TW202144818A - Polarizing plate and polarizing plate with retardation layer - Google Patents

Abstract

The present invention provides a polarizing plate having excellent durability despite being extremely thin. A polarizing plate according to the present invention has a polarizer, and a protective layer that is disposed on one side of the polarizer. The protective layer is formed from a cured product of an epoxy resin having a biphenyl skeleton. In one embodiment, the thickness of the protective layer is 10 [mu]m or less.

Description

Polarizing plate and polarizing plate with retardation layer

The present invention relates to a polarizing plate and a polarizing plate with retardation layer.

In an image display device (eg, a liquid crystal display device, an organic EL display device), a polarizing plate is usually disposed on at least one side of the display unit due to its image forming method. In recent years, with the development of thinning and flexibility of image display devices, there is also a strong demand for thinning polarizers. However, the thinner the polarizing plate is, the more serious the problem of durability is that the optical properties are degraded in a heated and humidified environment. prior art literature Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2015-210474

The problem to be solved by the invention The present invention was made in order to solve the above-mentioned conventional problems, and its main object is to provide a polarizing plate with excellent durability and a polarizing plate with retardation layer even if it is very thin.

means of solving problems The polarizing plate of the present invention has a polarizer and a protective layer disposed on one side of the polarizer. The protective layer is composed of a cured product of epoxy resin having a biphenyl skeleton. In one Embodiment, the said hardened|cured material is a cationic polymerization hardened|cured material. In one embodiment, the protective layer further contains oxetane resin. In one embodiment, the thickness of the protective layer is 10 µm or less. In one embodiment, the iodine adsorption amount of the protective layer is 10% by weight or less. In one embodiment, the softening temperature of the protective layer is 100°C or higher. In one embodiment, the total thickness of the polarizing plate is 10 µm or less. Another aspect of the present invention provides a polarizing plate with retardation layer. The polarizing plate with retardation layer has a retardation layer on the surface of the polarizing plate on which the protective layer is not arranged.

Invention effect According to the present invention, a polarizing plate excellent in durability can be obtained even if it is very thin by forming the protective layer arranged on the polarizer with a cured product of an epoxy resin having a biphenyl skeleton.

(Definition of Terms and Symbols) Definitions of terms and symbols in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index reaches the maximum (that is, the slow axis direction), "ny" is the refractive index in the in-plane direction orthogonal to the slow axis (that is, the fast axis direction), and " nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane retardation measured at 23°C with light having a wavelength of λnm. For example, "Re(550)" is an in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (film) is d(nm). (3) Phase difference in thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) can be obtained by the formula: Rth(λ)=(nx-nz)×d when the thickness of the layer (film) is d(nm). (4) Nz coefficient The Nz coefficient can be obtained by Nz=Rth/Re. (5) Angle When referring to an angle in this specification, the angle includes both a clockwise direction and a counterclockwise direction with respect to the reference direction. Thus, for example, "45°" means ±45°.

A. Outline of polarizer FIG. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. The polarizing plate 100 of the illustrated example has a polarizer 10 and a protective layer 20 disposed on one side of the polarizer 10 . The thickness of the polarizer 10 is preferably 8 µm or less. Another protective layer (not shown) can also be disposed on the opposite side of the polarizer 10 to the protective layer 20 according to requirements. When the polarizing plate 100 is applied to a liquid crystal display device, it may be arranged on the viewing side of the display unit, or may be arranged on the opposite side (back side) to the viewing side. In either case, the protective layer 20 may be arranged on the display unit side, or may be arranged on the opposite side (outer side) of the display unit. In one embodiment, the polarizing plate 100 is disposed on the viewing side of the display unit (resulting in an image display device), and the protective layer 20 is disposed on the viewing side (the side opposite to the display unit). The polarizing plate can be elongated or thin. When the polarizer is elongated, it should be wound into a roll to make a polarizer coil.

Representatively, the polarizing plate has an adhesive layer as the outermost layer of one side (representatively, the side opposite to the protective layer 20 of the polarizer 10 ), and can be attached to the display unit. The surface protection film and/or the carrier film can be temporarily adhered to the polarizing plate in a peelable manner as required to reinforce and/or support the polarizing plate. When the polarizing plate includes an adhesive layer, the surface of the adhesive layer is temporarily adhered with a separation piece in a releasable manner, so as to protect the adhesive layer before actual use, and the polarizing plate can be rolled.

In the embodiment of the present invention, the protective layer 20 is formed of a cured product of an epoxy resin having a biphenyl skeleton. With the above configuration, the protective layer can be made very thin (for example, 10 µm or less). In addition, the protective layer can be directly formed on the polarizer (ie, without passing through the adhesive layer or the adhesive layer). According to the embodiment of the present invention, as described above, the polarizer and the protective layer are very thin, and the adhesive layer or the adhesive layer can be omitted, so that the total thickness of the polarizing plate can be extremely thin. And the adhesion between the polarizer and the protective layer is also good. The total thickness of the polarizing plate is, for example, 40 µm or less, preferably 30 µm or less, more preferably 20 µm or less, more preferably 10 µm or less, and particularly preferably 7 µm or less. The total thickness of the polarizing plate may be, for example, 4 µm or more.

In addition, by forming the protective layer with a cured product of an epoxy resin having a biphenyl skeleton, a polarizing plate excellent in durability can be realized even if it is very thin. Specifically, it is possible to realize a polarizing plate in which the decrease in optical properties is suppressed even in a heated and humidified environment. After the polarizing plate was placed in an environment of 85° C. and 85% RH for 120 hours, the change amount ΔTs of the single transmittance Ts and the change amount ΔP of the polarization degree P were each very small. The monomer transmittance Ts is measured using, for example, an ultraviolet-visible light spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). The degree of polarization P is calculated by the following formula from the single transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance (Tc) measured using an ultraviolet-visible light spectrophotometer. Degree of polarization (P)(%)={(Tp-Tc)/(Tp+Tc)} ^{1 /2} ×100 In addition, the above-mentioned Ts, Tp and Tc are measured by the 2-degree field of view (C light source) of JIS Z 8701 And the Y value obtained by the visual sensitivity correction. In addition, Ts and P are substantially the characteristics of a polarizer. Each of ΔTs and ΔP can be obtained by the following equation. ΔTs(%)=Ts _{120 -Ts 0} ΔP(%)=P ₁₂₀ -P ₀ Here, Ts ₀ is the transmittance of the monomer before placing (initial), Ts ₁₂₀ is the transmittance of the monomer after placing, P ₀ is the polarization degree before (initial) placement, and P ₁₂₀ is the polarization degree after placement. ΔTs is preferably 3.0% or less, more preferably 2.7% or less, and more preferably 2.4% or less. ΔP should be -0.5%~0%, preferably -0.3%~0%, more preferably -0.1%~0%.

In the embodiment of the present invention, the thickness of the polarizing plate can be extremely thin. Therefore, it can be suitably applied to a flexible image display device. Preferably, the image display device has a curved shape (substantially a curved display), and/or is flexible or bendable. Specific examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (eg, an organic EL display device and an inorganic EL display device). Of course, the above description does not prevent the polarizing plate of the present invention from being applied to general image display devices.

The polarizer and the protective layer are described in detail below.

B. Polarizer Any suitable polarizer can be used as the polarizer. The polarizer can be typically produced by using a laminate of two or more layers. The manufacturing method of the polarizer is explained in the section D after the manufacturing method of the polarizing plate.

The thickness of the polarizer is preferably 1µm~8µm, preferably 1µm~7µm, and more preferably 2µm~5µm.

The content of boric acid in the polarizer is preferably 10% by weight or more, more preferably 13% by weight to 25% by weight. As long as the boric acid content of the polarizer is within the above-mentioned range, the easiness of adjusting the curling during lamination can be well maintained, and the curling during heating can be suppressed, and the curling during heating can be improved at the same time due to the synergistic effect with the iodine content described later. Appearance durability. The boric acid content can be calculated by the amount of boric acid per unit weight of the polarizer by the neutralization method using the following formula, for example. [Mathematical formula 1]

The iodine content of the polarizer is preferably 2 wt % or more, more preferably 2 wt % to 10 wt %. As long as the iodine content of the polarizer is within the above-mentioned range, the easiness of adjusting the curling during lamination can be well maintained, the curling during heating can be suppressed, and the curling during heating can be improved at the same time due to the synergistic effect of the above-mentioned boric acid content. Appearance durability. The "iodine content" in this specification means the total amount of iodine contained in the polarizer (PVA-based resin film). More specifically, iodine exists in the polarizer in the form of iodide ions (I ⁻ ), iodine molecules (I ₂ ), polyiodide ions (I ₃ ⁻ , I ₅ ⁻ ), etc., and the iodine content in this specification means Contains the amount of iodine in all such forms. The iodine content can be calculated by a calibration curve method such as X-ray fluorescence analysis. In addition, polyiodide ions exist in a state in which a PVA-iodine complex is formed in the polarizer. By forming the complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, the complex of PVA and triiodide ion (PVA·I ₃ ^- ) has an absorption peak near 470 nm, while the complex of PVA and pentaiodide ion (PVA·I ₅ ^- ) has an absorption peak near 600 nm absorbance peak. As a result, polyiodide ions can absorb light in a wide range of visible light according to their morphology. On the other hand, iodide ion (I ⁻ ) has an absorption peak around 230 nm, which is not substantially related to the absorption of visible light. Therefore, the polyiodide ions existing in the complex state with PVA are mainly related to the absorption performance of the polarizer.

The polarizer should exhibit absorption dichroism at any wavelength from 380nm to 780nm. The single transmittance Ts of the polarizer is preferably 40% to 48%, preferably 41% to 46%. The degree of polarization P of the polarizer is preferably above 97.0%, preferably above 99.0%, and even more preferably above 99.9%.

C. Protective layer The protective layer is formed of a cured product of an epoxy resin having a biphenyl skeleton as described above. The durability of the protective layer can be further enhanced by including the epoxy resin with biphenyl skeleton in the protective layer. The protective layer is preferably a cationic polymerized hardened product of an epoxy resin having a biphenyl skeleton. By being a cationic polymer cured product, a polarizing plate excellent in durability can be obtained even if it is very thin. Hereinafter, the constituent components of the protective layer will be specifically described, and then the characteristics of the protective layer will be described.

(式中，R¹ ~R⁸ 分別獨立表示氫原子、碳數1~12之直鏈狀或支鏈狀之取代或非取代的烴基、或鹵素元素)。C-1. Epoxy resin having biphenyl skeleton In one embodiment, the epoxy resin having biphenyl skeleton includes epoxy resins having the following structures. The epoxy resin which has a biphenyl skeleton may be used only by 1 type, and may be used in combination of 2 or more types. [Chemical formula 1]

(In the formula, R ¹ to R ⁸ each independently represent a hydrogen atom, a linear or branched substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms, or a halogen element).

R ¹ to R ⁸ each independently represent a hydrogen atom, a linear or branched substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms, or a halogen element. The linear or branched substituted or unsubstituted hydrocarbon groups of carbon number 1-12 include, for example: methyl, ethyl, n-propyl, isopropyl, n-butyl, tertiary butyl, tertiary butyl base, n-pentyl, isopentyl, neopentyl, tertiary pentyl, cyclopentyl, n-hexyl, isohexyl, cyclohexyl, n-heptyl, cycloheptyl, methylcyclohexyl, n-octyl, cyclohexyl Octyl, n-nonyl, 3,3,5-trimethylcyclohexyl, n-decyl, cyclodecyl, n-undecyl, n-dodecyl, cyclododecyl, phenyl, benzyl, methyl Benzyl, dimethylbenzyl, trimethylbenzyl, naphthylmethyl, phenethyl, 2-phenylisopropyl, etc. The linear or branched substituted or unsubstituted hydrocarbon group with 1 to 12 carbon atoms is preferably an alkyl group with 1 to 4 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl and the like. The halogen element includes fluorine and bromine.

(式中，R¹ ~R⁸ 如上述，n表示0~6之整數)。In one embodiment, the epoxy resin having a biphenyl skeleton is an epoxy resin represented by the following formula. [Chemical formula 2]

(wherein, R ¹ to R ^{8 are} as described above, and n represents an integer of 0 to 6).

In one embodiment, the epoxy resin having a biphenyl skeleton is an epoxy resin having only a biphenyl skeleton. By using an epoxy resin having only a biphenyl skeleton, the durability of the resulting protective layer can be further enhanced.

In one embodiment, the epoxy resin having a biphenyl skeleton may contain chemical structures other than the biphenyl skeleton. As a chemical structure other than a biphenyl skeleton, a bisphenol skeleton, an alicyclic structure, an aromatic ring structure, etc. are mentioned, for example. In this embodiment, the ratio (molar ratio) of chemical structures other than the biphenyl skeleton is preferably smaller than that of the biphenyl skeleton.

The epoxy resin which has a biphenyl skeleton can also use a commercial item. Commercially available products include, for example, the Mitsubishi Chemical Co. product, trade names: jER YX4000, jER YX4000H, jER YL6121, jER YL664, jER YL6677, jER YL6810, jER YL7399, and the like.

The glass transition temperature (Tg) of the epoxy resin having a biphenyl skeleton is preferably 100°C or higher. As a result, the softening temperature of the protective layer is almost 100°C or higher. As long as the Tg of the epoxy resin having a biphenyl skeleton is 100° C. or higher, the polarizing plate including the obtained protective layer tends to be excellent in durability. The Tg of the epoxy resin having a biphenyl skeleton is preferably 110°C or higher, more preferably 120°C or higher, and more preferably 125°C or higher. On the other hand, the Tg of the epoxy resin having a biphenyl skeleton is preferably 300°C or lower, more preferably 250°C or lower, more preferably 200°C or lower, and particularly preferably 160°C or lower. As long as the Tg of the epoxy resin having a biphenyl skeleton is within the above range, the moldability and workability are good.

The epoxy equivalent of the epoxy resin having a biphenyl skeleton is preferably 100 g/equivalent or more, more preferably 150 g/equivalent or more, and more preferably 200 g/equivalent or more. In addition, the epoxy equivalent of the epoxy resin having a biphenyl skeleton is preferably 3000 g/equivalent or less, more preferably 2500 g/equivalent or less, and more preferably 2000 g/equivalent or less. When the epoxy equivalent having a biphenyl skeleton is in the above-mentioned range, a more stable protective layer (a protective layer with less residual monomer and sufficiently hardened) can be obtained. In addition, in this specification, "epoxy equivalent" means "the mass of the epoxy resin containing 1 equivalent of an epoxy group", and it can measure based on JISK7236.

In the embodiment of the present invention, an epoxy resin having a biphenyl skeleton and other resins may be used in combination. That is, a blend of an epoxy resin having a biphenyl skeleton and other resins may be used for forming the protective layer. Other resins include, for example, styrene-based resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polystyrene, polyphenylene ether, polyacetal, and polyimide , thermoplastic resins such as polyetherimide, hardening resins such as acrylic resins and oxetane resins. Preferably, an acrylic resin and an oxetane-based resin can be used. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose, desired properties of the obtained film, and the like. For example, a styrene resin can be used together as a retardation control agent.

As the acrylic resin, any appropriate acrylic resin can be used. For example, the (meth)acrylic compound includes a (meth)acrylic compound having one (meth)acryloyl group in the molecule (hereinafter also referred to as "monofunctional (meth)acrylic compound"), (Meth)acrylic-type compound (henceforth "polyfunctional (meth)acrylic-type compound") of two or more (meth)acryloyl groups. These (meth)acrylic compounds may be used alone or in combination of two or more. About these acrylic resins, for example, it describes in Unexamined-Japanese-Patent No. 2019-168500. In this specification, the entire description of this gazette is incorporated by reference.

As the oxetane resin, any appropriate compound having one or more oxetane groups in the molecule can be used. For example: 3-ethyl-3-hydroxymethyl oxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(benzene Oxymethyl)oxetane, 3-ethyl-3-(cyclohexyloxymethyl)oxetane, 3-ethyl-3-(oxiranylmethoxy)oxetane Butane, (3-ethyloxetan-3-yl)methyl (meth)acrylate and other oxetane compounds with one oxetanyl group in the molecule; 3-ethyl-3 {[(3-Ethyloxetan-3-yl)methoxy]methyl}oxetane, 1,4-bis[(3-ethyl-3-oxetanyl) Methoxymethyl]benzene, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl, etc. having 2 or more oxetanyl groups in the molecule oxetane compounds, etc. These oxetane resins may be used alone or in combination of two or more.

It is suitable to use 3-ethyl-3-hydroxymethyl oxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 3-ethyl-3 -(2-Ethylhexyloxymethyl)oxetane, 3-Ethane-3-(oxiranylmethoxy)oxetane, (3-ethyl)(meth)acrylic acid oxetan-3-yl) methyl ester, 3-ethane-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, etc. These oxetane resins can be easily obtained, and have good diluting properties (low viscosity) and good compatibility.

In one embodiment, from the viewpoint of compatibility or adhesiveness, it is preferable to use an oxetane resin having a molecular weight of 500 or less and a liquid state at room temperature (25° C.). In one embodiment, an oxetane compound containing two or more oxetanyl groups in the molecule, one oxetanyl group and one (meth)acryloyl group in the molecule, or An oxetane compound with one epoxy group, preferably 3-ethane-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane , 3-ethyl-3-(oxiranylmethoxy)oxetane, (3-ethyloxetan-3-yl)methyl (meth)acrylate. By using these oxetane resins, the hardenability and durability of the protective layer can be improved.

A commercially available thing can also be used for oxetane resin. Specifically, ARON OXETANE OXT-101, ARON OXETANE OXT-121, ARON OXETANE OXT-212, and ARON OXETANE OXT-221 (all manufactured by Toagosei Corporation) can be used. Preferably, ARON OXETANE OXT-101 and ARON OXETANE OXT-221 can be used.

When an epoxy resin having a biphenyl skeleton and other resins are used together, the content of the epoxy resin having a biphenyl skeleton in the blend of the epoxy resin having a biphenyl skeleton and other resins is preferably 50% by weight to 100% by weight , preferably 60% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, and particularly preferably 80% by weight to 100% by weight. When the content is less than 50% by weight, the heat resistance of the protective layer and the sufficient adhesion to the polarizer may not be obtained.

When an epoxy resin having a biphenyl skeleton and an oxetane resin are used in combination, the oxetane resin is 100 parts by weight of the total amount of the epoxy resin having a biphenyl skeleton and the oxetane resin. The content is preferably 1 to 50 parts by weight, preferably 5 to 45 parts by weight, more preferably 10 to 40 parts by weight. By setting it as the said range, sclerosis|hardenability can be improved, and the adhesiveness of a protective layer and a polarizer can also be improved.

C-2. Hardener The epoxy resin which has a biphenyl skeleton can be hardened|cured by using together with any suitable hardening|curing agent. As the hardener, any suitable hardener that can harden the epoxy resin can be used. In one embodiment, the hardener contains a photocationic polymerization initiator. By including a photocationic polymerization initiator, a cationic polymerization cured product, that is, a protective layer can be formed. As a photocationic polymerization initiator, any appropriate compound which can harden the epoxy resin which has a biphenyl skeleton by light irradiation, such as an ultraviolet-ray, can be used. The photocationic polymerization initiator may be used alone or in combination of two or more.

Examples of the photocationic polymerization initiator include triphenyl perylene hexafluoroantimonate, triphenyl perylene hexafluorophosphate, p-(phenylthio)phenyldiphenyl perylene hexafluoroantimonate, p-(phenylthio) ) Phenyl diphenyl hexafluorophosphate, 4-chlorophenyl diphenyl hexafluorophosphate, 4-chlorophenyl diphenyl hexafluoroantimonate, bis[4-(diphenyl perionate) (2,4-Cyclopentadien-1-yl) [(1-methylethyl)benzene]-Fe-hexafluorophosphate, diphenyliodonium hexafluoroantimonate, etc. It is preferable to use a photocationic polymerization initiator of triphenyl perionium salt type hexafluoroantimonate type, and a photocationic polymerization initiator of diphenyliodonium salt type hexafluoroantimonate type.

Commercially available ones can also be used as the photocationic polymerization initiator. Commercially available products include SP-170 (manufactured by ADEKA), CPI-101A (manufactured by SAN-APRO), WPAG-1056 (manufactured by Wako Pure Chemical Industries, Ltd.) The diphenyliodonium salt is WPI-116 (manufactured by Wako Pure Chemical Industries, Ltd.) of the hexafluoroantimonate type, and the like.

The content of the photocationic polymerization initiator is preferably 0.1 to 3 parts by weight, preferably 0.25 to 2 parts by weight, relative to 100 parts by weight of the epoxy resin having a biphenyl skeleton. When the content of the photocationic polymerization initiator is less than 0.1 part by weight, there may be cases where it is not sufficiently cured even if it is irradiated with light (ultraviolet rays).

C-3. Composition and characteristics of protective layer The protective layer is formed of a cured product of an epoxy resin having a biphenyl skeleton as described above. As long as it is the hardened product, the thickness can be much thinner than that of an extruded film. The thickness of the protective layer is preferably 10µm or less, preferably 7µm or less, more preferably 5µm or less, and even more preferably 3µm or less. The thickness of the protective layer may be, for example, 1 µm or more. Compared with the cured products of aqueous coating films such as aqueous solutions or aqueous dispersions, the cured products of epoxy resins having a biphenyl skeleton have lower hygroscopicity and moisture permeability, and thus have the advantage of being excellent in humidification durability. As a result, a polarizing plate excellent in durability that can maintain optical properties even in a heated and humidified environment can be realized. Moreover, the hardened|cured material of the epoxy resin which has a biphenyl skeleton, ie, a protective layer, is excellent in the adhesiveness with a polarizer. Therefore, even with the above-mentioned thickness, the polarizer can be protected to the same extent as the protective layer using a conventional thin film. In addition, even if the thickness is as described above, the polarizer can still be prevented from occurrence of defects such as fading.

The softening temperature of the protective layer is preferably above 100°C. As long as the softening temperature of the protective layer is 100° C. or higher, the polarizing plate including the obtained protective layer is likely to be excellent in durability. The softening temperature of the protective layer is preferably 110°C or higher, more preferably 120°C or higher, and more preferably 125°C or higher. On the other hand, the softening temperature of the protective layer is preferably 300°C or lower, more preferably 250°C or lower, more preferably 200°C or lower, and particularly preferably 160°C or lower. As long as the softening point of the protective layer is within the above range, the formability and workability are good.

The iodine adsorption amount of the protective layer is preferably 10% by weight or less, more preferably 6.0% by weight or less, more preferably 3.0% by weight or less, particularly preferably 2.0% by weight or less. The smaller the amount of iodine adsorbed, the better. As long as the amount of iodine adsorption is within the range, a polarizing plate having more excellent durability can be obtained. The amount of iodine adsorption can be measured by the following method. The composition for forming a protective layer was applied to a substrate (PET film) with a sprayer to form a protective layer (thickness of about 3 µm). The obtained PET film with a protective layer was cut into 1 cm×1 cm (1 cm ² ) to prepare a sample, which was collected into a headspace vial (20 mL capacity) and weighed. Next, a screw-top vial (1.5 mL capacity) containing 1 mL of an iodine solution (1 wt % iodine concentration, 7 wt % potassium iodide concentration) was also placed in the headspace vial and capped tightly. Afterwards, the headspace vial was warmed in a desiccator at 65°C for 6 hours. Thereby, I ₂ in gaseous state is adsorbed on the sample. After that, the sample was collected in a ceramic boat and burned using an automatic sample burning device, and the generated gas was collected into 10 mL of the absorbing liquid. After the collection, the absorbing solution was prepared to 15 mL with pure water, and IC quantitative analysis was performed on the stock solution or the appropriately diluted solution. In addition, the iodine adsorption amount was almost zero when the same measurement was performed only with the PET film. Based on the weight of iodine obtained by IC quantitative analysis and the weight of the protective layer monomer ("weight of PET film with protective layer" - "weight of PET film"), the iodine adsorption amount (% by weight) was calculated from the following formula. Iodine adsorption amount (% by weight)=Iodine weight obtained by IC quantitative analysis/weight of protective layer monomer×100 For the analysis, the following measuring apparatus can be used, for example. [Measuring device] Automatic sample combustion device: "AQF-2100H" manufactured by Mitsubishi Chemical Analytech Co., Ltd. IC (anion): "ICS-3000" manufactured by Thermo Fisher Scientific Co., Ltd.

The protective layer is preferably substantially optically isotropic. In the present specification, "substantially optically isotropic" means that the retardation at a wavelength of 550 nm is -50 nm to +50 nm. The in-plane retardation Re(550) is preferably -30 nm to +30 nm, more preferably -10 nm to +10 nm, and particularly preferably 0 nm to 2 nm. The retardation Rth(550) in the thickness direction is preferably -5 nm to 5 nm, more preferably -3 nm to 3 nm, and particularly preferably -2 nm to 2 nm. As long as the Re(550) and Rth(550) of the protective layer are within the above-mentioned ranges, when the polarizing plate including the protective layer is applied to an image display device, adverse effects on display characteristics can be prevented. In addition, Re(550) is the in-plane retardation of the thin film measured at 23 degreeC with the light of wavelength 550nm. Re(550) can be obtained by the formula: Re(550)=(nx-ny)×d. Rth(550) is the retardation in the thickness direction of the thin film measured at 23°C with light having a wavelength of 550 nm. Rth(550) can be obtained by the formula: Rth(550)=(nx-nz)×d. Here, nx is the refractive index in the direction where the in-plane refractive index reaches the maximum (that is, the slow axis direction), ny is the refractive index in the in-plane direction orthogonal to the slow axis (that is, the fast axis direction), and nz is the thickness The refractive index in the direction, d is the thickness (nm) of the film.

When the thickness of the protective layer is 3µm, the light transmittance at 380nm is as high as possible. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and more preferably 90% or more. As long as the light transmittance is within the range, desired transparency can be ensured. The light transmittance can be measured according to the method of ASTM-D-1003, for example.

The lower the haze of the protective layer, the better. Specifically, the haze is preferably 5% or less, more preferably 3% or less, more preferably 1.5% or less, and particularly preferably 1% or less. When the haze is 5% or less, it is possible to impart a good sense of transparency to the film. Moreover, even if it is used for the polarizing plate on the viewing side of the image display device, the displayed content can be well viewed.

When the thickness of the protective layer is 3µm, the YI is preferably 1.27 or less, preferably 1.25 or less, more preferably 1.23 or less, and even more preferably 1.20 or less. When YI is more than 1.3, the optical transparency may be insufficient. In addition, YI can be obtained from the color tristimulus values (X, Y, Z) measured using a high-speed integrating sphere spectroscopic transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Technology Laboratory), for example, by the following formula out. YI=[(1.28X-1.06Z)/Y]×100

When the thickness of the protective layer is 3µm, the b value (according to the hue scale of the Hunter color system) should preferably be less than 1.5, and preferably less than 1.0. When the b value is 1.5 or more, an undesired color tone may appear. In addition, the b value can be obtained, for example, by cutting a sample of the film constituting the protective layer into a 3 cm square, and using a high-speed integrating sphere type spectroscopic transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Institute) Hue is measured and evaluated according to the Hunter Color System.

The protective layer (hardened product of an epoxy resin having a biphenyl skeleton) may contain any appropriate additives according to the purpose. Specific examples of additives include: ultraviolet absorbers; leveling agents; antioxidants such as hindered phenols, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fibers and carbon fibers. ;Near-infrared absorbers; ginseng (dibromopropyl) phosphate, triallyl phosphate, antimony oxide and other flame retardants; anionic, cationic, nonionic surfactants and other antistatic agents; inorganic pigments , organic pigments, dyes and other colorants; organic fillers or inorganic fillers; resin modifiers; organic fillers or inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants, etc. Additives are usually added to the solution when the protective layer is formed. The type, quantity, combination, addition amount, etc. of the additives can be appropriately set according to the purpose.

An easily bonding layer may also be formed on the polarizer side of the protective layer. The easily bonding layer contains, for example, a water-based polyurethane and an oxazoline-based crosslinking agent. By forming the easy bonding layer, the adhesion between the protective layer and the polarizer can be improved. The easy-bond layer can be laminated with the polarizer by any suitable method. For example, it can also be formed directly on the polarizer, or can be passed through any suitable adhesive layer or adhesive layer. In addition, a hard coat layer may be formed on the protective layer. The hard coat layer can be formed when the protective layer is used as the protective layer on the viewing side of the viewing-side polarizing plate. When both the easy-bond layer and the hard coat layer are formed, it means that these can be formed on different sides of the protective layer, respectively.

D. Manufacturing method of polarizing plate D-1. Manufacturing method of polarizer The manufacturing method of the polarizer described in the above item B includes the following steps: forming a polyvinyl alcohol-based resin layer (PVA-based resin) comprising a halide and a polyvinyl-alcohol-based resin (PVA-based resin) on one side of an elongated thermoplastic resin substrate resin layer) to produce a layered product; and the layered product is subjected to air-assisted stretching treatment, dyeing treatment, underwater stretching treatment, and drying shrinkage treatment in this order while conveying the above-mentioned layered product in the longitudinal direction. By heating, it shrinks by 2% or more in the width direction. The halide content in the PVA-based resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment should be carried out with a heating roller, and the temperature of the heating roller should be 60℃~120℃. According to the manufacturing method, the above-mentioned polarizer can be obtained. In particular, after a laminate containing a halide-containing PVA-based resin layer is produced, the above-mentioned laminate is stretched by multi-stage stretching including air-assisted stretching and underwater stretching, and then the stretched laminate is heated with a heating roller. This makes it possible to obtain a polarizer having excellent optical properties (representatively, single transmittance and degree of polarization) and suppressed variations in optical properties. Specifically, by using a heating roll in the drying shrinkage treatment step, the entire layered body can be uniformly shrunk while conveying the layered body. In this way, not only the optical properties of the obtained polarizer can be improved, but also the polarizer with excellent optical properties can be stably produced, and the variation in the optical properties (especially the transmittance of a single unit) of the polarizer can be suppressed. The halide and drying shrinkage treatment will be described below. Details of production methods other than these are described in, for example, Japanese Patent Laid-Open No. 2012-73580 and Japanese Patent No. 6470455 . In this specification, the entire description of this gazette is incorporated by reference.

D-1-1. Halide The PVA-based resin layer containing the halide and the PVA-based resin can be formed by coating a coating liquid containing the halide and the PVA-based resin on a thermoplastic resin substrate and drying the coating film. The coating liquid represents a solution obtained by dissolving the above-mentioned halide and the above-mentioned PVA-based resin in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, etc. Amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Among these, water is preferred. The PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight relative to 100 parts by weight of the solvent. As long as it is the said resin density|concentration, a uniform coating film which adheres to a thermoplastic resin base material can be formed.

As the halide, any suitable halide can be used. For example, iodide and sodium chloride are mentioned. Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide. Among them, potassium iodide is preferred.

The amount of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight, preferably 10 parts by weight to 15 parts by weight, relative to 100 parts by weight of the PVA resin. If the amount of the halide is too large, the halide may overflow and the polarizer finally obtained may become cloudy.

Generally speaking, when the PVA-based resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA-based resin layer will become higher, but if the stretched PVA-based resin layer is immersed in a water-containing liquid, there will be polyvinyl alcohol molecules A situation in which the orientation is disordered and the orientation is reduced. In particular, when the laminate of the thermoplastic resin base material and the PVA-based resin layer is stretched in boric acid water, the above-mentioned laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin base material. The tendency to decrease the degree of orientation is obvious. For example, the extension of the PVA film monomer in boric acid water is generally carried out at 60°C, while the extension of the laminate of A-PET (thermoplastic resin substrate) and the PVA-based resin layer is performed at 70°C At this time, the orientation of the PVA at the beginning of the stretching is reduced at a stage before it rises by the stretching in water. In this regard, by fabricating a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, and performing high temperature stretching (assisted stretching) in air before stretching the laminated body in boric acid water, the post-assisted stretching can be accelerated. Crystallization of the PVA-based resin in the PVA-based resin layer of the laminate. As a result, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed more than when the PVA-based resin layer does not contain a halide. Thereby, the optical characteristics of the polarizer obtained by the process steps of immersing the laminated body in liquid, such as dyeing process and underwater stretching process, can be improved.

D-1-2. Drying shrinkage treatment The drying shrinkage treatment can be performed by area heating by heating the entire area, or by heating a conveying roller (so-called using a heating roller) (heating roller drying method). It is preferable to use both. By drying it using a heating roll, the heating curl of the laminated body can be effectively suppressed, and a polarizer having an excellent appearance can be produced. Specifically, by drying the layered body in a state where a heated roll is attached, the crystallization of the thermoplastic resin substrate can be effectively promoted to increase the degree of crystallinity, and even at a relatively low drying temperature, the It can improve the crystallinity of thermoplastic resin substrates. As a result, the rigidity of the thermoplastic resin base material increases, and the PVA-based resin layer is in a state of being able to withstand shrinkage due to drying, and curling is suppressed. Moreover, since the laminated body can be dried while maintaining a flat state by using a heating roll, not only the curling but also the generation of wrinkles can be suppressed. At this time, the layered body can be shrunk in the width direction by drying shrinkage treatment to improve optical properties. This is because it can effectively improve the orientation of PVA and PVA/iodine complexes. The shrinkage rate in the width direction of the laminated body obtained by drying shrinkage treatment is preferably 2% to 10%, more preferably 2% to 8%, especially 4% to 6%. By using a heating roll, the laminated body can be continuously shrunk in the width direction while being conveyed, and high productivity can be realized.

FIG. 2 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage treatment, the layered body 200 is dried while being conveyed by the conveyance rollers R1 to R6 and the guide rollers G1 to G4 heated to a predetermined temperature. In the illustrated example, the conveying rollers R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin substrate, but for example, the conveying rollers R1 to R6 may be arranged to continuously heat only the layered body 200 one of the sides (such as the thermoplastic resin substrate side).

Drying conditions can be controlled by adjusting the heating temperature of the conveying rollers (the temperature of the heating rollers), the number of heating rollers, and the contact time with the heating rollers. The temperature of the heating roller is preferably 60°C to 120°C, more preferably 65°C to 100°C, and particularly preferably 70°C to 80°C. The crystallinity of the thermoplastic resin can be favorably increased, and curling can be favorably suppressed, and an optical laminate having extremely excellent durability can be produced. In addition, the temperature of the heating roller can be measured with a contact thermometer. In the illustrated example, six conveying rollers are provided, but there is no particular limitation as long as the number of conveying rollers is plural. The number of conveying rollers is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminated body and the heating roller is preferably 1 to 300 seconds, preferably 1 to 20 seconds, and more preferably 1 to 10 seconds.

The heating roller can be installed in a heating furnace (eg, an oven), or can be installed in a general manufacturing line (at room temperature). It should be installed in a heating furnace with an air supply mechanism. The rapid temperature change between the heating rollers can be suppressed by combining the drying with the heating roller and the hot air drying, and the shrinkage in the width direction can be easily controlled. The temperature of hot air drying should be 30℃~100℃. In addition, the hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air should be about 10m/s~30m/s. In addition, the wind speed is the wind speed in the heating furnace, which can be measured by a miniature fan-blade digital anemometer.

It is preferable to perform a washing treatment after the stretching treatment in water and before the drying shrinkage treatment. The above-mentioned cleaning treatment can be typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution.

In the above manner, a laminate of thermoplastic resin substrate/polarizer can be obtained.

D-2. Manufacturing method of polarizing plate A coating film can be formed by coating a composition comprising an epoxy resin having a biphenyl skeleton and a hardener on the surface of the laminate obtained in the above item D-1 (eg, the surface of a polarizer), and curing the coating film to form a protective layer . In one embodiment, the protective layer is a cationic polymer cured product. In this embodiment, a photocationic polymerization initiator can be used as a hardener. A composition comprising an epoxy resin having a biphenyl skeleton and a photocationic polymerization initiator can be coated on the surface of the laminate (such as the surface of the polarizer) to form a coating film, and then the coating film can be irradiated with light (such as ultraviolet rays) to thereby form a protective layer.

Any appropriate solvent that can dissolve or uniformly disperse the epoxy resin having a biphenyl skeleton and the hardener can be used as the solvent contained in the above-mentioned composition. Specific examples of the solvent include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone.

The epoxy resin concentration of the solution is preferably 10 parts by weight to 30 parts by weight relative to 100 parts by weight of the solvent. As long as it is the said resin density|concentration, a uniform coating film which adheres to a polarizer can be formed. In addition, the content of the hardener is as described in the above-mentioned item C.

The solution can be coated on any suitable substrate, and can also be coated on the polarizer. When the solution is applied to the substrate, the cured product of the coating film formed on the substrate is transferred to the polarizer. When the solution is applied to the polarizer, for example, the coating film is hardened by light irradiation, whereby a protective layer is directly formed on the polarizer. Preferably, the solution is coated on the polarizer, and the protective layer is directly formed on the polarizer. With the above-described configuration, the adhesive layer or the adhesive layer required for transfer can be omitted, so that the polarizing plate can be made thinner. Any appropriate method can be adopted for the coating method of the solution. Specific examples thereof include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and blade coating (cut-off wheel coating, etc.).

When hardening the coating film by light irradiation, light (representatively ultraviolet rays) can be irradiated to the coating film so as to have any appropriate irradiation amount using any appropriate light source. As the light source of ultraviolet rays, for example, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, electrodeless lamps, halogen lamps, carbon arc lamps, xenon lamps, metal halide lamps, chemical lamps, black light lamps, and LED lamps can be used. For example, the amount of ultraviolet radiation ^{2mJ / cm 2 ~ 3000mJ / cm} 2, is suitably ^{10mJ / cm 2 ~ 2000mJ / cm} 2. Specifically, when a high pressure mercury lamp as a light source, the irradiation dose is usually based ^{5mJ / cm 2 ~ 3000mJ / cm} 2, more suitably carried out at 50mJ / cm ² ~ 2000mJ / cm ² of conditions. When using electrodeless lamp as a light source, the irradiation dose is usually based ^{2mJ / cm 2 ~ 2000mJ / cm} 2, more suitably carried out at 10mJ / cm ² ~ 1000mJ / cm ² of conditions.

The irradiation time can be set to any appropriate value according to the type of the light source, the distance between the light source and the coating surface, the coating thickness and other conditions. The irradiation time is usually several seconds to several tens of seconds, and may also be a fraction of a second. The irradiation of light may be irradiated from any suitable direction. From the viewpoint of preventing uneven hardening, it is preferable to irradiate from the coating surface side of the composition for forming a protective layer.

