JPH04215236A - Color cathode-ray tube - Google Patents

Abstract

PURPOSE:To improve the resolution on a fluorescent screen by providing projection parts having a predetermined projection length in the periphery of through holes of a center beam of a focusing electrode or a final accelerating electrode of an in-line type color cathode-ray tube. CONSTITUTION:Recessed hole parts 29, 30 having the bottom, of which diameters in the arrangement direction of three electron beams 25B, 25G, 25R is formed longer than that of other directions, are provided in opposite parts of a focusing electrode 40 and a final accelerating electrode 50 forming a main lens of an electron gun, and projection parts 33, 34 are provided in the peripheral edges of through holes 31G, 32G of a center beam formed in the bottom of the recessed hole part having the bottom of, at least, one electrode so as to project toward the other electrode. Projection length of these projection parts 33, 34 in the long diameter direction of the recessed part having the bottom is made larger than the projection length in the short diameter direction or projected to the only long diameter direction. Spherical aberration and astigmatism are thereby reduced, and a main lens having the even focusing voltage of three electron beams is formed to improve the resolution.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color cathode ray tube, and more particularly to an in-line color cathode ray tube having an electron gun that improves resolution.

0002

2. Description of the Related Art Generally, in a color cathode ray tube, a phosphor screen made of three color phosphor layers is formed on the inner surface of a panel of an envelope, facing a shadow mask in which a large number of electron beam passage holes are formed. The three electron beams emitted from the electron gun are deflected by a magnetic field generated by a deflection yoke attached to the outside of the envelope, and the phosphor screen is horizontally and vertically scanned through the shadow mask. It is formed into a structure that displays a color image on top.

Among such color cathode ray tubes, there is currently an in-line color cathode ray tube in which the electron gun is an electron gun that emits three electron beams arranged in a row consisting of a center beam and a pair of side beams passing on the same plane. ,
It has become the mainstream color cathode ray tube.

By the way, the resolution of a color cathode ray tube generally depends on the size and shape of the beam spot on the phosphor screen, and in order to improve the resolution, the beam spot should be made as small as possible and shaped with less distortion. It is necessary to do so. The convergence characteristics of the three electron beams is also an important factor.

In order to make the beam spot smaller, the diameter of the electrode that forms the main lens of the electron gun that ultimately focuses the electron beam on the phosphor screen is increased.
It is effective to reduce spherical aberration. For this purpose, it is necessary to increase the mutual spacing between the three electron beams. However, increasing the mutual spacing between the electron beams deteriorates the convergence characteristics of the three electron beams, and the diameter of the electrode constituting the main lens is limited by the inner diameter of the neck of the envelope in which the electron gun is disposed.

Conventionally, as a means of reducing the spherical aberration of the main lens without increasing the mutual spacing between the electron beams or the inner diameter of the neck, an electron gun has been developed in which the main lens is a large-diameter lens that acts in common on three electron beams. There is.

As an example, FIG.
The electron gun described in No. 41 is shown. This electron gun is
Three cathodes 1B, 1G, 1R arranged in a row, three heaters (not shown) for heating these cathodes 1B, 1G, 1R, and one after another in front of the cathodes 1B, 1G, 1R (toward the phosphor screen). It consists of an array of control electrodes 2, acceleration electrodes 3, focusing electrodes 4, final acceleration electrodes 5, and convergence electrodes 6 attached to the final acceleration electrodes 5. Each electrode 2 to 6 of this electron gun has three cathodes 1
Three circular electron beam passing holes arranged in a row corresponding to cathodes 1B, 1G, and 1R are formed in the same direction as the arrangement direction of cathodes 1B, 1G, and 1R. In particular, as shown in FIG. 6, the focusing electrode 4 and the final accelerating electrode 5 each have an oval bottomed concave hole whose major axis is in the direction in which the cathodes are arranged, that is, in the direction in which the three electron beams are arranged. 9, 10 are formed, and three circular electron beam passing holes 11B, 11G, 11R and 12B, 12G are formed at the bottom of the bottomed concave holes 9, 10.
, 12R are formed. And the center beam passing holes 11G and 12 in each center.
Projections 13 and 14 projecting toward the other electrodes 5 and 4 are provided at the peripheral edge of G, respectively.

