece was wrapped with a polytetrafluoroethylene (PTFE) stretched porous membrane (NTF1122, 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 small piece of adhesive layer, the stretched porous membrane, and the kite string. It should be noted that the total weight B of the stretched porous membrane and kite string used was measured beforehand. Next, the test piece was immersed in a 50 mL container filled with ethyl acetate and left to stand at 23°C for 1 week. After standing, the test piece was removed from the container and dried in a desiccator set to 130°C for 2 hours, and the weight C of the test piece was measured. Then, based on the measured weights A, B, and C, the gel fraction of the adhesive layer is calculated using the formula: gel fraction (weight %) = (C - B) / (A - B) × 100 (%).

[0130] [Weight-average molecular weight (Mw) of the sol portion in the adhesive layer]

[0131] The adhesive layer was dissolved in tetrahydrofuran to prepare a 0.2% by weight solution, which was then left at room temperature for 20 hours. The solution was then filtered through a membrane filter with a filtration precision of 0.45 μm, and the weight-average molecular weight (Mw) of the filtrate was determined using GPC. The obtained value was taken as the weight-average molecular weight (Mw) of the sol portion in the adhesive layer. It should be noted that the GPC determination conditions were set to the same conditions as those used for determining the weight-average molecular weight (Mw) of (meth)acrylic acid polymers and (meth)acrylic acid oligomers.

[0132] [Tensive Modulus of Elasticity]

[0133] The tensile modulus of elasticity of the protective film was evaluated using a tensile testing machine (Shimadzu AG-IS). The sample was shaped as a strip with a width of 15 mm and a length of 50 mm. The initial chuck distance was set to 30 mm, and the tensile speed was set to 20 mm / min. It should be noted that the measurement was conducted at 23°C.

[0134] [Indentation]

[0135] In the fabricated optical laminate, the degree of indentation that might occur in the adhesive layer was evaluated as "indentation amount" as described below. A digital thickness gauge (DigitalUpright Gauge DG-205, Ozaki Manufacturing Co., Ltd.) with a measuring stage was prepared. A 5.5 mm diameter iron ball was fixed to the tip of the probe using double-sided adhesive tape (Nitto Denko No. 500). Next, the thickness gauge was operated, and the probe was moved up and down. The action of pressing the iron ball fixed to the tip of the probe onto the measuring stage and then releasing it was repeated 10 times. Then, the probe was removed, and the iron ball was pressed onto the measuring stage for 3 minutes with a constant load of 100 gf. This fully compressed the double-sided adhesive tape in the thickness direction and stabilized the fixed state of the probe and the iron ball, thereby enabling high-precision measurement. Next, the position where the iron ball, after the above treatment, contacts the measuring stage was set as the zero point. Next, the fabricated optical laminate was placed on the measuring stage with the protective film exposed. Next, the thickness gauge was operated, the probe was removed, and the iron ball was pressed onto the protective film with a constant load of 100 gf. The pressure applied to the protective film by the pressing of the iron ball was approximately 2 MPa. The displacement of the iron ball from the zero point at the moment the iron ball contacted the protective film (0 seconds after pressing) and the displacement of the iron ball from the zero point 60 seconds after pressing were measured using the thickness gauge. The absolute value of the difference was taken as the amount of indentation of the adhesive layer in the thickness direction, i.e., the amount of indentation. The zero point setting and the evaluation of the amount of indentation were performed at 23°C.

[0136] Next, the methods for preparing each adhesive layer in the embodiments and comparative examples will be described.

[0137] The abbreviations or names shown in the following description correspond to the compounds as follows.

[0138] BA: n-Butyl acrylate

[0139] LA: Lauryl acrylate

[0140] MA: Methyl acrylate

[0141] NVP: N-vinylpyrrolidone

[0142] AA: Acrylic acid

[0143] HBA: 4-Hydroxybutyl acrylate

[0144] DCPMA: Dicyclopentyl methacrylate (Hitachi Chemical Co., Ltd., FA-513M)

[0145] HEA: 2-Hydroxyethyl acrylate

[0146] 2EHA: 2-Ethylhexyl acrylate

[0147] MMA: Methyl methacrylate

[0148] AIBN: 2,2'-Azobisisobutyronitrile

[0149] Omnirad 651: 2,2-Dimethoxy-2-phenylacetophenone (manufactured by IGM Resins BV)

[0150] Omnirad 184: 1-Hydroxycyclohexylphenyl ketone (prepared by IGM Resins BV)

[0151] D110N: Trimethylolpropane / phenylenedimethyl diisocyanate adduct (Mitsui Chemicals Takenate D110N)

[0152] C / L: Trimethylolpropane / Toluene diisocyanate (Coronate L, manufactured by Nippon Polyurethane Kogyo Co., Ltd.)

[0153] A-HD-N: Hexanediol diacrylate (Shin-Nakamura Chemicals)

[0154] Peroxide: Benzoyl peroxide (NYPER BMT, manufactured by Nippon Yushi Co., Ltd.)

[0155] Irganox 1010: Pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (manufactured by BASF)

[0156] [Preparation of (meth)acrylic acid polymers]

[0157] (Synthesis example 1)

[0158] 99 parts by weight of BA and 1 part by weight of HBA were added to a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and condenser. Next, 0.1 parts by weight of AIBN as a polymerization initiator was added relative to 100 parts by weight of the BA and HBA mixture. The flask was then purged with nitrogen by slowly stirring and introducing nitrogen gas. The liquid temperature in the flask was maintained at approximately 55°C, and the polymerization reaction was carried out 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 acid polymer A1. The weight-average molecular weight (Mw) of (meth)acrylic acid polymer A1 was 1.6 million.

[0159] (Synthesis Examples 2 and 3)

[0160] The monomers and polymerization initiators of the types and amounts shown in Table 1 below were added to the flask, and otherwise, (meth)acrylic polymers A2 and A3 were obtained in the same manner as in Synthesis Example 1.

[0161] [Preparation of (meth)acrylic acid monomer slurry]

[0162] (Synthesis Example 4)

[0163] In a four-necked flask equipped with a nitrogen inlet tube and a shaft connected to a Type B viscometer (rotational viscometer), 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 Ominirad 651 and Omnirad 184 as photopolymerization initiators were added. Next, nitrogen was introduced while rotating the shaft to purge the flask, and then ultraviolet light was used to induce photopolymerization until the viscosity of the polymerization system, as measured by the viscometer, reached approximately 15 Pa·s, yielding a (meth)acrylic acid monomer slurry A4 containing a portion of the monomer group. It should be noted that a Toki Sangyo BH type viscometer was used, and the rotation speed of the shaft (rotor No. 5) was set to 10 rpm. Furthermore, the liquid temperature inside the flask was maintained at 30°C.

[0164] (Synthesis Example 5)

[0165] The monomers and photopolymerization initiators of the types and amounts shown in Table 1 below were added to the flask, and otherwise, (meth)acrylic acid monomer slurry A5 was obtained in the same manner as in Synthesis Example 4.

[0166] [Preparation of (meth)acrylic acid oligomers]

[0167] (Synthesis Example 6)

[0168] In a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and condenser, 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 were added. Next, the flask was purged with nitrogen by slowly stirring and introducing nitrogen gas. The liquid temperature in the flask was then maintained at approximately 70°C, and the polymerization reaction was carried out for 8 hours to obtain a solution of (meth)acrylic acid oligomer B1. The weight-average molecular weight of (meth)acrylic acid oligomer B1 was 4500.

[0169] (Synthesis Example 7)

[0170] 60 parts by weight of DCPMA and 40 parts by weight of MMA as monomers, 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 were added, and the mixture was reacted at 70°C for 2 hours, then the temperature was raised to 80°C and reacted for another 2 hours. Then, the reaction mixture was heated to 130°C, and the toluene, chain transfer agent, and unreacted monomers were dried to remove them, yielding (meth)acrylic acid oligomer B2.

[0171] The composition (monomer feed ratio) and weight-average molecular weight (Mw) of the (meth)acrylic polymers, (meth)acrylic monomer slurries and (meth)acrylic oligomers prepared in each synthesis example are shown in Table 1 below.

[0172]

[0173] [Creating the Adhesive Layer]

[0174] (Manufacturing Examples 1-8, 11)

[0175] A solvent-based adhesive composition was obtained by mixing (meth)acrylic acid polymers, (meth)acrylic acid oligomers, crosslinking agents, and additives in the manner shown in Table 2 below. Next, the obtained adhesive composition was coated onto the surface of a PET film (thickness 38 μm, 50 μm, or 75 μm) serving as a separator, and then dried in an air-circulating constant-temperature oven set at 155°C for 2 minutes to form the adhesive layer (thickness 50 μm) of Manufacturing Examples 1-8 and 11. A fountain coater was used for coating the adhesive composition.

[0176] (Manufacturing Examples 9 and 10)

[0177] A mixture was obtained by mixing (meth)acrylic acid monomer slurry, crosslinking agent, and additives in the manner shown in Table 2 below. Next, the mixture was coated onto the surface of a PET film (38 μm thick) serving as a diaphragm. Then, the PET film was further deposited onto the coated film of the mixture, and the coated film was held between two PET films. Next, the mixture was subjected to an illuminance of 4 mW / cm². 2 and light intensity 1200mJ / cm 2 The coated film was irradiated with ultraviolet light under certain conditions to cure it, forming an adhesive layer (50 μm thick). After the adhesive layer was formed, the further prepared PET film was peeled off to expose the adhesive layer.

[0178]

[0179] The evaluation results for each adhesive layer produced in Manufacturing Examples 1 to 11 are shown in Table 3 below.

[0180]

[0181] [Fabrication of Optical Layered Films]

[0182] Based on the combinations shown in Table 4 below, the diaphragm and adhesive layer, optical film, and protective film prepared in Manufacturing Examples 1-11 were sequentially stacked to obtain the optical laminated films of Examples 1-12 and Comparative Examples 1-3. However, no protective film was provided in Comparative Example 1. The optical film used was a polarizer with a thickness of 31 μm, which consisted of a polarizer protective film (thickness 20 μm), a polarizer (thickness 5 μm), a λ / 2 wave plate (1 / 2 wave plate, thickness 3 μm), and a λ / 4 wave plate (1 / 4 wave plate, thickness 3 μm) stacked sequentially from the side bonded to the protective film. For the protective film, PET film (thickness 25 μm, 38 μm, or 50 μm) was used in Examples 1-12 and Comparative Example 3, and polyethylene film (thickness 30 μm) was used in Comparative Example 2. The protective film was bonded to the optical film through an acrylic adhesive layer (thickness 10 μm). It should be noted that the layers constituting the optical film and the optical film were prepared as described below.

[0183] (λ / 4 waveplate and λ / 2 waveplate)

[0184] The phase retardation film, which is a laminate of λ / 4 waveplates (1 / 4 waveplates) and λ / 2 waveplates (1 / 2 waveplates), was fabricated using a polymerizable liquid crystal material (BASF, Paliocolor LC242) that exhibits a nematic liquid crystal phase after forming an alignment film. Specifically, as described above. The polymerizable liquid crystal material and a photopolymerization initiator (BASF, Irgacure 907) were dissolved in toluene. To improve coatability, 0.1–0.5% by weight of a fluorinated surfactant (DIC, Megafac) was further added based on the liquid crystal thickness to prepare a coating solution L. The solid content concentration of coating solution L was set to 25% by weight.

[0185] Next, preparations were made. Figure 4The apparatus 200 shown is a phase retardation film manufacturing apparatus. The manufacturing apparatus 200 includes: a supply spool 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 transport roller 231; die heads 222, 229, 232, and 239; and ultraviolet irradiation devices 225, 227, 235, and 237 for irradiating ultraviolet light using a high-pressure mercury lamp. Next, a solution 210 of an ultraviolet-curable resin is coated onto one side of the PET substrate 214 drawn from the supply spool 221 using the die head 222. Next, the coated film is brought into contact with the shaping roller 230 by the pressure roller 224. While maintaining contact, the PET substrate 214 is transported along the shaping roller 230, and simultaneously, ultraviolet light is irradiated from the PET substrate 214 side using the ultraviolet irradiation device 225 to cure the coated film. Linear irregularities (extending at a 75° angle relative to the MD direction of the PET substrate) are formed on the transport surface of the PET substrate 214 in the shaping roller 230. These linear irregularities form λ / 4 waveplates when the alignment film of the polymeric liquid crystal material is further formed. Through the above-mentioned curing, a cured film of UV-curable resin with a shape corresponding to the irregularities is formed on the exposed surface. Next, the PET substrate 214 with the cured film is peeled off from the shaping roller 230 by the peeling roller 226, and a coating liquid L is applied to the exposed surface of the cured film by the die head 229. The coated film is then oriented and cured by UV irradiation by the UV irradiation device 227. In this way, a λ / 4 waveplate (3 μm thick) formed by the cured film of UV-curable resin and the alignment cured film of polymeric liquid crystal material is formed on the PET substrate 214.

[0186] Next, a PET substrate 214 with λ / 4 waveplates is transported by a transport roller 231, and a solution 212 of the aforementioned UV-curable resin is applied to the exposed surface of the λ / 4 waveplates by a die 232, thereby forming a coated film. Next, the coated film is brought into contact with a shaping roller 240 by a pressure roller 234, and the PET substrate 214 is transported along the shaping roller 240 while both are in contact. Simultaneously, UV light is irradiated from the PET substrate 214 side by a UV irradiation device 235, causing the coated film to cure. Linear irregularities (extending at a 15° angle relative to the MD direction of the PET substrate) are formed on the transport surface of the PET substrate 214 in the shaping roller 240. These linear irregularities form λ / 2 waveplates during the further formation of the alignment film of the aforementioned polymeric liquid crystal material. Through the curing process, a cured film of UV-curable resin with a shape corresponding to these irregularities is formed on the exposed surface. Next, the PET substrate 214 with the cured film formed is peeled off from the shaping roller 240 by the peeling roller 236, and a coating liquid L is applied to the exposed surface of the cured film by the die head 239. Ultraviolet light is then irradiated by the ultraviolet irradiation device 237 to oriented and cure the coating film. In this way, a λ / 2 waveplate (3 μm thick) is further formed on the λ / 4 waveplate of the PET substrate 214, consisting of a cured film of ultraviolet-curable resin and an oriented cured film of polymeric liquid crystal material, resulting in a laminate (b).

[0187] (Polarizing film)

[0188] A polarizing film, which serves as a polarizer and a protective film for the polarizer, was fabricated as described below.

[0189] As a thermoplastic resin substrate, an amorphous IPA copolymer PET film (100 μm thick) containing 7 mol% isophthalic acid (IPA) units was prepared, and its surface was subjected to corona treatment (58 W / m). 2 / min). Furthermore, PVA (degree of polymerization 4200, degree of saponification 99.2%) obtained by adding 1% by weight of acetylated PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., GOHSEFIMER Z200, average degree of polymerization 1200, degree of saponification 98.5 mol%, degree of acetylation 5 mol%) was dissolved in water to obtain a PVA coating solution with a concentration of 5.5% by weight. Next, the above PVA coating solution was coated onto the corona-treated surface of an IPA copolymer PET film, resulting in a film thickness of 12 μm after drying. The coated film was then dried with hot air at 60°C for 10 minutes to obtain a laminate consisting of a substrate and a PVA layer on the substrate.

[0190] Next, the obtained laminate was stretched at 130°C in air with a stretching ratio of 1.8 times (assisted stretching in a gas atmosphere) to obtain a stretched laminate. Next, the stretched laminate was immersed in a boric acid-insoluble aqueous solution at 30°C for 30 seconds, thereby insolubleting the PVA layer. The boric acid content in the boric acid-insoluble aqueous solution was set to 3 parts by weight relative to 100 parts by weight of water. Next, the stretched laminate obtained by insolubleting the PVA layer was stained to obtain a colored laminate. Staining was performed by immersing the stretched laminate in a staining solution containing iodine and potassium iodide at 30°C. In the above staining, the PVA layer contained in the stretched laminate was stained with iodine. The staining time was adjusted to achieve a monomer transmittance of 40-44% for the PVA layer constituting the final polarizer. The staining solution used was an aqueous solution with an iodine concentration of 0.1-0.4% by weight and a potassium iodide concentration of 0.7-2.8% by weight. The ratio of potassium iodide concentration to iodine concentration in the staining solution was set to 7. Next, the stained laminate was immersed in a boric acid crosslinking aqueous solution at 30°C for 60 seconds, thereby performing a crosslinking treatment to form crosslinked structures between PVA molecules in the iodine-adsorbed PVA layer. The content of boric acid and potassium iodide in the boric acid crosslinking aqueous solution was both set to 3 parts by weight relative to 100 parts by weight of water.

[0191] Next, the cross-linked colored laminate was stretched in a boric acid aqueous solution at a stretching temperature of 70°C and a stretching ratio of 3.05 times, resulting in a stretched laminate with a final stretching ratio of 5.50 times. The stretching direction in the boric acid aqueous solution was aligned with the stretching direction of the initial assisted stretching in the gas atmosphere. 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 cleaned with a potassium iodide solution (4 parts by weight relative to 100 parts by weight of water). Next, the cleaned stretched laminate was dried with hot air at 60°C, resulting in a laminate consisting of a substrate and a polarizing mirror (5 μm thick) formed on the substrate.

[0192] Next, as a protective film for the polarizer, a stretched film of methacrylic resin with glutarimide ring units (thickness 20 μm, moisture permeability 160 g / m²) was prepared. 2 Next, the prepared polarizer protective film is bonded to the exposed surface of the polarizer in the above-prepared laminate, resulting in a laminate (c) of a substrate and a polarizing film having a polarizer and a polarizer protective film. A known acrylic adhesive is used to bond the polarizer and the polarizer protective film.

[0193] Next, using the laminates (b) and (c) prepared above, an optical film was fabricated as described below. First, the substrate was peeled off from the laminate (c) to expose the polarizer. Next, the exposed polarizer was bonded to the λ / 2 waveplate of the laminate (b) using a known acrylic adhesive to obtain the optical film. It should be noted that the bonding of the optical film to the adhesive layer was performed after the PET substrate 214 was peeled off from the laminate (b) to expose the λ / 4 waveplate.

[0194] Table 4 below shows the composition and evaluation results of each optical laminate of the embodiments and comparative examples.

[0195]

[0196] As shown in Table 4, the amount of depression is reduced in the optical laminate of the embodiment.

[0197] Industrial applicability

[0198] The optical laminate with adhesive layer of the present invention can be used in the manufacture of image display devices.

Claims

1. An optical laminated film with an adhesive layer, comprising a protective film, an optical film, an adhesive layer, and a separator, stacked sequentially. The thickness of the optical film is less than 35 μm. The thickness of the protective film is 30 μm or more and 50 μm or less, and the tensile elastic modulus of the protective film is 1 GPa or more and 100 GPa or less. The thickness of the adhesive layer is greater than 30 μm and less than 150 μm. The adhesive layer is formed from an acrylic adhesive composition containing (meth)acrylic polymers. The optical film is a polarizing film formed by bonding a polarizer protective film, a polarizer, and a phase difference film in this order, or a polarizing film formed by bonding a polarizer protective film to both sides of the polarizer. The creep ΔCr of the adhesive layer at 70°C, as determined by the following tests, is less than 50 μm. Test: For an adhesive layer bonded to a stainless steel test plate with a 20mm x 20mm joint surface, a 500gf load was applied vertically while the test plate was fixed. The creep of the adhesive layer relative to the test plate was measured at 100 seconds and 3600 seconds after the load was applied, denoted as Cr. 100 and Cr 3600 , determined by Cr 100 and Cr 3600 And through the formula ΔCr=Cr 3600 -Cr 100 Find the creep variable ΔCr.

2. The optical laminate with adhesive layer according to claim 1, wherein, The protective film is a polyester film.

3. The optical laminate with adhesive layer according to claim 1, wherein, The thickness of the diaphragm is 45 μm or more.

4. The optical laminate with adhesive layer according to claim 1, wherein, The adhesive layer has a gel fraction of 60% or more.

5. The optical laminate with adhesive layer according to claim 1, wherein, The weight-average molecular weight (Mw) of the sol portion in the adhesive layer is above 50,000.

6. An image display device comprising a portion of an optical laminate with an adhesive layer according to any one of claims 1 to 5, excluding the diaphragm.

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