WO2021095411A1

WO2021095411A1 - Liquid crystal display device

Info

Publication number: WO2021095411A1
Application number: PCT/JP2020/038352
Authority: WO
Inventors: 小間　徳夫; 矢田　竜也; 三井　雅志
Original assignee: 株式会社ピクトリープ
Priority date: 2019-11-15
Filing date: 2020-10-09
Publication date: 2021-05-20
Also published as: JP2021081521A

Abstract

Provided is a display device including a substrate (A) having a polarizing function, in which in the transmittance obtained by measuring the absorption axes of two substrates in parallel, the average transmittance at 520 nm to 590 nm is 30% or more, the absolute value of a difference between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is within 5%, and the absolute value of a difference between the average transmittance at 520 nm to 590 nm and the average transmittance at 590 nm to 660 nm is within 5%, and in each wavelength transmittance obtained by measuring the absorption axes of the two substrates orthogonally, the absolute value of a difference between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is within 2%, and the absolute value of a difference between the average transmittance at 520 nm to 590 nm and the average transmittance at 600 nm to 660 nm is within 2%.

Description

Liquid crystal display device

The present invention relates to a liquid crystal display device.

The polarizing element is generally manufactured by adsorbing and orienting iodine or a dichroic dye, which is a dichroic dye, on a polyvinyl alcohol resin film. A protective film made of triacetyl cellulose or the like is attached to at least one surface of the polarizing element via an adhesive layer to form a polarizing plate, which is used in liquid crystal display devices and the like. A polarizing plate using iodine as a dichroic dye is called an iodine-based polarizing plate, while a polarizing plate using a dichroic dye as a dichroic dye is called a dye-based polarizing plate. Of these, dye-based polarizing plates have high heat resistance, high humidity heat durability, and high stability, and are characterized by high color selectivity depending on the composition, while iodine-based polarizing plates having the same contrast. There was a problem that the transmittance was lower than that of. Therefore, it has been difficult to maintain high durability, have various color selectivity, and achieve higher transmittance.

However, even with dye-based polarizing plates having various color selectivity, conventional polarizing elements are polarizing elements that exhibit a yellowish tinge when the absorption axes are installed in parallel. In addition, the color of one iodine-based polarizing plate is a polarizing element that develops yellow-green when the absorption axes are installed in parallel and blue when the absorption axes are installed orthogonally. When used in (notation), the color of the polarizing element has a great influence on the display characteristics. In particular, in a display device using a liquid crystal, it is essential to provide at least one polarizing element on the observer side via a liquid crystal cell. Therefore, it is clear that the color of the polarizing plate can be confirmed by the observer. However, the color development due to the wavelength characteristics of such a polarizing element is one of the factors that greatly affect the display characteristics of the display, and in the conventional transmissive liquid crystal device using the backlight, the spectrum distribution of the backlight and the adjustment of the color filter are performed. It is necessary to optimize the display color.

On the other hand, in a display device that uses ambient light, especially a reflective liquid crystal device, the spectrum of the light source cannot be adjusted unlike a transmissive display, so the wavelength characteristic of the polarizing plate becomes the display color as it is. For this reason, improvement of the wavelength characteristics of the polarizing plate has been an important issue. Conventional reflective liquid crystal devices have a slightly yellowish white display and a bluish black display. Therefore, it has been regarded as inferior in display quality as compared with other reflective devices (electronic paper displays, etc.).

Further, as a polarizing plate for improving the display performance of a display, a polarizing plate using a method of adjusting the spectrum of a color filter or mixing a dye with an adhesive or the like to adjust the display color has been proposed. However, all of them result in lowering the transmittance of the polarizing plate and are costly, so that great improvement is required. In addition, although the wavelength characteristics of the polarizing plate have been improved, in the commonly used iodine-based polarizing plate, if the transmission spectrum (when the absorption axes are parallel) is made uniform at each wavelength, the wavelength is short when orthogonal. Light leaked to the light, and sufficient display could not be performed. As a method for improving the hue of this polarizing plate, techniques such as Patent Document 1 or Patent Document 2 are disclosed.

Patent Document 1 discloses a polarizing plate having a neutral coefficient calculated and an absolute value of 0 to 3. Patent Document 2 discloses a polarizing element that has a transmittance of 410 nm to 750 nm and is within ± 30% of the average value, and is adjusted by directly adding a dye, a reactive dye, or an acid dye in addition to iodine. ing. The polarizing element disclosed in the same document was obtained by setting the single transmittance, that is, the color when measured using only one polarizing element, within an absolute value of 2 in terms of a value and b value in the UCS color space. It is a polarizing element.

Japanese Patent No. 4281261 Japanese Patent No. 3357803

However, in Patent Document 1, as can be seen from the examples, even if the neutral coefficient (Np) is low, the a * value is -2 to -1 and b * is obtained only by the parallel hue obtained from JIS Z 8729. Since the value is 2.5 to 4.0, it can be seen that the color is yellowish green when expressed in white. Further, the hue at the orthogonal position has an a * value of 0 to 1, but a b * value of −1.5 to -4.0, so that the polarizing plate has a blue color.

Further, in Patent Document 2, the polarizing element is obtained by setting the single transmittance, that is, the color when measured using only one polarizing element, within an absolute value of 2 in terms of a value and b value in the UCS color space. It is a polarized light element. However, it is not possible to express an achromatic color at the same time by using two polarizing plates to simultaneously express the hues of white display (when parallel) and black display (when orthogonal). Further, as can be seen from the examples, the average value of the single transmittance is 31.95% in Example 1 and 31.41% in Example 2, and the transmittance is low, so that the transmittance is high. It did not have sufficient performance in the required fields, particularly in fields such as liquid crystal display devices and organic electroluminescence.

Therefore, the present invention has been made in view of the above problems, and provides a display device capable of realizing high-quality white display, black display, and excellent color display without coloring while having high reflectance. The purpose is.

As a result of diligent studies to solve the above problems, the present inventors have obtained a substrate containing an azo compound and having a polarizing function, which is obtained by measuring the absorption axes of the two substrates in parallel. In terms of wavelength transmittance, the average transmittance at 520 nm to 590 nm is 30% or more, the absolute value of the difference between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is within 5%, and The absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm is within 5%, and each is obtained by measuring with the absorption axes of the two substrates orthogonal to each other. In terms of wavelength transmittance, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 2%, and the average transmittance of 520 nm to 590 nm and the average of 600 nm to 660 nm. The display device including the base material (A) characterized in that the absolute value of the difference from the transmittance is within 2% expresses high-quality white and black without coloring while having high transmittance. The present invention has been completed by finding that it is possible to provide a display device capable of displaying a sufficient color as a reflective type.

