JP6936588B2 - Gray-white oxynitride niobium powder and its manufacturing method - Google Patents

Description

The present invention relates to an off-white niobium nitride powder and a method for producing the same, which can obtain an off-white conductive material having little variation in surface resistance at the time of forming a coating film. More specifically, the present invention relates to a method for producing a dispersion liquid and a conductive coating material in which gray-white niobium nitride powder is dispersed, and a method for forming a conductive film.

Conductive powders are currently widely used in antistatic, antistatic, antistatic, dustproof and other applications. As a conventional conductive powder, a white conductive powder is disclosed (see, for example, Patent Document 1). The white conductive powder of Patent Document 1 includes titanium oxide particles and tin oxide particles that coat the surface of the titanium oxide particles, and the titanium oxide particles contain K, Mg, Nb, and Zr, respectively. It contains 01 to 0.5% by mass, the crystal structure of the titanium oxide particles is a rutile structure, the average particle size of the titanium oxide particles is 100 to 500 nm, and the average particle size of the tin oxide particles is 1 to 50 nm. Is. That is, the white conductive powder of Patent Document 1 is composed of a white powder such as titanium oxide and tin oxide coating the white powder in order to enhance the conductivity. However, the white conductive powder using tin oxide is a core-shell particle having titanium oxide as a core and a tin oxide-based conductive material as a shell. When a high load is applied, the tin oxide-based conductive material, which is the shell, is peeled off, resulting in a decrease in conductivity and a problem of variation.

In order to solve the problem in preparing the dispersion of the core-shell particles, it is effective to use a single particle, and a method of reducing titanium oxide to obtain the single particle is disclosed (for example, a patent). Reference 2). In this method, the titanyl sulfate solution is held at a temperature of 170 ° C. or higher and at a pressure equal to or higher than the saturated water vapor pressure at that temperature to hydrolyze the titanyl sulfate to obtain hydrated titanium dioxide having a spherical shape. _{Spherical represented by the general formula TiO X} (where X is a positive real number less than 2), which is fired, the surface of the obtained titanium dioxide is coated with dense silica, and then reduced at a temperature of 500 to 1200 ° C. A conductive titanium compound is obtained. In addition, a reducing agent, alkylamine or ammonia is used. However, in the method of Patent Document 2, although titanium oxide becomes conductive when reduced, there is a problem that the resin is deteriorated due to photocatalytic property.

In order to solve this problem due to photocatalytic property, a method of using niobium oxide powder as a pigment is disclosed from the viewpoint of using a white pigment having lower photocatalytic property and coloring power than titanium oxide (Patent Document 3). reference). In Patent Document 3, the titanium oxide powder as the first component is provided with an oxide powder containing vanadium oxide, niobium oxide, manganese oxide, molybdenum oxide, tungsten oxide, chromium oxide, or two or more kinds of second components. The first component and the second component are mixed so that the weight ratio is in the range of 2: 8 to 8: 2, and the mixed powder is mixed at a high temperature so that the oxygen content is 15% or less and the nitrogen content is 10% or more. A black powder is produced by reducing with ammonia gas.

JP 2012-151107 (Claim 1, paragraph [0002]) JP-A-07-89721 (Claim 4, paragraphs [0005], [0013]) JP 2012-96946 (Claim 7, paragraph [0021])

However, there is a demand to make the appearance grayish white instead of pure white when it is desired to give a feeling of cleanliness such as electronic devices, housings of home appliances, clean wear, clean paper, and interior wall materials of medical institutions. Therefore, a grayish-white conductive powder is required. However, in the method shown in the above-mentioned conventional patent document 3, the obtained niobium oxide powder turns black by a reduction reaction and is insulating, and is grayish-white conductive. There is a problem that the material cannot be obtained. Further, if the reduction reaction of the niobium oxide powder proceeds too much, there is a problem that the surface resistance of the coating film formed by forming a paint obtained by converting the dispersion liquid of the niobium nitride powder into a paint film has a large variation in surface resistance.

