JPS62246222A - Chthode for electron tube - Google Patents

Abstract

PURPOSE:To prevent the peeling of an electron emissive material by coating a substrate with the electron emissive material layer which has barium- containing alkaline earth metal oxide as a principal component and contains the predetermined weight percentage of rare earth metal oxide with predermined mean particle size. CONSTITUTION:The upper face of the bottom part of a substrate 1 is coated with an electron emissive material layer 2 which has alkaline earth metal oxide 11 as a principal component containing barium at least and besides strontium or/and calcium and contains 0.1-20 weight percentage of rare earth metal oxide with mean particle size of 4.5 mum or less such as scandium oxide, yttrium oxide, etc.. Thereby it is prevented that interlayer composed of compound oxide is concentrated and formed in the neighborhood of the interface between the conductor and the electron emissive material layer 2 under high density current. Stable emission characteristics can be obtained for many hours and besides the peeling of the electron emissive material can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a cathode for a cathode used in a TV cathode ray tube or the like, and particularly to an improved Cζ of a 1ζ electron emissive material layer.

[Conventional technology]

Figure 2 shows a cathode used in conventional TV cathode ray tubes and camera tubes.
IIi Melon-containing bottomed S juice whose main component is nickel - (21 is deposited on the bottom surface of this substrate, contains at least barium (Ba), and 1ζ strontium (S)
r) or/and an electron emitting material j1, (3+) made of an alkaline earth metal oxide containing calcium (Ca). This is for emitting thermoelectrons from the material layer (2).

In the electron tube cathode 1ζ configured in this way, the base (
The electron emitting material layer (2) is deposited on the layer (1) as follows. First, alkaline earth metals (Ba, S
A suspension consisting of a carbonate of r, Ca) is applied to the substrate (1) Iζ and heated with a heater (30ζ) during the vacuum evacuation process.At this time, the alkaline earth metal carbonate is oxidized. After that, a part of the alkaline earth metal oxide is reduced to have semiconducting properties. An electron emitting material layer (2) consisting of the above is deposited.

In this activation step 1ζ, a part of the oxide of alkaline earth gold 14 undergoes 1ζ reaction as follows.

In other words, reducing elements such as silicon and magnesium contained in the substrate (1) are transferred from the diffusion group ζ to the interface 1ζ between the alkaline earth metal oxide and the substrate (1), and react with the alkaline earth metal oxide. do. For example, if barium oxide (Bad) is used as the alkaline earth oxide, it undergoes a 1ζ reaction as expressed by the following formula (1) (2+).

BaO+1/2Si = Ba+1/2SiO2・(
1) BaO+Mg = Ba+ MgO-(2+ As a result of this reaction, a part of the alkaline earth metal oxide deposited on the substrate (1) is reduced, becoming an oxygen-deficient semiconductor, and the cathode temperature is 700~soo. 0 at operating temperature of 'c
．． An electron emission of 5 to 0.8 A/d will be obtained. However, with the electron tube cathode lζ formed in this way, it is impossible to obtain a current density higher than 0.6 to 0.8 A/d in electron emission. The reasons for this are as follows. In other words, alkaline earth gold
^ When a part of the oxide is subjected to a reduction reaction, the above (11 (2)
As is clear from Equation 1, SiO2, MgO or BaO,
A composite oxide layer (intermediate layer) of SiO2 is formed, and this intermediate layer becomes a high-resistance layer and obstructs the flow of current. 2) It is thought that sufficient barium (Ba) is not produced because it prevents the barium from diffusing to the surface side.

In addition, as a conventional cathode for electron tubes, JP-A-69-209
Publication No. 41 fζ has the same structure as the one shown in Figure 2 above, and in order to obtain rapid action of the cathode, the plate thickness of the tζ substrate (1) is made thinner, and the NA ceramic of the reducing agent during its life is reduced. In order to prevent this and to prevent a decrease in the strength of the substrate (1), a substrate (1) containing Iζ lanthanum dispersed in the form of LaNi5 and Lag's is shown.

[Problem that the invention seeks to solve]

In the electron tube cathode constructed in this way, near the interface between the lζ substrate (1) and the electron emitting material (21),
In particular, the nickel grain boundary near the surface of the substrate (1) and the position fζ about 10 μm inside the electron emitting material layer (2) from the above interface.
Because the above-mentioned intermediate layer segregates, the flow of current and the diffusion of reducing elements toward the surface of the electron emitting material layer (21) are hindered.
There was a problem that the current density could not be lowered.

In addition, in the latter case, 1ζLaN1a and La g
Two sacells containing os, (y) L, aN in the substrate (1)
Variations in the content of i5 and Lag's were likely to occur.

This invention has been made in view of the above-mentioned points, and prevents the formation of an intermediate layer made of a composite oxide in a concentrated manner near the interface between the substrate and the electron emitting material layer under high current density. The object of the present invention is to obtain a highly reliable cathode for an electron tube that has stable emission characteristics over a long period of time and does not cause peeling of electron emitting material.

[Means for solving problems]

The cathode for an electron tube according to the present invention has an alkaline earth metal oxide containing at least barium as a main component, and has a
An electron-emitting material 1- containing a rare earth metal oxide having an average particle size of 4.5 μm or less at 201g% is formed into a 1> mound on a substrate mainly composed of nickel.

[Effect]

In this invention, 0 contained in the electron emitting material layer
, when a rare earth metal oxide with an average particle size of 4.5μ or less at 1 to 20% is activated to form an electron emitting material layer on a substrate, the carbonate of the alkaline earth metal decomposes. edge,
Alternatively, it prevents the oxidation reaction of the Ill'Xtζ substrate in which barium oxide undergoes a dissociation reaction during operation as a cathode, and also prevents the rare earth metal oxide from dissociating to form a solid solution layer of Ni and rare earth metal over the entire surface of the substrate. Since it is formed by
An intermediate layer made of a composite oxide containing a reducing element fζ is prevented from being intensively formed near the interface between the substrate and the electron emitting material layer, and is dispersed within the intermediate 1 m 8 m electron emitting material layer. It is. Furthermore, the effect of preventing the peeling phenomenon of the electron emitting material j1 from the base metal at a high current density of 1ζ is further improved.

[Implementation row]

An embodiment of the present invention will be described below with reference to FIG. 1. In FIG. 1ζ, (2) is the bottom upper surface 1 of the base (1)
scandium oxide, which is deposited on ζ and whose main component is an alkaline earth metal oxide υV which contains at least barium and also contains strontium or/and calcium, and has an average particle size of 4.6μ or less in an amount of 0.1 to 20% by weight; It is an electron emitting material layer containing rare earth metal oxides such as yttrium oxide.

Next fζ, in the electron tube cathode configured in this way Eζ,
To explain the method 1ζ of depositing the electron emitting material layer (2) on the substrate (1), first, scandium oxide powder of ternary carbonate 1ζ of barium, strontium, and calcium is added to a desired weight of 96 (the above ternary carbonate is All of the oxides (1ζ by weight) are added and mixed to create a suspension. This feeling 1112 is applied to the substrate (1) whose main component is nickel.
It is applied to a thickness of about 80 microns from the spray Iζ, and then the electron emitting material layer (21 is applied to the base (1).

Here, in order to investigate the effect of the particle size of scandium oxide powder, we first used 1ζ, a purchased Sc2Ua powder (Research
The particle size of hChemical Corp-purity 99.9%) was not adjusted and the 5C20B mixed suspension (SC
2σ10% by weight) and completed a cathode for an electron tube. This cathode for an electron tube was subjected to a life test at various current densities, and peeling of the electron emitting material from the Ni substrate after 6000 hours of operation was investigated. The results are shown in FIG. Here, the horizontal axis is the operating current density of a conventional color TV, 0.66 A/r-4.
It is expressed as a relative current density when is set to 1.

Note that the average particle size (particle size when the particle size distribution is 60%) of the 5C208 powder at this time was 8.0 μ. When the relative current density exceeds 8.1, it is recognized that the frequency of the above-mentioned peeling phenomenon tends to increase.

Next, the average particle size of the 5C20B powder was adjusted using an ultrafine pulverizer such as a fine micro mill, and a suspension containing 1ζScgOaIO by weight was similarly prepared by using the purchased 5C20B powder described above with a relative current density of 4. Figure 4) shows the results of investigating the frequency of occurrence of the exfoliation phenomenon of the electron emitting material and the relative value of the emission current (the value at 0 hours of operation is taken as 100%) after 6000 hours of operation.

When the average particle size of the Sc gos powder is 4.5μ or less, no peeling occurs, and the emission current maintenance characteristics are greatly improved. Special 1ζ average particle size 8. Below θμ, extremely good characteristics are exhibited.

The reason for such excellent characteristics is considered to be as follows. Sc 2011 in the electron emitting material dissociates during operation to form a Ni-5c @ solution or intermetallic compound 11 on the surface of the Ni base metal, and this Ni-8c layer forms a layer near the interface between the Ni base metal and the electron emitting material. BaS io++ΔM at
This suppresses the formation of an intermediate layer of gO5in2, maintains a sufficient emission current, and improves the adhesion between the electron emitting material and the Ni base metal. However, the Ni grain size of the Ni base metal is large, several microns in lO, but many Ni crystal grains are several microns in diameter.
Therefore, when the average particle size of the 5C201 powder is less than 4.delta.μ iζ, N i -8 cm is formed on the surface of most Ni crystal grains, and the above effect becomes remarkable 1ζ.

Note that in the above Example) ζ, the case where Sc gos was used as the rare earth metal oxide was explained, but although similar effects were obtained with other rare earth metal oxides, especially tζ SC
The effect was remarkable for gOs, YgOs, and Ce20s+c.

〔Effect of the invention〕

As described above, this invention provides an alkaline earth metal oxide P! containing at least barium that is deposited on an iζ substrate!
0.1 to 20% in the electron emitting material layer containing A as the main component
Because it contains rare earth metal oxides with an average particle size of 4.5μ or less, the current density is 2 to 6 times higher than that of the conventional 1ζ, which does not contain the electron emitting substance atζ. This has the effect of providing a highly reliable cathode for an electron tube that has a long life under Ii operation, is inexpensive, has few restrictions on manufacturing, and has high reliability.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view showing a conventional electron tube cathode, and FIG. 8 is a relative wttf
FIG. 4 is a diagram showing the relationship between the rt density and the frequency of exfoliation of the electron emitting material, and FIG. 4 is a diagram showing the relationship between the Sagos average particle diameter, the frequency of exfoliation of the electron emitting material, and the emission current ratio. In FIG. 1ζ, (1) is a base body, and t21 is an electron emitting material layer. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 0.1 to 20% by weight of a rare earth metal oxide with an average particle size of 4.5μ or less, which is mainly composed of an alkaline earth metal oxide containing at least barium, on a substrate mainly composed of nickel.
A cathode for an electron tube, characterized in that an electron emitting material layer containing an electron emitting material is deposited thereon.