WO2013141172A1

WO2013141172A1 - Conductive ink and production method for base material including conductor

Info

Publication number: WO2013141172A1
Application number: PCT/JP2013/057525
Authority: WO
Inventors: 智柏原; 平社　英之; 米田　貴重
Original assignee: 旭硝子株式会社
Priority date: 2012-03-21
Filing date: 2013-03-15
Publication date: 2013-09-26
Also published as: JP2015110682A; TW201339255A

Abstract

Provided is a conductive ink having good adhesiveness to a base material, and capable of forming a conductor having a small volume resistance. The conductive ink contains: a non-aqueous organic solvent; copper hydride fine particles dispersed in the organic solvent; an alkyl amine having an alkyl group having at least 7 carbon atoms and a boiling point of no more than 250°C; and a silane coupling agent having a specific chemical formula. Also provided is a production method for a base material including a conductor, obtained using this conductive ink.

Description

Method for manufacturing conductive ink and substrate with conductor

The present invention relates to a method for producing a conductive ink and a substrate with a conductor.

As a method for producing a base material with a conductor having a wiring pattern such as a printed wiring board, a conductive ink made of a dispersion liquid in which metal fine particles are dispersed in a solvent is printed on the base material by a method such as inkjet printing. A method of forming a conductor by heating is known.

As the metal fine particles dispersed in the conductive ink, silver (Ag) fine particles have been used from the viewpoint of ensuring high conductivity. However, in the conductor using the silver fine particles, migration of silver ions easily occurs. Problems such as short circuit between wirings may occur, and the reliability of the wiring board may be reduced. In view of this, there has been proposed a technique for improving the reliability of electronic components and wiring boards by using ink containing copper (Cu) fine particles that hardly cause a migration phenomenon instead of silver fine particles. The use of copper fine particles as metal fine particles is more advantageous in terms of cost than silver fine particles.

However, since the copper fine particles are easily oxidized, the ink containing the copper fine particles has a problem that the volume resistivity of the formed conductor increases and the conductivity decreases.

In order to suppress an increase in the volume resistivity of the conductor, a method of obtaining a dispersion of copper hydride fine particles that is difficult to be oxidized in the atmosphere is disclosed (for example, see Patent Document 1). In this method, an alkylamine such as dodecylamine and a water-insoluble organic liquid are added to an aqueous solution containing copper (II) ions having a pH of 3 or less, and the copper (II) ions are reduced with NaBH ₄ or the like. By separating the organic phase, a copper hydride fine particle dispersion can be obtained. In this method, fine particles of copper hydride produced by reduction of copper (II) ions in the aqueous phase are taken into the organic phase by coordination of alkylamine on the surface, thereby producing the produced copper hydride. Is inhibited from changing to copper (II) ions and copper (II) oxide in water.

When producing a substrate with conductor using the copper hydride fine particle dispersion thus obtained, the copper hydride fine particles are applied by applying the dispersion on a substrate made of glass or resin and then heating. The copper hydride contained therein is converted to metallic copper, the alkylamine on the surface of the fine particles is desorbed, and the metallic copper fine particles are melted and bonded together to form a conductor.

However, when the conductive ink composed of the copper hydride fine particle dispersion described in Patent Document 1 is used, the adhesion between the conductor and the base material is not sufficient, resulting in poor wiring adhesion. There was a problem that the reliability of the substrate was lowered.

In order to improve the adhesion between the conductive ink and the base material of the conductor, it is conceivable to add a resin to the conductive ink. Usually, however, the conductive ink contains a large amount of a dispersant and a surface protective agent. Therefore, it is difficult to add a resin, and even if a resin can be added, the resin is decomposed together with the dispersant and the surface protective agent in the process of making a conductor, and a sufficient effect cannot be obtained.

From such a viewpoint, copper-based nanoparticles prepared without using a dispersant as a copper conductor ink capable of forming a conductive layer having high adhesion to the substrate, and a thermosetting resin before thermosetting And a conductive ink containing a dispersion medium have been proposed (see, for example, Patent Document 2). However, since the ink described in Patent Document 2 contains a resin component, there is a problem that the volume resistivity of the conductor tends to increase.

International Publication No. 04/110925 Japanese Unexamined Patent Publication No. 2011-142052

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a conductive ink that can form a conductor having good adhesion to a substrate and having a small volume resistivity. Moreover, this invention aims at provision of the base material with a conductor which has a favorable adhesiveness with a base material and a small volume resistivity obtained using the said conductive ink.

The present invention provides the following conductive ink and method for producing a substrate with a conductor.
<1> a water-insoluble organic solvent;
Copper hydride fine particles dispersed in the organic solvent;
An alkylamine having an alkyl group having 7 or more carbon atoms and a boiling point of 250 ° C. or lower;
Formula (1): R ¹ _m R ² _n SiR ³ _4-mn
(In the formula (1), R ^1, glycidoxy group, an isocyanate group, a mercaptoalkyl group, an aminoalkyl group, N- aminoalkyl - is a monovalent organic group selected from an amino group, R ² Is an alkyl group or a hydrogen atom, R ³ is an alkoxyl group, m is an integer of 1 to 3, n is an integer of 0 to 2, and m + n is 3 or less. ): R ⁴ ₃ SiR ⁵ —S _k —R ⁵ SiR ⁴ ₃
(In the formula (2), R ⁴ is an alkoxyl group, R ⁵ is an alkylene group, and k is an integer of 1 to 4),
A conductive ink comprising:

<2> The conductive ink according to <1>, wherein a content ratio of the copper hydride fine particles is 10 to 50% by mass.
<3> The conductive ink according to <1> or <2>, wherein the content ratio of the alkylamine is 2 to 10% by mass.
<4> The conductive ink according to any one of <1> to <3>, wherein a content ratio of the silane coupling agent is 0.01 to 2.00% by mass with respect to the organic solvent.
<5> The conductive ink according to any one of <1> to <4>, wherein an average primary particle diameter of the copper hydride fine particles is 100 nm or less.

<6> a step of preparing a substrate;
Forming a conductive ink coating layer according to any one of <1> to <5> on the substrate;
And a step of heating the coating layer to form a conductor containing copper.
The conductor formed in the step of forming the conductor containing copper is a conductor mainly composed of copper. Here, “a conductor mainly composed of copper” means that copper is most contained among the elements constituting the conductor.

According to the conductive ink of the present invention, it is possible to form a conductor having good adhesion to the substrate, low volume resistivity, and excellent conductivity. Moreover, according to the manufacturing method of the base material with a conductor of this invention, the base material with a conductor which has a favorable adhesiveness and a small volume resistivity on a base material is obtained.

FIGS. 1A to 1D are views for explaining a mechanism for improving adhesion to a substrate by a silane coupling agent used in the conductive ink of the present invention. FIGS. 2 (a) to 2 (d) are diagrams showing the behavior of a silane coupling agent having a higher bondability to metal than alkylamine.

Hereinafter, embodiments of the present invention will be described. Note that the present invention is not limited to the embodiments described below.

[Conductive ink]
A conductive ink according to an embodiment of the present invention includes a water-insoluble organic solvent, copper hydride fine particles dispersed in the organic solvent, an alkylamine having an alkyl group having 7 or more carbon atoms and a boiling point of 250 ° C. or less. And a silane coupling agent having a specific chemical formula.

According to the conductive ink of the embodiment of the present invention, since the silane coupling agent having a specific chemical formula is blended together with the alkylamine which is a dispersant for the copper hydride fine particles, it has excellent adhesion to the substrate, A conductor having good conductivity can be formed. Hereinafter, each component contained in the conductive ink of the embodiment will be described.

<Copper hydride fine particles>
The copper hydride fine particles become a conductive component of the conductive ink of the embodiment.
As the copper hydride fine particles, it is preferable to use copper hydride fine particles in a copper hydride fine particle dispersion produced by a method to be described later, but it is not limited thereto. In addition, since the copper hydride fine particle dispersion produced by the method described later contains not only the copper hydride fine particles but also the alkylamine having a boiling point of 250 ° C. or less as a dispersant, the copper hydride fine particles. The conductive ink of the present invention can be obtained by using the dispersion as it is. A method for preparing the conductive ink of the present invention using the copper hydride fine particle dispersion will be described later.

The average primary particle size of the copper hydride fine particles (primary particles) is preferably 5 to 100 nm, more preferably 5 to 70 nm, and particularly preferably 5 to 35 nm. If the average primary particle diameter of the copper hydride fine particles is 100 nm or less, the sinterability at a low temperature, which is a feature of the fine particles, becomes good, and the volume resistivity of the obtained conductor can be lowered. Moreover, if the average primary particle diameter of the copper hydride fine particles is 5 nm or more, the copper hydride fine particles can be stably dispersed.
The average primary particle size of the copper hydride fine particles was determined by measuring the particle size of 100 randomly extracted fine particles using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). This is a value obtained by averaging the values of.

The content (concentration) of copper hydride fine particles in the conductive ink is preferably 10 to 50% by mass, more preferably 20 to 40% by mass. In the conductive ink, when the content (concentration) of the copper hydride fine particles as a solid content is 10% by mass or more, it is easy to form a conductor having a sufficient thickness. If the content ratio of the copper hydride fine particles is 50% by mass or less, it is easy to control ink characteristics such as viscosity and surface tension, and it becomes easy to form a conductor.

<Method for producing copper hydride fine particle dispersion>
The dispersion containing the copper hydride fine particles of the embodiment is preferably obtained by a method of reducing a copper (II) salt with a hydride-based reducing agent in the presence of an alkylamine (B) in a solvent (A). Hereinafter, this manufacturing method will be described.

As the copper (II) salt, a salt capable of forming a copper (II) amine complex with the alkylamine (B) can be used. The copper (II) salt may be an anhydride or a hydrate.
The copper (II) salt is represented as CuX ₂ or CuY. Here, X is a monovalent base and Y is a divalent base. When this copper (II) salt is reduced by a hydride-based reducing agent to produce copper hydride fine particles, it is considered that X contained in the copper (II) salt is liberated as HX and Y as H ₂ Y. In the present invention, a salt having a boiling point or decomposition point of this liberated HX or H ₂ Y (hereinafter also referred to as free acid) of 150 ° C. or less is preferable. This is because the free acid is likely to volatilize during heating during conductor formation, and a conductor having a low volume resistivity is likely to be formed.

Examples of the copper (II) salt include copper oxalate (II) (decomposition point of liberated oxalic acid: 189.5 ° C.), copper chloride (II) (boiling point of liberated hydrochloric acid 110 ° C.), copper acetate (II ) (Boiling point of free acetic acid: 118 ° C.), copper (II) formate (boiling point of free formic acid: 100.75 ° C.), copper (II) nitrate (boiling point of free nitric acid: 82.6 ° C.), copper sulfate (II) (boiling point of free sulfuric acid: 290 ° C), copper (II) tartrate (boiling point of free tartaric acid, decomposition point: unknown), copper (II) citrate (decomposition point of free citric acid: 175 ° C) , Copper carbonate (II) (boiling point of free carbonic acid, decomposition point: unknown), copper (II) oleate (boiling point of free oleic acid: 193 ° C./100 Pa, decomposition point: 400 ° C. or higher). Of these, copper (II) acetate, copper (II) formate, copper (II) nitrate, and copper (II) carbonate are preferred.
A copper (II) salt may be used individually by 1 type, and may use 2 or more types together.

Examples of hydride-based reducing agents include NaBH ₄ , LiBH ₄ , Zn (BH ₄ ) ₂ , (CH ₃ ) ₄ NBH (OCOCH ₃ ) ₃ , NaBH ₃ CN, LiAlH ₄ , (i-Bu) ₂ AlH (DIBAL ), LiAlH (t-BuO) ₃ , NaAlH ₂ (OCH ₂ CH ₂ OCH ₃ ) ₂ (Red-Al), and the like. Among these, at least one selected from the group consisting of NaBH ₄ , LiBH ₄ , and NaBH ₃ CN is preferable because the reduction rate, which is important for controlling the particle size of the copper hydride fine particles, can be easily adjusted.
A hydride type reducing agent may be used individually by 1 type, and may use 2 or more types together.

