WO2021261344A1

WO2021261344A1 - Retardation-layer-equipped polarizing plate and image display device using same

Info

Publication number: WO2021261344A1
Application number: PCT/JP2021/022774
Authority: WO
Inventors: 幸佑 ▲高▼永; 卓史上条; 一葵川緑
Original assignee: 日東電工株式会社
Priority date: 2020-06-26
Filing date: 2021-06-16
Publication date: 2021-12-30
Also published as: JPWO2021261344A1; CN115804264A; TW202204945A; KR20230028728A

Abstract

Provided is a retardation-layer-equipped polarizing plate in which the occurrence of cracking during heating is suppressed. The retardation-layer-equipped polarizing plate according to the present invention comprises: a polarizing plate including a polarizer made of a polyvinyl alcohol-based resin film containing a dichroic substance, and a protective layer arranged on one side of the polarizer; and a retardation layer. This retardation layer is an orientation-solidified layer of a liquid crystal compound, and the thickness of the protective layer is 10 μm or less. In one embodiment, the following equation (1) is satisfied when the single transmittance of the polarizer is x% and the birefringence of the polyvinyl alcohol-based resin is y. In one embodiment, the following equation (2) is satisfied when the single transmittance of the polarizer is x% and the in-plane phase difference of the polyvinyl alcohol-based resin film is z nm. In one embodiment, the following equation (3) is satisfied when the single transmittance of the polarizer is x% and the orientation function of the polyvinyl alcohol-based resin is f.　y < -0.011x + 0.525 (1) z < -60x + 2875 (2) f < -0.018x + 1.11 (3)

Description

A polarizing plate with a retardation layer and an image display device using it.

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

In recent years, image display devices represented by liquid crystal displays and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have rapidly become widespread. A polarizing plate and a retardation plate are typically used in an image display device. Practically, 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, as the demand for thinner image display devices has increased, the demand for thinner polarizing plates with retardation layers has also increased. Further, in recent years, there has been an increasing demand for a curved image display device and / or a bendable or bendable image display device. Therefore, the polarizing plate and the polarizing plate with a retardation layer are also required to be thinner and more flexible.

As a method of thinning the polarizing plate, it has been proposed to reduce the thickness of the protective layer and to laminate the protective layer only on one side of the polarizing element. However, these methods cannot sufficiently protect the polarizing element, and there is room for improvement in durability. Further, there is a problem that cracks are likely to occur not only in the polarizing element but also in the polarizing plate due to the heat treatment.

Japanese Unexamined Patent Publication No. 2001-343521

The present invention has been made to solve the above-mentioned conventional problems, and a main object thereof is to provide a polarizing plate with a retardation layer in which crack generation during heating is suppressed.

The polarizing plate with a retardation layer according to the embodiment of the present invention is polarized light including a polarizing element made of a polyvinyl alcohol-based resin film containing a dichroic substance and a protective layer arranged on one side of the polarizing element. It has a plate and a retardation layer. This retardation layer is an orientation-solidified layer of a liquid crystal compound, and the thickness of this protective layer is 10 μm or less. This polarizing element satisfies the following formula (1) when the simple substance transmittance is x% and the birefringence of the polyvinyl alcohol-based resin is y.
y <-0.011x + 0.525 (1)
In the polarizing plate with a retardation layer according to another embodiment of the present invention, a polarizing element made of a polyvinyl alcohol-based resin film containing a dichroic substance and a protective layer arranged on one side of the polarizing element are provided. It has a polarizing plate including the polarizing plate and a retardation layer. This retardation layer is an orientation-solidified layer of a liquid crystal compound, and the thickness of this protective layer is 10 μm or less. This polarizing element satisfies the following formula (2) when the simple substance transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film is znm.
z <-60x + 2875 (2)
The polarizing plate with a retardation layer according to still another embodiment of the present invention includes a polarizing element made of a polyvinyl alcohol-based resin film containing a dichroic substance, and a protective layer arranged on one side of the polarizing element. It has a polarizing plate containing the above and a retardation layer. This retardation layer is an orientation-solidified layer of a liquid crystal compound, and the thickness of this protective layer is 10 μm or less. This polarizing element satisfies the following formula (3) when its simple transmittance is x% and the orientation function of the polyvinyl alcohol-based resin is f.
f <-0.018x + 1.11 (3)
In one embodiment, the total thickness of the polarizing plate with a retardation layer is 30 μm or less.
In one embodiment, the thickness of the polarizing element is 10 μm or less.
In one embodiment, the simple substance transmittance of the above-mentioned extruder is 40.0% or more, and the degree of polarization is 99.0% or more.
In one embodiment, the protective layer is made from a solidified coating film of an organic solvent solution of a thermoplastic (meth) acrylic resin, a photocationic cured product of an epoxy resin, and a solidified coating film of an organic solvent solution of an epoxy resin. It is composed of at least one selected from the group.
In one embodiment, the thermoplastic (meth) acrylic resin comprises at least one repeating unit selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit and a maleimide unit. Have.
In one embodiment, the protective layer is a photocationic cured product of an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton.
In another aspect of the invention, an image display device is provided. This image display device includes the above-mentioned polarizing plate with a retardation layer.

According to the present invention, a polarizing element in which the single transmittance and the birefringence of polyvinyl alcohol (PVA) or the in-plane phase difference of the PVA-based resin film satisfy a predetermined relationship, a protective layer having a thickness of 10 μm or less, and a liquid crystal alignment compound. Provided is a polarizing plate with a retardation layer having a retardation layer of the orientation solidification layer of the above. By using such a polarizing plate with a retardation layer, the polarizing plate with a retardation layer can be made thinner and crack generation during heating can be suppressed. Further, the generation of cracks at the time of bending can be suppressed.

It is the schematic sectional drawing of the polarizing plate with a retardation layer by one Embodiment of this invention. It is the schematic sectional drawing of the polarizing plate with a retardation layer by another embodiment of this invention. It is schematic cross-sectional view of the polarizing plate with a retardation layer according to still another embodiment of this invention. It is a schematic diagram which shows an example of the drying shrinkage process using a heating roll in the method of manufacturing a polarizing element used for the polarizing plate with a retardation layer of this invention.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
Definitions of terms and symbols herein are as follows.
(1) Refractive index (nx, ny, nz)
"Nx" is the refractive index in the direction in which the refractive index in the plane is maximized (that is, the slow-phase axis direction), and "ny" is the direction orthogonal to the slow-phase axis in the plane (that is, the phase-advancing axis direction). Is the refractive index of, and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
“Re (λ)” is an in-plane phase difference measured with light having a wavelength of λ nm at 23 ° C. For example, "Re (550)" is an in-plane phase difference measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained by the formula: Re (λ) = (nx−ny) × d, where d (nm) is the thickness of the layer (film).
(3) Phase difference in the thickness direction (Rth)
“Rth (λ)” is a phase difference in the thickness direction measured with light having a wavelength of λ nm at 23 ° C. For example, "Rth (550)" is a phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23 ° C. Rth (λ) is obtained by the formula: Rth (λ) = (nx-nz) × d, where d (nm) is the thickness of the layer (film).
(4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re.
(5) Angle When referring to an angle herein, the angle includes both clockwise and counterclockwise with respect to the reference direction. Therefore, for example, "45 °" means ± 45 °.

A. Overall Configuration of Polarizing Plate with Difference Layer FIG. 1 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. The polarizing plate 100 with a retardation layer of the present embodiment has a polarizing plate 10 and a retardation layer 20. The polarizing plate 10 includes a polarizing element 11, a first protective layer 12 arranged on one side of the polarizing element 11, and a second protective layer 13 arranged on the other side of the polarizing element 11. .. Depending on the purpose, one of the first protective layer 12 and the second protective layer 13 may be omitted. For example, if the retardation layer 20 can also function as a protective layer for the polarizing element 11, the second protective layer 13 may be omitted. The retardation layer 20 is laminated to the polarizing element 11 or the second protective layer 13 via any suitable adhesive layer or adhesive layer (not shown). In the embodiment of the present invention, the polarizing element 11 is made of a polyvinyl alcohol-based resin film containing a dichroic substance, the single transmittance is x%, and the birefringence of the polyvinyl alcohol-based resin is y. Satisfies the following equation (1). Further, in one embodiment of the present invention, the polarizing element 11 is made of a polyvinyl alcohol-based resin film containing a dichroic substance, and the single transmittance is x%, and the in-plane of the polyvinyl alcohol-based resin film is set. When the phase difference is znm, the following equation (2) is satisfied. In one embodiment, the polarizing element 10 satisfies the following formula (3) when the simple substance transmittance is x% and the orientation function of the polyvinyl alcohol-based resin constituting the polarizing element is f.
y <-0.011x + 0.525 (1)
z <-60x + 2875 (2)
f <-0.018x + 1.11 (3)

FIG. 2 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. As shown in FIG. 2, in the polarizing plate 101 with a retardation layer according to another embodiment, another retardation layer 50 and / or a conductive layer or an isotropic base material 60 with a conductive layer may be provided. Another retardation layer 50 and the conductive layer or the isotropic base material 60 with the conductive layer are typically provided on the outside of the retardation layer 20 (opposite to the polarizing plate 10). The other retardation layer typically shows a relationship in which the refractive index characteristics are nz> nx = ny. Another retardation layer 50 and the conductive layer or the isotropic base material 60 with the conductive layer are typically provided in this order from the retardation layer 20 side. The other retardation layer 50 and the conductive layer or the isotropic base material 60 with the conductive layer are typically arbitrary layers provided as needed, and one or both of them may be omitted. For convenience, the retardation layer 20 may be referred to as a first retardation layer, and another retardation layer 50 may be referred to as a second retardation layer. When a conductive layer or an isotropic substrate with a conductive layer is provided, the polarizing plate with a retardation layer is a so-called inner in which a touch sensor is incorporated between an image display cell (for example, an organic EL cell) and the polarizing plate. It can be applied to a touch panel type input display device.

FIG. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to still another embodiment of the present invention. In the embodiment of the present invention, the first retardation layer 20 is an orientation-solidifying layer of a liquid crystal compound. The first retardation layer 20 may be a single layer of the orientation solidification layer as shown in FIGS. 1 and 2, and the first alignment solidification layer 21 and the second orientation solidification layer 22 as shown in FIG. It may have a laminated structure with.

The above embodiments may be combined as appropriate, and the components in the above embodiments may be modified in a manner obvious in the art. For example, the polarizing plate 102 with a retardation layer in FIG. 3 may be further provided with a second retardation layer 50 and / or an isotropic base material 60 with a conductive layer or a conductive layer. Further, for example, the configuration in which the isotropic base material 60 with a conductive layer is provided on the outside of the second retardation layer 50 is replaced with an optically equivalent configuration (for example, a laminate of the second retardation layer and the conductive layer). You may.

The polarizing plate with a retardation layer according to the embodiment of the present invention may further include another retardation layer. The optical characteristics (for example, refractive index characteristics, 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 a retardation layer of the present invention may be single-wafered or elongated. As used herein, the term "long" means an elongated shape having a length sufficiently long with respect to the width, and for example, an elongated shape having a length of 10 times or more, preferably 20 times or more with respect to the width. include. The long polarizing plate with a retardation layer can be wound in a roll shape.

Practically, an adhesive layer (not shown) is provided on the opposite side of the polarizing plate of the retardation layer, and the polarizing plate with the retardation layer can be attached to the image display cell. Further, it is preferable that a release film is temporarily attached to the surface of the pressure-sensitive adhesive layer until a polarizing plate with a retardation layer is used. Temporary attachment of the release film protects the pressure-sensitive adhesive layer and enables roll formation.

The total thickness of the polarizing plate with a retardation layer is preferably 30 μm or less, more preferably 25 μm or less, and further preferably 20 μm or less. The total thickness can be, for example, 10 μm or more. According to the embodiment of the present invention, it is possible to realize such an extremely thin polarizing plate with a retardation layer. Furthermore, the generation of cracks during heating can be suppressed. Such a polarizing plate with a retardation layer can have extremely excellent flexibility and bending durability. Such a polarizing plate with a retardation layer may be particularly preferably applied to a curved image display device and / or a bendable or bendable image display device. The total thickness of the polarizing plate with a retardation layer is the total thickness of all the layers constituting the polarizing plate with a retardation layer, except for the pressure-sensitive adhesive layer for bringing the polarizing plate into close contact with an external adherend such as a panel or glass. The total thickness (that is, the total thickness of the polarizing plate with a retardation layer is the peeling that can be temporarily attached to the pressure-sensitive adhesive layer for attaching the polarizing plate with a retardation layer to an adjacent member such as an image display cell and its surface. Does not include film thickness).

The unit weight of the polarizing plate with a 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} , and more preferably 3. It is 0.0 ^{mg / cm 2} to 5.5 mg / cm ² , more preferably 3.5 mg / cm ² to 5.0 mg / cm ² . If the display panel is thin, the weight of the polarizing plate with a retardation layer may cause the panel to be slightly deformed, resulting in display defects. According to a polarizing plate with a retardation layer having a unit weight of 6.5 mg / cm ^{2 or less, such deformation of the panel can be prevented.} Further, the polarizing plate with a retardation layer having the above unit weight has good handleability even when it is thinned, and can exhibit extremely excellent flexibility and bending durability.

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

B. Polarizing plate B-1. Polarizer The polarizing film according to one embodiment of the present invention is composed of a PVA-based resin film containing a dichroic substance, and when the single transmittance is x% and the double refraction of the PVA-based resin is y. The following equation (1) is satisfied. Further, the polarizing film according to another embodiment of the present invention is composed of a PVA-based resin film containing a dichroic substance, has a single transmittance of x%, and has an in-plane retardation of the PVA-based resin film of znm. In this case, the following equation (2) is satisfied. In one embodiment, the polarizing element satisfies the following formula (3) when the simple substance transmittance is x% and the orientation function of the polyvinyl alcohol-based resin constituting the polarizing element is f.
y <-0.011x + 0.525 (1)
z <-60x + 2875 (2)
f <-0.018x + 1.11 (3)

Double refraction of PVA-based resin (hereinafter referred to as PVA double refraction or PVA Δn) and in-plane phase difference of PVA-based resin film (hereinafter referred to as “PVA in-plane phase difference”) in the above-mentioned extruder. Are all values related to the degree of orientation of the molecular chains of the PVA-based resin constituting the polarizing element, and can become large as the degree of orientation increases. Since the orientation of the molecular chain of the PVA-based resin in the absorption axis direction is gentler than that of the conventional polarizing element, the above-mentioned polarizing element suppresses breakage along the absorption axis direction. As a result, a polarizing element having very excellent flexibility (as a result, a polarizing plate) can be obtained. Such a polarizing element (as a result, a polarizing plate) may be applied to a preferably curved image display device, more preferably a foldable image display device, and even more preferably a foldable image display device. Conventionally, it has been difficult to obtain acceptable optical characteristics (typically, simple substance transmittance and degree of polarization) with a polarizing element having a low degree of orientation. The satisfying polarizing element can achieve both a lower degree of orientation of the PVA-based resin and an acceptable optical characteristic than before.

The polarizing element according to the embodiment of the present invention preferably satisfies the following formulas (1a) and / or the following formulas (2a), and more preferably the following formulas (1b) and / or the following formulas (2b).
The polarizing element preferably satisfies the following formulas (1a) and / or the following formula (2a), and more preferably the following formulas (1b) and / or the formula (2b).
-0.004x + 0.18 <y <-0.011x + 0.525 (1a)
-0.003x + 0.145 <y <-0.011x + 0.520 (1b)
-40x + 1800 <z <-60x + 2875 (2a)
-30x + 1450 <z <-60x + 2850 (2b)

In the present specification, the in-plane retardation value of 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 measurement wavelength in the near-infrared region, the influence of absorption of iodine in the polarizing element can be eliminated, and the phase difference can be measured. The birefringence of PVA (in-plane birefringence) is a value obtained by dividing the in-plane phase difference of PVA by the thickness of the polarizing element.

The in-plane phase difference of PVA is evaluated as follows. First, the phase difference value is measured at a plurality of wavelengths having a wavelength of 850 nm or more, the measured phase difference value: R (λ) and the wavelength: λ are plotted, and this is fitted to the following Selmeyer equation by the least squares method. Let me. Here, A and B are fitting parameters and coefficients determined by the least squares method.
R (λ) = A + B / (λ 2 -600 2)
At this time, the phase difference value R (λ) is divided into the in-plane phase difference (Rpva) of PVA having no wavelength dependence and the in-plane phase difference value (Ri) of iodine having a strong wavelength dependence as follows. Can be separated.
Rpva = A
^{Ri = B / (λ 2 -600} 2)
Based on this separation formula, the in-plane phase difference (that is, Rpva) of PVA at a wavelength of λ = 1000 nm can be calculated. The method for evaluating the in-plane phase difference of the PVA is also described in Japanese Patent No. 5923760, and can be referred to as necessary.
Further, the birefringence (Δn) of PVA can be calculated by dividing this phase difference by the thickness.

Examples of commercially available devices for measuring the in-plane phase difference of PVA at a wavelength of 1000 nm include KOBRA-WR / IR series and KOBRA-31X / IR series manufactured by Oji Measurement Co., Ltd.

The orientation function (f) of the polyvinyl alcohol-based resin constituting the polarizing element used in the present invention preferably satisfies the following formula (3a), and more preferably the following formula (3b). If the orientation function is too small, acceptable single transmittance and / or degree of polarization 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 determined by total internal reflection spectroscopy (ATR) measurement using, for example, a Fourier transform infrared spectrophotometer (FT-IR) and polarized light as measurement light. Specifically, germanium is used as the crystallite to which the polarizing element is brought into close contact, the incident angle of the measurement light is 45 °, and the polarized infrared light (measurement light) to be incident is the surface to which the sample of the germanium crystal is brought into close contact. the intensity of the polarized light (s-polarized light), and with respect to the polarization direction of the measuring light, measurements were performed in a state of parallel and vertically disposed stretching direction of the polarizer, the resulting absorbance spectra 2941Cm ^-1 which vibrates parallel to Is calculated according to the following formula. Here, the intensity I, as a reference peak to 3330cm ^{^-1,} a value of 2941cm ^-1 / 3330cm -1. When f = 1, it is completely oriented, and when f = 0, it is random. Further, ^{the peak of 2941 cm -1} is considered to be absorption caused by the vibration of the main chain (-CH _{2-) of PVA in the polarizing element.}
f = (3 <cos ² θ> -1) / 2
= (1-D) / [c (2D + 1)]
= -2 x (1-D) / (2D + 1)
However,
^{In the case of vibration of 2941 cm -1} with c = (3cos ² β-1) / 2, β = 90 °.
θ: Angle of molecular chain with respect to stretching direction β: Angle of transition dipole moment with respect to molecular chain axis D = (I _⊥ ) / (I _// ) (In this case, D becomes larger as the PVA molecule is oriented)
I _⊥ : Absorption intensity when the polarization direction of the measurement light and the extension direction of the modulator are perpendicular I _// : Absorption intensity when the polarization direction of the measurement light and the extension direction of the modulator are parallel

The thickness of the polarizing element is preferably 10 μm or less, more preferably 8 μm or less. The lower limit of the thickness of the transducer can be, for example, 1 μm. The thickness of the polarizing element may be 2 μm to 10 μm in one embodiment and 2 μm to 8 μm in another embodiment. By making the thickness of the stator very thin in this way, the heat shrinkage can be made very small. It is presumed that such a configuration can also contribute to suppressing breakage in the absorption axis direction.

The polarizing element preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance of the polarizing element is preferably 40.0% or more, more preferably 41.0% or more. The upper limit of the simple substance transmittance can be, for example, 49.0%. The simple substance transmittance of the polarizing element is 40.0% to 45.0% in one embodiment. The degree of polarization of the polarizing element is preferably 99.0% or more, more preferably 99.4% or more. The upper limit of the degree of polarization can be, for example, 99.999%. The degree of polarization of the polarizing element is 99.0% to 99.99% in one embodiment. Despite the fact that the polarizing element according to the embodiment of the present invention has a lower degree of orientation of the PVA-based resin constituting the polarizing element than the conventional one and has the above-mentioned in-plane phase difference, birefringence and / or orientation function. One of the features is that such a practically acceptable single-unit transmittance and degree of polarization can be realized. It is presumed that this is due to the manufacturing method described later. The single transmittance is typically a Y value measured with an ultraviolet-visible spectrophotometer and corrected for luminosity factor. The degree of polarization is typically determined by the following equation based on the parallel transmittance Tp and the orthogonal transmittance Tc measured with an ultraviolet-visible spectrophotometer and corrected for luminosity factor.
Polarization degree (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100

The puncture strength of the polarizing element is, for example, 30 gf / μm or more, preferably 35 gf / μm or more, more preferably 40 gf / μm or more, still more preferably 45 gf / μm or more, and particularly preferably 50 gf / μm or more. That is all. The piercing strength can be, for example, 80 gf / μm or less. By setting the piercing strength of the polarizing element within such a range, it is possible to remarkably suppress the polarizing element from tearing along the absorption axis direction. As a result, a polarizing element having very excellent flexibility (as a result, a polarizing plate) can be obtained. The piercing strength indicates the cracking resistance of the polarizing element when the polarizing element is pierced with a predetermined strength. The piercing strength can be expressed as, for example, the strength (breaking strength) at which the polarizing element is cracked when a predetermined needle is attached to a compression tester and the needle is pierced into the polarizing element at a predetermined speed. As is clear from the unit, the piercing strength means the piercing strength per unit thickness (1 μm) of the polarizing element.

As described above, the polarizing element is composed of a PVA-based resin film containing a dichroic substance. Preferably, the PVA-based resin constituting the PVA-based resin film (substantially, a polarizing element) contains an acetoacetyl-modified PVA-based resin. With such a configuration, a polarizing element having a desired piercing strength can be obtained. The blending amount of the acetoacetyl-modified PVA-based resin is preferably 5% by weight to 20% by weight, more preferably 8% by weight to 12% by weight, when the total amount of the PVA-based resin is 100% by weight. .. When the blending amount is in such a range, the piercing strength can be in a more suitable range.

The decoder can typically be made using a laminate of two or more layers. Specific examples of the polarizing element obtained by using the laminated body include a polarizing element obtained by using a laminated body of a resin base material and a PVA-based resin layer coated and formed on the resin base material. The polarizing element obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying it. It is produced by forming a PVA-based resin layer on the PVA-based resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; and stretching and dyeing the laminate to make the PVA-based resin layer a stator. obtain. In the present 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 base material. Stretching typically involves immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching preferably further comprises stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in an aqueous boric acid solution. In the embodiment of the present invention, the total magnification of stretching is preferably 3.0 to 4.5 times, which is significantly smaller than usual. Even at the total magnification of such stretching, a stator having acceptable optical properties can be obtained by combining the addition of a halide and the drying shrinkage treatment. Further, 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. With such a configuration, it is possible to obtain a polarizing element having acceptable optical characteristics even if the total magnification of stretching is small. In addition, the laminate is preferably subjected to a dry shrinkage treatment of shrinking by 2% or more in the width direction by heating while transporting in the longitudinal direction. In one embodiment, the method for producing a polarizing element includes subjecting a laminate to an aerial auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when the PVA-based resin is coated on the thermoplastic resin, the crystallinity of the PVA-based resin can be enhanced, and high optical characteristics can be achieved. At the same time, by increasing the orientation of the PVA-based resin in advance, it is possible to prevent problems such as deterioration of the orientation of the PVA-based resin and dissolution when immersed in water in the subsequent dyeing step or stretching step. , It becomes possible to achieve high optical characteristics. Further, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecule and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This makes it possible to improve the optical characteristics of the polarizing element obtained through a treatment step of immersing the laminate in a liquid, such as a dyeing treatment and a stretching treatment in water. Further, the optical characteristics can be improved by shrinking the laminated body in the width direction by the drying shrinkage treatment. The obtained resin base material / polarizing element laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizing element), and the resin base material is peeled off from the resin base material / polarizing element laminate. Then, an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface and used. The details of the method for manufacturing the polarizing film will be described later.

B-2. Method for Producing a Polarizer In the method for producing a polarizing element according to one embodiment of the present invention, polyvinyl alcohol containing a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin base material is used. By forming a based resin layer (PVA-based resin layer) to form a laminated body, and by heating the laminated body while transporting it in the longitudinal direction, which is an aerial auxiliary stretching treatment, a dyeing treatment, and an underwater stretching treatment. A drying shrinkage treatment of shrinking by 1% to 10% in the width direction and a drying shrinkage treatment are performed in this order. The content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably performed using a heating roll, and the temperature of the heating roll is preferably 60 ° C. to 120 ° C. The shrinkage rate in the width direction of the laminated body by the drying shrinkage treatment is preferably 1% to 10%. According to such a manufacturing method, the polarizing element described in the above section B-1 can be obtained. In particular, by preparing a laminate containing a PVA-based resin layer containing a halide, stretching the laminate to multi-step stretching including aerial auxiliary stretching and underwater stretching, and heating the stretched laminate with a heating roll. , It is possible to obtain a stator having excellent optical properties (typically, single transmittance and degree of polarization).

B-2-1. Preparation of Laminate As a method for preparing a laminate of a thermoplastic resin base material and a PVA-based resin layer, any appropriate method can be adopted. Preferably, a coating liquid containing a halide and a PVA-based resin is applied to the surface of the thermoplastic resin base material and dried to form a PVA-based resin layer on the thermoplastic resin base material. As described above, the content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

Any appropriate method can be adopted as the application 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 knife coating method (comma coating method, etc.) and the like can be mentioned. The coating / drying temperature of the coating liquid is preferably 50 ° C. or higher.

The thickness of the PVA-based resin layer is preferably 2 μm to 30 μm, more preferably 2 μm to 20 μm. By making the thickness of the PVA-based resin layer before stretching so thin and reducing the total stretching ratio as described later, the permissible single transmittance and the allowable single transmittance even though the orientation function is very small. A polarizing element having a degree of polarization can be obtained.

Before forming the PVA-based resin layer, the thermoplastic resin base material may be surface-treated (for example, corona treatment or the like), or the easy-adhesion layer may be formed on the thermoplastic resin base material. By performing such a treatment, the adhesion between the thermoplastic resin base material and the PVA-based resin layer can be improved.

B-2-1-1. Thermoplastic Resin Substrate As the thermoplastic resin substrate, any suitable thermoplastic resin film can be adopted. Details of the thermoplastic resin base material are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The entire description of the publication is incorporated herein by reference.

