JPS6153704B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a liquid crystal cell.

Recently, liquid crystal display devices with low power consumption,
Twisted nematic type (TN type) liquid crystal display devices, which can operate with low power, are used as display devices for small electronic calculators, electronic clocks, etc.

That is, in a TN liquid crystal display device, between two electrode substrates on which electrodes of a predetermined pattern are formed,
A liquid crystal made by enclosing a nematic liquid crystal with a positive dielectric anisotropy so that the long axis direction of the liquid crystal molecules is parallel to the substrate surface and the liquid crystal molecules are arranged in a spiral structure with a continuous 90° twist between the substrates. By applying voltage to the electrodes of the liquid crystal cell while the cell is sandwiched between a pair of polarizing plates whose polarization directions are perpendicular to each other, the orientation direction of liquid crystal molecules between the electrodes is changed, creating a light-opaque area in the liquid crystal layer. The characters, symbols, and symbols corresponding to the pattern shape of the voltage applying electrode are created by
It is configured to display numbers, etc.

By the way, as a general method for manufacturing the liquid crystal cell, conventionally, a transparent electrode of a predetermined pattern is formed using tin oxide or indium oxide on a transparent substrate such as glass, and silicon dioxide ( SiO ₂ ) is deposited by vapor deposition or CVD to form an insulating film. This insulating film prevents a chemical reaction between the liquid crystal and the electrode surface, and also acts as a resistance when a DC voltage is applied to reduce the voltage applied to the liquid crystal, thereby preventing damage to the liquid crystal material. Furthermore, silicon oxide (SiO) is vapor-deposited on top of this insulating film to form an alignment treatment film, and the surface is rubbed with cloth such as cotton to perform alignment treatment to align the liquid crystal molecules. There is a manufacturing method in which two electrode substrates are bonded and fixed via a spacer so as to face each other with a predetermined gap therebetween, and liquid crystal is sealed in this gap.

However, in the manufacturing method of such a liquid crystal cell, in manufacturing the electrode substrate, an insulating film is formed on the electrode forming surface of the substrate by vapor deposition or CVD, and an alignment treatment film is further formed on the insulating film by vapor deposition. As a result, the number of manufacturing steps is large and the steps are complicated, resulting in poor workability and mass productivity, and high costs.

In addition, regarding the manufacturing method of such a liquid crystal cell,
Recently, a thin film of an organic polymer material such as polyester, silicone resin, phenol resin, fluororesin, or polyimide resin has been deposited on the electrode forming surface of the substrate as an insulating film and an alignment treatment film, and this film is directly rubbed. It is considered that the manufacturing process can be simplified by applying an orientation treatment to the resin.
Either the orientation of the liquid crystal molecules, the transparency, the adhesion with the substrate, the characteristics when a DC voltage is applied (DC resistance), etc. are poor. In particular, polyimide resins have the disadvantage of being colored and having low transmittance.

This invention was made in view of the above-mentioned circumstances, and its purpose is to provide a material with slight coloring, high transparency, and good direct current resistance and adhesion between the insulating film and the substrate. An object of the present invention is to provide a method for manufacturing a liquid crystal cell that can obtain a highly reliable liquid crystal cell.

Hereinafter, one embodiment of the method for manufacturing a liquid crystal cell of the present invention will be described with reference to the drawings.

Figure 1 shows a liquid crystal cell manufactured by this manufacturing method, where 1 indicates a transparent insulating substrate such as glass;
2 is a transparent electrode of a predetermined pattern formed on this substrate 1; 3 is a base film made of amino-based silane that is deposited on the entire electrode-forming surface of the substrate 1; and 4 is a base film that is deposited on this base film surface. This is an insulating coating that also serves as an alignment treatment film made of polyimide, and the surface of this insulating coating is subjected to an alignment treatment to align the long axis direction of liquid crystal molecules. B is assembled via spacer 5,
A nematic liquid crystal is sealed inside.

That is, in this liquid crystal cell, an insulating coating 4 which also serves as an alignment treatment film and is made of polyimide is formed using amino-based silane as a base on the electrode forming surface of a substrate 1 on which electrodes 2 of a predetermined pattern are formed, and the surface of this insulating film 4 is The liquid crystal cell is formed by sealing a liquid crystal 6 between two electrode substrates A and B that have been subjected to alignment treatment by rubbing, and is manufactured through the following steps.

