JP2008143722A - Precursor aqueous solution for forming titanium oxide and method for producing the aqueous solution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precursor aqueous solution for forming a titanium oxide film which has high operation safety, has no corrosiveness and can form a firm titanium oxide thin film, and to provide a method for producing the precursor aqueous solution for forming the titanium oxide film. <P>SOLUTION: A complex is formed from alkyl titanate and carboxylic acids having no hydroxyl groups, and, using the complex, an aqueous solution is prepared. Namely, this invention is a precursor aqueous solution for forming titanium oxide comprising alkyl titanate, carboxylic acids having no hydroxyl groups, and a precursor for forming titanium oxide as a reaction product with water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a titanium oxide film forming precursor aqueous solution and a method for producing a titanium oxide film forming precursor aqueous solution. More specifically, a titanium oxide film-forming precursor aqueous solution and a titanium oxide film-forming precursor aqueous solution that have high work safety, are not corrosive, and can produce a strong titanium oxide thin film. It relates to a manufacturing method.

  Conventionally, dry methods such as sputtering, vapor deposition, and chemical vapor deposition (CVD), and wet methods such as sol-gel, plating, and electrolytic polymerization are known as methods for producing metal oxide thin films. It has been.

  According to the dry method, a uniform thin film having excellent crystallinity can be obtained relatively well. However, since the apparatus is complicated and expensive, the manufacturing cost is high, and it is difficult to obtain a thin film having a large area.

  In contrast, the wet method uses a relatively simple apparatus, and can obtain a thin film having a large area. However, in the sol-gel method using titania sol or organic titanate, which is generally adopted as a wet method, an organic solvent is used for the purpose of maintaining the stability and transparency of the titania sol or organic titanate used. Alternatively, it is necessary to add a corrosive acid such as hydrochloric acid or nitric acid (see Patent Document 1). For this reason, the harmfulness of the organic solvent has become a problem from the viewpoint of work safety, and the production apparatus has become expensive due to the corrosiveness of hydrochloric acid, nitric acid and the like.

  Then, the method of apply | coating aqueous solution using a water-soluble titanium compound, without using an organic solvent is examined (refer patent document 2). In the method described in Patent Document 2, a thin film can be produced by synthesizing a water-soluble titanium compound having excellent stability from titanium alkoxide and hydroxycarboxylic acid, and applying the compound to a substrate. .

Japanese Patent Laid-Open No. 06-136545 JP 2000-302442 A

  However, in the method described in Patent Document 2, since the stability of the water-soluble titanium compound is too high, hydrolysis and polycondensation reactions in the next step are difficult to proceed, and thus a strong thin film is produced. It was difficult.

  The present invention has been made in view of the above problems, and the object of the present invention is to provide a titanium oxide thin film that has high work safety, is not corrosive, and is strong. An object of the present invention is to provide a titanium oxide film forming precursor aqueous solution and a method for producing a titanium oxide film forming precursor aqueous solution.

  The present inventors have made extensive studies in view of the above problems. As a result, a complex is formed from an alkyl titanate and a carboxylic acid having no hydroxyl group, and the complex is made into an aqueous solution, so that the work safety is high, and there is no corrosive and strong oxidation. The inventors have found that a titanium oxide-forming precursor aqueous solution capable of producing a titanium thin film can be obtained, and have completed the present invention.

  That is, the present invention provides an aqueous solution for forming titanium oxide, which includes an alkyl titanate, a carboxylic acid having no hydroxyl group, and a titanium oxide-forming precursor that is a reaction product with water. This is an aqueous precursor solution.

  Another aspect of the present invention is a method for producing an aqueous precursor solution for forming titanium oxide, wherein a complex containing an alkyl titanate complex is prepared by mixing an alkyl titanate and a carboxylic acid having no hydroxyl group. A precursor for forming titanium oxide comprising: a complex forming step for obtaining a containing solution; and a precursor forming step for mixing the complex-containing solution and water to obtain a precursor aqueous solution for forming titanium oxide containing a precursor for forming titanium oxide. It is a manufacturing method of body aqueous solution.

  The precursor aqueous solution for forming titanium oxide of the present invention has high work safety because it does not use an organic solvent, and suppresses corrosion of equipment and the like since it is not necessary to add corrosive acids such as hydrochloric acid and nitric acid. Can do. In addition, since the stability of the titanium oxide forming precursor is not too high, hydrolysis and polycondensation reactions in the next step are likely to proceed, and thus a strong titanium oxide thin film can be produced. Furthermore, since the aqueous titanium oxide forming precursor solution of the present invention is also excellent in coating properties, it is possible to efficiently perform the coating operation for forming a thin film.

Hereinafter, the present invention will be described in detail.
<Precursor aqueous solution for titanium oxide formation>
The titanium oxide-forming precursor aqueous solution of the present invention is an aqueous solution containing an alkyl titanate, a carboxylic acid having no hydroxyl group, and a titanium oxide-forming precursor that is a reaction product with water.
Here, the “precursor for forming titanium oxide” means a substance capable of producing a titanium oxide structure (network) by a sol-gel reaction, and the “precursor aqueous solution for forming titanium oxide” “Titanium forming precursor” means an aqueous solution in which water is used as a solvent.

  The aqueous precursor solution for forming titanium oxide of the present invention is excellent in the stability of the aqueous solution. As a preferred stability of the solution, generally, a transparent solution is maintained for about 2 to 3 days from the production, and hydrolysis and polycondensation reactions proceed gradually at room temperature, resulting in an increase in the viscosity of the solution or a white sedimentation. It is the extent that the production of the product is confirmed. The aqueous precursor solution for forming titanium oxide of the present invention has just this level of stability.

<Constituent components of precursor aqueous solution for titanium oxide formation>
Next, the components for preparing the aqueous titanium oxide precursor aqueous solution of the present invention will be described. The aqueous precursor solution for forming titanium oxide of the present invention uses alkyl titanate, carboxylic acids having no hydroxyl group, and water as essential components.

[Alkyl titanate]
Examples of the alkyl titanate that is an essential component of the aqueous precursor solution for forming titanium oxide of the present invention include, for example, titanium tetramethoxide, titanium tetraethoxide, titanium tetranormal propoxide, titanium tetraisopropoxide, titanium tetranormal butoxide, Examples include titanium tetratertiary butoxide. Among these, titanium tetraisopropoxide and titanium tetranormal butoxide are preferable because they are easily available.

[Carboxylic acids having no hydroxyl group]
In the titanium oxide forming precursor aqueous solution of the present invention, carboxylic acids having no hydroxyl group are used as essential components. Here, the carboxylic acid having no hydroxyl group becomes a stabilizer that stabilizes the alkyl titanate to a good degree by forming a complex with the alkyl titanate. On the other hand, when a carboxylic acid having a hydroxyl group is used, since the carboxylic acid having a hydroxyl group is bidentately coordinated to the titanium atom, the stability of the compound produced by the reaction between the alkyl titanate and the carboxylic acid having a hydroxyl group is stabilized. Therefore, the hydrolysis and polycondensation reaction in the next step are difficult to proceed, and as a result, it becomes difficult to produce a strong titanium oxide thin film.

  Among the carboxylic acids having no hydroxyl group, it is preferable to use an aliphatic carboxylic acid because the degree of stabilization of the alkyl titanate is good. From the viewpoint of solution uniformity, water-soluble aliphatic carboxylic acids are more preferable. Furthermore, acetic acid is most preferred because of its low boiling point and easy removal in the next step. The “water-soluble” in the present invention means mixing with water at an arbitrary ratio.

  Next, the content of carboxylic acids having no hydroxyl group in the aqueous precursor solution for forming titanium oxide will be described. In the aqueous precursor solution for forming titanium oxide, the ratio of carboxylic acids having no hydroxyl group to 1 equivalent of alkyl titanate is preferably 2 equivalents or more and 100 equivalents or less. When the content of carboxylic acids having no hydroxyl group is less than 2 equivalents, the aqueous solution is not sufficiently stable and titanium hydroxide is generated, which is not preferable. On the other hand, when the amount exceeds 100 equivalents, the organic matter contained in the aqueous solution increases, which is not preferable because the uniformity of the coating is lowered. The more preferable content of the carboxylic acids having no hydroxyl group is 3 equivalents or more and 20 equivalents or less, and more preferably 5 equivalents or more and 10 equivalents or less with respect to 1 equivalent of the alkyl titanate.

[water]
Water that is an essential component of the aqueous precursor solution for forming titanium oxide of the present invention is not particularly limited, but if metal ions are contained as impurities, the metal remains in the resulting titanium oxide, which is not preferable. . For this reason, as water used for this invention, distilled water and ion-exchange water are preferable.

  The content of water in the titanium oxide-forming precursor aqueous solution is not particularly limited as long as a good titanium oxide structure (network) is obtained. It is preferable to set it as the range of mass% or more and 90 mass% or less. More preferably, it is the range of 20 mass% or more and 50 mass% or less.

[Other ingredients]
In the titanium oxide forming precursor aqueous solution of the present invention, titanium oxide can be formed from the aqueous solution, and components other than the above essential components can be used as long as they do not exceed the gist of the present invention. You may make it contain as a component of.

  In the present invention, it is preferable to add a thickener for the purpose of adjusting the viscosity of the solution. As the thickener, a water-soluble organic polymer can be used, and examples thereof include polyethylene oxide, polyvinyl alcohol, polyvinyl ester, polyvinyl ether, polyvinyl pyridine, polyacrylamide, ether cellulose, pectin, and starch. .

<Method for producing aqueous precursor solution for titanium oxide formation>
Next, the aspect for manufacturing the precursor aqueous solution for titanium oxide formation of this invention is demonstrated. Any method may be adopted as a method for producing the aqueous precursor solution for forming titanium oxide of the present invention as long as it is a method capable of obtaining the aqueous precursor solution for forming titanium oxide. A complex forming step of obtaining a complex-containing solution containing an alkyl titanate complex by mixing with carboxylic acids that do not have, and a titanium oxide-forming solution containing a titanium oxide-forming precursor by mixing the complex-containing solution and water A method including a precursor forming step of obtaining a precursor aqueous solution can be mentioned as a preferred embodiment.

[Complex formation process]
In the complex formation step, an alkyl titanate complex is formed by mixing an alkyl titanate and a carboxylic acid having no hydroxyl group.
A complex-containing solution containing an alkyl titanate complex obtained by mixing an alkyl titanate and a carboxylic acid having no hydroxyl group becomes a uniform solution.
The mixing method is not particularly limited, and a known method such as stirring can be employed. Also, the order of mixing is not particularly limited, and the mixing may be performed in a form in which one of them is added as a base, or in a form in which substantially the same amount is added simultaneously.

[Precursor forming step]
In the precursor forming step, the complex-containing solution containing the alkyl titanate complex prepared in the complex forming step and water are mixed to form a titanium oxide forming precursor.
When a complex-containing solution containing an alkyl titanate complex is mixed with water, a gel is generated. In the precursor forming step, the produced gel is dissociated to finally prepare a transparent precursor solution for forming titanium oxide.

When mixing a complex-containing solution containing an alkyl titanate complex and water, if the concentration of water locally increases, a gel that is difficult to dissociate may be generated. For this reason, it is preferable to add water gradually, stirring the complex containing solution containing an alkyl titanate complex. In addition, when adding water, it is preferable to use what cooled beforehand the complex containing solution containing an alkyl titanate complex, and water for the purpose of preventing a rapid hydrolysis and polycondensation reaction.
Moreover, in dissociating the produced | generated gel, it can be made to dissociate by continuing further stirring. When the gel is dissociated, a transparent precursor solution for forming titanium oxide can be obtained.

<Shape of titanium oxide>
The shape of the titanium oxide structure (network) formed from the aqueous titanium oxide-forming precursor aqueous solution of the present invention is not particularly limited. A planar body is preferred.
The method for producing the thin film is not particularly limited, and a known method can be employed. For example, methods such as spray coating, dip coating, flow coating, spin coating, and roll coating can be used.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to any particulars as long as the gist thereof is not exceeded.

<Example 1>
[Complex formation process]
By adding and mixing 1 part by mass of titanium tetranormal butoxide (manufactured by Wako Pure Chemical Industries, Ltd., first grade) and 1.3 parts by mass of acetic acid (special grade by Wako Pure Chemical Industries, Ltd.), a uniform complex-containing solution is obtained. It was.

[Precursor forming step]
When 1 part by mass of ion-exchanged water was added to the obtained complex-containing solution while stirring, a gel was generated in the solution. By further stirring, the produced gel was dissociated, and an aqueous solution containing a transparent precursor for forming titanium oxide could be prepared.

[Applicability evaluation]
A film was formed on the glass by the dip coating method using the adjusted precursor aqueous solution for forming titanium oxide. The applicability was good.

Claims (6)

An aqueous solution for forming titanium oxide,
A titanium oxide-forming precursor aqueous solution comprising an alkyl titanate, a carboxylic acid having no hydroxyl group, and a titanium oxide-forming precursor that is a reaction product with water.   The aqueous precursor solution for forming titanium oxide according to claim 1, wherein the carboxylic acid having no hydroxyl group is an aliphatic carboxylic acid.   The aqueous precursor solution for forming titanium oxide according to claim 2, wherein the aliphatic carboxylic acid is a water-soluble aliphatic carboxylic acid.   The aqueous precursor solution for forming titanium oxide according to claim 3, wherein the water-soluble aliphatic carboxylic acid is acetic acid.   The precursor aqueous solution for forming titanium oxide according to any one of claims 1 to 4, wherein the aqueous precursor solution for forming titanium oxide is for forming a titanium oxide film. A method for producing an aqueous solution containing a titanium oxide forming precursor for forming titanium oxide,
A complex forming step of obtaining a complex-containing solution containing an alkyl titanate complex by mixing an alkyl titanate and a carboxylic acid having no hydroxyl group;
A precursor forming step of mixing the complex-containing solution and water to obtain a precursor aqueous solution for forming titanium oxide containing a precursor for forming titanium oxide, and a method for producing a precursor aqueous solution for forming titanium oxide.