JPH02288043A - Cathode for electron tube - Google Patents

Abstract

PURPOSE:To obtain the emission property being stable in a long period even in high current density operation by overlaying a mixture and an alkaline earth metallic oxide in order on a substrate. CONSTITUTION:The topside of the bottom of a substrate 1 whose main ingredient consists of nickel is covered with a mixture layer 4. This layer 4 contains at least one kind among scandium oxide, iron, aluminum, titanium, zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, rhenium, osmium, indium, platinum, palladium, rhodium, gold, vanadium, chrom, magnanese, copper, zinc, bismuth, indium, and silicon. The layer 4 is covered with an electron emitter layer 5 which contains alkaline earth metallic oxide containing barium. As a result, the conductivity at the bonding interface between the substrate 1 and the layer 5 can be maintained stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cathode for an electron tube used in a di-braun tube for TV.

[Conventional technology]

Figure 2 shows a cathode used in a conventional di-cathode ray tube for TVs. A cylindrical base 2 with a bottom is adhered to the upper surface of the bottom of the base 1, and contains an alkaline earth metal oxide containing at least barium (Ba) and also strontium (Sr) and/or calcium (Ca). The electron emitting material layer 3 made of a material is a heater disposed within the base 1, and is used to cause the electron emitting material layer 2 to emit thermoelectrons by heating.

In the cathode for an electron tube having such a configuration, the electron emitting material layer 2 is deposited on the substrate 1 in the following manner. First, a suspension consisting of a ternary carbonate of alkaline earth metals (Ba, Sr, Ca) is applied to the bottom upper surface of the substrate 1, and heated by the heater 3 during the evacuation process. At this time, the alkaline earth metal carbonate changes to an alkaline earth metal oxide. Thereafter, a part of the alkaline earth metal oxide is reduced and activated to have semiconductor properties, thereby obtaining an electron emitting material layer 2 made of the alkaline earth metal oxide on the substrate 1.

In the activation step, a portion of the alkaline earth metal oxide reacts as follows. That is, reducing elements such as silicon and magnesium in the base 1 move to the interface between the alkaline earth metal oxide and the base 1 by diffusion and react with the alkaline earth metal oxide. For example, if the alkaline earth metal oxide is barium oxide (BaO), the following formula (1
), reacts as shown in (2).

BaO+ KSI = Ba 1'/2S+Oz
++ ・+ (1) BaO+ Mg = Ba
+ Mg'O-- (2) Through this reaction, a part of the alkaline earth metal oxide on the substrate 1 is reduced, becoming an oxygen-deficient semiconductor, and the cathode temperature is 0.5 at an operating temperature of 700-800''C. An electron emission of ~0.8 A/cd will be obtained.

However, in the above cathode for an electron tube, the electron emission is 0.5~
A current density of 0.8 A/cd or higher cannot be obtained.

The reason for this is that when a part of the alkaline earth metal oxide is subjected to a reduction reaction, as is clear from (1) and (2) above, SiO2 is formed at the interface between the substrate 1 and the alkaline earth metal oxide layer. A composite oxide layer (intermediate layer) of □, NGO or BaO/SiO□ is formed, and this intermediate layer becomes a high resistance layer and obstructs the flow of current, and the intermediate layer reduces the reduction in the substrate l. It is considered that a sufficient amount of barium (Ba) is not generated because it prevents the chemical elements (Si, Mg) from diffusing to the surface side of the electron emitting material layer 2. That is, during electron tube operation, the intermediate layer segregates near the interface between the substrate 1 and the electron emitting material layer 2, particularly at the nickel grain boundary near the surface of the substrate 1 and at a position about 10p1 inside the electron emitting material layer 2 from the interface. Therefore, the flow of current and the diffusion of the reducing element toward the surface of the electron emitting material layer 2 are hindered, resulting in a problem that sufficient electron emission characteristics under high current density cannot be obtained.