The solvent (A) is a solvent having an SP value of 8 to 12. When the SP value is 8 to 12, the compatibility between the solvent (A) and water is low, and the mixing of water into the reaction system can be suppressed. Thereby, it can suppress that the hydride type | system | group reducing agent melt | dissolved in the solvent (A) reacts with water and inactivates.
The SP value of the solvent (A) is more preferably 8.5 to 9.5.

Examples of the solvent (A) include cyclohexane (SP value 8.2), isobutyl acetate (SP value 8.3), isopropyl acetate (SP value 8.4), butyl acetate (SP value 8.5), and tetrachloride. Carbon (SP value 8.6), ethylbenzene (SP value 8.8), xylene (SP value 8.8), toluene (SP value 8.9), ethyl acetate (SP value 9.1), tetrahydrofuran (SP value) 9.1), benzene (SP value 9.2), chloroform (SP value 9.3), methylene chloride (SP value 9.7), carbon disulfide (SP value 10.0), acetic acid (SP value 10. 1), pyridine (SP value 10.7), dimethylformamide (SP value 12.0) and the like.

Further, as the solvent (A), a solvent inert to the hydride reducing agent used for the reduction reaction is used. That is, as the solvent (A), a solvent that is not reduced by the hydride reducing agent used in the reduction reaction or a solvent that does not have active hydrogen is preferable because it can suppress the inactivation of the hydride reducing agent.

As the solvent (A), hydrocarbons such as toluene, xylene, benzene, etc .; ethers such as tetrahydrofuran; ethyl acetate, from the viewpoint of easy control of the reduction reaction and the dispersibility of the produced copper hydride fine particles Esters such as isopropyl acetate and isobutyl acetate are preferred, and toluene and xylene are particularly preferred.
A solvent (A) may be used individually by 1 type, and may use 2 or more types together.

Further, hydride-based reducing agents have different reducing power depending on the type. For example, NaBH ₄ does not reduce esters, whereas LiAlH ₄ reduces esters. Therefore, an appropriate solvent is selected from the solvent (A) depending on the type of hydride-based reducing agent used.

The alkylamine (B) is an alkylamine having an alkyl group having 7 or more carbon atoms and having a boiling point of 250 ° C. or lower.
If the carbon number of the alkyl group in the alkylamine (B) is 7 or more, the dispersibility of the produced copper hydride fine particles will be good. In the present invention, since the reaction field is an organic phase, it is not necessary to use an alkylamine having a large carbon number for the purpose of protection from water. The number of carbon atoms of the alkyl group in the alkylamine (B) is preferably 11 or less from the viewpoint of suppressing the boiling point from becoming too high.

If the boiling point of the alkylamine (B) is 250 ° C. or lower, when the conductor is formed using the conductive ink, the alkylamine (B) is detached from the surface of the fine particles even when heated at 150 ° C. or lower, and volatilizes. Low rate conductors can be formed. The boiling point of the alkylamine (B) is preferably 250 ° C. or less, and more preferably 200 ° C. or less, from the viewpoint of desorption and volatility during heating. Moreover, the boiling point of the alkylamine (B) is usually preferably 150 ° C. or higher from the viewpoint that the alkyl group has 7 or more carbon atoms.

The alkyl group of the alkylamine (B) is preferably a linear alkyl group from the viewpoint of dispersion stability of the obtained copper hydride fine particles. However, the alkyl group of the alkylamine (B) may be a branched alkyl group.

Examples of the alkylamine (B) include n-heptylamine (alkyl group having 7 carbon atoms and a boiling point of 157 ° C.), n-octylamine (alkyl group having 8 carbon atoms and a boiling point of 176 ° C.), n-nonylamine (carbon of the alkyl group). (9, boiling point: 201 ° C.), 1-aminodecane (alkyl group having 10 carbon atoms, boiling point: 220 ° C.), 1-aminoundecane (alkyl group having 11 carbon atoms, boiling point: 242 ° C.), n-heptylamine, n- Octylamine is more preferred.
An alkylamine (B) may be used individually by 1 type, and may use 2 or more types together.

In such a method for producing a copper hydride fine particle dispersion, copper hydride fine particles are generated by reducing a copper (II) salt with a hydride-based reducing agent in the presence of an alkylamine (B). In the presence of alkylamine (B), after alkylamine (B) is coordinated to copper (II) to form a copper (II) amine complex, the copper (II) amine complex is formed by a hydride reducing agent. Reduced. Thereby, formation of the copper hydride lump by rapid reduction of the copper (II) salt can be suppressed, and copper hydride fine particles in which alkylamine (B) is coordinated on the surface of the copper hydride fine particles are generated.

Moreover, in this manufacturing method, since the solubility with respect to the solvent (A) of a hydride type | system | group reducing agent is not so high, most of a hydride type | system | group reducing agent exists in a solvent (A) in a solid state, and a part is solvent (A ) Is dissolved in. When the hydride reducing agent dissolved in the solvent (A) reduces and consumes the copper (II) salt, the hydride reducing agent present in a solid state gradually dissolves in the solvent (A). And since the hydride type | system | group reducing agent which melt | dissolved in the solvent (A) gradually contributes to a reduction reaction, a reduction reaction does not advance rapidly but a copper hydride microparticles | fine-particles produce | generate stably.
The produced copper hydride fine particles can be dispersed in the solvent (A) because the alkylamine (B) is coordinated on the surface.

The order of adding the copper (II) salt, hydride reducing agent, and alkylamine (B) to the solvent (A) is preferably the order of alkylamine (B), copper (II) salt, and hydride reducing agent. Thereby, after the said copper (II) amine complex is formed, reduction | restoration by the hydride type | system | group reducing agent of this copper (II) amine complex becomes easy to advance, and copper hydride microparticles | fine-particles are obtained more stably.
However, the order of adding the copper (II) salt, the hydride reducing agent, and the alkylamine (B) to the solvent (A) is the order in which the reduction reaction with the hydride reducing agent proceeds in the presence of the alkylamine (B). If there is, the order is not limited. For example, the alkylamine (B), the hydride reducing agent, and the copper (II) salt may be added to the solvent (A) in this order. In this case, the hydride reducing agent is present in a solid state in the solvent (A), and after the copper (II) amine complex is formed in the solvent (A), the copper (II) present in the solid state. ) Amine complex reacts with hydride reducing agent. Further, a hydride reducing agent, an alkylamine (B), and a copper (II) salt may be added in this order.