B-2-1-2. Coating liquid The coating liquid contains a halide and a PVA-based resin as described above. The coating liquid is typically a solution in which the halide and the PVA-based resin are dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Among these, water is preferable. The PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, it is possible to form a uniform coating film in close contact with the thermoplastic resin base material. 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 may be added to the coating liquid. Examples of the additive include a plasticizer, a surfactant and the like. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer.

Any suitable resin can be adopted as the PVA-based resin. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymers can be mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. .. The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizing element having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur. As described above, the PVA-based resin preferably contains an acetoacetyl-modified PVA-based resin.

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 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined according to JIS K 6726-1994.

As the above-mentioned halide, any suitable halide can be adopted. For example, iodide and sodium chloride can be mentioned. Iodides include, for example, potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferable.

The amount 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, and more preferably 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the PVA-based resin. It is a department. If the amount of the halide exceeds 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, the halide may bleed out and the finally obtained polarizing element may become cloudy.

Generally, the stretching of the PVA-based resin layer increases the orientation of the polyvinyl alcohol molecules in the PVA-based resin. However, when the stretched PVA-based resin layer is immersed in a liquid containing water, the polyvinyl alcohol molecules become more oriented. The orientation may be disturbed and the orientation may decrease. In particular, when the laminate of the thermoplastic resin and the PVA-based resin layer is stretched in boric acid water, the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin. The tendency of the degree of orientation to decrease is remarkable. For example, while stretching a PVA film alone in boric acid water is generally performed at 60 ° C., stretching of a laminate of A-PET (thermoplastic resin base material) and a PVA-based resin layer is performed. It is carried out at a high temperature of about 70 ° C., and in this case, the orientation of PVA at the initial stage of stretching may decrease before it is increased by stretching in water. On the other hand, by preparing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin base material, and stretching the laminate in air at a high temperature (auxiliary stretching) before stretching it in boric acid water. , Crystallization of the PVA-based resin in the PVA-based resin layer of the laminated body after the auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecule and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This makes it possible to improve the optical characteristics of the polarizing element obtained through a treatment step of immersing the laminate in a liquid, such as a dyeing treatment and a stretching treatment in water.

B-2-2. Aerial auxiliary stretching treatment In particular, in order to obtain high optical properties, a two-stage stretching method that combines dry stretching (auxiliary stretching) and boric acid water stretching is selected. By introducing auxiliary stretching as in the case of two-step stretching, it is possible to stretch while suppressing the crystallization of the thermoplastic resin base material. Furthermore, when the PVA-based resin is applied on the thermoplastic resin base material, it is compared with the case where the PVA-based resin is applied on a normal metal drum in order to suppress the influence of the glass transition temperature of the thermoplastic resin base material. Therefore, it is necessary to lower the coating temperature, and as a result, the crystallization of the PVA-based resin becomes relatively low, which may cause a problem that sufficient optical characteristics cannot be obtained. On the other hand, by introducing auxiliary stretching, it is possible to improve the crystallinity of the PVA-based resin even when the PVA-based resin is applied on the thermoplastic resin, and it is possible to achieve high optical characteristics. Become. At the same time, by increasing the orientation of the PVA-based resin in advance, it is possible to prevent problems such as deterioration and dissolution of the orientation of the PVA-based resin when immersed in water in a subsequent dyeing step or stretching step. , It becomes possible to achieve high optical characteristics.

The stretching method of the aerial auxiliary stretching may be fixed-end stretching (for example, a method of stretching using a tenter stretching machine) or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). .. Free-end stretching can be positively adopted in order to obtain high optical properties. In one embodiment, the aerial stretching treatment includes a heating roll stretching step of stretching the laminate by the difference in peripheral speed between the heating rolls while transporting the laminated body in the longitudinal direction thereof. The aerial stretching treatment typically includes a zone stretching step and a heating roll stretching step. The order of the zone stretching step and the heating roll stretching step is not limited, and the zone stretching step may be performed first, or the heating roll stretching step may be performed first. The zone stretching step may be omitted. In one embodiment, the zone stretching step and the heating roll stretching step are performed in this order. Further, in another embodiment, in the tenter stretching machine, the film is stretched by grasping the end portion of the film and widening the distance between the tenters in the flow direction (the widening of the distance between the tenters is the stretching ratio). At this time, the distance of the tenter in the width direction (perpendicular to the flow direction) is set to approach arbitrarily. Preferably, it can be set to be closer to the free end stretch with respect to the stretch ratio in the flow direction. In the case of free end stretching, it is calculated by shrinkage rate in the width direction = (1 / stretching magnification) ^1/2.

The aerial auxiliary stretching may be performed in one step or in multiple steps. When performed in multiple stages, the draw ratio is the product of the draw ratios in each stage. The stretching direction in the aerial auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching.

The draw ratio in the aerial auxiliary stretching is preferably 1.0 to 4.0 times, more preferably 1.5 to 3.5 times, and further preferably 2.0 to 3.0 times. be. When the stretching ratio of the aerial auxiliary stretching is in such a range, the total stretching ratio can be set in a desired range when combined with the underwater stretching, and a desired orientation function can be realized. As a result, it is possible to obtain a polarizing element in which breakage along the absorption axis direction is suppressed. Further, as described above, it is preferable that the stretching ratio of the aerial auxiliary stretching is larger than the stretching ratio of the boric acid water stretching. With such a configuration, it is possible to obtain a polarizing element having acceptable optical characteristics even if the total magnification of stretching is small. More specifically, the ratio of the stretching ratio of the aerial auxiliary stretching to the stretching ratio of the underwater stretching (underwater stretching / aerial auxiliary stretching) is preferably 0.4 to 0.9, more preferably 0.5 to 0. It is 8.8.

The stretching temperature of the aerial auxiliary stretching can be set to an arbitrary appropriate value depending on the forming material of the thermoplastic resin base material, the stretching method, and the like. The stretching temperature is preferably the glass transition temperature (Tg) or higher of the thermoplastic resin base material, more preferably the glass transition temperature (Tg) of the thermoplastic resin base material (Tg) + 10 ° C. or higher, and particularly preferably Tg + 15 ° C. or higher. On the other hand, the upper limit of the stretching temperature is preferably 170 ° C. By stretching at such a temperature, it is possible to suppress the rapid progress of crystallization of the PVA-based resin and suppress defects due to the crystallization (for example, hindering the orientation of the PVA-based resin layer due to stretching). can.

B-2-3. Insolubilization treatment, dyeing treatment and cross-linking treatment If necessary, an insolubilization treatment is performed after the aerial auxiliary stretching treatment and before the underwater stretching treatment or the dyeing treatment. The insolubilization treatment is typically performed by immersing a PVA-based resin layer in a boric acid aqueous solution. The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). If necessary, a cross-linking treatment is performed after the dyeing treatment and before the underwater stretching treatment. The cross-linking treatment is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution. Details of the insolubilization treatment, the dyeing treatment and the crosslinking treatment are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 (above).

B-2-4. Underwater stretching treatment The underwater stretching treatment is performed by immersing the laminate in a stretching bath. According to the underwater stretching treatment, the thermoplastic resin base material or the PVA-based resin layer can be stretched at a temperature lower than the glass transition temperature (typically, about 80 ° C.), and the PVA-based resin layer is crystallized. Can be stretched while suppressing. As a result, it is possible to manufacture a polarizing element having excellent optical characteristics.

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

The underwater stretching is preferably carried out by immersing the laminate in a boric acid aqueous solution (boric acid water stretching). By using the boric acid aqueous solution as the stretching bath, it is possible to impart rigidity to withstand the tension applied during stretching and water resistance that does not dissolve in water to the PVA-based resin layer. Specifically, boric acid can generate a tetrahydroxyboric acid anion in an aqueous solution and crosslink with a PVA-based resin by hydrogen bonding. As a result, the PVA-based resin layer can be imparted with rigidity and water resistance, can be stretched satisfactorily, and a polarizing element having excellent optical characteristics can be produced.

The boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight, more preferably 2.5 parts by weight to 6 parts by weight, and particularly preferably 3 parts by weight to 5 parts by weight with respect to 100 parts by weight of water. Is. 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 polarizing element having higher characteristics can be produced. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde or the like in a solvent can also be used.

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

The stretching temperature (liquid temperature of the stretching bath) is preferably 40 ° C to 85 ° C, more preferably 60 ° C to 75 ° C. At such a temperature, the PVA-based resin layer can be stretched at a high magnification while suppressing dissolution. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin base material is preferably 60 ° C. or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40 ° C., there is a possibility that the thermoplastic resin base material cannot be stretched satisfactorily even if the plasticization of the thermoplastic resin base material by water is taken into consideration. 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 possibility that excellent optical characteristics cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

The stretching ratio by stretching in water is preferably 1.0 to 3.0 times, more preferably 1.0 to 2.0 times, and even more preferably 1.0 to 1.5 times. .. When the stretching ratio in underwater stretching is in such a range, the total stretching ratio can be set in a desired range, and a desired orientation function can be realized. As a result, it is possible to obtain a polarizing element in which breakage along the absorption axis direction is suppressed. As described above, the total stretching ratio (the total stretching ratio when the aerial auxiliary stretching and the underwater stretching are combined) is, for example, 3.0 to 4.5 times the original length of the laminated body. It is preferably 3.0 times to 4.0 times, and more preferably 3.0 times to 3.5 times. By appropriately combining the addition of a halide to the coating liquid, the adjustment of the stretching ratios of the aerial auxiliary stretching and the underwater stretching, and the drying shrinkage treatment, even the total magnification of such stretching has acceptable optical properties. A modulator can be obtained.

B-2-5. Dry shrinkage treatment The dry shrinkage treatment may be performed by heating the entire zone by heating the zone, or by heating the transport roll (using a so-called heating roll) (heating roll drying method). Preferably both are used. By drying using a heating roll, it is possible to efficiently suppress the heating curl of the laminated body and produce a polarizing element having an excellent appearance. Specifically, by drying the laminated body along the heating roll, the crystallization of the thermoplastic resin base material can be efficiently promoted and the crystallinity can be increased, which is relatively low. Even at the drying temperature, the crystallinity of the thermoplastic resin substrate can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material is increased, and the PVA-based resin layer is in a state of being able to withstand shrinkage due to drying, and curling is suppressed. Further, by using the heating roll, the laminated body can be dried while being maintained in a flat state, so that not only curling but also wrinkles can be suppressed. At this time, the laminated body can be improved in optical characteristics by shrinking in the width direction by a drying shrinkage treatment. This is because the orientation of PVA and the PVA / iodine complex can be effectively enhanced. The shrinkage ratio in the width direction of the laminate by the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%.

FIG. 4 is a schematic view showing an example of the drying shrinkage treatment. In the drying shrinkage treatment, the laminate 200 is dried while being transported by the transport rolls R1 to R6 heated to a predetermined temperature and the guide rolls G1 to G4. In the illustrated example, the transport rolls 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 base material. For example, one surface of the laminate 200 (for example, thermoplasticity) is arranged. The transport rolls R1 to R6 may be arranged so as to continuously heat only the resin substrate surface).

Drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like. The temperature of the heating roll 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 satisfactorily increased, curling can be satisfactorily suppressed, and an optical laminate having extremely excellent durability can be produced. The temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six transport rolls are provided, but there is no particular limitation as long as there are a plurality of transport rolls. The number of transport rolls is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and further preferably 1 to 10 seconds.

The heating roll may be provided in a heating furnace (for example, an oven) or in a normal production line (in a room temperature environment). Preferably, it is provided in a heating furnace provided with a blowing means. By using both the drying with the heating roll and the hot air drying together, it is possible to suppress a steep temperature change between the heating rolls, and it is possible to easily control the shrinkage in the width direction. The temperature of hot air drying is preferably 30 ° C to 100 ° C. The hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air is preferably about 10 m / s to 30 m / s. The wind speed is the wind speed in the heating furnace and can be measured by a mini-vane type digital anemometer.

B-2-6. Other Treatments Preferably, a washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment. The cleaning treatment is typically performed by immersing a PVA-based resin layer in an aqueous potassium iodide solution.

B-3. Protective layer In the embodiment of the present invention, the thickness of the protective layer is 10 μm or less. When the thickness of the protective layer is 10 μm or less, it can contribute to the thinning of the polarizing plate. The polarizing plate with a retardation layer can prevent cracks from occurring during heating even if the thickness of the protective layer is 10 μm or less. The thickness of the protective layer is preferably 7 μm or less, more preferably 5 μm or less, and further preferably 3 μm or less. The thickness of the protective layer is, for example, 1 μm or more.

The protective layer can be formed of any suitable material. Cellulosic resins such as triacetylcellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth) acrylics Transparent resins such as (meth) acrylics, urethanes, (meth) acrylic urethanes, epoxys, and silicones; thermosetting resins or ultraviolet curable resins; glassy resins such as siloxane polymers Examples include polymers.

The protective layer may be a film, a solidified coating film, or a cured product (for example, a photocationic cured product). In one embodiment, the protective layer is a solidified epoxy of a coating film of an organic solvent solution of a thermoplastic (meth) acrylic resin (hereinafter, the (meth) acrylic resin may be simply referred to as an acrylic resin). It is composed of at least one selected from the group consisting of a photocationically cured product of a resin and a solidified coating film of an organic solvent solution of an epoxy resin. Hereinafter, a specific description will be given.

B-3-1. Solidification of the coating film of the organic solvent solution of the thermoplastic acrylic resin In one embodiment, the protective layer is composed of the solidification of the coating film of the organic solvent solution of the thermoplastic acrylic resin.

