JPS6322041B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dielectric electric element having at least a resin layer to which an alternating current voltage is applied, and a pair of electric conductors facing each other with the resin layer interposed therebetween. . Here, the dielectric type electric element is an electric element that accurately detects the impedance of a resin layer determined by the volume impedance specific to the resin.

Such dielectric electric elements are widely used as sensors for detecting changes in the environment. Examples include heat-sensitive elements made of polyamide compositions or compositions in which a semiconductor material such as an organic semiconductor is dispersed in a polyolefin composition such as polyethylene or polypropylene or a thermoplastic resin such as polyvinylidene fluoride. The overall structure of the heat-sensitive element is to wrap one electric conductor wire around the core wire in a spiral shape, cover the outside with a resin layer, wrap the outer electric conductor wire around it, and then In some cases, the entire structure is made up of multiple flexible concentric cylindrical wires covered with an electrically insulating jacket, and in other cases, electrical conductor wires are arranged in a meandering manner on both sides of a sheet-like resin layer, and the outside A typical example is a case in which the whole is covered with an electrically insulating jacket and the whole is constructed as a sandwich-like multilayer structure plate. Those with a structure that generates heat by energizing these electric conductor wires are generally used.
Among these, those configured as multiple concentric cylindrical wires are widely used as heat-sensitive elements in heating devices such as electric blankets and electric carpets.

Incidentally, as the resin used in these dielectric type electric elements, polymer compositions having stable electrical properties such as the above-mentioned polyamide, polyethylene, polypropylene or polyvinylidene fluoride are often used. However, all of these have high crystallinity as polymers and have large rigidity at around room temperature. For this reason, when an electrical conductor is attached to the resin layer of a dielectric type electric element, the electrical conductor receives repulsion from the resin layer and does not make sufficient contact between the two, which prevents accurate detection of the impedance of the resin layer. .

Furthermore, new problems arise when such dielectric type electrical elements are used or stored under high humidity conditions. For example, this is the case when you want to use it again after storing it under high humidity conditions, such as using an electric blanket. In other words, under these conditions, water molecules are adsorbed to the resin layer of the dielectric type electric element, and ionic impurities and plasticizers in the resin layer are leached into this adsorption layer, creating a layer with low resistance. Create. This improves the electrical contact between the electrical conductor and the resin layer, reducing the contact resistance that existed between them during drying as described above. As a result, this change is detected as being larger than the difference in impedance inherent to the resin when it absorbs moisture and when it dries.

The present invention improves these conventional drawbacks by accurately detecting the impedance of the resin layer during drying, and
Moreover, it is possible to detect an impedance value close to that in dry conditions even during humidification, in other words, to provide a dielectric type electric element that is not affected by humidity.

In short, the features of the present invention are that the gap created when the electrical conductor receives repulsion from the highly rigid resin layer is so small that it can be ignored compared to the impedance of the resin, and that the resistance of the resin is small enough to be ignored. In comparison, the size is sufficiently large and a water-repellent dielectric layer is interposed therebetween. Here, the electrical operating mechanism of the dielectric type electric element will be described under two conditions: dry and humid.

(1) Operating mechanism in dry state In this case, the dielectric layer interposed in the gap region (the gap formed between the electrical conductor and the resin layer will be simply referred to as this below) is the electrical conductor. It can be understood that it acts as an electrical bridge between the resin layer and the resin layer. That is, it can be considered that the dielectric layer is in close contact with both of these and reduces the contact resistance that exists between the interfaces with both. The thickness of this dielectric layer is negligibly thin compared to that of the resin layer, and the capacitance is considered to be sufficiently large compared to that of the resin layer, so that it is possible to accurately detect the impedance of the resin layer. An equivalent circuit diagram schematically representing this situation is shown in FIG. Here, c and C are the capacitances of the dielectric layer and the resin layer, respectively, and c≫C. r and R are the resistances of the dielectric layer and the resin layer, respectively.

(2) Operation mechanism in humidified state In this case, in addition to the dielectric layer mentioned in (1), a moisture layer is formed by adsorbed water molecules and contains impurities such as ionic substances and plasticizers in the resin. intervenes in the gap. An equivalent circuit diagram schematically showing this situation is shown in FIG. Here r _W ,
c _W is the resistance and capacitance of the water layer, r′, c′ are the contact resistance and capacitance of the interface between the water-repellent dielectric layer and the water layer. Here the value of r _W is quite small. However, the water-repellent dielectric layer and the water layer are not compatible with each other, so that r' and impedance cannot be ignored. As a result, the dielectric type electric element detects an impedance larger than the impedance of the resin. In many resins, the impedance value decreases due to moisture absorption, but by offsetting this change, the influence of humidity can be removed. This effect is particularly great when using polyamide compositions that undergo the above-mentioned changes due to moisture absorption.

The operating mechanism has been described above, but in reality, the dielectric layer material selected will result in differences in leakage properties with the electrical conductor or resin layer, or differences in the degree of water repellency. It is necessary to select the most suitable material depending on the element or its usage conditions. Dielectric type electric elements manufactured by the methods described below depending on the difference in these materials or their forms have extremely excellent electric properties.

(1) Coating/dipping method This method can be applied when the composition forming the dielectric layer does not change its composition before and after the treatment process. That is, if the composition is in liquid form, it may be directly applied or immersed in the composition; if it is solid, it may be dissolved in an appropriate solvent, treated, and then dried. In these cases, coating is applied to at least one of the parts of at least one of the pair of electrical conductors including the part facing the resin layer or the resin layer facing the electrical conductor, or at least one of the electrical conductors is coated. Possible methods include immersing the entire conductor or resin layer.

(2) Baking and surface treatment method This method can be applied when the composition of the dielectric layer is changed before and after the treatment process. Generally, baking by heat treatment is performed after the step described in (1).

Now, various materials can be considered as the material for the dielectric layer, but among them, a polymeric substance containing fluorine atoms or silicon atoms provides excellent results. Among these, those in the form of grease, oil, rubber, or varnish are particularly preferred. Of these, it is appropriate to use method (1) for the first two, and method (2) for the latter two.

Next, the present invention will be specifically explained using a multiple concentric cylindrical heat-sensitive element as shown in FIG. 3 as an example. The procedure for constructing this heat-sensitive element is as follows.

(1) An electric conductor wire (hereinafter referred to as a conductor wire) 2 is wound around a core wire 1 made of heat-resistant wire fiber such as polyester or glass.

(2) Melt tubing the polymer temperature sensitive layer 3 on top of this. Here, the polymer thermosensitive material refers to a polymer composition whose impedance changes according to temperature changes.

(3) After the temperature sensitive layer in (2) is cooled and solidified, the conducting wire 4 similar to that in 2 is wound thereon.

(4) Furthermore, the insulating jacket 5 is coated.

The step of interposing the dielectric layer in the above is, for example,
It is added as a processing step for the state after the conducting wire 2 is wound in (1) or the state before the conducting wire 4 is wound in (3).

Here, it is also possible to use the following method. That is, there is a method in which the core wire 1 is made of a material that has good adhesion to the polymer thermosensitive material, thereby improving the adhesion between the inner conductor 2 and the polymeric thermosensitive material layer; When melt-tubing the body layer, with the inner conductor 2 wrapped around the core wire 1, the part to which the melted temperature-sensitive body layer is attached is placed under high vacuum, and the conductor 2 and temperature-sensor layer are placed under high vacuum. This includes methods for improving adhesion to body layers. When such a method is used in combination, the object of the present invention can be achieved by interposing a dielectric layer only in the outer one of the two gap portions.

Furthermore, important effects that can be achieved by the present invention will be described. One of the methods is to protect the electrical conductor by interposing a dielectric layer to prevent direct contact with the resin layer, thereby preventing corrosion or deterioration of the electrical conductor. This suppresses the occurrence of contact resistance due to the corroded layer and stabilizes the electrical characteristics.

Another effect is that when the resistance of the dielectric layer is sufficiently greater than that of the resin layer, the resin layer can be protected. In other words, when applying a voltage having a DC component to one of the electrical conductors in order to use the dielectric electric element as a heat generating element, this voltage is also applied to the temperature sensitive layer, but the resin layer is polarized by DC polarization. If it is composed of a composition that is likely to cause polarization, the impedance value will change due to polarization. However, when the resistance of the dielectric layer is sufficiently larger than that of the resin layer, most of the DC voltage component will be applied to this portion, and will hardly be applied to the resin layer. When detecting the impedance of the resin layer, an alternating current voltage is applied to the other electrical conductor and the alternating current is detected, so the above-mentioned direct current voltage component has no effect here. Therefore, even after long-term use, the dielectric type electric element of the present invention can maintain stable electrical characteristics.

In general, compositions made of polymer compounds containing fluorine atoms or silicon atoms can have extremely high resistance values even when made into extremely thin layers, but can also have sufficiently large capacitance values. It is possible to make the impedance negligibly small compared to that of the resin layer.
Therefore, it is fully suitable for this purpose.

In addition, as seen in Utility Model Publication No. 45-10145, as having the same purpose as the present invention,
A method is known in which a conductive adhesive paint is applied to the outer surface of a hollow cylindrical resin layer and an outer electrical conductor wire is wound thereon. However, such a method has a drawback in that the temperature fusibility of the resin layer is significantly impaired. That is,
When the electric element is also used as a heat generating element by energizing one of the electric conductors of the electric element, the resin layer may melt when part or all of the electric element becomes abnormally heated for some reason. However, according to the method disclosed in Publication No. 10145-197,
The conductive adhesive paint layer generally contains a conductive agent such as carbon, which results in poor meltability.
The normal operation of this temperature fuse function is prevented.

Needless to say, another major difference between the method of Utility Model Publication No. 45-10145 and the present invention is that in the former, the intervening layer located in the gap is a conductive material, whereas in the latter, it is a dielectric layer. That's true.

The present invention will be explained in detail below with reference to Examples.

Example 1 For 70 parts by weight of polypropylene, the resistance at room temperature is 3×10 ⁶ Ω・cm and 3×10 ⁻³ Ω・
15 parts by weight of each of potassium salt of 7,7,8,8-tetracyanoquinodimethane (hereinafter abbreviated as TCNQ) and graphite of cm were added, and the mixture was dried in a heating oven at 100°C overnight. This was melt-kneaded at a temperature of 190°C, extruded into a gut shape using an extruder, and then pelletized and further dried for one day and night.

On the other hand, an aluminum conducting wire was wrapped around a core wire made of glass fiber, and the wire was immersed in a solution of trifluorochloroethylene oligomer. Thereto, the pellets of the polypropylene composition prepared above were melt-tubed, cooled and solidified, and then immersed again in the trifluorochloroethylene oligomer solution. An aluminum conducting wire was wound on top of this, and the top was further covered with a polyvinyl chloride jacket to form a heat-sensitive element. This is designated as sample 1.

In addition, the above pellets can be melt-pressed to size
A sheet measuring 10 cm x 10 cm and 1 mm thick was made, and colloidal carbon was coated on both sides in a circular shape with a diameter of 5 cm to prepare a test piece for measuring electrical characteristics.

FIG. 4 shows the impedance-temperature characteristics of the heat-sensitive element constructed as described above and the test piece when completely dry (drying at 100°C all day and night). We also show the impedance-temperature characteristics of these samples after they were left in an atmosphere of 45°C and 95% RH for 100 hours. As a comparative example, the characteristics of a heat-sensitive element not subjected to the treatment as in the examples are also shown.

Example 2 For 65 parts by weight of polyvinylidene fluoride resin, the resistance at room temperature was 10 ⁵ Ω・cm and 0.1, respectively.
20 and 15 parts by weight of Ωcm TCNQ sodium salt and channel black were added, respectively, and melt-kneaded in the same manner as in Example 1, followed by pelletization.

On the other hand, a stainless steel conductor wire is wrapped around a core wire made of glass fiber, and the part to be melt-tubed is placed in a vacuum atmosphere of 20 mmHg.
The above-prepared pellets were melt-tubed into the above-mentioned conductor wire using an extruder for wire making. cooling,
After solidification, a flat stainless steel conducting wire which had been subjected to the following surface treatment was wound thereon, and further covered with a polyvinyl chloride jacket to form a heat-sensitive element. This is designated as sample 2. Here, the surface treatment is a process in which a stainless steel conductive wire is immersed in silicone alkyd varnish diluted with xylene and then baked at 150° C. for one hour.

In addition, a heat-sensitive element of a comparative example that was not subjected to such treatment and a test piece similar to that of Example 1 were simultaneously produced.

The impedance-temperature characteristics of the above samples are expressed as
As shown in the figure. In addition, the impedance-temperature characteristics of these samples after being continuously energized with a DC50V voltage for 500 hours in an atmosphere of 120℃, and the impedance-temperature characteristics of these samples after being left in an atmosphere of 45℃ and 95%RH for 100 hours were also measured at the same time. show.

Example 3 After impregnation with thermoplastic polyurethane melt,
A copper wire with a flat rectangular cross section is wrapped around a core wire made of dried polyethylene terephthalate fiber, and polydodecaneamide (nylon
The dried pellets of 12) were melt-tubed using an extruder for wire making. After cooling and solidifying, a flat copper wire with the following surface treatment is wrapped around it.
Further, it was covered with a polyvinyl chloride jacket to form a heat-sensitive element.

Now, the following various methods were adopted to treat the outer copper wire.

(1) Immersion in dimethylpolysiloxane (sample 3)
-1) (2) Application of silicone varnish diluted with xylene-butanol to the surface facing the nylon layer and subsequent baking at 150°C for 1 hour (Sample 3-2) (3) Fluorine-based water repellent (product Famous Deitku Guard F-
3320, manufactured by Dainippon Ink & Chemicals Co., Ltd.) in a diluted trichloroethane solution (sample 3-3).

A comparative example without such treatment and a test piece similar to Example 1 were also created.

The impedance-temperature characteristics of the above samples are expressed as
- Shown in Figure 8. The impedance-temperature characteristics after being energized or left under humidification under exactly the same conditions as in Example 2 are also shown.

In the above examples, the volume specific impedance was simply calculated from the thickness of the resin layer and the electrode area (in the case of a wire-wound electrical conductor, it was calculated from the wire width and pitch) for each sample.

Also, in the graphs of FIGS. 5, 6, and 8, parts with complicated lines have been appropriately omitted to make it easier to see.

Next, consideration will be given to the above embodiments.

In Example 1, as can be seen from Fig. 4, the trifluorochloroethylene oligomer treatment produced characteristics close to the theoretical characteristics (impedance-temperature characteristics for a test piece with colloidal carbon coated on both sides). Indicates that

Similarly, in Example 2, as can be seen from FIG. 5, the heat-sensitive element obtained by baking with silicone alkyd varnish showed good agreement with the theoretical characteristics. The temperature sensitive body used in the thermal element or test piece of Examples 1 and 2 is a composition that exhibits typical electron conduction, and in Examples 1 and 2, the impedance value does not depend on humidity.
In Example 2, the fact that the impedance value does not change even when a DC voltage is applied is a phenomenon specific to electronically conductive materials. The heat-sensitive elements of Examples 1 and 2 fully bring out this property.

On the other hand, in Examples 1 and 2, which were not processed, the impedance was at a high level and the slope of the curve was gentle, indicating that the temperature detection ability was reduced. Furthermore, as shown in Fig. 5, the impedance value increases due to energization, but this can be interpreted to be due to deterioration of the stainless steel electrode and an increase in the resistance at the contact site between it and the polyvinylidene fluoride composition. can. Furthermore, in FIGS. 4 and 5, the impedance tends to decrease due to humidification, and the slope of the curve also tends to become steeper. This can be considered to be because a water adsorption layer is formed in the gap region due to humidification, and this improves the electrical contact between the electrode and the temperature sensing layer.

Example 3 is polydodecanamide (nylon 12)
The present invention relates to a heat-sensitive element using. 6th to 8th
The figures show initial characteristics, characteristics after humidification, and characteristics after energization, respectively. FIG. 6 shows that the thermal elements treated with dimethylpolysiloxane, silicone varnish, and fluorine-based water repellent exhibit better characteristics than those without treatment.
FIG. 7 shows that while the test piece suffers a large drop in impedance due to moisture absorption, the water-repellent sample shows almost the same impedance value as when completely dry. That is, these materials do not suffer from changes in characteristics due to humidity. In addition, for samples that have not been subjected to water repellent treatment, the impedance generally decreases and the slope of the curve becomes steeper.
This can also be understood in the same way as Examples 1 and 2. Furthermore, FIG. 8 shows that the water-repellent treated material does not cause DC polarization even when a DC voltage is applied. On the other hand, a test piece or a heat-sensitive element that is not subjected to water-repellent treatment causes direct current polarization and increases the impedance value. This difference can be explained by the presence or absence of a function in which most of the DC voltage is applied to the water-repellent layer of the water-repellent layer, and only a small amount of DC voltage is applied to the temperature-sensitive element. It is.

As can be seen from Examples 1 to 3 described above,
The heat-sensitive element of the present invention has extremely excellent electrical properties and extremely excellent properties in use, being hardly susceptible to changes in humidity. All of the embodiments described above relate to heat-sensitive elements, but as described in detail above, the present invention provides a dielectric type electric element having the above-mentioned excellent characteristics.

[Brief explanation of the drawing]

Figures 1 to 2 are diagrams showing the equivalent circuit of a dielectric type electric element, Figure 3 is a diagram showing the structure of a heat sensitive element, and Figures 4 to 8.
The figure shows the impedance-temperature characteristics of the heat-sensitive elements of Examples and Comparative Examples. 1... Core system, 2, 4... Electric conductor, 3... Polymer temperature sensitive body.

Claims (1)

[Claims] 1. A resin layer to which at least an AC voltage is applied;
In a dielectric type electric element having a pair of electric conductors facing each other with a resin layer in between, a large impedance exists between the resin layer and a portion of at least one of the electric conductors facing the resin layer. 1. A dielectric electric element characterized by interposing a dielectric layer having a water repellency so small as to be negligible compared to that of a resin layer. 2. The dielectric type electric element according to claim 1, wherein the dielectric layer is a polymer material containing fluorine atoms or silicon atoms. 3. The dielectric type electric element according to claim 2, wherein the polymer substance containing fluorine atoms is selected from the group consisting of fluorine rubber, fluorine grease, fluorine varnish, and fluorine oil. 4. The dielectric type electric device according to claim 2, wherein the silicon atom-containing polymer substance is selected from the group consisting of silicone rubber, silicone grease, silicone varnish, and silicone oil. 5. The dielectric type electric element according to any one of claims 1 to 4, wherein the resin layer is made of a polyamide composition. 6 Claim 1, wherein the resin layer has a tubular shape
The dielectric electric element according to any one of items 1 to 4.