HK1216671B

HK1216671B - Achromatic polarization element, and polarization plate

Info

Publication number: HK1216671B
Application number: HK16104688.1A
Authority: HK
Inventors: 望月典明
Original assignee: 日本化药株式会社; 宝来技术有限公司
Priority date: 2013-04-03
Filing date: 2013-12-04
Publication date: 2018-06-29

Abstract

[Problem] To provide a highly-transmissive polarization plate that can express achromatic white when a polarization element is arranged parallel to an absorbing axis, and achromatic black when the polarization element is arranged orthogonal to the absorbing axis. [Solution] a* and b* values, which define the hue of a polarization element or a polarization plate using JISoZo8729, are adjusted such that the absolute value of the a* and b* values is: less than 1 during a single-body transmittance measurement; less than 2 when two sheets of a base material are arranged parallel to the absorbing axis direction and the a* and b* values are measured; and less than 2 when two sheets of the base material are arranged orthogonal to the absorbing axis direction and the a* and b* values are measured.

Description

Achromatic polarizing element and polarizing plate

Technical Field

The present invention relates to a dye-based polarizing element or polarizing plate.

Background

The polarizing element is generally manufactured by adsorbing and aligning iodine or a dichroic dye as a dichroic dye onto a polyvinyl alcohol resin film. A protective film made of triacetyl cellulose or the like is attached to at least one surface of the polarizing element via an adhesive layer to form a polarizing plate, which is used in a liquid crystal display device or the like. A polarizing plate using iodine as a dichroic dye is called an iodine-based polarizing plate, and a polarizing plate using a dichroic dye as a dichroic dye is called a dye-based polarizing plate. Wherein the dye-based polarizing plate has the following characteristics: has high heat resistance, high humidity and heat durability, high stability and high color selectivity brought by mixing; on the other hand, when a polarizing plate having the same degree of polarization is compared with an iodine-based polarizing plate, the dye-based polarizing plate has a problem of low transmittance, that is, low contrast. Therefore, a dye-based polarizing plate is desired to maintain high durability, have various color selectivities, have a higher transmittance, and have high polarization characteristics. However, even in the dye-based polarizing plate having such a variety of color selectivity, the polarizing element has been a polarizing element which exhibits a yellow color when it is disposed parallel to the absorption axis to display white. When a polarizing plate in which the yellow color in the parallel arrangement is suppressed is manufactured in order to improve the yellow color in the parallel arrangement, there is a problem that black appears blue when the polarizing element is arranged along an axis orthogonal to the absorption axis. Therefore, a polarizing plate that exhibits achromatic white in white display and achromatic black in black display is required as a polarizing element, but there has been no polarizing element or polarizing plate that exhibits an achromatic white in white display and an achromatic black in black display, with a monolithic transmittance of 35% or more.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4281261

Patent document 2: japanese patent No. 3357803

Non-patent document

Non-patent document 1: application of functional pigment, 1 st printing release, CMC publication, Jiangyanghao, P98-100

Disclosure of Invention

Problems to be solved by the invention

As a method for improving the color tone of the polarizing plate, a technique as in patent document 1 or patent document 2 is disclosed. Patent document 1 discloses a polarizing plate in which a neutral point is calculated and an absolute value thereof is 0 to 3, but it is understood from the examples that even if the neutral point (Np) is low, a is a value of-2 to-1 and b is a value of 2.5 to 4.0, because the color is only the color of the parallel bits determined in JIS-Z-8729, it is recognized that the polarizing plate exhibits yellowish green when white is displayed. In addition, regarding the color tone of the cross bits, the value of a is 0 to 1, but the value of b is-1.5 to-4.0, so the polarizing plate presents blue. Patent document 2 discloses a polarizing element prepared by adding a direct dye, a reactive dye or an acid dye in addition to iodine to the average value of ± 30% of the transmittance of 410nm to 750nm, but the polarizing element is a polarizing element in which the absolute values of the values of a and b in the UCS color space are within 2 for the color when the single-sheet transmittance measurement is performed, that is, when the measurement is performed using only 1 polarizing element, and the color tone is not expressed as achromatic color at the same time when white display is performed using 2 polarizing plates (in the case of being parallel) and when black display is performed (in the case of being orthogonal). In addition, as is clear from the examples, since the single-sheet transmittance is 31.95% in example 1 and 31.41% in example 2, and the transmittance is low, the polarizer having sufficient performance with a higher transmittance and a high degree of polarization is not used in the field where a high transmittance and a high contrast are required, particularly in the field of a liquid crystal display device, an organic electroluminescence, and the like.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have newly found that: a polarizing element comprising a base material containing iodine and a dichroic dye as an azo compound, having a single-chip transmittance of 35% or more, characterized in that, regarding a value a and b value obtained according to JIS-Z-8729, a value a and b value in absolute value of 1 or less in single sheet transmittance measurement, a value a and b value obtained by measuring 2 sheets of the base material in parallel with the absorption axis direction of the 2 sheets of the base material are 2 or less in absolute value, a value a and b value obtained by measuring 2 sheets of the base material in orthogonal to the absorption axis direction of the 2 sheets of the base material are 2 or less in absolute value, the polarizing element has high transmittance, and can express achromatic white when the absorption axes of the polarizing elements are arranged in parallel and achromatic black when the absorption axes of the polarizing elements are arranged orthogonally.

Namely, the present invention relates to:

"(1) A polarizing element comprising a base material having a polarizing function and containing iodine and an azo compound, wherein,

regarding a value a and a value b of the color tone obtained according to JIS Z8729, the value a and the value b of the single sheet transmittance measurement are within 1 in absolute value, the value a and the value b obtained by measuring 2 sheets of the base material in parallel with the absorption axis direction of the 2 sheets are within 2 in absolute value, and the value a and the value b obtained by measuring 2 sheets of the base material in orthogonal to the absorption axis direction of the 2 sheets are within 2 in absolute value; and is

The single-chip transmittance is 35% or more.

(2) The polarizing element according to (1), wherein the degree of polarization is 99% or more.

(3) The polarizing element according to (1) or (2),

when the polarized light with the vibration direction of the absolute polarized light being the direction orthogonal to the absorption axis direction of the substrate polarizing element is irradiated, regarding the transmittance of each wavelength, the difference between the average transmittance of 550nm to 600nm and the average transmittance of 400nm to 460nm is within 4%, and the difference between the average transmittance of 600nm to 670nm and the average transmittance of 550nm to 600nm is within 3%; when the polarized light is irradiated in the direction parallel to the absorption axis direction of the base material polarizing element, the difference between the average transmittance of 550nm to 600nm and the average transmittance of 400nm to 460nm is within 1%, and the difference between the average transmittance of 600nm to 670nm and the average transmittance of 550nm to 600nm is within 1%, with respect to the transmittance of each wavelength.

(4) The polarizing element according to any one of (1) to (3), wherein the azo compound contains the azo compound represented by formula (1) and the azo compound represented by formula (2) in the form of a free acid; or an azo compound represented by the formula (1) and an azo compound represented by the formula (3).

