JPH0554821A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To extremely reduce the size of a beam spot on a target. CONSTITUTION:A cathode-ray tube is provided with an electron gun 24 having both an electron-beam forming portion having at least a cathode and a first and a second filament, and a main lens portion, and an electron beam 25 emitted from the electron gun is made to scan a target 23 by the deflecting action of a deflecting device 26. An electron-beam through-hole comprising a circular or noncircular main hole and an auxiliary hole located near or connected via a small-diameter portion to the main hole is formed in the first grid.

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 a cathode ray tube which has a good resolution by reducing a beam spot on a target.

[0002]

2. Description of the Related Art Generally, a cathode ray tube displays an image by deflecting an electron beam emitted from an electron gun by horizontal and vertical deflection magnetic fields generated by a deflection yoke and horizontally and vertically scanning a phosphor screen. Is formed into a structure.

With respect to the most typical color picture tube today, a phosphor screen composed of phosphor layers of three colors emitting blue, green and red is formed on the inner surface of the panel of the envelope, and faces the phosphor screen. Then, a shadow mask is arranged inside the electron gun, and the electron gun is used as an electron gun for emitting three electron beams. The three electron beams emitted from this electron gun horizontally and vertically scan the phosphor screen through the shadow mask. By doing so, the structure is such that a color image is displayed.

Particularly in such a color picture tube, the phosphor screen is composed of a striped three-color phosphor layer which is elongated in the vertical direction, and the electron gun emits three electron beams arranged in a row passing through the same horizontal plane. A self-convergence in-line type color picture tube that self-focuses the three electron beams by deflecting the electron beam emitted from the electron gun by a pincushion type horizontal deflection magnetic field and a barrel type vertical deflection magnetic field is widely used. It is used.

In addition to such color cathode ray tubes, there are various cathode ray tubes such as a color cathode ray tube which displays a color image by switching a single electron beam, a mokukuro cathode ray tube, a projection tube and an oscilloscope tube.

In order to improve the resolution of these cathode ray tubes, it is basically necessary to improve the performance of the electron gun and reduce the beam spot on the phosphor screen.

That is, an example of the color picture tube electron gun shown in FIG. 17 will be described. The electron gun is composed of a cathode K and first to fourth grids arranged in the direction of the phosphor screen 1 so as to be sequentially adjacent to the cathode K. It has a plurality of electrodes G1 to G4. In this electron gun, the first and second grids G1 and G2 are made of plate electrodes and provided with relatively small electron beam passage holes. The third grid G3 is a cup-shaped electrode, the fourth grid G4 is a cylindrical electrode, and a relatively large electron beam passage hole is provided on the second grid G2 side of the third grid G3. 3rd grid G3 4th grid G4 side and 4th grid
G4 has a larger electron beam passage hole.

In this electron gun, the cathode K and the first to third grids G1 to G3 control the electron emission from the cathode K and focus the emitted electrons to form an electron beam forming unit. A GEA is formed, and the electron beam forming unit GEA is formed by the third and fourth grids G3 and G4.
A main lens portion MLA that accelerates and focuses the electron beam emitted from the phosphor screen 1 is formed. That is, an electron lens is formed by applying a predetermined potential to each of the electrodes, and the electrons emitted from the cathode K are
The crossover CO is formed by the cathode lens KL formed on the front surface of the cathode K by the first and second grids G1 and G2, and slightly focused by the prefocus lens PL formed by the second and third grids G2 and G3. Then, a virtual crossover VCO is formed and is incident on the third grid G3. The electron beam incident on the third grid G3 is then focused on the phosphor screen 1 by the main lens portion MLA formed by the third and fourth grids G3 and G4.

Therefore, the resolution of the cathode ray tube can be improved by making the beam spot on the phosphor screen 1 as small as possible.

However, in such an electron gun, the electrons emitted from the cathode K are emitted from the first and second grids G1,
By the cathode lens KL formed by G2, the off-axis beam 3b is more strongly focused than the paraxial beam 3a, and the crossover CO already has aberration. Further, since the aberration is added by the prefocus lens PL and the main lens unit MLA, even if the electron beam is properly focused on the phosphor screen 1, the beam spot SP on the phosphor screen 1 is the paraxial beam 3a. Is unfocused, the off-axis beam 3b is overfocused, and it is difficult to reduce the beam spot SP.

In order to solve this problem, various electron guns are known which reduce aberrations by forming an Astig lens such as a quadrupole lens or an elliptical lens in the electron lens portion. However, when these Astig lenses are used, aberrations in one direction, for example, in the horizontal direction can be reduced, but in the vertical direction, the aberrations increase or the magnification of the electron lens deteriorates. In particular, the aberration at the crossover becomes considerably large.

FIG. 18 is a diagram showing a state of an electron beam forming unit by three-dimensional computer simulation in order to explain the aberration at the crossover. In this figure, for easy understanding, a vertical section (YZ section) is shown on the upper side and a horizontal section (XZ section) is shown on the lower side with the central axis (Z axis) of the electron gun as a boundary. It was This figure shows the first and second grids G made of plate electrodes as shown in FIG.
Each of the electron beam passage holes on the side of the second grid G2 of the first, G2 and the third grid G3 has a circular shape, the potential of the cathode K is 0 to 200V, the potential of the first grid G1 is 0V, the second.
This is a state in which the potential of the grid G2 is set to about 1 kV and the potential of the third grid G3 is set to about 8 kV. In addition, 4 is an equipotential line and 5 is a trajectory of an electron beam.

As shown in (b), the high potential of the second grid G2 permeates to the cathode K side through the electron beam passage holes of the first grid G1 and draws out electrons from the cathode K.
Of the electron beams extracted from the cathode K, the paraxial beam 3a intersects on the central axis far from the cathode K, but the off-axis beam 3b is due to the aberration of the electron lens.
They intersect on the central axis closer to the cathode K than that. Therefore, the crossover diameter becomes large and the off-axis beam 3b
Is more strongly focused than the paraxial beam 3a. Such an aberration in the electron beam forming unit directly becomes a large factor for thickening the beam spot on the phosphor screen. Note that θ1Hmax and θ1Vmax shown in FIG.
Are the maximum divergence angle in the horizontal direction (X-axis direction) and the maximum divergence angle in the vertical direction (Y-axis direction) of the electron beam, respectively.

When such an electron beam is deflected to the peripheral portion of the phosphor screen by the deflecting action of the deflecting device, it is subject to the deflection aberration of the deflecting device and the beam spot on the phosphor screen is significantly distorted. As shown in FIG. 19A, for example, in a self-convergence in-line type color picture tube in which the horizontal deflection magnetic field 6 is a pincushion type, the electron beam 2 deflected to the peripheral portion in the horizontal direction.
Becomes significantly over-focused in the vertical direction, and the beam spot on the phosphor screen causes a large halo portion 8 (bleeding) in the vertical direction as shown in FIG.

As a countermeasure against this, Japanese Patent Laid-Open No. 54-85667.
The publication discloses means for forming a quadrupole lens between the cathode and the second grid.

In this case, as shown in FIG. 20, assuming that the cathode K side of the first grid G1 is a horizontally long hole and the second grid G2 side is a vertically long hole, the maximum divergence angle θ2H in the horizontal direction is shown.
Compared with max, the maximum vertical divergence angle θ2vmax decreases (θ2Hmax> θ2vmax), but paraxial beam 3a and off-axis beam
The difference in the focusing power from 3b becomes large, and the aberration in the vertical direction becomes rather large. This means that the extension of the electron beam incident on the third grid G3 to the cathode K side is the central axis (Z
It can be easily understood from the point Lvc intersecting the axis).

FIG. 21 is a diagram showing the relationship between the horizontal axis indicating the radial distance r from the center of the electron emission surface of the cathode and the vertical axis indicating the point Lvc. The curve CH shows the characteristics of the electron beam in the horizontal direction, and the curve CV shows the characteristics of the electron beam in the vertical direction. If it is a straight horizontal line like the line 9b shown in FIG.
As shown by 10, 11, and 12, one point O (O1, O
2, O3) means that the electron beam is emitted (aberration free), and if the line is a line rising to the right like line 9a, it means having positive aberration as shown in FIG. 22 (a). Then line 9c
If the line is a line descending to the right, it means that it has a negative aberration as shown in FIG. Therefore, from this, in the electron gun in which the quadrupole lens is formed between the cathode and the second grid as described above, the aberration in the vertical direction becomes considerably large as can be seen from the curve CV. Therefore, in such an electron gun, although the deflection aberration of the electron beam deflected to the peripheral portion of the phosphor screen can be reduced, the vertical diameter of the beam spot in the central portion of the phosphor screen becomes large and the resolution deteriorates. To do.

In Japanese Patent Laid-Open No. 55-124933 and Japanese Patent Laid-Open No. 56-91360, the structure of the electron beam passage hole is shown in FIG. 23 as an in-line type color picture tube electron gun. It is shown that three electron beam passage holes 14 arranged in a row are connected to the electrodes forming the main lens portion. However, the electron beam passage hole 14 is intended to increase the diameter of the cylindrical lens forming the main lens portion, and does not adjust the lens action for the off-axis beam and the lens action for the paraxial beam.

Further, in Japanese Utility Model Laid-Open No. 55-52764, in order to improve the resolution of a color picture tube, FIG.
As shown in, the electron beam passage hole 15 of at least one of the first and second grids of the electron gun is formed into a circular hole and a rectangular hole long in the longitudinal direction of the stripe-shaped three-color phosphor layer forming the phosphor screen. The shape in which and are overlapped is shown. Furthermore, in Japanese Utility Model Publication No. 59-41966,
In order to improve the beam spot shape of the beam index type color picture tube, as shown in FIG. 25, the electron beam passage hole 16 of the first grid is formed into a shape provided with notches 17 in the four corners of a rectangular hole. Things are shown.

[0020]

As described above, in order to improve the resolution of the cathode ray tube, it is basically necessary to improve the performance of the electron gun and reduce the beam spot on the phosphor screen. is necessary. However, in the conventional electron gun, the decentered beam is more strongly focused than the paraxial beam due to the cathode lens formed by the first and second grids, and there is already aberration at the crossover. Since aberration is added in the main lens portion, it is difficult to reduce the beam spot on the phosphor screen even if the electron beam is properly focused on the phosphor screen. In order to solve this, there is known a means for reducing aberration by forming an astigmatic lens such as a quadrupole lens or an elliptical lens in the electronic lens part. However, when such an astigmatic lens is used, one direction, for example, Even though the horizontal aberration can be reduced, in the vertical direction,
Aberration increases or the magnification of the electron lens deteriorates. In particular, the aberration at the crossover becomes considerably large, and the beam spot on the phosphor screen cannot be reduced.

The present invention has been made to solve the above-mentioned problems, and a target (phosphor screen)
The purpose is to reduce the upper beam spot and to construct a cathode ray tube with excellent resolution.

[0022]

An electron beam forming unit having at least a cathode, first and second grids, for controlling electron emission from the cathode and focusing the emitted electrons to form an electron beam. In a cathode ray tube equipped with an electron gun having a main lens for focusing the electron beam on a target, a circular or non-circular main hole is provided in the first grid, and a proximity or small diameter portion is provided around the main hole. An electron beam passage hole composed of an auxiliary hole connected through the hole was formed.

[0023]

As described above, an electron beam passage hole is formed in the first grid, the main hole having a circular or non-circular shape, and the auxiliary hole that is connected to the periphery of the main hole through a proximity or a small diameter portion. Then, the potential penetrating to the cathode side through the electron beam passage holes of the first grid can be greatly relaxed, and the focusing power of the cathode lens for the off-axis beam is weakened to be equal to or opposite to the focusing force for the paraxial beam. It can be weaker than the focusing force on the axial beam. Therefore, by forming the auxiliary holes in the predetermined direction with respect to the main holes of the first grid, the aberration at the crossover in the predetermined direction can be eliminated or the reverse aberration can be provided. The beam spot on the target can be made extremely small even if the aberrations of are added.

[0024]

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

FIG. 1 shows a monochrome picture tube which is an embodiment of the present invention. This monochrome picture tube has a face plate 20
And the cone portion 21 welded to this face plate 20
Further, it has an envelope including a neck 22 welded to the cone portion 21, a phosphor screen 23 is formed on the inner surface of the face plate 20, and an electron gun 24 is arranged in the neck 22. Then, the electron beam 25 emitted from the electron gun 24 is deflected by a magnetic field generated by a deflection yoke 26 mounted on the outside of the envelope, and the phosphor screen 23 is horizontally and vertically scanned to obtain a black and white image. It is formed in a structure for displaying an image.

As shown in FIG. 2, the electron gun 24 has one cathode K, a heater (not shown) for heating the cathode K, and the cathode K, which are sequentially adjacent to each other and are arranged in the direction of the phosphor screen 23. 1st to 4th grids G1 to G4
And they are integrally fixed by a pair of insulating supports (not shown).

The first grid G1 is composed of a plate-shaped electrode, and in a portion facing the cathode K, as shown in FIG. 3 (a), a circular main hole 28M and a main hole 28M close to the main hole 28M. And an electron beam passage hole 29 in which two circular auxiliary holes 28S are formed vertically (vertically). The auxiliary hole 28S is smaller than the main hole 28M and is provided at a minute distance d from the main hole 28M. The electron beam passage hole 29 can be easily formed by press working or etching.

The second grid G2 is also composed of a plate-like electrode, and the second grid G2 has a circle of approximately the same size as the main hole of the first grid, as shown in FIG. 3 (b). A shaped electron beam passage hole 30 is provided. Further, the third grid G3 is composed of a cup-shaped electrode, and the second grid G2 is provided on the second grid G2 side as shown in FIG. 3 (c).
A circular electron beam passage hole 31 that is slightly larger than the electron beam passage hole 30 of FIG.
As shown in (d), a larger circular electron beam passage hole 32 is provided. Furthermore, the fourth grid G4
Consists of cylindrical electrodes, and these electrodes are shown in FIG.
As shown in, a circular electron beam passage hole 33 having the same size as the electron beam passage hole on the fourth grid G4 side of the third grid G3 is provided.

Specifically, each electrode of the electron gun 24 is set as follows.

Diameter of the main hole 28M of the first grid G1: 0.54 mm Diameter of the auxiliary hole 28S of the first grid G1: 0.20 mm Distance between the main hole 28M and the auxiliary hole 28S d: 0.1 mm Second grid G2 Diameter of electron beam passage hole 30: 0.54
mm Diameter of the electron beam passage hole on the second grid G2 side of the third grid G3: 1.3 mm Electron beam passage hole on the fourth grid G4 side of the third grid G3
Diameter of 31: 4.52 mm Diameter of electron beam passage hole of fourth grid G4: 4.52 mm Thickness of first grid G1: 0.10 mm Thickness of second grid G2: 0.20 mm Cathode K and first grid Distance from G1: 0.10 mm Distance between first grid G1 and second grid G2: 0.20 mm Distance between second grid G2 and third grid G3: 1.0 mm Third grid G3 and fourth grid G4 Distance: 1.0mm This electron gun 24 has 0-200V at cathode K during operation.
The voltage of the video signal superimposed on the voltage of 0, 0 to the first grid G1
V, a voltage of 500 to 1000 V is applied to the second grid G2, a voltage of 5 to 10 kV is applied to the third grid G3, and a voltage of 25 to 32 kV is applied to the fourth grid G4.

By applying these voltages, in the electron gun 24, the electron beam forming part GEA is formed by the cathode K and the first to third grids G1 to G3.
The main lenses MLA are formed by the grids G3 and G4, and the electrons emitted from the cathode K form a crossover by the cathode lenses formed on the first and second grids G1 and G2, and the second and third grids are formed. The main lens MLA formed by the third and fourth grids G3, G4 after being slightly converged by the prefocus lens formed by G2, G3 and entering the third grid G3 while diverging.
Are focused on the phosphor screen 23 by.

In this case, the second beam in the electron beam forming unit GEA
The potential from the grid G2 permeates to the cathode K side through the electron beam passage hole 29 of the first grid G1 and, as shown in the upper half of FIG. The potential penetrating to the side raises the potential penetrating through the main pores. Therefore, the off-axis beam 34b is a paraxial beam.
Similar to 34a, it intersects on the central axis far away from the cathode K, and the diameter of the crossover CO becomes smaller. At the same time, the vertical maximum divergence angle θ3Vmax decreases. As a result, the point LVC at which the extension of the electron beam 25 incident on the third grid G3 toward the cathode K side intersects the central axis becomes as shown by the curve CV in FIG. That is, as compared with the conventional electron gun shown in FIG. 21, the inclination of the curve CV becomes gentle, and the aberration in the vertical direction at the crossover CO can be remarkably reduced.

On the other hand, in the horizontal direction, the first grid
The potential from the second grid G2 penetrating to the cathode K side through the electron beam passage hole 29 of G1 is almost unaffected by the auxiliary hole, and as shown in the lower half of FIG. The maximum divergence angle θ3Hmax in the direction is almost the same as in the case of the conventional electron gun (see FIG. 20), and the curve CH regarding the point LVC shown in FIG. 5 is almost the same as that of the conventional electron gun, and about the same. With aberration.

Therefore, when focusing such an electron beam 25 on the phosphor screen 23 by the main lens MLA, if the horizontal direction is properly focused, the focusing conditions are different between the horizontal direction and the vertical direction. , In the vertical direction, it is in an unfocused state. However, since there is no aberration in the vertical direction as described above, the vertical diameter of the beam spot on the phosphor screen 23 should be approximately the same as the horizontal diameter of the properly focused beam spot. You can

Further, even if such an electron beam 25 is deflected by the pincushion type horizontal deflection magnetic field shown in FIG. 19, it is in an unfocused state in the vertical direction. Therefore, as shown in FIG. By canceling the overfocusing, a good beam spot SP can be obtained even in the peripheral portion of the phosphor screen. Therefore, the resolution of the cathode ray tube can be improved without deteriorating the vertical diameter of the beam spot in the peripheral portion of the phosphor screen as in the electron gun disclosed in Japanese Patent Laid-Open No. 54-85667. it can.

In the electron gun disclosed in Japanese Patent Laid-Open No. 54-85667, the maximum divergence angle .theta.2Hma of the electron beam in the horizontal direction.
x is the maximum horizontal divergence angle θ1Hma of a conventional electron gun in which a quadrupole lens is not formed between the cathode and the second grid.
It becomes larger than x (θ2Hmax> θ1Hmax), while the electron gun 24 of this example has almost the same value.

The degree to which the vertical aberration in the crossover CO is reduced is determined by the size of the main hole 28M, the size of the auxiliary hole 28S, the distance d between the main hole 28M and the auxiliary hole 28S,
Distance between first grid G1 and second grid G2, cathode K
And the first grid G1 and the like. In particular, if the distance d between the main hole 28M and the auxiliary hole 28S becomes too wide, the effect of raising the potential that permeates through the auxiliary hole 28S with respect to the potential that permeates the cathode K through the main hole 28M weakens, and the desired effect is obtained. May not be obtained.

Furthermore, what is important in the electron gun 24 of this example is that the electric potential formed between the cathode K and the first grid G1 is manipulated. That is, since the electron emission surface of the cathode K spreads close to the electron beam passage hole 29 of the first grid G1, the electric potential of the electron emission surface of the cathode K passes through the electron beam passage hole 29 of the first grid G1. In response to the penetrating potential, the lens action on the off-axis beam 34b can be easily adjusted. Furthermore, the lens action on the off-axis beam 34b is weakened more than the lens action on the paraxial beam 34a, and the aberration in the opposite direction is reduced. (Negative aberration) can be produced.

If the hole diameter of the auxiliary hole 28S is further increased or the distance d between the main hole 28M and the auxiliary hole 28S is increased, the cathode K side is passed through the electron beam passage hole 29 of the first grid G1. The electric potential of the second grid G2 penetrating into the space becomes as shown in FIG.
The point LVC at which the extension of the electron beam 25 incident on the grid G3 toward the cathode K side intersects the central axis is the curve C shown in FIG.
As shown in v, the electron beam can be made to have a negative aberration at the crossover. By injecting such an electron beam into the main lens, the positive aberration of the main lens is canceled and the phosphor is It is possible to obtain an effect that a beam spot with few aberration components can be formed on the screen.

In the above-mentioned embodiment, the main lens portion is the third lens.
The cylindrical lens formed by the fourth grid has been described, but the main lens portion may be a compound type main lens disclosed in, for example, Japanese Patent Laid-Open No. 54-89472, and other asymmetrical lenses. It may be a lens.

In the above embodiment, the electron beam passage hole of the first grid is composed of the circular main hole and the circular auxiliary hole. However, at least the main hole and the auxiliary hole of the first grid are formed. One of them may be a non-circular hole, for example, an elliptical main hole 28M and a circular auxiliary hole 28S, as shown in FIG.

Further, in the above-described embodiment, the auxiliary hole is provided in the direction perpendicular to the main hole. However, as shown in FIGS. 9 (a) to 9 (e), the main hole 28M is a circular or non-circular hole. (The shape is elliptical in the drawing), and the auxiliary hole 28S may be provided in the horizontal direction (left and right) and the oblique direction with respect to the main hole 28M. That is, even if the auxiliary hole is provided in the vertical direction with respect to the main hole as in the above-described example, the aberration in the crossover CO is reduced to some extent not only in the vertical direction but also in the oblique direction. By installing it diagonally, crossover CO
The aberration at can be reduced.

Furthermore, in the above-mentioned embodiment, the auxiliary hole is provided at a minute distance d from the main hole. However, as shown in FIG. 10, this auxiliary hole 28S has a main hole 28M and a small diameter portion 32. You may connect through.

Next, another embodiment will be described.

FIG. 11 shows an electron gun having the same electrode arrangement as that of the electron gun disclosed in Japanese Patent Laid-Open No. 2-202641.
The cathode K, a heater (not shown) for heating the cathode K, and first to sixth grids G1 to G6 arranged in the phosphor screen direction are sequentially arranged adjacent to the cathode K, and they are a pair of insulating supports. The body 38 is integrally fixed.

The first grid G1 is composed of a plate-shaped electrode, and has an elliptical main hole 28M shown in FIG. 8 at a portion facing the cathode K, and is located vertically above and below the main hole 28M. An electron beam passage hole composed of individual circular auxiliary holes 28S is provided. The second grid G2 is also composed of a plate-like electrode, and the second grid G2 has an elliptical electron of approximately the same size as the main hole of the first grid, as shown in FIG. 12 (a). A beam passage hole 40 is provided. Furthermore, the third
The fifth to fifth grids G3 to G5 are cylindrical electrodes, the sixth grid G6 is a cup-shaped electrode, and the third grid G3 has a second grid G2 side as shown in (b). A circular electron beam passage hole 41 is provided. The fourth grid G4 side of the third grid G3, the fourth grid G4
3rd grid G3 side, 4th grid G4 5th grid G5
On the side, on the side of the fourth grid G4 of the fifth grid G5 and on the side of the fifth grid G5 of the sixth grid G6, as shown in (c), a lateral (horizontal) long electron beam passage hole 42 is provided. There is. Further, on the sixth grid G6 side of the fifth grid G5, as shown in FIG.
43 is provided.

In this electron gun, the cathode K has a value of 0-200.
A voltage obtained by superimposing a video signal on a voltage of V, 0 V for the first grid G1, 500-1000 V for the second grid G2, 5-10 kV for the third grid G3, 0-5 kV for the fourth grid G4, and the fifth.
15-25kV on grid G5, 25-3 on 6th grid G6
A voltage of 0 kV is applied.

By applying these voltages, this electron gun
The cathode K and the first to third grids G1 to G3 form an electron beam forming portion GEA, and the third and sixth grids G3 and G6 form a main lens portion MLA.
As shown in (b) and (c) in comparison with the electrode configuration of (a), the electrons emitted from the cathode K are crossed over by the cathode lenses formed in the first and second grids G1 and G2. Forming CO, 2nd and 3rd grid
The light is slightly converged by the prefocus lens PL formed by G2 and G3 and enters the third grid G3 while diverging. Then in the horizontal direction, 5th and 6th grids
The quadrupole lens QL formed by G5 and G6 is focused on the phosphor screen 23 by the focusing action, so that a beam spot sp with a small aberration component is obtained.

On the other hand, in the vertical direction, the quadrupole lens QL is focused by the electron lens VL formed by the third and fourth grids G3 and G4, and is further formed by the fifth and sixth grids G5 and G6. Is focused on the phosphor screen 23 by being diverged. Therefore, as the electron lens VL acting only in the vertical direction is formed in the main lens portion MLA in the vertical direction, the aberration increases compared to the horizontal direction. However, in the vertical direction, the main hole 28 is formed in the first grid G1.
Since the electron beam passage holes 29 in which the auxiliary holes 28S are located above and below M are provided, the aberration of the electron beam formed in the electron beam forming unit GEA is extremely small and the divergence angle of the electron beam is also small. Also in the vertical direction, the beam spot sp on the phosphor screen 23 can be reduced.

In the electron gun of this example, the main holes of the first grid and the electron beam passage holes of the second grid are each elliptical, but as shown in FIG.
Even with a circular shape, the effect can be expected sufficiently.

The electron gun shown in FIG. 14 corresponds to Japanese Patent Application No. 1-25.
This is an in-line type color picture tube electron gun having the same electrode arrangement as the electron guns shown in Japanese Patent Application No. 7091 and Japanese Patent Application No. 1-275953. This electron gun consists of three cathodes KB, KG, KR arranged in a line in the horizontal direction, and their respective cathodes KB,
Three heaters H (not shown) for separately heating KG and KR,
Phosphor screens adjacent to the cathodes KB, KG, KR sequentially
1st to 10th grids G1 having a one-piece structure arranged in 23 directions
G10, which are fixed together by a pair of insulating supports (not shown).

The first grid G1 is composed of a plate-shaped electrode, and in the portion facing the cathodes KB, KG, KR, as shown in FIG. 15, a circular main hole 28M and a main hole 28M close to the main hole 28M. And three electron beam passage holes 29, each of which is composed of an auxiliary hole 28S which is located above and below, are provided. The second grid G2 also consists of plate-shaped electrodes, and there are three cathodes in this second grid G2.
Corresponding KB, KG, and KR are provided with circular electron beam passage holes of approximately the same size as the main holes 28M of the first grid G1. Further, the third grid G3 has a butt structure of two cup-shaped electrodes, and the second grid G2 has an electron beam of the second grid G2 corresponding to the three cathodes KB, KG, and KR. Three circular electron beam passage holes, which are larger than the passage holes, are formed. And the cathodes KB, KG,
The part from KR to this third grid G3 is the cathode KB,
An electron beam forming unit GEA is formed which controls and focuses electron emission from KG and KR to form a three electron beam.

The fourth grid G4 has a butt structure of two cup-shaped electrodes, and the fifth grid G5 has a butt structure of four cup-shaped electrodes. The fourth grid G4 of the third grid G3. Side, 4th grid G4 and 5th grid
Three cathodes KB, KG, KR on the fourth grid G4 side of G5
Corresponding to the above, three circular electron beam passage holes having substantially the same size as the electron beam passage holes on the second grid G2 side of the third grid G3 are formed. Further, the sixth to eighth grids G6 to G8 have a butted structure of two cup-shaped electrodes, and the ninth grid G9 has a butted structure of three cup-shaped electrodes, and particularly the tip of the ninth grid G9. The cup-shaped electrode 45 on the side of the portion is composed of a cup-shaped electrode having a larger diameter than the other two cup-shaped electrodes. Then, the 6th grid G6 side of the 5th grid G5, the 6th grid G6, the 7th grid G7, the 8th grid G8 and the 8th grid G8 side of the 9th grid G9 are common to the three elongated electron beams in the horizontal direction. , One horizontally elongated electron beam passage hole is formed. Also, especially the ninth
Inside the large-diameter cup electrode 46 forming the tip of the grid G9, three non-circular electron beam passage holes are formed in a line in the horizontal direction corresponding to the three cathodes KB, KG, KR. Has been done. Furthermore, the 10th grid G10 is the 9th grid G9
It is composed of a cylindrical electrode surrounding the tip end side of the. Then, the main lens unit MLA is formed by the third to tenth grids G3 to G10.
In particular, a common large-diameter lens for three electron beams is substantially formed between the tip of the ninth grid G9 and the tenth grid G10.

In this electron gun, each cathode KB, KG, KR has a voltage of about 150 V plus a video signal, the first grid G1.
0V to 500V to 1kV to the second grid G2, 5 to 10kV to the third, fifth, seventh and ninth grids G3, G5, G7, G9, and 4th
500 to 1 kV on the grid G4, 0 to 3 kV on the sixth grid G6,
15-20kV on 8th grid G8, 25-30k on 10th grid G10
A voltage of kV is applied.

By applying these voltages, as shown in FIGS. 16B and 16C in comparison with the electrode configuration of FIG.
The electron beam emitted from each cathode KB, KG, KR forms a first crossover CO1 by the cathode lens formed by the first and second grids G1, G2, and further the second and third grids G2. , G3, the light is slightly focused by the prefocus lens PL, and is incident on the third grid G3 while diverging. The three electron beams incident on the third grid G3 are transmitted to the third to tenth grids G3 to G10.
The main electron lens portion MLA formed by the above is subjected to the focusing and concentrating action to focus and concentrate on the phosphor screen 23.

That is, the three electron beams that form the first crossover CO1 and enter the third grid G3 are relatively weak three formed by the third to fifth grids G3 to G5.
With the unipotential type electron lens ELS,
It is slightly focused vertically. Then, it is strongly focused mainly in the vertical direction by the electron lens VL1 (first electron lens) formed by the fifth to seventh grids G5 to G7. As a result, the three electron beams vertically cross the second crossover in the middle part of the seventh grid G7.
CO2 is formed and then enters the eighth grid G8 while diverging. Then, the electron lenses VL2 (second electron lenses) formed by the seventh to ninth grids G7 to G9 are slightly focused respectively, and then the three electron beams common to the ninth and tenth grids G9 and G10 are common. With the large-diameter electron lens LEL, the light beams are horizontally and vertically focused, and the pair of side beams are subjected to a concentrating action and focused on the phosphor screen 23.

In FIG. 16, 47 is the deflection center.

Also in this electron gun, since the electron lens VL1 that acts more strongly in the vertical direction than in the horizontal direction is formed, the aberration increases, but the main hole 28 is formed in the first grid G1.
Since the electron beam passage holes 29 located at the auxiliary holes 28S above and below M are provided, the aberration of the electron beam formed in the electron beam forming unit GEA can be reduced, and the divergence angle of the electron beam is also reduced. The bee spot SP on the body screen 23 can be reduced.

[0059]

EFFECT OF THE INVENTION An electron beam having a circular or non-circular main hole in the first grid located adjacent to the cathode, and an auxiliary hole connected to the periphery of the main hole in the vicinity of the main hole or through a small diameter portion. By forming the passage hole, the potential penetrating to the cathode side through the electron beam passage hole of the first grid can be greatly relaxed, the focusing power of the cathode lens for the off-axis beam can be weakened, and the focusing force for the paraxial beam can be equalized or On the contrary, it can be made weaker than the focusing force for the paraxial beam. As a result, by forming the auxiliary hole in the predetermined direction with respect to the main hole of the first grid, it is possible to eliminate the aberration at the crossover point in the predetermined direction or to have the reverse aberration. Even if the aberration of the electron lens is added after passing over, the beam spot on the target can be made extremely small, and a cathode ray tube with good resolution can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a monochrome picture tube which is an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of the electron gun.

FIG. 3 (a) is a view showing the shape of an electron beam passage hole of the first clit, FIG. 3 (b) is a view showing a shape of an electron beam passage hole of the second clide, and FIG. 3 (c). FIG. 3D is a view showing the shape of an electron beam passage hole on the second clad side of the third clit, FIG. 3D is a view showing the shape of an electron beam passage hole on the fourth clide side of the third clide, and FIG. FIG. 7 is a diagram showing a shape of an electron beam passage hole of a fourth crid.

FIG. 4 is a diagram showing a state of an electron beam forming unit of the electron gun of the above-described one embodiment by three-dimensional computer simulation.

FIG. 5 is a diagram for explaining crossover characteristics of the electron gun of the above-described embodiment.

FIG. 6 is a diagram showing the shape of a beam spot when an electron beam emitted from the electron gun of the above-described embodiment is deflected by a pincushion type deflection magnetic field.

FIG. 7 is a three-dimensional computer simulation of a case where the auxiliary hole of the electron beam passage hole of the first grid of the electron gun of the one embodiment is enlarged or the distance between the main hole and the auxiliary hole is increased. It is a state of an electron beam forming unit of the electron gun.

FIG. 8 is a diagram showing the shapes of electron beam passage holes having different first crids.

9 (a) to 9 (e) are views showing the shapes of electron beam passage holes of the first clit which are different from each other.

FIG. 10 is a diagram showing the shape of an electron beam passage hole of a different first crid.

FIG. 11 is a diagram showing a configuration of an electron gun according to another embodiment of the present invention.

FIG. 12 (a) is a view showing the shape of an electron beam passage hole of the second clit, and FIG. 12 (b) is a view showing a shape of an electron beam passage hole of the third clyd on the second clide side;
FIG. 12C is a diagram showing the shapes of the electron beam passage holes on the fourth clad side of the third clyde, the fourth clyde side, the fourth clyde side of the fifth clyde, and the fifth clyde side of the sixth clide. FIG. 6D is a view showing the shape of the electron beam passage hole on the side of the sixth grid of the fifth grid.

13A and 13B are views for explaining the operation of the electron gun of the other embodiment, FIG. 13A is an electrode configuration diagram of the electron gun, and FIGS. 13B and 13C are operation explanatory diagrams thereof. Is.

FIG. 14 is a diagram showing the structure of an electron gun of another embodiment of the present invention.

FIG. 15 is a view showing the shape of an electron beam passage hole of the first crid.

16A and 16B are views for explaining the operation of the electron gun according to the other different embodiment. FIG. 16A is an electrode configuration diagram of the electron gun, and FIGS. 16B and 16C are explanations of the operation. It is a figure.

FIG. 17 is a diagram showing a configuration of a conventional electron gun of a color picture tube.

18A is a diagram showing a configuration of the electron beam forming unit, and FIG. 18B is a diagram showing a state of the electron beam forming unit by three-dimensional computer simulation.

19A is a diagram showing the effect of a pincushion type horizontal deflection magnetic field on an electron beam, and FIG. 19B is a diagram showing the shape of a beam spot in that case.

FIG. 20 is a diagram showing a state of an electron beam forming unit of a conventional different electron gun by three-dimensional computer simulation.

FIG. 21 is a diagram for explaining the crossover characteristics of the above-mentioned different conventional electron guns.

22A to 22C are diagrams showing different crossover characteristics.

FIG. 23 is a diagram showing an electrode structure of still another conventional electron gun.

FIG. 24 is a view showing an electrode structure of a different electron gun of the related art.

FIG. 25 is a view showing an electrode structure of a different electron gun of the related art.

[Explanation of symbols]

 23 ... Phosphor screen 24 ... Electron gun 25 ... Electron beam 26 ... Deflection yoke 28M ... Main hole 28S ... Auxiliary hole 29 ... Electron beam passage hole 34a ... Paraxial beam 34b ... Off axis beam CO ... Crossover G1 ... First grid G2 ... 2nd grid G3 ... 3rd grid G4 ... 4th grid G5 ... 5th grid G6 ... 6th grid G7 ... 7th grid G8 ... 8th grid G9 ... 9th grid G10 ... 10th grid GEA ... Electron beam forming Part K ... Cathode MLA ... Main lens part SP ... Beam spot

Claims (1)

[Claims] 1. An electron beam forming unit having at least a cathode, first and second grids, for controlling electron emission from the cathode and focusing the emitted electrons to form an electron beam, and the electron beam. In a cathode ray tube including an electron gun having a main lens for focusing on a target, a circular or non-circular main hole is formed in the first grid, and the main hole is connected to the periphery of the main hole through a proximity or a small diameter portion. A cathode ray tube, characterized in that an electron beam passage hole including an auxiliary hole is formed.