TWI653301B - Metal nanoparticle aqueous dispersion - Google Patents

Abstract

The present invention provides a metal nanoparticle aqueous dispersion containing a composite of metal nanoparticle (X) and an organic compound (Y) (excluding the composite of the organic compound (Y) as polyvinylpyrrolidone), and Polyvinylpyrrolidone (Z). Furthermore, the present invention provides an aqueous dispersion of a metal nanoparticle, wherein the organic compound (Y) is a polymer of a monomer mixture containing a (meth)acrylic monomer having an anionic functional group, the anionic functional The base is one or more 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 nanoparticle aqueous dispersion has excellent dispersion stability and sufficient adsorption property to the substrate even if it is heated during storage or transportation, or is melted after freezing, that is, a heat load is applied. And surface activity.

Description

 Metal nanoparticle aqueous dispersion  

The present invention relates to an aqueous dispersion of metal nanoparticles, which has excellent dispersion stability even when it is heated during storage or transportation, or is melted after freezing, and has excellent dispersion stability and has a base material. Adequate adsorption, and surface activity.

The metal nanoparticle is used industrially as a catalyst, an antibacterial, a conductive material, or the like. The main form is a paste, an ink, or a coating material obtained by dispersing and dispersing metal nanoparticles, and the metal nanoparticles can be applied to any target substrate by a method such as printing, coating, or immersion treatment.

As a solvent for dispersing the metal nanoparticles, both the organic solvent and the aqueous solvent have been studied, and can be selected according to the purpose or process of imparting the metal nanoparticles to the substrate, but from the viewpoint of reducing the load on the environment. Preferably, an aqueous solvent is used.

One of the basic properties required for the aqueous dispersion of metal nanoparticles as described above is dispersion stability over a long period of time. In general, it can be increased by increasing the amount of dispersion in the dispersion, but the remaining dispersant tends to adversely affect the surface activity of the metal nanoparticles or the adsorption to the substrate, and the material is damaged. The original function (catalytic activity, antibacterial activity, electrical conductivity, etc.).

As a technique for dispersing stability and function, a method of using a polymer dispersant having high dispersing property instead of increasing a dispersing amount is disclosed (for example, refer to Patent Document 1), and an aqueous dispersion of metal nanoparticles of the invention is disclosed. As the catalyst for electroless plating, it is possible to have adsorption property to the substrate and surface activity (for example, refer to Patent Document 2).

In the temperature range from normal temperature to refrigerated state, as described above, the dispersion stability and function for a long period of time can be achieved by using a minimum amount of a high-performance dispersant. On the other hand, depending on the storage environment or transportation conditions of the product, freezing or temperature rise of the aqueous dispersion of metal nanoparticles is assumed. In the conventional aqueous dispersion of silver nanoparticles, irreversible agglomeration due to the aforementioned heat load and a decrease in performance accompanying the above problems are problems. Therefore, in order to maintain the quality of the metal nanoparticle dispersion, the use conditions are limited, and temperature management is also required during storage or transportation, and management costs also become a problem.

 [Previous Technical Literature]    [Patent Literature]  

Patent Document 1: Japanese Patent No. 4697356

Patent Document 2: Japanese Patent No. 5648232

An object of the present invention is to provide an aqueous dispersion of a metal nanoparticle having excellent dispersion stability even when a temperature rises during storage or transportation, or is melted after freezing, that is, a heat load is applied thereto. Adequate adsorption and surface activity to the substrate.

As a result of intensive studies in order to solve the above problems, the inventors of the present invention have found that the above-mentioned problems can be solved by configuring the metal nanoparticle aqueous dispersion to have a specific composition, and the present invention has been completed.

That is, the present invention provides an aqueous dispersion of metal nanoparticles, which is characterized by comprising a composite of metal nanoparticles (X) and an organic compound (Y) (excluding the organic compound (Y) is polyvinylpyrrolidone Complex), and polyvinylpyrrolidone (Z).

The aqueous metal nanoparticle dispersion of the present invention does not lower the adsorptivity and activity of the silver nanoparticles to the substrate, and can improve the dispersion stability. Therefore, the practicality as an industrial material is not impaired, and even if it is heated or melted after freezing, that is, a heat load is applied, deterioration of characteristics (coagulation or deterioration of liquid appearance) can be prevented. As described above, the aqueous metal nanoparticle dispersion of the present invention has excellent dispersion stability with respect to heat load, so that the temperature management cost of transportation (land transportation, sea transportation, air transportation) and storage can be reduced.

