KR20210031840A - Optical laminate and display apparatus using the same - Google Patents

Abstract

Provided is an optical laminate capable of improving the visibility regardless of the presence or absence of polarized sunglasses even after being placed in a high-temperature environment. A polarizing plate and a high retardation film are provided in this order. The polarizing plate has a polarizer and a protective film laminated on a surface opposite to the high retardation film of the polarizer. The high retardation film has an in-plane retardation value of 3000 to 30000 nm. An angle between the slow axis of the high retardation film and the absorption axis of the polarizer is 40° to 50°. An absolute value of the photoelastic coefficient of the protective film is less than or equal to 8×10^(-12) Pa^(-1).

Description

Optical laminated body and display device using the same TECHNICAL FIELD

The present invention relates to an optical laminate and a display device using the same.

In recent years, with the rapid spread of liquid crystal displays, scenes used under strong sunlight such as smartphones and vehicle-mounted applications are increasing. Under such strong sunlight, sunglasses with polarization characteristics (polarized sunglasses) are sometimes used in a state of wearing.When the liquid crystal display device is visually recognized over the polarized sunglasses, the liquid crystal display device becomes dark depending on the direction in which it is visually recognized. There was a case where this remarkably decreased.

In Patent Document 1, 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 30000 nm is provided on the viewer side of the polarizer, and the absorption axis of the polarizer and the slow axis of the polymer film. A method for improving visibility is described which is arranged and used so that the angle formed by 軸) is approximately 45°. According to the method for improving visibility of Patent Document 1, it is said that the visibility when the screen is observed through polarized sunglasses can be improved. However, in the case of using a polymer film having a high retardation value, the front luminance of the liquid crystal display device during black display increases when it is placed in a high-temperature environment for a long time, and when the screen is visually recognized without wearing polarized sunglasses, visibility is improved. There was a case of deterioration.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2011-215646

An object of the present invention is to solve the above problems, and to provide an optical laminate capable of improving visibility even after being placed in a high temperature environment, regardless of the presence or absence of polarized sunglasses.

As a result of intensive examination, the inventor of the present invention gave a polymer film having a retardation value of 3000 to 30000 nm through an adhesive on the surface of the polarizing plate used for the viewing side surface of a liquid crystal display device (hereinafter, also simply referred to as a "high phase difference film"), When a liquid crystal display device bonded so that the angle between the absorption axis of the polarizer and the slow axis of the polymer film is approximately 45° is placed in a high-temperature environment for a long time, the front luminance in the black display of the liquid crystal display device rises because of the following reasons. I thought it was due to.

The high-order difference film is produced by being stretched at a high temperature at a high draw ratio, and cooled with residual stress remaining. When the polarizing plate to which such a high-order phase difference film is obliquely bonded is stored for a long time in a high-temperature environment, residual stress in the oblique direction of the high-order phase difference film is released. The stress in the oblique direction is also applied to the protective film of the polarizing plate, and in particular, with respect to the protective film disposed between the polarizer and the liquid crystal display, a phase difference having an optical axis obliquely with respect to the absorption axis of the polarizer occurs, causing light leakage. It was estimated that it was because of.

Based on this estimation, as a result of using a protective film on the liquid crystal device side having a low photoelastic modulus and having a specific value, it was found that the above problem could be solved, and the present invention was completed. It is presumed that the protective film having a low photoelastic modulus is unlikely to generate a retardation having an optical axis obliquely.

The present invention provides an optical laminate exemplified below and a display device using the same.

[1] A polarizing plate and a high-order difference film are provided in this order,

The polarizing plate has a polarizer and a protective film laminated on a surface of the polarizer opposite to the high-order phase difference film side,

The in-plane retardation value of the high-order retardation film is 3000 to 30000 nm,

The angle formed by the slow axis of the high-order phase difference film and the absorption axis of the polarizer is 40° to 50°,

An optical laminate having an absolute value of the photoelastic coefficient of the protective film of 8×10 ^-12 Pa ^{-1 or less.}

[2] The optical laminate according to [1], wherein the protective film contains at least one selected from the group consisting of (meth)acrylic resins, polystyrene resins, and maleimide resins.

[3] The optical laminate according to [1], in which the protective film contains a cyclic olefin resin.

[4] The optical laminate according to any one of [1] to [3], wherein the in-plane retardation value of the protective film is 10 nm or less.

[5] The optical laminate according to any one of [1] to [3], wherein the protective film has an in-plane retardation value of 50 nm to 300 nm.

[6] The optical laminate according to any one of [1] to [5], wherein the thickness of the high-order phase difference film is 200 µm or less.

[7] The optical laminate according to any one of [1] to [6], in which the high-order phase difference film and the polarizing plate are laminated through an adhesive layer.

[8] A display device in which the optical laminate according to any one of [1] to [7] is laminated on a display element.

According to the present invention, it is possible to provide an optical laminate capable of improving visibility regardless of the presence or absence of polarized sunglasses even after being placed in a high-temperature environment.

1 is an example of a schematic cross-sectional view showing a layer structure of an optical laminate.
Fig. 2 is an example of a schematic cross-sectional view showing a layer structure of an optical laminate in which a front plate is laminated.

(Definition of terms and symbols)

Definitions of terms and symbols in this specification are as follows.

(1) refractive index (nx, ny, nz)

"Nx" is a refractive index in a direction in which the in-plane refractive index is maximum (ie, a 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.

(2) In-plane retardation value

The in-plane retardation value (Re[λ]) refers to an in-plane retardation value of the film at 23°C and a wavelength of λ (nm). Re[λ] is determined by Re[λ] = (nx-ny)×d when the film thickness is d (nm).

(3) The retardation value in the thickness direction

The retardation value Rth[λ] in the thickness direction refers to a retardation value in the thickness direction of the film at 23°C and a wavelength lambda (nm). Rth[λ] is determined by Rth[λ]=((nx+ny)/2-nz)×d when the film thickness is d (nm).

<Optical laminate>

The optical laminate of the present invention includes a polarizing plate and a high-order phase difference film in this order. The polarizer and the protective film constituting the polarizing plate can be laminated through an adhesive layer, for example. Examples of the adhesive layer include an adhesive layer and an adhesive layer described later.

Hereinafter, an example of the layer configuration of the optical laminate of the present invention will be described with reference to FIG. 1. On the other hand, in FIG. 1, the adhesive layer for bonding the polarizer 10 and the protective films 11, 12, respectively, is not shown. In the optical laminate 100 shown in FIG. 1, a first protective film 11 is laminated on one surface of a polarizer 10, and a second protective film 12 is laminated on the other surface of the polarizer 10. The laminated polarizing plate 1 and the high-order retardation film 13 have a layered configuration through the pressure-sensitive adhesive layer 14. In addition, the optical laminated body 100 has the adhesive layer 15 on the surface opposite to the polarizer 10 in the 1st protective film 11. The pressure-sensitive adhesive layer 15 may be a pressure-sensitive adhesive layer for bonding to a display device or the like.

