White conductive powder and method for producing the same

The present invention relates to a white powder having conductivity and excellent whiteness. More specifically, the present invention relates to a white conductive powder having a conductive layer on the surface of the white inorganic powder. The white conductive powder of the present invention is used in fields requiring functions such as conductivity, antistatic, antistatic, and dustproof, and more specifically, for fiber / rubber applications, conductive or antistatic synthetic. Antistatic films for textiles / flooring and films, IC packages and tapes for semiconductors, antistatic plastics / inks for paints / inks, antistatic paints and electrostatic coating materials, electrophotographic applications Is applied to antistatic additives, electrostatic recording papers, antistatic rolls and the like.

A technique has been published in which titanium oxide is used as a white inorganic powder as a white conductive powder and titanium oxide is coated with antimony-doped tin oxide to further enhance the whiteness of the white conductive powder (Patent Document 1, Patent Document 1, 2).

However, when the white conductive powder produced by the above technique is used, for example, as a primer for electrostatic coating, although desired results in terms of whiteness and conductivity are initially obtained, a base coat is applied to the upper layer of the primer layer. When a layer, a clear coat layer, or the like was overcoated, the conductivity was sometimes extremely lowered. If electrostatic coating is attempted on a layer with reduced conductivity, the coating efficiency will decrease, and a good coating effect due to electrostatic coating cannot be expected (compared to spray coating, coating loss cannot be reduced. ), There is a problem that coating spots may occur on the coating film, in some cases, it may not be possible to move to the next process, or the layer may be charged when a high voltage is applied. Therefore, only one layer can be coated on the primer layer by the electrostatic coating method, and electrostatic coating cannot be performed on the upper layer. However, since it may not be possible to obtain a desired color, gloss, etc. with one layer on the primer layer, coating of two or more layers on the primer layer is desired.

Further, when carbon powder is used as the conductive powder, it is possible to coat two or more layers on the primer layer, but even if a color coat or the like is applied on the layer containing carbon, it is desired due to dullness or the like. I can't get the color.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2009-199775</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2009-199776</text></patcit></p>

<p> The present inventors have found that a white conductive powder having a conductive layer on the surface of a specific composite oxide powder can solve the above-mentioned problems in the conventional conductive powder. The present invention is a white conductive powder having excellent conductivity and whiteness. Further, a white conductive powder that is excellent in conductivity and whiteness and can easily form a white conductive layer as a primary layer capable of electrostatic coating of two or more layers such as a base coat layer and a clear coat layer. I will provide a.</p>

<p> The present invention relates to a white conductive powder that solves the above problems by the configuration shown below. (1) Al₂O₃, TiO₂And SiO₂A white conductive powder characterized by the presence of an antimony-doped tin oxide layer on the surface of the composite oxide powder containing the above. (2) The composite oxide powder is Al₂O₃TiO for 1 part by weight₂3 to 30 parts by weight, and SiO₂The white conductive powder according to (1) above, which contains 1 to 2 parts by weight. (3) Composite oxide powder: 1/2 to 2/3 parts by weight of the antimony-doped tin oxide layer is contained with respect to 1 part by weight, and the antimony-doped tin oxide layer is SnO.₂Sb for 1 part by mass₂O₅The white conductive powder according to (1) or (2) above, which contains 1/15 to 1/8 parts by mass. (4) The white conductive powder according to any one of claims 1 to 3, wherein the powder volume resistance value is less than 100 Ω · cm, and the L value of the white conductive powder in the Lab color system is 70 or more. (5) A dispersion liquid obtained by dispersing the white conductive powder according to any one of (1) to (4) above in a medium. (6) A paint obtained by adding a resin to the dispersion liquid described in (5) above. (7) A paint containing 100 to 200 parts by weight of a white conductive powder with respect to 100 parts by weight of a resin, and the surface resistance value of a white conductive layer having a thickness of 10 to 30 μm formed by the paint. In terms of the surface resistance value of the coating film when a coating film with a thickness of 10 to 30 μm formed on the white conductive layer was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. , [(Surface resistance value of coating film) / (Surface resistance value of white conductive layer)] is less than 100, the coating material according to (6) above. (8) A coating film containing a white conductive layer formed by the coating material according to (6) or (7) above, having a surface resistance value of 10.⁸A coating film having an L value of less than Ω / and an L value of 70 or more in the Lab color system of the white conductive layer. (9) (A) TiO₂Powder and SiO₂Source and Al₂O₃Crystalline SiO obtained by heat-treating the source₂ Al₂O₃A step of uniformly mixing the powder to prepare a composite oxide powder, (B) a step of dispersing the composite oxide powder in water to prepare a dispersion, and (C) a tin source and an antimony source in the dispersion. A step of dropping an aqueous solution containing the above solution together with an alkaline aqueous solution to precipitate antimony-doped tin oxide on the surface of the composite oxide powder, and (D) firing the composite oxide powder having an antimony-doped tin oxide compound precipitated on the surface in the air. The method for producing a white conductive powder according to any one of (1) to (4) above, wherein the steps are carried out in this order.</p>

