JPS60244930A - Liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To enable the mass production of an excellent product having uniform quality by providing a pair of electrode substrates, oriented films and liquid crystal to the titled device, forming the oriented films of a cyclized polybutadiene resin and providing grating-shaped ruggedness on the surface thereof. CONSTITUTION:Front glass 3 and transparent electrodes 1 are adhered and plural spacers 10 are sealed between said glass and the substrate 7 for the liquid crystal display by a sealant 8. The liquid crystal is sealed in the space thus formed. The oriented film 2 is provided to the electrodes 1. TFT elements 4 (TR for switching of picture element electrode) and a picture element part 5 are disposed to the substrate 7. The oriented film 6 is formed thereon. Polarizing plates 11, 12 are adhered to the glass 3 and the substrate 7. The films 2, 6 are formed by coating the cyclized polybutadiene resin to about 2,000Angstrom film thickness on the substrate and preheating the resin at about 80 deg.C then irradiating two-beam interference fringes of laser light thereto thereby generating the grating. The resin is then exposed, developed and rinsed to form about 100Angstrom ruggedness. The mass production of the excellent product having uniform quality is thus executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a liquid crystal display device for displaying characters or images and a method for manufacturing the same, and in particular to a liquid crystal display device with a structure in which the surface of an alignment film is given liquid crystal alignment performance by a novel method. The present invention relates to a liquid crystal display device and a method for manufacturing the same.

Conventional configuration and its problems The basic configuration of a liquid crystal display device is a combination of a polarizing plate and a panel filled with liquid crystal between a pair of electrode substrates. It displays shades of light and shade based on the difference in birefringence with the rearranged liquid crystal molecules. In order to initially align the liquid crystal, various treatments called alignment treatments are usually performed on the inner wall of the panel in contact with the liquid crystal.

An example of an orientation treatment is a method in which nylon or vinyl fibers are rubbed in a fixed direction on a film coated with an organic material such as polyimide and cured, which is called a rubbing method for orientation treatment. Another example of alignment treatment is to deposit an inorganic material such as SiO on the electrode substrate from an oblique direction, which is called an oblique vapor deposition method of alignment treatment.

The phenomenon in which liquid crystal molecules are aligned in a certain direction on the surface of an alignment film that has been subjected to alignment treatment is because the potential energy of liquid crystal molecules, which are long-chain polymers, is minimized when they are aligned in that direction. The mechanism by which the alignment film obtained by rubbing has the alignment performance is due to physical irregularities on the surface due to rubbing.
There are theories that this is due to scratch-like unevenness like the so-called hairline processed surface, and theories that it is due to organic substances from the rubbing cloth adhering to the surface in a directional manner. Not yet reached.

For this reason, the rubbing process that has been put into practical use is
The reality is that we have experimented with combinations of the material of the organic alignment film, the curing conditions, the material of the rubbing cloth, the fiber structure, the pressing force of rubbing, the relative speed 9 times, etc., and determined the optimal conditions empirically. . In particular, in the case of rubbing, since the surface of the alignment film is mechanically rubbed, defects and abnormal scratches are likely to occur on the surface of the alignment film due to fallen rubbing cloth fibers and dust.
Since the durability of the rubbing cloth is not sufficient, there are drawbacks such as uneven alignment due to changes in alignment performance each time it is used. Furthermore, in a liquid crystal display device for displaying images, in which thin film transistors for switching corresponding to each of a large number of pixel elements are configured on an electrode substrate, uneven alignment may occur near uneven steps on the substrate surface. be. Furthermore, charging due to rubbing may cause electrostatic damage to such active elements.

Alignment treatment by oblique evaporation has relatively fewer defects such as these than alignment treatment by rubbing, but it is difficult to process large electrode substrates due to the size of the evaporation equipment and constraints on the substrate slanting equipment, and it requires a large amount of man-hours. The optimal condition range (
In particular, the deposition angle, deposition rate, substrate temperature, etc.) are relatively narrow, and there are drawbacks such as the need to control the deposition conditions.

