JPS62297470A - Paste for forming metal oxide thin film - Google Patents

Abstract

PURPOSE:To obtain an oxide thin film appropriate for screen-process printing and having high mechanical strength by using nitrocellulose as a thickener along with an unsaturated fatty acid to secure the viscosity of the obtained title paste. CONSTITUTION:An unsaturated fatty acid and nitrocellulose are added to a system consisting of a metal compd. as the essential component and a mixed org. solvent of benzyl alcohol, an acetic ester, etc., to obtain the title paste. Besides, ZnO, In2O3-SnO2, and SnO2-Sb2O3 are preferably used as the title metal oxide. Moreover, one or more kinds of compds. selected from a group consisting of the salt of a 8-20C higher fatty acid such as linoleic acid and a metal forming the metal oxide on baking, and the salt of a 5-8C diketone type chelate such as acetylacetone and the metal are preferably used as the metal compd. Furthermore, a 6-22C unsaturated fatty acid such as oleic acid is preferably used as the unsaturated fatty acid.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention provides metal oxidation on a glass or ceramic substrate? 'J This invention relates to a screen printing paste for forming a desired pattern on a thin film by screen printing and baking.

[Conventional technology]

The following methods are conventionally known as methods for forming metal oxide thin films.

(1) Vacuum deposition or sputtering method: A metal or metal oxide is deposited directly on a substrate in vacuum.

(2) Spray method: A spray of metal compound water or alcohol 78 liquid is sprayed onto a substrate that has been preheated to a high temperature.

(3) CVD method; vapor of an organometallic compound that volatilizes at a relatively low temperature is introduced onto a substrate heated to a high temperature.

(4) Coating method: An organic solvent containing a metal compound is coated on a substrate by a method such as dipping, and then baked at a high temperature.

(5) Printing method; After screen printing a paste composition containing a metal compound onto a substrate, it is fired at a high temperature.

Among these, method (1) requires a vacuum system, so the equipment is expensive and the workability is also inferior. (2), (3), (4
) is more economical because it is carried out under normal pressure, but requires an etching step for pattern formation. (
Since the method 5) allows direct pattern formation, it is expected that a transparent R electrical film can be formed at the lowest cost.

The inventors have already disclosed in Japanese Patent Publication No. 54-28396,
It has been found that the addition of unsaturated higher fatty acids such as linoleic acid and lylunic acid to a coating liquid for forming an In2O, -5nJil film by a dipping method significantly improves the film quality.

[Problem that the invention seeks to solve]

However, in order to form a thin film by screen printing, the addition of the above-mentioned unsaturated higher fatty acids alone does not produce the desired results, and therefore it has been necessary to develop a thickener suitable for screen printing pastes.

[Means for solving problems]

As a result, the inventors have found that by using nitrocellulose as a thickener in addition to unsaturated fatty acids, a clear paste-like viscous liquid can be obtained, which can be used to create a clear and mechanically stable liquid suitable for screen printing. It has been found that a strong oxide thin film can be obtained.

That is, the present invention provides a metal oxide thin film forming paste in which nitrocellulose and unsaturated organic fatty acid are added to a mixed system of a metal compound and an organic solvent as main components.

The details of the present invention will be explained below.

The metal oxides used in the present invention include divalent metals such as Zn, In
This includes all oxides of trivalent metals such as Sn, and tetravalent metals such as Sn.

The metal compound used in the present invention can be made into ZnO by firing.
, In2O3.5nOz, 5bt03, etc., which produce the above metal oxides, can be used, but those that are soluble in the solvent of the paste are preferable, such as linoleic acid,
Lyrinic acid, 2-ethylhexanoic acid, etc. Cs ``” C2
C5~ metal salts of higher fatty acids, acetylacetone, etc.
C6 diketone type chelate compounds, alkoxide compounds, and the like can be used alone or in combination.

The organic solvent is preferably one that has the ability to dissolve the metal compounds, unsaturated higher fatty acids, and nitrocellulose, and has a relatively high boiling point in order to reduce viscosity changes during screen printing.

For example, high boiling alcohols such as 2-ethylhexyl alcohol, benzyl alcohol, terpinenol,
High boiling point esters such as ethyl acetoacetate, hensyl acetate and dibutyl phthalate, high boiling point ketones such as acetylacetone and isophorone, etc. can be used. These solvents can be used alone or in a mixture of two or more.

Further, as the unsaturated fatty acids used together with nitrocellulose, C4 to C22 fatty acids are preferable, and linoleic acid, oleic acid, etc. are particularly preferable.

The mixing ratio of each of these components is preferably that of normal batter.

Metal compound 0.5 to 10 wt% (as its oxide) Unsaturated fatty acid 10 to 50 wt% Nitrocellulose 5 to 20 wt% Organic solvent Balance However, in this case, unsaturated fatty acid/nitrocellulose 0.5 to 3.0 If the unsaturated fatty acid added is too much than the above range, the coating will become cloudy and opaque when heated, and
If the amount is too small, the fired film tends to be non-uniform, which is not preferable.

The thin film forming paste having the above composition is printed by a commonly known screen printing method, dried, and then fired to form a thin film.

〔Example〕

Example 1. ZnO thin film The following composition was used as the coating liquid composition.

Zinc 2-ethylhexanoate 13.0wt% Linoleic acid 13
．． 0wt% acetylacetone 52.8wt
% dibutyl phthalate 13.2 wt % nitrocellulose 8.0 wt % The above solution was a clear pasty viscous liquid.

This was printed circularly on a glass substrate by screen printing method, dried at 110°C for 30 minutes, and dried at 550°C for 30 minutes.
As a result of baking for a minute, a transparent circular ZnO thin film was obtained. The transparency of the obtained thin film, j! J, mechanical strength, etc., when compared with the values of the ZnOgt film obtained by the dipping method using a low-viscosity solution from which nitrocellulose was removed, good results were observed. Obtained.

Example 2. The following composition was used as a conductive Ingot 5nOzffi film coating solution.

Indium acetylacetonate 3.5wt%2-
Stannous ethylhexanoate 0.4wt% linoleic acid
15.0ivt% acetylacetone
53.9wt% butyl phthalate 17.
2t% nitrocellulose 10.0w
The resulting solution was a clear pasty viscous liquid.

This was screen-printed in a square shape on a soda-lime glass substrate, dried at 45°C for 20 minutes, and fired at 550°C for 30 minutes. As a result, a transparent InzO:+ thin film was obtained, and its specific resistance was approximately 5X10-3 Ωcm. there were. This value, the transparency of the thin film, the mechanical strength, etc. are all obtained by the dipping method using a low viscosity coating liquid from which nitrocellulose in the above composition has been removed.
□Almost no difference was observed when comparing the properties of the han membrane, and good results were obtained.

Example 3. Conductive 5nOz 5bzOs TR film The following composition was used as the fabric solution.

2-ethylhexane IIMI tin 10.0wt% antimony triptoxide 1.0wt%
Cynic acid
20 t% terpineol 59
匈L% Nitrocellulose 10.0wt
% The coating solution obtained was a clear, paste-like viscous liquid. After applying this on a quartz glass substrate with a roller, 1
After drying at 10°C for 30 minutes and baking at 550°C for 30 minutes, an extremely strong and transparent SnO□ thin film was obtained, with a specific resistance of about 2×10 −2 Ωcm. These properties were obtained using a spinner method using a low-viscosity coating solution with nitrocellulose removed from the above composition.
Oz St+zO3F! [No difference was observed when comparing the properties of the membrane, and good results were obtained.

〔effect〕

The effects of the combined use of unsaturated fatty acids and thickeners other than those of the present invention are listed below.

Natural rubber or synthetic resins such as polystyrene: Not only is it extremely difficult to increase the viscosity to a paste even if the amount added is increased, but it also decomposes in the solution and forms metal hydroxide or oxide particles. It precipitated and became cloudy, and even when it was coated on a substrate, dried and baked, the thin film turned into powder and peeled off from the substrate.

Hydroxypropylcellulose: A paste-like viscous liquid was obtained, but when this was applied onto a substrate, dried, and baked, the thin film became cloudy, especially when
In the case of conductive thin films such as n02, In2O:1, etc., the specific resistance increased by about four orders of magnitude compared to the case where no thickener was used.

Ethylcellulose: A transparent viscous liquid was obtained, and when a thin film was made using this, although a transparent thin film was obtained, its mechanical strength was significantly reduced (conductive 5N02S
When used in thin films such as Inz03, the specific resistance thereof increased by approximately two orders of magnitude, and most thickeners are undesirable because they adversely affect the mechanical strength, transparency, conductivity, etc. of the thin film.

On the other hand, when nitrocellulose (the present invention) is used as a thickener together with unsaturated fatty acids, unlike the above-mentioned thickeners, the viscosity, etc. required for screen printing is ensured, and SnO,... A remarkable effect was obtained in that the mechanical strength, transparency, conductivity, etc. of the thin film of InzOl etc. were not adversely affected.

The reason why nitrocellulose shows such a remarkable effect is that the thermal decomposition temperature of other thickeners is 300 to 400°C (almost the same as the decomposition temperature of the metal compound used in the present invention). The decomposition temperature of nitrocellulose is 200℃
Therefore, the metal compound thermally decomposes to form oxide II! ! Since the decomposition of nitrocellulose is completed before the formation of nitrocellulose, it is thought that the formation of the thin film is not adversely affected.

Claims (1)

[Scope of Claims] 1) A paste for forming a metal oxide thin film, characterized in that nitrocellulose and unsaturated fatty acids are added to a mixed system of a metal compound as a main component and an organic solvent. 2) Metal oxide is ZnO, In_2O_3-SnO_2
, SnO_2-Sb_2O_3, the metal oxide thin film forming paste according to claim 1. 3) The metal compound is at least one compound selected from the group consisting of C_8 to C_2_0 higher fatty acid salts of the metal and C_5 to C_8 diketone type chelate compound salts. The metal oxide thin film forming paste according to item 2. 4) The metal oxide thin film forming paste according to claims 1 to 3, wherein the unsaturated organic fatty acid is C_6 to C_2_2.