JP2000306521A - Cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high resolution by alleviating degradation of a resolution at the periphery of a screen, and improving the convergent state of an electron beam over the entire screen. SOLUTION: A cathode-ray tube is constituted such that a drive voltage, which is variable according to a video signal, is applied to a first grid G1, a first electron lens having horizontal convergent force greater than vertical convergent force with respect to an electron beam is formed between the first and second grids G1, G2, and a second electron lens having vertical convergent force greater than horizontal convergent force with respect to the electron beam is formed between the second and third grids G2, G3.

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 such as a color cathode ray tube, and more particularly to a cathode ray tube capable of improving a focusing property of an electron beam and obtaining a high resolution over the entire screen.

[0002]

2. Description of the Related Art Generally, a cathode ray tube emits an electron beam emitted from an electron gun disposed in a neck of a funnel, in a horizontal direction generated by a deflection yoke mounted outside the funnel.
The image is displayed by deflecting by a vertical deflection magnetic field and horizontally and vertically scanning a phosphor screen provided on the inner surface of the panel.

In particular, in a color cathode ray tube, the electron gun is an electron gun that emits three electron beams, and the three electron beams emitted from the electron gun are selected by a shadow mask disposed opposite to a phosphor screen, and a fluorescent light is emitted. It is formed in a structure for displaying a color image by being incident on the three-color phosphor layer constituting the body screen. At present, such a color cathode ray tube is an in-line type in which an electron gun emits three electron beams arranged in a line in the same horizontal plane, a horizontal deflection magnetic field generated by a deflection yoke is a pincushion type, and a vertical deflection magnetic field is a barrel. As a form, a self-convergence in-line type color cathode-ray tube in which the three electron beams arranged in a row are concentrated by these deflection magnetic fields is mainly used.

FIG. 4 shows an example of an electron gun of this in-line type color cathode ray tube. This electron gun has three cathodes KB, KG, arranged in a row in the horizontal direction (X-axis direction).
KR, three heaters H for separately heating the cathodes KB, KG and KR, and first to fourth grids G1 to G4 arranged in the direction of the phosphor screen at predetermined intervals from the cathodes KB, KG and KR. Having. In this electron gun, an electron beam generator for generating three electron beams is formed by cathodes KB, KG, KR and first, second, and third grids G1, G2, G3 sequentially adjacent to these cathodes KB, KG, KR. The main lens which focuses the three electron beams from the electron beam generator on the phosphor screen is formed by the third and fourth grids G3 and G4.

In such a color cathode ray tube, in order to improve the characteristics of an image drawn on the phosphor screen, the three electron beams emitted from the electron gun are appropriately focused on the phosphor screen. There is a need. However, if the three electron beams emitted from the electron gun are deflected by non-uniform horizontal and vertical deflection magnetic fields of a pincushion type and a barrel type as in the self-convergence in-line type color cathode ray tube described above, the electron beams become astigmatism. Due to the aberration (deflection aberration), it is not properly focused.

For example, as shown in the horizontal deflection magnetic field in FIG. 5A, an electron beam 1 deflected in the peripheral direction of a screen is caused by an arrow 3H by a pincushion type horizontal deflection magnetic field 2.
, 3V, the beam spot 4 at the peripheral portion of the screen becomes over-focused in the vertical direction as shown in FIG. And a halo 6 (bleeding) having a low luminance occurs.

[0007] The deflection aberration of the electron beam 1 becomes remarkable as the tube becomes larger and the deflection angle becomes wider, and the resolution of the peripheral portion of the screen is remarkably deteriorated.

As an electron gun for reducing the deterioration of the resolution at the peripheral portion of the screen, there is an electron gun having a horizontally long recess in the horizontal direction around the electron beam passage hole on the surface of the second grid on the third grid side. is there. When the electron gun is configured in this manner, a quadrupole lens is formed between the second and third grids so as to focus the electron beam more strongly in the vertical direction than in the horizontal direction. It is possible to reduce the vertical halo by reducing the deflection aberration in the vertical direction by making the shape longer in the horizontal direction.

As another example, the third grid of the electron gun shown in FIG. 4 is divided into two electrodes, and the horizontal and vertical focusing forces differ between these divided electrodes.
As shown in FIG. 6, a dynamic type electron gun configured to form a pole lens and applying a dynamic voltage 9 changing in synchronization with a deflection current 8 to one of these two electrodes is provided. is there.

In this electron gun, a potential difference is generated between the two divided electrodes at the time of deflection due to the application of the dynamic voltage 9 which changes in synchronization with the deflection current 8, and as a result, a quadrupole lens formed between these divided electrodes is formed. With this, the electron beam is focused in the horizontal direction and diverged in the vertical direction. As a result, the electron beam becomes insufficiently focused in the vertical direction, but compensates for the overfocus due to the deflection aberration, and enters an appropriate focusing state, thereby reducing the vertical halo.

However, even if the electron gun is configured as described above, there is a problem that the beam spot deteriorates when the current amount of the electron beam changes.

That is, in a cathode ray tube, the brightness and contrast of a screen are generally adjusted by the amount of current of an electron beam. The amount of current is increased when the screen is brightened, and the amount of current is decreased when the screen is darkened. ing. On the other hand, the diameter of the electron beam in the deflection region changes depending on the amount of current of the electron beam. The diameter of the electron beam in the deflection region increases when the amount of current is large, and decreases when the amount of current is small. Therefore, the deflection aberration increases as the current amount of the electron beam increases, and decreases as the current amount decreases.

However, the above-mentioned electron gun having a horizontally long concave portion around the electron beam passage hole on the surface of the second grid on the third grid side, or the third grid is divided into two electrodes. In a dynamic electron gun in which a dynamic voltage that changes in synchronization with a deflection current is applied to one of the electrodes, a horizontally long recess or a dynamic voltage is set by a current value (a set current value) of a certain electron beam. You. Therefore, a deviation from the set value occurs at a current value other than the set current value.

In general, the set current value is often set almost in the middle of the current region when actually used.
Therefore, when the current value becomes larger than the set current value (when the screen is bright), the deflection aberration increases, and a halo occurs in the vertical direction of the beam spot at the periphery of the screen.
Conversely, when the current value becomes smaller than the set current value (when the screen is dark), the deflection aberration is reduced, the lens is in an insufficiently focused state at the periphery of the screen, and the beam spot is increased in the vertical direction. In other words, the beam spot deteriorates due to a change in the amount of current of the electron beam, and the resolution around the screen is significantly deteriorated.

[0015]

As described above, as an electron gun for reducing the deterioration of the resolution at the peripheral portion of the screen, the electron gun extends horizontally around the electron beam passage hole on the third grid side surface of the second grid. An electron gun provided with a horizontally long concave portion, and the third grid are divided into two electrodes, and a dynamic voltage that changes in synchronization with the deflection current is applied to one of the electrodes, thereby forming a quadrupole lens between these electrodes. There is a dynamic electron gun that forms

However, in the above-mentioned electron gun, since the concave portion and the dynamic voltage are set at a substantially middle set current value of the current region of the electron beam when actually used, the set value is set when the color cathode ray tube is actually driven. When the current value is larger than the set current value, the deflection aberration increases, and a halo occurs in the vertical direction of the beam spot at the periphery of the screen. Conversely, when the current value is smaller than the set current value, the deflection aberration is small, the lens is in an insufficient focusing state at the periphery of the screen, and the beam spot becomes large in the vertical direction. That is, there is a problem that the beam spot is deteriorated due to the change in the amount of current of the electron beam, and the resolution of the peripheral portion of the screen is significantly deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to reduce the deterioration of the resolution at the periphery of the screen and improve the focusing state of the electron beam over the entire screen to obtain a high resolution cathode ray. The purpose is to construct a tube.

[0018]

(1) An electron beam generator is formed by a cathode and first, second, and third grids sequentially arranged from the cathode in the direction of the phosphor screen. In a cathode ray tube having an electron gun that forms a main lens unit that focuses an electron beam from an electron beam generating unit on a phosphor screen by a grid arranged on the phosphor screen side of the three grids, a video signal is applied to a first grid. Is applied to the first and second grids to form a first electron lens between the first and second grids in which the horizontal focusing force on the electron beam is stronger than the vertical focusing force. The second electron lens is formed between the three grids so that the focusing power in the vertical direction with respect to the electron beam is stronger than the focusing power in the horizontal direction.

(2) In the cathode ray tube of (1), the first
A long horizontally long recess was formed in the horizontal direction around the electron beam passage hole on the second grid side surface of the grid.

(3) In the cathode ray tube according to (1) or (2), a horizontally long concave portion is formed around the electron beam passage hole on the surface of the second grid on the third grid side.

(4) In the cathode ray tube of (1) or (2), a vertically long recess is formed around the electron beam passage hole on the surface of the third grid on the second grid side.

(5) In the cathode ray tube according to (1) or (2), a horizontally elongated concave portion is formed around the electron beam passage hole on the third grid side surface of the second grid, and the third grid is formed. A vertically long recessed portion was formed around the electron beam passage hole on the second grid side surface.

[0023]

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

FIG. 1 shows a color cathode ray tube which is one embodiment of the present invention. This color cathode ray tube has an envelope composed of a panel 10 and a funnel-like funnel 11 integrally joined to the panel 10, and blue, green,
A phosphor screen 12 made of a striped three-color phosphor layer that emits red light is provided. Further, a shadow mask 13 having a large number of apertures is arranged inside the phosphor screen 12 so as to face the phosphor screen 12.
On the other hand, three electron beams 16B, 16G, 16R arranged in a line in the neck 15 of the funnel 11 and passing on the same horizontal plane.
Is provided. The three electron beams 16B, 16G emitted from the electron gun 17
, 16R are deflected by horizontal and vertical deflection magnetic fields generated by a deflection yoke 19 mounted outside the funnel 11,
The phosphor screen 12 is horizontally and vertically scanned through a shadow mask 13 to display a color image.

As shown in FIG. 2, the electron gun 17 heats three cathodes KB, KG, KR arranged in a row in the horizontal direction (X-axis direction), and separately heats the cathodes KB, KG, KR. Three heaters H and the cathode K
There are first to fourth grids G1 to G4 which are arranged at predetermined intervals in the direction of the phosphor screen from B, KG and KR.

The first grid G1 includes cathodes KB,
As shown in FIG. 3 (a), three plate-shaped electrodes G1B, G1G, G1R corresponding to KG, KR are provided, and each of the electrodes G1B, G1G, G1R is connected to each cathode. Correspondingly, small diameter electron beam passage holes 21B, 21G, 21R are provided in a line. Furthermore, horizontally long (X-axis direction) horizontally long concave portions 22B, 22B around the electron beam passage holes 21B, 21G, 21R on the surface on the second grid G2 side.
G and 22R are provided.

The second grid G2 is composed of a plate-like electrode having an integral structure. As shown in FIG. 3B, three grids having substantially the same size as the electron beam passage holes of the first grid correspond to each cathode. Of the electron beam passing holes 23B, 23G, 23R are provided in a line. Furthermore, horizontally long recesses 24B, 24G, 24R that are long in the horizontal direction around the electron beam passage holes 23B, 23G, 23R on the surface on the third grid G3 side.
Is provided.

The third and fourth grids G3 and G4 are each composed of an integral cylindrical electrode, and the third grid G3
On the second grid G2 side, the cathodes KB, KG,
Three electron beam passage holes larger than the electron beam passage holes of the second grid G2 are provided corresponding to KR.
The surface of the third grid G3 on the side of the fourth grid G4, the surface of the fourth grid G4 on the side of the third grid G3, and the surface on the opposite side are provided on the second grid G2 of the third grid G3.
Three electron beam passage holes which are larger than the electron beam passage holes on the side surface are provided.

