JP6822825B2 - Conductive ink - Google Patents

Description

The present invention relates to a novel conductive ink, a method of forming an electronic component using the conductive ink, and an electronic device including the electronic component made of a sintered body of the conductive ink.

Conventionally, electronic parts such as circuits, wirings, and electrodes have been manufactured by an etching method. However, there is a problem that the process is complicated and the cost is high. Therefore, as an alternative method, a method of directly forming by printing is being studied.

Among metals, bulk silver has a high melting point of 962 ° C., but nano-sized silver particles (silver nanoparticles) fuse with each other at a temperature of about 100 ° C., so if this is used, heat resistance It is possible to form an electronic component having excellent conductivity on a general-purpose plastic substrate having a low temperature. However, the problem is that nano-sized metal particles tend to aggregate.

Patent Document 1 describes that aggregation is suppressed by coating the surface of silver nanoparticles with amines, and the surface-modified silver nanoparticles are subjected to hydrocarbons such as n-octane, decalin, and tetradecane. The conductive ink obtained by dispersing 50% by weight in a dispersion medium containing 50% by weight and 50 to 90% by weight of alcohol such as n-butanol and cyclohexanemethanol has excellent dispersion stability of silver nanoparticles, and direct electrons are obtained by a printing method. It is described that it can be suitably used for the purpose of forming parts, and that a sintered body having excellent conductivity can be obtained by sintering the conductive ink.

International Publication No. 2014/021270

However, since the sintered body obtained by using the conductive ink described in Patent Document 1 has low adhesion to the substrate, for example, in order to prevent damage to the sintered body during transportation, it may be applied to the surface of the sintered body. When the protective film is attached, there is a problem that the sintered body is also peeled off from the substrate when the protective film is peeled off.

When a ceramic substrate is used as the substrate, a certain degree of adhesion can be obtained between the substrate and the sintered body due to the anchor effect caused by the unevenness existing on the substrate surface, but a substrate having excellent surface smoothness such as a glass substrate can be obtained. In the case of, the problem was that the anchor effect could not be obtained and the sintered body was easily peeled off from the substrate. Further, it is conceivable to apply a surface treatment to the substrate to improve the adhesion to the sintered body, but there is a problem that the number of steps increases and the cost increases.

Therefore, the conductive ink containing metal nanoparticles is required to have the following characteristics 1 to 4.
1. 1. 2. Have a viscosity suitable for coating. 2. It contains metal nanoparticles in a highly dispersed state and has a uniform composition. 3. By subjecting to sintering, a sintered body with excellent conductivity can be obtained. By subjecting to sintering, a sintered body with excellent substrate adhesion can be obtained.

As a method for improving the adhesion of the sintered body to the substrate, for example, an adhesive-imparting material such as a rubber-like elastic body, a terpene resin, a rosin resin, a petroleum resin, or a silane coupling agent can be added. Conceivable. However, when these are added to the conductive ink, the coatability may be lowered due to the thickening, or the conductivity of the obtained sintered body may be lowered.
In addition, a method of adding a compound having a hydroxyl group, a carbonyl group, an ether bond, etc. to improve the adhesion of the sintered body to the substrate by an interaction such as a hydrogen bond can be considered, but these are added to the conductive ink. Then, the metal nanoparticles tend to aggregate, and it becomes difficult to maintain the composition uniformly.
That is, at present, no method has been found for imparting the characteristics (4) (adhesion to the substrate) to the conductive ink without impairing the above-mentioned characteristics 1 to 3.

Therefore, an object of the present invention is to provide a conductive ink which is excellent in coatability and dispersibility of metal nanoparticles, and which forms a sintered body which is excellent in substrate adhesion and excellent in conductivity by sintering. is there.
Another object of the present invention is to provide a method for forming an electronic component using the conductive ink.
Another object of the present invention is to provide an electronic device including an electronic component made of a sintered body of the conductive ink.

As a result of diligent studies to solve the above problems, the present inventor has found that a conductive ink obtained by dispersing metal nanoparticles whose surface is coated with an organic protective agent in a specific dispersion medium is high in quality without agglomeration of the metal nanoparticles. To be able to maintain a dispersed state stably for a long period of time, a specific amount of polyfunctional (meth) acrylate and a thermal radical polymerization initiator are added to the conductive ink, and heat treatment is performed after application to perform the polyfunctional (meth) acrylate. It has been found that by forming a crosslinked structure in the acrylate, excellent substrate adhesion can be imparted without lowering the coatability and without lowering the conductivity of the obtained sintered body. The present invention has been completed based on these findings.

In the present specification, the “nanoparticle” means a particle having a primary particle size (average primary particle diameter) of less than 1000 nm. The particle size is determined by the dynamic light scattering method. The boiling point in the present specification is a value under normal pressure (760 mmHg).

That is, the present invention contains the following components (A), (B), (C), and (D), and the component (B) is 20 to 100 parts by weight, (C) with respect to 100 parts by weight of the component (A). ) Is contained in an amount of 0.1 to 4 parts by weight based on 100 parts by weight of the component (A).
Component (A) Component: Surface-modified metal nanoparticles having a structure in which the surface of the metal nanoparticles is coated with an organic protective agent (B) Component: Dispersion containing alcohol (b-1) and hydrocarbon (b-2) Medium (C) component: Polyfunctional (meth) acrylate (D) component having a molecular weight of 300 or more: Thermal radical polymerization initiator

The present invention also comprises a compound in which the organic protective agent constituting the component (A) has at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an amino group, a sulfo group, and a thiol group. Provided is the above-mentioned conductive ink.

In the present invention, the organic protective agent constituting the component (A) has at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an amino group, a sulfo group, and a thiol group. The above-mentioned conductive ink, which is a compound of the number 4 to 18, is provided.

The present invention also provides the conductive ink having a (meth) acryloyl equivalent (g / eq) of a polyfunctional (meth) acrylate of 250 or more and less than 2500.

The present invention also provides the conductive ink in which the polyfunctional (meth) acrylate is a urethane (meth) acrylate.

The present invention also provides the conductive ink in which the thermal radical polymerization initiator is an organic peroxide.

The present invention also provides the conductive ink in which the alcohol (b-1) is an alicyclic secondary alcohol and / or an alicyclic tertiary alcohol.

The present invention also relates to the conductive ink having a viscosity (at 25 ° C. and a shear rate of 10 (1 / s)) of 1 to 100 mPa · s.

The present invention also provides the conductive ink in which the metal nanoparticles constituting the component (A) are silver nanoparticles.

The present invention also provides the conductive ink used for inkjet printing, gravure printing, or flexographic printing.

The present invention also provides a method for manufacturing an electronic device, which comprises a step of applying the conductive ink on a substrate by an inkjet printing method, a gravure printing method, or a flexographic printing method, and a step of sintering. ..

The present invention also provides an electronic device provided with the above-mentioned sintered body of the conductive ink on a substrate.

The conductive ink of the present invention has a low viscosity and is excellent in coatability. Therefore, for example, when applying using the inkjet printing method, the conductive ink adheres to the nozzle opening and causes flight bending (injection at an angle different from the set injection angle), or the nozzle opening is clogged. It is possible to print with high accuracy without making it impossible to inject. Further, the conductive ink of the present invention can be applied to the surface of a base material and then sintered (even for low-temperature sintering) to cover the base material (particularly, to a smooth substrate such as a glass substrate). ) Form a sintered body with excellent adhesion. Therefore, even if a protective film is attached to the surface of the sintered body for the purpose of preventing damage, for example, the sintered body will not be peeled off together when the protective film is peeled off. In addition, the sintered body has excellent conductivity. Therefore, the conductive ink of the present invention can be suitably used for manufacturing electronic components on a smooth substrate.

[Conductive ink]
The conductive ink of the present invention contains the following components (A), (B), (C), and (D), and the component (B) is 20 to 100 parts by weight with respect to 100 parts by weight of the component (A). The component (C) is contained in an amount of 0.1 to 4 parts by weight based on 100 parts by weight of the component (A).
Component (A) Component: Surface-modified metal nanoparticles having a structure in which the surface of the metal nanoparticles is coated with an organic protective agent (B) Component: Dispersion containing alcohol (b-1) and hydrocarbon (b-2) Medium (C) component: Polyfunctional (meth) acrylate (D) component having a molecular weight of 300 or more: Thermal radical polymerization initiator

(Surface-modified metal nanoparticles (A))
The surface-modified metal nanoparticles (A) in the present invention have a structure in which the surface of the metal nanoparticles is coated with an organic protective agent. Therefore, in the surface-modified metal nanoparticles (A) in the present invention, the spacing between the metal nanoparticles is secured and aggregation is suppressed. That is, the surface-modified metal nanoparticles (A) in the present invention are excellent in dispersibility.

The surface-modified metal nanoparticles (A) are a metal nanoparticle portion and a surface-modified portion that covers the metal nanoparticles (that is, a portion that is coated with the metal nanoparticles and is formed by an organic protective agent). The proportion of the surface-modified portion is, for example, about 1 to 20% by weight (preferably 1 to 10% by weight) of the weight of the metal nanoparticle portion. The weight of each of the metal nanoparticles and the surface-modified portion of the surface-modified metal nanoparticles can be obtained from, for example, the thermogravimetric analysis of the surface-modified metal nanoparticles and the weight loss rate in a specific temperature range.

The average primary particle diameter of the metal nanoparticles portion of the surface-modified metal nanoparticles (A) is, for example, 0.5 to 100 nm, preferably 0.5 to 80 nm, more preferably 1 to 70 nm, and further preferably 1 to 60 nm. Is.

The metal constituting the metal nanoparticles portion of the surface-modified metal nanoparticles (A) may be any metal having conductivity, for example, gold, silver, copper, nickel, aluminum, rhodium, cobalt, ruthenium and the like. Can be mentioned. Among the metal nanoparticles in the present invention, silver nanoparticles are capable of forming electronic components having excellent conductivity even on a general-purpose plastic substrate having low heat resistance by fusing to each other at a temperature of about 100 ° C. Particles are preferred. Therefore, the surface-modified metal nanoparticles in the present invention are preferably surface-modified silver nanoparticles, and the conductive ink of the present invention is preferably silver ink.

The organic protective agent constituting the surface-modified portion of the surface-modified metal nanoparticles (A) is at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an amino group, a sulfo group, and a thiol group. A compound having at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an amino group, a sulfo group, and a thiol group is preferable, and a compound having 4 to 18 carbon atoms is most preferable. Is a compound having an amino group, and particularly preferably a compound having an amino group and having 4 to 18 carbon atoms (that is, an amine having 4 to 18 carbon atoms).

As the surface-modified metal nanoparticles (A), for example, surface-modified silver nanoparticles can be produced by a production method described later or the like.

(Dispersion medium (B))
The dispersion medium (B) in the present invention is a dispersion medium for dispersing the surface-modified metal nanoparticles (A). The dispersion medium (B) contains at least an alcohol (b-1) and a hydrocarbon (b-2). The (b-1) and the (b-2) can each contain one type alone or in combination of two or more types. The above (b-1) and (b-2) may be liquid or solid at room temperature and normal pressure by themselves, but the dispersion medium (B) containing both of them is , A liquid dispersion medium (liquid dispersion medium) under normal temperature and pressure.

Since the conductive ink of the present invention contains the above (b-1) and the above (b-2) in combination as the dispersion medium (B), the dispersibility and dispersion of the surface-modified metal nanoparticles (A) Excellent stability.

(Alcohol (b-1))
The (b-1) includes primary alcohols, secondary alcohols, and tertiary alcohols. In the present invention, the surface-modified metal nanoparticles (A) have low reactivity with the surface-modified portion, and the loss of the surface-modified portion can be suppressed. Therefore, the surface-modified metal nanoparticles (A) are dispersed. The property can be stably maintained for a long period of time, that is, the dispersion stability is excellent, and the sinterability of the metal nanoparticles is improved by rapidly evaporating even in the case of low temperature sintering, that is, low temperature baking. Secondary alcohols and / or tertiary alcohols are particularly preferred in that they can impart binding properties.

Further, the above (b-1) includes an aliphatic alcohol, an alicyclic alcohol, and an aromatic alcohol, and among them, the alicyclic type is excellent in the dispersibility of the surface-modified metal nanoparticles (A). Alcohols (ie, alcohols with an alicyclic structure) are preferred.

Therefore, as the above (b-1), an alicyclic secondary alcohol and / or an alicyclic tertiary alcohol is preferable.

The alicyclic alcohol includes a monocyclic alcohol and a polycyclic alcohol. In particular, the monocyclic alcohol is particularly excellent in dispersibility of the surface-modified metal nanoparticles (A), and has low viscosity and applicability. (When coating by the inkjet printing method, it is preferable because it is excellent in injection stability from the head nozzle).

The boiling point of (b-1) is preferably, for example, 130 ° C. or higher, more preferably 170 ° C. or higher, and particularly when the surface-modified metal nanoparticles (A) are contained in a high concentration (for example, (for example,). A) The content (when the metal element equivalent) is 45% by weight or more of the total amount of the conductive ink) is preferably 185 ° C. or higher, more preferably 190 ° C. or higher. The upper limit of the boiling point is, for example, 300 ° C., preferably 250 ° C., particularly preferably 220 ° C. When the boiling point is 130 ° C. or higher, volatilization at the printing temperature can be suppressed, and excellent coatability (in the case of coating by the inkjet printing method, injection stability from the head nozzle) can be obtained. Further, when the boiling point is 300 ° C. or lower, the sintered body rapidly volatilizes even in the case of low-temperature sintering, and a sintered body having excellent conductivity can be obtained. That is, it is excellent in low-temperature sinterability. On the other hand, if the boiling point is lower than the above range, the fluidity of the conductive ink may decrease during coating, making it difficult to form a uniform coating film. For example, when applying by the inkjet printing method, the conductive ink solidifies and easily adheres to the nozzle opening of the head, and especially when the injection is performed intermittently, the injection becomes unstable and the desired pattern due to flight bending. There is a risk that it will be difficult to print accurately, or that the nozzle opening will be clogged and injection will not be possible.

Examples of the monocyclic secondary alcohol include cyclohexanol, 2-ethylcyclohexanol, 1-cyclohexanol, 3,5-dimethylcyclohexanol, 3,3,5-trimethylcyclohexanol, 2,3,5-. Trimethylcyclohexanol, 3,4,5-trimethylcyclohexanol, 2,3,4-trimethylcyclohexanol, 4- (tert-butyl) -cyclohexanol, 3,3,5,5-tetramethylcyclohexanol, 2- Cyclohexanol, which may have a substituent such as isopropyl-5-methyl-cyclohexanol (= menthol), and the corresponding cyclohexanol are preferable, and cyclohexanol having an alkyl group having 1 to 3 carbon atoms is particularly preferable. Alternatively, cyclohexanol is preferable, and cyclohexanol having an alkyl group having 1 to 3 carbon atoms is particularly preferable.

Examples of the monocyclic tertiary alcohol include 1-methylcyclohexanol, 4-isopropyl-1-methylcyclohexanol, 2-cyclohexyl-2-propanol, 2- (4-methylcyclohexyl) -2-propanol and the like. , A tertiary alcohol having a 6-7 membered ring (particularly cyclohexane ring) structure is preferred.

As the (b-1), in particular, containing at least a secondary alcohol (particularly, a monocyclic secondary alcohol) is excellent in the initial dispersibility of the surface-modified metal nanoparticles (A). It is preferable in that the dispersibility can be maintained stably for a long period of time. The content of the secondary alcohol is preferably, for example, 60% by weight or more, more preferably 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight, based on the total amount of (b-1). % Or more. The upper limit is 100% by weight.

(Hydrocarbon (b-2))
The above (b-2) includes aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. In the present invention, aliphatic hydrocarbons and / or alicyclic hydrocarbons are particularly preferable in that the surface-modified metal nanoparticles (A) are particularly excellent in dispersibility.

For the same reason as in (b-1), the boiling point of (b-2) is preferably, for example, 130 ° C. or higher, more preferably 170 ° C. or higher, still more preferably 190 ° C. or higher, and particularly the surface. When the modified metal nanoparticles (A) are contained in a high concentration (for example, when the content (A) (in terms of metal element) is 45% by weight or more of the total amount of the conductive ink), 200 ° C. or higher is preferable. It is more preferably 230 ° C. or higher, particularly preferably 250 ° C. or higher, and most preferably 270 ° C. or higher. The upper limit of the boiling point is, for example, 300 ° C.

Examples of the aliphatic hydrocarbon include n-decane, n-dodecane, n-tridecane, n-tetradecane, n-pentadecane, n-hexadecan, n-heptadecane, n-octadecane, n-nonadecane and the like having 10 carbon atoms. Above (for example, 10 to 20), in particular, a chain having 12 or more carbon atoms (for example, 12 to 20, preferably 12 to 18), particularly 15 or more carbon atoms (for example, 15 to 20, preferably 15 to 18). Aliphatic hydrocarbons are preferred.