[0008] The voltages shown in Table 1 are applied to each electrode of this electron gun.

[0009] By applying this voltage, the cathode 1
Electrons emitted from B, 1G, and 1R are accelerated and focused by the control electrode 2 and the acceleration electrode 3 to form three electron beams 7B, 1R, and
The beams are extracted as 7G and 7R, and are finally accelerated and focused toward the phosphor screen by the main lens formed by the next focusing electrode 4 and the final accelerating electrode 5, to form a beam spot on the phosphor screen.

The potential distribution of the main lens formed by the focusing electrode 4 and the final accelerating electrode 5 in the direction in which the three electron beams are arranged is as shown in FIG. The beam has a distribution given by a common relatively gentle equipotential line 16, and a non-rotationally symmetric large-diameter lens with small spherical aberration is formed, and each electron beam passing hole 11
B, 11G, 11R and 12B, 12G, 12R
A small diameter lens for each of the three electron beams is formed near the three electron beams.

However, when the main lens is formed of the electrodes 4 and 5 having elliptical bottomed concave holes 9 and 10 to form a rotationally asymmetric electron lens as in this electron gun, the following problems arise. occurs.

That is, between the bottomed concave holes 9 and 10 where the large-diameter lens is formed, an equipotential line 16a
As shown, the inclination angle of the equipotential line common to the three electron beams is the direction in which the three electron beams are arranged (the long diameter direction of the bottomed concave holes 9 and 10) and the direction perpendicular to this arrangement direction (the direction of the long axis of the bottomed concave holes 9 and 10). ,1
0), the focusing action in the arrangement direction of the three electron beams is weaker than the focusing action in the direction orthogonal to the arrangement direction, and the central center beam passing holes 11G, 12
The focusing effect on the center beam passing through G is the side beam passing holes 11B, 11R, 12B, 12R on both sides.
The focusing effect is weaker than that for the pair of side beams passing through.

On the other hand, each electron beam passing hole 11B, 11G, 11R, 12B, 12 in which the small diameter lens is formed
In the vicinity of G and 12R, the protrusions 13 and 14 are provided only at the periphery of the center beam passage holes 11G and 12G, so the equipotential lines become like 16b and 16c, and the arrangement of the three electron beams is The focusing effect in the direction is stronger than the focusing effect in the direction orthogonal to the arrangement direction, and the focusing effect on the center beam is stronger than the focusing effect on the pair of side beams, and this compensates for the non-rotational symmetry of the large diameter lens. becomes.

However, in the electrode configuration of the main lens of this electron gun, the large diameter lens formed between the bottomed concave holes 9 and 10 has a focusing effect on the center beam in a direction perpendicular to the arrangement direction of the three electron beams. This is much stronger than the focusing effect in the array direction of the three electron beams, so it is necessary to make the focusing effect in the array direction of the three electron beams on the center beam much stronger than the focusing effect in the orthogonal direction. However, the protrusions 13 and 14 provided on the periphery of the central center beam passage holes 11G and 12G through which the center beam passes have their protrusion lengths in the direction in which the three electron beams are arranged and in the direction orthogonal to this arrangement direction. Since they are all the same, the focusing effect on the center beam is strong both in the direction in which the three electron beams are arranged and in the direction orthogonal to this direction. As a result, the focusing effect on the center beam in the direction perpendicular to the arrangement direction of the three electron beams becomes stronger than the focusing action in the arrangement direction of the three electron beams, and the focusing action on the center beam in the direction perpendicular to the arrangement direction of the three electron beams. The effect becomes stronger than the focusing effect in the same direction on the pair of side beams.

