JP6657573B2 - Conductive ink - Google Patents

Description

  The present invention relates to a conductive ink.

  The conductive ink is used as a material for forming a wiring pattern of a circuit board. Specifically, after a conductive ink containing metal nanoparticles or metal complexes is applied on a substrate in a pattern, the coating is heat-treated (baked) to form a wiring pattern.

  In order to apply the conductive ink in a limited space on the substrate in a pattern, it is necessary to reduce the line width or the distance between adjacent wirings. Therefore, as a method of applying the conductive ink, a screen printing method or an inkjet printing method is employed.

  Then, in order to fuse (sinter) the metal nanoparticles and the metal complex contained in the coating film of the conductive ink, the coating film is heat-treated (baked). The heat treatment (baking) is usually performed at a high temperature of 300 ° C. or higher.

  As the conductive ink used in this manner, for example, a conductive ink containing a metal colloid liquid and a stabilizer containing an amine compound having one or more amino groups is known (for example, Patent Document 1). According to Patent Document 1, the amine compound constituting the stabilizer interacts with the hydrophilic group of the organic component localized on the metal particle surface of the metal colloid liquid, whereby the metal particles can be dispersed uniformly and for a long time. Has been described. It is described that by improving the dispersibility of the conductive ink, a conductive film can be obtained even at a low sintering temperature.

  Further, a conductive ink containing fine particles (A) of a copper salt comprising a carboxylic acid having reducing power and copper ions and a coordinating compound (B) is also known (for example, Patent Document 2). Patent Document 2 discloses that copper ions of fine particles (A) are reduced by a carboxylic acid during heat treatment to become metallic copper, thereby imparting conductivity; and the coordinating compound (B) is formed of fine particles of copper salts ( It is described that it plays a role in improving the dispersibility of A) and stabilizing the reduction reaction of copper ions.

Furthermore, a conductive ink containing a metal mixture containing an amine compound, metal nanoparticles capped with a dispersant, and an organic solvent is also known (for example, Patent Document 3). Patent Document 3 describes that the amine compound is a compound having a structure of CH ₃ (CH ₂ ) nNH ₂ ; and that the dispersant is an aliphatic amine.

JP 201424091A JP 2011-241309 A JP 2006-332051 A

  By the way, in order to obtain a conductive layer having sufficient conductivity, it is desired to sufficiently remove the coordination compound and the stabilizer during the heat treatment (baking) of the coating film of the conductive ink. However, the conductive inks disclosed in Patent Documents 1 to 3 need to be heat-treated (baked) at a high temperature in order to sufficiently remove the coordination compound and the stabilizer. Therefore, a conductive layer having sufficient conductivity could not be formed on a substrate having low heat resistance.

  On the other hand, simply lowering the sintering temperature cannot sufficiently remove the coordination compound and the stabilizer in the conductive ink, so that the sheet resistance of the obtained conductive layer increases, and sufficient conductivity is obtained. I can't get it.

  The present invention has been made in view of such circumstances, and has as its object to provide a conductive ink capable of forming a conductive layer having sufficient conductivity even on a substrate having low heat resistance.

（一般式（１）中、
Ｘ_１〜Ｘ_１０は、−ＣＲ_１又は窒素原子を表し、かつ少なくとも一つは窒素原子を表し；
Ｒ_１は、水素原子又は置換基を表し；
Ｌ_１は、置換基を表す）
［４］ 前記含窒素芳香族複素環化合物が、下記一般式（２）で表される構造を有する、［１］または［２］に記載の導電性インク。

（一般式（２）中、
Ｙ_１〜Ｙ_８は、−ＣＲ_２又は窒素原子を表し、かつ少なくとも一つは窒素原子を表し；
Ｒ_２は、水素原子又は置換基を表し；
Ｌ_２及びＬ_３は、それぞれ置換基を表す）
［５］ 前記焼結温度低下剤の含有量は、前記導電性インクに対して０．１質量％以上５質量％以下である、［１］〜［４］のいずれかに記載の導電性インク。
［６］ 前記金属ナノ粒子又は前記金属錯体を構成する金属は銀である、［１］〜［５］のいずれかに記載の導電性インク。
［７］ 前記分散剤は、脂肪族アミン化合物を含む、［１］〜［６］のいずれかに記載の導電性インク。 [1] 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 has at least one of an imidazole ring and a pyridine ring. A conductive ink which is a nitrogen-containing aromatic heterocyclic compound.
[2] The conductive ink according to [1], wherein the nitrogen-containing aromatic heterocyclic compound has a weight average molecular weight of 150 to 1,000.
[ 3 ] The conductive ink according to [1] or [2] , wherein the nitrogen-containing aromatic heterocyclic compound has a structure represented by the following general formula (1).

(In the general formula (1),
X _{1 to} X ₁₀ represent —CR ₁ or a nitrogen atom, and at least one represents a nitrogen atom;
R ₁ represents a hydrogen atom or a substituent;
L ₁ represents a substituent)
[ 4 ] The conductive ink according to [1] or [2] , wherein the nitrogen-containing aromatic heterocyclic compound has a structure represented by the following general formula (2).