[ solution 1]

(A₁Represents a substituted phenyl or naphthyl group, R₁～R₄Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo groupOr lower alkoxy having a sulfo group, X₁Represents an amino group with or without a substituent, a benzoylamino group with or without a substituent, a phenylamino group with or without a substituent, or a phenylazo group with or without a substituent, k represents an integer of 0 or 1, and X represents an integer of 1₁Represents a benzoylamino group with or without a substituent).

[ solution 2]

(A₂Represents a substituted phenyl or naphthyl group, R₅Represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, X₂Represents a hydrogen atom, a lower alkyl group or a lower alkoxy group).

[ solution 3]

(A₃Represents a substituted phenyl group, R₆～R₉Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, R₁₀And R₁₁Each independently represents a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group or a substituted amino group. Wherein R is₆～R₉Not satisfying the condition that all are lower alkoxy at the same time).

(5) The polarizing element according to (4), wherein X in the formula (1)₁Represented by formula (4).

[ solution 4]

(R₁₂Represents a hydrogen atom, a methyl group, a methoxy group, a sulfo group or an amino group).

(6) The polarizing element according to (4), wherein X in the formula (1)₁Represented by formula (5).

[ solution 5]

(R₁₃Represents a hydrogen atom, a methyl group, a methoxy group, a sulfo group, or an amino group. )

(7) The polarizing element according to any one of (4) to (6), wherein R of formula (2)₅Is methyl or methoxy.

(8) The polarizing element according to any one of (4) to (7), wherein A in the formula (2)₂Is naphthyl with substituent.

(9) The polarizing element according to (8), wherein X of the formula (2)₂Is hydrogen atom, methyl or methoxyl.

(10) The polarizing element according to any one of (4) to (6), wherein R of formula (3)₈And R₉At least 1 of which is methoxy.

(11) The polarizing element according to any one of (4) to (6) or (11), wherein R of formula (3)₆And R₇At least 1 of which is methoxy.

(12) The polarizing element according to any one of claims (1) to (11), wherein the base material is formed of a polyvinyl alcohol resin film.

(13) The polarizing plate according to any one of (1) to (12), wherein the polarizing plate is formed by providing a support film on at least one surface of the polarizing element.

(14) A liquid crystal display device using the polarizing element or the polarizing plate "according to any one of (1) to (13).

ADVANTAGEOUS EFFECTS OF INVENTION

The polarizing element of the present invention has high transmittance, and can express achromatic white when the absorption axes of the polarizing elements are arranged in parallel and achromatic black when the absorption axes of the polarizing elements are arranged orthogonally.

Detailed Description

A polarizing element of the present invention is a polarizing element comprising a base material containing iodine and a dichroic dye composed of an azo compound, wherein, regarding a value a and a value b of a color tone obtained in accordance with JIS Z8729, the value a and the value b in the case of measuring a single sheet of the base material are within 1 in absolute value, the value a and the value b in the case of measuring 2 sheets of the base material in parallel with the absorption axis direction of the 2 sheets of the base material are within 2 in absolute value, and the value a and the value b in the case of measuring 2 sheets of the base material in orthogonal to the absorption axis direction of the 2 sheets of the base material are within 2 in absolute value; and a monolithic transmittance of 35% or more. The method for representing object colors defined in JIS Z8729 corresponds to the method for representing object colors defined in the international commission on illumination (CIE for short). The single-plate transmittance is a transmittance when the transmittance of 1-plate (single-plate) polarizing element is measured when the polarizing element is irradiated with natural light, and the value of a (hereinafter, referred to as a) and the value of b (hereinafter, referred to as a) need to be within 1 in absolute value for the color tone when the single-plate transmittance is measured. Further, when natural light is incident, the a value (hereinafter, referred to as a-p) and the b value (hereinafter, referred to as b-p) obtained by measuring 2 substrates with the absorption axis directions of 2 substrates being parallel are within 2 in absolute value, and when natural light is incident, the a value (hereinafter, referred to as a-c) and the b value (hereinafter, referred to as b-c) obtained by measuring 2 substrates with the absorption axis directions of 2 substrates being orthogonal are within 2 in absolute value, whereby a polarizing plate capable of expressing an achromatic color can be realized. More preferably, the absolute values of a-p and b-p are within 1.5, and the absolute values of a-c and b-c are within 1.5, still more preferably, the absolute values of a-p and b-p are within 1.0, and the absolute values of a-c and b-c are within 1.0. Regarding the absolute values of a-p and b-p, even if the absolute values have a difference of only 0.5, the difference in color can be perceived as human perceptibility, and therefore, it is very important to control the numbers. In particular, if the absolute values of a-p and b-p are within 1, a good polarizing plate can be formed in which the appearance of color is not substantially recognized when the color is substantially white or substantially black.

As the performance of the polarizing plate, high transmittance and high polarization degree are required, and if the single-sheet transmittance is 35%, brightness can be exhibited even when the polarizing plate is used in a display device, and the single-sheet transmittance is preferably 38% or more, more preferably 39% or more, and further preferably 40% or more. A polarizing function is exhibited as a display device when the degree of polarization is 99% or more, but a polarizing plate having a higher contrast is recently required, and thus a polarizing plate having a degree of polarization of more preferably 99.9% or more, and further preferably 99.95% or more is required.

In order to produce a polarizing element, can contain iodine and dichroic dyestuffs formed by azo compound in the substrate, the characteristic of this polarizing element lies in, regarding a value and b value measured according to JIS-Z-8729, a value and b value when the single sheet transmittance is measured are within 1 in terms of absolute value, make 2 pieces of this substrate absorb the axle direction and measure 2 pieces of this substrate and a value and b value that are within 2 in terms of absolute value that 2 pieces of this substrate absorb the axle direction and measure 2 pieces of this substrate orthogonally and obtain a value and b value in terms of absolute value are within 2; and a monolithic transmittance of 35% or more.

The base material is obtained by forming a film of a material composed of a hydrophilic polymer that may contain iodine or a dichroic dye that is an azo compound. The hydrophilic polymer is not particularly limited, and examples thereof include polyvinyl alcohol resins, amylose resins, starch resins, cellulose resins, and polyacrylate resins. When the dichroic dye is contained, a resin composed of a polyvinyl alcohol resin and a derivative thereof is most preferable in terms of processability, dyeability, crosslinkability, and the like. These resins are formed into a film shape, and the dye and the complex thereof of the present invention are incorporated, and orientation treatment such as stretching is applied, whereby a polarizing element or a polarizing plate can be produced.