On the other hand, Japanese Patent Application No. 1983-229303 discloses a method of incorporating 0.01 to 0.5% of rare earth metal into the substrate. This is caused by oxidation of the substrate when alkaline earth metal carbonate decomposes during the activation described above when depositing an electron emitting material layer on the substrate, or when barium oxide undergoes a dissociation reaction during operation as a cathode. This is an attempt to prevent a reaction. In addition, the diffusion of the reducing element contained in the substrate into the electron emitting material layer is moderately controlled,
It is intended to prevent the intermediate layer made of a composite oxide of the reducing element from being formed intensively near the interface between the substrate and the electron emitting material layer, and to disperse the intermediate layer within the electron emitting material layer. In other words, the electron tube cathode of this second conventional example has excellent characteristics in that emission deterioration is reduced during high current density operation of about 1 to 2^/cd due to the dispersion of the intermediate layer. However, even in this cathode for an electron tube, there is a problem that emission deterioration is large when operating at a high current density exceeding 2 A/d, for example, 2.5^/ctl.

Next, in the application of Japanese Patent Application No. 160851/1985, the substrate oxidation is prevented by containing 0.1 to 20% by weight of rare earth metal oxide in the electron emitting material layer, as in the second conventional example mentioned above. Techniques have been shown to prevent and disperse intermediate layers. In this case, the deterioration of emissions can be reduced by operating at a high current density of 2 A/cd, as described above. However, 2
In operation at a high current density of A/crj or higher, evaporation of barium becomes significant due to Joule heat caused by the current flowing through the electron emitting material layer, and electron emission characteristics may deteriorate.

In order to solve the above problems, the inventors
First, on a substrate whose main component is nickel, the main component is an alkaline earth metal oxide containing at least barium, which also contains a compound of scandium and one type of oxide of aluminum, silicon, titanium, etc. An electron tube cathode tube coated with an electron emissive material layer was proposed.

As a result, it was possible to provide an electron tube cathode that exhibits long-term stable emission characteristics even in high current density operation exceeding 2 A/d.

[Problem to be solved by the invention]

However, in the above-mentioned conventional example and the cathode for an electron tube proposed earlier by the inventors, the substrate of the electron tube cathode and the electron emitting material layer, especially in high current density operation exceeding 2A/c+a, and after long-term use. At the interface between the electron tube and the electron tube, the conductivity decreases, although the reason is not clear. There was a problem that caused serious deterioration of the product and reduced the reliability of the product.

This invention has been made to solve these problems.

[Means to solve the problem]

In this invention, a first
Scandium oxide as a layer and iron, aluminum, titanium, zirconium, hafnium.

depositing a mixture layer containing at least one of niobium, tantalum, molybdenum, tungsten rhenium, osmium, iridium, platinum, palladium, rhodium, gold, vanadium, chromium, manganese, copper, zinc, bismuth, indium, and silicon; The cathode for an electron tube further comprises an electron emitting material layer formed by depositing an alkaline earth metal oxide containing at least barium on the first mixture layer.

(Function) In this invention, a mixture of at least one of iron, aluminum, titanium, copper, etc. and scandium oxide is deposited on the substrate as a first layer, and an alkali containing at least barium is further applied on the mixture. An electron emitting material layer of earth metal oxide is deposited.

Therefore, the presence of metals such as iron and uA in the first layer mixture maintains high conductivity at the interface between the substrate and the electron emitting material layer, and as a result, maintains the electron emission characteristics especially under high current density. This shows an effect of preventing deterioration of the emission characteristics.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

In this figure, ■ is a substrate whose main component is nickel, and this substrate 1 contains a reducing agent such as Si or Mg.

Next, 4 is a first mixture layer deposited on the bottom top surface of the substrate l, comprising scandium oxide, iron, aluminum, titanium, zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, rhenium, osmium. , iridium, platinum, palladium, rhodium, gold, vanadium, chromium, manganese, copper, zinc, bismuth, indium, and silicon. The average particle size of these iron, aluminum, copper, etc. is preferably about 2 microns, but there is no particular restriction, and the mixing amount of these iron, aluminum, copper, etc. with respect to scandium oxide is 0.5 to 10%, preferably 3% by weight. %.

