Optical laminate and image display device

Abstract

Provided is an optical laminate which is suitable for suppressing display defects even when a small object collides with a screen or squeezes the screen with a narrow contact area in an image display device produced using the optical laminate. The optical laminate has a configuration in which a first optical film, a first adhesive sheet, a second optical film, and a second adhesive sheet are laminated in this order. The thickness T1 of the first adhesive sheet is 30 [mu] m or more and 1000 [mu] m or less. In addition, the elongation at break of the first adhesive sheet is 500% or less.

Description

Technical Field

[0001] This invention relates to optical laminates and image display devices. Background Technology

[0002] In recent years, image display devices, represented by liquid crystal displays (LCDs) and electroluminescent (EL) displays (e.g., organic EL displays and inorganic EL displays), have become increasingly widespread. These various image display devices, for example, have a stacked structure of image display units such as liquid crystal cells and EL light-emitting elements, along with an optical laminate. The optical laminate includes optical films such as retardation films and polarizing films, as well as an adhesive sheet. The adhesive sheet is mainly used for bonding the films contained in the optical laminate and for bonding the image display units to the optical laminate.

[0003] Patent Document 1 discloses an adhesive composition for optical films and an optical film having an adhesive layer obtained from the composition disposed on at least one side.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-158702 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] During the use and handling of image display devices, small objects may sometimes collide with or compress the screen, placing a significant load on the device. If this load is applied to an image display device made using optical laminates, damage may occur to the optical films contained within the optical laminates. Damage to the optical laminates can lead to display defects in the image display device.

[0009] Therefore, the object of the present invention is to provide an optical laminate that, in an image display device made using the optical laminate, is suitable for suppressing display defects even when a small object collides with or squeezes the image with a narrow contact area.

[0010] Problem Solving Methods

[0011] This invention provides an optical laminate, wherein a first optical film, a first adhesive sheet, a second optical film, and a second adhesive sheet are sequentially stacked.

[0012] The thickness T1 of the first adhesive sheet is 30 μm or more and 1000 μm or less, and the elongation at break of the first adhesive sheet is 500% or less.

[0013] Furthermore, the present invention provides an image display device having the above-described optical laminate.

[0014] The effects of the invention

[0015] According to the present invention, an optical laminate can be provided that, in an image display device made using the optical laminate, is suitable for suppressing display defects even when a small object collides with or squeezes the image with a narrow contact area. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view schematically showing an example of an optical laminate of this embodiment.

[0017] Figure 2 This is a schematic diagram illustrating an example of a method for manufacturing a first adhesive sheet.

[0018] Figure 3 This is a schematic diagram illustrating another example of the manufacturing method of the first adhesive sheet.

[0019] Figure 4A This is a cross-sectional view schematically showing an example of a second optical film.

[0020] Figure 4B This is a cross-sectional view schematically showing another example of a second optical film.

[0021] Figure 5 This is a cross-sectional view schematically showing another example of the optical laminate of this embodiment.

[0022] Figure 6 This is a cross-sectional view schematically showing an example of the image display device of this embodiment.

[0023] Figure 7 The diagram schematically shows cross-sectional views of the optical laminates of Examples 1-4, 6 and Comparative Examples 1-4.

[0024] Figure 8 This is a schematic cross-sectional view of the optical laminate of Embodiment 5. Detailed Implementation

[0025] The optical laminate of the first embodiment of the present invention is an optical laminate in which a first optical film, a first adhesive sheet, a second optical film and a second adhesive sheet are sequentially stacked, wherein the thickness T1 of the first adhesive sheet is 30 μm or more and 1000 μm or less, and the elongation at break of the first adhesive sheet is 500% or less.

[0026] In a second aspect of the invention, for example, in the optical laminate of the first aspect, the first adhesive sheet is formed from a photocurable adhesive composition (I) comprising a monomer group and / or a portion of the polymer of the monomer group.

[0027] In a third aspect of the present invention, for example, in the optical laminate of the second aspect, the photocurable adhesive composition (I) contains a crosslinking agent, and the amount of the crosslinking agent in the photocurable adhesive composition (I) is 0.4 parts by weight or more and 20 parts by weight or less, relative to a total of 100 parts by weight of the monomer group and the polymer.

[0028] In the fourth aspect of the present invention, for example, in the optical laminate described in any of the first to third aspects, the thickness T of the optical laminate is 200 μm or more.

[0029] In a fifth aspect of the present invention, for example, in the optical laminate described in any of the first to fourth aspects, the second optical film comprises multiple layers, the multiple layers comprising a polarizer and at least one film disposed between the polarizer and the second adhesive sheet, wherein the photoelastic coefficient of the at least one film is 4 × 10⁻⁶. -11 m 2 / N and below.

[0030] The image display device of the sixth aspect of the present invention includes the optical laminate described in any one of the first to fifth aspects.

[0031] The present invention will now be described in detail, but the present invention is not limited to the following embodiments and can be implemented in any way without departing from the spirit of the present invention.

[0032] First, the meanings of the terms used in this specification are explained. "Main surface" refers to the surface of a film or layer with the largest area. "(Meth)acrylic acid" refers to acrylic acid and methacrylic acid. For example, "(meth)acrylate" refers to acrylate and methacrylate. "Main component" refers to the component with the highest content in the composition. "Substantially free" means that the content of substances such as compounds, polymers, or solvents is, for example, 0.1% by weight or less, preferably 0.05% by weight or less, more preferably 0.01% by weight or less. "Main unit" refers to a unit that occupies 50% or more by weight, preferably 60% or more by weight, more preferably 70% or more by weight, and even more preferably 80% or more of all structural units possessed by the polymer. "Long-chain alkyl" refers to an alkyl group having 6 to 30 carbon atoms. "Substantially parallel" means that the angle between the two directions is 0°±7°, preferably 0°±5°, and even more preferably 0°±3°. "Substantially orthogonal" means that the angle between the two directions is 90°±7°, preferably 90°±5°, and even more preferably 90°±3°.

[0033] [Implementation of Optical Laminations]

[0034] In this embodiment, the optical laminate comprises a first optical film, a first adhesive sheet, a second optical film, and a second adhesive sheet stacked sequentially. The thickness T1 of the first adhesive sheet is 30 μm or more and 1000 μm or less. Furthermore, the elongation at break of the first adhesive sheet is 500% or less.

[0035] Figure 1 This is a schematic cross-sectional view illustrating an example of an optical laminate according to this embodiment. The optical laminate 10A includes a first optical film 1, a first adhesive sheet 2, a second optical film 3, and a second adhesive sheet 4. The optical laminate 10A has a structure in which the first optical film 1, the first adhesive sheet 2, the second optical film 3, and the second adhesive sheet 4 are sequentially stacked.

[0036] The first optical film 1 is in contact with the first adhesive sheet 2. The first optical film 1 and the first adhesive sheet 2 are disposed with one main surface in contact with the ground. Figure 1 In this configuration, the first optical film 1 is entirely in contact with one main surface of the first adhesive sheet 2. However, it is also possible for the first optical film 1 to be in contact with only a portion of one main surface of the first adhesive sheet 2.

[0037] The first adhesive sheet 2 is formed on the second optical film 3. The first adhesive sheet 2 is formed on one main surface of the second optical film 3. Figure 1 In this case, the first adhesive sheet 2 is formed entirely on one main surface of the second optical film 3. However, the first adhesive sheet 2 can also be formed only on a portion of one main surface of the second optical film 3.

[0038] The second adhesive sheet 4 is formed on the second optical film 3. Specifically, the second adhesive sheet 4 is formed on the main surface of the second optical film 3 opposite to the main surface on which the first adhesive sheet 2 is formed. Figure 1 In this process, the second adhesive sheet 4 is formed entirely on one main surface of the second optical film 3. However, the second adhesive sheet 4 may also be formed only on a portion of one main surface of the second optical film 3.

[0039] (First adhesive sheet)

[0040] As described above, the thickness T1 of the first adhesive sheet 2 is 30 μm or more and 1000 μm or less, preferably 40 μm or more and 800 μm or less, more preferably 45 μm or more and 700 μm or less, further preferably 50 μm or more and 500 μm or less, and particularly preferably 80 μm or more and 300 μm or less. By making the thickness T1 of the first adhesive sheet 2 30 μm or more and 1000 μm or less, even when strong pressure is applied to the thickness direction of the optical laminate 10A, the pressure can be dispersed. Therefore, the stress applied to the second optical film 3 is less likely to increase, and damage to the second optical film 3 can be further suppressed. As a result, the optical laminate 10A can suppress display defects.

[0041] As described above, the elongation at break of the first adhesive sheet 2 is 500% or less, preferably 400% or less, more preferably 350% or less, even more preferably 200% or less, and particularly preferably 100% or less. The lower limit of the elongation at break of the first adhesive sheet 2 is, for example, 10%. By ensuring that the elongation at break of the first adhesive sheet 2 is 500% or less, the first adhesive sheet 2 is less prone to deformation even when strong pressure is applied in the thickness direction of the optical laminate 10A. As a result, damage to the second optical film 3 can be further suppressed.

[0042] The first adhesive sheet 2 is formed from a photocurable adhesive composition (I) or a solvent-based adhesive composition (II). The photocurable adhesive composition (I) is an adhesive composition that forms the first adhesive sheet 2 by irradiation with light. The solvent-based adhesive composition (II) is, for example, an adhesive composition containing a polymer and a solvent. The details of the photocurable adhesive composition (I) and the solvent-based adhesive composition (II) will be described below.

[0043] (Photocurable adhesive composition)

[0044] The photocurable adhesive composition (I) comprises, for example, a monomer group and / or a portion of a polymer of that monomer group. Preferably, the monomer group in the photocurable adhesive composition (I) comprises (meth)acrylic monomers. The photocurable adhesive composition (I) may contain (meth)acrylic components, i.e., (meth)acrylic monomers and their polymers as main components. That is, the content of (meth)acrylic monomers and their polymers in the photocurable adhesive composition (I) may be 50% by weight or more, 60% by weight or more, 70% by weight or more, and further, 80% by weight or more. In this case, a first (meth)acrylic adhesive sheet 2 with (meth)acrylic polymers and their crosslinks as main components can be formed. However, the photocurable adhesive composition (I) is not limited to the above examples.

[0045] Examples of (meth)acrylic monomers are alkyl (meth)acrylates having an alkyl group having 1 to 20 carbon atoms in the side chain. The alkyl group may have 7 or fewer carbon atoms, 6 or fewer, 5 or fewer, or even 4 or fewer. The alkyl group may be linear or branched. Examples of alkyl methacrylates are methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl 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, n-tetradecyl methacrylate, n-pentadecanyl methacrylate, n-hexadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, and octadecyl methacrylate. Alkyl methacrylates can be n-butyl methacrylates.

[0046] The amount of alkyl (meth)acrylate in 100 parts by weight of monomer group is, for example, 40 parts by weight or more, or 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, and further, 95 parts by weight or more. It should be noted that when calculating the amount of a specific monomer, the weight of a portion of the polymer is converted to the weight of each monomer before polymerization.

[0047] The monomer group may contain carboxyl-containing monomers. Carboxyl-containing monomers may be (meth)acrylic acid monomers; in other words, (meth)acrylic acid monomers may include carboxyl-containing monomers. Examples of carboxyl-containing monomers are (meth)acrylic acid, carboxyethyl (meth)acrylic acid, carboxypentyl (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The amount of carboxyl-containing monomer in 100 parts by weight of the monomer group may be, for example, 10 parts by weight or less, and may be 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, 5 parts by weight or less, 4.8 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, and further may be 0.5 parts by weight or less. The lower limit of the amount may be, for example, 0.1 parts by weight or more, and depending on the circumstances, may also be 0.5 parts by weight or more. The monomer group may also not contain carboxyl-containing monomers.

[0048] The monomer group may include hydroxyl-containing monomers. Hydroxyl-containing monomers may be (meth)acrylate monomers; in other words, (meth)acrylate monomers may include hydroxyl-containing monomers. Hydroxyl-containing monomers can contribute to improved cohesiveness of the adhesive sheet. Examples of hydroxyl-containing monomers are 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and methyl (4-hydroxymethylcyclohexyl)acrylate. Preferably, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are hydroxyl-containing monomers. The amount of hydroxyl-containing monomer in 100 parts by weight of the monomer group may be, for example, 20 parts by weight or less, and may be 15 parts by weight or less, 10 parts by weight or less, 7.5 parts by weight or less, 5 parts by weight or less, 4 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, and further may be 0.5 parts by weight or less. The lower limit of the amount of the compound is, for example, 0.01 parts by weight or more, 0.03 parts by weight or more, and further, 0.05 parts by weight or more. The monomer group may also not contain hydroxyl-containing monomers.

[0049] The monomer group may include ether-containing monomers. These ether-containing monomers may be (meth)acrylic acid monomers; in other words, (meth)acrylic acid monomers may include ether-containing monomers. Ether-containing monomers can contribute to improved adhesion between the first optical film 1 and the first adhesive sheet 2.

[0050] The ether-containing monomer is preferably an alkoxy-containing monomer. Examples of alkoxy-containing monomers include, for instance, the epoxide alkane adducts represented by the following chemical formula (1). R in formula (1) 1 R is a hydrogen atom or a methyl group. In formula (1), R... 2 It is an alkyl group. Alkyl groups can be straight-chain or branched. R 2 Preferably, it is a straight-chain alkyl group. R 2 Examples of methyl and ethyl. In formula (1), n ​​is an integer from 1 to 30, preferably an integer from 1 to 12, and more preferably an integer from 1 to 5.

[0051] [Chemical Formula 1]

[0052]

[0053] Examples of the epoxyalkane adducts shown in formula (1) are 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, methoxytriethylene glycol (meth)acrylate and methoxypolyethylene glycol (meth)acrylate, preferably 2-methoxyethyl acrylate (MEA).

[0054] The ether-containing monomer is not limited to the above-mentioned epoxide alkane adducts. The ether-containing monomer may have a cyclic structure, which may contain an ether group. Examples of cyclic structures containing an ether group include tetrahydrofuran rings and dialkyl rings. Examples of ether-containing monomers with cyclic structures are cyclic trimethylolpropane methyl acetal (meth)acrylate and tetrahydrofurfuryl (meth)acrylate.

[0055] The amount of the ether-containing monomer in 100 parts by weight of the monomer group may be, for example, 1 part by weight or more, but can be 5 parts by weight or more, 10 parts by weight or more, 20 parts by weight or more, 25 parts by weight or more, 30 parts by weight or more, 40 parts by weight or more, 50 parts by weight or more, 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, and further can be 90 parts by weight or more. The upper limit of the amount is, for example, 99 parts by weight or less, and depending on the circumstances, it can be 50 parts by weight or less. The monomer group may also not contain any ether-containing monomer.

[0056] In the photocurable adhesive composition (I), the aforementioned monomers may be included in the form of a partial polymer. The partial polymer may be any polymer among homopolymers and copolymers. The partial polymer can contribute to the stable formation of the coating layer described later by moderately increasing the viscosity of the photocurable adhesive composition (I).

[0057] Photocurable adhesive compositions (I) typically contain photopolymerization initiators. Examples of photopolymerization initiators are photoradiogenin generators that generate free radicals upon exposure to visible light and / or ultraviolet light with wavelengths shorter than 450 nm.

[0058] Examples of photopolymerization initiators include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzoin dimethyl ether; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkyl acetophenones such as 1-hydroxycyclohexylphenyl ketone; substituted α-alcohol ketones such as 2-methyl-2-hydroxyphenylacetophenone; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; and 1-phenyl... Photoactive oximes such as -1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone and other benzophenone compounds; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone Thioxanone compounds such as isopropyl thioxanone, 2,4-diisopropyl thioxanone, and 2,4-diethyl thioxanone; 2,4,6-trichloro-triazine, 2-phenyl-4,6-bis(trichloromethyl)-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-triazine, 2-(p-tolyl)-4,6-bis(trichloromethyl)-triazine, and 2-piperyl-4,6-bis(trichloromethyl)-triazine. Triazine compounds, including 2,4-bis(trichloromethyl)-6-styryl-triazine, 2-(naphthyl-1-yl)-4,6-bis(trichloromethyl)-triazine, 2-(4-methoxy-naphthyl-1-yl)-4,6-bis(trichloromethyl)-triazine, 2,4-trichloromethyl-(piperyl)-6-triazine, and 2,4-trichloromethyl-(4'-methoxystyryl)-6-triazine; 1,2-octanedione, Oxime esters such as 1-[4-(phenylthio)-, 2-(O-benzoyl oxime)], O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethoxy)hydroxylamine; phosphine compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide; quinone compounds such as 9,10-phenanthroquinone, camphorquinone, ethylanthraquinone; borate esters; carbazole compounds; imidazole compounds; and titanium ceramsite compounds. The photocurable adhesive composition (I) may contain one or more photopolymerization initiators.

[0059] The amount of photopolymerization initiator in the photocurable adhesive composition (I) is, for example, 0.02 to 10 parts by weight, or 0.05 to 5 parts by weight, relative to a total of 100 parts by weight of the monomer group and some of the polymers.

[0060] The photocurable adhesive composition (I) may also contain a crosslinking agent. Examples of crosslinking agents are polyfunctional monomers having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic acid monomer. Examples of polyfunctional monomers include monomers having two or more C=C bonds in one molecule, and monomers having one or more C=C bonds and one or more polymerizable functional groups such as epoxy, aziridinyl, α-zolinyl, hydrazyl, or hydroxymethyl in one molecule. Preferably, the polyfunctional monomer is a monomer having two or more C=C bonds in one molecule.

[0061] Examples of multifunctional monomers include: 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, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (NDDA), 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, and other multifunctional acrylates (ester compounds formed by polyols and (meth)acrylic acid, etc.); allyl methacrylate, vinyl methacrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The multifunctional monomer is preferably a multifunctional acrylate, more preferably trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentaerythritol hexa(meth)acrylate.

[0062] The crosslinking agent may include other crosslinking agents besides the multifunctional monomers mentioned above. Isocyanate crosslinking agents are an example of such crosslinking agents. The photocurable adhesive composition (I) may include an isocyanate crosslinking agent as a crosslinking agent, preferably both the multifunctional monomers and the isocyanate crosslinking agent mentioned above. Isocyanate crosslinking agents can contribute to improving the adhesion between the first optical film 1 and the first adhesive sheet 2.

[0063] As isocyanate crosslinking agents, compounds having at least two isocyanate groups (isocyanate compounds) can be used. The number of isocyanate groups in the isocyanate compound is preferably three or more. There is no particular upper limit to the number of isocyanate groups, for example, five. Examples of isocyanate compounds include aromatic isocyanate compounds, alicyclic isocyanate compounds, and aliphatic isocyanate compounds.

[0064] Examples of aromatic isocyanate compounds include: phenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, phenyl dimethyl diisocyanate, etc.

[0065] Examples of alicyclic isocyanate compounds include: 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated phenyl diisocyanate, hydrogenated toluene diisocyanate, and hydrogenated tetramethylphenyl diisocyanate.

[0066] Examples of aliphatic isocyanate compounds include: trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), 1,2-propylidene diisocyanate, 1,3-butylidene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0067] Examples of isocyanate crosslinking agents include polymers (dimers, trimers, pentamers, etc.) of the aforementioned isocyanate compounds, adducts obtained by addition reactions with polyols such as trimethylolpropane, urea-modified compounds, biuret-modified compounds, urethane-modified compounds, isocyanurate-modified compounds, carbodiimide-modified compounds, and urethane prepolymers obtained by addition reactions with polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc.

[0068] The isocyanate crosslinking agent preferably comprises an aliphatic isocyanate compound and / or a derivative thereof. Particularly preferred are at least one selected from pentamethylene diisocyanate (PDI) crosslinking agents (PDI and its derivatives) and hexamethylene diisocyanate (HDI) crosslinking agents (HDI and its derivatives). Specific examples of PDI crosslinking agents include isocyanurate modified PDI. Specific examples of HDI crosslinking agents include isocyanurate modified HDI, biuret modified HDI, etc.

[0069] The amount of crosslinking agent in the photocurable adhesive composition (I) varies depending on the molecular weight, number of functional groups, etc., but is preferably 0.4 parts by weight or more and 20 parts by weight or less, more preferably 0.4 parts by weight or more and 10 parts by weight or less, and more preferably 0.5 parts by weight or more and 5 parts by weight or less, relative to 100 parts by weight of the monomer group and some of the polymers. By appropriately adjusting the amount of crosslinking agent in the photocurable adhesive composition (I), display defects in the image display device can be further suppressed. In addition, by appropriately adjusting the amount of crosslinking agent in the photocurable adhesive composition (I), the adhesion between the first adhesive sheet 2 and the first optical film 1 and / or the second optical film 3 can be improved.

[0070] It should be noted that when the photocurable adhesive composition (I) contains an isocyanate crosslinking agent, the amount of the isocyanate crosslinking agent is, for example, 0.02 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.5 parts by weight or more, and even 1 part by weight or more, relative to a total of 100 parts by weight of the monomer group and some of the polymer.

[0071] When isocyanate crosslinking agents are added, especially at high temperatures, the adhesive sheet can sometimes harden. In such cases, the stress relaxation properties of the adhesive sheet are impaired, and therefore, the expansion and contraction stresses of the optical film are easily transmitted to the interface between the adhesive sheet and the adherend, leading to a tendency for peeling. Where the adhesion between the adhesive sheet and the optical film can be ensured by methods other than adding isocyanate crosslinking agents, it is desirable to eliminate isocyanate crosslinking agents from the photocurable adhesive composition (I).

[0072] The light-curing adhesive composition (I) may also contain additives other than those described above. Examples of additives include chain transfer agents, silane coupling agents, viscosity modifiers, adhesion promoters, plasticizers, softeners, anti-aging agents, fillers, colorants, antioxidants, surfactants, antistatic agents, and ultraviolet absorbers.

[0073] The solvent content in the photocurable adhesive composition (I) is, for example, 5% by weight or less, and can be 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, and further can be 0.5% by weight or less. The photocurable adhesive composition (I) may substantially not contain any solvent.

[0074] The viscosity of the photocurable adhesive composition (I) is preferably 5 to 150 poise. The photocurable adhesive composition (I) having a viscosity within the above range is particularly suitable for the formation of the coating layer described later.

[0075] The polymerization rate of the monomer group in the first adhesive sheet 2 is preferably 90% or higher. The polymerization rate can be 95% or higher, 98% or higher, and further, 99% or higher.

[0076] The gel fraction of the first adhesive sheet 2 is, for example, 50% or more, 75% or more, 80% or more, and even 85% or more.

[0077] [Manufacturing method of the first adhesive sheet]

[0078] When the first adhesive sheet 2 is formed from a light-curing adhesive composition (I), the first adhesive sheet 2 can be manufactured, for example, by the following method. Figure 2 This is a schematic diagram illustrating an example of a method for manufacturing the first adhesive sheet. For example... Figure 2 As shown in (a), a first laminate 15 is fabricated, sequentially comprising a substrate sheet 21, a coating layer 22 containing a photocurable adhesive composition (I), and a release liner 23. Next, the first laminate 15 is irradiated with light 14. At this time, the light 14 passes through the substrate sheet 21 and reaches the coating layer 22, causing the coating layer 22 to cure. Typically, the irradiation of the first laminate 15 by the light 14 is performed from one side of the substrate sheet 21. However, the irradiation by the light 14 can also be performed from one side of the release liner 23. Thus, as... Figure 2 As shown in (b), the first adhesive sheet 2 is formed from the coating layer 22. That is, a second laminate 16 is obtained, which sequentially includes the substrate sheet 21, the first adhesive sheet 2, and the release liner 23.

[0079] When the first adhesive sheet 2 is formed from a light-curing adhesive composition (I), the first adhesive sheet 2 can also be manufactured by other methods, for example. Figure 3 This is a schematic diagram used to illustrate another example of a method for manufacturing the first adhesive sheet. For example... Figure 3 As shown in (a), a first laminate 15 is fabricated, sequentially comprising a substrate sheet 21, a coating layer 22 containing a photocurable adhesive composition (I), and a release liner 23. Next, the first laminate 15 is irradiated with light 14. Figure 3 As shown in (a), the light 14 is applied from both sides of the release liner 23 and the substrate sheet 21. Thus, as... Figure 3 As shown in (b), the first adhesive sheet 2 is formed from the coating layer 22. That is, a second laminate 16 is obtained, which sequentially includes the substrate sheet 21, the first adhesive sheet 2, and the release liner 23.

[0080] Until the release liner 23 is peeled off, the first adhesive sheet 2 formed by the coating layer 22 is sandwiched between the substrate sheet 21 and the release liner 23 to form part of the second laminate 16.

[0081] An example of a substrate (hereinafter, "substrate") for peeling off liner 23 is a resin film. Examples of resins that may be included in the substrate include polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. The resin is preferably a polyester such as polyethylene terephthalate.

[0082] The release liner 23 may have light 14 transmittance, or it may have the same degree of light 14 transmittance as the substrate sheet 21.

[0083] The thickness of the peeling liner 23 is, for example, 10~200μm, or 25~150μm.

[0084] The release liner 23 may have layers other than the substrate. The release liner 23 may have a release layer. For example, the release liner 23 may have a substrate and a release layer formed on one side of the substrate. The release liner 23 may be used such that the release layer is on the side of the coating layer 22.

[0085] Typically, the release layer is a cured layer of a release agent composition containing a release agent. Various release agents can be used, such as silicone-based release agents, fluorinated release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, and silica powder. The release liner 23 may have a cured layer of a release agent composition containing a silicone-based release agent as the main component (hereinafter, "silicone release layer"). The silicone release layer is particularly suitable for balancing adhesion and peelability relative to the first adhesive sheet 2.

