JP3245919B2 - Coating solution for forming insulating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating liquid for forming an insulating film, and more particularly to a coating liquid for forming a transparent insulating film in a liquid crystal cell.

[0002]

2. Description of the Related Art As a method for forming an insulating film on a substrate, a vapor phase growth method and a coating method are known. With respect to the transparent insulating film in a liquid crystal cell, a coating method has attracted attention because the device is simple and suitable for upsizing, and a method using a coating solution containing titanium alkoxide or silicon alkoxide has been put to practical use.

[0003] In this case, it is necessary to satisfy conditions such as not containing impurities that impair the insulating property, being transparent, and having a refractive index equivalent to that of liquid crystal. It is known that the refractive index is controlled by changing the molar ratio of the TiO ₂ —SiO ₂ based composite oxide.
Therefore, many proposals have been made on a method of forming a TiO ₂ —SiO ₂ based composite oxide film by an alkoxide method.

Japanese Patent Application Laid-Open No. 55-25487 discloses M
(OR) ₄ (M: Ti, 0-100 wt%, Si, 0
Alkoxide, H ₂ O (M (O
R) ₄ (1.7-4 moles per mole), a clear solution comprising an alcohol and an acid is disclosed. The addition of less than the theoretical amount of complete hydrolysis of M (OR) ₄ prevents the formation of coarse precipitates, and the addition of acid disperses the fine particles to make them transparent.
By spin-coating this solution, a film thickness of 200 to
1000 ° (after baking at 400 ° C.), refractive index 1.4 to 2.4
Is obtained.

JP-A-55-34258 discloses a silica-based reaction product obtained by reacting a mixture of an alkoxysilane, a lower carboxylic acid and an alcohol in the presence of an organic acid-based reaction accelerator. A coating solution for coating is disclosed. In this reaction system, the lower carboxylic acid reacts with the alcohol released during the hydrolysis of the alkoxide to form an ester, and the organic acid-based reaction accelerator has the effect of accelerating the reaction. By spin-coating this coating solution, a film having a thickness of 650 to 4200 ° (after baking at 500 to 700 ° C.) is formed.

Japanese Patent Application Laid-Open No. Sho 57-64212 discloses an insulating coating having a composition of TiO ₂ —SiO ₂ based oxide formed by firing a mixture of an organic titanium compound and an organic silicon compound to which oxygen is directly bonded. Is disclosed. Examples of the organic titanium compound include tetraoctylene lenitate, tetrastearyl titanate, and titanium oxyacetylacetonate, and examples of the organic silicon compound include vinyl tris (2-methoxyethoxy) silane. A paste is prepared by adding a viscous agent and a solvent to the paste, and a paste is prepared.
The thickness of the film obtained by the printing method is 900-1000Å.
(After baking at 500 ° C.).

Japanese Patent Application Laid-Open No. 54-43241 discloses a method of forming a film by adding water to a titanium alkoxide, polymerizing the solution, and applying a solution stabilized using a chelating agent such as acetylacetone. ing. As chelating agents, β-diketones, α or β-ketones, esters of α or β-oxy acids, α or β-oxyketones, α or β-oxyaldehydes, α-amino acids, α And β-amino alcohols and the like. After immersing the glass plate in the solution of this reference and lifting it up,
By firing at 500 ° C., 2000 ° TiO 2
_Two films are obtained.

[0008]

In the case of mass production in the coating method, the coating liquid is exposed to the atmosphere for a long time. During that time, the solution components may be altered by absorbing moisture in the atmosphere, and thus there is a problem that the pot life of the coating solution is limited. Among alkoxides, titanium alkoxide is particularly liable to be altered (hydrolyzed) by moisture, and stabilizing the alkoxide has been a problem. Also,
It has been found by experiments of the present inventors that silicon alkoxides, which are relatively stable, also become unstable in the presence of titanium.

Regarding the alteration due to moisture in the atmosphere, none of JP-A-55-25487, JP-A-55-34258 and JP-A-57-64212 have not been solved. Furthermore, the presence of an acid is not preferred because the acid has a corrosive effect on the electrodes of the liquid crystal cell. JP-A-54-43
The method disclosed in Japanese Patent No. 241 is stabilization of a titanium alkoxide alone, and does not describe a coexistence system with a silicon alkoxide.

