JP7048213B2 - Polarizer - Google Patents

Description

The present invention relates to a polarizing plate.

As an image display device with low power consumption and space saving, the spread of liquid crystal display devices is remarkable. In a liquid crystal display device, a polarizing plate is arranged on at least one side of a liquid crystal cell due to the image forming method. With the widespread use of liquid crystal display devices, the applications of liquid crystal display devices are steadily expanding, and various characteristics corresponding to such expanded applications are required. Along with this, the polarizing plate is also required to have unprecedented characteristics and significantly superior characteristics, and various studies have been made to realize such requirements. There is.

Japanese Patent No. 5305997

The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a polarizing plate having high transmittance, excellent smoothness, and improved reflection characteristics. be.

The polarizing plate of the present invention has a substrate, a polarizing element, and a high refractive index layer in this order, and when the refractive index of the polarizing element in the absorption axis direction is na and the refractive index in the transmission axis direction is nt, at least na has a wavelength dependence.
In one embodiment, the high refractive index layer is formed as a refractive index adjusting region in the pressure-sensitive adhesive layer.
In one embodiment, in the polarizing plate, the refractive index na (450) of the substituent in the absorption axis direction at a wavelength of 450 nm and the refractive index na (650) of the polarizing element in the absorption axis direction at a wavelength of 650 nm. The absolute value of the difference is 1.0 or more.
In one embodiment, the refractive index of the refractive index adjusting region is 1.60 to 2.14.
In one embodiment, the difference between the reflectance of the substituent in the absorption axis direction and the reflectance of the substituent in the transmission axis direction is 10% or more.
In one embodiment, the modulator comprises an aromatic disazo compound. In one embodiment, the thickness of the stator is 1000 nm or less.

According to the present invention, a transmittance having a specific wavelength dependence of refractive index and a high refractive index layer (in one embodiment, a refractive index adjusting region in the pressure-sensitive adhesive layer) are used in combination to obtain a transmittance. It is possible to realize a polarizing plate having high refractive index, excellent smoothness, and improved reflection characteristics, which was conventionally difficult to achieve at the same time as transmittance. Specifically, the reflected hue can be neutralized (the coloring of the reflected light can be suppressed), and the reflectance can be lowered while maintaining the excellent characteristics of the above-mentioned modulator.

It is schematic cross-sectional view explaining the polarizing plate by one Embodiment of this invention.

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

A. Overall Configuration of Polarizing Plate The polarizing plate of the present invention has a substrate, a polarizing element, and a high refractive index layer in this order. As the high refractive index layer, a high refractive index layer having any suitable configuration can be adopted. Specific examples include a high-refractive index layer made of a high-refractive index resin film, a layer in which high-refractive index particles are dispersed in a resin matrix (for example, such a coating layer), and a pressure-sensitive adhesive layer. A high refractive index region (for example, a refractive index adjusting region) can be mentioned. Hereinafter, a form in which the high refractive index layer is a refractive index adjusting region formed in the pressure-sensitive adhesive layer will be described. It is self-evident to those skilled in the art that the present invention can employ other forms of high-refractive index layers (eg, the above-mentioned high-refractive index layers), and similar effects can be obtained with such high-refractive index layers. be.

FIG. 1 is a schematic cross-sectional view illustrating a polarizing plate according to the present embodiment. The polarizing plate 100 of the illustrated example has a base material 10, a polarizing element 20, and an adhesive layer 30 in this order. If necessary, a protective layer (not shown) may be provided between the polarizing element 20 and the pressure-sensitive adhesive layer 30. Further, if necessary, a cover glass (not shown) may be provided as the outermost layer of the polarizing plate. The cover glass may be provided on the outside of the pressure-sensitive adhesive layer 30, may be provided on the outside of the base material 10, or may be provided on both sides. The polarizing plate of the present invention can be typically applied to an image display device so that the pressure-sensitive adhesive layer 30 is arranged on the visual recognition side.

In the present invention, the refractive index of the polarizing element 20 has a wavelength dependence. Typically, the substituent has a wavelength dependence of at least na when the refractive index in the absorption axis direction is na and the refractive index in the transmission axis direction is nt. For example, in the polarizing element, na may have a wavelength dependence (the refractive index on the long wavelength side becomes high), and nt may have a flat wavelength dependence that hardly changes depending on the wavelength. By using such a polarizing element, it is possible to obtain a polarizing plate having a very high transmittance and excellent smoothness. The characteristics of the stator, the constituent materials, and the like will be described in detail in Section C, which will be described later.