<p> The white conductive powder of the present invention (1) is a white conductive powder having excellent conductivity and whiteness. Further, since this white conductive powder can be dispersed in a solvent such as water or an organic solvent, it can be used as a dispersion liquid or a conductive material such as a paint, and has excellent conductivity and whiteness. Layers can be easily formed. This white conductive powder is used in fields that require functions such as conductivity, antistatic, antistatic, and dustproof. Specifically, it is a conductive or antistatic synthetic fiber / floor material, antistatic film, IC. It is suitably used as a conductive material in applications such as packages and tapes, antistatic plastic inks, antistatic paints and electrostatic coating materials, antistatic additives, electrostatic recording papers, and antistatic rolls. Further, according to the coating material of the present invention (7), a white conductive layer as a primary layer capable of electrostatic coating of two or more layers such as a base coat layer and a clear coat layer can be easily formed.</p>

Hereinafter, the present invention will be specifically described based on the embodiments. Note that% is mass% unless otherwise specified and unless it is unique to a numerical value.

[White conductive powder] The white conductive powder of the present invention is Al.₂O₃, TiO₂And SiO₂It is characterized in that an antimony-doped tin oxide layer is present on the surface of the composite oxide powder containing the above. Al₂O₃, TiO₂And SiO₂By using the complex oxide powder containing, for example, TiO₂It is possible to remarkably suppress a decrease in conductivity after forming the topcoat coating layer, as compared with the case of using only. Here, the composite oxide is Al₂O₃, TiO₂And SiO₂Is the main component, and the main component is Al for 100 parts by weight of composite oxide.₂O₃, TiO₂And SiO₂It means that the total of is 95 parts by weight or more. Here, the analysis of Al, Ti, and Si is performed by the ICP method, and Al is all Al.₂O₃And all Ti is TiO₂And all Si is SiO₂Calculate as if.

The composite oxide powder is TiO₂Powder and SiO₂ Al₂O₃A mixed powder with the powder is preferable from the viewpoint of whiteness, hiding property, and coating property of the conductive material (antimony-doped tin oxide). TiO₂Is preferably a rutile type, and the anatas type and the brookite type are inferior in the coating property of the conductive material, so that it is difficult to obtain good conductivity. Here, SiO₂ Al₂O₃TiO during heat treatment of powder₂When the powder coexists, reduction of Ti occurs and the composite oxide powder may be colored. Therefore, TiO₂Powder and SiO₂ Al₂O₃It is preferable to use a mixed powder of powder. Also, TiO₂ SiO₂ Al₂O₃When the powder of the three components described above is used, Ti is preferably tetravalent from the viewpoint of whiteness and coating property of the conductive material (antimony-doped tin oxide).

TiO₂The crystal form of is not particularly limited, but the rutile type is preferable. In the anatase type and the brookite type, it is difficult to precipitate or form an antimony-doped tin oxide layer on the surface by a coprecipitation method or the like, so some ingenuity is required. TiO₂The powder preferably has a median diameter of 0.01 to 0.5 μm. When the median diameter is 0.01 μm or less, TiO₂There are problems such as agglomeration of powder and / or white conductive powder, impaired whiteness, high cost due to the need for a large amount of antimony-doped tin oxide, and inability to obtain good hiding power. .. If the median diameter is 0.5 μm or more, problems such as sedimentation during dispersion are likely to occur, and the aesthetic appearance of the coating film is lost due to the surface roughness of the coating film. Here, the median diameter is measured by a laser diffraction / scattering method. Also, TiO₂Examples of the shape of the powder include a spherical shape, a flaky shape, a rod shape, and a needle shape. The median diameter is the so-called primary particle diameter, but the so-called secondary particle diameter is preferably 1 to 30 μm from the viewpoint of the conductive layer coating state. Here, the secondary particle size is determined by observation with an electron microscope (SEM). TiO₂The powder may be used alone or in combination of two or more.

