JPS63143718A - Manufacture of multi-layer cathode sleeve - Google Patents

Abstract

PURPOSE:To enable a multi-layer cathode sleeve for a long life oxide cathode to be obtained by forcibly pressing a cup-state body structure to a cylindrical sleeve body structure by applying pressure to both body structures made unitedly. CONSTITUTION:A cylindrical sleeve body structure 2 which is made to be a substrate metal is formed by only a nickelchrome alloy and furthermore a cup-state body structure 1 having a whole shape adaptable to a tip opening part of the cylindrical sleeve body structure is formed and prepared by only a cathode nickel. In this case a mouth edge of the cup-state body structure 1 has a ring-state expansion part 1a. The cup-state body structure 1 of nickel is engaged and united with a tip closing part of the cylindrical sleeve body structure 2 of the nickel-chrome alloy, placed on an under side die 3 of a super hard metal of a pressure device, an upper side die 4 of the super hard metal is made to descend in a moment, and thereby a shockingly high pressure F is applied to the cup-state body structure 1. A cathode sleeve in which both body structures are firmly united is obtained with the cup-state body structure 1 forcibly pressed in or pressed to the cylindrical sleeve body structure 2.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a cathode sleeve for an oxide cathode in an electron tube, particularly for a cylindrical indirectly heated oxide cathode using a clad material made of a nickel-chromium alloy such as nickel. The present invention relates to a method of manufacturing a cut sleeve.

[Prior art]

As a practical thermionic emitting cathode in an electron tube,
In addition to bulk materials such as tungsten and lanthanum polide, composite materials in which the work function ρ of the cathode forming substance is effectively lowered are used. In the cathode made of such a composite material, a monoatomic layer of alkali metal, alkaline earth metal, thorium, zirconium, etc. is adsorbed on one main surface of a base metal such as nickel, and the work function is increased by the dipole action of this adsorption layer. A cathode coated with a single atomic layer of strontium oxide, a cathode with barium oxide sealed inside porous tungsten, and a solid solution layer of semiconductor such as strontium oxide or barium oxide coated on one main surface of the base metal to release free tungsten. There is an oxide cathode whose work function φ is lowered by the impurity level created by barium metal. This oxide cathode is used in cathode ray tubes, which are the main application of electron tubes, especially T
This is the most commonly used type of V monochrome or color picture tube, and its typical structure is, for example, as follows. That is, a thermoelectron emitting material such as barium oxide is coated on the top end surface of a cylindrical cathode sleeve whose base metal is nickel to form the semiconductor solid solution layer, and a tungsten wire is placed inside the cathode sleeve. It has a configuration in which it is helically wound and insulated from the cathode by sintering alumina and provided with a heater.

By the way, in order to be able to supply a constant amount of reducing agent, which is a dominant factor in electron radioactivity and its lifetime, in an oxide cathode over a long period of time, the cathode sleeve is made of a bimetallic structure of nickel and nickel-chromium alloy. Generally, the mechanism of thermionic emission in such oxide cathodes is that barium oxide is
(1) thermal dissociation, or (II) electric field dissociation, or chemical dissociation with a reducing agent such as silicon, magnesium, or tungsten contained in the base metal at the interface with the base metal. It is explained that barium is generated, and this metal barium becomes an active center and electrons are emitted, but among these, the chemical dissociation of [1ii) is the dominant factor, for example, RCA R
EVIEW, Vol. 45. SEPTEMBER.

1984, p. 379"Operating Mech
anism of theone-piece cat
It is described in many literatures such as "One Piece Spring Cathode Actuation Mechanism", by T. CHIANG and J. J. MALEY.

According to the analysis in these documents, the consumption of the reducing agent mentioned above is directly related to the lifetime of the oxide cathode. Therefore, it may be possible to pre-contain the amount of reducing agent necessary to complete the specified life in the base metal, but the reducing agent content of the base metal itself is within a certain limit (generally, 0.1
% or less), an unnecessary amount of excess barium is produced, which evaporates, resulting in excessive consumption of barium oxide in the oxide, which actually shortens the service life.

That is, the amount of reducing agent required to generate enough metallic barium to saturate the entire volume of the porous oxide coating at a given temperature can be supplied to the interface for as long as possible. Doing so is the key to improving lifespan.

However, in a bimetallic cathode sleeve, the interface with the oxide coating is normal cathode nickel and contains normal amounts of reducing agents such as silicon and magnesium; When the consumption of the reducing agent reaches a certain level, at that point chromium selectively diffuses from the nickel-chromium layer and reaches the interface, and further diffuses into the oxide coating in the vapor phase, causing the barium oxide chemical reaction. This will promote dissociation.

That is, to explain the manufacturing process of this type of cathode sleeve and its final structure with reference to FIGS. , laminated together to prepare a sheet of bimetallic structure as shown in Figure 7 (ta), and punching out from this sheet a disk having an appropriate size and shape determined by the size of the cathode sleeve. A press molded body as shown in FIG. 7(b) is formed by a process such as a transfer press method. The outer surface of this compact is entirely made of nickel, while the inner surface is entirely made of a nickel-chromium alloy. Subsequently, only the cup-shaped portion including the top of the press-formed body was coated.
For example, if a negative type photoresist is applied and exposed to ultraviolet light, the result will be as shown in FIG. 7(C). continue,
By immersing it in an etching solution containing dilute nitric acid, only the exposed nickel layer was dissolved, and the bimetallic nickel-chromium layer was exposed in areas other than the solidified photoresist (Fig. 7 1d). get. Therefore,
After cleaning to remove the solidified photoresist and etchant, only the cup-shaped portion at the top had a bimetallic structure of nickel and nickel-chromium alloy, and the other peripheral surfaces were composed of a single layer of nickel-chromium alloy. The one-piece bimetallic cathode sleeve of FIG. 7(e) is obtained.

[Problem that the invention seeks to solve]

As you can see from the above manufacturing process, the conventional one-piece
For bimetallic cathode sleeves, a resist process, an etch process, and a resist and etchant cleaning process are essential. Moreover, in the final cleaning process for removing etchant, if the etchant is cylindrical with a closed end, there is no guarantee that the etchant will be completely removed. The undesirable result is that the cathode function is significantly impaired and its lifespan is significantly shortened.

[Means for solving problems]

The present invention is directed to solving the above-mentioned problems in the prior art, by supplying a constant amount of a reducing agent over a long period of time, which is a dominant factor in the electron radioactivity and lifetime of an oxide cathode for an electron tube. Regarding cathode sleeves with a so-called bimetal structure that can improve lifespan, by eliminating the need for the resist process, etching process, and etchant cleaning process that were considered indispensable in conventional methods, the function as a cathode can be reduced over time. To provide a method for manufacturing a glazed cathode sleeve, which makes it possible to significantly extend the life of the glazed cathode sleeve, and further extend this manufacturing method to provide a method for manufacturing a multilayered cathode sleeve. The purpose is to

〔Example〕

Next, embodiments of the present invention will be described with reference to FIGS. 1 to 6.

1(a) to (eJ) embody the present invention. Each step in the manufacturing method of a two-piece bimetallic cathode sleeve is shown. In this embodiment, as in the prior art shown in FIG. Rather than molding the cathode sleeve from a bimetallic sheet of nickel and nickel-chromium alloy, the cylindrical sleeve structure 2 of FIG. As shown in (a) and FIG. 2, a cup-shaped structure 1 having an overall shape that can be adapted to the closed end portion of this cylindrical sleeve structure is prepared by molding only nickel for the cathode. The point is that the lip of this cup-shaped structure 1 has a ring-shaped enlarged part 1a.The present invention is characterized in that it starts from two pieces specially prepared in this way.

Next, as shown in Figure 1 (a), a nickel cup-shaped structure 1
is fitted into the closed end portion of the cylindrical sleeve structure 2 made of nickel-chromium alloy, and placed on the lower die 3 made of ultra-hard metal of the pressurizing device shown in FIG. 1 (dJ). Impulsively high pressure F is applied to this cup-shaped structure 1 by momentarily lowering the upper die 4 made of ultra-hard metal.

Then, the cup-shaped structure 1 is forcibly press-fitted or crimped into the cylindrical sleeve structure 2, and as shown in FIG. 1(e), a cathode sleeve in which both structures are firmly integrated is obtained.

As mentioned above, since the cup-shaped structure l has the enlarged portion 1a formed at its mouth edge, as shown in FIG. 1(d).
In the pressurizing step, the pressure is applied to this enlarged portion 1a. The pressure is much higher than that on other parts of the cup-shaped structure, so that part of the ampulla 1a digs into the nickel-chromium alloy that is the base metal of the cylindrical sleeve structure 2 inside it. become. FIG. 3 is an enlarged view showing how the biting has occurred in this way.

The cathode sleeve shown in Fig. 1, manufactured by the above-mentioned processes, undergoes a heat treatment process in high-purity hydrogen before applying the oxide, which is usually performed, to selectively diffuse chromium and form a diffusion bond. This results in a two-layer structure. In this case, the biggest problem is the adhesive strength between the base of the cathode sleeve, that is, the cylindrical structure 2, and the cup-shaped structure 1 to which the oxide electron emitter is applied. In the method, as shown in Fig. 1 (al), the lip of the cup-shaped structure 1 has an enlarged portion 1a that is slightly thicker than the side surface, so this enlarged portion is removed by a forced press-fitting step using a pressurizing device shown in Fig. tdl. A part of the portion 1a bites into the side wall of the cylindrical sleeve structure 2 as shown in FIG.
This ensures sufficient adhesive strength. The present inventors were able to experimentally confirm this fact. That is, FIG. 5 was created based on this experimental data, and is a comparison chart of adhesive strength when a cup-shaped structure and a cylindrical sleeve structure are bonded by various methods. In FIG. 5, method I in the horizontal row uses a nickel cup-shaped structure without the enlarged portion 1a as in the present invention, and adheres this to a cylindrical structure similar to the present invention by spot welding. Then, 100 samples before heat treatment in the above-mentioned high-purity hydrogen are taken in the left column, and 100 samples after heat treatment are taken in the right column, and the car required to break the adhesion for each sample is as follows: The vertical axis represents the adhesive strength, and its frequency distribution is shown as dots. In the case of spot welding, it can be seen that the adhesive strength decreases due to heat treatment. The heat treatment conditions are as follows:
Similarly, for (2), the temperature was 900°C for 110 minutes. The next method is
Using each structure similar to (2), laser welding was performed, and the frequency distribution of adhesive strength was measured for 50 samples each before and after heat treatment, and the frequency distributions are shown on the left and right sides, respectively. There is not much change before and after heat treatment. Method ■ is the above-mentioned RC
Regarding a cup-shaped structure that is equivalent to the one published in AREVIEW, and has a cup-shaped structure without a ring-shaped enlarged portion on its mouth edge as shown in FIG. The frequency distribution of the adhesive strength is shown. In this case, the number of samples before and after the heat treatment was 100 each, and as mentioned above, it can be seen that the adhesive strength is significantly increased by the heat treatment. The last method (■) shows the frequency distribution of adhesive strength for the cap according to the method of the present invention, and since the cap of the present invention had an enlarged portion 1a at the mouth edge of the cup-shaped structure 1 as shown in FIG. The pressurization process causes a biting into the cylindrical sleeve structure, so that even before heat treatment, the adhesive strength is already higher than a cap without a ring-shaped bulge at the lip. What should be noted is that the adhesive strength becomes even more significant after heat treatment. The adhesion strength of the sample after heat treatment of the cathode sleeve obtained by the method of the present invention showed a much higher value compared to any of the above I, It is noteworthy that they are concentrated in more than twice as many areas. This is one of the features of the present invention. This is based on the use of a cup-shaped structure having an ampulla.

Furthermore, after heat treating the cathode sleeve according to the method of the present invention, the sleeve itself was coated with an ordinary oxide, and the life characteristics of the completed oxide cathode were conducted in a mounting test, and the life characteristics are shown in FIG.

This test was conducted under the condition of an accelerating voltage of 20% of the filament rated voltage. In Figure 6, the horizontal axis shows time (h),
The vertical axis indicates the descending layer of the maximum cathode current, and the life characteristics of the two-piece bimetallic cathode having the cathode sleeve obtained according to the present invention are compared with those of the conventional type. As described above, it is known that the two-piece cathode according to the present invention has an effective life that is approximately twice that of the conventional single-layer cathode, which is similar to the life pattern of the one-piece bimetallic cathode disclosed in the above-mentioned RCA REVIEW. have similar tendencies. From the experimental data, the present invention has 1
The cathode sleeve obtained by a manufacturing method different from that of the piece bimetallic cathode provides an excellent oxide cathode that can exhibit at least the same cathode performance over a longer lifetime. I understand.

Although the order of explanation has been reversed, Figure 4 shows the nickel and oxide coating for the cathode after the aoooo mounting test of the two-piece bimetallic cathode sleeve made by the manufacturing method of the present invention. This shows the diffusion pattern.

In the embodiments described above, only ordinary cathode nickel was used as the material for the cup-shaped structure for forming the cathode sleeve. As described above, it is important for one embodiment of the present invention that the cup-shaped structure to be forcibly pressed into the closed end portion of the cylindrical structure made of a nickel-chromium alloy by the pressurizing process is made of nickel. However, if the constituent requirements stipulated in claim 1 are satisfied,
Furthermore, within the scope of the basic spirit of the present invention supported by the main text of the specification, the present invention can also be embodied in various improved aspects. For example, the following is one such improved embodiment.

As already mentioned, as a result of the chemical reaction between barium oxide in the oxide coating and a reducing agent such as silicon, magnesium, or tungsten, a layer of amphoteric compounds of silicon, magnesium, and barium (so-called interface) is formed in the base metal. are formed, but these amphoteric compounds generally have extremely high electrical resistance, so if we assume a diode consisting of only a cathode and an anode, a resistor will be inserted on the equal side. Moreover, as the life time passes,
As these reaction products build up, the isometric resistance increases over time, which is also a significant factor hindering the electron emission of oxide cathodes. Thus, in the present invention, such undesirable problems are also effectively solved by the following technical means. In other words, the controlling factor for the electron radioactivity of the oxide cathode is the chemical reaction between the reducing agent contained in the base metal and barium oxide, and although it is inevitable that the reaction product remains, this By coming to the new understanding that as long as the reaction product is an electrical conductor, it must have no effect on its function as a cathode, and we found a way to solve the above problem. Through trial and error experiments conducted by the present inventors, it has been found that the metals barium, titanium, and zirconium are examples of elements that satisfy the above-mentioned condition that the reaction product becomes an electrical conductor. Taking zirconium as an example, as is well known, zirconium oxide has a temperature of about 70°C, which corresponds to the cathode operating temperature.
It is the only metal oxide that has approximately the same level of electrical conductivity as metallic zirconium at temperatures between 0''C and 800°C.

However, when zirconium forms an alloy with nickel, which is the cathode base metal, it becomes a so-called eutectic, but since this eutectic has the property of being physically brittle, it is used to obtain a cup-shaped structure. Therefore, press molding into a predetermined shape cannot be performed.

However, as a result of research by the present inventor, a multilayer structure was created in which zirconium, etc., was coated on the surface of nickel, which is normally used for cathode substrates, by sputtering, and then a cathode metal such as nickel was coated on top. If you keep it,
We came to the realization that it could be easily press-molded. Thus, a cup-shaped oxide-coated support structure press-molded from this multilayer structure and a cylindrical nickel-chromium alloy cylindrical structure were prepared, and the subsequent steps were carried out as in the first embodiment described above. Accordingly, in the two-piece multilayer cathode sleeve obtained by processing by applying the manufacturing method of the present invention, zirconium reaches the aforementioned reaction product layer (interface) by diffusion after a predetermined life time. This reduces the electrical resistance of the interface, allowing oxide cathodes using this multilayer cathode sleeve to maintain high levels of electron emission for extremely long periods of time, further extending the useful life of the cathode. be done. Although a detailed description will be omitted, the effects comparable to those described above for zirconium are found in barium metals and titanium, as well as in composites of zirconium, barium metals, and titanium. I was able to confirm.

〔Effect of the invention〕

As is clear from the above description, the present invention has the following remarkable effects. In other words, the known one-piece bimetal
Prior art methods for manufacturing cathode sleeves required chemical treatments such as photoetching steps and etchant removal/cleaning steps, which can shorten cathode life if even trace amounts of treated materials remain. However, in the present invention, at least in terms of the macroscopic structure, a two-piece ψ multilayer cathode sleeve similar to this one-piece bimetallic cathode sleeve is freed from chemicals harmful to the life of the cathode. It can be manufactured reliably and highly efficiently by a mechanical pressurization process without manual processing, resulting in high productivity and low cost. In addition, when an oxide cathode is formed using the two-piece multilayer cathode sleeve manufactured by the manufacturing method of the present invention, the function itself as a cathode, which mainly uses electron radioactivity, cannot be achieved by the conventional method. Peace Bimetal
Even if it is substantially equivalent to an oxide cathode that uses a cathode sleeve, it does not require chemical treatment, which inevitably leaves harmful substances for the duration of electron radiation. It has a much longer lifespan than a cathode, and there is no variation in individual lifespan characteristics. In addition, in the manufacturing method of the present invention, since the mouth edge of the cup-shaped structure is formed into a ring-shaped enlarged portion, this enlarged portion is strongly bitten into the circumferential side of the cylindrical sleeve structure during the pressurizing process. By increasing the adhesive strength and applying a subsequent heat treatment process, which is itself unusual, this adhesive strength can be further enhanced, making it possible to create a cathode sleeve that is highly useful for oxide cathodes. It can be realized. Furthermore, according to the present invention, as a material for obtaining a small cup-shaped structure by press molding, a layer consisting of at least one of metal barium, zirconium, or titanium is sandwiched in the middle, and nickel layers are provided on both the upper and lower surfaces. A cup-shaped structure formed from the laminate having a ring-shaped enlarged portion on the rim is forcibly bonded to a cylindrical sleeve structure of nickel-chromium alloy by applying pressure, thereby producing a two-heath multilayer structure. In this case, in particular, multilayer cathode sleeves are produced, so that in oxide cathodes using cathode sleeves obtained in this way, zirconium, metallic barium, or titanium forms a reactive composition layer over time. Provides a cathode sleeve for oxide cathodes that acts to reduce the electrical resistance of the interface stand and thus can sustain high levels of electron radiation for extremely long periods of time, further extending its useful life. be done.

Note that when using the above-mentioned laminate in which an intermediate layer made of at least one of metal barium, zirconium, or titanium is bonded between two nickel layers, the tip of the cylindrical sleeve structure into which the cup-shaped structure is to be fitted is not necessarily It does not have to be a closed part as in the embodiment shown in the paper, but even if it is an open part, the desired effect can be sufficiently achieved.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(tel) of the accompanying drawings are drawings for explaining an embodiment of the method for manufacturing a two-piece multilayer cathode sleeve of the present invention, and FIGS. FIG. 1(e) corresponds to each step in the manufacturing method. FIG. 2 is an enlarged partial side view of the cup-shaped structure in the manufacturing method of the present invention, and FIG. 3 is a diagram showing the state of adhesion between the cup-shaped structure and the cylindrical sleep structure after forced press-fitting. FIG. 3 is a partial side sectional view. FIG. 4 is a chart of the diffusion pattern of chromium into the nickel and oxide coating for the cathode after a 5°00 hour mounting test of the two-piece bimetallic cathode sleeve manufactured by the method of the present invention. FIG. 5 shows experimental data for comparing the adhesive strength between the cup-shaped structure and the cylindrical sleeve structure in the manufacturing method of the present invention with that of the corresponding member of the prior art. FIG. 6 is a graph showing the life characteristics obtained from a mounting test of an oxide cathode having a two-piece bimetallic cathode sleeve made by the manufacturing method of the present invention. FIGS. 7(a) to 7(tel) show each step in a conventional method for manufacturing a one-piece bimetallic cathode sleeve. Substitute! A: 41”, 4.. rT: , lbu ・, 7.1-1゛ ≦ゝIh(lightゝ・′ Fig. 4

Claims (1)

[Claims] a cylindrical sleeve structure having a closure at its distal end; an outer surface whose general shape is adaptable to the shape of the distal closure of the cylindrical sleeve structure and to which an electron-emitting oxide layer is to be deposited; A step of individually molding and preparing a cup-shaped structure having a lip in which a ring-shaped enlarged portion is formed and made of cathode metal; a step of fitting and integrating the cup-shaped structure; and a step of forcibly crimping the cup-shaped structure to the cylindrical sleeve structure by applying pressure to both structures integrated as described above; A method for manufacturing a multilayer cathode sleeve for an oxide cathode, comprising: