JP5002478B2 - Metal nanoparticle paste and pattern forming method - Google Patents

Description

  The present invention relates to a paste (metal nanoparticle paste or metal colloid particle) comprising metal nanoparticles (or metal fine particles, silver nanoparticles, etc.) and a metal nanoparticle surface protective agent called protective colloid. Paste). More specifically, the present invention relates to a metal nanoparticle paste capable of forming a metal film or a sintered pattern at a very low heat treatment temperature (for example, 150 ° C. or less) by printing such as screen printing.

  Metal nanoparticles (or metal colloid particles) have a large specific surface area and a high reaction activity. For this reason, it is known that it has a property of being fused (low temperature sintering) at a low temperature as compared with bulk or metal atoms, and it is expected to be applied to various fields by taking advantage of this property. For example, an attempt has been made to form a pattern using a paste containing metal nanoparticles. Conventionally, such a pattern has been formed using a hybrid paste in which metal nanoparticles and metal filler (particles having a particle size of the order of microns) are mixed. However, in such a paste, since the metal filler is mixed, the sintering temperature has to be increased, and the metal filler having a large particle size is used, so that there is a limit to the miniaturization of the pattern.

  Under such circumstances, attempts have been made to form a fine pattern using only metal nanoparticles. For example, in Japanese Patent Application Laid-Open No. 2004-273205 (Patent Document 1), a conductive nanoparticle paste containing metal nanoparticles, wherein the average particle diameter of the metal nanoparticles is selected in the range of 1 to 100 nm. The conductive nanoparticle paste is a dispersion obtained by uniformly dispersing the metal nanoparticles in a dispersion solvent, and the metal nanoparticle surface is coordinated with a metal element contained in the metal nanoparticles. A group having a specific melting point and boiling point, including a nitrogen, oxygen, or sulfur atom as a group capable of forming a simple bond, a group capable of coordinative bonding by a lone pair of electrons of these atoms, and a specific melting point and boiling point The dispersion solvent has a specific melting point and boiling point with high solubility capable of dissolving the compound that coats the surface of the metal nanoparticles. A conductive nanoparticle paste comprising 8 to 220 parts by mass of the dispersion solvent with respect to 100 parts by mass of the metal nanoparticles, and a sintered body layer of metal nanoparticles on the substrate. A method for forming a fine wiring pattern with good conductivity, comprising: forming a coating layer of the fine wiring pattern to be drawn on the substrate surface using the paste; and in the coating layer And forming a sintered body layer between the metal nanoparticles by performing a baking treatment on the metal nanoparticles, and forming the sintered body layer between the metal nanoparticles is performed at 300 ° C. When the coating layer is heated to a temperature that does not exceed the temperature, the compound is dissociated and eluted from the surface of the metal nanoparticles in the dispersion solvent, and the metal nanoparticles interact with each other. Surface contact It is achieved, and sintering of the metal nanoparticles each other, method of forming a fine wiring pattern stripped off and is made of a dispersion solvent (claim 7) is disclosed.

  In this document, the compound uses a group having a lone pair of electrons on a nitrogen, oxygen, or sulfur atom when forming a coordinate bond with a metal element. For example, a group containing a nitrogen atom is used. As an amino group, a group containing a sulfur atom, a sulfanyl group (-SH), a sulfide type sulfanediyl group (-S-), a group containing an oxygen atom as a hydroxy group (-OH), an ether type oxy group (-O-) is mentioned, and it is described that alkylamine can be mentioned as a typical compound having an available amino group. Further, in this document, when a coating layer having a fine wiring pattern is drawn using the paste-like dispersion liquid, it is possible to use a screen printing method or an ink jet printing method. It is also described that when the paste is used for screen printing, the liquid viscosity (25 ° C.) of the paste is preferably selected in the range of 50 Pa · s to 200 Pa · s. Furthermore, the paste is redispersed in a high boiling point solvent such as 1-decanol after removing the dispersion solvent contained in the metal nanoparticle dispersion liquid while suppressing the separation of surface coating molecules such as alkylamine. It can be produced and the dispersion solvent is removed by using a protective solvent component having a significantly high boiling point or a liquid organic compound having a high boiling point (dipropylene glycol, diethylene glycol, propylene glycol, various glycols such as ethylene glycol; 2-ethylhexylamine, It is described that Jeffamine EDR148 (2,2- (ethylenedioxy) bisethylamine etc.) can be added and mixed, and then distilled under reduced pressure.

However, although the paste of this document can form a pattern at a relatively low temperature, there is a limit to the reduction of the baking temperature because of the use of a high-boiling component such as dipropylene glycol or Jeffamine EDR148. Therefore, the substrate on which the pattern is formed is limited, and it is difficult to actually form a practical pattern (such as a low resistance value pattern) that can be used as a wiring material on a resin substrate. Even with the paste of this document, there is a limit to pattern miniaturization.
JP 2004-273205 A (claims, paragraph numbers [0017], [0019], [0025], [0026])

  Accordingly, an object of the present invention is to form a metal nanoparticle paste capable of efficiently forming a sintered layer (particularly a conductive layer) or a sintered pattern even at a low temperature of about 150 ° C. or less, and formation of a pattern using this paste. It is to provide a method.

  Another object of the present invention is to provide a metal nanoparticle paste capable of forming a sintered pattern at a low temperature by a screen printing method or an intaglio printing method, and a pattern forming method using the paste.

  Still another object of the present invention is to provide a metal nanoparticle paste useful for forming a fine pattern and a pattern forming method using the paste.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that a protective colloid (or dispersant) for coating or protecting metal nanoparticles is composed of amines and a carboxylic acid having a specific carbon number. It has been found that when a paste (concentrated dispersion) containing specific metal colloidal particles is used, a sintered layer or a sintered pattern can be formed at a very low temperature of 150 ° C. or lower, and the present invention has been completed.

  That is, the metal nanoparticle paste of the present invention (metal nanoparticle-containing paste) is composed of metal nanoparticles (A) and protective colloids (B) covering the metal nanoparticles (A), And a paste containing the dispersion medium of the metal colloid particles, wherein the protective colloid (B) is composed of amines (B1) and a carboxylic acid having 1 to 3 carbon atoms (B2). It is a paste. In such a metal nanoparticle paste, the metal constituting the metal nanoparticle (A) may be, in particular, a single noble metal or a noble metal alloy. Moreover, the average particle diameter of the metal nanoparticles (A) may be, for example, about 2 to 40 nm. Typically, the metal constituting the metal nanoparticles (A) may be silver alone, and the average particle diameter of the metal nanoparticles (A) may be 10 nm or less.

In the metal nanoparticle paste, the amines (B1) may be, for example, alkylamines (for example, monoalkylamines having 4 or more carbon atoms such as mono-C _6-20 alkylamine). The carboxylic acid (B2) may be a C _1-3 saturated aliphatic monocarboxylic acid (particularly propionic acid).

  In the metal nanoparticle paste, the proportion of the protective colloid (B) may be, for example, about 1 to 60 parts by mass with respect to 100 parts by mass of the metal nanoparticles (A), and amines (B1) The ratio of carboxylic acid (B2) to the former / the latter (mass ratio) may be about 85/15 to 10/90.

