JPH02283001A - Composition of heat-generating body - Google Patents

Abstract

PURPOSE:To obtain a low-resistance heat-generating body having a heat resisting property by using crystallized glass containing conductive fine powder and crystallized glass frit at a specific ratio. CONSTITUTION:The mixing ratio of a conductive substance to crystallized glass frit in this heat-generating body is set at 30:70 to 95:5 in weight. When the content of the conductive substance is smaller than 30wt.%, the conductivity of the exothermic body drops. When the content is >=95wt.%, the sinterability of the body becomes worse. When the above-mentioned composition of a specific mixing ratio is used, a low-resistance heat-generating body having a heat resisting property can be obtained. Moreover, since the body contains a crystalline phase, the heat-generating body can be increased in toughness and strength and, accordingly, in resistance against crack generation.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a heating element composition that utilizes electrical resistance heat and can be used at home or in industry.

(b) Prior Art A resistor composition made by mixing a mixture of one or more conductive substances such as molybdenum silicide, tantalum silicide, magnesium silicide, manganese silicide, etc. and glass frit in a specific ratio is disclosed in Japanese Patent Application Laid-Open No. 53-1993- No. 50496.

(c) Problems to be solved by the invention In the prior art, the softening point of the glass frit is 6.
Since it is ordinary glass with a temperature of 00 to 700 degrees Celsius, when printed on a substrate as a sheet heating element, it has a temperature of 900 to 100 degrees Celsius.
If fired and used at 0°C, the printed pattern will collapse and, in extreme cases, there is a risk of short circuiting. Further, when used as a rod-shaped heating element by sintering, there is a drawback that deformation becomes large during use.

The present inventors have solved the problems of the above-mentioned conventional technology.
We have succeeded in developing a heat-resistant, low-resistance heating element.

(D) Means for Solving the Problems The present invention provides that the glass frit to be mixed with the conductive substance is a crystallized glass frit in which the glass crystallizes during firing, and the mixing ratio of the conductive substance and the crystallized glass frit is The weight ratio is 30:70 to 95:5.

The reason why the mixing ratio of the conductive substance and the crystallized glass frit is set as above is that if the conductive substance is less than 30% by weight, the conductivity will be poor, and if it is more than 95% by weight, the sinterability of the heating element will be poor. Because it will get worse.

Furthermore, in the present invention, as the crystallized glass frit,
By using a composition having the following specific ratio, a heat-resistant and low-resistance heating element could be obtained. Furthermore, by including a crystalline phase, when used as a heating element, toughness and strength were increased and crack resistance was improved.

Incidentally, even if a glass frit has a composition having the following specific ratio, a glass frit that does not crystallize during firing does not correspond to the crystallized glass frit of the present invention.

Furthermore, when producing a sheet heating element, the heating element obtained from the composition of the present invention is not only economically advantageous because its film thickness can be reduced due to its low resistance, but also has excellent thermal shock resistance. A heating element with excellent properties could be obtained.

The composition and mixing ratio of the crystallized glass frit are as follows.

Wataru M O: 5-50 wt% BO: 20-80 wt% Mllo: 0-10 wt% Mlo: O-5 wt% SiO: 0-40 wt% Al2O3: 0-40 wt% BiO: O-10 Weight % Weight % Third agent: 0 to 20 weight % However, Mn, one or more alkali metals, MIL,
- more than one species of alkaline earth metal, MrL: scandium;
Yttrium and/or Lanthanide Note that lanthanide in this specification is a general term for elements from lanthanum (La) to lutetium (Lu).

In addition, nucleating agents that form crystal nuclei include T i O2, Zr
O2, P205.5n02, Zno, MoO3, Ta
At least one or two or more of 2o5, Nb205, and AS203 are used.

The reasons for limiting the above composition and mixing ratio are as follows.

MxO is an oxide of one or more alkaline earth metals such as Mg, Ca, Sr, Ba, etc., and MTLo-xB203
It is an essential component together with B2O3 for the formation of the crystalline phase of the system. If MILO is less than 5% by weight, the glass will consist mainly of boric acid, and phase separation will occur during the glass forming process, making it impossible to form a homogeneous glass. Furthermore, when M"O exceeds 50% by weight, B2O3 in the glass decreases relatively, so the resistance value of the heating element obtained by mixing it with a conductive substance increases and it becomes difficult to vitrify. This MO is 25 to 45
% by weight is more preferred.

BO is essential together with MILO for the formation of the MTLO xB203 crystal phase. Moreover, it has a great influence on the resistance value when used as a heating element. i.e. 20% by weight
If it is less than 80% by weight, the resistance of the heating element becomes high, and if it exceeds 80% by weight, the phase of boric acid will separate during the glass forming process, making it impossible to obtain a uniform glass. From 20 to 80% by weight, the resistance value decreases with increasing amount of B2O3. This B2O3 is 20
-60% by weight is more preferred.

M-03 is an oxide of Sc (scandium), Y (yttrium) and/or lanthanide, and is added to increase the adhesion strength between the heating element and the substrate, but even if it exceeds 10% by weight, its effect will be reduced. 0-10 because it doesn't get any better
The weight is 1%. This M2O3 is more preferably 1 to 5% by weight.

M2O is an oxide of one or more alkali metals such as Li, Na, Rb, etc. If it exceeds 5% by weight, the movement of alkali ions will occur when the glass is mixed with a conductive material and used as a heating element. Since this causes compositional changes and resistance value changes, the amount is at most 5% by weight, and may be 0% by weight.

Actually, it is contained as an impurity in the glass raw material in an amount of about 0.1% or less.

S i O 2 is added in an appropriate amount in order to obtain a stable glass, but if it exceeds 40% by weight, 8203 becomes relatively small and the above-mentioned resistance value becomes high, which is not preferable. This S i O2 is more preferably 2 to 10% by weight.

Like S i O2, Al2O3 is also added in an appropriate amount in order to obtain a stable glass, but if it exceeds 40% by weight, B2O3 becomes relatively small, which is not preferable. This A
I203 is more preferably 2 to 10% by weight.

Bi2O3 is added in an appropriate amount to improve adhesion to the substrate and reduce resistance, but if it exceeds 10% by weight, it is not preferred because the physical properties of the glass will vary greatly. This Bi2O
3 is more preferably 5 to 10% by weight.

TiO2, ZrO2, P205.5n02, Zno,
At least one or two or more of MoO3, Ta2o5, Nb205, and As2O3 are added as crystal nucleation agents to form a crystal phase. Usually, the amount of this nucleating agent added is 20% by weight or less. This crystal nucleating agent does not necessarily need to be added if the glass can be crystallized by appropriately selecting the composition of the glass.

As shown in the attached figure, by providing the heating element 1 with an overcoat layer of glass 2, not only the ability to prevent electric leakage is imparted, but also the ability to prevent leakage is provided. No change in resistance was observed even after standing for o-oo hours, indicating that a better heating element could be obtained.

The glass used has an expansion coefficient that matches that of the heating element, and is preferably a glass that does not react with the heating element. In the overcoating method, by selecting the composition of the glass, simultaneous firing with the heating element is possible, and no deterioration in performance is observed due to overcoating.

As shown in the following examples, the heating element of the present invention can be produced by printing it on a substrate as a paste, pressing it into a molded body, sandwiching it between green sheets and sintering it, or It is also possible to embed the above-mentioned molded body in ceramic powder and fire it, and the application method is not limited to the application method described in the following examples.

(E) Effect The heating element of the present invention is produced by the reaction of MO and 820 as described above, resulting in M"O.x B203 (M" is Mg
, Ca, Ba, and Sr form a crystalline phase of x = 0.3 to 3) system, which improves heat resistance and lowers resistance.

Furthermore, by reacting this crystallized glass with molybdenum silicide, such as MoSi2, which is one of the conductive substances, the low-resistance MoB becomes molybdenum silicide, such as M
Produced at the interface between o S i 2 and glass frit,
It is thought that this becomes a conductive layer and the resistance value decreases. (This generation of MoB was confirmed by X-ray diffraction method.

) (f) Example Toru Ohki A glass was prepared by the following method so as to have the glass composition 1 shown in Table 1 below, and a crystallized glass frit was manufactured.

That is, using each carbonate, hydroxide, oxide, etc. as raw materials so as to have composition 1 in Table 1, 13
After melting at 50°C for 30 minutes, it was rapidly cooled with a roll to obtain glass flakes. The obtained glass flakes were milled in a ball mill for 6
The glass powder (frit) was pulverized for a period of time to obtain a glass powder (frit) with an average particle size of 2 to 3 microns.

This glass frit and M o S with an average particle size of 3 microns
After thoroughly mixing i2 at various ratios (weight ratios) shown in A of Table 2, the mixture was mixed with a vehicle containing an organic polymer (e.g., acrylic resin) as a binder at a ratio of about 80:
Mix thoroughly at a ratio of 20% (weight ratio) to form a paste. This paste was printed to a thickness of 20 microns on an alumina substrate using a 200 mesh screen, dried at 130°C for 30 minutes, and then fired at 1000°C for 10 minutes in a nitrogen atmosphere to crystallize the glass. After cooling, the resistor was formed. The results are shown in 1 of Table 2.

Example 1 was prepared using a crystallized glass frit obtained by preparing glass to have the composition shown in Glass Composition 2 in Table 1.
Table 2 shows the results of measuring the resistance value using exactly the same process as above.
It is shown in 2.

Silicon carbide with a particle size of 0.1 to several microns is used as a conductive fine powder using a crystallized glass frit obtained by preparing glass to have the composition shown in Glass Composition 3 in Table 1. After mixing thoroughly at various ratios (weight ratios) shown in A of Table 2 using
They were thoroughly mixed at the ratio (weight ratio) to form a paste.

This paste was printed to a thickness of 20 microns on an alumina substrate using a 200 mesh screen, dried at 130°C for 30 minutes, then fired at 1200°C for 10 minutes in a nitrogen atmosphere to crystallize, and after cooling, the resistance was measured. The results are shown in Table 2-3.

Toru Inuyoshi A: Using a crystallized glass frit obtained by preparing glass to have glass composition 3 in Table 1, using tungsten silicide as the conductive fine powder, baking at 1000°C for 10 minutes in a nitrogen atmosphere. Except for this, the process was carried out in exactly the same manner as in the above example, and the resistance was measured. The results are shown in Table 2-4.

Using a crystallized glass frit prepared by preparing glass to have glass composition 5 in Table 1 and using MoSi2 as the conductive fine powder, the process was carried out in exactly the same manner as in Example 1, and the resistance was The measured results are shown in 5 of Table 2.

Using a crystallized glass frit obtained by adjusting the glass so that the glass composition 6 in Table 1 was obtained, MoSi2 was used as the conductive fine powder, the process was carried out in exactly the same manner as in Example 1, and the resistance was The measurement results are shown in Table 2, 6.

Rizuzuri JP-A-53-5049 cited as prior art of the present invention
A heating element similar to that disclosed in No. 6 (with the exception of firing in a nitrogen atmosphere, using a glass frit having the composition in the Comparative Example column of Table 1) was prepared, and a heating element was prepared that was exactly the same as Example 1 of the present invention. The results of measuring the resistance values are shown in the Comparative Example column of Table 2. Incidentally, since the glass of this comparative example does not contain a nucleating agent, it does not crystallize under the firing conditions of about 1000°C.

(Hereinafter, blank space) Table 1 Nigarasu composition (wt%) Table 2 Sheet resistance value (Ω/5 square) Some of them had a value, but since it was about 0.1 wt%, they were ignored. ) (However, A is the weight ratio of conductive fine powder/glass frit) (F) Other test results of the heating element of the example As mentioned above, the heating element of the example of the present invention is the same as that of the comparative example. The resistance value is lowered by one order of magnitude compared to the previous one, and the film can be made thinner by that amount, making it more economical and having a wider range of applications.The following tests have confirmed that it also has excellent heat resistance and thermal shock resistance. Ta.

Even in a heat cycle test (heating to 800°C in 3 minutes, holding at this temperature for 2 minutes, and then rapidly cooling), no peeling from the substrate was observed when the heating element paste of the present invention was printed. Also, changes in resistivity were not a problem.

In addition, in order to examine thermal shock resistance, the heating element printed board was
Even when the heating element was heated to .degree. C. and placed in water, no peeling from the substrate was observed, making it possible to obtain a heating element with good adhesion.

(G) Effect The present invention uses crystallized glass having a specific composition and ratio as described above to make a heat-resistant and low-resistance heating element, so its film thickness can be reduced, and therefore, ,
It can be made into an economically advantageous heating element with excellent thermal shock resistance, has a wide range of applications, and has an extremely large effect on industry.

[Brief explanation of drawings]

The figure is a sectional view of a heating element obtained by overcoating the heating element composition of the present invention with glass. 1...Heating element composition, 2...
...Glass.

Claims (6)

[Claims] (1) Conductive fine powder and crystallized glass frit at 30:7
A heating element composition characterized in that it contains in a ratio of 0 to 95:5% by weight. (2) The conductive fine powder is molybdenum silicide, titanium silicide,
The heating element composition according to claim (1), characterized in that it comprises at least one of tungsten silicide, silicon carbide, molybdenum carbide, molybdenum boride, and the like. (3) The heating element composition according to claim (1) or (2), wherein the crystallized glass frit has the following composition. M^IIO: 5-50% by weight B_2O_3: 20-80% by weight ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ SiO_2: 0-40% by weight Al_2O_3: 0-40% by weight Bi_2O_3: 0 to 10% by weight Nucleating agent: 0 to 20% by weight However, M^I: one or more alkali metals, M^II: one or more alkaline earth metals, M^III: scandium, yttrium, and/or or lanthanide (4) The heating element composition according to any one of claims (1) to (3), wherein the crystallized glass frit has the following composition. M^IIO: 25-45% by weight B_2O_3: 20-60% by weight ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ SiO_2: 2-10% by weight Al_2O_3: 2-10% by weight Bi_2O_3: 5-10% by weight Nucleating agent: 0-20% by weight However, M^I: one or more alkali metals, M^II or more alkaline earth metals, M^III: scandium, yttrium and/or lanthanide (5) Nucleating agents are TiO_2, ZrO_2, P_2O_
5, SnO_2, ZnO, MoO_3, Ta_2O_5
, Nb_2O_5, and As_2O_3, the heating element composition according to claim (4). (6) A heating element obtained by overcoating the heating element composition according to any one of claims (1) to (5) with glass.