JPH0542799B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a conductive floor for preventing damage caused by static electricity in an electronic parts assembly factory or the like.

[Prior art] In order to protect electronic parts and equipment from damage caused by static electricity, it is necessary to reduce the charged voltage on the human body. (2) A method of constructing a conductive floor by laying a conductive sheet made of rubber or plastic mixed with a conductivity agent such as carbon black, and dissipating the electric charge from the human body to the ground; (3) A method of dissipating the electric charge of the human body to the ground; A conductive floor is constructed by laying a composite sheet in which a colorable vulcanized rubber sheet containing no black is used as the surface layer, and the conductive sheet described in (2) above is laminated as the back layer. There is a known method to avoid this.

[Problems to be Solved by the Invention] In method (1), if the lead wire is broken or is not connected to the human body due to inadvertence, static electricity countermeasures are not taken during that time.
There is a problem in that it is not possible to guarantee the performance of constantly suppressing human body charging below the level required by the system.

Method (2) above is effective in preventing static electricity because it can reduce the electrical resistance of the conductive sheet.
There is a design problem in that the hue is limited to black, which is aesthetically unsuitable for modern electronic component factories.

In method (3), since the surface layer can be colored, the design is excellent, but from the viewpoint of antistatic effect, it is necessary to use rubber that has essentially low electrical resistance. Rubber must be vulcanized to maintain its shape, but in the case of vulcanized rubber, it is difficult to easily heat-seal the surface layer and back layer, which reduces manufacturing efficiency. Further, when a plurality of sheets are laid in the same plane, it is difficult to thermally fuse the boundaries between the sheets, and dust tends to accumulate in the joints, which limits the use in clean rooms and the like.

In addition, as a general problem, in order to fully demonstrate the antistatic performance of the human body, conductive sheets are
It is grounded to the earth with a grounding resistance of about 100KΩ.
Care must be taken to ensure that static charges are quickly transferred from the surface of the conductive sheet to the ground. but,
Stable electrical properties (contact resistance) over long periods of time
Currently, no proposals have been made for a method that maintains the conductive floor structure and is extremely easy to construct a conductive floor.

The present invention has been made based on the above, and aims to provide a conductive floor that has excellent antistatic performance and aesthetics, is easy to construct, and has long-term stability.

[Means for solving the problems] The conductive bed of the present invention is mainly composed of a vinyl chloride resin and an acrylonitrile-butadiene copolymer,
A colorable conductive polymer composition that does not contain carbon black has a volume resistivity of 1×10 ¹² Ω
-cm or less, and a back layer with a volume resistivity of 1 x 10 ⁶ Ω-cm or less, which is made of a conductive polymer composition made of rubber or plastic mixed with a conductivity imparting agent such as carbon black or metal powder. Multiple layers of conductive floor sheets are laid in the same plane, and adjacent conductive floor sheets are electrically connected with conductive adhesive tape, and the boundaries are filled with thermoplastic resin welding material. The electrically conductive floor sheets are continuously connected to each other, and at least one of the conductive floor sheets is connected to a grounding lead wire.

In the present invention, the volume resistivity is 1×10 ¹² Ω−
A colorable conductive polymer composition that forms a surface layer of 1.0 cm or less is made by adding a plasticizer with a small volume resistivity, for example, 1 x 10 ⁸ Ω-cm or less, to a vinyl chloride resin and an acrylonitrile-butadiene copolymer. This can be easily achieved by blending.

As vinyl chloride resin, vinyl chloride is usually used.
Any resin containing 50% by weight or more may be used, such as a homopolymer of vinyl chloride, a copolymer of vinyl chloride and a monomer that can be copolymerized with it, or a graft copolymer with other resin materials. good.

There are no particular restrictions on the acrylonitrile-butadiene copolymer, but it is desirable to have a high acrylonitrile content from the viewpoint of compatibility with vinyl chloride resin and electrical resistance, and the molecular weight and presence or absence of partial crosslinking are not subject to consideration. It is best to select one depending on the intended use.

The content ratio of the vinyl chloride resin and the acrylonitrile-butadiene copolymer is preferably in the range of 95-20/5-80 in weight ratio of the vinyl chloride resin/acrylonitrile-butadiene copolymer. If the acrylonitrile-butadiene copolymer content is 5% by weight or less, the desired electrical conductivity tends not to be obtained. When the acrylonitrile-butadiene copolymer exceeds 80% by weight, raw rubber-like properties become noticeable, resulting in poor processability and a tendency to be unable to obtain a product with a smooth surface.Additionally, vulcanization becomes necessary and the initial objective is not met. becomes difficult to achieve.

As a plasticizer having a volume resistivity of 10 ⁸ Ω-cm or less, a plasticizer that is liquid at room temperature and has low volatility is desirable.

For example, cresyl diphenyl phosphate,
Di(2,3-dibromopropyl) 2,3- phosphate
Dichloropropyl ester, di(2-ethylhexyl) phosphate, dioctyl phosphate, triamyl phosphate, tri(2-ethylhexyl) phosphate
-butoxyethyl) ester, tri(2-butoxyethyl) phosphate
Phosphate esters such as chloroethyl) ester, tri(chloropropyl) phosphate, tricresyl phosphate, tri(2,3-dibromopropyl) phosphate, tri(dichloropropyl) phosphate, diethylene glycol-
Glycol fatty acid esters such as dicaproic acid ester, triethylene glycol dicaprylic acid ester, triethylene glycol dicapric acid ester, phthalic acid and triethylene glycol.
Examples include esters in which one side of the glycol is a fatty acid and the other side is an ester of an aromatic carboxylic acid, such as esters with monocaprylic acid ester.

In addition, about 0.005 to 2% of electrolyte may be added to the above-mentioned plasticizer. The electrolyte is preferably a chemically stable electrolyte that does not easily deteriorate, such as lithium chloride or sodium chloride.

The amount of plasticizer blended is preferably in the range of 5 to 100 parts by weight based on 100 parts by weight of the total amount of vinyl chloride resin and acrylonitrile-butadiene copolymer.
If it is less than 5 parts by weight, it will be difficult to obtain the desired volume resistivity, and if it is about 100 parts by weight, the volume resistivity will be almost saturated, and if the amount is more than that, there will be almost no change in electrical resistance, and the compatibility will be reduced. This may lead to deterioration of the mechanical properties and make them unsuitable for use in the field of thermoplastic resins.

In addition to the above ingredients, of course DOP
plasticizers, other additives such as stabilizers, antioxidants, crosslinking agents, vulcanizing agents, vulcanization aids, lubricants, processing aids, flame retardants, fillers, colorants, ultraviolet absorbers, etc. It can be used as appropriate and can be made into a composition with no practical problems.

The back layer with a volume resistivity of 1×10 ⁶ Ω-cm is made of a conventionally known conductive polymer composition, i.e., rubber or plastic containing a conductivity imparting agent such as carbon black, carbon fiber, metal powder, or metal fiber. It can be formed by a composition having a formulation.

In addition, it is preferable to line the back layer with a coarse cloth in order to improve adhesion to the base. For example, use a cloth with a rough mesh size of 3 to 15 mm square using yarn with a count of 10 to 40 English cotton. Fabrics in the range are preferred. If the thread is too thick, it may easily cause poor contact when electrically connecting conductive floor sheets with conductive adhesive tape.
If it is too thin, the adhesion to the base tends to be insufficient.

[Example] An example of the present invention will be described with reference to FIG. 1 and FIG. 2. In addition, FIG. 1 is a back view showing a state in which multiple conductive floor sheets are laid;
FIG. 2 is a sectional view including the state of adhesion between the conductive floor sheet and the base, and is a sectional view of a portion corresponding to line A--A in FIG. 1.

1 is a surface layer with a volume resistivity of 1×10 ¹² Ω-cm or less, 2 is a back layer with a volume resistivity of 1×10 ⁶ Ω-cm or less, and 3 is a coarse cloth lined with the back layer 2. The conductive floor sheet 4 is constructed by laminating these materials.

A plurality of conductive floor sheets 4 are laid on top of a base 5 such as flooring material with an adhesive 6 such as epoxy interposed therebetween, and the electrical connection is maintained by a conductive adhesive tape 7, and the thermoplastic resin is welded. The boundaries are continuously connected by filling the material 11.

The conductive adhesive tape 7 is a conductive tape coated with an adhesive containing 10% by weight or more of conductive carbon black on one or both sides. If the connection length between adjacent conductive floor sheets is 10 mm or more, an electrical resistance of 1×10 ⁶ Ω or less can be achieved. As a result of detailed research by the inventors, the electrical resistance at the electrical connection point between adjacent conductive floor sheets 4 has been determined to be 1×10 ⁶ Ω or less, and providing one point every 10 m is sufficient to prevent static electricity. It has been found that performance can be improved.

At least one of the conductive floor sheets electrically connected via the conductive adhesive tape 7 is connected to a corrosion-resistant metal plate (18-
8 (nickel chrome steel, etc.) 9 is attached to the metal plate 9, and a grounding lead wire 10 is connected to this metal plate 9. According to this grounding method, there is no fear of corrosion, and the grounding resistance is stable over a long period of time. In addition,
It is preferable for the area of the metal plate 9 to be 1 cm ² or more in order to stabilize the connection resistance, and the number of metal plates 9 to be provided is not particularly limited, but it is sufficient to provide one metal plate for every 100 m ² .

In order to structurally integrate the conductive floor sheet 4, the boundaries of the conductive floor sheet 4 are filled with a welding material 11 of thermoplastic resin. In this case welding material 1
In order to improve the filling workability of the conductive floor sheet 4, it is preferable to cut the end of the conductive floor sheet 4 at an angle of 30 to 45 degrees to provide a groove. Apply adhesive 12 to the groove so that it adheres.
It is preferable to provide

The adhesive 12 is preferably a vinyl chloride resin since the surface layer 1 of the conductive floor sheet 4 contains vinyl chloride resin.

The welding material 11 may have a hardness close to that of the conductive floor sheet 4, but in order to obtain sufficient bonding strength, it is preferably made of vinyl chloride resin, which is the same material as the adhesive 12, as its main component. . Welding material 11
does not necessarily have to be conductive.

Surface layer 1 has a composition containing 50 parts by weight of vinyl chloride resin, 50 parts by weight of acrylonitrile-butadiene copolymer, 50 parts by weight of tri(2-butoxyethyl) phosphate, and 1 part by weight of phthalocyanine green (green coloring agent). The material was kneaded using two electric heated rolls and then formed into a sheet with a thickness of 0.5 mm using a steam press. The volume resistivity of this surface layer 1 is
It was 1.5×10 ⁸ Ω−cm.

Back layer 2 was made of a composition containing 100 parts by weight of vinyl chloride resin, 70 parts by weight of dioctyl phthalate, 80 parts by weight of carbon black, and 5 parts by weight of other stabilizers, etc., in the same manner as for surface layer 1, to a thickness of 2.5 mm. It was made by molding it into a sheet. The volume resistivity of this back layer 2 was 3×10 ² Ω-cm.

Top layer 1, back layer 2, and 10 pieces of 30 English cotton count thread.
A conductive floor sheet 4 was prepared by laminating fabrics woven into mm squares using a steam press, and was used to construct a conductive floor as shown in FIGS. 1 and 2. When we actually measured the electrostatic voltage of the human body using this conductive floor in a humidity range of 20 to 30RH%, we found that when wearing work shoes with soles with an electrical resistance of 1 x 10 ⁶ Ω, the electrostatic voltage is
It was below 50V.

Semiconductor devices are extremely susceptible to electrostatic damage, but if the charging voltage of the human body can be reduced to 50V or less, the semiconductor device is perfect and electrically sufficient for use as a floor for handling semiconductors. .

[Effects of the Invention] As explained above, the conductive floor of the present invention has an excellent aesthetic appearance because the surface layer is made of a colorable conductive composition, and also exhibits sufficient antistatic performance. be. Furthermore, since the joints are connected by welding, a clean environment with little dust can be easily achieved.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of one embodiment of the present invention, in which FIG. 1 is a back view of a state in which a plurality of conductive floor sheets are laid down, and FIG. 2 is a cross-sectional explanatory diagram. 1: Surface layer, 2: Back layer, 3: Rough cloth,
4: Conductive floor sheet, 5: Base, 6: Adhesive,
7: Conductive adhesive tape, 8: Conductive double-sided adhesive tape, 9: Metal plate, 10: Lead wire, 11: Welding material, 12: Adhesive.

Claims (1)

[Claims] 1. A surface layer with a volume resistivity of 1×10 ¹² Ω-cm or less consisting of a colorable conductive polymer composition mainly composed of vinyl chloride resin and acrylonitrile-butadiene copolymer and containing no carbon black, and rubber. Or a conductive polymer composition made of plastic mixed with a conductivity imparting agent such as carbon black or metal powder, with a volume resistivity of 1 x 10 ⁶ Ω.
A plurality of conductive floor sheets laminated with a back layer of less than cm are laid in the same plane, and adjacent conductive floor sheets are electrically connected by conductive adhesive tape, and the boundaries are thermoplastic. 1. A conductive floor, characterized in that the conductive floor sheets are continuously connected by being filled with a resin welding material, and a grounding lead wire is connected to at least one of the conductive floor sheets.