<polarizing plate>

In the present invention, a polarizing plate means a laminate having a polarizer and at least one protective film. The protective film provided by the polarizing plate may have surface treatment layers such as a hard coat layer, an antireflection layer, and an antistatic layer to be described later. The polarizer and the protective film can be laminated through an adhesive layer or an adhesive layer, for example. The member included in the polarizing plate will be described below.

(1) polarizer

The polarizer 10 provided in the polarizing plate 1 absorbs linearly polarized light having a vibrational surface parallel to its absorption axis, and transmits linearly polarized light having a vibrational surface orthogonal to the absorption axis (parallel to the transmission axis). It may be an absorption type polarizer. As the polarizer 10, a polarizer in which a dichroic dye is adsorbed and oriented to a polyvinyl alcohol-based resin film uniaxially stretched can be suitably used. The polarizer 10 is, for example, a step of uniaxially stretching a polyvinyl alcohol-based resin film; A step of adsorbing a dichroic dye by dyeing a polyvinyl alcohol-based resin film with a dichroic dye; A step of treating a polyvinyl alcohol-based resin film to which a dichroic dye is adsorbed with a crosslinking solution such as an aqueous boric acid solution; And it can be produced by a method including a step of washing with water after treatment with a crosslinking liquid.

As the polyvinyl alcohol-based resin, one obtained by saponifying a polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and (meth)acrylamides having an ammonium group.

In this specification, "(meth)acryl" means at least one selected from acrylic and methacrylic. The same applies to "(meth)acryloyl", "(meth)acrylate" and the like.

The degree of saponification of the polyvinyl alcohol-based resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually 1000 to 10000, preferably 1500 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726.

What formed such a polyvinyl alcohol-based resin into a film is used as a raw film of a polarizer. The method of forming a film of the polyvinyl alcohol-based resin is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol-based master film is not particularly limited, but, for example, in order to make the thickness of the polarizer 25 µm or less, it is preferable to use a material having a thickness of 40 to 75 µm. More preferably, it is 45 micrometers or less.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing of the dichroic dye. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before or during crosslinking treatment. Further, uniaxial stretching may be performed in a plurality of these steps.

In the case of uniaxial stretching, it may be uniaxially stretched between rolls having different circumferential speeds, or uniaxially stretched using a hot roll. Further, uniaxial stretching may be dry stretching performed in the air, or wet stretching performed in a state in which the polyvinyl alcohol-based resin film is swollen using a solvent or water. The draw ratio is usually 3 to 8 times.

As a method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing a dichroic dye is adopted. As the dichroic dye, iodine or a dichroic organic dye is used. On the other hand, it is preferable to immerse the polyvinyl alcohol-based resin film in water before the dyeing treatment.

As a crosslinking treatment after dyeing with a dichroic dye, a method of immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid is usually employed. When iodine is used as a dichroic dye, it is preferable that this boric acid-containing aqueous solution contains potassium iodide.

The thickness of the polarizer is usually 50 µm or less, preferably 5 to 30 µm, more preferably 5 to 25 µm or less, and still more preferably 5 to 20 µm or less. By setting the thickness of the polarizer into these ranges, it is possible to maintain handling properties while preventing breakage or cracking at the time of manufacture of the polarizer, and high optical properties can be achieved. Further, by setting the thickness of the polarizer to 20 µm or less, a decrease in visibility when placed in a high-temperature environment can be further suppressed.

As the polarizer, for example, as described in Japanese Unexamined Patent Application Publication No. 2016-170368, in a cured film in which a liquid crystal compound is polymerized, a dichroic dye may be used. As the dichroic dye, one having absorption in the wavelength range of 380 to 800 nm can be used, and it is preferable to use an organic dye. As a dichroic dye, an azo compound is mentioned, for example. The liquid crystal compound is a liquid crystal compound that can be polymerized while being aligned, and may have a polymerizable group in a molecule. Further, as described in WO2011/024891, a polarizer may be formed from a dichroic dye having liquid crystal properties.

(2) protective film

The polarizing plate 1 used in the present invention has a polarizer 10 and a first protective film 11 laminated on a surface of the polarizer 10 opposite to the high-order phase difference film 13 side. The polarizing plate 1 has at least one protective film corresponding to the first protective film 11, and the second protective film 12 laminated on the surface of the polarizer 10 on the side of the high-order phase difference film 13 You may have another corresponding protective film.

(1st protective film (11))

In the first protective film 11, the absolute value of the photoelastic coefficient at a temperature of 23° C. is 8×10 ^-12 Pa ^-1 or less. By using the first protective film 11 having a small photoelastic coefficient, the phase difference expressed by the distortion of the first protective film 11 caused by the shrinkage stress of the high-order phase difference film 13 when placed in a high-temperature environment The value is small, and as a result, it is considered that the visibility can be improved regardless of the presence or absence of polarized sunglasses even after being placed in a high-temperature environment.

The first protective film 11 is not particularly limited, but a (preferably optically transparent) thermoplastic resin having a light transmittance having ^{an absolute value of the photoelastic coefficient of 8×10 -12} Pa ^{-1 or less, for example, a chain polyolefin resin (} Polyolefin-based resins such as polypropylene-based resins) and cyclic polyolefin-based resins (norbornene-based resins, etc.); Cellulose resins such as triacetyl cellulose and diacetyl cellulose; Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate resin; (Meth)acrylic resins such as methyl methacrylate resins; Polystyrene resin; Polyvinyl chloride resin; Acrylonitrile/butadiene/styrene resin; Acrylonitrile-styrene resin; Polyvinyl acetate-based resin; Polyvinylidene chloride resin; Polyamide resin; Polyacetal resin; Modified polyphenylene ether resin; Polysulfone resin; Polyethersulfone resin; Polyarylate resin; Polyamide-imide resin; Polyimide resin; It may be a film containing a maleimide-based resin or the like.

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

The photoelastic coefficient of the first protective film 11 at a temperature of 23° C. is preferably 0.05×10 ^{-12 to} 8.0×10 ^-12 Pa ^-1 , more preferably 0.1×10 ^{-12 to} 5.0×10 ^-12 Pa ^-1 , more preferably 0.2 × 10 ^{-12 to} 3.0 × 10 ^-12 Pa ^-1 . Meanwhile, the photoelastic coefficient is a value measured by the method described in Examples to be described later.

