JPH1114955A - Manufacture of liquid crystal display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display panel manufacturing method capable of arraigning spacers in areas other than display pixels efficiently and selectively and manufacturing the panel at low cost while suppressing increases in workload and scatter quantity. SOLUTION: In this method, two substrates 1 and 11 having transparent electrodes 2 and 21 and orientation films 3 and 31 thereupon are arranged facing each other and liquid crystal is injected into the gap formed with spacers interposed between them, in the process for interposing the spacers, resin films 4 are formed on the orientation film at parts which do not become display pixels, the exposed orientation film is electrostatically charged; after the spacers are scattered over the orientation films 3 and 31 and unset resin film surface, the resin film 4 is set by a heat-treatment or light irradiation to fix the spacers arranged on the resin film surface and unset spacers are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display panel used in a display section of a notebook computer, a liquid crystal television, a liquid crystal projector and the like.

[0002]

2. Description of the Related Art In a liquid crystal display panel, a liquid crystal material is injected into a gap between two substrates and driven to perform display. In order to keep the gap between the substrates constant, spherical spacer particles are usually interposed between the substrates. In the most common method of manufacturing a liquid crystal display panel, spacer particles are uniformly dispersed on the surface of an alignment film of one substrate, and an alignment film of the other substrate is bonded to the substrate.

However, in the above method, since the spacer particles are scattered over the entire surface of the alignment film, many spacer particles remain in the display pixel region of the liquid crystal display panel. In a direct-view type liquid crystal display panel, individual spacers are hardly visually recognized, but light leaking from the spacers causes "white spots" on the display.
Causing a reduction in overall contrast. On the other hand, in a projection type liquid crystal display panel such as a liquid crystal projector, spacer particles in display pixels are enlarged and projected on a screen, and appear as "black spots" on a display surface, so that the effect on image quality is more serious.

[0004] In order to avoid the above problem, it is effective to eliminate the spacer in the display portion.
Several methods have been proposed for that purpose. For example, Japanese Patent Application Laid-Open No. 3-293328 describes a method in which, when dispersing spacer particles, a transparent electrode is charged, and the spacer particles are charged to the same sign as this, so that the spacer particles are not arranged in the display area. Have been.

[0005] Also, JP-A-2-157728 discloses that
A method of applying a photosensitive resin on a base material, forming a pattern by exposure and development, spraying spacers, fixing the resin pattern, and removing unfixed spacers by washing to leave spacers only in predetermined areas. Are listed.

In the method described in Japanese Patent Application Laid-Open No. 3-293328, since only the charging of the transparent electrode is used, it is difficult to accurately control the area where the spacers are arranged. Cannot be fixed. Further, according to the method described in JP-A-2-157728, the spacers can be fixed outside the display area. However, the spacers are once uniformly arranged on the entire surface of the substrate at the time of spraying, and then the unfixed spacers are removed. For,
There is a problem that the application amount of the spacer must be increased more than usual.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and allows the spacers to be selectively and efficiently arranged in areas other than the display pixels. It is an object of the present invention to provide a method for manufacturing a liquid crystal display panel which can be manufactured in a wide range.

[0008]

According to a method of manufacturing a liquid crystal display panel of the present invention, a transparent electrode and two substrates having an alignment film formed thereon are arranged so that the alignment films are opposed to each other, and the diameter between the substrates is reduced. A method of manufacturing a liquid crystal display panel in which a spacer made of substantially uniform fine particles is interposed and a liquid crystal is injected into a gap formed by the spacer, wherein the step of arranging the spacer includes a portion that does not become a display pixel on an alignment film. Forming a resin film on the surface, a step of charging the exposed alignment film,
A step of spraying the spacer on the alignment film and the uncured resin film surface, a step of fixing the spacer arranged on the resin film surface by curing the resin film by heat treatment or light irradiation,
Removing the unfixed spacer.

As a method of forming a resin film on a portion of the alignment film that is not a display pixel, for example, a method using photolithography, a method using screen printing, or the like may be adopted.

As a method for performing a charging treatment on the exposed alignment film, corona discharge or plasma treatment can be used.
It is most simple to perform a rubbing treatment in which the surface of the alignment film is rubbed with a cloth or the like in order to impart liquid crystal alignment to the alignment film. According to this method, the alignment treatment of the alignment film and the charging treatment can be performed in one process.

The resin film according to the present invention is for disposing a spacer only outside a display pixel, and a resin film having the following properties may be selected. First, when the charging treatment of the alignment film is performed, the charge amount of the resin film is smaller than the charge amount of the alignment film, or the charge amount is reversed. In the case where the charging treatment of the alignment film is performed by the above rubbing treatment, it may be selected as a resin film whose charging order is close to that of the material of the rubbing cloth. Alternatively, the charge amount of the resin film can be reduced by setting the electric resistivity of the resin film to be higher than the electric resistivity of the alignment film. Electrical resistivity of the resin film in this case may be determined within a range that does not affect the display characteristics of the liquid crystal display panel but is generally 10 ⁹ to 10 ¹²
A material having a resistivity in the range of Ω · cm is preferably used.

