JP2012102001A - Aqueous solution for forming perovskite type oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous titanium solution stable over a long period, formable of a dense perovskite titanium oxide film exhibiting high photocatalytic activity, in a base material, in particular, even in an amorphous glass base material containing an alkali ion on its surface.SOLUTION: The aqueous titanium solution contains: a titanium complex in which a first ligand having 6 of coordination number to titanium ion, expressed by formula: Z-CO-CH-CO-Z(Zand Zare independently alkyl groups or alkoxy groups in the formula), and functioning as a bidentate ligand; a second ligand of carboxylate; a third ligand and a fourth ligand selected respectively from the group comprising alkoxides and hydroxide ions, and a fifth ligand of HO, are coordinated to the titanium ion, a metal ion capable of occupying an A site in a perovskite titanium oxide, and water as a solvent, and the aqueous titanium solution can form the dense perovskite titanium oxide film exhibiting the high photocatalytic activity, and is stable over the long period.

Description

  The present invention relates to an aqueous solution containing a titanium complex capable of forming a perovskite-type titanium oxide film.

Among the composite oxides having a perovskite type crystal structure represented by the general formula ABO ₃ , a perovskite type crystal containing at least one selected from calcium, strontium, barium and lead at the A site and further containing titanium at the B site A complex oxide having a structure is excellent in electrical characteristics such as semiconductor properties, dielectric properties, piezoelectricity, and pyroelectricity, and is applied to various electronic components.

For example, barium titanate (BaTiO ₃ ), which is a high dielectric constant material, has been put into practical use as a ceramic capacitor, and by partially replacing the A site with a metal element called a shifter such as Ca, Sr, Ba, Pb, etc. It is known that temperature dependence can be controlled.

Strontium titanate (SrTiO ₃ ) is also known as a high dielectric constant material, and since it does not have a Curie point, the temperature change of the dielectric constant is small, so it is used as a material for ceramic capacitors. Since electron conductivity can be easily controlled by doping with niobium or the like, application to varistors, thermoelectric conversion elements, and the like is also expected.

In addition, strontium titanate (SrTiO ₃ ) is known to function as an n-type semiconductor capable of absorbing ultraviolet rays, and has attracted attention as a highly active photocatalytic material. Photocatalytic materials are materials that cause oxidative degradation and hydrophilization due to electrons and holes generated by interband transitions, maintain a low environmental impact aesthetics as a self-cleaning film, and completely decompose water by sunlight. Based on this, hydrogen energy production is expected.

However, the use of SrTiO ₃ as a photocatalytic material has the following problems.

Usually, as means for film most easily SrTiO ₃ film, a SrTiO ₃ particles prepared by a solid phase reaction method is dispersed in a solvent, there is a colloidal coating method of coating the substrate. However, since SrTiO ₃ prepared by the solid phase reaction method has a coarse particle shape with a primary particle size of several hundred nm, the film after film formation becomes opaque and porous.

Further, a sol-gel method in which an organic solvent in which a monomer composed of titanium and strontium alkoxides or chlorides is dissolved is applied to a substrate and then heated to crystallize is also used as a means for forming an SrTiO ₃ film. However, since an organic solvent is used, the environmental load is large, and the hydrolysis of the precursor due to the ingress of moisture may cause deterioration of the solution over time, resulting in large variations in performance.

  In order to suppress the hydrolysis reaction due to this hydrolysis, it includes a bisacetylacetonato titanium complex in which two alkoxy groups are bonded and two β-diketones are coordinated, and a compound containing a metal element at the A site. There is a sol-gel method in which a substrate is coated with a solution and then baked to crystallize. It is disclosed that the SrTiO3 film produced by this method is dense and transparent to translucent (Japanese Patent Laid-Open No. 2008-143760 (Patent Document 1)). However, the bisacetylacetonatotitanium complex used here has extremely low water solubility, and the solubility may decrease due to water intrusion due to long-term storage.

Furthermore, as another problem that the photocatalyst film has, titanium oxide and titanium can be used against a substrate (for example, ceramic substrate such as soda-lime glass, borosilicate glass, glaze-treated ceramics) containing an amorphous glass layer on the surface. When baking a film containing strontium acid when baking at a temperature of 400 ° C. or higher, inorganic ion components (Na ⁺ , K ⁺ , Si ^4+, etc.) in the glass layer of the base material diffuse into the film, It is known that the photocatalytic activity is remarkably lowered by the generation of impurity phases and the promotion of crystal growth ("The Journal of Physical Chemistry", 2004, 108, 8254-8259 (Non-patent Document 1)). .

