JPH09223470A - Cathode ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make beam spots on a screen small and distortion free to enhance the resolution of a cathode ray tube by dividing a focusing electrode and a final accelerating electrode into three, and supplying the specified voltage to each divided electrode. SOLUTION: In an electron gun 16, a part of a third grid G3 (a focusing electrode) on a fourth grid G4 (a final accelerating electrode) side is divided into first, second, third electrode elements G31, G32, G33, and the part of the grid G4 on the grid G3 side is divided into first, second, third electrode elements G41, G42, G43. The elements G31 and G33, and G41 and G43 are connected within the tube, and focusing voltage is applied to the elements G41, G43, and final accelerating voltage is applied to the elements G41, G43. The final accelerating voltage supplied to a high voltage supply terminal 23a of a resistor 17 is resistance-divided, and voltage higher than focusing voltage is applied from an intermediate terminal 23c to the element G32, and high voltage supplied to the terminal 23a of the resistor 17 is resistance-divided, and voltage lower than final accelerating voltage is applied from an intermediate terminal 23d to the element G42.

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 capable of obtaining good resolution.

[0002]

2. Description of the Related Art Generally, a cathode ray tube displays an image by deflecting an electron beam emitted from an electron gun by a horizontal and vertical deflection magnetic field generated by a deflection device and horizontally and vertically scanning a phosphor screen. Is formed into a structure.

In a color picture tube, an electron gun is used as an electron gun for emitting three electron beams, the three electron beams are deflected by a magnetic field generated by a deflecting device, and a phosphor screen is horizontally and vertically scanned through a shadow mask. As a result, the structure for displaying an image is formed. In such a color picture tube, the electron gun is an in-line type electron gun that emits a row of three electron beams passing through the same horizontal plane, and the row of three electron beams is used as a pincushion type horizontal deflection magnetic field and a barrel type vertical deflection. The self-convergence in-line color picture tube, which can concentrate three electron beams without the need for a special concentrator by deflecting with a non-uniform magnetic field, is now the mainstream of color picture tubes. There is.

Incidentally, the resolution of a color picture tube generally depends on the size and shape of the beam spot on the phosphor screen. Therefore, in order to improve the resolution, it is necessary to make the beam spot on the phosphor screen as small as possible and with less distortion. Further, the convergence characteristic of the three electron beams is also an important factor.

In order to reduce the beam spot, it is effective to reduce the spherical aberration by increasing the diameter of the electrode forming the main lens of the electron gun that finally focuses the electron beam on the phosphor screen. Is. For that purpose, it is necessary to increase the mutual interval of the three electron beams. However, if the mutual spacing of electron beams is increased,
The convergence characteristics of the three electron beams deteriorate, and the diameter of the electrode forming the main lens is limited by the inner diameter of the neck of the envelope in which the electron gun is arranged.

FIG. 4 shows an in-line type color picture tube electron gun which is generally used at present. This electron gun is a bi-potential type electron gun, and has three cathodes KB, KG, KR arranged in a row, and these cathodes KB, KG, KR.
Heaters (not shown) for heating the cathode K
The first grid G1, the second grid G2, the third grid G3 (focusing electrode), the fourth grid G4 (final accelerating electrode), and the fourth grid G1 which are sequentially arranged on the front surface (on the phosphor screen side) of B, KG and KR. It consists of a convergence cup C mounted on a grid G4. Each electrode G of this electron gun
1 to G4 have three circular electron beam passage holes corresponding to the three cathodes KB, KG and KR.
They are arranged in a line in the same direction as the arrangement direction of G and KR.

In this electron gun, by applying a predetermined voltage to each electrode, the cathodes KB, KG, KR and the first and second grids G1, G2 are used to form the cathodes KB, K.
It controls the electron emission from G and KR, and accelerates and concentrates the electrons emitted from these cathodes KB, KG and KR.
An electron beam forming part for forming the electron beams 1B, 1G, 1R is formed, and the next third and fourth grids G3, G4 form the three electron beams 1B, 1 from the electron beam forming part.
G, 1R is drawn out, and finally the main lens is formed that is accelerated and focused toward the phosphor screen. Then, each electron beam 1B, 1G, 1R is incident on the phosphor screen to form a beam spot.

Therefore, in such an electron gun,
Third and fourth grids G3, G4 forming the main lens
Electron beam passage holes 2B, 2G, 2R, 3B, 3G, 3
The beam spot on the phosphor screen can be reduced by increasing the diameter D of R 3 and reducing the magnification and the aberration. However, the electron beam passage hole 2B,
In order to increase the diameter D of 2G, 2R, 3B, 3G, 3R, the electron beam passage holes 2B, 2G, 2R, 3B,
It is necessary to increase the eccentricity h of 3G and 3R. However, increasing the eccentricity h leads to deterioration of the convergence characteristics.

As a means for solving such a problem, the opposing ends of the focusing electrode and the final accelerating electrode are formed into an elliptic cylindrical shape which forms an electric field common to the three electron beams, and the inside of these electrodes is provided with three. It is known to arrange an electric field correction plate for adjusting the focusing of the electron beam.

However, if the electron gun is constructed in this way,

(A) Center electron beam 1G has three electron beam arrangement directions, a pair of side beams 1B and 1R has three electron beam arrangement directions on the center beam 1G side, and one pair of side beams 1B and 1R has an opposite side of the center beam 1G. There is a difference in the focusing force in the three electron beam arranging directions and in the direction orthogonal to the three electron beam arranging directions of the center beam 1G and the pair of side beams 1B and 1R, and all of these can be controlled and matched by the electric field correction plate. It will be extremely difficult.

(B) There is a difference in the focusing power between the three-electron beam arrangement direction and the direction orthogonal to the arrangement direction between low brightness and high brightness, which causes astigmatism, resulting in low brightness and high brightness. The shape of the beam spot changes depending on the brightness.

(C) Even if the position of the electric field correction plate deviates even a little, the focusing force for each electron beam changes significantly.
Therefore, the assembly becomes difficult.

There are problems such as

[0015]

As described above, conventionally, as a means for improving the resolution of the in-line type color picture tube, there is a means for enlarging the electron beam passage hole of the electrode forming the main lens. If the electron beam passage holes are simply made large, for example, in the case of an in-line type color picture tube, the eccentric distance h of each electron beam passage hole becomes large and
This causes deterioration of the convergence characteristics of the electron beam. On the other hand, enlarging the electron beam passage hole is limited by the inner diameter of the neck in which the electron gun is arranged.

As a means for solving such a problem, the focusing electrode and the final accelerating electrode forming the main lens are formed into an elliptic cylindrical shape which forms an electric field common to three electron beams at their opposing ends, It is known to arrange an electric field correction plate inside the electrode to adjust the focusing of the three electron beams.
However, when the electron gun is configured in this way, it becomes difficult to control the focusing of each electron beam by the electric field correction plate. In addition, the beam spot changes between low brightness and high brightness.
Further, there is a problem that it is difficult to attach the electric field correction plate, and a sufficient resolution cannot be obtained.

The present invention has been made in order to solve the above problems, and an object thereof is to make the beam spot on the phosphor screen small and free from distortion so as to improve the resolution of the cathode ray tube. To do.

[0018]

An electron beam forming device having a cathode and a plurality of electrodes sequentially arranged in the phosphor screen direction from the cathode, and formed by a cathode and a plurality of electrodes successively adjoining the cathode. To an electron gun that finally accelerates and focuses an electron beam from a part on a phosphor screen by a main lens composed of an adjacent focusing electrode and a final accelerating electrode, and an electrode selected from a plurality of electrodes forming the electron gun. In a cathode ray tube comprising a resistor for supplying a predetermined voltage by dividing a final acceleration voltage supplied to a final acceleration electrode, a focusing electrode is divided into first, second and third electrode elements on the final acceleration electrode side. Then, a focusing voltage is supplied to the first and third electrode elements of this focusing electrode, and a voltage higher than the focusing voltage is supplied to the second electrode element via a resistor, and the final accelerating electrode is set to the focusing electrode. Is divided into first, second, and third electrode elements in three, and the final accelerating voltage is lower than the final accelerating voltage for the first and third electrode elements of the final accelerating electrode and the resistor for the second electrode element. It has a structure to supply voltage.

[0019]

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

FIG. 2 shows a color picture tube which is one of the forms. This color picture tube has an envelope composed of a panel 10 and a funnel 11 integrally joined to the panel 10, and a stripe-shaped phosphor layer emitting blue, green, and red light on the inner surface of the panel 10. Phosphor screen 1
2 is provided, facing the phosphor screen 12,
A shadow mask 13 in which a large number of electron beam passage holes are formed is arranged inside thereof. On the other hand, funnel 11
An electron gun 16 for emitting three electron beams 15B, 15G, 15R arranged in a row and composed of a center beam 15G passing through the same horizontal plane and a pair of side beams 15B, 15R is arranged in the neck 14 of the. Further, a resistor 17 described later is arranged inside the neck 14 along the electron gun 16. Then, 3 emitted from the electron gun 16
A color image is displayed by horizontally and vertically scanning the phosphor screen 12 by deflecting the electron beams 15B, 15G and 15R by the horizontal and vertical deflection magnetic fields generated by the deflection device 19 mounted outside the funnel 11. It is formed in the structure.

As shown in FIG. 1, the electron gun 16 has three cathodes KB, KG, which are arranged in a line in the horizontal direction.
KR, three heaters (not shown) for individually heating the cathodes KB, KG, KR, the cathodes KB, KG
, KR from the first to fourth grids G1 to G4 sequentially arranged in the direction of the phosphor screen, and a convergence cup C attached to the end of the fourth grid G4 on the phosphor screen side, and its heater, Cathode KB
, KG, KR and the first to fourth grids G1 to G4
Are integrally fixed by a pair of insulating supports (not shown). In particular, in this electron gun 16, a portion of the third grid G3 (focusing electrode) on the fourth grid G4 side is divided into first, second and third electrode elements G31, G32, G33 into three parts and a fourth grid G4 (final). The third grid G3 side portion of the accelerating electrode is formed on the first, second and third electrode elements G41, G42, G43.
It is formed in a divided structure.

Each of the first and second grids G1 and G2 is composed of a plate-shaped electrode having an integral structure, and each of the first, second and third electrode elements divided into third and fourth grids G3 and G4. G31, G32, G33, G41, G42, G43 are each 2
It is composed of a cylindrical electrode having an integrated structure in which the open ends of individual cup-shaped electrodes are butted.

In the first and second grids G1 and G2,
Corresponding to three cathodes KB, KG and KR,
Three circular electron beam passage holes having a relatively small diameter are formed in a line. The first electrode element G31 of the third grid G3
On the second grid G2 side end surface of the three cathodes KB,
Corresponding to KG and KR, three circular electron beam passage holes, which are larger than the electron beam passage holes of the second grid G2, are formed in a line. The second electrode element G32 side end surface of the first electrode element G31 of the third grid G3 and the second and third electrodes
Three cathodes K are provided on both end surfaces of the electrode elements G32 and G33, the first and second electrode elements G41 and G42 of the fourth grid G4, and the end surface of the third electrode element G43 on the second electrode element G42 side.
Corresponding to B, KG, and KR, three circular electron beam passage holes, which are larger than the electron beam passage holes on the end surface of the first electrode element G31 of the third grid G3 on the second grid G2 side, are formed in a line. Has been done. Each electron beam passage hole is provided with a burring protruding inside the electrode. Further, the end face of the fourth grid G4 on the side of the convergence cup C of the third electrode element G43 has the same diameter as the electron beam passage holes provided with the burring corresponding to the three cathodes KB, KG and KR. The three circular electron beam passage holes are formed in a line. Furthermore, at the bottom of the convergence cup C, three cathodes KB, K
Corresponding to G and KR, three circular electron beam passage holes having the same diameter as the electron beam passage holes on the end face of the third electrode element G43 of the fourth grid G4 on the convergence cup C side are formed in a line. There is.

Further, the resistor 17 is a high resistance resistor unit 2.
2 has a high voltage supply terminal 23a at one end, a ground connection terminal 23b at the other end, and two intermediate terminals 23c and 23d between the high voltage supply terminal 23a and the ground connection terminal 23b. 23c and 23d are the second electrode elements G32 of the third grid G3 of the electron gun 16, respectively.
And the second electrode element G42 of the fourth grid G4.

The electron gun 16 has three cathodes KB.
, KG, and KR are applied with a voltage in which an image signal is superimposed on a DC voltage of about 100 to 200 V, and the first grid G1
Is grounded, and the second grid G2 has a voltage of 500 to 1000V.
Voltage is applied. The first electrode element G31 and the third electrode element G33 of the third grid G3 are connected in a tube, and a voltage (focusing voltage) of about 6 to 10 kV is applied to these first and third electrode elements G31 and G33. It The first electrode element G41 and the third electrode element G43 of the fourth grid G4 are connected in a tube, and these first and third electrode elements G41 and G43 have
A high voltage (final acceleration voltage) of about 32 kV is applied.
Further, the high voltage (final acceleration voltage) supplied to the high voltage supply terminal 23a at one end of the resistor 17 is resistance-divided to the second electrode element G32 of the third grid G3, and the intermediate terminal 2
3c to the first and third electrode elements G of the third grid G3
A voltage higher than that applied to 31 and G33 by 2 to 6 kV is applied. Also, the second electrode element G of the fourth grid G4
Similarly, the high voltage supplied to the high voltage supply terminal 23a at one end of the resistor 17 is resistance-divided into the resistor 42, and the first and third electrode elements G41 and G43 of the fourth grid G4 are divided from the intermediate terminal 23d. The voltage applied is 2-6 kV lower than the high voltage applied to.

By applying such a voltage, in the electron gun 16, the cathodes KB, KG, KR and the cathodes KB, KG, KR and the first and second grids G1, G2, which are sequentially adjacent to the cathodes KB, KG, KR, are used. An electron beam forming unit is formed which controls the electron emission from KG and KR and focuses the emitted electrons into an electron beam.
The grids G2 and G3 form a prefocus lens for prefocusing the electron beam from the electron beam forming unit. Furthermore, the first, second, and third electrode elements G31, G32, G33, G41, G4 of the third and fourth grids G3, G4, respectively.
2, G43 forms a main lens that finally accelerates and focuses the electron beam prefocused by the prefocus lens onto the phosphor screen.

By the way, when the electron gun 26 is constructed as described above, the main lens can be a large-diameter lens.

That is, the third grid G3 is a portion on the side of the fourth grid G4, and the first, second and third electrode elements G31, G32,
Since the voltage is higher than the voltage applied to the first and third electrode elements G31 and G33 on both sides, the second electrode element G32 in the middle is divided into three parts. The penetration of the electric potential into the grid G3 increases, and the curvature of the equipotential line decreases. Similarly, the fourth grid G4 is the third
At the grid G3 side portion, the first, second and third electrode elements G41,
It is divided into three parts G42 and G43, and the second electrode element G42 in the middle
Since a voltage lower than the voltage applied to the first and third electrode elements G41 and G43 on both sides is applied to the third grid G
The penetration of the electric potential from 3 to the 4th grid G4 also becomes large,
The curvature of the equipotential line becomes smaller. As a result, the main lens formed by the third and fourth grids G3 and G4 becomes a large aperture lens in which the equipotential line 24 has a small curvature, as shown in FIG. Therefore, by increasing the diameter of the main lens, the beam spot on the screen can be reduced, and the resolution of the color picture tube can be greatly improved.