Further, in the present embodiment, the refractive index adjusting region (high refractive index region) is formed in the pressure-sensitive adhesive layer as described above. In the illustrated example, the pressure-sensitive adhesive layer 30 has a base pressure-sensitive adhesive region 30a arranged on the side opposite to the polarizing element 20 and a refractive index adjusting region 30b arranged on the polarizing element 20 side. By arranging the pressure-sensitive adhesive layer including such a refractive index adjusting region on the visible side of the polarizing element, the following advantages can be obtained. As described above, by using a polarizing element having a refractive index dependent on the wavelength, a polarizing plate having a very high transmittance and excellent smoothness can be obtained. On the other hand, when a polarizing plate using such a polarizing element is applied to various image display devices, a new problem has been found in which the reflectance is high and the reflected hue has undesired coloring. According to the embodiment of the present invention, by arranging the pressure-sensitive adhesive layer including the refractive index adjusting region on the visible side of the polarizing element, the excellent characteristics (high transmittance and excellent smoothness) of the above-mentioned polarizing element are maintained. At the same time, it was possible to improve the reflection characteristics, which is a newly discovered problem in the stator. This is a finding obtained by repeating trial and error for the above-mentioned new problem, and is an unexpectedly excellent effect. The characteristics of the pressure-sensitive adhesive layer, constituent materials, and the like will be described in detail in Section D below.

B. Substrate The substrate is preferably transparent and substantially optically isotropic. In the present specification, "substantially optically isotropic" means not only the case where the refractive index characteristics of the substrate show the relationship of nx = nz = ny, but also the relationship of nx ≈ nz ≈ ny. The purpose is to include cases. More specifically, 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 -10 nm to +10 nm. Say something. The in-plane retardation Re (550) is preferably 0 nm to 5 nm, more preferably 0 nm to 3 nm. The phase difference Rth (550) in the thickness direction is preferably −5 nm to 5 nm, and more preferably -3 nm to 3 nm. 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 a refractive index, and nz is a refractive index in the thickness direction. The in-plane phase difference Re (λ) is an in-plane phase difference measured with light having a wavelength of λ nm at 23 ° C. Therefore, 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). The phase difference Rth (λ) in the thickness direction is the phase difference in the thickness direction measured with light having a wavelength of λ nm at 23 ° C. Therefore, 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 equation: Rth (λ) = (nx-nz) × d.

The substrate can be made of any suitable material as long as the desired properties are obtained. Examples of the material constituting the base material include glass, quartz, and resin. In one embodiment, the substrate can be a resin film. Typical examples of the resin include a cyclic olefin resin (for example, norbornen resin), a polycarbonate resin, a cellulosic resin (for example, triacetyl cellulose (TAC)), and a (meth) acrylic resin (for example, a glutarimide structure). Including (meth) acrylic resin). In addition, in this specification, "(meth) acrylic" means acrylic and / or methacrylic.

The thickness of the base material is preferably 50 μm to 500 μm, more preferably 70 μm to 300 μm, and further preferably 80 μm to 300 μm.

The base material may be subjected to a predetermined surface treatment. For example, a hardcourt layer (not shown) may be formed on the surface of the substrate opposite to the polarizing element. The hardcoat layer preferably has a pencil hardness of 2H or higher, more preferably 3H or higher. The hardcourt layer may be composed of any suitable material. Specific examples of the constituent materials include thermosetting resins, thermoplastic resins, active energy ray-curable resins (for example, ultraviolet curable resins and electron beam curable resins), and two-component mixed resins. UV curable resin is preferable. This is because the hard coat layer can be efficiently formed by a simple processing operation. Examples of the ultraviolet curable resin include various resins such as polyester-based, acrylic-based, urethane-based, amide-based, silicone-based, and epoxy-based resins. The thickness of the hard coat layer is, for example, about 1 μm to 5 μm.

C. Polarizer As used herein, the term "polarizer" means an element capable of converting natural light or polarized light into arbitrary polarized light. As the polarizing element used in the present invention, any suitable polarizing element can be adopted. As the splitter, preferably, natural light or one that converts polarized light into linear polarization is used.

