JP6019214B2 - Conductive particles and method for producing the same - Google Patents

Description

  The present invention relates to conductive particles and a method for producing the same.

  Conventionally, as a method of imparting conductivity to a non-conductive material, for example, plastic, a method of adding a material imparting conductivity to plastic is known. As materials that impart such conductivity, for example, surfactants, metal powders, carbon black, tin oxide powders that do not contain dopant elements, and the like are known. However, the conductivity of a surfactant may vary depending on temperature and humidity. When metal powder or carbon black is added to a plastic, the resulting plastic becomes black, and the use of the plastic may be limited. The tin oxide powder that does not contain a dopant element may vary in conductivity during long-term use.

  Apart from these materials, tin oxide powder containing a dopant element such as antimony is also known. A tin oxide powder containing a dopant element has a low resistance, and the conductivity tends to be stable over time. However, tin oxide powder containing a dopant element is not economically advantageous due to the use of the dopant element, and has a problem of environmental burden. Furthermore, when tin oxide powder doped with antimony is added to the plastic, the resulting plastic becomes bluish black, and the use of the plastic may be limited as in the case of carbon black. As a tin oxide powder containing a dopant element, for example, as described in Patent Document 1, a solution of tin chloride is neutralized to produce a tin oxide hydrate, and then the tin oxide hydrate. An antimony chloride hydrate is added to the liquid containing the above, followed by neutralization to form an antimony oxide hydrate on the surface of the tin oxide hydrate, followed by firing. Moreover, as described in Patent Document 2, the base material is dispersed in water, an antimony-containing tin source is added thereto, and hydrolyzed under a low pH to precipitate an antimony-containing tin compound on the surface of the base material. The thing manufactured by heat-processing this is mentioned.

Japanese Patent Laid-Open No. 08-319118 JP 2009-199776 A

  However, the powder described in Patent Document 1 tends to have insufficient conductivity because part of antimony, which is a dopant element, exists alone on the particle surface. In order to increase the conductivity of the powder described in Patent Document 1, it is necessary to increase the amount of the dopant element used or to increase the firing temperature in the manufacturing process to diffuse the dopant element into the tin oxide. When the firing temperature is increased, the dispersibility of the obtained conductive particles in the resin tends to decrease. Moreover, since the powder of patent document 2 reduces the content of a dopant element in order to suppress bluishness or improve economy, the resistance of the outermost surface of the particles is increased, so that the conductivity is high. It tends to be insufficient.

The present invention is a conductive particle having a coating layer made of conductive tin oxide containing a dopant element on the surface of a core material,
In the coating layer, the dopant element is unevenly distributed on the surface side of the coating layer ,
Dopant element is intended to provide at least antimony, niobium or tantalum der Ru conductive particles.

The present invention also provides a method for producing the conductive particles as described above.
A first step of coating the surface of the core material with a tin compound by neutralizing a slurry containing a tin source and in which the core material is dispersed;
Second step of coating the tin compound containing the dopant element on the tin compound by adding the dopant element source and neutralizing the slurry in a state where the tin source is present in the slurry after the first step. When,
A third step of firing the particles obtained in the second step, the possess,
Dopant element is intended to provide at least antimony, a method for manufacturing niobium or tantalum der Ru conductive particles.

  Furthermore, this invention provides the electroconductive composition containing the said electroconductive particle.

  Hereinafter, the electroconductive particle of this invention is demonstrated based on the preferable embodiment. In the following description, the conductive particles may refer to individual particles depending on the context, or may refer to powder as an aggregate of particles. The conductive particles of the present invention have a coating layer made of conductive tin oxide containing a dopant element on the surface of a core material made of a non-conductive material. A core material is a site | part which occupies most volume in the electroconductive particle of this invention, and is located in the center area | region of electroconductive particle. On the other hand, a coating layer is located in the outermost surface of the electroconductive particle of this invention. The conductive particles of the present invention having a core material have the advantage of being easily dispersed in the resin as compared with the powder not having the core material described in Patent Document 1.

As the nonconductive material constituting the core material, either an inorganic material or an organic material may be used. The term “non-conductive” as used herein means that the resistivity is, for example, 10 ⁵ Ω · cm or more. As the inorganic substance, for example, oxides, nitrides, carbides, or the like of various elements can be used. Further, for example, salts of various elements can be used. Examples of various elements include various metal elements. As the organic substance, for example, various polymer materials can be used. The core material may be water-insoluble or water-soluble. Considering the method for producing conductive particles described later, the core material is advantageously water-insoluble. Examples of the core material that is preferably used include inorganic substances, and specific examples include titanium oxide, which is a metal oxide, alumina and silica, and barium sulfate, which is a metal salt.

  The shape of the core material only needs to be a shape capable of forming a conductive tin oxide layer on the surface, and various shapes such as a spherical shape, a polyhedral shape, a flake shape, and a needle shape are used depending on the use of the conductive particles. A shape is used. In the present invention, since the thickness of the coating layer is very small compared to the size of the core material, it can be generally regarded that the shape of the core material and the conductive particles are substantially the same.

The core material, BET specific surface area is preferably at most 5.0 m ² / g or more 20.0 m ² / g, more preferably not more than 6.0 m ² / g or more 18.0m ² / g. When the BET specific surface area of the core is within this range, the conductive particles obtained by forming the coating layer on the surface of the core are easily dispersed in the resin and the coating uniformity of the coating layer made of tin oxide To preferred. The BET specific surface area of the core material can be measured using, for example, a mono soap manufactured by Yuasa Ionics.

  The coating layer preferably covers the surface evenly and continuously so that the surface of the core material is not exposed at all, from the viewpoint of increasing the conductivity of the conductive particles. However, as long as the effect of the present invention is not impaired, the surface of the core material may be coated discontinuously so that a part of the surface of the core material is exposed.

  The coating layer need not be excessively thick as long as the conductivity of the coating layer of the conductive particles of the present invention is sufficiently developed. When the thickness of the coating layer is expressed in terms of the amount of tin oxide, the proportion of tin oxide in the conductive particles of the present invention is 20% by mass to 60% by mass, particularly 25% by mass to 50% by mass. A preferable thickness is preferable. The amount of tin in the conductive particles can also be determined by measuring the solution obtained by dissolving the coating layer of the conductive particles with an alkali with an ICP emission spectrometer.

  As described above, the conductive particles of the present invention contain a dopant element in the tin oxide that constitutes the coating layer. The dopant element is an element that can increase the conductivity of the tin oxide after the dopant element is added as compared with the tin oxide before the addition. Specifically, as the dopant element, antimony (Sb), niobium (Nb), tantalum (Ta), tungsten (W), phosphorus (P), fluorine (F), chlorine (Cl), bismuth (Bi), aluminum (Al), boron (B), molybdenum (Mo), nitrogen (N), zinc (Zn), and the like can be given. One or more of these dopant elements can be used. In particular, the dopant element is at least one of antimony (Sb), niobium (Nb), tantalum (Ta), phosphorus (P), fluorine (F), and tungsten (W), particularly antimony (Sb). It is preferable from the viewpoint of conductive environmental stability. In particular, when the conductive particles of the present invention contain antimony as a dopant element, the conductive particles have an advantage of excellent whiteness as compared with conventional antimony-doped tin oxide particles. In addition, the coating layer is allowed to contain a small amount of inevitable impurities as long as the effects of the present invention are not impaired.

