JPH03105826A - Impregnated type cathode composition - Google Patents

Abstract

PURPOSE:To increase the heat efficiency of a heater, to reduce the temperature of the heater, and to prevent a thermal deformation of the heater and the deterioration of insulation between the heater and the cathode, by forming a blackened layer of TaOx (x=1-2) at the inner surface of a cathode sleeve. CONSTITUTION:A cathode sleeve 5 housing a built-in heater 11 and fixing an emitter impregnated type cathode disk 1 at one end, plural straps 8 whose one ends are installed to the lower end of the cathode sleeve 5, and a cylindrical holder 9 provided concentrically placing a specific interval to the outer side of the cathode sleeve 5 to whose upper end the other ends of the straps 8 are installed, are provided, and a blackened layer 4 of TaOx (x=1-2) is formed by an oxidization to the inner surface of the cathode sleeve 5which is made of Ta. As a result, the heat absorption efficiency of the heater is increased and the heater temperature can be decreased, and the poor insulation of the heater 11 can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a high-performance impregnated cathode structure used in color picture tubes and the like, and particularly to improvements in the cathode sleeve thereof.

(Prior Art) In recent years, there has been a demand for the development of color picture tubes with increased scanning lines and improved resolution, picture tubes compatible with ultra-high frequencies, and the like. Furthermore, it is desired to improve the brightness of projection tubes and the like. To meet these demands, it is necessary to significantly increase the density of electrons emitted from the cathode.

However, impregnated cathodes can obtain larger current densities than oxide cathodes, and have been used in electron tubes such as image pickup tubes, traveling wave tubes, and klystrons. was.

Such an impregnated cathode structure has conventionally been constructed as follows.

That is, the heater is arranged inside the cathode sleeve made of Ta,
A cup having a cathode disk impregnated with an emitter is fitted into one end of the cathode sleeve. Furthermore, the cathode sleeve has a holder coaxially arranged on the outside of the cathode sleeve.
It is fixed with three straps.

However, the disadvantage of the impregnated cathode is that the operating temperature is approximately 200°C higher than that of the oxide cathode, and as a result, the heater temperature is also high, rising to approximately 1300°C during rated operation, resulting in thermal deformation of the heater and The breakdown voltage between the cathodes had deteriorated.

(Problems to be Solved by the Invention) In the conventional example, the temperature of the heater for operating the impregnated cathode was high, which caused problems such as thermal deformation of the heater and deterioration of the pressure resistance between the heater and the cathode. The present invention aims to increase the thermal efficiency of the heater and lower the temperature of the heater.

[Structure of the Invention] (Means for Solving the Problem) The present invention comprises a cathode sleeve having a built-in heater and an emitter-impregnated cathode disk fixed to one end, and one end attached to the lower end of the cathode sleeve. an impregnated cathode assembly comprising: a plurality of straps; and a cylindrical holder having the other end of each strap attached to an upper end and coaxially disposed outside the cathode sleeve at a predetermined interval; '17aOx (x=1・~2) on the inner surface of the cathode sleeve
This is an impregnated cathode structure characterized by the formation of a blackened layer.

(Function) The inner surface of the Ta cathode sleeve is oxidized to form TaOx (
By forming the blackened layers x-1 to x-2), the heat absorption rate of the heater can be increased, and as a result, the heater temperature can be reduced.

Furthermore, since the sleeve is made of Ta, it has good weldability and is excellent in workability.

(Example) Hereinafter, an example of the impregnated cathode structure of the present invention will be described in detail with reference to the drawings.

First, a method for blackening the Ta sleeve will be described.

The first method is to prepare a Ta sleeve (11) with an outer diameter of 1.8 mm, a wall thickness of 25 μm, and a length of 1 m, as shown in Figure 2 (al).
The outside of this Ta sleeve is placed in an A r (12) atmosphere, and the inside of the Ta sleeve is placed in an air (13) 0. In
The sample was fed at a flow rate of /min, and in this state it was heated at 610°C±10°C for 5 minutes using a surrounding heater (14).

Note that the temperature at which air is introduced is preferably 800 to 830°C.

Further, the holding time is preferably 3 to 10 minutes.

As a result, a blackened ffl (15) is formed inside the Ta sleeve as shown in FIG. 2(b).

Next, as a second method, as shown in Fig. 3(a), the outer diameter is 1.6 111%, the wall thickness is 25 μm, the length is 10
0 am Ta sleeve (1l) with inner diameter of 1.85 1
111, inserted into a Kovar tube (t8) with a wall thickness of 30 μm and a length of 12 km, and heated in the air at EIIO°C ± lO°C for 5 minutes, then remove the Kovar tube (1B>) and take out the Ta sleeve.

As a result, as shown in FIG. 3(b), blackening i (15) is formed on the inner surface of the Ta sleeve and on the outer surface of the sleeve at positions approximately 10 mm from both ends of the sleeve.

The thickness of this blackened layer is about 2 μm, and according to X-ray diffraction, it is an oxide of TaOx (x-1-2). The thickness is preferably in the range of 0.5 to 5 μm, preferably 1 to 3 μm.

After cutting the inner surface oxidized sleeve thus formed into a length of 4.5 nm using a laser (after removing the outer surface blackened layer in the second method), it was heated at 1300°C under vacuum for 1 hour. Heat treatment is performed to remove gas, and the inner surface blackened sleeve of the present invention is completed. This vacuum heat treatment time was 11
The temperature may be 00 to 1400°C, preferably 1200 to 1300°C. As a result, harmful gases contained in the blackened layer are released, and a stable blackened layer can be obtained.

An embodiment of an impregnated cathode assembly using this sleeve with a blackened inner surface will be described with reference to FIG.

That is, B a O sC a is added to porous tungsten obtained by sintering tungsten powder with a particle size of 3 to 10 μm.
A cathode substrate (1) impregnated with an electron-emitting substance consisting of O-A jl2 0a is placed in a cup (2) made of T'a.
After welding through a brazing material (3) such as u-MO, a Ta sleeve (5) has a blackened layer (4) due to internal oxidation.
After being inserted into the top of the holder, it is fixed by welding at the welding point (8). The bottom outer periphery of this cathode sleeve (5) has a welding point (7
> welded with a thickness of 0.05+u. , width 0.
A strap (8) made of a 7o+m Ta ribbon is provided, and the other end of the strap (8) is manufactured by press-forming a Fe-Ni-Co alloy plate with a wall thickness of 0.125 mm. There is a welding point (
10). Furthermore, a heater (11) is built inside the sleeve made of Ta.

FIG. 4 shows the relationship between the heater temperature and cathode temperature of the impregnated cathode structure according to the present invention and the conventional example. That is, according to the present invention, it is clear that the heater temperature is reduced by about 120° C. at the same cathode temperature. Additionally, the cathode temperature was forced (
For the rated 960℃b, the number of pressure failures between the heater and sleeve in the life test was 15 in a 1000-hour lifespan (n-each eop), as shown in Figure 5. )e In contrast, no defects were observed in the present invention. In this way, the present invention, which forms a blackened layer by oxidation on the inner surface, can reduce the heater temperature by about 120 degrees Celsius, and as a result, it is possible to prevent the occurrence of poor pressure resistance between the heater and cathode and defective thermal deformation of the heater. It became.

Furthermore, the gas release rate of the sleeve due to oxidation of the inner surface of the Ta sleeve was 3 x 10' Torr cc/seesg for the product of the present invention after 80 minutes at 1100°C, while that for the conventional Ta sleeve was 2.6 x 10-5 Torr
cc/seesg is at a level with no problems. Also,
As shown in FIG. 6, the change in heater temperature during the life test is smaller than in the conventional example, and good results can be obtained.

[Effects of the Invention] According to the present invention, the heater temperature can be significantly lowered, and it is possible to eliminate breakdown voltage failures of the heater.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the impregnated cathode assembly of the present invention, FIGS. 2 and 3 are explanatory diagrams showing the manufacturing process of the inner surface blackened Ta sleeve of the present invention, and FIG. 4 is a cathode FIG. 5 is a characteristic diagram showing the relationship between temperature and heater temperature, FIG. 5 is a characteristic diagram showing the number of defects occurring during the life test, and FIG. 6 is a characteristic diagram showing the heater current change rate during the life test. 1... Cathode disk 4, l5... Blackening layer 5, 11... Cathode sleeve

Claims (1)

[Claims] A cathode sleeve with a built-in heater and an emitter-impregnated cathode disk fixed to one end, a plurality of straps each having one end attached to the lower end of the cathode sleeve, and the other end of each strap. is attached to the upper end and a cylindrical holder is disposed coaxially at a predetermined interval outside the cathode sleeve. 2) An impregnated cathode structure characterized by forming a blackened layer.