JP2002334611A - Conductive particle composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite having electric characteristics similar to precious metal particles by way of a mixture of precious metal coated particles and precious metal particles. SOLUTION: The conductive particle composite consists of precious metal coated particles with smaller average diameter than that of precious metal particles with precious metal coated on the surface of precious metal particles and inorganic fine particles. And it is connected to a manufacturing method of precious metal coated particles by adding precious metal salt solution to dispersion liquid under agitation with inorganic particles dispersed in reducer solution, or a method of manufacturing precious metal coated particles by adding precious metal salt solution and reducer at the same time to dispersion liquid of inorganic particles under agitation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to conductive particles comprising a noble metal coating layer formed around inorganic particles typified by ceramic particles and a composition thereof, and more particularly to a conductive particle composition and a conductive paste. The present invention relates to an electronic component, a multilayer ceramic capacitor, and a method for producing conductive noble metal-coated particles.

[0002]

2. Description of the Related Art Noble metals such as palladium, platinum and silver are widely used as electrode forming materials because of their excellent conductivity. When forming electrodes, usually, a noble metal powder (noble metal particles), a flammable binder and a solvent are mixed to form a conductive paste, and then the conductive paste is applied to a substrate such as a ceramic substrate, and then the conductive paste is formed. A method is employed in which the flammable binder is burned off and the noble metal powder is sintered by baking the coated substrate at a predetermined temperature to form an electrode layer substantially consisting only of the noble metal component.

When forming an electrode of a noble metal material, usually,
In order to realize appropriate sintering of the noble metal powder, a noble metal material having a melting point close to the firing temperature of the substrate is used.
That is, an unfired substrate precursor (referred to as a green sheet) is usually used as a substrate on which the conductive paste is applied. Is done. Therefore, the noble metal material used as the electrode material is selected in consideration of the melting point of the green sheet in accordance with the firing temperature of the green sheet. Conventionally, the firing temperature of the green sheet is about 1200 to 1400 ° C.
Therefore, palladium, which has a melting point slightly higher than the sintering temperature in that range and is likely to cause appropriate sintering of the noble metal powder, has been generally used as a noble metal material for forming an electrode. However, in recent years, a technique of lowering the sintering temperature of the green sheet and using a relatively low-melting and inexpensive conductive noble metal such as silver to manufacture a substrate with electrodes has been developed.

[0004] Since noble metals for forming electrodes, such as palladium, are expensive and prices fluctuate widely in the market, ceramic material particles and the like are used instead of noble metal powder (ie, pure noble metal powder) as core particles. As
The use of conductive powder composed of noble metal-coated particles having a noble metal coating layer formed around it has been studied for some time, and has already been realized.

The present inventor has been conducting research and development on noble metal-coated conductive particles, and has filed a patent application for a noble metal-coated conductive particle completed as a result of the development research and a method for producing the same. Japanese Patent No. 22028 (Japanese Patent No. 1356848), Japanese Patent Publication No. 61-22029 (Japanese Patent No. 1356853), Japanese Patent Publication No. 7-48444 (Japanese Patent No. 2028871), and Japanese Patent No. 2799916.

A typical method for producing the noble metal-coated conductive particles described in each of the above patents is to disperse ceramic particles as core particles in a noble metal complex compound solution in the presence of a gelling agent. While stirring the liquid, an aqueous solution of a reducing agent such as an aqueous hydrazine solution is added thereto, and the noble metal complex compound is reduced and the noble metal component generated by the reduction is precipitated around the core particles to obtain noble metal-coated conductive particles. Is the way.

The above-described method for producing the noble metal-coated conductive particles is a method which enables a high-purity noble metal-coating layer to be produced around the core particles by a simple operation. Purity is easily affected by the degree of gelation and the operation of adding the reducing agent solution.In the production of a large amount of conductive particles coated with noble metal in industrial production, there is a slight difference in the gelation state and the operation of adding the reducing agent solution. However, there is a problem that a sufficient homogeneous and high-purity noble metal coating layer may not always be obtained due to the difference.

[0008] In order to solve the above-mentioned problems, it has heretofore been possible to increase the thickness of the noble metal coating layer (that is, to increase the ratio of the volume of the noble metal coating layer to the volume of the core particles) and / or to mix the noble metal coated conductive particles with the noble metal. Countermeasures such as mixing and using particles (pure noble metal particles) have been devised. And
By utilizing such measures, the noble metal-coated conductive particles have already been used in large quantities as various conductive materials such as electrode materials.

[0009]

SUMMARY OF THE INVENTION The noble metal-coated conductive particles that have been developed so far have been used as practical materials for manufacturing electrodes as a result of improvements in the practical use as described above. However, it has become difficult to adequately respond to recent various requirements for electrode materials.

One of the requirements is a demand for a further reduction in the thickness of the electrode. To meet this demand, it is necessary to reduce the size of the noble metal particles and the noble metal-coated conductive particles. In order to reduce the size of the noble metal-coated conductive particles, it is necessary to reduce the size of the core particles.However, since the finely divided core particles have a strong cohesive force, highly disperse the ultrafine core particles. Preparing the noble metal uniformly on the surface of the core particles while preventing agglomeration is not easy to set the conditions.

Another requirement is to reduce the ratio of the noble metal in the noble metal-coated conductive particles. This requirement presupposes, of course, the condition that the conductive properties of the noble metal-coated conductive particles must not be reduced.

[0012]

Means for Solving the Problems In consideration of the above-mentioned requirements, the present inventor has conducted research on the development of a conductive material satisfying such requirements. As a result, the average of the noble metal-coated particles mixed with the noble metal particles has been studied. By reducing the particle size as compared to the average particle size of the noble metal particles, even if slight impurities are mixed in the noble metal layer on the surface of the noble metal coated particles, the defects of the noble metal coated particles surround the periphery thereof. Thus, it has been found that the noble metal particles (pure noble metal particles) that are present compensate for, thereby making it possible to relatively increase the usage amount of the noble metal coated particles without lowering the properties as the conductive material.

The present inventor further provides a method of preparing a dispersion in which core particles are dispersed in a reducing agent solution before producing the noble metal-coated conductive particles, and adding a noble metal complex solution while stirring the dispersion. By using a method of simultaneously adding the reducing agent solution and the noble metal complex solution to the dispersion of the core particles under stirring, the ratio of the volume of the coated noble metal layer to the volume of the core particles is 1 or more. However, it has been found that a high-purity noble metal coating layer can be formed around core particles.

Accordingly, the present invention provides a conductive particle composition comprising a noble metal coated on a surface of a noble metal particle and an inorganic fine particle and having an average particle size smaller than the average particle size of the noble metal particle. .

The present invention also resides in a conductive paste containing the above-described conductive particle composition of the present invention, and an electronic component including an electrode layer formed from the conductive paste.

The present invention also provides a multilayer ceramic capacitor formed from an electrode layer formed of the above-mentioned conductive paste and a ceramic sheet made of an inorganic material having the same composition as the inorganic particles contained in the conductive paste. is there.
This multilayer ceramic capacitor is prepared by heating a green ceramic sheet coated with the conductive paste at 900 to 1300 ° C.
It is advantageously produced by firing at a temperature in the range of

The present invention also provides a noble metal coating, wherein inorganic particles (preferably noble metal pre-coated inorganic particles) are dispersed in a reducing agent solution, and a noble metal salt solution is added to the dispersion under stirring. There is also a method for producing particles.

The present invention also provides a method for producing precious metal-coated particles, comprising simultaneously adding a precious metal salt solution and a reducing agent to a dispersion of inorganic particles (preferably precious metal pre-coated inorganic particles) under stirring. There is also.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention are as follows. (1) The weight ratio between the noble metal particles and the noble metal-coated particles in the conductive particle composition is in the range of 9: 1 to 1: 9. (2) The weight ratio between the noble metal particles and the noble metal-coated particles in the conductive particle composition is in the range of 9: 1 to 4: 6. (3) The average particle size of the noble metal-coated particles is 0.01 to 0.8 μm
m. (4) The difference between the average particle size of the noble metal particles and the average particle size of the noble metal-coated particles is 0.05 μm or more. (5) The difference between the average particle size of the noble metal particles and the average particle size of the noble metal-coated particles is 0.1 μm or more.

(6) The noble metal particles are palladium, platinum,
It is formed from one or more noble metals selected from the group consisting of gold and silver. (7) The inorganic particles are metal oxide particles. (8) The noble metal layer covering the inorganic particles is formed of one or more noble metals selected from the group consisting of palladium, platinum, gold and silver. (9) The noble metal layer covering the inorganic particles is an alloy of two or more noble metals selected from the group consisting of palladium, platinum, gold and silver, and has a relatively high melting point and a relatively low melting point. Is in the range of 1: 9 to 9: 1. (10) The noble metal layer covering the inorganic particles contains less than 50% by weight of a base metal (eg, nickel). (11) The element composition of the noble metal coating the inorganic particles and the element composition of the noble metal particles have a common component. (12) The average particle diameter of the inorganic particles is 0.05 to 0.5 μm
And the average particle size of the noble metal-coated particles is 0.8 μm or less.

Examples of the inorganic particles serving as the core particles of the noble metal-coated particles of the present invention include titanium dioxide, alumina, barium titanate, PZT, ferric oxide, calcium oxide,
Inorganic compounds centered on metal oxides such as silicon dioxide, zirconium dioxide, tungsten carbide, silicon carbide and titanium nitride, and particles made of metals such as copper, nickel, cobalt and iron or alloys thereof. . The average particle size of the inorganic particles is 0.01 to
It is preferably in the range of 0.7 μm, particularly 0.05
It is preferably in the range of 0.5 μm. Most preferred are inorganic particles ranging from 0.1 to 0.4 μm.

The method of forming the noble metal coating layer around the inorganic particles is not particularly limited, and includes various coating methods known so far, including the coating method according to the present invention described above. Can be used. However,
In order to form a relatively thin noble metal coating layer on inorganic particles with high purity, it is desirable to use any one of the following methods disclosed for the first time in this specification.

(1) A method in which inorganic particles (preferably, precious metal pre-coated inorganic particles) are dispersed in a reducing agent solution, and a noble metal salt solution is added to the dispersion under stirring to produce noble metal coated particles.

(2) A method of producing a noble metal-coated particle by simultaneously adding a noble metal salt solution and a reducing agent to a dispersion of inorganic particles (preferably precious metal pre-coated inorganic particles) under stirring (simultaneous addition coating). Law).

In a dispersion liquid of inorganic particles (aqueous medium dispersion liquid) or a reducing agent solution containing an inorganic particle in a dispersed state (aqueous reducing agent solution), a water-soluble polymer functioning as a thickener may be dissolved. desirable. As the water-soluble polymer, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, water-soluble cellulose derivatives such as carboxymethyl cellulose, polyvinyl alcohol, water-soluble synthetic polymers such as polyvinyl pyrrolidone, or gelatin, casein and the like Various polymers such as a water-soluble natural polymer can be used.

As the reducing agent, a reducing agent such as hydrazine, hydrazine hydrochloride, formic acid, formalin, hypophosphorous acid or the like is used, and usually used as an aqueous solution.

Examples of the noble metal complex used as a raw material for forming the noble metal coating layer include water-soluble salts such as ammonium tetrachloropalladate, tetraamminepalladium chloride, ammonium tetrachloroplatinate, and tetraammineplatinate chloride. The noble metal component can optionally be changed to other noble metal components such as gold, silver and the like.

In any of the above-mentioned methods of forming a noble metal coating layer, when a reducing agent is added to an aqueous medium containing inorganic particles, not only stirring but also ultrasonic treatment is carried out in order to increase the dispersion state of the inorganic particles. It is desirable to perform

When the noble metal-coated particles are used in a mixture with the noble metal particles, the ratio of the noble metal particles to the noble metal-coated particles is preferably in the range of 9: 1 to 1: 9 (weight ratio), and particularly preferably 9: 1. To 4: 6 (weight ratio, former: latter).

The noble metal particles include palladium, platinum,
Particles composed of a noble metal component such as gold or silver, or particles composed of an alloy thereof are used. The difference between the average particle size of the noble metal particles and the average particle size of the noble metal-coated particles is desirably 0.05 μm or more, and particularly desirably 0.1 μm or more.

The composition of the noble metal particles and the noble metal coated particles or the noble metal coated particles of the present invention can be advantageously used as a conductive component of a conductive paste according to a known method. Then, as described above, the conductive paste is printed and applied to a fired substrate or an unfired substrate (green sheet) using a screen printing method or the like, and the conductive paste-coated substrate is fired at a predetermined temperature. Thus, a substrate with electrodes can be obtained. In addition, when the inorganic substance of the core particles of the noble metal-coated particles is the same kind of inorganic substance as the green sheet material, the coefficient of thermal expansion can be adjusted, so that the production control of the substrate with electrodes becomes easy.

The substrate with electrodes manufactured using the conductive particle composition of the present invention is used by being incorporated in various electric products, electronic parts, electric appliances and the like. Specific examples of products in which a substrate with electrodes is incorporated include electronic components such as ceramic capacitors, thermistors, varistors, various resistors, CR composite components, IC substrates, conductive patterns for printed wiring, multilayer capacitors, multilayer varistors, Examples include a laminated coil, a multilayer IC package, and a BL ceramic capacitor.

[0034]

[Example 1] Ag / Pd (30% by weight / 20%)
Barium titanate fine particles (50% by weight)
(1) Preparation of palladium pre-coated barium titanate particles Pure water was added to 10.0 g of barium titanate powder (average particle size: 0.2 μm, specific surface area: 7.3 m ^{2 /} g) to make a liquid volume of 50 mL. And stirred for 5 minutes while applying ultrasonic waves. To this, a palladium nitrate solution (containing 8 mg as Pd) was added, and ultrasonic stirring was further performed for 10 minutes. After standing and decanting to adjust the liquid volume to 50 mL, the mixture was stirred again to obtain hydrazine monohydrate 0.1.
A solution obtained by diluting 05 mL to 1.0 mL was added, and then stirring was continued for 30 minutes. Finally, standing and decantation were performed to obtain palladium pre-coated barium titanate particles.

(2) Preparation of mixed solution of palladium complex and silver complex 22.2 g of a palladium nitrate solution (containing 4.0 g as Pd) was diluted to 40.0 mL with pure water, and 16.0 mL of aqueous ammonia was added thereto. Was added, and the mixture was stirred. When the liquid temperature reached about room temperature, the mixture was filtered to remove impurities. 9.5 g of silver nitrate (containing 6.0 g as Ag) and 6.0 mL of aqueous ammonia were added to the filtrate, and dissolved by stirring. ) Was obtained.

(3) Production of Ag / Pd-coated barium titanate fine powder 0.4 g of carboxymethylcellulose was added to the palladium pre-coated barium titanate particles obtained in (1) above.
An aqueous solution dissolved in 7 mL of pure water was added, and the mixture was stirred for 10 minutes while applying ultrasonic waves. After stopping the application of ultrasonic waves, 0.4 g of carboxymethylcellulose was further added to 2 g.
An aqueous solution to which 6.7 mL was added was added, and the mixture was stirred. An aqueous solution obtained by mixing 0.6 g of benzoic acid, 10.0 mL of pure water, and 4.0 mL of hydrazine monohydrate was added thereto, the liquid temperature was adjusted to 30 ° C., and tetraamine palladium nitrate obtained in the above (2) was added 60 mixed solution with silver diammine nitrate
After that, the mixture was stirred for 60 minutes, and then metal silver and metal palladium were deposited around the palladium pre-coated barium titanate particles. Thereafter, the particles were washed and dried to obtain 20.0 g of silver (30% by weight) and palladium (20%).
Barium titanate powder (average particle size: 0.3 μm, specific surface area: 4.3 m ² / g).

