JP2006111850A - Solution for forming silica-based film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solution for forming a silica-based film, capable of forming the silica-based film having hardness similar to that of molten glass by a sol-gel method. <P>SOLUTION: This solution for forming the silica-based film is provided by setting the concentration of an acid and water content in a prescribed concentration range so as to be able to form a dense film without having a crack even if it is a thick film. In the forming solution, a sufficient amount of water for silicon alkoxide is added in advance, i. e., the number of moles of water required for the hydrolysis of the number of moles of the silicon atoms of the silicon alkoxide, i.e., ≥4 folds water is added. Also, the concentration of a strong acid is set as 0.001-0.2 mol/kg range or in some cases as 0.0001-0.2 mol/kg range expressed by the mass molar concentration of proton on assuming that the proton completely dissociates from the strong acid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solution for forming a silica-based film by a sol-gel method.

  General glass is produced by a melting method in which a raw material is melted at a high temperature exceeding 1500 ° C. and cooled. On the other hand, the sol-gel method is a relatively new method for producing glass and ceramics at a low temperature.

  In the sol-gel method, a solution of a metal organic or inorganic compound is used as a starting material, and the solution is made into a sol in which fine particles of metal oxide or hydroxide are dissolved by hydrolysis / polycondensation reaction of the compound in the solution. In this method, the reaction is allowed to progress to gelation and solidification, and the gel is heated to obtain an oxide solid.

  In the sol-gel method, it is possible to produce a thin film on various substrates in order to produce glass from a solution, and it is possible to produce glass at a lower temperature than the glass production temperature by the melting method. Has characteristics.

  Many methods for forming a silica-based coating film by this sol-gel method have been proposed. In the sol-gel method, the heat treatment is usually performed at a temperature of 500 ° C. or higher although it is at a lower temperature than the melting method (for example, JP-A-55-034258).

  Further, techniques for curing the silica-based coating film by heating at about 450 ° C. have been proposed (for example, Japanese Patent Application Laid-Open Nos. 63-241076 and 08-027422). In addition, techniques for curing the silica-based coating film in a low temperature range from room temperature to about 200 ° C. have been proposed (for example, JP-A-63-268772 and JP-A-2002-088304).

  Furthermore, in Japanese Patent Application Laid-Open Nos. 05-085714 and 06-052796, “a treatment liquid and a forming method of a silica coat film capable of forming a non-glare film that can be fired at a low temperature (room temperature to 100 ° C.)” are described. Proposed.

  Here, in Japanese Patent Laid-Open No. 05-085714, a value as a hydrolysis rate is defined, and by setting this to 300% to 1500%, a hard film having excellent adhesiveness can be obtained. . The hydrolysis rate defined here is a value indicating the addition ratio of water, and when tetramethoxysilane or water having a mole number twice the number of moles of tetraethoxysilane is added, It is a value converted as a percentage. A hydrolysis rate of 300% to 1500% indicates that tetramethoxysilane or water of 6 to 30 times the number of moles of tetraethoxysilane is added.

  Japanese Patent Application Laid-Open No. 2002-088304 states that when a coating liquid having an average molecular weight of tetraalkoxysilane oligomer of 85000 to 500000 is used, a strong silica film without cracks can be obtained.

  Furthermore, Japanese Patent Application Laid-Open No. 63-168470 discloses a coating composition in which a film having a pencil hardness of 6H to 8H can be obtained by heating at 150 ° C. The composition includes colloidal silica.

  By the way, such a coating film by the sol-gel method is useful because it can impart a chemical protection function and optical characteristics to the target substrate surface. In addition, this coating film can be used as a base film for forming a functional film such as a water repellent film. Further, this coating film is used as a matrix, and functional fine particles are dispersed in the film. In addition, the coating film is also required to have mechanical durability.

Therefore, the present inventor has proposed a “method for producing a silica-based film-coated article” in Japanese Patent Application Laid-Open No. 11-269657. The content is intended to “manufacture excellent silica-based film-coated articles without the need for firing or pretreatment”, and includes “acid and silicon alkoxide dissolved in alcohol, At least one of the alkoxide and its hydrolyzate (including the partial hydrolyzate) contains 0.010 to 3% by weight in terms of silica, 0.0010 to 1.0N acid, and 0 to 10% by weight water. Is a method for producing an article coated with a silica-based film by applying a coating liquid to a substrate.
The silica-based film obtained by this method was able to withstand the dry cloth abrasion test.

JP 55-034258 (US Pat. No. 4,277,525) Japanese Patent Laid-Open No. 63-241076 (US Pat. No. 4,865,649) Japanese Patent Application Laid-Open No. 08-027422 Japanese Unexamined Patent Publication No. 63-268772 JP 2002-088304 A JP 05-085714 A Japanese Patent Application Laid-Open No. 06-052796 JP 63-168470 A JP-A-11-269657 (WO 99/28534, EP 0967297, US6465108)

  In order to obtain a dense silica-based film by the sol-gel method, heat treatment at 450 ° C. or higher is required. For this reason, the material of the base material used may be restricted. Furthermore, when functional fine particles are dispersed in a film even at a heat treatment at 450 ° C., the fine particles may be decomposed or the function thereof may be impaired depending on the type of functional fine particles. For example, it is the case of organic fine particles or ITO fine particles.

  In JP-A-63-241076, although heat treatment at 450 ° C. is performed in the examples, there is no description regarding film hardness. In JP-A-8-27422, heat treatment at 450 ° C. is performed in the examples, the film thickness is 300 nm, and the film hardness is 9H in pencil hardness.

  Furthermore, in Japanese Patent Application Laid-Open No. 63-268772, the film was cured at room temperature and the film thickness was unknown, but the film hardness was about 3H to 7H in pencil hardness. Japanese Patent Application Laid-Open No. 2002-88304 performs heat treatment at 80 ° C. in the examples. The evaluation of the film shows only the shrinkage rate and does not show the specific hardness. In addition, the film thickness in the Example was about 100 nm.

  In addition, according to Japanese Patent Laid-Open Nos. 05-085714 and 06-052796, “9H is obtained in pencil hardness in a film (thickness unknown) fired at a low temperature (room temperature to 100 ° C.). .

  Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 11-269657 by the present inventor, the obtained silica-based film can withstand the dry cloth abrasion test, but further improvement in film hardness has been required. In addition, the film thickness in an Example was 250 nm at maximum.

  Here, in the coating film by the sol-gel method, the film thickness obtained by one operation is generally about 100 to 200 nm.

  In a silica-based film by the sol-gel method, if it is desired to increase the film thickness, multiple coatings are necessary. Furthermore, since the crack is easily generated by increasing the film thickness, a countermeasure for the crack is also necessary. Therefore, for example, a production method for obtaining a silica-based film having a film thickness exceeding 250 nm by a single operation has also been demanded.

  Accordingly, the present invention has been made to solve the above-described problems, and is a silica-based film capable of forming a silica-based film having a hardness comparable to that of molten glass by a sol-gel method by a relatively low temperature heat treatment. A film forming solution is provided.

  First, the sol-gel process will be described. As an example, formation of a silica-based film by a sol-gel method will be described.

  For example, in a sol-gel method using silicon alkoxide as a starting material, silicon alkoxide is converted into an oligomer via a siloxane bond in a solution by a hydrolysis reaction and dehydration condensation reaction with water and a catalyst to be in a sol state.

  When this solution is applied to the substrate, the water and the solvent are volatilized, whereby the oligomer is concentrated and the molecular weight is increased, and eventually the solution loses fluidity and becomes a semi-solid gel. Immediately after gelation, the gap between the siloxane polymer networks is filled with a solvent or water. When this gel dries and water and solvent volatilize, the siloxane polymer shrinks and solidifies.

  In the solidified gel, the gap filled with the solvent and water is not completely filled and remains as pores even when heat treatment up to about 400 ° C. is performed. For this reason, in the sol-gel method, a hard film cannot be obtained by heat treatment at about 400 ° C. In order to obtain a hard film, a heat treatment at a higher temperature, for example, 500 ° C. or more, was required.

The relationship between the reaction and temperature in the heat treatment of the silica-based film by the sol-gel method described above will be described in more detail.
First, in a temperature range of about 100 to 150 ° C., water, a solvent and the like contained in the solution are evaporated.
Subsequently, if the raw material contains an organic material in a temperature range of about 250 to 400 ° C., it decomposes and evaporates.
Further, when the temperature is about 500 ° C. or higher, the gel skeleton contracts and a dense film is formed.

  As described above, in a normal sol-gel reaction, a gap between the formed networks is filled with a solvent and water in a state after gelation. It is known that the size of the gap depends on the form of polymerization of silicon alkoxide in the solution.

Moreover, the form of polymerization varies greatly depending on the pH of the solution.
That is, in an acidic solution, the oligomer of silicon alkoxide is likely to grow in a straight chain. When such a solution is applied to a substrate, the linear oligomers are folded to form a network structure, and the resulting film becomes a dense film with relatively small gaps.
However, since the linear polymer is folded and solidified, the micro structure is not strong, and cracks are easily generated when the solvent or water volatilizes from the gap.

  On the other hand, spherical oligomers are likely to grow in an alkaline solution. When such a liquid is applied to the substrate, a structure in which spherical oligomers are connected to each other is formed, and a film having a relatively large gap is formed. Since this gap is formed by bonding and growing a spherical oligomer, when the solvent or water volatilizes from the gap, it is difficult for cracks to enter.

  The present inventors paid attention to the pH of the solution and examined the acid concentration and the amount of water in an acidic region where a relatively dense film can be formed. In a certain concentration region, even a thick film is dense and free of cracks. It has been found that a film can be formed, and further, when such a film is heat-treated at, for example, about 150 to 300 ° C., a film having a hardness comparable to that of molten glass can be obtained.

  Now, it is known that the isoelectric point of silanol is 2. This indicates that when the pH of the solution is 2, silanol can exist most stably in the solution. That is, even when a large amount of hydrolyzed silicon alkoxide is present in the solution, if the pH of the solution is about 2, the probability that an oligomer is formed by the dehydration condensation reaction is very low. As a result, the hydrolyzed silicon alkoxide can exist in the solution in a monomer or low polymerization state.

  For example, when a strong acid is added to the sol-gel solution and the proton of the strong acid is completely dissociated, the proton molar concentration (hereinafter simply referred to as proton concentration) is 0.001 to 0.1 mol / kg. Then, the pH of the solution is about 3 to 1. Therefore, an oligomer having a relatively low degree of polymerization can be stably present in this solution.

  For example, in Japanese Patent Application Laid-Open No. 2002-088304, it was recommended that the average molecular weight of the tetraalkoxysilane oligomer be 85,000 to 500,000, but in the present invention, it is much smaller, about 500 to 10,000. It is a molecular weight oligomer. The present inventors have found that it is important that a thick film without a strong crack is present in the solution as an oligomer having a relatively low polymerization degree.

