EP0641006A1 - Cathode pour un tube à électrons - Google Patents

Cathode pour un tube à électrons Download PDF

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Publication number
EP0641006A1
EP0641006A1 EP93309889A EP93309889A EP0641006A1 EP 0641006 A1 EP0641006 A1 EP 0641006A1 EP 93309889 A EP93309889 A EP 93309889A EP 93309889 A EP93309889 A EP 93309889A EP 0641006 A1 EP0641006 A1 EP 0641006A1
Authority
EP
European Patent Office
Prior art keywords
cathode
oxide
group
electron
electron emissive
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.)
Withdrawn
Application number
EP93309889A
Other languages
German (de)
English (en)
Inventor
Kyung-Cheon Shon
Jong-Seo Choi
Kwi-Seok Choi
Gyu-Nam Ju
Sang-Won Lee
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Samsung SDI Co Ltd
Original Assignee
Samsung Display Devices Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Samsung Display Devices Co Ltd filed Critical Samsung Display Devices Co Ltd
Publication of EP0641006A1 publication Critical patent/EP0641006A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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

Definitions

  • the present invention relates to a cathode for an electron tube for use in such display devices as a picture tube, and more particularly, to a novel cathode for an electron tube having high current density and a long lifetime.
  • thermoelectron emitting cathode for an electron tube which is used in a picture tubes and other display devices, a so-called "oxide cathode” which includes alkaline earth metal oxide layer having Ba as a main component on a metal base containing Ni as a main component and a small amount of Si, Mg, etc. as a reducing agent is widely used.
  • This oxide cathode emits electrons provided by free atoms produced from oxides through the reaction between reducing agents in the metal base and oxides.
  • FIG. 1 illustrates a schematic cross-sectional view of the conventional oxide cathode.
  • the cathode comprises a circular pellet-type metal base 1, circular tube-type sleeve 2 and electron emissive material layer 4 which is coated and formed on the metal base 1 and contains a barium compound as a main component.
  • the reference numeral 3 designates a heater for heating the cathode.
  • the electron emissive material layer is formed by the following method. That is, carbonate powder which contains barium carbonate as a main component is mixed with solvents in which nitrocellulose or so is dissolved. The mixture is then coated on the base metal by spray or electrodeposition, etc.
  • the cathode having each components is later installed in a cathode ray tube and then assembled in an electron tube. During an exhaust process to make the inside of the electron tube vacuous, the cathode is heated to about 1000°C. At this time, barium carbonate in the electron emissive material layer thermally decomposes and changes into barium oxide as the following chemical formula.
  • the produced barium oxide reacts with the reducing agents in the metal base, Si and Mg at the interface of the metal base and the electron emissive material layer during the cathode operation as the following chemical formula.
  • the thus-produced free Ba contributes to an electron emission.
  • MgO and Ba2SiO4 also are produced as described in formulae (2) and (3) at the interface between electron emissive material layer and the metal base. This reaction product accumulates around the interface and becomes a barrier, called an "interlayer" which interrupts diffusion of Mg or Si from the metal base.
  • the interlayer results in undesirable effects such as a reduction in cathode lifetime.
  • the interlayer since the interlayer has high resistance and interrupts the electron emission current flow, the problem of restriction of emittable current density occurs, which in turn results in dissatisfactory requirements for large electron tubes having high luminance.
  • An impregnated-type cathode is a kind of cathode satisfying the above requirements and is manufactured by the process including melting electron emissive materials under a reducing atmosphere or in a vacuum and impregnating a porous metal base with the melted electron emissive materials.
  • the impregnated cathode can realise the high current density and long lifetime.
  • the manufacturing process is complicated and the operation temperature is higher; as much as 300-400°C higher than that of a carbonate cathode, and can be as high as 1100°C or more. Therefore, the electrode materials should be changed as those which are heat-resistant and this heightens production cost.
  • An object of the present invention considering the above-mentioned problems and solving the problem of lifetime reduction owing to the interlayer is to provide a cathode for an electron tube which has the characteristics of stable electron emission over a long time and high current density.
  • a cathode for an electron tube comprising: a cup provided in a sleeve; and a pellet of an electron emissive materials including: at least one oxide selected from the group consisting of europium oxide (Eu2O3), lanthanum oxide (La2O3), and scandium oxide (SC2O3) in an amount of 1 to 20 wt% based on the total amount of the electron emissive materials, and at least one carbonate selected from the group consisting of BaCO3, SrCO3 and CaCO3; at least one reducing material selected from the group consisting of Ni, W, Mg, Si and Mo; and an oxide containing Ba.
  • Eu2O3 europium oxide
  • La2O3 lanthanum oxide
  • SC2O3 scandium oxide