Example 2 Ag / Pd (35% by weight / 1
5% by weight) Coating of barium titanate fine particles (50% by weight) In Example 1, a mixed solution of a palladium complex and a silver complex of (2) was prepared by the method of (2b) below. The same operation was carried out, and barium titanate fine powder coated with 20.0 g of silver (35% by weight) and palladium (15% by weight) (average particle size: 0.3 μm, specific surface area:
4.3 m ² / g).

(2b) Preparation of mixed solution of palladium complex and silver complex 16.6 g of a palladium nitrate solution (containing 3.0 g as Pd) was diluted to 30.0 mL with pure water, and 12.0 mL of aqueous ammonia was added thereto. Was added, and the mixture was stirred. When the liquid temperature reached about room temperature, the mixture was filtered to remove impurities. 11.0 g of silver nitrate (including 7.0 g as Ag) and 10.0 mL of aqueous ammonia were added to the filtrate, and the mixture was stirred and dissolved.
A mixed solution of an ammine complex of palladium nitrate (tetraamminepalladium nitrate) and an ammine complex of silver nitrate (silver diammine nitrate) was obtained.

Example 3 Ag / Pd (40% by weight / 1
0% by weight) Coating of barium titanate fine particles (50% by weight) In Example 1, a mixed solution of a palladium complex and a silver complex of (2) was prepared by the following method (2c). The same operation was performed (however, the amount of hydrazine monohydrate used in (3) was set to 3.0 mL), 20.0
g of barium titanate fine powder coated with silver (40% by weight) and palladium (10% by weight) (average particle size: 0.3
μm, specific surface area: 4.3 m ² / g).

(2c) Preparation of mixed solution of palladium complex and silver complex 11.1 g of palladium nitrate solution (containing 2.0 g as Pd) was diluted to 20.0 mL with pure water, and 8.0 mL of aqueous ammonia was added thereto. Was added, and the mixture was stirred. When the liquid temperature reached about room temperature, the mixture was filtered to remove impurities. In the filtrate,
12.6 g of silver nitrate (containing 8.0 g as Ag) and 9.2 mL of aqueous ammonia were added and dissolved by stirring, and a mixture of an ammine complex of palladium nitrate (tetraamminepalladium nitrate) and an ammine complex of silver nitrate (silver diammine nitrate) was added. A solution was obtained.

Example 4 Ag / Pd (30% by weight / 2
(1%) Preparation of Barium Titanate Particles Preliminarily Coated with Palladium According to the method described in (1) of Example 1, Barium acid particles were obtained.

(2) Preparation of mixed solution of palladium complex and silver complex A mixed solution of a palladium complex and a silver complex was prepared by the method described in (2) of Example 1.

(3) Preparation of Ag / Pd-coated barium titanate fine powder 0.4 g of carboxymethylcellulose was added to the palladium pre-coated barium titanate particles obtained in (1) above.
An aqueous solution dissolved in 7 mL of pure water was added, and the mixture was stirred for 10 minutes while applying ultrasonic waves. After stopping the application of ultrasonic waves, 0.4 g of carboxymethylcellulose was further added to 2 g.
An aqueous solution to which 6.7 mL was added was added, and the mixture was stirred. A solution obtained by dissolving 0.7 g of ammonium benzoate in 7.0 mL of pure water was added thereto, the solution temperature was adjusted to 30 ° C., and a mixed solution of tetraamminepalladium nitrate and silver diammine nitrate obtained in (2) above, Hydrazine monohydrate 4.0m
50.0 mL of an aqueous solution obtained by diluting L with pure water was simultaneously added dropwise over 60 minutes, and then stirred for 60 minutes to precipitate metallic silver and metallic palladium around the palladium pre-coated barium titanate particles. Was. Thereafter, the particles are washed and dried, and barium titanate fine powder coated with 20.0 g of silver (30% by weight) and palladium (20% by weight) (average particle size: 0.3 μm, specific surface area: 4) .3m ² / g)
I got

Example 5 Ag / Pd (35% by weight / 1
5% by weight) Coating of barium titanate fine particles (50% by weight) (simultaneous addition coating) In Example 4, a mixed solution of the palladium complex and the silver complex of (2) was prepared by the following method (2b). Barium titanate fine powder coated with 20.0 g of silver (35% by weight) and palladium (15% by weight) (average particle size: 0.3 μm, specific surface area:
4.3 m ² / g).

(2b) Preparation of mixed solution of palladium complex and silver complex 16.6 g of a palladium nitrate solution (containing 3.0 g as Pd) was diluted to 30.0 mL with pure water, and 12.0 mL of aqueous ammonia was added thereto. Was added, and the mixture was stirred. When the liquid temperature reached about room temperature, the mixture was filtered to remove impurities. 11.0 g of silver nitrate (including 7.0 g as Ag) and 10.0 mL of aqueous ammonia were added to the filtrate, and the mixture was stirred and dissolved.
A mixed solution of an ammine complex of palladium nitrate (tetraamminepalladium nitrate) and an ammine complex of silver nitrate (silver diammine nitrate) was obtained.

Example 6 Ag / Pd (40% by weight / 1
0% by weight) Coating of barium titanate fine particles (50% by weight) (simultaneous addition coating) In Example 4, the mixed solution of the palladium complex and the silver complex of (2) was prepared by the following method (2c). The same operation was performed except that the operation was performed (however, the amount of hydrazine monohydrate used in (3) was 3.0 mL), 20.0
g of barium titanate fine powder coated with silver (40% by weight) and palladium (10% by weight) (average particle size: 0.3
μm, specific surface area: 4.3 m ² / g).

(2c) Preparation of mixed solution of palladium complex and silver complex 11.1 g of palladium nitrate solution (containing 2.0 g as Pd) was diluted to 20.0 mL with pure water, and 8.0 mL of aqueous ammonia was added thereto. Was added, and the mixture was stirred. When the liquid temperature reached about room temperature, the mixture was filtered to remove impurities. In the filtrate,
12.6 g of silver nitrate (containing 8.0 g as Ag) and 9.2 mL of aqueous ammonia were added and dissolved by stirring, and mixed with an ammine complex of palladium nitrate (tetraamminepalladium nitrate) and an ammine complex of silver nitrate (silver diammine nitrate). A solution was obtained.

Example 7 Production of Conductive Paste Pd / Ag-coated barium titanate particles 2 obtained in Example 1
0 g, 25 g of palladium particles having an average particle diameter of 0.5 μm (pure palladium particles), 0.8 g of ethyl cellulose, 3.8 g of dibutyl phthalate, and butyl carbitol 4
After mixing 2.5 g, the mixture was sufficiently kneaded using a three-roll kneader to obtain a conductive paste for electrode production.

Reference Example 1 Production of Conductive Paste 45 g of palladium particles (pure palladium particles) having an average particle size of 0.5 μm, 0.8 g of ethylcellulose, 3.8 g of dibutyl phthalate, and 42.5 g of butyl carbitol
g, and then sufficiently kneaded using a three-roll kneader to obtain a conductive paste for electrode production.

Example 8 Production of Multilayer Capacitor The conductive paste obtained in Example 7 and a barium titanate substrate (green sheet) were fired at 0 ° C.
A multilayer capacitor having 35 layers (interelectrode interval after firing: 16 μm) was manufactured. The conductive paste obtained in Reference Example 1 (using only palladium powder as the conductive powder)
Similarly, a barium titanate substrate (green sheet) was simultaneously baked to perform 35 layers (electrode spacing after firing: 1).
6 μm). When the electrical characteristics of the obtained multilayer capacitor were measured, the multilayer capacitor manufactured using the conductive paste of Example 7 was substantially different from the multilayer capacitor manufactured using the conductive paste of Reference Example 1. Did not.

[0051]

According to the present invention, the conductive particle composition of the noble metal-coated particles and the noble metal particles provides the same electrical characteristics as a conductive material using only noble metal particles. Further, the method for producing noble metal-coated particles provided by the present invention, even if the noble metal coating layer is a thin film, high uniformity of the noble metal layer, to produce conductive particles that give the same electrical properties as the noble metal particles. enable.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09C 3/00 C09C 3/00 H01B 1/00 H01B 1/00 C J H01G 4/12 361 H01G 4/12 361 364 364 4/30 301 4/30 301Z F-term (reference) 4J037 AA04 CA03 DD05 DD20 EE03 EE08 EE22 EE28 EE43 4K018 AA02 BA01 BA20 BB04 BC24 BC32 BD04 KA33 KA39 5E001 AB03 AH01 AH09 AJ01 504 DA43 DA46 DA51 DA53 DA60 DD03

Claims (23)

[Claims] 1. A conductive particle composition comprising noble metal particles and inorganic fine particles coated on a surface of a noble metal, and having noble metal-coated particles having an average particle size smaller than the average particle size of the noble metal particles. 2. The conductive particle composition according to claim 1, wherein the weight ratio of the noble metal particles to the noble metal-coated particles is in the range of 9: 1 to 1: 9. 3. The conductive particle composition according to claim 2, wherein the ratio between the noble metal particles and the noble metal-coated particles is in the range of 9: 1 to 4: 6 by weight. 4. The precious metal-coated particles have an average particle size of 0.01 to 0.01.
The conductive particle composition according to any one of claims 1 to 3, which is in a range of 0.8 µm. 5. The conductive particle composition according to claim 1, wherein a difference between the average particle size of the noble metal particles and the average particle size of the noble metal-coated particles is 0.05 μm or more. 6. The conductive particle composition according to claim 5, wherein the difference between the average particle size of the noble metal particles and the average particle size of the noble metal-coated particles is 0.1 μm or more. 7. The precious metal particles are palladium, platinum, gold,
The conductive particle composition according to any one of claims 1 to 6, wherein the conductive particle composition is formed from one or more noble metals selected from the group consisting of silver and silver. 8. The conductive particle composition according to claim 1, wherein the inorganic particles are metal oxide particles. 9. The noble metal layer covering the inorganic particles,
The conductive particle composition according to any one of claims 1 to 8, wherein the conductive particle composition is formed from one or more noble metals selected from the group consisting of palladium, platinum, gold, and silver. 10. The conductive particle composition according to claim 1, wherein the element composition of the noble metal coating the inorganic particles and the element composition of the noble metal particles have a common component. object. 11. An inorganic particle having an average particle size of 0.05 to 0.05.
0.5 μm, and the average particle size of the noble metal-coated particles is 0.8
The conductive particle composition according to any one of claims 1 to 10, wherein the composition is not more than μm. 12. A conductive paste comprising the conductive particle composition according to any one of claims 1 to 11. 13. An electronic component comprising an electrode layer formed from the conductive paste according to claim 12. 14. A multilayer ceramic capacitor formed from an electrode layer formed from the conductive paste according to claim 12, and a ceramic sheet made of an inorganic material having the same composition as the inorganic particles contained in the conductive paste. 15. An unfired ceramic sheet to which the conductive paste according to claim 12 is applied, at 900 to 1300 ° C.
A multilayer ceramic capacitor comprising an electrode layer obtained by firing at a temperature in the range described above and a fired ceramic sheet. 16. The noble metal-coated particles are particles obtained by dispersing inorganic particles in a reducing agent solution, and obtained by adding a noble metal salt solution to a dispersion under stirring. The conductive particle composition according to any one of the above. 17. The conductive particle composition according to claim 16, wherein the inorganic particles are precious metal pre-coated inorganic particles. 18. The noble metal-coated particles obtained by simultaneously adding a noble metal salt solution and a reducing agent to an inorganic particle dispersion under stirring.
12. The conductive particle composition according to any one of Items 11 to 11. 19. The conductive particle composition according to claim 18, wherein the inorganic particles are precious metal pre-coated inorganic particles. 20. A method for producing noble metal-coated particles, wherein inorganic particles are dispersed in a reducing agent solution, and a noble metal salt solution is added to the dispersion under stirring. 21. The method according to claim 20, wherein the inorganic particles are precious metal pre-coated inorganic particles. 22. A method for producing noble metal-coated particles, comprising simultaneously adding a noble metal salt solution and a reducing agent to an inorganic particle dispersion under stirring. 23. The method according to claim 22, wherein the inorganic particles are precious metal pre-coated inorganic particles.