JP2006196278A - Composite particle dispersion and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite particle dispersion compatibly establishing expression of conductivity without hindering contact and sintering of metal particles, and adhesion of composite particles to a base material, and also to provide a manufacturing method of the composite particle dispersion. <P>SOLUTION: In this composite particle dispersion, when a hydrocarbon compound having a hydrocarbon unsaturated cyclic structure, a carbonyl group and a hydroxide group in each molecule is called a compound A, each of the composite particles has a structure where the metal particle obtained by reducing metal ions corresponding to the metal particle by the compound A is covered with a surface protection layer having the compound A as a constituent. A gallic acid is preferable for the compound A. It is preferable that it does not contain a substance having capability for reducing the metal ions or capability for being coordinated or adsorbed to the metal after the reduction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite particle dispersion that can be used as a conductive material having conductivity, and a method for producing the composite particle dispersion.

  Various materials having excellent conductivity have been developed. Specifically, solar panel wiring, electrodes for flat panel displays, wiring for circuit boards and IC cards, through holes or circuits themselves, electromagnetic wave shielding for cathode ray tubes, infrared shielding for building materials and automobiles, electronic devices and mobile phones Examples thereof include an electrostatic antistatic agent, a frosted glass heat wire, and a coating for imparting conductivity to a resin. As disclosed in Patent Documents 1 to 5, a conductive material suitably used for these materials and a conductive material therefor Various protective coatings have been developed.

  Conventionally, for example, metal vacuum deposition, chemical vapor deposition, ion sputtering and the like have been performed as a method for producing a conductive coating. However, since these methods require work in a vacuum system or a closed system, the operation is complicated, and because the apparatus is large, space is required, investment is expensive, and mass productivity is poor. There was a problem.

  In addition, there is a method of forming a conductive film by plating, but in this case, it is necessary to treat a large amount of waste liquid, resulting in a large material loss, an extra cost, and a large burden on the environment.

  Furthermore, when forming the patterning of the wiring, a photolithography method is widely used. In this case, an extra step of masking a necessary portion of the conductive film formed on the substrate is necessary. Since a large amount of the photosensitive resin used, the removed metal coating, and the waste liquid in which they are dissolved are discharged, the processing cost is high in this respect as well, and the environmental load is large.

  In contrast to these methods, the method of drawing a coating liquid made of a liquid material that forms a conductive film on a substrate can be produced with simple equipment without the need for a special environment, and therefore occupies a large space. It is not necessary and requires less investment. In addition, since there is almost no material loss or waste liquid, it is advantageous in terms of cost and the environmental load can be reduced.

Conventionally, a metal paste obtained by bringing silver or other metal particles into a resin component or an organic solvent, or a so-called conductive ink is often applied to the coating liquid by a dispenser or screen printing. Recently, a method of drawing a colloidal metal dispersion having a low viscosity by an ink jet method to form a wiring pattern has also been attempted.
JP 2001-167647 A (publication date June 22, 2001) JP 2003-187640 A (publication date July 4, 2003) JP 2004-143325 A (publication date May 20, 2004) Japanese Patent No. 3162405 (publication date April 25, 2001) Japanese Patent No. 3425645 (publication date: July 14, 2003)

  In the method of forming such a conductive film, both the conductivity of the formed film and the adhesion to the base material are directly linked to the reliability, so that compatibility is very important.

  In these metal pastes and conductive inks, if the protective layer or binder resin on the surface of the metal particles has a strong adsorptive power / adhesive force, the metal particles and the substrate are firmly fixed, while the contact and firing between the metal particles are performed. It inhibits stagnation and causes a decrease in the conductivity of the coating.

  On the other hand, when designing with the use of a protective layer or a binder resin having a weak adsorbing force / adhesive strength, giving priority to the conductivity of the film, the adhesion of the film to the substrate becomes insufficient, making it difficult to achieve both.

  The present invention has been made in view of the above problems, and its purpose is to develop conductivity without inhibiting the contact and sintering of the metal particles, and to bring the metal particles and the substrate into close contact with each other. It is to realize a composite particle dispersion and a method for producing the composite particle dispersion that can satisfy both of these requirements.

  In order to solve the above problems, a composite particle dispersion according to the present invention is a composite particle dispersion in which composite particles having metal particles are dispersed in a dispersion, wherein a hydrocarbon unsaturated cyclic structure and a carbonyl group are present in the molecule. And the hydrocarbon compound having a hydroxyl group is referred to as Compound A, the metal particles obtained by reducing the metal ions corresponding to the metal particles with the compound A have the compound A as a component. It has a structure covered with a surface protective layer.

