JPH11191357A - Impregnated type cathode-ray structure, manufacture of impregnated type cathode-ray structure, electron gun structure and electron tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exhibit sufficient ion impact resistance and satisfactory electron emitting property and low-temperature operability even under a high voltage and high frequency condition by providing a composite layer consisting of a layer containing a high melting point metal and a layer containing scandium on the electron emitting surface-side surface of a porous cathode base impregnated with an electron emitting material. SOLUTION: A porous tungsten base 21 consisting of tungsten particle is manufactured by sintering, and an electron emitting material 22 consisting of a mixture of BaO, CaO and Al2 O3 is fused and impregnated in the pore part of the base 21 by heating it under hydro gen atmosphere. An undefined ratio tungsten oxide layer 23 formed by sputtering with oxygen-containing guseous argon by using tungsten as target material and an undefined ratio hydrogen scandium layer 24 formed by sputtering with oxygen-containing gaseous argon by use of metal scandium as target material are alternately formed on the surface of the base 21 so that the thickness per layer is 50 nm or less to constitute a composite layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a color picture tube,
The present invention relates to an electron tube such as a klystron and a traveling wave tube, an electron gun structure used for the tube, and an impregnated cathode structure thereof.

[0002]

2. Description of the Related Art In recent years, there has been a demand for the development of a color picture tube with an increased number of scanning lines and improved resolution, and a picture tube for ultra-high frequency. Further, it is desired that the luminance of the projection tube be improved. In order to meet these demands, it is necessary to greatly increase the emission current density from the cathode used compared to the related art.

[0003] An impregnated cathode, which is one of such cathodes, can obtain a higher radiation current density than an oxide cathode.
Heretofore, it has been used for electron tubes such as image pickup tubes, traveling wave tubes, and klystrons. Conventionally, the use of the impregnated cathode has been limited to only special applications such as HD-TV tubes and ED-TV tubes in the field of color picture tubes. However, in recent years, there has been an increasing demand for the use of impregnated cathodes for large-sized CRTs and the like, and their use has been rapidly expanding.

[0004] In the impregnated cathode structure, for example, porous tungsten having a porosity of 15 to 20% is used as the cathode substrate, and for example, barium oxide (BaO), calcium oxide (CaO) is formed in the pores of the cathode structure. And an electron-emitting substance such as aluminum oxide (Al ₂ O ₃ ). For example, in a metal coat type impregnated cathode structure, a thin film layer of iridium (Ir) or the like is further provided on the electron emission surface of the cathode substrate by a thin film forming means such as a sputtering method. When this cathode assembly is heated by a heater in the electron tube, for example, barium (Ba) or oxygen (O) impregnated in the cathode assembly diffuses, and an electric double layer is formed on the electron emission surface of the cathode assembly surface. As a result, high-density current emission becomes possible.

As an impregnated cathode structure for an electron tube, a scandium-based impregnated cathode structure has recently been receiving attention.

The cathode structure for an electron tube has been conventionally formed in a compact structure for the purpose of power saving. For this reason, the cathode substrate is necessarily limited in its thickness and diameter,
The electron emitting material cannot be sufficiently impregnated.

Generally, the life characteristics of an impregnated cathode structure are as follows:
When Ba is consumed by evaporation, which is governed by the amount of evaporation of Ba, which is a main component of the electron-emitting substance, the coverage of the monoatomic layer of Ba on the cathode substrate decreases, and the required long life characteristics cannot be obtained. It is a problem. For these reasons, there is a strong demand for the development of an impregnated cathode assembly capable of operating at lower temperatures and higher current densities. As such a cathode, an impregnated cathode in which scandium oxide (Sc ₂ O ₃ ) is dispersed, or scandium (S
c) Development of a scandium-based impregnated cathode coated with a compound has been attempted.