In this electron gun 17, the cathode KB, KG
, KR at a constant voltage of about 100 to 200 V, a drive voltage varying in accordance with a video signal at each of the plate electrodes G1B, G1G, G1R of the first grid G1, and about 50 at a second grid G2.
0-600V constant voltage, about 6-9 in the third grid G3
A constant voltage of about 22 to 32 kV is applied to the fourth grid G4 at kV. The drive voltage of the first grid G1 is set to 0 V in a cutoff state in which no image is displayed,
The brighter the screen, the larger it becomes in the positive direction.

Due to the application of the voltage, in the electron gun 17, the horizontal focusing force on the electron beam is stronger than the vertical focusing force between the first and second grids G1 and G2, and the electron beam is moved in the vertical direction. A first electron lens having a longer length is formed. Also, the second and third grids G2,
Between G3, a second electron lens is formed in which the focusing power in the vertical direction with respect to the electron beam is stronger than the focusing power in the horizontal direction, and makes the electron beam longer horizontally in the horizontal direction. Further, between the third and fourth grids G3 and G4, there is formed a main lens for finally focusing the electron beam focused by the first and second electron lenses on the phosphor screen.

As described above, the first and second grids G1, G2
First and second electron lenses having different functions are formed between the second and third grids G2 and G3.
In order to achieve an appropriate focusing state at a drive voltage substantially in the middle of actual use conditions, that is, to substantially eliminate a vertical halo at the periphery of the screen at a drive voltage substantially in the middle of use conditions, Adjust the second electronic lens.

When the drive voltage is set as described above,
When the drive voltage increases from a drive voltage that is substantially intermediate between the use conditions, the voltage of the first grid G1 approaches the second grid G2, so that the first electron lens between the first and second grids G1 and G2 weakens, The effect of making the electron beam vertically elongated in the vertical direction is weakened. As a result, it is possible to compensate for the increase in the deflection aberration caused by the increase in the current amount of the electron beam, to make the electron beam appropriately focused, and to eliminate the halo caused by the conventional over-focusing at the periphery of the screen in the vertical direction. it can.

Conversely, when the drive voltage is lowered from a drive voltage substantially in the middle of the operating conditions, the voltage difference between the first grid G1 and the second grid G2 increases, so that the first and second grids G1 and G2 become large.
The first electron lens between the grids G1 and G2 is strengthened, and the effect of making the electron beam vertically elongated in the vertical direction is enhanced. As a result, the reduction in deflection aberration due to the reduction in the amount of current of the electron beam is compensated for, and the increase in the beam spot diameter in the vertical direction caused by insufficient focusing at the peripheral portion of the conventional screen can be eliminated.

That is, when the electron gun 17 is configured as described above, the focusing state at the peripheral portion of the screen can be optimized over almost all drive voltages, and the beam spot over the entire screen from low luminance to high luminance can be reduced. , The resolution can be greatly improved.

In the above embodiment, a horizontally long recess is provided around the electron beam passage hole on the surface of the second grid on the third grid side, and the electron beam is provided between the second and third grids. Is formed so as to be long horizontally long in the horizontal direction. However, a vertically long concave portion may be provided around the electron beam passage hole on the second grid side surface of the third grid. An electron gun formed by a second electron lens having a similar effect can be provided.

In addition, a long horizontally long recess is provided around the electron beam passage hole on the third grid side surface of the second grid, and the electron beam passage hole on the second grid side surface of the third grid is provided. The electron gun formed by the second electron lens having the same function can be obtained even if a vertically long recess is provided around the periphery.

In the above embodiment, an electron gun having a bi-potential type main lens has been described. However, the present invention can be applied to an electron gun of a uni-potential type, a tri-potential type, a quadra-potential type, etc. A color CRT having a similar effect can be configured.

The present invention can be applied to a cathode ray tube other than a color cathode ray tube.