  With the above configuration, the composite particles have a structure in which the metal particles obtained by reducing metal ions corresponding to the metal particles with the compound A are covered with a surface protective layer having the compound A as a component. Have.

  The reduction is performed in the liquid phase, for example.

  The metal is, for example, one or more metals selected from the group consisting of gold, silver, copper, platinum, palladium, rhodium, ruthenium, iridium and osmium.

  Therefore, there is an effect that it is possible to achieve both the development of conductivity without inhibiting the contact and sintering of the metal particles and the close contact between the metal particles and the substrate.

  Moreover, the composite particle dispersion according to the present invention does not belong to the above compound A and has the ability to reduce the metal ion, or the ability to coordinate or adsorb to the metal after the reduction, in addition to the above configuration. It is characterized by not containing a substance having

  Due to the above configuration, the compound A has a different structure and does not contain a substance having the ability to reduce the metal ion or the ability to coordinate or adsorb to the metal after the reduction. Examples of such substances include glycine and glycolic acid. Therefore, in addition to the effect by said structure, there exists an effect that film electroconductivity and base-material adhesiveness can be improved further.

  The composite particle dispersion according to the present invention is characterized in that, in addition to the above configuration, the compound A is gallic acid.

  With the above configuration, the compound A is gallic acid. Therefore, in addition to the effect by said structure, there exists an effect that film electroconductivity and base-material adhesiveness can be improved further.

  Further, the method for producing a composite particle dispersion according to the present invention is a method for producing a composite particle dispersion in which composite particles having metal particles are dispersed in a dispersion. When a hydrocarbon compound having an unsaturated cyclic structure and a carbonyl group and a hydroxyl group is referred to as Compound A, the metal ion is reduced by the Compound A, and the metal particles obtained by the reduction are used as a component having the Compound A as a component. It is characterized by covering with a protective layer.

  According to the above configuration, the metal ion corresponding to the metal particles is reduced with the compound A, and the metal particles obtained by the reduction are covered with a surface protective layer having the compound A as a component, thereby providing a stable dispersion. make. Therefore, the composite particles having a structure in which the metal particles obtained by reducing metal ions corresponding to the metal particles with the compound A are covered with a surface protective layer having the compound A as a component are manufactured. can do. Therefore, there is an effect that it is possible to achieve both the development of conductivity without inhibiting the contact and sintering of the metal particles and the close contact between the metal particles and the substrate.

  As described above, when the composite particle dispersion according to the present invention refers to a hydrocarbon compound having a hydrocarbon unsaturated cyclic structure, a carbonyl group, and a hydroxyl group in the molecule as the compound A, the composite particle becomes the metal particle. The metal particles obtained by reducing the corresponding metal ions with the compound A have a structure covered with a surface protective layer having the compound A as a component.

  In the method for producing a composite particle dispersion according to the present invention, when a hydrocarbon compound having a hydrocarbon unsaturated cyclic structure, a carbonyl group and a hydroxyl group in the molecule is referred to as Compound A, the metal ion is reduced with Compound A above. In addition, the metal particles obtained by the reduction are covered with a surface protective layer having the compound A as a component.

  Thereby, there exists an effect that it can be made to make electroconductivity expressed without inhibiting the contact and sintering of a metal particle, and to make a metal particle and a base material closely_contact | adhere.

  In the present embodiment, the metal ions are reduced with a reducing agent to become metal atoms (metal particles), and the plurality of metal atoms are used by the amount of the reducing agent that is not used for the reduction reaction (dispersant). By being covered (coordinated or adsorbed) as a surface protective layer, colloidal particulate composite particles are obtained.

  For example, when reducing metal ions generated by dissolving a metal salt to obtain an aqueous dispersion of metal particles, an unreacted reducing agent is attached to the surface of the metal particles after reduction to form a surface protective layer, Thereby, an aqueous dispersion (composite particle dispersion) of the composite particles in the form of colloidal particles is obtained. When this aqueous dispersion is dried by vacuum drying or the like, colloidal particulate composite particles can be obtained.

  Moreover, the electroconductive film which is a baked film can be formed by forming a film by apply | coating this aqueous dispersion to a base material, and baking the film.

  This surface protective layer can suppress the metal particles from coming into contact with each other in a dispersion medium (water or the like) and agglomerating, so that they can be stably dispersed without being settled for a long time. That is, the dispersion stability (storage stability) in the aqueous dispersion can be imparted to the composite particles.

  Moreover, at the time of baking, this surface protective layer becomes an adhesive layer, thereby bonding the base material and the composite particles. However, the electrical conductivity inhibition caused by the contact and sintering of the metal particles is slight. Therefore, it is possible to improve the adhesion of the fired coating formed using the obtained composite particle dispersion such as an aqueous dispersion to the base material and not to impair the conductivity of the fired coating.

  Only a substance having such characteristics can be used as a reducing agent or a dispersing agent that coordinates or adsorbs to the metal after reduction. That is, when there is a reducing agent or dispersant having such characteristics, reduction without such characteristics under the same conditions that cause the reduction reaction of the metal ions and the coordination or adsorption of the dispersant. An agent or a dispersant can be prevented from being contained in the composite particle dispersion. For this purpose, such a reducing agent or dispersant may be prevented from being contained in the liquid phase of the metal salt solution when the composite particle dispersion is produced.

  The metal component of the composite particle of the present invention is made of, for example, one or more metals selected from the group consisting of gold, silver, copper, platinum, palladium, rhodium, ruthenium, iridium and osmium. Among the above metals, silver, copper, platinum, and palladium are preferable.

  The metal salt is not particularly limited as long as it can be dissolved in an appropriate solvent. For example, silver such as silver nitrate, silver sulfate, silver chloride, silver oxide, silver acetate, silver nitrite, silver chlorate, and silver sulfide. Salts: Gold salts such as chloroauric acid, potassium gold chloride, sodium gold chloride; platinum salts such as chloroplatinic acid, platinum chloride, platinum oxide, potassium chloroplatinate; palladium nitrate, palladium acetate, palladium chloride, palladium oxide, sulfuric acid Palladium salts such as palladium and other white metal salts can be mentioned. These may be used alone or in combination of two or more.

  In the present invention, as a substance (reducing agent or dispersant) for reducing these metal ions and forming a surface protective layer when making fine particles, an unsaturated cyclic structure of hydrocarbon and C═O group ( A hydrocarbon compound having a carbonyl group and a hydroxyl group (referred to as compound A) is used. As this hydrocarbon compound, gallic acid, 2. Hydroxy-1,4-naphthoquinone, 2,3-dihydroxy-1,4-naphthoquinone, 1,4-dihydroxynaphthalene-2-carboxylic acid, 3-alkyl-2-hydroxy-1,4-naphthoquinone, 2,2- Examples thereof include, but are not limited to, bis (3-hydroxy-1,4-naphthoquinone), 5-hydroxyisophthalic acid, salicylic acid, tannic acid, catechins, and the like. Among these, gallic acid is preferable in terms of film conductivity and substrate adhesion.

  The reducing agent or dispersant not belonging to the present invention is other than the reducing agent or dispersant belonging to the present invention. Examples include glycine and glycolic acid.

  In the present invention, the amount of the organic component in the composite particle is preferably 0.5 to 30% by weight. The organic component in the composite particles is mainly a component of the protective layer. When the additive mentioned later is also used, the additive is also included. When the amount of the organic component in the metal colloid particles is less than 1% by weight, the storage stability of the resulting metal colloid solution tends to deteriorate. When the amount exceeds 30% by weight, the obtained metal colloid solution is used. There exists a tendency for the electrical conductivity of a conductive film to worsen. More preferably, it is 1.0 to 20% by weight.

  The solvent used for the synthesis and dispersion medium of the composite particles of the present invention is not particularly limited as long as it is compatible with the hydrocarbon compound, but it is preferable to use water, a water-soluble solvent, or both. By using water or a water-soluble solvent as the solvent, the solvent odor is not strong at the time of drying or baking the conductive ink produced using the obtained metal colloidal liquid, and there is little adverse effect on the environment.

  The conductive paste or conductive ink produced using the composite particles of the present invention preferably has a solid content concentration of the composite particles as a main component (hereinafter also simply referred to as solid content) of 3 to 70% by weight. Here, the solid content is a solid content that remains when a volatile component such as a solvent other than the fine particles is dried using silica gel or the like at 30 ° C. or less. Usually, the solid content is the surface of the metal particles and the fine particles. The protective layer is the main component.

  If the solid content is less than 3% by weight, the metal content is too small, so when forming a conductive film using the resulting metal colloid liquid, the thickness is insufficient or a continuous film is formed. I cannot do it. When the concentration of the solid content exceeds 70% by weight, it becomes difficult to handle, for example, the viscosity increases or the metal easily precipitates. The concentration of the solid content is more preferably 5 to 60% by weight.

  Furthermore, the average particle size of the composite particles of the present invention is preferably 1 to 400 nm. Even if the particle diameter of the metal colloidal particles is less than 1 nm, a good conductive ink can be obtained, but in general, the production of such fine particles is expensive and impractical. If it exceeds 400 nm, the dispersion stability of the metal colloid particles tends to change over time. The average particle diameter of the metal colloid particles is more preferably 5 to 80 nm.

  Examples of a method for producing a solution containing metal colloidal particles using the metal salt and the hydrocarbon compound (compound A) defined in the present invention include the metal salt and the hydrocarbon compound (compound A) (present A reducing agent or a dispersing agent belonging to the invention may be dissolved in a solvent to prepare a solution, and the solution may be mixed while stirring.

  In the solution containing the metal colloidal particles obtained as described above, the reducing agent residue and impurity ions are present in addition to the metal colloidal particles, and the dispersion stability of the composite particles and the conductivity of the coating film are present. It is desirable to remove it.

  As the method for removing the impurities, for example, the liquid containing the obtained metal colloid particles is allowed to stand for a certain period, and the resulting supernatant is removed, and then pure water is added and stirred again, and the liquid is further allowed to stand for a certain period. The method of repeating the process of removing the resulting supernatant liquid several times, the method of performing centrifugation instead of the above-mentioned standing, the filtration with an ultrafiltration membrane or a reverse osmosis membrane, the method of desalting with an ion exchange device, etc. Can be mentioned.

  In addition, the conductive paste or conductive ink using the composite particles of the present invention is a viscosity modifier, thixotropic agent, surface tension modifier, film-forming aid, etc. in order to improve processing characteristics such as coating and drawing. The additive may be contained. When these conductive additives are formed, these additives fill the space between the metal particles or cover the surface of the metal particles together with the surface protective layer.

  The viscosity modifier is not particularly limited, but is emulsion such as polyester emulsion resin, acrylic emulsion resin, polyurethane emulsion resin, blocked isocyanate, polyester resin, polyacrylate resin, polyacrylamide resin, polyether. Resin, melamine resin, cellulose resin, acrylate resin, polyvinyl alcohol resin, aqueous polyaniline resin, and the like. These may be used alone or in combination of two or more.

  The addition amount of the viscosity modifier is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the composite particles. When the addition amount of the viscosity modifier exceeds 10 parts by weight with respect to 100 parts by weight of the composite particles, the conductivity may be deteriorated. If it is less than 0.1 part by weight, the effect of adding a viscosity modifier is not observed. More preferably, it is 1 to 6 parts by weight.

  Examples of the thixotropic agent include clay minerals such as clay, bentonite, and hectorite, emulsions such as polyester emulsion resins, acrylic emulsion resins, polyurethane emulsion resins, and blocked isocyanates. These may be used alone or in combination of two or more.

  The addition amount of the thixotropic agent is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the composite particles. If the amount of the thixotropic agent added exceeds 10 parts by weight with respect to 100 parts by weight of the composite particles, the conductivity may deteriorate. If it is less than 0.1 part by weight, the effect of adding a thixotropic agent is not observed. More preferably, it is 1 to 6 parts by weight.

  The surface tension adjusting agent is not particularly limited as long as it has various surface activity capabilities.

  The addition amount of the surface tension adjusting agent is preferably 0.01 to 0.5 parts by weight with respect to 100 parts by weight of the solvent. When the addition amount of the surface tension adjusting agent exceeds 0.5 parts by weight with respect to 100 parts by weight of the solvent, conductivity may be deteriorated. If it is less than 0.01 part by weight, the effect of adding the surface tension adjusting agent is not observed. More preferably, it is 0.03 to 0.1 parts by weight.

  The film-forming aid is not particularly limited, but emulsions such as polyester emulsion resins, acrylic emulsion resins, polyurethane emulsion resins, blocked isocyanates, polyester resins, polyacrylate resins, polyacrylamide resins, Examples thereof include ether resins, melamine resins, cellulose resins, acrylate resins, polyvinyl alcohol resins, and aqueous polyaniline resins. These may be used alone or in combination of two or more.

