JPS6346789B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a transparent conductive film forming paste for forming a transparent conductive film made of a metal oxide with excellent adhesion into a desired shape on an insulating substrate such as glass or ceramics by screen printing and baking. It is something. It is well known that oxide films such as In, Sn, Sb, and Cd formed on insulating substrates such as glass and ceramics have high transmittance and good conductivity, and are used in semiconductor devices, liquid crystal display devices, It is used in electrochromic display devices, etc., or as a conductive film to prevent freezing on window glass, etc.
In recent years, the scope of its application has been expanding more and more. Methods for forming such a metal oxide transparent conductive film include a chemical spray method, a vacuum evaporation method, a dipping method, and a screen printing method. The chemical spray method is advantageous for obtaining a film with a relatively large area, but is not economical because it requires extra steps such as etching treatment for obtaining a film with a fine and complicated shape. In the vacuum evaporation method, the mask evaporation method has recently been developed and the need for etching has been eliminated, but since the process is performed in batches, it is difficult to mass-produce. Although the dipping method can be said to be suitable for mass production, the properties of the film formed are significantly inferior to those of the former method, and etching treatment is also required, making it impractical. On the other hand, the screen printing method has the advantage that it does not have such problems, can obtain the desired shape by printing and firing, and does not require waste liquid treatment accompanying etching treatment. However, in the past, the stability of the paste itself for forming transparent conductive films was not good;
The workability during screen printing was also poor, resulting in the disadvantage that particularly fine patterns could not be stably printed. That is, conventionally, as this type of paste, an organic metal compound such as an organic acid indium soap having strong ionic bonding properties such as indium octylate [(C ₇ H ₁₅ CO ₂ ) ₃ In] has been used. However, these materials are easily hydrolyzed, and when made into a paste, they gel quickly and chemically change relatively easily, and the paste itself is not stable, causing poor workability during screen printing. Ta. Furthermore, although ethyl cellulose was used as the binder for the paste using the organometallic compound, for example, the binder did not burn completely when fired at 500°C, and as a result, the film formed had a high specific resistance. Only a film with weak film strength was obtained. As a result of various studies to overcome these drawbacks, the present inventors have discovered, for example, trisacetylacetonatoindium (Hacac)-coordinated compound that forms a metal oxide film upon firing. ) [In(acac) ₃ ], or as a tin compound for adjusting the resistance value, such as dimethyltin acetope [(CH ₃ ) ₂ Sn(acac) ₂ ]. We have found that the stability of the paste can be increased using organotin complexes and good results can be obtained. We also found that by using nitrocellulose as the cellulose compound used as a binder, a film with high adhesion strength and low resistance can be obtained. However, when nitrocellulose was used, the paste life was shorter than when ethylcellulose was used, and problems with workability during screen printing still remained. Therefore, the present inventors discovered that the properties could be improved by using nitrocellulose that had been further deoxidized and a mixed solvent of butyl carbitol, butyl cellosolve, benzyl acetate, and dimethyl phthalate as an organic solvent. I tried to improve, but it still wasn't enough.
In particular, problems remained with printability when screen printing fine patterns of about 0.1 mm. In order to solve this problem, the present inventors created a paste containing an organometallic compound, an organic solvent, and a binder that is sparingly soluble in the organic solvent and burns almost completely at a high temperature of about 400°C, so that it can contain alkali ions and metals. We have found that the properties can be greatly improved by adding a methyl group-substituted monoazo organic pigment that does not contain any components.
As for the characteristics required of such organic pigments, it is desirable that the following conditions be satisfied. In other words, it is poorly soluble in the organic solvent used to make the paste, and its solubility is approximately 0.2wt% or less. The weight starts to change before 300℃, and there is very little organic residue at 300℃, and there is no residue at 500℃. Those that have poor reactivity with paste compositions. Contains no alkali ions or metal components. It is. It has been found that it is easy to satisfy the conditions , , and the above-mentioned characteristics are improved with the organic pigment, but since the conditions are not completely satisfied, a paste without organic pigment is used. The properties were slightly inferior to those of the film formed from the above. The present invention eliminates the above-mentioned drawbacks, provides a film with good film properties, that is, low resistance, good transparency and adhesion, and has the same stability of paste, printability of fine patterns, and printability as before. This was done for the purpose of providing a paste for forming a transparent conductive film with good workability. In order to achieve this object, the present invention provides a method for dissolving a coordinated organoindilam complex in which acetylacetone is coordinated, a coordinated organotin complex in which acetylacetone is coordinated, and the coordinated organoindium complex and the coordinated organotin complex. A paste containing an organic solvent and a binder made of nitrocellulose, which is sparingly soluble in the organic solvent, most of which disappears by sublimation at a temperature of 300°C or lower, and leaves no residue at least at 500°C, It is also characterized by the addition of a sublimable organic dye that does not contain alkali ions or metal components. That is, in the case of organic pigments whose process of disappearance due to temperature is combustion, it is difficult to achieve a final state of zero residue, which is thought to have a negative effect on the film properties. The present invention focuses on this and significantly improves the coating properties by adding an appropriate amount of a sublimable organic dye that can be easily produced in a state of zero residue. The paste containing the sublimable organic dye is prepared as follows. That is, an organic indium compound such as In(acac) ₃ which is soluble in an organic solvent and becomes a metal oxide upon firing, and (CH ₃ ) ₂ Sn for resistance adjustment.
(acac) An organic tin compound such as ₂ , an organic solvent, and a binder are mixed respectively. The sublimable organic dye is then added. Note that the organic dye may be added before adding the binder. Examples of organic solvents include terpineol, 2-
High boiling point alcohols such as ethylhexanol and benzyl alcohol, high boiling point esters such as benzyl acetate, carbitol acetate and dimethyl phthalate, high boiling point alcohol ethers such as butyl cellosolve, carbitol and butyl carbitol, etc. are used. Further, as the binder, deoxidized nitrocellulose is suitable. A more detailed explanation will be given below based on examples. Example 1 In order to examine the relationship between the type of sublimable organic dye added to the paste and printability and film properties, a mixed organic solvent (butyl carbitol:
The solubility in butyl cellosolve: benzyl acetate: dimethyl phthalate = 4:2:2:2) was investigated. Next, in order to create a paste for examining printability and film characteristics, In(acac) ₃ 2.69wt%,
(CH ₃ ) ₂ Sn(acac) ₂ 0.31 wt%, the above mixed organic solvent as the organic solvent, and 13.8 wt% of deoxidized nitrocellulose 80 seconds as the binder, and the solubility of the sublimable organic dye ( wt%) + 1wt% to create a paste. Meanwhile, a 0.1 mm pattern is created on a 250-mesh screen plate made of stainless steel net. The prepared paste was screen printed using the screen plate described above, printability was examined, and further pre-dried at 150°C for 20 minutes, and then dried at 500°C for 30 minutes.
The properties of the film formed by firing for a minute were investigated. The solubility, printability and coating properties are summarized in Table 1 below. The solubility test in the figure was conducted at room temperature, and those with transparency of 98% or more of the visible area are marked with ◎.
95-98% is marked with ○, 90-95% is △
Those with a score of 90% or less are marked with an x. For comparison, examples of a sublimable organic dye whose thermal conditions are not satisfied and a combustion type are shown in Comparative Example 1 for the former;
The latter was shown in Comparative Examples 2 and 3. Furthermore, Comparative Example 4 shows an example in which no organic dye or the like was added.

[Table] As is clear from this table, it can be seen that various properties are excellent when the sublimable organic dye of Example 1 is used. The reason for this is that the solubility of the organic dye in organic solvents is relatively low in terms of printability, and that the organic dye is almost scattered by 300℃, and the solubility of the organic dye is relatively low at 500℃. This can be explained by the fact that the residue is completely reduced to zero. To explain the latter more clearly, we investigated the thermal behavior of organic dyes and pigments, and the results are shown in the figure. In addition, this combustion test was carried out at a sublimation rate of 5℃/
I did it in minutes. As is clear from this figure, the organic pigment of Comparative Example 3 had a considerable amount of residue at 500°C.
It can be seen that the film properties are significantly deteriorated.
On the other hand, in the other three cases, the residue at 500℃ is zero, but when comparing the residue at 300℃, Example 1
The order is <Comparative Example 2<Comparative Example 1. This difference is considered to influence the properties of the formed film. This is because film formation starts at around 300°C. Therefore, the results in Table 1 are supported by the results in the figure. That is, it was found that by adding a sublimable organic dye having solubility and thermal properties as in Example 1, the paste properties were greatly improved. Example 2 In the above example, a sublimable organic dye that satisfies the conditions applicable to the paste for forming a transparent conductive film was selected, but in order to determine the appropriate amount of addition, a dye with almost the same composition as in the above example was selected. , pastes were prepared in which the amount of organic dye added in Example 1 was varied,
Each item was examined in the same manner as in the previous example. The results are shown in Table 2.

【table】

[Table] As is clear from this table, the amount added is 1.0 to 10wt%
It can be seen that the film exhibits excellent printability and film properties. The present invention has the above-mentioned configuration, and provides a paste for forming a transparent conductive film that has good paste stability, allows printing of fine patterns, has good workability, and has good film properties. can be provided.

[Brief explanation of drawings]

The figure is a combustion characteristic diagram comparing the combustion characteristics of a sublimable organic dye according to an example of the present invention and a conventional combustible organic pigment.

Claims (1)

[Claims] 1. A coordinated organic indium complex in which acetylacetone is coordinated, a coordinated organotin complex in which acetylacetone is coordinated, an organic solvent that dissolves the coordinated organic indium complex and the coordinated organotin complex, and a binder made of nitrocellulose. A paste containing
A transparent conductive film-forming paste characterized by having no residue at 500°C and containing a sublimable organic dye that does not contain alkali ions or metal components.