JPH10316901A - Electroconductive coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive coating material which, when applied to an elastically deformable substrate and dried, forms a coating film which can retain a high electroconductivity even when subjected to expansion, contraction, or deformation or brought into contact with water, etc. SOLUTION: This coating material contains a rubber or resin binder 14, filler particles 15 comprising a metallic material and dispersed in the binder 14, and metal fibers 16 dispersed in the binder 14 and capable of being in contact with the filler particles 15. In a coating film 13, the contact of filler particles 15 with each other or the contact between the filler particle 15 and the fibers 16 maintains an electrically conductive state, and thus an electromagnetic shielding material having a high electric conductivity can be obtd. from this coating material. When the coating film 13 is subjected to expansion, contraction, or deformation or is brought into contact with water, etc., the contact of filler particles 15 with each other disappears; however, the fibers 16 can be in contact with separated filler particles 15 and thus the electrically conductive state is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paint, and more particularly, to a conductive paint applied to an elastically deformable substrate.

[0002]

2. Description of the Related Art In recent years, with the rapid development of the electronics industry, equipment, devices, systems, and the like utilizing electricity and electronics have become sources and receivers of all kinds of noises and cause electromagnetic wave pollution. ing. Under such circumstances, there is a demand for an electromagnetic wave shield having conductivity that can prevent electromagnetic wave pollution.

Generally, an electromagnetic wave shield provided with conductivity by applying a treatment such as plating to the surface of a base material made of a resin material or the like as an insulator or painting a conductive paint is used. Is done. In particular, a method of applying a conductive paint to the surface of a base material has been mainly employed since it can be applied according to the type and complexity of the shape of the base material and is excellent in cost.

As shown in FIG. 6, when a conventional conductive paint is applied to the surface of a substrate and dried, a coating layer 21 is formed. The coating layer 21 has a binder 22 made of rubber or resin, and is scattered in the binder 22 to form a silver or metal material.
It consists of countless fillers 23 made of nickel or copper. Here, the fillers 23 in the coating layer 21 are brought into contact with each other to be in a conductive state,
When used as an electromagnetic wave shield, a desired high conductivity is obtained.

[0005]

However, when the above-mentioned conductive paint is applied to a substrate made of an elastically deformable material such as rubber, and dried to form a coating layer 21, which is used as an electromagnetic wave shield. Had the following problems.

That is, as shown in FIG. 7, when an external force or the like is applied to the electromagnetic wave shield, not only the base material but also the coating layer 21 can be expanded or contracted. At this time, a gap may be formed between the fillers 23 in the coating layer 21 and the contact state may be released. However, even if external force or the like is subsequently removed, the gap remains between the fillers 23. There was a case that did not return. For this reason, the conduction between the fillers 23 is cut off, and the conductivity is extremely reduced, and there is a possibility that the initially expected conductivity (for example, the electromagnetic wave shielding effect) may not be secured.

If the coating layer 21 comes into contact with water or the like, the binder 22 in the coating layer 21 may absorb water or the like and swell. In this case, a gap is generated between the fillers 23 under the influence of the swelling of the binder 22, and as a result, there is a possibility that a problem that the conductivity is not ensured as described above may occur.

On the other hand, it is conceivable to use carbon instead of a metal material as a material constituting the filler 23. Carbon is a filler 23 made of the above metal material.
Since the particle size is smaller than that of
The problem that a gap is formed between the three and the conductivity is extremely reduced hardly occurs. However, carbon originally has a high resistance value and low conductivity compared to metal, and therefore is unsuitable for use when high conductivity is required.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a coating film layer formed by coating and drying an elastically deformable substrate. It is an object of the present invention to provide a conductive paint which can ensure high conductivity even when it is stretched, deformed or comes into contact with water or the like.

[0010]

According to the first aspect of the present invention, there is provided an electroconductive paint applied to an elastically deformable base material, comprising a binder made of rubber or resin. The gist of the present invention is to provide a filler made of a metal material scattered in the binder and a metal fiber scattered in the binder and capable of contacting the filler.

According to a second aspect of the present invention, in the conductive paint according to the first aspect, the metal material constituting the filler is at least one selected from silver, nickel, and copper. This is the gist.

