JPH06124663A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To make the focusing quality uniform by forming slits extened to the thickness direction of a dielectric substrate and facing to each other in rectangular direction and forming an electrode in both front and rear sides and the slits. CONSTITUTION:A resistor 33 and a capacitor 34 are installed respectively in a rear side of a pair of insulating supports 31 of an electron gun and in the other rear side. A terminal 36 in one end of the resistor 33 is connected with a shield cup C at the tip part and a terminal 37 in the other end is earthed through a variable resistor 40 and middle terminals 41, 42 are connected with middle electrodes Gm1, Gm2. Electron beams from a cathode are converged on a phosphor screen ultimately by main lens composed of an electrode G5, the electrodes Gm1, Gm2, and an electrode G6. Dynamic focusing voltage forms slits in the thickness direction from both front and rear sides of the dielectric substrates of the capacitor connected with electrodes to which voltage is not applied and to the direction rectangular to the thickness direction and an electrode is formed in the slits and thus electrostatic capacity is made large. As a result, a cathode-ray tube having uniform focusing quality is provided.

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 picture tube, and more particularly to a cathode ray tube provided with an electron gun which improves resolution and uniforms focus quality over the entire phosphor screen.

[0002]

2. Description of the Related Art In general, a color picture tube has an envelope made up of a panel and a funnel, and an inner surface of the panel is provided with an envelope.
A phosphor screen including a color phosphor layer is formed. On the other hand, an electron gun that emits three electron beams is arranged in the neck of the funnel. Then, the three electron beams emitted from this electron gun are deflected by the horizontal and vertical deflection magnetic fields generated by the deflection yoke mounted outside the funnel, and the phosphor screen is horizontally and vertically scanned to form a color image. It is formed in a display structure.

In such a color picture tube, in particular, the electron gun is an in-line type electron gun which emits three electron beams arranged in a row passing through the same horizontal plane, and a deflection yoke is generated as shown in FIG. 9 (a). The horizontal deflection magnetic field 1H is a pincushion type, and as shown in (b), the vertical deflection magnetic field 1V is a barrel-shaped distorted non-uniform magnetic field, so that the three electron beams 2B arranged in a row pass on the same horizontal plane. The self-convergence in-line color picture tube that self-focuses 2G, 2R is now the mainstream color picture tube for general use.

However, in this color picture tube, there is a problem that the resolution in the peripheral portion of the screen is deteriorated due to the nonuniformity of the deflection magnetic field. That is, the cross-sectional shape of the electron beam is distorted as the deflection angle increases, and as shown in FIG. 10, even if the beam spot 3c at the central portion of the screen becomes a perfect circle, the beam spot 3s at the peripheral portion of the screen becomes In addition to the horizontally long elliptical core portion 4 and the vertically extending low-luminance halo portion 5, the resolution is significantly deteriorated in the peripheral portion of the screen.

The distortion of the beam spot is caused by the fact that the deflection magnetic field for deflecting the electron beam is an inhomogeneous magnetic field. As shown in FIGS. 9 (a) and 9 (b), the electron beams 2B, 2G, This is because the horizontal focusing of 2R becomes weaker, and conversely the vertical focusing becomes stronger.

As a means for improving the deterioration of resolution due to such deflection distortion, Japanese Patent Laid-Open No. 64-389 of the present inventor has proposed.
In Japanese Patent Publication No. 47, as shown in FIG. 11, in addition to the first to sixth electrodes G1 to G6, a fifth electrode G5 (focusing electrode) and a sixth electrode are provided.
Two intermediate electrodes Gm1 and Gm2 between G6 (final acceleration electrode)
Is arranged so that the anode high voltage applied to the sixth electrode G6 is divided into a predetermined voltage value by the resistor 4 and supplied to the intermediate electrodes Gm1 and Gm2, and the deflection yoke is supplied to the fifth electrode G5. There is shown an electron gun that applies a focusing voltage composed of a dynamic focus voltage having an AC voltage component that changes in a parabola shape in synchronization with a deflection current flowing in.

