WO2007027184A1 - Écran magnétique interne de dispositif d’affichage à balayage orthogonal - Google Patents

Écran magnétique interne de dispositif d’affichage à balayage orthogonal Download PDF

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Publication number
WO2007027184A1
WO2007027184A1 PCT/US2005/031285 US2005031285W WO2007027184A1 WO 2007027184 A1 WO2007027184 A1 WO 2007027184A1 US 2005031285 W US2005031285 W US 2005031285W WO 2007027184 A1 WO2007027184 A1 WO 2007027184A1
Authority
WO
WIPO (PCT)
Prior art keywords
display device
magnetic shield
internal magnetic
cut
short sides
Prior art date
Application number
PCT/US2005/031285
Other languages
English (en)
Inventor
Peter Finkel
Original Assignee
Thomson Licensing
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 Thomson Licensing filed Critical Thomson Licensing
Priority to PCT/US2005/031285 priority Critical patent/WO2007027184A1/fr
Priority to TW095131592A priority patent/TW200733167A/zh
Publication of WO2007027184A1 publication Critical patent/WO2007027184A1/fr

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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
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/06—Screens for shielding; Masks interposed in the electron stream

Definitions

  • the invention generally relates to a display device and, more particularly, to an internal magnetic shield for use in a display device such as a cathode ray tube.
  • An ambient magnetic field in a vicinity of a cathode ray tube can affect the color rendition of an image projected on a viewing faceplate of the cathode ray tube.
  • the ambient magnetic field is mainly caused by the earth's magnetic field and can be affected by local magnetic fields and magnetic materials in the area. Because the ambient magnetic field is unidirectional, it can be vectorally decomposed into vertical and horizontal components that vary depending on geographical location. The effect of the North/South and East/West components of the ambient magnetic field on the electron beams in a cathode ray tube with respect to a given cathode ray tube coordinate system completely depends on the orientation of the cathode ray tube.
  • the effect of the vertical component on the path of the electron beams of the cathode ray tube is relatively constant and will vary as the geographic latitude of the cathode ray tube changes.
  • the effect of the horizontal components (which can be North/South and/or East/West oriented with respect to the cathode ray tube) on the path of the electron beams of the cathode ray tube changes as a function of the orientation of the cathode ray tube.
  • the vertical component of the ambient magnetic field deflects the electron beams horizontally, which affects the register of each of the electron beams on the desired luminescent element.
  • the North/South components of the ambient magnetic field cause lateral deflection of the electron beam at the top and bottom of the screen.
  • the East/West component of the ambient magnetic field deflects the electron beams vertically along the luminescent element, which does not significantly affect the register of each of the electron beams on the desired luminescent element.
  • the cathode ray tube can be set to minimize vertical field misregister.
  • the East/West component has little effect on register when the orientation of the cathode ray tube is varied in the horizontal plane direction.
  • Magnetic shielding could be designed to minimize the effect of north and south orientation and keep the overall effects of the earth's magnetic field to within the tolerance of the system. Such magnetic shielding systems are well known in the art.
  • cathode ray tubes having inline electron guns aligned in a vertical plane and horizontally oriented luminescent elements.
  • the vertical component of the ambient magnetic field causes the electron beams to deflect horizontally along the phosphor lines, which does not significantly affect the register of each of the electron beams on the desired luminescent element.
  • the horizontal component of the ambient magnetic field causes the electron beams to deflect vertically, which affects the register of each of the electron beams on the desired luminescent elements.
  • the effect of the horizontal component on the path of the electron beams changes dramatically as the orientation of the cathode ray tube in the east to west direction is varied, it is significantly more difficult to design adequately balanced shielding for all north, south, east, and west orientations. Additionally, the relationship between the orientation of the cathode ray tube and the horizontal component is entirely under the control of the consumer, who will orient the cathode ray tube based on personal preference. The purity of the cathode ray tube is also affected, especially at high deflection angles in the comers, where the residual horizontal component of the magnetic field, even in a vertical ambient field, is high because of the effect of residual magnetism in the ferromagnetic internal CRT components.
  • the corners In internal magnetic shields, the corners often have magnetic properties which are better (i.e. high magnetic permeability and low coercivity) than other areas of the internal magnetic shield. If the corners are too good (i.e. even higher magnetic permeability and lower coercivity), large magnetic residuals of opposite sign (with respect to ambient magnetic fields) will remain in the corners even after degaussing, causing overcompensation of the shielding in the corners. It is therefore desirable to develop an internal magnetic shield that reduces the effect of ambient magnetic fields in cathode ray tubes having inline electron guns aligned in a vertical plane and horizontally oriented luminescent elements.
  • the invention relates to a display device comprising an envelope including a faceplate panel and a neck connected by a funnel.
  • the faceplate panel has a screen with horizontally oriented luminescent elements.
  • An electron gun assembly is positioned in the neck and directs electron beams toward the screen where the electron beams are scanned vertically.
  • An internal magnetic shield has opposing short sides and opposing long sides. The short sides extend substantially vertically and the long sides extend substantially horizontally. Each of the short sides has at least one cut-out extending generally horizontally therethrough. The internal magnetic shield thereby minimizes the effect of an ambient magnetic field to ensure that the electron beams are accurately directed toward the screen, particularly at comers of the screen.
  • Figure 1 is a partial sectional view of a display device having an internal magnetic shield according to a first embodiment of the invention
  • Figure 2 is a perspective view of the internal magnetic shield of Figure 1 ;
  • Figure 3 is a plan view of the internal magnetic shield of Figure 1;
  • Figure 4 is a plan view of an internal magnetic shield according to a second embodiment of the invention
  • Figure 5 is a plan view of an internal magnetic shield according to a third embodiment of the invention.
  • Figure 6 is a plan view of an internal magnetic shield according to a fourth embodiment of the invention.
  • FIGS 1 -3 show a display device having an internal magnetic shield 15 according to a first embodiment of the invention.
  • the display device is a cathode ray tube 1.
  • the cathode ray tube 1 has a glass envelope 2 comprising a rectangular faceplate panel 3 and a tubular neck 4 connected by a funnel 5.
  • the funnel 5 has an internal conductive coating (not shown) that extends from an anode button 6 toward the faceplate panel 3 and to the neck 4.
  • the faceplate panel 3 comprises a viewing faceplate 8 and a peripheral flange or sidewall 9.
  • the peripheral flange or sidewall 9 is sealed to the funnel 5 by a glass frit 7.
  • a luminescent screen 12 such as a three-color phosphor screen having a plurality of alternating luminescent elements (not shown), is carried by an inner surface of the faceplate panel 3.
  • the luminescent elements (not shown) extend generally parallel to a major axis (X- axis) of the screen 12 and are arranged in triads. Each of the triads includes a luminescent element of each of three colors (red, green, and blue).
  • a mask assembly 10 is removably mounted in predetermined spaced relation to the screen 12.
  • the mask assembly 10 includes a mask (not shown) that has a multiplicity of elongated slits extending generally parallel to the major axis of the screen 12. It will be appreciated by those skilled in the art that the mask assembly 10 may be any of a variety of conventional tension or shadow mask assemblies, which are well known in the art.
  • An electron gun assembly 13 shown schematically by dashed lines in Figure 1, is centrally mounted within the neck 4.
  • the electron gun assembly 13 comprises three inline electron guns (not shown) aligned generally parallel to a minor axis (Y-axis) of the screen 12.
  • Each of the electron guns (not shown) generates and directs an electron beam for each of the three colors (red, green, and blue) along convergent paths through the mask assembly 10 to the screen 12.
  • An external magnetic deflection yoke 14 is positioned on an exterior surface of the funnel 5 in a neighborhood of the funnel-to-neck junction. When activated, the yoke 14 subjects the three electron beams to magnetic fields that cause the electron beams to scan vertically and horizontally in a rectangular raster over the screen 12.
  • the internal magnetic shield 15 is supported on the mask assembly 10.
  • the internal magnetic shield 15 is substantially cone-like in shape and encompasses an internal volume of the cathode ray tube 1 from a point slightly forward from the neck 4 to a point slightly rearward of the mask (not shown).
  • An opening 16 extends from a rear end 22 to a front end 23 of the internal magnetic shield 15 for allowing passage of the electron beams therethrough.
  • the internal magnetic shield 15 has opposing short sides 18 and opposing long sides 19.
  • the short sides 18 extend substantially parallel to the minor axis of the cathode ray tube 1 and the long sides 19 extend substantially parallel to the major axis of the cathode ray tube 1. Between each of the short sides 18 and the long sides 19 is a corner 20.
  • Cut-outs 17 are formed in the short sides 18.
  • the cut-outs 17 are formed in an approximate center of the short sides 18 and extend from proximate the rear end 22 to proximate the front end 23 generally parallel to the major axis.
  • the cut-outs 17 are substantially elongated in shape and have a width 21 of approximately 0.5-2 inches. It will be appreciated by those skilled in the art that although only one of the cut-outs 17 is illustrated and described as being formed in each of the short sides 18, the short sides 18 could alternatively be formed with multiple cut-outs. Additionally, it will be appreciated by those skilled in the art that although the cut-outs 17 are illustrated and described as being substantially elongated in shape, the cut-outs 17 could alternatively have other geometric configurations.
  • the internal magnetic shield 15 may be formed of a ferromagnetic material, such as steel, low carbon steel, iron-nickel alloy, or the like.
  • each of the electron guns (not shown) of the electron assembly 13 generates and directs the electron beams for each of the three colors (red, green, and blue) through the opening 16 in the internal magnetic shield 15, through the mask assembly 10, and onto the screen 12, as shown in Figure 1.
  • the internal magnetic shield 15 is provided with the cut-outs 17 that extend generally parallel to the major axis, the effect of the East/West component of the ambient magnetic field on the electron beams (not shown) is minimized so that the electron beams (not shown) are not deflected as far parallel to the minor axis.
  • the internal magnetic shield 15 thereby reduces misregister of the electron beams (not shown) on the respective luminescent elements (not shown), particularly at corners of the screen 12.
  • Figure 4 shows an internal magnetic shield 115 according to a second embodiment of the invention. Elements of the second embodiment that are identical to elements of the first embodiment will be described using the same reference numerals and will not be explained in further detail.
  • the short sides 18 of the internal magnetic shield 115 are provided with cut-outs 117.
  • the cut-outs 117 are formed proximate the corners 20 of the internal magnetic shield 115 and extend from proximate the rear end 22 to proximate the front end 23 generally parallel to the major axis.
  • the cut-outs 117 are substantially triangular in shape.
  • cut-outs 117 are illustrated and described as being formed in each of the short sides 18, the short sides 18 could alternatively be formed with more or less than two of the cut-outs. Additionally, it will be appreciated by those skilled in the art that although the cut-outs 117 are illustrated and described as being substantially triangular in shape, the cut-outs 117 could alternatively have other geometric configurations. Because the operation of the internal magnetic shield 115 of the second embodiment of the invention is substantially identical to the operation of the internal magnetic shield 15 of the first embodiment, further description thereof has been omitted.
  • Figure 5 shows an internal magnetic shield 215 according to a third embodiment of the invention. Elements of the third embodiment that are identical to elements of the first embodiment will be described using the same reference numerals and will not be explained in further detail.
  • the short sides 18 of the internal magnetic shield 215 are provided with cut-outs 217.
  • the cut-outs 217 are formed in an approximate center of the short sides 18 and extend from proximate the rear end 22 to proximate the front end 23 generally parallel to the major axis.
  • the cut-outs 217 are substantially rectangular in shape.
  • Each of the cut-outs 217 is covered by a plate 224. Ends of the plate 224 are attached to a surface of the internal magnetic shield 215, for example, by an adhesive or welding 225.
  • the plate 224 is made from a non-magnetic material, such as stainless steel. Alternatively, the plate 224 can be made from a material which is less magnetic (i.e., lower permeability and higher coercivity) than the material of the internal magnetic shield 215.
  • the plate 224 has a thickness substantially the same as or less than a thickness of the internal magnetic shield 215. It will be appreciated by those skilled in the art that although only one of the cut-outs 217 is illustrated and described as being formed in each of the short sides 18, the short sides 18 could alternatively be formed with multiple cut-outs. Additionally, it will be appreciated by those skilled in the art that although the cut-outs 217 are illustrated and described as being substantially rectangular in shape, the cut-outs 217 could alternatively have other geometric configurations.
  • Figure 6 shows an internal magnetic shield 315 according to a fourth embodiment of the invention. Elements of the fourth embodiment that are identical to elements of the first embodiment will be described using the same reference numerals and will not be explained in further detail.
  • the short sides 18 of the internal magnetic shield 315 are formed to have sections 326 which are less magnetic than the material of the internal magnetic shield 315.
  • the sections 326 may be fabricated, for example, by heat treating the internal magnetic shield 315, saturating the internal magnetic shield 315 with nickel or aluminum, or changing the concentration of the material of the internal magnetic shield 315.
  • the sections 326 are formed in an approximate center of the short sides 18 and extend from proximate the rear end 22 to proximate the front end 23 generally parallel to the major axis.
  • the sections 326 are substantially triangular in shape and have a thickness substantially the same as the thickness of the internal magnetic shield 315. It will be appreciated by those skilled in the art that although only one of the sections 326 is illustrated and described as being formed in each of the short sides 18, the short sides 18 could alternatively be formed with multiple sections. Additionally, it will be appreciated by those skilled in the art that although the sections 326 are illustrated and described as being substantially triangular in shape, the sections 326 could alternatively have other geometric configurations.
  • Figure 7 shows an internal magnetic shield 415 according to a fifth embodiment of the invention.
  • the internal magnetic shield 415 has either an aperture or material with lower (inferior) magnetic properties (i.e. lower permeability and higher coercivity) at position 426 at the corners 20 of the internal magnetic shields and expands onto portions of the short sides 18 and the long sides 19.
  • the position 426 can have various shapes such as an elliptical, an oval, a slot, or triangle and will have a size large enough to prevent overcompensation in the corners.
  • This feature prevents the corners from having magnetic properties superior (i.e. higher magnetic permeability and lower coercivity) to the entire magnetic shield. Such magnetic properties would otherwise cause the internal magnetic shields to possess large magnetic residuals of opposite sign in the comers (with respect to ambient magnetic fields), thereby causing overcompensation of the shielding in the corners, even after degaussing.
  • the internal magnetic shields 15, 115, 215, 315, 415 are particularly useful in display devices where the electron guns (not shown) in the electron gun assembly 13 are oriented generally parallel to the minor axis, the electron beams generated from the electron guns (not shown) are scanned generally parallel to the minor axis, and the luminescent elements (not shown) are oriented generally parallel to the major axis.
  • the configurations of the internal magnetic shields 15, 115, 215, 315, 415 effectively minimize the effect of the horizontal magnetic field component in an ambient vertical magnetic field on the electron beams (not shown) in the corners so that the electron beams are not deflected along a dimension parallel to the minor axis.
  • the internal magnetic shields 15, 115, 215, 315, 415 thereby reduce misregister of the electron beams (not shown) on the respective luminescent elements (not shown), particularly at corners of the screen 12.

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  • Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)

Abstract

Cette invention concerne un dispositif d’affichage comprenant une enveloppe contenant un panneau de dalle et un col raccordé par un entonnoir. Le panneau de dalle comporte un écran à éléments luminescents orientés horizontalement. Un ensemble canon électronique est placé dans le col et dirige des faisceaux électroniques vers l’écran où ils sont balayés verticalement. Un écran magnétique interne possède des petits côtés opposés et des grands côtés opposés. Les petits côtés s’étendent sensiblement à la verticale et les grands côtés à l’horizontale. Chaque petit côté présente au moins une découpe le traversant en général à l’horizontale. L’écran magnétique interne minimise ainsi l’effet d’un champ magnétique local pour permettre aux faisceaux électroniques d’être précisément dirigés vers l’écran, en particulier dans ses coins.
PCT/US2005/031285 2005-08-31 2005-08-31 Écran magnétique interne de dispositif d’affichage à balayage orthogonal WO2007027184A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/US2005/031285 WO2007027184A1 (fr) 2005-08-31 2005-08-31 Écran magnétique interne de dispositif d’affichage à balayage orthogonal
TW095131592A TW200733167A (en) 2005-08-31 2006-08-28 Internal magnetic shield for display devices with orthogonal scanning

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2005/031285 WO2007027184A1 (fr) 2005-08-31 2005-08-31 Écran magnétique interne de dispositif d’affichage à balayage orthogonal

Publications (1)

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WO2007027184A1 true WO2007027184A1 (fr) 2007-03-08

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PCT/US2005/031285 WO2007027184A1 (fr) 2005-08-31 2005-08-31 Écran magnétique interne de dispositif d’affichage à balayage orthogonal

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TW (1) TW200733167A (fr)
WO (1) WO2007027184A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0464576A2 (fr) * 1990-06-25 1992-01-08 VIDEOCOLOR S.p.A. Appareil de compensation de champ magnétique
EP0570065A1 (fr) * 1992-05-15 1993-11-18 Koninklijke Philips Electronics N.V. Tube image en couleur muni d'un blindage magnétique interne
JP2003187717A (ja) * 2001-12-17 2003-07-04 Matsushita Electric Ind Co Ltd 陰極線管の内部磁気シールド及び陰極線管を用いた表示装置
EP1557859A1 (fr) * 2004-01-20 2005-07-27 MT Picture Display Germany GmbH Tube d'affichage en couleur muni d'un blindage magnétique amélioré

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0464576A2 (fr) * 1990-06-25 1992-01-08 VIDEOCOLOR S.p.A. Appareil de compensation de champ magnétique
EP0570065A1 (fr) * 1992-05-15 1993-11-18 Koninklijke Philips Electronics N.V. Tube image en couleur muni d'un blindage magnétique interne
JP2003187717A (ja) * 2001-12-17 2003-07-04 Matsushita Electric Ind Co Ltd 陰極線管の内部磁気シールド及び陰極線管を用いた表示装置
EP1557859A1 (fr) * 2004-01-20 2005-07-27 MT Picture Display Germany GmbH Tube d'affichage en couleur muni d'un blindage magnétique amélioré

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 2003, no. 11 5 November 2003 (2003-11-05) *

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Publication number Publication date
TW200733167A (en) 2007-09-01

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