As described above, the refractive index of the polarizing element is wavelength-dependent. For example, in the polarizing element, the refractive index na in the absorption axis direction is wavelength-dependent (the refractive index on the long wavelength side becomes high), and the refractive index nt in the transmission axis direction is flat wavelength-dependent, which hardly changes depending on the wavelength. Can have sex. The absolute value of the difference between the refractive index na (450) in the absorption axis direction at a wavelength of 450 nm and the refractive index na (650) in the absorption axis direction at a wavelength of 650 nm is preferably 1.0 or more, more preferably. Is 1.1 or more, more preferably 1.2 or more. The maximum value of the absolute value of the difference in the visible wavelength region can be, for example, about 1.6. The absolute value of the difference between the refractive index na (450) in the absorption axis direction and the refractive index nt (450) in the transmission axis direction at a wavelength of 450 nm is preferably 0.2 or less, more preferably 0.1 or less. The absolute value of the difference between the refractive index na (650) in the absorption axis direction and the refractive index nt (650) in the transmission axis direction at a wavelength of 650 nm is preferably 1.0 or more, more preferably 1.1. The above is more, and more preferably 1.2 or more. By using such a polarizing element, it is possible to obtain a polarizing plate having a very high transmittance and excellent smoothness.

The difference between the reflectance in the absorption axis direction and the reflectance in the transmission axis direction in the polarizing element can be 10% or more in one embodiment and 12% or more in another embodiment. While the polarizing element used in the present invention has a very excellent effect of having a very high transmittance and excellent smoothness as described above, the reflectance is thus caused by the wavelength dependence of the refractive index. As a result, there may be a problem that the reflected hue is not neutral. According to the present invention, by using such a substituent in combination with the pressure-sensitive adhesive layer including the refractive index adjusting region, it is possible to remarkably improve the reflection characteristics while maintaining the excellent characteristics of the modulator. ..

The splitter preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance of the polarizing element is preferably 43.0% to 46.0%, more preferably 44.5% to 46.0%. The degree of polarization of the polarizing element is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

The stator can be made of any suitable material as long as it has the desired properties described above. In one embodiment, the polarizing element is an oriented solidified layer or an oriented cured layer of a lyotropic liquid crystal. As used herein, the term "lyotropic liquid crystal" refers to a liquid crystal that undergoes a phase transition between an isotropic phase and a liquid crystal phase by changing the temperature and the concentration of a solute (liquid crystal compound). The "solidified layer" refers to a state in which the liquid crystal composition in a softened, melted or solution state is cooled and solidified, and the "cured layer" refers to a part or all of the liquid crystal composition having heat, a catalyst, or the like. Cross-linked by light and / or radiation to become insoluble or sparingly insoluble.

According to the classification according to the chemical structure, the lyotropic liquid crystal is, for example, an azo dye, an anthraquinone dye, perylene dye, indanthrone dye, imidazole dye, indigoid dye, xanthene dye, phthalocyanine dye, and tri. Phenylmethane dyes, pyrazolone dyes, stylben dyes, diphenylmethane dyes, naphthoquinone dyes, metosianin dyes, quinophthalone dyes, xanthene dyes, alizarin dyes, acridine dyes, quinoneimine dyes, thiazole dyes, methines. Examples thereof include system dyes, nitro dyes, and nitroso dyes.

The modulator preferably comprises an aromatic disazo compound. The aromatic disazo compound is preferably represented by the following general formula (1).

In the general formula (1), Q ¹ represents a substituted or unsubstituted aryl group, Q ² represents a substituted or unsubstituted arylene group, and R ¹ independently represents a hydrogen atom, substituted or unsubstituted. Alkyl group, substituted or unsubstituted acetyl group, substituted or unsubstituted benzoyl group, substituted or unsubstituted phenyl group, M represents a counterion, m represents an integer of 0 to 2, and n Represents an integer from 0 to 6. However, at least one of m and n is not 0, but 1 ≦ m + n ≦ 6. When m is 2, each R ¹ is the same or different. The OH, (NHR ¹ ) _m , and (SO ₃ M) _n represented by the general formula (1) may be bound to any of the seven substitution sites of the naphthyl ring, respectively. In addition, in this specification, "substitution or non-substitution" means "substituted with a substituent or not substituted with a substituent".

