JP2020047378A - Conductive fine particle dispersion - Google Patents

Abstract

To provide a conductive fine particle dispersion that can achieve both low resistance and adhesion even when fired under a sintering temperature condition of 100°C or lower.SOLUTION: The conductive fine particle dispersion comprises silver fine particles, a compound having a nitrogen-containing heterocycle, and a dispersion medium. The compound having a nitrogen-containing heterocycle has two or more nitrogen atoms in at least one heterocycle, and has one or more alkoxy groups and/or alkoxysilyl groups in the molecule.SELECTED DRAWING: None

Description

The present invention relates to a conductive fine particle dispersion.

2. Description of the Related Art In recent years, attention has been focused on a printed electronic technology for forming an extremely fine electronic circuit or device by printing and baking a conductive ink containing metal fine particles on a base material. The metal fine particles used in conductive ink are nanometer-sized particles that are much smaller than the conductive fillers in conductive pastes known in the past. And high electrical conductivity close to that of a metal foil can be realized. Silver nanoparticles are known as metal fine particles used in such a conductive ink.

Documents that disclose the prior art relating to such a conductive ink include, for example, Patent Documents 1 and 2.

Patent Literature 1 discloses a metal nanoparticle dispersion including metal nanoparticles, a liquid carrier and a specific non-polymeric dispersion stable compound, and a conductive ink and paste prepared therefrom. Is disclosed to provide improved stability to the dispersion even at low viscosities and to be made conductive at lower sintering temperatures.

Patent Document 2 includes at least one of a metal nanoparticle and a metal complex, a dispersant, a sintering temperature reducing agent, and a solvent, wherein the sintering temperature reducing agent is a nitrogen-containing aromatic heterocyclic compound. Certain conductive inks have been disclosed. Further, it is disclosed that by containing a nitrogen-containing aromatic heterocyclic compound, heat treatment at a high temperature becomes unnecessary, and a conductive layer having sufficient conductivity can be formed on a substrate such as a resin having low heat resistance. ing.

JP-T-2018-508925 JP-A-2006-164225

As described above, a method for stabilizing the metal nanoparticle dispersion and a method for lowering the sintering temperature necessary for obtaining a conductive layer or a conductive pattern have been conventionally studied.

The metal nanoparticle dispersion described in Patent Literature 1 has a combination of a polymer dispersant having a decomposition rate of 95% by mass at a temperature of less than 300 ° C. and a dispersion stable compound to achieve a dispersion stability and low-temperature sinterability. I am trying to balance them. However, even though the metal nanoparticle dispersion is fired at a high temperature sintering condition of 150 ° C. for 30 minutes, the volume resistivity of the sintered body exceeds 100 μΩ · cm. In terms of resistance, it has never reached the level required in the recent printed electronics technology field (for example, 10 μΩ · cm or less).
In the cited document 1, a polymer support (for example, polycarbonate, polyethylene terephthalate (PET) or polyvinyl chloride (PVC)) is disclosed as a support on which a conductive layer or a conductive pattern is formed. In order to improve the adhesion of ink having a substance, an undercoat layer to a resin substrate, or addition of an adhesive and a tackifier is disclosed. When such a configuration is used, it is expected that the resistance value of the conductive layer or the conductive pattern formed on the polymer support will further increase. Further, it has been difficult to achieve both low resistance and adhesion to a resin having a relatively low heat resistance such as an ABS resin as a polymer support.

Further, the conductive ink described in Patent Literature 2 achieves low-temperature sinterability by containing a nitrogen-containing aromatic heterocyclic compound, but the sintering temperature conditions in the examples are 100 ° C. or higher. No studies have been made on lowering the resistance of the conductive layer obtained by firing at a sintering temperature lower than ℃. Further, no consideration has been given to the adhesion of the conductive ink to the substrate.

As described above, in the related art, in order to reduce the resistance value, it is necessary to sinter the metal nanoparticle dispersion or the conductive ink under the sintering condition of 100 ° C. or more, and the applicable printing base material is limited. Was. Further, the adhesiveness when firing under low-temperature sintering conditions has not been studied.

The present invention has been made in view of the above circumstances, and has an object to provide a conductive fine particle dispersion capable of achieving both low resistance and adhesion even when fired at a sintering temperature of 100 ° C. or less. It is assumed that.

The present inventors have conducted various studies on methods for achieving both low resistance and adhesion even when the conductive fine particle dispersion is sintered at a low temperature. It has been found that the adhesion can be improved without increasing the value, and the present invention has been completed.

The conductive fine particle dispersion of the present invention contains silver fine particles, a compound having a nitrogen-containing hetero ring, and a dispersion medium, and the compound having a nitrogen-containing hetero ring has two or more nitrogen atoms in at least one hetero ring. It has an atom and has one or more alkoxy groups and / or alkoxysilyl groups in the molecule.

The silver fine particles preferably have an alkoxyamine attached to at least a part of the surface.

The compound having a nitrogen-containing hetero ring preferably has at least one of an alkoxy group and / or an alkoxysilyl group at at least one of a substituent bonded to the hetero ring and a terminal of the substituent.

The compound having a nitrogen-containing hetero ring is preferably contained in an amount of 0.1 to 9.1 parts by mass based on 100 parts by mass of the silver fine particles.

The dispersion medium is preferably a compound having at least one hydroxy group and having 1 to 10 carbon atoms.

ADVANTAGE OF THE INVENTION According to the electroconductive fine particle dispersion of this invention, even if sintering temperature conditions are low temperature, it can improve adhesiveness, without causing an increase in resistance value.

The conductive fine particle dispersion of the present invention contains silver fine particles, a compound having a nitrogen-containing hetero ring, and a dispersion medium, and the compound having a nitrogen-containing hetero ring has two or more nitrogen atoms in at least one hetero ring. It has an atom and has one or more alkoxy groups and / or alkoxysilyl groups in the molecule.

