JPH06338264A - Color cathode-ray tube - Google Patents

Abstract

PURPOSE:To beam spot diameter formation of each electron beam, and improve resolution for the whole range of an image surface by specifying forms of a field correcting electrode on the inner side of a first electrode, and a field correcting electrode on the inner side of a second electrode. CONSTITUTION:In an electron gun of a color cathode-ray tube, a pair of field correcting electrodes 29, 30 are disposed at a fifth and a sixth grid G5, G6 along a gun axis Z in such a way as to hold electron beam passage holes 31B-32R formed on the inner side of respective facing parts between them. The field correcting electrode 29 of the fifth grid G5 is formed to have a short recess length L5c in the gun axis Z direction at a corresponding part to the center beam passage hole 31G to length L5s in the gun axis Z direction at corresponding parts to the side beam passage holes 31B, 31R. The field correcting electrode 30 of the sixth grid G6 is formed to have a long protrusion length L6c in the gun axis Z direction at a corresponding part to the center beam passage hole 32B to length L6s in the gun axis Z direction at corresponding parts to the side beam passage holes 32B, 32R.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-line type color cathode ray tube, and more particularly to a color cathode ray tube which improves the resolution on a phosphor screen.

[0002]

2. Description of the Related Art Generally, a color cathode ray tube is provided with a phosphor screen composed of a phosphor layer of three colors on the inner surface of a panel constituting an envelope, and an electron beam is provided inside the phosphor screen so as to face the phosphor screen. A shadow mask for selection is placed. Then, the three electron beams emitted from the electron gun are horizontally generated by a deflection yoke mounted outside the envelope,
A structure for displaying a color image is formed by scanning the phosphor screen by deflecting with a vertical deflection magnetic field.

In such a color cathode ray tube, particularly, the electron gun is an in-line type electron gun which emits three electron beams arranged in a row consisting of a center beam passing through the same horizontal plane and a pair of side beams, and is emitted from this electron gun. A self-convergence in-line type color collar for self-focusing the three electron beams arranged in a row as described above by combining the three electron beams with a deflection yoke for generating an inhomogeneous uniform magnetic field composed of a pincushion type horizontal deflection magnetic field and a barrel type vertical deflection magnetic field. Cathode ray tubes are currently the mainstream of color cathode ray tubes.

FIG. 6 shows an electron gun generally used for the self-convergence in-line type color cathode ray tube. This electron gun is a QPF (Quadra Potential Foc)
us) type electron gun, three cathodes KB arranged in a row,
KG, KR, three heaters (not shown) for individually heating the cathodes KB, KG, KR, cathodes KB, KG
, KR, which are sequentially separated from each other by a predetermined distance in the direction of the phosphor screen, have first to sixth grids G1 to G6,
The cathodes KB, KG, KR and the cathodes KB, K
First and second grids G1 and G2 which are adjacent to G and KR in sequence
By the three-pole part, the second and third grids G2, G3 by the prefocus lens, and the third through sixth grids G3.
G6 forms the main lens part which finally focuses the three electron beams on the phosphor screen.

By the way, according to the self-convergence in-line type color cathode ray tube, it is possible to concentrate the three electron beams on the phosphor screen without using a concentrating device such as a dynamic convergence device. Since the deflection magnetic field generated by is an inhomogeneous magnetic field, there is a problem that the resolution in the peripheral portion of the screen is deteriorated by the deflection aberration.

That is, as shown in FIG. 7A and FIG. 7B for the side beam 1R, the three electron beams 1B, 1G, 1R arranged in a row are pincushion type horizontal deflection magnetic field 2H and barrel type vertical deflection magnetic field. 2V weakens horizontal focusing and strengthens vertical focusing.
Therefore, as shown in FIG. 8, even if the beam spot 3c in the central portion of the screen can be made into a perfect circle, the beam spot 3p in the peripheral portion of the screen is the same as the elliptical high-brightness core portion 4 elongated in the horizontal direction. , And has a halo portion 5 of low brightness extending in the vertical direction, which deteriorates the resolution of the peripheral portion of the screen.