An object of the present invention is to provide an off-white niobium nitride powder and a method for producing the same, which can obtain an off-white conductive material having little variation in surface resistance at the time of forming a coating film.

The first aspect of the present invention is an off-white niobium nitride powder containing niobium, oxygen, and nitrogen as main components, having an oxygen concentration of 15 to 25% by mass and a nitrogen concentration of 2 to 10% by mass, and having an L value of 2 to 10% by mass. A gray-white niobium nitride powder having a value of 14 or more, a b value of -0.5 or less, and a powder volume resistance of 0.5 × 10 ² Ω · cm or more and 1 × 10 ^{5 Ω · cm or less.} It is characterized by.

A second aspect of the present invention is a method for producing an off-white niobium oxynitride powder according to the first aspect by heating and reducing niobium oxide with ammonia gas.

The third aspect of the present invention is a method for producing a dispersion liquid by dispersing the gray-white niobium nitride powder of the first aspect or the gray-white niobium nitride produced by the method of the second aspect in a solvent. It is characterized by.

A fourth aspect of the present invention is a method for producing a conductive coating material by mixing the dispersion liquid of the third aspect with a binder.

A fifth aspect of the present invention is a method of applying the conductive coating material of the fourth aspect to form a conductive film.

The niobium nitride powder according to the first aspect of the present invention contains niobium, oxygen, and nitrogen as main components, has an oxygen concentration of 15 to 25% by mass, a nitrogen concentration of 2 to 10% by mass, and an L value of 14 or more. The b value is −0.5 or less, and the powder volume resistivity is 0.5 × 10 ² Ω · cm or more and 1 × 10 ⁵ Ω · cm or less. As a result, since the niobium nitride powder is not a core shell but a single particle, the conductivity does not decrease during pulverization and strengthening.

In the method for producing niobium nitride powder according to the second aspect of the present invention, niobium oxide is heated and reduced with ammonia gas to produce grayish white niobium nitride powder. Since the gray-white oxynitride niobium powder is the first aspect, when a high load is applied at the time of pulverization in an attempt to further atomize the dispersion during the production of the dispersion as in the case of core-shell particles, the tin oxide-based conductive material which is the shell becomes. There is no problem of peeling, deterioration of conductivity, and variation.

In the method for producing a dispersion liquid according to the third aspect of the present invention, the niobium nitride powder according to the first aspect or the niobium nitride powder produced by the method according to the second aspect is dispersed in a solvent. , A dispersion liquid capable of producing a conductive film exhibiting grayish white color can be obtained.

In the method for producing a conductive coating material according to the fourth aspect of the present invention, since the dispersion liquid of the third aspect is mixed with a binder to produce a conductive coating material, a conductive film having a grayish white color can be produced from the conductive coating material. Since the specific gravity is large, a low-viscosity conductive coating material can be obtained.

In the method of forming a fifth aspect of the conductive film of the present invention, since is made by forming a conductive coating material of the fourth aspect, small variations in the surface resistance, can coating resistance control of the ultra-high-precision Therefore, it is possible to form a conductive film having a thin film thickness.

Next, a mode for carrying out the present invention will be described. The niobium nitride powder of the present invention is a niobium nitride powder containing niobium, oxygen, and nitrogen as main components, having an oxygen concentration of 15 to 25% by mass and a nitrogen concentration of 2 to 10% by mass, and has an L value of 14. As described above, the b value is −0.5 or less, and the powder volume resistance is 0.5 × 10 ² Ω · cm or more and 1 × 10 ⁵ Ω · cm or less. Here, the oxygen concentration is limited to 15 to 25% by mass because the L value is less than 14 and a black film is formed when the oxygen concentration is less than 15% by mass, and the volume resistivity deteriorates when the oxygen concentration exceeds 25% by mass. be. Further, the nitrogen concentration was limited to 2 to 10% by mass because the volume resistivity deteriorates when it is less than 2% by mass, and when it exceeds 10% by mass, the L value becomes less than 14 and the niobium nitride powder becomes black. This is because it does not turn grayish white. This is because as nitriding progresses, the particles become hard and the crystal structure is easily destroyed by dispersion treatment, etc., and because the particles have a sharp shape, the contact points between the particles cannot be increased and the conductivity is lost. It is believed that there is. The reason why the L value is limited to 14 or more is that if it is less than 14, the niobium nitride powder becomes black. The b value is limited to -0.5 or less because the coating film resistance becomes insulating when it is larger than -0.5.

The gray-white oxynitride niobium powder has a volume resistivity of 0.5 × 10 ² Ω · cm or more and 1 × 10 ⁵ Ω · cm or less, preferably 1.1 ×, in the state of a green compact hardened at a pressure of 10 MPa. It is 10 Ω ² cm or more and 0.8 × 10 ⁴ Ω cm or less. The volume resistivity is measured by, for example, a four-terminal four-probe method using a digital multimeter (model: DM7561) manufactured by Yokogawa Electric Corporation. In this four-terminal four-probe method, four needle-shaped electrodes are placed on the surface of a sample (compact powder) in a straight line at predetermined intervals, and a constant current is applied between the two outer needle-shaped electrodes. This is a method of obtaining the volume resistance by measuring the potential difference between the two inner needle-shaped electrodes. In addition, the volume resistivity of the gray-white oxynitride niobium powder in the state of the green compact ^{was limited to 0.5 × 10 2} Ω · cm or more because the gray-white oxynitride niobium ^{was limited to less than 0.5 × 10 2 Ω · cm.} This is because the nitriding of the material progresses too much and sufficient conductivity cannot be obtained. Further, the volume resistivity ^{is limited to 1.0 × 10 5} Ω · cm or less ^{because if it is higher than 1.0 × 10 5} Ω · cm, the desired conductivity disappears.

The average particle size of the gray-white oxynitride niobium powder is preferably in the range of 50 to 200 nm. The average particle size of this gray-white oxynitride niobium powder is a volume accumulation measured by a particle size distribution measuring device (manufactured by HORIBA, Ltd., dynamic light scattering type particle size distribution measuring device LB-550) using a dynamic light scattering method. Refers to the medium diameter (Median diameter, D _50). Here, the reason why the preferable range of the average particle size of the niobium nitride powder is limited to 50 nm to 200 nm is that the coloring power is lowered when the average particle size is less than 50 nm, and the particles are too large when the average particle size is more than 200 nm, resulting in insufficient uniformity of the coating film. Because it does.

Examples of the niobium oxide powder used for producing the mixed powder for forming an off-white film include Nb ₂ O ₃ (niobium trioxide), NbO ₂ (niobium dioxide), and Nb ₂ O ₅ (niobium pentoxide) powder. However, oblique crystal niobium pentoxide powder is preferable from the viewpoint of high whiteness and high production rate of niobium oxynitride powder. This niobium oxide powder has an average primary particle size of 300 nm or less in terms of sphere from the measured value of the specific surface area, in order to obtain a niobium oxynitride powder having ^{a specific surface area of 2 to 20 m 2 / g measured by the BET method.} It is preferable that the average primary particle size is 20 nm or more and 250 nm or less from the viewpoint of easy handling of the powder.

For the powder color tone in the present invention, the L, a, and b indices proposed by Hunter are used. The brightness index L value of the gray-white oxynitride niobium powder is determined by using, for example, a color computer (model: SE7700) manufactured by JASCO Corporation. Here, the reason why the lightness index L value of the gray-white oxynitride niobium powder is limited to 14 or more is that if it is less than 14, the whiteness is insufficient and the gray-white pigment cannot be obtained.

The L value in the Lab color system after irradiating the grayish white conductive powder with ultraviolet rays (UV) having an intensity of ^{0.25 mW / cm 2 up to an irradiation amount of 2 J / cm 2 (that is, 8000 seconds) at room temperature.} The absolute value of the difference (ΔL) from the L value before ultraviolet irradiation is preferably 3 or less. In this case, there is little change in the whiteness of the grayish white conductive powder.