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

 [Formation of the Invention]  

The metal nanoparticle aqueous dispersion of the present invention is a composite containing metal nanoparticle (X) and an organic compound (Y) (excluding the composite of the above organic compound (Y) as polyvinylpyrrolidone) and polyethylene Pyrrolidone (Z).

Examples of the metal constituting the metal nanoparticle (X) include a monomer of silver, copper, and palladium, or an alloy thereof. In addition, examples of the metal nanoparticle (X) include silver core copper shell particles, copper shell silver core particles, particles obtained by substituting silver with a part of palladium, particles obtained by substituting copper with a part of palladium, and the like. . These metals or alloys may be used alone or in combination of two or more. When the metal or the alloy is appropriately selected according to the purpose, it is preferably silver or copper for the purpose of forming a wiring or a conductive layer, and is preferably silver or copper from the viewpoint of catalyst function. ,palladium. Further, from the viewpoint of cost, silver, copper, alloys thereof, a part of the substituents, or a mixture of the above are preferred.

The shape of the metal nanoparticle (X) is not particularly limited as long as it does not inhibit the dispersion stability in an aqueous medium, and various shapes of nanoparticles can be appropriately selected depending on the purpose. Specifically, a spherical shape, a polyhedral shape, a plate shape, a rod shape, and a combination of these shapes may be mentioned. As the metal nanoparticle (X), a single shape or a mixture of plural shapes can be used. Further, among these shapes, spherical or polyhedral particles are preferred from the viewpoint of dispersion stability.

The metal constituting the metal nanoparticle (X) is an organic compound which adsorbs as a dispersing agent on the surface of the metal nanoparticle (X) in order to maintain a stable dispersion state in a long-term dispersion in an aqueous dispersion medium. A composite of (Y) a metal nanoparticle (X) and an organic compound (Y). The organic compound (Y) may be appropriately selected and used according to the purpose, and is preferably a compound (Y1) having an anionic functional group from the viewpoint of dispersion stability. Further, the organic compound (Y) is other than the polyvinylpyrrolidone (Z) described later.

The compound (Y1) having an anionic functional group is a compound having one or more anionic functional groups in the molecule. Further, as long as the dispersion stability is not inhibited, a compound having a cationic functional group other than an anionic functional group in the molecule may be used. The compound (Y1) having an anionic functional group may be used alone or in combination of two or more.

From the viewpoint of having long-term dispersion stability in an aqueous dispersion medium and maintaining the activity on the surface of the metal nanoparticles after being applied to the substrate, the compound (Y1) having an anionic functional group is particularly preferred. a polymer (Y2) of a monomer mixture (I) containing a (meth)acrylic monomer having an anionic functional group selected from the group consisting of a carboxyl group, a phosphoric acid group, a phosphorous acid group, and a sulfonic acid group. One or more of the group of the sulfinic acid group and the sulfenic acid group.

The polymer (Y2) may be a homopolymer or a copolymer. Further, in the case of a copolymer, it may be a random copolymer or a block copolymer.

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 phosphite group, a sulfonic acid group, a sulfinic acid group, and a sulfenic acid group, The non-covalent electron pair of the atom has the function of adsorbing on the metal nanoparticle (X), and also imparts a negative charge to the surface of the metal nanoparticle (X), so that the colloidal particle can be prevented by the charge repulsion between the particles. It is agglomerated, and a composite of the polymer (Y2) and the metal nanoparticle (X) can be stably dispersed in water.

The polymer (Y2) preferably has three or more anionic functional groups in one molecule, based on the fact that the adsorption of the metal nanoparticles (X) and the dispersion stability in the aqueous dispersion can be further improved.

Further, the weight average molecular weight of the polymer (Y2) is preferably in the range of 3,000 to 20,000, based on the fact that the adsorption of the metal nanoparticles (X) and the dispersion stability in the aqueous dispersion can be further improved. More preferably in the range of 4,000 to 8,000.

Further, when the polyoxyalkylene chain such as a polyethylene glycol chain is introduced into the polymer (Y2), the repulsive force due to electric charge is exhibited, and the colloidal protection by the steric repulsion effect can be further utilized to further enhance the dispersion. Stability is therefore preferred.

For example, by copolymerizing the monomer mixture (I) with a (meth)acrylic monomer having a polyethylene glycol chain and a (meth)acrylic monomer having the anionic group, The aforementioned polymer (Y2) having a polyethylene glycol chain is easily obtained.

In particular, the polymer (Y2) obtained by polymerizing a (meth)acrylic monomer having a polyethylene glycol chain having an average number of ethylene glycol of 20 or more, which will be a noble metal, particularly silver, Copper nanoparticles are preferred because they have a high ability to stabilize and can be a suitable protective agent. The synthesis of the polymer having the anionic functional group and the polyethylene glycol chain as described above can be easily carried out, for example, by the method described in JP-A No. 4,697,356 and JP-A-2010-209421.