  The acid used in the forming solution of the present invention must be a strong acid. Examples of the strong acid include the following. Examples include hydrochloric acid, nitric acid, trichloroacetic acid, trifluoroacetic acid, sulfuric acid, phosphoric acid, methanesulfonic acid, paratoluenesulfonic acid, and oxalic acid. Of the strong acids, volatile acids can be preferably used because they do not volatilize when heated and remain in the cured film. If an acid remains in the cured film, it may hinder the bonding of inorganic components and reduce the film hardness.

  In calculating the molar concentration of protons, it is not necessary to consider protons having an acid dissociation index in water of 4 or more. For example, since the acid dissociation index of acetic acid, which is a weak acid, in water is 4.8, even when acetic acid is included in the forming solution, the proton of acetic acid is not included in the proton concentration. In the present specification, the strong acid specifically refers to an acid having a proton having an acid dissociation index of less than 4 in water.

  In the formation solution of the present invention, the reason why the proton concentration is defined as the concentration when the proton of the strong acid is completely dissociated as described above is that in the mixed solution of the organic solvent and water as in the present invention. This is because it is difficult to accurately determine the degree of acid dissociation.

  When the pH of the solution is 3 to 1, this is applied to the substrate surface and dried, the oligomer derived from silicon alkoxide having a low polymerization degree is densely filled, and a film without cracks is formed. As a result, the pores formed are small and a fairly dense film can be obtained.

  It is one of the important points of the present invention that such oligomers derived from silicon alkoxide having a low polymerization degree are closely packed. However, with this alone, a sufficiently high hardness film cannot be obtained even when heated at 200 to 300 ° C.

  As described above, the oligomer having a relatively low degree of polymerization is stably present by setting the pH of the solution to about 3 to 1. However, in such a pH range, even if water necessary for hydrolyzing all of the silicon alkoxide stoichiometrically is added, it is stabilized in a state where unreacted alkoxide remains. Even if heating is performed with insufficient hydrolysis, a siloxane bond cannot be sufficiently formed by the polymerization reaction, and a hard film cannot be obtained.

  Therefore, in the present invention, at least the stoichiometric amount of water necessary for hydrolysis is added in advance. That is, the number of moles required for hydrolysis, that is, four times or more of water is added to the number of moles of silicon atoms in the silicon alkoxide. In this way, the hydrolysis reaction is promoted, and as a result, the curing caused by the polymerization is sufficiently performed.

  Furthermore, in this invention, it is preferable to add water exceeding the 4 times mole number required for a hydrolysis. The reason for this is as follows. For example, in a low-viscosity solution, as long as there is a stoichiometrically sufficient amount of water, the hydrolysis reaction proceeds with sufficient diffusion. However, the fluidity of the liquid decreases during drying or heating, and the diffusion does not occur sufficiently, so that the hydrolysis reaction may not proceed sufficiently. As a result, there is a possibility that a film having high hardness cannot be obtained only by heat treatment at a temperature up to about 400 ° C.

  That is, at the time of drying, water evaporates in parallel with the volatilization of the solvent. Even if water is added to the solution in advance, if the amount is small, incompletely hydrolyzed silicon alkoxide is filled without being fully hydrolyzed at the stage where silicon alkoxide is concentrated. . Therefore, sufficient water is added to the solution in advance. Specifically, it is preferable to add 5 to 20 moles of water.

  For example, in the case of tetraalkoxysilane which is an example of silicon alkoxide, if 4 moles of water are present per mole of tetraalkoxysilane, all the alkoxyl groups are hydrolyzed stoichiometrically. Become. Therefore, in the present invention, the number of moles of water more than 4 times the number of moles of silicon atoms in the silicon alkoxide, preferably the number of moles of water exceeding 4 times is added. As a result, it is possible to obtain a film having a high hardness only by sufficiently proceeding with the hydrolysis reaction of silicon alkoxide and performing a heat treatment at a temperature up to about 400 ° C.

  Further, in the case of a tetraalkoxysilane polymer (for example, ethyl silicate 40 manufactured by Colcoat Co., Ltd.), assuming that the number of moles of Si in the polymer is n, the number of moles of water stoichiometrically required for hydrolysis. Is (2n + 2) moles. Therefore, as the alkoxysilane raw material having a higher degree of polymerization is used, the number of moles of water stoichiometrically required for hydrolysis is reduced with respect to 1 mole of Si.

  In the forming solution of the present invention, a component having a surface active function may be contained. For example, the hydrophilic organic polymer contained in the forming solution of the present invention may have a surface active function or may contain a surfactant separately. For example, the hydrophilic organic polymer may have a polyether group or may be a polyether having a hydrophilic end.

Although it does not specifically limit as surfactant, The following can be illustrated.
Any of nonionic surfactants, anionic surfactants, cationic surfactants, and zwitterionic surfactants can be used.
Among these, specific examples of nonionic surfactants include sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, sorbitan trioleate. Sorbitan fatty acid esters such as ate, sorbitan sesquioleate, sorbitan distearate; glycerol fatty acid esters such as glycerol monostearate, glycerol monooleate, diglycerol monooleate, self-emulsifying glycerol monostearate; alkyl alkanolamides, etc. Is mentioned. These may be used individually by 1 type and may use 2 or more types together.

