JP2010153118A - Metallic particle paste and method for manufacturing conductive substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic particle paste of which a sintered layer or a sintered pattern having high conductivity is efficiently formed even at a low temperature (in particular, at about 150°C or less). <P>SOLUTION: In the metallic particle paste containing metal colloid particles (A) formed of metal nano-particles (A1) and protective colloid (A2) to cover this metal nano-particles (A1), a metal filler (B), and a dispersion medium (C), the protective colloid (A2) is constituted of an organic compound (A2-1) having a carboxyl group and a polymer dispersant (A2-2). The metal filler (B) may be silver filler with a volume average particle size of 0.2-10 μm. The ratio (mass ratio) of the organic compound (A2-1) having carboxyl group and the polymer dispersant (A2-2) is the former/the latter=about 95/5-50/50. It may be acceptable that coating is formed on the substrate with the metallic particle paste and the coating is sintered to manufacture the conductive substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a metal particle paste that can be used as a circuit-forming material for a substrate and a method for producing a conductive base material using the paste.

The conductive paste material using silver filler (silver powder) is classified into a low-temperature firing type and a high-temperature firing type. The low-temperature fired paste material is a material in which a silver filler is mixed in a resin, and is used in a heat treatment at 200 ° C. or lower. However, since conductivity is obtained by contact between silver fillers, a relatively specific resistance ( 10 ⁻⁴ Ω · cm) is high. On the other hand, the high-temperature sintered paste material has a low specific resistance (about 10 ⁻⁶ Ω · cm) because the silver fillers are fused together, but it must be heat-treated at a high temperature of 500 ° C. or higher. The board | substrate which becomes is limited.

  For example, JP 2008-91250 A (Patent Document 1) contains at least metal nanoparticles covered with an organic protective colloid, a silver filler, and a dispersion medium, and the organic protective colloid and the dispersion medium have a decomposition temperature. Or the low-temperature baking type silver paste whose boiling point is 70-250 degreeC is proposed. In this document, hydrocarbons having 3 to 18 carbon atoms are described as the organic protective colloid and the dispersion medium, and it is described that the silver filler can be fused via the silver colloid particles at a low heat treatment temperature. Has been.

However, even if this silver paste is used, firing at a low temperature is not sufficient, and high conductivity cannot be expressed by firing at a low temperature of less than 150 ° C., for example.
JP 2008-91250 A (claims, paragraphs [0045] [0046], Examples)

  An object of the present invention is to provide a metal particle paste 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), and a sintered layer using this paste. Another object is to provide a method for forming a sintered pattern.

  Another object of the present invention is to provide a metal particle paste that has high fluidity even at a high concentration and is excellent in dispersibility and storage stability at room temperature, and a method for producing a conductive substrate using this paste. There is to do.

  As a result of diligent studies to achieve the above-mentioned problems, the present inventors have combined a metal nanoparticle coated with a protective colloid composed of an organic compound having a carboxyl group and a polymer dispersant and a metal filler into a paste ( By preparing a thick dispersion), it was found that a sintered layer or a sintered pattern having high conductivity can be efficiently formed even at a low temperature (particularly a low temperature of about 150 ° C. or less), and the present invention has been completed. .

  That is, the metal particle paste of the present invention includes metal colloid particles (A) formed of metal nanoparticles (A1) and protective colloid (A2) covering the metal nanoparticles (A1), metal filler (B), and In the metal particle paste containing the dispersion medium (C), the protective colloid (A2) is composed of an organic compound (A2-1) having a carboxyl group and a polymer dispersant (A2-2). In the metal particle paste of the present invention, the metal constituting the metal nanoparticles (A1) is silver, and the organic compound (A2-1) having a carboxyl group is selected from the group consisting of a monocarboxylic acid and a hydroxycarboxylic acid. It may be at least one kind. The metal filler (B) may be a silver filler having a volume average particle diameter of 0.2 to 10 μm. The ratio (mass ratio) of the organic compound (A2-1) having a carboxyl group and the polymer dispersant (A2-2) is about the former / the latter = 95/5 to 50/50. The ratio (mass ratio) between the metal colloid particles (A) and the metal filler (B) is about metal colloid particles (A) / metal filler (B) = 90/10 to 10/90.

  The present invention also includes a method for producing a conductive substrate including a step of forming a film with the metal particle paste on the substrate, and a step of baking the film. The substrate may be an organic substrate or an inorganic substrate. The firing temperature may be 150 ° C. or lower. Furthermore, the present invention includes a conductive substrate obtained by the above production method.

  In the present invention, since specific metal colloidal particles and metal fillers are combined, a sintered layer or a sintered pattern having high conductivity can be efficiently formed even at a low temperature (especially a low temperature of about 150 ° C. or less). it can. Furthermore, even at a high concentration, the fluidity is high and the dispersibility and storage stability at room temperature are excellent.

[Metal particle paste]
The metal particle paste of the present invention is a paste containing metal colloid particles (A) having a specific compound as a protective colloid, a metal filler (B), and a dispersion medium (C).

(A) Metal colloid particles The metal colloid particles (A) of the present invention are composed of metal nanoparticles (A1) and protective colloids (A2) covering the metal nanoparticles (A1).

(A1) Metal nanoparticles As the metal (metal atom) constituting the metal nanoparticles (A1), for example, transition metals (for example, periodic table group 4A metals such as titanium and zirconium; periodic tables such as vanadium and 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.), Periodic table group 4B metals (eg, germanium, tin, lead, etc.), periodic table group 5B metals (eg, antimony, bismuth, etc.), etc. Can be mentioned. 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 protective colloid, for example, a Group 8 metal of the periodic table, a Group 1B metal of the periodic table, or the like.

  The metal nanoparticles (A1) 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 (A1) can be used alone or in combination of two or more. In many cases, the metal nanoparticles (A1) are usually single metal particles or metal alloy particles. Among them, the metal constituting the metal nanoparticles (A1) 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 (A1) are nanometer size. For example, the maximum primary particle diameter of the metal nanoparticles (A1) in the metal colloid particles of the present invention is, for example, 200 nm or less, preferably 150 nm or less, more preferably 100 nm or less, and the number average particle diameter (average primary particle diameter). May be about 1 to 100 nm, preferably 1.5 to 80 nm, more preferably about 2 to 70 nm (particularly 3 to 50 nm), and usually about 1 to 40 nm (for example, 2 to 30 nm). .

  In addition, the particle diameter of the metal colloid particles is also generally the same as the particle diameter of the metal nanoparticles (A1).

(A2) Protective colloid The protective colloid (A2) is composed of an organic compound (A2-1) having a carboxyl group and a polymer dispersant (A2-2).

(A2-1) Organic compound having a carboxyl group The organic compound (A2-1) has a carboxyl group. The number of such carboxyl groups is not particularly limited as long as it is 1 or more per molecule of the organic compound (A2-1). For example, it is 1 to 10, preferably 1 to 5, and more preferably about 1 to 3. There may be.

  In the organic compound (A2-1), some or all of the carboxyl groups may form a salt (a salt with an amine, a metal salt, or the like). In particular, in the present invention, an organic compound in which a carboxyl group (particularly, all carboxyl groups) does not form a salt [particularly, a salt with a basic compound (a salt with an amine or an amine salt)] The organic compound having a carboxyl group can be preferably used.

Moreover, as long as the organic compound (A2-1) has a carboxyl group, the organic compound (A2-1) may have a functional group other than the carboxyl group (or a coordination group with respect to the metal compound or the metal nanoparticle). The functional group (or coordinating group) other than the carboxyl group is selected from, for example, a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), nitrogen atom, oxygen atom, and sulfur atom. A group having at least one heteroatom {or a functional group such as a group having a nitrogen atom [amino group, substituted amino group (dialkylamino group etc.), imino group (—NH—), nitrogen ring group (pyridyl group) 5-8 membered nitrogen ring group, carbazole group, morpholinyl group, etc.), amide group (—CON <), cyano group, nitro group etc.), group having oxygen atom [hydroxyl group, alkoxy group (for example, methoxy group, etc.) , An ethoxy group, a propoxy group, a butoxy group and other C _1-6 alkoxy groups), a formyl group, a carbonyl group (—CO—), an ester group (—COO—), oxygen A cyclic group (such as a 5- to 8-membered oxygen ring group such as a tetrahydropyranyl group)], a group having a sulfur atom [for example, a thio group, a thiol group, a thiocarbonyl group (—SO—), an alkylthio group (a methylthio group, C _1-4 alkylthio group such as ethylthio group, etc.), sulfo group, sulfamoyl group, sulfinyl group (—SO ₂ —) and the like], groups forming these salts (such as ammonium base), etc.}. These functional groups may be contained in the organic compound (A2-1) alone or in combination of two or more.

  The organic compound (A2-1) is a compound that does not have a basic group (in particular, an amino group, a substituted amino group, an imino group, or an ammonium base) that can form a salt with a carboxyl group among these functional groups. Is preferred.

  Representative organic compounds (A2-1) include carboxylic acids. Examples of such carboxylic acid include monocarboxylic acid, polycarboxylic acid, and hydroxycarboxylic acid (or oxycarboxylic acid).

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.

  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).

  The organic compound (A2-1) may be used alone or in combination of two or more.

Of these organic compounds (A2-1), aliphatic carboxylic acid (for example, C _1-24 aliphatic carboxylic acid, preferably C _1-20 aliphatic carboxylic acid, more preferably C _1-18 aliphatic carboxylic acid). ) And aliphatic hydroxycarboxylic acids (aliphatic hydroxymonocarboxylic acids and aliphatic hydroxypolycarboxylic acids such as _C2-34 aliphatic hydroxycarboxylic acids) are preferred. Among aliphatic carboxylic acids, saturated aliphatic carboxylic acids (for example, C _1-24 alkanoic acids (alkane carboxylic acids) such as formic acid, acetic acid, propionic acid, stearic acid, preferably C _1-20 alkanoic acids, more preferably C _1-18 alkanoic acid) is preferred. Among the aliphatic hydroxycarboxylic acids, alicyclic hydroxycarboxylic acids (or hydroxycarboxylic acids having an alicyclic skeleton, for example, C _6-34 alicyclic hydroxycarboxylic acids such as cholic acid, preferably C _10-34 alicyclic hydroxycarboxylic acid, more preferably _C16-30 alicyclic hydroxycarboxylic acid) is preferable.

In addition, polycyclic aliphatic hydroxycarboxylic acids such as cholic acid (for example, condensed polycyclic aliphatic hydroxycarboxylic acids, preferably _C10-34 condensed polycyclic aliphatic hydroxycarboxylic acids, preferably _C14-34 condensed). Polycyclic aliphatic hydroxycarboxylic acids, more preferably _C18-30 condensed polycyclic aliphatic hydroxycarboxylic acids), dehydrocholic acid, colanic acid, and other polycyclic aliphatic carboxylic acids (eg, condensed polycyclic aliphatic acids) Aliphatic carboxylic acids, preferably C _10-34 condensed polycyclic aliphatic carboxylic acids, preferably C _14-34 condensed polycyclic aliphatic hydroxy carboxylic acids, more preferably C _18-30 condensed polycyclic aliphatic carboxylic acids ) polycyclic aliphatic carboxylic acids _{(e.g., C 10-50} condensed polycyclic aliphatic carboxylic acids such as, preferably _{C 12-40} condensed polycyclic aliphatic Carboxylic acid, more preferably C _14-34 condensed polycyclic aliphatic carboxylic acids, particularly C _18-30 condensed polycyclic aliphatic carboxylic acids), has a bulky structure, agglomeration of the metal nanoparticles It is preferable because of the large suppression effect.

In particular, it is a relatively low-molecular saturated aliphatic group having a free carboxyl group from the point that it can be eliminated or disappeared from the metal particles at the firing temperature to improve the continuity and conductivity of the metal film by forming a sintering site. Carboxylic acids are preferred, for example C _1-16 alkanoic acids (alkanecarboxylic acids) such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, preferably C _1-12 alkanoic acids (eg C _1-6 alkanoic acids) More preferably, it may be a C _1-4 alkanoic acid, particularly a C _1-3 alkanoic acid (for example, C _1-2 alkanoic acid).

  The molecular weight of the organic compound (A2-1) 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, 55 to 200). Degree).

  Further, the pKa value of the organic compound (A2-1) 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).

(A2-2) Polymer dispersing agent In this invention, a protective colloid is comprised combining the said organic compound (A2-1) and a polymer dispersing agent (A2-2). By forming the protective colloid in such a combination, metal colloid particles containing metal nanoparticles with extremely few coarse particles can be obtained. In particular, the combination of the specific protective colloids can increase the proportion of the metal nanoparticles, and the storage stability of the metal colloid particles (and paste thereof) is also excellent. The reason why such an excellent colloidal metal particle is obtained by the combination is not clear, but the following reasons are conceivable.

  First, the polymer dispersant is excellent in the effect of stabilizing the dispersion of relatively large particles due to its structure, but since the stabilization effect of relatively small particles is not sufficient, the concentration of the metal nanoparticle raw material is increased. Then, the generated particles cannot be sufficiently stabilized. On the other hand, the organic compound disperses and stabilizes relatively small particles generated at the initial synthesis stage of such nanoparticles. Such a synergistic action of the organic compound (A2-1) and the polymer dispersant (A2-2) is considered to be able to generate metal nanoparticles even when the raw material of the metal nanoparticles is high. .

  In addition, the protective colloid repeatedly adsorbs and desorbs on the surface of the metal nanoparticles on a short time scale. However, when the protective colloid is protected with a polymer dispersant, the adsorbed portion is desorbed momentarily. However, the steric hindrance is large, and even when desorbed, other groups are adsorbed on the surface of the metal nanoparticles instead of the groups involved in the adsorption, so that aggregation and sintering between the particles hardly occur. Therefore, while exhibiting good storage stability, due to its high protective ability and decomposition temperature, the sintering of the metal nanoparticles does not occur unless the firing temperature is also high. I can't get it. On the other hand, an organic compound having a carboxyl group usually has a weak adsorptive power on the surface of metal nanoparticles and often has a low vaporization temperature. Therefore, it is easy to obtain a low-resistance conductor by low-temperature firing, but metal nanoparticles are likely to agglomerate and sinter even at low temperatures such as room temperature, and storage stability is not sufficient, so a metal film or the like is stably formed. Is difficult.

  Therefore, in the present invention, a polymer dispersant and an organic compound having a carboxyl group are combined. By such a combination, a portion where the polymer dispersant is adsorbed and a portion where the organic compound is adsorbed are formed on the surface of the metal nanoparticles. And, the portion adsorbed by the polymer dispersant is stabilized by strong surface protection ability, and the storage stability is improved, while the portion adsorbed by the organic compound is easily detached from the surface of the metal nanoparticles, It plays a role as a reaction site for low-temperature sintering. Such reaction sites are protected by the action of the polymer dispersant in an atmosphere of about room temperature, but at a relatively low firing temperature (for example, several tens of degrees or more), between nanoparticles or between nanoparticles and metal. It seems that a sintering reaction is started with the filler, and as a result, 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 the bulk. 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.

  The polymer dispersant (or polymer type dispersant) (A2-2) is not particularly limited as long as it can coat the metal nanoparticles (A1), but the amphiphilic polymer dispersant (or oligomer type dispersion) is not limited. Agent) can be preferably 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, etc.), polyethylene sulfonic acid or salt thereof, polystyrene sulfonic acid or salt thereof, naphthalene sulfonic acid Formalin condensates, nitrogen atom-containing polymer compounds [for example, polymer compounds having amino groups such as polyalkyleneimine (polyethyleneimine, etc.), polyvinylpyrrolidone, polyallylamine, polyether polyamine (polyoxyethylene polyamine, etc.), etc. included.

  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 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 comb-type copolymer (or a comb-type 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 (A2-2) 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 (A2-2) alone or in combination of two or more.

  Among these functional groups, the polymer dispersant (A2-2) preferably has an acid group or a basic group, particularly a free carboxyl group.

  When the polymer dispersant (A2-2) 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 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 a salt). A polymeric dispersant that does not form an amine salt or the like] [that is, a polymeric dispersant having a free acid group (particularly a carboxyl group)] can be suitably used.

