JPH06349419A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To obtain a high resolution over the whole area of a phosphor screen by forming an electron beam generating unit of three negative electrodes and two electrodes, and forming a main lens unit of two electrodes and a shielding cup electrode in a neck part of an electron gun. CONSTITUTION:In a neck part of an electron gun, an electron beam generating unit is formed of negative electrodes K1-K3, a first and a second electrodes 11, 12, and a main lens is formed of a third and a forth electrodes 13, 14 and a shielding cup electrode 14. Electron beam from the generating unit is made to enter the main lens along each center axes 17-19 in parallel with each other, and the center axes of the electron beam of the electrodes 13, 15 of the main lens are made to coincide with the axes 17-19. With this structure, potential of the electrode 12 is set at a value lower than that of the electrode 14, and this potential is set as same as the potential of the electrode 15, namely, the potential of a conductive film coated on the inner wall of a funnel. Converged voltage to be fluctuated synchronously with the deflection quantity of the electron beam is applied from a focus power source Vf to the electrode 13. Three beams are thereby focused, and simultaneously, overlapped on a shadow mask.

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, and in particular, has a high resolution over the entire area of a phosphor screen,
The present invention relates to a cathode ray tube equipped with an electron gun having an electron lens structure that is highly reliable, has a long life, and is easy to manufacture.

[0002]

2. Description of the Related Art A color cathode ray tube used as a monitor of a television image or an information terminal device is a face panel portion which is an image display screen, a neck portion which houses an electron gun, and a funnel which connects the face panel portion and the neck portion. A vacuum envelope that serves as a part and a shadow mask, which is a porous electrode for color selection, are suspended in the face panel section in close proximity to the screen, and an electron gun is fired on the outer surface of the funnel section. A deflection yoke is mounted for scanning the electron beam on the screen in two directions, horizontal and vertical.

FIG. 3 is a sectional view for explaining the schematic structure of this type of color cathode ray tube. 1 is a face panel, 2 is a funnel, 3 is a neck, 4 is an electron gun, 5 is a deflection yoke, and 6 is a screen. , 7 is a mask frame, 8 is a shadow mask, and R, G and B are electron beams. In the figure, the face panel 1 and the neck 3 are connected by a funnel 2 to form an integral vacuum envelope,
On the inner surface of the face panel 1, a screen 6 made of a mosaic of phosphors of at least three colors is formed. A mask frame 7 having a shadow mask 8 fixed thereto is suspended on the inner surface of the side wall of the face panel 1.

The three electron beams R, G and B emitted from the electron gun 4 are deflected by the deflection yoke 5 in two directions, horizontal and vertical, and after being color-selected by the shadow mask 8, the screen 6 is required. To form an image. FIG. 4 is a cross-sectional view for explaining an essential part of the electron gun housed in the neck, where K ₁ , K ₂ , and K ₃ are cathodes (cathodes), 11 is a first electrode (G1), and 12 is a second electrode. (G2), 13 is the third
Electrodes (G3), 14 is a fourth electrode (G4), 15 is a shield cup electrode, 16 is a conductive spring connected to the conductive film applied to the inner wall of the funnel, Vf is a dynamic focus power supply applied to the third electrode 13. is there.

Further, 11-1, 11-2, 11-3 are electron beam passage holes of the first electrode 11, 12-1, 12-2,
12-3 is an electron beam passage hole of the second electrode 12, 13-
1, 13-2 and 13-3 are electron beam passage holes of the third electrode, 14-1, 14-2 and 14-3 are electron beam passage holes of the fourth electrode 14, and 17, 18 and 19 are cathodes K _1. , K ₂ ,
The central axes passing through K ₃ and 20, 21 are the central axes of the electron beam passage holes of the fourth electrode 14.

In the electron gun having the above structure, the cathodes K ₁ , K ₂ ,
K ₃ , the first electrode 11 and the second electrode 12 constitute an electron beam generating portion, and the third electrode 13, the fourth electrode 14 and the shield cup electrode 15 constitute a so-called main lens portion. The first electrode 11 has circular electron beam passage holes 11-1 and 11-.
2, 11-3 are formed, and circular electron beam passage holes 12-1, 12-2, 12-3 are also formed in the second electrode 12. These electron beam passage holes 11-1, 1
1-2, 11-3 and 12-1, 12-2, 12-3 are
The aperture diameter is the same, or the aperture diameter of the electron beam passage holes 12-1, 12-2, 12-3 of the second electrode 12 is the electron beam passage holes 11-1, 11-2, 11- of the first electrode 11.
3 is larger than the opening diameter.

The electron beam emitted from the electron beam generator is incident on the main lens portion along the respective central axes 17, 18 and 19 substantially in parallel. The main lens portion includes a third electrode 13, a fourth electrode 14, and a shield cup electrode 15 which are main lens electrodes.
The central axes of the electron beam passage holes of the third electrode 13 and the shielding cup electrode 15 respectively coincide with the central axes 17, 18 and 19. Further, the central electron beam passage hole 14-2 of the other fourth electrode 14 constituting the main lens portion coincides with the central axis 18, but the central axis of both outer electron beam passage holes 14-1 and 14-3. 20 and 21
Are slightly displaced outward from the central axes 17 and 18, respectively.

The third electrode 12 is set to a lower potential than the fourth electrode 14, and the fourth electrode 14 having a high potential is the potential of the shield cup electrode 15, that is, the conductive film 5 applied to the inner wall of the funnel 2. They are at the same potential. Further, the focusing voltage Vf is applied to the third electrode 13 from the focusing power supply Vf, which converges in synchronization with the deflection amount of the electron beam. Third electrode 13
Since the apertures 13-2 and 14-2 in the central portion of the fourth electrode 14 are coaxial with each other, an axially symmetric main lens is formed in the central portion between the third electrode 13 and the fourth electrode 14, After being focused by the central electron beam main lens, it travels straight along a trajectory along this axis 18. On the other hand, the electron beam passage holes 131, 13-3 and 14-1, 14-3 on the outside of both electrodes are off-axis from each other, so that a non-axisymmetric main lens is formed on the outside.

Therefore, the outer electron beam passes through a portion of the main lens region, which is located in the divergent lens region formed on the side of the fourth electrode 14 and is deviated from the central axis of the lens in the direction of the central electron beam, and is caused by the main lens. At the same time as the focusing action, it receives a concentration force in the central beam direction. Thus, the three electron beams are focused and simultaneously focused on the shadow mask 8 so as to overlap each other. The operation of concentrating each electron beam in this way is called static convergence.

Each of the electron beams passes through the small holes of the shadow mask 8 and undergoes color selection, and reaches the screen 6 only at the portion where the phosphor of the corresponding color is excited to emit light. The deflection yoke 5 two-dimensionally scans the electron beam to reproduce an image on the screen. The resolution characteristics of the color cathode ray tube as described above are greatly affected by the synergistic effect of the aberration of the main lens and the aberration of the electron beam generating portion. If both of these aberrations can be reduced, it is possible to suppress a decrease in resolution due to an increase in the spot diameter of the electron beam on the screen.

During high current operation, the electron beam spreads in the main lens, and the main lens aberration is dominant. It is well known that in order to reduce the main lens aberration, it is effective to enlarge the diameter of the electrode forming the main lens. For example, as disclosed in Japanese Examined Patent Publication No. 2-189842, it is proposed to improve the resolution by using a non-cylindrical main lens that can effectively enlarge the main lens aperture from a limit value by the inner diameter of the neck portion. Has been done.

On the other hand, when operating at a low current, the electron beam has a small spread in the main lens, so the influence of the main lens aberration is small, and the aberration of the electron beam generating portion becomes dominant.
FIG. 5 illustrates the aberration of the electron beam generator that determines the resolution characteristic during low current operation, and illustrates the configuration of the electron beam generator that is conventionally used when the electron beam passage holes of the first electrode and the second electrode are circular. 6 is a schematic diagram for explaining the operation of the electron beam generator in the central electron beam of FIG. 5, the same reference numerals as those in FIG. 4 correspond to the same portions, and 24 is a crossover.

In each of the figures, the electron beams emitted from the cathodes K ₁ , K ₂ and K ₃ pass through the electron beam passage holes 11-1, 11-2 and 11-3 of the first electrode 11 and then, Electron beam passage holes 12-1, 12-2, 12- of the two electrodes 12
Just before 3, it converges once and then enters the main lens unit. This converged portion is called a crossover, and the electron beam diameter of this portion is called a crossover diameter Dc.

Since the main lens unit projects the crossover 24 onto the screen, the smaller the crossover diameter Dc, the smaller the spot diameter of the electron beam on the screen and the higher the resolution. When there is no aberration in the electron beam generating portion, the crossover diameter Dc becomes 0, but in reality, the crossover diameter Dc becomes finite due to the thermal initial velocity dispersion of the electron beam in the radial direction. The crossover diameter Dc is The following relation is found from the logical expression of Langmuir.

Dc ∞ √ (Ik / Jk) where Ik is the cathode current and Jk is the cathode current density.
From the above formula, when the cathode current Ik is constant, the cathode current density Jk must be increased in order to reduce the crossover diameter Dc during the small current operation. Cathode current density Jk
Can be increased by decreasing the diameter of the electron beam passage holes 11-1, 11-2, 11-3 of the first electrode 11.

On the other hand, when the size of the electron gun is not changed, the cathode current density Jk increases when the cathode current Ik increases. This means that if the area of the electron beam passage hole of the first electrode 11 is made small in order to improve the resolution at the time of small current operation, the available cathode area becomes small, and at the time of large current operation, the cathode current density Jk becomes higher. Indicates an increase.

The life of the cathode due to the reduced electron beam emission capability becomes shorter as the cathode current density Jk during large current operation increases. Further, the cathode voltage for preventing generation from the cathodes K ₁ , K ₂ and K ₃ is called a cutoff voltage Ekco,
H. From the H. Moss equation, there is the following relationship.

Ekco ∞ D / d Here, if the diameter D of the electron beam passage hole of the first electrode is reduced, the distance d between the cathode and the first electrode must be reduced.

[0019]

However, the conventional color cathode ray tube described above has the following problems due to the structure of the electron gun electrodes. That is, if the electron beam passage hole diameters of the first electrode and the second electrode are reduced in order to improve resolution during low current operation, the cathode current density during high current operation increases and the cathode life shortens. Moreover, since the distance between the cathode and the first electrode must be set small, precision is required and the working time increases.

An object of the present invention is to solve the above-mentioned problems of the prior art and to have a high resolution in the entire operating current range and the entire phosphor screen, a highly reliable, long-life and easy-to-manufacture electronic lens. An object is to provide a cathode ray tube including an electron gun having a configuration.

[0021]

SUMMARY OF THE INVENTION The object is to make the shape of the electron beam passage hole of the first electrode coaxial with the electron beam passage hole of the second electrode and to have the same side as the diameter of the electron beam passage hole of the second electrode. This is achieved by making the square long. That is, the present invention provides an evacuated envelope including a face panel portion, a neck portion, and a funnel portion connecting these portions, and a mosaic color phosphor formed on the inner surface of the face panel portion. A screen, a porous electrode for color selection which is arranged apart from the screen, an electron gun which is housed in the neck portion, generates three electron beams, and projects the electron beams toward the screen. A deflection magnetic field region mounted on the outer surface near the junction between the neck portion and the funnel portion of the envelope for deflecting the electron beams in both horizontal and vertical directions to draw a scanning raster on the screen. in at least comprising a cathode ray tube and a deflection yoke for forming the electron gun, arranged in sequence as the cathode K _1, K _2, K ₃ from the cathode to the screen direction , First electrode 11 for converging the electron beam generated from the cathode on the screen, the second electrode 1
2, ... At least one of the plurality of electrodes is provided with a convergent voltage that varies in synchronization with the deflection amount of the electron beam, and is applied to at least one electrode of the plurality of electrodes. Electron beam passage hole 11-1 '(1 "), 11
-2 '(2 "), 11-3'(3"), 12-1 '
The centers of (1 ″), 12-2 ′ (2 ″), 12-3 ′ (3 ″) are arranged on the same axis as the cathode, and the second
Electron beam passage holes 12-1 ′ (1 ″), 12− of electrodes
2 ′ (2 ″) and 12-3 ′ (3 ″) are circular, and the electron beam passage holes 11-1 ′ (1 ″) and 11− of the first electrode are formed.
2 ′ (2 ″) and 11-3 ′ (3 ″) are connected to the second electrode 12
It is characterized in that it has a square shape with sides having a length equal to the aperture diameter of the electron beam passage hole.

[0022]

Function: Electron beam passage hole 11-1 'of the first electrode 11
The shapes of (1 ″), 11-2 ′ (2 ″), and 11-3 ′ (3 ″) are formed into the electron beam passage holes 12-2 ′ of the second electrode 12.
(2 ″), 12-3 ′ (3 ″) A square having the same side length as the diameter or a substantially square with each corner having a curvature allows the electron beam passage of the second electrode during low current operation. It operates at a cathode current density almost equal to that of a circular electron beam passage hole having the same diameter as the hole. Therefore, the crossover diameter can be reduced and the resolution characteristic is improved.

On the other hand, at the time of high current operation, since the electron beam passage hole of the square (or substantially square) first electrode is larger than the electron beam passage hole of the circular shape, the area of the usable cathode increases. Therefore, in the case of the same large current value,
If the electron beam passage hole of the first electrode is square (or approximately square), it can operate with a lower cathode current density than a circle, and the life of the cathode is extended.

Further, since the resolution characteristic at the time of high current operation is determined by the aberration of the main lens, there is almost no effect that the electron beam passage hole of the first electrode is square (or substantially square). Since the area of the electron beam passage hole of the square (or substantially square) first electrode is larger than that in the case of being circular,
The distance between the cathode and the first electrode when the electron beam passage hole of the first electrode is effectively increased and the cutoff voltage is constant is
It becomes wider than the case of a circular electron beam passage hole, which facilitates manufacturing.

Further, by making the shape of the electron beam passage hole of the first electrode a square (or substantially square) having the same side length as the diameter of the electron beam passage hole of the second electrode, the second electrode and the first electrode Can be extremely easily positioned and fixed by inserting a pin-shaped jig having the same diameter into the electron beam passage hole of the first electrode and the electron beam passage hole of the second electrode.

[0026]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic view of an essential part of an electron gun for explaining an embodiment of a cathode ray tube according to the present invention.
It is a block diagram corresponding to the electron beam generator shown in FIG. In the figure, K ₁ , K ₂ and K ₃ are cathodes, 11 is a first electrode, 12 is a second electrode, 11-1 ′, 11-2 ′ and 11−.
3'is an electron beam passage hole of the first electrode, 12-1 ', 12
-2 'and 12-3' are electron beam passage holes of the second electrode.

In this embodiment, electron beam passage holes 12-1 ', 12-2', 12-3 'formed in the second electrode 12 are formed.
Is a circular opening similar to the conventional electron gun. on the other hand,
An electron beam passage hole 11-1 ′ formed in the first electrode 11,
11-2 'and 11-3' are squares having a side length equal to the diameter of the electron beam passage hole of the second electrode 12.

According to this embodiment, the electron beam passage holes 11-1 ', 11-2' and 11-3 'are formed in the first electrode 11 as described above, so that the second electrode is operated during the low current operation. The electron beam passage hole having the same diameter as that of the electron beam passage hole operates at substantially the same cathode current density, the crossover diameter is reduced, and the resolution characteristic is improved. On the other hand, at the time of high current operation, the electron beam passage hole of the first electrode is larger than the circular electron beam passage hole, so that the area of the cathode that can be used is increased, and the cathode current density lower than that of the circle can be used to operate the cathode. Becomes longer.

In addition, the electron beam passage hole of the first electrode is effectively increased and the cutoff voltage is kept constant.
The space between the first electrodes is wider than in the case of a circular electron beam passage hole, which facilitates manufacturing. FIG. 2 is a schematic view of an essential part of an electron gun for explaining another embodiment of the cathode ray tube according to the present invention, and is a constitutional view corresponding to the same electron beam generating part as in FIG.

In this embodiment, electron beam passage holes 11-1 ", 11-2", 11-3 "formed in the first electrode 11 are formed.
Is a square having a side length that is the same as the diameter of the electron beam passage holes 12-1, 12-2, 12-3 of the second electrode 12 in the same manner as in the above embodiment. Has a curvature R. According to this embodiment, the same effect as that of the above-described embodiment is obtained, and since the corners of the square are rounded, the electron beam passage hole can be manufactured more easily.

The present invention is not limited to the color cathode ray tube as in the above embodiment, but can be applied to a projection type cathode ray tube, an ordinary monochromatic cathode ray tube, and other cathode ray tubes, and an electrode of an electron gun. Needless to say, the structure is not limited to the structure shown in the above embodiment, but can be applied to various types of electron guns.

[0032]

As described above, according to the present invention,
The electron beam spot system during small current operation can be downsized, and the current density during large current operation can be increased.
The resolution can be improved, the increase in the load on the cathode can be suppressed, and a margin can be given to the reduction in the distance between the cathode and the first electrode.

As a result, the life of the cathode ray tube can be extended and the reliability can be secured, and the resolution can be greatly improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a main part of an electron gun for explaining an embodiment of a cathode ray tube according to the present invention.

FIG. 2 is a schematic view of an essential part of an electron gun for explaining another embodiment of the cathode ray tube according to the present invention.

FIG. 3 is a sectional view illustrating a schematic structure of a color cathode ray tube.

FIG. 4 is a cross-sectional view illustrating a main part of an electron gun housed in a neck.

FIG. 5 shows the configuration of the electron beam generation unit in the case where the electron beam passage holes of the first electrode and the second electrode which are conventionally used are circular, regarding the aberration of the electron beam generation unit that determines the resolution characteristic during low current operation. It is a schematic diagram explaining.

FIG. 6 is an operation explanatory diagram of an electron beam generation unit in the central electron beam of FIG.

[Explanation of symbols]

1 Face Panel 2 Funnel 3 Neck 4 Electron Gun 5 Deflecting Yoke 6 Fluorescent Material Constituting Screen 7 Mask Frame 8 Shadow Mask R, G, B Electron Beams K ₁ , K ₂ , K ₃ Cathode 11 First Electrode ( G1) 12 2nd electrode (G2) 13 3rd electrode (G3) 14 4th electrode (G4) 15 Shielding cup electrode 16 Conductive spring 11-1 (1 ', 1 "connected with the electrically conductive film apply | coated to the funnel inner wall. ), 11-2 (2 ', 2 "), 1
1-3 (3 ′, 3 ″) Electron beam passage hole 12-1, 12-2, 12-3 of the first electrode 11 Electron beam passage hole 13-1, 13-2, 13-3 of the second electrode 12 Electron beam passage holes 14-1, 14-2, 14-3 of third electrode Electron beam passage holes 17, 18, 19 of the fourth electrode 14 are central axes 20, 21 passing through the cathodes K ₁ , K ₂ , K _3. The central axis of the electron beam passage hole of the fourth electrode 14.

Claims (1)

[Claims] 1. An exhausted envelope comprising a face panel portion, a neck portion, and a funnel portion connecting these portions to each other, and a mosaic color phosphor formed on the inner surface of the face panel portion. A screen, a porous electrode for color selection which is arranged apart from the screen, an electron gun which is housed in the neck portion, generates three electron beams, and projects the electron beams toward the screen, A deflection magnetic field region is attached to the outer surface near the junction between the neck portion and the funnel portion of the envelope to deflect the electron beams in both horizontal and vertical directions to draw a scanning raster on the screen. In a cathode ray tube including at least a deflection yoke to be formed, the electron guns are sequentially arranged in the screen direction from the cathode and the cathode, and are generated from the cathode. A first electrode, a second electrode for focusing the electron beam on the screen, ...
At least one electrode of the plurality of electrodes is provided with a convergence voltage that varies in synchronization with the deflection amount of the electron beam, and an electron beam passage hole of the first electrode and the second electrode. Is arranged on the same axis as the cathode, the electron beam passage hole of the second electrode is circular, and the electron beam passage hole of the first electrode is the opening diameter of the electron beam passage hole of the second electrode. A cathode ray tube having a square shape having sides of equal length.