JPH0682787A - Liquid crystal display element - Google Patents

Abstract

PURPOSE:To provide two kinds or more of liquid crystal orienting layers differed in orienting direction of liquid crystal molecule by one orienting treatment, and moderate the limitation of visual angle. CONSTITUTION:A liquid crystal composite 17 is nipped between two bases 1, 2. On the bases, two kinds or more of liquid crystal orienting layers 4, 5, 14, 15 different in liquid crystal molecule arrangement direction which are induced by rubbing orienting treatment are formed adjacent to the liquid crystal composite.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal alignment layer thereof.

[0002]

2. Description of the Related Art Liquid crystal display devices have been widely used as display devices such as OA equipment such as word processors and personal computers and televisions because of their advantages of thinness, light weight and low power consumption. The liquid crystal display element used for these is a twisted nematic liquid crystal and operates in either an optical rotation mode or a birefringence mode.

The optical rotation mode element is, for example, a twisted nematic (TN) type liquid crystal having a molecular arrangement twisted by 90 °, and is a monocolor display in principle, and exhibits a high contrast ratio and a good gradation display property, and also has a response. The speed is as high as several tens of milliseconds, and it is applied to clocks, calculators, simple matrix drives, active matrix drives with switching elements for each pixel, and color LCD televisions combined with color filters.

On the other hand, the element of the birefringence mode display system is
In general, it is a super twist (ST) type liquid crystal having a molecular arrangement twisted by 90 ° or more and has steep electrical characteristics,
Large-capacity display can be easily obtained by time-division driving with a simple matrix electrode structure without disposing a switching element made of a thin film transistor for each pixel.

However, these liquid crystal display elements have a viewing angle dependency in which the contrast ratio and the display color change depending on the viewing direction of the display. As one method of improving the viewing angle dependency of the liquid crystal display element, there is a technique of providing a region in which the rising direction of liquid crystal molecules is changed by 180 ° in one pixel or in a pixel unit (KH Yang, 1991, IRD).
C, p68), (JP-A-63-106642).

[0006]

Conventionally, the following methods have been mainstream as means for aligning the molecules of liquid crystals of these liquid crystal display devices.

A. Rubbing method: An organic polymer thin film typified by polyimide is formed on a substrate by spin coating or printing, and this film is lightly rubbed with a cloth or the like to impart liquid crystal alignment ability.

B. Oblique vapor deposition method: An inorganic compound such as silicon oxide is obliquely vapor-deposited in a vacuum on a substrate, and liquid crystal alignment ability is given by a regular arrangement of silicon oxide.

C. LB method: A Langmuir-Blodgett (LB) film is developed on the water surface, the substrate is pulled up from the water to the water surface, and transferred onto the substrate to form an alignment layer.

D. Photolithography method: A photosensitive resin is formed on a substrate, and the photosensitive resin is exposed through a mask and developed to form fine irregularities on the resin surface, thereby imparting liquid crystal aligning ability.

Now, in order to change the alignment direction of liquid crystal molecules in the same substrate by using such a method, 1
Perform a second alignment treatment (eg rubbing method), then
The mask is moved to perform the second alignment treatment (for example, oblique vapor deposition). However, when using such means,
Usually, a plurality of alignment treatments are required.

The present invention eliminates such inconvenience.

[0013]

The present invention provides a liquid crystal display device comprising a liquid crystal layer sandwiched between two substrates each having an electrode and an alignment layer on the surface so that the electrodes face each other. A liquid crystal display device, characterized in that two or more kinds of liquid crystal alignment layers having different liquid crystal molecule alignment directions induced by a rubbing alignment treatment are respectively formed on the substrate in contact with the liquid crystal layer.

Further, according to the present invention, a liquid crystal display is provided in which two substrates each having an electrode and an alignment layer on the surface are installed so that the electrodes face each other, and a liquid crystal layer is sandwiched between the two substrates so as to contact the alignment layer. In the device, the alignment layer of the substrate is an alignment layer in which at least two kinds of liquid crystal molecules are arranged in different alignment directions, and at least one of them is different in the rubbing treatment direction and the liquid crystal molecule alignment direction. To obtain a liquid crystal display device.

[0015]

The present invention achieves the above object, and the principle and means for achieving the object will be described.

As shown in FIG. 4A, it is generally known that when a polyimide surface is subjected to a rubbing orientation treatment, liquid crystal molecules 1 are aligned in the rubbing direction, and the liquid crystal molecules 1 have a pretilt angle α 0. However, when polystyrene or bovine serum albumin, which is a kind of polymer film, is subjected to a rubbing treatment, liquid crystal molecules are not aligned in the rubbing direction, but are aligned substantially perpendicular to the rubbing treatment direction. That is, by selecting the material of the alignment layer, the alignment direction of the liquid crystal molecules induced with respect to the rubbing direction, that is, the alignment direction in the substrate surface, the pretilt angle, and the rising direction can be freely controlled.

