JPH06293535A - Coating liquid for forming silica based coating film and production thereof - Google Patents

Abstract

PURPOSE:To prevent alkali ions from being eluted and to form a coating film having high film strength by using a coating liquid for forming silica based coating film, which contains an organic solvent, a specific silanol oligomer and no organic carboxylic acid. CONSTITUTION:The coating liquid for forming the silica based coating film is produced in an organic solvent (e.g. methanol) by allowing a 3-55wt.% alkoxysilane based on the weight of the organic solvent to react in the presence of water (e.g. deionized water) and a 1000-2000ppm phosphoric acid based catalyst to obtain a silanol oligomer having 1000 to 10000 molecular weight without adding any organic carboxylic acid. Although various catalysts can be used for this purpose, phosphoric acid based catalysts are effective when the coating liquid is used for coating the substrate of the liquid crystal character display element. It is important that the coating liquid contains the silanol oligomer having 1000 to 10000, preferably 2000 to 8000 molecular weight. Namely, when the coating liquid contains no organic carboxylic acid, only to specify the amount of catalyst is not sufficient as to the coating liquid and it is required further to contain a silanol oligomer having the specified molecular weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel coating liquid for forming a silica based coating film and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, soda lime glass has been generally used as a substrate for liquid crystal character display elements. But,
Alkali ions in the substrate glass are gradually eluted into the liquid crystal layer, and there is a problem that the display performance of the device deteriorates with time. Therefore, an alkali elution preventing film has been formed.

As the material for forming the film, organic alkoxysilane compounds, organic chlorosilane compounds and the like are known. These organic silicon compounds are dissolved in an organic solvent,
A method of forming a silicon dioxide film by applying a heat treatment after coating by an appropriate method is used.

[0004]

However, a silicon film obtained by applying such a silicon solution and then heat-treating it has drawbacks in that it contains a large amount of impurities and the film thickness is not uniform, and pinholes are likely to occur.

In order to improve such a defect, a tetraalkoxysilane compound is added to the phosphoric acid catalyst 10 to 100.
A method has been proposed in which 0 ppm is reacted with an organic carboxylic acid such as acetic acid or acetic anhydride to stabilize the solution, and in the presence of water in an organic solvent, and the product is used (Japanese Examined Patent Publication No. 60- 33117).

In this method, the film is made non-uniform and the content of impurities is improved, but it is difficult to control the composition of the solution due to the organic carboxylic acid added for stabilizing the solution, and the molecular weight is lowered. There is a problem that the film strength is small. An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art.

[0007]

DISCLOSURE OF THE INVENTION The present invention is a coating liquid for forming a silica-based film, which contains an organic solvent and a silanol oligomer having a molecular weight of 1,000 to 10,000 and does not contain an organic carboxylic acid. .

In the present invention, the alkoxysilane is used in the presence of water in an organic solvent in a phosphoric acid catalyst of 1000 to 2000 p.
It is a process for producing a coating liquid for forming a silica-based film, which is characterized in that a silanol oligomer having a molecular weight of 1,000 to 10,000 is obtained by reacting under pm without adding an organic carboxylic acid.

Various catalysts can be used in the present invention, and a phosphoric acid catalyst is effective in the case of a coating liquid for a substrate for a liquid crystal character display device. The amount of the catalyst in the present invention is not particularly limited, but 500 p
If it is less than pm, the stability of the solution will be poor, the strength of the coating will be small, and if it exceeds 2000 ppm, the stability of the solution will be poor. Therefore, preferably 1000 to 2000
ppm, and particularly preferably 1200 to 1500 pp
m.

In the present invention, the molecular weight is 100.
It is important to include 0 to 10000, preferably 2000 to 8000 silanol oligomers. That is,
When the organic carboxylic acid is not contained, it is not sufficient to specify the amount of the catalyst, and by containing a silanol oligomer having a specific molecular weight, the stability of the solution can be further increased and the film strength is also large. it can.

The content of the alkoxysilane used in the present invention is not particularly limited, but the molecular weight is 1000 to 10
In order to obtain 000 silanol oligomers, 3 to 55% by weight based on the solvent is preferable. The organic solvent used in the present invention is not particularly limited, methyl alcohol, ethyl alcohol, isopropyl alcohol,
Butyl alcohol, ethylene glycol, acetone, etc. can be used. The water used in the present invention is not particularly limited, but ion-exchanged water is preferable.

[0012]

【Example】

Example 1 In a 300 ml flask equipped with a thermometer, stirrer and condenser,
After 38 g of ethyl silicate and 169 g of methanol were charged and sufficiently stirred, 0.30 g of phosphoric acid and 6.6 g of ion-exchanged water were added, and the mixture was reacted under reflux for 3 hours. After cooling to room temperature, 6.6 g of ion-exchanged water was further added, and the mixture was reacted again under reflux for 30 hours, and the silanol oligomer produced had a molecular weight of 6000. 0.4 for this
It was filtered through a 5 μm filter. The solid content concentration of this reaction liquid was 5.9%.

By dipping the coating solution thus obtained,
It was coated on a glass substrate at various speeds by a pulling method and heat-treated at 100 ° C./30 minutes and 500 ° C./30 minutes to obtain a silica-based glass film.

SnO ₂ was formed on the obtained silica-based glass film.
A membrane was attached, and alkali elution was performed at 550 ° C. for 30 minutes in a steam atmosphere. Next, the SnO ₂ film is dissolved with hydrochloric acid, and the alkali ions contained in this are quantified by atomic absorption,
The amount of a ₂ O eluted was measured. The results are shown in Table 1. This means that Na of a glass plate not coated with the coating liquid of the present invention is used.
It was about 1/10 of the amount of ₂ O eluted.

[0015]

[Table 1]

Example 2 A 300 ml flask equipped with a thermometer, a stirrer, and a cooling tube was charged with 38 g of ethyl silicate and 169 g of methanol and stirred sufficiently, and then 0.30 g of phosphoric acid and 6.
6 g was added, and the mixture was reacted under reflux for 3 hours. After cooling to room temperature, after adding 6.6 g of ion-exchanged water,
The reaction was completed by stirring overnight at room temperature. The molecular weight of the silanol oligomer in this reaction solution was 1500.

Comparative Example 1 38 g of ethyl silicate, 169 g of methanol, 22 of acetic acid were placed in a 300 ml flask equipped with a thermometer, a stirrer and a cooling tube.
After charging g and stirring thoroughly, 0.18 g of phosphoric acid was added and the reaction was carried out under reflux for 3 hours. After cooling to room temperature, 6.6 g of ion-exchanged water was added, and the mixture was stirred at room temperature for 24 hours to complete the reaction. The molecular weight of the silanol oligomer in this reaction solution was 400.

Example 3 Each of the coating solutions prepared in Examples 1 and 2 and Comparative Example 1 was dipped in a glass substrate and then pulled up to obtain a film thickness of 1000.
It was made Å and heat-treated at 100 ° C./30 minutes and 500 ° C./30 minutes to obtain a silica-based glass film.

In order to compare the film strengths of the respective silica-based glass coatings obtained, the amount of reduction of the silica-based glass coatings when treated with acid and alkali was measured. The results are shown in Table 2. The acid treatment means hydrofluoric nitric acid (volume ratio of water:
Etching with hydrofluoric acid: nitric acid = 600: 15: 10) at 25 ° C. for 1 minute is shown, and alkali treatment means immersing in a 30% caustic soda solution at 60 ° C. for 1 hour.

[0020]

[Table 2]

[0021]

EFFECT OF THE INVENTION The silica-based coating film obtained by using the coating liquid for forming a silica-based coating film of the present invention has the effects of preventing the elution of alkali ions and having a large film strength. It is suitable for preventing alkali elution from a certain soda lime glass into the liquid crystal.

Claims (3)

[Claims] 1. A coating liquid for forming a silica-based film, which contains an organic solvent and a silanol oligomer having a molecular weight of 1,000 to 10,000, and does not contain an organic carboxylic acid. 2. Alkoxysilane is reacted in an organic solvent in the presence of water at a phosphoric acid catalyst of 1000 to 2000 ppm to give a molecular weight of 1 without adding an organic carboxylic acid.
000 to 10,000 silanol oligomers are obtained. 3. The alkoxysilane is 3 to 3 with respect to the solvent.
The method for producing a coating liquid for forming a silica-based coating film according to claim 2, wherein the content is 55% by weight.