Object of the Invention The present invention is directed to a liquid crystal display device having an alignment film that is aligned by a novel method that solves or improves the drawbacks of the conventional alignment film, and a method for manufacturing the same. In order to achieve the object, the liquid crystal display device of the present invention has an alignment film interposed between a pair of electrode substrates, the alignment film is made of cyclized polybutadiene resin, and grating-like irregularities on the surface of the alignment film are formed by laser light. It is formed by exposure using binary bundle interference fringes, etc., and is characterized in that the grating-like unevenness on the surface of the alignment film has a rectangular cross section.

Furthermore, the liquid crystal display device is characterized in that the liquid crystal molecules are arranged parallel to the direction of the grooves of the grating-like unevenness of the alignment film, and the assembled liquid crystal display device has a structure in which the display is directional. It is effective for attaching.

Therefore, in order to manufacture a liquid crystal display device having grating-like irregularities on the surface of the alignment film, there are two steps: applying an alignment film made of cyclized polybutadiene resin to the electrode surface of the substrate, and applying laser light to the surface of the alignment film. The method includes a step of irradiating original bundle interference fringes, a step of forming grating-like irregularities on the surface of the alignment film by developing the surface of the alignment film, and a step of heating and curing the alignment film.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a liquid crystal display device includes a front glass plate 3 having a transparent electrode 1 and an alignment film 2 thereon, a TPT element (a transistor element composed of a thin film transistor and used for switching the voltage applied to a pixel electrode) part 4, and Between the pixel section 5 and the liquid crystal display substrate 7 on which the alignment film 6 is attached,
A sealant 8 with a predetermined spacer mixed in the peripheral area
There is a liquid crystal 9 and a large number of spacers 10 in the panel surrounded by a sealant. And polarizing plate 11゜12
are both sides of the front glass plate 3 and the liquid crystal display substrate 7.

For example, an electroluminescent material 13 serving as a light source is attached to a polarizing plate 12 on a liquid crystal display substrate 7.
It is constructed by pasting it on.

FIG. 2 shows the structure on the side of the substrate 7, in which the gate electrode of the GidTFT element, the insulating film A, the channel active region made of amorphous silicon, and the source and drain electrodes M.

In order to initially align the liquid crystal 9, a photosensitive resin is applied to the electrode surface side of the lower electrode substrate and the electrode surface side of the other electrode substrate, and then three-beam interference fringes of laser light are irradiated thereon. Forms grating-like unevenness.

FIG. 3 shows a principle diagram of an irradiation device for three-beam interference fringes of laser light, in which the light rays emitted from the laser light source 14 enter the condensing lens 17 through the reflecting mirrors 16 and 16, and the pinhole 1
8 and then passes through a collimator lens 19 to become an expanded parallel light beam. Thereafter, this parallel light beam is further reflected by the reflecting mirror 2o, split into two by the beam splitter 21, reflected by the reflecting mirrors 22 and 23, and then incident on the photosensitive resin 25 coated on the electrode substrate 24. The three beams of parallel laser beams divided into two interfere with each other in the space around the photosensitive resin 26, producing slit-like interference fringes on the surface of the photosensitive resin. Figure 3 shows the case where the optical axes of the three beams are incident at equal angles to the normal direction of the photosensitive resin 25 surface, and the light intensity distribution on the photosensitive resin 26 surface at this time and the photoresistivity after development. FIGS. 4a and 4b show grating-like unevenness 26 formed on the plastic resin.

FIG. 5 shows a model diagram in which liquid crystal molecules are aligned parallel to grating-like uneven grooves on the surface of an alignment film. In addition, it is desirable that the pitch of the grating be smaller in order to increase the degree of alignment of the liquid crystal;
A grating with a pitch of about 1008 showed good orientation. As a laser light source, He-Cd laser wavelength λ=
44168 was used, but the pitch can be made smaller by using an ultraviolet laser with a shorter wavelength or by changing the incident angle conditions of the three beams.

As the alignment film made of photosensitive resin, we use a cyclized polybutadiene resin that exhibits good alignment similar to polyimide or polyvinyl alcohol, which is widely used as a rubbing alignment film for liquid crystal display devices. I will explain about it.

First, a cyclized polybutadiene resin having a viscosity of about 3.0 centipoise is applied to an electrode substrate at a film thickness of about 2,000,000 cm and about 400 Or, p, m. The substrate after applying the alignment film is 8
Pre-bake at about 0℃ for about 16 minutes.

A grating is generated on the surface of the alignment film by irradiation with three-beam interference fringes of a laser beam, and after exposure for about 180 to 190 seconds, development and washing with water cause the unevenness of the grating to be approximately 10 degrees on the alignment film. Ru. To promote crosslinking of the alignment film, heat treatment was performed at about 200°C. It's Kade.
In addition to heat treatment, deep ultraviolet light irradiation, X-ray irradiation, electron beam irradiation, ion beam irradiation, etc. are effective for promoting crosslinking of the alignment film. The degree of orientation could be increased by promoting crosslinking.

Here, the relationship between the contrast ratio of the liquid crystal display device and the pitch of the unevenness on the surface of the alignment film is shown in FIG. It has been observed that when the pitch of the unevenness on the surface of the alignment film becomes finer, the contrast ratio of the liquid crystal display device subjected to the alignment treatment of the present invention tends to be superior to the contrast ratio of the liquid crystal display device subjected to the alignment treatment such as rubbing. Ta. 28 is a contrast curve of a panel subjected to alignment treatment according to the present invention, and 29 is a contrast curve of a liquid crystal display device subjected to alignment treatment by rubbing. Therefore, it was found that the performance of the alignment treatment of the present invention has a remarkable effect in terms of contrast compared to conventional methods such as rubbing.

- Effects of the invention As described above, according to the present invention, the following effects can be obtained.

(1) Various defects and abnormal scratches on the surface, which were problems caused by conventional mechanical surface scrubbing 9, do not occur.

(2) Homogeneous alignment quality with less macroscopic and microscopic unevenness in alignment can be obtained.

(3) A liquid crystal display device with excellent display quality can be obtained.

(4) Compared to the conventional orientation treatment using oblique vapor deposition, a process using a direct-flowing device is not required (@) A large amount of treatment can be performed relatively stably.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a sectional view of the TPT element section and pixel section of the same device, and FIG. 3 is a three-beam interference pattern of laser light used in the present invention. 4 is an explanatory diagram showing the light intensity distribution on the surface of the alignment film and the grating-like unevenness of the alignment film. FIG. 5 is a schematic diagram of the surface of the alignment film on which grating-like unevenness is formed. FIG. 6 is a diagram showing the relationship between the contrast ratio of a liquid crystal display device and the pitch of unevenness on the surface of an alignment film. 1...Transparent electrode, 2...Alignment film, 3...
...Front glass plate, 4...TFT element section, 5
... Pixel section, 6 ... Alignment film, 7 ... Liquid crystal display substrate, 8 ... Sealing agent, 9 ...
・Liquid crystal, 10... Spacer, 11...
Polarizing plate (upper surface of front glass), 12... Polarizing plate (upper surface of liquid crystal display substrate), 13... Electroluminescent, 14-... Laser light source, 15...
...Reflector, 16...Reflector, 17...
・Condensing lens, 18・°°・Pinhole, 19...
・Collimator lens, 20...Reflector,
21...Beat Splinter, 22...
...Reflector, 23...Reflector, 24...
Electrode substrate, 26...Alignment film, 26.River/grating-like unevenness, 27...Liquid crystal molecules, 28...
Contrast curve of a liquid crystal display device subjected to alignment treatment according to the present invention, 29... Contrast curve of a liquid crystal display device subjected to alignment treatment by rubbing. Name of agent: Patent attorney Toshio Nakao and 1 other person1-
I Ji~ Figure 3 4 Figure 4 4 ＼ ? Otsu

Claims (2)

[Claims] (1) A liquid crystal display device comprising a pair of electrode substrates, an alignment film, and a liquid crystal, the alignment film being made of a cyclized polybutadiene resin, and having grating-like irregularities on the surface of the alignment film. (2) When manufacturing a liquid crystal display device in which a liquid crystal is filled between a pair of electrode substrates via an alignment film, a step of applying an alignment film made of a photosensitive negative cyclized polybutadiene resist; a step of irradiating the surface of the alignment film with a binary flux interference pattern of a laser beam, a step of forming grating-like irregularities on the surface of the alignment film by developing the surface of the alignment film, and curing the alignment film by heating. A method for manufacturing a liquid crystal display device, characterized by a process of: