JPH03116636A - Color cathode-ray tube - Google Patents

Abstract

PURPOSE:To enhance lens magnification by sequentially forming elliptical electron beam through holes with longitudinal axes perpendicular to the direction of arrangement of a third electron beam, through respective faces of third and fifth grids in opposite directions, which faces are opposite to a fourth grid, and also forming a circular electron beam through hole. CONSTITUTION:Elliptical electron-beam through holes 39a, 39b of vertical longitudinal axes disposed through the respective sides 37, 38 of third and fifth grids G3, G5, which sides are opposed to a fourth grid G4, form a non-rotation symmetrical lens and cause flattening of electron beams in their horizontal direction; therefore, flattening of electron beams in their horizontal direction resulting from that a second electrode element 32 produced when the three electrode elements 31 to 33 of the fourth grid 4 have the same potential has an elliptical electron-beam through hole 36 with a vertical longitudinal axis is cancelled out. Thus a voltage Vg4 to be applied to first and third electrode element 31, 33 during non-deflection is heightened to equal the voltage of the second grid G2 so that sufficient and necessary lens magnification of a main lens system is obtained.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a color cathode ray tube, and in particular to a color cathode ray tube that can obtain high resolution over the entire phosphor screen by improving its electron gun. Regarding.

(Prior Art) The mainstream color cathode ray tube is the so-called in-line electron gun type, which has an electron gun that emits three parallel electron beams on the same horizontal plane. One of the causes of deterioration of the resolution characteristics of the tube is a deflection aberration in which the beam spot on the phosphor screen becomes larger when the electron beam is deflected from the center of the phosphor screen to the periphery. This deflection aberration consists of a superposition of the following two different deflection aberrations.

One of these is that the trajectory of the electron beam from the electron gun to the phosphor screen becomes longer as the amount of electron beam deflection increases, so a small-diameter, perfectly circular beam spot forms at the center of the phosphor screen. Assuming that the focus voltage is set so as to obtain this, a deflection aberration (hereinafter referred to as a first deflection aberration) is caused by the beam spot being in an overfocus state in the peripheral area of the phosphor screen.

The other one is a deflection aberration (hereinafter referred to as a second deflection aberration) caused by the non-uniformity of the deflection magnetic field.

In other words, in an in-line electron gun type color cathode ray tube, as shown in FIGS. 3(A) and 3(B), the horizontal deflection magnetic field (■) of the deflection device is of the Binkushion type, and the vertical deflection magnetic field (■) is
The three electron beams (3B), (3G), and (3R) are self-converged by a barrel-shaped non-uniform deflection magnetic field. Therefore, the electron beam (3B) that has passed through this non-uniform deflection magnetic field ).

(3G) and (3R) have a diverging effect in the horizontal direction and a converging effect in the vertical direction, and in an under-focus state, they have a flattened elliptical shape with the long axis in the horizontal direction. The beam spot at the periphery of the screen has a non-circular, distorted shape.

As a result, as shown in Fig. 4, even if the beam spot (5a) at the center of the phosphor screen 0 is a new circle, the beam spot (5b) at the periphery is divided into a high-luminance core part ■ and a low-luminance one. The halo is distorted into a non-circular shape consisting of part (■) and the resolution of the periphery of the phosphor screen (A) is significantly degraded.

As a means for correcting the shape of the beam spot which degrades the resolution in the peripheral area of such a phosphor screen, Japanese Patent Application Laid-Open No. 143725/1983 discloses the following electron gun.

That is, as shown in FIG. 5, the cathode (K), the first to sixth grids (G1) to (G6
), the fourth grid (G4) is composed of three electrode elements (21) to (23), and the first electrode element (21) is adjacent to the third grid (G3). and a third electrode element (23) adjacent to the fifth grid (G5), which corresponds to three electron beams, respectively.
circular electron beam passage holes (24a) and (24b) are provided, and a long slit is formed in the second electrode element (22) between them in the direction orthogonal to the arrangement direction of the three electron beams, that is, in the perpendicular direction. It has a structure in which an electron beam passage hole (25) consisting of a circular shape is provided. Then, the same voltage Vgz as that of the second grid (G2) is applied to the second electrode element (22), and the voltage Vgz that is the same as that of the second grid (G2) is applied to the second electrode element (22). Third electrode element (21).

In (23), there is a dynamic voltage Vg that changes depending on the amount of deflection of the electron beam, that is, 7g when the deflection current is zero.
4°, and a voltage is applied that gradually increases from 7g4° as the deflection current increases.

Therefore, in this electron gun, when the electron beam is deflected, a non-rotationally symmetric lens is formed between the three electrode elements (21) to (23) constituting the fourth grid (G4), and the deflection magnetic field is It is possible to compensate for the second deflection aberration caused by the non-uniformity of. Furthermore, the increase in dynamic voltage vg4 is
In order to weaken the strength of the UPF lens (sub-lens) formed between the third to fifth grids (G3) to (G5), the fifth
When the focusing voltage Vf applied to the grid (G5) is constant, a main lens system consisting of a BPF lens (main lens) formed between the fifth grid (G5) and the sixth grid (G6) and the above sub-lenses. The entire beam is weakened, and the first deflection aberration can be compensated for.

As a result, deflection aberrations in the periphery (of the phosphor screen) are completely eliminated and the beam spot is minimized.

However, in this electron gun, the fourth grid (G4)
Since the second electrode element (22) has a vertical slit,
3-electrode elements (21) to (23) of the fourth grid (G4)
Even if the potentials are the same, a non-rotationally symmetric lens is formed by the penetrating magnetic fields from the third grid (G3) and the fifth grid (G5), resulting in the effect that the passing electron beam becomes vertically elongated. When the electron beam is not deflected, it is necessary to remove this effect, and the first and third electrode elements (21), (23)
The voltage Vg4° applied to the second electrode element (22) must be lower than the voltage Vlh applied to the second electrode element (22).

In this case, the UPF lens (sub-lens) formed between the third to fifth grids (G3) to (G5) becomes stronger than necessary, and the magnification of the main lens system becomes inappropriately large, causing the phosphor screen (to The upper beam spot diameter becomes larger.

As a countermeasure for this, the above publication further proposes that the first and third electrode elements (21) and (23) be
A long slit in the direction in which the electron beams are arranged, that is, in the horizontal direction, and a circular electron beam passage hole (26a).

(26b) is proposed. In this case, the first and third electrode elements (21) when not deflected.

It becomes possible to make the voltage Vg4° of (23) the same as the voltage Vgz of the second electrode element (22).

However, in this case, the first and third electrode elements (21),
(23) has a large horizontal hole diameter, so the third to fifth grids (G
3) to (G5) is weakened and becomes insufficient. Therefore, the dynamic voltage required to compensate for the deflection aberration increases, which poses a problem in terms of the withstand voltage reliability of the cathode ray tube, and further increases the cost of the dynamic voltage generation circuit.

(Problem to be Solved by the Invention) As described above, in order to improve the resolution over the entire phosphor screen of an in-line electron gun type color cathode ray tube, the electron gun is conventionally configured with a cathode and the first to sixth grids. However, there is a method in which the fourth grid is composed of three electrode elements, and an appropriate voltage is applied to each electrode element in order to improve the resolution particularly in the peripheral area of the phosphor screen.

However, this conventional electron gun has problems such as a large beam spot on the phosphor screen or a large dynamic voltage value, resulting in lower reliability and higher circuit cost.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to enable high resolution to be obtained over the entire phosphor screen in an in-line electron gun type color cathode ray tube.

[Structure of the invention]

(Means for Solving Problem 11) An electron gun that emits three parallel electron beams on the same plane including the tube axis is provided, and the electron gun is arranged along the tube axis in the direction of the phosphor screen. In a color cathode ray tube consisting of a cathode and first to sixth grids, the fourth grid is arranged in order from the third grid to the fifth grid. consisting of a third electrode element;
and forming at least a circular electron beam passage hole in the third electrode element, and applying a voltage to these electrode elements that increases as the deflection of the three electron beams increases.

On the other hand, an elliptical electron beam passing hole whose long axis is perpendicular to the direction in which the three electron beams are arranged is formed in the second electrode element, and a constant voltage is applied to this electrode element.
The grid and the surface of the fifth grid facing the fourth grid, and an elliptical electron beam passing hole and a circular electron beam passing hole whose major axis is in a direction perpendicular to the arrangement direction of the three electron beams, which are sequentially arranged in the facing direction. This is a color cathode ray tube that forms an array.

(Function) As described above, in an in-line electron gun having at least a cathode and first to sixth grids, the fourth grid is composed of three electrode elements, and the first electrode is located on the third grid side. At least a circular electron beam passing hole is formed in the element and a third electrode element located on the fifth grid side, while an elliptical hole having a long axis in a direction perpendicular to the arrangement direction of the three electron beams is formed in the second electrode element. An electron beam passing hole is formed, and the fourth grid of the third grid and the fifth grid is formed.
Elliptical electron beam passing holes and circular electron beam passing holes whose long axes are perpendicular to the arrangement direction of the three electron beams are sequentially formed on the surface facing the grid, and the first ．． By applying a voltage that increases as the deflection of the three electron beams increases to the third electrode element and applying a constant voltage to the second electrode element, the deterioration in resolution around the phosphor screen can be significantly improved. It is possible to improve the resolution of the entire area of the phosphor screen.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 8 shows the overall structure of a color cathode ray tube which is an embodiment of the present invention. This color cathode ray tube has a panel (1
0) and an envelope (12) consisting of a funnel (11)
A phosphor screen (A) consisting of a three-color phosphor layer that emits red, green, and blue light is formed on the inner surface of the panel (10), facing this phosphor screen (2) and spaced apart for a predetermined period. A shadow mask (13) in which a large number of electron beam passage holes are formed is disposed inside the shadow mask (13). Also,
Inside the neck (14) of the funnel (11), three electron beams (3R), (3G), and (3B) are installed outside the boundary between the cone (16) of the funnel (11) and the neck (14). deflected by a deflection device (17),
It is formed in a structure that displays a color image on the phosphor screen 0 by scanning the phosphor screen (4) in the horizontal and vertical directions.

The electron gun (15) emits three parallel electron beams (3B), (3G), (3R) on the same plane including the tube axis (18), that is, on the horizontal plane in this example, As shown in FIG. 1, there are three cathodes (K) arranged in a row, and first to sixth grids (1st to 6th grids) of an integral structure arranged sequentially in front of the cathodes (K) (in the direction of the phosphor screen).
G1) to (G6), and the fourth grid (G4) is an integrated structure arranged sequentially from the third grid (G3) side to the fifth grid (G5). 1st. Second. Third electrode element (31).

It is composed of (32) and (33). and,
1st゜2nd. 6th grid (Gl), (G2),
(G6), three circular electron beam passing holes of a predetermined size are formed in parallel in the horizontal direction on the second grid side of the third grid (G3), and on the sixth grid side of the fifth grid (G5). ing. On the other hand, the fourth grid (G4)
A groove having circular electron beam passing holes (35a) and (35b) at the bottom with the first and horizontal directions of
34a) and (34b) are formed, and the second electrode element (32) has an elliptical electron beam passage hole (36) whose major axis is in the vertical direction, as shown in FIG. 2(B). It is formed. Further, the side of the third grid (G3) and the fifth grid (G5) facing the fourth grid (G4) (
37), (38) have elliptical electron beam passing holes (39a), (3
9b) and circular electron beam passing holes (40a), (40b)
) are arranged and formed.

Then, apply 50 to 150V to the cathode (K), and apply 50 to 150V to the first grid (
G1) to ground potential, second grid (G2) d600~
800V, 3rd and 5th grid (G3), (G5
) are commonly connected in the tube and a focusing voltage Vf of 8 KV is applied to them, and 27 KV is applied to the sixth grid (G6).
Furthermore, the second electrode element (32) of the fourth grid is connected to the second grid (G2) in the tube and the same potential Vgz is applied, and the first and third electrode elements (31) and (33) are connected in the tube. As shown in FIG.
z is a voltage (19) that changes in synchronization with the deflection current (18).
) is applied. A dynamic voltage g4 is applied.

Therefore, by applying each of the above voltages, this electron gun (1
5) There are sub-lenses between the third and fifth grids (G3) and (G5), and the fifth and sixth grids (G5).

(G6) A main lens is formed between them.

Three electrode elements (31) of the fourth grid (G4)
(33) A non-rotationally symmetric lens is formed in between, and by applying the dynamic voltage, the strength of the non-rotationally symmetric lens can be adjusted to compensate for the second deflection aberration according to the deflection of the electron beam. . Furthermore, since the sub-lens strength is weakened by applying the dynamic voltage, the first deflection aberration can also be compensated for.

Here, the third and fifth grids (G3), (G5)
The side facing the fourth grid (G4) (37), (3
The elliptical electron beam passing holes (39a) and (39b) whose major axes are in the vertical direction, provided in g), form rotationally asymmetric lenses and have the effect of flattening the electron beam in the horizontal direction.

Therefore, the three electrode elements (3
1) to (33) are set to the same potential, the second electrode element (32) has an elliptical electron beam passage hole (36) whose major axis is in the vertical direction, and the electron beam is transmitted in the vertical direction. It can offset the flattening effect. As a result, the first. The voltage Vg*a applied to the third electrode elements (3], ), (33) is the same as the voltage of the second grid (G2).
The lens magnification of the main lens system can be increased to the necessary and sufficient level. Also, 3rd. 5th grid (G3)
, the side (3) facing the fourth grid (G4) of (G5)
7), (38) and the first grid of the fourth grid (G4).
Since the third electrode elements (31) and (33) are each formed with a circular electron beam passage hole, the effect of weakening the sub-lens by the dynamic voltage, that is, the first deflection aberration compensation effect is not impaired.

Therefore, it is possible to obtain a uniform and smallest beam spot over the entire phosphor screen by applying a relatively low dynamic voltage.

In the above embodiment, long grooves are provided in the horizontal direction in the first and third electrode elements (31) and (33) of the fourth grid (G4), but it is also possible to form only circular electron beam passage holes. A similar effect can be obtained.

〔Effect of the invention〕

In a color cathode ray tube that has an electron gun that emits three electron beams arranged in parallel on the same plane, the fourth grid is
At least circular electron beam passing holes are formed in the first and third electrode elements arranged on the third and fifth grid sides, and the deflection of the electron beam is increased in these electrode elements. A dynamic voltage that increases as the electron beam is applied is applied, and an elliptical electron beam passing hole whose major axis is in a direction perpendicular to the direction in which the electron beams are arranged is formed in the second electrode element between the first and third electrode elements. A constant voltage is applied to this electrode element, and a third. On the fourth grid side of the fifth grid, an elliptical electron beam passing hole and a circular electron beam passing hole whose major axis is in a direction perpendicular to the arrangement direction of the electron beams are formed in sequence in the direction facing the fourth grid. Accordingly, the first . The deflection aberration compensation effect can be obtained with a relatively low dynamic voltage without lowering the voltage of the third electrode element and therefore without increasing the lens magnification, and the resolution of the entire area of the phosphor screen can be improved.

[Brief explanation of drawings]

1, 2, 8, and 9 are detailed explanatory diagrams of the present invention, and FIG. 1 is a diagram showing the configuration of an electron gun for a color cathode ray tube, which is an embodiment of the invention. (A) and (B) are respectively a plan view and a cross-sectional view showing the structure of the first or third electrode element constituting the fourth grid, a plan view and a cross-sectional view showing the structure of the second electrode element, and (C ) are a plan view and a sectional view showing the configuration of the surfaces of the third and fifth grids in the direction facing the fourth grid, FIG. 8 is a diagram showing the overall configuration of the color cathode ray tube of the above embodiment, and FIG. Figures 3 (A) and (B) are diagrams showing the relationship between the deflection current and the dynamic voltage applied to the first and third electrode elements constituting the fourth grid.
The figures show the distribution of the horizontal deflection magnetic field and the vertical deflection magnetic field, respectively. Figure 4 is a diagram for explaining the deflection aberration of a conventional color cathode ray tube. Figures 5 to 7 are diagrams of a conventional color cathode ray tube electron gun. FIG. 5 is a configuration diagram of an electron gun, and FIG. 6 is a configuration diagram of a three-electrode display constituting a fourth grid. FIG. 7 is a plan view and a sectional view of other first and third electrode elements. 38.3G, 3R...3 electron beam 4...phosphor screen 15...electron gun 17...
・Deflection device 21.31...first electrode element 2
2.32...Second electrode element 23.33...Third
Electrode elements 24a, 24b...electron beam passage hole 2
5...Electron beam passing hole 34a, 34b...Groove 3
5a, 35b...Electron beam passing hole 36...Electron beam passing hole 39a, 39b...Electron beam passing hole 40a, 4
0b...Electron beam passing hole K...Cathode
G1...first grid G2...second grid
G3...Third grid G4...Fourth grid
G5...5th grid G6...6th grid

Claims (1)

[Claims] It has an electron gun that emits three parallel electron beams on the same plane including the tube axis, and this electron gun is composed of at least a cathode and first to sixth grids, and deflects the electron beam emitted from the electron gun. In a color cathode ray tube that is deflected horizontally and vertically by a device to display an image on a phosphor screen, the fourth grid of the electron gun has first, first, and second grids arranged in sequence from the third grid to the fifth grid.
The first and third electrode elements each include at least a circular electron beam passing hole, and a voltage that increases as the deflection of the electron beam increases is applied to the first and third electrode elements. The second electrode element is formed with an elliptical electron beam passing hole whose major axis is perpendicular to the arrangement direction of the three electron beams, and a constant voltage is applied to the third grid and the fifth grid. On the surface facing the fourth grid, elliptical electron beam passing holes and circular electron beam passing holes are formed in sequence in the facing direction, with the long axis being perpendicular to the direction in which the three electron beams are arranged. A color cathode ray tube characterized by: