JPS5838435A - Oxide cathode structure - Google Patents

Abstract

PURPOSE:To enhance the electron emission characteristic of the captioned structure and thereby extend the life thereof, by making the inside oxide particles of reducing agent to be dispersed within the specified range from the surface of a cathode substrate on which the electron emission substance is to be spread. CONSTITUTION:Carbonate of an alkaline earth metal is applied on a cathode substrate made of Ni base alloy containing a trace amount of reducing agent and said coated carbonate is heated under vacuum, decomposed, and inverted into an oxide, which is used as an electron emission substance. Here, in the atmosphere whose partial pressure of oxygen is suitably controlled, the cathode substrate containing the reducing agent is subjected to heat-treatment and the reducing agent is forced to be internally oxidized and to be dispersed as oxide particles. In this case, by selecting the suitable oxidizing conditions, the internal oxide particles of said reducing agent are dispersed within 10mu, at least 3mu from the surface of the cathode substrate. By doing this, on the surface of the cathode substrate, the formation of an intermediate layer which deteriorates the electron emission characteristic can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a single oxide electrode structure suitable for use in cathode specimens for electron tubes, particularly cathode ray tubes such as color cathode ray tubes.

In a typical oxide cathode, carbonate salts of alkaline earth metals such as barium, strontium, and calcium are coated on a cathode substrate made of a nickel-based alloy to which a reducing agent has been added, and this is heated in a By heating, oxides (dicomposed and converted) are used as electron-emitting substances.Reducing agents include silicone, magnesium, zirconium, and tungsten.

Aluminum, titanium, etc. are widely used. These balancing agents are used during the electron beam movement in order to activate the electron emitting material and achieve good electron emitting properties.

At the same time, these reducing agents also react with electron-emitting substances,
It is called the nT sublayer and is the cause of the formation of a high-resistance layer without having a negative effect on electron emission.

Figure 1 is a cross-sectional view of the conventional oxide cathode structure, showing the middle part (
It is believed that 14 is formed between the XI and the cathode substrate α stage.

Intermediate j4 generally has the effect of increasing the resistance and lowering the electron emission ability, and at the same time, it also causes the separation of electron emission vIJ* from the cathode substrate.

The degree of production depends on the strength of the reducing agent and its content. Generally, as the amount of reducing agent increases, the degree of tearing becomes more pronounced as the intermediate layer is formed.

Therefore, in the case of a gruesome substrate for color cathode ray tubes, when magnesium and silicone are combined and separated as reduction agent 11, the reducing agent should be kept at about 0.1% by weight or less, and when tungsten is added, the reducing agent should be kept at 4°C IJ or less. It is generally used in a controlled manner.

The mechanism of intermediate layer generation and growth can be considered in three stages as follows. That is, (1) oxidation of the reducing agent on the surface of the cathode substrate due to the generation of carbon dioxide gas during the decomposition of the electron-emitting substance from the alkaline earth metal carbonate to the oxide, and the formation of a composite oxide with the electron-emitting substance. formation.

(II) Oxidation of the reducing agent and formation of a composite oxide with the electron-emitting substance during the reduction of the electron-emitting substance during operation.

(1) Oxidation of the reducing agent and formation of a composite oxide with the ``16-element emitting substance'' due to deterioration of the vacuum level (particularly increase in oxygen pressure) during operation.

It is.

Among the above conditions, the most severe condition for forming an intermediate layer on the surface of the cathode substrate for the reducing agent is (1). [11] For example, when a reducing agent is used to cause a slight deviation from the stoichiometric composition of barium oxide, Y(j
This is because in normal cases, as long as the getter device is installed in the electron tube and performs the getter function, there is hardly any problem.

The present invention improves the electron emission properties by preventing the formation of an oxide layer on the surface of the cathode substrate of the reducing agent that is accompanied by carbon dioxide residue during the decomposition of alkaline earth metal carbonate into oxides. The purpose is to prevent the formation of an intermediate layer that impairs the energy efficiency, and to provide an oxide layer with excellent electron emission characteristics and a long life.

That is, at least when the alkaline earth metal carbonate is decomposed into an oxide, an active reducing agent is substantially added to the inside of the cathode substrate surface and the vicinity of the next surface where the alkaline earth metal carbonate is attacked. This prevents the formation of an intermediate layer on the surface of the cathode substrate due to carbonate decomposition (reaction between carbon dioxide generated from two processes and the reducing agent).

As a result, after carbonate decomposition, the reducing agent inside the cathode substrate is efficiently supplied for activation to produce excess barium in the electron-emitting material, resulting in a short and long electron-emitting property. A long-life oxide cathode structure is now possible.

The present invention ('-) As a means for producing such a one-shima polar substrate, (
1) Free evaporation of the reducing agent from the layer near the surface by heating, (11) Pure nickel coating method in which a pure nickel layer is formed by cladding or plating, (ii) The reducing agent in the layer near the surface is oxidized internally. An internal oxidation method, etc. that can be considered as a physical property is considered.However, methods (1) and (11) are sufficiently effective in realizing an uninvented cathode structure for the following reasons. Can not do it.

That is, according to method (1), Il of the reducing agent from the surface
(written by W. Jost; Diffusi
on Academic Press + 1960)
It has a distribution.

here, X is the distance π from the surface of the cathode substrate (thickness h); pi co Reducing agent first [concentration] ■) Diffusion coefficient t Heating time It is.

As can be seen from this formula, it is also possible to use 1 in the later examples.
- (1) With this method, it is not possible to create a layer in which the reducing agent is not substantially flat near the surface.In other words, the reducing agent becomes zero at the outermost surface and monotonically increases toward the center. Therefore, when carbonate, an electron-emitting substance, is decomposed, the reducing agent easily diffuses to the surface, resulting in the formation of an intermediate layer on the surface or very close to the surface. , unable to achieve the goal.

In addition, in the case of cladding, plating, etc. in method (11), heating in hydrogen or an inert atmosphere may be used to remove processing materials, clean the surface, and degas from the bonding interface. It is required even before use.

At that time, the internal reducing agent diffuses into the surface coating material (diffuses, peels off,
Samurai would no longer consider it to be pure nickel material. Conversely, heat treatment at a temperature at which secondary diffusion does not substantially occur cannot achieve sufficient effects such as removing processing strain or purifying the surface layer.
It is unreasonable to use such materials as part of the cathode structure.

On the other hand, method ii+) sets the oxygen partial pressure to 1Il.
A back electrode substrate containing a reducing agent is heat-treated in a moderate atmosphere to oxidize the reducing agent inside the substrate,
This is a method of dispersing oxidized particles as oxide particles. According to this method, the depth of dispersion of oxidized particles can be easily controlled by appropriately selecting the enzyme partial pressure, heating temperature, processing strain of the cathode substrate material, etc. be able to.

In the cathode substrate obtained in this way, in which the reducing agent near fi + mi has been oxidized, there is no longer a reducing agent near the surface that is oxidized by carbon dioxide when the carbonate is decomposed, so that reduction on the surface of the electrode substrate is possible. In addition, the formation of a composite oxide with the material that emits radiation, that is, the formation of an intermediate layer, cannot occur. The ``electron'' U used in the oxide cathode structure of the present invention has excellent emission characteristics and a long life.

The present invention will be explained in detail below with reference to Examples.

Example 1) 0.03 MLi% magnesium and 0.03]
A nickel alloy rolled plate containing <fi silicon is pressed to a thickness Q, lll1t, and a diameter of 1.4 mm.
The disk was extracted by 1'J, washed with trichlorethylene and warm water, and annealed at 700° for 0.10 minutes in dry hydrogen. Next, a mixed gas of carbon dioxide and carbon dioxide (response/loss ratio 1:5) qJ in the mudflow, 1
Heat treatment was performed at 000° C. for 11 hours to internally oxidize the reduced layer from both surfaces of the disk to a depth of approximately 8 μm, as shown in FIG. As shown in Fig. 2, the disk in which the oxide particles are partially dispersed is coated with a sleeve (two pieces of indirectly heated cathode base material welded together, and an electron-emitting material 121 on the surface). After that, it was assembled into an electron gun of a color cathode ray tube, and a color cathode ray tube was produced by conventional methods such as evacuation, lighting (separation of electron-emitting substance from carbonate to e-oxide M I 7 (W), getter flash, aging, etc.).

A color cathode ray tube using a conventional cathode substrate that had not been subjected to internal oxidation treatment was similarly prepared and subjected to a strong Mill life test to compare the life characteristics.

These life curves are shown in FIG. In Figure 21, A
B is a life curve when a conventional cathode substrate is used, and B is a life curve when a cathode substrate according to the present invention is used, which shows the superiority of the present invention.

Example 2) A nickel alloy rolled plate containing 0.06 wt % magnesium and 0.06 i M % silicon with a thickness of 1 o.

Example 1) A disk with a diameter of 1.4 mTL was punched out.
Using the same method as above, a color cathode ray tube was fabricated by incorporating it into an electron gun as an indirectly heated cathode substrate. In this example, internal oxidation occurs at a depth of approximately 5 μm from the surface of the cathode substrate, and oxide particles of the reducing agent are observed as being dispersed.

In addition, a color cathode ray tube was fabricated using a conventional cathode substrate that had not been subjected to internal indoctrination treatment, and a forced life test was conducted to compare the life characteristics. These life curves are shown in FIG. In Figure 4, C is the conventional cathode substrate, D)
This is a life curve when the cathode substrate according to the present invention is used.

As in Example 1), the backward nature of the present invention is demonstrated.

In Examples 1) and 2), only the results were shown where the mixing ratio of oxidized carbon and dillidized carbon was 1:5 and internal oxidation treatment was performed for 100''0.60 minutes, but the mixing ratio, temperature.

Internal weighting of % freshness was performed by changing the time little by little. As a result, it was found that a cathode substrate in which an area within 10 μm or at least 3 μm from the surface was internally treated had a longer lifespan than a conventional cathode substrate.

These internal liquefaction treatments can be confirmed by polishing or etching the cross section of the negative substrate and then using an optical microscope or a scanning electron microscope.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional oxide cathode structure, FIG. 2 is a cross-sectional view of the nip part of the r-grained cathode structure of the present invention, and FIGS. This figure shows the results of a forced life test of a color cathode ray tube using an oxide cathode structure. If, 21... Electron emitting material 12... Intermediate layer 13.23... Cathode substrate 22... Internal oxide particle (7317) Agent ㅅP Physician Nori Kon O Yuuka 1
Name) Figure 1 Figure 2

Claims (1)

[Claims] In an oxide cathode structure comprising a cathode substrate made of a Ni-based alloy containing a small amount of a reducing agent, and an electron emitting material formed on the cathode substrate, the electron emitting material is coated on the substrate. A region within 10 μm, at least 3 μm from the surface of the self-propelled product (two agents W; e, R, 7 of the original agents)
An oxide M polar body characterized in that xl+ 11-oxide particles are dispersed therein.