Cathode ray tube having an improved shadow mask

1. A cathode ray tube, comprising:

a panel having a fluorescent formed on an inner surface thereof;

a funnel connected to the panel;

an electron gun housed in the funnel, emitting electron beams;

a deflection yoke for deflecting the electron beams in horizontal and vertical directions;

a shadow mask for selecting colors of the electron beams; and

a mask frame for supporting the shadow mask,

wherein an outer surface of the panel is substantially flat and an inner surface has a designated curvature,

wherein a radius of curvature from a center of the shadow mask in a major-axis, minor-axis and diagonal-axis direction is substantially the same, and

wherein the shadow mask satisfies a curvature radius expansion expressed by Z(x, y)=ax 2 +bx 4 +cy 2 +dy 4 +ex 2 y 2 +fx 4 y 2 +gx 2 y 4 +hx 4 y 4 , b/a satisfies a condition of 2.2×10 −6 <b/a<4.4×10 −6 , x and y being a distance (mm) from the center of the shadow mask to a point respectively, and Z being a height difference (mm) between the center of the shadow mask and the point on the shadow mask.

2. The cathode ray tube according to claim 1 , wherein radii of curvature of the shadow mask are substantially the same within the length H/12 from the center of the shadow mask, H being a minor-axis direction length of the shadow mask.

3. The cathode ray tube according to claim 1 , wherein radii of curvature of the shadow mask are substantially the same as a distance from the center of the shadow mask is increased in the major-axis, minor-axis and diagonal-axis directions.

4. The cathode ray tube according to claim 1 , wherein the shadow mask satisfies a curvature radius expansion expressed by Z(x, y)=ax 2 +bx 4 +cy 2 +dy 4 +ex 2 y 2 +fx 4 y 2 +gx 2 y 4 +hx 4 y 4 , d/c satisfies a condition of 2.2×10 −6 <d/c<4.4×10 −6 , x and y being a distance (mm) from the center of the shadow mask to a point respectively, and Z being a height difference (mm) between the center of the shadow mask and the point on the shadow mask.

5. The cathode ray tube according to claim 1 , wherein the shadow mask satisfies a curvature radius expansion expressed by Z(x, y)=ax 2 +bx 4 +cy 2 +dy 4 +ex 2 y 2 +fx 4 y 2 +gx 2 y 4 +hx 4 y 4 , b/a satisfies a condition of 2.2×10 −6 <b/a<4.4×10 −6 , and d/c satisfies a condition of 2.2×10 −6 <d/c<4.4×10 −6 , x and y being a distance (mm) from the center of the shadow mask to a point respectively, and Z being a height difference (mm) between the center of the shadow mask and the point on the shadow mask.

6. The cathode ray tube according to claim 1 , wherein the radius of curvature from a center of the shadow mask in a major-axis direction is Rxo, the radius of curvature in a minor-axis direction Ryo, and the radius of curvature in a diagonal-axis direction Rdo, the Ryo has the lowest value among the Rxo, Ryo and Rdo.

7. The cathode ray tube according to claim 1 , wherein a thickness of the shadow mask is not greater than 0.1 mm.

8. The cathode ray tube according to claim 1 , wherein a transmittance at a central portion of the panel is in a range of 45–75%.

9. A cathode ray tube comprising:

a panel having a fluorescent formed on an inner surface thereof;

a funnel connected to the panel;

an electron gun housed in the funnel, emitting electron beams;

a deflection yoke for deflecting the electron beams in horizontal and vertical directions;

a shadow mask for selecting colors of the electron beams; and

a mask frame for supporting the shadow mask,

wherein an outer surface of the panel is substantially flat and an inner surface has a designated curvature,

wherein a radius of curvature from a center of the shadow mask in a major-axis direction is Rxo, a radius of curvature in a minor-axis direction Ryo, and a radius of curvature in a diagonal-axis direction Rdo, the Rxo, Ryo and Rdo are not less than 85% of a maximum value among the Rxo, Ryo and Rdo, and

wherein the radius of curvature in the major-axis direction from the shadow mask center is Rxo, the radius of curvature in the minor-axis direction Ryo, the radius of curvature in the diagonal-axis direction Rdo, a radius of curvature at an end of an effective surface in the major-axis direction of the shadow mask Rxf, a radius of curvature at an end of the effective surface in the minor-axis direction Ryf, and a radius of curvature at an end of the effective surface in the diagonal-axis direction Rdf, at least one of Rxf/Rxo, Ryf/Ryo and Rdf/Rdo satisfies conditions of 44.7%<Rxf/Rxo<77.6%, 59.0%<Ryf/Ryo<86.1% and 34.6%<Rdf/Rdo<69.2%.

10. The cathode ray tube according to claim 9 , wherein the Ryo has the lowest value among the Rxo, Ryo and Rdo.

11. The cathode ray tube according to claim 9 , wherein the Rxo, Ryo and Rdo are not less than 88% of a maximum value among the Rxo, Ryo and Rdo.

12. The cathode ray tube according to claim 11 , wherein the Ryo has the lowest value among the Rxo, Ryo and Rdo.

13. The cathode ray tube according to claim 9 , wherein the minimum value among the Rxo, Ryo and Rdo within the length H/12 from the center of the shadow mask substantially ranges between 85% and 88% of the maximum value among the Rxo, Ryo and Rdo, H being a minor-axis direction length of the shadow mask.

14. The cathode ray tube according to claim 13 , wherein the Ryo has the lowest value among the Rxo, Ryo and Rdo.

15. The cathode ray tube according to claim 9 , wherein the radius of curvature in the major-axis direction from the shadow mask center is Rxo, the radius of curvature in the minor-axis direction Ryo, the radius of curvature in the diagonal-axis direction Rdo, a radius of curvature at an end of an effective surface in the major-axis direction of the shadow mask Rxf, a radius of curvature at an end of an effective surface in the minor-axis direction Ryf, and a radius of curvature at an end of an effective surface in the diagonal-axis direction Rdf, at least one of Rxf/Rxo, Ryf/Ryo and Rdf/Rdo satisfies conditions of 62.6%<Rxf/Rxo<77.6%, 74.9%<Ryf/Ryo<86.1% and 52.1%<Rdf/Rdo<69.2%.

16. The cathode ray tube according to claim 9 , wherein a thickness of the shadow mask is not greater than 0.1 mm.

17. The cathode ray tube according to claim 9 , wherein a transmittance at a central portion of the panel is in a range of 45–75%.

18. A cathode ray tube comprising:

a panel having a fluorescent formed on an inner surface thereof;

a funnel connected to the panel;

an electron gun housed in the funnel, emitting electron beams;

a deflection yoke for deflecting the electron beams in horizontal and vertical directions;

a shadow mask for selecting colors of the electron beams; and

a mask frame for supporting the shadow mask

wherein an outer surface of the panel is substantially flat and an inner surface has a designated curvature, and a minor-axis direction length of the shadow mask is H, a radius of curvature from a center of the shadow mask in a major-axis direction is Rxo, a radius of curvature in a minor-axis direction Ryo, and a radius of curvature in a diagonal-axis direction Rdo, the Rxo, Ryo and Rdo within the length H/12 from the center of the shadow mask satisfy a condition of

Max

⁡

(

Rxo

,

Ryo

,

Rdo

)

-

Min

⁡

(

Rxo

,

Ryo

,

Rdo

)

Max

⁡

(

Rxo

,

Ryo

,

Rdo

)

≤

0.15

.

19. The cathode ray tube according to claim 18 , wherein the radius of curvature in the major-axis direction from the shadow mask center is Rxo, the radius of curvature in the minor-axis direction Ryo, the radius of curvature in the diagonal-axis direction Rdo, a radius of curvature at an end of an effective surface in the major-axis direction of the shadow mask Rxf, a radius of curvature at an end of an effective surface in the minor-axis direction Ryf, and a radius of curvature at an end of an effective surface in the diagonal-axis direction Rdf, at least one of Rxf/Rxo, Ryf/Ryo and Rdf/Rdo satisfies conditions of 44.7%<Rxf/Rxo<77.6%, 59.0%<Ryf/Ryo<86.1% and 34.6%<Rdf/Rdo<69.2%.

20. The cathode ray tube according to claim 18 , wherein the radius of curvature in the major-axis direction from the shadow mask center is Rxo, the radius of curvature in the minor-axis direction Ryo, the radius of curvature in the diagonal-axis direction Rdo, a radius of curvature at an end of an effective surface in the major-axis direction of the shadow mask Rxf, a radius of curvature at an end of an effective surface in the minor-axis direction Ryf, and a radius of curvature at an end of an effective surface in the diagonal-axis direction Rdf, at least one of Rxf/Rxo, Ryf/Ryo and Rdf/Rdo satisfies conditions of 62.6%<Rxf/Rxo<77.6%, 74.9%<Ryf/Ryo<86.1% and 52.1%<Rdf/Rdo<69.2%.

21. The cathode ray tube according to claim 18 , wherein the Ryo has the lowest value among the Rxo, Ryo and Rdo.

22. The cathode ray tube according to claim 18 , wherein a thickness of the shadow mask is not greater than 0.1 mm.

23. The cathode ray tube according to claim 18 , wherein a transmittance at a central portion of the panel is in a range of 45–75%.