JPH01255832A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve voltage-contrast characteristics by forming a liquid crystal as a polymer dispersion type liquid crystal and changing the size of the liquid crystal capsules of the polymer dispersion type liquid crystals corresponding to respective colors in order to correct the differences in the optical characteristics to respective light rays of red, green and blue. CONSTITUTION:An NCA (nematic curve type aligned layer) liquid crystal layer 12 is the aggregate of the liquid crystals 16 which are dispersed into a matrix 17 of a polymer and are capsulated. The voltage-contrast characteristics to the light rays of red and green are adjusted by increasing the grain size of the liquid crystals 16 of the liquid crystal capsules of the NCAP liquid crystal layer 7 corresponding to a blue color filter 3, by which nearly the same characteristics as the voltage-contrast characteristics to the light rays of red and green are obtd. The voltage-contrast characteristics to the respective light rays of red, green and blue are thereby improved and the fluctuation in contrast by the difference in the optical characteristics to the red, green and blue colors is eliminated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a liquid crystal display device, and particularly to a liquid crystal display device that includes a substrate in which a first transparent electrode and a plurality of color filters are laminated, and a second transparent electrode. The present invention relates to a liquid crystal display device in which a transparent electrode is arranged to face a substrate, and a liquid crystal is filled between the substrates.

[Prior Art] Liquid crystal display elements are thin, can be driven at low voltages, consume low power, and can be directly driven by ICs, so they have the advantage of being easy to make devices smaller and thinner. In particular, TN type liquid crystals are excellent in terms of low voltage and low power consumption, and have been widely used in wristwatches, calculators, and the like.

In recent years, small portable televisions using TN-type liquid crystals have become popular, and research and development of wall-mounted televisions is also progressing. In these applications, colorization is desired for compatibility with CRT.

FIG. 4 is a partial cross-sectional view showing an example of the configuration of a conventional matrix type TN type color liquid crystal display element.

In the same figure, on the glass substrate 5&, transparent electrodes 6a are patterned in rows (here, transparent electrodes 6a1 .6a2 are used for simplicity).

The price is 6a3. ) is formed, and an alignment film 18a is roughly formed. A red color filter 1. is attached to the glass substrate 5b. A green color filter 2, a blue color filter 3, and a black mask 4 are formed, and furthermore, transparent electrodes 6b patterned in rows and orientation [18b] are formed. A TN type liquid crystal 19 is filled between the glass substrate 5a and the glass substrate 5b with a constant distance maintained between them. glass substrate 5
Polarizing plates 20a and 20b are provided on the other surfaces of the glass substrate a and the glass substrate 5b, respectively.

[Object of the Invention] The above-mentioned TN type color liquid crystal display element is sensitive to the thickness of the liquid crystal layer, so it is difficult to produce a large-area display, and
Contrast generally depends on the sharpness of the voltage-luminance characteristics, but because the voltage-luminance characteristics differ depending on the optical characteristics for each color of red, green, and blue, the contrast may differ depending on each color.

In recent years, the development of liquid crystals used in large-area display devices has progressed, and in recent years, polymer-dispersed liquid crystals (1), in which small spheres of liquid crystal are dispersed in a polymer matrix, have been developed.
(Nematic CurvilinearAlig
A new liquid crystal technology called liquid crystal (nematic curve aligned phase) has been developed, and the thickness of the liquid crystal layer can be easily controlled, allowing for large areas and fast response times.
Because it does not require a polarizing plate and has a wide viewing angle, it is expected to be suitably used in display devices with a relatively large area.

The object of the present invention is to improve voltage-contrast characteristics and voltage-contrast characteristics of polymer-dispersed liquid crystals depending on the size of liquid crystal capsules.
It is an object of the present invention to provide a liquid crystal display device that utilizes the property that brightness characteristics change to improve contrast variations due to differences in optical characteristics for each color of red, green, and blue.

[Summary of the Invention] The liquid crystal display device of the present invention includes a base body on which a first transparent electrode and a plurality of color filters are laminated, and a base body on which a second transparent electrode is formed, such that both transparent electrodes face each other. In a liquid crystal display device in which a liquid crystal is filled between two substrates, the liquid crystal is a polymer-dispersed liquid crystal, and the liquid crystal is red and green.

It is characterized by changing the size of the liquid crystal capsule of the polymer-dispersed liquid crystal corresponding to each color in order to correct the difference in optical properties for each color of blue.

Note that the size of the liquid crystal capsule here refers to the size of the liquid crystal dispersed in the polymer.

[Effect] As mentioned above, contrast generally depends on the sharpness of voltage-luminance characteristics, but it also depends on the color filters and dichroic dyes used, the wavelength dependence of scattering in the liquid crystal layer, or the dichroic dyes. Inappropriate combinations, quantity ratios, etc. (in many cases).

(The dichroic ratio of dichroic dyes with maximum absorption at short wavelengths is not very good.) This causes differences in voltage-luminance characteristics, so when viewing the screen through red, green, and blue color filters, each color differs. Depending on the color, the contrast may be different or certain colors may be emphasized.

In the present invention, as shown in Figure 52, the polymer-dispersed liquid crystal exhibits a characteristic that the larger the size of the liquid crystal capsule is, the contrast rises at a lower voltage, and the smaller the size of the liquid crystal capsule is, the contrast increases when voltage is applied. (In Figure 2, the liquid crystal capsule is spherical, the broken line indicates a particle size of approximately 1 lm, and the solid line indicates a particle size of approximately 5p.
), the size of the liquid crystal capsule is controlled according to the difference in optical properties for red, green, and blue.
This is intended to improve the voltage-contrast characteristics for each of green and blue light.

[Example] Hereinafter, an example of the present invention will be described in detail using the drawings.

In addition, the following examples will be described in the case where NCAP liquid crystal is selected as an example of the polymer-dispersed liquid crystal.

First, prior to explaining the liquid crystal display device of the present invention, NCAP
Explain the structure and operation of liquid crystals (the following explanations are based on "Principles and Applications of New Liquid Crystal Displays" Electronic Materials 1)
987,12. P, 87-P, 71. Patent application publication fl
(Based on the lQ58-501f131 publication)
.

5(A), 5(B), and 5(G) are schematic configuration diagrams for explaining an example of the configuration of the NCAP liquid crystal.
) shows the configuration of the liquid crystal component, FIG. 5 (CB) shows the configuration of the liquid crystal layer, and FIG. 5(C) shows the configuration of the liquid crystal capsule.

As shown in FIG. 5(A), the NCAP liquid crystal element
The AP liquid crystal layer 12 is sandwiched between plastic films 14, and the plastic films 14 are coated with transparent conductive layers such as ITO as electrodes to and it. FIG. 5(f?) shows the structure of a portion 13 of the NCAP liquid crystal layer 12, and FIG. 5(C) shows the structure of the liquid crystal capsule portion 15 of the NCAP liquid crystal layer 12. As shown in Figure 5 (B) and (G), NC
The AP liquid crystal layer 12 is a collection of liquid crystals 16 dispersed and encapsulated in a polymer matrix 17.Normally, the liquid crystals 16 are often spherical; Sometimes the bodies combine to form liquid crystals.

Figure 6 (A) and (B) show N
6A and 6B are schematic explanatory diagrams showing the operation of the CAP liquid crystal, with FIG. 6(A) showing a no-voltage state and FIG. 6(B) showing a voltage applied state.

As shown in FIG. 6(A), in the no-voltage state, the liquid crystal body 16
The liquid crystal molecules 16b inside tend to line up along the outer wall of the capsule. In this case, due to the birefringence of the liquid crystal molecules 16b, the incident light is scattered on the surface and inside of the liquid crystal capsule, and is absorbed by the dichroic dye 16a. As a result, the film appears dark black.