Examples of the alicyclic hydrocarbon include monocyclic compounds such as cyclohexanes, cyclohexenes, terpene-based 6-membered ring compounds, cycloheptane, cycloheptene, cyclooctane, cyclooctene, cyclodecane, and cyclododecene; bicyclo [2.2. 2] Examples thereof include polycyclic compounds such as octane and decalin.

The cyclohexanes include, for example, ethylcyclohexane, n-propylcyclohexane, isopropylcyclohexane, n-butylcyclohexane, isobutylcyclohexane, sec-butylcyclohexane, tert-butylcyclohexane, and other 6-membered rings with 2 or more carbon atoms (for example, 2). ~ 5) Compound having an alkyl group; Bicyclohexyl and the like are included.

The terpene-based 6-membered ring compound includes, for example, α-pinene, β-pinene, limonene, α-terpinene, β-terpinene, γ-terpinene, terpinene and the like.

The (b-2) preferably contains at least an aliphatic hydrocarbon (particularly preferably a chain aliphatic hydrocarbon, most preferably a chain aliphatic hydrocarbon having 15 or more carbon atoms). The content of the aliphatic hydrocarbon is preferably, for example, 60% by weight or more, more preferably 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight, based on the total amount of (b-2). % Or more. The upper limit is 100% by weight.

(Polyfunctional (meth) acrylate (C))
The conductive ink of the present invention contains 0.1 to 4 parts by weight of polyfunctional (meth) acrylate (C) with respect to 100 parts by weight of the component (A). Therefore, the coating property is not impaired, and the conductivity of the sintered body of the conductive ink is not impaired, and the substrate adhesion of the sintered body of the conductive ink is excellent (particularly, smoothness of a glass substrate or the like). Adhesion to the substrate) can be imparted. In addition, in this specification, "(meth) acrylate" means "acrylate" and "methacrylate", and "(meth) acryloyl" means "acryloyl" and "methacryloyl". The "polyfunctional (meth) acrylate" is a compound having two or more (meth) acryloyl groups in one molecule.

The molecular weight of the polyfunctional (meth) acrylate (C) (polystyrene-equivalent molecular weight by GPC, weighted average value of the molecular weight when two or more compounds are contained as the polyfunctional (meth) acrylate (C)) is 300 or more. Yes, preferably 500 to 10000, particularly preferably 750 to 5000, and most preferably 1000 to 2000. When the molecular weight of the polyfunctional (meth) acrylate (C) is 300 or more, the substrate adhesion (particularly, glass substrate, etc.) excellent for the sintered body of the conductive ink containing the polyfunctional (meth) acrylate (C) is obtained. Adhesion to the smoothing substrate) can be imparted. When the molecular weight of the polyfunctional (meth) acrylate (C) is 10,000 or less, the conductive ink containing the polyfunctional (meth) acrylate (C) has good coatability and can be applied at a low temperature for a short time. A sintered body having good conductivity can be obtained even by sintering.

When the molecular weight of the polyfunctional (meth) acrylate (C) exceeds the above range, the solubility in the dispersion medium (B) tends to decrease, and even if it is dissolved in the dispersion medium (B), good coatability is obtained. It tends to be difficult to obtain. Further, the polyfunctional (meth) acrylate (C) having a molecular weight lower than the above range tends to be difficult to obtain the effect of imparting substrate adhesion even when added to the conductive ink.

(Meta) acryloyl equivalent (g / eq) of the polyfunctional (meth) acrylate (C) [When two or more compounds are contained as the polyfunctional (meth) acrylate (C), the weight of the (meth) acryloyl equivalent is weighted. The average value] is, for example, 250 or more and less than 2500, preferably 300 to 1500, more preferably 400 to 1000, particularly preferably 500 to 1000, and most preferably 550 to 950. When the (meth) acryloyl equivalent (g / eq) exceeds the above range, it tends to be difficult to obtain sufficient substrate adhesion. Further, when the (meth) acryloyl equivalent (g / eq) is less than the above range, low-temperature sintering becomes difficult and the conductivity tends to decrease.

The glass transition temperature (Tg) of the polyfunctional (meth) acrylate (C) is preferably, for example, −70 ° C. to 0 ° C., more preferably −60 ° C. to −10 ° C., and even more preferably −60 ° C. to −20 ° C. Is. The glass transition temperature (Tg) of the polyfunctional (meth) acrylate (C) can be measured by, for example, differential scanning calorimetry (DSC), dynamic viscoelasticity measurement, or the like.

As the polyfunctional (meth) acrylate (C), it is preferable to use urethane (meth) acrylate in terms of solubility in the dispersion medium (B).

The urethane (meth) acrylate is a urethane compound having (meth) acryloyl groups at both ends, which is obtained by reacting a hydroxy (meth) acrylate with a terminal isocyanate group of an addition reaction product of a polyol and a polyisocyanate.

The urethane (meth) acrylate includes an aliphatic urethane (meth) acrylate and an aromatic urethane (meth) acrylate, and among them, the aliphatic urethane (meth) acrylate suppresses aggregation between metal nanoparticles. It is preferable because it has an excellent effect.

The polyol includes, for example, an aliphatic polyol, an alicyclic polyol, and an aromatic polyol, and among them, an aliphatic or alicyclic polyol is preferable. Further, the polyol includes polyester polyol, polyether polyol, polycarbonate polyol, low molecular weight glycol and the like.

Examples of the polyester polyol include dicarboxylic acids (for example, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1,3-cyclopentanedicarboxylic acid, and 1,4-cyclohexane. Dicarboxylic acid, etc.) and diols (eg, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Hexanediol, neopentyl glycol, trimethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1 , 3-Propanediol, 2-methyl-1,3-Propanediol and other aliphatic diols; 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, alicyclic diols such as hydride bisphenol A, etc.) Reactants of.

Examples of the polyether polyol are alkylenes of compounds having two or more hydroxyl groups (for example, polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, etc.). Examples thereof include poly (oxyalkylene) glycol which is an oxide (for example, ethylene oxide, propylene oxide, butylene oxide, etc.) addition polymer.

Examples of the polycarbonate polyol include diols (for example, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc.) and dimethyl carbonate. And reaction products with phosgen and the like.

Examples of the low molecular weight glycol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6. -Hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propane Diols, aliphatic diols such as 2-methyl-1,3-propanediol; alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A hydride; glycerin, trimethylolpropane, etc. Examples thereof include trifunctional or higher functional hydroxyl group-containing compounds such as pentaerythritol.

The polyisocyanate includes an aliphatic polyisocyanate, an alicyclic polyisocyanate, and an aromatic polyisocyanate, and among them, an aliphatic or alicyclic polyisocyanate is preferable. Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate. Examples of the alicyclic polyisocyanate include isophorone diisocyanate.

Examples of the hydroxy (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and pentaerythritol tri. Examples include acrylate.

As the urethane (meth) acrylate, for example, commercially available products such as trade names "EBECRYL 230", "EBECRYL 270", "EBECRYL 303", and "EBECRYL 767" (all manufactured by Daicel Ornex Co., Ltd.) are preferably used. Can be used.

(Thermal Radical Polymerization Initiator (D))
The thermal radical polymerization initiator includes azo compounds such as azobisisobutyronitrile and organic peroxides. In the present invention, the use of organic peroxides is a metal nano. It is preferable from the viewpoint of particle dispersibility and fluidity of the conductive ink.

On the other hand, in the azo compound, the unshared electron pair contained in the N atom in the compound acts on the metal nanoparticles in the same manner as the above-mentioned organic protective agent. Therefore, when the azo compound is added to the conductive ink of the present invention, It is not preferable because the dispersibility of the metal nanoparticles tends to decrease, the viscosity increases, and the coatability tends to decrease. The proportion of the azo compound in the total amount (100% by weight) of the thermal radical polymerization initiator contained in the conductive ink of the present invention is preferably, for example, 30% by weight or less, more preferably 20% by weight or less, and particularly preferably. Is 10% by weight or less, most preferably 1% by weight or less. The lower limit is zero.

Examples of the organic peroxides include hydroperoxide, dialkyl peroxide, peroxyester, diacyl peroxide, peroxydicarbonate, peroxyketal, ketone peroxide and the like (specifically, benzoyl peroxide, etc.). tert-Butylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-di (2-ethylhexanoyl) peroxyhexane, tert-butylperoxybenzoate, tert-butyl peroxide, cumenhydro Peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-dibutylperoxyhexane, 2,4-dichlorobenzoyl peroxide, 1,4-di (2-tert-) Butylperoxyisopropyl) Benzene, 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane, methylethyl ketone peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethyl Hexanoate, etc.). These can be used alone or in combination of two or more.

In addition to the above components (A) to (D), the conductive ink of the present invention contains, for example, additives such as a dispersant, a surface energy adjusting agent, a plasticizer, a leveling agent, and a defoaming agent, if necessary. can do.

(Manufacturing method of conductive ink)
The conductive ink of the present invention is, for example, a step of mixing a metal compound and an organic protective agent to form a complex containing the metal compound and the organic protective agent (complex formation step), and a step of thermally decomposing the complex (complex formation step). The surface-modified metal nanoparticles (A) are produced through a step (thermal decomposition step) and, if necessary, a step of washing the reaction product (washing step), and dispersed in the obtained surface-modified metal nanoparticles (A). It can be produced through a step of mixing the medium (B) and the polyfunctional (meth) acrylate (C) (step of preparing a conductive ink).

(Complex formation step)
The complex formation step is a step of mixing the metal compound and the organic protective agent to form a complex containing the metal compound and the organic protective agent. In the present invention, when a silver compound is used as the metal compound, nano-sized silver particles are fused to each other at a temperature of about 100 ° C., so that they have excellent conductivity even on a general-purpose plastic substrate having low heat resistance. It is preferable in that an electronic component can be formed, and in particular, it is preferable to use a silver compound which is easily decomposed by heating to produce metallic silver. Examples of such silver compounds include silver carboxylate such as silver formate, silver acetate, silver oxalate, silver malonate, silver benzoate, and silver phthalate; silver fluoride, silver chloride, silver bromide, and iodide. Silver halide such as silver; silver sulfate, silver nitrate, silver carbonate and the like can be mentioned. In the present invention, silver oxalate has a high silver content, can be thermally decomposed without using a reducing agent, and is less likely to contain impurities derived from the reducing agent in the conductive ink. preferable.

As an organic protective agent, the unshared electron pair in the hetero atom is coordinated with the metal nanoparticles, so that the effect of strongly suppressing the aggregation between the metal nanoparticles can be exerted. A compound having at least one functional group selected from the group consisting of a group, an amino group, a sulfo group and a thiol group is preferable, and a group consisting of a carboxyl group, a hydroxyl group, an amino group, a sulfo group and a thiol group is particularly preferable. A compound having 4 to 18 carbon atoms having at least one functional group selected from the above is preferable.

As the organic protective agent, a compound having an amino group is particularly preferable, and a compound having an amino group having 4 to 18 carbon atoms, that is, an amine having 4 to 18 carbon atoms is most preferable.

The amine is a compound in which at least one hydrogen atom of ammonia is substituted with a hydrocarbon group, and includes a primary amine, a secondary amine, and a tertiary amine. Further, the amine may be a monoamine or a polyvalent amine such as a diamine. These can be used alone or in combination of two or more.

The amine is represented by the following formula (a-1), and R ¹ , R ² , and R ³ in the formula are the same or different, and a hydrogen atom or a monovalent hydrocarbon group (R ¹ , R) is used. ⁽ Except when both ² and R ³ are hydrogen atoms), monoamine (1) having a total carbon number of 6 or more, represented by the following formula (a-1), R ¹ , R ² in the formula A monoamine (2) in which R ³ is the same or different, is a hydrogen atom or a monovalent hydrocarbon group (except when R ¹ , R ² , and R ³ are all hydrogen atoms) and has a total carbon number of 5 or less. ) And the following formula (a-2), R ^{4 to} R ⁷ in the formula are the same or different, a hydrogen atom or a monovalent hydrocarbon group, and R ⁸ is a divalent hydrocarbon group. It preferably contains at least one selected from the hydrocarbons (3) having a total carbon number of 8 or less, and in particular, the monoamine (1) and the monoamine (2) and / or the diamine (3). It is preferable to contain them together.

The hydrocarbon group includes an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Among them, an aliphatic hydrocarbon group and an alicyclic hydrocarbon group are preferable, and a fat is particularly preferable. Group hydrocarbon groups are preferred. Therefore, as the monoamine (1), monoamine (2), and diamine (3), the aliphatic monoamine (1), the aliphatic monoamine (2), and the aliphatic diamine (3) are preferable.

Further, the monovalent aliphatic hydrocarbon group includes an alkyl group and an alkenyl group. The monovalent alicyclic hydrocarbon group includes a cycloalkyl group and a cycloalkenyl group. Further, the divalent aliphatic hydrocarbon group includes an alkylene group and an alkenylene group, and the divalent alicyclic hydrocarbon group includes a cycloalkylene group and a cycloalkenylene group.

Examples of the monovalent hydrocarbon group in R ¹ , R ² and R ³ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group and a pentyl group. , Hexyl group, decyl group, dodecyl group, tetradecyl group, octadecyl group and other alkyl groups having about 1 to 18 carbon atoms; vinyl group, allyl group, metallicyl group, 1-propenyl group, isopropenyl group, 1-butenyl group, Alkenyl groups having about 2 to 18 carbon atoms such as 2-butenyl group, 3-butenyl group, 1-pentenyl group, 2-pentenyl group, 3-pentenyl group, 4-pentenyl group, 5-hexenyl group; cyclopropyl group, Cycloalkyl groups having about 3 to 18 carbon atoms such as cyclobutyl group, cyclopentyl group, cyclohexyl group and cyclooctyl group; cycloalkenyl groups having about 3 to 18 carbon atoms such as cyclopentenyl group and cyclohexenyl group can be mentioned. it can.

Examples of the monovalent hydrocarbon group in R ^{4 to} R ⁷ include an alkyl group having about 1 to 7 carbon atoms, an alkenyl group having about 2 to 7 carbon atoms, and a cyclo having about 3 to 7 carbon atoms in the above examples. Examples thereof include an alkyl group and a cycloalkenyl group having about 3 to 7 carbon atoms.

Examples of the divalent hydrocarbon group in R ⁸ include methylene group, methylmethylene group, dimethylmethylene group, ethylene group, propylene group, trimethylene group, tetramethylene group, pentamethylene group, heptamethylene group and the like having 1 carbon number. Alkylene group of ~ 8; alkenylene group having 2 to 8 carbon atoms such as vinylene group, propenylene group, 1-butenylene group, 2-butenylene group, butadienylene group, pentenylene group, hexenylene group, heptenylene group, octenylene group and the like. Can be done.

The hydrocarbon groups in R ^{1 to} R ⁸ are various substituents [for example, halogen atom, oxo group, hydroxyl group, substituted oxy group (for example, C _1-4 alkoxy group, C _6-10 aryloxy group, C). _7-16 aralkyloxy group, C _1-4 acyloxy group, etc.), carboxyl group, substituted oxycarbonyl group (eg, C _1-4 alkoxycarbonyl group, C _6-10 aryloxycarbonyl group, C _7-16 aralkyloxycarbonyl) Group, etc.), cyano group, nitro group, sulfo group, heterocyclic group, etc.] may be used. Further, the hydroxyl group and the carboxyl group may be protected by a protecting group commonly used in the field of organic synthesis.

The monoamine (1) is a compound having a function of suppressing the aggregation and enlargement of the metal nanoparticles by adsorbing on the surface of the metal nanoparticles, that is, imparting high dispersibility to the metal nanoparticles. , For example, primary amines having linear alkyl groups such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine; Primary amines with branched chain alkyl groups such as isohexylamine, 2-ethylhexylamine, tert-octylamine; primary amines with cycloalkyl groups such as cyclohexylamine; primary amines with alkenyl groups such as oleylamine Secondary amines, etc .; N, N-dipropylamine, N, N-dibutylamine, N, N-dipentylamine, N, N-dihexylamine, N, N-dipeptylamine, N, N-dioctylamine, N, N- Secondary amines with linear alkyl groups such as dinonylamine, N, N-didecylamine, N, N-diundesylamine, N, N-didodecylamine, N-propyl-N-butylamine; N, N-di Secondary amines with branched alkyl groups such as isohexylamines, N, N-di (2-ethylhexyl) amines; tertiary amines with linear alkyl groups such as tributylamines and trihexylamines; tri Examples thereof include tertiary amines having a branched alkyl group such as isohexylamine and tri (2-ethylhexyl) amine.

