JPS6144951B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of forming titanium oxide from an alkyl titanate, and more specifically to a method of forming a titanium oxide film by applying an alkyl titanate solution onto a substrate and heat-treating the substrate to remove the solvent and cause a crosslinking reaction. . A titanium oxide thin film is an important component of a transparent conductive film or a selective light transmitting film as a high refractive index dielectric layer. Conventionally, as a method for forming these titanium oxide thin film layers, for example, a vacuum evaporation method, a cathode sputtering method, etc. have been used. However, these methods have drawbacks such as difficulty in forming a thin film of uniform thickness and low productivity. In order to improve these drawbacks, attempts have been made to coat a solution containing an alkyl titanate and obtain a thin titanium oxide layer by heat treatment, etc. However, due to the poor stability of the alkyl titanate to water, However, it was difficult to obtain a uniform and transparent coating layer in the alkyl titanate coating process, and it was difficult to form a desired titanium oxide thin film. Therefore, attempts have been made to convert alkyl titanates into complex salts to obtain stable coating solutions in order to improve their instability with water and ease of handling. For example, there is a method in which acetylacetone or ethyl acetoacetate is added to an alkyl titanate. Forming a complex salt of a titanium compound in this way stabilizes the coating solution and improves the operability of the coating itself, but
The titanium oxide thin film formed by heat-treating the coating layer after coating is not completely converted into the desired titanium oxide component, and the organic compound used to form the complex salt and the alkyloxy component of the raw alkyl titanate are The disadvantage is that it remains and does not allow the formation of a fully satisfactory titanium oxide thin film layer. The present invention focuses on a method of coating an alkyl titanate to form a titanium oxide thin film, in which the alkyl titanate is stable against moisture in the coating process and quickly forms a titanium oxide thin film in the heat treatment process. research,
We have discovered a new method that meets these objectives. That is, the present invention is characterized in that an organic compound having a carbonyl group is added to an alkyl titanate or a solution thereof, and this is heated to remove the solvent and/or cause a crosslinking reaction to form a transparent titanium oxide film. This is a method for manufacturing a transparent titanium oxide film. The coating solution prepared by the method of the present invention is stable against moisture and can be easily coated in a uniform layer on the surface of a glass plate, film, metal plate, etc. in air at room temperature. Furthermore, it has the characteristic that the desired titanium oxide thin film can be quickly formed by heating the coated substrate in, for example, a hot air dryer. Furthermore, by adjusting the concentration and amount of the coating liquid to be prepared, the thickness of the titanium oxide thin film produced can be easily controlled. The alkyl titanate used in the present invention has the general formula Ti _l O _n R _o (where R is an alkyl group,
l, m, n are positive integers). Among the alkyl titanates represented by the above general formula, those where m=3l+1, n=2l+2, and l=1 to 40 are preferably used from the viewpoint of ease of coating. Although the l value may not be uniform and may have a distribution, alkyl titanates having a l value distribution with a maximum value of 25 or less are particularly preferred in coating operations. In the above general formula, R has 1 to 20 carbon atoms.
Preferably. In particular, those having an alkyl group having 2 to 15 carbon atoms are desirable from the viewpoint of film forming operations. When the alkyl titanate reacts with an organic compound having a carbonyl group, some of the titanium atoms become complex titanium, and when it is applied as a solution to the surface of a molded object, most of it becomes a network due to a decomposition reaction and a subsequent condensation reaction. It is thought that titanium oxide has a structure. Examples of the alkyl titanate used in the present invention include tetrabutyl titanate, tetraethyl titanate, tetrapropyl titanate, tetrastearyl titanate, and condensates thereof. By using an alkyl titanate solution modified with an organic compound having a carbonyl group as in the method of the present invention, the coating solution in the coating process can be stabilized and a uniform transparent coating film can be formed. In addition, a titanium oxide thin film is formed by applying heat treatment to the surface of the above-mentioned molded product, but the titanium oxide thin film made from alkyl titanate treated with an organic compound having a carbonyl group according to the present invention has a sufficient network of titanium oxide. Form. As a result, it is characterized by very little organic matter originating from the raw material alkyl titanate and the carbonyl group-containing organic compound component used. Organic compounds having a carbonyl group used in the present invention include aldehydes, ketones and esters. These compounds may have either one carbonyl group or a plurality of carbonyl groups, preferably two carbonyl groups, in the molecule.
However, when it has multiple carbonyl groups,
If each carbonyl carbon is at the 1.3 position and these carbonyl carbons are bonded with a carbon atom containing an active hydrogen, a very stable complex is formed with the alkyl titanate, and the coating solution itself is stable. However, it is difficult to form a transparent titanium oxide film, and a large amount of organic matter ends up remaining in the resulting film. Therefore, a carbonyl-containing compound (that is, a compound having one carbonyl group, or a compound having two carbonyl groups) that forms a complex with appropriate stability as in the present invention.
The bond that connects the carbonyl group of (ke) is a direct bond or a carbon atom that does not have an active hydrogen)
is good in all respects. In the present invention, carbonyl group refers to hydroxyl group (-
It does not contain a carbonyl group directly bonded to (OH), that is, a carboxylic acid group (-COOH), and examples include aldehydes, ketones, and esters as mentioned above. These compounds are preferably compounds that do not easily evaporate during the coating operation, but are easily evaporated and removed during the formation of a titanium oxide thin film by heat treatment after coating. In particular, the boiling point of these compounds is between 50℃ and
200℃ is desirable. When the temperature exceeds 200°C, the content of organic matter in the formed titanium oxide thin film often becomes high. For example, preferred aldehyde compounds include acetaldehyde, propylaldehyde, butyraldehyde, and the like. Further, examples of the ketone compound include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, ethyl propyl ketone, methyl butyl ketone, cyclopentanone, cyclohexanone, and the like. Ester compounds include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate,
Examples include propyl acetate, butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate, diethyl oxalate, dimethyl succinate, and the like. The amount of these carbonyl-containing compounds used in the present invention is preferably such that the carbonyl group equivalent is in the range of 0.05 to 3.0, particularly preferably in the range of 0.1 to 1.0, relative to the titanium atom of the alkyl titanate. Below the lower limit of this range, the effect of treatment with carbonyl compounds is small, and above the upper limit of this range,
The coating solution becomes cloudy or the storage stability of the coating solution is low. Furthermore, the formed titanium oxide film often does not have a sufficient crosslinked (network) structure. Solvents that can be used in forming the film of the present invention are those that sufficiently dissolve the titanium compound for coating, have affinity for the surface of the molded product to be coated, are easy to coat, and are easy to dry after coating. Solvents are preferred. Examples of such solvents include hexane, heptane, cyclohexane, methylcyclohexane, benzene, toluene, xylene, methanol, ethanol, isopropyl alcohol, propyl alcohol, butanol, cyclohexanol, tetrahydrofuran, dioxane, methyl cellosolve, and the like. These solvents may be used alone or in combination of two or more. Adjustment after coating in the present invention can be carried out by adding a predetermined proportion of an organic compound having a carbonyl group to the alkyl titanate, and adding a predetermined amount of a solvent thereto. At this time, the concentration of the applied titanium solution can be appropriately selected depending on the thickness of the finally formed titanium oxide thin film, the application method, the molded object to be applied, etc. For example, in order to uniformly provide a titanium oxide thin film layer with a thickness of several hundred angstroms or less, the concentration is particularly preferably adjusted to 1 to 7.5% by weight. When applying this solution to the surface of a molded article, for example, a dipping method, a spraying method, a method using a coating machine, etc. are used. The desired titanium oxide thin film layer can be obtained by heat-treating the solution at the same time or after coating. This heat treatment is 50~
It takes about 10 seconds to 1 hour at a temperature of 220°C. The effects of forming a titanium oxide thin film by the method of the present invention are as follows. 1. The applied titanium solution becomes stable against moisture and has a longer pot life. 2. As a result of the coating liquid becoming stable, strict control during the coating process is no longer necessary. 3. The titanium oxide thin film formed has a highly transparent network structure with good performance. Examples will be described below. Examples 1 to 4 The following T ₄ is obtained by mixing and reacting the alkyl titanate of T ₁₀ with the organic compound shown in the table below having a carbonyl group, and adding an initial proportion of alkyl titanate to 3.
A coating solution was obtained using the solvents shown in the table below so that the weight percentages were adjusted. This was applied to a polyethylene terephthalate film with a light transmittance of 86% and a thickness of 75 μm and aluminum foil to a thickness of several microns using a bar coater.
A titanium oxide thin film was formed by heat treatment for 2 minutes in a hot air dryer at 130°C. The results obtained are also shown in the table below.

【formula】

【formula】 [However, Bu represents a butyl group. ]

【table】

Claims (1)

[Claims] 1. A method for forming a transparent titanium oxide film by heat-treating an alkyl titanate or a solution containing the same to remove the solvent and/or cause a crosslinking reaction; A method for producing a transparent titanium oxide film, characterized in that the solution contains at least one carbonyl group-containing compound selected from the group consisting of (a) and (b) below. (a) A compound having one carbonyl group [Formula] that is not directly connected to a hydroxyl group (-OH); (b) A compound that has two carbonyl groups [Formula] that is not directly connected to a hydroxyl group (-OH); Compounds in which the carbonyl group is bonded by a direct bond or by one carbon atom without active hydrogen. 2. The method for producing a transparent titanium oxide film according to claim 1, wherein the carbonyl group-containing compound is an ester, aldehyde or ketone compound having a boiling point (normal pressure) of 200°C or lower.