JPH02117932A - Electrically conductive elastic unit - Google Patents

Abstract

PURPOSE:To obtain the subject elastomer, freely foldable, bendable and compressible, having electric conductivity and used for avoiding electromagnetic trouble due to static electricity and electromagnetic wave noise by fixing electrically conductive particles to the surface of an expansion molded elastomer. CONSTITUTION:The objective elastomer obtained by fixing electrically conductive particles (e.g., Cu, Ag or carbon black) to at least the surface of an elastomer expansion molded into a prescribed shape. Furthermore, the surface of the elastomer is preferably subjected to densifying treatment for increasing the structure density thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Field of Industrial Application] The present invention relates to a conductive elastic body used to avoid electromagnetic interference due to static electricity and electromagnetic noise.

[Traditional Techniques] In recent years, digital devices (hereinafter referred to as electronic components), mainly microcomputers, have developed at a remarkable rate, and are rapidly becoming popular in office machines, household electrical devices, automobiles, and the like. Further, the number of microcomputers used is increasing, the degree of integration is improving, and clock frequencies are becoming higher.

Therefore, when storing, housing, or transporting various electronic components that are driven and controlled by weak currents, static electricity generated by friction, vibration, etc., and electromagnetic noise that rides on flat cables or enters through gaps in the housing are generated. In order to protect these electronic components from electromagnetic disturbances such as damage, failure, and malfunction, the following conductive elastic bodies have been proposed.

That is, an elastomer (hereinafter referred to as conductive elastomer) containing conductive particles such as highly conductive metal particles or carbon black particles as a conductive filler in its narrow collar is loaded into the gap of a housing housing electronic components. It is also used as packaging material for transporting electronic components.

[Problem H to be solved by the invention] However, such conductive elastomers are still insufficient, and the following problems have been pointed out.

A conductive elastomer has conductivity imparted by conductive particles contained in its structure and elasticity of the elastomer itself, which is a base material. However, as the content of conductive particles increases, the electrical resistivity decreases and the elasticity of the elastomer itself gradually decreases. Furthermore, it is well known that when the content of conductive particles exceeds a predetermined value, this elasticity is significantly impaired.

In setting the electrical resistivity of a conductive elastomer to a value appropriate for its use, the following problems remain.

In general, electrical resistivity (hereinafter referred to as
The electrical resistivity of the conductive elastomer (referred to as the optimum resistivity) is in the range of 103 to 10" Ωcm. However, as the content of conductive particles increases, the electrical resistivity of the conductive elastomer increases to 1010 Ωcm.
It decreases extremely rapidly from a value of about 102Ωφcm to about 102Ωφcm. For this reason, it is difficult to set the electrical resistivity to the optimum resistivity. Furthermore, even if the resistivity can be set to the optimum value, it is inevitable that the elasticity of the elastomer will be impaired.

On the other hand, in order to suitably shield electromagnetic noise, the electrical resistance of the conductive elastomer needs to be approximately 10 Ω·cm. However, if such conductive particles are contained, the content exceeds the above-mentioned predetermined value and the elasticity of the conductive elastomer is significantly impaired.

The present invention has been made to solve the above-mentioned problems, and its purpose is to provide a conductive elastic body having an electrical resistivity suitable for its use without impairing its elasticity.

Structure of the Invention [Means for Solving the Problem] In order to achieve the above object, the means adopted in the invention of Hyouka 1 is to fix conductive particles on at least the surface of an elastic body formed into a predetermined shape. The gist of the invention is a conductive elastic body characterized by:

In addition, the means adopted by the invention of Hyouka 2 to achieve this object is characterized in that the surface of the conductive elastic body obtained by the above-mentioned first invention is subjected to an interrogation treatment to increase the tissue density. The gist is a conductive elastic body that

[Function] The conductive elastic body of the invention of ice candy 1 having the above structure is already formed into a predetermined shape as a material equivalent to the conventional conductive elastomer; a wrapped elastic body, for example, a latex sponge is used. However, at least on the back surface thereof, highly conductive metal particles such as copper or silver or conductive particles such as carbon blank particles are fixed.

As is well known, latex sponges have a large number of bubbles inside due to air or a foaming agent blown in during the foaming process, and have elasticity based on these bubbles. Since the size of the bubbles is extremely large compared to the diameter of the conductive particles, the conductive particles will be fixed to the surface of the latex sponge or the wall surface of the bubbles, and the state of formation of the bubbles will be due to the conductive particles. It remains unchanged before and after it is established.

Therefore, the conductive elastic body of the invention of Hyouka 1 can be folded,
It has the inherent elastic properties of a latex sponge, such as being able to bend and compress freely, and the conductivity imparted by conductive particles fixed on at least the surface of the latex sponge.

The conductive particles can be fixed by soaking a latex sponge in a solution obtained by adding the particles to a binder, solvent, etc., or by spraying the above solution, and then adding the binder, solvent, etc. This is done by evaporating. Therefore, the surface resistivity does not indicate the degree of conductivity of the conductive elastic body of the invention of Hyouka 1, and the surface resistivity is determined by the type of conductive particles and the amount of fixation (specifically, the degree of conductivity of the conductive particles in the solution) or the immersion time. , spray time); adjusted accordingly.

Next, the conductive elastic body of the invention of Hyouka 2 has the surface texture of the latex sponge according to the invention of Hyouka 1, which has uniform elastic properties and conductivity based on the above surface treatment.
It is modified into a high-density structure by heat treatment or dense treatment such as solvent treatment that dissolves or swells the latex. Alternatively, for high-density organization, a method may be used in which a highly viscous conductive liquid is first applied to the surface, and then a dense surface structure is formed by heat treatment.

In other words, the conductive elastic body of the invention of youngest brother 2 consists of a core part that has not been subjected to the J/I dense treatment and maintains elasticity based on bubbles, and a high-density Mi woven layer around the core, and has a high-density Mi woven layer around it.
! Based on the high density of the i-weave, the conductive particles on the surface of the conductive elastic body are aggregated to reduce the surface resistivity.

Therefore, the surface resistivity indicating the degree of conductivity of the conductive elastic body of the invention of the youngest brother 2 is adjusted by the surface resistivity of the conductive elastic body of the invention of the youngest brother 1, the processing time of the densification process, and the processing method. .

[Example] Next, physical properties (based on direct experimental results) of an example of the conductive elastic body according to the present invention will be described.

-Experiment- Measurement results of physical property values regarding the first and second embodiments of the conductive elastic bodies of the youngest brother 1 and second inventions using polyester-type foamed polyurethane sponges obtained by subjecting polyester and isocyanate to a urethane reaction. , shown in Tables 1 and 2.

The particle size of the conductive particles used was about 3 to 6 μm, and the fixation of the conductive particles in the first example was carried out by dipping a foamed polyurethane sponge in a solution containing the conductive particles. .

Further, CB in Table 1 indicates carbon black, and material No. in Table 2 indicates sample No. of the first example.

From these results, the physical property values such as tensile strength and compression set based on the elastic properties of the polyurethane sponges in the first and second examples are comparable to those of the comparative example, which was simply exposed. Therefore, it is useful as a cushioning material, a cushioning material, a sealing material, etc. In addition, the desired surface resistivity can be easily imparted, and the surface resistivity is greatly reduced, so it can be said that the conductivity is excellent. To be more specific, the surface resistivity ranges from 10 Ω/pm” to 103
The polyurethane sponge of the first example, which has a value of Ω/cW12, has the effect of preventing static electricity charging, and the polyurethane sponge of the second example has a surface resistivity of 10"Ω/cm2 to 10-4 Ω/cm2. The polyurethane sponge acts as an electromagnetic shield to block out electromagnetic noise.

For this reason, the polyurethane sponge of the first embodiment, which is foam-molded into a sheet shape, prevents electrostatic charging that occurs when storing and transporting various electronic components, thereby avoiding destruction of electronic components due to electrostatic discharge, and also prevents vibrations and It is a material for envelope-shaped antistatic packaging that can protect electronic components from impact.

Also, the cross-sectional shape is annular, circular, or oval.

The polyurethane sponge of the second embodiment, which is foam-molded into a rod having an irregular cross section such as an Ω-shape, a T-shape, an L-shape, etc., is compressed and filled into gaps such as opening/closing parts, joints, etc. of housing casings for electronic components. This is an electromagnetic shielding casket that can keep the casing airtight and watertight, as well as shield electromagnetic noise from entering through gaps.

Although the embodiments of the present invention have been described above, the present invention is not equally limited to these embodiments, and it goes without saying that the present invention can be implemented in various forms without departing from the spirit thereof. For example, it is obvious that in addition to polyurethane sponges, various sponges such as chloroprene sponges, silicone sponges, and latinx sponges may be used.

Effects of the Invention As described above in detail including Examples, the conductive elastic body of the invention of Hyouka 1 has conductive particles fixed to at least the surface of the elastic body that has already been formed into a predetermined shape. Because it is a foamed material, it has the inherent elastic properties of a foamed elastic material that can be folded, bent, compressed, etc., and the conductivity, or electrical resistance, imparted by conductive particles to a degree suitable for preventing static electricity. It becomes a conductive elastic body with $ (surface resistivity). Moreover, conductivity can be easily imparted. For this reason, the conductive elastic body of the invention of Hyouka 1 is
It is extremely useful and inexpensive as a material for antistatic packaging for transporting electronic components.

In addition, the conductive elastic body of the invention of Hyouka 2 has a high-density structure by dense processing only the surface texture of the conductive elastic body of the invention of Hyouka 1, which has uniform elastic properties and conductivity based on surface treatment. Because it has been altered to a core, it becomes an elastic body consisting of a core that has not been densified and maintains elasticity based on bubbles, and a high-density tissue layer around the core. Therefore, since the conductive particles on the surface of the conductive elastic body are aggregated due to the densification of the structure through the densification process, the conductive elastic body of the invention of Hyouka 2 is approximately equivalent to the wrapped elastic body. The conductive elastic body has both elastic properties and a low electrical resistivity (surface resistivity) suitable for electromagnetic shielding. Therefore, the conductive elastic body of the invention of Hyouka 2 can be suitably used as an electromagnetic shielding gasket for shielding electromagnetic noise.

Claims (1)

[Scope of Claims] 1. A conductive elastic body, characterized in that conductive particles are fixed to at least the surface of the elastic body foam-molded into a predetermined shape. 2. A conductive elastic body characterized in that the surface of the conductive elastic body according to claim 1 has been subjected to a densification treatment to increase the tissue density.