JPH07121817B2 - Zirconium oxide-based precursor gel and its production method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precursor gel-like material for producing a zirconium oxide thin film which can be stored for a long period of time, and a method for producing the same.

[0002]

2. Description of the Related Art Stabilized zirconium oxide thin films doped with zirconium oxide and yttrium oxide, calcium oxide, magnesium oxide, etc. as stabilizers have been utilized for various purposes as alkali resistant and abrasion resistant films.
Further, the transparent thin film is used as a high refractive index thin film as a component of a selective light reflecting coating or a selective light transmitting coating. As a method for producing these zirconium oxide-based thin films, a solution containing a metal alkoxide is applied to a molded article because of its advantages such as high productivity and low apparatus cost.
A method of forming an oxide thin film has been proposed.

However, since zirconium alkoxide undergoes hydrolysis and condensation very rapidly, the stability of the solution against water and moisture is poor, and zirconium oxide hydrate is easily hydrolyzed as shown in the following chemical reaction formula. It forms and precipitates.

Embedded image Zr (OR ′) ₄ + H ₂ O → ZrO (OR ′) ₂ + R′OH (1) 2ZrO (OR ′) ₂ → ZrO ₂ ↓ + Zr (OR ′) ₄ (2)

Therefore, it was difficult to obtain a uniform and transparent coating layer when the solution was coated. Therefore, it is necessary to strictly control the moisture during application, or to form a chelate for a part or all of the alkoxy groups of the alkoxide,
For example, a method has been proposed in which the solution is stabilized by significantly suppressing hydrolysis by substituting it with acetylacetone or the like.

However, the thin film formed by using this solution contains a large amount of unreacted alkoxy groups and groups substituted with alkoxy groups because hydrolysis-polycondensation has not progressed sufficiently, and the thin film formed by heating is oxidized. In the case of obtaining a physical thin film, there is a problem that a dense film cannot be formed due to pinholes and cracks generated by the decomposition of these groups.

Further, even if hydrolysis is suppressed by using the above method, a solution containing zirconium alkoxide having an unreacted alkoxy group is subjected to hydrolysis-polycondensation when left in the atmosphere for a long time. As a result, the viscosity of the solution changes and precipitates are produced. Therefore, in order to store this solution for a long period of time, there is a problem that a solution storage device whose atmosphere is controlled is necessary.

[0007]

The problem to be solved by the present invention is that the zirconium oxide-based precursor prepared from zirconium alkoxide has poor stability to moisture, and, moreover, it is That is, a large amount of residual organic substances that cause pinholes and cracks are present in the precursor. Another problem to be solved is that the zirconium oxide-based precursor has a large amount of unreacted alkoxy groups, and thus lacks stability and cannot be stored for a long period of time.

[0008]

As a means for solving the above problems, zirconium alkoxide is reacted with a small amount of carboxylic acid and a small amount of ethanolamine,
Part of the alkoxy group of the alkoxide, OCOR group and O
By substituting a (CH ₂ ) ₂ NH ₂ group, the hydrolysis rate is controlled, and by slow hydrolysis-polycondensation of the compound as represented by the following chemical reaction formula,
By rapid hydrolysis-condensation if not controlled, as described above.
A transparent zirconium oxide-based precursor polymer gel having Zr-O-Zr bonds without unreacted alkoxy groups, which is completely different from the precipitation products from the formulas (1) and (2), is provided. The main feature.

Embedded image Zr (OR ′) _4-xy (O (CH ₂ ) ₂ NH ₂ ) _x (OCOR) _y + H ₂ O → Zr (OR ′) _3-xy (O (CH ₂ ) ₂ NH ₂ ) _x (OCOR) _y (OH) + R'OH (3) 2Zr (OR ') _3-xy (O (CH ₂ ) ₂ NH ₂ ) _x (OCOR) _y (OH) → (OR') _3-xy ( _{O (CH 2) 2 NH 2} ) x (OCOR) y Zr-O-Zr (OR ') 3-xy (O (CH 2) 2 NH 2) x (OCOR) y + H 2 O ...... (4)

By using the solid polymer gel material, it was possible to achieve the purpose of obtaining a zirconium oxide-based precursor which is extremely stable against moisture in the air for a long period of time.
Further, a solution in which this gel-like material is dissolved is also very stable, and by applying this solution, the purpose of obtaining a zirconium oxide-based thin film with almost no residual organic matter was realized.

[0010]

The alkyl group of the zirconium alkoxide used in the present invention preferably has 4 or less carbon atoms from the viewpoint of easy availability and easy handling. As carboxylic acid,
To reduce the amount of residual carbon in the precursor gel,
The following are preferred. Further, ethanolamine also replaces the alkoxy group of the alkoxide and remains in the gel even after gelation. Therefore, it is better that the amount of carboxylic acid and ethanolamine is smaller (carboxylic acid + ethanolamine)
/ Zirconium alkoxide ≦ 2 [mol ratio] is desirable. The role of ethanolamine is to control the hydrolysis of alkoxides like carboxylic acids, but O (CH
₂ ) Since the bond between the ₂ NH ₂ group and Zr is stronger and more stable than that in the OCOR group and Zr, it is considered that the gel is further stabilized as compared with the case where only the carboxylic acid is used. As the organic solvent, alcohols having 5 or less carbon atoms are desirable from the viewpoint of solubility with water or alkoxide.

To prepare the zirconium oxide precursor gel, zirconium alkoxide and ethanolamine are first heated and refluxed in an organic solvent. Next, a mixed solution of acetic acid and water is added to this solution and stirred. In the case of preparing the zirconium oxide-based complex oxide precursor gel, an acetic acid aqueous solution is further added with an acetate salt (or nitrate salt) and optionally nitric acid of the metal and added dropwise to the alkoxide solution. After that, by allowing to stand at room temperature, hydrolysis-polycondensation proceeds, and gelation occurs while maintaining transparency. By gelling, a sufficiently polymerized precursor was obtained, which enabled long-term storage. To prepare a solution for forming a thin film from this gel-like material,
All that is required is to put the gel in an organic solvent, add a small amount of acetic acid, and stir. A dense ZrO ₂ -based ceramic thin film can be easily obtained by applying this solution to a substrate, drying and firing.

[0012]

Example 1 1 mol / zirconium n-proxide
The mixture was diluted with n-butyl alcohol to give l, ethanolamine (zirconium alkoxide / ethanolamine = 1 [mol ratio]) was added, and the mixture was refluxed for 24 hours. While stirring this solution in a beaker, a mixed solution of acetic acid (acetic acid / zirconium alkoxide = 1 [mol ratio]) and water (water / zirconium alkoxide = 1.5 [mol ratio]) was added dropwise, and then for 1 hour. Stirring was continued. The beaker was sealed with a film and allowed to stand. By reaction of ethanolamine and acetic acid with an alkoxy group of alkoxide and hydrolysis-polycondensation, O (CH ₂ ) ₂ NH ₂ group and OCOCH ₃ group are contained in a side chain, and Zr-O-Zr bond is formed as a main chain. A polymer was formed, and the viscosity of the solution increased with time, and after mixing, gelation was carried out within a few days to give a transparent zirconium oxide precursor gel. When the beaker containing the gel-like substance was left as it was, the gel-like substance did not change even after 3 months.

[0013]

Example 2 1 mol of zirconium n-propoxide
/ L was diluted with n-butyl alcohol, ethanolamine (zirconium alkoxide / ethanolamine = 1 [mol ratio]) was added, and the mixture was refluxed for 24 hours.
While stirring this solution in a beaker, acetic acid (acetic acid / zirconium alkoxide = 1 [mol ratio]), calcium nitrate (calcium / zirconium = 0.11 [atomic ratio]), water (water / zirconium alkoxide = 1.5).
[Mole ratio]) was added dropwise, and stirring was continued for 1 hour thereafter. The beaker was sealed with a film and allowed to stand.
Zr has an O (CH ₂ ) ₂ NH ₂ group and an OCOCH ₃ group in its side chain by the reaction of ethanolamine and acetic acid with an alkoxy group of an alkoxide, and further by hydrolysis-polycondensation.
A polymer having an r-O-Zr bond as a main chain was formed, the viscosity of the solution increased with time, and gelled within several days after mixing. In the solution, calcium nitrate is dissolved and uniformly dispersed, and after gelation, calcium ions are uniformly dispersed in the gelled material. By this operation, a calcium oxide-doped zirconium oxide precursor gel in which calcium was uniformly dispersed was obtained.

[0014]

Example 3 Zirconium n-propoxide (1 mol)
/ L was diluted with n-butyl alcohol, ethanolamine (zirconium alkoxide / ethanolamine = 1 [mol ratio]) was added, and the mixture was refluxed for 24 hours.
This solution was mixed with yttrium acetate (yttrium / zirconium = 0.185 [atomic ratio]) dried at 110 ° C. and further refluxed. While stirring this solution in a beaker, acetic acid (acetic acid / zirconium alkoxide = 1.
5 [mol ratio]) and nitric acid (nitric acid / yttrium acetate = 4)
[Mol ratio]) and water (water / zirconium alkoxide =
2 [mol ratio]) of the mixed solution was added dropwise, and then for 1 hour,
Stirring was continued. The beaker was sealed with a film and allowed to stand. OCOC of ethanolamine and yttrium acetate
H ₃ group and the reaction of the added acetic acid with the alkoxy group of the alkoxide, and further, by hydrolysis-polycondensation, having an O (CH ₂ ) ₂ NH ₂ group and an OCOCH ₃ group in the side chain, Z
A polymer having an r-O-Zr bond as a main chain was formed, the viscosity of the solution increased with time, and after mixing, gelation occurred within a few days to obtain a yttrium oxide-doped zirconium oxide precursor gel.

A part or most of the OCOCH ₃ groups of yttrium acetate are coordinated with the zirconium alkoxide by refluxing, and the yttrium ions are uniformly dispersed in the solution. Further, yttrium acetate has a not so high solubility in an alcohol solvent and recrystallizes when the solution is left for a long time. Therefore, by adding nitric acid, a part or most of the OCOCH ₃ groups of yttrium acetate are replaced with NO ₃ groups. This prevents recrystallization. By this operation, a zirconium oxide precursor gel material in which yttrium was uniformly dispersed was obtained. When the beaker containing the gel-like substance was left as it was, the gel-like substance did not change at all even after 3 months.

[0016]

Example 4 A gel-like product was prepared under the same conditions as in Example 1 except that n-butyric acid was used as the carboxylic acid instead of acetic acid. Even after the mixed solution of n-butyric acid and water was added dropwise to the alkoxide solution, the solution was transparent. After a few weeks, the solution gelled and a zirconium oxide precursor gel was obtained. When the number of carbon atoms in the carboxylic acid is increased, hydrolysis is further suppressed, resulting in a longer gelation time.

[0017]

Reference Example Using the zirconium oxide-based precursor gels obtained in Examples 1 and 3, acetic acid: ethanol: gels = 0.4: 5: 10 [weight ratio] Weighed, and the gel-like material was mixed with a mixed solution of acetic acid and ethanol. Then, the gel-like substance was completely dissolved by ultrasonic stirring. These solutions were applied on a glass substrate and heat-treated at 500 ° C. to obtain a transparent and dense zirconium oxide thin film. In addition, even if the solution thus prepared was left in the atmosphere for 6 months, no change in viscosity and no change in precipitation was observed.

[0018]

As described above in the Examples, in the present invention, hydrolysis is controlled by the addition of a small amount of ethanolamine and a carboxylic acid to slowly and sufficiently hydrolyze.
By causing polycondensation, rapid hydrolysis of zirconium alkoxide-precipitation of ZrO ₂ hydrate due to polycondensation is suppressed, oxidation having a Zr-O-Zr network and containing almost no unreacted alkoxy group. By forming a zirconium-based precursor gel-like material, a precursor that was not affected by moisture in the atmosphere, which was previously impossible, can be stably and for a long period of time.
It became possible to save. In addition, as described in Reference Example, by dissolving the gel-like material of the present invention in an organic solvent, it is difficult to obtain a solution for forming a thin film having extremely high stability, which was difficult by the conventional method. Became possible. Furthermore, by applying this solution to a molded product and firing it, a dense and transparent zirconium oxide-based thin film, which was difficult due to the effect of residual organic substances, can be obtained from the conventional thin film-forming solution. This greatly expands the use of thin films as optical materials.

Claims (6)

[Claims] 1. A Zr—O—Zr bond as a main chain, and an OCOR group (wherein R represents a linear or branched alkyl group having 1 to 4 carbon atoms) and O (CH ₂ ) in the side chain. ) ₂ N
A zirconium oxide precursor gel, which is composed of a polymer having H ₂ groups. _2. A polymer having a Zr—O—Zr bond as a main chain and having an OCOR group and an O (CH ₂ ) ₂ NH ₂ group in a side chain and Y, La, Mg, Ca, Sr, and Ba, A zirconium oxide-based composite oxide precursor gel containing one or more metal ions. 3. Zr (OR ′) ₄ (wherein R ′ represents a linear or branched alkyl group having 1 to 4 carbon atoms), RCOOH, ethanolamine and water are mixed in an organic solvent, The method for producing a zirconium oxide precursor gel-like product according to claim 1, wherein the reaction is carried out. 4. The method according to claim 2, wherein Zr (OR ') ₄ , RCOOH, ethanolamine, water, M (OCOCH ₃ ) _n and nitric acid are mixed and reacted in an organic solvent. Method for producing zirconium oxide-based precursor gel-like material. (M is Y, La, Mg, Ca, Sr,
Indicates either Ba. n represents the valence of M. ) 5. Zirconium oxide according to claim 2, wherein Zr (OR ') ₄ , RCOOH, ethanolamine, water and M (NO ₃ ) _n are mixed and reacted in an organic solvent. Method for producing gel-like precursor. 6. The production method according to claim 3, claim 4 or claim 5, wherein the organic solvent is an alcohol having 1 to 5 carbon atoms.