CN115113317A

CN115113317A - Optical laminate, method for producing same, and image display device

Info

Publication number: CN115113317A
Application number: CN202210253369.8A
Authority: CN
Inventors: 萩原慎也; 太田裕史
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2021-03-18
Filing date: 2022-03-15
Publication date: 2022-09-27
Also published as: KR20220130604A; TW202243895A

Abstract

The invention provides an optical laminate excellent in high-temperature durability, an image display device provided with the optical laminate, and a method for manufacturing the optical laminate. The optical laminate of the present invention comprises a 1 st protective film, a polarizing element, and a high retardation film in this order, wherein the absolute value of the photoelastic coefficient at 23 ℃ of the 1 st protective film is 8X 10 ^‑ ¹² Pa ^‑1 The water content of the polarizing element is not less than 20% at 20 ℃ relative humidity and not more than 48% at 20 ℃ relative humidity, and the in-plane retardation value Re [550] at a wavelength of 550nm of the high retardation film]Is 3000nm or more and 30000nm or less, and an angle formed by the slow axis of the high retardation film and the absorption axis of the polarizing element is 40 ° or more and 50 ° or less.

Description

Optical laminate, method for producing same, and image display device

Technical Field

The present invention relates to an optical laminate, a method for producing the same, and an image display device.

Background

In an in-vehicle image display device, there is described a method of improving visibility in which a white light emitting diode is used as a backlight of a liquid crystal display device, and a polymer film having a retardation of 3000 to 30000nm is disposed on an observer side of a polarizing plate so that an angle formed by an absorption axis of the polarizing plate and a slow axis of the polymer film is approximately 45 ° (patent document 1).

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 2011-81219

Disclosure of Invention

Problems to be solved by the invention

Image display devices used in vehicle-mounted applications are often exposed to high-temperature environments, and optical laminates used in image display devices are also required to have high-temperature durability.

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 manufacturing the optical laminate.

Means for solving the problems

The invention provides an optical laminate, an image display device and a method for manufacturing the optical laminate.

[1] An optical laminate comprising a 1 st protective film, a polarizing element, and a high retardation film in this order,

the absolute value of the photoelastic coefficient of the 1 st protective film at the temperature of 23 ℃ is 8 multiplied by 10 ^-12 Pa ^-1 In the following, the following description is given,

the water content of the polarizing element is more than the equilibrium water content of 20% relative humidity at the temperature of 20 ℃ and less than the equilibrium water content of 48% relative humidity at the temperature of 20 ℃,

an in-plane retardation value Re 550 at a wavelength of 550nm of the high retardation film is 3000nm or more and 30000nm or less,

an angle formed by the slow axis of the high retardation film and the absorption axis of the polarizer is 40 ° or more and 50 ° or less.

[2] An optical laminate comprising a 1 st protective film, a polarizing element, and a high retardation film in this order,

the water content of the optical laminate is not less than 20% of equilibrium water content at a temperature of 20 ℃ and a relative humidity of not more than 48%,

[3] The optical laminate according to [1] or [2], wherein the 1 st protective film comprises at least one selected from the group consisting of a cyclic polyolefin resin, a (meth) acrylic resin, a polystyrene resin, and a maleimide resin.

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

[5] The optical laminate according to any one of [1] to [4], wherein the thickness of the high retardation film is 200 μm or less.

[6] The optical laminate according to any one of [1] to [5], wherein the optical laminate is used for an image display device,

in the image display device, a layer other than an air layer is provided in contact with both surfaces of the optical layered body.

[7] An image display device comprising an image display unit, a 1 st adhesive layer laminated on a visible surface of the image display unit, and an optical laminate according to any one of [1] to [6] laminated on a visible surface of the 1 st adhesive layer.

[8] The image display device according to [7], further comprising a 2 nd adhesive layer laminated on a visible-side surface of the optical laminate, and a transparent member laminated on a visible-side surface of the 2 nd 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 an optical laminate according to [1],

the manufacturing method includes a water content adjustment step of adjusting the water content so that the water content of the polarizing element is equal to or higher than an equilibrium water content at a temperature of 20 ℃ and a relative humidity of 20% and equal to or lower than an equilibrium water content at a temperature of 20 ℃ and a relative humidity of 48%.

[12] A method for producing an optical laminate according to [2],

the manufacturing method includes a moisture content adjustment step of adjusting the moisture content so that the moisture content of the optical laminate is not less than an equilibrium moisture content at a temperature of 20 ℃ and a relative humidity of 20%, and not more than an equilibrium moisture content at a temperature of 20 ℃ and a relative humidity of 48%.

Effects of the invention

According to the present invention, an optical laminate having excellent high-temperature durability, an image display device including the optical laminate, and a method for producing the optical laminate can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of the layer structure of the optical laminate.

Fig. 2 is a schematic cross-sectional view showing another example of the layer structure of the optical laminate.

Fig. 3 is a schematic cross-sectional view showing still another example of the layer structure of the optical laminate.

Fig. 4 is a schematic cross-sectional view showing an example of the layer structure of the image display device.

Description of the reference numerals

10. 20, 30, 40 optical laminated body, 11, 21, 31, 41 protective film, 12, 22, 32, 42 polarizing element, 13, 23, 33, 43 high phase difference film, 34, 44 transparent member, 35, 36 laminating layer, 37 touch panel, 45 2 nd adhesive layer, 46 st adhesive layer, 47 image display unit, 100 image display device.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments below. In all the drawings below, the components are appropriately scaled and displayed in order to facilitate understanding of the components, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

< optical laminate >

[ first mode ]

The optical laminate of the first embodiment is described below with reference to the drawings. The optical laminate 10 shown in FIG. 1 comprises a 1 st protective film 11, a polarizing element 12, and a high retardation film 13 in this order, and the absolute value of the photoelastic coefficient at 23 ℃ of the 1 st protective film 11 is 8X 10 ^-12 Pa ^-1 Hereinafter, the water content of the polarizer 12 is not less than the equilibrium water content at a relative humidity of 20% at a temperature of 20 ℃ and not more than the equilibrium water content at a relative humidity of 48% at a temperature of 20 ℃ and the in-plane retardation Re [550] at a wavelength of 550nm of the high retardation film 13]Is 3000nm or more and 30000nm or less, and the angle formed by the slow axis of the high retardation film 13 and the absorption axis of the polarizer 12 is 40 ° or more and 50 ° or less.

The optical stack 10 may further include other layers than the above-described layers. Examples of the other layer include a 2 nd protective film, a bonding layer, and the like.

[1 st protective film ]

The 1 st protective film 11 is a layer for protecting the polarizing element 12, particularly protecting the surface of the polarizing element 12. As shown in fig. 1, the 1 st protective film 11 is disposed on the opposite side of the polarizing element 12 from the high retardation film 13 side. The 1 st protective film 11 may be laminated on the polarizer layer 12 only via a lamination layer, or directly.

The absolute value of photoelastic coefficient of the 1 st protective film 11 at 23 ℃ is 8X 10 ^-12 Pa ^-1 The following. By using the 1 st protective film 11 having a small photoelastic coefficient, the retardation value exhibited by the deformation of the 1 st protective film 11 caused by the shrinkage stress of the high retardation film 13 when the film is placed in a high-temperature environment changesIs small. As a result, visibility tends to be improved even after the film is left in a high-temperature environment.

The 1 st protective film 11 is not particularly limited, and may have a photoelastic coefficient of 8 × 10 in absolute value ^-12 Pa ^-1 The following light-transmitting (preferably optically transparent) film containing a thermoplastic resin may be, for example, a polyolefin resin such as a chain polyolefin resin (e.g., a polypropylene resin) or a cyclic polyolefin resin (e.g., a norbornene resin); cellulose resins such as triacetyl cellulose and diacetyl cellulose; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; a polycarbonate-based resin; (meth) acrylic resins such as methyl methacrylate resins; polystyrene resin; a polyvinyl chloride resin; acrylonitrile-butadiene-styrene resins; acrylonitrile-styrene resins; polyvinyl acetate resin; a polyvinylidene chloride resin; a polyamide resin; a polyacetal resin; modified polyphenylene ether resin; a polysulfone-based resin; a polyether sulfone-based resin; a polyarylate-based resin; a polyamide imide resin; a polyimide-based resin; a film of maleimide resin or the like.

The 1 st protective film 11 is particularly preferably a film having a small photoelastic coefficient. That is, it is preferable to use a film containing at least one selected from the group consisting of a cyclic polyolefin resin, a (meth) acrylic resin, a polystyrene resin, and a maleimide resin.

The photoelastic coefficient of the 1 st protective film 11 at 23 ℃ is preferably 0.05X 10 ^-12 Pa ^-1 Above and 8.0X 10 ^- ¹² Pa ^-1 Hereinafter, more preferably 0.1 × 10 ^-12 Pa ^-1 Above and 5.0X 10 ^-12 Pa ^-1 Hereinafter, more preferably 0.2 × 10 ^-12 Pa ^-1 Above and 3.0X 10 ^-12 Pa ^-1 The following. The photoelastic coefficient is a value measured by the method described in the examples described below.