Second, there is a choice of a spacer which can be fixed to the resin film by heat treatment or light irradiation. Examples of such a resin film include polymers having a highly polar structure such as polyvinyl alcohol, polyvinyl butyral, and polyethylene oxide, or urethane (meth) acrylate having at least one acryloyl group or methacryloyl group in the molecule; A photo- or thermo-polymerizable compound containing a photo- or thermo-polymerizable prepolymer such as polyester (meth) acrylate or epoxy (meth) acrylate and a polymerizable monomer such as monofunctional or bifunctional or trifunctional (meth) acrylate;
Alternatively, a photo- or heat-crosslinkable polymer containing a polyfunctional compound having an isocyanate group, a carboxyl group or the like as a crosslinking agent can be used.

Although the thickness of the resin film formed by the method of the present invention is not particularly limited, it is preferably thinner in view of the influence on the alignment state of the liquid crystal, usually 0.5 μm or less, more preferably 0 μm or less. 0.3 μm or less.

In order to increase the ratio of the spacer particles arranged in the predetermined region and to suppress the amount of the spacers to be sprayed by the method of the present invention, it is effective to charge the spacer particles to the same polarity as the alignment film at the time of spraying. It is. As means for achieving this, frictional charging between the spacer particles and the container containing the spacer particles may be used, or a forced charging process such as corona discharge may be added.

(Operation) According to the method of the present invention, since the alignment film is subjected to the charging treatment, when the spacer particles are sprayed, the spacer particles receive an electric repulsive force from the alignment film and are selected on the resin film having less charge. Are arranged in a way. Further, since the resin film is cured by heat treatment or light irradiation and the spacer particles are fixed on the resin film, the spacer particles do not move in a subsequent step, and only the unfixed spacer is removed in the subsequent step.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIGS. 1 to 3 are sectional views showing an embodiment of a method of manufacturing a liquid crystal display panel according to the present invention. As shown in FIG. 1, a stripe-shaped ITO transparent electrode 2 (electrode width: 90 μm, electrode interval: 15 μm) is formed on a glass substrate 1 (size: 10 cm × 10 cm), and a polyimide-based alignment film (manufactured by Nissan Chemical Industries, product number “ SE-150 ") solution over the entire surface,
After drying, an alignment film 3 having a thickness of about 0.1 μm was formed by a heat treatment at 230 ° C. for 30 minutes.

An ultraviolet-curable polyvinyl alcohol (manufactured by Toyo Gosei Kogyo Co., Ltd., product number "SPP-H") is provided on the alignment film 3.
The aqueous solution was applied over the entire surface by a spin coater, dried, and then exposed through a photomask to polymerize and cure only the polyvinyl alcohol aqueous solution between the transparent electrodes 2 and 2. Next, development with pure water is performed to remove the uncured aqueous solution of polyvinyl alcohol. Finally, a portion having a width of about 12 μm and a thickness of 0.5 μm is formed between the electrodes outside the display pixel as shown in FIG.
Was formed.

Next, after rubbing the substrate surface in one direction with a rubbing device using rayon cloth, the substrate is set in a spacer sprayer, and spacer particles 5 are scattered over the entire surface as shown in FIG. went. At the time of spraying, a corona discharge treatment was performed on the spacer particles 5 so that the spacer particles 5 were almost uniformly charged to a negative polarity.

FIG. 4 is a plan view showing the substrate on which the spacer particles 5 are dispersed. As a result of the observation, 95% of the scattered spacer particles 5 were disposed on the uncured polyvinyl alcohol films 4 formed between the transparent electrodes 2.

Thereafter, a heat treatment was performed at 200 ° C. for 1 hour to completely cure the polyvinyl alcohol films 4 and 4 to fix the spacer particles, and finally washed with pure water to remove unfixed spacers. The spacer particles remaining in the display portion were finally 1% or less of the total number.

As shown in FIG. 3, the glass substrate 1 on which the spacer particles 5 are arranged outside the display area is bonded to the surface of the polyvinyl alcohol film 31 of another glass substrate 11 on which the spacers are not scattered. After a liquid crystal material was injected into the gap 6 formed by the spacer particles 5, the injection port was sealed to produce a liquid crystal display panel. This liquid crystal display panel had high image contrast and displayed a good image.

The following experiment was conducted to investigate the cause of the spacer being selectively disposed on the polyvinyl alcohol film. A glass substrate on which only an alignment film is formed, and a substrate on which a polyvinyl alcohol film is further formed on the entire surface of the alignment film are prepared. It was measured with an electrostatic voltmeter. As a result, the surface voltage is -2.4 k for a substrate having only an alignment film.
V, -0.6 kV for a substrate having a polyvinyl alcohol film formed on an alignment film. From this, it is considered that the spacer particles were selectively disposed on the polyvinyl alcohol film due to a difference in charging voltage between the two types of films.

(Example 2) An aqueous solution of a polyethylene oxide resin into which an unsaturated bond was introduced was printed on a glass substrate having the same alignment film layer as that of Example 1 by a screen printing method to form a gap between transparent electrodes. A striped resin pattern was formed. The resin film after drying had a width of about 12 μm and a thickness of 0.4 μm. Rubbing treatment and spacer dispersion were performed on the substrate in the same manner as in Example 1. As a result, 96% of the sprayed spacers were placed on the uncured polyethylene oxide resin.

Thereafter, a heat treatment was performed at 180 ° C. for 1 hour to cure the polyethylene oxide resin and fix the spacer particles. Finally, unfixed spacers were removed by air blow. The spacer particles remaining in the display portion were finally 1% or less of the total number. Using this substrate, a liquid crystal display panel was manufactured in the same procedure as in Example 1. This liquid crystal display panel also has high image contrast,
Good images were displayed.

A glass substrate on which only an alignment film was formed and a substrate on which a polyethylene oxide film was further formed on the entire alignment film were prepared, and the charging voltage immediately after the rubbing treatment was measured in the same manner as in Example 1. As a result, the charging voltage of the substrate on which only the alignment film was formed was -2.4 kV, and the charging voltage of the polyethylene oxide film was almost 0. Furthermore, when the resistivity of the material was calculated from the measurement of the surface resistance value, it was 10 ¹⁵ Ω · cm or more for the polyimide film, and was about 10 ¹¹ Ω · cm for the polyethylene oxide film. From this, it is considered that the reason why the spacer particles were selectively disposed on the polyethylene oxide film is that the electrification of the polyethylene oxide film was suppressed due to the difference in resistivity between the two types of films.

Comparative Example 1 In the same manner as in Example 1, spacer particles were sprayed on an alignment film formed on a glass substrate by a conventional method. That is, the alignment film was subjected to a rubbing treatment, washed, and then placed in a sprayer to spray spacer particles. FIG. 5 is a plan view of the substrate in this state. 90% of the scattered spacer particles were arranged on the stripe electrode, that is, in the display area.

When a liquid crystal display panel was manufactured using this substrate, the completed liquid crystal display panel had low contrast and uneven display. As a result of detailed examination, it has been clarified that the cause is light leakage due to disturbance of liquid crystal alignment in the spacer particles existing in the display region and the periphery thereof.

[0028]

According to the method of manufacturing a liquid crystal display panel of the present invention, it is possible to arrange spacer particles only in a display area on a substrate, and as a result, high quality display characteristics are obtained without light leakage or the like. A liquid crystal display panel can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a transparent electrode and an alignment film are formed on a glass substrate according to an embodiment of the present invention.

FIG. 2 is a sectional view showing an embodiment of the present invention, showing a state where spacer particles are scattered.

FIG. 3 is a sectional view showing an embodiment of a liquid crystal display panel manufactured according to the present invention.

FIG. 4 is a plan view showing a state where spacer particles are scattered in the present invention.

FIG. 5 is a plan view showing a state in which spacer particles are dispersed by a conventional method.

[Explanation of symbols]

 1,11: glass substrate 2, 21: transparent electrode 3, 31: alignment film 4: polyvinyl alcohol film 5: spacer particle 6: gap

Claims (4)

[Claims] 1. A transparent electrode and two substrates having an alignment film formed thereon are disposed with the alignment films facing each other, and a spacer made of fine particles having a substantially uniform diameter is interposed between the transparent electrodes and formed by the spacer. A method of manufacturing a liquid crystal display panel in which liquid crystal is injected into a gap to be formed, wherein the step of interposing the spacer includes forming a resin film on a portion of the alignment film that does not become a display pixel, and charging the exposed alignment film. Applying the spacers to the alignment film and the uncured resin film surface, fixing the spacers arranged on the resin film surface by heat treatment or curing the resin film by light irradiation, and removing the unfixed spacers. Removing the liquid crystal display panel. 2. The method for manufacturing a liquid crystal display panel according to claim 1, wherein the charging treatment applied to the alignment film is performed by a rubbing treatment for imparting liquid crystal orientation. 3. The method for manufacturing a liquid crystal display panel according to claim 1, wherein the electrical resistivity of the resin film formed on the alignment film is lower than the electrical resistivity of the alignment film. . 4. The method of manufacturing a liquid crystal display panel according to claim 1, wherein the spacer particles are charged to have the same polarity as the alignment film when the spacers are scattered on the alignment film and the resin film surface. Method.