JPH052999A - Color picture tube - Google Patents

Abstract

PURPOSE:To improve resolution of the whole picture area, by newly inserting an auxiliary electrode to be A.C.-grounded, between a focusing electrode composing color picture tube and an intermediate electrode adjoining thereto. CONSTITUTION:An auxiliary electrode Gs is newly placed between the 5th grid G5 and an intermediate electrode Gm1 composing an electron gun. Thus capacitance C5s, Cmm, and Cm6 are generated between respective electrodes: the grid G5, auxiliary electrode Gs, intermediate electrodes Gm1 and Gm2, and 6th grid G6. Especially, it means that the capacitance C5s is grounded through a capacitance CCRT of a picture tube itself formed by an inner conductive film and an outer conductive film of the picture tube. On the other hand, the capacitance Csm between the electrode Gs and Gm1, and the capacitance are turned into a short circuit state with a lead wire connecting the electrode Gs and the grid G6. An A.C. voltage component 10a shaped in palabola applied to the grid G5 is thus not inducted to electrodes Gm1 and Gm2, and only appropriate D.C. voltage is applied to the electrodes Gm1 and Gm2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color picture tube, and more particularly to a color picture tube provided with an electron gun for improving resolution and making focus quality uniform.

[0002]

2. Description of the Related Art Generally, a color picture tube deflects a three-electron beam emitted from an electron gun by a magnetic field generated by a deflection yoke attached to the outside of an envelope, and selects the three-electron beam by a shadow mask. The phosphor screen is horizontally and vertically scanned to form a color image on the phosphor screen.

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 line consisting of a center beam passing through the same horizontal plane and a pair of side beams. 10
The pincushion-type horizontal deflection magnetic field 1H shown in (a) and the deflection yoke for generating an inhomogeneous uniform magnetic field consisting of the barrel-shaped deflection magnetic field 1V shown in (b) are combined to form the above-mentioned three-row arrangement.
A self-convergence in-line type color picture tube that self-focuses an electron beam is widely used. In addition,
In FIGS. 9A and 9B, 2G is a center beam, and 2B and 2R are a pair of side beams.

However, this self-convergence in-line type color picture tube has a problem that the cross-sectional shape of the electron beam is distorted (deflection distortion) as the deflection angle increases, and the resolution at the peripheral portion of the screen deteriorates. That is, FIG.
As shown in, the beam spot 4a in the central portion of the screen 3 is almost a perfect circle, but the beam spot 4b in the peripheral portion of the screen 3 is
In addition to the elliptical high-luminance core portion 5 which is long in the horizontal direction, a low-luminance halo portion 6 which is long in the vertical direction is generated, and the resolution of the peripheral portion of the screen 3 is significantly deteriorated. Due to the inhomogeneity of the deflection magnetic field, the beam spot distortion in the peripheral portion of the screen 3 is caused by the horizontal focusing as shown by 2R ′ for the side beam 2R in FIGS. 10 (a) and 10 (b). It is caused by weakening and increased vertical focusing.

As one of means for improving the deterioration of resolution due to the above-mentioned deflection distortion, Japanese Unexamined Patent Publication No. 64-38 of the present inventor has proposed.
Japanese Patent No. 947 discloses the electron gun shown in FIG. This electron gun consists of three cathodes KB, KG,
KR, having first to sixth grids G1 to G6 of integral structure sequentially arranged on the cathodes KB, KG, and KR, and two intermediate electrodes between the fifth grid G5 and the sixth grid G6. Gm1,
It is formed in the structure where Gm2 is arranged. In this electron gun, the main lens portion that focuses the three electron beams toward the phosphor screen is the fifth grid G5, 2 as the focusing electrode.
The intermediate electrodes Gm1 and Gm2 and the sixth grid G6 as the final accelerating electrode are arranged, and the high voltage supplied to the final accelerating electrodes is arranged along the electron gun to the two intermediate electrodes Gm1 and Gm2. The voltage is divided into a predetermined voltage by the resistor 8 and supplied to the focusing electrode, and the focusing voltage is supplied to the focusing electrode in synchronization with the deflection of the deflection yoke by superimposing the parabolic AC voltage component on the constant DC voltage. It