First, as shown in FIG. 2a, a predetermined pattern of electrodes is formed on a transparent substrate 1 made of glass or the like using tin oxide or indium oxide by a well-known method, and then the upper surface of the substrate 1 on which the electrodes 2 are formed. Apply a methanol solution containing 1% by weight of amino-based silane to the entire surface using a spinner, and then
The substrate is baked for a minute to form a base coat 3 as shown in FIG. 2b. After this, on the base film 3, Toray Industries, Inc., Toray Electronics Insulating Coating Agent SP-510 is applied.
(Product name) is diluted to a resin concentration of 2.5% using a spinner and baked at 320°C for 20 minutes in a vacuum or inert gas to form an insulating coating 4 as shown in Figure 2c. Form. The insulating film 4 was formed on the base film 3 made of amino-based silane because polyimide resin has high insulating properties and good heat resistance, but has the disadvantage of poor adhesion to the substrate 1 made of glass or the like. Also, since polyimide resin is generally colored,
This must be diluted to make it nearly transparent before use, but diluting the concentration deteriorates the insulation and direct current resistance. As mentioned above, the adhesion of the polyimide insulating film 4 can be improved by coating the polyimide resin on the base film 3 using amino-based silane, which has good adhesion to the substrate 1 and is compatible with polyimide, as a coupling agent. I can do it. In addition, by using amino-based silane as the base film 4, insulation and direct current resistance can be improved.
Coloring can be suppressed by reducing the concentration of polyimide resin. Further, the reason why the applied amino-based silane was fired in air in forming the base film 3 is that firing amino-based silane in a vacuum would cause poor orientation of the insulating film 4 formed thereon. Note that amino-based silane itself becomes colored when the concentration is high, but this coloring property can be ignored by reducing the concentration. Furthermore, the reason why the polyimide resin applied in the formation of the insulating coating 4 was fired in a vacuum or in an inert gas is that even if the resin concentration is quite thin when polyimide resin is fired in the air, it becomes colored due to the influence of oxygen in the air. This is because when polyimide resin is fired in vacuum or in an inert gas, no coloring occurs because there is no effect of oxygen. In other words, polyimide resin fired in air has a wavelength of 550 nm when the film thickness is 1100 Å.
When the film thickness is 1350 Å, the spectral transmittance decreases on the shorter wavelength side, but on the other hand, polyimide resin fired in vacuum or inert gas Wavelength for thickness 1000Å
Spectral transmittance is 4%~ for light of 500nm~400nm
When the wavelength is 7% higher and the film thickness is 1600Å,
Spectral transmittance up to 5% in the 500-600nm range
More expensive than that. Therefore, since there is little change in spectral transmittance due to wavelength, almost no coloring occurs, and the transmittance over the entire visible light range is higher than that of polyimide resin fired in air, resulting in high transparency of the liquid crystal cell. . Moreover, it has no effect on orientation at all.

It should be noted that the formation process of the base film 3 and the insulating film 4 is coating and baking using a spinner, and therefore can be performed extremely easily and efficiently.

After forming the base film 3 on the substrate 1 and further forming the insulating film 4 thereon,
The surface of this insulating coating 4 is directly rubbed with a cloth such as cotton to perform an orientation treatment as shown in FIG. They are bonded and fixed with a predetermined gap left, and the liquid crystal 6 is injected and sealed into the gap to complete the liquid crystal cell shown in FIG.

In other words, according to this method of manufacturing a liquid crystal cell, a liquid crystal cell can be manufactured with good workability using extremely few steps as described above, and the polyimide used as the insulating coating 4 that also serves as an alignment treatment film can be rubbed well in the alignment treatment. It can be carried out. Further, by applying a polyimide resin on the amino-based silane base film 3, the adhesion between the polyimide insulating film 4 and the substrate 1 can be improved. Furthermore, by forming the base film 3 of amino-based silane by firing in air, and forming the insulating film 4 of polyimide on it by firing in air or in an inert gas,
It is possible to suppress the coloring of polyimide and to perform good alignment treatment by rubbing.
It also has good insulation properties. Therefore, the liquid crystal display device manufactured by the above method has liquid crystal molecules that are uniformly and stably aligned for a long time, has high and uniform transparency, and can effectively avoid damage to the liquid crystal material due to the application of DC voltage. , high reliability can be obtained.

In this embodiment, polyimide was used as an insulating film that also serves as an alignment treatment film, but polyimide may be used only as an insulating film in a liquid crystal display device that does not require alignment of liquid crystal molecules. Furthermore, it goes without saying that the method for manufacturing this liquid crystal cell is not limited to the method described in the above embodiments as long as it does not depart from the gist of the invention.

Since this invention is made as described above, an amino-based silane base film is formed by firing in air, and an insulating film of polyimide is formed thereon by firing in vacuum or in an inert gas. By doing so, the polyimide resin film can be extremely slightly colored, and a highly transparent liquid crystal cell can be manufactured. Further, according to the present invention, a highly reliable liquid crystal cell with excellent direct current resistance can be manufactured with good workability and at low cost.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a liquid crystal cell manufactured according to the present invention, and FIG. 2 is a cross-sectional view of an electrode substrate at each step showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Electrode, 3...Undercoat, 4
...Insulating coating that also serves as an alignment treatment film, 5...Spacer,
6...Liquid crystal.

Claims (1)

[Claims] 1 A process of applying amino-based silane to an insulating substrate on which a predetermined pattern of electrodes is formed and firing it in air, and applying polyimide on the base film made of this amino-based silane and then baking it in vacuum or in an inert gas. A liquid crystal cell is formed by a step of firing the two electrode substrates obtained through these steps, joining and fixing them with a predetermined gap between them, and filling the gap with liquid crystal. A method for manufacturing a liquid crystal cell characterized by: