JPS6039741A - Electron gun for cathode-ray tube - Google Patents

Abstract

PURPOSE:To reduce the diameter of beam-spot on a target, by providing an eletrode between 5th grid and 6th grid of the main lens part and applying an intermediate potential between the potential of the 5th grid and that of the 6th grid onto said electrode. CONSTITUTION:An electron gun is built up with a 4 poles part 56 containing a cathode 9 and 1st-3rd grid 12-14 and a main lens part 57 containing 3rd-7th grid 14-18, and 6th grid 17 is provided between 5th grid 16 and 7th grid 18. An intermediate potential of about 8kV is given to the 3rd grid 14 and the 5th grid 16. A low-grade potential of about 700V is given to the 4th grid 15, a high- grade potential of about 25kV is given to the 7th grid 18, and further an intermediate potential of about 16.5kV which is between the potential of the 5th grid 16 and that of the 7th grid 18 is given to the 6th grid 17. Consequently, the lens performance can be greatly enhanced and the diameter of beam-spot can be remarkably reduced by using the beam of best quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electron gun for a cathode ray tube, and more particularly to a magnetostatic lens for focusing the electron beam.

[Technical background and problems of the invention]

Cathode ray tube electron guns generally consist of two basic parts.

One is an object point forming section including an electron beam generating section, and the other is an accelerating and focusing lens section that focuses the electron beam onto a predetermined screen.

Usually, the former is called a quadrupole section and the latter is called a main lens section, and the final stage electrode of the quadrupole section and the first electrode of the main lens section are the same. Most of the main lens portions are in the form of a white lens,
It is formed by applying a predetermined potential to at least two electrodes having magneton beam apertures.

On the other hand, in such an electron gun, the spot diameter DT of the electron beam focused on a predetermined sphere IJ- is determined by the quality of the beam incident on the main lens part from the quadrupole part and the lens performance of the main lens part. The lens performance of the main lens section can be changed depending on the potential of each electrode, the length of each electrode, the distance between each electrode, and the size of the electrode aperture, but in reality there are limitations due to the physical design of the electron gun. receive. Furthermore, the quality of the beam incident from the quadrupole section to the main lens section is determined by the final stage electrode of the quadrupole section, that is, the first electrode potential Ec3 of the main lens section, and this is best when Ec3 is 8 to 9 KV. is shown in [Multi-Step Focus] ("Electronics" November 1973 issue, pages 1147-1151).

A typical example of such an electron gun for a cathode ray tube is one in which the main lens portion is of the pi potential type. This pi-potential type sensor consists of a first focusing magnetic pole and a second focusing electrode, a high anode potential is applied to the second focusing electrode, and a relatively medium potential is applied to the first focusing electrode.

When such an electron gun is used, for example, in an in-line array or shadow mask type color picture tube, three electron guns are integrated in a row in the horizontal direction and are enclosed in the neck of a glass cylinder. Therefore, first, the aperture of the electrode, that is, the lens aperture is physically limited. Next, the distance between the electrodes is limited so that the focused electric field formed between the electrodes is not influenced by other electric fields. The electrode length or electrode potential is then limited for proper focusing onto a given screen.

That is, if the electrode length of the first focusing magnetic pole is determined, the electrode potential is determined logically. Therefore, in such an electron gun, the only way to change the lens performance of the main lens section is to change the magnetic pole length, but even if the electrode length is changed, no significant improvement in lens performance can be expected.

However, if, for example, at least one or more electrodes are provided between the first focusing electrode and the second focusing electrode, and a potential between the first focusing electrode potential and the second focusing electrode potential is appropriately applied to these electrodes,
That is, it is possible to practically form a lens equivalent to one in which the distance between the first focusing electrode and the second focusing electrode is increased, and the lens performance can be greatly improved. Such an electron gun is shown in Japanese Patent Publication No. 55-48674.

