JP6151893B2 - Method for producing silver nanoparticles and silver nanoparticles - Google Patents

Description

  The present invention relates to a method for producing silver nanoparticles and silver nanoparticles. Moreover, this invention is applied also to the manufacturing method and metal nanoparticle of metal nanoparticle containing metals other than silver.

  Silver nanoparticles can be sintered even at low temperatures. Utilizing this property, in the manufacture of various electronic devices, a silver coating composition containing silver nanoparticles is used to form electrodes and conductive circuit patterns on a substrate. Silver nanoparticles are usually dispersed in an organic solvent. Silver nanoparticles have an average primary particle diameter of about several nanometers to several tens of nanometers, and the surface thereof is usually coated with an organic stabilizer (protective agent). When the substrate is a plastic film or sheet, it is necessary to sinter the silver nanoparticles at a low temperature (for example, 200 ° C. or less) lower than the heat resistance temperature of the plastic substrate.

  In recent years, not only heat-resistant polyimide that has already been used as flexible printed wiring boards, but also made of various plastics such as PET (polyethylene terephthalate) and polypropylene, which have lower heat resistance than polyimide but are easy to process. Attempts have also been made to form fine metal wiring (for example, silver wiring) on these substrates. When a plastic substrate with low heat resistance is used, it is necessary to sinter metal nanoparticles (for example, silver nanoparticles) at a lower temperature.

  Silver nanoparticles have an average primary particle diameter of about several nanometers to several tens of nanometers, and are more easily aggregated than micron (μm) size particles. Therefore, the reduction reaction of the silver compound (thermal decomposition reaction of the silver oxalate complex compound) so that the surface of the resulting silver nanoparticles is coated with an organic stabilizer (protective agent such as aliphatic amine or aliphatic carboxylic acid) Is carried out in the presence of an organic stabilizer.

  On the other hand, the silver nanoparticles are a silver coating composition (silver ink, silver paste) containing the particles in an organic solvent. In order to develop conductivity, it is necessary to remove the organic stabilizer covering the silver nanoparticles and sinter the silver particles at the time of firing after application on the substrate. If the firing temperature is low, the organic stabilizer is difficult to remove. If the degree of sintering of the silver particles is not sufficient, a low resistance value cannot be obtained. That is, the organic stabilizer present on the surface of the silver nanoparticles contributes to the stabilization of the silver nanoparticles, but prevents the silver nanoparticles from being sintered (particularly, sintering at low temperature firing).

  When an aliphatic amine compound and / or an aliphatic carboxylic acid compound having a relatively long chain (for example, having 8 or more carbon atoms) is used as the organic stabilizer, the distance between the individual silver nanoparticles is easily secured. Nanoparticles are easy to stabilize. On the other hand, long-chain aliphatic amine compounds and / or aliphatic carboxylic acid compounds are difficult to remove if the firing temperature is low.

  Thus, the stabilization of silver nanoparticles and the expression of a low resistance value at low temperature firing are in a trade-off relationship.

  For example, in Japanese Patent Application Laid-Open No. 2008-214695, silver oxalate and oleylamine are reacted to produce a complex compound containing at least silver, oleylamine and oxalate ion, and the produced complex compound is thermally decomposed to produce silver. A method for producing ultrafine silver particles comprising producing ultrafine particles is disclosed (claim 1). In the above method, when a saturated aliphatic amine having 1 to 18 carbon atoms is reacted in addition to the silver oxalate and the oleylamine (Claims 2 and 3), a complex compound can be easily formed, and silver ultrafine particles It is disclosed that the time required for the production of can be reduced, and furthermore, these amine-protected silver ultrafine particles can be produced in higher yield (paragraph [0011]). Further, the publication discloses that a solvent such as methanol, ethanol, water or the like may be added in forming the complex compound (paragraph [0017]).

  JP 2010-265543 A discloses a silver compound that decomposes by heating to produce metallic silver, a medium-short chain alkylamine having a boiling point of 100 ° C to 250 ° C, and a medium-short chain alkyldiamine having a boiling point of 100 ° C to 250 ° C. A method for producing coated silver ultrafine particles comprising a first step of preparing a complex compound containing a silver compound, the alkylamine and the alkyldiamine, and a second step of thermally decomposing the complex compound is disclosed. (Claim 3, paragraphs [0061] and [0062]). Further, the publication discloses that there is no restriction on using a reaction solvent such as methanol or water in order to produce a complex compound (paragraph [0068]).

JP 2008-214695 A JP 2010-265543 A

  However, Japanese Patent Application Laid-Open No. 2008-214695 discloses that a solvent such as methanol, ethanol, water or the like may be added when forming the complex compound. Since the reaction temperature at the time of thermally decomposing the complex compound cannot be raised, the thermal decomposition does not occur sufficiently, which hinders the formation of silver particles. When water is used, it is difficult to completely remove the water after the formation of silver particles.

  Japanese Patent Application Laid-Open No. 2010-265543 discloses that there is no restriction on using a reaction solvent such as methanol or water in order to produce a complex compound. Since the reaction temperature during heat decomposition cannot be increased, thermal decomposition does not occur sufficiently, which hinders the formation of silver particles. When water is used, it is difficult to completely remove the water after the formation of silver particles.

  On the other hand, when a complex compound between a silver compound such as silver oxalate and an amine is formed without a solvent, the silver compound is in a powder form and is extremely difficult to stir, and the reaction between the silver compound and the amine is exothermic. Therefore, there is a big risk in terms of safety from the viewpoint of scaled-up industrial production.

  Thus, a so-called pyrolysis method for producing silver nanoparticles by thermal decomposition of a complex compound of a silver compound such as silver oxalate and an amine is safe from the viewpoint of scaled-up industrial production, and A method for producing silver nanoparticles that yields silver nanoparticles that can be sintered at a low temperature has not been developed so far.

  Accordingly, an object of the present invention is to provide a silver nanoparticle that is safe and simple from the viewpoint of industrial production that has been scaled up for a so-called pyrolysis method in which silver nanoparticles are produced by thermal decomposition of a silver-amine complex compound. It is to provide a manufacturing method. Furthermore, the object of the present invention is to provide a so-called thermal decomposition method for producing silver nanoparticles by thermal decomposition of a silver-amine complex compound, which is safe and simple from the viewpoint of scaled-up industrial production, and at a low temperature. An object of the present invention is to provide a method for producing silver nanoparticles that can yield silver nanoparticles that can be sintered.

The present invention includes the following inventions.
(1) A method for producing silver nanoparticles,
A silver compound and an alcohol solvent are mixed to obtain a silver compound-alcohol slurry,
To the obtained silver compound-alcohol slurry, an aliphatic hydrocarbon amine is added to form a complex compound containing the silver compound and the amine,
The complex compound is heated and thermally decomposed to form silver nanoparticles.
The manufacturing method of the silver nanoparticle containing this.

  (2) The method for producing silver nanoparticles according to (1), wherein the silver compound is silver oxalate.

  (3) The method for producing silver nanoparticles according to (1) or (2), wherein the alcohol solvent is an alcohol having 3 to 10 carbon atoms.

(4) The aliphatic hydrocarbon amine includes an aliphatic hydrocarbon monoamine (A) comprising an aliphatic hydrocarbon group and one amino group, and the total number of carbon atoms of the aliphatic hydrocarbon group is 6 or more. further,
An aliphatic hydrocarbon monoamine (B) comprising an aliphatic hydrocarbon group and one amino group, the aliphatic hydrocarbon group having a total carbon number of 5 or less, and an aliphatic hydrocarbon group and two amino groups And at least one of the aliphatic hydrocarbon diamines (C) in which the total number of carbon atoms of the aliphatic hydrocarbon group is 8 or less, the silver nanoparticle according to any one of the above (1) to (3) Particle production method.

  (5) The method for producing silver nanoparticles according to (4), wherein the aliphatic hydrocarbon monoamine (A) is an alkyl monoamine having 6 to 12 carbon atoms.

  (6) The method for producing silver nanoparticles according to (4) or (5), wherein the aliphatic hydrocarbon monoamine (B) is an alkyl monoamine having 2 to 5 carbon atoms.

  (7) The aliphatic hydrocarbon diamine (C) is an alkylene diamine in which one of two amino groups is a primary amino group and the other is a tertiary amino group (4) )-The manufacturing method of the silver nanoparticle in any one of (6).

  (8) The method for producing silver nanoparticles according to any one of (1) to (7), wherein 120 parts by weight or more of the alcohol solvent is used with respect to 100 parts by weight of the silver compound.

(9) The silver nanoparticles according to any one of the above (1) to (8), wherein 1 to 50 mol of the aliphatic hydrocarbon amine is used as a total with respect to 1 mol of silver atom of the silver compound. Manufacturing method.
Silver oxalate molecules contain two silver atoms. When the silver compound is silver oxalate, any one of the above (1) to (8), wherein 2 to 100 mol of the aliphatic hydrocarbon amine is used as a total per 1 mol of silver oxalate. The manufacturing method of the silver nanoparticle of crab.

  The production of silver nanoparticles according to any one of the above items, wherein the aliphatic hydrocarbon amine contains the aliphatic hydrocarbon monoamine (A) and the aliphatic hydrocarbon monoamine (B). Method.

  The production of silver nanoparticles according to any one of the above items, wherein the aliphatic hydrocarbon amine contains the aliphatic hydrocarbon monoamine (A) and the aliphatic hydrocarbon diamine (C). Method.

  The aliphatic hydrocarbon amine includes the aliphatic hydrocarbon monoamine (A), the aliphatic hydrocarbon monoamine (B), and the aliphatic hydrocarbon diamine (C). The manufacturing method of the silver nanoparticle in any one.

  The method for producing silver nanoparticles according to any one of the above items, wherein, in the step of producing a complex compound containing the silver compound and the amine, an aliphatic carboxylic acid is used in addition to the aliphatic amine. .

  -The manufacturing method of the silver nanoparticle in any one of said each item which does not use aliphatic carboxylic acid other than the said aliphatic amine in the production | generation process of the complex compound containing the said silver compound and the said amine.

  (10) Silver nanoparticles produced by the method according to any one of (1) to (9) above.

  A silver nanoparticle having a surface coated with a protective agent, manufactured by the method according to any one of the above items, wherein the protective agent includes the aliphatic amine used. Silver nanoparticles.

  -The silver coating composition containing the silver nanoparticle manufactured by the method in any one of said each item, and the organic solvent. The silver coating composition can take various forms without limitation. For example, a silver coating composition (silver ink) in which silver nanoparticles are dispersed in an organic solvent in a suspended state. Alternatively, a silver coating composition (silver paste) in which silver nanoparticles are dispersed in a kneaded state in an organic solvent.

A substrate,
A silver conductive layer formed by applying and baking a silver coating composition containing silver nanoparticles and an organic solvent produced by the method according to any one of the above items on the substrate, and
Silver conductive material containing.
The silver conductive layer may be patterned.
Calcination can be performed at a temperature of 200 ° C. or lower, for example 150 ° C. or lower, preferably 120 ° C. or lower, for 2 hours or shorter, for example 1 hour or shorter, preferably 30 minutes or shorter, more preferably 15 minutes or shorter. More specifically, it can be performed in a temperature range of about 80 ° C. to 120 ° C. under conditions of about 10 minutes to 60 minutes. For example, it can be performed under conditions of 80 ° C. for 60 minutes and 120 ° C. for 15 minutes.

A method for producing metal nanoparticles,
A metal compound and an alcohol solvent are mixed to obtain a metal compound-alcohol slurry,
An aliphatic hydrocarbon amine is added to the obtained metal compound-alcohol slurry to produce a complex compound containing the metal compound and the amine,
The complex compound is heated and thermally decomposed to form metal nanoparticles.
The manufacturing method of the metal nanoparticle containing this.

  The aliphatic hydrocarbon amine includes an aliphatic hydrocarbon monoamine (A) composed of an aliphatic hydrocarbon group and one amino group, and the total number of carbons of the aliphatic hydrocarbon group is 6 or more; An aliphatic hydrocarbon monoamine (B) comprising an aliphatic hydrocarbon group and one amino group, the aliphatic hydrocarbon group having a total carbon number of 5 or less, and an aliphatic hydrocarbon group and two amino groups And the manufacturing method of the said metal nanoparticle containing at least one of the aliphatic hydrocarbon diamine (C) whose carbon total number of this aliphatic hydrocarbon group is 8 or less.

  Metal nanoparticles coated on the surface with a protective agent, the metal nanoparticles produced by the method described above, wherein the protective agent contains the aliphatic amine used.

  -The metal coating composition containing the metal nanoparticle manufactured by the said method, and the organic solvent. The metal coating composition can take various forms without limitation. For example, a metal coating composition (metal ink) in which metal nanoparticles are dispersed in an organic solvent in a suspended state. Alternatively, a metal coating composition (metal paste) in which metal nanoparticles are dispersed in a kneaded state in an organic solvent.

  In the present invention, when producing a complex compound containing a silver compound and an aliphatic hydrocarbon amine, first, a powdery silver compound and an alcohol solvent were mixed to obtain a silver compound-alcohol slurry. An aliphatic hydrocarbon amine is added to the silver compound-alcohol slurry to form a complex compound containing the silver compound and the amine. For this reason, in the production | generation process of a complex compound, sufficient stirring operation can be performed and the reaction heat accompanying formation of a complex compound can be escaped out of the system. Therefore, a safe and simple method for producing silver nanoparticles is also provided in scaled-up industrial production.

  In the present invention, as the aliphatic amine compound that functions as a complexing agent and / or a protective agent, an aliphatic hydrocarbon monoamine (A) having 6 or more carbon atoms, an aliphatic hydrocarbon monoamine (B) having 5 or less carbon atoms, and When at least one of the aliphatic hydrocarbon diamines (C) having a total carbon number of 8 or less is used, the surface of the formed silver nanoparticles is covered with these aliphatic amine compounds.

  Since the aliphatic hydrocarbon monoamine (B) and the aliphatic hydrocarbon diamine (C) have a short carbon chain length, they are calcined at a low temperature of 200 ° C. or lower, for example 150 ° C. or lower, preferably 120 ° C. or lower. Furthermore, it is easily removed from the surface of the silver particles in a short time of 2 hours or less, for example 1 hour or less, preferably 30 minutes or less. Further, due to the presence of the monoamine (B) and / or the diamine (C), the amount of the aliphatic hydrocarbon monoamine (A) deposited on the silver particle surface can be small. Accordingly, even in the case of firing at the low temperature, these aliphatic amine compounds are easily removed from the surface of the silver particles in the short time, and the sintering of the silver particles proceeds sufficiently.

  Thus, according to the present invention, excellent conductivity (low resistance value) is obtained even when a silver film that is a relatively thick film of, for example, 1 μm or more is formed by baking at a low temperature and in a short time. ) And a method for producing the same are provided. Moreover, according to this invention, the silver coating composition which contains the said silver nanoparticle in the organic solvent in the stable dispersion state is provided. Furthermore, according to this invention, it applies also to the manufacturing method of metal nanoparticle containing metals other than silver, and this metal nanoparticle. According to the present invention, a conductive film and conductive wiring can be formed on various plastic substrates having low heat resistance such as PET and polypropylene.

In the present invention, a silver compound and an alcohol solvent are mixed to obtain a silver compound-alcohol slurry,
To the obtained silver compound-alcohol slurry, an aliphatic hydrocarbon amine is added to form a complex compound containing the silver compound and the amine,
The complex compound is heated and thermally decomposed to form silver nanoparticles.
Thus, silver nanoparticles are produced. Thus, the method for producing silver nanoparticles in the present invention mainly includes a slurry formation step, a complex compound generation step, and a complex compound thermal decomposition step.

  In the present specification, the term “nanoparticle” means that the size of the primary particles (average primary particle diameter) is less than 1000 nm. The particle size is intended to exclude the protective agent (stabilizer) present (coated) on the surface (that is, the size of silver itself). In the present invention, the silver nanoparticles have an average primary particle diameter of, for example, 0.5 nm to 100 nm, preferably 0.5 nm to 50 nm, more preferably 0.5 nm to 25 nm, and still more preferably 0.5 nm to 20 nm. Yes.

