JPS6358191B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing a coating liquid for forming a silica film. Vapor growth methods and coating methods are known as methods for forming silica films. Since the vapor phase growth method requires special equipment, has limitations on the size of the substrate on which the film is formed, and is difficult to mass-produce, the coating method has attracted attention in recent years. The silica film formed by the coating method is required to be a uniform film without pinholes, but in addition to this, especially in the field of electronic materials, a film with few impurities is required. In order to meet these demands, various methods for producing coating liquids for forming silica films have been proposed. For example, a method has been proposed in which a carboxylic acid, a halogenated silane, and an alcohol are reacted (Tokuko Sho
48-24665 and 52-16488). In these methods, halogenated silane is used as a raw material, and carboxylic acid or carboxylic anhydride is added to it to react to obtain tetracarboxysilane, which is then reacted with alcohol to obtain a coating solution. When reacting carboxylic acid or carboxylic acid anhydride, tetracarboxysilane precipitates, so it is extremely difficult to remove the by-product hydrochloric acid or carboxy chloride, and vacuum distillation or recrystallization is required to remove this by-product. Since tetracarboxysilane precipitates as crystals, it is extremely difficult to completely remove undesirable by-products, making it impossible to obtain a highly pure reaction solution. In addition, this method has the drawback that the reaction process is long and the production efficiency is extremely low since the coating liquid is obtained by reacting tetracarboxysilane and alcohol. Furthermore, tetracarboxysilane obtained by the reaction of halogenated silane and carboxylic acid or carboxylic acid anhydride is unstable and immediately decomposes into silicon oxide when exposed to the outside air, so if shielding from the outside air is incomplete, There is a drawback that when reacted with alcohol in the next step, the reaction solution becomes cloudy and the filtration efficiency of the reaction solution decreases. On the other hand, JP-A No. 54-24831, No. 55-34258 and No. 55-
No. 34276 proposes a method of obtaining a coating liquid by adding an inorganic or organic acid as a reaction accelerator to a mixed solution of alkoxysilane and carboxylic acid or carboxylic anhydride and alcohol. These methods are superior to the methods proposed in the above-mentioned Japanese Patent Publications No. 48-24665 and No. 52-16488 in that the reaction steps are simplified, but because they use carboxylic acids or carboxylic anhydrides, It has a strong pungent odor, and if it comes in contact with the skin, it can cause severe burns, and if the thick vapor is inhaled, it can harm the nose, throat, bronchial tubes, and lung tissue, so be extremely careful when handling it. Consideration needs to be given. Furthermore, the reaction accelerator added to the reaction system often remains in the reaction solution as an undesirable impurity, making it impossible to obtain a highly pure coating solution. Therefore, there is a need for a method for producing a highly pure coating liquid that has simple reaction steps, is non-hazardous, and does not contain undesirable impurities. The inventors of the present invention have conducted extensive research to meet these demands, and as a result have discovered a method for producing a coating liquid for forming a silica film, which has an extremely simple reaction process and is free from acidic odor and danger. That is, the present invention has the general formula R′Si(OR) ₃ (where R′ is
OR or an alkyl group, an alkenyl group, an aryl group, or an aralkyl group; R is an alkyl group, an alkenyl group, an aryl group, or an aralkyl group; even if multiple R's present in one molecule are the same They can be different. ) or a partial condensate thereof, a silicon compound represented by 2-(n
−1)/n mole times (where n represents 1 in the case of the silane derivative and the number of mer (n mer) in the case of the partial condensate) and a non-acid A coating solution for forming a silica film is prepared by reacting in the presence of an organic solvent and an acidic heterogeneous catalyst at a temperature below the boiling point of the mixed solution, and adding and/or removing the solvent as necessary. The gist is the manufacturing method. The silane derivative used in the present invention has a relatively high reaction rate, and R or
It is preferable that R' has 1 to 8 carbon atoms. R is more preferably selected from an alkyl group or an alkenyl group having 1 to 4 carbon atoms, and even more preferably 1 to 3 carbon atoms. OR is liberated as an alcohol with the structure ROH when the silicon compound reacts with water, and is a component of the solvent of the silicon compound or the hydroxysilane or hydroxysilane condensate produced by its hydrolysis. becomes.
In order to provide a good solvent for these compounds and water, R has 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms.