  Specific examples of the anionic surfactant include fatty acid salts such as sodium oleate and castor oil potassium, alkyl sulfate salts such as sodium lauryl sulfate and ammonium lauryl sulfate, and alkylbenzene sulfonic acids such as sodium dodecylbenzene sulfonate. Examples thereof include salts, alkyl naphthalene sulfonates, alkali sulfonates, dialkyl sulfosuccinates, alkyl phosphate ester salts, and naphthalene sulfonate formalin condensates. These may be used individually by 1 type and may use 2 or more types together.

  Specific examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride. These may be used individually by 1 type and may use 2 or more types together.

  Specific examples of the zwitterionic surfactant include lauryl dimethylamine oxide. These may be used individually by 1 type and may use 2 or more types together.

  When a thick film is obtained, a film stress is generated along with the shrinkage at the time of curing, and cracks are likely to occur in order to relieve the stress. By containing at least the hydrophilic organic polymer in the forming solution, it is possible to follow the structural change accompanying the film shrinkage, and a dense film can be obtained without generating cracks.

  Moreover, in the manufacturing method of the silica type film | membrane using the formation solution of this invention, it is good to perform the heat processing for hardening a film | membrane at the temperature of 400 degrees C or less. In this case, after the film is densified, the organic matter contained therein is burned and the portion becomes a void, so that the film hardness does not decrease. In other words, a dense and hard structure is maintained in a state containing organic matter.

  The heat treatment temperature may be appropriately selected according to the required film hardness. For example, a film hardness of about pencil hardness B can be obtained by drying at room temperature. Further, a film hardness of about H is obtained by heat treatment at 90 ° C. and a film hardness of 9H or more at 120 ° C. Furthermore, if a heat treatment at 150 ° C. or higher is performed, the film hardness exceeds the category of the pencil hardness test, so it is preferable to measure by a wear test in accordance with JIS R 3212. That is, it evaluates using a commercially available Taber abrasion tester. When heat treatment of about 150 ° C. or higher is performed, the haze ratio after performing a 1000-time wear test with a Taber abrasion tester with a load of 500 g becomes 4% or less, which is equivalent to the surface hardness of the molten glass plate. It is obtained.

  The silica-based film coating solution may contain a small amount of phosphoric acid. This phosphorus acts as a curing catalyst particularly during curing. Phosphorus remains in the film without volatilization at a temperature of 400 ° C. or lower. Also, since there are many polymorphs of phosphorus, it is preferable because it does not increase the residual stress and does not lower the film hardness.

  The use of a compound having both the above-described phosphoric acid and a polyether group, for example, a polyether phosphate ester, is particularly preferred because the above-described effects, curing catalyst and film stress relaxation can be achieved by one compound.

  The forming solution of the present invention may further contain at least one of functional fine particles, molecules or ions.

  The functional fine particles are preferably conductive oxide fine particles and / or organic fine particles. The functional molecule is preferably an organic dye.

From the above, the present invention can be grasped as follows.
That is, as an invention according to claim 1,
A silica-based film forming solution for forming a silica-based film,
Including silicon alkoxide, strong acid, water and alcohol,
As a component different from the strong acid as at least a part of the strong acid, further comprising a hydrophilic organic polymer that becomes at least a part of the organic matter,
The concentration of the silicon alkoxide exceeds 3 mass% as indicated by SiO ₂ concentration when converted to silicon atoms contained in the silicon alkoxide to SiO _2,
a) When the forming solution contains a phosphorus source, the concentration of the strong acid is expressed by the molar concentration of protons assuming that the proton is completely dissociated from the strong acid, and is 0.0001-0 In the range of 2 mol / kg,
b) When the forming solution does not contain a phosphorus source, the concentration of the strong acid is expressed by the molar concentration of protons assuming that the protons are completely dissociated from the strong acid, and 0.001 to In the range of 0.2 mol / kg, and the concentration of the silicon alkoxide, expressed by the SiO ₂ concentration, is less than 13% by mass,
The silica-based film forming solution is characterized in that the number of moles of water is at least four times the total number of moles of silicon atoms contained in the silicon alkoxide.

As invention of Claim 2,
The concentration of the hydrophilic organic polymer is
c) When the concentration of the silicon alkoxide is 9% by mass or less expressed by the SiO ₂ concentration, it is 30% by mass or less with respect to the SiO ₂ ;
If d) the concentration of the silicon alkoxide is more than 9% by mass displayed by the SiO ₂ concentration, the SiO ₂ concentration as A, is (5A-15)% by mass or less,
A silica-based film forming solution according to claim 1.

As invention of Claim 3,
3. The silica-based film forming solution according to claim 1, wherein the forming solution contains 5 to 20 times as many moles of water as the total number of moles of silicon atoms contained as the silicon alkoxide.

As invention of Claim 4,
4. The silica-based film forming solution according to claim 1, wherein the total amount of the tetraalkoxysilane and the polymer thereof is 3 to 30% by mass in terms of silica. 5.

As invention of Claim 5,
The silica-based film forming solution according to claim 1, wherein the forming solution contains a component having a surface active function.

As invention of Claim 6,
6. The silica-based film forming solution according to claim 5, wherein the component having a surface active function is a surfactant or the hydrophilic organic polymer having a surface active function.

As invention of Claim 7,
7. The silica-based film forming solution according to claim 6, wherein the hydrophilic organic polymer having a surface active function is a polyether having a polyether group or having a hydrophilic end.

As invention of Claim 8,
The said formation solution is a formation solution of a silica type film given in any 1 paragraph of Claims 1-7 which further contain phosphoric acid.

As invention of Claim 9,
The said formation solution is a formation solution of the silica type film according to any one of claims 1 to 8, further comprising a polyether phosphate ester.

As an invention according to claim 10,
The said formation solution is a formation solution of the silica-type film | membrane of any one of Claims 1-9 containing further at least any one among the fine particle, molecule | numerator, or ion which has functionality.

As invention of Claim 11,
The silica-based film forming solution according to claim 10, wherein the functional fine particles are conductive oxide fine particles and / or organic fine particles.

As invention of Claim 12,
The solution for forming a silica-based film according to claim 10, wherein the functional molecule is an organic dye.

  In this specification, the silica-based film is defined as a film having the largest mass fraction of silicon oxide among the film constituent components. That is, the film constituent components are classified not as atoms but as molecules, and a film having the largest mass fraction of silicon oxide is defined as a silica-based film. For example, when an oxide other than silicon oxide is included in the film and it is an amorphous body of a composite oxide with silicon oxide, after classifying it into an oxide for each cation, When the mass fraction of silicon oxide is the largest among the film constituent components, the film is referred to as a silica-based film.

  Moreover, the polymer contained in the silicon alkoxide in the silica-based film forming solution of the present invention includes those in which some or all of the alkoxyl groups are hydrolyzed.

  The silica-based film by the forming solution of the present invention has a film hardness comparable to that of molten glass by heat treatment at a relatively low temperature. Even if this silica-based film is applied to window glass for automobiles or buildings, it is sufficiently practical.

  In the forming solution of the present invention, the hydrolysis and polymerization state of the silicon alkoxide in the solution is controlled by adding a strong acid and adjusting the pH. Further, during drying, a volatile strong acid is used so that the pH of the solution changes, and the water content is further adjusted. By doing so, a film having high hardness can be obtained by heat treatment at a relatively low temperature. Furthermore, it can be applied to the production of a silica-based film having a film thickness of more than 250 nm and several μm by one operation.

  Furthermore, a functional substance can be introduced into the resulting silica-based film as a matrix. At this time, a functional substance whose function is impaired after a heat treatment step of about 400 ° C. or higher can be introduced into the silica-based film without impairing the function.

  Furthermore, many organic substances that can be used as functional substances often start to decompose at a temperature of 200 to 300 ° C. Further, it is known that the heat shielding ability of the ITO fine particles is lowered by heating at, for example, 250 ° C. or more. In such a substance, it is possible according to the present invention to sufficiently cure the silica-based film even at a temperature lower than the temperature that impairs its characteristics such as the decomposition temperature, for example, 200 ° C. As a result, when the forming solution of the present invention is used, a thermally unstable functional substance can be introduced into a silica-based film having a hardness that can withstand a wide range of practical use without impairing its function.

(First embodiment)
The first embodiment of the present invention will be described below.
In the first embodiment, the forming solution of the present invention contains a polyether phosphate surfactant as a hydrophilic organic polymer, and tetraethoxysilane as an inorganic silica raw material. The polyether phosphate ester surfactant is a raw material of phosphorus and literally a surfactant.

23.7 g of ethyl alcohol (made by Katayama Chemical Co., Ltd.), 45.14 g of tetraethoxysilane (made by Shin-Etsu Chemical Co., Ltd.), 27.16 g of pure water, 0.1 g of concentrated hydrochloric acid (35% by mass, made by Kanto Chemical Co., Inc.), polyether 3.9 g of a phosphate ester surfactant (manufactured by Nippon Lubrizol Corporation: Solsperse 41000) was added and stirred to obtain a forming solution. The tetraethoxysilane (in terms of silica), proton concentration and water content in this solution are as shown in Table 1.
The water content is calculated by adding water contained in ethyl alcohol as 0.35% by mass.

(Table 1)
────────────────────────────────────────
Silicon Proton Water Organic P ^**
Alkoxide concentration (to Si content; (vs. SiO ₂ weight; phosphorus
(Mass%) ^* (mol / kg) molar ratio) mass%)
────────────────────────────────────────
1st Example 13.0 0.01 8 30 Yes 2nd Example 13.0 0.01 7 30 Yes 3rd Example 13.0 0.01 7 29 Yes 4th Example 6.0 0.029 9 2.5 Yes 5th Example 6.0 0.003 7 25 Yes 1st Comparative Example 13.0 0.01 7 30 No 2nd Comparative Example 13.0 0.01 7 0 Yes ─────── ─────────────────────────────────
*: Mass% is in terms of SiO ₂ .
**: Organic P is an organic polymer.

  Subsequently, this forming solution was applied by a flow coating method on a cleaned soda-lime silicate glass substrate (100 × 100 mm) at a humidity of 30% and room temperature. As it was, after drying at room temperature for about 30 minutes, it was put into an oven preheated to 200 ° C., heated for 40 minutes, and then cooled. The obtained film was a 2900 nm thick crack-free and highly transparent film.

  Furthermore, the film hardness was evaluated by an abrasion test in accordance with JIS R 3212. That is, using a commercially available Taber abrasion tester, abrasion was performed 1000 times with a load of 500 g, and the haze ratio before and after the abrasion test was measured. Table 2 shows the film thickness, the presence or absence of cracks, the haze ratio before and after the Taber test, and the presence or absence of film peeling after the Taber test. Table 2 also shows the haze ratio before and after the Taber test on the molten glass plate as a blank.