Further, according to the third aspect of the present invention, in the conductive paint according to the first or second aspect, the material of the metal fiber is stainless steel.

According to a fourth aspect of the present invention, in the conductive paint according to any one of the first to third aspects, the metal fiber is contained in a coating layer obtained by drying the conductive paint. The gist is that the content is 1% by weight or more and less than 5.0% by weight.

Here, in the invention according to claim 4, the metal fibers contained in the dried coating film layer are:
It must be at least 0.1% by weight and less than 5.0% by weight.
If the content of the metal fiber is less than 0.1% by weight, the desired high conductivity may not be obtained because the content of the metal fiber is too small. On the other hand, when the content of the metal fiber is 5.0% by weight or more, there is a possibility that the content of the metal fiber is too large to be easily dispersed. The content of the metal fiber in the coating layer is more preferably from 0.1% by weight to 3% by weight, and still more preferably from 0.3% by weight to 1% by weight.

[0015] In addition, in the invention according to claim 5, in the conductive paint according to any one of claims 1 to 4, the gist is that the diameter of the metal fiber is 1 μm or more and 20 μm or less. .

Here, in the invention described in claim 5, the diameter of the metal fiber needs to be 1 μm or more and 20 μm or less. When the diameter of the metal fiber is less than 1 μm, the strength of the metal fiber is weakened and the metal fiber is broken in the middle, so that the conductivity may be reduced. When the diameter of the metal fiber exceeds 20 μm, it is difficult to disperse, and it is difficult to form a conductive paint, so that a coating layer may not be formed. The diameter of the metal fiber is preferably 4 μm or more and 8 μm or less, and more preferably 8 μm.

According to a sixth aspect of the present invention, in the conductive paint according to any one of the first to fifth aspects, the length of the metal fiber is from 0.5 mm to 5.0 mm. This is the gist.

Here, in the invention according to claim 6, the length of the metal fiber is not less than 0.5 mm and not more than 5.0 m.
m. If the length is shorter than 0.5 mm, a desired high conductivity may not be obtained. If the length is longer than 5.0 mm, the metal fibers become entangled with each other, making it difficult to disperse.
There is a possibility that the conductive paint becomes difficult to form a film and a coating layer cannot be formed. The length of the metal fiber is 1m
It is more preferably not less than m and not more than 2 mm, and still more preferably about 2 mm.

According to the first aspect of the present invention, the conductive paint comprises a binder made of rubber or resin, a filler made of a metal material scattered in the binder, and the filler scattered in the binder. It is composed of metal fibers that can come into contact with each other. When this conductive paint is applied to an elastically deformable substrate and then dried, a coating layer is formed on the substrate, and fillers and metal fibers are scattered in a binder of a component forming the coating layer. Can contact each other. For this reason, not only the contact between the fillers, but also the mutual contact between the filler and the metal fibers in the coating layer formed on the base material ensures a conductive state, and a desired high conductivity is obtained.

Further, the base material is formed of an elastically deformable material, and the base material expands and contracts and deforms when an external force or the like is applied thereto. I do. At this time, the interval between the fillers in the coating film layer will fluctuate. However, in the present invention, since the metal fibers that bridge the fillers are provided, the contact state is easily maintained, and the conductivity of the coating film layer is maintained. The state is maintained.

Furthermore, when the coating layer comes into contact with water or the like, the binder in the coating layer absorbs water or the like and swells, and the spacing between the fillers fluctuates under the influence of the swelling of the binder. Although there is a possibility that the conductivity does not extremely decrease due to the presence of the metal fiber as described above.

According to the second aspect of the present invention, in addition to the function of the first aspect, the metal material constituting the filler is at least one selected from silver, nickel and copper. Consisting of For this reason, since the filler is formed of a metal material having excellent conductivity, conductivity can be more reliably imparted to the coating layer, and the conductivity is further enhanced.

Further, according to the third aspect of the present invention,
In addition to the effects of the inventions described in claims 1 and 2, the material forming the metal fiber is stainless steel. Therefore, the metal fiber is hardly corroded, and the conductivity can be easily maintained. In addition, since the metal fiber is hardly corroded, the durability of the metal fiber and thus the coating layer can be improved.

In addition, according to the invention described in claim 4,
In addition to the function of the invention described in any one of claims 1 to 3, the metal fiber may be contained in a coating film layer obtained by drying a conductive coating material.
% By weight and less than 5.0% by weight. Therefore, a desired high conductivity can be exhibited only by adding a small amount of metal fiber of 0.1% by weight or more and less than 5.0% by weight in the coating layer. In addition, the metal fibers are easily dispersed in the conductive paint, thereby easily forming a film.

In addition, according to the fifth aspect of the present invention,
In addition to the functions of the invention described in claims 1 to 4, the diameter of the metal fiber is 1 μm or more and 20 μm or less. For this reason, the metal fibers are easily dispersed in the conductive paint, and the metal fibers can be used without a problem that the strength of the metal fibers is weakened.

According to the sixth aspect of the present invention, in addition to the functions of the first to fifth aspects, the length of the metal fiber is 0.5 mm or more and 5.0 mm or less. Therefore, the metal fibers are dispersed in the conductive paint without being entangled with each other, and a desired high conductivity can be exhibited.

[0027]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an embodiment of an electromagnetic wave shielding paint using a conductive paint according to the present invention; FIG.

As shown in FIG.
Consists of an elastically deformable substrate 12 and a coating layer 13 formed by applying and drying a conductive paint on the surface of the substrate 12. The base material 12 is formed into a predetermined shape by, for example, a known injection molding method using a rubber component (for example, chloroprene rubber) or a resin component having flexibility.

As shown in FIGS. 1 to 4, the conductive paint
A binder 14 made of rubber (for example, chloroprene rubber) or resin, and a filler 15 made of a metal material (for example, silver, nickel, or copper) dispersed in the binder 14
And a metal material (for example, stainless steel) that can come into contact with the fillers 15 scattered in the binder 14.
Metal fibers (hereinafter, simply referred to as “fibers”) 16. The filler 15 may have various shapes such as a flat plate, a sphere, a tree, or a scale, and the diameter of the filler 15 is not particularly limited. A filler 15 having a small diameter is preferable.

The fiber 16 is formed into a fiber having a large aspect ratio and has flexibility. Due to such properties, the fiber 16 is easily brought into contact with the filler 15. The coating layer 13 is formed by applying the conductive paint on the substrate 12 by, for example, a spray gun or the like, and then drying. The thickness of the coating layer 13 is, for example, 50 μm.
It is about.

As shown in FIG. 2, in the present embodiment, the fillers 15 in the coating layer 13 are in contact with each other or, as shown in FIGS. Are separated, but their filler 1
The fibers 16 come into contact with each other or become entangled with each other, so that they are all in a conductive state.

Next, the operation and effect of this embodiment will be described. In the present embodiment, the electromagnetic wave shield 11 has an elastically deformable base material 12 and a coating layer 13 formed by applying and drying a conductive paint on the surface of the base material 12. For this reason, as shown in FIGS.
When the fillers 15 in the inside or the fillers 15 and the fibers 16 are in contact with each other and become conductive, even when used as the electromagnetic wave shield 11,
Desired high conductivity can be secured. In addition, since the base material 12 is formed of an elastically deformable material, when an external force or the like is applied to the electromagnetic wave shield 11, the contact between the fillers 15 in the coating layer 13 is released and the conduction is cut off. However, in the present embodiment, even if a gap is generated between the fillers 15, as shown in FIG. 5, the fiber 16 may come into contact with the fillers 15 having the gap. Therefore, electrons (e ⁻ ) can flow in the direction of the arrow.
Therefore, high conductivity can be secured by maintaining the conductive state of the coating layer 13. Further, when the electromagnetic wave shield 11 comes into contact with water or the like, the binder 14 in the coating layer 13 absorbs water or the like and swells, and the swelling of the binder 14 causes a gap between the fillers 15. There is a risk that it will. But,
In this case as well, the presence of the fiber 16 can prevent the conductivity from being extremely reduced. In addition, since the filler 15 in the coating layer 13 is formed of at least one selected from silver, nickel, and copper, the filler 15 has excellent conductivity, and more reliably imparts conductivity to the coating layer 13. And the conductivity can be further improved. In addition, since the fibers 16 in the coating layer 13 are made of stainless steel, the fibers 16 can be prevented from being corroded, and the conductivity of the electromagnetic wave shield 11 can be easily maintained. At the same time, the desired high conductivity can be secured in a stable state.
Further, since the fiber 16 is hardly corroded, the durability of the fiber 16 and thus the coating layer 13 can be improved. The fiber 16 is contained in the coating layer 13 of the electromagnetic wave shield 11 in an amount of 0.1% by weight or more and less than 5.0% by weight. Therefore, when the electromagnetic wave shield 11 is used only by adding a small amount of the fiber 16 of 0.1% by weight or more and less than 5.0% by weight in the coating layer 13, a desired high conductivity can be obtained. it can. Further, since the fibers 16 are easily dispersed in the conductive paint, the film can be easily formed and the coating layer 13 can be formed.・ Furthermore, the diameter of the fiber 16 in the conductive paint is 1μ.
m or more and 20 μm or less. Therefore, the fibers 16 can be easily dispersed in the conductive paint, and the fibers 16 can be used without causing a problem that the strength of the fibers 16 is weakened. -In addition, the length of the fiber 16 in the conductive paint is
It is 0.5 mm or more and 5.0 mm or less. Therefore, the fibers 16 are dispersed without being entangled in the conductive paint, and when used as the electromagnetic wave shield 11, a desired high conductivity can be exhibited.

[0033]

EXAMPLES Examples of the above embodiment will be described below. In Examples 1 to 11 and Comparative Examples 1 to 6, 50 × 50 × 3
(Mm) chloroprene rubber was prepared.

Further, as the conductive paint, binder 14
Equipped with a chloroprene rubber as the filler, a nickel filler as the filler 15 (80% by weight in the coating layer), and a stainless steel fiber as the fiber 16. After applying this conductive paint on the chloroprene rubber surface, baking at a high temperature of 80 ° C. for 60 minutes,
A coating layer 13 having a thickness of 50 μm was formed on the surface of the chloroprene rubber to obtain a test piece. The length (mm), diameter (μm), and content (% by weight) in the coating layer 13 of the stainless steel fiber were prepared according to the compositions described in Table 1 below.

Then, the conductivity [surface resistance (Ω / □)] of each test piece surface, the coating property of the conductive paint on the chloroprene rubber, and the dispersibility of the stainless steel fiber in the conductive paint were evaluated. Table 1 shows the evaluation results at that time. In the table, ○ indicates that there was no problem in use, △ indicates that some contrivance was required for use, and × indicates that use was impossible. Also,
In the table, “initial” refers to the state as it is after the test piece is formed, “after expansion and contraction” refers to the state after the test piece has been pulled after being pulled by 50%, and “after water resistance” refers to the state after the test. This is the state after the pieces have been immersed in water at 60 ° C. for 24 hours and then dried.

[0036]

[Table 1] As shown in Table 1 above, when the conductive paints of Examples 2, 7 and 10 were used, the coatability of the conductive paint with respect to chloroprene rubber and the dispersibility of stainless steel fibers in the conductive paint were quite problematic. However, the values of the sheet resistance (Ω / □) of the test piece surfaces were extremely low, and it was found that the desired high conductivity was exhibited extremely well.

In the case where the conductive paints of Examples 3 and 4 were used, although some measures were required for painting,
The dispersibility of the stainless fibers was not a problem at all, and the values of the sheet resistance (Ω / □) of the test piece surfaces were extremely low, and it was found that the desired high conductivity was exhibited extremely well.

When the conductive paints of Examples 5, 8, 9 and 11 were used, although some measures were required for the paintability and the dispersibility of the stainless steel fibers, the surface of the test piece surface was changed. The value of the resistance (Ω / □) was low, and it was found that the desired high conductivity was favorably exhibited.

Further, when the conductive paints of Examples 1 and 6 were used, the paintability and the dispersibility of the stainless steel fiber were not a problem at all, and the values of the sheet resistance (Ω / □) of the test piece surfaces were also low. As compared with Examples 2, 7, and 10, slight inferiority was observed, but it was low, indicating that desired high conductivity was exhibited.

On the other hand, when the conductive paints of Comparative Examples 1 and 3 were used, the paintability and the dispersibility of the stainless steel fiber were not problematic, but the surface resistance (Ω / □) of the test piece surface. Was extremely high, and the desired high conductivity was not obtained, and was extremely lowered.

When the conductive paints of Comparative Examples 4, 5 and 6 were used, there were problems in the paintability and the dispersibility of stainless steel fibers, and the sheet resistance (Ω / □) of the test piece surface was low. The values could not be measured and Comparative Examples 4 and 5
And 6 were unsuitable for use.

Furthermore, when the conductive paint of Comparative Example 2 was used, the value of the sheet resistance (Ω / □) of the test piece surface was extremely low, and the desired high conductivity was exhibited. However, there was a problem in the paintability and the dispersibility of the stainless steel fiber, and it was impossible to actually use it.

Note that the present invention is not limited to the above-described embodiment, and may be implemented as follows by appropriately changing a part of the configuration without departing from the spirit of the invention. In the above embodiment, at least one metal selected from silver, nickel, and copper is used as the metal material forming the filler 15, but any other metal (for example, a metal having excellent conductivity) may be used. Gold, aluminum, stainless steel, etc.). In the above-described embodiment, stainless steel is used as a material constituting the fiber 16, but any other metal may be used as long as the metal has excellent corrosion resistance. In the above-described embodiment, the base material 12 is formed by the injection molding method. However, the base material 12 may be formed by any other method such as a blow molding method, as long as the base material 12 can be formed into a predetermined shape. May be performed in any suitable manner. In the above embodiment, the base material 12 is sprayed by the spray gun.
Although the conductive paint is applied to the base material, any other material (eg, curtain flow coater, roller, brush, iron) can be used as long as it can be applied according to the type and shape of the substrate 12. May be painted.

The technical ideas, which are not described in each claim of the claims but can be grasped from the above embodiment, are described below together with their effects. -The conductive paint according to any one of claims 1 to 6, wherein the base material is made of rubber.

With such a configuration, the conductive paint can be applied to rubber products.

[0046]

As described in detail above, according to the conductive paint of the present invention, when a paint film layer is formed by coating and drying on an elastically deformable substrate, the paint film layer expands and contracts. It has an excellent effect that high conductivity can be ensured even when it is deformed or comes into contact with water or the like.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a coating layer made of a conductive paint according to an embodiment of the present invention.

FIG. 2 is a schematic enlarged plan view of a main part showing a state where fillers are in contact with each other or a filler and a fiber.

FIG. 3 is an enlarged plan view of a main part showing a state in which a gap is formed between fillers.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is an operation diagram showing a conductive state of a coating film layer.

FIG. 6 is a plan view showing a coating layer made of a conductive paint according to a conventional technique.

FIG. 7 is a plan view showing a problem of a conductive paint in the related art.

[Explanation of symbols]

12 ... substrate, 13 ... coating layer, 14 ... binder, 15 ...
Filler, 16 ... (metal) fiber.

Claims (6)

[Claims] 1. A conductive paint applied to an elastically deformable substrate, comprising: a binder made of rubber or resin; a filler made of a metal material scattered in the binder; and also scattered in the binder. And a metal fiber that can come into contact with the fillers. 2. The metal material constituting the filler,
The conductive paint according to claim 1, comprising at least one selected from silver, nickel and copper. 3. The material constituting the metal fiber,
The conductive paint according to claim 1, wherein the conductive paint is stainless steel. 4. The method according to claim 1, wherein the metal fiber is contained in a coating layer obtained by drying the conductive paint in an amount of 0.1% by weight or more and less than 5.0% by weight. The conductive paint according to any one of the above. 5. The conductive paint according to claim 1, wherein the diameter of the metal fiber is 1 μm or more and 20 μm or less. 6. The length of the metal fiber is 0.5 m.
2. The length is not less than m and not more than 5.0 mm.
The conductive paint according to any one of claims 1 to 5.