[0039]

As described above, the drive voltage that changes in response to the video signal is applied to the first grid, and the first and second drive voltages are applied.
The first electron lens in which the horizontal focusing force on the electron beam between the grids is stronger than the vertical focusing force, and the vertical focusing force on the electron beam between the second and third grids is higher than the horizontal focusing force. When a strong second electron lens is formed, the first electron lens can make the electron beam longer vertically in the vertical direction, and the second electron lens can make the electron beam longer horizontally in the horizontal direction. Therefore, when the drive voltage increases, the voltage of the first grid approaches the second grid, weakens the first electron lens, and weakens the effect of making the electron beam longer vertically in the vertical direction. As a result, it is possible to compensate for the increase in the deflection aberration caused by the increase in the current amount of the electron beam, to make the electron beam appropriately focused, and to eliminate the halo caused by the conventional over-focusing at the periphery of the screen in the vertical direction. it can.

Conversely, when the drive voltage is reduced, the voltage difference between the first grid and the second grid is increased, the first electron lens is strengthened, and the effect of making the electron beam longer vertically in the vertical direction is enhanced. As a result, the reduction in deflection aberration due to the reduction in the amount of current of the electron beam is compensated for, and the increase in the beam spot diameter in the vertical direction caused by insufficient focusing at the peripheral portion of the conventional screen can be eliminated.

Therefore, with the above-described configuration, it is possible to optimize the focusing state at the peripheral portion of the screen over almost all drive voltages, to reduce the beam spot in the entire screen from low luminance to high luminance, and to reduce the resolution. Can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a color cathode ray tube according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an electron gun of the color cathode ray tube.

FIG. 3A is a diagram illustrating a configuration of a first grid of the electron gun, and FIG. 3B is a diagram illustrating a configuration of a second grid.

FIG. 4 is a diagram showing a configuration of a conventional electron gun of a color cathode ray tube.

5A is a diagram for explaining deflection aberration caused by a pincushion horizontal deflection magnetic field, and FIG. 5B is a diagram illustrating distortion of a beam spot due to the deflection aberration.

FIG. 6 is a diagram showing a relationship between a deflection current and a dynamic voltage applied to an electrode of a dynamic electron gun.

[Explanation of symbols]

 12 phosphor screens 21B, 21G, 21R ... electron beam passage holes 22B, 22G, 22R ... recesses 23B, 23G, 23R ... electron beam passage holes 24B, 24G, 24R ... recesses G1 ... first grid G2 ... second grid G3 ... Third grid G4 ... Fourth grid KB, KG, KR ... Cathode

Claims (5)

[Claims] An electron beam generating portion is formed by a cathode and first, second, and third grids sequentially arranged in the direction of a phosphor screen from the cathode, and the third grid and the fluorescent light are more than the third grid. A cathode ray tube having an electron gun that forms a main lens unit that focuses an electron beam from the electron beam generator on the phosphor screen by a grid disposed on a body screen side, wherein the first grid corresponds to a video signal; And a drive voltage that changes is applied to form a first electron lens between the first and second grids in which the horizontal focusing force on the electron beam is stronger than the vertical focusing force. Third
A cathode ray tube comprising a second electron lens formed between grids, the second electron lens having a stronger focusing power in the vertical direction with respect to the electron beam than a focusing power in the horizontal direction. 2. The cathode ray tube according to claim 1, wherein a long horizontally long concave portion is formed around an electron beam passage hole on a surface of the first grid on the second grid side. 3. The cathode ray tube according to claim 1, wherein a long horizontally long concave portion is formed around an electron beam passage hole on a surface of the second grid on the third grid side. 4. The cathode ray tube according to claim 1, wherein a vertically long recess is formed around an electron beam passage hole on a surface of the third grid on the second grid side. 5. An elongated horizontally long concave portion is formed around an electron beam passage hole in a surface of the second grid on a third grid side, and the recess is formed in the electron beam passage hole in a surface of the third grid on a second grid side. 3. The cathode ray tube according to claim 1, wherein a vertically long recess is formed around the periphery of the cathode ray tube.