JPS58166021A - Manufacture of conductive sheet - Google Patents

Abstract

PURPOSE:To obtain a conductive sheet different in electric resistance value in an intended area by a method wherein after an uncalcined polytetrafluoroethylene sheet containing conductive powder is compacted by pressure, it is stretched as that draw ratios differ from each other in several areas. CONSTITUTION:A conductive uncalcined polytetrafluoroethylene sheet is passed between metallic rolls and compacted by pressure, then the desired area of this sheet that is divided at least into two parts is stretched or kept in the unstretched state and another area that is adjacent to this area is stretched so that the draw ratio is different from that of the above-mentioned desired area. In this way, the sheets having various kinds of electric resistances or relatively large electric resistances even for their small lengths are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a conductive sheet made of polytetrafluoroethylene (hereinafter referred to as PTFK) and having different electrical resistance values in predetermined regions.

Conventionally, a conductive sheet obtained by uniformly mixing PTFFf powder and conductive powder and forming the mixture into a sheet is known.In this conductive sheet, when changing the electrical resistance, the main method is to change the electrical resistance of the conductive powder. Although the blending amount is increased or decreased, the electrical resistance of the conductive sheet obtained by this method is approximately constant, and it is not possible to partially give a predetermined electrical resistance value. As a result of intensive studies to solve the above-mentioned problems of the prior art, we have consolidated the surface vicinity of an electrically conductive unfired PTv1 sheet, and then polished a predetermined area of the sheet or left it in an unstretched state. By holding the scissors and stretching another area adjacent to the predetermined area so that the stretching ratio is the same as that of the predetermined area, conductive sheets with various electrical resistances can be obtained. It was discovered that a conductive sheet with a large electrical resistance can be obtained, and the present invention was completed. That is, the method for producing a conductive sheet according to the present invention comprises a conductive sheet containing a conductive powder. Unfired FT? After the 1e sheet is consolidated, it is divided into at least 42 regions, and a predetermined region of the Kumo sheet is stretched, or the other region adjacent to the predetermined region is stretched with scissors at a stretching rate of 10. O In the present invention, unsintered PTI containing conductive powder is used.
0 unfired FT where the vicinity of the surface of the Fm sheet is consolidated! P
Consolidation of the II sheet can be carried out, for example, by passing the unfired FTFI sheet between rolling rolls once or twice or more at a temperature of room temperature to 300°C, preferably about 60 to 250°C, to reduce its thickness to the original thickness. about 60- or less preferably 40-20
This can be done by a method of This makes the work of abrasive stretching, which is performed at different stretching rates for each area of the unfired sheet after consolidation, easier. If densification is not applied or consolidation is insufficient, it becomes difficult to stretch the film by changing the stretching ratio for each region. 1m sheet is unfired FT
It can be obtained by uniformly mixing conductive powder such as carbon, graphite, metal powder, etc. with FII@ powder and forming this into a sheet.The conductive powder is usually about 20 to 40 parts by weight per 100 parts by weight of p'rym powder. Parts by weight are added. In addition, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene,
Vinyritine polysulfate, tetrafluoroethylene-hexafluoropropylene copolymer, etc. can be blended.

The thickness of the unfired FTiF111 sheet is determined depending on the stretching ratio, the mechanical strength required of the sheet, etc., and is usually about 100 to 500 mA.

The unfired FTIFm sheet consolidated as described above is
Next, it is stretched at a temperature below the melting point of PIFI, preferably from room temperature to 80°C. In this stretching, a predetermined region of the sheet divided into at least two regions is maintained in an unstretched state or stretched to a predetermined stretching ratio, and other regions that are within the predetermined region are stretched □twue the predetermined region. -The elongation rate is 1 and 5 different.

The stretching ratio of each region of the unfired p'rym sheet in the present invention can be determined depending on the amount of conductive powder mixed, the intended electrical resistance of the conductive sheet, etc., but is usually about 5
It is set within the range of ~50 inches.

Unfired P'l'lFI+ compacted in this way! By stretching the sheet so that adjacent regions have different stretching ratios, a conductive sheet with different electrical resistances in the adjacent regions can be obtained. The electrical resistance of each region in the conductive sheet (K) is determined by its stretching ratio, and the higher the stretching ratio of the region, the higher the electrical resistance.

In the present invention, various aspects can be applied to setting the stretching ratio of each region of the unfired p'rym sheet. For example, when the sheet is divided into three regions, (a) 211 The stretching ratio of each area increases sequentially.
II, (2) an embodiment in which the stretching ratios of both end regions are equal and the stretching ratio of the central region is smaller or larger than the stretching ratio of both end regions, (C) an embodiment in which the stretching ratios of both end regions are different and the stretching ratio of the central region A conductive sheet obtained in this way may be heated to the stretching temperature, and the dimension in the stretching direction will be the same as that before stretching. When the sheet is used at a temperature higher than the stretching temperature, the stretched state of each region is maintained and
It is preferable to perform the heat treatment by heating to a temperature higher than the stretching temperature (while the length of each region in the stretching direction is fixed so as not to change).

It is not possible to obtain a conductive sheet that does not shrink even when subjected to heavy use at temperatures above the stretching temperature. Note that if the heat treatment is performed at 327°C or higher, which is the melting temperature of FTPK, p'rym is fired and a conductive sheet with particularly high mechanical strength is obtained.The conductive sheet obtained by the method of the present invention is For example, it can be used for a reddening resistance layer whose electrical resistance can vary over a wide range, a heat-generating sheet whose electrical resistance varies locally, etc. The present invention is constructed as described above, and is made by compacting an unfired FTIPm sheet. Since the stretching process is carried out after stretching, it is easy to stretch each area.Also, by changing the stretching ratio of adjacent areas, sheets with various electrical resistances can be obtained. It has the characteristic that a sheet can be obtained.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
unfired FTFL with a thickness of 400 μm, evenly mixed with
The sheet was heated to 80°C, 150°C, 1 part to 0°C and 230°C, respectively, and then passed sequentially between 94 pairs of metal rolling rolls to achieve a thickness of 130 μm. Next, the sheet was consolidated. The length of the unfired FTIFm sheet was 140 mm.
The sheet was cut into 5110 strips, divided into 7 regions with 20 layers as one region, and one end of the sheet was maintained in an unstretched state, and the stretching ratio gradually increased toward the other end of the sheet.
ts, 15s, 20 strokes, 25s and 30-stretching (stretching temperature [30°C).

Next, while maintaining the stretched state of each region, the conductive sheet is heated and fired at 370° C. for 1 minute to obtain a conductive sheet with an electric current of (111) per mg per unit length of each region in this conductive sheet. The resistance increases sequentially from one end of the notebook to the other: 40Ω, 50Ω, 70Ω, 100Ω.
Ω, 170Ω, 280Ω and 420Ω, 90 Example 2 6 parts of carbon and 22 parts of ethylene-tetrafluoroethylene copolymer powder were uniformly mixed with 100 parts of the FTIK powder used in Example 1. 450μ tone unfired P
TF111 sheet at 130℃, 170℃ and 200℃
The sheet was consolidated by successively passing between three pairs of metal abrasive rolls, each heated to a thickness of 18 mm.Next, this consolidated sheet was cut and stretched in the same manner as in Example 1. and fired to obtain a conductive sheet O per unit length of each area in this conductive sheet (lQ
The electrical resistance of the +w shoulder contact increases from one end of the sheet to the other, and is 9.250Ω and 380Ω.
, 550Ω, 700Ω, 1250fl, 1900fl and 2700Ω.

patent applicant Nitto Electric Industry Co., Ltd. Representative Sanbe Hijikata

Claims (1)

[Claims] After compacting an unstretched polytetrafluoroethylene sheet containing conductive powder, a predetermined region of the sheet divided into at least two regions is stretched or maintained in an unstretched state, and the predetermined region is A method for producing a conductive sheet, which comprises stretching another adjacent region at a stretching rate different from that of the predetermined region.