B-3-1-1. Acrylic resin The acrylic resin has a glass transition temperature (Tg) of preferably 100 ° C. or higher. As a result, the Tg of the protective layer becomes 100 ° C. or higher. When the Tg of the acrylic resin is 100 ° C. or higher, the polarizing plate including the protective layer obtained from such a resin can be excellent in durability. The Tg of the acrylic resin is preferably 110 ° C. or higher, more preferably 115 ° C. or higher, still more preferably 120 ° C. or higher, and particularly preferably 125 ° C. or higher. On the other hand, the Tg of the acrylic resin is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower. When the Tg of the acrylic resin is in such a range, the moldability can be excellent.

As the acrylic resin, any suitable acrylic resin can be adopted as long as it has Tg as described above. The acrylic resin typically contains an alkyl (meth) acrylate as a main component as a monomer unit (repeating unit). As used herein, the term "(meth) acrylic" means acrylic and / or methacryl. Examples of the alkyl (meth) acrylate constituting the main skeleton of the acrylic resin include linear or branched alkyl groups having 1 to 18 carbon atoms. These can be used alone or in combination. Further, any suitable copolymerization monomer may be introduced into the acrylic resin by copolymerization. The repeating unit derived from alkyl (meth) acrylate is typically represented by the following general formula (1):

In the general formula (1), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ is a hydrogen atom or an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms which may be substituted. show. Examples of the substituent include halogens and hydroxyl groups. Specific examples of alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and t-butyl (meth) acrylate. Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, (meth) acrylic Dicyclopentanyl acid, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2, (meth) acrylate 2, 3,4,5,6-pentahydroxyhexyl, (meth) acrylate 2,3,4,5-tetrahydroxypentyl, 2- (hydroxymethyl) methyl acrylate, 2- (hydroxymethyl) ethyl acrylate, 2 -(Hydroxyethyl) Methyl acrylate can be mentioned. In the general formula (1), R ⁵ is preferably a hydrogen atom or a methyl group. Therefore, a particularly preferred alkyl (meth) acrylate is methyl acrylate or methyl methacrylate.

Acrylic resins may also include only a single alkyl (meth) acrylate units, even if R ⁴ and R ⁵ include a plurality of different alkyl (meth) acrylate unit in the above general formula (1) good.

The content ratio of the alkyl (meth) acrylate unit in the acrylic resin is preferably 50 mol% to 98 mol%, more preferably 55 mol% to 98 mol%, still more preferably 60 mol% to 98 mol%, and particularly preferably. It is 65 mol% to 98 mol%, most preferably 70 mol% to 97 mol%. If the content ratio is less than 50 mol%, the effects expressed from the alkyl (meth) acrylate unit (for example, high heat resistance and high transparency) may not be sufficiently exhibited. If the content ratio is more than 98 mol%, the resin is brittle and easily cracked, high mechanical strength cannot be sufficiently exhibited, and productivity may be inferior.

The acrylic resin preferably has a repeating unit containing a ring structure. Examples of the repeating unit including a ring structure include a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide (N-substituted maleimide) unit. Only one type of the repeating unit including the ring structure may be contained in the repeating unit of the acrylic resin, or two or more types may be contained.

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

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

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

In the general formula (3), R ¹¹ and R ¹² each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ¹³ is an alkyl group having 1 to 18 carbon atoms and 3 to 12 carbon atoms. The cycloalkyl group of the above, or an aryl group having 6 to 10 carbon atoms is shown. In the general formula (3), preferably R ¹¹ and R ¹² are independently hydrogen or methyl groups, and R ¹³ is a hydrogen, methyl group, butyl group or cyclohexyl group, respectively. More preferably, R ¹¹ is a methyl group, R ¹² is a hydrogen, and R ¹³ is a methyl group. The acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units having different ^{R 11} , R ¹² and R ^{13 in the above general formula (3).} .. Examples of the acrylic resin having a glutarimide unit include JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328334, JP-A-2006-337491, and JP-A-2006-337492. It is described in Japanese Patent Application Laid-Open No. 2006-337493 and Japanese Patent Application Laid-Open No. 2006-337569, and the description of this publication is incorporated herein by reference. Note that the glutaric anhydride units, nitrogen atom substituted by R ¹³ in the general formula (3), except that the oxygen atom, the above description is applied about the glutarimide units.

The structure of the maleic anhydride unit and the maleimide (N-substituted maleimide) unit is specified from the name, so specific description thereof will be omitted.

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

The acrylic resin may contain a repeating unit other than an alkyl (meth) acrylate unit and a repeating unit including a ring structure. Examples of such a repeating unit include a repeating unit derived from a vinyl-based monomer copolymerizable with the monomer constituting the above unit (another vinyl-based monomer unit). Examples of other vinyl-based monomers include acrylic acid, methacrylic acid, crotonic acid, 2- (hydroxymethyl) acrylic acid, 2- (hydroxyethyl) acrylic acid, acrylonitrile, methacrylonitrile, etacrylonitrile, and allyl. Glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, methacryl Cyclohexylaminoethyl acid, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methylallylamine, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acroyl-oxazoline, N-phenylmaleimide, Examples thereof include phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, 2-styryl-oxazoline and the like. These may be used alone or in combination. The type, number, combination, content ratio, etc. of other vinyl-based monomer units can be appropriately set according to the purpose.

The weight average molecular weight of the acrylic resin is preferably 1,000,000 to 2000000, more preferably 5000 to 1,000,000, still more preferably 10,000 to 500,000, particularly preferably 50,000 to 500,000, and most preferably 60,000 to 150,000. The weight average molecular weight can be determined by polystyrene conversion using, for example, a gel permeation chromatograph (GPC system, manufactured by Tosoh). Tetrahydrofuran can be used as the solvent.

The acrylic resin can be polymerized by any suitable polymerization method by appropriately combining the above-mentioned monomer units.

In the embodiment of the present invention, an acrylic resin and another resin may be used in combination. That is, the monomer component constituting the acrylic resin and the monomer component constituting the other resin may be copolymerized, and the copolymer may be used for molding the protective layer described later; the acrylic resin and the other resin. The blend of may be used for forming the protective layer. Examples of other resins include thermoplastic resins such as styrene resin, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, and polyetherimide. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose and the desired characteristics of the obtained film. For example, a styrene resin (preferably an acrylonitrile-styrene copolymer) can be used in combination as a retardation control agent.

When the acrylic resin is used in combination with another resin, the content of the acrylic resin in the blend of the acrylic resin and the other resin is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight. By weight%, more preferably 70% by weight to 100% by weight, and particularly preferably 80% by weight to 100% by weight. If the content is less than 50% by weight, the high heat resistance and high transparency inherent in the acrylic resin may not be sufficiently reflected.

B-3-2. Photocationic cured product of epoxy resin In one embodiment, the protective layer is composed of a photocationic cured product of epoxy resin. By using such a protective layer, it is possible to provide a polarizing plate having both excellent durability and excellent flexibility, and a polarizing plate with a retardation layer. As described above, since the protective layer is a photocationic cured product, the composition for forming the protective layer contains a photocationic polymerization initiator. The photocationic polymerization initiator is a photosensitizer having a function of a photoacid generator, and a typical example thereof is an ionic onium salt composed of a cation portion and an anion portion. In this onium salt, the cation part absorbs light and the anion part becomes a source of acid. Ring-opening polymerization of the epoxy group proceeds by the acid generated from this photocationic polymerization initiator. The protective layer, which is the obtained cured photocationic product, has a high glass transition temperature, and the amount of iodine adsorbed can be reduced. Therefore, it is possible to provide a polarizing plate capable of achieving both excellent durability and excellent flexibility.

B-3-2-1. Epoxy resin As the epoxy resin, any suitable epoxy resin can be used. In the embodiment of the present invention, an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton can be preferably used. Examples of the aromatic skeleton include a benzene ring, a naphthalene ring, a fluorene ring and the like. Only one type of epoxy resin may be used, or two or more types may be used in combination. An epoxy resin having a biphenyl skeleton is preferably used as the aromatic skeleton. By using an epoxy resin having a biphenyl skeleton, a polarizing plate having both better durability and better flexibility can be provided. Hereinafter, as a representative example, an epoxy resin having a biphenyl skeleton will be described in detail.

In one embodiment, the epoxy resin having a biphenyl skeleton is an epoxy resin containing the following structure. Only one type of epoxy resin having a biphenyl skeleton may be used, or two or more types may be used in combination.

(In the formula, R ¹⁴ to R ²¹ each independently represent a hydrogen atom, a linear or branched substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms, or a halogen element).

R ¹⁴ to R ²¹ independently represent a hydrogen atom, a linear or branched substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms, or a halogen element. Examples of the linear or branched substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group and a sec-butyl group. tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, cyclopentyl group, n-hexyl group, isohexyl group, cyclohexyl group, n-heptyl group, cycloheptyl group, methylcyclohexyl group, n- Octyl group, cyclooctyl group, n-nonyl group, 3,3,5-trimethylcyclohexyl group, n-decyl group, cyclodecyl group, n-undecyl group, n-dodecyl group, cyclododecyl group, phenyl group, benzyl group, Examples thereof include a methylbenzyl group, a dimethylbenzyl group, a trimethylbenzyl group, a naphthylmethyl group, a phenethyl group, a 2-phenylisopropyl group and the like. The linear or branched substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms preferably has 1 to 1 to 12 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group and an n-butyl group. The alkyl group of 4 is mentioned. Preferred halogen elements include fluorine and bromine.

In one embodiment, the epoxy resin having a biphenyl skeleton is an epoxy resin represented by the following formula.

(In the equation, R ¹⁴ to R ²¹ are as described above, and n represents an integer of 0 to 6).

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

In one embodiment, the epoxy resin having a biphenyl skeleton may contain a chemical structure other than the biphenyl skeleton. Examples of the chemical structure other than the biphenyl skeleton include a bisphenol skeleton, an alicyclic structure, an aromatic ring structure and the like. In this embodiment, the proportion (molar ratio) of the chemical structure other than the biphenyl skeleton is preferably smaller than that of the biphenyl skeleton.

A commercially available product may be used as the epoxy resin having a biphenyl skeleton. Examples of commercially available products include Mitsubishi Chemical Corporation, trade names: jER YX4000, jER YX4000H, jER YL6121, jER YL664, jER YL6677, jER YL6810, jER YL7399 and the like.

The epoxy resin having a biphenyl skeleton preferably has a glass transition temperature (Tg) of 90 ° C. or higher. As a result, the Tg of the protective layer becomes 90 ° C. or higher. When the Tg of the epoxy resin having a biphenyl skeleton is 90 ° C. or higher, the obtained polarizing plate including the protective layer tends to have excellent durability. The Tg of the epoxy resin having a biphenyl skeleton is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, still more preferably 120 ° C. or higher, and particularly preferably 125 ° C. or higher. On the other hand, the Tg of the epoxy resin having a biphenyl skeleton is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower. When the Tg of the epoxy resin having a biphenyl skeleton is in such a range, the moldability can be excellent.

The epoxy equivalent of the epoxy resin having a biphenyl skeleton is preferably 100 g / equivalent or more, more preferably 150 g / equivalent or more, still more preferably 200 g / equivalent or more. The epoxy equivalent of the epoxy resin having a biphenyl skeleton is preferably 3000 g / equivalent or less, more preferably 2500 g / equivalent or less, still more preferably 2000 g / equivalent or less. When the epoxy equivalent of the epoxy resin having a biphenyl skeleton is in the above range, a more stable protective layer (a protective layer having less residual monomer and sufficiently cured) can be obtained. In the present specification, "epoxy equivalent" means "mass of epoxy resin containing 1 equivalent of epoxy group" and can be measured according to JIS K7236.

In the embodiment of the present invention, an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton may be used in combination with another resin. That is, a blend of an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton and another resin may be used for molding the protective layer. Examples of other resins include thermoplastic resins such as styrene resins, polyethylenes, polypropylenes, polyamides, polyphenylene sulfides, polyether ether ketones, polyesters, polysulfones, polyphenylene oxides, polyacetals, polyimides, and polyetherimides, acrylic resins and Examples thereof include curable resins such as oxetane resins. Preferably, an acrylic resin and an oxetane resin are used. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose and the desired characteristics of the obtained film. For example, the styrene resin can be used in combination as a retardation control agent.

As the acrylic resin, any suitable acrylic resin can be used. For example, as the (meth) acrylic compound, for example, a (meth) acrylic compound having one (meth) acryloyl group in the molecule (hereinafter, also referred to as “monofunctional (meth) acrylic compound”), intramolecular. Examples thereof include (meth) acrylic compounds having two or more (meth) acryloyl groups (hereinafter, also referred to as “polyfunctional (meth) acrylic compounds”). These (meth) acrylic compounds may be used alone or in combination of two or more. These acrylic resins are described in, for example, Japanese Patent Application Laid-Open No. 2019-168500. The entire description of the publication is incorporated herein by reference.

As the oxetane resin, any suitable compound having one or more oxetanyl groups in the molecule is used. For example, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3-ethyl-3- (cyclohexyloxymethyl). Oxetane compound having one oxetane group in the molecule such as oxetane, 3-ethyl-3- (oxylanylmethoxy) oxetane, (meth) acrylic acid (3-ethyloxetane-3-yl) methyl; 3-ethyl- 3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 4,4'-bis [(3-ethyl) -3-Oxetane) methoxymethyl] An oxetane compound having two or more oxetane groups in a molecule such as biphenyl; and the like. Only one kind of these oxetane resins may be used, or two or more kinds thereof may be combined.

