JPH03158826A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a good orientation state by using a mixture composed of >=2 kinds of silane coupling agents varying in the carbon atoms of long chain alkyl as oriented films. CONSTITUTION:After transparent electrodes 12, 15 are formed to prescribed shapes on upper and lower glass substrates 11, 14, the silane coupling agents are applied thereon by spin coating to form the oriented films 13, 16. The films are baked for one hour at 200 deg.C and thereafter, both substrates are stuck to each other. A liquid crystal 17 having positive dielectric anisotropy is packed therebetween to form the liquid crystal display device. The tilt can be arbitrarily controlled simply by changing the mixing ratio of the silane coupling agent having <=8C long chain alkyl having substantially no tilt and the silane coupling agent having >=8C long chain alkyl maintaining nearly 90 deg. tilt at this time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device having an alignment film used in color televisions, personal computers, etc., and particularly relates to the alignment film.

[Summary of the Invention 1 The present invention relates to a liquid crystal display device having an alignment film, and in particular,
A good alignment state can be obtained by using a mixture of two or more types of silane coupling agents having different carbon numbers in the long chain alkyl as the alignment film.

[Conventional technology] In recent years, liquid crystal display devices have made remarkable progress and have reached the point where high-definition image quality comparable to that of CRTs can be obtained, but the application of new liquid crystal display elements is being considered to further improve image quality and increase size. has been done.

FIG. 2 shows an example of a TN type liquid crystal display device applied to displays of digital watches, calculators, etc. In FIG. 2, 21 is a transparent substrate.

22 is an electrode made of a transparent conductive film patterned with arbitrary figures or characters; 23 is an alignment film formed of polyimide or the like by printing, spin code, dipping, etc.; 25 is a transparent second electrode; and 24 is a transparent second electrode. This is the board. The space sandwiched between the two substrates 21 and 24 is filled with liquid crystal 27, and the long axis of the liquid crystal polymer is twisted by about 90 degrees by the alignment particles 23 and 26 on the upper and lower substrates, and the liquid crystal 27 is sandwiched between a polarizer and an analyzer. This results in a liquid crystal display device that opens and closes light by applying voltage.

Conventionally, in order to align liquid crystal molecules, the surface of an alignment film made of polyimide or the like is rubbed in one direction with a cloth, etc. 3 Usually, at this time, the liquid crystal molecules are aligned at an angle of about 90 degrees at the interface of the alignment film. It can have a tilt of about 0 to 1 degree, which is sufficient for this purpose.

Figure 3 shows an example of an STN type liquid crystal display device applied to word processors, parts chill combinators, etc. Similar to Figure 2, a liquid crystal 37 is placed in the space sandwiched between two substrates 31 and 34. Fill and align 11133 on top and bottom substrates
．． 36, the long axis of the liquid crystal polymer is twisted by about 200 degrees in this case, and sandwiched between a polarizer and an analyzer to form a liquid crystal display device that opens and closes light by applying a voltage. STN type liquid crystal display devices have liquid crystal molecules twisted by about 200 degrees, so they have excellent electro-optical properties and are used as large-capacity display devices. A special alignment film is required that has a tilt of 5 to 10 degrees at the interface of the alignment film. Additionally, in order to further improve the electro-optical properties, it is being considered to twist the liquid crystal molecules by 260 to 270 degrees, but this is considered impractical as it would require a tilt of about 10 to 30 degrees. .

FIG. 4 shows an example of an ECB type liquid crystal display device.

Similarly to FIGS. 2 and 3, the space between the two substrates 41 and 44 is filled with liquid crystal 47, and the orientation 1!143 on the upper and lower substrates is
．． 46, the tilt of the liquid crystal polymer is oriented almost vertically, and it is sandwiched between a polarizer and an analyzer to provide a liquid crystal display device that opens and closes light by applying a voltage. In order to obtain a stable vertical alignment of liquid crystal molecules, an ECB type liquid crystal display device can be obtained by forming a silane coupling agent having a long chain alkyl having 8 or more carbon atoms using a spin cord or the like. However, with this vertical orientation, it is difficult to obtain unidirectionality by rubbing, which poses a problem in mass production.

[The problem that the invention aims to solve! 11 Therefore, the present invention aims to realize an alignment film that can set the tilt of liquid crystal molecules at the interface of the alignment film to an arbitrary value of 90 degrees or less and has excellent one-way isotropy.
It is designed to be easily compatible with all kinds of N and ECB liquid crystal display devices.

[Means for Solving the Problems] The present invention provides a silane coupling agent having a long chain alkyl having 8 or less carbon atoms and having almost no tilt.

By appropriately mixing with a silane coupling agent having a long chain alkyl having 8 or more carbon atoms and having a tilt of about 90 degrees, arbitrary tilt and good unidirectionality can be obtained.

[Function] By arbitrarily controlling the tilt in this way, the mixing ratio of the silane coupling agent having a long chain alkyl of 8 or less carbon atoms and the silane coupling agent having a long chain alkyl of 8 or more carbon atoms can be changed. S with good display condition just by ^
I was able to get TN and ECB.

[Example J (Example 1) The present invention will be described in detail with reference to FIG. First, after forming transparent electrodes 12.15 in a predetermined shape on upper and lower glass substrates 11.14, a liquid containing a silane coupling agent having a structure as shown in the following formula is mixed as shown below and oriented using a spin code. It was set as 1g13.16.

■ Cs H+w S j (QCs
Hs) x■ Cm Ht St
(OCtHs) This pus was fired at 200 degrees for 1 hour, and a rubbing treatment was performed by rubbing both substrates in one direction with a cotton cloth so that the liquid crystal molecules were twisted 260 degrees. Thereafter, both substrates were pasted together, and a liquid crystal 17 having a positive dielectric anisotropy was filled between them to produce a liquid crystal display device as shown in FIG. 1, which had a tilt of 15 degrees. A good alignment state with no unevenness was obtained.

Also, when a liquid crystal display device was created in the same way using only the silane coupling agent ■ without mixing the silane coupling agent ■, the tilt was only 1 degree, and the liquid crystal molecules could not take a 260 degree twisted state. Ta.

<Example 2> Similarly to Example 1, a liquid in which a silane coupling agent having a structure as shown in the following formula was mixed as shown below was formed into an alignment film using a spin cord.

■CI-H-5i (OCx Hs)-■
C, H, Si (OC, H,)=200
Both substrates were rubbed in one direction with a cotton cloth so that the liquid crystal molecules were tilted in parallel. After this 1
When a liquid crystal display device was produced in the same manner as in Example 1 by bonding both substrates together and filling the space between them with a liquid crystal having negative dielectric anisotropy, an even vertical alignment state with a tilt of approximately 90 degrees was obtained. Ta. Also, when a voltage was applied between these two substrates, the liquid crystal molecules changed! A uniform display state was obtained with a tilt in the direction.

Also, when a liquid crystal display device was made in the same way without mixing the silane coupling agent ■, a tilt of about 90 degrees was obtained, but the liquid crystal molecules could not be tilted uniformly when voltage was applied, and a good result was obtained. No orientation was obtained.

[Effect of the invention 1] According to the present invention, a silane coupling agent having a long chain alkyl having carbon atoms of 8 or less and having almost no tilt can be used.
By simply changing the mixing ratio of the silane coupling agent with a long-chain alkyl having 8 or more carbon atoms, the tilt can be controlled as desired, making it possible to obtain STN and ECB with good display conditions. Yes, the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an apparatus showing one embodiment of the present invention;
The figure is a sectional view showing an embodiment of TN, FIG. 3 is STN, and FIG. 4 is ECB. that's all

Claims (2)

[Claims] (1) A liquid crystal display device having an alignment film for regulating the alignment of liquid crystal molecules, characterized in that a mixture of two or more types of silane coupling agents having different numbers of carbon atoms in their long chain alkyls is used as the alignment film. Display device. (2) The liquid crystal display device according to claim 1, wherein at least one of the silane coupling agents has a long chain alkyl having 8 or more carbon atoms.