JP3078148B2 - Method for forming pattern of transparent conductive film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display (LC)
D) Electrodes of display elements such as electroluminescence (EL) display elements, or glass, ceramics and other substrates used as heating elements for preventing fogging or icing of window glasses of automobiles, aircraft, buildings, etc. The present invention relates to the formed transparent conductive film, and particularly to a method for forming a transparent conductive film pattern.

[0002]

2. Description of the Related Art Conventionally, electrodes for display elements such as LCDs and ELs, and heating resistors for preventing fogging or icing of window glasses of automobiles, aircraft, buildings, etc. A transparent conductive film having transparency is used.

As a transparent conductive material for forming the transparent conductive film, tin oxide / antimony oxide (ATO), indium oxide / tin oxide (ITO), and the like are known. A film can be easily formed on a ceramic substrate to form a transparent conductive film.

[0004] As a method of forming a transparent conductive film, there are generally known two methods in terms of patterning.
The first method is a method (1) in which a printing / firing type transparent conductive film forming ink is printed by screen printing or the like, and a patterned transparent conductive film is formed by firing the printing film. The second method is to print and cure a transparent conductive film obtained by a vacuum evaporation method (2), a sputtering method (3), a coating and baking method (4), etc. with a photolithography or screen printing resist ink. Pattern by etching.

[0005]

However, in the above method (1), a paste-like composition containing a tin salt and an indium salt of an organic acid containing a photocurable functional group, an inorganic indium salt and an inorganic tin salt And a method of screen printing a composition comprising an organic solution of a non-aqueous silica sol and a cellulose compound, and a method of offset printing a composition comprising an indium compound, a tin compound, a gum natural resin rosin, and a terpene high boiling solvent. Has the following two problems.

The first problem is that the fate of the screen printing method and the offset printing method is a problem in that the variation in the film thickness in the solid portion is large and the film thickness in the end portion of the pattern is small. Secondly, these compositions contain a resin such as a cellulose compound or a gum-based natural resin rosin in order to obtain printability, and these generally tend to remain as free carbon in the film during thermal decomposition. However, there is a problem that the deterioration of the electrical characteristics, optical characteristics, and mechanical characteristics cannot be avoided.

Next, the above methods (2) and (3) have good electrical, optical and mechanical properties of the obtained film, but the cost and cost are high because the apparatus is complicated and expensive. There is a problem in terms of mass productivity. Method (4) is
It has the potential to solve the problems of the above methods (1), (2) and (3) .Even though the properties of the obtained film are better than those of the above method (1), Only for characteristics,
It is inferior to the methods (2) and (3). This is a problem in the manufacturing method.Since the above methods (2) and (3) form a transparent conductive film in a vacuum, oxygen vacancies are easily introduced into the film, and electric charges contributing to electric conduction are formed. The carrier concentration increases, the specific resistance of the film decreases, and a low-resistance transparent conductive film is easily formed.On the other hand, in the method (4), the composition for forming a transparent conductive film is completely heated. Since heat treatment is usually performed in the air or oxygen to cause decomposition, oxygen defects are reduced in the obtained transparent conductive film, and the film is thinner than the methods (2) and (3) described above. Has a high specific resistance. Therefore, in order to improve the electrical characteristics of the film, it is usually necessary to perform a heat treatment in a reducing atmosphere, which has a disadvantage of increasing the number of steps.

An object of the present invention is to solve the above-mentioned problems and to provide a method for forming a transparent conductive film pattern in which a patterned transparent conductive film having low resistance and high transmittance can be easily obtained at low cost. And

[0009]

In order to achieve the above object, the present invention provides a transparent conductive film formed on a substrate by thermally decomposing a resist ink containing carbon powder as a filler. A step of printing on the surface of, a step of curing the resist ink by heat or light, a step of etching the transparent conductive film, a step of heat-treating the substrate, and a step of removing residues of the resist ink. A method for forming a pattern of the transparent conductive film provided.

[0010]

According to the method for forming a transparent conductive film pattern of the present invention, first, a resist ink containing carbon powder as a filler is treated with a transparent conductive film formed on a substrate by thermal decomposition of a composition for forming a transparent conductive film. Print on the surface. Here, by using carbon powder as the filler, the printability and printing accuracy of the resist ink and the etching resistance of the resist itself after curing are remarkably improved. Also, compared to oxide powder etc.
Since it does not react with the transparent conductive film, removal of the resist becomes easy. Then, the resist ink is cured by heat or light, and in particular, the etching resistance of the resin component in the resist using carbon powder as a filler to an etchant is improved. Thus, the transparent conductive film having the resist pattern formed on the film surface is etched to form a transparent conductive film pattern. Further, the transparent conductive film which is in contact with the resist by heat-treating the substrate and thermally decomposing the resin component in the resist and reacting carbon powder and oxygen contained as a filler with oxygen. Is reduced to introduce oxygen vacancies into the film, improving the electrical properties of the transparent conductive film and removing the resin component from the resist.
The heat treatment can be performed twice. Finally, residues of the resist such as carbon powder remaining after the thermal decomposition are removed to obtain a patterned transparent conductive film.