In the present invention, as the silver compound, a silver compound that is easily decomposed by heating to form metallic silver is used. Examples of such silver compounds include silver formate, silver acetate, silver oxalate, silver malonate, silver benzoate, and silver phthalate; silver fluoride, silver chloride, silver bromide, silver iodide, etc. Silver sulfate; silver sulfate, silver nitrate, silver carbonate, and the like can be used, but silver oxalate is preferably used from the viewpoint that metal silver is easily generated by decomposition and impurities other than silver are hardly generated. Silver oxalate is advantageous in that it has a high silver content and does not require a reducing agent, so that metallic silver can be obtained as it is by thermal decomposition, and impurities derived from the reducing agent do not easily remain.

  When producing metal nanoparticles containing a metal other than silver, a metal compound that is easily decomposed by heating to produce the target metal is used instead of the silver compound. As such a metal compound, a metal salt corresponding to the above silver compound, for example, a metal carboxylate; a metal halide; a metal salt compound such as a metal sulfate, a metal nitrate, or a metal carbonate is used. be able to. Of these, metal oxalate is preferably used from the viewpoint of easily generating metal by decomposition and hardly generating impurities other than metal. Examples of other metals include Al, Au, Pt, Pd, Cu, Co, Cr, In, and Ni.

  Moreover, in order to obtain the composite with silver, you may use together said silver compound and other metal compounds other than said silver. Examples of other metals include Al, Au, Pt, Pd, Cu, Co, Cr, In, and Ni. The silver composite is composed of silver and one or more other metals, and examples thereof include Au—Ag, Ag—Cu, Au—Ag—Cu, and Au—Ag—Pd. Based on the total metal, silver accounts for at least 20% by weight, usually 50% by weight, for example 80% by weight.

  In the present invention, first, a silver compound and an alcohol solvent are mixed to obtain a silver compound-alcohol slurry [slurry forming step]. The slurry represents a mixture in which a solid silver compound is dispersed in an alcohol solvent.

  As the alcohol solvent, an alcohol having 3 to 10 carbon atoms, preferably an alcohol having 4 to 8 carbon atoms can be used. For example, n-propanol (boiling point bp: 97 ° C.), isopropanol (bp: 82 ° C.), n-butanol (bp: 117 ° C.), isobutanol (bp: 107.89 ° C.), sec-butanol (bp: 99. 5 ° C), tert-butanol (bp: 82.45 ° C), n-pentanol (bp: 136 ° C), n-hexanol (bp: 156 ° C), n-octanol (bp: 194 ° C), 2-octanol ( bp: 174 ° C.). Among these, n-butanol, isobutanol, sec-butanol, in consideration of the ability to increase the temperature of the thermal decomposition step of the complex compound to be performed later, convenience in post-treatment after the formation of silver nanoparticles, etc. Butanols and hexanols selected from tert-butanol are preferred. In particular, n-butanol and n-hexanol are preferable.

  The alcohol solvent is, for example, 120 parts by weight or more, preferably 130 parts by weight or more, more preferably 150 parts by weight with respect to 100 parts by weight of the silver compound for sufficient stirring operation of the silver compound-alcohol slurry. It is better to use more than one part. The upper limit of the amount of the alcohol solvent is not particularly limited, and may be, for example, 1000 parts by weight or less, preferably 800 parts by weight or less, more preferably 500 parts by weight or less.

  Next, an aliphatic hydrocarbon amine is added to the obtained silver compound-alcohol slurry to generate a complex compound containing the silver compound and the amine [complex compound generation step].

  In the present invention, the aliphatic hydrocarbon amine that functions as a complexing agent and / or a protective agent includes, for example, an aliphatic hydrocarbon monoamine (A) in which the total number of carbon atoms of the hydrocarbon group is 6 or more, and an aliphatic group. An aliphatic hydrocarbon monoamine (B) consisting of a hydrocarbon group and one amino group, wherein the aliphatic hydrocarbon group has a total carbon number of 5 or less, and consisting of an aliphatic hydrocarbon group and two amino groups; At least one of the aliphatic hydrocarbon diamines (C) in which the total number of carbon atoms of the aliphatic hydrocarbon group is 8 or less is used. Each of these components is usually used as an amine mixed solution. However, the mixing of the amine with the silver compound-alcohol slurry is not necessarily performed using the mixed amines. The amines may be sequentially added to the silver compound-alcohol slurry.

  In the present specification, the term “aliphatic hydrocarbon monoamine” is a compound composed of 1 to 3 monovalent aliphatic hydrocarbon groups and one amino group. A “hydrocarbon group” is a group consisting only of carbon and hydrogen. However, the aliphatic hydrocarbon monoamine (A) and the aliphatic hydrocarbon monoamine (B) are, as necessary, a hetero atom (an atom other than carbon and hydrogen) such as an oxygen atom or a nitrogen atom. ). This nitrogen atom does not constitute an amino group.

  In addition, “aliphatic hydrocarbon diamine” means a divalent aliphatic hydrocarbon group (alkylene group), two amino groups intervening the aliphatic hydrocarbon group, and, in some cases, hydrogen of the amino group. It is a compound comprising an aliphatic hydrocarbon group (alkyl group) substituted with atoms. However, the aliphatic hydrocarbon diamine (C) may have a substituent containing a hetero atom (atom other than carbon and hydrogen) such as an oxygen atom or a nitrogen atom in the hydrocarbon group as necessary. Good. This nitrogen atom does not constitute an amino group.

  The aliphatic hydrocarbon monoamine (A) having 6 or more carbon atoms has a high function as a protective agent (stabilizing agent) on the surface of the silver particles to be generated due to the hydrocarbon chain.

  Examples of the aliphatic hydrocarbon monoamine (A) include primary amines, secondary amines, and tertiary amines. Examples of primary amines include hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine Examples thereof include saturated aliphatic hydrocarbon monoamines such as amines (that is, alkyl monoamines). Examples of the saturated aliphatic hydrocarbon monoamine include branched aliphatic hydrocarbon amines such as isohexylamine, 2-ethylhexylamine, and tert-octylamine, in addition to the above-mentioned linear aliphatic monoamine. Also included is cyclohexylamine. Furthermore, unsaturated aliphatic hydrocarbon monoamines (namely, alkenyl monoamines) such as oleylamine can be mentioned.

  Secondary amines include N, N-dipropylamine, N, N-dibutylamine, N, N-dipentylamine, N, N-dihexylamine, N, N-dipeptylamine, N, N-dioctylamine, N , N-dinonylamine, N, N-didecylamine, N, N-diundecylamine, N, N-didodecylamine, N-methyl-N-propylamine, N-ethyl-N-propylamine, N-propyl-N -Dialkyl monoamines such as butylamine. Examples of the tertiary amine include tributylamine and trihexylamine.

  Among these, a saturated aliphatic hydrocarbon monoamine having 6 or more carbon atoms is preferable. By setting the number of carbon atoms to 6 or more, when the amino group is adsorbed on the surface of the silver particle, a space between the silver group and other silver particles can be secured, so that the effect of preventing aggregation of the silver particles is improved. The upper limit of the number of carbon atoms is not particularly defined, but saturated aliphatic monoamines having up to 18 carbon atoms are usually preferred in consideration of availability, ease of removal during firing, and the like. In particular, alkyl monoamines having 6 to 12 carbon atoms such as hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, and dodecylamine are preferably used. Among the aliphatic hydrocarbon monoamines (A), only one type may be used, or two or more types may be used in combination.

  Since the aliphatic hydrocarbon monoamine (B) having a total carbon number of 5 or less has a shorter carbon chain length than the aliphatic monoamine (A) having a total carbon number of 6 or more, it itself has a low function as a protective agent (stabilizer). However, compared with the aliphatic monoamine (A), the polarity is higher and the coordination ability of the silver compound to silver is higher, which is considered to be effective in promoting complex formation. Further, since the carbon chain length is short, it can be removed from the surface of the silver particles in a short time of 30 minutes or less or 20 minutes or less even in low-temperature firing of 120 ° C. or less, or about 100 ° C. or less. Effective for low-temperature firing of silver nanoparticles.

  Examples of the aliphatic hydrocarbon monoamine (B) include ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, isopentylamine, tert-pentylamine and the like. Examples thereof include saturated aliphatic hydrocarbon monoamines having 2 to 5 carbon atoms (that is, alkyl monoamines). Moreover, dialkyl monoamines, such as N, N-dimethylamine and N, N-diethylamine, are mentioned.

  Among these, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, isopentylamine, tert-pentylamine and the like are preferable, and the above butylamines are particularly preferable. Among the aliphatic hydrocarbon monoamines (B), only one type may be used, or two or more types may be used in combination.

  The aliphatic hydrocarbon diamine (C) having a total carbon number of 8 or less has a high coordination ability to the silver of the silver compound, and is effective in promoting complex formation. The aliphatic hydrocarbon diamine generally has a higher polarity than the aliphatic hydrocarbon monoamine, and the coordination ability of silver compounds to silver is increased. In addition, the aliphatic hydrocarbon diamine (C) has an effect of promoting thermal decomposition at a lower temperature and in a shorter time in the thermal decomposition step of the complex compound, and can produce silver nanoparticles more efficiently. . Furthermore, since the protective film of the silver particle containing the said aliphatic diamine (C) has high polarity, the dispersion stability of the silver particle in the dispersion medium containing a highly polar solvent improves. Furthermore, since the aliphatic diamine (C) has a short carbon chain length, the surface of the silver particles can be obtained in a short time of 30 minutes or less or 20 minutes or less even when firing at a low temperature of, for example, 120 ° C. Therefore, it is effective for low-temperature and short-time firing of the obtained silver nanoparticles.

  Although it does not specifically limit as said aliphatic hydrocarbon diamine (C), Ethylenediamine, N, N-dimethylethylenediamine, N, N'-dimethylethylenediamine, N, N-diethylethylenediamine, N, N'-diethylethylenediamine, 1 , 3-propanediamine, 2,2-dimethyl-1,3-propanediamine, N, N-dimethyl-1,3-propanediamine, N, N′-dimethyl-1,3-propanediamine, N, N— Diethyl-1,3-propanediamine, N, N′-diethyl-1,3-propanediamine, 1,4-butanediamine, N, N-dimethyl-1,4-butanediamine, N, N′-dimethyl- 1,4-butanediamine, N, N-diethyl-1,4-butanediamine, N, N′-diethyl-1,4-butanediamine, , 5-pentanediamine, 1,5-diamino-2-methylpentane, 1,6-hexanediamine, N, N-dimethyl-1,6-hexanediamine, N, N′-dimethyl-1,6-hexanediamine 1,7-heptanediamine, 1,8-octanediamine and the like. These are all alkylene diamines having a total carbon number of 8 or less, in which at least one of the two amino groups is a primary amino group or a secondary amino group, and the ability of the silver compound to coordinate to silver is high, Effective in promoting complex formation.

Among these, N, N-dimethylethylenediamine, N, N-diethylethylenediamine, N, N-dimethyl-1,3-propanediamine, N, N-diethyl-1,3-propanediamine, N, N-dimethyl One of two amino groups such as -1,4-butanediamine, N, N-diethyl-1,4-butanediamine, and N, N-dimethyl-1,6-hexanediamine is a primary amino group ( An alkylenediamine having a total carbon number of 8 or less in which —NH ₂ ) and the other one is a tertiary amino group (—NR ¹ R ² ) is preferable. A preferred alkylenediamine is represented by the following structural formula.

R ¹ R ² N—R—NH ₂
Here, R represents a divalent alkylene group, R ¹ and R ² may be the same or different and each represents an alkyl group, provided that the total number of carbon atoms of R, R ¹ and R ² is 8 It is as follows. The alkylene group usually does not contain a hetero atom (an atom other than carbon and hydrogen) such as an oxygen atom or a nitrogen atom, but may optionally have a substituent containing the hetero atom. The alkyl group usually does not contain a heteroatom such as an oxygen atom or a nitrogen atom, but may optionally have a substituent containing the heteroatom.

  When one of the two amino groups is a primary amino group, the ability of the silver compound to coordinate to silver is increased, which is advantageous for complex formation, and the other is a tertiary amino group. Since the tertiary amino group has poor coordination ability to silver atoms, the complex formed is prevented from having a complex network structure. When the complex has a complex network structure, a high temperature may be required for the thermal decomposition process of the complex. Further, among these, a diamine having a total carbon number of 6 or less is preferable, and a diamine having a total carbon number of 5 or less is more preferable from the viewpoint that it can be removed from the surface of the silver particles in a short time even in low-temperature firing. Of the aliphatic hydrocarbon diamine (C), only one type may be used, or two or more types may be used in combination.

In the present invention, the aliphatic hydrocarbon monoamine (A) having 6 or more carbon atoms, the aliphatic hydrocarbon monoamine (B) having 5 or less carbon atoms, and the aliphatic hydrocarbon diamine (C) having 8 or less carbon atoms. The use ratio with either one or both is not particularly limited, but based on the total amines [(A) + (B) + (C)], for example,
Aliphatic monoamine (A): 5 mol% to 65 mol%
Total amount of the aliphatic monoamine (B) and the aliphatic diamine (C): 35 mol% to 95 mol%
It is good to do. By setting the content of the aliphatic monoamine (A) to 5 mol% to 65 mol%, the function of protecting and stabilizing the surface of the silver particles to be produced is easily obtained by the carbon chain of the component (A). When the content of the component (A) is less than 5 mol%, the protective stabilization function may be weakly expressed. On the other hand, when the content of the component (A) exceeds 65 mol%, the protective stabilization function is sufficient, but the component (A) is difficult to be removed by low-temperature firing.

When the aliphatic monoamine (A) and both the aliphatic monoamine (B) and the aliphatic diamine (C) are used, their use ratio is not particularly limited, but the total amines Based on [(A) + (B) + (C)], for example,
Aliphatic monoamine (A): 5 mol% to 65 mol%
Aliphatic monoamine (B): 5 mol% to 70 mol%
Aliphatic diamine (C): 5 mol% to 50 mol%
It is good to do.

  In this case, about the minimum of content of the said (A) component, 10 mol% or more is preferable and 20 mol% or more is more preferable. About the upper limit of content of the said (A) component, 65 mol% or less is preferable and 60 mol% or less is more preferable.

  By adjusting the content of the aliphatic monoamine (B) to 5 mol% to 70 mol%, a complex formation promoting effect can be easily obtained, and it itself can contribute to low temperature and short time baking. In this case, the effect of assisting the removal of the aliphatic diamine (C) from the surface of the silver particles is easily obtained. If the content of the component (B) is less than 5 mol%, the effect of promoting complex formation may be weak, or the component (C) may be difficult to remove from the surface of the silver particles during firing. On the other hand, when the content of the component (B) exceeds 70 mol%, a complex formation promoting effect can be obtained, but the content of the aliphatic monoamine (A) is relatively decreased, and silver particles are generated. It is difficult to achieve surface protection and stabilization. About the minimum of content of the said (B) component, 10 mol% or more is preferable and 15 mol% or more is more preferable. About the upper limit of content of the said (B) component, 65 mol% or less is preferable and 60 mol% or less is more preferable.

  By making content of the said aliphatic diamine (C) into 5 mol%-50 mol%, the complex formation promotion effect and the thermal decomposition promotion effect of a complex are easy to be obtained, and the said aliphatic diamine (C) is included. Since the protective film of silver particles has a high polarity, the dispersion stability of silver particles in a dispersion medium containing a highly polar solvent is improved. When the content of the component (C) is less than 5 mol%, the complex formation promoting effect and the thermal decomposition promoting effect of the complex may be weak. On the other hand, if the content of the component (C) exceeds 50 mol%, the complex formation promoting effect and the thermal decomposition promoting effect of the complex are obtained, but the content of the aliphatic monoamine (A) is relatively reduced. Therefore, it is difficult to achieve protection and stabilization of the surface of the silver particles to be produced. About the minimum of content of the said (C) component, 5 mol% or more is preferable and 10 mol% or more is more preferable. About the upper limit of content of the said (C) component, 45 mol% or less is preferable and 40 mol% or less is more preferable.