Among the above monoamines (1), when an amino group is adsorbed on the surface of metal nanoparticles, the distance from other metal nanoparticles can be secured, so that the effect of preventing aggregation of the metal nanoparticles can be obtained and sintering is performed. Amines (particularly primary amines) having a linear alkyl group with a total carbon number of 6-18 (upper limit of total carbon number is more preferably 16, particularly preferably 12) in that they can sometimes be easily removed. ) Is preferable, and n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, n-undecylamine, n-dodecylamine and the like are particularly preferable.

Since monoamine (2) has a shorter hydrocarbon chain than monoamine (1), it has a low function of imparting high dispersibility to metal nanoparticles by itself, but it has higher polarity than monoamine (1) and becomes a metal atom. Because of its high coordination ability, it has a complex formation promoting effect. Further, since the hydrocarbon chain is short, it can be removed from the surface of the metal nanoparticles in a short time (for example, 30 minutes or less, preferably 20 minutes or less) even in low temperature sintering, and a sintered body having excellent conductivity can be obtained. can get.

Examples of the monoamine (2) include total carbon having a linear or branched alkyl group such as n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, isopentylamine, and tert-pentylamine. A primary amine having a number of 2 to 5 (preferably a total carbon number of 4 to 5) and a total carbon number of 2 to 5 (preferably a total carbon number) having a linear or branched alkyl group such as N, N-diethylamine. Examples of the secondary amines of numbers 4 to 5) can be mentioned. In the present invention, a primary amine having a linear alkyl group and having a total carbon number of 2 to 5 (preferably a total carbon number of 4 to 5) is preferable.

Since the total carbon number of the diamine (3) is 8 or less, the polarity is higher than that of the monoamine (1), and the coordination ability to the metal atom is high, it has a complex formation promoting effect. Further, the diamine (3) has an effect of accelerating the thermal decomposition at a lower temperature and in a short time in the thermal decomposition step of the complex, and the use of the diamine (3) makes the production of surface-modified metal nanoparticles more efficient. Can be done. Further, the surface-modified metal nanoparticles having a structure coated with a protective agent containing diamine (3) exhibit excellent dispersion stability in a highly polar dispersion medium. Further, since the diamine (3) has a short hydrocarbon chain, it can be removed from the surface of metal nanoparticles in a short time (for example, 30 minutes or less, preferably 20 minutes or less) even in low temperature sintering, and it becomes conductive. An excellent sintered body can be obtained.

Examples of the diamine (3) include 2,2-dimethyl-1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, and 1,7-heptandiamine. , 1,8-Octanediamine, 1,5-diamino-2-methylpentane, etc., R ^{4 to} R ⁷ in the formula (a-2) are hydrogen atoms, and R ⁸ is linear or branched. Diamine which is an alkylene group; N, N'-dimethylethylenediamine, N, N'-diethylethylenediamine, N, N'-dimethyl-1,3-propanediamine, N, N'-diethyl-1,3-propanediamine, In the formula (a-2) of N, N'-dimethyl-1,4-butanediamine, N, N'-diethyl-1,4-butanediamine, N, N'-dimethyl-1,6-hexanediamine, etc. R ⁴ and R ⁶ are the same or different linear or branched alkyl groups, R ⁵ and R ⁷ are hydrogen atoms, and R ⁸ is a linear or branched alkylene group. N, N-dimethylethylenediamine, N, N-diethylethylenediamine, N, N-dimethyl-1,3-propanediamine, N, N-diethyl-1,3-propanediamine, N, N-dimethyl-1,4- butanediamine, N, N-diethyl-1,4-butanediamine, N, N-dimethyl -1,6- R ^4, R ⁵ are the same or different and straight-chain in the formula (a-2), such as hexanediamine Examples thereof include diamine, which is a linear or branched alkyl group, R ⁶ and R ⁷ are hydrogen atoms, and R ⁸ is a linear or branched alkylene group.

Among these, R ⁴ and R ⁵ in the above formula (a-2) are the same or different linear or branched chain alkyl groups, R ⁶ and R ⁷ are hydrogen atoms, and R ⁸ is. Diamine which is a linear or branched chain alkylene group [In particular, R ⁴ and R ⁵ in the formula (a-2) are linear alkyl groups, R ⁶ and R ⁷ are hydrogen atoms, and R ⁸ Is a linear alkylene group, diamine] is preferable.

Diamines in which R ⁴ and R ⁵ in the formula (a-2) are the same or different linear or branched alkyl groups and R ⁶ and R ⁷ are hydrogen atoms, that is, primary amino groups and the first A diamine having a tertiary amino group is a complex formed because the primary amino group has a high coordinating ability with respect to a metal atom, but the tertiary amino group has a poor coordinating ability with respect to a metal atom. Is prevented from becoming excessively complicated, which enables thermal decomposition at a lower temperature and in a shorter time in the thermal decomposition step of the complex. Among these, diamines having a total carbon number of 6 or less (for example, 1 to 6, preferably 4 to 6) are preferable, and diamines having a total carbon number of 5 or less (for example, 1 to 6, preferably 4 to 6) are preferable because they can be removed from the surface of metal nanoparticles in a short time by low temperature sintering. For example, diamines of 1 to 5, preferably 4 to 5) are more preferable.

The ratio of the content of monoamine (1) to the total amount of the organic protective agent contained in the conductive ink of the present invention and the ratio of the total content of monoamine (2) and diamine (3) shall be within the following ranges. Is preferable.
Content of monoamine (1): for example 5 to 65 mol% (lower limit is preferably 10 mol%, particularly preferably 20 mol%, most preferably 30 mol%, and upper limit is preferably 60 mol%. , Particularly preferably 50 mol%)
Total content of monoamines (2) and diamines (3): for example 35-95 mol% (lower limit is preferably 40 mol%, particularly preferably 50 mol%; upper limit is preferably 90 mol%, Especially preferably 80 mol%, most preferably 70 mol%)

The proportion of the monoamine (2) content and the proportion of the diamine (3) content in the total amount of the organic protective agent contained in the conductive ink of the present invention are preferably in the following ranges.
Content of monoamine (2): for example 5 to 65 mol% (lower limit is preferably 10 mol%, particularly preferably 20 mol%, most preferably 30 mol%, and upper limit is preferably 60 mol%. , Particularly preferably 50 mol%)
Content of diamine (3): for example 5 to 50 mol% (the lower limit is preferably 10 mol%, and the upper limit is preferably 40 mol%, particularly preferably 30 mol%).

By containing the monoamine (1) in the above range, the dispersion stability of the metal nanoparticles can be obtained. When the content of the monoamine (1) is less than the above range, the metal nanoparticles tend to agglomerate easily. On the other hand, when the content of the monoamine (1) exceeds the above range, it becomes difficult to remove the organic protective agent from the surface of the metal nanoparticles in a short time when the sintering temperature is low, and the conductivity of the obtained sintered body is obtained. Tends to decrease.

By containing the monoamine (2) in the above range, a complex formation promoting effect can be obtained. Further, even if the sintering temperature is low, the organic protective agent can be removed from the surface of the metal nanoparticles in a short time, and a sintered body having excellent conductivity can be obtained.

By containing the diamine (3) in the above range, the complex formation promoting effect and the thermal decomposition promoting effect of the complex can be easily obtained. Further, the surface-modified metal nanoparticles having a structure coated with a protective agent containing diamine (3) exhibit excellent dispersion stability in a highly polar dispersion medium.

In the present invention, when monoamine (2) and / or diamine (3) having a high coordinating ability to a metal atom of a metal compound is used, the amount of monoamine (1) used is reduced according to the ratio of their use. It is preferable because the organic protective agent can be removed from the surface of the metal nanoparticles in a short time even if the sintering temperature is low, and a sintered body having excellent conductivity can be obtained.

The amine used as an organic protective agent in the present invention may contain other amines in addition to the above monoamines (1), monoamines (2), and diamines (3), but all amines contained in the protective agent. The ratio of the total content of the monoamine (1), monoamine (2), and diamine (3) to the above is preferably, for example, 60% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more. is there. The upper limit is 100% by weight. That is, the content of the other amine is preferably 40% by weight or less, particularly preferably 20% by weight or less, and most preferably 10% by weight or less.