In a scandium-based impregnated cathode structure, for example, several tens of amperes / cm ² at an operating temperature of 900 to 1000 ° C.
It has been reported that a radiation current density of

In an example in which a scandium-based impregnated cathode assembly is applied to a diode, the pulse emission current evaluation is about 10 times that of a conventional metal-coated impregnated cathode assembly under the conditions of a pulse width of 5 μs and a frequency of 50 Hz. It is reported that a radiation current density can be obtained, and it is expected that the conventional radiation current will be greatly improved. However, the situation is different for high-frequency pulses. In this pulse evaluation using a diode, if the frequency is 15.75 kHz generally used in a picture tube or the like, only a radiation current equivalent to that of a conventional metal-coated type can be obtained. In other words, in the scandium-based impregnated cathode assembly, under low-duty operating conditions, sufficient emission can be obtained even when the cathode temperature is relatively low, but when operating in a high-duty region, this low-temperature operation effect decreases. However, there is no remarkable difference in characteristics between the metal-coated impregnated cathode structure and the scandium-based impregnated cathode structure.

The cause is considered as follows. In the low-duty operation, the electric double layer on the electron emission surface of the cathode structure is maintained because the supply of Ba, O, and Sc diffused from the pores of the porous substrate is sufficient. In operation, the electric double layer is destroyed by ion bombardment. Therefore, the low-temperature operability of the scandium-based cathode, which was superior in the low-duty operation region, is no longer different from that of the metal-coated type in the high-duty operation region. It is thought that it is caused by not being able to obtain. Surface analysis of a scandium-based impregnated cathode by Auger electron spectroscopy revealed that when subjected to ion bombardment, Sc on the surface disappeared and it took a considerable amount of time to recover to a good Sc concentration of electron emission. .

In order to make a scandium-based impregnated cathode exhibit sufficient ion bombardment resistance under high voltage and high frequency operating conditions, it has been attempted to produce a surface which shows a fast recovery after ion bombardment. Have been.

[0012] For example, (Publication of Japanese Patent Application Laid-Open No. 63-9192)
In 4), Sc (W), tungsten dioxide (WO ₂ ), and scandium oxide (Sc ₂ O ₃ ) are simultaneously sputtered on the electron emission side surface of the cathode assembly to obtain Sc.
_A composite oxide thin film such as ₂ W ₃ O ₁₂ or Sc ₆ WO ₁₂ is formed. These composite oxides are fr
It is reported that ee Sc can be liberated effectively, and that the high diffusion rate of this free Sc can improve the ion impact resistance. However, even with these improvements, they have not been put to practical use.

[0013]

As described above, with the conventional scandium-based impregnated cathode, sufficient ion impact resistance cannot be obtained under high voltage and high frequency conditions. When the scandium-based impregnated cathode is subjected to ion bombardment at a high frequency operation, the recovery of the disappeared Sc is slow, so that there is a disadvantage that the low-temperature operability is reduced, which is insufficient for practical use.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art.
It has sufficient ion impact resistance even under high frequency conditions, has good electron emission characteristics, and also has good low temperature operability.
An object of the present invention is to provide a high-performance, long-life impregnated cathode assembly.

A second object of the present invention is to provide a high-performance device having sufficient ion impact resistance under high voltage and high frequency conditions, good electron emission characteristics, and good low-temperature operation. Another object of the present invention is to provide a method for producing a long-life impregnated cathode assembly.

Further, a third object of the present invention is to provide a high voltage,
It has sufficient ion impact resistance even under high frequency conditions, has good electron emission characteristics, and also has good low temperature operability.
An object of the present invention is to provide a high-performance, long-life electron gun assembly using a high-performance, long-life impregnated cathode assembly.

Further, a fourth object of the present invention is to have a sufficient ion impact resistance even under high voltage and high frequency conditions,
An object of the present invention is to provide a high-performance, long-life electron tube using a high-performance, long-life impregnated cathode assembly having good electron emission characteristics and good low-temperature operability.

[0018]

The present invention firstly provides a cathode substrate impregnated with an electron emitting material, a layer containing a high melting point metal and a scandium formed on the electron emitting surface side surface of the cathode substrate. And a composite layer comprising:

The composite layer preferably has a thickness of 50 nm or less.

