JPH0680151B2 - Conductive paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a conductive paint, particularly a conductive paint containing aluminum alloy powder.

(Prior Art) Recently, conductive materials having a specific resistance of about 10 ^-3 to 10 ¹⁰ Ω-cm are used for many parts such as electronic parts such as resistors, antistatic materials, electromagnetic wave shields, printed circuits, etc. However, as the conductive material, a material in which an electrically non-conductive material such as plastic is made to have conductivity has become very popular. The conductive paint is used as one means for applying conductivity to such an electrically non-conductive material to impart conductivity.

Although carbon black, metal powder and metal oxide are blended as conductive components in conventional conductive paints, all of them have the following drawbacks and are unsatisfactory as conductive paints. It was

In the case of a conductive paint containing carbon black, its conductivity is inferior to that of a metal, so its application is limited.In addition, the desired conductivity can be obtained by the dispersing method and conditions for compounding carbon black. There is also a drawback that it does not exist,
Furthermore, since the hue is limited, the decorativeness is poor.

A paint containing a metal oxide such as tin oxide or zinc oxide cannot provide sufficient conductivity.

Further, in the case of a coating material containing a metal powder such as silver powder, copper powder, or nickel powder, even if high conductivity can be obtained, it has a drawback that it tends to settle because of its large specific gravity, which makes the coating workability poor. In addition to the above-mentioned drawbacks, silver powder has a drawback that it is not practical because it is expensive, and copper powder requires a special surface treatment to obtain stable conductivity. Further, nickel powder is also limited in terms of resources, and the carbonyl nickel powder produced by the carbonyl method has a problem of residual metal carbonyl.

Aluminum powder is inexpensive and has a low specific gravity, so it has good coating workability and is excellent in decorativeness. However, a conductive paint containing aluminum powder as a conductive component lacks practicality. This is because although aluminum originally has high conductivity next to silver and copper, the electrically insulating oxide film formed on the surface of aluminum powder increases the contact resistance between aluminum particles, and This is because it is significantly reduced.

(Object and Structure of the Invention) An object of the present invention is to solve the drawbacks of the prior art and to provide a conductive paint having excellent conductivity without impairing the cost, painting workability and decorativeness of aluminum powder. It is in.

A characteristic of the conductive paint provided by the present invention is that aluminum alloy powder containing aluminum as a main component and 5 to 40% by weight of nickel is blended.

The metal powder blended in the conductive paint of the present invention is a powder made of an aluminum-nickel alloy containing nickel in an amount of 5 to 40% by weight. In the aluminum-nickel alloy of the present invention, if the nickel content is less than 5% by weight, sufficient conductivity cannot be obtained, while if the nickel content exceeds 40% by weight, the specific gravity of the alloy becomes large and the coating becomes difficult. It is not preferable because the workability becomes poor and the cost becomes high. The preferred nickel content is 20-30% by weight.

Furthermore, if required for the aluminum-nickel alloy of the present invention, silicon, iron, copper, titanium, magnesium, manganese,
Features of aluminum-nickel alloys that contain cobalt, chromium, vanadium, molybdenum, silver, zinc, tin, calcium, indium, bismuth, lead, beryllium, antimony, zirconium (conductivity, painting workability) , Decorativeness, cost) may be added to the extent that the properties are not significantly impaired.

The grain size of the aluminum alloy powder having the above alloy composition is
It is preferably 100 mesh (149 μm) or less, more preferably 200 mesh (74 μm or less). Coarse particles having a particle size of more than 100 mesh are not preferable because they tend to settle and the workability of coating deteriorates, and the physical properties of the coating film such as appearance, adhesion strength and moisture resistance are adversely affected.

The shape of the aluminum alloy powder of the present invention is not particularly limited,
It may be in the form of particles, flakes, or a mixture thereof, but in the case of the granular aluminum alloy powder, higher conductivity is obtained as compared with the flaky aluminum alloy powder.
In the case of flake-shaped aluminum alloy powder, it is preferable in handling to be a paste containing a hydrocarbon solvent such as mineral spirit, solvent naphtha, xylene and toluene in an amount of 1 to 50% by weight. The addition of Al can suppress the oxidation of the aluminum alloy powder, and the effect of not lowering the conductivity even after long-term storage can be achieved.

The composition of the coating material containing the aluminum alloy powder of the present invention is not particularly limited, and contains the same components as conventional coating materials, that is, a synthetic resin, a solvent, and optionally other optional components. Any synthetic resin can be used as long as it is commonly used in paints.
Examples thereof include acrylic (lacquer type or cross-linking type), epoxy type, urethane type, acrylic-urethane type, vinyl type and polyester type resins. As the solvent, those generally used for paints, for example, hydrocarbon-based, ester-based, ketone-based, alcohol-based, ether-based solvents and the like are used, and are selected according to the type of synthetic resin. As other optional ingredients,
Color pigments, anti-settling agents, leveling agents, color separation inhibitors,
Examples include coupling agents, antioxidants, other conductive fillers (carbon black, silver powder, copper powder, nickel powder).

The blending amount of the aluminum alloy powder is set according to the required conductivity, but is preferably 70 to 700 parts by weight with respect to 100 parts by weight of the resin content. If the amount is less than 70 parts by weight, sufficient conductivity cannot be obtained, and if it exceeds 700 parts by weight, physical properties of the coating film are deteriorated and stable conductivity cannot be obtained, which is not preferable. A more preferable blending amount of the aluminum alloy powder is 150 to 600 parts by weight, and a smaller blending amount (90 to 400 parts by weight) is sufficient when the aluminum alloy powder is flaky.

The conductive coating material of the present invention is a coating material for resistors which requires a specific resistance of about 10 ⁷ to 10 ¹⁰ Ω-cm, an antistatic coating material which requires a specific resistance of about 10 ⁴ to 10 ⁷ Ω-cm, 10 ^{0 ~10 4 Ω-cm} approximately electromagnetic wave shielding paint resistivity is required, 10 ^-3 ~10 ⁰ Ω-c
It can be used in a wide range as paints for printed circuits that require a specific resistance of about m.

(Examples) The following examples are examples for specifically explaining the present invention, and the present invention is not limited to these examples.

Example 1 80% by weight of Al and 20% by weight of Ni by the air atomizing method
Granular aluminum alloy powder containing
Pass through a 0 mesh screen and have a grain size of 200 mesh (74
A granular aluminum alloy powder having a particle size of less than μm was obtained.

Examples 2 to 6 and Comparative Examples 1 to 6 In the same manner as in Example 1, granular aluminum alloy powder having the alloy composition and particle size as shown in Table 1 was obtained.

Example 7 80% by weight of Al and 20% by weight of Ni by the air atomizing method
Granular aluminum alloy powder containing
After passing through a 0 mesh screen, the granular aluminum alloy powder with a particle size of 100 mesh (149 μm) or less obtained in this way was further crushed using an attritor mill containing 10 kg of steel balls of 6.4 mm in diameter (180 rpm, 1 hour). ).

Alloy powder 170g Mineral spirits 200ml Oleic acid 10g Washed crushed alloy powder with a large amount of mineral spirits, pass through a 200 mesh screen to remove coarse particles, and then solid-liquid separate due to excess to make 80% metal aluminum alloy powder. I got a paste. The resulting alloy powder has a particle size of 20.
It was in the form of flakes with an average thickness of about 2 μm at 0 mesh or less.

Examples 8 to 12 and Comparative Example 7 In the same manner as in Example 7, alloy compositions as shown in Table 2,
A paste containing a flaky aluminum alloy powder having a particle size and an average thickness was obtained.

However, only in the case of Example 11, the grinding time was set to 3 hours.

Example 13 A coating material was prepared by mixing the aluminum alloy powders obtained in Examples 1 to 12 and Comparative Examples 1 to 7 with a resin in the proportions shown in Table 3. As the resin, acrylic lacquer (Anidic A-165 manufactured by Dainippon Ink and Chemicals, Inc .; solid content 45)
%) Was used.

This paint was spray-coated on an ABS plate and dried at 50 ° C. for 20 minutes to form a coating film having a film thickness as shown in Table 3. The specific resistance of the coating film thus formed was measured according to ASTM D257 and calculated from the surface resistance of the coating film.

The measurement results are shown in Table 3.

In addition, in the case of the coating material containing the alloy powder obtained in Comparative Example 3, the precipitation of the alloy particles during spray coating was severe, and it was necessary to coat with stirring.

It was confirmed that the coating film formed by using the coating material containing the aluminum alloy powder containing 5 to 40% by weight of nickel had high conductivity.

Example 14 A coating film was formed in the same manner as in Example 13 by using a coating material prepared by changing the compounding amount of aluminum alloy powder with respect to the resin, and the specific resistance of the coating film was measured. The results are shown in the table below.

Example 15: Moisture resistance test of coating film The coated plate obtained in Example 13 was subjected to an atmosphere of 35 ° C. and a humidity of 90%.
The sample was allowed to stand for one day, and changes in the resistivity of the coating film were examined immediately after the coating film was formed (before the test) and after being left for 56 days (after the test). The results are shown in the table below.

Only in the comparative example, there was a phenomenon in which metal particles fell off from the coating film after the test.

It was confirmed that when the conductive coating material of the present invention was used, a coating film having stable conductivity with little decrease in specific resistance was formed.

(Effects of the Invention) When the conductive coating material containing the aluminum alloy powder of the present invention is used, a coating film having unexpectedly high conductivity can be formed even when a simple substance aluminum powder is mixed. The physical properties of the formed coating film are stable even after long-term storage, and the conductive coating material of the present invention is extremely practical.

Further, since the conductive coating material of the present invention contains a large amount of aluminum in the aluminum alloy powder to be blended, metal particles do not settle during coating, so that coating can be easily performed without using any special means or device. Furthermore, as described above, since the aluminum alloy powder containing a large amount of aluminum is used, the alloy powder acts not only as a conductive component in the paint but also as a pigment, and exhibits a metallic luster with an excellent color tone. A film can be formed. In addition, the cost of the paint can be kept low.

Claims (7)

[Claims] 1. Main component is aluminum, and nickel 5
Conductive paint compounded with aluminum alloy powder containing 40% by weight. 2. The paint according to claim 1, wherein the particle size of the aluminum alloy powder is 149 μm or less. 3. The paint according to claim 2, wherein the particle size of the aluminum alloy powder is 74 μm or less. 4. The coating material according to any one of claims 1 to 3, wherein the shape of the aluminum alloy powder is granular. 5. The coating material according to claim 1, wherein the aluminum alloy powder has a flake shape. 6. The paint according to claim 5, wherein the aluminum alloy powder has a paste-like appearance containing 1 to 50% by weight of an organic solvent. 7. The blending amount of aluminum alloy powder is 100 resin.
The coating material according to any one of claims 1 to 6, which is 70 to 700 parts by weight with respect to parts by weight.