JPH08212940A - Electron gun for cathode ray tube - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to improve the beam spot of a unipotential type electron gun and to construct an electron gun having sufficient withstand voltage characteristics. [Structure] Of the first to fifth electrodes G1 to G5 sequentially arranged adjacent to the cathode k, the third, fourth, and fifth electrodes are formed in a tubular shape, and the cathode and the first to fifth electrodes are formed. An equivalent voltage is applied to the third and fifth electrodes and a focusing voltage is applied to the fourth and fifth electrodes, which are integrally held by an insulating support, and two equivalent lenses forming a main lens are formed by the third, fourth, and fifth electrodes. In the electron gun for a unipotential type cathode ray tube to be formed, the inner diameters of the third and fifth electrodes are made larger than the inner and outer diameters of the fourth electrode, and both ends of the fourth electrode are inserted inside the third and fifth electrodes. It has a complicated structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun for a cathode ray tube, and more particularly to an electron gun for a cathode ray tube used for a projection type cathode ray tube and emitting a single electron beam.

[0002]

2. Description of the Related Art Generally, in a projection type cathode ray tube, an electron gun for emitting a single electron beam is sealed in a neck of a vacuum envelope,
An image of a size of 5 to 7 inches drawn by scanning the phosphor screen formed on the inner surface of the face plate by the electron beam emitted from this electron gun is output by the optical lens system arranged outside the face plate. The image is enlarged and projected on a screen of 50 to 300 inches.

Therefore, for this projection type cathode ray tube, in order to make the resolution of the image projected on the screen similar to that of a normal direct-viewing type cathode-ray tube, the diameter of the electron beam emitted from the electron gun is set to the normal direct-viewing type. It is necessary to make the diameter 1/10 or less of the electron beam diameter of the cathode ray tube. Therefore, in the projection-type cathode ray tube, an electromagnetic focusing electron gun capable of forming a large-diameter electromagnetic lens and an electrostatic focusing method configured to form a large-diameter electrostatic lens by increasing the neck diameter are used. An electron gun is used.

However, when the electron gun of such a system is used, the total length of the cathode ray tube becomes long, and it becomes difficult to make the projection type cathode ray tube device compact. In addition, the cost becomes high. Therefore, it is not suitable for consumer products that require low cost and compact size. Furthermore, as the total length of the cathode ray tube becomes longer, the distance from the electron gun to the phosphor screen becomes longer,
The lens magnification increases and the beam spot cannot be effectively improved. In the case of the electrostatic focusing method, if the neck diameter is increased to form a large-diameter electrostatic lens,
The deflection power increases.

On the other hand, as a conventional projection-type cathode ray tube electron gun for consumer use, a unipotential type electron gun as shown in Japanese Patent Publication No. 55-31580 and a Japanese Patent Publication No. 55-31696 are shown. A bipotential electron gun that forms a large-diameter electrostatic lens as described above is used. Further, in order to shorten the distance from the electron gun to the phosphor screen and reduce the lens magnification, the deflection angle is also increased.

However, the bipotential type electron gun generally has a good resolution in a low beam, but has a problem that a high beam cannot provide a sufficient resolution for a projection type cathode ray tube even if the main lens has a large diameter. .

On the other hand, the unipotential type electron gun has the following problems.

Generally, the beam spot diameter DT on the phosphor screen is M when the lens magnification, dx is the diameter of the virtual crossover seen from the lens of the electron beam, Cs is the spherical aberration of the lens, and when the electron beam is incident on the lens. Let α be the divergence angle of

[Equation 1] Here, dx and α are values determined by the cathode of the electron gun and the three-pole portion including the first, second, and third electrodes sequentially adjacent to the cathode, and they are in a reciprocal relationship. Therefore, in order to reduce the beam spot diameter DT,
The best method is to reduce the lens magnification M and the lens aberration coefficient. In this case, in order to satisfy both the lens magnification M and the aberration coefficient of the lens, the aperture may be increased without changing the position of the lens.

