JPH08212938A - Electron gun for color cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the spherical aberration of an electron lens formed by the limited aperture of each electrode, so as to enhance focusing characteristic of an electron gun having a cathode forming a triode portion and a plurality of predetermined electrodes, by forcing an electron beam from the cathode to cross under specific conditions. SOLUTION: This electron gun includes a cathode 11 forming a triode portion, a control electrode 12, a screen electrode 13, a plurality of focusing electrodes 14, 15, 16 provided sequentially from the screen electrode 13 and forming an auxiliary lens portion 100, and a final accelerating electrode 17 forming a main lens portion 200 provided adjacent to the focusing electrodes 14, 15, 16. In the electron gun, an electron beam emitted from the cathode 11 is forced to cross ahead of the main lens portion 200 by the auxiliary lens portion 100.

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 color cathode ray tube, and more particularly to an electron gun for a color cathode ray tube capable of reducing a spherical aberration component within a limited aperture of electrodes forming an electron lens.

[0002]

2. Description of the Related Art Generally, an electron gun for a color cathode ray tube has a triode portion, a plurality of focus electrodes which are sequentially provided from the triode portion, and which form an auxiliary beam portion through which electron beam passage holes are formed, and the focus electrodes. And a final accelerating electrode which is provided adjacent to and forms a main lens.

In such an electron gun, a unipotential electron lens or a bipotential electron lens is formed as a predetermined voltage is applied to the triode and each electrode.
In order to reduce the spherical aberration of the electron lens formed between the electrodes in this way, conventionally, a method of reducing the diameter of the electron beam has been used.

In order to reduce the diameter of the electron beam, the diameter of the neck portion is increased as shown in FIG. 9 so that the electron beam passage hole of the electron gun electrode is enlarged and the electron lens is relatively enlarged. A method and a method of increasing the size of the effective electron beam passage hole by forming a large diameter electron beam passage hole through which all three electron beams pass in the electrode of the electron gun forming the main lens or the auxiliary lens have been tried.

Among the above-mentioned methods, the method of enlarging the electron beam passage hole of the electrode by forming the diameter of the neck portion to be large is a factor that increases the deflection power of the deflection yoke which occupies most of the total consumption electrode of the cathode ray tube. However, there is a problem that the power consumption of the cathode ray tube increases. Further, the latter method has a structural limit in making the electron beam passage hole large.

However, in order to reduce the deflection power, the diameter of the electron beam passage hole of the electrode is relatively reduced by reducing the diameter of the neck portion. Therefore, as shown in FIG. 10, the electron beam 1 passing through the central portion of the electron lens L and the peripheral portion thereof are separated by the magnification and the spherical aberration component of the electron lens L formed by the reduced electron beam passage hole. The focus length of the passing electron beam 2 becomes different,
There is a problem that the size of the electron beam spot 3 landed on the fluorescent film becomes large.

[0007]

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to provide an electron lens formed by a limited effective aperture of each electrode of an electron gun. An object of the present invention is to provide an electron beam for a color cathode ray tube capable of reducing a spherical aberration and forming a small and uniform electron beam spot on the entire fluorescent screen.

[0008]

In order to achieve the above-mentioned object of the present invention, the present invention provides a cathode, a control electrode and a screen electrode which form a triode, and an auxiliary lens part which is sequentially provided from the screen electrode. And a final accelerating electrode that is provided adjacent to the focus electrode and forms a main lens unit, and an electron beam emitted from the cathode is forwarded to the front of the main lens unit by the auxiliary lens unit. It is characterized by being crossed over with.

In order to achieve the above-mentioned object of the present invention, the present invention is provided with a cathode, a control electrode and a screen electrode which form a triode, and the screen electrode, which are sequentially provided to cross over an electron beam. A first focus electrode forming a first auxiliary lens portion, a second focus electrode forming a second auxiliary lens portion for prefocusing the crossed-up electron beam, and a second auxiliary lens portion for prefocusing And a final accelerating electrode for final focusing and accelerating the electron beam.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The electron gun for a color cathode ray tube according to the present invention is mounted on the neck portion of the cathode ray tube and emits thermoelectrons for emitting light from the fluorescent film. As shown in FIG. The gun includes a cathode 11, a control electrode 12, and a screen electrode 13 that form a triode, and first, second, and third auxiliary lenses that are formed by a unipotential electron lens or a bipotential electron lens.
The focus electrodes 14, 15 and 16 and a final acceleration lens 17 that is provided adjacent to the third focus electrode 16 and serves as a main lens unit are configured.

Here, as shown in FIGS. 1 and 4, the focusing force of the auxiliary lens portion 100 formed by the first, second and third focus electrodes 14, 15 and 16 is the final acceleration with respect to the third focus electrode 16. The crossover point P of the electron beam is formed in front of the main lens unit 200, which is formed to be much larger than the focusing power of the main lens unit 200 formed between the electrode 17. Thus, in order to form the electron beam crossover point P between the auxiliary lens unit 100 and the main lens unit 200, a strong auxiliary lens unit 100 should be formed. In order to form the strong auxiliary lens unit 100, the potential difference between the electrodes forming the auxiliary lens unit 100 is increased, and the lengths of the first focus electrode 14 and the second focus electrode 15 that affect the focusing power are set. It is possible to make the length longer than that of a normal electron gun.

As an example, the second focus electrode 15
Voltage of 0 V is applied to the first and third focus electrodes 14,
A voltage of 7 kV is applied to 16 and the first focus electrode 1
Make the length of 4 within 2 mm to 4 mm. Then, the length of the third focus electrode 16 is set within 10 mm to 16 mm, and a voltage of 25 kV is applied to the final acceleration electrode 17. As described above, when the electrodes are adjusted in length and the above voltage is applied to each electrode, a crossover point of the electron beam is formed in front of the main lens.

Another embodiment of the electron gun according to the present invention is shown in FIG.
It was shown to.

The electron gun of the present invention has a cathode 2 forming a triode.
1, a control electrode 22, a screen electrode 23, focus electrodes 24, 25, 26, 27, 28 that form an auxiliary lens portion in which a plurality of unipotential electron lenses or bipotential electron lenses are arranged, and a cathode 21.
The final accelerating electrode 29, which is provided adjacent to the focus electrode 28 farthest away from and forms a main lens, is configured.

Here, the auxiliary lens unit focuses the electron beam in multiple stages by a plurality of electron lenses so that the electron beam is crossed in front of the main lens.

As described above, when the auxiliary lens portion is composed of two or more electron lenses, the length L of the first auxiliary lens portion is L.
1 is the three focus electrodes 24, 2 of the first auxiliary lens section
It is preferable that the diameter of the electron beam passage hole 25H of the focus electrode 25 located between 5 and 26 is 3 to 5 times, and the thickness t of the focus electrode 27 of the second auxiliary lens portion is t.
Is preferably 0.1 to 0.5 times or less the diameter of the electron beam passage hole 25H of the focus electrode 25.

According to the experiment of the present invention, the focus electrode 2
When the electron beam passage hole 25H of No. 5 has a diameter of 3.9 mm, the voltage of 0 to 800 V actually applied to the control electrode 22 and the screen electrode 23 is applied to the three focus electrodes 24, 25, 26 of the first auxiliary lens unit. The voltage is applied to the focus electrode 25 located at the center and the focus electrode 27 of the second auxiliary lens portion, and the length of the first focus electrode 24 of the first auxiliary lens portion is 2.0 mm to 3.0 mm,
The length of the second focus electrode 25 of the first auxiliary lens portion is 3.0 mm to 5.0 mm, and the length of the second focus electrode 25 of the first auxiliary lens portion is the third.
The length of the focus electrode 26 is 3.0 mm to 5.0 m
m, and the thickness of the focus electrode 27 of the second auxiliary lens portion is 0.4 mm to 2.0 mm.
When the length of 8 is set to 10 mm to 16 mm, the trajectory of the electron beam crossed in front of the main lens can be obtained as described above.

An electron gun according to still another embodiment of the present invention is shown in FIGS. 3 and 5.

