JPH01187744A - Color image receiving tube - Google Patents

Abstract

PURPOSE:To produce a beam spot near a genuine circle with a minor dia. by introducing a specific relation to three factors; i,e. the distance of the electron emitting surface of a cathode to that surface of G2 electrode which faces the G3 electrode, the distance of the mating surfaces of the G2 and G3 electrodes, and the bore of an electron beam passing hole formed in the G3 electrode. CONSTITUTION:Three grooves 2b are provided at that surface of G1 electrode 2 which faces the G2 electrode 3, and an electron beam passing hole 2a having a horizontal direction dia. of a and a vertical direction dia. of b is provided in the middle of the grooves 2b. Therein the relation according to Eq. I shall hold for, where c is the distance of the electron emitting surface of cathode to that surface of G2 electrode 3 which faces the G3 electrode 4, d is the distance of the mating surfaces of G2 electrode 3 and G3 electrode 4, and e is the bore of a circular electron beam passing hole 4a formed at the G2 electrode 3 side face of G3 electrode 4. Thereby a main lens with large dia. is produced, and the inconvenience that main lens is asymmetrical about axis, can be eliminated complementarily by a prefocusing lens, and a beam spot having a minor dia. and with less shape distortion can be produced on the fluorescent screen.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a color picture tube equipped with an in-line electron gun;
In particular, it relates to a high-resolution color picture tube with the ability to generate a large-diameter main lens.

Conventional technology In general, the beam spot generated when an electron beam impinges on the phosphor screen of a color picture tube has a large beam current (i.e., becomes large in diameter at high brightness, and as the beam spot becomes large in diameter, the resolution decreases). Come.

In addition, since the electron beam emitted from the in-line electron gun passes through a horizontal deflection magnetic field that is distorted in a binction tendency and a vertical deflection magnetic field that is distorted in a barrel tendency, its cross-sectional shape and beam spot are likely to be distorted, and the resolution is Such a deflection aberration also causes a decrease. In particular, 110
Large color picture tubes of wide-angle deflection type such as the ° deflection type and having a flat rectangular screen surface called a "flat square" have difficulty obtaining high resolution due to the large average value of the beam current.

Therefore, by using an electron gun with a large diameter main lens such as that disclosed in US Pat. No. 4,275,332, the influence of spherical aberration can be reduced and resolution can be improved.

Problem to be Solved by the Invention However, as in the electron gun described in the above-mentioned US patent specification, each of the opposing end surfaces of the G3 electrode and the G4 electrode has one horizontally long opening, and each When the space inside the electrode leading to the aperture is partitioned into three electron beam paths by a metal plate, the three main lenses generated between both electrodes are distorted in an axially asymmetrical manner. Therefore, the lens electric field is corrected by forming an indented recess at the opposite end of the metal plate provided in the picture electrode, but the axial asymmetry of the main lens remains.

Means for Solving the Problems According to the present invention, three cathodes arranged in-line in the horizontal direction, a GI electrode, a plate-shaped 62 electrode having three circular electron beam passage holes, a box-shaped G3 electrode, and the G3 It is equipped with 64 electrodes for generating three main lenses together with the electrodes, and has one horizontally long opening on each end face where the G3 electrode and the G4 electrode face each other, and the internal space leading to each opening is used for electric field. In a color picture tube partitioned into three electron beam paths by a correction plate, three vertically long grooves are provided on the surface of the G1 electrode on the G2 electrode side, and approximately in the middle of the bottom of each groove. An electron beam passing hole having a horizontal diameter a and a vertical diameter b is provided. Then, the distance from the electron emitting surface of the cathode to the surface of the G2 electrode on the G3 electrode side is c, and the G2
The relative facing distance between the electrode and the G3 electrode is d1 the G3
When the diameter of the circular electron beam passage hole formed on the end surface of the electrode on the G2 electrode side is e, 0, 5 a≦b≦0.8a 1.25a≦c≦2.25 a o, 8a≦d≦ 1.8a 1.0a≦e≦1.8a.

Function: With this configuration, not only can a main lens with a large diameter be generated, but also the problem of axial asymmetry of the main lens can be compensated by the axially asymmetrical brifocus lens, and the small beam current can be reduced. It becomes possible to generate a beam spot with a small diameter and little shape distortion on the phosphor screen regardless of the time or the case of a large beam current.

Embodiments Next, the present invention will be explained in detail with reference to embodiments shown in the drawings.