The weight average molecular weight of the (meth)acrylic 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 in this range, the water dispersibility of the composite with the metal nanoparticle (X) is further improved.

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-methylpropenyloxy phosphate (for example, Kyoeisha Chemical Co., Ltd.) "LIGHT ESTER P-1M" and a commercially available methacrylate monomer having a polyethylene glycol chain (for example, "Blenmer PME-1000" manufactured by Nippon Oil Co., Ltd.) using a polymerization initiator (for example, oil-soluble) The azo polymerization initiator "V-59" is a method of copolymerization.

In this case, if the ratio of the (meth) acrylate monomer having a phosphate group is set to be less than 30% by mass in the monomer mixture (I), it is possible to suppress the protection of the metal nanoparticles (X) not involved. The generation of a by-product such as a homopolymer of a (meth)acrylic monomer of a polyethylene glycol chain enhances the dispersion stability of the obtained polymer (Y2).

The monomer mixture (I) may further include a (meth)acrylic monomer having an anionic group or a third polymerizable monomer other than a (meth)acrylic monomer having a polyethylene glycol chain. In this case, when the third polymerizable monomer is a hydrophobic monomer, the amount thereof is 100 parts by mass based on the (meth)acrylic monomer having a polyethylene glycol chain, because it can maintain good water dispersibility. It is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. Further, when the third polymerizable monomer is a non-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 monomer having a polyethylene glycol chain is used in combination, a polymer obtained by polymerization (Y2) is used. Will have a molecular weight distribution. Since the smaller the weight average molecular weight is, the more the structure is derived from the (meth)acrylic monomer having a polyethylene glycol chain, the less the complex with the metal nanoparticle (X) is dispersed in the aqueous solution. From the viewpoint of the dispersion stability of the medium, the weight average molecular weight of the polymer (Y2) is more preferably 4,000 or more. On the other hand, when the weight average molecular weight is increased, the composite with the metal nanoparticle (X) is likely to be coarsened, and precipitation in the catalyst liquid is likely to occur. From this viewpoint, the weight of the polymer (Y2) The average molecular weight is more preferably 8,000 or less.

In order to adjust the weight average molecular weight of the polymer (Y2) to the above range, a chain transfer agent described in, for example, JP-A-2010-209421, or a polymerization agent may be used without using a chain transfer agent. Take control.

As the composite used in the aqueous dispersion of the metal nanoparticles of the present invention, the above-mentioned polymer (Y2) can be used as a colloidal protective agent, and metal nanoparticles (X) such as silver, copper or palladium can be used. Complex.

Moreover, as a method of preparing the composite used in the aqueous dispersion of the metal nanoparticles of the present invention, for example, a method of dissolving or dispersing the polymer (Y2) in an aqueous medium, adding silver nitrate thereto, a metal compound such as copper acetate or palladium nitrate, and if necessary, a complexing agent is added to form a uniform dispersion, and then a reducing agent is mixed to reduce the metal compound, so that the reduced metal becomes a nano-sized particle (having a nanometer size) The microparticles) simultaneously obtained an aqueous dispersion of the metal nanoparticles (X) compounded with the aforementioned polymer (Y2). Further, when a miscible agent is used, it may be mixed with a reducing agent at the same time.

The composite of the metal nanoparticle (X) and the organic compound (Y) used in the present invention is preferably from the viewpoint of facilitating wiring, formation of a conductive layer at low temperature, and catalytic activity. The average particle diameter of the metal nanoparticle (X) is in the range of 0.5 to 100 nm.

In addition, the average particle diameter of the metal nanoparticles (X) can be estimated by a transmission electron micrograph, and the average value of 100 is 0.5 to 100 nm. For example, the aforementioned Japanese Patent No. 4697356 can be used. It is easily obtained by the method described in the publication of Japanese Laid-Open Patent Publication No. 2010-209421. The metal nanoparticles (X) obtained as described above are obtained by being protected by the polymer (Y2) and each of them is independently present, and can be obtained by being dispersed in an aqueous dispersion medium.

The average particle diameter of the metal nanoparticle (X) can be determined by the kind of the metal compound, the molecular weight of the organic compound (Y) which is a colloidal protective agent, the chemical structure and the amount of use, the type of the crosslinking agent or the reducing agent, and the use thereof. The amount can be easily controlled by the amount of the reaction, the temperature at the time of the reduction reaction, etc., and the examples described in the above-mentioned patent documents and the like can be referred to.

Moreover, the content ratio of the organic compound (Y) in the composite of the organic compound (Y) and the metal nanoparticle (X) is preferably in the range of 1 to 30% by mass, more preferably 2 to 20% by mass. The range of %. That is, the composite is preferably used before being used for wiring, conductive layer formation, and various catalyst applications, and the metal nanoparticle (X) is suitable for most of the mass.

The metal nanoparticle (X) may be dispersed in a mixed solvent of the aqueous medium (that is, water or a water-miscible organic solvent) by a complex protected by the polymer (Y2) to 0.01 to 70. In the range of the mass%, and by further coexisting the above-mentioned polyvinylpyrrolidone (Z) in the dispersion, even if it is heated or melted after freezing, a thermal load is applied, and the aforementioned metal nanoparticles (X) The complex with the organic compound (Y) can also maintain excellent dispersion stability, high adsorption property to the substrate, and surface activity.

The mechanism for exhibiting the above-described effects by coexisting polyvinylpyrrolidone (Z) is not clear, but it is presumed to be as follows, depending on the mechanism of aggregation with the metal nanoparticles (X). The reason why the metal nanoparticles (X) are agglomerated in the dispersion due to heating is considered to be because the temperature rise causes the equilibrium to tilt toward the direction in which the organic compound (Y) is detached from the surface of the metal nanoparticles (X). At the same time, the Brownian motion of the particles is made active, and the collision frequency of the metal nanoparticles (X) exposed on the active surface is increased. On the other hand, the reason for the agglomeration caused by the freezing is considered to be because when the metal nanoparticle dispersion is frozen and the water in the dispersion crystallizes and becomes ice, it is excluded as an inclusion for water. The metal nanoparticle composite causes crystal growth and causes the metal nanoparticle composite to be extremely concentrated. Therefore, in order to suppress irreversible aggregation of particles due to heating or freezing, it is effective to coexist a compound having a property of being adsorbed on the surface of the metal nanoparticles (X) in a dispersion.

The driving force of the metal nanoparticle composite adsorbed on the substrate is mainly the electrostatic interaction between the charge on the surface of the substrate and the charge of the metal nanoparticle composite. Therefore, when an additive having the same sign of charge as the metal nanoparticle composite is allowed to exist, the additive and the metal nanoparticle composite compete for the adsorption point on the substrate, and the metal nanoparticle composite is hindered. Adsorption of the substrate. On the other hand, when an additive having a charge opposite to the metal nanoparticle composite is coexisted, the electrostatic repulsion force between the metal nanoparticle composites is shielded, and aggregation of the metal nanoparticle composite is induced. Therefore, in order to maintain the dispersion stability and the high adsorption property to the substrate, it is considered that a compound which adsorbs to the metal nanoparticle (X) and has a protective property is preferably a nonionic compound as an additive. .

Further, the stronger the compound adsorbed to the metal nanoparticle (X) and having the protective property is strongly adsorbed on the metal nanoparticle (X), the more difficult it is to expose the active surface of the metal nanoparticle (X) to cause it to Conductivity or catalytic activity is exhibited after the substrate is imparted. Therefore, in order to maintain the surface activity, it is considered that the compound which adsorbs to the metal nanoparticle (X) and has a protective property is not suitable for the metal nanoparticle (X).

As described above, in order to maintain excellent dispersion stability, high adsorptivity to a substrate, and surface activity of the metal nanoparticles (X), the compound adsorbed on the metal nanoparticles (X) and having a protective property is It is preferable that the metal nanoparticle (X) is not too weak and does not have too strong adsorption property, and is water-soluble or nonionic. Polyvinylpyrrolidone (Z) meets this condition.

In addition to the composite of the metal nanoparticle (X) and the organic compound (Y), the aqueous dispersion of the metal nanoparticle of the present invention also contains polyvinylpyrrolidone (Z) as an essential component, and The method for mixing polyvinylpyrrolidone is not particularly limited, but a method of adding polyvinylpyrrolidone (Z) to an aqueous dispersion of a composite of the aforementioned metal nanoparticle (X) and the aforementioned organic compound (Y) The system is simple and appropriate.

Polyvinylpyrrolidone (Z), which may be added to the aqueous dispersion of the complex of the organic compound (Y) and the metal nanoparticle (X) obtained by the above-mentioned preparation method, may be added to: the remaining miscible agent And a reductant or a purification step of various purification methods such as super-filtration method, precipitation method, centrifugal separation, vacuum distillation, and reduced-pressure drying, which are contained in a metal compound used as a raw material, alone or in combination of two or more kinds. Or the residue (non-volatile) or aqueous medium is further modified to form a dispersion after the purification step. When it is used for the purpose of assembly use such as formation of an electronic circuit, it is preferred to use a method of adding an aqueous medium which has been subjected to the above-described purification step.

The weight average molecular weight (hereinafter abbreviated as "Mw") of the polyvinylpyrrolidone (Z) used in the present invention can be provided while maintaining better dispersion even if it is heated or melted after freezing. From the viewpoint of stability, high adhesion to the substrate, and surface active metal nanoparticle aqueous dispersion, it is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 30,000 to 500,000. Further, the weight average molecular weight is a value obtained by measurement by a colloidal permeation chromatography (GPC) method.

The polyvinylpyrrolidone used in the present invention can be synthesized by a conventionally known method, and a commercially available product can also be used. For example, "PITZCOL K-30" (Mw: 40,000), "PITZCOL K-90" (Mw: 360,000), etc., manufactured by Daiichi Kogyo Co., Ltd., may be mentioned.

The addition amount of the polyvinylpyrrolidone (Z) can simultaneously satisfy more excellent dispersion stability, high adsorption property to a substrate, and surface activity even when it is heated or melted after freezing. In view of the above, 100 parts by mass of the composite of the metal nanoparticle (X) and the organic compound (Y) is preferably in the range of 0.1 to 20% by mass, more preferably 0.5 to 15 parts by mass. More preferably, it is in the range of 1 to 10 parts by mass, and particularly preferably in the range of 2 to 8.

When the aqueous metal nanoparticle dispersion of the present invention is used as an ink or a coating liquid for forming a wiring or a conductive layer, the concentration of the composite in the aqueous dispersion is preferably in the range of 0.5 to 40% by mass. More preferably, it is in the range of 1 to 30% by mass.

When the metal nanoparticle aqueous dispersion of the present invention is used as an ink or a coating liquid for wiring and formation of a conductive layer, the composite of the metal nanoparticle (X) and the organic compound (Y) is applied to a substrate. The method is not particularly limited, and any of various conventional printing and coating methods may be appropriately selected depending on the shape, size, rigidity, and the like of the substrate to be used. Specific examples thereof include a gravure method, a lithography method, a gravure lithography method, a relief method, a letterpress inversion method, a flexographic method, a screen method, a microcontact method, a reversal method, a pneumatic blade coating machine method, and a knife coating method. , air knife coater method, extrusion coater method, impregnation coater method, transfer roll coater method, light touch coater method, cast coater method, spray coater method, ink jet method, mold method, rotation Coating machine method, bar coater method, etc.

When the composite is printed or applied onto a substrate to apply the composite to a substrate to form a wiring or a conductive layer, the printed or coated substrate can be dried and fired. The wiring and the conductive layer are formed directly, and electroless or electrolytic plating may be further performed.

Further, the aqueous metal nanoparticle dispersion of the present invention may be used as a catalyst liquid for electroless plating which is used in a usual plating treatment step by immersion treatment. When the metal nanoparticle aqueous dispersion of the present invention is used as a catalyst for electroless plating, the adhesion between the plating film and the material to be plated can be improved by ensuring the amount of adsorption to the object to be plated. The concentration of the above-mentioned composite in the aqueous dispersion of rice particles 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.

According to the above method, the object to be plated on the surface of the composite of the metal nanoparticle particles of the present invention can be formed on the surface by a well-known electroless plating treatment with good efficiency. Metal film.

The aqueous medium used for the aqueous dispersion of the metal nanoparticles of the present invention may, for example, be a mixed solvent of water, water and a compatible organic solvent. The organic solvent is not particularly limited 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, acetone, and the like. 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 from the viewpoint of convenience in the plating step. Below mass%.

The base material to which the composite of the metal nanoparticle (X) and the organic compound (Y) is provided is not particularly limited, and for example, it may be one type of material or Combination of various glass fiber reinforced epoxy, epoxy insulation, polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, liquid crystal polymer (LCP), resin such as cycloolefin polymer (COP), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), glass, ceramic, metal oxide, metal, paper, synthetic or natural fiber. The shape may be any of a plate shape, a film shape, a cloth shape, a fiber shape, a tube shape, and the like.

The metal nanoparticle aqueous dispersion of the present invention can form a wiring, a conductive layer, etc. by applying a composite of a metal nanoparticle and an organic compound to a substrate by a simple method such as printing, coating, or immersion. A catalyst liquid for electroless plating can be suitably used.

 [Examples]  

Hereinafter, the present invention will be described in detail based on examples.

[Analysis of sample]

The analysis of the samples was carried out using the following apparatus. The transmission electron microscope (TEM) observation was carried out by "JEM-1400" manufactured by JEOL Ltd. The ultraviolet-visible absorption spectrometry was carried out by "Nanodrop ND-1000" manufactured by Thermo Fisher Scientific.

