JPS608263B2 - Manufacturing method of coating liquid for silica film formation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a novel coating liquid for forming a silica-based film.

The vapor phase growth method and the coating method are known as methods for forming a silica-based film on a substrate, and the former is generally used, but this method requires special equipment and requires a long processing time. There are restrictions on the size of the substrate to be used, and mass production is difficult.
Since it has drawbacks such as the difficulty of simultaneously forming a mixed film of organic and inorganic substances, the latter method has recently attracted attention as a simpler method.

However, coating methods tend to cause precipitation in the liquid and result in non-uniform film thickness, such as when particulate CJ and glass are dispersed in a solvent together with a polymer compound and applied onto a substrate. This method has disadvantages such as easy formation of pinholes in thin and thin films, and is not yet satisfactory as a method for industrial implementation.

In order to improve these drawbacks, a method has been proposed in which a reaction product of carboxylic acid, halogenated silane, and alcohol is used instead of particulate silica (Japanese Patent Publication No. 52-1).
No. 6488, Hakama Kosho No. 52-20825). In this method, since the film-forming components are in solution, precipitation and non-uniformity of the film can be avoided, but since it is necessary to use halogenated silane, halogenated It is inevitable that hydrogen and halides such as acetic acid halide will be produced as by-products. If this halide is completely removed, the desired reaction will not proceed, and if it exists in a large amount, the safety of the solution will decrease and it will cause gelation, so the concentration should be kept at a specified level during the reaction. In addition to the inconvenience of having to control it within a range, its presence in the final reaction solution poses the problem of corrosion of the substrate during coating or heating. therefore,
Regarding the production of this type of coating liquid, there has been a demand for a method for producing a coating liquid in which the formation reaction proceeds smoothly and which does not contain halides.

As a result of extensive research in order to meet these demands, the present inventors have discovered that the purpose can be achieved by using an alkoxysilane instead of the halogenated silane and reacting it in the presence of a reaction accelerator. The present invention was made based on this finding.

That is, in the present invention, phosphoric acid is added to a mixture of 1 mole of alkoxysilane, 2 to 5 moles of organic carboxylic acid, and 2 to 10 moles of alcohol, and the alkoxysilane and organic carboxylic acid in the reaction solution are removed without adding water. Hydroxysilane is produced by reacting until the content of hydroxysilane becomes 2% by weight or less of the original amount.

The present invention provides a method for producing a coating liquid for forming a silica film containing xysilane monomer as a main component. Examples of alkoxysilanes used in the present invention include tetramethoxysilane, monomethyltriethoxysilane, tetraethoxysilane, monoethyltriethoxysilane, tetrapropoxysilane, tetraptoxysilane, and mixtures thereof.

Examples of organic carboxylic acids include glacial acetic acid, acetic anhydride, propionic acid, lower monocarboxylic acids or their anhydrides such as propionic anhydride, lower dicarboxylic acids such as oxalic acid, fumaric acid, maleic acid, succinic acid, The anhydride can be mentioned.These can be used alone,
Moreover, two or more types may be mixed and used. Next, examples of alcohol include methyl alcohol, ethyl alcohol,
Mention may be made of propyl alcohol, butyl alcohol, ethylene glycol, 2-methoxychetanol and mixtures thereof. In the present invention, it is necessary to mix the above-described alkoxysilane, organic carboxylic acid, and alcohol, and add phosphoric acid as a reaction accelerator to the mixture to cause the mixture to react.

Phosphoric acid as used herein is a general term for acids produced by hydration of phosphorus pentoxide, and includes not only olithophosphoric acid but also metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, polyphosphoric acid, and the like. These phosphoric acids may be prepared in advance or may be added in the form of phosphorus pentoxide and formed in the reaction mixture. To produce a coating liquid according to the method of the present invention, a predetermined alkoxysilane, a predetermined organic carboxylic acid, and a predetermined alcohol are mixed, and a predetermined reaction accelerator is added thereto.

This causes an exothermic reaction and gradually produces organic carboxylic acid ester and hydroxysilane. Then, 2 to 5 hours after the start of the reaction, the alkoxysilane disappears, and the amount of organic carboxylic acid gradually decreases, and after 2 to 5 days at room temperature, the amount becomes less than 2% by weight of the initial amount. At this time, if the reaction temperature is raised to 50 to 7000, this reaction time is shortened. In this way, hydroxysilane monomer,
A reaction product containing organic carboxylic acid ester and alcohol as main components is obtained.