Such a unipotential type electron gun is
Since the potential difference between the second electrode and the third electrode is larger than that of the bipotential type electron gun, the strength of the prefocus lens formed by these second and third electrodes becomes stronger.
Therefore, when the divergence angle α of the beam at a large current is small, 2 is formed between the third and fourth electrodes and between the fourth and fifth electrodes.
With two equivalent lenses, the beam spot diameter DT can be reduced from low beams to high beams.

Therefore, as an electron gun for a projection type cathode ray tube, it is best to form a unipotential type main lens and increase the diameter of the main lens. FIG. 3 shows an example of an electron gun whose main lens has a large diameter. This electron gun uses the conventional high unipotential (HI-
The UPF type electron gun has its fourth and fifth electrodes G4,
This is a lens with a large diameter formed between G5.

That is, in the electron gun shown in FIG. 4, a pair of cathodes K and first to fifth electrodes G1 to G5, which are arranged adjacent to the cathodes K and have substantially the same outer diameter, are arranged via the strap 1 respectively. It is formed in a structure integrally held by the insulating support body 2. In the figure, H
Is a heater for heating the cathode K, C is a convergence cup attached to the fifth electrode G5, and 3 is a valve attached to the convergence cup C for press-contacting the inner conductive film 5 formed by coating on the inner surface of the neck 4. It is a spacer. In this electron gun, the third electrode G3 and the fifth electrode G5 are connected by a connector (not shown), an anode voltage is applied through the inner conductive film 5, the valve spacer 3 and the convergence cup, and the fourth electrode A focusing voltage is applied to G4 (focusing electrode) through a stem lead (not shown) at the end of the neck 4, whereby the third and fourth electrodes G3
, G4 and between the fourth and fifth electrodes G4, G5, two equivalent lenses ML34, ML45 shown by broken lines are formed.
On the other hand, in the electron gun shown in FIG. 3, the cathode K and the first to fourth electrodes G1 to G4 are almost the same as those of the electron gun, but the inner diameter of the fifth electrode G5 is particularly equal to that of the fourth electrode G4. Of the two equivalent lenses ML34 and ML45 formed between the third and fourth electrodes G3 and G4 and between the fourth and fifth electrodes G4 and G5. G4,
A lens ML45 having a larger diameter than the lens formed between the fourth and fifth electrodes of the electron gun is formed between G5.

By the way, the unipotential type electron gun is
The problem is the withstand voltage characteristic. This is because in the bi-potential type electron gun, the anode voltage is applied only to the fifth electrode, and the relatively high intermediate voltage is applied to the fourth electrode adjacent to the fifth electrode so that the fourth electrode and the fifth electrode are connected to each other. The potential difference is relatively small, but in the unipotential type electron gun, an anode voltage is applied to the third electrode and the fifth electrode, and the second and fourth electrodes adjacent to the third and fifth electrodes are relatively low. A voltage is applied, between the fourth and fifth electrodes, between the third and fourth electrodes, second,
This is because the potential difference between the third electrodes is large. As a result, undesired phenomena such as discharge, grid emission, and inter-electrode leakage are likely to occur between these electrodes.

In order to improve the withstand voltage characteristics of such a unipotential type electron gun, it is sufficient to increase the distance between the electrode to which the anode voltage is applied and the adjacent electrode, but it is shown in FIGS. 3 and 4. In such an electron gun, when the electrode spacing is increased, the insulating support is charged, the lens formed between the electrodes is distorted, and the shape of the beam spot on the phosphor screen is deteriorated. Therefore, the electrode spacing is sufficiently increased. It is not possible.

Further, if foreign matter adheres to the fourth electrode to which a low voltage is applied or if there is a burr, it acts as an emitter source for the third electrode and the fifth electrode and emits electrons. It may collide with the insulating support that holds the electrodes, the inner wall of the neck, or the like to generate stray emission, and in some cases, progress to discharge.

More importantly, in the unipotential type electron gun, since the main lens is composed of two equivalent lenses formed between the third and fourth electrodes and between the fourth and fifth electrodes, As in the electron gun shown in Fig. 5, by increasing the inner diameter of the fifth electrode and increasing the diameter of only one lens, a sufficient effect can be obtained for reducing the beam spot from the low beam to the high beam. Absent.

[0016]

As described above, in the projection type cathode ray tube, an electromagnetic focusing type electron gun capable of forming a large-diameter electromagnetic lens or a large-diameter electrostatic lens with a large neck diameter is formed. An electrostatic focusing type electron gun configured to do so is used. However, in such an electron gun, the total length of the cathode ray tube becomes long, and it is difficult to make the projection type cathode ray tube device compact. In addition, the cost becomes high.
Therefore, it is not suitable for consumer products that require low cost and compactness. Further, if the total length of the cathode ray tube becomes long, the distance from the electron gun to the phosphor screen becomes long, so that the lens magnification increases and the beam spot cannot be effectively improved. Further, in the case of an electrostatic focusing type electron gun, if the neck diameter is increased to form a large-diameter electrostatic lens, the deflection power increases.

On the other hand, as a conventional projection-type cathode ray tube electron gun for consumer use, a unipotential electron gun and a bipotential electron gun forming a large-diameter electrostatic lens have been used. Further, in order to shorten the distance from the electron gun to the phosphor screen and reduce the lens magnification, the deflection angle is also increased.

In general, the bipotential type electron gun has an excellent resolution in a low beam, but a high beam has a problem that a sufficient resolution cannot be obtained for a projection type cathode ray tube even if the main lens has a large diameter. .

On the other hand, in principle, the unipotential type electron gun can reduce the beam spot diameter from a low beam to a high beam. There is an electron gun in which the inner diameter of the fifth electrode of the unipotential type electron gun is made larger than the outer diameter of the fourth electrode to enlarge the lens formed between the fourth and fifth electrodes. However, in this unipotential type electron gun, an anode voltage is applied to the third electrode and the fifth electrode, and a relatively low voltage is applied to the second and fourth electrodes adjacent to the third and fifth electrodes. Between the fourth and fifth electrodes, the third,
Since the potential difference between the fourth electrode and between the second and third electrodes is large,
Discharge, grid emission, inter-electrode leakage, etc. easily occur between these electrodes, and the withstand voltage characteristic becomes a problem.

In order to improve the withstand voltage characteristic of this unipotential type electron gun, the distance between the electrode to which the anode voltage is applied and the adjacent electrode may be increased. Since the lens is charged and the lens formed between the electrodes is distorted and the shape of the beam spot on the phosphor screen is deteriorated, the electrode interval cannot be made sufficiently large. Further, if foreign matter adheres to the fourth electrode to which a low voltage is applied or if there is a burr, it acts as an emitter source for the third electrode and the fifth electrode to emit electrons,
It may collide with an insulating support holding each electrode, an inner wall of the neck, or the like to generate stray emission, and in some cases, may progress to discharge. More importantly, in the unipotential type electron gun, since the main lens is composed of two equivalent lenses formed between the third and fourth electrodes and between the fourth and fifth electrodes, the inner diameter of the fifth electrode However, there is a problem in that it is not possible to obtain a sufficient effect for reducing the beam spot from the low beam to the high beam simply by increasing the aperture and increasing the diameter of only one lens.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the beam spot of a unipotential type electron gun and to construct an electron gun having sufficient withstand voltage characteristics.

[0022]

The present invention has a cathode and first to fifth electrodes which are sequentially arranged adjacent to the cathode. Of these electrodes, the third, fourth and fifth electrodes are formed in a tubular shape. The cathode and the first to fifth electrodes are integrally held by an insulating support, and the anode voltage is applied to the third and fifth electrodes and the focusing voltage is applied to the fourth electrode. In a unipotential type electron gun for a cathode ray tube in which two equivalent lenses forming a main lens are formed by, the inner diameters of the third and fifth electrodes are made larger than the outer diameter of the fourth electrode, and the third and fifth electrodes are formed. Both ends of the fourth electrode are inserted inside the.

Further, in the electron gun for a cathode ray tube, the third electrode is composed of two electrodes which are divided so that they can be combined, and the electrode on the second electrode side of the two electrodes is made into a cathode by the first insulating support. Also, the first and second electrodes were held integrally, and the electrode on the fourth electrode side of the two electrodes was held integrally with the fourth and fifth electrodes by the second insulating support.

