JP3727519B2 - Sleeve for hot cathode assembly and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a hot cathode assembly sleeve used for an electron tube such as a color picture tube and a manufacturing method thereof.
[0002]
[Prior art]
In an electron tube such as a color picture tube, a hot cathode is used to emit an electron beam, and an impregnated cathode is known as a kind of the hot cathode.
[0003]
The impregnated cathode has been used for electron tubes such as traveling wave tubes and klystrons, but has recently been used in large-sized, high-definition color picture tubes, etc., taking advantage of the high current density characteristics of the impregnated cathode. .
[0004]
Such an impregnated-type cathode assembly is configured as shown in FIG. 1, and a short columnar cathode substrate 1 impregnated with an electron-emitting substance is accommodated in a bottomed short cylindrical cup 2, and the cup 2 Then, it is inserted into one end opening of the cylindrical sleeve 3 from the bottom side, and is fixed to the sleeve 3 with the cathode substrate 1 exposed. A heater 4 is built in the sleeve 3. The heater 4 is made of 3% rhenium-tungsten alloy wire, and its surface is coated with alumina as an insulator. Further, a dark layer made of a mixture of tungsten and alumina is coated on the surface of the alumina in order to improve thermal radiation characteristics. On the other hand, the sleeve 3 is coaxially supported and fixed to the center portion of the stepped cylindrical holder 5 via three ribbons 6. The sleeve 3 is provided with a flare (expansion) 3a at one open end so that the heater 4 can be easily inserted. The sleeve 3, the cup 2, and the three ribbons 6 are all made of tantalum, niobium, molybdenum, or an alloy containing at least one of them as a main component. A thin black film 7 is formed on the inner surface of the sleeve 3 so that the sleeve can efficiently absorb the heat generated from the heater. The sleeve 3 is an elongated pipe having a wall thickness of 15 to 20 μm, a diameter of 1.25 mm, and a length of 4.0 mm, for example.
[0005]
As a method of attaching a black film to such a sleeve, for example, there is the following method disclosed in JP-A-8-287824.
[0006]
That is, an aluminum thin film is deposited on the inner surface of the sleeve made of molybdenum by a sputtering method, and further, a first heat treatment is performed in a vacuum atmosphere at 600 ° C. for 30 minutes, and then in the same vacuum atmosphere. A secondary heat treatment is performed by heating at 800 ° C. for 1 hour. Subsequently, a final heat treatment is performed by heating at 10,000 ° C. for 1 hour in a wet hydrogen atmosphere to form a rough surface layer made of an intermetallic compound of aluminum and molybdenum, aluminum-molybdenum oxide, alumina, or the like. Since this rough surface layer has fine irregularities on the surface, there is an advantage that the heat absorption area is increased and the heat absorption is excellent.
[0007]
[Problems to be solved by the invention]
The conventional method of forming a black film on a sleeve is a method with a large number of steps and high cost in mass production.
[0008]
In addition, it is difficult to form a uniform black film on the entire inner surface of the sleeve.
[0009]
The present invention provides a sleeve for a hot cathode assembly having a simple process, low cost, high mass productivity, and a black heat-absorbing coating having a uniform and sufficient mechanical strength and heat resistance on the entire inner surface of the sleeve, and a method for manufacturing the same Is to provide.
[0010]
[Means for Solving the Problems]
The present invention relates to tantalum and tungsten or rhenium or a mixture of tungsten and rhenium, in which the black film formed on the inner surface of the sleeve constituting a part of the electron emission cathode has a fine crack structure or a fine uneven structure on the surface. It is a composite film.
[0011]
The composition of the black film is tantalum and tungsten or rhenium or a mixture of tungsten and rhenium in a mass ratio (tantalum: tungsten or rhenium or a mixture of tungsten and rhenium) (80:20) to (10:90). Range.
[0012]
Further, the sleeve material used is made of tantalum or an alloy containing tantalum as a main component, niobium or an alloy containing niobium as a main component, or molybdenum or an alloy containing molybdenum as a main component.
[0013]
Furthermore, although a sputtering method is used for the black coating film formation, the sputtering device, the sleeve placed between the sputtering anode and sputtering cathode is a method having the electrically insulated structure with respect to both electrodes.
[0014]
[Action]
According to the above means, a uniform black rough surface is formed on the entire inner surface of the sleeve.
[0015]
Further, since the formed black film has fine cracks or fine irregularities on the surface, the heat absorption area is increased, the heat absorption is excellent, the mechanical strength is sufficient, and the impregnated cathode assembly and heater It is possible to obtain a heat absorbing layer that does not peel off at the time of insertion, does not change the blackness even when a heater is inserted and is heated, and does not cause evaporation of the contained components.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 2 is a cross-sectional configuration diagram illustrating an example of a sputtering apparatus used for adhesion formation of a black film according to the present invention.
