CN107430234B

CN107430234B - Polarizing element and polarizing plate

Info

Publication number: CN107430234B
Application number: CN201680014838.3A
Authority: CN
Inventors: 望月典明
Original assignee: Nippon Kayaku Co Ltd; Polatechno Co Ltd
Current assignee: Nippon Kayaku Co Ltd; Polatechno Co Ltd
Priority date: 2015-03-26
Filing date: 2016-03-08
Publication date: 2019-12-06
Anticipated expiration: 2036-03-08
Also published as: TW201700623A; TWI668275B; JPWO2016152498A1; KR20170131340A; HK1246402A1; JP6178539B2; CN107430234A; WO2016152498A1

Abstract

[ problem ] to provide a polarizing element which has high transmittance and high contrast, can express achromatic white when the absorption axes of the polarizing elements are arranged in parallel, and can express achromatic black when the absorption axes of the polarizing elements are arranged orthogonally. [ solution ] the color tone of a polarizing element or a polarizing plate is adjusted by blending iodine and an azo compound having a specific structure as follows: regarding the a value and b value specified in JIS Z8729, 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 two sheets of the base material in parallel to the absorption axis direction are within 2 in absolute value, and the a value and b value obtained by measuring two sheets of the base material orthogonally to the absorption axis direction are within 2 in absolute value.

Description

Polarizing element and polarizing plate

Technical Field

The present invention relates to a polarizing element and a polarizing plate made of iodine and an azo compound.

background

The polarizing element is generally manufactured by adsorbing iodine or a dichroic dye as a dichroic dye onto a polyvinyl alcohol resin film and aligning the same. 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 matching; on the other hand, the dye-based polarizing plate has a problem of low transmittance, i.e., low contrast, compared to the iodine-based polarizing plate having the same degree of polarization. Therefore, it is desired that the dye-based polarizing plate maintains high durability, has various color selectivities, and has high polarization characteristics at higher transmittance. However, even in such a dye-based polarizing plate having a variety of color selectivity, the conventional polarizing element exhibits a yellow hue when it is disposed parallel to the absorption axis and exhibits white color. When a polarizing plate in which the yellow tone in the parallel arrangement is suppressed is produced in order to improve the yellow tone in the parallel arrangement, the polarizing element has a problem that black appears blue when the polarizing element is arranged on an axis orthogonal to the absorption axis. In order to realize an achromatic polarizing plate, it is necessary to have a constant transmittance without wavelength dependency in both the parallel and orthogonal bits, but such a polarizing plate has not been obtained so far.

The reason why the colors are different between the parallel bits and the orthogonal bits is that: even if a dichroic dye is used for the polarizing element, the same wavelength dependence cannot be exhibited in the parallel and orthogonal positions, that is, dichroism is not constant, and transmittance at each wavelength is not constant.

Here, the wavelength dependence of the iodine-based polarizing plate will be described. In the case of using polyvinyl alcohol (hereinafter abbreviated as PVA) as a base material and iodine as a dichroic dye, it generally has absorption centered at 480nm and 600 nm. The absorption at 480nm is said to be due to the complex of polyiodide I3-with PVA and the absorption at 600nm is said to be due to the complex of polyiodide I5-with PVA. With respect to the degree of polarization based on each wavelength, the degree of polarization of the complex of polyiodide I5-with PVA was higher than that of the complex of polyiodide I3-with PVA. This causes the following phenomenon: that is, when the transmittance is constant at the orthogonal position of each wavelength, the transmittance at 600nm is higher than 480nm at the parallel position, and the parallel position is colored yellow. Conversely, when the transmittance is constant at the parallel position, the transmittance at 600nm is lower than 480nm at the orthogonal position, and therefore the orthogonal position is colored blue. Further, since there is no absorption mainly by 550nm, which is high in visibility, it is difficult to perform color control. That is, since the degree of polarization (dichroic ratio) of each wavelength is not constant, wavelength dependence occurs. In this regard, even if the polarizing plate is not an iodine-based polarizing plate, the wavelength dependency of the azo compound having dichroism is different between the parallel position and the orthogonal position, and a dye showing the same color tone in the parallel position and the orthogonal position is not generally present.

Heretofore, depending on the kind of a general azo compound having dichroism, there is also an azo compound in which the wavelength dependency such as yellow color at the parallel position and blue color at the orthogonal position is completely different between the orthogonal position and the parallel position. Further, since it is known that the sensitivity of light and shade provided to the human in the quadrature bit and the parallel bit is different from each other by the polarized light, if the color correction is required, the color correction is also required depending on the sensitivity. The transmittance at each wavelength cannot be achieved unless the transmittance is substantially constant at each position of the parallel bit and the orthogonal bit, and specifically, the transmittance must be a constant value and there is no transmittance dependency at each wavelength. In addition, in the polarizing element or the polarizing plate, if the constant transmittance dependency must be satisfied at the parallel position and the orthogonal position at the same time, and further, if the transmittance and the contrast ratio must be high, the degree of polarization (dichroic ratio) of each wavelength must be constant. Even when only 1 type of azo compound is applied to the polarizing element, the wavelength dependence is different between the orthogonal position and the parallel position, and when the composition is mixed, the relationship between the transmittance and the dichroic ratio of each of the 1 type of parallel position and orthogonal position is not precisely controlled, and the degree of polarization is not high, the achromatic polarizing plate of the present application cannot be realized. It is thus difficult to obtain an achromatic polarizer, which is not achieved by simply applying the three primary colors of color. To control the parallel bit and the orthogonal bit to be constant, it is extremely difficult to make the polarization degrees of the respective wavelengths the same.

therefore, as the polarizing element, a polarizing plate which exhibits achromatic white in white display and achromatic black in black display is required, but it has been difficult to obtain a polarizing element or a polarizing plate which exhibits achromatic white in white display and 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 (application of functional pigment) No. 1 print release edition, published by CMC, Jiangyanghao main, p98-100

Disclosure of Invention

Problems to be solved by the invention

As a method for improving the color tone of the polarizing plate, techniques such as patent document 1 and patent document 2 are disclosed. Patent document 1 discloses a polarizing plate having a calculated neutral coefficient and an absolute value of 0 to 3, and it is understood from the examples that even if the neutral coefficient (Np) is low, the color tone of the parallel bits obtained in JIS Z8729 is only recognized, and a is-2 to-1 and b is 2.5 to 4.0, so that the polarizing plate exhibits yellowish green as a color when displayed in white. 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 that the polarizing plate shows 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, wherein the transmittance at 410nm to 750nm is within ± 30% of the average value. This polarizer is a polarizer in which the single-sheet transmittance, that is, the absolute values of the values of a and b in the UCS color space are within 2 for the color measured using only one polarizer, but the values of a and b cannot be represented within 2 at the same time for the color tones in white display (in the case of parallel) and black display (in the case of orthogonal) using two polarizing plates, and achromatic colors cannot be represented in the orthogonal and parallel positions. Further, it is found from the examination of examples that the monolithic transmittance is 31.95% in example 1 and 31.41% in example 2, and the transmittance is low, and therefore, in the field where high transmittance and high contrast are required, particularly in the field of liquid crystal display devices, organic electroluminescence and the like, it is not sufficient in terms of higher transmittance and higher degree of polarization.