The bonding position of the naphthyl group and the azo group (-N = N-) of the general formula (1) is not particularly limited. The naphthyl group refers to the naphthyl group represented on the right side in the formula (1). Preferably, the naphthyl group and the azo group are bonded at the 1- or 2-position of the naphthyl group.

When the alkyl group, acetyl group, benzoyl group, or phenyl group of R ¹ of the general formula (1) has a substituent, examples of the substituent include each substituent exemplified by the following aryl group or arylene group. .. The R ¹ is preferably a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted acetyl group, and more preferably a hydrogen atom. Examples of the substituted or unsubstituted alkyl group include substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms.

The M (counterion) of the general formula (1) is preferably a hydrogen ion; an alkali metal ion such as Li, Na, K, Cs; an alkaline earth metal ion such as Ca, Sr, Ba; and other metal ions; Ammonium ions which may be substituted with an alkyl group or a hydroxyalkyl group; salts of organic amines and the like can be mentioned. Examples of the metal ion include Ni ⁺ , Fe ³⁺ , Cu ²⁺ , Ag ⁺ , Zn ²⁺ , Al ³⁺ , Pd ²⁺ , Cd ²⁺ , Sn ²⁺ , Co ²⁺ , Mn ²⁺ , and Ce ³⁺ . Examples of the organic amine include an alkylamine having 1 to 6 carbon atoms, an alkylamine having 1 to 6 carbon atoms having a hydroxyl group, and an alkylamine having 1 to 6 carbon atoms having a carboxyl group. In the general formula (1), when there are two or more SO ₃ Ms, each M may be the same or different. Further, in the general formula (1), when M of SO ₃ M is a cation having a valence of 2 or more, it binds to SO ₃ ⁻ of another adjacent azo compound of the general formula (1) and is a supramolecular aggregate. Can be formed.

The m of the general formula (1) is preferably 1. Further, n in the general formula (1) is preferably 1 or 2.

Specific examples of the naphthyl group of the general formula (1) include those represented by the following formulas (a) to (l). ^R1 and M of the formulas (a) to (l) are the same as those of the general formula (1).

In the general formula (1), the aryl group represented by ^Q1 includes a fused ring group in which two or more benzene rings are condensed, such as a naphthyl group, in addition to a phenyl group. Examples of the arylene group represented by ^Q2 include a fused ring group in which two or more benzene rings are condensed, such as a naphthylene group, in addition to a phenylene group.

The aryl group of Q ¹ or the arylene group of Q ² may each have a substituent or may not have a substituent. The aromatic disazo compound of the general formula (1) having a polar group is excellent in solubility in an aqueous solvent regardless of whether the aryl group or the arylene group is substituted or unsubstituted.

When the aryl group or arylene group has a substituent, the substituents include, for example, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylamino group having 1 to 6 carbon atoms, and a phenyl group. Amino group, acylamino group with 1 to 6 carbon atoms, hydroxyalkyl group with 1 to 6 carbon atoms such as dihydroxypropyl group, carboxyl group such as COOM group, sulfonic acid group such as _SO3M group, hydroxyl group, cyano group, nitro Examples include a group, an amino group, a halogeno group and the like. Preferably, the substituent is one selected from an alkoxy group having 1 to 6 carbon atoms, a hydroxyalkyl group having 1 to 6 carbon atoms, a carboxyl group, a sulfonic acid group, and a nitro group. Aromatic disazo compounds having such a substituent are particularly excellent in water solubility. These substituents may be substituted by one or more. Further, the substituent may be substituted at any ratio.

^Q1 of the general formula (1) is preferably a substituted or unsubstituted phenyl group, and more preferably a phenyl group having the above-mentioned substituent. ^Q2 is preferably a substituted or unsubstituted naphthylene group, more preferably a naphthylene group having the substituent, and particularly preferably a 1,4-naphthylene group having the substituent.

The aromatic disazo-based compound in which Q ¹ of the general formula (1) is a substituted or unsubstituted phenyl group and Q ² is a substituted or unsubstituted 1,4-naphthylene group is represented by the following general formula (2). expressed.

