JPH0221082B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composition for forming a transparent conductive film on a substrate such as a glass plate. Transparent conductive films are widely used as transparent electrodes for liquid crystal display devices, electroluminescence devices, etc., and as anti-frost and anti-fog films for window glass of automobiles, aircraft, buildings, etc. Conventionally, transparent conductive films made of tin oxide, tin oxide-antimony oxide, or indium oxide-tin oxide have been formed by vacuum evaporation, sputtering, CVD, etc., but all of these methods have a low raw material utilization rate. It was not suitable for mass production because of its low yield and expensive manufacturing equipment. Therefore, attempts have been made to develop a method suitable for mass production that has a high raw material utilization rate and can form a transparent conductive film using a simple device. A tin compound or a tin compound and an antimony compound are dissolved in a suitable solvent, the solution is applied to the surface of the substrate by brushing, dipping, spraying, etc. at room temperature, and then the coating film is baked to form a transparent conductive film. The method is attracting attention. Antimony is added to increase the conductivity of the film.
For example, US Pat. No. 2,118,795 describes a method using an aqueous solution containing stannic chloride and hydrochloric acid as a coating liquid. However, this method requires 600~
The high temperature of 750℃ is necessary, and for that reason,
There have been problems in that the substrate such as glass may be damaged and the formed film has insufficient light transmittance. Also, in JP-A No. 55-10466,
Tin tetraalkoxide (Sn
A method using an organic solvent solution containing (OR) ₄ ) and a small amount of an antimony compound is described. According to this method, a transparent conductive film with good transparency, film adhesion, film strength, and conductivity can be formed.
It had a major practical drawback: the coating solution was unstable and the pot life was short. That is, this coating solution can be stored for at most 30 minutes even when placed in a sealed storage container.
It becomes unusable because precipitation occurs within a few days, and if it is exposed to air during coating, it gradually produces precipitation, which hinders coating operations. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a coating composition that can form a conductive film having good properties, and is highly stable and has a long pot life, making it highly practical. . The present inventors have found that this problem can be solved by using alkoxytin chloride as a tin compound, which is one of the main components, and adjusting the composition of the coating liquid. That is, the present invention provides the formula SnClx(OR) _4-x [where,
R represents an alkyl group, x is an integer of 1 to 3], an antimony compound, a suitable organic solvent, and water; content of the tin compound; is SnO ₂ per organic solvent
The amount of tin and antimony in the composition does not exceed 200 g in terms of SnO ₂ and Sb ₂ O ₃ respectively.
When converted as Sb ₂ O ₃ / (SnO ₂ +
A transparent conductive film in which the weight ratio of Sb ₂ O ₃ ) is in the range of 0.01 to 0.15, and the amount of water is 0.1 to 10% by weight of the amount of organic solvent, and is completely compatible with the organic solvent. A forming composition is provided. The tin compounds used in the present invention include monoalkoxytin trichloride, dialkoxytin dichloride, trialkoxytin monochloride, where the alkoxy group has 1 to 10 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl,
Nonyl and decyl are preferred. The concentration of the tin compound in the composition is determined depending on the required thickness of the conductive film to be formed. Tin compound is 200 in terms of _SnO2
If it exceeds g/- of the solvent, it will not dissolve sufficiently and the composition will not be uniform, making it impossible to form a good conductive film. The preferred range of the amount of the tin compound is 10 to 100 g per organic solvent in terms of SnO ₂
It is. The antimony compound used in the present invention is important in increasing the conductivity of the formed film, and any antimony compound may be used as long as it is soluble in the organic solvent used. Examples include antimony alkoxy such as triethoxyantimony, triisopropoxyantimony, and pentaethoxyantimony; antimol carboxylates such as antimony acetate; and antimony salts such as antimony chloride and antimony nitrate. Among these, triethoxyantimony and triisopropoxyantimony are preferred. The amount of antimony compound in the composition is determined by the amount of Sb ₂ O ₃ /
The weight ratio of (SnO ₂ +Sb ₂ O ₃ ) is in the range of 0.01 to 0.15, preferably 0.01 to 0.10. As a result, sheet resistance of 10 ² to 5 × 10 ⁵ is required for applications such as transparent electrodes for liquid crystal display devices and electroluminescence, and anti-frost and anti-fog films for window glass of automobiles, etc.
A transparent conductive film having Ω/□ can be formed. Even if the weight ratio is smaller than 0.01 or larger than 0.15, it is difficult to obtain the desired electrical conductivity. As the organic solvent used in the present invention, any organic solvent can be used as long as it can dissolve other components and can easily evaporate and dry the coating film after coating the composition on the substrate. A person skilled in the art can easily select a suitable organic solvent. Such organic solvents include, for example, ethyl acetate, isopropyl acetate,
Carboxylic acid esters such as n-butyl acetate, isoamyl acetate, ethyl propionate; alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, butyl alcohol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone , and other aliphatic hydrocarbons, as well as cyclohexane, methylcyclohexane, benzene,
Included are cycloaliphatic or aromatic hydrocarbons such as toluene, xylene, and ethylbenzene. The amount of water in the composition of the present invention is 0.1 to 10% by weight based on the amount of the organic solvent, and is in a range that is completely compatible with the organic solvent. If it is less than 0.1% by weight, it is not preferable because the strength of the formed film is low. If the amount of water exceeds 10% by weight of the organic solvent, it is not preferable because a good film cannot be obtained. Furthermore, depending on the type of organic solvent used, even if the amount of water is 10% by weight or less of the organic solvent, it may not be completely compatible with the organic solvent. In this case, the uniformity of the composition as a whole is lost and the properties of the resulting film are also adversely affected, which is not good. The composition of the present invention can be prepared by mixing required amounts of a tin compound, an antimony compound, an organic solvent, and water. The composition of the invention thus obtained is highly stable and has a long shelf life. When stored in an airtight container,
It remains stable for more than 6 months without any deterioration. Furthermore, even if exposed to the atmosphere during coating, changes such as precipitation or thickening do not occur. Therefore, the coating operation can be performed smoothly and a good transparent conductive film can be stably formed. In order to form a transparent conductive film using the composition of the present invention, the composition, which is a coating liquid, may be applied to the surface of a substrate by an appropriate method, and after drying, the coating film may be baked in an oxidizing atmosphere. To apply the coating liquid to the substrate,
Although conventional methods such as dipping, spraying, spinner coating, and brushing can be used, the dipping method is particularly preferred. The coating film on the substrate is dried at a temperature of room temperature to about 150°C.
For example, it may be dried by leaving it at room temperature for 30 minutes and then placing it at 100°C for 15 minutes. Various drying temperatures and times can be selected. Firing after drying may normally be carried out in air, but may also be carried out in an oxygen atmosphere to promote oxidation of the composition. The firing temperature is preferably 300°C or higher, and an appropriate temperature is selected depending on the heat resistance of the substrate. At temperatures below 300°C, it is difficult to obtain a complete oxide film.
The time required for firing is about 10 seconds to about 1 hour, and is determined depending on the firing temperature and other factors. A transparent conductive film can be formed on a substrate by the method described above. This film has good properties such as translucency, conductivity, strength, and adhesion to the substrate. The substrate on which a transparent conductive film is formed using the composition of the present invention can be made of any material as long as the composition exhibits wettability (wettability) and can withstand the firing temperature of the coating film. It may be something that exists. Examples of such materials include inorganic materials such as soda lime glass, borosilicate glass, quartz glass, quartz, various optical glasses, and alumina, as well as synthetic resins such as silicone resins and fluorine resins. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but these Examples are merely illustrative of the present invention. Examples 1 to 15 In a 200 ml flask, 10 g of various tin compounds and 0.5 g of triethoxyantimony were mixed with 100 g of an organic solvent.
ml and the amount of water shown in Table 1 to prepare a coating solution. A 25 x 75 mm soda lime glass plate with a well-washed surface was immersed in this coating solution, pulled out, left in the air at room temperature for 30 minutes, then dried at 100°C for 15 minutes, and then heated at 500°C. Heat for 30 minutes. As a result, a colorless and transparent conductive film was obtained on the surface of the glass plate. The average sheet resistance of the film was measured, and the light transmittance, film strength, and adhesion to the substrate were also examined. The results are also shown in Table 1. In addition, the shelf life of the prepared coating solution was measured as follows. After putting the coating solution into a sealed container and performing the above operations every month to form a transparent conductive film on the substrate, the average sheet resistance, translucency, film strength, and adhesion of the film were measured. Stability was determined by comparing with the value of . The results are also shown in Table 1.

【table】

[Table] ** Stability of Comparative Example 1: Coating became impossible after 6 months due to precipitation.
Examples 6-20 As shown in Table 2, coating solutions were prepared by dissolving 10 g of diethoxytin dichloride and various amounts of triethoxyantimony in 100 ml of ethyl acetate and 1 g of distilled water in a 200 ml flask. Example 1
A film was formed on the surface of the glass plate using the same procedure as above. The results are shown in Table 2. In addition, light transmittance, film strength,
The adhesion of the film was good in all cases.

[Table] Example 21 A plate made of silicone resin and a plate made of fluororesin were respectively immersed in the coating solution produced according to Example 1, pulled out, and left in the air at room temperature for 30 minutes, then 100% Dry for 15 minutes at °C. After heating at 300°C for 30 minutes, a colorless and transparent conductive film was obtained on the plate surface in each case. The conductive film had good translucency, strength, and adhesion. The average sheet resistance is 6.2×10 ³ kΩ/□ (silicone resin plate), respectively.
and 4.5×10 ³ kΩ/□ (fluororesin plate).

Claims (1)

[Claims] 1. A tin compound represented by the formula SnClx(OR) _4-x [where R represents an alkyl group, and x is an integer of 1 to 3], an antimony compound, and a suitable A composition comprising an organic solvent and water, wherein the content of the tin compound is SnO ₂ per 1 organic solvent.
The amount of tin and antimony in the composition does not exceed 200 g in terms of SnO ₂ and
When converted as Sb ₂ O ₃ , Sb ₂ O ₃ / (SnO ₂ +
A transparent conductive material in which the weight ratio of Sb ₂ O ₃ ) is in the range of 0.01 to 0.15, and the amount of water is 0.1 to 10% by weight of the amount of organic solvent, and is completely compatible with the organic solvent. Composition for film formation.