(Table 2)
────────────────────────────────────────
Film thickness Crack After initial Taber test After Taber test
Existence of (nm) Haze ratio (%) Haze ratio (%) Existence of film peeling ────────────────────────────── ──────────
1st Example 2900 None 0.2 2.1 None 2nd Example 2900 None 0.1 2.4 None 3rd Example 3300 None 0.1 2.6 None 4th Example 1000 None 0.0 2. 8 None 5th Example 1000 None 0.2 2.4 None 1st Comparative Example 2800 None 0.2 2.3 Yes 2nd Comparative Example --- Yes --- ---- ---
Glass plate --- --- 0.0 1.5 ---
────────────────────────────────────────

  As shown in Table 2, the haze ratio after the Taber test was as low as 2.5% and had a hardness comparable to a molten glass plate. As a result, the glass plate with a silica-based film produced using the forming solution according to the present invention is sufficiently practical as a window glass for automobiles or buildings. In addition, in the window glass for motor vehicles, 4% or less is calculated | required as a haze rate after a Taber test.

(Second embodiment)
In the second embodiment, ethyl silicate is added together with the tetraethoxysilane in the first embodiment as a silica raw material.

  30.02 g of ethyl alcohol (manufactured by Katayama Chemical Co., Ltd.), 22.57 g of tetraethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.), 16.25 g of ethyl silicate 40 (manufactured by Colcoat Co., Ltd.), 27.16 g of pure water, concentrated hydrochloric acid (35% by mass) , Manufactured by Kanto Chemical Co., Ltd.) 0.1 g, polyether phosphate ester surfactant (manufactured by Nippon Lubrizol Corporation: Solsperse 41000) was added and stirred to obtain a forming solution. The silicon alkoxide (silica conversion), proton concentration and water content in this solution are as shown in Table 1. The water content is calculated in the same manner as in the first embodiment.

In addition, the ethyl silicate 40 used here is a colorless and transparent liquid which is represented by the following molecular formula of n = 5 on average and contains 40 mass% equivalent as a silica content (SiO ₂ ). Furthermore, in addition to the condensate having a chain structure, a condensate having a branched or cyclic structure is also included. This ethylsilicate 40 is excellent in silica supply efficiency, viscosity, specific gravity, storage stability, and is easy to handle during use.

(Chemical formula 1)
CH ₃ CH ₂ O— (Si (OCH ₂ CH ₃ ) ₂ ) _n —OCH ₂ CH ₃

  Subsequently, this forming solution was applied by a flow coating method on a cleaned soda-lime silicate glass substrate (100 × 100 mm) at a humidity of 30% and room temperature. As it was, after drying for about 30 minutes at room temperature, it was put into an oven preheated to 200 ° C., heated for 40 minutes, and then cooled. The obtained film was a highly transparent film without cracks of 2900 nm.

  Furthermore, the film hardness was evaluated in the same manner as in the first example. As shown in Table 2, the haze ratio after the Taber test was as low as 2.4% and had a hardness comparable to that of the molten glass plate.

(Third embodiment)
In the third embodiment, polyethylene glycol is used as the hydrophilic organic polymer in place of the polyether phosphate ester surfactant in the second embodiment, and phosphoric acid is further added as a raw material of phosphorus.

  23.69 g of ethyl alcohol (manufactured by Katayama Chemical Co., Ltd.), 45.14 g of tetraethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.), 27.16 g of pure water, 0.1 g of concentrated hydrochloric acid (35 mass%, manufactured by Kanto Chemical Co., Ltd.), phosphoric acid (85 mass%, manufactured by Kanto Chemical Co., Inc.) 0.11 g, polyethylene glycol 4000 (manufactured by Kanto Chemical Co., Inc.) 3.81 g was added and stirred to obtain a forming solution. The tetraethoxysilane (in terms of silica), proton concentration and water content in this solution are as shown in Table 1. The water content is calculated in the same manner as in the first embodiment.

  Subsequently, this forming solution was applied by a flow coating method on a cleaned soda-lime silicate glass substrate (100 × 100 mm) at a humidity of 30% and room temperature. As it was, after drying for about 30 minutes at room temperature, it was put into an oven preheated to 200 ° C., heated for 40 minutes, and then cooled. The obtained film was a highly transparent film free from cracks of 3300 nm.

  Furthermore, the film hardness was evaluated in the same manner as in the first example. As shown in Table 2, the haze ratio after the Taber test was as low as 2.6% and had a hardness comparable to that of the molten glass plate.

(Fourth embodiment)
The fourth embodiment is an example in which ITO fine particles are dispersed in an organic-inorganic composite film.
ITO fine particle dispersion (Mitsubishi Materials Co., Ltd .: Ethyl alcohol solution containing 40% by mass of ITO) 7.5g, polyether phosphate ester surfactant (Tsubakimoto Kasei Co., Ltd .: Disparon DA-375) 0.15g, Tetra 20.8 g of ethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.), 55.45 g of ethyl alcohol (manufactured by Katayama Chemical Co., Ltd.), 15.8 g of pure water, and 0.3 g of concentrated hydrochloric acid (35% by mass, manufactured by Kanto Chemical Co., Ltd.) were added in this order. A forming solution. The tetraethoxysilane (in terms of silica), proton concentration and water content in this solution are as shown in Table 1. The water content is calculated in the same manner as in the first embodiment.

  Subsequently, this forming solution was applied by a flow coating method on a cleaned soda-lime silicate glass substrate (100 × 100 mm) at a humidity of 30% and room temperature. As it was, it was dried at room temperature for about 30 minutes, and then placed in an oven preliminarily heated to 90 ° C. and heated for 30 minutes. Further, it was placed in an oven preliminarily heated to 200 ° C. and heated for 1 hour, and then cooled. The obtained film was a highly transparent film without cracks of 1000 nm.

  Furthermore, the film hardness was evaluated in the same manner as in the first example. As shown in Table 2, the haze ratio after the Taber test was as low as 2.8% and had a hardness comparable to a molten glass plate.

(5th Example)
The fifth embodiment is also an example in which ITO fine particles are dispersed in the organic-inorganic composite film.
ITO fine particle dispersion (Mitsubishi Materials Co., Ltd .: ethyl alcohol solution containing 40% by mass of ITO) 2.25 g, polyether phosphate ester surfactant (Avisia Co .: Solsperse 41000) 0.16 g, polyethylene glycol 400 ( 0.36 g tetraethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) 6.25 g, ethyl alcohol (manufactured by Katayama Chemical Co., Ltd.) 17.59 g, pure water 3.7 g, concentrated nitric acid (60 mass%, manufactured by Kanto Chemical Co., Inc.) ) 0.01 g was added in order to form a forming solution. The tetraethoxysilane (in terms of silica), proton concentration and water content in this solution are as shown in Table 1. The water content is calculated in the same manner as in the first embodiment.

  Subsequently, this forming solution was applied by a flow coating method on a cleaned soda-lime silicate glass substrate (305 × 305 mm) at a humidity of 30% and room temperature. As it was, after drying for about 30 minutes at room temperature, it was put into an oven preheated to 200 ° C. and heated for 14 minutes, and then cooled. The obtained film was a highly transparent film without cracks of 1000 nm.

  Furthermore, the film hardness was evaluated in the same manner as in the first example. As shown in Table 2, the haze ratio after the Taber test was as low as 2.4% and had a hardness comparable to that of the molten glass plate.

  Since the films obtained in the fourth and fifth examples contain ITO fine particles, the infrared rays contained in sunlight are cut, and the heat felt when sunlight hits the skin through normal glass. It has the function to reduce.

  It is known that when ITO fine particles are exposed to temperatures exceeding 200 ° C., the function of cutting infrared rays is lost due to oxidation. When the forming solution of the present invention is used, a silica film having practically sufficient hardness can be obtained at a firing temperature as low as 200 ° C., so that the function of the ITO fine particles is not impaired. As a result, a film having sufficient practicality and having an infrared cut function using ITO fine particles can be obtained.

(First comparative example)
In this first comparative example, polyethylene glycol is used as the hydrophilic organic polymer instead of the polyether phosphate ester surfactant in the first embodiment. No phosphorus material is added.

  Ethyl alcohol (made by Katayama Chemical Co., Ltd.) 23.7 g, tetraethoxysilane (made by Shin-Etsu Chemical Co., Ltd.) 45.14 g, pure water 27.16 g, concentrated hydrochloric acid (35 mass%, produced by Kanto Chemical Co., Ltd.) 0.1 g, polyethylene glycol 400 (manufactured by Kanto Chemical Co., Inc.) 3.9 g was added and stirred to obtain a forming solution. The tetraethoxysilane (in terms of silica), proton concentration and water content in this solution are as shown in Table 1. The water content is calculated in the same manner as in the first embodiment.

  Subsequently, this forming solution was applied by a flow coating method on a cleaned soda-lime silicate glass substrate (100 × 100 mm) at a humidity of 30% and room temperature. As it was, after drying for about 30 minutes at room temperature, it was put into an oven preheated to 200 ° C., heated for 40 minutes, and then cooled. The obtained film was a highly transparent film without cracks of 2800 nm.

  Furthermore, the film hardness was evaluated in the same manner as in the first example. As a result, as shown in Table 2, it was shown that after the Taber test, the film was partially peeled and the film hardness was low.

(Second comparative example)
This first comparative example uses only phosphoric acid instead of the polyether phosphate ester-based surfactant in the first example, and does not add a raw material for the hydrophilic organic polymer.

  27.49 g of ethyl alcohol (manufactured by Katayama Chemical Co., Ltd.), 45.14 g of tetraethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.), 27.16 g of pure water, 0.1 g of concentrated hydrochloric acid (35% by mass, manufactured by Kanto Chemical Co., Ltd.), phosphoric acid (85% by mass, manufactured by Kanto Chemical Co., Inc.) 0.11 g was added and stirred to obtain a forming solution. The tetraethoxysilane (in terms of silica), proton concentration and water content in this solution are as shown in Table 1. The water content is calculated in the same manner as in the first embodiment.

  Subsequently, this forming solution was applied by a flow coating method on a cleaned soda-lime silicate glass substrate (100 × 100 mm) at a humidity of 30% and room temperature. As it was, after drying for about 30 minutes at room temperature, it was put into an oven preheated to 200 ° C., heated for 40 minutes, and then cooled. As a result, a crack accompanied with peeling occurred and was not formed as a film.

  In the formation solutions of the first to fifth embodiments described above, instead of tetraethoxysilane or ethyl silicate mentioned in the second embodiment, tetramethoxysilane, ethyl silicate having a different degree of polymerization (for example, Colcoat Co., Ltd.) Ethyl silicate 48) and methyl silicate may be used.

  It is also possible to add organically modified metal alkoxides such that the number of moles of metal atoms in the metal alkoxide is 10% or less of the number of moles of silicon atoms in the unmodified organic alkoxide. It is.

  As a strong acid, nitric acid, trichloroacetic acid, or trifluoroacetic acid may be used instead of hydrochloric acid.

  Instead of ethyl alcohol as a solvent, methyl alcohol, 1-propyl alcohol, isopropyl alcohol, t-butyl alcohol or a mixture thereof may be used.

  Moreover, it is also possible to add surfactant and another organic solvent as needed.

  Furthermore, as a functional material, organic molecules, organic polymers, inorganic ions and inorganic fine particles can be added within a range not exceeding the silica equivalent mass concentration of the total silicon alkoxide.

  In the present invention, a metal oxide other than Si may be added within a range not exceeding the mass fraction of silicon oxide to form a composite oxide. At that time, it is desirable to add by a method which does not affect the reactivity of the silicon alkoxide.

  A method of adding a necessary amount of a metal compound that dissolves in water or alcohol, particularly one that is simply ionized and dissolved is preferably used. For example, chloride, oxide, nitrate, etc. of metals such as lithium, sodium, potassium, cesium, magnesium, calcium, cobalt, iron, nickel, copper, aluminum, gallium, indium, scandium, yttrium, lanthanum, cerium, zinc It is possible to add a necessary amount.

  Regarding boron, it is possible to add boric acid or boron alkoxide after chelating with β-diketone such as acetylacetone.

Regarding titanium and zirconium, oxychloride, oxynitrate, or alkoxide can be chelated with β-diketone and added.
Also, aluminum can be added after alkoxide is chelated with β-diketone.

  Since the hydrophilic organic polymer is included in the silica-based film formation solution of the present invention, a thick film can be formed without cracks. Although the reason for this is not clear, it is considered that the surface active component enters between the silanol groups so that it can flexibly follow the structural change at the time of curing shrinkage and relieve the stress in the film.

  Further, when fine particles such as ITO and colloidal silica are dispersed in the silica-based film, this surfactant functions as a dispersant. In particular, a phosphoric acid surfactant having a polyether group is excellent in fine particle dispersibility. In addition, it is preferably used because it has the effect of reducing the stress of the entire film and suppressing cracks.

  The addition amount of these surfactants is preferably in a range not exceeding the silica equivalent mass concentration of the total silicon alkoxide. These surfactants remain in the film even after heat curing. If this addition amount increases, the residual amount also increases, and if it is added excessively, the film strength after heat-curing decreases, which is not preferable.

  The silica-based film forming solution according to the present invention is useful for the production of a base film, a protective film, a low reflection film, an ultraviolet shielding film, an infrared shielding film, a colored film, and the like.

Claims (12)

A silica-based film forming solution for forming a silica-based film,
Including silicon alkoxide, strong acid, water and alcohol,
As a component different from the strong acid as at least a part of the strong acid, further comprising a hydrophilic organic polymer that becomes at least a part of the organic matter,
The concentration of the silicon alkoxide exceeds 3 mass% as indicated by SiO ₂ concentration when converted to silicon atoms contained in the silicon alkoxide to SiO _2,
a) When the forming solution contains a phosphorus source, the concentration of the strong acid is expressed by the molar concentration of protons assuming that the proton is completely dissociated from the strong acid, and is 0.0001-0 In the range of 2 mol / kg,
b) When the forming solution does not contain a phosphorus source, the concentration of the strong acid is expressed by the molar concentration of protons assuming that the protons are completely dissociated from the strong acid, and 0.001 to In the range of 0.2 mol / kg, and the concentration of the silicon alkoxide, expressed by the SiO ₂ concentration, is less than 13% by mass,
A silica-based film forming solution, wherein the number of moles of water is at least four times the total number of moles of silicon atoms contained in the silicon alkoxide. The concentration of the hydrophilic organic polymer is
c) When the concentration of the silicon alkoxide is 9% by mass or less expressed by the SiO ₂ concentration, it is 30% by mass or less with respect to the SiO ₂ ;
If d) the concentration of the silicon alkoxide is more than 9% by mass displayed by the SiO ₂ concentration, the SiO ₂ concentration as A, is (5A-15)% by mass or less,
The solution for forming a silica-based film according to claim 1.   3. The silica-based film forming solution according to claim 1, wherein the forming solution contains 5 to 20 times as many moles of water as the total number of moles of silicon atoms contained as the silicon alkoxide.   The total amount of the said tetraalkoxysilane and its polymer is 3-30 mass% in conversion of a silica, The formation solution of the silica type film | membrane of any one of Claims 1-3.   The silica-based film-forming solution according to claim 1, wherein the forming solution contains a component having a surface active function.   6. The solution for forming a silica-based film according to claim 5, wherein the component having a surface active function is a surfactant or the hydrophilic organic polymer having a surface active function. The solution for forming a silica-based film according to claim 6, wherein the hydrophilic organic polymer having a surface active function is a polyether having a polyether group or having a hydrophilic end.   The silica-based film forming solution according to claim 1, wherein the forming solution further contains phosphoric acid.   The silica-based film forming solution according to claim 1, wherein the forming solution further contains a polyether phosphate ester.   The silica-based film forming solution according to claim 1, wherein the forming solution further includes at least one of functional fine particles, molecules, or ions.   The solution for forming a silica-based film according to claim 10, wherein the functional fine particles are conductive oxide fine particles and / or organic fine particles.   The solution for forming a silica-based film according to claim 10, wherein the functional molecule is an organic dye.