JPH04138637A - Activation method for cathode - Google Patents

Abstract

PURPOSE:To prevent carbonate from cracking and falling off by applying and increasing heater voltage continuously or stepwise. CONSTITUTION:Heater voltage is increased from 0 to specified voltage continuously at a gradient of 0.02 times the heater rated voltage/sec or less. A difference between thermal expansion amounts between carbonate and a heater 2 is suppressed. That is, increase of the voltage per each second is determined by the heater rated voltage, and the gradient of the increase is set to 0.02 times the rated heater voltage or less. The heater voltage can be applied to increase stepwise 10 steps. In this way, the carbonate can be prevented from cracking and falling off.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for activating an electron tube, and more particularly to a method for activating a directly heated cathode ray tube using a coiled cathode.

Conventionally, in the activation treatment of a cathode sprayed with carbonate, the rated voltage of the heater is instantaneously applied as preheating, and then a voltage 1.5 to 2 times the rated voltage of the heater is instantaneously applied to the heater. Ta.

However, in recent years cathode ray tubes (especially video cameras - type VT
As efforts have been made to reduce the power consumption of cathode ray tubes for viewfinders (R), cathodes with carbonate attached to coil-shaped heaters have appeared. Since this cathode is coil-shaped, its development length is much longer than conventional pellet-shaped cathodes. In the cathode activation process, a specified voltage is applied to the heater to thermally decompose the carbonate, but since heat is supplied from the heater at this time, the temperature of the carbonate is lower than that of the heater immediately after voltage application. is low, and the amount of thermal expansion of the heater is higher than that of carbonate.Since carbonate is in the form of particles, there is a difference in the amount of elongation of the heater, causing cracks, and in some cases, chipping. The problem was that it was not possible to obtain accurate electron radiation.

- In order to solve the above-mentioned problems, the present invention increases the voltage applied to the heater continuously or stepwise in the cathode activation process. In particular, heater rated voltage X O,0
Continuously increase the voltage at a gradient of 2/sec or less, or apply more than IO step and heater rated voltage X O,02/
It is characterized by upward application in a stepwise manner that satisfies a gradient of seconds or less.

That is, the heater voltage is characterized in that it is gradually increased to a specified applied voltage value desired for activation processing, and specifically, the heater voltage is increased to 0 of the heater rated voltage per second.
．． It is characterized by increasing at a rate of 0.02 times or less.

By the above method, when voltage is applied to the heater, the temperature of the heater rises slowly, so there is no difference between the temperature of the carbonate due to heat conduction from the heater and the temperature of the heater. There is almost no difference in the amount of expansion, so cracks in the carbonate can be eliminated, and uniform electron emission can be obtained.

Practical JL4 Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 shows a time schedule for continuous application of power to the heater, which is an embodiment of this invention. As shown in the figure, by increasing the heater voltage continuously from O to the specified voltage at a gradient of less than the heater rated voltage Prevent omissions. In other words, the voltage increase per second is determined by the heater rated voltage, and its slope is less than or equal to 0.02 times the rated heater voltage.

Note that this effect occurs when the heater voltage is increased as shown in Figure 2.
It can also be obtained by increasing the application voltage stepwise in O steps. In this case, the number of steps is preferably IO steps or more, and the average slope is 0.02 times or less of the rated heater voltage per second, as described above.

As explained above, the present invention has the effect of preventing cracking and chipping of carbonate by increasing the heater voltage continuously or stepwise during the activation process of the coil cathode.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram of a time schedule for applying a continuous increase in heater voltage according to the present invention, FIG. 2 is a characteristic diagram of a time schedule for applying a stepwise increase in heater voltage according to another embodiment of the present invention, and FIG. Figure 4 is a schematic perspective view of a coil-type cathode, Figure 5 is an enlarged sectional view before heater voltage is applied, and Figure 6 is a time schedule characteristic diagram of conventional heater voltage application. It is an enlarged sectional view of the cathode immediately after. 1... Lead, 2... Heater,
3... Carbonate, 4... Cathode. ] Figure Figure Figure Easy Figure Figure Figure

Claims (1)

[Scope of Claims] 1) A cathode characterized in that in the activation treatment process of a directly heated cathode with carbonate attached to the heater, the heater voltage is gradually increased continuously or stepwise under a predetermined gradient. activation processing method. 2) The cathode activation treatment method according to item 1, wherein the step-up gradient of the heater voltage is continuously increased to a predetermined value at 0.02 times or more the heater rated voltage per second. 3) The method for activating a cathode according to item 1, wherein the ramp-up gradient of the heater voltage is set to 0.02 times or less of the heater rated voltage per second, and is increased stepwise in 10 or more steps.