JP4495798B2 - Method for forming transparent conductive film - Google Patents

Description

【００４０】
【発明の効果】
本発明の効果は、広範な種類の基板を使用可能な２００℃程度の低温での焼成でも透明導電膜を形成でき、且つ塗布液の調製が容易で種々の用途に対応できるだけの広範な濃度範囲で調製することができる透明導電膜形成用塗布液および透明導電膜の形成方法を提供したことにある。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating solution for forming a transparent conductive film and a method for forming a transparent conductive film, which are suitably used for various electronic devices such as liquid crystal display devices and touch panels.
[0002]
[Prior art]
Conventionally, transparent conductive films have been widely used for liquid crystal display elements, touch panels, electromagnetic shielding materials, infrared reflective films and the like.
As the transparent conductive film, tin-doped indium oxide film (ITO) is most widely used because of its excellent electrical characteristics and ease of processing by etching. This method includes vapor deposition, sputtering, and baking (coating pyrolysis). Etc.).
[0003]
[Problems to be solved by the invention]
Among the methods for forming transparent conductive films, the vapor deposition method and the sputtering method are intended to grow a film by depositing a target substance on a substrate in the gas phase. The efficiency of use is poor and productivity is low. In addition, it was difficult to form a film with a large area.
On the other hand, the firing method is to form a film by applying a precursor of a target substance to a substrate by spin coating, dip coating, printing, etc., and firing (thermally decomposing) it. Has the advantage that it is simple, excellent in productivity, and easy to form a film with a large area, but usually requires a high temperature treatment of 400 ° C. to 500 ° C. at the time of firing, so that the base material is limited. Had.
[0004]
Japanese Patent Application Laid-Open No. 9-86967 proposes a technique for forming a film in which ITO fine particles are dispersed in a silicate matrix at 200 ° C. or lower. However, this technique is difficult to pattern by etching or the like, and is not suitable for applications such as liquid crystal display elements.
[0005]
In order to solve such problems, the present inventors previously described in Japanese Patent Application No. 10-79691 for forming a transparent conductive film in which indium formate and an organic tin compound that can be formed at around 200 ° C. are dissolved in a solvent. A coating solution is proposed.
However, since indium formate has poor solubility in a solvent, it is difficult to prepare a coating solution, and it is also difficult to prepare in a wide concentration range that can be used for various applications.
[0006]
The object of the present invention is to solve the above-mentioned problems, to use a wide variety of substrates, to form a transparent conductive film even at a low temperature of about 200 ° C., and to prepare a coating solution. An object of the present invention is to provide a coating solution for forming a transparent conductive film and a method for forming the transparent conductive film, which can be prepared in a wide concentration range that can be easily adapted to various uses.
[0007]
[Means for Solving the Problems]
That is, in the present invention, a transparent conductive film forming coating solution obtained by dissolving indium formate, an organic tin compound, and an organic amine as essential components in a solvent is applied on a substrate and heat-treated at a temperature range of 190 ° C to 350 ° C. It is the formation method of the transparent conductive film which forms a transparent conductive film by this.
Further, the present invention applies a transparent conductive film-forming coating solution obtained by dissolving indium formate, an organic tin compound, an organic amine and a nitro compound as essential components onto a substrate, and a temperature range of 190 ° C. to 350 ° C. It is a formation method of the transparent conductive film which forms a transparent conductive film by heat-processing by .
Moreover, this invention is the formation method of the said transparent conductive film which pre-drys at the temperature which an indium formate and an organotin compound do not thermally decompose before heat processing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Indium formate used in the coating solution of the present invention is a compound represented by In (OCOH) ₃ and is thermally decomposed to crystalline indium oxide when heated to about 200 ° C. Suitable as an ingredient.
In addition, the transparent conductive film preferably has a high hardness as a film characteristic, but the transparent conductive film obtained using indium formate is more in comparison with the case where an indium compound other than indium formate which is thermally decomposed at about 200 ° C. is used. Therefore, it becomes a good transparent conductive film with high hardness.
[0009]
The organic tin compound used in the coating solution of the present invention may be any compound as long as it is thermally decomposed at a temperature of about 200 ° C. or lower to form crystalline tin oxide. Examples thereof include alkoxides, tin organic acid salts (for example, carboxylates), and various organic complexes of tin.
Particularly preferable examples of such an organic tin compound include tetraisopropoxytin, tetra-t-butoxytin, tin (II) formate, and di-n-butyltin diformate.