As a result, the beam spot on the phosphor screen is distorted, and the three electron beams 7B, 7G, 7R are not focused uniformly on the phosphor screen, the beam spot is not minimized, and the resolution is reduced. to degrade.

[0016]

[Problems to be Solved by the Invention] As mentioned above, in order to improve the resolution of conventional in-line color cathode ray tubes, the direction in which the three electron beams are arranged is aligned with the long axis at the opposing part of the electrodes that form the main lens of the electron gun. An elliptical bottomed concave hole is formed, and three circular electron beam passing holes are formed in the bottom of the bottomed concave hole to make the main lens a large diameter lens. In order to compensate for the non-rotational symmetry of the center beam passage hole, there is one in which a protrusion is provided at the periphery of the center beam passage hole. However, with this electrode configuration of the main lens, the focusing effect on the center beam in a direction perpendicular to the direction in which the three electron beams are arranged is stronger than the focusing effect in the direction in which the three electron beams are arranged in relation to the center beam. The focusing effect in the direction perpendicular to the direction becomes stronger than the focusing effect in the same direction on the pair of side beams, and the resulting astigmatism distorts the beam spot on the phosphor screen, causing the beam spot to be at its minimum. Therefore, there is a problem that the resolution deteriorates.

The present invention was made to solve the above problems, and provides a color cathode ray having an electron gun that emits three electron beams arranged in a row, consisting of a center beam and a pair of side beams passing on the same plane. An object of the present invention is to construct a color cathode ray tube in which the beam spot on a phosphor screen is not distorted and the beam spot can be made small.

[Configuration of the invention]

[0019]

[Means for Solving the Problem] The present invention has an electron gun that emits three electron beams arranged in a row, consisting of a center beam and a pair of side beams passing on the same plane, and the three electron beams are finally directed onto a phosphor screen. An elliptical bottomed concave hole whose major diameter is in the direction in which the three electron beams are arranged is formed in the opposing portion of the cylindrical focusing electrode and the cylindrical final acceleration electrode, which form a main lens that focuses the electron beams. In the color cathode ray tube, three electron beam passing holes are formed in the bottom of the bottomed concave hole, each consisting of a center beam passing hole through which the three electron beams pass separately and a pair of side beam passing holes. A protrusion protruding toward the other electrode is provided at the periphery of the center beam passage hole on the bottom surface of the bottomed concave hole of at least one of the focusing electrode and the final acceleration electrode, and the protrusion has the above-mentioned properties. The protrusion length of the bottom concave hole in the major axis direction is made larger than the protrusion length of the bottomed concave hole in the minor axis direction, or the protrusion length is made to protrude only in the major axis direction.

[0020]

[Operation] As described above, an elliptical bottomed concave hole whose major diameter is in the direction in which the three electron beams are arranged is formed in the facing part of the focusing electrode and the final accelerating electrode that form the main lens, and each Three electron beam passing holes are formed in the bottom of the bottomed concave hole, consisting of a center beam passing hole through which the three electron beams pass separately, and a pair of side beam passing holes, and one of the focusing electrode and the final accelerating electrode is formed. , a protrusion protruding toward the other electrode is provided at the peripheral edge of the center beam passage hole on the bottom surface of the bottomed concave hole of at least one electrode, and the protrusion extends in the longer diameter direction of the bottomed concave hole of at least one electrode. If the protrusion length is made larger than the protrusion length in the minor axis direction of the bottomed concave hole, or if it is made to protrude only in the major axis direction, the three electron beams are arranged between the focusing electrode and the final accelerating electrode in the direction of arrangement. A non-rotationally symmetric large-diameter lens whose focusing action is weaker than the focusing action in the direction orthogonal to the arrangement direction is formed near each electron beam passage hole, and the focusing action in the arrangement direction of the three electron beams is smaller than that in the arrangement direction. A small-diameter lens is formed that has a stronger focusing action in a direction orthogonal to the center beam, and a sufficient difference is created between the focusing action in the direction in which the three electron beams are arranged on the center beam and the focusing action in the direction orthogonal to the arrangement direction. I can do it. Therefore, it compensates for the non-rotational symmetry of the large-diameter lens, and has small spherical aberration and extremely small astigmatism.
Furthermore, it is possible to form a main lens with a uniform focusing voltage for the three electron beams, and the resolution on the phosphor screen can be greatly improved.