The amount of the organic protective agent [particularly monoamine (1) + monoamine (2) + diamine (3)] used is not particularly limited, but is about 1 to 50 mol with respect to 1 mol of the metal atom of the metal compound as a raw material. It is preferably, particularly preferably 2 to 50 mol, most preferably 6 to 50 mol. If the amount of the organic protective agent used is less than the above range, the metal compound that is not converted into the complex tends to remain in the complex formation step, and it tends to be difficult to impart sufficient dispersibility to the metal nanoparticles. ..

In the present invention, for the purpose of further improving the dispersibility of the metal nanoparticles, as an organic protective agent, a compound having an amino group and a compound having a carboxyl group (for example, a compound having a carboxyl group and having 4 to 18 carbon atoms) are used. , Preferably an aliphatic monocarboxylic acid having 4 to 18 carbon atoms) may be contained alone or in combination of two or more.

Examples of the aliphatic monocarboxylic acid include butanoic acid, pentanoic acid, hexanoic acid, heptanic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid and hexadecanoic acid. Saturated aliphatic monocarboxylic acid having 4 or more carbon atoms such as heptadecanoic acid, octadecanoic acid, nonadecanoic acid and icosanoic acid; Monocarboxylic acid can be mentioned.

Among these, saturated or unsaturated aliphatic monocarboxylic acids having 8 to 18 carbon atoms (particularly, octanoic acid, oleic acid, etc.) are preferable. When the carboxyl group of the aliphatic monocarboxylic acid is adsorbed on the surface of the metal nanoparticles, the saturated or unsaturated aliphatic hydrocarbon chain having 8 to 18 carbon atoms becomes a steric obstacle, so that the distance from the other metal nanoparticles Can be ensured, and the action of preventing aggregation of metal nanoparticles is improved.

The amount of the compound having a carboxyl group to be used is, for example, about 0.05 to 10 mol, preferably 0.1 to 5 mol, particularly preferably 0.5 to 2 mol, with respect to 1 mol of the metal atom of the metal compound. Is. If the amount of the compound having a carboxyl group used is less than the above range, it is difficult to obtain the effect of improving the dispersion stability. On the other hand, even if the compound having a carboxyl group is excessively used, the effect of improving the dispersion stability is saturated, but it tends to be difficult to remove it by low-temperature sintering.

The reaction between the organic protective agent and the metal compound is carried out in the presence or absence of a dispersion medium. As the dispersion medium, for example, an alcohol having 3 or more carbon atoms can be used.

Examples of the alcohol having 3 or more carbon atoms include n-propanol (boiling point: 97 ° C.), isopropanol (boiling point: 82 ° C.), n-butanol (boiling point: 117 ° C.), and isobutanol (boiling point: 107.89 ° C.). , Se-butanol (boiling point: 99.5 ° C), tert-butanol (boiling point: 82.45 ° C), n-pentanol (boiling point: 136 ° C), n-hexanol (boiling point: 156 ° C), n-octanol (boiling point: 156 ° C) Boiling point: 194 ° C.), 2-octanol (boiling point: 174 ° C.) and the like. Among these, alcohols having 4 to 6 carbon atoms are preferable, and in particular, alcohols having 4 to 6 carbon atoms are preferable in terms of being able to set a high temperature in the subsequent thermal decomposition step of the complex and being convenient in the post-treatment of the obtained surface-modified metal nanoparticles. n-butanol and n-hexanol are preferable.

The amount of the dispersion medium used is, for example, 120 parts by weight or more, preferably 130 parts by weight or more, and more preferably 150 parts by weight or more with respect to 100 parts by weight of the metal compound. The upper limit of the amount of the dispersion medium used is, for example, 1000 parts by weight, preferably 800 parts by weight, and particularly preferably 500 parts by weight.

The reaction between the organic protective agent and the metal compound is preferably carried out at room temperature (5 to 40 ° C.). Since the reaction is accompanied by heat generation due to the coordination reaction of the organic protective agent with the metal compound, it may be carried out while appropriately cooling so as to be within the above temperature range.

The reaction time between the organic protective agent and the metal compound is, for example, about 30 minutes to 3 hours. As a result, a metal-organic protective agent complex (when amine is used as the organic protective agent, a metal-amine complex) is obtained.

(Pyrolysis process)
The thermal decomposition step is a step of thermally decomposing the metal-organic protective agent complex obtained through the complex formation step to form surface-modified metal nanoparticles. By heating the metal-organic protective agent complex, the metal compound thermally decomposes to form a metal atom while maintaining the coordination bond of the organic protective agent to the metal atom, and then the organic protective agent coordinates. It is considered that the metal atoms are aggregated to form metal nanoparticles coated with an organic protective film.

The thermal decomposition is preferably carried out in the presence of a dispersion medium, and the above-mentioned alcohol can be preferably used as the dispersion medium. The thermal decomposition temperature may be any temperature at which surface-modified metal nanoparticles are formed, and when the metal-organic protective agent complex is a silver oxalate-organic protective agent complex, for example, about 80 to 120 ° C. The temperature is preferably 95 to 115 ° C, particularly preferably 100 to 110 ° C. From the viewpoint of preventing detachment of the surface-modified portion of the surface-modified metal nanoparticles, it is preferable to carry out the process at a temperature as low as possible within the above temperature range. The thermal decomposition time is, for example, about 10 minutes to 5 hours.

Further, the thermal decomposition of the metal-organic protective agent complex is preferably carried out in an air atmosphere or in an atmosphere of an inert gas such as argon.

(Washing process)
After the completion of the thermal decomposition reaction of the metal-organic protective agent complex, if excess organic protective agent is present, it is preferable to repeat decantation once or twice or more in order to remove it. Further, the surface-modified metal nanoparticles after the decantation are not dried and solidified, but are subjected to the preparation step of the conductive ink described later in a wet state to suppress the reaggregation of the surface-modified metal nanoparticles. It is preferable in that it can maintain high dispersibility.

Decantation is performed, for example, by washing suspended surface-modified metal nanoparticles with a cleaning agent, precipitating the surface-modified metal nanoparticles by centrifugation, and removing the supernatant. As the cleaning agent, for example, one or more linear or branched alcohols having 1 to 4 carbon atoms (preferably 1 to 2) such as methanol, ethanol, n-propanol, and isopropanol are used. This is preferable in that the surface-modified metal nanoparticles have good sedimentation property and the cleaning agent can be efficiently separated and removed by centrifugation after cleaning.

(Preparation process of conductive ink)
The step of preparing the conductive ink includes surface-modified metal nanoparticles (A) (preferably wet surface-modified metal nanoparticles (A)), dispersion medium (B), and polyfunctionality (meth) obtained through the above steps. ) This is a step of preparing the conductive ink of the present invention by mixing the acrylate (C) and, if necessary, an additive. For the mixing, for example, a commonly known mixing device such as a self-revolving stirring defoaming device, a homogenizer, a planetary mixer, a three-roll mill, and a bead mill can be used. Further, each component may be mixed at the same time or sequentially. The blending ratio of each component can be appropriately adjusted within the following range.

The content (metal element equivalent) of the surface-modified metal nanoparticles (A) in the total amount (100% by weight) of the conductive ink of the present invention is, for example, about 35 to 70% by weight. The lower limit is preferably 40% by weight, particularly preferably 45% by weight, most preferably 50% by weight, and particularly preferably 55% by weight, from the viewpoint of obtaining a coating film or a sintered body having a higher film thickness. The upper limit is preferably 65% by weight, particularly preferably 60% by weight, from the viewpoint of coatability (in the case of coating by the inkjet printing method, injection stability from the head nozzle).

The content of the dispersion medium (B) (in terms of metal element) in the conductive ink of the present invention is 20 to 100 parts by weight, preferably 30 to 90 parts by weight, based on 100 parts by weight of the surface-modified metal nanoparticles (A). Parts, more preferably 40 to 80 parts by weight, still more preferably 50 to 75 parts by weight, particularly preferably 55 to 75 parts by weight, and most preferably 60 to 75 parts by weight.

The content of the dispersion medium (B) in the total amount (100% by weight) of the conductive ink of the present invention is, for example, 20 to 65% by weight, preferably 25 to 60% by weight, more preferably 30 to 55% by weight, and most preferably. Is 30 to 50% by weight. Since the conductive ink of the present invention contains the dispersion medium (B) in the above range, it has excellent coatability. For example, when it is coated by an inkjet printing method, the injection stability from the nozzle of the head should be maintained well. Is possible.

The content of (b-1) (particularly, monocyclic secondary alcohol) is, for example, 15 to 70 parts by weight, preferably 20 to 60 parts by weight, based on 100 parts by weight of the surface-modified metal nanoparticles (A). , Particularly preferably 30 to 55 parts by weight, most preferably 40 to 55 parts by weight.

The content of (b-2) (particularly an aliphatic hydrocarbon) is, for example, 5 to 50 parts by weight, preferably 10 to 40 parts by weight, particularly preferably 10 parts by weight, based on 100 parts by weight of the surface-modified metal nanoparticles (A). Is 15 to 30 parts by weight, most preferably 15 to 25 parts by weight.

The ratio of the content of the (b-1) to the content of the (b-2) in the total amount of the dispersion medium (B) contained in the conductive ink of the present invention (former / latter (weight ratio)) is, for example, 50/50. ~ 95/5, preferably 60/40 to 90/10, particularly preferably 65/35 to 85/15. When the content of (b-1) is less than the above range, the smoothness of the coating film tends to decrease. In addition, the low temperature sinterability tends to decrease. On the other hand, when the content of (b-2) is less than the above range, the coatability tends to decrease.

The dispersion medium (B) in the present invention may contain one or more other dispersion media in addition to the above (b-1) and (b-2), but the above (b-). The total content of 1) and (b-2) is preferably 70% by weight or more, particularly preferably 75% by weight or more, and most preferably 80% by weight or more of the total amount of (B). Therefore, the content of the other dispersion medium (the total amount when two or more kinds are contained) is preferably 30% by weight or less of (B) the total amount, particularly preferably 25% by weight or less, and most preferably 20% by weight. % Or less. When the content of the other dispersion medium exceeds the above range, the coatability tends to decrease due to the thickening, or the metal nanoparticles tend to aggregate and the dispersibility tends to decrease.

Further, the content of the primary alcohol in the total amount (100% by weight) of the dispersion medium (B) contained in the conductive ink of the present invention is preferably, for example, about 30% by weight or less, more preferably 25% by weight. % Or less, particularly preferably 20% by weight or less, most preferably 15% by weight or less, and particularly preferably 5% by weight or less.

The content of polyfunctional (meth) acrylate (C) (particularly urethane (meth) acrylate) in the conductive ink of the present invention is 0 with respect to 100 parts by weight (metal element equivalent) of the surface-modified metal nanoparticles (A). It is 1 to 4 parts by weight, and the lower limit is preferably 0.2 parts by weight, particularly preferably 0.3 parts by weight, most preferably 0.4 parts by weight, and particularly preferably 0.5 parts by weight. The upper limit is preferably 3 parts by weight, particularly preferably 2 parts by weight, and most preferably 1 part by weight. When the polyfunctional (meth) acrylate (C) is used in the range of 0.1 parts by weight or more, a sintered body having excellent substrate adhesion can be obtained. Further, when the polyfunctional (meth) acrylate (C) is used in the range of 4 parts by weight or less, a sintered body having excellent conductivity can be obtained.

The polyfunctional (meth) acrylate (C) in the present invention may contain other polyfunctional (meth) acrylates in addition to the urethane (meth) acrylate, but is contained in the conductive ink of the present invention. The proportion of the urethane (meth) acrylate content in the total amount of the functional (meth) acrylate (C) is, for example, 50% by weight or more, preferably 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight. % Or more. The upper limit is 100% by weight.

Further, the conductive ink of the present invention may contain other curable compounds in addition to the polyfunctional (meth) acrylate (C), but the polyfunctional ink in the fully curable compound contained in the conductive ink. The proportion of (meth) acrylate (C) (particularly urethane (meth) acrylate) is, for example, 50% by weight or more, preferably 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more. Is. The upper limit is 100% by weight.

Further, the ratio of the total amount of the surface-modified metal nanoparticles (A), the dispersion medium (B) and the polyfunctional (meth) acrylate (C) to the total amount (100% by weight) of the conductive ink of the present invention is, for example, 70% by weight. % Or more, preferably 80% by weight or more, particularly preferably 90% by weight or more.

The content of the thermal radical polymerization initiator (D) (the total amount when two or more kinds are contained) is preferably 0.1 to 10 parts by weight, for example, with respect to 100 parts by weight of the polyfunctional (meth) acrylate (C). Is 0.5 to 5.0 parts by weight, particularly preferably 1 to 5 parts by weight.

The viscosity of the conductive ink of the present invention (at 25 ° C. and a shear rate of 10 (1 / s)) is, for example, 1 to 100 mPa · s. The upper limit of the viscosity is preferably 50 mPa · s, particularly preferably 20 mPa · s, and most preferably 15 mPa · s. The lower limit of the viscosity is preferably 2 mPa · s, particularly preferably 3 mPa · s, and most preferably 5 mPa · s.

The conductive ink of the present invention has excellent dispersion stability. For example, when a conductive ink having a metal concentration of 65% by weight is stored at 5 ° C., aggregation of metal nanoparticles can be suppressed for a period of one month or longer.

As described above, the conductive ink of the present invention has a low viscosity and is excellent in coatability. In addition, the surface-modified metal nanoparticles (A) are excellent in dispersion stability, and good coatability can be maintained even if the surface-modified metal nanoparticles (A) are contained in a high concentration. Further, the conductive ink of the present invention is excellent in low-temperature sintering property, and a sintered body having excellent substrate adhesion and conductivity can be obtained by low-temperature sintering. Therefore, the conductive ink of the present invention has a substrate (particularly a substrate having low heat resistance such as a general-purpose plastic substrate or a glass substrate having high heat resistance but a smooth surface) by inkjet printing, gravure printing, or flexo printing. It can be suitably used for forming electronic components on a substrate on which an anchor effect is difficult to obtain).

[Method of forming electronic components]
The method for forming an electronic component of the present invention includes a step of applying the conductive ink on a substrate by an inkjet printing method, a gravure printing method, or a flexographic printing method, and a step of sintering.

As for the thickness of the coating film obtained by applying the conductive ink, the thickness of the sintered body obtained by sintering the coating film is, for example, 0.1 to 5 μm (preferably 0.5 to 2 μm). It is preferably in the range.

Since the conductive ink is used in the method for forming an electronic component of the present invention, sintering is possible at a low temperature, and the sintering temperature is, for example, 150 ° C. or lower (the lower limit of the sintering temperature is, for example, 60 ° C.). 100 ° C. is more preferable in that it can be sintered in a short time), particularly preferably 130 ° C. or lower, and most preferably 120 ° C. or lower. The sintering time is, for example, 0.5 to 3 hours, preferably 0.5 to 2 hours, and particularly preferably 0.5 to 1 hour.

When the conductive ink of the present invention is used, the sintering of metal nanoparticles proceeds sufficiently even in low temperature sintering (for example, sintering at low temperature for a short time such as 60 minutes at 120 ° C.). As a result, a sintered body having excellent substrate adhesion (particularly, a sintered body having excellent adhesion to a substrate having excellent surface smoothness such as glass) can be obtained. Therefore, even if a protective film is attached to the surface of the sintered body for the purpose of preventing damage, for example, the sintered body will not be peeled off together when the protective film is peeled off.

Further, when the conductive ink of the present invention is used, the sintering of metal nanoparticles proceeds sufficiently even in low temperature sintering (for example, sintering at low temperature for a short time such as 60 minutes at 120 ° C.). .. As a result, a sintered body having excellent conductivity (volume resistivity is, for example, 12 μΩcm or less, preferably 10 μΩcm or less) can be obtained. The conductivity (or volume resistivity) of the sintered body can be measured by the method described in Examples.

If the conductive ink of the present invention is used, a sintered body having excellent adhesion to the base material can be obtained as described above. Therefore, as a substrate, the surface of a glass substrate or the like is smooth and it is difficult to obtain an anchor effect. The substrate can be preferably used.

Further, since low-temperature sintering is possible as described above by using the conductive ink of the present invention, the substrate may be polyethylene terephthalate (PET) in addition to a glass substrate or a heat-resistant plastic substrate such as a polyimide film. A general-purpose plastic substrate having low heat resistance such as a film, a polyester-based film such as polyethylene terephthalate (PEN) film, and a polyolefin-based film such as polypropylene can also be preferably used.

Electronic devices equipped with electronic components obtained by the method for forming electronic components of the present invention include, for example, liquid crystal displays, organic EL displays, field emission displays (FEDs), IC cards, IC tags, solar cells, LED elements, and organic transistors. , Condenser (capacitor), electronic paper, flexible battery, flexible sensor, membrane switch, touch panel, EMI shield and the like.

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

Preparation Example 1 (Preparation of surface-modified silver nanoparticles)
Complex formation step Silver oxalate (molecular weight: 303.78) was obtained from silver nitrate (manufactured by Wako Pure Chemical Industries, Ltd.) and oxalic acid dihydrate (manufactured by Wako Pure Chemical Industries, Ltd.).
20.0 g (65.8 mmol) of the silver oxalate was charged in a 500 mL flask, and 30.0 g of n-butanol was added thereto to prepare an n-butanol slurry of silver oxalate.
To this slurry, at 30 ° C., n-butylamine (molecular weight: 73.14, manufactured by Daicel Co., Ltd.) 57.8 g (790.1 mmol), n-hexylamine (molecular weight: 101.19, Tokyo Kasei Kogyo Co., Ltd.) 40.0 g (395.0 mmol), n-octylamine (molecular weight: 129.25, trade name "Farmin 08D", manufactured by Kao Corporation) 38.3 g (296.3 mmol), n-dodecylamine (molecular weight) 185.35, trade name "Farmin 20D", manufactured by Kao Corporation, 18.3 g (98.8 mmol), and N, N-dimethyl-1,3-propanediamine (molecular weight: 102.18, Koei Chemical Industry Co., Ltd.) 40.4 g (395.0 mmol) of an amine mixed solution (manufactured by Co., Ltd.) was added dropwise.
After the dropping, the mixture was stirred at 30 ° C. for 2 hours to promote a complex formation reaction between silver oxalate and amine to obtain a white substance (silver oxalate-amine complex).

Pyrolysis step After the formation of the silver-amine oxalate complex, the temperature of the reaction solution is raised from 30 ° C. to 105 ° C. (103 to 108 ° C.), and then heated for 1 hour while maintaining the above temperature. The silver acid-amine complex was pyrolyzed to give a suspension of dark blue surface-modified silver nanoparticles suspended in an amine mixture.

Washing step After cooling, 200 g of methanol is added to the obtained suspension and stirred, then surface-modified silver nanoparticles are precipitated by centrifugation, the supernatant is removed, and 60 g of methanol is added again and stirred. Then, the surface-modified silver nanoparticles were precipitated by centrifugation, and the supernatant was removed. In this way, wet surface-modified silver nanoparticles were obtained.

Example 1 (Preparation of silver ink)
Weigh each component according to the formulation (unit: parts by weight) shown in Table 1 below, stir in an oil bath (100 rpm) for 3 hours, and then use a rotating and revolving kneader (Kurashiki Spinning Co., Ltd., Mazerustar KKK2508). Stir and knead (2 minutes x 3 times) to make black-brown silver ink (1) (silver concentration: 50% by weight, viscosity (at 25 ° C., shear rate 10 (1 / s)): 10.1 mPa · s). Got
With respect to the obtained silver ink (1), the average particles of surface-modified silver nanoparticles were subjected to a dynamic light scattering method using the trade name "Zeta Nanosizer Series Nano-S" (manufactured by Malvern) as an analyzer. When the diameter was confirmed, it was 25 nm.

Comparative Examples 1 to 4
A silver ink (silver concentration: 50% by weight) was obtained in the same manner as in Example 1 except that the formulation was changed as shown in Table 1 below.

The substrate adhesion and conductivity of the silver ink sintered body obtained in Examples and Comparative Examples were evaluated by the following methods.

(Evaluation of substrate adhesion of sintered body)
The silver inks obtained in Examples and Comparative Examples were applied onto a non-alkali glass plate to form a coating film. The obtained coating film was rapidly sintered at 100 ° C. for 30 minutes and then at 120 ° C. for 60 minutes using a hot plate to obtain a sintered body having a thickness of about 1 μm.
A tape peeling test (based on JIS K 5600) was performed on the obtained sintered body / non-alkali glass plate laminate, and the ratio (residual rate) of the sintered body remaining on the non-alkali glass plate when the tape was peeled off. :%) Was calculated and the substrate adhesion was evaluated according to the following criteria.
Evaluation criteria ○: Residual rate exceeds 90% ×: Residual rate is 90% or less

(Evaluation of conductivity of sintered body)
For the sintered body obtained by the same method as the substrate adhesion evaluation of the sintered body, the surface resistivity value was measured using the 4-terminal method (Loresta GP MCP-T610), and the volume resistivity was calculated from the following formula. , The conductivity was evaluated according to the following criteria.
Volume resistivity (μΩcm) = Surface resistivity × Film thickness ○: Volume resistivity is 10 μΩcm or less ×: Volume resistivity is over 10 μΩcm

<Surface-modified metal nanoparticles>
-Surface-modified silver nanoparticles: Surface-modified silver nanoparticles obtained in Preparation Example 1 <dispersion medium>
-Hexadecane: Boiling point 287 ° C, reagent manufactured by Tokyo Chemical Industry Co., Ltd.-3,3,5-trimethylcyclohexanol: Boiling point 193-196 ° C, reagent manufactured by Tokyo Chemical Industry Co., Ltd. <(meth) acrylate>
EBECRYL 270: Bifunctional aliphatic urethane acrylate, manufactured by Daicel Ornex Co., Ltd., molecular weight: 1500, acryloyl equivalent: 750, Tg: -27 ° C, resin content 100% by weight
-ODA-N: Octyl / decyl acrylate, manufactured by Daicel Ornex Co., Ltd., average molecular weight: 200, acryloyl equivalent: 200, Tg: -58 ° C, 100% resin weight-EBECRYL1039: monofunctional aliphatic urethane acrylate, Daicel -Manufactured by Ornex Co., Ltd., 100% weight of resin content-HDDA: 1,6-hexanediol diacrylate, manufactured by Daicel Ornex Co., Ltd., average molecular weight 226, acryloyl equivalent: 113, Tg: 105 ° C., 100% resin content Weight <Thermal radical polymerization initiator>
Perbutyl O: tert-butylperoxy-2-ethylhexanoate, manufactured by NOF CORPORATION, heat generation start temperature 106 ° C

Claims (13)

It contains the following components (A), (B), (C), and (D), the component (B) is 20 to 100 parts by weight with respect to 100 parts by weight of the component (A), and the component (C) is (A). A conductive ink containing 0.1 to 4 parts by weight with respect to 100 parts by weight of the component.
Component (A): the surface of the metal nanoparticles, the surface-modified metal nanoparticles having a structure that is coated with an organic protective agent component (B): an alcohol (b-1) and hydrocarbon (b-2), wherein Dispersion medium (C) component in which the content ratio (former / latter (weight ratio)) of (b-1) and (b-2) is in the range of 60/40 to 90/10 : molecular weight of 300 or more Polyfunctional (meth) acrylate (D) component: Thermal radical polymerization initiator According to claim 1, the organic protective agent constituting the component (A) is a compound having at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an amino group, a sulfo group, and a thiol group. The conductive ink described. A compound having 4 to 18 carbon atoms, wherein the organic protective agent constituting the component (A) has at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, an amino group, a sulfo group, and a thiol group. The conductive ink according to claim 1. The conductive ink according to any one of claims 1 to 3, wherein the component (C) is a polyfunctional (meth) acrylate having a molecular weight of 500 or more. The conductive ink according to any one of claims 1 to 4 , wherein the (meth) acryloyl equivalent (g / eq) of the polyfunctional (meth) acrylate is 250 or more and less than 2500. The conductive ink according to any one of claims 1 to 5 , wherein the polyfunctional (meth) acrylate is a urethane (meth) acrylate. The conductive ink according to any one of claims 1 to 6 , wherein the thermal radical polymerization initiator is an organic peroxide. The conductive ink according to any one of claims 1 to 7 , wherein the alcohol (b-1) is an alicyclic secondary alcohol and / or an alicyclic tertiary alcohol. The conductive ink according to any one of claims 1 to 8 , which has a viscosity (at 25 ° C. and a shear rate of 10 (1 / s)) of 1 to 100 mPa · s. The conductive ink according to any one of claims 1 to 9 , wherein the metal nanoparticles constituting the component (A) are silver nanoparticles. The conductive ink according to any one of claims 1 to 10 , which is used for inkjet printing, gravure printing, or flexographic printing. An electronic device including a step of applying the conductive ink according to any one of claims 1 to 11 on a substrate by an inkjet printing method, a gravure printing method, or a flexographic printing method, and a step of sintering. Production method. An electronic device comprising a sintered body of the conductive ink according to any one of claims 1 to 11 on a substrate.