Most preferred is tetra-t-butoxy tin in terms of obtaining good conductivity.
[0010]
The ratio of the number of elements of indium and tin in the coating liquid of the present invention is the ratio of indium and tin in the finally formed transparent conductive film. Therefore, in obtaining the transparent conductive film, What is necessary is just to select the ratio of the indium formate and organotin compound used for a coating liquid so that it may become a ratio of an indium and a tin.
[0011]
The organic amine used in the present invention is not particularly limited, and various organic amines can be used. For example, n-butylamine, di-n-butylamine, diethylamine, pyrrolidine, piperidine, 1,1 , 3,3-tetramethylguanidine and the like, and these organic amines may be used alone or in combination of two or more.
Indium formate used in the present invention is poorly soluble in various solvents, but the addition of the organic amine exhibits the effect of solubilizing such indium formate in various solvents. Although the mechanism of action of such an effect is not clear, it is considered that the organic amine coordinates with the indium atom to increase the solubility of the compound.
The preferable addition amount of the organic amine used in the present invention is 0.2 to 5 equivalents (more preferably 0.5 to 3 equivalents) with respect to indium (as the total amount of the organic amine).
If the amount is less than the above amount, the solubility of indium formate may not always be sufficient. If the amount exceeds the above amount, amine that does not coordinate to indium increases in the solution, and thus the stability of the coating solution tends to be impaired.
[0012]
In the present invention, a nitro compound as described below can be used as necessary.
That is, the nitro compound used in the present invention may be an inorganic nitro compound or an organic nitro compound, and is not particularly limited. Examples thereof include nitric acid, nitrocellulose, 2,4-dinitrotoluene, and guanidine nitrate. These nitro compounds may be used alone or in combination of two or more.
The addition of these nitro compounds accelerates the thermal decomposition of the coating solution, and exhibits the effect of obtaining a transparent conductive film with fewer impurities at the same temperature. Similarly, an effect that can be obtained at a lower temperature is exhibited if the transparent conductive film has the same level of impurities.
Although the mechanism of action of such an effect is not clear, it is considered that when the coating solution is heated, the nitro compound becomes an oxygen supply source and promotes oxidative thermal decomposition of indium formate.
The preferable addition amount of the nitro compound used in the present invention is 0.05 to 5 equivalents, more preferably 0.2 to 1 equivalent, relative to indium (as the total amount of the nitro compound).
If the amount is less than the above amount, the effect of adding the nitro compound may not always be sufficient. If the amount exceeds the above amount, indium formate tends to be hydrolyzed, so that the stability of the coating solution tends to be impaired.
[0013]
As a solvent used in the present invention, both indium formate and the above-mentioned organic acid tin compound can be dissolved in the presence of the above-mentioned organic amine, preferably in the vicinity of room temperature. Any one that does not react or is difficult to react can be selected. Here, “dissolving” means that the solubility at the temperature to be dissolved is approximately 5 (g / 100 g) or more.
Such a solvent is preferably an organic polar solvent, and examples thereof include N, N-dimethylformamide (DMF), formamide, ethanol, 2-propanol, 1-propanol, and the like. A mixture of more than one type may be used.
[0014]
The concentration of indium formate and the organic tin compound in the coating solution of the present invention is represented by the concentration of the total amount of indium formate and the organic tin compound because the ratio of indium formate and the organic tin compound is as described above. I will decide. The concentration of the total amount of indium formate and the organic tin compound is not limited as long as the concentration of the indium compound and the tin compound in the coating solution for forming a transparent conductive film by the conventional baking method is the same, but for example, about 5 to 5 It may be 30% by weight, and is preferably 5 to 15% by weight from the viewpoint of obtaining good film formability.
[0015]
In the method for forming a transparent conductive film of the present invention, the transparent conductive film is formed by applying the above-mentioned coating solution on a substrate and performing a heat treatment.
The substrate used here can be arbitrarily selected as long as it can withstand the heat treatment temperature and is resistant to the solvent to be used, and a substrate conventionally used for forming a transparent conductive film should be used. Can do. For example, glass substrates such as non-alkali glass substrates are widely used as substrates for transparent conductive films, and can be used.
[0016]
The heat treatment in the transparent conductive film forming method of the present invention may be performed in the atmosphere at a temperature at which effective thermal decomposition of the indium formate and the organotin compound used in the present invention is possible, but a wide variety of substrates can be used. In order to obtain the effect of the present invention, it is preferably carried out in the air at a temperature range of 190 ° C to 350 ° C, more preferably 190 ° C to 250 ° C.
In such a temperature range, not only the above glass substrate but also materials such as polyimide, polyarylate, polyarylsulfone, polyarylene sulfide and the like can be preferably used as the substrate.
[0017]
In addition, although the transparent conductive film formation method of this invention can heat-process at comparatively low temperature, there is no restriction | limiting in the selection of board | substrate material, for example, high temperature (for example, 400 degreeC-500 degreeC etc. conventionally used). If a substrate that can be used for the heat treatment is usable, there is no problem in the heat treatment at such a high temperature, and in this case, the obtained transparent conductive film can have a lower resistance value. Exhibits excellent effects when used in heat treatment at a high temperature as in the conventional method.
[0018]
In addition, the transparent conductive film forming method of the present invention is smoother when pre-dried at a temperature at which indium formate and organotin compounds at about 100 ° C., specifically about 80 to 120 ° C., are not thermally decomposed before the heat treatment. Since a film surface can be obtained, it is preferable.
[0019]
【Example】
The present invention will be further described below with reference to examples and comparative examples.
Example 1
Indium formate (5.00 g), 1,1,3,3-tetramethylguanidine (0.35 g) and n-butylamine (1.98 g) were added to DMF (45.00 g) and 2-propanol (1.80 g). The mixture was dispersed in a mixed solvent (total organic amine amount was 1.5 equivalents with respect to indium), and heated and stirred at 60 ° C. for 2 hours to obtain a transparent solution.
After this solution was cooled to room temperature, t-butoxytin (IV) was added to prepare a coating solution. The amount of t-butoxytin (IV) added was adjusted so that the element content ratio of indium and tin in the coating solution was 90:10.
This coating solution was applied onto a washed alkali-free glass substrate by a spin coating method, dried at room temperature for 10 minutes, and then heat-treated at 200 ° C. for 40 minutes in the air to obtain a transparent conductive film. Table 1 shows the characteristics of the obtained film.
[0020]
Example 2
The same procedure as in Example 1 was performed except that the coating solution was applied to the substrate and then dried at 100 ° C. for 10 minutes. Table 1 shows the characteristics of the obtained film.
[0021]
Example 3
Indium formate (5.00 g) is dispersed in a mixed solvent of DMF (35.00 g) and 2-propanol (1.80 g), and 61% nitric acid (1.01 g) is added (the total amount of nitro compounds is based on indium). 0.6 equivalents) and heated and stirred at 60 ° C. for 30 minutes.
Further, 1,1,3,3-tetramethylguanidine (0.35 g) and n-butylamine (1.98 g) dissolved in DMF (10.00 g) were added (the total amount of organic amine was based on indium). 1.5 equivalents) and heated and stirred at 60 ° C. for 2 hours to obtain a transparent solution.
After this solution was cooled to room temperature, t-butoxytin (IV) was added to prepare a coating solution. The amount of t-butoxytin (IV) added was adjusted so that the element content ratio of indium and tin in the coating solution was 90:10.
This coating solution was applied on a washed alkali-free glass substrate by spin coating, dried at 100 ° C. for 10 minutes, and then heat-treated at 200 ° C. for 40 minutes in the air to obtain a transparent conductive film. Table 1 shows the characteristics of the obtained film.
[0022]
Example 4
The same procedure as in Example 3 was performed except that the organic amine was replaced with 1.5 equivalents of diethylamine. Table 1 shows the characteristics of the obtained film.
[0023]
Example 5
The same procedure as in Example 3 was performed except that the organic amine was replaced with 1.5 equivalents of pyrrolidine. Table 1 shows the characteristics of the obtained film.
[0024]
Example 6
The same operation as in Example 3 was conducted except that the organic amine was changed to 0.7 equivalent of n-butylamine. Table 1 shows the characteristics of the obtained film.
[0025]
Example 7
The same procedure as in Example 3 was performed except that the organic amine was changed to 2.7 equivalents of n-butylamine. Table 1 shows the characteristics of the obtained film.
[0026]
Example 8
The same procedure as in Example 3 was performed except that the organic amine was changed to 0.3 equivalent of n-butylamine. Table 1 shows the characteristics of the obtained film.
[0027]
Example 9
The same procedure as in Example 3 was performed except that the organic amine was replaced with 4.5 equivalents of n-butylamine. Table 1 shows the characteristics of the obtained film.
[0028]
Example 10
The same procedure as in Example 3 was performed except that the nitro compound was replaced with 0.6 equivalent of 2,4-dinitrotoluene. Table 1 shows the characteristics of the obtained film.
[0029]
Example 11
The same procedure as in Example 3 was performed except that the nitro compound was replaced with 0.6 equivalent of guanidine nitrate. Table 1 shows the characteristics of the obtained film.
[0030]
Example 12
The same procedure as in Example 3 was performed except that the nitro compound was replaced with 0.3 equivalent of nitric acid. Table 1 shows the characteristics of the obtained film.
[0031]
Example 13
The same procedure as in Example 3 was performed except that the nitro compound was replaced with 0.9 equivalent of nitric acid. Table 1 shows the characteristics of the obtained film.
[0032]
Example 14
The same procedure as in Example 3 was performed except that the nitro compound was replaced with 0.07 equivalent of nitric acid. Table 1 shows the characteristics of the obtained film.
[0033]
Example 15
The same procedure as in Example 3 was performed except that the nitro compound was replaced with 4.5 equivalents of nitric acid. Table 1 shows the characteristics of the obtained film.
[0034]
Example 16
The same procedure as in Example 3 was performed except that 35.00 g of DMF was replaced with 35.00 g of ethanol and 10.00 g of DMF was replaced with 10.00 g of ethanol. Table 1 shows the characteristics of the obtained film.
[0035]
Example 17
The same procedure as in Example 3 was conducted except that 5.00 g of indium formate was replaced with 12.00 g of indium formate. Table 1 shows the characteristics of the obtained film.
[0036]
Comparative Example 1
Indium 2-ethylhexanoate and tin 2-ethylhexanoate were dissolved in xylene so as to be 10% by weight to obtain a coating solution.
This coating solution was applied on a non-alkali glass substrate by a spin coating method, dried at 100 ° C. for 10 minutes, and then heat-treated at 200 ° C. for 60 minutes in the atmosphere, but thermal decomposition of indium and tin compounds did not occur, A transparent conductive film was not obtained.
[0037]
Comparative Example 2
Indium formate (5.00 g) and t-butoxytin (IV) were mixed with DMF (45.00 g) and 2-propanol (1.80 g) so that the content ratio of indium and tin in the coating solution was 90:10. ) Dispersed in a mixed solvent to prepare a coating solution, but this coating solution was a solution in which indium formate was not completely dissolved but solid matter was dispersed.
This coating solution was applied on a washed alkali-free glass substrate by a spin coating method, dried at 100 ° C. for 10 minutes, and then heat-treated at 200 ° C. for 40 minutes in the atmosphere, but the ITO film was rough. It was peeled off when rubbed with a finger.
[0038]
Comparative Example 3
Indium formate (12.00 g) and t-butoxytin (IV) were dispersed in DMF (50.00 g) solvent so that the elemental content ratio of indium and tin in the coating solution was 90:10 to obtain a coating solution. However, in this coating solution, indium formate was not completely dissolved but solid matter was dispersed.
This coating solution was applied on a washed alkali-free glass substrate by a spin coating method, dried at 100 ° C. for 10 minutes, and then heat-treated at 200 ° C. for 40 minutes in the atmosphere, but the ITO film was rough. It was peeled off when rubbed with a finger.
[0039]
[Table 1]

[0040]
【The invention's effect】
The effect of the present invention is that a transparent conductive film can be formed even by baking at a low temperature of about 200 ° C. where a wide variety of substrates can be used, and a coating solution can be easily prepared, and a wide concentration range capable of responding to various applications. And a method for forming a transparent conductive film, which can be prepared by the method.

Claims (3)

A transparent conductive film is formed by applying a coating solution for forming a transparent conductive film obtained by dissolving indium formate, an organic tin compound, and an organic amine in a solvent as essential components on a substrate and heat-treating it in a temperature range of 190 ° C to 350 ° C. A method for forming a transparent conductive film, comprising: forming a transparent conductive film . Transparent by applying a coating solution for forming a transparent conductive film in which indium formate, organic tin compound, organic amine and nitro compound are dissolved in a solvent as essential components on a substrate and heat-treating in a temperature range of 190 ° C to 350 ° C. A method for forming a transparent conductive film, comprising forming a conductive film . The method for forming a transparent conductive film according to claim 1 or 2, wherein, prior to the heat treatment, preliminary drying is performed at a temperature at which the indium formate and the organic tin compound are not thermally decomposed.