The in-plane retardation value of the protective film 11 is preferably 10 nm or less or adjusted to 50 to 300 nm as long as it is within the above-described photoelastic coefficient. In particular, preferably, a higher effect can be obtained by setting it as a 10 nm or less film. This is based on the estimation that the retardation value changes due to stress relaxation in the oblique direction of the high-order retardation film and the optical axis of the film having a retardation difference increases, thereby increasing light leakage during black display. When a retardation film is applied as an optical compensation film in a liquid crystal display device or the like, it is also a useful design means to arrange the optical compensation film on another polarizing plate used as a pair. On the other hand, the retardation value refers to a value at a wavelength of 550 nm unless otherwise specified, and is a value measured by the method described in Examples to be described later.

Cyclic polyolefin resin is a generic term for a resin polymerized by using a cyclic olefin as a polymerization unit, and for example, Japanese Unexamined Patent Publication No. 1-240517, Japanese Unexamined Patent Publication No. 3-14882, and Japanese Unexamined Patent Publication No. 3 The resin described in Publication No. -122137 and the like can be mentioned. Specific examples of the cyclic polyolefin resin include a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin and a chain olefin such as ethylene and propylene (typically a random copolymer), and these These are graft polymers modified with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among them, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

The method of producing a protective film from a cyclic olefin resin is not particularly limited, and a method according to the resin may be appropriately selected. For example, a solvent casting method in which a resin dissolved in a solvent is cast into a metal band or drum to dry and remove the solvent to obtain a film, and the resin is heated and kneaded above its melting temperature to be extruded from a die, A melt extrusion method in which a film is obtained by cooling with a cooling drum is adopted. Among them, the melt extrusion method is preferably employed from the viewpoint of productivity.

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

Next, a method of controlling the retardation value of the cyclic olefin resin film to satisfy the above condition will be described. In order to make the in-plane retardation value 10 nm or less, it is necessary to minimize the distortion during stretching remaining in the in-plane direction. Further, in order to make the retardation in the thickness direction less than the predetermined value of the present invention, the distortion remaining in the thickness direction It is necessary to make it as small as possible.

For example, in the solvent casting method, a method of mitigating residual stretching distortion in the in-plane direction and residual shrinkage distortion in the thickness direction generated when the cast resin solution is dried by heat treatment, or the like is employed. In addition, in the melt extrusion method, in order to prevent stretching of the resin film from the die to the extrusion and cooling, the distance from the die to the cooling drum is shortened as much as possible, and the extrusion amount and the rotation speed of the cooling drum A method of controlling so that the film is not stretched or the like is employed. Further, a method of mitigating distortion remaining in the film obtained in the same manner as the melt extrusion method is also employed by heat treatment.

Moreover, it is good also as a retardation film which gave the function as an optical compensation film of a liquid crystal display device within the range which satisfies the photoelastic coefficient of this invention. Such a retardation film can be produced by stretching the cyclic olefin resin film to provide an in-plane retardation value. Stretching can be performed by known longitudinal uniaxial stretching, tenter transverse uniaxial stretching, simultaneous biaxial stretching, sequential biaxial stretching, or the like, and stretching so as to obtain a desired retardation value.

For example, in a liquid crystal display device in an in-plane switching mode, a retardation film in which the in-plane retardation is adjusted to 50 to 300 nm is preferably used. Specifically, the retardation film described in JP 2010-20287 A, the retardation film described in JP 3880996 A, or the like can be used.

The thickness of the cyclic olefin resin film is preferably 10 µm to 200 µm, more preferably 10 µm to 100 µm, and most preferably 10 µm to 65 µm. If the thickness is less than 10 µm, there is a fear that the strength may decrease. When the thickness exceeds 200 µm, there is a fear that the transparency may decrease.

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

The in-plane retardation value Re[550] at a wavelength of 550 nm of the (meth)acrylic resin film is preferably 10 nm or less, more preferably 7 nm or less, further preferably 5 nm or less, particularly It is preferably 3 nm or less, and most preferably 1 nm or less. The retardation value Rth[550] in the thickness direction of the (meth)acrylic resin film at a wavelength of 550 nm is preferably 15 nm or less, more preferably 10 nm or less, further preferably 5 nm or less, particularly It is preferably 3 nm or less, and most preferably 1 nm or less. In order to make the in-plane retardation and the retardation in the thickness direction into such a range, it can be obtained using, for example, a (meth)acrylic resin having a glutarimide structure described later.

The (meth)acrylic resin may further have other structural units. Other structural units include, for example, lactone ring, polycarbonate, polyvinyl alcohol, cellulose acetate, polyester, polyarylate, polyimide, polyolefin, and the like, and structural units represented by general formula (1) described below. Can be mentioned. As a structural unit expressing negative birefringence, for example, a structural unit derived from a styrene-based monomer, a maleimide-based monomer, or the like, a structural unit of polymethyl methacrylate, and represented by the general formula (3) described below. And structural units.

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, it is a (meth)acrylic resin which has a glutarimide structure. When a (meth)acrylic resin having a glutarimide structure is used, as described above, a (meth)acrylic resin film having low moisture permeability and a low retardation and ultraviolet transmittance can be obtained. The (meth)acrylic resin having a glutarimide structure (hereinafter, also referred to as glutarimide resin) is, for example, Japanese Patent Laid-Open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560, and Japanese Patent Laid-Open No. 2006. -328329, JP 2006-328334, JP 2006-337491, JP 2006-337492, JP 2006-337493, JP 2006 -337569, Japanese Patent Laid-Open No. 2007-009182, and Japanese Patent Laid-Open No. 2009-161744. These descriptions are incorporated herein by reference.

Preferably, the glutarimide resin is 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, (meth )), also referred to as an acrylic acid ester unit).

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

If necessary, 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).

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

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

The glutarimide resin may contain only a single type as a glutarimide unit, or may contain a plurality of different types ^{of R 1} , R ² , and R ^{3 in the general formula (1).}

The glutarimide unit can be formed by imidizing the (meth)acrylic acid ester unit represented by the general formula (2). Further, the glutarimide unit may be an acid anhydride such as maleic anhydride, or a half ester of such an acid anhydride and a linear or branched alcohol having 1 to 20 carbon atoms; It can also be formed by imidizing α,β-ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, crotonic acid, fumaric acid, and citraconic acid. .

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

The glutarimide resin may contain only a single type as a (meth)acrylic acid ester unit, and even contain a plurality of different types ^{of R 4} , R ⁵ , and R ^{6 in the general formula (2).} good.

The glutarimide resin is an aromatic vinyl unit represented by the general formula (3), preferably styrene, α-methylstyrene, and the like, and more preferably styrene. 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 phase difference can be obtained.

