TW202208174A - Retardation-layer-equipped polarizing plate and image display device using same - Google Patents

Abstract

The present invention provides a retardation-layer-equipped polarizing plate in which the occurrence of cracking during heating is suppressed even while having a thin shape. The retardation-layer-equipped polarizing plate comprises: a polarizing plate including a polarizer; and a retardation layer provided to one side of the polarizing plate. The polarizing plate does not include a protective layer on the side opposite to the side where the retardation layer of the polarizer is provided. The retardation layer is an alignment fixed layer of a liquid crystal compound. In one embodiment, formula (1) is satisfied when the polarizer is formed from a film of a PVA-based resin containing a dichroic substance, and when the transmittance of the polarizer alone is defined as x% and the birefringence of the PVA-based resin is defined as y. In another embodiment, formula (2) is satisfied when the polarizer is formed from a film of a PVA-based resin containing a dichroic substance, and when the transmittance of the polarizer alone is defined as x% and the in-plane retardation of the PVA-based resin film is defined as z nm. In further another embodiment, formula (3) is satisfied when the polarizer is formed from a film of a PVA-based resin containing a dichroic substance, and when the transmittance of the polarizer alone is defined as x% and an alignment function of the PVA-based resin is defined as f. In still another embodiment, the polarizer is formed from a PVA-based resin film containing a dichroic substance, and has a piercing strength of 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 with retardation layer and image display device using the same

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

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 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, there is room for improving the durability, and there is a problem that the polarizer is prone to cracks due to heat treatment. prior art literature Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2001-343521

The problem to be solved by the invention The present invention is made in order to solve the above-mentioned conventional problems, and its main object is to provide a polarizing plate with a retardation layer that suppresses the occurrence of cracks during heating despite being thin.

means of solving problems According to an aspect of the present invention, a polarizing plate with retardation layer is provided, which has a polarizing plate including a polarizing member and a retardation layer disposed on one side of the polarizing plate; the polarizing plate is provided with the polarizing member and the polarizing member. The opposite side of the retardation layer does not contain a protective layer; the retardation layer is a directional solidification layer of a liquid crystal compound; the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and allows the monomer to transmit When the ratio is x% and the birefringence of the polyvinyl alcohol-based resin is y, the following formula (1) is satisfied. y＜-0.011x+0.525 (1) According to another aspect of the present invention, a polarizing plate with a retardation layer is provided, which has a polarizing plate including a polarizing member and a retardation layer disposed on one side of the polarizing plate; The opposite side of the retardation layer does not contain a protective layer; the retardation layer is a directional curing layer of a liquid crystal compound; the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and the monomer is When the transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film is znm, the following formula (2) is satisfied. z＜-60x+2875 (2) According to yet another aspect of the present invention, there is provided a polarizing plate with a retardation layer, which has a polarizing plate including a polarizing member and a retardation layer disposed on one side of the polarizing plate; the polarizing plate is arranged between the polarizing member and the polarizing plate. The opposite side of the side with the retardation layer does not contain a protective layer; the retardation layer is a directional solidification layer of a liquid crystal compound; the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and is placed on a single The following formula (3) is satisfied when the volume transmittance is x% and the orientation function of the polyvinyl alcohol-based resin is set to f. f＜-0.018x+1.11 (3) According to yet another aspect of the present invention, there is provided a polarizing plate with a retardation layer, which has a polarizing plate including a polarizing member and a retardation layer disposed on one side of the polarizing plate; the polarizing plate is arranged between the polarizing member and the polarizing plate. The opposite side of the side with the retardation layer does not include a protective layer; the retardation layer is a directional solidification layer of a liquid crystal compound; the puncture strength of the polarizer is more than 30gf/µm. In one embodiment, the total thickness of the polarizing plate with the retardation layer is 30 μm or less. In one embodiment, the thickness of the polarizer is 10 μm or less. In one embodiment, the single transmittance of the polarizer is 40.0% or more, and the polarization degree is 99.0% or more. Another aspect of the present invention provides an image display device comprising the above-mentioned polarizing plate with a retardation layer.

Invention effect According to the present invention, by using the polarizer whose orientation state of the polyvinyl alcohol (PVA) resin is controlled, even if a protective layer is not provided on at least one side of the polarizer, the occurrence of cracks during heating can be suppressed, resulting in A polarizing plate with a retardation layer that suppresses the occurrence of cracks during heating can be obtained despite being extremely thin. In addition, the polarizer can exhibit optical properties acceptable for practical use.