(Synthesis Example 1: Synthesis of Polymer (Y2-1) having anionic Functional Group)

In 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 mixture was stirred under a nitrogen stream while raising the temperature to 80 ° C. . Next, 20 parts by mass of methoxyethyl methacrylate ("LIGHT ESTER P-1M" manufactured by Kyoeisha Chemical Co., Ltd.) and methoxypolyethylene glycol methacrylate (manufactured by Nippon Oil Co., Ltd.) "Blenmer PME-1000", a molecular weight of 1,000), 80 parts by mass, a methyl ester of 3-mercaptopropionate, 4.1 parts by mass, and a mixture of MEK and 80 parts by mass, and a polymerization initiator (Wako Pure Chemical Co., Ltd. "V-65", 2, A mixture of 0.5 parts by mass of 2'-azobis(2,4-dimethylvaleronitrile) and 5 parts by mass of MEK was added dropwise for 2 hours. After the completion of the dropwise addition, 0.3 parts by mass of a polymerization initiator ("PERBUTYL O" manufactured by Nippon Oil Co., Ltd.) was added twice every 4 hours, and the mixture was stirred at 80 ° C for 12 hours. Water was added to the obtained resin solution, phase transfer emulsification was carried out, and the solvent was removed 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. The polymer (Y2-1) is a methoxycarbonylethylthio group, a phosphoric acid group, and a polyethylene glycol chain, and its weight average molecular weight (polystyrene equivalent value measured by colloidal permeation chromatography) is 4,300, acid The price was 97.5 mgKOH/g.

(Modulation 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 (polymer (Y2-1): 23 g), and 1,250 g of water , modulating the reducing agent solution.

Next, 15 g of an aqueous solution of the polymer (Y2-1) obtained in Synthesis Example 1 (polymer (Y2-1): 11.5 g) was dissolved in 333 g of water, and added thereto, 500 g (2.94 mol) of silver nitrate was dissolved in water 833 g. The solution was thoroughly stirred. To the mixture, the reducing agent solution obtained above was added dropwise at room temperature (25 ° C) for 2 hours. The obtained reaction mixture was filtered through a membrane filter (pore size: 0.45 μm), and the filtrate was applied to a hollow fiber type ultrafiltration module ("MOLSEP module FB-02 type" manufactured by DAICEN MEMBRANE-SYSTEMS, with a molecular weight cutoff of 150,000). The medium is circulated, and the amount of water corresponding to the amount of the filtrate flowing out is added at any time for purification. After confirming that the conductivity of the filtrate became 100 μS/cm or less, the water injection was stopped and concentrated. By recovering the concentrate, an aqueous dispersion of a composite of silver-containing nanoparticles containing 36.7 mass% of non-volatile matter 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 by a transmission electron microscope (TEM) image.

(Example 1)

272.5 parts by mass of the silver nanoparticle aqueous dispersion obtained in Preparation Example 1 (100 parts by mass of the composite containing silver nanoparticles), and polyvinylpyrrolidone (PITZCOL K-made by Daiichi Kogyo Co., Ltd.) was added. 20 parts by mass of a 20% by mass aqueous solution of 30" and Mw: 40,000) (4 parts by mass of polyvinylpyrrolidone), and then uniformly stirred, and ion-exchanged water was added to adjust the concentration of the composite containing silver nanoparticles. 10% by mass, an aqueous dispersion of silver nanoparticles (1) was obtained.

[Evaluation of the appearance of silver nanoparticle aqueous dispersion]

As an evaluation index of the dispersion stability of the silver nanoparticle aqueous dispersion (1) obtained above, the appearance was visually observed, and the presence or absence of the suspension was confirmed. In addition, the change in color was also confirmed together with respect to the heating test described later or the appearance evaluation after the freeze-melt test.

[Adsorption evaluation of substrate and measurement of plating coverage]

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

A glass slide was prepared as a substrate, and the glass slide was immersed in a 2% by mass aqueous solution of polyethyleneimine ("EPOMIN SP-200" manufactured by Nippon Shokubai Co., Ltd.) for 1 minute, and taken out, and washed with running water for 1 minute. After that, the water was drained by blast to obtain a surface-treated slide.

Next, as an electroless copper plating bath, an aqueous solution containing 0.04 mol/L of copper sulfate pentahydrate, 0.04 mol/L of formaldehyde, and 0.08 mol/L of disodium ethylenediaminetetraacetate was prepared, and the pH was adjusted by sodium hydroxide. 12.3 The resulting solution was prepared to warm it to 55 °C.