  In the polymer dispersant (A2-2) 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, it can be selected from the range of about 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 (A2-2) having an acid group (particularly a carboxyl group) is a compound having a hydrophilic unit and a hydrophobic unit, the acid value is 1 mg KOH / g or more (for example, 2 to 2). 100 mg KOH / g), preferably 3 mg KOH / g or more (for example, about 4 to 90 mg KOH / g), more preferably 5 mg KOH / g or more (for example, about 6 to 80 mg KOH / g), particularly 7 mg KOH / g or more (for example, 8 ˜70 mgKOH / g), or generally 3-50 mgKOH / g (for example, 5-30 mgKOH / g). In the polymer dispersant (A2-2) 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 (A2-2) 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, Disperbic 193, Disperbic 194, Disperbic 2001, Disperbic 2050, etc. Disperbic series [manufactured by Big Chemie Co., Ltd.]; 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 [EFKA Chemical Co., Ltd.] Manufactured by Ajisper PB711, Azisper PAl11, Azisper PB811, Azisper PB821, Azisper PW911, etc. [Ajinomoto Co., Ltd.]; Lorne series such as Len DOPA-158, Floren DOPA-22, Floren DOPA-17, Floren TG-700, Floren TG-720W, Floren-730W, Floren-740W, Floren-745W [manufactured by Kyoeisha Chemical Co., Ltd.]; John Examples include John Crill series [manufactured by Johnson Polymer Co., Ltd.] such as Kuril 678, John Crill 679, and John Crill 62.

  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 (A2-2) can be selected from a range of 1000 to 1000000 (for example, 1200 to 800000), for example, 1500 to 500000 (for example, 1500 to 100,000), preferably 2000 to 80000 ( For example, it may be 2000 to 60000), more preferably 3000 to 50000 (for example 5000 to 30000), particularly about 7000 to 20000.

  In the metal colloid particles (A), the ratio of the protective colloid (A2) (the total amount of the organic compound (A2-1) and the polymer dispersant (A2-2)) is 100% of the metal nanoparticles (A1) in terms of solid content. It can select from the range of about 0.01-100 mass parts with respect to a mass part, for example, 0.05-50 mass parts, Preferably it is 0.1-30 mass parts, More preferably, it is 0.3-20 mass parts It may be about (especially 0.5 to 10 parts by mass). In particular, in the metal colloid particles of the present invention, the proportion of the protective colloid (A2) is 5 parts by mass or less (for example, 0.1 to 5 parts by mass), preferably 100 parts by mass of the metal nanoparticles (A1), preferably It may be about 0.3 to 4.5 parts by mass, more preferably about 0.5 to 4 parts by mass (particularly 1 to 3 parts by mass). In the present invention, the protective colloid is constituted by the specific combination. Therefore, even with a relatively small amount of the protective colloid as described above, generation of coarse nanoparticles of 100 nm or more can be suppressed, and metal nanoparticles can be used. Can be dispersed stably.

  In the metal colloid particles (A), the ratio of the organic compound (A2-1) is, for example, about 0.01 to 70 parts by mass in terms of solid content with respect to 100 parts by mass of the metal nanoparticles (A1). It can be selected from the range, for example, 0.05 to 50 parts by mass, preferably 0.1 to 40 parts by mass, more preferably 0.3 to 30 parts by mass (particularly 0.5 to 20 parts by mass). Good. In particular, in the metal colloid particles of the present invention, the proportion of the organic compound (A2-1) is 5 parts by mass or less (for example, 0.1 to 5 parts by mass) with respect to 100 parts by mass of the metal nanoparticles (A1), Preferably, it may be about 0.2 to 4.5 parts by mass, more preferably about 0.3 to 4 parts by mass (particularly 0.5 to 3 parts by mass).

  Moreover, in metal colloid particle (A), the ratio of a polymer dispersing agent (A2-2) is 0.005-50 mass parts with respect to 100 mass parts of metal nanoparticles (A1) in conversion of solid content, for example. For example, 0.01 to 30 parts by weight, preferably 0.05 to 20 parts by weight, more preferably 0.1 to 10 parts by weight (particularly 0.1 to 5 parts by weight). May be. In particular, in the metal colloid particles of the present invention, the ratio of the polymer dispersant (A2-2) is 2 parts by mass or less (for example, 0.01 to 2 parts by mass) with respect to 100 parts by mass of the metal nanoparticles (A1). ), Preferably 0.03 to 1.5 parts by mass, more preferably about 0.05 to 1 part by mass (particularly 0.1 to 0.5 parts by mass).

  Furthermore, in the metal colloidal particles (A), the ratio of the organic compound (A2-1) to the polymer dispersant (A2-2) (the ratio of the solid content when a solvent is included) is the former / the latter (mass ratio). ) = 99/1 to 1/99 or so, for example, 98/2 to 10/90, preferably 97/3 to 30/70 (for example, 86/14 to 20/80), more preferably It may be about 95/5 to 50/50.

  In particular, in the case of colloidal metal particles, where conductivity is required rather than paste dispersion stability, the ratio of the organic compound (A2-1) to the polymer dispersant (A2-2) is the former / the latter (mass). Ratio) = 99/1 to 60/40, preferably 97/3 to 80/20, more preferably about 95/5 to 85/15. By adding an excessive amount of the low molecular weight organic compound (B2) to the polymer dispersant (A2-2), the sintering site of the colloidal particles can be increased, so that the conductivity can be improved.

  In addition to the combination of the organic compound (A2-1) and the polymer dispersant (A2-2), another protective colloid component may be further contained. The other protective colloid component may be an inorganic compound, but is usually an organic compound.

