JP6609260B2 - Polarizing element, polarizing plate having the polarizing element, and liquid crystal display device having the polarizing element or the polarizing plate - Google Patents

Description

  The present invention relates to a polarizing element, a polarizing plate having the polarizing element, and a liquid crystal display device having the polarizing element or the polarizing plate, and more particularly to an achromatic thin dye-based polarizing element.

  Generally, a polarizing element is manufactured by adsorbing and orienting iodine or dichroic dye, which is a dichroic dye, on a polyvinyl alcohol resin film or the like. In addition, this polarizing element is used in a liquid crystal display device or the like as a polarizing plate by attaching a protective film made of triacetyl cellulose or the like to at least one surface thereof through an adhesive layer.

  A polarizing plate using iodine as a dichroic dye is called an “iodine polarizing plate”, while a polarizing plate using a dichroic dye as a dichroic dye is called a “dye polarizing plate”. Among these, the dye-based polarizing plate is characterized by high heat resistance, high wet heat durability, high stability, and high color selectivity by blending. However, such a dye-based polarizing plate has a problem that the transmittance is low, that is, the contrast is low, as compared with an iodine-based polarizing plate having the same degree of polarization. Therefore, there has been a demand for a dye-based polarizing plate that maintains a high durability, has a variety of color selectivity, and has a higher transmittance and polarization characteristics.

  On the other hand, even with dye-based polarizing plates with various color selectivity, the conventional polarizing plates have two polarizing plates in which the absorption axis directions are parallel to each other (hereinafter simply referred to as “parallel position”). There is a problem that the white color exhibits a yellowish white color when it is arranged so as to be white (hereinafter simply referred to as “when white is displayed”). Moreover, in order to improve the problem that the white color is yellowish, even in the case of a polarizing plate made with a yellowish color suppressed, the conventional polarizing plates have two polarizing plates whose absorption axis directions are orthogonal to each other. When black is displayed (hereinafter sometimes simply referred to as “black display”) in a positional relationship (hereinafter sometimes simply referred to as “orthogonal position”), black is colored blue. There was a problem to do. For this reason, there has been a demand for a polarizing plate that exhibits an achromatic white color when displaying white and an achromatic black color when displaying black.

  However, since such a polarizing plate emphasizes white when displaying white and black when displaying black, the polarizing plate is particularly suitable for a display having a high transmittance and a high luminance, or a display having no backlight. When there was, there existed a problem that a double image generate | occur | produced in the glass with which the polarizing plate was bonded. For example, in the case of a reflective liquid crystal display, a polarizing plate is bonded to a glass cell enclosing liquid crystal, but when the thickness of the polarizing plate is about 180 μm, the display is viewed obliquely. A double image was generated in the display.

Japanese Patent No. 4281261 Japanese Patent No. 3357803

Application of functional dyes, 1st edition, CMC Publishing, supervised by Masahiro Irie, P98-100 Dye chemistry, Yutaka Hosoda, Gihodo

Incidentally, Patent Documents 1 and 2 disclose techniques relating to a method for improving the chromaticity of a polarizing plate.
However, although Patent Document 1 attempts to improve chromaticity, it cannot be said that each of the parallel position and the orthogonal position has sufficient chromaticity as an achromatic color.
Also, in Patent Document 2, the spectral transmittance at wavelengths of 410 nm to 750 nm is within ± 30% of the average value, and the polarization is adjusted by adding a direct dye, reactive dye or acid dye in addition to iodine. Although an element is disclosed, it has not been possible to achieve both achromatic colors in parallel and orthogonal positions. Further, the average value of the single transmittance is as low as 31.95% in the first embodiment and 31.41% in the second embodiment, and the fields where high transmittance and high contrast are required (for example, liquid crystal display devices, head-ups). In the field of displays, organic electroluminescence, etc.), the performance has not been satisfactory yet.

  On the other hand, the generation of a double image caused by the reflection of the display can be usually reduced by controlling the luminance and color light of the display by adjusting the transmittance and chromaticity of the polarizing element. However, in the case of a polarizing plate (that is, a polarizing plate with constant transmissivity in parallel and orthogonal positions) that can clearly express white in white display and black in black display, It was difficult to control the brightness of the display and the color light.

As a result of intensive studies to solve the above problems, the present inventor is a polarizing element comprising a base material containing an azo compound as a constituent component, and has a film thickness of 1 μm to 30 μm and a single transmittance of 35% to The absolute value of the chromaticity a ^* value and b ^* value determined at the time of measuring the transmittance of natural light in accordance with JIS Z 8781-4: 2013 is 1 or less for the polarizing element alone, and the polarizing element In a state where the two sheets are arranged so that the absorption axis directions thereof are parallel to each other, both are 2 or less, and in the state where the two polarizing elements are arranged so that the absorption axis directions thereof are orthogonal to each other, both are two. The polarizing element characterized by the following is capable of expressing achromatic white when displaying white and achromatic black when displaying black, even when the transmittance is high. For example, the polarizing plate has high transmittance and brightness. High display When used in a display that does not have a backlight, even if white at the time of white display and black at the time of black display are emphasized, it is possible to suppress the generation of a double image on the glass on which the polarizing plate is bonded. Newly found.

（式中、Ａ_１は置換基を有するフェニル基又はナフチル基を示し、Ｒ_１およびＲ_２は、各々独立に、水素原子、低級アルキル基、低級アルコキシ基、スルホ基、又はスルホ基を有する低級アルコキシ基を示し、Ｘ_１は置換基を有してもよいフェニルアミノ基を示す。）

（式中、Ｒ_３乃至Ｒ_６は、各々独立に、水素原子、低級アルキル基、低級アルコキシ基、スルホ基、スルホ基を有する低級アルコキシ基、カルボニル基、又はハロゲン原子を示す。）
［４］ 前記アゾ化合物は、前記式（１）に示される化合物又はその塩と、遊離酸の形式で下記式（３）に示される化合物又はその塩とを含む、上記［１］又は［２］に記載の偏光素子。

（式中、Ａ_２およびＡ_３は、各々独立に、置換基の少なくとも１つがスルホ基、低級アルキル基、低級アルコキシ基、スルホ基を有する低級アルコキシ基、カルボキシ基、ニトロ基、アミノ基若しくは置換アミノ基である、ナフチル基又はフェニル基を示し、Ｒ_７およびＲ_８は、各々独立に、水素原子、低級アルキル基、低級アルコキシ基、スルホ基、又はスルホ基を有する低級アルコキシ基を示す。）
［５］ 前記アゾ化合物は、前記式（１）に示される化合物又はその塩と、前記式（２）に示される化合物又はその塩と、前記式（３）に示される化合物又はその塩とを含む、上記［１］又は［２］に記載の偏光素子。
［６］ 前記アゾ化合物は、遊離酸の形式で下記式（４）に示される化合物、その塩又はその金属錯体を含む、上記［１］乃至［５］のいずれか一項に記載の偏光素子。

（式中、Ａ_４はニトロ基又はアミノ基を示し、Ｒ_９は水素原子、ヒドロキシル基、低級アルキル基、低級アルコキシ基、スルホ基、又はスルホ基を有する低級アルコキシ基を示し、Ｘ_２は置換基を有してもよいフェニルアミノ基を示す。）
［７］ 前記アゾ化合物は、遊離酸の形式で下記式（５）に示される化合物、その塩又はその金属錯体を含む、上記［１］乃至［６］のいずれか一項に記載の偏光素子。

（式中、Ｒ_１０およびＲ_１１は、各々独立に、スルホ基、カルボキシ基、ヒドロキシ基、低級アルキル基、又は低級アルコキシル基を示し、ｎは１乃至３の整数を示す。）
［８］ 前記式（１）のＡ_１が、置換基を有するフェニル基である、上記［３］乃至［７］のいずれか一項に記載の偏光素子。
［９］ 前記アゾ化合物は、前記式（４）に示される化合物の銅錯体を含む、上記［６］乃至［８］のいずれか一項に記載の偏光素子。
［１０］ 前記式（４）のＡ_４が、ニトロ基である、上記［６］乃至［９］のいずれか一項に記載の偏光素子。
［１１］ 前記式（３）のＡ_２およびＡ_３が、それぞれスルホ基を有するナフチル基である、上記［４］乃至［１０］のいずれか一項の偏光素子。
［１２］ 前記基材が、前記アゾ化合物を含むポリビニルアルコール系樹脂フィルムである、上記［１］乃至［１１］のいずれか一項に記載の偏光素子。
［１３］ 前記単体透過率が３５％乃至６０％であり、
下記に示す式（Ｉ）に前記単体透過率を代入して得られる最小偏光度ρｙ_ｍｉｎ１の数値以上の偏光度ρｙを有する、上記［１］乃至［１２］のいずれか一項に記載の偏光素子。

（式中、ρｙ_ｍｉｎ１は最小偏光度を示し、Ｙｓは単体透過率を示す。）
［１４］ 前記単体透過率が６０％超、８０％以下であり、
下記に示す式（ＩＩ）に前記単体透過率を代入して得られる最小偏光度ρｙ_ｍｉｎ２の数値以上の偏光度ρｙを有する、上記［１］乃至［１２］のいずれか一項に記載の偏光素子。

（式中、ρｙ_ｍｉｎ２は最小偏光度を示し、Ｙｓは単体透過率を示す。）
［１５］ 上記［１］乃至［１４］のいずれか一項に記載の偏光素子の少なくとも片面に、３μｍ乃至２２μｍの感圧型粘着層を有する、偏光素子。
［１６］ 上記［１］乃至［１５］のいずれか一項に記載の偏光素子の少なくとも片面に、１μｍ乃至６５μｍの膜厚を有する透明保護層を有する、偏光板。
［１７］ 上記［１６］に記載の偏光板の少なくとも片面に、３μｍ乃至２２μｍの感圧型粘着層を有する、偏光板。
［１８］ 上記［１］乃至［１５］のいずれか一項に記載の偏光素子又は上記［１６］若しくは［１７］に記載の偏光板を有する、液晶表示装置。」、に関する。 That is, the present invention
“[1] A polarizing element comprising a substrate containing an azo compound as a constituent component,
The film thickness is 1 μm to 30 μm,
The single transmittance is 35% to 80%,
The absolute values of the chromaticity a ^* value and b ^* value obtained when measuring the transmittance of natural light according to JIS Z 8781-4: 2013 are:
The polarizing elements alone are both 1 or less,
In a state where the two polarizing elements are arranged so that the absorption axis directions thereof are parallel to each other, both are 2 or less, and
A polarizing element characterized in that both of the polarizing elements are 2 or less in a state where the absorption axis directions are orthogonal to each other.
[2] For the transmittance of each wavelength measured by irradiating with absolute polarized light so that the vibration direction of light is perpendicular to the absorption axis direction of the polarizing element, the average transmittance is measured in a plurality of wavelength regions. When compared, the absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 4% or less, the average transmittance of 600 nm to 670 nm, and the average transmittance of 550 nm to 600 nm. The absolute value of the difference from the rate is 3% or less,
Furthermore, the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is parallel to the absorption axis direction of the polarizing element is compared with the average transmittance in a plurality of wavelength regions. The absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 2% or less, the average transmittance of 600 nm to 670 nm, and the average transmittance of 550 nm to 600 nm. The polarizing element according to the above [1], wherein the absolute value of the difference between and is 2 or less.
[3] The azo compound includes a compound represented by the following formula (1) or a salt thereof in the form of a free acid and a compound represented by the following formula (2) or a salt thereof in the form of a free acid. The polarizing element according to [1] or [2].

