JPS5855913A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To sharpen the contrast of an LCD with respect to orientation films to be provided on patterned electrode substrates by using the orientation films prepd. by binding amino silane to polyimide produced by polymn. of polyhydric carboxlyic acid and diamine. CONSTITUTION:Electrodes 2, 2' are provided on glass substrates 1, 1', and orientation films 3, 3' are formed thereon. A liquid crystal 4 of TN type is sealed between the films 3 and 3' by a sealant 5, whereby an LCD is obtained. As the resin for the orientation films, the polyhydric carboxylic acid of the formula A and the diamine of the formula B are mixed at an equal ratio and the mixture is caused to react, whereby a polyimide resin is polymerized. Four parts of the amino silane of the formula C is caused to react with 100 parts the polyimide resin, whereby a synthetic resin contg. Si on the side chains is obtd. The resultant synthetic resin is made into the films 3, 3' which are used after the surfaces are rubbed. By the use of said films, the rising intensity of transmitted light by applied voltage is made sharper than that of conventional polyimide films and good contrast is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which a substrate surface on which an electrode pattern is formed is covered with an alignment film.

In a liquid crystal display device, display is performed by changes in the arrangement state of liquid crystal molecules that occur before and after the application of an electric field, so the initial orientation of liquid crystal molecules when no voltage is applied is important. An alignment in which the long axes of liquid crystal molecules are perpendicular to the substrate of a liquid crystal display device is called a vertical alignment, and an alignment in which the long axes of the liquid crystal molecules and the substrate are parallel is called a horizontal alignment.

Conventionally, in a TN-FEM type liquid crystal display device, the liquid crystal molecules are horizontally aligned in the initial state without applying an electric field.
Display is performed by vertically aligning liquid crystal molecules with positive electric field anisotropy by applying an electric field. As an initial orientation method for liquid crystal molecules, a method is often adopted in which a polyimide resin is deposited on a substrate on which an electrode pattern is formed, and this polyimide resin film is rubbed. The alignment method involves applying a polyimide resin and then rubbing it.The resin itself has the function of aligning liquid crystal molecules horizontally, and since polyimide resin has excellent heat resistance, it can be used as an alignment film for liquid crystal cells sealed with glass frits. It also depends on what is useful.

Recently, since sufficient alignment cannot be obtained with the above-mentioned polyimide resin alone, there are examples in which a resin containing a silicon-containing organic compound is mechanically mixed into the resin and used as an alignment film.

However, as mentioned above, with an alignment film mechanically mixed with an organosilicon compound, it is not possible to obtain a steep rise characteristic in the curve of transmitted light intensity vs. applied voltage, and it is difficult to obtain a steep rise characteristic in the curve of transmitted light intensity vs. applied voltage.
7. , 1/8 duty or less), there is a problem that sufficient contrast cannot be obtained.

It is well known that the alignment characteristics of liquid crystal molecules are influenced by the molecular structure of the polymer in the alignment film, but in the present invention, the upper silicon-containing material is chemically bonded to the polyimide resin skeleton. An object of the present invention is to provide a liquid crystal display device in which the intensity of transmitted light rapidly changes due to the electro-optical behavior of liquid crystal molecules before and after the application of an electric field, using an alignment film.

The structure of the liquid crystal display device of the present invention is as shown in FIG.

41, 1' is a glass substrate, 2, 2' are electrodes, 3, 3'
Reference numeral 4 indicates an alignment film having a structure explained in the following examples, 4 a liquid crystal layer, and 5 a sealant.

Examples of the method for manufacturing the alignment films 3, 3' used in the present invention will be described below.

The compounds used are the following (5), a3) and (C1).

(C) NH2(CHz)z NH(CH2)3
5i(OCH3)3A and B are mixed in a molar ratio of 1:1 to proceed with the polymerization reaction. During the reaction, the weight of the mixture of A and B is 10
C is added at a weight ratio of 40 to 0. As a result, a polymer compound having the following structural formula is obtained. The above m and n are integers indicating the degree of polymerization. This polymer compound was dissolved in a solvent (for example, N-methyl-2-pyrrolidone, etc.) and applied to the substrate as an alignment film at 280°C under a nitrogen gas atmosphere.
As a result, the following compound E is formed on the substrate.

The above m and n are integers indicating the degree of polymerization. As described above, the alignment film E used in the present invention is a polymer film having a structure in which a carboxyl group that does not participate in polymerization in a polyimide resin and an amine group of aminosilane are peptide-bonded, and is simply a polyimide resin containing silicon. This is clearly different from an alignment film made by mechanically mixing materials.Next, a liquid crystal display device using the above-mentioned polymer compound as an alignment film is manufactured. In a liquid crystal display device in which the liquid crystal molecules are arranged horizontally so that the directions of the liquid crystal molecules are twisted by approximately 90 degrees on the surfaces of opposing glass substrates, the voltage is In the zero-line display mode, in which changes in transmitted light intensity before and after application were investigated, light is transmitted when no electric field is applied, but when an electric field is applied, a dark image can be displayed on a transparent background.

Figure 2 shows the results. Curve (2) is a graph of a liquid crystal display device equipped with a conventional alignment film made of only polyimide resin, and curve (2) is a graph of a liquid crystal display device equipped with an alignment film of the present invention. The horizontal axis V of the graph shows the applied voltage, and the vertical axis shows the transmitted light intensity T.

In Figure 2, the transmitted light intensity T shows 100% in the off state where no voltage is applied between the electrodes, and when the voltage is applied and its level is gradually increased, the liquid crystal molecules transition from horizontal alignment to vertical alignment. The light enters the on state, blocking the transmission of light. Here, if we compare the liquid crystal display device (■) of the conventional example and the liquid crystal display device (2) of the present invention, we can see that the curve of the transmitted light intensity T with respect to the change in the applied voltage V is different from that of the liquid crystal display device (2) of the present invention. It can be seen that the change is more steep than that of display device (■).

In general, when displaying with multiplexing drive, especially in the case of drive waveforms with a duty of 1/7 or 1/8 or less, a display with good contrast is required because the ratio of lighting voltage to non-lighting voltage cannot be kept large. In order to get
Although a sharp rise is required for the V-T curve, it has been demonstrated that the liquid crystal display device equipped with the alignment film of the present invention is effective in obtaining the above-mentioned steep rise characteristic. It tells a story. 1. Furthermore, the liquid crystal display device of the present invention can be expected to have the effect of providing a higher quality display than the conventional liquid crystal display device in a liquid crystal display device driven by a drive toy.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal display device equipped with an alignment film of the present invention, and FIG. 2 is a characteristic diagram of the liquid crystal display device. 1.1'...Glass substrate, 2,2'...Electrode, 3.
3'...Alignment film, 4...Liquid crystal layer, 5...Sealant 0 Agent: Aihiko Fukushi, patent attorney

Claims (1)

[Claims] 1. In a liquid crystal display device in which an alignment film is adhered to the surface of a substrate on which an electrode pattern is formed, the alignment film is made of polyimide formed by polymerizing two types of monomers, namely, a polyhydric carboxylic acid and a diamine. a carboxyl group of the resin that does not participate in the polymerization of the polycarboxylic acid;
A liquid crystal display device characterized in that it is formed of a polymer film formed by peptide bonding the amino groups of aminosilane. 2. A compound of the following chemical formula as the polyhydric carboxylic acid,
The liquid crystal display device according to claim 1, wherein the diamine is a compound of the following chemical formula (B), and the aminosilane is a compound of the following chemical formula (Q) as the alignment film. (C) H2N (CHz)2 NH (CH2)3
Si(OCH3):+