JP4865772B2 - Metal colloidal particles and dispersions thereof - Google Patents

Description

  The present invention relates to a metal colloid particle containing metal nanoparticles (such as silver nanoparticles), a dispersion containing the metal colloid particles, and a method for producing the metal colloid particles.

  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.

  Such a method for producing metal nanoparticles is roughly classified into a gas phase method and a liquid phase method. Regarding the gas phase method, Japanese Patent No. 3341361 (Patent Document 1) discloses that ultrafine particles are heated and evaporated in an inert gas, and the vapor is rapidly cooled by collision with the inert gas to form ultrafine particles. In the method of manufacturing the ultrafine particle dispersed material by alternately performing the step of attaching the ultrafine particles on the substrate and the step of forming the matrix on the substrate, the step of forming the matrix includes tetramethoxysilane and the like. A method for producing an ultrafine particle dispersed material, which is a process by a chemical vapor deposition method in which a gas of an organic compound or silicon hydride is involved in a chemical reaction, is disclosed. In this method, it is possible to suppress the ultrafine particle agglomeration growth by the alternate deposition method, and it is possible to produce an ultrafine particle dispersed material with a small variation in particle size distribution. However, the vapor phase method requires an expensive and large-scale apparatus such as an induction heating apparatus or a vacuum apparatus, and metal nanoparticles are generated in the vacuum apparatus, so that the amount of metal nanoparticles obtained at one time is small. It is not suitable for mass production of metal nanoparticles.

  On the other hand, the liquid phase method is not only simple but also suitable for mass production. As a method for producing metal nanoparticles by such a liquid phase method, a method is known in which a metal compound is reduced in a solution in the presence of a compound (or a dispersant) that can be a protective colloid of the metal compound. .

  In such a method using a protective colloid, it has been proposed to use a pigment dispersant known in the field of ink or the like as the protective colloid. For the purpose of improving colorability and metallic luster, use of a polymer dispersant as a protective colloid has also been proposed.

  For example, Japanese Patent Application Laid-Open No. 11-80647 (Patent Document 2) discloses a colloidal solution of noble metal or copper including colloidal particles of noble metal or copper and a high molecular weight pigment dispersant. In this document, as a high molecular weight pigment dispersant, (1) a comb-shaped structure having a pigment affinity group in a main chain and / or a plurality of side chains and a plurality of side chains constituting a solvation part. A polymer, (2) a polymer having a plurality of pigment-affinity moieties comprising pigment affinity groups in the main chain, and (3) a linear chain having a pigment affinity moiety comprising a pigment affinity group at one end of the main chain. Examples of commercially available products that can be used as polymers include Solsperse 20000, Solsperse 24000, Solsperse 26000, Solsperse 27000, Solsperse 28000 (manufactured by Geneca); Dispersic 160, Dispersic 161, Dispersic 162 Dispersic 163, Dispersic 166, Dispersic 170, Dispersic 180, Dispa Bic 182, Disperbic 184, Disperbic 190 (manufactured by Big Chemie); EFKA-46, EFKA-47, EFKA-48, EFKA-49 (manufactured by EFKA Chemical); 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.); Examples include DOPA-22, florene DOPA-17, florene TG-730W, florene G-700, and florene TG-720W (manufactured by Kyoeisha Chemical Co., Ltd.).

  Japanese Patent Application Laid-Open No. 2004-256722 (Patent Document 3) describes a metallic luster color for writing instruments which contains at least colloidal particles selected from gold, silver, platinum and copper, a solvent, and a dispersant as a colorant. An ink composition is disclosed. This document describes an amphiphilic copolymer in which a functional group having a high affinity for the pigment (colloid particle) surface is introduced into a polymer as a dispersant, and can be specifically used. Examples of the dispersant include the same dispersants as described above.

  As in the methods described in these documents, when a polymer is used as a dispersant, the polymer adsorbed on the particle surface prevents aggregation between the particles, so that the nanoparticles exhibit good dispersibility and can be stored at room temperature. A stable nanoparticle dispersion is obtained. However, in the methods described in these documents, although metal nanoparticles are obtained, coarse particles (for example, particles having a primary particle diameter of 100 nm or more) are easily generated. In particular, when the concentration of the metal compound in the reaction system is increased, coarse particles are remarkably easily generated, and the yield of the metal nanoparticles is greatly reduced. In addition, when the metal nanoparticles obtained in these documents are applied to a substrate to form a conductive metal film, the decomposition and vaporization temperature of the polymer as the dispersant is high, so low temperature firing (for example, less than 300 ° C.) ), It is difficult to obtain a low resistance metal film.

