JPH02120374A - Production of transparent conductive ultramicroparticle and formation of transparent conductive thin film - Google Patents

Abstract

PURPOSE:To obtain an ultramicroparticulate coating material which can form a thin film excellent in conductivity and transparency by a coating process comprising reacting an aqueous solution of an acid salt of indium, an acid salt of tin or a mixture thereof with an aqueous alkali solution and heating the obtained insoluble indium compound and tin oxide in a reducing atmosphere. CONSTITUTION:Transparent conductive ultramicroparticles can be obtained by reacting an aqueous solution of an acid salt of indium, an acid salt of tin or a mixture thereof with an aqueous alkali solution, removing the formed oxides and/or hydroxides of indium and tin and heating them at 240-320 deg.C in a reducing atmosphere. To form a transparent conductive thin film by using the obtained ultramicroparticles, the microparticles are mixed in a solvent or a coating material, and the mixture is applied to a substrate, calcined to remove the binder and heated to 200-400 deg.C in a reducing atmosphere. As the acid salts of indium and tin, their chlorides, sulfates and nitrates are desirable. As the alkalis, ammonia, sodium hydroxide, potassium hydroxide, etc., are desirable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing transparent conductive ultrafine particles. In particular, it relates to a method for producing a thin film with excellent conductivity and transparency.

[Prior Art and Problems to be Solved by the Invention] Transparent electrodes are generally used in solar cells, liquid crystal display devices (T-), electroluminescent Y-sense (EL) display devices, and the like. These elements have a structure in which a glass substrate, a thin transparent electrode, and thin films having various functions are stacked on top of each other. It is necessary to manufacture this transparent electrode at low cost,
Current technologies include vacuum evaporation, sputtering, CD
There are the V method and the spray method, but the vacuum evaporation method, the S/ The spray method and the coating method are highly productive and inexpensive methods.The spray method has a fast film formation speed, but in the JJ method, an aqueous solution of tin chloride is sprayed onto the glass surface heated to about 500°C. When sprayed onto the glass, tin oxide and hydrogen chloride are generated on the glass surface, and this tin oxide adheres to the glass surface as a thin film, forming a transparent electrode film. However, since the fog is generated by radiation from the nozzle, there is a difference in concentration in the film deposited on the glass plate, and droplets are generated due to the aggregation of the fog.
There is a problem of fog dehydrating in a high-temperature furnace, which tends to cause spots, and tin chloride powder adhering to thin films. It is limited to low-grade applications such as anti-fog glass.

On the other hand, with advances in electronics technology, clean room technology, etc., the demand for conductive thin films that have transparency is increasing.

Therefore, the present invention provides a method for producing an ultrafine particle coating material for producing a thin film with significantly improved conductivity and transparency compared to a coating method, and a method for producing a transparent conductive thin film using the same. Make it lj-like.

[Means for Solving the Problems] In order to solve the above-mentioned technical problems, the present invention involves reacting an aqueous solution of an acid salt of indium, an acid salt of tin, or a mixed aqueous solution of both with an alkaline aqueous solution, and producing indium. and a method for producing transparent conductive ultrafine particles characterized by taking out tin oxides and/or water oxides and heating them to 240°C to 320°C in a reducing atmosphere. The acid salts of indium and tin are preferably chlorides, sulfates, and nitrates.Also, the alkaline component is ammonia:-
A. Sodium hydroxide, potassium hydroxide, and sodium carbonate are preferable. Furthermore, the present invention utilizes the transparent conductive ultrafine particles prepared as described above, mixes them in a solvent and a paint, applies them on a substrate, calcinates them, removes the binder, and then heats them in a reducing atmosphere. , a method for producing a transparent conductive thin film characterized by heat treatment at 200°C to 400°C.

According to the present invention, an aqueous solution of an acid salt of indium and tin is prepared such that tin oxide is about 1 to 10% by weight relative to the total of indium oxide and tin oxide, and this is Use as starting material. In this case, "acidic salts" are water-soluble and acidic salts such as chlorides, sulfates, and nitrates, which react with alkali to form ζ-soluble indium compounds and insoluble tin compounds. occurs. “Alkaline aqueous solution”
is prepared using a soluble alkali salt, for example, a sulfite, a nitrite, a phosphate, an ochinoate, and the like.

Preparation of alkaline aqueous solution to react with acidic aqueous solution! As the alkali component, sodium hydroxide, potassium hydroxide 2, and sodium carbonate are preferable. This alkaline content, by nature, must be washed away from the indium and tin precipitate by washing with water after one reaction; therefore, other alkaline substances may also be used as long as they can be easily washed away with water. For example, sodium bicarbonate, barium hydroxide, barium hydroxide, etc. can also be used.

The precipitate deposited by such a neutralization reaction is washed with water to remove substrates (chlorine, sulfate groups, nitrate groups, etc.) and alkali groups (sodium, potassium 11, calcium, etc.), and then dehydrated and dried.

When this drying process is performed, some of the agglomerated parts are disintegrated and dried to obtain ultrafine powder, but
If the volume resistivity value of this powder itself is measured, it can be seen that it is a completely electrically insulating material. This dry powder is
By heat treatment in a reducing gas atmosphere at a temperature of 240 to 320°C, preferably at a temperature of 260' to 280°C, the particle size is 100 to 300 μm, and the volume resistivity value is 1 to 1. A transparent and electrically conductive ultrafine particle material was obtained at 3×10-”00m. In this case, hydrogen, ammonia gas, carbon oxide, etc. can be used as the reducing gas. Among them, a mixed gas of two or more types of reducing gases can also be used.Also, it can also be used diluted with an inert gas such as nitrogen or argon.

However, if the reducing gas treatment is not carried out, the volume resistivity value will always be high (below 104 Ωcta).8 This reducing gas atmosphere heat treatment according to the present invention is also very effective. This effect has been clarified for the first time by the present invention. In other words, this may be because the reduction process causes hydrogen atoms to bond with tin atoms, which have a fixed charge, making it easier for electrons as majority carriers to drift, in other words, the Fermi level becomes very close to the conduction level. However, the real reason is unknown. That is, since the transparent conductive ultrafine particle material according to the present invention is neutralized, there is no damage caused by acid content and it can be used safely. In addition, by using such ultrafine particle materials, the surface resistance value can be increased to 50.
A thin film having a light transmittance of 80% or more near Ω/mouth and excellent transparency and conductivity of L can be obtained.

That is, this transparent conductive ultrafine particle/material can be mixed with a paint resin to form a transparent conductive paint.

As the resin that can be used in the transparent conductive paint according to the present invention, resins that can be prepared and used by ordinary paint techniques can be used, but there are no special restrictions, such as polyvinyl acetate, ureaformanodehyde resin, epoxy resin, Polyester resin, phenol resin, Alky2F resin, polyurethane resin, vinyl resin, etc. can be used. That is, synthetic resins that are generally used in transparent paints can be used as the main component for forming the coating film.

As a solvent for the above tree 1n, water, alcohol,
Solvents such as benzene, olefins, boiled oil, etc. can also be used. Examples of such solvents include menal ethyl ketone (MEK), cyclohexanone, tetrahydrofuran (
(THF), ethyl acetate, acetone, and lower alcohols. In addition, toluene, xylene, cellosolves such as acetic acid, petroleum spirits,
It may also contain r4I agents commonly used in paints, such as sulfur naphtha and methylene chloride.

The transparent conductive paint thus prepared can be applied to a substrate, for example a glass plate, by a conventional method. As for substrates, anything can be used as long as it does not lose its transparency or undergo significant deformation or damage through the following treatment. Glass plates, snow N, crystal, transparent alumina, sodium chloride 1, single crystal plates, gypsum single crystal plates, etc. can be used! Ru. Generally, a glass plate is used.

First, the glass plate coated with the ultrafine transparent conductive paint prepared in step 1 is dried and heated. Varies, but preferably from 350°C to 500°C,
A temperature sieve with a temperature of 420° C. to 470° C. is used to sufficiently evaporate and blow away the binder. In this way, in the binder removal process, the surface resistance value is 10'Ω
/ About a mouthful.

Next, it is heated to 200-400'C1, preferably 250-300'C in a reducing atmosphere, and the total light transmittance is 80%.
As described above, a transparent conductive thin film having a surface resistance value of about 50 Ω/mouth, which is superior to the fourth in performance, can be obtained.

On the other hand, with conventional transparent 4-electrode paints, only those with a transmittance of 40 to 60% and a surface resistance value of 10' to 10'Ω can be produced, and are limited to low-grade products. In other words, due to the characteristics of the ultrafine particle material produced by the present invention, it has excellent dispersibility and uniformity in paints, and as a result, it is a transparent material with excellent transmittance and surface resistance. TIF is a technology that enables the production of conductive thin films at a lower cost than vapor phase methods or sputtering.

In the suberet method and coating method using paint containing the ultrafine particle material produced in the present invention, transparent conductive fine powder is sprayed or applied, but the transparency and conductivity of the film formed in this way are It depends on the characteristics of the transparent conductive fine particles. In contrast, in the conventional technique, an aqueous solution of indium and/or tin chloride is sprayed or applied onto a glass plate and heated to perform hydrolysis. That is, in the conventional manufacturing method, the surface resistance is 1
The chloride solution itself has a very high 0" to 104 Ω/mouth (for example, even in the case of graphite, <20 Ω/mouth), and the visible light transmittance is low at 40 to 50%, giving it a milky white color. Hydrogen chloride, which is corrosive as a strong acid and is generated during hydrolysis, also poses a problem.

So, in the present invention, as a transparent conductive material for spraying and coating methods, it has indium-tin-based transparency and surface conductivity superior to graphite, and is not harmful to the environment. We have established a manufacturing method for ultrafine particle coating 41 material that does not emit or contain toxic components such as hydrogen chloride.

In other words, since it is a paint made of ultrafine particles, it has very good dispersibility, so it is very easy to make a uniform coating film, and it is possible to provide a transparent conductive coating material with excellent properties. .

In the method for producing a transparent conductive thin film using a coating method according to the present invention, the neutralization reaction product is heated at 240°C in a reducing atmosphere.
Heating at ~320°C shows that the reaction product remains as an insulator due to its gel-like amorphous state, and the transmission The ratio is also about 50%. However, this reduction heat treatment is omitted, and heat treatment (500°C) and reduction treatment (200°C to 400'C) after ultrafine particle formation and coating are performed.
), the surface specific resistance value is 1 with a transmittance of about 50%.
The value is about 0', which is unsatisfactory and impractical.

In addition, usually after applying a transparent conductive material to the substrate,
In order to blow away the binder, it is heated, but at this time,
Since the conductive fine particles dispersed in the binder can be removed from the binder, they can come closer to each other and increase their conductivity, but the heating temperature for this purpose must be set to suit the fine particle conductive material. Should. On the other hand, according to the manufacturing method of the present invention, when the heat treatment for removing the binder is followed by the reduction heat treatment at a temperature of 200 to 400°C, the total light transmittance increases to 80% or more. The surface resistance is now 50Ω/hole, and both transparency and conductivity are excellent, which was not possible before.
Obtained. Furthermore, according to the present invention! ! ! Since the crushed transparent conductive coating material is ultrafine particles, a binder,
It has excellent dispersibility in resins, can be obtained as a highly uniform dispersion, and at the same time has excellent reproductive performance, making it possible to produce inexpensive and economical transparent conductive paints.

The transparent conductive paint of the present invention can form a film with excellent mechanical and chemical strength.

Further, resin components that can be used in the transparent four-electrode coating of the present invention include polyester resin, polyvinyl acetate,
Examples include urea formaldehyde resin, eboxo P4 resin, phenol resin, alkyd resin, and polyurethane resin.

Moreover, water, alcohol, bempine, olefin, boiled oil, etc. can be used as a solvent.

The binder used in the material of the present invention can be a known binder and a known technique. V14 is not limited to a particular method.For example, as the binder, inorganic binders such as ethyl silicate and water glass, and organic binders such as Bossester resin and acrylic resin can be used.

The coating film produced using the coating material obtained according to the present invention can be obtained by heating and doping dry smoke powder according to the prior art.
Compared to the coating film produced using the paint obtained by the J method, the V value is significantly inferior in terms of transparency and mass productivity.

The coating material obtained according to the present invention can be effectively used as a transparent conductive film or electrode for products such as electrodes for Rabi/Tostart fluorescent lamps and touch panels.

Next, the method for producing a conductive coating material and the method for producing a transparent conductive thin film according to the present invention will be specifically explained using Examples, but the present invention is not limited thereto.

[Example 1] So that S n O was 3% by weight in terms of oxide,
The blended aqueous solution of 1 n Cl s and S n Cl * was poured into an excess ammonia aqueous solution, and the generated In
The gel-like precipitate of hydroxides of Sn and Sn was filtered, dehydrated, and then washed with water. When ammonium ions and chloride ions could no longer be detected in the filtered cake, water washing and filtration were stopped to obtain a precipitated cake. This precipitate cake is dehydrated,
The dehydrated cake was dried at 100°C, and the loosely lumpy parts of the cake were crushed and placed in a sorted manner in a furnace filled with H and gas, heated at 270°C for 30 minutes, and dried at 100°C. Ultrafine particles with a particle size of ~200 were obtained. Polyester+
61 fat binder at a ratio of 30% by weight was mixed, applied to the surface of the glass plate using a doctor blade, dried, heated at 450 ° C. to remove the binder, and heated in a furnace in an H gas atmosphere. At 300℃, place in a U-shaped
Heating was performed for a minute to obtain a transparent conductive film on the surface of the glass plate.

When this film inner body was measured, the total light transmittance was 88% and the surface resistance was 500Ω/hole.

[Example 2] InC blended to have Sn of 0.1% by weight! , and 5
An aqueous solution of nC1 was poured into an excess ammonia aqueous solution, and the resulting gel precipitate was filtered, dehydrated, and then washed with water. The filter cake was washed with water until ammonia and chloride ions were no longer detected. The resulting dehydrated
After drying at 100°C, the loosely lumpy parts were crushed, and then placed in a flat plate in an NHs gas atmosphere and heated for 250"0120 minutes, resulting in a particle size of 100". A powder of ultrafine particles of ~300 particles was obtained.A polyester resin was mixed with this powder as a binder at a ratio of 35% by weight, and the mixture was applied onto the surface of a glass plate using a doctor blade, and after drying, °C for 30 min, then heated to 250'C in a NH, gas atmosphere,
A transparent conductive thin film was obtained. When this film inner body was measured, the results were that the total light transmittance was 87% and the surface resistance was 55%.
It was Ω/mouth.

[Example 3] An aqueous solution of InCII was poured into an excess aqueous ammonia solution, and the resulting gel-like precipitate was passed through 6Ii to dehydrate it, and then washed with water. &1 The overcook was washed with water until ammonia and chlorine ions were no longer detected. The resulting dehydrated cake was dried at 100"C, the cake was crushed and then placed in a flat plate in an H gas atmosphere for 3
Heated to 00°C and added as a binder to the obtained powder,
Mix polyvinyl acetate resin at a ratio of 40% by weight,
Apply 111 onto the glass plate surface using a doctor blade.
After drying, it was heated to 480°C, and then heated at 300°C for 30 minutes in an H gas atmosphere to obtain a transparent conductive thin film. The dimensions of this film inner body were measured and the results were that the total light transmittance was 85% and the surface resistance was 45Ω/hole.

[Example 4] An aqueous solution of 5n(NOl)4 was poured into an excess ammonia aqueous solution, and the resulting gel-like precipitate was filtered, dehydrated, and then washed with water. The filter cake was washed with water until ammonia and chloride ions were no longer detected. The obtained dehydrated cake was dried at 1°0°C, crushed, and then c
It was placed in a flat plate shape in an O gas atmosphere and heated to 300"C to obtain a powder. Acrylic resin was mixed as a binder at a ratio of 30% by mass to this powder, and the powder was mixed with a doctor blade using a doctor blade. After coating on the glass plate surface and drying,
The binder was blown off by heating at 480° C., and then heated at 300° C. for 30 minutes in a CO gas atmosphere to obtain a thin film. When measuring this inner membrane, the total light transmission was 86%,
The surface resistance was 50Ω/mouth.

[Example 5] Sn0. InCe3 blended to achieve affi Shun%
and SnCl a were poured into an excess ammonia aqueous solution, and the resulting gel precipitate was filtered, dehydrated, and then washed with water. The filter cake was washed with water until ammonia and chloride ions were no longer detected. The resulting dehydrated cake was dried at 100°C, crushed, and then treated with H
, placed on a plate in a gas atmosphere furnace at 270°C for 30 minutes.
Heated for 0 minutes. The obtained powder of 41 filler was added to the polyester M4 at a ratio of 30% by weight, and mixed with a pole in a bottle/tower mill. The mixture was sufficiently mixed in about 5 minutes.

On the other hand, as a conductive filler for comparison, silver powder (particle size 0
．． 1 μm), copper (particle size o, tam) and graphite were each added to the poly sprue resin at a ratio of 30 ff1-11%, and similarly mixed with a bot mill using a pole.

As a result, in both cases, the mixture was insufficiently mixed.

[Effect of the invention] In the method for creating a transparent conductive thin film according to the present invention,
The manufacturing method produced the following remarkable technical effects.

First, it becomes possible to form a transparent conductive thin film with improved transparency and conductivity compared to the conventionally known coating material γ1 by a coating method.

Second, it is possible to produce a transparent conductive thin film that can meet the recent strict demands for transparency and conductivity.

Third,! We were able to provide an economical method for producing transparent, conductive thin films that can reduce manufacturing costs.

Patent applicant: Sumitomo Himento Co., Ltd. Agent: Patent attorney Yutaka Kuramochi

Claims (4)

[Claims] (1) React a mixed aqueous solution of indium acid salt, tin acid salt, or both with an alkaline aqueous solution, take out the produced indium and tin oxide and/or hydroxide, and heat the mixture at 240°C to 320°C in a reducing atmosphere. A method for producing transparent conductive ultrafine particles characterized by heating to ℃. (2) The acid salt of indium and the acid salt of tin are chloride,
2. The method according to claim 1, which is a sulfate or a nitrate. (3) The production method according to claim 1, wherein the alkali is ammonia, sodium hydroxide, potassium hydroxide, or sodium carbonate. (4) The transparent conductive ultrafine particles according to claim 1 are mixed with a solvent or paint, applied onto a substrate, calcined to remove the binder, and then heated at 200°C to 400°C in a reducing atmosphere. A method for producing a transparent conductive thin film, characterized by heat treatment.