JPS642669B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to tantalum oxide thin film forming compositions. Transparent tantalum oxide films have been widely used in recent years as antireflection coatings for solar cells, optical contrast agents in liquid crystal devices, thin film capacitors, etc., and further demand is expected in the future. As a method for forming a transparent tantalum oxide film on a substrate, the coating method has recently attracted attention due to its economic efficiency, and the method used is to apply a solution of tantalum alcoholate onto the substrate, form a coating film, and then bake it. However, in this method, tantalum alcoholate is easily hydrolyzed by water, and the solution becomes cloudy even with a small amount of water, so it is difficult to obtain a homogeneous coating film even if such a transparent liquid is applied to the substrate. Furthermore, tantalum is expensive, and it is economically necessary to extend the life of the solution. The present inventors completed the present invention as a result of intensive research to find a transparent tantalum oxide film-forming agent that does not have the above drawbacks. In the present invention, tantalum alcoholate (a) and aliphatic oxyacid (b) are dissolved in their common organic solvent (c) in a ratio of (a)/(b) = 1/1 to 5 molar ratio). A tantalum oxide thin film-forming composition characterized in that it consists of a solution in which the reaction product of (a) and (b) in the above ratio is dissolved in an organic solvent (c). This is a tantalum oxide thin film-forming composition. The tantalum alcoholate used in the present invention contains 2 to 50 (TaO) units in addition to the monomer represented by the general formula Ta(OR) ₅ (R is a hydrocarbon group having 1 to 18 carbon atoms).
It shall also include linear or branched polymers containing . Preferred tantalum alcoholates are those in the above general formula in which R has 1 to 4 carbon atoms, and specific examples include pentamethoxytantalum, pentaethoxytantalum, pentaisopropoxytantalum, and penta-n-butoxytantalum. The oxyacids used in the present invention are aliphatic oxyacids such as lactic acid, glycolic acid, oxyacids, hydroxypropionic acid, malic acid, tartaric acid, and citric acid. Among them, lactic acid is particularly disliked. In the present invention, the mixing molar ratio or reaction molar ratio of tantalum alcoholate (a) and aliphatic oxyacid (b) is (a)/(b) = 1/1 to 5, preferably 1/2 to 4.
It is. If the molar ratio of (b) to (a) is less than 1, the desired stability improvement cannot be obtained. Any organic solvent (c) used in the present invention can be used as long as it can dissolve tantalum alcoholate, aliphatic oxyacid, and their reaction products. Examples include aliphatic or aromatic hydrocarbons, alcohols, ethers, esters, halogenated hydrocarbons, and ketones, with alcohols being preferred for ease of handling. The composition of the present invention can be prepared by dissolving tantalum alcoholate in an organic solvent to a predetermined concentration, and then adding an oxyacid;
It is possible to first dissolve the oxyacid in a solvent and then add tantalum alcoholate thereto, or to dissolve both in an organic solvent at the same time. In the present invention, (a) tantalum alcoholate and (b)
The reaction product may be reacted with an oxyacid in advance and the resulting reaction product may be dissolved in an organic solvent. The reaction conditions may generally be 30 minutes to 5 hours at a temperature of 40 to 120°C, and are appropriately selected depending on the types of (a) and (b), the type of solvent, etc. The composition of the present invention is significantly improved in liquid stability compared to an organic solvent solution of tantalum alcoholate, and is also suitable for use on objects on which tantalum thin films are to be formed (metal plates, ceramic plates, glass plates, granular or A tantalum oxide thin film that has excellent physical properties such as transparency and adhesion, and chemical properties such as acid resistance, alkali resistance, and chemical resistance, by coating it on a powdered catalyst carrier and oxidizing it by heating. can be caused to form. As the above-mentioned coating method, any conventional method such as a dipping method, a spray method, or a reduced pressure CVD method can be applied. The present invention will be explained in more detail below by giving examples and comparative examples. Examples 1 to 5 and Comparative Examples 1 to 3 In the formulation shown in Table 1, (a) tantalum alcoholate,
(b) Oxyacid and (c) organic solvent were mixed, and the resulting liquid was placed in a wide mouth bottle and left open in the air at room temperature for 30 days to conduct a stability test of the liquid. The results are shown in Table 1. Also, use the liquid after 30 days as the first
The properties of the obtained tantalum oxide film were measured by visual observation after applying it to a glass plate under the treatment conditions shown in the table, and the results are also shown in Table 1. Similar test results without oxyacid are also listed in the same table as a comparative example. As seen in Table 1, it is recognized that the composition of the present invention has significantly improved liquid stability.

[Table] Examples 6 to 12 In the formulation shown in Table 2, (a) tantalum alcoholate and
(b) The oxyacid was reacted in an organic solvent to obtain an organic solvent solution of the reaction product of (a) and (b). The resulting solution was placed in a wide-mouth bottle and left open in the air at room temperature for 30 minutes.
A stability test was conducted after 1 day. The results are shown in Table 2. Table 2 also shows the results of applying the liquid after 30 days to a glass plate under the treatment conditions shown in Table 2 and measuring the properties of the resulting tantalum oxide film by visual observation. As shown in Table 2, the organic solvent solution of the reaction product of (a) and (b) is stable and can form a transparent and excellent tantalum oxide thin film.

【table】

Claims (1)

[Claims] 1. Tantalum alcoholate (a) and aliphatic oxyacid (b)
and in a ratio of (a)/(b) = 1/1 to 5 (molar ratio),
A tantalum oxide thin film-forming composition comprising a solution dissolved in the common organic solvent (c). 2. The composition according to claim 1, wherein the aliphatic oxyacid is lactic acid. 3 Tantalum alcoholate (a) and aliphatic oxyacid (b)
A tantalum oxide thin film-forming composition comprising a solution of a reaction product of (a)/(b) = 1/1 to 5 (molar ratio) dissolved in an organic solvent. 4. The composition according to claim 3, wherein the aliphatic oxyacid is lactic acid.