CN1221965A - Cathode used in electron gun - Google Patents

Abstract

The present invention relates to cathodes for electron guns suitable for cathode ray tubes, in particular to ensure the post-diffusion paths of reducing elements contained in base metals, and to smoothly realize the generation of barium radicals, thereby realizing long life under high current density loads for purpose. The cathode for an electron gun has nickel as its main component, a base metal containing at least one reducing metal, and a metal layer whose main component is nickel is arranged on it, and an alkaline earth metal oxide containing at least barium is arranged on the metal layer layer.

Description

Cathode for electron gun

The present invention relates to a cathode for an electron gun used in a cathode ray tube, and more particularly 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 realizes a long life under a high current density load.

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. 6 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.

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

However, as shown in FIG. 7, the above-mentioned cathode generates an intermediate layer 10 composed of a reaction product between the interface of the base metal 6 and the electron emissive material layer 8, which will cause 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 that contributes to the generation of barium radicals that generate 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, since the above-mentioned intermediate layer 10 has a high resistance, the flow of the electron emission current is hindered, and the current density that can be emitted is limited.

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 nickel or nickel-zirconium on the base metal with nickel as the main component and at least one reducing metal, and a metal layer containing at least A cathode for an electron gun of an electron emitting material layer containing an alkaline earth metal oxide layer containing barium.

Here, the metal layer of the present invention is obtained by coating nickel or nickel-zirconium on the base metal, and heat-treating this, or adhering nickel or nickel-zirconium powder, and setting it so that it has an average The particle size is small.

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 base metal particles effectively disperses the intermediate layer as a reaction product, prevents the intermediate layer from forming a high-resistance layer, ensures the path of the reducing metal, and contributes to the later stage. Diffusion, so as to continuously maintain the formation reaction of barium free radicals required for the above-mentioned reducing metals, and achieve long life under a high current density load of 2 to 3A/cm ² .

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

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

Fig. 5 is a life characteristic of a cathode for an electron gun according to another embodiment of the present invention.

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

Fig. 7 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

Hereinafter, the best embodiment 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.

Example 1

The cathode for an electron gun of one embodiment of the present invention shown in Fig. 1 is arranged on the upper side opening of the casing 2 provided with a heater 4 inside, and includes Ni as the main component, and a trace amount such as Si, Mg The capping base metal 6 of the reducing metal.

A metal layer 12 composed of pure Ni or Ni-Zr 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 di An electron-emitting material layer 8 composed of carbonate (Ba·Sr)CO ₃ .

In this embodiment, when barium radicals are generated, as a solution to disperse the reaction products of BaO and Si with Mg accumulated on the interface between the base metal 6 and the electron emissive material layer 8, the interface is provided with pure Ni or Ni - Metal layer 12 composed of Zr microparticles.

The metal layer 12 of this embodiment is enlarged as shown in FIG. 2, and it is arranged so that it has a particle diameter smaller than the average particle diameter of the base metal 6. Since the diffusion path itself of the reducing element contained in the base metal 6 is dispersed, The reaction of BaO with Si and Mg proceeds in many places in the particles of the metal layer 12, the intermediate layer 10 of the reaction product is dispersed, the accumulation is suppressed, and the diffusion of Si and Mg, which are reducing elements, proceeds smoothly, so that there is Contributes to the formation of barium free radicals. In addition, the composition of the metal layer 12 is pure Ni or Ni—Zr, which is the same as that of the base metal 6 , and does not generate an intermediate layer as a reaction product compared with a conventional W-coated metal layer.

For this reason, the metal layer 12 of the present embodiment is to set Ni or Ni-Zr with a thickness of 200-20000 angstroms on the base metal 6 with a sputtering (sputtering) method, and place it in an inert atmosphere or a vacuum atmosphere at a temperature of 700-1100 angstroms. It is obtained by heat treatment at ℃, so that it can be alloyed and diffused between the base metal 6 and the metal layer 12 .

The thickness of the metal layer 12 is preferably 200-20000 angstroms. If it is less than 200 angstroms, it will be too thin to ensure the path of reducing elements, and if it is more than 20000 angstroms, it will hinder the diffusion of reducing metals. On the other hand, the thickness of the metal layer 12 in this embodiment is the best implementation form, which is 3000-10000 angstroms.

On the other hand, the metal layer 12 of this embodiment is provided on the base metal 6 by coating Ni or Ni-Zr powder. The covering method at this time can be realized by physical, chemical and mechanical methods such as spray method, printing method, electrodeposition method and metal salt solution method.

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

The cathode for an electron gun according to the second embodiment of the present invention provides a second electron-emitting material layer instead of the electron-emitting material layer of the first embodiment.

The present embodiment is described with reference to FIG. 1. On the metal layer 12 composed of pure Ni or Ni-Zr, 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 containing both a lanthanum compound and a magnesium compound or 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 the content is less than 0.01% by weight, the effect of suppressing barium radicals during driving is slight, and if it is more than 1% by weight, the electron emission characteristics during initial 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 to coat Ni or Ni-Zr with a thickness of 200 to 20000 angstroms on the base metal 6, and carry out heat treatment in an inert atmosphere or a vacuum atmosphere, so that it can be coated on the base metal 6 and the metal layer 12. Alloyed and diffused between layers 12. The metal layer 12 of this embodiment is set on the base metal 6 by Ni or Ni-Zr powder.

On the metal layer 12 that is set up in this way, it is 20～80 μ m that in ternary carbonate or dibasic carbonate, contain lanthanum compound and magnesium compound or further contain lanthanum-magnesium composite compound with a thickness of 20～80 μm by spray coating The total thickness of the second electron emissive material layer 80 and the cathode in this embodiment is not more than 200 μm.

