TW202208181A - Polarizing plate, retardation-layer-equipped polarizing plate, and image display device - Google Patents

Abstract

The present invention provides a polarizing plate in which the occurrence of cracking during heating is suppressed even while having a thin shape. The polarizing plate according to the present invention includes: a polarizer formed from a film of a polyvinyl alcohol-based resin containing a dichroic substance; and a protective layer disposed on one side of the polarizer. The protective layer is formed from a resin film having a thickness not more than 10 [mu]m. In one embodiment, formula (1) is satisfied when the transmittance of the polarizer alone is defined as x% and the birefringence of the polyvinyl alcohol-based resin is defined as y. In one embodiment, formula (2) is satisfied when the transmittance of the polarizer alone is defined as x% and the in-plane retardation of the polyvinyl alcohol-based resin film is defined as z nm. In one embodiment, formula (3) is satisfied when the transmittance of the polarizer alone is defined as x% and an alignment function of the polyvinyl alcohol-based resin is defined as f. In one embodiment, the piercing strength of the polarizer is 30 gf/[mu]m or more. (1): y < -0.011x+0.525 (2): z < -60x+2875 (3): f < -0.018x+1.11.

Description

Polarizing plate, polarizing plate with retardation layer and image display device

The present invention relates to a polarizing plate, a polarizing plate with retardation layer and an image display device.

In recent years, image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) have rapidly spread. Image display devices generally use polarizers and retardation plates that include a polarizer and a protective layer for protecting the polarizer. In practical applications, a polarizing plate with a retardation layer in which a polarizing plate and a retardation plate are integrated is widely used (for example, Patent Document 1). Recently, with the increasing demand for thinning of image display devices, the demand for thinning polarizing plates and polarizing plates with retardation layers is also increasing.

As a method of reducing the thickness of the polarizer, it has been proposed to reduce the thickness of the protective layer and to laminate the protective layer only on one side of the polarizer. However, these methods cannot sufficiently protect the polarizer, and there is a problem that cracks easily occur due to heating. 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 that suppresses the occurrence of cracks caused by heating even if it is very thin.

means of solving problems According to an aspect of the present invention, a polarizing plate is provided, which has a polarizing member composed of a polyvinyl alcohol-based resin film containing a dichroic substance and a protective layer disposed on one side of the polarizing member; When the volume transmittance is x% and the birefringence of the polyvinyl alcohol-based resin is y, the following formula (1) is satisfied; the protective layer is composed of a resin film having a thickness of 10 µm or less. y＜-0.011x+0.525 (1) According to an aspect of the present invention, a polarizing plate is provided, which has a polarizing member composed of a polyvinyl alcohol-based resin film containing a dichroic substance and a protective layer disposed on one side of the polarizing member; When the volume transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film is znm, the following formula (2) is satisfied; the protective layer is composed of a resin film having a thickness of 10 µm or less. z＜-60x+2875 (2) According to an aspect of the present invention, a polarizing plate is provided, which has a polarizing member composed of a polyvinyl alcohol-based resin film containing a dichroic substance and a protective layer disposed on one side of the polarizing member; When the volume transmittance is x% and the orientation function of the polyvinyl alcohol-based resin is set to f, the following formula (3) is satisfied; the protective layer is composed of a resin film having a thickness of 10 µm or less. f<-0.018x+1.11 (3). According to an aspect of the present invention, a polarizing plate is provided, which has a polarizing member made of a polyvinyl alcohol-based resin film containing a dichroic substance and a protective layer disposed on one side of the polarizing member; the puncture strength of the polarizing member is 30gf/µm or more; the protective layer is composed of a resin film with a thickness of 10µm or less. In one Embodiment, the said resin film contains at least 1 sort(s) of resin chosen from epoxy resin, (meth)acrylic-type resin, polyester-type resin, and urethane-type resin. In one Embodiment, the said resin film is comprised with the photocation hardened|cured material of epoxy resin, and the softening temperature of the said resin film is 100 degreeC or more. In one Embodiment, the said resin film consists of the hardened|cured material of the coating film of the organic solvent solution of an epoxy resin, and the softening temperature of the said resin film is 100 degreeC or more. In one Embodiment, the said resin film consists of the hardened|cured material of the coating film of the organic solvent solution of a thermoplastic (meth)acrylic resin, and the softening temperature of the said resin film is 100 degreeC or more. In one embodiment, the thermoplastic (meth)acrylic resin has a compound selected from the group consisting of lactone ring units, glutaric anhydride units, glutarimide units, maleic anhydride units, and maleimide units. At least 1 species in the group. In one embodiment, the iodine adsorption amount of the protective layer is 25% by weight or less. In one embodiment, the thickness of the polarizer is 10 μm or less. In one embodiment, the polarizing plate is wound in a roll shape. According to another aspect of the present invention, the polarizer and the retardation layer are included; and the retardation layer is arranged on the opposite side of the polarizer and the side where the protective layer is arranged. In one Embodiment, the said retardation layer is laminated|stacked on the said polarizing plate via an adhesive agent. In one embodiment, Re(550) of the retardation layer is 100 nm to 190 nm, Re(450)/Re(550) is 0.8 or more and less than 1, and the slow axis of the retardation layer and the absorption of the polarizer The angle formed by the axis is 40°~50°. According to another aspect of the present invention, there is provided an image display device including the above-mentioned polarizing plate or the polarizing plate with a retardation layer.

Invention effect According to the polarizing plate of the present invention, by using the polarizer in which the orientation state of the polyvinyl alcohol (PVA)-based resin is controlled, even when an extremely thin resin film is used as a protective layer, the occurrence of cracks during heating can be suppressed. . In addition, the polarizer can exhibit acceptable optical properties in practical use, so even if the polarizing plate of the present invention is very thin, both acceptable optical properties in practical use and suppression of cracks during heating can be achieved.

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In addition, the respective embodiments can be appropriately combined.

(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. Polarizing plate A-1. Outline of polarizing plate 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 includes a polarizer 10 , a first protective layer 20 disposed on one side of the polarizer 10 , and a second protective layer 30 disposed on the other side. The polarizer 10 is composed of a polyvinyl alcohol-based resin film containing a dichroic substance. The first protective layer 20 is formed of a resin film having a thickness of 10 µm or less. The second protective layer 30 may be omitted depending on the purpose. In addition, although not shown, a hard coat layer can be provided on the opposite side of the first protective layer 20 to the polarizer 10 according to needs, and an easy-bonding layer can be provided between the first protective layer 20 and the polarizer 10 .

In one embodiment, the polarizer 10 satisfies the following formula (1) when the monomer transmittance is x% and the birefringence of the polyvinyl alcohol-based resin constituting the polarizer is y. In one embodiment, the polarizer 10 satisfies the following formula (2) when the monomer transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film constituting the polarizer is znm. In one embodiment, the polarizer 10 satisfies the following formula (3) when the monomer transmittance is x% and the orientation function of the polyvinyl alcohol-based resin film constituting the polarizer is f. In one embodiment, the penetration strength of the polarizer is 30 gf/µm or more. y＜-0.011x+0.525 (1) z＜-60x+2875 (2) f＜-0.018x+1.11 (3)

The total thickness of the polarizing plate 100 is, for example, 20 µm or less, preferably 15 µm or less, more preferably 12 µm or less, and more preferably 10 µm or less. In addition, the total thickness of the polarizing plate is, for example, 5 µm or more.

Each layer or optical film constituting the polarizing plate may be bonded through the adhesive layer, or may be formed in close contact without passing through the adhesive layer. As an adhesive layer, an adhesive bond layer and an adhesive bond layer are mentioned. In the embodiment of the present invention, an adhesive layer can be suitably used. With the above-described configuration, the polarizing plate can be made thinner. Representative examples of the adhesive constituting the adhesive layer include active energy ray-curable adhesives (eg, UV-curable adhesives).

In the embodiment of the present invention, the thickness of the polarizing plate can be made 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.

After the polarizing plate is placed in an environment of 60°C and 95% RH for 500 hours, the variation ΔTs of the single transmittance Ts and the variation ΔP of the degree of polarization P are preferably very small. The monomer transmittance Ts can be 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 ₅₀₀ -Ts ₀ ΔP(%)=P ₅₀₀ -P ₀ Here, Ts ₀ is the transmittance of the monomer before placing (initial), Ts ₅₀₀ is the transmittance of the monomer after placing, P ₀ is the degree of polarization before placing (initial), and P ₅₀₀ is the degree of polarization after placing. ΔTs is preferably 3.0% or less, more preferably 2.5% or less, more preferably 2.0% or less, and more preferably 1.5% or less. ΔP should be -5.0%~0%, preferably -3.0%~0%, more preferably -1.0%~0%, and still more preferably -0.5%~0%.

The polarizing plate of the present invention can be either a single sheet or a long strip. In the present specification, the term "stripe" means an elongated shape with a sufficiently long length relative to the width, and includes, for example, an elongated shape having a length of 10 times or more and preferably 20 times or more of the width. The long polarizing plate can be wound into a roll.

A-2. Polarizer The above-mentioned polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance. In one embodiment, the polarizer satisfies the following formula (1) when the monomer transmittance is x% and the birefringence of the polyvinyl alcohol-based resin constituting the polarizer is y. In one embodiment, the polarizer satisfies the following formula (2) when the monomer transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film constituting the polarizer is znm. In one embodiment, the polarizer satisfies the following formula (3) when the monomer transmittance is x% and the orientation function of the polyvinyl alcohol-based resin film constituting the polarizer is f. In one embodiment, the penetration strength of the polarizer is 30 gf/µm or more. y＜-0.011x+0.525 (1) z＜-60x+2875 (2) f＜-0.018x+1.11 (3)

In the polarizer composed of a polyvinyl alcohol-based resin film containing dichroic substances, the birefringence of the PVA-based resin (hereinafter referred to as the birefringence of PVA or the Δn of PVA), the in-plane retardation of the PVA-based resin film (hereinafter referred to as the Denoted as "in-plane retardation of PVA"), orientation function of PVA-based resin (hereinafter denoted as "orientation function of PVA"), and puncture strength of the polarizer, all of which are related to the molecular chains of the PVA-based resin constituting the polarizer. Orientation related value. Specifically, the birefringence, in-plane retardation, and orientation function of PVA become large as the orientation degree increases, and the puncture intensity decreases as the orientation degree increases. The polarizer used in the present invention (that is, the polarizer that satisfies the above formulas (1) to (3) or the puncture strength), the orientation of the molecular chain of the PVA resin in the direction of the absorption axis is gentler than that of the conventional polarizer, so the absorption axis Heat shrinkage in the direction is suppressed. As a result, it is possible to obtain a polarizing plate which is extremely thin and which suppresses the occurrence of cracks during heating. In addition, because the flexibility of the polarizer is also good, a polarizer with excellent flexibility and bending resistance and durability can be obtained. The image display device can be preferably applied to a foldable image display device. In the past, it was difficult for a polarizer with a low degree of orientation to obtain acceptable optical properties (representatively, monomer transmittance and degree of polarization). allowable optical properties.

The polarizer preferably satisfies the following formula (1a) and/or the formula (2a), more preferably the following formula (1b) and/or the formula (2b). -0.004x+0.18＜y＜-0.011x+0.525 (1a) -0.003x+0.145＜y＜-0.011x+0.520 (1b) -40x+1800＜z＜-60x+2875 (2a) -30x+1450＜z＜-60x+2850 (2b)

In this specification, the in-plane retardation of the PVA is the in-plane retardation value of the PVA-based resin film at 23° C. and a wavelength of 1000 nm. By setting the near-infrared region as the measurement wavelength, the retardation can be measured excluding the influence of the absorption of iodine in the polarizer. In addition, the birefringence (in-plane birefringence) of the above-mentioned PVA is a value obtained by dividing the in-plane retardation of PVA by the thickness (nm) of the polarizer.

The in-plane phase difference of PVA was evaluated as follows. First, measure the retardation value with a plurality of wavelengths above 850 nm, and draw a plot of the measured retardation value: R(λ) and wavelength: λ, and fit it to the following Chromeyer using the least squares method (Sellmeier) formula. Here, A and B are fitting parameters, which are coefficients determined by the least squares method. R(λ)=A+B/(λ ² -600 ² ) At this time, the retardation value R(λ) can separate the in-plane retardation (Rpva) of the wavelength-independent PVA and the wavelength dependence as follows In-plane retardation value (Ri) of strong iodine. Rpva=A Ri=B/(λ ² -600 ² ) According to this separation formula, the in-plane phase difference (ie, Rpva) of PVA at wavelength λ=1000 nm can be calculated. In addition, the evaluation method of the in-plane phase difference of the PVA is also described in Japanese Patent No. 5932760, and can be referred to as necessary. In addition, the birefringence (Δn) of PVA can be calculated by dividing the retardation by the thickness.