The layer containing the high melting point metal is preferably made of one of tungsten and tungsten oxide.

The layer containing scandium preferably comprises at least one selected from the group consisting of scandium, scandium oxide, and scandium hydride.

The present invention provides, secondly, an impregnated cathode assembly having a composite layer composed of a layer containing a high melting point metal and a layer containing scandium on the electron emission surface side surface of a cathode substrate impregnated with an electron emission substance. In the manufacturing method, there is provided a method for manufacturing an impregnated cathode assembly, wherein the layer containing the refractory metal and the layer containing scandium are alternately formed in different atmospheres.

The present invention provides, in a third aspect, a composite layer of a cathode substrate impregnated with an electron-emitting substance, a layer containing a high-melting-point metal and a layer containing scandium formed on the electron-emitting surface of the cathode substrate. An electron gun structure using an impregnated cathode structure having the following.

A fourth aspect of the present invention is a composite layer comprising a cathode substrate impregnated with an electron-emitting substance, a layer containing a high-melting-point metal and a layer containing scandium formed on the electron-emitting surface of the cathode substrate. An electron tube using an electron gun assembly provided with an impregnated cathode assembly having the following.

The layer containing the high melting point metal is preferably formed in an atmosphere containing oxygen, and the layer containing scandium is preferably formed in an atmosphere containing hydrogen.

The layer containing the refractory metal and the layer containing scandium are each preferably formed by a sputtering method.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention have proposed a scandium-based impregnated cathode having sufficient resistance to ion bombardment under high voltage and high frequency operating conditions. The oxygen, scandium, and barium that make up the overlay attempted to create an improved surface such that the electrical double layer showed very fast recovery after ion bombardment.

In order to obtain an improved electron emission surface, in the present invention, a composite layer of a layer containing a high melting point metal and a layer containing scandium formed on the surface of the cathode substrate on the electron emission surface side is formed.

By obtaining such an electron emitting surface,
According to the present invention, it is possible to obtain an impregnated cathode having an electron emission surface in which scandium atoms having a very high diffusion rate and having a high diffusion rate are uniformly distributed. Therefore, the scandium recovery time after ion bombardment is greatly reduced, and good electron emission characteristics can be obtained. In addition, since low-temperature operation is possible, the amount of thermal evaporation of barium can be reduced even if the size of the cathode substrate is compact, and the life characteristics resulting from insufficient absolute impregnation amount, which has been a problem with conventional power-saving impregnated cathodes, have been improved. can do.

The composite layer used in the impregnated cathode structure of the present invention can be obtained, for example, by alternately forming a layer containing a refractory metal and a layer containing scandium on a cathode substrate in different atmospheres. .

For example, when a thin film layer of a scandium compound or a tungsten compound is formed on the cathode surface by a sputtering method, a rare gas element and oxygen,
Alternatively, by using a mixed gas of a rare gas element and hydrogen, a thin film having a composition different from that of the target material can be formed. For example, by using tungsten (W) as a target material and performing sputtering using a mixed gas of a rare gas element and oxygen, tungsten oxide (WO
_x ) Forming a film or forming a non-stoichiometric scandium hydride (ScH _x ) film by sputtering using a mixed gas of a rare gas element and hydrogen with scandium (Sc) as a target material. Can be.

Scandium hydride (ScH _x ) is a relatively stable compound, but is reduced by reacting with strong oxides. Therefore, ScH ₂ is suitable as a supply source of the Sc alone. Tungsten oxide (WO _x ) is suitable as a reducing agent for scandium hydride.

The composition ratio of each compound can be controlled by changing the ratio of oxygen or hydrogen in a gas atmosphere at the time of forming a thin film. That is, if _x of ScH _x is too small, there is a tendency that unnecessary oxidation is caused by an impregnating material or the like in a manufacturing process of the electron tube, while if it is too large, reduction by tungsten oxide tends to be weak. WO _x
If x in the formula is too small, the reduction of scandium hydride tends to be insufficient, and if x is too large, the scandium tends to be oxidized.