In the general formula (2), R ¹ , M, m and n are the same as those in the above general formula (1). In the general formula (2), A and B represent a substituent, and a and b represent the number of substitutions thereof. Each of A and B independently has an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an alkylamino group having 1 to 6 carbon atoms, a phenylamino group, and an acylamino having 1 to 6 carbon atoms. It represents a hydroxyalkyl group having 1 to 6 carbon atoms such as a group and a dihydroxypropyl group, a carboxyl group such as a COOM group _, a sulfonic acid group such as a SO MM group, a hydroxyl group, a cyano group, a nitro group, an amino group and a halogeno group. The a is an integer of 0 to 5, and the b is an integer of 0 to 4. However, at least one of a and b is not 0. When the a is 2 or more, the substituent A may be the same or different. When the number of b is 2 or more, the substituents B may be the same or different.

Among the aromatic disazo compounds contained in the general formula (2), it is preferable to use the aromatic disazo compound represented by the following general formula (3). In the aromatic disazo compound of the general formula (3), the substituent A is bonded to the para position with respect to the azo group (-N = N-). Further, in the aromatic disazo compound of the general formula (3), the OH group of the naphthyl group is bonded to the position (ortho position) adjacent to the azo group. By using the aromatic disazo compound of the general formula (3), it is possible to form a polarizing element that does not easily shrink by heating.

In the general formula (3), R ¹ , M, m and n are the same as those in the general formula (1), and A is the same as that in the general formula (2). In the general formula (3), p represents an integer of 0 to 4. The p is preferably 1 or 2, and more preferably 1.

The aromatic disazo compounds represented by the above general formulas (1) to (3) are, for example, "Theoretical Manufacturing Dye Chemistry (5th Edition)" by Yutaka Hosoda (published by Gihodo, July 15, 1968, pp. 135-152). Can be synthesized according to page). For example, the aromatic disazo compound of the general formula (3) is obtained by diazotizing and coupling an aniline derivative and a naphthalene sulfonic acid derivative to obtain a monoazo compound, then diazotizing the monoazo compound, and then further 1-. It can be synthesized by coupling reaction with an amino-8-naphthol sulfonic acid derivative.

As the thickness of the splitter, any appropriate thickness may be adopted depending on the intended purpose. The lower limit of the thickness of the stator is preferably 100 nm, more preferably 200 nm, and particularly preferably 300 nm. The upper limit of the thickness of the stator is preferably 1000 nm, more preferably 700 nm, and particularly preferably 500 nm.

The splitter can be formed, for example, by a method including the following steps A to D.
Step A: Mixing a lyotropic liquid crystal with a solvent (eg, water) to prepare a solution exhibiting a liquid crystal phase (eg, nematic liquid crystal phase);
Step B: Orientation treatment of the substrate;
Step C: Applying the solution obtained in Step A to the surface of the aligned substrate;
Step D: Drying the coating film.

D. Adhesive layer As described above, the adhesive layer 30 has a base adhesive region 30a arranged on the opposite side of the polarizing element 20 and a refractive index adjusting region 30b arranged on the polarizing element 20 side. The base pressure-sensitive adhesive region 30a may typically be composed of a pressure-sensitive adhesive base material (eg, a conventional pressure-sensitive adhesive). The refractive index adjusting region 30b has a higher refractive index than the base pressure-sensitive adhesive region 30a. By adopting the pressure-sensitive adhesive layer having the refractive index adjusting region, it is possible to remarkably improve the reflection characteristics of the polarizing plate while maintaining the excellent characteristics of the polarizing element according to the above item C.

As the pressure-sensitive adhesive base material, any suitable material can be used as long as it is a material having adhesiveness and transparency that can be used for optical applications. Specific examples include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. The pressure-sensitive adhesive base material may be used alone or in combination of two or more. Acrylic adhesives are preferred from the viewpoint of transparency, processability, durability and the like. The refractive index of the pressure-sensitive adhesive base material is typically 1.40 to 1.55.

In one embodiment, the refractive index adjusting region 30b may be composed of a resin material having a higher refractive index than the pressure-sensitive adhesive base material. The refractive index of such a resin material can be, for example, 1.59 to 2.04. Examples of such a resin material include a styrene resin and a copolymer resin containing a styrene monomer as a monomer unit. The resin material may be, for example, an acrylic polymer containing at least one aromatic ring-containing copolymerizable monomer selected from an aromatic ring-containing acrylic monomer and a styrene-based monomer as a monomer unit. Details of such materials are described in, for example, Japanese Patent Application Laid-Open No. 2002-173656. The description of this publication is incorporated herein by reference. The refractive index adjusting region is, for example, applied to the surface of the pressure-sensitive adhesive layer (finally becoming the base pressure-sensitive adhesive region) formed of the pressure-sensitive adhesive base material by applying a solution or dispersion of such a resin material to the surface and drying. Can be formed by.