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. The overall composition of the polarizing plate with retardation layer The polarizing plate with retardation layer according to the embodiment of the present invention has a polarizing plate including a polarizer and a retardation layer provided on one side of the polarizing plate, and the retardation layer is an orientation cured layer of a liquid crystal compound. 1A to 1D respectively show schematic cross-sectional views of an example of a polarizing plate with a retardation layer according to an embodiment of the present invention.

The polarizing plate 100A with retardation layer illustrated in FIG. 1A has a polarizing plate 10 and a retardation layer 20 provided on one side of the polarizing plate 10 . The polarizing plate 10 includes a polarizer 11 and a protective layer 12 provided on the side of the retardation layer 20 , and no protective layer is provided on the side opposite to the side where the retardation layer 20 is provided.

The polarizing plate 100B with retardation layer illustrated in FIG. 1B has the polarizing plate 10 and the retardation layer 20 provided on one side of the polarizing plate 10 . The polarizing plate 10 includes the polarizing element 11 , and no protective layer is provided on either side of the polarizing plate 10 .

The polarizing plate 100C with retardation layer illustrated in FIG. 1C has a polarizing plate 10 and a retardation layer 20 provided on one side thereof. The polarizing plate 10 includes the polarizing element 11 , and no protective layer is provided on either side of the polarizing plate 10 . The retardation layer 20 has a laminated structure of the first directional solidification layer 21 and the second directional solidification layer 22 .

1D is a schematic cross-sectional view of a polarizing plate with a retardation layer according to yet another embodiment of the present invention. In the polarizing plate 100D with retardation layer illustrated in FIG. 1D , in addition to the polarizing plate 10 and the retardation layer 20 (the first directional solidified layer 21 and the second directional solidified layer 22 ), another retardation layer 30 and a conductive layer (or an isotropic substrate with a conductive layer) 40 is sequentially disposed on the opposite side of the retardation layer 20 and the side on which the polarizing plate 10 is disposed. The other retardation layer 30 exhibits a relationship of nz>nx=ny on behalf of the upper refractive index characteristic. The other retardation layer 30 and the conductive layer (or the isotropic substrate with the conductive layer) 40 represent any layers that can be provided as required, and either or both can be omitted. In addition, for the sake of convenience, the retardation layer 20 may be referred to as a first retardation layer, and the other retardation layer 30 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.

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.

The polarizing plate with the retardation layer according to the embodiment of the present invention may be in the form of 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 with retardation layer can be rolled into roll.

In practical applications, it is attached to either or both of the outer surfaces of the polarizing plate with retardation layer, specifically, it is attached to the image display unit side and/or the opposite side of the polarizing plate with retardation layer (representing the An adhesive layer (not shown) is provided on the outer surface of the upper surface, which can be attached to the adjacent member. Moreover, before the polarizing plate with retardation layer is put into use, a release film should be temporarily adhered to the surface of the adhesive layer. By temporarily adhering the release film, the roll can be formed while protecting the adhesive layer.

The total thickness of the polarizing plate with retardation layer is preferably 30µm or less, preferably 25µm or less, and more preferably 20µm or less. The total thickness may be, for example, 10 µm or more. According to the embodiment of the present invention, the polarizing plate with the retardation layer as described above can be realized. In addition, the occurrence of cracks during heating can also be suppressed. In addition, the polarizing plate with retardation layer can have excellent flexibility and durability against bending. Therefore, the polarizing plate with retardation layer is particularly suitable for use in curved image display devices and/or flexible or bendable image display devices. In addition, the so-called total thickness of the polarizing plate with retardation layer refers to the polarized light with retardation layer after deducting the adhesive layer used to make the polarizing plate with retardation layer and the external adherend such as panel or glass closely adhered The total thickness of all layers of the plate (that is, the total thickness of the polarizing plate with retardation layer does not include the adhesive layer used to attach the polarizing plate with retardation layer to adjacent components such as image display units and temporarily adhere to the thickness of the peeling film on its surface).

The unit weight of the polarizing plate with retardation layer according to the embodiment of the present invention is, for example, 6.5 mg/cm ² or less, preferably 2.0 mg/cm ² to 6.0 mg/cm ² , preferably 3.0 mg/cm ² to 5.5 mg/cm 2 . cm ² , more preferably 3.5 mg/cm ² to 5.0 mg/cm ² . When the display panel is thin, the panel may be slightly deformed by the weight of the polarizing plate with the retardation layer, which may cause poor display. However, if a polarizing plate with a retardation layer having a unit weight of 6.5 mg/cm ² or less is used, the deformation of the panel can be prevented. In addition, the polarizing plate with the retardation layer having the above-mentioned unit weight has good handleability even when it is thinned, and can exhibit extremely excellent flexibility and durability against bending.

