JPS6151723A - Directly heating impregnated cathode structure - Google Patents

Abstract

PURPOSE:To obtain a compact cathode structure having a quick-acting property by performing connection of supporting materials and heaters on the back of an insulation base body. CONSTITUTION:Cathodes 1 are fixed to cups 5 while fixing said cups 5 to the flat parts of heaters 2 for making directly heating impregnation type cathodes. A insulation base body 3 is provided with holes while setting up heaters 2 inside said holes while connecting to supporting materials 4 on the back of the insultion base body 3. Thereby, the hole space of the insulation base body 3 can be effectively used while making further the supporting materials on the front side to be unrequired thus becoming structurally simplified.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is applicable to electron tubes such as cathode ray tubes and image pickup tubes.
The present invention relates to a direct heat impregnated cathode structure with rapid action.

[Background of the invention]

Conventional cathodes for electron tubes are made of metals such as BaCO3, (Ba,
The main type of cathode is an oxide cathode covered with an electron emitting material such as Sr, Ca) CO3, etc. by coating or spraying.

This oxide cathode has a low temperature for emitting thermoelectrons (operating temperature) and a small heat capacity, so it has relatively fast behavior even in an indirectly heated type where the heating element (heater) and cathode are separate. Also, by making this a directly heated type, it became possible to create a cathode with even faster action. These oxide cathodes are currently used in multi-layer TV di-cathode ray tubes and the like. In order to obtain emission with even higher current density, the cathode temperature can be increased. However, in this case, the evaporation of the oxide on the base metal becomes intense and the life of the cathode becomes extremely short. Other disadvantages include shortening the lifespan of the heater, peeling off oxides when a large amount of emissions are extracted, and occasionally causing sparks with the anode.

Impregnated cathodes are seen as promising as cathodes that enable high current density emissions, and are being developed for use in electron tubes such as cathode ray tubes and image pickup tubes.

Impregnated cathodes are generally made by sintering high-melting point metal powder such as tungsten (W) to create a porous fully curved pellet base.
It has a structure in which barium aluminate is infiltrated into this hole as an @-radiating material by heating and melting it at about 170o~1800'C, and the operating temperature is generally 10oO~120oC.
It is selected in the range of about 0°C, and the emission current density at that time is about 10 A/- or more. Further, the life of an impregnated cathode is approximately proportional to the thickness of the cathode. Because the operating temperature of the impregnated cathode is high, it is generally combined with a sleeve made of a high-melting point metal such as Ta or MO, and the core wire (W wire) is It is used as an indirectly heated cathode that is heated with a heater and is coated with a coating layer such as alumina.

Furthermore, in order to prevent the electron emitting material from evaporating toward the heater side and damaging the characteristics of the heater, a structure must be provided with a backing plate.In such an indirectly heated cathode, the capacitance of the porous W substrate is It is large, has a high operating temperature of over 1000℃, and has a backing plate, etc., so the time required to reach the operating temperature after turning on the power is several times longer than with conventional oxides. It takes. In addition, in this method of using radiant heat, the heater temperature must be several hundred degrees higher than the extreme temperature of 118 degrees, for example, 1000 degrees Celsius.
When used in To make it durable, the heater wire must be made thicker, and if it is made thicker, the heater power will further increase.Therefore, it has the disadvantage that it can reach the operating temperature in a short time, and the heater wire must be made thicker. In order to reduce the difference, as shown in Figure 1, the cathode 1 is fixed to a heater (heating element) 2, and a heating method using heat conduction from a reheater that conducts electricity inside the cathode, that is, an indirect heating method, is used. Direct heating method was selected, and absolute substrate 3 such as forsterite
It is considered that the cathode structure is bonded to a stem 6 having a support material 4 implanted in the cathode structure. In order to prevent wasteful evaporation of the electron emitting material from the outside of the cathode 1, the cathode 1 is often fixed in a cup-shaped part 5.

The support member 4 supports the cathode 1 fixed to the heater (heating element) 2, and also serves as a terminal for supplying power to the heater 2.

Usually, the support material 4 is provided penetrating the insulating base 3 and supports the cathode 1 with the heater 2 on the front side thereof, and a power supply source is connected to the support material 4 on the back side.

