JP2015090824A - Conductive particle and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide conductive particles capable of suppressing increase in electric resistance of a material imparted with electrical conductivity even if dispersed for a long time when conductive particles are kneaded and dispersed in a non-conductive material such as a resin to impart conductivity to the non-conductive material.SOLUTION: There are provided conductive particles obtained by forming a surface layer composed of tin oxide on a surface of a core material. In the conductive particles, the ratio SSA/Dbetween the specific surface area SSA(m/g) and the volume cumulative particle diameter D(μm) at the cumulative volume of 90% by volume as determined by a laser diffraction/scattering particle size distribution measuring method is 10 or more and 105 or less. The value of the cumulative particle diameter Dpreferably is 0.2 μm or more and 2.1 μm or less. The value of the cumulative particle diameter Dpreferably is 0.1 μm or more and 1.2 μm or less.

Description

  The present invention relates to conductive particles having a conductive tin oxide layer and a method for producing the same.

  The present applicant has previously proposed a conductive powder in which a tin oxide layer is formed on the surface of a granular core material (see Patent Document 1). The conductive powder is formed by adding a water-soluble tin compound to a slurry in which a granular core material is dispersed in water, and then performing a neutralization reaction to form a coating layer made of tin hydroxide, and firing the coating layer. It is obtained by.

  In addition, as a method for improving the manufacturing method of the conductive powder described in Patent Document 1, the present applicant circulated a mother liquor in which core material particles are dispersed in a medium, and provided strong strength provided in a part of the circulation path. A reactant for forming a coating layer is supplied to a dispersing device, and the core material particles and the reactant are reacted in a state where the mother liquor is strongly dispersed in the strong dispersing device, and the surface of the core material particles is reacted. A method for forming a coating layer was proposed (see Patent Document 2). According to the method described in Patent Document 2, a layer of conductive tin oxide can be formed more uniformly than the method described in Patent Document 1.

JP 2005-108732 A JP 2009-255042 A

  In order to impart conductivity to a non-conductive material such as a resin using the conductive powder described above, the conductive powder may be kneaded and dispersed in the non-conductive material using a bead mill or a kneader. The longer the time required for this dispersion, the better the dispersibility of the conductive powder in the nonconductive material. However, on the contrary, the electrical resistance of the material imparted with conductivity tends to increase. This is considered to be because the tin oxide layer in the conductive powder peels off due to the longer time required for dispersion, and the surface of the core material is exposed.

  An object of the present invention is to provide conductive particles having various performances further improved as compared with the above-described prior art and a method for producing the same.

The present invention is a conductive particle formed by forming a surface layer made of tin oxide on the surface of the core material,
SSA / D ₉₀ which is a ratio of specific surface area SSA (m ² / g) and volume cumulative particle diameter D ₉₀ (μm) at ₉₀ volume% cumulative volume by laser diffraction scattering particle size distribution measurement method is 10 or more and 105 or less Some conductive particles are provided.

The present invention also provides a method for producing the conductive particles as described above.
After adding a water-soluble tin compound to the slurry in which the core material is dispersed in the medium, the slurry is subjected to a neutralization reaction to obtain a conductive particle precursor in which the surface of the core material is coated with tin hydroxide. And generating the conductive tin oxide by firing the precursor,
As a core material, the ratio D ₅₀ / D ₉₀ of the volume cumulative particle diameter D ₅₀ at a cumulative volume of ₅₀ % by volume and the volume cumulative particle diameter D ₉₀ at a cumulative volume of 90% by volume measured by a laser diffraction / scattering particle size distribution measurement method is 0. The present invention provides a method for producing conductive particles using a particle having a particle size of 4 or more and 0.9 or less.

  According to the present invention, when conductive particles are kneaded and dispersed in a non-conductive material such as a resin to impart conductivity to the non-conductive material, conductivity is imparted even if the dispersion is performed for a long time. An increase in electrical resistance of the formed material can be suppressed.

Fig.1 (a) is a schematic diagram which shows the electroconductive particle of this invention, FIG.1 (b) is a schematic diagram which shows the conventional electroconductive particle.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. In the following description, “conductive particles” may refer to individual particles depending on the context, or may represent powder as an aggregate of particles. The conductive particles of the present invention are roughly classified into a central region and a surface region located outside the central region. A core material is located in the central region. And the surface layer which consists of electroconductive tin oxide as a surface area is formed so that the surface of this core material may be coat | covered. The surface layer made of conductive tin oxide preferably covers the entire surface of the core material.