Hereinafter, the constituent elements of the polarizing plate with retardation layer will be described in more detail.

B. Polarizing plate The polarizer includes a polarizer composed of a PVA-based resin film containing a dichroic substance. The polarizer may further include a protective layer on the side of the polarizer where the retardation layer is provided, or may not include a protective layer, but does not include a protective layer on the opposite side of the polarizer and the side where the retardation layer is provided. By omitting at least one side of the protective layer, and preferably omitting the protective layer on both sides, and using the directional solidification layer of the liquid crystal compound as the retardation layer, a very thin polarizer with retardation layer can be obtained.

B-1. Polarizer The above-mentioned polarizer is composed of a PVA-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)

The birefringence of the PVA-based resin of the polarizer (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 in-plane retardation of PVA"), the PVA-based resin The orientation function (hereinafter referred to as "the orientation function of PVA") and the penetration strength of the polarizer are values related to the degree of orientation of the molecular chains of the PVA-based resin constituting the polarizer. 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 with a retardation layer that suppresses cracking during heating despite being extremely thin. In addition, because the flexibility of the polarizer is also good, a polarizer with a retardation layer with excellent flexibility and bending resistance and durability can be obtained, which is suitable for use in curved image display devices, preferably It can be applied to a bendable image display device, and more preferably, it can be 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 used in the present invention preferably satisfies the following formula (1a) and/or formula (2a), and more preferably meets the following formula (1b) and/or 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 above-mentioned birefringence (in-plane birefringence) of PVA is a value obtained by dividing the in-plane retardation of PVA by the thickness 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 dense plane 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 upper limit of the monomer transmittance may be, for example, 49.0%. 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 upper limit of the degree of polarization may be, for example, 99.999%. In one embodiment, the degree of polarization of the polarizer is 99.0% to 99.9%. 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. In addition, when measuring the single transmittance of the polarizer using a polarizing plate having a structure of [polarizer/resin substrate (protective layer)], the single transmittance of the polarizer is the refractive index of one surface of the polarizing plate. Convert it to 1.50, and convert the refractive index of the other surface to 1.53. 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 B-2.

B-2. Manufacturing method of polarizer The manufacturing method of the above-mentioned polarizer preferably includes the following steps: forming a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a halide and a polyvinyl-alcohol-based resin (PVA-based resin) on one side of an elongated thermoplastic resin substrate , and a layered body is produced; and, the layered body 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 heat the layered body while transporting it in the longitudinal direction, thereby Make it shrink by more than 2% 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 2% or more. Moreover, the extension ratio of the aerial auxiliary extension should be greater than that of the underwater extension. According to the manufacturing method, the polarizer described in the above-mentioned item B-1 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 air-assisted stretching and underwater stretching is performed, and the stretched laminate is heated with a heating roller to shrink by 2% or more in the width direction.

B-2-1. 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 and reducing the total stretching ratio as described later, it is possible to obtain an allowable monomer transmittance and The polarizer of the degree of polarization.

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.

B-2-1-1. 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. In this specification, the entire description of this gazette is incorporated by reference.

B-2-1-2. 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.

B-2-2. Air Auxiliary 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) , but in order to obtain high optical properties, the free end extension can be actively used. 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 extension magnification of the aerial auxiliary extension is within the stated range, the total extension magnification can be set to the desired range when combined with the underwater extension, and the desired birefringence, in-plane retardation and/or orientation can be achieved function. 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 auxiliary stretching in the air is preferably larger than the stretching ratio of the stretching in the water. 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.

B-2-3. 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.

B-2-4. Water 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.

B-2-5. 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 200 is dried while being conveyed by the conveyance rollers R1 to R6 and the guide rollers G1 to G4 heated to a predetermined temperature. In the illustrated example, the conveying rollers R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin substrate, but for example, the conveying rollers R1 to R6 may be arranged to continuously heat only the layered body 200 one of the sides (such as the thermoplastic resin substrate side).

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

B-2-6. 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.

B-3. Protective layer The above-mentioned protective layer can be formed of any appropriate material according to the purpose. Specific examples of the material for forming the protective layer include cellulose-based resins such as triacetate cellulose (TAC), polyester-based, polyvinyl-alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, and polyamide-based resins. Ether-based, poly-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based and acetate-based transparent resins; (meth)acrylic-based, urethane-based Thermosetting resins, (meth)acrylate urethane-based, epoxy-based, and polysiloxane-based resins or UV-curable resins; glass-based polymers such as siloxane-based polymers.

