Optical laminate, manufacturing method thereof and picture display unit

Abstract

To provide an optical laminate excellent in high-temperature durability, a picture display unit having the optical laminate and a manufacturing method of the optical laminate.SOLUTION: An optical laminate includes a first protective film, a polarization element and a high retardation film in this order. An absolute value of a photoelastic coefficient at a temperature of 23°C of the first protective film is 8×10-12 Pa-1 or less. A moisture content of the polarization element is equal to or higher than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or lower than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%. An in-plane retardation value Re[550] at a wavelength 550nm of the high retardation film is 3000 to 30000 nm inclusive. An angle formed by a slow axis of the high retardation film and an absorption axis of the polarization element is 40° to 50° inclusive.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an optical laminate, and further to a method for producing the same and an image display device. [Background technology]

[0002] A method for improving visibility in an in-vehicle image display device is described in which a white light-emitting diode is used as the backlight of a liquid crystal display device, and a polymer film having a retardation of 3000 to 30000 nm is arranged on the viewer's side of the polarizer so that the angle between the absorption axis of the polarizer and the slow axis of the polymer film is approximately 45° (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-81219 Summary of the Invention [Problem to be solved by the invention]

[0004] Image display devices used in vehicles are often exposed to high-temperature environments, and optical laminates used in image display devices are also required to have high-temperature durability.

[0005] An object of the present invention is to provide an optical laminate having excellent high-temperature durability, an image display device including the optical laminate, and a method for producing the optical laminate. [Means for solving the problem]

[0006] The present invention provides the following optical laminate, image display device, and method for producing an optical laminate. [1] An optical laminate having a first protective film, a polarizing element, and a high retardation film in this order, The absolute value of the photoelastic coefficient of the first protective film at a temperature of 23°C is 8×10 -12 Pa-1 is as follows: the moisture content of the polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%; The in-plane retardation value Re

[0550] of the high retardation film at a wavelength of 550 nm is 3000 nm or more and 30000 nm or less, The optical laminate, wherein the angle formed between the slow axis of the high retardation film and the absorption axis of the polarizing element is 40° or more and 50° or less. [2] An optical laminate having a first protective film, a polarizing element, and a high retardation film in this order, The moisture content of the optical laminate is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%, The absolute value of the photoelastic coefficient of the first protective film at a temperature of 23°C is 8×10 -12 Pa -1 is as follows: The high retardation film has an in-plane retardation value Re

[0550] at a wavelength of 550 nm of 3000 nm or more and 30000 nm or less, The optical laminate, wherein the angle formed between the slow axis of the high retardation film and the absorption axis of the polarizing element is 40° or more and 50° or less. [3] The optical laminate according to [1] or [2], wherein the first protective film contains at least one selected from the group consisting of cyclic polyolefin resins, (meth)acrylic resins, polystyrene resins, and maleimide resins. [4] The optical laminate according to any one of [1] to [3], wherein the first protective film has an in-plane retardation value Re

[0550] of 10 nm or less at a wavelength of 550 nm. [5] The optical laminate according to any one of [1] to [4], wherein the high retardation film has a thickness of 200 μm or less. [6] The optical laminate is used in an image display device, The optical laminate according to any one of [1] to [5], wherein in the image display device, a layer other than an air layer is provided on both sides of the optical laminate in contact with them. [7] An image display device comprising: an image display cell; a first pressure-sensitive adhesive layer laminated on the viewing side surface of the image display cell; and an optical laminate according to any one of [1] to [6] laminated on the viewing side surface of the first pressure-sensitive adhesive layer. [8] The image display device described in [7], further comprising a second adhesive layer laminated on the viewing side surface of the optical laminate, and a transparent member laminated on the viewing side surface of the second adhesive layer. [9] The image display device according to [8], wherein the transparent member is a glass plate or a transparent resin plate.

[10] The image display device according to [8], wherein the transparent member is a touch panel.

[11] A method for producing the optical laminate according to [1], A method for producing an optical laminate, comprising a moisture content adjusting step of adjusting the moisture content of the polarizing element so that the moisture content is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.

[12] A method for producing the optical laminate according to [2], A method for producing an optical laminate, comprising a moisture content adjusting step of adjusting the moisture content of the optical laminate so that the moisture content is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical laminate having excellent high-temperature durability, an image display device including the optical laminate, and a method for manufacturing the optical laminate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic cross-sectional view showing an example of a layer structure of an optical laminate. [Figure 2] FIG. 2 is a schematic cross-sectional view showing another example of the layer structure of the optical laminate. [Figure 3] FIG. 10 is a schematic cross-sectional view showing yet another example of the layer structure of the optical laminate. [Figure 4] FIG. 1 is a schematic cross-sectional view showing an example of a layer structure of an image display device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all of the drawings, the scales of the components are appropriately adjusted to make them easier to understand, and the scales of the components shown in the drawings do not necessarily match the scales of the actual components.

[0010] <Optical laminate> [First aspect] The optical laminate according to the first embodiment will be described below with reference to the drawings. The optical laminate 10 shown in Fig. 1 has a first protective film 11, a polarizing element 12, and a high retardation film 13 in this order. The absolute value of the photoelastic coefficient of the first protective film 11 at a temperature of 23°C is 8 x 10 -12 Pa -1 the moisture content of the polarizing element 12 is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%; the in-plane retardation value Re

[0550] of the high retardation film 13 at a wavelength of 550 nm is 3000 nm or more and 30000 nm or less; and the angle formed by the slow axis of the high retardation film 13 and the absorption axis of the polarizing element 12 is 40° or more and 50° or less.

[0011] The optical laminate 10 may further include layers other than the layers described above, such as a second protective film and an attachment layer.

[0012] [First protective film] The first protective film 11 is a layer for protecting the polarizing element 12, particularly the surface of the polarizing element 12. As shown in Fig. 1, the first protective film 11 is disposed on the side of the polarizing element 12 opposite to the side on which the high retardation film 13 is disposed. The first protective film 11 can be laminated only via an attachment layer or directly.

[0013] The first protective film 11 has an absolute value of the photoelastic coefficient of 8×10 at a temperature of 23° C. -12 Pa -1By using first protective film 11 having such a small photoelastic coefficient, the retardation value exhibited by distortion of first protective film 11 caused by shrinkage stress of high retardation film 13 when placed in a high-temperature environment is reduced, and as a result, visibility tends to be improved even after being placed in a high-temperature environment.

[0014] The first protective film 11 is not particularly limited, but preferably has an absolute value of a photoelastic coefficient of 8×10 -12 Pa -1 The film may be made of the following light-transmitting (preferably optically transparent) thermoplastic resin, for example, a polyolefin resin such as a linear polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a norbornene resin); a cellulose resin such as triacetyl cellulose or diacetyl cellulose; a polyester resin such as polyethylene terephthalate or polybutylene terephthalate; a polycarbonate resin; a (meth)acrylic resin such as a methyl methacrylate resin; a polystyrene resin; a polyvinyl chloride resin; an acrylonitrile-butadiene-styrene resin; an acrylonitrile-styrene resin; a polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; a modified polyphenylene ether resin; a polysulfone resin; a polyethersulfone resin; a polyarylate resin; a polyamideimide resin; a polyimide resin; or a maleimide resin.

[0015] In particular, it is preferable to use a film having a small photoelastic coefficient for the first protective film 11. That is, it is preferable to use a film containing at least one resin selected from the group consisting of cyclic polyolefin resins, (meth)acrylic resins, polystyrene resins, and maleimide resins.

[0016] The photoelastic coefficient of the first protective film 11 at a temperature of 23° C. is preferably 0.05×10 -12 Pa -1 Over 8.0 x 10 -12 Pa -1 Less than or equal to 0.1 × 10 -12 Pa-1 Over 5.0 x 10 -12 Pa -1 or less, and more preferably 0.2 × 10 -12 Pa -1 Over 3.0 x 10 -12 Pa -1 The photoelastic coefficient is a value measured by the method described in the examples below.

[0017] As long as the in-plane retardation value Re

[0550] of the first protective film 11 is within the above-mentioned range of photoelastic coefficient, it is preferable to use one adjusted to 10 nm or less or 50 to 300 nm. In particular, a film having a retardation value of 10 nm or less can achieve a higher effect. This is presumably because, in a film with retardation, the retardation value changes due to stress relaxation in the oblique direction of the high retardation film, and the optical axis also changes, resulting in increased light leakage during black display. When a retardation film is used as an optical compensation film in a liquid crystal display device or the like, arranging the optical compensation film on the other polarizing plate used as a pair is also a useful design method.

[0018] In this specification, the in-plane retardation value Re[λ] refers to the in-plane retardation value of a film at 23°C and a wavelength of λ (nm). For example, the in-plane retardation value Re

[0550] refers to the in-plane retardation value of a film at 23°C and a wavelength of 550 (nm). Re[λ] is calculated by Re[λ] = (nx - ny) × d, where d (nm) is the thickness of the film. Furthermore, the thickness direction retardation value Rth[λ] refers to the retardation value in the thickness direction of a film at 23°C and a wavelength of λ (nm). Rth[λ] is calculated by Rth[λ] = ((nx + ny) / 2 - nz) × d, where d (nm) is the thickness of the film. "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the in-plane direction perpendicular to the slow axis, and "nz" is the refractive index in the thickness direction.

[0019] Cyclic polyolefin resin is a general term for resins polymerized using cyclic olefins as polymerization units, and examples thereof include resins described in JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, etc. Specific examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically random copolymers) of cyclic olefins with chain olefins such as ethylene and propylene, graft polymers modified with unsaturated carboxylic acids or their derivatives, and hydrogenated products thereof. Among these, norbornene resins using norbornene monomers such as norbornene or polycyclic norbornene monomers as the cyclic olefin are preferred.

[0020] The method for producing the first protective film 11 from a cyclic olefin resin is not particularly limited, and a method appropriate for the resin may be selected. For example, a solvent casting method is used in which a resin dissolved in a solvent is cast onto a metal band or drum, and the solvent is dried and removed to obtain a film, and a melt extrusion method is used in which a resin is heated and kneaded to a temperature above its melting point, extruded through a die, and cooled on a cooling drum to obtain a film. Of these, the melt extrusion method is preferably used from the viewpoint of productivity.

[0021] The in-plane retardation value Re

[0550] of the cyclic olefin resin film at a wavelength of 550 nm is preferably 10 nm or less, more preferably 7 nm or less, even more preferably 5 nm or less, particularly preferably 3 nm or less, and most preferably 1 nm or less. The thickness direction retardation value Rth

[0550] of the cyclic olefin resin film at a wavelength of 550 nm is preferably 15 nm or less, more preferably 10 nm or less, even more preferably 5 nm or less, particularly preferably 3 nm or less, and most preferably 1 nm or less.

[0022] Next, a method for controlling the retardation value of the cyclic olefin resin film so as to satisfy the above conditions will be described. In order to set the in-plane retardation value to 10 nm or less, it is necessary to minimize the distortion remaining in the in-plane direction during stretching, and in order to set the thickness direction retardation to the specified value or less of the present invention, it is necessary to minimize the distortion remaining in the thickness direction.

[0023] For example, in the solvent casting method, a method is employed in which residual stretching strain in the in-plane direction and residual shrinkage strain in the thickness direction that occur when the casting resin solution is dried are alleviated by heat treatment. In addition, in the melt extrusion method, in order to prevent the resin film from being stretched during the period from extrusion through the die to cooling, a method is employed in which the distance from the die to the cooling drum is shortened as much as possible and the extrusion amount and the rotation speed of the cooling drum are controlled so as not to stretch the film. Similarly to the melt extrusion method, a method is also employed in which residual strain in the obtained film is alleviated by heat treatment.

[0024] Furthermore, the retardation film may function as an optical compensation film for a liquid crystal display device within a range that satisfies the photoelastic coefficient of the present invention. Such a retardation film can be produced by stretching the cyclic olefin resin film to impart an in-plane retardation value. The stretching can be performed by known methods such as longitudinal uniaxial stretching, tenter transverse uniaxial stretching, simultaneous biaxial stretching, and sequential biaxial stretching, and the film may be stretched so as to obtain a desired retardation value.

[0025] For example, in an in-plane switching mode liquid crystal display device, a retardation film having an in-plane retardation adjusted to 50 nm or more and 300 nm or less is preferably used. Specifically, the retardation film described in JP-A-2010-20287 or the retardation film described in Japanese Patent No. 3880996 can be used.

[0026] The thickness of the cyclic olefin resin film is preferably 10 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less, and most preferably 10 μm or more and 65 μm or less. If the thickness is less than 10 μm, the strength may decrease. If the thickness is more than 200 μm, the transparency may decrease.

[0027] The (meth)acrylic resin is a resin whose main constituent monomer is a compound having a (meth)acryloyl group. Specific examples of the (meth)acrylic resin include poly(meth)acrylic acid esters such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate-(meth)acrylic acid ester copolymers; methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymers; methyl (meth)acrylate-styrene copolymers (MS resins, etc.); and copolymers of methyl methacrylate and compounds having alicyclic hydrocarbon groups (e.g., methyl methacrylate-cyclohexyl methacrylate copolymers, methyl methacrylate-norbornyl (meth)acrylate copolymers, etc.). Preferably, poly(meth)acrylic acid C such as polymethyl (meth)acrylate is used. 1-6 A polymer containing an alkyl ester as a main component is used, and more preferably, a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by mass, preferably 70 to 100% by mass) is used.

[0028] The in-plane retardation value Re

[0550] of the (meth)acrylic resin film at a wavelength of 550 nm is preferably 10 nm or less, more preferably 7 nm or less, even more preferably 5 nm or less, particularly preferably 3 nm or less, and most preferably 1 nm or less. The thickness direction retardation value Rth

[0550] of the (meth)acrylic resin film at a wavelength of 550 nm is preferably 15 nm or less, more preferably 10 nm or less, even more preferably 5 nm or less, particularly preferably 3 nm or less, and most preferably 1 nm or less. In order to achieve the in-plane retardation and thickness direction retardation in these ranges, for example, a (meth)acrylic resin having a glutarimide structure, which will be described later, can be used.

[0029] The (meth)acrylic resin may further have another structural unit. Examples of the other structural unit include structural units constituting lactone rings, polycarbonates, polyvinyl alcohols, cellulose acetate, polyesters, polyarylates, polyimides, polyolefins, etc., and structural units represented by the general formula (1) described below. Examples of structural units that exhibit negative birefringence include structural units derived from styrene-based monomers, maleimide-based monomers, etc., structural units of polymethyl methacrylate, and structural units represented by the general formula (3) described below.

[0030] As the (meth)acrylic resin, a (meth)acrylic resin having a lactone ring structure or a glutarimide structure is preferably used. A (meth)acrylic resin having a lactone ring structure or a glutarimide structure has excellent heat resistance. A (meth)acrylic resin having a glutarimide structure is more preferred. By using a (meth)acrylic resin having a glutarimide structure, it is possible to obtain a (meth)acrylic resin film having low moisture permeability, retardation, and ultraviolet transmittance, as described above. (Meth)acrylic resins having a glutarimide structure (hereinafter also referred to as glutarimide resins) are described in, for example, JP 2006-309033 A, JP 2006-317560 A, JP 2006-328329 A, JP 2006-328334 A, JP 2006-337491 A, JP 2006-337492 A, JP 2006-337493 A, JP 2006-337569 A, JP 2007-009182 A, and JP 2009-161744 A. These descriptions are incorporated herein by reference.

[0031] Preferably, the glutarimide resin contains a structural unit represented by the following general formula (1) (hereinafter also referred to as a glutarimide unit) and a structural unit represented by the following general formula (2) (hereinafter also referred to as a (meth)acrylic acid ester unit).

[0032] [ka]

[0033] In formula (1), R 1 and R 2 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R 3 is hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a substituent containing an aromatic ring having 5 to 15 carbon atoms. 4 and R 5 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R 6is hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a substituent containing an aromatic ring having 5 to 15 carbon atoms.

[0034] The glutarimide resin may further contain a structural unit represented by the following general formula (3) (hereinafter also referred to as an aromatic vinyl unit) as needed.

[0035] [ka]

[0036] In equation (3), R 7 is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R 8 is an aryl group having 6 to 10 carbon atoms.

[0037] In the above general formula (1), preferably, R 1 and R 2 are each independently a hydrogen atom or a methyl group, and R 3 is hydrogen, a methyl group, a butyl group, or a cyclohexyl group, and more preferably, R 1 is a methyl group, and R 2 is hydrogen and R 3 is a methyl group.

[0038] The glutarimide resin may contain only one type of glutarimide unit, or may contain only one type of glutarimide unit represented by R 1 , R 2 , and R 3 It may include a plurality of types having different

[0039] The glutarimide unit can be formed by imidizing a (meth)acrylic acid ester unit represented by the above general formula (2). Alternatively, the glutarimide unit can be formed by imidizing an acid anhydride such as maleic anhydride, or a half ester of such an acid anhydride with a linear or branched alcohol having 1 to 20 carbon atoms, or an α,β-ethylenically unsaturated carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, crotonic acid, fumaric acid, or citraconic acid.

[0040] In the above general formula (2), preferably, R 4 and R 5 are each independently a hydrogen atom or a methyl group, and R 6 is hydrogen or a methyl group, and more preferably, R 4 is hydrogen and R 5 is a methyl group, and R 6 is a methyl group.

[0041] The glutarimide resin may contain only one type of (meth)acrylic acid ester unit, or ... 4 , R 5 , and R 6 It may include a plurality of types having different

[0042] The glutarimide resin preferably contains styrene, α-methylstyrene, etc., and more preferably styrene, as the aromatic vinyl unit represented by the general formula (3). By containing such an aromatic vinyl unit, the positive birefringence of the glutarimide structure can be reduced, and a (meth)acrylic resin film with a lower retardation can be obtained.

[0043] The glutarimide resin may contain only one type of aromatic vinyl unit, or may contain only one type of aromatic vinyl unit, such as R 7 and R 8 It may include a plurality of types having different

[0044] The content of the glutarimide unit in the glutarimide resin is, for example, R 3 It is preferable to vary the content of glutarimide units depending on the structure of the glutarimide resin. The content of glutarimide units is preferably 1% by mass to 80% by mass, more preferably 1% by mass to 70% by mass, even more preferably 1% by mass to 60% by mass, and particularly preferably 1% by mass to 50% by mass, based on the total structural units of the glutarimide resin. When the content of glutarimide units is within this range, a (meth)acrylic resin film with excellent heat resistance and low retardation can be obtained.

[0045] The content of the aromatic vinyl units in the glutarimide resin can be appropriately set depending on the purpose and desired properties. Depending on the application, the content of the aromatic vinyl units may be 0. When the aromatic vinyl units are contained, the content thereof is preferably 10% by mass to 80% by mass, more preferably 20% by mass to 80% by mass, still more preferably 20% by mass to 60% by mass, and particularly preferably 20% by mass to 50% by mass, based on the glutarimide units of the glutarimide resin. When the content of the aromatic vinyl units is within this range, a (meth)acrylic resin film having low retardation and excellent heat resistance and mechanical strength can be obtained.

[0046] The glutarimide resin may further contain, as necessary, other structural units copolymerized therein besides the glutarimide unit, the (meth)acrylic acid ester unit, and the aromatic vinyl unit. Examples of the other structural units include structural units composed of nitrile-based monomers such as acrylonitrile and methacrylonitrile, and maleimide-based monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide. These other structural units may be directly copolymerized or graft-copolymerized in the glutarimide resin.

[0047] The (meth)acrylic resin film may contain any suitable additive depending on the purpose. Examples of additives include hindered phenol-based, phosphorus-based, and sulfur-based antioxidants; stabilizers such as light stabilizers, ultraviolet absorbers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; near-infrared absorbers; flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic and inorganic fillers; resin modifiers; plasticizers; lubricants; and retardation reducers. The type, combination, and content of the additives contained may be appropriately determined depending on the purpose and desired properties.

[0048] The method for producing the (meth)acrylic resin film is not particularly limited, but for example, the (meth)acrylic resin, the UV absorber, and, if necessary, other polymers and additives may be thoroughly mixed by any appropriate mixing method to form a thermoplastic resin composition in advance, which may then be molded into a film. Alternatively, the (meth)acrylic resin, the UV absorber, and, if necessary, other polymers and additives may each be prepared into separate solutions, which may then be mixed to form a uniform mixture, which may then be molded into a film.

[0049] To produce the thermoplastic resin composition, the film raw materials are preblended in any suitable mixer such as an omnimixer, and then the resulting mixture is extrusion-kneaded. In this case, the mixer used for extrusion-kneading is not particularly limited, and any suitable mixer can be used, for example, an extruder such as a single-screw extruder or a twin-screw extruder, or a pressure kneader.

[0050] The film forming method may be any suitable film forming method, such as solution casting, melt extrusion, calendaring, or compression molding. Melt extrusion is preferred. Since melt extrusion does not use a solvent, it can reduce production costs and the burden on the global environment and working environment caused by solvents.

[0051] Examples of the melt extrusion method include a T-die method, an inflation method, etc. The molding temperature is preferably 150 to 350°C, more preferably 200 to 300°C.

[0052] When forming a film using the T-die method, a T-die is attached to the tip of a known single-screw extruder or twin-screw extruder, and the extruded film is wound up to obtain a roll of film. At this time, uniaxial stretching can be performed by appropriately adjusting the temperature of the winding roll and stretching in the extrusion direction. Simultaneous biaxial stretching, sequential biaxial stretching, etc. can also be performed by stretching the film in a direction perpendicular to the extrusion direction.

[0053] The (meth)acrylic resin film may be either an unstretched film or a stretched film as long as the desired retardation can be obtained. In the case of a stretched film, it may be either a uniaxially stretched film or a biaxially stretched film. In the case of a biaxially stretched film, it may be either a simultaneous biaxially stretched film or a sequential biaxially stretched film.

[0054] The stretching temperature is preferably near the glass transition temperature of the thermoplastic resin composition that is the raw material for the film. Specifically, it is preferably within the range of (glass transition temperature - 30°C) to (glass transition temperature + 30°C), and more preferably (glass transition temperature - 20°C) to (glass transition temperature + 20°C). If the stretching temperature is below (glass transition temperature - 30°C), the haze of the resulting film may increase, or the film may tear or crack, preventing the desired stretch ratio from being achieved. Conversely, if the stretching temperature exceeds (glass transition temperature + 30°C), the resulting film may have significant thickness unevenness, and mechanical properties such as elongation, tear propagation strength, and flexural fatigue resistance may not be sufficiently improved. Furthermore, problems such as the film sticking to the roll may easily occur.

[0055] The stretching ratio is preferably 1.1 to 3 times, more preferably 1.3 to 2.5 times. A stretching ratio within this range can significantly improve the film's mechanical properties, such as elongation, tear propagation strength, and flexural fatigue resistance. As a result, a film can be produced that has little thickness variation, substantially zero birefringence (hence, small retardation), and low haze.

[0056] The (meth)acrylic resin film may be subjected to heat treatment (annealing) or the like after stretching in order to stabilize its optical isotropy and mechanical properties. Any appropriate conditions may be adopted for the heat treatment.

[0057] The thickness of the (meth)acrylic resin film is preferably 10 μm to 200 μm, more preferably 15 μm to 100 μm, and most preferably 15 μm to 65 μm. If the thickness is less than 10 μm, the strength may decrease. If the thickness exceeds 200 μm, the transparency may decrease.

[0058] First protective film 11 may have, on its outer surface (the surface opposite to polarizing element 12), a hard coat layer, as described below, or a functional layer such as an antiglare layer, an antireflection layer, a light diffusion layer, an antistatic layer, an antifouling layer, or a conductive layer. When first protective film 11 has a hard coat layer or a functional layer, the thickness of first protective film 11 includes the thickness of the hard coat layer or the functional layer.

[0059] [Hard coat layer] The hard coat layer is a layer containing a cured product of a curable resin. Examples of curable resins include thermosetting resins and active energy ray-curable resins. The cured product of the curable resin can be formed from a cured resin layer-forming composition containing the curable resin. The cured resin layer-forming composition may be, for example, a thermosetting composition, a cationic curable composition, or a radical curable composition. The cured resin layer-forming composition may contain, for example, a polymerizable monomer, a polymerization initiator, an additive, a solvent, etc. Examples of additives include plasticizers, ultraviolet absorbers, infrared absorbers, colorants such as pigments and dyes, fluorescent brighteners, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants, lubricants, surfactants, etc.

[0060] When the first protective film 11 has a hard coat layer, it is possible to easily improve the hardness and scratch resistance of the polarizing element 12 or the first protective film 11. When the first protective film 11 is a thermoplastic resin film having a hard coat layer, for example, a hard coat layer-forming composition can be applied to the thermoplastic resin film that forms the first protective film 11 and cured to form a cured product of the hard coat layer-forming composition, thereby producing a thermoplastic resin film having a hard coat layer, which can then be attached to the polarizing element 12 via an adhesive layer. A commercially available thermoplastic resin film having a cured resin layer can also be used as the first protective film 11.

[0061] The hard coat layer can be formed from a cured product of a hard coat layer-forming composition containing an active energy ray-curable resin. Examples of active energy ray-curable resins include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The hard coat layer may contain an additive to improve strength. The additive is not limited, and examples include inorganic fine particles, organic fine particles, and mixtures thereof. The hard coat layer preferably contains an ultraviolet absorber.

[0062] The thickness of the hard coat layer may be, for example, 10 μm or less, and preferably 8 μm or less, and is usually 0.5 μm or more.

[0063] [Polarizing element] The polarizing element 12 may be a polarizing element formed by adsorbing and aligning a dichroic dye in a layer containing a polyvinyl alcohol (hereinafter also referred to as "PVA")-based resin (also referred to as a "PVA-based resin layer" in this specification). Examples of such polarizing elements include a polarizing element formed by using a PVA-based resin film, dyeing this PVA-based resin film with a dichroic dye, and uniaxially stretching it, and a polarizing element formed by using a laminated film obtained by applying a coating liquid containing a PVA-based resin onto a base film, dyeing the PVA-based resin layer, which is a coating layer of this laminated film, with a dichroic dye, and uniaxially stretching the laminated film.

[0064] The polarizing element 12 is made of a PVA resin obtained by saponifying a polyvinyl acetate resin. Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other copolymerizable monomers. Examples of other copolymerizable monomers include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

[0065] The saponification degree of the PVA resin is preferably about 85 mol% or more, more preferably about 90 mol% or more, and even more preferably about 99 mol% to 100 mol%. The polymerization degree of the PVA resin is 1,000 to 10,000, preferably 1,500 to 5,000. The PVA resin may be modified, and may be, for example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral, or the like, modified with aldehydes.

[0066] The thickness of the polarizing element 12 is preferably 5 μm to 50 μm, more preferably 5 μm to 40 μm, and even more preferably 8 μm to 30 μm. When the thickness of the polarizing element 12 is 50 μm or less, the influence of polyenation of the PVA resin on the deterioration of optical properties in a high-temperature environment can be suppressed, and when the thickness of the polarizing element 12 is 5 μm or more, it becomes easy to achieve the desired optical properties.

