EP0570065B1 - Farbbildröhre mit innerer magnetischer Abschirmung - Google Patents

Farbbildröhre mit innerer magnetischer Abschirmung Download PDF

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Publication number
EP0570065B1
EP0570065B1 EP93201325A EP93201325A EP0570065B1 EP 0570065 B1 EP0570065 B1 EP 0570065B1 EP 93201325 A EP93201325 A EP 93201325A EP 93201325 A EP93201325 A EP 93201325A EP 0570065 B1 EP0570065 B1 EP 0570065B1
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EP
European Patent Office
Prior art keywords
display screen
aperture
wall
display tube
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.)
Expired - Lifetime
Application number
EP93201325A
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English (en)
French (fr)
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EP0570065A1 (de
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
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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/de
Publication of EP0570065A1 publication Critical patent/EP0570065A1/de
Application granted granted Critical
Publication of EP0570065B1 publication Critical patent/EP0570065B1/de
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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:
  • 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) such as in document EP-A-0 217 473.
  • 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.
  • 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 such as in document EP-A-0 403 010.
  • the following problems then occur.
  • a display tube of the type described in the opening paragraph is therefore characterized in that the magnetic resistance of the wall being locally higher than at both sides of the elongate aperture between at least one end of the elongate 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 30 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.

Landscapes

  • Electrodes For Cathode-Ray Tubes (AREA)

Claims (6)

  1. Farbbildröhre (1) mit:
    einer Hülle mit einer Längsachse, die einen Halsteil (2), einen Trichterteil (4) und einen Fensterteil (6) umfaßt;
    einem in dem Halsteil vorgesehenen Elektronenstrahlerzeugungssystem (3);
    einem Wiedergabeschirm (7) mit einer kurzen Achse und einer langen Achse und mit einem Muster aus Phosphorlinien parallel zu einer Achse des Wiedergabeschirms auf der inneren Oberfläche des Fensterteils;
    einem in der Nähe des Wiedergabeschirms vorgesehenen Farbselektionsmittel (8);
    einer innerhalb des trichterförmigen Teils vorgesehenen inneren magnetischen Abschirmstruktur (5, 30, 40, 50) mit zwei zu der langen Bildschirmachse parallelen langen Wänden und zwei zu der kurzen Bildschirmachse parallelen kurzen Wänden, und an dem strahlerzeugungssystemseitigen Ende mit einer Öffnung, die sich quer zu der Längsachse erstreckt und eine Abtastöffnung für von dem Erzeugungssystem erzeugte, den Bildschirm abtastende Elektronenstrahlen bildet, wobei jeder der langen Wandteile der Abschirmstruktur wenigstens eine längliche Öffnung (10A, 10B, 32, 42, 52, 62, 62') aufweist, die sich quer zu der Längsrichtung der Wand erstreckt und in einem Abstand von den Rändern der Wand liegt, dadurch gekennzeichnet, daß der magnetische Widerstand der Wand örtlich höher ist als auf beiden Seiten der länglichen Öffnung zwischen wenigstens einem Ende der länglichen Öffnung und dem benachbarten Rand (33, 53) der Wand.
  2. Farbbildröhre nach Anspruch 1, dadurch gekennzeichnet, daß der magnetische Widerstand örtlich dadurch vergrößert wird, daß zwischen wenigstens einem Ende wenigstens einer länglichen Öffnung und dem benachbarten Rand (53) der Wand ein Querschlitz (54) vorgesehen wird.
  3. Farbbildröhre nach Anspruch 2, dadurch gekennzeichnet, daß auf der Schirmseite der wenigstens eine länglichen Öffnung ein Querschlitz vorgesehen wird.
  4. Farbbildröhre nach Anspruch 2, dadurch gekennzeichnet, daß der Querschlitz eine geringere Länge hat als die längliche Öffnung.
  5. Farbbildröhre nach Anspruch 1, dadurch gekennzeichnet, daß der magnetische Widerstand durch mechanische Verformung vergrößert wird.
  6. Farbbildröhre nach Anspruch 1, dadurch gekennzeichnet, daß der magnetische Widerstand durch Diffusion eines nicht-magnetischen Materials örtlich gesteigert wird.
EP93201325A 1992-05-15 1993-05-07 Farbbildröhre mit innerer magnetischer Abschirmung Expired - Lifetime EP0570065B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP93201325A EP0570065B1 (de) 1992-05-15 1993-05-07 Farbbildröhre mit innerer magnetischer Abschirmung

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP92201386 1992-05-15
EP92201386 1992-05-15
EP93201325A EP0570065B1 (de) 1992-05-15 1993-05-07 Farbbildröhre mit innerer magnetischer Abschirmung

Publications (2)

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

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EP93201325A Expired - Lifetime EP0570065B1 (de) 1992-05-15 1993-05-07 Farbbildröhre mit innerer magnetischer Abschirmung

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Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0650180B1 (de) * 1993-10-22 1997-09-17 Koninklijke Philips Electronics N.V. Farbbildröhre mit einer magnetischen Abschirmung
TW434631B (en) * 1996-11-30 2001-05-16 Lg Electronics Inc Flat cathode-ray tube
WO2007027184A1 (en) * 2005-08-31 2007-03-08 Thomson Licensing Internal magnetic shield for display devices with orthogonal scanning

Family Cites Families (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
DE3677310D1 (de) * 1985-10-03 1991-03-07 Philips Corp Farbbildroehre mit innerer magnetischer abschirmung.
NL8901524A (nl) * 1989-06-16 1991-01-16 Philips Nv Werkwijze voor het vervaardigen van een beeldbuis, en beeldbuis.

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EP0570065A1 (de) 1993-11-18

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