  The electroconductive particle of this invention has one of the characteristics in the raise of the electrical resistance after applying external force to this particle | grain and performing a dispersion process. Specifically, in this type of conductive particles known in the art, a surface layer S of conductive tin oxide is formed on the surface of the core material C in an aggregated state as shown in FIG. As a result, when an external force is applied to the conductive particles P, the aggregated core material C is crushed, and as a result, the surface of the core material C may be exposed to the outside. Since the exposed portion E does not have conductivity, the number of conductive paths between the conductive particles P is reduced, which easily causes an increase in electrical resistance. The exposed portion E having no electrical conductivity is more likely to be generated as the time for dispersing by applying external force is longer, and the exposed portion E is more likely to be aggregated. In contrast, in the conductive particles of the present invention, as shown in FIG. 1A, a surface layer S of conductive tin oxide is formed on the surface of the core material C having a low degree of aggregation. Therefore, even when an external force is applied to the conductive particles P of the present invention for dispersion, the surface of the core material C is difficult to be exposed to the outside due to the low degree of pulverization of the core material C. As a result, even if the dispersion treatment is performed for a long time, it is possible to effectively suppress a decrease in the conductive path between the conductive particles P, and thus it is possible to effectively suppress an increase in electrical resistance. .

As is clear from the above description, the conductive particles of the present invention have a low degree of aggregation of the core material constituting the conductive particles. This means that the number of core materials contained per conductive particle of the present invention is small. As a result of intensive studies by the present inventors on the conductive particles of the present invention having such characteristics, the cumulative volume of 90 by the laser diffraction scattering type particle size distribution measurement method with the specific surface area of the conductive particles set to SSA (m ² / g). When the volume cumulative particle diameter in volume% is D ₉₀ (μm), it has been found that the characteristics of the conductive particles of the present invention can be described successfully by using the value of SSA / D ₉₀ which is the ratio of the two. Specifically, when the conductive particles of the present invention have an SSA / D ₉₀ value of 10 or more and 105 or less, even when dispersion of kneading the conductive particles into a non-conductive material such as a resin is performed for a long time, It has been found that an increase in electrical resistance of a material imparted with conductivity can be suppressed. The suppression of the increase in electrical resistance is more effective when the value of SSA / D ₉₀ is preferably 25 or more and 95 or less, more preferably 30 or more and 85 or less.

The D ₉₀ of the conductive particles is measured by, for example, a laser diffraction / scattering particle size distribution measurement method. When preparing a measurement sample, 0.1 g of conductive particles are mixed with 100 ml of a 20 mg / L aqueous solution of sodium hexametaphosphate and dispersed with an ultrasonic homogenizer (US-300T, manufactured by Nippon Seiki Seisakusho) for 10 minutes. The SSA value of the conductive particles can be measured by the BET method (He / N ₂ mixed gas) using, for example, “Monosorb” manufactured by Yuasa Ionics. In this specification, the amount of the measured powder was 0.3 g, and the pre-degassing conditions were 10 minutes at 105 ° C. under atmospheric pressure.

The value of SSA / D ₉₀ in the conductive particles of the present invention is preferably in the above-mentioned range, and the value of D ₉₀ itself is preferably 0.2 μm or more and 2.1 μm or less. It became clear as a result of examination of an inventor. Setting the D ₉₀ of within this range, even if the conductive particles kneaded Komu dispersion of the present invention in a non-conductive material such as resin for a long time, an increase in the electrical resistance of the conductivity is imparted material Since it can suppress, it is preferable. From this viewpoint, the value of D ₉₀ is more preferably 0.2 μm or more and 1.8 μm or less, and further preferably 0.2 μm or more and 1.5 μm or less.

Conductive particles of the present invention, in addition to D ₉₀ of the range described above, preferably the value of the cumulative volume particle diameter D ₅₀ in the cumulative volume 50% by volume by laser diffraction scattering particle size distribution measurement method 0 It is advantageous that the thickness is 1 μm or more and 1.2 μm or less from the viewpoint of further suppressing an increase in electrical resistance after the dispersion treatment. From this viewpoint, the value of D ₅₀ is more preferably 0.1 μm or more and 1.0 μm or less, and further preferably 0.1 μm or more and 0.4 μm or less. The value of D _{50 can} be measured by the same method as the value of _{D 90.}

For the specific surface area SSA, preferably not more than ^{5 m} 2 / g or more ^{95 m} 2 / g, still more preferably not more than ^36m 2 / g or more ^{95 m} 2 / g, more preferably ^52m 2 / g or more ^{95 m} 2 / g or less It is. Setting the specific surface area SSA within this range also makes it easy to reduce the degree of aggregation of the core material.

