JP5399100B2 - Metal colloidal particle aggregate and method for producing the same - Google Patents

Description

  The present invention relates to an aggregate of metal colloidal particles including metal nanoparticles (such as silver nanoparticles), a production method thereof, and a metal nanoparticle paste including the aggregate.

  Metal nanoparticles (or metal colloid particles) are known to have physical properties such as nonlinear optical properties and properties different from those of bulk and metal atoms, and can be applied to various fields such as electrical and communication fields. Is expected. A liquid phase method is known as one method for producing metal nanoparticles. The liquid phase method is a method in which a metal compound is reduced in a solution in the presence of a compound (or dispersant) that can be a protective colloid of the metal compound, and is simple and suitable for mass production. .

  As a technique for preparing a metal colloid solution by a production method using a liquid phase method, Japanese Patent No. 3594803 (Patent Document 1) is prepared by dissolving a noble metal or copper compound in a solvent and adding a high molecular weight pigment dispersant. Thereafter, a method for producing a colloidal solution of noble metal or copper that is reduced to noble metal or copper by further adding an amine is disclosed. In this document, the aim is to prepare a coating composition with high saturation and colorability by utilizing the coloration of metal colloidal particles such as gold and silver by plasmon resonance. The resulting colloidal solution (hydrosol or organosol) is It produces vivid colors of red and yellow, and is extremely stable with no color change or precipitation even after storage for 3 months. Furthermore, even when a resin is added to this solution to prepare a coating material to form a coating film, the above-mentioned coloring can be realized in the coating film. In particular, this document describes that in order to maintain such dispersion stability, the content and blending amount of the high molecular weight pigment dispersant is 50 to 1000 parts by weight with respect to 100 parts by weight of noble metal or copper. Has been.

  However, since this metal colloid solution has high dispersion stability, in order to take out the metal colloid particles from the solution, a precise refining operation such as ultrafiltration is required, and the productivity is low. Furthermore, this document denies the aggregation of nano-sized metal colloidal particles for the purpose of color development by plasmon resonance.

  On the other hand, as a technique for forming a conductive film using a metal colloid solution, Japanese Patent Application Laid-Open No. 2007-301461 (Patent Document 2) describes metal colloid particles, a high molecular weight pigment dispersant having a number average molecular weight of 7000 to 500,000, and Step (1) for producing a solution containing a low molecular weight pigment dispersant having a number average molecular weight of 180 to 5,000, and all or part of the low molecular weight pigment dispersant in the solution produced in the step (1) is removed. The manufacturing method of the metal colloid solution including process (2) is disclosed. In this document, while maintaining the dispersion stability of the colloidal solution, the amount of the high molecular weight pigment dispersant used to reduce the amount of the high molecular weight pigment dispersant to improve the metal concentration in the solid content. It is described that it is 1-150 mass parts (solid content mass ratio) with respect to 100 mass parts of metal mass in the inside. Examples of the low molecular weight pigment dispersant include a copolymer containing a hydrophobic part composed of acrylic units and hydrocarbons and a hydrophilic part composed of polyoxyethylene units. On the other hand, it is described that high molecular weight pigment dispersant / low molecular weight pigment dispersant = 1/20 to 10/1 (mass ratio). In the examples of this document, a large amount of a low molecular weight pigment dispersant not in the above range is used. Furthermore, in step (2), it is described that residual dispersants, miscellaneous ions, salts, and amines that adversely affect the stability of the metal colloid solution are removed by ultrafiltration.

  However, this method also has low productivity because it is necessary to purify surplus components containing a low molecular weight pigment dispersant by ultrafiltration. Further, in an example in which about 16 parts by mass of the high molecular weight dispersant is used with respect to 100 parts by mass of silver without using the low molecular weight pigment dispersant, it is described that silver is aggregated and precipitated. Further, in the example in which the high molecular weight dispersant is used in an amount of about 19 parts by mass with respect to 100 parts by mass of silver without using the low molecular weight pigment dispersant, the colloidal silver particles are dispersed, but the resulting coating has low conductivity. It is described.

  Further, in Japanese Patent No. 4070741 (Patent Document 3), a noble metal or copper compound is dissolved in a solvent, a high molecular weight pigment dispersant is added, and then the noble metal or copper is reduced to the high molecular weight pigment dispersant. A method for producing a solid sol of noble metal or copper that forms a solid sol by forming colloidal particles of noble metal or copper protected with, and then removing the solvent is disclosed. Also in this document, in order to prevent aggregation even when a solid sol is added to a paint or resin, the content of the high molecular weight pigment dispersant is 20 to 1000 parts by weight with respect to 100 parts by weight of noble metal or copper. It is described that it is.

  However, the solid sol obtained by this method is a precipitate that can be easily redispersed in a good solvent and exhibits plasmon absorption and does not have an appropriate cohesive force. A highly conductive sintered film cannot be formed.

Japanese Patent No. 3594803 (Claim 1, paragraphs [0012] [0037] [0047], Examples) JP 2007-301461 A (claims, paragraphs [0049] [0091], examples) Japanese Patent No. 4070741 (claims, paragraphs [0009] and [0034])

  Accordingly, an object of the present invention is to provide a metal colloidal particle aggregate containing metal nanoparticles, which can form a dense hard film with high conductivity, by a simple method, a method for producing the same, and a metal nanoparticle paste. .

  Another object of the present invention is to provide a metal colloidal particle aggregate capable of efficiently forming a sintered layer or a sintered pattern having high conductivity even at a low temperature (particularly a low temperature of about 150 ° C. or less), a method for producing the same, and a method for producing the same It is to provide a metal nanoparticle paste.

  Still another object of the present invention is to provide a metal colloidal particle aggregate capable of firmly bonding an inorganic material such as a metal even when fired at a low temperature and a low pressure, a method for producing the same, and a metal nanoparticle paste.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors reduced the metal compound in the presence of a specific agglomeration aid and / or its precursor and a polymer dispersant to produce metal nanoparticles. In the liquid phase, the colloidal metal particles can be easily prepared as aggregates, and the aggregates are moderately aggregated with nanometer-sized metal particles. The present invention has been completed.

  That is, the metal colloid particle aggregate of the present invention is an aggregate of metal colloid particles composed of metal nanoparticles (A) and a dispersant (B), and the dispersant (B) contains nitrogen atoms. A coagulation aid (B1) having at least one functional group selected from the group consisting of a group having a hydroxyl group and a carboxyl group, and a polymer dispersant (B2). The ratio of the dispersing agent (B) is about 1 to 10 parts by weight with respect to 100 parts by weight of the metal nanoparticles (A), and the coagulant aid (B1), the polymer dispersing agent (B2), The former / the latter may be about 90/10 to 1/99. The aggregation assistant (B1) may have about 1 to 10 carbon atoms.

  In the present invention, the coagulation assistant (B1) and / or precursor thereof having at least one functional group selected from the group consisting of a group having a nitrogen atom, a hydroxyl group and a carboxyl group, and a polymer dispersant (B2). ) In the presence of a metal compound in a solvent to produce metal colloidal particles, and to produce aggregates of metal colloidal particles as precipitates, and separate and collect the aggregates produced in this step Also included is a method for producing the agglomerates comprising steps. In this method, the aggregation assistant (B1) and / or its precursor may be used as a reducing agent. Further, after removing the supernatant from the reaction solution and collecting it, the aggregate may be purified by washing with a washing solvent, and the aggregate may be further purified by filtration.

  The present invention also includes a metal nanoparticle paste composed of an aggregate of the metal colloid particles and an organic solvent. The metal nanoparticle paste of the present invention may further contain a metal filler having a volume average particle diameter of 0.2 to 10 μm. The present invention also includes a method for producing a conductive substrate including a step of forming a film with the metal nanoparticle paste on the substrate, and a step of baking the film. Furthermore, the metal nanoparticle paste of the present invention may be a bonding agent for inorganic materials.

  In the present invention, by using metal colloidal particles obtained by a liquid phase method utilizing reduction treatment as an aggregate, a highly conductive and dense hard film can be formed by a simple method. In addition, the metal nanoparticle paste containing this aggregate can be fired at a low temperature and can be used for various applications, for example, it can efficiently form a sintered layer or a sintered pattern having high conductivity, a metal, etc. Inorganic materials can be firmly joined.

[Aggregates of colloidal metal particles]
The aggregate of metal colloidal particles of the present invention is an aggregate of metal colloidal particles composed of metal nanoparticles (A) and a dispersant (B).

(A) Metal nanoparticle The metal (metal atom) constituting the metal nanoparticle (A) is, for example, a transition metal (for example, a periodic table group 4A metal such as titanium or zirconium; a periodic table such as vanadium or niobium). Periodic Table Group 6A metals such as molybdenum and tungsten; Group 7A Metals such as manganese; Periodic Table Group 8 such as iron, nickel, cobalt, ruthenium, rhodium, palladium, rhenium, iridium and platinum Metal; periodic table group 1B metals such as copper, silver, gold), periodic table group 2B metals (for example, zinc, cadmium, etc.), periodic table group 3B metals (for example, aluminum, gallium, indium, etc.), Examples include Periodic Table Group 4B metals (eg, germanium, tin, lead, etc.), Periodic Table Group 5B metals (eg, antimony, bismuth, etc.), and the like. It is done. Metals are periodic group 8 metal (iron, nickel, rhodium, palladium, platinum, etc.), periodic table group 1B metal (copper, silver, gold, etc.), periodic table group 3B metal (aluminum, etc.) and periodic table. It may be a Group 4B metal (such as tin). In many cases, the metal (metal atom) is a metal having a high coordination property to the dispersant (B), for example, a Group 8 metal of the periodic table, a Group 1B metal of the periodic table, or the like.

  The metal nanoparticles (A) may be the metal simple substance, the metal alloy, metal oxide, metal hydroxide, metal sulfide, metal carbide, metal nitride, metal boride and the like. These metal nanoparticles (A) can be used alone or in combination of two or more. In many cases, the metal nanoparticles (A) are usually single metal particles or metal alloy particles. Among them, the metal constituting the metal nanoparticles (A) is a metal (metal simple substance and metal alloy) including at least a noble metal such as silver (especially Group 1B metal of the periodic table), particularly a noble metal simple substance (for example, silver simple substance). Is preferred.

  The metal nanoparticles (A) are nanometer size. For example, the number average particle diameter (average primary particle diameter) of the metal nanoparticles (A) in the metal colloid particles of the present invention is 1 to 100 nm, preferably 1.5 to 80 nm, more preferably 2 to 70 nm, particularly 3 to 3. About 50 nm may be sufficient and it may be about 1-40 nm (for example, 2-30 nm) normally.

  Further, the metal colloid particles of the present invention may contain almost no coarse particles. Therefore, the maximum primary particle diameter of the metal nanoparticles (A) is, for example, 200 nm or less, preferably 150 nm or less, and more preferably 100 nm or less. Furthermore, in the metal nanoparticles (A) (or metal colloid particles), the proportion of particles having a primary particle diameter of 100 nm or more is, for example, 10% by mass or less (for example, 0 to 0%) based on the mass of the metal (or metal component). 8 mass%), preferably 5 mass% or less (for example, 0.01 to 3 mass%), more preferably 1 mass% or less (for example, about 0.02 to 0.5 mass%). .

  In addition, the particle diameter of the metal colloid particles is also generally the same as the particle diameter of the metal nanoparticles (A).

(B) Dispersant The dispersant (B) may cover the surface of the metal nanoparticle, and has a coagulation aid (B1) having a functional group having affinity or bondability with the surface of the metal nanoparticle. And a polymer dispersant (B2).

(B1) Aggregation aid (low molecular aggregation aid)
The aggregation aid (B1) is a component that acts on the metal nanoparticles to control the dispersibility of the colloidal particles by the polymer dispersant described later in the solvent, for example, a low molecular organic compound, and the metal nanoparticles. Any component may be used as long as it has a physical or chemical affinity for or has a site capable of binding (chemical bond such as hydrogen bond, ionic bond, and coordinate bond). In particular, in order to moderately promote the aggregation of colloidal particles while suppressing the growth of metal nanoparticles (increase in particle size) in a solvent, a low molecular organic compound is coordinated on the surface of the metal nanoparticles. Are preferably combined. Therefore, it can also be said that a preferred aggregation assistant is an affinity compound or a coordinating compound that coordinates to metal nanoparticles.

  The aggregation assistant (B1) usually has a functional group (or an affinity group for a metal atom) that can be coordinated to the metal nanoparticles. Such a functional group may be a group having a halogen atom, but is usually a hetero atom (nitrogen atom, oxygen atom, sulfur atom, phosphorus atom, etc.), typically a nitrogen atom, oxygen atom. And a group (functional group) having at least one heteroatom selected from sulfur atoms. The functional group may have the same or different hetero atoms. The functional group may form a salt (an alkali metal salt such as a sodium salt or an ammonium salt).

  In this specification, “coordinable” and “coordinating” mean that an electron can be donated to a metal, and it is not always necessary to actually coordinate to a metal atom. Therefore, the “coordinating compound” may be a compound that can donate electrons (or has an electron-donating group), and may not be coordinated to a metal.

Specific functional groups include groups having a nitrogen atom [amino group, substituted amino group (dialkylamino group etc.), imino group (—NH—), amide group (—CON <), cyano group, nitro group, nitrogen Ring groups (5- to 8-membered nitrogen ring groups such as pyridyl groups, carbazole groups, morpholinyl groups, etc.)], oxygen-containing groups [hydroxyl groups, ether groups, carboxyl groups, alkoxy groups (for example, methoxy groups, ethoxy groups) , C _1-6 alkoxy groups such as propoxy group and butoxy group), formyl group, carbonyl group (—CO—), ester group (—COO—), oxygen ring group (tetrahydropyranyl group and other 5- to 8-membered oxygen Ring group, etc.], a group having a sulfur atom [e.g., thio group (-S-), thiol group (-SH), thiocarbonyl group (-SO-), alkylthio group (methylthio). And C _1-4 alkylthio groups such as an ethyl group and an ethylthio group), a sulfo group, a sulfamoyl group, a sulfinyl group (—SO ₂ —) and the like], and a group forming these salts.

  Among such aggregating aids having functional groups, the aggregating aid for coating the metal nanoparticles has at least one functional group selected from the group consisting of a group having a nitrogen atom, a hydroxyl group and a carboxyl group. Compounds are preferred. Such compounds include amines, amides, hydroxy compounds, carboxylic acids and the like.

(Amines)
Amines include monoamines and polyamines, and are further classified into primary to tertiary amines.

Among the monoamines, primary amines include, for example, monoalkylamines [for example, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine (n-octylamine, 2- such as hexylamine to ethyl), nonyl, etc. C _1-10 alkylamines such as decylamine, alkanolamine [e.g., monoethanolamine (2-aminoethyl alcohol), mono-propanolamine, monoisopropanolamine, butanol amine, hexanol amine, 2-amino-2-methyl-1-propanol, 2-amino-2-methyl-1,3-propanediol _{mono-C 2-6} alkanolamines or their ethylene oxide adducts, such as, etc.], cyclo Rukiruamin compound (such as cyclopentylamine, _{C 4-10} cycloalkyl amines, such as cyclohexylamine), arylamines (e.g., aniline, toluidine, anisidine, phenetidine, _{C 6-10} aryl amines such as amino naphthalene), aralkyl amines (For example, benzylamine and the like).

Secondary amines include, for example, dialkylamines (eg, diC _1-10 alkylamines such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine), alkylalkanolamines (eg, N- such as N-C _1-3 alkyl mono- C _2-6 alkanolamines or their ethylene oxide adducts, such as methyl ethanolamine), di-alkanolamines (e.g., diethanolamine, di-propanolamine, di-and di-isopropanolamine C _{2- 6} alkanolamines or their ethylene oxide adducts), alkylcycloalkylamines (eg, methylcyclohexylamine), alkylarylamines (eg, N-methylaniline), alkyl Examples thereof include aralkylamines (for example, N-methylbenzylamine), cyclic amines (for example, 5- to 8-membered cyclic amines such as pyrrolidine, piperidine, hexamethyleneimine, morpholine).

Examples of the tertiary amine include trialkylamines (for example, tri-C _1-10 alkylamines such as dimethylethylamine, diethylmethylamine, triethylamine, and tripropylamine), alkylalkanolamines [for example, N-methyl Di-C _1-3 alkyl mono-C such as N-C _1-3 alkyl di-C _2-10 alkanolamine such as diethanolamine or these ethylene oxide adducts, N, N-dimethylethanolamine (dimethylaminoethanol), dimethylaminopropanol _2-10 alkanolamine or an ethylene oxide adduct, trialkanolamine (e.g., triethanolamine, tripropanolamine, tri C _2-10 alkanol such as triisopropanolamine Diamines or their ethylene oxide adducts), cycloalkyldialkylamines (eg, cyclohexyldimethylamine), dialkylarylamines (eg, N, N-dimethylaniline), dialkylaralkylamines (eg, N, N). N-dimethylbenzylamine), cyclic amines (for example, 5- to 8-membered cyclic amines such as pyridine, picoline, quinoline, N-methylpyrrolidine, N-methylpiperidine, 1,8-diazabicyclo [5.4.0]) Undecene-1, etc.).

Examples of polyamines include polyamines corresponding to the monoamines such as chain primary polyamines [eg, alkane diamines (C _2-10 alkane diamine such as ethylene diamine, propylene diamine, tetramethylene diamine, hexamethylene diamine, etc. ), Polyalkylene polyamines (or polyalkylene imines such as poly C _2-4 alkylene polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine), alkanolamines (2- (3-aminopropylamino) ethanol, etc.) Etc.], chain secondary polyamines (eg, alkaneamines such as N, N′-dimethylethylenediamine, N, N′-dimethyl-1,3-diaminopropane, etc.), chain tertiary polyamines (eg, , N, N ′, N′-tetramethylethylenediamine, alkaneamines such as N, N, N ′, N′-tetramethyl-1,3-diaminopropane), aromatic primary polyamines (for example, xylylene diene) Amine), aromatic secondary polyamine (eg, N, N′-dimethylxylylenediamine, etc.), aromatic tertiary polyamine (eg, N, N, N ′, N′-tetramethylxylylenediamine, etc.) ), Heterocyclic secondary polyamines (eg, piperazine, 1,4,8,11-tetraazacyclotetradecane, triethylenediamine, etc.), heterocyclic tertiary polyamines (pyrimidine, N, N′-dimethylpiperazine, etc.) ) And the like.

These amines may be used alone or in combination of two or more. Among these amines, C _1-10 alkylamine (eg, methylamine, ethylamine, propylamine, octylamine), mono C _2-4 alkanolamine (eg, monoethanolamine), diC _1-3 Alkylamine (eg, dimethylamine, diethylamine, etc.), N—C _1-3 alkylmono C _2-6 alkanolamine (eg, N-methylethanolamine, etc.), diC _2-4 alkanolamine (eg, diethanolamine, etc.) , Tri C _1-3 alkylamine (eg, dimethylethylamine, diethylmethylamine, triethylamine, etc.), N—C _1-3 alkyl diC _2-6 alkanolamine (eg, N-methyldiethanolamine, etc.), diC _1-3 alkyl _{mono-C 2-6} alkanol Triethanolamine (e.g., N, N-dimethylethanolamine, etc.) are preferred. Furthermore, among these amines, hydrophilic or water-soluble amines are particularly preferable.

(Amides)
The amides, such as formamide, acetamide, amide propionic acid, butyric acid amide, _{C 1-10} acyl amides, such as caprylic acid amide, N- methylformamide, N- methylacetamide, N- methylpropionic acid amide, N- methyl Butyric acid amide, N-methylcaprylic acid amide, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylpropionic acid amide, N, N-dimethylbutyric acid amide, N, N-dimethylcaprylic acid amide, etc. Mono- or di-C _1-4 alkyl C _1-10 acylamides, oxalic acid amide, malonamide, succinic acid amide, glutaric acid amide, adipic acid amide, pimelic acid amide, corkic acid amide, azelaic acid amide, sebacic acid amide, _{C 2-1,} such as dodecanedioic acid amide ₀ aliphatic dicarboxylic acid amide and the like.

These amides can be used alone or in combination of two or more. Among these amides, _C1-4 acylamides such as acetamide and propionic acid amide, N-methylformamide, N-methylacetamide, N-methylpropionic acid amide, N, N-dimethylformamide, N, N-dimethylacetamide Mono or di C _1-2 alkyl C _1-4 acylamides are preferred. Furthermore, among these amides, hydrophilic or water-soluble amides are particularly preferable.

(Hydroxy compound)
Examples of the hydroxy compound include alkanols (for example, C _1-20 alkane monools such as methanol, ethanol, isopropanol, butanol, pentanol, hexanol, octanol, decanol, dodecanol, octadecanol, etc.), cycloalkanols (for example, , Cyclohexanol, etc.), alkanediols (eg, C _2-6 alkanediols such as ethylene glycol, propylene glycol, butanediol), polyalkylene glycols (eg, diethylene glycol, dipropylene glycol, triethylene glycol, polyethylene glycol) and poly C _2-4 alkylene glycol), such as, aralkyl alcohols (e.g., benzyl alcohol), polyhydric alcohols (e.g. If, glycerin, polyglycerin, etc.) and the like.

These hydroxy compounds can be used alone or in combination of two or more. Of these hydroxy compounds, C _1-4 alkanol (eg, methanol, ethanol, etc.), C _2-4 alkanediol (eg, ethylene glycol, etc.), glycerin and the like are preferable. Furthermore, among these hydroxy compounds, hydrophilic or water-soluble hydroxy compounds are particularly preferable.

(Carboxylic acids)
Examples of the carboxylic acids include monocarboxylic acids, polycarboxylic acids, hydroxycarboxylic acids (or oxycarboxylic acids), phenolic hydroxyl groups, and carboxylic acids having aminocarboxylic acids.

Examples of monocarboxylic acids include aliphatic monocarboxylic acids [saturated aliphatic monocarboxylic acids (eg, formic acid, acetic acid, propionic acid, butyric acid, caprylic acid, caproic acid, hexanoic acid, capric acid, lauric acid, myristic acid, C _1-34 aliphatic monocarboxylic acid such as stearic acid, cyclohexanecarboxylic acid, dehydrocholic acid, colanic acid, preferably _C1-30 aliphatic monocarboxylic acid), unsaturated aliphatic monocarboxylic acid (for example, olein) _C4-34 unsaturated aliphatic carboxylic acid such as acid, erucic acid, linoleic acid, and abietic acid, preferably _C10-30 unsaturated aliphatic carboxylic acid)], aromatic monocarboxylic acid (benzoic acid, naphthoic acid, etc.) C _7-12 aromatic monocarboxylic acid, etc.).

Examples of polycarboxylic acids include aliphatic polycarboxylic acids [for example, aliphatic saturated polycarboxylic acids (for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, cyclohexanedicarboxylic acid, etc. C _2-14 aliphatic saturated polycarboxylic acid, preferably C _2-10 aliphatic saturated polycarboxylic acid, etc., aliphatic unsaturated polycarboxylic acid (eg maleic acid, fumaric acid, itaconic acid, sorbic acid, tetrahydro C _4-14 aliphatic unsaturated polycarboxylic acid such as phthalic acid, preferably C _4-10 aliphatic unsaturated polycarboxylic acid etc.], aromatic polycarboxylic acid (eg phthalic acid, trimellitic acid etc.) C _8-12 aromatic polycarboxylic acid and the like).

Hydroxycarboxylic acids include hydroxymonocarboxylic acids [aliphatic hydroxymonocarboxylic acids (eg, glycolic acid, lactic acid, oxybutyric acid, glyceric acid, 6-hydroxyhexanoic acid, cholic acid, deoxycholic acid, chenodeoxycholic acid, 12-oxo C _2-50 aliphatic hydroxymonocarboxylic acids, preferably C _2-34 aliphatic hydroxymonocarboxylic acids such as chenodeoxycholic acid, glycocholic acid, lithocholic acid, hyodeoxycholic acid, ursodeoxycholic acid, apocholic acid, taurocholic acid More preferably, C _2-30 aliphatic hydroxy monocarboxylic acid, etc.), aromatic hydroxy monocarboxylic acid (eg, C _7-12 aromatic hydroxy monocarboxylic acid such as salicylic acid, oxybenzoic acid, gallic acid, etc.)], hydroxy Polica Rubonic acid [aliphatic hydroxypolycarboxylic acid (for example, C _2-10 aliphatic hydroxypolycarboxylic acid such as tartronic acid, tartaric acid, citric acid, malic acid and the like)] and the like.

  Examples of the carboxylic acid having a phenolic hydroxyl group include salicylic acid, oxybenzoic acid, protocatechuic acid, gentisic acid, resorcinic acid, orthoric acid, caffeic acid, umperic acid, gallic acid, oxyphthalic acid, and tannic acid.

The amino acids, e.g., glycine, alanine, valine, leucine, amino heptanoic acid, _{C 2-10} aminocarboxylic acids such as aminononanoic acid, N- methylamino acid, N, N- dimethylamino acetate, N, N- _Examples thereof include C _1-4 alkyl C _2-10 aminocarboxylic acids such as dimethylaminopropionic acid and N, N-dimethylaminobutyric acid.

  These carboxylic acids may form a salt, and may be anhydrides, hydrates, and the like. As described above, the carboxylic acid often does not form a salt (in particular, a salt with a basic compound such as a salt with an amine).

These carboxylic acids may be used alone or in combination of two or more. Among these carboxylic acids, C _1-24 saturated aliphatic monocarboxylic acid (eg, acetic acid, propionic acid, stearic acid, etc.), C _4-24 unsaturated aliphatic monocarboxylic acid (eg, linoleic acid, oleic acid, etc.) ), C _10-34 condensed polycyclic aliphatic hydroxycarboxylic acid (eg, cholic acid), C _10-34 condensed polycyclic aliphatic carboxylic acid (eg, dehydrocholic acid, colanic acid, etc.), C _{2− 10} aliphatic hydroxy monocarboxylic acids (eg, glycolic acid, lactic acid, oxybutyric acid, etc.), C _2-10 aliphatic hydroxy polycarboxylic acids (eg, tartaric acid, citric acid, malic acid, etc.), C _2-6 aminocarboxylic acid (e.g., glycine, _{alanine), C 1-4} alkyl _{C 2-6} amino acids (e.g., N, N-dimethylamino acetate, N, N Dimethylamino such acid) and the like are preferable. Furthermore, among these carboxylic acids, hydrophilic or water-soluble carboxylic acids are particularly preferable.

  The molecular weight of the aggregation aid (B1) is, for example, 1000 or less (for example, about 46 to 900), preferably 800 or less (for example, about 50 to 500), and more preferably 300 or less (for example, about 55 to 200). There may be.

  Further, the pKa value of the aggregation aid (B1) may be, for example, about 1 or more (for example, about 1 to 10), preferably about 2 or more (for example, about 2 to 8).

The aggregation assistant (B1) may be not only the same type of compound but also a combination of different types of compounds. However, since the carboxyl group of the carboxylic acid has a high affinity with the metal nanoparticles, it contains at least a carboxylic acid. Is preferred. Carboxylic acids may be used alone or as other agglomeration aids such as amines (for example, C _1-10 alkylamines such as dimethylamine and octylamine, N-methyldiethanolamine and N, N-dimethylethanolamine). C _1-3 alkyl C _2-6 alkanol tertiary amine, etc.), amides (eg, N, N-dimethylformamide, etc.), hydroxy compounds (eg, C _1-4 alkanols such as ethanol, etc.) and the like A combination of these may be used.

  Further, the agglomeration aid (B1) is a carbon material because the produced colloidal particles are aggregated in a solvent in the production process of the colloidal particles and can be decomposed at a low temperature to form a sintered site in the formation of the sintered film. The number is preferably 1 to 18, preferably 1 to 10, more preferably about 1 to 6 (particularly 1 to 4). Such an agglomeration aid can be desorbed or disappeared from the metal particles at the firing temperature to improve the continuity and conductivity of the metal film by forming sintered sites.

Specifically, from the point of high affinity with the surface of the metal nanoparticles, excellent cohesiveness and sinterability, carboxylic acids having the above carbon number, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, etc. C _1-10 alkanoic acid (alkanecarboxylic acid) of C _1-6 alkanoic acid such as acetic acid and propionic acid (preferably C _1-4 alkanoic acid, more preferably C _2-3 alkanoic acid, especially acetic acid) Is more preferable. In particular, when a _C1-4 alkanoic acid such as acetic acid is used, the generation of cracks and voids during combustion is suppressed because the metal colloidal particles are appropriately aggregated, and a dense and hard fired film can be formed.

  The boiling point of the aggregation aid (B1) is preferably 200 ° C. or less, for example, 80 to 180 ° C., preferably 90 to 170 ° C., more preferably 100 to 150 ° C. (particularly 110 to 130 ° C.). Also good.

(B2) Polymer Dispersant In the present invention, the dispersant (B) is constituted by combining the aggregation aid (B1) and the polymer dispersant (B2). By configuring the dispersant (B) in such a combination, metal colloidal particles containing metal nanoparticles with extremely few coarse particles can be obtained. In particular, the combination of the dispersant (B) can increase the proportion of the metal nanoparticles, and can stably produce the metal colloid particles in the reduction reaction step. Since it aggregates and precipitates, it can be easily removed from the reaction solution. The reason why such an excellent colloidal metal particle is obtained and agglomerated by the combination is not clear, but the following reasons are conceivable.

  First, the polymer dispersant (B2) is excellent in the effect of stabilizing the dispersion of relatively large particles due to its structure, but the effect of stabilizing the relatively small particles is not sufficient. When the concentration is increased, the generated particles cannot be sufficiently stabilized. On the other hand, the agglomeration aid (B1) stabilizes dispersion of relatively small particles generated in the initial synthesis stage of such nanoparticles. It is considered that the metal nanoparticles can be generated even when the raw material of the metal nanoparticles is at a high concentration by such a synergistic action of the aggregation assistant (B1) and the polymer dispersant (B2).

  Further, in the present invention, since the proportion of the dispersant (B) is relatively small, the dispersion stability of the relatively large metal colloid particles produced cannot be maintained, and the binding of the aggregation aid (B1). It is considered that the site becomes a weak point, colloidal metal particles are generated, and aggregation starts. In particular, in the present invention, although aggregation of the metal colloid particles occurs, the aggregation assistant (B1) and the polymer dispersant (B2) combined at a specific ratio appropriately coat the metal nanoparticles. The growth of the particles is moderately suppressed, and metal particles with a unit of several hundred nm are not generated. Therefore, in this invention, it can be estimated that nanometer-sized metal colloidal particles can be easily taken out as a precipitate by such an action mechanism.

  Furthermore, in the present invention, although the metal colloidal particles are aggregated, the metal particles have a nanometer size, so that a highly conductive, hard and dense sintered film can be formed by firing. In particular, cracking of the fired film and generation of voids can be suppressed because the metal colloidal particles are aggregated before firing and the nanoparticles are close to each other. That is, by the combination, an adsorption part of the polymer dispersant (B2) and an adsorption part of the aggregation aid (B1) are formed on the surface of the metal nanoparticles. The adsorbing part of the polymer dispersant (B2) is stabilized by a strong surface protection ability, whereas the adsorbing part of the coagulation aid (B1) is easily detached from the surface of the metal nanoparticle, and is subjected to low-temperature sintering. Play a role as a reaction site. Such a reaction site is protected by the action of the polymer dispersant (B2) in an atmosphere of about room temperature, but is baked between nanoparticles at a relatively low firing temperature (eg, about 50 ° C. or more). As a result, it seems that a low-resistance metal film or the like can be obtained even by low-temperature firing. In particular, the higher the firing temperature, the higher the interparticle collision and sinterability than the protective ability of the polymer dispersant, so that the conductivity is comparable to that of a bulk metal. In addition, the polymer dispersant not only has an effect of improving the adhesion to the substrate, but in the present invention, the residual amount of the polymer dispersant in the substrate can be reduced. Therefore, in the present invention, a dense and highly adhesive film with small volume shrinkage can be formed, so that these points are also excellent in adhesion to the substrate and firmly fixed to the substrate, and the conductivity of the metal film is improved. It is a possible factor.

  As the polymer dispersant (or polymer type dispersant) (B2), an amphiphilic polymer dispersant (or oligomer type dispersant) can be suitably used.

  Examples of the polymer dispersant include polymer dispersants usually used for dispersing colorants in the paint and ink fields. Such dispersants include styrene resins (styrene- (meth) acrylic acid copolymers, styrene-maleic anhydride copolymers, etc.), acrylic resins ((meth) methyl acrylate- (meth) acrylic acid). Copolymers, (meth) acrylic acid resins such as poly (meth) acrylic acid), water-soluble urethane resins, water-soluble acrylic urethane resins, water-soluble epoxy resins, water-soluble polyester resins, cellulose derivatives (nitrocellulose; Cellulose ethers such as alkyl celluloses such as ethyl cellulose, alkyl-hydroxyalkyl celluloses such as ethyl hydroxyethyl cellulose, hydroxyalkyl celluloses such as hydroxyethyl cellulose and hydroxypropyl cellulose, and carboxyalkyl celluloses such as carboxymethyl cellulose. Ters), polyvinyl alcohol, polyalkylene glycol (liquid polyethylene glycol, polypropylene glycol, etc.), natural polymer (gelatin, dextrin, arabic gum, casein, etc.), polyethylene sulfonic acid or salt thereof, polystyrene sulfonic acid or salt thereof, Formalin condensate of naphthalene sulfonic acid, nitrogen atom-containing polymer compound [for example, polymer having amino group such as polyalkyleneimine (polyethyleneimine etc.), polyvinylpyrrolidone, polyallylamine, polyether polyamine (polyoxyethylene polyamine etc.) Compound] and the like.

  As a typical polymer dispersant (amphiphilic polymer dispersant), a resin (or water-soluble resin, water-dispersible resin) containing a hydrophilic unit (or hydrophilic block) composed of a hydrophilic monomer. Is included.

  Examples of the hydrophilic monomer include carboxyl group or acid anhydride group-containing monomers ((meth) acrylic monomers such as acrylic acid and methacrylic acid, unsaturated polycarboxylic acids such as maleic acid, and maleic anhydride. Acid), hydroxyl group-containing monomers (hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, vinylphenol, etc.) and other addition polymerization monomers; condensation monomers such as alkylene oxide (ethylene oxide, etc.) Etc. can be exemplified. The condensed monomer may form a hydrophilic unit by a reaction with an active group such as a hydroxyl group (for example, the hydroxyl group-containing monomer). The hydrophilic monomers may form a hydrophilic unit alone or in combination of two or more.

The polymer dispersant only needs to contain at least a hydrophilic unit (or hydrophilic block), and may be a homopolymer or a copolymer of a hydrophilic monomer (for example, polyacrylic acid or a salt thereof). It may be a copolymer of a hydrophilic monomer and a hydrophobic monomer, such as an exemplary styrene resin or acrylic resin. Examples of hydrophobic monomers (nonionic monomers) include (meth) acrylic acid esters [methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate. , (Meth) acrylic acid lauryl, (meth) acrylic acid C _1-20 alkyl such as stearyl (meth) acrylate, (meth) acrylic acid cycloalkyl such as cyclohexyl, (meth) acrylic acid phenyl, etc. (Meth) acrylic monomers such as aryl (meth) acrylate, benzyl (meth) acrylate, aralkyl (meth) acrylate such as 2-phenylethyl (meth) acrylate, etc .; styrene, α-methylstyrene, styrenic monomers such as vinyl toluene; _{α-C 2-20} olefin (ethylene , Propylene, 1-butene, isobutylene, 1-hexene, 1-octene, 1-dodecene, etc.) olefin monomers such as, vinyl acetate, and the like carboxylic acid vinyl ester monomers such as vinyl butyrate. Hydrophobic monomers may constitute a hydrophobic unit alone or in combination of two or more.

  When the polymeric dispersant is a copolymer (eg, a copolymer of a hydrophilic monomer and a hydrophobic monomer), the copolymer can be a random copolymer, an alternating copolymer, a block copolymer (eg, a hydrophilic block composed of hydrophilic monomers). And a copolymer composed of a hydrophobic block composed of a hydrophobic monomer), a star polymer (or a star block copolymer), a comb copolymer (or a comb graft copolymer), and the like. The structure of the block copolymer is not particularly limited, and may be a diblock structure, a triblock structure (ABA type, BAB type), or the like. In the comb copolymer, the main chain may be composed of the hydrophilic block, the hydrophobic block, or the hydrophilic block and the hydrophobic block.

  As described above, the hydrophilic unit may be composed of a condensation block such as a hydrophilic block (polyalkylene oxide such as polyethylene oxide or polyethylene oxide-polypropylene oxide) composed of alkylene oxide (such as ethylene oxide). it can. The hydrophilic block (such as polyalkylene oxide) and the hydrophobic block (such as polyolefin block) may be bonded via a linking group such as an ester bond, an amide bond, an ether bond, or a urethane bond. For example, the hydrophobic block (polyolefin, etc.) is modified with a modifying agent [unsaturated carboxylic acid or its anhydride ((anhydrous) maleic acid), lactam or aminocarboxylic acid, hydroxylamine, diamine, etc.]. Later, it may be formed by introducing a hydrophilic block. In addition, a polymer obtained from a monomer having a hydrophilic group such as a hydroxyl group or a carboxyl group (such as the hydroxyalkyl (meth) acrylate) is reacted (or bonded) with the condensed hydrophilic monomer (such as ethylene oxide). By doing so, a comb-type copolymer (comb-type copolymer having a main chain composed of a hydrophobic block) may be formed.

  Furthermore, the balance between hydrophilicity and hydrophobicity may be adjusted by using a hydrophilic nonionic monomer as a copolymerization component. Examples of such components include monomers having alkyleneoxy (particularly ethyleneoxy) units such as 2- (2-methoxyethoxy) ethyl (meth) acrylate and polyethylene glycol monomethacrylate (for example, a number average molecular weight of about 200 to 1,000). An oligomer etc. can be illustrated. Further, the balance between hydrophilicity and hydrophobicity may be adjusted by modifying (for example, esterifying) a hydrophilic group (such as a carboxyl group).

  The polymer dispersant (B2) may have a functional group. Examples of such functional groups include acid groups (or acidic groups such as carboxyl groups (or acid anhydride groups) and sulfo groups (sulfonic acid groups)), basic groups (such as amino groups), A hydroxyl group etc. are mentioned. These functional groups may be contained in the polymer dispersant (B2) alone or in combination of two or more.

  Among these functional groups, the polymer dispersant (B2) preferably has an acid group or a basic group, particularly a free carboxyl group.

  Further, when the polymer dispersant (B2) has an acid group (such as a carboxyl group), at least a part or all of the acid group (such as a carboxyl group) is a salt (a salt with an amine, a metal salt, or the like). In particular, in the present invention, an acid group such as a carboxyl group (especially all carboxyl groups) is a salt [especially a salt with a basic compound (a salt with an amine or an amine salt). Etc.]] [that is, a polymer dispersant having a free acid group (particularly a carboxyl group)] can be suitably used.

  In the polymer dispersant (B2) having an acid group (particularly a free carboxyl group), the acid value is, for example, 1 mgKOH / g or more (for example, about 2 to 1500 mgKOH / g), preferably 3 mgKOH / g or more (for example, 4 to 1200 mgKOH / g), more preferably 5 mgKOH / g or more (for example, about 8 to 1000 mgKOH / g), particularly 10 mgKOH / g or more (for example, about 12 to 900 mgKOH / g). In particular, when the polymer dispersant (B2) having an acid group (particularly a carboxyl group) is a compound having a hydrophilic unit and a hydrophobic unit, the acid value is 1 mgKOH / g or more (for example, 2 to 100 mgKOH / g), preferably 3 mgKOH / g or more (for example, about 4 to 90 mgKOH / g), more preferably 5 mgKOH / g or more (for example, about 6 to 80 mgKOH / g), particularly 7 mgKOH / g or more (for example, 8 to 70 mgKOH). / G) or about 3 to 50 mg KOH / g (for example, 5 to 30 mg KOH / g). In the polymer dispersant (B2) having an acid group, the amine value may be 0 (or almost 0).

  In the polymer dispersant, the position of the functional group as described above is not particularly limited, and may be a main chain, a side chain, or a main chain and a side chain. Good. Such a functional group may be, for example, a hydrophilic monomer or a functional group derived from a hydrophilic unit (for example, a hydroxyl group), or a copolymerizable monomer having a functional group (for example, maleic anhydride). It can also be introduced into the polymer by copolymerization.

  The polymer dispersant (B2) may be used alone or in combination of two or more.

  As the polymer dispersant, a polymer dispersant (high molecular weight pigment dispersant) described in JP-A No. 11-80647 may be used.

  The polymer dispersant may be a synthesized one or a commercially available product. Specific examples of commercially available polymer dispersants (or dispersants composed of at least an amphiphilic dispersant) include Solsperse 13240, Solsperse 13940, Solsperse 32550, Solsperse 31845, Solsperse 24000, Solsperse 26000, Solsperse series such as Solsperse 27000, Solsperse 28000, Solsperse 41090 [manufactured by Avicia Co., Ltd.]; Dispersic 160, Dispersic 161, Dispersic 162, Dispersic 163, Dispersic 164, Dispersic 166, Dispersic 170, Dispers Big 180, Dispersic 182, Dispersic 184, Dispersic 190, Dispersic 191, Dispersic 92, Dispersic 193, Dispersic 194, Dispersic 2001, Dispersic 2010, Dispersic 2050, Dispersic 2090, Dispersic 2091, etc. Dispersic series [manufactured by BYK Chemie Corp.]; EFKA-46, EFKA-47, EFKA-48, EFKA-49, EFKA-1501, EFKA-1502, EFKA-4540, EFKA-4550, polymer 100, polymer 120, polymer 150, polymer 400, polymer 401, polymer 402, polymer 403, polymer 450, polymer 451 , Polymer 452, polymer 453 [manufactured by EFKA Chemical Co., Ltd.]; Ajisper PB711, Azisper PAl11, Azisper PB811, Ajisper P 821, Ajisper series such as Ajisper PW911 [manufactured by Ajinomoto Co., Inc.]; Floren DOPA-158, Floren DOPA-22, Floren DOPA-17, Floren TG-700, Floren TG-720W, Floren-730W, Floren-740W, Florene series such as Floren-745W [manufactured by Kyoeisha Chemical Co., Ltd.]; John Kuryl series such as John Kuril 678, John Kuryl 679, and John Kuryl 62 [Johnson Polymer Co., Ltd.].

  Among these, polymer dispersants having typical acid groups include poly (meth) acrylic acids [or polyacrylic resins such as poly (meth) acrylic acid and (meth) acrylic acid. Polymers mainly composed of (meth) acrylic acid, such as copolymers with monomers (for example, (meth) acrylate, maleic anhydride, etc.), and salts thereof (for example, alkali metal salts such as sodium polyacrylate) Etc.), Dispersic 190, Dispersic 194 and the like. Examples of the polymer dispersant having a typical basic group (amino group) include polyalkyleneimine (polyethyleneimine etc.), polyvinylpyrrolidone, polyallylamine, polyether polyamine (polyoxyethylene polyamine etc.) and the like. .

  The number average molecular weight of the polymer dispersant (B2) can be selected from the range of 1000 to 1000000 (for example, 1200 to 800000), for example, 1500 to 500000 (for example, 1500 to 100000), preferably 2000 to 80000 (for example, 2000 to 60000), more preferably 3000 to 50000 (for example, 5000 to 30000), particularly about 7000 to 20000.

  In the metal colloidal particles, the ratio of the dispersant (B) (the total amount of the coagulation aid (B1) and the polymer dispersant (B2)) is, in terms of solid content, 100 parts by mass of the metal nanoparticles (A). From the point which can be selected from the range of about 0.1-15 mass parts, and is excellent in the balance of operativity and the electroconductivity of a sintered film, for example, 0.5-12 mass parts (for example, 0.5-10 mass parts), Preferably, it may be about 1 to 10 parts by mass (for example, 2 to 10 parts by mass), more preferably about 3 to 8 parts by mass (particularly 4 to 6 parts by mass). Furthermore, the ratio of the dispersing agent (B) is, for example, 0.5 to 5 parts by mass with respect to 100 parts by mass of the metal nanoparticles (A) from the viewpoint of obtaining a highly dense and highly conductive fired film. Preferably it may be about 1 to 4 parts by mass, more preferably about 1.5 to 3 parts by mass.

  The ratio of the agglomeration aid (B1) and the polymer dispersant (B2) (the ratio of the solid content when a solvent or the like is included) is, for example, the former / the latter (mass ratio) = about 99/1 to 1/99. The range can be selected, for example, 90/10 to 1/99, preferably 80/20 to 3/97 (for example, 70/30 to 5/95), more preferably 50/50 to 10/90 (particularly 30 / 70 to 15/85). Furthermore, the former / the latter (mass ratio) = 90/10 to 10/90, preferably 70/30 to the point that a sintered film of colloid is enlarged to obtain a highly dense and highly conductive fired film. It may be about 20/80, more preferably about 60/40 to 30/70. In order to increase the proportion of the aggregation assistant (B1), it is effective to add an aggregation assistant (particularly alkanecarboxylic acid) in addition to the reducing agent.

  In the present invention, by setting the ratio of the dispersing agent (B) in such a range, colloidal particles containing metal nanoparticles can be obtained as aggregates as described above.

  The proportion of the coagulation aid (B1), polymer dispersant (B2), etc. in the metal colloid particles is measured by a conventional method, for example, thermal analysis (for example, thermal mass / differential thermal simultaneous analysis, etc.). be able to.

(Characteristics of metal colloid particle aggregates)
In the metal colloidal particle aggregate of the present invention, each colloidal particle is moderately aggregated while the metal particle maintains the nano size. In such an aggregate, metal nanoparticles are aggregated via the dispersant (B). For example, metal colloidal particles in which the surfaces of the metal nanoparticles (A) are coated with the dispersant (B) In the dispersant (B), it is presumed that the portion of the dispersing agent (B1) adsorbed (or coated) attracts and becomes a weak point and aggregates. That is, in the metal colloid particle aggregate of the present invention, each metal colloid particle is aggregated more strongly via the dispersant (B) than the colloid particles coated with the conventional protective colloid, and the dispersant (B) ( In particular, neither good solvent nor poor solvent of the polymer dispersant (B2) is uniformly finely dispersed by mechanical stirring (especially when the dispersant is hydrophilic, it is used as a good solvent such as water). (Not dispersed by mechanical agitation), and when ultrasonically treated, the polymer dispersant (B2) has a characteristic of exhibiting brown to yellow plasmon absorption by slightly dispersing with respect to a good solvent (for example, water) Have. The ultrasonic treatment is, for example, a treatment in which irradiation is performed for 10 seconds to 5 hours (preferably 1 minute to 3 hours, more preferably 10 minutes to 2 hours) at 20 to 100 kHz (particularly 30 to 50 kHz). Good. In the present invention, due to such characteristics of the metal colloid particles, aggregates precipitate in a good solvent for the dispersant (B) used in the reduction reaction, and the metal colloid particles can be easily recovered.

  In addition, although the aggregate of the present invention does not disperse in the solvent, it has an appropriate flexibility and disaggregation or peptization, so an organic solvent having an affinity for the dispersant (B) is used. If mixed at a high concentration, a uniform paste for forming a fired film can be prepared. Furthermore, the metal colloidal particles are low-temperature fired because they contain a small amount of the dispersing agent (B) and an aggregating aid (B1) that can form a sintering site, and the colloidal particles are appropriately aggregated. In addition, the metal nanoparticles can be sintered to form a dense and highly conductive sintered film.

[Method for producing metal colloid particle aggregate]
The metal colloidal particle aggregate of the present invention corresponds to the metal nanoparticle (A) in a solvent in the presence of the aggregation assistant (B1) and / or its precursor and the polymer dispersant (B2). The metal compound is reduced to produce metal colloidal particles, and can be prepared by a production method including a step of producing aggregates of metal colloidal particles as precipitates, and a step of separating and collecting the aggregates produced in this step .

  In the reaction step, the metal compound corresponding to the metal nanoparticles (A) includes, for example, metal oxide, metal hydroxide, metal sulfide, metal halide, metal acid salt [metal inorganic acid salt (sulfate, Nitrates, oxoacid salts such as perchlorate), metal organic acid salts (such as acetate), and the like]. In addition, the form of the metal salt may be any of a single salt, a double salt, or a complex salt, and may be a multimer (for example, a dimer). These metal compounds can be used alone or in combination of two or more. Among these metal compounds, metal halides, metal acid salts [metal inorganic acid salts (such as sulfates, nitrates, perchlorates, etc.), metal organic acid salts (such as acetates), etc.] Often used. These metal compounds may be used by dissolving or dispersing in a solvent (for example, in the form of a solution of an aqueous solvent such as an aqueous solution).

  Examples of the reducing agent for the metal compound include conventional components such as sodium borohydrides (sodium borohydride, sodium cyanoborohydride, sodium triethylborohydride, etc.), lithium aluminum hydride, hypophosphorous acid or the like. Examples thereof include salts (such as sodium salts), boranes (such as diborane and dimethylaminoborane), hydrazine, formalin, amines, alcohols (hydroxy compounds), hydroxycarboxylic acids, and carboxylic acids having a phenolic hydroxyl group. These reducing agents can be used alone or in combination of two or more.

  The reducing agent may be an aggregation assistant (B1) constituting the aggregate or a precursor thereof. That is, the coagulant aid (B1) or precursor may be used as the reducing agent, and the residual (excess) product may constitute the aggregate dispersant (B), and the decomposition product or derivative thereof is the aggregate. The dispersant (B) may be constituted. Examples of such a reducing agent include amines, hydroxy compounds, hydroxycarboxylic acids, and carboxylic acids having a phenolic hydroxyl group described in the above-mentioned aggregation aid (B1).

Of these reducing agents, tertiary amines (for example, tri-C _1-3 alkylamines such as dimethylethylamine, diethylmethylamine, triethylamine, etc.) are preferable from the viewpoint of safety and strong reduction power (reduction rate), and a surplus. Since the component or the decomposition component can function as an aggregation aid (B1) for the aggregate and has high dispersibility in a solvent (particularly an aqueous solvent), alkylalkanol tertiary amines (for example, N- _{N-C 1-3} alkyl di _{C 2-6} alkanolamines such as methyldiethanolamine, N, _{N-di-C 1-3} alkyl mono- _{C 2-6} alkanolamines such as dimethylethanolamine) are particularly preferred. For example, when the reducing agent is dimethylaminoethanol, after completion of the reduction reaction, in addition to excess dimethylethanolamine, decomposition products such as carboxylic acids such as acetic acid, alcohols such as ethanol, alkylamines such as alkylamine and dimethylformamide It can be presumed that a formamide, alkylaminocarboxylic acid, nitrate, complex with nitrate ion or hydroxide ion, etc. is generated and adsorbed or bound to the metal nanoparticles. In the present invention, the aggregation aid (B1) or the precursor may be used as the reducing agent, or an aggregation aid (B1) such as carboxylic acid may be further blended. In particular, when amines are used as a reducing agent, low-molecular carboxylic acids such as acetic acid have strong adsorptivity to metal nanoparticles, and are preferentially adsorbed to metal nanoparticles over aggregation agents derived from reducing agents. It is estimated that the cohesiveness and the characteristics of the fired film can be expressed.

  The amount of the reducing agent used is 1 to 30 mol (for example, 1.2 to 20 mol), preferably 1.5 to 15 mol, based on 1 equivalent (or 1 mol) of the metal compound in terms of metal atom. Preferably, it may be about 2 to 10 mol, and usually about 1 to 5 mol.

  The reduction reaction can be performed by a conventional method, for example, at a temperature of about 10 to 75 ° C. (for example, about 15 to 50 ° C., preferably about 20 to 35 ° C.). The atmosphere of the reaction system may be air, an inert gas (such as nitrogen gas), or an atmosphere containing a reducing gas (such as hydrogen gas). Moreover, you may perform reaction under stirring (or stirring) normally.

  Although the compounding quantity of a polymer dispersing agent (B2) will not be specifically limited if the ratio in an aggregate exists in the said range, For example, 0.1-10 mass parts (for example, with respect to 100 mass parts of metals of a metal compound) 0.1 to 7.5 parts by mass), preferably 0.5 to 8 parts by mass, more preferably about 1 to 7.5 parts by mass (particularly 3 to 7 parts by mass).

  The blending amount of the aggregation aid (B1) is not particularly limited as long as the ratio in the aggregate is within the above range, and can be selected depending on whether or not the aggregation aid is used as the reducing agent. For example, it may be 100 parts by mass or less, preferably 0.1 to 50 parts by mass, and more preferably 1 to 40 parts by mass (particularly 10 to 30 parts by mass) with respect to 100 parts by mass of the metal.

  The reaction solvent may be a polar solvent (water-soluble solvent) or a hydrophobic solvent (water-insoluble solvent) depending on the type of reducing agent or dispersant (B).

Examples of the polar solvent include water, alcohols (C _1-4 alkanols such as methanol, ethanol, propanol, isopropanol, and butanol), aliphatic polyhydric alcohols (ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, Polyethylene glycol, glycerol, etc.), amides (formamide, acylamides such as acetamide, N-methylformamide, N-methylacetamide, N, N-dimethylformamide, N-mono or N, N, such as N, N-dimethylacetamide - di C _1-4 acyl amides, etc.), ketones (such as acetone), ethers (dioxane, tetrahydrofuran, etc.), organic carboxylic acids (such as acetic acid), cellosolves (methyl cellosolve, Echirusero Lube and C _1-4 alkyl cellosolve such as butyl cellosolve), cellosolve acetates (C _1-4 alkyl cellosolve acetates such as ethyl cellosolve acetate), carbitol (methyl carbitol, ethyl carbitol, propyl carbitol And C _1-4 alkyl carbitols such as butyl carbitol), halogenated hydrocarbon solvents (halogenated hydrocarbons such as methylene chloride, chloroform, dichloroethane, etc.). These polar solvents can be used alone or in combination of two or more. The polar parameters of these polar solvents are usually in the range of the polar parameters described later in many cases.

Of these polar solvents, a polar solvent containing at least water may be used from the viewpoints of environmental conservation and simplicity. Further, depending on the application, from the standpoint of suppressing the evaporation of the solvent, alcohol (for example, C _1-4 alkanol such as ethanol, aliphatic polyhydric alcohol such as ethylene glycol and glycerin, etc.) is combined with water. Also good. The proportion of alcohol is, for example, about 0.1 to 50 parts by mass, preferably 1 to 30 parts by mass, and more preferably about 3 to 20 parts by mass (particularly 5 to 15 parts by mass) with respect to 100 parts by mass of water. There may be.

  Examples of the hydrophobic solvent include hydrocarbons (aliphatic hydrocarbons such as hexane, trimethylpentane, octane, decane, dodecane, and tetradecane; alicyclic hydrocarbons such as cyclohexane; aromatic carbonization such as toluene and xylene. Hydrogens: halogenated hydrocarbons such as dichloromethane and trichloroethane), esters (such as methyl acetate and ethyl acetate), ketones (such as methyl ethyl ketone and methyl isobutyl ketone), ethers (such as diethyl ether and dipropyl ether) Can be illustrated. These hydrophobic solvents can be used alone or in combination of two or more.

  The solvent is preferably composed of at least a polar solvent (particularly a non-aromatic polar solvent or an aliphatic polar solvent). The polarity parameter (polarity parameter by Snyder) of such a solvent may be, for example, 2.8 to 11, preferably 3 to 10.5, and more preferably about 3.1 to 10.2. In the present invention, the solvent is preferably a water-soluble solvent, particularly water-soluble solvent (especially water) such as at least water and / or alcohols from the viewpoint that the environmental load is small and handling is simple.

  The concentration of the metal compound in the reaction solution is, for example, 0.1% by mass or more (for example, 1 to 50% by mass), preferably 3% by mass or more (for example, 5 to 45% by mass) in terms of metal mass. More preferably, it may be a high concentration of 10% by mass or more (for example, 12 to 40% by mass), usually about 5 to 35% by mass. In the present invention, metal nanoparticles can be efficiently obtained even when the reaction is performed at such a high concentration.

  The pH of the reaction system may be adjusted according to the type of reaction solvent. The pH is adjusted by a conventional method, for example, an acid (an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, an organic acid such as acetic acid), an alkali [an inorganic base such as sodium hydroxide or ammonia, or an amine (for example, an alkyl). Bases such as organic bases such as tertiary amines such as amines and alkanolamines].

  In the present invention, since the produced metal colloid particles start to aggregate and precipitate together with the reduction reaction, the aggregate can be recovered simply by washing with a washing solvent after removing the supernatant from the reaction solution in the collecting step.

  As a method for removing the supernatant, a conventional method can be used, and methods such as concentration, centrifugation, and filtration can be used, but from the viewpoint of simplicity, a removal method by decantation is preferable. In particular, in the present invention, the aggregate is not dissolved or uniformly finely dispersed in the good solvent of the dispersant (B), and the good solvent can be used as a washing solvent for the dispersant (B) and the reducing agent. Eliminate impurities (reducing agent or its degradation products, residual dispersant, ions, salts, etc.) on the precipitate from which the supernatant liquid has been removed by aflation, without using precise and complicated processing such as ultrafiltration. Can be removed.

  In the washing method using a washing solvent, as the washing solvent, the polar or hydrophobic solvent that can be used as a reaction solvent can be used, and a solvent (for example, water) used for a reduction reaction may be used. The amount of the washing solvent used may be, for example, 2 to 100 times, preferably 3 to 50 times, and more preferably about 5 to 30 times by weight with respect to the aggregate. Such a cleaning process may be repeated a plurality of times (for example, 2 to 5 times). When repeating a plurality of times, different types of cleaning solvents (for example, solvents having higher volatility) may be used. Furthermore, after washing with a washing solvent, it may be naturally dried or purified by simple filtration such as a membrane filter.

[Metal nanoparticle paste]
The metal colloid particle aggregate of the present invention may be prepared by blending an organic solvent. As described above, since the aggregate of the present invention is appropriately aggregated, it has moderate flexibility and peptization. When a specific organic solvent is added, the aggregate is redispersed and homogeneous. A viscous paste can be easily prepared. The redispersion of the aggregate in the paste means that the aggregate is not in a state where the nanometer-sized primary particles are uniformly finely dispersed in the solvent, but the finely dispersed primary particles exhibiting yellow to blue plasmon absorption. And secondary particles or aggregates in which primary particles are associated with a size that does not exhibit plasmon absorption. The viscosity [share rate: 50 (1 / s)] of the paste at 25 ° C. is, for example, 0.1 to 100 mPa · s, preferably 1 to 80 mPa · s, and more preferably about 5 to 50 mPa · s. Good.

  As the organic solvent, the polar solvent and the hydrophobic solvent described as the reaction solvent can be used depending on the type of the dispersant (B), but in order to prepare a homogeneous paste, the affinity with the dispersant (B) For example, when the dispersant (B) is hydrophilic, it is preferable to use a polar solvent. Preferred polar solvents include, for example, alcohols such as ethyl alcohol, propyl alcohol, isopropyl alcohol, and butyl alcohol, cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, and carbitols such as methyl carbitol, ethyl carbitol, and butyl carbitol. Examples include tall polyols, aliphatic polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, and glycerin. These polar solvents can be used alone or in combination of two or more. Of these polar solvents, aliphatic polyhydric alcohols such as ethylene glycol, diethylene glycol and glycerin (especially alkylene glycols such as ethylene glycol) are preferred because of their excellent affinity for the dispersant (B).

  The concentration of the metal nanoparticles (A) in the paste is, for example, about 30 to 95% by mass, preferably about 50 to 93% by mass, more preferably about 60 to 90% by mass (especially 65 to 85% by mass). Also good. Such a metal nanoparticle paste is excellent in long-term stability without causing precipitation or the like even if it contains the metal nanoparticles (A) at a high concentration. Furthermore, since the metal colloidal particles are highly aggregated at a high concentration, even if a metal film (sintered film) is formed, a dense and hard metal film can be formed and the resistance value does not increase. , Excellent conductivity can be maintained.

(Metal filler)
By adding a metal filler (metal powder) to the metal nanoparticle paste of the present invention, the paste can be given fluidity and the conductivity of the sintered film can be improved.

  In a paste containing colloidal metal particles, as the particle concentration in the paste increases, the distance between the particles decreases, interaction due to entanglement of the dispersing agent (B) existing between the particles or on the surface occurs, and the viscosity rapidly increases. As a result, the handleability decreases. In the present invention, by adding a metal filler having a large particle size, high fluidity can be imparted even with a high-concentration paste. In addition, the following reasons can be considered as a mechanism in which fluidity develops.

  (1) The distance D between the surfaces of the particles is expressed by the formula: D = [{(√2 × π) / (6f)} 1 / 3-1] × d (where f: volume fraction of fine particles in the paste) When the comparison is made with pastes having the same metal concentration, it is estimated that the dispersion containing the component having a larger particle size has a larger distance between the particle surfaces and thus the viscosity is lowered. .

  (2) The sedimentation velocity D of the particles is expressed by the formula: D = kT / (3πηd) (where k: Boltzmann constant, T: absolute temperature, η: solvent viscosity, d: particle size), and the same metal Since large particles have a large sedimentation speed in a paste having a concentration, if large particles are present in the dispersion, it is presumed that the aggregated structure is easily broken and fluidity is developed.

  Furthermore, in the present invention, by adding a metal filler having a larger particle size to the metal nanoparticle paste, the ratio of the dispersant (B) contained in the paste is reduced, and the dispersant (B) generated during firing is derived. The amount of gas is reduced and the occurrence of blistering and cracking due to outgassing from the film can be suppressed. Furthermore, a coating film having high conductivity can be obtained even if firing is performed at a low temperature (for example, 150 ° C. or less) because the filling efficiency is improved by the combination of the nanoparticles and the metal filler.

  The volume-based average particle diameter of such a metal filler may be 200 nm or more, but is, for example, 0.2 to 10 μm, preferably 0.3 to 8 μm (for example, 0.5 to 7 μm), and more preferably 0. About 7 to 6 μm (particularly 1 to 5 μm). The particle size range of the metal filler (B) is, for example, 0.1 to 30 μm, preferably 0.2 to 20 μm (for example, 0.25 to 10 μm), more preferably 0.3 to 8 μm (particularly 0.5 to About 7 μm). If the particle diameter of the metal filler is too large, clogging is likely to occur in screen printing, for example. On the other hand, when the particle diameter is too small, the dispersibility of the metal filler is lowered, so that the amount of the dispersant (B) used is increased and the amount of gas generated during firing is also increased.

The specific surface area of the metal filler, for example, 0.1 to 5 m ² / g, preferably about 0.3~2.6m ² / g. In low-temperature firing, the specific surface area is relatively small, so that the resistivity of the fired film can be improved. For example, 0.1 to 2.6 m ² / g (for example, 0.1 to 1.5 m ² / g), Preferably, it may be about 0.3 to 1.2 m ² / g (for example, 0.3 to 0.6 m ² / g). On the other hand, in high-temperature firing, a relatively large specific surface area is more likely to cause interparticle sintering, and the specific resistance of the fired film can be improved. For example, 0.3 to ⁵ m ² / g, preferably 0.4 to It may be about 2.6 m ² / g.

  The ratio of the average particle diameter of the metal nanoparticles and the metal filler is as follows: metal nanoparticles / metal filler = 1/1000/1 to 1/5, preferably 1/500 to 1/10 (for example, 1/300 to 1 / 20), more preferably about 1/250 to 1/50 (particularly 1/200 to 1/100). When the ratio between the two is in this range, the filling efficiency of the metal nanoparticles and the metal filler is improved, so that the conductivity of the fired film can be improved.

  Examples of the metal constituting the metal filler include simple metals, alloys, and metal compounds exemplified in the section of metal nanoparticles (A). Among these metals, a metal (a simple metal and a metal alloy) including at least a noble metal such as silver or gold (particularly a Group 1B metal of the periodic table), particularly a simple noble metal (for example, a simple gold) is preferable. The metal constituting the metal nanoparticles and the metal constituting the metal filler may be different, but are preferably the same or the same group metals (particularly the same metal) from the viewpoint of easy sintering.

  The ratio (mass ratio) between the metal colloid particle aggregate and the metal filler is: metal colloid particle aggregate / metal filler = 90/10 to 10/90, preferably 80/20 to 20/80, more preferably 70/30. About 30/70 (especially 60 / 40-40 / 60). If the ratio between the two is in this range, the sintering of the two is densely performed, so that the conductivity of the fired film can be improved.

  In the metal nanoparticle paste of the present invention, conventional additives such as colorants (dyeing pigments), hue improvers, dye fixing agents, gloss imparting agents, metal corrosion inhibitors, stabilizers (for example) Antioxidants, UV absorbers, etc.), surfactants or dispersants (anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, etc.), dispersion stabilizers, thickeners Alternatively, a viscosity modifier, a humectant, a thixotropic agent, a leveling agent, an antifoaming agent, a disinfectant, a filler, and the like may be included. These additives can be used alone or in combination of two or more.

(Application of metal nanoparticle paste)
The metal particle paste of the present invention can be used for various applications, for example, a paste for forming a metal film (particularly a conductive film), a bonding agent for bonding inorganic materials, and the like.

(Conductive film)
When forming a conductive film, the metal particle paste of the present invention contains metal nanoparticles at a high concentration and can be sintered at a relatively low temperature (for example, 150 ° C. or lower). Among the sintered films), a sintered layer having a predetermined pattern (such as a circuit pattern, particularly a conductive pattern) is formed, which is suitable as a paste for producing a conductive substrate. Hereinafter, a method for producing a conductive substrate using the metal particle paste will be described in detail.

  In such a method, usually, a coating (coating layer or pattern) is formed (drawn) on the base material by the metal particle paste (or coating of the metal particle paste), and the formed coating (drawing pattern) is baked. By processing, a sintered layer (sintered film, sintered pattern, metal film, sintered body layer, conductor layer) can be formed.

  It does not specifically limit as a base material (or board | substrate), According to a use, it can select suitably. The material constituting the substrate may be an inorganic material or an organic material. Examples of inorganic materials include glasses (soda glass, borosilicate glass, crown glass, barium-containing glass, strontium-containing glass, boron-containing glass, low alkali glass, alkali-free glass, crystallized transparent glass, silica glass, and quartz glass. And heat-resistant glass), metal oxides (alumina, sapphire, zirconia, titania, yttrium oxide, indium oxide-tin oxide composite oxide (ITO), fluorine-doped tin oxide (FTO), etc.). Examples of the organic material include polymethyl methacrylate resin, styrene resin, vinyl chloride resin, polyester resin [including polyalkylene arylate resin (polyethylene terephthalate, etc.), polyarylate resin and liquid crystal polymer], Examples include polyamide resins, polycarbonate resins, polysulfone resins, polyethersulfone resins, polyimide resins, cellulose derivatives, and fluororesins. Since these materials undergo a baking process, they are highly heat-resistant materials, such as inorganic materials, engineering plastics (for example, aromatic polyester resins (including polyarylate resins), polyimide resins, polysulfone resins, etc.) A liquid crystal polymer, a fluororesin and the like are preferable. In particular, in the present invention, since it can be sintered at low temperature, a pattern can be formed even on a base material made of resin. In addition, the base material may be surface-treated.

  The base material may be subjected to easy adhesion treatment (surface treatment). The use of a base material (organic base material) that has been subjected to an easy adhesion treatment can improve the adhesion of the metal colloid particles (or the metal film thereof) to the base material, and is advantageous for obtaining a strongly fixed metal film.

  Easy adhesion treatment includes oxidation treatment [surface oxidation treatment, for example, discharge treatment (corona discharge treatment, glow discharge, etc.), acid treatment (chromic acid treatment, etc.), ultraviolet irradiation treatment, wrinkle treatment, etc., surface unevenness treatment (solvent In addition to a process, a sandblast process, etc., the method of forming an easily bonding layer on a base material (base material surface), etc. are mentioned. That is, you may use the base material in which the easily bonding layer was formed as an organic base material.

  The component constituting (or forming) the easy-adhesion layer is not particularly limited as long as it can improve the adhesion between the metal colloidal particles (or the dispersant (B) thereof) and the base material. For example, the olefin resin [For example, polyethylene (linear low density polyethylene, low density polyethylene, etc.), ethylene-acrylate copolymer (such as ethylene-ethyl acrylate copolymer), ethylene-methacrylate copolymer, ethylene- ( (Meth) acrylic acid copolymer, ionomer resin, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-acrylonitrile-acrylic acid copolymer polyethylene resin, amorphous polypropylene resin, etc.] , Vinyl chloride resin (vinyl chloride-vinyl acetate copolymer, etc.), vinylidene chloride resin ( Vinylidene chloride-vinyl chloride copolymer, vinylidene chloride- (meth) acrylic acid ester copolymer, vinylidene chloride-acrylonitrile copolymer, etc.), acrylic resin [for example, (meth) acrylic monomer (for example, ( (Meth) acrylic acid, (meth) acrylic acid ester) etc.] or a copolymer thereof, and these (meth) acrylic monomers and copolymerizable monomers (styrene monomers, vinyl acetate, etc. Ester monomers, copolymers with unsaturated dicarboxylic acids or their esters, etc.], vinyl acetate resins [polyvinyl acetate, vinyl acetate and other copolymerizable monomers (olefin monomers ( Ethylene, etc.), (meth) acrylic acid esters, unsaturated dicarboxylic acids or their copolymers, etc.)], styrenic resins [for example, styrene- (meta Acrylic acid ester copolymer, styrene- (meth) acrylic acid ester- (meth) acrylic acid copolymer, etc.], polyester resin [aliphatic polyester resin, amorphous polyester resin (for example, amorphous aliphatic or Aromatic polyester), urethane resin (thermoplastic urethane resin, isocyanate group-containing polymer, etc.), rubbery polymer (styrene-butadiene copolymer, etc.), imino group-containing polymer (polyalkyleneimine, such as polyethyleneimine) Etc.). These components may be used alone or in combination of two or more to form an easy adhesion layer.

  Typical easy-adhesion layers include acrylic resins, polyester resins, urethane resins, and the like.

  In addition, the easy-adhesion process should just be given with respect to the one part or all part of the surface of a base material, and especially forms at least in the site | part (surface) which forms a metal film among base materials (base material surface). May be. That is, the said base material is a base material by which the easily bonding process was carried out, and the metal film may be formed in the site | part by which the easily bonding process was carried out among this base materials. For example, a base material in which an easy adhesion layer is formed on at least one surface may be used, and a metal film may be formed on the surface of the base material on which the easy adhesion layer is formed.

  The drawing method (or printing method) for drawing the coating layer (pattern) is not particularly limited as long as it is a pattern forming printing method. For example, a screen printing method, an ink jet printing method, an intaglio printing method (for example, Gravure printing method), offset printing method, intaglio offset printing method, flexographic printing method and the like.

  The average thickness of the sintered layer (or sintered pattern) may be, for example, about 0.5 to 30 μm, preferably 0.6 to 25 μm, more preferably about 0.8 to 15 μm (particularly 1 to 12 μm). . In the present invention, since a paste containing metal nanoparticles and a metal filler at a high concentration is used, such a micron-order thick film can be formed efficiently.

  The baking treatment can be usually performed by heating (or baking or heat treatment) the coating layer at a predetermined baking temperature. The firing temperature is not particularly limited as long as the metal nanoparticles can be fused to form a continuous film, and can be appropriately selected from about 500 ° C. or less. In particular, since the metal particle paste of the present invention sinters even at a relatively low temperature, the firing temperature is 350 ° C. or lower (for example, about 50 to 350 ° C.), preferably 70 to 320 ° C., more preferably 80 ° C. It may be about ˜300 ° C. (for example, 100 to 280 ° C.), and may be usually about 100 to 350 ° C. Further, in the present invention, even at a low temperature of 150 ° C. or less [eg, 40 to 150 ° C., preferably 45 to 145 ° C. (eg 50 to 140 ° C.), more preferably 55 to 135 ° C., particularly about 60 to 130 ° C.]. Sinterable. Therefore, a metal film or pattern can be formed on a resin substrate or the like, and the application range is wide. In addition, when high electroconductivity is requested | required, you may bake by 200 degreeC or more high temperature (for example, 200-500 degreeC, Preferably about 300-450 degreeC).

  The firing time (heating time) may be, for example, 10 minutes to 6 hours, preferably 15 minutes to 5 hours, more preferably about 20 minutes to 3 hours, depending on the firing temperature and the like.

  In this way, a sintered layer (sintered pattern) is formed. The sintered layer has high conductivity when a conductive metal is used as the metal nanoparticles.

(Inorganic material)
The joined body of inorganic materials can be obtained by sintering the paste with the metal nanoparticle paste of the present invention interposed between the first inorganic material and the second inorganic material.

  As the inorganic material, an inorganic material such as glass or carbon material may be used. However, since the paste is composed of metal nanoparticles, at least the bonding surface contains a metal (from the point of improving bonding strength) In particular, a material in which substantially the entire joining surface is made of metal is preferable. Examples of the metal include simple metals, alloys, and metal compounds exemplified in the section of metal nanoparticles (A). Among these metals, a metal (a simple metal and a metal alloy) including at least a noble metal such as silver or gold (particularly a Group 1B metal of the periodic table), particularly a simple noble metal (for example, a simple gold) is preferable. When the bonding surface of the inorganic material includes a metal, the metal constituting the metal nanoparticle may be different from the metal included in the inorganic material, but a metal that is not alloyed is preferable, and is the same or a similar metal. Is preferred.

  The first inorganic material and the second inorganic material to be joined may be different materials or the same kind of materials. From the viewpoint of bonding force, the same kind of material (for example, the same metal material or a metal material of the same family) is preferable.

  The shape of the inorganic material is not particularly limited, and may be, for example, a shape in which the contact area between the materials to be joined increases, for example, a shape having a flat joining surface (usually a plate or a sheet).

The coating amount of the bonding agent for inorganic material (coating amount before drying) can be appropriately selected according to the use and size of the inorganic material to be bonded. From the point of strong bonding, for example, 10 to 100 mg / cm ² , Preferably it is 20-80 mg / cm < ² >, More preferably, it is about 30-70 mg / cm < ² >.

  The application method is not particularly limited, and conventional methods such as a method using a coater, spray coating, dipping, and the like can be used.

The firing temperature for sintering the metal nanoparticle paste may be, for example, about 150 to 500 ° C, preferably 200 to 450 ° C, more preferably about 250 to 400 ° C (particularly 300 to 380 ° C). The firing may be pressurized, for example, a load of about 1 to 500 g / cm ² , preferably 3 to 300 g / cm ² , more preferably 5 to 100 g / cm ² (particularly 10 to 50 g / cm ² ). You may bake in the state which provided. In the present invention, the inorganic material can be firmly joined even when firing at such a relatively low temperature and low pressure.

  The firing time (heating time) may be, for example, 1 minute to 10 hours, preferably 20 minutes to 5 hours, more preferably about 30 minutes to 3 hours, depending on the firing temperature and the like.

  Although the thickness of the sintered film (metal film) formed between the layers of the inorganic material after firing can be appropriately selected from the range of about 1 μm to 1 cm depending on the application, for example, 5 to 300 μm, preferably 10 to 200 μm, More preferably, it is about 30-100 micrometers.

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

Example 1
(Preparation of silver colloidal particle aggregates)
336 g of silver nitrate, polymer dispersant (manufactured by Big Chemie, “Dispervic 190”, amphiphilic dispersant having a polyethylene oxide chain as a hydrophilic unit and an alkyl group as a hydrophobic unit, solvent: water, non-volatile component 40% 36 g of an acid value of 10 mg KOH / g and an amine value of 0) was added to 500 g of ion-exchanged water and stirred vigorously. When 500 g of 2-dimethylaminoethanol (manufactured by Wako Pure Chemical Industries, Ltd.) was gradually added thereto, the reaction solution rose to 60 ° C. When the liquid temperature dropped to 50 ° C, the mixture was heated and stirred in a water bath set at 70 ° C. After 1 hour, silver colloidal particle aggregates were obtained as black precipitates. When this silver colloid aggregate was irradiated with ultrasonic waves at 37 kHz for 60 minutes, most of the particles remained aggregated, but were dispersed to such an extent that they exhibited a slight yellow-brown plasmon absorption.

  The supernatant of the reaction solution in which the silver colloid particle aggregates were precipitated was removed and diluted with ion-exchanged water. After standing, the supernatant was removed and further diluted with methanol. After standing again, the supernatant was removed and diluted with methanol. Thereafter, the silver colloidal particle aggregates were collected with a pressure filter equipped with a membrane filter (manufactured by Advantech, pore size 0.5 μm).

(Analysis of silver colloidal particle aggregates)
A part of the obtained silver colloid particle aggregate is taken out, and after the methanol and water contained in the collected silver colloid particle aggregate are completely volatilized, the content of the dispersant (B) contained in the silver colloid particle Was measured with a thermogravimetric apparatus (TG / DTA, manufactured by Seiko Instruments Inc., EXSTAR6000). The measurement by TG / DTA was calculated from the decrease in mass when the temperature was raised from 30 ° C. to 550 ° C. at a rate of 10 ° C. per minute. Further, the amount of the coagulation aid (B1) is calculated from the mass decrease from 30 ° C. to 200 ° C., and the amount of the polymer dispersant (B2) is calculated from the amount of the dispersant (B). ) Minus the amount (B-B1). The results are shown in Table 1.

(Sintering of silver colloidal particle paste)
Ethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., boiling point: 197.3 ° C., polarity parameter: 6.9) is added to the obtained silver colloid particle aggregate and mixed in a mortar, and is contained in the aggregate. Methanol was volatilized to prepare a silver nanoparticle paste having a silver concentration of 70% by mass. This paste was applied onto an alkali-free glass substrate (manufactured by Corning Co., Ltd., product number 1737) and baked at 120 ° C. for 30 minutes on a hot plate to form a silver film having a thickness of 4 μm on the substrate. When the specific resistance of the fired film was measured, it was 16 μΩ · cm.

Example 2
Silver colloid particles were produced in the same manner as in Example 1 except that the amount of the polymer dispersant used was 25.4 g in the production of silver colloid particle aggregates. As obtained. When this silver colloid aggregate was irradiated with ultrasonic waves at 37 kHz for 60 minutes, most of the particles remained aggregated, but were dispersed to such an extent that they exhibited a slight yellow-brown plasmon absorption.

  The results of collecting and analyzing silver colloidal particles in the same manner as in Example 1 are shown in Table 1. As a result of preparing and firing a silver nanoparticle paste having a silver concentration of 70% by mass on the obtained silver colloidal particle aggregate in the same manner as in Example 1, the volume resistivity (specific resistance) of the fired film was 15 μΩ. -It was cm.

Example 3
In the production of the silver colloidal particle aggregate, 336 g of silver nitrate, 36.0 g of a polymer dispersant (Disperbic 190), 50 g of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 118 ° C., carbon number 2) are added to 500 g of ion-exchanged water. When colloidal silver particles were produced in the same manner as in Example 1 except that they were added to the above, a silver colloidal particle aggregate was obtained as a gray precipitate. When this silver colloid aggregate was irradiated with ultrasonic waves at 37 kHz for 60 minutes, most of the particles remained aggregated, but were dispersed to such an extent as to exhibit a slight yellow plasmon absorption.

  The results of collecting and analyzing silver colloidal particles in the same manner as in Example 1 are shown in Table 1. As a result of preparing and firing a silver nanoparticle paste with a silver concentration of 70% by mass in the same manner as in Example 1 for the obtained silver colloidal particle aggregate, the specific resistance of the fired film was 13.8 μΩ · cm. there were.

Example 4
In the production of the silver colloidal particle aggregate, 336 g of silver nitrate, 25.2 g of a polymer dispersant (Disperbic 190), 50 g of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 118 ° C., carbon number 2), 500 g of ion-exchanged water Silver colloidal particles were produced in the same manner as in Example 1 except that they were added to the above. As a result, silver colloidal particle aggregates were obtained as gray precipitates. When this silver colloid aggregate was irradiated with ultrasonic waves at 37 kHz for 60 minutes, most of the particles remained aggregated, but were dispersed to such an extent as to exhibit a slight yellow plasmon absorption.

  The results of collecting and analyzing silver colloidal particles in the same manner as in Example 1 are shown in Table 1. As a result of preparing and firing a silver nanoparticle paste having a silver concentration of 75% by mass in the same manner as in Example 1 with respect to the obtained silver colloidal particle aggregate, the specific resistance of the fired film was 11 μΩ · cm. .

Example 5
In the production of silver colloidal particle aggregates, 336 g of silver nitrate, 10.8 g of a polymer dispersant (Disperbic 190), 50 g of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 118 ° C., carbon number 2), 500 g of ion-exchanged water Silver colloidal particles were produced in the same manner as in Example 1 except that they were added to the above. As a result, silver colloidal particle aggregates were obtained as gray precipitates. When this silver colloid aggregate was irradiated with ultrasonic waves at 37 kHz for 60 minutes, most of the particles remained aggregated, but were dispersed to such an extent as to exhibit a slight yellow plasmon absorption.

  The results of collecting and analyzing silver colloidal particles in the same manner as in Example 1 are shown in Table 1. As a result of preparing and firing a silver nanoparticle paste having a silver concentration of 75% by mass in the same manner as in Example 1 for the obtained silver colloidal particle aggregate, the specific resistance of the fired film was 6.5 μΩ · cm. there were.

Example 6
In the production of the silver colloidal particle aggregate, 336 g of silver nitrate, 3.6 g of a polymer dispersant (Disperbic 190), 50 g of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 118 ° C., carbon number 2), 500 g of ion-exchanged water Silver colloidal particles were produced in the same manner as in Example 1 except that they were added to the above. As a result, silver colloidal particle aggregates were obtained as gray precipitates. When this silver colloid aggregate was irradiated with ultrasonic waves at 37 kHz for 60 minutes, most of the particles remained aggregated, but were dispersed to such an extent as to exhibit a slight yellow plasmon absorption.

  The results of collecting and analyzing silver colloidal particles in the same manner as in Example 1 are shown in Table 1. As a result of preparing and firing a silver nanoparticle paste having a silver concentration of 80% by mass with respect to the obtained silver colloidal particle aggregate in the same manner as in Example 1, the specific resistance of the fired film was 5.8 μΩ · cm. there were.

Comparative Example 1
In the production of silver colloidal particle aggregates, silver colloidal particles were produced in the same manner as in Example 1 except that the amount of the polymer dispersant used was 2472.5 g. A dispersion of silver colloidal particles was obtained. This dispersion was centrifuged at 7000 rpm for 1 hour using a high-speed centrifuge (manufactured by Kokusan, H-200 SERIES), but the silver colloid particles could not be recovered as a precipitate. In addition, since this dispersion liquid contained a large amount of a polymer dispersant, it was impossible to measure the specific resistance.

Comparative Example 2
In the production of silver colloidal particle aggregates, an attempt was made to produce silver colloidal particles in the same manner as in Example 1 except that the amount of the polymer dispersant used was 10.8 g. Insufficient particles obtained as precipitates were submicron-sized silver particles.

  The results of collecting and analyzing silver particles in the same manner as in Example 1 are shown in Table 1. As a result of preparing and baking a silver nanoparticle paste having a silver concentration of 80% by mass on the obtained silver particles in the same manner as in Example 1, the specific resistance of the fired film was 65 μΩ · cm.

Comparative Example 3
In the production of silver colloidal particle aggregates, an attempt was made to produce silver colloidal particles in the same manner as in Example 1 except that the amount of the polymeric dispersant used was 3.6 g. Insufficient particles obtained as precipitates were submicron-sized silver particles.

  The results of collecting and analyzing silver particles in the same manner as in Example 1 are shown in Table 1. For the obtained silver particles, a silver nanoparticle paste having a silver concentration of 80% by mass was prepared and fired in the same manner as in Example 1. As a result, the specific resistance of the fired film was 58 μΩ · cm.

  In Table 1, “B2 blending amount” indicates the blending amount of the polymer dispersant with respect to silver nitrate (in terms of silver), and “the ratio of B in the aggregate” refers to the dispersant (B) in the colloidal particles. The ratio with respect to silver nanoparticles is shown, and “B1 / B2” shows the ratio (weight ratio) of (B1) aggregation aid and (B) polymer dispersant in the colloidal particles.

  As is apparent from Table 1, a fired film having high conductivity can be easily obtained in the example as compared with the comparative example.

  Since the obtained fired film has high conductivity, the metal nanoparticle paste of the present invention can also be used as conductive ink (or conductive paste). Therefore, various conductors, for example, display devices such as plasma display panels (PDP), fluorescent display tubes (VFD), liquid crystal displays (LCD), organic and inorganic electroluminescent displays (ELD), silicon semiconductor systems, Gretzels, etc. It can also be used as a coating liquid for conductive printing or conductive printing used in electrodes such as solar cells, touch panel display devices, RFID tags, electromagnetic wave shields, home or learning wiring kits, and the like. In particular, it is suitable for RFID tags and electronic paper because it can be finely and strongly patterned on a base material made of paper without heating or light treatment.

  Furthermore, since the metal nanoparticle paste of the present invention can be firmly adhered to a base material, particularly an inorganic material, the inorganic material such as a metal material, for example, an inorganic substrate such as a metal plate can be strongly bonded. It can also be used as an agent.

Claims (11)

An aggregate of metal colloidal particles containing metal nanoparticles (A) having a number average particle diameter of 1 to 100 nm and a dispersant (B), wherein the dispersant (B) is a group having a nitrogen atom, a hydroxyl group, and A metal colloidal particle aggregate comprising an aggregation assistant (B1) having at least one functional group selected from the group consisting of carboxyl groups and a polymer dispersant (B2).   The ratio of the dispersant (B) is 1 to 10 parts by weight with respect to 100 parts by weight of the metal nanoparticles (A), and the ratio of the aggregation aid (B1) to the polymer dispersant (B2) ( The aggregate according to claim 1, wherein the mass ratio) is the former / the latter = 90/10 to 1/99.   The aggregate according to claim 1 or 2, wherein the aggregation assistant (B1) has 1 to 10 carbon atoms.   In the presence of a coagulation aid (B1) and / or precursor thereof having at least one functional group selected from the group consisting of a group having a nitrogen atom, a hydroxyl group and a carboxyl group, and a polymer dispersant (B2) And a step of reducing the metal compound in a solvent to generate metal colloidal particles, generating aggregates of the metal colloidal particles as precipitates, and separating and recovering the aggregates generated in this step. The manufacturing method of the aggregate in any one of 1-3.   The production method according to claim 4, wherein the aggregating aid (B1) and / or a precursor thereof is used as a reducing agent.   6. The production method according to claim 4 or 5, wherein the supernatant is removed from the reaction solution and recovered, and then the aggregate is purified by washing with a washing solvent.   Furthermore, the manufacturing method in any one of Claims 4-6 which refine | purifies an aggregate by filtration.   The metal nanoparticle paste comprised with the aggregate of the metal colloid particle in any one of Claims 1-3, and the organic solvent.   Furthermore, the metal nanoparticle paste of Claim 8 containing a metal filler with a volume average particle diameter of 0.2-10 micrometers.   The manufacturing method of the electroconductive base material including the process of forming a film with the metal nanoparticle paste of Claim 8 or 9 on a base material, and the process of baking this film.   The metal nanoparticle paste according to claim 9, which is a bonding agent for inorganic materials.