In another embodiment, the refractive index adjusting region 30b can be formed by dispersing the high refractive index material particles in the pressure-sensitive adhesive base material. The refractive index of the high refractive index material particles can be, for example, 1.60 to 2.74. The difference between the refractive index of the high refractive index material particles and the refractive index of the pressure-sensitive adhesive base material is preferably 0.20 to 1.30. Specific examples of the materials constituting the high refractive index material particles include TiO ₂ , ZrO ₂ , CeO ₂ , Al ₂ O ₃ , BaTiO ₂ , Nb ₂ O ₅ and SnO ₂ , and combinations thereof. The average primary particle diameter of the high refractive index material particles is preferably 3 nm to 100 nm. In the refractive index adjusting region, for example, a coating treatment liquid in which high refractive index material particles are dispersed is applied to a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive base material, and the high-refractive index material particles are infiltrated into the pressure-sensitive adhesive base material. Thereby, it can be formed over a certain region in the thickness direction of the pressure-sensitive adhesive layer. The refractive index of the refractive index adjusting region thus formed can be, for example, 1.60 to 2.14.

As the thickness of the pressure-sensitive adhesive layer, any appropriate thickness may be adopted depending on the purpose. The thickness of the pressure-sensitive adhesive layer is, for example, 5 μm to 500 μm, preferably 10 μm to 300 μm, and more preferably 20 μm to 200 μm. Of these, the thickness of the refractive index adjusting region is preferably 20 nm to 600 nm, more preferably 20 nm to 300 nm, and further preferably 20 nm to 200 nm. The boundary between the base pressure-sensitive adhesive region and the refractive index adjusting region has an irregular fine uneven shape as shown in FIG. 1. However, in FIG. 1, the thickness and unevenness of the refractive index adjusting region are emphasized for easy viewing. ing). The thickness of the refractive index adjustment region is determined by averaging the thicknesses at a plurality of positions. The thickness of each of the plurality of positions is determined as the thickness of the region where 90% of the high refractive index material particles are present. The thickness of the base pressure-sensitive adhesive region is obtained by subtracting the thickness of the refractive index adjusting region from the total thickness of the pressure-sensitive adhesive layer.

The higher the total light transmittance of the pressure-sensitive adhesive layer, the more preferable. The total light transmittance of the pressure-sensitive adhesive layer is preferably 80% or more, more preferably 90% or more. Total light transmittance can be measured according to JIS K7361.

Details of the pressure-sensitive adhesive layer including the refractive index adjusting region are described in, for example, WO2015 / 108159. The description of this publication is incorporated herein by reference.

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 in the examples is as follows. Unless otherwise specified, "parts" and "%" in the examples are based on weight.

(1) Refractive index The average refractive index was measured using an Abbe refractive index meter manufactured by Atago.
(2) Reflectance and Reflective Hue The polarizing plates obtained in Examples and Comparative Examples were attached to a blackboard via an adhesive. Further, a glass plate was attached to the pressure-sensitive adhesive layer of the polarizing plate to prepare an image display device substitute. The reflected hue and reflectance of the obtained substitute image display device were measured using a spectrocolorimeter "CM-2600d" manufactured by Konica Minolta. The reflectance was measured for light at incident angles of 2 ° and 30 °, respectively.

<Example 1>
1. 1. Synthesis of Organic Dyes (Riotropic Liquid Liquid) 4-Nitroaniline and 8-amino-2-naphthalene sulfonic acid are commonly used (Yutaka Hosoda, "Theoretical Manufacturing Dye Chemistry 5th Edition", published by Technique Hall on July 15, 1968. , Pages 135-152), and the diazotization and coupling reaction were carried out to obtain a monoazo compound. The obtained monoazo compound was diazotized by the above-mentioned conventional method, and further subjected to a coupling reaction with 1-amino-8-naphthol-2,4-disulfonic acid lithium salt to obtain a crude product. This was salted out with lithium chloride to obtain an aromatic disazo compound of the following structural formula (4).

