JPH062234Y2 - Sheet heating element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a sheet heating element used in electrical products, and more specifically, by using an electrode having a specific shape and structure, The present invention relates to a sheet heating element capable of remarkably uniforming temperature distribution.

[Problems to be Solved by Conventional Techniques and Inventions] As electrodes of a conventional sheet heating element, electrodes having a pair of opposing electrodes provided at both ends thereof, or comb-shaped electrodes are generally used. Especially when it is used for low voltage, it is necessary to reduce the resistance of the element.
A comb-shaped electrode is used because it is necessary to substantially increase the electrode length (Japanese Utility Model Publication No. 55-129397 and Japanese Utility Model Publication 55-1628).
No. 96, No. 59-292, etc.).

However, in the comb-teeth shaped electrode, when electricity is applied, current concentrates on the tips of the comb teeth, and that part becomes particularly hot,
There is a problem that temperature distribution occurs in each part of the planar heating element.

Furthermore, in order to prevent abnormal heat generation and electrode damage due to excessive current in the initial stage of energization, the comb-teeth electrode is designed with a fairly wide comb tooth portion, and the main parts (main The electrodes are also designed to be wide. Since the portion directly below these electrodes is a non-heat generating portion, the planar heating element having such a form has uneven temperature in each portion, and in particular, the electrodes (mainly the main electrode) generate a planar heat. Since a structure surrounding the body is usually used, there is a drawback that a wide low temperature region is formed in the peripheral portion and a uniform heating surface cannot be obtained.

[Means for Solving the Problems] As a result of intensive studies to solve the above-mentioned conventional problems, the present inventors have used parallel-line electrodes instead of the comb-teeth electrodes and have a gap between the insulating layers, It was found that by alternately electrically connecting to the main electrode (main trunk), a local heating element can be prevented, and a planar heating element with a uniform temperature distribution that minimizes non-heating portions such as electrode mounting portions can be obtained. The present invention has been completed based on this knowledge.

That is, the present invention is a planar heating element comprising a thin film electrode attached to an element sheet made of a composition in which a conductive material is mixed with a crystalline polymer, and the sheet heating element (A) is sequentially formed on the sheet.
A plurality of parallel linear electrodes, (B) insulating layer, and (C) main electrodes that are orthogonal to the parallel linear electrodes and face each other are formed, and the parallel linear electrodes are the main electrodes. And a sheet heating element characterized by being electrically connected alternately with.

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 planar heating element of the present invention, and FIG. 2 is a partially enlarged view of the aa section of FIG.

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 having a positive temperature coefficient characteristic of electric resistance in which a conductive material is mixed with a crystalline polymer.

There are no particular restrictions on the crystalline polymer, and various crystalline polymers can be used. Usually, high density polyethylene,
Polyolefins such as low density polyethylene, linear low density polyethylene and polypropylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, olefin copolymers such as ethylene-ethyl acrylate copolymers, 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. Of these, polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer and the like are preferable as the crystalline polymer.

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 μm, preferably 15 to 100 μm are used. If the average particle size is less than 10 μm, the positive temperature coefficient characteristic becomes insufficient, which is not preferable. On the other hand, the average particle size is 200μ
If it exceeds m, the electric resistance value at room temperature increases, which is not preferable.

The conductive material may be a mixture of two or more kinds of conductive powders 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, sufficient positive temperature coefficient characteristics cannot be exhibited, 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 may 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-Al ₂
O _{3 and the} like may be mentioned, and these may be added alone or as a mixture. 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 12 to 200 parts by weight. Here, if the compounding amount of the semiconductive inorganic substance is less than 10 parts by weight, sufficient withstand voltage cannot be obtained, 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, an extrusion kneader, etc., and then by a known press such as a heating press, an extrusion molding machine, etc., 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 sheet heating element of the present invention is obtained by attaching thin film electrodes to the element sheet 1 having a positive temperature coefficient characteristic (PTC) thus obtained.

In the present invention, a plurality of parallel linear electrodes 2 (2A and 2B) are first formed on the body sheet 1. Here, reference numeral 2A indicates one pole of the electrode, and 2B indicates the other pole. That is, the adjacent parallel linear electrodes 2 are counter electrodes, and when one parallel linear electrode 2A is an anode, the parallel linear electrode 2B adjacent thereto is a cathode, and an electric field is generated between them. Shows.

