JPH05135708A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To attain a spot shape on the periphery of a screen of multiple electron beams and the reduction of the dynamic circuit correction quantity by uniformly applying the astigmatic action by a quadruple lens to multiple electron beams. CONSTITUTION:An electron gun having at least a cathode and a focus electrode Gf and having electrostatic deflecting plates 1 concentrating three electron beams R, G, B from the cathode on a fluorescent screen at the tip of the fluorescent screen side is provided. The quadruple magnetic field is formed on the side walls near an accelerating electrode Ga of beam passing ports 2R, 2G, 2B on the electrostatic deflecting plates 1. The quadruple magnetic field can be formed by sheet-like magnets 3 stuck on the side walls of the beam passing ports 2R, 2G, 2B.

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 more particularly to the structure of its electron gun.

[0002]

2. Description of the Related Art Recently, for example, a so-called self-convergence type has been adopted as a deflection yoke for a color picture tube. For example, as shown in FIG. 7, the horizontal deflection magnetic field is a pin type and the vertical deflection magnetic field is a barrel type, and the convergence of the R, G, and B three-color electron beams is automatically realized simultaneously with the deflection to the periphery. System.

However, when this deflection yoke is adopted, the magnetic field is distorted into a pin type and a barrel type, respectively, so that the electron beam spot is defocused in the peripheral portion of the screen as shown in FIG. Becomes (distortion). This is because the diameter of the electron beam has a certain finite spread, and the force is different depending on the place.

The above phenomenon will be described with reference to FIG. 9 by taking a horizontal deflection magnetic field (pin magnetic field) as an example. In addition, in FIG. 9, the electron beam e is assumed to pass from the bottom to the top.
Now, the periphery of the cross section of the electron beam e is shifted by 90 degrees 4
Assuming that each of the locations is A, B, C and D, respectively. Here, since the magnetic field at the point B is stronger than that at the point A, the electron beam e receives a force that is laterally pulled from both sides. Also,
At points C and D, a force acting toward the center of the electron beam e acts.

Therefore, the electron beam spot is weakly underfocused in the horizontal direction (before the electron beam is completely stopped down), and strongly overfocused in the vertical direction (too much stopward to diverge in the opposite direction, resulting in a halo). It can be seen that they are equivalently subjected to the lens action as shown in FIG. 10B. 10A and 10B are schematic diagrams in which the above-mentioned phenomenon at the screen center and the screen X end (see FIG. 8) are replaced by an optical lens system, in which a is an object point on the cathode and f is a fluorescence. An image forming point on the surface, 21 is a main lens,
Reference numeral 22 denotes a deflection yoke. Further, with the Z axis as a boundary, the upper part shows a lens action in the vertical (V) direction, and the lower part shows a horizontal (H) direction.
Shows the lens action in the direction.

Looking at the relationship between the spot size and the focus voltage for the lens action, as shown in FIG. 11, the electron beam has a just focus voltage Vfv in the vertical and horizontal directions of the spot at the center of the screen. V
Since fh is the same and the minimum size in each direction is also the same, the spot shape is almost circular.

On the other hand, at the edge of the screen X, the vertical just focus potential Vfv is higher than the horizontal just focus potential Vfh by ΔVfo (about 1.3 kv in the illustrated example), and the minimum spot size is also vertical. And in the horizontal direction, and the horizontal direction is about 2.
It is about 5 times larger. The ΔVfo is called an astigmatic amount, and the correction voltage applied to the dynamic quadrupole and the dynamic focus, which will be described later, is the astigmatic amount ΔVfo.
Proportional to.

From this, the electron beam shifts the image forming point f in the vertical direction to the front due to the above deflection, and as shown in FIGS. 8 and 10B, halos are generated vertically in the peripheral portion of the screen and are distorted. It becomes a spot shape (astigmatism).

Also, in a cathode ray tube equipped with a deflection yoke that is not a self-convergence type, a quadrupole coil (CY: Convergenceor) is provided at the rear portion of the deflection yoke.
It is necessary to establish convergence by installing the device k) and passing a predetermined current in synchronization with the deflection, and in this case also, in this case, the same spot distortion as in the self-convergence type is usually applied to the periphery of the screen. It will be.

