Electric lamp and discharge devices – Cathode ray tube – Shadow mask – support or shield
Patent
1998-03-10
2000-02-01
Day, Michael H.
Electric lamp and discharge devices
Cathode ray tube
Shadow mask, support or shield
313405, 313407, H01J 2907
Patent
active
060206802
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a color cathode ray tube of the type which may be incorporated in a color monitor or in a color TV set; and, more particularly, the invention relates to a color cathode ray tube which decreases the occurrence of beam landing error caused by the movement of a shadow mask structure resulting from a rise in the temperature in the set or a rise in the temperature of the shadow mask, when the color monitor or the color TV set is operated.
A color cathode ray tube is generally constituted by a panel portion, which forms a picture screen, a neck portion for housing an electron gun, and a funnel portion for connecting the panel portion to the neck portion. On the funnel portion, there is provided a deflection device for scanning an electron beam, emitted from an electron gun, on a fluorescent screen formed on the inner surface of the panel.
FIG. 1 is a diagram schematically illustrating the basic structure of a cathode ray tube, which includes a panel 1, a funnel 2, a neck portion 3, a fluorescent screen (screen) 4, a shadow mask structure 5, panel pins 51 for supporting the shadow mask structure, a magnetic shield 6, deflection yokes 7, a magnet 8 for adjusting the purity, a magnet 9 for adjusting the center beam static convergence, a magnet 10 for adjusting the side beam static convergence, and an electron gun 11 which produces electron beams B.
The electron beams for R (red), G (green) and B (blue) colors are deflected in the horizontal direction and in the vertical direction by the deflection device (yokes), provided on the funnel portion, on the way from the electron gun to the fluorescent screen, are selected depending upon the colors by the shadow mask disposed in the panel portion, and impinge upon the fluorescent screen, whereby the fluorescent screen emits light in different colors so that an image is formed on the fluorescent screen.
FIG. 2 is a diagram schematically illustrating the shadow mask structure which comprises a shadow mask 12 having a plurality of electron beam passing openings for selecting colors, a support frame 13 for holding the shadow mask 12, and mask springs 14 for holding the support frame 13 in the panel. The shadow mask structure 5 is held by joining the mask spring-holding holes 141 to the panel pins 51 formed on the panel. Furthermore, the mask spring-holding holes 141 are positioned on a vertical axis or on a horizontal axis that passes nearly through the center of the shadow mask structure 5.
In general, the shadow mask 12 is made of invar (e.g., having a coefficient of thermal expansion of 6.9.times.10.sup.-6 /.degree.C.), the support frame 13 is made of a steel (e.g., having a coefficient of thermal expansion of 1.15.times.10.sup.-5 /.degree.C.), and the mask springs 14 are made of a stainless steel (e.g., having a coefficient of thermal expansion of 1.04.times.10.sup.-5 /.degree.C.). Hereinafter, the term coefficient of thermal expansion refers to the coefficient of linear thermal expansion. In this case, the shadow mask 12 which is nearly flat, suppresses the doming of the shadow mask having low thermal expansion of the invar. In order to decrease the change with time of beam landing in the case of full-luster display, furthermore, the mask springs 14 are often made of a single material without a bimetal function.
When the cathode ray tube incorporated in a color monitor or in a color TV set (hereinafter referred to as the set) is operated, the temperature in the set containing the funnel portion and the neck portion gradually rise, due to heat energy generated by the circuit components in the set, and eventually reaches an equilibrium. Since the screen of the panel is exposed, it has a temperature lower than the temperature inside the set. The heat energy generated by the circuit components in the set raises the temperature in the set and, then, raises the temperature of the funnel. Moreover, the temperature of the inner shield is raised due to radiant heat, causing the temperatures of the support frame and the
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Day Michael H.
Hitachi , Ltd.
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