Thus, in the present invention, two different substances, a scandium compound and a tungsten compound, are
When film formation is performed in different gas atmospheres, a simultaneous film formation method is impossible. Therefore, these compound layers have a sandwich-like multilayer structure. Here, when the film thickness per layer increases, the reaction between the scandium compound and the tungsten compound becomes insufficient. Therefore, in order to perform a sufficient reaction and secure a sufficient life of the cathode, it is preferable that these compound layers are used by alternately laminating thin layers.

According to the experiment, metal scandium (Sc) was used.
Instead of forming a hydrogen atmosphere, even by forming a hydrogenated scandium (ScH ₂₎ hydrogen or an oxygen atmosphere, even if the scandium oxide (Sc ₂ O ₃₎ was formed in the hydrogenation atmosphere, substantially the same Is obtained. Even if tungsten dioxide (tungsten oxide: WO ₂ ) is used as tungsten oxide, tungsten trioxide (tungsten oxide: W 2
Almost the same results can be obtained by using metal tungsten (W) instead of O ₃ ).

The thickness of the composite layer composed of a layer composed of tungsten or a tungsten compound and a layer composed of scandium or a scandium compound is 50 nm per layer.
Or less, more preferably 20 nm or less per layer. When the thickness of the composite layer is 20 nm or less per layer, each of the layer made of tungsten or a tungsten compound and the layer made of scandium or a scandium compound has an island structure, and the scandium or scandium compound in the composite layer has: The reactivity of tungsten or a tungsten compound sharply increases. (The thickness of the film having the island-like structure is the thickness that this film would have if it were formed with a uniform thickness, for example, (weight change of the cathode substrate before and after film formation) /
It is defined by {(specific gravity of membrane substance) × (surface area of cathode substrate)}. On the other hand, the thickness of the composite layer is 50 nm per layer.
When the ratio exceeds 2, the reaction between the scandium compound and the tungsten compound becomes insufficient, so that the electron emission characteristics tend to decrease.

For example, in the case of sputtering, the volume ratio of oxygen is preferably 20% or less, more preferably 10% or less in an oxidizing atmosphere, and the volume ratio of hydrogen is 5% or less in a reducing atmosphere. Preferably, it is more preferably at most 3%. When the volume ratio of oxygen is 20% or the volume ratio of hydrogen is 5% or more, the film forming rate tends to be remarkably reduced and the film forming property tends to be deteriorated.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Example 1 FIG. 1 is a schematic diagram showing a first example of an impregnated cathode structure according to the present invention. This cathode structure is a cathode structure for a cathode ray tube.

As shown in the figure, the impregnated cathode assembly comprises a cathode sleeve 11 and a cup-shaped fixing member fixed inside the one end of the cathode sleeve 11 so as to be substantially flush with the opening edge of the one end. 12 and the cup-shaped fixing member 1
2, so as to surround the porous cathode substrate 13 impregnated with the electron emitting substance and the cathode sleeve 11,
A cylindrical holder 14 coaxially disposed inside the cylindrical holder 14, one end of the cylindrical holder 14 is attached to the outer surface of the other end of the cathode sleeve 11, and the other end is formed on an inner protrusion formed at one end of the cylindrical holder 14. A plurality of strip-shaped straps 15 which are attached and coaxially support the cathode sleeve 11 inside the cylindrical holder 14, and are attached to an inner protrusion formed at one end of the cylindrical holder 14 by a support piece 16. The cathode sleeve 11 and a plurality of straps 15 and a shielding tube 17 disposed between the cathode sleeve 11 and the plurality of straps 15, and is heated by a heater 18 inserted inside the cathode sleeve 11. The material of the porous cathode substrate 13 is W. For example, BaO: Ca
It is impregnated with an electron emitting material consisting of a mixture of O: Al ₂ O ₃ = 4: 1: 1 molar ratio.