Other protective colloid components include, for example, oxygen atom-containing organic compounds {eg, alcohols [eg, alkanols (C _6-20 alkane monools such as hexanol, octanol, decanol, dodecanol, octadecanol, etc.), cycloalkanol] (Such as cyclohexanol), aralkyl alcohols, polyhydric alcohols, etc.], ketones [eg alkanones, cycloalkanones, diketones (β-diketones such as acetylacetone)], esters (eg, Fatty acid esters, glycol ether esters, etc.), aldehydes (C _6-20 aliphatic aldehydes such as caprylaldehyde, lauryl aldehyde, palmitoaldehyde, stearyl aldehyde, etc.)}, organic compounds containing sulfur atoms [for example, Sulfoxides, sulfonic acids (eg, arene sulfonic acids such as alkane sulfonic acid, benzene sulfonic acid, toluene sulfonic acid, etc.)] and the like. These other protective colloids may be used alone or in combination of two or more.

  The ratio of the other protective colloid components is, for example, 0.1 to 100 parts by weight, preferably 0.5 to 50 parts by weight, and more preferably 1 to 30 parts by weight with respect to 100 parts by weight of the total combination of the protective colloids. It may be about a part.

  The ratio of the organic compound (A2-1), the polymer dispersant (A2-2), etc. in the metal colloidal particles is determined by a conventional method, for example, thermal analysis (for example, thermal mass / differential thermal simultaneous analysis, etc.). Can be measured.

(B) Metal filler (metal powder)
In the present invention, by combining the metal colloid particles (A) with the metal filler (B), the paste can be given fluidity and the conductivity of the sintered film can be improved.

  In the paste containing the metal colloidal particles (A), as the particle concentration in the paste increases, the distance between the particles becomes smaller, interaction due to entanglement of protective colloids existing between the particles or on the surface occurs, and the viscosity rapidly increases. As a result, the handleability decreases. In this invention, high fluidity | liquidity can be provided even if it is a high concentration paste by adding the metal filler (B) of a large particle size. 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 = [{√2π / (6f)} 1 / 3-1] × d (where, f: volume fraction of fine particles in the paste, d: When the comparison is made with pastes having the same metal concentration, it is presumed that the dispersion containing a component having a larger particle size has a larger distance between the particle surfaces, so that the viscosity decreases.

  (2) The sedimentation velocity D of the particles is expressed by the formula: D = kT / (3πηd) (wherein, 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 the metal filler (B) having a larger particle size to the paste containing the metal colloid particles (A), the proportion of the protective colloid contained in the paste is reduced, and the protection that occurs during firing is achieved. The amount of colloid-derived 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 number average particle diameter of such a metal filler (B) may be 200 nm or more, for example, 0.2 to 10 μm, preferably 0.3 to 8 μm (for example, 0.5 to 7 μm), more preferably. It is about 0.7-6 micrometers (especially 1-5 micrometers). 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 size of the metal filler is too large, for example, clogging is likely to occur in screen printing. On the other hand, when the particle diameter is too small, the dispersibility of the metal filler is lowered, so that the amount of protective colloid used is increased and the amount of gas generated during firing is also increased.

  The ratio of the average particle diameter of the metal colloid particles (A) and the metal filler (B) is: metal colloid particles (A) / metal filler (B) = 1/1000/1 to 1/5, preferably 1/500 to It is about 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 colloid particles 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 (B) include simple metals, alloys, and metal compounds exemplified in the section of metal nanoparticles (A1). Among these metals, a metal (a simple metal and a metal alloy) containing at least a noble metal such as silver or gold (particularly a Group 1B metal of the periodic table), particularly a noble metal simple substance (for example, a simple gold substance) is preferable. The metal constituting the metal nanoparticles may be different from the metal constituting the metal filler, but is preferably the same or the same group metal (particularly the same metal) from the viewpoint of easy sintering.

  The ratio (mass ratio) between the metal colloid particles (A) and the metal filler (B) is as follows: metal colloid particles (A) / metal filler (B) = 90/10 to 10/90, preferably 80/20 to 20 / 80, more preferably about 70/30 to 30/70 (particularly 60/40 to 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.

(C) Dispersion medium The dispersion medium is a solvent that generates a sufficient viscosity in a paste (paste-like dispersion) by combining the metal colloid particles (or metal nanoparticles) (A) and the metal filler (B). If it is, it will not specifically limit, A general purpose solvent can be used. In addition, a solvent may be newly mixed, may be comprised with the solvent used in manufacture of the below-mentioned metal colloid particle, and may combine these.

  The solvent is not particularly limited as long as the metal colloid particles can be dispersed. Depending on the type of protective colloid, the solvent may be a polar solvent (water-soluble solvent) or a hydrophobic solvent (water-insoluble solvent). Also good.

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.

  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 dispersion medium 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 a water-soluble solvent such as at least water and / or alcohols, because it has a low environmental burden and is easy to handle. Furthermore, since it can impart viscosity to the paste and can moderate the growth of particles upon heating, a water-soluble solvent having a hydroxyl group, for example, alcohols such as ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, Cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, carbitols such as methyl carbitol, ethyl carbitol and butyl carbitol, aliphatic polyhydric alcohols such as ethylene glycol, diethylene glycol and glycerin (especially aliphatic such as ethylene glycol) Polyhydric alcohols) are preferred.

  In the paste containing such a dispersion medium (C), metal colloid particles (A) and metal filler (B), metal colloid particles (A) (or metal nanoparticles (A1)) and metal filler (B) are: High dispersibility with respect to the dispersion medium and high dispersion stability over a long period of time. The concentration of the metal nanoparticles (A1) in the paste is, for example, about 30 to 95% by mass, preferably about 50 to 93% by mass, more preferably about 70 to 90% by mass (particularly about 80 to 90% by mass). Also good.

  Even if such metal particle paste contains metal nanoparticles (A1) and metal filler (B) at a high concentration, it has excellent long-term stability (storage stability) without causing sedimentation. Therefore, for example, even if a metal film (sintered film) is formed after storing the paste for a long period of time, excellent conductivity can be maintained without increasing the resistance value in the metal film.