2. 2. Preparation of Polarizer The aromatic disazo compound of the above structural formula (4) was dissolved in ion-exchanged water to prepare a coating liquid having a concentration of 4% by weight. The coating liquid exhibited a nematic liquid crystal phase. On the other hand, a norbornene-based resin film (manufactured by Nippon Zeon Corporation: product name "Zeonoa", Re (550) = 1 nm, Rth (550) = 3 nm) was prepared as a base material, and the surface of this film was subjected to rubbing treatment and hydrophilicity. Chemical treatment (corona treatment) was applied. A coating liquid is applied to the treated surface using a bar coater (manufactured by BUSHMAN: product name "Mayer rot HS4", the coating film is naturally dried in a constant temperature room at 23 ° C., and a dry coating film (dried coating film) is applied to the surface of the substrate. The polarizing element was formed. The thickness of the obtained polarizing element was 300 nm, na (450) was 1.4, and na (650) was 2.7.

3. 3. Formation of adhesive layer including refractive index adjustment region 3-1. Preparation of Adhesive Base Material 60 parts by weight of dicyclopentanyl acrylate (DCPMA, dicyclopentanyl methacrylate), 40 parts by weight of methyl methacrylate (MMA, methyl methacrylate), α-thioglycerol 3.5 as a chain transfer agent A part by weight and 100 parts by weight of toluene as a polymerization solvent were put into a four-necked flask, and these were stirred at 70 ° C. for 1 hour under a nitrogen atmosphere. Next, 0.2 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator was put into a four-necked flask and reacted at 70 ° C. for 2 hours, followed by a reaction at 80 ° C. for 2 hours. I let you. Then, the reaction solution was put into a 130 ° C. temperature atmosphere, and toluene, the chain transfer agent and the unreacted monomer were dried and removed to obtain a solid acrylic polymer (A-1). The weight average molecular weight (Mw) of this acrylic polymer (A- ¹ ) was 5.1 × 103.
On the other hand, a monomer composed of 68 parts by weight of 2-ethylhexyl acrylate (2EHA), 14.5 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 17.5 parts by weight of 2-hydroxyethyl acrylate (HEA). The mixture was blended with 0.035 parts by weight of a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF) and 0.035 parts by weight of a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF). After that, the prepolymer composition in which a part of the above monomer components was polymerized was irradiated with ultraviolet rays until the viscosity (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 ° C.) reached about 20 Pa · s. Obtained.

3-2. Formation of pressure-sensitive adhesive layer (base pressure-sensitive adhesive region) Next, 5 parts by weight of the acrylic polymer (A-1), 0.15 parts by weight of hexanediol diacrylate (HDDA), and silane coupling were added to the prepolymer composition. An acrylic pressure-sensitive adhesive composition was obtained by adding and mixing 0.3 parts by weight of an agent (trade name "KBM-403", manufactured by Shin-Etsu Chemical Industry Co., Ltd.). The acrylic pressure-sensitive adhesive composition is applied to the peel-processed surface of a release film (trade name "MRF # 38", manufactured by Mitsubishi Plastics Co., Ltd.) so that the thickness after forming the pressure-sensitive adhesive layer is 150 μm. A coating layer was formed, and then a release film (trade name "MRN # 38", manufactured by Mitsubishi Plastics Co., Ltd.) was attached to the surface of the coating layer. Then, ultraviolet irradiation was performed under the conditions of illuminance: 5 mW / cm ² and light amount: 1500 mJ / cm ² , and the coating layer was photocured to form a pressure-sensitive adhesive layer (refractive index: 1.48).

3-3. Formation of Refractive Index Adjusting Region A dispersion liquid manufactured by CIK Nanotech Co., Ltd. was used as a coating treatment liquid in which high refractive index material particles were dispersed. The dispersion is a dispersion in which zirconia particles (ZrO ₂ , refractive index: 2.17, average primary particle diameter: 20 nm) are dispersed in ethanol (particle concentration: 1.5% by weight, transmittance of dispersion: 75). %)Met. The average primary particle diameter of the zirconia particles was measured from the TEM image.
One of the release films was peeled off from the pressure-sensitive adhesive layer (adhesive sheet) on which the release films were temporarily adhered to both sides obtained in 3-2. On the surface of the exposed pressure-sensitive adhesive layer, the above-mentioned coating treatment liquid was applied to Barcoater RDS No. 1 so that the thickness of the refractive index adjusting region was 20 nm to 300 nm. It was applied in step 5 and dried in a drying oven at 110 ° C. for 180 seconds. In this way, the refractive index adjusting region (refractive index: 1.62) was formed. Next, a release film was attached to the surface of the pressure-sensitive adhesive layer on which the refractive index adjustment region was formed to obtain a pressure-sensitive adhesive sheet.

