EP1200973B1 - Oxidkathode und zugehöriges herstellungsverfahren - Google Patents

Oxidkathode und zugehöriges herstellungsverfahren Download PDF

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Publication number
EP1200973B1
EP1200973B1 EP01945372A EP01945372A EP1200973B1 EP 1200973 B1 EP1200973 B1 EP 1200973B1 EP 01945372 A EP01945372 A EP 01945372A EP 01945372 A EP01945372 A EP 01945372A EP 1200973 B1 EP1200973 B1 EP 1200973B1
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EP
European Patent Office
Prior art keywords
support
particles
cathode
conducting material
metal
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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
EP01945372A
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English (en)
French (fr)
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EP1200973A1 (de
Inventor
Jean-Luc Ricaud
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Thomson Licensing SAS
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Thomson Licensing SAS
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    • 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
    • H01J1/14—Solid thermionic cathodes characterised by the material
    • 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
    • H01J9/042—Manufacture, activation of the emissive part

Definitions

  • the present invention relates to the field of tubes electronics, including cathodes which have a role in these tubes to emit electrons and thus constitute the source of a current electronic.
  • cathodes said to be oxides.
  • These cathodes which are the most commonly used, include a layer of highly electron-emitting oxides on one side of a metal support.
  • the support is connected to a negative electrical potential relative to the surrounding potential, allowing the emission of a flux of electrons from the oxide layer.
  • FIG. 1 is a simplified sectional view showing a section of a conventional oxide cathode 2.
  • the support 1 consists of a thin nickel plate forming a patch, which has a covered face 1a a layer of oxides 3 in the form of whitewash.
  • the whitewash is a deposit consisting of a charge of active compound and a binder.
  • the compound active is generally based on barium carbonates (BaCO3) and others elements, which are subsequently transformed into barium oxides (BaO) and other elements.
  • the oxide layer normally needs to be at a relatively high temperature for emitting.
  • a heat source such as a filament near the support, connected to a low voltage current source.
  • an electronic current crosses the thickness of the oxide layer 3 (arrow I) under the effect of the electric field surrounding.
  • the electric field is created by establishing a difference of potential between the support 1 and an electrode 5 located near the surface exterior 3a of layer 3.
  • the support is referenced to a ground voltage while electrode 5 is biased at a positive voltage high + V.
  • the electronic flux obtained by cathode 2 is proportional to the intensity of this electronic current I.
  • Figure 2 shows the same section of cathode 2 after a evolution over time.
  • a resistive layer 6 said interface layer, develops between the metal support 1 and the whitewash layer 3.
  • cathode ray tubes for the screens of "multimedia” and “high resolution” visualization, as well as for video projectors, and other types of electronic tubes, such as those used in the microwave field.
  • oxide cathodes resist poorly high current density, especially when the current is temporally constant, due to their electrical conductivity insufficient.
  • Figure 3 is an equivalent electrical diagram of the components R1 and R2 of the electrical resistivity of the oxide cathode coming from emissive whitewash layer 3 and layer 3 respectively interface interface 6. These two layers being superimposed, the components R1 and R2 combine as resistors in series.
  • the contribution to the electrical resistivity of the interface layer 6 evolves during the lifetime because this interface develops.
  • the development of this interface is due to chemical reactions between the whitewash and the reducing elements contained in nickel (such as Mg, Si, Al, Zr, W, ...) which accumulate compounds in this interface.
  • These compounds are not very conductive, because they are mainly oxides such as MgO, Al 2 O 3 , SiO 2 , Ba 2 SiO 4 , BaZrO 3 , Ba 3 WO 6 , etc ...
  • US-A-4,310 777 recommends, in the case of a nickel support having a high amount of tungsten, a low concentration of zirconium in nickel in a relatively narrow range.
  • US-A-4,313 854 offers, in the case of a nickel support with a high percentage of refractory metal, to interpose a layer of metal carbides (Si, B, Ti, Zr, Hf, V, Nb, Ta, Mo, W) between nickel and whitewash to limit the interface development.
  • cathodes impregnated which allow a regime supported with an electronic current important, even if this current is temporally constant.
  • These cathodes comprise a porous metallic pellet impregnated with an emissive material.
  • they are complex and their manufacturing costs exclude them from numerous applications, in particular in cathode ray tubes intended consumer markets.
  • the subject of the present invention is a oxide cathode comprising a support and an oxide layer on the support. It further comprises grains of conductive material having a first end incorporated in the support and a second end housed in the oxide layer, so as to form bridges conductors passing through an interface layer forming between the support and the oxide layer.
  • the support can be made of metal, preferably based on nickel.
  • the invention also relates to an electronic tube, for example a cathode ray tube, comprising an oxide cathode of the type supra.
  • Cathode ray tube can be used for applications say "multimedia" from television.
  • the step of garnishing grains of conductive material consists in spreading the grains on said surface and apply force to the grains to encrust the first end of the grains in the support.
  • the step of garnishing grains of conductive material consists in incorporating the grains in the support and bring out the second end of the grains by a treatment surface, for example by means of a selective chemical attack.
  • the grains can be incorporated into the support during of the metallurgical development of the latter.
  • the second end of the grains either before or after stamping.
  • a conductive support 1 based on nickel on a surface 1a of which is deposited a layer of oxides 3 under whitewash shape.
  • an interface layer 6 is formed between the aforementioned surface 1a and the oxide layer 3, as described previously with reference to Figure 2.
  • a cathode with indirectly heated oxides i.e. a cathode which is mounted in temperature by a heat source external to the support 1, for example by means of a filament near the support and connected to a source of low voltage current.
  • the invention can also be applied in the case of a direct heating cathode.
  • the cathode 2 has grains 8 of conductive material located at the junction of the support 1 and the layer of oxides 3.
  • the grains 8 are distributed substantially uniformly over the whole the surface (or at least a part) occupied by the oxide layer 3.
  • each grain 8 has a first end 8a which penetrates the abovementioned surface 1a of the support 1 so as to be embedded in the support and a second end 8b which is housed in the thickness of the oxide layer 3.
  • These two ends 8a and 8b are, within the limit of the irregularity of shape of the grain, mutually opposite on an axis A perpendicular to the surface 1a of support.
  • An intermediate part 8c of the grain crosses the entire thickness of the interface layer 6.
  • the grain 8 constitutes a conductive bridge which establishes an electrically conductive connection connecting the body of the support 1 to the end point of the second end 8b, that is to say within the oxide layer 3.
  • the average grain size compared to the thickness of the oxide layer 3 can be adapted so that the projection P in the aforementioned axis A of the part of a grain 8 housed in the oxide layer 3 occupies a greater or lesser proportion of the thickness E of this layer according to the characteristics sought.
  • cathode 2 is referenced to a ground potential, as in the case of FIGS. 1 and 3, and we neglect the electrical resistivity of the support, the latter being a good conductor.
  • R3 the resistivity of the first part (compare to R1 in Figure 3)
  • R4 the resistivity of the second part (compare to R2 in Figure 3).
  • the resistivity R4 of the part of cathode 2 containing the layer interface 6 appears to be negligible. Indeed, the grains 8 being of good conductors, this layer is effectively short-circuited by the effect conductive bridge provided by each grain 8. In addition, all of the grains 8 constitute a set of parallel connections distributed over the entire active surface of the oxide layer.
  • this single means provides decrease in the resistivity of both the interface layer 6 (this becoming substantially zero) and of the oxide layer 3.
  • a material is chosen for the grains 8 which meets several criteria: be tough enough to be embedded in the nickel (or other metal) of support 1, not be a poison of the emission of cathode 2, be electrically conductive, resist oxidation (in particular that caused by the conversion of carbonates into oxides), be stable chemically and in particular not to react with the elements of the cathode, and not to evaporate too much nor to diffuse too much in the conditions of operation of the cathode.
  • FIGS. 6a to 6c first method of manufacturing oxide cathodes in accordance with the invention.
  • cathode preform comprising simply the conductive support 1.
  • it is a strip continuous of nickel-based material 1 which will be cut and stamped to form the support in its final dimensions.
  • Figure 6a is spread over a surface 1a of this strip a powder composed of grains 8 of one or more metal carbides according to the composition described above.
  • the part 8a of the grains 8 forming the end is encrusted in contact with the surface 1a in the material of the support 1 by applying a compression force on the opposite end 8b of the grains in the direction arrow F ( Figure 6b).
  • a compression force on the opposite end 8b of the grains in the direction arrow F ( Figure 6b).
  • Figure 6b Several techniques can be used to apply this overlay pressure. In the example shown, it is obtained by means of a vertical press 10 positioned above the grains, controlled to obtain the desired degree of incrustation. It is also possible to pass the strip 1 with its powder deposit on the surface between a pair of road rollers to achieve the same effect technical. If necessary, the support 1 can be heated to allow a better grain penetration 8.
  • the layer is deposited of oxides 3 so as to cover the exposed portions of the surface 1a of the strip and grains 8.
  • the layer completely drowns the exposed parts of the grains.
  • the grains therefore have an end 8a incorporated in the nickel, and an end 8b in the whitewash, and form thus conductive bridges as explained above.
  • Layer 3 is prepared in the form of a whitewash consisting of or carbonates (s) and a binder. Typically, as carbonates, barium carbonates, strontium, and possibly calcium.
  • the interface layer 6 is not shown in the figure because it does not appear and develops that during the aging of cathode 2, by transformation of the part of the oxide layer near the surface 1a of support. It is possible to know in advance the thickness of this interface layer and accordingly provide that the height of the parts not encrusted with grains 8 is large enough to pass through all this thickness and thus ensure its function as a conductive bridge.
  • FIGS. 7a to 7d other method of manufacturing cathode 2 in accordance with this invention according to which the grains 8 are incorporated into the constituent material of support 1 during the metallurgical development of the latter.
  • the support is nickel-based.
  • the support 1 is in the form metallic ribbon during the grain incorporation phase 8. This ribbon will then be cut and stamped to obtain the support in its shape final.
  • the ribbon 1 is moved in the direction of the arrow G by means of rollers 12 so that its surface 1a intended to receive the layer of oxides passes successively past a heat source 14 and a barrel 16 which pulverizes the grains 8.
  • the composition of the grains used for this technique can be the same as for the first manufacturing method.
  • the function of the heat source 14 is to raise the temperature to level of surface 1a sufficient for the metal of the strip to be softened (plastic phase).
  • the heat source may be a device to eddy current induction in the metal strip 1.
  • the barrel 16 projects the grains 8 with force against the surface 1a ribbon. This surface having been softened, the grains penetrate almost entirely in the mass of the strip and are therefore found immersed in it, near surface 1a, as shown by in more detail Figure 7b.
  • strip 1 is subjected to a selective chemical attack aimed at removing material from this strip at its surface 1a without altering the constitution of the grains.
  • this attack is carried out by depositing an acid 18 in liquid phase on the surface 1a of the ribbon (FIG. 7b).
  • Other techniques can be considered, like a vapor phase or plasma attack.
  • the exposed parts of the grains 8 after the chemical attack are sufficiently protrusion from the surface 1a to pass through a possible interface layer and penetrate the oxide layer of the cathode.
  • the strip thus prepared is cut into preforms of cathode support and then stamped to obtain the cathode body.
  • Another variant of the first manufacturing method consists to incorporate the grains throughout the thickness of the support 1 during a step of making this tape.
  • those of the grains located at proximity to surface 1a will serve as conductive bridges when their end 8a will have been embedded in whitewash 3, and the other grains will be inactive without disturbing the operation of the cathode.
  • oxide cathode according to the present invention has very broad applications, including all areas where oxide cathodes are normally used: viewing tubes (TRC), microwave tubes, grid tubes, etc ...

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
  • Solid Thermionic Cathode (AREA)
  • Cold Cathode And The Manufacture (AREA)
  • Inert Electrodes (AREA)

Claims (19)

  1. Oxidkathode (2) mit einem Träger (1) und einer Oxidschicht (3) auf dem Träger,
    dadurch gekennzeichnet, dass
    sie außerdem Partikel (8) aus einem elektrisch leitenden Material enthält und jedes Partikel ein erstes Ende (8a) aufweist, das innerhalb des Trägers (1) liegt, und ein zweites Ende (8b) aufweist, das in der Oxidschicht (3) liegt, derart, dass elek-trisch leitende Brücken gebildet werden, die sich über eine Schnittstellenschicht (6) erstrecken, die sich zwischen dem Träger (1) und der Oxidschicht (3) ausbildet.
  2. Oxidkathode (2) nach Anspruch 1, dadurch gekennzeichnet, dass das leitende Material der Partikel (8) ein Karbid von einem oder mehreren Metallen ist.
  3. Oxidkathode (2) nach Anspruch 2, dadurch gekennzeichnet, dass das leitende Material der Partikel (8) ein Karbid von einem oder mehreren Metallen aus der Gruppe IV B und vorzugsweise wenigstens ein Metall ist aus der Gruppe : Titan (Ti), Zirkon (Zr) und Hafnium (Hf).
  4. Oxidkathode (2) nach Anspruch 2 oder 3, dadurch gekennzeichnet, dass das leitende Material der Partikel (8) ein Karbid aus einem oder mehreren der Metalle der Gruppe V B und vorzugsweise wenigstens eines der folgenden Metalle ist: Vanadium (V), Niobium (Nb) und Tantal (Ta).
  5. Oxidkathode (2) nach einem der Ansprüche 2 bis 4, dadurch gekennzeichnet, dass das leitende Material der Partikel (8) ein Karbid eines oder mehreren der Metalle der Gruppe VI B und vorzugsweise wenigstens ein Metall der folgenden Gruppe ist: Chrom (Cr), Molybdän (Mo) und Wolfram (W).
  6. Oxidkathode (2) nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass der Träger (1) aus Metall, vorzugsweise auf Nickelbasis besteht.
  7. Elektronenröhre, dadurch gekennzeichnet, dass sie eine Oxidkathode (2) nach einem der Ansprüche 1 bis 6 enthält.
  8. Kathodenstrahlröhre, dadurch gekennzeichnet, dass sie eine Oxidkathode (2) nach einem der Ansprüche 1 bis 6 enthält.
  9. Verfahren zur Herstellung einer Oxidkathode (2), in dem eine Oxidschicht (3) auf einen Träger (1) aufgebracht wird, gekennzeichnet durch folgende Schritte:
    die Oberfläche (1 a) des Trägers (1), die zur Aufnahme der Oxidschicht (3) vorgesehen ist, wird mit Partikeln (8) aus einem elektrisch leitenden Material versehen, derart, dass die Partikel ein erstes, in dem Träger (1) liegendes Ende (8a) und ein zweites, freiliegendes Ende (8b) enthalten, und
    Beschichtung der Oberfläche (1 a) mit einer Oxidschicht (3).
  10. Verfahren nach Anspruch 9, dadurch gekennzeichnet, dass der Schritt zur Bildung der Partikel (8) aus leitendem Material darin besteht, dass die Partikel über die Oberfläche (1a) versprüht werden und eine Kraft auf die Partikel angewendet wird, um das erste Ende (8a) der Letzteren in dem Träger (1) zu inkrustrieren.
  11. Verfahren nach Anspruch 9, dadurch gekennzeichnet, dass der Schritt zur Bildung der Partikel (8) aus leitendem Material in dem Einschluss der Partikel in dem Träger (1) und darin besteht, dass das zweite Ende (8b) aus dem Träger durch eine Oberflächenbehandlung hervorsteht, zum Beispiel durch eine selektive chemische Ätzbehandlung.
  12. Verfahren nach Anspruch 11, dadurch gekennzeichnet, dass die Partikel (8) in den Träger (1) während der metallurgischen Herstellung des Letzteren eingebracht werden.
  13. Verfahren nach Anspruch 11 oder 12, in dem der Träger (1) durch einen Ziehvorgang geformt wird, dadurch gekennzeichnet, dass das zweite Ende (8b) der Partikel (8) vor dem Ziehvorgang hervorragt.
  14. Verfahren nach Anspruch 11 oder 12, in dem der Träger (1) durch einen Ziehvorgang geformt wird, dadurch gekennzeichnet, dass das zweite Ende (8b) der Partikel (8) nach dem Ziehvorgang hervorragt.
  15. Verfahren nach einem der Ansprüche 9 bis 14, dadurch gekennzeichnet, dass das leitende Material der Partikel (8) ein Karbid aus einem oder mehreren Metallen ist.
  16. Verfahren nach Anspruch 15, dadurch gekennzeichnet, dass das leitende Material der Partikel (8) ein Karbid aus einem oder mehreren Metallen der Gruppe IV B und vorzugsweise wenigstens ein Metall aus der folgenden Gruppe ist: Titan (Ti), Zirkon (Zr) und Hafnium (Hf).
  17. Verfahren nach Anspruch 15 oder 16, dadurch gekennzeichnet, dass das leitende Material der Partikel (8) ein Karbid aus einem oder mehreren der Metalle aus der Gruppe V B und vorzugsweise wenigstens ein Metall aus der folgenden Gruppe ist: Vanadium (V), Niobium (Nb) und Tantal (Ta).
  18. Verfahren nach einem der Ansprüche 15 bis 17, dadurch gekennzeichnet, dass das leitende Material der Partikel (8) ein Karbid aus einem oder mehreren der folgenden Metalle der Gruppe VI B und vorzugsweise wenigstens ein Metall aus der folgenden Gruppe ist: Chrom (Cr), Molybdän (Mo) und Wolfram (W).
  19. Verfahren nach einem der Ansprüche 9 bis 18, dadurch gekennzeichnet, dass der Träger (1) aus Metall, vorzugsweise einem Metall auf Nickelbasis, besteht.
EP01945372A 2000-06-14 2001-06-07 Oxidkathode und zugehöriges herstellungsverfahren Expired - Lifetime EP1200973B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR0007540 2000-06-14
FR0007540A FR2810446A1 (fr) 2000-06-14 2000-06-14 Cathodes a oxyde amelioree et son procede de fabrication
PCT/FR2001/001762 WO2001097247A1 (fr) 2000-06-14 2001-06-07 Cathode a oxydes amelioree et son procede de fabrication

Publications (2)

Publication Number Publication Date
EP1200973A1 EP1200973A1 (de) 2002-05-02
EP1200973B1 true EP1200973B1 (de) 2004-04-07

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EP01945372A Expired - Lifetime EP1200973B1 (de) 2000-06-14 2001-06-07 Oxidkathode und zugehöriges herstellungsverfahren

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US (1) US6759799B2 (de)
EP (1) EP1200973B1 (de)
JP (1) JP2004503905A (de)
KR (1) KR20020019981A (de)
CN (1) CN1214436C (de)
AU (1) AU6761001A (de)
DE (1) DE60102648T2 (de)
FR (1) FR2810446A1 (de)
MX (1) MXPA02001603A (de)
WO (1) WO2001097247A1 (de)

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Publication number Priority date Publication date Assignee Title
US8385506B2 (en) 2010-02-02 2013-02-26 General Electric Company X-ray cathode and method of manufacture thereof
US8938050B2 (en) 2010-04-14 2015-01-20 General Electric Company Low bias mA modulation for X-ray tubes
CN102254766B (zh) * 2010-05-19 2013-03-06 中国科学院电子学研究所 一种制备稀土贮存式氧化物阴极的方法
KR20180062812A (ko) * 2016-12-01 2018-06-11 삼성전자주식회사 이종의 메모리 소자들을 포함하는 집적회로 소자 및 그 제조 방법

Family Cites Families (16)

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Publication number Priority date Publication date Assignee Title
FR1107589A (fr) * 1954-06-18 1956-01-03 Csf Perfectionnements aux supports de cathodes à oxydes
US3257703A (en) * 1961-09-29 1966-06-28 Texas Instruments Inc Composite electrode materials, articles made therefrom and methods of making the same
US4273683A (en) 1977-12-16 1981-06-16 Hitachi, Ltd. Oxide cathode and process for production thereof
JPS5566819A (en) * 1978-11-15 1980-05-20 Hitachi Ltd Oxide cathode for electron tube
JPS5596531A (en) 1979-01-19 1980-07-22 Hitachi Ltd Directly heated cathode for electron tube
GB2059676B (en) * 1979-09-12 1983-07-20 Hitachi Ltd Oxide-coated cathodes
JPS5641636A (en) * 1979-09-12 1981-04-18 Hitachi Ltd Directly heated type oxide cathode
GB2060991A (en) * 1979-09-20 1981-05-07 Matsushita Electric Ind Co Ltd Oxide-coated cathode and method of producing the same
CA1270890A (en) 1985-07-19 1990-06-26 Keiji Watanabe Cathode for electron tube
KR910009660B1 (ko) 1988-02-23 1991-11-25 미쓰비시전기 주식회사 전자관용 산화물피복음극
DE4207220A1 (de) 1992-03-07 1993-09-09 Philips Patentverwaltung Festkoerperelement fuer eine thermionische kathode
KR100294485B1 (ko) 1993-08-24 2001-09-17 김순택 산화물음극
US5925976A (en) 1996-11-12 1999-07-20 Matsushita Electronics Corporation Cathode for electron tube having specific emissive material
KR100247820B1 (ko) 1997-08-07 2000-03-15 손욱 전자관용 음극
KR100249714B1 (ko) * 1997-12-30 2000-03-15 손욱 전자총용 음극
KR20000038644A (ko) * 1998-12-08 2000-07-05 김순택 전자총용 음극

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Publication number Publication date
US6759799B2 (en) 2004-07-06
EP1200973A1 (de) 2002-05-02
MXPA02001603A (es) 2002-07-02
FR2810446A1 (fr) 2001-12-21
AU6761001A (en) 2001-12-24
CN1214436C (zh) 2005-08-10
CN1388979A (zh) 2003-01-01
DE60102648D1 (de) 2004-05-13
WO2001097247A1 (fr) 2001-12-20
KR20020019981A (ko) 2002-03-13
DE60102648T2 (de) 2005-03-24
JP2004503905A (ja) 2004-02-05
US20040000854A1 (en) 2004-01-01

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