That is, the present invention
(1) Containing an azo compound or a salt thereof,
In the transmittance obtained by measuring the absorption axes of two substrates in parallel,
The average transmittance of 520 nm to 590 nm is 30% or more,
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 5%, and
The absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm is within 5%.
Further, in each wavelength transmittance obtained by measuring the absorption axes of the two base materials at right angles,
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 2%, and
A display characterized by comprising a substrate (A) having a polarizing function, wherein the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm is within 2%. apparatus.

(2) The display device according to (1), which comprises a color filter.

(3) The display device according to (2), wherein the NTSC ratio when light is transmitted twice through the color filter is 1 to 20.

(4) The display device according to (2) or (3), wherein the color filter includes a red color layer, a green color layer, and a blue color layer.

(5) The display device according to (2) or (3), wherein the color filter includes a red color layer, a reddish green color layer, a blue color layer, and a blueish green color layer.

(6) The display device according to (2) to (5), wherein the color filter has a colorless and transparent region.

(7) The display device according to (6), wherein the area of the colorless and transparent area is 1/4 or more of the area of the entire area of the color filter.

(8) Substrate (A) In each wavelength transmittance obtained by measuring with the two absorption axes orthogonal to each other,
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is larger than 0.3%, and
The display device according to (1) to (7), wherein the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm is larger than 0.3%.

(9) The display device according to (1) to (8), wherein the display device is a liquid crystal display device.

(10) The display device according to (9), wherein the liquid crystal display device is a reflective liquid crystal display device.

(11) Described in (2) to (10), wherein at least a reflector, a base material (A), a liquid crystal layer, a color filter, and a base material (A) are arranged in this order from the back side of the display device. Display device.

(12) The display device according to (11), wherein the liquid crystal layer is arranged as a reflective electrode, a liquid crystal layer, and a transparent electrode in this order from the back surface side.

(13) The display device according to (11) or (12), wherein the reflector is a diffuse reflection type.

(14) The display device according to (12), wherein the reflective electrode is a diffuse reflection type.

(15) The display device according to (11) to (14), wherein a base material having a light diffusing function is provided between the base material (A) and the liquid crystal layer.

(16) The display device according to (1) to (15), wherein a base material having a retardation value of 120 to 160 nm and the base material (A) are laminated.

The display device of the present invention can realize high-quality white display, black display, and excellent color display without coloring while having high reflectance.

It is a figure which showed the relationship between the NTSC ratio and the transmittance when light transmitted through a color filter twice. It is a vertical sectional view of the display device which concerns on Example 1. FIG. It is a top view of the color filter of the display device shown in FIG. 2 (a). It is a figure which shows the relationship between the parallel transmittance and the orthogonal transmittance of the polarizing plate made from the same material as the base material (A). It is a figure which showed the relationship between the parallel transmittance and contrast. It is a vertical sectional view of the display device which concerns on Example 2. FIG. It is a top view of the color filter of the display device shown in FIG. 5A. It is a vertical sectional view of the display device which concerns on Example 3. FIG. It is a top view of the color filter of the display device shown in FIG. 6A. It is a vertical sectional view of the display device which concerns on Example 4. FIG. It is a top view of the color filter of the display device shown in FIG. 7A. It is a vertical sectional view of the display device which concerns on Example 5. FIG. It is a vertical sectional view of the display device which concerns on Example 6. FIG.

In the present invention, it is a base material having a polarizing function and containing an azo compound.
In each wavelength transmittance obtained by measuring the absorption axes of the two substrates in parallel,
The average transmittance from 520 nm to 590 nm is 30% or more,
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 5%, and
The absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm is within 5%.
Further, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 2% in each wavelength transmittance obtained by measuring the absorption axes of the two substrates at right angles. And
The present invention relates to a display device comprising a base material (A) characterized in that the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm is within 2%.

(About base material (A))
The transmittance of the display device provided with the base material (A) of the present invention includes an average transmittance of 30 for each wavelength of 520 nm to 590 nm obtained by measuring the two absorption axes of the base material (A) in parallel. % Or more. As a result, the display device provided with the base material (A) of the present invention can be bright and have high brightness.

In particular, each wavelength of 520 nm to 590 nm is the wavelength with the highest visibility based on the color matching function used in the calculation when showing a color in JIS Z 8701, and the transmittance of each wavelength in this range can be visually confirmed. It is important to control the transmittance of each wavelength from 520 nm to 590 nm to 30% or more because the transmittance is close to the available transmittance.

For example, what is the average transmittance of 520 nm to 590 nm obtained by measuring the absorption axes of two base materials in parallel and the visible sensitivity-corrected parallel transmittance obtained by making the absorption axes of two base materials parallel to each other? , Shows almost the same value. From this, it can be seen that it is very important to adjust the transmittance between 520 nm and 590 nm.

The transmittance required for the display device is 30% to 45% as the average transmittance of each wavelength of 520 nm to 590 nm obtained by measuring the two absorption axes of the base material (A) in parallel, and is preferable. It is 35% to 40%, more preferably 36% to 37%. The degree of polarization at that time may be 50% to 100%, preferably 60% to 100%, and more preferably 70% to 100%.

A higher degree of polarization is preferable, but a higher degree of polarization tends to reduce the transmittance. Therefore, it is necessary to select a polarizing element having a degree of polarization suitable for the display device in terms of the relationship between the degree of polarization and the transmittance. is there.

In the present invention, in each wavelength transmittance obtained by measuring the absorption axes of the two substrates (A) in parallel, not only the average transmittance of 520 nm to 590 nm but also the average transmittance of 420 nm to 480 nm and 520 nm. The absolute value of the difference from the average transmittance of ~ 590 nm is within 5%, and the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm is within 5%. Also needs. Each wavelength of 420 nm to 480 nm, 520 nm to 590 nm, and 590 nm to 660 nm is a main wavelength band based on the color matching function used in the calculation when showing a color in JIS Z 8729.

Specifically, in the XYZ color matching function of JIS Z 8701, which is the basis of JIS Z 8729, x (λ) having a maximum value of 600 nm, y (λ) having a maximum value of 550 nm, and 455 nm as a maximum value are used. When the maximum value of each z (λ) is set to 100, the wavelengths showing a value of 20 or more are the wavelengths of 420 nm to 480 nm, 520 nm to 590 nm, and 590 nm to 660 nm.

Using a polarizing element or a polarizing plate in which the respective wavelength transmittances of 420 nm to 480 nm, 520 nm to 590 nm, and 590 nm to 660 nm are adjusted to a predetermined transmittance, the base material (A) having a polarizing function is used as the base material. By using (A), the display device of the present invention can be achieved. The adjustment range is the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm in each wavelength transmittance obtained by measuring the two absorption axes of the base material (A) in parallel. The absolute value needs to be within 5%, preferably within 3%.

It is also necessary to adjust the predetermined transmittance for each wavelength transmittance obtained by measuring the absorption axes of the two base materials (A) at right angles. The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 2%, and the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm. The absolute value of is required to be within 2%.

Further, in each wavelength transmittance obtained by measuring the absorption axes of the two base materials (A) at orthogonal angles, in the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm. Must be within 2%, but preferably within 1%. Moreover, the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm needs to be within 2%, but is preferably within 1%.

Furthermore, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm in each wavelength transmittance obtained by measuring the absorption axes of the two substrates (A) at orthogonal angles. In, it is necessary to make it larger than 0.3% due to the problem in the process, but it is preferably 0.5% or more. Moreover, the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm needs to be larger than 0.3% due to process problems, but is preferably 0. It is 5% or more. Here, the problem in the process is the variation in dyeing when a plurality of azo dyes are mixed and dyed.

On the other hand, it is necessary to adjust the average transmittance of 380 nm to 420 nm, 480 nm to 520 nm, and 660 nm to 780 nm, but by adjusting 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 660 nm, depending on the dye. It is not significantly affected and does not need to be adjusted.

In a reflective liquid crystal display device, how to increase the reflectance is important. This is because it is necessary to ensure sufficient visibility even in a relatively dark environment such as indoors. However, in the color reflective liquid crystal display device, the transmittance of the color filter is low, so that the reflectance is lowered. As a diagram showing that the reflectance is lowered by the color filter, FIG. 1 shows a diagram showing the relationship between the NTSC ratio and the transmittance when light is transmitted twice through the color filter.

Here, the NTSC ratio when light is transmitted twice through the color filter is the chromaticity when light is transmitted twice through each color element of the color filter on the chromaticity (x, y) diagram of the CIE1931XYZ color system. The three primary colors of the standard method defined by the CIE1931XYZ color system chromaticity (x, y) by the area plotted in and connected by a straight line and the National Television Standards Committee. , Red (0.670, 0.330), green (0.210, 0.710), and blue (0.140, 0.080) are expressed in% as a ratio to the area of the triangle.

Further, in the color reflection type liquid crystal display device, since the light from the outside is transmitted through the color filter twice, the NTSC ratio of the color filter is set to the NTSC ratio when the light is transmitted twice.

From FIG. 1, it can be seen that the transmittance is low when the NTSC ratio is large, but the transmittance increases as the NTSC ratio is small. Therefore, in order to increase the reflectance of the color reflective liquid crystal display device, the transmittance may be increased, that is, the NTSC ratio may be decreased. In our research on color-reflective liquid crystal display devices, we have found that in color-reflective liquid crystal display devices, the human eye can sufficiently perceive colors even if the NTSC ratio is small. As a result, the value of the NTSC ratio at which the human eye can sufficiently perceive the color is 1% to 20%, preferably 1% to 10%, and more preferably 1% to 5%.

In a color reflective liquid crystal display device that uses a color filter with a small NTSC ratio, the reflectance is improved and the sensitivity to the color of the human eye is improved. Therefore, when a conventional polarizing plate is used, coloring occurs in white display and / or black display, and the display quality is deteriorated by visually recognizing it. By using a color filter with a small NTSC ratio and the base material (A) at the same time in a color reflective liquid crystal display device, for the first time, there is no coloring in bright color display with high reflectance and white display and / or black display. We have found that excellent color display can be achieved.

As a method of increasing the NTSC ratio of the color filter to 1% to 20%, a method of reducing the concentration of the dye or pigment forming the color layer, a method of reducing the thickness of the color layer, and a method of forming a transparent region without the color layer are formed. There is a way to do it. In particular, in the method of forming a transparent region without a color layer, it is possible to suppress coloring of the transparent region without a color layer by a polarizing plate, so that the use of the base material (A) is particularly effective.

In the method of forming a transparent region without a color layer, the area of the transparent region without a color layer needs to be 1/4 or more of the area of the total region. Preferably, the area of the transparent region without the color layer is ½ or more of the area of the total region. More preferably, the area of the transparent region without the color layer is 2/3 or more of the area of the total region. As a result, it is possible to realize a color-reflecting liquid crystal having a high transmittance, that is, a bright color display having a high reflectance.

By providing the display device with a polarizing element or a polarizing plate provided with the base material (A), it is possible to control the color expression of the display device. In particular, when the polarizing element or the polarizing plate provided with the base material (A) is provided in the display device as in general usage, the hue based on the polarizing plate can be controlled, and the display device is of high quality when displaying white. It is possible to express white like paper, and when displaying black, it is possible to express jet-black black.

With a general polarizing plate, when controlled so that black can be expressed, the white purity decreases in the transmittance when the polarizing elements are parallel, and the color develops yellow or yellowish green. On the contrary, when the transmittance when the polarizing elements are parallel to each other so as to express white is controlled, the black purity is lowered in the transmittance when the polarizing elements are orthogonal to each other, and the color is colored blue. .. When a polarizing element having such a hue is provided in the display device, it is natural that the display device colors the hue of the polarizing element.

The color of this display device can be optimized by adjusting the spectral distribution of the backlight and the color filter in the conventional transmissive liquid crystal device using the backlight. However, it was necessary to adjust the color of the polarizing plate with a backlight or a color filter.

However, since the reflective display device that displays using external light, especially the reflective liquid crystal device, does not have a backlight, the yellow color at the time of white display and the blue color at the time of black display are displayed. At the same time, it cannot be improved with color filters. Further, when it is used in a display device that uses a polarizing plate to prevent reflection of external light, for example, an organic electroluminescence display device (hereinafter abbreviated as OLED), a plasma display, or the like, the polarizing plate emits light. It is provided together with a retardation plate on the side of the display device that is observed by a person.

With conventional general polarizing plates, improvement of the hue of the polarizing plate has been very important because it reduces the color purity of the color of the OLED. The formulation of the present invention is also effective for display devices such as OLEDs that want to control such reflected light. That is, in the present invention, the color development caused by the problem of yellow coloration at the time of white display and blue coloration at the time of black display, which is possessed by the conventional polarizing plate, is improved, and it is similar to high-quality paper at the time of white display. Achieved to provide a display device that displays white and jet-black black when displayed in black, and can improve the brightness at the time of display and also improve the contrast, especially in a reflective display. did.