[0010]

SUMMARY OF THE INVENTION In view of the above circumstances, the present inventors have developed a coating film which is stable to atmospheric moisture, contains no corrosive acid, and has a relatively low temperature. As a result of intensive studies on the coating solution to be formed, the present inventors have found an additive (acetylacetone) which dramatically improves the stability of alkoxides, especially titanium alkoxides and silicon alkoxides, in coexistence with respect to moisture, and have completed the present invention. Was.

That is, in the present invention, the structural unit has the general formula (1)

Embedded image And general formula (2)

Embedded image (Wherein, R ^{1 to} R ⁴ are the same or different,
Consist C ₁ represents an alkoxy group or acetylacetone residue of -C _8), the content of acetylacetone residue [(Ti moles of) × 4 + (number of moles of Si) moles ≧ of × 4 ≧ acetylacetone residue (Mol number of Ti) × 2 +
(Mol number of Si) × 1].
A coating solution for forming an insulating film, comprising an alcohol solution (having an alkyl group of C _{3 to} C ₈ ) of a compound.

Hereinafter, the present invention will be described in detail. Generally, chelating agents such as acetylacetone and ethyl acetoacetate are known to improve the hydrolysis stability of titanium alkoxide. It is said that two oxygens coordinate to Ti to form a chelate. Usually, the ratio of acetylacetone to 1 mole of Ti is 1 to
2 mol, and commercially available titanium acetylacetonate and titanium oxyacetylacetonate are 2 mol per 1 mol of Ti.

[0013] Silicon alkoxides are not easily hydrolyzed, and in the studies using the conventional sol-gel method, studies on catalysts that promote hydrolysis have been actively conducted. Little literature. Therefore, for the purpose of the present invention, it is necessary to improve the hydrolytic stability of silicon alkoxide in an open-to-air system. Thus, the present inventors have found that acetylacetone, which is effective for improving the hydrolysis stability of titanium alkoxide, is also effective for silicon alkoxide.

Si has no d-orbital electrons and is difficult to form a chelate.
It is clear that the OC bond is protected. This will be elucidated by future research.

The polymetalloxane chelate compound containing Ti and Si according to the present invention has a structural unit represented by the general formula (3):

Embedded image And general formula (4)

Embedded image (Wherein, X ^{1 to} X ⁴ are the same or different,
(Representing an alkoxy group of C _{1 to} C ₈ ) and acetylacetone by mixing such that the molar ratio of Ti, Si, and acetylacetone residues satisfies the following formula.

(Mol number of Ti) × 4 + (mol number of Si)
× 4 ≧ mol number of acetylacetone residue ≧ (mol number of Ti) × 2 + (mol number of Si) × 1

The solution thus obtained can be used as it is or after adjusting the concentration to a more appropriate one as needed.

The polymetalloxan chelate compounds containing Ti and Si are represented by the general formula TiY _n X _4-n and the general formula SiX ₄ (where n = 0, 1 or 2, Y is an acetylacetone residue, X Represents a C ₁ -C ₈ alkoxy group)
If necessary, acetylacetone is further added to the mixed solution of the organotitanium compound and silicon alkoxide consisting of so that the total amount of acetylacetone satisfies the following formula. It can also be manufactured by adding.

(Mol number of Ti) × 4 + (mol number of Si)
× 4 ≧ mol number of acetylacetone residue ≧ (mol number of Ti) × 2 + (mol number of Si) × 1

The ratio of Ti to Si in the polymetalloxane chelate compound of the present invention is such that Si mole is
The range is from 10 mol to 1000 mol, preferably from 10 mol to 500 mol of Si per 100 mol of Ti.

Examples of the alkyl group in the C ₁ -C ₈ alkoxy group include methyl, ethyl, iso-propyl, n-
Butyl, sec-butyl, iso-butyl, tert-
Examples thereof include butyl, n-amyl, sec-amyl, tert-amyl, and 2-ethyl-butyl.

As the solvent for dilution, an alcohol having a C ₃ -C ₈ alkyl group is used, and a C ₄ -C ₆ alcohol is particularly preferred.

As a method for forming a coating film of a coating solution, a usual coating method, for example, a dipping method, a spin coating method, or the like can be used. After coating, the solvent is evaporated and heated to about 150 ° C. or higher to form a transparent film.

[0024]

The coating solution for forming an insulating film of the present invention is stable against moisture, has a long pot life, and has an advantage that it does not contain an acid and thus has no corrosiveness. Things.

[0025]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Note that “%” used in Examples means “% by weight”. Also,
ACAC acetylacetone, an n- butyl group Bu ^n,
The ethyl Et, abbreviated an iso- propyl group and Pr ^i.

[0026] Example _{^{1 Ti (OBu n) 4 0.681g}} ( molar ratio _{1) Si (OEt) 4 0.417g} ( molar ratio 1) Bu ⁿ OH consisting 0.746g solution H ₂ O 0.058 g ( molar ratio 1.6) Bu ⁿ OH consisting 2.842g was added and after standing for 1 day, ACAC 0.800 g (molar ratio 4) was added. Solid content of this liquid (in terms of TiO ₂ and SiO ₂ )
Is 5.0%. This solution was transparent yellow immediately after preparation, but became transparent yellow brown one day later, indicating that the polymerization had proceeded. Even when this solution was sealed and allowed to stand at room temperature for 30 days, no precipitation or gelation occurred. A part of this solution was placed in a glass bottle having an inner diameter of 9 mm, and was left still in a desiccator filled with water at the bottom (left open in wet air). As a result, no change was observed for 14 days. This solution was used as a coating solution, and after dipping a glass plate, the glass plate was pulled up at a rate of 15 mm / min.
After air drying, baking was performed at 300 ° C. According to SEM observation, it was a smooth film having a thickness of 0.2 μm and no cracks. The refractive index was 1.83.

[0027] consists of Example _{^{2 Ti (OBu n) 4 0.681g}} ( molar ratio _{1) Si (OEt) 4 0.417g} ( molar ratio 1) ACAC 0.800 g (molar ratio 4) Bu ⁿ OH 0.746g solution H ₂ O 0.058 g (molar ratio 1.6) Bu ⁿ OH consisting 2.842g solution was added and allowed to stand for 1 day. This solution did not undergo precipitation or gelation even when sealed and allowed to stand at room temperature for 30 days, and did not change at all when allowed to stand still in wet air for 14 days. This solution was used as a coating solution, and after dipping a glass plate, 1
It was pulled up at 5 mm / min, fired at 300 ° C. after air drying.
According to SEM observation, it was a smooth film having a thickness of 0.2 μm and no cracks.

[0028] Example _{^{3 Ti (OBu n) 4 0.681g}} ( molar ratio _{1) Si (OEt) 4 0.417g} ( molar ratio 1) ACAC 0.600 g (molar ratio 3) consisting Bu ⁿ OH 0.946 g solution H ₂ O 0.058 g (molar ratio 1.6) Bu ⁿ OH consisting 2.842g solution was added and allowed to stand for 1 day. This solution did not undergo precipitation or gelation even when sealed and allowed to stand at room temperature for 30 days, and did not change at all when allowed to stand still in wet air for 14 days.

[0029] Example _{^{4 Ti (OBu n) 4 0.681g}} ( molar ratio _{1) Si (OEt) 4 0.209g} ( molar ratio 0.5) ACAC 0.600 g (molar ratio 3) Bu ⁿ OH 1.854g consisting of a solution in H ₂ O 0.044 g (molar ratio 1.2) Bu ⁿ OH consisting 2.156g solution was added and allowed to stand for 1 day. This solution did not undergo precipitation or gelation even when sealed and allowed to stand at room temperature for 30 days, and did not change at all when allowed to stand still in wet air for 14 days.

Example 5 0.681 g (molar ratio 1) Ti (OBu ⁿ ) ₄ 0.626 g (molar ratio 1.5) Si (OEt) ₄ 1.000 g ACAC (molar ratio 5) 2.872 g Bu ⁿ OH consisting of a solution in H ₂ O 0.073 g (molar ratio 2) Bu ⁿ OH 0.292g consisting of a solution, and the mixture was allowed to stand for 1 day. This solution did not undergo precipitation or gelation even when sealed and allowed to stand at room temperature for 30 days, and did not change at all when allowed to stand still in wet air for 14 days. This solution was used as a coating solution, and after dipping a glass plate, 1
It was pulled up at 5 mm / min, fired at 300 ° C. after air drying.
According to SEM observation, it was a smooth film having a thickness of 0.2 μm and no cracks. The refractive index was 1.71.

[0031] consists of Example _{^{6 Ti (OBu n) 4 0.681g}} ( molar ratio _{1) Si (OEt) 4 0.417g} ( molar ratio 1) ACAC 0.800 g (molar ratio 4) Bu ⁿ OH 1.846g solution H ₂ O 0.360 g (molar ratio 10) Bu ⁿ OH consisting 1.440g solution was added and allowed to stand for 1 day. This solution did not undergo precipitation or gelation even when sealed and allowed to stand at room temperature for 30 days, and did not change at all when allowed to stand open in humid air for 14 days.

Example 7 Ti (OPr ⁱ ) ₄ 4.0 g EBA 50.0 g (where EBA is an abbreviation for 2-ethyl-1-butanol)
Was placed in a flask, heated and distilled under atmospheric pressure to distill off most of the solvent, thereby obtaining 8.238 g of a residual liquid. 6 in terms of TiO ₂ was diluted by adding EBA8.54g thereto.
67%. 2.390 g of the diluent (molar ratio 1) 0.417 g of Si (OEt) ₄ (molar ratio 1) 0.860 g of ACAC (molar ratio 4) 0.360 g of H ₂ O (molar ratio 10) EBA 1 A solution consisting of .440 g was added and left for 1 day. This solution did not undergo precipitation or gelation even when sealed and allowed to stand at room temperature for 30 days, and did not change at all when allowed to stand still in wet air for 14 days.

Example 8 In Example 7, tert-AmOH was used instead of EBA.
Distillation was carried out in the same manner using 50 g of (tert-amyl alcohol) to obtain 7.443 g of a residual liquid. This is tert-
8.468 g of AmOH was added, and 6.6 in terms of TiO ₂ was added.
7%. 1.327 g (molar ratio 1) of the above-mentioned diluent 0.417 g (molar ratio 1) of Si (OEt) ₄ 0.800 g (molar ratio ₄ ) of ACAC 0.860 g of tert-AmOH 0.360 g of H ₂ O ( Molar ratio: 10) A solution consisting of 1.440 g of tert-AmOH was added and left for 1 day. This solution did not undergo precipitation or gelation even when sealed and allowed to stand at room temperature for 30 days, and did not change at all when allowed to stand open in humid air for 14 days.

Example 9 Titanium butoxide tetramer was used as a titanium alkoxide. Bu ⁿ O [Ti (OBu ⁿ⁾ ₂ O] ₄ Bu ⁿ 0.48
5 g (molar ratio _{1) Si (OEt) 4 0.417g} ( molar ratio 1) ACAC 0.800 g (molar ratio 4) Bu ⁿ OH consisting 3.477g solution H ₂ O 0.072 g (molar ratio 2) Bu ^A solution consisting of 0.293 g of nOH was added and left for 1 day. This solution did not undergo precipitation or gelation even when sealed and allowed to stand at room temperature for 30 days, and did not change at all when allowed to stand open in humid air for 14 days. This solution was used as a coating solution, and after dipping a glass plate, 1
It was pulled up at 5 mm / min, fired at 300 ° C. after air drying.
According to SEM observation, it was a smooth film having a thickness of 0.2 μm and no cracks.

Comparative Example 1 A solution was prepared in exactly the same manner as in Example 2 except that the amount of ACAC was changed to 0.400 g (molar ratio 2), and the solution was allowed to stand for one day. This solution did not form a precipitate nor gelled even when it was sealed and allowed to stand at room temperature for 30 days, but gelled after 7 days when left open in moist air.

Comparative Example 2 A solution was prepared in the same manner as in Example 2 except that no ACAC was added, and the solution was allowed to stand for one day. The solution gelled after one day in the sealed standing.

COMPARATIVE EXAMPLE 3 In Example 2, Ti (OBu ⁿ ) ₄ and ACAC
Was prepared in exactly the same manner as in Example 2 except that no was added, and the solution was left for one day. This solution did not form a precipitate nor gelled even when it was sealed and allowed to stand at room temperature for 30 days, but gelled after 7 days when left open in moist air.

[0038]

[Table 1]

Claims (2)

(57) [Claims] (1) The structural unit has a general formula (1) And general formula (2) (Wherein R ^{1 to} R ⁴ are the same or different,
_{1 to} C ₈ alkoxy group or acetylacetone residue), and the content of acetylacetone residue is [(T
(mol number of i) × 4 + (mol number of Si) × 4 ≧ mol number of acetylacetone residue ≧ (mol number of Ti) × 2 + (mol number of Si) × 1] (C ₃ having an alkyl group of -C ₈₎ insulating film-forming coating liquid, characterized by comprising. (2) The alcohol in the alcohol solution is C _Four ~ C ₆ of
2. The alcohol according to claim 1, which is an alcohol having an alkyl group.
Coating solution for forming edge coating.