As the dichroic dye composed of an azo compound, for example, an organic compound shown in non-patent document 1 can be used. Particularly preferred are dichroic dyes with high dichroism. Examples thereof include C.I. direct yellow 12, C.I. direct yellow 28, C.I. direct yellow 44, C.I. direct orange 26, C.I. direct orange 39, C.I. direct orange 107, C.I. direct red 2, C.I. direct red 31, C.I. direct red 79, C.I. direct red 81, C.I. direct red 247, C.I. direct green 80, C.I. direct green 59, and organic dyes described in Japanese patent laid-open Nos. 2001-33627, 2002-296417 and 60-156759. These organic dyes may be used in the form of alkali metal salts (e.g., Na salts, K salts, Li salts), ammonium salts, or salts of amines, in addition to the free acids. However, the dichroic dye is not limited to these, and known dichroic dyes can be used. The optical properties can be particularly improved by using a free acid, a salt thereof, or a copper complex salt dye thereof as the azo compound. The azo compound may be used alone or in combination with other azo compounds, and the combination is not limited. By adjusting the transmittance of the polarizing element using such dichroic dyes, a polarizing element having the following characteristics can be realized: regarding a value a and b value obtained according to JIS-Z-8729, a value a and b value in the single sheet transmittance measurement are within 1 in absolute value, a value a and b value obtained by measuring 2 sheets of the base material with the absorption axis direction of the 2 sheets of the base material being parallel are within 2 in absolute value, and a value a and b value obtained by measuring 2 sheets of the base material with the absorption axis direction of the 2 sheets of the base material being orthogonal are within 2 in absolute value; and a monolithic transmittance of 35% or more.

This polarizing element can be realized by controlling the transmittance at each wavelength, and has the following characteristics: regarding a value a and b value obtained according to JIS-Z-8729, a value a and b value in the single sheet transmittance measurement are within 1 in absolute value, a value a and b value obtained by measuring 2 sheets of the base material with the absorption axis direction of the 2 sheets of the base material being parallel are within 2 in absolute value, and a value a and b value obtained by measuring 2 sheets of the base material with the absorption axis direction of the 2 sheets of the base material being orthogonal are within 2 in absolute value; and a monolithic transmittance of 35% or more. As a control method, it can be realized by: when the polarized light with the vibration direction of basically 100 percent polarized light (hereinafter referred to as absolute polarized light) is irradiated in the direction orthogonal to the absorption axis direction of a substrate (a polarizing element), the difference between the average transmittance of 550 nm-600 nm and the average transmittance of 400 nm-460 nm is controlled within 4 percent, the difference between the average transmittance of 600 nm-670 nm and the average transmittance of 550 nm-600 nm is controlled within 3 percent, the difference between the average transmittance of 550 nm-600 nm and the average transmittance of 400 nm-460 nm is controlled within 1 percent, and the difference between the average transmittance of 600 nm-670 nm and the average transmittance of 550 nm-600 nm is controlled within 1 percent when the polarized light with the vibration direction of absolute polarized light parallel to the absorption axis direction of the substrate polarizing element is irradiated. Preferably, when the absolute polarized light is irradiated with polarized light in a direction orthogonal to the absorption axis direction of the substrate (polarizing element), the transmittance of each wavelength is controlled so that the difference between the average transmittance of 550nm to 600nm and the average transmittance of 400nm to 460nm is within 3.5%, and the difference between the average transmittance of 600nm to 670nm and the average transmittance of 550 to 600nm is within 2.5%; more preferably, when the substrate (polarizing element) is irradiated with polarized light having an absolute polarization vibration direction perpendicular to the absorption axis direction of the substrate, the transmittance of each wavelength is controlled so that the difference between the average transmittance of 550nm to 600nm and the average transmittance of 400nm to 460nm is within 3.0%, and the difference between the average transmittance of 600nm to 670nm and the average transmittance of 550 to 600nm is within 2.0%.

As a useful dye which is used in combination with iodine and can control each wavelength, a dichroic dye containing an azo compound represented by formula (1) in the form of a free acid and further containing an azo compound represented by formula (2) or an azo compound represented by formula (3) in addition thereto can realize a polarizing plate having a high transmittance and a high degree of polarization as well as a neutral color tone, and the useful dye can control each wavelength in the following manner: regarding the a value and b value obtained according to JIS-Z-8729, the a value and b value in the single sheet transmittance measurement are within 1 in absolute value, the a value and b value obtained by measuring 2 sheets of the base material with the absorption axis direction of the 2 sheets being parallel are within 2 in absolute value, and the a value and b value obtained by measuring 2 sheets of the base material with the absorption axis direction of the 2 sheets being orthogonal are within 2 in absolute value. That is, it can be achieved by using any combination of iodine and the azo compound represented by the formula (1) and the azo compound represented by the formula (2), or any combination of iodine and the azo compound represented by the formula (1) and the azo compound represented by the formula (3). In order to obtain a polarizing element of white and black with higher transmittance and achromatic color, a combination of iodine with the azo compound represented by formula (1) and the azo compound represented by formula (2) is preferable. In order to obtain not only a polarizing element of achromatic white and black with high transmittance but also a polarizing plate with high degree of polarization, a combination of iodine with the azo compound represented by formula (1) and the azo compound represented by formula (3) is preferable.

[ solution 6]

(A₁Represents a substituted phenyl or naphthyl group, R₁～R₄Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, X₁Represents an amino group with or without a substituent, a benzoylamino group with or without a substituent, or a phenylamino group with or without a substituent, a phenylazo group with or without a substituent, k represents an integer of 0 or 1, and X represents an integer of 1₁Is shown as havingOr a benzoylamino group having no substituent).

[ solution 7]

[ solution 8]

In order to produce a polarizing element having a high transmittance with a higher degree of polarization, X in the formula (1)₁Having the substituent represented by the formula (4), a polarizing element having further high performance can be obtained. As R₁、R₂Preferably a hydrogen atom or an amino group, more preferably an amino group. In particular, in the case where k is 1, X₁Represents a benzoylamino group which may or may not have a substituent, and as a preferable substituent, a hydrogen atom or an amino group is preferable, and particularly, an amino group is more preferable.

[ solution 9]

In order to produce a polarizing element which has high transmittance with a higher degree of polarization and further displays achromatic white and black, by using X of formula (1)₁Having the substituent represented by formula (5), a polarizing element having higher performance can be obtained. As R₁₃The hydrogen atom, methyl group and methoxy group are preferable, and the hydrogen atom is more preferable.

[ solution 10]

(R₁₃Each independently represents a hydrogen atom, a methyl group, a methoxy group, a sulfo group or an amino group).

The azo compound represented by the formula (1) can be produced by the methods described in Japanese patent application laid-open Nos. 2003-215338, 9-302250, 3881175, 4452237, 4662853 and the like, but the methods are not limited thereto.

R of an azo compound represented by the formula (2)₅Represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, and R is preferably R in order to further realize high transmittance, high polarization degree, and achromatic white and achromatic black₅Is methyl or methoxy.

A of an azo compound represented by the formula (2)₂Represents a substituted phenyl group or naphthyl group, and A is preferably A in order to further realize high transmittance, high degree of polarization, and achromatic white and achromatic black₅Is naphthyl with substituent.

X of an azo compound represented by the formula (2)₂Represents a hydrogen atom, a lower alkyl group or a lower alkoxy group. To further realize high permeabilityRefractive index, high degree of polarization, achromatic white and achromatic black, preferably X₂Is hydrogen atom or lower alkyl such as methyl, methoxy, etc.

The azo compound represented by the formula (2) can be produced, for example, by the method described in Japanese examined patent publication (Kokoku) No. 01-005623, but the method is not limited thereto.

A for azo compound represented by the formula (3)₃，A₃Represents a substituted phenyl group, and the substituent represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, a lower alkoxy group having a sulfo group, or a carbonyl group. Among these, sulfo, methyl, methoxy, and carbonyl groups are preferable as a preferable substituent for further realizing high transmittance, high polarization degree, and achromatic white and achromatic black. The number of the substituents may be 1, or may be 2 or more. When the substituent group has 2 or more substituents, a plurality of the same substituents may be present in a combination of the substituents, and the combination is not limited, and may have different substituents. For example, the group may be selected such that 1 substituent is a sulfo group and another 1 substituent is a carbonyl group.

R for an azo compound represented by the formula (3)₆～R₉，R₆～R₉Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, wherein R is preferably R in order to further realize high transmittance, high degree of polarization, and achromatic white and achromatic black₈And R₉At least one of which is methoxy. In addition, R is more preferable₆And R₇At least one of which is methoxy. Wherein, in R₆～R₉And all of them are lower alkoxy groups, it is not preferable because achromatic white and achromatic black cannot be expressed.

R for an azo compound represented by the formula (3)₁₀And R₁₁，R₁₀And R₁₁Each independently represents a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group or a substituted amino group, whereinFurther, it is preferable to realize a high transmittance, a high degree of polarization, and an achromatic white and achromatic black color, and R is₁₀And R₁₁At least one of them is a hydrogen atom, a methyl group or a methoxy group.

The azo compound represented by formula (3) can be produced, for example, by the methods described in japanese patent No. 2622748, japanese patent No. 4825135, WO2007/148757, and WO2009/142192a1, but is not limited to these methods.

Specific examples of the azo compound represented by the formula (1) include dyes described in c.i. direct red 81, c.i. direct red 117, c.i. direct red 127, japanese patent No. 3881175, japanese patent No. 4033443, japanese patent No. 4162334, japanese patent No. 4452237, and japanese patent No. 4662853.

A more specific example of the azo compound represented by formula (1) is shown below as a free acid.

[ Compound example 1]

[ solution 11]

[ Compound example 2]

[ solution 12]

[ Compound example 3]

[ solution 13]

[ Compound example 4]

[ solution 14]

[ Compound example 5]

[ solution 15]

[ Compound example 6]

[ solution 16]

[ Compound example 7]

[ solution 17]

[ Compound example 8]

[ solution 18]

[ Compound example 9]

[ solution 19]

[ Compound example 10]

[ solution 20]

[ Compound example 11]

[ solution 21]

[ Compound example 12]

[ solution 22]

[ Compound example 13]

[ solution 23]

[ Compound example 14]

[ solution 24]

[ Compound example 15]

[ solution 25]

[ Compound example 16]

[ solution 26]

Next, a more specific example of the azo compound represented by formula (2) is shown below as a free acid.

[ Compound example 17]

[ solution 27]

[ Compound example 18]

[ solution 28]

[ Compound example 19]

[ solution 29]

[ Compound example 20]

[ solution 30]

[ Compound example 21]

[ solution 31]

Next, a more specific example of the azo compound represented by formula (3) is shown below as a free acid.

[ Compound example 22]

[ solution 32]

[ Compound example 23]

[ solution 33]

[ Compound example 24]

[ chemical 34]

[ Compound example 25]

[ solution 35]

[ Compound example 26]

[ solution 36]

[ Compound example 27]

[ solution 37]

[ Compound example 28]

[ solution 38]

[ Compound example 29]

[ solution 39]

[ Compound example 30]

[ solution 40]

Hereinafter, a method for producing a specific polarizing element will be described with reference to a polyvinyl alcohol resin film as an example of the substrate. The method for producing the polyvinyl alcohol resin is not particularly limited, and the polyvinyl alcohol resin can be produced by a known method. The production method can be obtained by, for example, saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate which is a vinyl acetate homopolymer, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, and preferably 95 mol% or more. The polyvinyl alcohol resin may be further modified, and for example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The polymerization degree of the polyvinyl alcohol resin is a viscosity-average polymerization degree, and can be determined by a method known in the art. Usually about 1000 to 10000, and preferably about 1500 to 6000.

The film-formed product of the polyvinyl alcohol resin can be used as a green film. The method for forming the film of the polyvinyl alcohol resin is not particularly limited, and the film can be formed by a known method. In this case, glycerin, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, or the like may be contained as a plasticizer in the polyvinyl alcohol resin film. The amount of the plasticizer is 5 to 20% by weight, preferably 8 to 15% by weight. The film thickness of the green film formed of the polyvinyl alcohol resin is not particularly limited, and is, for example, about 5 to 150 μm, preferably about 10 to 100 μm.

Next, the green film obtained as described above is subjected to a swelling step. The swelling treatment is carried out by immersing the substrate in a solution at 20 to 50 ℃ for 30 seconds to 10 minutes. The solution is preferably water. The draw ratio is preferably adjusted to 1.00 to 1.50 times, and more preferably 1.10 to 1.35 times. When the time for producing the polarizing element film is shortened, swelling occurs also in the dyeing treatment of the dye, and therefore the swelling treatment can be omitted.

The swelling step is performed by immersing the polyvinyl alcohol resin film in a solution at 20 to 50 ℃ for 30 seconds to 10 minutes. The solution is preferably water. When the time for producing the polarizing element is shortened, swelling occurs also in the dyeing treatment of the dye, and therefore the swelling treatment may be omitted.

After the swelling step, a dyeing step is performed. In the dyeing step, dyeing can be performed using iodine and a dichroic dye as shown in non-patent document 1 and the like. The polyvinyl alcohol resin film may be impregnated with iodine, and a method of impregnating the polyvinyl alcohol resin film with iodine or an iodide dissolved in water is preferred. Examples of the iodide include potassium iodide, ammonium iodide, cobalt iodide, and zinc iodide, but are not limited to the iodide shown here. The iodine concentration is 0.0001 to 0.5 wt%, preferably 0.001 to 0.4 wt%, and the iodide concentration is preferably 0.0001 to 8 wt%. The azo compound described in non-patent document 1 or the azo compound represented by formula (1), formula (2), or formula (3) can be used to adsorb a dye to a polyvinyl alcohol film through a dyeing step. In the dyeing step, there is no particular limitation as long as the dichroic dye is adsorbed on the polyvinyl alcohol film, and for example, the dyeing step may be performed by immersing the polyvinyl alcohol resin film in a solution containing the dichroic dye. The solution temperature in this step is preferably 5 to 60 ℃, more preferably 20 to 50 ℃, and particularly preferably 35 to 50 ℃. The time for immersion in the solution may be appropriately adjusted, and is preferably adjusted to 30 seconds to 20 minutes, and more preferably 1 to 10 minutes. The dyeing method is preferably a method of immersing in the solution, but may be performed by coating the solution on a polyvinyl alcohol resin film. The solution containing the dichroic pigment may contain sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate, or the like as a dyeing auxiliary. The content of these can be adjusted at any concentration depending on the time and temperature depending on the dyeing property of the dichroic dye, and the content is preferably 0 to 5% by weight, more preferably 0.1 to 2% by weight. The film may be treated simultaneously in the order of containing iodine and the azo compound, but from the viewpoint of management of a dyeing solution, productivity, and the like, a dyeing method in which the film is further containing an azo compound after containing iodine is preferred, or a method in which the film is further containing iodine after containing an azo compound is more preferred. The azo compound described in non-patent document 1 as a dichroic dye may be used in the form of a free acid, or may be a salt of the compound. Such salts may be used in the form of alkali metal salts such as lithium salts, sodium salts, and potassium salts, or organic salts such as ammonium salts and alkylamine salts. Sodium salts are preferred.

