JPH0646073Y2 - Sheet heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a planar heating element used for electric appliances and the like, and more specifically, to increase a heating area by using a comb-shaped electrode having a specific shape. The present invention relates to a sheet heating element capable of achieving a uniform temperature distribution.

[Problems to be Solved by Conventional Techniques and Inventions] As electrodes of a conventional sheet heating element, one having a pair of opposing electrodes at both ends or one having a comb tooth shape is generally used. Especially when used for bottom voltage, it is necessary to reduce the resistance of the element. Therefore, since it is necessary to reduce the distance between the electrodes and to lengthen the substantial electrode length, a tooth-shaped electrode as shown in FIG. 3 is used. .

However, in such a comb-teeth shaped electrode, if the width of the comb teeth is narrow, there is a risk of abnormal heat generation and electrode damage due to an excessive current in the initial stage of energization.

Therefore, in the comb-teeth-shaped electrode, in order to prevent abnormal heat generation and electrode damage due to an excessive current, the electrode comb-teeth part is designed to have a considerably wide width (for example, Japanese Utility Model Laid-Open No. 55-129397). (Japanese Utility Model Laid-Open No. 55-162876, Japanese Utility Model Laid-Open No. 59-292, etc.), which reduces the effective heating area, and because the non-heating area directly below the electrode is wide, a uniform temperature distribution cannot be obtained. There was a problem.

[Means and Actions for Solving the Problems] The inventors of the present invention have conducted extensive studies to solve the above-mentioned conventional problems. As a result, the inventor found out that the electrode damage and abnormal heat generation due to the electric current were mainly due to the large inrush current generated in the initial stage of energization, and the portion for passing the inrush current in the narrow comb tooth-shaped electrode was found. It was found that the use of the provided electrode can prevent electrode damage and abnormal heat generation due to the excessive current that occurs at the beginning of energization, and further, the effective heating area can be made as large as possible, and based on this finding, the present invention was completed. Came to do.

That is, the present invention is a planar heating element in which a comb-shaped thin-film electrode is attached to a base sheet made of a composition in which a conductive material is mixed with a crystalline polymer, and the width of the comb-shaped electrodes is adjacent to each other. A sheet heating element that is less than one-tenth of the distance between the comb-teeth electrodes and the width of at least one of the comb-teeth electrodes is two-tenths or more of the distance between the comb-teeth electrodes. Is provided.

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing one mode of the sheet heating element of the present invention.

In the figure, reference numeral 1 is an element sheet that serves as a heat generating portion. The size and shape of the body sheet 1 are not particularly limited, and those normally used may be adopted. This body sheet 1 is
Basically, it is composed of a composition in which a conductive material is mixed with a crystalline polymer, and exhibits a positive temperature coefficient characteristic of resistance.

There are no particular restrictions on the crystalline polymer, and various crystalline polymers can be used. Usually, high density polyethylene,
Bottom density polyethylene, linear bottom density polyethylene, polyolefin such as polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, olefin copolymer such as ethylene-ethyl acrylate copolymer, trans-1,4 -Polyisoprene, polyamide,
Examples thereof include polyesters, fluorine-containing ethylene copolymers, and modified products thereof. These may be used alone or in combination of two or more kinds. Among these, as the crystalline polymer, polyethylene, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer and the like are preferable.

Next, various conductive materials can be used, and specific examples thereof include carbon black such as oil furnace black, thermal black, and acetylene black, graphite, metal powder, pulverized carbon fiber, or a mixture thereof. However, carbon black is particularly preferable.
As these conductive materials, powdery materials having an average particle size of 10 to 200 mμ, preferably 15 to 100 mμ are used. Here, if the average particle size is less than 10 mμ, the positive temperature coefficient characteristic cannot be sufficiently obtained, which is not preferable. On the other hand, if the average particle size exceeds 200 mμ, the resistance of the composition becomes high and it becomes difficult to control the resistance, which is not preferable.

The conductive material may be a mixture of two or more kinds of conductive particles having different particle sizes.

The compounding ratio of the crystalline polymer and the conductive material is the former 10
~ 90 wt%, preferably 50-80 wt%, the latter 90 ~
It is 10% by weight, preferably 50 to 20% by weight. Here, if the mixing ratio of the conductive material is higher than the above ratio, it becomes difficult to exhibit sufficient positive temperature coefficient characteristics, which is not preferable.
On the other hand, if the mixing ratio of the conductive material is less than the above ratio, sufficient conductivity cannot be obtained, which is not preferable.

In the present invention, in addition to the above materials, a semiconductive inorganic substance can be added as a material for the body sheet. Here, as the semiconductive inorganic substance, specifically, SiC, B ₄ C, Si, Ge, SnO,
GaSb, GaP, GaAs, InSb, InSe, GaSe, InTe, GaTe, Li ₃ N, β-A
L ₂ O _{3 and the} like may be mentioned, and these may be added alone or in combination. This semiconductive inorganic substance is usually used as a powder, and in this case, the powder having an average particle diameter of 300 μm or less, preferably 100 μm or less is used. Here, if the average particle diameter of the powder exceeds 300 μm, the effect of improving the withstand voltage becomes small, which is not preferable.

This semiconductive inorganic substance is 10 to 300 parts by weight, particularly preferably 100 to 100 parts by weight of the mixture of the crystalline polymer and the conductive material.
It is preferably used in a proportion of 15 to 200 parts by weight. Here, if the compounding amount of the semiconductive inorganic substance is less than 10 parts by weight, it becomes difficult to obtain sufficient withstand voltage, which is not preferable.
On the other hand, if the compounding amount of the semiconductive inorganic material exceeds 300 parts by weight, kneading becomes difficult, which is not preferable.

The above materials are kneaded by a Banbury mixer, a kneading roll, a pressure kneader, etc., and then a known press such as a heat press, a pressure molding machine, etc., having a wall thickness of 0.1 to 3 mm, preferably
It is formed into a sheet of 0.2 to 2 mm. The kneading temperature and the kneading time are not particularly limited, and may be the usual conditions. Further, the crystalline polymer may be crosslinked with an organic peroxide during or after the kneading. After molding the kneaded product, crosslinking by radiation may be performed.

The planar heating element of the present invention has a thin film electrode 2 having a positive temperature coefficient (PTC) thus obtained, and a thin film electrode 2 having a comb tooth shape (the whole shaded portion in the drawing is a comb tooth electrode 2). Yes.) Is installed.

In the present invention, the width of the conventional comb-shaped electrode 2 is as narrow as possible. FIG. 2 is an explanatory view showing the pattern of the comb-teeth shaped electrode used in Example 1 of the present invention.
Describing with reference to this figure, the width of a normal comb tooth-shaped electrode 2
w ₁ is 1/10 (0.1) of the distance W between adjacent comb-teeth electrodes
Less than, preferably 0.01 to 0.09.

In the present invention, the width w ₂ of at least one comb tooth-shaped electrode (buffer electrode) of the comb tooth-shaped electrodes ₂ is made significantly wider than the others, and the inter-comb tooth-shaped electrode distance W is 10
It is set to 2 (0.2) or more, preferably 0.4 to 1.0. Here, the width w ₂ of the buffer electrode is the distance W between the interdigital electrodes.
If it is less than two-tenths, the rush current in the initial stage of energization cannot be sufficiently buffered. It suffices to provide at least one buffer electrode, and two or more buffer electrodes may be provided in consideration of the width w ₁ of the normal comb-shaped electrode and the width w ₂ of the buffer electrode.

In FIG. 2, reference symbol T is the thickness of the main part of the comb-shaped electrode,
The symbol L indicates the thickness of the comb-teeth electrodes, and the symbol l indicates the distance between the comb-teeth electrodes.

The sheet heating element of the present invention as described above can be manufactured, for example, as follows.

First, the body sheet 1 is manufactured as described above. Next, an electrode as shown in FIG. 1 is formed on the surface of the base sheet 1 using a conductive material.

There are various methods for forming the electrodes, and for example, any of the following methods may be used.

The conductive paste is screen-printed on the surface of the material sheet in the pattern shown in FIG.

A constant temperature cream solder is overlaid by a method such as screen printing or coating, and this is heated to form a metal film.

A metal foil such as nickel is heat-pressed. In this case, a pattern made of a metal foil may be prepared and pressure-bonded, or a flat plate may be pressure-bonded and then the pattern may be formed by etching.

Apply electroplating or electroless plating of nickel.

After attaching the lead wire or terminal to the pattern electrode thus obtained, cover both surfaces of the electrode with insulating coating,
Furthermore, an exterior is attached and it is used as a sheet heating element.

In the present invention, since at least one wide comb tooth-shaped electrode is used as described above, the inrush current generated at the initial stage of energization flows into the wide comb tooth-shaped electrode and is relaxed,
Abnormality does not cause heat generation or electrode damage.

Therefore, the width of the other comb tooth-shaped electrodes can be made as thin as possible, and the effective heating area can be widened.

[Embodiment] Next, the present invention will be described in detail with reference to an embodiment.

Example 1 58% by weight of ethylene / ethyl acrylate copolymer (“DPDJ6182” manufactured by Nippon Unicar Co., Ltd.), carbon black (“Dia Black E” manufactured by Mitsubishi Kasei Co., Ltd., average particle size 43)
mμ) 42 wt% was kneaded using a pressure kneader, and 100 parts by weight of the mixture of both was mixed with an organic oxide (NOF Corporation).
0.17 part by weight of "Perhexin 25B") was added and further kneaded to obtain a PTC composition. This was molded into a sheet having a thickness of 0.5 mm using a pressing sheet molding machine.

The pattern of Figure 2 (pattern dimensions
A: 88.5mm, L: 38mm, Normal comb-shaped electrode width w ₁ : 0.5mm, Buffer electrode w ₂ width: 5mm, Distance between adjacent comb-shaped electrodes W: 5mm,
Thickness of the main part of the comb-shaped electrode: 6 mm, spacing between the comb-shaped electrodes
(l: 5 mm) was screen printed with a conductive silver paste and dried in an oven at 80 ° C. for 3 hours.

When a lead wire was connected to each of the two pole terminals and the resistance was measured, it was 9.6Ω. When DC12V was applied to this, the temperature of the main part of the comb tooth-shaped electrode and the temperature of the buffer electrode were slightly low, and almost uniform heat generation was exhibited over the entire surface of the heating element.

[Advantage of the Invention] According to the present invention, by using at least one wide comb-teeth electrode, the width of the other comb-teeth electrodes can be made as thin as possible.

Therefore, the heat generation area can be increased, and the non-heat generation area immediately below the electrode can be reduced.

Therefore, according to the present invention, it is possible to provide a planar heating element having an excellent heating ability and a uniform temperature distribution.

[Brief description of drawings]

FIG. 1 is an explanatory view showing one mode of a planar heating element of the present invention, FIG. 2 is an explanatory view showing a pattern of a comb tooth-shaped electrode used in Example 1 of the present invention, and FIG. 3 is a conventional planar heating element. It is explanatory drawing which shows an example of a body. 1 ... Element sheet, 2 ... Comb-shaped electrode, w ₁ ... Normal comb-shaped electrode width, w ₂ ... Buffer electrode width, W ... Distance between adjacent comb-shaped electrodes

Claims (1)

[Scope of utility model registration request] 1. A planar heating element in which a comb tooth-shaped thin film electrode is attached to an element sheet made of a composition in which a conductive material is mixed with a crystalline polymer, wherein the widths of the comb tooth-shaped electrodes are adjacent to each other. A sheet heating element that is less than one-tenth of the distance between the comb-teeth electrodes and the width of at least one of the comb-teeth electrodes is two-tenths or more of the distance between the comb-teeth electrodes. .