  Furthermore, Japanese Patent Application Laid-Open No. 2007-63580 (Patent Document 4) discloses a method for producing silver nanoparticles, comprising (1) an amine compound, (2) a silver salt, and (3) a polycyclic ring having a carboxyl group. Formula hydrocarbon compounds (cholic acid, deoxycholic acid, dehydrocholic acid, chenodeoxycholic acid, 12-oxochenodeoxycholic acid, glycocholic acid, colanic acid, lithocholic acid, hyodeoxycholic acid, ursodeoxycholic acid, apocholic acid, taurocholic acid And a starting material containing abietic acid, glycyrrhizic acid, glycyrrhizic acid, etc.) is disclosed.

However, the method described in this document requires a polycyclic hydrocarbon compound having a large amount of carboxyl groups in order to obtain metal nanoparticles, and is not practical. Moreover, since it is used in a large amount, it is practically necessary to purify the metal colloidal particles. Further, when the amount of the hydrocarbon compound is reduced, coarse particles are generated. Therefore, it is difficult to obtain metal colloidal particles containing metal nanoparticles having a high concentration and a small particle size.
Japanese Patent No. 3341361 (Claim 1) JP 11-80647 A (Claim 1, paragraph numbers [0020], [0035]) JP 2004-256722 A (Claims 1 to 5, paragraphs [0008] to [0016]) JP 2007-63580 A (Claims)

  Therefore, an object of the present invention is to provide a metal colloid particle (metal nanoparticle composite) containing metal nanoparticles in which the generation of coarse particles (or relatively large particles) is suppressed, a dispersion containing the metal colloid particles, and the It is to provide a manufacturing method.

  Another object of the present invention is to provide a metal colloid particle having excellent long-term storage stability despite containing metal nanoparticles at a high concentration, a dispersion containing the metal colloid particle, and a method for producing the same. It is to provide.

  Still another object of the present invention is to provide metal colloidal particles that are excellent in dispersibility and storage stability and that can be sintered at a low temperature (for example, sintering at less than 300 ° C.), dispersions containing the metal colloidal particles, and the like It is to provide a manufacturing method.

  Another object of the present invention is to provide metal colloid particles (or dispersions thereof) that can obtain metal nanoparticles in a high yield with little generation of coarse particles even when the metal concentration in the reaction system (in the reaction solvent) is high. ) Manufacturing method.

  As described above, when the protective colloid (or dispersant) that coats or protects the metal nanoparticles is used as a polymer dispersant, coarse particles are easily generated, and a low-resistance metal film is obtained by low-temperature firing. Is difficult. On the other hand, when a low molecule is used as a dispersant, the low molecular decomposition or vaporization temperature is low, and therefore, it is possible to obtain a good conductive metal film even in low-temperature firing (for example, firing at less than 300 ° C.). However, there is a problem that the particles are easily aggregated and sintered, and the resistance value increases due to long-term storage.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventor has obtained a protective colloid (or dispersant) for coating or protecting metal nanoparticles, an organic compound having a carboxyl group, and a polymer dispersant (in particular, a carboxyl group). In this way, it is possible to obtain metal colloidal particles in which the formation of coarse particles is suppressed, and in particular, by using such protective colloids, the metal concentration in the reaction system is increased. However, the production of coarse particles can be remarkably suppressed, and metal colloidal particles containing metal nanoparticles at a high concentration can be obtained. In addition, the combination of the specific dispersants allows for dispersibility, storage stability, and low temperature sintering. It is possible to obtain metal colloidal particles that have compatible properties and to maintain excellent conductivity in a metal film (sintered film) even when stored for a long period of time. Found that sinterable metal colloid particles are obtained, and have completed the present invention.

  That is, the metal colloid particles of the present invention are metal colloid particles composed of metal nanoparticles (A) and a protective colloid (B) covering the metal nanoparticles (A), and the protective colloid (B ) Is composed of an organic compound (B1) having a carboxyl group and a polymer dispersant (B2). The metal constituting the metal nanoparticles (A) may be a metal (for example, silver) containing at least a noble metal.

The organic compound (B1) may be an aliphatic carboxylic acid (for example, a C _1-24 aliphatic carboxylic acid, preferably a C _1-20 aliphatic carboxylic acid, more preferably a C _1-18 aliphatic carboxylic acid, particularly C _{1- 18} alkanoic acid) and a hydroxycarboxylic acid [for example, an aliphatic hydroxycarboxylic acid (for example, a C _14-34 condensed polycyclic aliphatic hydroxycarboxylic acid such as cholic acid, etc.)] Also good.

The polymer dispersant (B2) may have a carboxyl group. Typically, the organic compound (B1) may be at least one selected from C _1-18 aliphatic carboxylic acid and C _2-34 aliphatic hydroxycarboxylic acid.

  In the metal colloid particles, the ratio of the organic compound (B1) and the polymer dispersant (B2) is, for example, the former / the latter (mass ratio) = 95/5 to 2/98 (for example, 86/14 to It may be about 4/96). Typically, the ratio of the protective colloid (B) is about 1.0 to 60 parts by mass with respect to 100 parts by mass of the metal nanoparticles (A), and the organic compound (B1) and the polymer dispersant. The ratio with (B2) may be the former / the latter (mass ratio) = 90/10 to 3/97 (for example, 86/14 to 4/96).

  As described above, the metal colloid particles of the present invention contain metal nanoparticles with few coarse particles. For example, in the metal colloidal particles, the average primary particle diameter of the metal nanoparticles (A) is about 1 to 100 nm, and the proportion of particles having a primary particle diameter of 100 nm or more is 1% by mass or less based on the mass of the metal. It may be.

  The present invention also includes a dispersion containing the metal colloid particles and a solvent. In such a dispersion, the solvent may be a solvent containing at least water (water, a mixed solution of water and a water-soluble solvent, particularly water). The polarity parameter of the solvent constituting the dispersion may be about 3.1 to 10.2.

  In the present invention, the metal compound corresponding to the metal nanoparticle (A) is reduced in a solvent (reaction solvent) in the presence of the protective colloid (B) and a reducing agent to produce the metal colloid particle. The method of doing is also included. In such a method, the concentration of the metal compound in the solvent (reaction solvent) may be about 5 to 30% by mass in terms of metal mass. In the present invention, the formation of coarse particles can be suppressed even when the reaction is performed at such a high concentration. In the above method, the reducing agent may be, for example, sodium borohydride, tertiary amine, ethylene glycol, tannic acid and the like. Typically, the reducing agent may be an alkanolamine (for example, dimethylaminoethanol, etc.), and the amount of the reducing agent used is about 1 to 5 moles per mole of the metal compound in terms of metal atoms. There may be.

  In the present invention, since a specific protective colloid is used as the protective colloid for coating the metal nanoparticles, metal colloid particles (metal nanoparticle composite) containing metal nanoparticles in which the generation of coarse particles is suppressed can be obtained. In particular, the metal colloidal particles of the present invention are excellent in long-term storage stability despite containing metal nanoparticles at a high concentration. Moreover, the metal colloid particles of the present invention are excellent in dispersibility and storage stability, and can be sintered at a low temperature (for example, sintering at less than 300 ° C.). Therefore, the metal colloid particles of the present invention can obtain a metal film having sufficient conductivity even after long-term storage. Furthermore, in the method of the present invention, by using the specific protective colloid, even when the metal concentration (or the metal compound concentration) in the reaction system (in the reaction solvent) is high, metal nanoparticles with little generation of coarse particles are obtained. It can be obtained in high yield.

[Metallic colloidal particles]
The metal colloid particles of the present invention are metal colloid particles composed of metal nanoparticles (A) and protective colloids (B) covering the metal nanoparticles (A), wherein the protective colloids (B) are: It consists of a combination of specific compounds.

(Metal nanoparticles (A))
Examples of the metal (metal atom) constituting the metal nanoparticle (A) include transition metals (for example, periodic table group 4A metals such as titanium and zirconium; periodic table group 5A metals such as vanadium and niobium; molybdenum, Periodic Table Group 6A metals such as tungsten; Periodic Table Group 7A metals such as manganese; Periodic Table Group 8 metals such as iron, nickel, cobalt, ruthenium, rhodium, palladium, rhenium, iridium, platinum; copper, silver, Periodic Table Group 1B metals such as gold), Periodic Table Group 2B metals (eg, zinc, cadmium, etc.), Periodic Table Group 3B metals (eg, aluminum, gallium, indium, etc.), Periodic Table Group 4B metals (Eg, germanium, tin, lead, etc.), periodic table group 5B metals (eg, antimony, bismuth, etc.), and the like. 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 (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 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, and particularly 3 to 50 nm. It may be about 1 to 40 nm (for example, 2 to 30 nm).

  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%). .

(Protective colloid (B))
The protective colloid (B) is composed of an organic compound (B1) having a carboxyl group and a polymer dispersant (B2).

(Organic compound having carboxyl group (B1))
The organic compound (B1) 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 (B1), and is, for example, 1 to 10, preferably 1 to 5, and more preferably about 1 to 3. Also good.

  In the organic compound (B1), 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 (B1) has a carboxyl group, the organic compound (B1) may have a functional group other than the carboxyl group (or a coordinating group for 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 (B1) alone or in combination of two or more.

  The organic compound (B1) 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 (B1) 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 (B1) may be used alone or in combination of two or more.

Of these organic compounds (B1), 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) or Hydroxy carboxylic acids such as aliphatic hydroxy carboxylic acids (aliphatic hydroxy monocarboxylic acids and aliphatic hydroxy polycarboxylic acids such as _C2-34 aliphatic hydroxy carboxylic 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.

  The molecular weight of the organic compound (B1) is, for example, 1000 or less (for example, about 46 to 900), preferably 800 or less (for example, about 50 to 700), and more preferably 600 or less (for example, about 100 to 500). It may be.

  Further, the pKa value of the organic compound (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).

(Polymer dispersant (B2))
In the present invention, the protective colloid is constituted by combining the organic compound (B1) and the polymer dispersant (B2). 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, in the present invention, the combination of the specific protective colloids can increase the proportion of metal nanoparticles even though there are few coarse particles, and the storage stability of the metal colloid particles (and dispersions thereof) is also excellent. Yes. 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. A synergistic action of the organic compound (B1) and the polymer dispersant (B2) that can generate metal nanoparticles while suppressing the formation of coarse particles even when the concentration of the metal nanoparticles is high. it is conceivable that.

  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 high. I can't get it. On the other hand, an organic compound having a carboxyl group usually has a weak adsorption force 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 the 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 where the polymer dispersant is adsorbed is stabilized by strong surface protection ability, and the storage stability is improved, while the portion where the organic compound is adsorbed is easily detached from the surface of the metal nanoparticles, It plays a role as a reaction site for low-temperature sintering. Such a reaction site is protected by the action of the polymer dispersant in an atmosphere of about room temperature, but starts a sintering reaction at a relatively low firing temperature (for example, several tens of degrees or more). It seems that a low-resistance metal film 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 has an effect of improving the adhesion to the substrate, and in the conductive substrate of the present invention, the residual amount of such a polymer dispersant can be reduced and the volume shrinkage is small. In addition, since a film having high adhesion can be formed, these points are also factors that are excellent in adhesion to the base material, are firmly fixed to the base material, and can improve the conductivity of the metal film.

  The polymer dispersant (or polymer type dispersant) (B2) is not particularly limited as long as it can coat the metal nanoparticles (A), but the 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 polymers (gelatin, dextrin, etc.), polyethylene sulfonic acid or its salt, polystyrene sulfonic acid or its salt, 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 (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 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 (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 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 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 4). It can be selected from the range of about 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.

  In addition, you may use the polymer dispersing agent (high molecular weight pigment dispersing agent) of the said patent document 2 as a polymer dispersing agent.

  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 such as Kuril 678, John Crill 679, and John Crill 62 [manufactured by 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 colloid particles of the present invention, the ratio of the protective colloid (B) (total amount of the organic compound (B1) and the polymer dispersant (B2)) is, for example, 0 with respect to 100 parts by mass of the metal nanoparticles (A). 0.1 to 100 parts by mass (for example, 0.5 to 80 parts by mass), preferably 1.0 to 60 parts by mass (for example, 1.5 to 50 parts by mass), and more preferably 2 to 40 parts by mass (for example, 3 to 30 parts by mass), particularly about 4 to 25 parts by mass (for example, 5 to 20 parts by mass), and usually about 10 to 50 parts by mass. In particular, in the metal colloid particles of the present invention, the proportion of the protective colloid (B) is 0.5 to 20 parts by mass (for example, 0.8 to 18 parts by mass) with respect to 100 parts by mass of the metal nanoparticles (A). 1 to 15 parts by mass, preferably 1.2 to 12 parts by mass (for example, 1.5 to 10 parts by mass). In the present invention, since the protective colloid is constituted by the specific combination, even a relatively small amount of the protective colloid as described above can be formed into metal nanoparticles with few coarse particles.

  In addition, in a metal colloid particle, the ratio of an organic compound (B1) is 0.05-70 mass parts (for example, 0.1-50 mass parts) with respect to 100 mass parts of metal nanoparticles (A), for example. ), Preferably 0.5 to 40 parts by mass (eg 1 to 30 parts by mass), more preferably about 2 to 20 parts by mass (eg 3 to 15 parts by mass). In particular, in the metal colloid particles of the present invention, the proportion of the organic compound (B1) is 0.05 to 10 parts by mass (for example, 0.1 to 8 parts by mass) with respect to 100 parts by mass of the metal nanoparticles (A). The amount may be preferably about 0.12 to 7 parts by mass (for example, 0.15 to 5 parts by mass), more preferably about 0.18 to 4 parts by mass (for example, 0.2 to 3 parts by mass).

  In the metal colloidal particles, the ratio of the polymer dispersant (B2) is, for example, 0.01 to 50 parts by mass (for example, 0.05 to 30) with respect to 100 parts by mass of the metal nanoparticles (A). Part by mass), preferably 0.1 to 30 parts by mass (for example, 0.5 to 20 parts by mass), and more preferably about 1 to 15 parts by mass (for example, 2 to 10 parts by mass). In particular, in the metal colloid particles of the present invention, the ratio of the polymer dispersant (B2) is 0.05 to 15 parts by mass (for example, 0.1 to 12 parts by mass with respect to 100 parts by mass of the metal nanoparticles (A)). Part), preferably 0.12 to 10 parts by mass (for example, 0.15 to 8 parts by mass), more preferably about 0.18 to 7 parts by mass (for example, 0.2 to 6 parts by mass). Good.

  Further, in the metal colloid particles, the ratio of the organic compound (B1) to the polymer dispersant (B2) (solid content when a solvent or the like is included) is the former / the latter (mass ratio) = 99/1 to 1/99. (For example, 95/5 to 5/95), preferably 85/15 to 10/90 (for example, 75/25 to 15/85), more preferably 70/30 to 20/80 (for example, 60/40 to 25/75), especially about 55/45 to 30/70 (for example, 50/50 to 35/65). In particular, in the metal colloid particles, the ratio of the organic compound (B1) and the polymer dispersant (B2) is the former / the latter (mass ratio) = 97/3 to 1/99 (for example, 96/4 to 1/99). ), Preferably 95/5 to 2/98 (e.g. 93/7 to 2/98), more preferably 92/8 to 3/97 (e.g. 90/10 to 3/97), usually 87/13 to It may be about 3/97 (for example, 86/14 to 4/96).

  In addition, the metal colloid particle of this invention should just contain the said protective colloid (B) at least as a protective colloid, and may contain the other protective colloid. Other protective colloids may be inorganic compounds, but are usually organic compounds.

Other protective colloids 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.), cycloalkanols] (Cyclohexanol, etc.), alkanediols (ethylene glycol, propylene glycol, etc.), polyalkylene glycols (diethylene glycol, triethylene glycol, polyethylene glycol, etc.), aralkyl alcohols, polyhydric alcohols, etc.], ethers (cellosolves) , Carbitols, etc.), ketones [eg, alkanones, cycloalkanones, diketones (β-diketones such as acetylacetone)], esters (eg, fatty acid esters). Ethers, such as glycol ether esters), aldehydes (capryl aldehyde, lauryl aldehyde, palmitoyl aldehydes, C _6-20 aliphatic aldehydes such as stearyl aldehyde) such}, a sulfur atom-containing organic compound [e.g., sulfoxides, sulfones 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 is, for example, 0.1 to 100 parts by mass, preferably 0.5 to 50 parts by mass, and more preferably about 1 to 30 parts by mass with respect to 100 parts by mass of the protective colloid (B). It may be.

  The ratio of (B1), (B2), etc. in the metal colloid particles can be measured by a conventional method, for example, thermal analysis (for example, thermal mass / differential thermal simultaneous analysis).

[Dispersion]
The present invention also includes a dispersion containing the metal colloid particles. Such a dispersion contains the metal colloid particles and a solvent. 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 polar solvents include water, alcohols (C _1-4 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, etc.), aliphatic polyhydric alcohols (ethylene glycol, diethylene glycol, polyethylene glycol, glycerin, etc.), Amides (acylamides such as formamide and acetamide, mono- or di-C _1-4 acylamides such as N-methylformamide, N-methylacetamide, N, N-dimethylformamide and N, N-dimethylacetamide), ketones (such as acetone), ethers (dioxane, tetrahydrofuran, etc.), (such as acetate) organic carboxylic acids, cellosolves (methyl cellosolve, C _1-4 alkyl cellosolve such as ethyl cellosolve, etc.), cellosolves Seteto acids (C _1-4 alkyl cellosolve acetates such as ethyl cellosolve acetate), carbitol (methyl carbitol, ethyl carbitol, propyl carbitol, C _1-4 alkyl carbitols such as butyl carbitol, etc.), Examples thereof include halogenated solvents (halogenated hydrocarbons such as methylene chloride, chloroform and dichloroethane). 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. Furthermore, alcohol (especially aliphatic polyhydric alcohols such as glycerin) may be combined with water from the standpoint 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.

  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 a water-soluble solvent, particularly a solvent containing at least water (water or a mixed solvent containing water and a water-soluble solvent, etc. Particularly preferred is water).

  In such a dispersion, the metal colloid particles (or metal nanoparticles (A)) have a high dispersibility in the solvent and show a high dispersion stability over a long period of time. Although the density | concentration of the metal nanoparticle (A) in a dispersion liquid has high dispersibility, it is not restrict | limited especially, For example, 0.1-60 mass%, Preferably it is 1-50 mass%, More preferably, it is 3-40. It is about mass%.

  In particular, the concentration of the metal nanoparticles (A) in the dispersion is 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), and more preferably. The high concentration may be 10% by mass or more (for example, 12 to 30% by mass), usually about 5 to 30% by mass.

  The dispersion includes paste. The concentration of the metal nanoparticles (A) in the paste (paste-like dispersion) may be, for example, 30 to 95% by mass, preferably 50 to 90% by mass, and more preferably about 70 to 85% by mass. .

  The dispersion of the present invention (including the paste-like dispersion) is excellent in long-term stability (storage stability) without causing sedimentation even when the metal nanoparticles (A) are contained at such a high concentration. Yes. Therefore, for example, even if a metal film (sintered film) is formed after a dispersion (paste, etc.) is stored for a long period of time, excellent conductivity can be maintained without increasing the resistance value in the metal film.

  In the dispersion, the metal nanoparticles (A) coated with the protective colloid are also nanometer-sized, and the average particle size (average primary particle size) can be selected from the same range as described above.

  In the dispersion of the present invention, conventional additives such as binder resins (hydrophilic polymers such as polyvinyl alcohol and polyethylene glycol), colorants (dyeing pigments, etc.), hue improvers, dyes are used depending on the application. 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 may be included. These additives can be used alone or in combination of two or more.

  Note that the solid content concentration of the metal nanoparticles (A) relative to the entire solid content of the dispersion (which constitutes the dispersion) (or the concentration of the metal nanoparticles (A) in the metal colloid particles) is not limited depending on the application. For example, 50% by mass or more (for example, 55 to 99.5% by mass), preferably 60% by mass or more (for example, 70 to 99% by mass), and more preferably 80% by mass or less (for example, 85 to 98.5). Mass%), usually about 90 to 99 mass%. When used as an inkjet ink, the solid content concentration of the metal nanoparticles (A) with respect to the total solid content of the dispersion is 60% by mass or less (for example, about 1 to 60% by mass), preferably 50% by mass or less. (For example, 3 to 45% by mass), preferably 40% by mass or less (for example, 5 to 35% by mass), more preferably about 30% by mass or less (for example, 8 to 25% by mass). When the concentration of the metal nanoparticles in the dispersion or the metal colloid particles is adjusted within the above range, a sufficient metallic luster is easily obtained.

[Method of producing metal colloidal particles and dispersion]
The metal colloid particles (or the dispersion liquid) of the present invention are prepared by a conventional method, for example, by applying a metal compound corresponding to the metal nanoparticles (A) to the protective colloid (B) (and, if necessary, the other protective colloids). ) And a reducing agent in the presence of a reducing agent.

  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, 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 dispersion may be used, or a solvent different from the solvent constituting the dispersion 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. In addition, the density | concentration of the said metal compound in a reaction solvent is the density | concentration similar to the density | concentration of the metal nanoparticle (A) in the said dispersion liquid in conversion of the mass of a metal, for example, 5 mass% or more (for example, 6-50 mass) %), Preferably 8% by mass or more (for example, 9 to 40% by mass), more preferably 10% by mass or more (for example, 12 to 30% by mass), usually even at a high concentration of about 5 to 30% by mass. Good. In the present invention, even when the reaction is performed at such a high concentration, metal nanoparticles can be obtained efficiently while suppressing the generation of coarse particles.

  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].

  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 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, it is possible to obtain a metal nanoparticle with few coarse particles. Without it, metal colloid particles can be prepared. The obtained dispersion containing the metal colloid particles and the solvent may be used as the dispersion as it is, and the solvent used in the reaction is removed from the obtained dispersion containing the metal colloid particles and the solvent to obtain a new different solvent. (If necessary, other additives) may be added to prepare a new dispersion. Further, a new same or different solvent or additive may be added to the dispersion.

  The metal colloidal particles (and dispersion) of the present invention have few coarse particles despite the high metal nanoparticle concentration. In addition, metal nanoparticles or metal colloid particles are stably dispersed, and are excellent in long-term storage.

  In particular, such metal colloidal particles of the present invention are excellent in low-temperature sinterability because there are few coarse particles and the concentration of metal nanoparticles is high. Therefore, the metal colloidal particles of the present invention are useful for printing or printing characters and images having excellent metallic luster without heating or light treatment. Therefore, the metal colloid particles and the dispersion liquid of the present invention can be used as inks for various printing or printing instruments and apparatuses. Examples of such instruments or devices include drawing devices such as inkjet plotters, inkjet printers, inkjet dispensers, and pen plotters, and writing tools (pens) such as ballpoint pens, felt pens, and fountain pens. Especially, since it can also be used as a water-based ink, it is useful as a water-based ballpoint pen or felt pen ink.

  In addition, when a conductive metal is used for the metal, not only a decorative property such as a metallic luster but also a printed image or film obtained is conductive, so as a conductive ink (or conductive paste) Is also available. 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.

  The metal colloid particles and the dispersion liquid of the present invention can exhibit gloss on various substrates (printed plates) and are firmly fixed on the substrates. Examples of substrates include paper (craft paper, glossy paper coated with a coating agent containing inorganic particles such as silica and alumina), cloth (woven fabric and non-woven fabric), chemical fiber paper, synthetic paper, and plastic film. (Or OHP sheet) (olefin film such as polypropylene film, polyester film such as polyethylene terephthalate (PET) film) and the like can be used.

  In addition, since the metal colloid particles and the dispersion of the present invention are excellent in adhesion to inorganic materials, the metal colloid particles and the dispersion are directly applied to an inorganic substrate such as a glass substrate (an inorganic substrate on which an easy adhesion layer is not formed). A film can also be formed.

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

( Reference Example 1)
66.8 g of silver nitrate, polymer dispersant having a carboxyl group (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%, acid value 10 mgKOH / g, amine value 0) 7.2 g, and cholic acid (manufactured by Wako Pure Chemical Industries) 1.8 g were put into 100 g of ion-exchanged water, vigorously stirred, suspension Got. To this suspension, 100 g of dimethylaminoethanol (manufactured by Wako Pure Chemical Industries) was gradually added and then heated and stirred for 4 hours in a water bath at a water temperature of 50 ° C. The obtained reaction liquid (dispersion) was filtered through a glass filter (GC-90 manufactured by ADVANTEC, pore size 0.8 micrometer) to obtain a silver nanoparticle dispersion containing 15% by mass of silver.

(Comparative Example 1)
In Reference Example 1, a dispersion and silver nanoparticles were obtained in the same manner as Reference Example 1 except that cholic acid was not used. Although silver nanoparticles were produced, many coarse particles having a primary particle diameter of 100 nm or more were produced.

(Comparative Example 2)
In Reference Example 1, a dispersion was obtained in the same manner as in Reference Example 1 except that Dispersic 190 was not used. In the dispersion, a lot of coarse particles having a primary particle diameter of 100 nm or more were generated, and sedimentation of the particles was observed.

(Example 2) (I) Production 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 an organic compound (B1) having a carboxyl group, and a polymer dispersant As (B2), 3.0 g of polyacrylic acid (manufactured by Wako Pure Chemical Industries, degree of polymerization 5000, acid value 780 mgKOH / g) was added to 1000 g of ion-exchanged water and vigorously stirred. To this was added 100 g of 2-dimethylaminoethanol (manufactured by Wako Pure Chemical Industries), 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 in which silver nanoparticles were protected by a protective colloid (primary particle diameter of 1 to 100 nm, number The precipitate in which the average particle diameter was 20 nm) was collected. In addition, the particle size of the silver nanoparticles was measured with a transmission electron microscope (TEM).

(II) Evaluation of silver colloid particles (II-1) Dispersant amount measurement The amount of the protective colloid (dispersant) (B) contained in the silver colloid particles is measured by TG-DTA (at a rate of 10 ° C. per minute). (Calculated from mass reduction when the temperature was raised from 30 ° C. to 550 ° C.). Moreover, (B1) amount was computed from the mass reduction | decrease from 30 degreeC to 200 degreeC, (B2) was computed from (B)-(B1), and these mass ratio (B1) / (B2) was calculated | required. The results are shown in Table 1.

(II-2) Specific Resistance and Storage Stability Evaluation A silver concentration 80% paste prepared by adding ethylene glycol (polarity parameter 6.9) to silver colloid particles was applied to a glass substrate using an applicator and 150 ° C. Alternatively, baking was performed at 250 ° C. for 30 minutes, and the specific resistance was measured. The paste was allowed to stand at room temperature for 6 months and then the specific resistance was measured in the same manner to evaluate the storage stability of the silver colloidal particle paste. The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

(Example 3)
The same procedure as in Example 2 was performed except that (B1) was propionic acid (manufactured by Wako Pure Chemical Industries, boiling point 141 ° C., carbon number 3). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

Example 4
The same procedure as in Example 2 was conducted except that (B1) was formic acid (manufactured by Wako Pure Chemical Industries, boiling point 100.7 ° C., carbon number 1). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

( Reference Example 2 )
The same procedure as in Example 2 was conducted except that (B1) was cholic acid (manufactured by Wako Pure Chemicals, decomposition temperature 198 ° C.). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

(Example 6)
(B2) was performed in the same manner as in Example 2 except that 7.2 g was used for Dispersic 190 (BIC Chemie, acid value 10 mgKOH / g, containing 60% water). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

(Example 7)
(B2) was carried out in the same manner as in Example 3 except that 7.2 g was used for Disperbic 190 (produced by Big Chemie, acid value 10 mgKOH / g, containing 60% water). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

(Example 8)
(B2) was carried out in the same manner as in Example 4 except that 7.2 g was used for Disperbic 190 (produced by Big Chemie, acid value 10 mgKOH / g, containing 60% water). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

( Reference Example 3 )
(B2) was performed in the same manner as Reference Example 2 except that 7.2 g was used for Disperbic 190 (Bic Chemie, acid value: 10 mgKOH / g, containing 60% water). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

(Example 10)
The same procedure as in Example 2 was performed except that (B2) was changed to 0.12 g of Dispersic 190 (manufactured by Big Chemie, acid value of 10 mg KOH / g, containing 60% water). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

(Example 11)
(B2) was carried out in the same manner as in Example 2 except that 0.72 g of Dispersic 190 (manufactured by Big Chemie, acid value 10 mg KOH / g, containing 60% water) was used. The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

(Example 12)
The same procedure as in Example 2 was performed except that 2.12 g of (B2) was changed to Disperbic 190 (manufactured by Big Chemie, acid value 10 mgKOH / g, containing 60% water). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

(Example 13)
(B2) was carried out in the same manner as in Example 2 except that Dispersic 190 (produced by Big Chemie, acid value 10 mgKOH / g, containing 60% water) was 5.04 g. The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

(Example 14)
The same procedure as in Example 2 was performed except that (B2) was changed to 14.4 g of Dispersic 190 (manufactured by Big Chemie, acid value of 10 mgKOH / g, containing 60% water). The formed silver film had a thickness of 5 μm. The results are shown in Table 1.

( Reference Example 4 )
The same procedure as in Example 2 was performed except that (B1) was stearic acid (manufactured by Wako Pure Chemical Industries, boiling point 376 ° C., carbon number 18). The formed silver film had a thickness of 5 μm. The results are shown in Table 1. In addition, since the boiling point of stearic acid (B1) is 200 ° C. or more, and the mass reduction due to decomposition of (B2) and the boiling point of stearic acid (B1) overlap, the ratio of (B1) / (B2) is obtained. I couldn't.

Claims (8)

A metal colloidal particle comprising a metal nanoparticle (A) and a protective colloid (B) covering the metal nanoparticle (A), wherein the protective colloid (B) is formic acid, acetic acid, and propionic acid. Metal colloidal particles composed of an organic compound (B1) having at least one carboxyl group selected from the above and a polymer dispersant (B2).   The metal colloidal particle according to claim 1, wherein the metal constituting the metal nanoparticle (A) is a metal containing at least a noble metal. The metal colloidal particle according to claim 1 or 2 , wherein the polymer dispersant (B2) has a carboxyl group. The metal colloid particles according to any one of claims 1 to 3 , wherein the ratio of the organic compound (B1) to the polymer dispersant (B2) is the former / the latter (mass ratio) = 86/14 to 4/96. The ratio of the protective colloid (B) is 1.0 to 60 parts by mass with respect to 100 parts by mass of the metal nanoparticles (A), and the ratio of the organic compound (B1) and the polymer dispersant (B2) is the former. / The latter (mass ratio) = 86/14 to 4/96. The metal colloidal particles according to any one of claims 1 to 4 . A dispersion containing the metal colloid particles according to any one of claims 1 to 5 and a solvent.   The method for producing metal colloidal particles according to claim 1, wherein a metal compound corresponding to the metal nanoparticles (A) is reduced in a solvent in the presence of the protective colloid (B) according to claim 1 and a reducing agent. The method according to claim 7 , wherein the concentration of the metal compound in the solvent is 5 to 30% by mass in terms of metal mass.