JPH0267378A - Screen printing ink for forming transparent electrode - Google Patents

Abstract

PURPOSE:To prepare a screen printing ink which does not form bubbles even when passing through a mesh during printing and which gives a high-quality transparent electrode, by mixing a vehicle and a solvent with a mixture of a cadmium compd. and a tin compd. CONSTITUTION:A vehicle, comprising pref. a carboxylic acid (ester) of terpenoid (e.g., abietic acid) and an ammonium or amine salt of a carboxylic acid of terpenoid (e.g., ethylamine salt of abietic acid), and a solvent (e.g., tetralin) are mixed with a mixture of a cadmium compd. (e.g., cadmium 2-ethylhexanoate) and a tin compd. (e.g., tin 2-ethylhexanoate).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an ink for manufacturing transparent electrodes used in the electronics industry by a screen printing method.

Background of the Invention Transparent electrodes are widely used in flat display devices, solar cells, etc., and the main material used is a soot-doped indium oxide thin film, which has excellent visible light transmittance and electrical conductivity. Another possible material for transparent electrodes is cadmium stannate, which is attracting attention because its raw material cost is lower than soot-doped indium oxide. At present, this thin film is formed using sputtering or vacuum evaporation, and a transparent electrode is manufactured by applying pattern precision using wet etching.

Furthermore, recently, with the aim of reducing manufacturing costs, a method has been proposed in which a compound containing a metal in its structure, such as a metal-organic substance, is coated on a substrate and then thermally decomposed.

Problems to be Solved by the Invention However, there have been practical problems in terms of the smoothness and pattern accuracy of the transparent electrodes produced.

Means for Solving the Problems In the present invention, a terpenoid carboxylic acid or an ester thereof and an ammonium salt of a terpenoid carboxylic acid or a salt with an amine are added as a vehicle for a screen printing ink for forming a transparent electrode. This is what I used.

Function: The vehicle of the present invention imparts thixotropic properties to the ink, so that it can be transferred onto the printing substrate without generating bubbles even when it passes through the mesh during printing. Therefore, a very smooth and even printed film surface can be obtained, and since it decomposes at high temperatures and leaves no ash, the quality of the transparent electrode obtained after firing is good, and the flow characteristics of the ink are improved. Even precise patterns can be made with good resolution.

Example First, the present invention will be explained in detail.

There are no particular limitations on the metal compounds that can be used in the present invention, as long as they are compatible with the vehicle in an appropriate solvent. Examples include salts such as carboxylates and nitrates, organic complexes such as acetylacetone complexes, and organic metals. however,
Substances that exist relatively stably up to high temperatures, such as chlorides and sulfates, are not preferred because they may impair the electrical properties of the formed thin film. Further, the mixing ratio of the soot-containing compound and the cadmium-containing compound affects the resistance value of the manufactured transparent electrode, and can be arbitrarily changed in order to obtain the desired resistance value.

Next, terpenoid carboxylic acids that can be used in the present invention include abietic acid and its derivatives such as pimaric acid, neoabietic acid, and levopimaric acid, which are contained in natural resins, as well as guaiaconic acid and its derivatives, guaiaconic acid, etc. acids, such as lupenic acid. Furthermore, dammarolic acid and its derivatives, ursolic acid, oleanolic acid, betulinic acid, etc. contained in dammar gum can also be used. Most monoterpenoid carboxylic acids are liquid at room temperature, so they cannot be used alone, but they may be used if mixed with the aforementioned diterpenoid or triterpenoid carboxylic acids. Since purified and separated products are generally difficult to obtain and are expensive, natural resins containing them such as rosin, guaiac, dammar, and copa can be used. The ingredients of natural resins such as these vary greatly depending on the production area and manufacturer.
Components other than carboxylic acids may also be contained, but they can be used without any problem for the purpose of the present invention. As these esters, abietic acid esters can mainly be used, and any type of rosin ester that is generally commercially available may be used.

As ammonium salts of terpenoid carboxylic acids or salts with amines, those synthesized by the neutralization reaction of the acid with ammonia or amines as described above can be used. Regarding amines, all types of primary, secondary, and tertiary, and aliphatic.

Any type of aromatic or heterocyclic compound can be used, but it is preferable that the number of carbon atoms contained in the alkyl group is not too large. This is because as the number of carbon atoms increases, the inorganic salt properties of the salt disappear, making it impossible to expect the effects described in the section of this specification. In reality, it seems desirable that each alkyl group has 6 or less carbon atoms, and the total number of carbon atoms is about 15 or less. Note that the preferred composition range of the vehicle varies depending on the type of acid or amine used, and this will be described later.

Next, a specific example will be described.

(Example 1) 100g of vehicle was prepared with the composition shown in Table 1, and 2Of of a mixture of cadmium 2-ethylhexanoate and tin 2-ethylhexanoate at a molar ratio of 1:1 was added. 30y of tetralin was added as a solvent and kneaded to produce screen printing inks of various compositions. These inks were printed in a rectangular pattern of 10 Jff x 301 ff on a glass substrate using an emulsion thickness of 16 μm and a 200 mesh screen plate. 150″C
After drying for 30 minutes, the surface of the printed film was evaluated. Evaluation,
Two points were checked: the presence or absence of unevenness on the film surface, the sagging of the pattern edges, and the presence or absence of bubbles during printing.

These evaluation results are also shown in Table 1. As can be seen, the ink containing the ammonium salt of terpenoid carboxylic acid or the salt with amines eliminates bubbling during printing and provides a good printed film surface. The composition in which this effect appears depends on the type and composition of the terpenoid carboxylic acid used, but from the results in Table 1,
The minimum amount of these salts required to obtain a good ink increases in the order of ammonia, primary amine, secondary amine, and tertiary amine, and increases as the number of carbon atoms in the amine increases. It can be seen that there is a trend.

These printed materials with good film surfaces were exposed to air at 550°C.
When heated at 'C for 1 hour, a transparent electrode with a film thickness of about 1800 Å was obtained. These resistivities are 5X10'Ω~
Although there was a tendency to increase as the molecular weight of the vehicle used increased in the case of 3×10'Ω, the durability was good, and a transparent electrode with no particular problems could be produced in practical use.

(Left below) (Example 2) A vehicle 1ooy was prepared with the composition shown in Table 2, and 13p of a mixture of cadmium nitrate and soot nitrate in a molar ratio of 2:1 was added thereto as a solvent. 30y of α-terpineol was added and kneaded to produce an ink. The results of evaluating these inks using the same method as in Example 1 are also shown in the second example.
Shown in the table.

From this, it can be seen that, as in Example 1, the ink of the vehicle containing the ammonium salt of terpenoid carboxylic acid or the salt with amines gives a good film surface. It can also be seen from Table 2 that the minimum amount of these salts that must be included in the vehicle to obtain a good printing ink increases as the number of carbon atoms in the amine increases.

As is clear from this example, just as terpenoid carboxylic acids can be a mixture of several types, their ammonium salts or salts with amines can also be a mixture of several types. It doesn't matter.

The resistivity of the transparent electrode obtained by firing the printed matter with a good film surface in the same manner as in Example 1 was 2X10'ΩC.
The bacteria were 1n to 1×10 −2 Ω.

(Left below) (Example 3) 100p of vehicle was prepared with the composition shown in Table 3, and 18p of a mixture of cadmium 2-ethylhexanoate and diptyltin ookinde in a molar ratio of 1=2 was added to this. death,
30 f of benzyl acetate was added as a solvent and kneaded to produce an ink. The results of evaluating these inks using the same method as in Example 1 are also shown in Table 3. From this, it can be seen that, as in the above-mentioned examples, the ink of the vehicle containing the ammonium salt of terpenoid carboxylic acid or the salt with amines gives a good printed film surface.

Among these, those with good printed film surfaces were dried and baked in the same manner as in Example 1, and the resistivity of the transparent electrode was 2X.
It was from 10"ΩG to 5X10'Ω mouth.

(Margin below) (Example 4) How much pattern accuracy can be achieved using the inks shown in Tables 1 to 3 that give a good film using a screen plate with an emulsion thickness of 10 μm and 300 mesonules? When we conducted a test, we found that all inks had 2
A stripe pattern with ooμ pitch could be printed with good reproducibility.

The transparent electrode manufactured in the above example had a wavelength of 5501H.
The light transmittance of all samples was 85% or more, and the transparency was good.

Effects of the Invention As can be seen from the above examples, the screen printing ink for forming transparent electrodes of the present invention allows production of high-quality transparent electrodes at low cost, and its industrial effects are significant.

Claims (2)

[Claims] (1) Adding a vehicle and a solvent to a mixture of a compound containing cadmium in its structure and a compound containing tin in its structure,
A screen printing ink for forming transparent electrodes, which is made by kneading. (2) The transparent electrode forming method according to claim 1, wherein the vehicle is formed by adding a terpenoid carboxylic acid or an ester thereof and an ammonium salt of the terpenoid carboxylic acid or a salt with an amine. screen printing ink.