The protective layer may be a resin film or a cured product of a coating film of a resin solution. When the protective layer is a resin film, it means that the upper protective layer is bonded to the polarizer through the adhesive layer. In addition, when the protective layer is a cured product of the coating film of the resin solution, an easily bonding layer can be formed on the surface of the polarizer, and the resin solution can be coated thereon and the coating film can be cured to form the protective layer.

The thickness of the protective layer is preferably 2µm~80µm, preferably 5µm~40µm, more preferably 5µm~25µm, and more preferably 5µm~20µm.

The protective layer is preferably 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 protective layer are within the above-mentioned ranges, when the polarizing plate including the protective layer is applied to an image display device, adverse effects on display characteristics can be prevented.

C. The first retardation layer The first retardation layer 20 is, for example, an alignment cured layer of the above-mentioned liquid crystal compound. By using a liquid crystal compound, the difference between nx and ny of the resulting retardation layer can be much larger than that of a non-liquid crystal material, so that the thickness of the retardation layer for obtaining the desired in-plane retardation can be greatly reduced. As a result, further thinning and weight reduction of the polarizing plate with retardation layer can be realized. The term "orientation-cured layer" in this specification refers to a layer in which the liquid crystal compound is oriented in a predetermined direction within the layer, and the orientation state thereof has been fixed. In addition, the concept of "orientation hardening layer" includes the orientation hardening layer obtained by hardening a liquid crystal monomer as mentioned later. In this embodiment, the upper rod-like liquid crystal compound is aligned in a state in which the first retardation layer is aligned in the slow axis direction (grain alignment).

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

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (ie, hardening) the liquid crystal monomer. After the liquid crystal monomers are aligned, for example, if the liquid crystal monomers are polymerized or crosslinked with each other, the above-mentioned alignment state can be thereby fixed. Here, a polymer is formed by polymerization, a 3-dimensional mesh structure is formed by cross-linking, and these are non-liquid crystalline. Therefore, the formed first retardation layer does not change into a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change, which is peculiar to a liquid crystal compound, for example. As a result, the first retardation layer becomes a retardation layer that is extremely stable without being affected by temperature changes.

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

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

The alignment curing layer of the liquid crystal compound can be formed by the following method: performing alignment treatment on the surface of a predetermined substrate, and coating the surface with a coating liquid containing the liquid crystal compound, so that the liquid crystal compound is aligned in the direction corresponding to the above alignment treatment , and fix the orientation state. In one embodiment, the base material is any appropriate resin film, and the orientation cured layer formed on the base material can be transferred to the surface of the polarizing plate 10 . In another embodiment, the substrate can be the protective layer 12 . In this case, the transfer step is omitted, and after forming the directionally solidified layer (the first retardation layer), the layering can be performed in a roll-to-roll manner, and thus productivity can be further improved.

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

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

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

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

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

In one embodiment, as shown in FIGS. 1A and 1B , the first retardation layer 20 is a single layer of a directionally cured layer of a liquid crystal compound. When the first retardation layer 20 is constituted by a single layer of a directional solidification layer of a liquid crystal compound, its thickness is preferably 0.5 μm to 7 μm, preferably 1 μm to 5 μm. By using the liquid crystal compound, the in-plane retardation equivalent to that of the resin film can be realized at a thickness much thinner than that of the resin film.

The first retardation layer represents that the upper refractive index characteristic exhibits a relationship of nx>ny=nz. The first retardation layer is typically provided to impart antireflection properties to the polarizing plate, but can function as a λ/4 plate when the first retardation layer is a single layer of the directionally cured layer. 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 cases where ny>nz or ny<nz.

The Nz coefficient of the first retardation layer is preferably 0.9 to 1.5, preferably 0.9 to 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 the reverse dispersion wavelength characteristic that the retardation value increases with the wavelength of the measurement light, the normal wavelength dispersion characteristic that the retardation value becomes smaller with the wavelength of the measurement light, or the retardation value that hardly varies with the wavelength of the measurement light. Measure the flat wavelength dispersion characteristic of the wavelength change of 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 angle θ formed by the slow axis of the first retardation layer 20 and the absorption axis of the polarizer 11 is preferably 40° to 50°, more preferably 42° to 48°, and more preferably about 45°. If the angle θ is within the above-mentioned range, by making the first retardation layer into a λ/4 plate as described above, it is possible to obtain a phase with very excellent circular polarization characteristics (resulting in very excellent anti-reflection characteristics) The polarizing plate of the poor layer.