After exposure by light irradiation such as ultraviolet irradiation, a heat treatment may be further performed in order to complete curing by photoreaction. The heat treatment can be performed at any appropriate temperature and time. The heating temperature is, for example, 80°C to 250°C, preferably 100°C to 150°C. The heating time is, for example, 10 seconds to 2 hours, preferably 5 minutes to 1 hour.

As a result of forming the protective layer in the above manner, a laminate of thermoplastic resin substrate/polarizer/protective layer can be obtained. By peeling the thermoplastic resin base material from the laminate, a polarizing plate having the polarizer 10 and the protective layer 20 as shown in FIG. 1 can be obtained. Alternatively, a resin film constituting another protective layer can be pasted on the surface of the polarizer of the laminate of the thermoplastic resin substrate/polarizer, and then the thermoplastic resin substrate is peeled off to form a protective layer on the peeled surface. At this time, a polarizing plate with another protective layer can be obtained.

E. Polarizing plate with retardation layer E-1. Outline of polarizing plate with retardation layer In one embodiment of the present invention, a polarizing plate with a retardation layer can be provided. The polarizing plate with retardation layer further has a retardation layer on the surface of the polarizing plate that is not provided with the protective layer. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. The polarizing plate 110 with retardation layer in the illustrated example includes a polarizer 10 , a protective layer 20 disposed on one side of the polarizer 10 , and a retardation layer 40 disposed on the other side of the polarizer 10 . The polarizer 10 and the protective layer 20 constitute the above-mentioned polarizer. Therefore, the polarizer with retardation layer has a polarizer and a retardation layer, the polarizer includes a polarizer and a protective layer disposed on one side of the polarizer, and the retardation layer is disposed between the polarizer and the protective layer the opposite side of the layer. The polarizer can also include another protective layer (not shown) on the opposite side of the polarizer 10 to the protective layer 20 according to requirements. In other words, the polarizing plate 110 with the retardation layer may further include another protective layer (not shown) between the polarizer 10 and the retardation layer 40 . As described above, an easily bonding layer may be formed on the polarizer side of the protective layer. The easy-bond layer can be laminated with the polarizer by any suitable method. For example, it can also be formed directly on the polarizer, or can be passed through any suitable adhesive layer or adhesive layer.

In the embodiment shown in FIG. 3, the retardation layer 40 is a single layer. At this time, Re(550) of the retardation layer 40 is, for example, 100 nm to 190 nm, and the angle formed by the slow axis of the retardation layer 40 and the absorption axis of the polarizer 10 is, for example, 40° to 50°. At this time, it is preferable to set another retardation layer (not shown) on the outer side of the retardation layer 40 (the side opposite to the polarizer 10 ). The other retardation layer represents the upper refractive index characteristic exhibiting the relationship of nz>nx=ny. Or as shown in FIG. 4 , in the polarizing plate 111 with retardation layer according to another embodiment, the retardation layer 40 has a laminated structure of the first layer 41 and the second layer 42 . At this time, the Re (550) of the first layer 41 is, for example, 200 nm to 300 nm, and the angle formed by the slow axis of the first layer 41 and the absorption axis of the polarizer 10 is, for example, 10° to 20°; the Re of the second layer 42 (550) is, for example, 100 nm to 190 nm, and the angle formed by the slow axis of the second layer 42 and the absorption axis of the polarizer 10 is, for example, 70° to 80°. Regardless of the embodiment, the retardation layer 40 may be a resin film or a directional solidification layer of a liquid crystal compound. When the retardation layer 40 has a laminated structure, it means that the upper first layer 41 and the second layer 42 are respectively a resin film or a directionally cured layer of a liquid crystal compound.

E-2. A retardation layer composed of a single layer When the retardation layer is composed of a single layer, the Re(550) of the retardation layer is, for example, 100 nm to 190 nm as described above, and the angle formed by the slow axis of the retardation layer 40 and the absorption axis of the polarizer 10 is, for example, 40° to 50° °. The retardation layer is typically provided to impart anti-reflection properties to the polarizing plate, and in one embodiment, functions as a λ/4 plate. As mentioned above, the retardation layer may be a resin film, or may be an orientation curing layer of a liquid crystal compound.

The retardation layer preferably exhibits the relationship of nx>ny≧nz in refractive index characteristics. As mentioned above, the in-plane retardation Re(550) of the retardation layer is, for example, 100 nm to 190 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm. In addition, "ny=nz" here includes not only the case where ny and nz are completely identical, but also the case where they are substantially the same. Therefore, in the range which does not impair the effect of this invention, there may be a case where ny<nz is satisfied.

The Nz coefficient of the retardation layer is preferably 0.9~3, more preferably 0.9~2.5, more preferably 0.9~1.5, preferably 0.9~1.3. By satisfying the above relationship, when the obtained polarizing plate with retardation layer is used in an image display device, a very excellent reflection hue can be achieved.

The angle θ formed by the slow axis of the retardation layer 40 and the absorption axis of the polarizer 10 is, for example, 40°-50°, preferably 42°-48°, and more preferably about 45°. As long as the angle θ is within the above-mentioned range, by making the retardation layer into a λ/4 plate, polarized light with a retardation layer having very excellent circular polarization properties (resulting in very excellent antireflection properties) can be obtained plate.

The retardation layer can exhibit a reverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light, and a positive wavelength dispersion characteristic in which the retardation value becomes smaller with the wavelength of the measurement light, and can also exhibit a retardation value that hardly changes with the measurement light. Flat wavelength dispersion characteristics of light wavelength variation. In one embodiment, the retardation layer exhibits reverse dispersion wavelength characteristics. At this time, Re(450)/Re(550) of the retardation layer is preferably 0.8 or more and less than 1, and more preferably 0.8 or more and 0.95 or less. With the above-described configuration, very excellent antireflection properties can be achieved.

The absolute value of the photoelastic coefficient contained in the retardation layer is preferably 2.0×10 ^-11 m ² /N or less, preferably 2.0×10 ^-13 m ² /N~1.5×10 ^-11 m ² /N, more preferably 1.0 Resin of ×10 ^-12 m ^{2 /N~1.2×10 -11} m ² /N. As long as the absolute value of the photoelastic coefficient is within the above-mentioned range, a change in phase difference hardly occurs when shrinkage stress is generated during heating. As a result, thermal unevenness of the resulting image display device can be well prevented.

E-2-1. Resin film When the retardation layer is a resin film, the resin film is typically a stretched film. At this time, the thickness of the retardation layer is preferably 60µm or less, preferably 30µm~55µm. As long as the thickness of the retardation layer is within the above-mentioned range, the curl at the time of heating can be suppressed favorably, and the curl at the time of lamination can be adjusted favorably.

The retardation layer may be composed of any appropriate resin film that can satisfy the above-mentioned properties. Representative examples of the resins include polycarbonate-based resins, polyester carbonate-based resins, polyester-based resins, polyvinyl acetal-based resins, polyarylate-based resins, cyclic olefin-based resins, cellulose-based resins, Polyvinyl alcohol-based resin, polyamide-based resin, polyimide-based resin, polyether-based resin, polystyrene-based resin, and acrylic resin. These resins may be used alone or in combination (eg, blending, copolymerization). When the retardation layer is formed of a resin film exhibiting reverse dispersion wavelength characteristics, a polycarbonate-based resin or a polyester-carbonate-based resin (hereinafter referred to only as a polycarbonate-based resin) can be suitably used.

As long as the effect of the present invention can be obtained, any appropriate polycarbonate-based resin can be used as the above-mentioned polycarbonate-based resin. For example, the polycarbonate-based resin contains a structural unit derived from a perylene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from the group consisting of alicyclic diol, alicyclic dimethanol, A structural unit of at least one dihydroxy compound in the group consisting of di-, tri- or polyethylene glycol, and alkylene glycol or spiroglycerol. The polycarbonate resin preferably contains a structural unit derived from a perylene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, a structural unit derived from alicyclic dimethanol, and/or a structural unit derived from di- or tri-dihydroxyl compounds. or a structural unit of polyethylene glycol; more preferably, it includes a structural unit derived from a perylene dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from di-, tri- or polyethylene glycol. The polycarbonate-based resin may also contain structural units derived from other dihydroxy compounds as required. In addition, the details of the polycarbonate-based resin that can be suitably used in the present invention are described in, for example, Japanese Patent Laid-Open No. 2014-10291, Japanese Patent Laid-Open No. 2014-26266, Japanese Patent Laid-Open No. 2015-212816, In Unexamined-Japanese-Patent No. 2015-212817 and Unexamined-Japanese-Patent No. 2015-212818, the description is incorporated herein by reference.

The glass transition temperature of the polycarbonate-based resin is preferably 110°C or higher and 150°C or lower, and more preferably 120°C or higher and 140°C or lower. If the glass transition temperature is too low, the heat resistance tends to be deteriorated, and there is a possibility of dimensional change after film forming, or the image quality of the obtained organic EL panel may be lowered. If the glass transition temperature is too high, the forming stability of the film may be deteriorated, or the transparency of the film may be impaired. In addition, the glass transition temperature can be calculated|required according to JIS K 7121 (1987).

The molecular weight of the above-mentioned polycarbonate resin can be represented by a reduced viscosity. The reduced viscosity was measured with an Ubbelohde viscometer at a temperature of 20.0°C ± 0.1°C after precisely adjusting the polycarbonate concentration to 0.6 g/dL using dichloromethane as a solvent. The reduced viscosity should normally be above 0.30dL/g, preferably above 0.35dL/g. In addition, the reduced viscosity is usually preferably 1.20 dL/g or less, more preferably 1.00 dL/g or less, and more preferably 0.80 dL/g or less. If the reduced viscosity is less than 0.30 dL/g, there may be a problem that the mechanical strength of the molded product is reduced. On the other hand, if the reduced viscosity exceeds 1.20 dL/g, the fluidity at the time of molding may be lowered, and the productivity or formability may be lowered.

A commercially available film can also be used for the polycarbonate-based resin film. Specific examples of commercially available products include "PURE-ACE WR-S", "PURE-ACE WR-W", "PURE-ACE WR-M" manufactured by Teijin Corporation, and "NRF" manufactured by Nitto Denko Corporation. ".

The retardation layer 40 can be obtained, for example, by extending a film formed of the above-mentioned polycarbonate-based resin. Any appropriate molding method can be adopted as a method of forming a film from a polycarbonate resin. Specific examples include compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, cast coating (eg, casting), and calender molding. , hot pressing, etc. Rather, it is preferably an extrusion forming method or a casting coating method. This is because the smoothness of the resulting film can be improved, thereby obtaining good optical uniformity. The molding conditions can be appropriately set according to the composition and type of the resin to be used, the properties desired for the retardation layer, and the like. Moreover, as mentioned above, since many film products of polycarbonate-type resins are commercially available, the commercially available films can be directly used for the stretching process.

The thickness of the resin film (unstretched film) can be set to any appropriate value according to the desired thickness of the retardation layer, desired optical properties, stretching conditions described later, and the like. It should be 50µm~300µm.

Any appropriate stretching method and stretching conditions (eg, stretching temperature, stretching ratio, stretching direction) can be used for the above-mentioned stretching. Specifically, various extension methods such as free-end extension, fixed-end extension, free-end shrinkage, and fixed-end shrinkage can be used alone, or they can be used simultaneously or sequentially. The extending direction may be carried out in various directions or dimensions such as the longitudinal direction, the width direction, the thickness direction, and the diagonal direction. The stretching temperature is preferably Tg-30°C to Tg+60°C, preferably Tg-10°C to Tg+50°C, relative to the glass transition temperature (Tg) of the resin film.

By appropriately selecting the above-described stretching method and stretching conditions, a retardation film having the above-described desired optical properties (eg, refractive index properties, in-plane retardation, and Nz coefficient) can be obtained.

In one embodiment, the retardation film can be produced by uniaxially extending a resin film or by uniaxially extending a fixed end. A specific example of the uniaxial stretching at the fixed end includes a method of stretching the resin film in the width direction (horizontal direction) while moving the resin film in the longitudinal direction. The extension ratio should be 1.1 times to 3.5 times.

In another embodiment, the retardation film can be produced by continuously extending the elongated resin film obliquely in the direction of the above-mentioned angle θ with respect to the longitudinal direction. By adopting oblique stretching, a long stretched film with an orientation angle of angle θ (with a slow axis in the direction of angle θ) can be obtained with respect to the longitudinal direction of the film. For example, when laminating with a polarizer, it can be Roll-to-roll, which simplifies manufacturing steps. In addition, the angle θ may be the angle formed by the absorption axis of the polarizer and the slow axis of the retardation layer in the polarizing plate with retardation layer. As mentioned above, the angle θ is preferably 40° to 50°, more preferably 42° to 48°, and more preferably about 45°.

The stretching machine used for the oblique stretching can be a tenter-type stretching machine, which is, for example, adding a conveying force, a stretching force, or a pulling force to the transverse direction and/or the longitudinal direction with different speeds on the left and right. As tenter stretching machines, there are horizontal uniaxial stretching machines, simultaneous biaxial stretching machines, and the like, and any appropriate stretching machine can be used as long as the elongated resin film can be continuously stretched obliquely.

By appropriately controlling the left and right speeds in the above-mentioned stretching machine, a retardation layer (substantially an elongated retardation film) having the above-mentioned desired in-plane retardation and having a slow axis in the above-mentioned desired direction can be obtained. ).

The stretching temperature of the film can be changed according to the desired in-plane retardation value and thickness of the retardation layer, the type of resin used, the thickness of the film used, the stretching ratio, and the like. Specifically, the extension temperature is preferably Tg-30°C to Tg+30°C, more preferably Tg-15°C to Tg+15°C, and most preferably Tg-10°C to Tg+10°C. By extending at the above temperature, a retardation layer having characteristics suitable for the present invention can be obtained. In addition, Tg is the glass transition temperature of the constituent material of the thin film.

E-2-2. Directionally cured layer of liquid crystal compound When the retardation layer is a directionally cured layer of liquid crystal compound, by using the liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be much larger than that of the non-liquid crystal material, so it can be used to obtain the desired in-plane retardation The thickness of the retardation layer is much smaller. As a result, further thinning of the polarizing plate with retardation layer can be realized. The term "orientation-cured layer" in this specification refers to a layer in which the liquid crystal compound is oriented in a predetermined direction within the layer, and the orientation state thereof has been fixed. In addition, the concept of "orientation hardening layer" includes the orientation hardening layer obtained by hardening a liquid crystal monomer as mentioned later. In the present embodiment, the upper rod-like liquid crystal compound is aligned in the state of alignment in the slow axis direction of the retardation layer (grain alignment).

As a liquid crystal compound, the liquid crystal compound (nematic liquid crystal) whose liquid crystal phase is a nematic phase is mentioned, for example. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The expression mechanism of the liquid crystallinity of the liquid crystal compound may be lyotropic or thermotropic. Each of the liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (ie, hardening) the liquid crystal monomer. After the liquid crystal monomers are aligned, for example, the above-mentioned alignment state can be fixed by polymerizing or crosslinking the liquid crystal monomers with each other. Here, a polymer is formed by polymerization, a 3-dimensional mesh structure is formed by cross-linking, and these are non-liquid crystalline. Therefore, the formed retardation layer does not change into a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change, which is peculiar to a liquid crystal compound, for example. As a result, the retardation layer becomes a retardation layer which is not affected by temperature changes and has excellent stability.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on the type. Specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

Any appropriate liquid crystal monomer can be used as the above-mentioned liquid crystal monomer. For example, polymerizable mesogenic compounds described in Japanese Patent Application Laid-Open No. 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, GB2280445 and the like can be used. Specific examples of the polymerizable mesogen compound include BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Silicon-CC3767. The liquid crystal monomer is preferably, for example, a nematic liquid crystal monomer.

The alignment curing layer of the liquid crystal compound can be formed by the following method: performing alignment treatment on the surface of a predetermined substrate, and coating the surface with a coating liquid containing the liquid crystal compound, so that the liquid crystal compound is aligned in the direction corresponding to the above alignment treatment , and fix the orientation state. In one embodiment, the base material is any suitable resin film, and the orientation cured layer formed on the base material can be transferred to the surface of the polarizer 10 . In another embodiment, the substrate can be another protective layer. In this case, the transfer step is omitted, and after the formation of the directionally solidified layer (retardation layer), the layering can be carried out in a roll-to-roll manner, so that the productivity can be further improved.

The above-mentioned orientation process can adopt any suitable orientation process. Specifically, a mechanical orientation treatment, a physical orientation treatment, and a chemical orientation treatment can be mentioned. Specific examples of the mechanical orientation treatment include rubbing treatment and stretching treatment. Specific examples of the physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of the chemical alignment treatment include oblique vapor deposition and photo alignment treatment. The treatment conditions for the various orientation treatments can be any appropriate conditions according to the purpose.

The alignment of the liquid crystal compound can be performed by processing at a temperature at which a liquid crystal phase can be exhibited according to the type of the liquid crystal compound. By performing the temperature treatment, the liquid crystal compound becomes a liquid crystal state, and the liquid crystal compound is oriented according to the orientation treatment direction of the surface of the substrate.

In one embodiment, the fixation of the alignment state is performed by cooling the liquid crystal compound aligned in the above-described manner. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the orientation state is fixed by subjecting the liquid crystal compound oriented in the above-described manner to a polymerization treatment or a crosslinking treatment.

Specific examples of the liquid crystal compound and details of the method for forming the alignment cured layer are described in Japanese Patent Laid-Open No. 2006-163343. In this specification, the description of this gazette is used as a reference.

Another example of the alignment cured layer includes a form in which the discotic liquid crystal compound is aligned in any state of vertical alignment, hybrid alignment, and oblique alignment. The discotic liquid crystalline compound is oriented substantially perpendicularly with respect to the film surface of the retardation layer on the surface of the disk representing the upper discotic liquid crystalline compound. The so-called discotic liquid crystal compound is substantially vertical means that the average value of the angle formed by the film surface and the disc surface of the discotic liquid crystal compound is preferably 70°~90°, more preferably 80°~90°, more preferably 85°~ 90°. The so-called discotic liquid crystal compound generally refers to a liquid crystal compound with a discotic molecular structure, and the discotic molecular structure is configured by cyclic cores such as benzene, 1,3,5-tris-arene, calixarene, etc. In the center of the molecule, straight-chain alkyl, alkoxy, substituted benzyloxy, etc. are radially substituted as their side chains. Representative examples of discotic liquid crystals include: the research report of C. Destrade et al., Mol. Cryst. Liq. Cryst. No. 71, p. 111 (1981), the benzene derivatives, triphenyl derivatives, and reference Indenacene derivatives, phthalocyanin derivatives; research reports by B. Kohne et al., Angew. Chem. No. 96, p. 70 (1984) cyclohexane derivatives; and JMLehn et al. Research report, J.Chem.Soc.Chem.Commun. p. 1794 (1985), J. Zhang et al. research report, J.Am.Chem.Soc. No. 116 p. 2655 (1994) Recorded The macrocycle of the azacrown ether system or phenylacetylene system. More specific examples of the discotic liquid crystal compound include compounds described in JP 2006-133652 A, JP 2007-108732 A, and JP 2010-244038 A. In the present specification, the descriptions of the above-mentioned documents and gazettes are incorporated by reference.

When the retardation layer is a directional solidification layer of a liquid crystal compound, its thickness is preferably 0.5µm~7µm, more preferably 1µm~5µm. By using the liquid crystal compound, the in-plane retardation equivalent to that of the resin film can be realized at a thickness much thinner than that of the resin film.

E-2-3. Another retardation layer As described above, when the retardation layer is constituted by a single layer, it is preferable to provide another retardation layer. The other retardation layer can be a so-called positive C-plate which exhibits the relation of nz>nx=ny in the refractive index characteristic as described above. By using the positive C plate as another retardation layer, the oblique reflection can be prevented well, and the anti-reflection function can be widened. At this time, the retardation Rth(550) in the thickness direction of the other retardation layer is preferably -50nm~-300nm, more preferably -70nm~-250nm, more preferably -90nm~-200nm, especially -100nm~ -180nm. Here, "nx=ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re(550) of the other retardation layer may be less than 10 nm.

The other retardation layer having the refractive index characteristic of nz>nx=ny can be formed of any suitable material. The other retardation layer is preferably composed of a thin film comprising a liquid crystal material fixed in a homeotropic orientation. The liquid crystal material (liquid crystal compound) that can orient the homeotropic alignment can be either a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include the methods for forming the liquid crystal compound and the retardation layer described in paragraphs [0020] to [0028] of Japanese Patent Laid-Open No. 2002-333642. At this time, the thickness of the other retardation layer is preferably 0.5µm~10µm, more preferably 0.5µm~8µm, more preferably 0.5µm~5µm.

Phase difference layer of E-3.2 layer structure When the retardation layer 40 has a laminated structure having the first layer 41 and the second layer 42, either one of the first layer 41 and the second layer 42 can function as a λ/4 plate, and the other can function as a λ/4 plate. 2 boards are functional. For example, when the first layer 41 functions as a λ/2 plate and the second layer 42 functions as a λ/4 plate, the in-plane retardation Re(550) of the first layer is, for example, 200 nm to 300 nm, preferably 230 nm, as described above. ~290nm, preferably 250nm~280nm. The in-plane retardation Re(550) of the second layer is, for example, 100 nm to 190 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm, as described above. The angle formed by the slow axis of the first layer and the absorption axis of the polarizer is, for example, 10° to 20°, preferably 12° to 18°, and more preferably about 15°, as described above. The angle formed by the slow axis of the second layer and the absorption axis of the polarizer is, for example, 70° to 80°, preferably 72° to 78°, and more preferably about 75°, as described above. With the above-described configuration, properties close to ideal reverse wavelength dispersion properties can be obtained, and as a result, very excellent antireflection properties can be realized.

One of the first layer 41 and the second layer 42 may be a resin film and the other may be an orientationally cured layer of a liquid crystal compound, or both may be a resin film, or both may be an orientationally cured layer of a liquid crystal compound. Preferably, both the first layer 41 and the second layer 42 are directional cured layers of resin films or liquid crystal compounds.

The thicknesses of the first layer 41 and the second layer 42 can be adjusted to obtain a desired in-plane retardation of the λ/4 plate or the λ/2 plate. For example, when the first layer 41 functions as a λ/2 plate and the second layer 42 functions as a λ/4 plate, and the first layer 41 and the second layer 42 are resin films, the thickness of the first layer 41 is, for example, 40 µm ~75µm, the thickness of the second layer 42 is, for example, 30µm~55µm. When the first layer 41 and the second layer 42 are orientationally cured layers of liquid crystal compounds, the thickness of the first layer 41 is, for example, 2.0 μm to 3.0 μm, and the thickness of the second layer 42 is, for example, 1.0 μm to 2.0 μm.

The resin films constituting the first layer and the second layer, the liquid crystal compound, the method for forming the first layer and the second layer, the optical properties, and the like are as described above for the single layer.

Example Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. The measurement method of each characteristic is as follows. In addition, unless otherwise noted, "parts" and "%" in the examples are based on weight.

(1) Fading and shrinkage of protective layer Test pieces (50 mm×50 mm) were cut out from the polarizing plates obtained in the examples and comparative examples, and the test pieces were formed to face the direction perpendicular to the absorption axis direction and the absorption axis direction of the polarizer, respectively. to both sides. So that the protective layer becomes the inner side, the test piece is attached to the glass plate with an adhesive to make a test sample, and the test sample is placed in an oven at 85°C and 85% RH for 120 hours for heating and humidifying, and After arranging in a state of orthogonal polarization with the standard polarizing plate, the fading state of the polarizing plate after humidification was checked with the naked eye, and the evaluation was performed according to the following criteria. In addition, the presence or absence of shrinkage of the protective layer after heating and humidifying was also confirmed with the naked eye. No problem: no fading was observed. Partial fading: fading was observed at the end. Overall fading: the polarizing plate was obviously faded as a whole (2) Transmittance and polarization degree of monomers For the evaluation of fading, the transmittance and polarized light were measured for those who were not overall faded Spend. Test pieces (50 mm×50 mm) were cut out from the polarizing plates obtained in the examples and comparative examples, and the test pieces were formed on two sides opposite to the direction perpendicular to the absorption axis direction and the absorption axis direction of the polarizer, respectively. With the protective layer on the outside, the test piece was attached to an alkali-free glass plate with an adhesive to prepare a test sample, and an ultraviolet-visible light spectrophotometer (manufactured by JASCO Corporation, product name "V7100" was used for the test sample. ") to measure the single transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance (Tc), and obtain the degree of polarization (P) by the following formula. At this time, the measurement light was made incident from the protective layer side. Degree of polarization (P)(%)={(Tp-Tc)/(Tp+Tc)} ^{1 /2} ×100 In addition, the above-mentioned Ts, Tp and Tc are measured by the 2-degree field of view (C light source) of JIS Z 8701 And the Y value obtained by the visual sensitivity correction. In addition, Ts and P are substantially the characteristics of a polarizer. Then, the polarizing plate was placed in an oven at 85°C and 85% RH for 120 hours for heating and humidification (heating test), and the transmittance of the monomer before the heating test Ts ₀ and the monomer transmittance after the heating test Ts ₁₂₀ The individual transmittance change amount ΔTs was obtained by the following formula. ΔTs(%)=Ts _{120 −Ts 0} Similarly, the polarization degree change amount ΔP was obtained from the polarization degree P ₀ before the heating test and the polarization degree P _{120 after the heating test by the following formula.} ΔP(%)=P ₁₂₀ -P _{0 In} addition, the heating test was performed in the same manner as in the case of discoloration described above to prepare a test sample.

(3) The amount of iodine adsorption A protective layer (thickness: about 3 µm) was formed on one side of the PET film in the same manner as the protective layer in each Example and Comparative Example. The obtained PET film with a protective layer was cut into 1 cm×1 cm (1 cm ² ) to prepare a sample, which was collected into a headspace vial (20 mL capacity) and weighed. Next, a screw-top vial (1.5 mL capacity) containing 1 mL of an iodine solution (1 wt % iodine concentration, 7 wt % potassium iodide concentration) was also placed in the headspace vial and capped tightly. After that, the headspace vial was placed in a desiccator at 65°C for 6 hours (thereby, I _{2 in} gaseous state was adsorbed on the sample). After that, the sample was collected in a ceramic boat and burned using an automatic sample burning device, and the generated gas was collected into 10 mL of the absorbing liquid. After the collection, the absorption solution was prepared to 15 mL with pure water, and IC quantitative analysis was performed on the stock solution or the appropriately diluted solution. In addition, the iodine adsorption amount was almost 0 after the same measurement was carried out only with the PET film, so the iodine weight and the weight of the protective layer monomer obtained by the IC quantitative analysis ("The weight of the PET film with the protective layer" - "The weight of the PET film" The iodine adsorption amount (% by weight) was calculated from the following formula. Iodine adsorption amount (% by weight)=Iodine weight obtained by IC quantitative analysis/weight of protective layer monomer×100 Also, the measuring apparatus and measuring conditions are as follows. [Measuring device] Automatic sample combustion device: "AQF-2100H" manufactured by Mitsubishi Chemical Analytech Co., Ltd. IC (anion): "ICS-3000" manufactured by Thermo Fisher Scientific Co., Ltd.

(4) Softening temperature of protective layer Local thermal analysis (Nano-TA measurement) was performed on the surface of the protective layer of the polarizing plates obtained in Examples and Comparative Examples, and the softening temperature of the protective layer was calculated. The measurement apparatus and measurement conditions are as follows. Measuring device: Hitachi High-Tech Science Co., product name "AFM5300E//Nano-TA2" Measurement Mode: Contact Mode Probe: AN2-200 Measurement area: 8µm Scanning Measurement gas environment: atmospheric pressure

(5) Judgment The obtained polarizing plate was judged according to the following criteria. Good: The value of ΔP is 0% to -4.0% Yes: The value of ΔP is greater than -4.0% and -10.0% Poor: The value of ΔP is greater than -10% and -99.9% (complete decolorization)

<Example 1> 1. Fabrication of polarizer/resin base laminate The resin substrate is a long strip of amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100µm) with a water absorption rate of 0.75% and a Tg of about 75°C. Corona treatment was performed on one side of the resin substrate. PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetylacetate modified PVA (manufactured by Mitsubishi Chemical Co., trade name "GOHSEFIMER Z410") at a ratio of 9:1 To 100 parts by weight, 13 parts by weight of potassium iodide was added to prepare an aqueous PVA solution (coating liquid). The above-mentioned PVA aqueous solution was coated on the corona-treated surface of the resin substrate and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained layered body was uniaxially stretched by 2.4 times the free end in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130°C (aerial-assisted stretching treatment). Next, the layered body was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubility treatment). Next, it was immersed for 60 seconds in a dyeing bath with a liquid temperature of 30° C. (an aqueous iodine solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) for 60 seconds so that the final The single transmittance (Ts) of the obtained polarizer was 41.5%±0.1% (dyeing treatment). Next, it was immersed in a cross-linking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (cross-linking treatment) at a liquid temperature of 40° C. ). Then, while immersing the layered body in a boric acid aqueous solution (boric acid concentration 4.0 wt %, potassium iodide 5 wt %) at a liquid temperature of 70° C., uniaxial stretching was performed in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds. so that the total extension ratio was 5.5 times (in water extension treatment). Then, the layered body was immersed in a cleaning bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (cleaning treatment). After that, while drying in an oven maintained at 90° C., the contact surface temperature was maintained at 75° C. with a heating roll made of SUS for about 2 seconds (drying shrinkage treatment). The shrinkage rate in the width direction of the laminate obtained by drying shrinkage treatment was 5.2%. In the above-described manner, a polarizer with a thickness of 5 µm was formed on the resin substrate to produce a polarizer/resin substrate laminate. The single transmittance (initial single transmittance) Ts0 of the polarizer was 42.0%, and the polarization degree (initial polarization degree) P0 was 99.996%.

2. Production of polarizing plate A cycloolefin-based film (ZT-12, 23 µm in thickness, manufactured by Japan Zeon Co., Ltd.) was attached to the surface of the polarizer obtained above as a film constituting the second protective layer through an ultraviolet curable adhesive. Specifically, it was applied so that the total thickness of the hardening adhesive was 1.0 µm, and was bonded using a rolling mill. After that, UV light is irradiated from the film side to harden the adhesive. Next, the resin base material was peeled off, and the polarizing plate which has the structure of a 2nd protective layer (ZT-12)/polarizer was obtained.

3. Production of protective layer 15 parts of an epoxy resin having a biphenyl skeleton (manufactured by Mitsubishi Chemical Co., trade name: jER (registered trademark) YX4000) was dissolved in 83.8 parts of methyl ethyl ketone to obtain an epoxy resin solution. To the obtained epoxy resin solution, 1.2 parts of a photocationic polymerization initiator (San-Apro Ltd., trade name: CPI (registered trademark)-100P) was added to obtain a protective layer forming composition. The obtained protective layer-forming composition was applied to the polarizer surface of the above-obtained polarizing plate with a wire bar, and the coated film was dried at 60° C. for 3 minutes. Next, ultraviolet rays were irradiated using a high-pressure mercury lamp so that the accumulated light amount would be 600 mJ/cm ^{2 to} form a protective layer. The thickness of the protective layer is 2µm~3µm. In the above manner, a polarizing plate having a configuration of protective layer/polarizer/another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the evaluation of the above-mentioned (1)-(4).

<Example 2> 15 parts of epoxy resin having a biphenyl skeleton (manufactured by Mitsubishi Chemical Co., trade name: jER (registered trademark) YX4000) and oxetane resin (manufactured by Toagosei Co., Ltd., trade name: ARON OXETANE (registered trademark)) 10 parts of OXT-221) were dissolved in 73 parts of methyl ethyl ketone to obtain an epoxy resin solution. To the obtained epoxy resin solution, 2 parts of a photocationic polymerization initiator (San-Apro Ltd., trade name: CPI (registered trademark)-100P) was added to obtain a protective layer forming composition. A protective layer was formed in the same manner as in Example 1, except that the epoxy resin solution was used to obtain a protective layer-forming composition. The thickness of the protective layer is 2µm~3µm. In the above manner, a polarizing plate having a configuration of protective layer/polarizer/another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the evaluation of the above-mentioned (1)-(4).

(Comparative Example 1) A protective layer was formed in the same manner as in Example 1, except that a hydrogenated bisphenol-type epoxy resin (manufactured by Mitsubishi Chemical Co., trade name: jER (registered trademark) YX8000) was used in place of the epoxy resin having a biphenyl skeleton . The thickness of the protective layer is 2µm~3µm. In the above manner, a polarizing plate having a configuration of protective layer/polarizer/another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the same evaluation as in Examples. The results are listed in Table 1.

(Comparative Example 2) A protection was formed in the same manner as in Example 2, except that a hydrogenated bisphenol-type epoxy resin (manufactured by Mitsubishi Chemical Co., trade name: jER (registered trademark) YX8000) was used in place of the epoxy resin having a biphenyl skeleton Floor. The thickness of the protective layer is 2µm~3µm. In the above manner, a polarizing plate having a configuration of protective layer/polarizer/another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the same evaluation as in Examples. The results are listed in Table 1.

(Comparative Example 3) A protective layer was formed in the same manner as in Example 1, except that a bisphenol-type epoxy resin (manufactured by Mitsubishi Chemical Co., trade name: jER (registered trademark) 828) was used in place of the epoxy resin having a biphenyl skeleton . The thickness of the protective layer is 2µm~3µm. In the above manner, a polarizing plate having a configuration of protective layer/polarizer/another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the same evaluation as in Examples. The results are listed in Table 1.

(Comparative Example 4) A protective layer was formed in the same manner as in Example 2, except that a bisphenol-type epoxy resin (manufactured by Mitsubishi Chemical Co., trade name: jER (registered trademark) 828) was used in place of the epoxy resin having a biphenyl skeleton . The thickness of the protective layer is 2µm~3µm. In the above manner, a polarizing plate having a configuration of protective layer/polarizer/another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the same evaluation as in Examples. The results are listed in Table 1.

(Comparative Example 5) 20 parts of polyester-based resins (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name: Nichigo-POLYESTER WR905) were dissolved in 80 parts of pure water to obtain a coating resin solution (20%). The coating resin solution was coated on the surface of the polarizer of the polarizing plate used in the examples using a wire bar, and the coating film was dried at 60° C. for 5 minutes to form a protective layer composed of a cured product of the coating film. The thickness of the protective layer is 2µm~3µm. In the above manner, a polarizing plate having a configuration of protective layer/polarizer/another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the same evaluation as in Examples. The results are listed in Table 1.

(Comparative Example 6) A protective layer/polarizer/another protective layer ( ZT-12) of the composition of the polarizing plate. The obtained polarizing plate was used for the same evaluation as in Examples. The results are listed in Table 1.

(Comparative Example 7) Polyurethane-based water-based dispersion resin (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., product name: SUPERFLEX SF210) was coated on the polarizer surface of the polarizing plate having the second protective layer (ZT-12)/polarizer An easy-adhesion layer was formed as a thickness of 0.1 µm as an easy-adhesion layer. Separately, 20 parts of an acrylic resin (manufactured by Kusumoto Chemical Co., Ltd., product name "B-734") of a copolymer of methyl methacrylate/butyl methacrylate (mol ratio 35/65) was dissolved in methyl ethyl acetate. In 80 parts of base ketones, an acrylic resin solution (20%) was obtained. Next, this acrylic resin solution was coated on the easily bonding layer with a wire bar, and the coating film was dried at 60° C. for 5 minutes to form a protective layer composed of a cured product of the coating film. The thickness of the protective layer was 3 µm, the softening temperature was 80.4°C, and the iodine adsorption amount was 30.4% by weight. In the above manner, a polarizing plate having a configuration of protective layer/polarizer/another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the same evaluation as in Examples. The results are listed in Table 1.

(Comparative Example 8) The same procedure as in Comparative Example 8 was carried out except that an acrylic resin (manufactured by Kusumoto Chemical Co., Ltd., product name "B-722") of a copolymer of methyl methacrylate/ethyl acrylate (mol ratio 55/45) was used. form a protective layer. The thickness of the protective layer was 3 µm, the softening temperature was 57.2°C, and the amount of iodine adsorption was 1.3% by weight. In the above manner, a polarizing plate having a configuration of protective layer/polarizer/another protective layer (ZT-12) was obtained. The obtained polarizing plate was used for the same evaluation as in Examples. The results are listed in Table 1.

[Table 1]

＜Assessment＞ As is clear from Table 1, even if the polarizing plates obtained in the examples are very thin, the decrease in optical properties is suppressed in a heating and humidifying environment, and they are excellent in durability.

industrial availability The polarizing plate of the present invention can be suitably used in an image display device. Examples of image display devices include portable devices such as portable information terminals (PDAs), smart phones, mobile phones, clocks, digital cameras, and portable game consoles; OA devices such as computer monitors, notebook computers, and copiers; Video cameras, televisions, microwave ovens and other household electrical appliances; rear-light monitors, monitors for car navigation systems, car audio and other in-vehicle appliances; digital signage, display devices such as information guide screens for commercial stores; monitors, etc. Alarm equipment; nursing care monitors, medical monitors and other nursing care medical equipment.

10: Polarizer 20: Protective layer 40: retardation layer 41: Tier 1 42: Tier 2 100: polarizer 110,111: Polarizing plate with retardation layer 200: Laminate G1~G4: Guide roller R1~R6: Conveying roller

FIG. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of drying shrinkage treatment using a heating roller in the method for producing a polarizing plate according to an embodiment of the present invention. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. 4 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention.

10: Polarizer

20: Protective layer

100: polarizer

Claims (8)

A polarizer, which has a polarizer and a protective layer disposed on one side of the polarizer; The protective layer is composed of a cured product of epoxy resin having a biphenyl skeleton. The polarizing plate of claim 1, wherein the cured product is a cationic polymer cured product. The polarizing plate according to claim 1 or 2, wherein the aforementioned protective layer further comprises an oxetane resin. The polarizing plate according to any one of claims 1 to 3, wherein the thickness of the aforementioned protective layer is 10 µm or less. The polarizing plate according to any one of claims 1 to 4, wherein the iodine adsorption amount of the protective layer is 10% by weight or less. The polarizing plate according to any one of claims 1 to 5, wherein the softening temperature of the protective layer is above 100°C. The polarizing plate according to any one of claims 1 to 6, whose total thickness is 10µm or less. A polarizing plate with retardation layer, which is provided with a retardation layer on the surface of the polarizing plate according to any one of claims 1 to 7 on which the protective layer is not arranged.

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