JP2003166006A - Dispersion liquid of copper fine-particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dispersion liquid of copper fine-particles having particle diameters of less than 200 nm. <P>SOLUTION: This dispersion liquid is obtained by suspending a copper compound having the particle diameter of less than 200 nm, in a polyol solvent, and subsequently reducing it at a lower temperature than 150&deg;C and in an atmosphere of pressurized hydrogen. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper fine particle dispersion liquid used in applications such as conductive paste and conductive ink in the field of mounting electronic equipment.

[0002]

2. Description of the Related Art Copper fine particle dispersion liquids that have been used in the past in the field of mounting electronic equipment, such as conductive pastes and conductive inks, require a reduction in filler size as wiring density increases in recent years. It is said that. There are methods such as a physical method and a chemical method for producing the copper fine particles. Among the physical methods, a method for producing copper fine particles having a particle diameter of 100 nm or less by a gas evaporation method is known (Japanese Patent Laid-Open No. 3-34211). However, in this method, copper is used to prevent aggregation between copper fine particles. The fine particles need to be coated with an alcohol having 5 or more carbon atoms or an organic ester (α-terpineol, citronenol, methyl oleate, linoleic acid glyceride, etc.). Since these coated organic substances have a sterically bulky long-chain alkyl or cyclic skeleton, therefore, when these particles are used as a filler for a copper fine particle dispersion, for example, contact between copper fine particles is insufficient. is there. It is possible to remove the coating organic matter by heating, but in that case, there is a problem that a high temperature of about 400 ° C. or higher is required.

On the other hand, as a chemical preparation method, there is a method of reducing a copper compound in a solution with a reducing agent such as hydrazine. However, in this method, a strong cohesive force acts between the prepared copper particles, so that it is impossible to prepare fine copper particles having a particle diameter of less than 200 nm without addition of a protective polymer or the like. That is, the conductivity is insufficient even if the wiring density can be increased. Further, a method of obtaining copper fine particles by a method of heating and reducing a copper compound in a polyol solvent at the boiling point of the polyol (for example, 198 ° C. when ethylene glycol is used as the polyol) is also known (Japanese Patent Publication No. 4-24402). In this method, since the dissolution-precipitation reaction of the copper compound at a high temperature is used, the particle size of the obtained copper particles becomes large, and it is not possible to obtain the copper particles having a particle size of less than 200 nm. That is, this method cannot cope with the increase in wiring density even if the conductivity is sufficient.

Further, a method of hydrogen-reducing a copper compound at atmospheric pressure has been proposed (JP-A-64-47801), but this method usually requires a high reaction temperature of 150 ° C. or higher. In such a reaction at a high temperature, the copper fine particles produced easily aggregate, so that it is not possible to obtain copper fine particles having a particle diameter of less than 200 nm.

[0005]

That is, the object of the present invention is to provide a copper fine particle dispersion having a particle size of less than 200 nm without impairing the intrinsic conductivity of copper.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor suspended ultrafine particles of a copper compound having a particle diameter of less than 200 nm in a polyol solvent and The present invention has been completed by finding that a dispersion liquid of copper particles obtained by reduction treatment with hydrogen under the temperature and pressure of 1 can respond to a high density of distributive density without impairing the intrinsic conductivity of copper. Of.

That is, the present invention provides a copper fine particle dispersion characterized in that fine copper particles having a particle size of less than 200 nm are dispersed in a polyol solvent, and particularly, the copper characterized in that the polyol solvent is diethylene glycol. The present invention relates to a fine particle dispersion, which is obtained by suspending a copper compound having a particle size of less than 200 nm in a polyol solvent, and subsequently performing a reduction treatment under pressurized hydrogen at a temperature of less than 150 ° C. The present invention relates to a method for producing a copper fine particle dispersion.

The present invention will be described in detail below. The copper fine particle dispersion of the present invention is characterized in that copper particles having a particle diameter of less than 200 nm are dispersed in a polyol solvent. The copper fine particles of the present invention have a spherical shape, a cubic shape, or a polyhedral shape, and have a particle diameter of 1 nm or more and less than 200 nm, and more specifically, 1 nm or more and less than 100 nm. The content of copper in the entire dispersion is 0.01% by mass or more, 9
Less than 0 mass%, more preferably 0.01 mass% or more 8
It is less than 5% by mass.

The polyol that can be used as a solvent in the copper fine particle dispersion of the present invention is a compound that has two or more hydroxyl groups in the molecule and is a solution at room temperature, and includes polyethylene glycol, polypropylene glycol, alkylene glycol, Glycerol and the like. It is known that the polyol itself has a reducing property when heated at a high temperature, and its reducing power greatly varies depending on the difference in molecular structure.However, since the present invention is a reaction utilizing the reducing power of hydrogen, There is no limit to the reducing power.

Ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2, whose viscosity is low at room temperature, Those having a small carbon number such as 3-butanediol are preferable, but those having a large carbon number such as pentanediol, hexanediol, octanediol and polyethylene glycol can also be used. Only one of these polyol solvents may be used as a single solvent, or a plurality of polyol solvents may be mixed and used as a mixed solvent.
Of the polyol solvents, the most preferred solvent is diethylene glycol.

Next, a method for producing the copper fine particle dispersion of the present invention will be described. The copper fine particle dispersion of the present invention has a thickness of 200 nm.
It is characterized by being obtained by suspending a copper compound having a particle size of less than in a polyol solvent and performing a reduction treatment with hydrogen under a specific temperature and pressure.

The details will be described below. As a copper compound that can be used in the present invention, a cuprous compound, for example, cuprous oxide, cuprous chloride, cuprous bromide, cuprous iodide, cuprous sulfate, cuprous nitrate, acetic acid. It is cuprous. As the cupric compound, for example, cupric oxide, cupric hydroxide, cupric chloride, cupric bromide, cupric iodide, cupric sulfate, cupric nitrate, cupric acetate. , Cupric azide and the like. Among these copper compounds, more preferable are cuprous oxide and cupric oxide containing no halogen ion.

In the present invention, the above copper compound has a particle size of 20.
The particle diameter is less than 0 nm. These may be commercially available products or can be synthesized by a known synthesis method. For example, the particle size is 200
As a method of synthesizing cuprous oxide having a thickness of less than nm, a method of synthesizing an acetylacetonato copper complex by heating at about 200 ° C. in a polyol solvent is known (Angevante Chemi International Edition, No. 40, 2).
Vol., P. 359, 2001). If the particle diameter of the copper compound as a raw material exceeds 200 nm, the reduction treatment causes
Copper fine particles of less than 0 nm cannot be obtained.

In the present invention, the ultrafine particles of the copper compound are first dispersed in a polyol solvent. As a method of dispersing the copper compound in the polyol solvent, a general method of dispersing the copper compound powder in the solution can be used. For example, an ultrasonic method, a mixer method, a three-roll method, a ball mill method and the like can be mentioned. Above all, the ultrasonic method and the ball mill method are particularly preferable. Usually, a plurality of these dispersion means are combined to perform dispersion. These dispersion treatments may be performed at room temperature, or may be performed by heating to reduce the viscosity of the solvent.

The weight of the copper compound ultrafine particles to be dispersed in the polyol solvent is not particularly limited, but since the powder to be mixed is an ultrafine particle having a large surface area, a uniform dispersion liquid is obtained under the condition of more than 90 wt%. It is impossible to create. The dispersion treatment can be omitted by synthesizing ultrafine particles of a copper compound having a particle diameter of less than 200 nm in a polyol solvent.

The copper compound dispersed in the polyol solvent by the above-mentioned method is brought into contact with hydrogen in a reaction vessel, and heat is applied to reduce the copper compound to synthesize copper fine particles.
The contact with hydrogen is carried out by using a pressure-resistant reaction vessel, sufficiently replacing oxygen in the reaction vessel with an inert gas such as nitrogen using a vacuum pump, and then filling hydrogen up to a predetermined pressure. The pressure of hydrogen and the amount of heat applied vary depending on the particle size of the copper compound ultrafine particles as the raw material, but the pressure applied must be greater than atmospheric pressure. The pressure is preferably higher than atmospheric pressure and lower than 10 MPa, and more preferably higher than atmospheric pressure and lower than 8 MPa. Generally, when the particle diameter of the copper compound ultrafine particles as a raw material becomes small, the particles are easily reduced, so that the reduction reaction proceeds in a low-pressure hydrogen atmosphere. The use of pressurized hydrogen is more preferable because the amount of heat applied can generally be reduced.

The reaction temperature range is below 150 ° C, more preferably below 120 ° C. Generally, when the particle size of the copper compound ultrafine particles used as a raw material becomes small, the amount of heat applied may be small. Further, when the amount of heat applied is too large, agglomeration progresses among the generated copper fine particles, and even if a copper compound having a particle diameter of less than 200 nm is used as a raw material, the particle diameter of the generated copper fine particles becomes larger than 200 nm. In the reduction treatment of the present invention, the reaction atmosphere may be a mixed atmosphere of hydrogen with an inert gas such as nitrogen, argon or helium.
The presence of oxygen promotes the elution of copper ions from the copper compound and is not preferred.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to Examples, but the present invention should not be limited to these Examples. In addition, the particle diameters of the copper compound particles and the copper particles described in Comparative Examples in the following examples are all laser scattering type particle size distribution analyzer (LA-92, manufactured by Horiba, Ltd.).
It was measured in 0). Further, the fact that the ultrafine particles in the dispersion liquid obtained by the hydrogen treatment are copper means that X is manufactured by Rigaku Corporation.
It confirmed with the line diffraction apparatus (Rigaku-RINT 2500).

[0019]

Example 1 Copper acetate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.3
g is diethylene glycol (Wako Pure Chemical Industries, Ltd.)
Suspend in 50 ml, add 0.5 ml of water and add 3 at 190 ° C.
The mixture was heated and reacted for a time to obtain a cuprous oxide dispersion having an average particle size of 80 nm. This dispersion was placed in a stainless steel reactor (autoclave), a magnetic stirrer for stirring was placed, and oxygen was removed from the reactor using a vacuum pump, so that the pressure became 4.4 MPa. The container was filled with hydrogen. The reactor was overheated for 5 hours in an oil bath set at 70 ° C. while stirring the inside with a magnetic stirrer to obtain a copper fine particle dispersion. The average particle size of the obtained copper fine particles was 75 nm.

[0020]

Example 2 1 g of CuO nanoparticles having an average particle diameter of 30 nm (manufactured by CI Kasei Co., Ltd.) was added to 50 ml of diethylene glycol, and a dispersion treatment was carried out with an ultrasonic disperser and a ball mill disperser. The obtained dispersion was placed in an autoclave, oxygen in the reactor was removed using a vacuum pump, and then hydrogen was filled in the container so that the pressure became 3.9 MPa. 5 hours in an oil bath set at 70 ° C
The reactor was heated while stirring the inside with a magnetic stirrer to obtain a copper fine particle dispersion. The average particle size of the copper fine particles was 50 nm.

[0021]

Example 3 Average particle size 80 obtained by the same operation as in Example 1
The cuprous oxide dispersion having a particle size of 120 nm was further stirred at room temperature for 1 week to obtain a cuprous oxide dispersion having an average particle size of 120 nm. This dispersion was put into an autoclave, oxygen in the reactor was removed using a vacuum pump, and then hydrogen was filled in the container so that the pressure was 1.2 MPa. The reactor was heated in an oil bath set at 102 ° C. for 2 hours while stirring the inside with a magnetic stirrer to obtain a copper fine particle dispersion. The average particle diameter of the obtained copper fine particles was 94 nm.

[0022]

Comparative Example 1 The reaction was performed under the same conditions as in Example 3 except that the hydrogen pressure was atmospheric pressure, but the cuprous oxide particles were not reduced and a copper fine particle dispersion was not obtained.

[0023]

Comparative Example 2 Example 1 except that the reaction temperature was 200 ° C.
The reaction was carried out under the same conditions as. Although the cuprous oxide particles were reduced, copper settled as aggregates having a size of about 1 mm square, and a copper fine particle dispersion liquid was not obtained.

[0024]

The method according to the present invention does not require additives such as a coating organic substance and a protective polymer, and is 200 n
Since a copper fine particle dispersion having a particle diameter of less than m can be synthesized, it is possible to provide a conductive paste for high-density wiring and a conductive ink in which the insulating component is reduced.

Claims (4)

[Claims] 1. A copper fine particle dispersion liquid containing copper fine particles having a particle diameter of less than 200 nm in a polyol solvent. 2. The copper fine particle dispersion liquid according to claim 1, wherein the polyol solvent is diethylene glycol. 3. A copper compound having a particle size of less than 200 nm is suspended in a polyol solvent and then continuously heated to a temperature of 1.
The method for producing a copper fine particle dispersion according to claim 1 or 2, which is obtained by a reduction treatment under pressurized hydrogen at a temperature of less than 50 ° C. 4. The method for producing a copper fine particle dispersion according to claim 3, wherein the copper compound is cuprous oxide or cupric oxide.