JPH0118579B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for partially forming an insulating film of silicon dioxide (SiO ₂ ) on a desired portion of an arbitrary substrate surface.

SiO ₂ insulating films are widely used, for example, as alignment films for transparent electrodes in liquid crystal display panels and as insulating layers for current cut. Moreover, although there is a form in which this insulating film is applied uniformly over the entire surface, it is more often formed in a pattern on a desired portion. However, the chemical properties of the SiO ₂ film are extremely stable, and conventionally known methods for patterning include only wet etching with hydrofluoric acid, mask evaporation, and lift-off. The disadvantages of these conventional methods are that although it is possible to remove the SiO ₂ film with hydrofluoric acid, hydrofluoric acid is a strong acid, and there are no practical resist films that can withstand this. Hard to find.

'The mask vapor deposition method is not suitable for mass production and leads to high costs, and it is difficult to achieve alignment accuracy of the pattern obtained as a SiO ₂ film and accuracy of the pattern itself.

′ The lift-off method is unavoidable due to its method.
Disturbances tend to occur at the edges of the SiO ₂ film, and the adhering surface is dirty with lift-off material residue, etc., and this dirt has the disadvantage of poor adhesion of the SiO ₂ film to the adhering surface.

In view of the above-mentioned conventional methods, the present invention provides a method for forming a patterned silicon dioxide insulating film without causing the above-mentioned drawbacks.

That is, the present invention involves a step of forming a coating film of a monomer or polymer of tetraalkoxysilane on the entire surface on which an insulating film of silicon dioxide is to be partially formed, followed by pre-baking at 100 to 140°C. a step of hardening the coating film, and then applying an alkali-resistant resist film to desired areas on the hardening film,
The process of etching away the dura film on which the resist film is not applied using an alkaline solution, and then heating at 450 to 600℃.
This method of forming an insulating film is characterized by comprising the step of converting the hard film into a silicon dioxide film by performing main firing.

A detailed explanation will be given below based on FIGS. 1 to 6 of the drawings showing an example of the method of the present invention. In this example, an insulating film is applied to a transparent electrode with a transparent conductive film formed on one side of a transparent substrate such as glass, but in FIG.
A solution of a tetraalkoxysilane monomer or polymer is applied to the entire surface of the surface that has been formed into a desired shape by a dipping method, a roll coating method, a spraying method, or the like to form a coating film 3. Tetraalkoxysilane is an organosilicon compound represented by the general formula: Si(OR) ₄ <R is an alkyl group>, and by using a solution of its monomer or condensed low-molecular polymer, such as an alcohol solution, Paint film 3
is formed. In this state, the coating film 3 is, so to speak, a soft organic film, which is not suitable for post-processing, and also has poor etching suitability for alkaline solutions. Therefore, as shown in FIG. 2, temporary firing is performed to form the coating film 3 into a hardened film 4. By performing preliminary firing at a temperature of 100 to 140°C for a firing time of about 20 to 60 minutes, the above-mentioned tetraalkoxysilane undergoes hydrolysis, etc., and organic components are removed, resulting in a siloxane compound containing Si, O, and H as constituent elements. It is thought that this will change. This pre-calcination hardens the film and makes it suitable for etching with an alkaline solution.

Next, as shown in FIG. 3, an alkali-resistant resist film 5 is formed in a pattern on a portion desired to remain as an insulating film. As a forming means, direct printing of resist ink using a screen printing method is convenient. As the resist ink, it is preferable to use an organic solvent soluble ink in consideration of releasability after etching. In addition to the screen printing method described above, the resist film 5 can also be formed by a photographic method using a photoresist. However, although this method has high pattern accuracy, it requires time and effort.

Subsequently, wet etching with an alkaline solution is performed to dissolve and remove portions of the dura mater 4 that are not covered by the resist film 5. As an etching solution, use sodium hydroxide or potassium hydroxide with a concentration of 20 to 30%.
A wt% solution may be used, the solution temperature may be 40 to 60°C, and the etching time may be set according to the film thickness. As for the etching specifications, normal specifications such as a dipping method or a spray etching method can be used. FIG. 4 shows the point at which the etching of the dura mater 4 has been completed.

Next, as shown in FIG. 5, the resist film 5 is peeled off. If the resist film 5 is an ink film, it can be dissolved with an ink solvent, and if it is a photoresist film, a predetermined film stripping solution may be used.

The dura mater 4 patterned as above is
By performing the main firing at 450 to 600°C, the insulating film 6 of silicon dioxide can be formed for the first time. A firing time of about 20 to 60 minutes is often sufficient.

Examples of the present invention will be described below, but it goes without saying that the present invention is not limited thereto.

Example A transparent electrode plate on which a transparent conductive film made of indium oxide to tin oxide was formed in a desired shape on a glass substrate was coated with a methanol solution of tetraalkoxysilane polymer (manufactured by Nippon Soda Co., Ltd., product name "NSi310": SiO ₂
(equivalent content 5.9% by weight) and pulling speed 15
A coating film of approximately 1000 Å was obtained at cm/min. then 120
℃ for 30 minutes to harden the coating film.
After making it suitable for etching, apply an alkali-resistant ink (manufactured by Taiyo Ink Co., Ltd., trade name "Chemical Ink 150P") to the desired area for about 10 minutes using a screen printing method.
It was printed to a micron thickness to form a resist film. Subsequently, the hard film not covered by the resist film was etched away by immersing it in a 30% by weight aqueous solution of caustic soda (liquid temperature: 55°C) for about 3 minutes.

After washing with water and drying, the resist film was dissolved and removed with 1,1,1-trichloroethane, and then heated to 500°C.
Main firing was performed for 30 minutes, and a silicon dioxide insulating film was obtained. The obtained insulating film had no disturbance at the pattern end, had good adhesion to the transparent electrode plate, and had no gap between the transparent conductive film and the insulating layer where foreign matter could infiltrate.

The method for forming an insulating film of the present invention is as described above.According to the present invention, a silicon dioxide film, which is difficult to pattern by etching because of its stable chemical properties, can be etched using etching technology. The resulting insulating film has high alignment accuracy, has no disturbances at the pattern edges unlike when created using the lift-off method, and the SiO ₂ film has a clean surface. Since the film is formed on the substrate, the adhesion is good and the insulation performance is even more reliable. Although the method of the present invention involves two operations, pre-baking and final baking, there are several steps such as printing a resist film using a printing method.
This method is suitable for mass production, and is a practical method of forming a high-quality insulating layer.

[Brief explanation of drawings]

FIG. 1 to FIG. 6 are explanatory cross-sectional views showing one embodiment of the insulating film forming method of the present invention in the order of steps. DESCRIPTION OF SYMBOLS 1...Transparent substrate, 2...Transparent conductive film, 3...Coating film, 4...During film, 5...Resist film, 6...Insulating film.

Claims (1)

[Claims] 1. A coating film of a monomer or polymer of tetraalkoxysilane is formed on the entire surface on which an insulating film is to be partially formed, and the coating film is hardened by pre-baking at 100 to 140°C, After that, an alkali-resistant resist film is applied to desired areas on the dura film, and the dura film on which the resist film is not applied is removed by etching with an alkaline solution, and then main firing is performed at 450 to 600°C. A method for forming an insulating film, characterized in that the dura film is a silicon dioxide film.