  In the metal particle paste of the present invention, a conventional additive, for example, a binder resin (such as a hydrophilic polymer such as polyvinyl alcohol or polyethylene glycol), a colorant (such as a dye / pigment), a hue improver, Dye fixing agent, gloss imparting agent, metal corrosion inhibitor, stabilizer (antioxidant, UV absorber, etc.), surfactant or dispersant (anionic surfactant, cationic surfactant, nonionic surfactant) , Amphoteric surfactants, etc.), dispersion stabilizers, thickeners or viscosity modifiers, humectants, thixotropic agents, leveling agents, antifoaming agents, bactericides, fillers and the like. These additives can be used alone or in combination of two or more.

[Method for producing metal particle paste]
In the metal particle paste of the present invention, the metal colloid particles are obtained by a conventional method, for example, by applying a metal compound corresponding to the metal nanoparticles (A1) to the protective colloid (B) (and the other protective colloid if necessary). And can be prepared by reduction in a solvent in the presence of a reducing agent.

  Examples of the metal compound corresponding to the metal nanoparticle (A1) include metal oxide, metal hydroxide, metal sulfide, metal halide, metal acid salt [metal inorganic acid salt (sulfate, nitrate, perchloric acid). Oxo acid salts such as salts), metal organic acid salts (such as acetates), 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 include conventional components such as sodium borohydride (sodium borohydride, sodium cyanoborohydride, sodium triethylborohydride, etc.), lithium aluminum hydride, hypophosphorous acid or a salt thereof (sodium). Salts), boranes (diborane, dimethylamine borane, etc.), hydrazine, formalin, amines, alcohols (the alcohols exemplified above, such as ethylene glycol), carboxylic acids having a phenolic hydroxyl group (eg, tannic acid) And the like.

Examples of amines include aliphatic amines (for example, propylamine, butylamine, hexylamine, diethylamine, dipropylamine, dimethylethylamine, diethylmethylamine, triethylamine, ethylenediamine, N, N, N ′, N′-tetramethylethylenediamine). 1,3-diaminopropane, alkaneamines such as N, N, N ′, N′-tetramethyl-1,3-diaminopropane; polyalkylene polyamines such as triethylenetetramine and tetraethylenepentamine), and alicyclic rings Formula amines (eg piperidine, N-methylpiperidine, piperazine, N, N′-dimethylpiperazine, pyrrolidine, N-methylpyrrolidine, morpholine, etc.), aromatic amines (eg aniline, N-methylaniline, N, N-dimethyl Nilin, toluidine, anisidine, phenetidine, etc.), araliphatic amines (for example, benzylamine, N-methylbenzylamine, N, N-dimethylbenzylamine, phenethylamine, xylylenediamine, N, N, N ′, N ′ Aralkylamines such as tetramethylxylylenediamine), alcohol amines [especially alkanolamines such as methylaminoethanol, dimethylaminoethanol (2- (dimethylamino) ethanol), ethanolamine, diethanolamine, triethanolamine, methyl diethanolamine, propanolamine, 2- (3-aminopropyl amino) ethanol, butanol amine, hexanol amine, _{C 2-10} alkanol amines such as dimethylamino propanol, preferably May be mentioned is _{C 2-6} alkanolamine.

  Among these, sodium borohydride, tertiary amine (for example, tertiary alkanolamine such as 2- (dimethylamino) ethanol and N-methyldiethanolamine), ethylene glycol, tannic acid and the like can be preferably used. In view of safety, amines, particularly alcohol amines such as alkanolamines are preferred. Alkanolamines are usually water-soluble in many cases, and are suitable when water or an aqueous solvent is used as a solvent.

  These reducing agents can be used alone or in combination of two or more.

  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.

  In addition, the solvent (for example, water etc.) similar to the above can be used for the reaction solvent. As the reaction solvent, the solvent constituting the paste may be used, or a solvent different from the solvent constituting the paste may be used. Specifically, the reaction solvent can be selected from the polar solvent and the hydrophobic solvent according to the type of the protective colloid. Usually, when the protective colloid is a water-soluble compound, a polar solvent such as water is used. Often used. The polar solvent may be derived from a component added to the reaction system, for example, a solvent such as a reducing agent. On the other hand, when the protective colloid is a water-insoluble compound, a hydrophobic solvent such as aliphatic hydrocarbons (such as trimethylpentane) is often used, and if necessary, a hydrophobic solvent and a polar solvent (for example, ethanol, Alcohols such as isopropanol, ketones such as acetone, cyclic ethers such as dioxane and tetrahydrofuran, and amides such as dimethylacetamide) may be used.

  Of these reaction solvents, a polar solvent containing at least water may be used from the viewpoints of environmental conservation and simplicity. Furthermore, alcohols (particularly, aliphatic polyhydric alcohols such as ethylene glycol and glycerin) may be combined with water from the viewpoint of suppressing evaporation of the solvent, depending on the application. 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.

  The concentration of the metal compound in the reaction solvent is, for example, 5% by mass or more (for example, 6 to 50% by mass), preferably 8% by mass or more (for example, 9 to 40% by mass), in terms of metal mass. Preferably, the concentration may be as high as 10% by mass or more (for example, 12 to 30% by mass), usually about 5 to 30% by mass. In the present invention, even when the reaction is performed at such a high concentration, metal nanoparticles can be efficiently obtained while suppressing the generation of coarse nanoparticles exceeding 100 nm.

  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, an amine (for example, alkyl Bases such as organic bases such as tertiary amines such as amines and alkanolamines].

  After completion of the reduction reaction, the reaction mixture is concentrated and purified by conventional methods (for example, centrifugation, membrane filter, ultrafiltration, etc.), so that the metal colloid has dispersibility in the solvent. Particles (A) can be prepared. In the present invention, since the protective colloid is constituted by the specific combination, as described above, even with a relatively small amount of protective colloid, metal nanoparticles with few coarse nanoparticles can be obtained and purified. Even if not, the metal colloidal particles (A) can be prepared. Moreover, the obtained dispersion liquid containing the metal colloid particles (A) and the solvent may be used as it is or concentrated to obtain the paste, and the solvent used in the reaction from the obtained dispersion liquid containing the metal colloid particles (A) and the solvent. May be removed, and a new different solvent (other additives as required) may be added to prepare a new paste. Further, a new same or different solvent or additive may be added to the paste. The compounding of the metal filler (B) may be added at any stage in each method. For example, the solvent used for the reaction may be removed from the dispersion, and the metal filler (B) may be added together with the addition of a new different type of dispersion medium.

  The paste can be prepared by stirring. For example, the metal colloid particles (A), the metal filler (B), and the dispersion medium (C) may be mixed in a mortar.

[Method for producing conductive substrate]
The metal particle paste of the present invention can be used for various applications. For example, the metal particle paste of the present invention is useful as a paste for forming a metal film (particularly a conductive film). In particular, the metal particle paste of the present invention contains metal nanoparticles and metal fillers at a high concentration and can be sintered at a relatively low temperature (for example, 150 ° C. or less). Among these, 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 protective colloids thereof) and the base material. For example, an olefin resin [for example, Polyethylene (linear low density polyethylene, low density polyethylene, etc.), ethylene-acrylic acid ester copolymer (ethylene-ethyl acrylate copolymer, etc.), ethylene-methacrylic acid ester copolymer, ethylene- (meth) acrylic Acid copolymers, ionomer resins, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, polyethylene resins such as ethylene-acrylonitrile-acrylic acid copolymers, amorphous polypropylene resins, 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 and the metal filler can be fused to form a continuous film, and can be appropriately selected. 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. In particular, 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.

  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 and the metal filler.

  Since the metal particle paste of the present invention contains metal nanoparticles and metal filler at a high concentration, it is useful, for example, as a paste for forming a metal film (sintered film). In particular, since it does not contain an organic binder and can be sintered at a low temperature, it is excellent in printability and is therefore suitable for a paste used as a circuit forming material for a substrate. Such pastes include, for example, printing pastes, embedding pastes, printing etching pastes, etc., depending on the process used. For example, printing pastes for address electrodes and bus electrodes, and raw materials for die bonding materials It can be used effectively as a paste.

  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
(Synthesis of silver colloidal particles)
66.8 g of silver nitrate, 10 g of acetic acid (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 118 ° C., carbon number 2) as the organic compound (A2-1) having a carboxyl group, carboxyl group as the polymer dispersant (A2-2) (Dispersic 190, manufactured by Big Chemie, amphiphilic dispersant having a polyethylene oxide chain as a hydrophilic unit and an alkyl group as a hydrophobic unit, solvent: water, 40% non-volatile component, 2 g of acid value 10 mgKOH / g, amine value 0) was put into 1000 g of ion-exchanged water and stirred vigorously. To this was added 100 g of 2-dimethylaminoethanol (manufactured by Wako Pure Chemical Industries, Ltd.), and the mixture was heated and stirred at 70 ° C. for 2 hours. This reaction product was centrifuged at 7000 rpm for 1 hour using a high-speed centrifuge (manufactured by Kokusan, H-200 SERIES), and silver colloidal particles (number average particle diameter 20 nm) in which silver nanoparticles were protected by a protective colloid were aggregated. The collected precipitate was collected.

(Analysis of silver colloid particles)
When the content of the protective colloid was measured with a thermogravimetric measuring apparatus (TG / DTA, manufactured by Seiko Instruments Inc., EXSTAR6000), 3 parts by mass of protective colloid was contained with respect to 100 parts by mass of silver. In addition, the measurement by TG / DTA was computed from the mass reduction | decrease when it heated up from 30 degreeC to 200 degreeC at the speed | rate of 10 degreeC per minute. The mass ratio of the organic compound (A2-1) to the polymer dispersant (A2-2) was organic compound (A2-1) / polymer dispersant (A2-2) = 35/65.

(Sintering of silver colloidal particles)
6 g of silver colloidal particles prepared by the above synthesis, silver filler (manufactured by Mitsui Kinzoku Co., Ltd., trade name “SPN20J”, particle size D10 with an integrated value in a volume-based particle size distribution curve of less than 10%: 1.80 μm, 50% Less than D50: 3.16 μm, less than 90% D90: 5.2 μm) 6.3 g and ethylene glycol (polarity parameter 6.9) 1.5 g were mixed in a mortar to prepare a silver particle paste. This paste was applied onto an alkali-free glass substrate (manufactured by Corning Co., Ltd., product number 1737) and baked at 150 ° C. for 30 minutes on a hot plate to form a silver film having a thickness of 10 μm on the substrate. The specific resistance of the silver film was measured and found to be 8.0 × 10 ⁻⁶ Ω · m.

Example 2
In the synthesis of silver colloidal particles, silver colloidal particles were synthesized in the same manner as in Example 1 except that the amount of the polymer dispersant (A2-2) used was 7 g. The content of the protective colloid is 5 parts by mass with respect to 100 parts by mass of silver, and the mass ratio of the organic compound (A2-1) to the polymer dispersant (A2-2) is the organic compound (A2-1). / Polymer dispersant (A2-2) = 18/82. Further, using this silver colloidal particle, a silver particle paste was prepared in the same manner as in Example 1, and the specific resistance of the silver film was measured. As a result, it was 9.5 × 10 ⁻⁶ Ω · m.

Example 3
In the synthesis of silver colloidal particles, Example 1 was used except that 10 g of propionic acid (manufactured by Wako Pure Chemical Industries, Ltd., boiling point 141 ° C., carbon number 3) was used as the organic compound (A2-1) instead of acetic acid. Similarly, silver colloidal particles were synthesized. The content of the protective colloid is 5 parts by mass with respect to 100 parts by mass of silver, and the mass ratio of the organic compound (A2-1) to the polymer dispersant (A2-2) is the organic compound (A2-1). / Polymer dispersant (A2-2) = 30/70. Further, using this silver colloidal particle, a silver particle paste was prepared in the same manner as in Example 1, and the specific resistance of the silver film was measured. As a result, it was 9.0 × 10 ⁻⁶ Ω · m.

Example 4
In the synthesis of silver colloidal particles, silver colloidal particles were synthesized in the same manner as in Example 1 except that the amount of the polymer dispersant (A2-2) used was 0.12 g. The content of the protective colloid is 2 parts by mass with respect to 100 parts by mass of silver, and the mass ratio of the organic compound (A2-1) to the polymer dispersant (A2-2) is the organic compound (A2-1). / Polymer dispersant (A2-2) = 86/14. Further, a silver particle paste was prepared in the same manner as in Example 1 using the silver colloid particles. This paste was applied on an alkali-free glass substrate (Corning Co., Ltd., product number 1737) and baked on a hot plate at 120 ° C. for 30 minutes to form a 10 μm thick silver film on the substrate. The specific resistance of the silver film was measured and found to be 7.0 × 10 ⁻⁶ Ω · m.

Example 5
Silver filler (made by Mitsui Kinzoku Co., Ltd., trade name "SPQ05S", integrated value in a volume-based particle size distribution curve is less than 10%, particle size D10: 0.45 μm, less than 50% D50: 0.82 μm as silver filler , less than 90% D90: 1.50μm) except for using in the same manner as in example 4, the silver particle paste was prepared, was measured the specific resistance of the silver film, 11.0 × ^{10 -6} Ω · m.

Example 6
Silver filler (trade name “FHD” manufactured by Mitsui Kinzoku Co., Ltd.), particle diameter D10 of less than 10% as a silver filler D10: 0.31 μm, D50 of less than 50%: 0.48 μm The silver particle paste was prepared and the specific resistance of the silver film was measured in the same manner as in Example 4 except that less than 90% D90: 0.78 μm) was used, and 15.0 × 10 ⁻⁶ Ω · m.

Example 7
In the synthesis of silver colloidal particles, 2 g of cholic acid (manufactured by Wako Pure Chemical Industries, Ltd., decomposition temperature 198 ° C.) instead of acetic acid as the organic compound (A2-1), and Dispersic as the polymer dispersant (A2-2) Colloidal silver particles were synthesized in the same manner as in Example 1 except that 3 g of polyacrylic acid (manufactured by Wako Pure Chemical Industries, degree of polymerization 5000, acid value 780 mgKOH / g) was used instead of 190. The content of the protective colloid is 3 parts by mass with respect to 100 parts by mass of silver, and the mass ratio of the organic compound (A2-1) to the polymer dispersant (A2-2) is the organic compound (A2-1). / Polymer dispersant (A2-2) = 20/80. Further, using this silver colloidal particle, a silver particle paste was prepared in the same manner as in Example 1, and the specific resistance of the silver film was measured. As a result, it was 7.0 × 10 ⁻⁶ Ω · m.

Example 8
Example 4 except that a paste is applied on a polyethylene terephthalate (PET) film (product number A-4300, a film having a polyester easy-adhesion layer formed on the surface) instead of alkali-free glass as a base material In the same manner as above, a silver film having a thickness of 10 μm was formed on the easy-adhesion layer of the substrate. The specific resistance of the silver film was measured and found to be 7.0 × 10 ⁻⁶ Ω · m. When the silver film was cross-cut in a grid pattern (100 pieces of 10 × 10 in total) and subjected to a tape peeling test, there was no peeled (100/100) and the film was firmly adhered.

Claims (9)

  Metal particle paste comprising metal colloid particles (A), metal filler (B) and dispersion medium (C) formed of metal nanoparticles (A1) and protective colloid (A2) covering the metal nanoparticles (A1) A metal particle paste in which the protective colloid (A2) is composed of an organic compound (A2-1) having a carboxyl group and a polymer dispersant (A2-2).   The metal constituting the metal nanoparticles (A1) is silver, and the organic compound (A2-1) having a carboxyl group is at least one selected from the group consisting of monocarboxylic acids and hydroxycarboxylic acids, and a metal filler (B Is a silver filler having a volume average particle size of 0.2 to 10 µm.   The ratio (mass ratio) of the organic compound (A2-1) having a carboxyl group and the polymer dispersant (A2-2) is the former / the latter = 95/5 to 50/50. Metal particle paste.   The ratio (mass ratio) between the metal colloid particles (A) and the metal filler (B) is metal colloid particles (A) / metal filler (B) = 90/10 to 10/90. The metal particle paste according to crab.   The manufacturing method of the electroconductive base material including the process of forming a film with the metal particle paste in any one of Claims 1-4 on a base material, and the process of baking this film.   The production method according to claim 5, wherein the substrate is an organic substrate.   The production method according to claim 5, wherein the substrate is an inorganic substrate.   The manufacturing method in any one of Claims 5-7 which bake-process at 150 degrees C or less.   The electroconductive base material obtained by the method in any one of Claims 5-7.