An alkyl group is preferable. Butanol is not very preferable because it has a strange odor. When R′ is OR, the above applies as is. When R' is not OR, a more preferred embodiment is a phenyl group or an alkyl group or alkenyl group having 1 to 4 carbon atoms, and even more preferably an alkyl group or alkenyl group having 1 to 2 carbon atoms. The partial condensate can be produced by reacting the silane derivative with less than 1 mole of water in the presence of an organic solvent and an acid catalyst.
mer is commercially available under the trademark "ethyl silicate 40". Preferred examples of silicon compounds used in the present invention include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, and ethyltriethoxysilane. Silane, ethyltripropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltripropoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltripropoxysilane and partial condensates thereof, and two of these Mention may be made of mixtures of more than one species. The non-acid organic solvent used in the present invention has excellent compatibility with the silicon compound, hydroxysilane or hydroxysilane condensate produced by hydrolysis thereof, and water, and provides good stability of the solution of the hydroxysilane condensate. It is desirable that it be something that gives sex. Examples of solvents that can be used include monohydric alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol,
Esters such as methyl acetate, ethyl acetate, propyl acetate, ketones such as acetone, methyl ethyl ketone, acetylacetone, etc. may be mentioned. Among these, monohydric alcohols, especially carbon atoms 1 to 4
Alcohols other than monohydric alcohols generally have poor solubility in the silicon compounds and the like, and when used, they are preferably mixed with monohydric alcohols, particularly monohydric alcohols having 1 to 4 carbon atoms. Among monohydric alcohols having 1 to 4 carbon atoms, butyl alcohol has relatively poor compatibility with water and has an unpleasant odor, so monohydric alcohols having 1 to 3 carbon atoms are preferred. The amount of the non-acid organic solvent used in the reaction in the present invention is preferably 0.07 to 10 parts by weight, preferably 0.4 to 5 parts by weight, per 1 part by weight of the silicon compound. When the amount of the non-acid organic solvent is less than 0.07 parts by weight, the concentration of the silicon compound is high, so as the reaction of the reaction mixture progresses, the viscosity of the reaction mixture gradually increases, eventually causing gelation. There is a risk that the performance as a coating liquid may be lost.
On the other hand, when the amount of the non-acid organic solvent is more than 10 parts by weight, the concentration of the hydroxysilane condensate produced by the reaction is low, and when this is used as a coating solution, the thickness of the film is too thin to be suitable for the application. In some cases, the desired film thickness cannot be achieved without reapplication or repeated application several times. In the present invention, whereas the conventional method uses acetic acid or acetic anhydride for the reaction of alkoxysilane, water is used instead of acetic acid or the like. In the present invention, a lower carboxylic acid such as acetic acid or its acid anhydride is added to the reaction mixture for the reasons mentioned above.
The content is preferably 0.8% by weight or less. Preferably it is 0.5% by weight or less, more preferably 0.2% by weight or less, and most preferably absent. It is also desirable that other organic or inorganic acids are not substantially present in the reaction system as a liquid. The water used in the present invention is preferably pure water.
In the case of the silane derivative, the amount of water used is 2 mol or more, preferably 10 mol or less, more preferably 2.5 to 6 mol, and still more preferably 3 mol, per 1 mol of the silane derivative.
-4 mol is good. Regarding the preferable amount of water to be used in the case of the partial condensate, if the partial condensate is an n-mer, 1 mole of silicon atoms in the partial condensate is required to form the partial condensate from the silane derivative. Since (n-1)/n mol of water per unit is consumed, a value correspondingly lower than that indicated for the amount of water required in the case of the silane derivative applies. The reason why the lower limit of the range of the amount of water to be used was specified as above is because the less water is used, the less likely it is that the degree of crosslinking of the hydroxysilane condensate produced by the reaction will become large. This is because the uniformity of the coating surface tends to deteriorate. On the other hand, the upper limit was stipulated as mentioned above.
This is because the more water there is, the more water remains in the reaction solution, which impairs the uniformity of the coating obtained by coating on the substrate and deteriorates the stability of the coating solution. Examples of the acidic heterogeneous catalyst used in the present invention include acidic ion exchange resins and solid acidic catalysts in which an inorganic acid is supported on a carrier. As the acidic ion exchange resin, sulfonic acid-based strongly acidic cation and super acidic cation exchange resins are preferable, such as Diaion SK, Diaion PK,
Examples include HPK, Amberlite IR, and Nafion. Commercially available acidic ion exchange resins are
Some Na forms are substituted with H forms, but even those with H forms are not completely substituted with H forms. Therefore, if the degree of substitution to the H type is incomplete, Na ions will be eluted into the reaction solution and mixed as impurities, which will limit the use in the field of electronic materials where Na ions are particularly problematic. Therefore, it is desirable to achieve a high degree of substitution into the H form before use as a reaction promoter. This pretreatment method may be carried out according to a known method. The amount of acidic ion exchange resin used is 5 to 50% of the mixture of the silicon compound, non-acidic organic solvent, and water.