Further, in the cathode ray tube electron gun,
The outer diameters of both ends of the fourth electrode were larger than the outer diameter of the middle portion and smaller than the inner diameters of the third and fifth electrodes, respectively.

[0025]

As described above, the inner diameters of the third and fifth electrodes are made larger than the outer diameter of the fourth electrode, and the fourth and third electrodes are formed inside the third and fifth electrodes.
When the electrode is formed with both ends inserted, the inner diameter of the electrode, which was conventionally limited by the neck diameter of the cathode ray tube and the insulating support that integrally holds the electrode, is increased without being limited by the insulating support. It becomes possible, and the third, the fourth
Both of the two equivalent lenses formed between the electrodes and between the fourth and fifth electrodes can have a large aperture. As a result, the lens magnification M and the spherical aberration Cs of the lens can be reduced, and the beam spot diameter on the phosphor screen can be sufficiently reduced from the low beam to the high beam.

Further, the third electrode is divided into two pieces which can be combined.
Of the two electrodes, the electrode on the second electrode side is held integrally with the cathode and the first and second electrodes by the first insulating support, and the electrode on the fourth electrode side is held by the second electrode. By integrally holding the fourth and fifth electrodes by the insulating support, the inner diameter of not only the fifth electrode but also the third electrode forming the two equivalent lenses can be increased without being restricted by the insulating support. You can

Further, by making the outer diameters of both ends of the fourth electrode larger than the outer diameter of the intermediate portion and smaller than the inner diameters of the third and fifth electrodes, respectively, between the third and fourth electrodes and the fourth electrode. A large-diameter lens can be formed between the fifth electrode and the fifth electrode, and the beam spot diameter on the phosphor screen can be made smaller.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 1 shows a unipotential type electron gun which is an embodiment of the present invention. This electron gun has one cathode K,
A heater H for heating the cathode K, and first, second, third, fourth and fifth heaters which are sequentially arranged adjacent to the cathode K.
It is composed of electrodes G1 to G5. Reference numeral 3 is a valve spacer attached to the fifth electrode G5.

Of the electrodes G1 to G5, the first and second electrodes G1 and G2 are cup-shaped electrodes having relatively small outer diameters with their end faces facing each other. A small electron beam passage hole corresponding to the cathode K is formed on each of the facing surfaces of the first and second electrodes G1 and G2. The third electrode G3 is a stepped cylindrical electrode having a relatively large outer diameter. The second electrode G2 side is formed in a cylindrical shape having an outer diameter smaller than the inner diameter of the second electrode G2, and the surface of the cylindrical portion on the second electrode G2 side passes the electron beam of the second electrode G2. One electron beam passage hole larger than the hole is formed. On the other hand, an opening having an inner diameter larger than the outer diameter of the fourth electrode G4 is formed on the fourth electrode G4 side of the third electrode G3. The fourth electrode G4 is the first and second electrodes G1 and G2.
And a cylindrical electrode having a relatively small outer diameter having substantially the same outer diameter as that of the third electrode G3. ing. The fifth electrode G5 is composed of a stepped cylindrical electrode having a relatively large outer diameter and having substantially the same outer diameter as the third electrode G3. On the side of the fourth electrode G4, an opening having an inner diameter larger than the outer diameter of the fourth electrode G4 is formed. on the other hand,
On the opposite end face, one electron beam passage hole having substantially the same size as the openings at both ends of the fourth electrode G4 is formed.

In this electron gun, the fourth electrode G
Both ends of 4 are inserted into the openings of the third and fifth electrodes G3 and G5, which are opposed to each other, and are inserted into these third and fifth electrodes G3 and G5. Further, in this electron gun, the third electrode G3 is composed of two electrodes G3B and G3T which are divided so that they can be combined, and the electrode G3B on the side of the second electrode G2 is
Is cathode K, heater H and first and second electrodes G1, G
2 and the electrodes G3T on the side of the fourth electrode G4, which are held by the pair of insulating supports 10 via the straps 1, respectively.
Is held together with the fourth and fifth electrodes G4 and G5 by the other pair of insulating supports 11 via the strap 1, respectively, and the divided electrode G of the third electrode G3 held separately from each other.
It is formed in a structure that combines 3B and G3T.

Such an electron gun includes a cathode supporting portion for supporting the cathode K on the assembly jig, a heater mounting portion, one of the divided electrodes G3B of the first and second electrodes G1 and G2 and the third electrode G3. Built-in, its cathode support part, heater mounting part and first and second electrodes G1, G2, split electrode G3B
The straps 1 attached to, for example, are embedded in the pair of insulating supports 10 softened by heating. The assembly jig also includes the other divided electrode G3T of the third electrode G3, the fourth and fifth electrodes G3.
4, straps 1 attached to these electrodes are embedded in a pair of insulating supports 11 softened by heating. Then, each pair of these insulating supports 1
It is manufactured by integrally combining the divided electrodes G3B and G3T attached to Nos. 0 and 11 with an assembling jig and welding them.

In the electron gun, the cathode K and the first to third electrodes G1 to G3 form a triode, and the second and third electrodes G2 and G3 form the cathode K.
A prefocus lens is formed to prefocus the electron beam from. Also, the third, fourth and fifth electrodes G3, G4,
G5 forms a main lens that focuses the electron beam prefocused by the prefocus lens onto the final phosphor screen. This main lens includes a third electrode G3 to which an anode voltage is applied and a fourth electrode G4 to which a focusing voltage lower than that is applied, and between the fourth electrode G4 and a fifth electrode G5 to which an anode voltage is applied. It is composed of two equivalent lenses ML34 and ML45 to be formed. Especially, in the electron gun shape of this example, the inner diameters of the third and fifth electrodes G3 and G5 are made larger than the outer diameter of the fourth electrode G4, so that two A large-diameter equivalent lens is formed.

As a result, the neck diameter of the conventional cathode ray tube shown in FIG. 3 and the insulating support that integrally holds the electrodes are limited, and as shown in FIG. 3, the third and fifth electrodes G3 and G5 are provided.
Among them, only the outer diameter of the fifth electrode G5 is increased and one of the two equivalent lenses constituting the main lens is enlarged, so that the beam spot is reduced from the low beam to the high beam. On the other hand, the sufficient effect was not obtained, but in the electron gun of this example, the inner diameters of the third and fifth electrodes G3 and G5 can be increased without being limited by the insulating support, and thus the lens magnification can be increased. The spherical aberration Cs of M and the lens can be reduced, and not only the beam spot of the low beam can be reduced, but also the beam spot of the high beam can be significantly improved.

Moreover, the structure in which both ends of the fourth electrode G4 are inserted inside the third and fifth electrodes G3 and G5 is less susceptible to the charging of the insulating support, and therefore the anode voltage is applied. The distance between the third and fifth electrodes G3 and G5 and the fourth electrode G4 to which a lower focusing voltage is applied can be made sufficiently large, and the withstand voltage, which is a problem of the unipotential electron gun, can be improved. You can

Next, another embodiment will be described.

In the above embodiment, the fourth electrode is a cylindrical electrode having the same outer diameter over its entire length, but the electron gun shown in FIG. 2 has a third electrode inserted inside the third and fifth electrodes G3 and G5. Four
The inner and outer diameters of both ends of the electrode G4 are larger than the outer diameter of the middle part, and the outer diameters of both ends thereof are the third and fifth electrodes G3, G5.
The inner diameter is smaller than the inner diameter. Since the other structure of this electron gun is the same as that of the above-mentioned embodiment, the same reference numerals are given to the same portions and detailed description thereof will be omitted.

The specific dimensions of such an electron gun are shown in Table 1 in comparison with those of the conventional electron gun.

[0039]

[Table 1] With this structure of the electron gun, a large-diameter lens with less distortion can be formed between the third and fourth electrodes and between the fourth and fifth electrodes, and the beam spot diameter on the phosphor screen can be reduced. It can be made smaller, from low beams to high beams.

[0040]

The present invention has a cathode and first to fifth electrodes which are sequentially arranged adjacent to the cathode. Of these electrodes, the third, fourth and fifth electrodes are formed in a tubular shape. The first to fifth electrodes are integrally held by an insulating support, an anode voltage is applied to the third and fifth electrodes, and a focusing voltage is applied to the fourth electrode. The third, fourth, and fifth electrodes form a main lens. In a unipotential electron gun for a cathode ray tube in which two equivalent lenses are formed,
When the inner diameter of the electrode is made larger than the inner and outer diameters of the fourth electrode and both ends of the fourth electrode are inserted inside the third and fifth electrodes, two equivalent lenses forming the main lens are formed. The inner diameters of the third and fifth electrodes can be increased without being limited by the insulating support, whereby the lens magnification M and the spherical aberration Cs of the lens can be reduced, and not only the beam spot of the low beam can be reduced. Especially, the beam spot of a high beam can be significantly improved. Moreover, the structure in which both ends of the fourth electrode G4 are inserted inside the third and fifth electrodes G3 and G5 makes it less susceptible to the charging of the insulating support, and therefore the third electrode to which the anode voltage is applied. The distance between the fifth electrode and the fourth electrode to which a focusing voltage lower than that is applied can be made sufficiently large, and the withstand voltage, which is a problem of the unipotential electron gun, can be improved.

Further, the second electrode is divided into two parts which can be combined.
Of the two electrodes, the electrode on the second electrode side is held integrally with the cathode and the first and second electrodes by the first insulating support, and the electrode on the fourth electrode side is held by the second electrode. By holding the fourth and fifth electrodes integrally by the insulating support, the inner diameter of not only the fifth electrode but also the third electrode forming the two equivalent lenses can be easily increased without being limited by the insulating support. can do.

Furthermore, by making the outer diameters of both ends of the fourth electrode larger than the outer diameter of the intermediate portion and smaller than the inner diameters of the third and fifth electrodes, respectively, between the third and fourth electrodes and the fourth electrode. A large-diameter lens can be formed between the fifth electrode and the fifth electrode, and the beam spot diameter on the phosphor screen can be made smaller from a low beam to a high beam.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an electron gun for a cathode ray tube which is an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an electron gun for a cathode ray tube which is another embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional improved unipotential type electron gun.

FIG. 4 is a diagram showing a configuration of a conventional general unipotential electron gun.

[Explanation of symbols]

 10 ... Insulating support 11 ... Insulating support G1 ... First electrode G2 ... Second electrode G3 ... Third electrode G4 ... Fourth electrode G5 ... Fifth electrode G34 ... Divided electrode of third electrode G45 ... Third electrode Divided electrodes H ... Heater K ... Cathode ML34 ... Lens ML45 ... Lens

Claims (3)

[Claims] 1. A cathode and a first to a fifth electrode which are sequentially arranged adjacent to the cathode, wherein the third, fourth and fifth electrodes are cylindrically formed, and the cathode and The first to fifth electrodes are integrally held by an insulating support, an anode voltage is applied to the third and fifth electrodes, and a focusing voltage is applied to the fourth electrode, and the third, fourth, and fifth electrodes mainly In a unipotential electron gun for a cathode ray tube in which two equivalent lenses forming a lens are formed, the inner diameters of the third and fifth electrodes are larger than the outer diameter of the fourth electrode. An electron gun for a cathode ray tube, characterized in that both ends of the fourth electrode are formed inside of the inside. 2. The electron gun for a cathode ray tube according to claim 1, wherein the third electrode is composed of two electrodes which are divided so that they can be combined.
Of the two electrodes, the electrode on the second electrode side is held integrally with the cathode and the first and second electrodes by the first insulating support, and the electrode on the fourth electrode side of the two electrodes is the second electrode. An electron gun for a cathode ray tube, which is held integrally with the fourth and fifth electrodes by an insulating support. 3. The electron gun for a cathode ray tube according to claim 2, wherein the outer diameters of both ends of the fourth electrode are larger than the outer diameter of the middle portion and smaller than the inner diameters of the third and fifth electrodes. Electron gun for cathode ray tube.