As shown in FIG. 1, the heater 2 has a gate-shaped rotating structure having a flat part for fixing the cathode 1, legs bent at a curved angle, and arms extending in opposite directions from the legs. , Figure 2 (
a) As shown in (b), use it as a ribbon,
Furthermore, a heater 2 having a structure consisting of a flat part for fixing the cathode 1 and leg parts bent at a curved angle is also used. However, the heater 2 shown in FIG. 1 is advantageous in that the thermal expansion during heating can be escaped through rotation, and the length of the heater 2 can be increased. When fixing the cathode 1 and the heater 2, sometimes a method is used in which two heaters are glued to the side of the cathode 16. In the direct heating method, the cathode 1 is fixed to the heater 2, and the heater 2 is energized to generate Joule heat. It generates heat and is heated by thermal conduction. As a heater material, it has high high temperature resistance and high temperature strength.
Moreover, those with low vapor pressure are selected. Since high-temperature resistance is a heating method that utilizes Joule heat, it is a factor that affects the heating current and, in turn, the power consumption. The need for high strength at high temperatures causes problems such as unstable images during use due to changes in the distance between the anode and the cathode if the cathode is not stably fixed. Furthermore, if the vapor pressure is too high, the heater components may evaporate during use, which may cause the heater characteristics to change over time, which is disadvantageous, and the evaporated substances may contaminate other electrodes.

An alloy of Ni and W is used as the heater material for the directly heated oxide cathode, and its resistance at operating temperatures of 700 to 800°C is as high as 110 to 120 μΩ. It can be almost the same as, or even smaller. On the other hand, since the operating temperature is high, W and Re are used as heater materials for impregnated anodes.

A high melting point metal with high high temperature resistance such as Mo or Ta is used. Among these, the element showing the highest specific resistance is Re, which has a resistivity of 100
It is 77μΩ'C11l at 0°C. Since Ra is expensive, it is not used alone except for special purposes. Generally used in alloys, usually alloys with W. However, there is no alloy that outperforms pure Re within the mutual solid solution range. In this way, the specific resistance of the heater material for direct heat impregnated shadow electrodes is about 2/3 lower than that for oxides. If the heater is shortened, the heating current becomes extremely large1, and heat escape from the lead wire becomes large, which is inefficient. When an impregnated cathode is used, the length of the heater affects not only the current applied, but also the temperature difference between the cathode and the heater and the power consumption. The most efficient heater shape for impregnated cathodes is one in which the width of the heater is about 30 to 40% of the diameter of the cathode and the length is 9 to 1.
It was 2 mm. Comparing this to a heater used for an oxide cathode, apart from the width of the heater, the length of the heater has a structure in which the distance between the supporting members 4 of the insulating base 3 is increased, or the distance between the insulating base 3 and the anode section is increased. There must be. As a result, it is necessary to increase the size of the insulating base 3 or to lengthen the electron gun section of the electron tube. Recently, there has been a trend to make the cathode structure as small as possible. In an impregnated cathode structure, when the supporting material 4 on the front side of the insulating substrate 3 is used to fix the cathode structure using a heater, there is a problem that the cathode structure becomes large.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned difficulties and to provide a compact directly heated impregnated cathode structure that uses an efficient heating method and is quick-acting.

[Summary of the invention]

The present invention provides a heater 2 and a support material 4 implanted in an insulating base 3.
The connections are made on the back side of the insulating base 3, thereby making effective use of the space occupied by the insulating base. By using a system 6 in which a hole is provided in the insulating base 3, installing a heater in this hole, and connecting it to the support material 4 on the back side of the insulating base 3, the hole space in the insulating base 3 can be used effectively. This eliminates the need for a supporting material on the front side, making the structure simple6.Furthermore, by using this hole to provide a radiation plate made of a thin metal plate, heat escape from the heater is prevented.

It can be said that the supplied power can be used effectively, leading to lower power consumption. As explained above, a direct heat impregnation type 113-electrode structure can be produced without increasing the size of the cathode plant, and the present invention has the characteristics that it is possible to reduce the power consumption.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 3 is a perspective view showing each component used in manufacturing the direct heat impregnation type cathode groove body of the present invention.

4 and 5 are diagrams showing a direct heat impregnation type cathode structure according to the present invention. 4(a) and 5(a) are plan views seen from the front side of the insulating substrate 3, that is, the electron emitting surface side of the cathode 1, and FIG. 4(b) and FIG. 5(b) are plan views of the insulating substrate 3. 4(c) and 5(c) are cross-sectional views taken along the longitudinal center line of the insulating base 3. FIG. Further, in the figures, the same reference numerals as those mentioned above indicate the same or equivalent parts.

Cathode 1 with porous W body impregnated with Ba aluminate compound (diameter 1.45 mm + thickness 0.5 mm),
Cup 5 made of Ta with a thickness of 25 μm (inner diameter 1.45 m
m, outer diameter 1.5 mm, height 0.45 mm), thickness 3
A flat part 21 is formed by punching and molding a 0 μm W-25wt% Re plate, and a leg part 2251 is bent from the flat part.
A heater 2 having arm portions 23 extending in opposite directions from the leg portions was prepared. The length of the center of the flat part 21 of the heater 2 is 1.5
ml11, the length of the leg part 22 is 2.8 mm, the length of the arm part 23 is 1.75 mm (the length after welding to the support material 4), and the effective current-carrying length (the center line length of the heater 2) is 10.7 mm. It is.

