JPH0670194B2 - Copper powder for electromagnetic wave shielding and conductive coating composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electromagnetic wave shielding material, and more specifically,
The present invention relates to a copper powder surface-coated with an organometallic compound and a conductive coating composition containing the copper powder for electromagnetic wave shielding (EMI shielding).

[Conventional technology]

As one of the electromagnetic wave shielding materials that protect electronic devices from electromagnetic interference, there has been a conductive paint in which a conductive filler such as nickel powder, silver powder, copper powder or carbon powder is kneaded with various resin binders. Is applied to the surface of a plastic molded product by spraying or brushing to shield it from electromagnetic waves. Of the various conductive paints, the copper-based conductive paint is
It is less expensive than paints that use silver powder or nickel powder, and has excellent shielding effects.

However, the copper-based conductive coating material, copper powder is not aggregated in the coating material in a good dispersion state, and moreover, it is easily oxidized in an environment such as heat and humidity, and therefore has poor storage stability.
There is a problem that deterioration of aging resistance (damage of shield effect) is likely to occur. Various proposals have heretofore been made to solve this problem. For example, treating electrolytic copper powder with an organic carboxylic acid (JP-A-60-258273), surface-treating copper powder with a coupling agent (JP-A-60-30200), copper powder Is coated with silver (JP-A-60-243277) and copper powder is coated with an organic titanate (JP-A-59-174661 and JP-A-56).
-36553), coating copper powder with organic aluminum (JP-A-59-179671), plating copper powder with solder (JP-A-57-113505), copper powder It has been proposed to coat copper oxide with copper oxide (JP-A-60-35405).

[Problems to be Solved by the Invention]

By coating the copper powder with a surface coating agent as described above,
Although some effects can be obtained, the rust preventive property of the copper powder is not good, and the copper powder and the conductive coating composition have insufficient conductivity and environment resistance.

This invention has been made based on the above background, and its purpose is to eliminate the drawbacks of the above-mentioned conventional copper-based conductive paint, without lowering the copper powder performance such as the conductive characteristics, It is an object of the present invention to provide a copper powder and a conductive coating composition having good conductivity and environment resistance.

[Means for Solving the Problems]

As a result of various tests and studies conducted on copper powder and a copper-based conductive coating, the present inventor selects an organic zirconate compound, and if this is used as a surface coating agent for copper powder, it cannot be obtained with conventional coating agents. It was found that the surface-treated copper powder exhibited excellent rust-preventing property and conductivity, and was obtained from the knowledge that it showed the above effect, and completed the present invention and further researched based on the knowledge. The inventors have found that the conductive paint has excellent conductivity and environmental resistance, and completed the present invention.

That is, the electromagnetic wave shielding copper powder of the present invention is coated with a surface coating agent made of an organic zirconate compound.

In a preferred embodiment of this invention, the organic zirconate compound is represented by the following general formula.

(RO) x-Zr- (OR ') _4- x (In the formula, RO is an easily hydrolyzable organic group, OR' is an organic group exhibiting hardly hydrolyzable and lipophilic properties, and x is 1 to 3). In a specific embodiment of the present invention, the coating amount of the organic zirconate compound can be 0.05 to 10% by weight with respect to the copper powder.

The conductive coating composition of the present invention contains copper powder coated with the surface coating agent comprising the organic zirconate compound according to the present invention, a resin binder, a solvent, and.

In a specific embodiment of this invention, the particle shape of the copper powder,
It can be dendritic, flaky, granular, or spherical.

In a preferred embodiment of the present invention, the content of copper powder in the conductive coating composition excluding the solvent content can be 40 to 90% by weight.

Hereinafter, the present invention will be described in more detail.

Copper powder The shape of the copper powder used in the present invention is electrolysis, reduction,
There are dendritic shapes, granular shapes, and spherical shapes obtained by the atomizing method and the like, and further there are flaky shapes obtained by mechanically processing these.

The preferred copper powder used in the present invention is 1.00 m ² / BET method.
2 particles with a specific surface area of less than g and a particle size of 50 μm or more by the light transmission method
It has a particle size distribution of less than 0% by weight and an average particle size of less than 30 μm.

