JPH0372012B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a white coated powder which has good electrical conductivity and is particularly used for forming a conductive layer on copy paper such as electrically conductive thermal paper and electrostatic recording paper. It is related to.

[Conventional technology and its problems]

Generally, to form a current-carrying layer in copy paper such as current-carrying thermal paper or electrostatic recording paper, a powder having a white tone and good conductivity is required. However, although the copper iodide (CuI) powder currently used in the conductive layer of current-carrying thermal paper has good conductivity, it does not exhibit a perfect white color and is unstable in production. It is difficult to stably produce a uniform product, and there is also a problem in terms of the toxicity of iodine. On the other hand, in the case of electrostatic recording paper, compared to electrically conductive thermal paper,
The conductive layer only needs to have low conductivity, that is, high resistance, so white inorganic electrolyte powders such as ammonium sulfate are used. And because it has the property of adsorbing moisture in paper,
This adsorbed moisture changes the resistance of the current-carrying layer, making it difficult to ensure stable conductivity.

[Means for solving problems]

From the above-mentioned viewpoints, the present inventors have developed a paper that exhibits white color and stably has good conductivity, and that is particularly suitable for use in forming a conductive layer on copying paper such as current-carrying thermal paper and electrostatic recording paper. As a result of our research to produce a suitable powder at low cost without quality or toxicity problems, we have developed a heated suspension consisting of titanium oxide (hereinafter referred to as TiO ₂ ) powder dispersed in heated water. When a solution consisting of tin chloride (hereinafter referred to as SnCl ₄ ) and antimony chloride (hereinafter referred to as SbCl ₃ ) dissolved in ethanol is added to ethanol, the ethanol instantly evaporates upon contact with heated water and is simultaneously hydrolyzed. As a result, tin oxide (hereinafter referred to as SnO ₂ ) in which antimony (Sb) is uniformly dissolved is precipitated on the surface of the TiO ₂ powder, and the Sb due to the hydrolysis is precipitated on the surface of the TiO 2 powder.
Since the precipitation of SnO ₂ contained on the TiO ₂ powder surface is significantly promoted by the activity of TiO ₂ , the Sb-containing SnO ₂ is precipitated in a uniform layer thickness. The obtained coated powder is
They found that it is pure white, has good conductivity, that is, a specific resistance of 1 to 1000 Ω·cm, is non-hygroscopic, and is stable in quality.

This invention was made based on the above findings, and has a specific surface area of 1 to 10 m ² /g.
On the surface of the TiO ₂ powder, a coating layer containing 1.5 to 15% by weight of Sb and the remainder consisting essentially of SnO ₂ is applied to the surface of the TiO 2 powder.
The present invention is characterized by a white conductive coating powder for forming a conductive layer on copy paper formed with a layer thickness of less than 0.05 μm.

Next, the reason for limiting the numerical values as described above in the white conductive coating powder of the present invention will be explained.

(a) Specific surface area of TiO ₂ powder If the specific surface area is less than 1 m ² /g, the particle size of the TiO ₂ powder itself becomes coarse, and when used to form a conductive layer on copy paper, the smoothness of the paper surface may be lost. On the other hand, if the specific surface area exceeds 10 m ² /g and becomes too fine, the cohesive force of the TiO ₂ powder becomes strong and it becomes difficult to disperse it uniformly in heated water. 10m ² /g
It was determined that

The specific surface area of TiO ₂ powder can be determined using the nitrogen gas adsorption method (BET method), in which containers A and B of equal volume are connected across a manometer, the left and right volumes of the manometer are equal, and adsorption is performed at the same pressure. The difference between container A containing TiO ₂ powder as a sample and empty container B, filled with gaseous nitrogen and cooled using liquid nitrogen as a coolant so that the volumes below the liquid surface are equal. The pressure Δh is read and calculated from this Δh using a calculation formula.

(b) Sb content in the coating layer If the Sb content is less than 1.5%, good electrical conductivity with a resistivity of 1000 Ω cm or less cannot be secured in relation to the layer thickness, while if it exceeds 15%. If it is added, the white color will be lost and it will become blueish, so the content should be reduced to 1.5 to 15%.
It was determined that

In addition, in the coated powder of this invention, the Sb content of the coating layer is 150Kg/ ^cm2 for 5g of coated powder.
Formed into a compacted powder sample with a diameter of 25 mm at a pressure of
Using a rhodium tube for this compacted powder sample,
The fluorescent X-ray intensity of the SnKa and SbKa rays generated from the green compact sample was measured by irradiating X-rays generated at an output of 50 KV and 40 mA, and the measured values were calculated based on the composition of Sn and Sb in advance. Compared with known standard samples, Sn in the green compact sample was
and Sb content, and from this result Sb content
It is obtained by calculating the Sb content in SnO ₂ .

