JP2001068040A - Color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color cathode-ray tube which generates high grade images by reducing the elliptical distortion of beam spot over the whole screen surface. SOLUTION: A color cathode-ray tube device includes an electron gun 27, having a main lens configured with a focus electrode G32 on which a dynamic voltage incremental in synchronization with the deflection of an electron beam made by a deflection yoke, an anode electrode G4, and an additional electrode Gm which is installed between them G32 and G4 and supplied with a voltage formed by dividing the anode electrode voltage by a resistor, where an additional electrode is furnished with noncircular electron beam passing holes, and with this additional electrode a capacitance element 32 is connected, and a grounding or a connection to other electrode is made via the capacitance element.

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 device, and more particularly to a color cathode ray tube device which displays a high-quality image by reducing elliptic distortion of a beam spot in a peripheral portion of a screen.

[0002]

2. Description of the Related Art Generally, a color cathode ray tube device has an envelope composed of a panel and a funnel, and three electron beams emitted from an electron gun disposed in the neck of the funnel are mounted on the outside of the funnel. Deflected by the horizontal and vertical deflection magnetic fields generated by the deflection yoke, and horizontally and vertically scanned by a phosphor screen provided on the inner surface of the panel via a shadow mask, thereby forming a structure for displaying a color image. I have.

At present, such a color cathode ray tube apparatus is of an inline type in which an electron gun emits three electron beams arranged in a line composed of a center beam and a pair of side beams passing on the same horizontal plane, and a horizontal deflection generated by a deflection yoke. Self-convergence, in which the magnetic field is made into a pincushion type and the vertical deflection magnetic field is made into a barrel type, these three horizontal and vertical deflection magnetic fields concentrate three electron beams over the entire screen.
In-line type color CRT devices have become mainstream.

However, in this self-convergence in-line type color CRT device, the sectional shape of the electron beam is distorted as the deflection angle increases, and as shown in FIG. Also, the beam spot 1 at the periphery of the screen is distorted into a shape with a low-brightness halo portion 3 in the vertical direction (V-axis direction) of the high-brightness core portion 2 that is long in the horizontal direction (H-axis direction). There is a problem that the resolution is deteriorated.

[0005] This is because a non-uniform horizontal and vertical deflection magnetic field acts as an equivalent quadrupole lens in which the electron beam diverges in the horizontal direction and converges in the vertical direction. This is because there is an underfocusing and astigmatism that causes an overfocusing state in the vertical direction.

Japanese Patent Application Laid-Open No. 61-99249 discloses an electron gun for improving the resolution deterioration caused by such a deflection aberration. The bi-potential [BPF (Bi-
Potential Focus)] type DAC & F (D
dynamic Astigmatism Correc
1 shows an electron gun of a T.I.T. and Focus type.

This electron gun has three cathodes K arranged in a row, and first and second plate-like grids G1, G2 arranged in the direction of the phosphor screen in order from the cathodes K.
, Two cylindrical divided electrodes G31, G3 of the third grid G3.
2 and a cup-shaped fourth grid G4. In each of these electrodes, three electron beam passage holes are formed in a row so as to correspond to three cathodes K. In particular, on the divided electrode G32 side of the divided electrode G31, as shown in FIG. , Three vertically elongated electron beam passage holes 5 having a long axis in the vertical direction are formed, and the divided electrode G32 side of the divided electrode G32 is
As shown in FIG. 2B, a horizontally long 3 with the long axis in the horizontal direction.
The plurality of electron beam passage holes 6 are formed.

In this electron gun, about 150 V is applied to the cathode K.
And the first grid G1 is grounded. About 600 V is applied to the second grid G2, about 6 kV is applied to the divided electrode G31 of the third grid G3, and about 6 kV is applied to the divided electrode G32.
A voltage of about 26 kV is applied to the fourth grid G4, which is a dynamic voltage in which a parabolic voltage Vd rising in synchronization with the deflection of the electron beam is superimposed on this voltage.

As a result, the cathode K and the first and second
The grids G1 and G2 form a triode that generates an electron beam and forms an object point with respect to a main lens described later. The pre-focus lens for pre-focusing the electron beam from the triode is formed by the divided electrodes G31 of the second grid G2 and the third grid G3. The divided electrode G32 of the third grid G3 and the fourth grid G4 form a BPF-type main lens that finally accelerates and focuses the prefocused electron beam on the phosphor screen.