As means for improving the distortion of the beam spot caused by such deflection aberration, Japanese Patent Laid-Open No. 1-26555 has been proposed.
In Japanese Patent Laid-Open No. 4, as shown in FIG. 9, first to fourth grids G1 are arranged on the three cathodes KB, KG, KR arranged in a row in order in the direction of the phosphor screen with a predetermined separation.
Inside the respective facing portions of the relatively low potential third grid G3 (focusing electrode) and the relatively high potential fourth grid G4 (final accelerating electrode) forming the main lens of the electron gun having .about.G4, Three electron beam passage holes 6 formed on each facing surface.
B, 6G, 6R, 7B, 7G, and 7R are sandwiched by a pair of electric field correction electrodes 8 and 9, and the third grid G3 side has a relatively stronger focusing action in the vertical direction than in the horizontal direction. On the side of the fourth grid G4, an electron lens having a relatively strong diverging action in the vertical direction rather than in the horizontal direction is formed,
As a result, there is shown an electron gun in which the vertical focusing angle in the deflection magnetic field is reduced to reduce the deflection aberration in the peripheral portion of the screen.

However, when the electric field correction electrodes 8 and 9 are arranged as described above, FIG. 10A shows an electron lens in the direction perpendicular to the center beam, FIG. 10B shows an electron lens in the direction perpendicular to the side beam, and FIG. ) As shown for the horizontal electron lens with respect to the center beam and the pair of side beams, the penetration of the horizontal electric field indicated by equipotential lines 10H and 11V, and the vertical electric field indicated by equipotential lines 10V and 11V are shown. Center beam 1G and side beam 1
Unlike B and 1R, the electron lens for the pair of side beams is weaker than the electron lens for the center beam 1G, so as shown in FIG. 11, in the horizontal direction,
Side beams 1B, 1R for center beam 1G
Are focused in front of the phosphor screen 13 as shown by the broken line. That is, by the action of the focusing region I and the diverging region II, the relationship between the focus voltage applied to the third grid and the beam spot is horizontal as shown in FIG.
The beam spot of the side beam becomes as shown by the curve 15H in contrast to the beam spot of the center beam shown by the curve 14H, which is in the overfocus state. In addition, as shown in FIG. 11, the center beam 1
With respect to G, the side beams 1B and 1R are focused behind the phosphor screen 13 as shown by a chain line. The relationship between the focus voltage and the beam spot is shown in FIG.
As shown in, the beam spot of the side beam becomes as shown by the curve 15V with respect to the beam spot of the center beam shown by the curve 14V, resulting in an underfocus state.

As a result, with respect to the focus voltage Vf applied to the third grid shown in FIG. 12, the center beam becomes almost a perfect circle from the curves 12H and 12V, but the side beam becomes from the curves 13H and 13V. It becomes an ellipse that is long in the vertical direction and reduces the resolution of the entire screen.

Further, as another means for improving the distortion of the beam spot due to the deflection aberration, there is a means for reducing the shape difference between the beam spot of the center beam and the beam spot of the side beam by using the prefocus lens as an asymmetric lens. However, with this means, the resolution at the center of the screen is degraded.

[0011]

As described above, the electron gun which emits the three electron beams arranged in a line passing through the same horizontal plane is provided, and the pin which causes the deflection yoke to generate the three electron beams emitted from this electron gun. For a self-convergence in-line type color cathode ray tube that is deflected by an inhomogeneous magnetic field consisting of a cushion-type horizontal deflection magnetic field and a barrel-type vertical deflection magnetic field, three electron beams can be concentrated on the phosphor screen, but a deflection yoke is generated. Since the generated magnetic field is an inhomogeneous magnetic field, there is a problem that the beam spot in the peripheral portion of the screen is distorted due to the deflection aberration and the resolution in the peripheral portion of the screen is deteriorated.

As a means for improving the distortion of the beam spot due to this deflection aberration, the facing portion of the focusing electrode of relatively low potential forming the main lens portion and the final accelerating electrode of relatively high potential facing the focusing electrode. Inside, the pair of electric field correction electrodes are arranged so as to sandwich the electron beam passage holes formed in a row on each facing surface, and the focusing electrode side has a stronger focusing action in the vertical direction than in the horizontal direction. On the side of the final accelerating electrode, an electron lens having a relatively strong divergence action in the vertical direction rather than the horizontal direction is formed to reduce the vertical focusing angle in the deflection magnetic field and There is an electron gun designed to reduce deflection aberration. However, even if the electric field correction electrode is arranged inside the facing portion of the focusing electrode and the final accelerating electrode that form the main lens portion in this way, the center beam can be made almost a perfect circle, but the side beam is However, there is a problem that the ellipse becomes long in the vertical direction, the resolution of the entire screen is deteriorated, and the advantage of the correction electrode cannot be utilized.

The present invention has been made to solve the above problems, and an object of the present invention is to construct a color cathode ray tube capable of obtaining a good resolution over the entire screen.

[0014]

An electron gun having a main lens unit for finally focusing on a phosphor screen a three-electron beam arranged in a line consisting of a center beam passing through the same plane and a pair of side beams, The center beam passage formed on each facing surface inside each facing portion of the first electrode of relatively low potential and the second electrode of relatively high potential facing the first electrode which constitutes the main lens portion. In the color cathode ray tube in which each pair of electric field correction electrodes is arranged so as to sandwich the three electron beam passage holes arranged in a line, each of which is composed of a hole and a pair of side beam passage holes, the electric field correction electrode inside the first electrode is The length of the portion corresponding to the center beam passage hole in the gun axis direction is made shorter than the length of the portion corresponding to the side beam passage hole in the gun axis direction, and the electric field correction electrode inside the second electrode is Beam gun axial length of the passage portion corresponding to the hole is formed longer than the length of the gun axis direction of the portion corresponding to the side beam through holes.

[0015]

As described above, inside the facing portion of the first electrode and the second electrode forming the main lens portion, the three electron beam passage holes arranged in a row are formed so as to sandwich each facing surface. A pair of electric field correction electrodes are arranged, and the electric field correction electrodes inside the first electrode are arranged such that the length in the gun axis direction of the portion corresponding to the center beam passage hole is in the gun axis direction of the portion corresponding to the side beam passage hole. It is formed shorter than the length, and the electric field correction electrode of the second electrode is formed so that the length in the gun axis direction of the portion corresponding to the center beam passage hole is longer than the length in the gun axis direction of the portion corresponding to the side beam passage hole. Then, on the first electrode side, the pair of side beams is strongly focused in the vertical direction with respect to the center beam, and on the second electrode side, the pair of side beams is weakly diverged in the vertical direction with respect to the center beam. . In addition, the focusing effect on the side beam also weakens in the horizontal direction,
Divergent action is strengthened. As a result, overfocus in the horizontal direction of the side beam with respect to the center beam generated in the case of the conventional electric field correction electrode, underfunucus in the vertical direction is reduced, and the shape of the beam spot of each electron beam is made uniform, The resolution of the entire screen can be improved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 2 shows a color cathode ray tube which is one embodiment thereof. The color cathode ray tube includes a panel 20 and a funnel-shaped funnel 21 integrally joined to the panel 20.
The outer surface of the panel 20 is blue,
A phosphor screen 22 including a stripe-shaped three-color phosphor layer that emits green and red light is provided, and a shadow mask 23 is arranged inside the phosphor screen 22 so as to face the phosphor screen 22. On the other hand, in the neck 24 of the funnel 21, a three-column arrangement of a center beam 25G and a pair of side beams 25B and 25R that pass on the same horizontal plane is arranged.
Electron gun 2 that emits electron beams 25B, 25G, 25R
6 are provided. Then, the three electron beams 25B, 25G, 25R emitted from the electron gun 26 are deflected by the horizontal and vertical deflection magnetic fields generated by the deflection yoke 27 mounted outside the funnel 21, and the phosphor screen 2
2 is scanned to form a structure for displaying a color image.

As shown in FIG. 1, the electron gun 26 has three cathodes KB, KG and K arranged in a line in the horizontal direction.
R, the cathodes KB, KG, and KR are heated separately 3
Individual heaters (not shown), the cathodes KB, KG, K
Formed in a structure in which first to sixth grids G1 to G6 are sequentially arranged in the phosphor screen direction at a predetermined distance from R and are fixed integrally by a pair of insulating supports (not shown). Has been done.

The first and second grids G1 and G2
Is a plate-shaped electrode having an integral structure whose major axis is the arrangement direction of the above-mentioned cathodes KB, KG, KR, and the plate surface has a relatively small three electrodes corresponding to the three cathodes KB, KG, KR.
The individual electron beam passage holes are formed in a line in the horizontal direction. The third to sixth grids G3 to G6 are cylindrical electrodes of an integral structure whose major axis is the arrangement direction of the cathodes KB, KG, and KR, and the third grid G3 and the second grid G2 face each other. Three cathodes KB, KG,
Corresponding to KR, three electron beam passage holes larger than the electron beam passage holes of the second grid G2 are formed in a line in the horizontal direction. The surface of the third grid G3 facing the fourth grid G4 and the fourth, fifth and sixth grids G4,
Three cathodes KB and KG are provided on the respective facing surfaces of G5 and G6.
, KR, three electron beam passage holes, which are larger than the electron beam passage holes on the surface of the third grid G3 facing the second grid G2, are formed in a line in the horizontal direction.

Further, in this electron gun 26, inside the respective facing portions of the fifth and sixth grids G5 and G6, the three electron beam passing holes formed in the facing surfaces are sandwiched so as to sandwich the gun. Each pair of electric field correction electrodes 29, 30 along the axis Z
Are arranged.

Particularly in the electron gun 26, the electric field correction electrodes 29, 30 have arcuate tips facing each other, and the electric field correction electrode 29 inside the fifth grid G5 has the fifth grid G5. The center beam passage hole 3 with respect to the length L5s in the gun axis direction of the portion corresponding to the side beam passage holes 31B and 31R on the sixth grid G6 side.
The length L5c of the portion corresponding to 1G in the gun axis direction is formed in a short concave shape. On the other hand, regarding the electric field correction electrode 30 inside the sixth grid G6, the side beam passage holes 32B and 32R on the fifth grid G5 side of the sixth grid G6 are provided.
The length L6c in the gun axis direction of the portion corresponding to the center beam passage hole 32G is formed in a long convex shape with respect to the length L6s in the gun axis direction of the portion corresponding to.

In this electron gun 26, the cathodes KB, KG
, KR is applied with a video signal added to the cutoff voltage of about 150 V, and the first grid G1 is set to the ground potential,
500 to 1000 V for the second grid G2, 5 to 10 kV for the third grid G3, 0 to 5 kV for the fourth grid G4,
15-25 kV on 5th grid G5, 6th grid G6
A voltage of 25 to 30 kV is applied to.

Thus, the cathodes KB, KG, KR and the first and second grids G1, G2 control the emission of electrons from the cathodes KB, KG, KR, and the emitted electrons are focused and arranged in a line. An electron beam forming part for forming three electron beams is formed, and the second and third grids G2 are formed.
, G3, a prefocus lens for pre-focusing the electron beam from the electron beam forming unit
Through the sixth grids G3 to G6, a main lens unit for finally focusing the pre-focused electron beam on the phosphor screen is formed.

By the way, inside the fifth and sixth grids G5 and G6 constituting the main lens portion as described above, electron beam passage holes 31B and 31 are formed respectively on the facing surfaces thereof.
G, 31R, 32B, 32G, and 32R are sandwiched by a pair of electric field correction electrodes 29 having a concave arcuate tip and a pair of electric field correction electrodes 3 having a convex arcuate tip.
If 0 is arranged, these fifth and sixth grids G5, G6
The electron lens shown in FIG. 3 is formed in between.

That is, in the vertical direction, the electron lens shown by equipotential lines 33cV and 34cV in FIG. 3A with respect to the center beam 25G and the equipotential line 33B with respect to the side beams 25B and 25R are shown in FIG. Electron lenses indicated by 33sV and 34sV are formed. Further, in the horizontal direction, electron lenses indicated by equipotential lines 33H and 34V are formed in the same (c). The vertical electron lens has a stronger focusing action on the side beams 25B and 25R on the fifth grid G5 side than on the center beam 25G, and on the sixth grid G6 side on the center beam 25G. Relative to the diverging action, the side beams 25B,
The divergent effect on 25R is weakened. The horizontal electron lens has a weaker focusing effect on the side beams 25B and 25R on the fifth grid G5 side and a diverging effect on the side beams 25B and 25R on the sixth grid G6 side due to the influence of the vertical electric field. Becomes stronger.

As a result, as shown in FIG.
And the divergence region II, the underfocus condition of the side beams 25B and 25R with respect to the center beam 25G is reduced in the vertical direction, and the side beams 25B and 25R with respect to the center beam 25G in the horizontal direction.
The overfocus condition of the 5th grid G
As shown in FIG. 5, the relationship between the focus voltage applied to 5 and the beam spot on the phosphor screen 22 is as shown in the curve 35H for the horizontal center beam beam spot and the curve 35V for the vertical center beam beam spot. With respect to the beam spot, the horizontal and vertical beam spots of the side beam approach the horizontal and vertical beam spots of the center beam as indicated by curves 36H and 36V, respectively, and the focus voltage Vf applied to the fifth grid G5 is applied. On the other hand, not only the center beam but also the beam spots of the side beams can both be formed into a substantially perfect circle, and the resolution of the entire screen can be improved.

[0027]

EFFECT OF THE INVENTION An electron gun having a main lens section for finally focusing on a phosphor screen three electron beams arranged in a line consisting of a center beam passing through the same plane and a pair of side beams is provided, and this main lens section is provided. Of the first electrode having a relatively low potential and the second electrode having a relatively high potential that faces the first electrode inside the respective facing portions, and the center beam passage hole formed in each facing surface, and In a color cathode ray tube in which each pair of electric field correction electrodes is arranged so as to sandwich three electron beam passage holes arranged in a line consisting of a pair of side beam passage holes, the electric field correction electrode inside the first electrode is The length of the portion corresponding to the beam passage hole in the gun axis direction is made shorter than the length of the portion corresponding to the side beam passage hole in the gun axis direction, and the electric field correction electrode inside the second electrode is If the length of the portion corresponding to the through hole in the gun axis direction is made longer than the length of the portion corresponding to the side beam passage hole in the gun axis direction, a pair of side beams is formed on the first electrode side with respect to the center beam. The pair of side beams is strongly focused in the vertical direction and weakly diverges on the second electrode side in the vertical direction with respect to the center beam. In addition, the focusing effect on the side beam also weakens in the horizontal direction,
Divergent action is strengthened. As a result, overfocus in the horizontal direction and underfocus in the vertical direction of the side beam with respect to the center beam, which occurs in the case of the conventional electric field correction electrode, is reduced, and the beam spot shape of each electron beam is made uniform. The resolution of can be improved.

[Brief description of drawings]

FIG. 1 (a) is an XZ sectional view showing the structure of an electron gun of a color cathode ray tube according to an embodiment of the present invention, FIG.
(B) is a YZ sectional view.

FIG. 2 is a diagram showing a configuration of a color cathode ray tube which is an embodiment of the present invention.

FIGS. 3A to 3C are views for explaining an electron lens formed in a main electron lens portion of the electron gun.

FIG. 4 is a diagram for explaining focusing of an electron beam by an electron lens of the main electron lens unit.

FIG. 5 is a diagram for explaining the shape of a beam spot of an electron beam focused on the phosphor screen by the electron lens of the main electron lens unit.

6A is an XZ sectional view showing the structure of an electron gun of a conventional color cathode ray tube, and FIG. 6B is a YZ sectional view.

FIG. 7A is a diagram for explaining distortion of an electron beam due to a pincushion type horizontal deflection magnetic field, and FIG. 7B is a diagram for explaining distortion of an electron beam due to a barrel type vertical deflection magnetic field. Is.

FIG. 8 is a diagram for explaining a distortion shape of a beam spot on a screen due to the pincushion type horizontal deflection magnetic field and the barrel type vertical deflection magnetic field.

9 (a) is an XZ sectional view showing the structure of an electron gun in which a field correction electrode of a conventional color cathode ray tube is arranged, and FIG. 9 (b) is a YZ sectional view.

10A to 10C are views for explaining an electron lens formed in a main electron lens portion of an electron gun in which the above-described conventional electric field correction electrode is arranged.

FIG. 11 is a diagram for explaining focusing of an electron beam by an electron lens of a main electron lens portion of an electron gun in which the above-described conventional electric field correction electrode is arranged.

FIG. 12 is a diagram for explaining the shape of the beam spot of the electron beam focused on the phosphor screen by the electron lens of the main electron lens part of the electron gun in which the conventional electric field correction electrode is arranged.

[Explanation of symbols]

 22 ... Phosphor screen 25B, 25R ... Pair of side beams 25G ... Center beam 26 ... Electron gun 27 ... Deflection yoke 29 ... Electric field correction electrode 30 ... Electric field correction electrodes 31B, 31G, 31R ... Electron beam passage holes 32B, 32G, 32R ... Electron beam passage hole G1 ... First grid G2 ... Second grid G3 ... Third grid G4 ... Fourth grid G5 ... Fifth grid G6 ... Sixth grid KB, KG, KR ... Cathode

Claims (1)

[Claims] 1. An electron gun having a main lens section for finally focusing on a phosphor screen a three-electron beam arranged in a line consisting of a center beam and a pair of side beams passing on the same plane, the main lens section being provided. Of the first electrode having a relatively low electric potential and the second electrode having a relatively high electric potential which faces the first electrode, and the center beam passage hole and the pair of center beam passing holes formed in the respective facing surfaces inside the facing portions. In a color cathode ray tube in which a pair of electric field correction electrodes are arranged so as to sandwich three electron beam passage holes arranged in a row composed of side beam passage holes, the electric field correction electrode inside the first electrode passes the center beam passage. The length of the portion corresponding to the hole in the gun axis direction is formed shorter than the length of the portion corresponding to the side beam passage hole in the gun axis direction, and the electric field correction electrode inside the second electrode is the center electrode. Color cathode ray tube, characterized in that the gun axial length of the portion corresponding to the beam passage holes are formed to be longer than the length of the gun axis direction of the portion corresponding to the side beam through holes.