(c) Layer thickness of the coating layer If the layer thickness is less than 0.007 μm, good conductivity with a specific resistance of 1000 Ω・cm or less cannot be secured in relation to the Sb content;
Even if the layer thickness was increased above, no further improvement in conductivity was observed, and rather a peeling phenomenon occurred, so the layer thickness was determined to be less than 0.007 to 0.05 μm.

The layer thickness of the coating layer: x is the weight of the coating layer per unit weight of TiO ₂ powder, where the specific surface area of the TiO ₂ powder is S (m ² /g) and the specific gravity of the coating layer is ρ. _{is ( S _ _} The calculation formula =(S×x×ρ)×W ₁ holds true, and x is calculated from this calculation formula.

In addition, in the coated powder of the present invention, the specific resistance of the coated powder is 5 g of the coated powder as a sample.
was placed in the center of a ring-shaped die made of Al ₂ O ₃ with an inner diameter of 25 mm, and a brass round bar punch with an outer diameter of 25 mm was inserted into the die from above and below to apply pressure to the sample, to the said punch
It is determined by measuring the electrical resistance of the sample under a pressure of 100 kg/cm ² and calculating the specific resistance from this measured value.

[Examples and effects of the invention]

Next, the coated powder of the present invention will be explained using examples.

TiO ₂ powder with specific surface area of 5 m ² /g: 30 g
Add to water: 800c.c., heat and maintain at temperature: 90℃,
By stirring, a heated suspension in which the TiO ₂ powder is uniformly dispersed is prepared, and to this heated suspension, ethanol: 200 c.c., SnCl ₄ : 75 g,
A solution consisting of 2.46 g of SbCl ₃ dissolved in 2
A coating layer of Sb-containing SnO ₂ is precipitated and formed on the surface of the TiO ₂ powder by slowly injecting the TiO 2 powder over a period of time, followed by filtering, washing, and injecting the TiO 2 powder in air at temperature to improve crystallinity. The coated powder of the present invention was prepared by holding at 500°C for 2 hours.

The coated powder of the present invention obtained as a result has Sb: 2.9
% by weight, with the remainder consisting essentially of _SnO2
It had a white coating layer with a uniform layer thickness of 0.042 μm, and had good electrical conductivity with a specific resistance of 10 Ω·cm.

Example 2 TiO ₂ powder with a specific surface area of 3 m ² /g: 100 g
Add to water: 1000c.c., heat and maintain at temperature: 90℃,
By stirring, a heated suspension in which the TiO ₂ powder is uniformly dispersed is prepared, and to this heated suspension, ethanol: 75 c.c., SnCl ₄ : 25 g,
SbCl ₃ : 1 solution consisting of 3.28g dissolved
The mixture was slowly added dropwise over a period of time, and the coated powder of the present invention was then produced using the same operations and conditions as in Example 1.

The coated powder of the present invention obtained as a result has Sb: 10.8
% by weight, with the remainder consisting essentially of _SnO2
It had a white coating layer with a uniform layer thickness of 0.007 μm, and had good conductivity with a specific resistance of 380 Ω·cm.

Example 3 TiO ₂ powder with specific surface area of 3 m ² /g: 43.5
Add g to 200c.c. of water, heat and maintain at 90℃,
A heated suspension was prepared by adding stirring. Next, separately prepared SbCl ₃ : 0.41g, 0.82
and 1.64 g of each dissolved in 75 c.c. of ethanol together with 25 g of SnCl ₄ were slowly injected separately into the heated suspension over 1 hour. The ethanol was then evaporated and hydrolyzed to form a coating layer made of Sb-containing SnO ₂ on the surface of the TiO ₂ powder. Thereafter, the coated powder of the present invention was applied under the same conditions and operations as in Example 1. Manufactured.

The coated powders of the present invention obtained as a result are as follows:
Contains Sb: 1.5% by weight, 2.9% by weight, and 5.7% by weight, with the remainder essentially consisting of SnO ₂ , and each has a white coating layer with a uniform layer thickness of 0.016μm, and has a specific resistance. are 600Ω・cm and 27Ω・cm respectively.
cm, and had good conductivity of 10Ω·cm.

As mentioned above, the coated powder of the present invention is non-toxic and non-hygroscopic, has stable quality, and has good conductivity and desired properties, so it is particularly suitable for use in forming a conductive layer on copy paper. It is suitable.

Claims (1)

[Claims] 1. On the surface of titanium oxide powder having a specific surface area of 1 to 10 m ² /g, a coating layer containing 1.5 to 15% by weight of antimony and the remainder substantially consisting of tin oxide,
A white conductive coating powder for forming a conductive layer on copying paper formed with a layer thickness of 0.007 to less than 0.05 μm.