The shielding effect can be improved by processing granular or spherical copper powder into a flaky powder by a ball mill or the like. Also, V
A good shielding effect can be obtained by mixing the dendritic copper powder with the granular or spherical copper powder using a mold mixer or the like.

In the present invention, a copper powder whose surface is wholly or partially covered with silver can be used. At this time, the silver coating amount is 0.1 to 20% by weight, preferably 1.0 to 10% by weight, based on the copper component. By using this silver-coated copper powder, it is possible to obtain a coating film having a better shielding effect than uncoated copper powder.
Examples of the silver coating method include a chemical displacement plating method, a CVD method, an electroplating method, and a mechanical bonding method. Examples of the composite copper powder other than the silver-coated copper powder that can be used in the present invention include copper powder coated with a metal such as nickel, zinc, platinum, or palladium.

In addition to the above metals, the copper powder may be coated in advance with the components used for producing the conductive coating.

Further, the oxide film on the surface of the copper powder, as a pretreatment, inorganic acids, organic acids, reagents such as various reducing agents or ammonia gas,
It can be removed by a reducing gas such as hydrogen gas. By this pretreatment, the coating with the organic zirconate compound can be efficiently carried out.

Surface Coating Agent The copper powder of the conductive coating composition according to the present invention is coated with a surface coating agent containing this specific zirconium compound. This zirconium compound has both an organic group which is hydrolyzable and cheap and an organic group which is hardly hydrolyzed and exhibits lipophilicity. Specifically, it is an organic zirconate compound represented by the following formula.

(RO) x-Zr- (OR ') _4- x (In the formula, RO is an easily hydrolyzable organic group, OR' is an organic group exhibiting hardly hydrolyzable and lipophilic properties, and x is 1 to 3). Examples of such compounds include isopropyl triisostearoyl zirconate, isopropyl tridodecylbenzenesulfonyl zirconate, isopropyl tris (dioctyl pyrophosphate) zirconate, tetraisopropyl bis (dioctyl phosphate) zirconate, tetraoctyl bis ( Ditridecyl phosphite) zirconate, tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl) phosphite zirconate, bis (dioctyl pyrophosphate)
Oxyacetate zirconate, bis (dioctyl pyrophosphate) ethylene zirconate, isopropyl trioctanoyl zirconate, isopropyl dimethacryl isostearoyl zirconate, isopropyl isostearoyl diacryl zirconate, isopropyl tri (dioctyl phosphate) zirconate, isopropyl tricumylphenyl Zirconate, isopropyl tri (N-aminoethyl-aminoethyl) zirconate,
Dicumylphenyloxyacetate zirconate, diisostearoyl ethylene zirconate, n-butyl triisostearoyl zirconate, isobutyl triisostearoyl zirconate, tert-butyl triisostearoyl zirconate, isopropyl trioleyl zirconate, isobutyl trioleyl zirconate And isobutyl (diisostearoyl) oleyl zirconate.

In the present invention, the amount of the surface coating agent used is 0.01 to 15% by weight, preferably 0.05 to 10% by weight, based on the copper powder. If it is less than the lower limit of the amount used, the oxidation resistance is poor and the generation of patina, discoloration and aggregation of copper powder are likely to occur. This is because if the upper limit is exceeded, an excessive hydrophobic film is formed on the surface of the copper powder and conductivity is hindered.

The coating treatment method is a method of adding an organic zirconate compound dissolved in a solvent to copper powder, and then removing the solvent,
Add the required amount of organic zirconate compound to copper powder,
There is a method of mixing and stirring.

Conductive Coating Composition The conductive coating composition of the present invention basically contains copper powder coated with a surface coating agent comprising the organic zirconate compound according to the present invention, a resin binder, and a solvent.

The resin binder that can be used in the present invention has good adhesion to plastics that are commonly used in electronic devices. For example, acrylic resin, polyurethane resin, polyester resin, styrene resin, phenol resin, epoxy resin, etc. can be used for plastics for electronic device housings such as ABS, polystyrene, PPO, and polycarbonate. .

Further, as a solvent that can be used in the present invention, toluene that dissolves additives such as a resin binder,
Thinner, hexane, methyl ethyl ketone, xylene,
One or a mixture of two or more organic solvents such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, methyl isobutyl ketone, ethyl acetate, butyl acetate, methyl carbitol, ethyl carbidol, methyl cellosolve and ethyl cellosolve is preferable. .

The copper powder blended in this composition is 35 to 95% by weight, preferably 40 to 90% by weight, based on the solid content of the conductive composition.

The resin binder blended in this composition is 5 to 70% by weight, preferably 10 to 60% by weight, based on the solid content of the conductive composition.

In addition to the above components, various additives may be included depending on the purpose. Examples of such agents include reducing agents, surfactants, anti-settling agents, defoamers, thickeners, thixotropic agents, rust preventives, flame retardants and the like.

The conductive composition of the present invention is produced by adding a resin binder and a solvent to the copper powder already coated with the organic zirconate compound of the present invention.
For example, an electrically conductive composition may be prepared by adding an organic zirconate compound to a mixture of uncoated copper powder, a resin binder and / or a solvent.

[Work]

In the present invention having the above-mentioned constitution, the organic zirconate compound as the surface coating agent has a hydrophilic organic group which is easily hydrolyzed centering on the zirconium atom, and a lipophilic organic group which is hard to be hydrolyzed. During the surface treatment of powder, a hydrophilic organic group causes a substitution reaction or coordination with water adsorbed on the copper powder surface, and a hydrophobic film of an organic zirconate compound in which lipophilic organic groups are arranged outside the copper powder surface. To form. Therefore, high hydrophobicity is imparted to the surface of the copper powder.

〔Example〕

 The present invention will be specifically described with reference to the following examples.

Experimental Example 1 Apparent density 0.8 to 1.1 g / cm ³ , specific surface area 0.4 m ² / g, average particle size 8.
Dendritic copper powder with 0 μm, purity 99.2% or more, HNO ₃ insoluble content less than 0.03%, reduction reduction less than 0.80% (Mitsui Mining & Smelting, MF-D
Using 2), the oxide film was removed from this copper powder with an acidic solution, neutralized and dried. The treated copper powder was dispersed in toluene, and the organic zirconate compound of Table 1 as a surface coating agent and the metal organic compound of Table 2 were added little by little to the dispersion bath to form a coating on the copper powder. Formed. Table 1 Organic Zirconate Compound (Scope of the Invention) (1) Isopropyltriisostearoyl zirconate (2) Isopropyltridodecylbenzenesulfonyl zirconate (3) Isopropyltris (dioctylpyrophosphate) zirconate (4) Tetraisopropylbis (dioctyl) Phosphite) zirconate (5) Tetraoctylbis (ditridecylphosphite) zirconate (6) Tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl) phosphite zirconate (7) Bis (dioctyl) Pyrophosphate) Oxyacetate zirconate (8) Bis (dioctyl pyrophosphate) ethylene zirconate (9) Isopropyltrioctanoyl zirconate (10) Isopropyl dimeta Kuryl Isostearoyl Zirconate (11) Isopropyl Isostearoyl Diacryl Zirconate (12) Isopropyl tri (dioctyl phosphate)
Zirconate (13) Isopropyltricumylphenyl zirconate (14) Isopropyltri (N-aminoethyl-aminoethyl) zirconate (15) Dicumylphenyloxyacetate zirconate (16) Diisostearoylethylene zirconate (17) n-Butyl Triisostearoyl Zirconate (18) Isobutyl Triisostearoyl Zirconate (19) tert-Butyl Triisostearoyl Zirconate (20) Isopropyl Trioleyl Zirconate (21) Isobutyl Trioleyl Zirconate (22) Isobutyl (Diisostearoyl) oleyl zirconate table 2 organometallic compound (outside the scope of the present invention) (1) isopropyl Le pills titanate (2) isopropyl tridodecylbenzenesulfonyl titanate (3 Isopropyl tris (dioctyl pyrophosphate) titanate (4) Tetra isopropyl bis (dioctyl phosphate) titanate (5) Tetra octyl bis (didodecyl phosphite) titanate (6) Tetra (2,2-diallyloxymethyl-1-butyl) bis (Di-tridecyl) phosphite titanate (7) Bis (dioctyl pyrophosphate) oxyacetate titanate (8) Bis (dioctyl pyrophosphate) ethylene titanate (9) Isopropyl trioctanoyl titanate (10) Isopropyl dimethacryl isostearoyl titanate (11) ) Isopropyl isostearoyl diacrylic titanate (12) Isopropyl tri (dioctyl phosphate)
Titanate (13) Isopropyltricumylphenyl titanate (14) Isopropyltri (N-aminoethyl-aminoethyl) titanate (15) Dicumylphenyloxyacetate titanate (16) Diisostearoylethylene titanate (17) Acetoalkoxyaluminum diisopropylate (18) Vinyltriethoxysilane (19) Vinyltris (β-methoxyethoxy) silane (20) γ-methacryloxypropyltrimethoxysilane (21) γ-glycidoxypropyltrimethoxysilane (22) β- (3,4 -Epoxycyclohexyl) ethyltrimethoxysilane (23) N-β (aminoethyl) γ-aminopropyltrimethoxysilane (24) N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane (25) γ-aminopropyltrimethoxysilane Ethoxysilane (26) N-phenyl-γ-aminopropyltrimethoxysilane (27) γ-mercaptopropyltrimethoxysilane (28) γ-chloropropyltrimethoxysilane After drying the copper powder, a temperature of 85 ° C and a temperature of 65 ° C. It was left in a humidity environment of / 95% RH for 2000 hours and the discoloration of copper powder and the occurrence of patina were observed.

In addition, the addition amount of the coating agent in Table 1 and Table 2 was changed to 0.01, 0.05, 0.5, 1.0, 5.0, 10, 10.5 wt% with respect to the copper powder, and the experiment was conducted.

As a result, when treated with the organozirconium compounds shown in Table 1, no discoloration was observed and no patina was generated with the addition amount of 0.05 to 10.5% by weight. The copper powder coated with 0.01% by weight of zirconate of the present invention had some dark brown discoloration and generation of patina.

On the other hand, the copper powder treated with the coating agent shown in Table 2 had a noticeable discoloration of brown color and generation of patina.

From the above results, it is understood that the copper powder of the present invention has excellent aging resistance at high temperature and high humidity.

Experimental Example 2 The surface-coated copper powder used in Experimental Example 1 and the copper powder obtained by leaving it for 2000 hours in a temperature environment of 85 ° C. and a humidity environment of 65 ° C./95% RH were 45 weights based on the weight of the copper powder. % Acrylic resin (solid content 60% by weight) and solvent toluene were stirred for 10 minutes with a homomixer to prepare a conductive paint.

A circuit was formed from the obtained conductive paint on an acrylic plate by a screen printer, and dried at 50 ° C. for 30 minutes in the atmosphere. Then, the volume resistivity of this circuit was measured.

As a result, the circuit obtained from the conductive paint according to the present invention has a volume resistivity of about 3.0 × 10 ^{−4 to} 6.0 × 10 ⁻⁴ Ω · cm, and a circuit from copper powder left for 2000 hours is also The volume resistivity of approximately 6.0 × 10 ^{-4 to} 9.0 × 10 ^-4 Ωcm at 85 ° C
It had a volume resistivity of about 1.0 × 10 ^{-4 to} 6.0 × 10 ^-4 Ω · cm at 65 ℃ / 95% RH.

On the other hand, the circuit obtained from the copper powder treated with the coating material in Table 2 has a volume resistivity of about 1.0 × 10 ^{−3 to} 3.0 × 10 ⁻³ Ω · cm, and is left for 2000 hours. Circuit from powder, 85 ℃
With a volume resistivity of approximately 2.0 × 10 ^{-2 to} 5.0 × 10 ^-2 Ω ・ cm at 65 ° C / 95% RH, approximately 3.0 × 10 ^{-3 to} 6.0 × 10 ^-3 Ω ・ cm.
It had a volume resistivity of.

From this result, the conductive paint of the present invention has excellent initial conductivity, and even after aging at high temperature and high humidity,
It can be seen that it exhibits good conductivity.

Experimental Example 3 The surface-coated copper powder used in Experimental Example 1 was added to the weight of the copper powder.
A conductive paint was prepared by stirring 45% by weight of an acrylic resin (60% by weight of solid content) and toluene as a solvent with a homomixer for 10 minutes.

The obtained conductive paint was left in a humidity environment of 25 ° C./70% RH for 90 days, then a circuit was formed on an acrylic plate by a screen printing machine, and dried at 50 ° C. for 30 minutes in the atmosphere. Then, the volume resistivity of this circuit was measured.

As a result, the circuit obtained from the conductive paint according to the present invention has a volume resistivity of about 3.0 × 10 ^{−4 to} 6.0 × 10 ⁻⁴ Ω · cm, and the rate of change in resistance after standing is almost zero. It was

On the other hand, the circuit obtained from the copper powder treated with the coating material in Table 2 has a volume resistivity of about 1.8 × 10 ^{-3 to} 3.8 × 10 ^-3 Ω · cm, and changes in resistance after standing. The rate was 27-80%.

From this result, it is understood that the conductive coating material of the present invention has excellent storage stability.

Experimental Example 4 The surface-coated copper powder used in Experimental Example 1 was added to the weight of the copper powder.
A conductive paint was prepared by stirring 45% by weight of an acrylic resin (60% by weight of solid content) and toluene as a solvent with a homomixer for 10 minutes.

A circuit was formed on the obtained conductive paint on an acrylic plate by a screen printer, and dried at 50 ° C. for 30 minutes in the atmosphere. This circuit was left for 2000 hours in a temperature environment of 85 ° C and a humidity environment of 65 ° C / 95% RH, and the volume resistivity of this circuit was measured.

As a result, the circuit obtained from the conductive paint according to the present invention showed a change rate of about 10 to 15% at 85 ° C. and about 0 to 5% in a humidity environment of 65 ° C./95% RH.

On the other hand, the circuit obtained from the copper powder treated with the coating material in Table 2 shows a change rate of about 80 to 120% at 85 ° C and 65 ° C / 95% RH.
Showed a change rate of about 40-60%. From this result, it is understood that the coating film obtained from the conductive coating material of the present invention has excellent conductivity and shows good conductivity after aging at high temperature and high humidity.

〔The invention's effect〕

As demonstrated by the above example, the copper powder of claim 1 is coated with the organic zirconate compound, and therefore has excellent rust prevention and excellent aging resistance at high temperature and high humidity. Furthermore, the paint obtained from this copper powder has excellent environmental resistance.

In the copper powder of claim 3, since the coating amount is in the optimum range, it has complete rust prevention and aging resistance as shown in the examples, and the coating obtained from this copper powder is ,
Exhibits extremely good environmental resistance. Further, within this range, the original conductivity of the copper powder is not impaired, and the coating material obtained from this copper powder has excellent conductivity.

In the conductive coating composition according to the fourth aspect, since the copper powder according to the first aspect is used, the storage stability can be greatly improved. Furthermore, excellent heat resistance and environment resistance can be imparted to this coating film.

Claims (4)

[Claims] 1. A copper powder for electromagnetic wave shielding, which is coated with a surface coating agent comprising an organic zirconate compound represented by the following general formula. (RO) x-Zr- (OR ') _4- x where RO is an easily hydrolyzable organic group, OR' is an organic group exhibiting hardly hydrolyzable and lipophilic properties, and X is an integer of 1 to 3. Is. 2. The copper powder for electromagnetic wave shielding according to claim 1, wherein the coating amount of the organic zirconate compound is 0.05 to 10% by weight with respect to the copper powder. 3. A conductive coating composition containing the copper powder according to claim 1, a resin binder, and a solvent. 4. The conductive coating composition according to claim 3, wherein the content of copper powder in the conductive coating composition excluding the solvent is 40 to 90% by weight.