Below the lower limit, the conductivity will not be sufficient, and above the upper limit, there will be no need for it and the adhesion will decrease. The binder used is preferably, for example, butyl acetate lacquer containing nitrocellulose. Scandium oxide and the metal powder mentioned above are dispersed in an amount of about 3% by weight, applied by a spray method, and dried. The dry film thickness is 5 to 20. The thickness is desirably about 10 microns.

Then, sintering is further performed at 1000° C. for about 5 minutes in a hydrogen atmosphere.

Next, 5 is an electron emissive material layer deposited on the first mixture layer 4, specifically barium.

The main ingredients are ternary oxides of strontium and calcium. The above-mentioned alkaline earth metal oxides such as barium are first mixed with carbonate as described above, and as in the past, the decomposition process from carbonate to oxide and the activity of reducing a part of the oxide are carried out as in the conventional method. It is formed through a process of oxidation.

Figure 3 shows a specific example of the present invention, in which scandium oxide mixed with 3 wt. (a) Adhering to strontium and calcium oxides, copper powder is applied to scandium oxide as the first layer.
% by weight (b), scandium oxide mixed with 2% by weight of iron powder and 1% by weight of copper powder (C), and a conventional example of scandium oxide oxidized to oxides of barium, strontium, and calcium. 4% scandium by weight
Electron emitting material layers (d) containing scandium oxide and (e) containing no scandium oxide are respectively formed on the above substrate by a method similar to the method described above to prepare a cathode for an electron tube. This figure shows the results of examining changes in emission current when a diode vacuum tube was fabricated using a tube cathode and a life test was performed by operating it at a current density of 2.5 A/afl.

According to the results shown in FIG. 3, the example products (a), (b) and (C) of the present invention, that is, the first layer Those in which layers of scandium oxide, iron, copper, or a mixture of both were formed exhibited significantly less emission deterioration over time and had a long life.

Moreover, compared to (d), in which barium, strontium, and calcium oxides contain scandium oxide and are formed as a single layer on a substrate, it is particularly
After long-term use of up to 8,000 hours, the difference in emission deterioration was obvious.

The reason why the cathode for electron tubes of the present invention is able to maintain the above-mentioned excellent characteristics, which are higher than those of conventional products, is considered to be as follows.

Iron and aluminum are first layered on the fi1 substrate.

Titanium, ! 1; A mixture of at least one of I and scandium oxide is deposited, and an electron emitting material layer made of an alkaline earth metal oxide containing at least barium is further deposited thereon. The presence of metals such as iron and copper in the one-layer mixture maintains high conductivity at the interface between the substrate and the electron emitting material layer, and as a result, maintains the electron emission characteristics especially under high current density and improves the emission characteristics. This will prevent deterioration.

The presence of the mixed layer of scandium oxide and metal between the fiil substrate and the electron emitting material layer improves the current density, which also contributes to the improvement of the above characteristics.

〔Effect of the invention〕

As described above, the cathode for an electron tube of the present invention has scandium oxide and iron on a substrate mainly composed of nickel.

It is made by depositing a mixture of metal powder such as copper, and then depositing an alkaline earth metal oxide containing at least barium on top of this, and the interposition of the scandium oxide and metal powder layer creates a bond between the substrate and electron radiation. The conductivity at the adhered interface with the material layer is maintained stably, and the current density is also improved, making it possible to reliably achieve a long life, especially under operation at high current densities of 2A/C or more. have an effect.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing a cathode for an electron tube according to an embodiment of the present invention, Fig. 2 is a sectional view showing a conventional cathode for an electron tube, and Fig. 3 is a life test time of a two-rod vacuum tube using the cathode for an electron tube. FIG. In each figure, the same reference numerals indicate the same or corresponding parts. Figure 1 Figure 2

Claims (1)

[Claims] Scandium oxide as a first layer on a substrate mainly composed of nickel, iron, aluminum, titanium, zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, rhenium, osmium, iridium, platinum, palladium, rhodium, gold, A mixture layer containing at least one of vanadium, chromium, manganese, copper, zinc, bismuth, indium, and silicon is deposited, and an alkaline earth metal oxide containing at least barium is further coated on the first mixture layer. A cathode for an electron tube, comprising a deposited electron emitting material layer.