A range of 50% by weight, preferably from 5 to 20% by weight, is suitable. When the reaction mixture is packed in a column in the form of particles or in the form of a multi-layered thin film, and the reaction mixture is allowed to flow between these layers, it may be used in an amount exceeding 50% by weight up to the upper limit that allows the above-mentioned flow. As the catalyst in which an inorganic acid is supported on a carrier, those in which sulfuric acid or phosphoric acid is supported on silica, alumina-silica, zirconia, activated carbon, etc. can be used. The inorganic acid can be supported on the carrier according to a known method. For example, after drying the carrier, add the above inorganic acid aqueous solution to impregnate it.
It can be obtained by firing at 200-400℃. The amount of inorganic acid supported on the carrier is usually preferably about 1 to 10% by weight. The amount of the supported solid acidic catalyst is 5% based on the mixture of the silicon compound, non-acidic organic solvent and water.
It is preferable to use it in a range of 50% to 50% by weight, preferably 5 to 20% by weight. If this solid acidic catalyst is packed in a column in the form of particles or in the form of a multi-layered thin film, and the reaction mixture is to be distributed between these, the proportion used exceeds 50% by weight, up to the upper limit that allows the above-mentioned distribution. Of course it is possible. To produce the coating liquid of the present invention, a predetermined silicon compound, a predetermined water, and a predetermined non-acidic organic solvent are mixed, a predetermined acidic heterogeneous catalyst is added thereto, and the mixture is stirred. As the reaction progresses, a hydroxysilane condensate is produced and the amounts of the silicon compound and water decrease. At this time, the reaction time can be shortened by heating the reaction vessel to a temperature that does not exceed the boiling point of the reaction solution. After continuing the reaction until the content of the silicon compound in the reaction solution becomes 1% or less, the heterogeneous catalyst is separated by filtration to produce a highly pure reaction product containing a hydroxysilane condensate as the main component. can get things. As another method for producing the coating liquid targeted by the present invention, after adding a reaction accelerator to the mixture of the silicon compound and the non-acid organic solvent, the total amount of water is preferably adjusted to 1 mole of the silicon compound. [3-(n-
1)/n] to [4-(n-1)/n] and react until the concentration of the silicon compound in the mixture becomes 1% or less. can be manufactured. The obtained reaction product liquid is adjusted to a desired solvent composition and concentration by removing and/or adding an organic solvent as necessary, and is preferably used as a coating liquid after being filtered. If produced by such a method, it is extremely safe and easy, without being bothered by the strong odor caused by the acid, and there is no need to take into account the risk of contact with the skin or the risk of acid vapor to the eyes, nose, mouth, bronchi, etc. Moreover, a highly pure coating liquid can be obtained efficiently. In addition, there is an advantage that an organic solvent can be added to the reaction product liquid as necessary to adjust a coating liquid having a desired solvent composition. The type of organic solvent used to adjust the concentration and solvent composition varies depending on the purpose of use of the coating solution.
Examples include alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol, and butyl alcohol, esters such as methyl acetate, ethyl acetate, and butyl acetate, ketones such as acetone, methyl ethyl ketone, and acetylacetone, and mixtures thereof. A glass-forming agent or an organic polymer film-forming agent may be added to the coating liquid of the present invention, if necessary. Examples of glass-forming agents include compounds soluble in organic solvents containing alcohol and esters as main components, such as phosphorus pentoxide, phosphoric acid, boric anhydride, orthoarsenic acid, antimony trichloride, lead acetate, zinc acetate, and acetic acid. Mention may be made of aluminum and mixtures thereof. Organic polymer film-forming agents are compounds that are soluble in organic solvents and whose main components are alcohols and esters. Organic polymer compounds are preferred, such as polyvinyl acetal,
Examples include polyvinyl butyral, polyvinyl ether, and ethyl cellulose. In the case of glass-forming agents, the concentration of such additives is determined based on the amount of silicon compounds in the coating solution, taking into account the hardness of the film, etching speed, hygroscopicity, etc.
It is preferable to use it in a range of 0.5 to 10% by weight.
In addition, in the case of organic polymer film-forming agents, 2 to 10% of the coating liquid is
Preferably, weight percentages are used. Substrates suitable for applying the coating solution obtained according to the present invention include materials that cannot be soaked in organic solvents containing alcohol and esters as main components, such as inorganic materials such as glass, ceramics, and mica, and silicon, germanium, and gallium. The third periodic table of
Group and Group 4 semiconductors, as well as aluminum, copper,
Examples include metal materials such as iron, silver, gold, and stainless steel, and plastics such as polyester, polyimide, polycarbonate, and acrylic resin (all including homopolymers and copolymers). The coating solution of the present invention can be applied to these substrates by conventionally known methods such as a spinner method, a dipping method, a spray method, a printing method, and a brush coating method. After coating with such a known method, it is baked at a temperature of 100°C or higher in air or inert gas to easily form a continuous high-purity silica film with a thickness of 0.005 to 2 μm with a uniform surface and no pinholes. It can be formed and deposited on. The high-purity coating obtained by this method has wear resistance,
Aluminum because of its excellent chemical resistance,
Used to protect the surfaces of metal materials such as iron, copper, and gold, and plastics such as polyester and polyimide.
It is also suitable as a surface protection agent and an impurity diffusion agent when applied to the surface of a semiconductor, and can also be used as an insulating film for electronic material parts, a surface stabilization film (passivation film) for liquid crystal display material, and an alignment agent for liquid crystals. can also be used. The coating liquid obtained by the present invention is very stable, and even if left at room temperature in a closed container,
No clouding or precipitation occurs for over a month. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. Example 1 46 g of tetramethoxysilane and 16 g of water were placed in a 300 ml three-necked flask equipped with a stirrer, condenser and thermometer.
g and 110 g of ethanol, and this mixed solution was pretreated with 9.5 g of strongly acidic ion exchange resin.
was added and stirred to react at 60°C. After confirming by gas chromatography that the concentration of tetramethoxysilane in the reaction solution was 1% by weight or less, the reaction was stopped and 73% ethanol and 26% methanol were added.
A reaction product liquid having a liquid composition of 0.05% and tetramethoxysilane was obtained. After filtering this reaction product solution to remove the strongly acidic ion exchange resin, it was analyzed by atomic absorption spectrometry, elemental analysis, and potentiometric titration.
The results shown in 1 were obtained. In this table, the unit of numbers is ppm.

[Table] Next, add ethyl acetate to this reaction solution to determine the solid content.
Adjust the coating solution to 6.0% (residual solid content when heated at 150℃ for 3 hours), apply it on a glass plate using a spinner, and bake at 150℃ for 30 minutes and then at 500℃ for 30 minutes. As a result, a silica coating shown in Table 2 was obtained.

[Table] When these films were observed using a scanning electron microscope, they were found to be uniform and smooth without pinholes or cracks. The physical properties of this film were as follows. Etching rate: 400 Å/min (1 mol% HF) Coefficient of thermal expansion: 6 x 10 ^-7 /°C Specific resistance: 8 x 10 ¹⁵ Ω・cm A portion of the coating solution was left in a closed container at room temperature for 10 months, but no damage occurred. Neither cloudiness nor precipitation occurred. Example 2 Into a reaction vessel similar to Example 1, 63 g of tetraethoxysilane, 22 g of water, and 110 g of ethanol were added.
20g of a solid catalyst obtained by supporting sulfuric acid on zirconium oxide was added, and a reaction was carried out at 60°C. The method for supporting sulfuric acid on zirconium oxide was carried out according to the following process. That is, aqueous ammonia is added to an aqueous solution of zirconium nitrate to precipitate zirconium hydroxide, and the resulting zirconium hydroxide is thoroughly washed with pure water and dried at 100° C. for 24 hours. Next, 100 g of dried zirconium hydroxide was impregnated with 110 ml of 1N nitric acid, and then dried at 100° C. for 24 hours.
This is further baked in air at 500°C for 3 hours. The reaction was stopped when the concentration of tetraethoxysilane in the reaction solution became 1% by weight or less, and the catalyst was removed to obtain a reaction solution having a liquid composition of 98.5% by weight of ethanol and 1.0% by weight of tetraethoxysilane.
The analytical values of this reaction solution were the same as those in Table 1. Ethyl acetate was added to this reaction solution to obtain a solid content of 3.2%.
I adjusted it so that Add 2.5g of phosphoric acid to 100ml of this adjusted solution, stir to dissolve, filter through a 0.2μ filter, and apply it on a P-type silicone using a spinner.
It was applied at 3000 rpm. After application, preheat at 300℃ for 10 minutes
Diffusion was carried out at 1150°C for 1 hour. After diffusion, the silica film was removed using an HF solution, and the sheet resistance and surface dopant concentration were measured to be 9.3Ω/cm ² and 3, respectively.
× ¹⁰²⁰ atoms/ ^cm3 . In addition, the above adjustment solution with a solid content of 3.2% was added to a spinner.
Apply on soda glass plate for about 10 seconds at 3000 rpm,
After heating at 150°C for 30 minutes, it was further baked at 500°C for 30 minutes. A transparent electrode is formed on this coated glass plate, and a liquid crystal cell is made using cyclohexanecarboxylic acid liquid crystal. After this cell is maintained at a temperature of 80°C for a predetermined time, a DC voltage of 32Hz3V is applied to the liquid crystal cell. When we investigated the current changes, we obtained the results shown in Figure 1. Note that in this figure, the symbols indicate the following. Jo: Initial current value Jt: Current value of the cell held for t time (a): When not applied to soda glass (b): When applied to soda glass In this way, the coating liquid is coated on soda glass. Therefore, it is clear that the life of the liquid crystal display cell becomes extremely long. Further, a portion of the above-mentioned adjustment solution was placed in a closed container and left at room temperature for 10 months, but neither cloudiness nor precipitation occurred.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing changes in liquid crystal current when the coating liquid of the present invention described in Example 4 is used in a liquid crystal cell.

Claims (1)

[Claims] 1 General formula R′Si(OR) ₃ (where R′ is OR or an alkyl group, alkenyl group, aryl group, or aralkyl group, and R is an alkyl group, alkenyl group, aryl group, or is an aralkyl group,
A plurality of R's present in one molecule may be the same or different. ) of a silicon compound which is a silane derivative or a partial condensate thereof represented by 2-(n-1)/n mole times the silicon atom (where n is 1 in the case of the above-mentioned silane derivative,
In the case of the partial condensate, the number of mer (n-mer)
represents. ) with the above water in the presence of a non-acidic organic solvent and an acidic heterogeneous catalyst at a temperature below the boiling point of the mixture, and adding and/or removing the solvent as necessary. A method for producing a coating liquid for forming a silica film, characterized by: 2 In the general formula R′Si(OR) ₃ , R has 1 carbon number
-8 alkyl group, alkenyl group, aryl group or aralkyl group, and R' is OR or an alkyl group, alkenyl group, aryl group or aralkyl group having 1 to 8 carbon atoms. The method described in Section 1. 3. The method according to item 2, wherein R is an alkyl group or an alkenyl group having 1 to 4 carbon atoms. 4. The method according to item 3, wherein R is an alkyl group or an alkenyl group having 1 to 3 carbon atoms. 5. The method according to any one of items 1 to 4, wherein R' is OR or an alkyl group having 1 to 4 carbon atoms, an alkenyl group, or a phenyl group. 6. The method according to item 5, wherein R' is OR or 1 to 2 alkyl or alkenyl groups. 7. The method according to any one of Items 1 to 6, wherein the non-acid organic solvent contains a monohydric alcohol as a main component. 8. The method according to item 7, wherein the alcohol is a monohydric alcohol having 1 to 4 carbon atoms. 9. The method according to item 8, wherein the alcohol is a monohydric alcohol having 1 to 3 carbon atoms. 10 The silicon compound has a ratio of [2-(n-1)/n] to [10-
(n-1)/n] mole times preferably [2.5-(n-
1)/n] to [6-(n-1)/n], more preferably [3-(n-1)/n] to [4-(n
-1)/n] The method according to any one of Items 1 to 9, characterized in that the reaction is carried out with water in an amount twice the molar amount. 11. The method according to any one of Items 1 to 10, characterized in that the reaction is carried out in the presence of the non-acidic organic solvent in an amount of 0.07 to 10 times the weight of the silicon compound. 12. The method according to item 11, wherein the reaction is carried out in the presence of the non-acidic organic solvent in an amount of 0.12 to 1 times the weight of the silicon compound. 13 Items 1 to 12, wherein the acidic heterogeneous catalyst is an acidic ion exchange resin.
The method described in any of the paragraphs. 14. The method according to item 13, wherein the acidic ion exchange resin is a sulfonic acid-based strongly acidic cation exchange resin or a super-strongly acidic cation exchange resin. 15. The method according to any one of Items 1 to 12, wherein the acidic heterogeneous catalyst is a solid acidic catalyst obtained by supporting an inorganic acid on a carrier and post-calcining the same. 16. The method according to item 15, wherein the inorganic acid is sulfuric acid or phosphoric acid. 17. The method according to item 15 or 16, wherein the carrier is at least one selected from a silica carrier, a silica-alumina carrier, a zirconia carrier, and an activated carbon carrier.