JPS6060624A - Liquid crystal display panel and its production - Google Patents

Abstract

PURPOSE:To obtain uniform and homogeneous orientation and to obtain a display panel having excellent display quality by using a photosensitive resin for the oriented film of the liquid crystal display panel, irradiating the two-beam interference fringes of laser light to the surface of the resin film and forming grating-shaped ruggedness. CONSTITUTION:Light from a laser light source 20 is made incident via reflection mirrors 21, 22 to a condensing lens 23 and after passage through a pinhole 24, the light is passed through a collimator lens 25 and is made into parallel rays which are reflected by a reflection mirror 26. The light bisected by a beam splitter 27 are made into two-beam intereference fringes by reflection mirros 28, 29 to irradiate. Said fringes are irradiated to the surface of a photosensitive PVA, photosensitive polyimide resin film 31 of a base plate 30 coated with said film 31, etc. on transparent electrodes. Both luminous fluxes are irradiated to the surface of the film 31 at an equal angle with the direction normal to said surface to irradiate a rugged surface 32 in such a way as to have the angle different from each other with the normal, by which a rugged surface 33 is formed. The grating paralleling with the orienting direction of a liquid crystal and the grating having the sawlike section giving a tilt angle theta intersecting approximately orthogonally therewith are thus formed by utilizing the difference in volume shrinkage of the film 31 between the region irradiated with the light and the non-irradiated region, by which the uniform orientation and the excellent display quality is obtd.

Description

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

Conventional configuration and its problems As is well known, a liquid crystal display panel is a panel in which liquid crystal is filled between a pair of substrates (hereinafter simply referred to as electrode substrates) each having an electrode formed on the opposite side. It is a combination of polarizing plates, and displays shading based on the difference in birefringence between the initially oriented liquid crystal molecules and the liquid crystal molecules that are rearranged when a voltage is applied to the electrodes. 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 to apply an organic material such as polyimide and rub nylon or vinyl fibers in a fixed direction on the cured film, which is called a rubbing method for orientation treatment. Another example of the alignment treatment is to deposit an inorganic material such as SiO from an oblique direction with respect to one electrode substrate, which is called an oblique vapor deposition method of alignment treatment.

The phenomenon in which liquid crystal molecules align 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.Alignment by zero rubbing The mechanism by which the film has alignment properties 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. is not.

For this reason, the optimum conditions for the rubbing process are the quality of the organic alignment film, the curing conditions, and the grain quality of the rubbing cloth.

The reality is that the fiber structure, the pressing force of rubbing, the number of relative speeds, etc. are tested and determined 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 debris, and the durability of the rubbing cloth is not sufficient, resulting in the number of times it is used. There are drawbacks such as the alignment performance changing each time the layers are stacked and non-uniform alignment. Furthermore, in liquid crystal display panels for displaying images, in which film transistors for switching corresponding to each of a large number of pixel elements are constructed on an electrode substrate, the surface of the substrate is uneven, and alignment due to rubbing is difficult. Non-uniform orientation may occur near the step of this unevenness. Furthermore, charging due to rubbing may cause electrostatic damage to such active elements.

Alignment processing by oblique vapor deposition has relatively fewer defects such as these compared to alignment processing by rubbing, but it is difficult to process large electrode substrates due to the size of the vapor deposition equipment and restrictions on the substrate tilting equipment, and the number of man-hours is extremely large. The optimal condition range (
In particular, the deposition angle, deposition rate, substrate temperature, etc.) are relatively narrow, and the deposition conditions must be controlled. Another object of the present invention is to provide a liquid crystal display panel having an alignment film subjected to an alignment treatment using an improved and novel method, and a method for manufacturing the same.

Structure of the Invention The liquid crystal display panel of the present invention is a liquid crystal display panel in which liquid crystal is filled between a pair of electrode substrates via an alignment film, in which a photosensitive resin is used for the alignment film, and the surface of the alignment film is coated with a photosensitive resin. It is characterized by having a structure having grating-like irregularities onto which the two-beam interference fringes of the laser source are irradiated.

Furthermore, if necessary, this grating-like unevenness can be configured with two types of gratings: a grating parallel to the alignment direction of the liquid crystal, and a grating having a serrated cross section that is substantially perpendicular to this and giving a tilt angle of the liquid crystal. .

Providing a tilt angle to the liquid crystal using such a configuration of two types of gratings is effective for imparting directivity to the display in, for example, a twisted nematic liquid crystal display panel.

As the alignment film, photosensitive polyvinyl alcohol or photosensitive polyimide is good in terms of alignment performance.

In order to manufacture such a liquid crystal display panel having grating-like irregularities on the surface of the alignment film, an alignment film made of photosensitive resin is coated, and the surface of this alignment film is exposed to two rays of laser light.
If the intensity of the 0 laser beam that irradiates the original bundle interference pattern is appropriate,
There is a difference in crosslinking rate between the laser beam irradiated area and the non-irradiated area of this photosensitive resin, and this causes a difference in volume shrinkage, resulting in minute grating-like irregularities on the surface. Although liquid crystal alignment is possible even in this state, in order to improve the alignment performance, heat curing or irradiation with the above-mentioned binary flux interference fringes of the laser beam should be performed in the same way as the exposure of photorenost in normal photon 1-briquefon. After irradiation with laser light, this photosensitive resin may be chemically etched, plasma ashed, or spack etched to form grating-like irregularities.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows an example (configuration diagram) of a liquid crystal display panel according to the present invention.
A liquid crystal 5 is filled between the lower electrode substrate 2 having a transparent electrode 3 and the other electrode substrate 4 having a fully transparent electrode 3, the periphery of which is sealed with a seal 6. This liquid crystal self has polarizing plates 8, 9
In addition to the surface light emitting body 10, the whole constitutes a transmissive liquid crystal display panel 11 for displaying images.

In order to initially bring the liquid crystal 5 to the front, a photosensitive resin is applied to the electrode surface side of the lower electrode substrate 2 and the electrode surface side of the other electrode substrate 4, and then the binary flux interference fringes of the laser beam are applied to this surface. Figures 2 and 3 show the principle of the irradiation device for two-beam interference fringes of laser light, and the light beam exiting the laser light source 2° is reflected by the reflecting mirror .22, enters the condensing lens 23, passes through the pinhole 24, passes through the collimating lens 25, and becomes an expanded parallel light beam. Thereafter, this parallel light beam is further reflected by a reflecting mirror 26, split into two by a beam splitter 27, reflected by reflecting mirrors 28 and 29, and incident on the photosensitive resin 31 coated on the one-electrode substrate 30. The two beams of the laser beam divided into two interfere with each other in the space near the sample, producing spot-like interference fringes on the sample surface.

Figure 2 shows the case where the optical axis of the il''j:2 beam is incident at equal angles to the normal direction of the sample surface, and the light intensity distribution on the sample surface and the light formed on the sample surface at this time are shown. The grating-like unevenness 32 is shown in Figures 4a and 4b, respectively. Figure 3 shows the case where the optical axis of the t/'i2i bundle is incident at an inclined angle with respect to the sample surface. The light intensity distribution on the sample surface and the grating-like unevenness 33 formed on the sample surface are shown in FIGS. In some cases, the unevenness formed on the sample surface becomes a grating with a serrated cross section.

FIG. 6 shows the surface of a sample on which grating-like irregularities were formed in directions substantially orthogonal to each other using the two methods described above. 6th
In the figure, the liquid crystal molecules 34 arranged on the sample surface are schematically shown in a cylindrical shape, and the liquid crystal molecules 34 are arranged in one direction with a tilt angle θ. Such a tilt angle is effective in imparting directivity to the display in a twisted nematic liquid crystal display panel and preventing partial unevenness in display shading due to reverse tilt. It is desirable that the pitch of the grating be smaller in order to increase the degree of alignment of the liquid crystal, but experimentally produced gratings with a pitch depth of 500 and 0.2 μm showed good alignment. As a laser light source, He
Although a -Cd laser light source (wavelength: 224,416) 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 two beams.

As alignment films made of photosensitive resins, highly photosensitive polyimide and photosensitive polyvinyl alcohol, which are widely used as rubbing alignment films for liquid crystal display panels, exhibit good alignment.

Formation of a grating can be achieved simply by irradiating the binary interference fringes of the laser beam described above (a difference in crosslinking rate occurs between the laser beam irradiated area and the non-irradiated area of the photosensitive resin, resulting in volumetric shrinkage). to increase the degree of alignment of the liquid crystal (after irradiation with laser light).

It is effective to increase the grating depth by performing the following process.

(1) Laser) After irradiating the photosensitive resin with the binary bundle interference fringes, the photosensitive resin is etched with a developer.

(2) The photosensitive resin is heated and cured, and the unevenness is expanded using the difference in thermal contraction between the laser beam irradiated area and the non-irradiated area.

(3) Lightly incinerate the surface of the photosensitive resin with a plasma asher to enlarge the irregularities.

(4) Spack etching the surface of the photosensitive resin to enlarge the irregularities.

As described in detail, according to the present invention, since the alignment process is performed using photofabrication technology, various defects and abnormal scratches on the surface, which were problems when the surface was conventionally rubbed mechanically, are generated. It is possible to obtain a homogeneous alignment quality with less macroscopic unevenness and microscopic unevenness in alignment, and to provide a liquid crystal display panel with excellent display quality.0 Furthermore, compared to the conventional alignment treatment using oblique vapor deposition, it is possible to obtain a homogeneous alignment quality with less macroscopic unevenness and microscopic unevenness. It is possible to process large quantities relatively stably without requiring any process using equipment.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a liquid crystal display panel according to the present invention, and FIGS.
4a, 5a, 4s and 5s are explanatory diagrams showing the light intensity distribution on the sample surface and grating-like unevenness on the sample surface, respectively; FIG. 6 is a schematic diagram of a sample surface on which grating-like irregularities are formed in substantially orthogonal directions. 2.4. ．． 30... Electrode substrate, 5...
Liquid crystal, 20... Laser light source, 31...
Alignment film (photosensitive resin), 32.33...Grating-like unevenness 0 Name of agent Patent attorney Toshio Nakao and 1 other person No. 1 Figure 2 Figure 0 3 Figure 0

Claims (1)

[Scope of Claims] (1) Liquid crystal is filled between a pair of substrates via an alignment film, and the alignment film is a photosensitive resin, and the surface of the alignment film has two-beam interference of laser light. A liquid crystal display panel characterized by having grating-like unevenness formed by striped irradiation. (2) The grating-like unevenness consists of a grating parallel to the orientation direction of the liquid crystal, and a grating having a serrated cross section that is substantially perpendicular to the grating and provides a tilt angle of the liquid crystal. The liquid crystal display panel according to item 1. (3) The liquid crystal display panel according to claim 1, wherein the alignment film is made of photosensitive polyvinyl alcohol or photosensitive polyimide. (4) Forming grating-like irregularities on the surface of the alignment film by coating the substrate with an alignment film made of photosensitive resin and irradiating the surface of the alignment film with two-beam interference fringes of laser light. A method for manufacturing a liquid crystal display panel, comprising the steps of: (6) The process of forming grating-like irregularities on the surface of the alignment film is a laser beam irradiation process that utilizes the difference in volume shrinkage depending on the crosslinking rate between the laser source irradiation area and the non-irradiation area of the alignment film. A method for manufacturing a liquid crystal display channel according to claim 4, characterized in that (6) the step of forming grating-like irregularities on the surface of the alignment film is located in a region that is not irradiated with the laser source of the alignment film; 5. The method of manufacturing a liquid crystal display panel according to claim 4, wherein the etching process takes advantage of the difference in solubility in a solvent in the irradiated area. (7) A patent characterized in that the process of forming grating-like irregularities on the surface of the alignment film is a heat curing process that utilizes the difference in heat shrinkage between the laser source irradiation area and the non-irradiation area of the alignment film. Method for manufacturing a liquid crystal display panel according to claim 4 0(8) The step of forming grating-like irregularities on the surface of the alignment film is based on the difference in oxidation property between the laser beam irradiated area and the non-irradiated area of the alignment film. 5. The method for manufacturing a liquid crystal display panel according to claim 4, wherein the method is a plasma ashing step using. (9) The process of forming grating-like irregularities on the surface of the alignment film is a sputter etching process that utilizes the difference in ioless back ratio between the laser beam irradiated area and the non-irradiated area of the alignment film. A method for manufacturing a liquid crystal display panel according to claim 4.