In another embodiment, the first retardation layer 20 may have a laminated structure of the first directional solidification layer 21 and the second directional solidification layer 22 as shown in FIGS. 1C and 1D . At this time, either one of the first directional hardening layer 21 and the second directional hardening layer 22 can function as a λ/4 plate, and the other can function as a λ/2 plate. Therefore, the thicknesses of the first directionally solidified layer 21 and the second directionally solidified layer 22 can be adjusted in order to obtain a desired in-plane retardation of a λ/4 plate or a λ/2 plate. For example, when the first directionally solidified layer 21 functions as a λ/2 plate and the second directionally solidified layer 22 functions as a λ/4 plate, the thickness of the first directionally solidified layer 21 is, for example, 2.0 μm to 3.0 μm, and the thickness of the second directionally solidified layer 21 is, for example, 2.0 μm to 3.0 μm. The thickness of the directionally solidified layer 22 is, for example, 1.0 μm to 2.0 μm. At this time, the in-plane retardation Re(550) of the first directionally solidified layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and more preferably 250 nm to 280 nm. As for the in-plane retardation Re(550) of the second directionally solidified layer, the single-layered directionally solidified layer is as described above. The angle formed by the slow axis of the first directionally solidified layer and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and more preferably about 15°. The angle formed by the slow axis of the second directionally solidified layer and the absorption axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and more preferably about 75°. With such a configuration, properties close to ideal reverse wavelength dispersion properties can be obtained, and as a result, very excellent antireflection properties can be realized. The liquid crystal compound constituting the first and second orientationally cured layers, the method of forming the first and second orientationally cured layers, optical properties, etc. are as described above for the single-layered orientationally cured layer.

D. 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.

E. 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). Preferably, the above-mentioned substrate is optically isotropic, so the conductive layer can be used as an isotropic substrate with a conductive layer for a polarizer 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.

F. Video display device The above-mentioned polarizing plate with retardation layer can be applied to an image display device. Therefore, the present invention includes an image display device using the polarizing plate with the 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 includes the above-mentioned polarizing plate with a retardation layer 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 Examples and Comparative Examples are based on weight.

(1) Thickness 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. (2) In-plane retardation (Re) of PVA For the polarizer (polarizer alone) after peeling off the resin substrate from the laminate of the polarizer/thermoplastic resin substrate obtained in the Examples and Comparative Examples, the phase difference was used. A difference measuring device (product name "KOBRA-31X100/IR" manufactured by Oji Scientific Instruments Co., Ltd.) evaluates the in-plane retardation (Rpva) of PVA at a wavelength of 1000 nm (according to the principle described, from the total surface at a wavelength of 1000 nm) The value obtained by subtracting the in-plane retardation of iodine (Ri) from the in-plane retardation). The absorption edge wavelength was set to 600 nm. (3) Birefringence (Δn) of PVA The birefringence (Δn) of PVA was calculated by dividing the in-plane retardation of PVA measured in (2) above by the thickness of the polarizer. (4) 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. (5) Puncture strength (breaking strength per unit thickness) The polarizer was peeled from the laminate of the polarizer/thermoplastic resin substrate obtained in Examples and Comparative Examples, and the polarizer was placed in a compression tester (KATO TECH CO., LTD.) equipped with a needle. ., LTD., product name "NDG5" needle penetration force measurement specification), at room temperature (23°C ± 3°C), puncture at a puncture speed of 0.33cm/sec, and the strength at which the polarizer breaks is taken as breakage 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) Orientation function of PVA For the polarizer (polarizer monomer) after peeling off the resin substrate from the laminate of the polarizer/thermoplastic resin substrate obtained in the Examples and Comparative Examples, for the polarizer (polarizer monomer) with the peeled resin substrate The surface is the surface on the opposite side, and a Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, trade name: "Frontier") is used, and the polarized infrared ray is used as the measurement light, and the total attenuation of the surface of the polarizer is carried out. Spectroscopic reflection (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 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 at 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°⇒y=-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 _// : Measure the absorption intensity when the polarization direction of the light is parallel to the extending direction of the polarizer (7) The incidence of cracks The polarizing plates with retardation layers obtained in Examples and Comparative Examples were cut into 10mm×10mm size. The cut out polarizer with retardation layer was attached to the glass plate (thickness 1.1mm) through an acrylic adhesive layer with a thickness of 20 µm so that the retardation layer side became the glass plate side. After the sample attached to the glass plate was placed in an oven at 100° 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. The evaluation was performed using three polarizing plates with retardation layers, and the number of polarizing plates with retardation layers that had cracks was evaluated.

[Example 1] 1. Preparation of polarizing plate (polarizer) The thermoplastic resin substrate is a long strip of amorphous isophthalic acid copolymerized polyethylene terephthalate with a water absorption rate of 0.75% and a Tg of about 75°C Ester film (thickness: 100µm). Corona treatment was performed on one side of the resin substrate (treatment condition: 55W·min/m ² ). The PVA system is a 9:1 mixture of polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetylacetate modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") To 100 parts by weight of resin, 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 with different peripheral speeds in an oven at 130° C. (a mid-air 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 40.5% (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 an aqueous solution of boric acid (boric acid concentration 4.0 wt %, potassium iodide 5.0 wt %) at a liquid temperature of 62° C., uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to The total magnification of stretching was made 3.0 times (in-water stretching treatment: the stretching magnification in underwater stretching treatment was 1.25 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 the oven maintained at 90 degreeC, the contact surface temperature was made to pass through the heating roll made of SUS maintained at 75 degreeC for about 2 seconds (drying shrinkage treatment). The shrinkage rate in the width direction of the laminate obtained by drying shrinkage treatment was 2%. Through the above procedures, a polarizer with a thickness of 7.4 μm was formed on the resin substrate.

使用擦拭布擦拭聚對苯二甲酸乙二酯(PET)薄膜(厚度38μm)表面，施行定向處理。定向處理之方向係設為貼合至偏光板時由視辨側觀看時相對於偏光件之吸收軸方向呈15°方向。利用棒塗機將上述液晶塗敷液塗敷至該定向處理表面，並於90℃下進行2分鐘加熱乾燥，藉此使液晶化合物定向。使用金屬鹵素燈對依上述方式形成的液晶層照射100mJ/cm² 的光，使該液晶層硬化，藉此於PET薄膜上形成第1定向固化層。第1定向固化層之厚度為2.5μm，面內相位差Re(550)為270nm。並且，第1定向固化層具有nx＞ny=nz之折射率分布。 變更塗敷厚度，並將定向處理方向設為由視辨側觀看時相對於偏光件之吸收軸方向呈75°方向，除此之外依與上述相同方式於PET薄膜上形成第2定向固化層。第2定向固化層之厚度為1.3μm，面內相位差Re(550)為140nm。並且，第2定向固化層具有nx＞ny=nz之折射率分布。2. Preparation of the first and second orientationally cured layers constituting the retardation layer. A polymerizable liquid crystal (manufactured by BASF: trade name "Paliocolor LC242", represented by the following formula) exhibiting a nematic liquid crystal phase 10 g and 3 g of a photopolymerization initiator (manufactured by BASF: trade name "IRGACURE 907") of the polymerizable liquid crystal compound was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid). [Chemical formula 1]

The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was wiped with a wiping cloth to perform orientation treatment. The direction of the orientation treatment is set to be a 15° direction with respect to the absorption axis direction of the polarizer when viewed from the viewing side when it is attached to the polarizer. The above-mentioned liquid crystal coating liquid was applied to the alignment-treated surface by a bar coater, and the liquid crystal compound was aligned by heating and drying at 90° C. for 2 minutes. The liquid crystal layer formed as described above was irradiated with light of 100 mJ/cm ² using a metal halide lamp to harden the liquid crystal layer, thereby forming a first orientationally cured layer on the PET film. The thickness of the first directionally cured layer was 2.5 μm, and the in-plane retardation Re(550) was 270 nm. In addition, the first directionally solidified layer has a refractive index distribution of nx>ny=nz. A second orientation cured layer was formed on the PET film in the same manner as above, except that the coating thickness was changed, and the orientation treatment direction was set to be 75° with respect to the absorption axis direction of the polarizer when viewed from the viewing side. . The thickness of the second directionally cured layer was 1.3 μm, and the in-plane retardation Re(550) was 140 nm. In addition, the second directionally cured layer has a refractive index distribution of nx>ny=nz.

3. Production of polarizing plate with retardation layer The 1st directional hardening layer and the 2nd directional hardening layer obtained in the above 2. were sequentially transferred to the polarizer surface of the laminated body which has the structure of the above-mentioned 1. obtained [polarizer/resin base material]. At this time, the rotation was performed so that the angle formed by the absorption axis of the polarizer and the slow axis of the first orientationally solidified layer was 15° and the angle formed by the absorption axis of the polarizer and the slow axis of the second orientationally solidified layer was 75°. print (fit). In addition, each transfer (bonding) was performed through an ultraviolet curable adhesive (thickness 1.0 μm). The resin base material was peeled off from the obtained laminated body, and the polarizing plate with retardation layer which has the structure of [polarizer/adhesive layer/retardation layer (1st orientationally hardened layer/adhesive layer/2nd orientationally hardened layer)] was obtained. The total thickness of the obtained polarizing plate with retardation layer was 13.2 μm.

[Examples 2 to 4] A polarizer (thickness: 7.4 µm) was formed on the resin substrate in the same manner as in Example 1, except that dyeing baths with different iodine concentrations were used (weight ratio of iodine to potassium iodide = 1:7). In the same manner as in Example 1, except that a laminate having the configuration of the [polarizer/resin base material] was used, a layer having the [polarizer/adhesive layer/retardation layer (first directional cured layer/adhesive layer/third layer) was obtained. 2. The polarizing plate with retardation layer composed of directional solidification layer)]. The total thickness of the obtained polarizing plate with retardation layer was 13.2 μm.

[Examples 5 to 8] The stretching magnification of stretching in water was set to 1.46 times (as a result, the total stretching magnification was set to 3.5 times), and dyeing baths with different iodine concentrations were used (weight ratio of iodine to potassium iodide = 1:7), except Otherwise, in the same manner as in Example 1, a polarizer (thickness: 6.7 µm) was formed on the resin substrate. In the same manner as in Example 1, except that a laminate having the configuration of the [polarizer/resin base material] was used, a layer having the [polarizer/adhesive layer/retardation layer (first directional cured layer/adhesive layer/third layer) was obtained. 2. The polarizing plate with retardation layer composed of directional solidification layer)]. The total thickness of the obtained polarizing plate with retardation layer was 12.5 μm.

[Examples 9 to 12] The stretching magnification of stretching in water was set to 1.67 times (as a result, the total stretching magnification was set to 4.0 times), and dyeing baths with different iodine concentrations were used (weight ratio of iodine to potassium iodide = 1:7), except Otherwise, in the same manner as in Example 1, a polarizer (thickness: 6.2 µm) was formed on the resin substrate. In the same manner as in Example 1, except that a laminate having the configuration of the [polarizer/resin base material] was used, a layer having the [polarizer/adhesive layer/retardation layer (first directional cured layer/adhesive layer/third layer) was obtained. 2. The polarizing plate with retardation layer composed of directional solidification layer)]. The total thickness of the obtained polarizing plate with retardation layer was 12.0 μm.

[Examples 13 to 16] The stretching ratio in water was set to 1.88 times (as a result, the total stretching ratio was set to 4.5 times), and dyeing baths with different iodine concentrations were used (weight ratio of iodine to potassium iodide = 1:7), except Otherwise, in the same manner as in Example 1, a polarizer (thickness: 6.0 µm) was formed on the resin substrate. In the same manner as in Example 1, except that a laminate having the configuration of the [polarizer/resin base material] was used, a layer having the [polarizer/adhesive layer/retardation layer (first directional cured layer/adhesive layer/third layer) was obtained. 2. The polarizing plate with retardation layer composed of directional solidification layer)]. The total thickness of the obtained polarizing plate with retardation layer was 11.8 μm.

[Comparative Examples 1 to 4] The stretching ratio in water was set to 2.29 times (as a result, the total stretching ratio was set to 5.5 times), and dyeing baths with different iodine concentrations were used (weight ratio of iodine to potassium iodide = 1:7), except Otherwise, in the same manner as in Example 1, a polarizer (thickness: 5.5 µm) was formed on the resin substrate. In the same manner as in Example 1, except that a laminate having the configuration of the [polarizer/resin base material] was used, a layer having the [polarizer/adhesive layer/retardation layer (first directional cured layer/adhesive layer/third layer) was obtained. 2. The polarizing plate with retardation layer composed of directional solidification layer)]. The total thickness of the obtained polarizing plate with retardation layer was 11.3 μm.

The polarizers or polarizers with retardation layers obtained in Examples and Comparative Examples were used for the evaluations of (2) to (7) above. The results are listed in Table 1.

[Table 1]

As is apparent from Table 1, although the polarizing plate with retardation layer of the Example is extremely thin without a protective layer, cracks caused by heating are suppressed.

3 to 5 respectively show the relationship between the single transmittance of the polarizers obtained in Examples and Comparative Examples and the Δn of PVA, in-plane retardation or orientation function. As shown in FIGS. 3 and 5 , even if the birefringence, the in-plane retardation, and the orientation function are at the same level (as a result, the orientation degree is at the same level), when the transmittance of the single body is high, it is easy to be damaged by heating. Cracks occur. Therefore, in order to effectively suppress the occurrence of cracks due to heating, it was found that not only the orientation degree of the PVA-based resin but also the adjustment of the monomer transmittance (resulting in the adsorption amount of the dichroic substance) is important. In addition, it can be seen that the polarizer satisfying the formula (1), the formula (2) and/or the formula (3) has been properly adjusted, and the occurrence of cracks caused by heating can be appropriately suppressed.

industrial availability The polarizing plate with retardation layer of the present invention can be suitably used in an image display device.

10: Polarizer 11: Polarizer 12: Protective layer 20: retardation layer 21: The first directionally cured layer 22: The second directionally cured layer 30: Another retardation layer 40: Conductive layer (or isotropic substrate with conductive layer) 100A~100D: polarizing plate with retardation layer 200: Laminate G1~G4: Guide roller R1~R6: Conveying roller

1A is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. 1B is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. 1C is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. 1D is a schematic cross-sectional view of a polarizing plate with a retardation layer according to an embodiment of the present invention. 2 is a schematic diagram showing an example of drying shrinkage treatment using a heating roller in the manufacturing method of the polarizer used in the polarizing plate with retardation layer of the present invention. 3 is a graph showing the relationship between the single transmittance of the polarizers produced in Examples and Comparative Examples and the birefringence of PVA-based resins. 4 is a graph showing the relationship between the single transmittance of the polarizers produced in Examples and Comparative Examples and the in-plane retardation of PVA-based resin films. FIG. 5 is a graph showing the relationship between the single transmittance of the polarizers produced in Examples and Comparative Examples and the orientation function of the PVA-based resin.

10: Polarizer

11: Polarizer

12: Protective layer

20: retardation layer

100A: Polarizing plate with retardation layer

Claims (8)

A polarizing plate with a retardation layer, comprising a polarizing plate comprising a polarizer and a retardation layer disposed on one side of the polarizing plate; The polarizer does not include a protective layer on the opposite side of the polarizer and the side provided with the retardation layer; The retardation layer is a directional solidification layer of liquid crystal compound; The polarizer is composed of a polyvinyl alcohol-based resin film containing dichroic substances, and satisfies the following formula when the transmittance of the monomer is x% and the birefringence of the polyvinyl alcohol-based resin is y 1): y<-0.011x+0.525 (1). A polarizing plate with a retardation layer, comprising a polarizing plate comprising a polarizer and a retardation layer disposed on one side of the polarizing plate; The polarizer does not include a protective layer on the opposite side of the polarizer and the side provided with the retardation layer; The retardation layer is a directional solidification layer of liquid crystal compound; The polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and satisfies the following conditions when the transmittance of the monomer is x% and the in-plane retardation of the polyvinyl alcohol-based resin film is znm Formula (2): z<-60x+2875 (2). A polarizing plate with a retardation layer, comprising a polarizing plate comprising a polarizer and a retardation layer disposed on one side of the polarizing plate; The polarizer does not include a protective layer on the opposite side of the polarizer and the side provided with the retardation layer; The retardation layer is a directional solidification layer of liquid crystal compound; The polarizer is composed of a polyvinyl alcohol-based resin film containing dichroic substances, and satisfies the following formula when the transmittance of the monomer is x% and the orientation function of the polyvinyl alcohol-based resin is f 3): f<-0.018x+1.11 (3). A polarizing plate with a retardation layer, comprising a polarizing plate comprising a polarizer and a retardation layer disposed on one side of the polarizing plate; The polarizer does not include a protective layer on the opposite side of the polarizer and the side provided with the retardation layer; The retardation layer is a directional solidification layer of liquid crystal compound; The puncture intensity of the polarizer is above 30gf/µm. The total thickness of the polarizing plate with retardation layer as claimed in any one of claims 1 to 4 is 30 µm or less. The polarizing plate with retardation layer according to any one of claims 1 to 5, wherein the thickness of the polarizer is 10 µm or less. The polarizing plate with retardation layer according to any one of claims 1 to 6, wherein the single transmittance of the polarizer is 40.0% or more, and the polarization degree is 99.0% or more. An image display device, comprising the polarizing plate with retardation layer according to any one of claims 1 to 7.

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