For example, as shown in FIG. 4B, a polyimide alignment layer 11 is formed on a part of the substrate surface, and a polystyrene alignment layer 12 is formed on the other part, and these layers are formed in the rubbing direction shown by the arrow. Rubbing alignment processing is performed. When a nematic liquid crystal is brought into contact with the rubbing-treated surface, the directors (long axes) of the liquid crystal molecules 1 are aligned on the polyimide alignment layer 11 in the rubbing direction and are substantially orthogonal to the rubbing direction on the polystyrene alignment layer 12. To arrange.

That is, according to the present invention, these two or more kinds of alignment layers are formed on the same substrate, and the liquid crystal layers have different alignment directions within the same substrate. Moreover, the liquid crystal alignment layer can be obtained such that the alignment directions of the liquid crystal molecules are different by one rubbing alignment treatment. The present invention utilizes the above-mentioned property of the alignment layer to provide a plurality of regions in the same pixel or change the alignment direction of liquid crystal molecules for each adjacent pixel.
That is, the liquid crystal molecule alignment directions between pixels are, for example, 9
When it is shifted by 0 °, the twist direction of the liquid crystal layer is also shifted by 90 °, and since this relationship is distributed in a mosaic pattern over the entire display surface, the limitation of the visual field caused by the tilt angle and the twist direction is relaxed.

The alignment layer can be formed by a photolithography method or a printing method.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 (a) shows the structure of upper and lower substrates 1 and 2, and FIG. 1 (b) shows the alignment state of liquid crystal molecules. Shown in FIG.
3A to 3F are process charts (a to f) of steps a to f for forming an alignment layer.

First, a glass substrate 1 on which transparent electrodes are formed
Then, the glass substrate 2 on which the pixel electrode 3a and the TFT drive element 3b are formed for each pixel 10 is prepared. That is, the ITO electrode 3a having a pixel size of 110 × 330 μm is connected to each TFT driving element 3b.

The process of forming the alignment layer will be described with reference to FIG. 2. (Step a) The polystyrene alignment layer 4 is formed on the substrate 2 by the spin coating method to a thickness of 1000 angstroms.

(Process b) Negative photosensitive polyimide (Probimide 400 series: manufactured by Ciba Geigy)
Is used to form a photosensitive polyimide layer 5a having a thickness of 850 angstrom.

(Step c) 110 on this polyimide layer
When the i-line is exposed through a mask having a large number of transmitted light portions having a rectangular shape of × 165 μm, the exposed portion is photo-cured and the non-exposed portion is removed by development. As a result, the polyimide alignment layer 5 is formed in the exposed portion, and the polystyrene alignment layer 4 previously applied is exposed in the portion where the non-exposed portion is removed.

(Step d) A black light absorbing layer 6a made of epoxy is spin-coated thereon.

(Step e) This photosensitive light absorbing layer is subjected to mask exposure by photolithography to form a black matrix layer 6 at the boundary between the polystyrene alignment layer 4 and the polyimide alignment layer 5. That is, as shown in FIG. 1B, the polystyrene alignment layer 4 and the polyimide alignment layer 5 bisect the area of one pixel 10 on the substrate 2, and an alignment layer different from the adjacent pixel area is in contact therewith. Thus, the black matrix 6 is formed at the boundaries between the alignment layers, which are alternately arranged in a grid mosaic pattern.

(Step f) The substrate 2 thus obtained is subjected to rubbing orientation treatment in the direction of a constant arrow. That is, in FIG. 2G showing one pixel 10, the rubbing process is performed in the arrow direction r inclined by 45 ° with respect to the horizontal direction of the substrate display surface. As a result, the directors of the liquid crystal molecules 1 are arranged on the polystyrene alignment layer 4 in the direction orthogonal to the rubbing treatment direction and on the polyimide alignment layer 5 in the rubbing treatment direction.

On the other hand, as shown in FIG. 1A, the substrate 1 also has a mosaic oriented polystyrene alignment layer 14 and a polyimide alignment layer 15 corresponding to one pixel of the substrate 2 on the common electrode 1a in the same manner as the substrate 2. Form alternately. This formation is selected such that when the substrate 2 and the alignment layer are opposed to each other, the liquid crystal sandwiched between the regions of each pixel is twisted by 90 °. Further, the black matrix layer 16 is arranged at the boundary of each region.

Next, both substrates 1 and 2 were arranged with the alignment layer inside and via a spacer, and sealed with a sealant to prepare a liquid crystal cell. Liquid crystal composition ZLI-113 for liquid crystal cell
2 (manufactured by E. Merck) 17 (FIG. 1A) was injected to complete a liquid crystal display device.

In this embodiment, as shown in FIG. 1B, since the orientation directions are different within the pixel, disclination occurs at the boundary, but the black matrix 6 is located at the disclination generation position. However, this can be avoided. With the above structure, uniform alignment of 90 ° twist was obtained in both the polystyrene alignment layer portion and the polyimide alignment layer portion, and when this liquid crystal display device was driven, the viewing angle dependency was improved and the contrast was high and good display was obtained. .

(Embodiment 2) In Embodiment 1, a substrate 1 in which 480 transparent electrodes are formed in the X direction on a glass substrate
Then, using the substrate 2 in which 640 transparent electrodes were formed on the glass substrate in the Y direction, both substrates were rubbed so that the rubbing direction was 30 ° with respect to the end face of the substrate. After that, a liquid crystal alignment layer of polystyrene and polyimide is formed in the same manner as in Example 1, and both substrates 1 and 2 are sealed so that the liquid crystal molecules are twisted to the left by 240 °, and a liquid crystal display element is manufactured.

When the liquid crystal orientation of this liquid crystal display element was examined, a uniform orientation of 240 ° twist was obtained on both the polyimide orientation layer and the polystyrene orientation layer, and when this liquid crystal display element was driven, good display was obtained. Was given.

Example 3 The orientation layer of this example is composed of a polyimide layer and a bovine serum albumin layer. FIG. 3 shows a flowchart of the alignment layer forming process.

As the substrates 1 and 2, glass substrates having the same structure as in Example 1 are used.

(Step a) First, a polyimide alignment layer 21 (AL-) is formed on the substrates 1 and 2 on which the black matrix layer 20 is formed.
1051 (manufactured by Japan Synthetic Rubber Co., Ltd.)) 110 × 165 μm
Area is printed and baked at 180 ° C. for 1 hour.

(Step b) Next, bovine serum albumin is printed on the unprinted area of the polyimide alignment layer 21 to form the bovine serum albumin alignment layer 22.

A liquid crystal display block was produced on the obtained substrate in the same manner as in Example 1. When the orientation of the liquid crystal was examined for this liquid crystal display element, a uniform orientation of 90 ° twist was obtained in both the polyimide orientation layer portion 21 and the bovine serum albumin orientation layer portion 22, and the orientation of the director of liquid crystal molecules was
The polyimide alignment layer was in the rubbing direction, and the bovine serum albumin alignment layer was in the rubbing direction. When this liquid crystal display device was driven, good display was obtained with high contrast as well as viewing angle characteristics.

Although the case where the orientation directions in one pixel are different has been described in the above embodiment, the same effect can be obtained even in a structure in which the orientation is changed between adjacent pixels (in units of one pixel).

[0040]

According to the present invention, two or more kinds of liquid crystal alignment layers having different alignment directions of liquid crystal molecules, which cannot be obtained by the conventional alignment treatment, can be obtained, and a liquid crystal display device of high quality display is provided. be able to. Needless to say, even if the present invention is applied to a two-terminal element such as MIM and applied to an active matrix liquid crystal display element and a ferroelectric liquid crystal display element, excellent effects can be obtained.

[Brief description of drawings]

1A is a partially enlarged sectional view showing an embodiment of the present invention, and FIG. 1B is a partially perspective view of the same.

2A to 2F are partially enlarged cross-sectional views illustrating a manufacturing process of an embodiment of the present invention, and FIG. 2G is a schematic view illustrating an alignment direction of liquid crystal molecules in an alignment layer.

3A and 3B are partially enlarged cross-sectional views illustrating a manufacturing process of another embodiment of the present invention.

4 (a) and 4 (b) are schematic diagrams for explaining the operation of the present invention.

[Explanation of symbols]

 1, 2 ... Substrate 3a ... Pixel electrode 3b ... TFT driving element 4, 14 ... Polystyrene alignment layer 5, 15 ... Polyimide alignment layer 6, 16 ... Black matrix layer

Claims (2)

[Claims] 1. A liquid crystal display device comprising a liquid crystal layer sandwiched between two substrates each having an electrode and an alignment layer on the surface so that the electrodes face each other, and a liquid crystal induced by a rubbing alignment treatment. A liquid crystal display device comprising: two or more kinds of liquid crystal alignment layers having different molecular alignment directions, each of which is formed on the substrate in contact with the liquid crystal layer. 2. A liquid crystal display device comprising two substrates, each having an electrode and an alignment layer on its surface, arranged so that the electrodes face each other, and a liquid crystal layer is sandwiched between the substrates so as to be in contact with the alignment layer. The alignment layer of the substrate is an alignment layer in which at least two kinds of liquid crystal molecules have different alignment directions, and at least one of them has a rubbing treatment direction and a liquid crystal molecule alignment direction different from each other. element.