JPS6159425A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain a display image which is uniform over the entire screen without causing any decrease in contrast even in a large-screen display by making the resistance of column electrodes of the display element lower at the center part than at substrate end parts. CONSTITUTION:A heat write type display device has a row electrode group and a column electrode group arranged on and under a liquid-crystal layer which shows thermo-optic effect greatly so that they cross each other nearly at right angles; the resistance of the row electrodes is made lower at the center part than at end parts of the substrate. Namely, the resistance value is varied by forming an electrode 1-1 on, for example, a glass substrate 2, forming an electrode 1-2 except at parts of 2/3L (L: half of substrate width) from both end parts of the substrate, and further forming an electrode 1-3 thereupon except at parts of 6/7L from both the parts of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to a liquid crystal display element that utilizes the thermo-optic effect of liquid crystal.

[Prior Art] The operating principle of the thermal writing type display system according to the present invention will be explained below. Figure 2 is a diagram showing the electrode patterns on two substrates sandwiching a liquid crystal layer.One substrate (X) is provided with row electrode groups (scanning electrodes) X1 to Xn, and the other substrate (X) is provided with row electrode groups (scanning electrodes) X1 to Xn. The substrate (Y) is provided with column electrode groups (signal electrodes) Y+ to Yn orthogonal to the row electrode groups XI-Xn.

In such an electrode configuration, when a voltage pulse is applied to the row electrode group, the liquid crystal layer is heated and enters an isotropic liquid phase state. Then with the movement of the voltage pulse, the liquid.

The upper layer is sequentially cooled, and in the process, the liquid crystal layer changes from an isotropic liquid phase to a nematic phase and a smectic phase.
The orientation state is stabilized in the smectic phase. When the state in the liquid crystal layer passes through the nematic phase, when a voltage is applied through the column electrodes, the molecular alignment in the liquid crystal layer becomes vertically aligned due to the effect of slow cooling of the liquid crystal and the alignment effect caused by the electric field, resulting in optical alignment. It becomes transparent. On the other hand, in the cooling process, if no voltage is applied, the molecular arrangement within the liquid crystal layer is rapidly cooled while remaining in a random state of an isotropic liquid phase, resulting in an optically cloudy state. In other words, the display state of "transparent" and "cloudy" is selected depending on whether or not a signal voltage is applied while the state inside the liquid crystal layer passes from an isotropic liquid phase to a nematic phase. The stable state can be maintained until heating is caused by the voltage pulse.

In this type of thermal writing display method, so-called crosstalk occurs.
Since there is no problem of lag, a thin display device with high display capacity can be obtained.

[Problems to be Solved by the Invention] However, in conventional thermal writing type displays, when the display screen is enlarged, it is very difficult to obtain display image quality with uniform contrast in the center of the screen. The reason for this is that as the display screen expands, it becomes harder for heat to escape from the center of the screen than from the edges of the screen. For this reason, cooling in the center of the screen progresses more slowly than in the edges. Therefore, pixels that should normally be rapidly cooled by selecting "white turbidity" are slowly cooled, resulting in a decrease in white turbidity at the center of the screen, leading to a decrease in contrast.

The present invention was made in order to solve these conventional problems, and it is an object of the present invention to provide a liquid crystal display element that can display a uniform display image over the entire screen without causing a decrease in contrast even in large screen displays. The purpose is

[Means for Solving the Problems] FIG. 1 shows the basic concept of the present invention, and is a sectional view of a substrate X on which row electrode groups are formed. In the figure, 1 is a row electrode, 2
is a glass substrate.

First, ITO (IndiuI) was applied to the entire surface of the glass substrate 2.
An electrode 11 is formed by depositing a l-Tin Owide film. Next, an ITO film is deposited on both ends of the substrate except for 2/3L (L is 1/2 of the width of the substrate), thereby forming electrodes 1-2. Further, an ITO film is deposited on the substrate except for 6/7L from both ends of the substrate to form electrodes 1-3. The substrate thus obtained is used as a substrate Y, and as a counter substrate corresponding to the substrate X, an ITO film is deposited on a glass substrate and column electrodes are formed thereon. These substrates X and Y are faced with an electrode configuration as shown in Fig. 2, and smectic liquid crystal is filled in the gap between them.
Form an element.

[Function] The display element obtained in this manner has a film thickness at the center of the substrate that is thicker than at the edges and has a lower resistance, so that the amount of heat generated is small. Therefore, when heating the liquid crystal, the temperature at the center of the substrate is lower than at the edges, and when cooling the substrate, heat is diffused more at the edges than at the center, so the cooling time is shorter between the center and edges.
They will be exactly the same. Therefore, when an image is displayed by passing a current through the element, there is no reduction in contrast at the center of the screen as in the conventional case.

[Example] In this example, ITO formed on the glass substrate 2
The thickness of the electrode film is l ILrn for electrode 1-1.
, 0 and 1 gm for electrodes l-2 and l-3, respectively.
It was set to In addition, BI3 is used as the liquid crystal sealed between the electrodes.
A smectic liquid crystal RS-5J manufactured by Co., Ltd. was used.

As a result of image display using the following electrode configuration, uniform display quality could be obtained over the entire screen.

In this embodiment, the resistance of the row electrode is divided into three parts and the resistance values thereof are changed, but the number of divisions may be any number as long as there are multiple parts. In the above embodiment, the resistance value of the row electrodes was changed by partially varying the film thickness of the electrodes. Other methods may be used to change the resistance value.

For example, the same effect can be obtained by changing the width of the electrode stepwise as shown in FIG.

Further, the film thickness and material of the electrode are not limited to those in the above embodiments, and for example, aluminum can be used as the electrode material.

[Effects of the Invention] According to the present invention, even when displaying an image on a large screen using a thermal writing type display device, it is possible to obtain uniform display image quality over the entire screen without causing a decrease in contrast at the center of the screen. can.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a substrate portion of a liquid crystal display element according to the present invention. FIG. 2 is an explanatory diagram showing the structure of electrodes on a substrate in a thermal writing type display device. FIG. 3 is a diagram showing an electrode structure in another embodiment of the present invention. 1: row electrode, 2 glass substrate, 1-l 1st layer row electrode, 1-2 = 2nd layer row electrode, 1-3: 3rd layer row electrode, L 2 substrate width 172 length , Xl-Xn: row electrode group, YI-Yn: column electrode group,

Claims (1)

[Claims] In a thermal writing type display device in which row electrode groups and column electrode groups arranged above and below of a liquid crystal layer exhibiting a remarkable thermo-optical effect are formed so as to be perpendicular to each other, the resistance of the row electrodes is lower than the edge of the substrate. A liquid crystal display element characterized by being lower in the center.