With the above structure, the main lens portion of the electron gun is composed of the fifth grid G5 and the intermediate electrode Gm1 adjacent to the fifth grid G5, and the first four electrodes relatively strongly focus the electron beam in the vertical direction. A polar lens is formed, and the second quadrupole lens that relatively strongly diverges the electron beam in the vertical direction is formed by the intermediate electrode Gm2 and the sixth grid G6 adjacent to the intermediate electrode Gm2. The first and second quadrupole lenses are in equilibrium when the electron beam goes to the center of the screen,
An almost circular beam spot is obtained in the center of the screen. On the other hand, when it is deflected to the peripheral part of the screen, the focusing voltage of the fifth grid G5 rises and the potential difference between the fifth grid G5 and the intermediate electrode Gm1 becomes small, so that the first quadrupole lens becomes weak. The electron beam is relatively strongly affected by the second quadrupole lens. As a result, the deflection distortion that is strongly focused in the vertical direction is canceled out.

However, as described above, in the fifth grid G5,
When a focusing voltage in which a parabolic AC voltage component is superimposed on a constant DC voltage is applied, the fifth grid G5 and the intermediate electrode Gm1 adjacent to the fifth grid G5, the intermediate electrode Gm1 and the intermediate electrode Gm2, and the intermediate electrode Gm1. Electrode Gm2 and sixth adjacent to this
Since an electrostatic capacitance exists between the grid G6 and the fifth grid G5, the parabolic AC component of the voltage applied to the fifth grid G5 passes through this electrostatic capacitance and the intermediate electrodes Gm1, Gm2.
Is induced, the potentials of the intermediate electrodes Gm1 and Gm2 change in synchronization with the deflection of the deflection yoke.

Originally, however, this electron gun had an intermediate electrode Gm1,
Since the first quadrupole lens and the second quadrupole lens are designed to be balanced with the potential of Gm2 being constant, when the potentials of the intermediate electrodes Gm1 and Gm2 change as described above,
The quadrupole lens and the second quadrupole lens are out of balance, and the beam spot at the center of the screen is distorted.

FIG. 13 is a diagram shown for explaining the above phenomenon. The high grid applied to the fifth grid G5 which is the focusing electrode shown in FIG. 13A, for example, the sixth grid G6 which is the final accelerating electrode. About 28% of the DC voltage is the intermediate electrode Gm1
Similarly, when a DC voltage of about 40% and an intermediate electrode Gm2 of about 65% is applied to the fifth grid G5 and an AC voltage component that changes in a parabolic shape in synchronization with the deflection of the deflection yoke is superimposed on the fifth grid G5, for example, each electrode Assuming that the capacitances between them are the same, 2/3 of the parabolic AC voltage component superimposed on the fifth grid G5 is induced to the intermediate electrode Gm1 and 1/3 to the intermediate electrode Gm2. Corresponding to FIG. 9A, solid lines 10a to 10d are set to predetermined values in FIG.
It changes as shown in. That is, the focusing voltage (solid line 10a
) Falls at the center of the screen as shown by the broken line 11a, but the decrease of the focusing voltage at the center of the screen can be adjusted to a predetermined value by the DC component shown by the solid line 12. On the other hand, the potentials of the intermediate electrodes Gm1 and Gm2 are also broken lines 11
As shown by b and 11c, the potential of the intermediate electrodes Gm1 and Gm2 is not adjusted, although it is lower than a predetermined value in the central portion of the screen. As a result, in the center of the screen, the first quadrupole lens is weak, while the second quadrupole lens is strong. Therefore, as shown in FIG. 14, the beam spot 4a in the central portion of the screen is distorted, and the resolution in the central portion of the screen deteriorates. On the other hand, in the peripheral portion of the screen, the potentials of the intermediate electrodes Gm1 and Gm2 both rise, so the first quadrupole lens is stronger than the designed value and the second
Quadrupole lens becomes weak. As a result, as shown in FIG. 15, the beam spot 4b in the peripheral portion of the screen 3 is also distorted, and the resolution is not sufficiently improved.