The in-plane retardation Re 550 of the 1 st protective film 11 is preferably adjusted to 10nm or less or 50 to 300nm as long as it is within the above-mentioned range of photoelastic coefficient. It is particularly preferable to form a film having an in-plane retardation value of 10nm or less, whereby higher effects can be obtained. This is presumably because the film having a retardation has a phase difference value that changes as the stress in the oblique direction of the high retardation film is relaxed, and the optical axis thereof also changes, thereby increasing light leakage at the time of black display. When the retardation film is applied to a liquid crystal display device or the like as an optical compensation film, it is also a useful design method to arrange the optical compensation film in another polarizing plate used in a pair.

The in-plane retardation Re [ lambda ] in the present specification means an in-plane retardation of the film at 23 ℃ and a wavelength of lambda (nm). For example, the in-plane retardation Re 550 refers to the in-plane retardation of the film at 23 ℃ and a wavelength of 550 (nm). When the film thickness is d (nm), Re λ is obtained using (nx-ny) × d. The thickness direction retardation value Rth [ λ ] is a retardation value in the thickness direction of the film at 23 ℃ and a wavelength λ (nm). When the film thickness is d (nm), Rth [ λ ] is obtained by using Rth [ λ ] (nx + ny)/2-nz) × d. "nx" is a refractive index in a direction in which the in-plane refractive index is maximized (i.e., the slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis in the plane, and "nz" is a refractive index in the thickness direction.

The cyclic polyolefin resin is a general term for resins polymerized by using a cyclic olefin as a polymerization unit, and examples thereof include those described in Japanese patent application laid-open Nos. H1-240517, H3-14882, and H3-122137. Specific examples of the cyclic polyolefin resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins with linear olefins such as ethylene and propylene (typically random copolymers), graft polymers obtained by modifying these with unsaturated carboxylic acids and derivatives thereof, and hydrogenated products of these. Among these, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferably used.

The method for producing the 1 st protective film 11 from the cycloolefin-based resin is not particularly limited as long as a method corresponding to the resin is appropriately selected. For example, a solvent casting method (Japanese: solvent キャスト method) in which a resin dissolved in a solvent is cast onto a metal belt or drum and the solvent is dried and removed to obtain a film; and a melt extrusion method in which a resin is heated to a temperature equal to or higher than its melting temperature, kneaded, extruded from a die, and cooled by a cooling drum to obtain a film. Among them, the melt extrusion method is preferably used from the viewpoint of productivity.

The cycloolefin resin film has an in-plane retardation value Re 550 at a wavelength of 550nm of preferably 10nm or less, more preferably 7nm or less, further preferably 5nm or less, particularly preferably 3nm or less, and most preferably 1nm or less. The thickness-direction retardation value Rth [550] of the cycloolefin-based resin film at a wavelength of 550nm is preferably 15nm or less, more preferably 10nm or less, further preferably 5nm or less, particularly preferably 3nm or less, and most preferably 1nm or less.

Next, a method of controlling such that the phase difference value of the cycloolefin resin film satisfies the above-described condition will be described. In order to make the in-plane retardation value 10nm or less, it is necessary to reduce the strain remaining in the in-plane direction during stretching as much as possible, and in order to make the thickness direction retardation value equal to or less than the value specified in the present invention, it is necessary to reduce the strain remaining in the thickness direction as much as possible.

For example, in the solvent casting method, a method of relieving a residual tensile strain in an in-plane direction and a residual shrinkage strain in a thickness direction, which are generated when the casting resin solution is dried, by heat treatment, or the like can be employed. In addition, in the melt extrusion method, in order to prevent the resin film from being stretched during the period from extrusion from the die to cooling, a method of reducing the distance from the die to the cooling drum as much as possible and controlling the extrusion amount and the rotation speed of the cooling drum so as not to stretch the film, or the like may be employed. Further, a method of relieving the strain remaining in the film obtained in the same manner as the melt extrusion method may be employed by heat treatment.

In addition, a retardation film having a function as an optical compensation film of a liquid crystal display device in a range satisfying the photoelastic coefficient of the present invention can be produced. Such a retardation film can be produced by stretching the cycloolefin-based resin film to impart an in-plane retardation value. The stretching may be performed by known longitudinal uniaxial stretching, tenter transverse uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, or the like, as long as the stretching is performed so as to obtain a desired phase difference value.

For example, in an in-plane switching mode liquid crystal display device, a retardation film whose in-plane retardation value is adjusted to 50nm or more and 300nm or less is preferably used. Specifically, a retardation film described in japanese patent application laid-open No. 2010-20287, a retardation film described in japanese patent 3880996, or the like can be used.

The thickness of the cycloolefin 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 be lowered. If the thickness is more than 200. mu.m, the transparency may be lowered.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of the (meth) acrylic resin include, for example, poly (meth) acrylates such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylate copolymers; methyl methacrylate-acrylate- (meth) acrylic acid copolymers; methyl (meth) acrylate-styrene copolymers (MS resins and the like); copolymers of methyl methacrylate and a compound having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylic acid norbornyl ester copolymer, etc.). Preferably, a poly (meth) acrylic acid C such as poly (methyl (meth) acrylate) is used _1-6 The polymer containing an alkyl ester as a main component is preferably a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by mass, preferably 70 to 100% by mass).

The (meth) acrylic resin film preferably has an in-plane retardation value Re 550 at a wavelength of 550nm of 10nm or less, more preferably 7nm or less, still more preferably 5nm or less, particularly preferably 3nm or less, and most preferably 1nm or less. The thickness direction retardation value Rth [550] of the (meth) acrylic resin film at a wavelength of 550nm is preferably 15nm or less, more preferably 10nm or less, still more preferably 5nm or less, particularly preferably 3nm or less, and most preferably 1nm or less. In order to set the in-plane retardation value and the thickness direction retardation value in such ranges, for example, a (meth) acrylic resin having a glutarimide structure described later can be used.

The (meth) acrylic resin may further have other structural units. Examples of the other structural units include structural units forming a lactone ring, polycarbonate, polyvinyl alcohol, cellulose acetate, polyester, polyarylate, polyimide, polyolefin, and the like, and structural units represented by the general formula (1) described later. Examples of the structural unit exhibiting negative birefringence include structural units derived from styrene monomers, maleimide monomers, and the like, structural units of polymethyl methacrylate, structural units represented by the general formula (3) described later, and the like.

As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure or a glutarimide structure is preferably used. The (meth) acrylic resin having a lactone ring structure or a glutarimide structure is excellent in heat resistance. More preferably a (meth) acrylic resin having a glutarimide structure. When a (meth) acrylic resin having a glutarimide structure is used, a (meth) acrylic resin film having low moisture permeability and small retardation and ultraviolet transmittance can be obtained as described above. (meth) acrylic resins having a glutarimide structure (hereinafter also referred to as glutarimide resins) are described in, for example, Japanese patent application laid-open Nos. 2006-. These descriptions are incorporated herein by reference.

The glutarimide resin preferably 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) acrylate unit).

[ solution 1]

In the formula (1), R ¹ And R ² Each independently hydrogen or C1-C8 alkyl, R ³ Is hydrogen, alkyl group having 1 to 18 carbon atoms, cycloalkyl group having 3 to 12 carbon atoms, or a substituent comprising aromatic ring having 5 to 15 carbon atoms. In the formula (2), R ⁴ And R ⁵ Each independently hydrogen or C1-C8 alkyl, R ⁶ Is hydrogen, alkyl group having 1 to 18 carbon atoms, cycloalkyl group having 3 to 12 carbon atoms, or a substituent comprising aromatic ring having 5 to 15 carbon atoms.

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.

[ solution 2]

In the formula (3), R ⁷ Is hydrogen or C1-8 alkyl, R ⁸ Is an aryl group having 6 to 10 carbon atoms.

In the above general formula (1), R is preferably ¹ And R ² Each independently is hydrogen or methyl, R ³ Is hydrogen, methyl, butyl, or cyclohexyl, more preferably R ¹ Is methyl, R ² Is hydrogen, R ³ Is methyl.

The above-mentioned glutarimide resin may contain only a single type of glutarimide unit, or may contain R in the above-mentioned general formula (1) ¹ 、R ² And R ³ A plurality of different categories.

The glutarimide unit can be formed by imidizing the (meth) acrylate ester unit described by the above general formula (2). Alternatively, the glutarimide unit may be prepared by reacting 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; and α, β -ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, itaconic anhydride, crotonic acid, fumaric acid, and citraconic acid.

In the above general formula (2), R is preferably ⁴ And R ⁵ Each independently is hydrogen or methyl, R ⁶ Is hydrogen or methyl, more preferably R ⁴ Is hydrogen, R ⁵ Is methyl, R ⁶ Is methyl.

The glutarimide resin may contain only a single type as the (meth) acrylate ester unit, or may contain R in the general formula (2) ⁴ 、R ⁵ And R ⁶ A plurality of different categories.

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

The above glutarimide resin may contain only a single type of aromatic vinyl unit, or may contain R ⁷ And R ⁸ A plurality of different categories.

The content of the above glutarimide unit in the above glutarimide resin is preferably made to depend on R, for example ³ The structure of (a) and (b) varies. The content of the glutarimide unit is preferably 1 to 80% by mass, more preferably 1 to 70% by mass, still more preferably 1 to 60% by mass, and particularly preferably 1 to 50% by mass, based on the total structural units of the glutarimide resin. When the content of the glutarimide unit is in such a range, a (meth) acrylic resin film having a low retardation and excellent heat resistance can be obtained.

The content of the aromatic vinyl unit in the glutarimide resin may be appropriately set according to the purpose and the desired characteristics. The content of the aromatic vinyl unit may be 0 depending on the use. When the aromatic vinyl unit is contained, the content thereof is preferably 10 to 80% by mass, more preferably 20 to 80% by mass, further preferably 20 to 60% by mass, and particularly preferably 20 to 50% by mass, based on the glutarimide unit of the glutarimide resin. When the content of the aromatic vinyl unit is in such a range, a (meth) acrylic resin film having a low phase difference and excellent heat resistance and mechanical strength can be obtained.

In the above glutarimide resin, if necessary, other structural units than the glutarimide unit, (meth) acrylate unit, and aromatic vinyl unit may be further copolymerized. Examples of the other structural units include structural units derived from nitrile monomers such as acrylonitrile and methacrylonitrile, and maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide and N-cyclohexylmaleimide. These other structural units may be directly copolymerized or graft-copolymerized in the above glutarimide resin.

The (meth) acrylic resin film may contain any appropriate additive according to the purpose. Examples of the additives include antioxidants such as hindered phenol type, phosphorus type, and sulfur type; stabilizers such as light-resistant stabilizers, ultraviolet absorbers, weather-resistant stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers; a near infrared ray absorber; 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 fillers, inorganic fillers; a resin modifier; a plasticizer; a lubricant; a retardation reducing agent, etc. The kind, combination, content and the like of the additives to be contained can be appropriately set according to the purpose and the desired characteristics.

The method for producing the (meth) acrylic resin film is not particularly limited, and for example, the (meth) acrylic resin, the ultraviolet absorber, and other polymers and additives used as needed may be sufficiently mixed by any appropriate mixing method to prepare a thermoplastic resin composition in advance, and then the thermoplastic resin composition may be subjected to film forming. Alternatively, the (meth) acrylic resin, the ultraviolet absorber, and other polymers, additives, and the like used as needed may be separately prepared into separate solutions, and then mixed to prepare a uniform mixed solution, followed by film formation.

In the production of the thermoplastic resin composition, the film raw material is premixed by an arbitrary appropriate mixer such as a universal mixer, and the resulting mixture is extruded and kneaded. In this case, the mixer used for extrusion kneading is not particularly limited, and any appropriate mixer such as a single-screw extruder, a twin-screw extruder, and the like, and a pressure kneader can be used.

Examples of the film forming method include any appropriate film forming method such as a solution casting method (solution casting method), a melt extrusion method, a rolling method, and a compression molding method. Melt extrusion is preferred. Since the melt extrusion method does not use a solvent, the production cost and the burden on the global environment and the operation environment due to the solvent can be reduced.

Examples of the melt extrusion method include a T-die method and a blow molding method. The molding temperature is preferably 150 to 350 ℃, and more preferably 200 to 300 ℃.

In the case of film formation by the T-die method, a T-die may be attached to the tip of a known single-screw extruder or twin-screw extruder, and the film extruded in a film form may be wound to obtain a roll-like film. In this case, the temperature of the winding roll may be appropriately adjusted to apply the stretching in the extrusion direction, thereby performing the uniaxial stretching. Further, simultaneous biaxial stretching, sequential biaxial stretching, or the like may be performed by stretching the film in a direction perpendicular to the extrusion direction.

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 the stretched film, it may be either a uniaxially stretched film or a biaxially stretched film. In the case of the biaxially stretched film, the biaxially stretched film may be either a simultaneously biaxially stretched film or a sequentially biaxially stretched film.

The stretching temperature is preferably in the vicinity of the glass transition temperature of the thermoplastic resin composition as a film raw material, more specifically preferably in the range of (glass transition temperature-30 ℃) to (glass transition temperature +30 ℃), still more preferably in the range of (glass transition temperature-20 ℃) to (glass transition temperature +20 ℃). When the stretching temperature is lower than (glass transition temperature-30 ℃), the haze of the obtained film becomes large, or the film may be torn or broken, and the predetermined stretching ratio may not be obtained. On the other hand, if the stretching temperature is higher than (glass transition temperature +30 ℃), the resulting film tends to have large thickness unevenness, or to have insufficient improvement in mechanical properties such as elongation, tear propagation strength, and flex fatigue resistance (japanese original: flex fatigue resistance ). Further, there is a tendency that troubles such as adhesion of the film to a roll are liable to occur.

The stretching ratio is preferably 1.1 to 3 times, and more preferably 1.3 to 2.5 times. When the stretch ratio is in this range, the mechanical properties of the film, such as elongation, tear propagation strength, and flex fatigue resistance, can be greatly improved. As a result, a film having small thickness unevenness, substantially zero birefringence (and thus a small retardation), and small haze can be produced.

The (meth) acrylic resin film may be subjected to a heat treatment (annealing) or the like after the stretching treatment in order to stabilize the optical isotropy and mechanical properties. The heat treatment conditions may be any appropriate conditions.

The thickness of the (meth) acrylic resin film is preferably 10 to 200. mu.m, more preferably 15 to 100. mu.m, and most preferably 15 to 65 μm. If the thickness is less than 10 μm, the strength may be reduced. If the thickness is more than 200. mu.m, the transparency may be lowered.

The 1 st protective film 11 may have functional layers such as a hard coat layer, an antiglare layer, an antireflection layer, a light diffusion layer, an antistatic layer, an antifouling layer, and a conductive layer, which will be described later, on its outer surface (a surface opposite to the polarizing element 12 side). When the 1 st protective film 11 has a hard coat layer or a functional layer, the thickness of the 1 st protective film 11 includes the thickness of the hard coat layer or the functional layer.

[ hard coating layer ]

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

When the 1 st protective film 11 has a hard coat layer, the hardness and scratch resistance of the polarizing element 12 or the 1 st protective film 11 can be easily improved. In the case where the 1 st protective film 11 is a thermoplastic resin film having a hard coat layer, for example, a thermoplastic resin film having a hard coat layer can be produced by applying and curing a composition for forming a hard coat layer on the thermoplastic resin film forming the 1 st protective film 11 to form a cured product of the composition for forming a hard coat layer, and then bonded to the polarizing element 12 via an adhesive layer. A commercially available thermoplastic resin film having a cured resin layer may be used as the 1 st protective film 11.

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 the active energy ray-curable resin include acrylic resins, silicone resins, polyester resins, urethane resins, amide resins, and epoxy resins. The hard coating may contain additives for the purpose of improving strength. The additive is not limited, and may be inorganic fine particles, organic fine particles, or a mixture thereof. The hard coat layer preferably contains an ultraviolet absorber.

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

[ polarizing element ]

As the polarizing element 12, a polarizing element in which a layer containing a polyvinyl alcohol (hereinafter also referred to as "PVA") resin (also referred to as "PVA resin layer" in the present specification) adsorbs a dichroic dye and the dichroic dye is aligned can be used. Examples of such polarizing elements include polarizing elements formed by using a PVA-based resin film, dyeing the PVA-based resin film with a dichroic dye, and uniaxially stretching; the polarizing element is formed by using a laminate film obtained by applying a coating liquid containing a PVA-based resin to a base film, dyeing the PVA-based resin layer as a coating layer of the laminate film with a dichroic dye, and uniaxially stretching the laminate film.

The polarizing element 12 is formed of a PVA-based resin obtained by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate resin may be a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of the other copolymerizable monomer include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, and unsaturated sulfonic acids.

The saponification degree of the PVA-based resin is preferably about 85 mol% or more, more preferably about 90 mol% or more, and still more preferably about 99 mol% to 100 mol%. The PVA-based resin has a polymerization degree of 1000 to 10000, preferably 1500 to 5000. The PVA-based resin may be modified, and examples thereof include polyvinyl formal, polyvinyl acetal, and polyvinyl butyral modified with aldehydes.

The thickness of the polarizer 12 is preferably 5 μm to 50 μm, more preferably 5 μm to 40 μm, and still more preferably 8 μm to 30 μm. By setting the thickness of the polarizer 12 to 50 μm or less, the influence of polyene formation of the PVA-based resin on the degradation of the optical properties in a high-temperature environment can be suppressed, and by setting the thickness of the polarizer 12 to 5 μm or more, the configuration for realizing desired optical properties can be easily realized.

The water content of the polarizer 12 is not less than the equilibrium water content at a temperature of 20 ℃ and a relative humidity of 20%, and not more than the equilibrium water content at a temperature of 20 ℃ and a relative humidity of 48%. Preferably, the water content is at least the equilibrium water content at a temperature of 20 ℃ and a relative humidity of 30%, and is at most the equilibrium water content at a temperature of 20 ℃ and a relative humidity of 45%. More preferably, the equilibrium moisture content is not more than 42% at a temperature of 20 ℃ relative humidity, still more preferably not more than 40% at a temperature of 20 ℃ relative humidity, and most preferably not more than 38% at a temperature of 20 ℃ relative humidity. If the equilibrium moisture content is less than 20% at a temperature of 20 ℃ and a relative humidity of 20%, the handling property of the polarizing element 12 is lowered, and the polarizing element is likely to be broken. By setting the equilibrium water content at a temperature of 20 ℃ and a relative humidity of 48% or less, an optical laminate excellent in high-temperature durability can be provided. The water content of the polarizer 12 is the water content of the polarizer in the polarizing plate.

The method for producing the polarizing element 12 is not particularly limited, and a typical method is a method in which a polyvinyl alcohol resin film wound in a roll form in advance is fed out and then stretched, dyed, crosslinked, or the like (hereinafter referred to as "production method 1"), and a method including a step of applying a coating liquid containing a polyvinyl alcohol resin onto a base film to form a polyvinyl alcohol resin layer as a coating layer and then stretching the resulting laminate (hereinafter referred to as "production method 2").

The production method 1 can be produced through a step of uniaxially stretching a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye such as iodine by dyeing the polyvinyl alcohol resin film with the dichroic dye, a step of treating the polyvinyl alcohol resin film adsorbed with the dichroic dye with an aqueous boric acid solution, and a step of washing with water after the treatment with the aqueous boric acid solution.

The swelling step is a treatment step of immersing the polyvinyl alcohol resin film in a swelling bath, and can remove stains, blocking agents (ブロッキング) and the like on the surface of the polyvinyl alcohol resin film, and can suppress uneven dyeing by swelling the polyvinyl alcohol resin film. The swelling bath generally uses a medium containing water as a main component, such as water, distilled water, or pure water. The swelling bath may be added with a surfactant, an alcohol, or the like as appropriate according to a conventional method.

The temperature of the swelling bath is preferably 10 to 60 ℃, more preferably 15 to 45 ℃, and further preferably 18 to 30 ℃. The immersion time in the swelling bath is not generally determined since the degree of swelling of the polyvinyl alcohol resin film is affected by the temperature of the swelling bath, but is preferably 5 to 300 seconds, more preferably 10 to 200 seconds, and still more preferably 20 to 100 seconds. The swelling step may be performed only 1 time, or may be performed a plurality of times as needed.

The dyeing step is a treatment step of immersing the polyvinyl alcohol resin film in a dyeing bath (iodine solution), and may be performed by adsorbing a dichroic substance such as iodine or a dichroic dye to the polyvinyl alcohol resin film and aligning the dichroic substance. The iodine solution is preferably an aqueous iodine solution containing iodine and an iodide as a dissolution aid. The iodide includes potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. Among them, potassium iodide is preferable from the viewpoint of controlling the content of potassium in the polarizing element.

The concentration of iodine in the dyeing bath is preferably 0.01 to 1% by mass, more preferably 0.02 to 0.5% by mass. The concentration of the iodide in the dyeing bath is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, and still more preferably 0.1 to 3% by mass.

The temperature of the dyeing bath is preferably 10-50 ℃, more preferably 15-45 ℃, and further preferably 18-30 ℃. The immersion time in the dyeing bath is not generally determined because the degree of dyeing of the polyvinyl alcohol resin film is affected by the temperature of the dyeing bath, but is preferably 10 to 300 seconds, and more preferably 20 to 240 seconds. The dyeing step may be performed only 1 time, or may be performed a plurality of times as needed.

The crosslinking step is a treatment step of immersing the polyvinyl alcohol resin film dyed in the dyeing step in a treatment bath (crosslinking bath) containing a boron compound, and the polyvinyl alcohol resin film is crosslinked with the boron compound, so that iodine molecules or dye molecules can be adsorbed to the crosslinked structure. Examples of the boron compound include boric acid, borate, and borax. The crosslinking bath is usually an aqueous solution, and may be, for example, a mixed solution of an organic solvent having miscibility with water and water. In addition, from the viewpoint of controlling the content of potassium in the polarizing element, the crosslinking bath preferably contains potassium iodide.

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

The temperature of the crosslinking bath is preferably 20 to 70 ℃, and more preferably 30 to 60 ℃. The immersion time in the crosslinking bath is not generally determined because the degree of crosslinking of the polyvinyl alcohol resin film is affected by the temperature of the crosslinking bath, but is preferably 5 to 300 seconds, and more preferably 10 to 200 seconds. The crosslinking step may be performed only 1 time, or may be performed a plurality of times as needed.

The stretching step is a treatment step of stretching the polyvinyl alcohol resin film to a predetermined magnification at least in one direction. In general, a polyvinyl alcohol resin film is uniaxially stretched in the conveying direction (longitudinal direction). The method of stretching is not particularly limited, and either wet stretching or dry stretching may be employed. The stretching step may be performed only 1 time, or may be performed a plurality of times as needed. The stretching step may be performed at any stage in the production of the polarizing element.

In the wet stretching method, a solvent such as water or a mixed solution of an organic solvent miscible with water and water is usually used as the treatment bath (stretching bath). From the viewpoint of controlling the content of potassium in the polarizing element, the stretching bath preferably contains potassium iodide. When potassium iodide is used in the stretching bath, the concentration of potassium iodide in the stretching bath is preferably 1 to 15% by mass, more preferably 2 to 10% by mass, and still more preferably 3 to 6% by mass. In addition, the treatment bath (stretching bath) may contain a boron compound from the viewpoint of suppressing film breakage during stretching, and in this case, the concentration of the boron compound in the stretching bath is preferably 1 to 15% by mass, more preferably 1.5 to 10% by mass, and further preferably 2 to 5% by mass.

The temperature of the stretching bath is preferably 25 to 80 ℃, more preferably 40 to 75 ℃, and further preferably 50 to 70 ℃. The immersion time in the stretching bath is not generally determined because the degree of stretching of the polyvinyl alcohol resin film is affected by the temperature of the stretching bath, but is preferably 10 to 800 seconds, and more preferably 30 to 500 seconds. The stretching treatment in the wet stretching method may be performed together with any 1 or more treatment steps of the swelling step, the dyeing step, the crosslinking step, and the washing step.

Examples of the dry stretching method include an inter-roll stretching method, a hot-roll stretching method, and a compression-stretching method. The dry drawing method may be performed together with the drying step.

The total draw ratio (cumulative draw ratio) to be applied to the polyvinyl alcohol resin film may be set as appropriate depending on the purpose, and is preferably 2 to 7 times, more preferably 3 to 6.8 times, and still more preferably 3.5 to 6.5 times.

The cleaning step is a treatment step of immersing the polyvinyl alcohol resin film in a cleaning bath, and can remove foreign matter remaining on the surface of the polyvinyl alcohol resin film or the like. The cleaning bath generally uses a medium containing water as a main component, such as water, distilled water, or pure water. In addition, from the viewpoint of controlling the potassium content in the polarizing element, potassium iodide is preferably used in the cleaning bath, and in this case, the concentration of potassium iodide in the cleaning bath is preferably 1 to 10 mass%, more preferably 1.5 to 4 mass%, and still more preferably 1.8 to 3.8 mass%.

The temperature of the cleaning bath is preferably 5-50 ℃, more preferably 10-40 ℃, and further preferably 15-30 ℃. The immersion time in the cleaning bath is not generally determined because the degree of cleaning of the polyvinyl alcohol resin film is affected by the temperature of the cleaning bath, but is preferably 1 to 100 seconds, more preferably 2 to 50 seconds, and still more preferably 3 to 20 seconds. The cleaning step may be performed only 1 time, or may be performed as many times as necessary.

The drying step is a step of drying the polyvinyl alcohol resin film washed in the washing step to obtain a polarizing element. The drying may be carried out by any appropriate method, and examples thereof include natural drying, air-drying, and heat-drying.

The production method 2 can be produced through a step of applying a coating liquid containing the above-mentioned polyvinyl alcohol resin to a base film, a step of uniaxially stretching the obtained laminated film, a step of preparing a polarizing element by dyeing the polyvinyl alcohol resin layer of the uniaxially stretched laminated film with a dichroic dye and adsorbing the dichroic dye, a step of treating the film having the dichroic dye adsorbed thereto with an aqueous boric acid solution, and a step of washing with water after treatment with an aqueous boric acid solution. The base material film for forming the polarizing element may also be used as a protective layer of the polarizing element. The base material film may be peeled off and removed from the polarizing element as necessary.

[ high retardation film ]

Has a high retardation film 13. In the present specification, a high retardation film means a film having an in-plane retardation value of 3000nm or more at a wavelength of 550 nm. By providing the optical laminate 10 with the high retardation film 13, it is possible to easily suppress a change in color tone (rainbow unevenness) that may be observed when a liquid crystal display device provided with the optical laminate is observed through a polarizing sunglass. The high retardation film 13 includes a transparent thermoplastic resin film having birefringence. The in-plane retardation value Re 550 of the high retardation film 13 at a wavelength of 550nm is preferably 3000nm or more, more preferably 5000nm or more, and particularly preferably 7000nm or more. The upper limit of the in-plane retardation Re 550 of the high retardation film 13 is, for example, 30000 nm.

The high retardation film 13 can be obtained by stretching a thermoplastic resin film, for example. Specific examples of the thermoplastic resin include polyolefin resins such as polyethylene and polypropylene; cyclic polyolefin resins such as norbornene polymers; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; (meth) acrylic resins such as (meth) acrylic acid and 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; a polycarbonate-based resin; a polystyrene-based resin; a polyarylate-based resin; a polysulfone-based resin; a polyether sulfone-based resin; a polyamide resin; a polyimide-based resin; a polyether ketone resin; polyphenylene sulfide-based resin; a polyphenylene ether resin; and mixtures, copolymers, and the like thereof. From the viewpoint of ease of acquisition and transparency, polyethylene terephthalate, cellulose ester, cycloolefin resin, or polycarbonate is preferable.

These thermoplastic resins may be subjected to uniaxial or biaxial heat stretching treatment to produce a film having a desired phase difference value. The stretching ratio is usually 1.1 to 6 times, preferably 1.1 to 4 times.

In addition, in order to enable the roll-to-roll manufacturing, it is also preferable to use a method of stretching in an oblique direction. The method of stretching in the oblique direction is not particularly limited as long as the orientation axis can be continuously tilted at a desired angle, and a known stretching method can be employed. Examples of such a drawing method include the methods described in Japanese patent application laid-open Nos. 50-83482 and 2-113920. When a retardation is imparted to a film by stretching, the thickness after stretching is determined by the thickness before stretching and the stretching ratio.

The angle formed by the slow axis of the high retardation film 13 and the absorption axis of the polarizer 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 reduction in front luminance when the liquid crystal display device is observed through the polarized sunglasses.

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 setting the thickness of the high retardation film 13 to 200 μm or less, curling of the optical laminate 10 can be suppressed, and defects such as air bubbles when bonding to a liquid crystal display device can be suppressed.

The high retardation film 13 has a moisture permeability of, for example, 100g/m ² Less than day, may be 50g/m ² Day or less. The high retardation film 13 has a moisture permeability of, for example, 0g/m ² More than day, may be 1g/m ² More than day. Even when the high retardation film 13 has a low moisture permeability, the optical laminate 10 is less likely to have a low transmittance in a high-temperature environment, and has excellent high-temperature durability. May be in accordance with JISK 7129: 2008, appendix B, the moisture permeability is measured in an atmosphere at a temperature of 40 ℃ and a relative humidity of 90%.

By providing the optical laminate 10 on the viewer side of the liquid crystal cell of the liquid crystal display device, it is possible to suppress a reduction in visibility when the liquid crystal display device is viewed through a polarizing sunglass without providing a separate film having a high retardation. Specifically, a decrease in front luminance and a change in hue (color shift) according to the viewing angle can be suppressed. A hard coat layer or an antiglare layer may be laminated on the high retardation film 13 as necessary.

[2 nd protective film ]

The optical laminate 10 may have a 2 nd protective film on the high retardation film 13 side of the polarizing element 12. The 2 nd protective film may be disposed between the polarizing element 12 and the high retardation film 13. As the 2 nd protective film, the resin film described above as a film that can be used as the 1 st protective film 11 may be used, or another resin film may be used. When the optical laminate 10 has the 2 nd protective film, the 2 nd protective film may be the same kind as the 1 st protective film 11 or may be a different kind. The optical layered body 10 may not have the 2 nd protective film. That is, the optical layered body 10 may have a protective film (1 st protective film 11) on only one surface of the polarizing element 12.

Examples of the second protective film 2 include films such as cellulose acylate films, chain olefin resin films, films containing polycarbonate resins, films containing cycloolefin resins such as norbornene resins, (meth) acrylic polymer films, and polyester resin films such as polyethylene terephthalate. Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resins (polyethylene resins that are homopolymers of ethylene, and copolymers mainly composed of ethylene), polypropylene resins (polypropylene resins that are homopolymers of propylene, and copolymers mainly composed of propylene), and copolymers containing 2 or more kinds of chain olefins.

The thickness of the 2 nd protective film is usually 1 μm or more and 100 μm or less, but from the viewpoint of strength, handling properties, and the like, it is preferably 5 μm or more and 60 μm or less, more preferably 10 μm or more and 55 μm or less, and still more preferably 15 μm or more and 50 μm or less.

The 2 nd protective film may have a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, a light diffusion layer, an antireflection layer, a low refractive index layer, an antistatic layer, and an antifouling layer on its outer surface (surface on the opposite side to the polarizing element). The thickness of the 2 nd protective film includes the thickness of the surface treatment layer.

[ adhesive layer ]

In the optical laminate 10, a bonding layer is used to bond the layers. Examples of the adhesive layer include an adhesive layer and an adhesive layer.

(adhesive layer)

The adhesive layer can be used, for example, for bonding the 1 st protective film 11 and the 2 nd protective film to the polarizing element 12. Any appropriate adhesive can be used as the adhesive for forming the adhesive layer. As the adhesive, an aqueous adhesive, a solvent adhesive, an active energy ray-curable adhesive, or the like can be used, but an aqueous adhesive is preferable.

The thickness of the adhesive at the time of application may be set to any appropriate value. For example, the adhesive layer is set so as to have a desired thickness after curing or after 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, still 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.

(aqueous adhesive)

As the water-based adhesive, any appropriate water-based adhesive can be used. Among them, an aqueous adhesive (PVA-based adhesive) containing a PVA-based resin is preferably used. The average polymerization degree of the PVA-based resin contained in the aqueous adhesive is preferably 100 to 5500, and more preferably 1000 to 4500, from the viewpoint of adhesiveness. The average saponification degree is preferably 85 to 100 mol%, more preferably 90 to 100 mol%, from the viewpoint of adhesiveness.

The reason why the PVA-based resin contained in the aqueous adhesive preferably contains an acetoacetyl group is that the PVA-based resin layer has excellent adhesion to the protective film and excellent durability. The acetoacetyl group-containing PVA-based resin can be obtained by, for example, reacting a PVA-based resin with diketene by an arbitrary method. The acetoacetyl group modification degree of the acetoacetyl group-containing PVA-based resin is typically 0.1 mol% or more, and preferably 0.1 mol% to 20 mol%.

The resin concentration of the aqueous adhesive is preferably 0.1 mass% or more and 15 mass% or less, and more preferably 0.5 mass% or more and 10 mass% or less.

The aqueous adhesive may contain a crosslinking agent. As the crosslinking agent, a known crosslinking agent can be used. Examples thereof include water-soluble epoxy compounds, dialdehydes, and isocyanates.

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

The aqueous adhesive may contain an organic solvent. The organic solvent is preferably an alcohol, and more preferably methanol or ethanol among alcohols, from the viewpoint of miscibility with water. Some of the urea compounds have low solubility in water but sufficient solubility in alcohol. In this case, it is also one of preferable embodiments to prepare an adhesive by dissolving the urea compound in an alcohol to prepare an alcohol solution of the urea compound, and then adding the alcohol solution of the urea compound to the PVA aqueous solution.

The concentration of methanol in the aqueous adhesive is preferably 10 mass% or more and 70 mass% or less, more preferably 15 mass% or more and 60 mass% or less, and still more preferably 20 mass% or more and 60 mass% or less. When the concentration of methanol is 10% by mass or more, the polyene formation in a high-temperature environment can be further easily suppressed. Further, by setting the content of methanol to 70% by mass or less, deterioration of color tone can be suppressed.

(active energy ray-curable adhesive)

The active energy ray-curable adhesive is an adhesive that is cured by irradiation with an active energy ray such as ultraviolet ray, and examples thereof include an adhesive containing a polymerizable compound and a photopolymerization initiator, an adhesive containing a photoreactive resin, and an adhesive 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, and oligomers derived from these monomers. Examples of the photopolymerization initiator include compounds containing active species that generate neutral radicals, anionic radicals, cationic radicals, and the like by irradiation with active energy rays such as ultraviolet rays.

(adhesive layer)

The adhesive layer can be used, for example, for bonding the high retardation film 13 to the polarizing element 12.

The pressure-sensitive adhesive layer may be formed from a pressure-sensitive adhesive composition containing, as a main component, a resin such as a (meth) acrylic resin, a rubber-based resin, a urethane-based resin, an ester-based resin, a silicone-based resin, or a polyvinyl ether-based resin. Among them, the pressure-sensitive adhesive composition is suitable for use as a base polymer of a (meth) acrylic resin which is excellent in transparency, weather resistance, heat resistance and the like. The adhesive composition may be an active energy ray-curable type or a heat-curable 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.

As the (meth) acrylic resin (base polymer) used in the adhesive composition, for example, a polymer or copolymer containing 1 or 2 or more kinds of (meth) acrylic acid esters such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate as monomers can be suitably used. The base polymer is preferably copolymerized with a polar monomer. Examples of the polar monomer include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N-dimethylaminoethyl (meth) acrylate, and glycidyl (meth) acrylate.

The adhesive composition may comprise only the above-mentioned base polymer, but usually also contains a crosslinking agent. Examples of the crosslinking agent include a crosslinking agent which is a metal ion having a valence of 2 or more and forms a metal carboxylate salt with a carboxyl group; a crosslinking agent which is a polyamine compound and forms an amide bond with a carboxyl group; a crosslinking agent which is a polyepoxy compound, a polyol, and forms an ester bond between the polyepoxy compound and a carboxyl group; a crosslinking agent which is a polyisocyanate compound and forms an amide bond with a carboxyl group. Among them, polyisocyanate compounds are preferable.

The thickness of the pressure-sensitive adhesive layer is preferably 1 μm or more and 200 μm or less, more preferably 2 μm or more and 100 μm or less, still more preferably 2 μm or more and 80 μm or less, and particularly preferably 3 μm or more and 50 μm or less.

[ second mode ]

An optical layered body according to a second embodiment will be described below with reference to the drawings. The optical laminate 20 shown in fig. 2 includes a 1 st protective film 21, a polarizing element 22, and a high retardation film 23 in this order, the optical laminate 20 has a water content of not less than 20% at a relative humidity of 20 ℃ at a temperature of 20 ℃ and not more than 48% at a relative humidity of 20 ℃, and the absolute value of the photoelastic coefficient of the 1 st protective film 21 at a temperature of 23 ℃ is 8 × 10 ^-12 Pa ^-1 Hereinafter, the in-plane retardation Re [550] of the high retardation film 23 at a wavelength of 550nm]Is 3000nm or more and 30000nm or less, and the angle formed by the slow axis of the high retardation film 23 and the absorption axis of the polarizer 22 is 40 ° or more and 50 ° or less.

The water content of the optical laminate 20 is not less than the equilibrium water content at a temperature of 20 ℃ and a relative humidity of 20%, and not more than the equilibrium water content at a temperature of 20 ℃ and a relative humidity of 48%. Preferably, the water content is not less than 30% at a temperature of 20 ℃ and not more than 45% at a relative humidity of 20 ℃. More preferably, the equilibrium moisture content is not more than 42% at a temperature of 20 ℃ relative humidity, still more preferably not more than 40% at a temperature of 20 ℃ relative humidity, and most preferably not more than 38% at a temperature of 20 ℃ relative humidity. If the equilibrium moisture content is less than 20% at a temperature of 20 ℃ and a relative humidity of 20%, the handling property of the optical laminate 20 is lowered and the optical laminate is likely to be broken. By setting the water content of the optical laminate 20 to the equilibrium water content of 48% relative humidity at 20 ℃, an optical laminate having excellent high-temperature durability can be provided.

The optical laminate 20 may include, for example, a 2 nd protective film, a bonding layer, and the like as other layers.

The examples and preferred ranges described in the description of the 1 st protective film 11, the polarizer 12, the high retardation film 13, the 2 nd protective film, and the adhesive layer in the optical laminate 10 can be applied to the 1 st protective film 21, the polarizer 22, the high retardation film 23, the 2 nd protective film, and the adhesive layer, respectively.

[ high temperature durability ]

The optical laminate is excellent in high-temperature durability. In this specification, the high temperature durability can be evaluated by the method described in the section of examples described later. The time for the decrease in the transmittance measured when the optical laminate is left to stand at 23 ℃ and 55% relative humidity for 24 hours and the sample for evaluation is stored at 95 ℃ in a heated environment may be 240 hours or longer, preferably 480 hours or longer, more preferably 720 hours or longer, and still more preferably 960 hours or longer, compared to the transmittance measured when the optical laminate is left to stand at 23 ℃ and 55% relative humidity for 24 hours.

[ use ]

The optical laminate can be used for image display devices such as liquid crystal display devices and organic EL display devices. The optical laminate may be disposed on the visible side (front side) of the image display device, or may be disposed on the back side. When the optical laminate is disposed in the image display device, the high retardation film, the polarizing element, and the 1 st protective film are preferably disposed in this order from the viewing side. In the case where the optical laminate is used in an image display device, a layer other than an air layer may be provided in contact with both surfaces of the optical laminate in the image display device. Examples of the layer other than the air layer include a pressure-sensitive adhesive layer and a transparent member. The pressure-sensitive adhesive layer described in the above-mentioned optical laminate can be used as the pressure-sensitive adhesive layer. The transparent member will be described later.

Fig. 3 is a cross-sectional view showing a configuration of a laminate in which a transparent member 34 and a touch panel 37 are disposed on an optical laminate 30 including 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 may be laminated via

adhesive layers

35 and 36. The laminate shown in fig. 3 may be disposed on an image display device or the like such that the transparent member 34 side is a visible side, for example.

[ transparent Member ]

Examples of the transparent member disposed on the visible side of the image display device include a front panel (window layer), a touch panel, and the like. As the front panel, a transparent plate having appropriate mechanical strength and thickness can be used. Examples of such transparent plates include transparent resin plates such as polyimide resin, acrylic resin, and polycarbonate resin, and glass plates. A functional layer such as an antireflection layer may be laminated on the visible side of the front panel. In addition, in the case where the front panel is a transparent resin plate, a hard coat layer may be laminated in order to improve physical strength, and a low moisture-permeable layer may be laminated in order to reduce moisture permeability.

As the touch panel, various touch panels such as a resistive film type, a capacitive type, an optical type, and an ultrasonic type, a glass plate having a touch sensor function, a transparent resin plate, and the like can be used. When a capacitive touch panel is used as the transparent member, a front panel formed of glass or a transparent resin plate is preferably provided on the visible side of the touch panel.

In the bonding of the optical laminate and the transparent member, an adhesive or an active energy ray-curable adhesive can be suitably used. When an adhesive is used, the adhesive can be attached in an appropriate manner. As a specific method of attaching, for example, a method of attaching an adhesive layer used for bonding the image display unit and the optical laminate is given.

In the case of using an active energy ray-curable adhesive, for the purpose of preventing the adhesive solution before curing from spreading, a method of providing a bank material so as to surround the peripheral edge portion on the image display panel, placing a transparent member on the bank material, and injecting the adhesive solution can be suitably used. After the adhesive solution is injected, alignment and defoaming are performed as necessary, and then the adhesive solution is cured by irradiation with an active energy ray.

< image display device >

The image display device of the present embodiment may include an image display unit, a 1 st adhesive layer laminated on a visible-side surface of the image display unit, and an optical laminate laminated on a visible-side surface of the 1 st adhesive layer. The image display device may further include a 2 nd adhesive layer laminated on the visible-side surface of the optical laminate, and a transparent member laminated on the visible-side surface of the 2 nd adhesive layer.

Fig. 4 shows an example of the layer structure of the 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 unit 47 via a 1 st adhesive layer 46, and a transparent member 44 is laminated on the visible surface of the optical laminate 40 via a 2 nd adhesive layer 45.

< method for producing optical laminate >

[ method for producing optical laminate of first embodiment ]

The method for producing an optical laminate according to the first aspect includes a water content adjustment step of adjusting the water content of the polarizing element so that the water content is equal to or higher than an equilibrium water content at a temperature of 20 ℃ and a relative humidity of 20% and equal to or lower than an equilibrium water content at a temperature of 20 ℃ and a relative humidity of 48%. Preferably, the method further comprises a 1 st lamination step of laminating a 1 st protective film on the polarizing element side. The order of the water content adjusting step and the 1 st laminating step is not limited, and the water content adjusting step and the 1 st laminating step may be performed in parallel. The method for producing an optical laminate of the present embodiment may further include a 2 nd laminating step of laminating a high retardation film on one side of the polarizing plate.

In the moisture content adjustment step of the present embodiment, the moisture content of the polarizer is adjusted so that the moisture content of the polarizer is equal to or higher than the equilibrium moisture content at a temperature of 20 ℃ and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20 ℃ and a relative humidity of 48%. The method for preparing the polarizer having such a water content is not particularly limited, and for example, the polarizer can be adjusted by storing the polarizer in an environment adjusted to the temperature and the relative humidity for 10 minutes to 3 hours, or by performing a heat treatment at 30 to 90 ℃.

As another preferable method, the polarizing plate obtained in the 1 st lamination step may be stored in an environment adjusted to the temperature and the relative humidity for 10 minutes to 120 hours, or may be subjected to a heat treatment at 30 to 90 ℃. The water content adjusting step may be performed before the 1 st laminating step, or may be performed after the 1 st laminating step.

[ method for producing optical laminate of second embodiment ]

The method for producing an optical laminate according to the second aspect includes a water content adjustment step of adjusting the water content of the optical laminate so that the water content is equal to or higher than an equilibrium water content at a temperature of 20 ℃ and a relative humidity of 20% and equal to or lower than an equilibrium water content at a temperature of 20 ℃ and a relative humidity of 48%. Preferably, the method further includes a 1 st laminating step of laminating a 1 st protective film on the polarizing element side and a 2 nd laminating step of laminating a high retardation film on the polarizing plate side.

In the moisture content adjusting step of the present embodiment, the moisture content of the optical laminate is adjusted so that the moisture content of the optical laminate is equal to or higher than the equilibrium moisture content at a temperature of 20 ℃ and a relative humidity of 20% and equal to or lower than the equilibrium moisture content at a temperature of 20 ℃ and a relative humidity of 48%. The method for preparing the optical laminate having such a water content is not particularly limited, and for example, the method for adjusting the water content by keeping the optical laminate in an environment adjusted to the temperature and the relative humidity for 10 minutes to 3 hours, or the method for performing a heat treatment at 30 to 90 ℃.

As a method of confirming whether or not the water contents of the polarizing element and the optical laminate are within a range of not less than the equilibrium water content at a temperature of 20 ℃ and a relative humidity of 20% and not more than the equilibrium water content at a temperature of 20 ℃ and a relative humidity of 48%, there can be mentioned a method of confirming that there is no change in mass by keeping the polarizing element or the optical laminate for a certain period of time in an environment adjusted to the range of the temperature and the relative humidity; or a method of calculating in advance the equilibrium moisture content of the polarizing element or the optical laminate in the environment adjusted to the temperature and the relative humidity range, and comparing the moisture content of the polarizing element or the optical laminate with the calculated equilibrium moisture content. When the polarizing element or the optical laminate is stored for a certain period of time without changing its mass, it can be considered that the moisture content is balanced in the storage environment.

Examples

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, the parts and% indicating the content or amount used are on a mass basis unless otherwise specified. The measurement of each physical property in the following examples was performed by the following method.

(1) Method for measuring film thickness

The measurement was carried out using MH-15M as a digital micrometer manufactured by Nikon K.K.

(2) Method for measuring phase difference value

The measurement was carried out using a phase difference measuring apparatus KOBRA-WPR (manufactured by Okinson instruments Co., Ltd.).

(3) Method for measuring photoelastic coefficient

A phase difference value (23 ℃/wavelength 550nm) at the center of a sample was measured while applying stress (0.5N to 8N) to both ends of the sample (1.5 cm. times.6 cm in size) with the use of a phase difference measuring device KOBRA-WPR (manufactured by Okinson instruments Co., Ltd.), and the value was calculated from the slope of a function of the stress and the phase difference value.

(4) The brightness measurement method comprises the following steps:

measured using a spectral radiance meter SR-UL1 manufactured by TOPCON. The measurement was performed with a 2 ° field of view.

[ production of polarizing element ]

A polyvinyl alcohol film having a thickness of 40 μm and containing polyvinyl alcohol having an average polymerization degree of about 2400 and a saponification degree of 99.9 mol% or more was prepared. The polyvinyl alcohol film was uniaxially stretched about 5 times in a dry manner, and then immersed in pure water at 60 ℃ for 1 minute while maintaining the stretched state. Thereafter, the polyvinyl alcohol film was immersed in an aqueous solution of iodine/potassium iodide/water at 28 ℃ in a mass ratio of 0.05/5/100 for 60 seconds. Thereafter, the polyvinyl alcohol film was immersed in an aqueous solution at 72 ℃ having a potassium iodide/boric acid/water mass ratio of 8.5/8.5/100 for 300 seconds. The polyvinyl alcohol film was then washed with pure water at 26 ℃ for 20 seconds and then dried at 65 ℃. In this manner, a polarizing element having a thickness of 15 μm, in which iodine was adsorbed and oriented in polyvinyl alcohol, was obtained.

[ preparation of protective film ]

Protective film a (2 nd protective film):

(preparation of composition for hard coat layer formation 1)

The following components were mixed to prepare a composition 1 for forming a hard coat layer.

PET 3097.0 parts by mass

Irgacure 9073.0 parts by mass

MEK 81.8 parts by mass

The materials to be used are indicated below.

PET 30: mixture of pentaerythritol tetraacrylate and pentaerythritol triacrylate [ manufactured by Nippon Kagaku Co., Ltd ]

Irgacure 907: photopolymerization initiator [ manufactured by BASF Ltd ]

MEK: methyl ethyl ketone

< preparation of hard coating film >

A commercially available cellulose acylate film TD40 (manufactured by Fuji photo film Co., Ltd., width 1340mm, thickness 40 μm) was wound out from a roll form, and the composition 1 for forming a hard coat layer was applied by a die coating method using a slit die at a carrying speed of 30 m/min and dried at 60 ℃ for 150 seconds.

Thereafter, the resultant was again irradiated with 400mW/cm of light under a nitrogen purge using an air-cooled metal halide lamp (manufactured by EYE GRAPHICS K) having an oxygen concentration of about 0.1% and an output of 160W/cm ² The dose of irradiation was 120mJ/cm ² The coating layer (hard coat layer) is cured by the ultraviolet ray of (2) to wind the hard coat film. The thickness of the coating layer was adjusted so that the film thickness of the hard coat layer was 7 μm. Thus, the protective film a was obtained.

The protective film a prepared in the above-described manner was immersed in a 1.5mol/L NaOH aqueous solution (saponification solution) maintained at 55 ℃ for 2 minutes, and then the film was washed with water. Thereafter, the membrane was immersed in a 0.05mol/L aqueous sulfuric acid solution at 25 ℃ for 30 seconds, and then washed with water under running water for 30 seconds to make the membrane neutral. Thereafter, the water removal by air knife was repeated 3 times, and after removing the water, the mixture was left in a drying zone at 70 ℃ for 15 seconds to be dried, and then saponified.

Protective film B (1 st protective film):

100 parts by mass of imide MS resin pellets (weight average molecular weight: 105000) described in production example 1 of Japanese patent application laid-open No. 2010-284840 were dried under 100.5kPa at 100 ℃ for 12 hours, and extruded from a T-die by a uniaxial extruder at a die temperature of 270 ℃ to form a film (thickness: 160 μm). The film was further stretched in the carrying direction at 150 ℃ in an atmosphere (thickness: 80 μm), and then in the direction orthogonal to the film carrying direction at 150 ℃ in an atmosphere, to obtain a protective film B ((meth) acrylic resin film) having a thickness of 40 μm. The protective film B had an in-plane retardation Re of 0.5nm at a wavelength of 550nm and a retardation Rth of 0.82nm in the thickness direction. The photoelastic coefficient of the resulting film was 2.0X 10 ^- ¹² Pa ^-1 。

[ preparation of adhesive ]

50g of a modified PVA-based resin containing an acetoacetyl group (GOHSENX Z-410, manufactured by Mitsubishi chemical corporation) was dissolved in 950g of pure water, heated at 90 ℃ for 2 hours, and then cooled to room temperature to obtain a PVA solution.

Then, the PVA solution, maleic acid, glyoxal, and pure water were mixed so that the respective compounds had the following concentrations to prepare a PVA-based adhesive.

PVA concentration 3.0% by mass

Maleic acid 0.01% by mass

Glyoxal 0.15% by mass

[ preparation of high retardation film ]

COSMOSHINE SRF (Super Retardation Film) (thickness 80 μm) manufactured by Toyobo Co., Ltd. was used. The in-plane phase difference Re (550) was 8400 nm. The moisture permeability under the condition of 40 ℃ and 90% of relative humidity is 10g/m ² Day.

[ preparation of adhesive ]

Adhesive A: sheet-like acrylic adhesive having a thickness of 15 μm ("P-3132-15 μ", manufactured by LINTEC corporation)

And (3) adhesive B: sheet-like acrylic adhesive having a thickness of 25 μm ("P-3132" manufactured by LINTEC corporation)

[ example 1]

A protective film A is bonded to one surface of the polarizing element with an adhesive, and a protective film B is bonded to the other surface of the polarizing element with an adhesive. Thereafter, the sheet was dried at 80 ℃ for 5 minutes to obtain a polarizing plate 1. When the protective film B is bonded, the bonding surface of the protective film B is subjected to corona treatment.

(measurement of equilibrium Water content)

The polarizing plate 1 obtained in the above-described manner was stored at a temperature of 20 ℃ and a relative humidity of 30%, 35%, 40%, 45%, or 50% for 72 hours, and the water content was measured by the karl fischer method at 66 hours, 69 hours, and 72 hours of storage. The water content values did not change when stored for 66 hours, 69 hours, or 72 hours under any humidity condition. Therefore, the water content of the polarizing plate 1 can be considered to be equal to the equilibrium water content in the storage environment. When the moisture content of the polarizing plate is balanced at a certain storage temperature, the moisture content of the polarizing element in the polarizing plate can be similarly considered to be balanced at the storage temperature. In addition, when the moisture content of the polarizing element in the polarizing plate reaches equilibrium in a certain storage environment, the moisture content of the polarizing plate can be similarly considered to reach equilibrium in the storage environment.

