JP2941722B2 - White conductive substance and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white conductive substance having a high whiteness and having a conductive layer made of tin oxide on the surface of a substrate, a method for producing the same, and a conductive composition containing the white conductive substance. It is about things.

[0002]

2. Description of the Related Art Conventionally, with the remarkable development of the electronics industry, development of conductive materials has been desired. Carbon black or metal powder, which is generally used as a conductive material, has a very low electric resistance and is excellent in conductivity, but its use is limited due to its black color tone.

[0003] As a white conductive substance that can be colored, those in which the surface of titanium oxide is coated with tin oxide and white conductive titanium oxide in which tin oxide doped with antimony is coated are disclosed (Japanese Patent Application Laid-Open (JP-A) No. 2002-112733). JP-A-53-92854 and JP-A-58-209002).

It is known that a conductive material having an anisotropic shape such as a needle shape or a fibrous shape can provide a desired conductivity with a smaller blending ratio than a spherical shape. Have been. Accordingly, development of a white conductive material in which a conductive layer such as tin oxide is formed on the surface of a fibrous base material or the like has been actively conducted.

Japanese Patent Publication No. 61-26933 discloses a white conductive substance mainly composed of fibrous potassium titanate whose surface is coated with tin oxide. In addition, Japanese Unexamined Patent Publication
JP-A-3-233016 discloses acicular conductive titanium oxide in which the surface of high-quality acicular titanium oxide is coated with tin oxide and antimony oxide. Also, Japanese Patent Laid-Open No. 6-18 / 1994
Japanese Patent No. 3737 discloses a conductive titanium oxide fiber in which the surface of a monoclinic titanium oxide fiber is coated with tin oxide and antimony oxide.

In these conventional white conductive materials, if the conductive layer is formed only of tin oxide, sufficient conductivity cannot be obtained. Therefore, antimony is doped to cause oxygen defects in the crystal lattice. , Exhibiting higher conductivity. However, antimony has problems such as toxicity, and it is desired that tin oxide coating layer containing no antimony exhibit conductivity.

In JP-A-6-207118, only a tin compound is adhered to a substrate without using antimony, and then heat treatment is performed in a non-oxidizing atmosphere or a reducing atmosphere, so that oxygen vacancies are contained in the tin oxide. And a method of expressing conductivity is disclosed.

[0008]

However, when heat treatment is carried out in a non-oxidizing atmosphere or a reducing atmosphere, tin oxide is colored blue-gray to black, and a white conductive substance having high whiteness is obtained. However, such a tendency became more remarkable as higher conductivity was obtained.

In addition, of course, in order to perform heat treatment in a non-oxidizing atmosphere or the like, a hermetically sealed facility and a gas and a facility for introducing the gas according to the atmosphere are required, which is disadvantageous in manufacturing cost.

An object of the present invention is to provide a white conductive substance which can obtain high conductivity without containing antimony and has high whiteness, a method for producing the same, and a conductive composition containing the white conductive substance. Is to provide.

[0011]

The invention according to claim 1 is a white conductive material having a conductive layer made of tin oxide on the surface of a substrate, wherein the conductive layer is formed from a stannic compound. A first tin oxide layer and a second tin oxide layer formed from a stannous compound, wherein the first tin oxide layer and the second tin oxide layer substantially contain an antimony component. It is not characterized by.

Here, the expression "substantially contains no antimony component" means that the content is such that the antimony component is not intentionally added. 0.1% by weight or less.

[0013] According to a second aspect of the present invention, the first tin oxide layer is formed on the surface of the substrate, and the second tin oxide layer is formed on the first tin oxide layer. It is characterized by: The invention according to claim 3 is a method capable of producing the white conductive material according to claim 1 or 2, wherein the base material is dispersed in water to form an aqueous dispersion, and the aqueous dispersion A stannic compound is added to the mixture, and a water-insoluble substance of stannic tin, which is precipitated by reacting the stannic compound, is deposited on the substrate surface, and then the stannous compound is added to the aqueous dispersion. Is deposited on the water-insoluble substance of tin, dehydrated, and heat-treated in an oxidizing atmosphere.

According to a fourth aspect of the present invention, in the method of the third aspect, when the stannic compound and the stannous compound are added to the aqueous dispersion, an alkaline solution is added at the same time. By adjusting the pH of the aqueous dispersion to 2 to 5, each water-insoluble substance is precipitated.

According to the fourth aspect of the present invention, the addition of the stannic compound and the addition of the stannous compound may be carried out at pH 2-5.
In the acidic region. When the water-insoluble substance of the tin compound is precipitated in the alkaline region, the deposition tends to occur rapidly, so that the adhesion tends to be non-uniform. In order to moderate such precipitation, it is necessary to use a dripping solution and a reaction system diluted in a large amount, which is not industrially preferable.

According to a fifth aspect of the present invention, there is provided a white conductive substance according to the first or second aspect of the invention or a white conductive substance produced by the method according to the third or fourth aspect, and a binder. Is a conductive composition.

Hereinafter, technical matters common to each of the first to fifth aspects of the present invention will be described as "the present invention". The substrate used in the present invention is not particularly limited, and examples thereof include needle-like or fibrous substances, flake-like or plate-like substances, powder-like or granular-like substances, and balloon-like substances. it can.
Moreover, it may be a natural mineral or an artificial substance. Specific examples of the needle-like or fibrous substance include ceramic fibers such as alumina fiber, titanium dioxide fiber, and silica fiber. As the scale-like or plate-like substance, a mica-based substance is generally used, but a flake-like substance such as talc or alumina flake or titania flake may be used. Examples of the powdery, granular or balloon-like substance include titanium dioxide, silica powder, zinc white, barium sulfate, kaolinite, silica balloon, glass balloon, silicon beads, glass beads and the like.

In the invention according to claim 4, since the aqueous dispersion in which the base material is dispersed is produced while adjusting the pH to 2 to 5, it is preferably a substance insoluble in an acidic solution.
In the invention described in claim 3 and the invention described in claim 4, since the base material is manufactured by dispersing in water, it is preferable that the base material be dispersible in water.

The stannic compound used in the present invention is 4
It is a valent tin compound, and for example, stannic chloride, stannic sulfate, stannic nitrate and the like can be used. The stannous compound used in the present invention is a divalent tin compound, and for example, stannous chloride, stannous sulfate, stannous nitrate and the like can be used.

The conductive layer of the white conductive material according to the present invention comprises a first tin oxide layer formed from a stannic compound and a second tin oxide layer formed from a stannous compound. Features. The amount of the conductive layer made of tin oxide covering the substrate is preferably 5 to 100 parts by weight, more preferably 10 to 30 parts by weight, in terms of SnO ₂ , based on 100 parts by weight of the substrate. . If the coating amount of the conductive layer is too small, the developed conductivity is not sufficient, and if it is too large, an excessive amount of tin oxide will be attached, and the improvement in conductivity as compared with the coating amount will be improved. Since it cannot be expected, it is economically disadvantageous, and may adversely affect other physical properties.

Further, the first aspect of the present invention is characterized in that the first tin oxide layer and the second tin oxide layer do not substantially contain an antimony component. As described above, in the present invention, since the second tin oxide layer which can easily generate oxygen vacancies and exhibit high conductivity is provided, high conductivity can be exhibited without containing an antimony component. it can.

According to the second aspect of the present invention, the first tin oxide layer is formed on the surface of the substrate, and the second tin oxide layer is formed on the first tin oxide layer. The reason for this is that the first tin oxide layer formed from the stannic compound generally has a more uniform coating than the second tin oxide layer formed from the stannous compound. Because you can. From such a viewpoint, it is preferable that at least 3 parts by weight or more of the first tin oxide layer is formed with respect to 100 parts by weight of the base material.
The coating amount of the first tin oxide layer is more preferably 5 to 2
0 parts by weight. The second tin oxide layer formed from a stannous compound has a function of introducing oxygen vacancies into tin oxide and imparting higher conductivity. Since the second tin oxide layer is formed from a stannous compound that is divalent tin, the second tin oxide layer is oxidized in the manufacturing process to be tetravalent tin oxide. Therefore, oxygen vacancies easily occur, and higher conductivity is easily developed. The coating amount of the second tin oxide layer is not particularly limited, and can be arbitrarily set according to required physical properties. It is preferably at least 3 parts by weight, more preferably 5 to 20 parts by weight.

According to the third aspect of the present invention, first, the base material is dispersed in water to form an aqueous dispersion. The concentration of the base material in the aqueous dispersion is appropriately set according to the base material to be used, sufficient mixing and stirring is possible, and the water-insoluble substance to be adhered and deposited on the base material in the subsequent step is uniform. Any concentration may be used so long as it can adhere.

As a first step, a stannic compound is first added to the aqueous dispersion of the substrate. The stannic compound is added in the form of a solution, preferably in the form of an aqueous solution. The stannic compound is converted into a hydroxide by, for example, hydrolysis in an aqueous dispersion, and adheres and deposits on the substrate surface as a water-insoluble substance of stannic. At this time, as described in claim 4, the alkaline solution is simultaneously dropped, and the pH of the aqueous dispersion is adjusted.
Is preferably maintained in the acidic region of 2 to 5. By maintaining the pH in the system in the acidic region of 2 to 5, the water-insoluble substance of stannic tin precipitates in a form that can more uniformly coat the base material, so that more uniform coating is possible. As the alkali solution to be dropped, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, aqueous ammonia and the like can be used.

After the reaction in the first step, as a second step, a stannous compound is added to the aqueous dispersion. By converting the stannous compound added to the aqueous dispersion to a hydroxide, for example, by hydrolysis, a water-insoluble substance of stannous is precipitated,
The stannous water-insoluble substance is deposited on the stannic water-insoluble substance. At this time, as described in claim 4, the stannous compound reacts while adding the alkali solution simultaneously with the addition of the stannous compound and keeping the pH of the aqueous dispersion in the acidic range of 2 to 5. Preferably. As the alkaline solution, the same alkaline solution as that added in the first step can be used.

According to the third and fourth aspects of the present invention, in the first step, a stannic compound is added to deposit and coat a water-soluble substance of stannic, and in the second step, the stannous compound is added. A water-insoluble substance of stannous is deposited and coated. This is because the water-insoluble substance of stannic tin, which is tetravalent tin, can more uniformly coat the substrate surface. In addition, when the pH is on the acidic side, the base material tends to be more uniformly coated. When the pH of the reaction system is set to the acidic side to precipitate the water-insoluble substance of stannous from the stannous compound, the viscosity of the reaction system tends to increase due to the precipitation of the water-insoluble substance. Since the base material is uniformly coated with the water-insoluble substance of stannic in the above, even if the stannous compound is added, the viscosity in the system does not increase so much. It can be uniformly deposited on the water-insoluble substance of ditin.
Therefore, according to the third and fourth aspects of the present invention, a water-insoluble substance can be uniformly attached to form a more uniform conductive layer.

The temperature of the solution at the time of adding the stannic compound and the stannous compound may be room temperature, but is preferably 5
Heat to about 0-80 ° C. Such heating enables a more uniform reaction.

As the addition amount of the stannic compound and the stannous compound, the first tin oxide layer formed from the stannic compound and the second tin oxide layer formed from the stannous compound are preferably used. The amount of addition is selected so that the coating amount of is obtained.

After the completion of the precipitation reaction of the water-insoluble substance by the addition of the above-mentioned stannic compound and stannous compound, while stirring at the same liquid temperature, for a while, for example, 0.5 to 5
It is preferable to leave for about an hour. Thereby, formation of a stronger coating layer can be promoted. At this time, p
As for H, the pH during the reaction may be maintained as it is, or may be maintained at a slightly increased pH within the range of the acidic region.

Next, the aqueous dispersion is filtered, dehydrated, and dried. The drying step may be performed in a series of steps including a subsequent heat treatment step. After drying, the water-insoluble substance deposited and deposited on the base material is subjected to a heat treatment to obtain conductive tin oxide. The heating temperature is not particularly limited as long as the coating layer on the substrate can be made of tin oxide having conductivity.
Usually, heat treatment is performed at a temperature of 350 to 600 ° C. Also,
The heat treatment time varies depending on the treatment temperature and the like, but is usually 30 minutes to 5 hours, preferably about 1 to 3 hours.

The atmosphere for the heat treatment is performed in an oxidizing atmosphere containing oxygen because it is necessary to oxidize a water-insoluble substance of stannous, which is divalent tin, to tetravalent. Therefore, it can be performed in the atmosphere. For this reason, it is not necessary to perform heat treatment in a closed state as in heat treatment in a non-oxidizing atmosphere or a reducing atmosphere.

In the fifth aspect of the present invention, the white conductive material of the present invention and a binder are mixed to form a conductive composition. As the binder, synthetic polymer compounds such as thermoplastic resins and thermosetting resins, natural resins and their derivatives, metal-containing organic compounds, inorganic binders, emulsions of inorganic or organic compounds, and the like can be used. These binders are selected according to the purpose and application of the conductive composition,
Can be used. Main applications include conductive resin compositions such as resin molded articles, paints, films, sheets, and inks that require conductivity, and can be applied according to other commonly used methods of use.

The mixing ratio of the white conductive substance and the binder is as follows:
It is appropriately set according to the type of the white conductive substance and the binder and the purpose and use of the conductive composition, and is not particularly limited, but is not limited to 100 parts by weight of the binder,
1 to 200 parts by weight of white conductive substance, preferably 5 to 10 parts
A range of 0 parts by weight is common.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the following examples.

Example 1 Anatase type titanium oxide fiber (trade name "NT-10")
0 ", manufactured by Fuji Titanium Industry Co., Ltd.)
The mixture was dispersed in the slurry and stirred for 10 minutes with a stirrer while maintaining the water temperature at 70 ° C. to form a slurry. Next, an aqueous solution of stannic chloride (23% by weight in terms of Sn) was added to the slurry.
g and 66.6 g of 12% by weight hydrochloric acid were added dropwise over about 1 hour, and at the same time, a 15% by weight aqueous sodium hydroxide solution was separately added dropwise to the slurry. Adjustment was made to fall within the range of ~ 4. After the completion of the dropping reaction in the first stage, the mixture was stirred for 30 minutes while maintaining the pH and the liquid temperature.

Next, an aqueous solution of stannous chloride (23 in terms of Sn)
A solution in which 100 g of 12% by weight of hydrochloric acid was added dropwise to 130 g of the mixture over a period of about 1 hour, and a 15% by weight aqueous solution of sodium hydroxide was separately slurried at the same time as in the first stage addition. , And the pH was adjusted to be in the range of 3-4. After the completion of the dropping reaction in the second stage, the mixture was stirred for 30 minutes while maintaining the pH and the liquid temperature as they were. Then, after cooling to room temperature, the reaction product was filtered, washed with water, dehydrated, and dried. The obtained dried product was subjected to a heat treatment at 400 ° C. for 1 hour in the atmosphere of an oxidizing atmosphere to obtain a white conductive material.

Example 2 A rutile type titanium oxide fiber (trade name "F
TL-200 ", manufactured by Ishihara Sangyo Co., Ltd.), and a white conductive material was obtained in the same manner as in Example 1.

Example 3 A silicon oxide spherical powder (trade name "Nipsil L") was used as a substrate.
-300 "(manufactured by Nippon Silica Industry Co., Ltd., average particle diameter 7 μm), and a white conductive substance was obtained in the same manner as in Example 1.

Comparative Example 1 Using the same anatase type fiber as in Example 1, 250 g of this anatase type fiber was dispersed in 2500 ml of water.
While maintaining the temperature at 0 ° C., a slurry was formed. Next, an aqueous solution of stannous chloride (23% by weight in terms of Sn) was added to the slurry.
0 g and a mixture of 66.6 g of 12% by weight hydrochloric acid were added dropwise over about 1 hour, and at the same time, a 15% by weight aqueous sodium hydroxide solution was separately added dropwise to adjust the pH to 3-4.
Kept in the range. Thereafter, dehydration, drying, and heat treatment were performed in the same manner as in Example 1 to obtain a white conductive substance.

Comparative Example 2 A white conductive substance was obtained in the same manner as in Comparative Example 1, except that the tin material to be added was changed to stannic chloride.

Comparative Example 3 A white conductive substance was obtained in the same manner as in Comparative Example 2, except that the fiber used as the base material was changed to the rutile type titanium oxide fiber used in Example 2.

Comparative Example 4 A white conductive material was obtained in the same manner as in Example 2 except that stannous chloride was used in both the first and second stages as a tin raw material to be added.

COMPARATIVE EXAMPLE 5 In Comparative Example 4, the amount of a 15% by weight aqueous sodium hydroxide solution added dropwise for pH adjustment was slightly excessively added, and the reaction was allowed to proceed in an alkaline range of 10 to 11 during the reaction. A white conductive substance was obtained in the same manner as in Comparative Example 4 except for the above.

Comparative Example 6 In Example 1, 12.8 g of antimony trichloride was added to 12% by weight hydrochloric acid 6 in a stannic chloride solution dropped in the first stage.
A white conductive substance was obtained in the same manner as in Example 1, except that a solution dissolved in 6.6 g was added and dropped as a mixed solution.

Comparative Example 7 The solution dropped in the first stage was a solution containing antimony as in Comparative Example 6, and the reaction was carried out in an alkaline region by adding a slightly excessive amount of aqueous sodium hydroxide solution as in Comparative Example 5. A white conductive substance was obtained in the same manner as in Comparative Example 5 except that the experiment was performed.

Table 1 shows the base materials, the first and second stages of the tin raw material, the pH at the time of adding the tin raw material, and the presence or absence of antimony in Examples 1 to 3 and Comparative Examples 1 to 7. . Further, for the obtained white conductive substance, the volume resistivity (Ω · cm) of the powder was measured. The measured value is a value measured under a load of 100 kg / cm ² .

Further, with respect to the obtained white conductive substance, the Hunter whiteness of the powder was measured. Measurement is performed on powder
A green compact (diameter 40 mm, thickness 2 mm) was prepared by applying a pressure of t / cm ² , and was subjected to JIS Z-8722-8730.
The L value (brightness index) defined in was measured and defined as Hunter whiteness.

Table 1 shows the volume resistivity and Hunter whiteness of the powders of the above Examples and Comparative Examples.

[0049]

[Table 1]

As is clear from Table 1, the white conductive substances of Examples 1 to 3 according to the present invention have low volume resistivity and excellent conductivity. Further, it can be seen that the hunter whiteness is high and the whiteness is high. Also,
Comparative Examples 6 and 7 containing antimony have high conductivity, but have low Hunter whiteness and poor whiteness.

Next, the white conductive substances of the above Examples and Comparative Examples were kneaded with various resins shown in Table 2 to prepare conductive resin compositions. The mixing ratio is based on 100 parts by weight of the resin.
The white conductive material was kneaded and compounded to be 40 parts by weight.
Resins include urethane resin (trade name "V-Top", manufactured by Dainippon Paint Co., Ltd.), acrylic resin (trade name "Acrose Super," manufactured by Dainippon Paint Co., Ltd.), and phenolic resin (trade name "Fenolite", Manufactured by Dainippon Ink and Chemicals, Inc.).

The obtained resin composition is formed into a sheet,
The surface resistivity was measured. As a sample, one side
Create a square sheet of 0cm and thickness of 2mm, JIS
It was calculated based on the following equation in accordance with the K-6911 method.

[0053]

(Equation 1)

Here, D is the inner diameter of the annular electrode on the surface (c
m) and d represent the outer diameter (cm) of the inner circle of the surface electrode, Rs represents the measured resistance value (Ω), and π represents the pi (≒ 3.14). Table 2 shows the surface resistivity (Ω) measured as described above.

[0055]

[Table 2]

As is clear from Table 2, the resin compositions containing the white conductive substances of Examples 1 to 3 according to the present invention are as follows:
It can be seen that all of them show excellent conductivity.

[0057]

The white conductive substance of the present invention is a white conductive substance which can exhibit high conductivity without containing antimony, and has high whiteness.

According to the production method of the present invention, the white conductive substance of the present invention can be produced efficiently. Since the conductive composition of the present invention contains the white conductive substance of the present invention, the conductive composition can have excellent conductivity and high whiteness.

Claims (5)

(57) [Claims] 1. A white conductive substance having a conductive layer made of tin oxide on a surface of a base material, wherein the conductive layer has a first tin oxide layer formed of a stannic compound, A second tin oxide layer formed from a monotin compound, wherein the first tin oxide layer and the second tin oxide layer do not substantially contain an antimony component. Substance. 2. The method according to claim 1, wherein the first tin oxide layer is formed on a surface of the base material, and the second tin oxide layer is formed on the first tin oxide layer. Claim 1
The white conductive substance according to 1. 3. A method for producing a white conductive material having a conductive layer made of tin oxide on the surface of a substrate, comprising dispersing the substrate in water to form an aqueous dispersion, A stannic compound is added, and a stannic water-insoluble substance precipitated by reacting the stannic compound is deposited on the surface of the base material, and then a stannous compound is added to the aqueous dispersion. After depositing the water-insoluble substance of stannous deposited by the reaction on the water-insoluble substance of the stannic, dehydration,
A method for producing a white conductive substance, comprising performing heat treatment in an oxidizing atmosphere. 4. When the stannic compound and the stannous compound are added to the aqueous dispersion, an alkaline solution is simultaneously added to adjust the pH of the aqueous dispersion to 2 to 5, The method for producing a white conductive substance according to claim 3, wherein the water-insoluble substance is precipitated. 5. A conductive composition comprising a white conductive substance according to claim 1 or 2, or a white conductive substance produced by the method according to claim 3 or 4, and a binder.