A cathode 1 is fixed to a cup 5, and a tube 5 of the cathode 1 is fixed to a flat part 21 of a heater 2 to form a direct heat impregnation type cathode. cup 5
The fixing of the heater 2 to the cathode 1 and cup 5 was performed by laser welding. Apart from this, as shown in Fig. 3(d), there is an absolute base 3 made of forsterite (width 9
m+n, length 19mm, thickness 2mm+), there are three through holes with a diameter of 2nua spaced at equal intervals, and Ni wires of 0.75mmφ are placed on the back side of the insulating base 3 between the holes, and the supporting material 4 is placed at intervals of 3.5mm. A stem in which the plant was planted was prepared. We also prepared a stem with a radiation plate 8 in which a Ta pipe with a thickness of 25 μm was fixed by pressure bonding inside the hole (see Fig. 3).
d)).

A heater 2 was attached to the supporting material 4 implanted in the insulating substrate 3, and an electrical heating test was conducted in a vacuum container. As a result, the current (Ir), voltage (Er) and power (P) necessary to obtain a cathode temperature of 1000''C are I,=2.OA,
E, = 0.67V, P = 1.34W, and the radiation plate 8
If the stem shown in Fig. 3(e) is used, If=
By using the stem provided with the radiant plate 8 at 1.9A, Ef=0.63V, and P=1.20W, heating was possible with about 10% less power. In addition, when the same lI 3 pole 1 is used for heating by indirect heating method, the consumption power P is 2,94W (Er
= 5, 5 V, Ir = 0, 535 A
) By using the direct heating method, the power consumption is less than half, and it can be said to be an effective heating method. Furthermore, by using the direct heating method, the operating state is reached in about 4 seconds after the power is turned on, which is about 1710 seconds for the indirect heating method. This rise time is as fast as that of an oxide cathode. By using a stem with a hole in the insulating base 3, a part of the heater 2 is included in this space.

It can be seen that even in the case of a directly heated impregnated cathode, which requires a longer heater 2, the cathode structure does not become larger. Therefore, the present invention can be applied to cathode ray tubes and image pickup tubes without changing the design of conventional electron guns. When there is only one cathode 1, it is preferable to use a circular insulating base 3.

〔Effect of the invention〕

As described above in detail, by using the direct heat impregnation type cathode structure of the present invention.

Compared to using an indirectly heated cathode structure, the rise time is about 1/10, the power consumption is less than half, and a stem with a hole in the insulating base 3 is used, and a part of the heater 2 is contained in this space. As a result, even in the case of a directly heated impregnated cathode that requires a longer heater 2, there is no need to increase the size of the cathode structure, making it more compact, and without changing the design of the electron gun that has been used so far. , it can be applied directly to cathode ray tubes and image pickup tubes. Furthermore, by using the radiation plate 8, the power consumption can be further reduced.

[Brief explanation of drawings]

Figure 1 is a perspective view showing a part of a conventional direct heat impregnation type 1ta electrode structure, Figures 2 (a) and (b) are perspective views of a direct heat impregnation type cathode, and Figures 3 (a) and ( b) , (c) , (
d), (e) are perspective views of parts used in the production of the direct heat impregnation type cathode assembly of the present invention, and Figures 4 (a), (b), (
c) and Figures 5(a) and (b). (C) is a diagram showing a direct heat impregnation type cathode structure produced according to the present invention. 1... Impregnated cathode, 2... Direct heating heater (heating element)
, 21... Flat part, 22... Leg part, 23... Arm part, 3... Insulating base, 4... Support material, 5... Metal cup, 6... Conventional stem , 8...Radiation plate. Figure χ1 is shown in Figure 2.

Claims (1)

[Claims] 1. In a cathode structure composed of an insulating base, a support material implanted in the insulating base, and a directly heated impregnated cathode consisting of an impregnated cathode and a heating element, A direct heat impregnated cathode assembly characterized in that the support material and the heating element are connected on the back side of the insulating base. 2. The direct heat impregnation type cathode assembly according to claim 1, wherein the insulating substrate is provided with a penetrating hole, and is assembled so that a part of the heating element is contained within the hole. 3. The direct heat impregnation type cathode structure according to claim 2, characterized in that a radiation plate made of a thin metal plate is provided in the hole through which the insulating substrate passes.