(Silver fine particles)
The average particle size of the silver fine particles is preferably 1 to 400 nm, more preferably 1 to 70 nm. When the average particle size of the silver fine particles is 1 nm or more, the silver fine particles have good low-temperature sinterability, and a conductive fine particle dispersion capable of forming a conductive film having excellent conductivity is obtained. The production cost of the fine particles can be suppressed. When the average particle diameter of the silver fine particles is 400 nm or less, the dispersion stability of the silver fine particles is unlikely to change with time.

The average particle diameter of the silver fine particles can be measured, for example, as a median diameter (D50) using a particle diameter standard as a volume standard using a dynamic light scattering method (Doppler scattering light analysis). Such a measurement can be performed by, for example, a dynamic light scattering type particle size distribution analyzer “LB-550” manufactured by Horiba, Ltd.

The conductive fine particle dispersion of the present invention may contain submicron-sized silver fine particles having an average particle size of more than 400 nm and 1 μm or less in addition to silver fine particles having an average particle size of 1 to 400 nm as silver fine particles. . By using silver microparticles having a submicron size in combination, the silver microparticles having an average particle diameter of 1 to 400 nm decrease in melting point around the silver microparticles having a submicron size, so that a good conductive path can be obtained.

The conductive fine particle dispersion of the present invention may contain at least one kind of metal particles other than silver in addition to the silver fine particles. By incorporating particles of a metal other than silver, migration is less likely to occur in the conductive film formed by the conductive fine particle dispersion of the present invention. As a metal other than silver, a metal whose ionization sequence is more noble than hydrogen is preferable. As the metal whose ionization sequence is more noble than hydrogen, gold, copper, platinum, palladium, rhodium, iridium, osmium, ruthenium and rhenium are preferable, and gold, copper, platinum and palladium are more preferable. One of these metals may be used alone, or two or more thereof may be used in combination. The metal particles other than silver may be nano-sized particles or sub-micron sized particles.

(Organic components)
It is preferable that an organic component is attached to at least a part of the surface of the silver fine particles. Further, the surface of the silver fine particles is more preferably coated with an organic component. The form of the coating is not particularly limited, but the organic component substantially forms inorganic colloid particles together with the silver fine particles as a so-called dispersant. The term "organic component" refers to a trace amount of organic matter that is initially contained as an impurity in silver fine particles, a trace amount of organic matter mixed in during the manufacturing process described below and adhered to the silver fine particles, a residual reducing agent that cannot be completely removed in the washing process, This is a concept that does not include organic substances and the like that are slightly attached to silver fine particles, such as dispersants. Note that, specifically, the “trace amount” is intended to be less than 1% by mass in the inorganic colloid particles.

The organic component is an organic substance that can adhere to the surface of the silver fine particles to prevent aggregation of the silver fine particles and form inorganic colloid particles.From the viewpoint of dispersibility and conductivity, amine and carboxylic acid are used. It is preferred to include. When these organic components are chemically or physically bonded to the silver fine particles, it is considered that they are converted into anions or cations. Included in ingredients.

Various amines can be used as the amine, and may be linear or branched, and may have a side chain. Specifically, N- (3-methoxypropyl) propane-1,3-diamine, 1,2-ethanediamine, 2-methoxyethylamine, 3-methoxypropylamine, 3-ethoxypropylamine, 1,4-butane Diamines such as diamine, 1,5-pentanediamine, pentanolamine and aminoisobutanol; alkoxyamines and aminoalcohols; and alkylamines such as propylamine, butylamine, pentylamine and hexylamine (linear alkylamines, side chains Cycloalkylamines such as cyclopentylamine and cyclohexylamine; primary amines such as aniline and allylamine; secondary amines such as dipropylamine, dibutylamine, piperidine and hexamethyleneimine; Tripropylamine, dimethi Propanediamine, cyclohexyldimethylamine, pyridine, tertiary amines such as quinoline. Among them, alkoxyamine is preferred.

The amine may be a compound containing a functional group other than an amine, such as a hydroxyl group, a carboxyl group, an alkoxy group, a carbonyl group, an ester group, and a mercapto group. The amines may be used alone or in combination of two or more. The amine has a boiling point at 1 atm (atmospheric pressure) of preferably 300 ° C or lower, more preferably 250 ° C or lower.

As long as the effects of the present invention are not impaired, a carboxylic acid may be contained in addition to the above amine. The carboxyl group in one molecule of the carboxylic acid has a relatively high polarity and easily causes an interaction by a hydrogen bond, but portions other than these functional groups have a relatively low polarity. Furthermore, carboxyl groups tend to exhibit acidic properties.

As the carboxylic acid, compounds having at least one carboxyl group can be widely used, and examples thereof include formic acid, oxalic acid, acetic acid, hexanoic acid, acrylic acid, octylic acid, and oleic acid. Some carboxyl groups of the carboxylic acid may form a salt with the metal ion. In addition, about the said metal ion, two or more types of metal ions may be contained.

The carboxylic acid may be a compound containing a functional group other than a carboxyl group, such as an amino group, a hydroxyl group, an alkoxy group, a carbonyl group, an ester group, and a mercapto group. In this case, the number of carboxyl groups is preferably equal to or more than the number of functional groups other than carboxyl groups. The carboxylic acids may be used alone or in combination of two or more. The carboxylic acid preferably has a boiling point at 1 atm (atmospheric pressure) of 300 ° C or lower, more preferably 250 ° C or lower. Also, amines and carboxylic acids form amide groups. Since the amide group also appropriately adsorbs on the surface of the silver fine particles, the organic component may contain an amide group.

The content of the organic component in the inorganic colloid in the conductive fine particle dispersion of the present invention is preferably 0.5 to 50% by mass. When the organic component content is 0.5% by mass or more, the storage stability of the obtained conductive paste tends to be improved, and when the content is 50% by mass or less, the conductivity of the conductive pattern tends to be good. . The more preferable content of the organic component is 1 to 30% by mass, and the more preferable content is 1.5 to 15% by mass.

When the amine and the carboxylic acid are used in combination, the composition ratio (weight) of the amine and the carboxylic acid can be arbitrarily selected in the range of 1/99 to 99/1. Preferably, the composition ratio between the amine and the carboxylic acid is from 20/80 to 98/2, and more preferably from 30/70 to 97/3. The amine or the carboxylic acid may be a plurality of types of amines or carboxylic acids. The surface of the silver fine particles is preferably coated with an alkoxyamine.

As a method for producing silver fine particles having the organic component adhered to the surface, for example, a first step of preparing a mixed solution of a silver compound capable of decomposing by reduction to produce silver, an amine, and a dispersant; A second step of reducing the silver compound in the mixed solution to produce silver fine particles having the amine attached to at least a part of the surface.

In the first step, it is preferable to add the amine in an amount of 2 mol or more per 1 mol of silver. By setting the addition amount of the amine to 2 mol or more per 1 mol of silver, an appropriate amount of the amine can be attached to the surface of the silver fine particles generated by reduction, and the silver fine particles can be excellently dispersed in various dispersion media. And low-temperature sinterability.

The composition of the mixed solution in the first step and the reduction conditions (for example, heating temperature and heating time) in the second step are adjusted so that the particle size of the obtained silver fine particles is in a nanometer size. Is preferred. The reason is that by setting the particle size of the silver fine particles to the nanometer size, the melting point is lowered and firing can be performed at a low temperature. The particle size of the obtained silver fine particles is more preferably 1 to 400 nm. Micron-sized particles may be included as needed. The method of extracting the silver fine particles from the colloid liquid containing the silver fine particles obtained in the second step is not particularly limited, and examples thereof include a method of washing the colloid liquid.

The colloid liquid obtained in the second step contains a dispersant and the like in addition to the silver fine particles, and the electrolyte concentration of the entire solution tends to be high. In the colloid liquid in such a state, silver fine particles are coagulated due to high conductivity and the like, and are likely to precipitate. Therefore, it is preferable to wash the colloid solution to remove excess electrolyte.

As a method of washing the colloid solution, for example, after removing the supernatant by leaving the prepared colloid solution for a certain period of time, adding pure water and stirring, and further leaving it for a certain period of time to remove the supernatant solution There is a method that is repeated several times. Other washing methods include, for example, a method of performing centrifugal separation instead of the above-mentioned standing, a method of desalting with an ultrafiltration device, an ion exchange device, and the like. Among them, a desalting method is preferable. The desalted liquid may be appropriately concentrated.

As the silver compound, various known silver compounds can be used, and for example, a silver salt or a hydrate of a silver salt can be used. Specific examples include silver salts such as silver nitrate, silver sulfate, silver chloride, silver oxide, silver acetate, silver oxalate, silver formate, silver nitrite, silver chlorate, and silver sulfide. These are not particularly limited as long as they can be reduced, and may be dissolved in an appropriate solvent or used while being dispersed in the solvent. These may be used alone or in combination of two or more. Among them, silver oxalate is preferred. Silver oxalate is the simplest silver dicarboxylate, and the silver oxalate amine complex synthesized using silver oxalate is reduced in temperature and in a short time. It is suitable. Furthermore, when silver oxalate is used, by-products are not generated at the time of synthesis, and only carbon dioxide derived from oxalate ions is emitted out of the system, so that there is little labor for purification after the synthesis.

As the dispersant, for example, a commercially available wet dispersant can be used. Commercially available wet dispersants include, for example, SOLSPERSE 11200, Solsperse 13940, Solsperse 16000, Solsperse 17000, Solsperse 18000, Solsperse 20000, Solsperse 24000, Solsperse 26000, Solsperse 27000, Solsperse 28000 (manufactured by Nippon Lubrizol Co.); DISPERBYK-102, 110, 111, 170, 190.194N, 2015, 2090, 2096 (manufactured by BYK Japan); EFKA-46, EFKA-47, EFKA-48, EFKA-49 (manufactured by EFKA Chemical); polymer 100, polymer 120, polymer 150, polymer 400, polymer 401, polymer 402, polymer 403, polymer 450 Polymer 451, Polymer 452, Polymer 453 (manufactured by EFKA Chemical); Azispar PB711, Azispar PA111, Azispar PB811, Azispar PW911 (manufactured by Ajinomoto Co.); Floren DOPA-15B, Floren DOPA-22, Floren DOPA-17, Floren TG- 730W, Floren G-700, Floren TG-720W (manufactured by Kyoeisha Chemical Industry Co., Ltd.) and the like. In addition, 610, 610S, 630, 651, 655, 750W, 755W, etc. of TEGO Dispers series of Evonik; DA-375, DA-1200 of Kusumoto Kasei's dispalon series may be used. From the viewpoint of low-temperature sinterability and dispersion stability, it is preferable to use DISPERBYK-102, Solsperse 11200, Solsperse 13940, Solsperse 16000, Solsperse 17000, Solsperse 18000, Solsperse 28000, or the like.

As a method of reducing the silver compound, a method of heating is preferable. The heating method is not particularly limited. As a method of reducing the silver compound by the heating, for example, heating a complex compound formed from a silver compound such as silver oxalate and an organic component such as an amine to form an oxalate ion or the like contained in the complex compound There is a method of aggregating atomic silver generated by decomposing a metal compound. By the above method, silver fine particles protected by a protective film of an organic component such as an amine can be produced.