The proportions of each component used in this case are selected in the range of 2 to 5 moles of organic carboxylic acid and 2 to 10 moles of alcohol per 1 mole of alkoxysilane.

A suitable ratio is 4 moles of organic carboxylic acid (carboxyl group unit) and 4 to 4 moles of alcohol per mole of alkoxysilane.
It is 8 moles. Furthermore, ``The amount of reaction accelerator added is preferably in the range of 0.001 to 1% by weight based on the weight of the alkoxysilane.Hydroxysilane is a monomer and is generally said to be unstable. The hydroxysilane produced by the method of the present invention does not have a high concentration in the reaction product, so it can exist in a very stable state.It also does not undergo dehydration condensation to form a polymer. Therefore, it is convenient for forming a uniform silica-based film.
The progress of the reaction between these components can be tracked by gas chromatography, infrared absorption spectrum analysis, etc. of the reaction solution.

Then, the lower carboxylic acid content in the reaction solution was reduced to 2
% by weight or less, a stable coating solution can be obtained that can form a smooth, non-repellent film with a constant thickness at room temperature and in the atmosphere. When hydrolyzed by strong acids, alkoxysilanes produce a reaction solution that has low stability and is prone to gelation.

Furthermore, when hydrolyzed in the presence of water and an inorganic acid, the viscosity of the reaction solution increases, that is, the hydroxyl groups of the silanol are more likely to undergo a dehydration condensation reaction with each other to form a polymer. Furthermore, if a mixture of alkoxysilane, lower carboxylic acid, and alcohol is left without a reaction accelerator, the reaction will not proceed easily even when heat is applied, and a large amount of alkoxysilane and organic carboxylic acid will remain in the reaction solution. remain. and,
If a reaction solution in which a large amount of alkoxysilane and organic carboxylic acid remain as described above is used as a coating solution, repulsion occurs on the substrate surface when it is applied, making it impossible to form a uniform film. Therefore, in the present invention, it is necessary to react a mixture of an alkoxysilane, an organic carboxylic acid, and an alcohol in the presence of a predetermined reaction promoter. In order to add this reaction accelerator, if it is liquid, it is preferable to add it as it is to the mixture of alkoxysilane, organic carboxylic acid, and alcohol from the viewpoint of workability. However, especially when the reaction promoter is solid and difficult to dissolve, it is advantageous to dissolve it in alcohol or organic carboxylic acid in advance and mix this with the alkoxysilane. The reaction mixture obtained as described above is then added with an organic solvent as necessary to adjust the concentration, filtered through a filter with a sieve size of 0.2 to 1.0 mm, and then used as a coating solution. be done. At this time, examples of organic solvents used for concentration adjustment are:
Alcohols such as methyl alcohol and ethyl alcohol, esters such as methyl acetate, ethyl acetate, and butyl acetate, ketones such as acetone, methylkethyltone, and acetylacetone, polyhydric alcohols and their ethers, and their ethers. Although mixtures and the like can be mentioned, alcohols or mixed solvents mainly composed of alcohols are preferable.

A glass-forming agent or an organic polymer film-forming agent can be added to the coating liquid obtained by the method of the present invention as desired upon use.