(Method for producing a polarizing element and a polarizing plate for the base material (A) of the present invention)
As an element capable of containing an azo compound, particularly a dichroic dye in general, an element made of a hydrophilic polymer is used, for example. The hydrophilic polymer is not particularly limited, and examples thereof include polyvinyl alcohol-based resins, amylose-based resins, starch-based resins, cellulosic-based resins, and polyacrylate-based resins. When a dichroic dye is contained, a polyvinyl alcohol-based resin and a resin made of a derivative thereof are most preferable from the viewpoint of processability, dyeability, crosslinkability and the like. A polarizing element or a polarizing plate can be produced by using these resins as a film shape, containing the dye of the present invention and a compound thereof, and applying an orientation treatment such as stretching.

As the dichroic dye composed 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, Sea. Ai. direct. Examples thereof include Green 59 and the organic dyes described in JP-A-2001-33627, JP-A-2002-296417, and JP-A-60-156759.

These organic dyes can be used as alkali metal salts (for example, Na salt, K salt, Li salt), ammonium salts, or amine salts in addition to free acids. However, the dichroic dye is not limited to these, and a known dichroic dye can be used. When the azo compound is a free acid, a salt thereof, or a copper complex salt dye thereof, the optical properties are particularly improved. This azo dye may be used alone or in combination with another azo compound, and the composition is not limited. Using such an azo compound, the transmittance of the polarizing element is measured with the absorption axes of the two substrates (A) parallel to each other, and the average transmittance of 520 nm to 590 nm is 30 at each wavelength transmittance. % Or more, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 5%, and the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm. The absolute value of the difference from the average transmittance is within 5%, and the average transmittance of 420 nm to 480 nm is obtained at each wavelength transmittance obtained by measuring the two substrates (A) with the absorption axes orthogonal to each other. The absolute value of the difference between the rate and the average transmittance of 520 nm to 590 nm is within 2%, and the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm is 2%. By adjusting within the range, a polarizing element for realizing the present invention can be produced.

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

A film formed from such a polyvinyl alcohol-based resin is used as a raw film. The method for forming the film of the polyvinyl alcohol-based resin is not particularly limited, and the film 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 5 to 20% by weight, preferably 8 to 15% by weight. The film thickness of the raw film made of the polyvinyl alcohol-based resin is not particularly limited, but is preferably about 5 μm to 150 μm, preferably about 10 μm to 100 μm, for example.

The raw film obtained as described above is then subjected to a swelling step. The swelling treatment is applied by immersing 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 from 1.00 to 1.50 times, preferably 1.10 to 1.35 times. When the time for producing the polarizing element is shortened, the swelling treatment may be omitted because it swells even during the dyeing treatment of the azo compound.

The swelling step is performed by immersing the polyvinyl alcohol resin film in a solution at 20 ° C. to 50 ° C. for 30 seconds to 10 minutes. The solution is preferably water. When the time for manufacturing the polarizing element is shortened, the swelling step can be omitted because the swelling occurs even during the dyeing process of the dye.

After the swelling process, a dyeing process is performed. In the dyeing step, it can be impregnated with an azo compound (commonly known as a dichroic dye) shown in Non-Patent Document 1 or the like. Since impregnating this azo compound is a step of coloring the color, it is called a dyeing step. Here, as the azo compound, the dye described in Non-Patent Document 1 or the azo compound represented by the formula (1) or the like can be adsorbed and impregnated on the polyvinyl alcohol film in the dyeing step. Alternatively, a group having the polarization function of the present application is obtained by immersing in an aqueous solution impregnated with iodine and potassium iodide to adsorb iodine, and then adsorbing and impregnating each of the azo compounds represented by the formula (1). It can also be used as the material (A). In addition to the azo compound represented by the formula (1), the azo compound to be adsorbed together with iodine includes the azo compounds shown in Examples 1 to 5 of Japanese Patent Application Laid-Open No. 64-5623 and Examples of JP-A-03-12606. The azo compounds shown in 1 to 4 may be used.

(In the formula, A ₁ represents a phenyl group or a naphthyl group having a substituent, and R ₁ or R ₂ independently have a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, or a lower group having a sulfo group. Indicates an alkoxy group, and X ₁ indicates a phenylamino group which may have a substituent.)

The dyeing step is not particularly limited as long as it is a method of adsorbing and impregnating the dye on the polyvinyl alcohol film, but for example, the dyeing step is performed by immersing the polyvinyl alcohol resin film in a solution containing the dichroic dye. .. The solution temperature in this step is preferably 5 to 60 ° C, more preferably 20 to 50 ° C, and particularly preferably 35 to 50 ° C. The time of immersion in the solution can be appropriately adjusted, but is preferably adjusted to 30 seconds to 20 minutes, more preferably 1 to 10 minutes. The dyeing method is preferably immersed in the solution, but it can also be performed by applying the solution to a polyvinyl alcohol resin film.

The solution containing the dichroic dye can contain sodium carbonate, sodium hydrogen carbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate, etc. as a dyeing aid. The content thereof can be adjusted at an arbitrary concentration depending on the time and temperature depending on the dyeability of the dye, and the respective contents are preferably 0 to 5% by weight, more preferably 0.1 to 2% by weight. The azo compound which is a dichroic dye described in Non-Patent Document 1 and the azo compound represented by the formula (1) are used as a free acid and may be a salt of the compound. Such salts can also be used as alkali metal salts such as lithium salts, sodium salts and potassium salts, or organic salts such as ammonium salts and alkylamine salts. A sodium salt is preferred.

After the dyeing process, the cleaning process (hereinafter referred to as cleaning process 1) can be performed before starting the next process. The cleaning step 1 is a step of cleaning the dye solvent adhering to the surface of the polyvinyl alcohol resin film in the dyeing step. By performing the washing step 1, it is possible to suppress the transfer of the dye into the liquid to be treated next. In the cleaning step 1, water is generally used as the cleaning solution. The cleaning method is preferably immersed in a solvent, but cleaning can also be performed by applying a cleaning solution to a polyvinyl alcohol resin film. The washing time is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the cleaning solution in the cleaning step 1 needs to be a temperature at which the hydrophilic polymer does not dissolve. Generally, it is washed at 5 to 40 ° C. However, since there is no problem in performance even if the cleaning step 1 is not performed, this step can be omitted.

After the dyeing step or the cleaning step 1, a step of adding a cross-linking agent and / or a water resistant agent can be performed. Examples of the cross-linking agent include a boron compound such as boric acid, boric acid or ammonium borate, a polyvalent aldehyde such as glyoxal or glutaraldehyde, a polyvalent isocyanate compound such as biuret type, isocyanurate type or block type, and titanium oxy. Titanium-based compounds such as sulfate can be used, but ethylene glycol glycidyl ether, polyamide epichlorohydrin and the like can also be used. Examples of the water resistant agent include succinic acid peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride and the like, but boric acid is preferable. Used. A step of incorporating the cross-linking agent and / or the water-resistant agent using at least one or more of the cross-linking agents and / or the water-resistant agents shown above is performed. The solvent at that time is preferably, but not limited to, water.

The concentration of the cross-linking agent and / or the water-resistant agent in the solvent in the step of containing the cross-linking agent and / or the water-resistant agent is 0.1 to 6.0 with respect to the solvent when boric acid is taken as an example. By weight% is preferable, and 1.0 to 4.0% by 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 impregnating the polyvinyl alcohol resin film with a cross-linking agent and / or a water resistant agent is preferably to immerse the solution in a solvent, but the solution may be applied or applied to the polyvinyl alcohol resin film. The treatment time in this step is preferably 30 seconds to 6 minutes, more preferably 1 to 5 minutes. However, it is not essential to contain a cross-linking agent and / or a water-resistant agent, and if it is desired to shorten the time and the cross-linking treatment or the water-resistant treatment is unnecessary, this treatment step may be omitted. ..

After performing the dyeing step, the cleaning step 1, or the step of containing the cross-linking agent and / or the water resistant agent, the stretching step is performed. The stretching step is a step of stretching the polyvinyl alcohol film uniaxially. The stretching method may be either a wet stretching method or a dry stretching method, and the present invention can be achieved when the stretching ratio is 3 times or more. The stretching ratio is preferably 3 times or more, preferably 5 to 7 times.

In the case of the dry stretching method, when the stretching heating medium is an air medium, the temperature of the air medium is preferably room temperature to 180 ° C. Further, the humidity is preferably treated in an 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 carried out in one step, but can also be carried out by multi-step stretching in two or more steps.

In the case of the wet stretching method, stretching is performed in water, a water-soluble organic solvent, or a mixed solution thereof. It is preferable to carry out the stretching treatment while immersing in a solution containing a cross-linking agent and / or a water resistant agent. Examples of the cross-linking agent include a boron compound such as boric acid, boric acid or ammonium borate, a polyvalent aldehyde such as glyoxal or glutaraldehyde, a polyvalent isocyanate compound such as biuret type, isocyanurate type or block type, and titanium oxy. Titanium-based compounds such as sulfate can be used, but ethylene glycol glycidyl ether, polyamide epichlorohydrin and the like can also be used. Examples of the water resistant agent include succinic acid peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride and magnesium chloride. Stretching is performed in a solution containing at least one of the above-mentioned cross-linking agents and / or water resistant agents. Boric acid is preferable as the cross-linking agent.

The concentration of the cross-linking agent and / or the water resistant agent in the stretching step is preferably, for example, 0.5 to 15% by weight, more preferably 2.0 to 8.0% by weight. The draw ratio is preferably 2 to 8 times, more preferably 5 to 7 times. The stretching temperature is preferably 40 to 60 ° C, more preferably 45 to 58 ° C. The stretching time is usually 30 seconds to 20 minutes, but more preferably 2 to 5 minutes. The wet stretching step can be carried out in one step, but it can also be carried out by multi-step stretching in two or more steps.

After the stretching step, a cross-linking agent and / or a water resistant agent may precipitate on the film surface, or foreign matter may adhere to the film surface. Therefore, a cleaning step (hereinafter referred to as cleaning step 2) for cleaning the film surface may be performed. it can. The washing time is preferably 1 second to 5 minutes. The cleaning method is preferably to immerse in a cleaning solution, but the solution can be washed by coating or coating on a polyvinyl alcohol resin film. The cleaning treatment can be performed in one stage, or the multi-stage treatment in two or more stages can be performed. The solution temperature in the washing step is not particularly limited, but is usually 5 to 50 ° C, preferably 10 to 40 ° C.

Examples of the solvent used in the treatment steps up to this point include water, dimethylsulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol or tri. Examples thereof include alcohols such as methylolpropane and solvents such as amines such as ethylenediamine or diethylenetriamine, but the present invention is not limited thereto. It is also possible to use a mixture of one or more of these solvents. The most preferred solvent is water.

After the stretching step or the washing step 2, the film drying step is performed. The drying treatment can be carried out by natural drying, but in order to further improve the drying efficiency, the surface moisture can be removed by compression with a roll, an air knife, a water absorption roll or the like, and / or air drying is performed. You can also do it. The drying treatment temperature is preferably 20 to 100 ° C., more preferably 60 to 100 ° C. The drying treatment time can be applied from 30 seconds to 20 minutes, but is preferably 5 to 10 minutes.

With the above method, the transmittance of the substrate (A) having a polarizing function, that is, the transmittance obtained by containing the azo compound and measuring the two absorption axes of the substrate (A) in parallel, is 520 nm. The average transmittance of about 590 nm is 30% or more, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 5%, and the average of 520 nm to 590 nm. The absolute value of the difference between the transmittance and the average transmittance of 590 nm to 660 nm is within 5%, and each wavelength transmittance obtained by measuring the absorption axes of the two substrates (A) at orthogonal angles. The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 2%, and the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm. It is possible to obtain a polarizing element in which the absolute value of the difference between the two is within 2%.

The obtained polarizing element is used as a polarizing plate by providing a transparent protective layer on one side or both sides thereof. The transparent protective layer can be provided as a coating layer made of a polymer or as a laminated layer of a film. As the transparent polymer or film forming the transparent protective layer, a transparent polymer or film having high mechanical strength and good thermal stability is preferable. Examples of the substance used as the transparent protective layer include cellulose acetate resins such as triacetyl cellulose and diacetyl cellulose or films thereof, acrylic resins or films thereof, polyvinyl chloride resins or films thereof, nylon resins or films thereof, polyester resins or films thereof. A film, a polyarylate resin or a film thereof, a cyclic polyolefin resin having a cyclic olefin such as norbornene as a monomer or a film thereof, polyethylene, polypropylene, a polyolefin having a cyclo-based or norbornene skeleton or a copolymer thereof, a main chain or a side chain Examples thereof include imide and / or amide resins or polymers, or films thereof. Further, as the transparent protective layer, a resin having a liquid crystal property or a film thereof may be provided. The thickness of the protective film is, for example, about 0.5 to 200 μm. A polarizing plate is produced by providing one or more layers of the same or different resin or film therein on one side or both sides.