As a commercially available apparatus for measuring the in-plane retardation of the above-mentioned PVA at a wavelength of 1000 nm, KOBRA-WR/IR series and KOBRA-31X/IR series manufactured by Oji Scientific Instruments Co., Ltd., etc. are mentioned.

The orientation function (f) of the polarizer used in the present invention preferably satisfies the following formula (3a), more preferably the following formula (3b). If the orientation function is too small, an allowable single transmittance and/or polarization degree may not be obtained. -0.01x+0.50＜f＜-0.018x+1.11 (3a) -0.01x+0.57＜f＜-0.018x+1.1 (3b)

The orientation function (f) is obtained, for example, by attenuated total reflection (ATR: attenuated total reflection) measurement using a Fourier transform infrared spectrophotometer (FT-IR) using polarized light as measurement light. Specifically, germanium is used for the microcrystalline system for adhering the polarizer, the incident angle of the measurement light is set at 45°, and the polarized infrared (measurement light) to be incident is directed toward the sample for crystallizing germanium. The polarized light (s-polarized light) of the parallel vibration of the close surface is measured in a state where the extending direction of the polarizer is parallel and perpendicular to the polarization direction of the measured light, and then the intensity of 2941 cm ^-1 of the obtained absorbance spectrum is used. , calculated according to the following formula. Here, the intensity I is a value of 2941 cm ^-1 /3330 cm ^-1 with 3330 cm ^-1 as a reference peak. In addition, f=1 is fully oriented, and f=0 is random. Also, we believe that the peak at 2941 cm ^-1 is due to the absorption of vibrations due to the PVA backbone (-CH ₂ -) in the polarizer. f=(3＜cos ² θ＞-1)/2 =(1-D)/[c(2D+1)] =-2×(1-D)/(2D+1) However, with c=( 3cos ² β-1)/2, when the vibration of 2941cm ^-1 , β=90°. θ: The angle of the molecular chain relative to the extension direction β: The angle of the transition dipole moment relative to the molecular chain axis D=(I _⊥ )/(I _// ) (At this time, the more oriented the PVA molecule is, the larger the D is) I _⊥ : The absorption intensity when the polarization direction of the measured light is perpendicular to the extending direction of the polarizer I _// : The absorption intensity when the polarization direction of the measured light is parallel to the extending direction of the polarizer

The thickness of the polarizer is preferably 10µm or less, preferably 8µm or less. The lower limit of the thickness of the polarizer may be, for example, 1 μm. The thickness of the polarizer can also be 2µm~10µm in one embodiment, and 2µm~8µm in another embodiment. By making the thickness of the polarizer very thin as described, thermal shrinkage can be made very small. It is presumed that the above-described configuration also contributes to suppressing the occurrence of cracks caused by heating.

The polarizer should exhibit absorption dichroism at any wavelength from 380nm to 780nm. The single transmittance of the polarizer is preferably 40.0% or more, more preferably 41.0% or more. The single transmittance may be, for example, 49.0% or less. In one embodiment, the single transmittance of the polarizer is 40.0% to 45.0%. The degree of polarization of the polarizer should preferably be above 99.0%, preferably above 99.4%. The degree of polarization may be, for example, 99.999% or less. In one embodiment, the degree of polarization of the polarizer is 99.0% to 99.99%. One of the characteristics of the polarizer used in the present invention is that even if the PVA-based resin constituting the polarizer has a lower degree of orientation and has the above-mentioned in-plane retardation, birefringence and/or orientation function, the above-mentioned The allowable monomer transmittance and polarization degree in practice. We speculate that it is due to the manufacturing method described later. In addition, the monomer transmittance represents the Y value obtained by measuring using an ultraviolet-visible light spectrophotometer and performing a visual sensitivity correction. The degree of polarization can be determined by the following formula based on the parallel transmittance Tp and the orthogonal transmittance Tc obtained by measuring using an ultraviolet-visible light spectrophotometer and correcting the visual sensitivity. Polarization (%)={(Tp-Tc)/(Tp+Tc)} ^{1 /2} ×100

The puncture intensity of the polarizer is, for example, 30gf/µm or more, preferably 35gf/µm or more, more preferably 40gf/µm or more, more preferably 45gf/µm or more, especially 50gf/µm or more. The upper limit of the puncture strength may be, for example, 80 gf/μm. By setting the puncture strength of the polarizer to the above-mentioned range, it is possible to significantly suppress the occurrence of cracks in the polarizer and the splitting of the polarizer in the direction of the absorption axis during heating. As a result, a polarizer (a polarizing plate as a result) that is very excellent in flexibility can be obtained. The puncture strength represents the crack resistance of the polarizer when the polarizer is punctured with a predetermined strength. The piercing strength can be represented by, for example, installing a predetermined needle in a compression tester, and expressing the strength (breaking strength) at which the polarizer breaks when the needle pierces the polarizer at a predetermined speed. Further, as apparent from the unit, the piercing strength means the piercing strength per unit thickness (1 µm) of the polarizer.

The polarizer is composed of a PVA-based resin film containing a dichroic substance as described above. Preferably, the PVA-based resin constituting the PVA-based resin film (substantially a polarizer) includes an acetyl-modified PVA-based resin. With the above configuration, a polarizer having a desired penetration strength can be obtained. When the entire PVA-based resin is 100% by weight, the blending amount of the acetylacetate-modified PVA-based resin is preferably 5% by weight to 20% by weight, more preferably 8% by weight to 12% by weight. If the blending amount is within the above-mentioned range, the puncture strength can be set to a more suitable range.

The polarizer can be typically produced by using a laminate of two or more layers. As a specific example of the polarizer obtained using the laminated body, the polarizer obtained by using the laminated body of the resin base material and the PVA-type resin layer formed in the resin base material by apply|coating is mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate, and This is dried to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; and the laminate is stretched and dyed to make the PVA-based resin layer a polarizer. In this embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. The stretching typically involves immersing the layered body in an aqueous solution of boric acid and stretching. In addition, the stretching preferably further includes a step of in-air stretching the layered body at a high temperature (eg, 95° C. or higher) before stretching in a boric acid aqueous solution. In the embodiment of the present invention, the total extension ratio is preferably 3.0 times to 4.5 times, which is significantly smaller than the general one. Even at the total magnification of the stretch, a polarizer with acceptable optical properties can be obtained by a combination of halide addition and drying shrink treatment. In addition, in the embodiment of the present invention, the stretching ratio of the aerial auxiliary stretching is preferably larger than the stretching ratio of the boric acid water stretching. By making such a configuration, even if the total magnification of extension is small, a polarizer having acceptable optical characteristics can be obtained. In addition, the layered body is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. In one embodiment, the manufacturing method of the polarizer includes sequentially performing air-assisted stretching treatment, dyeing treatment, underwater stretching treatment and drying shrinkage treatment on the laminate. By introducing auxiliary stretching, the crystallinity of the PVA-based resin can be improved even when the PVA-based resin is coated on the thermoplastic resin, and high optical properties can be achieved. In addition, by improving the orientation of the PVA-based resin in advance, problems such as lowering of the orientation or dissolution of the PVA-based resin when immersed in water in the subsequent dyeing step or stretching step can be prevented, and high optical properties can be achieved. In addition, when the PVA-based resin layer is immersed in a liquid, the disorder of orientation of the polyvinyl alcohol molecules and the decrease in 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. In addition, by shrinking the laminate in the width direction by drying shrinkage treatment, the optical properties can be improved. The obtained laminate of resin substrate/polarizer can be used as it is (that is, the resin substrate can also be used as a protective layer of the polarizer), or the resin substrate can be peeled off from the laminate of resin substrate/polarizer and the Any suitable protective layer of the area layer is then used depending on the purpose. The details of the manufacturing method of the polarizer will be explained in detail in item A-3.

A-3. Manufacturing method of polarizer The manufacturing method of a polarizer according to an embodiment of the present invention includes the following steps: forming a polyvinyl alcohol-based resin layer (PVA) containing 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 sequence, and the drying shrinkage treatment is to convey the layered body in the longitudinal direction. Heating, thereby shrinking it by 1% to 10% in the width direction. The content of the halide 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℃. The shrinkage rate in the width direction of the laminate obtained by drying shrinkage treatment is preferably 1% to 10%. According to the manufacturing method, the polarizer described in the above item A-2 can be obtained. In particular, a polarizer having excellent optical properties (representatively, monomer transmittance and degree of polarization) can be obtained by: after producing a laminate containing a PVA-based resin layer containing a halide, extending the laminate Multi-stage stretching including aerial auxiliary stretching and underwater stretching is performed, and the stretched laminate is heated with a heating roller.

A-3-1. Fabrication of laminated body Any appropriate method can be adopted as a method of producing the laminate of the thermoplastic resin base material and the PVA-based resin layer. Preferably, the coating liquid containing halide and PVA-based resin is coated on the surface of the thermoplastic resin substrate and dried, thereby forming a PVA-based resin layer on the thermoplastic resin substrate. As described above, the content of the halide 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.

Any appropriate method can be adopted for the coating method of the coating liquid. For example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a blade coating method (a notch coating method, etc.) etc. are mentioned. The coating and drying temperature of the above-mentioned coating liquid is preferably 50°C or higher.

The thickness of the PVA-based resin layer is preferably 2µm~30µm, more preferably 2µm~20µm. By making the thickness of the PVA-based resin layer before stretching very thin as described above, and reducing the total stretching ratio as described later, a polarizer having an allowable monomer transmittance and degree of polarization can be obtained even if the orientation function is very small.

Before forming the PVA-based resin layer, a surface treatment (eg, corona treatment, etc.) may be performed on the thermoplastic resin substrate, and an easily bonding layer may be formed on the thermoplastic resin substrate. The adhesiveness between the thermoplastic resin base material and the PVA-based resin layer can be improved by performing the above-mentioned treatment.

A-3-1-1. Thermoplastic resin substrate Any appropriate thermoplastic resin film can be used as the thermoplastic resin substrate. Details of the thermoplastic resin film substrate are described in, for example, Japanese Patent Laid-Open No. 2012-73580 or Japanese Patent No. 6470455. In this specification, the entire description of this gazette is incorporated by reference.

A-3-1-2. Coating liquid The coating liquid system contains a halide and a PVA-based resin as described above. The above-mentioned 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. If it is the said resin concentration, a uniform coating film adhering to a thermoplastic resin base material can be formed. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

Additives can also be mixed in the coating liquid. The additives include, for example, plasticizers, surfactants, and the like. As a plasticizer, polyhydric alcohols, such as ethylene glycol and glycerol, are mentioned, for example. As a surfactant, a nonionic surfactant is mentioned, for example. These can be used in order to further improve the uniformity, dyeability, and extensibility of the obtained PVA-based resin layer.

Any appropriate resin can be used as the above-mentioned PVA-based resin. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers can be obtained by saponifying ethylene-vinyl acetate copolymers. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be obtained in accordance with JIS K 6726-1994. By using the PVA-based resin having the above degree of saponification, a polarizer excellent in durability can be obtained. When the saponification is too high, there is a risk of gelation. As mentioned above, the PVA-based resin preferably includes a PVA-based resin modified with an acetyl acetyl group.

The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average degree of polymerization is usually 1000~10000, preferably 1200~4500, more preferably 1500~4300. In addition, the average degree of polymerization can be obtained according to JIS K 6726-1994.

Any appropriate halide can be used as the above-mentioned halide. 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 solution is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA resin, preferably 10 to 15 parts by weight relative to 100 parts by weight of the PVA resin. If the amount of the halide relative to 100 parts by weight of the PVA resin is more than 20 parts by weight, 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, in order to stabilize the stretching of the thermoplastic resin base material, the above-mentioned laminate is stretched in boric acid water at a relatively high temperature. 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, whereas the extension of the laminate of A-PET (thermoplastic resin substrate) and the PVA-based resin layer is performed at around 70°C. At a higher temperature, the orientation of the PVA at the beginning of the extension is reduced at the stage before the rise by the extension in water. In this regard, by fabricating a laminate of a halide-containing PVA-based resin layer and a thermoplastic resin substrate, and subjecting the laminate to high-temperature stretching (assisted stretching) in air before stretching 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.

A-3-2. Air Aid Extension Processing In particular, in order to obtain high optical properties, a two-stage stretching method combining dry stretching (assisted stretching) and boric acid water stretching is selected. As in the two-stage stretching method, by introducing auxiliary stretching, the stretching can be performed while suppressing the crystallization of the thermoplastic resin base material. In addition, in order to suppress the influence of the glass transition temperature of the thermoplastic resin substrate when applying the PVA-based resin to the thermoplastic resin substrate, the application temperature must be higher than that of applying the PVA-based resin to a general metal drum. If it is lower, as a result, the crystallization of the PVA-based resin becomes relatively low and sufficient optical properties cannot be obtained. In this regard, by introducing auxiliary stretching, even when the PVA-based resin is coated on the thermoplastic resin, the crystallinity of the PVA-based resin can be improved, and high optical properties can be achieved. In addition, by improving the orientation of the PVA-based resin in advance, problems such as lowering of the orientation or dissolution of the PVA-based resin when immersed in water in the subsequent dyeing step or stretching step can be prevented, and high optical properties can be achieved.

The stretching method of aerial auxiliary stretching can be either fixed-end stretching (such as a method of stretching using a tenter stretching machine) or free-end stretching (such as a method of uniaxial stretching of the laminated body through rolls with different peripheral speeds) . In order to obtain high optical properties, free end extensions can be actively employed. In one embodiment, the in-air stretching treatment includes a heating roll stretching step of extending the above-mentioned layered body using the difference in peripheral speed between the heating rolls while conveying the above-mentioned layered body in the longitudinal direction thereof. The in-air stretching process typically includes a zone stretching step and a heating roll stretching step. In addition, the sequence of the zone stretching step and the heating roller stretching step is not limited, and the zone stretching step may be performed first, or the heating roller stretching step may be performed first. The region extension step can also be omitted. In one embodiment, the zone stretching step and the heating roll stretching step are performed in sequence. Moreover, in another embodiment, the film edge part is hold|gripped in a tenter-stretching machine, and the distance between tenters is extended in the advancing direction, and it stretches (the increase of the distance between tenters is a stretching ratio). At this time, the distance of the tenter in the width direction (vertical direction with respect to the traveling direction) is set to be arbitrarily close. It should be possible to set the extension ratio relative to the travel direction to use the free end extension for approaching. When it is extended at the free end, it is calculated by the shrinkage rate in the width direction = (1/extension ratio) ^1/2 .

Aerial assist extension can be performed in one stage or in multiple stages. When it is carried out in multiple stages, the stretching ratio is the product of the stretching ratios of each stage. The extension direction of the aerial auxiliary extension should be approximately the same as the extension direction of the underwater extension.

The extension magnification of the aerial auxiliary extension should be 1.0 times to 4.0 times, preferably 1.5 times to 3.5 times, and more preferably 2.0 times to 3.0 times. If the stretching magnification of the aerial auxiliary stretching is within the above-mentioned range, the total stretching magnification can be set to a desired range when combined with the underwater stretching, and the desired orientation function can be realized. As a result, a polarizing plate with a retardation layer in which the occurrence of cracks caused by heating is suppressed can be obtained. Also, as mentioned above, the stretching ratio of the air-assisted stretching is preferably larger than the stretching ratio of the boric acid water stretching. By making such a configuration, even if the total magnification of extension is small, a polarizer having acceptable optical characteristics can be obtained. More specifically, the ratio of the extension magnification of the aerial auxiliary extension to the extension magnification of the underwater extension (the underwater extension/the aerial auxiliary extension) is preferably 0.4 to 0.9, more preferably 0.5 to 0.8.

The stretching temperature of the air-assisted stretching can be set to any appropriate value according to the forming material of the thermoplastic resin substrate, the stretching method, and the like. The stretching temperature is preferably above the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably above the glass transition temperature (Tg) of the thermoplastic resin substrate + 10°C or higher, particularly preferably Tg + 15°C or higher. On the other hand, the upper limit of the stretching temperature is preferably 170°C. The rapid progress of crystallization of the PVA-based resin can be suppressed by elongation at such a temperature, and the inconvenience caused by the crystallization (for example, hindering the orientation of the PVA-based resin layer due to elongation) can be suppressed.

A-3-3. Insolubility treatment, dyeing treatment and cross-linking treatment If necessary, insolubilization treatment is performed after the air-assisted extension treatment and before the water extension treatment or dyeing treatment. The above-mentioned insolubilization treatment is performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. The above dyeing treatment is performed by dyeing the PVA-based resin layer with a dichroic substance (iodine in the representative). If necessary, after the dyeing treatment and before the extension treatment in water, a cross-linking treatment is performed. The above-mentioned crosslinking treatment can be typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. Details of the insolubilization treatment, dyeing treatment, and crosslinking treatment are described in, for example, Japanese Patent Laid-Open No. 2012-73580 (above).

A-3-4. Underwater extension treatment The underwater stretching treatment is performed by immersing the layered body in a stretching bath. By the underwater stretching treatment, stretching can be performed at a temperature lower than the glass transition temperature (about 80°C in the representative) of the thermoplastic resin substrate or the PVA-based resin layer, and the crystallization of the PVA-based resin layer can be suppressed. extend. As a result, a polarizer with excellent optical properties can be produced.

Any appropriate method can be adopted as the method of extending the layered body. Specifically, it may be either fixed-end stretching or free-end stretching (for example, a method of uniaxially stretching the layered body through rolls having different peripheral speeds). The free end extension should be selected. The extension of the laminate may be performed in one stage or in multiple stages. When it is carried out in multiple stages, the total stretching ratio is the product of the stretching ratios of each stage.

The stretching in water is preferably performed by immersing the layered body in an aqueous boric acid solution (stretching in water with boric acid). By using the boric acid aqueous solution as the stretching bath, the PVA-based resin layer can be provided with rigidity and water-insoluble water resistance capable of withstanding the tension applied during stretching. Specifically, boric acid generates tetrahydroxyboronic acid anion in an aqueous solution and can be cross-linked with PVA-based resin by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, and good extension can be performed, thereby producing a polarizer with excellent optical properties.

The above boric acid aqueous solution is preferably obtained by dissolving boric acid and/or borate in water which is a solvent. The boric acid concentration is preferably 1 to 10 parts by weight relative to 100 parts by weight of water, preferably 2.5 to 6 parts by weight, and particularly preferably 3 to 5 parts by weight. By setting the boric acid concentration to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizer with higher characteristics can be produced. In addition to boric acid or borate, an aqueous solution obtained by dissolving boron compounds such as borax, glyoxal, and glutaraldehyde in a solvent can also be used.

The above-mentioned extension bath (aqueous boric acid solution) is preferably admixed with iodide. By blending the iodide, the elution of the iodine adsorbed on the PVA-based resin layer can be suppressed. Specific examples of the iodide are as described above. The concentration of iodide relative to 100 parts by weight of water is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight.

The extension temperature (the liquid temperature of the extension bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. If it is such a temperature, the dissolution of the PVA-based resin layer can be suppressed, and at the same time, it can be stretched at a high rate. Specifically, as described above, in relation to the formation of the PVA-based resin layer, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60° C. or higher. At this time, if the stretching temperature is lower than 40° C., even if it is considered that the thermoplastic resin base material is plasticized with water, it may not be able to be stretched well. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and there is a fear that excellent optical properties cannot be obtained. The immersion time for the layered body to be immersed in the stretching bath is preferably 15 seconds to 5 minutes.

The stretching magnification for the underwater stretching is preferably 1.0 times to 2.2 times, more preferably 1.1 times to 2.0 times, more preferably 1.1 times to 1.8 times, and more preferably 1.2 times to 1.6 times. If the stretching magnification for underwater stretching is within the range, the total stretching magnification can be set to a desired range, and the desired birefringence, in-plane retardation and/or orientation function can be achieved. As a result, a polarizing plate with a retardation layer in which the occurrence of cracks caused by heating is suppressed can be obtained. The total stretching magnification (the sum of the stretching magnification when combining aerial auxiliary stretching and underwater stretching) is as described above, relative to the original length of the layered body, it should be 3.0 times to 4.5 times, preferably 3.0 times to 4.3 times, and more preferably 3.0 times. times ~ 4.0 times. By adding a halide to the coating solution, adjusting the stretching ratios of air-assisted stretching and underwater stretching, and drying shrinking treatment, a polarizer with acceptable optical properties can be obtained even if the total stretching ratio is the same.

A-3-5. Drying shrinkage treatment The above-mentioned drying shrinkage treatment can be performed by zone heating by heating the entire zone, 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 occurrence of wrinkling 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 1% to 10%, more preferably 2% to 8%, especially 4% to 6%.

FIG. 2 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage treatment, the layered body 50 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 50 . 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 there are plural conveying rollers. The number of conveying rollers is usually 2 to 40, and 4 to 30 should be set. 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.

A-3-6. Other processing 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.

A-4. 1st layer of protection The thickness of the above-mentioned first protective layer is 10 µm or less. By setting the thickness of the first protective layer to be 10 µm or less, it can contribute to the thinning of the polarizing plate. Furthermore, conventionally, from the viewpoint of protecting the polarizer by following the shrinkage of the polarizer during heating, a protective layer having a thickness of 20 µm or more is used. In contrast, the polarizer used in the embodiment of the present invention is as described above, and the degree of orientation of the PVA-based resin is lower than that of the prior art, and as a result, the shrinkage due to heating is small, so even when a protective layer with a thickness of 10 µm or less is used, it can still be suppressed. Cracks occur during heating.

The thickness of the first protective layer is preferably 7µm or less, more preferably 5µm or less, and more preferably 3µm or less. The thickness of the first protective layer is, for example, 1 µm or more.

The first protective layer is formed of a resin film. As the resin forming the resin film, any appropriate resin can be used according to the purpose. Specific examples include (meth)acrylic resins, cellulose-based resins such as triacetate cellulose (TAC), polyester-based, polyurethane-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, Polyimide-based, polyether-based, poly-based, polystyrene-based, polynorbornene-based, polyolefin-based, and acetate-based thermoplastic resins; (meth)acrylic-based, urethane-based , (meth)acrylate urethane series, epoxy series, polysiloxane series and other thermosetting resins or active energy ray curing resins; glassy polymers such as siloxane series polymers. In one embodiment, at least one resin selected from the group consisting of epoxy resins, (meth)acrylic resins, polyester resins, and urethane resins can be used as the resin forming the resin film.

The resin film constituting the first protective layer may be, for example, a molded product of a molten resin, a cured product of a coating film of a resin solution obtained by dissolving or dispersing the resin in an aqueous solvent or an organic solvent, or a cured resin. Hardened product (eg photocationic hardened product).

In one embodiment, the first protective layer is composed of at least one selected from the group consisting of thermoplastic (meth)acrylic resins (hereinafter, only (meth)acrylic resins may be used in some cases) The cured product of the coating film of the organic solvent solution called "acrylic resin"), the photocation hardened product of epoxy resin, and the cured product of the coating film of the organic solvent solution of epoxy resin. The concrete description will be given below.

A-4-1. Cured product of coating film of organic solvent solution of thermoplastic acrylic resin In one Embodiment, the 1st protective layer consists of the hardened|cured material of the coating film of the organic solvent solution of thermoplastic acrylic resin. From the viewpoint of humidification durability, the softening temperature of the first protective layer of the present embodiment is preferably 100°C or higher, more preferably 115°C or higher, more preferably 120°C or higher, particularly preferably 125°C or higher; and, From the viewpoint of formability, it 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.

A-4-1-1. Acrylic resin The glass transition temperature (Tg) of the acrylic resin is preferably 100°C or higher. As a result, the softening temperature of the first protective layer is almost 100°C or higher. When the Tg of the acrylic resin is 100° C. or higher, the polarizing plate including the protective layer obtained from the resin will be excellent not only in crack resistance but also in humidification durability. The Tg of the acrylic resin is preferably 110°C or higher, more preferably 115°C or higher, still more preferably 120°C or higher, particularly preferably 125°C or higher. On the other hand, the Tg of the acrylic resin 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. When the Tg of the acrylic resin is within the above range, the moldability is good.

Any appropriate acrylic resin can be used as long as the acrylic resin has the above-mentioned Tg. The acrylic resin typically contains an alkyl (meth)acrylate as a monomer unit (repeating unit) as a main component. In this specification, "(meth)acrylic acid" means acrylic acid and/or methacrylic acid. The alkyl (meth)acrylate constituting the main skeleton of the acrylic resin can be exemplified by those having 1 to 18 carbon atoms in a linear or branched alkyl group. These may be used alone or may be used in combination. Moreover, arbitrary appropriate comonomers can also be introduce|transduced into acrylic resin by copolymerization. The repeating unit derived from alkyl (meth)acrylate is represented by the following general formula (1):

[Chemical formula 1]

In the general formula (1), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrogen atom or a substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. As a substituent, halogen and a hydroxyl group are mentioned, for example. Specific examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, (meth)acrylate base) tertiary butyl acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, (meth)acrylic acid Dicyclopentyloxyethyl, (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, ( 3-hydroxypropyl meth)acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate, 2,3,4,5-tetrahydroxypentyl (meth)acrylate, 2- Methyl (hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, methyl 2-(hydroxyethyl)acrylate. In the general formula (1), R ⁵ is preferably a hydrogen atom or a methyl group. Therefore, particularly desirable alkyl (meth)acrylates are methyl acrylate or methyl methacrylate.