A method for producing the grayish white niobium nitride powder configured as described above will be described. _{First, niobium pentoxide powder (Nb 2} O ₅ ) having an average particle size of 100 to 300 nm and an orthorhombic structure is prepared. Next, this niobium oxide powder is crushed and granulated by a ball mill. Here, the reduction can be carried out by gas reduction with ammonia gas or by using metallic titanium and alkylamine, but it is easier to control the composition by using ammonia gas. Reduction with ammonia gas, chemical formula: _NbN X _{O Y} (where, X = 0.1~2.0, Y = 0.1~2.0 ) off-white niobate nitride represented by is generated. Reduction ratio of the off-white niobium oxide powder (NbN X _{O Y)} is or higher reaction temperature, or raising the ammonia gas flow rate, or by extending the reaction time can be controlled, and a low reduction rate nitride The composition can be controlled without proceeding, and the whiteness of the powder is improved. That is, the L value becomes high. Here, the reduction reaction temperature is in the range of 500 to 850 ° C., and the reduction reaction time (contact time of niobium oxide powder with ammonia gas) is in the range of 60 to 1500 minutes. This is because if the reduction reaction temperature is lower than 500 ° C., the reduction reaction does not proceed and the conductivity is insufficient. If the reduction reaction temperature is higher than 850 ° C., the nitriding reaction proceeds too much and the color becomes black. This is because the powder is sintered when it becomes uniform and is longer than 1500 minutes. Further, the powder base of this niobium nitride is pulverized to obtain a grayish white conductive powder. This pulverization is performed by pulverizing with a hammer mill until the average particle size is within the range of 50 nm to 200 nm.

In Patent Document 3, when the niobium oxide powder is heated and reduced with ammonia gas, only black and insulating niobium nitride powder is obtained, whereas in the present invention, grayish white and conductive niobium nitride powder is obtained. It is presumed that it is obtained for the following reasons. In Patent Document 3, titanium oxide as the first component and niobium oxide powder as the second component are heat-reduced in an ammonia gas atmosphere, whereas in the present invention, niobium oxide powder alone is heat-reduced in an ammonia gas atmosphere. It is thought that this is because there is a difference. Secondly, while the reaction temperature is 950 ° C. in Patent Document 3, in the present invention, by setting the reaction temperature range to 550 to 850 ° C., the nitriding reaction does not proceed and the reaction becomes grayish white without blackening. Is considered to be.

[Dispersion]
The dispersion liquid of the present embodiment contains a solvent and the grayish white conductive powder of the present embodiment dispersed in the solvent. Examples of the solvent include water, ethanol, methanol, isopropyl alcohol, toluene, methyl ethyl ketone, propylene glycol monomethyl ether and the like.

The solid content concentration of the dispersion liquid is 10 to 70%, preferably 20 to 60%, on a mass basis. The pH of the aqueous dispersion is 3-10, preferably 4-9. This is because if the solid content concentration is less than 10%, the thickness of the coating film is insufficient and sufficient coloring cannot be obtained, and if it is more than 70%, the viscosity of the paint becomes high and handling becomes difficult. If it is less than 10, the resin and atmosphere will be oxidized, and if it is more than 10, the viscosity will increase and it will be difficult to handle. Here, the solid content includes an off-white conductive powder, an inorganic dispersant, and an organic dispersant.

〔paint〕
The coating material of this embodiment contains the above dispersion liquid and a binder. When the dispersion liquid is mixed with the binder to produce the coating material, the dispersion energy at the time of forming the coating material can be reduced. In addition, energy related to dehydration and drying in the manufacturing process of the grayish white conductive powder can be reduced. Here, examples of the binder include resins, silica sol gels, soda glass and the like. The resin, silica sol gel, and soda glass can be used alone, but silica sol gel and soda glass may be used together with the resin. By containing silica sol gel or soda glass, the packing effect of the grayish white conductive powder is enhanced. Therefore, when the paint is used for the substrate, the filling effect of the grayish white conductive powder on the substrate is enhanced, and good conductivity can be obtained. Further, silica sol gel and soda glass are excellent in heat resistance. Therefore, when the film composition formed by using the paint is subjected to a heat treatment such as a device making step, deterioration due to heat can be prevented. 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, fibrous resin, and phenol. Examples thereof include natural resins such as resins, amino resins, fluororesins, silicone resins, petroleum resins, cellacs, rosin derivatives, and rubber derivatives.