When the electron beam is deflected in the peripheral direction of the phosphor screen, a potential difference occurs between the divided electrodes G31 and G32 due to the dynamic voltage applied to the divided electrode G32, so that the electron beam is focused in the horizontal direction and vertically focused. A quadrupole lens diverging in the direction is formed to compensate for the deflection aberration generated by the pincushion horizontal deflection magnetic field and the barrel vertical deflection magnetic field of the deflection yoke.

However, in this electron gun, as shown in FIG. 18, the lateral collapse of the core portion 2 of the beam spot 1 at the peripheral portion of the screen is not eliminated, and the lateral collapse of the beam spot 1 is caused by the passage of the electron beam through the shadow mask. Moire is caused by interfering with the holes, making it difficult to see characters and the like when displayed.

The lateral collapse of the beam spot 1 will be described using an optical model. FIG. 19A shows the case where the electron beam enters the center of the phosphor screen without being deflected, and FIG. 19B shows the case where the electron beam is deflected and enters the peripheral portion of the phosphor screen. In these drawings, reference numeral 8 denotes an electron beam, 9 denotes a phosphor screen, ML denotes a main lens, QL denotes a quadrupole lens formed by two divided electrodes of a third grid, and DL denotes an equivalent having a non-uniform deflection magnetic field. It is a quadrupole lens.

In general, the size of the beam spot 1 on the screen depends on the magnification M. The magnification M is a ratio α between the divergence angle αo of the electron beam 4 and the incident angle αi on the phosphor screen.
o / αi. Therefore, the magnification in the horizontal direction is Mh, the magnification in the vertical direction is Mv, and the divergence angle αo in the horizontal direction.
Assuming h, incident angle αih, vertical divergence angle αov, and incident angle αiv, Mh = αoh / αih Mv = αov / αiv

Therefore, when αoh = αov, when there is no deflection shown in FIG. 19A, αih = αiv Mh = Mv, and the beam spot at the center of the screen is circular. However, at the time of deflection shown in FIG. 19 (b), αih <αivMh> Mv, and the beam spot in the peripheral portion collapses horizontally.

The reason why the beam spot at the peripheral portion of the screen is laterally collapsed is that the astigmatism caused by the deflection magnetic field is compensated by the quadrupole lens QL formed at a position apart from the deflection magnetic field. Therefore, in order to reduce the horizontal collapse of the beam spot at the periphery of the screen, the quadrupole lens QL may be brought as close as possible to the deflection magnetic field. That is, if the quadrupole lens QL for compensating the astigmatism caused by the deflecting magnetic field is made to coincide with the deflecting magnetic field, αih = αiv, and the beam spot at the periphery of the screen can be made circular. Thus, it is structurally impossible to make the quadrupole lens QL and the deflection magnetic field coincide with each other.
If the pole lens QL is brought closer to the deflection magnetic field, it is possible to reduce the horizontal collapse of the beam spot at the peripheral portion of the screen as compared with the conventional color CRT device.

As means for bringing the quadrupole lens QL closer to the deflection magnetic field, Japanese Patent Application Laid-Open No. 64-38947 discloses an electron gun in which two quadrupole lenses having different functions are formed on the main lens.

As shown in FIG. 20, this electron gun comprises three cathodes K arranged in a row, first to sixth grids G1 to G6 arranged in the direction of the phosphor screen from the cathode K in that order. It comprises two intermediate electrodes Gm1, Gm2 arranged between the fifth grid G5 and the sixth grid G6. In this electron gun, a main lens is formed by a fifth grid G5, two intermediate electrodes Gm1, Gm2 and a sixth grid G6. The intermediate electrode Gm1 of the fifth grid G5
On the side, three horizontally long electron beam passage holes 11 long in the horizontal direction shown in FIG. 21A are formed, and the intermediate electrodes Gm1, Gm
m2 has three circular electron beam passage holes 1 shown in FIG.
2 are formed on the intermediate electrode Gm2 side of the sixth grid G6, and three horizontally long electron beam passage holes 13 long in the horizontal direction shown in FIG.

The fifth grid G5 is applied with a dynamic voltage in which a predetermined DC voltage is superimposed with a parabolic voltage Vd that rises in synchronization with the deflection of the electron beam. The intermediate electrodes Gm1 and Gm2 are The high voltage applied to the sixth grid G6 is divided by the resistor 14 so that the intermediate electrode G
A voltage of about 40% of the voltage applied to the sixth grid G6 is applied to m1, and a voltage of about 65% is applied to the intermediate electrode Gm2.

With the application of the above-mentioned voltage, in this electron gun, when there is no deflection, as shown in FIG.
A quadrupole lens QL1 having a function of diverging in the horizontal direction and converging in the vertical direction (V-axis direction) by the fifth grid and the intermediate electrode adjacent thereto, a cylindrical lens CL between the two intermediate electrodes, and a sixth grid. G6 and the intermediate electrode adjacent thereto have the function of converging horizontally and diverging vertically.
The pole lens QL2 is formed. And at the time of deflection,
Fifth grid G that increases in synchronization with the deflection of electron beam 8
5 As the voltage rises, the potential difference between the fifth grid and the intermediate electrode adjacent to the fifth grid decreases, and the quadrupole lens QL1 weakens, as shown in FIG. As a result, the action of focusing in the horizontal direction and diverging in the vertical direction by the quadrupole lens QL2 becomes relatively strong, and the shape of the beam spot at the periphery of the screen is improved.

That is, the incident angles αih and αiv in the horizontal and vertical directions on the phosphor screen are αih> αiv, and as shown in FIG. 23, the lateral collapse of the beam spot 1 around the phosphor screen is improved. However, the central beam spot 1 is vertically long.

[0021]

As described above, in order to improve the image quality of a color CRT device, it is necessary to maintain good focus characteristics over the entire surface of the phosphor screen and to reduce the lateral collapse of the beam spot. is necessary.

In a conventional BPF type DAC & F type electron gun, a dynamic voltage in which a parabolic voltage which rises in synchronization with the deflection of an electron beam is applied to a low-voltage electrode of the main lens is applied to the main lens. By making the intensity variable and forming a dynamically changing quadrupole lens, the vertical bleeding of the beam spot due to deflection aberration is eliminated, and the entire screen is focused. But,
With this electron gun, it is not possible to eliminate the collapsing of the beam spot at the periphery of the screen. Therefore, there is a problem that the horizontal collapse of the beam spot interferes with the electron beam passage hole of the shadow mask to cause moire or the like, making it difficult to see characters and the like when displayed.

As an electron gun for reducing the horizontal collapse of the beam spot at the peripheral portion of the screen, a quadrupole lens having a function of diverging the main lens in the horizontal direction and converging in the vertical direction, a function of converging in the horizontal direction and diverging in the vertical direction There is a type that forms a quadrupole lens having the following function. With this electron gun, the beam spot at the center becomes long vertically even if the beam spot at the periphery of the screen can be reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to constitute a color CRT device which displays a high-quality image by reducing elliptic distortion of a beam spot over the entire screen. I do.

[0025]

An electron gun having a cathode and a plurality of electrodes forming an electron lens for focusing an electron beam from the cathode onto a phosphor screen;
In a color cathode ray tube device having a deflection yoke for deflecting the electron beam emitted from the electron gun, a main lens for finally focusing the electron beam of the electron gun on the phosphor screen is used to deflect the electron beam of the deflection yoke. A focus electrode to which a dynamic voltage that rises in synchronization is applied, an anode electrode, and at least one additional electrode provided between these electrodes and supplied with a voltage obtained by dividing the voltage of the anode electrode by a resistor, A non-circular electron beam passage hole was formed in the additional electrode, and a capacitor was connected to the additional electrode. The capacitor was connected to ground or another electrode via the capacitor.

The non-circular electron beam passage hole of the additional electrode was formed in a vertically long shape having a long axis in the vertical direction, and this additional electrode was grounded via a capacitor.

Further, the non-circular electron beam passage hole of the additional electrode was formed in a vertically long shape having a long axis in the vertical direction, and this additional electrode was connected via a capacitor to an electrode to which no dynamic voltage was applied.

Further, the non-circular electron beam passage hole of the additional electrode was formed in a horizontally long shape having a long axis in the horizontal direction, and this additional electrode was connected to an electrode to which a dynamic voltage was applied via a capacitive element.