[0086] Organosilicon release agents include various curing types of organosilicon materials, such as addition reaction type, condensation reaction type, UV curing type, electron beam curing type, and solvent-free type, with addition reaction curing type organosilicon materials being preferred. Addition reaction curing type organosilicon materials are particularly suitable for forming a release layer that balances adhesion and peelability relative to the first adhesive sheet 2. The curing type organosilicon material can be an organosilicon-modified resin obtained by introducing reactive organosilicon into organic resins such as urethane, epoxy, and alkyd resins through graft polymerization or the like.

[0087] Examples of addition-reaction-curable silicone materials are polyorganosiloxanes containing vinyl or alkenyl groups within the molecule. Addition-reaction-curable silicone materials may also lack hydrogenated silyl groups. Examples of alkenyl groups include 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl, and 11-dodecenyl. Examples of polyorganosiloxanes include polyalkylalkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane, polyalkylarylsiloxanes, and copolymers of various Si-containing monomers such as poly(dimethylsiloxane-diethylsiloxane). Polyorganosiloxanes are preferably polydimethylsiloxane.

[0088] Release agent compositions containing silicone-based release agents as the main component (hereinafter, "silicone release agent compositions") typically contain crosslinking agents. Examples of crosslinking agents are polyorganosiloxanes having hydrogenated silyl groups. Crosslinking agents may have two or more hydrogenated silyl groups in one molecule.

[0089] Organosilicon release agent compositions may also contain curing catalysts. Examples of curing catalysts are platinum-based catalysts. Examples of platinum-based catalysts include chloroplatinic acid, platinum olefin complexes, and chloroplatinic acid olefin complexes. The amount of platinum-based catalyst relative to the total solids content of the composition is, for example, 10 to 1000 ppm (by weight, converted to platinum).

[0090] The silicone release agent composition may also contain additives. Examples of additives are peel control agents and adhesion improvers. Examples of peel control agents are unreactive silicone resins, more specifically, organosiloxanes such as octamethylcyclotetrasiloxane and MQ resins. The amount of peel control agents and adhesion improvers, in total, is, for example, 1 to 30% by weight relative to the total solids content of the composition. Other examples of additives are fillers, antistatic agents, antioxidants, UV absorbers, plasticizers, and colorants. The amount of other additives, in total, is, for example, less than 10% by weight relative to the total solids content of the composition.

[0091] The silicone release agent composition may also contain organic solvents. Examples of organic solvents include hydrocarbon solvents such as cyclohexane, n-hexane, and n-heptane; aromatic solvents such as toluene and xylene; ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and alcohol solvents such as methanol, ethanol, and butanol. Two or more organic solvents may also be included. The preferred amount of organic solvent is 80-99.9% by weight of the silicone release agent composition.

[0092] A release layer can be formed, for example, by heating and drying a coating film containing a release agent composition formed on a substrate. The release agent composition can be applied using various methods such as roller coating, licking coating, gravure coating, reverse coating, brush coating, spraying, dip roller coating, bar coating, doctor blade coating, air knife coating, curtain coating, die lip coating, and die coating. Heating and drying can be performed using hot air drying, for example. The heating temperature and time vary depending on the heat resistance of the substrate, typically ranging from 80 to 150°C for approximately 10 seconds to 10 minutes. If necessary, irradiation with active energy rays such as ultraviolet light can also be used in combination.

[0093] The thickness of the release layer is, for example, 10~300nm. The upper limit of the thickness can be below 200nm, below 150nm, below 120nm, below 110nm, below 100nm, less than 100nm, below 90nm, below 80nm, below 70nm, less than 70nm, and further below 65nm. The lower limit of the thickness can be above 15nm, above 20nm, above 25nm, above 30nm, above 35nm, above 40nm, above 45nm, and further above 50nm.

[0094] The peeling liner 23 can be in the form of a single sheet or in the form of a strip.

[0095] An example of substrate sheet 21 is a resin film. Examples of resins contained in substrate sheet 21 are the same as examples of resins that may be contained in a substrate.

[0096] The preferred substrate sheet 21 has excellent transmittance to light 14.

[0097] The thickness of the substrate sheet 21 is, for example, 10~200μm, or 25~150μm.

[0098] The substrate sheet 21 may have a release layer on one side of the coating layer 22. Examples of the release layer that the substrate sheet 21 may have and its manufacturing method are the same as examples of the release layer that the release liner 23 may have and its manufacturing method. Alternatively, both the release liner 23 and the substrate sheet 21 may have release layers. In this case, both release layers may be formed from a release agent composition containing the same release agent as a main component. Furthermore, the thicknesses of the two release layers may differ; for example, the release layer of the substrate sheet 21 may be thicker.

[0099] The substrate sheet 21 can typically be selected as a sheet with a greater peel force than the first adhesive sheet 2 compared to the adhesive sheet 1.

[0100] The substrate sheet 21 can be a single sheet or a strip.

[0101] The first laminate 15 can be formed, for example, by forming a coating layer 22 on a substrate sheet 21 (or release liner 23) and placing the release liner 23 (or substrate sheet 21) on the formed coating layer 22. Alternatively, the first laminate 15 can be formed by coating a photocurable adhesive composition (I) into a space between substrate sheets 21 and release liner 23 held at a given interval with their main surfaces facing each other.

[0102] The coating layer 22 can be formed by various coating methods such as roller coating, roller licking coating, gravure coating, reverse coating, roller brushing, spraying, dip roller coating, bar coating, scraping coating, air knife coating, curtain coating, die lip coating, and die coating.

[0103] The thickness of the coating layer 22 can be adjusted according to the thickness of the first adhesive sheet 2 of the target, for example, 5~500μm, 5~250μm, 5~150μm, 5~100μm, 5~50μm, 5~30μm, 5~25μm, and further, 5~20μm.

[0104] The light 14 irradiating the first laminate 15 is, for example, visible light or ultraviolet light with a wavelength shorter than 450 nm. The light 14 may contain light with a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the photocurable adhesive composition. The light 14 obtained by irradiating with a filter or the like to cut off short-wavelength light with a wavelength below 300 nm is suitable for suppressing the degradation of the substrate sheet 21 caused by the light 14. The light source of the light 14 is, for example, a lighting device equipped with an ultraviolet irradiation lamp. Examples of ultraviolet irradiation lamps include ultraviolet LEDs, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, microwave-excited mercury lamps, black lights, chemical lamps, germicidal lamps, low-pressure discharge mercury lamps, and excimer lasers. Two or more ultraviolet irradiation lamps may also be combined.

[0105] The illumination of light 14 can be continuous or intermittent.

[0106] The illuminance of light 14 is, for example, 1~20 mW / cm². 2 The irradiation time of light 14 is, for example, 5 minutes to 5 hours. The cumulative light intensity of light 14 on the first stack 15 is, for example, 100 to 5000 mJ / cm. 2 .

[0107] (Soluble-based adhesive composition)

[0108] As described above, the solvent-based adhesive composition (II) is, for example, an adhesive composition comprising a polymer and a solvent. When the first adhesive sheet 2 is formed from the solvent-based adhesive composition (II), examples of adhesives constituting the first adhesive sheet 2 include acrylic adhesives, rubber adhesives, vinyl alkyl ether adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, fluoropolymer adhesives, epoxy adhesives, and polyether adhesives. It should be noted that the adhesives constituting the first adhesive sheet 2 can be used alone or in combination of two or more. From the perspectives of transparency, processability, durability, and adhesion, it is preferable to use an acrylic adhesive (composition) containing a (meth)acrylic polymer alone. In other words, the first adhesive sheet 2 preferably contains a (meth)acrylic polymer as the polymer.

[0109] [(Meth)acrylic polymer (A)]

[0110] The (meth)acrylic polymer (A) preferably has structural units derived from a (meth)acrylic monomer (A1) having an alkyl group having 1 to 30 carbon atoms in its side chain as the main unit. The alkyl group can be linear or branched. The (meth)acrylic polymer (A) may have one or more structural units derived from the (meth)acrylic monomer (A1). Examples of (meth)acrylate monomers (A1) are methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)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.

[0111] (Meth)acrylic polymers (A) may have structural units derived from (meth)acrylic monomers (A1) having long-chain alkyl groups in their side chains. An example of such monomer (A1) is dodecyl (meth)acrylate (laurate).

[0112] (Meth)acrylate polymers (A) can have structural units derived from (meth)acrylate monomers (A1) whose glass transition temperature (Tg) is in the range of -70 to -20°C when formed as homopolymers. An example of such monomer (A1) is n-butyl acrylate.

[0113] (Meth)acrylic polymers (A) may also have structural units other than those derived from (meth)acrylic monomers (A1). These structural units are derived from monomers (A2) capable of copolymerizing with (meth)acrylic monomers (A1). (Meth)acrylic polymers (A) may have one or more of these structural units.

[0114] Examples of monomers (A2) are aromatic ring monomers. Aromatic ring monomers can be aromatic ring (meth)acrylate monomers. Examples of aromatic ring monomers include phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, hydroxyethylated β-naphthol (meth)acrylate, and biphenyl (meth)acrylate. The content of structural units derived from aromatic ring monomers in the (meth)acrylate polymer (A) is, for example, 0-50% by weight, and can be 1-30% by weight, 5-25% by weight, 8-20% by weight, 10-18% by weight, 12-16% by weight, and further, 12-16% by weight. The presence of structural units derived from aromatic ring monomers in the (meth)acrylate polymer (A) can contribute to improved compatibility between the (meth)acrylate polymer (A) and the crosslinking agent (B) and its self-polymers.

[0115] Other examples of monomers (A2) are hydroxyl-containing monomers. Hydroxyl-containing monomers can be hydroxyl-containing (meth)acrylate monomers. Examples of hydroxyl-containing monomers 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, and 12-hydroxylaurate (meth)acrylate, as well as methyl (4-hydroxymethylcyclohexyl)acrylate. It should be noted that hydroxyl groups can react with various crosslinking agents. From the viewpoint of improving the uniformity of the formed crosslinked structure, the content of structural units from hydroxyl-containing monomers in the (meth)acrylate polymer (A) can be less than 1% by weight, less than 0.5% by weight, less than 0.1% by weight, or even 0% by weight (excluding this structural unit).

[0116] The monomer (A2) can be a carboxyl-containing monomer, an amino-containing monomer, or an amide-containing monomer. Examples of carboxyl-containing monomers are (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 are N,N-dimethylaminoethyl (meth)acrylic acid and N,N-dimethylaminopropyl (meth)acrylic acid. Examples of amide-containing monomers include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethyl-N-propyl(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, and mercaptoethyl(meth)acrylamide, etc.; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and N-vinyl lactam monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam.

[0117] The monomer (A2) can be a multifunctional monomer. 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, and urethane acrylate, as well as divinylbenzene. The multifunctional acrylates are preferably 1,6-hexanediol diacrylate and dipentaerythritol hexa(meth)acrylate.

[0118] The total content of structural units derived from carboxyl-containing monomers, amino-containing monomers, amide-containing monomers, and polyfunctional monomers in the (meth)acrylic polymer (A) is preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 8% by weight or less. When the (meth)acrylic polymer (A) has this structural unit, the total content is, for example, 0.01% by weight or more, or possibly 0.05% by weight or more. The (meth)acrylic polymer (A) may also not contain structural units derived from polyfunctional monomers. By giving the (meth)acrylic polymer (A) structural units derived from carboxyl-containing monomers, particularly acrylic acid, and / or structural units derived from amide-containing monomers, the self-polymerization property of the crosslinking agent (B) can be improved, for example. The improved self-polymerization property of the crosslinking agent (B) can particularly help suppress the peeling of adhesive sheets in humid environments and stabilize the physical properties of adhesive sheets in systems with a high content of crosslinking agent (B).

[0119] Examples of other monomers (A2) include alkoxyalkyl esters of methacrylates such as 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, methoxytriethylene glycol acrylate, 3-methoxypropyl acrylate, 3-ethoxypropyl acrylate, 4-methoxybutyl acrylate, and 4-ethoxybutyl acrylate; epoxy monomers such as glycidyl acrylate and methylglycidyl acrylate; sulfonic acid monomers such as sodium vinyl sulfonate; phosphate monomers; cyclopentyl acrylate, cyclohexyl acrylate, and isobornyl acrylate, which are methacrylates with alicyclic hydrocarbon groups; 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; and vinyl chloride.

[0120] The total content of structural units from the other monomers (A2) mentioned above in the (meth)acrylic polymer (A) is, for example, 30% by weight or less, or 10% by weight or less, and preferably 0% by weight (excluding the structural unit).

