JPH03115379A - Manufacture of coating fluid for forming siliceous film - Google Patents

Abstract

PURPOSE:To obtain the title coating fluid which gives a film free from defects such as pinholes and excellent in mechanical strength, chemical resistance, etc., by partially hydrolyzing an alkoxysilane in the presence of an organic solvent, etc., and bringing the partial hydrolysate solution into contact with an alkali. CONSTITUTION:At least one alkoxysilane of the formula (wherein R1 is a hydrocarbon group; R2 is 1-4C alkyl; n is 0 to 3) in an amount of 3-25wt.% (based on a reaction mixture) in terms of SiO2 is hydrolyzed at 10-100 deg.C within 5hr in the presence of an organic solvent, such as methanol, and water in an amount of 0.1-2mol per mol of Si-OR by adding an acid such as hydrochloric acid to adjust the pH to 0 to 6, giving a condensation polymer of a partially hydrolyzed alkoxysilane having a molecular weight of 100 to 5,000. An alkali such as ammonia is added to the hydrolysate in such an amount as to bring the pH value to 6 to 11 and left in contact at 10-100 deg.C for 0.5-5hr, and an acid is then added thereto to lower the pH below 6, thus giving an objective coating fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for producing a coating liquid for forming a silica-based film, and more specifically, it is free from defects such as pinholes and cracks, has excellent mechanical strength, and has chemical resistance. , moisture resistance,
The present invention relates to a method for producing a coating liquid for forming a silica-based film that can form a silica-based film with excellent insulation properties.

Technical Background of the Invention Silica-based coatings are formed on various substrates such as glass, plastic, ceramic, or metal, and are used as protective films to protect the substrates from corrosion, etc., or as insulating films formed on semiconductor substrates. It will be done.

Conventionally, methods for forming these silica-based films include vapor phase methods such as vapor deposition, CVD, and sputtering, or by applying a coating solution for forming a silica-based film onto a substrate and heating and baking to form a silica-based film. There are known coating methods for forming . Among these, the coating method has advantages over the vapor phase method, such as easier operation for film formation and no restrictions on the size of the substrate used.

Conventionally, as a coating solution for forming a silica-based film, an alkoxysilane solution such as tetraalkoxysilane or trialkoxysilane is dissolved in an organic solvent such as alcohol, ketone, or ester to prepare an alkoxysilane solution, and water is added to this alkoxysilane solution. It has been produced by adding alkali or acid as well as partially hydrolyzing alkoxysilane in an organic solvent to produce a condensation product of a partially hydrolyzed alkoxysilane.

However, when the coating liquid for forming a silica-based film obtained in this way is applied to a substrate, dried, and baked to form a film, organic residues such as alkyl groups of alkoxysilane remaining in the film immediately after application are removed. The group decomposes during calcination, resulting in pinholes or voids (structural defects or pores resulting from decomposition of organic residues, incomplete 5i-0-3i bonds) in the coating. However, there have been problems in that a dense film cannot be formed and a silica-based film that is still satisfactory in terms of chemical resistance and the like cannot be obtained. Further, such voids tend to adsorb moisture in the atmosphere, and therefore, when used as an insulating film, for example, a problem arises in that the insulation properties deteriorate.

Therefore, it is possible to form a silica-based film that is dense without pinholes or voids, and has excellent mechanical strength, chemical resistance, moisture resistance, insulation properties, etc. It is desired that a coating liquid for forming a film based on the above-mentioned coatings be developed.

Purpose of the Invention The present invention has been completed in view of the prior art as described above, and has a structure that does not have pinholes or voids, is dense, has mechanical strength, chemical resistance, and moisture resistance. It is an object of the present invention to provide a method for producing a coating liquid for forming a silica-based film that can form a silica-based film that has excellent properties, insulation properties, etc., and has a low dielectric constant.

