JPS6116124B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention has a white color and good conductivity, and particularly when mixed into a plastic film or silicone rubber film, it can be made conductive without impairing its transparency. The present invention relates to a method for producing a composite powder that can be imparted with the following properties.

In recent years, plastic films and silicone rubber films that are both transparent and conductive have been used for surface electrodes, protective films, antistatic films,
Currently, such conductive transparent films are made of transparent plastic film or silicone film (hereinafter referred to as plastic film) with a very thin layer of metal or oxide on the surface. Only those coated with a conductive layer such as indium are known. However, such a transparent plastic film whose surface is coated with a conductive layer has the problem that the surface conductive layer easily peels off, and cracks occur when bent or the like, resulting in a loss of conductivity. On the other hand, it is also known to impart conductivity to a plastic film by incorporating conductive powder such as metal powder or carbon powder into the plastic film, but the resulting plastic film is black or gray. and cannot be used because it is not transparent.

From the above-mentioned viewpoints, the present inventors have devised a material that has good electrical conductivity, does not impair the transparency of the plastic film when mixed in the plastic film, and also imparts electrical conductivity to the plastic film. As a result of conducting research to produce a powder with characteristics that can In other words, it has a white color and its optical refractive index is close to that of plastic: 1.6 to 1.7, or its average particle size is
It must be 0.1 μm or less, that is, smaller than the wavelength of visible light.

(b) Tin oxide (hereinafter referred to as SnO ₂ ) powder is white and has electrical conductivity, but when antimony (Sb) is added to it, the electrical conductivity is further improved.

(c) Sb-containing SnO ₂ powder has an optical refractive index of 2.0 to 2.1, so when using it for the purpose of imparting conductivity to a transparent plastic film, please refer to (a) above. In conjunction with the above, it is necessary to refine the average particle size to 0.1 μm or less.

(d) Conventionally, methods for producing SnO ₂ powder containing Sb include a method in which SnO ₂ powder and an Sb compound are fired, and a method in which a Sn compound and an Sb compound are mixed and then fired. However, the average particle size exceeds 1 μm, making it impossible to obtain fine powder of 1 μm or less.

(e) tin chloride (hereinafter referred to as SnCl ₄ ) in any of alcohol, acetone, and aqueous hydrochloric acid;
When a solution consisting of dissolved antimony and antimony chloride (hereinafter referred to as SbCl ₃ ) is added to heated water, Sb-containing SnO ₂ powder with a minimum particle size of about 0.2 μm is precipitated.

(f) In item (e) above, if barium sulfate (hereinafter referred to as BaSO ₄ ) powder is dispersed in the heated water, this BaSO ₄ powder will be mixed with SnCl ₄ in the heated water.
To act as a dispersant during the hydrolysis reaction that occurs when a solution containing SbCl ₃ is added, and to make the Sb-containing phase SnO ₂ powder that is precipitated into a fine powder with an average particle size of 0.1 μm or less.

(g) Since BaSO ₄ powder is white and has an optical refractive index of 1.6, which is almost the same as that of plastic, even if it is mixed into plastic film, its transparency will not be impaired.

(h) Therefore, even if the mixed powder consisting of Sb-containing SnO ₂ powder and BaSO ₄ powder obtained in (f) above is mixed into a transparent plastic film as it is, it will not be Since it does not become a source of light scattering, the transparency of the plastic film is maintained, and the Sb-containing SnO ₂ powder imparts good conductivity.

The findings shown in sections (a) to (h) above were obtained.

Therefore, the present invention has been made based on the above knowledge, and has a white color and good conductivity, and in particular, when mixed into a plastic film, it impairs the transparency of the plastic film. _Alcohol ^, acetone,
and 78 to 783 g/hydrochloric acid aqueous solution
of SnCl ₄ and 0.085 to 212 g/SbCl ₃ are added to give a concentration of 0.1 to 20% by weight.
A fine powder containing Sb (hereinafter all % means weight %) with an average particle size of 0.1 μm or less and having a composition consisting essentially of SnO ₂ is added to the BaSO ₄
It is characterized in that it is produced by precipitating and forming it in a state mixed with powder.

Next, the reason why the numerical values are limited as described above in the method for producing a conductive composite powder of the present invention will be explained.

(a) Specific surface area of BaSO ₄ When the specific surface area is less than 1 m ² /g, the particle size of the BaSO ₄ powder itself becomes coarse, and when mixed into a plastic film, the strength of the plastic film deteriorates. On the other hand, its specific surface area is 10m ² /
If it exceeds g, it becomes difficult to uniformly disperse it in heated water during the production of composite powder, so the specific surface area was determined to be 1 to 10 m ² /g.

(b) Content of SnCl ₄ in the solution If the content is less than 78 g /
The content of SnCl ₄ is too low, SnO ₂ due to hydrolysis
The precipitation rate of fine powder becomes slow and requires a long processing time, making it uneconomical.
If the content exceeds 783g/, precipitation will occur.
Since the particle size of the Sb-containing SnO ₂ powder exceeds 0.1 μm, its content was determined to be 78 to 783 g/.

(c) Content of SbCl ₃ in solution In relation to SnCl ₄ , its content is
If it is less than 0.085g/, Sb-containing SnO ₂ will precipitate.
The Sb content in the powder was less than 0.1%,
On the other hand, if the content exceeds 212g/
Since the Sb content in the Sb-containing _SnO2 powder exceeds 20%, the content should be reduced from 0.085 to 212g/
It was determined that

(d) Sb content in Sb-containing SnO ₂ powder If the content is less than 0.1%, the desired good conductivity cannot be secured; on the other hand, if the content exceeds 20%, the composite powder The content was determined to be between 0.1 and 20% because it loses its white color and takes on a bluish tinge, impairing its transparency when mixed into plastic film.

(e) Average particle size of Sb-containing SnO ₂ As mentioned above, the length of 0.1 μm is close to the wavelength of visible light, so Sb-containing SnO ₂ powder with an average particle size exceeding 0.1 μm is If mixed into the film, the transparency of the plastic film will be impaired, so the upper limit of the average particle diameter was set at 0.1 μm.

In addition, the Sb content in the composite powder of this invention
The relative proportion of SnO ₂ powder and BaSO ₄ powder is Sb-containing
It is preferable that SnO ₂ powder: 10 to 90%, BaSO ₄ powder: the remainder, because if the total proportion of Sb-containing SnO ₂ powder is less than 10%, it will impart the desired good conductivity to the composite powder. Because it cannot be done, and also 0.1
Sb-containing _SnO2 powder with an average particle size of less than μm is
This is because it is difficult to efficiently obtain a composite powder containing more than 90%.

Next, the present invention will be specifically explained using examples.

Example 1 BaSO ₄ powder with a specific surface area of 5 m ² /g: 100
g was added to 1000 c.c. of water, heated and maintained at a temperature of 90°C, and stirred to form a heated suspension in which the BaSO ₄ powder was uniformly dispersed, while adding 300 c.c. of methanol. A solution consisting of 86.5 g of SnCl ₄ and 10.4 g of SbCl ₃ dissolved in c. was slowly injected over 1 hour to form a composite powder consisting of Sb-containing SnO ₂ powder and BaSO ₄ powder. The composite powder of the present invention was produced by separating, washing, and maintaining the powder in air at a temperature of 500° C. for 2 hours to improve crystallinity.

The resulting composite powder of the present invention has a 10%
Sb-containing SnO ₂ powder: 33%, with an average particle size of 0.04 μm (no particle size exceeds 0.1 μm), with a composition containing Sb and the remainder substantially consisting of SnO ₂ ; BaSO ₄ powder: It consisted of the remainder and was white in color and had good electrical conductivity with a specific resistance of 250 Ωcm.

Furthermore, this 50 μm thick vinyl chloride resin film mixed with 40% of the composite powder of the present invention has a surface resistance of 10 ⁹ Ω, good conductivity, and extremely good transparency. Ta.

Example 2 BaSO ₄ powder with a specific surface area of 3 m ² /g: 100
g to 1000 c.c. of water, heated and maintained at a temperature of 90°C, and stirred to form a heated suspension in which the BaSO ₄ powder was uniformly dispersed, while adding 6N hydrochloric acid aqueous solution: 300c.c., _SnCl4 :86.5g and _SbCl3 :
Sb-containing SnO ₂ powder was precipitated by slowly injecting a solution consisting of 4.93 g of dissolved Sb over 1 hour, and the resulting composite powder was separated, washed, and further exposed to air. The composite powder of the present invention was produced by performing a crystallinity improvement treatment at a temperature of 500° C. for 2 hours.

The resulting composite powder of the present invention has a 5%
Sb-containing SnO ₂ powder with an average particle size of 0.04 μm (none of which has a particle size exceeding 0.1 μm) with a composition that contains Sb and the remainder essentially consists of SnO ₂ : 33%
and BaSO ₄ powder: the remainder, it was white in color and had an extremely low resistivity of 600Ω·cm.

In addition, the thickness of the composite powder containing 45% of this invention composite powder
The 50 μm vinyl chloride resin film was transparent and had good conductivity with a surface resistance of 10 ⁹ Ω.

Example 3 BaSO ₄ powder with a specific surface area of 5 m ² /g: 100
Add 1,000 c.c. of water to 1,000 c.c. of acetone, heat and maintain the temperature at 90°C, stir to form a heated suspension in which the BaSO ₄ powder is uniformly dispersed, and add 300 c.c. of acetone. A solution consisting of 86.5 g of SnCl ₄ and 10.4 g of SbCl ₃ dissolved in c. was slowly injected over 1 hour to form Sb-containing SnO ₂ powder and precipitate.
Next, the resulting composite powder consisting of Sb-containing SnO ₂ powder and BaSO ₄ powder was separated, washed, and kept in air at a temperature of 500°C for 2 hours to further improve crystallinity. Thus, a composite powder of the present invention was produced.

The resulting composite powder of the present invention has a 10%
Sb-containing SnO ₂ powder: 33%, with an average particle size of 0.05 μm (no particle size exceeding 0.1 μm exists), with a composition containing Sb and the remainder substantially consisting of SnO ₂ ; BaSO ₄ powder: It consisted of the remainder, was white in color, and had good electrical conductivity with a specific resistance of 290 Ωcm.

In addition, this 50 μm thick vinyl chloride resin film mixed with 40% of the composite powder of the present invention has a surface resistance of 10 ⁹ Ω, good conductivity, and extremely good transparency. Ta.

Although the above Example 1 describes the case where methanol is used as the alcohol, it goes without saying that similar results can be obtained using other alcohols such as ethanol, butyl alcohol, and even isopropyl alcohol. be.

As described above, according to the method of the present invention, a white composite powder with good conductivity can be produced by a simple operation.
It can be produced at a low cost, and the resulting composite powder can impart conductivity to plastic films without impairing their transparency, even if they are mixed into plastic films. Industrially useful effects are brought about.

Claims (1)

[Claims] 1 To a heated suspension consisting of barium sulfate powder having a specific surface area of 1 to 10 m ² /g dispersed in heated water, add 78 to 783 g/g of barium sulfate powder to any of alcohol, acetone, and aqueous hydrochloric acid solution. By adding a solution consisting of tin chloride and 0.085 to 212 g of antimony chloride,
Contains 0.2% by weight of antimony, with the remainder consisting essentially of tin oxide, with an average particle size of 0.1 μm
A method for producing a conductive composite powder, characterized in that the following fine powder is precipitated and formed in a state mixed with the barium sulfate powder.