[0121] (Meth)acrylic acid polymers (A) can be formed by polymerizing one or more of the aforementioned monomers using known methods. Polymerization can also be performed by polymerizing monomers 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. Since adhesive sheets with excellent optical transparency can be formed, solution polymerization and active energy radiation polymerization are preferred. Polymerization is preferably carried out while avoiding contact between the monomers and / or a portion of the polymer and oxygen; for this purpose, 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 (A) to be formed can be any form of random copolymer, block copolymer, graft copolymer, etc.

[0122] The polymerization system that forms the (meth)acrylic acid polymer (A) 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 thermal polymerization initiator or a photopolymerization initiator.

[0123] 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.

[0124] The polymerization initiators used in solution polymerization are, for example, azo polymerization initiators, peroxide polymerization initiators, and redox polymerization initiators. Peroxide polymerization initiators include, for example, 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.

[0125] The active energy rays used in active energy radiation polymerization include, for example, 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 a (meth)acrylic acid polymer (A) can be formed.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] The weight-average molecular weight (Mw) of (meth)acrylic polymers (A) is, for example, 1 million to 2.8 million. From the viewpoint of durability and heat resistance of the adhesive sheet, it can be 1.2 million or more, and further, 1.4 million or more. The weight-average molecular weight (Mw) of polymers and oligomers in this specification is a value obtained based on GPC (gel permeation chromatography) determination (converted to polystyrene).

[0130] The content of (meth)acrylic polymer (A) in the adhesive composition (II) is, for example, 50% by weight or more, and can be 60% by weight or more, 70% by weight or more, and further can be 80% by weight or more, based on the solid content ratio. The upper limit of the content is, for example, 99% by weight or less, and can be 97% by weight or less, 95% by weight or less, 93% by weight or less, and further can be 90% by weight or less.

[0131] [Crosslinking agent (B)]

[0132] Crosslinking agent (B) is typically a multifunctional crosslinking agent with two or more crosslinking reactive groups per molecule. Crosslinking agent (B) can also be a trifunctional or higher crosslinking agent with three or more crosslinking reactive groups per molecule. Trifunctional or higher crosslinking agents (B) readily form self-polymers. The upper limit for the number of crosslinking reactive groups per molecule is, for example, five.

[0133] Crosslinking agent (B) is, for example, an isocyanate crosslinking agent. Isocyanate crosslinking agents contain isocyanate groups as crosslinking reactive groups. Isocyanate crosslinking agent (B) can be an aromatic isocyanate compound, an alicyclic isocyanate compound, or an aliphatic isocyanate compound.

[0134] Examples of aromatic isocyanate compounds that can be used as crosslinking agents (B) include phenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, and phenyl dimethyl diisocyanate.

[0135] Examples of alicyclic isocyanate compounds that can be used as crosslinking agents (B) include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated phenyl diisocyanate, hydrogenated toluene diisocyanate, and hydrogenated tetramethylphenyl diisocyanate.

[0136] Examples of aliphatic isocyanate compounds that can be used as crosslinking agents (B) include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylidene diisocyanate, 1,3-butylidene diisocyanate, dodecamethyl diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0137] The crosslinking agent (B) may also be a derivative of the above-mentioned isocyanate compound. Examples of derivatives include polymers (dimers, trimers, pentamers, etc.), adducts (adducts) obtained by addition reaction with polyols such as trimethylolpropane, urea-modified compounds, biuret-modified compounds, urethane-modified compounds, isocyanurate-modified compounds, carbodiimide-modified compounds, and urethane prepolymers obtained by addition reaction with polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc.

[0138] The crosslinking agent (B) is preferably an aromatic isocyanate compound or its derivatives, more preferably toluene diisocyanate or its derivatives (in other words, more preferably a toluene diisocyanate-based (TDI) crosslinking agent). TDI crosslinking agents exhibit superior reaction uniformity compared to phenyl diisocyanate or its derivatives (in other words, phenyl diisocyanate-based (XDI) crosslinking agents). Examples of TDI crosslinking agents include adducts of toluene diisocyanate with polyfunctional alcohols, and more specifically, trimethylolpropane / toluene diisocyanate trimer adducts.

[0139] The crosslinking agent (B) can be a commercially available product. Examples of commercially available products are Millionate MT, Millionate MTL, Millionate MR-200, Millionate MR-400, Coronate L, Coronate HL, and Coronate HX (all manufactured by Tosoh; all are trade names), and Takenate D-102, Takenate D-103, Takenate D-110N, Takenate D-120N, Takenate D-140N, Takenate D-160N, Takenate D-165N, Takenate D-170HN, Takenate D-178N, Takenate 500, and Takenate 600 (all manufactured by Mitsui Chemicals; all are trade names). The crosslinking agent (B) can preferably be Coronate L, Takenate D-102 and Takenate D-103 (all of which are trimethylolpropane / toluene diisocyanate trimer adducts).

[0140] The amount of crosslinking agent (B) in the adhesive composition (I) relative to 100 parts by weight of (meth)acrylic polymer (A) is 5 parts by weight or more, and can be 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, 10 parts by weight or more, more than 10 parts by weight, and further can be 11 parts by weight or more. The upper limit of the amount is, for example, 30 parts by weight or less, and can be 28 parts by weight or less, 25 parts by weight or less, 23 parts by weight or less, 20 parts by weight or less, 19 parts by weight or less, 18 parts by weight or less, and further can be 15 parts by weight or less.

[0141] The adhesive composition (I) may contain one or more crosslinking agents (B).

[0142] The adhesive sheet formed from the adhesive composition (II) can have an interpenetrating network (IPN) structure of a crosslinker of (meth)acrylic polymer (A) and a self-polymer of crosslinking agent (B). The IPN structure is suitable for improving the durability of the adhesive sheet.

[0143] Other examples of crosslinking agent (B) are peroxide-based crosslinking agents, epoxy-based crosslinking agents, imine-based crosslinking agents, and multifunctional metal chelates. However, isocyanate-based crosslinking agent (B) is preferred. When the adhesive composition (II) contains crosslinking agent (B) other than isocyanate-based crosslinking agent, its total amount relative to 100 parts by weight of (meth)acrylic polymer (A) is preferably 0.1 to 5 parts by weight, more preferably in the order of 0.1 to 3 parts by weight, 0.1 to 2 parts by weight, and 0.1 to 1 part by weight. The adhesive composition (II) may also be free of crosslinking agent (B) other than isocyanate-based crosslinking agent, such as epoxy-based crosslinking agent.

[0144] [additive]

[0145] Other additives may also be included in the adhesive composition (II). Examples of additives include silane coupling agents, polyfunctional alcohols, colorants such as pigments and dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, reprocessing improvers, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, antistatic agents (alkali metal salts, ionic liquids, ionic solids, etc., as ionic compounds), inorganic fillers, organic fillers, powders, particles, and foils such as metal powders. The additives may be formulated in amounts up to 10 parts by weight, preferably up to 5 parts by weight, and more preferably up to 1.5 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer (A).

[0146] Examples of silane coupling agents include epoxy-containing silane coupling agents such as 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylene)propylamine and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acryloylsilane coupling agents such as 3-acryloyloxypropyltrimethoxysilane and 3-methacryloyloxypropyltriethoxysilane; and isocyanate-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane.

[0147] When the adhesive composition (II) contains a silane coupling agent, its amount relative to 100 parts by weight of the (meth)acrylic polymer (A) is, for example, 5 parts by weight or less, or 3 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, 0.2 parts by weight or less, 0.1 parts by weight or less, and further, 0.05 parts by weight or less. The adhesive composition (I) may also be free of the silane coupling agent.

[0148] The adhesive composition (II) may also contain a polyfunctional alcohol. The molecular weight of the polyfunctional alcohol is, for example, 240 or less, and may be 230 or less, 220 or less, 210 or less, 200 or less, 190 or less, 180 or less, 170 or less, 160 or less, and more preferably 150 or less. The lower limit of the molecular weight is, for example, 60 or more, and may be 80 or more, 90 or more, and more preferably 100 or more.

[0149] Examples of polyfunctional alcohols include alkylene glycols such as ethylene glycol and propylene glycol and their polymers; ether glycols such as diethylene glycol and their polymers; trimethylolethane; trimethylolpropane; glycerol; and sugar alcohols such as pentaerythritol and sorbitol. Preferred polyfunctional alcohols are trimethylolpropane, glycerol, and diethylene glycol and their polymers, more preferably trimethylolpropane.

[0150] Polyfunctional alcohols can also be trifunctional or more. Examples of trifunctional polyfunctional alcohols are trimethylolpropane and glycerol.

[0151] Polyfunctional alcohols may not have reactive groups other than hydroxyl groups that are reactive with crosslinking agent (B). Such reactive groups are, for example, at least one selected from amino, carboxyl, and epoxy groups, especially amino.

[0152] The amount of the polyfunctional alcohol in the adhesive composition (II) relative to 100 parts by weight of the (meth)acrylic polymer (A) is, for example, 0.5 parts by weight or more and 20 parts by weight or less. The upper limit of the amount can be 15 parts by weight or less, 10 parts by weight or less, 8 parts by weight or less, 5 parts by weight or less, 4 parts by weight or less, and more preferably 3 parts by weight or less.

[0153] The adhesive composition (II) may also not contain a crosslinking accelerator such as a catalyst. Examples of crosslinking accelerators include polyethers, polyether polyols, and phosphate esters having reactive groups that are reactive with the crosslinking agent (B). The reactive groups are, for example, at least one selected from hydroxyl, amino, carboxyl, and epoxy groups, particularly hydroxyl or amino. The adhesive composition (II) may not contain an amino-containing polyether polyol, or it may not contain a hydroxyl-containing phosphate ester. Solvent-based adhesives (II) may also not contain a UV-curing agent such as a UV curing agent.

[0154] [Manufacturing method of the first adhesive sheet]

[0155] When the first adhesive sheet 2 is formed from a solvent-based adhesive composition (II), the first adhesive sheet 2 may, for example, contain a crosslinked product of a (meth)acrylic polymer (A). The first adhesive sheet 2 may be formed from the solvent-based adhesive composition (II) by the following method.

[0156] The method for manufacturing the first adhesive sheet 2 includes, for example, coating a solvent-based adhesive composition (II) comprising a (meth)acrylic polymer (A) and a crosslinking agent onto a substrate to form a coated film; and drying the resulting coated film.

[0157] As a substrate, a release film can be used, for example. The first adhesive sheet 2 formed on the release film can be transferred to an optical film, for example. The substrate can be a first optical film 1 or a second optical film 3. In this case, the first adhesive sheet 2 can be formed on the first optical film 1 or the second optical film 3, thereby obtaining an optical film with the first adhesive sheet.

[0158] The release film can be used as a release liner after the first adhesive sheet 2 is transferred to the first optical film 1 or the second optical film 3 until the first adhesive sheet 2 is supplied for actual use, thereby simplifying the process.

[0159] Examples of suitable materials for release films include: plastic film, paper, cloth, non-woven fabric and other porous materials, mesh, foam sheet, metal foil and their laminates, etc. Considering the excellent surface smoothness, plastic film is preferred.

[0160] As for plastic films, there are no particular limitations. Examples include: polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate copolymer film, etc.

[0161] The thickness of the release film is typically 5-200 μm, preferably around 5-100 μm. The release film can be treated with release agents such as silicone, fluorine, or long-chain alkyl compounds. It can also be treated with release and antifouling agents such as fatty acid amides, silica powder, etc., and with antistatic treatments such as coating, blending, or vapor deposition.

[0162] Alternatively, a solution (adhesive solution) containing a solvent-based adhesive composition (II) can be applied to the substrate. The solid content concentration of the adhesive solution is, for example, 5 to 50% by weight, preferably 10 to 40% by weight. It should be noted that the adhesive solution can be prepared by appropriately adding the same solvent or a different solvent as the polymerization solvent to the solvent-based adhesive composition (II) in accordance with the polymerization method of the (meth)acrylic polymer (A).

[0163] Various methods can be used to coat the solvent-based adhesive composition (II) onto the substrate, such as: roller coating, licker 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. The coating amount of the solvent-based adhesive composition (II) can be appropriately adjusted according to the thickness of the target first adhesive sheet 2.

[0164] By drying the coated film, it cures to form the first adhesive sheet 2. The drying temperature of the coated film is, for example, 130°C or below, preferably 125°C or below, more preferably 120°C or below, even more preferably 110°C or below, and particularly preferably 100°C or below. The drying temperature of the coated film can be 60°C or above, or 80°C or above. When the drying temperature is 60°C or above, the reaction of, for example, isocyanate crosslinking agents proceeds smoothly, which can improve the cohesion of the first adhesive sheet 2 and reduce the tendency for uneven display in the image display device. When the drying temperature is 130°C or below, there is a tendency to appropriately adjust, for example, the reaction rate of isocyanate crosslinking agents, and to ensure transparency.

[0165] The drying time of the coating film can be appropriately adjusted according to the composition of the solvent-based adhesive composition (II), preferably 30 seconds to 300 seconds, more preferably 40 seconds to 240 seconds, and particularly preferably 60 seconds to 180 seconds.