The oxetane resin is preferably 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (2-ethylhexyloxymethyl). Oxetane, 3-Ethyl-3- (oxylanylmethoxy) oxetane, (meth) acrylic acid (3-ethyloxetane-3-yl) methyl, 3-ethyl-3 {[(3-ethyloxetane-3-yl) Methyl] methyl} oxetane and the like are used. These oxetane resins are easily available and can be excellent in dilutability (low viscosity) and compatibility.

In one embodiment, an oxetane resin having a molecular weight of 500 or less and liquid at room temperature (25 ° C.) is preferably used from the viewpoint of compatibility and adhesiveness. In one embodiment, it preferably contains an oxetane compound containing two or more oxetanel groups in the molecule, one oxetaneyl group and one (meth) acryloyl group or one epoxy group in the molecule. Oxetane compounds are used, more preferably 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane, 3-ethyl-3- (oxylanylmethoxy) oxetane, (meth) acrylic. Acid (3-ethyloxetane-3-yl) methyl is used. By using these oxetane resins, the curability and durability of the protective layer can be improved.

As the oxetane resin, a commercially available product may be used. Specifically, Aron Oxetane OXT-101, Aron Oxetane OXT-121, Aron Oxetane OXT-212, and Aron Oxetane OXT-221 (all manufactured by Toagosei Co., Ltd.) can be used. Preferably, Aron Oxetane OXT-101 and Aron Oxetane OXT-221 can be used.

When an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton is used in combination with another resin, the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton is used. The content of the epoxy resin having at least one selected from the group consisting of the aromatic skeleton and the hydrogenated aromatic skeleton in the blend of the epoxy resin having at least one selected and the other resin is preferable. It is 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight, still more preferably 70% by weight to 100% by weight, and particularly preferably 80% by weight to 100% by weight. If the content is less than 50% by weight, the heat resistance of the protective layer and sufficient adhesion to the polarizing element may not be obtained.

When the epoxy resin having a biphenyl skeleton and the oxetane resin are used in combination, the content of the oxetane resin is preferably 1 part by weight to 50 parts by weight with respect to the total amount of 100 parts by weight of the epoxy resin having a biphenyl skeleton and the oxetane resin. , More preferably 5 parts by weight to 45 parts by weight, still more preferably 10 parts by weight to 40 parts by weight. Within the above range, the curability can be improved and the adhesion between the protective layer and the polarizing element can be improved.

B-3-2-2. Photocationic polymerization initiator The photocationic polymerization initiator is a photosensitive agent having a function of a photoacid generator, and a typical example thereof is an ionic onium salt composed of a cation portion and an anion portion. In this onium salt, the cation part absorbs light and the anion part becomes a source of acid. Ring-opening polymerization of the epoxy group proceeds by the acid generated from this photocationic polymerization initiator. As the photocationic polymerization initiator, any suitable compound capable of curing an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton by irradiation with light such as ultraviolet rays. Can be used. Only one type of photocationic polymerization initiator may be used, or two or more types may be used in combination.

Examples of the photocationic polymerization initiator include triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, p- (phenylthio) phenyldiphenylsulfonium hexafluoroantimonate, p- (phenylthio) phenyldiphenylsulfonium hexafluorophosphate, and the like. 4-Chlorphenyl diphenyl sulfonium hexafluorophosphate, 4-chlorphenyl diphenyl sulfonium hexafluoroantimonate, bis [4- (diphenyl sulfonio) phenyl] sulfide bishexafluorophosphate, bis [4- (diphenyl sulfonio) phenyl ] Sulfoxybishexafluoroantimonate, (2,4-cyclopentadiene-1-yl) [(1-methylethyl) benzene] -Fe-hexafluorophosphate, diphenyliodonium hexafluoroantimonate and the like. Preferably, a triphenylsulfonium salt-based hexafluoroantimonate type photocationic polymerization initiator and a diphenyliodonium salt-based hexafluoroantimonate type photocationic polymerization initiator are used.

A commercially available product may be used as the photocationic polymerization initiator. Commercially available products include triphenylsulfonium salt-based hexafluoroantimonate type SP-170 (manufactured by ADEKA), CPI-101A (manufactured by San-Apro), WPAG-1056 (manufactured by Wako Pure Chemical Industries, Ltd.), and diphenyliodonium salt-based. Hexafluoroantimonate type WPI-116 (manufactured by Wako Pure Chemical Industries, Ltd.) and the like can be mentioned.

The content of the photocationic polymerization initiator is preferably from 0.1 part by weight with respect to 100 parts by weight of the epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton. It is 3 parts by weight, more preferably 0.25 parts by weight to 2 parts by weight. When the content of the photocationic polymerization initiator is less than 0.1 parts by weight, it may not be sufficiently cured even when irradiated with light (ultraviolet rays).

B-3-3. Solidification of the coating film of the organic solvent solution of the epoxy resin In one embodiment, the protective layer is composed of the solidification of the coating film of the organic solvent solution of the epoxy resin.

B-3-3-1. Epoxy resin In this embodiment, the epoxy resin preferably has a glass transition temperature (Tg) of 90 ° C. or higher. As a result, the Tg of the protective layer becomes 90 ° C. or higher. When the Tg of the epoxy resin is 90 ° C. or higher, the polarizing plate containing the protective layer obtained from such a resin tends to have excellent durability. The Tg of the epoxy resin is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, still more preferably 120 ° C. or higher, and particularly preferably 125 ° C. or higher. On the other hand, the Tg of the epoxy resin is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower. When the Tg of the epoxy resin is in such a range, the moldability can be excellent.

As the epoxy resin, any suitable epoxy resin can be adopted as long as it has Tg as described above. The epoxy resin typically refers to a resin having an epoxy group in its molecular structure. As the epoxy resin, an epoxy resin having an aromatic ring in the molecular structure is preferably used. By using an epoxy resin having an aromatic ring, an epoxy resin having a higher Tg can be obtained. Examples of the aromatic ring in the epoxy resin having an aromatic ring in the molecular structure include a benzene ring, a naphthalene ring, a fluorene ring and the like. Only one type of epoxy resin may be used, or two or more types may be used in combination. When two or more kinds of epoxy resins are used, an epoxy resin containing an aromatic ring and an epoxy resin not containing an aromatic ring may be used in combination.

Specific examples of the epoxy resin having an aromatic ring in its molecular structure include bisphenol A diglycidyl ether type epoxy resin, bisphenol F diglycidyl ether type epoxy resin, bisphenol S diglycidyl ether type epoxy resin, and resorcin diglycidyl ether. Type epoxy resin, hydroquinone diglycidyl ether type epoxy resin, terephthalic acid diglycidyl ester type epoxy resin, bisphenoxyethanol full orange glycidyl ether type epoxy resin, bisphenol full orange glycidyl ether type epoxy resin, biscresol full orange glycidyl ether type epoxy resin, etc. Epoxy resin having two epoxy groups; novolak type epoxy resin, N, N, O-triglycidyl-P- or -m-aminophenol type epoxy resin, N, N, O-triglycidyl-4-amino-m -Or-5-Amino-o-cresol type epoxy resin, 1,1,1- (triglycidyloxyphenyl) methane type epoxy resin and other epoxy resins with three epoxy groups; glycidylamine type epoxy resin (eg, diamino) Examples thereof include epoxy resins having four epoxy groups such as diphenylmethane type, diaminodiphenylsulfone type, and metaxylene diamine type). Further, a glycidyl ester type epoxy resin such as a hexahydrophthalic anhydride type epoxy resin, a tetrahydrophthalic anhydride type epoxy resin, a dimer acid type epoxy resin, and a p-oxybenzoic acid type may be used.

The weight average molecular weight of the epoxy resin is preferably 1,000,000 to 2000000, more preferably 5000 to 1,000,000, still more preferably 10,000 to 500,000, particularly preferably 50,000 to 500,000, and most preferably 60,000 to 150,000. The weight average molecular weight can be determined by polystyrene conversion using, for example, a gel permeation chromatograph (GPC system, manufactured by Tosoh). Tetrahydrofuran can be used as the solvent.

The epoxy equivalent of the epoxy resin is preferably 1000 g / equivalent or more, more preferably 3000 g / equivalent or more, and further preferably 5000 g / equivalent or more. The epoxy equivalent of the epoxy resin is preferably 30,000 g / equivalent or less, more preferably 25,000 g / equivalent or less, and further preferably 20,000 g / equivalent or less. When the epoxy equivalent is in the above range, a more stable protective layer can be obtained. In the present specification, "epoxy equivalent" means "mass of epoxy resin containing 1 equivalent of epoxy group" and can be measured according to JIS K7236.

In the embodiment of the present invention, the epoxy resin and another resin may be used in combination. That is, a blend of the epoxy resin and another resin may be used for molding the protective layer. Examples of other resins include thermoplastic resins such as styrene resin, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, and polyetherimide. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose and the desired characteristics of the obtained film. For example, the styrene resin can be used in combination as a retardation control agent.

When the epoxy resin is used in combination with another resin, the content of the epoxy resin in the blend of the epoxy resin and the other resin is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight. It is more preferably 70% by weight to 100% by weight, and particularly preferably 80% by weight to 100% by weight. If the content is less than 50% by weight, the heat resistance of the protective layer and sufficient adhesion to the polarizing element may not be obtained.

B-3-4. Configuration and Characteristics of Protective Layer In one embodiment, the protective layer is a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin, a photocationic cured product of an epoxy resin, and an organic solvent solution of an epoxy resin, as described above. It is composed of at least one selected from the group consisting of solidified coating films. With such a protective layer, the thickness can be significantly reduced as compared with the extruded film. The thickness of the protective layer is 10 μm or less as described above. Further, although it is not theoretically clear, such a protective layer shrinks during film molding as compared with a cured product of other thermosetting resin or active energy ray curable resin (for example, ultraviolet curable resin). It has the advantage that deterioration of the film itself can be suppressed and adverse effects on the polarizing plate (polarizer) caused by the residual monomer or the like can be suppressed because the film itself is small and does not contain the residual monomer or the like. Further, it has an advantage that it is excellent in humidification durability because it has a smaller hygroscopicity and moisture permeability than a solidified water-based coating film such as an aqueous solution or an aqueous dispersion. As a result, it is possible to realize a polarizing plate having excellent durability, which can maintain optical characteristics even in a heated and humidified environment.

The Tg of the protective layer is as described for the acrylic resin and the epoxy resin, respectively.

The protective layer is preferably substantially optically isotropic. As used herein, "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. Say something. The in-plane retardation Re (550) is more preferably 0 nm to 5 nm, further preferably 0 nm to 3 nm, and particularly preferably 0 nm to 2 nm. The phase difference Rth (550) in the thickness direction is more preferably −5 nm to +5 nm, further preferably -3 nm to +3 nm, and particularly preferably −2 nm to +2 nm. When Re (550) and Rth (550) of the protective layer are in such a range, it is possible to prevent adverse effects on the display characteristics when the polarizing plate containing the protective layer is applied to an image display device. Re (550) is an in-plane phase difference of the film measured with light having a wavelength of 550 nm at 23 ° C. Re (550) is obtained by the formula: Re (550) = (nx-ny) × d. Rth (550) is a phase difference in the thickness direction of the film measured with light having a wavelength of 550 nm at 23 ° C. Rth (550) is obtained by the formula: Rth (550) = (nx-nz) × d. Here, nx is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow-phase axis direction), and ny is the in-plane direction orthogonal to the slow-phase axis (that is, the phase-advancing axis direction). It is the refractive index, nz is the refractive index in the thickness direction, and d is the thickness (nm) of the film.

The higher the light transmittance at 380 nm when the thickness of the protective layer is 3 μm, the more preferable. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, still more preferably 90% or more. If the light transmittance is in such a range, the desired transparency can be ensured. The light transmittance can be measured, for example, by a method according to ASTM-D-1003.

The lower the haze of the protective layer, the more preferable. Specifically, the haze is preferably 5% or less, more preferably 3% or less, still more preferably 1.5% or less, and particularly preferably 1% or less. When the haze is 5% or less, a good clear feeling can be given to the film. Further, even when the polarizing plate on the visual recognition side of the image display device is used, the displayed contents can be visually recognized satisfactorily.

The YI at a thickness of 3 μm of the protective layer is preferably 1.27 or less, more preferably 1.25 or less, still more preferably 1.23 or less, and particularly preferably 1.20 or less. If the YI exceeds 1.3, the optical transparency may be insufficient. The YI is obtained from, for example, the tristimulus values (X, Y, Z) of the color obtained by measurement using a high-speed integrating sphere type spectral transmittance measuring machine (trade name: DOT-3C: manufactured by Murakami Color Technology Laboratory). , Can be calculated by the following equation.
YI = [(1.28X-1.06Z) / Y] × 100

The b value (a measure of hue according to the Munsell color system of the hunter) at a thickness of 3 μm of the protective layer is preferably less than 1.5, more preferably 1.0 or less. When the b value is 1.5 or more, an undesired color may appear. For the b value, for example, a sample of the film constituting the protective layer is cut into 3 cm squares, and a high-speed integrating sphere type spectral transmittance measuring machine (trade name: DOT-3C: manufactured by Murakami Color Technology Laboratory) is used to determine the hue. Can be obtained by measuring and evaluating the hue according to the color system of the hunter.

