JPH03107925A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display element having high display quality and good visibility by using polyimide films as perpendicularly oriented films and rubbing the films to provide the pretilt of a prescribed angle. CONSTITUTION:The cell is formed by successively forming transparent electrodes 2A, 2B and the perpendicularly oriented polyimide films 3A, 3B on one surface of a pair of glass substrates 1A, 2B, rubbing the films with a cloth to provide the pretilt angle (angle theta), then facing the substrates at a slight spacing. A liquid crystal 4 mixed with a chiral agent and a dichromatic dye 5 are sealed in this cell. If such pretilt is provided, the molecules of the liquid crystal 4 fall uniformy in a specified direction and twist in a horizontal direction when a voltage is impressed between the transparent electrodes 2A and 2B facing each other. The coloration display by the dye 5 is executed according to this twist. The display having the high quality free from the unequal display is obtd. in this way and the unequal display when the display is viewed from a diagonal direction is eliminated. The good visibility is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a liquid crystal display element in which a liquid crystal containing a chiral agent and a dichroic dye are aligned so that they are vertically aligned.

[Conventional technology]

The conventional positive display PC (phase change) mode liquid crystal display element is
The structure is as shown in FIG.

Immediately, a transparent electrode Ij is placed on one side of the pair of glass substrates 1A and IB.
2A, 2B and vertical alignment films 3A', 3B' are sequentially formed, these are opposed to each other at a minute interval to form a cell, and a liquid crystal 4 containing a chiral agent and a dichroic dye 5 are sealed in this cell. It becomes. For vertical alignment treatment, DMOAP
A silane coupling agent such as , 0DS-E is used.

This liquid crystal display element has transparent electrodes 2A facing each other.

When a voltage is applied between 2B, the liquid crystal 4 and the dichroic dye 5, which were oriented perpendicularly to the glass substrates IA and IB when no voltage is applied, are twisted in the horizontal direction, and a display is performed by coloring the dye 5.

[Problem to be solved by the invention]

Conventionally, since silane coupling agents such as DMOAP and 0DS-E are used for vertical alignment processing, the alignment process does not have pretilt, and when a voltage is applied, the direction in which liquid crystal molecules fall differs depending on the location, resulting in display unevenness. occurs.

Particularly, large unevenness occurs when the liquid crystal display element is viewed from an oblique direction.

An object of the present invention is to provide a liquid crystal display element with high display quality and good visibility.

[Means to solve the problem]

In the present invention, a transparent electrode and a vertical alignment film are sequentially formed on one surface of a pair of transparent substrates, and these are opposed to each other at a minute interval to form a cell, and within this cell, a liquid crystal containing a chiral agent and a dichroic dye are placed. In the encapsulated liquid crystal display element, a polyimide film is used as a vertical alignment film on at least one substrate side, and this film is rubbed to give a pretilt of a required angle.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 shows an embodiment of the present invention, in which a transparent electrode 2A is formed on one surface of a pair of glass substrates IA, 1[3.

2B and vertically aligned polyimide films 3A and 3B are sequentially formed.
Rub the membrane with cloth (cotton, nylon, etc.) and pre-tilt it (
After forming an angle θ), a cell is formed by facing each other at a minute interval, and a liquid crystal 4 containing a chiral agent and a dichroic dye 5 are sealed in this cell.

The vertically oriented polyimides WA3A and 3B can be formed by using a vertically oriented polyimide, forming a thin film by transfer printing, spinner coating, etc., and baking at 100 to 300°C.

Further, the pretilt angle can be controlled by rubbing conditions (type of cloth, rubbing intensity, number of times of rubbing). As an example, the relationship between the number of rubbings and the pretilt angle is shown in a table. In this example, the liquid crystal is ZLI-2806 (manufactured by Merck & Co.)
It was used.

When a pretilt is provided in this way, when a voltage is applied between the opposing transparent electrodes 2A and 2B, the molecules of the liquid crystal 4 are aligned in a certain direction and are twisted in the horizontal direction. Along with this twisting, a colored display using a dye is performed. This display is uniform and of high quality. Further, even when viewed from an oblique direction, display unevenness is eliminated and visibility is improved.

Note that even if only one of the two substrates is rubbed, uniform orientation can be obtained. Therefore, the polyimide film may be used only on one substrate side as the vertical alignment film.

〔Effect of the invention〕

As described above, according to the present invention, a polyimide film is used as the vertical alignment film, and the film is rubbed to give it a pre-tilt of the required angle, so that the liquid crystal molecules are tilted in a certain direction when turned on. High-quality display with no display unevenness is achieved. Furthermore, even when viewed from an oblique direction, display unevenness is eliminated and visibility is improved. In addition, by having a pre-tilt, the liquid crystal molecules tend to fall horizontally,
The rise time (response time) can be shortened with a low threshold voltage. Furthermore, by using a polyimide film, the stability of alignment with respect to the liquid crystal increases, and reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a structural explanatory diagram showing one embodiment of a liquid crystal display element according to the present invention, and FIG. 2 is a structural explanatory diagram showing a conventional example. 1A and 1B...Glass substrates 2A and 2B...Transparent electrodes 3A and 3B...Vertical alignment polyimide film 4...Liquid crystal mixed with chiral agent 5...Dichroic dye

Claims (1)

[Claims] A transparent electrode and a vertical alignment film are sequentially formed on one surface of a pair of transparent substrates, and these are made to face each other at a minute interval to form a cell.
In a liquid crystal display element in which a chiral agent-mixed liquid crystal and a dichroic dye are sealed in the cell, a polyimide film is used as a vertical alignment film on at least one substrate side, and by rubbing this film, a pretilt angle of a desired angle can be achieved. A liquid crystal display element characterized by having.