The present inventors have conducted extensive studies to solve the above problems, and as a result, have newly found that, in order to maintain the relationship between the transmittance and the wavelength dependence of each of the parallel and orthogonal positions, and to maintain the relationship between the polarization (dichroic ratio) of the parallel and orthogonal positions at a high level and a high level of polarization even at a high transmittance, the polarization element can be realized by merely blending a specific azo compound, and as a result, the polarization element can realize a high contrast, exhibit a high transmittance and a high degree of polarization, and exhibit achromatic color at both the parallel and orthogonal positions. Namely, it was found that: a polarizer having a single-piece transmittance of 35% to 45% which is a substrate containing iodine and a specific azo compound, and which, with respect to a value a and a value b determined according to JIS Z8729, is capable of expressing an achromatic white color when the absorption axes of the polarizer are arranged in parallel and a value b and a value a and a value b when the single-piece transmittance is measured are within 1 in absolute value, and two pieces of the substrate measured in parallel to the direction of the absorption axis are within 2 in absolute value, and two pieces of the substrate measured orthogonally to the direction of the absorption axis are within 2 in absolute value, has a high transmittance and is capable of expressing an achromatic black color when the absorption axes of the polarizer are arranged in parallel and a value b when the absorption axes of the polarizer are arranged orthogonally.

Namely, the present invention relates to:

(1) A polarizing element comprising a base material containing iodine and an azo compound, characterized in that,

The azo compound is: a) a combination of an azo compound represented by formula (1) and an azo compound represented by formula (2); or b) a combination of the azo compound represented by the formula (1) and the compound represented by the azo compound represented by the formula (3), a salt thereof, or a transition metal complex thereof,

regarding the a value and b value obtained according to JIS Z8729, 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 two sheets of the base material in parallel to the absorption axis direction are within 2 in absolute value, the a value and b value obtained by measuring two sheets of the base material orthogonally to the absorption axis direction are within 2 in absolute value,

The single-chip transmittance is 35% -45%;

[ CHEM 1]

(A1 represents a substituted phenyl group or naphthyl group, R1 or R2 each 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, X1 represents an amino group with or without a substituent, a benzoylamino group with or without a substituent, an aminobenzoylamino group with or without a substituent, a phenylamino group with or without a substituent, a phenylazo group with or without a substituent.)

[ CHEM 2]

(wherein A2 and A3 each independently represent a phenyl group or a naphthyl group having a substituent in which at least 1 is a hydrogen atom, a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group or a substituted amino group, and R3 and R4 each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group.)

[ CHEM 3]

(wherein A4 represents a nitro group or an amino group, R9 represents a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, and X2 represents an amino group which may or may not have a substituent, a phenylamino group which may or may not have a substituent.)

(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), wherein regarding the transmittance at each wavelength when the polarized light in which the vibration direction of the absolute polarized light is orthogonal to the absorption axis direction of the polarizing element is irradiated, the difference between the average transmittance at 550nm to 600nm and the average transmittance at 400nm to 460nm is within 4%, and the difference between the average transmittance at 600nm to 670nm and the average transmittance at 550nm to 600nm is within 3%, and regarding the transmittance at each wavelength when the polarized light in which the vibration direction of the absolute polarized light is parallel to the absorption axis direction of the polarizing element, the difference between the average transmittance at 550nm to 600nm and the average transmittance at 400nm to 460nm is within 1%, and the difference between the average transmittance at 600nm to 670nm and the average transmittance at 550nm to 600nm is within 1%;

(4) The polarizing element according to any one of (1) to (3), wherein the base material is composed of a polyvinyl alcohol resin film; and

(5) A polarizing plate comprising the polarizing element of (1) to (4) and a support film provided on at least one surface of the polarizing element;

(6) A liquid crystal display device using the polarizing elements described in (1) to (4) or the polarizing plate described in claim 5.

ADVANTAGEOUS EFFECTS OF INVENTION

The polarizing element of the present invention can exhibit 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 while having high transmittance.

Detailed Description

In the present invention, the polarizing element is a polarizing element comprising a base material containing iodine and a dichroic dye, the dichroic dye being composed of a specific azo compound, wherein 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 two pieces of the base material in parallel to the absorption axis direction are within 2 in absolute value, the a value and the b value obtained by measuring two pieces of the base material orthogonally to the absorption axis direction are within 2 in absolute value, and the single-sheet transmittance is 35% to 45%. The method for displaying object colors defined in JIS Z8729 corresponds to the method for displaying object colors defined by the international commission on illumination (abbreviated as CIE). The monolithic transmittance indicates a transmittance when the transmittance of one sheet (monolithic) is measured when the polarizing element is irradiated with natural light, and in order to make the element achromatic, it is necessary to set the value of a (hereinafter, referred to as a-s) and the value of b (hereinafter, referred to as b-s) to be within 1 in absolute value for the color tone when the monolithic 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 the two substrates in parallel to the absorption axis direction 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 the two substrates in perpendicular to the absorption axis direction are within 2 in absolute value, whereby a polarizing plate capable of expressing an achromatic color in parallel 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. As the absolute values of a and b, even if there is a difference of only 0.5 in absolute value, the difference in color can be perceived as human sensitivity, and therefore, it is very important to control a and b. In particular, if the absolute values of the single-bit, parallel-bit, and orthogonal-bit are within 1 as the absolute values of a-p and b-p, respectively, a good polarizer is obtained in which color appearance is hardly recognized in white and black.

As the performance of the polarizing element, high transmittance and high polarization degree are required. When the single transmittance is 35%, the luminance can be exhibited even when used in a display device, but it is preferably 38% or more, more preferably 39% or more, and still more preferably 40% or more. A polarizing element having a polarization degree of 99% or more, which can exhibit a polarizing function as a display device, is required to have a polarizing plate with a higher contrast, and is more preferably 99.9% or more, and still more preferably 99.95% or more.

In order to produce a polarizing element having a single-piece transmittance of 35% or more (the polarizing element is characterized in that, with respect to the a value and the b value obtained according to JIS Z8729, the a value and the b value at the time of measuring the single-piece transmittance are within 1 in absolute value, the a value and the b value obtained by measuring two sheets of the base material in parallel to the absorption axis direction are within 2 in absolute value, and the a value and the b value obtained by measuring two sheets of the base material orthogonally to the absorption axis direction are within 2 in absolute value), the base material may be made to contain iodine and an azo compound of a specific combination described later. When iodine is contained, iodine alone may be difficult to dissolve in a solvent and difficult to impregnate a base material, and therefore, iodine compounds such as potassium iodide, copper iodide, sodium iodide, and calcium iodide, and chlorides such as sodium chloride, lithium chloride, and potassium chloride are generally used together.

The substrate is obtained by forming a film of a material composed of a hydrophilic polymer, and may contain iodine or various azo compounds described in non-patent document 1. 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, the polyvinyl alcohol resin and the resin composed of a derivative thereof are most preferable in terms of processability, dyeability, crosslinkability, and the like. The polarizing element or the polarizing plate can be produced by forming these resins into a film shape, incorporating the dye of the present invention and a compound thereof into the film, and applying an orientation treatment such as stretching.

The polarizing element of the present invention can be obtained by combining a) an azo compound represented by formula (1) and an azo compound represented by formula (2); or b) a combination of the azo compound represented by formula (1) and the compound represented by the azo compound represented by formula (3), a salt thereof, or a transition metal complex thereof, and iodine into a base material. Next, azo compounds represented by the formulae (1) to (3) will be described.

[ CHEM 4]

In the formula (1), a1 represents a substituted phenyl group or naphthyl group, R1 or R2 each 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, and X1 represents an amino group with or without a substituent, a benzoylamino group with or without a substituent, an aminobenzoylamino group with or without a substituent, a phenylamino group with or without a substituent, or a phenylazo group with or without a substituent. X1 is preferably 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, more preferably X1 is a phenylamino group with or without a substituent, and still more preferably a1 is a phenyl group with a substituent, in which case the polarizing element of the present application with a higher degree of polarization can be obtained, and therefore is preferable. In the present application, the lower alkyl group or lower alkoxy group represents a group having 1 to 3 carbon atoms.

In the formula (1), when a1 specifically represents a substituted phenyl group, examples of the substituent on the phenyl group in a1 include a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group, and a substituted amino group. A1 preferably has at least one sulfo group as substituent. In the case where the compound has two or more substituents, one of the substituents is a sulfo group or a carboxyl group, preferably a sulfo group, and the other substituent is preferably a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group, or a substituted amino group. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy terminal, and more preferably 3-sulfopropoxy or 4-sulfobutoxy. Examples of the substituted amino group include an acetylamino group and the like. Among the other substituents mentioned above, sulfo, lower alkyl or lower alkoxy is more preferable. The number of substituents on the phenyl group in a1 is preferably 1 or 2, the substitution position is not particularly limited, and a combination of the 2-position and the 4-position is preferred. When a1 represents a substituted naphthyl group, examples of the substituent of the naphthyl group represented by a1, which does not include a hydrogen atom, include a sulfo group, a hydroxyl group, an amino group, a substituted amino group, a nitro group, a substituted amide group, and an alkoxy group having a sulfo group and having 1 to 5 carbon atoms, and the sulfo group, the hydroxyl group, and the alkoxy group having a sulfo group and having 1 to 5 carbon atoms are preferred. The substituent in the naphthyl group represented by a1 preferably has at least one sulfo group. When the naphthyl group represented by a1 has two or more substituents, one of the substituents is preferably a sulfo group, and the other substituent is preferably at least one selected from the group consisting of a sulfo group, a hydroxyl group, and an alkoxy group having a sulfo group and having 1 to 5 carbon atoms. The alkoxy group having 1 to 5 carbon atoms and having a sulfo group is preferably a linear alkoxy group having 1 to 5 carbon atoms and having a sulfo group, more preferably a linear alkoxy group having 1 to 5 carbon atoms and having a sulfo group at the end of the alkoxy group, and further preferably a 3-sulfopropoxy group or a 4-sulfobutoxy group. As the naphthyl group represented by a1, preferred is a naphthyl group substituted by 2 or 3 sulfo groups; or a naphthyl group substituted by at least one group selected from the group consisting of a hydroxyl group, a 3-sulfopropoxy group and a 4-sulfobutoxy group and 1 or 2 sulfo groups, more preferably a naphthyl group substituted by 2 or 3 sulfo groups, or a naphthyl group substituted by a 3-sulfopropoxy group and a sulfo group. Further, in some cases, disulfobutylphenyl or trisulphobutylphenyl is more preferable, and trisulphobutylphenyl is most preferable. Regarding the preferred substitution positions of these substituents on the naphthalene ring, in the case of 2 substituents, 1-and 3-positions, and in the case of 3 substituents, 1-and 3-and 6-positions. The substitution position of the azo group in the naphthyl group is preferably the 2-position.

X1 specifically represents an amino group with or without a substituent, a benzoylamino group with or without a substituent, an aminobenzoylamino group with or without a substituent, a phenylamino group with or without a substituent, or a phenylazo group with or without a substituent. X1 may have a substituent, and in the case of benzoylamino, phenylamino or phenylazo, for example, the substituent is preferably lower alkyl, lower alkoxy, hydroxy, carboxy, sulfo, amino or substituted amino, and examples of the substituted amino group include acetylamino and the like. When X1 is a phenylamino group which may or may not have a substituent, the substituent is a methyl group, a methoxy group, an amino group, or a substituted amino group, preferably an acetylamino group or a sulfo group, more preferably a methyl group, a methoxy group, or an amino group. The number and substitution position of the substituent on the phenyl group are not particularly limited. The number of substituents is usually preferably 0 to 2, and when a substituent other than hydrogen is present, at least one substituent is preferably present in a para-position with respect to the bonding position with the amino group. Examples of the phenylamino group which may or may not have a substituent include a phenylamino group, a 4-methylphenylamino group, a 4-methoxyphenylamino group, a 4-aminophenylamino group, a 4-amino-2-sulfophenylamino group, a 4-amino-3-sulfophenylamino group, a 4-sulfomethylaminophenylamino group, a 4-carboxyethylaminophenylamino group and the like. Among these, unsubstituted phenylamino and p-methoxyphenylamino groups are more preferable. When X1 is a benzoylamino group which may or may not have a substituent, the substituent is a substituted amino group exemplified by an amino group and an acetylamino group, preferably a hydroxyl group, more preferably an amino group and a substituted amino group exemplified by an acetylamino group, and still more preferably an amino group. The number of the substituents on the phenyl group is usually 0 to 1, and the substitution position is not particularly limited, and when a substituent other than a hydrogen atom is present, the para-position is preferable. When X1 is a benzoylamino group, the substituent represents a hydrogen atom, a hydroxyl group, an amino group or a substituted amino group, and preferably a hydrogen atom, an amino group or a substituted amino group exemplified by acetylamino group. The position of the substituent is preferably the para position. Examples of the benzoylamino group include a benzoylamino group, a 4-aminobenzoylamino group, a 4-hydroxybenzoylamino group, a 4- (3-carboxy-1-oxopropylamino) benzoylamino group, and a 4- (2-carbomethoxy-1-oxoethylamino) benzoylamino group. Among the benzoylamino groups, aminobenzoylamino groups are more preferable. When X1 is a phenylazo group which may or may not have a substituent, examples of the substituent include a hydroxyl group, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group or a substituted amino group, preferably a hydroxyl group, an amino group, a methyl group, a methoxy group or a carboxyl group, and more preferably a hydroxyl group. The number of the substituents is usually 0 to 3, preferably 1 to 2. Examples of the phenylazo group include a 2-methylphenylazo group, a 3-methylphenylazo group, a2, 5-dimethylphenylazo group, a 3-methoxyphenylazo group, a 2-methoxy-5-methylphenylazo group, a2, 5-dimethoxyphenylazo group, a 4-aminophenylazo group, a 4-hydroxyphenylazo group, and a 4-carboxyethylaminophenylazo group, and preferably a 4-aminophenylazo group, a 4-hydroxyphenylazo group, and a 4-carboxyethylaminophenylazo group.

