JPS6235277Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention uses polytetrafluoroethylene powder (hereinafter referred to as PTFE) as a conductive powder and a binder.
The present invention relates to an improvement in a planar heating element using a flexible planar heating element formed by coating a base fabric with a conductive paint containing as a main component. Such planar heating elements are used, for example, in floor mats, electric blankets, and the like. In planar heating elements used in such applications, the heating element and the insulating layer are bonded together by heating and pressure in order to prevent a decrease in heat conduction efficiency due to air stagnation between the heating element and the thermoplastic insulation layer. I am forced to do it. The heating element and the insulating layer are bonded by fusing the PTFE in the conductive paint applied to the heating element and the thermoplastic plastic forming the insulating layer. It is difficult to increase the strength. As a result, after the planar heating element starts to be used, partial peeling occurs between the heating element and the insulating layer within a short period of time, and air often remains in this peeled part, causing a decrease in heat conduction efficiency. Furthermore, if air remains between the two, a "heat trap" phenomenon may occur due to the insulating properties of the air, and the temperature distribution may become uneven. In order to solve these problems, it has been proposed to improve the bonding strength between the two insulating layers by integrating them through small holes provided in the heat generating element, thereby preventing the heat generating element and the insulating layer from peeling off (Jikosho). 49
-13953 Publication). However, when this planar heating element is put into practical use, it is difficult to simply form small holes in the heating element and bond and integrate the insulating layers on both sides of the element.
It has been found that there are problems such as a loss of flexibility or an inability to obtain a bonding strength that can withstand practical use. As a result of various studies to solve the above problem, the inventors of the present invention found that while maintaining the flexibility of the planar heating element,
It was discovered that in order to make the bonding strength between the heating element and the insulating layer practical, the porosity of the heating element must be within a predetermined range,
This led to the present invention. That is, the planar heating element according to the present invention has a
A conductive paint mainly composed of PTFE powder and conductive powder is applied, and a large number of small pores are formed, with a porosity of 0.01% to 70%, on both sides of the flexible sheet heating element. Insulating thin layers made of plastic are fused together, and the insulating thin layers are joined together through the small holes. The flexible planar heating element in this invention is as follows:
For example, a conductive paint containing PTFE powder as a binder and conductive powder such as carbon powder or metal powder as the main components is applied to a flexible base fabric such as a woven fabric or non-woven fabric with a thickness of about 0.03 to 10 mm, This can be used with holes drilled at predetermined intervals. The porosity in this planar heating element is preferably 0.01 to 70% in order to maintain the flexibility of the heating element and improve the bonding strength between the heating element and the thin insulating layer.
It is set to be between 0.5% and 50%. Note that this porosity is a value calculated using the following formula. Porosity (%) = total area of small pores/area of heating element x 100 In addition, in this invention, the flexibility of the sheet heating element and the bonding strength between the heating element and the thin insulating layer are balanced in the optimum range. , the diameter of the small holes provided in the heating element is 0.5 to 20 mm, and the small hole installation density is 500 to 20 mm.
It is preferable to set the number to 100,000 pieces/m ² . Hereinafter, examples of the present invention will be explained with reference to the drawings. In FIGS. 1 and 2, reference numeral 1 denotes a flexible planar heating element, in which a large number of small holes 2 are bored at predetermined intervals. Thin insulating layers 3 and 4 made of thermoplastic such as polyester, polyethylene terephthalate, polyvinyl chloride, and fluororesin and having a thickness of usually 0.01 to 5 mm are fused to both sides of the heating element 1. The thin layers 3 and 4 are joined together through small holes 2. Note that 5 and 6 are electrodes such as copper foil provided at both ends of the planar heating element. Although not shown, one end of a lead wire is connected to each of the electrodes 5 and 6. The present invention is constructed as described above, and the porosity of the flexible planar heating element is set within a predetermined range, and the thin insulating layers are bonded to each other through small holes provided in the heating element. This has the effect that the heat generating element and the insulating layer can be firmly bonded while maintaining the flexibility of the heat generating element. The present invention will be explained below with reference to examples. Example A fluororesin dispersion containing carbon powder (manufactured by Hoechst, trade name: Hostaflon) was used as a conductive paint, and this was applied to a glass cloth with a thickness of 0.1 mm (manufactured by Nittobo, trade name: WE-116). The paint is baked onto the glass cloth by applying it and heating it in a heating oven at 350-400°C for 3 minutes. Next, this glass cloth was cut into 500 x 500 mm pieces, and copper foil electrodes with a width of 10 mm and a thickness of 30 microns were attached to both ends. Thereafter, circular small holes with a diameter of 5 mm were bored in this glass cloth at intervals of 10 mm to obtain a flexible planar heating element with a porosity of 20% and a hole installation density of 10,000 pieces/m ² . Next, a polyvinyl chloride film with a thickness of 0.3 mm and a length and width of 550 mm is placed on both sides of the heating element, and heated and pressed using a press to fuse the heating element and the polyvinyl chloride, and the polyvinyl chloride is By joining and integrating the same elements through the small holes of the heating element, a planar heating element (sample number 1) having the same structure as the drawing and maintaining flexibility was obtained. Furthermore, apart from this, the two planar heating elements were prepared in the same manner as in the case of sample number 1, except that the small hole spacing, porosity, and small hole installation density were set as shown in Table 1. (Sample numbers 2 and 3) were obtained. In order to understand the characteristics of these planar heating elements, we measured their flexibility using a VF RUBBING TESTER manufactured by Kamishima Seisakusho and the bonding strength (peel force) between the heating element and the insulating layer using JIS-K-6772. The results obtained are shown in Table 1. In the flexibility test, the sample was kneaded under the conditions of chuck spacing of 50 mm, load of 400 g, and number of kneading cycles of 1000 times, the electrical resistance before and after the movement was measured, and the rate of change in resistance was calculated using the following formula. Resistance change rate (%) = (Resistance after exercise) - (Resistance before exercise) / Resistance before exercise x 100 For comparison, a sheet heating element without small holes and a polyvinyl chloride film were sampled. All except for the planar heating element (sample number 4) obtained by heating and pressurizing under the same conditions as No. 1, and the small hole spacing, porosity, and small hole installation density were set as shown in Table 1. Data for a planar heating element (sample number 5) obtained by the same procedure as for sample number 1 is also shown.

[Table] As is clear from Table 1 above, the planar heating element of the present invention not only has a small resistance change rate due to kneading motion and is excellent in flexibility, but also has excellent flexibility due to the bond between the planar heating element and the insulating thin layer. It can be seen that the strength is also great.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway plan view showing an example of a planar heating element according to the present invention, and FIG. 2 is a sectional view taken along the line AB in FIG. 1 and viewed from the direction of the arrow. 1... Flexible planar heating element, 2... Small hole, 3, 4...
Insulating thin layer.

Claims (1)

[Scope of utility model registration request] A conductive paint consisting mainly of polytetrafluoroethylene powder and conductive powder is applied to the base fabric, and a large number of small pores are formed, with a porosity of 0.01 to 70%.
A planar heating element comprising a flexible planar heating element, in which thin insulating layers made of thermoplastic plastic are fused to both sides, and the thin insulating layers are joined together through the small holes.