In some cases, when the obtained polarizing plate is attached to a display device such as a liquid crystal or an organic electroluminescence (commonly known as OLED or OEL), the viewing angle is improved and / or on the surface of a protective layer or film which will be a non-exposed surface later. Alternatively, various functional layers for improving contrast, a layer having brightness improving property, or a film may be provided. It is preferable to use an adhesive to attach the polarizing plate to these films and display devices.

Further, the various functional layers indicate a layer or a film that controls the phase difference. In particular, in order to impart antireflection, a polarizing element or a polarizing plate is provided with a retardation plate (hereinafter, 1 / 4λ) adjusted to have a phase difference of 1/4 with respect to 550 nm, which has high visibility. Alternatively, it is generally provided by bonding at 45 ° to the absorption axis of the polarizing plate. The 1 / 4λ retardation value is a retardation plate adjusted to 120 nm to 160 nm, preferably 130 nm to 145 nm.

However, since the antireflection function may be insufficient with only 1 / 4λ, a retardation plate adjusted to a retardation value of 240 nm to 300 nm in order to further improve the antireflection function (hereinafter, 1). There is also a method of improving antireflection by using two retardation plates in which 1 / 4λ is bonded at 15 ° to the absorption axis of the polarizing plate (abbreviated as / 2λ).

Further, this polarizing plate may have various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer on the other surface, that is, the protective layer or the exposed surface of the film. A coating method is preferable for producing layers having various functions, but a film having the functions can also be attached via an adhesive or an adhesive.

With the above method, the average transmittance of 520 nm to 590 nm is 30% or more in each wavelength transmittance obtained by containing the azo compound and measuring the two absorption axes of the base material (A) in parallel. , The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 5%, and the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm. The absolute value of the difference is within 5%, and the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 520 nm in each wavelength transmittance obtained by measuring the two base materials (A) with the absorption axes orthogonal to each other. A polarizing element in which the absolute value of the difference from the average transmittance of 590 nm is within 2%, and the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm is within 2%. And a polarizing plate can be obtained.

The liquid crystal display device using the polarizing element or the polarizing plate of the present invention can be bright and have high brightness. The result is a liquid crystal display device that is highly reliable, has high contrast over the long term, and has high color reproducibility.

The polarizing plate of the present invention thus obtained is used as a base material (A) having a polarizing function by providing a protective layer or a functional layer and a support such as flat glass as necessary, and is used as a liquid crystal projector, a calculator, a clock, a notebook, etc. It is used in personal computers, word processors, LCD TVs, polarized lenses, polarized glasses, car navigation systems, and indoor and outdoor measuring instruments and displays. In particular, it is suitable for a reflective liquid crystal display device, a transflective liquid crystal display device, an organic electroluminescence, and the like.

A general reflective liquid crystal display device has a structure of a reflector, a polarizing plate, a liquid crystal cell, and a polarizing plate in order from the back side, and in order to improve the display quality, a light diffusing plate or a retardation plate (a retardation plate) or a retardation plate ( For example, it is a general configuration to use 1 / 4λ).

For the general configuration, using the base material (A) having a polarization function of the present application, a diffuse reflector, a base material (A) having a polarization function, a liquid crystal cell, and a group having a polarization function are used in this order from the back side. The structure of the material (A), or the structure exemplified by the reflector, the diffuser, the base material (A) having a polarization function, the liquid crystal cell, and the base material (A) having a polarization function in this order from the back side. As a result, it becomes possible to provide a display device that displays high-quality paper-like white when white is displayed and displays jet-black black when black is displayed, so that the display quality is dramatically improved.

The light diffusing plate is generally provided between the reflecting plate and the polarizing plate on the back side, but the laminated structure is not limited as long as the light diffusing effect is obtained. Alternatively, a method such as a single polarizing plate method (SPD mode) as shown in Non-Patent Document 3 and a configuration as shown in Non-Patent Document 4 have been reported. In such a configuration, in a general polarizing plate, when an attempt is made to display a jet-black black color, a white display in which a yellow color is developed is obtained in a white display, and conversely, an attempt is made to display a high-quality paper-like white color. Then, when displaying black, it turned blue.

Due to such a problem, in a reflective liquid crystal, particularly a color reflective liquid crystal display device, it has been necessary to improve white in white display and black in black display with a color filter or a liquid crystal element. It has been considered low reflectance, dark display, and low display quality. By using the base material (A) having a polarization function in such a reflective liquid crystal display device, it is caused by the problem that the polarizing plate has a yellow color when displaying white and a blue color when displaying black. Since there is no dependency on the transmittance of each wavelength in both parallel and orthogonal positions, high-quality paper-like white is displayed when white is displayed, and jet-black black is displayed when black is displayed. A wide range of display devices can be provided.

In particular, since the transmittance is constant and there is no wavelength dependence of the transmittance at each wavelength, it is particularly effective for a black-and-white reflective display whose color cannot be corrected by a color filter. Further, the base material (A) having the present polarization function has a required transmittance range of the average transmittance of each wavelength of 520 nm to 590 nm obtained by measuring the absorption axes of the two base materials in parallel. Since the transmittance can be adjusted arbitrarily from 25% to 45%, it can be achieved that the brightness at the time of display can be improved and the contrast can also be improved.

Further, in order to improve the display quality, a base material (A) having a polarizing function is laminated with a reflective polarizing plate with a liquid crystal cell sandwiched therein, and a base material having a light diffusing function is provided, and the polarizing function is provided. By installing the base material (A) having the above on the observer side with respect to the liquid crystal cell, the display quality thereof is improved. The reflective polarizing plate includes a polarizer having regular irregularities as exemplified in Japanese Patent No. 4162645 and Japanese Patent No. 4442760, and thermoplastics such as JP-A-2006-215175 and JP-A-2007-298634. It is possible to use an alternating laminated type of resin, a BEF series manufactured by 3M, particularly a DBEF series, or a resin molding type having a special shape such as BEFRP.

Further, an anisotropic light diffusing plate as described in Japanese Patent Application Laid-Open No. 2012-37611 can also be used as a reflective polarizing plate because it has a polarization function by anisotropic light diffusion. This anisotropic light diffuser has an anisotropic light diffuser in an exemplary configuration of a reflector, a liquid crystal cell, a retardation plate (for example, 1 / 4λ), and a base material (A) having a polarizing function in this order from the back surface side. It may be provided between the reflector and the liquid crystal cell, between the liquid crystal cell and the retardation plate, or between the retardation plate and the polarizing plate.

Furthermore, it can be applied to active matrix type reflective displays. A reflective liquid crystal display device in which a base material having a light diffusion function is provided between a base material (A) having a polarization function and a liquid crystal cell, and the electrode of the liquid crystal cell is a specular reflection type electrode. Can be achieved by As a specific configuration example, a reflective electrode, a liquid crystal cell, a light diffusing plate, and a base material (A) having a polarizing function are configured in this order from the back surface side. At that time, in order to improve visibility, a retardation plate may be provided between any of the layers.

In particular, since the active matrix type reflective display is suitably used for a reflective color liquid crystal display device, it is easily affected by the color of the polarizing element or the polarizing plate, and is wavelength-dependent in each wavelength transmittance of the parallel position and the orthogonal position. A substrate having no property, having a substantially constant transmittance, no color shift, and a high degree of polarization is required. For such a reflective color liquid crystal display, the base material (A) having a polarizing function is effective, and the display device provided with the base material (A) becomes a display device having a very high color rendering property.

Further, as an application to an active matrix type reflective display, as described in Non-Patent Document 4, the electrode of the liquid crystal cell is made uneven by resin or the like, and an aluminum electrode is used without using a transparent ITO electrode. By using and reflecting the diffuse reflection type electrode, the display quality can be further improved. As a specific configuration example, a diffusion type reflective electrode, a liquid crystal cell, and a base material (A) having a polarizing function are configured in this order from the back surface side. At that time, in order to improve visibility, a retardation plate may be provided between any of the layers. Further, a base material having a light diffusing function may be provided between any of the layers, and further light diffusing property may be provided to improve visibility.

By the above method, even if it is a reflective liquid crystal device that has been considered to have low display quality, the display quality is dramatically improved, and the yellow color of the white plate and the black color of the black plate are displayed. Improves the color of the display device caused by the problem of blue coloration during display, displays white when displaying white, displays black when displaying black, and shows high color playability in a reflective color liquid crystal display device. A display device can be provided.

Furthermore, the base material (A) having a polarizing function has an average transmittance of each wavelength of 520 nm to 590 nm obtained by measuring the absorption axes of the two base materials (A) in parallel as the range of transmittance. Since the transmittance can be adjusted arbitrarily from 25% to 45%, it is possible to improve the brightness at the time of display and also to improve the contrast. Further, depending on the configuration of the reflective liquid crystal, the display quality can be improved to each stage.

(Example 1)
The display device according to the first embodiment of the present invention will be described with reference to FIG. FIG. 2A is a vertical cross-sectional view of the display device of the first embodiment, in which the base material (A) 1, the retardation plate 2, and the top surface (observer side) of the display device (hereinafter, simply referred to as the top surface) are used. A diffuser plate 3, a first glass substrate 4, a color filter 5, a counter electrode (ITO6), a liquid crystal layer 7, a reflector / pixel electrode (Al) 8, and a second glass substrate 9 are arranged. Here, the aspect ratio of the drawing is different from the actual ratio for the sake of clarity. In the following examples, the parts with the same reference numerals represent the same products. FIG. 2B is a plan view of the color filter 5, and shows that the color filter 5 is composed of pixel elements of red 5a, green 5b, and blue 5c. In an actual display device, the period of this red, green, and blue pattern is repeated by the number of pixels.

The base material (A) 1 is a dye-based polarizing plate obtained by dyeing PVA with a dye. FIG. 3 is a diagram showing the relationship between the parallel transmittance and the orthogonal transmittance of a polarizing plate made of the same material as the base material (A) 1. That is, a dye-based polarizing plate is produced by adjusting the dyeing concentration with the same material as the base material (A) 1 used, and the transmittance (parallel) obtained by measuring the absorption axes of the two polarizing plates in parallel. It is a figure which showed the relationship between the transmittance (transmittance) and the transmittance (orthogonal transmittance) obtained by measuring with the absorption axes of two polarizing plates made orthogonal to each other. From FIG. 3, it can be seen that as the parallel transmittance increases, the orthogonal transmittance also increases. FIG. 4 is a diagram showing the relationship between parallel transmittance and contrast. From FIG. 4, it can be seen that the contrast decreases as the parallel transmittance increases. Here, the contrast is the contrast of the polarizing plate represented by the following equation.
Contrast = parallel transmittance / orthogonal transmittance

The parallel transmittance of the base material (A) 1 was adjusted to a value of 36% to 39% because the contrast of the polarizing plate needs to be 10 or more and the decrease in reflectance is suppressed. In a reflective liquid crystal display device, it is important to increase the reflectance to realize a bright display. In this example, the NTSC ratio of the color filter was adjusted to 5% to 15% so that a reflectance of 20% or more could be obtained and a good color display could be realized.

By the way, in terms of reflectance, the product of the transmittance of the color filter and the parallel transmittance of the base material (A) 1 is the largest factor. For example, referring to FIG. 1 showing the relationship between the NTSC ratio and the transmittance when light is transmitted twice through the color filter, the transmittance of the color filter is 70 to 90 when the NTSC ratio of the color filter is 5% to 15%. %, A reflectance of 20% or more can be obtained, and a good color display can be realized. The color filter can adjust the color depth by changing the layer thickness and the pigment density.

Further, in the transmittance obtained by measuring the two absorption axes of the base material (A) in parallel,
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is 1.0% to 2%, and
The absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm is 1.0% to 2.0%.
Further, in each wavelength transmittance obtained by measuring the absorption axes of the two substrates at right angles,
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is 0.5% to 1.0%.
The absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm was adjusted to be 0.5% to 1%. In the reflective liquid crystal display device of Example 1 produced by such a method, high-quality white and black displays having high reflectance, brightness, and no coloring, and excellent color display have been realized.

(Example 2)
The display device of the second embodiment of the present invention will be described with reference to FIG. FIG. 5A is a vertical sectional view of the display device of the second embodiment, and is a collar provided with a base material (A) 1, a retardation plate 2, a diffusion plate 3, a glass substrate 4, and a transparent region in this order from the top surface. A filter 51, a counter electrode (ITO) 6, a liquid crystal layer 7, a reflector / pixel electrode (Al) 8, and a second glass substrate 9 are arranged. Here, the aspect ratio of the drawing is different from the actual ratio in order to make the effect easy to understand.

FIG. 5B is a plan view of the color filter 51 provided with a transparent region, and shows that the color filter 51 is composed of pixel elements of red 51a, green 51b, and blue 51c. Each color of the color filter 51 is provided with a transparent region without a color layer as a part of each color region. By changing the area of the transparent region, the NTSC ratio of the color filter 51 can be adjusted in the range of 1% to 20%, and the reflectance can be increased. It is more preferable that the transparent region is provided in the central portion because there is less variation during production. Then, by using the base material (A) 1, coloring of the transparent region formed on the color filter 51 is also prevented, and high-quality white display and black display without coloring while having high reflectance are displayed. And excellent color display can be realized.

(Example 3)
Example 3 of the present invention is shown in FIGS. 6 (a) and 6 (b). Example 3 of the present invention has a different pixel configuration from that of Example 2, and is composed of red, green, blue, and transparent pixels. In addition to the color layers of the color filter 52, red 52a, green 52b, and blue 52c, transparent pixels 52d without a color layer are formed. By adding the transparent pixels 52d to the color layers 52a to 52c, the NTSC ratio becomes as small as 1% to 20%, the reflectance is improved, and a bright display becomes possible.

Further, by making each color layer 52a to 52c and the transparent pixel 52d substantially square and arranging them in a U-shape, the invalid area becomes smaller than when they are arranged side by side, the aperture ratio can be increased, and the reflection becomes possible. It is possible to realize a high-rate color display. Further, by using the base material (A) 1, coloring of the transparent pixel 52d formed on the color filter 52 is prevented, and high-quality white display and black display without coloring while having high reflectance are displayed. And excellent color display can be realized.

(Example 4)
Example 4 of the present invention is shown in FIGS. 7 (a) and 7 (b). The pixel configuration is different from that of Examples 2 and 3, and it is composed of semi-transparent pixels of red, green closer to red, blue, and green closer to blue. The color filter 53 includes a color layer of red 53a, reddish green 53b, blue 53c, and blued green 53d. In the color filter 53, red 53a, reddish green 53b, blue 53c, and blued green 53d are provided with a transparent region without a color layer as a part of each color layer, and the area of the transparent region is changed. As a result, the NTSC ratio of the color filter 53 can be adjusted in the range of 1% to 20% without changing the material and thickness of the color filter 53, and the reflectance can be increased.

In addition, by making each of the four pixels approximately square and arranging them in a U-shape, the invalid area is smaller than when they are arranged side by side, the aperture ratio can be increased, and a color display with high reflectance is realized. can do. Further, by using the base material (A) 1, coloring of the transparent region formed on the color filter 53 is prevented, and high-quality white display and black display without coloring while having high reflectance and black display and Excellent color display can be realized.

(Example 5)
Example 5 of the present invention is shown in FIG. In the fifth embodiment, the reflector / display electrode (Al) having the diffused shape 81 formed is formed. Due to the diffusing function of the reflector and the effect of the diffusing plate 3, external light can be diffused over a wider range.

(Example 6)
Example 6 of the present invention is shown in FIG. In the sixth embodiment, the reflector 10 is arranged on the back surface side of the display device, and the second base material 11 and the second glass substrate 9 are arranged in this order on the reflector 10. A transparent pixel electrode (ITO or IZO) 82 is arranged on the second glass substrate 9. With this structure, it is not necessary to form a reflecting plate in the region sandwiched between the first glass substrate 4 and the second glass substrate 9, and the reflecting plate 10 reflects a specific polarized light. By using the type polarizing plate, it is possible to display using the light incident from the back side through the reflective polarizing plate.

1 base material (A), 2 retardation plate, 3 diffusion plate, 4 first glass substrate, 5 color filter, 6 counter electrode (ITO), 7 liquid crystal layer, 8 reflector and pixel electrode (Al), 9th 2 glass substrate, 5a color filter red area, 5b color filter green area, 5c color filter blue area, 51 color filter with transparent area, 51a color filter red with transparent area Area, 51b green area of color filter provided with transparent area, 51c blue area of color filter provided with transparent area, 51d red area of color filter provided with transparent area, 52a red area of color filter of Example 3 , 52b Green area of the color filter of Example 3, 52c Blue area of the color filter of Example 3, 52d Transparent area of the color filter of Example 3, 53a Red area of the color filter of Example 4, 53b Color of Example 4. Green area near red of the filter, 53c Blue area of the color filter of Example 4, 53d Green area of the color filter of Example 4, 81 Reflector and display electrode (Al) forming a diffused shape, 82 Transparent Pixel electrode (ITO or IZO).

Claims

Contains the azo compound represented by the formula (1) or a salt thereof,

(In the formula, A 1 represents a phenyl group or a naphthyl group having a substituent, and R 1 or R 2 independently have a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, or a lower group having a sulfo group. Indicates an alkoxy group, and X 1 indicates a phenylamino group which may have a substituent.)
In the transmittance obtained by measuring the absorption axes of two substrates in parallel,
The average transmittance of 520 nm to 590 nm is 30% or more,
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 5%, and
The absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 590 nm to 660 nm is within 5%.
Further, in each wavelength transmittance obtained by measuring the absorption axes of the two base materials at right angles,
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is within 2%, and
A display characterized by comprising a base material (A) having a polarizing function, wherein the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm is within 2%. apparatus.
The display device according to claim 1, further comprising a color filter.
The display device according to claim 2, wherein the NTSC ratio when light is transmitted twice through the color filter is 1 to 20.
The display device according to claim 2 or 3, wherein the color filter includes a red color layer, a green color layer, and a blue color layer.
The display device according to any one of claims 2 or 3, wherein the color filter includes a red color layer, a reddish green color layer, a blue color layer, and a blueish green color layer.
The display device according to any one of claims 2 to 5, wherein the color filter has a colorless and transparent region.
The display device according to claim 6, wherein the area of the colorless and transparent region is 1/4 or more of the area of the entire region of the color filter.
In each wavelength transmittance obtained by measuring the absorption axes of the two base materials (A) at right angles,
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is larger than 0.3%, and
The display device according to any one of claims 1 to 7, wherein the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 660 nm is larger than 0.3%.
The display device according to any one of claims 1 to 8, wherein the display device is a liquid crystal display device.
The display device according to claim 9, wherein the liquid crystal display device is a reflective liquid crystal display device.
The method according to any one of claims 2 to 10, wherein at least the reflector, the base material (A), the liquid crystal layer, the color filter, and the base material (A) are arranged in this order from the back side. Display device.
The display device according to claim 11, wherein the liquid crystal layer is arranged in order from the back surface side with a reflective electrode, the liquid crystal layer, and a transparent electrode.
The display device according to claim 11 or 12, wherein the reflector is a diffuse reflection type.
The display device according to claim 12, wherein the reflective electrode is a diffuse reflection type.
The display device according to any one of claims 11 to 14, wherein a base material having a light diffusing function is provided between the base material (A) and the liquid crystal layer.
The display device according to any one of claims 1 to 15, wherein a base material having a retardation value of 120 to 160 nm and the base material (A) are laminated.