JPH0695100A - Color liquid crystal display device - Google Patents

Abstract

PURPOSE:To lessen the leakage of light by dark display parts and to obtain the good display with high contrast by forming color filters of filter materials formed by dispersing pigment particles of a specific value or below of grain sizes into transparent resins. CONSTITUTION:The color filters RF, GF, BF provided on the lower substrate 2 of a liquid crystal cell 1 are formed of the filter materials formed by using the transparent resins, such as polyimide, as a binder and dispersing the pigment particles of <=50nm grain size into such transparent resins. The red filters RF consisting of the filter material dispersed with the red pigment particles, the green filters GF consisting of the filter material dispersed with the green pigment particles and the blule filters BF consisting of the filter material dispersed with the blue pigment particles are alternately provided in correspondence to respective picture element arrays. Then, this liquid crystal display device is constituted by providing the liquid crystal cell 1 with the color filters consisting of the filter materials formed by dispersing the pigment particles into the transparent resins but the scattering of the light by the pigment particles is lessened and the leakage of the light in the dark display parts is lessened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color liquid crystal display device.

[0002]

2. Description of the Related Art In general, a liquid crystal display device has a TN type or STN type liquid crystal cell in which liquid crystal is enclosed between a pair of transparent substrates provided with transparent electrodes and molecules of the liquid crystal are twisted between the substrates. , A color liquid crystal display device which displays a multicolor image such as a full-color image, is composed of a pair of polarizing plates arranged on both sides (light incident side and light emitting side) of the liquid crystal cell. Red, green, and blue color filters are provided on one of the substrates of the liquid crystal cell so as to correspond to each pixel portion.

The color filter is generally formed of a filter material in which a transparent resin such as polyimide is used as a binder and pigment particles having a particle diameter of several hundred nm are dispersed in the transparent resin.

A color liquid crystal display device which displays a multicolor image is in a normally black mode, and liquid crystal molecules of a liquid crystal cell are twisted in the transmission axis direction of the incident side polarization plate and the emission side polarization plate. The light that has passed through the liquid crystal cell is absorbed by the emission side polarizing plate when in the state, and the light that has passed through the liquid crystal cell is transmitted through the emission side polarizing plate when a voltage is applied to the liquid crystal cell and the liquid crystal molecules are vertically aligned. Is set to be emitted.

[0005]

However, in the conventional color liquid crystal display device, a large amount of light leaks in the dark display portion (the portion where the liquid crystal molecules of the liquid crystal cell are in the twist alignment state), and therefore the contrast (brightness ratio) is increased. Had a problem that it would get worse.

This is because light that is uniaxially polarized by the incident-side polarization plate and is incident on the liquid crystal cell is reflected by the surface of the pigment particles when passing through the color filter to cause light scattering, and light having various polarization components. Therefore, in the dark display portion, light of a certain polarization component out of the light emitted from the liquid crystal cell is transmitted through the emission-side polarization plate to generate leakage light, which lowers the contrast.

According to the present invention, a liquid crystal cell is provided with a color filter made of a filter material in which pigment particles are dispersed in a transparent resin, but the leakage of light in the dark display portion caused by the scattering of light by the pigment particles is prevented. An object of the present invention is to provide a color liquid crystal display device capable of obtaining a good display with a high contrast by reducing the number of display devices.

[0008]

A color liquid crystal display device of the present invention includes a first transparent substrate provided with a transparent electrode and a color filter, and a transparent electrode facing the transparent electrode of the first transparent substrate. A liquid crystal cell in which liquid crystal is enclosed between a second transparent substrate and molecules of the liquid crystal are twist-aligned between both substrates, and a pair of polarizing plates arranged on both sides of the liquid crystal cell. In addition, the color filter is formed of a filter material in which pigment particles having a particle size of 50 nm or less are dispersed in a transparent resin.

[0009]

In the color liquid crystal display device of the present invention, a color filter made of a filter material in which pigment particles are dispersed in a transparent resin is provided in a liquid crystal cell, and the particle size of the pigment particles is reduced to 50 nm or less. Therefore, the light scattering by the pigment particles is small, and therefore the light leakage in the dark display portion is small.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a color liquid crystal display device using a TN type liquid crystal cell will be described below with reference to FIG.

This color liquid crystal display device comprises a TN type liquid crystal cell 1 and a pair of polarizing plates 11 and 12 arranged on both sides of the liquid crystal cell 1 (light incident side and light emitting side). Has become.

In the liquid crystal cell 1, a pair of transparent substrates 2 and 3 made of glass or epoxy resin or the like are adhered to each other via a frame-shaped sealing material 4 surrounding the liquid crystal enclosed area.
A nematic liquid crystal LC having a positive dielectric anisotropy is enclosed in a gap surrounded by the sealing material 4 between the three transparent substrates 2 and 3, and the first substrate (the lower side in the drawing) A substrate (hereinafter referred to as a lower substrate) 2 is provided with a transparent electrode 5 for display and color filters RF, GF, and BF for red, green, and blue, and a second substrate (upper substrate in the drawing, hereinafter, upper substrate). A transparent electrode 6 facing the transparent electrode 5 of the lower substrate 2 is provided on the substrate 3.

The liquid crystal cell 1 is of a simple matrix type. The transparent electrodes 5 on the lower substrate 2 are a plurality of scanning electrodes formed in parallel with each other, and the transparent electrodes 6 on the upper substrate 3 are formed.
Are a plurality of signal electrodes used as the scanning electrodes 5.

The color filters RF, GF, BF provided on the lower substrate 2 of the liquid crystal cell 1 will be described. The color filters RF, GF, BF use a transparent resin such as polyimide as a binder, and the transparent resin has a particle size. Are formed of a filter material in which pigment particles of 50 nm or less are dispersed, and a red filter RF made of a filter material in which red pigment particles are dispersed, and a green filter GF made of a filter material in which green pigment particles are dispersed. And a blue filter RF made of a filter material in which blue pigment particles are dispersed are provided alternately corresponding to each pixel column.

The color filters RF, GF, BF are
The transparent electrode (scanning electrode) 5 on the lower substrate 2 side is covered with the transparent protective insulating film 7, and is formed on the protective insulating film 7. In FIG. 1, reference numeral 10 denotes a light-shielding black mask formed of a metal film such as chromium formed on the lower substrate 2 so as to correspond to each pixel column of the liquid crystal cell 1.

On both substrates 2 and 3 of the liquid crystal cell 1, horizontal alignment films 8 and 9 made of polyimide or the like are provided so as to cover the transparent electrodes 5 and 6, respectively. These alignment films 8 and 9 are rubbed in a direction substantially orthogonal to each other, and the molecules of the liquid crystal LC in the liquid crystal cell 1 are disposed on both substrates 2.
The pair of polarizing plates 11 and 12 are arranged with a twist angle of about 90 ° between the three, and the transmission axes of the pair of polarizing plates 11 and 12 are substantially orthogonal to each other.

In the above color liquid crystal display device, color filters RF, GF and BF made of a filter material in which pigment particles are dispersed in a transparent resin are provided in the liquid crystal cell 1, and the particle diameter of the pigment particles is 50 nm. Since it is as small as possible, light leakage in the dark display portion is small.

That is, also in this color liquid crystal display device, the light which is uniaxially polarized by the incident side polarization plate, for example, the lower polarization plate 11 in FIG. 1 and enters the liquid crystal cell 1 is the color filters RF, GF, BF. The pigment particles are irradiated with light when passing through, and the particle diameter of the pigment particles is 50 nm.
Since it is as small as the following, the scattering of light due to the reflection on the surface of the pigment particles is small, and therefore the color filters RF, G
The disturbance of the polarization state of the light transmitted through F and BF is small.

The color filters RF, GF, BF
If the light transmitted through is close to the linearly polarized light, light of a certain polarization component of the light emitted from the liquid crystal cell 1 is transmitted through the emission side polarization plate 12 and the amount of leakage light in the dark display portion is reduced.

The result is obtained by sandwiching a color filter with a pair of polarizing plates whose transmission axes are orthogonal to each other, and measuring the transmittance of light which is incident from one polarizing plate side and is emitted through the other polarizing plate. Also confirmed from.

That is, as a sample for measuring the transmittance,
A color filter using pigment particles having a particle diameter of 200 nm and a color filter using pigment particles having a particle diameter of 20 nm were manufactured, and the transmittances of these color filters were measured. The transmittance of the color filter using is 10% compared to the transmittance of the color filter using pigment particles with a particle diameter of 200 nm.
It was confirmed to be low.

This means that the smaller the particle size of the pigment particles, the less the scattering of light by the pigment particles, and the light incident on the color filter through one of the polarizing plates passes through the color filter in a state close to linearly polarized light. Is coming.

Therefore, according to the color liquid crystal display device described above, although the color filters RF, GF, and BF made of the filter material in which the pigment particles are dispersed in the transparent resin are provided in the liquid crystal cell 1, the surface of the pigment particles is It is possible to reduce leakage of light in the dark display portion caused by the disturbance of the polarization state due to the light scattering due to the reflection of, and to obtain a good display with high contrast.

Although the liquid crystal cell 1 is of a simple matrix type in the above embodiment, the liquid crystal cell 1 has pixel electrodes and active devices such as thin film transistors arranged in an array on one substrate and the other substrate. Alternatively, an active matrix type may be provided in which a counter electrode facing each pixel electrode of the one substrate is provided.

Further, the color liquid crystal display device of the above-mentioned embodiment uses the TN type liquid crystal cell 1, but in the present invention, the STN type in which the liquid crystal molecules are twist-arranged at a twist angle of 180 to 270 °. It can also be applied to a color liquid crystal display device using the liquid crystal cell.

In the liquid crystal display device using the STN type liquid crystal cell, linearly polarized light that has entered the liquid crystal cell through the incident side polarizing plate is changed to elliptically polarized light due to the birefringence of the liquid crystal layer, and the outgoing side polarizing plate is used. An image is displayed by controlling the transmission of light emitted from the liquid crystal cell.This liquid crystal display device has a different refractive index anisotropy for light of each wavelength in the liquid crystal layer of the liquid crystal cell. In the case of a color liquid crystal display device using a STN type liquid crystal cell, since the transmittance of light in the region increases and the display screen is colored, between the liquid crystal cell for display and one of the polarizing plates, It is desirable to dispose a liquid crystal cell for color compensation (STN type liquid crystal cell in which liquid crystal molecules are twisted in the opposite direction to the liquid crystal cell for display) or a retardation plate.

[0027]

In the color liquid crystal display device of the present invention, since the color filter is formed of a filter material in which pigment particles having a particle diameter of 50 nm or less are dispersed in a transparent resin, the pigment particles are dispersed in the transparent resin. Although a liquid crystal cell is provided with a color filter made of such a filter material, light leakage from the dark display portion due to light scattering by pigment particles can be reduced, and good display with high contrast can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a color liquid crystal display device showing an embodiment of the present invention.

[Explanation of symbols]

 1 ... Liquid crystal cell 2, 3 ... Substrate 5,6 ... Electrode RF, GF, BF ... Color filter 7 ... Protective insulating film 8, 9 ... Alignment film 10 ... Black mask LC ... Liquid crystal 11, 12 ... Polarizing plate

Claims (1)

[Claims] 1. A first device provided with a transparent electrode and a color filter.
A liquid crystal cell in which liquid crystal is enclosed between the transparent substrate and the second transparent substrate provided with a transparent electrode facing the transparent electrode of the first transparent substrate, and the molecules of the liquid crystal are twisted between the two substrates. And a pair of polarizing plates arranged on both sides of the liquid crystal cell, and the color filter is formed of a filter material in which pigment particles having a particle diameter of 50 nm or less are dispersed in a transparent resin. A color liquid crystal display device characterized by.