(In the formula, A ₁ represents a phenyl group or naphthyl group having a substituent, and R ₁ and R ₂ are each independently a lower group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, or a sulfo group. Represents an alkoxy group, and X ₁ represents an optionally substituted phenylamino group.)

(In the formula, R _{3 to} R ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, a lower alkoxy group having a sulfo group, a carbonyl group, or a halogen atom.)
[4] The above-mentioned [1] or [2], wherein the azo compound includes a compound represented by the formula (1) or a salt thereof and a compound represented by the following formula (3) or a salt thereof in the form of a free acid. ] The polarizing element of description.

(In the formula, A ₂ and A ₃ each independently represent at least one substituent having a sulfo group, a lower alkyl group, a lower alkoxy group, a lower alkoxy group having a sulfo group, a carboxy group, a nitro group, an amino group, or a substituent. An amino group is a naphthyl group or a phenyl group, and R ₇ and R ₈ 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.
[5] The azo compound comprises a compound represented by the formula (1) or a salt thereof, a compound represented by the formula (2) or a salt thereof, and a compound represented by the formula (3) or a salt thereof. The polarizing element according to [1] or [2] above.
[6] The polarizing element according to any one of [1] to [5], wherein the azo compound includes a compound represented by the following formula (4) in the form of a free acid, a salt thereof, or a metal complex thereof: .

(In the formula, A ₄ represents a nitro group or an amino group, R ₉ 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 X ₂ represents a substituted group. A phenylamino group which may have a group is shown.)
[7] The polarizing element according to any one of [1] to [6], wherein the azo compound includes a compound represented by the following formula (5) in the form of a free acid, a salt thereof, or a metal complex thereof: .

(Wherein R ₁₀ and R ₁₁ each independently represent a sulfo group, a carboxy group, a hydroxy group, a lower alkyl group, or a lower alkoxyl group, and n represents an integer of 1 to 3)
[8] The polarizing element according to any one of [3] to [7], wherein A _{1 in the} formula (1) is a phenyl group having a substituent.
[9] The polarizing element according to any one of [6] to [8], wherein the azo compound includes a copper complex of the compound represented by the formula (4).
[10] The polarizing element according to any one of [6] to [9], wherein A _{4 in the} formula (4) is a nitro group.
[11] The polarizing element according to any one of [4] to [10], wherein A ₂ and A _{3 in} the formula (3) are each a naphthyl group having a sulfo group.
[12] The polarizing element according to any one of [1] to [11], wherein the base material is a polyvinyl alcohol-based resin film containing the azo compound.
[13] The single transmittance is 35% to 60%,
The polarized light according to any one of [1] to [12], which has a polarization degree ρy equal to or greater than a value of a minimum polarization degree ρy _min1 obtained by substituting the single transmittance in the formula (I) shown below. element.

(In the formula, ρy _min1 represents the minimum degree of polarization, and Ys represents the single transmittance.)
[14] The single transmittance is more than 60% and 80% or less,
The polarized light according to any one of [1] to [12], which has a polarization degree ρy equal to or greater than a value of a minimum polarization degree ρy _min2 obtained by substituting the single transmittance in the formula (II) shown below. element.

(In the formula, ρy _min2 represents the minimum degree of polarization, and Ys represents the single transmittance.)
[15] A polarizing element having a pressure-sensitive adhesive layer of 3 μm to 22 μm on at least one surface of the polarizing element according to any one of [1] to [14].
[16] A polarizing plate having a transparent protective layer having a thickness of 1 μm to 65 μm on at least one surface of the polarizing element according to any one of [1] to [15].
[17] on at least one surface of the polarizing plate according to [16], having a pressure-sensitive adhesive layer of 3μm to 22 .mu.m, a polarizing plate.
[18] A liquid crystal display device comprising the polarizing element according to any one of [1] to [15] or the polarizing plate according to [16] or [17]. ".

  According to the present invention, even when the transmittance is high, an achromatic white color can be expressed when displaying white and an achromatic color black when displaying black. For example, a display or backlight having high transmittance and high luminance of a polarizing plate can be provided. Polarizing element and polarized light that can suppress the generation of a double image on the glass on which the polarizing plate is bonded, even when white for white display and black for black display are emphasized when used in a display that does not have A board can be obtained.

FIG. 1 is an example of the intensity of reflected light of each wavelength at an electrode of a reflective liquid crystal.

<Polarizing element>
The polarizing element according to the present invention comprises a substrate containing an azo compound as a constituent component, has a film thickness of 1 μm to 30 μm, has a single transmittance of 35% to 80%, and conforms to JIS Z 8781-4: 2013. The absolute values of the chromaticity a ^* value and b ^* value obtained when measuring the transmittance of natural light are both 1 or less for the polarizing element alone, and the absorption axis directions of the two polarizing elements are parallel to each other. Both of the polarizing elements are 2 or less, and both of the polarizing elements are 2 or less in a state where the absorption axis directions thereof are orthogonal to each other.

  According to such a polarizing element, even when it has a high transmittance, it is possible to represent achromatic white when displaying white and achromatic black when displaying black. For example, the polarizing plate has high transmittance and brightness. When used for a high display or a display that does not have a backlight, even if white at the time of white display and black at the time of black display are emphasized, a double image is generated on the glass to which the polarizing plate is bonded. A polarizing element and a polarizing plate that can be suppressed and have high durability can be obtained.

(Chromaticity a ^* value and b ^* value)
In the present invention, the chromaticity a ^* value and b ^* value are values obtained when measuring the transmittance of natural light according to JIS Z 8781-4: 2013. The object color display method defined in JIS Z 8781-4: 2013 corresponds to the object color display method defined by the International Commission on Illumination (abbreviated as CIE). Such measurement of the chromaticity a ^* value and b ^* value is performed by irradiating a measurement sample (for example, a polarizing element or a polarizing plate) with natural light. In the following, chromaticity a ^* value and b ^* value obtained for one measurement sample are a ^* -s and b ^* -s, and two measurement samples are arranged so that their absorption axis directions are parallel to each other. Chromaticity a ^* value and b ^* value obtained for the state (when white is displayed) are a ^* -p and b ^* -p, and two measurement samples are arranged so that their absorption axis directions are orthogonal to each other (black display) The chromaticity a ^* value and b ^* value obtained with respect to time) are indicated as a ^* -c and b ^* -c.

In the polarizing element according to the present invention, the absolute values of a ^* -s and b ^* -s are both 1 or less, and a ^* -p and b ^* -p, a ^* -c and b ^* -c Each absolute value is 2 or less. According to such a polarizing element, it is possible to realize a polarizing element and a polarizing plate that can express achromatic white during white display and achromatic black during black display. In addition, the absolute values of a ^* -p, b ^* -p, a ^* -c and b ^* -c are each preferably 1.5 or less, and more preferably 1.0 or less. Usually, even if a ^* -p, b ^* -p, a ^* -c, and b ^* -c each have a difference of about 0.5 in absolute value, a human can perceive a difference in color. Therefore, it is very important to control these numerical values in the polarizing element. In particular, when the absolute values of a ^* -p, b ^* -p, a ^* -c, and b ^* -c are each 1 or less, white when white is displayed and black when black is displayed A good polarizing element in which the color can hardly be confirmed can be obtained.

  In particular, in order to obtain a polarizing element having a predetermined chromaticity relationship as described above, it is preferable to control the transmittance of each wavelength to a predetermined relationship for the polarizing element. Specifically, with respect to the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is perpendicular to the absorption axis direction of the polarizing element, the average transmittance in a plurality of wavelength regions When the absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 4% or less, the average transmittance of 600 nm to 670 nm and the average transmittance of 550 nm to 600 nm The absolute value of the difference from the rate is 3% or less, and the transmission of each wavelength measured by irradiating the absolute polarized light so that the vibration direction of the light is parallel to the absorption axis direction of the polarizing element. When the average transmittance is compared in a plurality of wavelength ranges, the absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 2% or less, and As the absolute value of the difference between 00nm to average transmittance of 670nm and 550nm to 600nm average transmission becomes 2 or less, it is preferable to control the transmittance. Here, “absolutely polarized light” means light after polarization that has passed through a polarizing plate having a degree of polarization of almost 100%, and means almost 100% of polarized light. To do.

More preferably, the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is orthogonal to the absorption axis direction of the polarizing element is averaged in a plurality of wavelength ranges. When the transmittance is compared, the absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 2% or less, the average transmittance of 600 nm to 670 nm and the average transmittance of 550 nm to 600 nm It is desirable to control so that the absolute value of the difference from the average transmittance is 2% or less.
More preferably, the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is orthogonal to the absorption axis direction of the polarizing element is averaged in a plurality of wavelength ranges. When the transmittance is compared, the absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 1.5% or less, and the average transmittance of 600 nm to 670 nm is compared to 550 nm to 600 nm. The absolute value of the difference from the average transmittance is 1.5% or less, and further measured by irradiating with absolute polarized light so that the vibration direction of light is parallel to the absorption axis direction of the polarizing element. As for the transmittance of each wavelength, when the average transmittance is compared in a plurality of wavelength ranges, the absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 1. % Or less A, and it is desirable that the absolute value of the difference between 600nm to average transmittance of 670nm and 550nm to 600nm average transmission is controlled to be 1.5% or less.

(Single transmittance Ys)
In the present invention, the single transmittance is a single transmittance Ys after visibility correction, which is obtained in accordance with JIS Z 8722: 2009. The single transmittance Ys is measured by measuring the spectral transmittance Ts every 5 nm or 10 nm for each wavelength of 400 to 700 nm for one measurement sample (for example, polarizing element or polarizing plate), and measuring this twice. It can be obtained by correcting the visibility with the field of view (C light source).

  The polarizing element according to the present invention has a single transmittance Ys of 35% to 80%. The performance of the polarizing plate is required to be higher, but if the single transmittance Ys is 35% to 80%, the brightness can be expressed without a sense of incompatibility even if it is used in a display device. Since the degree of polarization tends to decrease as the transmittance increases, the single unit transmittance Ys is preferably 38% to 55%, more preferably 40% to 55% from the viewpoint of balance with the degree of polarization. 55%.

In addition, even with a polarizing element having a significantly reduced degree of polarization and a single transmittance of more than 60% and 80% or less, the polarizing element according to the present invention can improve visibility. That is, the polarizing element of the present invention can make white when displaying white and black when displaying black, achromatic, depending on the presence or absence of polarized light, can express white and black clearly, and improves the brightness due to its high transmittance. Can be made. Therefore, the visibility is improved by the clear difference in the brightness, and the visibility is good depending on the display. For a polarizing element having a single transmittance of more than 60% and 80% or less , the degree of polarization is preferably 10% or more, more preferably 20% or more, and further 30% or more.
In addition, it is important to use a display in which reflection is actually desired (for example, a display such as a reflective liquid crystal display or an OLED) in consideration of the balance between the luminance of the polarizing element and the polarization. In particular, in a reflective liquid crystal display, it is sufficient that the polarizing element has a degree of polarization that can control reflection at the time of display. Such a polarizing element can be used for a display having high luminance or high reflectance. Can be designed. Therefore, even a polarizing element having a single transmittance of more than 60% and 80% or less can be effectively used.

(Degree of polarization ρy)
The polarizing plate is required to have a higher degree of polarization. In this embodiment, the polarization degree of the polarizing element (hereinafter sometimes referred to as “ρy”) is preferably 50% or more. More preferably, it is 75% or more, more preferably 90% or more, and particularly preferably 99% or more.
The degree of polarization ρy of the polarizing element according to this embodiment is expressed by the following formula (I) when the single transmittance Ys (hereinafter sometimes simply referred to as “Ys”) is 35% to 60%. ) Is preferably not less than the numerical value of the minimum polarization degree ρy _min1 obtained by substituting the single transmittance Ys, and when the single transmittance Ys is more than 60% and 80% or less, the following formula is shown: It is preferable to be not less than the numerical value of the minimum polarization degree ρy _min2 obtained by substituting the single transmittance Ys for (II). The polarizing element of the present invention has a polarization degree equal to or greater than the minimum polarization degree ρy _min1 or the minimum polarization degree ρy _min2 , and thus can maintain a high degree of polarization with respect to the transmittance even when the transmittance is high. it can.

上記式（Ｉ）および式（ＩＩ）中、Ｙｓは偏光素子の単体透過率（実測値）であり、ρｙ_ｍｉｎ１は、単体透過率Ｙｓが３５％乃至６０％の場合における偏光度の好ましい最小偏光度（閾値）であり、ρｙ_ｍｉｎ２は、単体透過率Ｙｓが６０％超、８０％以下の場合における偏光度の好ましい最小偏光度（閾値）である。

In the above formulas (I) and (II), Ys is the single transmittance (actually measured value) of the polarizing element, and ρy _min1 is the preferred minimum polarization with a degree of polarization when the single transmittance Ys is 35% to 60%. Degree (threshold), and ρy _min2 is a preferable minimum degree of polarization (threshold) when the single transmittance Ys is more than 60% and 80% or less.

The polarization degree ρy of the polarizing element according to this embodiment is the minimum obtained by substituting the single transmittance Ys into the following formula (III) when the single transmittance Ys is 35% to 60%. More preferably, the degree of polarization ρy _min3 is greater than or _{equal to} the numerical value. When the single transmittance Ys is more than 60% and 80% or less, it is obtained by substituting the single transmittance Ys into the following formula (IV). It is more preferable that the value be _equal to or greater than the value of the minimum polarization degree ρy _min4 .

上記式（ＩＩＩ）および式（ＩＶ）中、Ｙｓは偏光素子の単体透過率（実測値）であり、ρｙ_ｍｉｎ３は、単体透過率Ｙｓが３５％乃至６０％の場合における偏光度のより好ましい最小偏光度（閾値）であり、ρｙ_ｍｉｎ４は、単体透過率Ｙｓが６０％超、８０％以下の場合における偏光度のより好ましい最小偏光度（閾値）である。

In the above formulas (III) and (IV), Ys is the single transmittance (measured value) of the polarizing element, and ρy _min3 is a more preferable minimum of the degree of polarization when the single transmittance Ys is 35% to 60%. It is a degree of polarization (threshold), and ρy _min4 is a more preferable minimum degree of polarization (threshold) when the single transmittance Ys is more than 60% and 80% or less.

  The above formulas (I) to (IV) are relational expressions related to product performance that the present inventors have derived empirically based on research and development knowledge conducted over many years. It becomes an index when developing a polarizing element having a degree of polarization. That is, by controlling the degree of polarization to the above relationship, it is possible to realize a polarizing element having a higher degree of polarization than a conventional polarizing element having the same single transmittance Ys.

(Thickness of polarizing element)
The polarizing element of the present invention has a film thickness of 1 μm to 30 μm. By controlling the thickness of the polarizing element to 1 μm to 30 μm or less, it is possible to effectively prevent the generation of a double image on the display when used in a liquid crystal display device. The thickness of the polarizing element is preferably 5 μm to 25 μm, and more preferably 8 μm to 20 μm.

(Base material containing azo compound as a constituent)
The polarizing element of the present invention comprises a substrate containing an azo compound as a constituent component.
In the present embodiment, the azo compound is preferably a dichroic dye. As the dichroic dye made of an azo compound, for example, an organic compound as shown in Non-Patent Document 1 can be used. In particular, those having high dichroism are preferable. For example, Sea. Ai. direct. Yellow 12, sea. Ai. direct. Yellow 28, Sea. Ai. direct. Yellow 44, Sea. Ai. direct. Orange 26, Sea. Ai. direct. Orange 39, sea. Ai. direct. Orange 107, sea. Ai. direct. Red 2, sea. Ai. direct. Red 31, sea. Ai. direct. Red 79, Sea. Ai. direct. Red 81, Sea. Ai. direct. Red 247, Sea. Ai. direct. Green 80 and Sea. Ai. direct. Examples include Green 59, and organic dyes described in JP-A Nos. 2001-33627, 2002-296417, and 60-156759. These organic dyes can be used as free metal, alkali metal salt (for example, Na salt, K salt, Li salt), ammonium salt, or amine salt. However, a dichroic dye is not limited to these, A well-known dichroic dye can also be used.

The azo compound is preferably a dye comprising a free acid, a salt thereof or a metal complex salt thereof. In these cases, optical properties are particularly improved. The metal complex is not particularly limited, but is preferably a transition metal complex, and particularly preferably a copper complex.
Moreover, the dye containing an azo compound may be used only by 1 type, may be mix | blended and used with another azo compound, and a mixing | blending is not limited. Moreover, the polarizing element of this invention is realizable by adjusting the transmittance | permeability of a base material, etc. using these azo compounds.

  In the present embodiment, the azo compound contains a compound represented by the following formula (1) or a salt thereof in the form of a free acid and a compound represented by the following formula (2) or a salt thereof in the form of a free acid. Is preferred. Moreover, it is preferable that an azo compound contains the compound or its salt shown by following formula (1) in the form of a free acid, and the compound or its salt shown by following formula (3) in the form of a free acid. According to the base material toned with such an azo compound, it is possible to obtain a polarizing element capable of expressing white at the time of white display and black at the time of black display more achromatic.

上記式（１）中、Ａ_１は置換基を有するフェニル基又はナフチル基を示し、Ｒ_１およびＲ_２は、各々独立に、水素原子、低級アルキル基、低級アルコキシ基、スルホ基、又はスルホ基を有する低級アルコキシ基を示し、Ｘ_１は置換基を有してもよいフェニルアミノ基を示す。
また、透過率および偏光度をさらに高め、白表示時の白色および黒表示時の黒色をより無彩色に表現する観点からは、Ａ_１は置換基を有するフェニル基であることが好ましい。このとき、好ましい置換基としては、例えばスルホ基、カルボニル基、ヒドロキシル基、低級アルキル基、低級アルコキシ基、スルホ基を有する低級アルキル基およびスルホ基を有するアルコキシル基が挙げられるが、中でも、スルホ基又はカルボニル基であることがより好ましい。さらに、フェニル基において、上記のような置換基は、１つでもよいが、２つ以上有していてもよい。なお、本明細書において、低級アルキル基および低級アルコキシ基の「低級」とは、炭素数が１乃至３であることを示す。

In the above formula (1), A ₁ represents a phenyl group or naphthyl group having a substituent, and R ₁ and R ₂ each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, or a sulfo group. And X ₁ represents a phenylamino group which may have a substituent.
Further, from the viewpoint of further increasing the transmittance and the degree of polarization and expressing white at the time of white display and black at the time of black display more achromatic, A ₁ is preferably a phenyl group having a substituent. In this case, preferred substituents include, for example, a sulfo group, a carbonyl group, a hydroxyl group, a lower alkyl group, a lower alkoxy group, a lower alkyl group having a sulfo group, and an alkoxyl group having a sulfo group. Or it is more preferable that it is a carbonyl group. Furthermore, in the phenyl group, the number of substituents as described above may be one, or may be two or more. In the present specification, “lower” in the lower alkyl group and the lower alkoxy group means 1 to 3 carbon atoms.

上記式（２）中、Ｒ_３乃至Ｒ_６は、各々独立に、水素原子、低級アルキル基、低級アルコキシ基、スルホ基、スルホ基を有する低級アルコキシ基、カルボニル基、又はハロゲン原子を示す。

In the above formula (2), R _{3 to} R ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, a lower alkoxy group having a sulfo group, a carbonyl group, or a halogen atom.

上記式（３）中、Ａ_２およびＡ_３は、各々独立に、置換基の少なくとも１つがスルホ基、低級アルキル基、低級アルコキシ基、スルホ基を有する低級アルコキシ基、カルボキシ基、ニトロ基、アミノ基若しくは置換アミノ基である、ナフチル基又はフェニル基を示し、Ｒ_７およびＲ_８は、各々独立に、水素原子、低級アルキル基、低級アルコキシ基、スルホ基、又はスルホ基を有する低級アルコキシ基を示す。
また、透過率および偏光度をさらに高め、白表示時の白色および黒表示時の黒色をより無彩色に表現する観点からは、Ａ_２およびＡ_３はスルホ基又はカルボニル基を有するナフチル基であることが好ましい。特に、スルホ基を有する場合が好ましく、偏光素子又は偏光板において高コントラストを実現し得る。

In the above formula (3), A ₂ and A ₃ are each independently a lower alkoxy group having at least one of a substituent having a sulfo group, a lower alkyl group, a lower alkoxy group, or a sulfo group, a carboxy group, a nitro group, an amino group. A naphthyl group or a phenyl group which is a group or a substituted amino group, and R ₇ and R ₈ 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. Show.
Further, from the viewpoint of further increasing the transmittance and the degree of polarization and expressing white at the time of white display and black at the time of black display more achromatic, A ₂ and A ₃ are naphthyl groups having a sulfo group or a carbonyl group. It is preferable. In particular, a case having a sulfo group is preferable, and high contrast can be realized in a polarizing element or a polarizing plate.

  Moreover, it is preferable that the azo compound which concerns on this embodiment further contains the compound shown by following formula (4) in the form of a free acid, its salt, or its metal complex. According to the base material toned with such an azo compound, a white light at the time of white display and a black color at the time of black display can be expressed in a more achromatic color, and a polarizing element having higher transmittance and degree of polarization can be obtained. It is done. The metal complex is not particularly limited, but is preferably a transition metal complex, and particularly preferably a copper complex.

上記式（４）中、Ａ_４はニトロ基若しくはアミノ基を示し、Ｒ_９は水素原子、ヒドロキシル基、低級アルキル基、低級アルコキシ基、スルホ基、又はスルホ基を有する低級アルコキシ基を示し、Ｘ_２は置換基を有してもよいフェニルアミノ基を示す。
また、透過率および偏光度をさらに高め、白表示時の白色および黒表示時の黒色をより無彩色に表現する観点からは、Ａ_４はニトロ基であることが好ましく、Ｒ_９はメトキシ基であることが好ましい。特に、Ａ_４がニトロ基であることによって偏光性能が向上する。

In the above formula (4), A ₄ represents a nitro group or an amino group, R ₉ 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 X ₂ represents a phenylamino group which may have a substituent.
Further, from the viewpoint of further increasing the transmittance and the degree of polarization, and expressing white at the time of white display and black at the time of black display more achromatic, A ₄ is preferably a nitro group, and R ₉ is a methoxy group. Preferably there is. In particular, the polarization performance is improved when A ₄ is a nitro group.

  Moreover, it is preferable that an azo compound further contains the compound shown by following formula (5) in the form of a free acid, its salt, or its metal complex. According to the base material toned with such an azo compound, a white light at the time of white display and a black color at the time of black display can be expressed in a more achromatic color, and a polarizing element having higher transmittance and degree of polarization can be obtained. It is done. The metal complex is not particularly limited, but is preferably a transition metal complex, and particularly preferably a copper complex.

上記式（５）中、Ｒ_１０およびＲ_１１は、各々独立に、スルホ基、カルボキシ基、ヒドロキシ基、低級アルキル基、又は低級アルコキシル基を示し、ｎは１乃至３の整数を示す。
また、透過率および偏光度をさらに高め、白表示時の白色および黒表示時の黒色をより無彩色に表現する観点からは、Ｒ_１０およびＲ_１１はスルホ基又はカルボニル基であることが好ましい。Ｒ_１０およびＲ_１１がスルホ基又はカルボニル基であることによって、白表示時の白色および黒表示時の黒色をより無彩色に表現できる偏光素子が得られる。また、上記式（５）において、末端の置換基は異なることが好ましい。末端の置換基を変えることによって、偏光素子の短波長側の偏光度、特に４００ｎｍ乃至４８０ｎｍの偏光度が向上し、偏光板のｂ^＊−ｐ又はｂ^＊−ｃがよりゼロに近づく、つまりは、より無彩色に近づく。

In the above formula (5), R ₁₀ and R ₁₁ each independently represent a sulfo group, a carboxy group, a hydroxy group, a lower alkyl group, or a lower alkoxyl group, and n represents an integer of 1 to 3.
Further, from the viewpoint of further increasing the transmittance and the degree of polarization, and expressing white at the time of white display and black at the time of black display more achromatic, R ₁₀ and R ₁₁ are preferably a sulfo group or a carbonyl group. When R ₁₀ and R ₁₁ are a sulfo group or a carbonyl group, a polarizing element capable of expressing white at the time of white display and black at the time of black display more achromatic is obtained. In the above formula (5), the terminal substituents are preferably different. By changing the substituent at the end, the degree of polarization on the short wavelength side of the polarizing element, particularly the degree of polarization of 400 nm to 480 nm, is improved, and b ^* -p or b ^* -c of the polarizing plate is closer to zero. , Closer to achromatic.

  In particular, by using a compound represented by the above formula (4) or formula (5), a salt thereof or a metal complex thereof as an azo compound, a highly durable achromatic polarizing element having no color change even after a durability test is obtained. Can be obtained.

  In addition, from the viewpoint of obtaining a polarizing element capable of increasing the transmittance and the degree of polarization and expressing white at the time of white display and black at the time of black display more achromatic, the compound represented by the above formula (1) or a salt thereof More preferably, the compound represented by the above formula (2) or a salt thereof and the compound represented by the above formula (3) or a salt thereof are simultaneously contained.

  As a method for obtaining the compound represented by the above formula (1), for example, Japanese Patent Application Laid-Open No. 2003-215338, Japanese Patent Application Laid-Open No. 9-302250, Japanese Patent No. 3881175, Japanese Patent No. 4462237, and Japanese Patent No. 4662853 are disclosed. However, it is not limited to these methods. Below, the specific example of the azo compound represented by the said Formula (1) is shown in the form of a free acid.

  Moreover, the compound represented by the said Formula (2) can be manufactured by coupling according to the manufacturing method of the normal azo dye as described in the nonpatent literature 2. FIG. As a specific production method, for example, an amino compound represented by the following formula (6) is diazotized by a known method, and N, N-bis (1-hydroxy-3-sulfo-6-naphthyl) amine (usually used) (Name: di-J acid) at 10 to 20 ° C. to obtain a disazo compound. The obtained disazo compound is added with, for example, copper sulfate, aqueous ammonia, amino alcohol, and hexamethylenetetramine, and subjected to a copperation reaction at 85 to 95 ° C. to obtain a solution containing the compound of the above formula (2). Then, the compound of the above formula (2) can be obtained by evaporating this solution to dryness, or salting out, drying, pulverizing and pulverizing.

上記式（６）中、ＲｘおよびＲｙは、式（２）におけるＲ_３乃至Ｒ_６と同じ意味を表す。

In the above formula (6), Rx and Ry represent the same meaning as R _{3 to} R ₆ in the formula (2).

  Below, the specific example of the azo compound represented by the said Formula (2) is shown in the form of a free acid.

  Examples of the method for obtaining the compound represented by the formula (3) include, but are not limited to, the methods described in International Publication No. 2012/165223. Below, the specific example of the azo compound represented by the said Formula (3) is shown in the form of a free acid.

  Moreover, as a method of obtaining the compound represented by the above formula (4), for example, the method described in JP2013-057909A is not limited thereto. Below, the specific example of the azo compound represented by the said Formula (4) is shown in the form of a free acid.

  Examples of a method for obtaining the compound represented by the above formula (5) include, but are not limited to, methods described in International Publication No. 2007/138980 and the like. Examples of the azo compound represented by the above formula (5) include dyes described in International Publication No. 2007/138980, C.I. I. Direct Yellow 4, C.I. I. Direct Yellow 12, C.I. I. Direct Yellow 72, C.I. I. An azo compound having a stilbene structure such as Direct Orange 39 can be preferably used. Below, the specific example of the azo compound represented by the said Formula (5) is shown in the form of a free acid.

  The method for obtaining a substrate containing an azo compound is not particularly limited. For example, an azo compound is used as a constituent component by impregnation or coating on the surface or inside of a material previously formed into a film shape. The method of making it contain, the method of shape | molding the material which contains an azo compound previously in a film form, etc. are mentioned.

The material containing the azo compound is not particularly limited, and examples thereof include a hydrophilic polymer that can generally contain a dichroic dye. Such hydrophilic polymers are not particularly limited, and examples thereof include polyvinyl alcohol resins, amylose resins, starch resins, cellulose resins, and polyacrylate resins. Among these, when a dichroic dye is contained, a resin comprising a polyvinyl alcohol-based resin and a derivative thereof is most preferable from the viewpoints of processability, dyeability, crosslinkability, and the like.
Furthermore, such a material is formed into a film shape, and a substrate containing the azo compound according to the present invention can be obtained by incorporating the dye and the compound thereof as described above by orientation treatment such as stretching. it can.

  Hereinafter, a specific method for producing a polarizing element will be described by taking as an example the case of producing a substrate containing an azo compound using a polyvinyl alcohol resin. In addition, the manufacturing method of the polarizing element which concerns on this invention is not limited to the following manufacturing method.

(Preparation of raw film)
First, a raw film made of a polyvinyl alcohol resin is prepared.

A polyvinyl alcohol-type resin is not specifically limited, A commercially available thing may be used and what was synthesize | combined by the well-known method may be used.
Specifically, the polyvinyl alcohol-based resin can be obtained, for example, by saponifying a polyvinyl acetate-based resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids.

The saponification degree of the polyvinyl alcohol-based resin is usually preferably about 85 to 100 mol%, more preferably 95 mol% or more. Such a polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used.
The degree of polymerization of the polyvinyl alcohol-based resin means a viscosity average degree of polymerization and can be determined by a well-known technique in the technical field, and is usually preferably about 1000 to 10000, more preferably about 1500 to 6000. is there.

Next, a polyvinyl alcohol-based resin is formed into a raw film.
The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. In this case, the polyvinyl alcohol-based resin film may contain glycerin, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, or the like as a plasticizer. The amount of the plasticizer is preferably 5 to 20% by weight of the whole film, more preferably 8 to 15% by weight. Although the film thickness of the raw film which consists of polyvinyl alcohol-type resin is not specifically limited, For example, it is preferable that it is about 5 micrometers-70 micrometers, More preferably, it is about 10 micrometers-65 micrometers.

(Swelling process)
Next, the original film is subjected to a swelling treatment. The swelling treatment is preferably performed by immersing the raw film in a solution at 20 ° C. to 50 ° C. for 30 seconds to 10 minutes. The solution is preferably water. The draw ratio is preferably adjusted to 1.00 to 1.50 times, more preferably 1.10 to 1.35 times. In addition, when shortening the time which manufactures a polarizing element, since a swelling process is performed also at the time of the dyeing | staining process of a pigment | dye, a swelling process can also be skipped.

(Dyeing process)
After the swelling step, a dyeing step is performed. In the dyeing process, the resin film after the treatment is impregnated with an azo compound. Since the treatment for impregnating the azo compound in this manner is a step of coloring the resin film, it is a dyeing step.

  Here, as the azo compound, an azo compound which is a dichroic dye described in Non-Patent Document 1, Formula (1), Formula (2), Formula (3), Formula (4), Formula (5), etc. The azo compound shown by can be used. These azo compounds are used as free acids and may be salts of these compounds. As such salts, alkali metal salts such as lithium salts, sodium salts and potassium salts, and organic salts such as ammonium salts and alkylamine salts can be used, and sodium salts are preferable.

  Moreover, it is preferable to perform a dyeing process by immersing a resin film in the dyeing solution containing the said azo compound, for example. The dyeing method is not particularly limited as long as it is a method of adsorbing and impregnating an azo compound to the resin film, but it is preferable to immerse the resin film in a dyeing solution, and to apply the dyeing solution to the resin film. You can also.

  Moreover, 5-60 degreeC is preferable, as for the solution temperature in this process, 20-50 degreeC is more preferable, and 35-50 degreeC is especially preferable. Although the time immersed in a solution can be adjusted moderately, it is preferable to adjust in 30 second-20 minutes, and 1-10 minutes are more preferable.

  Further, the content of the azo compound in such a dyeing solution can be arbitrarily adjusted depending on the dyeing property of the dye containing the azo compound, the dyeing time and the temperature, etc., but preferably 0.001 to 10% by weight of the whole solution Is preferable, and 0.01 to 1 weight% is more preferable.

  Further, such a dyeing solution may contain sodium carbonate, sodium hydrogen carbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate, and the like as a dyeing aid. Their content can be adjusted at an arbitrary concentration depending on the time and temperature depending on the dyeability of the dye, but each content is preferably 5% by weight or less, more preferably 0.1 to 2% by weight of the whole solution. .

(Washing process 1)
After the dyeing step, a washing step (hereinafter referred to as washing step 1) can be performed before entering the next step. The washing step 1 is a step of washing the dye solvent adhering to the surface of the resin film in the dyeing step. By performing the washing step 1, it is possible to prevent the dye from transferring to the solution used in the next step. In the washing step 1, water is generally used as a solvent. As for the cleaning method, it is preferable to immerse the resin film in the solution, but the cleaning can also be performed by applying the solution to the resin film. The time for washing 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 a material constituting the resin film (for example, a hydrophilic polymer, here, a polyvinyl alcohol resin) does not dissolve. Generally, it is washed at 5 to 40 ° C. However, since there is no problem in performance even without the cleaning step 1, this step can be omitted.

(Step of containing at least one of a crosslinking agent and / or a water resistance agent)
After the dyeing step or the washing step 1, a step of adding a crosslinking agent and / or a water resistance agent can be performed. Examples of the crosslinking agent include boron compounds such as boric acid, borax or ammonium borate, polyhydric aldehydes such as glyoxal or glutaraldehyde, polyhydric isocyanate compounds such as biuret type, isocyanurate type or block type, titanium oxy Titanium compounds such as sulfate can be used, but ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can also be used. As the water-proofing agent, succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride or magnesium chloride can be used, preferably boric acid. Is used. The step of containing a crosslinking agent and / or a water-resistant agent is performed using at least one or more crosslinking agents and / or a water-resistant agent as described above.

  In this step, water is preferable as the solvent, but it is not limited. The concentration of the cross-linking agent and / or water-proofing agent in the solvent in the step of containing the cross-linking agent and / or water-proofing agent is 0.1 to 6. 0 weight% is preferable and 1.0 to 4.0 weight% is more preferable. The solvent temperature in this step is preferably 5 to 70 ° C, more preferably 5 to 50 ° C. The method of incorporating a crosslinking agent and / or a water resistance agent into the resin film is preferably immersed in the solution, but the solution may be applied or applied to the resin film. The treatment time in this step is preferably 30 seconds to 6 minutes, and more preferably 1 to 5 minutes. However, it is not essential to contain a crosslinking agent and / or a water-resistant agent, and if it is desired to shorten the production time, this treatment step may be omitted if a crosslinking treatment or a water-resistant treatment is unnecessary. Good.

(Stretching process)
After performing the dyeing process, the cleaning process 1, or the process of containing a crosslinking agent and / or a water resistance agent, the stretching process is performed. The stretching step is a step of stretching the resin film uniaxially. The stretching method may be either a wet stretching method or a dry stretching method. The stretching ratio is preferably 3 times or more, more preferably 5 to 7 times.

  In the case of the dry stretching method, when the stretching heating medium is an air medium, the temperature of the air medium is preferably stretched at a room temperature to 180 ° C. Moreover, it is preferable to process in the atmosphere of 20 to 95% RH. Examples of the heating method include an inter-roll zone stretching method, a roll heating stretching method, a pressure stretching method, an infrared heating stretching method, and the like, but the stretching method is not limited. The stretching step can be performed in one stage, but can also be performed by multi-stage stretching of two or more stages.

  In the case of the wet stretching method, it is preferable to stretch in water, a water-soluble organic solvent, or a mixed solution thereof. Furthermore, it is more preferable to perform the stretching treatment while being immersed in a solution containing a crosslinking agent and / or a water resistance agent. Examples of the crosslinking agent include boron compounds such as boric acid, borax or ammonium borate, polyhydric aldehydes such as glyoxal or glutaraldehyde, polyhydric isocyanate compounds such as biuret type, isocyanurate type or block type, titanium oxy Titanium compounds such as sulfate can be used, but ethylene glycol glycidyl ether, polyamide epichlorohydrin, and the like can also be used. As the water-resistant agent, succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride, or the like can be used. It is preferable to perform stretching in a solution containing at least one or more crosslinking agents and / or water resistance agents as described above, and it is particularly preferable to contain boric acid as a crosslinking agent. For example, the concentration of the crosslinking agent and / or the waterproofing agent in the stretching step is preferably 0.5 to 15% by weight and more preferably 2.0 to 8.0% by weight, respectively, with respect to the solution. The draw ratio is preferably 2-8 times, more preferably 5-7 times. The stretching temperature is preferably 40 to 60 ° C, and more preferably 45 to 58 ° C. The stretching time is usually 30 seconds to 20 minutes, but 2 to 5 minutes is more preferable. The wet stretching step can be performed in one step, but can also be performed by two or more steps.

(Washing process 2)
After performing the stretching process, since the precipitation of the crosslinking agent and / or waterproofing agent or foreign matter may adhere to the resin film surface, a cleaning process for cleaning the resin film surface (hereinafter referred to as cleaning process 2) is performed. be able to. The washing time is preferably 1 second to 5 minutes. In the cleaning method, it is preferable to immerse the resin film in a cleaning solution, but the cleaning may be performed by applying or applying the cleaning solution to the resin film. The cleaning process can be performed in one stage, and the multi-stage process of two or more stages can be performed. Although the solution temperature of a washing | cleaning process is not specifically limited, Usually, 5-50 degreeC, Preferably it is 10-40 degreeC.

  The solvent used in the treatment steps so far includes, in addition to water, for example, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol. , Alcohols such as tetraethylene glycol or trimethylolpropane, amines such as ethylenediamine or diethylenetriamine, and the like, but are not limited thereto. These solvents can be used alone, but two or more kinds may be mixed and used. The most preferred solvent is water.

(Drying process)
After the stretching process or the washing process 2, a resin film drying process is performed. The drying process can be performed by natural drying, but in order to further increase the drying efficiency, it can be performed by compression with a nip roll after the cleaning step 2, removal of moisture on the surface with an air knife or a water absorption roll, etc. Furthermore, it can also carry out by ventilation drying as needed. As a drying process temperature, it is preferable to dry-process at 20-100 degreeC, and it is more preferable to dry-process at 60-100 degreeC. A drying treatment time of 30 seconds to 20 minutes can be applied, but 5 to 10 minutes is preferable.

(Control of film thickness)
As a method for controlling the film thickness after stretching of the resin film, (i) the processing temperature is set to a relatively high temperature (for example, 45 ° C.) in the swelling and dyeing step, (ii) the stretching ratio is set to a high ratio ( For example, (iii) to (8 times) are applied, and (iii) the nip roll pressure in the drying step after the cleaning step 2 is set high. The film thickness of the resin film after stretching is preferably 1 μm to 30 μm, but preferably 5 μm to 25 μm, more preferably 8 μm to 20 μm, and even more preferably 9 μm to 16 μm. It is suitable for improvement of physical intensity and double image.

  By the above method, a polarizing element having a predetermined film thickness, single transmittance and chromaticity, which is a base material containing a dichroic dye made of an azo compound, can be obtained.

<Polarizing plate>
The polarizing plate of the present invention can be obtained by providing a transparent protective layer on at least one surface of the polarizing element of the present invention. In addition, the polarizing plate may be provided with a transparent protective layer on both surfaces of the polarizing element.
The transparent protective layer can be provided as a polymer coating layer or as a film laminate layer. The transparent polymer or film forming the transparent protective layer is preferably a transparent polymer or film having high mechanical strength and good thermal stability. Examples of substances used as the transparent protective layer include cellulose acetate resins such as triacetyl cellulose and diacetyl cellulose, acrylic resins, polyvinyl chloride resins, nylon resins, polyester resins, polyarylate resins, and cyclic olefins such as norbornene. Cyclic polyolefin resins, polyethylene, polypropylene, polyolefins having a cyclo or norbornene skeleton or copolymers thereof, resins or polymers having imides and / or amides in the main chain or side chains, or films thereof. In addition, a resin having liquid crystallinity or a film thereof can be provided as the transparent protective layer. As for the thickness of a transparent protective layer, the thing of about 0.5-65 micrometers is mentioned, for example. These resins or films may be used alone, or may be used in two or more layers by combining the same type or different types.

  The film thickness of the transparent protective layer is preferably 1 μm to 65 μm, preferably 5 μm to 45 μm, more preferably 8 μm to 30 μm, and still more preferably 10 μm to 25 μm. In addition, since the expression of a double image reduces so that the film thickness of a transparent protective layer is thin, it is preferable. However, since the strength of the film decreases if it is too thin, it is desirable to select the preferable film thickness from the viewpoint of handling and visibility.

  An adhesive is required for the transparent protective layer to be bonded to the polarizing element of the present invention. Although it does not specifically limit as an adhesive agent, A polyvinyl alcohol adhesive agent is preferable. Examples of the polyvinyl alcohol adhesive include, but are not limited to, GOHSENOL NH-26 (manufactured by Nihon Gosei Co., Ltd.) and EXEVAL RS-2117 (manufactured by Kuraray Co., Ltd.). A cross-linking agent and / or a waterproofing agent can be added to the adhesive. As the polyvinyl alcohol adhesive, a maleic anhydride-isobutylene copolymer is used, but an adhesive mixed with a crosslinking agent can be used if necessary. As maleic anhydride-isobutylene copolymer, for example, isoban # 18 (manufactured by Kuraray), isoban # 04 (manufactured by Kuraray), ammonia-modified isoban # 104 (manufactured by Kuraray), ammonia-modified isoban # 110 (manufactured by Kuraray) ), Imidized isoban # 304 (manufactured by Kuraray), imidized isoban # 310 (manufactured by Kuraray), and the like. A water-soluble polyvalent epoxy compound can be used as the crosslinking agent at that time. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (manufactured by Nagase Chemtech) and Tetrat-C (manufactured by Mitsui Gas Chemical Co., Ltd.). Moreover, as adhesives other than polyvinyl alcohol resin, well-known adhesives, such as a urethane type, an acrylic type, and an epoxy type, can also be used. Further, for the purpose of improving the adhesive strength of the adhesive or improving the water resistance, additives such as zinc compounds, chlorides, iodides and the like can be simultaneously contained at a concentration of about 0.1 to 10% by weight. The additive is not limited. After laminating the transparent protective layer with an adhesive, the polarizing plate is obtained by drying or heat treatment at a suitable temperature.

  In some cases, when the obtained polarizing plate is bonded to a display device such as a liquid crystal or organic electroluminescence (commonly referred to as OLED or OEL), the viewing angle is improved on the surface of the protective layer or film that will later become an unexposed surface and / or Various functional layers for improving contrast, and a layer or film having brightness enhancement can also be provided. In order to attach the polarizing plate to these films and display devices, it is preferable to use an adhesive. The thickness of the pressure-sensitive adhesive is not limited as long as it is 30 μm or less, but is preferably 3 μm to 22 μm, more preferably 5 μm to 20 μm, and further preferably 8 μm to 16 μm. In addition, since the expression of a double image reduces so that the film thickness of an adhesion layer is thin, it is preferable.

  The polarizing plate may have various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer on the exposed surface of the protective layer or film. A coating method is preferable for producing the layer having various functions, but a film having the function can be bonded through an adhesive or a pressure-sensitive adhesive. The various functional layers can be a layer or a film for controlling the phase difference.

  The polarizing element or polarizing plate of the present invention can be suitably used for a liquid crystal display device or the like. The liquid crystal display device using the polarizing element or polarizing plate of the present invention is highly reliable, has a long-term high contrast, and has a high color reproducibility.

In particular, since the reflective liquid crystal uses a transparent electrode such as ITO (Indium tin Oxide), an aluminum electrode, or the like as the material of the drive electrode, the reflected light of the electrode reflects each wavelength as shown in FIG. It shows intensity, and its reflected color is green. The reflected light intensity shown in FIG. 1 is a result obtained by measuring using a spectrophotometer U-4100 (manufactured by Hitachi, Ltd.) and converting the highest reflected light intensity as 100.
As can be seen from this, in order to correct the reflected color, the value of the a ^* value obtained by measuring the two polarizing elements in a state where their absorption axis directions are parallel to each other is adjusted, It is more preferable that the color is slightly red. A preferable range of the a ^* value obtained by measuring two polarizing elements in a state where their absorption axis directions are parallel to each other is −0.5 to 1.7, more preferably 0 to 1. .5, more preferably 0.3 to 1.2.

  The polarizing element or polarizing plate of the present invention thus obtained is provided with a protective layer or a functional layer and a support as necessary, and a liquid crystal projector, a calculator, a watch, a notebook computer, a word processor, a liquid crystal television, a polarizing lens, and polarizing glasses. Used for car navigation and indoor / outdoor measuring instruments and displays. In particular, it is used as an effective polarizing element or polarizing plate in reflective liquid crystal display devices, transflective liquid crystal display devices, head-up displays, organic electroluminescence, and the like.

  As an application method of the polarizing plate of the present invention, it may be used as a polarizing plate with a support. In order to attach a polarizing plate, the support preferably has a flat portion, and since it is used for optical purposes, a glass molded product is preferable. Examples of the glass molded product include a glass plate, a lens, and a prism (for example, a triangular prism and a cubic prism). A lens attached with a polarizing plate can be used as a condenser lens with a polarizing plate in a liquid crystal projector. Also, a prism attached with a polarizing plate 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. Moreover, you may affix on a liquid crystal cell. Examples of the material of the glass include inorganic glass such as soda glass, borosilicate glass, inorganic base made of quartz, inorganic base made of sapphire, and organic plastic plates such as acrylic and polycarbonate. Is preferred. The glass plate may have a desired thickness and size. In order to further improve the single plate light transmittance, it is preferable to provide an AR layer on one or both of the glass surface and the polarizing plate surface of the polarizing plate with glass. To such a support, for example, a transparent adhesive (adhesive) agent is applied to the flat surface of the support, and then the polarizing plate of the present invention is attached to the coated surface. Alternatively, a transparent adhesive (adhesive) agent may be applied to the polarizing plate, and then a support may be attached to the coated surface. The adhesive (adhesive) agent used here is preferably, for example, an acrylic ester-based one. In addition, when using this polarizing plate as an elliptical polarizing plate, it is normal to stick the phase difference plate side to a support body side, but you may affix a polarizing plate side to a glass molded product.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these.

(dye)
First, the dye used in the examples and the synthesis method or the obtaining method thereof will be described.
Dye (1): A dye containing an azo compound having the chemical structure of the above formula (1). It produced according to Example 1 of the patent 4033443 gazette.
Dye (2): A dye containing an azo compound having the chemical structure of the above formula (2). It was produced by the method shown in Synthesis Example 1 below.
Dye (3): A dye containing an azo compound having the chemical structure of the above formula (3). It manufactured according to the synthesis example 1 of international publication 2012/165223.
Dye (4): A dye containing an azo compound having the chemical structure of the above formula (4). It manufactured according to Example 3 of Unexamined-Japanese-Patent No. 2013-057909.
Dye (5): a dye containing an azo compound having the chemical structure of the above formula (5). C. which is a commercial product. I. Direct Orange 39 (Nippon Kayaku Kayara Supra Orange 2GL) was used.

(Synthesis Example 1)
2-Nitro-4-sulfoaniline 17.9 parts by weight is dissolved in 145 parts by weight of water, added to 140 parts by weight of water containing 26 parts by weight of 35% by weight hydrochloric acid, and at 15 to 20 ° C., sodium nitrite is further added. 6.9 parts by weight was added and diazotized over 1 hour.
Then, this was mixed with 31.5 parts by weight of N, N-bis (1-hydroxy-3-sulfo-6-naphthyl) amine (common name: di-J acid), 125 parts by weight of water, and 11 parts by weight of soda ash. In addition, the soda ash solution is poured into this aqueous solution, the pH is kept at 8.5 to 9.5, and a disazo compound is not observed in the spot test over 3 hours at 20 ° C. Until the disazo compound was obtained.

Further, an aqueous solution of a previously prepared copper complex salt (prepared by adding 30.5 parts by weight of monoethanolamine to 25 parts by weight of copper sulfate) was added to the obtained disazo compound, and a thin layer was formed at 95 ° C. for 10 hours. The copperation reaction was carried out until no unreacted material was observed on the chromatograph.
Thereafter, 25% by weight of sanuki salt was added to the obtained solution, salted out, filtered, and evaporated to dryness at 60 ° C. to obtain Compound Example 12 having the chemical structure of the above formula (2).

Example 1
A polyvinyl alcohol film (VF-PE # 60 manufactured by Kuraray Co., Ltd.) having a film thickness of 60 μm, a saponification degree of 99% or more and an average polymerization degree of 2400 is immersed in warm water at 45 ° C. for 2 minutes, applied with a swelling treatment, and a draw ratio Was 1.30 times.

  Next, the swelling-treated film is composed of 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate (manufactured by Junsei Kagaku), 1.5 parts by weight of anhydrous sodium sulfate (manufactured by Junsei Chemical), 0.038 In an aqueous solution obtained by mixing 0.17 part by weight of dye (2) 0.17 part by weight, 0.16 part by weight of dye (3), 0.105 part by weight of dye (4) and 0.13 part by weight of dye (5), It was immersed for 4 minutes and 00 seconds at 45 ° C. to contain the dye (dyeing step).

  Next, the obtained film was immersed in a 20.0 g / l aqueous solution of boric acid (manufactured by Societa Chimerica Ladderello spa) at 40 ° C. for 1 minute. The film was immersed in a 30.0 g / l boric acid aqueous solution at 50 ° C. for 5 minutes and stretched. Further, the film was immersed in a 20.0 g / l aqueous solution of potassium iodide (manufactured by Junsei Chemical Co., Ltd.) at 30 ° C. for 20 seconds while maintaining the tension state of the obtained film. Thereafter, the obtained film was dried at 70 ° C. for 9 minutes to obtain a polarizing element having a thickness of 15 μm.

  Further, a triacetyl cellulose film (ZRD-60 manufactured by Fuji Photo Film Co., Ltd.) having a film thickness of 60 μm was applied as a transparent protective layer to the obtained polarizing element, and a polyvinyl alcohol adhesive (NH- 26. 4% aqueous solution) to obtain a polarizing plate.

  Next, the obtained polarizing plate was cut into 38 mm × 23 mm, and transferred to a 20 μm-thick transfer film (transfer adhesive; Polatechno AD-ROC) using an adhesive (PTR-3000 manufactured by Nippon Kayaku Co., Ltd.). They were pasted and installed on the observer side of the liquid crystal cell of a digital watch (Daiso Co., Ltd., table clock DO11 watch A No. 7) which is a reflective liquid crystal display. Further, on the reflecting plate side (non-observer side) of the digital timepiece, instead of the attached polarizing plate, a light anisotropic diffusion plate described in JP 2012-37611 A, a reflective polarizing plate manufactured by 3M Company A board (product name DBEF) and a black board (black drawing paper manufactured by King Corporation) were each bonded to AD-ROC (transfer adhesive: manufactured by Polatechno Co., Ltd.) and installed. The reflection type liquid crystal display thus produced has the following configuration: polarizing plate / AD-ROC / liquid crystal cell / AD-ROC / light anisotropic diffusion plate / AD-ROC / reflection type polarizing plate / AD-ROC / black plate It has become.

(Example 2)
As a film to which the swelling treatment is applied, a polyvinyl alcohol film having a film thickness of 45 μm (VF-PE # 45 manufactured by Kuraray Co., Ltd.) was used instead of a polyvinyl alcohol film having a film thickness of 60 μm (VF-PE # 60 manufactured by Kuraray Co., Ltd.). Produced a polarizing element, a polarizing plate and a reflective liquid crystal display in the same manner as in Example 1. In addition, the film thickness of the obtained polarizing element was 15 micrometers.

(Example 3)
Except for using a triacetyl cellulose film having a thickness of 40 μm (TG40 manufactured by Fuji Film Co., Ltd.) instead of the triacetyl cellulose film having a film thickness of 60 μm (ZRD-60 manufactured by Fuji Photo Film Co., Ltd.) as the transparent protective layer. A polarizing element, a polarizing plate, and a reflective liquid crystal display were prepared in the same manner as in No. 2.

Example 4
Example 2 except that a 25 μm thick triacetyl cellulose film (Konica KC2UA) was used instead of the 60 μm thick triacetyl cellulose film (Fuji Photo Film ZRD-60) as the transparent protective layer. A polarizing element, a polarizing plate, and a reflection type liquid crystal display were prepared in the same manner as described above.

(Example 5)
A polarizing element and a polarizing plate were produced in the same manner as in Example 4 except that a transfer film having a film thickness of 10 μm was used instead of the transfer film having a film thickness of 20 μm as the transfer adhesive used for pasting the reflective liquid crystal display. And a reflective liquid crystal display.

(Example 6)
In the dyeing process of Example 5, the time for immersing the swelled film in the dyeing solution was adjusted to 3 minutes 00 seconds, and polarized light was produced in the same manner as in Example 5 except that polarizing elements having different transmittances were produced. An element, a polarizing plate, and a reflective liquid crystal display were produced.

(Example 7)
In the dyeing process of Example 5, the polarizing element was prepared in the same manner as in Example 5 except that the time for immersing the swelled film in the dyeing solution was adjusted to 20 seconds and a polarizing element having a different transmittance was produced. A polarizing plate and a reflective liquid crystal display were prepared.

(Comparative Example 1)
As a film to which the swelling treatment is applied, instead of a polyvinyl alcohol film having a thickness of 60 μm (VF-PE # 60 manufactured by Kuraray Co., Ltd.), a polyvinyl alcohol film having a thickness of 75 μm (VF-PE # 75 manufactured by Kuraray Co., Ltd.) is used for dyeing. In the process, the dyeing time was adjusted so that the transmittance was the same as that of the polarizing element of Example 2, and instead of a triacetyl cellulose film having a thickness of 60 μm (ZRD-60 manufactured by Fuji Photo Film Co., Ltd.) as a transparent protective layer, Using a 80 μm thick triacetyl cellulose film (TD-80U manufactured by Fuji Film Co., Ltd.), and as a transfer adhesive used for pasting a reflective liquid crystal display, instead of a 20 μm thick transfer film, a film thickness of 25 μm A polarizing element in the same manner as in Example 1 except that the transfer film of A light plate and reflective liquid crystal displays were produced. In addition, the film thickness of the obtained polarizing element was 31 micrometers.

(Comparative Example 2)
A reflective liquid crystal display was prepared in the same manner as in Example 1 except that a dye-based polarizing plate SHC-125 (film thickness 180 μm) manufactured by Polatechno Co., Ltd. was obtained and used.

(Comparative Example 3)
A reflective liquid crystal display was produced in the same manner as in Example 1 except that a dye-based polarizing plate SHC-115 (film thickness 180 μm) manufactured by Polatechno Co., Ltd. was obtained and used.

(Comparative Example 4)
A reflective liquid crystal display was prepared in the same manner as in Example 1 except that a dye-based polarizing plate SKN-18242 (film thickness 180 μm) manufactured by Polatechno Co., Ltd. was obtained and used.

(Comparative Example 5)
A reflective liquid crystal display was prepared in the same manner as in Example 1 except that an iodine-based polarizing plate SKW-18245 (film thickness 180 μm) manufactured by Polatechno Co., Ltd. was obtained and used.

(Evaluation 1)
First, the polarizing plates obtained in Examples 1, 2, 6 and 7 and the polarizing plates of Comparative Examples 2 to 5 were each cut into 40 mm × 40 mm, and an adhesive PTR-3000 (manufactured by Nippon Kayaku Co., Ltd.) was used. Then, it was bonded to a 1 mm glass plate to obtain a measurement sample having a thickness of 1.150 mm. The following measurement and evaluation were performed on the obtained measurement sample. In addition, it has been confirmed in advance that the measurement sample has substantially the same evaluation result as that of the polarizing element before laminating (the same applies to evaluation 3).

[Transmissivity Ts, Tp and Tc]
About each measurement sample, the transmittance | permeability Ts, Tp, and Tc in each wavelength was measured using the spectrophotometer (Hitachi Ltd. make "U-4100").
Here, the transmittance Ts is a spectral transmittance of each wavelength when a single measurement sample is measured. The transmittance Tp is the spectral transmittance of each wavelength when two measurement samples are overlapped and measured so that their absorption axis directions are parallel, and the transmittance Tc is the two measurement samples. It is the spectral transmittance of each wavelength when measured by overlapping the absorption axis directions so as to be orthogonal.

[Single transmittance Ys, parallel transmittance Yp, and orthogonal transmittance Yc]
For each measurement sample, single transmittance Ys, parallel transmittance Yp, and orthogonal transmittance Yc were determined. The single transmittance Ys, the parallel transmittance Yp, and the orthogonal transmittance Yc are the transmittances Ts, Tp, and Tc obtained at predetermined wavelength intervals dλ (here, 10 nm) in the wavelength region of 400 to 700 nm. , The transmittance corrected to the visibility according to JIS Z 8722: 2009. Specifically, the transmittances Ts, Tp, and Tc were substituted into the following formulas (V) to (VII) and calculated. In the following formulas (V) to (VII), Pλ represents a spectral distribution of standard light (C light source), and yλ represents a 2 ° visual field color matching function. The results for the single transmittance Ys are shown in Table 1.

[Degree of polarization ρy]
The degree of polarization ρy was determined for each measurement sample. The degree of polarization ρy was calculated by substituting the parallel transmittance Yp and the orthogonal transmittance Yc into the following formula (VIII). The results are shown in Table 1.

[Chromaticity a ^* value and b ^* value]
For each measurement sample, according to JIS Z 8781-4: 2013, the chromaticity a ^* value and b ^* value at the time of measuring the transmittance Ts, measuring the parallel transmittance Tp, and measuring the orthogonal transmittance Tc are measured. did. Note that the measurement apparatus used the above spectrophotometer, and both the transmitted color and the reflected color were incident from the outdoor side and measured. A C light source was used as the light source. The results are shown in Table 1. In Table 1, a ^* -s and b ^* -s, a ^* -p and b ^* -p, and a ^* -c and b ^* -c are transmittance Ts, parallel transmittance Tp and orthogonal transmission. This corresponds to the chromaticity a ^* value and b ^* value in the measurement of the rate Tc, respectively.

As shown in Table 1, the polarizing element according to the present invention comprises a base material containing an azo compound as a constituent component, has a film thickness of 1 μm to 30 μm, a single transmittance of 35% to 80%, and JIS The absolute value of the chromaticity a ^* value and b ^* value obtained when measuring the transmittance of natural light according to Z 8781-4: 2013 is 1 or less for both of the polarizing elements, and the absorption axis direction of the two polarizing elements is It was confirmed that both were 2 or less in the state of being arranged parallel to each other, and both were 2 or less in the state where the two polarizing elements were arranged so that their absorption axis directions were orthogonal to each other. Further, it was confirmed that the polarizing element according to the comparative example was not particularly controlled in the chromaticity relationship within a predetermined range.

(Evaluation 2)
[Evaluation of reflective liquid crystal display (1)]
The liquid crystal displays obtained in Examples 1 to 7 and Comparative Examples 1 to 5 were placed in a room with a brightness of 300 cd and observed visually by 10 observers. The observation was performed for each of the color at the time of white display, the color at the time of black display, and the double image of the image viewed from an oblique angle of 60 ° from the front to the left. The appearance color is basically “white” for white display and “black” for black display. In this embodiment, for example, yellowish white is “yellow” or “yellow”. “Green” and purple-colored black are indicated as “purple”.

表２に示されるように、本発明の偏光素子を用いて作製された液晶ディスプレイでは、白表示時および黒表示時のぞれぞれの場合において、無彩色な白色および無彩色の黒色を表示でき、かつ、ディスプレイの２重像が観察されなかった。一方、特に色度の関係が所定の範囲に制御されていない偏光素子を用いて作製された液晶ディスプレイでは、白表示時および黒表示時のそれぞれの場合に、無彩色な白色および無彩色の黒色に表示できていないことが確認された（比較例２〜５）。さらに、膜厚が所定の範囲に制御されていない偏光素子を用いて作製された液晶ディスプレイでは、２重像が観察された（比較例１〜５）。

As shown in Table 2, the liquid crystal display manufactured using the polarizing element of the present invention displays achromatic white and achromatic black in each case of white display and black display. And a double image on the display was not observed. On the other hand, in a liquid crystal display manufactured using a polarizing element whose chromaticity relationship is not controlled within a predetermined range, achromatic white and achromatic black in each of white display and black display (Comparative Examples 2 to 5). Furthermore, in the liquid crystal display produced using the polarizing element whose film thickness was not controlled within a predetermined range, double images were observed (Comparative Examples 1 to 5).

(Evaluation 3)
[Transmissivity Ky and Kz]
With respect to the measurement sample prepared in Evaluation 1, the transmittances Ky and Kz at each wavelength when irradiated with absolutely polarized light were measured using the above spectrophotometer. The measurement was performed according to JIS Z 8722: 2009 (C light source 2 degree visual field). Specifically, on the light source side of the spectrophotometer, iodine-based polarizing plate (SKN-18043P, manufactured by Polatechno Co., Ltd.) having a single transmittance Ys after correction of visibility of 43% and a polarization degree ρy of 99.99%. The layer is triacetyl cellulose having no ultraviolet absorbing ability.) The polarized light that has passed through this iodine-based polarizing plate is irradiated to the measurement sample, and the spectral transmittance is measured.

  Here, the transmittance Ky was measured so that the vibration direction of the absolute polarized light and the absorption axis direction of the measurement sample were orthogonal to each other (the absorption axis direction of the absolute polarizing plate and the absorption axis direction of the measurement sample were parallel). The spectral transmittance of each wavelength at the time, hereinafter referred to as “absolute parallel transmittance Ky”. Further, the transmittance Kz is measured when the vibration direction of the absolute polarized light and the absorption axis direction of the measurement sample are parallel (the absorption axis direction of the absolute polarizing plate and the absorption axis direction of the measurement sample are orthogonal). The spectral transmittance of each wavelength, hereinafter referred to as “absolute orthogonal transmittance Kz”.

[Absolute value of difference between average transmittance and average transmittance]
For each measurement sample, the average transmittance [A] in each wavelength region ([A] 400 nm to 460 nm, [B] 550 nm to 600 nm, and [C] 600 nm to 670 nm) of the absolute parallel transmittance Ky and the absolute orthogonal transmittance Kz. , [B] and [C] were obtained. These average transmittances were calculated by averaging the absolute parallel transmittance Ky and the absolute orthogonal transmittance Kz in the three wavelength regions. Further, regarding the absolute parallel transmittance Ky and the absolute orthogonal transmittance Kz, the absolute value of the difference between the average transmittance [A] and the average transmittance [B] and the difference between the average transmittance [A] and the average transmittance [B]. The absolute value of was calculated respectively. Each is shown in Table 3. In Table 3, a value corresponding to the absolute parallel transmittance Ky is indicated as “parallel position”, and a value corresponding to the absolute orthogonal transmittance Kz is indicated as “orthogonal position”.

  As shown in Table 3, the polarizing element according to the present invention has a transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is orthogonal to the absorption axis direction. When comparing the average transmittance in a plurality of wavelength ranges, the absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 4% or less, and the average of 600 nm to 670 nm The absolute value of the difference between the transmittance and the average transmittance between 550 nm and 600 nm is 3% or less, and measured by irradiating with absolute polarized light so that the vibration direction of light is parallel to the absorption axis direction. For the transmittance of each wavelength, when the average transmittance is compared in a plurality of wavelength ranges, the absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 2% or less. And it was confirmed that the absolute value of the difference between the average transmittance and 550nm to 600nm average transmittance of 600nm to 670nm is adjusted to 2 or less.

(Evaluation 4)
[Evaluation of reflective liquid crystal display (2)]
The liquid crystal displays obtained in Examples 1 to 7, Comparative Example 1 and Comparative Example 5 were placed in a 300 cd room and visually observed by 10 observers. Observation was performed on a double image of the image seen from the front at an angle of 75 ° diagonally from the front, and the most frequent opinion was verified. The results are as follows.

In the liquid crystal display of Comparative Example 1 using the polarizing element that displays white when displaying white and black when displaying black, Comparative Example 5 where white when displaying white and black when displaying black cannot be displayed achromatic. Compared with the liquid crystal display, a double image was particularly visually recognized when displaying black.
On the other hand, in Examples 1 to 5 using the polarizing element of the present invention, the visibility of the double image decreases in the order of Examples 1 to 5, and in Example 6, the double image is hardly visually recognized. In Example 7, the double image was not visually recognized at all. From this, it was confirmed that the reflection of the double image can be improved by controlling not only the thickness of the polarizing element but also the thickness of the polarizing plate, and further the adhesive for bonding the polarizing plate. It was.

Claims (16)

A polarizing element comprising a base material containing an azo compound as a constituent component,
The film thickness is 1 μm to 30 μm,
The single transmittance is 35% to 80%,
The absolute values of the chromaticity a ^* value and b ^* value obtained when measuring the transmittance of natural light according to JIS Z 8781-4: 2013 are:
The polarizing elements alone are both 1 or less,
In a state where the two polarizing elements are arranged so that the absorption axis directions thereof are parallel to each other, both are 2 or less, and
In a state where two polarizing elements that absorption axis direction was perpendicular to each other state, and are both 2 or less,
The azo compound includes a compound represented by the following formula (1) or a salt thereof in the form of a free acid, and a compound represented by the following formula (2) or a salt thereof in the form of a free acid , Polarizing element.

(In the formula, A ₁ represents a phenyl group or naphthyl group having a substituent, and R ₁ and R ₂ are each independently a lower group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, or a sulfo group. Represents an alkoxy group, and X ₁ represents an optionally substituted phenylamino group.)

(In the formula, R _{3 to} R ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, a lower alkoxy group having a sulfo group, a carbonyl group, or a halogen atom.) When the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is perpendicular to the absorption axis direction of the polarizing element, the average transmittance is compared in multiple wavelength regions Further, the absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 4% or less, and the average transmittance of 600 nm to 670 nm and the average transmittance of 550 nm to 600 nm are The absolute value of the difference is less than 3%,
Furthermore, the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is parallel to the absorption axis direction of the polarizing element is compared with the average transmittance in a plurality of wavelength regions. The absolute value of the difference between the average transmittance of 550 nm to 600 nm and the average transmittance of 400 nm to 460 nm is 2% or less, the average transmittance of 600 nm to 670 nm, and the average transmittance of 550 nm to 600 nm. The polarizing element according to claim 1, wherein the absolute value of the difference between and is 2 or less. The polarizing element according to claim 1, wherein the azo compound further comprises a compound represented by the following formula (3) or a salt thereof in the form of a free acid.

(In the formula, A ₂ and A ₃ each independently represent at least one substituent having a sulfo group, a lower alkyl group, a lower alkoxy group, a lower alkoxy group having a sulfo group, a carboxy group, a nitro group, an amino group, or a substituent. An amino group is a naphthyl group or a phenyl group, and R ₇ and R ₈ 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. A in the formula (3) ₂ And A ₃ The polarizing element according to claim 3, wherein each is a naphthyl group having a sulfo group. The said azo compound is a polarizing element as described in any one of Claims 1 thru | or 4 which further contains the compound shown by following formula (4) in the form of a free acid, its salt, or its metal complex.

(In the formula, A ₄ represents a nitro group or an amino group, R ₉ 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 X ₂ represents a substituted group. A phenylamino group which may have a group is shown.) The polarizing element according to claim 5, wherein the azo compound further includes a copper complex of the compound represented by the formula (4). A in the formula (4) ₄ The polarizing element according to claim 5 or 6, wherein is a nitro group. The azo compound is a compound represented by the following formula (5) in the form of the free acid, a salt thereof or further comprising a metal complex thereof, polarizing element according to any one of claims 1 to 7.

(Wherein R ₁₀ and R ₁₁ each independently represent a sulfo group, a carboxy group, a hydroxy group, a lower alkyl group, or a lower alkoxyl group, and n represents an integer of 1 to 3) The formula A ₁ (1), a phenyl group having a substituent, a polarizing element according to any one of claims 1 to 8. Wherein the substrate is a polyvinyl alcohol resin film containing the azo compound, the polarizing element according to any one of claims 1 to 9. The single transmittance is 35% to 60%,
The polarizing element as described in any one of Claims 1 thru | or 10 which has polarization degree (rho) y more than the numerical value of minimum polarization degree (rho) _ymin1 obtained by substituting the said single transmittance for the formula (I) shown below.

(In the formula, ρy _min1 represents the minimum degree of polarization, and Ys represents the single transmittance.) The single transmittance is more than 60% and 80% or less,
Having a number more than the degree of polarization Rowai minimum polarization Rowai _min2 obtained by substituting the single transmittance in formula (II) shown below, the polarizing element according to any one of claims 1 to 11.

(In the formula, ρy _min2 represents the minimum degree of polarization, and Ys represents the single transmittance.) At least one side, having a pressure-sensitive adhesive layer of 3μm to 22 .mu.m, the polarizing element of the polarizing element according to any one of claims 1 to 12. On at least one surface of the polarizing element according to any one of claims 1 to 13, having a transparent protective layer having a thickness of 1μm to 65 .mu.m, a polarizing plate. A polarizing plate having a pressure-sensitive adhesive layer of 3 to 22 μm on at least one side of the polarizing plate according to claim 14 . Having a polarizing plate according to the polarizing element or claim 14 or 15 of any one of claims 1 to 13, a liquid crystal display device.

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