Where it electrically conductive particles of the present invention are those having a relatively narrow particle size distribution are as described above, evaluation particle size distribution of the particles is generally the ratio D _{50 /} D ₉₀ of D ₅₀ and D ₉₀ as the measure it can. Specifically, it can be said that the closer the D ₅₀ / D ₉₀ is to 1, the narrower the particle size distribution of the particles. In the conductive particles of the present invention, this D ₅₀ / D ₉₀ is preferably 0.4 or more and 0.9 or less. From the viewpoint of more effectively suppressing the increase in electric resistance even when the dispersion treatment is performed for a long time, the value of D ₅₀ / D ₉₀ is more preferably 0.4 or more and 0.8 or less. More preferably, it is 4 or more and 0.7 or less.

In order to set the value of SSA / D _{90 and} the value of D ₅₀ / D _{90 in} the above-mentioned range in the conductive particles of the present invention, the core material constituting the conductive particles has a specific particle size distribution. It is advantageous to use. Specifically, in the state before the surface layer of the conductive tin oxide is formed, the volume cumulative particle size D ₅₀ at a cumulative volume of ₅₀ % by volume and the volume at a cumulative volume of 90% by volume by the laser diffraction scattering type particle size distribution measurement method. The ratio D ₅₀ / D ₉₀ to the cumulative particle diameter D ₉₀ is preferably 0.4 or more and 0.9 or less, more preferably 0.4 or more and 0.8 or less, and still more preferably 0.45 or more and 0.00. It is preferable to use a core material of 8 or less. Since the core material having such a particle size distribution has a low degree of aggregation between the core materials, by producing conductive particles using such a core material, the core material constituting the individual conductive particles Can be as close to 1 as possible. Method of measuring the _{D 50} and _{D 90} of the core material is the same as the method for measuring the _{D 50} and _{D 90} of the conductive particles.

The value of D ₅₀ / D ₉₀ of the core material is as described above. The value of D ₅₀ of the core material itself is agglomerated at an extremely small particle size, and conversely, sedimentation occurs at a large particle size. From the viewpoint of effectively preventing the phenomenon, it is preferably 0.1 μm or more and 0.9 μm or less, and preferably 0.1 μm or more and 0.6 μm or less in a state before the surface layer of conductive tin oxide is formed. More preferably, it is more preferably 0.1 μm or more and 0.4 μm or less. On the other hand, the D ₉₀ value itself of the core material is preferably 0.2 μm or more and 1.0 μm or less in the state before the surface layer of conductive tin oxide is formed from the viewpoint of preventing aggregation and sedimentation. 0.25 μm or more and 1.0 μm or less is more preferable, and 0.25 μm or more and 0.9 μm or less is more preferable.

Since the conductive particles of the present invention are already highly dispersible in the state immediately after synthesis, the particle size is almost constant regardless of the dispersion time even if it is subsequently subjected to a dispersion treatment. . This brings about the advantage that dispersion is completed in a short time when the conductive particles of the present invention are subjected to a dispersion treatment together with a resin and a solvent to obtain a conductive composition. Moreover, even if the dispersion time for obtaining the conductive composition is increased, the electrical resistance of the conductive composition is unlikely to increase. For example, the resistance of a conductive film formed using the conductive particles after being dispersed with a resin and a solvent for 1 hour is defined as R ₁ (Ω / □), and formed using the conductive particles after being dispersed for 3 hours. When the resistance of the conductive film is R ₃ (Ω / □), the value of log (R ₃ / R ₁ ) is preferably 0 or more and 3.0 or less, more preferably 0 or more and 1.0 or less. . That is, the resistance of the conductive film is less dependent on the dispersion time when preparing the resin composition. “Log” represents a common logarithm. A method for measuring the resistance (surface electrical resistance) of the conductive film will be described in Examples described later.

  As the core material, for example, a material made of a non-conductive material can be used. Examples of such materials include alumina, titanium dioxide, barium sulfate, silicon dioxide, mica, talc, aluminum borate, zinc oxide (ZnO), and alkali metal titanate. In particular, it is preferable to use alumina, titanium dioxide, barium sulfate, or silicon dioxide from the viewpoint of increasing the whiteness of the conductive particles and facilitating dispersion of the conductive particles in a resin or the like. In particular, it is preferable to use titanium dioxide.

  The shape of a core material should just be a shape which can form electroconductive tin oxide on the surface, and can be suitably selected according to the specific use of electroconductive particle. For example, a spherical shape, a flake shape, a needle shape, or the like can be used.

The surface layer of conductive tin oxide located on the surface of the core material is a layer that imparts conductivity to the conductive particles of the present invention. The conductive tin oxide is mainly composed of a compound represented by SnO ₂ which is a tetravalent tin oxide. In order to impart desired conductivity to the tin oxide represented by SnO ₂ , for example, a doping element (dopant) that can increase the conductivity of tin oxide can be added. Examples of the doping element include antimony. Instead of adding a doping element, oxygen vacancies may be generated in tin oxide. In this case, the tin oxide contains no doping element. In other words, this tin oxide is substantially free of doping elements.

  The oxygen-deficient conductive tin oxide can be obtained, for example, by reducing and firing tin hydroxide during the production of conductive particles described later. In addition, the fact that a doping element is substantially not included means that an element having an effect of enhancing the conductivity of tin oxide is not intentionally contained. Therefore, when an element having an effect of enhancing the conductivity of tin oxide is inevitably mixed in the conductive tin oxide due to impurities in the raw material, contamination in the manufacturing process, etc. Such conductive tin oxide is “substantially free of doping elements”.

  The proportion of tin oxide in the conductive particles of the present invention is preferably 20% by mass to 60% by mass, more preferably 22% by mass to 58% by mass, and more preferably 24% by mass to 56% by mass. It is more preferable that By setting the content ratio of the conductive tin oxide within this range, the conductivity of the conductive particles can be made sufficiently high. Further, the adhesion between the core material and the surface layer made of conductive tin oxide can be made sufficient. Furthermore, the dispersibility of the conductive particles can be made sufficient.

The ratio of tin oxide in the conductive particles is determined by, for example, dissolving the conductive particles in an acid to form a solution, and performing an ICP emission spectroscopic analysis device on the solution to determine the amount of tin. It can be obtained by converting to the amount of SnO ₂ ).

  Next, the suitable manufacturing method of the electroconductive particle of this invention is demonstrated. In this production method, a water-soluble tin compound is added to a slurry in which a core material is dispersed in a medium. The slurry is neutralized to produce a conductive particle precursor in which the surface of the core is coated with tin hydroxide. And a precursor is baked and electroconductive tin oxide is produced | generated.

In the manufacturing method of the electroconductive particle which has the above process, it is advantageous to use what has a specific particle size distribution as a core material. Specifically, as described above, D ₅₀ / D ₉₀ is preferably 0.4 or more and 0.9 or less, more preferably 0.4 or more and 0.8 or less, and still more preferably 0.45 or more. It is advantageous to use a core material of 0.8 or less. As the core material having such a particle size distribution, a commercially available product may be used, or a material whose particle size distribution is adjusted by crushing treatment may be used.

  In the case where the core material whose particle size distribution is adjusted by crushing treatment is used, examples of the crushing treatment include a method of wet crushing the core material using a media mill. As the media mill, for example, beads having a predetermined particle diameter can be used. The material of the beads may be selected appropriately in relation to the material of the core material. The particle size of the beads is preferably 50 μm or more and 500 μm or less, more preferably 100 μm or more and 300 μm or less, and still more preferably 100 μm or more and 200 μm or less. As a liquid medium used for making the core material into a slurry, for example, water, an organic solvent, a mixed solution of water and an organic solvent, or the like can be used.

If the degree of processing is too small in the wet crushing treatment of the core material, the core material in an agglomerated state cannot be sufficiently crushed, and D ₅₀ / D ₉₀ cannot be set in the above-described range. On the other hand, if the degree of treatment is too large, re-aggregation of the crushed particles proceeds, so that D ₅₀ / D ₉₀ cannot be set within the above-mentioned range. Therefore, it is necessary to appropriately perform the wet crushing process so that D ₅₀ / D ₉₀ is within the above-described range.

  The core material whose particle size distribution is adjusted in this way is mixed with water to obtain a slurry. The blending ratio of water and core material in the slurry is preferably 10 g or more and 100 g or less, and more preferably 30 g or more and 80 g or less, with respect to 1 liter of water. When the blending ratio of both is within this range, a uniform tin oxide layer is easily obtained.

  Next, a water-soluble tin compound is added to the slurry. The water-soluble tin compound is not particularly limited as long as it can form a coating layer made of tin hydroxide on the surface of the core material. For example, sodium stannate or tin tetrachloride can be used. The mixing ratio of water and the water-soluble tin compound in the slurry is such that the Sn concentration in the water-soluble tin compound with respect to water is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 10% by mass or less. is there. When the blending ratio of both is within this range, a uniform tin oxide layer is easily obtained.

  Next, an acid or a base is added to the slurry to which the water-soluble tin compound is added to perform a neutralization reaction. Examples of the method for performing the neutralization reaction include a method of adding an acidic substance or a basic substance to the slurry. Examples of the acidic substance include sulfuric acid, nitric acid, acetic acid and the like. When sulfuric acid is used, a uniform tin oxide layer is easily obtained when used in the state of dilute sulfuric acid. The concentration of dilute sulfuric acid is usually 10-50% by volume. Examples of the basic substance include sodium hydroxide and aqueous ammonia. Of these, sodium hydroxide is preferable because the concentration can be easily controlled.

  The pH of the slurry after neutralization is preferably 0.5 or more and 5 or less, more preferably 2 or more and 4 or less, and still more preferably 2 or more and 3 or less. By setting the pH of the slurry after neutralization within this range, tin hydroxide is produced from stannic acid obtained by dissolving the water-soluble tin compound in the slurry, and the surface of the core material is made of tin hydroxide. A covering layer is successfully formed.

  Thus, the precursor of the electroconductive particle by which the surface of the core material was coat | covered with the tin hydroxide is obtained. The precursor is then washed with water. The washed precursor is dehydrated and filtered and then dried.

  The dried precursor is subjected to a firing step. In this case, when oxygen-deficient conductive tin oxide is produced, it is advantageous to use a non-oxidizing atmosphere as the firing atmosphere. Examples of the non-oxidizing atmosphere include a nitrogen atmosphere, a nitrogen atmosphere containing hydrogen at a concentration less than the explosion limit, and an inert gas atmosphere such as argon. Among these, a nitrogen atmosphere containing hydrogen is preferable from an industrial viewpoint because it is inexpensive. When a nitrogen atmosphere containing hydrogen is used, the hydrogen concentration is less than the explosion limit, preferably 0.1 volume% or more and 10 volume% or less, more preferably 1 volume% or more and 3 volume% or less. This is because when the hydrogen concentration is within this range, it is easy to form a coating layer of conductive tin oxide having oxygen deficiency without reducing tin to metal.

  The firing temperature is preferably more than 600 ° C. and 1200 ° C. or less, more preferably 700 ° C. or more and 900 ° C. or less. The firing time is preferably 5 minutes or more and 60 minutes or less, more preferably 10 minutes or more and 30 minutes or less, provided that the firing temperature is within this range. If the firing conditions are within these ranges, it is easy to efficiently form oxygen vacancies in tin oxide while preventing sintering of tin oxide.

  As described above, target conductive particles can be obtained. The conductive particles obtained in this manner are obtained by using particles having a specific particle size distribution as the core material, and even if the conductive particles are dispersed for a long time, It is possible to effectively suppress a decrease in the conductive path, and thus to effectively suppress an increase in electrical resistance.

  The conductive particles thus obtained are suitably used as a conductive filler that is mixed with a nonconductive material such as paper, plastic, rubber, resin, paint, etc. and imparts conductivity thereto. It can also be used as an electrode modifier for batteries and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%”.

[Example 1]
(1) volume-cumulative particle diameter _{D 50} in the cumulative volume 50 volume% by wet disintegration laser diffraction scattering particle size distribution measuring method of the core material is 0.42 .mu.m, the value of the volume cumulative particle diameter _{D 90} of 1.15μm The spherical titanium oxide particles having a specific surface area SSA of 9.1 m ² / g were subjected to wet crushing treatment. The wet pulverization treatment was performed using a bead mill for a slurry obtained by mixing 150 g of titanium oxide particles and 0.6 liter of water. The beads used were made of zirconia having a diameter of 0.5 mm. The mixture containing these was processed in a paint shaker for 60 minutes. By wet disintegration treatment, the value of the cumulative volume particle diameter _{D 50} is the 0.13 [mu] m, the value of the cumulative volume particle diameter _{D 90} of 0.29 .mu.m, a specific surface area SSA is the titanium oxide particles is ^11m 2 / g Obtained. The titanium oxide particles were used as a core material.

(2) Production of precursor 200 g of titanium oxide particles were dispersed in 3.5 liters of water to obtain a slurry. To this slurry, 208 g of sodium stannate with a tin content of 41% was added and dissolved. 20% dilute sulfuric acid was added to this slurry and neutralized over 98 minutes until the pH of the slurry reached 2.5. Neutralization was performed while circulating the slurry. Further, during the neutralization operation, the slurry was continuously irradiated with ultrasonic waves. The neutralized slurry was washed with warm water. After washing, dehydration filtration was performed, and a filter cake (cake) made of the precursor of the target conductive particles was recovered.

(3) Production of conductive particles The obtained filter cake was left to dry in an atmosphere at 150 ° C. for 15 hours. The obtained dried cake was crushed using an atomizer. This crushed material was placed in a firing furnace and fired at 700 ° C. for 20 minutes while flowing nitrogen gas containing 2% by volume of hydrogen. Thus, the target electroconductive particle was obtained.

[Example 2]
In this example, spherical titanium oxide particles different from those in Example 1 were used as the core material. The titanium oxide particles have a volume cumulative particle diameter D ₅₀ value of 0.33 μm, a volume cumulative particle diameter D ₉₀ value of 0.57 μm, and a specific surface area SSA of 8.6 m. ² / g. Conductive particles were obtained in the same manner as in Example 1 except that the titanium oxide particles were used as a core material.

Example 3
In this embodiment, as the core material, using the titanium oxide particles having the same sphere as in Example 1, by wet disintegration treatment, the value of the cumulative volume particle diameter D ₅₀ is 0.39 .mu.m, a volume cumulative particle diameter D ₉₀ Of titanium oxide particles having a specific surface area SSA of 10 m ² / g. Conductive particles were obtained in the same manner as in Example 1 except that the titanium oxide particles were used as a core material.

Example 4
In this example, precursor particles were produced, dried and crushed according to Example 1. Thereafter, this crushed material was placed in a firing furnace and fired at 700 ° C. for 20 minutes while only nitrogen gas was circulated. Thus, the target electroconductive particle was obtained.

Example 5
In this example, spherical titanium oxide particles different from those in Examples 1 and 2 were used as the core material. The titanium oxide particles have a volume cumulative particle diameter D ₅₀ value of 0.18 μm, a volume cumulative particle diameter D ₉₀ value of 0.21 μm, and a specific surface area SSA of 15 m ² / g. Using the titanium oxide particles as a core material, precursor particles were formed, dried, and crushed according to Example 1. Then, only baking was performed according to Example 4 and the target electroconductive particle was obtained.

Example 6
In this example, the precursor formation, drying, and crushing were performed according to Example 5. Thereafter, the crushed material was placed in a firing furnace and fired at 700 ° C. for 20 minutes while flowing nitrogen gas containing 1% by volume of hydrogen. Thus, the target electroconductive particle was obtained.

Example 7
In this example, the precursor formation, drying, and crushing were performed according to Example 5. Thereafter, this crushed material was placed in a firing furnace and fired at 700 ° C. for 20 minutes while flowing nitrogen gas containing 2% by volume of hydrogen. Thus, the target electroconductive particle was obtained.

Example 8
In this example, spherical titanium oxide particles different from those in Examples 1 and 2 to 5 were used as the core material. The titanium oxide particles have a volume cumulative particle size D ₅₀ value of 0.35 μm, a volume cumulative particle size D ₉₀ value of 0.66 μm, and a specific surface area SSA of 17 m ² / g. Conductive particles were obtained in the same manner as in Example 1 except that the titanium oxide particles were used as a core material.

[Comparative Example 1]
This comparative example is an example in which the wet crushing treatment of the core material of (1) was not performed in Example 1. Other than that was carried out similarly to Example 1, and obtained electroconductive particle.

[Comparative Example 2]
In this comparative example, spherical titanium oxide particles different from those in Examples 1, 2, and 5 to 8 were used as the core material. The titanium oxide particles have a volume cumulative particle size D ₅₀ value of 0.09 μm, a volume cumulative particle size D ₉₀ value of 0.33 μm, and a specific surface area SSA of 10 m ² / g. Using the titanium oxide particles as a core material, conductive particles were obtained in the same manner as in Comparative Example 1.

[Evaluation]
The obtained conductive particles in Examples and Comparative Examples, the specific surface area SSA, volume was measured cumulative particle diameter D ₅₀ and the volume cumulative particle diameter D _90. Further, the ratio of tin oxide in the conductive particles was measured. Furthermore, using the obtained electroconductive particle, the coating film was formed with the following method and the surface electrical resistance of the coating film was measured. The results are shown in Table 1 below.

[Measurement of surface electrical resistance]
5.4 g of conductive particles and 12.4 g of binder resin (LR-167, manufactured by Mitsubishi Rayon Co., Ltd.) are mixed in a container, and the resulting mixture is dispersed using a paint shaker to form a coating solution. Got. Two types of coating liquids were prepared, one that was subjected to dispersion treatment for 1 hour and the other that was subjected to 3 hours. The coating solution thus obtained was applied onto an OHP film manufactured by Uchida Yoko using a bar coater to form a coating film having a thickness of 3 μm. The surface electrical resistance of the obtained coating film was measured using a four-point probe resistance measuring machine (Loresta GP manufactured by Mitsubishi Chemical Corporation).

  As is clear from the results shown in Table 1, the conductive particles obtained in each Example (product of the present invention) were more dispersed for the preparation of the coating liquid than the conductive particles obtained in Comparative Example 1. It can be seen that the increase in the surface electrical resistance of the coating film is suppressed when the treatment is performed for 1 hour and when the treatment is performed for 3 hours.

C core material S conductive tin oxide surface layer P conductive particles

Claims (8)

Conductive particles in which a surface layer made of tin oxide is formed on the surface of the core material,
SSA / D ₉₀ which is a ratio of specific surface area SSA (m ² / g) and volume cumulative particle diameter D ₉₀ (μm) at ₉₀ volume% cumulative volume by laser diffraction scattering particle size distribution measurement method is 10 or more and 105 or less Some conductive particles. 2. The conductive particle according to claim 1, wherein the volume cumulative particle diameter D ₉₀ is 0.2 μm or more and 2.1 μm or less. 3. The conductive particle according to claim 1, wherein the value of the volume cumulative particle diameter D ₅₀ is from 0.1 μm to 1.2 μm. In the state before the surface layer is formed, the core material has a volume cumulative particle size D ₅₀ at a cumulative volume of ₅₀ % by volume and a volume cumulative particle size at a cumulative volume of 90% by volume by a laser diffraction scattering type particle size distribution measurement method. D ₉₀ and the ratio _D 50 _{/ D 90} conductive particles described in any one of 3 claims 1 0.4 to 0.9. 5. The conductive material according to claim 1, wherein the core material has a volume cumulative particle size D ₅₀ of 0.1 μm or more and 0.9 μm or less in a state before the surface layer is formed. Sex particles. The resistance of the conductive film formed using the conductive particles after the dispersion treatment with the resin and the solvent for 1 hour is defined as R ₁ (Ω / □), and the conductive particles after the dispersion treatment is performed for 3 hours. The conductivity according to any one of claims 1 to 5, wherein a value of log (R ₃ / R ₁ ) is 0 or more and 3.0 or less when the resistance of the conductive film is R ₃ (Ω / □). particle. It is a manufacturing method of the electroconductive particle of Claim 1, Comprising:
After adding a water-soluble tin compound to the slurry in which the core material is dispersed in the medium, the slurry is subjected to a neutralization reaction to obtain a conductive particle precursor in which the surface of the core material is coated with tin hydroxide. And generating the conductive tin oxide by firing the precursor,
As a core material, the ratio D ₅₀ / D ₉₀ of the volume cumulative particle diameter D ₅₀ at a cumulative volume of ₅₀ % by volume and the volume cumulative particle diameter D ₉₀ at a cumulative volume of 90% by volume measured by a laser diffraction / scattering particle size distribution measurement method is 0. The manufacturing method of electroconductive particle using what is 4 or more and 0.9 or less. The manufacturing method according to claim 7, wherein the core material is subjected to wet crushing treatment using a media mill so that D ₅₀ / D ₉₀ of the core material is set to 0.4 or more and 0.9 or less.

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