JPS59201384A - Panel heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a planar heating element in which electric heating elements are integrally embedded in an electrically insulating hollow layer, and is used for heating, cooking, drying equipment, etc. It provides a heat source using energy.

Conventional Structures and Problems Conventionally, sheathed heaters, quartz heaters, planar heating elements, and the like are known as heating elements that utilize electrical energy.

Although sheathed heaters and quartz tube heaters are used for 27 different purposes, they are not suitable for uniformly heating objects to be heated.

On the other hand, planar heating elements have recently come into the spotlight as heating elements that meet the needs of thinning devices and uniform heating. However, conventional planar heating elements have a structure in which the heater is wound around an insulating substrate such as mica, which has poor heat transfer to the heated object, and because the electric heating material is not sealed, there are problems with moisture resistance. , the conditions of use were limited. In addition, in recent years, there have been sheet heating elements made by forming expensive and high-melting point conductive patterns such as tungsten on raw sheets such as alumina, bonding the sheets together and sintering them. It has excellent properties and can be used at high temperatures, but
The sintering temperature was high and there were problems with removing the electrodes.

Moreover, these are expensive, often have large variations in resistance value, and have problems in manufacturing workability and productivity. In addition, there are devices in which a conductive pattern is formed between organic films using a paste such as carbon, and a heating element is constructed using methods such as lamination.
11-ζ Since the heat resistance of the fat film is low, it is usually used at 50 to 120°C and cannot be used above 200°C.

There was also a problem with longevity.

Furthermore, recently, a planar heating element has been proposed in which a hollow layer is formed on a metal substrate, and a heat generating element is sandwiched between the hollow layers, in which a heating element is further covered and adhered to the surface of the hollow layer. has been done. The heating element of B is
The hollow layer that covers the heating element has excellent heat resistance, so
Suitable for use in medium to high temperature ranges of oo~400℃,
Moreover, it has characteristics such as being thin and expected to have a long life.

However, in order to put this heating element into practical use, there is a problem in the electrical insulation between the heating element and the metal substrate. In other words, the glass hollow frit, which is the main component of the hollow layer formed on the metal substrate, is made to match the firing temperature of the hollow and the expansion coefficient of the base metal.
It contains 20-36% by weight of alkali metals such as Na 201 K20 + L 120. For this reason, 2
When used at a high temperature of 00°C or higher, the above-mentioned alkali component ion movement occurs, and as described in JP-A-59-201384 (
2) Electrical properties such as insulation resistance and dielectric strength deteriorate significantly.

In order to improve these electrical characteristics, in the hollow layer,
For example, it is possible to add insulating materials such as alumina, zircon, and magnesium oxide as mill additives, but if the amount added is too large, they will lack the properties of a hollow, for example, many pinholes will occur, and the dielectric strength will decrease. The disadvantage is that it decreases. Conversely, if the amount added is small, the electrical properties approximate those of hollow metal, and cannot be improved by this method.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of a heating element in which a heating element is embedded in a hollow layer, and to provide a planar heating element that has excellent electrical characteristics and is suitable for mass production.

Structure of the Invention In the present invention, among the hollow layers in which the electric heating elements are embedded, the glass frit forming the hollow layer interposed between at least the heating elements and the metal substrate is composed of tita 572, a recrystallization type frit. It is characterized by

DESCRIPTION OF EMBODIMENTS FIG. 1 shows the basic structure of a heating element of the present invention. 1 is a metal substrate, on both or one side of which a first insulating hollow layer 2 is provided.
is formed. 3 is a thin strip-shaped metal heating element, which is installed on the surface of the hollow layer 2, and is further attached to the second hollow layer 4.
By covering the heating element 3 with the hollow layers 2 and 4
It has a clamped structure.

Each component will be explained below.

0) Metal base material The metal base material of the hollow substrate constituting the planar heating element of the present invention is aluminum or aluminum die-casting.

Cast iron, aluminized steel, low carbon steel, hollow steel plate, or stainless steel plate are used, and their selection depends on usage conditions, usage temperature, and shape of the base material.

It is determined based on workability, and pretreatment is performed as necessary.

The following explanation will focus on steel plates for hollow holes.

67. (2) Electric heating element The electric heating element applicable to the present invention is basically a ribbon-shaped element. It is necessary to completely cover the surface of the electric heating element with the hollow layer 4. For example, if a coil-shaped or thick band-shaped heating element is used, the thickness of the hollow layer 4 will increase accordingly. As a result, the adhesion of the hollow layer is extremely reduced, and an external shock easily peels off the hollow layer, exposing the electric heating element.