As described above, in the metal amine complex decomposition method for producing silver fine particles coated with an amine by thermally decomposing the complex compound of the silver compound in the presence of the amine, the decomposition of the silver amine complex which is a single kind of molecule is performed. Since atomic silver is generated by the reaction, it is possible to uniformly generate atomic silver in the reaction system, which constitutes a reaction as compared with a case where silver atoms are generated by a reaction between a plurality of components. Nonuniformity of the reaction due to the fluctuation of the composition of the components is suppressed, which is particularly advantageous when a large amount of silver powder is produced on an industrial scale.

In addition, in the metal amine complex decomposition method, an amine molecule is coordinated to a generated silver atom, and the movement of the silver atom during aggregation is controlled by the action of the amine molecule coordinated to the silver atom. It is assumed that As a result, according to the metal amine complex decomposition method, extremely fine metal particles having a narrow particle size distribution can be produced.

Furthermore, a large number of amine molecules also have relatively weak coordination bonds on the surface of the silver fine particles to be produced, and these form a dense protective film on the surface of the silver fine particles, so that they have excellent storage stability. It becomes possible to produce organic-coated silver fine particles having a clean surface. Further, since the amine molecules forming the coating can be easily detached by heating or the like, it becomes possible to produce silver fine particles that can be sintered at a very low temperature.

The content of the silver fine particles in the conductive fine particle dispersion of the present invention is preferably 1 to 90% by mass, more preferably 10 to 80% by mass, further preferably 10 to 70% by mass, and still more preferably 20 to 60% by mass. % By mass. When the content of the silver fine particles is 1% by mass or more, an amount of silver fine particles capable of realizing a conductive film having sufficient conductivity is secured in the conductive fine particle dispersion. When the content of the silver fine particles is 90% by mass or less, the conductive fine particle dispersion can be prevented from drying, and thus can be stably stored.

(Compound having a nitrogen-containing heterocycle)
The conductive fine particle dispersion of the present invention contains a compound having a nitrogen-containing heterocycle, thereby improving the adhesion without increasing the resistance even when the sintering temperature condition is low (for example, 100 ° C. or less). be able to. Therefore, a conductive layer (hereinafter, also referred to as a conductive coating) having a low resistance value and adhesion can be formed even on a resin having relatively low heat resistance. This is because a heterocyclic compound having two or more nitrogen atoms is considered to have good affinity with a resin, has excellent heat resistance, and has a high thermal conductivity in a conductive layer formed by sintering a conductive fine particle dispersion. It is considered that it is difficult to disassemble. That is, it is considered that the compound having a nitrogen-containing heterocycle remains in the conductive layer even after the conductive fine particle dispersion of the present invention is fired, and this is considered to provide adhesion to the resin.

In addition, since the compound having a nitrogen-containing heterocyclic ring has at least one alkoxy group and / or alkoxysilyl group, it undergoes an alcoholysis reaction under heating, and is easily chemically bonded to a functional group on the surface of silver fine particles. It is considered something. Therefore, since the conductive fine particle dispersion of the present invention contains a compound having a specific nitrogen-containing heterocycle, it is considered that the adhesion between the silver fine particles and the resin can be improved without increasing the resistance value. .

Further, the compound having a nitrogen-containing hetero ring preferably has at least one alkoxy group and / or alkoxy silyl group at at least one of a substituent bonded to the hetero ring and a terminal of the substituent.

The compound having a nitrogen-containing hetero ring used in the conductive fine particle dispersion of the present invention has two or more nitrogen atoms in at least one hetero ring, and has one or more alkoxy groups and / or alkoxysilyl groups in the molecule. There is no particular limitation as long as it has at least one. Specifically, for example, 2,4-diamino-6- {2- [3- (trimethoxysilyl) propylthio] ethyl} -1,3,5-triazine, 1- {2- [4,6-diamino -(1,3,5) triazin-2-yl] -ethyl} -3- [3- (trimethoxysilyl) propyl] urea, 1- {2- [4,6-diamino- (1,3,5 ) Triazin-2-yl] -ethyl {-3- [3- (triethoxysilyl) propyl] urea, 2,4-diamino-6- {2- [2- (methoxycarbonyl) ethylthio] ethyl} -1, 3,5 triazine, 2,4-diamino-6- {2- [2- (ethoxycarbonyl) ethylthio] ethyl} -1,3,5 triazine, 2,4-diamino-6- {2- [2- ( Propyloxycarbonyl) ethylthio] ethyl} -1,3 5-triazine, N- [3- (trimethoxysilyl) propyl] -5-amino-3- [3- (trimethoxysilyl) propylthio] -1H-1,2,4-triazole-1-carboxamide, 2-chloro -4,6-dimethoxy-1,3,5-triazine, 1- [2- (2-methylimidazol-1-yl) ethyl] -3- [3- (trimethoxysilyl) propyl] urea, 1- [ 3- (2-ethyl-4-methylimidazol-1-yl) propyl] -3- [3- (trimethoxysilyl) propyl] urea, 2,2'-dithiobis {1- [3- (trimethoxysilyl) Propylcarbamoyl] -1H-imidazole} and the like.

The compound having a nitrogen-containing hetero ring is preferably contained in an amount of 0.1 to 9.1 parts by mass based on 100 parts by mass of the silver fine particles. When the content of the compound having a nitrogen-containing hetero ring is lower than 0.1 part by mass with respect to 100 parts by mass of the silver fine particles, the effect of improving adhesion may not be obtained, and 9.1 parts by mass may be obtained. If the number is larger than the number of parts, the resistance value may increase.

(Dispersion medium)
The dispersion medium contained in the conductive fine particle dispersion of the present invention is for dispersing silver fine particles and contains an organic solvent. Aggregation of silver fine particles can be suppressed by using an organic solvent as a dispersion medium. In addition, since it generally has a high boiling point and is difficult to dry, it can be easily adjusted to a viscosity that can be ejected by inkjet printing, and the applicability of the conductive fine particle dispersion (for example, the ejectability from an inkjet head) can be improved.

