Electric lamp and discharge devices – Cathode ray tube – Screen
Reexamination Certificate
2001-10-04
2003-10-28
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Screen
C313S47700R, C220S00210A
Reexamination Certificate
active
06639347
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color cathode ray tube, and in particular o a color cathode ray tube which is capable of obtaining a high picture quality by minimizing the distortion of a picture by designing an internal curvature of a panel to an optimum shape.
2. Description of the Prior Art
In general, as depicted in
FIG. 1
, a color cathode ray tube includes a panel
3
coated on a rear surface with a R, G, B fluorescent screen
1
, an funnel
4
coupled to a rear edge of the panel
3
, an electron gun
7
inserted into a neck portion
5
of the funnel
4
and emitting an electron beam
6
, and a shadow mask
8
installed at the rear of the panel
3
with a certain distance and having a plurality of holes as passages for the electron beam
6
. The shadow mask is typically under a tension.
In the prior art, as depicted in
FIG. 2
, in an internal curvature of the panel
3
, a radius Rd of a diagonal curvature is larger than a radius Rv of a short side curvature and is smaller than a radius Rh of a long side curvature.
In more detail, in the panel
3
in accordance with the prior art, Rh/Rd is not less than 1.1, and Rv/Rd is not greater than 0.8.
When the radius difference between the long side curvature, short side curvature and diagonal curvature is large, because a structural stiffness at a corner portion of the shadow mask
8
is reduced especially, the shadow mask
8
may be easily deformed due to an outward impact, and accordingly a drop characteristic drastically decreases and an image distortion occurs.
In addition, when an electron beam is emitted in a horizontal direction or a vertical direction in a general cathode ray tube, the distance from a deflection center to a center portion, a short side portion or a long side portion of an screen effective surface area is different from each other, and accordingly when a vertical line or a horizontal line is displayed, an image distortion phenomenon occurs (i.e., the vertical line or the horizontal line is distorted). The image distortion phenomenon becomes more serious in a scaled-up and flat screen cathode ray tube.
In particular, when an operation such as a CAD (Computer Aided Design) is performed, a straight line may be distorted as a curved line or a true circle may be distorted as an oval shape, and accordingly the usefulness is drastically reduced.
SUMMARY OF THE INVENTION
In order to solve the above-mentioned problems, it is an object of the present invention to provide a color cathode ray tube which is capable of increasing the structural stiffness of a shadow mask and improving a reliability about an outward impact by designing a radius of long side curvature, short side curvature and diagonal curvature as an optimum state.
In order to achieve the above-mentioned object, there is provided a color cathode ray tube having an almost flat screen outer surface and an internal panel curvature satisfying the following conditions:
0.98
<Rh/Rd
<1.02,
0.95
<Rv/Rd
<1.04,
0.98
<Rt/Rh
<1.02, and
0.98
<Rs/Rv
<1.05,
wherein Rd is the radius of diagonal section curvature within a screen effective surface area, Rt is the radius of circumference section curvature along a long side, Rs is the radius of circumference section curvature along a short side, Rh is the radius of section curvature on the x axis passing through a center of the screen effective surface area and parallel to the long side, and Rv is the radius of section curvature on the y axis passing through the center of the screen effective surface area and parallel to the short side.
REFERENCES:
patent: 6025676 (2000-02-01), Ohama et al.
patent: 6433470 (2002-08-01), Watanabe et al.
LG Electronics Inc.
Patel Ashok
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