[0010]

As described above, the three electron beams emitted from the electron gun and arranged in a row on the same horizontal plane are arranged in a pincushion type horizontal deflection magnetic field and a barrel type vertical deflection magnetic field. The self-convergence in-line type color picture tube which is deflected by the magnetic field of the deflection yoke which generates the uniform magnetic field has a problem that the cross-sectional shape of the electron beam is distorted as the deflection angle increases and the resolution in the peripheral portion of the screen deteriorates. As a means for improving the deterioration of resolution due to this deflection distortion, two intermediate electrodes are arranged between the focusing electrode and the final accelerating electrode which form the main lens portion of the electron gun, and the final accelerating electrode is applied to this intermediate electrode. A high voltage supplied to the electrodes is divided to supply a predetermined voltage, and a focusing voltage in which a constant DC voltage is superposed with a parabolic AC voltage component in synchronization with the deflection of the deflection yoke is supplied to the focusing electrode. There is a color picture tube that is designed to be supplied.

However, even if the electron gun is constructed as described above, a parabolic AC voltage component of the voltage applied to the focusing electrode is a static voltage that is present between the electrodes forming the main lens portion. It is induced to two intermediate electrodes via the capacitance, and the potential of each intermediate electrode changes in synchronization with the deflection of the deflection yoke, so not only the beam spot in the center of the screen is distorted, but also the beam spot in the peripheral area of the screen. However, there is a problem that the distortion is not sufficiently improved.

The present invention has been made to solve the above problems, and an object of the present invention is to construct a color picture tube in which a good resolution can be obtained in the central portion and the peripheral portion of the screen.

[0013]

A main lens unit for focusing an electron beam emitted from an electron beam forming unit on a phosphor screen, the main lens unit focusing in the direction of the phosphor screen from the electron beam forming unit. Electron gun comprising electrodes, one or more intermediate electrodes and a final accelerating electrode arranged in this order, and a resistor for dividing a high voltage supplied to the final accelerating electrode and supplying a predetermined voltage to the intermediate electrode. With and
In a color picture tube in which a voltage that changes in synchronization with the deflection of the deflection yoke is applied to the focusing electrode, an auxiliary electrode grounded in an alternating current is interposed between the focusing electrode and an intermediate electrode adjacent to the focusing electrode. It was

[0014]

As described above, when an auxiliary electrode grounded in an alternating current is interposed between the focusing electrode and the intermediate electrode arranged adjacent to the focusing electrode, the focusing electrode and the auxiliary electrode are interposed between the focusing electrode and the auxiliary electrode. A capacitance is formed. On the other hand, when this auxiliary electrode is connected to the final accelerating electrode, for example, as an AC grounding means for the auxiliary electrode, the color picture tube generally has an inner conductive film formed on the inner surface of the funnel and an outer conductive film formed on the outer surface of the funnel. Since a large electrostatic capacitance is formed between the auxiliary electrode and the auxiliary electrode, the auxiliary electrode is grounded in an alternating current by the circuit of the final accelerating electrode, the inner conductive film, the outer conductive film, and the ground. Therefore, the AC voltage component that changes in synchronization with the deflection of the deflection yoke applied to the focusing electrode is grounded via the auxiliary electrode. On the other hand, the electrostatic capacitance between the auxiliary electrode and the intermediate electrode adjacent thereto and the electrostatic capacitance between the plurality of intermediate electrodes are short-circuited by the lead wire connecting the auxiliary electrode and the final acceleration electrode. As a result, the AC voltage component that changes in synchronization with the deflection of the deflection yoke is not superimposed on the intermediate electrode.

Further, even if the auxiliary electrode is grounded via, for example, the stem lead, the AC voltage component that changes in synchronization with the deflection of the deflection yoke is grounded via this auxiliary electrode. The AC voltage component that changes in synchronization with the deflection of the deflection yoke is not superimposed.

Therefore, only a predetermined DC voltage is applied to the intermediate electrode, and the first quadrupole lens formed by the focusing electrode and the intermediate electrode adjacent thereto and the final accelerating electrode and the intermediate electrode adjacent thereto. Second formed by and
The lens action of the quadrupole lens can be normalized.

[0017]

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

FIG. 2 shows a color picture tube which is one of the embodiments. This color picture tube consists of panel 20 and this panel
A phosphor screen 22 having a three-color phosphor layer that emits blue, green, and red is formed on the inner surface of the panel 20 having an envelope composed of a funnel 21 integrally joined to the phosphor 20. A shadow mask 23 having a large number of electron beam passage holes formed therein is arranged so as to face the screen 22. In the neck 24 of the funnel 21, a center beam 2G and a pair of side beams 2B, which pass on the same horizontal plane,
The following in-line type electron gun 25 that emits three electron beams 2B, 2G and 2R arranged in a line consisting of 2R, and a resistor 8 for supplying a predetermined voltage to a predetermined electrode of the electron gun 25 are provided in the electron gun 25. It is arranged along. Further, an internal conductive film 26 extends from the inner surface of the large-diameter portion of the funnel 21 to the adjacent portion of the inner surface of the neck 24, and an outer conductive film 27 on the outer surface of the large-diameter portion of the funnel 21.
Is formed by coating.

Then, the three electron beams 2B, 2G and 2R emitted from the electron gun 25 are generated as an inhomogeneous uniform magnetic field composed of a pincushion type horizontal deflection magnetic field and a barrel type vertical deflection magnetic field mounted outside the funnel 21. It is deflected by the deflection yoke 28, and the phosphor screen is passed through the shadow mask 23.
The phosphor screen 22 is formed so as to display a color image by scanning the phosphor 22 horizontally and vertically.

As shown in FIG. 1, the electron gun 25 includes three cathodes KB, KG, KR arranged in a row in the horizontal direction, and three cathodes KB, KG, KR for individually heating the three cathodes KB, KG, KR. Heater (not shown), first to sixth grids G1 to G6 sequentially arranged on the cathodes KB, KG and KR toward the phosphor screen, and a shield cup 30 attached to the sixth grid G6. And two intermediate electrodes Gm1 and Gm2 arranged between the fifth grid G5 and the sixth grid G6. Further, in the electron gun 25 of this example, the auxiliary electrode Gs is arranged between the fifth grid G5 and the intermediate electrode Gm1 adjacent to the fifth grid G5.

Each of the electrodes of the electron gun 25 is formed as an integral structure, and the first and second grids G1 and G2 are plate electrodes each having a relatively thin plate thickness.
Circular apertures are provided corresponding to the three cathodes KB, KG, KR arranged in a row. 3rd and 4th grid G3, G4
Is a cylindrical electrode formed by abutting two cup-shaped electrodes on each other, and these electrodes are similarly provided with circular openings corresponding to the three cathodes KB, KG, KR arranged in a row. There is. The fifth grid G5 is composed of a pair of cylindrical electrodes each having two cup-shaped electrodes abutting against each other, and the electrodes are circular or non-circular corresponding to the three cathodes KB, KG, KR arranged in a row. Is provided. The auxiliary electrode Gs is composed of a plate electrode having a relatively thin plate thickness, and as shown in FIG. 3, a circular opening 32 corresponding to the three cathodes KB, KG, KR arranged in a row.
However, each of the two intermediate electrodes Gm1 and Gm2 is composed of a plate electrode having a relatively large plate thickness, and these electrodes have circular openings corresponding to the three cathodes KB, KG and KR arranged in a row. A hole is provided. Further, the sixth grid G6 is composed of a cylindrical electrode formed by abutting two cup-shaped electrodes, and this electrode is provided with a circular or non-circular opening.

