EP1302969B1 - Hülse für eine beheizte Kathode und Verfahren zu ihrer Herstellung - Google Patents

Hülse für eine beheizte Kathode und Verfahren zu ihrer Herstellung Download PDF

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Publication number
EP1302969B1
EP1302969B1 EP20010308682 EP01308682A EP1302969B1 EP 1302969 B1 EP1302969 B1 EP 1302969B1 EP 20010308682 EP20010308682 EP 20010308682 EP 01308682 A EP01308682 A EP 01308682A EP 1302969 B1 EP1302969 B1 EP 1302969B1
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EP
European Patent Office
Prior art keywords
sleeve
tungsten
sputtering
tantalum
rhenium
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP20010308682
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English (en)
French (fr)
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EP1302969A1 (de
Inventor
Teruo Tokyo Cathode Laboratory Co. Ltd. Yajima
Kohshi Tokyo Cathode Laboratory Co. Ltd. Furuya
Yasuhiro Tokyo Cathode Laboratory Co. Ltd. Tawa
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Tokyo Cathode Laboratory Co Ltd
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Tokyo Cathode Laboratory Co Ltd
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Publication date
Application filed by Tokyo Cathode Laboratory Co Ltd filed Critical Tokyo Cathode Laboratory Co Ltd
Priority to EP20010308682 priority Critical patent/EP1302969B1/de
Priority to DE2001615904 priority patent/DE60115904T2/de
Publication of EP1302969A1 publication Critical patent/EP1302969A1/de
Application granted granted Critical
Publication of EP1302969B1 publication Critical patent/EP1302969B1/de
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment

Definitions

  • the present invention relates to a sleeve for a hot cathode structure used in an electron tube such as a color CRT and a manufacturing method for such a sleeve.
  • a hot cathode In an electron tube such as a color CRT, a hot cathode is used for emitting an electron beam.
  • An impregnated cathode is one known type of hot cathode.
  • An impregnated cathode has been used for an electron tube such as a traveling-wave tube and klystron.
  • the impregnated cathode has also come to be used in a large size, high resolution color CRT or the like, taking advantage of the high current density characteristic of the impregnated cathode.
  • Such an impregnated cathode structure is constructed, for example, as shown in Fig. 1.
  • column-shapedcathode substrate 1 onto which an electron emission material is impregnated is stored in a cup 2 having a cylindrical shape and a bottom.
  • the cup 2 is inserted at one end, which is an opening, of a cylinder-shaped sleeve 3 from the bottom of the cup 2, and fixed to the sleeve 3 with the cathode substrate 1 in an exposed condition.
  • a heater 4 is built into the sleeve 3.
  • the heater 4 is constructed from a 3% rhenium-tungsten alloy wiring with an alumina coating at the surface for insulation.
  • a dark layer constructed from a mixture of tungsten and alumina is coated on the alumina surface.
  • the sleeve 3, on the other hand, is coaxially supported and fixed at the central section of a holder 5, which has a cylindrical shape with a step, via three ribbons 6.
  • a flare (widening) 3a is provided at one opening end of the sleeve 3 in order to facilitate insertion of the heater 4.
  • the sleeve 3, cup 2, and three ribbons 6 are all constructed from tantalum, niobium, molybdenum, or an alloy having at least one of these elements as the main constituent.
  • the sleeve 3 may be, for example, a thin pipe having a thickness of 15 to 20 ⁇ m, a diameter of 1.25 mm, and a length of 4.0 mm.
  • sputtering is used for adhering a thin film of aluminum to the inner surface of a sleeve which is constructed from molybdenum
  • a first heating process is performed wherein the sleeve is subjected to heating for 30 minutes at 600 °C under a vacuum atmosphere
  • a second heating process is performed wherein the sleeve is subjected to heating for 1 hour at 800 °C under the same vacuum atmosphere
  • a final heating process is performed wherein the sleeve is subjected to heating for 1 hour at 1000 °C under a wetting hydrogen atmosphere.
  • a rough surface layer including intermetallic compound of aluminum and molybdenum, aluminum-molybdenum oxides, and alumina is formed. Because the rough surface layer has micro-bumps at the surface, the heat absorption area is increased, and thus, the rough surface layer has an advantage that it has a good heat absorption characteristic.
  • the conventional method for forming a black coating on a sleeve requires many steps and is costly when mass-production is desired.
  • US-A-5762997 discloses a sleeve for a hot cathode structure forming part of an electron emission cathode which has a black surface formed on its inner surface.
  • the coating is a sintered layer containing tungsten.
  • One object of embodiments of the present invention is to provide a sleeve for a hot cathode structure and a simple, low-cost manufacturing method for such sleeve, suitable for mass production, wherein a black heat absorbing coating is formed at the entire inner surface of the sleeve with sufficient mechanical strength and heat endurance.
  • a black coating adhered and formed at the inner surface of the sleeve which constructs a portion of an electron emission cathode wherein said black coating is a composite film of tantalum and one of a) tungsten, b) rhenium, or c) a mixture of tungsten and rhenium, with a micro-crack structure or micro-bump structure.
  • the composition of the black coating is in a range of 80 : 20 to 10 : 90 in mass ratio of tantalum with respect to the tungsten, the rhenium, or the mixture of tungsten and rhenium (tantalum : tungsten, rhenium, or the mixture of tungsten and rhenium).
  • the material of the sleeve to be used is tantalum or an alloy having tantalum as the main constituent, niobium or an alloy having niobium as the main constituent, or molybdenum or an alloy having molybdenum as the main constituent.
  • a sputtering method is used for forming the black coating.
  • a sleeve placed between a sputtering anode and a sputtering cathode is electrically insulated from both electrodes.
  • a black, rough surface can be uniformly formed at the entire inner surface of the sleeve.
  • the black coating that is formed has micro-cracks or micro-bumps on the surface, the heat absorption area is increased, and, thus, the black coating has superior heat absorption characteristic and sufficient mechanical strength such that a heat absorption layer which does not peel off during the assembly of the impregnated cathode or during the insertion of the heater can be obtained. Moreover, the degree of blackness does not change when a heater is inserted and heat is applied, and the constituents do not vaporize.
  • Fig. 2 is a cross sectional view showing an example of a sputtering device used for adhering and forming a black coating according to the present invention.
  • the sputtering device comprises a container 20; rotational axis 21; a sputtering anode 22 which is connected to the rotational axis 21; an insulator 23 which is connected to the rotational axis 21; a retaining plate 24 which is connected to the insulator; a target 25 which forms the sputtering cathode; a magnet 26, a shielding plate 27 surrounding the target 25; a high frequency power supply 28 which is connected between the container 20 and the target 25; a coolant insertion inlet 29; a vacuum emission outlet 30; and an inert gas insertion inlet 31.
  • a hole 24a is provided at a portion of the retaining plate 24 for placing the sleeve 3.
  • the target 25 which forms the sputtering cathode is constructed by mixing tantalum powder and tungsten powder in a mass ratio (tantalum : tungsten) of (20 : 80).
  • the mixture can be used in the powder form as the target or used as the target after the power is sintered.
  • the sleeve 3 When sputtering is performed using the sputtering device, the sleeve 3 is inserted into the hole 24a provided on the retaining plate 24 so that the sleeve 3 is held within the hole 24a by the flare section of the sleeve 3. Then, a high frequency voltage is applied by the high frequency power supply 28 between the sputtering anode 22 and the target 25, a coolant is supplied from the coolant insertion inlet 29, air is emission from the vacuum emission outlet 30, emission argon gas is supplied from the inert gas insertion inlet 31, and the retaining plate 24 is rotated by the rotational axis 21.
  • a composite coating of tantalum and tungsten is formed at the inner surface of the sleeve 3 with a thickness of about 1 ⁇ m and having a micro-crack structure at the surface of the coating.
  • the composite coating is only formed at the inner surface of the sleeve 3, and no composite coating is adhered to the outer surface.
  • Fig. 3 shows an electron micrograph of a composite film of tantalum and tungsten which is formed at the inner surface of the sleeve 3 by the above method.
  • the coating has a black rough surface with micro-cracks at the surface.
  • the composition of the film was (20 : 80) in mass ratio (tantalum : tungsten).
  • Fig. 4 shows an electron micrograph of a composite film of tantalum and tungsten which is formed at the inner surface of the sleeve 3 by a method similar to the above, using the sputtering device shown in Fig. 2 and a target which is obtained by mixing tantalum powder and tungsten powder in mass ratio (tantalum : tungsten) of (40 : 60).
  • the coating has a black rough surface with micro-bumps on the surface.
  • the composition of the film was (40 : 60) in mass ratio (tantalum : tungsten).
  • the composite film with micro-crack structure or with micro-bump structure can be formed when the composition of the film is in a range between (80 : 20) and (10 : 90) in mass ratio (tantalum : tungsten).
  • the adjustment of the composition can easily be attained by adjusting the mixing ratio between the tantalum powder and tungsten powder, which are the materials for the target, in a range between (80 : 20) and (10 : 90) in mass ratio (tantalum : tungsten).
  • the target which is the material for the black coating is formed by mixing tantalum and tungsten.
  • the present invention is not limited to this configuration, and similarly uniform black coating was obtained by using rhenium or a mixture of tungsten and rhenium in place of tungsten.
  • a uniform black rough surface can be formed at the entire inner surface of the sleeve using the sputtering device as shown in Fig. 2, that is, a sputtering device having a structure in which the sleeve placed between the sputtering anode and sputtering cathode is electrically insulated from both electrodes. This is believed possible because, when the sputtering device of Fig. 2 is used, the inner surface of the sleeve which touches a plasma and which is electrically insulated is negatively charged during the sputtering operation.
  • the inner surface of the sleeve attracts positive ions and a migration layer of positive ions is generated in the space between the sputtering anode and the sputtering cathode.
  • the migration layer then facilitates sputtered particles to move, and, therefore, a uniform thin film can be formed on the entire inner surface of the sleeve.
  • a black rough surface with micro-crack structure or micro-bump structure can be formed using the sputtering device of Fig. 2 and a mixture of tantalum and tungsten as the material for the target.
  • the sleeve placed between the sputtering anode and sputtering cathode is insulated from both electrodes. Because of this, the sleeve is negatively charged during the sputtering process and bombarded by ions. Thus, tantalum having appropriate amount of micro-cracks or micro-bumps is generated and mixed in the tungsten film, and a black rough surface is formed.
  • the sleeveplaced between the sputtering anode and the sputtering cathode is insulated.
  • similar effects can be achieved by applying an appropriate voltage between the anode potential and cathode potential to the insulated sleeve and performing bias sputtering.
  • a high frequency magnetron sputtering method is used.
  • the present invention is not limited to such a configuration, and similar effects can be achieved by other methods such as, for example, high frequency sputtering, magnetron sputtering, and DC sputtering methods.
  • the thickness of the black coating which can be obtained by the present invention is not limited to 1 ⁇ m as described above, but can be any other suitable thickness such as, for example, in a range between 0.5 ⁇ m and 5 ⁇ m.
  • the inner surface of the sleeve having the black coating formed by the embodiment has a thermal radiation ratio which is 0.3 to 0.4 higher than that for a sleeve without the black coating adhered, at a temperature range around 950°C which is the operation temperature of the impregnated cathode.
  • the black coating according to the described embodiment is a heat absorption layer which has a sufficient mechanical strength wherein the degree of blackness is not changed when a heater is inserted into the sleeve and heat is applied, and there is no vaporization of the compositions.
  • the material for the sleeve having the black coating can be selected from among tantalum or an alloy having tantalum as the main constituent, niobium or an alloy having niobium as the main constituent, or molybdenum or an alloy having molybdenum as the main constituent.
  • a heat absorbing black coating which is a composite film of tantalum and tungsten, rhenium, or a mixture of tungsten and rhenium and which has a micro-crack structure or micro-bump structure at its surface is adhered, by a sputtering method, to the inner surface of a sleeve which forms a portion of an electron emission cathode.
  • a heat absorption layer which exhibits superior mechanical strength and superior heat endurance; a superior heat absorption characteristic, due to the fact that the heat absorption layer has an increased heat absorbing area by the presence of micro-cracks or micro-bumps; and wherein the degree of blackness does not change and the composition metals do not vaporize, can be obtained through a procedure comprising simple steps, at low cost, and using a method suitable for mass production.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)

Claims (5)

  1. Hülse für eine heiße Kathodenstruktur, welche einen Teil einer Elektronenemissionskathode bildet, wobei die Hülse (3) eine auf ihrer inneren Oberfläche anhaftende und ausgebildete schwarze Beschichtung (7) aufweist,
    dadurch gekennzeichnet, dass
    die schwarze Beschichtung ein Verbundfilm aus Tantal und einem aus a) Wolfram, b) Rhenium oder c) einem Gemisch aus Wolfram und Rhenium mit einer Mikroriß-Struktur oder einer unebenen Mikrostruktur auf der Oberfläche ist.
  2. Hülse für eine heiße Kathodenstruktur gemäß Anspruch 1, worin die Zusammensetzung der schwarzen Beschichtung aus Tantal in Bezug auf Wolfram, Rhenium oder dem Gemisch aus Wolfram und Rhenium in einem Bereich zwischen 80:20 und 10:90 des Massenverhältnisses Tantal : Wolfram, Rhenium oder dem Gemisch aus Wolfram und Rhenium liegt.
  3. Hülse für eine heiße Kathodenstruktur gemäß Anspruch 1 oder Anspruch 2, worin die Hülse aus Tantal oder einer Tantal als Hauptbestandteil aufweisenden Legierung, Niob oder einer Niob als Hauptbestandteil aufweisenden Legierung oder Molybdän oder einer Molybdän als Hauptbestandteil aufweisenden Legierung gestaltet ist.
  4. Verfahren zur Herstellung einer Hülse für eine heiße Kathode unter Verwendung einer Zerstäubungsvorrichtung, welche eine Struktur mit einer Halteplatte, die zwischen einer Zerstäuberanode und einer Zerstäuberkathode bereitgestellt ist und die von der Zerstäuberanode und der Zerstäuberkathode elektrisch isoliert ist, aufweist, wobei das Verfahren den Schritt umfasst:
    Betreiben der Zerstäubervorrichtung zum Anhaften und Ausbilden einer schwarzen Beschichtung auf der inneren Oberfläche einer auf der Halteplatte plazierten Hülse, wobei die schwarze Beschichtung einen Verbundfilm aus Tantal und einem aus a) Wolfram, b) Rhenium oder c) einem Gemisch aus Wolfram und Rhenium mit einer Mikroriß-Struktur oder einer unebenen Mikrostruktur auf der Oberfläche umfasst.
  5. Verfahren zur Herstellung einer Hülse für eine heiße Elektrode wie in Anspruch 4 beansprucht, wobei die Halteplatte mit einem Vorspannungspotential zwischen dem Anodenpotential und dem Kathodenpotential vorgespannt ist.
EP20010308682 2001-10-11 2001-10-11 Hülse für eine beheizte Kathode und Verfahren zu ihrer Herstellung Expired - Lifetime EP1302969B1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP20010308682 EP1302969B1 (de) 2001-10-11 2001-10-11 Hülse für eine beheizte Kathode und Verfahren zu ihrer Herstellung
DE2001615904 DE60115904T2 (de) 2001-10-11 2001-10-11 Hülse für eine beheizte Kathode und Verfahren zu ihrer Herstellung

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP20010308682 EP1302969B1 (de) 2001-10-11 2001-10-11 Hülse für eine beheizte Kathode und Verfahren zu ihrer Herstellung

Publications (2)

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EP1302969A1 EP1302969A1 (de) 2003-04-16
EP1302969B1 true EP1302969B1 (de) 2005-12-14

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Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0677435B2 (ja) * 1985-03-18 1994-09-28 株式会社日立製作所 傍熱形陰極の製造方法
JPH03105826A (ja) * 1989-09-20 1991-05-02 Toshiba Corp 含浸型陰極構体
TW259878B (de) * 1993-03-17 1995-10-11 Toshiba Co Ltd
JPH08287824A (ja) * 1995-04-13 1996-11-01 Hitachi Ltd 熱陰極構体用スリーブの製造方法

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DE60115904T2 (de) 2006-06-14
EP1302969A1 (de) 2003-04-16
DE60115904D1 (de) 2006-01-19

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