SiO₂ Al₂O₃When the powder is crystalline, it is preferable from the viewpoint of whiteness and coating property of the conductive material (antimony-doped tin oxide). SiO₂ Al₂O₃As a powder, mullite (3Al₂O₃ 2SiO₂), Mica, Kaolinite (Al₂O₃ SiO₂ 2H₂O), dehydrated kaolinite, pyrophyllite (Al₂O₃ 2SiO₂ H₂O), dehydrated products of pyrophyllite, etc., and these and SiO₂, Al₂O₃Also include a mixture of. Also, SiO₂ Al₂O₃The powder preferably has a median diameter of 0.1 to 10 μm. When the median diameter is 0.1 μm or less, SiO₂ Al₂O₃The problem of agglomeration of powder and / or white conductive powder occurs, the whiteness is impaired, a large amount of antimony-doped tin oxide is required, which increases the cost, and suppresses the decrease in conductivity after forming the topcoat coating layer. There are problems such as difficulty in doing so. If the median diameter is 10 μm or more, problems such as sedimentation during dispersion are likely to occur, and the aesthetic appearance of the coating film cannot be obtained. In addition, SiO₂ Al₂O₃The powder may be brittle, in which case the median diameter may change during the dispersion step or the like. SiO₂ Al₂O₃Examples of the shape of the powder include spherical, triangular, square, hexagonal, and scaly. SiO₂ Al₂O₃The powder may be used alone or in combination of two or more.

Also, SiO₂ Al₂O₃The powder preferably contains an alkali metal or an alkaline earth metal from the viewpoints of lowering the heat treatment temperature, controlling the crystallinity, controlling the crystal form, etc., more preferably containing potassium and magnesium, and further containing potassium. preferable.

The composite oxide powder is Al₂O₃TiO for 1 part by weight₂3 to 30 parts by weight, and SiO₂Is preferable from the viewpoint of whiteness and hiding power. Al₂O₃TiO for 1 part by weight₂Is more preferably contained in an amount of 12 to 27 parts by weight, preferably SiO.₂Is more preferably contained in an amount of 1.3 to 1.6 parts by weight. If it is out of the above range, problems will occur in whiteness, suppression of decrease in conductivity, and the like. Here, the analysis of Al, Ti, and Si is performed by the ICP method, and Al is all Al.₂O₃And all Ti is TiO₂And all Si is SiO₂Calculate as if.

The antimony-doped tin oxide layer imparts conductivity to the white conductive powder, and the fact that it is antimony-doped tin oxide is the conductivity of the white conductive powder and the conductive stability of the white conductive layer using the white conductive powder. It is preferable from the viewpoint of. Antimony-doped tin oxide layer is SnO₂Sb for 1 part by mass₂O₅Is preferably contained in parts by mass (1/15) to (1/8). If it is less than 1/15 part by mass, it is difficult to obtain the desired conductivity, and there is a problem that the desired conductivity cannot be obtained. If it is more than 1/8 part by weight, the color tone of blue or gray becomes stronger and white. There is a problem that the degree is lowered. Here, the analysis of Sn and Sb is performed by the ICP method, and all Sn are SnO.₂And all Sb are Sb₂O₅Calculate as if.

Further, it is preferable that the antimony-doped tin oxide layer is contained in an amount of (1/2) to (2/3) by weight with respect to 1 part by weight of the composite oxide powder. If the antimony-doped tin oxide layer is less than 1/2 part by weight, it is difficult to obtain the desired conductivity, and if it is more than 2/3 parts by mass, agglomeration of the white conductive powder occurs, and the aesthetic appearance of the coating film is lost. The problem of being struck arises.

The powder volume resistance value of the white conductive powder is preferably less than 100 Ω · cm, more preferably 0.1 to 50 Ω · cm. When the powder volume resistance of the white conductive powder is 100 Ω · cm or more, when used as a primer layer, the surface resistance of the obtained coating film can be suppressed to less than 100 times after the top coating. Value: 10⁸It becomes difficult to achieve less than Ω / . Here, the powder volume resistance value is measured by putting the sample powder in a pressure vessel, compressing it at 10 MPa, and measuring this powder with a digital multimeter.

From the viewpoint of whiteness, the white conductive powder preferably has an L value of 70 or more, and more preferably 80 or more in the Lab color system. If the L value is less than 70, the whiteness is not satisfied, and if a color coat layer is provided for the top coat, the color of the color coat layer becomes dull and a clear color scheme cannot be achieved, or even if it is possible. , The color coat layer must be a considerably thick film, which increases the cost. Here, the L value of the white conductive powder is measured using, for example, an apparatus manufactured by Suga Test Instruments Co., Ltd. (model number: SM-7-IS-2B).

The particle size of the white conductive powder of the present invention is not particularly limited, but is preferably 0.01 to 1 μm. Here, the particle size refers to the median diameter measured by the laser diffraction / scattering method. The shape of the white conductive powder is preferably granular, flaky, rod-shaped, or needle-shaped.

[Production method] Below, the method for producing the white conductive powder of the present invention is (A) TiO.₂Powder and SiO₂Source and Al₂O₃Crystalline SiO obtained by heat-treating the source₂ Al₂O₃A step of uniformly mixing the powder to prepare a composite oxide powder, (B) a step of dispersing the composite oxide powder in water to prepare a dispersion, and (C) a tin source and an antimony source in the dispersion. A step of dropping an antimony-doped tin oxide compound on the surface of the composite oxide powder by dropping a mixed aqueous solution containing the above solution together with an alkaline aqueous solution, and (D) the composite oxide powder in which the antimony-doped tin oxide compound is precipitated on the surface in the air. The step of firing is performed in this order.

&lt;&lt; (A) process &gt;&gt; TiO₂The powder is as described above. SiO₂As a source, SiO₂, Water glass, silicon tetraethoxydo, silicon tetramethoxyde, etc., Al₂O₃As a source, Al₂O₃, Aluminum hydroxide, aluminum isopropoxide, aluminum nitrate, aluminum sulfate and the like. As a heat treatment, SiO is used as a raw material.₂And Al₂O₃When using, the method of heating after heating at 1400 to 1600 ° C and then cooling, when using water glass and aluminum hydroxide as raw materials, the method of pressurizing and heating using an autoclave or the like, silicon tetraethoxydo and aluminum isopropoxide as raw materials When using propoxide, a method of heating to 600 to 1000 ° C and cooling can be mentioned. Here, after the heat treatment, it is preferable to pulverize with a stamp mill, a ball mill, a hammer mill or the like.

&lt;&lt; (B) process &gt;&gt; Examples of the device for dispersing the composite oxide powder in water include a bead mill, a ball mill, and a sand mill. For example, an example of the dispersion time when using a bead mill is 15 to 180 minutes.

&lt;&lt; (C) process &gt;&gt; Examples of the tin source include tin halides such as tin chloride, tin oxide, tin hydroxide, tin sulfates, tin inorganic acid salts such as tin nitrate (first tin salt, second tin salt) and the like. , These may be used alone or in combination of two or more. The stannous salts include stannous fluoride, stannous chloride, stannous borofluoride, stannous sulfate, stannous oxide, stannous nitrate, tin pyrophosphate, tin sulfamate, and stannic acid. Examples thereof include inorganic salts such as salts, and organic salts such as stannous alkanolsulfonic acid, stannous sulfosuccinate, and stannous aliphatic carboxylic acid. Examples of the ditinous tin salt include the above stannous tin. Examples of the ditin salt of each of the salts include those which are gaseous and those which are poorly soluble. Therefore, as the raw material of the tin hydroxide compound, liquid ditin chloride or stannous chloride is used. In general, it is industrially desirable to use a hydrochloric acid aqueous solution of ditin chloride or stannous chloride. Examples of the antimony source include halogenated antimony such as tin chloride, antimony oxide, antimony hydroxide, sulfate of antimony, and inorganic acid salts such as tin nitrate, and these may be used alone or in combination of two or more. You may. Preferably, an aqueous hydrochloric acid solution of antimony chloride is used. Examples of the alkali used in the alkaline aqueous solution include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate, carbonates and ammonia, and these may be mixed alone or in combination of two or more. May be used. The antimony-doped tin oxide compound is mainly a hydroxide of antimony-doped tin oxide. A method known to those skilled in the art may be used as a method for dropping an aqueous solution containing a tin source and an antimony source into the dispersion together with an alkaline aqueous solution. When dropping, it is preferable to heat to 40 to 100 ° C.

After the antimony-containing tin compound is precipitated on the surface of the composite oxide powder, the residual salt is removed by decantation and dried. When tin chloride is used as the tin source, an aqueous hydrochloric acid solution is added to precipitate a tin compound at a pH of 10 or less, and in the subsequent washing, hydrochloric acid remains slightly, for example, the electrical conductivity of the dispersion is 0.4. It is better to stop until it is less than mS / cm.

&lt;&lt; (D) process &gt;&gt; The firing is preferably performed at 400 to 800 ° C. If it is lower than 400 ° C, sufficient conductivity cannot be obtained, and if it is higher than 800 ° C, sintering of the powder starts, which is not preferable. Further, by performing the firing in the atmosphere, the whiteness of the white conductive powder can be increased.

From the above, it is possible to produce a white conductive powder having high conductivity and whiteness.

[Dispersion / paint] The white conductive powder of the present invention can be dispersed in a medium and used as a dispersion liquid. Here, examples of the medium include water, ethanol, methanol, isopropyl alcohol, toluene, methyl ethyl ketone, propylene glycol monomethyl ether and the like. Inorganic and organic dispersants may be added to the dispersion.

The solid content concentration of the dispersion is 1 to 70%, preferably 10 to 50% on a mass basis, and the pH of the dispersion is 4 to 12, preferably 5 to 10. Here, the solid content includes white conductive powder, inorganic and organic dispersants.

A resin can be added to the dispersion and used as a paint. It is preferable to use the dispersion liquid for coating in order to reduce the dispersion energy at the time of coating, dehydration and drying energy in the white conductive powder manufacturing process. Here, examples of the resin include polyvinyl alcohol resin, vinyl chloride resin, acrylic resin, epoxy resin, urethane resin, alkyd resin, polyester resin, ethylene vinyl acetate copolymer, acrylic-styrene copolymer, and fibrous element. Examples thereof include natural resins such as resins, phenol resins, amino resins, fluororesins, silicone resins, petroleum resins, cellacs, rosin derivatives, and rubber derivatives.

The amount of the white conductive powder blended in the resin is 20 to 400 parts by mass, preferably 100 to 300 parts by mass with respect to 100 parts by mass of the resin.

A paint containing 100 to 200 parts by weight of the white conductive powder of the present invention with respect to 100 parts by weight of the resin was prepared, and first, this paint was applied or printed on a substrate as a primer paint, and then dried, and the thickness was: 20. A white conductive layer of ± 10 μm is prepared. As the resin, Supercron E-723 manufactured by Nippon Paper Chemicals Co., Ltd., Acridic A-168 manufactured by DIC Corporation, etc. are used.

At this time, examples of the substrate include various synthetic resins, glass, ceramics, metals, etc., which are widely used in various fields including electric and electronic devices, and these are sheet-like, film-like, and plate-like. It can be any shape such as a shape. Specific examples of the synthetic resin include polyethylene, polypropylene, polycarbonate, polyethylene terephthalate (PET) resin, acrylic resin, methacrylic resin, polyvinyl chloride, polyester resin, polyamide resin, phenol resin and the like, but are limited thereto. It is not something that is done.

The coating or printing on the substrate can be carried out by a conventional method, for example, by a method such as roll coating, spin coating, screen printing, or an applicator. The coating composition is then heated, if necessary, to evaporate the water or solvent and allow the coating to dry and cure. At this time, heating or irradiation with ultraviolet rays or the like may be performed.

The surface resistance value of the white conductive layer is measured as sheet resistance (unit: Ω / ). As the measuring instrument, a high rester manufactured by Mitsubishi Chemical Corporation or the like can be used. The coating material of the present invention has a surface resistance value of 10 for the white conductive layer.⁸Can be less than Ω / , 10⁸When it is less than Ω / , it is preferable from the viewpoint of topcoat coating property.

Further, in the paint containing the white conductive powder of the present invention, the L value of the white conductive layer in the Lab color system can be 70 or more, and if it is 70 or more, when a color coat is used for the top coating, etc. preferable. Here, the L value can be measured with SM-7 or the like manufactured by Suga Test Instruments Co., Ltd.

Next, the topcoat paint is further applied or printed on the white conductive layer and then dried to form a topcoat paint layer having a thickness of 20 ± 10 μm to prepare a coating film. Next, the surface resistance value of the coating film after holding the coating film in an atmosphere of temperature: 20 ° C. and humidity: 55% for 10 minutes is measured and used as the surface resistance value of the coating film. The coating material of the present invention can have a change in surface resistance value, that is, [(surface resistance value of coating film) / (surface resistance value of white conductive layer)] of less than 100. If the change in surface resistance value is 100 or more, the coating efficiency of electrostatic coating will decrease, and in some cases, it will not be possible to move to the next process, or the layer will be charged when a high voltage is applied. there's a possibility that. Here, the surface resistance value of the coating film is measured in the same manner as the surface resistance value of the white conductive layer.

As the topcoat paint, either conductive or non-conductive can be used, but the paint of the present invention can have a surface resistance value change of less than 100 even if it is a non-conductive topcoat paint. Examples of the topcoat paint include a base coat layer paint and a clear coat layer paint. As a base coat layer paint, TiO with an average particle size of 0.1 to 1 μm₂Examples of the dispersion paint and the clear coat layer paint include lacquer and the like. Here, TiO₂The above resin can be used as the dispersion coating material.

The surface resistance value of the coating film is 10⁸It is less than Ω / , and the L value of the white conductive layer in the Lab color system is preferably 70 or more.

The white conductive powder of the present invention is used in fields that require functions such as conductivity, antistatic, antistatic, and dustproof. Specifically, it is a conductive or antistatic synthetic fiber / floor material, an antistatic film. , IC packages and tapes, antistatic plastic inks, antistatic paints and antistatic coating materials, antistatic additives, antistatic recording paper, antistatic rolls, etc.

<p> Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited thereto. In each example, the powder volume resistance value is determined by pressurizing 5 g of the sample to 10 MPa using a measuring device (DM-7561) manufactured by Yokogawa Electric Co., Ltd., and determining the resistance value (R) and the thickness (H) of the sample during pressurization. Measure and formula: R (Ω) × S (electrode area: cm²) / H (Sample thickness: cm). The L values of the powder and the coating film were measured using a device manufactured by Suga Test Instruments Co., Ltd. (SM-7-IS-2B). The surface resistance value of the coating film was measured with a Mitsubishi Chemical Hiresta (model number: Hiresta surface high resistance meter HT-210).</p><p>[Example 1] SiO₂And Al₂O₃Is mixed at a weight ratio of 1.4: 1, heat-treated at 1500 ° C, and then crushed to an average particle size of 3 μm with a ball mill to make crystalline SiO.₂ Al₂O₃Obtained powder. Furthermore, TiO with an average particle size of 0.3 μm₂Powder and SiO₂ Al₂O₃Powder, TiO₂And Al₂O₃Was mixed so as to have a weight ratio of 27: 1 to obtain a white composite oxide powder. This composite oxide powder: 100 g was added to 500 g of water and dispersed in a bead mill for 60 minutes to obtain a dispersion. Furthermore, the weight ratio of the antimony-doped tin oxide layer to the composite oxide powder is 3: 2, and SnO constitutes the antimony-doped tin oxide layer.₂, Sb₂O₅A mixed solution of 55% tin chloride solution: 138 g and 60% antimony chloride solution: 7 g was added to the dispersion at the same time as the 35% aqueous sodium hydroxide solution so that the weight ratio was 15: 1. The solution was added dropwise so as to maintain a value of less than, and an antimony-doped tin oxide compound was precipitated. After the reaction, impurities were removed by decantation until the electrical conductivity of the dispersion was less than 0.4 mS / cm. The dispersion was filtered and then dried at 110 ° C. Then, after firing at 650 ° C in the air atmosphere, atomizer pulverization was performed to obtain 163 g of the white conductive powder of Example 1. The powder volume resistance value of the obtained white conductive powder was 23.7 Ω · cm, and the L value was 85.4.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 5.1 x 10⁵The Ω / and L values were 82.0. On top of this white conductive layer, an additional 30% by weight of TiO₂The coated paint was overcoated and dried to form a coating film with a thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance value was measured, it was 66.0 x 10⁶It was Ω / . In addition, TiO₂Acrylic resin (manufactured by DIC: model number: A-168) was also used for the paint.</p><p>[Example 2] SiO₂And Al₂O₃Is mixed at a weight ratio of 1.5: 1, heat-treated at 1500 ° C, and then crushed to an average particle size of 3 μm with a ball mill to make crystalline SiO.₂ Al₂O₃Obtained powder. Furthermore, TiO with an average particle size of 0.3 μm₂Powder and SiO₂ Al₂O₃Powder, TiO₂And Al₂O₃The white conductive powder of Example 2 was obtained in the same manner as in Example 1 except that a white composite oxide powder was obtained by mixing the powders so as to have a weight ratio of 3: 1. The powder volume resistance value of the obtained white conductive powder was 15.6 Ω · cm, and the L value was 76.4.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 1.0 x 10⁵The Ω / and L values were 78.1. On top of this white conductive layer, an additional 30% by weight TiO₂The coating film was coated with a dispersion of paint and dried to prepare a coating film with a topcoat coating layer of thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance was measured, it was 3.1 × 10.⁵It was Ω / .</p><p>[Example 3] The weight ratio of the antimony-doped tin oxide layer to the composite oxide powder is 2: 1 and SnO constitutes the antimony-doped tin oxide layer.₂, Sb₂O₅A mixed solution of 55% tin chloride solution: 92 g and 60% antimony chloride solution: 7 g was mixed so that the weight ratio was 8: 1, and the pH was adjusted to the pH in the dispersion at the same time as the 35% sodium hydroxide aqueous solution. The white conductive powder of Example 3: 140 g was obtained in the same manner as in Example 1 except that the antimony-doped tin oxide compound was precipitated by dropping so as to keep less than 2. The powder volume resistance value of the obtained white conductive powder was 18.3 Ω · cm, and the L value was 79.2.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 2.8 x 10⁵The Ω / and L values were 77.7. On top of this white conductive layer, an additional 30% by weight of TiO₂The coated paint was overcoated and dried to form a coating film with a thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance value was measured, it was 9.2 x 10⁵It was Ω / .</p><p>[Example 4] SiO₂And Al₂O₃In a weight ratio of 1.3: 1 and heat-treated at 1500 ° C to crystallize SiO₂ Al₂O₃Obtained powder. Furthermore, TiO with an average particle size of 0.3 μm₂Powder and SiO₂ Al₂O₃Powder, TiO₂And Al₂O₃The white conductive powder of Example 4 was obtained in the same manner as in Example 1 except that a white composite oxide powder was obtained by mixing the powders so as to have a weight ratio of 30: 1. The powder volume resistance value of the obtained white conductive powder was 35.4 Ω · cm, and the L value was 86.7.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 8.8 x 10⁵The Ω / and L values were 83.1. On top of this white conductive layer, an additional 30% by weight of TiO₂The coating film was coated with a dispersion of paint and dried to prepare a coating film with a topcoat coating layer of thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance was measured, it was 2.9 x 10⁷It was Ω / .</p><p>[Example 5] SiO₂And Al₂O₃In a weight ratio of 1.3: 1 and heat-treated at 1500 ° C to crystallize SiO₂ Al₂O₃Obtained powder. Further average particle size: 0.26 μm TiO₂Powder and SiO₂ Al₂O₃Powder, TiO₂And Al₂O₃The white conductive powder of Example 5: 135 g was obtained in the same manner as in Example 3 except that a white composite oxide was obtained by mixing the powders so as to have a weight ratio of 12: 1. The powder volume resistance value of the obtained white conductive powder was 12.7 Ω · cm, and the L value was 77.5.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 1.4 x 10⁵The Ω / and L values were 76.5. On top of this white conductive layer, an additional 30% by weight of TiO₂The coated paint was overcoated and dried to form a coating film with a thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance value was measured, it was 5.6 x 10⁵It was Ω / .</p><p>[Reference example 1] SiO₂And Al₂O₃In a weight ratio of 1.3: 1 and heat-treated at 1500 ° C to crystallize SiO₂ Al₂O₃Obtained powder. Furthermore, TiO with an average particle size of 0.3 μm₂Powder and SiO₂ Al₂O₃Powder, TiO₂And Al₂O₃The white conductive powder of Reference Example 1: 160 g was obtained in the same manner as in Example 1 except that a white composite oxide powder was obtained by mixing the powders so as to have a weight ratio of 40: 1. The powder volume resistance value of the obtained white conductive powder was 25.6 Ω · cm, and the L value was 87.0.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 6.5 x 10⁵The Ω / and L values were 83.4. On top of this white conductive layer, an additional 30% by weight of TiO₂The coated paint was overcoated and dried to form a coating film with a thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance value was measured, it was 9.8 x 10⁷It was Ω / .</p><p>[Reference example 2] The weight ratio of the antimony-doped tin oxide layer to the composite oxide powder is 5: 2, and SnO constitutes the antimony-doped tin oxide layer.₂, Sb₂O₅A mixed solution of 55% tin chloride solution: 76 g and 60% antimony chloride solution: 7 g in a 35% aqueous sodium hydroxide solution with a pH of less than 2 in the dispersion so that the weight ratio is 10: 1. The white conductive powder of Reference Example 2: 136 g was obtained in the same manner as in Example 1 except that the antimony-doped tin oxide compound was precipitated. The powder volume resistance value of the obtained white conductive powder was 153.1 Ω · cm, and the L value was 87.4.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 6.7 x 10⁶The Ω / and L values were 85.4. On top of this white conductive layer, an additional 30% by weight of TiO₂The coated paint was overcoated and dried to form a coating film with a thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance value was measured, it was 3.2 x 10⁸It was Ω / .</p><p>[Reference example 3] SiO₂And Al₂O₃In a weight ratio of 1.3: 1 and heat-treated at 1500 ° C to crystallize SiO₂ Al₂O₃Obtained powder. Furthermore, TiO with an average particle size of 0.3 μm₂Powder and SiO₂ Al₂O₃Powder, TiO₂And Al₂O₃The white conductive powder of Reference Example 3: 155 g was obtained in the same manner as in Example 1 except that a white composite oxide powder was obtained by mixing the powders so as to have a weight ratio of 2: 1. The powder volume resistance value of the obtained white conductive powder was 7.8 Ω · cm, and the L value was 63.2.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 1.2 x 10⁶The Ω / and L values were 65.9. On top of this white conductive layer, an additional 30% by weight of TiO₂The coated paint was overcoated and dried to form a coating film with a thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance value was measured, it was 4.3 × 10⁶It was Ω / .</p><p>[Reference example 4] SiO₂And Al₂O₃In a weight ratio of 0.1: 1 and heat-treated at 1500 ° C to crystallize SiO₂ Al₂O₃The white conductive powder of Reference Example 4: 129 g was obtained in the same manner as in Example 5 except that the powder was obtained. The powder volume resistance value of the obtained white conductive powder was 230.5 Ω · cm, and the L value was 79.9.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 2.8 x 10⁷The Ω / and L values were 78.1. On top of this white conductive layer, an additional 30% by weight of TiO₂The coated paint was overcoated and dried to form a coating film with a thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance value was measured, it was 5.5 × 10.¹⁰It was Ω / .</p><p>[Reference example 5] SiO₂And Al₂O₃In a weight ratio of 3.0: 1, heat-treated at 1500 ° C, and crystalline SiO₂ Al₂O₃The white conductive powder of Reference Example 5 was obtained in the same manner as in Example 2 except that the powder was obtained. The powder volume resistance value of the obtained white conductive powder was 20.0 Ω · cm, and the L value was 78.4.</p><p> This white conductive powder: 7 g was added to a toluene / xylene mixed solution: 8 g in a volume ratio of 1: 1 to prepare a dispersion. Next, an acrylic resin (manufactured by DIC Corporation: model number: A-168) was added so that the weight ratio was powder: resin = 7: 3.5, and further dispersed to prepare a paint. This paint was applied to a polypropylene test piece and dried to form a white conductive layer having a thickness of 15 μm. The surface resistance value of the white conductive layer is 8.7 x 10⁶The Ω / and L values were 76.3. On top of this white conductive layer, an additional 30% by weight of TiO₂The coated paint was overcoated and dried to form a coating film with a thickness: 15 μm, and the coating film was held for 10 minutes in an atmosphere of temperature: 20 ° C and humidity: 55%. When the surface resistance value was measured, it was 1.5 x 10⁹It was Ω / .</p><p> Tables 1 and 2 show the blending amounts and test results of Examples 1 to 5 and Reference Examples 1 to 5. In the table, "ATO" indicates "antimony-doped tin oxide", and "change in surface resistance value" indicates [(surface resistance value of coating film) / (surface resistance value of white conductive layer)]. In the "evaluation of powder volume resistance value", "" was given for less than 100Ω · cm, and "x" was given for 100Ω · cm or more. In the "evaluation of L value", an L value of 70 or more was evaluated as "", and an L value of less than 70 was evaluated as "x". In "Evaluation of white conductive layer", the surface resistance value of the white conductive layer is 10.⁸When it was less than Ω / and the L value was 70 or more, it was evaluated as "", and the others were evaluated as ×. In "Evaluation of coating film", the surface resistance value of the coating film is 10.⁸When it was less than Ω / and the L value was 70 or more, it was evaluated as "", and when it was not, it was evaluated as ×. "Possibility of electrostatic coating" has a surface resistance value of 10 for the coating film.⁸If it is less than Ω / and the change in surface resistance value is less than 100, it is OK, otherwise it is No, and in particular, the surface resistance value of the coating film is 1 × 10.¹⁰The case of Ω / was set as "impossible". Also, for example, the numerical value in the table: "5.1E + 05" is "5.1 x 10".⁰⁵".</p><p><tables num="1"><img file="JP2011253652A_D0001.tif" /></tables></p><p><tables num="2"><img file="JP2011253652A_D0002.tif" /></tables></p><p> As is clear from Table 1, in Examples 1 to 5, the powder volume resistance value and the L value of the white conductive powder were all good, and the evaluation of the white conductive layer and the coating film was also good. .. As you can see from Table 2, TiO₂In Reference Example 1, which includes 40 parts by weight, the change in surface resistance value was as large as 150.8, which was not suitable for electrostatic coating. In Reference Example 2 where the weight ratio of the composite oxide powder: ATO layer is 5: 2, the powder volume resistance value is as large as 153.1 Ω · cm, and the surface resistance value of the coating film is also 3.2 × 10.⁸The value was as large as Ω / , which was not suitable for electrostatic coating. TiO₂In Reference Example 3 containing 2 parts by weight, the L value of the white conductive powder was as low as 63.2, and the L value of the white conductive layer was also low. SiO₂In Reference Example 4, which includes 0.1 parts by weight, the powder constant volume resistance value is as large as 230.5Ω cm, and the surface resistance value of the coating film is 5.5 × 10.¹⁰The change in Ω / and surface resistance value was extremely large at 1964.3, which was a value at which electrostatic coating could not be performed. SiO₂In Reference Example 5, which includes 3.0 parts by weight, the surface resistance value of the coating film is 1.5 × 10.⁹The change in Ω / and surface resistance was as large as 172.4, which was not suitable for electrostatic coating.</p><p> As shown in Examples 1 to 5, the present invention is a white conductive tin powder having excellent conductivity and whiteness, and a coating material using the white conductive tin powder enables electrostatic coating of two or more layers. It was found that the conductive layer can be easily formed.</p>