The cathode assembly is connected to an insulating support 20 together with a plurality of electrodes arranged at predetermined intervals on the cathode assembly via a strap 19 attached to the outer surface of the cylindrical holder 14, for example. Fixed. FIG. 1 shows only G1 of the first grid among the plurality of electrodes.

FIG. 2 is a model diagram showing the structure of the porous cathode substrate 13 of the cathode assembly. The porous cathode substrate 13 is
As shown in the figure, a tungsten oxide (WO _2-x ) thin film layer, which is a non-stoichiometric compound, and a scandium hydride (ScH _2-x ) thin film layer, which is a non-stoichiometric compound, are alternately stacked. The porous cathode substrate 13 having such a structure was formed as described below.

First, a porous tungsten substrate 21 made of tungsten particles having a particle size of 3 μm and having a porosity of about 17%
Was produced by sintering. In the pores of the porous tungsten substrate 21, BaO: CaO: Al ₂ O ₃ = 4:
The electron emitting substance 22 consisting of a mixture in a molar ratio of 1: 1 is converted to H
Melting and impregnation were performed by heating at 1700 ° C. for about 10 minutes in _two atmospheres.

The nonstoichiometric tungsten oxide layer 23 is formed by sputtering to a thickness of 8 nm using tungsten (W) as a target material and argon gas in which 1% by volume of oxygen (O ₂ ) is mixed as a sputtering gas. The non-stoichiometric scandium hydride layer 24 is formed to a thickness of 2 nm by using a scandium metal (Sc) as a target material and using a 1% by volume hydrogen (H ₂ ) mixed argon gas as a sputtering gas. The film was formed by sputtering.

The formation of the nonstoichiometric tungsten oxide layer 23 and the nonstoichiometric scandium oxide layer 24 was repeated 10 times each, and a total of 20 layers were stacked on the electron emitting surface side of the porous tungsten substrate.

A test electron tube in which the anode was provided on the cathode structure thus manufactured was manufactured, and the operating temperature of the cathode was increased by 1350 K to 50 K higher than the normal operating temperature (1300 K).
A forced life test was performed to operate the device. As a result,
FIG. 3 is a graph showing the relationship between the elapsed time and the current density.

In the figure, the current density on the vertical axis indicates that 150 V
Is the emission current from the cathode obtained when the pulse is applied. Numeral 31 indicates a measurement result of a conventional iridium-coated type impregnated cathode assembly. As shown in the figure, an emission current of 12 A / cm ² at a point of 0 hour is shown. 80 A / cm ² and about 6.7 for the cathode
The double emission current value is shown. Thereafter, the emission current value slightly decreases with time, but even after 3000 hours, the emission current value of the conventional impregnated cathode is reduced by 10%.
A / cm ² , whereas the impregnated cathode has a capacity of 48 A / cm ^2.
The emission current value is 4.8 times that of cm ² . From this, it is clear that the present invention is extremely excellent in ion bombardment and thermal change that the cathode receives during the operation time.

In this example, the thickness of the composite layer composed of the nonstoichiometric tungsten oxide layer and the nonstoichiometric scandium hydride layer was set to 10 nm. However, the present inventors simultaneously made the thickness of the composite layer 20 nm (nonstoichiometric tungsten oxide layer). Layer: 16 nm,
A nonstoichiometric scandium hydride layer: 4 nm, wherein the thickness of the composite layer is 50 nm (nonstoichiometric tungsten oxide layer: 4 nm)
0 nm, nonstoichiometric scandium hydride layer: 10 nm, and the composite layer having a thickness of 100 nm (nonstoichiometric tungsten oxide layer: 80 nm, nonstoichiometric scandium hydride layer:
10 nm) was manufactured in the same manner, and the electron emission characteristics thereof were examined. As a result, FIG. 4 is a graph showing the relationship between the cathode operating temperature and the current density.

