Electron gun for cathode ray tube having third to fifth electrodes with different sized electron beam through holes

1. An electron gun for a cathode ray tube comprising a cathode that emits electron beams, a first electrode that controls the electron beams emitted from the cathode, a second electrode that accelerates the electron beams emitted from the first electrode, and third to fifth electrodes sequentially arranged in a screen direction to act as pre-focus lenses,

wherein the third to fifth electrodes have electron beam through holes, all of which are different in size from one another, and

wherein each electron beam through hole of the third and fourth electrodes is smaller than the electron beam through hole of the fifth electrode, and the electron beam through hole of the third electrode is smaller than that of the fourth electrode, and the size of the electron beam through hole of the third electrode is greater than the size of the electron beam through hole of the fifth electrode×0.1 and less than the size of the electron beam through hole of the fifth electrode×0.5.

2. The electron gun for a cathode ray tube as claimed in claim 1 , wherein the electron beam through hole of the fourth electrode has a rectangular shape and its vertical length is different from its horizontal length.

3. The electron gun for a cathode ray tube as claimed in claim 1 , wherein the third electrode has a first through hole opposite to the second electrode and a second through hole opposite to the fourth electrode.

4. The electron gun for a cathode ray tube as claimed in claim 3 , wherein the size of the first through hole is different from that of the second through hole.

5. The electron gun for a cathode ray tube as claimed in claim 4 , wherein the size of the first through hole is smaller than that of the second through hole.

6. The electron gun for a cathode ray tube as claimed in claim 1 , wherein the size of the electron beam through hole of the fourth electrode is greater than the size of the electron beam through hole of the fifth electrode×0.5 and less than the size of the electron beam through hole of the fifth electrode.

7. The electron gun for a cathode ray tube as claimed in claim 1 , wherein an electron beam spot does not degrade.

8. The electron gun for a cathode ray tube as claimed in claim 1 , wherein the third electrode has a first through hole opposite to the second electrode and a second through hole opposite to the fourth electrode, and the fourth electrode has a first through hole opposite to the third electrode and a second through hole opposite to the fifth electrode.

9. An electrode gun for a cathode ray tube comprising a cathode that emits electron beams, a first electrode that controls the electron beams emitted from the cathode, a second electrode that accelerates the electron beams emitted from the first electrode,

wherein third to fifth electrodes sequentially arranged in a screen direction to act as pre-focus lenses, and the third to fifth electrodes have electron beam through holes, all of which are different in size from one another, and the size of the electron beam through hole of the third electrode is greater than the size of the electron beam through hole of the fifth electrode×0.1 and less than the size of the electron beam through hole of the fifth electrode×0.5, and

wherein no separate supplemental electrode is provided.

10. An electron gun for a cathode ray tube comprising:

a cathode emitting electron beams;

a first electrode controlling the electron beams emitted from the cathode;

a second electrode accelerating the electron beams emitted from the first electrode; and

third to fifth electrodes sequentially arranged in a screen direction to act as pre-focus lenses, the third to fifth electrodes having electron beam through holes, all of which are different in size from one another, and the size of the electron beam through hole of the third electrode is greater than the size of the electron beam through hole of the fifth electrode×0.1 and less than the size of the electron beam through hole of the fifth electrode×0.5.

11. The electron gun as claimed in claim 10 , wherein each electron beam through hole of the third and fourth electrodes is smaller than the electron beam through hole of the fifth electrode.

12. The electron gun as claimed in claim 11 , wherein the electron beam through hole of the third electrode is smaller than that of the fourth electrode.

13. The electron gun as claimed in claim 10 , wherein the size of the electron beam through hole of the fourth electrode is greater than the size of the electron beam through hole of the fifth electrode×0.5 and less than the size of the electron beam through hole of the fifth electrode.

14. The electron gun as claimed in claim 10 , wherein the beam through hole of the fourth electrode is smaller than the electron beam through hole of the fifth electrode adjacent to the beam through hole of the fourth electrode.

15. The electron gun as claimed in claim 14 , wherein the electron beam through hole of the third electrode is smaller than the beam through hole of the fourth electrode adjacent to the beam through hole of the third electrode.

16. An electron gun for a cathode ray tube comprising:

a cathode emitting electron beams;

a first electrode controlling the electron beams emitted from the cathode;

a second electrode accelerating the electron beams emitted from the first electrode; and

third to fifth electrodes sequentially arranged in a screen direction to act as pre-focus lenses and each having at least one electron beam through hole, wherein the electron beam through hole of the fourth electrode and the electron beam through holes each included in the third and fifth electrode and adjacent to the electron beam through hole of the fourth electrode are different in size from one another, and the size of the electron beam through hole of the third electrode is greater than the size of the electron beam through hole of the fifth electrode×0.1 and less than the size of the electron beam through hole of the fifth electrode×0.5.