JPH0138882Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an improvement of a film-like thermistor. Metal foil electrodes such as copper foil or aluminum foil are thermally fused to the front and back surfaces of a polymer heat-sensitive film as a film thermistor that is superimposed on a sheet heating element, such as an electric carpet, to control the heat generation temperature of the sheet heating element. Those laminated by the above method are known. However, in such film-shaped thermistors, the rigidity of the electrodes is quite high, so the flexibility is poor, and the adhesive strength between the polymer thermosensitive film and the electrodes is not very strong, so they are often used like electric carpets. It is unsuitable as a temperature sensor for a sheet heating element that can be folded and unfolded. By the way, in the film-type thermistor using metal foil as an electrode, the characteristic impedance of the polymer thermosensitive film Z ₁ and the characteristic impedance of the electrode Z ₂
The ratio Z ₁ /Z ₂ is of the order of 10 ¹⁰ to 10 ¹⁴ . This impedance ratio Z ₁ /Z ₂ is related to the sensitivity of the thermistor, but according to the study results of the inventors, if the impedance ratio is 10 ² or more, it is possible to generate surface heat with sufficient sensitivity. Body temperature control is possible. Therefore, even if the impedance ratio is lowered, sensitivity can be sufficiently guaranteed within a certain limit, and under such an impedance ratio, the film has excellent flexibility and good adhesion to the polymer thermosensitive film. It is believed that a polymeric material containing excellent conductive particles can be used as an electrode, and that the disadvantages of the film thermistor using the metal foil as an electrode can be overcome. The film thermistor according to the present invention was devised in view of the above points, and an electrode layer made of a polymeric material containing conductive particles is provided on at least one side of a polymeric thermosensitive film. Lowest specific impedance within operating temperature range
For Z ₁ , the specific impedance of the above electrode layer Z ₂
This configuration is characterized in that Z ₁ /Z ₂ is set to be 10 ² to 10 ⁶ . The polymer thermosensitive film used in this invention is one whose intrinsic impedance changes significantly depending on temperature, such as polyamide containing an ionic conductivity imparting agent and whose intrinsic impedance ranges from 10 ⁵ to ^{10 12} Ωcm. , a polyvinyl chloride film can be used. Carbon particles and metal particles can be used as the conductive particles, and synthetic resins such as polyamide and polyvinyl chloride can be used as the polymer material with which the conductive particles are mixed to form the electrode material. In the present invention, the ratio of the lowest intrinsic impedance Z ₁ within the operating temperature range of the thermal film to the intrinsic impedance Z ₂ of the electrode layer, Z ₁ /Z _2, is limited to 10 ² to 10 ⁶ because 10 ² This is because the sensitivity as a thermistor becomes insufficient if it is less than 10 ⁶ , and the adhesive strength between the electrode layer and the polymer thermosensitive film becomes insufficient due to the large amount of conductive particles blended into the electrode layer. The preferred range of the impedance ratio Z ₁ /Z ₂ in the present invention is 10 ³ to 10 ⁵ . In the film-like thermistor according to the present invention, as shown in FIG. 1, electrode layers 2, 2 are usually provided on both sides of a polymer thermosensitive film 1, but as shown in FIG. It is also possible to provide the electrode layer 2 only on one side of the electrode layer 2 and use the electrode layer 2 and the electrode 31 of the planar heating element 3 on which the thermistor T is superimposed and integrated as a detection terminal. Example Polyvinyl chloride thermosensitive resin (manufactured by Mitsubishi Monsanto; A-784N) was rolled to a thickness of 0.3 mm using a calendar roll.
A polymer thermosensitive film with planar dimensions of 100 x 100 mm was obtained. Further, 40 parts by weight of carbon powder was kneaded with a soft vinyl chloride resin using a mixing roll, and the mixture was formed into a film with a thickness of 0.2 mm using a hot press to obtain an electrode film with planar dimensions of 100 x 100 mm. This electrode film was laminated on both sides of the polymer thermosensitive film, and these were press-molded at a temperature of 180° C., a pressure of 7 kg/cm ² , and a holding time of 10 minutes to obtain a film-like thermistor. The operating temperature range of this thermistor is 20°C to 80°C, and the specific impedance of the above polymer thermosensitive film at 20°C and 80°C is 2×
10 ⁹ Ω-cm and 1×10 ⁷ Ω-cm. In addition, the specific impedance of the above electrode film is 8×
10 ³ Ω-cm. Therefore, Z ₁ /Z ₂ =1250. Comparative Example 1 The same procedure was used as in the above example except that the carbon content of the electrode film was changed to 3 parts by weight. The Z ₁ /Z ₂ ratio of Comparative Example 1 was 20. Comparative Example 2 In contrast to the above example, aluminum foil with a thickness of 20 μm was used as the electrode, and the other conditions were the same as in the above example. For these Examples and Comparative Examples, the adhesion between the electrode and the polymeric thermosensitive film, flexibility, thermosensitive properties, etc. were measured and the adhesiveness was as shown in the table below.

[Table] As mentioned above, according to the present invention, the sensitivity is sufficiently good, and the flexibility and adhesive strength between the heat-sensitive film and the electrodes are far superior to the conventional example (using aluminum foil as the electrode). A film thermistor can be provided.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing one embodiment of the present invention;
FIG. 2 is an explanatory diagram showing a usage state of another embodiment of the present invention. In the figure, 1 is a polymer thermosensitive film, and 2 is an electrode layer.

Claims (1)

[Scope of utility model registration request] An electrode layer made of a polymer material containing conductive particles is provided on at least one side of the polymer thermosensitive film,
The characteristic impedance Z ₂ of the electrode layer is set so that Z ₁ /Z ₂ is 10 ² to 10 ⁶ with respect to the lowest intrinsic impedance Z ₁ within the operating temperature range of the thermal film. film-like thermistor.