Although the in-line type color picture tube has been described in the above embodiment, the electron gun described above is
Since three independent electron lenses are formed corresponding to three electron beams, the present invention can be applied to a color picture tube having a delta type electron gun, and a single electron beam such as a black and white picture tube can be used. It is also applicable to other emitting cathode ray tubes.

[0030]

With respect to the focusing electrode and the final accelerating electrode forming the adjacent main lens, the focusing electrode is divided into first, second and third electrode elements on the final accelerating electrode side, and the first and third electrodes are divided. A focusing voltage is supplied to the electrode element, a voltage higher than the focusing voltage is supplied to the second electrode element via a resistor, and the final accelerating electrode is divided into first, second, and third electrode elements on the focusing electrode side into three, If the structure is such that the final accelerating voltage is supplied to the first and third electrode elements and the voltage lower than the final accelerating voltage is supplied to the second electrode element through the resistor, the penetration of the potential into the focusing electrode and the final accelerating electrode. , The curvature of equipotential lines can be made smaller, the main lens formed by the focusing electrode and the final accelerating electrode can be made larger in diameter, and the beam spot on the screen can be made smaller, which significantly improves the resolution of the cathode ray tube. Can be improved.

[Brief description of drawings]

FIG. 1 (a) is a sectional front view showing the structure of an electron gun of a color picture tube according to an embodiment of the present invention;
(B) is a side view similarly showing in section.

FIG. 2 is a diagram showing a configuration of a color picture tube according to an embodiment of the present invention.

FIG. 3 is a diagram showing equipotential lines of a main lens of the electron gun.

FIG. 4 (a) is a front view showing a cross section of the structure of a conventional electron gun of an in-line type color picture tube, and FIG. 4 (b) is a side view showing the same cross section.

[Explanation of symbols]

 12 ... Phosphor screen 15B, 15G, 15R ... 3 electron beam 16 ... Electron gun 17 ... Resistor 19 ... Deflection device G1 ... First grid G2 ... Second grid G3 ... Third grid G4 ... Fourth grid G31 ... Third First electrode element of grid G32 ... Second electrode element of third grid G33 ... Third electrode element of third grid G41 ... First electrode element of fourth grid G42 ... Second electrode element of fourth grid G43 ... Fourth Third electrode element of the grid KB, KG, KR ... Cathode

Claims (1)

[Claims] 1. A cathode and a plurality of electrodes sequentially arranged in the phosphor screen direction from the cathode,
An electron beam from an electron beam forming unit formed by the cathode and a plurality of electrodes sequentially adjacent to the cathode is finally accelerated and focused on a phosphor screen by a main lens including an adjacent focusing electrode and a final accelerating electrode. In a cathode ray tube comprising an electron gun and a resistor that supplies a predetermined voltage by dividing a final acceleration voltage supplied to the final acceleration electrode into an electrode selected from a plurality of electrodes forming the electron gun, The focusing electrode has first, second, and third electrodes on the final accelerating electrode side.
The focusing electrode is divided into three parts, the focusing voltage is supplied to the first and third electrode elements of this focusing electrode, and the voltage higher than the focusing voltage is supplied to the second electrode element through the resistor, and the final accelerating electrode. Is divided into first, second, and third electrode elements on the side of the focusing electrode. The final accelerating voltage is applied to the first and third electrode elements of the final accelerating electrode, and the resistor is applied to the second electrode element. A cathode ray tube having a structure in which a voltage lower than the final acceleration voltage is supplied through the cathode ray tube.