In this electron gun, for example, its fifth electrode G5
In addition, a voltage obtained by superimposing an AC voltage component that changes in a parabolic shape in synchronization with the deflection current flowing in the deflection yoke on a direct current voltage of about 28% of the anode high voltage applied to the sixth electrode G6, and the intermediate electrode Gm1 A DC voltage of about 40% of the anode high voltage applied to the sixth electrode G6 and about 65% of the same to the intermediate electrode Gm2 is applied to the fifth electrode G5, the intermediate electrodes Gm1 and Gm.
The 2 and the sixth electrode G6 form a main lens part that finally focuses the electron beam on the phosphor screen. The main lens portion includes a first quadrupole lens for strongly focusing the electron beam formed by the fifth electrode G5 and the intermediate electrode Gm1 adjacent to the fifth electrode G5 in a relatively vertical direction, and the intermediate electrode.
It includes a second quadrupole lens that strongly diverges the electron beam formed by Gm2 and a sixth electrode G6 adjacent to the electrode Gm2 in a relatively vertical direction.

Such first and second quadrupole lenses are balanced when the electron beam is not deflected and goes to the center of the screen, and a substantially circular beam spot is obtained at the center of the screen. Further, when the electron beam is deflected and heads to the peripheral portion of the screen, the focusing voltage of the fifth electrode G5 rises, the potential difference between the fifth electrode G5 and the intermediate electrode Gm1 becomes small, and
The quadrupole lens becomes weak. As a result, the electron beam is relatively strongly affected by the action of the second quadrupole lens, diverges mainly in the vertical direction, and cancels the deflection distortion that the electron beam receives from the deflection yoke and is strongly focused in the vertical direction.

However, in this electron gun, as shown in FIG. 12 (a), an intermediate electrode Gm1 is provided between the fifth electrode G5 and the intermediate electrode Gm1.
And the intermediate electrode Gm2, and the electrostatic capacitance Cs exists between the intermediate electrode Gm2 and the sixth electrode G6. Therefore, of the focusing voltage applied to the fifth electrode G5, a parabolic AC voltage component that changes in synchronization with the deflection current is induced in the intermediate electrodes Gm1 and Gm2 via the electrostatic capacitance Cs. As a result, the potentials of the intermediate electrodes Gm1 and Gm2 also change in synchronization with the deflection current. Since the intermediate electrodes Gm1 and Gm2 are designed so that the first and second quadrupole lenses are balanced at a constant potential, when the potentials of the intermediate electrodes Gm1 and Gm2 change as described above, The balance between the quadrupole lens and the second quadrupole lens is deviated, and the beam spot at the center of the screen is also distorted.

That is, as shown in FIG. 12B corresponding to FIG. 12A, the deflection yoke is applied to the DC voltage 7 which is about 28% of the high voltage 6 applied to the fifth electrode G5 to the sixth electrode G6. When the parabolic AC voltage component 8 synchronized with the deflection current flowing in the fifth electrode G5 is superposed, the AC voltage component 8 of the fifth electrode G5 is induced to the intermediate electrodes Gm1 and Gm2 via the electrostatic capacitance Cs, and the fifth electrode
The potentials of G5 and the intermediate electrodes Gm1 and Gm2 are shown by broken lines 9
As shown by ~ 11, it drops in the center of the screen. This intermediate electrode
The AC voltage component induced in Gm1 and Gm2 is
Assuming that the electrostatic capacitances Cs interposed between 1, Gm2 and G6 are the same, the AC voltage component of the fifth electrode G5 is applied to the intermediate electrode Gm1.
About 2/3 of 8 and about 1/3 of the AC voltage component 8 of the fifth electrode G5 is induced in the intermediate electrode Gm2.

Even if an AC voltage component is induced in the intermediate electrodes Gm1 and Gm2 in this way, the first quadrupole lens formed by the fifth electrode G5 and the intermediate electrode Gm1 is applied to the fifth electrode G5. By adjusting the DC voltage 6, it is possible to correct to a predetermined strength. However, the intermediate electrode Gm2 and the sixth electrode
The second quadrupole lens formed by G6 has no adjusting means and becomes stronger than a predetermined strength at the center of the screen. As a result, as shown in FIG. 13, the beam spot 3c at the center of the screen has a shape with a vertically extending elliptical core 4 and a low-brightness halo 5 extending in the horizontal direction. The resolution of the part deteriorates.

In the peripheral portion of the screen, the potential of the intermediate electrode Gm1 rises and the potential of the intermediate electrode Gm2 also rises. Therefore, the first quadrupole lens is stronger than the designed value, and the second quadrupole lens is It is weaker than the design value. As a result, the resolution of the peripheral portion of the screen cannot be improved sufficiently.

As a means for solving such a problem, Japanese Patent Laid-Open No. 1-95444 discloses that one of two intermediate electrodes is grounded via a capacitor and an AC voltage component induced in these intermediate electrodes is bypassed. An electron gun that is adapted to do so is shown. As shown in FIG. 14, the capacitor has a thin film electrode 1 on both front and back sides with a dielectric substrate 13 in between.
4 and 15 are formed to face each other, and thin film electrodes 14 and 1
The larger the capacitance generated between the five, the greater the bypass effect.

By the way, generally, the capacitance of such a capacitor is determined by the facing distance between the thin film electrodes 14 and 15, the facing area, and the dielectric constant of the dielectric. Therefore, in order to increase the capacitance of the capacitor, the dielectric substrate 13
It is necessary to reduce the thickness of the thin film electrodes to reduce the facing distance between the two thin film electrodes 14 and 15, or to increase the facing area of the thin film electrodes 14 and 15.

However, since the capacitor for bypassing the AC voltage component induced in the intermediate electrode is arranged near the electron gun in the neck of the color picture tube, the arrangement space is narrow and the thin film electrode 14 of the capacitor is used. There is a limit to simply increasing the facing area of 15 and 15. Even if the dielectric substrate 13 is thinned to reduce the facing distance between the thin film electrodes 14 and 15, the withstand voltage between the facing surfaces of the thin film electrodes 14 and 15 can be kept relatively high. One electrode 14 connected to the electrodes has a potential of 40% to 65% of the anode high voltage, and the other electrode 15 has a ground potential.
Because the potential difference between 4 and 15 is extremely large, thin film electrodes 14 and 15
There is a problem that creeping discharge is generated through the surface of the dielectric body 13 between them, and the dielectric substrate 13 cannot be simply thinned.

As means for increasing the capacitance of this capacitor, Japanese Patent Application Laid-Open No. 1-187742 discloses a method shown in FIG.
As shown in FIG. 2, both surfaces of the dielectric substrate 13 are formed into uneven surfaces, and the thin film electrodes 14 and 15 are formed on the uneven surfaces.
It has been shown that increasing the surface area of the capacitor increases the capacitance of the capacitor. However, even if both surfaces of the dielectric substrate 13 are made uneven as described above and the thin film electrodes 14 and 15 are formed on both surfaces thereof, only the area of the drop portion 19 between the concave portion 17 and the convex portion 18 increases, and both thin films are formed. Since the true facing area of the electrodes 14 and 15 does not increase, the electrostatic capacitance is slightly increased as compared with the case of the planar electrode shown in FIG. 14, and a large increase in electrostatic capacitance cannot be expected.

[0017]

As described above, the self-convergence in-line color picture tube has a problem that the resolution in the peripheral portion of the screen is deteriorated due to the non-uniformity of the deflection magnetic field. In order to solve this deterioration of resolution, a plurality of intermediate electrodes are arranged between the focusing electrode forming the main lens section of the electron gun and the final accelerating electrode, and the focusing electrode is provided with a deflection yoke with a constant DC voltage. Applying a dynamic focus voltage that superimposes a parabolic AC voltage component that changes in synchronization with the flowing deflection current, these focusing electrodes,
Electrons configured to form a first quadrupole lens that strongly focuses the electron beam relatively vertically and a second quadrupole lens that strongly diverges relatively vertically by the intermediate electrode and the final accelerating electrode. I have a gun. However, in this electron gun, since there is a capacitance between the focusing electrode and the intermediate electrode adjacent to the focusing electrode, between the intermediate electrodes, and between the intermediate electrode and the final accelerating electrode adjacent to the intermediate electrode, respectively,
A parabolic AC voltage component applied to the focusing electrode is induced via this capacitance, and the induction of this AC voltage component causes the first and second AC voltage components to be balanced at a constant potential. The quadrupole lens loses balance and the beam spot in the center of the screen becomes distorted. There is also a problem that the resolution of the peripheral portion of the screen cannot be improved sufficiently.

As a means for solving such a problem, a capacitor having thin film electrodes formed on both front and back sides of a dielectric substrate is used as a capacitor with one of the intermediate electrodes arranged between the focusing electrode and the final accelerating electrode. There is an electron gun in which the parabolic AC voltage component induced in the intermediate electrode is bypassed by being grounded via.

In such an electron gun, the larger the capacitance of the capacitor, the greater the bypass effect. However, in order to increase the capacitance of a capacitor with thin film electrodes formed on both front and back sides across a dielectric substrate, simply increasing the facing area of both thin film electrodes is
There is a limit due to the location near the electron gun in the neck. If the dielectric substrate is made thinner and the facing distance is shortened,
There is a problem that surface discharge occurs.

In addition, in order to increase the electrostatic capacity, there is a method in which both surfaces of the dielectric substrate are made uneven and a thin film electrode is formed on the uneven surface to increase the surface area of both thin film electrodes.
Thus, even if both surfaces of the dielectric substrate are made uneven and the thin film electrodes are formed on both surfaces, the area of the drop portion between the concave portion and the convex portion only increases, and the true facing area of both thin film electrodes increases. Therefore, it is not possible to expect a large increase in electrostatic capacity as compared with the case of a flat electrode.

The present invention has been made to solve the above problems, and a dynamic focus voltage synchronized with a deflection current flowing through a deflection yoke is applied to one of a plurality of electrodes forming a main lens portion. In a cathode ray tube equipped with an electron gun in which a capacitor bypassing an AC voltage component induced by the application of the dynamic focus voltage is connected to at least one electrode other than the electrode to which the dynamic focus voltage is applied, the outer shape of the capacitor It is an object of the present invention to provide a cathode ray tube which has a high resolution and a good resolution and a uniform focus quality over the entire phosphor screen without increasing the size of the cathode ray tube.

[0022]

A plurality of electrodes forming a main lens portion for focusing an electron beam on a phosphor screen are provided, and one of the plurality of electrodes is synchronized with a deflection current flowing in a deflection yoke. And a capacitor for bypassing an AC voltage component induced by the application of the dynamic focus voltage is connected to at least one electrode other than the electrode to which the dynamic focus voltage is applied. In the tube, the capacitor was formed with slits extending from both front and back surfaces in the plate thickness direction and facing each other in a direction orthogonal to the plate thickness direction, and electrodes were formed on both the front and back surfaces of this dielectric substrate and in the slits. With the structure.

[0023]

As described above, the slits extending from the front and back surfaces of the dielectric substrate in the plate thickness direction and facing each other in the direction orthogonal to the plate thickness direction are formed, and the electrodes are formed on the front and back surfaces of the dielectric substrate and in the slits. Then, in addition to the electrostatic capacitance generated between the electrodes on the front and back surfaces, the electrostatic capacitance is also generated between the opposing electrodes in the slit. As a result, a capacitor with a high bypass effect for the AC voltage component induced by the application of the dynamic focus voltage can be obtained without increasing the outer shape of the dielectric substrate, and the AC voltage component induced by the application of the dynamic focus voltage can be achieved. It is possible to prevent the deterioration of the resolution caused by the above, and to provide a cathode ray tube with a uniform focus quality in the entire phosphor screen.

[0024]

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

FIG. 3 shows a self-convergence type in-line type color picture tube which is one of the embodiments. This color picture tube has an envelope consisting of a panel 20 and a funnel-shaped funnel 21 integrally joined to the panel 20, and an inner surface of the panel 20 vertically emits blue, green, and red light. A phosphor screen 22 made of a long stripe-shaped three-color phosphor layer is formed, and a shadow mask 23 having a large number of electron beam passage holes formed therein is arranged facing the phosphor screen 22. . Meanwhile, Funnel 21
Center beam 25 that passes on the same horizontal plane in the neck 24 of
An electron gun 26, which will be described later, that emits three electron beams 25B, 25G, and 25R arranged in a line and composed of G and a pair of side beams 25B and 25R is disposed. Also, the large diameter part of the funnel 21
An inner conductive film 29 is formed by coating from the inner surface of 27 to the inner surface of the adjacent portion of the neck 24, and is connected to the anode terminal 30 provided in the large diameter portion 27 of the funnel 21. The electron gun 26 is provided outside the boundary between the large-diameter portion 27 of the funnel 21 and the neck 24.
A deflection yoke 31 for generating a pincushion-type horizontal deflection magnetic field for horizontally deflecting the three electron beams 25B, 25G, 25R emitted from and a barrel-type vertical deflection magnetic field for vertically deflecting the three electron beams is mounted.

