KR102201639B1 - Aqueous dispersion of metal nanoparticles - Google Patents

Abstract

The present invention uses a composite of a metal nanoparticle (X) and an organic compound (Y) and an aqueous dispersion of metal nanoparticles containing a nonionic surfactant (Z). Further, more preferably, the aqueous dispersion of metal nanoparticles according to claim 1, wherein the organic compound (Y) is an organic compound (Y1) having an anionic functional group is used. In addition, the organic compound (Y1) having an anionic functional group is a (meth)acrylic acid-based monomer having at least one anionic functional group selected from the group consisting of a carboxy group, a phosphoric acid group, a phosphorous acid group, a sulfonic acid group, a sulfinic acid group, and a sulfonic acid group. It provides an aqueous dispersion of metal nanoparticles which is a polymer (Y2) of the monomer mixture (I) containing The aqueous dispersion of metal nanoparticles can reduce adhesion to a storage container, a storage liquid tank used in a process, a jig, an apparatus, and the like.

Description

Aqueous dispersion of metal nanoparticles

The present invention relates to an aqueous dispersion of metal nanoparticles in which adhesion to a liquid storage container, a storage liquid tank used in a process, a jig, a device, or the like is suppressed.

Metal nanoparticles are nanoscale metal particles in which an active surface is stabilized with a dispersant, and the development of electrical conductivity using a fusion phenomenon at low temperature, antibacterial using a large specific surface area, and application to catalyst applications are attracting attention. . In particular, industrially, by providing metal nanoparticles in a state in which they are dispersed in a liquid, it is a simple method such as printing, coating, adsorption, etc., on various target substrates, forming a metal film in a low-temperature process, or a catalyst. It is a great advantage to be able to impart metal.

Metal nanoparticles used to form a metal film on various substrates by printing, coating, adsorption, etc., or to impart a catalytic metal, are required to maintain a stable and uniform dispersion state in water for a long period of time. In addition, it is required for any use of conductive, antibacterial, and catalyst that the surface of the metal nanoparticles is active even after adhesion to the substrate. For this reason, as a dispersant adsorbed on the surface of metal nanoparticles, a polymer dispersant that is difficult to desorb and can impart high dispersion stability is used, and by reducing the amount used as much as possible, both dispersion stability and activity can be achieved. Yes (see, for example, Patent Document 1). In addition, metal nanoparticles using this polymeric dispersant can also be used as a catalyst for electroless plating (see, for example, Patent Document 2).

However, with regard to the technology of such an aqueous dispersion of metal nanoparticles that have been reported in the past, the function and stability of the dispersion alone have been disclosed, but the problem in the case of use in the process is not sufficiently disclosed, and storage In the liquid-reserved layer of containers and devices, jigs used in coating/printing/plating processes, etc., metal nanoparticles adhere to portions that are not desired to be adhered to the liquid-contacting portion of the device or the like. Unnecessary adhesion to the wetted part is wasteful of expensive materials due to the consumption of metal nanoparticles due to adhesion, the concentration of metal nanoparticles in the liquid decreases, or the metal nanoparticle aggregate adhered and agglomerated in the wetted part is re-peeled. As a result, it is mixed in the liquid, etc., thereby inducing a decrease in the performance of the dispersion. For this reason, in order to prevent performance degradation, it is necessary to frequently wash the liquid layer, jig, device, etc. of the device, the cleaning cycle is shortened and process efficiency deteriorates, or the device or jig contaminated with metal contaminates the substrate. It is a problem.

In addition, usually, in an aqueous dispersion of metal nanoparticles, by using a dispersing agent, the surface charge of the metal nanoparticles is adjusted to increase dispersibility in water. However, in the process, when the ionic compound from the substrate to be used is mixed into the dispersion, the electric double layer formed by the dispersant surrounding the metal nanoparticles becomes thin, reducing the repulsive force due to electric charges, and unnecessary parts. There was a case that the adhesion to the product increased more.

Japanese Patent No. 4697356 Japanese Patent No. 5648232

The problem to be solved by the present invention is to provide an aqueous dispersion of metal nanoparticles with reduced adhesion to a liquid-contacting portion such as a storage container, a storage liquid tank used in a process, a jig, or an apparatus.

As a result of intensive research in order to solve the above problems, the present inventors and the like found that the above problems can be solved by using an aqueous dispersion of metal nanoparticles added with a nonionic surfactant, and the present invention was completed.

That is, the present invention provides an aqueous dispersion of metal nanoparticles comprising a complex of metal nanoparticles (X) and organic compound (Y) and a nonionic surfactant (Z).

In order to maintain a high surface activity, the aqueous dispersion of metal nanoparticles of the present invention contains the metal nanoparticles even when the amount of the dispersant is reduced to the minimum amount in which aggregation does not occur, and even when an ionic compound is mixed in the dispersion. Since adhesion to storage containers, low red tide used in the process, jigs, devices, etc. can be suppressed, unnecessary consumption of expensive metal nanoparticles, concentration reduction due to adhesion, and adhesion-aggregated metal nanoparticles Deterioration in the performance of the dispersion liquid due to re-peelability of the particles and mixing into the liquid can also be suppressed. Further, for this reason, contamination of storage containers, storage liquid tanks, jigs, devices, etc. can be reduced, and since these cleaning cycles can be extended, process cost can also be reduced. In addition, since adhesion to storage containers, storage liquid tanks, jigs, devices, etc. is suppressed, transfer of the adhered metal nanoparticles onto the substrate can be suppressed, and the yield of products is also improved.

1 is a sample plate on the left side of a photograph of Example 1, and a sample plate on the right side of the photograph is of Comparative Example 1. FIG.
Fig. 2 is a sample plate on the left side of the photograph of Example 2, and a sample plate on the right side of the photograph is of Comparative Example 2.

The aqueous dispersion of metal nanoparticles of the present invention contains a complex of metal nanoparticles (X) and organic compound (Y), and a nonionic surfactant (Z).

Examples of the metal constituting the metal nanoparticles (X) include silver, copper, and palladium alone, or alloys thereof. Further, examples of the metal nanoparticles (X) include silver core copper shell particles, copper shell silver core particles, particles in which silver is partially substituted with palladium, and particles in which copper is partially substituted with palladium. These metals or alloys may be used alone or in combination of two or more. These metals or alloys may be appropriately selected according to the purpose, but when used for the purpose of wiring or forming a conductive layer, silver and copper are preferable, and from the viewpoint of catalytic function, silver, copper, and palladium are preferable. Do. In addition, from the viewpoint of cost, silver, copper, alloys thereof, some substituents, or mixtures thereof are preferable.

The shape of the metal nanoparticles (X) is not particularly limited as long as it does not impair dispersion stability in an aqueous medium, and nanoparticles of various shapes can be appropriately selected according to the purpose. Specifically, a spherical shape, a polyhedron shape, a plate shape, a rod shape, and particles of a shape in which these are combined are mentioned. As the metal nanoparticles (X), one having a single shape or one having a plurality of shapes can be mixed and used. In addition, among these shapes, spherical or polyhedral particles are preferable from the viewpoint of dispersion stability.

The metal constituting the metal nanoparticles (X) is adsorbed by an organic compound (Y) as a dispersant on the surface of the metal nanoparticles (X) in order to stably maintain a uniform dispersion state for a long time in an aqueous dispersion medium. It is used as a composite of a metal nanoparticle (X) and an organic compound (Y). The organic compound (Y) may be appropriately selected and used depending on the purpose, but the compound (Y1) having an anionic functional group is preferable from the viewpoint of storage stability.

The compound (Y1) having an anionic functional group is a compound having at least one anionic functional group in the molecule. Further, as long as the dispersion stability is not impaired, a compound having a cationic functional group in addition to an anionic functional group in the molecule may be used. The compound (Y1) having an anionic functional group may be used singly or in combination of two or more.

As the compound (Y1) having an anionic functional group, a carboxyl group, a phosphoric acid group, a phosphorous acid group, a sulfonic acid group, from the viewpoint of achieving both long-term stability in an aqueous dispersion medium and maintaining the activity of the surface of the metal nanoparticles after being imparted on the substrate. A polymer (Y2) of a monomer mixture (I) containing a (meth)acrylic acid-based monomer having at least one anionic functional group selected from the group consisting of a sulfinic acid group and a sulfenic acid group is particularly preferred.

The polymer (Y2) may be a homopolymer or a copolymer. Moreover, in the case of a copolymer, random polymerization may be sufficient and block polymerization may be sufficient.

Since the polymer (Y2) has at least one anionic functional group selected from the group consisting of a carboxyl group, a phosphoric acid group, a phosphorous acid group, a sulfonic acid group, a sulfonic acid group, and a sulfonic acid group, metal nanoparticles ( As it has the function of adsorbing to X) and imparts a negative charge to the surface of the metal nanoparticles (X), it is possible to prevent agglomeration of colloidal particles due to charge repulsion between particles, and the polymer (Y2) and metal in water The composite of nanoparticles (X) can be stably dispersed.

The polymer (Y2) preferably has three or more anionic functional groups in one molecule, since adsorption to the metal nanoparticles (X) and dispersion stability in an aqueous dispersion can be further improved.

In addition, the weight average molecular weight of the polymer (Y2) is preferably in the range of 3,000 to 20,000, and the range of 4,000 to 8,000, since adsorption to metal nanoparticles (X) and dispersion stability in an aqueous dispersion can be further improved. More preferable.

In addition, when a polyoxyalkylene chain such as a polyethylene glycol chain is introduced into the polymer (Y2), a repulsive force due to electric charges can be expressed, and a colloidal protective effect due to a steric repulsion effect can be used, and dispersion stability is further improved. desirable.

For example, the polymer (Y2) having a polyethylene glycol chain by copolymerizing the monomer mixture (I) with a (meth)acrylic acid monomer having a polyethylene glycol chain and a (meth)acrylic acid monomer having the anionic group, etc. Can be obtained easily.

In particular, the polymer (Y2) polymerized using a (meth)acrylic acid monomer having a polyethylene glycol chain having an average number of units of ethylene glycol of 20 or more has a high ability to stabilize nanoparticles of precious metals, particularly silver and copper, and is suitable. It is preferable to be a protective agent. Synthesis of such a polymer having an anionic functional group and a polyethylene glycol chain can be easily performed by, for example, a method described in Japanese Patent No. 4697356, Japanese Unexamined Patent Publication No. 2010-209421, or the like.

The weight average molecular weight of the (meth)acrylic acid monomer having a polyethylene glycol chain having an average number of units of ethylene glycol of 20 or more is preferably in the range of 1,000 to 2,000. When the weight average molecular weight is within this range, the water dispersibility of the composite with the metal nanoparticle (X) will be more favorable.

As a more specific synthesis method of the polymer (Y2) having a phosphoric acid group and a polyethylene glycol chain, for example, commercially available 2-methacryloyloxyphosphate (e.g., ``Light Ester P-1M") and a commercially available methacrylic acid ester monomer having a polyethylene glycol chain (for example, "Brenma PME-1000" manufactured by Nichiyu Corporation) is a polymerization initiator (for example, oil-soluble azo polymerization). The method of copolymerization using an initiator "V-59") is mentioned.

At this time, if the ratio of the (meth)acrylic acid ester monomer having a phosphoric acid group is less than 30% by mass in the monomer mixture (I), a (meth)acrylic acid system having a polyethylene glycol chain not involved in the protection of the metal nanoparticles (X) The generation of by-products such as a homopolymer of a monomer is suppressed, and dispersion stability by the resulting polymer (Y2) is improved.

The monomer mixture (I) may contain a third polymerizable monomer other than the (meth)acrylic acid monomer having an anionic group and the (meth)acrylic acid monomer having a polyethylene glycol chain. At this time, when the third polymerizable monomer is a hydrophobic monomer, the amount used is preferably 20 parts by mass or less with respect to 100 parts by mass of the (meth)acrylic acid-based monomer having a polyethylene glycol chain, since good water dispersibility can be maintained. The mass part or less is more preferable. Moreover, when the 3rd polymerizable monomer is not a hydrophobic monomer, it is not limited to this range.

As described above, the weight average molecular weight of the polymer (Y2) is preferably in the range of 3,000 to 20,000, but when a (meth)acrylic acid-based monomer having a polyethylene glycol chain is used in combination, the polymer (Y2) obtained by the polymerization reaction, It has a molecular weight distribution. The smaller the weight average molecular weight, the less it contains a structure derived from a (meth)acrylic acid monomer having a polyethylene glycol chain, and thus does not contribute to dispersion stability when the complex with metal nanoparticles (X) is dispersed in an aqueous medium. , From this viewpoint, the weight average molecular weight of the polymer (Y2) is more preferably 4,000 or more. Conversely, when the weight average molecular weight increases, the weight average molecular weight of the polymer (Y2) is 8,000 or less from the viewpoint of easy coarsening of the complex with the metal nanoparticles (X) and precipitation in the catalyst solution. More preferable.

In order to adjust the weight average molecular weight of the polymer (Y2) within the above-described range, a chain transfer agent described in publicly known literature, for example, Japanese Unexamined Patent Publication No. 2010-209421 may be used, and the polymerization condition without using a chain transfer agent You may control by.

As the composite to be used in the aqueous dispersion of metal nanoparticles of the present invention, a composite with metal nanoparticles (X) such as silver, copper, palladium, and the like, prepared by using the above-described polymer (Y2) as a colloidal protective agent, can be used.

In addition, as a method for preparing the composite used in the aqueous dispersion of metal nanoparticles of the present invention, for example, after dissolving or dispersing the polymer (Y2) in an aqueous medium, there may be used silver nitrate, copper acetate, palladium nitrate, or the like. A metal compound is added, and a complexing agent is added as necessary to make a homogeneous dispersion, and then the metal compound is reduced by mixing a reducing agent, and the reduced metal is nano-sized particles (fine particles having a size of nanometer order). ) And obtained as an aqueous dispersion of the metal nanoparticles (X) complexed with the polymer (Y2). Moreover, when using a complexing agent, you may mix simultaneously with a reducing agent.

The aqueous dispersion of metal nanoparticles of the present invention has an average particle diameter of the metal nanoparticles (X) in the range of 0.5 to 100 nm from the viewpoint of fusion at low temperature, which is advantageous for wiring and forming a conductive layer, and catalytic activity. It is preferable that the composite of the present metal nanoparticles (X) and the organic compound (Y) is dispersed in an aqueous dispersion medium.

In addition, the average particle diameter of the metal nanoparticles (X) can be estimated by a transmission electron micrograph, and that the average value of the 100 is in the range of 0.5 to 100 nm, for example, Japanese Patent No. 4697356 described above. It can be obtained easily by the method described in Japanese Unexamined Patent Publication No. 2010-209421 or the like. The metal nanoparticles (X) obtained in this way are protected by the polymer (Y2) and exist independently one by one, and can be stably dispersed in an aqueous dispersion medium.

The average particle diameter of the metal nanoparticles (X) is the type of the metal compound, the molecular weight of the organic compound (Y) used as a colloidal protective agent, the chemical structure and the amount used, the type and amount of the complexing agent or reducing agent, and the temperature at the time of the reduction reaction. Easily controllable by means of the like, and for these, it is sufficient to refer to the examples described in the above patent documents and the like.

In addition, the content ratio of the organic compound (Y) in the composite of the organic compound (Y) and the metal nanoparticles (X) is preferably in the range of 1 to 30% by mass, and more preferably in the range of 2 to 20% by mass. Do. That is, in the composite, most of the mass is occupied by the metal nanoparticles (X), which is suitable for use in wiring, forming a conductor layer, and various catalyst applications.

In particular, the composite in which the metal nanoparticles (X) are protected with the polymer (X-2) is in the range of about 0.01 to 70% by mass in an aqueous medium, that is, a mixed solvent with water or an organic solvent compatible with water. It is possible to disperse at, and under conditions without mixing of impurities, at room temperature (∼25°C), it can be stored stably without aggregation for several months or so.

In addition to the composite of the polymer (X) and the metal nanoparticle (Y), the aqueous dispersion of metal nanoparticles of the present invention contains a nonionic surfactant (Z) as an essential component.

As the nonionic surfactant (Z), general surfactants can be used. For example, glycerin fatty acid ester, sorbitan fatty acid ester, sucrose fatty acid ester, fatty alcohol ethoxylate, polyoxyalkylene alkylphenyl ether, polyoxyethylene Arylphenyl ether and the like.

By adding the nonionic surfactant (Z) to the aqueous dispersion of metal nanoparticles of the present invention, adhesion of metal nanoparticles to storage containers, storage tanks, jigs, devices, etc. to which this liquid contacts can be suppressed.

The amount of the nonionic surfactant (Z) to be used is preferably 1 to 100 parts by mass, and more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the composite. In addition, the nonionic surfactant (Z) may be added in advance to the aqueous dispersion of the complex of the metal nanoparticle (X) and the organic compound (Y), or may be added before using the aqueous dispersion of the complex. .

The aqueous dispersion of metal nanoparticles of the present invention can be used as it is, as an ink or coating solution for wiring and forming a conductive layer, and as a catalyst solution for electroless plating, but a metal compound used as an excess complexing agent, reducing agent, or raw material The counter ions contained in are subjected to a purification process in which various purification methods such as ultrafiltration, precipitation, centrifugation, distillation under reduced pressure, and drying under reduced pressure are used alone or in combination of two or more, but concentration (non-volatile content) after the purification process Alternatively, the aqueous medium may be changed and a newly prepared dispersion may be used. When using for the purpose of mounting purposes, such as forming an electronic circuit, it is preferable to use an aqueous medium that has undergone the above purification process. Moreover, it is preferable that the said purification process is performed after preparing the aqueous dispersion of the said complex, and the said nonionic surfactant (Z) is added after that.

When the aqueous dispersion of metal nanoparticles of the present invention is used as an ink or coating solution for wiring or forming a conductive layer, the concentration of the complex (non-volatile content concentration) in the aqueous dispersion is in the range of 0.5 to 40% by mass. It is preferable, and the range of 1-30 mass% is more preferable.

When performing wiring and conductive layer formation using the aqueous dispersion of metal nanoparticles of the present invention as an ink or coating solution, as a method of imparting the composite of the metal nanoparticles (X) and the organic compound (Y) onto a substrate, particularly There is no limitation, and it is sufficient to select appropriately known and common various printing/coating methods according to the shape, size, and degree of ferroelectric oil of the substrate to be used. Specifically, gravure method, offset method, gravure offset method, convex plate method, convex plate inversion method, flexo method, pad method, screen method, micro-contact method, reverse method, air doctor coater method, blade coater method, air knife coater method , A squeeze coater method, an impregnation coater method, a transfer roll coater method, a kiss coater method, a cast coater method, a spray coater method, an inkjet method, a die method, a spin coater method, a bar coater method, and the like.

When performing wiring or conductive layer formation by printing or coating the composite on a substrate and applying the composite on the substrate, direct, wiring and conductive layer formation can be performed by drying and firing the printed or coated substrate. It may be performed, and electroless or electrolytic plating treatment may be performed.

In addition, the aqueous dispersion of metal nanoparticles of the present invention can also be used as a catalyst liquid for electroless plating used in a normal plating process by immersion treatment. When the aqueous dispersion of metal nanoparticles of the present invention is used as a catalyst for electroless plating, the amount of adsorption to the object to be plated is ensured, and the adhesion of the plated film to the object to be plated can be improved. The concentration (non-volatile content) of the composite in the aqueous dispersion of nanoparticles is preferably in the range of 0.05 to 5 g/L, and in view of economic efficiency, it is more preferably in the range of 0.1 to 2 g/L.

By the above-described method, a metal film can be formed on the surface of the object to be plated by attaching the composite in the aqueous dispersion of metal nanoparticles of the present invention to the surface thereof by performing a known electroless plating treatment.

Examples of the aqueous medium used in the aqueous dispersion of metal nanoparticles of the present invention include water alone or a mixed solvent of water and a compatible organic solvent. As the organic solvent, as long as the dispersion stability of the composite is not impaired and the object to be plated is not subjected to unnecessary damage, it may be selected without particular limitation. Specific examples of the organic solvent include methanol, ethanol, isopropanol, and acetone. These organic solvents may be used alone or in combination of two or more.

In the aqueous medium, the mixing ratio of the organic solvent is preferably 50% by mass or less from the viewpoint of dispersion stability of the composite, and more preferably 30% by mass or less from the viewpoint of convenience in the plating process.

The substrate to which the composite of the metal nanoparticles (X) and the organic compound (Y) is provided by using the aqueous dispersion of metal nanoparticles of the present invention is not particularly limited, and as a material, for example, glass fiber reinforced epoxy , Epoxy insulation material, polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, liquid crystal polymer (LCP), cycloolefin polymer (COP), polyetheretherketone (PEEK), polyphenylene sulfide (PPS) plastic, glass, ceramics, metal oxides, metals, paper, synthetic or natural fibers, etc. made by one or a combination of a plurality of materials, the shape of which is a plate, film, pouch (布狀), fibrous, tube, or the like may be used.

The aqueous dispersion of metal nanoparticles of the present invention can form wirings, conductive layers, etc. by applying a composite of metal nanoparticles and an organic compound on a substrate by a simple method such as printing, coating, immersion, etc. As a catalyst solution for electroless plating, it can be suitably used.

In addition, the aqueous dispersion of metal nanoparticles of the present invention, when a composite of the metal nanoparticles (X) and the organic compound (Y) is applied to a substrate, suppresses performance degradation and appearance defects due to corrosion on the surface of the metal substrate. I can. Therefore, particularly excellent effects are exhibited when a metal substrate or a substrate having a metal such as a wiring or a conductive layer is used on the substrate.

(Example)

Hereinafter, the present invention will be described in detail by examples, but the present invention is not limited to these examples.

[Sample Analysis]

The sample was analyzed using the following apparatus. The transmission electron microscope (TEM) observation was performed with "JEM-1400" manufactured by Nippon Electric Corporation (Preparation Example 1).

(Synthesis Example 1: Synthesis of polymer (Y2-1) having an anionic functional group)

To a four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser, 32 parts by mass of methyl ethyl ketone (hereinafter abbreviated as "MEK") and 32 parts by mass of ethanol were added, and the temperature was raised to 80°C while stirring under a nitrogen stream. Next, 20 parts by mass of phosphooxyethyl methacrylate ("Lightester P-1M" manufactured by Kyoei Chemical Co., Ltd.), methoxypolyethylene glycol methacrylate ("Brenma" manufactured by Nichiyu Corporation) PME-1000", molecular weight 1,000) 80 parts by mass, a mixture of 4.1 parts by mass of methyl 3-mercaptopropionate and 80 parts by mass of MEK, and a polymerization initiator (Wako Pure Chemical Co., Ltd. "V-65", 2,2'- A mixture of 0.5 parts by mass of azobis (2,4-dimethylvaleronitrile) and 5 parts by mass of MEK was added dropwise over 2 hours, respectively. After completion of the dropwise addition, 0.3 parts by mass of a polymerization initiator ("Perbutyl O" manufactured by Nichiyu Corporation) was added twice every 4 hours, and stirred at 80°C for 12 hours. Water was added to the obtained resin solution to emulsify the entire phase, desolvated under reduced pressure, and then water was added to adjust the concentration to obtain an aqueous solution of a polymer (Y2-1) having a nonvolatile content of 76.8% by mass. This polymer (Y2-1) has a methoxycarbonylethylthio group, a phosphoric acid group, and a polyethylene glycol chain, and its weight average molecular weight (in terms of polystyrene measured by gel permeation/chromatography) is 4,300, and the acid value is 97.5. mgKOH/g.

(Preparation Example 1: Preparation of an aqueous dispersion of silver nanoparticles)

463 g (4.41 mol) of an 85% by mass aqueous solution of N,N-diethylhydroxylamine, 30 g of an aqueous solution of the polymer (Y2-1) obtained in Synthesis Example 1 (23 g as (Y2-1)) and 1,250 g of water were mixed A reducing agent solution was prepared.

Further, 15 g of an aqueous solution of the polymer (Y2-1) obtained in Synthesis Example 1 (11.5 g as a polymer (Y2-1)) was dissolved in 333 g of water, and 500 g (2.94 mol) of silver nitrate was dissolved in 833 g of water, and a solution was added. , Stirred well. The reducing agent solution obtained above was added dropwise to this mixture at room temperature (25°C) over 2 hours. The obtained reaction mixture was filtered through a membrane filter (pore size 0.45 micrometer), and the filtrate was circulated in a hollow fiber type ultrafiltration module ("MOLSEP module FB-02 type" manufactured by Daisen Membrane Systems Co., Ltd., a molecular weight cutoff of 150,000), and discharged. Water in an amount corresponding to the amount of the filtrate was added and purified from time to time. After confirming that the conductivity of the filtrate had become 100 µS/cm or less, watering was stopped and concentrated. By recovering the concentrate, an aqueous dispersion of a composite containing silver nanoparticles having a nonvolatile content of 36.7% by mass was obtained. The average particle diameter of the composite by the dynamic light scattering method was 39 nm, and was estimated to be 10 to 40 nm from a transmission electron microscope (TEM) image.

Next, ion-exchanged water was added to the aqueous dispersion of the silver nanoparticle-containing composite having a non-volatile content of 36.7% by mass obtained above to prepare the content of the silver nanoparticle-containing composite in the aqueous dispersion to be 10% by mass, thereby obtaining an aqueous dispersion of silver nanoparticles. .

[Comparative method of silver adhesion amount]

Since the silver nanoparticles are colored, when adhered to the substrate, even a very small amount can be visually confirmed by the coloring of the substrate. For this reason, an aqueous dispersion of silver nanoparticles having a constant concentration was prepared, and the substrate was immersed in it for 5 minutes, and then visually observed to compare the degree of silver adsorption according to the degree of coloration.

(Example 1)

5.0 g of 1 mass% polyoxyethylene (20) sorbitan monolaurate aqueous solution and 5.0 g of 10 mass% silver nanoparticle aqueous dispersion obtained in Preparation Example 1 were added to a 1 L beaker, and diluted with 990 g of ion-exchanged water. When each substrate of polyethylene, polypropylene, polyvinyl chloride, and glass was immersed, the substrate was not colored, and the silver nanoparticles hardly adhered. It was confirmed that adsorption of silver nanoparticles to the substrate can be suppressed by addition of a surfactant.

(Example 2)

5.0 g of a 1 mass% polyoxyethylene (23) lauryl ether aqueous solution and 5.0 g of a 10 mass% aqueous dispersion of silver nanoparticles obtained in Preparation Example 1 were added to a 1 L beaker, and diluted with 490 g of ion-exchanged water. To this, as an ionic compound, 10 g of trisodium citrate dissolved in 490 g of ion-exchanged water was added. When each substrate of polyethylene, polypropylene, polyvinyl chloride, and glass was immersed, the substrate was not colored, and silver nanoparticles hardly adhered. It was confirmed that adsorption of silver nanoparticles to the substrate can be suppressed even under conditions in which the ionic compound is present in a large amount.

(Comparative Example 1)

To a 1 L beaker, 5.0 g of an aqueous dispersion of 10% by mass silver nanoparticles obtained in Preparation Example 1 was added, and diluted with 995 g of ion-exchanged water. When each substrate of polyethylene, polypropylene, polyvinyl chloride, and glass was immersed, coloration was observed on the substrate, and it was confirmed that silver nanoparticles adhered in large amounts more clearly than in Examples 1 and 2. Moreover, this coloring could not be removed even if it was washed with running water.

(Comparative Example 2)

5.0 g of an aqueous dispersion of 10% by mass silver nanoparticles obtained in Preparation Example 1 was added to a 1 L beaker, and it was diluted with 495 g of ion-exchanged water. To this was added 10 g of trisodium citrate dissolved in 490 g of ion-exchanged water. When each substrate of polyethylene, polypropylene, polyvinyl chloride, and glass was immersed, strong coloring was observed, and it was confirmed that more silver nanoparticles adhered than in Comparative Example 1. Moreover, this coloring could not be removed even if it was washed with running water.

From the results of Examples 1 to 2 and Comparative Examples 1 to 2 described above, the following was confirmed.

In the aqueous dispersion of silver nanoparticles (Examples 1 and 2) of the present invention to which a nonionic surfactant was added, the adsorption (adhesion) of silver nanoparticles could be significantly suppressed regardless of the presence or absence of ionic components (Fig. 1 left side Of the sample plate, and the sample plate on the left of Fig. 2).

On the other hand, if a sample plate made of polypropylene was immersed in the aqueous dispersion of silver nanoparticles of Comparative Example 1 without adding a nonionic surfactant, it was found that the silver nanoparticles irreversibly adhered to the plate surface in a short period of 5 minutes. (The sample plate on the right side of Fig. 1). In addition, in the aqueous dispersion of silver nanoparticles of Comparative Example 2 in which an ionic component was added without adding a nonionic surfactant, it was confirmed that more silver nanoparticles adhered at the same time (the sample plate on the right of FIG. 2).

Claims (7)

An aqueous dispersion of metal nanoparticles containing a composite consisting of metal nanoparticles (X) and organic compound (Y) and a nonionic surfactant (Z), wherein the organic compound (Y) is an organic compound having an anionic functional group ( Y1), and the organic compound (Y1) having an anionic functional group is a (meth)acryl having at least one anionic functional group selected from the group consisting of a carboxyl group, a phosphoric acid group, a phosphorous acid group, a sulfonic acid group, a sulfinic acid group and a sulfenic acid group. A polymer (Y2) of the monomer mixture (I) containing an acidic monomer, wherein the content of the organic compound (Y1) having an anionic functional group in the complex is 1 to 30% by mass. The method of claim 1,
An aqueous dispersion of metal nanoparticles containing a (meth)acrylic acid-based monomer having a polyethylene glycol chain having an average number of units of ethylene glycol of 20 or more in the monomer mixture (I). The method according to claim 1 or 2,
The aqueous dispersion of metal nanoparticles having a weight average molecular weight of the polymer (Y2) in the range of 3,000 to 20,000. The method according to claim 1 or 2,
An aqueous dispersion of metal nanoparticles in which the metal nanoparticles (X) are metal paper, silver, copper, or palladium. The method according to claim 1 or 2,
An aqueous dispersion of metal nanoparticles having an average particle diameter in the range of 0.5 to 100 nm determined from a transmission electron microscope photograph of the metal nanoparticles (X). delete delete

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