[0018]
As shown in FIG. 2, the sputtering apparatus is connected to the container 20, the rotating shaft 21, the sputtering anode 22 connected to the rotating shaft 21, the insulator 23 connected to the rotating shaft 21, and the insulator 23. Holding plate 24, target 25 serving as a sputtering cathode, magnet 26, shield plate 27 surrounding target 25, high-frequency power source 28 connected between container 20 and target 25, cooling water insertion port 29, The vacuum exhaust port 30 and the inert gas insertion port 31 are provided with a hole 24 a for arranging the sleeve 3 in a part of the holding plate 24.
[0019]
A target 25 serving as a sputtering cathode is a mixture of tantalum powder and tungsten powder in a mass ratio (tantalum: tungsten) (20:80), and may be used as a target in a powder state. Moreover, you may use as a target in the state which sintered powder.
[0020]
When performing sputtering using this sputtering apparatus, first, the sleeve 3 is inserted into the hole 24a provided in the holding plate 24, and the sleeve 3 is held in the hole 24a by the flare portion. Next, a high frequency voltage is applied between the sputtering anode 22 and the target 25 by the high frequency power source 28, cooling water is supplied from the cooling water insertion port 29, exhausted from the vacuum exhaust port 30, and discharged from the inert gas insertion port 31. Argon gas is supplied, and the holding plate 24 is rotated by the rotating shaft 21.
[0021]
By this sputtering, a composite film of tantalum and tungsten having a thickness of about 1 μm and a fine crack structure on the surface is formed on the inner surface of the sleeve 3.
[0022]
In this sputtering, a composite coating is formed only on the inner surface of the sleeve 3, and deposition of the composite coating on the outer surface is avoided.
[0023]
FIG. 3 shows an electron micrograph of a composite film of tantalum and tungsten formed on the inner surface of the sleeve 3 by the above-described method. The coating is a black rough surface having fine cracks on the surface. The mass ratio (tantalum: tungsten) was (20:80).
[0024]
4 is a method similar to the above using a sputtering apparatus shown in FIG. 2 using a target obtained by mixing tantalum powder and tungsten powder in a mass ratio (tantalum: tungsten) at (40:60). 2 shows an electron micrograph of a composite film of tantalum and tungsten formed on the inner surface of the sleeve 3 by coating, the coating is a black rough surface with fine irregularities on the surface, and the composition of the film is a mass ratio (tantalum: tungsten) (40:60).
[0025]
A composite film having such a fine crack structure or fine uneven structure is formed when the composition of the film is in the range of (80:20) to (10:90) at a mass ratio (tantalum: tungsten). However, the result of the experiment was confirmed. In addition, the composition is adjusted by adjusting the mixing ratio of the target material tantalum powder and tungsten powder in a mass ratio (tantalum: tungsten) in the range of (80:20) to (10:90). Easily possible.
[0026]
In the above embodiment, the target that is the material of the black film is formed by mixing tantalum and tungsten. However, in the present invention, rhenium or a mixture of tungsten and rhenium is used instead of tungsten. Similarly, a uniform black film could be obtained.
[0027]
Further, when a sputtering apparatus as shown in FIG. 2, that is, a sputtering apparatus having a structure in which a sleeve disposed between a sputtering anode and a sputtering cathode is electrically insulated from both electrodes, is used on the entire inner surface of the sleeve. The reason why a uniform black rough surface can be formed can be considered as follows.
[0028]
That is, when a sputtering apparatus as shown in FIG. 2 is used, during the sputtering operation, the inner surface of the sleeve that is in contact with the plasma and is electrically insulated is negatively charged, and therefore attracts positive ions, thereby It appears that a fluidized bed of positive ions is created in the space between the sputtering cathodes and this fluidized bed facilitates the movement of the sputtered particles, thus forming a uniform thin film over the entire sleeve inner surface.
[0029]
Further, when a tantalum and tungsten mixed material is used as a target material by using a sputtering apparatus as shown in FIG. 2, a black rough surface having a fine crack structure or a fine uneven structure is formed. It seems like.
[0030]
That is, it is known that a tantalum thin film generally formed by sputtering tends to crack when violently bombarded with ions or electrons, and the surface is often not smooth.
[0031]
In this embodiment, the sleeve disposed between the sputtering anode and the sputtering cathode is insulated from both electrodes, and is negatively charged during sputtering and bombarded by ions. It appears that tantalum having a fine crack structure or fine concavo-convex structure is formed and a black rough surface is formed.
[0032]
When sputtering is performed using tantalum alone or tungsten alone as a target material, a black rough surface having sufficient mechanical strength and having fine cracks or irregularities, as seen in this embodiment, is used. Couldn't get.
[0033]
As apparent from the above description, in the sputtering apparatus of FIG. 2 is a sleeve disposed between the sputtering anode and sputtering cathode is insulated with respect to both poles, further suitable equivalent voltage to the insulated sleeve It is clear that the same effect can be obtained even when bias sputtering is performed with application of.
[0034]
In the present embodiment, the high-frequency magnetron sputtering method is used. However, it is obvious that the same effect can be obtained by using other methods, that is, the high-frequency sputtering method, the magnetron sputtering method, and the DC sputtering method.
[0035]
Further, the thickness of the black film obtained in the present invention may be selected so as to be other than 1 μm in the present embodiment, that is, about 0.5 to 5 μm.
[0036]
In addition, the inner surface of the sleeve having the black coating formed in the present embodiment has a thermal radiation rate in the temperature range near 950 ° C., which is the operating temperature of the impregnated cathode, as compared with the sleeve not coated with the black coating. Has been found to be about 0.3 to 0.4 higher.
[0037]
The black coating according to the present invention is a heat absorbing layer that has sufficient mechanical strength, does not change its blackness even when it is heated by inserting a heater in the sleeve, and does not evaporate contained components.
[0038]
The sleeve having a black coating according to the present invention can be selected from tantalum or an alloy containing tantalum as a main component, niobium or an alloy containing niobium as a main component, or molybdenum or an alloy containing molybdenum as a main component.
[0039]
【The invention's effect】
As described above in detail, in the present invention, tantalum and tungsten, rhenium, or tungsten and rhenium having a fine crack structure or a fine concavo-convex structure on the inner surface of the sleeve constituting a part of the electron emission cathode are provided. A heat-absorbing black coating that is a composite film of the mixture is deposited by sputtering.
[0040]
Thus, according to the present invention, it has excellent mechanical strength and heat resistance, has an increased heat absorption area due to fine cracks or irregularities, has excellent heat absorption, and the blackness does not change and is contained There is an effect that a heat absorption layer free from metal evaporation can be obtained by a simple process with a low-cost and mass-productive method.
[Brief description of the drawings]
FIG. 1 is a diagram showing an impregnated cathode assembly to which the present invention is applied.
FIG. 2 is a cross-sectional configuration diagram showing an example of a sputtering apparatus according to the present invention.
FIG. 3 is an electron micrograph showing an embodiment of the present invention.
FIG. 4 is an electron micrograph showing an embodiment of the present invention.
[Explanation of symbols]
1 cathode substrate, 2 cup, 3 sleeve, 4 heater, 5 holder, 6 ribbon, 7 black coating, 22 sputtering anode, 23 insulator, 25 sputtering cathode (target).

Claims (4)

In the sleeve for a hot cathode structure in which a black coating is formed on the inner surface of the sleeve constituting a part of the electron emission cathode,
A sleeve for a hot cathode assembly, wherein the black film is a composite film of tantalum and tungsten or rhenium or a mixture of tungsten and rhenium having a fine crack structure or a fine uneven structure on the surface.   The composition of the black coating is such that tantalum and tungsten or rhenium or a mixture of tungsten and rhenium are in a mass ratio (tantalum: tungsten or rhenium or a mixture of tungsten and rhenium) and are (80:20) to (10:90). The sleeve for a hot cathode assembly according to claim 1, wherein the sleeve is in a range. In the sleeve for a hot cathode structure in which a black coating is formed on the inner surface of the sleeve constituting a part of the electron emission cathode,
The sleeve is made of tantalum or an alloy based on tantalum, or niobium or an alloy based on niobium, or molybdenum or an alloy based on molybdenum.
A sleeve for a hot cathode assembly, wherein the black film is a composite film of tantalum and tungsten or rhenium or a mixture of tungsten and rhenium having a fine crack structure or a fine uneven structure on the surface.   Using a sputtering apparatus having a holding plate arranged between the sputtering anode and the sputtering cathode and electrically insulated from both electrodes, the inner surface of the sleeve arranged on the holding plate has a fine crack structure or fine unevenness on the surface. A method of manufacturing a sleeve for a hot cathode assembly, comprising forming a black film comprising a composite film of tantalum and tungsten or rhenium or a mixture of tungsten and rhenium having a structure.

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