4. Fabrication of Polarizing Plate A pressure-sensitive adhesive sheet obtained in 3-3 above was placed on the polarizing element surface of the substrate / polarizing element laminate obtained in 2 above so that the refractive index adjustment region was on the polarizing element side. I pasted them together. In this way, a polarizing plate having a structure of a base material / a polarizing element / a refractive index adjusting region / a base pressure-sensitive adhesive region was obtained. The obtained polarizing plate was subjected to the evaluation of (2) above. The results are shown in Table 1.

<Comparative Example 1>
A polarizing plate was produced in the same manner as in Example 1 except that the refractive index adjusting region was not formed in the pressure-sensitive adhesive layer. The same evaluation as in Example 1 was performed using the obtained polarizing plate. The results are shown in Table 1.

<Evaluation>
As is clear from Table 1, it can be seen that by forming the high refractive index layer (in the example, the refractive index adjusting region in the pressure-sensitive adhesive layer), the reflected hue becomes more neutral and the reflectance can be suppressed.

The polarizing plate of the present invention is a portable information terminal (PDA), a mobile phone, a clock, a digital camera, a portable device such as a portable game machine, an OA device such as a personal computer monitor, a laptop computer, a copy machine, a video camera, a liquid crystal television, and an electronic device. Household electrical equipment such as range, instrument panel, back monitor, car navigation system monitor, in-vehicle equipment such as car audio, exhibition equipment such as information monitor for commercial stores, security equipment such as monitoring monitor, nursing care It can be used for image display devices for various purposes such as nursing care / medical equipment such as monitors and medical monitors.

10 Base material 20 Polarizer 30 Adhesive layer 30a Base adhesive region 30b Refractive index adjustment region 100 Polarizing plate

Claims (5)

It has a substrate, a polarizing element directly formed on the substrate, and an adhesive layer directly formed on the polarizing element.
A refractive index adjusting region is formed on the polarizing element side of the pressure-sensitive adhesive layer, and the refractive index adjusting region is a high refractive index layer having a refractive index of 1.60 to 2.14.
The polarizing element contains an aromatic disazo compound represented by the following formula (1) and has a thickness of 1000 nm or less. When at least na has a wavelength dependence, the polarizing plate:

In formula (1), Q ¹ represents a substituted or unsubstituted aryl group, Q ² represents a substituted or unsubstituted arylene group, and R ¹ independently represents a hydrogen atom, substituted or unsubstituted. Alkyl group, substituted or unsubstituted acetyl group, substituted or unsubstituted benzoyl group, substituted or unsubstituted phenyl group, M represents a counterion, m represents an integer of 0 to 2, and n represents an integer of 0 to 2. , 0 to 6; however, at least one of m and n is not 0 but 1 ≦ m + n ≦ 6; if m is 2, R ¹ may be the same, respectively. It may be very different. The first aspect of the present invention, wherein the refractive index adjusting region is either a region made of a resin material having a higher refractive index than the pressure-sensitive adhesive base material or a region in which high-refractive index material particles are dispersed in the pressure-sensitive adhesive base material. The polarizing plate according to. Claimed that the absolute value of the difference between the refractive index na (450) in the absorption axis direction of the substituent at a wavelength of 450 nm and the refractive index na (650) in the absorption axis direction of the substituent at a wavelength of 650 nm is 1.0 or more. Item 2. The polarizing plate according to Item 1 or 2. The polarizing plate according to any one of claims 1 to 3, wherein the difference between the reflectance of the polarizing element in the absorption axis direction and the reflectance of the polarizing element in the transmission axis direction is 10% or more. The polarizing plate according to any one of claims 1 to 4, wherein the single-unit transmittance of the polarizing element is 43.0% to 46.0%.

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