The moisture content of the polarizing plate 1 obtained in the above procedure immediately after drying was measured by the karl fischer method and compared with the equilibrium moisture content. The water content of the polarizing plate 1 was equal to that at a temperature of 20 ℃ and a relative humidity of 30%. The polarizing plate 1 was stored at a temperature of 20 ℃ and a relative humidity of 30% for 72 hours.

(preparation of polarizing plates 2 to 5)

The polarizing plate 1 was stored at 20 ℃ for 72 hours under conditions of 35%, 40%, 45%, or 50% relative humidity, with the drying temperature or time changed so that the water content was equal to the equilibrium water content shown in table 1.

Then, an adhesive B was bonded to the surface of the protective film B of the obtained polarizing plates 1 to 5. In the lamination of these materials, the lamination surfaces of the respective materials are subjected to corona treatment.

The adhesive a was bonded to one surface of the high retardation film. In the lamination of these materials, the lamination surfaces of the respective materials are subjected to corona treatment.

The surfaces of the protective films a of the polarizing plates 1 to 5 produced as described above were bonded to the adhesive surface of the high retardation film so that the angle formed by 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. In the lamination of these materials, the lamination surfaces of the respective materials are subjected to corona treatment.

(preparation of polarizing plate 6)

The protective film B was bonded to one surface of the polarizing element obtained in the previous step with an adhesive, thereby producing a polarizing plate 6 having a protective film only on one surface of the polarizing element. When the protective film B is bonded, the bonding surface of the protective film B is subjected to corona treatment.

(measurement of equilibrium Water content)

The polarizing plate 6 obtained in the above-described manner was stored at 20 ℃ and a relative humidity of 30%, 35%, 40%, 45%, or 50% for 72 hours, and the water content was measured by the karl fischer method when the polarizing plate was stored for 66 hours, 69 hours, and 72 hours. The water content values did not change when stored for 66 hours, 69 hours, or 72 hours under any humidity condition. Therefore, the water content of the polarizing plate 6 can be considered to be equal to the equilibrium water content of the storage environment. When the moisture content of the polarizing plate is balanced at a certain storage temperature, the moisture content of the polarizing element in the polarizing plate can be similarly considered to be balanced at the storage temperature. In addition, when the moisture content of the polarizing element in the polarizing plate reaches equilibrium in a certain storage environment, the moisture content of the polarizing plate can be similarly considered to reach equilibrium in the storage environment.

The moisture content of the polarizing plate 6 obtained in the above procedure immediately after drying was measured by the karl fischer method and compared with the equilibrium moisture content. The water content of the polarizing plate 6 was equal to that at a temperature of 20 ℃ and a relative humidity of 30%. The polarizing plate 6 was stored at a temperature of 20 ℃ and a relative humidity of 30% for 72 hours.

(preparation of polarizing plates 7 to 10)

The polarizing plate 6 was stored at 20 ℃ for 72 hours under conditions of 35%, 40%, 45%, or 50% relative humidity, with the drying temperature or time changed so that the water content was equal to the equilibrium water content shown in table 1.

Then, an adhesive B was bonded to the surface of the protective film B of the obtained polarizing plates 6 to 10. In the lamination of these materials, the lamination surfaces of the respective materials are subjected to corona treatment.

The polarizing element surfaces (surfaces to which the protective film B is not attached) of the polarizing plates 6 to 10 produced as described above were bonded to the adhesive surface of the high retardation film so that the angle formed by the absorption axis of the polarizing plate and the slow axis of the high retardation film was 45 °, whereby optical laminates 6 to 10 were produced. In the lamination of these materials, the lamination surfaces of the respective materials are subjected to corona treatment.

The obtained optical laminate was stored for 72 hours under the same conditions as those for storing the polarizing plate for 72 hours so that the water content of the polarizing plate used to form the optical laminate was equal to that of the optical laminate, and the water content of the optical laminate was adjusted. The optical laminate was stored for 72 hours, and it was considered that the moisture content of the polarizing plate and the polarizing element in the optical laminate were balanced in the storage environment. In addition, when the moisture content of the polarizing plate or the polarizing element in the optical laminate is balanced under a certain storage environment, the moisture content of the optical laminate can be similarly considered to be balanced under the storage environment.

(evaluation of Black Brightness Change)

(preparation of sample for evaluation 1A)

The black luminance refers to luminance in black display. Alkali-free glass having a thickness of 0.7mm and a size of 300 mm. times.300 mm was prepared. The optical laminate 1 was cut into a size of 200mm × 200mm, and was bonded to one surface of the alkali-free glass with the adhesive B interposed therebetween. A polarizing plate 1 (to which a high retardation film was not attached) with an adhesive B was cut into a size of 200mm × 200mm, and was attached to the other surface of the alkali-free glass via the adhesive B so that the absorption axes of the polarizing plate were crossed nicols, thereby producing sample 1 for evaluation.

(preparation of evaluation samples 2A to 10A)

In the production of the evaluation sample 1, evaluation samples 2A to 10A were produced in the same manner except that the optical laminate 1 was replaced with the optical laminates 2 to 10, respectively.

The side to which the polarizing plate 1 with adhesive B (high retardation film was not attached) of the evaluation samples 1A to 10A prepared in the above-described manner was attached was placed at 20000cd/m ² The illumination surface of the white backlight module having the luminance of (2) is from the side of the optical laminate (high phase difference)Film) side (black brightness 1). The evaluation sample was stored in a heated environment at a temperature of 95 ℃ for 240 hours, then cooled to room temperature, and the brightness (black brightness 2) was measured again. The change rate (%) of the black luminance 2 with respect to the black luminance 1 is calculated and is defined as a change in black luminance. As a result, the amount of change in black luminance of all the evaluation samples was + 1%.

(evaluation of transmittance Change)

The optical layered bodies 1 to 10 were cut into a size of 50mm × 100 mm. Samples 1B to 10B for evaluation were produced by bonding the pressure-sensitive adhesive layer B exposed by peeling off the release film to alkali-free glass (trade name "EAGLE XG", manufactured by Corning corporation). The evaluation sample was heated at 50 ℃ under a pressure of 5kgf/cm ² (490.3kPa) was subjected to 1-hour autoclave treatment. After the plate was left to stand at 23 ℃ and 55% relative humidity for 24 hours, the transmittance (initial value) was measured. Thereafter, the evaluation sample was stored in a heated environment at a temperature of 95 ℃ and the transmittance was measured at intervals of 240 hours over 120 hours and 240 to 960 hours. The transmittance reduction amount was evaluated based on the time taken for the initial value to reach 5% or more according to the following criteria. The obtained results are shown in table 1. The same results were obtained even when the alkali-free glass was bonded to the high retardation film side of the sample for evaluation via a pressure-sensitive adhesive.

A: the reduction in transmission over 960 hours was less than 5%

B: the transmittance is reduced by 5% or more after 720 hours or 960 hours

C: the transmittance is reduced by 5% or more after 480 hours

D: the transmittance is reduced by 5% or more after 240 hours

E: the transmittance is reduced by 5% or more after 120 hours

[ TABLE 1]

Claims

1. An optical laminate comprising a 1 st protective film, a polarizing element and a high retardation film in this order,

the water content of the polarizing element is more than or equal to 20% of equilibrium water content at a temperature of 20 ℃ and less than or equal to 48% of equilibrium water content at a temperature of 20 ℃ and relative humidity,

2. An optical laminate comprising a 1 st protective film, a polarizing element and a high retardation film in this order,

the in-plane retardation value Re 550 of the high retardation film at a wavelength of 550nm is 3000nm or more and 30000nm or less,

3. The optical stack according to claim 1 or 2,

the 1 st 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 stack according to any one of claims 1 to 3,

the 1 st protective film has an in-plane retardation value Re 550 at a wavelength of 550nm of 10nm or less.

5. The optical stack according to any one of claims 1 to 4,

the thickness of the high retardation film is 200 [ mu ] m or less.

6. The optical stack according to any one of claims 1 to 5,

the optical laminate is used for an image display device,

7. An image display device comprising an image display unit, a 1 st adhesive layer laminated on a visible-side surface of the image display unit, and the optical laminate according to any one of claims 1 to 6 laminated on a visible-side surface of the 1 st adhesive layer.

8. The image display device according to claim 7, further comprising a 2 nd adhesive layer laminated on a visible-side surface of the optical laminate, and a transparent member laminated on a visible-side surface of the 2 nd adhesive layer.

9. The image display apparatus according to claim 8,

the transparent member is a glass plate or a transparent resin plate.

10. The image display apparatus according to claim 8,

the transparent member is a touch panel.

11. A method for producing an optical laminate according to claim 1,

12. A method for producing an optical laminate according to claim 2,