JPH05232489A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To improve the yield of production and display grade by providing optical anisotropy on the electrodes of at least one substrate of two sheets of the substrates. CONSTITUTION:Arsenic fluoride AsF5 is added to polyacetylene, which is then so stretched as to have 400nm optical phase value. The stretched polyacetylene is stuck to the glass substrate 5 in such a manner that the optical axis attains 120 deg. from a horizontal direction and to the glass substrate 6 in such a manner that the optical axis attains 50 deg. from the horizontal direction. These films are then respectively patterned in an X direction and a Y direction to form transparent electrodes 9, 10. Oriented films 11, 12 consisting of polyimide are then formed by a printing method. The two substrates are thereafter so stuck to each other in parallel by a sealant 14 consisting of an epoxy adhesive that a prescribed spacing is obtd. therebetween. A liquid crystal 13 having about 760nm optical phase value is encapsulated therebetween and polarizing plates 3, 4 are stuck to the outer sides of the two substrates 5, 6 in such a manner that the directions of the respective absorption axes attain 90 deg. and -6 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been widely used for display devices such as portable liquid crystal video and liquid crystal televisions, calculators, measuring instruments, etc., and have higher display quality and defects in the manufacturing process. There has been a demand for liquid crystal display elements that can be reduced in number.

The liquid crystal display element has a T
There are N type, DS type, GH type, DAP type, thermal writing type and the like. Among them, TN type liquid crystal display elements are often used as display elements for calculators and measuring instruments. A birefringence mode liquid crystal display device using a TN type liquid crystal is generally called an ST type having a molecular arrangement twisted by 90 degrees or more and has steep electro-optical characteristics. Therefore, even a simple matrix electrode structure is time-divided. A large capacity display can be easily obtained by driving. However, in the ST type liquid crystal display element, since the birefringence effect is used, the display is colored due to the interference of light, which causes a reduction in contrast. On the other hand, the TN type liquid crystal display element in the optical rotation mode has a molecular arrangement twisted by 90 degrees, has a high response speed, shows a high contrast ratio and a good gradation display property, and has switching elements (TFT elements, MIM elements, etc.) As an active matrix liquid crystal display element provided in a pixel, it has a large display capacity and high display performance. However, the liquid crystal display element using these TN type liquid crystals has a viewing angle dependency, and there is a problem that the display color and the contrast ratio change depending on the viewing angle and direction. In order to solve such a problem, there is the following conventional technique using an optical phase plate having optical anisotropy in a liquid crystal display element. FIG. 3 is a sectional view of a conventional liquid crystal display element. In the liquid crystal display element 1, optical phase plates 7 and 8 and polarizing plates 3 and 4 are sequentially formed on both surfaces of a liquid crystal cell 2. The liquid crystal cell 2 has electrodes 15 and 16 and an alignment layer 1 on the respective facing surfaces.
The twisted nematic liquid crystal 13 is sandwiched between the substrates 5 and 6 on which the substrates 1 and 12 are formed and sealed with a seal material 14. In the liquid crystal display element having this configuration, an optical phase plate is provided between the substrate and the polarizing plate that form the liquid crystal cell, thereby improving the viewing angle of the TN type liquid crystal display element and correcting the color of the ST type liquid crystal display element. ing.

[0004]

By the way, in the liquid crystal display device having such a structure, the optical phase plate provided between the substrate and the polarizing plate is usually formed by bonding it to the substrate.

However, in the process of attaching the optical phase plate to the substrate, foreign matter is sandwiched between the optical phase plate and the substrate, and in the TFT type liquid crystal display element, a defect is caused by static electricity, so that the liquid crystal display element is manufactured. It was reducing the yield.

Further, in response to the recent demand for lighter and thinner liquid crystal display elements, a reduction in the number of members has been required.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device having a high display quality with an improved manufacturing yield.

[0008]

A liquid crystal display device of the present invention has a structure in which a twisted and aligned liquid crystal composition is sandwiched between two substrates having at least one transparent electrode arranged substantially parallel to each other, and In a liquid crystal display element in which a polarizing plate is arranged outside the two substrates, the electrode of at least one of the two substrates has optical anisotropy.

In the present invention, an electrode having optical anisotropy means an electrode having a different refractive index in the thickness direction of the electrode and a refractive index in the plane direction, and having the functions of both the electrode and the optical phase plate.

Examples of such electrodes include those obtained by stretching a conductive polymer material. Conductive polymer materials include π such as polyacetylene, polypyrrole, polythiophene, etc.
There are electron-conjugated polymers and conjugated polymers such as polyphenylene sulfide, and polymers obtained by doping these with AsF ₅ , I ₂ , ClO ₄ ^−, etc. as a dopant can be used.

The electrically conductive polymer material is used by bonding a stretched material to a hard substrate such as glass or quartz to form an electrode, or an unstretched material is bonded to a substrate such as a plastic film and then together with a plastic film. It can be stretched to form an electrode. When a plastic film is used, the conductive polymer can be directly produced on the plastic film and then stretched to form an electrode.

Further, it is also a preferable method to stabilize the conductive polymer by heat treatment.

In the liquid crystal display device of the present invention, a liquid crystal cell is formed by using at least one of the substrates having the above electrodes.