However, an electron gun such as that disclosed in Japanese Patent Publication No. 55-48674 is characterized in that the focal length of the lens in the main lens portion is long. Therefore, in order to properly focus the beam on a given screen, the electrode length of the first focusing electrode must be made considerably long, or the first focusing electrode potential must be set quite low. When the magnetic pole lengths of the first focusing electrodes are made longer, the electron beam incident from the quadrupole section at a certain divergence angle becomes considerably longer at the main lens section, and becomes subject to strong spherical aberration. As a result, the diameter DT of the beam spot focused on the screen does not become very small. Moreover, too long electrode length is inconvenient when manufacturing an electron gun, and is also economically wasteful.

Furthermore, if the potential of the first focusing electrode is set quite low, the quality of the beam incident from the quadrupole section to the main lens section will deteriorate, as mentioned above, and the beam spot diameter DT focused on the screen will eventually be reduced to 6. There's no rush.

[Internality of the invention]

The present invention improves the lens performance of the main lens part in an electron gun for a cathode ray tube, and also uses a part when the beam entering the main lens part from the quadrupole part is in the best quality state. The purpose of this is to further reduce the diameter of the beam spot focused on the screen.

[Summary of the invention]

In the electron gun for a cathode ray tube of the present invention, the main lens part is made up of at least five electrodes, a relatively medium potential is applied to the first focusing electrode, a relatively low potential is applied to the second focusing electrode, and a relatively low potential is applied to the second focusing electrode. A relatively intermediate potential is applied to the three focusing electrodes, a relatively high potential is applied to the final focusing electrode, and at least one or more each focusing electrode is applied between the third focusing electrode and the final focusing electrode. The above objective is achieved by applying a potential between the third focusing electrode potential and the final focusing electrode potential to.

[Embodiments of the invention]

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a configuration diagram of an example of an inline array electron gun for color picture tubes embodying the present invention, as seen from the inline direction, and FIG. 2 is a configuration diagram (2
- biaxial cross section). In FIGS. 1 and 2, an electron gun (1) has a plurality of electrodes, which will be described later, and a plurality of insulating supports (2) that support them. The plurality of electrodes are connected to three heaters (3a) + (3b) and (3c), respectively, for generating three electron beams (3a) + (3b) and (3c) that impinge on the red, green, and blue phosphor layers. 6a) * (6b)
* One row of cathodes ('') containing (6c)
, (9b) t (9c), and a first grid base and a second grid base having an integrated structure (3-nitized structure) with predetermined electron beam passage holes protruding from positions relative to these three cathodes. 13. Consists of the third grid I, the fourth grid α stage, the fifth grid (Le1, the sixth grid (trI), the seventh grid α stage and the convergence electrode (L!1), respectively in this order, the insulating support (2 ).The first grid circle and the second grid base are composed of flat plate electrodes arranged close to each other, and the third grid I is disposed close to and connected to the second grid circle. Two cup-shaped magnetic poles (211° (23), the fourth
The grid haze consists of two cup-shaped electrodes (c), t24, which are shallower than the third grid, following the third grid I, and the fifth grid.
The grid αe is the fourth grid α9, followed by the fourth grid α■] Two deep cup-shaped electrodes 4, the power is from the top, and the sixth grid aη is the fifth grid r, followed by the flat plate electrode (2
7). The closed surface of each cup-shaped electrode and the plate-shaped electrode are provided with three electron beam passage holes that are aligned with each electron beam, respectively. The beam passage holes of the first grid t1a and the second grid a3 are relatively small, and the beam passage holes (32a), (32b), (32G) on the side facing the second grid aJ of the third grid α4 are smaller than that. Large beam passage holes (33a), (33b), (33c) on the side of the third grid α4 facing the fourth grid α9
OJ: 4th grid A5 small 6th grid (L?)
Beam passing holes (33a) to (38a), (33
b) ~(38b) and (33c) ~(38c)' have relatively large diameters. Next, the seventh grid level A has magnet beam passage holes (39a) arranged in a row at the closed end.

