JPH03219524A - Cathode for electron tube - Google Patents

Abstract

PURPOSE:To stabilize electron emission properties for a long duration under high current density by forming an intermediate layer containing a specified amount of nickel particles and scandium oxide between an electron emitting substance layer and a substrate. CONSTITUTION:An intermediate layer 2a is formed between an electron radiating substance layer 2 and a substrate 1. The intermediate layer 2a contains 5-20wt.% of nickel particles, oxides of alkaline earth metals including barium, and 0.1-20wt.% of scandium oxide. Composite oxide formation in the periphery area of in the interface of the substrate 1 is thus suppressed. Consequently electron emitting properties can be stabilized for a long duration even under high electric current density and a long life at high electric current is achieved.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is applied to cathode ray tubes for televisions, etc.
The present invention relates to an electron tube cathode that has a long life even at high current densities.

[Conventional technology]

Figure 5 shows the cathode of an electron tube used in conventional television cathode ray tubes and image pickup tubes. A bottomed cylindrical base made of nickel as a component, 2 is adhered to the bottom upper surface of this base,
The electron emitting material layer 73 made of an alkaline earth metal oxide containing at least barium (Ba) and also strontium (Sr) and calcium (Ca) is heated by a heater disposed within the base body 1. This is for emitting thermoelectrons from the electron emitting material layer 2.

In the electron tube cathode constructed in this way, the electron emitting material layer 2 is deposited on the base 1 as follows.

First, ternary carbonates of alkaline earth metals ((Ba, Sr,
A suspension consisting of Ca) Co, . At this time, the alkaline earth metal carbonate turns into an alkaline earth metal oxide. Thereafter, by reducing a part of the alkaline earth metal and activating it to have semiconductor properties, an electron emitting substance N2 made of an oxide of an alkaline earth metal is deposited on the substrate 1. .

In this activation step, a portion of the alkaline earth metal oxide reacts as follows. In other words, reducing elements such as silicon and magnesium contained in the substrate 1 move to the interface between the alkaline earth metal oxide and the substrate 1 by diffusion.
Reacts with alkaline earth metal oxides. For example, if barium oxide (BaO) is used as the alkaline earth metal oxide, it reacts as shown in the following formulas (1), (2), and (3).

2BaO+5i=2Ba+5iOz+
+ ・++ (DBaO+Mg=Ba+MgO−-(2
)4BaO+5i=2Ba+Ba2SiOs
・++ ++・(3) As a result of this reaction, substrate 1
A part of the alkaline earth metal oxide deposited on the top is reduced and becomes an oxygen-deficient semiconductor, and the cathode temperature is 700~
At an operating temperature of 800°C an electron emission of 0.5-0.8 people/CTM will be obtained.

[Problems to be Solved by the Invention] However, in the conventional electron tube cathode described above, the electron emission is 0.
．． A current density higher than 5 to 0.8 people/c+f1 cannot be obtained. The reason for this is that when a part of the alkaline earth metal oxide is reduced, the interface between the substrate 1 and the alkaline earth metal oxide layer is A complex oxide layer such as SiO2, MgO or Ba2SiO4 is formed on the substrate 1, and this complex oxide layer becomes a high resistance layer and blocks current flow. It is thought that this is because a sufficient amount of barium (Ba) is not formed because it prevents the diffusion of the electron emitting material layer 2 (Mg) to the surface side of the electron emitting material layer 2. That is, during electron tube operation, the composite oxide layer is formed 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 within the electron emitting material layer 2 about 10 μm from the interface. Due to the segregation, the flow of electrons 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 cannot be obtained under high current density.

This invention was made to solve the above-mentioned problems, and its object is to obtain a cathode for an electron tube that has stable electron emission characteristics over a long period of time under high current density.

(Means for Solving the Problems) A cathode for an electron tube according to the present invention has an electron emitting material layer mainly composed of an alkaline earth metal oxide containing barium deposited on a substrate mainly composed of nickel. In the cathode for an electron tube consisting of
It is characterized by forming an intermediate layer containing ~20% by weight of nickel particles, an alkaline earth metal oxide containing barium, and 0.1~20% by weight of scandium oxide.

[For production]

In this invention, since an intermediate layer made of the above components is formed between the electron emitting material layer and the substrate, it is possible to suppress the formation of a composite oxide layer near the interface of the substrate, and moreover, it is possible to suppress the formation of a composite oxide layer near the interface of the substrate. Longer life is possible.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure shows a cross-sectional view of the cathode for an electron tube according to the present invention.
Reference numeral 2a denotes an intermediate layer deposited on the bottom upper surface of the substrate 1, and this intermediate layer contains at least barium (Ba), and also strontium (Sr) and calcium (Ca).
The main component is an alkaline earth metal oxide containing 15% by weight of nickel particles (Ni) and 3% by weight of scandium oxide (Sc203). 2 is the above intermediate layer 2
An electron-emitting material layer is deposited on a and is made of an alkaline earth metal oxide containing at least barium and further containing strontium and calcium.

Next, a method for forming the intermediate layer 2a and the electron emitting material layer 2 described above will be explained. First, 3% by weight of scandium oxide powder (Sc203) is added to a ternary carbonate of Ba, Sr, and Ca, and 15% by weight of nickel particles are further mixed to create a suspension. This suspension is applied by spraying to a thickness of about 20 microns on the bottom upper surface of the substrate 1 whose main component is nickel, and a suspension of ternary carbonates of Ba, Sr, and Ca is applied on top by spraying to a thickness of about 60 microns. Apply in micron thickness. Thereafter, as in the conventional method, an activation process is performed to convert the carbonate into an oxide.

A diode vacuum tube was created using the electron tube cathode manufactured as described above, and a life test was conducted. The results are shown in the life characteristics in Figure 2. In addition, in the comparative example shown in FIG. 2, 3% by weight of scandium oxide powder (SczO: +
) mixed in a ternary carbonate of Ba, Sr, and Ca is applied to a thickness of approximately 80 microns by spraying, and then, as in the past, an activation process is performed to convert the carbonate into an oxide. The results of a similar test are shown.

As shown in Figure 2, the current density is about 4.5 times (2,97 people/ci) the current density of the conventional TV cathode, which is 0.66 people/ci.
When operated at 50% crR), the life of a conventional electron tube cathode was 4,000 hours (the life was defined as the time when the emission current decreased to 50% of the initial value), whereas the life of the example was more than 10,000 hours. Ta. Also, the lifespan of the comparative example is 8
It was 000 hours.

By the way, the reason why two layers 2 and 2a are provided on the base 1 is as follows. That is, scandium oxide powder (SC
203) The purpose of mixing is to suppress the above-mentioned complex oxide, and it is sufficient that it exists only in the vicinity of the substrate 1.

Furthermore, when nickel particles (Ni) are also contained in the electron emitting material layer 2, the concentration of barium (Ba) becomes relatively low, resulting in poor initial emission.

In this example, an example was shown in which 3% by weight of scandium oxide powder (SC203) and 15% by weight of nickel particles (Ni) were added; (Ni) 5 to 20
A similar effect was obtained even when the amount was added by weight%.

By the way, the reason why the concentration of scandium oxide powder (SC203) was set to 0.1 to 20% by weight is as follows.

In other words, as shown in the emission characteristics in Figure 3, 20
If more than % by weight is added, the amount of electron emission decreases, making it impossible to obtain the desired electron current. Further, if it is less than 0.1% by weight, the effect of suppressing the formation of a composite oxide layer is insufficient.

On the other hand, the reason why 5 to 20% by weight of nickel particles (Ni) is added is as follows. In other words, as shown in the emission characteristics in Part 4, when less than 5% by weight is added, the conductivity is not sufficiently improved, and when more than 20% by weight is added, the amount of electron emission decreases, making it difficult to obtain the desired electron current. This is so that you will not be affected.

〔Effect of the invention〕

As explained above, according to the present invention, 5 to 20% by weight of nickel particles, an alkaline earth metal oxide containing barium, and 0.1 to 20% by weight of scandium oxide are interposed between the electron emitting material layer and the substrate. By adding scandium oxide, it is possible to suppress the formation of a complex oxide layer, which is a high-resistance layer segregated near the substrate interface, and obtain sufficient emission characteristics under high current density. .

Further, high current and long life can be achieved.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an electron tube cathode according to an embodiment of the present invention, Fig. 2 is a life characteristic diagram of an example of the present invention, a conventional example, and a comparative example, and Fig. 3 is an emission characteristic diagram with respect to the content of scandium oxide powder. , FIG. 4 is an emission characteristic diagram with respect to the content of nickel particles, and FIG. 5 is a cross-sectional view of a conventional cathode for an electron tube. DESCRIPTION OF SYMBOLS 1... Base|substrate, 2... Electron emitting material layer, 2a... Intermediate layer, 3... Heater. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] In an electron tube cathode formed by depositing an electron emissive material layer mainly composed of an alkaline earth metal oxide containing barium on a substrate mainly composed of nickel, there is a gap between the electron emissive material layer and the substrate. 5-20% by weight of nickel particles, alkaline earth metal oxides containing barium and 0.1-20%
A cathode for an electron tube, characterized in that an intermediate layer containing % by weight of scandium oxide is formed.