EP0570065A1 - Tube image en couleur muni d'un blindage magnétique interne - Google Patents

Tube image en couleur muni d'un blindage magnétique interne Download PDF

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Publication number
EP0570065A1
EP0570065A1 EP93201325A EP93201325A EP0570065A1 EP 0570065 A1 EP0570065 A1 EP 0570065A1 EP 93201325 A EP93201325 A EP 93201325A EP 93201325 A EP93201325 A EP 93201325A EP 0570065 A1 EP0570065 A1 EP 0570065A1
Authority
EP
European Patent Office
Prior art keywords
aperture
display screen
display tube
wall
colour
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.)
Granted
Application number
EP93201325A
Other languages
German (de)
English (en)
Other versions
EP0570065B1 (fr
Inventor
Adrianus Johannes c/o Int. Van Mensvoort
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
Koninklijke Philips Electronics NV
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
Application filed by Koninklijke Philips Electronics NV, Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Priority to EP93201325A priority Critical patent/EP0570065B1/fr
Publication of EP0570065A1 publication Critical patent/EP0570065A1/fr
Application granted granted Critical
Publication of EP0570065B1 publication Critical patent/EP0570065B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/06—Screens for shielding; Masks interposed in the electron stream

Definitions

  • the invention relates to a colour display tube comprising: an envelope with a longitudinal axis, having a neck portion, a funnel portion and a window portion; an electron gun arranged in the neck portion; a display screen having a short axis and a long axis and a pattern of phosphor lines parallel to an axis of the display screen on the inner surface of the window portion; a colour selection means arranged proximate to the display screen; a magnetic shielding structure arranged within the funnel-shaped portion, which shielding structure has two long wall portions parallel to the long axis of the display screen and two short wall portions parallel to the short axis of the display screen, and an aperture at its gun-sided end, which aperature extends transversely to the longitudinal axis and constitutes a scanning aperture for electron beams produced by the gun and scanning the display screen.
  • a colour selection means is herein understood to mean, for example, an apertured shadow mask sheet or a wire mask.
  • the ratio between the dimension of the long central axis and the dimension of the short central axis of the display screen characterizes the picture format.
  • Modern display tubes are provided with an internal magnetic shielding structure (shield) to limit the deviation of the electron path due to the earth's magnetic field.
  • a complete shielding is not possible due to an aperture which is required for passing the electron beam.
  • a horizontally directed spot displacement caused by the lateral earth's magnetic produces a risk of discolouration (N effect) in the corners only.
  • the internal residual field can be influenced by means of an additional measure in such a way that the electron beam still passes the mask at the desired angle. This measure involves, for example the use of a shield with "vertically" directed slits (situated in a plane parallel to the short axis of the display screen). The internal residual field is then influenced in such a way that there is less spot displacement in the horizontal direction.
  • the slits enhance the magnetic resistance in the shield material in the horizontal direction so that there is more spot displacement in the vertical direction.
  • this is no problem because it does not lead to discolouration.
  • the shield is split fully magnetically ("split shield"). Overcompensation of the N effect may then even occur.
  • a problem of "vertically" directed slits is that the slit length is to be limited to ensure the mechanical stability of the shield so that an unacceptable spot displacement remains in the corners, particularly in large tubes.
  • large tubes having a picture diagonal of 41 cm or mor such as 80 FS ("Flat Square") and 36 inch WS ("Wide Screen") it has been attempted to lengthen the slits to a maximum extent and to restore the resultant loss of mechanical strength by welding on supporting strips of non-ferromagnetic material.
  • 80 FS Frat Square
  • 36 inch WS Wide Screen
  • a display tube of the type described in the opening paragraph is therefore characterized in that each of the long wall portions of the shielding structure has at least one elongated aperture extending transversely to in the longitudinal direction of the wall and being remote from the edges of the wall, the magnetic resistance of the wall being locally higher than at both sides of the aperture between at least one end of the aperture and the adjacent edge of the wall.
  • the magnetic resistance of the wall for the lateral field can be increased in different ways, for example, by
  • a very effective measure appears to be the provision of a transverse slit between at least one end of the elongate aperture and the adjacent edge of the wall.
  • a transverse slit may be provided at the gun side, at the display screen side or at both sides of the slit-shaped aperture. The effect is greatest at the display screen side because this is closest to the location where influence should be exerted on the electron beam.
  • the effect of the measures according to the invention is enhanced if the shield is made of a sheet material.
  • Fig. 1 shows a colour display tube 1 having a glass envelope which comprises a neck portion 2 accommodating an electron gun system 3, a funnel-shaped portion 4 within which a magnetic shield 5 is arranged, and a window portion 6 whose inner surface is provided with a display screen 7 having a pattern of phosphors arranged along parallel lines.
  • a shadow mask 8 is arranged opposite the display screen 7.
  • the shape of the magnetic shield 5 in display tube 1 roughly follows the contours of the funnel-shaped portion.
  • Modern display tubes are provided with an internal magnetic shield to reduce the deviation of the electron path due to the earth's magnetic field. A complete shielding is not possible due to the apertures required for the electron beams. In a lateral field only the horizontally directed spot displacement in the corners causes a risk of discolouration (N effect).
  • the internal residual field is influenced via an additional measure in such a way that the electron beam still passes the mask at the desired angle.
  • Fig. 2A shows an example of a shield 9 in a rear view, in which no residual field correction is realised.
  • Fig. 2B shows the associated spot displacement in the corners, similarly as in a lateral earth's magnetic field.
  • Fig. 2C shows a shield 5 with vertically directed slits 10a, 10b.
  • the internal residual field is influenced thereby in such a way that there is less spot displacement in the horizontal direction.
  • the slits increase the magnetic resistance in the shield material in the horizontal direction so that there is more spot displacement in the vertical direction (Fig. 2D).
  • this is not important for line tubes because it does not cause discolouration.
  • Fig. 2E shows the shield 25 split completely magnetically. Overcompensation of the N effect may even occur in this case (see Fig. 2F).
  • a problem of the vertically directed slits is that the slit length is to be limited to ensure the mechanical stability of the shield so that an unacceptable spot displacement remains in the corners, particularly in large tubes.
  • the mechanical stability can be restored by welding on supporting strips of a non-ferromagnetic material.
  • the slits are not extended any more than is justified in connection with the mechanical stability of the shield and the magnetic resistance for the lateral field in alignment with the afore-mentioned vertically directed slits is enhanced by
  • Figs. 3A to 3B show some embodiments. Their use is attractive in all "line” tubes with a screen diagonal from 41 cm onwards, particularly in tubes having an aspect ratio of more than 4:3, such as 14:9 and 16:9.
  • Fig. 3A is an elevational view of a corner portion of a shield 20 having a long side wall 31 provided with an elongate transversal aperture, or slit 32.
  • This treatment may be a mechanical deformation (for example, by means of a centre punch) or a deformation by means of a laser beam, or diffusion of a non-magnetic material (for example, Al).
  • a shield with two (or more) - particularly shorter - slits 62, 62' can be used in this embodiment (Fig. 3D).
  • Fig. 3B is an elevational view of a corner portion of a shield 40 having a long side wall 41 in which a "vertical" slit 42 is provided.
  • slit 42 is provided with a T-shaped end 44 in which the cross-piece of the T has a length l2 of several tens of millimetres (for example, 40).
  • Fig. 3C is an elevational view of a corner portion of a shield 50 having a long side wall 51 in which a "vertical" slit 52 is provided.
  • an auxiliary slit 54 having a length l3 of several tens of millimetres (for example, 40 to 80) and a width of several millimetres (for example, 3) is arranged transversely to the slit 52 between one end of the slit 52 and the opposite edge 53.
  • the length ( i.e . the dimension transverse to the axis of the vertical "major” slits) of the transverse slits is smaller than the length of the "vertical" slits in all these cases. This is favourable for the mechanical stability of the shield.
  • the shield may be formed from one part or, for example, from two parts (cf. 2E). In the latter case the two shield parts (cf. 2E). In the latter case the two shield parts (which are U-shaped in that case) may be fixed to each other in such a way that the afore-mentioned elongate aperture, or apertures is, or are formed at the area of fixation.

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  • Electrodes For Cathode-Ray Tubes (AREA)
EP93201325A 1992-05-15 1993-05-07 Tube image en couleur muni d'un blindage magnétique interne Expired - Lifetime EP0570065B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP93201325A EP0570065B1 (fr) 1992-05-15 1993-05-07 Tube image en couleur muni d'un blindage magnétique interne

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP92201386 1992-05-15
EP92201386 1992-05-15
EP93201325A EP0570065B1 (fr) 1992-05-15 1993-05-07 Tube image en couleur muni d'un blindage magnétique interne

Publications (2)

Publication Number Publication Date
EP0570065A1 true EP0570065A1 (fr) 1993-11-18
EP0570065B1 EP0570065B1 (fr) 1996-04-10

Family

ID=26131393

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93201325A Expired - Lifetime EP0570065B1 (fr) 1992-05-15 1993-05-07 Tube image en couleur muni d'un blindage magnétique interne

Country Status (1)

Country Link
EP (1) EP0570065B1 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0650180B1 (fr) * 1993-10-22 1997-09-17 Koninklijke Philips Electronics N.V. Tube d'affichage en couleur muni d'un blindage magnétique
FR2756662A1 (fr) * 1996-11-30 1998-06-05 Lg Electronics Inc Tube a rayons cathodiques plat muni d'un rail de support de masque perfore et d'ecran magnetique
WO2007027184A1 (fr) * 2005-08-31 2007-03-08 Thomson Licensing Écran magnétique interne de dispositif d’affichage à balayage orthogonal

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4622490A (en) * 1985-02-28 1986-11-11 Rca Corporation Cathode-ray tube with an internal magnetic shield
EP0217473A2 (fr) * 1985-10-03 1987-04-08 North American Philips Corporation Tube image couleur muni d'un écran magnétique interne
EP0403010A1 (fr) * 1989-06-16 1990-12-19 Koninklijke Philips Electronics N.V. Procédé pour la fabrication d'un tube image et tube image

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4622490A (en) * 1985-02-28 1986-11-11 Rca Corporation Cathode-ray tube with an internal magnetic shield
EP0217473A2 (fr) * 1985-10-03 1987-04-08 North American Philips Corporation Tube image couleur muni d'un écran magnétique interne
EP0403010A1 (fr) * 1989-06-16 1990-12-19 Koninklijke Philips Electronics N.V. Procédé pour la fabrication d'un tube image et tube image

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0650180B1 (fr) * 1993-10-22 1997-09-17 Koninklijke Philips Electronics N.V. Tube d'affichage en couleur muni d'un blindage magnétique
FR2756662A1 (fr) * 1996-11-30 1998-06-05 Lg Electronics Inc Tube a rayons cathodiques plat muni d'un rail de support de masque perfore et d'ecran magnetique
WO2007027184A1 (fr) * 2005-08-31 2007-03-08 Thomson Licensing Écran magnétique interne de dispositif d’affichage à balayage orthogonal

Also Published As

Publication number Publication date
EP0570065B1 (fr) 1996-04-10

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