White conductive powder, its manufacturing method, and usage

The present invention relates to a white conductive powder having excellent conductivity and color tone, and a method and application thereof. More specifically, the present invention relates to a white conductive powder using a white inorganic powder as a base material and provided a conductive layer having excellent conductivity and color tone on the surface thereof, and a method and application thereof.

Conductive powder is currently widely used in applications such as antistatic, antistatic, antistatic, and dustproof. Conventionally, a conductive powder doped with antimony or the like has been used in order to increase the conductivity. Specifically, as a white conductive powder, for example, a white conductive powder in which an antimony oxide-doped tin oxide film is formed on the surface of aluminum oxide-doped zinc oxide, titanium dioxide powder, or the like is known (Patent Document 1). , Patent Document 2, Patent Document 3).

Further, white conductive fibers in which a conductive film made of tin oxide containing an antimony component is formed on potassium titanate fibers are known (Patent Documents 4 and 5). Further, a white conductive titanium dioxide powder in which a conductive layer containing tin oxide and phosphorus is formed on the surface of titanium dioxide particles is known (Patent Document 6). On the other hand, surface-modified transparent conductive tin oxide powder that does not contain these doping components is known (Patent Document 7).

However, the white conductive powder having the tin oxide film doped with antimony oxide has stable conductivity, but the conventional powder is inferior in whiteness and specifically exhibits a strong blue or gray color tone, so that it is in a white environment. There is a problem that it is not suitable for the required applications.

On the other hand, titanium oxide having a phosphorus-doped tin oxide film has unstable conductivity and has a problem of uneven distribution of phosphorus. Further, the transparent conductive tin oxide powder made of surface-modified non-doped tin oxide has problems such as carbon residue.<patcit num="1"><text>JP-A-58-209002</text></patcit><patcit num="2"><text>JP-A-61-236612</text></patcit><patcit num="3"><text>Japanese Patent Application Laid-Open No. 62-180903</text></patcit><patcit num="4"><text>Japanese Unexamined Patent Publication No. 61-136532</text></patcit><patcit num="5"><text>Japanese Patent Application Laid-Open No. 07-053217</text></patcit><patcit num="6"><text>International Publication WO 2005/01 2449</text></patcit><patcit num="7"><text>Japanese Unexamined Patent Publication No. 2006-59806</text></patcit>

<p> The present invention solves the above-mentioned problems in the conventional white conductive powder, and the white conductive powder having an antimon-containing tin oxide layer contains antimon but does not show a blue or gray color tone and has excellent whiteness. Provided are a white conductive powder having the above, a method for producing the same, and the like.</p>

<p>The present invention relates to a white conductive powder that solves the above problems by the following constitution. [1] It has a tin oxide layer containing antimony on the surface of white inorganic powder, and has L = 80 or more, a = (-2) ~ (+2), b = (-4) ~ (+4) in the Lab color system. ), A white conductive powder characterized by having a color tone of). [2] BET specific surface area is 15 to 30 m²It is a powder of / g, and when the powder is added so as to have a solid content of 70% by mass to form a film composition having a film thickness of 2 μm, the surface resistance of the film composition is 1.0 × 10.¹⁰The white conductive powder according to [1] above, which is Ω / or less. [3] The white conductive powder according to the above [1] or the above [2], wherein the tin oxide layer has an antimony content of 1.0 to 10.0% by mass. [4] The white conductive powder according to any one of the above [1] to [3], wherein the proportion of the antimony-containing tin oxide layer in the powder is 20 to 40% by mass. [5] The white conductive powder according to any one of the above [1] to [4], wherein the white inorganic powder is titanium oxide. [6] The white color according to any one of the above [1] to [5], wherein the antimony-containing tin oxide layer forms an antimony-containing tin compound on the surface of a white inorganic powder by wet treatment, and is aged and heat-treated. Conductive powder.</p><p> The present invention further relates to the following manufacturing methods and uses. [7] The white inorganic powder of the base material is dispersed in water, an antimony source and a tin source are added thereto, and the powder is hydrolyzed at pH 2 or less to precipitate an antimony-containing tin compound on the surface of the powder, which is aged and dried. A method for producing a white conductive powder, which comprises forming a conductive tin oxide layer on the surface of the white inorganic powder by heat treatment. [8] A dispersion liquid obtained by dispersing the white conductive powder according to any one of the above [1] to [6] in a solvent. [9] A film composition containing the white conductive powder according to any one of the above [1] to [6]. [10] Contains 70% by mass of white conductive powder and has a surface resistance of 1.0 × 10 at a film thickness of 2 μm.¹⁰The film composition according to the above [9], which is Ω / or less.</p>

<p> The white conductive powder of the present invention is obtained by controlling the antimony content of the tin oxide layer on the surface of the powder so as to have excellent whiteness while maintaining high conductivity. Specifically, Lab. It has a color tone of L = 80 or more, a = (-2) ~ (+2), b = (-4) ~ (+4) in the color system, and although it contains antimony, it has a blue or gray color tone. It is a conductive powder that is not tinged and has a high degree of whiteness.</p><p> The white conductive powder of the present invention has, for example, a BET specific surface area of 15 to 30 m.²When the powder was added so as to have a solid content of 70% by mass with respect to the powder of / g to form a film composition having a film thickness of 2 μm, the surface resistance of the film composition was 1.0 × 10.¹⁰It is a white conductive powder with Ω / or less, and has high conductivity as well as excellent whiteness.</p><p> The white conductive powder of the present invention preferably has an antimony content of 1.0 to 10.0% by mass in the tin oxide layer and 20 to 40% by mass of the antimony-containing tin oxide layer in the powder, and the film composition to which the powder is added. When formed, it has excellent conductivity and hiding property due to white color.</p><p> Since the conductive layer (antimony-containing tin oxide layer) on the surface of the white conductive powder of the present invention can be formed by a wet treatment, it can be easily produced as compared with the vapor phase treatment.</p><p> Since the powder of the present invention is excellent in whiteness as well as conductivity, applications requiring a white environment in terms of appearance and function, such as electrostatic coating primers for automobiles, semiconductor manufacturing clean rooms and computer rooms, interior materials for hospitals, carpets, etc. It is suitable as a conductive material in. Moreover, not only the whiteness but also the concealing property is high, and it can be colored in various ways, and the performance is significantly improved as compared with the conventional ones.</p><p> Further, since the white conductive powder of the present invention is stable and has high conductivity, it can be widely used in various devices as a functional conductive material. Specifically, for example, as a conductive material in an electrostatic coating primer, a resin or tile having an antistatic effect, a conductive paint, an electrostatic recording material, a charging roller related to a copying machine, a photosensitive drum, a toner, an electrostatic brush, or the like. Suitable.</p><p> Further, the white conductive powder of the present invention is low in cost because the tin oxide layer does not contain phosphorus or indium. Further, since the white conductive powder of the present invention can be dispersed in a solvent such as water, it can be used as a conductive material such as a water-based paint.</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 conductive powder according to the present invention has a white inorganic powder as a base material, has a tin oxide layer containing 1.0 to 10.0% antimony on the surface of the base material, and has L = 80 or more in the Lab color system, a = (-. It is a white conductive powder characterized by having color tones of 2) to (+2) and b = (-4) to (+4).

The white conductive powder of the present invention can use titanium oxide, which is a white inorganic powder, as its base material. Titanium oxide may be either rutile type or anatase type. The rutile-type titanium oxide is preferable because the same conductivity can be obtained with a smaller amount of tin oxide than when the anatase-type titanium oxide is used.

The titanium oxide powder preferably has an average particle size of 0.01 to 1 μm and is spherical in order to obtain good dispersibility when dispersed in a solution or resin. In addition, the white conductive powder having an antimony-containing tin oxide layer on the surface of the titanium oxide powder is 15 to 30 m.²Those having a BET specific surface area of / g are preferable. In this case, the surface of the powder having the average particle size has slight irregularities, and the whiteness is increased due to light reflection or the like, which is preferable.

In the white conductive powder of the present invention, the proportion of the antimony-containing tin oxide layer in the powder is preferably 20 to 40%, preferably 25 to 35%. If this amount is less than 20%, it is difficult to obtain the desired conductivity. Further, if this amount is more than 40%, the resistance becomes low, but the problem of aggregation occurs, which is not preferable.

In the antimony-containing tin oxide layer, the antimony content in the tin oxide layer is preferably 1.0 to 10.0%. If the amount of antimony is less than 1.0%, the surface resistance does not decrease. On the other hand, if the amount of antimony is more than 10.0%, the color tone of blue or gray becomes strong, causing a problem in whiteness. In the above antimony content, it is possible to have L = 80 or more, a = (-2) to (+2), and b = (-4) to (+4) in the Lab color system. If the Lab value is out of the above range, the color tone related to whiteness is impaired, which is not preferable. In the white conductive powder of the present invention, each value of Lab is within the above range, and the white conductive powder has a good white color without turbidity.

The white conductive powder of the present invention has a tin oxide layer having the above-mentioned content, and in the case where the antimony content of the tin oxide layer is in the above-mentioned range, the powder is added so as to have a solid content of 70% by mass to form a film. When a film composition having a thickness of 2 μm is formed, the surface resistance of the film composition is 1.0 × 10.¹⁰It can have conductivity of Ω / or less.

[Production method] The white conductive powder of the present invention having an antimony-containing tin oxide layer forms an antimony-containing tin compound on the surface of the white inorganic powder by wet treatment, and heat-treats the antimony-containing tin oxide layer. It can be manufactured by forming.

Preferably, the white inorganic powder of the base material is dispersed in water, a tin source containing antimony is added thereto, and the mixture is hydrolyzed at a low pH, for example, pH 2 or less to precipitate an antimony-containing tin compound on the surface of the base material powder. After drying, the tin oxide layer is formed on the surface of the base material powder by heat treatment in an oxygen atmosphere.

Titanium oxide powder is used as the white inorganic powder of the base material. The base material powder is dispersed in water and heated to 40 to 100 ° C., a tin source containing antimony is added thereto, and this is hydrolyzed to precipitate and age a tin compound on the surface of the base material powder. .. As the tin source, tin chloride, tin nitrate, tin acetate, and other soluble tin salts can be used.

After the antimony-containing tin compound is precipitated on the surface of the base powder, the residual salt is removed by decantation and dried. When tin chloride is used as the tin source, it is preferable to add an aqueous hydrochloric acid solution to precipitate the tin compound at pH 4 or lower, and to stop the subsequent washing to the extent that hydrochloric acid remains slightly.

The white conductive powder of the present invention is dried after the wet treatment and heat-treated to form an antimony-containing tin oxide layer. The heat treatment temperature is preferably 400 ° C or higher and 800 ° C or lower. If the heat treatment temperature 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. In the above heat treatment, in order to further improve the whiteness, for example, it is preferable to perform the heat treatment in air.

The white conductive powder of the present invention can be used in various forms. For example, the white conductive powder can be used as a dispersion liquid dispersed in a solvent. Further, a conductive film can be formed by adding the white conductive powder to a paint and applying the white conductive powder to form a film. Specifically, for example, the white conductive powder of the present invention is added to the paint so as to have a solid content of 70% by mass, a film is formed to a film thickness of 2 μm, and a surface resistance of 1.0 × 10¹⁰A conductive film of Ω / or less can be obtained.

Examples of the present invention are shown below together with comparative examples. In Examples and Comparative Examples, the powder volume resistance is 100 kgf / cm when the sample powder is placed in a pressure vessel.²The powder was compressed with a digital multimeter (Yokogawa Electric product: model 7651-02) and measured. The L value, a value, and b value of the powder were measured using a device manufactured by Suga Test Instruments Co., Ltd. (SM-7-IS-2B). The surface resistance of the coating film was measured using a surface resistance tester (Hiresta: Mitsubishi Oil Chemicals: Model HT-210, supply voltage 100V) for a thin film with a film thickness of about 100 μm containing white conductive powder. The BET specific surface area was measured by the nitrogen adsorption method (Shibata Chemical Products: SA1100 type).

[Example 1] 50 g of titanium oxide powder (rutile type) was dispersed in 300 cc of water and heated to 95 ° C. Antimony-containing tin chloride was added to this dispersion so that the tin oxide content in the powder was as shown in Table 1, and an aqueous hydrochloric acid solution was added over 40 to 60 minutes to adjust the pH to 1 to 2. The wet-treated powder was taken out, washed and dried. Substantially the entire amount of antimony-containing tin chloride added by the above wet treatment was hydrolyzed, and an antimony-containing tin compound was precipitated on the powder surface. 20 g of this dry powder was placed in a quartz tube furnace and heat-treated at the temperatures shown in Table 1. The treated powder was taken out and compacted, and the powder volume resistance was measured. In addition, the BET specific surface area and Lab color system values were measured. The results are shown in Table 1.

[Comparative Example 1] A white conductive powder was produced in the same manner as in Example 1 except that the tin oxide content and the heat treatment temperature were set to the conditions shown in Table 2. The powder volume resistance, BET specific surface area and Lab color system values were measured for this powder. The results are shown in Table 1.

[Example 2 / Comparative Example 2] 23.0 g of the white conductive fine powder produced in Example 1 and Comparative Example 1 was added to 100 g of a commercially available acrylic paint (resin content: 10%), and the mixture was stirred with a paint shaker containing beads for 30 minutes. This paint was applied to a PET film with an applicator so that the film thickness after drying was about 2 μm, and the surface resistance after drying was measured with a surface resistance meter. In addition, the properties of the coating film (presence or absence of lumps due to aggregates) were visually confirmed. The results are shown in Table 1.

As shown in Table 1, all of the samples A1 to A5 of the present invention have an L value of 80 or more, a high whiteness, and a surface resistance of 1.0 × 10.¹⁰It is Ω / or less and has high conductivity. On the other hand, the comparative sample B1 is a powder having a low surface resistance of the coating film, a low L value, a powder having a high whiteness cannot be obtained, and a high b value and a strong blue color. In addition, B2 has an extremely high surface resistance, and it is not possible to obtain a powder having excellent conductivity.

Further, in the samples A1 to A2 of the present invention, since the amount of antimony in the tin oxide layer is small, the volume resistance of the powder is higher than that of A3 to A5, but the surface resistance when the coating film is formed is remarkably low, and A3. There is an advantage that the surface resistance is close to A5.

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