  As a result of intensive investigations on the relationship between the position of the dopant element in the coating layer of the conductive particles and the conductivity of the conductive particles, the present inventor made the dopant in the particles unevenly distributed on the surface side of the coating layer. It has been found that high conductivity can be obtained even if the element content is reduced. In particular, it has been found that by making antimony unevenly distributed on the surface side of the coating layer, it is possible to achieve both conductivity and whiteness, which has been a problem of conventional antimony-containing tin oxide powders. The state in which the dopant element is unevenly distributed on the surface side means that the dopant element present in the surface side portion of the coating layer (hereinafter also referred to as “surface side portion”) is the portion on the core material side (hereinafter referred to as “core”). It is also referred to as “material side part”.) A surface side site | part means the site | part melt | dissolved to 5% of the mass of the whole coating layer, when a coating layer is gradually dissolved from the surface. A core material side site | part means the site | part melt | dissolved from more than 5% to 100% of the mass of the whole coating layer. Specifically, when the number of moles of the dopant element contained in each part with respect to 1 mol of tin contained in each part is calculated, the value indicates that the surface side part is larger than the core side part.

  The molar ratio of the dopant element to tin in the entire coating layer can be obtained by measurement with an ICP emission spectrometer after suspending the coating layer in an alkaline solution and completely dissolving the coating layer. As another method, a cross section of the conductive particles is cut out, and the cross section of the cross section is subjected to elemental analysis using TEM and EDX to obtain the amount of dopant element and the amount of tin in the conductive particles. It can be determined by converting the ratio to the amount (mol) of tin.

The number of moles of the dopant element with respect to 1 mol of tin in the surface side part and the core material side part is measured by the following method. That is, the conductive particles are suspended in an alkali solution in an autoclave at 140 ° C., and the coating layer is gradually dissolved from the surface side of the particles. If it is difficult to dissolve, the temperature may be further increased. The number of moles of tin and dopant elements eluted up to 5% dissolution rate of the coating layer was measured with an ICP emission spectrophotometer, converted into a ratio to the amount (mol) of tin, and this value was converted to tin at the surface side site. The number of moles of dopant element relative to 1 mol. Further, the number of moles of tin and dopant element eluted while the dissolution rate of the coating layer was more than 5% and up to 100% was measured with an ICP emission spectrophotometer, and converted into a ratio to the amount (mol) of tin. The value is defined as the number of moles of the dopant element with respect to 1 mol of tin at the core side portion.

  From the viewpoint of further improving the whiteness and economic efficiency of the conductive particles, when the coating layer is viewed along the thickness direction, the amount of the dopant element is directed from the surface side of the coating layer toward the core material side. The taper is preferably gradually reduced. “Decreased” means both when the amount of the dopant element continuously decreases and when the amount of the dopant element discontinuously changes stepwise. Is included.

  The dopant element is preferably contained in an amount of 0.01 mol or more and 0.7 mol or less, and more preferably 0.02 mol or more and 0.6 mol or less with respect to 1 mol of tin in the surface side portion. On the other hand, the core side portion preferably contains 0.005 mol or more and 0.4 mol or less, and 0.01 mol or more and 0.3 mol or less, with respect to 1 mol of tin, on condition that it is less than the surface side portion. More preferably. By containing the dopant element in such a ratio, even higher conductivity can be obtained even if the content of the dopant element in the particles is reduced.

  In the entire coating layer including both the surface side portion and the core material side portion, the dopant element is preferably contained in an amount of 0.01 mol to 0.60 mol with respect to 1 mol of tin. It is preferable that it is 0.01 mol or more from a viewpoint of improving the electroconductivity of electroconductive particle. It is preferable that it is 0.60 mol or less from a viewpoint of improving the economical efficiency of electroconductive particle. From these viewpoints, the dopant element is more preferably contained in an amount of 0.01 mol to 0.50 mol with respect to 1 mol of tin. As described above, the amount of the dopant element in the conductive particles can be determined by measuring the solution obtained by dissolving the coating layer of the conductive particles with an alkali with an ICP emission spectrometer. From the viewpoint of achieving both conductivity and economic efficiency of the conductive particles, the proportion of the dopant element in the conductive particles is 0.5% by mass or more and 10% by mass or less, particularly 0.5% by mass or more and 7.0% by mass. The following is preferable.

The conductive particles of the present invention preferably have a BET specific surface area of 15 m ² / g or more and 50 m ² / g or less. Conductive particles having a BET specific surface area in this range have a small particle size, good filling properties into the resin, and good dispersibility in the resin, so that the conductivity of the conductive film formed using these particles is high. . In addition, since conductive particles having a small particle size have a small interaction with light, it is easy to reduce blueness of a conductive film formed using the conductive particles. From these viewpoints, the BET specific surface area of the conductive particles is more preferably 20 m ² / g or more and 45 m ² / g or less. The BET specific surface area of the conductive particles can be measured, for example, using a mono soap manufactured by Yuasa Ionics.

The conductive particles of the present invention have a low volume resistance. Specifically, the volume resistance of the conductive particles of the present invention is preferably 1.0 × 10 ⁰ Ω · cm or more and 1.0 × 10 ³ Ω · cm or less at 25 ° C., more preferably 1.0 × It is 10 ⁰ Ω · cm or more and 1.0 × 10 ² Ω · cm or less. The volume resistance is measured by, for example, the following method. A 5 g sample is pressed with a hydraulic jack at a pressure of 500 kgf / cm ² for 0.5 minutes to produce a 25 mm diameter pellet. The resistance value of the obtained pellet is measured by a four-end needle method using PD-1 (trade name) manufactured by Dia Instruments.

  The conductive particles of the present invention have improved hue as compared with conventional antimony-doped tin oxide. Specifically, the conductive particles preferably have an L value of 70 or more, particularly 75 or more in the L * a * b * color system color coordinates. The a value is preferably −5.5 or more and −3.0 or less, particularly preferably −5.0 or more and −3.5 or less. The b value is preferably from -9.0 to 0, particularly preferably from -8.0 to -1.0. Said L value, a value, and b value can be measured, for example using the Nippon Denshoku Industries Co., Ltd. product spectral color difference meter SE600.

The conductive particles of the present invention are low in not only the volume resistance of particles but also the surface resistance of a conductive film formed using a coating solution containing the conductive particles. The surface resistance is preferably 1.0 × 10 ⁷ Ω / □ or less, more preferably 1.0 × 10 ⁴ Ω / □ or more and 1.0 × 10 ⁶ Ω / □ or less. The conductive film used for measuring the surface resistance is formed by the following method. A plastic container having a volume of 50 mL is prepared, and 7.41 g of conductive particles are put therein. Next, 9.64 g of a mixed solvent of toluene and n-butanol is placed in the container. The volume ratio of toluene and n-butanol is 7: 3. Further, 6.41 g of Dainar LR-167, which is an acrylic coating resin manufactured by Mitsubishi Rayon, is placed in this container. LR-167 has a resin component of about 46% by mass, and the balance is a mixed solvent of toluene and n-butanol. The volume ratio of toluene to n-butanol is 7: 3. Next, dispersion is performed for 1 hour using a paint shaker (manufactured by Asada Steel). The operating conditions of the paint shaker are standard operating conditions in a 60 Hz environment. The coating liquid obtained by the dispersion is applied to an OHP film made of polyethylene terephthalate (transparency OHP film made by Uchida Yoko Co., Ltd.). For coating, a bar coater # 10 (ROD No. 10 manufactured by Tester Sangyo Co., Ltd.) is used, and a coating film is formed with a use liquid amount of about 1 mL. After forming the coating film, the film is dried at 80 ° C. for 15 minutes in the air to obtain a conductive film.

  The surface resistance of the conductive film thus obtained is measured using a Hiresta made by Mitsubishi Analitec. An UP probe is used for the measurement. The measurement voltage is 10V.

  It is preferable that the electroconductive particle of this invention has the low haze of the electrically conductive film formed into a film using the coating liquid containing this. Specifically, the haze of the conductive film is preferably 20% or less, and more preferably 17% or less. The conductive film used for haze measurement is formed by the method described above. The haze of the conductive film can be measured, for example, by the following method. It measures with MODEL 1001DP (brand name) which is a haze meter by Nippon Denshoku Industries Co., Ltd. The measurement is carried out according to JIS K7105 by an integrating sphere measurement method. The haze is calculated from (scattered light / total light transmitted light) × 100.

Next, the preferable manufacturing method of the electroconductive particle of this invention is demonstrated.
The manufacturing method includes a first step of coating the surface of the core material with a tin compound by neutralizing a slurry containing a tin source and in which the core material is dispersed;
Second step of coating the tin compound containing the dopant element on the tin compound by adding the dopant element source and neutralizing the slurry in a state where the tin source is present in the slurry after the first step. And a third step of firing the particles obtained in the second step.

  Usually, in a 1st process, after preparing a slurry by disperse | distributing a core material to a medium, this slurry is neutralized in the state in which a tin source exists. In the first step, no dopant element source is added to the slurry.

  As the core material, those described above can be used. Moreover, as a medium, a suitable liquid is selected according to the kind of core material, the conditions of the neutralization reaction of a 1st process and a 2nd process, etc. In general, water is used.

  In the slurry before adding the tin source, the mixing ratio of the medium and the core material is preferably 50 g or more and 240 g or less, particularly 60 g or more and 200 g or less, with respect to 1 liter of the medium. This is because a uniform coating layer of a tin compound is easily formed on the surface of the core material when the blending ratio of both is within this range.

  The tin source is used to form a layer of a tin compound that covers the core material. Examples of the tin compound include tin hydroxide and tin oxide hydrate. As the tin source, one capable of forming such a tin compound layer on the surface of the core material is used. The tin source is preferably a water-soluble compound. Examples of such a tin source include sodium stannate and tin tetrachloride which are compounds that are easily dissolved in water. These can be used individually by 1 type or in combination of 2 or more types.

  The mixing ratio of the core material and the tin source in the slurry of the first step is such that the Sn amount in the tin source with respect to 100 parts by mass of the core material is 10 parts by mass or more and 90 parts by mass or less, particularly 15 parts by mass or more and 85 parts by mass or less. It is preferable. When the blending ratio of the two is within this range, a uniform layer of a tin compound is easily formed on the surface of the core material.

  An acid or alkali is usually used for neutralization of the slurry. As the acid, for example, an aqueous solution of sulfuric acid, nitric acid, acetic acid or the like is used. When sulfuric acid is used, it is preferable to use dilute sulfuric acid, particularly dilute sulfuric acid having a concentration of 10% by volume or more and 50% by volume or less because a uniform layer of a tin compound is easily obtained. As the alkali, for example, an aqueous sodium hydroxide solution or ammonia water is used. In the neutralization of the slurry, either the addition of the tin source to the slurry or the addition of the acid or alkali may be performed first or simultaneously.

  The pH of the slurry at the time of neutralization is preferably 0.5 or more and 6.0 or less, more preferably 1.5 or more and 4.0 or less. By setting the pH during neutralization within this range, a tin compound layer can be easily formed on the surface of the core material.

  In the first step, in particular, when neutralization is performed by adding an acid to the slurry after adding the tin source, the pH of the slurry is 9 to 13 and particularly 10 to 12 using an alkali prior to the addition of the acid. You may raise it below. This is preferable because it facilitates uniform deposition of tin oxide on the core material and forms a uniform coating layer. As this alkali, sodium hydroxide aqueous solution, sodium carbonate, ammonia, etc. can be used.

  In the first step, after neutralizing the slurry, it is preferable to perform aging by continuing the stirring of the liquid. The aging is preferably performed for 30 minutes to 180 minutes, particularly 60 minutes to 120 minutes. Aging can be generally performed at 70 ° C. or higher and 80 ° C. or lower. By aging, a tin compound is easily formed uniformly on the surface of the core material. This tin compound does not contain a dopant element. By the above first step, the core material surface is coated with the tin compound.

