JPS6228712B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming a transparent conductive film on a heat-resistant substrate such as glass or ceramics. Transparent conductive films are widely used in electrodes of display devices such as liquid crystal display devices, electroluminescent display devices, and electrochromic display devices. It is also used in solar cells, photovoltaic cells, and anti-fog windows of aircraft and automobiles. Conventionally, there are the following methods for manufacturing transparent conductive films. (a) Vacuum deposition method (b) Sputtering method (c) CVD method (d) Coating method The above methods (a) and (b) have the advantage of producing a transparent conductive film with low resistance, but at the same time Since continuous production is difficult due to the use of a vacuum system, the batch method is adopted, which also has the disadvantage of increasing production costs. Method (c) allows continuous production and may eliminate the drawbacks of methods (a) and (b) above, but it is difficult to control the vapor flow and it is difficult to continuously produce a homogeneous transparent conductive film. The disadvantage is that it is difficult to produce. Although method (d) has the potential to eliminate the above-mentioned drawback, it has the drawback that it is difficult to obtain a low-resistance film using conventionally used materials. An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional techniques and to provide an inexpensive manufacturing method for a transparent conductive film with low resistance that can be put to practical use. In order to produce a transparent conductive film with a low resistance that can be used practically by a coating method, the present invention uses a ditin compound represented by the general formula RSn-SnR (where R is an alkyl group having 1 to 8 carbon atoms) as a doping tin compound. It is characterized by using a compound. In ₂ O ₃ doped with Sn or SnO ₂ doped with Sb are known as transparent conductive films.
The former is generally used because it has lower resistance and can be easily etched for patterning. Doped with Sn by coating method
The materials for producing a transparent conductive film made of In ₂ O ₃ are an indium compound, a tin compound and a solvent. A transparent conductive film obtained by a coating method cannot easily have a resistance low enough to withstand practical use if conventional materials are used. The resistance value of a transparent conductive film obtained by a coating method varies depending on the type of material used, but is most influenced by the type of doping tin compound. For example, when inorganic tin compounds such as stannous chloride (SuCl ₂ ) or stannic chloride (SnCl ₄ ) are used, chlorine tends to remain when baked after coating, causing high resistance. Furthermore, since dimethyltin dichloride ((CH ₃ ) ₂ SnCl ₂ ), which is an organic tin compound, is sublimable, it volatilizes during firing, resulting in high resistance. Further, since tin compounds such as dialkyltin dicarboxylate and trialkyltin monocarboxylate are solid substances, they are difficult to uniformly disperse in the coating film, causing high resistance. Furthermore, tin alkoxides such as tetraethoxytin (Sn(OCH ₂ CH ₃ ) ₄ ) and etramethoxytin (Sn(OCH ₃ ) ₄ ) have the disadvantage that they are easily hydrolyzed and the coating solution tends to become cloudy. As mentioned above, all of the conventionally used doping tin compounds have drawbacks, and the resulting transparent conductive film has a high resistance and is difficult to put into practical use. However, by using the ditin compound according to the present invention, all of the above-mentioned problems of conventional doped tin compounds can be solved, and a transparent conductive film with a practical level of low resistance can be manufactured at low cost by a coating method. In other words, since the ditin compound is a liquid, it is possible to create a coating film that is uniformly dispersed in the indium compound, and since the organic component is completely baked before being volatilized by evaporation or sublimation, it is a transparent conductor with low resistance. membrane can be obtained. In the ditin compound used in the present invention, the alkyl preferably has 1 to 8 carbon atoms. If the number of carbon atoms is larger than this, the density of the resulting transparent conductive film will be impaired and the resistance will be high. The appropriate doping amount is 5 to 30% by weight based on the indium compound. When the doping amount is less than 5%, the resistance value becomes high, and when it is more than 30%, the film tends to become cloudy and the resistance value becomes high. Indium compounds include indium alkoxides such as triethoxyindium (In(OC ₂ H ₅ ) ₃ ), alkylindium alkoxides such as diethoxymonobutyl indium (C ₄ H ₉ In(OC ₂ H ₅ ) ₂ ), tri( Indium carboxylates such as indium mer-ethylhexanoate (In(OCOC ₇ H ₁₅ ) ₃ ) can be used. Further, an indium compound formed from an inorganic indium compound such as indium nitrate or indium chloride and a ligand such as a monocarboxylic acid, a dicarboxylic acid, a hydroxy acid, or a dicarboxylic acid monoester can also be used. Solvents suitable for the present invention include alcohols such as methanol, ethanol, propanol, cellosolve, carbitol, glycols,
Examples include acetone, methyl ethyl ketone, methyl acetate, and ethyl acetate. When using a glass substrate, the firing temperature is preferably 300 to 700°C. temperature is 300
If it is lower than ℃, the combustion of organic matter is incomplete, and
If the temperature is higher than 700℃, the glass will deform. When using a ceramic substrate such as alumina, a firing temperature of 300°C or higher is suitable. Next, the present invention will be explained by examples. Examples 1 to 7 Indium octylate, ditin compound, and ethyl cellosolve were each weighed in amounts shown in Table 1 to prepare a coating solution. This coating solution was applied onto a glass substrate using a spinner, and after drying,
It was baked at ℃ for 1 hour. The sheet resistance value and film thickness of the obtained transparent conductive film are shown in Table 1.

[Table] Example 8 Triethoxyindium (15g), hexamethylditine (1.5g), ethyl cellosolve (100g)
A coating solution was prepared from the above, and then a transparent conductive film was formed in the same manner as in Examples 1 to 7. The sheet resistance value is
The resistance was 0.8KΩ/□, and the film thickness was 710Å. Examples 9 to 15 Indium nitrate, a ligand, hexamethylditine, and ethyl cellosolve were weighed in amounts shown in Table 2 to prepare a coating solution. Then, a transparent conductive film was formed in the same manner as in Examples 1 to 7. Example 16 A coating solution was prepared from indium octylate (15 g), hexamethylditine (1.5 g), and ethyl cellosolve (100 g). This coating liquid was applied onto an alumina substrate using a spinner, and then baked at 900°C for 10 minutes. The sheet resistance value of the obtained transparent conductive film was 0.4Ω/□.

[Table] According to the present invention, a practically usable, low-resistance transparent conductive film can be manufactured at low cost, and it has great industrial significance.

Claims (1)

[Claims] 1 After applying a solution containing an indium compound, a ditin compound represented by the general formula RSn-SnR (where R is an alkyl group having 1 to 8 carbon atoms), and an organic solvent as essential components onto a substrate, this is heated. A transparent conductive film forming method characterized by the following.