[0014]

In the liquid crystal display device of the present invention, by using the electrode-bearing substrate having optical anisotropy, the electrode-bearing substrate having optical anisotropy serves as a conventional optical phase plate and an electrode. .. As a result, the step of bonding the optical phase plate to the substrate after manufacturing the liquid crystal cell is not necessary, and a defect occurs in the liquid crystal display element due to static electricity, or a defect such that a foreign substance is sandwiched between the substrate and the defect is reduced. Manufacturing yield is improved. Moreover, a liquid crystal display device which is lightweight and thin and has high transmittance can be obtained.

[0015]

【Example】

 Example 1 Hereinafter, an example of the present invention will be described with reference to FIG.

First, arsenic fluoride AsF is added to polyacetylene.
0.1% of ₅ is added and stretched so that the optical phase value becomes 400 nm. The optical axis of the glass substrate 5 is 120 degrees from the horizontal direction, and the optical axis of the glass substrate 6 is 5 degrees from the horizontal direction.
It was pasted so that it would be 0 degree. Then each X
Patterning in the Y direction and the Y direction to form transparent electrodes 9 and 10. Then, the alignment films 11 and 12 made of polyimide were formed by a printing method and baked at about 180 ° C. The liquid crystal molecules twist counterclockwise from the substrate 6 toward the substrate 5 in a counterclockwise direction depending on the orientation direction r _{1 of} the substrate 5 and the orientation direction r ₂ of the substrate 6.
+30 from the horizontal direction so that it is twisted and oriented
The substrate 6 was rubbed at −30 degrees from the horizontal direction. Next, the substrates were bonded in parallel with each other with a sealant 14 made of an epoxy adhesive so that the distance between both substrates was 6.6 μm. Then, the liquid crystal 13 having an optical phase value of about 760 nm is enclosed, and the polarizing plates 3 and 4 are attached to the outer surfaces of both substrates so that the directions of the absorption axes are 90 degrees and -6 degrees, respectively. And The liquid crystal display device manufactured as described above is lightweight and thin, and has a high contrast and a wide viewing angle in the normally black mode.

Example 2 In Example 1, polyacetylene was added to arsenic fluoride AsF.
A film obtained by adding 0.1% of ₅ and stretching it so that the optical phase value was 400 nm was attached to a glass substrate in the same manner as in Example 1. After that, heat treatment (N
₂ atmosphere, 160 ° C., 1.5 hours). The optical phase value after the heat treatment was 400 nm. Then, a liquid crystal display element was prepared in the same manner as in Example 1. When the same evaluation as in Example 1 was performed, a high contrast and a wide viewing angle were obtained in the normally black mode.

Embodiment 3 An embodiment of the present invention will be described below with reference to FIG. 0.1% of arsenic fluoride AsF ₅ was added to polyacetylene and stretched so that the optical phase value was 300 nm. Then, the film is placed on the CF substrate 5a with the optical axis from the rubbing direction.
The first layer 10a is attached so that it becomes 0 degrees, and then
Second layer 1 so that the optical axis is 90 degrees from the rubbing direction
0b was used as the bonded electrode. Next, the CF substrate 5a and T
An alignment film 11 made of polyimide on the FT array substrate 6a,
12 was formed by a printing method and baked at about 180 ° C. Orientation direction r ₁ of the liquid crystal molecules is CF substrate 5a, C from the TFT array substrate by the alignment direction r ₂ of the TFT array substrate 6a
The CF substrate 5a was rubbed by +45 degrees from the horizontal direction, and the TFT array substrate 6a was rubbed by -45 degrees from the horizontal direction so that the F substrate was twisted counterclockwise by 90 ° and oriented. Next, the substrates were bonded in parallel with each other with a sealing material 14 made of an epoxy adhesive so that the distance between both substrates was 5.5 μm. Then, the liquid crystal 13 is enclosed so that the optical phase value becomes about 500 nm, and the directions of the absorption axes are 45 degrees on the outer surfaces of both substrates.
The liquid crystal display element 1 was obtained by laminating the polarizing plates 3 and 4 at 45 degrees. The liquid crystal display device manufactured as described above is lightweight and thin, and has high contrast and a wide viewing angle.

[0019]

In the liquid crystal display element of the present invention, since at least one electrode has optical anisotropy, it is not necessary to attach an optical phase plate to the outside of the substrate, and static electricity causes a defect in the liquid crystal display element. It is possible to obtain a liquid crystal display device having a good manufacturing yield without any defects such as a foreign matter being caught between the substrate and a substrate.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a cross section of a liquid crystal display element for explaining a first embodiment.

FIG. 2 is a diagram showing a cross section of a liquid crystal display element for explaining a second embodiment.

FIG. 3 is a view showing a cross section of a conventional liquid crystal display element.

[Explanation of symbols]

1 ... Liquid crystal display element, 2 ... Liquid crystal cell, 3,4 ... Polarizing plate, 5,6 ... Substrate, 5a ... CF substrate, 6a ... TF
T array substrate, 7, 8 ... Optical phase plate, 9, 10, 10
a, 10b ... Transparent electrodes, 11, 12 ... Alignment film, 13
...... Liquid crystal, 14 ...... Sealant material, 15, 16 ...... Counter electrode.

Claims (1)

[Claims] 1. At least one of the electrodes has a transparent electrode.
In a liquid crystal display element in which a twisted liquid crystal composition is sandwiched between two substrates arranged substantially in parallel, and a polarizing plate is arranged outside the two substrates, the two substrates The liquid crystal display element, wherein the electrode on at least one of the substrates has optical anisotropy.