The glass slide surface-treated as described above was immersed in the aqueous dispersion of silver nanoparticle particles (1) obtained by diluting it to 200 times at 25 ° C for 10 minutes to adsorb the silver nanoparticles to the glass. The surface of the piece. At this time, since the silver nanoparticles are colored, the more the amount of adsorption of the silver nanoparticles on the surface of the slide, the yellower the color of the slide. The degree of the coloring was visually observed, and the additive to the substrate (Comparative Example 1), which will be described later, was used as a standard, and the adsorption property to the substrate was evaluated in accordance with the following criteria.

○: It is equivalent to those in which no additive is added.

△: The color of the person who is not added with the additive is lighter.

×: Almost no coloring, and it is nearly colorless and transparent.

Then, the glass slide to which the silver nanoparticles were adsorbed was taken out, washed with water for 1 minute, and then immersed for 30 minutes while stirring the air in the prepared electroless copper plating bath, and then taken out and washed with water for 1 minute. Electroless copper plating.

According to the image processing of the photograph of the slide glass plated by electroless copper, white black was binarized on the basis of lightness, and the plating coverage was calculated from the area of the portion to be plated. The activity of the silver nanoparticle composite was evaluated from the obtained plating coverage. Here, when the catalyst activity is extremely high, plating is deposited on the entire surface of the substrate, and if the activity is lowered, the deposition area of the plating is reduced. Therefore, when the entire surface of the slide glass was plated (the plating coverage rate was 100%), it was judged that the activity of the silver nanoparticle composite was good.

[heating test]

In a 50 mL spiral tube, the silver nanoparticle aqueous dispersion (1) obtained above was added and sealed. Next, it was heated in a thermostat at 50 ° C for 14 days. After heating, the appearance evaluation was performed in the same manner as the above method. Further, with respect to the silver nanoparticle aqueous dispersion (1) before and after heating, after the concentration of the silver nanoparticle composite was diluted to 50 ppm and the ultraviolet visible absorption spectrum was measured (refer to FIG. 1), silver nanoparticles were observed. The plasmonic absorption spectrum associated with the surface state of the particles. When the silver nanoparticles are agglomerated, the surface state and the spectral shape change. However, since the spectral shape does not change before and after the heating, it is confirmed that the silver nanoparticles are dispersed in the silver nanoparticle aqueous dispersion (1). no change.

Next, it was prepared to dilute the heated silver nanoparticle aqueous dispersion (1) to 200 times, and the plating coverage was measured in the same manner as above.

[Freeze-melting test]

In a 50 mL spiral tube, the silver nanoparticle aqueous dispersion (1) obtained above was added and sealed. Then, it was allowed to freeze with a dry borneol for 5 minutes, and then thawed at normal temperature. The operation of freezing and thawing was performed as one cycle, and three cycles were repeated. The operation of freezing and thawing was performed, and after three cycles, the appearance evaluation was performed in the same manner as the above method. Further, the ultraviolet visible absorption spectrum (see Fig. 2) was measured for the silver nanoparticle aqueous dispersion (1) after three cycles of freezing and thawing before freezing. From the measurement results of the ultraviolet-visible absorption spectrum, it was confirmed that the dispersion state of the silver nanoparticles in the silver nanoparticle aqueous dispersion (1) did not change even if the freezing and thawing were repeated.

Next, the operation of freezing and thawing was carried out, and the silver nanoparticle aqueous dispersion (1) after three cycles was diluted to 200 times, and the plating coverage was measured in the same manner as above.

[Overview]

From the results of the heating test and the freeze-thaw test conducted as described above, the dispersion stability and the adsorptivity to the substrate were evaluated, and the evaluation was carried out in accordance with the following criteria.

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

×: There was a problem in any of the dispersion stability and the adsorption property to the substrate in the heating test and the freeze-melting test.

(Example 2)

The same procedure as in Example 1 was carried out except that the 20% by mass aqueous solution of the polyvinylpyrrolidone used in Example 1 was changed from 20 parts by mass to 10 parts by mass (polyvinylpyrrolidone was 2 parts by mass). The operation was carried out to obtain an aqueous dispersion of silver nanoparticles (2). Moreover, the obtained silver nanoparticle aqueous dispersion (2) was measured and evaluated in the same manner as in Example 1.

(Example 3)

In the same manner as in Example 1, except that the 20% by mass aqueous solution of the polyvinylpyrrolidone used in Example 1 was changed from 20 parts by mass to 50 parts by mass (polyvinylpyrrolidone was 10 parts by mass). The operation was carried out to obtain an aqueous dispersion of silver nanoparticles (3). Moreover, the obtained silver nanoparticle aqueous dispersion (3) was measured and evaluated in the same manner as in Example 1.