(In the general formula (2),
Y _{1 to} Y ₈ represent —CR ₂ or a nitrogen atom, and at least one represents a nitrogen atom;
R ₂ represents a hydrogen atom or a substituent;
L ₂ and L ₃ each represent a substituent)
[ 5 ] The conductive ink according to any one of [1] to [ 4 ], wherein the content of the sintering temperature reducing agent is 0.1% by mass or more and 5% by mass or less based on the conductive ink. .
[ 6 ] The conductive ink according to any one of [1] to [ 5 ], wherein the metal constituting the metal nanoparticles or the metal complex is silver.
[ 7 ] The conductive ink according to any one of [1] to [ 6 ], wherein the dispersant includes an aliphatic amine compound.

  According to the present invention, it is possible to provide a conductive ink capable of forming a conductive layer having sufficient conductivity even on a substrate having low heat resistance.

FIG. 2 is a schematic sectional view illustrating an example of an organic EL device.

  The present inventors can lower the sintering temperature of the conductive ink by adding a specific nitrogen-containing aromatic heterocyclic compound to the conductive ink containing the metal nanoparticles and the dispersant; It has been found that a conductive layer having sufficient conductivity can be formed even on a substrate having low heat resistance.

  The reason why the sintering temperature of the conductive ink can be lowered by including a specific nitrogen-containing aromatic heterocyclic compound is not necessarily clear, but is considered as follows. The dispersant in the conductive ink is coordinated with the metal nanoparticles and covers the periphery thereof like a shell. The dispersant coordinated to the metal nanoparticles is detached from the metal nanoparticles by heating during sintering, and the metal nanoparticles fuse to form a conductive layer. Therefore, in order to obtain a conductive layer having sufficient conductivity, it is desirable to remove (preferably completely) the dispersant as much as possible (preferably completely) by heating during sintering.

  On the other hand, a specific nitrogen-containing aromatic heterocyclic compound has a larger interaction with the metal constituting the metal nanoparticle than the dispersant, and thus attacks the metal nanoparticle under heating at the time of sintering. It is easy to replace with a coordinated dispersant. As a result, the specific nitrogen-containing aromatic heterocyclic compound promotes the dissociation of the dispersant from the metal nanoparticles; as a result, the fusion between the metal nanoparticles can proceed sufficiently even at a low sintering temperature. it can.

  Such substitution between the specific nitrogen-containing aromatic heterocyclic compound and the dispersant occurs under heating at the time of sintering, but hardly occurs at normal temperature. That is, unless a certain external energy, such as heating during sintering, is applied, the two are not replaced. At room temperature, it is considered that the aliphatic amine compounds serving as dispersants have a hydrophobic interaction with each other and have a stable structure. Therefore, at room temperature, the dispersibility of the metal nanoparticles is not impaired. The present invention has been made based on such findings.

1. Conductive Ink The conductive ink of the present invention contains at least one of metal nanoparticles and metal complexes, a dispersant, a nitrogen-containing aromatic heterocyclic compound that is a sintering temperature reducing agent, and a solvent.

1-1. Metal nanoparticles / metal complexes (metal nanoparticles)
The metal nanoparticles contained in the conductive ink of the present invention are metal particles having a nano-sized average particle diameter. The metal constituting the metal nanoparticles is not particularly limited, and examples thereof include silver (Ag), copper (Cu), nickel (Ni), gold (Au), platinum (Pt), palladium (Pd), and iron. (Fe) or an alloy thereof. From the viewpoint of excellent conductivity, gold (Au), silver (Ag), or copper (Cu) is preferable, and silver (Ag) is more preferable.

  The average particle size of the metal nanoparticles is preferably from 1 to 50 nm, more preferably from 1 to 20 nm, further preferably from 1 to 10 nm. The smaller the average particle diameter of the metal nanoparticles, the greater the quantum size effect and the lower the melting point of the metal nanoparticles. That is, the sintering temperature is lowered, and the range of choice of the base material is easily expanded. When a transparent electrode is manufactured, it is desirable to reduce the thickness of the conductive layer to about 10 nm in order to obtain a sufficiently high light transmittance. By reducing the average particle diameter of the metal nanoparticles, the conductive layer can be easily formed thin, and thus a conductive layer having high light transmittance can be easily obtained. The average particle size of the metal nanoparticles can be measured by the BET method (specific surface area measurement).

(Metal complex)
The metal complex contained in the conductive ink of the present invention is a compound containing a metal atom or metal ion and a ligand coordinated thereto. Examples of the metal constituting the metal complex include those similar to the metal constituting the metal nanoparticles, and gold (Au), silver (Ag) or copper (Cu) is preferable in terms of excellent conductivity, Silver (Ag) is more preferred.

Examples of the ligand constituting the metal complex include NO ₃ ⁻ , CN ⁻ , SCN ⁻ , SO ₃ ²⁻ , thiourea, ammonia, ammonium carbamate compounds, ammonium carbonate compounds, and the like.

Among these, the metal complex is preferably a silver complex, and more preferably a silver complex compound represented by the following general formula (3).

A in the general formula (3) represents a ligand represented by the following general formulas (4) to (6). m is 0.5 to 1.5.

