JPH08148095A - Electron gun and color cathode-ray tube provided with this electron gun - Google Patents

Abstract

PURPOSE: To provide a color cathode-ray tube provided with an electron gun capable of obtaining good resolution in a total surface of a fluorescent material screen. CONSTITUTION: Cathodes K1 , K2 , K3 for an electron beam outgoing are arranged, to arrange against these cathodes a control electrode 10, accelerating electrode 20, focusing electrode and an anode electrode 60. The focusing electrode is constituted of the first/second/third focusing electrodes 30, 40, 50, to provide the first four-electrode lens structure in at least one of an opposed surface to the second focusing electrode 40 of the first focusing electrode 30 or of an opposed surface to the first focusing electrode of the second focusing electrode 40. The second four-electrode lens structure is provided in at least one of an opposed surface to the third focusing electrode of the second focusing electrode or of an opposed surface to the second focusing electrode of the third focusing electrode.

Description

Detailed Description 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 electron gun for improving the resolution on the entire surface of a phosphor screen and a color cathode ray tube equipped with this electron gun.

[0002]

2. Description of the Related Art The resolution of a color cathode ray tube depends on the size and shape of a beam spot on a phosphor screen.

That is, if the electron beam emitted from the electron gun impinges on the phosphor screen and emits the phosphor screen, the beam spot generated has a small diameter and is close to a perfect circle. Can be obtained.

While the electron beam emitted from the electron gun reaches the phosphor screen by being deflected horizontally and vertically while reaching the phosphor screen, the electron beam is emitted from the center of deflection in the central portion and the peripheral portion of the phosphor screen. Since the distance is different, the shape of the beam spot is deformed mainly vertically as the amount of deflection increases.

Further, in an electron gun which emits a so-called in-line array of three electron beams, since the electron beams on both sides are offset from the tube axis, the convergence is deteriorated in the peripheral portion of the phosphor screen and the resolution is lowered. Let

FIG. 3 is a schematic cross-sectional view for explaining a structural example of a color cathode ray tube to which the present invention is applied, in which 1 is a panel portion, 2 is a funnel portion, 3 is a neck portion, 4 is a phosphor screen, and 5 is a phosphor screen. Is a shadow mask which is a color selection electrode.
Further, 6 is a third electrode, 7 is a fourth electrode, 8 is a shield cup, 14 is a deflection yoke, 15, 16 and 17 are central axes of electron beams, and 18 and 19 are side electron beam passage holes of the fourth electrode 7. Is the center of.

The cathode portions K _1, K _2, K ₃ and the first electrode 10
The second electrode 20 constitutes a so-called three-pole part.

As shown in FIG. 1, the color cathode ray tube comprises a panel portion 1 and a neck portion 3 connected to a side wall portion of the panel portion 1 through a funnel 2 to form a vacuum envelope. An electron gun installed inside, a deflection yoke 14 mounted on the outer wall of the funnel portion 2 and the neck portion 3,
It comprises a phosphor screen 4 and a shadow mask 5 having a large number of apertures, which are opposed to each other at a predetermined interval.

The phosphor screen is coated with red, green, and blue phosphors in stripes or dots.

The three electron beams emitted from the electron gun are color-selected by the shadow mask 5, and each phosphor is bombarded to emit light.

The electron gun is a cathode part K _1, K _2, K _{3 of} an electron beam generator for generating, accelerating and controlling three parallel in-line electron beams and a prefocus lens part for controlling the electron beam. And a main lens portion for focusing the electron beam on the phosphor screen 4, and these three electron beams are deflected and scanned by the deflection yoke 14 over the entire surface of the phosphor screen 4 to form a two-dimensional raster.

The configuration shown in the figure is an example, and in addition to this, the number of first electrodes, second electrodes, ... Constituting the electron gun and the shape and configuration of the electron beam passage hole of each electrode are various. Things are known.

FIG. 4 is an explanatory view of the deflection magnetic field acting on the electron beam generated by the deflection yoke. The deflection magnetic field generated by the deflection yoke is pincushion-shaped 14 _H for horizontal deflection as shown in FIG. , Vertical deflection has barrel-like strain of 14 _V.

FIG. 5 is an explanatory view of the deflection action of the electron beam by the deflection magnetic field and its spot shape distortion. The electron beam B deflected and scanned around the phosphor screen is as shown in FIG. in addition to acting F _h for deflecting the electron beam, the divergence f _h in the horizontal direction as shown in FIG. (b), receives a focusing f _v in the vertical direction, it will form the spot of distorted shape.

FIG. 6 is an explanatory view of the beam spot shape on the phosphor screen. While the beam spot 00 in the central portion of the phosphor screen 3 is circular, it is generated in the peripheral portion of the phosphor screen. The beam spot is distorted into a non-circular shape composed of a high brightness core portion BC and a halo portion BH,
In particular, a large vertical expansion of the halo portion BH adversely affects the focus characteristics.

In order to prevent the deterioration of the focus characteristic, for example, a technique disclosed in Japanese Patent Laid-Open No. 62-58549 can be cited.

FIG. 7 is a sectional view for explaining the structure of the electron gun disclosed in the above-mentioned prior art, in which K ₁ , K ₂ , and K ₃ are cathodes, 10 is a control electrode, 20 is an acceleration electrode, and 30 is a first electrode. 1 focusing electrode, 40 a 2nd focusing electrode, 48 a rim electrode, 50 a 3rd focusing electrode, 60 an anode, 11, 12, 13, 2
1, 22, 23, 31, 32, 33, 41a, 42a,
43a, 41b, 42b, 43b, 51a, 52a, 5
Reference numerals 3a, 51b, 52b, 53b, 61, 62 and 63 denote electron beam passage holes, 44, 45, 46,
Reference numeral 47 is a vertical plate, and 54 (55) is a horizontal plate.

C is the electron gun axis (coincident with the tube axis), S ₁
Is the off-axis distance of the side electron beam from the electron gun axis C, S2
Indicates the off-axis distance of the side electron beam passage holes 61, 63 of the anode 60 from the electron gun axis C.

FIG. 8 is a plan view of the accelerating electrode viewed from the arrow A in FIG. 7, FIG. 9 is a plan view of the second focusing electrode viewed from the arrow B, and FIG. 10 is a third focusing electrode viewed from the arrow C. FIG.

As shown in FIG. 8, the accelerating electrode 20 has three circular electron beam passage holes 21, 22 and 23 on the side of the first focusing electrode 30 and a slit hole 2 long in the electron beam arrangement direction.
4, 25, 26 are formed.

As shown in FIG. 9, the second focusing electrode 40 has a circular electron beam passage hole 4 on the side of the third focusing electrode 50.
Four parallel plates 4 having 1b, 42b and 43b, which are vertically erected in the direction of the third electrode 50, sandwiching these electron beam passage holes from the horizontal direction, facing the third focusing electrode 50.
It has a first plate electrode (vertical plate) composed of 4, 45, 46 and 47.

And surrounding the first plate electrode, and
The rim electrode 48 extends from the tips 44a, 45a, 46a, 47a of the parallel plate to the third focusing electrode 50 side to a certain distance.

As shown in FIG. 10, the third electrode 5
Reference numeral 0 has three circular electron beam passage holes 51a, 52a, 53a on the end face of the second focusing electrode 40, and the electron beam passage holes are sandwiched from the vertical direction in the horizontal direction in the direction of the second focusing electrode 40. It has a second flat plate electrode (horizontal plate) composed of a pair of upright parallel plates 54, 55. The tip portion 54a (5) of the parallel plate that constitutes the second plate electrode is
5a) is extended into the rim electrode 48 of the second focusing electrode 40, and the front end portion 44 of the parallel plate of the second focusing electrode 40 is formed.
a, 45a, 46a, 47a are installed at a constant interval L in the axial direction of the electron gun.

Further, three circular electron beam passage holes 61, 62, 63 are provided on the end face on the anode 60 side,
The off-axis distance S ₂ of the side electron beam passage holes 61, 63 from the electron gun axis is K ₁ , K ₂ , K ₃ , which are the pre-stage electrodes, the control electrode 10, the acceleration electrode 20, the second focusing electrode 40, and the third focusing electrode 40. The second focusing electrode 50 has a relationship of S ₂ > S _{1 with} respect to the off-axis distance S ₁ of the side electron beam passage hole of the focusing electrode 50.
A main lens is formed between the anode 60 and the anode 60 to concentrate the side electron beams SB ₁ and SB ₂ on the phosphor screen surface.

The voltage applied to each electrode during operation is 50 to 170 V at the cathodes K ₁ , K ₂ and K ₃ and 0 at the control electrode 10.
V, 400 to 800 V for the acceleration electrode 20, the second focusing electrode 4
The applied voltage Vf to 0 is 5 to 8 kV and the voltage (anode voltage) Eb to the anode 60 is 25 kV. The first focusing electrode 30 and the third focusing electrode 50 are synchronized with the vertical and horizontal deflection of the electron beam. A changing dynamic voltage DVf is applied.

When the deflection amount of the electron beam is 0, there is no potential difference between the first focusing electrode 30, the second focusing electrode 40, and the third focusing electrode 50, so that the parallel flat plate (vertical plate) inside the second focusing electrode 40. ) 44, 45, 46, 47 and the parallel plates (horizontal plates) 54, 55 attached to the third focusing electrode 50 have no influence, and the electron beam arrangement direction is long on the first focusing electrode 30 side of the acceleration electrode 20. Although the electron beam becomes horizontally long due to the quadrupole lens action by the slit holes 24, 25, 26,
The main lens between the third focusing electrode 50 and the anode 60 concentrates the light on the phosphor screen with optimum focus.

FIG. 11 is an explanatory diagram of an electron beam bundle emitted from the acceleration electrode 20 under the above operating voltage conditions, and FIG. 12 is a schematic diagram electron-optically expressing the electron beam trajectory.

As shown in FIG. 11, the shape of the beam spot on the phosphor screen is such that the electron beam emitted from the slit holes 24, 25 and 26 of the accelerating electrode 20 receives a strong focusing action in the vertical direction. Becomes landscape. The current density at that time is composed of an H part having a high central part and an L part having a low current density on both sides thereof.

As shown in FIG. 12, the electron trajectory when the deflection amount of the electron beam is 0 is overfocused in the horizontal direction P _h and underfocused in the vertical direction P _v due to the influence of spherical aberration, and the phosphor screen is displayed. Part of the illustrated W
The focus voltage is adjusted within the range.

At this time, the shape of the beam spot on the phosphor screen is a vertically long shape of the H portion having a high current density.

FIG. 13 shows parallel plates (vertical plates) 44, 45, 46, 47 inside the second focusing electrode 40 and the third focusing electrode 50.
Of the parallel plates (horizontal plate) 54, 55 attached to the beam spot, and FIG. 14 shows the parallel plates (horizontal plate) 5 attached to the third focusing electrode 50.
It is explanatory drawing of the influence on the beam spot by 4,55.

When the deflection amount of the electron beam is increased, the potentials of the first focusing electrode 30 and the third focusing electrode 50 become higher than that of the second focusing electrode 40. Therefore, as shown in FIG. Parallel plate (vertical plate) (44), 45, 46,
In (47), a lens having a strong focusing action (F _v <F _h ) in the horizontal direction and the parallel flat plates (horizontal plates) 54 and 55 attached to the third focusing electrode 50 are used to move in the vertical direction as shown in FIG. A quadrupole lens electric field having a strong diverging lens action F _vv is formed to shape the electron beam in a vertically long shape, and the potential difference between the third focusing electrode 50 and the anode is reduced, so that the focusing action by the main lens is weakened and the phosphor screen is reduced. Focus on the best focus around the area.

However, since the action of the quadrupole lens acts in the direction of canceling the action on the electron beam due to the magnetic deflection aberration, it is concentrated at the optimum focus on the screen screen, but it is formed by the third focusing electrode 50 and the anode 60. Since the angle of incidence on the main lens and the beam diameter are horizontal and vertical, the lens magnification in the main lens is horizontal and vertical, and therefore the beam spot shape cannot be close to a circle.

FIG. 15 shows second and third electron beam trajectories when the electron beam is horizontally deflected and replaced with an optical system.
It is an explanatory view of a quadrupole lens action by a focusing electrode,
(A) is a horizontal sectional view, (b) is a vertical sectional view, 70 is an electron beam crossover portion corresponding to an object point of a lens system, 72 is a second focusing electrode and a third focusing electrode A convex lens showing the focusing action of the quadrupole lens electric field in the horizontal direction generated between and, 73 a main lens, 74 a concave lens showing a horizontal diverging action by the deflection magnetic field, 75 a phosphor screen portion, and 76 an electron A beam orbit, 78 is a concave lens which also exhibits a diverging action in the vertical direction, 79 is a convex lens which shows a focusing action in the vertical direction by the same magnetic field, and 80 is a projecting point on the phosphor screen.

As shown in the figure, when the optical system is replaced by an optical system in which convex and concave lenses are arranged in the horizontal and vertical directions from the object point 70 side, when the horizontal and vertical directions are optimally focused, the horizontal and vertical directions are changed. The incident angle at which the phosphor screen 75 impinges has a relationship of αH <αV.

Generally, the magnification M of the electron lens system is 7
Assuming that the incident angle from the 0 side to the projection point 80 on the phosphor screen through the lens system at the exit angle α is α ′ and the potentials of the object point 70 and the phosphor screen are V and V ′, M = (α /
α ′) √ (V / V ′), and the horizontal magnification MH of the lens system is MH = (α / αH ′) √
(V / V ′), the magnification MV in the vertical direction is MV = (α /
It can be represented by αV ′) √ (V / V ′).

Then, as described above, the phosphor screen 7
Since the incident angle of incidence on 5 is αH <αV, the lens magnification is MV <MH, and the beam spot diameter is small at the vertical diameter where the lens magnification is small.

In order to correct the lens magnification in the horizontal direction and the vertical direction, slit holes 24, 25, 26 of the acceleration electrode 20 are provided as shown in FIG.

16A and 16B are explanatory views in which the correction of the lens magnification in the horizontal direction and the vertical direction by the slit hole of the accelerating electrode is replaced by an optical system. FIG. 16A is a horizontal section, and FIG. 16B is a vertical section. FIG.

As shown in FIG. 16, the quadrupole lens electric field generated by the slit hole of the acceleration electrode becomes a convex lens 71 having a weak focusing action in the horizontal direction and a convex lens 77 having a strong focusing action in the vertical direction.

The electron beam emitted from the object point 70 at an angle α has convex lenses 71 and 7 which are weak in the horizontal direction with respect to the vertical direction.
Since 7 incidents, the exit angle α'is close to α in the horizontal direction.
It becomes H, and the emission angle becomes α′V smaller than α in the vertical direction. At this time, the object point position seen from the object point electron beam passing through the convex lenses 71 and 77 is generally behind the object point 70. However, since the acceleration electrode is on the crossover, this deviation amount is small and can be ignored. is there.

The quadrupole lens electric fields (convex lenses) 71 and 77 generated by the slit holes of the accelerating electrode narrow the emission angle of the electron beam in the vertical direction with respect to the horizontal direction, and as a result, the fluorescence passes through the electron lens system. The vertical incident angle α′V of the electron beam incident on the projecting point 80 of the body screen does not become larger than the horizontal incident angle α′H, and α′V≈α′H can be obtained.
That is, the lens magnifications in the vertical direction and the horizontal direction can be set to MV≈MH.

From the above, optimum focus characteristics can be obtained over the entire phosphor screen.

[0044]

In the above-mentioned prior art, when the deflection amount of the electron beam is 0, the quadrupole lens by the slit hole of the acceleration electrode acts to make the electron beam laterally elongated and the phosphor screen. The upper beam spot shape has a vertically long beam shape on the phosphor screen due to the relationship with the current density distribution described above, and the electron beam is thickened by correcting the focal length difference in the horizontal and vertical directions. Resolution deterioration is likely to occur.

Moreover, since the current density distribution of the electron beam is high in the central part and low on both sides, it is possible to deviate from the current density distribution due to the accuracy of the electron gun.
If this electron beam is deflected to the screen edge of the phosphor screen, the portion having a low current density is further biased by the deflection magnetic field, and there is a problem that the image quality is deteriorated.

An object of the present invention is to solve the above problems of the prior art and to provide a color cathode ray tube equipped with an electron gun capable of obtaining a good resolution on the entire surface of the phosphor screen.

[0047]

In order to achieve the above object, the present invention provides a quadrupole lens structure in an electrode system constituting an electron gun, and provides a quadrupole lens structure between the first focusing electrode and the second focusing electrode. This is achieved by providing an electrode structure of a quadrupole lens function, which has a diverging action in the horizontal direction and a focusing action in the vertical direction on either side.

That is, in the first aspect of the present invention, a cathode for emitting an electron beam and at least a control electrode, an accelerating electrode, a focusing electrode, and an anode electrode are arranged in this order with respect to the cathode. In an electron gun arranged in one or more sets in the axial direction, when the focusing electrode is composed of a first focusing electrode, a second focusing electrode and a third focusing electrode, the first focusing electrode faces the second focusing electrode. At least one of the surface or the surface of the second focusing electrode facing the first focusing electrode is provided with the electrode structure having the first quadrupole lens action, and the surface of the second focusing electrode facing the third focusing electrode, or the third surface. At least one of the surfaces of the focusing electrode facing the second focusing electrode is provided with a second quadrupole lens action electrode structure.

In the second aspect of the present invention, a cathode for emitting an electron beam and at least a control electrode, an accelerating electrode, a focusing electrode, and an anode electrode are arranged in this order with respect to the cathode. In a color cathode ray tube including an electron gun arranged in one or more sets in the axial direction, when the focusing electrode of the electron gun includes a first focusing electrode, a second focusing electrode, and a third focusing electrode, At least one of the surface of the focusing electrode facing the second focusing electrode and the surface of the second focusing electrode facing the first focusing electrode is provided with the first quadrupole lens action electrode structure, and the second focusing electrode is At least one of the surface facing the focusing electrode and the surface facing the second focusing electrode of the third focusing electrode is provided with a second quadrupole lens action electrode structure, and the first focusing electrode and the third focusing electrode forming the focusing electrode are provided. The second focusing electrode is deflected by the electron beam The electron beam is made horizontally long by the first quadrupole lens and the electron beam is made vertically long by the second quadrupole lens by applying a focusing voltage that changes to a value higher than the voltage applied to the bundle electrode. And

[0050]

According to the structure of the present invention, the electron beam emitted from the cathode when the deflection amount of the electron beam is 0 has the same lens magnification in the horizontal direction and the vertical direction in the main lens between the third focusing electrode and the anode. Therefore, the electron beam spot can be made substantially circular and small.

When the deflection amount of the electron beam is increased, the first
The electron beam becomes horizontally long due to the quadrupole lens action having a horizontal diverging action between the focusing electrode and the second focusing electrode and a vertical focusing action, and the vertical diverging action by the second focusing electrode and the third focusing electrode. Is corrected by the quadrupole lens having a focusing function in the horizontal direction.

Further, since the correction amount changes depending on the deflection amount of the electron beam, the lens magnification can be appropriately corrected, and the current density distribution of the laterally long electron beam flux is almost uniform unlike the acceleration electrode. This reduces the amount of halo deviation due to the assembly accuracy of the electron gun.

[0053]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a sectional view for explaining the structure of one embodiment of an electron gun for a color cathode ray tube according to the present invention.

FIG. 2A is a front view of the first focusing plate electrode viewed from the direction of arrow A in FIG. 1, and FIG. 2B is an explanatory view of the action on the electron beam.

In FIGS. 1 and 2, K ₁ , K ₂ and K ₃ are cathodes, 10 are control electrodes, 20 is an acceleration electrode, 30 is a first focusing electrode, 35 is a first focusing flat plate electrode, and 40 is a second focusing electrode. Focusing electrode, 48 is a rim electrode, 50 is a third focusing electrode, 60 is an anode, 11, 12, 13, 21, 22, 23, 31a, 3
2a, 33a, 31b, 32b, 33b, 41a, 42
a, 43a, 41b, 42b, 43b, 51a, 52
a, 53a, 51b, 52b, 53b, 61, 62, 6
3 is each electron beam passage hole, 36, 37, 38 are vertically long rectangular holes, 44, 45, 46, 47 are vertical plates, 54
(55) indicates a horizontal plate.

C is the electron gun axis (matches the tube axis), S ₁
Is the off-axis distance of the side electron beam from the electron gun axis C, S2
Indicates the off-axis distance of the side electron beam passage holes 61, 63 of the anode 60 from the electron gun axis C.

The first focusing electrode 30 includes 31a, 32a, 33.
It has circular beam passage holes a, 31b, 32b and 33b. The first focusing plate electrode 35 has vertically elongated rectangular holes 36, 37, 38, and is electrically connected to the first focusing plate electrode 35.

Further, the second focusing electrode 40 is the third focusing electrode 5
Three circular electron beam passage holes 41b, 4 are formed on the end face on the 0 side.
Four parallel plates 44, 45, 46, 47 vertically set on the third focusing electrode 50 with 2b and 43b sandwiched in the horizontal direction.
It has a first plate electrode (vertical plate) consisting of. The third focusing electrode 5 is surrounded by the tips 44a, 45a, 46a, 47a of the parallel plate surrounding the first plate electrode.
It has a rim electrode 48 extended to a certain distance on the 0 side.

The third electrode 50 has three circular electron beam passage holes 51a, 52a, 53a on the end face of the second focusing electrode 40.
And a second flat plate electrode (horizontal plate) composed of a pair of parallel flat plates 54, 55 vertically erected in the direction of the first focusing electrode 40 with the electron beam passage hole interposed therebetween from the vertical direction. ing.

The front end portions 54a, 55a of the parallel flat plates 54, 55 constituting the second flat plate electrode extend to the inside of the rim electrode 48 of the second focus electrode 40, and the parallel flat plate of the second focus electrode 40 is formed. Tip portions 44a, 45a, 46a, 4 of the
7a are installed at a constant interval L in the axial direction of the electron gun.

Further, three circular electron beam passage holes 61, 62, 63 are provided on the end face on the anode 60 side,
Off-axis distance S ₂ from the electron gun axis of the side electron beam passage hole
Are the front electrodes K ₁ , K ₂ , and K ₃ , the control electrode 10,
Accelerating electrode 20, the second focusing electrode 40, S ₂ with respect to off-axis distance S ₁ of the side electron beam passage apertures of the third focus electrode 50>
The relationship of S ₁ is established, and the third focusing electrode 50 and the anode 60
A main lens is formed between the side electron beam S and
B ₁ and SB ₂ are concentrated on the phosphor screen surface.

The voltage applied to each electrode during operation is 50 to 170 V for the cathode, 0 V for the control voltage, and 400 to 400 V for the accelerating electrode.
800V, 5 as applied voltage Vf to the second focusing electrode 40
˜8 kV, anode voltage Eb is 25 kV, first focusing electrode 30, first focusing plate electrode 35, third focusing electrode 50
Is applied with a dynamic voltage DVf that changes in synchronization with vertical and horizontal changes of the electron beam.

When the deflection amount of the electron beam is 0, there is no potential difference between the first focusing electrode 30, the first focusing plate electrode 35, the second focusing electrode 40, and the third focusing electrode 50, and thus the first focusing plate electrode. Vertical rectangular holes 36, 37, 38 of 35 and parallel plates (vertical plate) 44, 45, 46, 4 inside the second focusing electrode 40.
7 and the parallel flat plates (horizontal plates) 54 and 55 attached to the third focusing electrode 50 have no influence, and the electron beam from the cathode is a phosphor by the main lens between the third focusing electrode 50 and the anode 60. The screen is circular and has a small beam spot shape.

When the deflection amount of the electron beam is increased, the potentials of the first focusing electrode 30, the first focusing plate electrode 35 and the third focusing electrode 50 become higher than that of the second focusing electrode. 2 through the slit holes 36, 37 and 38 of FIG.
As shown in (b), a vertically long divergence lens is formed, and the electron beam has a strong divergence action (F
The electron beam becomes horizontally long due to h> Fv).

Further, the parallel flat plates (vertical plates) 44, 45, 46, 47 inside the second focusing electrode 40 and the third focusing electrode 50.
The quadrupole lens electric field is formed by the parallel flat plates (horizontal plates) 54 and 55 attached to the first plate, and the potential difference between the third focusing electrode 50 and the anode 60 is reduced to weaken the focusing action of the main lens.

Since the laterally long electron beam formed by the quadrupole lens of the first focusing plate electrode 35 and the second focusing electrode 40 has a quadrupole lens aperture larger than the electron beam bundle, the current density distribution becomes uniform. . Further, the laterally long electron beam causes the correction of the unbalance of the lens magnification between the second focusing electrode 40 and the third focusing electrode 50 and between the third focusing electrode 50 and the anode 60 in the same manner as in the conventional case.

As described above, according to this embodiment, good resolution can be obtained on the entire surface of the phosphor screen.

[0069]

As described above, according to the present invention,
The electron beam emitted from the cathode when the deflection amount of the electron beam is 0 can make the lens magnification in the horizontal direction and the vertical direction of the main lens between the third focusing electrode and the anode the same. It becomes a perfect circle and becomes smaller.

When the deflection amount of the electron beam is increased, the first
The electron beam becomes horizontally long due to the quadrupole lens effect having a horizontal divergence action between the focusing electrode and the second focusing electrode and a vertical focusing action, and the electron beam becomes laterally long between the second focusing electrode and the third focusing electrode. A quadrupole lens having a diverging action and a focusing action in the horizontal direction is used to correct the imbalance between the vertical and horizontal lens magnifications.

As a result, a good resolution can be obtained from high luminance to low luminance over the entire phosphor screen surface.

[Brief description of drawings]

FIG. 1 is a sectional view illustrating the configuration of an embodiment of an electron gun for a color cathode ray tube according to the present invention.

2A and 2B are a front view of a first focusing plate electrode viewed from the direction of arrow A in FIG. 1 and an explanatory view of its action on an electron beam.

FIG. 3 is a schematic cross-sectional view illustrating a structural example of a color cathode ray tube to which the present invention is applied.

FIG. 4 is an explanatory diagram of a deflection magnetic field that acts on an electron beam generated by a deflection yoke.

FIG. 5 is an explanatory diagram of the deflection action of an electron beam by a deflection magnetic field and its spot shape distortion.

FIG. 6 is an explanatory diagram of a beam spot shape on a phosphor screen.

FIG. 7 is a cross-sectional view illustrating the configuration of a conventional electron gun.

8 is a plan view of the accelerating electrode viewed from an arrow A in FIG.

9 is a plan view of the second focusing electrode viewed from the arrow B in FIG. 7. FIG.

10 is a plan view of the third focusing electrode viewed from the arrow C in FIG. 7. FIG.

FIG. 11 is an explanatory diagram of a beam spot shape on the phosphor screen under the operating voltage condition of FIG. 7.

FIG. 12 is a schematic diagram in which the action of the deflection magnetic field of the beam on the phosphor screen is electro-optically expressed.

FIG. 13 is an explanatory view of the influence on the beam spot by a parallel plate (vertical plate) inside the second focusing electrode and a parallel plate (horizontal plate) attached to the third focusing electrode.

FIG. 14 is an explanatory diagram of an influence on a beam spot by a parallel plate (horizontal plate) attached to a third focusing electrode.

FIG. 15 is an explanatory diagram in which an electron beam orbit when the electron beam is horizontally deflected is replaced with an optical system.

FIG. 16 is an explanatory diagram in which the correction of the lens magnification in the horizontal direction and the vertical direction by the slit hole of the acceleration electrode is replaced with an optical system.

[Explanation of symbols]

K ₁ , K ₂ , K ₃ cathode 10 control electrode 20 acceleration electrode 30 first focusing electrode 35 first focusing flat plate electrode 40 second focusing electrode 48 rim electrode 50 third focusing electrode 60 anode 11, 12, 13, 21, 22, 22 , 23, 31a, 32
a, 33a, 31b, 32b, 33b, 41a, 42
a, 43a, 41b, 42b, 43b, 51a, 52
a, 53a, 51b, 52b, 53b, 61, 62, 6
3 Electron beam passage hole 36, 37, 38 Vertically long rectangular hole 44, 45, 46, 47 Vertical plate 54 (55) Horizontal plate.

Claims (2)

[Claims] 1. An electron gun comprising a cathode for emitting an electron beam, and at least one set of a control electrode, an acceleration electrode, a focusing electrode and an anode electrode arranged in this order in the tube axis direction with respect to the cathode. In the above, when the focusing electrode is composed of a first focusing electrode, a second focusing electrode, and a third focusing electrode, a surface of the first focusing electrode facing the second focusing electrode, or a first focusing electrode of the second focusing electrode At least one of the facing surfaces of the second focusing electrode and the facing surface of the second focusing electrode facing the third focusing electrode, or the facing surface of the third focusing electrode facing the second focusing electrode. An electron gun comprising at least one electrode structure having a second quadrupole lens action. 2. An electron gun comprising a cathode for emitting an electron beam, and at least one set of a control electrode, an acceleration electrode, a focusing electrode and an anode electrode arranged in this order in the tube axis direction with respect to the cathode. A color cathode ray tube comprising: a first focusing electrode, a second focusing electrode, and a third focusing electrode, wherein the focusing electrode of the electron gun is a surface facing the second focusing electrode of the first focusing electrode; Alternatively, at least one of the surfaces of the second focusing electrode facing the first focusing electrode is provided with an electrode structure having a first quadrupole lens action, and the surface of the second focusing electrode facing the third focusing electrode, or the third focusing electrode. A second quadrupole lens action electrode structure on at least one of the surfaces of the second focusing electrode facing the second focusing electrode, and the second focusing with the deflection of the electron beam on the first focusing electrode and the third focusing electrode which constitute the focusing electrode. Value higher than the voltage applied to the electrodes Wherein the first quadrupole lens of the electron beam horizontally long, the color cathode ray tube, characterized in that the electron beam vertically long shape by the second quadrupole lens by applying a focusing voltage varying.