  The metal nanoparticle paste of the present invention may further contain other metal colloid particles in addition to the metal colloid particles. Such other metal colloidal particles are, for example, metal colloidal particles composed of metal nanoparticles (a) and protective colloids (b) covering the metal nanoparticles (a), wherein the protective colloids (B) may be metal colloidal particles composed of amines (b1) and carboxylic acid (b2) having 4 or more carbon atoms.

The dispersion medium may be a high boiling point solvent, for example, a solvent having a boiling point of 100 ° C. or higher (specifically, a solvent having a boiling point of 100 ° C. or higher and capable of dispersing metal colloid particles). The dispersion medium may typically be at least one selected from saturated or unsaturated C _6-20 aliphatic alcohols and terpene alcohols.

  The metal nanoparticle paste contains metal nanoparticles at a high concentration. For example, in the metal metal nanoparticle paste, the ratio of the metal nanoparticles (A) may be about 40 to 95% by mass. The viscosity of the metal nanoparticle paste at 25 ° C. may be, for example, about 1 to 400 Pa · s (for example, 1 to 200 Pa · s).

  In the present invention, a pattern (for example, an electrode or a wiring pattern) is formed (or drawn) on the substrate with the metal nanoparticle paste, and the formed pattern (drawing pattern) is baked to form a sintered pattern. A method of forming is also included. In such a pattern forming method, a pattern may be formed (drawn) by screen printing (method), intaglio printing (method), or the like. In the method of the present invention, a sintered pattern can be formed even at a very low firing temperature. For example, in the method, the firing treatment may be performed at a firing temperature of 150 ° C. or less. In particular, in the above-described method, a resin base material may be used as the substrate, and the firing process may be performed at a firing temperature of 150 ° C. or lower (for example, about 80 to 120 ° C.).

  In the method of the present invention, since a paste containing metal nanoparticles at a high concentration is used, an ultrafine (ultrafine) pattern can be formed. For example, in the method (for example, pattern formation by an intaglio printing method), the minimum A sintered pattern having a line width of 30 μm or less (particularly, 20 μm or less) can also be formed.

  In the metal nanoparticle paste of the present invention, the protective colloid covering the metal nanoparticles is not an organic binder (resin binder), but is composed of a specific compound that easily evaporates or decomposes at a low temperature and also acts as a binder. Even at a very low temperature of 150 ° C. or lower, a sintered layer (particularly a conductive layer) or a sintered pattern can be formed efficiently. Moreover, the metal nanoparticle paste of the present invention can form a sintered pattern at a low temperature also by a screen printing method for forming a relatively thick film or an intaglio printing method. In particular, the metal nanoparticle paste of the present invention can therefore form a sintered pattern even on a resin substrate or the like. Furthermore, the metal nanoparticle paste of the present invention does not contain a metal filler like a conventional paste, and is useful for forming a fine pattern. The paste does not contain an organic binder and can suppress organic residues remaining in the metal film (sintered film) after heat treatment as much as possible. Therefore, the paste can also suppress the influence on the metal film characteristics (for example, specific resistance) and is extremely useful. is there.

<Metal nanoparticle paste>
The metal nanoparticle paste of the present invention is a paste containing metal colloid particles having a specific compound as a protective colloid and a dispersion medium of the metal colloid particles.

[Metallic colloidal particles]
The metal colloid particle is a metal colloid particle coated with a metal nanoparticle (A) and a protective colloid (B) covering the metal nanoparticle (A), wherein the protective colloid (B) is a specific compound. It is composed of a combination of

(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. In addition, the metal nanoparticles (A) may be conductive metal particles, in particular. Among them, the metal constituting the metal nanoparticles (A) is a metal (noble metal simple substance and noble 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 (eg, silver simple substance). Is preferred.

  The metal nanoparticles (A) are nanometer-sized metal fine particles. 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 0.5 to 100 nm (for example, 1 to 80 nm), preferably 1.5 to 70 nm (for example, 1.8 to 50 nm), more preferably about 2 to 40 nm (for example, 2 to 30 nm), particularly 10 nm or less (for example, about 1 to 10 nm, preferably about 1 to 8 nm).

  The metal colloid particles may be particles that hardly contain coarse particles. In such metal colloidal particles, the maximum primary particle diameter of the metal nanoparticles (A) may be, for example, 200 nm or less, preferably 150 nm or less, and more preferably 100 nm or less. Furthermore, in such metal nanoparticles (A) (or metal colloid particles), the proportion of particles having a primary particle size of 100 nm or more is, for example, 10% by mass or less (for example, based on the mass of the metal (or metal component)) 0 to 8% by mass), preferably 5% by mass or less (for example, 0.01 to 3% by mass), more preferably 1% by mass or less (for example, about 0.02 to 0.5% by mass). May be.

(Protective colloid (B))
The protective colloid (B) is composed of an amine (B1) and a carboxylic acid (B2) having 1 to 3 carbon atoms. In the present invention, by forming such a protective colloid in combination with amines and a specific carboxylic acid, the metal nanoparticles can be efficiently protected with high stability. The reason why such high stability can be protected is not clear, but amines and carboxylic acids are electrostatically bonded by an acid / base reaction, and apparently polymerized, thereby efficiently forming metal nanoparticles. This is thought to be because it can be protected. When amines or carboxylic acids are used alone, the metal nanoparticles cannot be stably protected, and the metal nanoparticles tend to aggregate. In the present invention, the protective colloid is composed of an amine and a carboxylic acid having 1 to 3 carbon atoms, so that the colloidal metal particles are stable. , At 150 ° C. or lower), it can be separated from the metal colloidal particles, and can be sintered at such a low temperature.

(Amines (B1))
Examples of amines include monoamines, polyamines, aminocarboxylic acids (such as glycine), and the like.

Examples of monoamines include primary amines [eg, monoalkylamines (propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine (n-octylamine, 2-ethylhexylamine, etc.), nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine amine, _{C 3-20} alkyl amines such as cetylamine, preferably _{C 5-16} alkyl amine, more preferably _{C 6-12} alkyl amines, etc.), cycloalkyl amines (e.g., cyclopentylamine, _{C 4-10} cycloalkyl amines, such as cyclohexylamine), arylamines (e.g., aniline, toluidine, _{C 6-1,} such as amino naphthalene Arylamine), aralkyl amines (such as benzylamine), hydroxylamines (e.g., alkanolamines such as ethanol amine), etc.], secondary amines [e.g., dialkyl amines (dipropylamine, diisopropylamine, di butylamine, dihexylamine, dioctylamine, such as di-C _3-20 alkyl amines such as didecylamine), dicycloalkyl amines (e.g., such as dicyclohexylamine), diarylamines (e.g., diphenylamine, etc.), di-aralkyl amines (di Benzylamine, etc.), alkylcycloalkylamines (such as methylcyclohexylamine), alkylarylamines (such as N-methylaniline), and cyclic secondary amines (eg, piperidine, hexamethyle). Imine, 5- to 8-membered cyclic secondary amines such as morpholine), hydroxylamines (eg dialkanolamines such as diethanolamine)], tertiary amines [eg trialkylamines (tripropylamine) , Tributylamine, trihexylamine, trioctylamine, tridecylamine and the like _triC3-20 alkylamine, preferably _triC5-16 alkylamine), tricycloalkylamines (tricyclohexylamine etc.), tria Reel amines (such as triphenylamine), triaralkylamines (such as tribenzylamine), dicycloalkylalkylamines (such as dicyclohexylmethylamine), cycloalkyldialkylamines (such as cyclohexyldimethylamine), Dialkylamines (N, N-dimethylaniline, etc.), cyclic tertiary amines (for example, 5- to 8-membered cyclic tertiary amines such as pyridine, picoline, quinoline, N-phenylmorpholine, 1,8-diazabicyclo) (5.4.0) undecene-1 and the like), hydroxylamines (for example, trialkanolamines such as triethanolamine) and the like.

Examples of polyamines include polyamines corresponding to the monoamines such as chain polyamines {eg, alkane diamines (C _2-20 alkane diamines such as ethylene diamine, propylene diamine, tetramethylene diamine, and hexamethylene diamine). Diamines; primary polyamines such as polyalkylene polyamines (or polyalkylene imines such as poly _C2-4 alkylene polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine)}, cyclic polyamines [e.g. Cyclic secondary polyamines (for example, piperazine, 1,4,8,11-tetraazacyclotetradecane, triethylenediamine, etc.), cyclic tertiary polyamines (pyrimidine, etc.) and the like.

  These amines may be used alone or in combination of two or more.

Among these amines, for example, monoalkylamines [e.g., monoalkylamines having 4 or more carbon atoms (e.g., 4 to 30 carbon atoms) such as octylamine (e.g., mono _C6-20 alkylamine), etc. ], Alkylamines (especially primary alkylamines) such as alkanediamines (eg C _2-20 alkanediamine etc.) are preferred, especially long chain alkylamines (eg mono to tri C _6-30 alkyl). Amines, preferably mono to tri C _7-24 alkyl amines, more preferably mono C _8-20 alkyl amines).

  The amines may be liquid or solid at room temperature (or room temperature, for example, 25 ° C.), and particularly liquid. The boiling point of liquid amines is 45-350 degreeC (for example, 50-320 degreeC), for example, Preferably it is 60-300 degreeC (for example, 80-280 degreeC), More preferably, it is 100-250 degreeC (for example, 120- About 230 ° C.). Further, the amines (B1) may be a compound that decomposes or evaporates at a firing temperature described later (for example, about 100 to 350 ° C., preferably about 120 to 300 ° C.).

(Carboxylic acid (B2))
Carbon number 1-3 carboxylic acid (B2) should just be a compound which has at least 1 carboxyl group, and the number of carboxyl groups of carboxylic acid (B2) is about 1-2, for example, Also good.

  In the carboxylic acid (B2), some of the carboxyl groups may form a salt (such as a metal salt), but in the present invention, the carboxyl group (all the carboxyl groups) usually forms a salt. Unused carboxylic acids are often used.

In addition, as long as the carboxylic acid (B2) has a carboxyl group, a functional group other than the carboxyl group (or a coordinating group for the metal compound or metal nanoparticle, for example, a group having a halogen atom or a hetero atom {for example, A group having an oxygen atom [hydroxyl group, alkoxy group (for example, C _1-6 alkoxy group such as methoxy group, ethoxy group, propoxy group, butoxy group), formyl group, carbonyl group, ester group, etc.], sulfur atom Group [for example, thio group, thiol group, thiocarbonyl group, alkylthio group (C _1-4 alkylthio group such as methylthio group, ethylthio group, etc.), sulfo group, sulfamoyl group, sulfinyl group (—SO ₂ —), etc.] These functional groups can be used alone or in combination of two or more carboxylic acids (B2). May have.

Representative carboxylic acids (B2) include, for example, C _1-3 monocarboxylic acid [eg, C _1-3 aliphatic monocarboxylic acid (eg, formic acid, acetic acid, propionic acid, acrylic acid, etc.)], C _2-3 polycarboxylic acid (oxalic acid, propanedioic acid, etc.), C _2-3 hydroxycarboxylic acid (or oxycarboxylic acid, glycolic acid, lactic acid, etc.) and the like can be mentioned. These carboxylic acids may be anhydrides, hydrates, and the like.

  Carboxylic acid (B2) may be used alone or in combination of two or more.

Among these carboxylic acids (B2), C _1-3 saturated aliphatic monocarboxylic acids such as acetic acid and propionic acid are preferable, and propionic acid is particularly preferable.

  The pKa value of the carboxylic acid (B2) may be, for example, 1 or more (for example, about 1 to 10), preferably 2 or more (for example, about 2 to 8).

  In the metal colloid particles, the ratio of the protective colloid (B) (total amount of amines (B1) and carboxylic acid (B2)) is, for example, 0.1 to 100 with respect to 100 parts by mass of the metal nanoparticles (A). Parts by mass (eg, 0.5-80 parts by mass), preferably 1-60 parts by mass (eg, 1.5-50 parts by mass), more preferably 3-50 parts by mass (eg, 5-40 parts by mass). It may be a degree.

  In the metal colloid particles, the ratio of the amines (B1) is, for example, 0.01 to 70 parts by mass (for example, 0.1 to 50 parts by mass) with respect to 100 parts by mass of the metal nanoparticles (A). ), Preferably 0.5 to 40 parts by mass (eg 1 to 30 parts by mass), more preferably 1.5 to 20 parts by mass (eg 2 to 15 parts by mass).

  In the metal colloidal particles, the ratio of the carboxylic acid (B2) is, for example, 0.01 to 50 parts by mass (for example, 0.05 to 30 parts by mass) with respect to 100 parts by mass of the metal nanoparticles (A). ), Preferably 0.1 to 30 parts by mass (for example, 0.5 to 20 parts by mass), more preferably about 1 to 15 parts by mass (for example, 2 to 10 parts by mass).

  Further, in the metal colloid particles, the ratio of amines (B1) and carboxylic acid (B2) 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 (e.g. 75/25 to 15/85), more preferably 70/30 to 20/80 (e.g. 60/40 to 25/75), especially 55/45 to 30 / It may be about 70.

  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, dipropylene glycol, triethylene glycol, polyethylene glycol, etc.), aralkyl alcohols, polyhydric alcohols, etc.], ether (Cellosolves, carbitols, etc.), ketones [eg, alkanones, cycloalkanones, diketones (β-diketones such as acetylacetone)], S Le compounds (e.g., fatty acid esters, 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 [ Examples thereof include sulfoxides and sulfonic acids (eg, arene sulfonic acids such as alkane sulfonic acid, benzene sulfonic acid, and toluene sulfonic acid). 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 1 to 50 parts by mass, and more preferably about 5 to 30 parts by mass with respect to 100 parts by mass of the protective colloid (B). May be.

[Other colloidal metal particles]
The metal nanoparticle paste of the present invention only needs to contain at least the metal colloid particles (sometimes referred to as metal colloid particles (C)) as metal colloid particles, and may contain only metal colloid particles (C). In addition, other metal colloid particles may be included as long as low temperature sintering can be realized.