[0067] The moisture content of the polarizing element 12 is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 48% at 20°C. It is preferably equal to or greater than the equilibrium moisture content at a temperature of 30% at 20°C and a relative humidity of 45% at 20°C. It is more preferably equal to or less than the equilibrium moisture content at a temperature of 42% at 20°C and a relative humidity of 40%, and most preferably equal to or less than the equilibrium moisture content at a temperature of 38% at 20°C. If the moisture content is below the equilibrium moisture content at a temperature of 20% relative humidity, the polarizing element 12 becomes less easy to handle and more likely to crack. By keeping the moisture content at or less than the equilibrium moisture content at a temperature of 48% relative humidity at 20°C, an optical laminate with excellent high-temperature durability can be provided. The moisture content of the polarizing element 12 is the moisture content of the polarizing element in the polarizing plate.

[0068] The method for manufacturing the polarizing element 12 is not particularly limited, but typical examples include a method in which a polyvinyl alcohol-based resin film that has been previously wound into a roll is fed out and stretched, dyed, crosslinked, etc. (hereinafter referred to as "manufacturing method 1"), and a method that includes a step of applying a coating liquid containing a polyvinyl alcohol-based resin onto a substrate film to form a polyvinyl alcohol-based resin layer as a coating layer, and stretching the resulting laminate (hereinafter referred to as "manufacturing method 2").

[0069] Manufacturing method 1 can be achieved by carrying out the steps of uniaxially stretching a polyvinyl alcohol-based resin film, dyeing the polyvinyl alcohol-based resin film with a dichroic dye such as iodine to adsorb the dichroic dye, treating the polyvinyl alcohol-based resin film with the adsorbed dichroic dye with a boric acid aqueous solution, and washing the film with water after the treatment with the boric acid aqueous solution.

[0070] The swelling step is a treatment step in which the polyvinyl alcohol-based resin film is immersed in a swelling bath, which can remove dirt and blocking agents from the surface of the polyvinyl alcohol-based resin film and suppress uneven dyeing by swelling the polyvinyl alcohol-based resin film. The swelling bath typically uses a medium whose main component is water, distilled water, pure water, or the like. The swelling bath may contain, as appropriate, surfactants, alcohol, and the like, according to conventional methods.

[0071] The temperature of the swelling bath is preferably about 10 to 60°C, more preferably about 15 to 45°C, and even more preferably about 18 to 30°C. The immersion time in the swelling bath cannot be determined in general because the degree of swelling of the polyvinyl alcohol-based resin film is affected by the temperature of the swelling bath, but is preferably about 5 to 300 seconds, more preferably about 10 to 200 seconds, and even more preferably about 20 to 100 seconds. The swelling step may be carried out only once, or may be carried out multiple times as necessary.

[0072] The dyeing process is a treatment process in which a polyvinyl alcohol-based resin film is immersed in a dye bath (iodine solution), allowing iodine or a dichroic substance such as a dichroic dye to be adsorbed and aligned in the polyvinyl alcohol-based resin film. The iodine solution is typically preferably an aqueous iodine solution containing iodine and an iodide as a solubilizing agent. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide is preferred from the viewpoint of controlling the potassium content in the polarizing element.

[0073] The iodine concentration in the dye bath is preferably about 0.01 to 1 mass%, more preferably about 0.02 to 0.5 mass%, and the iodide concentration in the dye bath is preferably about 0.01 to 10 mass%, more preferably about 0.05 to 5 mass%, and even more preferably about 0.1 to 3 mass%.

[0074] The temperature of the dye bath is preferably about 10 to 50°C, more preferably about 15 to 45°C, and even more preferably about 18 to 30°C. The immersion time in the dye bath cannot be determined in general because the degree of dyeing of the polyvinyl alcohol-based resin film is affected by the temperature of the dye bath, but is preferably about 10 to 300 seconds, and more preferably about 20 to 240 seconds. The dyeing step may be carried out only once, or may be carried out multiple times as necessary.

[0075] The crosslinking step is a treatment step in which the polyvinyl alcohol-based resin film dyed in the dyeing step is immersed in a treatment bath (crosslinking bath) containing a boron compound. The boron compound crosslinks the polyvinyl alcohol-based resin film, allowing iodine molecules or dye molecules to be adsorbed to the crosslinked structure. Examples of boron compounds include boric acid, borate salts, and borax. The crosslinking bath is generally an aqueous solution, but may also be, for example, a mixed solution of water and an organic solvent miscible with water. In addition, the crosslinking bath preferably contains potassium iodide in order to control the potassium content in the polarizing element.

[0076] The concentration of the boron compound in the crosslinking bath is preferably about 1 to 15 mass%, more preferably about 1.5 to 10 mass%, and even more preferably about 2 to 5 mass%. When potassium iodide is used in the crosslinking bath, the concentration of potassium iodide in the crosslinking bath is preferably about 1 to 15 mass%, more preferably about 1.5 to 10 mass%, and even more preferably about 2 to 5 mass%.

[0077] The temperature of the crosslinking bath is preferably about 20 to 70° C., more preferably about 30 to 60° C. The immersion time in the crosslinking bath cannot be determined in general because the degree of crosslinking of the polyvinyl alcohol resin film is affected by the temperature of the crosslinking bath, but is preferably about 5 to 300 seconds, more preferably about 10 to 200 seconds. The crosslinking step may be carried out only once, or may be carried out multiple times as necessary.

[0078] The stretching step is a treatment step in which a polyvinyl alcohol-based resin film is stretched at least in one direction to a predetermined magnification. Generally, the polyvinyl alcohol-based resin film is uniaxially stretched in the conveying direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method can be used. The stretching step may be carried out only once, or may be carried out multiple times as necessary. The stretching step may be carried out at any stage in the production of a polarizing element.

[0079] The treatment bath (stretching bath) in the wet stretching method can typically be water or a solvent such as a mixture of water and a water-miscible organic solvent. The stretching bath preferably contains potassium iodide to control the potassium content in the polarizing element. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably about 1 to 15% by mass, more preferably about 2 to 10% by mass, and even more preferably about 3 to 6% by mass. Furthermore, the treatment bath (stretching bath) can contain a boron compound to prevent film breakage during stretching. In this case, the concentration of the boron compound in the stretching bath is preferably about 1 to 15% by mass, more preferably about 1.5 to 10% by mass, and even more preferably about 2 to 5% by mass.

[0080] The temperature of the stretching bath is preferably about 25 to 80°C, more preferably about 40 to 75°C, and even more preferably about 50 to 70°C. The immersion time in the stretching bath cannot be determined in general because the degree of stretching of the polyvinyl alcohol-based resin film is affected by the temperature of the stretching bath, but is preferably about 10 to 800 seconds, and more preferably about 30 to 500 seconds. The stretching treatment in the wet stretching method may be carried out together with one or more of the following treatment steps: swelling, dyeing, crosslinking, and washing.

[0081] Examples of the dry stretching method include a roll-to-roll stretching method, a heated roll stretching method, a compression stretching method, etc. The dry stretching method may be carried out together with a drying step.

[0082] The total stretching ratio (cumulative stretching ratio) applied to the polyvinyl alcohol-based resin film can be set appropriately depending on the purpose, but is preferably about 2 to 7 times, more preferably about 3 to 6.8 times, and even more preferably about 3.5 to 6.5 times.

[0083] The cleaning step is a treatment step in which the polyvinyl alcohol-based resin film is immersed in a cleaning bath, and foreign matter remaining on the surface of the polyvinyl alcohol-based resin film can be removed. The cleaning bath typically uses a medium whose main component is water, such as distilled water or pure water. To control the potassium content in the polarizing element, it is preferable to use potassium iodide in the cleaning bath. In this case, the concentration of potassium iodide in the cleaning bath is preferably about 1 to 10% by mass, more preferably about 1.5 to 4% by mass, and even more preferably about 1.8 to 3.8% by mass.

[0084] The temperature of the cleaning bath is preferably about 5 to 50°C, more preferably about 10 to 40°C, and even more preferably about 15 to 30°C. The immersion time in the cleaning bath cannot be determined in general because the degree of cleaning of the polyvinyl alcohol-based resin film is affected by the temperature of the cleaning bath, but is preferably about 1 to 100 seconds, more preferably about 2 to 50 seconds, and even more preferably about 3 to 20 seconds. The cleaning step may be carried out only once, or may be carried out multiple times as necessary.

[0085] The drying step is a step of drying the polyvinyl alcohol-based resin film washed in the washing step to obtain a polarizing element. The drying can be performed by any appropriate method, for example, natural drying, air drying, or heat drying.

[0086] The manufacturing method 2 can be carried out by applying a coating liquid containing the polyvinyl alcohol resin to a substrate film, uniaxially stretching the resulting laminated film, dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminated film with a dichroic dye to adsorb the dichroic dye to form a polarizing element, treating the film with the adsorbed dichroic dye with a boric acid aqueous solution, and washing with water after the treatment with the boric acid aqueous solution. The substrate film used to form the polarizing element may also be used as a protective layer for the polarizing element. If necessary, the substrate film may be peeled off and removed from the polarizing element.

[0087] [High retardation film] The optical laminate 10 includes a high-retardation film 13. In this specification, a high-retardation film refers to a film having an in-plane retardation value of 3000 nm or more at a wavelength of 550 nm. By including the high-retardation film 13 in the optical laminate 10, it is possible to easily suppress hue changes (rainbow unevenness) that can be observed when a liquid crystal display device having the optical laminate arranged thereon is viewed through polarized sunglasses. The high-retardation film 13 is made of a transparent thermoplastic resin film having birefringence. The in-plane retardation value Re

[0550] of the high-retardation film 13 at a wavelength of 550 nm is preferably 3000 nm or more, more preferably 5000 nm or more, and particularly preferably 7000 nm or more. The upper limit of the in-plane retardation Re

[0550] of the high-retardation film 13 is 30,000 nm.

[0088] The high retardation film 13 can be obtained, for example, by stretching a thermoplastic resin film. Specific examples of thermoplastic resins include polyolefin resins such as polyethylene and polypropylene; cyclic polyolefin resins such as norbornene-based polymers; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; (meth)acrylic acid resins such as polymethyl(meth)acrylate; cellulose ester resins such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; vinyl alcohol resins such as polyvinyl alcohol and polyvinyl acetate; polycarbonate resins; polystyrene resins; polyarylate resins; polysulfone resins; polyethersulfone resins; polyamide resins; polyimide resins; polyetherketone resins; polyphenylene sulfide resins; polyphenylene oxide resins; and mixtures and copolymers thereof. From the viewpoints of availability and transparency, polyethylene terephthalate, cellulose ester, cyclic olefin resins, and polycarbonate are preferred.

[0089] These thermoplastic resins can be subjected to uniaxial or biaxial heat stretching to form a film having a desired retardation value. The stretching ratio is usually 1.1 to 6 times, and preferably 1.1 to 4 times.

[0090] In addition, a method of stretching in an oblique direction is also preferably used so that the film can be produced by a roll-to-roll process. The method of stretching in an oblique direction is not particularly limited as long as it can continuously tilt the orientation axis at a desired angle, and known stretching methods can be used. Examples of such stretching methods include those described in JP-A-50-83482 and JP-A-2-113920. When retardation is imparted to the film by stretching, the thickness after stretching is determined by the thickness before stretching and the stretching ratio.

[0091] The angle between the slow axis of the high retardation film 13 and the absorption axis of the polarizing element 12 is 40° or more and 50° or less, more preferably 42° or more and 48° or less, and particularly preferably about 45°. This makes it possible to suppress a decrease in front luminance when the liquid crystal display device is viewed through polarized sunglasses.

[0092] The thickness of the high retardation film 13 is preferably 200 μm or less, more preferably 150 μm or less, and particularly preferably 100 μm or less. By making the thickness of the high retardation film 13 200 μm or less, curling of the optical laminate 10 can be suppressed, and defects such as the introduction of air bubbles when the film is attached to a liquid crystal display device can be suppressed.

[0093] The moisture permeability of the high retardation film 13 is, for example, 100 g / m 2 -day or less, 50g / m 2 The moisture permeability of the high retardation film 13 can be, for example, 0 g / m 2 day or more, 1g / m 2Even if the moisture permeability of the high retardation film 13 is low, the optical laminate 10 is less likely to experience a decrease in transmittance in a high-temperature environment and has excellent high-temperature durability. The moisture permeability can be measured in an atmosphere at a temperature of 40°C and a relative humidity of 90% in accordance with JIS K7129:2008, Appendix B.

[0094] By providing the optical laminate 10 on the viewer's side of the liquid crystal cell of a liquid crystal display device, it is possible to suppress a decrease in visibility when the liquid crystal display device is viewed through polarized sunglasses without requiring an additional high-retardation film. Specifically, it is possible to suppress a decrease in front luminance and a change in hue (color shift) depending on the viewing angle. A hard coat layer or an anti-glare layer may be laminated on the high-retardation film 13 as needed.

[0095] [Second protective film] The optical laminate 10 may have a second protective film on the high retardation film 13 side of the polarizing element 12. The second protective film can be disposed between the polarizing element 12 and the high retardation film 13. The second protective film may be the resin film described above as a film that can be used as the first protective film 11, or another resin film. When the optical laminate 10 has a second protective film, the second protective film may be the same type as or different from the first protective film 11. The optical laminate 10 does not necessarily have to have a second protective film. That is, the optical laminate 10 may have a protective film (first protective film 11) on only one side of the polarizing element 12.

[0096] The second protective film may be, for example, a cellulose acylate film, a linear olefin resin film, a polycarbonate resin film, a cycloolefin resin film such as norbornene, a (meth)acrylic polymer film, or a polyester resin film such as polyethylene terephthalate. Examples of linear polyolefin resins include linear olefin homopolymers such as polyethylene resins (polyethylene resins which are homopolymers of ethylene, and copolymers mainly composed of ethylene) and polypropylene resins (polypropylene resins which are homopolymers of propylene, and copolymers mainly composed of propylene), as well as copolymers composed of two or more linear olefins.

[0097] The thickness of the second protective film is usually 1 μm or more and 100 μm or less, but from the viewpoint of strength, handling, etc., it is preferably 5 μm or more and 60 μm or less, more preferably 10 μm or more and 55 μm or less, and even more preferably 15 μm or more and 50 μm or less.

[0098] The second protective film may have a surface treatment layer (coating layer) such as a hard coat layer, antiglare layer, light diffusion layer, antireflection layer, low refractive index layer, antistatic layer, or antifouling layer on its outer surface (the surface opposite to the polarizing element). The thickness of the second protective film includes the thickness of the surface treatment layer.

[0099] [Lamination layer] An attachment layer is used to attach each layer to the optical laminate 10. Examples of the attachment layer include an adhesive layer and a pressure-sensitive adhesive layer.

[0100] (adhesive layer) The adhesive layer can be used, for example, to bond the first protective film 11 and the second protective film to the polarizing element 12. Any appropriate adhesive can be used as the adhesive constituting the adhesive layer. The adhesive can be a water-based adhesive, a solvent-based adhesive, an active energy ray-curable adhesive, or the like, but a water-based adhesive is preferred.

[0101] The thickness of the adhesive when applied can be set to any appropriate value. For example, it is set so that an adhesive layer having a desired thickness is obtained after curing or heating (drying). The thickness of the adhesive layer is preferably 0.01 μm or more and 7 μm or less, more preferably 0.01 μm or more and 5 μm or less, even more preferably 0.01 μm or more and 2 μm or less, and most preferably 0.01 μm or more and 1 μm or less.

[0102] (water-based adhesive) Any appropriate aqueous adhesive can be used as the aqueous adhesive. Among them, aqueous adhesives containing PVA resins (PVA adhesives) are preferably used. The average polymerization degree of the PVA resin contained in the aqueous adhesive is preferably about 100 to 5500, more preferably 1000 to 4500, from the viewpoint of adhesiveness. The average saponification degree is preferably about 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, from the viewpoint of adhesiveness.

[0103] The PVA resin contained in the aqueous adhesive preferably contains an acetoacetyl group, because it has excellent adhesion between the PVA resin layer and the protective film and excellent durability. The acetoacetyl group-containing PVA resin can be obtained, for example, by reacting a PVA resin with diketene using any method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA resin is typically 0.1 mol% or more, and preferably about 0.1 mol% to 20 mol%. The resin concentration of the water-based adhesive is preferably 0.1% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 10% by mass or less.

[0104] The water-based adhesive may contain a crosslinking agent. Known crosslinking agents can be used, such as water-soluble epoxy compounds, dialdehydes, and isocyanates.

[0105] When the PVA-based resin is an acetoacetyl group-containing PVA-based resin, the crosslinking agent is preferably any one of glyoxal, glyoxylate, and methylolmelamine, more preferably any one of glyoxal and glyoxylate, and particularly preferably glyoxal.

[0106] The water-based adhesive may also contain an organic solvent. The organic solvent is preferably an alcohol because of its miscibility with water, and among alcohols, methanol or ethanol is more preferred. Some urea compounds have low solubility in water, but some have sufficient solubility in alcohol. In this case, one preferred embodiment is to dissolve the urea compound in alcohol to prepare an alcohol solution of the urea compound, and then add the alcohol solution of the urea compound to an aqueous PVA solution to prepare the adhesive.

[0107] The methanol concentration of the aqueous adhesive is preferably 10% by mass or more and 70% by mass or less, more preferably 15% by mass or more and 60% by mass or less, and even more preferably 20% by mass or more and 60% by mass or less. A methanol concentration of 10% by mass or more can more easily suppress polyenation in a high-temperature environment. Furthermore, a methanol content of 70% by mass or less can suppress deterioration of color.

[0108] (Active energy ray curing adhesive) The active energy ray-curable adhesive is an adhesive that cures upon irradiation with active energy rays such as ultraviolet rays, and examples thereof include adhesives containing a polymerizable compound and a photopolymerization initiator, adhesives containing a photoreactive resin, and adhesives containing a binder resin and a photoreactive crosslinking agent. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, as well as oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anion radicals, and cation radicals upon irradiation with active energy rays such as ultraviolet rays.

[0109] (Adhesive layer) The pressure-sensitive adhesive layer can be used, for example, to attach the high retardation film 13 to the polarizing element 12 .

[0110] The pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition whose main component is a resin such as a (meth)acrylic resin, a rubber resin, a urethane resin, an ester resin, a silicone resin, or a polyvinyl ether resin. Among these, a pressure-sensitive adhesive composition whose base polymer is a (meth)acrylic resin, which is excellent in transparency, weather resistance, heat resistance, etc., is preferred. The pressure-sensitive adhesive composition may be an active energy ray-curable or thermosetting type. The thickness of the pressure-sensitive adhesive layer is usually 3 μm or more and 30 μm or less, and preferably 3 μm or more and 25 μm or less.

[0111] The (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition is preferably a polymer or copolymer containing one or more (meth)acrylic acid esters as monomers, such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. It is preferable to copolymerize a polar monomer into the base polymer. Examples of polar monomers include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, or an epoxy group, such as (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate.

[0112] The pressure-sensitive adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. Examples of crosslinking agents include divalent or higher metal ions that form metal carboxylates with carboxyl groups; polyamine compounds that form amide bonds with carboxyl groups; polyepoxy compounds or polyols that form ester bonds with carboxyl groups; and polyisocyanate compounds that form amide bonds with carboxyl groups. Among these, polyisocyanate compounds are preferred.

[0113] The thickness of the pressure-sensitive adhesive layer is preferably from 1 μm to 200 μm, more preferably from 2 μm to 100 μm, even more preferably from 2 μm to 80 μm, and particularly preferably from 3 μm to 50 μm.

[0114] [Second aspect] The optical laminate according to the second embodiment will be described below with reference to the drawings. The optical laminate 20 shown in Fig. 2 includes a first protective film 21, a polarizing element 22, and a high retardation film 23 in this order. The optical laminate 20 has a moisture content equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%. The absolute value of the photoelastic coefficient of the first protective film 21 at a temperature of 23°C is 8 x 10 -12 Pa -1 The high retardation film 23 has an in-plane retardation value Re

[0550] at a wavelength of 550 nm of 3000 nm or more and 30000 nm or less, and the angle formed between the slow axis of the high retardation film 23 and the absorption axis of the polarizing element 22 is 40° or more and 50° or less.

[0115] The moisture content of the optical laminate 20 is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 48% relative humidity at 20°C. Preferably, it is equal to or greater than the equilibrium moisture content at a temperature of 30% relative humidity at 20°C and equal to or less than the equilibrium moisture content at a temperature of 45% relative humidity at 20°C. More preferably, it is equal to or less than the equilibrium moisture content at a temperature of 42% relative humidity at 20°C, even more preferably, it is equal to or less than the equilibrium moisture content at a temperature of 40% relative humidity at 20°C, and most preferably, it is equal to or less than the equilibrium moisture content at a temperature of 38% relative humidity at 20°C. If the moisture content is below the equilibrium moisture content at a temperature of 20% relative humidity at 20°C, the handleability of the optical laminate 20 will decrease and it will be more likely to crack. By having the moisture content of the optical laminate 20 equal to or less than the equilibrium moisture content at a temperature of 48% relative humidity at 20°C, an optical laminate with excellent high-temperature durability can be provided.

[0116] The optical laminate 20 may include other layers such as a second protective film and an adhesive layer.

[0117] The examples and preferred ranges of the first protective film 21, the polarizing element 22, the high retardation film 23, the second protective film, and the adhesive layer are the same as those described above for the first protective film 11, the polarizing element 12, the high retardation film 13, the second protective film, and the adhesive layer in the optical laminate 10.

[0118] [High temperature durability] The optical laminate has excellent high-temperature durability. In this specification, high-temperature durability can be evaluated according to the method described in the Examples section below. For example, the optical laminate may have a transmittance measured after leaving it in an environment at a temperature of 23°C and a relative humidity of 55% for 24 hours, and the time required for the transmittance measured when an evaluation sample is stored in a heated environment at a temperature of 95°C to decrease by 5% may be 240 hours or more, preferably 480 hours or more, more preferably 720 hours or more, and even more preferably 960 hours or more.

[0119] [Application] The optical laminate can be used in image display devices such as liquid crystal display devices and organic EL display devices. The optical laminate can be arranged on the viewing side (front side) or the back side of the image display device. When the optical laminate is arranged in an image display device, it is preferable that the high retardation film, the polarizing element, and the first protective film are arranged in this order from the viewing side. When the optical laminate is used in an image display device, layers other than an air layer may be provided in contact with both sides of the optical laminate in the image display device. Examples of layers other than the air layer include an adhesive layer and a transparent member. The same explanation as for the adhesive layer described in the optical laminate above applies to the adhesive layer. The transparent member will be described later.

[0120] 3 is a cross-sectional view showing the configuration of a laminate in which a transparent member 34 and a touch panel 37 are arranged on an optical laminate 30 having a high retardation film 33, a polarizing element 32, and a protective film 31 in this order. As shown in Fig. 3, the transparent member 34 and the touch panel 37 can be laminated via bonding layers 35 and 36. The laminate shown in Fig. 3 can be arranged in an image display device or the like so that the transparent member 34 side is the viewing side, for example.

[0121] [Transparent material] Examples of transparent members arranged on the viewing side of an image display device include a front panel (window layer) and a touch panel. A front panel having appropriate mechanical strength and thickness is used. Examples of such front panels include transparent resin plates such as polyimide resins, acrylic resins, and polycarbonate resins, and glass plates. A functional layer such as an anti-reflection layer may be laminated on the viewing side of the front panel. Furthermore, when the front panel is a transparent resin plate, a hard coat layer may be laminated to increase physical strength, or a low-moisture permeability layer may be laminated to reduce moisture permeability. As the touch panel, various types of touch panels such as resistive, capacitive, optical, and ultrasonic touch panels, as well as glass or transparent resin plates equipped with touch sensor functions, are used. When a capacitive touch panel is used as the transparent member, it is preferable to provide a front panel made of glass or transparent resin plate on the viewing side further than the touch panel.

[0122] A pressure-sensitive adhesive or an active energy ray-curable adhesive is preferably used to bond the optical laminate to the transparent member. When a pressure-sensitive adhesive is used, the pressure-sensitive adhesive can be applied by an appropriate method. Specific application methods include, for example, the application method of the pressure-sensitive adhesive layer used in bonding the image display cell and the optical laminate described above.

[0123] When an active energy ray-curable adhesive is used, a method is preferably used in which a dam material is provided around the periphery of the image display panel to prevent the adhesive solution from spreading before curing, a transparent member is placed on the dam material, and the adhesive solution is then poured in. After the adhesive solution is poured, alignment and degassing are performed as necessary, and then active energy rays are irradiated to cause curing.

[0124] <Image display device> The image display device according to this embodiment may include an image display cell, a first pressure-sensitive adhesive layer laminated on the viewing-side surface of the image display cell, and an optical laminate laminated on the viewing-side surface of the first pressure-sensitive adhesive layer. The image display device may further include a second pressure-sensitive adhesive layer laminated on the viewing-side surface of the optical laminate, and a transparent member laminated on the viewing-side surface of the second pressure-sensitive adhesive layer.

[0125] Fig. 4 shows an example of the layer structure of an image display device. In the image display device 100 shown in Fig. 4, an optical laminate 40 including a high-retardation film 43, a polarizing element 42, and a protective film 41 in this order is laminated on an image display cell 47 via a first pressure-sensitive adhesive layer 46, and a transparent member 44 is laminated on the viewing side surface of the optical laminate 40 via a second pressure-sensitive adhesive layer 45.

[0126] <Method of manufacturing optical laminate> [Method of manufacturing the optical laminate according to the first embodiment] The method for producing an optical laminate according to the first embodiment includes a moisture content adjusting step of adjusting the moisture content of a polarizing element to be equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%. Preferably, the method further includes a first lamination step of laminating a first protective film on one side of the polarizing element. The order of the moisture content adjusting step and the first lamination step is not limited, and the moisture content adjusting step and the first lamination step may be performed in parallel. The method for producing an optical laminate according to this embodiment may further include a second lamination step of laminating a high retardation film on one side of the polarizing plate.

[0127] In the moisture content adjusting step of this embodiment, the moisture content of the polarizing element is adjusted so that the moisture content of the polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%. There are no particular limitations on the method for preparing a polarizing element with such a moisture content, but it can be adjusted, for example, by storing the polarizing element in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes to 3 hours, or by heat-treating it at 30°C to 90°C.

[0128] As another preferred method, the moisture content can be adjusted by storing the polarizing plate obtained in the first lamination step in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes to 120 hours, or by heat treating the polarizing plate at 30° C. to 90° C. The moisture content adjustment step may be carried out before or after the first lamination step.

[0129] [Method of manufacturing an optical laminate according to the second embodiment] The method for producing an optical laminate according to the second aspect includes a moisture content adjusting step of adjusting the moisture content of the optical laminate to be equal to or greater than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%. Preferably, the method can further include a first lamination step of laminating a first protective film on one side of the polarizing element, and a second lamination step of laminating a high retardation film on one side of the polarizing plate.

[0130] In the moisture content adjusting step of this embodiment, the moisture content of the optical laminate is adjusted so that the moisture content of the optical laminate is equal to or greater than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 48%. There are no particular limitations on the method for preparing an optical laminate with such a moisture content, but it can be adjusted, for example, by storing the optical laminate in an environment adjusted to the above temperature and relative humidity ranges for 10 minutes to 3 hours, or by heat-treating it at 30° C. to 90° C.

[0131] Methods for checking whether the moisture content of a polarizing element or optical laminate is within a range from the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% to the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48% include storing the polarizing element or optical laminate for a certain period of time in an environment adjusted to the temperature and relative humidity ranges and checking that there is no change in mass, or calculating in advance the equilibrium moisture content of the polarizing element or optical laminate in an environment adjusted to the temperature and relative humidity ranges and comparing the moisture content of the polarizing element or optical laminate with the pre-calculated equilibrium moisture content. If there is no change in mass after storing the polarizing element or optical laminate for a certain period of time, it can be assumed that the moisture content has reached equilibrium in the storage environment. [Example]

[0132] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, parts and % representing the content or amount used are by mass unless otherwise specified. In the following examples, the physical properties were measured by the following methods.

[0133] (1) Film thickness measurement method Measurements were made using a digital micrometer, MH-15M, manufactured by Nikon Corporation.

[0134] (2) Measurement method of phase difference value The measurement was carried out using a phase difference measuring device KOBRA-WPR (manufactured by Oji Scientific Instruments Co., Ltd.).

[0135] (3) Measurement method of photoelastic coefficient Using a phase difference measuring device KOBRA-WPR (manufactured by Oji Scientific Instruments Co., Ltd.), the phase difference value (23°C / wavelength 550 nm) at the center of the sample was measured while clamping both ends of the sample (size 1.5 cm x 6 cm) and applying stress (0.5 N to 8 N), and the phase difference value was calculated from the slope of the function of stress and phase difference value.

[0136] (4) Luminance measurement method: Measurements were taken using a spectroradiometer SR-UL1 manufactured by Topcon Corporation, with a 2° field of view.

[0137] [Fabrication of polarizing elements] A 40 μm-thick polyvinyl alcohol film was prepared from polyvinyl alcohol with an average degree of polymerization of approximately 2,400 and a saponification degree of 99.9 mol% or greater. This polyvinyl alcohol film was uniaxially stretched approximately 5 times in a dry state and then immersed in pure water at 60°C for 1 minute while maintaining tension. The polyvinyl alcohol film was then immersed in an aqueous solution containing iodine, potassium iodide, and water in a mass ratio of 0.05 / 5 / 100 at 28°C for 60 seconds. The polyvinyl alcohol film was then immersed in an aqueous solution containing potassium iodide, boric acid, and water in a mass ratio of 8.5 / 8.5 / 100 at 72°C for 300 seconds. The polyvinyl alcohol film was then washed in pure water at 26°C for 20 seconds and then dried at 65°C. In this manner, a 15 μm-thick polarizing element was obtained in which iodine was adsorbed and aligned in the polyvinyl alcohol.

[0138] [Preparing the protective film] Protective film A (second protective film): (Preparation of hard coat layer-forming composition 1) The components shown below were mixed to prepare a composition 1 for forming a hard coat layer.

[0139] PET30 97.0 parts by mass Irgacure 907 3.0 parts by mass MEK 81.8 parts by mass

[0140] The materials used are listed below. PET30: A mixture of pentaerythritol tetraacrylate and pentaerythritol triacrylate [manufactured by Nippon Kayaku Co., Ltd.] Irgacure 907: Photopolymerization initiator [manufactured by BASF] MEK: Methyl ethyl ketone

[0141] <Preparation of hard coat film> A commercially available cellulose acylate film TD40 (manufactured by Fujifilm Corporation, width 1,340 mm, film thickness 40 μm) was unwound from a roll, and the above-mentioned hard coat layer forming composition 1 was applied to it using a die coating method using a slot die at a conveying speed of 30 m / min, and then dried at 60°C for 150 seconds. After that, under a nitrogen purge, an air-cooled metahalide lamp (manufactured by Eye Graphics Co., Ltd.) with an output of 160 W / cm and an illuminance of 400 mW / cm was used. 2 , irradiation amount 120mJ / cm 2 The coating layer (hard coat layer) was cured by irradiating it with ultraviolet light, and the hard coat film was then wound up. The thickness of the coating layer was adjusted so that the film thickness of the hard coat layer was 7 μm. In this way, protective film A was obtained.

[0142] The protective film A prepared above was immersed in a 1.5 mol / L NaOH aqueous solution (saponification solution) maintained at 55°C for 2 minutes, and then washed with water. It was then immersed in a 0.05 mol / L sulfuric acid aqueous solution at 25°C for 30 seconds, and then passed through a water washing bath under running water for 30 seconds to neutralize the film. The film was then drained three times with an air knife, after which it was allowed to dry in a drying zone at 70°C for 15 seconds and saponified.

[0143] Protective film B (first protective film): 100 parts by mass of imidized MS resin pellets (weight average molecular weight: 105,000) described in Production Example 1 of JP 2010-284840 A were dried at 100.5 kPa and 100°C for 12 hours and extruded through a T-die in a single-screw extruder at a die temperature of 270°C to form a film (thickness: 160 μm). The film was further stretched in its conveying direction in an atmosphere at 150°C to a thickness of 80 μm, and then in a direction perpendicular to the film conveying direction in an atmosphere at 150°C to obtain a 40 μm thick protective film B ((meth)acrylic resin film). The in-plane retardation value Re of protective film B at a wavelength of 550 nm was 0.5 nm, and the retardation value Rth in the thickness direction was 0.82 nm. The photoelastic coefficient of the obtained film was 2.0 × 10 -12 Pa -1 It was.

[0144] [Adhesive preparation] 50 g of a modified PVA resin containing acetoacetyl groups (Mitsubishi Chemical Corporation: Gohsenex Z-410) was dissolved in 950 g of pure water, heated at 90° C. for 2 hours, and then cooled to room temperature to obtain a PVA solution. Next, the PVA solution, maleic acid, glyoxal, and pure water were mixed together so that the concentrations of each compound were as follows, to prepare a PVA adhesive. PVA concentration 3.0% by mass Maleic acid 0.01% by mass Glyoxal 0.15% by mass

[0145] [Preparing high retardation film] Cosmoshine SRF (Super Retardation Film) (thickness: 80 μm) manufactured by Toyobo Co., Ltd. was used. The in-plane retardation value Re(550) was 8400 nm. The moisture permeability at a temperature of 40°C and a relative humidity of 90% was 10 g / m 2 ·day.

[0146] [Preparing the adhesive] Adhesive A: 15 μm thick sheet acrylic adhesive ("P-3132-15 μ" manufactured by Lintec Corporation) Adhesive B: 25 μm thick sheet-type acrylic adhesive ("P-3132" manufactured by Lintec Corporation)

[0147] [Example 1] Protective film A was attached to one surface of the polarizing element with an adhesive, and protective film B was attached to the other surface of the polarizing element with an adhesive. This was then dried at 80°C for 5 minutes to obtain polarizing plate 1. When protective film B was attached, the surface to which protective film B was attached was subjected to corona treatment.

[0148] (Measurement of equilibrium moisture content) The polarizing plate 1 obtained above was stored for 72 hours at a temperature of 20°C and relative humidity of 30%, 35%, 40%, 45%, or 50%, and the moisture content was measured using the Karl Fischer method at 66, 69, and 72 hours of storage. The moisture content did not change at 66, 69, or 72 hours of storage under any humidity condition. Therefore, the moisture content of polarizing plate 1 can be considered to be the same as the equilibrium moisture content of the storage environment. When the moisture content of the polarizing plate reaches equilibrium at a certain storage temperature, the moisture content of the polarizing elements in the polarizing plate can also be considered to have reached equilibrium at that storage temperature. Furthermore, when the moisture content of the polarizing elements in the polarizing plate reaches equilibrium under a certain storage environment, the moisture content of the polarizing plate can also be considered to have reached equilibrium under that storage environment.

[0149] The moisture content of the polarizing plate 1 obtained above immediately after drying was measured by the Karl Fischer method and compared with the above equilibrium moisture content. The moisture content of polarizing plate 1 was equivalent to the moisture content at a temperature of 20°C and a relative humidity of 30%. Polarizing plate 1 was then stored at a temperature of 20°C and a relative humidity of 30% for an additional 72 hours.

[0150] (Preparation of Polarizing Plates 2 to 5) For polarizing plate 1, the drying temperature or time was changed so that the moisture content was equivalent to the equilibrium moisture content listed in Table 1, and then the plate was stored for 72 hours at a temperature of 20°C and a relative humidity of 35%, 40%, 45%, or 50%.

[0151] Next, adhesive B was attached to the surface of protective film B of each of the obtained polarizing plates 1 to 5. When these materials were attached to each other, corona treatment was performed on the surface to be attached of each material.

[0152] The adhesive A was attached to one side of the high retardation film. When these materials were attached to each other, corona treatment was performed on the surfaces of the materials to be attached.

[0153] The surface of the protective film A of each of the polarizing plates 1 to 5 thus prepared was bonded to the adhesive surface of the high retardation film so that the angle between the absorption axis of the polarizing plate and the slow axis of the high retardation film was 45°, thereby producing optical laminates 1 to 5. When bonding these materials together, corona treatment was performed on the bonding surface of each material.

[0154] (Preparation of Polarizing Plate 6) Protective film B was attached to one side of the previously obtained polarizing element with an adhesive to prepare polarizing plate 6 having a protective film only on one side of the polarizing element. When protective film B was attached, the surface to which protective film B was attached was subjected to corona treatment.

[0155] (Measurement of equilibrium moisture content) The polarizing plate 6 obtained above was stored for 72 hours at a temperature of 20°C and relative humidity of 30%, 35%, 40%, 45%, or 50%, and the moisture content was measured using the Karl Fischer method at 66, 69, and 72 hours of storage. The moisture content did not change at 66, 69, or 72 hours of storage under any humidity condition. Therefore, the moisture content of polarizing plate 6 can be considered to be the same as the equilibrium moisture content of the storage environment. When the moisture content of the polarizing plate reaches equilibrium at a certain storage temperature, the moisture content of the polarizing elements in the polarizing plate can also be considered to have reached equilibrium at that storage temperature. Furthermore, when the moisture content of the polarizing elements in the polarizing plate reaches equilibrium under a certain storage environment, the moisture content of the polarizing plate can also be considered to have reached equilibrium under that storage environment.

[0156] The moisture content of the polarizing plate 6 obtained above immediately after drying was measured by the Karl Fischer method and compared with the above equilibrium moisture content. The moisture content of polarizing plate 6 was equivalent to the moisture content at a temperature of 20°C and a relative humidity of 30%. Polarizing plate 6 was then stored at a temperature of 20°C and a relative humidity of 30% for 72 hours.

[0157] (Preparation of polarizing plates 7 to 10) For polarizing plate 6, the drying temperature or time was changed so that the moisture content was equivalent to the equilibrium moisture content listed in Table 1, and then the plate was stored for 72 hours at a temperature of 20°C and a relative humidity of 35%, 40%, 45%, or 50%.

[0158] Next, adhesive B was attached to the surface of protective film B of each of the obtained polarizing plates 6 to 10. When these materials were attached to each other, corona treatment was performed on the surface to be attached of each material.

[0159] The adhesive A was attached to one side of the high retardation film. When these materials were attached to each other, corona treatment was performed on the surfaces of the materials to be attached.

[0160] The polarizing element surfaces (the surfaces to which protective film B was not attached) of the polarizing plates 6 to 10 thus prepared were attached to the adhesive surfaces of the high retardation films so that the angle between the absorption axis of the polarizing plate and the slow axis of the high retardation film was 45°, thereby producing optical laminates 6 to 10. When these materials were attached to each other, corona treatment was performed on the attachment surfaces of the materials.

[0161] The moisture content of the obtained optical laminate was adjusted by storing it for 72 hours under the same conditions as those for storing the polarizing plate used to construct it, so that the moisture content of the optical laminate was equivalent to that of the polarizing plate used to construct it. By storing the optical laminate for 72 hours, it can be assumed that the moisture content has reached equilibrium in the storage environment, and the moisture content of the polarizing plate and polarizing element in the optical laminate can also be assumed to have reached equilibrium in the storage environment. Furthermore, when the moisture content of the polarizing plate or polarizing element in the optical laminate reaches equilibrium in a certain storage environment, the moisture content of the optical laminate can also be assumed to have reached equilibrium in the storage environment.

[0162] (Evaluation of black luminance change) (Preparation of Evaluation Sample 1A) A piece of alkali-free glass measuring 300 mm × 300 mm and 0.7 mm thick was prepared. Optical laminate 1 was cut to a size of 200 mm × 200 mm and attached to one side of the alkali-free glass via adhesive B. Polarizing plate 1 with adhesive B (without a high retardation film attached) was cut to a size of 200 mm × 200 mm and attached to the other side of the alkali-free glass via adhesive B so that the absorption axes of the polarizing plates were in a crossed Nicol position, thereby producing evaluation sample 1.

[0163] (Preparation of evaluation samples 2A to 10A) Evaluation Samples 2A to 10A were produced in the same manner as in the production of Evaluation Sample 1, except that Optical Laminate 1 was replaced with Optical Laminates 2 to 10, respectively.

[0164] The side of the evaluation samples 1A to 10A to which the adhesive B-attached polarizing plate 1 (without a high retardation film) was attached was set to 20,000 cd / m 2 The sample was placed on the irradiated surface of a white backlight module with a brightness of 1000 uF, and the brightness was measured from the optical laminate side (high retardation film) side (black brightness 1). The evaluation sample was stored in a heated environment at 95°C for 240 hours, then cooled to room temperature, and the brightness was measured again (black brightness 2). The rate of change (%) of black brightness 2 relative to black brightness 1 was calculated and taken as the black brightness change. As a result, the amount of change in black brightness for all evaluation samples was +1%.

[0165] (Evaluation of transmittance change) The optical laminates 1 to 10 were each cut into a size of 50 mm x 100 mm. The release film was peeled off and the exposed pressure-sensitive adhesive layer B was attached to alkali-free glass (trade name "EAGLE XG", manufactured by Corning Incorporated) to prepare evaluation samples 1B to 10B. These evaluation samples were then heated at a temperature of 50°C and a pressure of 5 kgf / cm. 2The samples were autoclaved for 1 hour at a pressure of 490.3 kPa. After leaving the samples in an environment at 23°C and 55% relative humidity for 24 hours, the transmittance was measured (initial value). The evaluation samples were then stored in a heated environment at 95°C, and the transmittance was measured after 120 hours and every 240 hours from 240 to 960 hours. Evaluation was performed according to the following criteria, based on the time at which the transmittance had decreased by 5% or more from the initial value. The results are shown in Table 1. Similar results were obtained even when alkali-free glass was further attached to the high retardation film side of the evaluation samples via an adhesive. A: The decrease in transmittance after 960 hours is less than 5% B: The decrease in transmittance after 720 hours or 960 hours is 5% or more. C: The decrease in transmittance after 480 hours is 5% or more. D: The transmittance decreases by 5% or more after 240 hours. E: The transmittance decreases by 5% or more after 120 hours.

[0166] [Table 1] [Explanation of symbols]

[0167] 10, 20, 30, 40 Optical laminate, 11, 21, 31, 41 Protective film, 12, 22, 32, 42 Polarizing element, 13, 23, 33, 43 High retardation film, 34, 44 Transparent member, 35, 36 Bonding layer, 37 Touch panel, 45 Second adhesive layer, 46 First adhesive layer, 47 Image display cell, 100 Image display device

Claims

1. An optical laminate having a first protective film, a polarizing element, and a high retardation film in this order, The absolute value of the photoelastic coefficient of the first protective film at a temperature of 23° C. is 8×10 －１２ Pa －１ is as follows: the moisture content of the polarizing element is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%; The in-plane retardation value Re[550] of the high retardation film at a wavelength of 550 nm is 3,000 nm or more and 30,000 nm or less, an angle formed between the slow axis of the high retardation film and the absorption axis of the polarizing element of 40° or more and 50° or less;

2. An optical laminate having a first protective film, a polarizing element, and a high retardation film in this order, The moisture content of the optical laminate is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%, The absolute value of the photoelastic coefficient of the first protective film at a temperature of 23° C. is 8×10 －１２ Pa －１ is as follows: The high retardation film has an in-plane retardation value Re[550] at a wavelength of 550 nm of 3,000 nm or more and 30,000 nm or less, an angle formed between the slow axis of the high retardation film and the absorption axis of the polarizing element of 40° or more and 50° or less;

3. 3. The optical laminate according to claim 1, wherein the first protective film comprises at least one selected from the group consisting of cyclic polyolefin-based resins, (meth)acrylic-based resins, polystyrene-based resins, and maleimide-based resins.

4. The optical laminate according to any one of claims 1 to 3, wherein the first protective film has an in-plane retardation value Re[550] of 10 nm or less at a wavelength of 550 nm.

5. The optical laminate according to any one of claims 1 to 4, wherein the high retardation film has a thickness of 200 µm or less.

6. The optical laminate is used in an image display device, 6. The optical laminate according to claim 1, wherein in the image display device, a layer other than an air layer is provided on both sides of the optical laminate in contact with the both sides.

7. An image display device comprising: an image display cell; a first pressure-sensitive adhesive layer laminated on a viewing-side surface of the image display cell; and the optical laminate according to any one of claims 1 to 6 laminated on the viewing-side surface of the first pressure-sensitive adhesive layer.

8. The image display device according to claim 7 , further comprising: a second pressure-sensitive adhesive layer laminated on the viewer-side surface of the optical laminate; and a transparent member laminated on the viewer-side surface of the second pressure-sensitive adhesive layer.

9. 9. The image display device according to claim 8, wherein the transparent member is a glass plate or a transparent resin plate.

10. The image display device according to claim 8 , wherein the transparent member is a touch panel.

11. A method for producing the optical laminate according to claim 1, A method for producing an optical laminate, comprising a moisture content adjusting step of adjusting the moisture content of the polarizing element so that the moisture content is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.

12. The method for producing the optical laminate according to claim 2, A method for producing an optical laminate, comprising a moisture content adjusting step of adjusting the moisture content of the optical laminate so that the moisture content is equal to or greater than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 20% and equal to or less than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 48%.

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