The protective layer (for example, a solidified product of a coating film or a cured photocationic product) may contain any suitable additive depending on the purpose. Specific examples of the additives include ultraviolet absorbers; leveling agents; antioxidants such as hindered phenol-based, phosphorus-based and sulfur-based; stabilizers such as light-resistant stabilizers, weather-resistant stabilizers and heat-stabilizing agents; glass fibers, Reinforcing materials such as carbon fibers; Near infrared absorbers; Flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; Antistatic agents such as anionic, cationic and nonionic surfactants; Inorganic pigments , Organic pigments, colorants such as dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers and inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants; and the like. The additive may be added at the time of polymerizing the acrylic resin, or may be added to the solution at the time of film formation. The type, number, combination, amount of additive, etc. of the additive can be appropriately set according to the purpose.

An easy-adhesion layer may be formed on the polarizing element side of the protective layer. The easy-adhesion layer contains, for example, a water-based polyurethane and an oxazoline-based cross-linking agent. By forming such an easy-adhesion layer, the adhesion between the protective layer and the polarizing element can be enhanced. Further, a hard coat layer may be formed on the protective layer. When the hard coat layer is formed, the hard coat layer can be formed so that the total thickness of the protective layer (for example, the solidified coating film) and the thickness of the hard coat layer is 10 μm or less. The hardcourt layer can be formed when the protective layer is used as a protective layer on the visible side of the polarizing plate on the visible side. If both the easy-adhesion layer and the hardcourt layer are formed, typically they can be formed on different sides of the protective layer, respectively.

C. First Phase Difference Layer The first phase difference layer 20 is an orientation-solidified layer of a liquid crystal compound as described above. By using a liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be significantly increased as compared with the non-liquid crystal material, so that the thickness of the retardation layer for obtaining a desired in-plane retardation can be obtained. Can be made much smaller. As a result, it is possible to further reduce the thickness and weight of the polarizing plate with a retardation layer. As used herein, the term "aligned solidified layer" refers to a layer in which a liquid crystal compound is oriented in a predetermined direction within the layer and the oriented state is fixed. The "oriented solidified layer" is a concept including an oriented cured layer obtained by curing a liquid crystal monomer as described later. In the present embodiment, the rod-shaped liquid crystal compound is typically oriented in a state of being aligned in the slow axis direction of the first retardation layer (homogeneous orientation).

Examples of the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) in which the liquid crystal phase is a nematic phase. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal expression mechanism of the liquid crystal compound may be either lyotropic or thermotropic. 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 cross-linking (that is, curing) the liquid crystal monomer. After the liquid crystal monomers are oriented, for example, if the liquid crystal monomers are polymerized or crosslinked with each other, the oriented state can be fixed. Here, the polymer is formed by polymerization, and the three-dimensional network structure is formed by crosslinking, but these are non-liquid crystal. Therefore, the formed first retardation layer does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to a liquid crystal compound, for example. As a result, the first retardation layer becomes an extremely stable retardation layer that is not affected by temperature changes.

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

Any suitable liquid crystal monomer can be adopted as the liquid crystal monomer. For example, the polymerizable mesogen compounds described in Special Tables 2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US43884553), WO93 / 22397, EP0261712, DE19504224, DE4408171, and GB2280445 can be used. Specific examples of such a polymerizable mesogen compound include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Silicon-CC3767. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

Orientation of liquid crystal compound In the solidified layer, the surface of a predetermined base material is subjected to an orientation treatment, and a coating liquid containing the liquid crystal compound is applied to the surface to orient the liquid crystal compound in a direction corresponding to the orientation treatment. It can be formed by fixing the orientation state. In one embodiment, the substrate is any suitable resin film and the oriented solidified layer formed on the substrate can be transferred to the surface of the polarizing plate 10. In another embodiment, the substrate may be the second protective layer 13. In this case, the transfer step is omitted, and the stacking can be continuously performed by roll-to-roll from the formation of the oriented solidification layer (first retardation layer), so that the productivity is further improved.

As the alignment treatment, any appropriate orientation treatment can be adopted. Specific examples thereof include mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment. Specific examples of the mechanical orientation treatment include a rubbing treatment and a stretching treatment. Specific examples of the physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of the chemical alignment treatment include an orthorhombic vapor deposition method and a photoalignment treatment. As the treatment conditions for various orientation treatments, any appropriate conditions may be adopted depending on the purpose.

The orientation of the liquid crystal compound is performed by treating at a temperature indicating the liquid crystal phase according to the type of the liquid crystal compound. By performing such temperature treatment, the liquid crystal compound takes 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 alignment state is fixed by cooling the liquid crystal compound oriented as described above. 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 as described above to a polymerization treatment or a crosslinking treatment.

Specific examples of the liquid crystal compound and details of the method for forming the oriented solidified layer are described in Japanese Patent Application Laid-Open No. 2006-163343. The description of this publication is incorporated herein by reference.

Another example of the oriented solidified layer is a form in which the discotic liquid crystal compound is oriented in any of vertical orientation, hybrid orientation, and inclined orientation. In the discotic liquid crystal compound, typically, the disk surface of the discotic liquid crystal compound is oriented substantially perpendicular to the film surface of the first retardation layer. When the discotic liquid crystal compound is substantially vertical, the average value of the angles formed by the film surface and the disk surface of the discotic liquid crystal compound is preferably 70 ° to 90 °, more preferably 80 ° to 90 °. , More preferably, it means that it is 85 ° to 90 °. A discotic liquid crystal compound generally has a cyclic mother nucleus such as benzene, 1,3,5-triazine, or calixarene at the center of a molecule, and has a linear alkyl group, an alkoxy group, or a substituted benzoyl. A liquid crystal compound having a disk-shaped molecular structure in which an oxy group or the like is radially substituted as its side chain. As a typical example of a discotic liquid crystal, C.I. Research report by Destrade et al., Mol. Cryst. Liq. Cryst. Benzene derivative, triphenylene derivative, tolucene derivative, phthalocyanine derivative and B.I. Research report by Kohne et al., Angew. Chem. Cyclohexane derivatives described in Vol. 96, p. 70 (1984), and J. Mol. M. Research report by Lehn et al., J. Mol. Chem. Soc. Chem. Commun. , 1794 (1985), J. Mol. Research report by Zhang et al., J. Mol. Am. Chem. Soc. Examples thereof include the aza-crown-based and phenylacetylene-based macrocycles described in Vol. 116, p. 2655 (1994). Further specific examples of the discotic liquid crystal compound include the compounds described in JP-A-2006-133652, JP-A-2007-108732, and JP-A-2010-244038. The above documents and publications are incorporated herein by reference.

In one embodiment, the first retardation layer 20 is a single layer of the oriented solidification layer of the liquid crystal compound as shown in FIGS. 1 and 2. When the first retardation layer 20 is composed of a single layer of the oriented solidification layer of the liquid crystal compound, the thickness thereof is preferably 0.5 μm to 7 μm, more preferably 1 μm to 5 μm. By using the liquid crystal compound, it is possible to realize an in-plane phase difference equivalent to that of the resin film with a thickness much thinner than that of the resin film.

The first retardation layer typically shows a relationship in which the refractive index characteristic is nx> ny = nz. The first retardation layer is typically provided to impart antireflection characteristics to the polarizing plate, and functions as a λ / 4 plate when the first retardation layer is a single layer of an oriented solidification layer. Can be. In this case, 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 even more preferably 130 nm to 160 nm. Here, "ny = nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, ny> nz or ny <nz may occur within a range that does not impair the effect of the present invention.

The Nz coefficient of the first retardation layer is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3. By satisfying such a relationship, a very excellent reflected hue can be achieved when the obtained polarizing plate with a retardation layer is used in an image display device.

The first retardation layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, and a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It may be shown, and may show a flat wavelength dispersion characteristic in which the phase difference value hardly changes with the wavelength of the measured light. In one embodiment, the first retardation layer exhibits reverse dispersion wavelength characteristics. In this case, 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 characteristics can be realized.

The angle θ formed by the slow axis of the first retardation layer 20 and the absorption axis of the polarizing element 11 is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and even more preferably about. It is 45 °. If the angle θ is in such a range, by using the λ / 4 plate as the first retardation layer as described above, very excellent circularly polarized light characteristics (as a result, very excellent antireflection characteristics). A polarizing plate with a retardation layer can be obtained.

In another embodiment, the first retardation layer 20 may have a laminated structure of the first alignment solidification layer 21 and the second alignment solidification layer 22 as shown in FIG. In this case, either one of the first oriented solidifying layer 21 and the second oriented solidifying layer 22 may function as a λ / 4 plate, and the other may function as a λ / 2 plate. Therefore, the thicknesses of the first oriented solidifying layer 21 and the second oriented solidifying layer 22 can be adjusted so as to obtain the desired in-plane phase difference of the λ / 4 plate or the λ / 2 plate. For example, when the first oriented solidified layer 21 functions as a λ / 2 plate and the second oriented solidified layer 22 functions as a λ / 4 plate, the thickness of the first oriented solidified layer 21 is, for example, 2.0 μm or more. It is 3.0 μm, and the thickness of the second oriented solidification layer 22 is, for example, 1.0 μm to 2.0 μm. In this case, the in-plane retardation Re (550) of the first oriented solidified layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and further preferably 250 nm to 280 nm. The in-plane retardation Re (550) of the second oriented solidified layer is as described above with respect to the single oriented solidified layer. The angle formed by the slow axis of the first oriented solidification layer and the absorption axis of the polarizing element is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, still more preferably about 15 °. be. The angle formed by the slow axis of the second oriented solidification layer and the absorption axis of the polarizing element is preferably 70 ° to 80 °, more preferably 72 ° to 78 °, and even more preferably about 75 °. be. With such a configuration, it is possible to obtain characteristics close to the ideal reverse wavelength dispersion characteristic, and as a result, it is possible to realize extremely excellent antireflection characteristics. The liquid crystal compounds constituting the first oriented solidified layer and the second oriented solidified layer, the method for forming the first oriented solidified layer and the second oriented solidified layer, the optical properties, and the like are described above with respect to the single oriented solidified layer. As explained in.

D. Second Phase Difference Layer The second phase difference layer may be a so-called positive C plate having a refractive index characteristic of nz> nz = ny as described above. By using the positive C plate as the second retardation layer, it is possible to satisfactorily prevent reflection in the oblique direction, and it is possible to widen the viewing angle of the antireflection function. In this case, the retardation Rth (550) in the thickness direction of the second retardation layer is preferably −50 nm to −300 nm, more preferably −70 nm to −250 nm, still more preferably −90 nm to −200 nm, and particularly preferably. It is -100 nm to -180 nm. Here, "nx = ny" includes not only the case where nx and ny are exactly equal to each other, but also the case where nx and ny are substantially equal to each other. That is, the in-plane retardation Re (550) of the second retardation layer can be less than 10 nm.

The second retardation layer having a refractive index characteristic of nz> nx = ny can be formed of any suitable material. The second retardation layer preferably consists of a film containing a liquid crystal material fixed in a homeotropic orientation. The liquid crystal material (liquid crystal compound) that can be homeotropically oriented may be 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 [0020] to [0028] of JP-A-2002-333642. In this case, the thickness of the second retardation layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 μm to 5 μm.

E. Conductive layer or isotropic base material with conductive layer The conductive layer is an arbitrary suitable base material by any suitable film forming method (for example, vacuum deposition method, sputtering method, CVD method, ion plating method, spray method, etc.). It can be formed by forming a metal oxide film on top of it. Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimon composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Of these, indium-tin composite oxide (ITO) is preferable.

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 thickness of the conductive layer is preferably 10 nm or more.

Even if the conductive layer is transferred from the base material to the first retardation layer (or the second retardation layer if present) and the conductive layer alone is used as a constituent layer of the polarizing plate with the retardation layer. Often, it may be laminated on the first retardation layer (or the second retardation layer if present) as a laminate with the substrate (base material with a conductive layer). Preferably, the substrate is optically isotropic, and therefore the conductive layer can be used as an isotropic substrate with a conductive layer in a polarizing plate with a retardation layer.

Any suitable isotropic base material can be adopted as the optically isotropic base material (isotropic base material). As the material constituting the isotropic base material, for example, a material having a resin having no conjugate system such as a norbornene resin or an olefin resin as a main skeleton, or an acrylic resin having a cyclic structure such as a lactone ring or a glutarimide ring. Examples include the material contained in the main chain. When such a material is used, when an isotropic substrate is formed, the expression of the phase difference due to the orientation of the molecular chains can be suppressed to be small. The thickness of the isotropic substrate is preferably 50 μm or less, more preferably 35 μm or less. The thickness of the isotropic substrate is, for example, 20 μm or more.

The conductive layer and / or the conductive layer of the isotropic base material with the conductive layer can be patterned as needed. By patterning, a conductive part and an insulating part can be formed. As a result, electrodes can be formed. The electrode can function as a touch sensor electrode that senses contact with the touch panel. As the patterning method, any suitable method may be adopted. Specific examples of the patterning method include a wet etching method and a screen printing method.

F. Image display device The polarizing plate with a retardation layer according to the above items A to E can be applied to an image display device. Therefore, the present invention includes an image display device using such a polarizing plate with a retardation layer. Typical examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device). The image display device according to the embodiment of the present invention includes the polarizing plate with a retardation layer according to the above items A to E on the visual recognition side thereof. The polarizing plate with a retardation layer is laminated so that the retardation layer is on the image display cell side (for example, a liquid crystal cell, an organic EL cell, an inorganic EL cell) (so that the polarizing element is on the visual recognition side). In one embodiment, the image display device has a curved shape (substantially a curved display screen) and / or is bendable or bendable. In such an image display device, the effect of the polarizing plate with a retardation layer of the present invention becomes remarkable.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" in Examples and Comparative Examples are based on weight.

[Example 1]
1. 1. Preparation of A Polarizer As a thermoplastic resin base material, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption of 0.75%, and a Tg of about 75 ° C. was used. One side of the resin base material was subjected to corona treatment (treatment conditions: 55 W · min / m ² ).
100 weight of PVA-based resin in which polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z410") are mixed at a ratio of 9: 1. 13 parts by weight of potassium iodide was added to the part to prepare a PVA aqueous solution (coating liquid).
The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60 ° C. to form a PVA-based resin layer having a thickness of 13.5 μm, and a laminate was prepared.
The obtained laminate was stretched 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, in a dyeing bath having a liquid temperature of 30 ° C. (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1: 7 with respect to 100 parts by weight of water), the polarizing element finally obtained is charged. It was immersed for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) was 40.5% (staining treatment).
Then, it was immersed in a cross-linked bath having a liquid temperature of 40 ° C. (a boric acid aqueous solution obtained by blending 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. (Crossing treatment).
Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight, potassium iodide 5.0% by weight) having a liquid temperature of 62 ° C., the rolls having different peripheral speeds are subjected to the longitudinal direction (longitudinal direction). ) Was uniaxially stretched so that the total stretch ratio was 3.0 times (underwater stretching treatment: the stretching ratio in the underwater stretching treatment was 1.25 times).
Then, the laminate was immersed in a washing bath having a liquid temperature of 20 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while drying in an oven kept at 90 ° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75 ° C. for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the laminated body by the drying shrinkage treatment was 2%.
In this way, a polarizing element having a thickness of 7.4 μm was formed on the resin substrate.

2. 2. Preparation of Polarizing Plate A water-based polyurethane resin (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name: Superflex 210-R) is dissolved in a mixed solvent of pure water and isopropyl alcohol, and the obtained solution is the resin obtained above. It was applied to the surface of the polarizing element formed on the substrate. Then, it was dried at 60 ° C. to remove the solvent, and an easy-adhesion layer having a thickness of 0.15 μm was formed. 20 parts of an acrylic resin having a methyl methacrylate unit (manufactured by Kusumoto Kasei Co., Ltd., trade name: B728) was dissolved in 80 parts of methyl ethyl ketone to obtain an acrylic resin solution (20%). This acrylic resin solution was applied to the easy-adhesion layer using a wire bar, and the coating film was dried at 60 ° C. for 5 minutes to form an acrylic resin layer formed as a solidified product of the coating film. The thickness of the acrylic resin layer was 2 μm, and the Tg was 116 ° C. Next, 70 parts by weight of dimethylol-tricyclodecanediacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: light acrylate DCP-A), 20 parts by weight of isobornyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: light acrylate IB-XA), 1 , 9-Nonandiol diacrylate (Kyoeisha Chemical Co., Ltd., trade name: Light Acrylate 1.9NA-A) 10 parts by weight, and photopolymerization initiator (BASF Co., Ltd., trade name: Irgacure 907) 3 parts by weight as a solvent. It was mixed in and a coating liquid was obtained. The obtained coating liquid was applied onto the protective layer so that the thickness after curing was 3 μm. Next, the solvent was dried, and a hard coat layer was formed by irradiating with an ultraviolet ray under a nitrogen atmosphere so that the integrated light amount was 300 mJ / cm ^{2 using a high-pressure mercury lamp.} The thickness of the hard coat layer was 3 μm. Next, in order to stably perform the later bonding work with the retardation layer, the pressure-sensitive adhesive layer of the polyethylene terephthalate (PET) film with a pressure-sensitive adhesive layer was bonded to the protective layer and reinforced. After that, the resin base material is peeled off to obtain a polarizing plate having a structure of PET film with adhesive layer / protective layer (hard coat layer / acrylic resin layer (solidified coating film)) / easy-adhesive layer / polarizing element. Obtained.

3. 3. Preparation of First Oriented Solidified Layer and Second Aligned Solidified Layer Constituting the Phase Difference Layer With 10 g of polymerizable liquid crystal (manufactured by BASF: trade name "Pariocolor LC242", represented by the following formula) showing a nematic liquid crystal phase. , 3 g of a photopolymerization initiator (manufactured by BASF: trade name "Irgacure 907") for the polymerizable liquid crystal compound was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid).

The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed with a rubbing cloth and subjected to an orientation treatment. The direction of the alignment treatment was set to be 15 ° when viewed from the visual recognition side with respect to the direction of the absorption axis of the polarizing element when the polarizing plate was attached. The liquid crystal coating liquid was applied to the alignment-treated surface with a bar coater, and the liquid crystal compound was oriented by heating and drying at 90 ° C. for 2 minutes. ^{The liquid crystal layer thus formed was irradiated with light of 100 mJ / cm 2} using a metal halide lamp, and the liquid crystal layer was cured to form a liquid crystal oriented solidified layer A on the PET film. The thickness of the liquid crystal oriented solidified layer A was 2.5 μm, and the in-plane retardation Re (550) was 270 nm. Further, the liquid crystal oriented solidified layer A had a refractive index distribution of nx> ny = nz.
On the PET film in the same manner as above, except that the coating thickness was changed and the orientation processing direction was set to be 75 ° when viewed from the visual side with respect to the direction of the absorber's absorption axis. The liquid crystal oriented solidified layer B was formed. The thickness of the liquid crystal oriented solidified layer B was 1.5 μm, and the in-plane retardation Re (550) was 140 nm. Further, the liquid crystal oriented solidified layer B had a refractive index distribution of nx> ny = nz.

4. Fabrication of polarizing plate with retardation layer 2. On the polarizing element surface of the polarizing plate obtained in 3. above. The liquid crystal oriented solidified layer A and the liquid crystal oriented solidified layer B obtained in 1 above were transferred in this order. At this time, the angle between the absorption axis of the polarizing element and the slow axis of the oriented solidification layer A is 15 °, and the angle between the absorption axis of the polarizing element and the slow axis of the oriented solidification layer B is 75 °. Transferred (bonded). In addition, each transfer (bonding) is performed in the above 2. This was done via the ultraviolet curable adhesive (thickness 1.0 μm) used in. Then, the PET film with the pressure-sensitive adhesive layer was peeled off. In this way, the protective layer (hard coat layer / acrylic resin layer (solidified coating film)) / easy-adhesive layer / polarizing element / adhesive layer / retardation layer (first oriented solidified layer / adhesive layer / first A polarizing plate with a retardation layer having the structure of 2 oriented solidified layers) was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 19 μm.

[Examples 2 to 4]
A polarizing element having a thickness of 7.4 μm was formed on the resin substrate in the same manner as in Example 1 except that dyeing baths having different iodine concentrations (weight ratio of iodine to potassium iodide = 1: 7) were used.
Protective layer (hard coat layer / acrylic resin layer (solidified coating film)) / easy in the same manner as in Example 1 except that the obtained laminate having the structure of the polarizing element / resin base material was used. A polarizing plate with a retardation layer having a structure of an adhesive layer / a polarizing element / an adhesive layer / a retardation layer (a first alignment solidification layer / an adhesion layer / a second alignment solidification layer) was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 19 μm.

[Examples 5 to 8]
The stretching ratio of the underwater stretching treatment was 1.46 times, the total stretching ratio was 3.5 times, and dyeing baths with different iodine concentrations (weight ratio of iodine and potassium iodide = 1: 7) were used. Except for the above, in the same manner as in Example 1, a polarizing element having a thickness of 6.7 μm was formed on the resin substrate.
Protective layer (hard coat layer / acrylic resin layer (solidified coating film)) / easy in the same manner as in Example 1 except that the obtained laminate having the structure of the polarizing element / resin base material was used. A polarizing plate with a retardation layer having a structure of an adhesive layer / a polarizing element / an adhesive layer / a retardation layer (a first alignment solidification layer / an adhesion layer / a second alignment solidification layer) was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 18 μm.

[Example 9]
Except for the fact that instead of the acrylic resin having a methyl methacrylate unit (manufactured by Kusumoto Kasei Co., Ltd., trade name: B728), an acrylic resin (lactone ring unit 30 mol%) which is a polymethyl methacrylate having a lactone ring unit was used. A polarizing plate with a retardation layer was obtained in the same manner as in Example 7. The total thickness of the obtained polarizing plate with a retardation layer was 18 μm.

[Example 10]
Instead of the acrylic resin having a methyl methacrylate unit (manufactured by Kusumoto Kasei Co., Ltd., trade name: B728), an acrylic resin (glutarimide ring unit 4 mol%) which is a polymethyl methacrylate having a glutarimide ring unit was used. A polarizing plate with a retardation layer was obtained in the same manner as in Example 9 except for the above. The total thickness of the obtained polarizing plate with a retardation layer was 18 μm.

[Example 11]
In Example 9, instead of the acrylic resin solution, 20 parts of an epoxy resin (manufactured by Mitsubishi Chemical Co., Ltd., trade name: jER (registered trademark) YX6954BH30, weight average molecular weight: 36000, epoxy equivalent: 13000) was added to 80 parts of methyl ethyl ketone. The dissolved epoxy resin solution (20%) was used to form a protective layer composed of a solidified coating film. Specifically, this epoxy resin solution was applied to the easy-adhesion layer using a wire bar, and the coating film was dried at 60 ° C. for 3 minutes to form a protective layer. The thickness of the protective layer was 3 μm, and the Tg was 130 ° C. With a retardation layer in the same manner as in Example 9, except that the protective layer was formed, the easily adhesive layer was not formed on the polarizing element, and the hard coat layer was not formed. A polarizing plate 7 was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 16 μm.

[Example 12]
Polarized light with a retardation layer in the same manner as in Example 7 except that the protective layer was formed as follows, the easily adhesive layer was not formed on the polarizing element, and the hard coat layer was not formed. I got a board. The total thickness of the obtained polarizing plate with a retardation layer was 16 μm.
An epoxy resin solution was obtained by dissolving 15 parts of an epoxy resin having a biphenyl skeleton (manufactured by Mitsubishi Chemical Corporation, trade name: jER (registered trademark) YX4000) in 83.8 parts of methyl ethyl ketone. To the obtained epoxy resin solution, 1.2 parts of a photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., trade name: CPI (registered trademark) -100P) was added to obtain a protective layer forming composition. The obtained protective layer forming composition was applied to the easy-adhesion layer using a wire bar, and the coating film was dried at 60 ° C. for 3 minutes. Then, using a high-pressure mercury lamp, ^{ultraviolet rays were irradiated so that the integrated light amount was 600 mJ / cm 2,} and a protective layer was formed. The thickness of the protective layer was 3 μm.

[Example 13]
A polarizing plate with a retardation layer is used in the same manner as in Example 12 except that a bisphenol type epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: jER® 828) is used instead of the epoxy resin having a biphenyl skeleton. Got The total thickness of the obtained polarizing plate with a retardation layer was 16 μm.

[Example 14]
Polarizing with a retardation layer in the same manner as in Example 12 except that a hydrogenated bisphenol type epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: jER (registered trademark) YX8000) was used instead of the epoxy resin having a biphenyl skeleton. I got a board. The total thickness of the obtained polarizing plate with a retardation layer was 16 μm.

[Example 15]
15 parts of hydrogenated bisphenol type epoxy resin (manufactured by Mitsubishi Chemical Co., Ltd., trade name: jER (registered trademark) YX8000) and 10 parts by weight of oxetane resin (manufactured by Toa Synthetic Co., Ltd., trade name: Aron Oxetane (registered trademark) OXT-221) , Was dissolved in 73 parts of methyl ethyl ketone to obtain an epoxy resin solution. To the obtained epoxy resin solution, two parts of a photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., trade name: CPI (registered trademark) -100P) was added to obtain a protective layer forming composition. A polarizing plate with a retardation layer was obtained in the same manner as in Example 12 except that the obtained protective layer forming composition was used. The total thickness of the obtained polarizing plate with a retardation layer was 16 μm.

[Example 16]
A polarizing plate with a retardation layer was obtained in the same manner as in Example 15 except that the thickness of the protective layer was 8 μm.

[Example 17]
A polarizing plate with a retardation layer was obtained in the same manner as in Example 15 except that the thickness of the protective layer was 10 μm.

[Example 18]
A protective layer (cured product) was formed in the same manner as in Example 12 except that an ultraviolet curable epoxy resin (manufactured by Daicel Corporation, product name “Selokiside 2021P”) was used. Specifically, a composition containing 95% by weight of the epoxy resin and 5% by weight of a photopolymerization initiator (CPI-100P, manufactured by San-Apro) is applied onto the easy-adhesion layer, and a high-pressure mercury lamp is applied under an air atmosphere. The cured layer (protective layer) was formed by irradiating ultraviolet rays with an integrated light amount of 500 mJ / cm ^2. A polarizing plate with a retardation layer was produced in the same manner as in Example 7 except that this protective layer was used. The thickness of the polarizing plate was 16 μm.

[Examples 19 to 22]
The stretch ratio of stretching in water was 1.67 times (as a result, the total ratio of stretching was 4.0 times), and the dyeing baths with different iodine concentrations (weight ratio of iodine and potassium iodide = 1). : A decoder having a thickness of 6.2 μm was formed on the resin substrate in the same manner as in Example 1 except that 7) was used.
Protective layer (hard coat layer / acrylic resin layer (solidified coating film)) / easy in the same manner as in Example 1 except that the obtained laminate having the structure of the polarizing element / resin base material was used. A polarizing plate with a retardation layer having a structure of an adhesive layer / a polarizing element / an adhesive layer / a retardation layer (a first alignment solidification layer / an adhesion layer / a second alignment solidification layer) was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 18 μm.

[Examples 23 to 26]
The stretching ratio for stretching in water was 1.88 times, the total stretching ratio was 4.5 times, and dyeing baths with different iodine concentrations (weight ratio of iodine and potassium iodide = 1: 7) were used. Except for the above, a polarizing element having a thickness of 6.0 μm was formed on the resin substrate in the same manner as in Example 1.
Protective layer (hard coat layer / acrylic resin layer (solidified coating film)) / easy in the same manner as in Example 1 except that the obtained laminate having the structure of the polarizing element / resin base material was used. A polarizing plate with a retardation layer having a structure of an adhesive layer / a polarizing element / an adhesive layer / a retardation layer (a first alignment solidification layer / an adhesion layer / a second alignment solidification layer) was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 17.0 μm.

(Comparative Examples 1 to 4)
The stretching ratio for stretching in water was 2.29 times, the total stretching ratio was 5.5 times, and dyeing baths with different iodine concentrations (weight ratio of iodine and potassium iodide = 1: 7) were used. Except for the above, a polarizing element having a thickness of 5.5 μm was formed on the resin substrate in the same manner as in Example 1.
Protective layer (hard coat layer / acrylic resin layer (solidified coating film)) / easy in the same manner as in Example 1 except that the obtained laminate having the structure of the polarizing element / resin base material was used. A polarizing plate with a retardation layer having a structure of an adhesive layer / a polarizing element / an adhesive layer / a retardation layer (a first alignment solidification layer / an adhesion layer / a second alignment solidification layer) was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 16 μm.

(Comparative Example 5)
The thickness was 5. A 5 μm polarizing element was obtained. A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that an acrylic resin film having a thickness of 40 μm was laminated on the surface of the obtained polarizing element via an ultraviolet curable adhesive to form a protective layer. The total thickness of the obtained polarizing plate with a retardation layer was 53 μm.

(Comparative Example 6)
A polarizing plate with a retardation layer was obtained in the same manner as in Comparative Example 2 except that an acrylic film having a thickness of 20 μm was used as the protective layer. The total thickness of the obtained polarizing plate with a retardation layer was 33 μm.

(Comparative Example 7)
A polarizing plate with a retardation layer was obtained in the same manner as in Comparative Example 2 except that the protective layer was formed in the same manner as in Example 11. The total thickness of the obtained polarizing plate with a retardation layer was 15 μm.

(Comparative Example 8)
A polarizing plate with a retardation layer was obtained in the same manner as in Comparative Example 2 except that the protective layer was formed in the same manner as in Example 12. The total thickness of the obtained polarizing plate with a retardation layer was 15 μm.

(Comparative Example 9)
A polarizing plate with a retardation layer was obtained in the same manner as in Comparative Example 2 except that the protective layer was formed in the same manner as in Example 15. The total thickness of the obtained polarizing plate with a retardation layer was 15 μm.

[evaluation]
The following evaluations were performed using the polarizing plates with a retardation layer obtained in Examples and Comparative Examples. The results are shown in Table 1.
(1) Thickness The thickness of the polarizing element was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). The calculated wavelength range used for the thickness calculation was 400 nm to 500 nm, and the refractive index was 1.53. The thickness of the protective layer was measured by using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"), and the calculated wavelength range and refractive index were appropriately selected and measured. The thickness of the easy-adhesion layer was determined by observation with a scanning electron microscope (SEM). The thickness exceeding 110 μm was measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).
(2) In-plane phase difference (Re) of PVA
A phase difference measuring device (product name manufactured by Oji Measuring Instruments Co., Ltd.) is used for the polarizing element (polarizer unit) obtained by peeling and removing the resin base material from the laminate of the polarizing element / thermoplastic resin base material obtained in Examples and Comparative Examples. KOBRA-31X100 / IR ”) was used to evaluate the in-plane phase difference (Rpva) of PVA at a wavelength of 1000 nm (according to the explained principle, from the total in-plane phase difference at a wavelength of 1000 nm, the in-plane phase difference of iodine. (Ri) is subtracted). The absorption edge wavelength was set to 600 nm.
(3) Birefringence of PVA (Δn)
The birefringence (Δn) of PVA was calculated by dividing the in-plane phase difference of PVA measured in (2) above by the thickness of the substituent.
(4) Orientation function The spectroscopes used in the examples and comparative examples are polarized infrared rays using a Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, trade name: "Frontier"). Using light as the measurement light, total reflection spectroscopy (ATR) measurement on the surface of the extruder was performed. Germanium was used as the crystallite to which the polarizing element was brought into close contact, and the incident angle of the measured light was 45 °. The orientation function was calculated according to the following procedure. The incident polarized infrared light (measurement light) is polarized light (s-polarized light) that vibrates parallel to the surface to which the germanium crystal sample is in close contact, and the extension direction of the substituent is perpendicular to the polarization direction of the measurement light (measurement light). ⊥) and the absorption spectra of each were measured in parallel (//). From the obtained absorbance spectrum was calculated and a reference to (3330cm ^-1 intensity) (2941cm ^-1 intensity) I. I _⊥ is a stretching direction of the polarizer perpendicular to the polarization direction of the measuring light (⊥) obtained from the resulting absorbance spectrum when placed (2941cm ^-1 intensity) / (3330cm ^-1 strength). Further, I _// is obtained from the absorbance spectrum obtained when the stretching direction of the splitter is arranged parallel (//) with respect to the polarization direction of the measurement light (2941 cm ^-1 intensity) / (3330 cm ^-1 intensity). Is. Here, (2941cm ^-1 strength) is the bottom of the absorption spectrum, the absorbance of 2941cm ^-1 when the 2770Cm ^-1 and 2990cm ^-1 were the baseline, (3330cm ^-1 strength), 2990Cm ^{- 1} and 3650 cm ^-1 which is the absorbance of 3330cm ^-1 when the baseline. Using the obtained I _⊥ and I _// , the orientation function f was calculated according to Equation 1. When f = 1, it is completely oriented, and when f = 0, it is random. Further, ^{the peak of 2941 cm -1} is said to be absorption caused by vibration of the main chain (-CH _{2-) of PVA in the polarizing element.} The peak of 3330 cm ^-1 is said to be absorbed due to the vibration of the hydroxyl group of PVA.
(Equation 1) f = (3 <cos ² θ> -1) / 2
= (1-D) / [c (2D + 1)]
However, c = (3cos ² β-1) / 2
Then, when 2941 cm ^-1 is used as described above, β = 90 ° ⇒ f = -2 × (1-D) / (2D + 1).
θ: Angle of molecular chain with respect to stretching direction β: Angle of transition dipole moment with respect to molecular chain axis D = (I _⊥ ) / (I _// )
I _⊥ : Absorption intensity when the polarization direction of the measurement light is perpendicular to the stretching direction _{of the polarizing element I //} : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizing element are parallel (5) Crack occurrence rate The polarizing plates with a retardation layer obtained in Examples and Comparative Examples were cut out to a size of 10 mm × 10 mm. The cut-out polarizing plate with a retardation layer was attached to a glass plate (thickness 1.1 mm) via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm. After the sample attached to the glass plate was placed in an oven at 100 degrees for 120 hours, the presence or absence of cracks in the absorption axis direction (MD direction) of the polarizing element was visually confirmed. This evaluation was performed using three polarizing plates with a retardation layer, and the number of polarizing plates with a retardation layer in which cracks were generated was evaluated.
(6) Bending resistance The polarizing plates with a retardation layer obtained in Examples and Comparative Examples were cut out to a size of 50 mm × 100 mm. At this time, the polarizing element was cut out so that the absorption axis direction was the long side direction. Using a bending tester (manufactured by Yuasa System Co., Ltd., product name: DLDM111LH), the cut polarizing plate with a retardation layer was subjected to a bending test at room temperature. Specifically, the polarizing plate with a retardation layer is placed at a rotation speed of 60 rpm in the absorption axis direction so that the retardation layer side is on the inside and the protective layer or the hard coat layer formed on the protective layer is on the outside. The bending diameter was set to 1 mmφ (R is 0.5 mm), and the polarizing plate with a retardation layer was bent 50,000 times. Next, the presence or absence of cracks in the polarizing plate with a retardation layer after the test was visually confirmed, and those in which no cracks could be confirmed were regarded as good, and those in which cracks were confirmed were regarded as unacceptable. The bending direction is the transmission axis direction of the polarizing element.
(7) Single-unit transmittance and polarization degree The single-unit transmittance Ts, measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V-7100") for the polarizing elements used in Examples and Comparative Examples. The parallel transmittance Tp and the orthogonal transmittance Tc were defined as Ts, Tp and Tc of the spectrometers, respectively. These Ts, Tp and Tc are Y values measured by the JIS Z8701 two-degree visual field (C light source) and corrected for luminosity factor.
From the obtained Tp and Tc, the degree of polarization P was determined by the following formula.
Polarization degree P (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100
(8) Puncture strength A compression tester (manufactured by Kato Tech Co., Ltd., product name "NDG5" needle) in which the stator is peeled off from the laminate of the stator / thermoplastic resin base material used in the examples and comparative examples, and a needle is attached. It was placed on the penetrating force measurement specification) and pierced at a piercing speed of 0.33 cm / sec under a room temperature (23 ° C ± 3 ° C) environment, and the strength when the polarizing element was broken was defined as the breaking strength (piercing strength). As the evaluation value, the breaking strength of 10 sample pieces was measured, and the average value thereof was used. The needle used had a tip diameter of 1 mmφ and 0.5R. The polarizing element to be measured was fixed by sandwiching a jig having a circular opening having a diameter of about 11 mm from both sides of the polarizing element, and a needle was pierced into the center of the opening to perform a test.

As is clear from Table 1, the polarizing plates with retardation layers of Examples 1 to 26 suppressed the generation of cracks even when they were subjected to heat treatment. In addition, it was also excellent in durability at the time of bending.

The polarizing plate with a retardation layer of the present invention is suitably used for an image display device.

10 Polarizing plate 11 Polarizer 12 First protective layer 13 Second protective layer 20 Phase difference layer 100 Polarizing plate with retardation layer 101 Polarizing plate with retardation layer 102 Polarizing plate with retardation layer 102

Claims

It has a polarizing element made of a polyvinyl alcohol-based resin film containing a dichroic substance, a polarizing plate including a protective layer arranged on one side of the polarizing element, and a retardation layer.
The retardation layer is an orientation-solidified layer of a liquid crystal compound, and is
The thickness of the protective layer is 10 μm or less.
A polarizing plate with a retardation layer that satisfies the following formula (1) when the polarizing element has a single transmittance of x% and the birefringence of the polyvinyl alcohol-based resin is y.
y <-0.011x + 0.525 (1)
It has a polarizing element made of a polyvinyl alcohol-based resin film containing a dichroic substance, a polarizing plate including a protective layer arranged on one side of the polarizing element, and a retardation layer.
The retardation layer is an orientation-solidified layer of a liquid crystal compound, and is
The thickness of the protective layer is 10 μm or less.
A polarizing plate with a retardation layer that satisfies the following formula (2) when the polarizing element has a single transmittance of x% and the in-plane retardation of the polyvinyl alcohol-based resin film is znm.
z <-60x + 2875 (2)
It has a polarizing element made of a polyvinyl alcohol-based resin film containing a dichroic substance, a polarizing plate including a protective layer arranged on one side of the polarizing element, and a retardation layer.
The retardation layer is an orientation-solidified layer of a liquid crystal compound, and is
The thickness of the protective layer is 10 μm or less.
A polarizing plate with a retardation layer that satisfies the following formula (3) when the single-unit transmittance of the polarizing element is x% and the orientation function of the polyvinyl alcohol-based resin is f.
f <-0.018x + 1.11 (3)
The polarizing plate with a retardation layer according to any one of claims 1 to 3, wherein the total thickness is 30 μm or less.
The polarizing plate with a retardation layer according to any one of claims 1 to 4, wherein the polarizing element has a thickness of 10 μm or less.
The polarizing plate with a retardation layer according to any one of claims 1 to 5, wherein the polarizing element has a single transmittance of 40.0% or more and a degree of polarization of 99.0% or more.
The protective layer is selected from the group consisting of a solidified coating film of an organic solvent solution of a thermoplastic (meth) acrylic resin, a photocationically cured product of an epoxy resin, and a solidified coating film of an organic solvent solution of an epoxy resin. The polarizing plate with a retardation layer according to any one of claims 1 to 6, which is composed of at least one type.
7. The thermoplastic (meth) acrylic resin has at least one repeating unit selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit and a maleimide unit. The above-mentioned polarizing plate with a retardation layer.
The polarizing plate with a retardation layer according to claim 7, wherein the protective layer is a photocationically cured product of an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton.
An image display device including the polarizing plate with a retardation layer according to any one of claims 1 to 9.