(Example 4)

The polyvinylpyrrolidone used in Example 1 was changed to polyvinylpyrrolidone ("PITZCOL K-90", Mw: 360,000, manufactured by Dai-ichi Kogyo Co., Ltd.), and the concentration of the aqueous solution was changed to 10 masses. In the same manner as in Example 1, except that % was obtained, a silver nanoparticle aqueous dispersion (4) was obtained. Moreover, the obtained silver nanoparticle aqueous dispersion (4) was measured and evaluated in the same manner as in Example 1.

(Comparative Example 1)

In the aqueous dispersion of silver nanoparticles obtained in Preparation Example 1, ion-exchanged water was added to prepare a concentration of the silver-containing nanoparticle-containing composite in the aqueous dispersion to 10% by mass to obtain a silver nanoparticle aqueous dispersion. (R1). Further, the obtained silver nanoparticle aqueous dispersion (R1) was measured and evaluated in the same manner as in Example 1. Further, the silver nanoparticle aqueous dispersion (R1) was diluted to adjust the concentration of the silver nanoparticle composite to 50 ppm, and the ultraviolet visible absorption spectrum before heating was measured, and the addition of the polyvinylpyrrolidone was carried out. There is no difference in one. Further, after the ultraviolet visible absorption spectrum after heating was measured, the spectral shape did not change (refer to Fig. 1).

On the other hand, after the operation of freezing and thawing the silver nanoparticle aqueous dispersion (R1) in one cycle, the liquid color when diluted to 50 ppm changed from yellow to blackish green. After measuring the ultraviolet-visible absorption spectrum of the black-green liquid, it was confirmed that the intensity of the plasmon absorption peak due to aggregation of the silver nanoparticles was decreased and the absorption on the long-wavelength side was increased, and it was confirmed that the dispersion state was deteriorated (Fig. 2 reference).

(Comparative examples 2 to 15)

In the same manner as in Example 1, except that the polyvinylpyrrolidone used in Example 1 was changed to the additive and the amount shown in Table 1, the silver nanoparticle aqueous dispersion (R2) was prepared. ~(R15). Further, the obtained silver nanoparticle aqueous dispersions (R2) to (R15) were measured and evaluated for dispersion stability and activity in the same manner as in Example 1.

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

The details of the additives described in Table 1 are as follows.

Polyethylene glycol: weight average molecular weight 6,000

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

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

The presence of "Yes" in the appearance change after the heating test in Table 1 indicates the aggregation of the silver nanoparticles, resulting in a gray suspension. Further, the presence of "Yes" in the appearance change after the freeze-melting test indicates a change in plasmon absorption due to aggregation of silver nanoparticles, and the liquid color changes from yellow to black green.

From the evaluation results shown in Table 1, it was confirmed that the examples 1 to 4 of the metal nanoparticle dispersion of the present invention were excellent even if the heating was repeated or the operation of melting after freezing was applied, that is, the heat load was applied. Dispersion stability and sufficient adsorption to the substrate.

On the other hand, when it was confirmed that the additive (Comparative Example 1) and the additive other than the polyvinylpyrrolidone (Comparative Examples 2 to 15) were added, the operation was performed by heating or melting after freezing. The dispersion stability is lowered and the adsorption property to the substrate is lowered.

Claims (5)

A metal nanoparticle aqueous dispersion containing a composite of metal nanoparticle (X) and an organic compound (Y) (excluding the composite of the organic compound (Y) as polyvinylpyrrolidone), and polyethylene An aqueous dispersion of a metal nanoparticle of pyrrolidone (Z), characterized in that the organic compound (Y) is an organic compound (Y1) having an anionic functional group, and the organic compound (Y1) contains an anionic functional group. a polymer (Y2) of a monomer mixture (I) of a (meth)acrylic monomer 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 One or more of the group of sulfenic acid groups. An aqueous dispersion of a metal nanoparticle according to claim 1, which is a (meth)acrylic acid group having a polyethylene glycol chain having an average number of units of ethylene glycol of 20 or more in the monomer mixture (I). monomer. The aqueous dispersion of metal nanoparticles according to claim 1 or 2, wherein the polymer (Y2) has a weight average molecular weight in the range of 3,000 to 20,000. The aqueous dispersion of metal nanoparticles according to claim 1 or 2, wherein the metal species of the metal nanoparticles (X) is silver, copper or palladium. The aqueous dispersion of metal nanoparticles according to claim 1 or 2, wherein the average particle diameter of the metal nanoparticles (X) determined by a transmission electron micrograph is in the range of 0.5 to 100 nm.