JPH05323292A - Reflection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To decrease the light reflectivity at the time of a dark state and to obtain the reflection type liquid crystal display element having an excellent contrast by arranging a black member on the one opposite surface of substrates facing each other. CONSTITUTION:CrOx is selectively formed as the black member 2 on the transparent glass substrate 1a and ITO is similarly selectively formed as transparent electrodes 3a. The ITO is similarly selectively formed as transparent electrodes 3b on the glass substrate 1b. The substrates are thereafter so superposed on each other that the transparent electrodes 3b and the patterns of the black member 2 do not overlap. A mixture layer consisting of a liquid crystal compsn. 4 and a non-liquid crystalline high-polymer compd. 5 is held between these substrates and is then cured by irradiation with UV rays. Incident light is scattered at the boundary between the liquid crystal and the high-polymer compd. when a voltage is not applied to the PD-LCD produced in such a manner. The liquid crystal molecules, however, orient in an electric field direction and the incident light advances rectilinearly as it is in the mixed layer consisting of the liquid crystal compsn. 4 and the high-polymer compd. 5 when the voltage is applied to the device. The black member 2 is then visible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device capable of bright display with low power consumption.

[0002]

2. Description of the Related Art A liquid crystal display device (hereinafter abbreviated as LCD) is
It has features such as thinness, light weight, and low power consumption. In the display field, it has achieved remarkable growth both technically and in the market, and has established a solid position.

LCDs are used for segment displays such as calculators and wristwatches, and matrix displays for televisions and computers. Among them, the personal computers, word processors, etc. are being actively developed and commercialized. It is a display for OA. Currently, such OA
Matrix type LC using Super Twisted Nematic (STN) mode
D, a substrate on which a switching element such as a thin film transistor (TFT) is arranged for each pixel, and a twisted
A so-called active matrix type LCD, which is a combination of nematic (TN) mode liquid crystals, is used.

The structure of the display includes a transmissive type and a reflective type. The reflective type is a liquid crystal panel sandwiched by polarizing plates, on one side of which a reflective film such as Al is formed.

In such a reflection type structure, since the reflecting surface is made of metal, "white display" cannot be performed, and when a peripheral light amount is small due to the use of a polarizing plate, there are drawbacks such that it becomes very dark. ..

On the other hand, the transmissive structure requires a light source (backlight), which has a drawback that the power consumption of the liquid crystal display device is significantly increased.

In recent years, in addition to the above-mentioned liquid crystal display mode, a polymer dispersion type liquid crystal display device utilizing light scattering (hereinafter referred to as PD
-LCD is abbreviated), and research and development are being conducted.

This is because the PD-LCD does not need a polarizing plate and can perform bright display, and has a possibility of realizing display performance even in a reflection type structure which does not use a backlight.

However, in the structure of the conventional PD-LCD, it was not possible to obtain a sufficient contrast (contrast ratio <5 because of reflection at various thin film interfaces, insufficient light scattering performance of the liquid crystal layer, etc.). : 1).

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a reflective liquid crystal display device having a simple structure, a large contrast, and a high display quality.

[0011]

In a reflective liquid crystal display device of the present invention, a mixture layer composed of a liquid crystal composition and a non-liquid crystalline polymer compound is sandwiched between a pair of opposed substrates, and the pair of opposed liquid crystals is sandwiched. This is a new structure in which a black member is arranged on one of the opposing inner surfaces of the transparent substrates.

[0012]

As described above, by disposing the black member on one of the facing inner surfaces of the facing substrates, the light reflectance in the dark state is reduced, so that the contrast can be increased, which is excellent. It is possible to provide a high-performance reflective liquid crystal display device.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a basic cross-sectional configuration diagram of a reflection type liquid crystal display device according to a first embodiment of the present invention. In FIG. 1, 1a and 1b are transparent substrates, 2 is a black member,
3a and 3b are transparent electrodes, 4 is a liquid crystal composition, and 5 is a non-liquid crystalline polymer compound.

The principle of operation will be outlined below.
As shown in (FIG. 1), in a PD-LCD, a liquid crystal composition is usually dispersed in a polymer compound in the form of small spheres, and as shown in FIG. The molecules are randomly oriented. At this time, each material is selected so that the dielectric anisotropy Δε of the liquid crystal is positive and the refractive index to ordinary light is almost equal to that of the polymer compound.

When no voltage is applied, incident light is scattered in the liquid crystal and at the liquid crystal / polymer compound interface. The state at this time is made clear.

On the other hand, when a voltage is applied (as shown in FIG. 1 (b)), the liquid crystal molecules are aligned in the direction of the electric field, and the incident light goes straight through the mixture layer composed of the liquid crystal composition and the polymer compound, The black member placed on the lower side is visible. The state at this time is dark.

In the first embodiment of the present invention shown in FIG. 1, CrOx is selectively formed as the black member 2 and ITO is similarly selectively formed as the transparent electrode 3a on the transparent glass substrate 1a. did. Moreover, ITO is selectively formed as the transparent electrode 3b on the glass substrate 1b. After that, the transparent electrode 3b and the pattern of the black member 2 are aligned with each other so as to overlap each other, a mixture layer composed of the liquid crystal composition 4 and the non-liquid crystalline polymer compound 5 is sandwiched between the substrates, and UV irradiation is performed. Cured by.

PD-obtained by the above manufacturing method
The result of actually measuring the reflectance-voltage characteristics of the LCD is shown in FIG.

As can be seen from FIG. 2, the light reflectance when a voltage was applied was greatly reduced. On the other hand, the light reflectance when no voltage is applied is about 38%, and the contrast ratio is 30 to 50.
Was obtained, and a remarkable improvement could be achieved.

Next, FIG. 3 shows a basic configuration diagram of a reflection type liquid crystal display device having an active matrix array according to a second embodiment of the present invention.

The basic display operation principle is the same as that of the first embodiment. The manufacturing method of this embodiment will be briefly described with reference to FIG.

First, the gate metal 6 and the first transparent electrode 3c are selectively formed on the transparent glass substrate 1b. Cr was deposited on the gate metal and ITO was deposited on the transparent electrode by vapor deposition. Then, SiNx was deposited as the gate insulating layer 7 on the gate metal and the transparent electrode, and a-Si was selectively formed as the semiconductor layer 8 on the gate insulating film. next,
The ITO of the second transparent electrode 3b to be the pixel electrode was selectively formed. The gate insulating layer also serves as an insulating layer for the transparent electrodes 3b and 3c, and forms a storage capacitor together with the transparent electrodes. Source / drain electrodes 9a on the semiconductor layer 8,
Al was selectively formed as 9b. The transparent electrode 3b,
The drain electrode (or source electrode) 9b is electrically contacted. As described above, the active matrix array could be formed on the transparent substrate 1b. The constituent materials used at this time,
The structure and the like may be other materials or other structures as long as they fulfill the function of the active matrix array.

Next, CrOx as the black member 2 and ITO as the transparent electrode 3b are deposited on the transparent glass substrate 1a to form the opposing reflecting electrode.

The transparent substrates 1a and 1b are aligned so that the active matrix array and the black member are on the inner surface, and a mixture layer of a liquid crystal composition and a non-liquid crystalline polymer compound is sandwiched between the substrates and cured. did.

A reflective liquid crystal display device using PD-LC was obtained by the above manufacturing method.

The reflectance-voltage characteristic of the reflective liquid crystal display device using the active matrix array according to the present invention was also measured.
We were able to achieve 0: 1 or higher.

[0027]

As described above, by combining the polymer dispersion type liquid crystal and the structure in which the black member is arranged on one of the two substrates facing each other, a reflective type liquid crystal display device which is excellent in contrast and bright is obtained. Can be provided. This makes it possible to realize an OA display with low power consumption, and the effect is great.

[Brief description of drawings]

FIG. 1 is a basic structural diagram of a reflective liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a graph showing the measurement results of reflectance-voltage of the first embodiment of the present invention.

FIG. 3 is a basic configuration diagram of a reflective liquid crystal display device according to a second embodiment of the present invention.

[Explanation of symbols]

 1a, 1b Transparent substrate 2 Black member 3a, 3b, 3c Transparent electrode 4 Liquid crystal composition 5 Non-liquid crystalline polymer compound 6 Gate electrode 7 Gate insulating film 8 Semiconductor layer 9a, 9b Source / drain electrode

Claims (4)

[Claims] 1. A mixture layer composed of a liquid crystal composition and a non-liquid crystalline polymer compound is sandwiched between opposing transparent substrates, and a black member is disposed on one opposing inner surface of the opposing transparent substrate. A reflective liquid crystal display device characterized by: 2. The reflective liquid crystal display device according to claim 1, wherein the black member is a Cr-based alloy or an organic black material. 3. A mixture layer composed of a liquid crystal composition and a non-liquid crystalline polymer compound is sandwiched between opposed transparent substrates, and a black member is arranged on one of the opposed inner surfaces of the opposed transparent substrates. On the other opposing inner surface of the opposing transparent substrate,
A reflective liquid crystal display device characterized by arranging an active matrix array. 4. The reflection type liquid crystal display device according to claim 3, wherein the black member is a Cr-based alloy or an organic black member.