JPS6231983A - Surface heat generating body - 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 (Industrial Field of Application) The present invention relates to a sheet heating element for warming, in which a resistor is formed by printing and firing a thick film paste on a part of the surface of a ceramic electrically insulating substrate. It is something.

(Prior technology) Conventionally used planar heating elements include those using heat-resistant oil as a heating medium, panel-type heaters using positive temperature coefficient type thermistor heating elements, and resistance wires attached to mica plates. There are mica heaters that are wrapped around each other, and alumina ceramic heaters that have a tungsten resistor printed and fired on an alumina plate. There is also a planar heating element (for example, Japanese Utility Model Application Publication No. 17594/1983) in which a thick film resistor is printed and fired on a hollow substrate.

(Problems to be Solved by the Invention) According to the above configuration, heat-resistant oil is used as a heat medium,
A panel heater using a positive temperature coefficient thermistor heating element has a heat generating plate whose surface temperature is quite low at 90 to 120° C., so the amount of radiant heat energy generated is small, making it inefficient as a heating device.

In addition, in the case of mica heaters, the size of natural mica, which is an insulator, is extremely limited, making it difficult to create a large panel-shaped sheet heating element.Furthermore, the structure in which the mica heater is sandwiched between metal plates has poor heat conduction. Unfortunately, two localized heating occurs, resulting in a lack of safety. An alumina ceramic heater is made by printing a tungsten resistor in a thick film on an alumina green sheet, overlapping another green sheet, and firing it at a high temperature of 13oo to 1400°C in a reducing atmosphere with 3P. Therefore, it is difficult to match the resistance value to a predetermined value, and the defective rate is high, resulting in high cost. Furthermore, when this fired alumina substrate is used, the flatness of the substrate cannot be ensured, so there is a drawback that a large substrate cannot be formed.

In the case of hollow substrates, when the size is increased, flatness becomes a problem and pin poles are likely to form.Furthermore, the thickness of the frit is extremely thin at 50 to 100μ, so there are disadvantages such as poor insulation resistance and voltage resistance. There is.

Not put into practical use.

(Means for Solving the Problems) The present invention has been made to eliminate the above-mentioned drawbacks, and has excellent electrical insulation and voltage resistance, good flatness even in large size, and is resistant to shocks caused by rapid cooling and rapid heating. A sheet heating element is formed by printing a thick film of resistor on a part of the surface of a strong heat-resistant glass base and firing it. There are two types of heat-resistant glass: crystallized glass and amorphous glass. Crystallized glass has a smaller coefficient of thermal expansion and is therefore more resistant to thermal shock. Thick film resistors are ruthenium oxide, silver, nickel, and aluminum.

Fine powder such as is made into a paste as a binder for glass frit. The paste is printed according to a screen pattern and fired to form a thick resistor film. The thermal expansion of this thick film resistor is changed by the metal powder and glass frit binder, and the difference in thermal expansion between the thick film resistor and the heat-resistant glass substrate creates residual stress, making it easy to peel off. Furthermore, in order to alleviate this residual stress as much as possible, a lath layer is provided between the glass frisode 1-, which is between the thermal expansion of the heat-resistant glass base and the thick-film resistor, to prevent the peeling of the heat-resistant glass base and the thick-film resistor. prevent the risk of

(Function) As described above, since the thick film resistor, which is a heating element, is directly bonded to the heat-resistant glass substrate, heat conduction from the heating element is good, and the entire substrate becomes a heating element. Among heat-resistant glasses, the coefficient of thermal expansion of crystallized glass is 10x107°C, and in the case of thick film resistors, the glass frit of the binder melts at 70 to 90x107°C, and then solidifies as the temperature decreases. However, the difference in thermal expansion at room temperature results in the largest residual stress.

P The stress can be alleviated by providing an intermediate glass layer.

(Example) An example of the present invention will be described with reference to the drawings. A thick film resistor 2 is fired on the surface of a heat-resistant glass substrate 1.

For the heat-resistant glass substrate 11, crystallized glass such as Neoceram or amorphous glass such as Pyrex glass is used. Thick film resistor 2 is made of ruthenium oxide and silver.

A paste is prepared by mixing fine powders of nickel, aluminum, etc. and fine powders of glass frit, and adding an organic binder, and then printing according to a screen pattern. Ruthenium oxide and silver are used in this prototype as they are stable when heated and fired in air.

The glass frit used as the binder melts at around 5so'C. 600 after printing paste
Thick film resistor 2 was obtained by firing at ~650'C for 10 minutes. Furthermore, in order to prevent electric shock, a low melting point glass frit paste was coated as cover coat 3.
It was fired at o'C. When amorphous heat-resistant glass is used for the heat-resistant glass substrate 1, the difference in thermal expansion with the thick film resistor P body 2 is relatively small, but with crystalline heat-resistant glass, the difference in thermal expansion becomes large, resulting in large residual stress. remains as. As a result, delamination tends to occur, so an intermediate glass layer 4 is provided to prevent this.This intermediate glass layer 4 is made of aluminum borosilicate, which has a thermal expansion larger than that of the heat-resistant glass substrate 1 and smaller than that of the thick film resistor 2. A glass of about 10 μm is used to alleviate the difference in thermal expansion between each layer and prevent delamination.

The planar heating element thus prototyped was heated to 4oQ°C, which is the heat-resistant temperature of the cover coat 3.

Next, it was immersed in water at 20 to 30'C and rapidly cooled several times. As a result, no peeling between the two layers or hair cracks occurred.

In addition, no abnormal change in resistance value was observed, indicating good results. We also prototyped a large panel-shaped heater, maintained the surface temperature of the heat-resistant glass substrate 1 at 300 to 350'C, and measured the amount of radiated heat, and found that it generated more heat than conventional panel-type heaters, and the wavelength distribution also It has been found that it has a large amount of radiation of far infrared rays with a long wavelength of 5 to 15 microns, making it an excellent warming device.

7 P (Effects of the Invention) As described above, the planar heating element according to the present invention can be provided as a fairly large panel-shaped heating device, and has excellent electrical insulation and withstand voltage. In addition, when compared with conventional panel-type heaters, the surface temperature can be maintained at a high temperature of 300 to 3 tso'c:, so the amount of far-infrared rays radiated is large, and the heating efficiency is also improved. Furthermore, since the panel plates of the structure are directly heated, the temperature rises quickly.

[Brief explanation of the drawing]

The drawing is a sectional view of a planar heating element according to the present invention. 1... Heat-resistant glass substrate, 2... Thick film resistor, 3...
- Cover coat, 4... intermediate glass layer.

Claims (2)

[Claims] (1) In a planar heating element formed by printing and firing a thick film paste on the surface of a ceramic electrical insulating base to form a thick film resistor, the electrical insulating base is provided with a heat-resistant glass base (1).
A planar heating element characterized by using. (2) The thermal expansion coefficient between the heat-resistant glass substrate (1) and the thick film resistor (2) is greater than 10 x 10^-^7/℃, and 70
A planar heating element characterized in that an intermediate glass layer (4) whose temperature is smaller than ×10^-^7°C is provided.