CN1221966A - Cathode used in electron gun - Google Patents

Abstract

The purpose of the present invention is to ensure the post-diffusion path of the reducing agent contained in the matrix metal, to realize the formation of barium free radicals smoothly, and thus to realize the long life under high current density load. On the base metal 6 with nickel as the main component and containing at least one reducing metal, a metal layer 12 whose main component is tungsten, zirconium-tungsten or tungsten-nickel is set, and an alkaline earth material containing at least barium is set on the metal layer. The electron emitting substance layer 8 of the metal oxide layer. The above-mentioned metal layer is obtained by coating tungsten, zirconium-tungsten or tungsten-nickel on the base metal, and heat-treating this, and it is composed of particles smaller than the average particle diameter of the above-mentioned base metal.

Description

Cathode for electron gun

The present invention relates to a cathode for an electron gun used in a cathode ray tube, and particularly relates to a cathode for an electron gun that ensures a diffusion path for a reducing element that contributes to the generation of barium radicals and can be used for a long time at a high current density.

A cathode ray tube is a device that accelerates electrons emitted from an electron gun with a high voltage, lands them on a phosphor on a screen, and displays images by exciting the phosphor to emit light.

FIG. 5 shows a general structure of a cathode for an electron gun used for electron emission in such a cathode ray tube. In the figure, a heater (heater) 4 is provided inside the sleeve (sleeve) 2, and a reducing element such as nickel (Ni) containing trace amounts of silicon (Si) and magnesium (Mg) is installed on it. A cover-like base metal 6 is provided with an electro-emissive material layer 8 mainly composed of an alkaline earth metal oxide containing at least barium.

The oxide cathode installed in this way uses the heat emitted from the heater as an energy source, the metal oxide and the reducing metal react, and the barium radicals generated therein emit thermal electrons. The electron emission capability of the above-mentioned cathode for an electron gun depends on the supplied amount of barium radicals present in the metal oxide. Recently, however, cathode ray tubes tend to be finer and larger, and therefore development of a cathode capable of supplying barium radicals at a high current density for a long period of time is required.

Therefore, in the applicant's previous application, Korean Laid-Open Patent Publication No. 96-15634, it is disclosed that a lanthanum (La) compound and a magnesium (Mg) compound are simultaneously contained in an electron emitting material layer containing an alkaline earth metal oxide. , or further make the cathode containing La-Mg composite compound to suppress the evaporation consumption of barium free radicals.

However, the above-mentioned cathode, as shown in FIG. 6, forms an intermediate layer 10 composed of a reaction product between the interface between the base metal 6 and the electron emissive material layer 8, which will lead to a high current density of 2 to 3 A/cm ² . Shortened lifespan.

The intermediate layer 10 is formed by reacting barium oxide obtained by thermally decomposing barium carbonate, which is a metal oxide of barium radicals contributing to electron emission, with silicon and magnesium as reducing agents.

(1)

(2)

The barium radicals generated by Reaction Formula 1 and Reaction Formula 2 contribute to electron emission, but products like MgO and Ba ₂ SiO ₄ are produced accordingly, forming an intermediate layer at the interface between the base metal 6 and the electron emission material layer 8. Layer 10.

The intermediate layer 10 formed in this way acts as a barrier layer and prevents the subsequent diffusion of the reducing agent contained in the base metal 6, making it difficult to generate barium radicals that require the reducing agent, thereby shortening the lifetime of the cathode. In addition, there is a problem that the high resistance of the above-mentioned intermediate layer hinders electron emission current and limits the current density that can be emitted.

On the other hand, Japanese Laid-Open Patent Publication No. Hei 3-257735 discloses that a metal layer having a reducing property equal to or lower than that of silicon and magnesium but higher than that of nickel is provided between a base metal and an electron emitting material layer. A cathode for an electron gun in which a rare earth metal oxide is contained in the radioactive substance layer, and the reaction product is decomposed by the rare earth metal oxide so that the reducing element in the metal layer contributes to the generation of barium radicals.

However, the above-mentioned cathode further forms additional reaction products while generating barium radicals, and although the performance is stable at the beginning of use, there is a problem that the service life decreases rapidly as time goes by.

The object of the present invention is to achieve a long life under high current density load by ensuring the later diffusion path of the reducing agent contained in the base metal to smoothly realize the generation of barium radicals.

As a means to achieve the above-mentioned purpose, the present invention provides a metal layer whose main component is tungsten, zirconium-tungsten or tungsten-nickel on the base metal with nickel as the main component and at least one reducing metal, and on the metal layer A cathode for an electron gun provided with an electron emitting material layer including an alkaline earth metal oxide layer containing at least barium thereon.

Here, the metal layer of the present invention is obtained by coating tungsten, zirconium-tungsten or tungsten-nickel on the base metal, and heat-treating this, and setting it so that it has a particle size smaller than the average particle size of the base metal .

In addition, the present invention also includes a structure in which a second electron-emitting substance layer containing both a lanthanum compound and a magnesium compound or a lanthanum-magnesium composite compound in an alkaline earth metal oxide containing at least barium is provided on the above-mentioned electron-emitting substance layer.

Through the above-mentioned structure, in the present invention, the metal layer composed of particles smaller than the matrix metal particles is dispersed as the intermediate layer of the reaction product, ensuring the path of the reducing metal, facilitating the later diffusion, thereby continuously maintaining the resistance to the reducing metal. The formation reaction of the required barium radical realizes the long life under the high current density load of 2-3A/cm ² .

Hereinafter, best embodiments for realizing the present invention will be described with reference to the drawings. For reference, in the description of the present invention, the same reference numerals are used for the same parts as those described using the drawings cited from the conventional art to maintain clarity.

A brief description of the accompanying drawings is as follows:

Fig. 1 is a sectional view of a cathode for an electron gun according to one embodiment of the present invention.

Fig. 2 is an enlarged sectional view of a main part of a cathode for an electron gun according to an embodiment of the present invention.

Fig. 3 is a sectional view of a cathode for an electron gun according to another embodiment of the present invention.

Fig. 4 is a life characteristic of a cathode for an electron gun according to another embodiment of the present invention.

Fig. 5 is a sectional view of a conventionally disclosed cathode for an electron gun.

Fig. 6 is an enlarged sectional view of a conventionally disclosed cathode for an electron gun.

The symbols are explained as follows:

6 base metal

8 electron emission material layer

10 middle layer

12 metal layers

80 The second layer of electron emitting substances

Example 1

In FIG. 1 , the cathode for an electron gun according to the first embodiment of the present invention is provided at the upper opening of the sleeve 2 with the heater 4 inside, and contains Ni as the main component, and a small amount of, for example, Si, Mg is the capping base metal 6 of the reducing metal.

A metal layer 12 composed of W, Zr-W or W-Ni is set on the base metal 6, and an alkaline earth metal oxide containing at least barium, ternary carbonate (Ba·Sr·Ca) CO ₃ or an electron-emitting material layer 8 composed of binary carbonate (Ba·Sr)CO ₃ .

In this embodiment, when barium radicals are generated, reaction products of BaO and Si with Mg accumulated on the interface between the base metal 6 and the electron emissive material layer 8 are scattered and accumulated, and W, Zr- Metal layer 12 composed of W or W-Ni.

The metal layer 12 of this embodiment is to set W, Zr-W or W-Ni with a thickness of 1000-10000 angstroms on the base metal 6 by sputtering (sputtering), and place it in an inert atmosphere or a vacuum atmosphere at a temperature of 700-1000 angstroms. It is obtained by heat treatment at 1100° C. so that it can be alloyed and diffused between the base metal 6 and the metal layer 12 . The coating of W, Zr-W or W-Ni can be realized by physical, chemical and mechanical methods such as spray method, printing method, electrodeposition method and metal salt solution method.

At this time, the metal layer 12 has a particle size smaller than the average particle size of the base metal 6 as shown in an enlarged view in FIG. 2 . Due to the above-mentioned metal layer 12, the diffusion path itself of the reducing element contained in the base metal 6 is dispersed, and the reaction of BaO, Si, and Mg proceeds in many places in the particles of the metal layer 12, and the intermediate layer 10 of the reaction product is Dispersion and accumulation are suppressed, and the diffusion of Si and Mg, which are reducing elements, can proceed smoothly, thereby contributing to the generation of barium free radicals.

On the metal layer 12 thus provided, a ternary carbonate or a dicarbonate having a thickness of 20-80 μm is provided by a usual spraying method, so that the total thickness of the cathode of this embodiment is below 200 μm.

Example 2

In the cathode for an electron gun according to the second embodiment of the present invention, the second electron-emitting material layer is used instead of the electron-emitting material layer of the first embodiment.

That is, in FIG. 1, on the metal layer 12 composed of W, Zr-W or W-Ni, as an alkaline earth metal oxide containing at least barium, a ternary carbonate (Ba·Sr·Ca)CO ₃ or the second electron emissive material layer 80 that further contains a lanthanum compound and a magnesium compound or further contains a lanthanum-magnesium composite compound in the binary carbonate (Ba·Sr)CO ₃ .

The above-mentioned lanthanum compound and magnesium compound or lanthanum-magnesium compound compound suppresses the evaporation of barium free radicals and enables continuous supply of barium free radicals, and it is optimal to account for 0.01-1% by weight of the carbonate.

If its content is less than 0.01% by weight, the effect of inhibiting barium radicals during driving is very small, and if it reaches 1% by weight, the electron emission characteristics during driving will be reduced.

Therefore, according to the present embodiment, the evaporation of barium radicals generated by the reaction of BaO with Si and Mg is suppressed by the second electron emissive material layer 80 while the metal layer 12 effectively disperses the intermediate layer 10, thereby Sintering of metal oxides is prevented.

The metal layer 12 of this embodiment is coated with W, Zr-W or W-Ni with a thickness of 1000-10000 angstroms on the base metal 6, and heat treatment is carried out at 700-1100 °C in an inert atmosphere or a vacuum atmosphere. , so that it can be alloyed and diffused between the base metal 6 and the metal layer 12 . Above it, the second electron emissive material layer ternary carbonate or dibasic carbonate containing lanthanum compound and magnesium compound or further containing lanthanum-magnesium composite compound with a thickness of 20 to 80 μm is sprayed, so that The total thickness of the cathode in this embodiment does not exceed 200 μm.

Example 3

As shown in Figure 3, the electron gun cathode of the third embodiment of the present invention is on the base metal 6, is provided with a metal layer 12 composed of W, Zr-W or W-Ni, on which is formed a metal layer containing at least barium. Electron emissive material layer 8 composed of ternary carbonate or dibasic carbonate, on which a ternary carbonate or dibasic carbonate containing at least barium contains both lanthanum compound and magnesium compound or contains The second electron emissive material layer 80 of the lanthanum-magnesium composite compound.

This embodiment is based on the consideration that in the above-mentioned embodiment 2, the reducing elements composed of W, Zr-W or W-Ni and the reducing elements contained in the matrix metal 6 simultaneously promote the reduction of barium radicals, and the barium radicals The evaporation will be excessive.

In this embodiment, as a means of dispersing the reaction product of BaO and Si or Mg thermally decomposed from the carbonate accumulated on the interface of the base metal 6 and the electron emissive material layer 8, W, Metal layer 12 composed of Zr-W or W-Ni.

In addition, in this embodiment, as a plan for suppressing the evaporation and consumption of barium radicals in the electron emissive material layer 8, a second carbon dioxide containing both a lanthanum compound and a magnesium compound or 0.01 to 1% by weight of a lanthanum-magnesium compound compound in the carbonate is provided. Electron emitting material layer 80 .

For this reason, the metal layer 12 of the present embodiment is coated with W, Zr-W or W-Ni with a thickness of 1000-10000 angstroms on the base metal 6, which is heated at 700-1100 ° C in an inert atmosphere or a vacuum atmosphere. It can be obtained by performing heat treatment under heat treatment so that it can be alloyed and diffused between the base metal 6 and the metal layer 12 .

In addition, an electron emissive material layer 8 composed of ternary carbonate or dicarbonate is coated on the metal layer 12 with a thickness of 20 to 80 μm, and an electron-emitting material layer 8 with a thickness of 20 to 80 μm is coated thereon. The second electron emissive material layer 80 containing lanthanum compound and magnesium compound or further containing lanthanum-magnesium composite compound in primary carbonate or dibasic carbonate, so that the total thickness does not exceed 200 μm, so that the present embodiment can be manufactured. Electron gun cathode.

The cathode for the electron gun of the above-mentioned embodiment was assembled into a cathode ray tube, and its life was checked. The results are shown in FIG. 4 . A in the figure is a metal layer 12 with a thickness of 400 to 1200 angstroms, an electron emissive material layer 8 is arranged thereon, and a carbonate of 0.5% by weight of a lanthanum-magnesium compound is arranged thereon. cathode. B in the figure is a conventional oxide cathode.

The life test was carried out by measuring the amount of decrease in electron emission current in a state of continuous driving for 6000 hours, and performing a current of 2000 to 3000 μA for each cathode. As a result, the cathode for an electron gun according to the present invention has remarkably improved lifetime characteristics at high currents compared to conventional technologies. Specifically, the present invention still maintains 95% of the initial current value after 6000 hours under the drive of high current density.

Also, the cathode of the present invention shows a tendency for the maximum cathode current to increase as the time elapses from the maximum cathode current (maxi-mum cathode current; the maximum current emitted from the cathode under certain conditions) at the initial stage of driving.

As shown in the above embodiments, the cathode for an electron gun of the present invention substantially solves the problems of the prior art. That is, the structure of the present invention is to provide a metal layer composed of fine particles between the matrix metal containing reducing elements and the electron emitting material layer composed of carbonate, and to disperse the reaction products that occur when barium radicals are generated, ensuring reduction. The post-diffusion path of sexual elements, so as to achieve continuous radiation of barium free radicals.

In addition, in the present invention, the electron emitting material layer contains both a lanthanum compound and a magnesium compound or a lanthanum-magnesium compound compound, or a second electron emitting material layer containing both a lanthanum compound and a magnesium compound or a lanthanum-magnesium compound compound is provided, Therefore, the evaporative consumption of barium free radicals can be suppressed.

Therefore, according to the present invention, through the interaction between the metal layer and the electron-emitting material layer or the second electron-emitting material layer, the emission of barium radicals can be sustained, and evaporation consumption ^can be suppressed. The effect of improving the life characteristics can be obtained even under the density load.

In addition, although the oxide cathode of the present invention maintains a long life at a high current density, it is also practical to replace the impregnated cathode which is difficult to manufacture and expensive.

On the other hand, the present invention is not limited to the above-mentioned preferred invention, and anyone who has general knowledge in the field to which the present invention pertains can make various changes to the implementation within the scope of the summary required by the patent claims. .

Claims (18)

1. The cathode for an electron gun is characterized in that it includes a base metal mainly composed of nickel and containing at least one reducing metal, and a metal layer whose main component is tungsten is arranged on it, and a metal layer containing at least barium is arranged on the metal layer. The electron-emitting material layer of the alkaline earth metal oxide layer. 2. The cathode for an electron gun according to claim 1, wherein the metal layer is composed of tungsten, zirconium-tungsten or tungsten-nickel. 3. The cathode for an electron gun according to claim 1 or claim 2, wherein the metal layer is obtained by coating tungsten, zirconium-tungsten or tungsten-nickel on the base metal, and heat-treating this. 4. The cathode for an electron gun according to claim 1, wherein the metal layer is composed of particles having an average particle diameter smaller than that of the base metal. 5. The cathode for an electron gun according to claim 1, wherein the thickness of the metal layer is 1000-10000 angstroms. 6. 5. The cathode for an electron gun according to claim 5, wherein the total thickness of the base metal, the metal layer and the electron emitting material layer is in the range of 50 to 200 μm. 7. The cathode for an electron gun according to claim 1, wherein the electron emitting material layer contains both a lanthanum compound and a magnesium compound, or further contains a lanthanum-magnesium composite compound. 8. The cathode for an electron gun according to claim 7, wherein the metal layer is composed of tungsten, zirconium-tungsten, or tungsten-nickel. 9. The cathode for an electron gun according to claim 7 or claim 8, wherein the metal layer is obtained by coating tungsten, zirconium-tungsten or tungsten-nickel on the base metal and heat-treating it. 10. The cathode for an electron gun according to claim 7, wherein the metal layer is composed of particles having an average particle diameter smaller than that of the base metal. 11. The cathode for an electron gun according to claim 7, wherein the metal layer has a thickness of 1,000 to 10,000 angstroms. 12. The cathode for an electron gun according to claim 11, wherein the total thickness of the base metal, the metal layer, and the electron-emitting material layer is in the range of 50 to 200 μm. 13. The cathode for an electron gun according to claim 1, wherein a second alkaline earth metal oxide containing at least barium containing both a lanthanum compound and a magnesium compound or a lanthanum-magnesium composite compound is provided on the electron emitting material layer. 2 electron emitting material layer. 14. The cathode for an electron gun according to claim 13, wherein the metal layer is composed of tungsten, zirconium-tungsten, or tungsten-nickel. 15. The cathode for an electron gun according to claim 13 or claim 14, wherein the metal layer is obtained by coating tungsten, zirconium-tungsten or tungsten-nickel on the base metal and heat-treating this. 16. The cathode for an electron gun according to claim 13, wherein the metal layer is composed of particles having an average particle diameter smaller than that of the base metal. 17. The cathode for an electron gun according to claim 13, wherein the metal layer has a thickness of 1000 to 10000 angstroms. 18. The cathode for an electron gun according to claim 17, wherein the total thickness of the base metal, the metal layer, the electron-emitting material layer, and the second electron-emitting material layer is in the range of 50 to 200 μm.

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