[0029]

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

FIG. 1 shows a configuration of an in-line type color CRT device which is one embodiment thereof. This color cathode ray tube device has an envelope composed of a panel 20 and a funnel 21 having a funnel shape. On the inner surface of the panel 20, a phosphor screen 22 composed of a three-color phosphor layer which emits blue, green and red light is provided. Is provided. Further, a shadow mask 23 having a large number of electron beam passage holes formed therein is disposed opposite to the phosphor screen 22. On the other hand, in the neck 25 of the funnel 21, a center beam 26G and a pair of side beams 26B, 26B passing on the same horizontal plane are provided.
R consisting of three electron beams 26B, 26G, 2
An electron gun 27 for emitting 6R is provided. further,
A deflection yoke 29 is mounted from the large diameter portion 28 of the funnel 21 to the outside of the neck 25. Then, the three electron beams 26B, 26G,
26R is deflected by a horizontal and vertical deflection magnetic field generated by a deflection yoke 29, and the phosphor screen 22 is horizontally and vertically scanned through a shadow mask 23, so that a color image is displayed.

As shown in FIG. 2, the electron gun 27 has three cathodes K arranged in a row in the horizontal direction, three heaters (not shown) for individually heating these cathodes K, and A first grid G1, a second grid G2, and a third grid G3 of an integral structure are sequentially arranged in the direction of the phosphor screen from the cathode K.
G32, a fourth grid G4, and the heater, the cathode K, and the electrode are integrally fixed by a pair of insulating supports (not shown).

Of the above electrodes, the first and second grids G1
, G2 are plate-shaped electrodes having an integral structure, and three circular electron beam passage holes corresponding to three cathodes K are formed in a line in these electrodes. Third grid G
The two divided electrodes G31 and G32 of FIG. 3 are each formed of a cylindrical electrode having an integral structure.
Three circular electron beam passage holes are formed in one row corresponding to the three cathodes K. The fourth grid G4 is
It is composed of an integral cup-shaped electrode, and three circular electron beam passage holes corresponding to the three cathodes K are formed in a line on the surface of the electrode on the third grid G3 side.

Further, in the electron gun 27, as shown in FIG. 3, three cathodes are provided at the geometric center between the divided electrode G32 of the third grid G3 and the fourth grid G4. A plate-shaped additional electrode Gm in which three vertically elongated non-circular electron beam passage holes 31 having a long axis in the vertical direction is formed, and is integrally fixed together with the other electrodes by the pair of insulating supports. . The capacitor 32 is connected to the additional electrode Gm, and is grounded via the capacitor 32.

In this electron gun 27, the cathode K is
A voltage in which a video signal is superimposed on a voltage of V
Grid G1 is grounded. About 6 in the second grid G2
00V, about 6 k is applied to the divided electrode G31 of the third grid G3.
As shown in FIG. 4, a dynamic voltage 3 in which a DC voltage of about 6 kV and a parabolic voltage Vd which rises in synchronization with the sawtooth deflection current 34 are superimposed on the divided electrode G32 as shown in FIG.
5 is applied. A high voltage of about 26 kV is applied to the fourth grid G4. As shown in FIG. 1, the high voltage applied to the fourth grid G4 is divided by the resistor 36 disposed along the electron gun 27 to the third electrode Gm.
A voltage of about 16 kV which is intermediate between the DC component (about 6 kV) applied to the divided electrode G32 of the grid G3 and the voltage applied to the fourth grid G4 is applied.

By applying such a voltage, the cathode K
The first and second grids G1 and G2 form a triode that generates an electron beam and forms an object point with respect to a main lens described later. The divided electrodes G31 of the second grid G2 and the third grid G3 form a prefocus lens for prefocusing the electron beam from the triode. The split lens G32 (focus electrode) to the fourth grid G4 (final accelerating electrode) of the third grid G3 form a main lens that finally focuses the electron beam on the phosphor screen, and the arrangement of the additional electrode Gm. Thereby, a quadrupole lens is formed in the main lens.

When the electron beam is not deflected, the main lens shown in FIG. 5A has a central axis ZG of the electron beam passage hole.
Equipotential line 3 with the upper side as the vertical direction and the lower side as the horizontal direction
As shown by 8, an electric field 39a equivalent to the electric field 39 of the BPF type main lens in which the intermediate electrode Gm shown in FIG. 6A is not arranged is formed in both the horizontal and vertical directions, and the electron beam shown in FIG. The potential distribution 40a on the central axis of the passage hole is shown in FIG.
The potential distribution 40 on the central axis of the electron beam passage hole when the intermediate electrode Gm is not arranged as shown in FIG. Therefore, when the electron beam 26 (26B, 26G, 26R) is not deflected, no quadrupole lens is formed in the main lens, the focusing power in the horizontal and vertical directions is equal, and there is no astigmatism. Therefore, a substantially circular beam spot is formed at the center of the screen.