[0011]

Embodiments of the present invention will be described below. In the method for forming a pattern of a transparent conductive film of the present invention, first, a resist ink containing carbon powder as a filler is printed on the surface of the transparent conductive film formed on the substrate by thermal decomposition of the composition for forming a transparent conductive film. I do. Here, the composition for forming a transparent conductive film used contains at least an indium compound and / or a tin compound and a solvent, and the indium compound and the tin compound may be any of an inorganic metal compound and an organic metal compound. The resin component used in the resist ink is cured by heat or light.After curing, the resin component has excellent etching resistance to an etchant such as hydrochloric acid or nitric acid, and at least has a heat resistant temperature of the substrate (200 to 500).
C.) or less, and epoxy (meth) acrylate or urethane (meth) acrylate is preferable. By using carbon powder as a filler, the printability, printability, and etching resistance of the resist ink are improved, but the carbon powder content in the resist ink is reduced.
If it exceeds 30 wt%, printing becomes impossible, so it is preferably 30 wt% or less. Furthermore, as a type of carbon powder, natural graphite
Graphite, carbon black and acetylene black are preferred for artificial graphite powder, and activated carbon is preferred for amorphous carbon powder.

Next, the resist ink is cured by heat or light. At this time, in the case of hardening by heat, heat treatment is performed at a fixed temperature for a necessary time or a continuous furnace to a necessary temperature for a certain time in order to provide heat necessary for the hardening. Thermosetting temperature is 50 ~
Preferably, the temperature is 150 ° C. and the time is 1 to 20 minutes. In the case of curing with light, the wavelength and amount of light to be cured differ depending on the type and amount of the curing initiator, but the light to be cured is preferably ultraviolet (around 365 nm) or visible light, and the amount of light is 50 to 50 nm.
3000 mJ / cm ² is preferred.

As described above, the resist is patterned on the surface of the transparent conductive film, and the transparent conductive film is etched. Here, the etchant used varies depending on the type of the transparent conductive film. For ATO, a metal powder such as Zn and a strong acid such as hydrochloric acid or nitric acid, for ITO, an acid such as hydrochloric acid, nitric acid, or hydroiodic acid,
Examples thereof include Lewis acids such as an aqueous ferric chloride solution, and a mixed solution thereof.

Next, the substrate on which the transparent conductive film has been patterned by etching is subjected to heat treatment. At this time, the transparent conductive film in contact with the resist is reduced by the carbon monoxide gas generated by the thermal decomposition reaction of the resin component in the resist and the reaction between carbon powder and oxygen contained as a filler, and Oxygen vacancies are introduced into the conductive film, thereby improving the electrical properties of the transparent conductive film and removing the resin component in the resist at the same time. The temperature of the heat treatment may be not less than the thermal decomposition temperature of the resin component in the resist and not more than the heat resistant temperature of the substrate, and is preferably 200 to 500 ° C. The atmosphere is
Preferably in nitrogen or in an inert gas.

Finally, the resist residue such as carbon powder remaining after the thermal decomposition is removed to obtain a patterned transparent conductive film. At this time, in order to remove the resist residue,
Physical removal is required, and it is preferably performed by ultrasonic cleaning in water or by blowing a high-pressure gas such as an inert gas such as nitrogen.

Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to these examples. Example 1 In an Erlenmeyer flask, 45 g of indium nitrate [In (NO ₃ ) 3.3 H ₂ O] was weighed, 50 g of acetylacetone was added, and the mixture was mixed and dissolved at room temperature. 2.7 g [Sn / (In + Sn) × 100]
1%] of stannous oxalate (SnC ₂ O ₄ ) and acetone were added and refluxed. The solution after the reflux was cooled to around room temperature, 10 g of glycerin was added, and the mixture was stirred and mixed to obtain a desired composition for forming a transparent conductive film.

In FIG. 1, the composition for forming a transparent conductive film is spin-coated on a silica-coated glass substrate 1, left at room temperature for 5 minutes and dried at 100 ° C. for 5 minutes.
The transparent conductive film 2 was formed by firing at 00 ° C. for 1 hour. The state is shown in FIG.

Next, a thermosetting resist ink 10 comprising an epoxy acrylate, an organic curing initiator and an organic solvent is used.
2.5 g of graphite powder having an average particle size of 3 μm [graphite powder / (resist ink + graphite powder) × 20% by weight × 100) was added to and mixed with g to obtain a resist ink containing desired graphite powder as a filler. . The thermosetting resist ink is printed on the transparent conductive film 2 in a pattern having a line width of 2 mm and an interval of 0.5 mm by screen printing as shown in FIG. 1 (b), and dried at 60 ° C. for 10 minutes. Heat treatment was performed at 130 ° C. for 30 minutes to cure the resist, thereby forming a resist pattern 3.

Next, the substrate 1 on which the transparent conductive film 2 and the resist pattern 3 have been formed is subjected to 2N hydrochloric acid (HC).
1) and 50 wt% ferric chloride (FeCl ₃ ) and immersed in an etching solution, and etched at 30 ° C. for 1 minute. The state is shown in FIG.

The substrate 1 is heat-treated at 200 to 500 ° C. in nitrogen for 1 hour, and then ultrasonically cleaned with pure water for 1 minute to remove resist residues. I got The state is shown in FIG.

FIG. 2 shows the relationship between the heat treatment temperature of the resist and the specific resistance of the finally obtained transparent conductive film. (Example 2) 10 g of an ultraviolet curable resist ink comprising a urethane acrylate, an organic curing initiator, and an organic solvent
To 0 g of graphite powder having an average particle size of 3 μm [graphite powder / (resist ink + graphite powder) ×
100 at 0 wt%] to 4.3 g [(graphite powder / (resist ink + graphite powder) × 100) 30 wt%]
Was added and mixed to obtain a resist ink using a desired graphite powder as a filler. Instead of the thermosetting resist ink, use the above-mentioned UV-curable resist ink, screen-print it on a silica-coated normal glass substrate, dry it at 90 ° C for 10 minutes, and apply UV light with a high-pressure mercury lamp (irradiation intensity 80 W / cm). 1
Irradiated for minutes and cured. When the carbon powder content in the resist ink exceeded 30% by weight, printing was impossible.
The heat treatment of the cured substrate was performed at 500 ° C. for 1 hour in an argon gas. Others are the same as the first embodiment.

FIG. 3 shows the relationship between the graphite powder content in the resist ink / graphite powder / (resist ink + graphite powder) × 100 and the specific resistance of the finally obtained transparent conductive film. (Example 3) Instead of graphite powder, average particle size 1
2.5 g [mu] m artificial graphite (acetylene black) powder [graphite powder / (resist ink + graphite powder) .times.100 × 20 wt%] was added and mixed. Others are the same as the second embodiment. (Example 4) Instead of graphite powder, activated carbon 2.5
g [(Graphite powder) / (20% by weight of resist ink + graphite powder × 100)] was added and mixed as in Example 2. (Example 5) Instead of graphite powder, 2.5 g of natural graphite powder [ The graphite powder / (resist ink + graphite powder × 100, 20 wt%) was added and mixed, and the other conditions were the same as in Example 2.

Comparative Example 1 In an Erlenmeyer flask, 45 g of indium nitrate (In (NO ₃ ) 3.3H ₂ O) and 5.4 g of indium nitrate were added.
[Sn / (In + Sn) × 100), 9 mol%] stannic chloride (SnCl ₄ .5H ₂ O) is weighed, α-terpineol and nitrocellulose are added, and the mixture is stirred and mixed to form a transparent conductive film. The composition was synthesized. The composition for forming a transparent conductive film was screen-printed on a silica-coated flat glass substrate to form a pattern having a line width of 2 mm and an interval of 0.5 mm. The substrate was left at room temperature for 5 minutes, dried at 100 ° C. for 10 minutes, and baked at 500 ° C. for 1 hour to obtain a patterned transparent conductive film.

Comparative Example 2 In place of carbon powder, 2.5 g of calcium carbonate powder having an average particle size of 3 μm was used. Also,
Instead of heat treatment and ultrasonic cleaning with pure water, the resist was removed with a 3 wt% aqueous sodium hydroxide solution. Others are the same as the second embodiment.

Table 1 shows the results of Examples 3 to 5 and Comparative Examples 1 and 2.

[0026]

[Table 1]

[0027]

As is clear from the above description, by using the method for forming a pattern of a transparent conductive film of the present invention, a pattern having low resistance and high transmittance excellent in conductivity and transparency in the visible region is obtained. The transparent conductive film can be easily and inexpensively obtained, and is suitable for use as a transparent electrode such as a display element or a heating resistor.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a method for forming a pattern of a transparent conductive film of the present invention.

FIG. 2 is a diagram showing the relationship between the heat treatment temperature of a resist and the specific resistance of a transparent conductive film according to one embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the graphite powder content in a resist ink and the specific resistance of a transparent conductive film according to one embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 transparent conductive film 3 resist pattern 4 patterned transparent conductive film

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-93915 (JP, A) JP-A-3-276509 (JP, A) JP-A-6-139845 (JP, A) (58) Field (Int. Cl. ⁷ , DB name) H01B 13/00

Claims (5)

(57) [Claims] A step of printing a resist ink containing carbon powder as a filler on the surface of a transparent conductive film formed on a substrate by thermal decomposition of a composition for forming a transparent conductive film; A step of curing the transparent conductive film, a step of heating the substrate, and a step of removing a residue of the resist ink. 2. The method according to claim 1, wherein the resist ink contains at least one of epoxy acrylate, epoxy methacrylate, urethane acrylate, and urethane methacrylate. 3. A resist ink comprising natural graphite, artificial graphite,
2. The method according to claim 1, further comprising a carbon powder selected from the group consisting of amorphous carbon. 4. The carbon powder content of the resist ink is 30 wt%.
The method for forming a pattern of a transparent conductive film according to claim 1, wherein: 5. The method according to claim 1, wherein the composition for forming a transparent conductive film comprises at least an indium compound and / or a tin compound and an organic solvent.