The blending amount of the grayish white conductive powder is 10 to 90 parts by mass, preferably 20 to 80 parts by mass with respect to 100 parts by mass of the resin. This is because if the blending amount is less than 10 parts by mass, the coloring power is insufficient, and if it is more than 90 parts by mass, the adhesion is insufficient.

[Membrane composition]
The film composition of the present embodiment contains the grayish white conductive powder of the present embodiment. When the coating material of this embodiment is used in an application requiring conductivity, for example, the coating material is applied to an insulating substrate such as a plastic molded body, paper, or a polymer film. As a result, a conductive film composition having excellent surface smoothness and adhesion can be formed on the substrate.

Next, examples of the present invention will be described in detail together with comparative examples.

<Example 1>
First, a raw material niobium pentoxide powder having an average particle size of 250 nm and an orthorhombic structure was prepared. Next, this niobium pentoxide powder was crushed and granulated by a ball mill. This granulated powder was reduced at a temperature of 750 ° C. in an ammonia gas (reducing gas) atmosphere using a quartz tube furnace to obtain a grayish white niobium nitride powder base. Here, the reduction reaction time (contact time of niobium oxide powder with ammonia gas) was set to 240 minutes. Further, the powder base was pulverized using a hammer mill to obtain a single particle grayish white conductive powder. This gray-white oxynitride niobium powder was designated as Example 1.

<Example 2>
A single-particle gray-white niobium nitride powder was obtained in the same manner as in Example 1 except that the reduction temperature was 650 ° C. and the reduction time was 480 minutes. This gray-white oxynitride niobium powder was designated as Example 2.

<Example 3>
A single-particle gray-white niobium nitride powder was obtained in the same manner as in Example 1 except that the reduction temperature was 800 ° C. and the reduction time was 180 minutes. This gray-white oxynitride niobium powder was designated as Example 3.

<Example 4>
A single-particle gray-white niobium nitride powder was obtained in the same manner as in Example 1 except that the reduction temperature was 850 ° C. and the reduction time was 240 minutes. This gray-white oxynitride niobium powder was designated as Example 4.

<Example 5>
A single-particle gray-white niobium nitride powder was obtained in the same manner as in Example 1 except that the reduction temperature was 550 ° C. and the reduction time was 1200 minutes. This gray-white oxynitride niobium powder was designated as Example 5.

<Comparative example 1>
A single particle niobium nitride powder was obtained in the same manner as in Example 1 except that the reduction temperature was 950 ° C. and the reduction time was 120 minutes. This black oxynitride niobium powder was designated as Comparative Example 1.

<Comparative example 2>
Titanium oxynitride powder of core-shell particles was produced by a method according to an example of Patent Document 1. That is, average particle size: 210 nm, crystal structure: rutile type structure, rutileization degree: 97%, Mg content: 0.06%, K content: 0.07%, Zr content: 0.02%, Nb A titanium dioxide powder having a content of 0.10% was prepared. This titanium dioxide powder (100 g) was added to water (400 g) and dispersed by a bead mill to prepare a slurry. Next, while maintaining the pH at about 1 and the temperature at 90 to 100 ° C., _{a mixed solution of SnCl 4} (142 g) and H ₃ PO ₄ (5.9 g) and an aqueous solution of caustic soda were added to the slurry. Was added dropwise at the same time, and a neutralization reaction was carried out. After the reaction, the crystals were washed and then dried at 110 ° C. to remove by-products and metal impurities from the resulting crystals. The dried powder was calcined at 650 ° C. in a mixed gas atmosphere of _{0.04% NH 3} and 99.96% N _2. By pulverizing the fired product using a hammer mill, a white conductive powder having a core-shell structure was obtained. This white titanium nitride powder was designated as Comparative Example 2.

