JPS6258225A - Production of liquid crystal display element - Google Patents

Abstract

PURPOSE:To maintain a good display grade for a long period of time without generating 'bleeding' even under conditions of a high temp. and high humidity by diffusing and eluting sodium ions in a glass substrate onto the front layer by a high-temp. heating treatment then washing away the sodium ions by ultrasonic cleaning. CONSTITUTION:This process for production is basically the same as the conventional process for production in that an insulating film forming stage 1, transparent conductive film forming stage 2, etching stage 3, silver paste printing stage 4, baking stage 5 and if necessary transparent conductive coating material printing stage 6 and backing stage 7 are executed. In this process for production, however, an ultrasonic cleaning stage 8 is executed after the baking stage 5 in the case of not executing the stages 6, 7 and the ultrasonic cleaning stage 9 is executed after the baking stage 7 in the case of executing the stages 6, 7.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a method for manufacturing a liquid crystal display element that improves reliability and life under high temperature conditions.

"Prior Art and its Problems" As is well known, a liquid crystal display element has a structure in which a pair of glass substrates with electrode films formed on their inner surfaces are bonded together with a predetermined gap, and liquid crystal is sealed inside. . By applying a voltage between the electrode films having a predetermined pattern, the orientation of the liquid crystal in that portion is changed, and the transmission of transmitted light or reflected light is controlled to perform a predetermined display.

Conventionally, a glass substrate, which is a component of a liquid crystal display element, has been subjected to a treatment as shown in FIG. 2, for example. That is, an insulating film forming step 1 in which an insulating film such as 5iQ2 is formed on the inner surface of a glass substrate, and a transparent conductive film forming step 2 in which a transparent conductive film made of, for example, indium oxide and tin oxide is formed on this insulating film. , an etching process 3 in which this transparent conductive film is etched into a predetermined pattern, a process in which silver paste is printed in order to solder the flexible cable to the terminal part, and a process 5 in which this silver paste is fired. are giving. Furthermore, in order to prevent static electricity when attaching a polarizing plate, a step 8 of printing a transparent conductive coating agent on the outer surface of the glass substrate and a step 7 of firing the transparent conductive coating agent may be performed.

By the way, the liquid crystal display element manufactured in this way is subjected to high temperature and high humidity tests (for example, conditions of 80°C and 85% humidity).
After doing this, the display pattern sometimes appeared bulged. This phenomenon commonly displays pattern "bleeding"
It is called. The reason for this is that the sodium component in the glass substrate becomes sodium ions (Ha) and diffuses onto the substrate surface, which causes parts other than the transparent conductive film to become conductive, causing parts other than the display pattern to be displayed. It is said that this is to make it easier.

In the conventional method for manufacturing a liquid crystal display element, as described above, the step 4 of firing the silver paste and the step 7 of firing the transparent conductive coating agent are performed. These firing steps are performed at a temperature of about 300 to 500°C, which significantly promotes the diffusion of sodium ions from the glass substrate. Therefore, in order to prevent the diffusion of sodium ions to the surface layer, 5i
The process of forming an insulating film such as Q2! However, due to the above baking process, sodium ions diffuse into the insulating coating, and the occurrence of the "bleeding" phenomenon could not be sufficiently prevented.

In the conventional manufacturing method of liquid crystal display elements, cleaning with an organic solvent was sometimes performed for another purpose after the firing process, but even cleaning with an organic solvent does not remove the sodium ions that have eluted and diffused into the surface layer during firing. It was difficult to do so.

"Object of the Invention" In view of the above-mentioned problems of the prior art, the object of the present invention is to
An object of the present invention is to provide a method for manufacturing a liquid crystal display element that can maintain good display quality for a long period of time even under high humidity conditions.

"Structure of the Invention" The present invention provides a method for manufacturing a liquid crystal display element in which an insulating film is formed on a glass substrate and a transparent conductive film is formed on the insulating film, in which a high temperature heat treatment is performed at least after forming the insulating film. , which is characterized by performing ultrasonic cleaning in the subsequent process.

In this way, in the present invention, the sodium ions that have been eluted and diffused into the surface layer due to the high-temperature heat treatment are removed by ultrasonic cleaning, so that the liquid crystal display element assembled using this substrate can withstand high-temperature and high-humidity conditions. Even at the bottom, the diffusion and elution of sodium ions to the surface layer is reduced, causing "bleeding".
This prevents the phenomenon from occurring and maintains good display quality over a long period of time.

In the present invention, the high-temperature heat treatment may be carried out at least after forming the insulating film (1) For example, it may be carried out in the baking process of the silver paste printed on the terminals, or it may be carried out on the glass to prevent static electricity when pasting the polarizing plate. It may also be performed in the baking process of the transparent conductive coating agent printed on the opposite side of the substrate.
In addition, when forming a transparent conductive film by means such as screen printing, it may be performed in the baking process of the printed or applied transparent conductive film forming liquid. A high-temperature heat treatment may be performed immediately after forming the film.

Further, ultrasonic cleaning may be performed in any step after the high temperature heat treatment, and does not necessarily need to be performed immediately after the high temperature heat treatment. In addition, when performing the firing process multiple times, it is preferable to perform ultrasonic cleaning after the last firing process. Ultrasonic cleaning can be performed in various liquids such as water and organic solvents. However, it is most preferable to perform ultrasonic cleaning in warm water. When performing ultrasonic cleaning in pure water at room temperature, the cleaning time is preferably 30 minutes or more; If the washing time is shorter than the above value, which is preferably longer than 1 minute, it will be difficult to sufficiently wash away the sodium ions that have eluted and diffused into the surface layer.

Embodiments of the Invention FIG. 1 shows a preferred embodiment of the method for manufacturing a liquid crystal display element according to the present invention. This manufacturing method includes an insulating film forming step 1. Transparent conductive film formation process 2) Etching process 3
, a silver paste printing step 4, a firing step 5, and, if necessary, a transparent conductive coating agent printing step 8. The method is basically the same as the conventional manufacturing method shown in FIG. 2 in that the firing step 7 is performed.

However, in this manufacturing method, when the above step 6.7 is not performed, the ultrasonic cleaning step 8 is performed after the firing step 5, and when the above step 8.7 is performed, the firing step 7 is performed.
After that, an ultrasonic cleaning step 9 is performed. Each step will be explained in more detail below.

In the insulating film forming step 1, an insulating material such as 5iQ2 is deposited on the glass substrate using a vacuum evaporation method, a sputtering method, a dipping method,
This is done by coating by means such as a spinner method, a spray method, and a screen printing method.

In the transparent conductive film forming step 2, for example, a transparent conductive film forming material such as tin oxide or indium oxide is coated by a vacuum evaporation method, a sputtering method, etc., or a transparent conductive film forming liquid containing an organic tin compound, an organic indium compound, etc. It can be formed by applying by screen printing or other means and firing.

The etching step 3 can be carried out by conventional means such as photo etching. At this time, the sodium ions diffused and eluted into the surface layer of the insulating film etc. are washed away by the etching solution or the cleaning solution after etching. Note that if the transparent conductive film forming liquid is screen printed and fired, this etching step 3 is not necessary.

The silver paste printing step 4 is performed by screen printing a silver paste (for example, a mixture of silver powder, glass frit, and a binder) on the terminal portion of the transparent conductive film.

Firing step 5 is performed by heating the glass substrate to about 300 to 500°C to sinter the silver paste.

At this time, a large amount of sodium ions elute and diffuse from the glass substrate to the surface layer.

In the transparent conductive coating agent printing step 8, a transparent conductive coating agent containing, for example, an organic tin compound, an organic indium compound, etc.
This is done by coating the outer surface of a glass substrate by means such as screen printing.

Firing step 7 is performed by heating the glass substrate to 300 to 500°C and firing the transparent conductive coating agent.

If the above step 8.7 is not performed, the ultrasonic cleaning step 8 is performed after the firing step 5, and when the above steps θ and 7 are performed, the ultrasonic cleaning step 8 is performed after the firing step 7. .

Example 5102 is coated on a soda glass substrate by a dipping method (insulating film forming step 1) Next, a transparent conductive film having a composition of tin oxide and indium oxide is formed on the above insulating film by sputtering (transparent conductive film formation step 1). Film formation step 2), then pattern formation processing is performed by photoetching (etching step 3), and silver paste is screen printed on the terminal portion.In silver paste printing step 0, the glass substrate is placed in a furnace at approximately 500°C. A liquid crystal display element was assembled after heat treatment (baking step 5), ultrasonic cleaning for EO minutes in pure water (ultrasonic cleaning step 8), and drying.

The thus obtained liquid crystal display element was compared with a liquid crystal display element prepared in the same manner as above except that ultraviolet cleaning was not performed.
A high-temperature, high-humidity test was conducted at a temperature of 80°C and a humidity of 85%, and the time required for the display to smear or bulge was observed. The results showed that the liquid crystal display element of the above example showed " The time it took for the "bleeding" phenomenon to occur was approximately twice as long.

In addition, in the above example, the ultrasonic cleaning step 8 was carried out at 70°C.
When washing was carried out in warm water, similar effects were obtained even with a washing time of about 3 minutes.

"Effects of the Invention" As explained above, according to the present invention, after the sodium ions in the glass substrate are diffused and eluted to the surface layer by high-temperature heat treatment, the sodium ions are washed away by ultrasonic cleaning. A liquid crystal display element assembled using this glass substrate can maintain good display quality for a long time without causing the "bleeding" phenomenon even under high temperature and high humidity conditions.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a preferred embodiment of a method for manufacturing a liquid crystal display element according to the present invention, and FIG. 2 is a process diagram showing an example of a method for manufacturing a liquid crystal display element by a conventional method. In the figure, 1 is an insulating film forming process, 2 is a transparent conductive film forming process, 3 is an etching process, 4 is a silver paste printing process, 5 is a baking process, 8 is a transparent conductive coating agent printing process, 7 is a baking process, 8. 8 is an ultrasonic cleaning step.

Claims (2)

[Claims] (1) In a method for manufacturing a liquid crystal display element in which an insulating film is formed on a glass substrate and a transparent conductive film is formed on the insulating film, at least after the insulating film is formed, a high temperature heat treatment is performed, and in a subsequent step A method for manufacturing a liquid crystal display element, characterized by performing sonic cleaning. (2) The method for manufacturing a liquid crystal display element according to claim 1, wherein the ultrasonic cleaning is performed in warm water.