Summary of the Invention The method for producing a coating liquid for forming a silica film containing a first alkoxysilane partial hydrolyzate condensation product according to the present invention is as follows: (wherein R1 is a hydrocarbon group, R2 is a carbon number 1-4
(n is an alkyl group of 0 to 3) is partially hydrolyzed in the presence of an organic solvent, water and an acid, and then the resulting partially hydrolyzed solution is brought into contact with an alkali. It is characterized by

Further, the second method for producing a coating liquid for forming a silica-based film containing a condensation product of an alkoxysilane partial hydrolyzate according to the present invention is as follows: (wherein R is a hydrocarbon group and R2 has 1 carbon number -4 alkyl group, n is 0 to 3) is partially hydrolyzed in the presence of an organic solvent, water and an acid, and then the obtained portion is The method is characterized in that the hydrolysis solution is brought into contact with an alkali, and an acid is added to the resulting coating solution to make it acidic.

DETAILED DESCRIPTION OF THE INVENTION A method for producing a coating liquid for forming a silica film according to the present invention will be specifically described below.

The alkoxysilane used in the present invention is an alkyl group of 1 to 4, and n is 0 to 3).

Specific examples of the hydrocarbon group for R1 include a methyl group, an ethyl group, and a vinyl group.

Specifically, such alkoxysilanes include tetramethoxysilane, tetraethoxysilane, monomethyltrimethoxysilane, monomethyltriethoxysilane, dimethyldimethoxysilane, dimethyljethoxysilane, monoethyltrimethoxysilane, and monoethyltriethoxysilane. Silane, diethyldimethoxysilane, diethyljethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, etc. are used.

These alkoxysilanes may be used alone or in combination.

Examples of organic solvents for dissolving the alkoxysilanes mentioned above include alcohols such as methanol, ethanol, propatool, and butanol, ethylene glycol ethers such as methyl cellosolve and ethyl cellosolve, ethylene glycol, and propylene. Glycols such as glycol, esters such as methyl acetate, ethyl acetate, and methyl lactate are used.

These organic solvents may be used alone or in combination.

Specifically, the acid used is an inorganic acid such as hydrochloric acid, nitric acid, or sulfuric acid, an organic acid such as acetic acid or oxalic acid, or a compound that shows acidity in an aqueous solution such as metal soap.

In the present invention, first, the alkoxysilane as described above is
Partially hydrolyzed in the presence of organic solvents, water and acids.

At this time, the alkoxysilane is SiO□ in the reaction mixture.
It is desirable to use the amount of 3 to 25% by weight, preferably 5 to 20% by weight.

Water is used in an amount of 0.1 to 2 mol, preferably 0.5 to 1 mol, per mol of S1-OR group of the alkoxysilane. If the amount of water is less than 0.1 mole per mole of the 5i-OR group of the alkoxysilane, the hydrolysis of the alkoxysilane will tend to be insufficient, while if it exceeds 2 moles, the hydrolysis of the alkoxysilane will be insufficient. If the rate becomes too high, it tends to become difficult to control the degree of condensation polymerization of the alkoxysilane.

It is desirable to use the acid in an amount such that the pH of the reaction mixture is θ~6, preferably 2~4.

The lower the pH of the reaction mixture, the faster the rate of hydrolysis of the alkoxysilane, the amount of water added can be reduced, and the rate of partial hydrolysis can be lowered.

The partial hydrolysis reaction of alkoxysilane is 10 to 100
It is desirable to carry out the reaction at a temperature of preferably 20 to 60°C. The above reaction time is extremely fast at high temperatures and low pH, but it is usually carried out within 5 hours, preferably within 3 hours.

When the partial hydrolysis reaction of alkoxysilane is carried out in the presence of an acid as described above, the alkoxysilane is partially hydrolyzed and a condensation product of a partially hydrolyzed alkoxysilane is produced. The molecular weight (polystyrene equivalent molecular weight) of this condensation product is 100 to 5.000, preferably 500 to 2.
,000 is preferred.

If the molecular weight of the condensation product of the alkoxysilane partial hydrolyzate produced at this time is less than 100, organic residues (for example, OR groups) will remain in the silica-based film finally obtained, forming a dense film. On the other hand, 5,00
When it exceeds 0, the silica-based coating finally obtained tends to become porous.

In the present invention, next, the reaction mixture obtained by partially hydrolyzing alkoxysilane in the presence of an organic solvent, water and an acid as described above is brought into contact with an alkali. At this time, water may be added to the reaction mixture as necessary, or new alkoxysilane may be added.

When the reaction mixture obtained by partial hydrolysis as described above is brought into contact with an alkali, the remaining alkoxysilane is partially hydrolyzed, and if necessary, new alkoxysilane is partially hydrolyzed. It is thought that conversion of the OH groups and OR groups remaining in the polycondensation product obtained in step 1 to siloxane bonds and promotion of the polycondensation reaction proceed.

As the alkali, specifically, a compound showing alkalinity in an aqueous solution such as ammonia, amine, alkali metal hydroxide, quaternary ammonium compound, amine coupling agent, etc. is used, and the pH of the reaction mixture is 6 to 11. It is preferably used in an amount of 6 to 9.

It is desirable that the contact with the alkali be carried out at a temperature of 10 to 10 °C, preferably 20 to 60 °C.

Further, the above-mentioned contact time varies greatly depending on the contact temperature, but is usually about 0.5 to 5 hours, preferably about 1 to 3 hours.

By partially hydrolyzing alkoxysilane in the presence of an acid and then contacting it with an alkali, a coating solution for forming a silica film containing a condensation product of a partially hydrolyzed alkoxysilane is obtained. The liquid is usually alkaline. Then, by adding acid again to this coating liquid to make it acidic, preferably to a pH of 6 or less, the pot life of the coating liquid is improved and it becomes possible to store it for a longer period of time.

The coating liquid for forming a silica-based film obtained as described above is applied onto a substrate, and then dried and baked to form a film on the substrate. The molecular weight of the condensation product of the alkoxysilane partial hydrolyzate is usually 100 to 10,000, preferably 500 to 5,000. In addition, in order to apply the coating liquid onto the substrate, a spray method,
Spin code method, tip coat method, roll coat method,
Usual methods such as screen printing and transfer printing can be used.

The above firing temperature is usually about 300-900'C, preferably about 450-800'C.

The silica-based film formed using the coating solution for forming a silica-based film according to the present invention as described above is free from defects such as pinholes and cracks, is dense, has excellent mechanical strength, and has chemical resistance. It also has excellent moisture resistance and insulation properties.

In the present invention, the above-mentioned dense silica-based coating can be obtained by partially hydrolyzing alkoxysilane in the presence of an acid.
Next, by contacting with an alkali, a coating solution with a low content of organic residues is obtained, and when a film made of this coating solution is fired, the generation of voids caused by decomposition of these residues is suppressed. It is thought that there will be.

The thickness of the silica-based coating formed in the present invention varies depending on the purpose, but there are various thicknesses such as relatively thick coatings,
For example, if a silica-based coating with a thickness of 5000 Å or more is required, use trialkoxysilane such as monomethyltrimethoxysilane alone, tetraalkoxysilane and trialkoxysilane such as monomethyltrimethoxysilane, or dimethyldimethoxysilane as the alkoxysilane. mixtures with dialkoxysilanes, such as silanes,
Alternatively, it is preferable to use a mixture of tetraalkoxysilane, trialkoxysilane, and dialkoxysilane. In order to obtain a silica-based coating having a thickness of less than 5,000 silica, it is preferable to use a tetraalkoxysilane such as tetramethoxysilane or tetraethoxysilane as the alkoxysilane.

Tetraalkoxysilane and trialkoxysilane or dialkoxysilane may be used as a mixture from the beginning. For example, a partial hydrolysis step with an acid is performed using only tetraalkoxysilane, and upon contact with an alkali, trialkoxysilane is used. Alkoxysilane or dialkoxysilane may be added.

The mixing ratio of tetraalkoxysilane and trialkoxysilane or dialkoxysilane is 0.5 to 4.5:5 to 9:0 to 2 (weight ratio as S102). ) is desirable.

When the amount of tetraalkoxysilane increases, the resulting silica-based film has excellent heat resistance and moisture resistance, but when a silica-based film is formed with a thick film thickness, cracks tend to occur easily. When the amount of silane or dialkoxysilane increases, the resulting silica-based coating tends to have poor heat resistance and moisture resistance.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 357 g of tetraethoxysilane (ethyl silicate-28 manufactured by Tama Chemical Industry, tetramethoxysilane concentration 28% by weight in terms of S i 02), 120 g of water, and IPA 5
23g and stirred, then concentrated nitric acid was added to adjust the pH.
Adjusted to 1. The resulting mixture was kept at 50° C. for 1 hour to partially hydrolyze tetraethoxysilane. The condensation product of the alkoxysilane partial hydrolyzate obtained after partial hydrolysis has a molecular weight of 1500 in terms of polystyrene.
Met.

Next, 1% ammonia water was added to this reaction mixture to
After adjusting the temperature to H6, the temperature was maintained at 30° C. for 12 hours to prepare a coating solution for forming a silica-based film.

Example 2 250 g of tetraethoxysilane (ethyl silicate-40 manufactured by Tama Chemical Industry, tetra-ethoxysilane concentration 40% by weight in terms of S i 02), 60 g of water, and 690 g of ethyl cellosolve were mixed and stirred, and concentrated hydrochloric acid was added. pH2
Adjusted to. The resulting mixture was kept at 50°C for 2 hours to partially hydrolyze the tetraethoxysilane. The condensation product of the alkoxysilane partial hydrolyzate obtained after the partial hydrolysis had a molecular weight of 1000.

Next, 1% monoethanolamine was added to this reaction mixture [11 to adjust the pH to 7, and then the mixture was kept at 50° C. for 2 hours. Concentrated hydrochloric acid was again added to the solution thus obtained to adjust the pH to 4, thereby preparing a coating solution for forming a silica-based film.

Example 3 98 g of tetramethoxysilane (methyl silicate-5 manufactured by Tama Chemical Industry Co., Ltd., S + 02 equivalent tetramethoxysilane concentration 51% by weight), 90 g of water, and 812 g of propylene glycol monopropyl ether were mixed and stirred,
Tin octylate (TN-12 manufactured by Sakai Chemical Industries) was added to adjust the pH to 3. The resulting mixture was kept at 50°C for 30 minutes to partially hydrolyze tetramethoxysilane. The condensation product of the alkoxysilane partial hydrolyzate obtained after the partial hydrolysis had a molecular weight of 800.

Next, 1% triethanolamine was added to this reaction mixture to adjust the pH to 7, and the mixture was kept at 30° C. for 1 hour to prepare a coating solution for forming a silica-based film.

Example 4 151,118 g of methyl silica used in Example 3, 72 g of water, and 556 g of ethyl cellosolve were mixed and stirred, and the mixture was adjusted to pH 1 by adding concentrated nitric acid. The resulting mixture was kept at 50° C. for 1 hour to partially hydrolyze tetramethoxysilane.

The condensation product of the alkoxysilane partial hydrolyzate obtained after the partial hydrolysis had a molecular weight of 1,200.

Next, 1% ammonia water was added to this reaction mixture to
After adjusting to H6, 30 g of dimethyldimethoxysilane, 170 g of methyltrimethoxysilane, and 54 g of water were added with stirring and kept at 50° C. for 3 hours to prepare a coating solution for forming a silica-based film.

Example 5 Methyl silicate-31118g used in Example 3,
72 g of water and 491 g of propylene glycol monopropyl ether were mixed and stirred, and concentrated nitric acid was added to adjust the pH to 2.
Adjusted to. The resulting mixture was kept at 50°C for 1 hour,
Partial hydrolysis of tetramethoxysilane was carried out. The condensation product of the alkoxysilane partial hydrolyzate obtained after the partial hydrolysis had a molecular weight of 1000.

Next, 1% monoethanolamine was added to this reaction mixture to adjust the pH to 7, and then 205 g of methyltrimethoxysilane and 54 g of water were added with stirring, and the mixture was heated at 50°C.
The mixture was kept for 1 hour to prepare a coating solution for forming a silica-based film.

Example 6 In Example 2, instead of adding 1% monoethanolamine to the reaction mixture [1], an anion exchange resin (DIA1ON-3AIOA manufactured by Mitsubishi Kasei) was added to the reaction mixture [I].
The procedure was carried out except that the pH was adjusted to 7 by adding Log, and then the ion exchange resin was removed and kept at 50°C for 2 hours, and concentrated hydrochloric acid was added again to this solution to prepare a pH 4 coating solution for forming a silica-based film. Same as Example 2.

Example 7 In order to compare the pot lives of the coating solutions obtained in Examples 1 to 6, the viscosity of each coating solution was measured immediately after preparation and after storage for one month.

In addition, storage was placed in a constant temperature bath at 25°C.

Viscosity is the value at 25°C. The results are shown in Table 1.

Comparative Example 1 While mixing and stirring 23,357 g of ethyl silicate, 240 g of water, and 403 g of ethanol, the pH was adjusted to 1 by adding concentrated nitric acid. The resulting mixture was heated to 50℃ for 1
A coating solution for forming a silica-based film was prepared by partially hydrolyzing the tetraalkoxysilane for a certain period of time. The condensation product of the alkoxysilane partial hydrolyzate contained in this coating liquid had a molecular weight of 1,500.

Comparative Example 2 30 g of dimethyldimethoxysilane, 170 g of methyltrimethoxysilane, and 31118 g of methyl silicate
After mixing and stirring with 126 g of water, acetic acid was added to adjust the pH to 4, and the mixture was kept at 50°C for 10 hours to partially hydrolyze the alkoxysilane to prepare a coating solution for forming a silica-based film. did. The condensation product of the alkoxysilane partial hydrolyzate contained in this coating solution has a molecular weight of 220.
It was 0.

The coating liquids obtained in the above Examples and Comparative Examples were applied onto a glass substrate by a spin cord method, dried at 150°C for 10 minutes, and then baked in air at 350°C for 30 minutes. The film thickness of the obtained film was 2,000 in Examples (1) to (3) and Comparative Example (1), and in Examples (4) and (5).
) and Comparative Example (2), the number was 5,000.

The obtained film was evaluated for the following items.

(1) Cracks: Visually observe the film surface.

(2) Boiling resistance: Observe whether or not the film peels off after being immersed in boiling water for 1 hour.

(3) Alkali resistance: The presence or absence of peeling of the film was observed after immersion in a 5% NaOH aqueous solution at 50°C for 10 minutes.

(4) Pencil hardness: Its K-54 (according to 10).

(5) Refractive index: by ellipsometer.

The results are shown in Table 2.

Table 2 From Table 2, the coating formed using the coating liquid of the present invention is as follows:
It has excellent moisture resistance as determined by boiling resistance evaluation and chemical resistance as determined by alkali resistance evaluation.
) is higher than that of the coating of Comparative Example 1, indicating that a dense coating with almost no pinholes is formed.

In addition, the relative permittivity of the coating using the conventional coating solution (comparative example) It can be seen that it is lower than .

Claims (1)

[Claims] 1) General formula R^1_nSi(OR^2)_4_-_n(
In the formula, R^1 is a hydrocarbon group, and R^2 has 1 to 1 carbon atoms.
is an alkyl group of 4, and n is 0 to 3), one or more alkoxysilanes represented by
A coating for forming a silica-based film containing a condensation product of an alkoxysilane partial hydrolyzate, which is characterized by performing partial hydrolysis in the presence of water and an acid, and then contacting the obtained partial hydrolyzate with an alkali. Method of manufacturing liquid. 2) General formula R^1_nSi(OR^2)_4_-_n(
In the formula, R^1 is a hydrocarbon group, and R^2 has 1 to 1 carbon atoms.
is an alkyl group of 4, and n is 0 to 3), one or more alkoxysilanes represented by
partial hydrolysis in the presence of water and acid, and then contacting the resulting partial hydrolyzate with an alkali,
A method for producing a coating liquid for forming a silica-based film containing a condensation product of an alkoxysilane partial hydrolyzate, the method comprising adding an acid to the obtained coating liquid to make it acidic.