After the dyeing step, a washing step (hereinafter referred to as washing step 1) may be performed before proceeding to the next step. The cleaning step 1 is a step of cleaning the dye solvent adhering to the surface of the polyvinyl alcohol resin film in the dyeing step. By performing the washing step 1, the dye can be inhibited from transferring into a solution to be subsequently treated. In the cleaning step 1, water is generally used. The cleaning method is preferably a method of immersing in the solution, but cleaning may also be performed by applying the solution to a polyvinyl alcohol resin film. The time for cleaning is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the solvent in the cleaning step 1 needs to be a temperature at which the hydrophilic polymer is not dissolved. The cleaning treatment is usually carried out at 5 to 40 ℃. However, even if the step of the cleaning step 1 is not performed, there is no problem in terms of performance, and therefore, this step may be omitted.

After the dyeing step or the washing step 1, a step of incorporating a crosslinking agent and/or a water-resistant agent into the film may be performed. Examples of the crosslinking agent include boric acid, boron compounds such as borax and ammonium borate, polyaldehydes such as glyoxal and glutaraldehyde, polyisocyanate compounds such as biuret type, isocyanurate type and blocked type, titanium compounds such as titanyl sulfate, and the like, and ethylene glycol glycidyl ether and polyamide epichlorohydrin may be used. Examples of the water-resistant agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride, and magnesium chloride, and boric acid is preferably used. The step of incorporating the crosslinking agent and/or the water-resistant agent into the film is performed using at least one of the crosslinking agent and/or the water-resistant agent described above. The solvent in this case is preferably water, but is not limited thereto. In the step of incorporating the crosslinking agent and/or the water-resistant agent into the film, the concentration of the crosslinking agent and/or the water-resistant agent in the solvent is preferably 0.1 to 6.0 wt%, more preferably 1.0 to 4.0 wt% with respect to the solvent, as exemplified by boric acid. The temperature of the solvent in this step is preferably 5 to 70 ℃ and more preferably 5 to 50 ℃. The method of incorporating the crosslinking agent and/or the water-resistant agent into the polyvinyl alcohol resin film is preferably a method of immersing in the solution, but the solution may be coated or coated on the polyvinyl alcohol resin film. The treatment time in this step is preferably 30 seconds to 6 minutes, and more preferably 1 to 5 minutes. However, the crosslinking agent and/or the water-resistant agent are not necessarily contained, and when the time is desired to be shortened or the crosslinking treatment or the water-resistant treatment is not required, the treatment step can be omitted.

The stretching step is performed after the dyeing step, the washing step 1, or the step of adding a crosslinking agent and/or a water-resistant agent to the film. The stretching step is a step of uniaxially stretching the polyvinyl alcohol film. The stretching method may be either a wet stretching method or a dry stretching method, and the present invention can be realized by stretching at a stretching ratio of 3 times or more. The stretching ratio may be 3 times or more, and preferably 5 to 7 times.

In the case of the dry stretching method, when the stretching heating medium is an air medium, the stretching is preferably performed at room temperature to 180 ℃. The treatment is preferably carried out in an atmosphere having a humidity of 20 to 95% RH. Examples of the heating method include an inter-roll stretching method, a roll heating stretching method, a pressure stretching method, an infrared heating stretching method, and the like, and the stretching method is not limited. The stretching step may be performed by 1-step stretching, or may be performed by a multi-step stretching of 2 or more steps.

In the case of the wet stretching method, stretching is performed in water, a water-soluble organic solvent, or a mixed solution thereof. The stretching treatment is preferably performed while dipping in a solution containing a crosslinking agent and/or a water-resistant agent. Examples of the crosslinking agent include boric acid, boron compounds such as borax and ammonium borate, polyaldehydes such as glyoxal and glutaraldehyde, polyisocyanate compounds such as biuret type, isocyanurate type and blocked type, titanium compounds such as titanyl sulfate, and the like, and ethylene glycol glycidyl ether and polyamide epichlorohydrin may be used. Examples of the water-resistant agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride, and magnesium chloride. The stretching is performed in a solution containing at least one of the above-mentioned crosslinking agents and/or water-resistant agents. The crosslinking agent is preferably boric acid. The concentration of the crosslinking agent and/or the water-resistant agent in the stretching step is, for example, preferably 0.5 to 15 wt%, more preferably 2.0 to 8.0 wt%. The stretching ratio is preferably 2 to 8 times, and more preferably 5 to 7 times. The treatment is preferably carried out at a stretching temperature of 40 to 60 ℃, more preferably 45 to 58 ℃. The stretching time is usually 30 seconds to 20 minutes, and more preferably 2 to 5 minutes. The wet stretching step may be performed by 1-step stretching, or may be performed by a multi-step stretching of 2 or more steps.

After the stretching step, a cross-linking agent and/or a water-resistant agent may be deposited on the film surface or foreign matter may be deposited thereon, and therefore a cleaning step (hereinafter referred to as cleaning step 2) of cleaning the film surface may be performed. The washing time is preferably 1 second to 5 minutes. The cleaning method is preferably a method of dipping in a cleaning solution, but cleaning may also be performed by coating or applying the solution onto a polyvinyl alcohol resin film. The cleaning treatment may be performed in 1 step, or a multi-step treatment including 2 or more steps may be performed. The temperature of the solution in the cleaning step is not particularly limited, but is usually 5 to 50 ℃ and preferably 10 to 40 ℃.

Examples of the solvent used in the treatment step include, but are not limited to, water, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropanol, glycerol, alcohols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. In addition, a mixture of 1 or more of these solvents may also be used. The most preferred solvent is water.

After the stretching step or the cleaning step 2, a film drying step is performed. The drying treatment may be performed by natural drying, but in order to further improve the drying efficiency, compression may be performed by a roller, water on the surface may be removed by an air knife, a water suction roller, or the like, and/or air drying may be performed. The drying temperature is preferably 20 to 100 ℃, and more preferably 60 to 100 ℃. The drying time may be 30 seconds to 20 minutes, preferably 5 to 10 minutes.

The above method can provide a polarizing element comprising a substrate containing a dichroic dye composed of an azo compound, and having a single-sheet transmittance of 35% or more and a degree of polarization of 99% or more, wherein the values of a and b measured in single-sheet transmittance measurement are within 1 in absolute value, the values of a and b measured in 2 sheets of the substrate in parallel with the absorption axis direction of the 2 sheets of the substrate are within 2 in absolute value, and the values of a and b measured in 2 sheets of the substrate in orthogonal to the absorption axis direction of the 2 sheets of the substrate are within 2 in absolute value, with respect to the values of a and b measured in JIS-Z-8729.

A transparent protective layer is provided on one side or both sides of the obtained polarizing element, thereby producing a polarizing plate. The transparent protective layer may be provided in the form of a coating layer formed of a polymer, or in the form of a laminate of films. As the transparent polymer or film forming the transparent protective layer, a transparent polymer or film having high mechanical strength and good thermal stability is preferable. Examples of the substance used as the transparent protective layer include cellulose acetate resins such as triacetylcellulose and diacetylcellulose or films thereof, acrylic resins or films thereof, polyvinyl chloride resins or films thereof, nylon resins or films thereof, polyester resins or films thereof, polyarylate resins or films thereof, cyclic polyolefin resins or films thereof containing cyclic olefins such as norbornene as monomers, polyethylene, polypropylene, polyolefins having cyclic rings or norbornene skeletons or copolymers thereof, and resins or polymers or films thereof having imide and/or amide in the main chain or side chain. In addition, a resin having liquid crystallinity or a film thereof may be provided as the transparent protective layer. The thickness of the protective film is, for example, about 0.5 μm to 200 μm. A polarizing plate was produced by providing 1 or more layers of the same or different resins or films among the above on one side or both sides.

In order to bond the transparent protective layer to the polarizing element, an adhesive is required. The adhesive is not particularly limited, and a polyvinyl alcohol adhesive is preferred. Examples of the polyvinyl alcohol adhesive include, but are not limited to, Gohsenol NH-26 (manufactured by Nippon Synthesis Co., Ltd.) and Exceval RS-2117 (manufactured by KURAAY Co., Ltd.). The adhesive may contain a crosslinking agent and/or a water-resistant agent. The polyvinyl alcohol adhesive may be a maleic anhydride-isobutylene copolymer, and an adhesive mixed with a crosslinking agent may be used as needed. Examples of the maleic anhydride-isobutylene copolymer include Isobam #18 (manufactured by KURARAY corporation), Isobam #04 (manufactured by KURARAY corporation), ammonia-modified Isobam #104 (manufactured by KURARAY corporation), ammonia-modified Isobam #110 (manufactured by KURARAY corporation), imidized Isobam #304 (manufactured by KURARAY corporation), and imidized Isobam #310 (manufactured by KURARAY corporation). In this case, a water-soluble polyepoxy compound may be used as the crosslinking agent. Examples of the water-soluble polyepoxy compound include Denacol EX-521 (manufactured by Nagase ChemteX) and TETRAD-C (manufactured by Mitsui gas chemical Co., Ltd.). As the adhesive other than the polyvinyl alcohol resin, known adhesives such as urethane, acrylic, and epoxy adhesives can be used. In addition, in order to improve the adhesion of the adhesive or improve the water resistance, additives such as zinc compounds, chlorides and iodides may be added at a concentration of about 0.1 to 10 wt%. The additive is not limited. The transparent protective layer is bonded with an adhesive, and then dried or heat-treated at an appropriate temperature, thereby obtaining a polarizing plate.

The obtained polarizing plate may be provided with various functional layers for improving a viewing angle and/or improving a contrast, or a layer or film having a luminance improving property on the surface of a protective layer or film which is not exposed later, depending on the case, for example, when the polarizing plate is bonded to a display device such as a liquid crystal display or an organic electroluminescence display. When the polarizing plate is attached to these films or a display device, an adhesive is preferably used.

The other surface of the polarizing plate, that is, the exposed surface of the protective layer or the film may have various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer. In the production of the layers having various functionalities, a coating method is preferred, but the functional film may be bonded via an adhesive or a pressure-sensitive adhesive. In addition, the various functional layers may be layers or films that control phase difference.

As described above, the polarizing element and the polarizing plate having a single-sheet transmittance of 35% or more, characterized in that the a value and the b value at the time of measuring the single-sheet transmittance are within 1 in absolute value, the a value and the b value obtained by measuring 2 sheets of the base material with the absorption axis direction of 2 sheets of the base material being parallel are within 2 in absolute value, and the a value and the b value obtained by measuring 2 sheets of the base material with the absorption axis direction of 2 sheets of the base material being orthogonal are within 2 in absolute value, can be obtained. A liquid crystal display device using the polarizing element or the polarizing plate of the present invention has high reliability, high contrast for a long period of time, and high color reproducibility.

The polarizing element or polarizing plate of the present invention thus obtained can be used for liquid crystal projectors, calculators, clocks, notebook computers, word processors, liquid crystal televisions, polarizing lenses, polarizing glasses, satellite navigation, indoor and outdoor meters, displays, and the like, provided with a protective layer, a functional layer, a support, and the like as necessary. In particular, the polarizing plate is useful as a polarizing element or a polarizing plate effective in a reflective liquid crystal display device, a semi-transmissive liquid crystal display device, an organic electroluminescence device, and the like.

As a method of applying the polarizing plate of the present invention, it can be used in the form of a polarizing plate with a support. The support preferably has a flat surface portion because a polarizing plate is bonded thereto, and is preferably a glass molded product because of optical use. Examples of the glass molded article include a glass plate, a lens, and a prism (e.g., a triangular prism and a cubic prism). A lens obtained by attaching a polarizing plate to a lens can be used as a capacitor lens with a polarizing plate in a liquid crystal projector. In addition, a prism in which a polarizing plate is attached to a prism can be used as a polarizing beam splitter prism with a polarizing plate or a dichroic prism with a polarizing plate in a liquid crystal projector. Alternatively, the liquid crystal cell may be pasted. Examples of the material of the glass include inorganic glass such as an inorganic base made of soda glass, borosilicate glass, or crystal, an inorganic base made of sapphire, and an organic plastic plate such as acrylic or polycarbonate, and inorganic glass is preferable. The thickness and size of the glass sheet may be the desired size. In the polarizing plate with glass, in order to further improve the single-sheet light transmittance, an AR layer is preferably provided on one or both of the glass surface and the polarizing plate surface. On such a support, for example, a transparent adhesive (pressure-sensitive adhesive) is applied to the planar surface of the support, and then the polarizing plate of the present invention is bonded to the applied surface. Alternatively, a transparent adhesive (pressure-sensitive adhesive) may be applied to the polarizing plate, and then a support may be attached to the applied surface. The adhesive (bonding agent) used herein is preferably an acrylate-based adhesive (bonding agent), for example. When the polarizing plate is used as an elliptically polarizing plate, the phase difference plate side is usually bonded to the support side, but the polarizing plate side may be bonded to the glass molded article.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The transmittance was evaluated as follows in the examples.

The transmittance when 1 polarizing element or polarizing plate was measured was regarded as the transmittance Ts, the transmittance when 2 polarizing elements or polarizing plates were superimposed so that the directions of their absorption axes were the same was regarded as the parallel-bit transmittance Tp, and the transmittance when 2 polarizing plates were superimposed so that their absorption axes were orthogonal was regarded as the orthogonal-bit transmittance Tc.

The monolithic transmittance Ys is calculated by obtaining the spectral transmittance τ λ at predetermined wavelength intervals d λ (10 nm in this case) in a wavelength region of 400nm to 700nm and calculating the monolithic transmittance Ys by the following equation (6). In the formula, P λ represents a spectral distribution of standard light (C light source), and y λ represents a 2-degree field color matching function.

[ number 1]

Formula (6)

The spectral transmittance τ λ was measured using a spectrophotometer ("U-4100" manufactured by Hitachi Ltd.).

The polarization degree Py is obtained from the parallel-bit transmittance Tp and the orthogonal-bit transmittance Tc by equation (7).

[ number 2]

ρ y { (Tp-Tc)/(Tp + Tc) }1/2 × 100 formula (7)

Further, the transmittance when the sample was irradiated with absolute polarized light was measured using a spectrophotometer ("U-4100" manufactured by Hitachi Ltd.). In the measurement of the transmittance, an iodine-based polarizing plate (SKN-18043P manufactured by Polatechno) having a transmittance of 43% and a degree of polarization of 99.99% after the correction of the visual sensitivity based on JIS Z8729 (C light source 2 ° field) was provided on the light-emitting side so that the absolute polarized light can be incident on the measurement sample. The protective layer of the iodine-based polarizer in this case was triacetyl cellulose having no ultraviolet absorption ability.

An absolute polarized light is incident on the polarizing plate of the present invention, the absolute parallel transmittance at each wavelength measured so that the vibration direction of the absolute polarized light is orthogonal to the absorption axis direction of the polarizing plate of the present invention (the absorption axis of the absolute polarizer is parallel to the absorption axis of the polarizing plate of the present invention) is represented by Ky, the absolute orthogonal transmittance at each wavelength measured so that the vibration direction of the absolute polarized light is parallel to the absorption axis direction of the polarizing plate of the present invention (the absorption axis of the absolute polarizer is orthogonal to the absorption axis of the polarizing plate of the present invention) is represented by Kz, and K at each wavelength is measured_yAnd Kz.

Example 1

A polyvinyl alcohol film (VF-PS manufactured by KURARAAY) having an average polymerization degree of 2400 and a saponification degree of 99% or more was immersed in 45 ℃ hot water for 2 minutes, and subjected to swelling treatment to obtain a stretching ratio of 1.30 times. The membrane after the swelling treatment was immersed in an aqueous solution containing 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 0.2 part by weight of c.i. direct red 81 having a structure of formula (1), 0.27 part by weight of jp 64-5623 example 1 having a structure of formula (2) and adjusted to 45 ℃ for 3 minutes and 30 seconds, and the obtained membrane was immersed in an aqueous solution containing 28.6g/l of boric acid (manufactured by Societa chimaerellos. p. a. company), 0.25g/l of iodine (manufactured by genuine chemical company), 17.7g/l of potassium iodide (manufactured by genuine chemical company) and 1.0g/l of ammonium iodide (manufactured by genuine chemical company) at 30 ℃ for 2 minutes to perform iodine/iodide treatment. The dyed film was stretched 5.0 times and simultaneously subjected to stretching treatment in an aqueous solution containing 30.0g/l of boric acid at 50 ℃ for 5 minutes. The film obtained after the boric acid treatment was treated for 20 seconds while maintaining the film in a stretched state in an aqueous solution in which potassium iodide was adjusted to 20g/l and maintaining the temperature at 30 ℃. The film obtained by the treatment was dried at 70 ℃ for 9 minutes to obtain a polarizing element of the present invention. The polarizing element obtained after drying was laminated with an alkali-treated triacetyl cellulose film (TD-80U manufactured by fuji film corporation) using a polyvinyl alcohol adhesive to obtain a polarizing plate.

The obtained polarizing plate was cut into 40mm × 40mm, and bonded to a 1mm glass plate with an adhesive PTR-3000 (manufactured by Nippon chemical Co., Ltd.) to prepare a measurement sample.

Example 2

A polarizing element and a polarizing plate were produced in the same manner as in example 1 except that 0.2 part by weight of c.i. direct red 81 described in example 1 was replaced with 0.2 part by weight of c.i. direct red 117 as an azo compound having a structure of formula (1).

Example 3

A polarizing element and a polarizing plate were produced in the same manner as in example 1 except that 0.2 part by weight of c.i. direct red 81 described in example 1 was replaced with 0.14 part by weight of the dye having the structure of formula (1) described in example 1 of japanese patent No. 4033443.

Example 4

A polarizing element and a polarizing plate were produced in the same manner as in example 1 except that 0.2 part by weight of c.i. direct red 81 described in example 1 was replaced with 0.18 part by weight of the dye having the structure of formula (1) described in synthetic example 1 of japanese patent No. 4162334.

Example 5

A polarizing element and a polarizing plate were produced in the same manner as in example 3 except that 0.27 part by weight of example 1 of Japanese patent publication Sho 64-5623 having the structure of formula (2) used in example 3 was replaced with 0.3 part by weight of the azo compound having the structure of formula (2) described in example 4 of Japanese patent publication Sho 64-5623.

Example 6

A polarizing element and a polarizing plate were produced in the same manner as in example 3 except that 0.27 part by weight of example 1 of japanese kokokoku publication No. s 64-5623 having the structure of formula (2) used in example 3 was replaced with 0.3 part by weight of the azo compound having the structure of formula (3) described in example 1 of japanese patent No. 2622748.

Example 7

A polarizing element and a polarizing plate were prepared in the same manner as in example 3 except that the polyvinyl alcohol film having an average polymerization degree of 2400 (VF-XS manufactured by KURARAAY corporation) having a saponification degree of 99% or more was replaced with the polyvinyl alcohol film having an average polymerization degree of 4000 (VF-XH manufactured by KURAAY corporation).

Comparative example 1

A measurement sample was prepared in the same manner as in example 1, except that an iodine-based polarizing plate containing no azo compound was prepared according to the formulation of comparative example 1 of jp 2008 a-065222 a.

Comparative example 2

A polarizing plate was produced as a measurement sample in the same manner as in example 1, except that a polarizing element containing only an azo compound was produced by the method of example 1 in jp-a-11-218611 a, which is a neutral color polarizing film.