Various organic solvents can be used as the dispersion medium, and for example, alcohols can be used. The alcohol may be a polyhydric alcohol. Examples of the alcohol include methanol, ethanol, propanol, isopropanol, isobutanol, 1-butanol, isoamyl alcohol, furfuryl alcohol, cresol, ethylene glycol, glycerin, phenol, p-cresol, tert-butanol, 1-pentanol, 2- Pentanol, 4-methyl-2-pentanol, 3-methyl-1-pentanol, 3-methyl-2-pentanol, 2-butanol, 1-hexanol, 2-hexanol, 2-hexyloxyethanol, cyclohexanemethanol , 1-methoxy-2-propanol, 2-butoxyethanol, 1-octanol, 1-nonanol, 1-decanol, 1,3-propanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4 Pentanediol, 2-ethyl-1,3-hexanediol, texanol, terpineol (including α, β, γ isomers or any mixture thereof), terpene alcohols such as dihydroterpineol (monoterpene alcohols, etc.), dihydro Terpineol and the like can be exemplified. In the present invention, a compound having at least one hydroxyl group and having 1 to 10 carbon atoms is dispersed from the viewpoint of good compatibility with a compound having a specific nitrogen-containing heterocycle and excellent dispersibility of the silver fine particles. It is preferably used as a medium.

In addition, as a dispersion medium used in the present invention, in addition to the above-described compound having at least one hydroxyl group and having 1 to 10 carbon atoms, other solvents such as esters and ketones can be arbitrarily mixed and used. . Other solvents include 2-pentanone, 2-heptanone, 2- (2-ethoxyethoxy) ethyl acetate, 2-butoxyethyl acetate, 2- (2-butoxyethoxy) ethyl acetate, 2-methoxyethyl acetate, Examples thereof include 2-butoxyethyl acetate, 2-methoxy-1-methylethyl acetate, dihydroterpinyl acetate, methyl ethyl ketone, toluene, and tetralin.

The content of the above-mentioned dispersion medium with respect to the whole conductive fine particle dispersion of the present invention can be appropriately adjusted depending on the application method and application of the conductive fine particle dispersion.
When the viscosity is adjusted to be low as in the case of the inkjet ink, the conductive fine particle dispersion (silver ink) preferably contains the dispersion medium in an amount of about 40 to 80% by mass. When the viscosity is adjusted to be high as in the case of a silver paste, the conductive fine particle dispersion (silver paste) preferably contains the dispersion medium in an amount of about 10 to 30% by mass.

The conductive fine particle dispersion of the present invention may further contain a surfactant in addition to the above-described dispersion medium. In a multicomponent solvent-based inorganic colloidal dispersion, roughness of the coating surface and unevenness of solid content easily occur due to a difference in evaporation rate during drying. By adding a surfactant to the conductive fine particle dispersion of the present invention, these disadvantages can be suppressed and a uniform conductive film can be formed.

The surfactant is not particularly limited, and an anionic surfactant, a cationic surfactant, a nonionic surfactant and the like can be used. Specific examples include an alkylbenzene sulfonate and a quaternary ammonium salt. From the viewpoint that the effect can be obtained with a small amount of addition, a fluorine-based surfactant is more preferable.

The method for producing the conductive fine particle dispersion of the present invention is not particularly limited, and examples thereof include the following method. First, a colloid liquid containing silver fine particles having an organic component attached to the surface as a solid content is prepared. Next, by mixing the obtained colloid liquid, a dispersion medium, a compound having a nitrogen-containing heterocyclic ring, and optionally the above-described optional components, the conductive fine particle dispersion of the present invention is obtained. .

The conductive fine particle dispersion of the present invention can be applied to a substrate and then fired to form a conductive film. The conductive film can be used as an electronic circuit substrate (for example, a semiconductor integrated circuit), a printed wiring board, a wiring of a thin film transistor substrate, an electrode, and the like.

As the material of the base material, in addition to various ink-absorbing materials (for example, paper, cloth, porous ceramics, etc.), non-ink-absorbing materials may be used, and those having excellent heat resistance are preferably used. Can be Examples of the non-ink-absorbing material include polycarbonate (PC), ABS, AS, polypropylene (PP), polyethylene (PE), polyamide (PA), polyacetal (POM), polybutylene terephthalate (PBT), and polyethylene terephthalate (PET). ), Polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polystyrene (PS), polymethylmethacrylate (PMMA), polyphenyleneether (PPE), polysulfone (PSF), polyethersulfone (PES), polyamideimide ( PAI), polyetherimide (PEI), polyimide (PI), polyvinyl chloride (PVC), and other resins (engineering plastics, super engineering plastics). Here, the non-ink absorbing material means a material having no structure having an ink receiving function. A surface layer (primer layer) may be provided on the surface of the base material for the purpose of further increasing the adhesion to the conductive film, or a surface treatment such as a hydrophilic treatment may be performed. Examples of the surface treatment method include a dry treatment such as a corona treatment, a plasma treatment, a UV treatment, and an electron beam treatment. The conductive fine particle dispersion of the present invention can be suitably used for a resin having low heat resistance because the dispersion of the conductive fine particles can be reduced in resistance and the adhesiveness can be improved even at a low sintering temperature condition. In this specification, a resin having a heat resistance of 100 ° C. or lower is a resin having low heat resistance.

The application is a concept including a case where the conductive fine particle dispersion is applied in a plane and a case where the conductive fine particle dispersion is applied (drawn) in a linear manner. The shape of the coating film (conductive film) may be planar, linear, or a combination thereof. Further, the coating film (conductive film) may be a continuous pattern, a discontinuous pattern, or a combination of these.

The method for applying the conductive fine particle dispersion of the present invention is not particularly limited, and examples thereof include an inkjet printing method, a screen printing method, a letterpress printing method, an intaglio printing method, a reverse printing method, a microcontact printing method, a dipping method, and a spray method. , A bar coating method, a spin coating method, a dispenser method, a casting method, a flexo method, a gravure method, a syringe method, a coating method using a brush, and the like. Among them, the conductive fine particle dispersion of the present invention is preferably an ink for inkjet printing.