As shown in FIG. 1, three cathodes 1a, lb, lc, and if are arranged in line in the horizontal direction. G+ electrode 2 is a control grid, and G2 is a plate-shaped acceleration grid.
The electrode 3 has a front triode (14), and a box-shaped G3 electrode 4 as a focusing grid is arranged between a G2 electrode and a cup-shaped G4 electrode 5 as an anode.

The three electron beam passing holes 2a of the G1 electrode 2 are formed in a horizontally long rectangular shape, as shown in FIG. However, the G1 electrode 2 has three vertically long grooves 2b on the surface thereof facing the G2 electrode 3, and an electron beam passage hole 2a is formed approximately in the middle of the bottom of the grooves 2b. Note that each electron beam passage hole 2a has a horizontal diameter a and a vertical diameter b, and each groove 2b also has a horizontal diameter a. Further, the G2 electrode 3 has three circular electron beam passage holes 3a, and the G3 electrode 4 has three circular electron beam passage holes 4a on the end face on the G2 electrode 3 side.

The distance from the electron emission surface of the cathode to the surface of the G2 electrode 3 on the G3 electrode 4 side is c, and the distance between the opposing surfaces of the G2 electrode 3 and the G3 electrode 4 is d% of the electron beam passage hole 4a of the G3 electrode 4. When the diameter is e, 0.5a≦b≦0.8a 1.25a≦c≦2.25 a O08a≦d≦1.8a ■. It is set to satisfy the following relationship: 0a≦e≦1.8a.

Each of the opposing end surfaces of the G3 electrode 4 and the G4 electrode 5 is provided with one horizontally long oval opening 4b, 5a, and the internal space communicating with each opening 4b, 5a is as follows.
As shown in FIGS. 3 and 4, respective electric field correction plates 6a, 6b; 7a.

7b into three electron beam paths, a pair of electric field correction plates 5a, 6b and a pair of electric field correction plates 7.
a, 7b are concave portions 8a, 8b curved in a circular arc shape.
; 9a and 9b are provided at opposite ends.

Figures 5 and 6 show horizontal and vertical cross sections of the front triode section, and show the cathode 1 during large beam current.
The trajectory of the center beam, which is the electron beam emitted from b, is drawn with a thin line.

The electrons emitted from the cathode 1b pass through the cathode lens 10b.
A crossover is created through the cathode lens 10b.
has a strong spherical aberration, so the electrons emitted from the peripheral edge of the electron emitting surface of the cathode 1b are subjected to a very strong focusing effect, creating a crossover at a position 11b close to the cathode 1b. On the other hand, paraxial electrons emitted from the center of the electron emitting surface are hardly affected by the spherical aberration of the cathode lens 10b and are focused to a low degree.
A crossover is created at a position 12b relatively far from.

In the present invention, there is a cross-over position 112 in the pre-focus lens 13b generated near the exit of the G2 electrode 3.
The dimensions of each part of the front triode part are set so that b can fit therein. If the distance between the G2 electrode 3 and the G3 electrode 4 is set relatively small and a very strong lens electric field is generated there,
The crossover, which is the object point of a brifocus lens, can be made to enter the brifocus lens, and even if the lens electric field is strong (even though the electrons in question are hardly focused), the paraxial electrons that take the orbit 14b On the other hand, the magnification of the prefocus lens is small, and these paraxial electrons are not so affected by spherical aberration.

On the other hand, the trajectory 15b of electrons emitted from the peripheral edge of the electron emitting surface creates a crossover at a position 11b near the entrance of the G2 electrode 3. Since the position 11b is far from the prefocus lens 13b, the electrons are very strongly focused by the prefocus lens 13b and pass through the center of the main lens generated between the G3 electrode and the 64 electrode. Therefore, the degree of influence of spherical aberration in the main lens is significantly reduced.

The trajectory 15b of the electrons emitted from the peripheral edge of the electron emitting surface of the cathode 1b is strongly focused as described above, and the trajectory 15b is outside the beam JM.
Therefore, the electrons occupying the outer peripheral part of the beam are emitted from the middle part of the electron emission surface and follow the trajectory 16b.
The crossover occurs at position 17a. Since this position 17a is close to the prefocus lens 13b, even if the electrons taking the orbit 16b occupy the outermost periphery within the main lens, the degree of influence of spherical aberration is considerably lower than in the conventional case.

The prefocus lens generated in such an electrode configuration selectively and strongly focuses the electrons emitted from the periphery of the electron emitting surface of the cathode, so that all the electrons including the main lens are By reducing the spherical aberration of the lens system and appropriately selecting the beam diameter within the main lens, it is possible to improve the horizontal diameter of the beam spot by 30 to 40% at the time of a large beam current.

Next, referring to FIG. 6, since the electron beam passage hole 2a of the G+ electrode 2 is located approximately in the middle of the bottom of the groove 2b, the position of the crossover that occurs in the vertical plane is shown in FIG. The cross-over position and the road distance within the horizontal plane shown can be made equal. That is, as a result of making the electron beam passing hole 2a of the G1 electrode 2 horizontally elongated and reducing the plate thickness in the vertical plane, the degree of beam focusing by the cathode lens 17b, which is indicated by the reference numeral 17b, is improved by the above-mentioned cathode lens 1.
It can be approximated to the beam focusing degree by 0b,
The electrons are emitted from the center of the electron emitting surface of the cathode 1b and follow the trajectory 18.
An electron taking b is placed at position 19b, an electron emitted from the middle part of the same surface and taking orbit 20b is placed at position 21b, and an electron emitted from the peripheral part of the same surface taking orbit 22b is placed at position f.
Create a crossover for each f123b. position 19
Since b approximately corresponds to position 12b, position 21b to position 17b, and position 23b to position Llb, the positional relationship of each crossover with respect to the prefocus lens 13b is also the same as that in the horizontal plane, and the selective A prefocusing effect occurs, making it possible to reduce the diameter of the beam spot in the vertical direction.

Moreover, even though the operating area of the electron emission surface is relatively narrow, the crossover position can be made similar to that in the horizontal plane, so that the outermost portion of the electron beam after passing through the prefocus lens is spread out. The angle, that is, the beam divergence angle can be made small, and the cross-sectional shape of the electron beam within the main lens and within the deflection magnetic field becomes an ellipse long in the horizontal direction.

As mentioned above, the electron beam emitted from the in-line electron gun passes through the horizontal deflection magnetic field distorted in the bink tension tendency and the vertical deflection magnetic field distorted in the barrel tendency, so it is particularly focused in the vertical direction, and the beam spot will overfocus in the vertical direction, resulting in a long vertical haze (blur). Therefore, by offsetting the fact that the cross-sectional shape of the electron beam within the deflection magnetic field becomes an ellipse long in the horizontal direction as described above, the distortion of the beam spot due to deflection aberration is significantly reduced.

Incidentally, the degree of flattening of the electron beam that passes through the main lens toward the phosphor screen increases as the beam current increases. Although this is an advantage from the perspective of the vertical diameter of the beam spot, it is a disadvantage from the perspective of the horizontal diameter. This is because in the horizontal plane, the main lens is greatly affected by spherical aberration. Furthermore, since the electrons occupying the outermost portion of the main lens, that is, the electrons taking orbit 16b, have a relatively high density, the horizontally long haze caused by the spherical aberration has a relatively high brightness. Since haze occurs regardless of whether it is in the center or the periphery of the phosphor screen, it impairs the contrast of the screen, especially at high brightness.

According to the present invention, such an axially asymmetrical triode is combined with a large-diameter axially asymmetrical main lens portion as shown in FIGS. 3 and 4, and the inherent drawbacks of each are complementarily resolved. Therefore, the spherical aberration of the lens system as a whole can be reduced, and a beam spot that is well-balanced in both the horizontal and vertical directions can be generated.

The center beam that passes through the main lens when the beam current is small has a cross-sectional shape of an ellipse that is slightly elongated in the horizontal direction, but because the average diameter is small, it is hardly affected by spherical aberration, and the focus characteristics are based on the paraxial characteristics of the main lens. Determined by As the beam current increases, the degree of flattening of the electron beam increases, but since the main lens has the structure shown in Figures 3 and 4, the horizontal spherical aberration of the main lens is small ( Although the spherical aberration in the vertical plane of the main lens is relatively large, the vertical diameter of the electron beam entering the main lens can be made sufficiently small (as described above).
Haze rarely occurs.

Regarding the side beams, which are electron beams on both sides, electric field correction plates 6a, 6b, 7a, 7bi::l! Part 1 8a, 8
The effect of reducing horizontal in-plane spherical aberration by providing b * 9 a * 9 b occurs only on one side of the beam. However, since it is possible to compromise between the left and right sides by slightly biasing each electron beam path in the main lenses on both sides toward the electric field correction plate, the influence of spherical aberration in the horizontal plane can also be reduced for the side beams.

In order to obtain a beam spot with a small diameter and close to a perfect circle using the axially asymmetrical main lens part as described above, it is necessary to change the structural parameters of the axially asymmetrical front triode part as described above. must be limited in scope, and this limitation shall be
It is expressed by the inequality shown at the beginning of the example. Note that b is 0
．． If it exceeds 8a, the effect of improving deflection aberration cannot be sufficiently obtained, and the vertical diameter of the beam cross section cannot be reduced to a required value. Furthermore, if b is less than 0.5a, the beam cross section becomes too long in the horizontal direction, making it impossible to prevent long haze in the horizontal direction. If the values of d and e are out of the above range, it becomes difficult to obtain the selective brisfocusing effect described above. That is, if C is less than 1.25a, it becomes difficult to control the beam divergence angle by the brifocus lens,
If it exceeds 2.25a, it becomes difficult to locate the paraxial electron crossover within the brifocus lens. Furthermore, if d is less than 0.8a, there will be a problem in terms of withstand voltage, and if it exceeds 1.8a, it will be impossible to obtain a brifocal lens electric field of necessary strength. Furthermore, if e is less than 1.0a, not only will it be extremely difficult to assemble the electrodes, but there is a risk that the outer periphery of the electron beam will hit the 63 electrode, and if e exceeds 1.8a, the strength is insufficient. It is not possible to obtain a brifocal lens electric field. 1
A specific numerical example of a 10° deflection type in-line large color picture tube having a flat square screen surface is as follows.

a・・・・・・・・・0.9m b・・・・・・・・・0.64m C・・・・・・1.4ww d・・・・・・・・・0 .9- e・・・・・・・・・0.9m G1 electrode plate thickness・・・・・・・・・・・・・・・
・・・・・・・・・0.3mm Thickness of bottom plate of concave groove of G1 electrode ・・・・・・・・・0.1am Long diameter of main lens opening ・Automatic・・181IIIl Short diameter of main lens opening・・・・・・・・・・7. c.
, the distance between electric field correction plates...
・・・・・・・・・5.3-Radius of curvature of the concave part of the electric field correction plate・・・・・・2.6m Electron emission surface/main lens distance...33.0mG4 electrode voltage...・・・・・・
・27.5KVG3 electrode voltage 7.5
KVG2 electrode voltage...600VG1 electrode voltage...Ov Cathode voltage...4O-160V According to the color picture tube with this configuration, 0~ In a drive current range of 5 mA, it is possible to generate a beam spot that is close to a perfect circle with a small diameter over the entire screen surface.

Effects of the Invention Since the present invention is configured as described above, it is possible to display a clear color image with high resolution and high contrast.

[Brief explanation of the drawing]

Fig. 1 is a horizontal cross-sectional view of the electron gun of a color picture tube embodying the present invention, Fig. 2 is a perspective view of the Gl electrode of the color picture tube, and Fig. 3 is a side cross-section of the main lens portion of the color picture tube. 4 is a sectional view taken along the line IV--IV in FIG. 3, and FIGS. 5 and 6 are horizontal sectional views and vertical sectional views mainly of the front triode portion of the color picture tube. la, lb, lc...... cathode, 2...
・・・・・・G1 electrode, 2a・・・・・・Electron beam passing hole, 2b・・・・・・Concave groove, 3・・・・・・
...G2 electrode, 3a...Electron beam passage hole, 4...G3 electrode, 4a...
・・・・・・Electron beam passing hole, 5・・・・・・・・・G
4 electrodes, 4 b * 5 a......opening,
6 a * 6 b, 7 a, 7 b...
...Electric field correction plate, 8a, 8b, 9a, 9b...
・・・Concavity. Name of agent: Patent attorney Toshio Nakao and one other person Figure 2

Claims (1)

[Claims] A plate-shaped G_1 electrode having three cathodes arranged in-line in the horizontal direction, a G_1 electrode, and three circular electron beam passage holes.
2 electrodes, a box-shaped G_3 electrode and a G_4 electrode for generating three main lenses together with the G_3 electrode, and the G_3 electrode and the G_4 electrode have one horizontally long electrode on each of opposing end surfaces. In a color picture tube that has apertures and the internal space leading to each aperture is partitioned into three electron beam paths by an electric field correction plate, the G_1 electrode has three vertically long concave grooves G_1.
An electron beam passing hole with a horizontal diameter a and a vertical diameter b is provided on the surface of the G_2 electrode and the G_3 electrode of the G_2 electrode at approximately the center of the bottom of each groove. The distance to the side surface is c, the distance between the opposing surfaces of the G_2 electrode and the G_3 electrode is d, and the G_
When the diameter of the circular electron beam passing hole formed on the G_2 electrode side end surface of the 3 electrode is e, 0.5a≦b≦0.8
A color picture tube characterized by having the following relationships: a 1.25a≦c≦2.25a 0.8a≦d≦1.8a 1.0a≦e≦1.8a.