As shown in FIG. 6(B), when a voltage is applied, the liquid crystal molecules 16b rotate their axes to be aligned in the direction of the electric field. If the refractive index of the axis of the liquid crystal molecule 16b is equal to the refractive index of the polymer, light will not be scattered and will travel straight.

Becomes transparent. In this manner, by adjusting the voltage, it is possible to continuously change the state from a completely scattered and absorbed state to a fully transparent state for display.

Hereinafter, a liquid crystal display device of the present invention using the above NCAP liquid crystal will be explained.

1(A), CB) are explanatory diagrams of the configuration of the first embodiment of the liquid crystal display device of the present invention, FIG. 1(A) is a schematic partial sectional view, and FIG. 1(B) is a schematic partial sectional view. is a schematic partial plan view of one of the substrates.

As shown in FIG. 1(A), ITO is placed on the glass substrate 5a.
Transparent electrodes 6a are patterned in rows such as 6al, 5a2 .
The price is 6a3. ) at a constant pitch. A red color filter 1. is attached to the glass substrate 5b. A green color filter 2, a blue color filter 3, and a black mask 4 are formed, and transparent electrodes 6b patterned in rows are further formed. Glass substrate 5a and glass substrate 5b
The NCAP liquid crystal layer 7, which is the polymer-dispersed liquid crystal described above, is filled with a certain distance between the NCAP liquid crystal layer 7 and
is formed. The transparent electrode 6a and the transparent electrode 6b are arranged in a matrix.

Note that although a glass substrate or a PET substrate is often used as the substrate, it is not particularly limited to these, and other materials may be used.

As shown in FIG. 1(B), a transparent electrode 6a1.

6a2 and 6a3 are connected to the signal line 9 through the varistor film 8. A varistor is an element in which a current suddenly flows when a voltage of a certain value or more is applied, and is provided for purposes such as preventing crosstalk.

The varistor film is formed by binding varistor powder into a paste form and printing it on a substrate using thick film printing technology.

In this embodiment, 1. In the configuration of a normal liquid crystal display device,
Because the voltage-contrast characteristic of the contrast when viewing the screen through the blue color filter 3 rises more slowly than the contrast characteristics when viewing the screen through the red and green color filters 1.2,
Figure 1 (A).

As shown in (B), the particle size of the liquid crystal 16 of the liquid crystal capsule of the NCAP liquid crystal layer 7 corresponding to the blue color filter 3 is increased, and the voltage-contrast characteristics for blue light are adjusted. The characteristics are almost the same as the voltage-contrast characteristics for light.

By controlling the particle size of the liquid crystal capsules of the NCAP liquid crystal layer 7, transparent electrodes 5a1 . 6
a2. As a method of forming on 6a3, screen printing, printing using a metal mask, etc. can be used.

The method for manufacturing the NCAP liquid crystal layer 7 will be described below.

(Example) First, PVA purified by ion exchange with 15 g of liquid crystal E-44 (manufactured by BDH) containing dichroic dye M67B (manufactured by Mitsui Toatsu Dye Co., Ltd.).

40 g of lθ% solution of KM-11 (manufactured by Yabon Gosei Kagaku Kogyo Co., Ltd.) is mixed and emulsified. At this time, the stirring speed during emulsification is changed by ° to prepare an emulsion with a particle size of 1 to 4 gm and an emulsion with a particle size of 4 to 10 gm.0 particle size of 1 to 4 pm
The emulsion is red color filter 1. Green color filter 2. A transparent electrode 6 such as ITO on a glass substrate 5a corresponding to
a1, 6a2, 4~lOJLm (7) The emulsion is applied onto the transparent electrode 6a3 made of ITO or the like on the glass substrate 5a corresponding to the blue color filter 3, and then dried to form an NCAP
A liquid crystal layer 7 is formed. The layer thickness at this time was 15 JLm. After that, transparent electrode 6b, color filters 1 to 3
A liquid crystal display device was fabricated by sandwiching the NCAP liquid crystal layer 7 between glass substrates 5b on which were formed.

(Comparative Example) An emulsion having a particle size of 1 to 4 gm is prepared under the same conditions as in the above example. Apply this emulsion to a red color filter. Green color filter 2. Transparent electrodes 6a1.6a2.6 such as ITO on the glass substrate 5a corresponding to the blue color filter 3
Apply on A3. A liquid crystal display device is manufactured under the same conditions.

As shown in FIG. 3(A), a liquid crystal display device manufactured by coating particles with a particle size of 1 to 4 pm has voltage-contrast characteristics when the screen is viewed through a blue color filter 3 for red and green colors. Compared to the contrast characteristics when viewing the screen through filter 1.2, the rise is slower, but
NCA corresponding to blue color filter 3 according to the present invention
In a liquid crystal display device in which the particle size of the liquid crystal element 16 of the liquid crystal capsule of the P liquid crystal layer 7 is increased, the contrast of each color is as shown in Fig. 3 (B
), the voltage-contrast characteristics of each color are substantially constant. That is, by adjusting the particle size of the liquid crystal capsules of the NCAP liquid crystal layer, the contrast of R, G, and H can be adjusted to a level that does not cause any problems in practice.

[Effects of the Invention] As explained in detail above, according to the liquid crystal display device of the present invention, the polymer-dispersed liquid crystal exhibits a characteristic that the contrast rises at a lower voltage when the particle size of the liquid crystal capsule is larger,
Taking advantage of the property that the smaller the particle size of the liquid crystal capsule is, the higher the contrast becomes when a voltage is applied, the size of the liquid crystal capsule is controlled according to the difference in optical properties for red, green, and blue. By improving the voltage-contrast characteristics for each color of blue, it is possible to provide a liquid crystal display device with even better visibility.

[Brief explanation of the drawing]

FIGS. 1A and 1B are explanatory diagrams of the configuration of a first embodiment of a liquid crystal display device of the present invention. FIG. 2 is a diagram showing the difference in voltage-contrast characteristics depending on the particle size of liquid crystal capsules. FIG. 3(A) is a diagram showing the voltage-contrast test characteristics for each of the red, green, and blue colors, and FIG. 3(B) is a diagram showing voltage-contrast test characteristics for each of the red, green, and blue colors by the liquid crystal display device of the present invention. Voltage -
FIG. 3 is a diagram showing contrast characteristics. FIG. 4 is a partial cross-sectional view showing an example of the configuration of a conventional matrix type TNfi color liquid crystal display element. FIGS. 5(A), 5(B), and 5(C) are schematic configuration diagrams for explaining the configuration of the NCAP liquid crystal. Figure 6 (A) and (B) show N
FIG. 2 is a schematic explanatory diagram showing the operation of a CAP liquid crystal. 1: Red color filter, 2: Green color filter, 3
: Blue color filter, 4: Black mask, 5a, 5b Niglass substrate, 6al, 6a2.6a3 . 6b: transparent electrode, 7,
12: NCAP liquid crystal layer, 8: Crystal film, 9: Signal line, 10, 11: Electrode, 14 Niblast film, 1
6: Liquid crystal, 17: Polymer matrix, 16a dichroic dye, 1
6b: Liquid crystal molecule. Agent Patent Attorney Jo Yamashita Taira 2nd Figure 9 Hill m Figure 3 (A) (B) φ3 (V)! E1i Figure 4 Figure 5

Claims (1)

[Claims] A base on which a first transparent electrode and a plurality of color filters are laminated, and a base on which a second transparent electrode is formed are arranged so that both transparent electrodes face each other, and liquid crystal is filled between the two bases. In the liquid crystal display device, the liquid crystal is a polymer-dispersed liquid crystal, and the size of the liquid crystal capsule of the polymer-dispersed liquid crystal corresponding to each color is changed in order to correct the difference in optical characteristics for each color of red, green, and blue light. A liquid crystal display device featuring: