EP0436477A2 - Gettereinrichtung und Gettersystem für eine Kathodenstrahlröhre - Google Patents

Gettereinrichtung und Gettersystem für eine Kathodenstrahlröhre Download PDF

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Publication number
EP0436477A2
EP0436477A2 EP90830621A EP90830621A EP0436477A2 EP 0436477 A2 EP0436477 A2 EP 0436477A2 EP 90830621 A EP90830621 A EP 90830621A EP 90830621 A EP90830621 A EP 90830621A EP 0436477 A2 EP0436477 A2 EP 0436477A2
Authority
EP
European Patent Office
Prior art keywords
titanium
holder
particulate
cathode
vapour
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Withdrawn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
EP90830621A
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English (en)
French (fr)
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EP0436477A3 (en
Inventor
Claudio Boffito
Massimo Bolognesi
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.)
SAES Getters SpA
Original Assignee
SAES Getters SpA
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Filing date
Publication date
Application filed by SAES Getters SpA filed Critical SAES Getters SpA
Publication of EP0436477A2 publication Critical patent/EP0436477A2/de
Publication of EP0436477A3 publication Critical patent/EP0436477A3/en
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J7/00—Details not provided for in the preceding groups and common to two or more basic types of discharge tubes or lamps
    • H01J7/14—Means for obtaining or maintaining the desired pressure within the vessel
    • H01J7/18—Means for absorbing or adsorbing gas, e.g. by gettering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/94—Selection of substances for gas fillings; Means for obtaining or maintaining the desired pressure within the tube, e.g. by gettering

Definitions

  • the invention relates to a gettering system for a cathode ray tube and a method of manufacturing a cathode ray tube such as a colour display or television tube using a dispenser cathode which is subject to damage at first switch-on due to a sudden increase of the pressure of gas such as nitrogen within the cathode ray tube.
  • An evaporable titanium getter device is also described.
  • Cathode ray tubes are well known in the art and have been used for may years for the visual display of information in a wide variety of forms.
  • Cathode ray tubes are generally formed of a screen portion upon which has been deposited one or more phosphors which emit visible light on excitation by a beam of electrons.
  • One or more beams of electrons are generated from an electron gun situated in a neck portion of the cathode ray tube.
  • a cone portion separates the screen from the neck. Frequently there is also incorporated a metal magnetic screening cup within the cone portion.
  • the image produced on the screen of the cathode ray tube be as bright as possible. This can be accomplished by suitable choice of the phosphors, but also by ensuring that the electron beam which excites the phosphors, has as high a density as possible. This means that the cathode must emit a large number of electrons per square centimeter of its electron emitting area. Such cathodes are well known and are called "dispenser" cathodes.
  • the present invention provides a gettering system for a colour cathode ray display tube, or a monochrome projection tube, which has a sensitive cathode such as a dispenser cathode.
  • the gettering system is capable of rapidly sorbing nitrogen gas which is produced when the cathode ray tube is first switched-on. Thus a high pressure of nitrogen is prevented avoiding damage to the cathode by ionic bombardment.
  • the gettering system comprises a first getter metal vapour releasing material capable of releasing barium vapour upon heating and a second getter metal vapour releasing material capable of releasing titanium vapour upon heating.
  • getter metal vapour releasing material as used in the specification and claims herein is meant to include both the material prior to and after getter metal vapour release. This term embraces both the material in the form sold with the getter device and in the form in which it is found in an operating tube wherein the bulk of the getter metal has been evaporated from the material and is in the form of a film on the inside surfaces of the tube.
  • a colour cathode ray display tube 100 comprising a screen portion 102, a cone portion 104 and a neck portion 106.
  • Screen 102 is coated with a layer of phosphors 108 near to which is located a screen selection electrode or shadow mask 110 held in place by means of a frame 112.
  • Frame 112 also supports a metal magnetic screening cap 114 within cone portion 104.
  • the surface of cone portion 104 is coated with a graphite layer 116.
  • a dispenser cathode 118 is located within neck portion 106.
  • Cathode 118 is any of the various types of known dipenser cathode such as a tungsten dispenser cathode.
  • a gettering system within display tube 100 comprises a first getter metal vapour releasing material capable of releasing barium vapour upon heating and preferably comprises a first holder 120 which is preferably of stainless steel having an outer side wall and a bottom wall. Holder 120 supports a getter metal vapour releasing material capable of releasing barium vapour upon hearing.
  • the getter meal vapour releasing material comprises a mixture of a particulate alloy of approximately 50% barium and 50% aluminium together with an approximately equal weight of particulate nickel. It will be realized that small quantities of additional materials such as Fe4N may be added to this mixture to generate a pressure of nitrogen gas during evaporation of barium in order to control the spacial distribution and porosity of the resulting deposited barium film.
  • the gettering system also comprises a second getter metal vapour releasing material capable of releasing titanium vapour upon heating such as a titanium-tantalum alloy wire or a tantalum wire clad with titanium.
  • a second holder 122 which is shown in more detail in Fig. 2.
  • Holder 122 is preferably of ring shape having an outer side wall 124 and a bottom wall 126 in general having a pan-shaped appearance.
  • the holder 122 can be made from a ceramic material but it is preferably made from a metal having a higher melting point than the melting point of titanium. It could therefore be made from molybdenum, niobium (columbium), tantalum or tungsten.
  • Holder 122 supports a getter metal vapour relasing material 128 which comprises a mixture of particulate titanium and a particulate refractory metal. It is desirable to have the titanium in particulate form as it then has a large surface area per unit mass, thus aiding the evaporation of titanium.
  • the particle size should not be too large otherwise the surface area per unit mass is low and excessively long heating times are required to ensure release of sufficient titanium to provide the necessary high pumping speed for removing the nitrogen produced at first switch on of a cathode in a display tube. If the titanium particle size is too small then it becomes difficult to handle during manufacture of the getter device, with dangers of explosion.
  • the titanium particle size should therefore be between 2 and 100 ⁇ m and preferably between 5 and 44 ⁇ m.
  • titanium When titanium is heated to such a high temperature that its rate of evaporation is sufficiently large it is very near to its melting point and is subject to a reduction of its surface area, if in particulate form, due to thermal sintering. It is therefore preferable to mix the particulate titanium with an anti-sintering material such as a refractory metal.
  • a refractory metal Suitable refractory metals are molybdenum, niobium, tantalum and tungsten. Tantalum is preferred as it is also a getter material at high temperatures but does not oxidize on exposure to air at 400°C.
  • the tantalum particle size should be between 2 and 100 ⁇ m and preferably be between 5 and 44 ⁇ m to ensure even and easy mixture with the titanium powder.
  • the weight ratio of titanium to refractory metal can vary between wide limits. If the ratio of titanium is too high the refractory metal will be unable to perform its antisintering function. If the ratio of titanium is too low it may not be possible to evaporate the required quantity of titanium in an acceptably short time.
  • the weight ratio of titanium to refractory metal should therefore be from 19:1 to 1:19 and preferably be from 5:1 to 1:5.
  • the first getter metal vapour releasing material capable of releasing barium vapour upon heating is located within the cone portion of a cathode ray display tube in such an orientation that, upon heating, the barium vapours are preferentially directed towards the screen portion leaving a part of the cone portion substantially free from deposited barium.
  • the second getter metal vapour releasing material capable of releasing titanium vapour upon heating is located within the cathode ray display tube in such an orientation that, upon heating the titanium vapours are preferentially directed towards the part of the cone portion substantially free from deposited barium. It will be realized that the quantity of titanium deposited and the area over which it is deposited must be sufficiently large to ensure that the nitrogen released at first switch-on of the cathode is quickly removed to maintain its pressure below that which might cause damage to the cathode.
  • a getter sorption characteristics test apparatus 300 was constructed as shown very schematically in Fig 3.
  • Test apparatus 300 comprised a glass sphere 302 having an internal surface area of 450 cm2, and a cylindrical appendage 304 having a diameter of 3 cm. Provision was made for placing and substituting a barium getter metal vapour releasing material 306 in a position where sphere 302 joined appendage 304.
  • a titanium getter metal vapour releasing material 308 could also be placed centrally of bulb 302 by means of electrical support leads 310, 310'.
  • Apparatus 300 was also provided with means, not shown, for its evacuation and the introduction of nitrogen gas in such a way as to measure the sorption characteristics of getter materials evaporated within the apparatus 300 according to the procedure described in ASTM F 111.
  • This example is not representative of the present invention and was designed to show the sorption characteristics of a known barium film.
  • Example 1 is not representative of the present invention and was designed to show the sorption characteristics of another known barium film.
  • Example 1 was repeated in all respects except that the mixture contained an amount of Fe4N capable of producing a nitrogen pressure of between 10 ⁇ 3 and 5x10 ⁇ 2 mbar of nitrogen gas during barium evaporation.
  • the resulting sorption characteristics of the barium fim are shown in Fig. 4 as curve 2.
  • This example was repeated resulting in curve 3 in Fig. 4.
  • This example is not representative of the present invention and was designed to show the sorption characteristics of a known titanium film.
  • This example is not representative of the present invention and was designed to show the sorption characteristics of a barium film with a titanium film deposited thereon.
  • Example 2 The procedure of Example 2 was repeated to produce a barium film on the internal surface of the sphere. Successively there was evaporated a film of titanium over the barium as described in Example 3. The amount of titanium evaporated was 0.68 mg.
  • curve 3 of Fig. 4 is also reported on Fig. 6 as curve 3'.
  • This example is illustrative of the present invention.
  • test apparatus as previously described was used except that the titanium getter metal vapour releasing material was placed in the cylindrical appendage.
  • a barium film was produced on the inside surface of the sphere as described in Example 2 and titanium was evaporated within the cylindrical appendage. 0.6 mg of titanium were evaporated onto a surface area of 50 cm2 thus the barium and titanium films were deposited on separate surfaces but within cnnecting volumes. The sorption characteristics for nitrogen gas were measured and reported on Fig. 6 as curve 8.
  • curve 3 of Fig. 4 is also reported on Fig. 7 as curve 3".
  • This example describes a less preferred embodiment of getter metal vapour upon heating.
  • This example describes the most preferred embodiment presently known of a holder supporting a getter metal vapour releasing material capable of releasing titanium vapour upon heating.
  • pan-shaped holders were pressed from a molybdenum sheet of 0.15 mm thickness.
  • the holders were of 11 mm inside diameter having an outer side wall height of 1.5 mm.
  • Into the holder was compressed, with a force of 4000 kg, 100 mg of a mixture of 80% by weight of particulate titanium and 20% by weight of particulate tantalum.
  • the particle size of both the titanium and tantalum was sich that they passed through a U.S. standard sieve of 325 mesh per inch (128 mesh per cm).
  • the pan-shaped holders were then placed in a vacuum environment and heated by induction heating to cause evaporation of titanium. The heating was continued for 30 seconds.
  • the quantity of titanium evaporated from each sample is shown in Table II.
  • Example 7 A sample prepared exactly as in Example 7 was subjected to heating in air at 400°C for 10 min. before causing it to evaporate titanium in a vacuum environment. It was found to have evaporated 7.2 mg of titanium in 30 seconds.
  • Fig. 4 shows that barium films have a high sorption capacity but an undesirable low initial pumping speed for nitrogen gas.
  • Fig. 5 shows that titanium films have very high initial pumping speeds but very low sorption capacities for nitrogen gas.
  • Fig. 7 shows that is the barium and titanium films are separated than there is a resultant high initial pumping speed and a high sorption capacity.
  • a colour cathode ray display tube is constructed as shown in Fig. 1 .
  • a first stainless steel holder supporting approximately 1000 mg of a mixture of a particulate alloy of about 50% barium and 50% aluminium together with an approximately equal weight of particulate nickel and a small quantity of Fe4N sufficient to produce a pressure of between 10 ⁇ 3 and 5x10 ⁇ 2 mbar of nitrogen during evaporation of barium is attached to the metal screening cap.
  • a second pan-shaped holder manufactured exactly as described in Example 7 is attached to the metal screening cap, between the cap and the cone portion of the display tube.
  • Both first and second getter metal vapour releasing materials are subject to the frit sealing process during display tube manufacture. After evacuation and sealing of the tube the first holder is heated to release barium metal vapours. Then the second holder is heated to release titanium vapours which are deposited on an area where barium has not been deposited. When the tube is first switched on the pressure of nitrogen remains below that which would cause damage to the cathode.

Landscapes

  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
EP19900830621 1990-01-05 1990-12-31 Gettering device and system for a cathode ray tube Withdrawn EP0436477A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT01901790A IT1237948B (it) 1990-01-05 1990-01-05 Dispositivo getter ed insieme getterante per un tibo a raggi catodici
IT1901790 1990-01-05

Publications (2)

Publication Number Publication Date
EP0436477A2 true EP0436477A2 (de) 1991-07-10
EP0436477A3 EP0436477A3 (en) 1991-12-18

Family

ID=11153873

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19900830621 Withdrawn EP0436477A3 (en) 1990-01-05 1990-12-31 Gettering device and system for a cathode ray tube

Country Status (4)

Country Link
EP (1) EP0436477A3 (de)
JP (1) JPH04133250A (de)
KR (1) KR910014988A (de)
IT (1) IT1237948B (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0544351A1 (de) * 1991-11-18 1993-06-02 Koninklijke Philips Electronics N.V. Bildröhre mit entfernbarem Getter
US5898272A (en) * 1997-08-21 1999-04-27 Everbrite, Inc. Cathode for gas discharge lamp
FR2771549A1 (fr) * 1996-05-29 1999-05-28 Futaba Denshi Kogyo Kk Recipient hermetique sous vide

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4889947B2 (ja) * 2005-01-14 2012-03-07 パナソニック株式会社 気体吸着合金

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3387908A (en) * 1966-08-17 1968-06-11 Nat Video Corp Electron vacuum tube getter and method of using the same
GB1221107A (en) * 1967-04-21 1971-02-03 Thomson Csf Improvements in titanium vaporizers for use in vacuum getter pumps
US3792300A (en) * 1972-07-15 1974-02-12 Gte Sylvania Inc Cathode ray tube having a conductive metallic coating therein
JPS5291364A (en) * 1976-01-28 1977-08-01 Hitachi Ltd Crt and production thereof
GB2157073A (en) * 1984-03-16 1985-10-16 Getters Spa Cathode ray tube with an electrophoretic getter
WO1989010627A1 (en) * 1988-04-20 1989-11-02 Saes Getters S.P.A. High yield pan-shaped getter device

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3387908A (en) * 1966-08-17 1968-06-11 Nat Video Corp Electron vacuum tube getter and method of using the same
GB1221107A (en) * 1967-04-21 1971-02-03 Thomson Csf Improvements in titanium vaporizers for use in vacuum getter pumps
US3792300A (en) * 1972-07-15 1974-02-12 Gte Sylvania Inc Cathode ray tube having a conductive metallic coating therein
JPS5291364A (en) * 1976-01-28 1977-08-01 Hitachi Ltd Crt and production thereof
GB2157073A (en) * 1984-03-16 1985-10-16 Getters Spa Cathode ray tube with an electrophoretic getter
WO1989010627A1 (en) * 1988-04-20 1989-11-02 Saes Getters S.P.A. High yield pan-shaped getter device

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 1, no. 150 (E-77)(7866) December 5, 1977 & JP-A-52 91 364 (HITACHI SEISAKUSHO ) August 1, 1977 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0544351A1 (de) * 1991-11-18 1993-06-02 Koninklijke Philips Electronics N.V. Bildröhre mit entfernbarem Getter
FR2771549A1 (fr) * 1996-05-29 1999-05-28 Futaba Denshi Kogyo Kk Recipient hermetique sous vide
US5898272A (en) * 1997-08-21 1999-04-27 Everbrite, Inc. Cathode for gas discharge lamp

Also Published As

Publication number Publication date
IT1237948B (it) 1993-06-19
IT9019017A0 (it) 1990-01-05
IT9019017A1 (it) 1991-07-06
KR910014988A (ko) 1991-08-31
EP0436477A3 (en) 1991-12-18
JPH04133250A (ja) 1992-05-07

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