Patent Application
20060138929
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for SHADOW MASK FOR CATHODE RAY TUBE earlier filed in the Korean Intellectual Property Office on 7 Dec. 2004 and there duly assigned Serial No. 10-2004-0102270.
1. Field of the Invention
The present invention relates to a shadow mask for a cathode ray tube, and in particular, to a shadow mask for a cathode ray tube that defines a range of the minimum radius of curvature to improve properties in shock and howling simultaneously.
2. Description of the Related Art
Generally, a cathode ray tube is an electronic tube where electron beams emitted from an electron gun are deflected due to a magnetic deflection field, pass through a color selection shadow mask, and then strike and excite green, blue, and red phosphors on a phosphor film within a panel, thereby displaying desired images.
The shadow mask has a color selection function of selecting the emitted electron beams and landing them on the phosphor film.
The shape of the shadow mask is determined according to size and shape of a panel, that is, a front plane glass of the cathode ray tube. The shadow mask is formed with a radius of curvature of about R=2000 mm (millimeters) generally.
Recently, cathode ray tubes have become larger, and the front surface of the panel has been flattened. Accordingly, the shape of the shadow mask has changed to correspond to these tendencies of the cathode ray tube.
However, when the shadow mask has a large size and a large radius of curvature, the structural strength of the shadow mask becomes poor, and this may induce many problems.
That is, when the radius of curvature of the shadow mask is 1.6R or more, the shadow mask cannot maintain its own shape due to shocks from the outside. Deformation of the shadow mask deteriorates the quality of the cathode ray tube.
In addition, when the shadow mask has a large size and a large radius of curvature, it has poor properties in howling. That is, when the cathode ray tube with the shadow mask is used as a television, the shadow mask trembles due to the sound of the television. In this case, the shadow mask becomes fragile by the howling phenomenon due to the weakness of the structural strength.
When the outer surface of the panel is formed with a flat shape and has a large inner radius of curvature, the radius of curvature of the shadow mask also increases. Accordingly, the shadow mask becomes flat.
When the curved plane of the shadow mask becomes partially flat, deformations occur in the flat portion of the curved plane due to the shock load from the outside.
As the shock load is applied continually, the deformations are transferred to the edge portions of the shadow mask. Accordingly, plastic deformations occur in the shadow mask, and the electron beams emitted from the electron gun are distorted during passing through the shadow mask. Accordingly, the electrons cannot cause correct emission of the phosphors, and trembling of the images and deterioration of color purity occurs.
It is an object of the present invention to provide a shadow mask for a cathode ray tube that can improve shock and howling properties by defining a range of the radius of curvature according to the perpendicular and parallel axis.
It is another object of the present invention to provide a shadow mask having larger resonance frequency values and much smaller maximum amplitude values corresponding to each of the resonance frequencies than the shadow mask according to the prior art.
It is yet another object to provide a shadow mask according to the present invention that is applied for use in a cathode ray tube involving a wide-angled deflection angle to make it slimmer, the shadow mask exhibiting enhanced effects.
A shadow mask for a cathode ray tube according to an exemplary embodiment of the present invention, is formed with a curved surface such that a radius of curvature corresponding to a perpendicular axis which passes through the center of the shadow mask decreases monotonely along the perpendicular axis from the center of the shadow mask and a radius of curvature corresponding to a parallel axis which passes through the center of the shadow mask decreases monotonely along the parallel axis from the center of the shadow mask, and the curved surface satisfies the following condition:
[0.1RVmin+0.9RVmax, 0.9RVmin+0.1RVmax]⊂[RHmin, RHmax]
wherein RVmin and RVmax respectively represent the minimum and the maximum value of the minimum radius of curvature corresponding to the perpendicular axis, and RHmin and RHmax respectively represent the minimum and the maximum value of the minimum radius of curvature corresponding to the parallel axis.
In addition, in the case that the cathode ray tube has an aspect ratio of 16:9, the curved surface may decrease monotonely from a diagonal of an effective screen portion to the ⅓ point of the long side portion of the shadow mask, and may satisfy the following condition:
REmax<RVmin
wherein REmax represents the maximum value of the minimum radius of curvature in the part from the diagonal of the effective screen portion to the ⅓ point of the long side portion.
With the above structure, since the maximum amplitude is decreased, the mask shadow according to the present invention can improve howling properties.
In addition, since deformation energy which affects the strength is distributed uniformly, the shadow mask according to the present invention can improve shock properties.
A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which a certain exemplary embodiment of the present invention is shown.
As shown in
A phosphor film 3 is formed on the inner surface of the panel 2 with red R, green G, and blue B phosphors patterned while interposing a black matrix BM.
The electron gun 8 is mounted within the neck 6 to emit electrons, and the deflection yoke 9 is mounted around the outer circumference of the funnel 4 to deflect the electron beams emitted from the electron gun 8.
The panel 2, the funnel 4, and the neck 6 are integrated into one body to thereby form a vacuum vessel.
A shadow mask 10 is installed at the panel 2 such that it is spaced apart from the phosphor film 3 with a predetermined distance while being supported by a frame 18.
In addition, the shadow mask 10 has an effective screen portion 11 having beam passage holes 12 and practically serving to display the desired images, and a non-holed portion 13 having no beam-passage holes 12 and not serving to display the images.
The effective screen portion 11 is completely surrounded by the non-holed portion 13.
The shadow mask 10 has a skirt portion 14 bent from the edge of the non-holed portion 13 toward the frame 18 to fix the shadow mask 10 to the frame 18.
With the cathode ray tube, the electron beams emitted from the electron gun 8 are deflected due to the deflection magnetic field of the deflection yoke 9, and pass through the beam passage holes 12 of the color selection shadow mask 10. The electron beams then collide against the green, blue, and red phosphors of the phosphor film 3 formed on the inner surface of the panel 2. Consequently, the phosphors are excited to thereby display the desired images.
The shadow mask 10 has a radius of curvature corresponding to a perpendicular axis Y and to a parallel axis X which pass through the center of the shadow mask 10.
The radius of curvature corresponding to the perpendicular axis Y decreases monotonely along the perpendicular axis Y from the center of the shadow mask 10, and the radius of curvature corresponding to the parallel axis X decreases monotonely along the parallel axis X from the center of the shadow mask 10.
On moving from the center to the edge of the shadow mask 10 along the perpendicular axis Y, the radius of curvature corresponding to the perpendicular axis Y varies. And variation of the radius of curvature substantially exhibits a monotone decreasing function when it is expressed as a function.
In the same way, on moving from the center to the edge of the shadow mask 10 along the parallel axis X, the radius of curvature corresponding to the parallel axis X varies. And variation of the radius of curvature substantially exhibits a monotone decreasing function when it is expressed as a function.
That is, a polynomial expression such as a 4th order equation is induced in such a way that the distance from an axis of the tube to the curved surface along the perpendicular axis Y and the parallel axis X at regular intervals such as 10 mm (millimeters), 5 mm, 1 mm and so on.
In the case that the polynomial expression forms a monotone decreasing function, the curved surface that is represented by the monotone decreasing function is said to decrease monotonely.
Further, the shadow mask 10 is formed with a curved surface which satisfies the following condition, [0.1RVmin+0.9RVmax, 0.9RVmin+0.1RVmax]⊂[RHmin, RHmax] wherein RVmin and RVmax respectively represent the minimum and the maximum value of the minimum radius of curvature corresponding to the perpendicular axis Y, and RHmin and RHmax respectively represent the minimum and the maximum value of the minimum radius of curvature corresponding to the parallel axis X.
In the above, the minimum radius of curvature represents a radius of curvature which has a minimum value among the radii of curvature decreasing monotonely. The minimum values of the minimum radii of curvature are RVmin and RHmin, and the maximum values of the minimum radii of curvature are RVmax and RHmax.
The expression, [0.1RVmin+0.9RVmax, 0.9RVmin+0.1RVmax]⊂[RHmin, RHmax] means that a set which is composed of two elements, 0.1RVmin and 0.9RVmax, 0.9RVmin and 0.1RVmax is a subset of a set which is composed of two elements, RHmin, RHmax.
The expression is induced in such a way that multiple simulations were carried out and prototypes of shadow masks that satisfy the howling properties were made and tested and a relationship between the minimum radii of curvature were derived experimentally.
In the case that the aspect ratio is 16:9, the shadow mask 10 is formed with a curved surface which decreases monotonely from the diagonal of the effective screen portion 11 to the ⅓ point of the long side portion, and satisfies the following condition, REmax<Rmin wherein REmax represents the maximum value of the minimum radius of curvature in the part from the diagonal of the effective screen portion 11 to the ⅓ point of the long side portion.
The diagonal of the effective screen portion 11 represents a direction of a diagonal of the effective screen portion 11, and the ⅓ point of the long side portion represents a point which is moved from the diagonal of the effective screen portion 11 to the center of the effective portion 11 as much distance as ⅓ of the length of the long side portion.
As shown in
The following Table 1 shows comparison of the resonance frequencies in each of the 1st to the 4th resonance modes and the maximum amplitudes according to the resonance frequencies in a diagonal portion and a horizontal portion of the present invention and the prior art.
As shown in Table 1, the shadow mask according to the present invention has larger resonance frequency values and much smaller maximum amplitude values corresponding to each of the resonance frequencies than the shadow mask according to the prior art.
In the shadow mask according to the present invention, the conditions which determine the range of curvature are attained experimentally through multiple simulations and the making of various prototypes of shadow masks, with the results being shown in Table 1.
In the case that the shadow mask according to the embodiment of the present invention is applied for use in a cathode ray tube involving a wide-angled deflection angle of 115° or more (a conventional cathode ray tube involves a deflection angle of 102-106°) to make it slimmer, the shadow mask exhibits enhanced effects.
Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that many variations and/or modifications of the basic inventive concept herein taught which may appear to those skilled in the art will still fall within the spirit and scope of the present invention, as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2004-0102270 | Dec 2004 | KR | national |