Next, formula (2) will be described.

[ CHEM 5]

In formula (2), a2 and A3 each independently represent a phenyl group or a naphthyl group having a substituent, at least 1 of which is a hydrogen atom, a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group or a substituted amino group, and R3 and R4 each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group. A2 and A3 are preferably each independently a naphthyl group, more preferably a2 and A3 are each a naphthyl group having a sulfo group, and further preferably R3 and R4 are each independently a lower alkoxy group, and in this case, the polarizing element of the present application having a higher degree of polarization can be obtained, and therefore, these are preferable.

Next, formula (3) will be described.

[ CHEM 6]

In the formula (3), a4 represents a nitro group or an amino group, R9 represents a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, and X2 represents an amino group having or not having a substituent, a phenylamino group having or not having a substituent. A4 is preferably a nitro group, and R9 is more preferably a lower alkoxy group, and in this case, the polarizing element of the present invention having a higher degree of polarization can be obtained, and therefore, is preferable. The azo compound of formula (3) may be in the form of a salt or a complex, and particularly, a transition metal complex which forms a complex with a metal such as copper is preferable for further improvement in performance.

As the azo compound, an azo compound as a color correction may be added to such an extent that the performance of the present application is not impaired. Particularly preferred are azo compounds having high dichroism. Examples thereof include: azo compounds shown in non-patent document 1, 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 azo compounds described in Japanese Kokoku publication Sho-64-5623, Japanese unexamined patent publication Hei-3-12606, Japanese unexamined patent publication Hei-2001 33627, Japanese unexamined patent publication Sho-2002-296417, and Japanese unexamined patent publication Sho-60-156759, and the like. In particular, an azo compound having a phenyl J acid in a trisazo structure can be suitably used, and particularly, an azo compound described in Japanese patent application laid-open No. 3-12606 is more preferably used in a polarizing element together with the azo compounds of formulae (1) to (3) of the present invention, and further, an azo compound described in an azo compound of Japanese patent application laid-open No. 3-12606 having a phenyl J acid in a trisazo structure is more preferably used in a polarizing element together with iodine of the present invention and the azo compound of formula (1) and the azo compound of formula (3). These azo compounds may be used in the form of an alkali metal salt (e.g., Na salt, K salt, Li salt), ammonium salt, or amine salt, in addition to the free acid. However, the azo compound is not limited thereto, and a known azo compound having dichroism may be used. By making the azo compound a free acid, a salt thereof or a copper complex salt dye thereof, particularly optical characteristics are improved. 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 a dye as an azo compound, a polarizing element having a single-piece transmittance of 35% to 45% can be realized, which is characterized in that the a value and the b value at the time of measuring the single-piece transmittance are within 1 in absolute value, the a value and the b value obtained by measuring two pieces of the base material in parallel to the absorption axis direction are within 2 in absolute value, and the a value and the b value obtained by measuring two pieces of the base material orthogonally to the absorption axis direction are within 2 in absolute value, with respect to the a value and the b value obtained by measuring the base material in parallel to the absorption axis direction according to JIS Z8729.

In order to obtain a polarizing element having a single-piece transmittance of 35% or more (the polarizing element is characterized in that, with respect to the a value and the b value obtained according to JIS Z8729, the a value and the b value at the time of measuring the single-piece transmittance are within 1 in absolute value, the a value and the b value obtained by measuring two sheets of the base material in parallel to the absorption axis direction are within 2 in absolute value, and the a value and the b value obtained by measuring two sheets of the base material orthogonally to the absorption axis direction are within 2 in absolute value), the transmittance of each wavelength is controlled, whereby the transmittance can be easily realized. As a control method, it can be easily realized by: the transmittance for each wavelength when polarized light with a vibration direction of approximately 100% polarized light (hereinafter referred to as absolute polarized light) is irradiated in a direction orthogonal to the absorption axis direction of a substrate (polarizing element) is controlled so that 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 the transmittance for each wavelength when polarized light with a vibration direction of absolute polarized light parallel to the absorption axis direction of the substrate polarizing element is irradiated is adjusted so that 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%.

More preferably, the transmittance of each wavelength when polarized light in which the vibration direction of absolute polarized light is orthogonal is irradiated 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 550nm to 600nm is within 2.5%, and still more preferably, the transmittance of each wavelength when polarized light in which the vibration direction of absolute polarized light is orthogonal is irradiated 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 550nm to 600nm is within 2.0%.

the azo compound represented by the formula (1) can be produced by, but is not limited to, the methods described in Japanese patent application laid-open Nos. 2003-215338, 9-302250, 3881175, and the like. Specific examples of the azo compound represented by formula (1) include c.i. direct red 81, c.i. direct red 117, c.i. direct red 127, azo compounds of formula (2) described in japanese patent No. 3881175, dyes of formula (1) described in japanese patent No. 4033443, and the like.

The azo compound represented by formula (2) can be obtained, for example, by the method described in WO2012/165223, but is not limited thereto.

Examples of the method for obtaining the azo compound represented by the formula (3) include, but are not limited to, the methods described in Japanese patent application laid-open Nos. 60-156759, 2-61988 and 2011-197600.

As the formula (1) represents the azo compounds more specific examples, show the following compound examples 1-1 ~ 1-15 (note, all in the free acid form).

[ Compound examples 1-1]

[ CHEM 7]

[ Compound examples 1-2]

[ CHEM 8]

[ Compound examples 1 to 3]

[ CHEM 9]

[ Compound examples 1 to 4]

[ CHEM 10]

[ Compound examples 1 to 5]

[ CHEM 11]

[ Compound examples 1 to 6]

[ CHEM 12]

[ Compound examples 1 to 7]

[ CHEM 13]

[ Compound examples 1 to 8]

[ CHEM 14]

[ Compound examples 1 to 9]

[ CHEM 15]

[ Compound examples 1 to 10]

[ CHEM 16 ]

[ Compound examples 1 to 11]

[ CHEM 17 ]

[ Compound examples 1 to 12]

[ CHEM 18 ]

[ Compound examples 1 to 13]

[ CHEM 19 ]

[ Compound examples 1 to 14]

[ CHEM 20 ]

[ Compound examples 1 to 15]

[ CHEM 21 ]

Next, as more specific examples of the azo compound represented by the formula (2), the following compound examples 2-1 to 2-5 (all represented as free acids) are shown.

[ Compound examples 2-1]

[ CHEM 22 ]

[ Compound examples 2-2]

[ CHEM 23 ]

[ Compound examples 2 to 3]

[ CHEM 24 ]

[ Compound examples 2 to 4]

[ CHEM 25 ]

[ Compound examples 2 to 5]

[ CHEM 26 ]

further, as more specific examples of the azo compound represented by the formula (3), the following compound examples 3-1 to 3-14 (all represented in the form of free acids) are shown.

[ Compound examples 3-1]

[ CHEM 27 ]

[ Compound examples 3-2]

[ CHEM 28 ]

[ Compound examples 3 to 3]

[ CHEM 29 ]

[ Compound examples 3 to 4]

[ CHEM 30 ]

[ Compound examples 3 to 5]

[ CHEM 31 ]

[ Compound examples 3 to 6]

[ CHEM 32 ]

[ Compound examples 3 to 7]

[ CHEM 33 ]

[ Compound examples 3 to 8]

[ CHEM 34 ]

[ Compound examples 3 to 9]

[ CHEM 35 ]

[ Compound examples 3 to 10]

[ CHEM 36 ]

[ Compound examples 3 to 11]

[ CHEM 37 ]

[ Compound examples 3 to 12]

[ CHEM 38 ]

[ Compound examples 3 to 13]

[ CHEM 39 ]

[ Compound examples 3 to 14]

[ CHEM 40 ]

Next, 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 homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of the other monomer copolymerizable with vinyl acetate include: unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and the like. The saponification degree of the polyvinyl alcohol resin is usually about 85 mol% 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 1,000 to 10,000, preferably about 1,500 to 6,000.

The polyvinyl alcohol resin film is formed into a film, and the film is used as a base film. The method for forming the film from 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 plasticizer is preferably from 5 to 20% by weight, more preferably from 8 to 15% by weight. The film thickness of the green film made 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 applied by dipping in a solution at 20 ℃ to 50 ℃ for 30 seconds to 10 minutes. The solution is preferably water. The draw ratio may be adjusted to 1.00 to 1.50 times, preferably 1.10 to 1.35 times. 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.

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 step can be omitted.

After the swelling step, a dyeing step is performed. In the dyeing step, the dyeing may be performed using iodine and azo compounds represented by formulae (1) to (3). The iodine may be impregnated into the polyvinyl alcohol resin film, and a method of impregnating the polyvinyl alcohol resin film with iodine or an iodide dissolved in water is preferable. Examples of the iodide include potassium iodide, ammonium iodide, cobalt iodide, zinc iodide, and the like, but are not limited to the iodide shown here. The iodine concentration is preferably 0.0001 to 0.5 wt%, more preferably 0.001 to 0.4 wt%, and the iodide concentration is preferably 0.0001 to 8 wt%. The dye described in non-patent document 1 or the azo compound represented by formula (1) to formula (3) may be a dye adsorbed to a polyvinyl alcohol film in the dyeing step. The dyeing step is not particularly limited as long as the dye is adsorbed to the polyvinyl alcohol film, and is performed by, for example, immersing the polyvinyl alcohol resin film in a solution containing a 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 can be appropriately adjusted, and is preferably adjusted to 30 seconds to 20 minutes, and more preferably 1 minute to 10 minutes. The dyeing method is preferably carried out by dipping in the solution, and may be carried out by coating the solution on a polyvinyl alcohol resin film. The solution containing the dichroic dye may contain sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate, etc. as a dyeing assistant. The content of these compounds can be adjusted at any concentration by time and temperature based on the dyeing property of the dye, and the content of each compound 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, and a method in which the film is further containing iodine after containing an azo compound is more preferred. The azo compound may be used in the form of a free acid or a salt thereof. 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 transfer of the dye into a liquid to be treated later can be suppressed. In the cleaning step 1, water is generally used. The cleaning method is preferably immersion in the solution, and cleaning may 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 washing step 1 needs to be a temperature at which the hydrophilic polymer is insoluble. The washing treatment is usually carried out at 5 to 40 ℃. However, since there is no problem in performance even if the step of the cleaning step 1 is not provided, this step can be omitted.

After the dyeing step or the washing step 1, a step of adding a crosslinking agent and/or a water-resistant agent to the film may be performed. As the crosslinking agent, for example: 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, and titanium compounds such as titanyl sulfate, and in addition, ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can 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, magnesium chloride, or the like, 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 used in this case is preferably water, but is not limited thereto. When the concentration of the crosslinking agent and/or the water-resistant agent in the solvent in the step of adding the crosslinking agent and/or the water-resistant agent to the film is represented by boric acid as an example, the concentration is preferably 0.1 to 6.0% by weight, more preferably 1.0 to 4.0% by weight, relative to the solvent. The temperature of the solvent in this step is preferably 5 to 70 ℃ and more preferably 5 to 50 ℃. The polyvinyl alcohol resin film is preferably impregnated with the solution by a method of containing a crosslinking agent and/or a water resistant agent, 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, more preferably 1 minute to 5 minutes. However, it is not essential to contain a crosslinking agent and/or a water-resistant agent in the film, and when the time is desired to be shortened or when the crosslinking treatment or the water-resistant treatment is not necessary, the treatment step may be omitted.

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 performed. 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 or more. The stretching ratio may be 3 times or more, 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 under the condition that the temperature of the air medium is from 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, but are not limited to, an inter-roll zone stretching method, a roll heating stretching method, a pressure stretching method, an infrared heating stretching method, and the like. The stretching step may be performed in 1 stage, or may be performed by multistage stretching in 2 or more stages.

In 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 being immersed 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, and titanium compounds such as titanyl sulfate, and in addition, glycidyl ether of ethylene glycol, polyamide epichlorohydrin, and the like can 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, magnesium chloride, or the like. Stretching is performed in a solution containing at least one of the crosslinking agents and/or the water-resistant agents described above. The crosslinking agent is preferably boric acid. The concentration of the crosslinking agent and/or the water resistance improver in the stretching step is, for example, preferably 0.5 to 15 wt%, more preferably 2.0 to 8.0 wt%. The stretch 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 ℃ and more preferably 45 to 58 ℃. The stretching time is usually 30 seconds to 20 minutes, and more preferably 2 minutes to 5 minutes. The wet stretching step may be performed in 1-stage stretching, or may be performed in 2-stage or more multistage stretching.

After the stretching step, there may be a case where a crosslinking agent and/or a water-resistant agent is precipitated on the film surface or foreign matter is adhered thereto, and therefore, a cleaning step (hereinafter referred to as a cleaning step 2) of cleaning the film surface can be performed. The washing time is preferably 1 second to 5 minutes. The cleaning method is preferably immersed 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 stage, or a multi-stage treatment in 2 or more stages may be performed. The temperature of the solution in the washing step is not particularly limited, but is usually 5 to 50 ℃ and preferably 10 to 40 ℃.

Examples of the solvent used in the treatment steps include: 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, the moisture on the surface may be removed by compression with a roller, an air knife, a water suction roller, or the like, and/or air-blast drying may be performed. The drying temperature is preferably 20 to 100 ℃ and more preferably 60 to 100 ℃. The drying treatment time may be 30 seconds to 20 minutes, preferably 5 minutes to 10 minutes.

The polarizing element is characterized in that the a value and the b value in the measurement of the single-sheet transmittance are within 1 in absolute value, the a value and the b value in the measurement of the two substrates in parallel to the absorption axis direction are within 2 in absolute value, and the a value and the b value in the measurement of the two substrates in the direction orthogonal to the absorption axis direction are within 2 in absolute value, with respect to the a value and the b value obtained by the measurement of the single-sheet transmittance according to JIS Z8729.

The polarizing plate is produced by providing a transparent protective layer on one side or both sides of the obtained polarizing element. 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 using cyclic olefins such as norbornene as a monomer, polyethylene, polypropylene, cyclic polyolefins or polyolefins having a norbornene skeleton or copolymers thereof, resins or polymers having imide and/or amide in the main chain or side chain, or films thereof. Further, as the transparent protective layer, a resin having liquid crystallinity or a film thereof may be provided. The thickness of the protective film is, for example, about 0.5 μm to 200 μm. The polarizing plate is produced by providing 1 or more layers of the same or different resins or films on one or both surfaces.

Among the above, an adhesive is required for bonding the transparent protective layer to the polarizing element. The adhesive is not particularly limited, and a polyvinyl alcohol adhesive is preferred. Examples of the polyvinyl alcohol adhesive include: gohsenol NH-26 (manufactured by Nippon synthetic Co., Ltd.), Exceval RS-2117 (manufactured by KURAAY Co., Ltd.), and the like, but the present invention is not limited thereto. The adhesive may contain a crosslinking agent and/or a water resistant agent. The polyvinyl alcohol adhesive is a mixture of a maleic anhydride-isobutylene copolymer and, if necessary, a crosslinking agent. Examples of the maleic anhydride-isobutylene copolymer include: isobam #18 (KuraRay), Isobam #04 (KuraRay), ammonia-modified Isobam #104 (KuraRay), ammonia-modified Isobam #110 (KuraRay), imidized Isobam #304 (KuraRay), imidized Isobam #310 (KuraRay), and the like. 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), Tetoratto-C (manufactured by Mitsui gas Chemicals) and the like. As the adhesive other than the polyvinyl alcohol resin, known adhesives such as urethane, acrylic, and epoxy adhesives may be used. In addition, in order to improve the adhesion of the adhesive or improve the water resistance, additives such as zinc compounds, chlorides, iodides, and the like may be added at a concentration of about 0.1 to 10 wt%. The additive is not limited. After the transparent protective layers are bonded to each other with an adhesive, the resulting laminate is dried or heat-treated at an appropriate temperature to obtain a polarizing plate.

When the obtained polarizing plate is bonded to a display device such as a liquid crystal display or an organic electroluminescence display in some cases, various functional layers for improving a viewing angle and/or improving a contrast, or a layer or a film having a luminance improving property may be provided on a surface of a protective layer or a film which is not exposed later. In order to attach the polarizing plate to these films or display devices, an adhesive is preferably used.

The polarizing plate may have various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer on the other surface, i.e., the exposed surface of the protective layer or the film. In order to produce the layers having various functionalities, a coating method is preferable, but a film having the functions may be attached by an adhesive or a bonding agent. In addition, various functional layers may be made into a layer or film that controls the phase difference.

The polarizing element and the polarizing plate having a single sheet transmittance of 35% to 45% can be obtained by the above method, wherein the a value and the b value at the time of measuring the single sheet transmittance are within 1 in terms of absolute value, the a value and the b value obtained by measuring two sheets of the base material in parallel to the absorption axis direction are within 2 in terms of absolute value, and the a value and the b value obtained by measuring two sheets of the base material orthogonally to the absorption axis direction are within 2 in terms of absolute value, with respect to the a value and the b value obtained by measuring the b value according to JIS Z8729. 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 is provided with a protective layer, a functional layer, a support, and the like as necessary, and is used for a liquid crystal projector, a calculator, a clock, a notebook computer, a word processor, a liquid crystal television, a polarizing lens, polarizing glasses, a car navigation system, an indoor/outdoor measurement instrument, a display instrument, and the like. In particular, the polarizing plate is used as an effective polarizing element or polarizing plate in a reflective liquid crystal display device, a semi-transmissive liquid crystal display device, organic electroluminescence, or 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. For attaching the polarizing plate, the support preferably has a flat surface portion, and is preferably a glass molded product for 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 liquid crystal projector in which a polarizing plate is attached to a lens can be used as a condenser lens with a polarizing plate. The prism with the polarizing plate attached thereto can be used as a polarizing beam splitter with a polarizing plate or a dichroic prism with a polarizing plate in a liquid crystal projector. Alternatively, the liquid crystal cell may be bonded thereto. Examples of the material of the glass include inorganic glass such as soda lime glass, borosilicate glass, an inorganic substrate made of crystal, an inorganic substrate made of sapphire, and the like, organic plastic plates such as acrylic resin, polycarbonate, and the like, and inorganic glass is preferable. The thickness and size of the glass sheet may be of desired dimensions. In addition, in order to further improve the single-sheet light transmittance, the glass-equipped polarizing plate is preferably provided with an AR layer on one or both of the glass surface and the polarizing plate surface thereof. On such a support, for example, a transparent adhesive (pressure-sensitive adhesive) is applied to the planar portion 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 here 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 with reference to the following examples, but the present invention is not limited to these examples. The transmittance was evaluated as follows in the examples.

