JPS60221925A - Manufacture of heater for indirectly-heated electron tube - Google Patents

Abstract

PURPOSE:To improve the dielectric strength between heater and cathode by applying the mixture of alumina and molybdenum onto the surface of tungsten wire then burning under high temperature thereafter dissolving the molybdenum powder with acid and producing porous surface. CONSTITUTION:Alumina powder, molybdenum powder, water, alcohol, anhydrous aluminum nitrate and magnesium nitrate are agitated sufficiently in a ball mill to produce suspension of insulation material which is deposited through cataphoresis around tungsten wire. Then it is heated in a furnace of hydrogen gas ambience under the temperature higher than 1,550 deg.C for several minutes to burn the mixture of alumina and molybdenum. Thereafter, it is immersed in the mixture liquid of nitric acid and sulfric acid to dissolve the molybdenum powder in the insulator thus to remain porous alumina insulator having coarse surface, resulting in considerable reduction of the contact area with the cathode and increase of insulation resistance.

Description

[Detailed description of the invention] Technical fields> The present invention relates to a method for manufacturing an indirectly heated electron tube heater.

<Problems to be Solved by the Invention> A conventional indirectly heated electron tube heater is formed by coating a tungsten wire I with an insulating material 2 such as alumina, as illustrated in FIGS. 1 to 4. The surface of the insulator 2 is smooth even when observed under a microscope. When the insulator is alumina, the surface is white and the withstand voltage between the heater and the cathode is approximately 2.1KV.Also, in order to further improve heat radiation and increase the rate of temperature rise of the cathode, the alumina insulator is used to increase the temperature rise rate of the cathode. When a mixture of alumina and tungsten powder is layered and fired, the surface is black and the withstand voltage between the heater and the cathode is about 3 KV. However, with this level of withstand voltage, there is a risk of damaging the cathode ray tube when an unexpected high voltage is applied, and conventionally, compensation measures were used, such as installing an earth protector outside the cathode ray tube of a television receiver. .

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing an indirectly heated electron tube heater in which the dielectric strength between the heater and the cathode is increased.

<Means for Solving the Problems> The method for manufacturing an indirectly heated electron tube heater of the present invention is to apply a mixture of alumina and molybdenum powder to the surface of a tungsten wire, and then to bake the molybdenum powder at a high temperature. It is characterized by its surface becoming porous and uneven when dissolved in acid.

<Example> A tungsten wire processed into a predetermined shape is immersed in an insulating material liquid, and an insulating material is attached around the tungsten wire by electrophoresis. For example, 830 g of alumina powder, 830 g of molybdenum powder, 800 cc of water, 12 g of alcohol
00cc, anhydrous aluminum nitrate 30g, magnesium nitrate 3
0g is sufficiently stirred in a ball mill to create a suspended insulating material liquid, a tungsten wire is immersed in this insulating material liquid, and a voltage is applied using the tungsten wire as a negative electrode. A mixture of alumina and molybdenum is deposited. Next, ゛ζ15
The mixture of alumina and molybdenum is calcined by heating at a high temperature of 50° C. or higher for several minutes. Next, when this fired product is immersed in a mixed solution of nitric acid and sulfuric acid (for example, 2 parts nitric acid: 2 parts sulfuric acid: 1 part water), the molybdenum powder in the insulator dissolves away and a porous alumina insulator is obtained. The surface is uneven. When observed under a microscope, the size of the porous pores is
The size of the pores corresponds to that of the molybdenum particles, and therefore, a desired pore size can be obtained by appropriately selecting the size of the molybdenum particles.

Since the state of such an insulator changes depending on the mixing ratio of alumina and molybdenum, the withstand voltage between the heater and cathode when the heater of the present invention is incorporated into a cathode ray tube depends on the mixing ratio of alumina and molybdenum. As a result of a test to see if there was a change, the data shown in the following table was obtained.

The test data in this table shows that when the alumina:molybdenum mixing ratio is in the range of 6:4 to 9:1, the withstand voltage between the heater and the cathode exhibits a particularly high value.

In addition, on the insulator surface of the improved heater of the above example,
It is even more effective to not apply a so-called blackening treatment, which involves applying a mixture of alumina and tungsten powder, as in the past.

<Effects> According to the present invention, it is sufficient to apply a mixture of alumina and molybdenum powder to the surface of the tungsten wire, then sinter it at high temperature, and then immerse it in acid to remove the molybdenum component with IW. , it can be easily implemented even for heaters with complicated shapes.

Further, according to the present invention, the insulator surface of the heater is uneven, and the contact area with the cathode when the heater is inserted into the sleeve of the cathode is significantly reduced compared to the conventional case. This greatly increased the insulation resistance between the cathode and the heater, reducing the leakage current between the heater and cathode depending on the operating conditions, resulting in a cathode ray tube of even higher quality than before.

Furthermore, according to the present invention, since the insulator surface of the heater is uneven, heat radiation is good, and therefore the time for heating the cathode to a predetermined temperature after lighting the beak is significantly shortened compared to conventional methods. Ta.

[Brief explanation of the drawing]

1 to 4 are diagrams showing examples of the shape of the heater according to the present invention. ■...Tungsten wire 2...Insulator patent applicant Mitsubishi Electric Co., Ltd. Japan Electronics Monthly Co., Ltd. Agent Patent attorney Nishi 1) New Figure 1 Figure 3 Figure 2 Figure 4-[4]

Claims (1)

[Claims] An indirect heating type electronic device characterized by coating the surface of a tungsten wire with a mixture of alumina and molybdenum powder, then firing it at high temperature, and melting the molybdenum powder with acid to make the surface porous and uneven. A method of manufacturing a pipe heater.