FIG. 7A shows an optical model of the main lens in this case. As described above, the electric field of the main lens ML is BP
Since it is equivalent to the electric field of the F-type main lens, the horizontal incident angle αih and the vertical incident angle α
iv are equal, horizontal magnification Mh and vertical magnification Mv
Becomes equal to Mh = Mv. As a result, the electron beam emitted from the cathode K and pre-focused by the prefocus lens formed by the second grid G2 and the divided electrode G32 of the third grid G3 is focused at the center of the screen by the main lens ML. , Forming a substantially circular beam spot.

On the other hand, when the electron beam is deflected, the dynamic voltage applied to the divided electrode G32 of the third grid G3 increases in synchronization with the deflection of the electron beam, and the additional electrode Gm An AC voltage corresponding to the AC component of the dynamic voltage applied to the divided electrode G32 is induced via the capacitance between the divided electrode G32 and the divided electrode G32.

Here, the capacitance between the additional electrode Gm and the divided electrode G32 is represented by C1, the additional electrode Gm and the fourth grid G4.
And the AC voltage V1 induced on the additional electrode Gm, the capacitance C2 is expressed as follows: V1 = [C1 / (C1 + C2)] Vd when the capacitive element 32 is not connected to the additional electrode Gm. You. In this case, the additional electrode Gm is
And the fourth grid G4, it is located at the geometric center, so that C1 = C2 and V1 = (1/2) Vd. Therefore, when the electron beam is deflected, the voltage Ecm (1) of the additional electrode Gm becomes Becomes On the other hand, the voltage Ec3 (1) of the divided electrode G32 is Ec3 (1) = 6 kV + Vd.

Incidentally, the voltage Ecm (1) of the additional electrode Gm
When the voltage of the fourth grid G4 is Eb when the capacitance element 32 is not connected to the additional electrode Gm, [Ecm
(1) -Ec3 (1)] / [Eb-Ec3 (1)] = 1/2, which is an intermediate value of the main lens potential regardless of the dynamic voltage applied to the divided electrode G32 of the third grid G3. Therefore, even if a dynamic voltage is applied to the divided electrode G32,
The electric field on the divided electrode G32 side of the additional electrode Gm and the fourth grid G
The electric field on the 4 side is balanced, and no quadrupole lens is formed irrespective of the shape of the electron beam passage hole of the additional electrode Gm.

However, as shown in FIG.
Is connected to the additional electrode Gm.
Is V2 = [C1 / (C1 + C2 + C3)] Vd. In this case, since the additional electrode Gm is located at the geometric center between the divided electrode G32 of the third grid and the fourth grid G4, C1 = C2, and V2 = [C1 / (2C1 + C3)] Vd. Becomes

Thus, for example, if C1 = C2 = 2.5 pF C3 = 5 pF, Becomes

Therefore, the capacitive element 32 is connected to the additional electrode Gm.
And the voltage E of the additional electrode Gm when this is grounded.
cm (2), if the electron beam is deflected, It can be.

This means that the capacitive element 32 is connected to the additional electrode Gm.
And grounding it, the AC voltage induced on the additional electrode Gm is suppressed, and the voltage of the additional electrode Gm when the capacitive element 32 is not added can be made lower.

As a result, the balance between the electric field of the additional electrode Gm on the side of the divided electrode G32 of the third grid and the electric field of the additional electrode Gm on the side of the fourth grid G4 is disturbed. As shown in FIG. 9, the potential of the additional electrode Gm on the fourth grid G4 side passes through the non-circular electron beam passage hole 31 whose major axis is in the vertical direction of the additional electrode Gm. Penetrate to the side. As a result, as shown in FIG. 7B, a quadrupole lens QL that converges in the horizontal direction and diverges in the vertical direction is formed on the main lens ML, and the main lens ML has astigmatism, and is deflected. Compensate for magnetic field astigmatism. Further, the difference between the horizontal magnification Mh and the vertical magnification Mv is reduced, and the horizontal collapse of the beam spot 1 at the periphery of the screen is reduced.

As a result, when the electron gun is configured as described above, the beam spot at the center of the screen becomes substantially circular as described above, and the lateral beam spot at the peripheral portion is reduced, as shown in FIG. Thus, the shape of the beam spot 1 can be improved over the entire screen.

In the above embodiment, the capacitive element connected to the additional electrode is grounded.
Similar effects can be obtained by connecting to an electrode other than the grid to which no dynamic voltage is applied.

In the above embodiment, the capacitance of the capacitor connected to the additional electrode is twice the capacitance between the additional electrode and the divided electrode of the third grid adjacent thereto. The capacitance of the capacitor is not limited to this.

Next, another embodiment will be described.

The overall structure of the color cathode ray tube device is the same as that of the in-line type color cathode ray tube device shown in FIG. 1, and a description thereof will be omitted.

As shown in FIG. 11, the electron gun has three cathodes K arranged in a line in the horizontal direction, three heaters (not shown) for individually heating these cathodes K, and the cathode K , A first grid G1 and a second grid G2 of an integral structure sequentially arranged in the direction of the phosphor screen.
, A third grid G3, two divided electrodes G31 and G32, and a fourth grid G4. The heater, the cathode K, and the electrode are integrally fixed by a pair of insulating supports (not shown).

Of the above electrodes, the first and second grids G1
, G2 are plate-shaped electrodes having an integral structure, and three circular electron beam passage holes corresponding to three cathodes K are formed in a line in these electrodes. Third grid G
Each of the two divided electrodes G31 and G32 is a cylindrical electrode having an integral structure. At both ends of the electrodes, three circular electron beam passage holes corresponding to three cathodes K are arranged in a line. Is formed. The fourth grid G4 is composed of a cup-shaped electrode having an integral structure. The surface of the third grid G3 on the side of the divided electrode G32 also corresponds to three cathodes K.
The circular electron beam passage holes are formed in a line.

Further, in the electron gun 27, as shown in FIGS. 12 (a) and 12 (b), the geometrical center between the divided electrode G32 of the third grid G3 and the fourth grid G4 is Three non-circular electron beam passing holes 31 having a horizontal axis as a long axis and one non-circular electron beam passing hole common to a horizontal three electron beams having a long axis as a horizontal axis correspond to the three cathodes. A plate-shaped additional electrode Gm on which 31 is formed is arranged, and is integrally fixed together with the other electrodes by the pair of insulating supports. Further, the additional electrode Gm is connected to the divided electrode G32 of the third grid G3 via the capacitive element 32.

In this electron gun 27, the cathode K is
A voltage in which a video signal is superimposed on a voltage of V
Grid G1 is grounded. About 6 in the second grid G2
00V, about 6 k is applied to the divided electrode G31 of the third grid G3.
V, about 6 kV as shown in FIG.
Dynamic voltage 3 in which a parabolic voltage Vd rising in synchronization with the sawtooth deflection current 34 is superimposed on the DC voltage of
5 is applied. A high voltage of about 26 kV is applied to the fourth grid G4. As shown in FIG. 11, a voltage dividing resistor 36 disposed along the electron gun 27 is connected to the additional electrode Gm.
Divides the high voltage applied to the fourth grid G4, thereby dividing the high voltage applied to the divided electrode G32 of the third grid G3 (approximately 6 kV) from the voltage applied to the fourth grid G4. A voltage of kV is applied.

As a result, the cathode K and the first and second
The grids G1 and G2 form a triode that generates an electron beam and forms an object point with respect to a main lens described later. By the second grid G2 and the third grid G3,
A prefocus lens for prefocusing the electron beam from the triode is formed. The divided electrode G32 to the fourth grid G4 of the third grid G3 form a main lens that finally focuses the electron beam on the phosphor screen, and the main lens is further divided by the arrangement of the additional electrode Gm.
A pole lens is formed.

When the electron beam is not deflected, the electron gun 27 is also equivalent to the electric field 39 of the BPF main lens without the additional electrode Gm shown in FIG. A strong electric field is formed, and the potential distribution on the center axis of the electron beam passage hole becomes the same as the potential distribution 40 on the center axis of the electron beam passage hole when the additional electrode Gm is not arranged as shown in FIG. Therefore, no quadrupole lens is formed in the main lens, the focusing power in the horizontal and vertical directions is equal, no astigmatism is formed, and a substantially circular beam spot is formed at the center of the screen.

On the other hand, when the electron beam is deflected, the dynamic voltage applied to the divided electrode G32 of the third grid G3 increases in synchronization with the deflection of the electron beam, and the additional electrode Gm An AC voltage corresponding to the AC component of the dynamic voltage applied to the divided electrode G32 is induced via the capacitance between the divided electrode G32 and the divided electrode G32.

That is, as shown in FIG. 13, when the capacitance C3 of the capacitive element 32 connected to the additional electrode Gm is set, the AC voltage V3 induced at the additional electrode Gm is V3 = [(C1 + C3) / (C1 + C2 + C3)] Vd, and the additional electrode Gm is divided into the divided electrode G32 and the fourth grid G.
4 and C3 = C2, and V3 = [(C1 + C3) / (2C1 + C3)] Vd.

Thus, for example, if C1 = C2 = 2.5 pF C3 = 5 pF, then V3 = [(2.5 + 5) / (2 × 2.5 + 5)] Vd = (3/4) Vd.

Therefore, the additional electrode Gm is connected to the capacitive element 32
Is the voltage Ecm (3) of the additional electrode Gm when connected to the divided electrode G32 to which the dynamic voltage is applied via
If the electron beam is deflected, It can be.

This means that the capacitive element 32 is connected to the additional electrode Gm.
Connected to the electrode to which the dynamic voltage is applied, the AC voltage induced on the additional electrode Gm increases, and the additional electrode G when the capacitive element 32 is not added.
This indicates that the voltage can be higher than m.

As a result, the divided electrode G32 of the additional electrode Gm
The balance between the electric field on the side of the fourth grid G4 and the electric field on the side of the fourth grid G4 is broken, and the electric field on the divided electrode G32 side of the additional electrode Gm becomes stronger than the electric field on the side of the fourth grid G4, as shown in FIG.
The potential of the additional electrode Gm on the divided electrode G32 side penetrates into the fourth grid G4 through a non-circular electron beam passage hole whose major axis is the horizontal direction of the additional electrode Gm. As a result, FIG.
As shown in (1), a quadrupole lens QL converging in the horizontal direction and diverging in the vertical direction is formed on the main lens ML, the main lens ML has astigmatism, and the astigmatism of the deflection magnetic field is compensated. . Also, the difference between the horizontal magnification Mh and the vertical magnification Mv is reduced, and the horizontal collapse of the beam spot 1 around the phosphor screen is reduced.

As a result, similarly to the electron gun of the above-described embodiment, as shown in FIG. 10, the shape of the beam spot 1 can be made good over the entire screen.

In the above embodiment, the capacitance of the capacitive element connected to the additional electrode is set to twice the capacitance between the additional electrode and the electrode to which the dynamic voltage is applied. The capacitance of the connected capacitive element is not limited to this.

[0065]

As described above, at least one additional electrode is arranged between the focus electrode forming the main lens for finally focusing the electron beam on the phosphor screen and the anode electrode. When a capacitive element is connected to the ground and connected to the ground or to another electrode via this capacitive element, a dynamically changing quadrupole lens can be formed in the main lens so that astigmatism can be imparted. A color CRT device that can reduce spot distortion and display a good image can be configured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a color CRT device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an electron gun of the color CRT device.

FIG. 3 is a view showing a shape of an electron beam passage hole of an additional electrode of the electron gun.

FIG. 4 is a diagram showing a relationship between a deflection current of a deflection yoke and a dynamic voltage applied to a divided electrode of a third grid of the electron gun in synchronization with the deflection current.

5A is a diagram showing an electric field of a main lens provided with an additional electrode when an electron beam is not deflected; FIG.
(B) is a diagram showing a potential distribution on the center axis of the electron beam passage hole.

FIG. 6 (a) is a graph showing B when the electron beam is not deflected.
FIG. 6B is a diagram showing an electric field of the PF type main lens, and FIG. 6B is a diagram showing a potential distribution on the central axis of the electron beam passage hole.

7A is an optical model diagram for explaining an operation of a main lens provided with an additional electrode when the electron beam is not deflected, and FIG. 7B is a diagram showing a main model when the electron beam is deflected. FIG. 3 is an optical model diagram for explaining an operation of a lens.

FIG. 8 is a diagram for explaining an AC voltage induced on the additional electrode when a capacitor connected to the additional electrode is grounded.

FIG. 9 is a diagram showing an electric field of a main lens of the electron gun shown in FIG. 2 when an electron beam is deflected.

FIG. 10 is a diagram showing a shape of a beam spot on a phosphor screen of the color CRT device according to the embodiment of the present invention;

FIG. 11 is a diagram showing a configuration of an electron gun according to another embodiment of the present invention.

12 (a) and 12 (b) respectively show FIG.
FIG. 4 is a view showing a shape of an electron beam passage hole of an additional electrode of the electron gun shown in FIG.

FIG. 13 is a diagram for explaining an AC voltage induced on the additional electrode when the capacitive element connected to the additional electrode is connected to a third grid to which a dynamic voltage is applied.

FIG. 14 is a diagram showing an electric field of a main lens of the electron gun shown in FIG. 11 when the electron beam is deflected.

FIG. 15 is a diagram showing a shape of a beam spot on a phosphor screen of a conventional in-line type color CRT device.

FIG. 16 shows a BPF type DA of a conventional color CRT device.
FIG. 2 is a diagram illustrating a configuration of a C & F type electron gun.

17 (a) and 17 (b) show the above B
It is a figure showing the shape of the electron beam passage hole of two divided electrodes of the 3rd grid of the PF type DAC & F type electron gun.

FIG. 18 is a view showing the shape of a beam spot on a phosphor screen of a color CRT device having the BPF DAC & F type electron gun.

FIG. 19 (a) shows the conventional BPF type DAC &
FIG. 19B is an optical model diagram when the electron beam of the F-type electron gun is not deflected, and FIG. 19B is an optical model diagram when the electron beam is deflected.

FIGS. 20 (a) and 20 (b) are diagrams each showing a configuration of an improved conventional electron gun.

FIG. 21A is a view showing a fifth example of the electron gun shown in FIG. 20;
FIG. 21 is a view showing the shape of an electron beam passage hole in the grid, FIG.
(B) is a diagram showing the shape of an electron beam passage hole in the intermediate electrode;
FIG. 21C is a diagram showing the shape of the electron beam passage hole of the sixth grid.

22 (a) is an optical model diagram when the electron beam of the electron gun shown in FIG. 20 is not deflected, and FIG. 22 (b)
FIG. 3 is an optical model diagram when an electron beam is deflected.

FIG. 23 is a diagram showing a shape of a beam spot on a phosphor screen of the color CRT device having the electron gun shown in FIG. 20;

[Explanation of symbols]

 22 phosphor screens 26B, 26G, 26R 3 electron beams 27 electron gun 29 deflection yoke 31 electron beam passage hole 32 capacitive element 34 deflection current 35 dynamic voltage K cathode G1 first grid G2 Second grid G3 ... Third grid G31 ... Third grid divided electrode G32 ... Third grid divided electrode G4 ... Fourth grid Gm ... Additional electrode K ... Cathode ML ... Main lens

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hirofumi Ueno 7-1, Nisshincho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Toshiba Electronics Engineering Co., Ltd. (72) Inventor Tsutomu Takekawa 7-1, Nisshin-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa F-term (reference) in Toshiba Electronics Engineering Corporation 5C041 AA03 AB07 AC07 AC26 AC34 AC35 AD02 AD03 AE01

Claims (4)

[Claims] 1. An electron gun having a cathode and a plurality of electrodes forming an electron lens for focusing an electron beam from the cathode on a phosphor screen, and a deflection yoke for deflecting an electron beam emitted from the electron gun. In the color cathode ray tube device comprising: a dynamic voltage is applied to the electron gun so that the main lens that finally focuses the electron beam on the phosphor screen rises in synchronization with the deflection of the electron beam by the deflection yoke. A focus electrode, an anode electrode, and at least one additional electrode disposed between the electrodes and supplied with a voltage obtained by dividing the voltage of the anode electrode by a resistor. The additional electrode has a non-circular electron beam passage hole. Is formed, and a capacitance element is connected to the additional electrode. Color cathode ray tube apparatus characterized by being continued. 2. The non-circular electron beam passage hole of the additional electrode is formed in a vertically long shape having a vertical axis as a major axis, and the additional electrode is grounded via a capacitance element. Color CRT equipment. 3. The non-circular electron beam passage hole of the additional electrode is formed in a vertically long shape having a long axis in a vertical direction, and the additional electrode is connected to an electrode to which a dynamic voltage is not applied via a capacitor. The color CRT device according to claim 1, wherein 4. A non-circular electron beam passage hole of an additional electrode is formed in a horizontally long shape having a long axis in a horizontal direction, and the additional electrode is connected to an electrode to which a dynamic voltage is applied via a capacitive element. The color cathode ray tube device according to claim 1, wherein: