JPH08329854A - Color cathode-ray tube - Google Patents

Abstract

PURPOSE: To enhance the resolution in the peripheral zone of a screen with a low dynamic focus voltage using one convergence lens by forming a main lens for focusing electron beam from four electrodes installed in line, and impressing the requisite focusing voltage on the electrodes. CONSTITUTION: A main lens for focusing electron beam of a color cathode-ray tube is formed from G3-G6 electrodes 11-14 installed in line, and an accelerating voltage of potential Eb is impressed on the electrode 14. One voltage Vf on which a voltage Vd varying with increasing deflection amount of electron beam is superposed, is impressed as a focusing voltage on the electrodes 11, 13. The electrodes 11-13 constitute an asymmetric lens whose horizontal direction focusing force is stronger than the vertical direction and whose lens power can be heightened with increasing deflection amount of the electron beam, and the electrodes 13, 14 constitute a final stage lens which elongates the section shape of the electron beam in the horizontal direction. Thereby the resolution in the peripheral zone of the screen can be enhanced with a low dynamic focus voltage using one convergence lens.

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 a color cathode ray tube capable of obtaining a good resolution over the entire screen.

[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. 7 is a horizontal sectional view schematically showing the structure of a color cathode ray tube equipped with an electron gun having a conventional structure. 1 is a glass envelope, 2 is a face plate portion, 3 is a fluorescent screen,
4 is a shadow mask, 5 is a conductive film, 6, 7 and 8 are cathodes,
9 is a first electrode (G1 electrode), 10 is a second electrode (G2 electrode), 11 is a third electrode (G3 electrode), 12 is a fourth electrode (G4 electrode), 13 is a fifth electrode (G5 electrode), 14 is a sixth electrode (G6 electrode), 15 is a shield cup, 16, 17,
Reference numeral 18 is a central axis of the cathodes 6, 7 and 8, 19, 20 is a central axis of the outer electron beam passage hole of the G6 electrode 14, 21 is a deflection yoke, and 22 is a stem pin.

In the figure, a phosphor screen 3 coated with phosphors of three colors alternately in stripes is supported on the inner wall of the face plate portion 2 of the glass envelope 1.

The central axes 16, 1 of the cathodes 6, 7, 8
Reference numerals 7 and 18 denote the G1 electrode 9, the G2 electrode 10, the G3 electrode 11, the G4 electrode 12, the G5 electrode 13, and the cathodes 6 and 7 of the shield cup 15, which form the main lens for focusing the electron beam on the fluorescent screen. , 8 corresponding to the central axes of the openings (electron beam passage holes) corresponding to the holes 8 and 8 and arranged substantially parallel to each other on a common horizontal plane.

However, although the central axis of the electron beam passage hole at the center of the G6 electrode 14 coincides with the central axis 17,
The center axes 19 and 20 of the outer electron beam passage holes do not coincide with the corresponding center axes 16 and 18, and are slightly displaced outward.

The three electron beams emitted from the respective cathodes 6, 7, and 8 are incident on the main lens along the central axes 16, 17, and 18.

The G3 electrode 11 and the G5 electrode 13 have 5 to 1
A focusing voltage of about 0 kV is supplied from a focusing power source (not shown) through the stem pin 22.

An acceleration voltage of about 25 to 35 kV is applied to the G6 electrode 14, which is applied to the shield cup 15 and the inner wall of the glass envelope 1 to have the same potential as the conductive film 5.

Since the electron beam passage holes in the central portions of the G5 electrode 13 and the G6 electrode 14 are coaxial, the lens formed in the central portion is axisymmetric, and the electron beam emitted from the cathode 7 is this lens. After being focused by, it travels straight along an orbit along the tube axis.

On the other hand, the electron beam passage holes on the outside of the G5 electrode 13 and the G6 electrode 14 have their central axes displaced from each other,
A non-axisymmetric lens is formed in the electron beam passage hole on the outside. Therefore, the electron beams emitted from the cathodes 6 and 8 on both sides of the electron beam emitted from the cathodes 6 and 8 on the both sides of the lens center axis in the divergent lens region formed on the G6 electrode 14 side among the lens regions formed between the G5 electrode 13 and the G6 electrode 14. It passes through a portion deviated from, and receives a focusing force in the direction of the central axis 17 at the same time as the focusing action by the lens.