  The amount of the film-forming aid added is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the composite particles. If the amount of the film-forming aid added exceeds 10 parts by weight with respect to 100 parts by weight of the composite particles, the conductivity may deteriorate. If it is less than 0.1 part by weight, the effect of adding a film-forming aid is not observed. More preferably, it is 1 to 6 parts by weight.

  In the present invention, the base material on which the film is formed is not particularly limited. For example, a substrate made of an alumina sintered body, a phenol resin, a glass epoxy resin, glass or the like; a building material made of glass, resin, ceramic, or the like; An electronic device having a surface formed by, for example, can be given. Examples of the shape include a plate shape and a film shape.

  The conductive coating using the composite particles of the present invention expresses good adhesion to the above-mentioned base material. Especially, like a base material in which the surface of glass or the like is treated with ITO (indium tin oxide). Adhesion can be expressed even on a substrate that does not easily exhibit adhesion.

  The method for applying the conductive paste or conductive ink using the present invention on the substrate is not particularly limited, and examples thereof include dipping, screen printing, spray method, bar coating method, spin coating method, and brush method. be able to.

  In the present invention, it is possible to achieve both electrical conductivity without interfering with contact and sintering of metal particles and adhesion between composite particles and a substrate. In particular, it is possible to achieve both adhesion and conductivity on an ITO base material that is difficult to adhere.

  As a result, it has excellent adhesion to various substrates, especially adhesion to ITO substrates that are difficult to exhibit adhesion, and at the same time contains silver fine particles that enable designing of conductive paste and conductive ink that achieve both high conductivity. It becomes possible to develop composite particles. This technology can be widely applied as a material used in fields such as electronics, communication, and medical equipment.

  The composite particle of the present invention is composed of one or more metals selected from the group consisting of gold, silver, copper, platinum, palladium, rhodium, ruthenium, iridium and osmium, and has a hydrocarbon unsaturated cyclic structure in the molecule. These metal ions can be reduced in the liquid phase by a hydrocarbon compound having a C═O group and a hydroxyl group, and a particle surface protective layer can be formed to form fine particles.

  The composite particle of the present invention may have a structure in which the hydrocarbon having an unsaturated cyclic structure of hydrocarbon, C═O group and hydroxyl group in the molecule is gallic acid.

  The composite particles of the present invention were subjected to thermogravimetric analysis in the above-described configuration, with the solid content dried at 30 ° C. or lower being heated to 500 ° C. at a temperature increase rate of 10 ° C./min in a nitrogen atmosphere. The weight loss at the time may be 10% by weight or less. This is obtained by drying the dispersion at a low temperature (30 ° C. or lower) under reduced pressure or atmospheric pressure. In this way, the solid content from which moisture has been removed to such an extent that the weight reduction is 10% by weight or less reduces the amount of components that impede conductivity and exist between metal particles when formed into a film. become. Therefore, the rate at which the composite particles are brought into contact with each other and fired is increased, and good conductivity can be exhibited.

  The conductive material of the present invention may be configured using the composite particles having the above configuration.

〔Example〕
(A) 1.97 g of silver nitrate was dissolved in 100 mL of ion exchange water to prepare an aqueous silver nitrate solution. Next, while adding 0.8 g of gallic acid to 100 mL of ion exchange water and stirring, the silver nitrate aqueous solution prepared previously and 10 mL of 1N sodium hydroxide aqueous solution for pH adjustment were added and stirred for 1 hour, thereby colloiding silver. A solution was obtained. The obtained silver colloid solution was filtered using an ultrafiltration membrane (Advantech Toyo) with a molecular weight cut off of 50,000 to remove impurity ions. Filtration was performed 20 times with 100 mL of ion-exchanged water through a total of 2000 cc of ion-exchanged water. The results are shown in A of Table 1.

  (B) 1.97 g of silver nitrate was dissolved in 100 mL of ion exchange water to prepare an aqueous silver nitrate solution. Next, while adding 0.8 g of tannic acid to 100 mL of ion-exchanged water and stirring, the silver nitrate aqueous solution prepared previously and 10 mL of 1N sodium hydroxide aqueous solution for pH adjustment were added, and the mixture was stirred for 1 hour. A solution was obtained. The obtained silver colloid solution was filtered using an ultrafiltration membrane (Advantech Toyo) having a molecular weight cut off of 50,000 to remove impurity ions. Filtration was performed 20 times with 100 mL of ion-exchanged water through a total of 2000 cc of ion-exchanged water. The results are shown in Table 1B.

  (C) 1.97 g of silver nitrate was dissolved in 100 mL of ion-exchanged water to prepare an aqueous silver nitrate solution. Next, while adding 0.8 g of tannic acid and 0.35 g of glycine to 100 mL of ion-exchanged water and stirring, the previously prepared silver nitrate aqueous solution and 10 mL of 1N aqueous sodium hydroxide solution for pH adjustment are added and stirred for 1 hour. Thus, a silver colloid solution was obtained. The obtained silver colloid solution was filtered using an ultrafiltration membrane (Advantech Toyo) having a molecular weight cut off of 50,000 to remove impurity ions. Filtration was performed 20 times with 100 mL of ion-exchanged water through a total of 2000 cc of ion-exchanged water. The results are shown in C of Table 1.

  (D) 1.97 g of silver nitrate was dissolved in 100 mL of ion exchange water to prepare an aqueous silver nitrate solution. Next, while adding 0.8 g of tannic acid and 5.2 g of glycolic acid to 100 mL of ion-exchanged water and stirring, the previously prepared silver nitrate aqueous solution and 10 mL of 1N aqueous sodium hydroxide solution for pH adjustment were added and stirred for 1 hour. As a result, a colloidal silver solution was obtained. The obtained silver colloid solution was filtered using an ultrafiltration membrane (Advantech Toyo) having a molecular weight cut off of 50,000 to remove impurity ions. Filtration was performed 20 times with 100 mL of ion-exchanged water through a total of 2000 cc of ion-exchanged water. The results are shown in D of Table 1.

〔Evaluation methods〕
A coating heat treatment was performed. That is, first, it was applied to a substrate. The coating width is 5 mm. Then, the process to dry and sinter was performed.

  The film thickness was measured with a three-dimensional surface shape measuring device (Nihon Beco Co., Ltd./WYKO) NT1100.

The electrical resistance was measured with a double bridge 2769-10 (manufactured by Yokogawa M & C Co.) which is a DC precision measuring instrument. The volume resistivity was converted from the distance between the measurement terminals and the film thickness. The conversion formula is as follows. That is,
(Volume resistivity) = (resistance value) × (film width) × (film thickness) / (distance between terminals)
It is.

  Moreover, the peeling test was performed based on the method described in JIS K5600-5-6. In Table 1, “Category” indicates the peeling level described in this method.

  In Table 1 showing the results, the criterion is “◯: little peeling, no problem ×: many peeling, problematic”.

  In A and B, only gallic acid or tannic acid was used as the reducing agent or dispersant. On the other hand, in C and D, reducing agents or dispersants such as glycine and glycolic acid were used in addition to tannic acid, such as tannic acid and glycine, or tannic acid and glycolic acid. As a result, it can be seen that A and B are superior to C and D in terms of adhesion to the substrate.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  It is excellent in conductivity and adhesion, and can be applied to uses such as coating for imparting conductivity to a circuit board.

Claims (4)

In a composite particle dispersion in which composite particles having metal particles are dispersed in a dispersion,
When a hydrocarbon compound having a hydrocarbon unsaturated cyclic structure, a carbonyl group and a hydroxyl group in the molecule is referred to as compound A,
The composite particles are
A composite characterized in that the metal particles obtained by reducing metal ions corresponding to the metal particles with the compound A have a structure covered with a surface protective layer having the compound A as a component. Particle dispersion.   2. The substance according to claim 1, which does not belong to the compound A and does not contain a substance having the ability to reduce the metal ion, or the ability to coordinate or adsorb to the metal after reduction. Composite particle dispersion.   The composite particle dispersion according to claim 1 or 2, wherein the compound A is gallic acid. In the method for producing a composite particle dispersion for producing a composite particle dispersion in which composite particles having metal particles are dispersed in a dispersion,
When a hydrocarbon compound having a hydrocarbon unsaturated cyclic structure, a carbonyl group and a hydroxyl group in the molecule is referred to as compound A,
A method for producing a composite particle dispersion, wherein metal ions are reduced with the compound A, and metal particles obtained by the reduction are covered with a surface protective layer having the compound A as a component.