JPS6060168A - Electrically conductive paint - Google Patents

Abstract

PURPOSE:To provide an electrically conductive paint which is lightweight and has a low specific resistance (10<2>OMEGAcm or below), by dispersing two specified kinds of electrically conductive fillers in a synthetic resin binder. CONSTITUTION:Natural or synthetic mica (the ratio of thickness to length of a side being 1/100, particle size being 2-200mu) plated with a metal (e.g. Ni, Cu or Cr) in a deposit thickness of 0.1-1mu is used as a first electrically conductive filler, and carbon powder or carbon fiber is used as a second electrically conductive filler. 15-40vol% said first filler and 2-14vol% said second filler are blended with a synthetic resin binder (e.g. an org. solvent soln. of an ethylene/vinyl acetate copolymer or a butyral resin), each quantity being based on solid in paint. Pref. the first conductive filler is used in a quantity of at least twice by volume as much as that of the second conductive filler.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conductive paint containing a conductive filler mixed into a synthetic resin binder.

Plastic materials have the characteristics of electrical insulation, light weight,
It is used in a wide range of applications due to its properties such as workability, but
When used in electrical and electronic equipment, problems such as static electricity interference and electromagnetic interference occur, and as a result, there is a rapidly increasing demand for plastics to have electrical conductivity.

Conductive paint is known as one of the countermeasures, but the most common conventional conductive paint is a synthetic resin binder with graphite and car/black as conductive fillers. As a result, a relatively stable conductive paint can be obtained, but the conductivity is limited to a specific resistance of 102Ω.

In addition, silver and copper to obtain even higher conductivity.

Paints containing highly conductive metal powder, such as nickel snow, are also known, but the conductive mechanism is due to contact between particles, so if the amount added is low δ'1 degree, metal particles will reciprocate. If metal particles do not make sufficient contact and become isolated in the polymer matrix, high conductivity cannot be obtained.To obtain satisfactory high conductivity, metal particles are added to approximately 30 volumes or more. I needed to. However, when metal powder is added in a large amount as shown in the example above, it causes deterioration in film forming properties as a paint, adhesion to the substrate, mechanical strength of the skin, etc. This resulted in a loss of lightness, which is unique to plastic.

This invention has been made in view of the above circumstances, and an object thereof is to provide a synthetic resin paint that is lightweight and highly conductive.

That is, the present invention provides a conductive paint made by mixing and dispersing at least two kinds of conductive fillers in a synthetic resin binder, the first paint being made by metal plating plate-shaped crystals of synthetic mica or natural mica. Conductive filler and conductive carbon powder or carbon? The present invention provides a conductive paint characterized in that a second conductive 5P1 degree filler selected from conductive fibers is present in the binder.

The first conductive filler used in this invention has a thickness of -
Thin plate-like synthetic mica or natural mica with a side length ratio of about 1/100, and a particle size of 2 to 200 μnl, preferably 5 to 200 μnl.
The surface of the 80 μm plate-shaped crystal is plated (for example, chemically plated) with metal such as nickel, copper, or chromium to a thickness of about 0.1 to 1.0 μm. Here, natural clouds (
υ, the end is muscovite KAt2 (AtS1301o) (O
I()2. Sorb mica, red mica, black rust mica (Mg, F
e)3 (AtS1301o) (011)2, phlogopite) (ME3 (At5j301o) (0H)2, etc.) can be used, and as synthetic mica, one in which the OH group of the above plate crystal is replaced with F (fluorine) is used. Can be used.

If the particle size of mica is less than 2 mm, it will be difficult to handle, and the large surface area will cause a sudden reaction during chemical plating, which can be dangerous. Furthermore, it will be difficult to control the plating thickness, and it will be difficult to handle the mica. It is difficult to obtain a film thick enough to provide electromagnetic shielding. On the other hand, if the particle size is 200/1 m or more, problems arise in terms of suitability, such as lack of flowability as a paint.

On the other hand, the types of metals that can be plated include metals such as nickel, chromium, and copper, which are generally known for chemical plating, and also by dry plating methods such as S/J Tattering Ion Blating. Also aluminum, zinc,
Possible materials include molybdenum, and alloys such as brass are also possible. Furthermore, in order to improve the adhesion of the plating layer, metal oxides such as titanium oxide, iron oxide, aluminum oxide, etc. are coated on the mica surface in advance, and then gold +
i3 plating may also be performed.

Particle size 5 to 8 for ease of chemical plating, stable conductivity, etc.
Particularly preferred is a plate-shaped crystal of synthetic or natural cloud ci of 0 μn1, which is chemically plated with nickel 'io, i to about 1.0 μm.

Furthermore, conductive fibers used as the second conductive filler used in the present invention (for example, acetylene black, Ketjen black, etc. can be applied as the fibers, and rayon-based fibers, Polyacrylonitrile-based, P.

Chi-based fibers, etc. can be applied.

Car+ as the second conductive filler in the present invention? In addition to the lightweight nature of carbon fiber, the unique chain structure of carbon fiber reduces the uncontacted areas of the gold plating powder, making it uniform and stable. This is to obtain good conductivity, and further to prevent sedimentation and separation of metal powder and improve paint suitability.

FIG. 1 is an enlarged view of the state of the coating film formed by the conductive paint of the present invention. ) A second conductive filler (conductive carpin powder 3 or conductive carbon fiber 3') is interposed and dispersed so as to connect the two.

The amount of the first conductive filler added is 15 to 4 in the solid content of the paint.
0 volume) is preferable, and exceeding the upper limit is not preferable because it impairs the suitability of the paint. The second conductive filler is added so that the solid content of the paint is 2 to 14% by volume, and the first conductive filler is contained in a volume that is at least twice that of the second conductive filler. It is clever to do so.

However, if the amount of the second tetraelectric filler added exceeds the above upper limit, there is a risk that the shielding properties will be impaired.

Examples of the synthetic resin binder used in the paint of the present invention include ethylene-vinyl acetate copolymer, acrylic resin, alkyd (B4 fat, urethane%, l fat, unsaturated polyester resin, phenol resin, amine resin, chloride Vinyl] 1./1 fat, coated vinyl CIL acid vinyl copolymer,
These include cellulose resins, butyral resins, etc., which have been decomposed with a solvent. Further, in order to improve the dispersibility of the conductive filler, the fluidity of the R material, and the adhesion to the group 14, a coloring agent such as a titanate coupling agent may be used in combination.

Since the conductive paint of the present invention uses mica as a conductive filler, which is easily folded, as a base material, carbon powder or fibers are first synthesized using a gill mill, an attriter, a roll mill, etc., which have excellent shearing force. Evenly with resin binder a
It is preferable that the first conductive filler is dispersed by &M, and then the first conductive filler is mixed in using a dispersion device with low biological stress such as Neegoo or DiSilver.

In the conductive paint according to the present invention, since the first conductive filler has a volume fraction of mica and metal of about 3:1, there is little use of metal, and therefore the lightweight nature of glass can be utilized. Moreover, a conductive paint having a specific resistance of 102 Ω-α or less can be obtained.

Example Plate crystals of natural mica with a central particle diameter of 30 μm (specific gravity 2.89
) by chemical plating to form a nickel film with a thickness of 0.3 ttm, and nickel plating powder (specific gravity 4 = 25
) f3: Obtained. In other words, this natural mica is about 10μ
Pour into a box-shaped filter with a diameter of +11, apply Sibley, First (4J Sibley PTII process, conditioner, Catazolymp, Cata, I?Knot, and Accelerator, then apply nickel plating solution (PH = 9). The plated product in the filter was immersed for 10 minutes at 0 temperature (25°C), then the plated product in the filter was bent out, and the plated product was placed in a 20% atmosphere at 40°C and left overnight to dry. I got it.

Next, add this nickel plating powder to the solid content of the paint by 2
0% Q%, acetylene black (grain R0,00
5-0. I Itm, ratio 11.45) to be 5 volume @ relation and primed to 1δ 7+? Lipropylene/chlorinated E
VA = 1/2 (1) Synthetic resin pine! −(2
5% solid content) to form a paint, λrPl) propylene notebook with 40 jl/m2 and 60,! 7/
m2 was applied, dried, and the resistivity candy and electromagnetic shielding properties were measured.

This electromagnetic wave shielding characteristic is based on the TAGADA RIKEN-Hasebe method, in which the electromagnetic waves oscillated by a tracking generator are
The electromagnetic waves were transmitted from one of the openings by a Roots antenna, transmitted through a plate-shaped body installed in this opening, received by a similar loop antenna, and analyzed using a spectrum analyzer.

Comparative Example The same nickel plating powder as in the above example was placed in the same synthetic resin paint as in the above example.
o capacity factor (specifically soft Xanzol 1) and 25 volume Jij%
(ratio!) Mixed to obtain a paint so as to give a specific resistance of The results were shown in the table below and Figures 2 to 4. Figure 2 (a) shows the case where low frequency electromagnetic waves were applied to the example. , Figure 2 (bl is also the attenuation effect when applying magnetic waves to high frequency 1, Figures 3 (a) and 4 (a) are comparison samples (1, 2), respectively, showing the attenuation effect when applying low frequency electromagnetic waves to In this case, FIGS. 3(b) and 4(b) show the results when high-frequency electromagnetic waves were applied to comparative samples (1 and 2), respectively.

As is clear from these Examples and Comparative Examples, the use of the conductive car 1 as in the present invention is better than using nickel Meggi powder alone.
1! By using the powder in combination, it is possible to obtain a highly conductive paint that has good paint suitability and a good shielding effect against electromagnetic waves.

[Brief explanation of drawings]

Figure 1 is an enlarged view of one microorganism showing the state of the coating film of the conductive paint according to the present invention, Figures 2 (a) and (b) are diagrams showing the electromagnetic shielding effect of the paint of the present invention, and Figure 3 (a). ). 4(b), FIGS. 4(a) and 4(b) are diagrams showing the electromagnetic shielding effect of the paint according to the comparative example. In the figure, 1... synthetic resin pine goo, 2... first conductive filler, 3... carbine powder, 3'... carbine fiber.

Claims (4)

[Claims] (1) A conductive paint made by mixing and dispersing at least two types of conductive fillers in a synthetic resin binder,
The conductive filler @1, which is formed by fully bending plated crystals of synthetic mica or natural mica, and a second conductive filler selected from conductive carbon fibers or carbon fibers are made to coexist in the binder. A conductive paint that is characterized by: (2) Claim 1 in which the first conductive filler is added at least twice as much (by volume ratio) as the second conductive filler.
Conductive paint as described in section. (3) The solid content of the paint contains 15% of the first conductive filler.
~40 volume M%, second conductive filler 2~14 volume h
t%, and has a specific resistance of 102Ω·tM+ or less. (4) First 4Tf, sexual filler has a particle size of 2 to 200 μm
Add 0.1 nickel to synthetic mica or natural mica plate crystals.
The conductive +'1 paint according to claim 1, which is electrolessly plated to a thickness of ~1.0 μm.