Thus, the three electron beams form an image on the shadow mask 5 and, at the same time, are concentrated so as to overlap each other. The operation of concentrating each electron beam in this way is called static convergence (hereinafter abbreviated as STC).

Further, each electron beam has a shadow mask 4
Thus, only the component that excites and emits the phosphor of the color corresponding to each electron beam reaches the phosphor screen 3 through the opening of the shadow mask.

A deflection yoke 21 is mounted outside the glass envelope in order to scan the fluorescent screen 3 with an electron beam.

As described above, by combining an in-line electron gun having three electron beam paths arranged on one horizontal plane with a so-called self-convergence deflection yoke that forms a special non-uniform magnetic field distribution, S in the center
It is known that if TC is obtained, it is possible to obtain convergence over the entire screen.

However, in general, the self-convergence deflection yoke has a problem that the deflection aberration is large due to the inhomogeneity of the magnetic field formed and the resolution is lowered in the peripheral portion of the screen.

That is, the cross-sectional shape (beam spot shape) of the electron beam on the phosphor screen 3 is distorted due to the deflection by the deflection yoke 21.

FIG. 8 is a conceptual diagram for explaining the shape of the electron beam spot at each position on the phosphor screen in a color cathode ray tube equipped with a conventional electron gun. 3 is the phosphor screen, 3a is the central part of the screen. 3 is a beam spot in the peripheral portion of the screen, 3c is a beam spot in the peripheral portion of the screen in the horizontal direction, c is a core portion of the beam spot, and h is a halo portion of the beam spot. In addition, XX shows a horizontal direction and YY shows a vertical direction.

In the figure, the beam spot 3a, which is almost a perfect circle at the center of the screen, is shown by the hatched electron beam as shown in the beam spots 3b at the corners of the screen and the beam spots 3c at the peripheral portion in the horizontal direction. Core c (high brightness part)
Spread in the horizontal direction (X direction), and h
Since the (low-brightness portion) has a shape that extends in the vertical direction, the resolution in the peripheral portion of the screen is significantly reduced.

The reduction in resolution due to such deflection aberration can be mitigated by reducing the cross-sectional diameter of the electron beam passing through the final stage lens and the deflection magnetic field. For that purpose, in general, a method of strongly focusing the electron beam by the lens in the previous stage is adopted, but in such a case, the beam spot diameter at the center of the screen becomes large. That is, there is a drawback that the resolution at the center of the screen is reduced.

One means for solving this problem is disclosed in JP-A-2-72546.

FIG. 9 is a sectional view taken along the central electron beam showing an example of a conventional electron gun for a cathode ray tube having a structure for reducing the reduction in resolution. The same reference numerals as those in FIG. 7 denote the same parts. Correspondingly, 131 and 132 are a first member and a second member that constitute the fifth electrode (G5 electrode) 13 divided into two, 131a is an electrode plate installed inside the electrode of the first member,
Reference numeral 132a is a flat plate-shaped electrode provided so as to extend from the second member toward the first member.

The G5 electrode 13, which is one of the electrodes forming the lens at the final stage, is divided into two parts, a first member 131 and a second member 132, from the cathode 7 toward the phosphor screen. Second member 132
A pair of flat plate-shaped electrodes 132a are provided above and below the electron beam passage hole on the end face of the first member 131,
The member 131 extends to the inside of the first member 131 through a single opening provided on the end surface of the member 131 facing the second member 132.

Inside the first member 131, an electrode plate 131a provided with an electron beam passage hole is provided with a plate electrode 132a.
It is arranged at a constant distance from a.

The second member 132 has a voltage that dynamically changes in synchronization with the deflection current supplied to the deflection yoke.
That is, the dynamic focus voltage Vd is applied by being superimposed on the second focusing voltage Vf2.

Vf1 is the first focusing voltage, Ec2 is a fixed voltage applied to the G2 electrode 10 and the G4 electrode 12, and Ec2 is
b is an anode voltage (accelerating voltage: maximum voltage).

In the structure shown in the figure, when the deflection amount of the electron beam is large, the potential difference between the first member 131 and the second member 132 becomes large, so that the non-axisymmetric quadrupole lens formed by the plate electrode 132a is used. The effect becomes stronger, and a large astigmatism occurs in the electron beam passing between the flat electrodes.

If the potential of the second member 132 constituting the G5 electrode 13 is higher than the potential of the first member 131, the astigmatism produced in the electron beam will make the core c longer in the vertical direction and the halo h.
Is extended in the horizontal direction, the astigmatism associated with the electron beam deflection described in FIG. 7 can be canceled and the resolution at the peripheral portion of the screen can be improved.

On the other hand, when the electron beam is not deflected, it is possible to eliminate the potential difference between the first member 131 and the second member 132 and not form a non-axisymmetric lens, so that the resolution of the central portion of the screen deteriorates. Absent.

Further, in the color picture tube, the distance from the lens at the final stage to the peripheral portion of the screen is longer than the distance to the central portion of the screen. Therefore, the focusing condition of the electron beam differs between the central portion of the screen and the peripheral portion. . Therefore, under the condition that the electron beam is focused on the fluorescent screen in the central part of the screen, the electron beam cannot be focused on the fluorescent screen in the peripheral part of the screen and the resolution is lowered. This is called field curvature aberration.

However, in the electron gun according to the conventional example shown in FIG. 9, when the electron beam is deflected to the periphery of the screen, the potential of the second member 132 is increased, so that the acceleration voltage Eb applied to the G6 electrode 14 The voltage difference is reduced.

Therefore, the lens strength of the lens at the final stage formed between the G6 electrode 14 and the second member 132 of the G5 electrode 13 is weakened, the electron beam focusing point is extended in the fluorescent screen direction, and the peripheral portion of the screen is displayed. However, the electron beam can be focused on the fluorescent screen.

However, in this electron gun, as a focusing power source,
It is necessary to provide two of a constant focusing voltage Vf1 and a focusing voltage (Vf2 + Vd) that changes in synchronization with the deflection.

In general, the focusing voltage is relatively high, about 5 kV to 10 kV, so that conventionally, only one focusing voltage can be supplied from the socket connected to the stem pin 22.

In the above-mentioned conventional example, since it is necessary to supply two focusing voltages from the socket, special measures are required to prevent discharge at the socket. Furthermore, the need for two focusing power supplies makes them incompatible with conventional picture tubes.

On the other hand, as another means for solving the above problem, the one disclosed in Japanese Patent Laid-Open No. 64-38947 is known.

FIG. 10 is a schematic diagram for explaining the structure of a conventional electron gun in which compatibility is maintained by generating two focusing voltages in the cathode ray tube, and 14b and 14c are intermediate electrodes, and 23. Is a resistor, and the same symbols as in FIG. 8 correspond to the same parts.

In the figure, the second electrode means for focusing the electron beam on the fluorescent screen is G3 electrodes 11, G4.
A voltage obtained by dividing the acceleration voltage Eb applied to the G6 electrode 14 into a predetermined value by the electrode 12, the G5 electrode 13, the G6 electrode 14, and the resistor 22 arranged in the glass envelope and near the electron gun is supplied. It is composed of a plurality of intermediate electrodes 14b and 14c.

The plurality of intermediate electrodes 14b and 14c are G6.
It is arranged between the electrode 14 and the G5 electrode 13, and each intermediate electrode is provided with a circular electron beam passage hole corresponding to each electron beam.

The electron beam passage hole provided on the end face of the G5 electrode 13 facing the intermediate electrode 14b has an oval shape having a major axis in the horizontal direction, and the end face of the G6 electrode 14 facing the intermediate electrode 14b. The aperture of the electron beam passage hole provided in is also an ellipse having a major axis in the horizontal direction.

Further, a voltage Vd that rises in synchronization with the deflection amount of the electron beam is applied to the G3 electrode 11 and the G5 electrode 13 so as to be superimposed on the focusing voltage Vf.

Further, the lens at the final stage formed between the G5 electrode 13 and the G6 electrode 14 is the intermediate electrode 14b, 1
Due to the presence of 4c, the focusing region and the diverging region of the lens are separated and independent from each other, and the focusing region between the G5 electrode 13 and the intermediate electrode 14b has a function of extending the cross-sectional shape of the electron beam in the horizontal direction to a long extent. Electrode 14 and intermediate electrode 14
The divergence region between c and c has a function to elongate the cross-sectional shape of the electron beam in the vertical direction.

With such a configuration, the respective actions of the focusing region and the diverging region cancel each other out in the central portion of the screen and the resolution does not deteriorate.

On the other hand, in the peripheral portion of the screen, the voltage of the G5 electrode 13 increases with the deflection of the electron beam, so that the intermediate electrode 14
The voltage difference with b is reduced, and the lens strength in the focusing region is weakened.

Since the lens strength in the divergence area does not change, the lens strength in the divergence area is relatively increased. That is, the action of extending the cross-sectional shape of the electron beam in the divergent region in the vertical direction is longer than the action of extending the cross-sectional shape of the electron beam in the focusing region in the horizontal direction.

Therefore, the cross-sectional shape of the electron beam that has passed through the lens at the final stage becomes a shape that is long in the vertical direction, and it becomes possible to correct astigmatism caused by deflection aberration.

Further, since the lens strength of the final stage lens as a whole is weakened, the focal point of the electron beam is extended in the fluorescent screen direction, and it becomes possible to correct the field curvature aberration.

However, in the lens at the final stage of the electron gun according to the other conventional example, only the lens strength in the focusing region becomes weak in proportion to the deflection amount of the electron beam, so that the cross-sectional diameter of the electron beam in the diverging region is large. Results in an increase.

Therefore, the astigmatism due to the deflection aberration generated in the electron beam increases, and in order to correct this, the lens strength in the focusing region must be further weakened, which creates a vicious circle.

Therefore, when the value of the focusing voltage applied to the G5 electrode 13 is changed, the degree of improvement in resolution at the peripheral portion of the screen is low.

The intermediate electrodes 14b and 14c are
A phenomenon occurs in which a voltage due to electrostatic induction of a fluctuating focusing voltage applied to the G5 electrode 13 is divided into a desired voltage by the resistor 23 and superposed on the applied voltage. Therefore, reduction of the voltage difference between the G5 electrode 13 and the intermediate electrode 14b during the electron beam deflection is hindered.

Therefore, also in this point, the degree of improvement in the resolution of the peripheral portion of the screen when the value of the focusing voltage applied to the G5 electrode 13 is changed is low. That is, there is a drawback that the resolution of the peripheral portion of the screen cannot be sufficiently improved with a low dynamic focus voltage.

[0056]

As described above,
In the prior art, there are disadvantages that two focusing voltages are required, the socket portion of the image receiving device has a problem, the compatibility problem, or the resolution of the peripheral portion of the screen is not sufficiently improved with a low dynamic focus voltage. is there.

The present invention solves the above-mentioned problems of the prior art, uses a single focusing voltage, and is capable of sufficiently improving the resolution of the peripheral portion of the screen by a low dynamic focus voltage. To provide a tube.

[0058]

In order to achieve the above object, an electron gun used in a color cathode ray tube according to the present invention has a main lens for focusing an electron beam on a phosphor screen sequentially from the cathode to the phosphor screen side. Arranged G3 electrode, G4 electrode, G
The G6 electrode is provided with an acceleration voltage, which is the highest potential, and the G3 and G5 electrodes are provided with a focusing voltage that changes in accordance with an increase in the deflection amount of the electron beam. The G4 and G5 electrodes form a non-axisymmetric lens which has a stronger horizontal focusing action than a vertical focusing action and which strengthens the lens strength in response to an increase in the deflection amount of the electron beam. Is characterized in that a final stage lens having a function of strongly extending the cross-sectional shape of the electron beam in the horizontal direction is formed.

That is, in order to clarify the constitution of the present invention, when the reference numerals of the embodiment are additionally written and cut, the first invention according to claim 1 generates a plurality of electron beams and these are used. First electrode means 7, 9, 10 for directing an electron beam to the phosphor screen along initial paths parallel to each other on one horizontal plane, and a main means for focusing each electron beam on the phosphor screen. In a color cathode ray tube provided with an electron gun having at least second electrode means constituting a lens, the main lens is a third electrode 11 sequentially arranged from the first electrode means side to the phosphor screen side, The fourth electrode 12,
It is composed of a fifth electrode 13 and a sixth electrode 14, and the sixth electrode 14 is provided with an acceleration voltage Eb, which is the highest potential,
A focusing voltage (Vf + Vd) that changes according to an increase in the deflection amount of an electron beam is applied to the third electrode 11 and the fifth electrode 13, and the third electrode 11, the fourth electrode 12, and the fifth electrode 13 cause the focusing voltage (Vf + Vd) to change. A non-axisymmetric lens having a stronger horizontal focusing action than a vertical focusing action and strengthening the lens intensity in accordance with an increase in the deflection amount of the electron beam is formed, and the fifth electrode 13 and the sixth electrode 14 are provided. It is characterized in that a final-stage lens having an action of strongly stretching the cross-sectional shape of the electron beam in the horizontal direction is formed.

A second invention according to claim 2 is the first invention according to the first invention, wherein an electron beam passage hole is provided on a surface of the third electrode 11 facing the fourth electrode 12, An electron beam passage hole provided on the surface of the fourth electrode 12 facing the third electrode 11, and the fifth electrode of the fourth electrode 12
An electron beam passage hole provided on the surface facing the electrode 13;
At least one of the electron beam passage holes provided on the surface of the fifth electrode 13 facing the fourth electrode 12 has a non-axisymmetric shape.

[0061]

In the main lens according to the present invention as described above, G3
Since the non-axisymmetric lens formed by the electrode 11, the G4 electrode 12, and the G5 electrode 13 has a stronger horizontal focusing action than a vertical focusing action, the cross-sectional shape of the electron beam passing through the non-axisymmetric lens is shown. Enters a lens at the final stage after it has a long shape in the vertical direction.

At the center of the screen, the electron beam having a vertically long cross section due to the focusing action of the non-axisymmetric lens is the electron beam of the final stage lens formed by the G5 electrode 13 and the G6 electrode 14. By the action of strongly stretching the cross-sectional shape in the horizontal direction, it is corrected to have a circular cross-sectional shape.

As a result, the shape of the beam spot on the screen becomes substantially circular, and the deterioration of the resolution at the center of the screen does not occur.

On the other hand, in the periphery of the screen, the G5 electrode 1
Since the potential of the focusing voltage applied to No. 3 rises in accordance with the increase in the deflection amount of the electron beam, the voltage difference from the acceleration voltage Eb applied to the G6 electrode 14 decreases, and the G5 electrode 13 and the G6 electrode The lens strength is weakened in both the converging area and the diverging area of the final stage lens formed by 14. Further, at the same time that the lens strength is weakened, the action of strongly extending the cross-sectional shape of the electron beam of the final stage lens in the horizontal direction is also weakened, so that the electron beam having a long cross-sectional shape in the vertical direction passing through the non-axisymmetric lens Is strongly extended horizontally in the cross-sectional shape of the electron beam of the lens at the final stage, but is not completely corrected, and remains in the cross-sectional shape long in the vertical direction.

As a result, the astigmatism caused by the deflection aberration can be canceled. Further, at this time, since the lens strength of the final stage lens is weakened, the focusing point is extended in the fluorescent screen direction and the electron beam can be focused on the fluorescent screen even in the peripheral portion of the screen.

[0066]

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

FIG. 1 is a sectional view taken along a central electron beam for explaining an embodiment of an electron gun used in a color cathode ray tube according to the present invention, in which 7 is a cathode and 9 is a first electrode (G).
1 electrode), 10 is the second electrode (G2 electrode), 11 is the third electrode (G3 electrode), 12 is the fourth electrode (G4 electrode), 13 is the fifth electrode (G5 electrode), and 13a is the inside of the G5 electrode. Electrode plate installed in the, 14 is the sixth electrode (G6 electrode), 14a is G
Electrode plates installed inside the six electrodes, and 15 are shielding cups.

In the figure, the main lenses for focusing the electron beam on the fluorescent screen are G3 electrode 11 and G4 electrode 1.
2, G5 electrode 13, and G6 electrode 14.

An acceleration voltage Eb is applied to the G6 electrode 14 through the shield cup 15. The G3 electrode 11 and the G5 electrode 13 are applied with a voltage obtained by superposing the voltage Vd, which rises in synchronization with the increase in the deflection amount of the electron beam, on the focusing potential Vf. The voltage E of about 200 to 2000 V is applied to the G4 electrode 12.
v4 is applied.

The G4 electrode 12 is a plate-like electrode and has an electron beam passage hole whose vertical diameter is larger than its horizontal diameter.

FIG. 2 is a plan view showing the shape of the electron beam passage hole formed in the G4 electrode. 12c is the central electron beam passage hole and 12s is the outer electron beam passage hole.

As shown in the figure, the three electron beam passage holes 12c, 12s, 12s formed in the G4 electrode 12 are holes formed by cutting a part of a circle into a rectangle. If the circular arc portion is made to have the same diameter and coaxial as the electron beam passage hole provided on the facing surface of the adjacent electrode, the accuracy can be improved by the cylindrical penetrating jig that has been used in the assembly of the electron gun. It can be assembled well.

FIG. 3 is a plan view showing another example of the shape of the electron beam passage hole formed in the G4 electrode.
Is an ellipse having a long axis in the vertical direction, (b) is a rectangle having a long axis in the vertical direction, and (c) is a rhombus having a long axis in the vertical direction.

The electron beam passage hole formed in the G4 electrode is not limited to the above-mentioned shape, but another appropriate shape having a large diameter in the vertical direction can be adopted.

In FIG. 1, the G5 electrode 13 and the G6 electrode 14 for forming the final lens are
For example, it can be realized by the electrode shape disclosed in JP-A-58-103752.

FIG. 4 is a sectional view for explaining the main part of the electrode forming the final lens of this embodiment, where 113 is G
5 is an outer peripheral portion of the electrode 13, 113 is an outer peripheral portion of the G6 electrode 14,
13a is an electrode plate for correcting astigmatism provided inside the outer peripheral portion 113 of the G5 electrode 13, 14a is an electrode plate for correcting astigmatism provided inside the outer peripheral portion 114 of the G6 electrode 14, and 113c is An electron beam passage hole in the center of the electrode plate 13a, 113s is an electron beam passage hole beside the electrode plate 13a,
114c is an electron beam passage hole in the center of the electrode plate 14a,
14s is an electron beam passage hole outside the electrode plate 14a.

The electrode plate 13a has a central beam electron beam passage hole 113c and outer beam electron beam passage holes 113s and 113s. The electrode plate 14a has a central beam electron beam passage hole 114c and an outer beam electron beam passage hole 113c. The electron beam passage holes 114s and 114s are provided in a line. These electron beam passage holes 113c, 113s,
Each of 113s, 114c, 114s, and 114s has an elliptical shape that is long in the vertical direction, and the shapes and dimensions of the openings on the G5 electrode 13 side and the G6 electrode 14 side that face each other are the same.

FIG. 5 is a plan view seen from the AA line side of FIG. 4, and FIG. 6 is a plan view seen from the BB line side of FIG.

In such a structure, the retreat amount d ₁ from the opening end of the outer peripheral portion 113 of the electrode plate 13a, the electrode plate 14a
Amount d ₂ from the open end of the outer peripheral portion 114 of the
s, 113s horizontal diameter b ₁₃ , vertical diameter a ₁₃ , aperture 113c
Horizontal diameter b ₁₄ , vertical diameter a ₁₄ , horizontal diameter b ₂₃ of openings 114s and 114s, vertical diameter a ₂₃ , horizontal diameter b _{24 of} opening 114c,
By setting the dimension of the vertical diameter a ₂₄ to a desired value, the focusing action in the large diameter and in the vertical direction can be made stronger than the focusing action in the horizontal direction.

That is, it is possible to give the final stage lens an action of strongly extending the cross-sectional shape of the electron beam in the horizontal direction.

Typical dimensions in the embodiments shown in FIGS. 1, 2, 4, and 5 are as follows.

Plate thickness of G4 electrode 12 = 0.5 mm Vertical diameter of opening of G4 electrode 12 = 4.8 mm Horizontal diameter of opening of G4 electrode 12 φ = 4.4 mm b ₁₃ = 10.4 mm Single based on the horizontal diameter _{= 22.0mm d 1 = 5.5mm d 2} = 3.6mm a 14 = 6.4mm b 14 = 4.8mm a 24 = 10.4mm b 24 = 5.1mm above the size of the opening As a result of trial manufacture, it was confirmed that according to this example, the resolution of the peripheral portion of the screen can be sufficiently improved by the low dynamic focus voltage without impairing the resolution of the central portion of the screen.

Needless to say, since there is only one focusing voltage, there is no problem with respect to the socket of the image receiving device or compatibility.

[0084]

As described above, according to the present invention,
Since there is no problem of the structure change of the socket of the image receiving device and the compatibility of the cathode ray tube caused by the need of two focus power sources, and the resolution of the peripheral portion of the screen can be sufficiently improved by the low dynamic focus voltage. Good resolution can be obtained over the entire screen.

[Brief description of drawings]

FIG. 1 is a sectional view taken along a central electron beam for explaining an embodiment of an electron gun used in a color cathode ray tube according to the present invention.

FIG. 2 is a plan view showing a shape of an electron beam passage hole formed in a fourth electrode according to an embodiment of the present invention.

FIG. 3 is a plan view showing another example of the shape of the electron beam passage hole formed in the fourth electrode according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a main part of an electrode forming a final-stage lens according to an example of the present invention.

5 is a plan view as seen from the AA line side of FIG. 4. FIG.

6 is a plan view as seen from the BB line side of FIG. 4. FIG.

FIG. 7 is a horizontal sectional view schematically showing the configuration of a color cathode ray tube equipped with an electron gun having a conventional structure.

FIG. 8 is a conceptual diagram illustrating the shape of an electron beam spot at each position on a phosphor screen in a color cathode ray tube including a conventional electron gun.

FIG. 9 is a cross-sectional view taken along a central electron beam showing an example of a conventional electron gun for a cathode ray tube having a structure for reducing a reduction in resolution.

FIG. 10 is a schematic diagram illustrating a configuration of a conventional electron gun in which compatibility is maintained by generating two focusing voltages in a cathode ray tube.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Glass envelope 2 Face plate part 3 Fluorescent surface 4 Shadow mask 5 Conductive film 6,7,8 Cathode 9 G1 electrode 10 G2 electrode 11 G3 electrode 113 G5 electrode outer peripheral portion 114 G6 electrode outer peripheral portion 12 G4 electrode 12c, 12s, 113c, 113s, 114c, 11
4s Electron beam passage hole 13 G5 electrode 13a Astigmatism correction electrode plate 131 G5 electrode first member 131a Electrode plate 132 G5 electrode second member 132a Flat electrode 14 G6 electrode 14a Astigmatism correction electrode plate 14b, 14c Intermediate electrode 15 Shielding cup 16, 17, 18 Electron beam initial passage 21 External magnetic deflection yoke 22 Stem pin 23 Resistor.

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[Procedure amendment]

[Submission date] July 15, 1996

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 5

[Correction method] Change

[Correction content]

[Figure 5]

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 6

[Correction method] Change

[Correction content]

[Figure 6]

Claims (3)

[Claims] 1. A first electrode means for generating a plurality of electron beams and directing these electron beams to a fluorescent screen along initial paths parallel to each other on one horizontal plane, and each of the electron beams. In a color cathode ray tube including an electron gun having at least a second electrode means for forming a main lens for focusing on the phosphor screen, the main lens being arranged from the first electrode means side to the phosphor screen side. A third electrode, a fourth electrode, a fifth electrode, and a sixth electrode, which are sequentially arranged in the first electrode, an acceleration voltage having the highest potential is applied to the sixth electrode, and the third electrode and the fifth electrode are A focusing voltage that changes according to an increase in the deflection amount of the electron beam is applied, and the horizontal focusing action is stronger than the vertical focusing action by the third electrode, the fourth electrode, and the fifth electrode, and Increase in deflection Accordingly, a non-axisymmetric lens that strengthens the lens strength is formed, and the fifth electrode and the sixth electrode form a final-stage lens having an action of strongly extending the cross-sectional shape of the electron beam in the horizontal direction. Color cathode ray tube. 2. The electron beam passage hole provided on the surface of the third electrode facing the fourth electrode, and the electron provided on the surface of the fourth electrode facing the third electrode. A beam passage hole, an electron beam passage hole provided on a surface of the fourth electrode facing the fifth electrode, and an electron beam passage hole provided on a surface of the fifth electrode facing the fourth electrode, A color cathode ray tube, wherein at least one of them has a non-axisymmetric shape. 3. The color cathode ray tube according to claim 1, wherein the fourth electrode is a plate-shaped electrode, and the electron beam passage hole has a vertical diameter larger than a horizontal diameter.