EP0404244A1 - Cathode-ray tube - Google Patents

Cathode-ray tube Download PDF

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Publication number
EP0404244A1
EP0404244A1 EP90201573A EP90201573A EP0404244A1 EP 0404244 A1 EP0404244 A1 EP 0404244A1 EP 90201573 A EP90201573 A EP 90201573A EP 90201573 A EP90201573 A EP 90201573A EP 0404244 A1 EP0404244 A1 EP 0404244A1
Authority
EP
European Patent Office
Prior art keywords
tube
cathode
ray tube
hollow tube
getter
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Withdrawn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
EP90201573A
Other languages
German (de)
English (en)
French (fr)
Inventor
Gerardus Arnoldus Herman Maria Vrijssen
Willem Meijndert Van Alphen
Ger-Wim Jan Goorhuis
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.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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
Priority claimed from NL8901587A external-priority patent/NL8901587A/nl
Application filed by Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Gloeilampenfabrieken NV
Publication of EP0404244A1 publication Critical patent/EP0404244A1/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • 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
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/58—Arrangements for focusing or reflecting ray or beam
    • H01J29/62—Electrostatic lenses
    • H01J29/622—Electrostatic lenses producing fields exhibiting symmetry of revolution
    • H01J29/624—Electrostatic lenses producing fields exhibiting symmetry of revolution co-operating with or closely associated to an electron gun
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2229/00—Details of cathode ray tubes or electron beam tubes
    • H01J2229/48—Electron guns
    • H01J2229/4824—Constructional arrangements of electrodes
    • H01J2229/4827—Electrodes formed on surface of common cylindrical support

Definitions

  • the invention relates to a cathode ray tube having an envelope, comprising on the one side a luminescing screen and on the other side a neck portion, having an electron gun which is positioned in the neck portion and which includes a beam-forming portion and a focusing structure, the focusing structure including an open-ended hollow tube of an electrically insulating material, having an inner surface on which a layer of a material having a high electrical resistance is deposited and a getter arrangement provided in the envelope.
  • Such a cathode ray tube can be used in black/white colour and projection television, in arrangements for displaying figures and letters (Data Graphics Display) and in other arrangements in which a cathode ray tube is used.
  • an accurate focusing may be obtained by means of a layer of a material having a high electrical resistance, which layer is, for example, of a helical structure and over whose extremity a voltage difference is applied, it was found in practice that the focusing does not always come up to the expectations.
  • an object of the invention to provide a cathode ray tube provided with an electron gun having a focusing structure of the type defined in the opening paragraph which provides an accurate focusing.
  • a cathode ray tube of the type defined in the opening paragraph is characterized, in that the layer on the inner surface of the hollow tube is shielded from the getter arrangement.
  • the invention is based on the following recognition.
  • the envelope is evacuated during the production of a cathode-ray tube.
  • the cathode-ray tube is heated to a temperature of, for example, about 400 o C to promote degassing of the parts of the cathode-ray tube.
  • a getter arrangement in the cathode-ray tube to bind the gases released during evacuation and also during the operating life of the cathode-ray tube.
  • This getter arrangement contains a material which is able to bind the released gases.
  • the material contains inter alia metallic barium.
  • the getter material is generally placed in the envelope and vaporised in a manufacturing step (gettering), so that a layer of finely distributed getter material is formed, for example on the inner wall of the envelope.
  • the invention is based on the recognition that the required high electrical resistance of the layer (of the order of, for example 1010 ⁇ ) is unintentionally reduced during this gettering operation because electrically conducting getter material may land on the layer of resistance material. If the high-ohmic resistance layer has a helical structure, then the generated focusing field may be disturbed, as precipitated getter material causes a short-circuit between the individual turns.
  • the inner surface of the hollow tube is shielded from the getter arrangement, which means that the layer of a material having a high electrical resistance of the focusing arrangement is shielded from getter material precipitating thereon during the gettering operation.
  • This shielding is effected by a specific positioning of the hollow tube and the getter arrangement relative to each other and/or by using shielding means.
  • the inner surface of the hollow tube is effectively shielded in an embodiment of the invention, from the getter arrangement, because an open-ended auxiliary tube is provided at the end of the hollow tube facing the luminescing screen, the axis of which is substantially in line with the axis of the hollow tube. It was found in practice that the vaporised getter material mainly precipitates on the end of the hollow tube facing the luminescing screen. By providing the hollow tube with an open-ended auxiliary tube, the getter material vaporised towards the end of the hollow tube precipitates to a large extent or completely onto the auxiliary tube and not on the high ohmic resistance layer.
  • the auxiliary tube is, for example, cylindrical or conical.
  • the smallest inner diameter of the auxiliary tube is less than the inner diameter of the hollow tube. If the inner diameter of the auxiliary tube is less than the inner diameter of the hollow tube, then the auxiliary tube functions also as a diaphragm. As a result of its acting as a diaphragm, the shielding of the high ohmic layer of the inner surface of the hollow tube is efficient.
  • a further preferred embodiment of a cathode ray tube according to the invention is characterized in that the auxiliary tube is made of an electrically insulating material.
  • a generated electron beam is deflected over the luminescing screen by means of a deflection unit.
  • the deflection field generated by the deflection unit may extend as far as or even into the focusing structure.
  • An alternative embodiment of a cathode-ray tube according to the invention, in which the deflection field to be generated is substantially not influenced disadvantageously, is characterized in that the auxiliary tube is manufactured from an electrically insulating material and is provided with at least one gap which extends substantially parallel to the axis of the hollow tube.
  • the gaps in the auxiliary tube prevent eddy currents from occurring in the auxiliary tube, which might disturb the deflection field.
  • the getter arrangement is attached in a position between the said end and the luminescing screen at the said end of the hollow tube, so that the getter arrangement having the focusing structure is integrated and less separate parts are required in the cathode-ray tube.
  • a further preferred embodiment of a cathode-ray tube according to the invention is characterized, in that the getter arrangement is located in the neck portion between the hollow tube and the inner surface of the neck portion.
  • the getter arrangement is located in the neck portion between the hollow tube and the inner surface of the neck portion.
  • a shield is located, in a preferred embodiment of a cathode-ray tube according to the invention, between the end of the hollow tube opposite the phosphor screen and the inner surface of the neck portion of the cathode-ray tube. This causes the vaporised getter material to land on the shield.
  • a cathode-ray tube comprising a luminescing screen, for example a phosphor screen 40 deposited on a display window 41 and an electron gun 3 mounted in a neck portion 2, is shown.
  • a G1 (grid) electrode structure is provided with a typical aperture behind which a cathode 4 having an electron-emitting surface is deposited, with a heater 5 bordering thereon.
  • a G2 electrode structure in this case constituted by a metal sheet 6 having a central aperture, is located more to the front, bordering on the G1 electrode structure.
  • a G3 electrode structure, constituted by a metal sheet is located even more to the front.
  • a focusing structure 10 includes a hollow tube 12 of an electrically insulating material, for example glass or ceramic, which hollow tube 12 is coated on its inner surface with a layer 14 of a material having a high electrical resistance.
  • the tube 12 is rigidly connected to a fold edge 17 of a metal sheet 16 at its end 13, which fold edge 17 surrounds an aperture 18 in the sheet 16 via which metal sheet 16 it is attached to the mounting rods to which also the beam-forming portion of the gun is secured.
  • the tube 12 is secured to the mounting rods at its end 15 in a similar manner, by means of a metal sheet 31.
  • a voltage difference is applied across the ends of the layer by connecting the metal sheets 16 and 31 to external voltage sources (not shown in Fig. 1).
  • the layer 14 may have the shape of one or more rings, or it may have, for example a helical shape or a combination of one or more rings with a helix.
  • the electron gun 3 is positioned in the neck portion 2 by means of a centring unit having flexible elements 32 in this embodiment.
  • the flexible elements 32 also provide an electrical connection between the sheet 31 and an electrically conducting layer 33 deposited on the inner surface of the envelope of the cathode-ray tube.
  • the anode contact 42 is present for applying a desired potential to the conducting layer 33.
  • a getter arrangement 43 is provided on the anode contact 42.
  • the getter arrangement 43 contains getter material which is capable of binding the gases released and thus provides the vacuum in the envelope.
  • the getter material 44 is vaporised in a manufacturing step, so that a layer of finely distributed getter material is formed.
  • Connected to the end 15 of the hollow tube 12 facing the phosphor screen 14 is an open-ended auxiliary tube 45, the axis 46 of which is substantially located in the extension of the axis 47 of the hollow tube 12. Because of the fact that the getter material, vaporised in the direction of the hollow tube 12, precipitates largely or completely onto the auxiliary tube 45, the inner surface of the hollow tube 12 on which the resitance layer 14 is provided, is shielded from the getter material.
  • the electrical resistance of the resistance layer 14 and the focusing of the focusing structure 10 is not influenced disadvantageously by the vaporised getter material, neither substantially nor to a large extent, because of the presence of the auxiliary tube 45.
  • Fig. 2 shows schematically an alternative embodiment of a cathode ray tube according to the invention in a longitudinal cross-­sectional view.
  • the same reference numerals denote the same components in Figs. 1 and 2.
  • the getter arrangement 43 is provided with a shield 50.
  • This shield 50 is positioned between the getter material 43 and the hollow tube 12. Vaporised getter material will precipitate on the shield 50 and substantially no vaporised getter material will land on the high ohmic resistance layer 14. The resistance layer 14 is thus shielded from the getter arrangement 43.
  • the generated electron beams are deflected over the phosphor screen 40 by means of a deflection unit (not shown).
  • the deflection field generated by the deflection unit may extend to as far as or even into the hollow tube 12 of the focusing structure.
  • the auxiliary tube 45 must not exercise any substantially disadvantageous influence on this deflection field, especially at high frequencies.
  • the deflection field is not influenced substantially disadvantageously when the auxiliary tube 45 is provided with one or more slots 51.
  • the number of slots 51 to be made in the auxiliary tube 45 depends on the disadvantageous influence of the auxiliary tube 45 on the deflection field.
  • the auxiliary tube 45 is made of an electrically insulating material, for example glass.
  • a generated deflection field is not influenced disadvantageously in a simple manner.
  • the inner diameter of the auxiliary tube 45 is equal to that of the hollow tube 12.
  • the inner diameter of the auxiliary tube 45 is preferably smaller than that of the hollow tube 12, so that the resistance layer 14 is shielded from the getter arrangement to an improved extent.
  • Fig. 3 is a schematical longitudinal cross-sectional view of an alternative embodiment of a cathode ray tube according to the invention.
  • the hollow tube 12 carries both the focusing structure 10 and the electrodes of the beam-forming portion.
  • the supply of electrical potentials to the electrodes of the beam-­forming portion is, for example, achieved by means of feed-through wires (not shown in Fig. 3) through the hollow tube 12.
  • the hollow tube 12 is suspended in the neck portion 2 from connection pins 23 and by flexible elements 32.
  • the auxiliary tube 45 is an extended portion of the hollow tube 12.
  • the end of the auxiliary tube 45 is closed by a diaphragm 52, onto which a portion of the vaporised getter material precipitates.
  • the resistance layer 14 on the inner surface of the hollow tube 12 extends as far as the auxiliary tube 45.
  • Fig. 4 shows schematically a portion of a cathode-ray tube according to the invention, in which the hollow tube 12 carries both the focusing structure 10 and the auxiliary tube 45 and furthermore the getter arrangement 44.
  • the getter arrangement 44 is attached to the centering unit with flexible elements 32 by means of metal strips 48.
  • the getter arrangement is located at 22 mm from the end of the hollow tube 12 in the direction of the phosphor screen 40.
  • the hollow tube 12 has an inner diameter of 10 mm.
  • the auxiliary tube 45 has a length of 7 mm and an inner diameter of 6 mm. Because of the fact that the auxiliary tube 45 has a smaller inner diameter than the hollow tube 12, the auxiliary tube 45 functions as a diaphragm. A length of 7 mm was found to be sufficient to realise that substantially no vaporised getter material precipitates onto the resistance layer 14.
  • Fig. 5 shows an alternative embodiment of a cathode-ray tube according to the invention.
  • the getter arrangement 9 is located in the neck portion 2 around the hollow tube 12.
  • the getter arrangement 9 contains getter material 19 which after gettering forms a layer 20 of finely distributed getter material.
  • This layer 20 of vaporised getter material is located substantially completely on the outer surface of the hollow tube 12 and at the inner surface of the neck portion 2. Because of this structure substantially no getter material lands on the resistance layer 14.
  • the getter arrangement 9 is annular and is attached to the centring unit by means of strips 52.
  • the invention is not limited thereto. It is, for example, possible for the getter arrangement to be attached also to the mounting rods, one of which (8) is shown, or to be supported by the hollow tube 12 or the neck portion 2.
  • the shield 21 may, for example, be made from a metal or an insulating material.
  • the getter arrangement is formed by two annular channels 9 and 9′, which may be attached directly or indirectly to the hollow tube 12, whereby a simple structure is obtained.
  • the getter material is contained in the channels. After having been vaporised, the getter material is at least partly present on the outer surface of the hollow tube 12 and on the inner surface of the neck portion 2.
  • a conical shield 22 the diameter of which tapers down towards the phosphor screen in this case, is arranged between the hollow tube 12 and the inner surface of the neck portion 2 and thus prevents unwanted precipitation of getter material onto the high ohmic resistance layer 14.

Landscapes

  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
EP90201573A 1989-06-23 1990-06-18 Cathode-ray tube Withdrawn EP0404244A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
NL8901587A NL8901587A (nl) 1989-06-23 1989-06-23 Kathodestraalbuis.
NL8901587 1989-06-23
NL9000117 1990-01-18
NL9000117A NL9000117A (nl) 1989-06-23 1990-01-18 Kathodestraalbuis.

Publications (1)

Publication Number Publication Date
EP0404244A1 true EP0404244A1 (en) 1990-12-27

Family

ID=26646543

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90201573A Withdrawn EP0404244A1 (en) 1989-06-23 1990-06-18 Cathode-ray tube

Country Status (3)

Country Link
EP (1) EP0404244A1 (ja)
JP (1) JPH0340343A (ja)
NL (1) NL9000117A (ja)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4966913B2 (ja) 2007-05-15 2012-07-04 株式会社日立ハイテクノロジーズ 液体分注装置

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4220893A (en) * 1976-07-26 1980-09-02 Zenith Radio Corporation Electrically resistive arc suppressor shadowing getter flash
US4665340A (en) * 1985-03-07 1987-05-12 Tektronix, Inc. Cathode-ray-tube electrode structure having a particle trap
EP0233379A1 (en) * 1986-02-17 1987-08-26 Koninklijke Philips Electronics N.V. Cathode ray tube and method of manufacturing a cathode ray tube
US4806821A (en) * 1986-05-30 1989-02-21 U.S. Philips Corporation Cathode ray tube having an electron gun with bipotential focusing lens

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4220893A (en) * 1976-07-26 1980-09-02 Zenith Radio Corporation Electrically resistive arc suppressor shadowing getter flash
US4665340A (en) * 1985-03-07 1987-05-12 Tektronix, Inc. Cathode-ray-tube electrode structure having a particle trap
EP0233379A1 (en) * 1986-02-17 1987-08-26 Koninklijke Philips Electronics N.V. Cathode ray tube and method of manufacturing a cathode ray tube
US4806821A (en) * 1986-05-30 1989-02-21 U.S. Philips Corporation Cathode ray tube having an electron gun with bipotential focusing lens

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 12, no. 337 (E-657)(3184) 12 September 1988, & JP-A-63 98943 (HITACHI SEISAKUSHO K.K.) 30 April 1988, *

Also Published As

Publication number Publication date
JPH0340343A (ja) 1991-02-21
NL9000117A (nl) 1991-01-16

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