The appropriate thickness of the heating element ribbon is 10 to 200 μm.
Preferably it is in the range of 30 to 100 μm. It is difficult to process a thin ribbon of 10 μm or less into a thin ribbon, and when manufacturing a sheet heating element, the ribbon may be torn, bent, or bent, resulting in significantly poor workability. Also 2
If the diameter is 00 μm or more, in addition to the above-mentioned reasons, if a beat cycle is applied to the planar heating element, cracks may occur in the hollow layer, which is undesirable.

In addition to the usual methods of cold rolling and hot rolling, metal can be made into a thin ribbon using an ultra-quenching method. Etching and press working are suitable methods for forming a thin metal strip into a desired pattern. The etching method can be applied when the production quantity is small, and the press processing method can be applied for mass production. FIG. 2 shows an example of a patterned electric heating element.

The film thickness and pattern shape of the electric heating element can be arbitrarily determined in consideration of the rated power, heat generation area, temperature distribution, and the like.

Various electric heating materials can be used for the electric heating element, but the specific resistance and coefficient of thermal expansion, which are factors that determine the shape of the heating element (pattern width, length, thickness), etc., must be at appropriate values. A material that has excellent adhesion to the hollow layer, workability, etc. is selected. From these points of view, 2
Ferritic stainless steel having a specific resistance of 60 .mu..OMEGA..multidot. at 0.degree. C. and a thermal expansion coefficient of 10.sup.4 x 10.sup.-'deg.sup.-1 at 100'C is most preferable.

(3) Insulating hollow layer As a factor determining the electrical properties of the planar heating element of the present invention, the electrical properties (insulation resistance, dielectric strength, etc.) of the insulating hollow layer interposed between the heating element and the metal substrate are important. This is a great point.

As a result of various studies, the present inventors have focused on the fact that, in addition to the thickness of the hollow layer, the volume resistivity of the glass frit is an important factor that determines electrical properties, such as insulation resistance. It is expressed by the following formula.

Rv: Insulation resistance ρV: Volume resistivity A: Heating element area d: Thickness of the hollow layer Here, the thickness of the hollow layer is determined from the viewpoint of hollow adhesion, and is approximately 100 to 500 μm at most. . From this point of view, in order to improve the insulation resistance of the insulating hollow layer, it is necessary to configure the insulating hollow layer with a glass frit having excellent volume resistivity, and the selection of the glass frit becomes important.

Table 1 shows the hollow frit 9/z studied by the inventors.
(All product numbers are from Nippon Ferro Co., Ltd.)

Table 1, 10. These frits were milled with the mill composition shown in Table 2, milled in a ball mill for 2 hours, and prepared as sample slips. Pretreated size of these slips: 10o x 10OL
Approximately 150μ with a spray gun on +II++ hollow steel plate
It was coated to a thickness of m, and after drying, it was fired at a predetermined temperature for 6 minutes to form an insulating hollow layer. Furthermore, a heating element made of stainless steel 5US430 (thickness = 60 μm) with the pattern shown in Fig. 2 was placed on this hollow layer, and from above, the hollow slip used for the insulating hollow layer was sprayed with a spray gun to form a heating element of about 160 μm. It was coated to a certain thickness, dried, and then baked at a predetermined temperature for 6 minutes to form a hollow layer covering the heating element.

Table 2 Frit 100 parts by weight Clay (No. 9) 6 Sodium nitrite 0.1 Water 60 N At this time, the opacity W value of the hollow layer was measured.

L, a, b obtained from the color stimulus values x, y, z by C, I, E display were measured using a color difference meter, and the opalescence (
W value) was calculated using the formula shown below.

W=1oo-8τgv The larger the W value, the whiter the image. The W values are shown in Table 1.

Using these heating element samples, the volume resistivity of the insulating hollow layer was determined using equation (1). A high-resistance meter was used to measure the insulation resistance, and DC 6oo ■ was applied, and the resistance value was read after 1 minute. The measurement temperature was 100℃ using an electric furnace.
, 160℃, 200℃.

The temperature was set to 250°C. Figure 3 shows part of the results of plotting the correlation between the volume resistivity thus determined and the reciprocal of the insulation temperature T of the operating temperature. From this figure, the volume resistivity in case (8) using titanium opalescent frit is 10 to 1000 times higher than in case (B) using other hollow frits. Therefore, if this titanium milky white frit is used, 3oO ~
It has been found that it is possible to improve the volume resistivity and the thermistor B constant in a medium to high temperature range of 400°C.

Titanium opalescent frit is also called recrystallization precipitation type frit, and when a frit in which approximately 17 to 20% by weight of T 102 is melted in glass is reheated at a temperature of 800 to 850°C, fine T 102 crystals form. This is a frit that is deposited in the glass. The reason why the above-mentioned volume resistivity value is significantly better than that of other frits is because of this fine T.
This is presumed to be caused by IO2 crystal particles. Generally T
The size of the 102 crystal grains is 0.12 to 0.2 μm, which is very fine crystal.

Next, explanation will be given using the ion migration model shown in FIG. FIG. 4 (-) shows the case where a frit other than titanium opalescent frit is used, and the insulation resistance between the metal substrate 1 and the heating element 3 is related to the ion migration of the alkali ions in the hollow layer 2, and the ions are Move the shortest distance. In other words, the insulation resistance value is largely related to the thickness of the hollow layer 2.

On the other hand, when titanium milky white frit is used, the fourth
As shown in Fig. 0)), a large number of tiny Ti02 particles 6 are precipitated in the hollow layer, making it difficult for the alkali ions to move over the shortest distance, and they move in a meandering manner. That is, even though the apparent film thickness of the Ti○2 opalescent frit is the same, the effective film thickness in terms of electrical characteristics is significantly larger, and therefore the insulation resistance is considered to be significantly improved.

In this way, the electrical characteristics can be improved by using a titanium recrystallization type frit as the glass frit forming the insulating hollow layer.

As mentioned above, the titanium particles precipitated in the insulating hollow layer have a great deal to do with the electrical properties. That is, it is related to the size and number of precipitated titanium particles in the hollow layer. This is primarily related to the optical properties (opalescence) of the hollow layer. The degree of opacification varies depending on the firing conditions, mill addition conditions, etc.

Next, the results of investigating the opalescence and electrical characteristics will be explained. Using the frit shown in Table 1 ((J), the firing conditions (firing temperature 9 hours) as the mill addition composition in Table 2
The relationship between the W value and the insulation resistance was determined by changing the . A heating element having the pattern shown in FIG. 2 was used, and when the insulation resistance between the metal substrate and the heating element was 1 MΩ or less at 250° C. and 14°, it was represented by ×, and when it was more than that, it was represented by ○.

From Table 3, the W value of the insulating hollow layer is preferably 80 or more in terms of electrical characteristics.

Note that the W values in Table 3 are based on the original opalescence of the frit to which no pigment is added. It is also possible to add a pigment or the like to the insulating hollow layer to color it. However, if pigment is added at the time of mill addition (usually 0.1 to 6% by weight), of course,
The milky whiteness decreases. The preferred W value in this case is 60
That was it.

Effects of the Invention As described above, according to the present invention, by using a titanium recrystallization type frit as a glass frit that forms an insulating hollow layer interposed between a metal substrate and a heating element, electrical characteristics and practical use can be improved. Usage temperature: 15 liters; The improvement in the -4 degree range can be significantly improved.

If the sheet heating element of the present invention is replaced with an infrared lamp for a tower kotatsu, not only can the heater part be made much thinner, but also health heating can be achieved by emitting high-quality far infrared rays from the hollow layer. Become. Furthermore, when used in a hot warmer, radiant heat transfer is performed, so less heat insulating material is required at the bottom, making it possible to reduce weight and cost.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the main parts showing the basic structure of the heating element of the present invention,
Figure 2 is a plan view showing an example of a heating element pattern, Figure 3 is a diagram showing the relationship between the temperature and volume resistivity of a hollow layer using various frits, and Figure 4 is a diagram showing the movement of ions in the hollow layer. It is a model diagram explaining. DESCRIPTION OF SYMBOLS 1... Metal substrate, 2... First hollow layer, 3... Electric heating element, 4... Second
hollow layer. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Ward Figure 2 Procedural Amendment Document June 4, 1981 Patent Application No. 54356 2 Name of Invention Planar Heating Element 3 Relationship with the case of the person making the amendment Patent application Colonel Location Oaza, Kadoma City, Osaka Prefecture 1006 Kadoma Name (582) Representative of Matsushita Electric Industrial Co., Ltd.
Toshihiko Yamashita 4 Agent 571 Address 388- Matsushita Electric Industrial Co., Ltd., 1006 Kadoma, Kadoma City, Osaka Prefecture

Claims (1)

[Claims] A planar heating element comprising a metal substrate on which a first insulating hollow layer is formed, and an electric heating element covered and bonded to the hollow layer by a second hollow layer, the first hollow layer A planar heating element characterized in that the glass frit forming the glass frit is a titanium recrystallized frit.