In the resistor 8, the terminal 33 provided at one end is connected to the sixth grid G6, and the terminal 34 provided at the other end hermetically penetrates the stem 35.
(See FIG. 1), and is grounded directly or via a variable resistor 37. And the terminals 38 provided in the middle part,
39 are connected to the intermediate electrodes Gm1 and Gm2, respectively.

The following voltages are applied to the electrodes of the electron gun 25 during operation. That is, a voltage in which a video signal is superimposed on a DC voltage of 180V is applied to the cathodes KB, KG, KR, the first grid G1 is grounded, and the second grid G1 is grounded.
G2 and the fourth grid G4 are connected in the pipe and are about 800V
Is a voltage in which the third grid G3 and the fifth grid G5 are connected in the same tube and a DC voltage of 8 to 9 kV is superimposed on an AC voltage component that changes in a parabolic shape in synchronization with the deflection of the deflection yoke. Is applied. The auxiliary electrode Gs is connected to the sixth grid G6 in the tube, and a high voltage of about 30 kV is applied to the sixth grid G6 via an anode terminal, an internal conductive film, a valve spacer attached to the shield cup 30 and the like. Is applied. Further, about 40% of the high voltage (about 30 kV) divided by the resistor 8 is applied to the intermediate electrode Gm1,
Further, a voltage of about 60% is applied to the intermediate electrode Gm2.

By applying such a voltage, each cathode
The electron beams emitted from KB, KG, and KR diverge after forming crossovers in the vicinity of the first and second grids G1 and G2, and are a prefocus lens formed by the second and third grids G2 and G3. By the unipotential lens formed by the third, fourth, and fifth grids G2, G3, and G5, and then between the fifth grid G5 and the sixth grid G6. The formed main lens part is finally focused to form a beam spot on the phosphor screen.

In this case, in the main lens portion, a first grid for focusing the electron beam mainly in the vertical direction between the fifth grid G5 as a focusing electrode and the intermediate electrode Gm1 adjacent to the fifth grid G5. The quadrupole lens is also the intermediate electrode Gm
A second quadrupole lens that strongly diverges the electron beam mainly in the vertical direction is formed between 2 and the sixth grid G6 which is the final accelerating electrode.

By the way, in such an electron gun 25,
The fifth grid G5 and the intermediate electrode Gm forming the main lens part
By arranging the auxiliary electrode Gs between 1 and 1, the following effects can be obtained.

That is, the main lens portion of the conventional electron gun (see FIG. 12) having no auxiliary electrode arranged between the fifth grid G5 and the intermediate electrode Gm1 adjacent to the fifth grid G5 is shown in FIG. As shown by the equivalent circuit, it becomes an AC equivalent circuit, and electrostatic capacitances C5m and C are provided between the fifth grid G5, the intermediate electrodes Gm1 and Gm2, and the sixth grid G6, respectively.
mm and Cm6 are present. As a result, the parabolic AC voltage component 10a applied to the fifth grid G5 becomes an AC source,
This AC voltage component 10a is induced to the intermediate electrodes Gm1 and Gm2 via the electrostatic capacitances C5m and Cmm.

However, as shown by an equivalent circuit in FIG. 5, when the auxiliary electrode Gs is arranged between the fifth grid G5 and the intermediate electrode Gm1, the fifth grid G5, the auxiliary electrode Gs, the intermediate electrode Gm1,
Capacitances C5s, Csm, Cmm, Cm6 are respectively formed between the electrodes of Gm2 and the sixth grid G6, and in particular, the capacitance C5s between the fifth grid G5 and the auxiliary electrode Gs is inside the color picture tube. It is grounded via the capacitance CCRT of the tube itself formed by the conductive film and the external conductive film. Meanwhile, the auxiliary electrode
Capacitance Csm between Gs and intermediate electrode Gm1 and intermediate electrode
The capacitance Cmm between Gm1 and Gm2 is short-circuited by the lead wire 41 connecting the auxiliary electrode Gs and the sixth grid G6. As a result, the parabolic AC voltage component 10a applied to the fifth grid G5 is not induced in the intermediate electrodes Gm1 and Gm2, and only a predetermined DC voltage is applied to these intermediate electrodes Gm1 and Gm2. In this state, the first and second quadrupole lenses act as desired lenses.

Therefore, like the electron gun described above, an auxiliary electrode is provided between the fifth grid G5 and the intermediate electrode Gm1 adjacent to the fifth grid G5.
By arranging Gs, as shown in FIG. 6, the beam spot 4a in the central part of the screen 3 can be made into a perfect circle, and the halo part of the beam spot 4b in the peripheral part of the screen can be eliminated to improve the resolution of the entire screen. You can

Next, another embodiment will be described.

In the above embodiment, the auxiliary electrode arranged between the fifth grid and the intermediate electrode adjacent thereto was connected to the sixth grid, which is the final accelerating electrode, and was grounded in an alternating current. The electron gun shown is one in which the auxiliary electrode Gs is grounded outside the tube via a stem lead 36 that hermetically penetrates the stem. Since the other structure is the same as that of the electron gun, the same numbers are given and the description thereof is omitted.

With this structure, the main lens portion of the electron gun is configured such that the parabolic AC voltage component 10a applied to the fifth grid G5 as a focusing electrode is The electrostatic capacitance C5s formed between the 5 grid G5 and the auxiliary electrode Gs is grounded via the auxiliary electrode Gs, and the AC voltage component induced in the intermediate electrodes Gm1 and Gm2 can be significantly reduced. As a result, the intermediate electrodes Gm1 and Gm2 are in almost the same state as when a predetermined DC voltage is applied, and
And the second quadrupole lens can be made to have a desired lens function.

In the above embodiment, the auxiliary electrode has a structure having three circular holes, but this auxiliary electrode is shown in FIG.
As shown in, a long hole whose major axis is the electron beam array direction
A structure having 42 may be used. The auxiliary electrode is
Whichever shape the aperture is formed in, the lens electric field of the first quadrupole lens formed between the fifth grid as the focusing electrode and the intermediate electrode adjacent thereto should not be affected. It is desirable to use a plate electrode having a thin plate thickness. , Actually 0.4 ~ in relation to the strength of the electrode
It may be formed to a thickness of about 1.0 mm.

Further, in the above-mentioned embodiment, the electron gun in which the two intermediate electrodes are arranged in the main lens portion has been described, but the case of one or three intermediate electrodes can be similarly applied. Further, in the above embodiment, the composite type quadrapotential type electron gun has been described, but the present invention can be applied not only to other composite type electron guns, but also to the bipotential type electron gun and the unipotential type electron gun. ..

Further, in the above-mentioned embodiment, the color picture tube having the electron gun for emitting three electron beams arranged in a line passing through the same plane has been described, but the present invention is a color picture tube for emitting a single electron beam or a color picture tube. The same applies to a color picture tube that emits four or more electron beams.

[0036]

The main lens portion for focusing the electron beam on the phosphor screen is arranged in the order from the electron beam forming portion to the phosphor screen in the order of the focusing electrode, one or more intermediate electrodes and the final accelerating electrode. In a color picture tube that has an electron gun and a voltage that changes in synchronization with the deflection of a deflection yoke is applied to the focusing electrode, AC focusing is grounded between the focusing electrode and an intermediate electrode adjacent to the focusing electrode. When the auxiliary electrode is inserted, the AC component of the voltage that changes in synchronization with the deflection of the deflection yoke is not superimposed on the intermediate electrode due to its AC grounding, and a color picture tube with good resolution can be obtained over the entire screen. it can.

[Brief description of drawings]

FIG. 1 (a) is a front view showing in section a structure of an electron gun of a color picture tube which is an embodiment of the present invention, and FIG. 1 (b).
[Fig. 3] is a side view similarly shown in section.

FIG. 2 is a sectional view showing a configuration of a color picture tube which is an embodiment of the present invention.

FIG. 3 (a) is a plan view of an auxiliary electrode included in the electron gun, and FIG. 3 (b) is a BB sectional view thereof.

FIG. 4A is a wave form diagram of a voltage applied to a focusing electrode of a conventional electron gun shown for comparison with a main lens portion of an electron gun of a color picture tube which is an embodiment of the present invention. , Fig. 4
(B) is an equivalent circuit diagram of the main lens part.

5 (a) is a wave form diagram of a voltage applied to a focusing electrode of an electron gun of a color picture tube which is an embodiment of the present invention, and FIG. 5 (b) is a main lens portion of the electron gun. It is an equivalent circuit diagram.

FIG. 6 is a diagram showing a beam spot shape on the entire screen of a color picture tube which is an embodiment of the present invention.

FIG. 7 is a front view showing in section a structure of an electron gun of a color picture tube which is another embodiment of the present invention.

FIG. 8A is a wave form diagram of a voltage applied to a focusing electrode of the electron gun, and FIG. 8B is an equivalent circuit diagram of a main lens portion of the electron gun.

9 (a) is a plan view showing another structure of the auxiliary electrode which is different, and FIG. 9 (b) is a sectional view taken along line BB thereof.

10A is a diagram of a horizontal deflection magnetic field generated by a deflection yoke for a self-convergence in-line type color picture tube, and FIG. 10B is a diagram of a vertical deflection magnetic field thereof.

FIG. 11 is a diagram showing a beam spot shape over the entire screen of a conventional self-convergence in-line type color picture tube.

FIG. 12 (a) is a front view showing a cross section of the configuration of a conventional self-convergence in-line type electron gun;
FIG. 12B is a side view showing the same section.

13A is a diagram showing a configuration of a main lens section of the electron gun, and FIG. 13B is a diagram showing potentials of respective electrodes of the main lens section.

FIG. 14 is a diagram showing a beam spot shape at the center of the screen of the conventional self-convergence in-line type color picture tube.

FIG. 15 is a diagram showing a beam spot shape on the entire screen of the conventional self-convergence inline type screen.

[Explanation of symbols]

 2B, 2R ... Pair of side beams 2G ... Center beam 8 ... Resistor 22 ... Phosphor screen 25 ... Electron gun 26 ... Inner conductive film 27 ... Outer conductive film 32 ... Open hole 36 ... Stem lead 42 ... Open hole KB, KG , KR ... Cathode G1 ... First grid G2 ... Second grid G3 ... Third grid G4 ... Fourth grid G5 ... Fifth grid (focusing electrode) G6 ... Sixth grid (final acceleration electrode) Gm1 ... Intermediate electrode Gm2 ... Intermediate Electrode Gs ... auxiliary electrode

Claims (1)

Claim: What is claimed is: 1. A main lens section for focusing an electron beam emitted from an electron beam forming section onto a phosphor screen, the main lens section being provided from the electron beam forming section to the phosphor. An electron gun in which a focusing electrode, one or more intermediate electrodes and a final accelerating electrode are arranged in this order in the screen direction, and a high voltage supplied to the final accelerating electrode are divided to apply a predetermined voltage to the intermediate electrode. A resistor for supplying the voltage, and a voltage which changes in synchronization with the deflection of the deflection yoke is applied to the focusing electrode, in a color picture tube, between the focusing electrode and an intermediate electrode adjacent to the focusing electrode. A color picture tube, characterized in that an auxiliary electrode, which is grounded in an alternating current, is inserted in the color picture tube.