Therefore, conventionally, as shown in FIG.
The main lens portion (for example, the fourth grid G ₄ ) in which the main lens 21 is formed has a built-in quadrupole. For example, as shown in FIGS. 14 and 15, the fourth grid G ₄ is composed of three electrodes (G _4A , G _4B , G _4C ), and two electrodes (first electrode G _4A ) on both sides of the fourth grid G ₄ are formed. And the third
The electrode G _4C ) has a cylindrical shape, and the second electrode G _4B therebetween has a circular flat plate shape.

On the opposite sides of the first electrode G _4A and the third electrode G _4C , a circular flat plate 24 having a horizontally elongated oval beam passage hole 23 is attached by welding or the like, and at the same time, the second electrode G 4 is attached. _The oblong beam passage hole 25 is formed in _4B .

The fourth grid G ₄ constructed as described above
Among them, the fixed voltage Fc is supplied to the second electrode G _4B , and the focus voltage Fv synchronized with the deflection cycle is supplied to the first electrode G _4A and the third electrode G _4C , whereby the fourth grid (main lens unit) Form an electrostatic quadrupole at G ₄ . By appropriately correcting the focus voltage Fv and adjusting the strength of the quadrupole and the strength of the main lens 21, the focus at the peripheral portion of the screen is improved without degrading the focus at the screen center. You can

However, in reality, the dynamic circuit correction amount applied to the fourth grid G ₄ (dynamic focus and dynamic quadrupole amount necessary for just focusing in the peripheral portion of the screen), that is, the astigmatic amount ΔVfo is high. Therefore, it is usually necessary to superimpose an AC voltage waveform of about 1 kv on the focus voltage (usually 5 to 10 kv),
There is an inconvenience that the circuit load becomes large.

Therefore, recently, as shown in FIG.
Outside the neck between the grid G ₄ and the deflection yoke 22, FIG.
By attaching the sheet-shaped magnet 26 shown by
A method has been proposed in which a quadrupole magnetic field that performs astigmatism in the opposite direction to the astigmatism of the main lens 21 is formed between the fourth grid G ₄ and the deflection yoke 22 to improve the deflection distortion around the screen. ing.

In principle, this method has a configuration in which a quadrupole lens 27 is arranged between the main lens 21 and the deflection yoke 22 as shown in FIG. 16, and the vertical image magnification M _V (= b).
_V / a _V ) and the lateral image magnification M _H (= b _H / a _H ),
By setting M _V > M _H , it is possible to improve the peripheral focus.

In this case, the spot shape of the electron beam is
4th grid G
Dynamic circuit correction amount to be applied to ₄ (astigmatism ΔVf
o) decreases, and the spot shape around the screen becomes more circular.

[0017]

In the above-mentioned conventional cathode ray tube, the spot shape around the screen can be considerably improved, but the sheet-like magnet 26 shown in FIG. 13 is installed outside the neck. Quadrupole lens 27 (Fig. 1
6)) is formed, it is difficult to uniformly apply the astigmatism in the quadrupole lens 27 to the three electron beams R, G and B. Is mentioned.

For this reason, conventionally, it is unavoidable to adjust the electron beam G for green, which is important in terms of luminosity, as the center, and at this time, for the electron beams R and B for other red and blue, the adjustment is performed. There is a drawback that the spot shape is not improved so much.

The present invention has been made in view of the above problems, and an object thereof is to make it possible to uniformly apply the astigmatism of a quadrupole lens to a plurality of electron beams. It is an object of the present invention to provide a cathode ray tube capable of achieving a reduction in spot shape and a dynamic circuit correction amount in the periphery of a screen of an electron beam.

[0020]

The present invention has at least an electron beam generator (cathode) and a main lens portion (focus electrode Gf), and the electron beam generator (cathode).
In the cathode ray tube having the electron gun, the convergence means (electrostatic deflection plate 1) for concentrating the three electron beams R, G, and B from 1 to 1 at one point on the phosphor screen is used as the convergence means 1. Beam passing means (beam passing ports 2R, 2G and 2B) provided separately from each other corresponding to the three electron beams R, G and B in FIG.
A quadrupole magnetic field is formed in each of the above.

In this case, the quadrupole magnetic field is formed by the sheet-like magnet 3 attached to the peripheral portion of each beam passing means 2R, 2G and 2B. It should be noted that the main lens portion Gf may be provided with correction means (for example, a horizontally long beam passage hole 14) for performing quadrupole correction in the direction opposite to the quadrupole magnetic field.

[0022]

According to the above-described structure of the present invention, the beam passing means 2R, 2G provided corresponding to the three electron beams R, G, B in the convergence means 1 are provided separately from each other.
Since a quadrupole magnetic field is formed in each of 2 and 2B, the astigmatism due to the quadrupole magnetic field causes the three electron beams R,
It can be evenly applied to G and B.

Therefore, according to the cathode ray tube of the present invention, it is possible to improve the spot shapes of the three electron beams R, G and B around the screen together, and
It is possible to reduce the amount of dynamic circuit correction for the electron beams R, G and B of the book.

[0024]

Embodiments of the present invention will be described below with reference to FIGS. In the figure, (V) is the vertical direction,
(H) indicates the lateral direction.

FIG. 1A shows a cathode ray tube according to the first embodiment, for example, a cathode ray tube applied to one gun and three beams.
In particular, FIG. 1B is a perspective view showing a configuration after a focus electrode of an electron gun incorporated in a cathode ray tube, and FIG. 1B is a front view seen from the phosphor screen side. In these figures, Gf
Indicates a focus electrode (for example, the fourth grid) on which the main lens is formed, and Ga indicates an accelerating electrode (for example, the fifth grid).

This electron gun has respective beam passage ports 2R, 2G and 2 in the electrostatic deflection plate 1 for concentrating the three electron beams R, G and B at one point on a fluorescent screen (not shown).
A thin rectangular parallelepiped sheet-shaped magnet 3 is attached to the side wall of the B acceleration electrode Ga side.

That is, as seen from the phosphor screen side, as shown in FIG. 1B, the left outer wall of the first deflector 1B (inverted U-shaped section) and the outer side walls of both sides of the second deflector 1G (rectangular section). The sheet-shaped magnet 3 is attached to the right outer wall of the third deflection plate 1R (U-shaped cross section).

When viewed from the phosphor screen side of each sheet-shaped magnet 3, the upper left half and the lower right half are N poles (shown by diagonal lines), and the upper right half and the lower left half are S poles. The magnetic field direction is as shown by.

Actually, first, as shown in FIG. 2A, after welding the sheet magnet 3 to the stainless thin plate 4,
As shown in FIG. 2B, the sheet magnet 3 is magnetized to have a predetermined polarity and strength. After that, as shown in FIG. 2C, the stainless thin plate 4 to which the sheet-shaped magnet 3 is welded is fixed to the electrostatic deflection plate 1 by, for example, laser welding.

In this case, the sheet magnet 3 may be directly welded to each of the deflection plates 1R, 1G and 1B, but since there is a problem that the change (variation) in the magnetization amount due to welding becomes large, As in the example, once the sheet-shaped magnet 3 is welded to the stainless thin plate 4 and then magnetized,
After that, it is preferable to weld the stainless thin plate 4 and the electrostatic deflection plate 1.

In this way, by sticking the sheet-like magnet 3 to the side walls of the beam passage openings 2R, 2G and 2G, a uniform quadrupole action, that is, an astigmatism, is applied to each of the electron beams R, G and B. The action is exerted, and the force in the vertical direction is underfocus, and the force in the horizontal direction is overfocus, so that the spot shape of the electron beam becomes vertically long. At this time, the focus around the screen is significantly improved.

According to the first embodiment, sheet magnets 3 are attached to the side walls of the three beam passage openings 2R, 2G and 2B in the electrostatic deflection plate 1 to attach the focus electrode Gf (main lens portion). Since a quadrupole magnetic field is formed between the quadrupole magnetic field and the deflection yoke (not shown), the astigmatism due to the quadrupole magnetic field can be uniformly applied to the three electron beams R, G and B. it can.

Therefore, according to the cathode ray tube of the first embodiment, the spot shapes of the three electron beams R, G and B around the screen can be improved together and the three electron beams R, It is possible to reduce the amount of dynamic circuit correction for G and B.

Next, some modified examples of the first embodiment will be described with reference to FIGS. 3 and 4.

In the first modification shown in FIG. 3, when the attachment position of the sheet-like magnet 3 is viewed from the phosphor screen side, the left outer wall of the first deflecting plate 1B, through which the electron beam B relating to blue passes, is green. Second deflection plate 1 through which the electron beam G relating to
They are different in that they are the inner walls on both sides of G and the right outer wall of the third deflector 1R through which the electron beam R for red passes.

With this structure, the precision of the plate spacing between the deflection plates 1R, 1G and 1B can be improved, and misconvergence can be effectively reduced.

Next, in the second modification shown in FIG. 4, first,
As shown in FIG. 4A, the sheet-like magnet 3 used in the first embodiment and the first modified example is divided into two pieces (3a, 3b), respectively, and then as shown in FIG. After the divided sheet magnets 3a and 3b are welded to the stainless thin plates 4a and 4b, respectively, they are magnetized to have a predetermined polarity and strength. After that, stainless steel thin plates 4a and 4b
Is laser-welded to each of the deflection plates 1R, 1G and 1B.

In this case, the two sheet magnets 3a
And 3b as a set are attached to the left outer wall of the first deflector 1B, the inner walls on both sides of the second deflector 1G, and the right outer wall of the third deflector 1R at intervals t.

According to this second modification, the sheet-like magnets 3a and 3b are once attached to the stainless thin plates 4a and 4b.
Since the magnetic field is magnetized after the welding, it is possible to reduce the variation in the amount of magnetization due to the welding. Further, since the sheet-like magnet 3 used in the first embodiment is divided into two, it is possible to increase the clearance at the most severe portion of the beam. In particular, the stainless thin plate 4 of the electrostatic deflection plate 1
By reducing the plate thickness of the portions to which a and 4b are attached by, for example, coining or etching, it is possible to reduce the amount of protrusion of the sheet-like magnets 3a and 3b from the electrostatic deflection plate 1, and further increase the clearance. Can be made

Next, a second embodiment applied to a three-gun three-beam type cathode ray tube will be described with reference to FIG. Here, FIG. 5A is a partially cutaway perspective view showing the structure after the focus electrode of the electron gun incorporated in the cathode ray tube of the second embodiment, and FIG. 5B is a front view showing it from the phosphor screen side. Is. The same reference numerals are given to those corresponding to FIG.

In this electron gun, two thin sheets are provided around the beam passing holes 12R, 12G and 12B in the convergence cup 11 for concentrating the three electron beams R, G and B at one point on the fluorescent screen. The magnets 13a and 13b are attached to each other.

Each beam passage hole 12R, 12G and 12B
Set of sheet-shaped magnets 13a attached to the peripheral part of the
And 13b are each formed in a crescent shape, and when viewed from the side of the phosphor screen, as shown in FIG. 5B, when viewed in a quadrant with four divisions, the first and third quadrants have N poles (shown by diagonal lines), Two
The fourth quadrant is an S pole, and the magnetic field is directed in the direction indicated by the arrow.

These sheet magnets 13a and 13
By adhering b around each of the beam passage holes 12R, 12G and 12B, a uniform quadrupole effect, that is, an astigmatism is exerted on each of the electron beams R, G and B, and the underbeam is generated in the vertical direction. A force in the overfocus direction is applied to the focus and lateral directions, and the spot shape of the electron beam becomes vertically long. At this time, the focus around the screen is significantly improved.

According to the second embodiment, similar to the first embodiment, a pair of sheet magnets 13a and 13b are provided around the three beam passage holes 12R, 12G and 12B provided in the convergence cup 11, respectively. Is attached to form a quadrupole magnetic field between the focus electrode Gf (main lens portion) and the deflection yoke (not shown). The beams R, G and B can be evenly applied.

Therefore, according to the cathode ray tube of the second embodiment, similarly to the first embodiment, the spot shapes of the three electron beams R, G and B around the screen can be improved together. Together with three electron beams R and G
It is possible to reduce the amount of dynamic circuit correction for B and B.

By the way, in the first and second embodiments, since the vertical and horizontal image forming points at the screen center are different, the center focus is deteriorated. Therefore, as conventionally known, in the first embodiment, as shown in FIG. 6A, a laterally long beam passage hole common to the three electron beams R, G, and B is provided on the exit side of the focus electrode Gf. In the second embodiment, the focus electrode Gf is divided into three beams corresponding to the three electron beams R, G, and B as shown in FIG. 6B. By forming the holes 15R, 15G, and 15B, an inverse quadrupole is added to the focus electrode Gf so that the image forming points in the vertical and horizontal directions at the screen center coincide with each other or come close to each other. Focus can be improved.