In FIG. 4, reference numerals 41, 42, and 43 denote electron emission characteristics of the impregnated cathode structure according to the present invention in which the thickness of the composite layer is 10 nm, 20 nm, and 50 nm, respectively, and 45 denotes an electron emission characteristic of the conventional impregnated cathode structure. Shows release characteristics. When the thickness of the composite layer is 10 nm, as described above, the emission current value is far superior to that of the conventional impregnated cathode structure, and the lower the cathode operating temperature, the more the conventional impregnated cathode structure. And the difference between the emission current values becomes larger. On the other hand, as the thickness of the composite layer increases, the difference from the conventional impregnated cathode structure gradually decreases, and when the thickness is 50 nm, the operating temperature is 1350K.
, The emission current value approaches that of the conventional impregnated cathode assembly. This means that when the thickness of the composite layer exceeds 20 nm, the structure of the film changes, and when the thickness is more than that, the reaction between tungsten oxide and scandium hydride becomes insufficient, and a favorable This indicates that the area exhibiting electron emission tends to decrease.

Example 2 FIG. 5 is a partially cutaway schematic view showing a second example of the impregnated cathode structure according to the present invention. This cathode assembly is an impregnated cathode assembly for klystron, and is used under high output and high voltage.

As shown, the electron tube has a porous W shape.
A cathode tube 51 made of Mo or the like brazed to support the porous cathode substrate 51;
It is mainly composed of a heater 53 built in a support cylinder 52, and this heater 53 is fixed by being embedded in an embedding material 54 made of Al ₂ O ₃ or the like and sintered. The pores of the porous cathode substrate 51 include, for example, Ba
The electron emitting material is impregnated with a molar ratio of O: CaO: Al ₂ O ₃ = 4: 1: 1. The cathode assembly has a radius of 53 mm on the electron emission surface for focusing.

FIG. 6 is a model diagram showing the structure of the porous cathode substrate 51 of the cathode assembly. As shown in FIG. 6, the porous cathode substrate 51 includes a non-stoichiometric tungsten oxide (WO _2-x ) thin film layer 63 and a non-stoichiometric scandium oxide (Sc ₂ O _3-x ) thin film layer 64. It has a structure in which layers are alternately stacked. The porous cathode substrate 51 having such a structure was formed as described below.

First, a porous tungsten substrate 61 made of tungsten particles having a particle size of 3 μm and having a porosity of about 17%.
Is produced by sintering. This substrate has a diameter of 70, for example.
mm, the radius of curvature of the electron emitting surface is 53 mm.

An electron emitting material 62 composed of a mixture of BaO: CaO: Al ₂ O ₃ = 4: 1: 1 in a hole portion of the porous tungsten substrate 61 was placed in an H ₂ atmosphere in an atmosphere of 1: 1.
Melt impregnation by heating at 700 ° C. for about 10 minutes.

After removing the excess electron-emitting substance on the surface of the cathode substrate, the nonstoichiometric tungsten oxide layer 63 and the nonstoichiometric scandium oxide layer 64 were formed by sputtering. The non-stoichiometric tungsten oxide layer 63 is formed by sputtering to a thickness of 10 nm using W as a target material and an argon gas in which 1 vol.% O ₂ is mixed as a sputter gas. Scandium layer 6
In No. 4, a film was formed by using scandium oxide (Sc ₂ O ₃ ) as a target material and sputtering to a thickness of 5 nm using an argon gas mixed with 3 vol.% Hydrogen (H ₂ ) as a sputtering gas.

The formation of the nonstoichiometric tungsten oxide layer 63 and the nonstoichiometric scandium oxide layer 64 was repeated 10 times each, so that a total of 20 layers were stacked.

The cathode structure thus manufactured was heated to 1300 K in an Auger analyzer to perform ion etching, and the subsequent recovery of the cathode electron emission surface structure was performed by tracking the scandium Auger peak intensity. As a result, FIG. 7 is a graph showing the relationship between the elapsed time and the Auger peak intensity.

In the figure, reference numeral 71 denotes a measurement result of the conventional scandium-based impregnated cathode, and reference numeral 72 denotes a measurement result of the scandium-based impregnated cathode according to the present invention. As is apparent from this figure, the recovery of scandium on the electron emission surface of the scandium-based impregnated cathode according to the present invention is much faster than the recovery of scandium on the electron emission surface of the conventional scandium-based impregnated cathode. Is recognized. Therefore, high voltage,
It is clear that the low-temperature operation and high-current-density electron emission characteristic of scandium-based impregnated cathodes are possible even under the operating conditions of high frequency and extremely strong ion bombardment.

An electron gun assembly was obtained by using the impregnated cathode assembly of the above embodiment, and an electron tube was obtained by using the electron gun assembly.

These electron gun assemblies and electron tubes had sufficient life characteristics and high reliability.

[0061]

According to the present invention, high performance and long life have sufficient ion bombardment resistance even under high voltage and high frequency conditions, good electron emission characteristics, and good low temperature operability. Is obtained.

Further, according to the present invention, by using this impregnated type cathode assembly, an electron gun assembly and an electron tube having high performance and long life can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a first example of an impregnated cathode structure according to the present invention.

FIG. 2 is a model diagram showing the structure of the impregnated cathode substrate of FIG.

FIG. 3 is a graph showing a life test result of the impregnated cathode assembly of FIG. 1;

FIG. 4 is a graph showing electron emission characteristics when the thickness of the composite layer of the first example is changed.

FIG. 5 is a partially cutaway schematic view showing a second example of the impregnated cathode structure according to the present invention.

FIG. 6 is a model diagram showing the structure of the cathode substrate of FIG.

FIG. 7 is a graph showing emission characteristics of the impregnated cathode structure electron shown in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Cathode sleeve 12 ... Cup-shaped fixing member 13 ... Porous cathode base 14 ... Cylindrical holder 15 ... Strap 16 ... Support piece 17 ... Shielding cylinder 18 ... Heater 19 ... Strap 20 ... Insulating support 21 ... Porous tungsten base 22 ... Emitting material 23 ... Non-stoichiometric tungsten oxide layer 24 ... Non-stoichiometric scandium hydride layer 51 ... Cathode substrate 52 ... Support tube 53 ... Heater 54 ... Embedding material 61 ... Porous tungsten substrate 62 ... Electron emitting material 63 ... Tungsten layer 64: non-stoichiometric scandium hydride layer

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Toshiharu Higuchi 8 Shinsugitacho, Isogo-ku, Yokohama-shi, Kanagawa Inside Toshiba Yokohama Office

Claims (9)

[Claims] 1. A cathode substrate impregnated with an electron emitting material,
An impregnated cathode structure comprising: a composite layer of a layer containing a high melting point metal and a layer containing scandium formed on the electron emission surface side surface of the cathode substrate. 2. The impregnated cathode structure according to claim 1, wherein the composite layer has a thickness of 50 nm or less. 3. The impregnated cathode assembly according to claim 1, wherein the layer containing the refractory metal is made of one of tungsten and tungsten oxide. 4. The impregnated cathode assembly according to claim 1, wherein the scandium-containing layer is made of at least one selected from the group consisting of scandium, scandium oxide, and scandium hydride. 5. The method for producing an impregnated cathode assembly, comprising a cathode substrate impregnated with an electron emitting substance and having a composite layer comprising a layer containing a high melting point metal and a layer containing scandium on the surface on the electron emitting surface side of the cathode substrate. A method for manufacturing an impregnated cathode structure, wherein the layer containing the melting point metal and the layer containing scandium are alternately formed in different atmospheres. 6. The layer containing a refractory metal is formed in an atmosphere containing oxygen, and the layer containing scandium is
The method for producing an impregnated cathode assembly according to claim 5, wherein the method is formed in an atmosphere containing hydrogen. 7. The method according to claim 5, wherein the layer containing the refractory metal and the layer containing scandium are each formed by a sputtering method. 8. An electron tube using the impregnated cathode assembly according to claim 1. 9. An electron gun assembly comprising the electron gun assembly according to claim 8.