As shown in FIG. 1, the electron gun 26 has three cathodes KB, KG, KR arranged in a row in the horizontal direction, and three heaters for heating the cathodes KB, KG, KR separately ( (Not shown), the first electrode G1, the second electrode G2, the third electrode G3, the fourth electrode G4, and the fifth electrode G5, which are sequentially arranged in the phosphor screen direction at a predetermined distance from the cathodes KB, KG, and KR. (Focusing electrode), a first intermediate electrode Gm1, a second intermediate electrode Gm2, a sixth electrode G6, and a shield cup C attached to the sixth electrode G6, and the first to fifth electrodes G5, G1 , The second intermediate electrodes Gm1, Gm2 and the sixth electrode G6 are a pair of insulating supports
It is fixed integrally by 31. Shield cup C
A valve spacer (not shown) is attached to the inner surface of the funnel, the valve spacer being in pressure contact with the inner conductive film.

The first and second electrodes G1 and G2 are plate electrodes having a relatively thin plate thickness, and these electrodes G1 and G2 are
Corresponding to the cathodes KB, KG, KR, three circular electron beam passage holes are formed in a row. Third and fourth
The electrodes G3 and G4 are two cup-shaped electrodes G31 and G32, respectively.
And the tubular electrode with G41 and G42 butted against each other,
G5 is a cylindrical electrode formed by abutting four cup-shaped electrodes G51, G52, G53, G54, and its third and fourth electrodes G3, G4.
Also, on the fourth electrode G4 side of the fifth electrode G5, the same cathode
Corresponding to KB, KG, and KR, three circular electron beam passage holes are formed in a row, and three circular or non-circular electron beam passage holes are formed on the fifth intermediate electrode Gm1 side of the fifth electrode G5. Has been formed. The first and second intermediate electrodes Gm1 and Gm2 are made of plate electrodes having a relatively large plate thickness, and these electrodes Gm1 and Gm2 are arranged in a line corresponding to the cathodes KB, KG and KR.
Individual circular electron beam passage holes are formed. 6th electrode
G6 is a tubular electrode formed by butting two cup-shaped electrodes G61 and G62, and the cathode K is on the shield cup C side.
Three circular electron beam passage holes are formed in a line corresponding to B, KG, KR, and three circular or non-circular electron beam passage holes are formed on the second intermediate electrode Gm2 side. The shield cup C also has three circular electron beam passage holes arranged in a line corresponding to the cathodes KB, KG, and KR.

Further, a pair of insulating supports 31 of the electron gun 26.
A resistor 33 is provided on the back surface of one side, and a capacitor 34 is provided on the back side of the other insulating support 31.

In the resistor 33, the terminal 36 at one end is an electron gun.
Directly or through a variable resistor 40 via a stem lead 39 (see FIG. 1) that is connected to the shield cup C at the tip of 26, and the terminal 37 at the other end hermetically penetrates the stem 38 at the end of the neck 24. The terminals 41 and 42 in the intermediate portion are connected to the first and second intermediate electrodes Gm1 and Gm2, respectively.

The capacitor 34, as shown in FIG.
Thin film counter electrodes 45 and 46 formed on both front and back surfaces of the rectangular dielectric substrate 44, and along the long side surface of the dielectric substrate 44, extending from both front and back surfaces in the plate thickness direction and orthogonal to the plate thickness direction. A plurality of slits facing each other are formed, and a plurality of embedded electrodes 47, 48 are embedded in the slits and face each other in a direction orthogonal to the plate thickness direction. The front and back surfaces on which the thin film counter electrodes 45 and 46 are formed are covered with an insulating coating 49. The thin film counter electrode 45 and the buried electrode 47 on one surface, and the thin film counter electrode 46 on the other surface.
And the embedded electrode 48 are electrically connected to each other, and the thin film counter electrode 45 on one side thereof and the embedded electrode 47 connected thereto.
Is connected to the first intermediate electrode Gm1 and the other thin film counter electrode 46
And the embedded electrode 48 connected to this is grounded.

Such a capacitor 34 can be formed as follows. That is, as shown in FIG.
A plurality of slits 50, 51 extending in the plate thickness direction from both front and back surfaces of the rectangular dielectric substrate 44 are formed so as to be alternately opposed to each other in a direction orthogonal to the plate thickness direction. Next, a conductive paste is applied to both front and back surfaces of the dielectric substrate 44 so as to be embedded in the slits 50 and 51, and then fired, and then, as shown in FIG.
As shown in, the thin film counter electrode 45 and the buried electrode 47 electrically connected to one surface, the thin film counter electrode 46 and the buried electrode 48 electrically connected to the other surface are formed. . afterwards,
As shown in FIG. 6, it is formed by applying an insulating coating 49 on both front and back surfaces.

In the electron gun 26, for example, a video signal corresponding to an image is superimposed on a DC voltage of about 180 V on each of the three cathodes KB, KG, and KR, and the first electrode G1 is grounded. The second electrode G2 and the fourth electrode G4 are connected in a tube, and a DC voltage of about 800 V is applied to these electrodes G2 and G4. The third electrode G3 and the fifth electrode G5 are also connected in the tube, and a DC voltage of 8 to 9 kV and an AC voltage component that changes in a parabolic shape in synchronization with the deflection current flowing in the deflection yoke are connected to these electrodes G3 and G5. The superimposed dynamic focus voltage is applied. Further, an anode high voltage of about 30 kV is applied to the sixth electrode G6 from the anode terminal through the inner conductive film, the valve spacer and the shield cup C. Further, about 40% of the anode high voltage divided by the resistor 33 is applied to the first intermediate electrode Gm1, and about 6% to the second intermediate electrode Gm2.
A voltage of 5% is applied.

By applying such a voltage, each cathode
The electron beams emitted from KB, KG, and KR diverge by forming crossovers near the first and second electrodes G1 and G2, and a prefocus lens formed by the second and third electrodes G2 and G3. Received pre-focusing by the third, fourth, and fifth electrodes G
It is pre-focused by the auxiliary lens formed by 2, G3 and G5. Then, the fifth electrode G5, the first and second intermediate electrodes Gm1,
It is finally focused on the phosphor screen by the main lens formed by Gm2 and the sixth electrode G6.

The main lens has a first fourth lens which strongly focuses the electron beam formed near the first intermediate electrode Gm1 and the electrode G54 on the first intermediate electrode Gm1 side of the fifth electrode G5 relatively in the vertical direction. A polar lens and a second quadrupole lens that strongly diverges the electron beam formed in the vicinity of the second intermediate electrode Gm2 and the electrode G61 on the second intermediate electrode Gm2 side of the sixth electrode G6 relatively vertically. Including. These first and second quadrupole lenses are made thin by making the plate thickness around the electron beam passage holes of the electrodes G54 and G64 (1.0 mm or less).
It is formed by increasing the radius of curvature of the lens in the horizontal direction and making the lens strength in the horizontal direction relatively weaker than that in the vertical direction.

The two quadrupole lenses having different polarities work so that the central portion of the screen is in a balanced state and the beam spot at the central portion of the screen is substantially circular.
In the peripheral area of the screen, the dynamic focus voltage VD including the AC voltage component applied to the fifth electrode G5 causes
The quadrupole lens loses its balance and acts to reduce the distortion of the beam spot when it is deflected to the peripheral portion of the screen.

The AC voltage component of the dynamic focus voltage VD applied to the fifth electrode G5 is, as shown in FIG. 12, passed through the electrostatic capacitance between the fifth electrode G5 and the first intermediate electrode Gm1. The AC voltage component induced in the first intermediate electrode Gm1 but induced in the intermediate electrode Gm1 is bypassed via the capacitor 34 connected to the first intermediate electrode Gm1. In this case, by disposing the capacitor 34 having the above configuration, the AC voltage component induced in the first intermediate electrode Gm1 can be made almost zero.

That is, assuming that the capacitance of the capacitor connected to the first intermediate electrode Gm1 is Cp and the capacitance Cs between the fifth electrode G5 and the first intermediate electrode Gm1 is Cs, the first intermediate electrode Gm
The AC voltage component VL induced in 1 is expressed by Equation 1,

[Equation 1] As the capacitance Cp of the capacitor is increased, the AC voltage component VL induced via the capacitance Cs can be decreased.

In this respect, the capacitor 34 of this example includes the thin film counter electrodes 45 and 46 formed on both front and back surfaces of the dielectric substrate 44, and embedded electrodes extending in the plate thickness direction from both front and back surfaces of the dielectric substrate 44. Since 47 and 48 are formed, as shown in FIG. 7, in addition to the capacitance CT between the thin film counter electrodes 45 and 46 on both front and back surfaces of the dielectric substrate 44, also between the embedded electrodes 47 and 48. A capacitance CB is formed. Therefore, the capacitance can be made extremely large as compared with the conventional capacitor in which thin film electrodes are formed only on the front and back surfaces of the dielectric substrate shown in FIG. As a result, the AC voltage component induced in the first intermediate electrode Gm1 can be made almost zero, and the first intermediate electrode Gm1
1 can be grounded AC-wise. Further, thereby, it is possible to prevent the AC voltage component from being induced in the second intermediate electrode Gm2.

As a result, it is possible to prevent the deterioration of the resolution caused by the AC voltage component induced in the first and second intermediate electrodes Gm1Gm2 by the application of the dynamic focus voltage, and to make the focus quality uniform in the entire phosphor screen. it can. In addition, since the capacitance of the capacitor 34 has a margin, the area of the thin film counter electrodes 45 and 46 on the front and back surfaces of the dielectric substrate 44 is made smaller, or the dielectric substrate 44 is made smaller.
By increasing the thickness of 44 and increasing the creepage distance of the thin film counter electrodes 45 and 46, it is possible to prevent the creeping discharge that occurs between the thin film counter electrodes 45 and 46 from occurring.

In the above embodiment, the capacitor for bypassing the AC voltage component induced by the application of the dynamic focus voltage is formed with slits extending from the front and back surfaces in the plate thickness direction along the long side surfaces of the rectangular dielectric substrate. Then, an embedded electrode was provided in this slit. As the slit formed in the dielectric substrate of the capacitor for bypassing this AC voltage component, as shown in FIG. 8A, a rectangular dielectric substrate was used. Plural slits 50, 51 extending from the front and back sides along the short side of 44 in the thickness direction (only 50 is shown)
Alternatively, as shown in (b), a plurality of slits 50, 51 (inclined to the long side surface (or short side surface) of the rectangular dielectric substrate 44 and extending in the plate thickness direction from both front and back surfaces) may be formed. 50
(Only shown) may be formed.

Further, in the above-mentioned embodiment, the conductive paste is applied so as to be embedded in the slit formed in the dielectric substrate to provide the electrode, but the embedded electrode is also formed by another method such as vapor deposition of metal. can do.

Further, in the above embodiment, the case where the number of the intermediate electrodes is two has been described, but the present invention can be applied to the case where the number of the intermediate electrodes is one or more than two.

In the above embodiment, the QPF (Quadra Pot)
Although the ential focus) type electron gun has been described, the present invention can be applied to electron guns other than the QPF type.

The present invention is also applicable to cathode ray tubes other than color picture tubes.

[0045]

The capacitor connected to at least one electrode other than the electrode to which the dynamic focus voltage is applied among the electrodes forming the main lens for focusing the electron beam on the phosphor screen is connected to the dielectric substrate. If a plurality of slits that extend in the thickness direction from both the front and back sides and that face each other in the direction orthogonal to the thickness direction are formed, and electrodes are formed in the slits in addition to the electrodes on both the front and back sides, they will be formed between the electrodes on both the front and back sides. In addition to the generated electrostatic capacity, electrostatic capacity is also formed between the electrodes in the slit, and the electrostatic capacity can be increased without increasing the outer shape of the capacitor. As a result, a capacitor with a high bypass effect for the AC voltage component induced by the application of the dynamic focus voltage can be obtained, and the deterioration of the resolution caused by the AC voltage component induced by the application of the dynamic focus voltage can be prevented, and the focus quality can be improved. It is possible to obtain a cathode ray tube having a uniform thickness. In addition, because there is a margin in the capacitance of the capacitor, it is possible to reduce the area of the electrodes on both the front and back sides of the dielectric substrate, or increase the creepage distance of the electrodes on both the front and back sides by thickening the dielectric substrate. Therefore, it is possible to make it difficult to generate creeping discharge.

[Brief description of drawings]

FIG. 1 (a) is a front view showing the structure of an electron gun of a self-convergence in-line type color picture tube which is an embodiment of the present invention, and FIG. 1 (b) is a sectional view thereof.
(C) is a side view shown in section.

FIG. 2 is a perspective view showing a cutaway part of the capacitor.

FIG. 3 is a diagram showing a configuration of a self-convergence in-line type color picture tube which is an embodiment of the present invention.

FIGS. 4 (a) and 4 (b) are views for explaining the formation of slits in the dielectric substrate of the capacitor.

5 (a) and 5 (b) are views for explaining formation of electrodes of the capacitor.

FIGS. 6 (a) and 6 (b) are views for explaining the formation of the insulating coating of the capacitor.

FIG. 7 is a diagram for explaining an electrostatic capacitance generated by the capacitor.

FIG. 8A and FIG. 8B are views for explaining the structure of another capacitor according to the present invention.

9A is a diagram of a pincushion type horizontal deflection magnetic field generated by a deflection yoke attached to a self-convergence in-line type color picture tube, and FIG. 9B is a diagram of a barrel type vertical deflection magnetic field. is there.

FIG. 10 is a diagram for explaining the shape of a beam spot on the screen.

11 (a) is a sectional front view showing the structure of a conventional electron gun in which an intermediate electrode is arranged between a fifth electrode and a sixth electrode, and FIG. 11 (b) is a sectional view. FIG.

FIG. 12 (a) is a diagram for explaining the electrostatic capacitance generated in the electron gun in which the conventional intermediate electrode is arranged, FIG.
2B is a diagram for explaining induction of an AC voltage component of the dynamic focus voltage applied to the fifth electrode due to the capacitance.

FIG. 13 is a diagram showing the distortion of the beam spot at the center of the screen caused by the induction of the AC voltage component of the dynamic focus voltage.

FIG. 14 (a) is a cross-sectional front view showing the structure of a conventional capacitor for bypassing an AC voltage component induced via electrostatic capacitance between electrodes, and FIG. 14 (b) is its plan view. It is a figure.

FIG. 15 is a cross-sectional view showing the structure of another conventional capacitor.

[Explanation of symbols]

 22 ... Phosphor screen 25B, 25R ... A pair of side beams 25G ... Center beam 26 ... Electron gun 29 ... Inner conductive film 31 ... Insulating support 33 ... Resistor 34 ... Capacitor 44 ... Dielectric 45 ... Thin film counter electrode 46 ... Thin film Counter electrode 47 ... Embedded electrode 48 ... Embedded electrode 46 ... Insulator 50 ... Slit 51 ... Slit C ... Shield cup G1 ... First electrode G2 ... Second electrode G3 ... Third electrode G4 ... Fourth electrode G5 ... Fifth Electrode G6 ... Sixth electrode Gm1 ... First intermediate electrode Gm2 ... Second intermediate electrode KB, KG, KR ... Cathode

Front page continuation (72) Inventor Shigeo Fukuda 7-1 Nisshin-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Toshiba Toshiba Electronics Engineering Co., Ltd.

Claims (1)

[Claims] 1. A dynamic focus voltage synchronized with a deflection current flowing through a deflection yoke, comprising: a plurality of electrodes forming a main lens portion for focusing an electron beam on a phosphor screen. And a capacitor for bypassing an AC voltage component induced by the application of the dynamic focus voltage is connected to at least one electrode other than the electrode to which the dynamic focus voltage is applied. The capacitor has slits formed on both sides of the dielectric substrate in the thickness direction and facing each other in a direction orthogonal to the thickness direction, and electrodes are formed on both sides of the dielectric substrate and in the slits. Is a cathode ray tube.