The parallel linear electrodes 2 are linear electrodes that connect both end edges of the element sheet 1, usually both end edges in the longitudinal direction of the element sheet 1, and are parallel to each other. In the present invention, it is desirable to make the width (thickness) of the parallel linear electrode 2 itself as narrow as possible. As a result, the heat generation area can be widened, and even if the width of the parallel linear electrode 2 itself is narrowed, there is no problem because the main electrode is formed in the upper layer. Generally, the width of the parallel linear electrodes 2 is 0.2 to 3 mm, and the distance between the adjacent parallel linear electrodes (2A and 2B) is 2 to 50 mm.

It is sufficient that a plurality of parallel linear electrodes 2 are formed, and the number thereof may be selected in consideration of the size of the sheet heating element and the like.

Next, in the present invention, the main electrode 4 is formed on the parallel linear electrode 2 with the insulating layer 3 interposed therebetween.

Here, the insulating layer 3 is formed between both parts of the parallel linear electrodes 2 (2A and 2B) and the main electrode 4 except for the connection part (this point will be described later).

Further, the main electrodes (main trunk portions) 4 (4A and 4B) are formed orthogonal to the parallel linear electrodes 2 and are formed to face each other. The main electrode 4 may be located anywhere as long as it can be alternately connected to the parallel linear electrodes 2, but is usually both end edges of the element sheet 1 in the direction in which the parallel linear electrodes 2 are formed. It is formed at the end edge in the direction orthogonal to. In the present invention, the width (thickness) of the main electrode 4 itself is not particularly limited, but there is no problem even if it is considerably wide. From the standpoint of alleviating excessive heat generation of the parallel-line electrodes 2, the wider the main electrode 4, the better. In the present invention, unlike the conventional one, this main electrode 4
This is because the lower part also generates heat and does not expand the non-heat generating part.

In the present invention, the parallel linear electrodes 2 are electrically connected alternately with the upper main electrodes 4 in the gap between the insulating layers 3.

That is, in the present invention, one parallel linear electrode 2A
Is, for example, electrically connected to one main electrode 4A of the upper layer to become one pole, and the parallel linear electrode 2B adjacent to the one parallel electrode 2A is connected to the other main electrode 4B of the upper layer. It is electrically connected to form the other pole. This connection is made possible by the insulating layer 3. For this purpose, the insulating layer 3 is formed, for example, in the shape shown in FIG. FIG. 4 shows an insulating layer in which notches having the same width as the width of the main electrode 4 are alternately formed at the width of the parallel linear electrodes 2 and at the same intervals.
Therefore, by forming a main electrode having a pattern as shown in FIG. 5 on this insulating layer, the parallel linear electrodes 2 are electrically connected alternately with the upper main electrodes 4 in the cutouts of the insulating layer 3. The Rukoto.

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,
Parallel line electrodes 2 (2A, 2B) as shown in FIG. 3 are formed on the surface of the base sheet 1 using a conductive material. In this case, as described above, in order to widen the heat generation area, it is preferable that the width of the parallel linear electrode 2 itself be as narrow as possible to be a linear electrode.

There are various methods for forming the parallel line electrodes 2, but for example, conductive paste is screen-printed or applied. After low-temperature cream solder is screen-printed or applied, it is heated to form a metal film. A metal foil cut out in the shape of an electrode is thermocompression bonded, or the metal foil is thermocompressed over the entire surface of the sheet and then a pattern is formed by etching. There is a method of forming a metal layer by electroplating or electroless plating.

Next, the parallel linear electrodes are formed as described above, and then the insulating layer 3 is coated so as to expose a part of the parallel linear electrodes. For example, when the parallel linear electrodes as shown in FIG. 3 are used, the parallel linear electrodes adjacent to each other are alternately exposed (or, conversely, alternately covered) in the form shown in FIG. An insulating layer may be formed. The insulating layer can be easily formed, for example, by using a method such as screen-printing or applying an insulating paint or pasting an insulating film. The insulating layer may be coated on the back surface of the surface on which the parallel linear electrodes are formed.

Further, strip-shaped main electrodes made of a conductive material and facing each other are formed on the insulating layer formed as described above. There are various methods for forming this strip-shaped main electrode, for example, a method of screen printing or applying with a conductive paste, or a method of pressure-bonding a metal foil with a conductive paste or a conductive adhesive. Alternatively, there is a method of soldering and making electrical contact with the parallel linear electrodes. Specifically, using the pattern shown in FIG. 5, a main electrode is provided with a conductive paste on the insulating layer shown in FIG. At this time, the parallel linear electrodes in the lower layer and the two strip-shaped main electrodes in the upper layer are connected so that the polarities of the adjacent parallel linear electrodes are alternately inverted.

After taking out the terminals or the lead wires from the both electrodes thus obtained, the whole is covered with an insulating coating and is then used as a sheet heating element by applying an exterior.

[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 (“Diablack E” manufactured by Mitsubishi Kasei Co., Ltd., average particle size 43 m)
μ) 42 wt% was kneaded using a pressure kneader, and to 100 parts by weight of the mixture of both, 0.17 parts by weight of an organic oxide (NOF CORPORATION “Perhexin 25B”) was added and further kneaded. A PTC composition was obtained. This was molded into a sheet having a thickness of 0.5 mm using an extrusion sheet molding machine.

The pattern shown in FIG. 3 (width A: 55.5
mm, depth B: 32 mm, width C of parallel line electrodes C: 0.5 mm, distance D between parallel line electrodes D: 5 mm) is screen-printed using conductive silver paste and dried in an oven at 80 ° C for 3 hours. Then, parallel line electrodes were formed.

Then, from above, a pattern as shown in FIG. 4 (width E: 65 mm, electrode terminal insulating portion width E ′: 6 mm, depth F: 36 m
m, notch width G: 0.5 mm, notch length H: 10 mm)
Insulation paint was screen-printed with and dried at 50 ° C for 3 hours and cured.

Further, a pattern (width (width excluding lead wire terminal portion)) I: 5 shown in FIG.
5.5 mm, depth J: 32 mm, main electrode thickness K: 7 mm, lead wire terminal portion thickness L: 5 mm, lead wire terminal portion width M:
5 mm) was screen-printed and dried at 80 ° C. for 3 hours to form a laminated sheet heating element.

When a lead wire was connected to the two-pole terminal portion and the resistance was measured, it was 8.2 Ω. When DC12V was applied to this and heating was performed, a uniform temperature distribution was obtained over the entire surface.

[Advantages and effects of the invention] In the present invention, the lower parallel electrode and the upper main electrode are integrated and electrically connected so that the polarities of adjacent parallel electrodes are alternately inverted. There is.

Therefore, according to the present invention, heat is also generated under the upper main electrode.

Thus, in the present invention, not the comb-shaped electrode
Since the parallel linear electrodes are used, there is no local heat generation seen in the comb-shaped electrodes.

Moreover, since a wide main electrode is formed on the parallel linear electrodes, excessive heat generation of the parallel linear electrodes can be alleviated by the main electrodes. Therefore, the parallel linear electrodes can be made as thin as possible, which can reduce the non-heat generating portion below the electrodes as much as possible.

As described above, according to the present invention, since there is no local heat generation and the non-heat generating portion is in a very narrow range, it is possible to obtain a planar heating element with uniform heat generation and improve the heating capacity. it can.

Further, the planar heating element of the present invention is highly flexible, can be made large in area, and is easy to produce.

Therefore, the sheet heating element of the present invention is industrially useful as a heating element for electric appliances and the like.

[Brief description of drawings]

FIG. 1 is an explanatory view showing one mode of the planar heating element of the present invention, and FIG. 2 is a partially enlarged view of the aa section of FIG.
In the figure, reference numeral 1 indicates an element sheet, reference numeral 2 (2A and 2B) indicates parallel linear electrodes, reference numeral 3 indicates an insulating layer, and reference numeral 4 (4A and 4B) indicates a main electrode. FIG. 3 shows the pattern shape of the parallel linear electrodes on the element sheet formed in Example 1 of the present invention, and FIG. 4 is the intermediate insulating layer formed in Example 1 of the present invention. FIG. 5 is a view showing two upper strip-shaped main electrodes and power supply connection terminals formed in the first embodiment of the present invention.

Claims (1)

[Scope of utility model registration request] 1. A planar heating element comprising a thin film electrode attached to an element sheet made of a composition in which a conductive material is mixed with a crystalline polymer, and a plurality of (A) plural sheets are successively formed on the sheet. Parallel line electrodes, (B) insulating layer, and (C) main electrodes that are orthogonal to the parallel line electrodes and face each other are formed, and the parallel line electrodes alternate with the main electrodes. A sheet heating element characterized by being electrically connected to.