JPH02218763A - Surface-treatment of copper powder for electrically conductive paint - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a novel method for surface treatment of copper powder for conductive paints, and particularly to a method for obtaining copper powder for conductive paints with excellent conductivity and environmental resistance. .

[Conventional technology]

Conventionally, conductive paints containing copper powder are made by dispersing copper powder of an appropriate size, which has been prepared and surface-treated using various methods, into a resin binder dissolved in an organic solvent. . This copper powder for conductive coatings is required to have excellent electrical conductivity and environmental resistance such as heat resistance and moisture resistance.

In general, copper powder is very easily oxidized, which may lead to a decrease in conductivity, and therefore various surface treatment methods for copper powder have been proposed.

For example, surface treatment of copper powder with a coupling agent (JP-A-60-30200), electrolytic copper powder with organic titanate? (Japanese Unexamined Patent Publication No. 59-174661) and carboxylic acid treatment of copper powder (Unexamined Japanese Patent Publication No. 60-2
58273), soldering the surface of copper powder (Japanese Patent Laid-Open No. 57-113505), and displacing metallic silver on the surface of copper powder (Japanese Patent Laid-Open No. 60-243277).
Publication No. 2), etc. have been proposed.

However, although conductive paints made using copper powder surface-treated using these conventional techniques have been confirmed to be effective to some extent, most of them have failed in environmental tests such as heat resistance and moisture resistance. The change over time is large, and the conductivity is still insufficient, so that it has not reached a practical level of reliability.

[Object of the invention and summary]

Therefore, the present invention provides a surface treatment method for copper powder for producing copper powder for conductive paint that solves the problems of the prior art as described above, improves conductivity, and significantly reduces changes over time in environmental tests. The purpose is to provide

According to research conducted by the present inventors, it has been found that this object can be achieved by coating the surface of copper powder with two types of inorganic zirconium compounds.

Therefore, the present invention provides a method for surface treatment of copper powder for conductive paint, which comprises coating the surface of copper powder with two types of organic zirconium compounds.

[Detailed description of the invention]

The invention will be explained in detail below.

The copper powder to be surface-treated by the method of the present invention is produced by any conventionally known method such as electrolytic method, atomization method, chemical reduction method, etc., and it is preferable that the oxide film has been removed. However, the surface of the copper powder from which the oxide film has been removed is extremely active, so it is preferable to use one that has been pretreated with, for example, organic amines or carboxylic acids. This copper powder usually has an apparent density of 0. 5-2. 5g/cEa
, tap density 0. 9-4. 5g/c, the specific surface area is 0.5rf/g or more by BET method, and the average particle size is 0.5rf/g or less by the tip permeability. With a particle size distribution of 5 to 20 μm, those having the characteristics of first permeation and a maximum particle size of 50 μm are used.

The two types of organic zirconium compounds used in the present invention for surface treatment of copper powder as described above both have a white group that exhibits lipophilicity and a six group that exhibits hydrophilicity. One of them is a compound in which a higher fatty acid is added to tetraalkoxyzirconium. This is referred to herein as the first inorganic zirconium compound. Saturated or unsaturated higher fatty acids are used as the higher fatty acids, and the residue thereof exhibits lipophilicity. Preferred higher fatty acids include stearic acid, valmitic acid, myristic acid, lauric acid, capric acid, oleic acid, linoleic acid, liluic acid, and isomers thereof. As the tetraalkoxyzirconium compound having a hydrophilic group, those having a lower alkoxy group having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms are used, such as tetrapropoxyzirconium and tetrabutoxyzirconium. In production, it is usually obtained by reacting several times the mole of higher fatty acids, preferably 3 to 5 times the mole, with respect to 1 mole of tetraalkoxyzirconium, and the higher fatty acid ester as a by-product is reduced to 1 mole.
It may also be included in a large amount.

Another organic zirconium compound is a compound in which a p-cumylphenyl group exhibiting lipophilicity is introduced into tetraalkoxyzirconium having a hydrophilic group. This is referred to herein as a second organic zirconium compound. In producing this, one mole of the above-mentioned tetraalkoxyzirconium is reacted with several moles, preferably 1 to 3 moles, of an organic compound that has a p-cumylphenyl group in the molecule.

The total amount of these two types of lysirconium compounds is 0.005 to 1596, preferably 0.0 to the weight of copper powder.
The surface is coated with 1-10% of 2.

If the Il, 005 weight is less than 96 mm, the tendency of copper oxidation is significant, and if the weight exceeds 15 mm, the tendency of the conductivity of the copper powder to decrease is significant.

The two types of organic zirconium compounds are 0.005 to 70% by weight of the second organic zirconium compound, preferably 0.01 to 5% by weight of the first organic zirconium compound.
Amounts ranging from 0 to 96% by weight are used. If it is less than 0.005%, the heat resistance and moisture aging resistance of the copper powder tend to deteriorate significantly, and if it exceeds 70%, the electrical conductivity of the copper powder tends to decrease significantly.

For surface treatment, the above-mentioned organic zirconium compound can be added to the copper powder dispersed in a solvent, or the organic zirconium compound can be directly added using a mixer such as a mixer or mill. It is possible to take a method of processing the The two types of organic zirconium compounds may be used as a mixture at the same time, or they may be used separately, but in that case, the first a- shall be treated with organic zirconium compound. If it is reversed, the copper powder will be in a wet state, and homogeneous dispersion mixing will not be possible when adding the second compound later.

[For production]

In this invention having the above-mentioned structure, an organic zirconate compound obtained by adding an organic compound having a p-cumylphenyl group to tetraalkoxyzirconium suppresses oxidation of the surface of copper powder, and improves the resistance of copper powder over time in environmental tests such as heat resistance and moisture resistance. suppress change.

Furthermore, an organic zirconate compound obtained by adding a higher fatty acid to tetraalkoxyzirconium improves the conductivity of the copper powder in the organic resin binder.

These are due to the high hydrophobicity of the p-cumylphenyl group itself and the long chain portion of higher fatty acids that interact with the active site of the H-machine resin binder through van der Waals forces, ionic, covalent, and coordination intermolecular forces. It's because it fits.

〔Example〕

Examples of the present invention are given below, but the present invention is not limited thereto.

Resin-like electrolytic copper powder used in this invention - Mitsui Metal Mining Co., Ltd.
MF-D2 is shown in Table 1.

Table 2.3 shows the white zirconate compounds used in this invention.
Shown below.

Table 3 However, butoxy group is normal type and propoxy group is isotype.

Table 4 shows comparative samples used in this invention.

Table 4 Example 1 For the copper powder in Table 1 from which the oxidized wave film was removed, Table 2 (first organic zirconium compound lit), Table 3 (second organic zirconium compound 111), Table 2 and a mixture of both compounds in Table 3 (first H-organic zirconate compound 5 in Table 2)
and Table 4.
Copper powder amount [1, JJ and 0°5.1,0.
3.0.5. 0ffiffi% was reversed.

These coated copper powders are coated with acrylic resin (solid content:
A conductive paint was prepared using 60% by weight) and toluene, and its volume resistivity was measured.

As a result, conductive coatings prepared from copper powder surface-coated with a mixture of both compounds of Table 2.3 of the present invention were approximately 1.
It had an in-volume H resistance of 2X10 to 3.5X10-'Ω.

On the other hand, the first 1 of Table 2! A conductive coating prepared from copper powder surface-coated with a T machine zirconate compound is approximately 4
X10 ~ 7 lX1
0-3Ω・Comparison sample in Table 4: Approximately 8X10'
It had a volume resistivity of ˜3×10 −3 Ω·−.

From the above results, it was found that the conductive paint prepared from the copper powder coated with the surface coating agent of the present invention exhibits excellent conductivity.

Example 2 The coating substrate of Example 1 (acrylic plate ~ thickness 1.5 cm, conductor size 2 crn x 2 ttn) was heated at a high temperature of 85 °C, 60 °C/95
The coating film was left in a high humidity environment of %RH for 2000 hours, and the rate of change in resistance of the coating film was measured.

As a result, coating 11 of a conductive paint prepared from copper powder surface-coated with a mixture of both compounds of Table 2.3 of the invention! Mi
The aging of the board is at least 1% at a high temperature of 85℃.
, at most 7%, with most ranging from 3 to 496. In addition, at high humidity of 60℃/95%RH, at least 17%
, at most 4%, and mostly 0%.

On the other hand, the change over time of the coated substrate of the conductive paint prepared from the copper powder surface-coated with the first organic zirconate compound in Table 2 is at least 27% and at most 54% at a high temperature of 85°C. there were. Furthermore, at high humidity of 60° C./95% RH, it was at least 13% and at most 29%. Similarly, the second organic zirconate compound in Table 3 = at least 7% and at most 14% at a high temperature of 85°C. Also 60℃
At high humidity of /95% RH, it was at least 9% and at most 18%. Comparative sample in Table 4: at a high temperature of 85° C. it was at least 51% and at most 205%. Also 60℃/95
At high humidity of %RH it was at least 26% and at most 66%.

From the above results, it was found that the coating film of the conductive paint prepared from the copper powder coated with the surface coating agent of the present invention exhibits excellent heat resistance and moisture aging resistance.

[Effects of the Invention] The conductive paint obtained from surface-treated copper powder by the method of the present invention has excellent heat resistance and moisture resistance, shows significantly lower changes over time in environmental tests than conventional paints, and has improved conductivity. Therefore, the present invention is effective because it can provide a highly reliable and excellent copper powder for conductive paint.

Applicant's agent: Mr. Sato

Claims (1)

[Claims] 1. A method for surface treatment of copper powder for conductive paint, which comprises coating the surface of copper powder with two types of organic zirconium compounds. 2. Both of the above two types of organic zirconium compounds have an organic group exhibiting hydrophilicity and an organic group exhibiting lipophilicity; one is a compound obtained by adding a higher fatty acid to tetraalkoxyzirconium, and the other is a compound obtained by adding a higher fatty acid to tetraalkoxyzirconium. 2. The method according to claim 1, wherein one is a compound having a p-cumylphenyl group added to tetraalkoxyzirconium.