JP2000077009A - Cathode ray tube - Google Patents

Abstract

(57) [Object] To provide a color cathode ray tube capable of maintaining good electron beam focus characteristics over the entire phosphor screen and suppressing elliptic distortion of an electron beam spot over the entire phosphor screen. . When deflecting an electron beam to a peripheral portion of a phosphor screen, a first and a second lens are provided between a prefocus lens unit and a sub lens unit and between a sub lens unit and a main lens unit, respectively. Is formed. The second grid G2 that constitutes the prefocus lens unit is the third grid G2.
A non-circular groove 102 (B, R, G) having a long axis in the horizontal direction is provided around the electron beam passage hole provided on the surface of the grid G3 facing the first segment G3-1. Further, the first segment G3-1 of the third grid G3 is
A non-circular groove 103 having a long axis in the horizontal direction around an electron beam passage hole provided on the opposing surface of the second grid G2.
(B, R, G).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube, and more particularly to an in-line type color cathode ray tube capable of obtaining good image quality over the entire screen.

[0002]

2. Description of the Related Art In general, an in-line type color cathode ray tube has an in-line type electron gun assembly and a deflection yoke. The in-line type electron gun assembly emits three electron beams arranged in a row in the horizontal direction, each including a center beam and a pair of side beams passing on the same plane. The deflection yoke generates an asymmetric magnetic field that deflects the three electron beams emitted from the in-line type electron gun assembly in the horizontal and vertical directions. The non-uniform magnetic field is formed by a pincushion-type deflection magnetic field formed in the horizontal direction and a barrel-type deflection magnetic field formed in the vertical direction. The three electron beams emitted from the in-line type electron gun assembly are focused on the center of the phosphor screen. The three electron beams are scanned in the horizontal and vertical directions while being self-converged on the phosphor screen by the non-uniform magnetic field generated by the deflection yoke.

This in-line type electron gun structure, for example, QP
F (Quadra Potential Focus)
The double-focus type electron gun assembly has three cathodes K arranged in a row in the horizontal direction, a first grid G1, a second grid G2, and a third grid G3 sequentially arranged from the cathode in the direction of the phosphor screen. 4th grid G
4. Fifth grid G having first to third segments
5 and a sixth grid G6.

By applying a predetermined voltage to each of these grids, the electron gun assembly forms an electron beam generating section, a prefocus lens section, a sub lens section, and a main lens section. The electron beam generator is formed by the cathode K, the first grid G1, and the second grid. The prefocus lens portion is formed by the second grid G2 and the third grid G3. The sub lens portion is formed by the first segment G5-1 of the third grid, the fourth grid, and the fifth grid. The main lens section is the fifth
It is formed by the third segment G5-3 of the grid.

Further, in this electron gun assembly, a quadrupole lens whose lens intensity changes depending on the deflection amount of the electron beam is formed by the first to third segments G5-1 to G5-3 of the fifth grid. That is, by the deflection yoke,
When the electron beam is deflected around the phosphor screen,
Depending on the amount of deflection, the first segment G5-1 and the third segment G5-1
A preset voltage is applied to the segment G5-3. This voltage is the lowest when the electron beam is focused at the center of the phosphor screen, that is, when the deflection amount is zero, and becomes the highest when the electron beam is deflected to the phosphor screen corner, that is, when the deflection amount is the maximum. It is parabolic.

When the electron beam is deflected to the corner of the phosphor screen, the voltage applied to the first and third segments G5-1 and G5-3 becomes maximum. For this reason,
The potential difference from the fourth grid G4 becomes maximum, and the lens strength of the sub-lens portion increases. At the same time, the potential difference from the sixth grid is minimized, and the lens strength of the main lens unit is weakened. At the same time, a quadrupole lens is formed by the potential difference generated between the first to third segments G5-1 to G5-3, and the lens strength is maximized.

This quadrupole lens works to correct the deflection aberration of the non-uniform magnetic field generated by the deflection yoke, and the lens strength is defocused due to an increase in the distance until the electron beam reaches the phosphor screen. Is changed to correct.

[0008]

In general, in an in-line type color cathode ray tube having an in-line type electron gun, deflection aberration cannot be sufficiently corrected. Therefore, as shown in FIG. Is substantially circular, whereas the beam spot B2 of the electron beam deflected to the periphery of the phosphor screen is distorted in an elliptical shape that is long in the lateral direction. . That is, the beam spot B2 is composed of an elliptical high-brightness core portion 1 and a core portion 1 that are spread in the horizontal direction.
Is formed so as to have a low-luminance halo portion 2 spread around the periphery.

In order to solve this problem, the electron gun assembly of the QPF type double focus system described above forms a quadrupole lens according to the amount of deflection of the electron beam, so that the electron beam deflected to the peripheral portion of the phosphor screen. Although the halo portion 2 of the beam B2 can be eliminated as shown in FIG. 1B, the elliptical distortion in which the beam spot B2 is crushed horizontally at the end of the phosphor screen horizontal axis H and the end of the diagonal axis is as follows. Remains. For this reason, moire occurs due to interference with the shadow mask,
There is a problem that the image quality of the image formed by the beam spots is deteriorated.

As a countermeasure against this, the third grid G2
An electron gun structure having a horizontally long groove formed on the side opposite to the grid G3 has been proposed. In this electron gun assembly, the focusing power in the horizontal direction H of the prefocus lens formed by the second grid G2 and the third grid G3 is weakened, and the vertical direction V
Is increased, the virtual object point diameter in the horizontal direction H with respect to the main lens portion is reduced, and the virtual object point diameter in the vertical direction V is increased. Thereby, the vertical diameter of the beam spot of the electron beam reaching the phosphor screen is enlarged, the elliptic distortion of the electron beam around the phosphor screen is reduced, and moire is reduced.

However, in this method, the second grid G
The elliptical distortion of the beam spot B2 at the periphery of the phosphor screen is not alleviated as the width of the elongated groove formed in the main lens 2 becomes deeper, which is contrary to the reduction of the virtual virtual object point diameter with respect to the main lens portion. As a result, the horizontal diameter of the electron beam increases. For this reason, the electron beam passes through the periphery of the main lens portion having a large spherical aberration. Therefore, FIG.
As shown in (c), the beam spot B1 at the center of the phosphor screen has a vertical diameter that is enlarged and becomes vertically elongated.
Resolution deteriorates. Further, a halo portion 2 is generated in the beam spot B2 in the horizontal direction at the end of the phosphor screen horizontal axis H and the end of the diagonal axis, which causes a problem that the image quality is reduced.

As another countermeasure, as shown in FIG. 2, an electron gun assembly in which a third grid G3 is divided into a first segment G3-1 and a second segment G3-2 has been proposed. In this electron gun assembly, the first and second segments G3-1 and G3-2 form a quadrupole lens whose lens strength changes according to the amount of deflection of the electron beam. This quadrupole lens is set to have astigmatism opposite to that of the quadrupole lens formed by the fifth grid.

In such a double quadrupole type electron gun assembly, the first quadrupole lens is formed by the first and second segments G3-1 and G3-2 of the third grid G3 as the electron beam is deflected. The first to third segments G5-1 to G5-3 of the fifth grid G5 form a second quadrupole lens. In a cathode ray tube having such an electron gun assembly, the first quadrupole lens, the sub lens unit, the second quadrupole lens, the main lens unit, and the horizontal lens when the deflection magnetic field is considered as one lens in total. The difference in lens magnification between the direction and the vertical direction is reduced.

[0014] Thus, the lateral collapse of the electron beam around the phosphor screen can be theoretically eliminated.
Further, the quadrupole lens does not act on the electron beam focused at the center of the phosphor screen, and the phenomenon that the electron beam becomes vertically long does not occur. That is, the image quality does not deteriorate over the entire phosphor screen.

However, in this method, the first and second segments G3-1 and G3-2 of the third grid G3 are also used.
As the first quadrupole lens formed in step (1) is strengthened, the effect on the distortion of the beam spot is increased.
By strengthening the pole lens, the horizontal diameter of the beam spot is enlarged, so that the electron beam passes through the periphery of the main lens portion having a large spherical aberration. Accordingly, a halo portion 2 is generated in the beam spot B2 in the horizontal direction at the end of the horizontal axis H of the phosphor screen and at the end of the diagonal axis, thereby causing a problem that the image quality is reduced.

As described above, in order to improve the image quality of the color cathode ray tube, it is necessary to suppress the collapsing of the electron beam spot, that is, the elliptical distortion over the entire surface of the phosphor screen.

In a conventional QPF-type double focus type electron gun assembly, a voltage which changes in a parabolic manner in accordance with the amount of deflection of the electron beam is applied to a grid forming a quadrupole lens. The generation of the vertical halo can be eliminated, but the horizontal collapse of the electron beam around the phosphor screen remains.

By forming a horizontally long groove in the second grid G2 in order to reduce the collapsing of the electron beam, the collapsing of the electron beam around the phosphor screen can be reduced. Halo tends to occur in the horizontal direction.

Further, even if a conventional double quadrupole electron gun assembly is employed, it is difficult to sufficiently eliminate the lateral collapse of the electron beam around the phosphor screen. The present invention has been made to solve the above problems, and a color cathode ray tube capable of maintaining good electron beam focus characteristics over the entire phosphor screen and suppressing elliptic distortion of an electron beam spot over the entire phosphor screen. The purpose is to provide.

[0020]

According to a first aspect of the present invention, there is provided a cathode ray tube, comprising: an electron beam generator for generating an electron beam; and an electron beam generator. A pre-focus lens unit having at least two opposed first and second electrodes for pre-focusing the electron beam, and a sub-lens unit for further pre-focusing the electron beam pre-focused by the pre-focus lens unit. An electron gun assembly having a main lens unit that finally focuses the electron beam preliminarily focused by the sub-lens unit on the center of the phosphor screen; and an electron gun assembly focused on the phosphor screen by the electron gun assembly. A deflection yoke for generating a deflection magnetic field for deflecting the electron beam in a vertical direction and a horizontal direction orthogonal to the traveling direction of the electron beam. In the tube, the first electrode of the prefocus lens has a non-circular groove having a long axis in the horizontal direction around an electron beam passage hole provided on a surface facing the second electrode. , The second electrode is connected to the first electrode
A non-circular groove having a long axis in the horizontal direction around an electron beam passage hole provided on a surface facing the electrode,
With the deflection of the electron beam, a first multipole lens is formed between the prefocus lens and the sub lens, and the first multipole lens is formed between the sub lens and the main lens.
The present invention is characterized in that there is provided a means for forming a second multipole lens having an astigmatism effect always opposite to that of the multipole lens.

According to a second aspect of the present invention, there is provided a cathode ray tube, comprising: an electron beam generator for generating an electron beam; and at least two beams for pre-focusing the electron beam generated from the electron beam generator.
A prefocus lens unit having two opposed first and second electrodes; a sub lens unit for further prefocusing the electron beam preliminarily focused by the prefocus lens unit; An electron gun assembly having a main lens portion that finally focuses the electron beam at the center on the phosphor screen, and the electron beam focused on the phosphor screen by the electron gun assembly, A deflection yoke that generates a deflection magnetic field that deflects in a vertical direction and a horizontal direction perpendicular to the direction, wherein the first electrode of the prefocus lens is opposed to the second electrode. A non-circular groove having a long axis in the horizontal direction around an electron beam passage hole provided on the surface, wherein the second electrode is provided with the first electrode;
A non-circular electron beam passage hole having a long axis in the horizontal direction on a surface facing the first electrode, and a first lens between the prefocus lens and the sub-lens as the electron beam is deflected. Means for forming a pole lens and means for forming a second multipole lens having an astigmatism effect always opposite to that of the first multipole lens between the sub lens and the main lens. I do.

According to the cathode ray tube of the present invention, the first electrode of the prefocus lens has a converging lens function, and the first electrode is formed by a non-circular groove having a long axis in the horizontal direction. The virtual object point of the passing electron beam with respect to the prefocus lens has a reduced diameter in the horizontal direction and an increased diameter in the vertical direction. In addition, the divergence angle of the electron beam passing through the first electrode in the horizontal direction increases and the divergence angle in the vertical direction decreases.

On the other hand, the second electrode of the prefocus lens has a divergent lens function, and is formed by a non-circular groove having a major axis extending in the horizontal direction to prefocus the electron beam passing through the second electrode. The virtual object point with respect to the lens has a larger diameter in the horizontal direction and a smaller diameter in the vertical direction. The divergence angle of the electron beam passing through the third grid G3 in the horizontal direction is reduced and the divergence angle in the vertical direction is increased.

By combining these actions, the mutual action on the virtual object point diameter is canceled, and a circular virtual object point can be obtained. The effect on the divergence angle of the electron beam is greater in the groove formed in the second electrode than in the groove formed in the first electrode. For this reason, the horizontal direction of the electron beam that has passed through the prefocus lens can have a divergence angle smaller than the conventional one while having the same virtual object diameter as the conventional one.

For this reason, the horizontal diameter of the electron beam incident on the main lens is reduced. Therefore, the area of use of the main lens is reduced, and a portion of the electron beam does not pass through the periphery of the main lens having a large spherical aberration as in the conventional case, and the influence of the spherical aberration can be greatly improved. Becomes Thereby, the beam spot of the electron beam reaching the phosphor screen can be made substantially circular.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a cathode ray tube according to the present invention will be described with reference to the drawings. FIG.
1 is a sectional view schematically showing a structure of an in-line type color cathode ray tube as an example of a cathode ray tube of the present invention.

This in-line type color cathode ray tube has an envelope in which a substantially rectangular panel 10 and a funnel-like funnel 11 are integrally joined. This panel 10
Is provided with a phosphor screen 12 composed of a dot-shaped three-color phosphor layer that emits blue, green, and red light, respectively, on its inner surface. In addition, a shadow mask 13 is provided inside the panel 10 so as to face the phosphor screen 12.

The in-line type color cathode ray tube has an in-line type electron gun assembly 17 and a deflection yoke 20. The in-line type electron gun structure 17 is disposed in the cylindrical neck 15 of the funnel 11. The electron gun assembly 17 applies three electron beams arranged in a line, consisting of a center beam 16G and a pair of side beams 16B and 16R, passing on the same horizontal plane, in the tube axis direction, that is, Z direction.
Discharges axially. The deflection yoke 20 is mounted outside the vicinity of the boundary between the large diameter portion 18 of the funnel 11 and the neck 15. The deflection yoke 20 is adapted to receive the three electron beams 16 emitted from the in-line type electron gun assembly 17.
An asymmetric magnetic field is generated which deflects (R, G, B) in the horizontal direction, ie, the H axis, and in the vertical direction, ie, the V axis. This non-uniform magnetic field is formed by a pincushion-type horizontal deflection magnetic field formed in the horizontal direction and a barrel-type vertical deflection magnetic field formed in the vertical direction.

The three electron beams 16 (R, G, B) emitted from the in-line type electron gun assembly 17 are focused on the center of the phosphor screen 12. The three electron beams 1
6 (R, G, B) is scanned in the horizontal and vertical directions while being self-converged on the phosphor screen 12 by the non-uniform magnetic field generated by the deflection yoke 20. Thereby, a color image is displayed.

FIG. 4 shows an in-line type QPF (Quadra Potential Foal) for emitting three electron beams applied to the in-line type color cathode ray tube shown in FIG.
FIG. 2 is a diagram schematically showing the structure of a cus) type double focus type electron gun assembly.

As shown in FIG. 4, this electron gun
Is composed of three cathodes K (B, R, G) arranged in a line in the horizontal direction, that is, the H-axis direction, and these cathodes K
And three heaters (not shown) for individually heating (B, R, G), and first to fourth heaters arranged along the Z-axis from the cathode K (B, R, G) to the phosphor screen sequentially. It has six grids G1 to G6. These first to sixth grids G1 to G6 are arranged adjacent to each other at a predetermined interval.

The third grid G3 has a first segment G3-1 and a second segment G3-2 which are sequentially arranged along the Z-axis direction. In addition, the fifth grid G5
Has first to third segments G5-1 to G5-3 sequentially arranged along the Z-axis direction.

First grid G1 and second grid G2
Is a plate-shaped electrode, and has on its plate surface three substantially circular electron beam passage holes arranged in a row in the horizontal direction corresponding to the three cathodes K (B, R, G), respectively. are doing.
The first segment G3-1 and the second segment G3-2 of the third grid G3 are cylindrical electrodes, and each of the three cathodes K (B, R,
It has three substantially circular electron beam passage holes arranged in a line in the horizontal direction corresponding to G). Fourth grid G4
Is a thick plate-shaped electrode having three substantially circular electron beam passage holes arranged in a row in the horizontal direction corresponding to three cathodes K (B, R, G) on the plate surface. are doing.

The first segment G5- of the fifth grid G5
The first and third segments G5-3 are cylindrical electrodes, each having three cathodes K on a surface facing an adjacent grid.
It has three substantially circular electron beam passage holes arranged in a row in the horizontal direction corresponding to (B, R, G). The second segment G5-2 of the fifth grid G5 is a thick plate-like electrode, and three cathodes K (B, R,
It has three substantially circular electron beam passage holes arranged in a line in the horizontal direction corresponding to G).

The sixth grid G6 is a cylindrical electrode, and has three cathodes K on its surface facing the adjacent grid.
It has three substantially circular electron beam passage holes arranged in a row in the horizontal direction corresponding to (B, R, G).

As shown in FIG. 5, the second grid G2 corresponds to the three electron beam passage holes G2b, G2r, and G2g on the surface of the third grid G3 facing the first segment G3-1. 3 with the horizontal direction as the major axis
It has a plurality of non-circular grooves 102B, 102R, 102G. That is, these three grooves 102 (B, R,
G) is formed such that the diameter in the horizontal direction, that is, the H-axis direction is larger than the diameter in the vertical direction, that is, the V-axis direction. In the example shown in FIG. 5, these three grooves 102
(B, R, G) are horizontally long grooves, each having a rectangular shape having a long side in the H-axis direction and a short side in the V-axis direction.

The first segment G3- of the third grid G3
Numeral 1 is formed on the surface facing the second grid G2 so as to correspond to the three electron beam passage holes G3b, G3r, and G3g, respectively, as shown in FIG.
It has three non-circular grooves 103B, 103R and 103G. That is, these three grooves 103 (B, R,
G) is formed such that the diameter in the horizontal direction, that is, the H-axis direction is larger than the diameter in the vertical direction, that is, the V-axis direction. In the example shown in FIG. 6, these three grooves 103
(B, R, G) are horizontally long grooves, each having a rectangular shape having a long side in the H-axis direction and a short side in the V-axis direction.

In this electron gun assembly 17, each cathode K
A voltage of about 150 V is applied to (B, R, G). The first grid G1 is grounded. The second grid is connected in a tube to a fourth grid G4, and a voltage of about 800 V is applied to these grids. Third
The first segment G3-1 of the grid G3 is connected in a tube to the second segment G5-2 of the fifth grid G5, and a voltage of about 6 KV is applied to these grids.

The second segment G3- of the third grid G3
2 is connected in the tube together with the first segment G5-1 and the third segment G5-3 of the fifth grid G5, and a voltage according to the deflection amount of the electron beam is applied. This voltage is a voltage obtained by using a voltage of about 6 KV applied to the second segment G5-2 of the fifth grid G5 as a reference voltage, and superimposing a parabolic voltage that increases with the deflection amount of the electron beam on this reference voltage. It is. That is, this voltage is
When the electron beam is deflected toward the center of the phosphor screen without being deflected, it is 6KV, which is the lowest when deflected toward the periphery of the phosphor screen, gradually increases when deflected toward the periphery of the phosphor screen, and becomes the highest when traveling toward the corner of the phosphor screen. This is a parabolic voltage that is as high as 6.5 KV.

A voltage of about 26 KV is applied to the sixth grid G6. By applying a predetermined voltage to each grid of the above-described in-line type electron gun assembly, the electron gun assembly 17 forms an electron beam generator, a prefocus lens unit, a sub lens unit, and a main lens unit. .

The electron beam generator includes a cathode, a first grid G1, and a second grid G2.
The electron beam generator emits the electron beam toward the phosphor screen and forms a virtual object point with respect to the main lens unit.

The prefocus lens section is constituted by a second grid G2 and a third grid G3. The prefocus lens unit preliminarily focuses the electron beam emitted from the electron beam generation unit.

The sub-lens section includes the third grid G3, the fourth
It is constituted by a grid G4 and a fifth grid G5. The sub lens unit further preliminarily focuses the electron beam preliminarily focused by the prefocus lens unit.

The main lens section is constituted by a fifth grid and a sixth grid G6. The main lens unit finally focuses the electron beam prefocused by the sub lens unit on the phosphor screen.

In the third grid G3, when there is no deflection, the first segment G3-1 and the second segment G3-1
A voltage of 6 KV is applied to 3-2, and no potential difference occurs between both segments. On the other hand, in the third grid G3, at the time of deflection, a voltage of 6 KV is applied to the first segment G3-1 while the second segment G3-
2 is applied with a voltage that changes in a parabolic manner according to the amount of deflection of the electron beam. For this reason, a potential difference occurs between the two segments, and a first quadrupole lens unit for compensating for the deflection aberration is formed between the prefocus lens unit and the sub lens unit. The first quadrupole lens unit is set such that negative astigmatism, that is, astigmatism in which the focusing power in the vertical direction is stronger than the focusing power in the horizontal direction.

In the fifth grid G5, when there is no deflection, the first to third segments G5-1 to G5-3.
And a voltage of 6 KV is applied to each segment, so that there is no potential difference between the segments. On the other hand, in the fifth grid G5, 6 KV is applied to the second segment G5-2 during deflection.
And the third and third segments G5
A voltage that changes in a parabolic manner according to the amount of deflection of the electron beam is applied to −1 and G5-3. For this reason, a potential difference occurs between the segments, and a second quadrupole lens unit for compensating for the deflection aberration is formed between the sub lens unit and the main lens unit. The second quadrupole lens unit is set so as to have positive astigmatism, that is, astigmatism in which the horizontal focusing power is stronger than the vertical focusing power.

That is, when deflecting the electron beam to the peripheral portion of the phosphor screen, the first quadrupole lens portion having negative astigmatism is caused by the potential difference between both segments of the third grid G3. The second quadrupole lens unit having the positive astigmatism is formed by the formed potential difference between the segments of the fifth grid G5. The first quadrupole lens unit formed at this time is set so as to always have an astigmatism action opposite to that of the second quadrupole lens unit.

Here, the effect of the oblong grooves provided on the opposing surfaces of the first segment G3-1 of the second grid G2 and the third grid G3 forming the prefocus lens portion will be described.

The second grid G2 is located on the converging side of the prefocus lens unit. For this reason, the virtual object 102 with respect to the prefocus lens part of the electron beam which passed through the electron beam passage hole G2 (b, r, g) of the 2nd grid G2 by the horizontally long groove 102 (B, R, G) of the 2nd grid G2. A point has a smaller horizontal diameter and a larger vertical diameter. That is, the virtual object point of the electron beam passing through the second grid G2 has an elliptical shape extending in the vertical direction. Also,
The electron beam that has passed through the second grid G2 has an increased divergence angle in the horizontal direction and a reduced divergence angle in the vertical direction.

On the other hand, the first segment G3-1 of the third grid G3 is located on the diverging side of the prefocus lens portion. For this reason, the oblong groove 103 of the third grid G3
Due to (B, R, G), the virtual object point of the electron beam that has passed through the electron beam passage holes G3 (b, r, g) of the third grid G3 with respect to the prefocus lens portion has an increased horizontal diameter, The vertical diameter shrinks. That is, the virtual object point of the electron beam passing through the third grid G3 has an elliptical shape extending in the horizontal direction. The divergence angle of the electron beam passing through the third grid G3 in the horizontal direction is reduced and the divergence angle in the vertical direction is increased.

By combining these actions, the mutual action on the virtual object point diameter is canceled, and a circular virtual object point can be obtained. In addition, the effect on the divergence angle of the electron beam is greater than that of the elongated groove 102 (B, R, G) formed in the second grid G2 than in the elongated groove 1 formed in the first segment G3-1 of the third grid G3.
03 (B, R, G) is larger.

That is, considering only the horizontal direction, the virtual object point diameter is reduced by the converging lens function formed by the horizontally long grooves 102 (B, R, G) of the second grid G2. Due to the divergent lens action formed by the oblong groove 103 (B, R, G) of one segment G3-1, the reduced virtual object point diameter on the focusing lens side is enlarged, and the original circular virtual object point Obtainable. On the other hand, the divergence angle of the electron beam is enlarged by the horizontally long grooves 102 (B, R, G) of the second grid G2, and is stronger by the horizontally long grooves 103 (B, R, G) of the first segment G3-1. Scaled down.

As a result, the horizontal direction of the electron beam that has passed through the prefocus lens portion has the same virtual object point diameter as the conventional one, and can have a smaller divergence angle than the conventional one.

When the electron beam is focused on the central portion of the phosphor screen without deflection, the first quadrupole lens unit and the second quadrupole lens unit are not formed as described above. Therefore, the electron beam that has passed through the prefocus lens unit as described above is preliminarily focused by the sub lens unit, and is finally focused on the phosphor screen by the main lens unit. As a result, the electron beam reaching the center of the phosphor screen becomes a substantially circular beam spot.

At the time of deflection for deflecting the electron beam to the periphery of the phosphor screen, first and second quadrupole lens portions whose lens strength changes according to the amount of deflection are formed. As described above, the first quadrupole lens unit has negative astigmatism, and the second quadrupole lens unit has positive astigmatism. At the same time, the second segment G3-
The potential difference between the second and fourth grids G4 increases, and the lens strength of the sub-lens portion increases. On the other hand, the fifth grid G
The potential difference between the third segment G5-3 of No. 5 and the sixth grid G6 decreases, and the lens strength of the main lens unit decreases.

FIG. 7 is a diagram for explaining the vertical and horizontal lens action applied to the electron beam deflected to the periphery of the phosphor screen in the electron gun structure of the present invention shown in FIG. It is.

That is, at the time of deflection, as shown in FIG. 7, the electron beam that has passed through the prefocus lens portion is
The light is focused on the phosphor screen 12 by the first quadrupole lens unit QL1, the sub lens unit SL, the second quadrupole lens unit QL2, the main lens unit ML, and the deflection aberration DY of the deflection yoke.

As shown in FIG. 7, in the vertical direction, that is, in the V-axis direction, the electron beam that has passed through the prefocus lens unit is focused by the first quadrupole lens unit QL1, and preliminarily focused by the sub lens unit SL. Second 4
Diverged by the polar lens unit QL2 and the main lens unit ML
And the light is focused by the deflection aberration and reaches the phosphor screen. In the horizontal direction, that is, in the H-axis direction, the electron beam that has passed through the prefocus lens unit is diverged by the first quadrupole lens unit QL1, and the sub lens unit SL
, And further pre-focused by the second quadrupole lens QL2, converged by the main lens unit ML, diverged by the deflection aberration, and reaches the phosphor screen.

FIG. 8 is a view for explaining the vertical and horizontal lens action applied to the electron beam deflected to the periphery of the phosphor screen in the conventional electron gun structure shown in FIG. is there.

As shown in FIG. 8, in the conventional electron gun assembly, since the horizontal divergence angle α1 of the electron beam passing through the prefocus lens portion is large, the horizontal diameter of the electron beam incident on the main lens portion ML is large. Is enlarged. For this reason, a part of the electron beam passes through the periphery of the main lens portion ML having large spherical aberration, and the beam spot of the electron beam reaching the phosphor screen 12 is distorted.

On the other hand, as shown in FIG. 7, in the electron gun structure of the present invention, the first segments G3-1 of the second grid G2 and the third grid G3 forming the prefocus lens portion are respectively formed. Non-circular grooves 102 (B, R, G) and 103 (B, R, G) having a major axis in the horizontal direction are provided on opposing surfaces. Therefore, as in the related art, the shape of the virtual object point with respect to the prefocus lens unit can be made substantially circular, and the divergence angle α2 of the electron beam passing through the prefocus lens unit in the horizontal direction can be reduced. Therefore, the horizontal diameter of the electron beam incident on the main lens unit ML is reduced. Therefore, the use area of the main lens portion ML is reduced, and a part of the electron beam does not pass through the peripheral portion of the main lens portion ML having a large spherical aberration unlike the related art, and the influence of the spherical aberration is greatly improved. It is possible to do. Thereby, the beam spot of the electron beam reaching the phosphor screen 12 can be made substantially circular.

As a result, as shown in FIG. 9, the electron beam arriving at the center, the horizontal axis end, the diagonal axis end, and the vertical axis end of the phosphor screen has little horizontal bleeding and is flattened. It has a small substantially circular beam spot shape.

It should be noted that the cathode ray tube of the present invention is not applied only to the double quadrupole type electron gun structure having the structure described with reference to FIG. Can also be applied.

FIG. 10 is a diagram schematically showing the structure of an electron gun assembly having another configuration applied to the cathode ray tube of the present invention. That is, as shown in FIG. 10, this electron gun structure has three cathodes K (B, R, G) and first to sixth grids G1 to G6, similarly to the electron gun structure shown in FIG. have. Fifth grid G5 of this electron gun structure
Is the first segment G5- arranged sequentially in the Z-axis direction.
4 and a second segment G5-5. The first segment G5-4 of the fifth grid G5 is connected in a tube to the first segment G3-1 of the third grid G3, and a reference voltage of about 6 KV is applied to these grids. The second segment G5-5 of the fifth grid G5 is connected in a tube to the second segment G3-2 of the third grid G3, which has a reference voltage of about 6 KV,
A voltage that changes in a parabolic manner according to the amount of deflection of the electron beam is superimposed.

When deflecting the electron beam, the first segment G3-1 and the second segment G3 of the third grid G3 are used.
A first quadrupole lens unit having negative astigmatism is formed between the first quadrupole lens unit and the second quadrupole lens unit. Further, a second quadrupole lens unit having positive astigmatism is formed between the first segment G5-4 and the second segment G5-5 of the fifth grid G5.

As described above, even if the fifth grid G5 is composed of the first and second segments G5-4 and G5-5,
By providing a non-circular groove having a major axis in the horizontal direction on each of the opposing surfaces of the first segment G3-1 of the second grid G2 and the third grid G3, corresponding to the three electron beam passage holes. The same effect as that of the above-described electron gun structure can be obtained.

Further, the cathode ray tube of the present invention is different from the electron gun assembly having the structure shown in FIG. 4 and the electron gun assembly having the structure shown in FIG. On the surface of G3-1 facing the second grid G2, horizontally long holes 113B, 113R, 113 as shown in FIG.
An electrode provided with G may be used. That is, the first segment G3-1 of the third grid G3 is equal to the second grid G2.
As shown in FIG. 11, three non-circular oblong holes 113B, 113 having both functions as an electron beam passage hole and three non-circular grooves having a major axis in the horizontal direction.
R, 113G. That is, these three horizontally elongated holes 113 (B, R, G) are formed such that the diameter in the horizontal direction, that is, the H-axis direction is larger than the diameter in the vertical direction, that is, the V-axis direction. In the example shown in FIG. 11, these three holes 113 (B, R, G) are horizontally long holes,
It is formed in a rectangular shape having a long side in the H-axis direction and a short side in the V-axis direction.

The first grid G3 having such a structure has the first
Even when the segment G3-1 is applied, the same effect as that of the above-described electron gun structure can be obtained. As described above, according to the cathode ray tube of the present invention, when the electron beam is deflected to the peripheral portion of the phosphor screen, the first quadrupole lens portion is formed between the prefocus lens portion and the sub lens portion. Then, a second quadrupole lens unit having astigmatism always opposite to the first quadrupole lens unit is formed between the sub lens unit and the main lens unit. Also, a second grid G2 as a first electrode constituting the prefocus lens unit
Is located around the electron beam passage hole G2 (b, r, g) provided on the surface of the third grid G3 as the second electrode facing the first segment G3-1, and has a non-linear axis extending in the horizontal direction. It has a circular groove 102 (B, R, G). further,
The first segment G3-1 of the third grid G3 is formed by an electron beam passage hole G3 provided on the surface facing the second grid G2.
A non-circular groove 103 (B, R, G) having a long axis in the horizontal direction is provided around (b, r, g).

By adopting such a configuration, there is very little horizontal collapse even when the electron beam is not deflected at the center of the phosphor screen and when the electron beam is deflected to the periphery of the phosphor screen by the deflecting device. An electron beam spot can be provided. This allows
The electron beam focus characteristics can be kept good over the entire phosphor screen, and the elliptic distortion of the electron beam spot can be suppressed over the entire phosphor screen, so that the image quality can be improved over the entire screen.

[0070]

As described above, according to the present invention, an electron beam generator for generating an electron beam and at least two opposed arrangements for prefocusing the electron beam generated from the electron beam generator are provided. A pre-focus lens unit having first and second electrodes, a sub-lens unit for further pre-focusing the electron beam pre-focused by the pre-focus lens unit, and an electron beam pre-focused by the sub-lens unit. An electron gun assembly having a main lens portion that is focused on the center of the phosphor screen, and an electron beam focused on the phosphor screen by the electron gun assembly is orthogonal to the traveling direction of the electron beam. And a deflection yoke that generates a deflection magnetic field that deflects in the vertical and horizontal directions. The first electrode has a non-circular groove having a long axis in the horizontal direction around an electron beam passage hole provided on a surface facing the second electrode, and the second electrode has A non-circular groove having a major axis in the horizontal direction is provided around an electron beam passage hole provided on a surface facing the first electrode. Forming a first multipole lens between the sub-lenses and forming a second multipole lens between the sub-lens and the main lens, which has astigmatism always opposite to that of the first multipole lens. A cathode ray tube characterized by comprising means for performing the above.

According to this cathode ray tube, it is possible to maintain good electron beam focusing characteristics over the entire phosphor screen and to suppress elliptic distortion of the electron beam spot over the entire phosphor screen.

[Brief description of the drawings]

FIGS. 1A to 1C are diagrams schematically showing an electron beam spot in a first quadrant on a phosphor screen using a conventional electron gun assembly.

FIG. 2 is a horizontal sectional view schematically showing a structure of a conventional electron gun assembly.

FIG. 3 is a horizontal sectional view schematically showing a structure of an in-line type color cathode ray tube as an example of the cathode ray tube of the present invention.

FIG. 4 is a horizontal sectional view schematically showing the structure of an in-line type electron gun assembly applied to the cathode ray tube shown in FIG.

FIG. 5 is a perspective view schematically showing a structure of a second grid of the electron gun assembly shown in FIG. 4;

FIG. 6 is a perspective view schematically showing a structure of a first segment of a third grid of the electron gun structure shown in FIG. 4;

FIG. 7 is a view for explaining the vertical and horizontal lens action applied to the electron beam deflected to the periphery of the phosphor screen in the electron gun structure of the present invention shown in FIG. 4; FIG.

FIG. 8 is a view for explaining vertical and horizontal lens action applied to an electron beam deflected to a peripheral portion of a phosphor screen in the conventional electron gun structure shown in FIG. 2; It is.

FIG. 9 is a diagram schematically showing an electron beam spot in a first quadrant on a phosphor screen by the electron gun assembly of the present invention.

FIG. 10 is a horizontal sectional view schematically showing the structure of another in-line type electron gun assembly applied to the cathode ray tube shown in FIG.

FIG. 11 is a perspective view schematically showing another structure of the first segment of the third grid of the electron gun structure shown in FIGS. 4 and 10;

[Explanation of symbols]

 Reference Signs List 10 panel 11 funnel 12 phosphor screen 13 shadow mask 15 neck 16 (R, G, B) electron beam 17 electron gun assembly 20 deflection yoke K (R, G, B) cathode G1 First grid G2 Second grid G3 Third grid G3-1 First segment G3-2 Second segment G4 Fourth grid G5 Fifth grid G5-1 First segment G5-2 Second Segment G5-3: Third segment G6: Sixth grid 102 (R, G, B): Horizontal elongated groove 103 (R, G, B): Horizontal elongated groove

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tsutomu Takekawa 7-1 Nisshin-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term (reference) in Toshiba Electronic Engineering Corporation 5C041 AA02 AA14 AB05 AB07 AC05 AC07 AC19 AC35 AD02 AE01

Claims (2)

[Claims] 1. A prefocus lens comprising: an electron beam generator for generating an electron beam; and at least two opposed first and second electrodes for prefocusing an electron beam generated from the electron beam generator. A sub-lens section for further pre-focusing the electron beam preliminarily focused by the pre-focus lens section, and a main lens for finally converging the electron beam pre-focused by the sub lens section to the center on the phosphor screen. An electron gun assembly having a lens unit; and a deflection magnetic field for deflecting the electron beam focused on the phosphor screen by the electron gun assembly in vertical and horizontal directions orthogonal to the traveling direction of the electron beam. A deflection yoke that is generated, wherein the first electrode of the prefocus lens faces the second electrode. A non-circular groove having a long axis in the horizontal direction around an electron beam passage hole provided in the first electrode, wherein the second electrode is provided with an electron beam passage provided on a surface facing the first electrode. A non-circular groove having a long axis in the horizontal direction is provided around the hole, and a first multipole lens is formed between the prefocus lens and the sub lens with the deflection of the electron beam. And a means for forming a second multipole lens having an astigmatism effect always opposite to that of the first multipole lens between the sub lens and the main lens. 2. A prefocus lens comprising: an electron beam generator for generating an electron beam; and at least two opposed first and second electrodes for pre-focusing the electron beam generated from the electron beam generator. A sub-lens section for further pre-focusing the electron beam preliminarily focused by the pre-focus lens section, and a main lens for finally converging the electron beam pre-focused by the sub lens section to the center on the phosphor screen. An electron gun assembly having a lens unit; and a deflection magnetic field for deflecting the electron beam focused on the phosphor screen by the electron gun assembly in vertical and horizontal directions orthogonal to the traveling direction of the electron beam. A deflection yoke that is generated, wherein the first electrode of the prefocus lens faces the second electrode. A non-circular groove having a major axis in the horizontal direction around the electron beam passage hole provided in the second electrode, and the second electrode has a major axis in the horizontal direction on a surface facing the first electrode. A first multipole lens is formed between the prefocus lens and the sub-lens as the electron beam is deflected, and the sub-lens and the main lens are formed. A cathode ray tube comprising means for forming a second multipole lens having an astigmatism effect always opposite to that of the first multipole lens between lenses.