Cathode ray tube and manufacturing method of deflection coil

1. A cathode ray tube, comprising: a deflection yoke; a panel having a fluorescent screen on an inner surface; a funnel connected to the panel, an electron gun housed in the funnel; emitting electron beams; and a shadow mask for selecting colors of the electron beams emitted from the electron gun, wherein the deflection yoke comprises a deflection coil for deflecting the electron beams in horizontal and vertical directions, a holder for insulating the deflection coil, and a ferrite core for reducing a magnetic field generated by the deflection coil, and an opening is formed on a flange portion of an opening section on a screen side of the deflection coil;

wherein a maximum length of the flange portion of the opening section on the screen side of the deflection coil, L, and a length of the flange portion of the opening section on the screen side, starting from the opening to the direction of a neck, H, satisfy a condition of 0.15≦H/L≦0.45.

2. The cathode ray tube according to claim 1 , wherein a maximum length of the flange portion of the opening section on the screen side of the deflection coil, L, and a length of the flange portion of the opening section on the screen side, starting from the opening to the direction of a neck, H, satisfy a condition of 0.23≦H/L≦0.35.

3. The cathode ray tube according to claim 1 , wherein the opening is formed within ±45 degrees from a center of the deflection coil.

4. The cathode ray tube according to claim 1 , wherein the deflection coil is a horizontal deflection coil.

5. The cathode ray tube according to claim 1 , wherein a number of turns of the deflection coil covering a length (H) of the flange portion of the opening section on the screen side from the opening to the direction of the neck ranges from 2 to 7.

6. A cathode ray tube, comprising: a deflection yoke; a panel having a fluorescent screen on an inner surface; a funnel connected to the panel, an electron gun housed in the funnel; emitting electron beams; and a shadow mask for selecting colors of the electron beams emitted from the electron gun, wherein the deflection yoke comprises a deflection coil for deflecting the electron beams in horizontal and vertical directions, a holder for insulating the deflection coil, and a ferrite core for reducing a magnetic field generated by the deflection coil, and a flange portion of an opening section on a screen side of the deflection coil is split into at least two areas;

wherein a maximum length of the flange portion of the opening section on the screen side of the deflection coil, L, and a length of the flange portion of the opening section on the screen side, starting from the opening to the direction of a neck, H, satisfy a condition of 0.15≦H/L≦0.45.

7. The cathode ray tube according to claim 6 , wherein a maximum length of the flange portion of the opening section on the screen side of the deflection coil, L, and a length of the flange portion of the opening section on the screen side, starting from the opening to the direction of a neck, H, satisfy a condition of 0.23≦H/L≦0.35.

8. The cathode ray tube according to claim 6 , wherein the opening is formed within ±45 degrees from a center of the deflection coil.

9. The cathode ray tube according to claim 6 , wherein the deflection coil is a horizontal deflection coil.

10. The cathode ray tube according to claim 6 , wherein a number of turns of the deflection coil covering a length of the flange portion of the opening section on the screen side from the opening to the direction of the neck ranges from 2 to 7.

11. A manufacturing method of a deflection coil for deflecting electron beams in horizontal and vertical directions, the method comprising the steps of:

inserting the deflection coil between an upper former and a lower former; and

forming an opening by inserting a split pin on a flange portion of an opening section on a screen side of the deflection coil;

wherein the split pin is inserted to a position satisfying a condition of 0.15≦H/L≦0.45, L denoting a maximum length of the flange portion of the opening section on the screen side of the deflection coil, and H denoting a length of the flange portion of the opening section on the screen side, starting from the opening to the direction of a neck.

12. The cathode ray tube according to claim 11 , wherein the split pin is inserted within ±15 degrees from a center of the deflection coil.

13. The cathode ray tube according to claim 11 , wherein the split pin is inserted to a position satisfying a condition of 0.23≦H/L≦0.35, L denoting a maximum length of the flange portion of the opening section on the screen side of the deflection coil, and H denoting a length of the flange portion of the opening section on the screen side, starting from the opening to the direction of a neck.

14. The cathode ray tube according to claim 11 , wherein the opening is formed within ±45 degrees from a center of the deflection coil.

15. The cathode ray tube according to claim 11 , wherein the deflection coil is a horizontal deflection coil.

16. The cathode ray tube according to claim 11 , wherein a number of turns of the deflection coil covering a length (H) of the flange portion of the opening section on the screen side from the opening to the direction of the neck ranges from 2 to 7.