JPH01188828A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To attain a bright displaying with a satisfactory contrast by forming an electrode formed at one side substrate side with a transparent conducting film, providing a linear polarizing filter only at the substrate side and providing an optical element to generate a light reflection at other substrate side. CONSTITUTION:The title device is composed of a transparent substrate 1 composed of glass, acrylic, etc., a same transparent substrate or untransparent substrate 2 as this, a transparent conducting film 3 such as In2O3-SnO2 films, an orientation film 4 for a liquid crystal molecule, a so-called super twisted nematic layer 5 which is a nematic liquid crystal layer having a positive dielectric anisotropy, and in the range in which a twist angle between substrates is 180 deg.-300 deg. and preferably, 200 deg.-270 deg., a reflecting electrode 6, a linear polarizing filter 7 and a driving circuit 8 to drive a cell. Thus, the displaying, which is a high contrast ratio and close to the achromatic color, can be displayed, and a reflection type displaying to use a low power consumption, which is the merit of the liquid crystal displaying, can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application> The present invention relates to a liquid crystal display device using a reflective super-twisted nematic display method capable of providing a bright display with good contrast.

<Prior art> Liquid crystal display devices (LCDs) using conventional TN (twisted nematic) mode are used in watches, calculators, home appliances,
It has been widely applied as a display device for various electronic devices including measuring instruments. However, due to the unique electro-optical characteristics of this TN-LCD, the amount of display information increases, and when the drive duty ratio increases using the so-called voltage averaging method (AIL-Pleshko drive method), the drive margin decreases and the display contrast becomes extremely low. There was an inherent constraint that it would get worse. As a countermeasure to this problem, a super twisted nematic (STN) mode has been proposed in which the twist angle between the substrates is increased from 90 in the TN mode to 180 to 270 degrees, and even in high duty driving (1:50 or more). It is becoming possible to obtain high contrast. Figure 2 shows this schematic structure.

However, this 5TN-LCD uses the optical interference effect caused by the birefringence of the liquid crystal layer, so the display colors are yellowish-green/black or blue/white, as shown in Figure 3, and are unpopular from an ergonomic perspective. Ta. Another problem was that the display was dark due to the low effective utilization of light. As a countermeasure to this problem, a so-called two-layer 5TN-LCD has recently been developed in which a panel with a reverse twist direction is superimposed on the 5TN-LCD as a compensator for compensating for one coloring. However, although good panchromatic black/white display is possible in terms of display characteristics, the panel has a two-layer structure, which has the disadvantage of increasing weight, and also increases process and material costs, which is a factor in increasing costs. It contained.

In addition, attempts have been made to reduce the retardation (Δnd: birefringence value x liquid crystal layer value) of 5TN-LCD and reduce the saturation of displayed colors (called the OM1 method).
The problem remains that the display is still insufficient and the display is dark, making it impossible to use a reflective type that does not use a backlight.

As another method for making the display achromatic (white/black display), a guest-host method has been proposed in which dichroic dye is dissolved in the liquid crystal to perform color correction. However, this method also has the disadvantage that the brightness of the display is low and it cannot be used in a reflective type. In addition, the viscosity of liquid crystal increases due to the addition of dye,
Another problem is that the response characteristics are slow at about 500 msec even at room temperature.

<Object of the Invention> In view of the above-mentioned problems, the present invention provides a reflective display that can provide a display with a high contrast ratio and close to achromatic color, and also takes advantage of the low power consumption that is an advantage of liquid crystal displays, and has a simple structure. The purpose is to propose a new liquid crystal display device that can be manufactured using

<Summary of the Invention> FIG. 1 is an explanatory diagram for explaining the cell configuration of a substrate according to the present invention. 1 is glass and acrylic.

Transparent substrate made of polyester, polycarbonate, etc.%
2 is a transparent substrate or opaque substrate similar to l, 3 is I
Transparent conductive film such as TO (In2'03-5n02 film),
4 is an alignment film for liquid crystal molecules, specifically SiO, 5
Inorganic thin film such as i02 or polyimide type.

Polyvinyl alcohol-based, nylon-based, acrylic-based,
It is effective to use a polyurethane organic thin film that has been subjected to rubbing treatment, oblique vapor deposition, or oblique sputtering treatment. 5 is a nematic liquid crystal layer with positive dielectric anisotropy, and the twist angle between the substrates is 180° to 300°;
A so-called super twisted nematic layer having an angle of 2000 to 270° is preferred. This nematic liquid crystal layer is doped with an optically active substance (side-lighting cholesteryl nonanoate (0.3 to 3 wt%)) to control the twist direction and pitch.The phthaldation value of the liquid crystal layer is nil. In the case of an electric field, a value of 0.3 μm to 2 μm is selected as necessary.The direction of the helical axis of this super twisted nematic liquid crystal layer is substantially perpendicular to the substrate. Reflective electrode - AI, Ti in the shell.

A conductive material with high reflectance such as Ni or Au is used.

Note that the reflective electrode may be a combination of a transparent electrode and a reflective material. This combination may be stacked directly or via a transparent insulating layer such as glass, 5i02, SiN, etc. 7 is a linear polarizing filter, and only one filter is used for each cell, and the azimuth angle of the polarization direction is determined by Δn of the liquid crystal material.
Optimize each time depending on the value and twist angle, for example Δ
In the case of n=o, l3d=6 μm, and a twist angle of 240, an angle shifted by about 20 degrees from the long axis of the nearest liquid crystal molecule provides good display characteristics. Note that this azimuth can be changed as necessary. Reference numeral 8 denotes a drive circuit for driving the cells, and a multiplex drive using a general voltage averaging method or a static drive method is used. 9 is an observer who observes the display from the side where the polarizing filter is installed. Note that the seal structure, terminal processing structure, etc. are omitted in the figure.

FIG. 4 shows a reflection display spectrum, which is one of the display characteristics of the liquid crystal display device of the present invention.
It can be seen that both F and F exhibit relatively achromatic and good characteristics.

FIG. 5 similarly shows the reflectance voltage (
It can be seen that it has a very sharp RvsV characteristic suitable for high duty driving, and that high contrast display is possible.〈Example 1〉 Figure 6 shows the 1 shows a cell structure of a reflective liquid crystal display device according to one embodiment. Boards 1 and 2 are Corning 705
A 9F+, 1-inch thick glass substrate was used. 3 is an electrode group formed by patterning an ITO film (100 OA thick) formed by a sputtering method, 4 is a 5E-150 type polyimide film made by Nichiji Kagaku and rubbed with a nylon film, and 5 is Merck gzLt-3449. -000 nematic liquid crystal with 0.9% cholesteryl nonanoate added, the helical axis is perpendicular to the substrates, and the twist angle is 240 between the substrates. 6 is Al (
500A), an insulating film of 5i02 was formed at 800OA, and 07 was an electrode group of an ITO film patterned using the photorin method.
0-42). 8 is a driver consisting of an LSI.

This reflective (R)-9TN-L CD has 1/200 duty drive! Good contrast characteristics of 0:l were obtained.Example 2: Based on Example 1, the display contrast was improved by forming a light scattering layer on the insulating layer between the reflective material and the transparent electrode. Although it decreased to 5:l, brighter display became possible over a wider viewing angle range.

<Example 3> Based on Example 1, color display was made possible by installing a birefringent layer (liquid crystal layer, polyethylene stretched film, etc.) between the polarizing filter and the liquid crystal layer. Note that the display color can be varied by changing the retardation of the birefringent layer and the retardation value of the STN liquid crystal layer. Note that the reflective layer used in the above description may be colored for color display or color correction.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a liquid crystal cell structure used to explain the present invention. FIG. 2 is a schematic structural diagram of a conventional 5TN-LCD. FIG. 3 is an explanatory diagram of an example of a display spectrum of a conventional 5TN-LCD. FIG. 4 is a characteristic diagram showing the display spectrum characteristics of the present invention. FIG. 5 is a characteristic diagram showing the RvsV characteristics of the present invention. FIGS. 6(a) and 6(b) are configuration diagrams showing an embodiment of the present invention. FIGS. 7 and 8 are configuration diagrams showing another embodiment of the present invention. 1.2...Polarizing filter, 3...Transparent electrode, 4...
-Alignment film, 5...liquid crystal layer, 8...driver. Agent: Patent Attorney Takeshi Sugiyama (and 1 other person) (1, 1, 1, 2, 2, LCnm) *CV) Figure 6 (Q'' Figure 6 (b)

Claims (1)

[Claims] 1. A super twisted nematic layer having a helical axis in a direction perpendicular to the substrate surface and a pair of electrodes for applying voltage to the liquid crystal layer, and an electrode formed on at least one of the electrodes on the substrate side. is formed of a transparent conductive film, a linear polarizing filter is installed only on the substrate side on which the transparent conductive film is formed, and light is reflected on the other substrate side other than the substrate on which the linear polarizing filter is installed. A liquid crystal display device characterized in that an optical element is installed.