  • the preferred oxide containing Ba is at least one Ba compound selected from the group consisting of BaO ⁇ CaO ⁇ Al2O3, Ba3Ga2O6, Ba3Ir2O6, Ba4Ir4O7, Ba2V2O7, Ba3In2O6 and BaBeO2.
  • the cathode of the present invention is manufactured by removing the metal base portion from the conventional oxide cathode, covering a pellet made of electron emissive materials with a cup, and attaching the cup in an upper part and inner face of a sleeve by resistance welding, laser welding, etc.
  • the cathode is practical and easy to manufacture.
  • carbonate of alkaline earth metal containing barium as a main component and reducing metal are mixed at a mixing ratio of between 1:9 and 4:6 (e.g. 1:9, 2:8, 3:7, 4:6, etc.) and homogeneously mixed by means of a mortar.
  • the preferred reducing metal is at least one metal selected from the group consisting of Ni, Mg, W, Si and Mo, and the preferred size of ranges from 2 ⁇ 7 ⁇ m. More preferably, the metal is heat treated under vacuum or a reducing atmosphere such as a hydrogen gas atmosphere.
  • At least one oxide selected from the rare earth compound group consisting of europium oxide (Eu2O3), lanthanum oxide (La2O3) and scandium oxide (Sc2O3) may be added to the carbonate in an amount of 1 to 20 wt% based on the total weight of the electron emissive material.
  • At least one oxide containing barium selected from the group consisting of BaO ⁇ CaO ⁇ Al2O3, Ba3Ga2O6, Ba3Ir2O6, Ba4Ir4O7, Ba2V2O7, Ba3In2O6 and BaBeO2 is added and then mixed using a mortar. Since barium is slowly provided from these compounds, the diminution of the electron emission characteristic is compensated and electron emission from the cathode becomes stable.
  • the mixing ratio of the carbonate and barium-containing oxide ranges preferebly from 7:3 to 1:1.
  • the obtained mixture is press moulded into a predetermined size.
  • the press molding is preferably carried out at 5 ⁇ 10ton/cm2 pressure.
  • the porosity of the packet may be controlled by controlling the pressure when press molding. Through the porosity controlling, lifetime reduction and the lowering of current density may both be prevented. As the porosity increases, the current density and the evaporating amount of barium increase and thus the lifetime of the cathode decreases. As the porosity decreases, the lifetime characteristic is improved but high current density could not be obtained. According to the repeated experiment by the inventors, the cathode having appropriate current density characteristic and lifetime characteristic may be manufactured when the porosity of the pellet is about from 18 to 40%.
  • the manufactured pellet is preferably heat-treated under vacuum or a reducing atmosphere so as to activate the decomposition of the CO2 present in the carbonate and to use immediately after assembling without a separate decomposition process.
  • the heat treatment is preferably carried out at a temperature range of 800 ⁇ 1000°C for 30 ⁇ 90 minutes.
  • the thus-obtained pellet (5) is covered with a cup (6) made of heat-resistant metal.
  • the cup (6) is laser molded to the upper portion and inner part of a sleeve (2), and a heater (3) is provided in the sleeve (2) to finish a cathode according to the present invention as illustrated in FIG.2.
  • Ni was added to a three-element carbonate having a weight mixing ratio of Ba:Sr:Ca as 57:39:4, and mixed using a mortar.
  • the mixture was compacted in a metal mold and press-molded at about 10ton/cm2 to manufacture a pellet.
  • the pellet was heat-treated under a hydrogen atmosphere at about 900°C for about 50 minutes.
  • the heat-treated pellet was covered with a cup made of a heat-resistant metal, and this assembly was laser-molded on the upper portion and inner side of a sleeve as shown in FIG .2.
  • a heater was provided in the sleeve to manufacture a cathode for an electron tube of the present invention.
  • FIG. 3 a graph representing the lifetime characteristic of the conventional cathode with respect to that of the cathode according to the present invention is illustrated.
  • “a” corresponds to the conventional impregnated-type cathode
  • “b” corresponds to the cathode for an electron tube of the present invention
  • "c” corresponds to the conventional oxide cathode. From the graph, it is confirmed that the lifetime characteristic of the cathode of the present invention is somewhat lower and almost similar when compared with that of the conventional impregnated cathode, and has even better efficiency than that of the conventional oxide cathode.
  • FIG.4 is a graph representing current density with respect to the operating temperature of the conventional cathode and cathode of the present invention.
  • “a” corresponds to the conventional impregnated cathode
  • “b” corresponds to the cathode of the present invention
  • “c” corresponds to the conventional oxide cathode.
  • the operating temperature of the impregnated cathode is too high (approximately about 1100°C) even though it has the highest current density, while the current density of the conventional oxide cathode is too low even though the operation temperature is low.
  • the operation temperature is lower (by as much as 200°C) than that of the impregnated cathode and the current density is as high as that of the impregnated cathode, which confirms that the cathode of the present invention is very practical one.
  • the cathode of the present invention has the characteristic of a stable electron emission and a low operation temperature of about 800 ⁇ 900°C.
  • the operation temperature is about 200°C lower than that for the impregnated cathode. Therefore, the use of high-melting-point metals are not necessary, which lowers production costs.

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  • Solid Thermionic Cathode (AREA)
  • Luminescent Compositions (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
EP93309889A 1993-08-24 1993-12-08 Cathode pour un tube à électrons Withdrawn EP0641006A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR1019930016399A KR100294484B1 (ko) 1993-08-24 1993-08-24 전자관용음극
KR9316399 1993-08-24

Publications (1)

Publication Number Publication Date
EP0641006A1 true EP0641006A1 (fr) 1995-03-01

Family

ID=19361786

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93309889A Withdrawn EP0641006A1 (fr) 1993-08-24 1993-12-08 Cathode pour un tube à électrons

Country Status (5)

Country Link
EP (1) EP0641006A1 (fr)
JP (1) JPH0765694A (fr)
KR (1) KR100294484B1 (fr)
CN (1) CN1099514A (fr)
TW (1) TW233369B (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2294155B (en) * 1994-10-12 1999-03-03 Samsung Display Devices Co Ltd Cathode for electron tube
CN1087482C (zh) * 1995-10-30 2002-07-10 三星电管株式会社 电子管阴极
WO2002068731A3 (fr) * 2001-02-22 2002-11-07 Reytech Corp Cristaux optiques non lineaires a structure d'oxyde de beryllium (beo2)
US6833659B2 (en) * 2000-09-19 2004-12-21 Koninklijke Philips Electronics N.V. Cathode ray tube comprising a cathode of a composite material
DE10121442B4 (de) * 2000-09-19 2010-04-08 Philips Intellectual Property & Standards Gmbh Kathodenstrahlröhre mit Oxidkathode

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100262638B1 (ko) * 1997-05-21 2000-08-01 구자홍 음극선관용 음극구조체
KR20000034114A (ko) * 1998-11-27 2000-06-15 김영남 환원제가 투입된 음극선관의 산화물 캐소드와 그 제조방법
JP2001319558A (ja) * 1999-12-27 2001-11-16 Allied Material Corp カソード構体と、その製造方法と、それを用いた陰極線管
KR101551857B1 (ko) 2014-04-15 2015-09-18 한국생산기술연구원 바륨 마그네슘 합금의 제조 방법

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB182817A (en) * 1921-07-11 1923-08-09 Drahtlose Telegraphie Gmbh Improvements in the cathodes of electric discharge tubes
FR700645A (fr) * 1929-08-16 1931-03-05 Procédé pour la fabrication de cathodes chauffées pour tubes à décharges électriques
FR1086891A (fr) * 1953-07-18 1955-02-16 Csf Perfectionnements à la fabrication des cathodes thermioniques
EP0204477A1 (fr) * 1985-05-25 1986-12-10 Mitsubishi Denki Kabushiki Kaisha Cathode pour tube électronique et procédé de fabrication du même type
EP0210805A2 (fr) * 1985-07-19 1987-02-04 Mitsubishi Denki Kabushiki Kaisha Cathode pour tube électronique
GB2203588A (en) * 1987-02-19 1988-10-19 Christopher Edward Maloney Thermionic cathode
JPS63285836A (ja) * 1987-05-18 1988-11-22 Mitsubishi Electric Corp 線状熱陰極
EP0436360A2 (fr) * 1989-12-31 1991-07-10 Samsung Display Devices Co., Ltd. Cathode à réserve pour canon à électrons
EP0516503A1 (fr) * 1991-05-31 1992-12-02 Thomson Tubes Electroniques Cathode à oxydes et procédé de fabrication

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR900003175B1 (ko) * 1985-07-19 1990-05-09 미쓰비시전기 주식회사 전자관용음극

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB182817A (en) * 1921-07-11 1923-08-09 Drahtlose Telegraphie Gmbh Improvements in the cathodes of electric discharge tubes
FR700645A (fr) * 1929-08-16 1931-03-05 Procédé pour la fabrication de cathodes chauffées pour tubes à décharges électriques
FR1086891A (fr) * 1953-07-18 1955-02-16 Csf Perfectionnements à la fabrication des cathodes thermioniques
EP0204477A1 (fr) * 1985-05-25 1986-12-10 Mitsubishi Denki Kabushiki Kaisha Cathode pour tube électronique et procédé de fabrication du même type
EP0210805A2 (fr) * 1985-07-19 1987-02-04 Mitsubishi Denki Kabushiki Kaisha Cathode pour tube électronique
GB2203588A (en) * 1987-02-19 1988-10-19 Christopher Edward Maloney Thermionic cathode
JPS63285836A (ja) * 1987-05-18 1988-11-22 Mitsubishi Electric Corp 線状熱陰極
EP0436360A2 (fr) * 1989-12-31 1991-07-10 Samsung Display Devices Co., Ltd. Cathode à réserve pour canon à électrons
EP0516503A1 (fr) * 1991-05-31 1992-12-02 Thomson Tubes Electroniques Cathode à oxydes et procédé de fabrication

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 13, no. 114 (E - 730)<3462> 20 March 1989 (1989-03-20) *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2294155B (en) * 1994-10-12 1999-03-03 Samsung Display Devices Co Ltd Cathode for electron tube
CN1087482C (zh) * 1995-10-30 2002-07-10 三星电管株式会社 电子管阴极
US6833659B2 (en) * 2000-09-19 2004-12-21 Koninklijke Philips Electronics N.V. Cathode ray tube comprising a cathode of a composite material
DE10121442B4 (de) * 2000-09-19 2010-04-08 Philips Intellectual Property & Standards Gmbh Kathodenstrahlröhre mit Oxidkathode
WO2002068731A3 (fr) * 2001-02-22 2002-11-07 Reytech Corp Cristaux optiques non lineaires a structure d'oxyde de beryllium (beo2)

Also Published As

Publication number Publication date
CN1099514A (zh) 1995-03-01
KR950005487A (ko) 1995-03-20
KR100294484B1 (ko) 2001-09-17
TW233369B (en) 1994-11-01
JPH0765694A (ja) 1995-03-10

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