KR102283387B1 - Metal Nanoparticle Aqueous Dispersion - Google Patents

Abstract

The present invention provides a complex of metal nanoparticles (X) and an organic compound (Y) (excluding the complex in which the organic compound (Y) is polyvinylpyrrolidone) and polyvinylpyrrolidone (Z) An aqueous dispersion of metal nanoparticles is provided. In addition, the organic compound (Y) is a (meth) acrylic acid-based monomer 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 monomer mixture containing It provides an aqueous dispersion of metal nanoparticles that is a polymer of The aqueous dispersion of metal nanoparticles has excellent dispersion stability even when subjected to a thermal load such as melting after heating or freezing, which may occur during storage or transport, and has sufficient adsorption to the substrate; and It has surface activity.

Description

Metal Nanoparticle Aqueous Dispersion

The present invention has excellent dispersion stability even when a thermal load such as melting after heating or freezing, which may occur during storage or transportation, is applied, and has sufficient adsorption to a substrate, and surface activity It relates to an aqueous dispersion of metal nanoparticles.

BACKGROUND ART Metal nanoparticles are industrially used as catalysts, antibacterial agents, conductive materials, and the like. The main form is a paste, ink, or paint in which metal nanoparticles are dispersed and stabilized, and the metal nanoparticles can be imparted to any location on the target substrate by methods such as printing, application, and immersion treatment.

As a solvent for dispersing the metal nanoparticles, both an organic solvent and an aqueous solvent have been studied, and selection is possible depending on the purpose and process for providing the metal nanoparticles on the substrate, but from the viewpoint of reducing the load on the environment, an aqueous solvent It is preferable to use a solvent.

One of the basic properties required for such an aqueous dispersion of metal nanoparticles is long-term dispersion stability. In general, this can be increased by increasing the amount of the dispersant in the dispersion, but the excess dispersant tends to adversely affect the surface activity of the metal nanoparticles and the adsorption to the substrate, and the intrinsic function of the material (catalytic activity, antibacterial activity). activity, conductivity, etc.) may be damaged.

As a technique for achieving both dispersion stability and function, a method of using a polymer dispersing agent with high dispersion performance instead of increasing the amount of the dispersing agent is disclosed (for example, refer to Patent Document 1), the metal nanoparticles of the present invention It is disclosed that an aqueous dispersion liquid has adsorption property to a base material and surface activity which can be used as a catalyst for electroless plating (for example, refer patent document 2).

In the temperature range from room temperature to a refrigerated state, this method of using a high-performance dispersing agent in a minimum amount makes it possible to achieve both long-term dispersion stability and function. On the other hand, depending on the storage environment and transport conditions of the product, freezing or temperature rise of the aqueous dispersion of metal nanoparticles is assumed. In the conventional aqueous dispersion liquid of silver nanoparticles, irreversible aggregation by such a thermal load and the performance degradation accompanying it become a problem. Therefore, in order to maintain the quality of the metal nanoparticle dispersion, use conditions are limited, and temperature control is required during storage or transportation, and management cost is also a problem.

Japanese Patent Publication No. 4697356 Japanese Patent No. 5648232 Publication

The problem to be solved by the present invention is that it has excellent dispersion stability even when a thermal load such as temperature rise or melting after freezing, which may occur during storage or transportation, is applied, and sufficient adsorption to a substrate, and surface activity It is to provide an aqueous dispersion of metal nanoparticles having

The inventors of the present invention, as a result of earnest research to solve the above problems, found that the above problems could be solved by configuring the aqueous dispersion of metal nanoparticles with a specific composition, and completed the present invention.

That is, the present invention provides a complex of metal nanoparticles (X) and an organic compound (Y) (excluding the complex in which the organic compound (Y) is polyvinylpyrrolidone) and polyvinylpyrrolidone (Z). It is to provide an aqueous dispersion of metal nanoparticles characterized in that it contains.

The aqueous dispersion of metal nanoparticles of the present invention can improve dispersion stability without reducing the adsorption properties and activity of the metal nanoparticles to the substrate. For this reason, it is possible to prevent deterioration of properties (aggregation or deterioration of liquid appearance) even when a thermal load such as melting after heating or freezing is applied without impairing the usefulness of the industrial material in any way. As described above, since the aqueous dispersion of metal nanoparticles of the present invention has excellent dispersion stability with respect to a thermal load, it is possible to reduce the temperature control cost in transportation (land transportation, sea transportation, air transportation) and storage.