  Subsequently, the second step is performed. In the second step, the dopant element source is added while the tin source is present in the slurry after the first step, and the slurry is neutralized. As the tin source used in the second step, the same tin source as mentioned in the first step can be used. In the first step and the second step, the types of tin sources used may be different or the same. Usually, since the tin source is hardly present in the liquid after the first step after completion of neutralization, it is preferable to newly add the tin source used in the second step to the slurry after the first step. However, in some cases, such as when an unreacted tin source remains in the liquid after the first step, it may not be necessary to add a new tin source. When the tin source used in the second step is newly added to the slurry after the first step, the tin source and the dopant source may be added to the slurry after the first step at the same time. You may shift back and forth. Moreover, it is preferable that it is 0.01 mol or more and 0.35 mol or less with respect to 1 mol of tin of the tin source added at the 1st process, and the tin amount in the tin source added at the 2nd process is 0.02 mol or more and 0.00. More preferably, it is 30 mol or less. Within this range, conductive particles having the effects of the present invention can be easily obtained.

  As the dopant element source, the oxides, halides, hydroxides, water-soluble salts, and the like of the dopant elements described above can be used. Specifically, as the antimony source, for example, antimony acid, potassium antimonite, sodium antimonite, antimony oxide, antimony trichloride, antimony tribromide, antimony acetate, antimony fluoride, sodium antimonate and the like are used. be able to. As the niobium source, for example, potassium niobate, sodium niobate, niobium pentachloride, heptafluoroniobic acid and its salt, niobium fluoride and the like can be used. As the tantalum source, for example, potassium tantalate, sodium tantalate, tantalum pentachloride, heptafluorotantalic acid and its salt, tantalum fluoride, or the like can be used. Examples of the tungsten source include ammonium tungstate, potassium tungstate, sodium tungstate, ammonium metatungstate, potassium metatungstate, sodium metatungstate, ammonium paratungstate, potassium paratungstate, sodium paratungstate, and sodium oxychloride. Tungsten or the like can be used. As the phosphorus source, for example, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, phosphorous acid, hypophosphorous acid and their ammonium salts, sodium salts, potassium salts, calcium salts and the like can be used. As the fluorine source, tin (II) sodium fluoride, potassium fluoride, hydrofluoric acid, or the like can be used. As the chlorine source, tin (II) chloride, tin (IV) chloride, sodium chloride and potassium chloride can be used. As the bismuth source, dibismuth carbonate, bismuth chloride, bismuth nitrate, bismuth sulfate and the like can be used. Two or more dopant element sources can be used in combination. The specific kind of dopant element source is appropriately selected based on the neutralization conditions in the second step. Moreover, it is preferable that the addition amount of a dopant element source is 0.01 mol or more and 0.60 mol or less with respect to 1 mol of total tin amounts of the tin source of both the first and second steps, and 0.01 mol or more and 0.50 mol. More preferably, it is as follows. Within this range, conductive particles having the effects of the present invention can be easily obtained.

  An acid or an alkali can be used for neutralization in the second step. Examples of the acid and alkali include the same ones used in neutralization in the first step. When neutralization is performed by adding acid or alkali to the slurry after the first step, either addition of acid or alkali and addition of dopant element source or addition of dopant element source and tin source is performed first. You may go at the same time.

  The pH of the slurry at the time of neutralization is preferably 0.5 or more and 6.0 or less, more preferably 1.5 or more and 4.0 or less. By setting the pH during neutralization within this range, a tin compound containing a dopant element can be easily formed on the tin compound formed in the first step. As this tin compound, the same thing as the tin compound produced | generated at a 1st process can be mentioned.

  After neutralizing the slurry in the second step, it is preferable to perform aging by continuing stirring of the liquid. The aging is preferably performed for 30 minutes to 180 minutes, particularly 60 minutes to 120 minutes. A uniform layer of a tin compound containing a dopant element is easily formed by aging. Aging can be generally performed at 70 ° C. or higher and 80 ° C. or lower.

  By the above second step, particles in which a tin compound containing a dopant element is further coated on the tin compound covering the core material surface can be obtained.

  The particles produced in the second step are separated from the reaction system, and are preferably subjected to a third step, a firing step, through washing and drying steps. Thereby, conductive particles coated with tin oxide are obtained. In addition, the dopant element is diffused over the thickness direction of the coating layer by heat, and the dopant element is unevenly distributed. The dopant element diffuses from the upper surface side to the lower surface side (that is, the core material side) of the coating layer by thermal diffusion, and as a result, the concentration of the dopant element gradually decreases from the upper surface side to the lower surface side. Become. Thereafter, it is subjected to a crushing step as necessary, and adjusted to a desired particle size.

  The firing step can be performed in an oxidizing atmosphere such as air, but is preferably performed in a non-oxidizing atmosphere. Examples of the non-oxidizing atmosphere include a non-oxidizing and non-reducing atmosphere such as a nitrogen atmosphere and an argon atmosphere, and a weak reducing atmosphere such as a nitrogen atmosphere containing a small amount of hydrogen. Among these, it is preferable to use a weakly reducing atmosphere because oxygen vacancies are appropriately formed in tin oxide. When a nitrogen atmosphere containing hydrogen is used as the weakly reducing atmosphere, the hydrogen content is preferably 0.1 volume% or more and 10 volume% or less, more preferably 1 volume% or more and 3 volume% or less. When the hydrogen content is within this range, it is easy to form a conductive tin oxide coating layer having an appropriate amount of oxygen deficiency without reducing tin to metal.

  The firing temperature is preferably 400 ° C. or higher and 900 ° C. or lower, more preferably 500 ° C. or higher and 800 ° C. or lower, regardless of the firing atmosphere. The firing time is preferably 20 minutes to 120 minutes, more preferably 40 minutes to 100 minutes. This is because when the firing temperature and time are within these ranges, the conductive particles obtained by firing are less likely to agglomerate.

  Thus, the obtained electroconductive particle is used suitably in the state of the electroconductive composition containing this. For example, the conductive particles can be mixed with a vehicle and glass frit to form a conductive paste. Alternatively, the conductive particles can be mixed with an organic solvent or the like to form an ink. A conductive film having a desired pattern can be obtained by applying the conductive paste or ink thus obtained to the surface of the object to be applied.

  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) Production of conductive particles 150 g of titanium oxide particles (BET specific surface area 15 m ² / g) as a core material were dispersed in 1000 ml of water and heated to 75 ° C. to obtain a slurry. A 10% aqueous sodium hydroxide solution was added dropwise to the slurry to adjust the pH of the slurry to about 12. Separately, an aqueous tin solution prepared by dissolving 150 g of sodium stannate trihydrate (Na ₂ SnO ₃ .3H ₂ O, grade 91%) in 300 ml of water was prepared. The tin aqueous solution was added to the slurry over 30 minutes and then stirred for 30 minutes. Subsequently, 10% sulfuric acid aqueous solution was dropped over 120 minutes to adjust the pH of the slurry to 2.5. The slurry was aged by stirring for 60 minutes while maintaining the pH at 2.5 and 75 ° C. In addition to the above operations, antimony in which 50 g of tin tetrachloride pentahydrate (SnCl ₄ .5H ₂ O, grade 98%) and 5 g of antimony trichloride (SbCl ₃ , grade 98%) were dissolved in 300 ml of water. A tin mixed aqueous solution was prepared. This mixed aqueous solution was added to the slurry after aging over 60 minutes while maintaining the pH at 2.5. The slurry was then aged by stirring for 60 minutes while maintaining the pH at 2.5 and 75 ° C. Thereafter, the slurry was filtered, and the solid content was washed with water, and then dried at 85 ° C. for 12 hours. The obtained dried product was reduced and fired at 500 ° C. for 2 hours in a 2% by volume H ₂ / N ₂ atmosphere in a horizontal tube furnace to obtain conductive particles. The BET specific surface area of the core material was measured by the method described above (hereinafter, the same applies to the core materials used in Examples 2 to 8 and Comparative Example 1).

[Examples 2 to 4 and Comparative Example 1]
Other than changing the type of core material (material or BET specific surface area), sodium stannate trihydrate addition amount, tin tetrachloride pentahydrate addition amount or antimony trichloride addition amount as shown in Table 1 below Produced conductive particles in the same manner as in Example 1.

[Examples 5 to 8]
Table 1 below shows the type of core material (material or BET specific surface area), sodium stannate trihydrate addition amount, tin tetrachloride pentahydrate addition amount, dopant element type or dopant element addition amount. The electroconductive particle was manufactured like Example 1 except having changed as follows. Of the dopants used, niobium pentachloride was 95%, tantalum pentachloride was 97%, orthophosphoric acid was 85%, and potassium fluoride was 100%.

[Evaluation]
About the electroconductive particle obtained by the Example and the comparative example, the number of moles with respect to 1 mol of tin of dopant elements, such as antimony (Sb) doped by the coating layer, by the method using the ICP emission spectrometer described above. It was measured.
Furthermore, the BET specific surface area (m ² / g), volume resistance (Ω · cm), L value, a value, and b value of the conductive particles were measured by the method described above. Moreover, the electrically conductive film was formed from the obtained electroconductive particle by the method mentioned above, and surface resistance (ohm / square) was measured by the method mentioned above about this electrically conductive film. The results are shown in Table 2 below.

  As is apparent from the results shown in Table 2, it can be seen that in the conductive particles of Examples 1 to 8, the dopant element is unevenly distributed on the particle surface side in the coating layer. In contrast, in the conductive particles of Comparative Example 1, the dopant element is not unevenly distributed. For example, the conductive particles of Example 1 and the conductive particles of Comparative Example 1 have the same amount of antimony as a dopant element, but the former has a lower volume resistance than the latter, and the coating film It can be seen that the surface resistance is low. Further, the conductive particles of Example 3 and the conductive particles of Comparative Example 2 have the same content of antimony as a dopant element, but the former has an L value, a value, and b value of the particles as compared with the latter. Are both high and excellent in hue and low in volume resistance. Further, although not shown in the table, in the conductive particles obtained in each Example, the amount of the dopant element was continuously decreased from the surface side of the particle toward the core material side.

  Since the electroconductive particle of this invention has high electroconductivity even if content of a dopant element is reduced, it is excellent in economical efficiency. In particular, when the conductive particles of the present invention contain antimony as a dopant element, the whiteness is improved as compared with the conventional antimony-containing tin oxide powder.

Claims (7)

Conductive particles having a coating layer made of conductive tin oxide containing a dopant element on the surface of the core material,
In the coating layer, the dopant element is unevenly distributed on the surface side of the coating layer ,
At least antimony, niobium or tantalum der Ru conductive particles dopant element.   2. The conductive particle according to claim 1, wherein in the coating layer, the amount of the dopant element gradually decreases from the surface side of the coating layer toward the core material side. BET specific surface area is 15 m ² / g or more and 50 m ² / g or less,
The conductive particles according to claim 1, wherein the volume resistance is 1.0 × 10 ⁰ Ω · cm or more and 1.0 × 10 ³ Ω · cm or less.   L value of L * a * b * color system color coordinate is 70 or more, a value is -5.0 or more and -3.0 or less, b value is -9.0 or more and -4.0 or less The electroconductive particle according to any one of claims 1 to 3.   5. The conductive particle according to claim 1, wherein a dopant element is contained in an amount of 0.01 mol to 0.60 mol with respect to 1 mol of tin. It is a manufacturing method of the electroconductive particle of Claim 1, Comprising:
A first step of coating the surface of the core material with a tin compound by neutralizing a slurry containing a tin source and in which the core material is dispersed;
Second step of coating the tin compound containing the dopant element on the tin compound by adding the dopant element source and neutralizing the slurry in a state where the tin source is present in the slurry after the first step. When,
A third step of firing the particles obtained in the second step, the possess,
Method for producing a dopant element at least antimony, niobium or tantalum der Ru conductive particles. The electroconductive composition containing the electroconductive particle as described in any one of Claims 1 thru | or 5 .