In the electron gun of the present invention, the cathode 31, the control electrode 32, and the screen electrode 33 forming the triode portion, and the first auxiliary lens portion including the unipotential type electron lens or the bipotential type electron lens are formed. First, second and third focus electrodes 34, 35 and 36, fourth and fifth focus electrodes 37 and 38 provided adjacent to the third focus electrode 36 to form a second auxiliary lens portion, and The fifth accelerating electrode 38 is provided adjacently to the final accelerating electrode 39 forming a main lens portion. Here, the first, second and third focus electrodes 34,
A voltage having a large mutual potential difference is applied to 35 and 36 so that a crossover point P of the electron beam emitted from the triode can be formed between the first auxiliary lens part and the second auxiliary lens part. .

The operation of the electron gun for a color cathode ray tube according to the present invention will be described below.

As shown in FIG. 1, as a predetermined potential is applied to each electrode constituting the electron gun for a color cathode ray tube according to the present invention, namely, the first, second and third focus electrodes 14, 15, 16 are formed. As shown in FIG. 4, the final accelerating electrode 17 forms the auxiliary lens portion 100 and the main lens portion 200.

Therefore, the electron beam emitted from the cathode 11 is pre-focused and accelerated by the auxiliary lens unit 100, and then finally focused and accelerated by the main lens unit 200 and landed on the fluorescent film. At this time, the auxiliary lens unit 1
Since the electron beam having a focusing intensity of 00 is greater than that of the main lens unit 200 and has passed through the auxiliary lens unit 100, the electron beam is crossed in front of the main lens unit 200 and then is incident on the main lens unit 200. It is possible to reduce the influence of the spherical aberration component of the main lens unit 200 by increasing the difference in the incident angle of.

This will be described in more detail as follows.

4 and 5 show the trajectory of the electron beam passing through the main lens section 200.

When the electron beam passes through the edge of the electron lens, the focusing power becomes relatively large, which increases the spherical aberration component. Since the crossover point P of the electron beam (indicated by a thick solid line) of the electron gun according to the present invention is located between the auxiliary lens unit 100 and the main lens unit 200, the electron beam 40 passing through the edge of the main lens unit 200.
The incident angle of 1 becomes relatively large and becomes longer than the focus length of the conventional electron beam (shown by a thin solid line) 501 when observing the trajectory of the electron beam. The incident angle of the electron beam 402 entering the central portion of the main lens unit 200 from the crossover point P is smaller than the incident angle of the electron beam 401 passing through the edge of the main lens unit 200. Therefore, the change in the focus length of the electron beam passing through the central portion of the main lens unit 200 is the change in the focus length of the electron beam passing through the edge of the main lens unit 200 from the change from the electron beam 502 to the electron beam 402 ( Electron beam 50
Change from the focus length of 1 to the focus length of the electron beam 401).

The distribution of changes in overall incident angle is shown in FIG. In the figure, it can be seen that the change in the incident angle of the electron beam passing through the edge (line B) is large, and the change in the incident angle of the electron beam passing through the central portion (line A) is small.

The electron beam 402 entering the central portion of the main lens portion 200 from the crossover point P has a small incident angle to the main lens portion 200 and has a relatively longer focus than the existing electron beam 502.

Therefore, as shown in FIG. 5, the size of the electron beam spot 410 focused on the fluorescent film can be made smaller than that of the conventional electron beam.

In the electron gun shown in FIG. 2, the electron beam is focused by the first and second auxiliary lens portions 710 and 810 and crossed in front of the main lens portion 910.
Is shown in. The focusing action of the electron beam crossed in front of the main lens unit 910 and passing through the main lens unit 910 is as described above.

Then, the first and second auxiliary lens parts 710,
In the case of an electron gun whose crossover point is located between 810,
Focusing of the electron beam is performed as follows.

In the electron gun for a color cathode ray tube according to the present invention as shown in FIGS. 3 and 7, the first, second and third focus electrodes 3 are formed as a predetermined potential is applied to each of the constituent electrodes.
4, 35, 36 and the third, fourth, fifth focus electrodes 36,
The first and second auxiliary lenses 700 and 800 are formed by 37 and 38, and the main lens portion 900 is formed by the fifth focus electrode 38 and the final acceleration electrode 39.

Therefore, the electron beam emitted from the cathode 11 is pre-focused and accelerated by the first auxiliary lens unit 700 to be crossed over, refocused and accelerated by the second auxiliary lens 800, and then finalized by the main lens unit 900. It is focused and accelerated, and landed on the screen phosphor screen 600.

In this process, the focusing power of the first auxiliary lens 700 is relatively stronger than that of the other lenses, and the electron beam passing through the first auxiliary lens 700 is crossed over in front of the second auxiliary lens 800. Although the electron beam spot on the screen can be reduced as described above, the larger the radius of the electron beam passing through the main lens portion due to the influence of the deflection yoke, the poorer the state of the electron beam spot landed on the peripheral portion of the screen. As a result, the resolution of the entire screen can be improved by reducing the radius of the electron beam incident on the main lens unit using the second auxiliary lens unit.

In the electron gun according to the present invention, the same electron beam spot can be obtained in the case where the effective diameter in the low current region is smaller by 15% to 20% than that of the conventional electron gun.

The electron gun of the present invention is not limited to the above embodiment,
Many variations can be made by a person having ordinary knowledge within the technical idea described in the claims of the present invention.

[0037]

As described above, the electron gun for a color cathode ray tube for a color cathode ray tube according to the present invention can reduce the spherical aberration in the main lens portion and improve the focus characteristic to reduce the spot of the electron beam.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of an electron gun for a color cathode ray tube according to the present invention.

FIG. 2 is a side view showing another embodiment of the electron gun according to the present invention.

FIG. 3 is a side view showing another embodiment of the electron gun according to the present invention.

4 is a cross-sectional view in which the trajectory of an electron beam of the electron gun according to the present invention shown in FIG. 1 is visualized.

FIG. 5 is a diagram visualizing a state in which an electron beam by an electron gun according to the present invention and an electron beam by a conventional electron gun pass through a main lens.

6 is a cross-sectional view in which the trajectory of an electron beam of the electron gun according to the present invention shown in FIG. 2 is visualized.

7 is a cross-sectional view in which the trajectory of an electron beam of the electron gun according to the present invention shown in FIG. 3 is visualized.

FIG. 8 is a cross-sectional view showing a change in incident angle in front of the main lens section of the conventional electron gun and the electron gun according to the present invention.

FIG. 9 is a graph showing a relationship between a spot diameter of an electron beam and a diameter of a neck portion.

FIG. 10 is a view schematically showing a state in which an electron beam is focused by a conventional electron lens.

[Explanation of symbols]

 11, 21, 31 Cathode 12, 22, 32 Control electrode 13, 23, 33 Screen electrode 14, 24, 34 First focus electrode 15, 25, 35 Second focus electrode 16, 26, 36 Third focus electrode 100 Auxiliary lens 200,910 Main lens 401,402 Electron beam 410 Beam spot

Claims (7)

[Claims] 1. A cathode, a control electrode, and a screen electrode that form a triode, a plurality of focus electrodes that are sequentially provided from the screen electrode and that form an auxiliary lens portion, and are provided adjacent to the focus electrode. An electron gun for a color cathode ray tube comprising a final accelerating electrode forming a main lens portion, wherein an electron beam emitted from the cathode is crossed by the auxiliary lens portion in front of the main lens portion. 2. The electron gun for a color cathode ray tube according to claim 1, wherein the auxiliary lens portion is composed of three electrodes, and the voltage applied to the central electrode is lower than the voltage applied to both sides. 3. The electron gun for a color cathode ray tube according to claim 1, wherein the auxiliary lens unit is composed of one auxiliary lens, and the electron beam is crossed between the auxiliary lens and the main lens. 4. The electron gun for a color cathode ray tube according to claim 1, wherein the auxiliary lens portion includes at least two auxiliary lenses. 5. A cathode, a control electrode, and a screen electrode which form a triode, and a first auxiliary lens part which is sequentially provided from the screen electrode and crosses the electron beam passing through the triode. A first focus electrode and a second focus electrode for prefocusing the crossed-over electron beam
An electron gun for a color cathode ray tube, comprising: a second focus electrode forming an auxiliary lens part; and a final accelerating electrode for finally focusing and accelerating an electron beam prefocused by the second auxiliary lens part. 6. The electron beam is crossed over between the first and second auxiliary lens parts.
An electron gun for a color cathode ray tube according to. 7. The color according to claim 6, wherein the first and second auxiliary lens parts each include three electrodes, and the voltage applied to the central electrode is lower than the voltage applied to both sides. Electron gun for cathode ray tube.