The transmittance at each wavelength when measured with one polarizing element or polarizing plate is taken as transmittance Ts, the transmittance at each wavelength when two polarizing elements or polarizing plates are overlapped so that the absorption axis directions thereof are the same is taken as parallel-bit transmittance Tp, the transmittance at each wavelength when two polarizing plates are overlapped so that the absorption axes thereof are orthogonal is taken as orthogonal-bit transmittance Tc, the single transmittance corrected for visibility by the C light source 2 ° field color matching function is taken as Ys, the parallel transmittance after the visibility correction is taken as Yp, and the orthogonal transmittance after the visibility correction is taken as Yc, and the transmittance is measured at 5nm intervals with a spectrophotometer [ U-4100 "manufactured by hitachi corporation ], and the measurement values are calculated using the measured values. The color tone of the polarizing element or the polarizing plate was measured by a spectrophotometer U-4100 using a color system shown in JIS Z8729 (color representation methods L, a, b, and L, U, v). The "orthorhombic color tone" as used herein means a color tone exhibited when two polarizing plates are measured in a state where their absorption axes are orthogonal to each other, and the "parallel-phase color tone" means a color tone exhibited when two polarizing plates are measured in a state where their absorption axes are parallel to each other. In the L, a, b chromaticity system, the closer a, b are to zero, respectively, the more neutral the hue appears. In general, a positive value indicates a red hue, a negative value indicates a green hue, and b positive value indicates a yellow hue, and a negative value indicates a blue hue.

The polarization degree Py is obtained by the following equation using the parallel bit transmittance Yp after the visibility correction and the orthogonal bit transmittance Yc after the visibility correction.

Py＝{(Yp-Yc)/(Yp+Yc)}×100

Further, the transmittance when the sample was irradiated with absolute polarized light was measured by 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 visibility correction based on JIS Z8729 (C light source 2 ° field) was provided as an absolute polarizing plate on the light emission side, and the absolute polarized light was allowed to enter the measurement sample. The transmittance of the parallel bit and the orthogonal bit of the polarizing element of the present application when the absolute polarized light is incident is measured. The protective layer of SKN-18043P is triacetyl cellulose without UV absorbing ability.

The absolute parallel transmittance at each wavelength measured when the absolute polarized light is incident with the absorption axis of the polarizing plate of the present invention parallel to the absorption axis of the absolute polarizing plate is Ky, and the absolute orthogonal transmittance at each wavelength measured when the absolute polarized light is incident with the absorption axis of the polarizing plate of the present invention orthogonal to the absorption axis of the absolute polarizing plate is Kz, and Ky and Kz at each wavelength are measured.

Polarizing elements of the present invention were produced using a combination of the azo compound represented by the formula (1) and the azo compound represented by the formula (2), and the results are shown in examples 1 to 4.

example 1

A polyvinyl alcohol film having an average degree of polymerization of 2400 (VF-PS manufactured by KURARAAY corporation) having a degree of saponification of 99% or more was immersed in warm water at 45 ℃ for 2 minutes, and subjected to swelling treatment so that the draw ratio was 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, 810.1 parts by weight of c.i. direct red having a structure of formula (1), and 0.85 parts by weight of a dye shown in synthesis 2 of WO2012/165223 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 chimica polar dragello.p.a.), 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 contain iodine and iodide and then dyed. The dyed film was subjected to stretching treatment in an aqueous solution at 50 ℃ containing 30.0g/l of boric acid for 5 minutes while stretching the film 5.0 times. The film obtained after the boric acid treatment was treated for 20 seconds while maintaining the tension of the film in an aqueous solution adjusted to 20g/l of potassium iodide at 30 ℃. The film obtained by the treatment was dried at 70 ℃ for 9 minutes to obtain a polarizing element of the present invention.

Example 2

A polarizing element was prepared and a measurement sample was prepared in the same manner as in example 1 except that 0.07 part by weight of the azo compound described in Synthesis example 1 of Japanese patent No. 2003-215338 was used instead of 810.1 parts by weight of C.I. direct Red described in example 1.

Example 3

In example 2, a polarizing element was produced in the same manner as in the above example except that the time for containing the azo compound in the polyvinyl alcohol film was changed from 3 minutes 30 seconds to 3 minutes 00 seconds, and the film was immersed in an aqueous solution containing 28.6g/l of boric acid (manufactured by Societa chimica lardrello. p.a.), 0.25g/l of iodine (manufactured by Takeka chemical Co., Ltd.), 17.7g/l of potassium iodide (manufactured by Takeka chemical Co., Ltd.) and 1.0g/l of ammonium iodide (manufactured by Takeka chemical Co., Ltd.) at 30 ℃ for 1 minute 30 seconds to be dyed and to contain iodine and iodide, thereby obtaining a measurement sample.

Example 4

in example 2, a polarizing element was prepared in the same manner as the measurement sample except that 0.08 parts by weight of the azo compound described in example 1 of jp-a No. 3-12606 having a trisazo structure of a phenyl J acid was added to the azo compound containing an azo compound in the polyvinyl alcohol film, together with 0.07 parts by weight of the azo compound described in synthesis example 1 of japanese patent No. 2003-215338 having a structure of formula (1) and 0.85 parts by weight of the dye shown in synthesis 2 of WO2012/165223 having a structure of formula (2).

comparative example 1

An iodine-based polarizing element containing no dichroic dye was prepared according to the formulation of comparative example 1 of jp 2008 a-065222, and a measurement sample was prepared in the same manner as in example 1.

comparative example 2

A polarizing element was produced in the same manner as in example 1 except that a polarizing element containing only a dichroic dye was produced according to the method of example 1 of jp 11-218611 a, and a measurement sample was prepared.

Comparative example 3

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

Comparative example 4

A polarizing element was produced in the same manner as in example 1 except that a dye-based polarizing element containing only a dichroic dye was produced according to the method of example 1 of japanese patent No. 4360100, and a measurement sample was produced.

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

[ TABLE 2]

In addition, the polarizing element obtained by drying had no change in the optical properties even when a polarizing plate was produced by laminating an alkali-treated triacetyl cellulose film (TD-80U, manufactured by fuji photo film corporation) as a transparent protective layer with a polyvinyl alcohol adhesive. From this, it is also found that the polarizing plate obtained by using the polarizing element has the same performance.

Next, a polarizing element of the present invention was produced using a combination of the azo compound represented by the formula (1) and the azo compound represented by the formula (3), and the results are shown in examples 5 to 9.