The glutarimide resin may contain only a single type as an aromatic vinyl unit, and may contain a plurality of types different from ^{R 7} and R ^8.

It is preferable to change the content of the glutarimide unit in the glutarimide resin ^{depending on, for example, the structure of R 3.} The content of the glutarimide unit is preferably 1% by weight to 80% by weight, more preferably 1% by weight to 70% by weight, further preferably It is 1% by weight to 60% by weight, particularly preferably 1% by weight to 50% by weight. When the content of the glutarimide unit is within such a range, a low-phase difference (meth)acrylic resin film excellent in heat resistance can be obtained.

The content of the aromatic vinyl unit in the glutarimide resin may be appropriately set according to the purpose or desired properties. Depending on the application, the content of the aromatic vinyl unit may be zero. When the aromatic vinyl unit is contained, the content thereof is preferably 10% to 80% by weight, more preferably 20% to 80% by weight, based on the glutarimide unit of the glutarimide resin. , More preferably 20% by weight to 60% by weight, particularly preferably 20% by weight to 50% by weight. When the content of the aromatic vinyl unit is within such a range, a (meth)acrylic resin film excellent in low phase difference, heat resistance, and mechanical strength can be obtained.

In the glutarimide resin, if necessary, other structural units other than the glutarimide unit, the (meth)acrylic acid ester unit, and the aromatic vinyl unit may be further copolymerized. Other structural units include, for example, nitrile monomers such as acrylonitrile and methacrylonitrile, maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide. The structural unit to be constituted is mentioned. These other structural units may be directly copolymerized or graft copolymerized in the glutarimide resin.

The (meth)acrylic resin film may contain any appropriate additive depending on the purpose. Examples of the additive include antioxidants such as hindered phenol, phosphorus, and sulfur; Stabilizers such as light stabilizers, ultraviolet absorbers, weather stabilizers, and heat stabilizers; Reinforcing materials such as glass fiber and carbon fiber; Near-infrared absorbers; Flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; Antistatic agents such as anionic, cationic, and nonionic surfactants; Coloring agents such as inorganic pigments, organic pigments, and dyes; Organic or inorganic fillers; Resin modifiers; Plasticizer; Gulje(滑劑); And a retardation reducing agent. The type, combination, content, etc. of the additives to be contained may be appropriately set according to the purpose or desired properties.

Although it does not specifically limit as a manufacturing method of the said (meth)acrylic resin film, For example, (meth)acrylic resin, an ultraviolet absorber, and other polymers or additives, if necessary, are sufficiently mixed by any suitable mixing method. Then, after setting it as a thermoplastic resin composition in advance, this can be film-molded. Alternatively, a (meth)acrylic resin, an ultraviolet absorber, and, if necessary, other polymers or additives, etc. may be mixed into different solutions and then mixed to obtain a uniform liquid mixture, and then film-molded.

In order to prepare the thermoplastic resin composition, for example, after pre-blending the film raw material with an arbitrary suitable mixer such as an omni mixer, the obtained mixture is extruded and kneaded. In this case, the mixer used for extrusion and kneading is not particularly limited, and for example, any suitable mixer such as an extruder such as a single screw extruder and a twin screw extruder or a pressure kneader can be used.

As the method of forming the film, any suitable film forming method such as a solution casting method (solution casting method), a melt extrusion method, a calender method, and a compression molding method may be mentioned. The melt extrusion method is preferred. Since the melt extrusion method does not use a solvent, it is possible to reduce the manufacturing cost and the load on the global environment or work environment caused by the solvent.

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

In the case of forming a film by the T-die method, a T-die is attached to the tip of a known single-screw extruder or twin-screw extruder, and a film extruded in a film form is wound up to obtain a roll-shaped film. At this time, it is also possible to uniaxially stretch by appropriately adjusting the temperature of the take-up roll and applying stretching in the extrusion direction. In addition, simultaneous biaxial stretching and sequential biaxial stretching 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 is obtained. In the case of a stretched film, either a uniaxially stretched film or a biaxially stretched film may be used. In the case of a biaxially stretched film, either a simultaneous biaxially stretched film or a sequential biaxially stretched film may be used.

The stretching temperature is preferably in the vicinity of the glass transition temperature of the thermoplastic resin composition as a raw material for the film, specifically, preferably (glass transition temperature -30°C) to (glass transition temperature +30°C), more preferably It is within the range of (glass transition temperature -20°C) to (glass transition temperature +20°C). If the stretching temperature is less than (glass transition temperature -30° C.), there is a fear that the haze of the obtained film increases, or the film is torn or cracked, so that a predetermined draw ratio cannot be obtained. Conversely, when the stretching temperature exceeds (glass transition temperature +30° C.), there is a tendency that the thickness unevenness of the obtained film increases, or mechanical properties such as elongation, tear propagation strength, and oil fatigue resistance cannot be sufficiently improved. In addition, there is a tendency that the trouble that the film adheres to the roll tends to occur.

The draw ratio is preferably 1.1 to 3 times, more preferably 1.3 to 2.5 times. When the draw ratio is within such a range, mechanical properties such as elongation, tear propagation strength, and oil fatigue resistance of the film can be significantly improved. As a result, it is possible to produce a film having a small thickness non-uniformity, substantially zero birefringence (hence, a small phase difference), and a small haze.

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

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

(2nd protective film (12))

As the second protective film 12, the aforementioned resin film described as a film usable as the first protective film 11 may be used, or other resin films may be used. For example, a chain olefin resin film and a cellulose resin film are preferably used.

As a chain polyolefin resin, a polyethylene resin (a polyethylene resin which is a homopolymer of ethylene, a copolymer mainly composed of ethylene), a polypropylene resin (a polypropylene resin which is a homopolymer of propylene, a copolymer mainly composed of propylene), and In addition to the homopolymer of the same chain olefin, a copolymer containing two or more types of chain olefins may be mentioned.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and those in which some of the hydroxyl groups are modified with other substituents may be mentioned. Among these, cellulose triacetate (triacetyl cellulose) is particularly preferred.

The thickness of the second protective film 12 is usually 1 to 100 µm, but from the viewpoint of strength and handling properties, it is preferably 5 to 60 µm, more preferably 10 to 55 µm, and 15 to 50 µm. More preferable.

As described above, the second protective film 12 is on its outer surface (the surface opposite to the polarizer), 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. It may be provided with a surface treatment layer (coating layer). On the other hand, the thickness of the second protective film 12 includes the thickness of the surface treatment layer.

(3) adhesive layer

The protective film (the first protective film 11 and the second protective film 12) can be bonded to a polarizer through an adhesive layer, for example. The adhesive layer may be, for example, an adhesive layer or an adhesive layer. As the adhesive for forming the adhesive layer, a water-based adhesive, an active energy ray-curable adhesive or a thermosetting adhesive can be used, and preferably a water-based adhesive and an active energy ray-curable adhesive.