When the aliphatic monoamine (A) and the aliphatic monoamine (B) are used (without using the aliphatic diamine (C)), their use ratio is not particularly limited. Considering the action, based on the total amines [(A) + (B)], for example,
Aliphatic monoamine (A): 5 mol% to 65 mol%
Aliphatic monoamine (B): 35 mol% to 95 mol%
It is good to do.

In the case of using the aliphatic monoamine (A) and the aliphatic diamine (C) (without using the aliphatic monoamine (B)), the use ratio thereof is not particularly limited. Considering the action, based on the total amines [(A) + (C)], for example,
Aliphatic monoamine (A): 5 mol% to 65 mol%
Aliphatic diamine (C): 35 mol% to 95 mol%
It is good to do.

  The above-mentioned use ratios of the aliphatic monoamine (A), the aliphatic monoamine (B) and / or the aliphatic diamine (C) are all examples, and various changes are possible.

  In the present invention, when the aliphatic monoamine (B) and / or the aliphatic diamine (C) having a high coordination ability to silver of a silver compound is used, the total number of carbons is 6 depending on the use ratio thereof. The adhesion amount of the above aliphatic monoamine (A) on the silver particle surface is small. Therefore, even in the case of firing at a low temperature for a short time, these aliphatic amine compounds are easily removed from the surface of the silver particles, and the silver particles are sufficiently sintered.

In the present invention, the total amount of the aliphatic hydrocarbon amine [for example, (A), (B) and / or (C)] is not particularly limited, but is 1 mol of silver atoms of the silver compound as a raw material. , About 1 to 50 mol. When the total amount [(A), (B) and / or (C)] of the amine component is less than 1 mole relative to 1 mole of the silver atom, it is converted into a complex compound in the complex compound formation step. There is a possibility that a silver compound that is not left will remain, and in the subsequent pyrolysis step, the uniformity of the silver particles may be impaired, resulting in enlargement of the particles, or the silver compound may remain without being thermally decomposed. On the other hand, even if the total amount [((A), (B) and / or (C)]] of the amine component exceeds about 50 moles with respect to 1 mole of the silver atoms, it is considered that there is not much merit. In order to prepare a dispersion of silver nanoparticles in a substantially solvent-free state, the total amount of the amine component is preferably about 2 mol or more, for example, and the total amount of the amine component is about 2 to 50 mol. by, it is possible to satisfactorily perform generation step and thermal decomposition step of the complex compounds. the lower limit of the total amount of the amine component, of silver atoms 1 mole of the silver compound, preferably on 2 molar than , more preferably on 6 molar than. Incidentally, silver oxalate molecule contains two silver atoms.

  In the present invention, an aliphatic carboxylic acid (D) may be further used as a stabilizer in order to further improve the dispersibility of the silver nanoparticles in the dispersion medium. The aliphatic carboxylic acid (D) is preferably used together with the amines, and can be used by being included in the amine mixed solution. By using the aliphatic carboxylic acid (D), the stability of silver nanoparticles, particularly the stability in a paint state dispersed in an organic solvent, may be improved.

  As the aliphatic carboxylic acid (D), a saturated or unsaturated aliphatic carboxylic acid is used. For example, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, Examples thereof include saturated aliphatic monocarboxylic acids having 4 or more carbon atoms such as icosanoic acid and eicosenoic acid; unsaturated aliphatic monocarboxylic acids having 8 or more carbon atoms such as oleic acid, elaidic acid, linoleic acid, and palmitoleic acid.

  Among these, a saturated or unsaturated aliphatic monocarboxylic acid having 8 to 18 carbon atoms is preferable. By setting the number of carbon atoms to 8 or more, when the carboxylic acid group is adsorbed on the surface of the silver particle, a space between the silver particle and other silver particles can be secured, so that the effect of preventing aggregation of the silver particles is improved. In view of availability, easiness of removal during firing, etc., saturated or unsaturated aliphatic monocarboxylic acid compounds having up to 18 carbon atoms are usually preferred. In particular, octanoic acid, oleic acid and the like are preferably used. Among the aliphatic carboxylic acids (D), only one type may be used, or two or more types may be used in combination.

  When the aliphatic carboxylic acid (D) is used, it may be used in an amount of, for example, about 0.05 to 10 mol, preferably 0.1 to 5 mol, relative to 1 mol of the silver atom of the starting silver compound. More preferably 0.5 to 2 mol is used. When the amount of the component (D) is less than 0.05 mol with respect to 1 mol of the silver atom, the effect of improving the stability in the dispersed state by the addition of the component (D) is weak. On the other hand, when the amount of the component (D) reaches 10 mol, the effect of improving the stability in a dispersed state is saturated, and the component (D) is hardly removed by low-temperature firing. However, the aliphatic carboxylic acid (D) may not be used.

  In the present invention, usually, an amine mixed solution containing the aliphatic monoamine (A) and any one or both of the aliphatic monoamine (B) and the aliphatic diamine (C) is prepared. Step of preparing mixed solution].

  The amine mixed solution can be prepared by stirring each amine (A), (B) and / or (C) component, and, if used, the carboxylic acid (D) component at a predetermined ratio at room temperature. .

  An aliphatic hydrocarbon amine mixed solution containing each amine component is added to the silver compound-alcohol slurry obtained above to produce a complex compound containing the silver compound and the amine [complex compound producing step]. Each amine component may be sequentially added to the silver compound-alcohol slurry without forming a mixed solution.

  In the case of producing metal nanoparticles containing a metal other than silver, a metal compound-alcohol slurry containing the target metal is used in place of the silver compound-alcohol slurry.

  A silver compound-alcohol slurry (or a metal compound-alcohol slurry) is mixed with a predetermined amount of an amine mixture. In this case, the mixing is preferably carried out while stirring at room temperature, or while appropriately cooling to room temperature or lower and stirring because the coordination reaction of amines to the silver compound (or metal compound) involves heat generation. Since the silver compound is in a slurry state with alcohol in advance, stirring and cooling can be satisfactorily performed when the amine mixture is dropped. The excess of alcohol and amines serves as the reaction medium.

  Conventionally, in a thermal decomposition method of a silver amine complex, a liquid aliphatic amine component is first put in a reaction vessel, and a powdered silver compound (silver oxalate) is charged therein. The liquid aliphatic amine component is a flammable substance, and there is a danger in putting the powdered silver compound therein. In other words, there was a risk of ignition due to static electricity due to the introduction of the silver compound of the powder. Further, there is a risk that the complex formation reaction proceeds locally due to the introduction of the powdered silver compound, and the exothermic reaction is expelled. According to the present invention, such danger can be avoided.

  Since the complex compound to be formed generally exhibits a color corresponding to its constituent components, the end point of the complex compound formation reaction can be detected by detecting the end of the color change of the reaction mixture by appropriate spectroscopy or the like. . In addition, the complex compound formed by silver oxalate is generally colorless (observed as white when visually observed), but even in such a case, the complex compound is formed on the basis of a change in form such as a change in viscosity of the reaction mixture. The generation state can be detected. In this way, a silver-amine complex (or metal-amine complex) is obtained in a medium mainly composed of alcohol and amines.

  Next, the obtained complex compound is heated and thermally decomposed to form silver nanoparticles [complex compound thermal decomposition step]. When a metal compound containing a metal other than silver is used, target metal nanoparticles are formed. Silver nanoparticles (metal nanoparticles) are formed without using a reducing agent. However, if necessary, an appropriate reducing agent may be used as long as the effects of the present invention are not impaired.

  In such a metal amine complex decomposition method, in general, amines control the manner in which atomic metals generated by the decomposition of metal compounds aggregate to form fine particles, and on the surface of the formed metal fine particles. By forming a film, it plays the role of preventing reaggregation between the fine particles. That is, by heating a complex compound of a metal compound and an amine, the metal compound is thermally decomposed while maintaining the coordinate bond of the amine to the metal atom to produce an atomic metal, and then the amine is coordinated. It is considered that the metal atoms are aggregated to form metal nanoparticles covered with an amine protective film.