When the above-mentioned coating film is baked, the bonding between the silver fine particles contained in the coating film is increased and the coating is sintered. The sintering temperature of the coating film is in the range of normal sintering temperature in the range of 50 to 300 ° C., but the sintering temperature condition is not necessarily limited, and is a temperature at which a conductive film can be formed on the surface of the base material. And a temperature at which the dispersion medium of the conductive fine particle dispersion can be evaporated (a part may remain, but it is preferable that all of them are removed) as long as the effects of the present invention are not impaired. Is preferred. The baking time of the coating film is not particularly limited, and may be appropriately set according to the sintering temperature. When the conductive fine particle dispersion of the present invention is used, a conductive sintered body can be formed even on a low heat-resistant base material. In this case, the sintering temperature is preferably 50 to 100 ° C., and even under such a low sintering temperature condition, sufficient conductivity and adhesion can be exhibited. In addition, as a low heat resistant substrate, for example, a resin having a heat resistant temperature of 100 ° C. or less can be used.

The method for baking the coating film is not particularly limited, and examples thereof include a method using a conventionally known gear oven or the like.

The thickness of the conductive film is, for example, 0.1 to 5 μm, and preferably 0.2 to 3 μm. The volume resistivity of the conductive film is preferably 1.0 × 10 ⁻⁴ Ω · cm or less, more preferably 5.0 × 10 ⁻⁵ Ω · cm or less, and still more preferably 1.0 × 10 ⁻⁵ Ω · cm. cm or less.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to only these Examples.

<Example 1>
8.0 g of 3-methoxypropylamine and 0.2 g of DISPERBYK-102 (BIC Chemie Japan KK) as a dispersing agent were mixed and stirred well with a magnetic stirrer to produce an amine mixture. Then, while stirring, 3.0 g of silver oxalate was added. After the addition of silver oxalate, the stirring was continued at room temperature to change the silver oxalate into a viscous white substance, and the stirring was stopped when it was recognized that the change was apparently completed (first step). ).

The obtained mixture was transferred to an oil bath and heated and stirred at 110 ° C. Immediately after the start of stirring, a reaction involving the generation of carbon dioxide starts, and thereafter, stirring is performed until the generation of carbon dioxide is completed, whereby a suspension in which silver fine particles are suspended in the amine mixture is obtained. 2 steps).

In order to replace the dispersion medium of the suspension, 10 mL of a mixed solvent of methanol and water was added and stirred, and then silver fine particles were precipitated and separated by centrifugation. Next, 10 mL of a mixed solvent of methanol and water was added to the separated silver fine particles, and the mixture was stirred and centrifuged to precipitate the silver fine particles to obtain a slurry containing silver fine particles.

Compound (2,4-diamino-6- {2- [3- (trimethoxysilyl)) having a nitrogen-containing heterocycle in 44.5 parts by mass of cyclohexane methanol as a dispersion medium based on 55 parts by mass of the obtained slurry. 45 parts by mass of a mixed solution obtained by dissolving 0.5 parts by mass of propylthio] ethyl} -1,3,5-triazine was added and dispersed to obtain a conductive fine particle dispersion 1.

<Example 2>
1.7 g of butylamine, 3.5 g of hexylamine, and 0.2 g of DISPERMYK-102 (BIC Chemie Japan Co., Ltd.) as a dispersing agent are mixed and thoroughly stirred with a magnetic stirrer to obtain an amine mixture. Generated. Then, while stirring, 3.0 g of silver oxalate was added. After the addition of silver oxalate, the stirring was continued at room temperature to change the silver oxalate into a viscous white substance, and the stirring was stopped when it was recognized that the change was apparently completed (first step). ).

The obtained mixture was transferred to an oil bath and heated and stirred at 110 ° C. Immediately after the start of stirring, a reaction involving the generation of carbon dioxide starts, and thereafter, stirring is performed until the generation of carbon dioxide is completed, whereby a suspension in which silver fine particles are suspended in the amine mixture is obtained. 2 steps).

In order to replace the dispersion medium of the suspension, 10 mL of a mixed solvent of methanol and water was added and stirred, and then silver fine particles were precipitated and separated by centrifugation. Next, 10 mL of a mixed solvent of methanol and water was added to the separated silver fine particles, and the mixture was stirred and centrifuged to precipitate the silver fine particles to obtain a slurry containing silver fine particles.

Compound (2,4-diamino-6- {2- [3- (trimethoxysilyl)) having a nitrogen-containing heterocycle in 44.5 parts by mass of cyclohexane methanol as a dispersion medium based on 55 parts by mass of the obtained slurry. 45 parts by mass of a mixed solution obtained by dissolving 0.5 parts by mass of propylthio] ethyl} -1,3,5-triazine were added and dispersed to obtain a conductive fine particle dispersion 2.

<Example 3>
The compound having a nitrogen-containing heterocycle is converted into 1- {2- [4,6-diamino- (1,3,5) triazin-2-yl] -ethyl} -3- [3- (trimethoxysilyl) propyl]. A conductive fine particle dispersion 3 was obtained in the same manner as in Example 1 except that urea was used.

<Example 4>
A compound having a nitrogen-containing heterocycle is converted to 1- {2- [4,6-diamino- (1,3,5) triazin-2-yl] -ethyl} -3- [3- (triethoxysilyl) propyl]. A conductive fine particle dispersion 4 was obtained in the same manner as in Example 1 except that urea was used.

<Example 5>
A compound having a nitrogen-containing heterocycle (2,4-diamino-6- {2- [2- (methoxycarbonyl) ethylthio] ethyl} is added to 55 parts by mass of the slurry and 44.95 parts by mass of cyclohexane methanol as a dispersion medium. A conductive fine particle dispersion 5 was obtained in the same manner as in Example 1, except that 45 parts by mass of a mixed solution obtained by dissolving 0.05 parts by mass of -1,3,5-triazine was added and dispersed.

<Example 6>
Conduction was carried out in the same manner as in Example 1 except that the compound having a nitrogen-containing heterocycle was changed to 2,4 diamino-6- {2- [2- (methoxycarbonyl) ethylthio] ethyl-1,3,5-triazine. Thus, an aqueous fine particle dispersion 6 was obtained.

<Example 7>
A compound having a nitrogen-containing heterocycle (2,4-diamino-6- {2- [2- (methoxycarbonyl) ethylthio] ethyl} -1 is added to 40 parts by mass of cyclohexane methanol as a dispersion medium with respect to 55 parts by mass of the slurry. Conductive fine particle dispersion 7 was obtained in the same manner as in Example 1, except that 45 parts by mass of a mixed solution of 5 parts by mass of 2,3,5-triazine was added and dispersed.

<Example 8>
Example 1 was repeated except that the compound having a nitrogen-containing heterocycle was changed to 2,4-diamino-6- {2- [2- (ethoxycarbonyl) ethylthio] ethyl} -1,3,5-triazine. Thus, a conductive fine particle dispersion 8 was obtained.

<Example 9>
Same as Example 1 except that the compound having a nitrogen-containing heterocycle was changed to 2,4-diamino-6- {2- [2- (propyloxycarbonyl) ethylthio] ethyl} -1,3,5-triazine Thus, a conductive fine particle dispersion 9 was obtained.

<Example 10>
Compounds having a nitrogen-containing heterocycle were converted to N- [3- (trimethoxysilyl) propyl] -5-amino-3- [3- (trimethoxysilyl) propylthio] -1H-1,2,4-triazole-1- A conductive fine particle dispersion 10 was obtained in the same manner as in Example 1 except that the carboxamide was changed.

<Example 11>
A conductive fine particle dispersion 11 was obtained in the same manner as in Example 1, except that the compound having a nitrogen-containing heterocycle was changed to 2-chloro-4,6-dimethoxy-1,3,5-triazine.

<Example 12>
Example 1 was repeated except that the compound having a nitrogen-containing heterocycle was changed to 1- [2- (2-methylimidazol-1-yl) ethyl] -3- [3- (trimethoxysilyl) propyl] urea. Thus, a conductive fine particle dispersion 12 was obtained.

<Example 13>
Except that the compound having a nitrogen-containing heterocycle was changed to 1- [3- (2-ethyl-4-methylimidazol-1-yl) propyl] -3- [3- (trimethoxysilyl) propyl] urea. A conductive fine particle dispersion 13 was obtained in the same manner as in Example 1.

<Example 14>
Dispersion of conductive fine particles was performed in the same manner as in Example 1 except that the compound having a nitrogen-containing heterocycle was changed to 2,2′-dithiobis {1- [3- (trimethoxysilyl) propylcarbamoyl] -1H-imidazole}. Obtained body 14.

<Comparative Example 1>
A conductive fine particle dispersion 15 was obtained in the same manner as in Example 1, except that 2-methoxyethylamine was used instead of the compound having a nitrogen-containing heterocycle.

<Comparative Example 2>
A conductive fine particle dispersion 16 was obtained in the same manner as in Example 1, except that the compound having a nitrogen-containing heterocycle was changed to 4-methoxypyridine.

<Comparative Example 3>
A conductive fine particle dispersion 17 was obtained in the same manner as in Example 1, except that the compound having a nitrogen-containing heterocycle was changed to 2-amino-1H-imidazole.

<Comparative Example 4>
A conductive fine particle dispersion 18 was obtained in the same manner as in Example 1, except that the compound having a nitrogen-containing heterocycle was changed to 2-amino-1,3,5-triazine.

The compounds having a nitrogen-containing heterocycle used in Examples and Comparative Examples and the compounds used in place of them are shown in Table 1 below.

[Evaluation test]
The following physical property evaluations were performed using the conductive fine particle dispersions produced in Examples and Comparative Examples.

(1) The dispersible conductive fine particle dispersion was allowed to stand in a container and allowed to stand at room temperature for one day, and then the presence or absence of a precipitate and the state of the supernatant were visually observed. The dispersibility of the conductive fine particle dispersion was evaluated according to the following criteria.
〇: Almost no sediment was observed under the container.
Δ: A small amount of sediment was observed under the container.
X: There was a clear concentration difference between the upper and lower portions of the container, and sediment was clearly observed.

(2) Dilutable A sample obtained by diluting the conductive fine particle dispersion 100-fold with a dispersion medium (cyclohexanemethanol) was allowed to stand at room temperature for 7 days, and then the dispersibility was visually checked. The dilutability of the conductive fine particle dispersion was evaluated according to the following criteria.
〇: No aggregation or silver mirror was observed, and silver fine particles were dispersed.
Δ: Aggregation and silver mirror were observed in part.
×: Aggregation or precipitation occurred.
The silver mirror refers to a state in which most of the particles are dispersed, but some of the particles adhere to the wall surface of the sample tube, causing reflection such as luster.The precipitate is formed at the bottom of the sample tube. Is settled, and liquid and particles are separated.

(3) A conductive fine particle dispersion was applied on a slide glass having a volume resistance of 25 mm × 25 mm by a spin coating method under the conditions of a rotation speed of 2,000 rpm and a rotation time of 20 seconds, and then heated at 80 ° C. for 1 hour in a gear oven. By heating and baking under the conditions, the conductive fine particle dispersion was sintered to form a conductive film. The surface resistance of this conductive film was measured with a resistivity meter “Loresta GP MCP-T610” manufactured by Mitsubishi Chemical Analytech Co., Ltd. to obtain the surface resistance. Next, the thickness of the conductive film was measured with a laser microscope “VK-X150” manufactured by Keyence Corporation. Based on the following formula, the volume resistance was calculated from the surface resistance and the thickness of the conductive film, and evaluated according to the following criteria.
Formula: Volume resistance (Ω · cm) = Surface resistance (Ω / □) × Thickness of conductive film (μm) / 10000
A: The volume resistance value was 10 μΩ · cm or less.
〇: Volume resistance value was 20 μΩ · cm or less.
Δ: Volume resistance value was 100 μΩ · cm or less.
X: Volume resistance value was larger than 100 μΩ · cm.

(4) Adhesion test A conductive fine particle dispersion was applied on various substrates of 25 mm x 25 mm by a spin coating method under the conditions of a rotation speed of 2000 rpm and a rotation time of 20 seconds. By heating and baking under the conditions, the conductive fine particle dispersion was sintered to form a conductive film. Adhesion of the conductive film to various substrates was determined by forming 25 squares of 1 mm width on the conductive film with a cutter in accordance with ASTM D3359-09, and applying tape (CT-24 manufactured by Nichiban Co., Ltd.) ) Was strongly pressed, and the state in which the tape was peeled off at an angle of 45 to 60 ° was visually observed and evaluated according to the following criteria.
5B: The percentage of the stripped grid was 0%.
4B: The percentage of the stripped grid was 5% or less.
3B: The percentage of the stripped grid was 15% or less.
2B: The percentage of the stripped grid was more than 15% and 30% or less.
1B: The ratio of the peeled grating was more than 35% and 65% or less.
0B: The percentage of the stripped grid was greater than 65%.
In addition, three types of ABS, PET, and polycarbonate were evaluated as various substrates.

Further, the ABS was subjected to an adhesion test after the high humidity test. This is because the conductive film formed in the same manner as above is put into a high-temperature and high-humidity layer at 60 ° C. and 80 RH%, and the adhesion between the conductive film and the ABS resin after standing for 4 hours is the same as above. Was evaluated according to the same criteria in the procedure described above.

The comprehensive evaluation of the adhesion was evaluated as “Δ” for all the substrates having a rating of 4B or more, “Δ” for those having a rating of 3B or more, and “×” for any one of the substrates having a rating of 2B or less. "

Tables 2 and 3 below show the compositions of the conductive fine particle dispersions and the results of the evaluation tests for the examples and comparative examples.

Examples 1 to 14 were superior to Comparative Examples 1 to 4 in adhesion and low resistance value. Therefore, the effect of including a compound having a nitrogen-containing heterocycle having two or more nitrogen atoms in at least one heterocycle and having one or more alkoxy groups and / or alkoxysilyl groups in the molecule has been confirmed. Was done. In addition, when comparing Examples 1 and 2, although adhesion and low resistance value are all good, Example 1 using alkoxyamine as an organic component covering silver fine particles has better adhesion and lower resistance. It was excellent in any of the resistance values. Regarding the adhesion, it is considered that the reactivity between the alkoxyamine adhering to the surface of the silver fine particles and the alkoxy group in the compound having a nitrogen-containing heterocycle was increased, and thus the adhesion was improved. According to the results of Example 5, the adhesion was improved when the compound having a nitrogen-containing heterocycle was contained at 0.05% by weight, but the adhesion to the resin after the high humidity test was reduced. I was According to the results of Example 7, when the compound having a nitrogen-containing heterocycle was contained at 5.0% by weight, the adhesion to any resin was improved, but a slight increase in volume resistance was confirmed. Was.

In Comparative Example 1, 2-methoxyethylamine having an alkoxy group was used in place of the compound having a nitrogen-containing heterocycle, but no adhesion was obtained. This is because, compared with a compound having a specific nitrogen-containing heterocycle, the thermal decomposition temperature of 2-methoxyethylamine is lower, it is less likely to remain in the conductive coating after firing, and the affinity with organic substances is low, so that the adhesion is low. It is considered that it did not express. In Comparative Example 2, a compound having an alkoxy group but having a nitrogen-containing heterocycle having one nitrogen atom in the heterocycle was used, but no adhesion was obtained. This also has a lower thermal decomposition temperature than a compound having a specific heterocycle, hardly remains 4-methoxypyridine in the conductive film after firing, and has low affinity with organic substances, thereby exhibiting adhesion. Probably not. In Comparative Examples 3 and 4, a compound having a nitrogen-containing heterocycle having two or more nitrogen atoms in the heterocycle was used. However, since none of the compounds had an alkoxy group, no adhesion was exhibited.

In Examples 1 to 14, good results were obtained in any of the examples in terms of dispersibility, dilutability, volume resistance value, and adhesion.

Claims (5)

Silver fine particles, a compound having a nitrogen-containing heterocycle, and a dispersion medium,
The compound having a nitrogen-containing hetero ring has two or more nitrogen atoms in at least one hetero ring, and has one or more alkoxy groups and / or alkoxy silyl groups in the molecule. Fine particle dispersion. The conductive fine particle dispersion according to claim 1, wherein the silver fine particles have an alkoxyamine adhered to at least a part of a surface thereof. The compound having a nitrogen-containing hetero ring has at least one of an alkoxy group and / or an alkoxysilyl group at at least one of a substituent bonded to the hetero ring and a terminal of the substituent. Item 3. The conductive fine particle dispersion according to Item 1 or 2. The conductive compound according to any one of claims 1 to 3, wherein the compound having a nitrogen-containing heterocycle is contained in an amount of 0.1 to 9.1 parts by mass with respect to 100 parts by mass of the silver fine particles. Fine particle dispersion. The conductive fine particle dispersion according to any one of claims 1 to 4, wherein the dispersion medium is a compound having at least one hydroxy group and having 1 to 10 carbon atoms.