JPS60244926A - Liquid-crystal display device and its manufacture - Google Patents

Abstract

PURPOSE:To easily mass-produce products of homogeneous quality by providing a couple of electrode substrates and a transparent electrode film or insulating film, and forming recesses and projections on the surface of the transparent electrode or insulating film in a grating shape. CONSTITUTION:Front surface glass 2 and a transparent electrode plate 1 are adhered together and plural spacers 9 are arranged between the plate 1 and a substrate 6 for liquid-crystal display and sealed with a sealant 7 to form a space, where liquid crystal 8 is charged. Insulating films 5 on the reverse of the transparent electrode 1 and on the substrate 6 are coated with photosensitive resin. Then, the films 5 are irradiated with two-luminous-flux interference fringes of laser light, and development, fixation, and washing are carried out to for a grating with recesses and projections at 0.3mum pitch to about 100Angstrom depth. Polarizing plates 10 and 11 are stuck on the front surface glass plate 2 and substrate 11. Consequently, products of homogeneous quality are mass-produced.

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 shading based on the difference in birefringence between the rearranged liquid crystal molecules and the 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 cured film coated with an organic material such as polyimide, 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. Regarding the mechanism by which the alignment film obtained by rubbing has alignment properties, there is a theory that it is due to physical unevenness on the surface of the rubbing, such as scratch-like unevenness such as a so-called hairline processed surface, or that organic substances in the rubbing cloth are There are theories that this is because it adheres to the surface in a directional manner, but none of these theories has reached an established theory.

For this reason, the rubbing process that has been put into practical use is
The reality is that the optimum conditions are determined empirically by experimenting with combinations of the material of the organic alignment film, curing conditions, rubbing cloth material, fiber structure, rubbing force, relative speed 9 times, etc. . 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 the alignment performance changing each time it is used and non-uniform alignment. 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. becoming, optimal condition range C
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.

OBJECTS OF THE INVENTION The object of the present invention is to provide a liquid crystal display device having an alignment film that is aligned using a novel method that solves or improves the drawbacks of the conventional alignment film, and a method for manufacturing the same.

Structure of the Invention In order to achieve the above object, the liquid crystal display device of the present invention has a liquid crystal filled between a pair of electrode substrates having a transparent electrode film or an insulating film, and a grating-like unevenness on the surface of the transparent electrode film or insulating film. The present invention is characterized in that it is formed by exposure using three-beam interference fringes of laser light.

Furthermore, in the liquid crystal display device, the liquid crystal molecules are arranged parallel to the direction of the grating-like unevenness of the transparent electrode film or the insulating film, or the liquid crystal molecules are arranged in the first grating-like unevenness of the transparent electrode film or the insulating film. The second unevenness is formed perpendicularly to the direction of the liquid crystal, and the second unevenness of the transparent electrode film or the insulating film gives directivity to the liquid crystal molecules. It is effective in imparting directivity to the display in a liquid crystal display device.

Therefore, in order to manufacture a liquid crystal display device having grating-like irregularities with a rectangular or sawtooth cross section on the surface of a transparent electrode film or insulating film, a photoresist is applied on the transparent electrode film or insulating film on the electrode substrate. There are three steps: coating the photoresist surface, irradiating the photoresist surface with three-beam interference fringes of laser light, developing the photoresist to form grating-like irregularities on the shift resist, and etching the shift resist. The process includes a step of processing the surface of the transparent electrode film or insulating film on the electrode substrate in the recessed portion of the odoresist into a grating shape, and a step of removing the photoresist.

Furthermore, in the case of etching by ion beam irradiation, if the traveling direction of the ion beam is perpendicular to the electrode substrate, the cross section of the grating-like unevenness of the transparent electrode film or insulating film on the electrode substrate surface of the recessed part of the photoresist will be formed into a rectangular shape. Furthermore, when the traveling direction of the ion beam is oblique with respect to the electrode substrate, the cross section of the grating-like unevenness of the transparent electrode film or the insulating film on the electrode substrate surface of the recessed part of the photoresist is formed in a sawtooth shape. When ion beam irradiation is further performed in this state, two second gratings are formed in response to the first grating having a sawtooth cross section in accordance with the unevenness of the photoresist surface.

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 2 with a transparent electrode 1, a TPT element (a transistor element composed of a thin film transistor and used for switching the voltage applied to a pixel electrode) 3. ．． ! ? ! ,.

However, between the liquid crystal display substrate 6 and the periphery, there is a sealant 7 mixed with a predetermined spacer in advance, and the liquid crystal 8. A large number of spacers 9 are present. Then, polarizing plates 10 and 11 are pasted on both sides of the front glass plate 2 and the liquid crystal display substrate 6, and further, for example, a urectroluminescent material 12, which serves as a light source, is pasted on the polarizing plate 11 on the liquid crystal display substrate 6. Especially composed of many.

Figure 2 shows the structure on the substrate 6 side, where G is the gate electrode of the TPT element, A is the insulating film, A is the channel active area made of amorphous silicon, M is the source and drain electrodes, and P is the TPT element area. It is a protective film.

In order to initially align the liquid crystal 8, a photosensitive resin is applied to the electrode surface side of the lower electrode substrate 6 and the electrode surface side of the other electrode substrate 2, and then three-beam interference fringes of laser light are irradiated thereon. The grating-like unevenness is formed by ion beam irradiation, and the unevenness is formed on the surface of the transparent electrode film or the insulating film.

FIG. 3 shows a principle diagram of the three-beam interference fringe irradiation device of laser light, in which the light beam emitted from the laser light source 14 passes through reflectors 5 and 16, enters the condenser lens 17, and enters 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 a reflecting mirror 20, split into two by a beam splitter 21, reflected by reflecting mirrors 22 and 23, and then incident on a photosensitive resin 25 coated on an electrode substrate 24. The binary bundle of parallel laser beams divided into two causes interference in the space near the photosensitive resin 26, producing slit-like interference fringes on the photosensitive resin surface. Figure 3 shows the case where the optical axis of the binary flux is incident at equal angles to the normal direction of the photosensitive resin 25 surface, and the light intensity distribution on the photosensitive resin 25 surface at this time and after development. The grating-like unevenness 26 formed on the photosensitive resin is
Shown in figures a and b.

Here, processing steps for the surface of the transparent electrode film or insulating film on the electrode substrate will be explained. In particular, regarding the etching process, a case of etching using ion beam irradiation will be explained.

In order to initially align the liquid crystal 9, the photoresist coated on the electrode substrate with a spinner in advance is irradiated with three-beam interference fringes of light using a laser and developed, thereby forming grating-like irregularities on the shift resist. ,
It is necessary that the cross section of the alignment film surface be processed into a rectangular or sawtooth groove by ion beam irradiation with the ion beam traveling direction perpendicular or oblique to the substrate.

Next, a specific example will be explained. A 0-positive type 7 photoresist having a film thickness of approximately 1800 mm is applied onto the electrode substrate using a spinner. After creating a grating using three-beam interference fringes on the photoresist surface and exposing it to light for about 180 to 190 seconds,
By developing, grating-like unevenness is formed on the shift resist. In the case of ion beam irradiation in which the traveling direction of the ion beam is perpendicular to the substrate, the cross section of the transparent electrode film or insulating film exposed at the bottom of the recessed portion of the photoresist is formed into a rectangular shape. Further, the cross section of the transparent electrode film or insulating film exposed at the bottom of the recessed portion of the ion beam photoresist in which the traveling direction of the ion beam is oblique to the substrate is formed in a sawtooth shape.

In FIG. 5, liquid crystal molecules 28 arranged on the surface of a transparent electrode film or an insulating film are schematically shown in a cylindrical shape, and the liquid crystal molecules are arranged parallel to the direction of the unevenness of the grating due to the slits having a rectangular cross section. Furthermore, in FIG. 6, liquid crystal molecules 28 are arranged parallel to the direction of the unevenness of the grating having a smooth inclined surface due to the slits having a sawtooth cross section. Such a parallel arrangement is effective in imparting directivity to the display in a twisted nematic liquid crystal display device and preventing partial unevenness in display density due to non-periodic arrangement of liquid crystal molecules. The pitch of the grating is preferably small in order to increase the degree of alignment of the liquid crystal, but if the surface of the transparent electrode film or insulating film is 0.3 μm pitch depth 10
Approximately 0 people showed good orientation. H as a laser light source
Although the e-Cd laser wavelength λ=4416 was used, the pitch can be made smaller by using an ultraviolet laser with a shorter wavelength or by changing the incident angle conditions of the binary beam.

In addition, in ion beam irradiation, if the traveling direction of the ion beam is perpendicular to the substrate, or if the processing amount of the transparent electrode film or insulating film is small due to ion beam irradiation in an oblique direction to the substrate, photo There are no second irregularities caused by unevenness on the resist surface, and the resulting flat or inclined surface is smooth, but when the amount of processing of the transparent electrode film or insulating film is large due to ion beam irradiation in an oblique direction to the substrate. A second uneven groove 2e is formed on the slope of the first uneven surface due to the unevenness of the photoresist surface and has periodicity on the slope. In FIG. 7, liquid crystal molecules 28 arranged on the surface of a transparent electrode film or an insulating film are schematically shown in a cylindrical shape, and the liquid crystal molecules 28 are arranged in second unevenness 29. Such a parallel arrangement is effective in imparting directivity to the display in a twisted nematic liquid crystal display device and preventing partial unevenness in display shading due to reverse tilt or the like.

Here, FIG. 8 shows the relationship between the contrast ratio of a liquid crystal display device and the pitch of unevenness on the surface of a transparent electrode film or an insulating film.

When the pinch of unevenness on the surface of the transparent electrode film or insulating 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. was recognized.

3o is a contrast curve of a liquid crystal display device subjected to alignment treatment according to the present invention, and 31 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, 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 vacuum device is not required.

(5) A large amount of processing can be performed relatively stably.

(6) Since the liquid crystal display device of the present invention does not require an alignment film that is required in conventional liquid crystal display devices, there is no voltage loss due to the alignment film, and there is no loss in transparency due to the alignment film.

[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. Figure 4 is an explanatory diagram showing the light intensity distribution on the surface and grating-like unevenness of the alignment film. Figure 5 is a transparent electrode film or insulator with a rectangular cross section of grating-like unevenness. A schematic diagram of the film surface. FIG. 6 is a schematic diagram of the surface of a transparent electrode film or insulating film in which the cross section of the grating-like unevenness is formed into a sawtooth shape. FIG. FIG. 8 is a schematic diagram of the surface of a transparent electrode film or an insulating film having a second unevenness formed on an inclined surface, and FIG. . DESCRIPTION OF SYMBOLS 1... Transparent electrode film, 2... Front glass plate, 3... TFT element section, 4... Pixel section, 6...... Insulating film, 6...Liquid crystal display substrate, 7...Sealing agent, 8...Liquid crystal,
9... Spacer, 10... Polarizing plate (top surface of front glass), 11... Polarizing plate (top surface of liquid crystal display substrate), 12... Electroluminescence Cent, 13...Insulating film, 14...Laser light source, 15...Reflecting mirror, 16...Reflecting mirror, 17... Collection Optical lens, 18...Pinhole, 19...Collimator lens, 2o...
...Reflector, 21...Beam splitter, 22...Reflector, 23...Reflector, 24.
... Electrode substrate, 25 ... Alignment film, 26.
...Grating-like unevenness, 27...
transparent electrode film or insulating film, 28... liquid crystal molecules,
29...Second unevenness formed due to unevenness of resist surface, 30...Contrast curve of liquid crystal display device subjected to alignment treatment according to the present invention, 31...
- Contrast curve of a liquid crystal display device subjected to alignment treatment by rubbing. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 3
Figure A Figure 4 ↓ % Figure 5 2θ

Claims (1)

[Claims] (1) a pair of electrode substrates, a transparent electrode film or an insulating film,
A liquid crystal display device comprising: a liquid crystal, the transparent electrode film or the insulating film having grating-like irregularities on the surface thereof. ? ) When manufacturing a liquid crystal display device in which a liquid crystal is filled between a pair of electrode substrates, the steps include: applying a 7-photoresist to the electrode substrate, and irradiating the surface of the photoresist with three-beam interference fringes of laser light. , a step of forming grating-like unevenness on the photoresist by developing the photoresist, a step of processing the electrode substrate surface in the recessed portion of the shifted resist into a grating-like shape by etching; A method for manufacturing a liquid crystal display device, characterized by a step of removing photoresist.