JPH01159910A - Conductive material - Google Patents

Abstract

PURPOSE:To obtain an inexpensive transparent conductive film with excellent physical and chemical endurance by coating a conductive material composed of basic organic acid tin solution on a substrate. CONSTITUTION:A conductive material composed of basic organic acid tin solution is formed on a substrate. For the conductive material of such a construction, a tin compound is at first reacted with a metallic salt bicarbonate or ammonium bicarbonate to form gel. Stannic chloride, tin (II) sulfate, or the like is used as the tin compound, and sodium bicarbonate, calium bicarbonate, or the like is used as the metallic salt bicarbonate. The use of rate is determined so that the reaction liquid pH becomes 6 or more when the gel generating reaction is completed. Next, impurities are removed by cleaning, and an organic acid and water, when required, is added to dissolve the gel to get the basic organic acid tin. The kind of the organic acid used is selected among oxialic acid, actic acid, glicolic acid, and glicocholic acid to generate tin and soluble basic salt so that the equivalent to tin becomes 0.7 or less.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to novel electrically conductive materials.

Transparent conductive films made of conductive materials that have both electrical conductivity and optical transparency are industrial materials whose demand has been rapidly increasing in recent years, coupled with the remarkable development of electro-optical devices.

Among these, transparent conductive films made of tin oxide-based conductive materials are widely used because they have excellent physical and chemical durability and are cheaper than indium oxide-based materials.

(Prior Art) A transparent conductive film made of such a conductive material is usually deposited on a substrate by a film forming method such as a vapor phase method, for example, a CVD method, a vacuum evaporation method, a reactive ion blasting method, or a sputtering method. It is coated in a film and is used for practical purposes.

However, all of these methods not only have the drawbacks of complicated equipment and slow film formation speed, but also
There is a problem in that the film is formed on a small area and a film with a large area cannot be obtained.

On the other hand, the so-called coating method, in which a film is formed by coating a substrate with a liquid raw material, has the advantage that a large-area thin film can be obtained through a relatively simple process, and is an industrially promising method.

This coating method has been extensively studied for tin oxide based materials as well, and the thermal decomposition behavior of a wide variety of liquid tin based compounds has been studied.

The main ones include: - aqueous solutions of tin salts of inorganic or organic acids, - organic tin compounds that are liquid at room temperature, and - tin alkoxides and their hydrolysates, all of which are used in coatings and as conductive materials. has its drawbacks,
It has not yet been put into practical use.

That is, with the material (2), the salt crystals tend to crystallize on the substrate in the drying process after coating the substrate, making it difficult to obtain a uniform film.

Furthermore, with the material (3), since a dry thin film cannot be obtained, the film thickness cannot be controlled easily, and there are also problems in the method of holding the substrate during firing.

Furthermore, although material (■) has been developed recently, there are many industrial problems such as the coating liquid is extremely unstable and strict moisture management is required to form a uniform and transparent film. .

(Problems to be Solved by the Invention) In view of these circumstances, the present inventors have conducted intensive research to obtain a conductive material that can easily form an excellent transparent conductive film. This has led to the completion of the present invention.

(Means for Solving the Problems) That is, the present invention relates to a conductive material made of a basic organic acid tin solution.

(for production) The present invention will be explained in more detail below.

Characteristics of conductive materials that are desired not only for transparent conductive films but also as coating agents in general are: 1. Excellent film forming properties during coating, allowing a uniform film to be obtained; 2. Easy control of film thickness. That's true.

The present inventors investigated various aqueous solutions of tin salts as transparent conductive coating agents, and as a result, discovered that a specific type of aqueous solution of basic tin acid salts satisfies the above two characteristics.

Water-soluble organic acid tin acids having a normal salt composition are conventionally known.

However, as described above, even if this solution is coated on a substrate, crystals of the salt will precipitate on the substrate, making it impossible to form a uniform and transparent dry film. Furthermore, even if drying conditions are specially devised to prevent crystallization from a macroscopic perspective, precipitation as crystals is essentially unavoidable. In this case, the crystal becomes a mere skeleton and a microscopically uniform film cannot be obtained.

It is clear that these non-uniformities have an adverse effect on both electrical conductivity and optical transparency.

In contrast, when coating with the basic organic acid tin solution of the present invention, the dried film is uniform both macroscopically and microscopically, and the fired film, which has a tin oxide composition, is also uniform. It can be obtained as something.

The basic organic tin acid of the present invention is new, and therefore, it is currently unclear why the dried product of its solution does not exhibit the crystallization phenomenon like the normal salt.

The basic inventive method for obtaining a uniform coating film
There are several desirable ranges for the composition of tin acid.

First, the type of organic acid used must naturally form a soluble basic salt with tin.

As a result of studying various organic acids, the present inventors discovered that borate, lactate, glycolate, and gluconate are substantially useful as conductive materials.

As for organic acids other than these, for example, formic acid, acetic acid, dichloroacetic acid, malonic acid, tartaric acid, etc., soluble basic salts cannot be produced even by the production method described below.

Next, the basicity is closely related to the quality of film formation during coating; in other words, the higher the basicity, the better the film formation.

Therefore, using the above-mentioned organic acid, the basicity is set to 30% or more, and the upper limit is approximately 80%, and it is possible to prepare the basicity up to about 90% depending on the type of organic acid used.

Incidentally, it goes without saying that the higher the basicity, the smaller the amount of organic acid to be used relative to tin, and from this economic point of view basic salts are useful.

Although the basic organic acid tin of the present invention must have at least the above two conditions, the present invention is not limited to tin alone.

That is, generally antimony, indium, cadmium, gallium, bismuth, etc. are often added for the purpose of improving the electrical conductivity of tin oxide, but in the case of the basic organic acid tin of the present invention, the above substances are also added. By adding
It is possible to improve electrical conductivity.

For example, basic tin acid containing antimony, which exhibits superior conductivity, can be produced by the method described below.
can.

Furthermore, the conductive material of the present invention may contain additives for improving the physical properties of the transparent conductive film, particularly its strength.

For example, phosphate-based materials that develop bonding strength when fired,
Examples include low melting point glass compositions and organic silicates.

Furthermore, in order to improve the wettability with the substrate during coating, it is also possible to mix the conductive material of the present invention with a suitable organic solvent, such as alcohol or cellosolve, to make the workability easier. .

The conductive material of the present invention is completely unknown in the past, and creates new uses in the field of transparent conductive materials.

The characteristics of the conductive material of the present invention are listed below.

First, as mentioned above, a uniform coating film can be obtained by the coating method.

The film thickness can also be freely controlled by changing the concentration of the coating liquid.

Second, it does not generate corrosive gas during drying or firing.

The conductive material of the present invention consists essentially only of tin (and additives such as antimony) and organic substances.

Therefore, the only gases generated in the step of firing this into an oxide are carbon dioxide and water, and no measures are required.

In contrast, when stannic chloride, for example, is used as the inorganic tin salt aqueous solution, a large amount of harmful and corrosive hydrogen chloride gas is generated during firing, which is unfavorable in terms of furnace selection and working environment.

For these reasons, the conductive material of the present invention is industrially useful.

Thirdly, it has excellent stability.

Tin alkoxyl was extremely unstable and had a fatal defect of poor stability over time.

The conductive material of the present invention has not only high purity but also good stability, and can be said to be of higher quality.

The conductive material of the present invention having the above-mentioned excellent characteristics,
Not only is it very useful as a transparent conductive film material, but it can also be used as a conductivity imparting agent by coating various fillers.
Furthermore, it is useful for applications in the field of electroceramics such as gas sensor materials, and is a novel substance that can be applied to many other uses.

The basic organic acid tin of the present invention can be produced by the following method.

First of all, a gel is produced by reacting a tin compound with an alkali metal bicarbonate or an ammonium bicarbonate salt.

Examples of the tin compound include stannic chloride and stannic sulfate, and examples of the alkali metal bicarbonate include monolium bicarbonate and potassium bicarbonate.

The proportion used is the reaction solution P at the end of the gel formation reaction.
It is advisable to use it in such a proportion that H is 6 or more.

If the amount i of the alkali metal bicarbonate or ammonium bicarbonate used is smaller than this, the tin will not be completely gelled and the yield will be poor, which is also undesirable for economic reasons.

Another method is to add thorium stannate to the tin compound.
A gel may be produced by using potassium stannate or the like and reacting this with carbon dioxide.

In addition, if you want to obtain the above-mentioned additive for improving conductivity, for example, a basic organic acid tin containing antimony, add an antimony compound to an aqueous solution of the tin compound in advance and precipitate it together with the tin to obtain a gel. The method is simple.

Of course, tin and antimony may be precipitated separately, and then both gels may be mixed and subjected to subsequent processing.

The gel thus produced is then washed to remove impurities.

Regarding the amount of residual impurities, it is preferable to have a small amount in view of the production of basic organic acid tin and the intended use.

The cleaning means is not particularly limited, and any commonly used methods such as water filtration and repulp centrifugation can be used.

Also, proper ion exchange? ! A method may also be adopted in which impurities are removed by contacting with a pilgrim.

The basic organic acid tin of the present invention can be obtained by adding and dissolving an organic acid and, if necessary, water to the washed gel.

The organic acids used here include the aforementioned oxalic acid, lactic acid,
It is an acid selected from glycolic acid and gluconic acid.

In addition, the amount used is that the basicity is 30% or more, in other words,
The amount is such that the equivalent weight of organic acid to tin is 0.7 or less.

Furthermore, the amount of water may be appropriately used to obtain the desired concentration.

In addition, in order to improve the solubility of the gel, heating may be performed as necessary.

(Example) The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto.

In addition, all percentages indicate foreground percentage unless otherwise specified.

Example 1 Ammonium bicarbonate aqueous solution (N11.2.9%) 100
0 parts of stannic chloride aqueous solution (SnO2) while stirring.
16.5%) were gradually added.

After filtering out the generated gel, water injection filtration and cleaning were performed until no chlorine was found in the gel. As a result, 5n02
A gel containing 36.5% was obtained (11).

Then, using this gel, basicity 25%, SnO2
Various basic organic acid tin aqueous solutions having a concentration of 5% were produced.

The method is to add and mix organic acids and water in the amounts shown in Table 1 to 100 parts of each of the gels, and add 90 parts of water while stirring.
Heat treatment was performed at ℃ for 1 hour.

Table 1 shows the properties of the various basic organic acid tin solutions and other biological acids obtained.

As is clear from Table 1, it can be seen that the basic organic acid tin aqueous solution of the present invention can be obtained only when oxalic acid, 1'L acid, glycolic acid, and gluconic acid are used.

Example 2 Basic tin oxalate aqueous solutions of various basicities were prepared and their performance as conductive materials was investigated.

Gel 10 containing 6.5% of 5n02 obtained in Example 1
0 parts, oxalic acid (dihydrate) and water in the amounts shown in Table 2 were added and mixed, and heated to 90°C while stirring.
Heat treatment was performed for 1 hour.

As a result, SnO2 concentration 2%, basicity 30.50 and 8
A 0% basic aqueous tin oxalate solution was obtained. (Example of the present invention) As a comparative example, an aqueous tin oxalate solution having a normal salt composition was obtained by the same operation as described above, except that the amounts of oxalic acid and water added were changed to the amounts shown in Table 2.

(Comparative example) These aqueous solutions of the present invention and comparative example were
Svinco = 14--taing was performed on a slide glass of 1,100 rpm at a rotational speed of 1100 rpm.

Next, these coated glasses were dried at 100°C and the surface condition was observed. Furthermore, these were heated to 60O°C.
The surface resistance and light transmittance of the obtained transparent conductive coated glass were measured.

The results are shown in Table 2.

As is clear from Table 2, good transparent conductive glass can be obtained by the coating treatment using the basic tin oxalate aqueous solution of the present invention, whereas the coating treatment using the basic tin oxalate aqueous solution has a normal salt composition. Both surface resistance and light transmittance are inferior.

Example 3 A conductive material of the present invention comprising an aqueous basic tin oxide solution containing antimony as an additive for improving conductivity was produced by the following method.

5.4 parts of antimony trichloride was added to 1000 parts of stannic chloride aqueous solution 1 (Sn02 17.5%) and dissolved by heating to 80°C.

After cooling, this was gradually added to 3494 parts of ammonium bicarbonate aqueous solution 1 (NH33.0%) while stirring to form a gel.

The generated gel was filtered, about 1000 parts of water was added thereto, repulped, and then solid-liquid separated using a centrifuge.

This operation was repeated until no chlorine was observed in the gel, and as a result, SnO, 32.1%, Sb O, 52
A gel was obtained containing %.

Next, 19 parts of 50% 1L acid and 41 parts of water were added to 100 parts of the gel.
The mixture was heated at 90°C for 1 hour while stirring to dissolve the gel.

As a result, a basic tin lactate aqueous solution containing 20% Sn0 and antimony with a basicity of 75% was obtained.

After diluting this with water to give a SnO2 concentration of 2.5%, a coating treatment was performed on glass in the same manner as in Example 2 to obtain transparent conductive coated glass.

As a result of measuring the surface resistance and light transmittance of this glass, the surface resistance was 5.5Ω/hole, and the light transmittance was 91%.

Patent applicant: Taki Chemical Co., Ltd. = 18 -

Claims (1)

[Claims] A conductive material made of a basic organic acid tin solution.