In the general formulas (4) to (6), R _{1 to} R ₆ each represent a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, a cycloalkyl group, an aralkyl group, an aryl group, or a heteroaryl group. These groups may further have a substituent such as a hydroxy group, an amino group, an alkoxy group and a cyano group. However, at least one of R _{1 to} R ₆ is not a hydrogen atom. Examples of the ligands represented by the general formulas (4) to (6) include the compounds described in claim 5 of JP-T-2009-535661.

  The content of the metal nanoparticles or the metal complex in the conductive ink is preferably from 0.1 to 30% by mass, more preferably from 0.1 to 20% by mass, based on the conductive ink. When the content of the metal nanoparticles or the metal complex is equal to or more than a certain value, a conductive layer having sufficient conductivity is easily obtained. When the content of the metal nanoparticles or the metal complex is equal to or less than a predetermined value, an excessive increase in the viscosity of the conductive ink is easily suppressed.

1-2. Dispersant The dispersant contained in the conductive ink of the present invention may have a function of enhancing the dispersibility of the metal nanoparticles or the metal complex. Examples of such dispersants include amine compounds and thiol compounds.

  The amine compound is preferably an aliphatic amine compound, and more preferably an aliphatic amine compound having 4 to 10 carbon atoms in the alkyl portion. Examples of the aliphatic amine compound include an alkylamine such as octylamine, dodecylamine, and hexadecylamine; and an alkenylamine such as oleylamine. The thiol compound is preferably an aliphatic thiol compound. Examples of the aliphatic thiol include alkyl thiols such as hexane thiol, pentanedithiol, decane thiol and dodecane thiol. One type of dispersant may be used, or two or more types may be combined.

  The content of the dispersant in the conductive ink is preferably from 10 to 1000% by mass, more preferably from 50 to 500% by mass, based on the metal nanoparticles or the metal complex. When the content of the dispersant is equal to or more than a certain value, the dispersibility of the metal nanoparticles or the metal complex can be sufficiently increased. When the content of the dispersant is equal to or less than a certain value, an excessive increase in the viscosity of the conductive ink is easily suppressed.

1-3. Sintering Temperature Lowering Agent The sintering temperature lowering agent contained in the conductive ink of the present invention can be a compound containing a nitrogen-containing aromatic heterocycle (nitrogen-containing aromatic heterocyclic compound). The nitrogen-containing aromatic heterocycle is an aromatic heterocycle containing a nitrogen atom as a ring constituent atom. Since such a nitrogen atom can have a highly active lone pair, under heating, it strongly interacts with the metal constituting the metal nanoparticles and the metal complex, and the elimination of the dispersant from the metal. It is thought that it can promote.

  The weight average molecular weight of the nitrogen-containing aromatic heterocyclic compound is preferably from 125 to 1,000, more preferably from 150 to 1,000, and even more preferably from 300 to 1,000. The nitrogen-containing aromatic heterocyclic compound having a weight average molecular weight of 125 or more does not volatilize prior to the dispersant by heating during sintering and sufficiently interacts with the metal constituting the metal nanoparticles or the metal complex. Cheap. The nitrogen-containing aromatic heterocyclic compound having a weight-average molecular weight of 1000 or less does not remain in the obtained conductive layer in an excessive amount, so that an increase in sheet resistance can be easily suppressed.

The weight average molecular weight of the nitrogen-containing aromatic heterocyclic compound can be measured by using gel permeation chromatography. The measurement conditions can be as follows.
(Measurement condition)
Solvent: Tetrahydrofuran Column: TSKgel G4000 + 2500 + 2000HXL manufactured by Tosoh
Column temperature: 40 ° C
Injection volume: 100 μl
Detector: RI Model 504 (GL Science)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation) Mw = 10000-500 Calibration curves for 13 samples are used. Thirteen samples are used at approximately equal intervals.

  The nitrogen-containing aromatic heterocycle contained in the nitrogen-containing aromatic heterocyclic compound is an aromatic heterocycle containing a nitrogen atom as a ring constituent atom, and examples thereof include a pyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, Examples include a triazine ring, an oxazole ring, a thiazole ring, an oxadiazole ring, a thiadiazole ring, a pyrrole ring, an imidazole ring, a pyrazole ring, a triazole ring, and a tetrazole ring. Two or more of these rings may be condensed; or these rings may be condensed with an aromatic hydrocarbon ring (for example, a benzene ring) or another aromatic heterocycle (for example, a thiophene ring).

  Among them, a nitrogen-containing aromatic heterocycle containing a “nitrogen atom having a lone pair of electrons that does not participate in aromaticity” as a ring-constituting atom because it easily interacts with the metal constituting the metal nanoparticle or metal complex Is preferred.

  The “nitrogen atom having a lone pair that is not involved in aromaticity” is a nitrogen atom having a lone pair, and the lone pair is a non-local atom on a conjugated unsaturated ring structure (aromatic ring). It does not participate in the localized π-electron system as an essential element for the expression of aromaticity. The details of the "nitrogen atom having an unshared electron pair not involved in aromaticity" are as described in paragraphs 0057 to 0079 of Japanese Patent Application No. 2014-213474. Since such a nitrogen atom has strong nucleophilicity and high coordination property to a metal atom, it is considered that the nitrogen atom can express a high interaction with a metal constituting the metal nanoparticle or the metal complex.