  The other metal colloid particles are not particularly limited as long as they are metal colloid particles that do not belong to the category of the metal colloid particles, but they do not impair the low-temperature sinterability and can form fine patterns of the same level. From the above viewpoint, the following metal colloidal particles can be preferably used.

  Metal colloidal particles composed of metal nanoparticles (a) and protective colloids (b) covering the metal nanoparticles (a), wherein the protective colloids (b) are amines (b1), Metal colloidal particles composed of carboxylic acid (b2) having 4 or more carbon atoms.

  That is, the above metal colloid particles (sometimes referred to as metal colloid particles (c)) as other metal colloid particles have a carbon number of 4 or more instead of the protective colloid (B2) in the metal colloid particles (C). Metal colloidal particles using carboxylic acid (b2).

  In such other metal colloidal particles, the carboxylic acid constituting the protective colloid is composed of a carboxylic acid having a larger carbon number and is also stable, but its stability (protective ability of the protective colloid) Different from the metal colloid particles (C). Therefore, the combination of the metal colloid particles (C) and the metal colloid particles (c) can further improve the temporal stability of the metal nanoparticle paste.

  In the metal colloidal particles (c), as the metal nanoparticles (a), the same metal nanoparticles (metal nanoparticles (A)) as described above can be used, and the preferred embodiments are also the same as described above. Moreover, as amines (b1), the same amines as above (amines (B1)) can be used, and preferred amines are also the same as above.

  The carboxylic acid (b2) having 4 or more carbon atoms may be a compound having at least one carboxyl group, and the number of carboxyl groups in the carboxylic acid (b2) is, for example, 1 to 5, preferably 1 to 1. 4, more preferably about 1-3.

  In the carboxylic acid (b2), some of the carboxyl groups may form a salt (such as a metal salt), but in the present invention, the carboxyl group (all the carboxyl groups) usually forms a salt. Unused carboxylic acids are often used.

  In addition, the carboxylic acid (b2) may have a functional group other than the carboxyl group (or a coordinating group for the metal compound or the metal nanoparticles) as long as it has a carboxyl group. Examples of the functional group (or coordinating group) other than the carboxyl group include the same groups as described above. These functional groups may be contained in the carboxylic acid (b2) alone or in combination of two or more. The carboxylic acid (b2) is a compound that does not have a basic group (in particular, an amino group, a substituted amino group, an imino group, an ammonium base, or the like) that can form a salt with a carboxyl group among these functional groups. Is preferred.

  Representative carboxylic acids (b2) include various carboxylic acids having 4 or more carbon atoms, such as monocarboxylic acids, polycarboxylic acids, and hydroxycarboxylic acids (or oxycarboxylic acids).

Examples of monocarboxylic acids include aliphatic monocarboxylic acids [saturated aliphatic monocarboxylic acids (for example, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, dodecanoic acid, lauric acid, myristic acid, pentadecane. acid, hexadecanoic acid, octadecanoic acid, arachidic acid, behenic acid, lignoceric acid, montanic acid, cyclohexanecarboxylic acid, naphthenic acid, dehydrocholic acid, C _4-34 saturated aliphatic monocarboxylic acids, such as cholanic acid, preferably C _{4 -30} saturated aliphatic monocarboxylic acid, more preferably C _4-24 saturated aliphatic monocarboxylic acid, etc., unsaturated aliphatic monocarboxylic acid (for example, crotonic acid, itaconic acid, octenoic acid, Linderic acid, mascoic acid, Palmitooleic acid, oleic acid, elaidic acid, isooleic acid, petro Phosphoric acid, gadoleic acid, erucic acid, selacholeic acid, linoleic acid, linolenic acid, eleostearic acid, arachidonic acid, clupanodonic acid, _{C 4-34} unsaturated aliphatic carboxylic acids such as abietic acid, preferably _{C 8-30} Unsaturated aliphatic monocarboxylic acid, more preferably C _10-24 unsaturated aliphatic monocarboxylic acid)], aromatic monocarboxylic acid (for example, C _7-12 aromatic monocarboxylic acid such as benzoic acid, naphthoic acid, etc.) ) And the like.

Examples of the polycarboxylic acid include aliphatic polycarboxylic acid [for example, saturated aliphatic polycarboxylic acid (for example, C _4-14 saturated such as succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, cyclohexanedicarboxylic acid, etc. Aliphatic polycarboxylic acids, preferably C _4-10 saturated aliphatic polycarboxylic acids, etc., aliphatic unsaturated polycarboxylic acids (eg C ₄ such as maleic acid, fumaric acid, itaconic acid, sorbic acid, tetrahydrophthalic acid) _-14 unsaturated aliphatic polycarboxylic acids, preferably C _4-10 unsaturated aliphatic polycarboxylic acids, etc.]], aromatic polycarboxylic acids (eg C _8-12 aromatics such as phthalic acid, trimellitic acid, etc.) Polycarboxylic acid and the like).

Hydroxycarboxylic acids include hydroxymonocarboxylic acids [aliphatic hydroxymonocarboxylic acids (for example, oxybutyric acid, glyceric acid, 6-hydroxyhexanoic acid, cholic acid, deoxycholic acid, chenodeoxycholic acid, 12-oxochenodeoxycholic acid, glycochol. C _4-50 aliphatic hydroxy monocarboxylic acids such as acid, lithocholic acid, hyodeoxycholic acid, ursodeoxycholic acid, apocholic acid, taurocholic acid, preferably C _4-34 aliphatic hydroxy monocarboxylic acid, more preferably C _4-30 aliphatic hydroxy monocarboxylic acids, etc.), aromatic hydroxy monocarboxylic acids (such as C _7-12 aromatic hydroxy monocarboxylic acids such as salicylic acid, oxybenzoic acid, gallic acid, etc.)], hydroxypolycarboxylic acids [fats Tribe Loxypolycarboxylic acid (eg, C _4-10 aliphatic hydroxypolycarboxylic acid such as tartaric acid, citric acid, malic acid, etc.) and the like.

  These carboxylic acids may be anhydrides, hydrates, and the like. In many cases, the carboxylic acid does not form a salt as described above.

  Carboxylic acid (b2) may be used alone or in combination of two or more.

Among these carboxylic acids (b2), carbons such as aliphatic monocarboxylic acids having 4 or more carbon atoms (for example, C _4-30 saturated aliphatic monocarboxylic acids, C _8-30 unsaturated aliphatic monocarboxylic acids, etc.) An aliphatic carboxylic acid having a number of 4 or more is preferred. The carboxylic acid (b2) was selected from (i) a carboxylic acid having 4 to 9 carbon atoms (for example, a C _4-9 saturated aliphatic monocarboxylic acid and a C _4-9 unsaturated aliphatic monocarboxylic acid). At least one), or (ii) a carboxylic acid having 10 or more carbon atoms (for example, at least one selected from C _10-30 saturated aliphatic monocarboxylic acid and C _10-30 unsaturated aliphatic monocarboxylic acid) You may comprise only. In the carboxylic acid (i) or (ii), the carboxylic acids may be used alone or in combination of two or more.

  The carboxylic acid (b2) may be liquid or solid at room temperature (or room temperature, for example, 25 ° C.), and particularly liquid. The pKa value of the carboxylic acid (b2) 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).

  In the metal colloidal particles (c), the ratio of each component [metal nanoparticles (a), amines (b1), carboxylic acid (b2)] can be selected from the same range as described above.

  In the metal nanoparticle paste, the ratio of the metal colloid particles (C) to other metal colloid particles (other metal colloid particles (c)) is, for example, the former / the latter (mass ratio) = 99 / 1-30. / 70, preferably 97/3 to 50/50, more preferably 95/5 to 60/40, particularly about 93/7 to 70/30.

[Dispersion medium]
The dispersion medium is not particularly limited as long as it is a solvent that generates sufficient viscosity in the paste by combination with the metal colloid particles (or metal nanoparticles), and a general-purpose solvent can be used. Examples of the dispersion medium (dispersion solvent) include alcohols {for example, aliphatic alcohols (for example, heptanol, octanol (1-octanol, 2-octanol, etc.), decanol (1-decanol, etc.), lauryl alcohol, tetradecyl. Saturated, unsaturated C _6-30 aliphatic alcohols such as alcohol, cetyl alcohol, octadecyl alcohol, hexadecenol, oleyl alcohol, preferably saturated or unsaturated C _8-24 aliphatic alcohols), alicyclic alcohols [e.g. Cycloalkanols such as cyclohexanol; terpene alcohols such as terpineol and dihydroterpineol (eg, monoterpene alcohol)], araliphatic alcohols (eg, benzyl alcohol, phenethyla) Call etc.), polyhydric alcohols glycols such as C _2-4 alkylene glycol (ethylene glycol, propylene glycol, diethylene glycol, (poly and dipropylene glycol); and polyhydric alcohols having 3 or more hydroxyl groups such as glycerin Etc.}, glycol ethers (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, Dipropylene glycol monomethyl ether, tripropylene glycol (Poly) alkylene glycol monoalkyl ethers such as butyl ether; (poly) alkylene glycol monoaryl ethers such as 2-phenoxyethanol), glycol esters (eg, (poly) alkylene glycol acetates such as carbitol acetate), glycol ethers Esters (for example, (poly) alkylene glycol monoalkyl ether acetates such as ethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate), hydrocarbons [For example, aliphatic hydrocarbons (eg, tetradecane, o Saturated or unsaturated aliphatic hydrocarbons such as kutadecane, heptamethylnonane, tetramethylpentadecane), aromatic hydrocarbons (eg, toluene, xylene, etc.)], esters (eg, benzyl acetate, isoborneol acetate, And polar solvents (solvents having a polar group) such as methyl benzoate and ethyl benzoate). These solvents may be used alone or in combination of two or more.

Typical dispersion media include aliphatic alcohols (eg, saturated or unsaturated C _6-30 aliphatic alcohols such as octanol and decanol, preferably saturated or unsaturated C _6-20 aliphatic alcohols), alicyclic Alcohols [for example, terpene alcohols such as terpineol and dihydroterpineol (for example, monoterpene alcohol) and the like] and the like.

  Further, the boiling point of the dispersion medium (in the case of a mixed solvent, the boiling point of each solvent) varies depending on the use of the metal nanoparticle paste, but is preferably 100 ° C. or higher, for example, 100 to 400 ° C. (for example, 120-380 ° C.), preferably 130-370 ° C. (eg, 150-350 ° C.), more preferably about 170-320 ° C. (eg, 180-300 ° C.), usually 180-270 ° C. (eg, 185 to 250 ° C.).

  In the metal nanoparticle paste, the proportion of the dispersion medium is, for example, 0.1 to 100 parts by mass with respect to 100 parts by mass of metal colloid particles (the total amount of metal colloid particles when other metal colloid particles are included). 1 to 80 parts by mass, more preferably 2 to 50 parts by mass, particularly 3 to 30 parts by mass (for example, 5 to 20 parts by mass).

  For metal nanoparticle pastes, conventional additives such as binder resins (hydrophilic polymers such as polyvinyl alcohol and polyethylene glycol), hue improvers, gloss imparting agents, metal corrosion inhibitors, stable Agents, surfactants or dispersants (anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, etc.), dispersion stabilizers, thickeners or viscosity modifiers, humectants, A thixotropic agent, an antifoaming agent, a disinfectant, a filler and the like may be contained. These additives can be used alone or in combination of two or more. The metal nanoparticle paste preferably does not contain these additives from the viewpoint of conductivity and low-temperature sintering, and particularly preferably does not substantially contain a binder resin (organic binder).

  In the metal nanoparticle paste, the ratio of the metal nanoparticles (A) is, for example, 35% by mass or more (for example, about 40 to 95% by mass), preferably 45% by mass or more (for example, about 50 to 90% by mass), More preferably, it may be 55% by mass or more (for example, about 60 to 85% by mass), and particularly 60% by mass or more (for example, 63 to 90% by mass, preferably 65 to 85% by mass, and more preferably 70 to 85% by mass). About 80% by mass). In the metal nanoparticle paste, when the metal colloid particles include other metal colloid particles, the metal nanoparticles (A) and the metal nanoparticles constituting the other metal colloid particles (for example, the metal nanoparticles (a)) The total amount may be in the above range.

  Further, the viscosity of the metal nanoparticle paste varies depending on the application and the printing method to be applied, but is usually 0.5 Pa · s or more (for example, 1 to 400 Pa · s) at 25 ° C., preferably 3 Pa · s. Above (for example, 5 to 300 Pa · s), more preferably about 10 to 250 Pa · s, particularly about 20 to 200 Pa · s (for example, 30 to 150 Pa · s), and usually about 1 to 300 Pa · s. There may be. The viscosity is a value measured using a general-purpose viscometer (for example, a B-type viscometer or an E-type viscometer).

[Production Method of Metal Nanoparticle Paste]
The metal nanoparticle paste of the present invention is not particularly limited as long as the metal nanoparticle paste having the above configuration can be obtained, but it can be usually obtained by dispersing the metal colloid particles in the dispersion medium.

  The metal colloid particles (or dispersions thereof) may be prepared by a conventional method, for example, by applying a metal compound corresponding to the metal nanoparticles (A), a protective colloid (B) (and the other protective colloid if necessary) and It can be prepared by reducing in a solvent 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). Salt), boranes (diborane, dimethylamine borane, etc.), hydrazines (hydrazine, etc.), formalin, amines [eg, methylaminoethanol, dimethylaminoethanol (2- (dimethylamino) ethanol), ethanolamine, diethanolamine , Alkanolamines such as triethanolamine, methyldiethanolamine, propanolamine, 2- (3-aminopropylamino) ethanol, butanolamine, hexanolamine, dimethylaminopropanol], Machine acid (citric acid, tartaric acid, and ascorbic acid), and others. 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). In addition, the reaction may be usually performed under stirring (or while stirring).

  The reaction solvent may be the above-described dispersion medium constituting the final metal nanoparticle paste, or a solvent different from the solvent constituting the metal nanoparticle paste, or a mixed solvent thereof. There may be. The reaction solvent can be selected according to the type of the protective colloid. For example, when the protective colloid is a water-soluble compound, the reaction solvent is often composed of a polar solvent such as water, and a hydrophobic compound. In some cases, the reaction solvent is often composed of a hydrophobic solvent.

In addition to the dispersion medium, the reaction solvent is a hydrophobic solvent [for example, hydrocarbons (for example, aliphatic hydrocarbons such as hexane, heptane, trimethylpentane, octane, decane, dodecane, and tetradecane; alicyclic such as cyclohexane) Hydrocarbons; aromatic hydrocarbons such as toluene and xylene; 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 (diethyl ether, dipropyl ether, etc.)], polar solvents [water, alcohols (C _1-4 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, etc.), aliphatic polyhydric alcohols (ethylene glycol) , Polyethylene grease Coal, glycerin, etc.), ketones (acetone, etc.), ethers (dioxane, tetrahydrofuran, etc.), organic carboxylic acids (acetic acid, etc.) and the like. These solvents may be used alone or in combination of two or more. The reaction solvent may usually be composed of at least a hydrophobic solvent (a hydrophobic solvent that is not the dispersion medium).

  In addition, the density | concentration of the said metal compound in a reaction solvent is 5 mass% or more (for example, 6-50 mass%) in conversion of the mass of a metal, for example, Preferably it is 8 mass% or more (for example, 9-40 mass%). More preferably, it may be a high concentration of 10% by mass or more (for example, 12 to 30% by mass), usually about 5 to 30% by mass.

  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, phosphoric acid or perchloric acid, an organic acid such as formic acid, acetic acid, propionic acid or benzoic acid), an alkali [sodium hydroxide, Inorganic bases such as ammonia and bases such as amines (for example, organic bases such as tertiary amines such as alkylamines and alkanolamines) can be used.

  By the above reaction (reduction reaction), the metal colloid particles can be prepared in the form of a dispersion in which the metal colloid particles are dispersed in the reaction solvent. In addition, after completion | finish of a reductive reaction, you may refine | purify a reaction liquid mixture by a conventional method (For example, filtration processes, such as centrifugation, a membrane filter, ultrafiltration, etc.) as needed.

  Other metal colloid particles such as the metal colloid particles (c) can also be produced by the same method as described above.

  The metal nanoparticle paste can be prepared by concentrating unnecessary solvent components from the dispersion when the solvent containing the dispersion medium is used as the reaction solvent. It can be prepared by dispersing (redispersing) the metal colloidal particles separated from the dispersion in the dispersion medium.

  Separation of the metal colloid particles from the dispersion can be performed by a conventional method, for example, by separating and removing the reaction solvent from the dispersion. For removal of the reaction solvent, a conventional concentration operation or the like can be used. The removal of the reaction solvent may be performed in the presence of a dispersion medium using the difference in boiling point between the reaction solvent and the dispersion medium (that is, the removal of the reaction solvent and the dispersion in the dispersion medium are the same). System may be used). For example, the reaction solvent may be removed from a mixture obtained by mixing the dispersion medium with the dispersion.

  The amount of the dispersion medium used can be appropriately adjusted so as to obtain a desired viscosity, and may be appropriately selected from the same range as described above. The viscosity may be adjusted by mixing other solvent in addition to the dispersion medium and removing the other solvent.

  When other metal colloid particles such as the metal colloid particles (c) are used in combination, the metal colloid particles (C) and other metal colloid particles are mixed and then dispersed in a dispersion medium by the same method as described above. The metal nanoparticle paste can be prepared.

<Applications of metal nanoparticle paste>
The metal nanoparticle paste of the present invention can be used for various applications. For example, the metal nanoparticle paste of the present invention is useful as a paste for forming a metal film (particularly a conductive film). In particular, since the metal nanoparticle paste of the present invention contains metal nanoparticles at a high concentration and can be sintered at a relatively low temperature, a predetermined pattern (circuit) among metal films (continuous film, sintered film). It is suitable as a paste for forming a pattern, particularly a conductive pattern. Hereinafter, a method for forming a pattern using the metal nanoparticle paste will be described in detail.

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

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

  What is necessary is just to select the thickness of a base material (or board | substrate) suitably according to a use, for example, 0.001-10 mm, Preferably it is 0.01-5 mm, More preferably, it is 0.05-3 mm (especially 0.1-3 mm). 1 mm) or so.

  The drawing method (or printing method) for drawing the pattern (coating layer) is not particularly limited as long as it is a pattern forming printing method. For example, a screen printing method, an ink jet printing method, an intaglio printing method (for example, Gravure printing method) and flexographic printing method. In particular, in the present invention, since a paste containing metal nanoparticles at a high concentration is used, it is advantageous to form a pattern by a screen printing method. In screen printing, the material of the screen is not particularly limited, and may be a fiber (silk, polyamide fiber, polyester fiber, etc.), a wire, or the like. Further, the size of the screen can be appropriately selected according to the width of the pattern.

  In the present invention, since the concentration of the metal nanoparticles can be easily controlled by the dispersion medium, it is advantageous to form a pattern by an intaglio printing method that requires relatively fluidity. That is, the paste of the present invention is useful as an intaglio printing paste, and is excellent in scraping property by a doctor blade. In the screen printing method, the dimensional accuracy may be affected as the pattern becomes finer depending on the line width of the mesh constituting the screen plate. In the intaglio printing method, fine line drawing can be achieved by the plate processing technology. it can. Further, the intaglio printing method is characterized in that the ink is filled in the recesses of the plate cylinder, so that the halftone dots by the ink become clearer than the screen printing method.

  The average thickness of the coating layer (or sintered pattern) may be, for example, about 0.5 to 20 μm, preferably 1 to 15 μm, and more preferably about 1.5 to 10 μm. In the present invention, since a paste containing metal nanoparticles at a high concentration is used, such a thick film on the order of microns can be formed efficiently.

  The line width (minimum line width) of the coating layer (or sintered pattern) is not particularly limited depending on the application, and may be, for example, about 1 μm to 5 cm or 5 μm to 3 cm. In the present invention, a pattern can be formed even if the line width (minimum line width) of the coating layer (or sintered pattern) is, for example, 1 to 50 μm, preferably 3 to 40 μm, more preferably about 5 to 30 μm. In particular, in the present invention, fine firing with a minimum line width of 30 μm or less (for example, 1 to 30 μm, preferably 2 to 25 μm), preferably a minimum line width of about 20 μm or less (for example, 1 to 20 μm, preferably 2 to 18 μm). Even a bonded pattern can be formed efficiently. The ratio between the minimum line width and the average thickness of the coating layer (or sintered pattern) is the former / the latter = 1/20 to 1/2, preferably 1/18 to 1/3, more preferably 1/15. It may be about １ ／.

  The baking treatment can usually be performed by heating the pattern at a predetermined baking temperature (or baking or heat treatment). The firing temperature is not particularly limited as long as the metal nanoparticles can be fused to form a continuous film, and can be appropriately selected. In particular, since the metal nanoparticle paste of the present invention sinters even at a relatively low temperature, the firing temperature is 200 ° C. or less (for example, about 30 to 180 ° C.), preferably 40 to 170 ° C., more preferably It may be about 50 to 160 ° C. (for example, 55 to 155 ° C.), and is usually 150 ° C. or less [for example, 40 to 150 ° C., preferably 45 to 140 ° C. (for example, 50 to 135 ° C.), and more preferably 130 Or less (for example, 55 to 130 ° C.), particularly 125 ° C. or less (for example, 60 to 125 ° C., usually about 80 to 120 ° C.).

  The firing time (heating time) may be, for example, 10 minutes to 6 hours, preferably 15 minutes to 5 hours, more preferably about 20 minutes to 3 hours, depending on the firing temperature, etc. Sintering can be performed even for a baking treatment time of about 1 to 1 hour.

  A sintered pattern (sintered body layer) is thus formed. The sintered pattern has high conductivity when conductive metal particles are used as the metal nanoparticles. Note that the thickness and line width of the sintered pattern are in the same ranges as described above.

  Since the metal nanoparticle paste of the present invention contains metal nanoparticles at a high concentration, it is useful, for example, as a paste for forming a metal film (sintered film). In particular, it does not contain metal fillers or organic binders and can be sintered at low temperatures, so it has excellent printability. In particular, fine patterns (circuit or wiring patterns) can be efficiently formed even by printing methods such as screen printing. it can. Further, since sintering can be performed even at an ultra-low temperature of 150 ° C. or lower, a metal film can be formed on a resin substrate or the like.

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

Example 1
2.5 g of silver nitrate, 4.9 g of n-octylamine and 2.0 g of propionic acid were added to 1.0 L of trimethylpentane, and the mixture was stirred and dissolved. To this mixed solution, 1.0 L of a propanol solution containing 0.03 mol / L sodium borohydride was added dropwise over 1 hour to reduce silver. Furthermore, it stirred for 3 hours and obtained the black liquid. After the obtained black liquid was concentrated by an evaporator, 2.0 L of methanol was added thereto to produce a brown precipitate, and then the precipitate was collected by suction filtration. The resulting precipitate was redispersed in trimethylpentane, filtered and dried to obtain silver colloidal particles as a black solid. According to the transmission electron microscope (TEM), the number average particle diameter of the core part of the obtained silver nanoparticles is 3.5 nm. According to the dynamic light scattering particle size measurement (DLS), the silver colloid containing the protective colloid The number average particle size of the entire particles was 6.3 nm.

6.0 g of the obtained silver colloid particles and 0.8 g of 1-decanol were mixed in a mortar to prepare a silver nanoparticle paste. This silver nanoparticle paste had a viscosity (E-type viscometer, measured at 25 ° C.) of 74 Pa · s and a metal content of 67% by mass. This silver nanoparticle paste was applied (patterned) by screen printing on a polyethylene terephthalate substrate (thickness: 175 μm, manufactured by Teijin DuPont Films, Ltd., “Teijin Tetron Film HS175”). And after heat-treating in an oven at 100 ° C. for 30 minutes, when the conductivity was evaluated in a □ pattern (1 cm × 1 cm) with a film thickness of 5.5 μm, the volume resistivity was 3.5 × 10 ⁻⁴ Ω · cm. there were.

(Example 2)
8.0 g of silver colloidal particles prepared in Example 1 and 0.6 g of terpineol (manufactured by Wako Pure Chemical Industries, Ltd., isomer mixture) were mixed in a mortar to prepare a silver nanoparticle paste. The viscosity (E-type viscometer, measured at 25 ° C.) of this silver nanoparticle paste was 68 Pa · s, and the metal content was 71 mass%. This silver nanoparticle paste was applied (patterned) by screen printing on a polyethylene terephthalate substrate (thickness: 175 μm, manufactured by Teijin DuPont Films, Ltd., “Teijin Tetron Film HS175”). And after heat-processing for 30 minutes at 100 degreeC in oven, when electroconductivity was evaluated in the square pattern (1 cm x 1 cm) with a film thickness of 6.5 micrometers, volume resistivity is 2.0x10 < ^-3 > ohm * cm. there were.

(Example 3)
Silver colloidal particles 6.0 g prepared in Example 1 and 2-octanol 0.6 g were mixed in a mortar to prepare a silver nanoparticle paste. This silver nanoparticle paste had a viscosity (E-type viscometer, measured at 25 ° C.) of 70 Pa · s and a metal content of 78% by mass. This silver nanoparticle paste was applied (patterned) by screen printing on a polyethylene terephthalate substrate (thickness: 175 μm, manufactured by Teijin DuPont Films, Ltd., “Teijin Tetron Film HS175”). And after heat-treating in an oven at 120 ° C. for 30 minutes, when the conductivity was evaluated in a □ pattern (1 cm × 1 cm) having a film thickness of 6.5 μm, the volume resistivity was 2.3 × 10 ⁻⁴ Ω · cm. there were.

(Synthesis Example 1)
2.5 g of silver nitrate, 4.9 g of n-octylamine and 4.9 g of linoleic acid were added to 1.0 L of trimethylpentane, and the mixture was stirred and dissolved. To this mixed solution, 1.0 L of a propanol solution containing 0.03 mol / L sodium borohydride was added dropwise over 1 hour to reduce silver. Furthermore, it stirred for 3 hours and obtained the black liquid. After the obtained black liquid was concentrated by an evaporator, 2.0 L of methanol was added thereto to produce a brown precipitate, and then the precipitate was collected by suction filtration. The resulting precipitate was redispersed in trimethylpentane, filtered and dried to obtain silver colloidal particles as a black solid. According to a transmission electron microscope (TEM), the number average particle diameter of the core part of the obtained silver nanoparticles is 3.6 nm, and according to dynamic light scattering particle size measurement (DLS), a silver colloid containing a protective colloid The number average particle size of the entire particles was 8.0 nm.

Example 4
2.6 g of silver colloidal particles prepared in Example 1, 0.3 g of silver colloidal particles prepared in Synthesis Example 1 and 0.45 g of 1-decanol were mixed in a mortar to prepare a silver nanoparticle paste. The silver nanoparticle paste had a viscosity (E-type viscometer, measured at 25 ° C.) of 90 Pa · s and a metal content of 75 mass%. This silver nanoparticle paste was applied (patterned) by screen printing on a polyethylene terephthalate substrate (thickness: 175 μm, manufactured by Teijin DuPont Films, Ltd., “Teijin Tetron Film HS175”). Then, after heat treatment in an oven at 120 ° C. for 30 minutes, when the conductivity was evaluated in a line pattern having a line width of 420 μm and a film thickness of 3.0 μm, the volume resistivity was 4.8 × 10 ⁻³ Ω · cm. It was.

(Example 5)
20.0 g of silver colloid particles prepared in Example 1, 3.4 g of silver colloid particles prepared in Synthesis Example 1, 1.25 g of 1-decanol, and 1.25 g of terpineol (manufactured by Wako Pure Chemical Industries, Ltd., isomer mixture) Were mixed in a mortar to prepare a silver nanoparticle paste. The silver nanoparticle paste had a viscosity (E-type viscometer, measured at 25 ° C.) of 78 Pa · s and a metal content of 75 mass%. This silver nanoparticle paste was applied (patterned) by screen printing on a polyethylene terephthalate substrate (thickness: 175 μm, manufactured by Teijin DuPont Films, Ltd., “Teijin Tetron Film HS175”). Then, after heat treatment in an oven at 120 ° C. for 60 minutes, when the conductivity was evaluated in a line pattern having a line width of 400 μm and a film thickness of 8.3 μm, the volume resistivity was 3.7 × 10 ⁻³ Ω · cm. It was.

(Example 6)
19.8 g of silver colloidal particles prepared in Example 1, 3.4 g of silver colloidal particles prepared in Synthesis Example 1, and 2.2 g of terpineol (manufactured by Wako Pure Chemical Industries, Ltd., isomer mixture) were mixed in a mortar. A nanoparticle paste was prepared. The silver nanoparticle paste had a viscosity (E-type viscometer, measured at 25 ° C.) of 64 Pa · s and a metal content of 74% by mass. When this silver nanoparticle paste is applied (patterned) by screen printing on a polyethylene terephthalate substrate (thickness: 175 μm, manufactured by Teijin DuPont Films, Ltd., “Teijin Tetron Film HS175”), a pattern with a line and space of 50 μm is drawn. did it. Then, 120 ° C. in an oven, was heat treated for 60 minutes, conductivity can be confirmed, line width 4.7 [mu] m, a volume resistivity in the pattern of a line width 50μm was 1.1 × ^{10 -3} Ω · cm.

(Comparative Example 1)
10.0 g of silver particles (average particle size 0.3 μm, “SPQ03s” manufactured by Mitsui Kinzoku Co., Ltd.) and 1.0 g of 1-decanol were mixed in a mortar to prepare a silver particle paste. When this silver particle paste was applied (patterned) by screen printing onto a glass substrate (thickness 700 μm, manufactured by Matsunami Glass Co., Ltd., “Corning 1737 liquid crystal glass”), the particle size was large, and line and space 25 μm. This pattern could not be formed. Then, it apply | coated with the applicator on the glass substrate, and it heat-processed for 30 minutes at 250 degreeC with oven, However, The silver continuous film was not formed on the board | substrate.

(Example 7)
In Example 1, coating (patterning) was performed by screen printing in the same manner as in Example 1 except that heat treatment was performed at “80 ° C., 60 minutes” instead of “100 ° C., 30 minutes”. And when the electrical conductivity was evaluated in a □ pattern (1 cm × 1 cm) having a film thickness of 6.5 μm, the volume resistivity was 5.6 × 10 ⁻³ Ω · cm.

(Example 8)
Silver colloidal particles 10.0 g prepared in Example 1 and terpineol (Wako Pure Chemical Industries, Ltd., isomer mixture) 3.0 g were mixed in a mortar to prepare a silver nanoparticle paste. The silver nanoparticle paste had a viscosity (E-type viscometer, measured at 25 ° C.) of 10 Pa · s and a metal content of 55% by mass. On a polyethylene terephthalate substrate (thickness 100 μm, manufactured by Toyobo Co., Ltd.), this silver nanoparticle paste was patterned by intaglio printing (pitch 250 μm, width 20 μm). As a result, a fine line pattern having an average line width of 15.1 μm and a film thickness of 1.6 μm could be produced. And after heat-treating at 120 degreeC for 30 minute (s) in oven, when electrical conductivity was evaluated, the volume resistivity was 8.2 * 10 <^-5> ohm * cm.

(Comparative Example 2)
Nanoparticles were produced in the same manner as in Example 1 except that propionic acid was not added.

  That is, 2.5 g of silver nitrate and 6.0 g of n-octylamine were added to 0.5 L of trimethylpentane, and the mixture was stirred and dissolved. To this mixed solution, 0.5 L of a propanol solution containing 0.01 mol / L sodium borohydride was added dropwise over 1 hour to reduce silver. Furthermore, it stirred for 3 hours and obtained the black liquid. After the obtained black liquid was concentrated by an evaporator, 1.0 L of methanol was added thereto to produce a brown precipitate, and then the precipitate was collected by suction filtration. The resulting precipitate was redispersed in trimethylpentane, filtered and dried to obtain silver colloid particles as an ocher solid. According to dynamic light scattering particle size measurement (DLS), the number average particle size of the entire silver colloid particles including the protective colloid of the obtained silver nanoparticles was 7.0 nm.

  10.0 g of the obtained silver nanoparticles and 3.0 g of 1-decanol were mixed in a mortar, but could not be made into a paste because of low dispersion stability.

Claims (17)

And metal nanoparticles (A), a metal nanoparticle (A) protective colloids to coat (B) and de-configured metal colloid particles, and a paste comprising a dispersion medium of the colloidal metal particles, the metal nano The average primary particle diameter of the particles (A) is 1 to 30 nm, and the protective colloid (B) is a mono C _6-20 alkylamine amine (B1) and a carboxylic acid that is acetic acid and / or propionic acid. The metal nanoparticle paste comprised by (B2).   The paste according to claim 1, wherein the metal constituting the metal nanoparticles (A) is a single noble metal or a noble metal alloy.   The paste according to claim 1 or 2, wherein the metal constituting the metal nanoparticles (A) is a simple silver, and the average particle diameter of the metal nanoparticles (A) is 10 nm or less. The paste according to any one of claims 1 to 3 , wherein the carboxylic acid (B2) is propionic acid. The ratio of the protective colloid (B) is 1 to 60 parts by mass with respect to 100 parts by mass of the metal nanoparticles (A), and the ratio of the amines (B1) and the carboxylic acid (B2) is the former / the latter (mass). ratio) = 85/15 to 10/90 in which claims 1-4 paste according to any one. 6. The metal colloid particles are metal colloid particles prepared by reducing a metal compound corresponding to the metal nanoparticles (A) in a solvent in the presence of a protective colloid (B) and a reducing agent. The paste according to any one of the above. Further, the metal colloidal particles include other metal colloid particles, and the other metal colloid particles are composed of the metal nanoparticles (a) and the protective colloid (b) covering the metal nanoparticles (a). The paste according to any one of claims 1 to 6 , wherein the protective colloid (b) comprises an amine (b1) and a carboxylic acid (b2) having 4 or more carbon atoms. The paste according to any one of claims 1 to 7 , wherein the dispersion medium is a solvent having a boiling point of 100 ° C or higher and capable of dispersing the metal colloid particles. The paste according to any one of claims 1 to 8 , wherein the dispersion medium is at least one selected from saturated or unsaturated _C6-30 aliphatic alcohols and terpene alcohols. Claim 1-9 or the description of the paste fraction of the metal nanoparticles (A) is 40 to 95 mass%. The paste according to any one of claims 1 to 10 , which has a viscosity at 25 ° C of 1 to 400 Pa · s. A method for forming a sintered pattern by forming an electrode or a wiring pattern on the substrate using the metal nanoparticle paste according to any one of claims 1 to 11 , and firing the formed pattern. The pattern forming method according to claim 12, wherein the pattern is formed by screen printing or intaglio printing. The pattern forming method according to claim 12 or 13, baked at a firing temperature 0.99 ° C. or less. The pattern formation method in any one of Claims 12-14 which uses a resin-made base material as a board | substrate and performs baking processing at the baking temperature of 80-120 degreeC. The pattern forming method according to claim 12 , wherein a sintered pattern having a minimum line width of 30 μm or less is formed. The pattern forming method according to claim 12 , wherein a sintered pattern having a minimum line width of 20 μm or less is formed.