[0021]

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

FIG. 3 shows an in-line color cathode ray tube as an embodiment of the present invention. This color cathode ray tube has panel 2
0 and a funnel 21 integrally joined to this panel 20, and on the inner surface of the panel 20 is a phosphor screen 22 consisting of a striped three-color phosphor layer that emits blue, green, and red light. is formed, and a shadow mask 23 having a large number of electron beam passage holes formed therein is arranged opposite to this phosphor screen 22. In addition, three electron beams 2 are arranged in a row in the neck 24 of the funnel 21, consisting of a center beam 25G passing on the same horizontal plane and a pair of side beams 25B and 25R.
An electron gun 26 that emits 5B, 25G, and 25R is provided. The three electron beams 25B, 25G, and 25R emitted from the electron gun 26 are deflected by a magnetic field generated by a deflection yoke 27 attached to the outside of the funnel 21, and the phosphor screen 22 is scanned horizontally and vertically. As a result, a structure is formed in which a color image is displayed on this phosphor screen 22.

As shown in FIG. 1, the electron gun 26 has three cathodes 1B, 1G, 1 arranged in a row in the horizontal direction.
R, three heaters (not shown) for heating these cathodes 1B, 1G, and 1R; control electrodes 2 and accelerating electrodes 3 arranged in order toward the phosphor screen in front of the cathodes 1B, 1G, and 1R; Focusing electrode 40, final acceleration electrode 50
and a convergence electrode 6 attached to this final acceleration electrode 50.

The control electrode 2 and the accelerating electrode 3 are plate-shaped electrodes having an integral structure in the form of an ellipse whose major diameter is in the direction in which the cathodes 1B, 1G, and 1R are arranged (the direction in which the three electron beams are arranged). On the surface, there are three cathodes 1B, 1G,
Three circular electron beam passing holes are formed in a row in the horizontal direction corresponding to 1R. The focusing electrode 40 and the final accelerating electrode 50 are cylindrical electrodes having an elongated, integral structure whose major axis is in the direction in which the cathodes 1B, 1G, and 1R are arranged, and the surfaces of these electrodes 40 and 50 that face the adjacent electrodes. Three circular electron beam passing holes are formed in a row in the horizontal direction, corresponding to the three cathodes 1B, 1G, and 1R, respectively. Furthermore, the convergence electrode 6 consists of a cup-shaped electrode of the same shape, and the bottom part thereof has 3
A number of circular electron beam passing holes are formed in a row.

In particular, the focusing electrode 40 and the final accelerating electrode 50 of the electron gun 26 are arranged such that the focusing electrode 40 has a surface facing the final accelerating electrode 50, and the final accelerating electrode 50 has a surface facing the focusing electrode 40. As shown in FIG. 2, bottomed concave holes 29, 30 each having an oval shape with a major axis extending in the direction in which the three cathodes are arranged are formed.
Three electron beam passing holes 31B, 31G, and 31 are provided in the horizontal direction on the bottom of 30, corresponding to the three cathodes, respectively.
R, 32B, 32G, and 32R are arranged in a row. And the center beam passage hole 31G in each center
, 32G, the other electrodes 50, 40, respectively.
Projecting portions 33 and 34 are provided that project toward the front. These protrusions 33, 34 differ from conventional protrusions in that they protrude in the longer diameter direction of each bottomed concave hole 29, 30 (the direction in which the three cathodes 1B, 1G, 1R are arranged), and are perpendicular to the longer diameter direction. It has a shape that does not protrude in the short diameter direction.

During operation, the voltages shown in Table 1 are applied to each electrode of the electron gun 26. Thereby, a main lens is formed between the focusing electrode 40 and the final accelerating electrode 50, and electrons emitted from each cathode 1B, 1G, 1R are accelerated and focused by the control electrode 2 and the accelerating electrode 3, resulting in three electron beams 25B. , 25G, 25R, and these three electron beams 25B, 25G, 25R are finally accelerated and focused toward the phosphor screen 22 by the main lens.

By the way, when the focusing electrode 40 and the final acceleration electrode 50 are formed as described above, these electrodes 40, 5
The potential distribution of the main lens formed by 0 is as shown in FIG. That is, the focusing electrode 40 and the final acceleration electrode 5
Bottomed recessed holes 29 and 30 are formed in the opposite portions of the bottomed recessed holes 29 and 30, and each bottomed recessed hole is formed at the peripheral edge of the center beam passing holes 31G and 32G at the bottoms of these bottomed recessed holes 29 and 30. Since the protrusions 33 and 34 are provided only in the long axis direction of the holes 29 and 30 (the direction in which the three electron beams are arranged), the three
The potential distribution in the array direction of the electron beam is as shown in FIG. 4(a). That is, between the bottomed concave holes 29 and 30, there is a potential distribution given by a common relatively gentle equipotential line for the three electron beams, as shown by the equipotential line 16a, similar to the conventional large-diameter lens. Thus, a rotationally asymmetric large-diameter lens is formed. In addition, each electron beam passing hole 31B
, 31G, 31R, 32B, 32G, and 32R are also the same as before, as shown by equipotential lines 16b and 16c, and a small-diameter lens similar to the conventional small-diameter lens is formed. Compensate for non-rotational symmetry of the aperture lens.

On the other hand, center beam passing holes 31G, 32
Since the protrusions 33 and 34 are not provided in this direction, the potential distribution in the direction perpendicular to the arrangement direction of the three electron beams near G is a uniform one with a relatively large curvature, as shown in (b). Potential distributions are shown by potential lines 16d and 16e. Therefore, the focusing effect on the center beam 25G is stronger in the direction in which the three electron beams are arranged than in the direction perpendicular to the direction in which the three electron beams are arranged. Therefore, it is possible to compensate for the astigmatism of the center beam that has conventionally occurred, and to improve the resolution.

In the above embodiment, the center beam passage hole of the focusing electrode and the final acceleration electrode has a concave hole that protrudes only in the major axis direction of each bottomed concave hole at the periphery of the center beam passage hole, and protrudes in a direction perpendicular to the major axis direction. However, since the focusing action of the main lens formed by these focusing electrodes and the final acceleration electrode changes depending on the shape of the bottomed concave hole formed in each of these electrodes, the focusing action Accordingly, the bottomed recess may also be allowed to protrude toward the counter electrode in a direction perpendicular to the major axis direction with a protrusion length shorter than the protrusion length in the major axis direction.

Further, in the above embodiment, the protrusion is provided on both the focusing electrode and the final acceleration electrode, but the protrusion may be provided on only one of the two electrodes.

Furthermore, although the above embodiment has described a bipotential electron gun in which the main lens is formed of two electrodes, the present invention is applicable not only to bipotential electron guns but also to unipotential electron guns and quaternary electron guns. It can also be applied to other types of electron guns such as dora potential type electron guns.

[0032]

Effects of the Invention: It has an electron gun that emits three electron beams arranged in a row that pass on the same plane, and forms a main lens that ultimately focuses the three electron beams emitted from the electron gun onto a phosphor screen. An elliptical bottomed concave hole whose major diameter is in the direction in which the three electron beams are arranged is formed in the opposing portions of the cylindrical focusing electrode and the cylindrical final acceleration electrode, respectively. In a color cathode ray tube in which a beam passage hole is formed, at least one of the focusing electrode and the final acceleration electrode is formed at the periphery of the center beam passage hole at the bottom of the bottomed concave hole of at least one electrode toward the other electrode. A protruding portion is provided, and the protruding length of the protruding portion in the major axis direction of the bottomed concave hole is larger than the protruding length in the minor axis direction of the bottomed concave hole, or the protruding portion protrudes only in the major axis direction. With this shape, a common non-uniformity between the three electron beams is created between the bottomed concave hole of the focusing electrode and the final accelerating electrode, where the focusing action in the arrangement direction of the three electron beams is weaker than the focusing action in the direction perpendicular to the arrangement direction. A rotationally symmetrical large-diameter lens is formed, and a small-diameter lens is formed near each electron beam passage hole, the focusing effect of which is stronger in the direction in which the three electron beams are arranged than in the direction perpendicular to the direction in which they are arranged; In addition, it is possible to create a sufficient difference between the focusing effect of the three electron beams on the center beam in the arrangement direction and the focusing action in the direction orthogonal to the arrangement direction, thereby compensating for the non-rotational symmetry of the large-diameter lens. As a result, it is possible to form a main lens that has small spherical aberration, extremely small astigmatism, and uniform focusing voltage for the three electron beams, and can greatly improve the resolution on the phosphor screen. .

[Brief explanation of the drawing]

FIG. 1(a) is a plan view showing a cross section of an electron gun of an in-line color picture tube which is an embodiment of the present invention;
(b) is a side view also shown in cross section.

FIG. 2 is a perspective view showing the structure of a focusing electrode and a final acceleration electrode of the electron gun.

FIG. 3 is a diagram showing the configuration of the in-line color picture tube.

FIG. 4(a) is a diagram showing the potential distribution of the three electron beams in the main lens formed by the focusing electrode and the final accelerating electrode, and FIG. 4(b) is a diagram showing the potential distribution of the three electron beams of the main lens. FIG. 3 is a diagram showing a potential distribution in a direction perpendicular to the beam array direction.

FIG. 5(a) is a plan view showing an electron gun of a conventional in-line color picture tube in cross section, and FIG. 5(b) is a side view showing the same in cross section.

FIG. 6 is a perspective view showing the structure of a focusing electrode and a final acceleration electrode of the conventional electron gun.

FIG. 7 is a diagram showing the potential distribution of the main lens formed by the focusing electrode and the final accelerating electrode of the conventional electron gun in the direction in which the three electron beams are arranged.

[Explanation of symbols]

1B, 1G, 1R...Cathode 2...Control electrode 3...Acceleration electrode 6...Convergence electrode 22...Phosphor screen 25B, 25R...Pair of side beams 25G...Center beam 26...Electron guns 29, 30...Bottomed concave hole portion 31B , 31R...Pair of side beam passage holes 31G
...Center beam passing holes 32B, 32R...Pair of side beam passing holes 32G
…Center beam passage holes 33, 34…Protrusion portion 40…Focusing electrode 50…Final acceleration electrode

Claims (1)

[Claims] 1. An electron gun that emits three electron beams arranged in a row, consisting of a center beam and a pair of side beams that pass on the same plane, and a main beam that finally focuses the three electron beams onto a phosphor screen. An elliptical bottomed concave hole whose major axis is in the direction in which the three electron beams are arranged is formed in the facing portion of the cylindrical focusing electrode and the cylindrical final acceleration electrode that form the lens. 3 above on the bottom of the hole.
In a color cathode ray tube in which three electron beam passing holes are formed, each consisting of a center beam passing hole and a pair of side beam passing holes through which the electron beam passes separately, at least one of the focusing electrode and the final accelerating electrode is formed. A protrusion protruding toward the other electrode is provided at the peripheral edge of the center beam passage hole on the bottom of the bottomed concave hole of the electrode, and the protrusion length of this protrusion in the major axis direction of the bottomed concave hole is set as above. A color cathode ray tube characterized in that the protrusion length in the short diameter direction of the bottomed concave hole is larger than the protrusion length, or the protrusion length is made to protrude only in the long diameter direction.