  Examples of the nitrogen-containing aromatic heterocycle containing a `` nitrogen atom having an unshared electron pair not involved in aromaticity '' as a ring constituent atom include those other than the pyrrole ring among the nitrogen-containing aromatic heterocycles described above. And preferably a pyridine ring or an imidazole ring.

The nitrogen-containing aromatic heterocyclic compound preferably has a structure represented by the following general formula (1) or (2). Compounds having these structures not only have a nitrogen atom having an unshared electron pair that does not participate in aromaticity, but also have an improved nucleophilicity of the nitrogen atom, and a metal constituting a metal nanoparticle or a metal complex. Since a stronger interaction occurs between the layers, it is considered that a conductive layer having a sufficiently low sheet resistance can be obtained even at a low firing temperature.

X _{1 to} X _{10 in} the general formula (1) represent —CR ₁ or a nitrogen atom, and at least one represents a nitrogen atom. R ₁ of —CR ₁ represents a hydrogen atom or a substituent.
Examples of the substituent include an alkyl group (eg, a methyl group, an ethyl group), an aryl group (eg, a phenyl group, a naphthyl group, an anthracenyl group, a phenanthryl group, a pyrenyl group), a heteroaryl group (eg, a pyridinyl group, a pyrazinyl group, pyrimidinyl group, triazinyl group, a pyrrole group, an imidazolyl group, a thiazolyl group, a pyrazolyl group, a triazolyl group, an oxazolyl group, a carbazolyl group, Benzopirijiniru group, benzimidazolyl group, _{etc.), - P (= O)} R 2 R 3, halogen atom, amino And thiol groups. Among these, an aryl group or a heteroaryl group is preferable. _{-P (= O) R 2 R} 3 R 2 and _{R 3} in it can be a respective _{R 1} synonymous.

L _{1 in the} general formula (1) represents a substituent. The substituent represented by L ₁ has the same meaning as the substituent represented by R ₁ .

Y ₁ to Y _{8 in} the general formula (2) represent —CR ₂ or a nitrogen atom, and at least one of them represents a nitrogen atom. R ₂ of —CR ₂ represents a hydrogen atom or a substituent.

L ₂ and L _{3 in} the general formula (2) each represent a substituent. Substituents represented by L ₂ and L ₃ are the same meaning as the substituents represented by R ₁ of Formula (1).

Specific examples of the sintering temperature lowering agent include the following compounds.

  As for the sintering temperature reducing agent, for example, the sintering temperature of the conductive ink containing 0.5% by mass of the sintering temperature reducing agent is 40 ° C. or more lower than the sintering temperature of the ink not containing the sintering temperature reducing agent. Such compounds. The sintering temperature may be a temperature at which the sheet resistance of the conductive layer having a thickness of 200 nm and obtained by heating the coating film of the conductive ink for 5 minutes is 4Ω / □ or less.

  As described above, it is considered that the sintering temperature lowering agent promotes detachment of the dispersant from the metal nanoparticles or the metal complex, and promotes sintering (fusion) between the metal nanoparticles or the metal complexes.

  On the other hand, since the weight average molecular weight of the sintering temperature lowering agent is relatively large, volatilization is usually difficult at the temperature required for sintering. That is, the sintering temperature lowering agent is likely to remain in the obtained conductive layer. If the amount of the remaining sintering agent is too large, the conductivity may be reduced. Therefore, the content of the sintering temperature lowering agent is preferably as small as possible within a range in which the effect of promoting the desorption of the dispersant during sintering can be obtained.

  The content of the sintering temperature lowering agent in the conductive ink is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass, and more preferably 0.1 to 5% by mass based on the conductive ink. More preferably, it is １1% by mass. When the content of the sintering temperature lowering agent is 0.01% by mass or more, the sintering temperature in the conductive ink can be sufficiently lowered. When the content of the sintering temperature lowering agent is 10% by mass or less, the amount of the sintering temperature lowering agent remaining in the obtained conductive layer can be reduced, so that an increase in the sheet resistance value of the conductive layer is preferably suppressed. Can.

1-4. Solvent The solvent contained in the conductive ink of the present invention may be any one capable of stably dispersing the above-mentioned components, and may be alcohols, ethers, esters, aliphatic hydrocarbons or aromatic hydrocarbons. It is possible.

  Examples of alcohols include hexanol, heptanol, octanol, cyclohexanol, benzyl alcohol, terpineol and the like. Examples of ethers include diethyl ether, diisobutyl ether, dibutyl ether, methyl-t-butyl ether, methylcyclohexyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetrahydrofuran, tetrahydropyran, , 4-dioxane and the like. Examples of the esters include methyl formate, ethyl formate, butyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, ethyl propionate, butyl propionate, γ-butyrolactone, and the like. Examples of the aliphatic hydrocarbons include n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, cyclohexane, decalin and the like. Examples of the aromatic hydrocarbons include benzene, toluene, xylene, ethylbenzene, n-propylbenzene, i-propylbenzene, n-butylbenzene, mesitylene, chlorobenzene, dichlorobenzene and the like.

  Among these, from the viewpoint of cost and safety, one or more selected from the group consisting of hexanol, terpineol, methyl-t-butyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, n-hexane, and γ-butyrolactone are preferable.

1-5. Others The conductive ink of the present invention may further contain other components as necessary. Examples of other components include a binder resin, a surface tension modifier, a viscosity modifier and the like.

1-6. Physical Properties of Conductive Ink The viscosity of the conductive ink of the present invention at 25 ° C. is preferably 0.001 to 10 Pa · s from the viewpoint of application by, for example, an inkjet method. The viscosity of the ink can be measured at 25 ° C. and 1 rpm using an E-type viscometer.

1-7. Method for Preparing Conductive Ink The conductive ink of the present invention can be obtained by mixing the above-described components. The metal nanoparticles or the metal complex used for preparing the conductive ink may be in a powder form or may be a dispersion dispersed in a medium.

  The dispersion of the metal nanoparticles or the metal complex may include the metal nanoparticles or the metal complex, the dispersant described above, and the solvent described above. Examples of commercial products of such a dispersion include Sigma-Aldrich Co., Ltd., product numbers 741949, 730785; Tech Science Co., Copper, QSI-Nano; Ink Tech Co., Ltd., TEC-IJ-010, and the like. By mixing such a dispersion, a sintering temperature lowering agent, and if necessary, ion-exchanged water, a conductive ink can be obtained.

  The conductive ink of the present invention is preferably used as a material for forming a wiring pattern, an electrode, a reflective film and the like of an electronic device as described later.

2. Conductive Member The conductive member of the present invention has a substrate and a conductive layer provided thereon. The conductive layer is a layer obtained from the conductive ink of the present invention.

2-1. Substrate The substrate may be transparent or opaque. The material of the substrate may be glass or resin.

  Examples of the glass include silica glass, soda-lime silica glass, lead glass, borosilicate glass, and alkali-free glass.

  Examples of the resin include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC), cellulose acetate butyrate, and cellulose acetate propionate (CAP). ), Cellulose esters such as cellulose acetate phthalate and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyetherketone, polyimide, Polyethersulfone (PES), polyphenylene sulfide, polysulfones, polyetherimid , Polyether ketone imide, polyamide, fluorine resin, nylon, polymethyl methacrylate, acrylic or polyarylates, cycloolefin resins.

  Among these, a substrate having a low heat resistance, for example, a substrate mainly composed of a resin having a glass transition temperature of 150 ° C. or lower, preferably 130 ° C. or lower, more preferably 100 ° C. or lower can be used. This is because the sintering temperature can be lowered by using the conductive ink of the present invention. Examples of the substrate having low heat resistance include polyethylene terephthalate and polymethyl methacrylate.

  Although the thickness of the substrate depends on the application, it is, for example, about 1 to 10000 μm, and preferably 10 to 500 μm. As the thin resin film, for example, a film having a thickness of 100 to 500 μm, preferably 100 to 200 μm can be used. Since the sintering temperature can be lowered by using the conductive ink of the present invention, for example, a thin resin film can also be preferably used.

  The shape of the substrate can have various shapes depending on the application. For example, the substrate of the reflective material described below is not limited to a flat plate or a film, but may have an arbitrary shape such as a curved surface.

2-2. Conductive Layer The conductive layer is a layer obtained from the conductive ink of the present invention, and includes a metal and a nitrogen-containing aromatic heterocyclic compound having a weight average molecular weight of 125 or more and 1000 or less.

  The metal contained in the conductive layer has the same meaning as the metal constituting the metal nanoparticles or the metal complex described above, and is preferably gold (Au), silver (Ag) or copper (Cu), and silver (Ag). Is more preferable.

  From the viewpoint of obtaining sufficient conductivity, the content of the metal in the conductive layer is preferably 60% by mass or more, more preferably 90% by mass or more, and more preferably 98% by mass, based on the entire conductive layer. More preferably, it is the above.

  The nitrogen-containing aromatic heterocyclic compound having a weight average molecular weight of 125 or more and 1000 or less contained in the conductive layer may be a residue of the sintering temperature lowering agent contained in the conductive ink of the present invention. This is because the sintering temperature lowering agent promotes the dissociation of the dispersing agent from the metal nanoparticles or metal particles of the metal complex, but is itself likely to remain.

  The content of the nitrogen-containing aromatic heterocyclic compound in the conductive layer is, for example, 10% by mass or less, preferably 5% by mass or less, and more preferably 1% by mass or less based on the entire conductive layer. More preferred. This is because when the content of the nitrogen-containing aromatic heterocyclic compound is equal to or less than a certain value, the increase in the sheet resistance of the conductive layer is small.

  The sheet resistance value of the conductive layer is, for example, 20 Ω / □ or less, and preferably 10 Ω / □ or less. A conductive layer having such a sheet resistance value is suitable, for example, as a wiring pattern or an electrode layer. The sheet resistance value of the conductive layer can be measured by a four-probe constant current application method using a resistivity meter (MCP-T610 manufactured by Mitsubishi Chemical Analytech).

  The thickness of the conductive layer depends on the application, but is preferably, for example, 50 to 10000 nm, and more preferably 100 to 1000 nm.

2-3. Method for Producing Conductive Member The conductive member of the present invention includes: 1) a step of applying the conductive ink of the present invention on a substrate; and 2) a step of forming a conductive layer by heating a coating film of the conductive ink. And

Step 1) The conductive ink of the present invention is applied on a substrate. The method for applying the conductive ink is not particularly limited, but may be an inkjet method, a screen printing method, a spin coating method, a dip method, or the like. Among them, an ink jet method and a screen printing method are preferable because they can be easily applied in a fine pattern.

Step 2) The conductive ink film is heated to form a conductive layer. The heating temperature may be a temperature at which the metal nanoparticles or the metal complex in the conductive ink can be sufficiently fused (sintered) to form a continuous film and the dispersant can be sufficiently removed. ° C, preferably 60-150 ° C, more preferably 80-140 ° C.

  The heating time may be such that the sheet resistance of the coating film after sintering is not more than a certain value, for example, about 1 to 60 minutes, and preferably 5 to 30 minutes.

  In particular, since the conductive ink of the present invention contains a sintering temperature lowering agent, the sintering temperature can be lower than in the conventional case. Therefore, a conductive layer having sufficient conductivity can be formed over a substrate having low heat resistance.

2-4. Use of Conductive Member The conductive member of the present invention is used for a circuit board, an electrode substrate, a reflective material, and the like of various electronic devices such as an organic EL device, a liquid crystal display device, an LED (Light Emitting Diode), a solar cell, and a touch panel. be able to.

  The circuit board may be a single-sided printed wiring board, a double-sided printed wiring board, a multilayer printed wiring board, or a flexible printed wiring board. The circuit board includes a substrate (the above-described substrate) and a wiring pattern (the above-described conductive layer) provided thereon. The thickness of the wiring pattern can be about 100 to 1000 nm.

  The electrode substrate may be a transparent electrode substrate of a liquid crystal display device or a touch panel, an anode electrode substrate or a cathode electrode substrate of an organic EL device, a light incident side electrode substrate or a back surface electrode substrate of a solar cell. The electrode substrate includes a substrate (the above-described substrate) and an electrode (the above-described conductive layer) provided thereon. The thickness of the electrode is about 5 to 20 nm, preferably 5 to 12 nm.

  When the electrode is a transparent electrode, the light transmittance of the transparent electrode at a measurement light wavelength of 550 nm is preferably 50% or more, and more preferably 70% or more.

The light transmittance of the transparent electrode can be measured by the following procedure.
1) The light transmittance of the transparent electrode substrate at a measurement light wavelength of 550 nm is measured using a spectrophotometer (U-3300 manufactured by Hitachi High-Technologies Corporation).
2) As a reference, the light transmittance at a measurement light wavelength of 550 nm of a substrate provided with no transparent electrode is measured in the same manner as described above.
3) The difference between the light transmittances obtained in the above 1) and 2) is defined as "light transmittance of the transparent electrode".

  The reflection material may be a light reflection film or a lamp reflector in a liquid crystal display device. The reflection material includes a substrate (the above-described substrate) and a reflection film (the above-described conductive layer) provided thereon. The thickness of the reflection film can be, for example, about 100 to 1000 nm.

3. Organic EL Device The conductive member of the present invention can be used, for example, as an electrode substrate of an organic EL device.

  The organic EL device of the present invention includes a substrate provided with one of a cathode and an anode, the other of the cathode and the anode, and a light emitting layer disposed between the cathode and the anode. The substrate provided with one of the cathode and the anode can be the conductive member of the present invention.

  FIG. 1 is a schematic sectional view showing an example of the organic EL device. As shown in FIG. 1, the organic EL device 10 includes a transparent substrate (substrate) 13 on which a transparent electrode 11 is provided, a counter electrode 15, and an organic functional layer 17 provided therebetween.

  The transparent substrate 13 provided with the transparent electrode 11 can be the conductive member of the present invention. The transparent electrode 11 can function as an anode (anode). The transparent electrode 11 is the above-described conductive layer, and preferably contains silver as a main component. To lower the resistance of the transparent electrode 11, an auxiliary electrode 19 may be further provided.

  The organic functional layer 17 includes at least a light emitting layer 17c. Specifically, the organic functional layer 17 is formed by stacking a hole injection layer 17a / a hole transport layer 17b / a light emitting layer 17c / an electron transport layer 17d / an electron injection layer 17e in order from the transparent electrode 11 side serving as an anode. Can be configured. The hole injection layer 17a and the hole transport layer 17b may be provided as a hole transport injection layer; the electron transport layer 17d and the electron injection layer 17e may be provided as an electron transport injection layer.

The counter electrode 15 can function as a cathode (cathode). The counter electrode 15 is made of a metal, an alloy, an organic or inorganic conductive compound, a mixture thereof, or the like. Specifically, aluminum, silver, magnesium, lithium, a magnesium / copper mixture, a magnesium / silver mixture, a magnesium / aluminum mixture, a magnesium / indium mixture, indium, a lithium / aluminum mixture, a rare earth metal, ITO, ZnO, TiO ₂ , An oxide semiconductor such as SnO ₂ can be used. The counter electrode 15 is covered with a sealing material 21 so that its end is exposed to the outside.

  In the organic EL device 10 thus configured, the organic functional layer 17 becomes a light emitting region. Then, the generated light (hereinafter, referred to as emission light h) can be extracted from at least the transparent substrate 13 side.

