JPH0319062B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a conductive sheet.

Conductive sheets are often used as materials for storage containers or bags that contain semiconductor elements such as ICs and LSIs, electronic equipment parts, and precision equipment parts, or packaging sheets or films that wrap them. It plays the role of prevention and anti-static. Conventionally, conductive sheets have been manufactured by bonding a nonwoven fabric containing conductive fibers to a base material made of a thermoplastic synthetic resin sheet or film by means such as thermocompression bonding or heat fusion bonding.
However, in this production method, when the nonwoven fabric is attached to the base material using the roll press method, the temperature and pressure are lower than with the hot platen press method, so the nonwoven fabric does not adhere completely to the base material, and Some of the conductive fibers constituting the nonwoven fabric stood up from the surface of the nonwoven fabric in a fuzzy state. Therefore, when such a conductive sheet is used, the fluffy portions of the conductive fibers break and become loose from the sheet surface during use, which not only reduces the conductivity but also causes environmental deterioration as the loose fiber fragments turn into dust. I imitated it.

An object of the present invention is to provide a method for manufacturing a conductive sheet that can solve the above-mentioned problems.

The method for manufacturing a conductive sheet according to the present invention includes laminating a nonwoven fabric made of conductive fibers on at least one side of a base material made of a thermoplastic resin sheet, and adding fluffy portions of the fibers to the surface of the nonwoven fabric side of the obtained nonwoven fabric laminated sheet. A synthetic resin liquid for fiber attachment is applied to the same surface.

Examples of thermoplastic resins that make up the base material include vinyl chloride resin, acrylonitrile, butadiene,
Styrene copolymer resin, acrylic resin, ethylene/
Examples include vinyl acetate copolymer resin, and the thickness of the base material is usually 0.1 to 3.0 mm. If the base material is thick,
A base material containing carbon black inside may also be used.

The nonwoven fabric is made of conductive fibers alone or conductive fibers mixed with low softening point thermoplastic fibers, and the thermoplastic fibers are thermally fused or a binder is used to combine the fibers to form a web. It is manufactured by conventional methods such as the needle punching method, in which the fibers are stitched onto the web using needles without using a binder. Examples of conductive fibers include copper-adsorbing fibers, metal-plated fibers, carbon composite fibers, metal-deposited fibers, thin metal wires, and the like.
Further, the thermoplastic fiber with a low softening point is made of a resin that is compatible with the base material, and examples thereof include various fibers such as polyolefin fiber, nylon fiber, polyester fiber, and acrylic fiber.

The base material and the nonwoven fabric are bonded together by a roll press method. The pressing temperature is usually around 70°C, but this is set appropriately depending on the resin of the base material.
When the substrate is thick, the nonwoven fabric is laminated to both sides of the substrate.

The synthetic resin liquid for fiber attachment is a solution prepared by dissolving a resin compatible with the base material resin in a solvent, or an emulsion containing the same resin, whose viscosity is adjusted to 5 to 300 centipoise. used. If the viscosity of the synthetic resin liquid is less than 5 centipoise, even if the fluffed portion of the fibers is pressed against the surface of the nonwoven fabric, the elastic repulsive force of the fibers overcomes the adhesive force of the liquid, causing the fibers to stand up again. Also, if the viscosity of the synthetic resin liquid exceeds 300 centipoise,
The conductivity of the conductive sheet decreases below the required value, and the workability of the coating operation deteriorates.

As described above, according to the present invention, since the synthetic resin liquid for fiber attachment is applied to the surface of the nonwoven fabric side of the nonwoven fabric pasted sheet, the fluffed portions of the fibers constituting the nonwoven fabric can be pressed and attached to the surface of the sheet. Therefore, it is possible to solve all the problems described at the beginning, such as the reduction in conductivity and the generation of dust due to fiber fragments. Further, the conductivity of the product sheet does not decrease due to the application of the synthetic resin liquid. The reason for this is not certain, but the fluffy part of the conductive fibers
It is considered that even after being adhered to the surface of the sheet, at least the non-adhered portion is exposed and not all of it is covered with the coating liquid.

Next, embodiments of the present invention will be specifically described based on the drawings.

In FIG. 1, the base material 2 extruded by the sheet extrusion molding device 1 is transferred to a pair of pressure rolls 4 together with the conductive nonwoven fabric 3 fed out from the roll 13 while it is still in a thermally softened state. The nonwoven fabric 3 is pasted on one side of the substrate 2 by being passed through the substrate 2 in an overlapping manner. The substrate 2 is made of vinyl chloride resin and has a thickness of 0.4 mm. The nonwoven fabric 3 is manufactured by a binder method from acrylic fibers adsorbed with copper and polyethylene fibers. The temperature of the pressure roll 4 is adjusted to about 70°C. The high-temperature sheet 5 emerging from between the pair of rolls 4 is then passed through a plurality of cooling rolls 6 in a zigzag pattern and wound up into a roll. In this way, a roll of nonwoven fabric-covered sheet 7 is obtained.

Next, as shown in FIG. 2, the nonwoven fabric pasted sheet 7 is fed out from this roll, passed between a plurality of pinch rolls 8 with the nonwoven fabric side down, and then passed between a pair of upper and lower coating rolls 9. be done. The lower coating roll 9 is in close contact with a coating liquid supply roll 10, and the lower half of the roll 10 is coated with a synthetic resin liquid 11 for adhering fibers.
It is immersed in. . As a synthetic resin liquid, an acrylic resin solution (manufactured by Mitsubishi Rayon Co., Ltd., product name Acrynal, product number H-004) was diluted with methyl ethyl ketone in a ratio of 6:4 to reduce the viscosity to 10.
This is a solution adjusted to centipoise. By passing the nonwoven fabric-covered sheet 7 between the pair of application rolls 9 in this manner, approximately 20 g/m ² of the synthetic resin liquid is applied to the surface of the sheet 7 on the nonwoven fabric side. The sheet 7 is then dried while passing through a plurality of take-up rolls 12, and the obtained conductive sheet 13 having a thickness of 0.4 mm is wound into a roll.

When the surface of the nonwoven fabric side of this conductive sheet 13 was observed with a magnifying glass, no fluffing of the conductive fibers was observed, and the conductivity of the sheet 13 was completely different from the conductivity of the nonwoven fabric pasted sheet 7 before the coating process. Nakatsuta.

[Brief explanation of the drawing]

FIGS. 1 and 2 are process diagrams showing an embodiment of the present invention. 2...Base material, 3...Nonwoven fabric, 4...Pressure roll, 7...Nonwoven fabric pasted sheet, 9...Coating roll, 11...Synthetic resin liquid for fiber attachment, 13...
conductive sheet.

Claims (1)

[Claims] 1. A nonwoven fabric made of conductive fibers is laminated on at least one side of a base material made of a thermoplastic resin sheet, and a fluffed portion of the fibers is attached to the nonwoven fabric side surface of the obtained nonwoven fabric laminated sheet on the same surface. 1. A method for producing a conductive sheet, which comprises applying a synthetic resin liquid for fiber attachment so as to cause the fibers to adhere. 2. The method according to claim 1, wherein the resin of the synthetic resin liquid is compatible with the resin of the base material. 3. The method according to claim 1 or 2, wherein the synthetic resin liquid has a viscosity of 5 to 300 centipoise.