The cathode for the electron gun of this embodiment was assembled into a cathode ray tube, and its lifetime was checked. The results are shown in FIG. 3 . A in the figure is the cathode of this embodiment in which the carbonate contains 0.5% by weight of lanthanum-magnesium compound and the metal layer 12 is provided with a thickness of 3000-5000 angstroms. B in the figure is an oxide cathode containing 0.5% by weight of lanthanum-magnesium compound in carbonate, and no metal layer 12 is provided. C 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 life characteristics at high currents compared with B and C of the prior art. Specifically, the present invention still maintains 90% of the initial current value after 6000 hours under the drive of high current density.

Example 3

As shown in Figure 4, the negative electrode of the electron gun of the 3rd embodiment of the present invention is on the base metal 6, is provided with the metal layer 12 that is made up of pure Ni or Ni-Zr, is provided with the ternary carbon that contains barium at least on it. An electron-emitting material layer 8 composed of acid salt or dibasic carbonate, on which a ternary carbonate or dibasic carbonate containing at least barium contains both lanthanum compound and magnesium compound or further contains lanthanum- The second electron emissive material layer 80 of the magnesium composite compound.

This embodiment is to consider that in the above-mentioned embodiment 2, the reducing elements composed of Ni or Ni-Zr and the reducing elements contained in the base metal 6 promote the reduction of barium free radicals at the same time, and the evaporation of barium free radicals will be excessive. conduct.

In this embodiment, as a solution to disperse 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, a layer made of pure Ni is placed between the interfaces. Or the metal layer 12 composed of Ni-Zr.

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 to coat Ni or Ni-Zr with a thickness of 200 to 2000 angstroms on the base metal 6, and carry out heat treatment in an inert atmosphere or a vacuum atmosphere, so that it can be coated on the base metal. 6 and metal layer 12 obtained by alloying and diffusion. Here, the thickness of the metal layer 12 in this embodiment is preferably 200 to 2000 angstroms in consideration of the thicknesses of the electron emissive material layer 8 and the second electron emissive material layer 80 disposed thereon, and the best embodiment is 400-1200 Angstroms. On the other hand, the metal layer 12 of this embodiment is provided by adhering Ni or Ni-Zr powder on the base metal 6 .

On the metal layer 12 formed in this way, the electron emissive material layer 8 composed of ternary carbonate or dicarbonate is coated 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 on it. The second electron emissive material layer 80 containing lanthanum compound and magnesium compound or further containing lanthanum-magnesium composite compound in the ternary carbonate or dicarbonate, so that the total thickness is not more than 200 μm, this embodiment can be manufactured like this Electron gun with 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. 5 . D among the figure is provided with the metal layer 12 that thickness is 400～1200 angstroms, is provided with electron emissive material layer 8 on it, is provided with the carbonate of the present embodiment that contains lanthanum-magnesium compound 0.5 weight % again on it. cathode. E 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 (maximum 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 (21)

1. The cathode for an electron gun is characterized by comprising a base metal mainly composed of nickel and containing at least one reducing metal, and a metal layer whose main component is nickel 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 nickel or nickel-zirconium. 3. The cathode for an electron gun according to claim 1 or claim 2, wherein the metal layer is obtained by coating nickel or nickel-zirconium on the base metal and heat-treating this. 4. The cathode for an electron gun according to claim 3, 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 or claim 2, wherein the metal layer is provided by adhering nickel or nickel-zirconium powder on the base metal. 6. The cathode for an electron gun according to claim 5, wherein the metal layer is composed of particles having an average particle diameter smaller than that of the base metal. 7. The cathode for an electron gun according to claim 1, wherein the thickness of the metal layer is 200-20000 angstroms. 8. 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. 9. The cathode for an electron gun according to claim 8, wherein the metal layer is made of nickel or nickel-zirconium. 10. The cathode for an electron gun according to claim 8 or claim 9, wherein the metal layer is obtained by coating nickel or nickel-zirconium on the base metal and heat-treating this. 11. The cathode for an electron gun according to claim 10, wherein the metal layer is composed of particles having an average particle diameter smaller than that of the base metal. 12. The cathode for an electron gun according to claim 8 or claim 9, wherein the metal layer is provided by adhering nickel or nickel-zirconium powder on the base metal. 13. The cathode for an electron gun according to claim 12, wherein the metal layer is composed of particles having an average particle diameter smaller than that of the base metal. 14. The cathode for an electron gun according to claim 8, wherein the thickness of the metal layer is 200-20000 angstroms. 15. The cathode for an electron gun according to claim 1, wherein a second electrode containing both a lanthanum compound and a magnesium compound or a lanthanum-magnesium composite compound is disposed on the alkaline earth metal oxide containing at least barium on the electron emitting material layer. 2 electron emitting material layer. 16. The cathode for an electron gun according to claim 15, wherein the metal layer is made of nickel or nickel-zirconium. 17. The cathode for an electron gun according to claim 15 or claim 16, wherein the metal layer is obtained by coating nickel or nickel-zirconium on the base metal and heat-treating this. 18. The cathode for an electron gun according to claim 17, wherein the metal layer is composed of particles having an average particle diameter smaller than that of the base metal. 19. The cathode for an electron gun according to claim 15 or claim 16, wherein the metal layer is provided by adhering nickel or nickel-zirconium powder on the base metal. 20. The cathode for an electron gun according to claim 19, wherein the metal layer is composed of particles having an average particle diameter smaller than that of the base metal. twenty one. The cathode for an electron gun according to claim 15, wherein the thickness of the metal layer is 200-2000 angstroms.

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