The acrylic resin may contain only a single alkyl (meth)acrylate unit, or may contain a plurality of alkyl (meth)acrylate units in which R ⁴ and R ⁵ in the general formula (1) are different from each other. .

The content ratio of the alkyl (meth)acrylate units in the acrylic resin is preferably 50 mol% to 98 mol%, preferably 55 mol% to 98 mol%, and more preferably 60 mol% to 60 mol% to 98 mol%. 98 mol%, preferably 65 mol% to 98 mol%, most preferably 70 mol% to 97 mol%. If the content ratio is less than 50 mol %, there is a fear that the effects (eg, high heat resistance and high transparency) derived from the alkyl (meth)acrylate units cannot be fully exhibited. When the said content ratio exceeds 98 mol%, there exists a possibility that resin will become weak and will be easily broken, and high mechanical strength cannot fully be exhibited, and there exists a possibility that productivity may deteriorate.

The acrylic resin preferably has a repeating unit including a ring structure. The repeating unit including a ring structure includes a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide (N-substituted maleimide) unit. The repeating unit containing a ring structure may be contained in the repeating unit of an acrylic resin by only 1 type, and may be contained in 2 or more types.

The lactone ring unit is preferably represented by the following general formula (2):

通式(2)中，R¹ 、R² 及R³ 分別獨立表示氫原子或碳數1~20之有機殘基。此外，有機殘基亦可包含有氧原子。丙烯酸系樹脂中可僅包含有單一的內酯環單元，亦可包含有複數個上述通式(2)中之R¹ 、R² 及R³ 互異的內酯環單元。具有內酯環單元之丙烯酸系樹脂已記載於例如日本專利特開2008-181078號公報中，而本說明書即援用該公報之記載作為參考。[Chemical formula 2]

In the general formula (2), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. In addition, the organic residue may also contain oxygen atoms. The acrylic resin may contain only a single lactone ring unit, or may contain a plurality of lactone ring units in which R ¹ , R ² and R ³ in the general formula (2) are mutually different. The acrylic resin having a lactone ring unit is described in, for example, Japanese Patent Laid-Open No. 2008-181078, and the description of the publication is incorporated herein by reference.

The glutarimide unit is preferably represented by the following general formula (3):

[Chemical formula 3]

In the general formula (3), R ¹¹ and R ¹² independently represent hydrogen or an alkyl group with 1 to 8 carbon atoms, and R ¹³ represents hydrogen, an alkyl group with a carbon number of 1 to 18, a cycloalkyl group with a carbon number of 3 to 12 or a carbon number of 6 ~10 aryl. In the general formula (3), R ¹¹ and R ¹² are preferably each independently hydrogen or methyl, and R ¹³ is hydrogen, methyl, butyl or cyclohexyl. Preferably, R ¹¹ is methyl, R ¹² is hydrogen, and R ¹³ is methyl. The acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units in which R ¹¹ , R ¹² and R ¹³ in the general formula (3) are different from each other. Acrylic resins having a glutarimide unit are described in, for example, Japanese Patent Laid-Open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560, Japanese Patent Laid-Open No. 2006-328334, and Japanese Patent Laid-Open No. 2006 -337491, Japanese Patent Laid-Open No. 2006-337492, Japanese Patent Laid-Open No. 2006-337493, and Japanese Patent Laid-Open No. 2006-337569, and the description of these publications is incorporated herein by reference. In addition, regarding the glutaric anhydride unit, the above description regarding the glutarimide unit applies except that the nitrogen atom substituted by R ¹³ of the above-mentioned general formula (3) is changed to an oxygen atom.

About the maleic anhydride unit and the maleimide (N-substituted maleimide) unit, the structure can be specified by the name, and therefore the specific description is omitted.

The content ratio of the repeating unit including the ring structure in the acrylic resin is preferably 1 mol% to 50 mol%, preferably 10 mol% to 40 mol%, more preferably 20 mol% to 30 mol% . When the content ratio is too small, the Tg may be lower than 100°C, and the heat resistance, solvent resistance, and surface hardness of the obtained protective layer may be insufficient. When the content ratio is too large, the moldability and transparency may be insufficient.

The acrylic resin may contain a repeating unit other than the repeating unit containing an alkyl (meth)acrylate unit and a ring structure. The repeating unit may be a repeating unit (other vinyl-based monomer unit) derived from a vinyl-based monomer copolymerizable with the monomer constituting the above-mentioned unit. Examples of other vinyl-based monomers include acrylic acid, methacrylic acid, crotonic acid, 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, acrylonitrile, methacrylonitrile, ethacrylonitrile, Allyl glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, acrylic acid amine ethyl Esters, propylamine ethyl acrylate, dimethylamine ethyl methacrylate, ethyl amine propyl methacrylate, cyclohexyl amine ethyl methacrylate, N-vinyldiethylamine, N-acetyl Vinylamine, allylamine, methallylamine, N-methallylamine, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-propenyl- Oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, 2-benzene Vinyl-oxazoline, etc. These may be used alone or in combination. The kind, quantity, combination, content ratio, etc. of other vinyl-based monomer units can be appropriately set according to the purpose.

The weight average molecular weight of the acrylic resin is preferably 1,000-2,000,000, more preferably 5,000-1,000,000, more preferably 10,000-500,000, particularly preferably 50,000-500,000, and most preferably 60,000-150,000. The weight average molecular weight can be determined in terms of polystyrene using, for example, gel permeation chromatography (GPC system, manufactured by Tosoh Corporation). In addition, tetrahydrofuran can be used as a solvent.

The acrylic resin can be used by appropriately combining the above-mentioned monomer units, and can be polymerized by any appropriate polymerization method.

In the embodiment of the present invention, an acrylic resin and other resins may be used in combination. That is, the monomer components constituting the acrylic resin and the monomer components constituting other resins may be copolymerized, and the copolymer may be used for forming the protective layer described later; the blend of the acrylic resin and other resins may also be used for Forming of 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 , Polyetherimide and other thermoplastic resins. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose, the properties desired for the obtained film, and the like. For example, a styrene-based resin (preferably an acrylonitrile-styrene copolymer) can be used in combination as a retardation control agent.

The content of the acrylic resin in the first protective layer of the present embodiment is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight, more preferably 70% by weight to 100% by weight, particularly preferably 80% by weight % by weight to 100% by weight. When content is less than 50 weight%, there exists a possibility that the high heat resistance and high transparency which an acrylic resin originally has may not fully be reflected.

The first protective layer of the present embodiment can be formed by, for example, coating the surface of the polarizer with an organic solvent solution of an acrylic resin to form a coating film, and curing the coating film.

As the organic solvent, any appropriate organic solvent that can dissolve or uniformly disperse the acrylic resin can be used. Specific examples of the organic solvent include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone.

The acrylic 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. If it is the said resin density|concentration, a uniform coating film which adheres to a polarizer can be formed.

The solution can be coated on any suitable substrate, and can also be coated on the polarizer. When coated on a substrate, the cured product of the coating film formed on the substrate is transferred to the polarizer. When applying to the polarizer, the first protective layer is directly formed on the polarizer by drying (curing) the coating film. Preferably, the solution is coated on the polarizer, and the first 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.).

The first protective layer can be formed by drying (curing) the coating film of the solution. The drying temperature is preferably below 100°C, preferably 50°C to 70°C. If the drying temperature is within the above range, adverse effects on the polarizer can be prevented. The drying time may vary according to the drying temperature. The drying time may be, for example, 1 minute to 10 minutes.

A-4-2. Light cation hardened product of epoxy resin In one embodiment, the first protective layer is made of a photocationic cured epoxy resin. By using the protective layer, the occurrence of cracks can be suppressed, and excellent humidification durability can be obtained. As described above, since the first protective layer is a photocationic cured product, the composition for forming a protective layer contains a photocationic polymerization initiator. The photocationic polymerization initiator is a photosensitizer having the function of a photoacid generator, and representative examples thereof include ionic onium salts composed of a cation part and an anion part. In this onium salt, the cation part absorbs light, and the anion part becomes a source of acid generation. Ring-opening polymerization of epoxy groups is performed by the acid generated from the photocationic polymerization initiator. The softening temperature of the first protective layer of the obtained photocationic cured product is high, and the amount of iodine adsorption can be reduced. Therefore, it is possible to provide a polarizing plate in which the occurrence of cracks is suppressed and which has excellent humidification durability.

From the viewpoint of humidification durability, the softening temperature of the first protective layer of the present embodiment is preferably 100°C or higher, more preferably 110°C or higher, more preferably 120°C or higher, particularly preferably 125°C or higher; and, From the viewpoint of formability, it 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.

A-4-2-1. Epoxy resin As the epoxy resin, any appropriate epoxy resin can be used, and an epoxy resin having an aromatic ring or an alicyclic ring can be suitably used. In this embodiment, it is preferable to use the epoxy resin which has at least 1 sort(s) chosen from the group which consists of an aromatic skeleton and a hydrogenated aromatic skeleton. As an aromatic skeleton, a benzene ring, a naphthalene ring, a perylene ring, etc. are mentioned, for example. The epoxy resin may be used alone or in combination of two or more. It is preferable to use an epoxy resin having a biphenyl skeleton or a bisphenol skeleton as an aromatic skeleton or a hydrogenated product thereof. By using the epoxy resin, it is possible to provide a polarizing plate having more excellent durability and excellent flexibility. The epoxy resin having a biphenyl skeleton will be described in detail below as a representative example.

(式中，R¹⁴ ~R²¹ 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)。In one Embodiment, the epoxy resin which has a biphenyl skeleton contains the epoxy resin of the following structure. 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 4]

(In the formula, R ¹⁴ to R ²¹ 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 ¹⁴ to R ²¹ 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，R¹⁴ ~R²¹ 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 5]

(wherein, R ¹⁴ to R ²¹ 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 above epoxy resin (epoxy resin after photocationic hardening) preferably has a glass transition temperature (Tg) of 100°C or higher. As a result, the softening temperature of the protective layer is almost 100°C or higher. When the Tg of the epoxy resin 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 is preferably 110°C or higher, more preferably 120°C or higher, and particularly preferably 125°C or higher. On the other hand, the Tg of the epoxy resin 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. When the Tg of the epoxy resin is within the above range, the moldability can be excellent.

The epoxy equivalent of the above-mentioned epoxy resin 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 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 is in the above-mentioned range, a more stable protective layer (a protective layer with less residual monomer and sufficiently cured) 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 this embodiment, the said epoxy resin and other resin may be used together. That is, the above-mentioned epoxy resin (for example, an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton) and other resins may be used for protection. Formation of layers. 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. Acrylic resins and oxetane-based resins can be suitably used. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose, the properties desired for 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 (meth)acrylic compound 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.

As the oxetane resin, 3-ethyl-3-hydroxymethyl oxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl] benzene, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(oxiranylmethoxy)oxetane, (methyl ) (3-ethyloxetan-3-yl)methyl acrylate, 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxy Hetidine etc. These oxetane resins can be easily obtained, and have excellent diluting properties (low viscosity) and 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. The hardenability and durability of the protective layer can be improved by using these oxetane resins.

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 Co., Ltd.) can be used. ARON OXETANE OXT-101 and ARON OXETANE OXT-221 can be preferably used.

In the first protective layer of the present embodiment, the content of the epoxy resin (for example, an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton) 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, 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 or a bisphenol skeleton and an oxetane resin are used in combination, the amount of the oxetane resin is 100 parts by weight relative to the total amount of the epoxy resin and the oxetane resin. The content is preferably 1 part by weight to 50 parts by weight, preferably 5 parts by weight to 45 parts by weight, and more preferably 10 parts by weight 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.

A-4-2-2. Photocationic polymerization initiator The photocationic polymerization initiator is a photosensitizer having the function of a photoacid generator, and representative examples thereof include ionic onium salts composed of a cation part and an anion part. In this onium salt, the cation part absorbs light, and the anion part becomes a source of acid generation. Ring-opening polymerization of epoxy groups is performed by the acid generated from the photocationic polymerization initiator. As a photocationic polymerization initiator, any appropriate compound which can harden the epoxy resin which has at least 1 sort(s) chosen from the group which consists of an aromatic skeleton and a hydrogenated aromatic 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.

With respect to 100 parts by weight of the above epoxy resin (for example, an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton), the content of the photocationic polymerization initiator is preferably 100 parts by weight. 0.1 to 3 parts by weight, preferably 0.25 to 2 parts by weight. 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).

The first protective layer of the present embodiment can be formed by, for example, applying the composition containing the epoxy resin and the photocationic polymerization initiator to form a coating film, and irradiating the coating film with light (eg, ultraviolet rays).

Any appropriate solvent that can dissolve or uniformly disperse the epoxy resin 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 in the above composition is preferably 10 to 30 parts by weight relative to 100 parts by weight of the solvent. If it is the said resin density|concentration, a uniform coating film which adheres to a polarizer can be formed.

The above-mentioned composition can be coated on any suitable substrate, and can also be coated on the polarizer. When coated on a substrate, the cured product of the coating film formed on the substrate is transferred to the polarizer. When coating on a polarizer, for example, the coating film is cured by light irradiation, whereby the first protective layer is directly formed on the polarizer. Preferably, the above-mentioned composition is coated on the polarizer, and the first 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. The coating method of the composition is as described above.

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. The irradiation dose of ultraviolet rays is, for example, 2mJ/cm ² -3000mJ/cm ² , preferably 10mJ/cm ² -2000mJ/cm ² . Specifically, when using a high pressure mercury lamp as the light source, the irradiation amount is usually 5mJ/cm ² ~3000mJ/cm ² , preferably 50mJ/cm ² ~2000mJ/cm ² . When an electrodeless lamp is used as the light source, the irradiation amount is usually 2mJ/cm ² ~2000mJ/cm ² , preferably 10mJ/cm ² ~1000mJ/cm ² .

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.

A-4-3. Cured product of coating film of organic solvent solution of epoxy resin In one embodiment, the first protective layer is formed of a cured product of a coating film of an organic solvent solution of an epoxy resin. From the viewpoint of humidification durability, the softening temperature of the first protective layer of the present embodiment is preferably 100°C or higher, more preferably 110°C or higher, more preferably 120°C or higher, particularly preferably 125°C or higher; and, From the viewpoint of formability, it 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.

A-4-3-1. Epoxy resin In the present embodiment, the epoxy resin preferably has a glass transition temperature (Tg) of 100°C or higher. As a result, the softening temperature of the protective layer is almost 100°C or higher. When the Tg of the epoxy resin is 100° C. or higher, the polarizing plate including the protective layer obtained from the resin tends to be excellent in durability. The Tg of the epoxy resin is preferably 110°C or higher, more preferably 120°C or higher, and particularly preferably 125°C or higher. On the other hand, the Tg of the epoxy resin 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. When the Tg of the epoxy resin is within the above range, the moldability can be excellent.

Any appropriate epoxy resin can be used as long as the epoxy resin has the above-mentioned Tg. Epoxy resins represent resins with epoxy groups in their molecular structure. As an epoxy resin, the epoxy resin which has an aromatic ring in a molecular structure can be used suitably. By using an epoxy resin having an aromatic ring, an epoxy resin having a higher Tg can be obtained. As an aromatic ring of the epoxy resin which has an aromatic ring in a molecular structure, a benzene ring, a naphthalene ring, a perylene ring, etc. are mentioned, for example. The epoxy resin may be used alone or in combination of two or more. When two or more types of epoxy resins are used, an aromatic ring-containing epoxy resin and an aromatic ring-free epoxy resin may be used in combination.

Specific examples of epoxy resins having an aromatic ring in the molecular structure include: bisphenol A diglycidyl ether type epoxy resin, bisphenol F diglycidyl ether type epoxy resin, bisphenol S diepoxy resin Propyl ether type epoxy resin, Resorcinol diglycidyl ether type epoxy resin, Hydroquinone diglycidyl ether type epoxy resin, Diglycidyl terephthalate type epoxy resin , bisphenoxyethanol fendiglycidyl ether type epoxy resin, bisphenol fentanyl diglycidyl ether type epoxy resin, biscresol fentanyl diglycidyl ether type epoxy resin, etc. have 2 Epoxy epoxy resin; novolac epoxy resin, N,N,O-triglycidyl-p- or-m-aminophenol-type epoxy resin, N,N,O-triglycidyl -4-amino-m- or -5-amino-o-cresol type epoxy resin, 1,1,1-(triglycidoxyphenyl)methane type epoxy resin, etc. have 3 rings Oxygen-based epoxy resins; glycidylamine-type epoxy resins (such as diaminodiphenylmethane type, diaminodiphenylene type, metadiamine type), etc. have a ring with 4 epoxy groups Oxygen resin etc. Moreover, glycidyl ester type epoxy resins, such as a hexahydrophthalic anhydride type epoxy resin, a tetrahydrophthalic anhydride type epoxy resin, a dimer acid type epoxy resin, and a p-oxybenzoic acid type, can also be used.

The weight average molecular weight of the epoxy resin is preferably 1,000-2,000,000, more preferably 5,000-1,000,000, more preferably 10,000-500,000, particularly preferably 50,000-500,000, and most preferably 60,000-150,000. The weight average molecular weight can be determined in terms of polystyrene using, for example, gel permeation chromatography (GPC system, manufactured by Tosoh Corporation). In addition, tetrahydrofuran can be used as a solvent.

The epoxy equivalent of the epoxy resin is preferably 1000 g/equivalent or more, more preferably 3000 g/equivalent or more, and more preferably 5000 g/equivalent or more. Furthermore, the epoxy equivalent of the epoxy resin is preferably 30,000 g/equivalent or less, preferably 25,000 g/equivalent or less, and more preferably 20,000 g/equivalent or less. A more stable protective layer can be obtained by making an epoxy equivalent into the said range. 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 this embodiment, an epoxy resin and other resin may be used together. That is, a blend of epoxy resin and other resins can also 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 , Polyetherimide and other thermoplastic resins. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose, the properties desired for the obtained film, and the like. For example, a styrene resin can be used together as a retardation control agent.

The content of the epoxy resin in the first protective layer of the present embodiment 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, especially 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.

The first protective layer of the present embodiment can be formed by, for example, applying an organic solvent solution containing the epoxy resin to form a coating film and curing the coating film. The epoxy resin concentration in the organic solvent solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. If it is the said resin density|concentration, a uniform coating film which adheres to a polarizer can be formed.

Any appropriate solvent that can dissolve or uniformly disperse the epoxy resin can be used as the organic solvent. Specific examples of the solvent include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone.

The solution can be coated on any suitable substrate, and can also be coated on the polarizer. When coated on a substrate, the cured product of the coating film formed on the substrate is transferred to the polarizer. When applying to the polarizer, the first protective layer is directly formed on the polarizer by drying (curing) the coating film. Preferably, the solution is applied on the polarizer, and the first 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. The coating method of the solution is as described above.

By drying (curing) the coating film of the solution, a protective layer which is a cured product of the coating film can be formed. The drying temperature is preferably below 100°C, preferably 50°C to 70°C. If the drying temperature is within the above range, adverse effects on the polarizer can be prevented. The drying time may vary according to the drying temperature. The drying time may be, for example, 1 minute to 10 minutes.

A-4-4. Composition and characteristics of protective layer In one embodiment, the first protective layer is formed of at least one selected from the group consisting of: a cured product of a coating film of an organic solvent solution of a thermoplastic acrylic resin, an epoxy resin, as described above. The cured product of the coating film of the light cation cured product and the organic solvent solution of the epoxy resin. If it is the protective layer, its thickness can be much thinner than that of the extruded film. The thickness of the first protective layer is 10 µm or less as described above. In addition, although the theory is not clear, the shrinkage of this protective layer during film formation is smaller than that of other thermosetting resins or hardened products of active energy ray-curable resins (such as UV-curable resins), and does not contain residual sheets. Therefore, there is an advantage that the deterioration of the film itself can be suppressed, and the adverse effects of residual monomers and the like on the polarizing plate (polarizer) can be suppressed. In addition, its hygroscopicity and moisture permeability are lower than those of a cured product of an aqueous coating film such as an aqueous solution or an aqueous dispersion, so it has an 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.

It is preferable that the first protective layer is substantially optically isotropic. In this specification, "substantially optically isotropic" means that the in-plane retardation Re(550) is 0 nm to 10 nm, and the thickness direction retardation Rth(550) is -20 nm to +10 nm. The in-plane retardation Re(550) is preferably 0 nm to 5 nm, more preferably 0 nm to 3 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. If the Re(550) and Rth(550) of the first protective layer are within the above-mentioned ranges, adverse effects on display characteristics can be prevented when a polarizing plate including the protective layer is applied to an image display device.

The higher the transmittance of the first protective layer at 380nm when the thickness is 3µm, the better. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and more preferably 90% or more. When the light transmittance is within the above range, desired transparency can be ensured. The light transmittance can be measured, for example, in accordance with the method of ASTM-D-1003.

The lower the haze of the first 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. In addition, even in the case of using a polarizing plate on the viewing side of an image display device, the displayed content can be clearly seen.

When the thickness of the first 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 first protective layer is 3 μm, the b value (the hue scale according to the Hunter color system) is preferably 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 iodine adsorption amount of the first protective layer is preferably 25% by weight or less, more preferably 10% by weight or less, more preferably 6.0% by weight or less, particularly preferably 3.0% by weight or less. The smaller the amount of iodine adsorbed, the better. When the amount of iodine adsorption is within the above-mentioned range, a polarizing plate having more excellent durability can be obtained. The amount of iodine adsorption can be measured by the following method. A protective layer (thickness 3µm) was formed on the substrate (PET film) to obtain a PET film with a protective layer. 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 iodine solution was also placed in the headspace vial and capped tightly. After that, the headspace vial was placed in a dryer at 65° C. for 6 hours, so that 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 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 first protective layer (for example, a cured product of a coating film or a photocationic cured product) 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. The additive may be added during the polymerization of the resin, or may be added during the formation of the protective layer. The type, quantity, combination, addition amount, etc. of the additives can be appropriately set according to the purpose.

A-5. 2nd layer of protection In one embodiment, the second protective layer is formed of any appropriate thin film that can be used as a protective layer of a polarizer. Specific examples of the material used as the main component of the film include cellulose-based resins such as triacetate cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polymer Imide-based, polyether-based, poly-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based and acetate-based transparent resins, etc. Moreover, (meth)acrylic type, urethane type, (meth)acrylate urethane type, epoxy type, polysiloxane type|system|group thermosetting resin, ultraviolet-curable resin, etc. are also mentioned. Other examples include glass-based polymers such as siloxane-based polymers. The thickness of the second protective layer in this embodiment is preferably 5µm to 80µm, more preferably 5µm to 40µm, and more preferably 5µm to 25µm.

In another embodiment, the second protective layer may be a cured product of a coating film of a resin solution, or may be a cured product of a curable resin (eg, a photocation cured product). The same description as that of the first protective layer can be applied to the second protective layer of the present embodiment.

A-6. Other layers An easily bonding layer may also be formed on the polarizer side of the protective layer (representatively, the first 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. In addition, a hard coat layer may be formed on the opposite side of the polarizer of the protective layer (representatively, the first protective layer). In addition, when forming the hard coat layer, the thickness of the protective layer (for example, the cured product of the coating film) and the thickness of the hard coat layer may be 10 µm or less in total, preferably 7 µm or less, and more preferably 5 µm or less. coating. The hard coat layer may be formed on the visual side of the visual side protective layer. 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.

B. Polarizing plate with retardation layer B-1. Overall composition of polarizing plate with retardation 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 200a with retardation layer of the present embodiment includes a polarizing plate 100 and a retardation layer 110. The polarizing plate 100 includes a polarizing member 10 and a first protective layer 20 disposed on one side thereof, and the retardation layer 110 is disposed On the opposite side of the polarizer 10 to the side where the first protective layer 20 is arranged. In the polarizing plate 200 a with a retardation layer, the retardation layer 110 can also function as a protective layer of the polarizer 10 . The retardation layer 110 represents that the upper layer is laminated on the polarizing plate 100 via an adhesive layer (not shown). The next layer is an adhesive layer or an adhesive layer, and is preferably an adhesive layer (eg, an acrylic adhesive layer) from the viewpoint of reproducibility and the like. Although not shown, the polarizer 100 may also have a second protective layer on the side of the retardation layer 110 of the polarizer 10 as required.

As shown in FIG. 4 , in the polarizing plate 200b with retardation layer in another embodiment, another retardation layer 120 and/or a conductive layer or an isotropic substrate 130 with a conductive layer may also be provided. The other retardation layer 120 and the conductive layer or the isotropic substrate 130 with the conductive layer can be disposed on the outer side of the retardation layer 110 (opposite to the polarizing plate 100 ). The other retardation layer 120 exhibits a relationship of nz>nx=ny on behalf of the upper refractive index characteristic. The other retardation layer 120 and the conductive layer or the isotropic substrate 130 with the conductive layer are arranged in sequence from the retardation layer 110 side. The other retardation layer 120 and the conductive layer or the isotropic substrate 130 with the conductive layer represent any layers that can be provided as required, and either or both can be omitted. In addition, for convenience, the retardation layer 110 may be referred to as a first retardation layer, and the other retardation layer 120 may be referred to as a second retardation layer. In addition, when a conductive layer or an isotropic substrate with a conductive layer can be provided, the polarizer with retardation layer can be applied to incorporate a touch sensor between an image display unit (such as an organic EL unit) and the polarizer The so-called inner touch panel type input display device.

In the embodiment of the present invention, Re(550) of the first retardation layer 110 is preferably 100 nm to 190 nm, and Re(450)/Re(550) is preferably 0.8 or more and less than 1. In addition, the angle formed by the slow axis of the first retardation layer 110 and the absorption axis of the polarizer 10 is 40°˜50°.

The above-described embodiments may be appropriately combined, and modifications obvious in the art may be added to the constituent elements of the above-described embodiments. For example, the configuration in which the isotropic substrate 130 with the conductive layer is provided outside the second retardation layer 120 may be replaced with an optically equivalent configuration (eg, a laminate of the second retardation layer and the conductive layer).

The polarizing plate with retardation layer according to the embodiment of the present invention may further include other retardation layers. The optical properties (for example, refractive index properties, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, and the like of the other retardation layers can be appropriately set according to the purpose.

B-2. Polarizing plate The polarizing plate 100 is the polarizing plate described in item A.

B-3. 1st retardation layer The first retardation layer 110 may have any appropriate optical properties and/or mechanical properties according to the purpose. The first retardation layer typically has a slow axis. In one embodiment, the angle θ formed by the slow axis of the first retardation layer and the absorption axis of the polarizer 10 is 40° to 50°, preferably 42° to 48°, and more preferably about 45°, as described above. If the angle θ is within the stated range, as described later, by making the first retardation layer into a λ/4 plate, a phase difference layer with very excellent circular polarization properties (resulting in very excellent antireflection properties) can be obtained. polarizer.

The first retardation layer preferably exhibits the relationship of nx>ny≧nz in the refractive index characteristic. The first retardation layer is typically provided to impart antireflection properties to the polarizing plate, and can function as a λ/4 plate in one embodiment. At this time, the in-plane retardation Re(550) of the first retardation layer is preferably 100 nm to 190 nm, more 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 first retardation layer is preferably 0.9~3, more preferably 0.9~2.5, more preferably 0.9~1.5, especially 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 first retardation layer can exhibit a reverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the retardation value becomes smaller with the wavelength of the measurement light, and a retardation value that is almost invariant Flat wavelength dispersion characteristics as a function of wavelength of measurement light. In one embodiment, the first 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 such a configuration, very excellent antireflection properties can be realized.

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

The first retardation layer is composed of a stretched film of a resin film. In one embodiment, the thickness of the first retardation layer is preferably 70 µm or less, more preferably 45 µm to 60 µm. When the thickness of the first retardation layer is within the above range, the curl at the time of heating can be suppressed favorably, and the curl at the time of lamination can be favorably adjusted. Furthermore, as will be described later, in the embodiment in which the first retardation layer is formed of a polycarbonate resin film, the thickness of the first retardation layer is preferably 40 μm or less, more preferably 10 μm to 40 μm, and more preferably 20 μm to 30 μm. When the first retardation layer is formed of a polycarbonate-based resin film having the above-mentioned thickness, the occurrence of curl can be suppressed, and the bending resistance durability and the reflection hue can be improved.

The first 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 first retardation layer is formed of a resin film exhibiting reverse dispersion wavelength characteristics, a polycarbonate-based resin or a polyester-carbonate-based resin (hereinafter, may be simply referred to 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 aforementioned 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 lower limit of the reduced viscosity is usually 0.30 dL/g, preferably 0.35 dL/g or more. The upper limit of the reduced viscosity is usually 1.20 dL/g, preferably 1.00 dL/g, and more preferably 0.80 dL/g. If the reduced viscosity is less than the aforementioned lower limit value, there may be a problem that the mechanical strength of the molded product is reduced. On the other hand, if the reduced viscosity is larger than the above-mentioned upper limit value, the fluidity at the time of molding is lowered, and there is a possibility that the productivity or the moldability is 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 first retardation layer 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 first 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 stretching at the above temperature, a first 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.

B-4. Second retardation layer As described above, the second retardation layer may be a so-called positive C-plate which exhibits the relation of nz>nx=ny in the refractive index characteristic. By using the positive C plate as the second 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 second 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 second retardation layer may be less than 10 nm.

The second retardation layer having the refractive index characteristic of nz>nx=ny can be formed of any appropriate material. The second retardation layer is preferably composed of a thin film containing a liquid crystal material fixed in a homeotropic alignment. 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 liquid crystal compound and the method for forming the retardation layer described in paragraphs [0020] to [0028] of Japanese Patent Laid-Open No. 2002-333642. At this time, the thickness of the second retardation layer is preferably 0.5 μm to 10 μm, preferably 0.5 μm to 8 μm, and more preferably 0.5 μm to 5 μm.

B-5. Conductive layer or isotropic substrate with conductive layer The conductive layer can be formed by forming a metal oxide film on any suitable substrate by any suitable film-forming method (eg, vacuum evaporation method, sputtering method, CVD method, ion plating method, spray method, etc.). The metal oxide includes, for example, indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Among them, indium tin composite oxide (ITO) is suitable.

When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50 nm or less, more preferably 35 nm or less. The lower limit of the thickness of the conductive layer is preferably 10 nm.

The conductive layer can be transferred from the above-mentioned base material to the first retardation layer (or the second retardation layer if there is a second retardation layer), and the conductive layer alone can be used as the constituent layer of the polarizing plate with the retardation layer, and also It can be laminated on the first retardation layer (or the second retardation layer if there is a second retardation layer) in the form of a laminate of a conductive layer and a substrate (substrate with a conductive layer). It is preferable that the above-mentioned base material is optically isotropic, so the conductive layer can be used as an isotropic base material with a conductive layer for a polarizing plate with a retardation layer.

Any suitable isotropic substrate can be used as the optically isotropic substrate (isotropic substrate). The material constituting the isotropic base material includes, for example, a material whose main skeleton is a non-conjugated resin such as a norbornene-based resin or an olefin-based resin, and a material having a lactone ring or glutaric acid in the main chain of an acrylic resin. Materials with cyclic structures such as imine rings, etc. If such a material is used, the retardation exhibited by the molecular chain orientation when the isotropic substrate is formed can be suppressed to be small. The thickness of the isotropic substrate is preferably 50µm or less, more preferably 35µm or less. The lower limit of the thickness of the isotropic base material is, for example, 20 μm.

The conductive layer of the above-mentioned conductive layer and/or the above-mentioned conductive layer of the isotropic substrate with the conductive layer can be patterned as required. The conducting portion and the insulating portion can be formed by patterning. As a result, electrodes can be formed. The electrodes can function as touch sensing electrodes for sensing contact with the touch panel. As the patterning method, any suitable method can be used. Specific examples of the patterning method include wet etching and screen printing.

C. Video display device The above-mentioned polarizing plate or the polarizing plate with retardation layer can be applied to an image display device. Therefore, the present invention includes an image display device including the above-mentioned polarizing plate or the polarizing plate with retardation layer. Typical examples of image display devices include liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices, inorganic EL display devices). The image display device according to the embodiment of the present invention is provided with the polarizing plate described in the above item A or the polarizing plate with a retardation layer described in the B item on the viewing side. The polarizing plate with retardation layer is laminated so that the retardation layer is on the side of the image display unit (eg liquid crystal unit, organic EL unit, inorganic EL unit) (the polarizer is on the viewing side). In one embodiment, the image display device has a curved shape (substantially a curved display screen), and/or is flexible or bendable. In the image display device, the effect of the polarizing plate with retardation layer of the present invention is more remarkable.

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) Thickness The thickness of the polarizer was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). The calculation wavelength range used for the thickness calculation was 400 nm to 500 nm, and the refractive index was set to 1.53. In addition, the thickness of the protective layer was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"), and the calculation wavelength range and refractive index were appropriately selected. The thickness of the easily bonding layer was obtained by observation with a scanning electron microscope (SEM). Thickness factors larger than 10 μm were measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”). (2) Orientation function of PVA For the polarizer (polarizer monomer) after peeling off the resin substrate from the laminate of the polarizer/thermoplastic resin substrate used in the Examples and Comparative Examples, for the surface of the peeled resin substrate For the opposite side, a Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, trade name: "Frontier") was used, and polarized infrared light was used as measurement light, and attenuated total reflection on the surface of the polarizer was performed. Spectroscopic (ATR: attenuated total reflection) measurement. Germanium was used as the microcrystalline system for adhering the polarizer, and the incident angle of the measurement light was set at 45°. The calculation of the orientation function is performed according to the following procedure. The polarized infrared rays (measurement light) to be incident are set as polarized light (s-polarized light) that vibrates in parallel to the surface on which the germanium crystal sample adheres, and the extending direction of the polarizer is relative to the polarization direction of the measurement light. Each absorbance spectrum was measured in the state of vertical (⊥) and parallel (//) arrangement. From the obtained absorbance spectrum, (2941 cm ⁻¹ intensity) I was calculated with reference to (3330 cm ⁻¹ intensity). I⊥ is (2941 cm ^-1 intensity)/(3330 cm ^-1 intensity) obtained from the absorbance spectrum obtained when the extending direction of the polarizer is perpendicular ( _⊥ ) to the polarization direction of the measurement light. In addition, I _// is obtained from the absorbance spectrum obtained when the extending direction of the polarizer is parallel (//) with respect to the polarization direction of the measurement light (intensity at 2941 cm ⁻¹ )/(intensity at 3330 cm ⁻¹ . Here, (2941 cm ^-1 intensity) is the absorbance at 2941 cm ^-1 at the bottom of the absorbance spectrum with 2770 cm ^-1 and 2990 cm ^-1 as the baseline, (3330 cm ^-1 intensity) is the absorbance at 2990 cm ^-1 and 3650 cm ^-1 as the baseline The absorbance of 3330cm ^-1 . Using the obtained I _⊥ and I _// , calculate the orientation function f according to Equation 1. In addition, f=1 is fully oriented, and f=0 is random. In addition, it can be said that the peak at 2941 cm ^-1 is caused by the absorption of vibration of the PVA main chain (-CH ₂ -) in the polarizer. In addition, it can be said that the peak at 3330 cm ^-1 is caused by the absorption of vibration of the hydroxyl group of PVA. (Formula 1) f=(3<cos ² θ>-1)/2 =(1-D)/[c(2D+1)] However, with c=(3cos ² β-1)/2, as above When using 2941cm ^-1 , β=90°⇒f=-2×(1-D)/(2D+1). θ: The angle of the molecular chain relative to the extension direction β: The angle of the transition dipole moment relative to the molecular chain axis D=(I _⊥ )/(I _// ) I _⊥ : The polarization direction of the measured light is in the same direction as the extension direction of the polarizer. Absorption intensity I _// : The absorption intensity when the polarization direction of the measured light is parallel to the extending direction of the polarizer (3) In-plane retardation of PVA (Re) For the polarizers obtained in Examples and Comparative Examples / The laminate of the thermoplastic resin substrate was peeled off and the polarizer (polarizer monomer) was removed, and evaluated at a wavelength of 1000 nm using a retardation measuring device (product name "KOBRA-31X100/IR" manufactured by Oji Scientific Instruments Co., Ltd.). The in-plane retardation (Rpva) of the PVA (according to the described principle, the value obtained by subtracting the in-plane retardation of iodine (Ri) from the total in-plane retardation at a wavelength of 1000 nm). The absorption edge wavelength was set to 600 nm. (4) Birefringence (Δn) of PVA The birefringence (Δn) of PVA was calculated by dividing the in-plane retardation of PVA measured in (3) above by the thickness of the polarizer. (5) Puncture strength The polarizer was peeled from the laminate of the polarizer/resin base material used in the examples and comparative examples, and the polarizer was placed on a compression tester equipped with a needle (manufactured by KATO TECH CO., LTD., product name ""NDG5" needle penetration force measurement specification), at room temperature (23°C ± 3°C), puncture at a puncture speed of 0.33cm/s, and take the breaking strength of the polarizer as the breaking strength (puncture strength). As the evaluation value, the breaking strength of 10 test pieces was measured and the average value was used. In addition, the needle system used a tip diameter of 1 mmφ and 0.5R. For the polarizer to be measured, a jig having a circular opening with a diameter of 11 mm was clamped and fixed from both sides of the polarizer, and then the puncture needle at the center of the opening was tested. (6) Cracks The polarizing plate or the polarizing plate with retardation layer obtained in Examples and Comparative Examples was cut into a size of 100 mm×100 mm. The cut sample was attached to a glass plate (thickness 1.1 mm) through an acrylic adhesive layer with a thickness of 15 µm so that the protective layer became the outer side. After the sample attached to the glass plate was placed in an oven at 85° C. for 120 hours, the presence or absence of cracks in the absorption axis direction (MD direction) of the polarizer was visually checked with the naked eye. This evaluation was carried out using three polarizing plates with retardation layers, and those with cracks occurred in even one of the plates were evaluated as "occurring", and those with no cracks in all three plates were evaluated as "none". (7) Monomer transmittance and polarization degree For the polarizer (polarizer monomer) after peeling and removing the resin substrate from the laminate of the polarizer/thermoplastic resin substrate obtained in the Examples and Comparative Examples, the ultraviolet-visible light spectrophotometer was used. The single-piece transmittance Ts, the parallel transmittance Tp, and the orthogonal transmittance Tc were measured with a meter (“V-7100” manufactured by JASCO Corporation). These Ts, Tp, and Tc are Y values obtained by measuring with the 2-degree field of view (C light source) of JIS Z8701 and correcting the visual sensitivity. The degree of polarization P was obtained from the obtained Tp and Tc by the following formula. The degree of polarization P(%)={(Tp-Tc)/(Tp+Tc)} ^{1 /2} × 100 In addition, the spectrophotometer can also use the "LPF-200" manufactured by Otsuka Electronics Co., Ltd. to perform the same measurement. It can be confirmed that the same measurement results are obtained regardless of the spectrophotometer used. (8) Humidification Durability Test pieces (50 mm×50 mm) were cut out from the polarizing plates or the polarizing plates with retardation layers obtained in the examples and comparative examples, and the test pieces were formed in the direction perpendicular to the absorption axis of the polarizer, respectively. The opposite sides of the direction and the absorption axis direction. The test piece was attached to an alkali-free glass plate with an adhesive so that the protective layer was on the outside to prepare a test sample, and an ultraviolet-visible light spectrophotometer (manufactured by JASCO Corporation, product name "V7100") was used for the test sample. , and the single transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance (Tc) were measured in the same manner as in (7), and the degree of polarization (P) was obtained. At this time, the measurement light was made incident from the protective layer side. Next, the test sample was placed in an oven at 60°C and 95% RH for 500 hours for heating and humidifying (damp heat test), and the polarization degree P ₀ before the wet heat test and the polarization degree P ₅₀₀ after the wet heat test were used. The amount of change ΔP in the degree of polarization is obtained by the above formula. ΔP(%)=P ₅₀₀ -P ₀ The results from the obtained ΔP were evaluated according to the following criteria. Good: ΔP is -5.0% to 0% Unfavorable: ΔP is less than -5.0% or discoloration occurs (9) The softening temperature of the protective layer is in the same manner as the protective layer of each Example and Comparative Example, and in Comparative Example 1 A protective layer (thickness: 3µm) was formed on one side of the produced polarizer (total extension ratio: 5.5 times). Local thermal analysis (nano-TA measurement) was performed on the surface of the protective layer of the obtained polarizing plate [protective layer/polarizer], and the softening temperature of the protective layer was calculated. The measurement apparatus and measurement conditions are as follows. Measurement device: Hitachi High-Tech Science Co., product name "AFM5300E//Nano-TA2" Measurement mode: Contact mode Probe: AN2-200 Measurement area: 8 µm Scanning measurement gas environment: atmospheric pressure (10) iodine adsorption A protective layer (thickness: 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 is 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.

[Example 1-1] 1. Fabrication of a polarizer/resin substrate laminate The resin substrate is a long strip of amorphous isophthalic acid copolymerized with polyparaphenylene having a water absorption rate of 0.75% and a Tg of about 75°C Ethylene diformate film (thickness: 100µm). Corona treatment was performed on one side of the resin substrate. A 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 apply|coated to the corona-treated surface of a resin base material, and it dried at 60 degreeC, and the PVA-type resin layer of thickness 13 micrometers was formed by this, and the laminated body was produced. 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) while adjusting the concentration. So that the single transmittance (Ts) of the polarizer finally obtained was 41.5% (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 in a cross-linking bath (cross-linking treatment). ). Then, while immersing the layered body in a boric acid aqueous solution (boric acid concentration: 4.0 wt %) at a liquid temperature of 70° C., uniaxial stretching was performed 1.46 times (in water) in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds. stretching process) (as a result, the total stretching ratio is 2.4×1.46=3.5 times). 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). Then, while drying in an oven maintained at 90°C, the contact surface temperature was passed through a heating roll made of SUS maintained at 75°C for about 2 seconds (drying shrinkage treatment). The shrinkage rate in the width direction of the laminate obtained by drying shrinkage treatment was 2%. In the above-described manner, a polarizer having a thickness of 6.7 μm was formed on the resin substrate to produce a polarizer/resin substrate laminate. The single transmittance (initial single transmittance) Ts ₀ of the polarizer was 41.5%, and the polarization degree (initial polarization degree) P ₀ was 99.99%.

2. Formation of easy bonding layer On the polarizer surface of the obtained laminate, a polyurethane-based water-based dispersion resin (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., product name: SUPERFLEX SF210) was applied to a thickness of 0.1 µm as an easily bonding layer to form an easily bonding layer. .

3. Production of protective layer 20 parts by weight of 100% polymethyl methacrylate acrylic resin (manufactured by Kusumoto Chemical Co., Ltd., product name: B-728) was dissolved in 80 parts by weight of methyl ethyl ketone to obtain an acrylic resin solution (20% ). The acrylic resin solution was applied on the surface of the easily bonding layer of the laminate obtained above with a wire bar, and the coating film was dried at 60° C. for 5 minutes to form a protective layer in the form of a cured product of the coating film. . The thickness of the protective layer is 3µm. Next, the resin base material was peeled off from the obtained laminated body, and the polarizing plate which has the structure of a protective layer (hardened|cured material of a coating film)/easy-bonding layer/polarizer was obtained.

[Example 1-2] It was the same as Example 1-1 except that the thickness of the protective layer was 2 µm, and a hard coat layer (thickness 3 µm) was further formed on the surface of the protective layer opposite to the easily bonding layer. In this way, a polarizing plate having a structure of hard coat layer/protective layer (cured product of coating film)/easy bonding layer/polarizer was obtained. In addition, the hard coat layer was formed by mixing 70 parts by weight of dimethylol-tricyclodecane diacrylate (manufactured by Kyōeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE DCP-A), isobornyl acrylate (Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE IB-XA) 20 parts by weight, 1,9-nonanediol diacrylate (Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE 1.9NA-A) 10 weight parts , and further 3 parts by weight of a photopolymerization initiator (manufactured by BASF, trade name: IRGACURE 907), mixed with an appropriate solvent, and the resulting coating liquid was applied on the protective layer so that the thickness after curing was 3 µm, and then The solvent was dried and formed by irradiating ultraviolet rays in a nitrogen atmosphere using a high-pressure mercury lamp so that the cumulative light amount would be 300 mJ/cm ² .

[Example 1-3] The acrylic resin of polymethyl methacrylate with lactone ring unit (30 mol% of lactone ring unit) is used to replace the acrylic resin of 100% polymethyl methacrylate, and the thickness of the protective layer is 2µm, A hard coat layer (thickness of 3 µm) was further formed on the surface of the protective layer on the opposite side of the easily bonded layer, except that in the same manner as in Example 1-1, a hard coat layer/protective layer (coating layer) was obtained. Cured product of film)/easy bonding layer/polarizer composed of polarizing plate. In addition, the formation of the hard coat layer was carried out in the same manner as in Example 1-2.

[Example 1-4] Use the acrylic resin of polymethyl methacrylate having a glutarimide ring unit (4 mol% of glutarimide ring unit) to replace the acrylic resin of 100% polymethyl methacrylate, and let The thickness of the protective layer is 2 µm, and a hard coat layer (thickness 3 µm) is further formed on the surface of the protective layer opposite to the easily bonding layer, in the same manner as in Example 1-1, to obtain a hard coat layer A polarizing plate consisting of /protective layer (cured product of coating film)/easy bonding layer/polarizer. In addition, the formation of the hard coat layer was carried out in the same manner as in Example 1-2.

[Example 1-5] Except that the acrylic resin of the copolymer of methyl methacrylate/butyl methacrylate (mol ratio 80/20) is used to replace the acrylic resin of 100% polymethyl methacrylate, it is in accordance with Example 1- 1 In the same manner, a polarizing plate having a configuration of protective layer (cured product of coating film)/easy bonding layer/polarizer was obtained.

[Example 1-6] The acrylic resin of the copolymer of methyl methacrylate/butyl methacrylate (mol ratio 80/20) is used to replace the acrylic resin of 100% polymethyl methacrylate, and the thickness of the protective layer is 2µm, A hard coat layer (thickness of 3 µm) was further formed on the surface of the protective layer on the opposite side of the easily bonded layer, except that in the same manner as in Example 1-1, a hard coat layer/protective layer (coating layer) was obtained. Cured product of film)/easy bonding layer/polarizer composed of polarizing plate. In addition, the formation of the hard coat layer was carried out in the same manner as in Example 1-2.

[Example 1-7] In place of 100% polymethyl methacrylate, an acrylic resin (manufactured by Kusumoto Chemical Co., Ltd., product name "B-722") is used except that a copolymer of methyl methacrylate/ethyl acrylate (mol ratio 55/45) is used In the same manner as in Example 1-1, except for the acrylic resin, a polarizing plate having a configuration of protective layer (cured product of coating film)/easy-bonding layer/polarizer was obtained.

[Example 1-8] In place of 100% polymethacrylic acid, an acrylic resin (manufactured by Kusumoto Chemical Co., Ltd., product name "B-734") is used except that a copolymer of methyl methacrylate/butyl methacrylate (mol ratio 35/65) is used Except for the acrylic resin of methyl ester, in the same manner as in Example 1-1, a polarizing plate having a configuration of protective layer (cured product of coating film)/easy adhesion layer/polarizer was obtained.

[Example 2-1] 1. Fabrication of the polarizer/resin substrate laminate In the same manner as in Example 1-1, a polarizer with a thickness of 6.7 μm was formed on the resin substrate to produce a polarizer/ A laminate of resin substrates. 2. Preparation 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 directly (ie, without forming an easily adhesive layer) on the surface of the polarizer using a wire bar, and the applied 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 3µm. Next, the resin base material was peeled off from the obtained laminated body, and the polarizing plate which has the structure of a protective layer (photocationic hardening layer of epoxy resin)/polarizer was obtained.

[Example 2-2] 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 by weight of OXT-221) was 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. Using this epoxy resin solution to obtain a protective layer-forming composition, using dyeing baths of various iodine concentrations (weight ratio of iodine to potassium iodide = 1:7), and setting the stretching ratio in water during polarizer production to 1.25 times ( Total stretching ratio: 3.0 times), except that in the same manner as in Example 2-1, a polarizing plate having a protective layer (photocationic hardening layer of epoxy resin)/polarizer was obtained.

[Example 2-3] Use dyeing baths with various iodine concentrations (weight ratio of iodine to potassium iodide = 1:7), and set the stretching magnification in water during polarizer production to 1.46 times (total stretching magnification: 3.5 times). In the same manner as in Example 2-2, a polarizing plate having a protective layer (photocationic hardening layer of epoxy resin)/polarizer was obtained.

[Example 2-4] Use dyeing baths of various iodine concentrations (weight ratio of iodine to potassium iodide = 1:7), and set the stretching magnification in water during polarizer production to 1.67 times (total stretching magnification: 4.0 times), other than that In the same manner as in Example 2-2, a polarizing plate having a protective layer (photocationic hardening layer of epoxy resin)/polarizer was obtained.

[Example 2-5] Use dyeing baths with various iodine concentrations (weight ratio of iodine to potassium iodide = 1:7), and set the stretching magnification in water during polarizer production to 1.88 times (total stretching magnification: 4.5 times), other than In the same manner as in Example 2-2, a polarizing plate having a protective layer (photocationic hardening layer of epoxy resin)/polarizer was obtained.

[Example 2-6] 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 in the same manner as in Example 2-1, except that A polarizing plate with a protective layer (photocationic hardening layer of epoxy resin)/polarizer was obtained.

[Example 2-7] 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, in the same manner as in Example 2-3, except that A polarizing plate with a protective layer (photocationic hardening layer of epoxy resin)/polarizer was obtained.

[Example 2-8] In the same manner as in Example 2-1, 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, Thus, a polarizing plate having a protective layer (photocationic hardening layer of epoxy resin)/polarizer is obtained.

[Example 2-9] 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, in the same manner as in Example 2-3, except that Thus, a polarizing plate having a protective layer (photocationic hardening layer of epoxy resin)/polarizer is obtained.

[Example 2-10] 1. Production of polarizing plate In the same manner as in Example 2-3, a polarizing plate having a protective layer (photocationic hardening layer of epoxy resin)/polarizer was obtained.

2. Production of the first retardation layer Polymerization was performed using a batch polymerization apparatus consisting of two vertical reactors equipped with stirring blades and a reflux cooler controlled at 100°C. 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)perpen-9-yl]methane, 29.21 parts by mass (0.200 mol) of isosorbide (ISB), spiroglycerol (SPG) were fed 42.28 parts by mass (0.139 mol), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19×10 ^-2 parts by mass (6.78×10 ^-5 mol) of calcium acetate monohydrate as a catalyst. After the inside of the reactor was replaced with nitrogen under reduced pressure, it was heated with a heating medium, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of temperature increase, the internal temperature was brought to 220°C, and pressure reduction was started while maintaining the temperature, and 90 minutes after reaching 220°C, the internal temperature was adjusted to 13.3 kPa. The phenol vapor produced by the polymerization reaction was introduced into a reflux cooler at 100°C to return a small amount of monomer components contained in the phenol vapor to the reactor, and the uncondensed phenol vapor was introduced into a condenser at 45°C for recovery. After nitrogen was introduced into the first reactor and the pressure was temporarily returned to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Next, the temperature increase and pressure reduction in the second reactor were started, and the internal temperature was set to 240° C. and the pressure was set to 0.2 kPa over 50 minutes. Thereafter, polymerization is performed until a predetermined stirring power is reached. Nitrogen was introduced into the reactor to recover the pressure when the predetermined power was reached, and the produced polyester carbonate-based resin was extruded into water, and the bundle was cut to obtain pellets.

The obtained polyester carbonate-based resin (pellet) was vacuum-dried at 80° C. for 5 hours, and then a T-die (width 200 mm) equipped with a uniaxial extruder (manufactured by Toshiba Machine Co., Ltd., cylinder set temperature: 250° C.) was used. , set temperature: 250 ℃), cooling roll (set temperature: 120 ~ 130 ℃) and the film film making device of the winder, to produce a long resin film with a thickness of 130 μm. The obtained elongated resin film was stretched while adjusting so as to obtain a predetermined retardation, and a retardation film having a thickness of 48 μm was obtained. The stretching conditions were along the width direction, the stretching temperature was 143° C., and the stretching ratio was 2.8 times. Re(550) of the obtained retardation film was 141 nm, Re(450)/Re(550) was 0.86, and Nz coefficient was 1.12.

3. Second retardation layer As the second retardation layer, a retardation film (manufactured by Dai Nippon Printing Co., Ltd., "MCP-N") having a refractive index characteristic satisfying the relationship of nz>nx=ny and a retardation Rth(550) in the thickness direction of -135 nm was used.

4. Production of polarizing plate with retardation layer First, the second retardation layer is bonded to the first retardation layer through an ultraviolet curable adhesive. Next, the first retardation layer of the laminate of the first retardation layer/second retardation layer was bonded to the polarizer surface of the polarizing plate through an acrylic adhesive layer with a thickness of 12 µm. At this time, the slow axis of the first retardation layer and the absorption axis of the polarizer were bonded together at an angle of 45°. In the above manner, a polarizing plate with retardation layer having a configuration of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer/1st retardation layer/2nd retardation layer is obtained.

[Example 3-1] 1. Fabrication of polarizer/resin base laminate In the same manner as in Example 1-1, a polarizer with a thickness of 6.7 μm was formed on the resin substrate to produce a polarizer/resin substrate laminate. 2. Production of protective layer 20 parts of epoxy resin 1 (manufactured by Mitsubishi Chemical Co., trade name: jER (registered trademark) 1256B40, weight average molecular weight: 40000, epoxy equivalent: 7350) was dissolved in 80 parts of methyl ethyl ketone to obtain a ring. Oxygen resin solution (20%). The epoxy resin solution was applied to the polarizer surface of the laminate using a wire bar, and the applied film was dried at 60° C. for 3 minutes to form a protective layer as a cured product of the applied film. The thickness of the protective layer is 3µm. Next, the resin base material is peeled off from the obtained laminated body, and the polarizing plate which has the structure of a protective layer (the cured layer of the coating film of an epoxy resin) / a polarizer is obtained.

[Example 3-2] Epoxy resin 2 (manufactured by Mitsubishi Chemical Co., trade name: jER (registered trademark) YX6954BH30, weight average molecular weight: 36,000, epoxy equivalent: 13,000) was used instead of epoxy resin 1, in accordance with Example 3-1 In the same way, a polarizing plate having a composition of a protective layer (a cured layer of a coating film of epoxy resin)/polarizer was obtained.

[Example 4] No easy-bonding layer was formed (that is, a protective layer was formed directly on the polarizer), and a water-based polyester resin (manufactured by Nippon Synthetic Chemical Co., Ltd., product name "POLYESTER WR905") was used, except that it was in accordance with Example 1-1. In the same manner, a polarizing plate having a configuration of protective layer (cured product of coating film)/polarizer was obtained.

[Example 5] No easy adhesion layer is formed (that is, a protective layer is formed directly on the polarizer), and a water-based polyurethane resin (manufactured by Daiichi Industrial Pharmaceutical Co., Ltd., product name "SUPERFLEX SF210") is used. Example 1-1 In the same manner as in Example 1-1, a polarizing plate having a configuration of protective layer (cured product of coating film)/polarizer was obtained.

[Comparative Example 1] Except that the stretching ratio in water during the production of the polarizer was set to 2.29 times (total stretching ratio: 5.5 times), in the same manner as in Example 1-1, a protective layer (a cured product of coating film)/ A polarizing plate composed of an easily bonded layer/polarizer.

[Comparative Example 2] In the same manner as in Example 1-2, except that the stretching magnification in water during the production of the polarizer was set to 2.29 times (total stretching magnification: 5.5 times), a hard coat layer/protective layer (the coating film of the coating film) was obtained in the same manner as in Example 1-2. Cured product)/easy bonding layer/polarizing plate composed of polarizer.

[Comparative Example 3] Using dyeing baths of various iodine concentrations (weight ratio of iodine to potassium iodide = 1:7), and setting the stretching magnification in water during polarizer production to 2.29 times (total stretching magnification: 5.5 times), other In the same manner as in Example 2-3, a polarizing plate having a configuration of protective layer (photocationic hardening layer of epoxy resin)/easy bonding layer/polarizer was obtained.

[Comparative Example 4] In the same manner as in Example 2-10, except that the stretching magnification in water during the production of the polarizer was set to 2.29 times (total stretching magnification: 5.5 times), a protective layer (photocationic hardening layer of epoxy resin) was obtained. )/polarizer/adhesive layer/first retardation layer/second retardation layer polarizing plate with retardation layer.

[Comparative Example 5] Except that the stretching ratio in water during the production of the polarizer was set to 2.29 times (total stretching ratio: 5.5 times), in the same manner as in Examples 1-7, a protective layer (a cured product of coating film)/ A polarizing plate composed of an easily bonded layer/polarizer.

[Comparative Example 6] The stretching ratio in water during the production of the polarizer was set to 2.29 times (total stretching ratio: 5.5 times), and an acrylic resin film (refractive index: 1.50, thickness: 20 µm) that had been easily bonded to one side was used as the film. Except for the protective layer, in the same manner as in Example 1-1, a polarizing plate having a configuration of protective layer (acrylic resin film)/polarizer was obtained. The acrylic resin film is directly bonded to the polarizer surface through the ultraviolet curing 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. Then, the adhesive was cured by irradiating UV light from the acrylic resin film side.

The evaluation results are shown in Tables 1 to 3. [Table 1]

[Table 2]

[table 3]

As shown in Tables 1 to 3, the polarizing plate of the Example using the polarizer whose orientation degree of the PVA resin is controlled in a predetermined state (the result is a polarizer having a predetermined range of puncture intensity) is used even when the thickness of the protective layer is used. In a very small case, cracks during heating are still suppressed. Also, the polarizing plate with a specific protective layer exhibits excellent humidification durability.

5 to 7 respectively show the single transmittance of the polarizers (polarizers with a total extension ratio of 3.0, 3.5, 4.0, 4.5 or 5.5 times) used in Examples and Comparative Examples, Δn and in-plane phase of PVA difference or directional function. As shown in FIGS. 5 to 7 and Tables 1 to 3, it can be seen that the polarizer satisfying the formula (1), the formula (2) and/or the formula (3) shows the puncture intensity below a predetermined value, and the polarizer is used The polarizing plate produced can suppress cracks during heating even when the thickness of the protective layer is extremely small.

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, TVs, 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; monitoring screens, etc. Alarm equipment; nursing care monitors, medical monitors and other nursing care medical equipment.

10: Polarizer 20: 1st layer of protection 30: 2nd layer of protection 50: Laminate 100: polarizer 110: retardation layer, first retardation layer 120: Another retardation layer, the second retardation layer 130: Conductive layer, isotropic substrate with conductive layer 200a, 200b: Polarizing plate with retardation layer 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 a drying shrinkage treatment using a heating roller in the production of a polarizer. 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 an embodiment of the present invention. 5 is a graph showing the relationship between the single transmittance of polarizers used in Examples and Comparative Examples and the birefringence of PVA-based resins. 6 is a graph showing the relationship between the single transmittance of polarizers used in Examples and Comparative Examples and the in-plane retardation of PVA-based resin films. 7 is a graph showing the relationship between the single transmittance of polarizers used in Examples and Comparative Examples and the orientation function of PVA-based resins.

10: Polarizer

20: 1st layer of protection

30: 2nd layer of protection

100: polarizer

Claims (16)

A polarizer, comprising a polarizer composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and a protective layer disposed on one side of the polarizer; The polarizer satisfies the following formula (1) when its monomer transmittance is x% and the birefringence of the polyvinyl alcohol-based resin is y; y＜-0.011x+0.525 (1) The protective layer is formed of a resin film having a thickness of 10 µm or less. A polarizer, comprising a polarizer composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and a protective layer disposed on one side of the polarizer; The polarizer satisfies the following formula (2) when its monomer transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film is znm; z＜-60x+2875 (2) The protective layer is formed of a resin film having a thickness of 10 µm or less. A polarizer, comprising a polarizer composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and a protective layer disposed on one side of the polarizer; The polarizer satisfies the following formula (3) when its monomer transmittance is x% and the orientation function of the polyvinyl alcohol-based resin is f; f＜-0.018x+1.11 (3) The protective layer is formed of a resin film having a thickness of 10 µm or less. A polarizer, comprising a polarizer composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and a protective layer disposed on one side of the polarizer; The puncture intensity of the polarizer is above 30gf/µm; The protective layer is formed of a resin film having a thickness of 10 µm or less. The polarizing plate according to any one of claims 1 to 4, wherein the resin film comprises at least one selected from the group consisting of epoxy resins, (meth)acrylic resins, polyester resins and polyurethane resins resin. The polarizing plate according to any one of claims 1 to 5, wherein the resin film is composed of a photocationic cured epoxy resin, and The softening temperature of the said resin film is 100 degreeC or more. The polarizing plate according to any one of claims 1 to 5, wherein the aforementioned resin film is composed of a cured product of a coating film of an organic solvent solution of epoxy resin, and The softening temperature of the said resin film is 100 degreeC or more. The polarizing plate according to any one of claims 1 to 5, wherein the aforementioned resin film is constituted by a cured product of a coating film of an organic solvent solution of a thermoplastic (meth)acrylic resin, and The softening temperature of the said resin film is 100 degreeC or more. The polarizing plate of claim 8, wherein the thermoplastic (meth)acrylic resin has a compound selected from the group consisting of lactone ring units, glutaric anhydride units, glutarimide units, maleic anhydride units and maleimide At least one of the groups formed by the unit. The polarizing plate according to any one of claims 1 to 9, wherein the iodine adsorption amount of the protective layer is 25% by weight or less. The polarizing plate according to any one of claims 1 to 10, wherein the thickness of the aforementioned polarizer is 10 µm or less. The polarizing plate according to any one of claims 1 to 11, which is wound into a roll shape. A polarizing plate with a retardation layer, comprising the polarizing plate and the retardation layer as claimed in any one of claims 1 to 12; and The retardation layer is disposed on the opposite side of the polarizer to the side on which the protective layer is disposed. The polarizing plate with retardation layer according to claim 13, wherein the retardation layer is laminated on the polarizing plate via an adhesive. The polarizing plate with retardation layer as claimed in claim 13 or 14, wherein Re(550) of the retardation layer is 100 nm to 190 nm, and Re(450)/Re(550) is 0.8 or more and less than 1; and The angle formed by the slow axis of the retardation layer and the absorption axis of the polarizer is 40°˜50°. An image display device comprising the polarizing plate according to any one of claims 1 to 12 or the polarizing plate with a retardation layer according to any one of claims 13 to 15.

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