[0166] As described above, the first adhesive sheet 2 is formed from a photocurable adhesive composition (I) or a solvent-based adhesive composition (II). In other words, the first adhesive sheet 2 is a cured product of either the photocurable adhesive composition (I) or the solvent-based adhesive composition (II). The first adhesive sheet 2 is preferably formed from the photocurable adhesive composition (I). That is, the first adhesive sheet 2 is preferably formed from the photocurable adhesive composition (I) comprising a monomer group and / or a portion of a polymer of the aforementioned monomer group. The first adhesive sheet 2 formed from the photocurable adhesive composition (I) tends to have excellent surface smoothness. By smoothing the first adhesive sheet 2, the adhesion between the first adhesive sheet 2 and the first optical film 1 and / or the second optical film 3 can be improved. Furthermore, according to the smooth first adhesive sheet 2, there is a tendency to suppress the occurrence of color unevenness and appearance defects. That is, by using the first adhesive sheet 2 formed by the photocurable adhesive composition (I), the image display device can not only suppress display defects even when a small object hits or squeezes the screen with a narrow contact area, but also suppress the occurrence of appearance defects such as uneven color.

[0167] (Second adhesive sheet)

[0168] The thickness T2 of the second adhesive sheet 4 is, for example, 5 μm or more and 100 μm or less, preferably 8 μm or more and 80 μm or less, more preferably 10 μm or more and 50 μm or less, and even more preferably 12 μm or more and 30 μm or less. By appropriately adjusting the thickness of the second adhesive sheet 4, the adhesion between the second optical film 3 and the second adhesive sheet 4 can be improved.

[0169] The elongation at break of the second adhesive sheet 4 is, for example, 500% or more. Preferably, the elongation at break of the second adhesive sheet 4 is 700% or more, more preferably 800% or more, and even more preferably 1000% or more. The upper limit of the elongation at break of the second adhesive sheet 4 is, for example, 2000%.

[0170] The second adhesive sheet 4 can use a known adhesive. The second adhesive sheet 4 can be an adhesive sheet formed from a light-curing adhesive composition (I) or an adhesive sheet formed from a solvent-based adhesive composition (II). The first adhesive sheet 2 can also be used in the second adhesive sheet 4. The second adhesive sheet 4 is preferably an adhesive sheet formed from a light-curing adhesive composition (I).

[0171] (First optical film)

[0172] like Figure 1As shown, the first optical film 1 has two main surfaces that are opposite to each other. One main surface is exposed to the outside of the optical laminate 10A, for example. The other main surface of the first optical film 1 is opposite to the first adhesive sheet 2 and is the surface of the first optical film 1 on which the first adhesive sheet is laminated.

[0173] The first optical film 1 can be composed of a single layer or a stack of multiple layers. In other words, the first optical film 1 can be composed of a single film or a stack of multiple films. The films constituting the first optical film 1 can be bonded together using any adhesive and any adhesive sheet. The first optical film 1 may include at least one selected from polarizing films and retardation films. The first optical film 1 may include a polarizing film. The first optical film 1 may also be a stacked film including a polarizing film and / or a retardation film.

[0174] A polarizing film includes a polarizer. Typically, a polarizing film includes a polarizer and a protective film (a transparent protective film). The protective film is, for example, disposed grounded to the main surface of the polarizer. The polarizer may be disposed between two protective films. The protective film may be disposed on at least one side of the polarizer.

[0175] Examples of polarizers include: polarizers obtained by uniaxially stretching hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, after adsorbing dichroic substances such as iodine and dichroic dyes onto them; and polyene-oriented films such as dehydrated polyvinyl alcohol products and dehydrochlorinated polyvinyl chloride products. Typically, a polarizer is formed from a polyvinyl alcohol film (which may contain partially saponified ethylene-vinyl acetate copolymer films) and dichroic substances such as iodine.

[0176] The thickness of the polarizer can be, for example, 80 μm or less, but can be 50 μm or less, 30 μm or less, 25 μm or less, and even 20 μm or less. There is no particular limitation on the lower limit of the polarizer's thickness; for example, it can be 1 μm or more, but can be 5 μm or more, 10 μm or more, and even 15 μm or more. Suppressing dimensional variations in thin polarizers (e.g., thickness 20 μm or less) can contribute to improving the durability of optical laminates, especially their durability at high temperatures.

[0177] As materials for the protective film, thermoplastic resins with excellent properties such as transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy can be used. Specific examples of such thermoplastic resins include cellulose resins such as cellulose triacetate, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The protective film material can be thermosetting resins or UV-curable resins such as (meth)acrylic acid, urethane, acrylate urethane, epoxy, and silicone. In the case where the polarizing film has two protective films, the materials of the two protective films can be the same or different. For example, a protective film formed of thermoplastic resin can be bonded to one main surface of the polarizer via an adhesive, and a protective film formed of thermosetting resin or UV-curable resin can be bonded to the other main surface of the polarizer. The protective film can contain one or more arbitrary additives. Examples of additives include: ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and colorants.

[0178] The thickness of the protective film can be appropriately determined. Generally speaking, it is about 10~200μm, considering factors such as strength, operability, and thinness.

[0179] Polarizing lenses and protective films are typically bonded together using water-based adhesives. Examples of water-based adhesives include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, waterborne polyurethane, and waterborne polyester. Other adhesives besides those mentioned above include UV-curable adhesives and electron beam-curable adhesives. Electron beam-curable polarizer adhesives exhibit suitable adhesion to various protective films. The adhesive may also contain metallic compound fillers.

[0180] In polarizing films, a phase retardation film or similar material can be formed on the polarizer to replace the protective film. Alternatively, another protective film or a phase retardation film can be applied to the protective film.

[0181] Regarding the protective film, a hard coating can also be applied to the surface opposite to the surface to which the polarizer is bonded, and it can also be treated for purposes such as anti-reflection, anti-adhesion, diffusion, and anti-glare.

[0182] The polarizing film can be a circularly polarizing film.

[0183] As a retardation film, films obtained by stretching a polymer film or by aligning and immobilizing a liquid crystal material can be used. Retardation films, for example, exhibit birefringence in the in-plane and / or thickness directions.

[0184] Examples of phase retardation films include anti-reflection phase retardation films (see Japanese Patent Application Publication No. 2012-133303

[0221] ,

[0222] ,

[0228] ), phase retardation films for viewing angle compensation (see Japanese Patent Application Publication No. 2012-133303

[0225] ,

[0226] ), and tilt-oriented phase retardation films for viewing angle compensation (see Japanese Patent Application Publication No. 2012-133303

[0227] ).

[0185] As a phase retardation film, as long as it substantially has the above-mentioned functions, there are no particular limitations on aspects such as phase difference value, configuration angle, three-dimensional birefringence, whether it is a single layer or a multilayer, and known phase retardation films can be used.

[0186] The thickness of the phase retardation film is preferably 20 μm or less, more preferably 10 μm or less, even more preferably 1 to 9 μm, and particularly preferably 3 to 8 μm.

[0187] Phase retardation films can be composed of two layers, a quarter-wave plate and a half-wave plate, obtained by aligning and immobilizing liquid crystal materials.

[0188] (Second optical film)

[0189] like Figure 1 As shown, the second optical film 3 has two main surfaces that are opposite to each other. One main surface is opposite to the first adhesive sheet 2 and is the surface of the second optical film 3 on which the first adhesive sheet 2 is stacked. The other main surface of the second optical film 3 is opposite to the second adhesive sheet 4 and is the surface of the second optical film 3 on which the second adhesive sheet 4 is stacked.

[0190] The second optical film 3 can be composed of a single layer or a stack of multiple layers. In other words, the second optical film 3 can be composed of a single film or a stack of multiple films. The films constituting the second optical film 3 can be bonded together using any adhesive and any adhesive sheet. When the second optical film 3 is a stack of multiple films, the second optical film 3 may include, for example, at least one selected from polarizing films and retardation films. The second optical film 3 may also be a stack containing polarizing films and / or retardation films.

[0191] The second optical film 3 may comprise a stack of multiple retardation films. Alternatively, the second optical film 3 may comprise a stack of a first retardation film and a second retardation film. The first retardation film may be bonded to the second retardation film using any adhesive and any bonding sheet.

[0192] The second optical film 3 may comprise multiple layers. These multiple layers may be, for example, a laminate comprising a polarizer and at least one film. The at least one film of the second optical film 3 may be disposed between the polarizer and the second adhesive sheet. That is, the second optical film 3 may have at least one film disposed at a position closer to the second adhesive sheet than the polarizer.

[0193] Figure 4A This is a schematic cross-sectional view illustrating an example of a second optical film. (See diagram below.) Figure 4A As shown, the second optical film 3A is sequentially stacked with film A31, polarizer 32, film B33, and film C34. Films A31 and B33 can serve as protective films for the polarizer. Film C34 can serve as a phase retardation film. However, films A to C can also perform functions other than those described above. For example, film A and / or film B can also function as a phase retardation film.

[0194] The photoelastic coefficients of films B33 and C34, disposed between the polarizer 32 and the second adhesive sheet 4, are preferably 4 × 10⁻⁶. -11 m 2 / N or less. The photoelastic modulus is preferably 2×10. -11 m 2 / N or less, more preferably 1×10 -11 m 2 / N or less, further preferably 5×10 -12 m 2 / N and below. There is no specific lower limit for the photoelasticity coefficient; for example, it could be 2 × 10⁻⁶. -13 m 2 / N or higher, preferably 5×10 -13 m 2 / N or higher, more preferably 1×10 -12 m 2 / N or higher. At least one phase retardation film may also be disposed between the polarizer 32 and the second adhesive sheet 4.

[0195] The following discussion focuses on the function of both membranes B 33 and C 34 as phase retardation membranes. Sometimes membrane B 33 is referred to as the first phase retardation membrane 33, and membrane C 34 is referred to as the second phase retardation membrane 34.

[0196] (Polarizing filter)

[0197] The polarizer 30 is, for example, a laminate of a polarizer 32 and a protective film 31 disposed on the visible side of the polarizer 32. Typically, the protective film 31 is attached to the visible side of the polarizer 32 via any suitable adhesive sheet. The protective film 31 is located between the polarizer 32 and the first adhesive sheet 2, and is in contact with the first adhesive sheet 2. The polarizer 30 can be another laminate that further includes a second protective film on the opposite side of the visible side of the polarizer 32.

[0198] (Polarizing filter)

[0199] As the polarizer 32, any suitable polarizer can be used. For example, the resin film forming the polarizer 32 can be a single-layer resin film or a laminate of two or more layers.

[0200] As a specific example of a polarizer composed of a single-layer resin film, a polarizer obtained by performing iodine staining and stretching treatment (typically uniaxial stretching) on ​​a PVA-type resin film can be cited. The iodine staining can be performed, for example, by immersing the PVA-type film in an aqueous iodine solution. The stretching magnification of the uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after staining or during staining. Alternatively, staining can be performed after stretching. The PVA-type resin film can be subjected to swelling treatment, crosslinking treatment, cleaning treatment, drying treatment, etc., as needed. For example, by immersing the PVA-type resin film in water for washing before staining, not only can dirt and anti-blocking agents on the surface of the PVA-type film be cleaned, but the PVA-type resin film can also swell to prevent uneven staining.

[0201] Specific examples of polarizers using laminates include those using a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or those using a resin substrate and a laminate coated with a PVA-based resin layer formed on the resin substrate. A polarizer using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate can be manufactured by, for example, coating a PVA-based resin solution onto a resin substrate and drying it to form a PVA-based resin layer on the resin substrate, thus obtaining a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to form a polarizer from the PVA-based resin layer. For a polarizer using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate, it is preferable to form a polyvinyl alcohol resin layer comprising a halide and a polyvinyl alcohol resin on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Furthermore, stretching can be further included, as needed, stretching the laminate in a gas atmosphere at a high temperature (e.g., above 95°C) before stretching in a boric acid aqueous solution. Additionally, it is preferable to subject the laminate to a drying shrinkage treatment, which causes it to shrink by more than 2% in the width direction by heating while being transported along its length. Typically, a method for manufacturing a polarizing lens includes sequentially subjecting the laminate to assisted stretching in a gas atmosphere, dyeing, stretching in an aqueous solution, and drying shrinkage. By introducing assisted stretching, the crystallinity of PVA can be improved even when PVA is coated on a thermoplastic resin, resulting in high optical properties. Furthermore, by simultaneously improving the orientation of PVA beforehand, problems such as reduced orientation and dissolution of PVA during subsequent dyeing and stretching processes and immersion in water can be prevented, further achieving high optical properties. Moreover, when the PVA resin layer is immersed in a liquid, compared to the case where the PVA resin layer does not contain halides, the orientation disorder of polyvinyl alcohol molecules and the reduction of orientation can be suppressed. Therefore, the optical properties of the polarizer obtained by immersing the laminate in a liquid through processes such as dyeing and stretching in an aqueous solution can be improved. Furthermore, by using a drying shrinkage process to shrink the laminate in the width direction, the optical properties can be further improved. The resulting resin substrate / polarizer laminate can be used directly (i.e., the resin substrate can be used as a protective layer for the polarizer), or the resin substrate can be peeled off from the resin substrate / polarizer laminate, and any suitable protective layer corresponding to the purpose can be laminated on the peeled surface for use. Detailed descriptions of such a method for manufacturing a polarizer are provided, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0202] The polarizer 32 can preferably be composed of two or more layers, and more preferably is composed of a resin substrate and a PVA-type resin layer coated on the resin substrate.

[0203] The thickness of the polarizer 32 is preferably 15 μm or less, more preferably 12 μm or less, even more preferably 10 μm or less, particularly preferably 8 μm or less, typically 1 μm or more, and preferably 3 μm or more. If the thickness of the polarizer 32 is within such a range, the warping of the optical laminate in a high-humidity environment can be suppressed more stably.

[0204] The polarizer 32 preferably exhibits absorption dichroism at any wavelength within the range of 380 nm to 780 nm. The single-unit transmittance of the polarizer 32 is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, more preferably 44.5% to 46.0%. The degree of polarization of the polarizer 32 is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher.

[0205] (Protective film)

[0206] The protective film 31 can be formed from any suitable film that can be used as a protective layer for the polarizer 32. Specific examples of materials that form the main component of this film include: cellulose resins such as cellulose triacetate (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrene, polynorbornene, polyolefins, (meth)acrylic acids, acetates, and other transparent resins. Additionally, thermosetting resins or UV-curable resins such as (meth)acrylic acids, urethanes, (meth)acrylate urethanes, epoxy resins, and silicone resins can also be used. Furthermore, glassy polymers such as siloxane polymers can also be used. Alternatively, polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used. As the material for this membrane, resin compositions can be used, for example, thermoplastic resins containing substituted or unsubstituted imide groups on the side chains, and thermoplastic resins containing substituted or unsubstituted phenyl and nitrile groups on the side chains. Examples include resin compositions having alternating copolymers formed from isobutylene and N-methylmaleimide, and acrylonitrile-styrene copolymers. The polymer membrane can be, for example, an extruded product of the above-mentioned resin compositions.

[0207] The protective film 31 may contain, for example, a (meth)acrylic resin. As a (meth)acrylic resin, a (meth)acrylic resin having, for example, a glutarimide structure may be used. (Meth)acrylic resins having a glutarimide structure are described, for example, in Japanese Patent Application Publication Nos. 2006-309033, 2006-317560, 2006-328329, 2006-328334, 2006-337491, 2006-337492, 2006-337493, 2006-337569, 2007-009182, 2009-161744, and 2010-284840. These publications are incorporated herein by reference.

[0208] The thickness of the protective film 31 is typically 300 μm or less, preferably 100 μm or less, more preferably 5 μm to 80 μm, and even more preferably 10 μm to 60 μm.

[0209] (First phase difference film)

[0210] When film B 33 functions as a retardation film, the first retardation film 33 can be composed of a retardation film having any suitable optical and / or mechanical properties depending on the purpose. The first retardation film 33 may be composed of a single layer, for example. The first retardation film 33 is located on the side of the polarizer 30 opposite to the visible side. Specifically, the first retardation film 33 is attached to the side of the polarizer 32 opposite to the visible side via any suitable adhesive sheet. In this case, the first retardation film 33 is disposed between the polarizer 32 and the second adhesive sheet 4. That is, the first retardation film 33 is positioned closer to the second adhesive sheet 4 than the polarizer 32. The first retardation film 33 can also serve as a protective layer on the side of the polarizer 32 opposite to the visible side.

[0211] The thickness of the first phase difference film 33 is preferably 10 μm to 60 μm, more preferably 20 μm to 50 μm.

[0212] The in-plane phase difference Re(550) of the first phase difference film 33 is preferably 80nm~150nm, more preferably 90nm~140nm, and even more preferably 100nm~130nm.

[0213] The refractive index characteristics of the first retardation film 33 preferably exhibit a relationship of nx > ny > nz. The Nz coefficient of the first retardation film 33 is preferably 1.1 to 3.0, more preferably 1.3 to 2.7.

[0214] The first phase difference film 33 can preferably be configured such that its slow axis is substantially parallel to the absorption axis of the polarizer.

[0215] The photoelastic coefficient of the first retardation film 33 is as described above. By appropriately adjusting the photoelastic coefficient of the first retardation film 33, an optical laminate 10A can be obtained that is more suitable for suppressing display defects even when a small object hits or squeezes the screen with a narrow contact area. Furthermore, by appropriately adjusting the photoelastic coefficient of the first retardation film 33, phase difference changes are less likely to occur when shrinkage stress occurs during heating. Therefore, by appropriately adjusting the photoelastic coefficient of the first retardation film 33, thermal unevenness can be well prevented when the optical laminate 10A is applied to an image display device.

[0216] The first retardation film 33 can exhibit inverse dispersion wavelength characteristics where the phase difference increases with the wavelength of the measurement light, positive wavelength dispersion characteristics where the phase difference decreases with the wavelength of the measurement light, or flat wavelength dispersion characteristics where the phase difference hardly changes with the wavelength of the measurement light. Preferably, the first retardation film 33 exhibits flat wavelength dispersion characteristics. Specifically, the Re(450) / Re(550) ratio of the first retardation film 33 is preferably 0.99 to 1.03, and the Re(650) / Re(550) ratio is preferably 0.98 to 1.02. By arranging the λ / 2 plate and λ / 4 plate with flat wavelength dispersion characteristics at a given axial angle, characteristics approaching ideal inverse wavelength dispersion characteristics can be obtained, resulting in excellent anti-reflection properties.

[0217] The first retardation film 33 can be composed of any suitable resin film capable of satisfying the characteristics described above. Examples of such resins include cyclic olefin resins, polycarbonate resins, cellulose resins, polyester resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. Cyclic olefin resins can be suitably used for the first retardation film 33. The first retardation film 33 can be obtained, for example, by appropriately stretching a film formed from the above-described resins.

[0218] (Second phase difference film)

[0219] When film C 34 functions as a retardation film, the second retardation film 34 can be composed of a retardation film having any suitable optical and / or mechanical properties depending on the purpose. The second retardation film 34 may be composed of a single layer, for example. The second retardation film 34 is located on the side opposite to the visible side of the first retardation film 33. The second retardation film 34 is disposed between the polarizer 32 and the second adhesive sheet 4. That is, the second retardation film 34 is positioned closer to the second adhesive sheet 4 than the polarizer 32. The second retardation film 34 is preferably disposed between the first retardation film 33 and the second adhesive sheet 4.

[0220] The thickness of the second phase difference film 34 is preferably 5μm to 50μm, more preferably 5μm to 40μm.

[0221] The in-plane phase difference Re(550) of the second phase difference film 34 is preferably 10nm~60nm, more preferably 20nm~50nm, and even more preferably 30nm~40nm.

[0222] The refractive index characteristics of the second retardation film 34 preferably exhibit a relationship of nz > nx > ny. The Nz coefficient of the second retardation film 34 is preferably -10 to -0.1, more preferably -5 to -1.

[0223] The second phase difference film 34 can preferably be configured such that its slow axis is substantially orthogonal to the absorption axis of the polarizer.

[0224] The second phase retardation film 34 can be composed of any suitable resin film capable of satisfying the characteristics described above. Examples of such resins include polymers with negative birefringence. A polymer with negative birefringence is one in which the refractive index in the orientation direction decreases relatively when the polymer is oriented by stretching or the like. Examples of polymers with negative birefringence include polymers with highly polarized anisotropic chemical bonds and functional groups such as aromatics and carbonyl groups introduced into the side chains. Specific examples of polymers with negative birefringence include modified polyolefin resins (e.g., modified polyethylene resins), acrylic resins, styrene resins, maleimide resins, fumarate resins, etc. The second phase retardation film can be obtained, for example, by appropriately stretching a film formed from the aforementioned resin.

[0225] It should be noted that the optical laminate 10A may have at least one selected from the first phase difference film and the second phase difference film as the second optical film 3, or the optical laminate 10A may not have the first phase difference film and / or the second phase difference film.

[0226] Figure 4B This is a schematic cross-sectional view illustrating another example of a second optical film. (As shown) Figure 4BAs shown, the second optical film 3B comprises film A31, a polarizer 32, and film D35 stacked sequentially. Film A31 can be a protective film for the polarizer. Film D35 can be a phase retardation film or a protective film for the polarizer. When film D35 is a protective film for the polarizer, film A31 and film D35 can be the same type of protective film or different types of protective films. Film A can also be a film that performs functions other than those mentioned above. For example, film A can also function as a phase retardation film.

[0227] The photoelastic coefficient of the film D35 disposed between the polarizer 32 and the second adhesive sheet 4 is preferably 4 × 10⁻⁶. -11 m 2 / N or less. The photoelastic modulus is preferably 2×10. -11 m 2 / N or less, more preferably 1×10 -11 m 2 / N or less, further preferably 5×10 - 12 m 2 / N and below. There is no specific lower limit for the photoelasticity coefficient; for example, it could be 2 × 10⁻⁶. -13 m 2 / N or higher, preferably 5×10 -13 m 2 / N or higher, more preferably 1×10 -12 m 2 / N or higher. At least one phase retardation film may be disposed between the polarizer 32 and the second adhesive sheet 4.

[0228] The following explains how film D35 functions as a protective film for a polarizer.

[0229] like Figure 4B As shown, the second optical film 3B includes a polarizer 32. Furthermore, the second optical film 3B has a configuration in which a protective film 35 is disposed between the polarizer 32 and the second adhesive sheet 4. That is, in the second optical film 3B, the protective film 35 is disposed closer to the second adhesive sheet 4 than the polarizer 32.

[0230] The photoelasticity coefficient of the protective film 35 is as described above. By appropriately adjusting the photoelasticity coefficient of the protective film 35, an optical laminate 10A can be obtained that is more suitable for suppressing display defects even when a small object hits or squeezes the screen with a narrow contact area.

[0231] (Optical laminate)

[0232] The thickness T of the optical laminate 10A is, for example, 200 μm or more. The thickness of the optical laminate 10A is preferably 250 μm or more, more preferably 500 μm or more, even more preferably 1000 μm or more, and particularly preferably 1500 μm or more. The upper limit of the thickness of the optical laminate 10A is, for example, 5000 μm or less, preferably 3000 μm or less, more preferably 2000 μm or less, and even more preferably 1000 μm or less.

[0233] The optical laminate 10A may not include a cover glass on the surface of the first optical film 1 opposite to the side where the first adhesive sheet 2 is formed. Even with this configuration, since the optical laminate 10A includes the first adhesive sheet 2, in an image display device including the optical laminate 10A, display defects can be further suppressed even when a small object hits or squeezes the screen with a narrow contact area.

[0234] Figure 5 This is a cross-sectional view schematically illustrating another example of an optical laminate. (See diagram below.) Figure 5 As shown, the optical laminate 10B is a laminate comprising an optical laminate 10A, a third optical film 5, and a third adhesive sheet 6. Specifically, the optical laminate 10B has a laminated structure in which a first optical film 1, a first adhesive sheet 2, a second optical film 3, a second adhesive sheet 4, a third optical film 5, and a third adhesive sheet 6 are sequentially stacked. The optical laminate 10B can be used, for example, by being attached to an image forming layer via the third adhesive sheet 6.

[0235] The thickness of the optical laminate 10B is, for example, 200 μm or more. The thickness of the optical laminate 10B is preferably 250 μm or more, more preferably 300 μm or more. The upper limit of the thickness of the optical laminate 10B is, for example, 6000 μm or less, preferably 5000 μm or less, more preferably 3000 μm or less, more preferably 2000 μm or less, and particularly preferably 1000 μm or less.

[0236] (Third adhesive sheet)

[0237] The third adhesive sheet 6 is formed on the third optical film 5. The third adhesive sheet 6 is formed on one main surface of the third optical film 5. Figure 5 In this case, the third adhesive sheet 6 is formed entirely on one main surface of the third optical film 5. However, the third adhesive sheet 6 may also be formed only on a portion of one main surface of the third optical film 5.

[0238] The thickness T3 of the third adhesive sheet 6 is, for example, 5 μm or more and 100 μm or less, preferably 8 μm or more and 80 μm or less, more preferably 10 μm or more and 50 μm or less, and even more preferably 12 μm or more and 30 μm or less. By appropriately adjusting the thickness of the third adhesive sheet 6, the adhesion between the third optical film 5 and the third adhesive sheet 6 can be improved.

[0239] The third adhesive sheet 6 can use a known adhesive. The third adhesive sheet 6 can be an adhesive sheet formed of a light-curing adhesive composition (I) or an adhesive sheet formed of a solvent-based adhesive composition (II). The first adhesive sheet 2 or the second adhesive sheet 4 can also be used in the third adhesive sheet 6.