As a method of providing the inverse quadrupole on the focus electrode Gf, in addition to the method shown in FIG. 6, for example, a method of installing a quadrupole magnet outside the neck, and FIG.
The configurations shown in FIGS. 4 and 15 can be adopted, which is a known technique.

In the first and second embodiments,
Although the installation positions of the sheet magnets 3 and 13 are partially affected by the deflection magnetic field of the deflection yoke, the astigmatism is 3
Since the electron beams R, G, and B of the book are applied equally, the influence on the convergence is extremely small, and there is no practical problem.

[0049]

According to the cathode ray tube of the present invention, the astigmatism of the quadrupole lens can be uniformly applied to a plurality of electron beams, and the spot shapes and the dynamics of the plurality of electron beams around the screen can be improved. A reduction in the amount of circuit correction can be achieved.

[Brief description of drawings]

FIG. 1A is a perspective view showing a main part of a cathode ray tube applied to three beams of one gun according to the first embodiment (a structure after a focus electrode of an electron gun incorporated in the cathode ray tube). B is the front view shown from the fluorescent screen side.

FIG. 2 is a process drawing showing the method of attaching the sheet-shaped magnet according to the first embodiment.

FIG. 3 is a front view showing a first modification of the first embodiment as viewed from the phosphor screen side.

FIG. 4 is a process diagram showing a second modification of the first embodiment in accordance with the method of attaching the sheet-shaped magnet.

FIG. 5A is a partially cutaway perspective view showing a main part of a cathode ray tube applied to a three-gun three-beam system according to a second embodiment (a structure after a focus electrode of an electron gun incorporated in the cathode ray tube). B is the front view shown from the fluorescent screen side.

FIG. 6A is a front view showing the configuration when an inverse quadrupole is added to the focus electrode of the cathode ray tube according to the first embodiment as viewed from the phosphor screen side. FIG. 6B is a front view showing the configuration when an inverted quadrupole is added to the focus electrode of the cathode ray tube according to the second embodiment as viewed from the phosphor screen side.

FIG. 7 is an explanatory diagram showing a deflection magnetic field generated by a deflection yoke.

FIG. 8 is a schematic diagram showing spot distortion of an electron beam.

FIG. 9 is an explanatory diagram showing a force acting on an electron beam at an X edge of a screen.

FIG. 10A is a schematic diagram showing a lens action at a screen center by a deflection yoke. FIG. 6B is a schematic diagram showing the lens action at the screen X end by the deflection yoke.

FIG. 11A is a characteristic diagram showing the relationship between the spot size and the focus voltage at the screen center due to the conventional lens action. 9B is a characteristic diagram showing the relationship between the spot size and the focus voltage at the screen X end by the conventional lens action.

FIG. 12 is a configuration diagram showing a main part of a cathode ray tube applied to one gun and three beams according to a conventional example.

FIG. 13 is a front view showing a sheet-like magnet attached to a cathode ray tube of a conventional example as viewed from the phosphor screen side.

FIG. 14 is a cross-sectional view showing the configuration of a fourth grid as seen from the upper surface side.

FIG. 15 is a front view showing each electrode forming the fourth grid as viewed from the phosphor screen side.

FIG. 16 is a schematic diagram showing a lens action of a quadrupole lens.

[Explanation of symbols]

 Gf Focus electrode Ga Acceleration electrode 1 Electrostatic deflection plate 1R, 1G, 1B 1st, 2nd, 3rd deflection plate 2R, 2G, 2B Beam passage port 3 Sheet magnet 4 Stainless steel thin plate 11 Convergence cup 12R, 12G, 12B Beam passing holes 13a, 13b Sheet magnets

Claims (3)

[Claims] 1. Convergence means having at least an electron beam generating portion and a main lens portion for concentrating three electron beams from the electron beam generating portion at one point on the fluorescent surface is provided at the tip of the fluorescent surface side. In a cathode ray tube having an electron gun, a quadrupole magnetic field is formed in each of beam passing means provided separately from each other corresponding to the three electron beams in the convergence means. tube. 2. The cathode ray tube according to claim 1, wherein the quadrupole magnetic field is formed by a sheet-like magnet attached to a peripheral portion of each beam passage hole. 3. The cathode ray tube according to claim 1, wherein the main lens portion is provided with a correction means for performing quadrupole correction in a direction opposite to the quadrupole magnetic field.