Cup-shaped electrode (c) with (39b) + (39c)
Of the magneton beam passage holes, the center passage hole (39b) is aligned with the single beam passage holes from the first grid Q7J to the sixth grid αD described above. On the other hand, the passage holes (39a) on the intervening side (for example, the passage holes (39a) are slightly deviated outwardly from the central passage hole (39b)) from the first grid housing 2 described above. It is not aligned with the electron beam passage hole up to 6 grids an. The deviation of the electron beam passage holes on both sides mentioned above is 3
This is for giving a slight asymmetrical electric field deflection to the electron beams on both sides, excluding the central electron beam, in order to cause the main electron beam to intersect at one point on the target, and is another means for giving an asymmetrical electric field. Good too. The seventh grid (1 second also includes three electron beam passage holes (40a) + (4
A convergence electrode σl having a bottomed cylindrical shape (c) having 0b) and (40c) at its bottom is fixed, and a relatively high voltage of about 25 KV applied to an anode terminal (not shown) is applied to this convergence electrode part. A pulp spacer (21) is attached.

In the above electrode configuration, the following potentials are applied to each electrode. The cathode is held at a cutoff voltage of about 150 Å to which a modulation signal is applied. 1700V, the third grid a4 and the fifth grid αe have a relatively medium potential of about 8KV, and the fourth grid α9 has a second potential of about 700V.
The grid has a relatively low magnetic potential of about 25 KV, the seventh grid has a relatively high potential of about 25 KV, and the sixth grid (In) has a relatively low magnetic potential between the potentials of the fifth grid αυ and the seventh grid a8. A medium-high potential is applied.

Such an electron gun has a thin glass cylinder neck (not shown).
enclosed within.

The electron beam focusing 11A structure of such an electron gun is shown in FIG. 3, taking the central electron beam as an example. The beams on both sides are also essentially the same. As shown in Fig. 3, the electron beam (3) f emitted from the cathode (9 stations) is transmitted to the first grid aaO aperture (
) from the first grid ua to the second grid a3
A crossover image 61 is formed between the second grid (1
The lens passes through the aperture 01) of 31 and advances into the third grid side while being slightly focused by the pre-focus lens G1) formed mainly between the second grid circle, the third circle, and the lid I. A weak unipotential lens is formed by the 4th grid α9 to the 5th grid ill to the 3rd grid α.
Grid We - 6th grid same - 7th grid It is strongly focused by the pi-potential type lens 53 formed by the type α, and a beam spot 1l is formed on the screen I5 trench.
li! It is imaged as 9. At this time, the part from the cathode to the front part of the third grid is called a quadrupole part 6E9, and the part from the third grid to the seventh grid is called a main lens part 67). Electron beam (3) incident on the main lens section 67)
is the electron beam from the quadrupole (to), and this quadrupole (
A virtual crossover image t55 is created by tracing the electron beam from (to) in the opposite direction, and this image is formed on the screen (54) by the main lens portion Gη. Therefore, the better the quality of the electron beam from the quadrupole (a), the better the screen I! 54) The smaller the diameter of the upper beam spot (b) is, and the better the lens performance of the main lens portion 5'l), the smaller the diameter of the upper beam spot l551 on the screen 6. The quality of the electron beam referred to here is [Multi-Step Focus] ("Electronics" November 1978 issue).

1147 to 1151), and the smaller the emittance, the better the quality of the beam. In the above literature, the emittance (6) was actually measured when the third grid potential EC was changed, and it was reported that the emittance is minimum when Bc3 is 8 to 9 KV, as shown in Figure 5. The results similar to those shown in Fig. 5 were also measured.

That is, the electron beam from the quadrupole section (4) is the final electrode of the quadrupole section, and the best quality beam is when the electric potential ECs at the third grid a fathom, which is the front stage electrode of the main lens section 67), is 8 to 9 KV. It will become.

Next, in the main lens section 67), as shown in Fig. 4, the virtual crossover image (to) is used as an object point and is imaged on the screen 64). If the image expansion is DX, the beam expansion due to the spherical aberration of the main lens is DIIA, and the beam expansion due to the repulsion of space charges near the target is 9t Dso, the beam spot diameter DT on the target is DT. =((Dx+Dsa)"+Dso")"",! :
-1 Luko! : dl” THFiORBTICA
T, AND PRaCTICAL AS-PECT
OF FLECTRON-GUN DESIGN FO
RC0LORPICT-UaFI TUBB8” (
IIfE Trans, CE, Feb, 1975)
There is a water ceremony. Therefore, a lens having good lens performance in the main lens section as used herein refers to a lens that has a small magnification and is not susceptible to spherical aberration.

The typical lens form of the main lens section is shown in Figure 6 f.
The pi-potential type lens shown in a) is a uni-potential type lens, and the uni-potential type lens is shown in figure (b).The general pi-potential type lens is a lens system that can reduce the magnification of the lens, but is susceptible to spherical aberration. A unipotential lens is a lens system that can be made less susceptible to spherical aberration, but cannot reduce the magnification of the lens. Therefore, as an improved version of these lens systems, a geodora potential type lens has been proposed in Japanese Patent Application Laid-Open No. 54-89472 as shown in FIG. 54(C). This quad-potential type lens can have a smaller lens magnification than a unipotential type lens, and can be more susceptible to spherical aberration than a pi-potential type lens. In these lens systems, it is better to set the potential of the third grid to 8 to 9/V in order to use the quality of the electron beam from the quadrupole part in the best condition, but with unipotential type lenses, it is better to backfill. The third grid potential is a high potential of approximately 25 KV, which is preferable.0 On the other hand, in order to further improve the lens performance of pi-potential type lenses and geodora potential type lenses, the distance between the electrodes can be increased to further improve the axial potential distribution. It is best to keep it loose.

The situation at this time is shown in FIG. 7 in comparison with FIG. 6.

Figures 6 and 7 also show the axial potential distribution.

! 7 In a pi-potential type lens as shown in Figure (a), the third grid (114) and the fourth grid (115)
), the axial potential distribution becomes gentler, and the lens performance improves. However, in order to form an image of an object point on a screen at a certain distance, the third grid (11
4) The potential must be lowered to make the lens stronger. For example, the required focus voltage Vf (Vf - 3rd grid voltage/4th grid voltage) when the distance G between the 3rd grid and 4th grid is changed in an electron gun using an appropriate t-bipotential type lens. The change is as shown in FIG. 8(a)], and as the distance G increases, the focus voltage decreases.

It is not preferable to set the third grid potential low because the quality of the electron beam from the above-mentioned quadrupole section will deteriorate.

Therefore, it is possible to set the potential of the third grid (114) to 8 to 9 KV by increasing the length of the third grid (114) to increase the distance from the object point to the main surface of the lens. By increasing the length of the three grids (114), the beam entering from the quadrupole section with a certain divergence angle becomes considerably larger in diameter at the main lens section. As a result, it ends up being strongly affected by spherical aberration, so that the effect of improving lens performance by increasing the distance between the electrodes is lost. Figure 8(b) shows the third grid when the interval between the third and fourth grids is 00.
The graph shows the change in grid length Gs1 versus focus voltage Vf.

On the other hand, in the geodora potential type lens as shown in Fig. 7(b), the fifth grid (316) and the sixth grid (316)
If the interval 17) is set large, the axial potential distribution becomes gentle, and the lens performance can be improved in the same way as a bipotential type lens.

At this time, in order to form an image of the object point on a target at a certain distance, the lens must be made strong, but unlike the pi potential type lens, the geodora potential type lens is different from the pi potential type lens, and the third grid (314) - the fourth grid (314) - the fourth grid ( 315)
- Since a weak unipotential lens is formed between the fifth grid (316), the third grid (314)
By making this 22 potential type lens a little stronger while maintaining the potential at 8 to 9 KV, the lens action of the entire geodora potential type lens becomes strong, and an object point can be imaged on a predetermined target. That is, since the electron gun can be used with improved lens performance and without degrading the quality of the electron beam from the quadrupole, the beam spot diameter DT on the target can be reduced. The third grid (314) - the fourth grid (315) - the fifth grid
To make the unibotential lens formed between the grids (316) a little stronger, the 4th/IJ hood 315
) or the length of the fourth grid (315) is slightly increased or the third grid (314)
and the fourth grid (315) and the fourth grid (315)
The distance between the electrodes of the fifth grid (316) and the fifth grid (316) may be slightly increased. In the geotripotential type lens, unlike the pi-potential type lens, the lens effect can be strengthened just by slightly increasing the length of the 9th and 4th grids (315), so that the light is incident from the quadrupole part with a certain divergence angle. The beam does not occupy a large diameter in the main lens section. Therefore, it is no longer affected by spherical aberration. For example, in an electron gun using an appropriate Otripotential lens, the required focus voltage Vf (=3rd grid voltage/
The variation of the sixth grid voltage) is shown in FIG. 9(a), also at a certain interval G. FIG. 4B shows the change in focus voltage Vf when the length G4Z of the fourth grid is changed. 9th
As can be seen from the figure, in the case of the Geodra potential type lens, the focus voltage Vf changes rapidly even if the length of the fourth grid is slightly changed.

As mentioned above, the fifth grid (316) and the sixth grid (3
17) An electron gun that uses a geodora potential type lens with a large interelectrode distance as the main lens can considerably reduce the beam spot diameter DT on the target, but as mentioned above, such an electron gun Practically unfavorable. This is because if the distance between the electrodes is too large, the normal lens electric field formed between the electrodes will be disturbed by the influence of other electric fields in the neck, and normal lens action cannot be expected.

Therefore, in the present invention, in the geodora potential type lens, the fifth grid (316) and the sixth grid (317)
), and by applying thereto a suitable potential between the potential of the fifth grid (316) and the potential of the sixth grid (317), the result is that the seventh
The axial potential distribution shown in Figure (b) is obtained and the lens performance is improved. That is, in the embodiment of the present invention shown in FIGS. 1 to 3, a sixth grid (aη) is provided between the fifth grid (tQ) and the seventh grid a8,
A medium-high potential is applied between the 7th grid and the 7th grid α mark.

The method of supplying such a potential is as follows: for the third grid (141) and the fifth grid (7), from the stem (not shown) at the bottom of the electron gun to the stem bin (tooth not shown), as in the first grid Ria and the second grid A through the seventh grid (
II is supplied from an anode high voltage terminal (not shown) through a valve spacer (A). In the 6th grid circle, there is a 5th
Grid (similar to Le, it can also be supplied from the stem through the stem pin, but it is also possible to supply it from the stem through the stem pin,
As shown in Japanese Patent Application No. 9548, it can also be supplied from the high pressure of the seventh grillo lower α barrel by resistance division.

The detailed specifications of the embodiment are as follows, for example. Third
The length of grid I is 5.0 long, the length of feldspar of the fourth grid is 1.6, the length of the fifth grid is 20.0, and the length of the fifth grid is 20.0.
The length of the grid η is 2.0 ml @, the 7th grid α
The length of seconds is 6.0 heads. Also the third grid (14)
and the distance between the 5th grid (I5 and the 4th grid (19) and the 5th grid (e) is 0.6111, the distance between the 5th grid (e) and the 6th grid (In), and the distance between the 6th grid (η) and the 7th grid (1B) is 1.Q mrtr, and the diameter of the electron beam passage hole in each grid is 4.52 m at the center passage hole (excluding the hole diameter on the surface of the third grid facing the second grid). , immediately the 7th grid α
The distance from the tip of the barrel to the screen (54) is 342 meters.

At this time, as mentioned above, the third grid I and the fifth grid α
[9 is given a relatively medium potential of about 8 to ■, the fourth grid αQ is given a relatively low potential of about 700 V, and the seventh grid U is given a relative potential of about 25 KV. A high potential is applied to the sixth grid aη, and the seventh grid (approximately 16
．． 5KV is given.

With such an electron gun, the beam spot diameter on the target can be made very small.

In the above embodiment, an example was shown in which only one magnetic pole was disposed as the sixth grid between the fifth grid, which was the third focusing electrode, and the seventh grid, which was the final focusing electrode. However, the present invention is not limited to this, and a plurality of electrodes may be arranged to apply a potential so that the potential increases sequentially from the third focusing electrode through the plurality of electrodes to the final electrode.

Further, in the above embodiment, the third grid, which is the first focusing electrode, and the fifth grid, which is the third focusing electrode, are at the same potential by 751 degrees, but the present invention is not limited to this, and the present invention is not limited to this. Different potentials may be applied as long as they are potentials.

Further, in the above embodiment, the fourth grid, which is the second focusing electrode, is set to the same potential as the second grid, but the present invention is not limited to this, and the present invention can be applied to any relatively low potential. . That is, it goes without saying that the present invention can also be applied to a tri-potential type lens as described in US Pat. No. 3,995,194.

〔Effect of the invention〕

As described above, according to the present invention, the first focusing electrode and the second focusing magnetic pole are arranged in order from the one closest to the crab cathode part of the main lens part.

at least five electrodes arranged in the order of a third focusing electrode, a relatively intermediate potential is applied to the first focusing electrode, and a relatively medium potential is applied to the second focusing electrode.
A relatively low potential is applied to the focusing electrode, a relatively medium potential is applied to the third focusing electrode, a relatively high potential is applied to the final focusing electrode, and the third focusing electrode and the final focusing electrode are connected to each other. By applying a medium-high potential between the third and final focusing electrode potential to at least one focusing electrode between the electrodes, it is possible to provide a cathode ray tube electron needle with extremely good performance. The beam spot diameter on the target can be reduced, and a high-performance electron gun for cathode ray tubes can be provided.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing the configuration of an electron gun for a cathode ray tube to which the present invention is applied; FIGS. 3 and 4 are schematic views for explaining the focusing mechanism of the electron gun shown in FIG. 1; FIG. 5 is a characteristic diagram showing the relationship between third grid potential Hc3 and emittance ε, FIG. 6 (al), FIG. 6(b), FIG. 6(C), FIG. b) is a schematic diagram showing the form of the main lens portion and the corresponding axial potential distribution, and Fig. 8 fa)
is a characteristic diagram showing the relationship between the distance G between the third and fourth grids and the focus voltage Vf, FIG. 8(b) is a characteristic diagram showing the relationship between the length Gsl of the third grid and the focus voltage Vf, and FIG. (al is a characteristic diagram showing the relationship between the distance G between the fifth and sixth grids and the focus voltage Vf, FIG.
b) is the length G of the fourth grid, / and the focus voltage Vf
FIG. (1) Electron gun (2) Insulating support ■ Third grid (first focusing electrode) a9... Fourth grid (21st) 10... Fifth grid (third t) ) Qn... 6th grid (4th #1) a8... 7th grid (5th
〃 ) Agent: Kensuke Chika (1 other person)
Ho- Mimi-4 Figure 6 (C) Figure 7 (1)

Claims (1)

[Scope of Claims] A cathode ray tube electron gun comprising an electron beam generating section including at least a cathode and a main lens section for focusing the electron beam on a predetermined screen, wherein the electrode constituting the main lens section is connected to the electron beam generating section. A first focusing electrode and a second focusing electrode from the side closest to the generating part. a third focusing electrode, each having an aperture aligned with the electron beam path, the first focusing electrode having a relatively intermediate potential; The two focusing electrodes are provided with a relatively low potential, the third focusing electrode is provided with a relatively medium potential, the final focusing electrode is provided with a relatively high potential, and the third focusing electrode is provided with a relatively high potential. An electron gun for a cathode ray tube, characterized in that at least one focusing electrode between the electrode and the final focusing electrode is applied with a potential between the third focusing electrode potential and the final focusing electrode potential.