<Comparative example 3>
A single-particle gray-white niobium nitride powder was obtained in the same manner as in Example 1 except that the reduction temperature was 530 ° C. and the reduction time was 1400 minutes. This gray-white oxynitride niobium powder was designated as Comparative Example 3.

<Comparative example 4>
A single-particle gray-white niobium nitride powder was obtained in the same manner as in Example 1 except that the reduction temperature was 500 ° C. and the reduction time was 1400 minutes. This gray-white oxynitride niobium powder was designated as Comparative Example 4.

<Comparative example 5>
A single-particle gray-white niobium nitride powder was obtained in the same manner as in Example 1 except that the reduction temperature was 860 ° C. and the reduction time was 180 minutes. This gray-white oxynitride niobium powder was designated as Comparative Example 5.

<Comparative Example 6>
A single-particle gray-white niobium nitride powder was obtained in the same manner as in Example 1 except that the reduction temperature was 540 ° C. and the reduction time was 1200 minutes. This gray-white oxynitride niobium powder was designated as Comparative Example 6.

<Comparative test 1 and evaluation>
The oxygen concentration, nitrogen concentration, lightness index L value, b value, and volume resistance of the single particle niobium nitride powder of Examples 1 to 5 and Comparative Examples 1 to 6 or the titanium oxynitride powder of the core shell particles are as follows. Each was evaluated by the method shown in. These results are shown in Table 1.

(1) Oxygen concentration and nitrogen concentration The measurement was performed using an oxygen / nitrogen analyzer (model number: ON736) manufactured by LECO.

(2) L value The L value was measured using a color computer (model: SE7700) manufactured by JASCO Corporation, and those having an L value of 14 or more were considered to be good, and those having an L value of less than 14 were regarded as insufficient.

(3) b value The b value was measured using a color computer (model number: SE7700) manufactured by JASCO Corporation, and those having a b value of −0.5 or less were considered to be good.

(4) Volume resistivity The volume resistivity is determined by using a digital multimeter (model: DM7561) manufactured by Yokogawa Electric Co., Ltd. in the state of a green compact obtained by solidifying titanium oxynitride powder or core shell powder at a pressure of 10 MPa. measured by the terminal four-probe method ^was as good in the range of 0.5x10 2 ~1x10 ⁵ Ω · cm.

As is clear from Table 1, in Comparative Example 1, the nitrogen concentration was 12% by mass, the L value was 10, and the b value was 10, which was black. Moreover, the powder volume resistivity was low at 1.0x10 ⁰ Ω · cm. It is considered that this is because the reduction reaction proceeded too much and the nitrogen concentration in the powder became high.

In Comparative Example 2, the L value of the core-shell powder was 75 and the b value was 2.6, which were white.

In Comparative Example 3, the nitrogen concentration is 2% by mass, the powder volume resistivity was 2.5x10 ⁵ Ω · cm. It is considered that this is because the reduction reaction did not proceed because the reduction temperature was low.

In Comparative Example 4, the oxygen concentration was 26% by mass, the nitrogen concentration was 1% by mass, and the powder resistivity was 8.0 × 10 ⁵ Ω · cm. It is considered that this is because the reduction reaction did not proceed because the reduction temperature was low.

In Comparative Example 5, the nitrogen concentration is 11% by mass, the powder volume resistivity was 2.0x10 ⁰ Ω · cm. It is considered that this is because the reduction reaction proceeded too much because the reduction temperature was high.

In Comparative Example 6, the nitrogen concentration is 1 mass%, the powder volume resistivity was 1.5x10 ⁵ Ω · cm. It is considered that this is because the reduction reaction did not proceed because the reduction temperature was low.

On the other hand, in Examples 1 to 5, since the reduction reaction was carried out at an appropriate treatment temperature, the oxygen concentration in the powder was 15 to 25% by mass, the nitrogen concentration was 2 to 10% by mass, and the powder became grayish white. Further, niobium nitride powder having a powder volume resistivity in ^{the range of 0.5 × 10 2 to 1} × 10 ⁵ Ω · cm was obtained.

<Comparative test 2 and evaluation>
With respect to the single particle niobium nitride powder of Examples 1 to 5 and Comparative Examples 1 to 6 or the titanium oxynitride powder of core shell particles, the average particle size, the variation in coating surface resistance (fluctuation width), and before and after irradiation with ultraviolet rays. The change in L value was measured and evaluated by the methods shown below. These results are shown in Table 2.

(1) Average particle size The average particle size of the powder is the volume measured by a particle size distribution measuring device (manufactured by HORIBA, Ltd., dynamic light scattering type particle size distribution measuring device LB-550) using a dynamic light scattering method. cumulative median diameter (median _{diameter, D 50)} was determined by. The preferred range of the average particle size of the titanium oxynitride powder was set to 50 to 200 nm.

(2) Variation in coating film surface resistance For coating film surface resistance, niobium oxynitride powder or core shell powder is dispersed in a bead mill for 30 hours, acrylic resin is added to form a coating film having a thickness of 100 μm, and a sheet having a thickness of 300 × 300 mm is formed. After that, measurement was performed at 30 points using a resistance meter (Hiresta (trade name), model number MCP-HT450) manufactured by Mitsubishi Chemical Analytech Co., Ltd., and the variation was determined.

(3) Changes in L value before and after UV irradiation The L value before and after UV irradiation was measured using a color computer (model: SE7700) manufactured by JASCO Corporation, and before and after UV irradiation. The difference in the L value of was obtained.

In Comparative Example 1, the fluctuation width of the coating film surface resistance was ± 10% or more. It is considered that this is because the resistance value became unstable in Comparative Example 1 because the nitriding reaction proceeded too much.

In Comparative Example 2, the fluctuation width of the coating film surface resistance was ± 5% or more. It is considered that this is because the core and the shell coated by the dispersion treatment are peeled off in Comparative Example 1. Discoloration of titanium oxide was observed.

In Comparative Example 3, the fluctuation width of the coating film surface resistance was within ± 3%.

In Comparative Example 4, the fluctuation width of the coating film surface resistance was within ± 3%.

In Comparative Example 5, the fluctuation width of the coating film surface resistance was ± 5% or more. It is considered that this is because the resistance value became unstable in Comparative Example 5 because the nitriding proceeded too much.

In Comparative Example 6, the fluctuation width of the coating film surface resistance was within ± 3%.

On the other hand, in Examples 1 to 5, a conductive film having a variation in the surface resistance of the coating film within ± 3% and a change in the L value of the powder before and after irradiation with ultraviolet rays within 3 was obtained.

The niobium nitride powder of the present invention can be used as an antistatic paint, an antistatic clothing, an antistatic roller, etc., which are required to have high-precision control of conductivity and conductivity and long-term stability of a coating film.

Claims (5)

Niobium nitride powder containing niobium, oxygen, and nitrogen as main components, with an oxygen concentration of 15 to 25% by mass and a nitrogen concentration of 2 to 10% by mass, having an L value of 14 or more and a b value of −0. A grayish white niobium nitride powder having a powder volume resistance of 0.5 × 10 ² Ω · cm or more and 1 × 10 ⁵ Ω · cm or less. The method for producing the grayish white niobium nitride powder according to claim 1, wherein niobium oxide is heated and reduced with ammonia gas. A method for producing a dispersion liquid by dispersing the niobium nitride powder according to claim 1 or the niobium nitride powder produced by the method according to claim 2 in a solvent. A method for producing a conductive coating material by mixing the dispersion liquid according to claim 3 with a binder. A method for forming a conductive film by applying the conductive coating material according to claim 4.