The reduction reaction with the hydride-based reducing agent may be performed while stirring the solvent (A). This facilitates the reduction reaction.
The reaction temperature is preferably 0 to 80 ° C, more preferably 15 to 50 ° C. If reaction temperature is 0 degreeC or more, a reductive reaction will advance easily. If reaction temperature is 80 degrees C or less, the dispersibility of the copper hydride microparticles in the obtained copper hydride microparticle dispersion liquid will be favorable, As a result, it will become easy to form a conductor with small volume resistivity.

The addition amount of the copper (II) salt is preferably 0.1 × 10 ⁻³ mol or more with respect to 1 g of the solvent (A) from the viewpoint of productivity of copper hydride fine particles, and preferably 0.15 × 10 ^−3. Mole or more is more preferable, and 0.25 × 10 ⁻³ mol or more is particularly preferable. Further, the addition amount of the copper (II) salt is preferably 0.65 × 10 ⁻³ mol or less with respect to 1 g of the solvent (A) from the viewpoint of easy control of the reduction reaction, and 0.6 × 10 ^{− 3} mol or less is more preferable, and 0.5 × 10 ⁻³ mol or less is particularly preferable.

The addition amount of the alkylamine (B) is 0.2 × 10 ^{− with} respect to 1 g of the solvent (A) because the dispersibility of the copper hydride fine particles in the obtained copper hydride fine particle dispersion becomes good. ³ mol or more is preferable, 0.25 × 10 ⁻³ mol or more is more preferable, and 0.3 × 10 ⁻³ mol or more is particularly preferable. In addition, if the amount of alkylamine (B) added is excessive, alkylamine (B) that could not be coordinated to the copper (II) salt may remain at the time of conductor formation and increase the volume resistivity of the conductor. is there. Therefore, the upper limit of the amount of the alkylamine (B) is preferably 0.75 × 10 ⁻³ mol or less, more preferably 0.7 × 10 ⁻³ mol or less, with respect to 1 g of the solvent (A). 6 × 10 ⁻³ mol or less is particularly preferable.

The addition amount of the hydride-based reducing agent is preferably 0.25 × 10 ⁻³ mol or more with respect to 1 g of the solvent (A) from the viewpoint of the yield of copper hydride fine particles, preferably 0.3 × 10 ⁻³ mol. The above is more preferable, and 0.35 × 10 ⁻³ mol or more is particularly preferable. The amount of the hydride reducing agent added is preferably 0.65 × 10 ⁻³ mol or less with respect to 1 g of the solvent (A) from the viewpoint of easy control of the reduction reaction, preferably 0.55 × 10 ^−3. The molar amount is more preferably less than or equal to 0.5 × 10 ⁻³ mol or less.

The molar ratio of the copper (II) salt and the alkylamine (B) added to the solvent (A) (hereinafter referred to as Cu / B) is that the dispersion stability of the produced copper hydride fine particles becomes good. 1.8 or less, 1.4 or less is more preferable, and 1.2 or less is particularly preferable. In addition, the molar ratio (Cu / B) is preferably 0.64 or more, and preferably 0.85 or more from the viewpoint of easy desorption and volatilization of the alkylamine (B) from the surface of the fine particles by heating during conductor formation. Is more preferable.

The molar ratio of copper (II) salt and hydride reducing agent (R) added to the solvent (A) (hereinafter referred to as Cu / R) is preferably 1.42 or less from the viewpoint that the reduction reaction easily proceeds. 1.3 or less is more preferable, and 1.2 or less is particularly preferable. Further, the molar ratio (Cu / R) is preferably 0.7 or more, more preferably 0.8 or more, and particularly preferably 0.9 or more, from the viewpoint of easy control of the reduction reaction.

Thus, a copper hydride fine particle dispersion in which copper hydride fine particles (primary particles) having an average primary particle size of 100 nm or less, more preferably 5 to 70 nm, and particularly preferably 5 to 35 nm are dispersed in the solvent (A) is obtained. . The average primary particle diameter of the copper hydride fine particles can be adjusted by the addition amount of the alkylamine (B) and the addition amount of the hydride reducing agent. By increasing the addition amount of the alkylamine (B), the average primary particle diameter of the copper hydride fine particles tends to decrease. Moreover, there exists a tendency for the average primary particle diameter of a copper hydride microparticle to become small by reducing the addition amount of a hydride type | system | group reducing agent.

The concentration of the copper hydride fine particles as a solid content in the obtained copper hydride fine particle dispersion is preferably 1 to 6% by mass, more preferably 2.5 to 4.5% by mass, based on 100% by mass of the entire dispersion. . If the solid content concentration of the copper hydride fine particle dispersion is less than 1% by mass, the concentration process takes time, and the productivity may be reduced. When the solid content concentration of the copper hydride fine particle dispersion exceeds 6% by mass, the dispersion stability of the copper hydride fine particles in the dispersion may be lowered.

<Water-insoluble organic solvent>
As the water-insoluble organic solvent of the conductive ink of the embodiment, the solvent of the copper hydride fine particle dispersion obtained by the above production method (for example, the solvent (A) which is a solvent having an SP value of 8 to 12) is used. Other solvents (that is, a solvent having an SP value of less than 8 or more than 12, hereinafter referred to as solvent (C)) may be used. That is, the conductive ink of the embodiment can be obtained by adjusting the solid content concentration and the viscosity of the copper hydride fine particle dispersion produced by the production method. In addition, by replacing the solvent of the copper hydride fine particle dispersion obtained by the above production method, that is, for example, replacing the solvent (A) with the solvent (C), and further adjusting the solid content concentration and viscosity A conductive ink in the form can be obtained. In either case, the conductive ink of the embodiment contains the protective agent that functions to disperse the copper hydride fine particles in the solvent, or the alkylamine (B) that is a dispersant as it is.

As a method of replacing the solvent (A) of the copper hydride fine particle dispersion with the solvent (C), a known solvent replacement method can be employed. For example, the solvent (C) is added while concentrating the solvent (A) under reduced pressure. The method of doing is mentioned.

As the solvent (for example, the solvent (A) or the solvent (C)) of the conductive ink of the present invention, a water-insoluble organic solvent is used. In the present specification, “water-insoluble” means that the amount dissolved in 100 g of water at room temperature (20 ° C.) is 0.5 g or less. The solvent is preferably an organic solvent having a small polarity from the viewpoint of affinity with the alkylamine (B). The solvent is preferably a solvent that does not cause thermal decomposition by heating when forming the conductor.

Examples of the solvent include decane (insoluble in water), dodecane (insoluble in water), tetradecane (insoluble in water), decene (insoluble in water), dodecene (insoluble in water), tetradecene (in water). Insoluble.), Dipentene (dissolved in 100 g of water 0.001 g (20 ° C.)), α-terpineol (dissolved in 100 g of water 0.5 g (20 ° C.)), mesitylene (insoluble in water), etc. Is mentioned. Of these, α-terpineol, decane, dodecane, and tetradecane are preferable because the drying property and the coating property of the conductive ink can be easily controlled.
Only 1 type may be used for a solvent and it may use 2 or more types together.
The content of the solvent contained in the conductive ink is preferably 50 to 90% by mass, and more preferably 60 to 80% by mass.

<Alkylamine>
In the conductive ink of the embodiment, alkylamine is contained as a dispersant for dispersing copper hydride fine particles, which is a conductive component, in the solvent. When the copper hydride fine particle dispersion produced by the production method is used as it is or by replacing the solvent to obtain the conductive ink of the embodiment, the alkylamine (B) added in the production process is used in the conductive ink. Become a dispersant. The conductive ink of the embodiment is not limited to such an aspect, and an alkylamine may be added as a dispersant separately.

The alkylamine as a dispersant has an alkyl group having 7 or more carbon atoms and has a boiling point of 250 ° C. or lower. If the carbon number of the alkyl group in the alkylamine is 7 or more, the dispersibility of the copper hydride fine particles will be good. The number of carbon atoms of the alkyl group of the alkylamine is preferably 11 or less from the viewpoint of suppressing the boiling point from becoming too high.

If the boiling point of the alkylamine is 250 ° C. or lower, when the conductor is formed using the conductive ink, the alkylamine is desorbed from the surface of the copper hydride fine particles even when heated at 150 ° C. or lower, and volatilizes. Can be formed. The boiling point of the alkylamine is preferably 250 ° C. or less, and more preferably 200 ° C. or less, from the viewpoint of desorption and volatility during heating. The boiling point of the alkylamine is usually preferably 150 ° C. or higher from the viewpoint that the alkyl group has 7 or more carbon atoms.

The alkyl group of the alkylamine is preferably a linear alkyl group from the viewpoint of dispersion stability of the copper hydride fine particles, but may be a branched alkyl group.

Alkylamines include n-heptylamine (boiling point 157 ° C), n-octylamine (boiling point 176 ° C), n-nonylamine (boiling point 201 ° C), 1-aminodecane (boiling point 220 ° C), 1-aminoundecane (boiling point 242). ° C), and n-heptylamine and n-octylamine are more preferable. An alkylamine may be used individually by 1 type, and may use 2 or more types together.

The content of alkylamine is preferably 2 to 10% by mass of the entire conductive ink. If the content of the alkylamine is within the above range, good dispersibility of the copper hydride fine particles can be obtained.

<Silane coupling agent>
The silane coupling agent contained in the conductive ink according to the embodiment includes a functional group having a binding property (reactivity) to an organic material and a functional group having a binding property (reactivity) to an inorganic material in a molecule. The silane compound having two or more kinds of functional groups, and serves as an intermediary for binding the organic material and the inorganic material.

As a silane coupling agent,
Formula (1): R ¹ _m R ² _n SiR ³ _4-mn , or Formula (2): R ⁴ ₃ SiR ⁵ —S _k —R ⁵ SiR ⁴ ₃
The silane compound represented by these can be used.

Here, in the formula (1), R ¹ is a monovalent organic group selected from a glycidoxyalkyl group, an isocyanate alkyl group, a mercaptoalkyl group, an aminoalkyl group, and an N-aminoalkyl-aminoalkyl group, R ² is an alkyl group or a hydrogen atom, and R ³ is an alkoxyl group. The number of carbon atoms of the alkyl group in R ¹ and R ² is preferably 1 to 6. Further, the alkoxy group of R ³ preferably has 1 to 4 carbon atoms, particularly preferably a methoxy group or an ethoxy group. M is an integer from 1 to 3, n is an integer from 0 to 2, and m + n is 3 or less.
Specific examples of such silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3 -Aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltriethoxysilane and the like.

In the formula (2), R ⁴ is an alkoxyl group having 1 to 4 carbon atoms, R ⁵ is an alkylene group having 1 to 4 carbon atoms, and k is an integer of 1 to 4.
Specific examples of such silane coupling agents include bis (triethoxysilylpropyl) tetrasulfide.

The content of the silane coupling agent is preferably 0.01 to 2.00% by mass, more preferably 0.02 to 2.00% by mass with respect to the organic solvent. . When the content of the silane coupling agent is less than 0.01% by mass, the effect of improving the adhesion of the conductor formed by the conductive ink to the base material cannot be obtained. In addition, when the content of the silane coupling agent exceeds 2.00% by mass, excess silane coupling agent is present between the copper hydride particles, the specific resistance of the wiring is increased, and the conductivity is increased. There is a risk of failure, which is not preferable.

The conductive ink of the embodiment of the present invention may contain other additives in addition to the above-described water-insoluble organic solvent, copper hydride fine particles, alkylamine as a dispersant, and silane coupling agent. . Examples of other additives include antifoaming agents, wetting and dispersing agents, leveling agents, anti-drying agents, rheology control agents, and adhesion imparting aids.

The concentration of the solid content (copper hydride fine particles) of the conductive ink of the embodiment varies depending on the required viscosity, but is preferably 10 to 50% by mass, more preferably 20 to 40% by mass.

The viscosity of the conductive ink of the embodiment is preferably 5 to 60 mPa · s, and more preferably 8 to 40 mPa · s. If the viscosity of the conductive ink is 5 mPa · s or more, the ink can be ejected with high accuracy. If the viscosity of the conductive ink is 60 mPa · s or less, it can be applied to almost all available inkjet heads.

The surface tension of the conductive ink of the embodiment is preferably 18 to 45 dyn / cm, and more preferably 20 to 40 dyn / cm. If the surface tension of the conductive ink is 18 dyn / cm or more, the ink can be ejected with high accuracy. If the surface tension of the conductive ink is 45 dyn / cm or less, it can be applied to almost all available inkjet heads.
In this specification, the viscosity of the conductive ink is a value measured at 20 ° C. with a B-type viscometer (manufactured by Toki Sangyo Co., Ltd., apparatus name: TVB35L). The surface tension is a value measured by a surface tension meter (manufactured by Kyowa Interface Science Co., Ltd., device name: DY-500).

In the conductive ink of the embodiment, the alkylamine bonded to and coordinated with the copper hydride fine particles is released by heating. Then, the copper hydride from which the alkylamine has been released is changed into, for example, metal copper by heating at 60 ° C. or higher, and the metal copper fine particles thus produced are melted and bonded to form a conductor.

According to the conductive ink of the embodiment of the present invention, it is possible to form a conductor having good adhesion to the base material, small volume resistivity and excellent conductivity. This is because the silane coupling agent having a specific functional group contained in the conductive ink of the embodiment has sufficient binding properties to both a base material made of an organic material such as a resin and copper hydride fine particles. In addition, it is presumed that the binding property to the copper hydride fine particles is lower than that of the alkylamine as the dispersant.

Hereinafter, the mechanism for improving the adhesion to the substrate will be described by taking 3-mercaptopropyltrimethoxysilane as an example of the silane coupling agent having a specific functional group used in the present invention. The binding property to the copper hydride fine particles can also be referred to as affinity or reactivity with the metal surface.

3-mercaptopropyltrimethoxysilane has a methoxy group which is a hydrolyzable group having affinity and reactivity with a metal which is an inorganic material, and a mercapto group which is an organic functional group which has a binding property with an organic material.
In 3-mercaptopropyltrimethoxysilane (hereinafter, referred to as silane coupling agent S1), the binding ability of methoxy group to copper hydride fine particles is smaller than the binding ability of amino group to copper hydride fine particles of alkylamine. Therefore, in the state of the conductive ink, as shown in FIG. 1A, the alkylamine 2 as a dispersant is coordinated and coordinated around the copper hydride fine particles 1. Therefore, the copper hydride fine particles 1 exist in a stable dispersion state in the solvent. Without such a dispersant coordination, the copper hydride fine particles 1 tend to aggregate and precipitate. The silane coupling agent S1 exists in a solvent in a free state.

In the state where the conductive ink is applied and dried (conductive ink coating layer), as shown in FIG. 1B, the copper hydride fine particles 1 whose outer periphery is protected by the alkylamine 2 are present in the coating layer. The silane coupling agent S1 is bonded to the substrate 3 through a mercapto group.

Then, in the middle of heating, as shown in FIG. 1 (c), the alkylamine 2 begins to desorb from the outer periphery of the copper hydride fine particles 1, and at the same time, the silane coupling agent S1 passes through the methoxy group and the copper hydride fine particles 1 To join.

In the state after heating, as shown in FIG. 1 (d), the alkylamine 2 is completely desorbed from the surface of the copper hydride fine particles 1 and volatilizes. And the copper hydride microparticles | fine-particles 1 are ensured adhesiveness with the base material 3 by couple | bonding with the base material 3 through the silane coupling agent S1 couple | bonded with the outer periphery instead of the alkylamine 2. FIG. At the same time, the copper hydride is changed to metallic copper, and the produced metallic copper fine particles are melted and bonded together to form a conductor having good adhesion to the substrate 3.

On the other hand, when the silane coupling agent S2 having a hydrolyzable group larger than the amino group of the alkylamine is used for binding to the copper hydride fine particles, the volume of the obtained conductor is as follows. It is estimated that the resistivity increases.

That is, when the binding property of the silane coupling agent S2 to the copper hydride fine particles is larger than the binding property of the amino group of the alkylamine, as shown in FIG. A silane coupling agent S2 having a higher binding property is bonded around the copper hydride particles, and the copper hydride fine particles 1 are dispersed in the solvent in this state. Alkylamine 2 as a dispersant is present in the solvent in a free state.

In a state where the conductive ink is applied and dried (conductive ink coating layer), as shown in FIG. 2B, the copper hydride fine particles 1 in a state where the silane coupling agent S2 is bonded to the outer periphery are formed. , Present in the coating layer. Since the silane coupling agent S2 also has bonding properties with the base material 3, the adhesion of the copper hydride fine particles 1 to the base material 3 is ensured through the silane coupling agent S2. Alkylamine 2 is also present in the coating layer.

In the middle of heating, as shown in FIG. 2C, the alkylamine 2 present in the coating layer volatilizes, but the silane coupling agent S2 does not desorb from the outer periphery of the copper hydride fine particles 1 and remains as it is. Present around the microparticles 1. Then, after the heating, as shown in FIG. 2 (d), the silane coupling agent S 2 remains on the surface of the copper hydride fine particles 1. Therefore, melting and bonding between the metal copper fine particles generated from the copper hydride are hindered by the silane coupling agent S2, so that the volume resistivity of the formed conductor is increased and a conductor having good conductivity is obtained. Absent.

[Substrate with conductor and method for producing the same]
The base material with a conductor according to an embodiment of the present invention has a conductor formed by heating the above-described conductive ink coating layer on the base material. This base material with conductor is formed by applying the conductive ink of the embodiment to the surface of the base material to form a coating layer, and then heating to remove volatile components and melt the metallic copper fine particles changed from copper hydride. Can be manufactured by bonding to form a conductor.

As the substrate, a film substrate or substrate made of plastic such as glass substrate, polyimide, polyethylene phthalate (PET), polyethylene naphthalate (PEN), or substrate made of fiber reinforced composite material (for example, glass fiber reinforced plastic substrate). ) Etc. can be used.

Examples of the method for applying the conductive ink include known methods such as an inkjet printing method, a screen printing method, a roll coating method, an air knife coating method, a blade coating method, a bar coating method, a gravure coating method, a die coating method, and a slide coating method. It is done. Of these, inkjet printing is particularly preferred.

In the case of inkjet printing, from the viewpoint of easy formation of a conductor having a desired pattern, the diameter of the ink ejection holes is set to 0.5 to 100 μm, and the diameter of the conductive ink when adhered on the substrate is set to 1 to 100 μm. It is preferable to adjust to.

The heating temperature after applying the conductive ink on the substrate is preferably 60 to 300 ° C, more preferably 60 to 150 ° C.
The heating time is the time that the conductor can be formed by volatilizing the water-insoluble organic solvent that is the solvent of the conductive ink, the acid liberated from the copper (II) salt, and the alkylamine released from the surface of the copper hydride fine particles. What is necessary is just to set according to heating temperature.
Moreover, it is preferable to perform heating in inert atmosphere, such as nitrogen atmosphere, from the point which is easy to suppress the oxidation of the conductor to form.

The thickness of the conductor thus formed is preferably from 0.1 to 5.0 μm, more preferably from 0.2 to 2.0 μm, from the viewpoint of ensuring stable conductivity and easily maintaining the wiring shape. The volume resistivity of the conductor is preferably 3 to 35 μΩ · cm, and more preferably 3 to 20 μΩ · cm. When the volume resistivity of the conductor exceeds 35 μΩ · cm, there is a possibility that sufficient conductivity as a conductor for electronic equipment cannot be obtained.
The volume resistivity of the conductor was determined by measuring the surface resistance value of the conductor using a four-probe resistance meter (for example, manufactured by Mitsubishi Yuka Co., Ltd., device name: Loresta GP MCP-T610). It can be determined by multiplying the value by the conductor thickness.

According to the manufacturing method of a base material with a conductor explained above, since a conductor can be formed even by heating at 150 ° C. or less, even when using a base material with low heat resistance such as PET, PEN, etc., the adhesion to the base material is good. A conductor-equipped substrate having a conductor having a good volume resistivity is obtained.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples. Examples 1 to 3 are examples, and examples 4 to 6 are comparative examples. Examples of identification of fine particles, measurement of average particle diameter of fine particles, measurement of conductor thickness, measurement of conductor volume resistivity, and method of conductor peelability test in Examples and Comparative Examples are shown below. .

[Identification of fine particles]
The identification of the fine particles was performed using an X-ray diffraction apparatus (manufactured by Rigaku Instruments Co., Ltd., apparatus name: RINT2500).

[Average particle size of fine particles]
Using a transmission electron microscope (manufactured by Hitachi, Ltd., device name: H-9000) or a scanning electron microscope (manufactured by Hitachi, Ltd., device name: S-800) The average particle size was determined by averaging the values. If the particles are not spherical, the maximum particle size is measured to determine the average particle size.

[Conductor thickness]
It measured using the contact-type film thickness measuring apparatus (the product made by Veeco, apparatus name: DEKTAK150).

[Volume resistivity of conductor]
Using a four-probe resistance meter (manufactured by Mitsubishi Yuka Co., Ltd., apparatus name: Loresta GP MCP-T610), the surface resistance value of the conductor was measured. The volume resistivity was determined by multiplying the measured surface resistance value by the thickness of the conductor.

[Peelability test of conductor]
A cellophane tape (manufactured by Nichiban Co., Ltd., trade name: Nichiban 18 mm) was applied to the conductor surface, and then the cellophane tape was peeled off instantaneously to evaluate the peelability of the conductor. The cellophane tape was rubbed from the top with an eraser and adhered to the surface of the conductor. One to two minutes after the cellophane tape was adhered, the tape was held at a right angle to the conductor film surface and peeled off instantaneously.
After peeling off the tape, the conductor surface was observed and judged. A case where no peeling of the conductor was observed was evaluated as ◎, a case where peeling was observed in a part of the conductor was evaluated as Δ, and a case where most of the conductor was peeled off was evaluated as ×.

[Example 1]
(Manufacture of copper hydride particles)
To a glass container, 300 g of toluene, 30 g of copper (II) formate tetrahydrate as a copper (II) salt, and 15 g of n-heptylamine (boiling point 157 ° C.) were added and stirred. Next, 4.5 g of NaBH ₄ which is a hydride reducing agent was added and stirred to obtain a black dispersion liquid in which fine particles were dispersed in toluene.

When the fine particles in the obtained dispersion were collected and identified by X-ray diffraction, it was confirmed to be copper hydride fine particles. The average primary particle diameter of the copper hydride fine particles (primary particles) was 10 nm. Further, the solid content concentration of the obtained copper hydride fine particle dispersion was 4% by mass.

(Preparation of conductive ink)
The obtained copper hydride fine particle dispersion was subjected to solvent substitution under reduced pressure to prepare a conductive ink. That is, after the copper hydride fine particle dispersion was concentrated under reduced pressure, 0.1% by mass of 3-mercaptopropyltrimethoxysilane was added to dodecane (boiling point 216.3 ° C., surface tension 25.44 dyn / cm at 20 ° C.). The added solvent was added to perform solvent substitution so that the solid content concentration of the copper hydride fine particles was 30% by mass.

(Conductor pattern formation)
Using the conductive ink obtained above, a wiring pattern having a length of 5 cm and a width of 2 mm was printed on a PET film by an industrial ink jet printer (manufactured by Fuji Film Graphic System Co., Ltd., device name: DMP2813). The printed PET film was heated at 150 ° C. for 1 hour in a nitrogen atmosphere to obtain a PET film with a conductor. The thickness of the conductor was 0.51 μm, and the volume resistivity was 25 μΩ · cm.

[Example 2]
After the copper hydride fine particle dispersion shown in Example 1 was concentrated under reduced pressure, 0.1% by mass of 3-mercaptopropylmethyldimethoxysilane was added to dodecane and the solvent was replaced. A conductive ink having a partial concentration of 30% by mass was prepared.

Then, using the obtained conductive ink, a wiring pattern was printed on the PET film in the same manner as in Example 1 to obtain a PET film with a conductor. The thickness of the conductor was 0.53 μm, and the volume resistivity was 17 μΩ · cm.

[Example 3]
After concentrating the copper hydride fine particle dispersion shown in Example 1 under reduced pressure, 0.1 mass% of 3-aminopropyltrimethoxy was added to decane (boiling point 174.1 ° C., surface tension 23.92 dyn / cm at 20 ° C.). Solvent substitution was performed by adding the silane added to prepare a conductive ink having a solid content concentration of copper hydride fine particles of 30% by mass.

Then, using the obtained conductive ink, a wiring pattern was printed on the PET film in the same manner as in Example 1 to obtain a PET film with a conductor. The thickness of the conductor was 0.55 μm, and the volume resistivity was 11 μΩ · cm.

[Example 4]
After the copper hydride fine particle dispersion shown in Example 1 was concentrated under reduced pressure, dodecane was added as a solvent, and solvent substitution was performed so that the solid content concentration of the copper hydride particles was 30% by mass.

Then, using the obtained conductive ink, a wiring pattern was printed on the PET film in the same manner as in Example 1 to obtain a PET film with a conductor. The thickness of the conductor was 0.56 μm, and the volume resistivity was 20 μΩ · cm.

[Example 5]
After the copper hydride fine particle dispersion shown in Example 1 was concentrated under reduced pressure, 0.1 mass% of 3-acryloxypropyltrimethoxysilane added to decane was added to perform solvent substitution. A conductive ink having a solid content concentration of 30% by mass was prepared.

Next, using the obtained conductive ink, a wiring pattern was printed on a PET film in the same manner as in Example 1 to obtain a PET film with a conductor. The thickness of the conductor was 0.51 μm, and the volume resistivity was 24 μΩ · cm.
[Example 6]
After the copper hydride fine particle dispersion shown in Example 1 was concentrated under reduced pressure, 0.1 mass% of 3-methacryloxypropyltriethoxysilane added to decane was added to perform solvent substitution. A conductive ink having a solid content concentration of 30% by mass was prepared.

Then, using the obtained conductive ink, a wiring pattern was printed on the PET film in the same manner as in Example 1 to obtain a PET film with a conductor. The thickness of the conductor was 0.53 μm, and the volume resistivity was 35 μΩ · cm.

Next, a conductor tape peelability test was conducted on the PET films with conductors obtained in Examples 1 to 6. The test results are shown in Table 1 together with the measurement results of the volume resistivity.

From Table 1, in Examples 1 to 3 using a conductive ink in which a silane coupling agent having a mercapto group or an amino group and an alkoxyl group is blended with an alkylamine having a boiling point of 250 ° C. or less as a dispersant, It can be seen that a conductor having a small volume resistivity can be formed.

On the other hand, in Example 4 in which the conductive ink containing no silane coupling agent was used, the adhesion between the formed conductor and the PET substrate was not sufficient, and the tape peel test peeled off most of the conductor. Is observed.

Further, in the conductive inks of Example 5 and Example 6 using a silane coupling agent having no mercapto group or amino group and having an acryloxy group or a methacryloxy group, the adhesion between the silane coupling agent and the PET base material There is little contribution to improvement, and peeling is observed in part or most of the conductor in the tape peeling test. In particular, it can be seen that in the conductive ink of Example 6 using 3-methacryloxypropyltriethoxysilane as the silane coupling agent, the volume resistivity of the formed conductor increases and sufficient conductivity cannot be obtained.

Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on Japanese Patent Application No. 2012-063430 filed on March 21, 2012, the contents of which are incorporated herein by reference.

According to the conductive ink of the present invention, it is possible to form a conductor having good adhesion to the substrate and having a small volume resistivity. Moreover, according to the manufacturing method of the base material with a conductor of this invention, the base material with a conductor which has a favorable adhesiveness and a small volume resistivity on a base material is obtained. And the obtained base material with a conductor can be used conveniently as a highly reliable wiring board.

DESCRIPTION OF SYMBOLS 1 ... Copper hydride fine particle, 2 ... Alkylamine, 3 ... Base material, S1, S2 ... Silane coupling agent

Claims

A water-insoluble organic solvent,
Copper hydride fine particles dispersed in the organic solvent;
An alkylamine having an alkyl group having 7 or more carbon atoms and a boiling point of 250 ° C. or lower;
Formula (1): R 1 m R 2 n SiR 3 4-mn
(In the formula (1), R 1, glycidoxy group, an isocyanate group, a mercaptoalkyl group, an aminoalkyl group, N- aminoalkyl - is a monovalent organic group selected from an amino group, R 2 Is an alkyl group or a hydrogen atom, R 3 is an alkoxyl group, m is an integer of 1 to 3, n is an integer of 0 to 2, and m + n is 3 or less. ): R 4 3 SiR 5 —S k —R 5 SiR 4 3
(In the formula (2), R 4 is an alkoxyl group, R 5 is an alkylene group, and k is an integer of 1 to 4),
A conductive ink comprising:
The conductive ink according to claim 1, wherein the content of the copper hydride fine particles is 10 to 50% by mass.
The conductive ink according to claim 1 or 2, wherein a content ratio of the alkylamine is 2 to 10% by mass.
The conductive ink according to any one of claims 1 to 3, wherein a content ratio of the silane coupling agent is 0.01 to 2.00 mass% with respect to the organic solvent.
The conductive ink according to any one of claims 1 to 4, wherein an average primary particle diameter of the copper hydride fine particles is 100 nm or less.
Preparing a substrate;
Forming a conductive ink coating layer according to any one of claims 1 to 5 on the substrate;
And a step of heating the coating layer to form a conductor containing copper.