Comparative example 3

A polarizing plate was produced as a measurement sample in the same manner as in example 1, except that a dye-based polarizing element containing only an azo compound was produced by the method of example 3 of japanese patent No. 4162334.

Comparative example 4

A neutral color super contrast polarizing plate SHC-125 manufactured by Polatechno corporation was obtained and measured.

The measurement results of Ys, ρ y, a-s, b-s, a-p, b-p, a-c, and b-c in examples 1 to 7 and comparative examples 1 to 4 are shown in table 1.

[ Table 1]

Table 2 shows the average transmittance at 400nm to 460nm, the average transmittance at 550nm to 600nm, the average transmittance at 600nm to 670nm, the absolute value of the difference between the average transmittance at 400nm to 460nm and the average transmittance at 550nm to 600nm, and the absolute value of the difference between the average transmittance at 550nm to 600nm and the average transmittance at 600nm to 670nm when absolute polarized light is incident in examples 1 to 7 and comparative examples 1 to 4.

[ Table 2]

As is clear from the measurement results of Ys, ρ y, a-s, b-s, a-p, b-p, a-c, and b-c in examples 1 to 7 and comparative examples 1 to 4 of table 1, the polarizing plate of the present invention provides a polarizing element or a polarizing plate having a single-sheet transmittance of 35% or more, wherein a value a and a value b are within 1 in absolute value, and a value a and a value b obtained by measuring 2 sheets of the base material in parallel to the absorption axis direction of the 2 sheets of the base material are within 2 in absolute value, and a value a and a value b obtained by measuring 2 sheets of the base material in orthogonal to the absorption axis direction of the 2 sheets of the base material are within 2 in absolute value; by obtaining the polarizing element or the polarizing plate, it is understood that achromatic white and black are displayed in each of the cases of the white display in the parallel position and the black display in the orthogonal position. Further, it is found that the present invention has a transmittance higher than that of the polarizing plate having an average transmittance of about 31 to 32% as described in example 1 or 2 of Japanese patent No. 3357803 even when the average transmittance is 410 to 750 nm. When the average transmittance exceeds 40%, the L value also exceeds 70. This shows that a very good polarizing element is obtained. When the transmittance of each wavelength was confirmed, the polarizing plate of the present invention was: when the polarized light with the vibration direction of the absolute polarized light being the direction orthogonal to the absorption axis direction of the substrate polarizing element is irradiated, the difference between the average transmittance of 550nm to 600nm and the average transmittance of 400nm to 460nm is within 4%, the difference between the average transmittance of 600nm to 670nm and the average transmittance of 550nm to 600nm is within 3% with respect to the transmittance of each wavelength, and when the polarized light with the vibration direction of the absolute polarized light being the direction parallel to the absorption axis direction of the substrate polarizing element is irradiated, the difference between the average transmittance of 550nm to 600nm and the average transmittance of 400nm to 460nm is within 1% with respect to the transmittance of each wavelength, and the difference between the average transmittance of 600nm to 670nm and the average transmittance of 550nm to 600nm is within 1%. The polarizing plate thus obtained has high transmittance, and can express achromatic white when the absorption axes of the polarizing elements are arranged in parallel and achromatic black when the absorption axes of the polarizing elements are arranged orthogonally. In addition, a liquid crystal display device using the polarizing element or the polarizing plate of the present invention has high luminance, high contrast, high reliability, high contrast for a long period of time, and high color reproducibility.

Claims

1. A polarizing element comprising a base material having a polarizing function and containing iodine and an azo compound, characterized in that,

The monolithic transmittance measured in a wavelength region of 400nm to 700nm is 35% or more.

2. The polarizing element according to claim 1, wherein the degree of polarization is 99% or more.

3. The polarizing element according to claim 1 or 2,

when the polarized light with the vibration direction of the absolute polarized light being the direction orthogonal to the absorption axis direction of the substrate polarizing element is irradiated, regarding the transmittance of each wavelength, the difference between the average transmittance of 550nm to 600nm and the average transmittance of 400nm to 460nm is within 4%, and the difference between the average transmittance of 600nm to 670nm and the average transmittance of 550nm to 600nm is within 3%; and is

When the polarized light is irradiated in the direction parallel to the absorption axis direction of the base material polarizing element, the difference between the average transmittance of 550nm to 600nm and the average transmittance of 400nm to 460nm is within 1%, and the difference between the average transmittance of 600nm to 670nm and the average transmittance of 550nm to 600nm is within 1%, with respect to the transmittance of each wavelength.

4. The polarizing element according to claim 1, wherein the azo compound contains the azo compound represented by formula (1) and the azo compound represented by formula (2) in the form of a free acid; or an azo compound represented by the formula (1) and an azo compound represented by the formula (3),

[ solution 1]

A₁Represents a substituted phenyl or naphthyl group, R₁～R₄Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, X₁Represents an amino group with or without a substituent, with or withoutA substituted benzoylamino group, a substituted or unsubstituted phenylamino group, or a substituted or unsubstituted phenylazo group, k represents an integer of 0 or 1, and X represents an integer of 1₁Represents a benzoylamino group with or without a substituent,

[ solution 2]

A₂Represents a substituted phenyl or naphthyl group, R₅Represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, X₂Represents a hydrogen atom, a lower alkyl group or a lower alkoxy group,

[ solution 3]

A₃Represents a substituted phenyl group, R₆～R₉Each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, R₁₀And R₁₁Each independently represents a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group or a substituted amino group, wherein R₆～R₉The condition that all are lower alkoxy at the same time is not satisfied.

5. The polarizing element according to claim 4, wherein X of formula (1)₁Is represented by the formula (4),

[ solution 4]

R₁₂Represents a hydrogen atom, a methyl group, a methoxy group, a sulfo group or an amino group.

6. The polarizing element of claim 4, which isCharacterized in that X of formula (1)₁Is represented by the formula (5),

[ solution 5]

R₁₃Represents a hydrogen atom, a methyl group, a methoxy group, a sulfo group or an amino group.

7. The polarizing element according to any one of claims 4 to 6, wherein R of formula (2)₅Is methyl or methoxy.

8. The polarizing element according to any one of claims 4 to 6, wherein A of formula (2)₂Is naphthyl with substituent.

9. The polarizing element of claim 8, wherein X of formula (2)₂Is hydrogen atom, methyl or methoxyl.

10. A polarizing element as claimed in any one of claims 4 to 6, characterized in that R of formula (3)₈And R₉At least 1 of which is methoxy.

11. A polarizing element as claimed in any one of claims 4 to 6, characterized in that R of formula (3)₆And R₇At least 1 of which is methoxy.

12. The polarizing element according to claim 1 or 2, wherein the base material is formed of a polyvinyl alcohol resin film.

13. A polarizing plate formed by providing a support film on at least one surface of the polarizing element according to any one of claims 1 to 12.

14. A liquid crystal display device using the polarizing element according to any one of claims 1 to 12 or the polarizing plate according to claim 13.