WO2017183624A1

WO2017183624A1 - Metal nanoparticle aqueous dispersion

Info

Publication number: WO2017183624A1
Application number: PCT/JP2017/015532
Authority: WO
Inventors: 昭太新林; 深澤　憲正
Original assignee: Dic株式会社
Priority date: 2016-04-22
Filing date: 2017-04-18
Publication date: 2017-10-26
Also published as: KR20180122419A; CN109070208A; JP6255635B1; CN109070208B; TW201816182A; KR102169421B1; JPWO2017183624A1; TWI653360B

Abstract

The present invention provides a metal nanoparticle aqueous dispersion which is characterized by containing: a composite body of a metal nanoparticle (X) and an organic compound (Y); and one or more compounds (Z) selected from the group consisting of lactic acid, glycolic acid, malonic acid, succinic acid, fumaric acid, maleic acid, malic acid, tartaric acid, oxalic acid, citric acid and alkali metal salts of these carboxylic acids. This metal nanoparticle aqueous dispersion is able to be suppressed in deterioration over time and in suspension, aggregation and precipitation due to inclusion of a small amount of impurities. In addition, this metal nanoparticle aqueous dispersion is free from the occurrence of characteristics deterioration due to corrosion and appearance defects of a base due to coloring even if a metal having a higher ionization tendency than the metal that constitutes the metal nanoparticles is present on the base surface to which the metal nanoparticles are applied, and is thus able to be stabilized.

Description

Metal nanoparticle aqueous dispersion

The present invention relates to an aqueous dispersion of metal nanoparticles that can be used as a metal film or as various catalysts, has excellent stability, and has corrosion resistance.

Metals are attracting attention as materials with high specific activity and large specific surface area by making them nano-sized particles, and they are used for wiring, conductive layer formation, antibacterial materials, and various catalyst applications utilizing fusion phenomena at low temperatures. Application of is being studied. In particular, industrially, by providing metal nanoparticles dispersed in a liquid, a metal film or a catalytic metal can be imparted on various target substrates by methods such as printing, coating, and adsorption. This is a great merit.

As the solvent for dispersing the metal nanoparticles, both an organic solvent and an aqueous solvent have been studied and can be selected depending on the process of applying the metal onto the substrate, but from the viewpoint of reducing environmental burden, It is preferable to use a solvent.

Metal nanoparticles used to form metal films on various substrates or to apply catalytic metals by printing, coating, adsorption, etc. are dispersed uniformly and stably in an aqueous dispersion medium for a long period of time. It is required to maintain the state, and that the surface of the metal nanoparticle is active even after being applied on the substrate, is required for any of wiring, conductive layer formation, antibacterial, and catalyst applications. For this reason, as a dispersant to be adsorbed on the surface of the metal nanoparticles, a polymer dispersant that is difficult to desorb and can impart high dispersion stability is used, and by reducing the amount used as much as possible, the dispersion stability in the liquid And surface activity are compatible (for example, refer to Patent Document 1). Moreover, the metal nanoparticle using this polymer dispersing agent can be used also as a catalyst of electroless plating (for example, refer patent document 2).

However, aqueous dispersions of metal nanoparticles that ensure dispersion stability and high surface activity in this way are also destabilized due to changes in the storage environment over time and small amounts of impurities during use, irreversible suspension and aggregation There was a problem that precipitation occurred. In addition, when a metal nanoparticle is applied on a base material, if a metal having a higher ionization tendency than the metal constituting the metal nanoparticle exists on the base material, corrosion due to contact with a different metal occurs at the contact portion. There was a concern that the performance deteriorated due to corrosion and the appearance of the base material was poor.

Japanese Patent No. 4697356 Japanese Patent No. 5648232

The problem to be solved by the present invention is to suppress suspension, aggregation, and precipitation due to deterioration with time and mixing of a small amount of impurities, and the surface of the base material to which the metal nanoparticles are applied is more than the metal constituting the metal nanoparticles. To provide a stabilized aqueous dispersion of metal nanoparticles that does not cause deterioration in properties due to corrosion or poor appearance of a substrate due to coloring even in the presence of a metal having a high ionization tendency.

As a result of diligent research to solve the above-mentioned problems, the present inventors have used the above-described aqueous dispersion of metal nanoparticles to which an aqueous dispersion of metal nanoparticles is added a specific carboxylic acid or an alkali metal salt thereof. As a result, the present invention has been completed.

That is, the present invention relates to a composite of metal nanoparticles (X) and an organic compound (Y), lactic acid, glycolic acid, malonic acid, succinic acid, fumaric acid, maleic acid, malic acid, tartaric acid, oxalic acid, citric acid. And one or more kinds of compounds (Z) selected from the group consisting of alkali metal salts of these carboxylic acids.

The metal nanoparticle aqueous dispersion of the present invention suppresses suspension, aggregation, and precipitation due to changes in the storage environment over time and the incorporation of a small amount of impurities, and the metal nanoparticles are formed on the surface of the base material to which the metal nanoparticles are applied. Even when a metal having a higher ionization tendency than a metal to be present does not cause deterioration in characteristics due to corrosion or appearance defects due to coloring, it can be used as a wiring, a conductive material, an antibacterial material, and various catalysts.

It is the photograph at the time of visual observation which shows that the spotted corrosion of Example 1 has not arisen. It is an observation photograph with a scanning electron microscope (SEM) which shows that the silver particle has discretely adhered to the flat copper surface of Example 1. FIG. It is the photograph at the time of visual observation which shows that many spotted colored parts of the comparative example 2 have arisen. It is an observation photograph with a scanning electron microscope (SEM) which shows that the copper surface was eroded and fine unevenness was formed unlike the example 1 of the spotted colored part of comparative example 2. It is the photograph at the time of visual observation which shows that the spotted corrosion of Example 4 has not arisen. It is an observation photograph with a scanning electron microscope (SEM) which shows that there is no other than the physical unevenness which arose in the manufacture process in the steel plate surface of Example 4. FIG. It is the photograph at the time of visual observation which shows that many spotted colored parts of the comparative example 4 have arisen. It is the observation photograph in a scanning electron microscope (SEM) which shows that the uneven | corrugated colored part of the comparative example 4 eroded the steel plate surface unlike Example 4, and the fine unevenness | corrugation was formed.

The aqueous dispersion of metal nanoparticles of the present invention comprises a composite of metal nanoparticles (X) and an organic compound (Y), lactic acid, glycolic acid, malonic acid, succinic acid, fumaric acid, maleic acid, malic acid, tartaric acid, It contains at least one compound (Z) selected from the group consisting of oxalic acid, citric acid and alkali metal salts of these carboxylic acids.

Examples of the metal constituting the metal nanoparticles (X) include silver, copper, palladium alone, and alloys thereof. Examples of the metal nanoparticles (X) include silver core copper shell particles, copper shell silver core particles, particles in which silver is partially substituted with palladium, and particles in which copper is partially substituted with palladium. These metals or alloys can be used alone or in combination of two or more. These metals or alloys may be appropriately selected according to the purpose. However, when used for the purpose of forming a wiring or a conductive layer, silver and copper are preferable. From the viewpoint of the catalytic function, silver, copper Palladium is preferred. From the viewpoint of cost, silver, copper, alloys thereof, partially substituted products, or mixtures thereof are preferable.

The shape of the metal nanoparticles (X) is not particularly limited as long as the dispersion stability in an aqueous medium is not impaired, and various shapes of nanoparticles can be appropriately selected according to the purpose. Specific examples include spherical, polyhedral, plate-like, rod-like, and combinations of these particles. As said metal nanoparticle (X), the thing of a single shape or a thing of a some shape can be mixed and used. Among these shapes, spherical or polyhedral particles are preferable from the viewpoint of dispersion stability.

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

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

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

The polymer (Y2) may be a homopolymer or a copolymer. Moreover, when it is a copolymer, it may be random polymerization or block polymerization.

Since the polymer (Y2) has one or more anionic functional groups selected from the group consisting of carboxy group, phosphoric acid group, phosphorous acid group, sulfonic acid group, sulfinic acid group and sulfenic acid group, Since it has a function of adsorbing to the metal nanoparticle (X) through the lone pair of atoms, and at the same time, a negative charge is imparted to the surface of the metal nanoparticle (X), the repulsion of the colloidal particles Aggregation can be prevented, and the composite of polymer (Y2) and metal nanoparticles (X) can be stably dispersed in water.

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

In addition, when a polyoxyalkylene chain such as a polyethylene glycol chain is introduced into the polymer (Y2), it is possible to utilize a colloid protective effect due to a steric repulsion effect simultaneously with the expression of repulsive force due to electric charge, and more dispersion stability. It is preferable because it improves.

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

In particular, the polymer (Y2) polymerized using a (meth) acrylic acid monomer having a polyethylene glycol chain with an average unit number of ethylene glycol of 20 or more stabilizes nanoparticles of noble metals, particularly silver and copper. This is preferable because it is a suitable protective agent. Synthesis of such a polymer having an anionic functional group and a polyethylene glycol chain can be easily carried out by the methods described in, for example, Japanese Patent No. 4697356, Japanese Patent Application Laid-Open No. 2010-209421, and the like.

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

As a more specific method for synthesizing the polymer (Y2) having a phosphate group and a polyethylene glycol chain, for example, commercially available 2-methacryloyloxyphosphate (for example, “Light Ester P-1M” manufactured by Kyoeisha Chemical Co., Ltd.). )) And a commercially available methacrylic acid ester monomer having a polyethylene glycol chain (for example, “Blenmer PME-1000” manufactured by NOF Corporation) as a polymerization initiator (for example, oil-soluble azo polymerization initiator “V-59”). And a method of copolymerization using these.

At this time, if the ratio of the (meth) acrylic acid ester monomer having a phosphate group is less than 30% by mass in the monomer mixture (I), a polyethylene glycol chain that does not participate in the protection of the metal nanoparticles (X) Generation | occurrence | production of by-products, such as a homopolymer of the (meth) acrylic acid-type monomer which has, is suppressed, and the dispersion stability by the polymer (Y2) obtained improves.

The monomer mixture (I) contains a third polymerizable monomer other than the (meth) acrylic acid monomer having an anionic group and the (meth) acrylic acid monomer having a polyethylene glycol chain. May be. At this time, when the third polymerizable monomer is a hydrophobic monomer, the amount used thereof can maintain good water dispersibility, so that the amount of the (meth) acrylic acid monomer having a polyethylene glycol chain is 100 parts by mass. The amount is preferably 20 parts by mass or less, and more preferably 10 parts by mass or less. In addition, when the 3rd polymeric 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 has a molecular weight distribution. When the composite with the metal nanoparticles (X) is dispersed in an aqueous medium, the smaller the weight average molecular weight, the less the structure derived from a (meth) acrylic acid monomer having a polyethylene glycol chain. From this point of view, the weight average molecular weight of the polymer (Y2) is more preferably 4,000 or more. Conversely, when the weight average molecular weight is increased, the complex with the metal nanoparticle (X) is likely to be coarsened, and the weight average molecular weight of the polymer (Y2) is 8, from the viewpoint of easily causing precipitation in the catalyst solution. More preferably, it is 000 or less.

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

As a 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., produced using the polymer (Y2) as a colloid protective agent is used. be able to.

Moreover, as a preparation method of the composite used for the metal nanoparticle aqueous dispersion of the present invention, for example, the polymer (Y2) is dissolved or dispersed in an aqueous medium, and then silver nitrate, copper acetate, palladium nitrate is added thereto. After adding a metal compound such as a complexing agent as necessary to obtain a uniform dispersion, the metal compound is reduced by mixing a reducing agent, and the reduced metal is nanosized particles ( And a method of obtaining an aqueous dispersion of metal nanoparticles (X) combined with the polymer (Y2) at the same time. In addition, when using a complexing agent, you may mix simultaneously with a reducing agent.

In the aqueous dispersion of metal nanoparticles of the present invention, the average particle diameter of the metal nanoparticles (X) is 0.5, which is advantageous for the formation of wiring and conductive layers, from the viewpoint of low-temperature fusion properties and catalytic activity. It is preferable that a composite of metal nanoparticles (X) in the range of ˜100 nm and the organic compound (Y) is dispersed in an aqueous dispersion medium.

The average particle diameter of the metal nanoparticles (X) can be estimated by a transmission electron micrograph, and the average value of 100 particles in the range of 0.5 to 100 nm is, for example, the above-mentioned patent It can be easily obtained by the methods described in Japanese Patent No. 4697356, Japanese Patent Application Laid-Open No. 2010-209421, and the like. The metal nanoparticles (X) thus obtained are protected by the polymer (Y2) and exist individually one by one, and can be stably dispersed in an aqueous dispersion medium.

The average particle diameter of the metal nanoparticles (X) is the type of metal compound, the molecular weight of the organic compound (Y) to be a colloid protective agent, the chemical structure and the amount used, the type and amount of complexing agent and reducing agent, The temperature can be easily controlled by the temperature at the time of the reduction reaction. For these, the examples described in the above-mentioned patent documents and the like may be referred to.

The content ratio of the organic compound (Y) in the complex of the organic compound (Y) and the metal nanoparticles (X) is preferably in the range of 1 to 30% by mass, and in the range of 2 to 20% by mass. Is more preferable. That is, in the composite, one in which the metal nanoparticles (X) occupy most of the mass is suitable for use in wiring, conducting wire layer formation, and various catalyst applications.

Particularly, the composite in which the metal nanoparticles (X) are protected by the polymer (X-2) is 0.01% in an aqueous medium, that is, a mixed solvent of water or an organic solvent compatible with water. It can be dispersed in a range of about 70% by mass, and can be stably stored at room temperature (˜25 ° C.) without agglomeration at room temperature (˜25 ° C.) for a few months under conditions where no impurities are mixed.

In addition to the composite of the metal nanoparticles (X) and the organic compound (Y), the aqueous dispersion of metal nanoparticles of the present invention includes lactic acid, glycolic acid, malonic acid, succinic acid, fumaric acid, maleic acid, apple One or more compounds (Z) selected from the group consisting of acid, tartaric acid, oxalic acid, citric acid and alkali metal salts of these carboxylic acids are used as essential components.

By adding the compound (Z) to the aqueous dispersion of metal nanoparticles of the present invention, irreversible suspension, aggregation, and precipitation due to changes in storage environment over time and small amounts of impurities are suppressed, and the metal nanoparticle is suppressed. Even when a metal having a higher ionization tendency than the metal constituting the metal nanoparticles is present on the surface of the base material to which the particles (X) are adhered, it exhibits the effect of preventing deterioration in properties due to corrosion and appearance defects due to coloring. To do.

The amount of the compound (Z) used is preferably in the range of 1 to 100 parts by mass and more preferably in the range of 5 to 30 parts by mass with respect to 1 part by mass of the complex. The compound (Z) may be added in advance to the aqueous dispersion of the complex of the metal nanoparticles (X) and the organic compound (Y), and the aqueous dispersion of the complex is used. May be added before

The metal nanoparticle aqueous dispersion of the present invention can be used as it is as a wiring, conductive layer forming ink or coating solution, or as a catalyst solution for electroless plating, but an excess complexing agent, reducing agent, or raw material. As a counter ion contained in the metal compound used as the ultrafiltration method, precipitation method, centrifugal separation, vacuum distillation, vacuum purification, etc. various purification methods such as single or in combination of two or more, Furthermore, after refining process, the concentration (non-volatile content) and aqueous medium may be changed and newly prepared as a dispersion may be used. When using for the purpose of mounting applications such as electronic circuit formation, it is preferable to use an aqueous medium that has undergone the purification step. In addition, it is preferable that the said refinement | purification process is performed after preparing the aqueous dispersion of the said composite, and adds the said compound (Z) after that.

When the metal nanoparticle aqueous dispersion of the present invention is used as an ink or a coating liquid for forming a wiring or a conductive layer, the concentration (nonvolatile content) of the composite in the aqueous dispersion is 0.5 to A range of 40% by mass is preferable, and a range of 1 to 30% by mass is more preferable.

A method of applying a composite of the metal nanoparticles (X) and the organic compound (Y) on a substrate when wiring and conductive layer formation are performed using the metal nanoparticle aqueous dispersion of the present invention as an ink and a coating liquid. There is no particular limitation, and various known and commonly used printing / coating techniques may be appropriately selected depending on the shape, size, degree of flexibility, and the like of the substrate to be used. Specifically, gravure method, offset method, gravure offset method, relief printing method, relief printing inversion method, flexo method, pad method, screen method, microcontact method, reverse method, air doctor coater method, blade coater method, air knife coater method Squeeze coater method, impregnation coater method, transfer roll coater method, kiss coater method, cast coater method, spray coater method, ink jet method, die method, spin coater method, bar coater method and the like.

When the composite is printed or coated on a substrate and the composite is applied on the substrate to form a wiring or conductive layer, the printed or coated substrate is dried and fired. In this case, the wiring and the conductive layer may be directly formed, or electroless or electrolytic plating may be performed.

The metal nanoparticle aqueous dispersion of the present invention can also be used as a catalyst solution for electroless plating used in a normal 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 amount of adsorption to the object to be plated can be secured, and the adhesion of the plating film to the object to be plated can be improved. The concentration of the complex (nonvolatile content concentration) in the metal nanoparticle aqueous dispersion is preferably in the range of 0.05 to 5 g / L, and more preferably in the range of 0.1 to 2 g / L in consideration of economy. .

By the above method, the object to be plated with the composite in the metal nanoparticle aqueous dispersion of the present invention attached to the surface thereof is subjected to a known electroless plating treatment to form a metal film on the surface. be able to.

Examples of the aqueous medium used in the metal nanoparticle aqueous dispersion of the present invention include water alone and a mixed solvent of water and an organic solvent compatible with water. The organic solvent can be selected without particular limitation as long as it does not impair the dispersion stability of the composite and does not damage the object to be plated. Specific examples of the organic solvent include methanol, ethanol, isopropanol, acetone and the like. These organic solvents can be used alone or in combination of two or more.

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

The base material to which the composite of the metal nanoparticles (X) and the organic compound (Y) is applied using the metal nanoparticle aqueous dispersion of the present invention is not particularly limited. Fiber reinforced epoxy, epoxy insulation, polyimide, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate, liquid crystal polymer (LCP), cycloolefin polymer (COP), polyetheretherketone (PEEK), polyphenylene sulfide ( PPS) and other plastics, glass, ceramics, metal oxides, metals, paper, synthetic or natural fibers, etc. Any of cloth shape, fiber shape, tube shape, etc. may be sufficient.

The metal nanoparticle aqueous dispersion of the present invention provides a composite of metal nanoparticles and an organic compound on a substrate by a simple method such as printing, coating, or dipping. It can be formed and can be suitably used as a catalyst solution for electroless plating.

In addition, when the metal nanoparticle aqueous dispersion of the present invention imparts the composite of the metal nanoparticles (X) and the organic compound (Y) to the base material, the performance deteriorates due to corrosion of the metal base surface, and the appearance is poor. Can be suppressed. Therefore, a particularly excellent effect is exhibited when using a metal substrate or a substrate having a metal such as a wiring or a conductive layer on the substrate.

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

[Sample analysis]
Sample analysis was performed using the following apparatus. Observation with a transmission electron microscope (TEM) was performed with “JEM-1400” manufactured by JEOL Ltd. (Preparation Example 1). Scanning electron microscope (SEM) observations were made with “JSM-7800F” manufactured by JEOL Ltd. (FIG. 2 of Example 1 and FIG. 4 of Comparative Example 2) and “VE9800” manufactured by Keyence Corporation (FIG. 6 of Example 4). And in FIG. 8) of Comparative Example 4. The average particle size was measured by the dynamic light scattering method using “FPAR-1000” manufactured by Otsuka Electronics Co., Ltd. (Preparation Example 1).

(Synthesis Example 1: Synthesis of Polymer (Y2-1) Having Anionic Functional Group)
A four-necked flask equipped with a thermometer, a stirrer, and a reflux condenser was charged with 32 parts by mass of methyl ethyl ketone (hereinafter abbreviated as “MEK”) and 32 parts by mass of ethanol, and stirred at 80 ° C. under a nitrogen stream. The temperature was raised to. Next, 20 parts by mass of phosphooxyethyl methacrylate (Kyoeisha Chemical Co., Ltd. “Light Ester P-1M”), methoxypolyethylene glycol methacrylate (Nippon Co., Ltd. “Blenmer PME-1000”, molecular weight 1,000) 80 parts by mass , A mixture of 4.1 parts by weight of methyl 3-mercaptopropionate and 80 parts by weight of MEK and a polymerization initiator (Wako Pure Chemical Industries, Ltd. “V-65”, 2,2′-azobis (2,4-dimethylvaleronitrile) ) A mixture of 0.5 parts by mass and 5 parts by mass of MEK was added dropwise over 2 hours. After the completion of dropping, 0.3 parts by mass of a polymerization initiator (“Perbutyl O” manufactured by NOF Corporation) 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 for phase inversion emulsification, and after desolvation under reduced pressure, 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. It was. This polymer (Y2-1) has a methoxycarbonylethylthio group, a phosphoric acid group and a polyethylene glycol chain, and its weight average molecular weight (polystyrene conversion value measured by gel permeation chromatography) is 4. 300, and the acid value was 97.5 mgKOH / g.

(Preparation Example 1: Preparation of silver nanoparticle aqueous dispersion)
463 g (4.41 mol) of an 85% by mass aqueous solution of N, N-diethylhydroxylamine, 30 g of the aqueous solution of the polymer (Y2-1) obtained in Synthesis Example 1 (23 g as (Y2-1)), and 1,250 g of water Were mixed to prepare a reducing agent solution.

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

Next, ion-exchanged water is added to the aqueous dispersion of the silver nanoparticle-containing composite having a nonvolatile content of 36.7% by mass obtained above, and the content of the silver nanoparticle-containing composite in the aqueous dispersion is 0.5 g. / L to obtain a silver nanoparticle aqueous dispersion.

[Pretreatment of copper substrate]
The copper clad epoxy plate was taken out by being immersed in an aqueous solution of sodium peroxodisulfate (concentration 100 g / L) for 2 minutes and washed with running water for 2 minutes. Next, the copper substrate surface was pretreated by immersing it in a sulfuric acid aqueous solution (concentrated sulfuric acid 100 mL / L) for 2 minutes and washing it with running water for 2 minutes.

[Pretreatment of steel substrate]
The surface of the cold rolled steel sheet (SPCC-SD) was wiped with 2-propanol to sufficiently remove the oil on the surface. Next, the steel substrate surface was pretreated by immersing it in a sulfuric acid aqueous solution (concentrated sulfuric acid 100 mL / L) for 10 seconds and washing it with running water for 1 minute.

Example 1
The silver nanoparticle aqueous dispersion (0.5 g / L) obtained in Preparation Example 1 is mixed with trisodium citrate (10 g / L) to prepare an aqueous dispersion of silver nanoparticles, and pseudo impurities As a result, copper sulfate pentahydrate was further added (0.01 g / L). The copper base material subjected to the above pretreatment was taken out of this aqueous dispersion by being immersed at room temperature (25 ° C.) for 10 minutes, washed with running water for 2 minutes, and then dried. When the treated copper-clad epoxy substrate surface was visually observed, no black spots due to corrosion were observed on the copper foil surface of the substrate (see FIG. 1). Moreover, when the copper foil surface was observed with the scanning electron microscope (SEM), a mode that the silver nanoparticle adhered to the copper surface of a base material was observed (refer FIG. 2, a scale bar is 100 nm).

(Example 2)
A silver nanoparticle aqueous dispersion (5 g / L) obtained in Preparation Example 1 is mixed with sodium potassium tartrate (5 g / L) to prepare an aqueous dispersion of silver nanoparticles, and a pseudo storage environment As a change, this aqueous dispersion was heated at 50 ° C. for 3 days and then allowed to cool to room temperature (25 ° C.). Next, the copper base material obtained by the above pretreatment was immersed in a heated aqueous dispersion for 10 minutes at room temperature (25 ° C.), washed with running water for 2 minutes, and then dried. When the immersion-treated substrate surface was visually observed, no black spots due to corrosion were observed on the substrate copper foil surface.

(Example 3)
The silver nanoparticle aqueous dispersion (0.5 g / L) obtained in Preparation Example 1 was heated at 50 ° C. for 3 days as a pseudo storage environment change, and then disodium succinate (10 g / L) was added. In addition, an aqueous dispersion of silver nanoparticles was obtained. Next, the copper base material that had been subjected to the above pretreatment was taken out of this dispersion by being immersed for 10 minutes at room temperature (25 ° C.), washed with running water for 2 minutes, and then dried. When the immersion-treated substrate surface was visually observed, no black spots due to corrosion were observed on the copper surface of the substrate.

Example 4
A silver nanoparticle aqueous dispersion (5 g / L) obtained in Preparation Example 1 is mixed with sodium potassium tartrate (5 g / L) to prepare an aqueous dispersion of silver nanoparticles, and a pseudo storage environment As a change, the mixture was heated at 50 ° C. for 3 days and then allowed to cool to room temperature (25 ° C.). Next, the steel substrate that had been subjected to the above pretreatment was immersed in a heated dispersion for 10 minutes at room temperature (25 ° C.), taken out, washed with running water for 1 minute, and then dried. When the immersion-treated steel surface was visually observed, no change was visually confirmed on the steel surface of the base material (see FIG. 5). Moreover, when the steel material surface was observed with the scanning electron microscope (SEM), unevenness | corrugations other than the physical crack and crack considered to have generate | occur | produced at the time of steel plate manufacture were not recognized (refer FIG. 6, a scale bar is 500 nm).

(Comparative Example 1)
The copper substrate subjected to the above pretreatment was taken out by immersing it in the silver nanoparticle aqueous dispersion (0.5 g / L) obtained in Preparation Example 10 for 10 minutes, washed with running water for 2 minutes, and then dried. . When the immersion-treated substrate surface was visually observed, no black spots due to corrosion were observed on the copper surface of the substrate.

(Comparative Example 2)
A bath obtained by adding copper sulfate pentahydrate (0.01 g / L) to the silver nanoparticle aqueous dispersion (0.5 g / L) obtained in Preparation Example 1 for the copper base material subjected to the above pretreatment. The sample was immersed for 10 minutes at room temperature (25 ° C.), taken out, washed with running water for 2 minutes, and then dried. When the surface of the base material subjected to the immersion treatment was visually observed, many black spots were confirmed on the copper surface of the substrate (see FIG. 2). When the black spot portion was observed with an SEM, it was observed that nanoscale grooves and holes were generated in the copper of the base material (see FIG. 4, scale bar is 100 nm). It was confirmed that black spots due to corrosion occur on the copper surface by adding copper sulfate, which is a pseudo impurity.

(Comparative Example 3)
The silver nanoparticle aqueous dispersion (0.5 g / L) obtained in Preparation Example 1 was heated at 50 ° C. for 3 days and then cooled to room temperature (25 ° C.).

Next, the pretreated copper base material is taken out by being immersed in a heated silver nanoparticle aqueous dispersion (0.5 g / L) at room temperature (25 ° C.) for 10 minutes and washed with running water for 2 minutes. And then dried. When the surface of the base material subjected to the immersion treatment was visually observed, many black spots due to corrosion were confirmed on the copper surface of the substrate.

(Comparative Example 4)
The silver nanoparticle aqueous dispersion (0.5 g / L) obtained in Preparation Example 1 was previously heated at 50 ° C. for 3 days and then cooled to room temperature (25 ° C.). Next, the steel substrate subjected to the above pretreatment was taken out by being immersed in a bath of a heated solution at room temperature (25 ° C.) for 10 minutes, washed with running water for 1 minute, and then dried. When the surface of the base material subjected to the immersion treatment was visually observed, many brown spots due to corrosion were confirmed on the steel surface of the base material (see FIG. 7). When the brown spot portion was observed with a scanning electron microscope (SEM), it was observed that fine irregularities of nanoscale were generated on the steel of the base material (see FIG. 8, scale bar is 500 nm).

The results of Examples 1 to 4 and Comparative Examples 1 to 4 are summarized in Table 1. From this result, the following could be confirmed.

[Supplement under rule 26 12.05.2017]

Although copper sulfate, which is a pseudo impurity, promotes the formation of black spots due to corrosion (contrast with Comparative Example 1 and Comparative Example 2), the metal nanoparticle water of the present invention to which trisodium citrate is added In spite of the addition of copper sulfate, the dispersion (Example 1) did not produce black spots on the surface of the metal substrate immersed in the dispersion, and did not cause poor appearance due to corrosion or coloring.

In addition, the metal nanoparticle aqueous dispersions of the present invention in Examples 2, 3 and 4 were obtained even though the silver nanoparticle aqueous dispersion was heat-treated in order to simulate the temporal change of the storage environment. In addition, no black spots were formed on the surface of the metal substrate immersed in the dispersion, and appearance defects due to corrosion or coloring did not occur.

On the other hand, Comparative Examples 3 and 4 are examples in which the compound (Z) used in the present invention was not used. However, spotted coloring due to corrosion occurred on the surface of the metal substrate immersed in the dispersion, resulting in poor appearance. It was.

Claims

A complex of metal nanoparticles (X) and an organic compound (Y), lactic acid, glycolic acid, malonic acid, succinic acid, fumaric acid, maleic acid, malic acid, tartaric acid, oxalic acid, citric acid and carboxylic acids thereof An aqueous metal nanoparticle dispersion comprising one or more compounds (Z) selected from the group consisting of alkali metal salts.
The metal nanoparticle aqueous dispersion according to claim 1, wherein the organic compound (Y) is an organic compound (Y1) having an anionic functional group.
The organic compound (Y1) having an anionic functional group is one or more anionic functional groups selected from the group consisting of a carboxy group, a phosphoric acid group, a phosphorous acid group, a sulfonic acid group, a sulfinic acid group, and a sulfenic acid group. The metal nanoparticle aqueous dispersion according to claim 2, which is a polymer (Y2) of a monomer mixture (I) containing a (meth) acrylic acid-based monomer having a group.
The metal nanoparticle aqueous dispersion according to claim 3, wherein the monomer mixture (I) contains a (meth) acrylic acid monomer having a polyethylene glycol chain having an average unit number of ethylene glycol of 20 or more.
The metal nanoparticle aqueous dispersion according to claim 3 or 4, wherein the polymer (Y2) has a weight average molecular weight in the range of 3,000 to 20,000.
The metal nanoparticle aqueous dispersion according to any one of claims 1 to 5, wherein the metal species of the metal nanoparticles (X) is silver, copper, or palladium.
The metal nanoparticle aqueous dispersion according to any one of claims 1 to 6, wherein an average particle diameter determined from a transmission electron micrograph of the metal nanoparticles (X) is in the range of 0.5 to 100 nm.