[0240] (Third optical film)

[0241] like Figure 5 As shown, the third optical film 5 has two main surfaces that are opposite to each other. One main surface is opposite to the second adhesive sheet 4 and is the surface of the third optical film 5 on which the second adhesive sheet 4 is stacked. The other main surface of the third optical film 5 is opposite to the third adhesive sheet 6 and is the surface of the third optical film 5 on which the third adhesive sheet 6 is stacked.

[0242] The third optical film 5 may include, for example, at least one selected from polarizing films and retardation films. The third optical film 5 may also be a laminated film including polarizing films and / or retardation films.

[0243] [Implementation of the Image Display Device]

[0244] An example of the image display device of this embodiment is shown below. Figure 6 . Figure 6 The image display device 11 has a stacked structure in which an optical laminate 10A, an image forming layer (e.g., an organic EL layer or a liquid crystal layer) 7 and a substrate 8 are sequentially stacked. That is, Figure 6 The image display device 11 has a laminated structure in which a first optical film 1, a first adhesive sheet 2, a second optical film 3, a second adhesive sheet 4, an image forming layer 7, and a substrate 8 are sequentially stacked. The image display device 11 may also have... Figure 5 Optical laminate 10B is used instead of optical laminate 10A. Image forming layer 7 and substrate 8 may have the same configuration as image forming layer and substrate in known image display devices.

[0245] Figure 6The image display device 11 can be an organic EL display or a liquid crystal display. However, the image display device 11 is not limited to this example. The image display device 11 can also be an electroluminescent (EL) display, a plasma display (PD), a field emission display (FED), etc. The image display device 11 can be used for home appliances, automotive applications, public information displays (PIDs), etc.

[0246] The image display device of this embodiment can have any configuration as long as it has the optical laminate of this embodiment.

[0247] Example

[0248] The present invention will now be described in more detail through embodiments. The present invention is not limited to the embodiments shown below.

[0249] Figure 7 This is a schematic cross-sectional view of the optical laminates of Examples 1-4, 6, and Comparative Examples 1-4. Figure 7 As shown, the optical laminate 40 of Examples 1-4, 6, and Comparative Examples 1-4 is a laminate in which a first optical film 1, a first adhesive sheet 2, a second optical film 3A, and a second adhesive sheet 4 are sequentially laminated. The second optical film 3A has a structure in which a protective film 31, a polarizer 32, a first phase refraction film 33, and a second phase refraction film 34 are sequentially laminated. The first phase refraction film 33 and the second phase refraction film 34 are disposed between the polarizer 32 and the second adhesive sheet 4. That is, the first phase refraction film 33 and the second phase refraction film 34 are disposed closer to the second adhesive sheet 4 than the polarizer 32.

[0250] Figure 8 This is a schematic cross-sectional view of the optical laminate of Embodiment 5. (See diagram below.) Figure 8 As shown, the optical laminate 41 of Embodiment 5 is a laminate in which a first optical film 1, a first adhesive sheet 2, a second optical film 3B, and a second adhesive sheet 4 are sequentially laminated. The second optical film 3B has a structure in which a protective film 31, a polarizer 32, and a protective film 35 are sequentially laminated. The protective film 35 is disposed between the polarizer 32 and the second adhesive sheet 4. That is, the protective film 35 is disposed closer to the second adhesive sheet 4 than the polarizer 32.

[0251] For convenience, the following is based on Figure 7 and Figure 8 The reference symbols marked in the middle are explained.

[0252] [Evaluation Method]

[0253] <Elongation at break>

[0254] In Examples 1-5 and Comparative Examples 1-4, the thickness of the first adhesive sheet 2 was set to 20 μm. Otherwise, a laminate LX consisting of a release liner A, the first adhesive sheet 2 (20 μm thick), and a release liner B was fabricated using the same method as for the laminate L1b described later. The laminate LX was cut to a size of 3 cm wide × 10 cm long, and the release liner B was peeled off to create a test sample. In Example 6, the thickness of the first adhesive sheet 2 was set to 20 μm. Otherwise, a laminate LY with the first adhesive sheet 2 (20 μm thick) formed on the surface of a PET film was fabricated using the same method as for the laminate L6 described later. The laminate LY was cut to a size of 3 cm wide × 10 cm long to create a test sample. In each test sample, the first adhesive sheet 2 was rolled into a rope shape along the length of the release liner to create a test piece. The release liner was peeled off from the test piece, and the rope-shaped first adhesive sheet 2 was placed in a tensile testing machine. A tensile test was conducted under the conditions of an initial chuck distance of 10 mm and a tensile speed of 300 mm / min. The length of the test piece at which it broke due to the tensile test was measured and denoted as L1 [mm]. The elongation at break was calculated using the following formula.

[0255] Elongation at break [%] = {(L1-L0) / L0} × 100

[0256] In the above formula, L0[mm] represents the initial (before the tensile test) length of the test piece along its longitudinal direction. The tensile testing machine used was the Shimadzu Autograph AG-10G tensile testing machine. The tensile test is performed by stretching the test piece along its longitudinal direction.

[0257] The elongation at break of the second adhesive sheet 4 was calculated using the laminate L2a, and otherwise, the elongation at break of the second adhesive sheet 4 was calculated using the same method as described above.

[0258] <Puncture Test>

[0259] The optical laminates 40 and 41 of the examples and comparative examples were cut into 5cm × 5cm dimensions to prepare test samples. Next, the test samples were bonded to a 1.2mm thick glass plate via the second adhesive sheet 4, thereby preparing the measurement samples.

[0260] The test samples of the examples and comparative examples were placed on the stage of an Indenter CMS testing machine (Instron Corporation, product name: 5581) equipped with a puncture device. The tip of the puncture device was rounded and tapered. Furthermore, the radius of curvature R of the tip of the puncture device was 550 μm. The test samples on the stage were punctured with the puncture device under a 5 kg load at room temperature (23℃±3℃). The optical stacks 40 and 41 after the puncture test were configured such that the polarizer 32 of the optical stacks 40 and 41 and the polarizer attached to the microscope were orthogonal to each other. Light leakage was observed using a microscope (objective magnification: 5x). Evaluation was performed according to the following criteria.

[0261] A: No light leakage was detected.

[0262] B: Light leakage has been confirmed, but it has no impact on actual use.

[0263] C: The light leakage is so obvious that it is unacceptable in actual use.

[0264] <Photoelastic coefficient>

[0265] In the second optical films 3A and 3B used in the examples and comparative examples, samples were prepared by cutting the film (layer) disposed between the polarizer 32 and the second adhesive sheet 4 into dimensions of 20 mm × 100 mm. The photoelastic coefficient of the samples was measured using an ellipsometry (M-150, manufactured by Nippon Spectrophotometer Co., Ltd.) with light at a wavelength of 550 nm.

[0266] <Smoothness>

[0267] The optical laminates 40 and 41 of the embodiments and comparative examples were bonded to a black plate via the second adhesive sheet 4, thereby creating an evaluation sample. For this evaluation sample, its smoothness was confirmed by visual inspection from the first optical film 1 side, and an evaluation was performed according to the following criteria.

[0268] A: It has a subtle texture.

[0269] B: It has a very obvious textured surface.

[0270] <Weight-average molecular weight of (meth)acrylic polymers>

[0271] The weight-average molecular weight (Mw) of (meth)acrylic acid polymers was determined by GPC (gel permeation chromatography).

[0272] ·Analysis device: Made by Tosoh Corporation, HLC-8120GPC

[0273] • Chromatographic column: Tosoh Corporation, G7000H XL +GMHXL +GMH XL

[0274] • Column dimensions: 7.8mm φ × 30cm each, totaling 90cm

[0275] Column temperature: 40℃

[0276] • Flow rate: 0.8 mL / min

[0277] Injection volume: 100μL

[0278] • Eluent: Tetrahydrofuran

[0279] • Detector: Differential Refractive Index (RI)

[0280] Standard sample: polystyrene

[0281] [First optical film 1 (polarizing film)]

[0282] As a thermoplastic resin substrate, a strip-shaped amorphous polyethylene terephthalate copolymer film (thickness: 100 μm) with a Tg of approximately 75 °C was used to perform corona treatment on one side of the resin substrate.

[0283] A PVA aqueous solution (coating solution) was prepared by adding 13 parts by weight of potassium iodide to 100 parts by weight of a PVA resin made by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER") in a ratio of 9:1, and dissolving the resulting mixture in water.

[0284] The above-mentioned PVA aqueous solution was coated on the corona-treated surface of the resin substrate and dried at 60°C, thereby forming a PVA resin layer with a thickness of 13 μm and producing a laminate.

[0285] The resulting laminate was unidirectionally stretched to 2.4 times its original length in an oven at 130°C (assisted stretching treatment in a gas atmosphere).

[0286] Next, the laminated body after assisted stretching in a gas atmosphere is immersed in an insoluble bath at 40°C for 30 seconds (insoluble treatment). The insoluble bath is an aqueous solution of boric acid prepared by mixing 4 parts by weight of boric acid with 100 parts by weight of water.

[0287] Next, the polarizer was immersed in a staining bath at 30°C for 60 seconds while adjusting the concentration to achieve the desired monomer transmittance (Ts) of the final polarizer. The staining bath was an aqueous solution of iodine and potassium iodide prepared by mixing iodine and potassium iodide in a weight ratio of 1:7 relative to 100 parts by weight of water.

[0288] Next, the sample was immersed in a crosslinking bath at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). The crosslinking bath was an aqueous solution of boric acid prepared by adding 3 parts by weight of potassium iodide and 5 parts by weight of boric acid to 100 parts by weight of water.

[0289] Then, the laminate was immersed in a boric acid aqueous solution at 70°C, and simultaneously subjected to unidirectional stretching (stretching treatment in aqueous solution) along the longitudinal direction (length direction) between rollers with different circumferential speeds to achieve a total stretch ratio of 5.5. The boric acid aqueous solution contained 4% by weight boric acid and 5% by weight potassium iodide.

[0290] The laminate was then immersed in a cleaning bath at a temperature of 20°C (cleaning treatment). The cleaning bath was an aqueous solution containing 4 parts by weight of potassium iodide relative to 100 parts by weight of water.

[0291] Then, while drying in an oven maintained at approximately 90°C, it comes into contact with SUS heated rollers maintained at a surface temperature of approximately 75°C (drying shrinkage treatment).

[0292] In this way, a polarizer with a thickness of about 5 μm is formed on the resin substrate.

[0293] An acrylic resin film (thickness: 40 μm) with a glutarimide structure was bonded as a protective layer to the surface of the obtained polarizer (the side opposite to the resin substrate) using a UV-curable adhesive. Specifically, the adhesive was applied to achieve a total thickness of approximately 2.0 μm and then bonded using a roller mill. UV light was then irradiated from the acrylic resin film side to cure the adhesive. Next, the resin substrate was peeled off, resulting in a polarizing film (first optical film 1) consisting of an acrylic resin film (protective layer) and a polarizer.

[0294] [Second optical film]

[0295] In Examples 1-4, 6, and Comparative Examples 1-4 (see reference) Figure 7 In this design, the second optical film 3A uses a laminate X consisting of a protective film 31, a polarizer 32, a first retardation film 33, and a second retardation film 34 stacked sequentially. The polarizer 32 uses the polarizer fabricated above. The protective film 31 uses an acrylic resin film (manufactured by KANEKA Corporation, product name: HTX) with a glutarimide structure (thickness: 40 μm). The protective film 31 and the polarizer 32 are bonded together using a UV-curable adhesive.

[0296] The first phase retardation film 33 uses a cyclic olefin film (manufactured by Zeon Corporation, Japan; product name: ZeonorFilm ZT12-50135). The thickness of the first phase retardation film 33 is 18 μm.

[0297] The second phase difference film 34 was fabricated as described below.

[0298] [Polymer Synthesis and Dope Preparation]

[0299] In a high-pressure reactor equipped with a stirrer, condenser, nitrogen inlet pipe, and thermometer, 48 parts by weight of hydroxypropyl methylcellulose (Shin-Etsu Chemical, trade name Metolose 60SH-50), 1560 parts by weight of distilled water, 8161 parts by weight of diisopropyl fumarate, 240 parts by weight of 3-ethyl-3-oxetanebutyl methyl acrylate, and 45 parts by weight of tert-butyl peroxypentanoate as a polymerization initiator were added. After nitrogen bubbling for 1 hour, the mixture was stirred and maintained at 49°C for 24 hours to carry out free radical suspension polymerization. Next, the mixture was cooled to room temperature, and the suspension containing the generated polymer particles was centrifuged. The obtained polymer was washed twice with distilled water and twice with methanol, and then dried under reduced pressure to obtain a white fumarate resin.

[0300] The obtained fumarate resin was dissolved in methyl ethyl ketone to prepare a solution with a solid content of 20% by weight. Further, 5 parts by weight of tributyl trimellitate as a plasticizer were added to 100 parts by weight of the fumarate resin to prepare a paste.

[0301] A polyester film (biaxially oriented poly(ethylene terephthalate) / ethylene isophthalate copolymer) with a thickness of 75 μm was used as the support film. The above-mentioned adhesive paste was applied in such a way that the dried film thickness reached about 6 μm and then dried to obtain a laminate A in which a coating film of fumarate resin was tightly laminated on the support.

[0302] The aforementioned laminate A was subjected to uniaxial stretching at its free end, resulting in a laminate B on which a second retardation film 34 (positive B plate) with refractive index anisotropy (nz > nx > ny) was tightly laminated on a support. The support was then peeled off from laminate B, thereby obtaining the second retardation film 34 (positive B plate) with refractive index anisotropy. It should be noted that the first retardation film 33 and the second retardation film 34 were bonded together using an ultraviolet-curable adhesive.

[0303] The photoelasticity coefficient of protective film 31 is 3×10⁻⁶. -12 m 2 / N. The photoelastic coefficient of the first phase retardation film 33 is 1×10⁻⁶. - 12 m2 / N. The photoelastic coefficient of the second phase retardation film 34 is 5×10⁻⁶. -11 m 2 / N.

[0304] In Example 5 (see Figure 8 In this design, the second optical film 3B uses a laminate Y consisting of a protective film 31, a polarizer 32, and a protective film 35 stacked sequentially. The polarizer 32 is the same as described above. The protective films 31 and 35 are acrylic resin films (manufactured by KANEKA Corporation, product name: HTX) with a glutarimide structure (thickness: 40 μm).

[0305] [Peeling Liner A]

[0306] A silicone-based release agent composition was prepared by mixing 30 parts by weight of an addition-reaction curable silicone (containing LTC761 with hexenyl polysiloxane, 30% toluene solution, manufactured by Toray Dow Corning), 0.9 parts by weight of a release control agent (containing unreactive silicone resin BY24-850, manufactured by Toray Dow Corning), 2 parts by weight of a curing catalyst (containing platinum catalyst SRX212, manufactured by Toray Dow Corning), and a toluene / hexane mixed solvent (volume ratio 1:1) as a diluent. The concentration of the silicone solid component in the release agent composition was 1.0% by weight. Next, the release agent composition was coated onto one side of a substrate (Lumirror XD500P polyester film, 75 μm thick) using a wire rod, and heated at 130°C for 1 minute to produce a release liner A with a release layer (60 nm thick) on one side.

[0307] [Peeling Liner B]

[0308] The thickness of the release agent composition coated on the substrate was changed. Otherwise, a release liner B with a release layer (120 nm thick) on one side was produced by the same method as the release liner A.

[0309] [Monomeric slurry A1]

[0310] 100 parts by weight of n-butyl acrylate (BA), 5 parts by weight of acrylic acid (AA), 0.16 parts by weight of 1-hydroxycyclohexylphenyl ketone (Omnirad 184, manufactured by IGM Resins BV) as a photopolymerization initiator, and 0.04 parts by weight of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins BV) were added to a four-necked flask and irradiated with ultraviolet light in a nitrogen atmosphere, thereby obtaining a monomer slurry A1 after partial photopolymerization. The ultraviolet irradiation continued until the viscosity of the liquid in the flask (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached approximately 20 Pa·s.

[0311]

[0312] The abbreviations in Table 1 are as follows.

[0313] BA: n-Butyl acrylate

[0314] AA: Acrylic acid

[0315] [Photocurable adhesive compositions C1~C6]

[0316] Next, the monomer slurry and crosslinking agent were mixed in the manner shown in Table 2 below to obtain photocurable adhesive compositions C1 to C3. The abbreviation "NDDA" in Table 2 represents 1,9-nonanediol diacrylate.

[0317]

[0318] (Example 1)

[0319] Reference Figure 7 A photocurable adhesive composition C1 was applied to the surface of the release layer of the release liner A using an applicator, forming a coating layer (50 μm thick). Next, the aforementioned release liner B was placed on the formed coating layer to obtain a laminate L1a. The release liner B was positioned such that the release layer and the coating layer were in contact. Next, under an illuminance of 9 mW / cm²... 2 Conditions (cumulative light intensity 868 mJ / cm²) 2 Light is irradiated from one side of the release liner A of the laminate L1a. This causes the coating layer to photocur, forming the laminate L1b consisting of the release liner A, the first adhesive sheet 2 (50 μm thick), and the release liner B. A light source combining a black light source and an LED is used. The peak wavelength of the irradiated light in the LED is 340 nm. The cumulative light intensity is based on the sum of the cumulative light intensities from both light sources.

[0320] Next, the release liner B is peeled off from the laminate L1b, and the aforementioned polarizing film (first optical film 1) is placed on the exposed surface of the first adhesive sheet 2, thereby obtaining a laminate L1c in which the release liner A, the first adhesive sheet 2, and the polarizing film are sequentially stacked. It should be noted that the polarizing film is arranged such that the surface of the transparent protective film side formed of the modified acrylic polymer is in contact with the first adhesive sheet 2.

[0321] Separately, a photocurable adhesive composition C3 is applied to the surface of the release layer of the release liner A using an applicator, forming a coating layer (15 μm thick). Next, the aforementioned release liner B is placed on the formed coating layer to obtain a laminate L2a. The release liner B is positioned such that the release layer and the coating layer are in contact. Next, light is irradiated from the side of the release liner A of the laminate L2a. As a result, the coating layer undergoes photocuring, forming a laminate L2b consisting of the release liner A, the second adhesive sheet 4 (15 μm thick), and the release liner B. The light irradiation conditions are the same as those used when fabricating the first adhesive sheet 2.

[0322] Next, the release liner B is peeled off from the laminate L2b, and the laminate X, which serves as the second optical film 3A, is positioned on the exposed surface of the second adhesive sheet 4 so that the second retardation film 34 is in contact with the second adhesive sheet 4. This results in a laminate L2c in which the release liner A, the second adhesive sheet 4, and the second optical film 3A are sequentially laminated. It should be noted that the laminate X is positioned so that the second retardation film 34 is in contact with the second adhesive sheet 4.

[0323] The release liner A is peeled off from the laminate L1c to obtain the laminate L1d. The first adhesive sheet 2 of the laminate L1d is transferred to the protective film 31 of the laminate L2c, thereby obtaining the laminate L3 in which the polarizing film (first optical film 1), the first adhesive sheet 2, the second optical film 3A, the second adhesive sheet 4 and the release liner A are sequentially stacked. The release liner A is peeled off from the laminate L3 to obtain the optical laminate 40 of Example 1.

[0324] (Example 2)

[0325] The thickness of the first adhesive sheet 2 was changed to 100 μm. Otherwise, the optical laminate 40 of Example 2 was obtained by the same method as in Example 1.

[0326] (Example 3)

[0327] A photocurable adhesive composition C2 was used instead of a photocurable adhesive composition C1. Otherwise, the optical laminate 40 of Example 3 was obtained by the same method as in Example 1.

[0328] (Example 4)

[0329] The thickness of the first adhesive sheet 2 was changed to 100 μm. Otherwise, the optical laminate 40 of Example 4 was obtained by the same method as in Example 3.

[0330] (Example 5)

[0331] Reference Figure 8 As the second optical film, laminate Y was used instead of laminate X. Otherwise, the optical laminate 41 of Example 5 was obtained by the same method as in Example 4.

[0332] (Example 6)

[0333] [Preparation of (meth)acrylic acid polymer B1]

[0334] A monomer mixture containing 79.9 parts by weight of n-butyl acrylate (BA), 5 parts by weight of acrylic acid (AA), 0.1 parts by weight of 4-hydroxybutyl acrylate (HBA), and 15 parts by weight of benzyl acrylate was added to a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen inlet tube, and a condenser. Further, 0.1 parts by weight of 2,2'-azobisisobutyronitrile (AIBN; manufactured by Kishida Chemical Co., Ltd.) as a polymerization initiator, along with ethyl acetate, were added to 100 parts by weight of the monomer mixture to prepare a further mixture. The mixture was slowly stirred while nitrogen was introduced into the flask for nitrogen purging. The liquid temperature in the flask was maintained at approximately 55°C for 7 hours for polymerization. Then, ethyl acetate was added to the resulting reaction solution to adjust the solids concentration to 30%, preparing a solution of (meth)acrylic acid polymer B1 with a weight-average molecular weight (Mw) of 2.2 million.

[0335] [Adhesive sheet]

[0336] A solution of the (meth)acrylic adhesive composition D1 (solvent-based adhesive composition) of Example 6 was prepared by further combining 12 parts by weight of a crosslinking agent (manufactured by Mitsui Chemicals Co., Ltd., product name: Takenate D-101E), 0.1 parts by weight of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KBM-403), and 1 part by weight of an alkoxysilyl polyether compound (manufactured by KANEKA Co., Ltd., product name: SILYL SAT10) with 100 parts by weight of the solid component of the solution of (meth)acrylic polymer B1. Takenate D-101E is a trimethylolpropane / toluene diisocyanate trimer adduct. KBM-403 is 3-epoxypropoxypropyltrimethoxysilane.

[0337] A (meth)acrylic adhesive composition D1 was coated onto the surface of a PET film serving as a substrate film (release liner) to achieve a dried adhesive sheet thickness of 100 μm. The coating of the (meth)acrylic adhesive composition D1 was performed using a curtain coating machine. The coated film was dried at 90°C for 1 minute in an air-circulating constant-temperature oven, thereby obtaining a laminate L6 with a first adhesive sheet 2 formed on the surface of the PET film. The thickness of the adhesive sheet was 100 μm.

[0338] [Optical laminate]

[0339] Reference Figure 7 By transferring the first adhesive sheet 2 of the obtained laminate L6 to the aforementioned polarizing film (first optical film 1), a laminate L7 consisting of a polarizing film (first optical film 1), a first adhesive sheet 2, and a substrate film are sequentially stacked.

[0340] The substrate film is peeled off from the laminate L7, and the exposed surface of the first adhesive sheet 2 is transferred to the protective film 31 of the laminate L2c, thereby obtaining a laminate L8 in which the polarizing film (first optical film 1), the first adhesive sheet 2, the second optical film 3A, the second adhesive sheet 4, and the release liner A are sequentially stacked.

[0341] The release liner A is peeled off from the laminate L8, thereby obtaining the optical laminate 40 of Example 6.

[0342] (Comparative Example 1)

[0343] A photocurable adhesive composition C3 was used instead of a photocurable adhesive composition C1, and the thickness of the first adhesive sheet 2 was changed to 12 μm. Otherwise, the optical laminate 40 of Comparative Example 1 was obtained by the same method as in Example 1.

[0344] (Comparative Example 2)

[0345] The thickness of the first adhesive sheet 2 was changed to 50 μm. Otherwise, the optical laminate 40 of Comparative Example 2 was obtained by the same method as Comparative Example 1.

[0346] (Comparative Example 3)

[0347] The thickness of the first adhesive sheet 2 was changed to 100 μm. Otherwise, the optical laminate 40 of Comparative Example 3 was obtained by the same method as Comparative Example 1.

[0348] (Comparative Example 4)

[0349] The thickness of the first adhesive sheet 2 was changed to 12 μm. Otherwise, the optical laminate 40 of Comparative Example 4 was obtained by the same method as in Example 3.

[0350]

[0351]

[0352]

[0353] As shown in Table 3, the puncture test results were good in each embodiment. The optical laminate according to the embodiments is suitable for suppressing display defects.

[0354] Industrial applicability

[0355] The optical laminate of the present invention can be used, for example, in an image display device.

Claims

1. An optical laminate, wherein a first optical film, a first adhesive sheet, a second optical film, and a second adhesive sheet are sequentially stacked. The thickness T1 of the first adhesive sheet is 30 μm or more and 1000 μm or less, and the elongation at break of the first adhesive sheet is 500% or less.

2. The optical laminate according to claim 1, wherein, The first adhesive sheet is formed from a photocurable adhesive composition (I) comprising a monomer group and / or a portion of the polymer of the monomer group.

3. The optical laminate according to claim 2, wherein, The photocurable adhesive composition (I) includes a crosslinking agent, and the amount of the crosslinking agent in the photocurable adhesive composition (I) is 0.4 parts by weight or more and 20 parts by weight or less, relative to a total of 100 parts by weight of the monomer group and the polymer fraction.

4. The optical laminate according to claim 1, wherein, The thickness T of the optical laminate is 200 μm or more.

5. The optical laminate according to claim 1, wherein, The second optical film comprises multiple layers. The multilayer includes a polarizing mirror and at least one film disposed between the polarizing mirror and the second adhesive sheet. The photoelasticity of at least one of the films is 4×10. -11 m 2 / N and below.

6. An image display device comprising the optical laminate of claim 1.

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