  Therefore, when baking a film on a substrate having an amorphous glass layer on its surface, a barrier layer made of an oxide layer such as silica is used as a substrate and a photocatalytic film in order to suppress diffusion of inorganic ion components into the film. Or the like is used (Patent No. 2756474 (Patent Document 2)).

JP 2008-143760 A Japanese Patent No. 2756474

"The Journal of Physical Chemistry", 2004, 108, 8254-8259

  The present inventors now have an aqueous solution containing a titanium complex in which a ligand having a diketone structure is coordinated to a titanium ion, such as acetylacetone, and a metal compound that can occupy the A site of a perovskite-type titanium oxide. However, it has been found that it can exist stably for a long time. Furthermore, according to such a water-containing composition, the knowledge was obtained that a dense highly active photocatalytic film can be formed even on an amorphous glass substrate containing alkali ions on the surface. The present invention is based on these findings.

  Accordingly, an object of the present invention is to provide an aqueous solution containing a stable titanium complex and a metal element.

  Another object of the present invention is to provide an aqueous titanium solution capable of forming a dense perovskite titanium oxide film exhibiting high photocatalytic activity even on an amorphous glass substrate containing alkali ions on the surface.

The titanium aqueous solution according to the present invention has a coordination number of 6 with respect to titanium ions, is represented by the following general formula (1), and functions as a bidentate ligand:
Z ₁ —CO—CH ₂ —CO—Z ₂ (1)
(In the formula, Z ₁ and Z ₂ are each independently an alkyl group or an alkoxy group.)
A second ligand which is a carboxylate, a third ligand and a fourth ligand each independently selected from the group consisting of alkoxides and hydroxide ions, and H ₂ O. A fifth complex formed by coordination with a titanium ion;
A metal ion capable of occupying the A site in the perovskite-type titanium oxide;
Water as solvent,
It is characterized by including at least.

  Moreover, the titanium aqueous solution according to the present invention can be used for producing a perovskite-type titanium oxide film.

  Furthermore, according to the present invention, there is provided a method for producing a perovskite-type titanium oxide coating, the method comprising: applying a titanium aqueous solution on a substrate and firing the substrate to form a coating. Comprising.

  According to one aspect of the present invention, in the method for producing a perovskite-type titanium oxide film, the substrate has an amorphous glass layer on at least a surface thereof, and the amorphous glass layer has a titanium complex and a divalent A solution containing an alkaline earth metal compound is applied.

  Furthermore, according to the present invention, the glass substrate is a member in which a coating made of perovskite titanium oxide is directly formed, and the glass substrate contains alkali ions at least near the surface on which the coating is formed. The member made of the perovskite type titanium oxide has a primary particle diameter of 50 nm or less and is a dense film.

  The titanium aqueous solution for forming a perovskite oxide film containing a titanium complex according to the present invention is stable even under long-term storage. In addition, according to the aqueous titanium solution of the present invention, a dense highly active photocatalytic film that can be applied to an amorphous substrate containing glass can be realized. Further, in the titanium aqueous solution for forming a film of perovskite oxide containing a titanium complex according to the present invention, since doping with a different element is possible, a highly active visible light responsive photocatalytic film can also be produced. As a result, a film capable of decomposing organic matter and water can be formed.

It is an electron micrograph of SrTiO ₃ film surface of Example 1 obtained by the water-based coating solution of the present invention (magnification of 30,000 times). From this photograph, it can be seen that the film surface has no noticeable cracks and has a very smooth surface. It is an electron micrograph of SrTiO ₃ film surface of Example 1 obtained by the water-based coating solution of the present invention (magnification 100,000 ×). From this photograph, it can be seen that primary particles of about 30 nm are packed very densely. It is an electron micrograph (magnification 100,000 times) of the surface of the SrTiO ₃ film of Example 2 obtained by the water-containing coating liquid according to the present invention. It is an electron micrograph (magnification 100,000 times) of the surface of the SrTiO ₃ film of Example 4 obtained by the water-containing coating liquid according to the present invention. It is an X-ray diffraction pattern of the surface of the SrTiO ₃ film of Example 2 obtained by the water-containing coating liquid according to the present invention. It is an X-ray diffraction pattern of the surface of the SrTiO ₃ film of Example 4 obtained by the water-containing coating liquid according to the present invention.

Titanium complex The titanium complex used in the present invention is a titanium complex having a coordination number of 6 with respect to titanium ions, and is characterized in that five ligands are coordinated to titanium ions. And the 1st ligand is represented by following General formula (1), and functions as a bidentate ligand.
Z ₁ —CO—CH ₂ —CO—Z ₂ (1)
(In the formula, Z ₁ and Z ₂ are each independently an alkyl group or an alkoxy group, preferably a C _1-6 alkyl group or a C _1-6 alkoxy group.)

  According to a preferred embodiment of the present invention, this first ligand is more preferably acetylacetonate or ethyl acetoacetate.

The second ligand of the titanium complexes according to the invention is a carboxylate, preferably of the formula ^R 1 -COO ^- or a group represented by (wherein, ^{R 1} is _{C 1-4} alkyl group), Alternatively, it is a conjugate base of a hydroxy acid or dicarboxylic acid having 1 to 6 carbon atoms. A preferred specific example of the second ligand is a conjugate base of a carboxylic acid selected from acetic acid, propionic acid, butyric acid, lactic acid, tartaric acid, oxalic acid, and citric acid, and there is little residue in the film after firing. Therefore, acetate ion which is a conjugate base of acetic acid is most preferable.

The third and fourth ligands of the titanium complex used in the present invention are each independently selected from the group consisting of alkoxides and hydroxide ions, and preferably have the formula R ² − An alkoxide represented by O ⁻ (wherein R ² is a C _1-6 alkyl group), and most preferably an isopropoxy group.

  The titanium complex used in the present invention is water-soluble and exists stably in water. Although not intended to be bound by the following theory, the reason is considered as follows. In titanium ions, which normally have a six-coordinate structure, water molecules coordinated in two empty orbitals undergo a nucleophilic attack on the titanium ions, leading to a hydrolysis reaction that eventually forms insoluble amorphous aggregates. To settle. However, in the titanium complex according to the present invention, the diketone compound represented by the formula (1) and the organic carboxylate ion (carboxylate) are bonded to the titanium ion, so that the coordination number is increased. It is considered that the stability can be stably present in an aqueous solution by increasing the stability.

Metal ions capable of occupying the A site in the perovskite type titanium oxide The aqueous titanium solution according to the present invention contains metal ions capable of showing the A site in the perovskite type titanium oxide. This metal ion is preferably an ion of a metal element selected from the group consisting of Ca, Sr, Ba and Pb.

Solvent The aqueous titanium solution according to the present invention comprises water as a solvent. Furthermore, according to a preferred aspect of the present invention, the solvent has a relative dielectric constant lower than that of water, is compatible with water, and contains a non-alkaline second solvent, thereby increasing the solubility of the titanium complex. This is preferable. Preferable specific examples of the second solvent include monohydric alcohols, diol glycol solvents, ethylene glycol solvents, glycerol solvents, cellosolve solvents, and carbitol solvents.

  Specific examples of the second solvent include monohydric alcohols, preferably lower monohydric alcohols such as methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-butanol ( sec-butanol), 2-methyl-1-propanol (isobutanol), 2-methyl-2-propanol (tert-butanol) and the like.

  Examples of glycol solvents include 1,2-ethanediol (ethylene glycol), 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2-butanediol, and 1,3-butanediol. 1,4-butanediol, 2,3-butanediol and the like, and examples of the ethylene glycol solvent include 2,2′-oxydiethanol (diethylene glycol), triethylene glycol and the like.

  Examples of glycerin solvents include 1,2,3-propanetriol, and cellosolve solvents include ethylene glycol monoesters, more specifically ethylene glycol monomethyl ether (methyl cellosolve) and ethylene glycol monoethyl. Examples include ether (ethyl cellosolve / cellosolve), ethylene glycol monopropyl ether (propyl cellosolve), and ethylene glycol monobutyl ether (butyl cellosolve).

  Further, as carbitol solvents, diethylene glycol monoesters are more specifically, diethylene glycol monomethyl ether (methyl carbitol), diethylene glycol monoethyl ether (ethyl carbitol / carbitol), diethylene glycol monopropyl ether (propyl carbitol). ), Diethylene glycol monobutyl ether (butyl carbitol) and the like.

Preparation of Titanium Complex The water-soluble titanium complex used in the present invention can be obtained by sequentially bonding a diketone compound represented by the formula (1) and a carboxylate to titanium ions using a titanium precursor as a raw material.

  Specifically, a titanium-acetylacetone complex is obtained by mixing and stirring a precursor compound such as titanium alkoxide or titanium tetrachloride and a diketone compound represented by the formula (1). A stable aqueous solution containing the titanium complex according to the present invention can be obtained by gradually adding to an aqueous solution containing an organic carboxylic acid while stirring. The reaction can be carried out at a temperature of 0 ° C. or higher, preferably at a temperature around room temperature (about 20 ° C.). More preferably, in order to promote bond formation between a ketone compound and acetic acid and titanium ions, By stirring while heating at a temperature of 90 ° C., a more stable aqueous solution containing a titanium complex can be prepared. The aqueous solution containing the titanium complex obtained by such a method has no stability even after storage at room temperature for one year or more, and has excellent stability.

Production of titanium aqueous solution and production of perovskite-type titanium oxide film To the aqueous solution containing the titanium complex according to the present invention obtained as described above, a divalent metal ion compound is added, and the titanium aqueous solution according to the present invention is added. Get. This aqueous solution can be used to produce a perovskite-type titanium oxide film.

  The metal ion that can occupy the A site in the perovskite-type titanium oxide added to the aqueous solution according to the present invention may be added as a water-soluble compound containing this metal ion as a cation. , Bromide, acetic acid, sulfuric acid, citric acid, lactic acid, tartaric acid, malic acid, and at least one selected from acetylacetone are preferably used.

  When the titanium aqueous solution according to the present invention is provided as a coating liquid for producing a perovskite-type titanium oxide film, it is preferable to use the water and the above-mentioned second solvent in combination as a solvent. The contained concentration of water is preferably 1 to 50 wt%. By containing water within this range, it is possible to form a film which is stable and favorable for the hydrolysis reaction.

  When the titanium aqueous solution according to the present invention is provided as a coating liquid for producing a perovskite-type titanium oxide film, the concentration of the metal that can occupy the A site in the titanium complex and the perovskite-type titanium oxide is preferably 0.01 M or more. It is 10M or less, More preferably, it is 0.1M or more and 1M or less. In particular, in this concentration range, the coating solution is stable at room temperature for a long time without formation of a precipitate.

The coating liquid according to the present invention can form a thin film on various substrates by using a general-purpose coating method, and further, can produce a perovskite type titanium oxide film by baking after the film formation. it can. That is, a composite oxide having a perovskite type crystal structure represented by the general formula ABO ₃ , wherein the A site contains one kind selected from calcium, strontium, barium, and lead, and the B site contains titanium. A complex oxide having a type crystal structure is excellent in electrical properties such as semiconductor properties, dielectric properties, piezoelectricity, pyroelectricity, and the like, and is applied to various electronic components. According to the present invention, a highly active dielectric or photocatalytic film can be obtained.

  Although the coating method is not particularly limited, a coating method such as a spin coating method, a dip coating method, a spray coating method, a flow coating method, a bar coating method, or the like can be used. Moreover, in order to improve the wettability with a base material, it is also possible to add surfactant to a coating liquid. Furthermore, the base material is not particularly limited as long as it can be baked at 400 ° C. or higher, and glass, quartz, ceramics, tiles, glazed tiles, ceramics, porcelain, and the like can be used.

Firing to produce a perovskite-type titanium oxide film with the coating liquid according to the present invention can be performed in a wide temperature range of 400 ° C. or more and 900 ° C. or less, and the firing provides high sliding resistance due to strong adhesion. Compatibility with excellent dielectric properties or photocatalytic activity. Further, according to the coating liquid according to the present invention, even in a base material having an amorphous surface structure such as soda lime glass or glazed tile, the perovskite oxide can be crystallized at a firing temperature up to 800 ° C., The resulting film exhibits excellent dielectric properties or photocatalytic activity. When a film is baked as a perovskite oxide on a substrate containing an amorphous glass layer on its surface (for example, a ceramic substrate such as soda lime glass, borosilicate glass or glaze-treated ceramics), a temperature of 400 ° C. or higher In the case of firing with, the inorganic ion components (Na ⁺ , K ⁺ , Si ^4+, etc.) in the glass layer of the substrate may diffuse into the film. However, in the present invention, the coated film can form a dense structure in which the titanium complex and the metal are partially crosslinked at the stage of drying on the substrate. There are very few vacancies and grain boundaries, which are the main routes for the diffusion of components. Therefore, since the diffusion of the inorganic ion component into the film is suppressed, crystallization occurs even in a relatively low temperature region of, for example, 400 ° C., and since there are few impurities, a high photocatalytic activity can be exhibited.

  The film obtained by the coating liquid according to the present invention has a fine particle structure and is dense, and preferably comprises fine particles having a primary particle size of 50 nm or less. For example, even when baked on a glazed tile at 800 ° C. for 1 hour, a dense film made of fine particles having a very small primary particle diameter of 50 nm or less can be obtained. It is considered that both high sliding resistance and excellent photocatalytic activity can be achieved by having a small primary particle size and being dense.

In addition, the film thickness of the film formed and fired by the aqueous coating agent of the present invention is such that a polymer binder such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), ethyl cellulose, polyvinyl butyral is added. By doing so, it is possible to increase without the occurrence of cracks. Therefore, the film thickness is not particularly limited, but is preferably 5 nm or more and 10 μm or less.

  The following examples further illustrate the present invention. The present invention is not limited to these examples.

Example 1
Preparation of aqueous solution containing titanium complex and strontium To a 20 mL sample bottle, 0.02 mol (2.003 g) of acetylacetone (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred at room temperature while titanium tetraisopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added. ) 0.02 mol (5.684 g) was added in about 0.2 g portions over about 5 minutes. A yellow solution containing a titanium-acetylacetone complex was prepared by stirring for 5 minutes after the addition. This titanium-acetylacetone yellow solution was added to 50 mL of a 0.32 mol / L acetic acid aqueous solution in about 0.2 mL portions over about 5 minutes while stirring at room temperature. After the addition, the mixture was stirred at room temperature for about 1 hour, and further stirred at 60 ° C. for about 1 hour to prepare a yellow transparent aqueous solution containing a water-soluble titanium complex. Next, 0.02 mol (4.236 g) of strontium nitrate (made by Wako Pure Chemical Industries) dissolved in 50 mL of distilled water is added to an aqueous solution containing a titanium complex, and stirred at room temperature for 1 hour and at 50 ° C. for 3 hours. To produce a yellow suspension. This suspension was treated with a centrifugal separator at 4000 rpm for 5 minutes to recover a yellowish white gel as a precipitate (water content: 5.0 g). To this yellowish white gel, 45 mL of ethanol was added and stirred for 30 minutes to obtain a yellow transparent aqueous solution. This coating solution maintained stable properties without agglomeration after standing at room temperature for half a year.

Production of Perovskite SrTiO ₃ Film Using Water-containing Coating Liquid Using the water-containing coating liquid produced as described above, a film was formed by spin coating using a glazed tile (6 cm × 4 cm × 1 cm thickness) as a substrate. As production conditions, about 1 mL of a water-containing coating solution was collected, spread on a substrate, and spun at 5000 rpm for 10 seconds to form a film. After drying at room temperature for about 1 hour and further at 60 ° C. for 1 hour, SrTiO ₃ film was produced by baking at 800 ° C. for 1 hour.

Example 2
Preparation of aqueous solution containing titanium complex and strontium To a 20 mL sample bottle, 0.02 mol (2.003 g) of acetylacetone (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred at room temperature while titanium tetraisopropoxide (manufactured by Wako Pure Chemical Industries, Ltd.) was added. ) 0.02 mol (5.684 g) was added in about 0.2 g portions over about 5 minutes. A yellow solution containing a titanium-acetylacetone complex was prepared by stirring for 5 minutes after the addition. This titanium-acetylacetone yellow solution was added to 50 mL of a 0.32 mol / L acetic acid aqueous solution in about 0.2 mL portions over about 5 minutes while stirring at room temperature. After the addition, the mixture was stirred at room temperature for about 1 hour, and further stirred at 60 ° C. for about 1 hour to prepare a yellow transparent aqueous solution containing a water-soluble titanium complex. Subsequently, 0.02 mol of strontium acetate hemihydrate (manufactured by Wako Pure Chemical Industries, Ltd.) dissolved in 10 mL of distilled water is added to an aqueous solution containing a titanium complex, and stirred at room temperature for 1 hour and at 50 ° C. for 3 hours. To prepare a yellow suspension. To this suspension, 10 mL of ethanol was added and stirred for 30 minutes to obtain a yellow transparent aqueous solution. This coating solution maintained stable properties without agglomeration after standing at room temperature for half a year.
Production of perovskite-type SrTiO ₃ film with water-containing coating solution The same as Example 1 except that the quartz substrate (5 cm × 5 cm × 1 mm thickness) was used as the substrate using the water-containing coating solution produced as described above. The film was formed by the method. After drying, baking was performed at 900 ° C. for 5 hours to produce a SrTiO ₃ film.

Example 3
Preparation of aqueous solutions containing various alcohols Methanol (manufactured by Wako Pure Chemical Industries), 1-propanol (manufactured by Wako Pure Chemical Industries), 1-butanol (manufactured by Wako Pure Chemical Industries, Ltd.) and 1-butanol (manufactured by Wako Pure Chemical Industries, Ltd.) were used in place of ethanol as the co-solvent used in Example 2. Product) or ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.), and various aqueous solutions were prepared in the same manner as in Example 2. These aqueous solutions were all yellow and transparent, and this coating solution maintained stable properties without agglomeration even after standing at room temperature for 1 month.

Example 4
A butanol solution of rhodium (III) chloride trihydrate (9.38 wt% [Rh]) was gradually added to the aqueous solution prepared in Example 2, and the mixture was stirred at room temperature for 30 minutes. An aqueous solution was prepared. This was formed into a film by the same method as in Example 1. After drying, baking was performed at 900 ° C. for 5 hours to produce a SrTiO ₃ film.

SrTiO ₃ film of film characterization scanning electron microscope (manufactured by Hitachi, Ltd., S-800) by, were subjected to structural observation of SrTiO ₃ film surface of Example 1. An electron micrograph at a low magnification (magnification of 30,000) is shown in FIG. It can be seen that the film surface has no noticeable cracks and has a very smooth surface. Moreover, the observation photograph in high magnification (magnification 100,000 times) is shown in FIG. From this photograph, it can be seen that primary particles of about 20 nm are packed very densely. Moreover, the observation photograph in the high magnification of Example 2 and Example 4 is shown as FIG. 3 and FIG. From this photograph, even after firing at a high temperature of 900 ° C., it was confirmed that the film was packed with fine particles of about 30 nm densely. Further, the crystal structure of the film was examined by X-ray diffraction measurement (XRD: “X-pert Pro” manufactured by Panalical). As a result, it was revealed that the SrTiO ₃ film of Example 1 was composed of a single-phase film of perovskite type SrTiO ₃ . Further, the crystal structures of Example 2 and Example 4 were similarly examined. As a result, it was confirmed from the XRD diffraction patterns shown in FIG. 5 and FIG. 6 that it was a single-phase film of perovskite type SrTiO ₃ similar to that in Example 1.

By irradiating ultraviolet rays to the photo-induced hydrophilic Evaluation SrTiO ₃ film surface of SrTiO ₃ film, the water contact angle was evaluated photoinduced hydrophilicity to decrease. As a light source, a black light (manufactured by Toshiba Lighting & Technology) was used, and an ultraviolet illuminance was set to 1 mW / cm ² . Although the initial water contact angle was 19.4 °, it decreased to 4.0 ° after 8 hours of UV irradiation, confirming that a hydrophilization reaction occurred.

Comparative Example 1
Add 0.02 mol (2.003 g) of acetylacetone (Wako Pure Chemical) to a 20 mL sample bottle and stir at room temperature with 0.02 mol (5.684 g) of titanium tetraisopropoxide (Wako Pure Chemical). About 0.2 g was added over about 5 minutes. Next, 50 mL of ethanol was added as a solvent, and the mixture was stirred at room temperature for 30 minutes. 0.02 mol (4.236 g) of strontium nitrate was added to the titanium-acetylacetone-ethanol solution. After the addition, the mixture was stirred at room temperature for about 1 hour. However, since the hydrolysis reaction proceeded, a yellowish white precipitate was immediately formed, which was unsuitable for a coating solution.

Claims (18)

An aqueous titanium solution comprising titanium and a metal element,
A coordination number with respect to the titanium ion is 6, represented by the following general formula (1), and a first ligand that functions as a bidentate ligand;
Z ₁ —CO—CH ₂ —CO—Z ₂ (1)
(In the formula, Z ₁ and Z ₂ are each independently an alkyl group or an alkoxy group.)
A second ligand which is a carboxylate, a third ligand and a fourth ligand each independently selected from the group consisting of alkoxides and hydroxide ions, and H ₂ O. A fifth complex formed by coordination with a titanium ion;
A metal ion capable of occupying the A site in the perovskite-type titanium oxide;
Water as solvent,
A titanium aqueous solution characterized by comprising at least   2. The titanium aqueous solution according to claim 1, wherein the metal ion capable of occupying the A site in the perovskite-type titanium oxide is a metal element ion selected from the group consisting of Ca, Sr, Ba and Pb.   The titanium aqueous solution according to claim 1 or 2, which is used for producing a perovskite-type titanium oxide film. The titanium aqueous solution according to any one of claims 1 to 3, wherein Z ₁ and Z ₂ are a C _1-6 alkyl group or a C _1-6 alkoxy group. The carboxylate as the second ligand is a group represented by the formula R ¹ —COO ⁻ (wherein R ¹ is a C _1-4 alkyl group), or has 1 to 6 carbon atoms. The aqueous titanium solution according to any one of claims 1 to 4, which is a conjugate base of hydroxy acid or dicarboxylic acid. The third or alkoxide is a fourth ligand, wherein ^R 2 -O ^- (wherein, ^{R 2} is _{C 1-6} alkyl group) is a group represented by the claims 1 to 5 The titanium aqueous solution as described in any one.   The aqueous titanium solution according to any one of claims 1 to 6, wherein the first ligand is acetylacetonate or ethyl acetoacetate.   The second ligand is a conjugate base of a carboxylic acid selected from acetic acid, propionic acid, butyric acid, lactic acid, tartaric acid, oxalic acid, and citric acid, according to any one of claims 1 to 7. Titanium aqueous solution.   The titanium aqueous solution according to any one of claims 1 to 8, wherein the second ligand is an acetate ion which is a conjugate base of acetic acid.   The titanium aqueous solution according to any one of claims 1 to 9, wherein the third ligand and the fourth ligand are isopropoxy groups.   The titanium aqueous solution according to any one of claims 1 to 10, further comprising a second solvent that has a relative dielectric constant lower than that of water, is compatible with water, and is non-alkaline.   The second solvent according to claim 11, wherein the second solvent is at least one selected from the group consisting of a monohydric alcohol, a glycol solvent, an ethylene glycol solvent, a glycerin solvent, a cellosolve solvent, and a carbitol solvent. Titanium aqueous solution.   The coating agent according to claim 12, wherein the second solvent is selected from the group consisting of methanol, ethanol, propanol, and butanol. It is a manufacturing method of the coating agent as described in any one of Claims 1-13,
A titanium precursor and a compound represented by the general formula (1) are mixed to obtain a titanium-acetylacetone complex, and this solution is mixed with an aqueous solution containing carboxylate ions. Further, the obtained solution and an alkali are mixed. After mixing with an aqueous solution containing an earth metal ion, at least comprising mixing a non-alkaline second solvent having a relative dielectric constant lower than that of water and being compatible with water, in some cases. A manufacturing method.   The manufacturing method according to claim 14, wherein the titanium complex is titanium alkoxide or titanium tetrachloride. A method for producing a perovskite oxide film comprising titanium and an alkaline earth metal,
On the base material, the titanium aqueous solution according to claim 1 to 13 is applied,
A production method comprising a step of firing the base material to form a film.   The production according to claim 16, wherein the substrate has an amorphous glass layer on at least a surface thereof, an aqueous titanium solution is applied to the amorphous glass layer, and a perovskite type titanium oxide is formed on the layer. Method. A member obtained by the production method according to claim 17, wherein a film made of a perovskite titanium oxide is directly formed on a glass substrate,
The glass substrate contains at least alkali ions in the vicinity of the surface on which the film is formed,
A member characterized in that the film made of the perovskite type titanium oxide is a dense film having a primary particle diameter of 50 nm or less and a perovskite type oxide.