As the pressure-sensitive adhesive layer, what will be described later can be used.

Examples of the water-based adhesive include an adhesive composed of a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component urethane emulsion adhesive, and the like. Among them, a water-based adhesive comprising an aqueous polyvinyl alcohol-based resin solution is suitably used. Polyvinyl alcohol-based resins include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and polyvinyl alcohol-based copolymers obtained by saponifying a copolymer of vinyl acetate and other monomers copolymerizable thereto. It is possible to use a mixture or a modified polyvinyl alcohol-based polymer in which these hydroxyl groups are partially modified. The water-based adhesive may contain crosslinking agents such as aldehyde compounds (glyoxal, etc.), epoxy compounds, melamine compounds, methylol compounds, isocyanate compounds, amine compounds, and polyvalent metal salts.

In the case of using a water-based adhesive, after bonding a polarizer and a protective film, it is preferable to perform a drying step for removing water contained in the water-based adhesive. After the drying step, for example, a curing step of curing at a temperature of 20 to 45°C may be provided.

The active energy ray-curable adhesive is an adhesive containing a curable compound that is cured by irradiation with an active energy ray such as ultraviolet rays, visible light, electron rays, and X-rays, and is preferably an ultraviolet curable adhesive.

The curable compound may be a cationic polymerizable curable compound or a radical polymerizable curable compound. As a cationic polymerizable curable compound, for example, an epoxy compound (a compound having one or two or more epoxy groups in a molecule), an oxetane compound (a compound having one or two or more oxetane rings in a molecule), or these Combinations are mentioned. Examples of the radical polymerizable curable compound include a (meth)acrylic compound (a compound having one or two or more (meth)acryloyloxy groups in the molecule), other vinyl compounds having a radical polymerizable double bond, or Combinations of these are mentioned. A cationic polymerizable curable compound and a radically polymerizable curable compound may be used in combination. The active energy ray-curable adhesive usually further includes a cationic polymerization initiator and/or a radical polymerization initiator for initiating a curing reaction of the curable compound.

When bonding a polarizer and a protective film, in order to improve adhesiveness, you may apply surface activation treatment to at least one of these bonding surfaces. Examples of the surface activation treatment include dry treatment such as corona treatment, plasma treatment, discharge treatment (glo discharge treatment, etc.), flame treatment, ozone treatment, UV ozone treatment, and ionizing actinic ray treatment (ultraviolet treatment, electron beam treatment, etc.); And wet treatments such as ultrasonic treatment, saponification treatment, and anchor coat treatment using a solvent such as water or acetone. These surface activation treatments may be performed alone or in combination of two or more.

When the protective film is bonded to both surfaces of the polarizer, the adhesive for bonding these protective films may be the same type of adhesive or a different type of adhesive.

In the optical laminate of the present invention, a high-order phase difference film may be directly laminated on the polarizer 10 via the pressure-sensitive adhesive 14. In that case, the second protective film 12 can be omitted.

<High phase difference film (13)>

The optical laminate of the present invention has a high-order phase difference film 13 in order to ensure visibility beyond polarized sunglasses. The high-order phase difference film 13 contains a transparent thermoplastic resin film having birefringence. In this specification, the "high phase difference" means that the in-plane retardation value Re[550] at a wavelength of 550 nm is 3000 nm or more. The in-plane retardation value Re[550] of the high-order retardation film 13 at a wavelength of 550 nm is preferably 3000 nm or more, more preferably 5000 nm or more, and particularly preferably 7000 nm or more. The upper limit of the in-plane retardation value Re[550] of the high-order retardation film 13 is 30000 nm. By using such a film, color change according to the viewing angle when the liquid crystal display device is visually recognized through polarized sunglasses can be suppressed.

The high-order phase difference film 13 is obtained, for example, by stretching a thermoplastic resin film. Specific examples of the thermoplastic resin include polyolefin resins such as polyethylene and polypropylene; Cyclic polyolefin-based resins such as norbornene-based polymers; Polyester resins such as polyethylene terephthalate and polyethylene naphthalate; (Meth)acrylic acid-based resins such as (meth)acrylic acid and poly(meth)methyl acrylate; Cellulose ester resins such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; Vinyl alcohol-based resins such as polyvinyl alcohol and polyvinyl acetate; Polycarbonate resin; Polystyrene resin; Polyarylate resin; Polysulfone resin; Polyethersulfone resin; Polyamide resin; Polyimide resin; Polyether ketone resin; Polyphenylene sulfide resin; And polyphenylene oxide resins, and mixtures and copolymers thereof. From the viewpoint of availability and transparency, polyethylene terephthalate, cellulose ester, cyclic olefin resin, or polycarbonate is preferable.

A film having a desired retardation value may be obtained by performing uniaxial or biaxial hot stretching treatment on these thermoplastic resins. The draw ratio is usually 1.1 to 6 times, preferably 1.1 to 4 times.

In addition, a method of stretching in an oblique direction is also preferably used so that it can be produced by roll-to-roll. The method of stretching in an oblique direction is not particularly limited as long as the orientation axis can be continuously inclined at a desired angle, and a known stretching method can be employed. As such a stretching method, a method described in Japanese Unexamined Patent Application Publication No. 50-83482 or Japanese Unexamined Patent Application Publication No. 2-113920 can be mentioned, for example. In the case of imparting retardation to the 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-order phase difference film 13 and the absorption axis of the polarizer 10 is 40° to 50°, more preferably 42° to 48°, and particularly preferably about 45°. Thereby, when the liquid crystal display device is visually recognized over the polarized sunglasses, a decrease in front luminance can be suppressed.

The thickness of the high-order phase difference 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-order phase difference film 13 to 200 µm or less, curling of the optical laminate 100 can be suppressed, and problems such as air bubbles entering at the time of bonding to a liquid crystal display can be suppressed. The thickness of the high-order phase difference film 13 may be 10 µm or more, or 30 µm or more.

By installing the optical laminate 100 on the viewer side of the liquid crystal cell of the liquid crystal display device, a film having a higher phase difference is not required, and a decrease in visibility when the liquid crystal display device is visually recognized through polarized sunglasses can be suppressed. I can. Specifically, a decrease in front luminance and a change in hue (color shift) depending on the viewing angle can be suppressed. A hard coat layer or an anti-glare layer may be laminated to the high-level phase difference film 13 as necessary.

<Adhesive layer (14)>

The pressure-sensitive adhesive layer 14 laminates the polarizing plate 1 and the high-order phase difference film 13. The pressure-sensitive adhesive layer 14 can be composed of 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, and a polyvinyl ether-based resin. Among them, a pressure-sensitive adhesive composition comprising a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance and the like as a base polymer is suitable. The pressure-sensitive adhesive composition may be an active energy ray-curable type or a thermosetting type. The thickness of the pressure-sensitive adhesive layer is usually 3 to 30 µm, preferably 3 to 25 µm.

Examples of the (meth)acrylic resin (base polymer) used in the pressure-sensitive adhesive composition include (meth) butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Polymers or copolymers containing one or two or more types of acrylic acid esters as monomers are suitably used. It is preferable to copolymerize a polar monomer to the base polymer. Examples of the polar monomer include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, and glycy. Monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, and the like, such as diyl (meth)acrylate, may be mentioned.

The pressure-sensitive adhesive composition may contain only the base polymer, but usually further contains a crosslinking agent. Examples of the crosslinking agent include divalent or higher metal ions, which form a carboxylic acid metal salt between a carboxyl group; As a polyamine compound, what forms an amide bond between a carboxyl group; A polyepoxy compound or a polyol that forms an ester bond between a carboxyl group; As a polyisocyanate compound, what forms an amide bond between a carboxyl group is illustrated. Among them, polyisocyanate compounds are preferred.

The storage modulus of the pressure-sensitive adhesive layer 14 is preferably 0.001 to 0.350 MPa, more preferably 0.001 to 0.200 MPa, still more preferably 0.001 to 0.100 MPa, and 0.010 to 0.100 MPa at a frequency of 1 Hz and a temperature of 23°C. This is particularly preferred. If the storage modulus exceeds the above range, the relaxation of the shrinkage stress of the high-order phase difference film 13 in a high-temperature environment is not sufficient, causing distortion of the first protective film 11, thereby deteriorating normal visibility without polarized sunglasses. . In addition, if it is less than the above range, problems such as peeling may occur in a high temperature environment.

The thickness of the pressure-sensitive adhesive layer 14 is preferably 5 to 200 µm, more preferably 7 to 100 µm, still more preferably 8 to 80 µm, and particularly preferably 10 to 50 µm.

<display device>

The optical laminate of the present invention can be laminated to a liquid crystal cell via the pressure-sensitive adhesive 15 to constitute a liquid crystal display device. As the pressure-sensitive adhesive 15, those having the above-described composition, characteristics, and thickness described as the pressure-sensitive adhesive 14 may be used, and may be the same as or different from the pressure-sensitive adhesive layer 14.

<Front panel>

The optical laminated body 100 may be used with a front plate disposed on the viewing side surface thereof. The front plate may be laminated to the optical laminate 100 through an adhesive layer. As the adhesive layer, for example, the aforementioned pressure-sensitive adhesive layer or adhesive layer may be mentioned. 2 is a cross-sectional view showing the configuration of a laminate in which the front plate 4 is disposed on the surface of the optical laminate 100 on the viewing side. As shown in FIG. 2, the front plate 4 may be laminated on the high-order phase difference film 13 in the optical laminate 100 through the pressure-sensitive adhesive layer 16.

Examples of the front plate include glass and a resin film including a hard coat layer on at least one surface thereof. As the glass, for example, high transmission glass or tempered glass can be used. In particular, when using a thin transparent plate, glass subjected to chemical strengthening is preferable. The thickness of the glass can be, for example, 100 µm to 5 mm.

A front plate including a hard coat layer on at least one surface of the resin film may have a flexible property, not rigid like conventional glass. The thickness of the hard coat layer is not particularly limited, and may be, for example, 5 to 100 µm.

As the resin film, a cycloolefin derivative having a unit of a monomer containing a cycloolefin such as norbornene or a polycyclic norbornene monomer, cellulose (diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, isobutyl ester cellulose, Propionyl cellulose, butyryl cellulose, acetylpropionyl cellulose) ethylene-vinyl acetate copolymer, polycycloolefin, polyester, polystyrene, polyamide, polyetherimide, polyacryl, polyimide, polyamideimide, polyethersulfone, Polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, polyether ether ketone, polymethyl methacrylate, polyethylene terephthalate, polybutyl A film formed of a polymer such as len terephthalate, polyethylene naphthalate, polycarbonate, polyurethane, or epoxy may be used. As a resin film, an unstretched, uniaxial or biaxially stretched film can be used. These polymers may be used alone or in combination of two or more. As a resin film, a polyamideimide film or polyimide film excellent in transparency and heat resistance, a uniaxial or biaxially stretched polyester film, a cycloolefin derivative film excellent in transparency and heat resistance and capable of responding to the enlargement of the film, polymethyl A methacrylate film and a triacetyl cellulose and isobutyl ester cellulose film having no transparency and optically anisotropy are preferred. The thickness of the resin film may be 5 to 200 µm, preferably 20 to 100 µm.

The hard coat layer can be formed by curing a hard coat composition containing a reactive material that forms a crosslinked structure by irradiation with light or thermal energy. The hard coat layer can be formed by curing a hard coat composition containing a photocurable (meth)acrylate monomer, or an oligomer and a photocurable epoxy monomer, or an oligomer at the same time. The photocurable (meth)acrylate monomer may include at least one selected from the group consisting of epoxy (meth)acrylate, urethane (meth)acrylate, and polyester (meth)acrylate. The epoxy (meth)acrylate can be obtained by reacting an epoxy compound with a carboxylic acid having a (meth)acryloyl group.

The hard coat composition may further include one or more selected from the group consisting of a solvent, a photoinitiator, and an additive. The additive may include one or more selected from the group consisting of inorganic nanoparticles, leveling agents, and stabilizers. In addition, as each component generally used in the art, for example, antioxidants, UV absorbers, surfactants, It may further include a lubricant, an antifouling agent, and the like.

[Example]

Hereinafter, the present invention will be described in more detail by showing examples, but the present invention is not limited by these examples. In the examples, the parts and% indicating the content to the amount used are based on weight unless otherwise specified. In addition, the measurement of each physical property in the following examples was performed by the following method.

[How to measure]

(1) Measuring method of film thickness

It was measured using a digital micrometer MH-15M manufactured by Nikon Co., Ltd.

(2) Measurement method of phase difference value

It measured using the phase difference measuring apparatus KOBRA-WPR (Oji Keisoku Kiki Co., Ltd. product). Unless otherwise stated, a retardation value means a value at a wavelength of 550 nm.

(3) How to measure the photoelastic coefficient

Using a phase difference measuring device KOBRA-WPR (manufactured by Oji Keisoku Kiki Co., Ltd.), the sample (size 1.5 cm x 6 cm) was sandwiched between both ends and stress (0.5 N to 8 N) was applied, while the sample The central phase difference value (23° C./wavelength 550 nm) was measured, and calculated from the slope of the function of the stress and the phase difference value.

(4) Method of measuring storage modulus:

The storage modulus (G') of the pressure-sensitive adhesive layer was measured according to the following (I) to (III).

(I) Take out two samples of 25±1 mg each from the pressure-sensitive adhesive layer, and mold each into approximately bead shape.

(II) The two samples obtained in the above (I) were attached to the upper and lower surfaces of the I-type jig, and both upper and lower surfaces were sandwiched between the L-type jig. The configuration of the measurement sample is an L-type jig/adhesive/I-type jig/adhesive/L-type jig.

(III) The storage elastic modulus (G') of the sample thus prepared was measured using a dynamic viscoelasticity measuring device [DVA-220, manufactured by Keisoku Seiko Co., Ltd.] at a temperature of 23°C, a frequency of 1 Hz, and an initial distortion. It was measured under the condition of 1 N.

(5) How to measure luminance:

It was measured using a spectroradiometer SR-UL1 manufactured by Topcon Co., Ltd. On the other hand, the measurement was performed in a 2° field of view.

[Production Example 1] Preparation of polarizer 1

A 75 μm-thick polyvinyl alcohol film composed of polyvinyl alcohol having an average polymerization degree of about 2,400 and a saponification degree of 99.9 mol% or more was uniaxially stretched by about 5 times in a dry manner, and while maintaining a tension state, pure water at 60°C. ) For 1 minute, and then immersed in an aqueous solution having a weight ratio of 0.05/5/100 of iodine/potassium iodide/water at 28°C for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 at 72° C. for 300 seconds. Subsequently, after washing with pure water at 26° C. for 20 seconds, it was dried at 65° C. to obtain a polarizer 1 having a thickness of 28 μm in which iodine was adsorbed and oriented in polyvinyl alcohol.

[Production Example 2] Preparation of polarizer 2

A polyvinyl alcohol film with a thickness of 50 μm made of polyvinyl alcohol having an average polymerization degree of about 2,400 and a saponification degree of 99.9 mol% or more was uniaxially stretched by about 5 times in a dry manner, and while maintaining a tension state, in pure water at 60° C. for 1 minute After immersion, it was immersed in an aqueous solution having a weight ratio of iodine/potassium iodide/water of 0.05/5/100 at 28°C for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 at 72° C. for 300 seconds. Subsequently, after washing with pure water at 26° C. for 20 seconds, it was dried at 65° C. to obtain a polarizer 2 having a thickness of 18 μm in which iodine was adsorbed and oriented in polyvinyl alcohol.

[Preparation of protective film]

Protective Film A:

A triacetyl cellulose film having a thickness of 40 µm [trade name "KC4UYW" manufactured by Konica Minolta Opto Corporation].

Protective film B:

100 parts by weight of the imidized MS resin pellets (weight average molecular weight: 105,000) described in Preparation Example 1 of Japanese Patent Laid-Open No. 2010-284840 were dried at 100.5 kPa and 100°C for 12 hours, and a die temperature of 270°C with a single screw extruder It was extruded from a T-die and molded into a film shape (thickness 160 μm). Further, the film was stretched in an atmosphere at 150° C. in the conveying direction (thickness 80 μm), and then stretched in an atmosphere at 150° C. in a direction orthogonal to the film conveying direction, and a protective film B having a thickness of 40 μm ((Met )Acrylic resin film) was obtained. The in-plane retardation value Re of the protective film B at a wavelength of 550 nm was 0.5 nm, and the retardation value Rth in the thickness direction was 0.82 nm. The photoelastic coefficient of the obtained film was 2.0×10 ^-12 Pa ^-1 .

Protective film C:

Regarding the protective film B, the imidized MS resin pellet was changed to a transparent pellet of the acrylic copolymer described in Comparative Example 1 of Japanese Patent Laid-Open No. 2008-191426, except that the same was carried out, and the protective film C ((Met )Acrylic resin film) was obtained. The in-plane retardation value Re of the protective film C at a wavelength of 550 nm was 0.8 nm, and the retardation value Rth in the thickness direction was 1.02 nm. The photoelastic coefficient of the obtained film was 2.1×10 ^-12 Pa ^-1 .

Protective film D:

Regarding the protective film B, the imidized MS resin pellet was changed to a transparent pellet of the acrylic copolymer described in Example 1 of Japanese Patent Application Laid-Open No. 2008-191426, except that the same was carried out, and the protective film D ((Met )Acrylic resin film) was obtained. The in-plane retardation value Re of the protective film D at a wavelength of 550 nm was 0.4 nm, and the retardation value Rth in the thickness direction was 0.73 nm. The photoelastic coefficient of the obtained film was 1.3×10 ^-12 Pa ^-1 .

Protective film E:

A 23 µm-thick norbornene-based resin film [trade name "ZF14-023" manufactured by Nippon Xeon Co., Ltd.]. The in-plane retardation value Re of the protective film E at a wavelength of 550 nm was 0.7 nm, and the retardation value Rth in the thickness direction was 4.2 nm. The photoelastic coefficient was 1.6×10 ^-12 Pa ^-1 .

Protective film F:

With respect to the 1/4 wave plate A1 stretched in the oblique direction described in Production Example 3 of International Publication 2017/094485, except that the stretching direction was changed to the longitudinal direction, a roll-shaped 1/4 wave plate was produced in the same manner. The thickness of this quarter wave plate (protective film F) was 35 µm, the slow axis was in the longitudinal direction, and the in-plane retardation value Re was 136 nm. In addition, the photoelastic coefficient of the obtained film was 4.0×10 ^-12 Pa ^-1 .

Protective film G:

With respect to the 1/4 wave plate B4 stretched in the oblique direction described in Production Example 5 of International Publication 2017/094485, except for changing the stretching direction to the longitudinal direction, a roll-shaped 1/4 wave plate was produced in the same manner. The thickness of this quarter wave plate (protective film G) was 47 µm, the slow axis was in the longitudinal direction, and the in-plane retardation value Re was 140 nm. In addition, the photoelastic coefficient of the obtained film was 6.0 × 10 ^-12 Pa ^-1 .

Protective film H:

A triacetyl cellulose film having a thickness of 20 µm [trade name "ZRG20SL" manufactured by Fuji Film Co., Ltd.]. The in-plane retardation value Re of the protective film H at a wavelength of 550 nm was 1.1 nm, and the retardation value Rth in the thickness direction was 1.3 nm. The photoelastic coefficient was 9.4×10 ^-12 Pa ^-1 .

[Preparation of adhesive]

50 g of a modified PVA-based resin containing an acetoacetyl group (manufactured by Mitsubishi Chemical Co., Ltd.: Kosenex Z-410) was dissolved in 950 g of pure water, heated at 90° C. for 2 hours, then cooled to room temperature, and the PVA solution A was Got it.

Subsequently, the PVA solution A, maleic acid, glyoxal, and pure water were blended so that each compound had the following concentration to prepare a PVA-based adhesive.

PVA concentration 3.0% by weight

Maleic acid 0.01% by weight

Glyoxal 0.15% by weight

[Preparation of high-phase difference film]

Toyobo Corporation Cosmoshine Super Retardation Film (SRF) (thickness 80 µm) was used. The in-plane retardation value Re[550] was 8400 nm.

[Preparation of adhesive]

Adhesive A: A commercially available sheet-like acrylic adhesive having a thickness of 15 µm (storage modulus of 0.06 MPa)

Adhesive B: A commercially available sheet-like acrylic adhesive having a thickness of 25 µm (storage elastic modulus 0.06 MPa)

[Example 1]

A protective film A (second protective film) was applied to one side of the polarizer 1 obtained in Production Example 1, and a protective film A (second protective film) was applied to the other side of the polarizer, and the protective film B (first protective film) was bonded. Made it. Then, it dried and obtained the polarizing plate A. On the other hand, at the time of bonding these materials, corona treatment was performed on the bonding surfaces of each material.

A pressure-sensitive adhesive A was bonded to one side of the high-order phase difference film. On the other hand, at the time of bonding these materials, corona treatment was performed on the bonding surfaces of each material.

Optical laminate A was prepared by bonding the protective film A side of the polarizing plate prepared in this way and the adhesive side of the high-order difference film so that the angle (θ) between the absorption axis of the polarizer and the slow axis of the high-order difference film was 45°. I did. On the other hand, at the time of bonding these materials, corona treatment was performed on the bonding surfaces of each material.

Finally, the adhesive B was bonded to the protective film B side of the obtained optical laminated body A. On the other hand, at the time of bonding these materials, corona treatment was performed on the bonding surfaces of each material.

[Examples 2 to 8 and Comparative Example 1]

With respect to the optical laminate A prepared as Example 1, the optical laminate B to which the pressure-sensitive adhesive B was bonded was carried out in the same manner as in Example 1, except that the first protective film and/or the polarizer was used as described in Table 1. I (Examples 2 to 8 and Comparative Example 1) was prepared.

[Reference Example 1]

The optical laminate J with the pressure-sensitive adhesive B in the same manner as for the optical laminate A with the pressure-sensitive adhesive B of Example 1, except that the angle between the absorption axis of the polarizing plate and the slow axis of the high-order phase difference film is 90°. Example 1) was produced.

[Reference Example 2]

An adhesive A was applied to one side of the polarizer obtained in Production Example 1, a protective film A was applied, and an adhesive A was applied to the other side of the polarizer to bond the protective film H, respectively. Then, it dried and obtained the polarizing plate K. On the other hand, at the time of bonding these materials, corona treatment was performed on the bonding surfaces of each material.

Adhesive B was bonded to the protective film H surface of the obtained optical laminated body K, and the back side polarizing plate with an adhesive layer was obtained. On the other hand, at the time of bonding these materials, corona treatment was performed on the bonding surfaces of each material.

(Production of sample A for evaluation)

The optical laminated body A with the pressure-sensitive adhesive B was cut into a size of 20 mm×20 mm, and bonded to an alkali-free glass having a thickness of 0.7 mm and 30 mm×30 mm through the pressure-sensitive adhesive B. The optical laminate K with adhesive B (without bonding the high-phase difference film) was cut into a size of 20 mm×20 mm, and the absorption axes of the polarizing plate were crossed on the side where the optical laminate A of the alkali-free glass was not bonded. In order to become Nicole, the optical layered product K was bonded through the pressure-sensitive adhesive B to prepare a sample A for evaluation.

(Production of samples B to K for evaluation)

About sample A for evaluation, except having changed optical laminated body A to optical laminated bodies B-K, respectively, it carried out similarly, and produced samples B-K for evaluation.

(Evaluation of black luminance change)

The side to which the optical laminate K of the evaluation samples A to K prepared above was bonded was placed on the irradiation surface of a white backlight module having a luminance of 20000 ㏅/m 2, and the luminance was measured from the evaluation sample (high phase difference film) side (black After luminance 1), after storing for 240 hours in a heating environment at a temperature of 95°C, after cooling to room temperature, the luminance was measured again (black luminance 2), and the rate of change (%) of black luminance 2 relative to black luminance 1 was calculated, and black It was set as the luminance change. Specifically,

Black luminance change (%)={|black luminance 2-black luminance 1|/black luminance 1}×100

The black luminance change was determined by. Table 1 shows the evaluation results.

From the results shown in Table 1, the following are clear.

1. The optical laminate in which the high-order phase difference film is bonded at 45° may increase in black luminance after the high-temperature durability test, but it is durable at high temperature by using the first protective film with a ^{photoelastic coefficient of 8.0×10 -12} Pa ^{-1 or less.} The increase in black luminance after the test can be suppressed.

2. In addition to the above, the increase in black luminance after the high-temperature endurance test can be further suppressed by making the thickness of the polarizer 20 µm or less (the polarizer 2 is employed).

1: polarizer 4: front plate
10: polarizer 11: first protective film
12: second protective film 13: high-order car film
14, 15, 16: pressure-sensitive adhesive layer 100: optical laminate

Claims (8)

A polarizing plate and a high-order difference film are provided in this order,
The polarizing plate has a polarizer and a protective film laminated on a surface of the polarizer opposite to the high-order phase difference film side,
The in-plane retardation value of the high-order retardation film is 3000 to 30000 nm,
The angle formed by the slow axis of the high-order phase difference film and the absorption axis of the polarizer is 40° to 50°,
An optical laminate having an absolute value of the photoelastic coefficient of the protective film of 8×10 ^-12 Pa ^{-1 or less.} The optical laminate according to claim 1, wherein the protective film contains at least one selected from the group consisting of (meth)acrylic resins, polystyrene resins, and maleimide resins. The optical laminate according to claim 1, wherein the protective film contains a cyclic olefin resin. The optical laminate according to any one of claims 1 to 3, wherein the protective film has an in-plane retardation value of 10 nm or less. The optical laminate according to any one of claims 1 to 3, wherein the protective film has an in-plane retardation value of 50 nm to 300 nm. The optical laminate according to any one of claims 1 to 5, wherein the high-order phase difference film has a thickness of 200 µm or less. The optical laminate according to any one of claims 1 to 6, wherein the high-order phase difference film and the polarizing plate are laminated through an adhesive layer. A display device in which the optical laminate according to any one of claims 1 to 7 is laminated on a display element.

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