The glass-forming agent is a compound soluble in an organic solvent containing alcohol and ester as main components, and is vitrified by heat treatment, such as (RO)3P, (PO)2
POH, (RO)3P0, RP(OR')2, R2P(
Phosphorus compounds such as OH), R2P○(OH), RP0(OH)2, Ward 03, Day 3B03, (RO)3B, RB
(OR')2, R280R', RB(OH)2, R28
Day 0, R3B, (RBO). Boron compounds such as (R2B)20, 3As03, 3As04, (RO)3
As, (RO)2AsOH, RAs(OR)2, RAS
H2, R2$day, R3As, RAs0, (R2$)20
, R3As0, RAs(OH)2, RAs0(OH)2
, arsenic compounds such as R2$(OH), 3Sb04,
Sun3Sb03, Hb207, Sun5Sb30,o, (R
O)3Sb, (RO)2Sb(OH), RSb(OR'
)2, R5Sh, RSb○, (R2Sb)20, R3S
Antimony compounds such as b○, Rb○(OH), RSb○(OH)2, Zn(OCOCH3)2, Zn(O
R) Zinc compounds such as Pb(OCOCH3)4,
Bell compounds such as Pb(OR)4, R2Ga(OH),
Potassium compounds such as RGa(OH)2 (wherein R and R' in the above formula are alkyl groups or aryl groups) and mixtures thereof are used. In addition, as the organic polymer film forming agent, a polymer compound which is soluble in an organic solvent mainly composed of alcohol and ester and is compatible with hydroxysilane, such as polyvinyl acetate, polypynyl formal, polyvinyl acetal, polyvinyl butyral,
Polyvinyl ether, polyvinylpyrrolidone, ethyl cellulose, shellac, phenolic resin, epoxy resin,
Polyamide resins, polyurethane resins, mixtures thereof, etc. are used. The coating liquid for forming a silica-based film obtained by the present invention is usually adjusted to a concentration of 1 to 20% by weight in terms of silica (Si02) before use.

In addition, when adding a glass-forming agent, the concentration is 10 to 500% by weight based on silica, and when adding an organic polymer film-forming agent, the relationship between the viscosity of the coating solution and the thickness of the film formed should be adjusted. Taking this into account, it is preferable to use it at a concentration of 10 to 50% by weight based on the silicone. Substrates suitable for applying the coating solution of the present invention include materials that are not attacked by organic solvents containing alcohol and ester as main components, such as glass, ceramics,
Examples include mica, silicon, germanium, gallium, aluminum, copper, iron, silver, gold, stainless steel, copper alloy, mylar, gelatin, polyester, and polyimide.

The coating solution obtained according to the present invention can be applied to these substrates by a conventional method such as a spinner method, a dip-and-pull method, a spray method, a screen printing method, a roll coater method, or a brush coating method.

After applying in this way, usually 150
If heat treatment is performed at a temperature of oo or more, a silica film, a silica-based glass film, or a silica-based glass polymer film is formed. According to the present invention, there are no halides present in the raw materials or products, and since the progress of the reaction can be controlled by adjusting the amount of reaction accelerator added, the resulting coating solution is stable and has no difference between lots. Moreover, since it does not involve any created substances such as hydrogen chloride or acetic chloride, it has the advantage of simplifying the process.

On the other hand, when the coating liquid obtained according to the present invention is used, 0.
It is possible to easily form a continuous film that is smooth, uniform, and pinhole-free with a film thickness of 05 to 20 mounds.

Therefore, even when the coating is applied to a substrate with steps (irregularities) on the surface, the surface can be smoothed, preventing wire breakage at wiring intersections, and reducing yield and reliability due to this. Therefore, it is suitable as an insulating film for multilayer wiring for electronic components. In addition, the formed film is
Due to its excellent wear resistance and chemical resistance, it is suitable for metals such as aluminum, iron, copper, silver, gold, stainless steel, and brass, their plated surfaces, and surfaces of polymer coatings such as gelatin and polyester. It is also suitable for coating and protecting the skin. Furthermore, when applied to semiconductors or glass plates, it exhibits the effect of promoting anti-harm impurities such as sodium ions, so it can also be used as a surface stabilizing film (passivation film). In addition, it is suitable as a dielectric film for liquid crystal cells, an antistatic film, a doped oxide film for semiconductors, and the like. Next, the present invention will be explained in more detail with reference to Examples. Example 1 A solution prepared by dissolving 320 g of butyl orthosilicate and 232 g of maleic acid in 128 g of methyl alcohol was mixed (25 g.
Viscosity at °C: 2.9 ratio (p) When 30 minutes of 86.5% orthophosphoric acid is added as a catalyst while stirring at room temperature, the reaction proceeds due to exothermic reaction and the liquid temperature rises to about 500C.

After stirring as it is, leave it at room temperature for 4 days (viscosity 3.2&p).

The increase in viscosity in this reaction is due to the addition of phosphoric acid and the formation of butyl alcohol. Maleic acid ester and hydroxysilane are produced in the reaction solution.

The solid content concentration of this reaction solution was 10.5%. Add ethyl alcohol, ethyl acetate, and acetone to the above reaction solution.
: Add a solution mixed at a ratio of 1:1 to adjust the concentration to 8.0% by weight, dissolve boric anhydride, and filter through a 0.45 filter to obtain a coating solution for silica phosphorus-boron glass coating. Manufacture.