  The thermal decomposition at this time is preferably performed while stirring the complex compound in a reaction medium mainly composed of alcohol and amines. The thermal decomposition is preferably performed within a temperature range in which the coated silver nanoparticles (or coated metal nanoparticles) are generated. From the viewpoint of preventing amine from being removed from the silver particle surface (or metal particle surface), the above temperature range is used. It is preferable to carry out at as low a temperature as possible. In the case of a silver oxalate complex compound, for example, it may be about 80 ° C. to 120 ° C., preferably about 95 ° C. to 115 ° C., more specifically about 100 ° C. to 110 ° C. In the case of a complex compound of silver oxalate, decomposition occurs by heating at about 100 ° C. and silver ions are reduced to obtain coated silver nanoparticles. In general, the thermal decomposition of silver oxalate itself occurs at about 200 ° C., but it is not clear why the thermal decomposition temperature is lowered by about 100 ° C. by forming a silver oxalate-amine complex compound. This is presumably because the coordination polymer structure formed by pure silver oxalate is cleaved when a complex compound of silver oxalate and amine is formed.

  The thermal decomposition of the complex compound is preferably performed in an inert gas atmosphere such as argon, but the thermal decomposition can also be performed in the air.

  Due to the thermal decomposition of the complex compound, it becomes a suspension exhibiting a blue luster. From this suspension, removal operation of alcohol solvent and excess amine, for example, precipitation of silver nanoparticles (or metal nanoparticles), decantation / washing operation with an appropriate solvent (water or organic solvent) The target stable coated silver nanoparticles (or coated metal nanoparticles) can be obtained [post-treatment step of silver nanoparticles]. If it dries after washing | cleaning operation, the powder of the target stable covering silver nanoparticle (or covering metal nanoparticle) will be obtained.

  For the decantation / cleaning operation, water or an organic solvent is used. Examples of the organic solvent include aliphatic hydrocarbon solvents such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, and tetradecane; alicyclic hydrocarbon solvents such as methylcyclohexane and cyclohexane; toluene, xylene Aromatic hydrocarbon solvents such as mesitylene, etc .; alcohol solvents such as methanol, ethanol, propanol, butanol, etc .; acetonitrile; and mixed solvents thereof may be used.

  In the formation process of the silver nanoparticles of the present invention, since no reducing agent is required, there is no by-product derived from the reducing agent, and the separation of the coated silver nanoparticles from the reaction system is simple, and high purity coating is achieved. Silver nanoparticles are obtained. However, an appropriate reducing agent may be used as necessary as long as the effects of the present invention are not impaired.

  In this way, silver nanoparticles whose surface is coated with the protective agent used are formed. The protective agent includes, for example, the aliphatic monoamine (A), and further includes one or both of the aliphatic monoamine (B) and the aliphatic diamine (C). Contains the carboxylic acid (D). Their content in the protective agent is equivalent to their use in the amine mixture. The same applies to metal nanoparticles.

  A silver coating composition can be produced using the obtained silver nanoparticles. The silver coating composition can take various forms without limitation. For example, by dispersing silver nanoparticles in an appropriate organic solvent (dispersion medium) in a suspended state, a silver coating composition called a so-called silver ink can be produced. Alternatively, a silver coating composition called a so-called silver paste can be produced by dispersing silver nanoparticles in a state of being kneaded in an organic solvent. Examples of the organic solvent for obtaining the coating composition include aliphatic hydrocarbon solvents such as pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, and tetradecane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane Solvents; aromatic hydrocarbon solvents such as toluene, xylene, mesitylene, etc .; methanol, ethanol, propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n- Examples thereof include alcohol solvents such as decanol. Examples of the organic solvent for obtaining the silver coating composition include terpene solvents such as terpineol and dihydroterpineol to obtain a silver paste. The type and amount of the organic solvent may be appropriately determined according to the concentration and viscosity of the desired silver coating composition (silver ink, silver paste). The same applies to metal nanoparticles.

  The silver nanoparticle powder and silver coating composition obtained by the present invention are excellent in stability. For example, silver nanoparticle powder is stable at room temperature storage for a period of one month or longer. The silver coating composition is stable without causing aggregation and fusion at room temperature for a period of one month or more, for example, at a silver concentration of 50 wt%.

  The prepared silver coating composition is applied onto a substrate and then baked.

  Application is spin coating, inkjet printing, screen printing, dispenser printing, letterpress printing (flexographic printing), sublimation printing, offset printing, laser printer printing (toner printing), intaglio printing (gravure printing), contact printing, microcontact printing It can carry out by a known method such as When a printing technique is used, a patterned silver coating composition layer is obtained, and a patterned silver conductive layer is obtained by firing.

  Firing can be performed at a temperature of 200 ° C. or lower, for example, room temperature (25 ° C.) or higher and 150 ° C. or lower, preferably room temperature (25 ° C.) or higher and 120 ° C. or lower. However, in order to complete the sintering of silver by firing in a short time, it is preferable to carry out at a temperature of 60 ° C. to 200 ° C., for example, 80 ° C. to 150 ° C., preferably 90 ° C. to 120 ° C. . The firing time may be appropriately determined in consideration of the amount of silver ink applied, the firing temperature, etc., for example, within several hours (eg, 3 hours or 2 hours), preferably within 1 hour, more preferably within 30 minutes, More preferably, it may be 10 minutes to 20 minutes, more specifically 10 minutes to 15 minutes.

  Since the silver nanoparticles are configured as described above, the sintering of the silver particles sufficiently proceeds even by such a firing process at a low temperature and in a short time. As a result, excellent conductivity (low resistance value) is exhibited. A silver conductive layer having a low resistance value (for example, 15 μΩcm or less and in the range of 7 to 15 μΩcm) is formed. The resistance value of bulk silver is 1.6 μΩcm.

  Because it can be fired at low temperatures, the substrate can be a glass substrate, a heat resistant plastic substrate such as a polyimide film, or a polyester film such as a polyethylene terephthalate (PET) film or a polyethylene naphthalate (PEN) film. A general-purpose plastic substrate having low heat resistance such as a polyolefin-based film such as polypropylene can also be suitably used. Moreover, baking in a short time reduces the load on these general-purpose plastic substrates having low heat resistance, and improves production efficiency.

  The silver conductive material of the present invention includes an electromagnetic wave control material, a circuit board, an antenna, a heat sink, a liquid crystal display, an organic EL display, a field emission display (FED), an IC card, an IC tag, a solar cell, an LED element, an organic transistor, and a capacitor. (Capacitor), electronic paper, flexible battery, flexible sensor, membrane switch, touch panel, EMI shield, etc.

  The thickness of the silver conductive layer may be appropriately determined according to the intended use, and particularly high conductivity even when a silver conductive layer having a relatively large thickness is formed by using the silver nanoparticles according to the present invention. Can show. The thickness of the silver conductive layer may be selected from the range of, for example, 5 nm to 30 μm, preferably 100 nm to 25 μm, more preferably 500 nm to 20 μm.

  As mentioned above, although it mainly demonstrated centering on silver nanoparticle, according to this invention, it is applied also to the manufacturing method of metal nanoparticle containing metals other than silver, and this metal nanoparticle.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

[Specific resistance value of the fired silver film]
The obtained silver fired film was measured using a four-terminal method (Loresta GP MCP-T610). The measuring range limit of this device is 10 ⁷ Ωcm.

The following reagents were used in each example and comparative example.
n-Butylamine (MW: 73.14): Reagent n-hexylamine (MW: 101.19) manufactured by Tokyo Chemical Industry Co., Ltd. Reagent n-octylamine (MW: 129.25) manufactured by Tokyo Chemical Industry Co., Ltd. Reagent manufactured by Tokyo Chemical Industry Co., Ltd. Dodecylamine (MW: 185.35): Reagent N, N-dimethyl-1,3-propanediamine (MW: 102.18) manufactured by Wako Pure Chemical Industries, Ltd. Reagent manufactured by Tokyo Chemical Industry Co., Ltd. Methanol: Special reagent manufactured by Wako Pure Chemical Industries 1-propanol: Reagent manufactured by Wako Pure Chemical Industries 1-Butanol: Reagent special grade manufactured by Wako Pure Chemical Industries
tert-Butanol: Reagent manufactured by Wako Pure Chemical Industries 1-Hexanol: Reagent Decal manufactured by Wako Pure Chemical Industries: Reagent decane manufactured by Tokyo Chemical Industry Co., Ltd. Reagent dihydroterpineol manufactured by Wako Pure Chemical Industries: Silver oxalate manufactured by Nippon Terpene Co., Ltd. (MW: 303) .78): synthesized from silver nitrate (Wako Pure Chemical Industries, Ltd.) and oxalic acid dihydrate (Wako Pure Chemical Industries, Ltd.)

[Example 1]
(Preparation of silver nanoparticles)
A 100 mL flask was charged with 3.0 g (9.9 mmol) of silver oxalate, and then 4.5 g of 1-butanol was added and stirred at room temperature to prepare a 1-butanol slurry of silver oxalate.

  An amine mixed solution of 10.84 g (148.1 mmol) of n-butylamine and 3.00 g (29.6 mmol) of n-hexylamine was added dropwise at 30 ° C. to 1-butanol slurry of silver oxalate. After dripping, it stirred at 30 degreeC for 2 hours, the complex formation reaction of silver oxalate and an amine was advanced, and the white substance (silver oxalate-amine complex) was formed.

  After the formation of the silver oxalate-amine complex, the reaction mixture was heated and stirred. As a result, the reaction mixture was refluxed at 89 ° C., and no further temperature increase was observed. At this reflux temperature of 89 ° C., the silver oxalate-amine complex was thermally decomposed to obtain a suspension in which dark blue silver nanoparticles were suspended in the amine mixture.

  In both the complexing reaction stage and the thermal decomposition stage, the stirring was very good.

Next, the obtained suspension was cooled, 9 g of methanol was added and stirred, and then silver nanoparticles were precipitated by centrifugation, and the supernatant was removed. To the silver nanoparticles, 9 g of methanol was added again and stirred, and then the silver nanoparticles were precipitated by centrifugation, and the supernatant was removed. In this way, wet silver nanoparticles were obtained.
The silver equivalent yield was 97%. The high yield is due to the high pyrolysis temperature.

Silver conversion yield (%) =
[(Weight of silver contained in generated silver nanoparticles) / (weight of silver contained in prepared silver salt)] × 100

(Preparation and baking of silver nano paint)
Next, dihydroterpineol was added to the wet silver nanoparticles to a silver concentration of 70 wt% and kneaded to prepare a silver nanoparticle paste.

  The obtained silver nanoparticle paste was applied onto an alkali-free glass plate with an applicator so that the film thickness after firing was about 10 μm, thereby forming a coating film. After the formation of the coating film, it was immediately fired at 80 ° C. for 60 minutes in a blow drying oven to form a silver fired film. When the specific resistance value of the obtained silver fired film was measured by the 4-terminal method, it was 14.0 μΩcm.

(About silver oxalate-amine complex)
When the white substance obtained during the preparation of the silver nanoparticles was subjected to DSC (Differential Scanning Calorimetry) measurement, the heat generation starting average temperature value due to thermal decomposition was 102.5 ° C. On the other hand, when the DSC measurement was similarly performed on the raw material silver oxalate, the heat generation starting average temperature value due to thermal decomposition was 218 ° C. As described above, the thermal decomposition temperature of the white substance obtained during the preparation of the silver nanoparticles was lower than that of the raw material silver oxalate. This shows that the white substance obtained during the preparation of the silver nanoparticles is a combination of silver oxalate and alkylamine, and alkylamine with respect to the silver atom of silver oxalate. It was inferred that this was a silver oxalate-amine complex in which the amino group was coordinated.

The DSC measurement conditions were as follows.
Apparatus: DSC 6220-ASD2 (manufactured by SII Nanotechnology)
Sample container: 15 μL gold-plated sealed cell (manufactured by SII Nanotechnology)
Temperature increase rate: 10 ° C / min (room temperature to 600 ° C)
Atmospheric gas: Atmospheric pressure in cell
Nitrogen flow outside cell (50mL / min)

Also, the white material obtained during the preparation of the silver nanoparticles was subjected to IR spectrum measurement, absorption derived from the alkyl group of the alkyl amine (2900 cm around ^-1, around 1000 cm ^-1) were observed. This also shows that the viscous white substance obtained during the preparation of the silver nanoparticles is formed by the combination of silver oxalate and alkylamine, and the silver oxalate has silver atoms. On the other hand, it was guessed that it was a silver oxalate-amine complex in which an amino group was coordinated.

[Example 2]
In the preparation of silver nanoparticles, in the same manner as in Example 1, except that the amount of 1-butanol was changed to 9.0 g with respect to 3.0 g (9.9 mmol) of silver oxalate, A butanol slurry was prepared. To the obtained silver oxalate 1-butanol slurry, an amine mixture was dropped in the same manner as in Example 1 to form a white substance (silver oxalate-amine complex).

  After the formation of the silver oxalate-amine complex, the reaction product was heated and stirred. As a result, the reaction product was refluxed at 93 ° C., and no further temperature increase was observed. At this reflux temperature of 93 ° C., the silver oxalate-amine complex was thermally decomposed to obtain a suspension in which dark blue silver nanoparticles were suspended in the amine mixture. In both the complexing reaction stage and the thermal decomposition stage, the stirring was very good.

  From the obtained suspension, wet silver nanoparticles were obtained in the same manner as in Example 1. The silver equivalent yield was 97%.

  Next, using the obtained silver nanoparticles, a silver nanoparticle paste was prepared in the same manner as in Example 1, and a silver fired film was formed. The specific resistance value of the obtained silver fired film was measured by a four-terminal method and found to be 13.0 μΩcm.

[Example 3]
Silver oxalate was prepared in the same manner as in Example 1 except that 4.5 g of 1-propanol was used instead of 1-butanol for 3.0 g (9.9 mmol) of silver oxalate in the preparation of silver nanoparticles. 1-propanol slurry was prepared. In the same manner as in Example 1, the amine mixture was dropped into the obtained silver oxalate 1-propanol slurry to form a white substance (silver oxalate-amine complex).

  After the formation of the silver oxalate-amine complex, the reaction product was heated and stirred. As a result, the reaction product was refluxed at 86 ° C., and no further temperature increase was observed. At this reflux temperature of 86 ° C., the silver oxalate-amine complex was thermally decomposed to obtain a suspension in which dark blue silver nanoparticles were suspended in the amine mixture. In both the complexing reaction stage and the thermal decomposition stage, the stirring was very good.

  From the obtained suspension, wet silver nanoparticles were obtained in the same manner as in Example 1. The silver equivalent yield was 97%.

  Next, using the obtained silver nanoparticles, a silver nanoparticle paste was prepared in the same manner as in Example 1, and a silver fired film was formed. When the specific resistance value of the obtained silver fired film was measured by the 4-terminal method, it was 92.0 μΩcm.

[Comparative Example 1]
In the preparation of silver nanoparticles, silver oxalate decane was prepared in the same manner as in Example 1, except that 4.5 g of decane was used instead of 1-butanol for 3.0 g (9.9 mmol) of silver oxalate. A slurry was prepared. In the same manner as in Example 1, the amine mixture was dropped into the obtained silver oxalate decane slurry to form a white substance (silver oxalate-amine complex).

  After the formation of the silver oxalate-amine complex, the reaction product was heated and stirred. As a result, the reaction product was refluxed at 87 ° C., and no further temperature increase was observed. At this reflux temperature of 87 ° C., the silver oxalate-amine complex was thermally decomposed to obtain a suspension in which dark blue silver nanoparticles were suspended in the amine mixture. Stirring was successfully performed in the complex formation reaction stage, but stirring was difficult in the thermal decomposition stage.

  From the obtained suspension, wet silver nanoparticles were obtained in the same manner as in Example 1. The silver conversion yield was 96%.

  Next, using the obtained silver nanoparticles, a silver nanoparticle paste was prepared in the same manner as in Example 1, and a silver fired film was formed. When the specific resistance value of the obtained silver fired film was measured by the 4-terminal method, it was 20.0 μΩcm.

[Comparative Example 2]
In the preparation of silver nanoparticles, slurry preparation using a solvent was not performed.
A 100 mL flask was charged with 10.84 g (148.1 mmol) of n-butylamine and 3.00 g (29.6 mmol) of n-hexylamine, and 3.0 g (9.9 mmol) of silver oxalate was powdered. I added it as it was. After the addition, the mixture was stirred at 30 ° C. for 2 hours to advance the complex formation reaction between silver oxalate and amine to form a white substance (silver oxalate-amine complex). Agitation was difficult at this stage.

  After the formation of the silver oxalate-amine complex, the reaction product was heated to a reflux state at 82 ° C., and no further temperature increase was observed. At this reflux temperature of 82 ° C., the silver oxalate-amine complex was thermally decomposed to obtain a suspension in which dark blue silver nanoparticles were suspended in the amine mixture. Agitation was difficult even during the pyrolysis stage.

  From the obtained suspension, wet silver nanoparticles were obtained in the same manner as in Example 1. The silver equivalent yield was 86%.

  Next, using the obtained silver nanoparticles, a silver nanoparticle paste was prepared in the same manner as in Example 1, and a silver fired film was formed. When the specific resistance value of the obtained silver fired film was measured by the 4-terminal method, it was 10.0 μΩcm.

[Example 4]
(Preparation of silver nanoparticles)
A 100 mL flask was charged with 3.0 g (9.9 mmol) of silver oxalate, and then 4.5 g of 1-butanol was added and stirred at room temperature to prepare a 1-butanol slurry of silver oxalate.

  To a 1-butanol slurry of silver oxalate, at 30 ° C., 8.67 g (118.5 mmol) of n-butylamine, 6.00 g (59.3 mmol) of n-hexylamine, 5.74 g (44.4 mmol) of n-octylamine ), And 2.75 g (14.8 mmol) of dodecylamine and 6.05 g (59.3 mmol) of N, N-dimethyl-1,3-propanediamine) were added dropwise. After dripping, it stirred at 30 degreeC for 2 hours, the complex formation reaction of silver oxalate and an amine was advanced, and the white substance (silver oxalate-amine complex) was formed.

  After the formation of the silver oxalate-amine complex, the reaction mixture was heated and stirred. As a result, the reaction mixture was refluxed at 100 ° C., and no further temperature increase was observed. At this reflux temperature of 100 ° C., the silver oxalate-amine complex was thermally decomposed to obtain a suspension in which dark blue silver nanoparticles were suspended in the amine mixture.

  In both the complexing reaction stage and the thermal decomposition stage, the stirring was very good.

  Next, the obtained suspension was cooled, 30 g of methanol was added thereto and stirred, and then silver nanoparticles were settled by centrifugation, and the supernatant was removed. To the silver nanoparticles, 9 g of methanol was added again and stirred, and then the silver nanoparticles were precipitated by centrifugation, and the supernatant was removed. In this way, wet silver nanoparticles were obtained.

(Preparation and baking of silver nano paint)
Next, 1-hexanol / decalin mixed solvent (weight ratio = 1/1) was added to the wet silver nanoparticles so as to have a silver concentration of 40 wt%, and stirred to prepare a silver nanoparticle dispersion. This silver nanoparticle dispersion was applied onto an alkali-free glass plate by a spin coating method so that the film thickness after firing was about 0.5 μm to 1.0 μm to form a coating film.

  After the formation of the coating film, it was immediately fired at 120 ° C. for 15 minutes in a blast drying furnace to form a silver fired film having a thickness of about 0.8 μm. When the specific resistance value of the obtained silver fired film was measured by the four-terminal method, it was 7.0 μΩcm.

[Example 5]
Silver oxalate was prepared in the same manner as in Example 4 except that 4.5 g of 1-hexanol was used instead of 1-butanol for 3.0 g (9.9 mmol) of silver oxalate in the preparation of silver nanoparticles. 1-hexanol slurry was prepared. In the same manner as in Example 4, the amine mixed solution was dropped into the obtained silver oxalate 1-hexanol slurry to form a white substance (silver oxalate-amine complex).

  After the formation of the silver oxalate-amine complex, the reaction product was heated and stirred. As a result, the reaction product was refluxed at 102 ° C., and no further temperature increase was observed. At this reflux temperature of 102 ° C., the silver oxalate-amine complex was thermally decomposed to obtain a suspension in which dark blue silver nanoparticles were suspended in the amine mixture. In both the complexing reaction stage and the thermal decomposition stage, the stirring was very good.

  Next, using the obtained suspension, a silver nanoparticle dispersion was prepared in the same manner as in Example 4, and a silver fired film having a thickness of about 0.6 μm was formed. It was 15.4 microhm-cm when the specific resistance value of the obtained silver baking film | membrane was measured by the 4-terminal method.

[Example 6]
In the preparation of silver nanoparticles, silver oxalate was prepared in the same manner as in Example 4 except that 4.5 g of tert-butanol was used instead of 1-butanol for 3.0 g (9.9 mmol) of silver oxalate. A tert-butanol slurry was prepared. In the same manner as in Example 4, the amine mixture was dropped into the obtained silver oxalate tert-butanol slurry to form a white substance (silver oxalate-amine complex).

  After the formation of the silver oxalate-amine complex, the reaction product was heated and stirred. As a result, the reaction product was refluxed at 96 ° C., and no further temperature increase was observed. At this reflux temperature of 96 ° C., the silver oxalate-amine complex was thermally decomposed to obtain a suspension in which dark blue silver nanoparticles were suspended in the amine mixture. In both the complexing reaction stage and the thermal decomposition stage, the stirring was very good.

  Next, using the obtained suspension, a silver nanoparticle dispersion was prepared in the same manner as in Example 4, and a silver fired film having a thickness of about 0.7 μm was formed. When the specific resistance value of the obtained silver fired film was measured by the 4-terminal method, it was 12.9 μΩcm.

Claims (9)

A method for producing silver nanoparticles,
A silver compound and an alcohol solvent are mixed to obtain a silver compound- alcohol slurry in which a solid silver compound is dispersed in an alcohol solvent .
To the obtained silver compound-alcohol slurry, an aliphatic hydrocarbon amine is added to form a complex compound containing the silver compound and the amine,
The complex compound is heated and thermally decomposed to form silver nanoparticles.
A method for producing silver nanoparticles comprising :
The alcohol solvent is an alcohol having 3 to 10 carbon atoms,
The aliphatic hydrocarbon amine includes an aliphatic hydrocarbon monoamine (A) composed of an aliphatic hydrocarbon group and one amino group, and the total number of carbon atoms of the aliphatic hydrocarbon group is 6 or more,
An aliphatic hydrocarbon monoamine (B) comprising an aliphatic hydrocarbon group and one amino group, the aliphatic hydrocarbon group having a total carbon number of 5 or less, and an aliphatic hydrocarbon group and two amino groups And a method for producing silver nanoparticles, comprising at least one of the aliphatic hydrocarbon diamines (C) wherein the aliphatic hydrocarbon group has a total carbon number of 8 or less .   The method for producing silver nanoparticles according to claim 1, wherein the silver compound is silver oxalate. The method for producing silver nanoparticles according to claim 1 or 2 , wherein the aliphatic hydrocarbon monoamine (A) is an alkyl monoamine having 6 to 12 carbon atoms. The method for producing silver nanoparticles according to any one of claims 1 to 3, wherein the aliphatic hydrocarbon monoamine (B) is an alkyl monoamine having 2 to 5 carbon atoms. The aliphatic hydrocarbon diamine (C), one of the two amino groups is a primary amino group, the other one is a alkylenediamine a tertiary amino group, of claims 1 to 4 The manufacturing method of the silver nanoparticle in any one of them. The method for producing silver nanoparticles according to any one of claims 1 to 5 , wherein 120 parts by weight or more of the alcohol solvent is used with respect to 100 parts by weight of the silver compound. The method for producing silver nanoparticles according to any one of claims 1 to 6 , wherein 1 to 50 mol of the aliphatic hydrocarbon amine is used as a total per 1 mol of silver atoms of the silver compound. Silver nanoparticles are produced by the method according to any one of claims 1 to 7 ,
A method for producing a silver coating composition, comprising dispersing the silver nanoparticles in an organic solvent. Silver nanoparticles are produced by the method according to any one of claims 1 to 7 ,
Dispersing the silver nanoparticles in an organic solvent to produce a silver coating composition,
On the substrate, the silver coating composition is applied and baked to form a silver conductive layer.
The manufacturing method of the silver electrically-conductive material containing this.