1 is an ultraviolet-visible absorption spectrum of an aqueous dispersion of silver nanoparticles before heating (Example 1) and after heating (Example 1 and Comparative Example 1).
2 is an ultraviolet visible absorption spectrum of an aqueous dispersion of silver nanoparticles before freezing (Example 1) and after a freeze-thaw cycle (Example 1 and Comparative Example 1).

The aqueous dispersion of metal nanoparticles of the present invention includes a composite of metal nanoparticles (X) and an organic compound (Y) (excluding the composite in which the organic compound (Y) is polyvinylpyrrolidone) and polyvinylpyrrolidone (Z) is contained.

As a metal which comprises the said metal nanoparticle (X), silver, copper, a single substance of palladium, or these alloys, etc. are mentioned, for example. Moreover, as said metal nanoparticle (X), the particle|grains which substituted silver core copper shell particle|grains, the particle|grains which substituted silver partly with palladium, the particle|grains which substituted copper part with palladium, etc. are mentioned. These metals or alloys may be used alone or in combination of two or more. These metals or alloys may be appropriately selected depending on the purpose, but when used for the purpose of forming wirings and conductive layers, silver and copper are preferable, and from the viewpoint of a catalytic function, silver, copper, and palladium are preferable. . Moreover, from a viewpoint of cost, silver, copper, these alloys, some substituents, or a mixture thereof are preferable.

The shape of the metal nanoparticles (X) is not particularly limited as long as the dispersion stability in the aqueous medium is not impaired, and nanoparticles of various shapes can be appropriately selected according to the purpose. Specifically, spherical, polyhedral, plate-like, rod-like, and particles of a shape combining these are exemplified. As said metal nanoparticle (X), the thing of a single shape, or the thing of several shapes can be mixed and used. Moreover, among these shapes, a spherical or polyhedral particle is preferable from a viewpoint of dispersion stability.

The metal constituting the metal nanoparticles (X) is an organic compound (Y) adsorbed on the surface of the metal nanoparticles (X) as a dispersing agent in order to maintain a stable and uniform dispersion state for a long period of time in an aqueous dispersion medium. It is used as a complex of the metal nanoparticles (X) and the organic compound (Y). Although the said organic compound (Y) may be used, selecting it suitably according to the objective, from a viewpoint of dispersion stability, the compound (Y1) which has an anionic functional group is preferable. In addition, the said organic compound (Y) is a thing other than polyvinylpyrrolidone (Z) mentioned later.

The compound (Y1) having an anionic functional group is a compound having one or more anionic functional groups in the molecule. Moreover, as long as dispersion stability is not impaired, you may use the compound which has a cationic functional group other than an anionic functional group in a molecule|numerator. The compound (Y1) which has the said anionic functional group may be used individually by 1 type, and may use 2 or more types together.

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 dispersion stability in an aqueous dispersion medium and maintenance of activity on the surface of the metal nanoparticles after being imparted on the substrate. Polymer (Y2) of the monomer mixture (I) containing a (meth)acrylic acid-based monomer having at least one anionic functional group selected from the group consisting of , sulfinic acid group and sulfenic acid group is particularly preferable.

A homopolymer may be sufficient as the said polymer (Y2), and a copolymer may be sufficient as it. Moreover, in the case of a copolymer, a random copolymer may be sufficient and a block copolymer 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 sulfinic acid group, and a sulfenic acid group, the metal nanoparticles (X) through the lone pair of the hetero atoms ) and at the same time imparting a negative charge to the surface of the metal nanoparticles (X), it is possible to prevent aggregation of the colloidal particles by charge repulsion between the particles, and the polymer (Y2) and metal nanoparticles in water The composite of particles (X) can be stably dispersed.

The polymer (Y2) preferably has three or more anionic functional groups in one molecule because 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 is preferably in the range of 4,000 to 8,000, because adsorption to the metal nanoparticles (X) and dispersion stability in the aqueous dispersion can be further improved. more preferably.

In addition, when a polyoxyalkylene chain such as a polyethylene glycol chain is introduced into the polymer (Y2), it is possible to utilize the colloidal protection effect due to the steric repulsion effect as well as the expression of repulsive force due to the electric charge, and the dispersion stability is further improved. desirable.

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

In particular, the polymer (Y2) polymerized using a (meth)acrylic acid-based 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 noble metals, particularly silver and copper, and desirable protection It is preferable to be zero. The synthesis|combination of the polymer which has such an anionic functional group and a polyethyleneglycol chain can be performed easily by the method described in Unexamined-Japanese-Patent No. 4697356, Unexamined-Japanese-Patent No. 2010-209421, etc., for example.

As a weight average molecular weight of the (meth)acrylic acid type monomer which has a polyethyleneglycol chain|strand in which the average unit number of said ethylene glycol is 20 or more, the range of 1,000-2,000 is preferable. When the weight average molecular weight is within this range, the water dispersibility of the composite with the metal nanoparticles (X) becomes more favorable.

As a more specific method for synthesizing the polymer (Y2) having a phosphoric acid group and a polyethylene glycol chain, for example, commercially available 2-methacryloyloxyphosphate (for example, “Light” manufactured by Kyoei Chemicals Co., Ltd.) ester P-1M") and a commercially available methacrylic acid ester monomer having a polyethylene glycol chain (for example, "Brenma PME-1000" manufactured by Nichi Oil Co., Ltd.) with a polymerization initiator (for example, oil-soluble azo polymerization) The method of copolymerizing using initiator "V-59") is mentioned.

At this time, when 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), (meth)acrylic acid having a polyethylene glycol chain that does not participate in the protection of the metal nanoparticles (X) By suppressing generation of by-products such as a homopolymer of a monomer, dispersion stability by the resulting polymer (Y2) is improved.

The monomer mixture (I) may contain a third polymerizable monomer other than a (meth)acrylic acid monomer having an anionic group and a (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, because good water dispersibility can be maintained, and 10 A mass part or less is more preferable. Moreover, when a 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 monomer having a polyethylene glycol chain is used in combination, the polymer (Y2) obtained by the polymerization reaction is , has a molecular weight distribution. The smaller the weight average molecular weight, the less it does not contain a structure derived from a (meth)acrylic acid monomer having a polyethylene glycol chain, so it does not contribute to dispersion stability in the case of dispersing the complex with the metal nanoparticles (X) in an aqueous medium. , from this viewpoint, the weight average molecular weight of the polymer (Y2) is more preferably 4,000 or more. Conversely, if the weight average molecular weight is large, coarsening of the complex with the metal nanoparticles (X) is likely to occur, and from the viewpoint of easily causing precipitation in the catalyst solution, the weight average molecular weight of the polymer (Y2) is 8,000 or less more preferably.

In order to adjust the weight average molecular weight of the polymer (Y2) within the above range, a chain transfer agent described in a known document, for example, Japanese Patent Application Laid-Open No. 2010-209421 may be used, and the polymerization conditions without using a chain transfer agent may be controlled by

As the composite used for the aqueous dispersion of metal nanoparticles of the present invention, a composite with metal nanoparticles (X) such as silver, copper, palladium, etc. 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, a metal such as silver nitrate, copper acetate, or palladium nitrate is added thereto. A compound is added, a complexing agent is added as necessary to obtain a uniform 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 on the nanometer order). and a method of obtaining as an aqueous dispersion of the metal nanoparticles (X) complexed with the above-mentioned polymer (Y2). Moreover, when using a complexing agent, you may mix simultaneously with a reducing agent.

The composite of the metal nanoparticles (X) and the organic compound (Y) used in the present invention is advantageous for wiring and conductive layer formation, in terms of fusion properties at low temperatures, and catalytic activity, the metal nanoparticles (X) It is preferable that the average particle diameter of is in the range of 0.5-100 nm.

In addition, the average particle diameter of the metal nanoparticles (X) can be estimated by a transmission electron microscope photograph, and the average value of 100 of them is in the range of 0.5 to 100 nm, for example, the above-mentioned Japanese Patent No. 4697356 It can obtain easily by the method described in Unexamined-Japanese-Patent No. 2010-209421, etc. The metal nanoparticles (X) obtained in this way are protected by the polymer (Y2), exist independently one by one, and can be obtained in a state of being 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) serving as the colloidal protective agent, the chemical structure and the amount used, the type and amount of the complexing agent or the reducing agent, the temperature at the time of the reduction reaction It can be easily controlled by etc., and for these, it is good to refer to the Example described in the above-mentioned patent document etc.

Moreover, as a content rate of the said organic compound (Y) in the composite_body|complex of the said organic compound (Y) and metal nanoparticle (X), the range of 1-30 mass % is preferable, and the range of 2-20 mass % is more preferable. do. That is, in the composite, the metal nanoparticles (X) occupy most of the mass, which is suitable for wiring, formation of a conductive layer, and various catalyst applications.

The composite in which the metal nanoparticles (X) are protected by the polymer (Y2) is dispersed in an aqueous medium, ie, water or a mixed solvent of water and an organic solvent compatible with water, in the range of about 0.01 to 70 mass %. It is possible, and by coexisting the polyvinylpyrrolidone (Z) in this dispersion, even if a thermal load such as melting is applied after heating or freezing, the metal nanoparticles (X) and the organic compound (Y ), can maintain excellent dispersion stability, high adsorption to the substrate, and surface activity.

Although the mechanism for the appearance of such an effect by the coexistence of polyvinylpyrrolidone (Z) is not certain, it can be estimated as follows from the correlation with the aggregation mechanism of metal nanoparticles (X). The aggregation of the metal nanoparticles (X) in the dispersion liquid by heating causes the organic compound (Y) to desorb from the surface of the metal nanoparticles (X) due to the temperature rise, and the equilibrium shifts in the direction of the dissociation from the surface of the metal nanoparticles (X) It is thought that this is because the movement becomes active and the collision frequency between the metal nanoparticles (X) with the active surface exposed increases. On the other hand, aggregation by freezing occurs when the metal nanoparticle dispersion freezes, when the water in the dispersion crystallizes into ice, and crystal growth occurs while excluding the metal nanoparticle complex, which is a contaminant in water, This is thought to be because the metal nanoparticle composite is extremely concentrated. Therefore, in order to suppress irreversible aggregation of particles due to heating or freezing, it is considered effective to coexist in the dispersion a compound having a property of adsorbing and protecting the metal nanoparticles (X) to the surface.

The driving force that the metal nanoparticle composite adsorbs to the substrate is mainly an electrostatic interaction between the charge on the surface of the substrate and the charge of the metal nanoparticle composite. For this reason, when an additive having a charge of the same sign as that of the metal nanoparticle composite is coexisted, it is considered that the additive and the metal nanoparticle composite compete for an adsorption point on the substrate, thereby inhibiting the adsorption of the metal nanoparticle composite to the substrate. can Conversely, when the metal nanoparticle composite and an additive having an inverse sign coexist, it is considered that the electrostatic repulsive force between the metal nanoparticle composites is shielded and aggregation of the metal nanoparticle composite is caused. Therefore, in order to maintain dispersion stability and high adsorption property to a substrate, it is considered preferable to use a nonionic compound as an additive as a compound having a property of adsorbing and protecting the metal nanoparticles (X).

In addition, since the compound having the property of adsorbing and protecting the metal nanoparticles (X) is strongly adsorbed to the metal nanoparticles (X), conductivity and catalytic activity are expressed after the substrate is provided, so the metal nanoparticles ( It is considered that exposing the active surface of X) becomes more difficult. Therefore, in order to maintain the surface activity, it can be considered that as a compound having a property of adsorbing and protecting the metal nanoparticles (X), it is preferable not to have strong adsorption properties to the metal nanoparticles (X).

As described above, as a compound having the property of adsorbing and protecting the metal nanoparticles (X), those that are not too weak and not too strong have adsorption properties to the metal nanoparticles (X), are water-soluble, and are nonionic. , it is considered preferable in order to maintain excellent dispersion stability, high adsorption to the substrate, and the surface activity of the metal nanoparticles (X). Polyvinylpyrrolidone (Z) meets this condition.

The aqueous dispersion of metal nanoparticles of the present invention contains polyvinylpyrrolidone (Z) as an essential component in addition to the complex of the metal nanoparticles (X) and the organic compound (Y), but a mixture of polyvinylpyrrolidone Although there is no restriction|limiting in particular as a method, The method of adding polyvinylpyrrolidone (Z) to the aqueous dispersion of the composite_body|complex of the said metal nanoparticle (X) and the said organic compound (Y) is simple and preferable.

Polyvinylpyrrolidone (Z) may be added to the aqueous dispersion of the complex of the organic compound (Y) and the metal nanoparticles (X) obtained by the above preparation method, or used as an excess complexing agent, reducing agent, or raw material. Counter ions, etc. contained in metal compounds are subjected to a purification process using various purification methods such as ultrafiltration, precipitation, centrifugal separation, vacuum distillation, and reduced pressure drying, alone or in combination of two or more. volatile matter) or an aqueous medium may be changed and added to a newly prepared dispersion as a dispersion. When using for the purpose of a mounting use, such as formation of an electronic circuit, it is preferable to use the method of adding to the aqueous medium which passed through the said refinement|purification process.

The weight average molecular weight (hereinafter, abbreviated as "Mw") of the polyvinylpyrrolidone (Z) used in the present invention has superior dispersion stability and high adsorption to the substrate even when thawed after heating or freezing. , from the viewpoint of providing an aqueous dispersion of metal nanoparticles maintaining surface activity at the same time, preferably in the range of 10,000 to 1,000,000, more preferably in the range of 30,000 to 500,000. In addition, the said weight average molecular weight is the value obtained by the measurement by the gel permeation chromatography (GPC) method.

Polyvinylpyrrolidone used for this invention may use what was synthesize|combined using a well-known and usual method, and may use a commercial item. As a commercial item, "Fit's Call K-30" (Mw: 40,000), "Fit's Call K-90" (Mw: 360,000), etc. made from Daiichi Kogyo Seiyaku Co., Ltd. are mentioned, for example.

The amount of polyvinylpyrrolidone (Z) added is, even when subjected to thawing after heating or freezing, from the viewpoint of simultaneously satisfying better dispersion stability, high adsorption to a substrate, and surface activity, the metal nanoparticles With respect to 100 parts by mass of the complex of (X) and the organic compound (Y), 0.1 to 20 parts by mass is preferable, more preferably 0.5 to 15 parts by mass, more preferably 1 to 10 parts by mass, , particularly preferably in the range of 2 to 8 parts by mass.

When the aqueous dispersion of metal nanoparticles of the present invention is used for forming wiring and conductive layers as inks and coating solutions, the concentration of the composite in the aqueous dispersion is preferably in the range of 0.5 to 40% by mass, and 1 to 30% by mass. The range of mass % is more preferable.

When the metal nanoparticle aqueous dispersion of the present invention is used as an ink or coating solution to form wiring and a conductive layer, the method for applying the composite of the metal nanoparticles (X) and the organic compound (Y) onto the substrate is particularly limited. There is no such thing, and various known and customary printing and coating methods may be appropriately selected according to the shape, size, grade of ferrous oil, etc. of the substrate to be used. Specifically, the gravure method, the offset method, the gravure offset method, the convex plate method, the convex plate inversion method, the flexo method, the screen method, the micro contact method, the reverse method, the air doctor coater method, the blade coater method, the air knife coater method, the squeeze coater method method, the impregnation coater method, the transfer roll coater method, the kiss coater method, the cast coater method, the spray coater method, the inkjet method, the die method, the spin coater method, the bar coater method, etc. are mentioned.

When the composite is printed or coated on a substrate and the composite is applied on the substrate to form a wiring and a conductive layer, the printed or coated substrate is dried and fired to directly, wiring, and conductive layer formation. You may perform, and you may perform electroless or electroplating process.

In addition, the aqueous dispersion of metal nanoparticles of the present invention can be used also 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 plating film to the object to be plated can be improved. The concentration of the composite in the aqueous particle dispersion is preferably in the range of 0.05 to 5 g/L, and more preferably in the range of 0.02 to 2 g/L in consideration of economy.

A metal film can be efficiently formed on the surface of the object to be plated on which the composite in the aqueous dispersion of metal nanoparticles of the present invention is adhered to the surface by the above-described method by performing a known electroless plating treatment. there is.

Examples of the aqueous medium used for the aqueous dispersion of metal nanoparticles of the present invention include water alone and a mixed solvent of water and an organic solvent compatible with water. The organic solvent may be selected without particular limitation as long as it does not impair the dispersion stability of the composite and does not cause unnecessary damage to the object to be plated. Specific examples of the organic solvent include methanol, ethanol, isopropanol, and acetone. These organic solvents may be used by 1 type, and may be used together 2 or more types.

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

The base material 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. For example, as a material, glass fiber reinforced epoxy , Epoxy-based insulating material, polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, liquid crystal polymer (LCP), cycloolefin polymer (COP), polyether ether ketone (PEEK), polyphenylene sulfide (PPS) resin, glass, ceramic, metal oxide, metal, paper, synthetic or natural fiber, etc., is formed by combining one type or a plurality of types, and its shape is plate-like, film-like, and foam-like. (布狀), fibrous, tubular, etc. may be sufficient.

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

(Example)

Hereinafter, the present invention will be described in detail by way of Examples.

[Analysis of the sample]

The analysis of the sample was performed using the following apparatus. Transmission electron microscope (TEM) observation was performed with "JEM-1400" manufactured by Nippon Electronics Co., Ltd. Ultraviolet visible absorption spectrum measurement was performed with "Nanodrop ND-1000" manufactured by Thermo Fisher Scientific.

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

To a four-neck 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 charged, and the temperature was raised to 80° C. while stirring under a nitrogen stream. Next, 20 parts by mass of phosphooxyethyl methacrylate (“Light Ester P-1M” manufactured by Kyoei Chemicals Co., Ltd.), methoxypolyethylene glycol methacrylate (“Brenma” manufactured by Nichi Chemicals Co., Ltd.) 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 Industries, 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 Nichi Oil Co., Ltd.) was added twice every 4 hours, followed by stirring at 80°C for 12 hours. After adding water to the obtained resin solution for phase inversion emulsification and desolving under reduced pressure, an aqueous solution of a polymer (Y2-1) having a nonvolatile content of 76.8% by mass was obtained by adding water to adjust the concentration. This polymer (Y2-1) has a methoxycarbonylethylthio group, a phosphoric acid group and a polyethylene glycol chain, and the weight average molecular weight (polystyrene conversion value measured by gel permeation chromatography) is 4,300, and the acid value is It was 97.5 mgKOH/g.

(Preparation Example 1: Preparation of silver nanoparticle aqueous dispersion)

463 g (4.41 mol) of an 85 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 the polymer (Y2-1)) and 1,250 g of water are mixed Thus, a reducing agent solution was prepared.

Next, 15 g of an aqueous solution of the polymer (Y2-1) obtained in Synthesis Example 1 (11.5 g as the 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. added and stirred well. The reducing agent solution obtained above was dripped at room temperature (25 degreeC) over 2 hours to this mixture. The obtained reaction mixture was filtered with a membrane filter (pore diameter of 0.45 micrometers), and the filtrate was circulated in a hollow fiber type ultrafiltration module (“MOLSEP module FB-02 type” manufactured by Daisen Membrane Systems Co., Ltd., molecular weight cutoff weight of 150,000), and flowed out Water in an amount corresponding to the amount of the filtrate to be removed was added from time to time for purification. After confirming that the conductivity of the filtrate had become 100 µS/cm or less, water was stopped and concentrated. By recovering the concentrate, an aqueous dispersion of the silver nanoparticle-containing composite 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 it was estimated to be 10 to 40 nm from a transmission electron microscope (TEM) image.

(Example 1)

To 272.5 parts by mass of the aqueous dispersion of silver nanoparticles obtained in Preparation Example 1 (100 parts by mass as a composite containing silver nanoparticles), polyvinylpyrrolidone (“Fitscall K-30” manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Mw: 40,000) of 20 mass % aqueous solution (4 mass parts as polyvinylpyrrolidone) is added, stirred uniformly, and ion-exchanged water is added so that the concentration of the silver nano-particle-containing complex becomes 10 mass %, silver nanoparticles An aqueous dispersion (1) was obtained.

[Appearance evaluation of aqueous dispersion of silver nanoparticles]

As an evaluation index of the dispersion stability of the aqueous dispersion of silver nanoparticles (1) obtained above, the appearance was visually observed and the presence or absence of suspension was confirmed. In addition, about the appearance evaluation after the heating test or freeze-thaw test mentioned later, the change of color was also confirmed together.

[Evaluation of adsorption to substrate and measurement of plating coverage]

As an index for judging the activity of the silver nanoparticles, an electroless copper plating treatment was performed using the metal nanoparticles provided on the substrate as a catalyst.

A slide glass is prepared as a base material, the slide glass is immersed for 1 minute in a 2 mass % aqueous solution of polyethyleneimine ("Eformin SP-200" manufactured by Nippon Shokubai Co., Ltd.) and taken out, followed by running water for 1 minute. After washing, it was dehydrated by air blowing to obtain a surface-treated slide glass.

Next, as an electroless copper plating bath, an aqueous solution containing 0.04 mol/L of copper sulfate hydrate, 0.04 mol/L of formaldehyde, and 0.08 mol/L of disodium ethylenediaminetetraacetic acid was adjusted to pH 12.3 with sodium hydroxide. One solution was prepared, and the one heated to 55 degreeC was prepared.

The surface-treated slide glass was immersed in a 200-fold dilution of the silver nanoparticle aqueous dispersion (1) obtained above at 25° C. for 10 minutes to adsorb the silver nanoparticles to the surface of the slide glass. Since the silver nanoparticles were colored at this time, the glass slide was colored yellow as the amount of silver nanoparticles adsorbed to the surface of the slide glass increased. The degree of this coloring was visually observed, and the adsorption|suction property to a base material was evaluated according to the following criteria, using the thing without the additive mentioned later (Comparative Example 1) as a standard.

○: Equivalent to that without additives

△: color is lighter than that without additives

×: almost not colored, close to colorless and transparent

Next, the slide glass on which the silver nanoparticles are adsorbed is taken out and washed with water for 1 minute, then immersed in the electroless copper plating bath prepared above for 30 minutes while stirring with air, then taken out and washed with water for 1 minute, no electricity copper plating was performed.

By image processing of the photograph of the electroless-copper-plated slide glass, black-and-white binarization was performed on the basis of brightness, and the plating coverage was computed from the area of the part currently plated. From the obtained plating coverage, the activity of the silver nanoparticle composite was evaluated. Here, when the catalytic activity is sufficiently high, plating is deposited on the entire surface of the substrate, and when the activity is lowered, the deposition area of the plating is reduced. Therefore, it was judged that the activity of the silver nanoparticle composite|composite was favorable that the whole surface of the slide glass was coated with plating (plating coverage of 100%).

[Warming test]

The silver nanoparticle aqueous dispersion (1) obtained above was put into a 50 mL screw tube, and it sealed. Next, this was heated for 14 days in a 50 degreeC thermostat. After warming, the appearance was evaluated in the same manner as described above. In addition, with respect to the aqueous dispersion of silver nanoparticles (1) before and after heating, the concentration of the silver nanoparticle complex was diluted to 50 ppm and the ultraviolet and visible absorption spectrum was measured (see Fig. 1). Plasmons correlated with the surface state of silver nanoparticles Absorption spectra were observed. When silver nanoparticles aggregate, the surface state and spectral shape change, but since the spectral shape does not change before and after heating, it was confirmed that there is no change in the dispersion state of the silver nanoparticles in the silver nanoparticle aqueous dispersion (1).

Next, what diluted the silver nanoparticle aqueous dispersion (1) after heating 200 times was prepared, and the plating coverage was measured by the method similar to the above.

[Freeze-Thaw Test]

The silver nanoparticle aqueous dispersion (1) obtained above was put into a 50 mL screw tube, and it sealed. Next, this was brought into contact with dry ice chips for 5 minutes to freeze, and then thawed at room temperature. This freezing and thawing operation was made into 1 cycle, and 3 cycles were repeated. After 3 cycles of freezing and thawing, appearance was evaluated in the same manner as described above. Moreover, the ultraviolet-visible absorption spectrum was measured about the silver nanoparticle aqueous dispersion (1) before freezing and after 3 cycles of freezing and thawing (refer FIG. 2). From the measurement result of this ultraviolet visible absorption spectrum, it was confirmed that there was no change in the dispersion state of silver nanoparticles in the silver nanoparticle aqueous dispersion (1) even if freezing and thawing were repeated.

Next, a 200-fold dilution of the silver nanoparticle aqueous dispersion (1) after 3 cycles of freezing and thawing was prepared, and the plating coverage was measured in the same manner as above.

[Comprehensive evaluation]

From the results of the heating test and the freeze-thaw test performed above, dispersion stability and adsorption to a substrate were evaluated, and a comprehensive evaluation was performed in accordance with the following criteria.

○: In the heating test and the freeze-thaw test, there was no problem in dispersion stability and adsorption to the substrate.

×: In the heating test and the freeze-thaw test, there was a problem in either dispersion stability or adsorption to the substrate.

(Example 2)

It operates similarly to Example 1 except having changed the 20 mass % aqueous solution of polyvinylpyrrolidone used in Example 1 from 20 mass parts to 10 mass parts (2 mass parts as polyvinylpyrrolidone), and silver nanoparticle An aqueous dispersion (2) was obtained. Moreover, about the obtained silver nanoparticle aqueous dispersion (2), the measurement and evaluation were performed similarly to Example 1.

(Example 3)

It operates similarly to Example 1 except having changed the 20 mass % aqueous solution of polyvinylpyrrolidone used in Example 1 from 20 mass parts to 50 mass parts (10 mass parts as polyvinylpyrrolidone), and silver nanoparticle An aqueous dispersion (3) was obtained. In addition, about the obtained silver nanoparticle aqueous dispersion (3), it measured and evaluated similarly to Example 1.

(Example 4)

Polyvinylpyrrolidone used in Example 1 was changed to polyvinylpyrrolidone (Daichi Kogyo Seiyaku Co., Ltd. "Fit's Call K-90", Mw: 360,000), and the concentration of the aqueous solution was changed to 10 Except having set it as mass %, it operated similarly to Example 1, and obtained the silver nanoparticle aqueous dispersion (4). In addition, about the obtained silver nanoparticle aqueous dispersion (4), it measured and evaluated similarly to Example 1.

(Comparative Example 1)

Ion-exchanged water was added to the aqueous dispersion of silver nanoparticles obtained in Preparation Example 1 to prepare a concentration of the silver nanoparticle-containing composite in the aqueous dispersion of 10% by mass, thereby obtaining an aqueous dispersion of silver nanoparticles (R1). In addition, about the obtained silver nanoparticle aqueous dispersion (R1), it measured and evaluated similarly to Example 1. In addition, this silver nanoparticle aqueous dispersion (R1) was diluted so that the concentration of the silver nanoparticle composite was 50 ppm, and the ultraviolet and visible absorption spectrum before heating was measured. There was no difference from that of Example 1 in which polyvinylpyrrolidone was added. . Moreover, when the ultraviolet visible absorption spectrum after heating was measured, there was no change in the spectral shape (refer FIG. 1).

On the other hand, when the operation of freezing and thawing this silver nanoparticle aqueous dispersion (R1) was performed for one cycle, the liquid color when diluted to 50 ppm changed from yellow to black green. When the ultraviolet-visible absorption spectrum of the liquid changed to black-green color was measured, a decrease in the intensity of the plasmon absorption peak based on aggregation of silver nanoparticles and an increase in absorption on the long wavelength side were confirmed, confirming that the dispersion state deteriorated ( see Fig. 2).

(Comparative Examples 2 to 15)

Except having changed the polyvinylpyrrolidone used in Example 1 into the additive and addition amount shown in Table 1, it operated similarly to Example 1, and prepared silver nanoparticle aqueous dispersions (R2) - (R15). Moreover, dispersion stability and activity were measured and evaluated similarly to Example 1 about the obtained silver nanoparticle aqueous dispersions (R2)-(R15).

Table 1 shows the additives of the aqueous dispersions of silver nanoparticles (1) to (4) and (R1) to (R15) obtained in Examples 1 to 4 and Comparative Examples 1 to 15, their addition amounts, and the evaluation results. In addition, the addition amount in Table 1 shows the quantity of the additive with respect to 100 mass parts of silver nanoparticle containing composite_body|complex (composite of metal nanoparticles (X) and organic compound (Y)).

[Table 1]

The detail of the additive described in Table 1 is as follows.

Polyethylene glycol: weight average molecular weight 6,000

Polyvinyl alcohol: polymerization degree 500, saponification degree 86-90 mol%

Polymer (Y2-1): The polymer obtained in Synthesis Example 1 was used as it was as an additive.

"Present" in the change in appearance after the heating test in Table 1 indicates that the silver nanoparticles were suspended in gray due to aggregation of silver nanoparticles. In addition, "yes" in the appearance change after the freeze-thaw test indicates that the liquid color changed from yellow to black-green due to a change in plasmon absorption based on aggregation of silver nanoparticles.

From the evaluation results shown in Table 1, the metal nanoparticle dispersions of Examples 1 to 4 of the present invention have excellent dispersion stability even when subjected to a thermal load such as repeating the operation of melting after heating or freezing, and It was confirmed that it has sufficient adsorption to

On the other hand, the dispersion stability was improved in those with no additives (Comparative Example 1) and those with additives other than polyvinylpyrrolidone added (Comparative Examples 2 to 15) by performing a melting operation after heating or freezing. It was confirmed that the adsorption property to the substrate decreased.

Claims (7)

Number of metal nanoparticles containing a complex of metal nanoparticles (X) and an organic compound (Y) (excluding the complex in which the organic compound (Y) is polyvinylpyrrolidone) and polyvinylpyrrolidone (Z) As a dispersion, the organic compound (Y) is an organic compound (Y1) having an anionic functional group, and the organic compound (Y1) is 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 a monomer mixture (I) containing a (meth)acrylic acid-based monomer having at least one anionic functional group,
The amount of polyvinylpyrrolidone (Z) added is in the range of 0.1 to 20 parts by mass based on 100 parts by mass of the composite of the metal nanoparticles (X) and the organic compound (Y). water dispersion. According to claim 1,
An aqueous dispersion of metal nanoparticles comprising, in the monomer mixture (I), a (meth)acrylic acid monomer having a polyethylene glycol chain having an average number of units of ethylene glycol of 20 or more. 3. The method of claim 1 or 2,
An aqueous dispersion of metal nanoparticles, wherein the polymer (Y2) has a weight average molecular weight in the range of 3,000 to 20,000. 3. The method of claim 1 or 2,
An aqueous dispersion of metal nanoparticles, wherein the metal species of the metal nanoparticles (X) is silver, copper or palladium. 3. The method of claim 1 or 2,
An aqueous dispersion of metal nanoparticles having an average particle diameter in the range of 0.5 to 100 nm, as determined from the transmission electron micrograph of the metal nanoparticles (X). delete delete

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