The coating liquid thus obtained is used for photoprocessing by dipping and pulling up. Coated on a glass dry plate (gelatin-silver salt patterned negative) for 20 minutes.
When heat treated at 0oo for 30 minutes, the following silica-based glass coating was obtained. Pulling speed (arc/min)
Film thickness (A) 20 1,2
0030 1,50040
1,700 In this film, the three components Si02, P205, and B203 are homogeneously distributed, and Si-○-Si-"P-○-P, B-○-B, Si-○
-P, Si-0-B, and Si-◯-P-0-B units seem to form a network structure.

Coating applied on dry plate (thickness 1200-1700A)
The pencil hardness (scratching strength) was higher than the 7-day pencil hardness of the dry plate to which the present film was not coated, with no abnormalities up to the spots.

In addition, ultraviolet absorption was low, and the transmittance decreased by 5% at wavelengths of 400 to 70 mm. Example 2 100 parts of ethyl orthosilicate and 100 parts of acetic acid are dissolved in 260 parts of methyl alcohol.

At this time, the viscosity at 250 mm was 25 qo and 0.7 pm. Next, 0.46 g of phosphorus pentoxide was added to this solution while stirring it at room temperature, and the mixture was kept at 65 qC and stirred for 3 hours, and the hydrolysis reaction was almost completed. The viscosity at this time was 0.7&p, the same value as immediately after mixing.
The solid content obtained by evaporating this reaction solution to dryness was 7.5% by weight. Furthermore, methyl alcohol was added to this reaction solution to adjust the solid content concentration to 6% by weight, and then filtered using a filter with a pore diameter of 0.45 mm to prepare a coating solution for forming a silica film. Coated on a silicon substrate at 3,00 pm, 2,000 pm
After heat treatment at 0 for 30 minutes and then at 70,020 for 30 minutes, a uniform film with a thickness of 11 m was obtained.

Comparative Example Ethyl orthosilicate 60 times, ethyl alcohol 145 times, ethyl acetate 60 times, acetic anhydride 10 times and water 2 times
A solution (viscosity at 250 mm: 0.9
When phosphorus pentoxide 150 was added to the mixture and stirred for 3 hours while maintaining the temperature at 690, the viscosity of the reaction solution at 25CO had increased to 1.1 order p.

This increase is thought to be due to the dehydration condensation reaction between the hydroxyl groups of the silanol produced by the hydrolysis of ethyl orthosilicate, resulting in the production of oligomers. The solid content concentration in the reaction solution was 7.5% by weight. Further, ethyl alcohol was added to this reaction solution to adjust the solid content concentration to 6% by weight, and then a film was formed in the same manner as in Example 2. Straining was observed in the film.

Example 3 89 parts of monomethyltriethoxysilane, 80 parts of methyl alcohol, 105 parts of glacial acetic acid, and 160 parts of acetone are mixed.

Next, while stirring this solution at room temperature, add hypophosphorous acid and add 50% of hypophosphorous acid. After stirring, the solution is left at room temperature for 4 days. The solid content concentration of this reaction solution was 9.0% by weight.

The above reaction solution was filtered using a filter with a pore diameter of 0.45 mounds to obtain a coating solution for forming a silica film, which was coated onto a silicon substrate at 300 pm using a spinner.
When heat treated for 1 minute at 500°C and for 3 minutes at 500o0, a uniform film with a thickness of 25 m was obtained. Example
4 One day of phosphorus pentoxide was added to a solution of 96 times of monoethyltriethoxysilane, 296 times of butyl alcohol, and 210 times of glacial acetic acid, and when the mixture was kept at 5,500 and stirred for 6 hours, the hydrolysis reaction was almost completed. .

Claims (1)

[Claims] 1 Add phosphoric acid to a mixture of 1 mole of alkoxysilane, 2 to 5 moles of organic carboxylic acid, and 2 to 10 moles of alcohol, and determine the content of alkoxysilane and organic carboxylic acid in the reaction solution without adding water. is 20% of the original weight
A method for producing a coating liquid for forming a silica-based film containing a hydroxysilane monomer as a main component, which comprises reacting until the following reaction occurs to produce hydroxysilane.