Example 5

A polyvinyl alcohol film having an average degree of polymerization of 2400 (VF-PS manufactured by KURARAAY corporation) having a degree of saponification of 99% or more was immersed in warm water at 45 ℃ for 2 minutes, and subjected to swelling treatment so that the draw ratio was 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, 810.1 parts by weight of c.i. direct red having a structure of formula (1) and 0.135 parts by weight of a dye shown in example 3 of japanese examined patent publication No. 2-61988 having a structure of formula (3) 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 chimica polar gases.p.a), 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 contain iodine and iodide and then dyed. The dyed film was subjected to stretching treatment in an aqueous solution at 50 ℃ containing 30.0g/l of boric acid for 5 minutes while stretching the film 5.0 times. The film obtained after the boric acid treatment was treated for 20 seconds while maintaining the tension of the film in an aqueous solution adjusted to 20g/l of potassium iodide 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 by drying was laminated with an alkali-treated triacetyl cellulose film (TD-80U, manufactured by fuji film corporation) using a polyvinyl alcohol-based adhesive to obtain a polarizing plate. The obtained polarizing plate was cut into a size of 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 6

A polarizing element and a polarizing plate were prepared in the same manner as in example 5 except that the amount of C.I. direct red 810.1 was changed to 0.07 part by weight of the azo compound described in Synthesis example 1 of Japanese patent No. 2003-215338 having the structure of formula (1), and a measurement sample was prepared.

Example 7

In example 6, a polarizing element and a polarizing plate were prepared and a measurement sample was prepared in the same manner except that the time for containing the azo compound in the polyvinyl alcohol film was changed from 3 minutes 30 seconds to 3 minutes 00 seconds, and the film was immersed in an aqueous solution containing 28.6g/l of boric acid (manufactured by Societa chimica lardrellos. p.a.), 0.25g/l of iodine (manufactured by Takeka chemical Co., Ltd.), 17.7g/l of potassium iodide (manufactured by Takeka chemical Co., Ltd.) and 1.0g/l of ammonium iodide (manufactured by Takeka chemical Co., Ltd.) at 30 ℃ for 1 minute 30 seconds to be dyed and containing iodine and iodide.

Example 8

In example 6, a polarizing element and a polarizing plate were prepared in the same manner as in example 1 of Japanese patent application laid-open No. Hei 3-12606, except that 0.08 part by weight of the azo compound described in example 1 was added to the azo compound containing the azo compound in the polyvinyl alcohol film, together with 0.07 part by weight of the azo compound described in Synthesis example 1 of Japanese patent application laid-open No. 2003-215338 having the structure of formula (1) and 0.135 part by weight of the dye described in example 3 of Japanese examined patent publication No. Hei 2-61988 having the structure of formula (3), to prepare a measurement sample.

Example 9

A polarizing element and a polarizing plate were produced in the same manner as in example 6 except that 0.135 part by weight of the dye used in example 6 and having the structure of formula (3) in Japanese examined patent publication (Kokoku) No. 2-61988 was changed to 0.155 part by weight of the azo compound described in example 24 and having the structure of formula (3) in Japanese examined patent publication (Kokoku) No. 60-156759, and a measurement sample was prepared.

Comparative examples 5 to 8

Using the polarizing elements prepared in comparative examples 1 to 4, polarizing plates were prepared in the same manner as in example 5, and measurement samples were prepared.

The measurement results of Ys, ρ, a-s, b-s, a-p, b-p, a-c, and b-c in examples 5 to 9 and comparative examples 5 to 8 are shown in table 3.

[ TABLE 3]

Table 4 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 5 to 9 and comparative examples 5 to 8.

[ TABLE 4]

as is apparent from observation of the measurement results of Ys, ρ, a × s, b × s, a × p, b × p, a × c, and b × c in examples 1 to 4 and comparative examples 1 to 4 shown in table 1, and examples 5 to 9 and comparative examples 5 to 8 shown in table 3, the polarizing plate of the present invention is a polarizing element having a single sheet transmittance of 35% to 45%, and is characterized in that the a × value and b × value at the time of measuring the single sheet transmittance are within 1 in absolute value, the a × value and b × value obtained by measuring two sheets of the polarizing plate in parallel to the absorption axis direction are within 2 in absolute value, and the a × value and b × value obtained by measuring two sheets of the polarizing plate in perpendicular to the absorption axis direction are within 2 in absolute value, thereby obtaining a polarizing element or a polarizing element, in each case, white and black of an achromatic color are displayed in the white display of the parallel bit and the black display of the orthogonal bit. As for the average transmittance of 410nm to 750nm, it is found that the polarizing element and the polarizing plate of the present invention also have a transmittance higher than that of the polarizing plate of about 31% to 32% described in example 1 or 2 of japanese patent No. 3357803 (patent document 2) as a related art. When the average transmittance exceeds 40%, the value of L (L ×) also exceeds 70, and thus a very good polarizing element is obtained. It is said that a white color such as a high-quality paper can be realized by setting the color tone of the color medium to within ± 1.0 and L to more than 65, and L reaches 70, thereby obtaining a polarizing plate capable of realizing a high-quality white color such as a paper, that is, a so-called paper white color.

As shown in tables 2 and 4, when the transmittances at the respective wavelengths are compared, it is understood that the polarizing elements and polarizing plates of examples 1 to 9 are polarizing elements adjusted as follows: regarding the transmittance of each wavelength when the polarized light with the vibration direction of the absolute polarized light being 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%, and regarding the transmittance of each wavelength when the polarized light with the vibration direction of the absolute polarized light being parallel to the absorption axis direction of the substrate 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%. The polarizing plate obtained using the polarizing element can exhibit 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 while having high transmittance. Therefore, 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 containing iodine and an azo compound, characterized in that,

The single-chip transmissivity is 35-45%,

[ CHEM 1]

A1 represents a substituted phenyl group or naphthyl group, R1 or R2 each 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, X1 represents an amino group with or without a substituent, a benzoylamino group with or without a substituent, an aminobenzoylamino group with or without a substituent, a phenylamino group with or without a substituent, a phenylazo group with or without a substituent,

[ CHEM 2]

Wherein A2 and A3 each independently represent a phenyl group or a naphthyl group having a substituent, at least 1 of which is a hydrogen atom, a sulfo group, a lower alkyl group, a lower alkoxy group having a sulfo group, a carboxyl group, a nitro group, an amino group or a substituted amino group, R3 and R4 each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group,

[ CHEM 3]

Wherein A4 represents a nitro group or an amino group, R9 represents a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a sulfo group or a lower alkoxy group having a sulfo group, and X2 represents an amino group having or not having a substituent, a phenylamino group having or not having a substituent.

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,

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

Further, regarding the transmittance of each wavelength when polarized light having a vibration direction of absolute polarized light parallel to the absorption axis direction of the 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%, and the difference between the average transmittance of 600nm to 670nm and the average transmittance of 550nm to 600nm is within 1%.

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

5. The polarizing element according to claim 3, wherein the base material is a polyvinyl alcohol resin film.

6. A polarizing plate comprising the polarizing element according to any one of claims 1 to 5 and a transparent protective layer provided on at least one surface of the polarizing element.

7. A liquid crystal display device using the polarizing element according to any one of claims 1 to 5 or the polarizing plate according to claim 6.