  In the present invention, the transparent substrate 13 provided with the transparent electrode 11 can be used as the conductive member of the present invention. Therefore, a resin substrate having a low heat resistance (for example, a resin film) can be adopted as the transparent substrate 13, so that, for example, the organic EL device 10 can be made flexible, thin, or lightweight.

  Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto.

1. Materials 1-1. Material of conductive ink (1) Dispersion of metal nanoparticles or metal complex (including dispersant and solvent)
Dispersion A: gold (Au) nanoparticles (manufactured by Sigma-Aldrich Co., product number 741949, average particle size: 5 nm)
Dispersion B: Silver (Ag) nanoparticles (manufactured by Sigma-Aldrich, product number 730785, average particle size: 10 nm, silver nanoparticle content: 0.02 mg / mL)
Dispersion C: Copper (Cu) nanoparticles (Tech Science, Copper, QSI-Nano, average particle diameter: 20 nm)
Dispersion D: Silver (Ag) complex (TEC-IJ-010, manufactured by Ink Tech, a silver complex represented by the general formula (3), silver complex content: 15% by mass)
The dispersants contained in Dispersions A to D were all long-chain alkylamines such as octylamine.

(2) firing temperature lowering agent

(3) Comparative compound 1,3,5-triphenylbenzene represented by the following formula

1-2. Substrate Non-alkali glass substrate: Alkali-free glass substrate with a thickness of 1000 μm Polyethylene terephthalate 1: polyethylene terephthalate film with a thickness of 500 μm (Tg: 70 ° C.)
Polyethylene terephthalate 2: polyethylene terephthalate film having a thickness of 200 μm (Tg: 70 ° C.)
PMMA: 500 μm thick polymethyl methacrylate film (Tg: 100 ° C.)

2. Preparation of conductive ink and conductive member < Reference Example 1>
99.5 parts by mass of Dispersion A and 0.5 part by mass of Compound (1) as a sintering temperature lowering agent were mixed to obtain a conductive ink.

  The obtained conductive ink was applied on an alkali-free glass substrate by a spin coating method, and then the coating film was baked at 130 ° C. for 5 minutes to form a conductive layer having a thickness of 200 nm. Thereby, the conductive member 1 was obtained.

< Reference Examples 2-3>
A conductive ink was prepared in the same manner as in Reference Example 1 except that the types of the metal nanoparticles and the firing conditions of the conductive ink were changed as shown in Table 1, and conductive members 2 and 3 were obtained.

< Reference Examples 4 to 9>
A conductive ink was prepared in the same manner as in Reference Example 1 except that the composition of the conductive ink and the firing conditions of the conductive ink were changed as shown in Table 1, and conductive members 4 to 9 were obtained. The content of the metal nanoparticles or the metal complex in the conductive ink was the same as in Reference Example 1.

< Reference Example 10 and Examples 11 to 15>
A conductive ink was prepared in the same manner as in Reference Example 5 except that the type of the sintering temperature lowering agent contained in the conductive ink was changed as shown in Table 1, and conductive members 10 to 15 were obtained.

<Examples 16 to 18>
A conductive ink was prepared in the same manner as in Example 15 except that the type of the substrate was changed as shown in Table 2, and conductive members 16 to 18 were obtained.

<Comparative Examples 1-2>
A conductive ink was prepared in the same manner as in Reference Example 1 except that the firing temperature lowering agent was not added and the firing conditions of the conductive ink were changed as shown in Table 2, and conductive members 19 to 20 were obtained. Was.

<Comparative Examples 3 and 4>
A conductive ink was prepared in the same manner as in Reference Example 2 except that the firing temperature lowering agent was not added, and the firing conditions of the conductive ink were changed as shown in Table 2, to obtain conductive members 21 to 22. Was.

<Comparative Examples 5 to 6>
A conductive ink was prepared in the same manner as in Reference Example 3 except that the firing temperature lowering agent was not added and the firing conditions of the conductive ink were changed as shown in Table 2, and conductive members 23 to 24 were obtained. Was.

<Comparative Example 7>
A conductive ink was prepared in the same manner as in Reference Example 3, except that the comparative compound (1) was used as a firing temperature lowering agent, and the firing conditions of the conductive ink were changed as shown in Table 2. I got

  The sheet resistance of the obtained conductive member was measured by the following method. Further, it was confirmed by mass spectrometry whether or not the firing temperature reducing agent remained in the conductive layer of the obtained conductive member.

<Measurement of sheet resistance>
The sheet resistance value (Ω / □) of the conductive layer of the obtained conductive member was measured using a resistivity meter (MCP-T610 manufactured by Mitsubishi Chemical Analytech Co., Ltd.) by a four-probe method constant current application method.

<Mass spectrometry>
Fragments of the conductive layer of the obtained conductive member were collected and dissolved in nitric acid to obtain a sample solution. Using this solution, mass spectrometry was performed by ICP-MS (SPQ9700 manufactured by Hitachi High-Technologies Corporation).

Table 1 shows the evaluation results of Reference Examples 1 to 10 and Examples 11 to 15; Table 2 shows the evaluation results of Examples 16 to 18 and Comparative Examples 1 to 7.

As shown in Tables 1 and 2, the conductive inks of Reference Examples 1 to 10 and Examples 11 to 18 containing the sintering temperature lowering agent were the conductive inks of Comparative Examples 1 to 6 containing no sintering temperature lowering agent. This shows that a conductive layer having a low sheet resistance can be formed at a lower sintering temperature than the conductive ink of Comparative Example 7 including the comparative compound (1) instead of the ink or the sintering temperature lowering agent.

Specifically, at the baking temperatures of Comparative Examples 1, 3, and 5, the sheet resistance of the conductive layer exceeded 100 Ω / □, suggesting that a continuous film was not formed. On the other hand, in Reference Examples 1 to 3, the sheet resistance value of the conductive layer is lower than 4Ω / □ and the film is a continuous film even at the same baking temperature as Comparative Examples 1, 3 and 5. Is suggested. In addition, it was confirmed that the firing temperature lowering agent remained in the conductive layers of the conductive members obtained in Reference Examples 1 to 10 and Examples 11 to 18.

The comparison of Reference Examples 4 to 9 shows that a sufficient sintering temperature lowering effect can be obtained even when the content of the sintering temperature lowering agent is as small as about 0.1% by mass. On the other hand, it is shown that if the content of the sintering temperature lowering agent is too large, the sheet resistance value of the conductive layer increases.

The comparison between Reference Examples 5 and 10 and Examples 11 to 12 shows that when the sintering temperature-lowering agent contains an imidazole ring or a pyridine ring, the sheet resistance value of the conductive layer is even lower. Further, from the comparison between Examples 11 to 12 and 13 to 14, when the sintering temperature reducing agent has a structure represented by the general formula (1) or (2), the sheet resistance value of the conductive layer is further lower. Is shown.

  The comparison of Examples 15 to 17 shows that a good continuous film can be formed even on a resin substrate having a lower heat resistance than a non-alkali glass substrate, such as polyethylene terephthalate or PMMA. The comparison between Examples 16 and 18 shows that a good continuous film can be formed even when the thickness of the resin substrate is reduced.

<Example 19>
A transparent electrode substrate was obtained in the same manner as in Example 13, except that the amount of the conductive ink applied was adjusted to form a conductive layer having a thickness of 10 nm.

<Example 20>
A reflective material was obtained in the same manner as in Example 14, except that the amount of the conductive ink applied was adjusted to form a conductive layer having a thickness of 300 nm.

  The light transmittance of the conductive member of Example 19 and the reflectance of the conductive member of Example 20 were measured by the following methods.

(Light transmittance)
The light transmittance of the conductive layer of the conductive member was measured according to the following procedure.
1) The light transmittance of the conductive member at a measurement light wavelength of 550 nm was measured using a spectrophotometer (U-3300 manufactured by Hitachi High-Technologies Corporation).
2) As a reference, the light transmittance at a measurement light wavelength of 550 nm of a substrate provided with no conductive layer was measured in the same manner as described above.
3) The difference between the light transmittances obtained in the above 1) and 2) was defined as “light transmittance of the conductive layer”.

(Reflectance)
The light transmittance obtained above was applied to the following equation to obtain a reflectance.
Reflectance (%) = 100−Light transmittance (%)

  The light transmittance of the transparent electrode of Example 19 was 68.0%, and the sheet resistance was 18.5 Ω / □, which was sufficiently suitable for the transparent electrode. The reflectivity of the reflective material of Example 20 was 96.5%, which was sufficiently suitable as a reflective film.

  According to the present invention, it is possible to provide a conductive ink capable of forming a conductive layer having sufficient conductivity even on a substrate having low heat resistance.

Reference Signs List 10 organic EL device 11 transparent electrode 13 transparent substrate 15 counter electrode 17 organic functional layer 17a hole injection layer 17b hole transport layer 17c light emitting layer 17d electron transport layer 17e electron injection layer 19 auxiliary electrode 21 sealing material h emission light

Claims (5)

At least one of the metal nanoparticles and the metal complex, a dispersant, a sintering temperature reducing agent, and a solvent,
The sintering temperature lowering agent, have a structure represented by the following general formula (1) or (2), and a weight average molecular weight, a nitrogen-containing aromatic heterocyclic compound is 150 to 1,000,
Conductive ink.

(In the general formula (1),
X _{1 to} X ₁₀ represent —CR ₁ or a nitrogen atom, and at least one represents a nitrogen atom;
R ₁ represents a hydrogen atom or a substituent;
L ₁ represents a substituent)

(In the general formula (2),
Y ₁ to Y ₈ represents -CR ₂ or a nitrogen atom, provided that at least one represents a nitrogen atom;
R ₂ represents a hydrogen atom or a substituent;
L ₂ and L ₃ each represent a substituent) The substituent represented by L ₁ , L ₂ and L ₃ is an alkyl group, an aryl group, a heteroaryl group or a halogen atom, respectively.
The conductive ink according to claim 1 . The content of the sintering temperature lowering agent is 5 wt% or less than 0.1 wt% with respect to the conductive ink, conductive ink according to claim 1 or 2. The conductive ink according to any one of claims 1 to 3 , wherein the metal constituting the metal nanoparticles or the metal complex is silver. The conductive ink according to any one of claims 1 to 4 , wherein the dispersant includes an aliphatic amine compound.

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