JPH0757658A - Electron gun for color cathode-ray tube - Google Patents

Abstract

PURPOSE: To prevent a convergence characteristic from being fluctuated responding to the change of voltage. CONSTITUTION: Dynamic focusing voltage changed synchronously with deflection signal is applied to at least one of focusing electrodes 24, 25 and an auxiliary electrode 30 in which three electron beam passing holes are formed is installed on the opposite to the focusing electrodes 24, 25 to which the dynamic focusing voltage is applied. The respective electron beam passing holes positioned in the outsides of the auxiliary electrode 30 are so formed as to have the centers shifted from the centers of electron beam passing holes formed in both of the electron beam-coming-in sides of the focusing electrodes on the opposite to the auxiliary electrode 30.

Description

Detailed Description of the Invention

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 in-line type color cathode line having an improved convergence characteristic for making three electron beams emitted from the electron gun coincide with one point on the screen. Related to electron guns for tubes.

2. Description of the Related Art An electron gun for a color cathode ray tube is enclosed in the neck of a funnel and emits three electron beams of red, blue and green signals to excite a fluorescent film formed on a screen surface. Form an image. Therefore, in order to form a high-resolution image, various requirements such as current density among three electron beams, focus characteristics, convergence characteristics, formation of electrostatic lenses by electrodes, and deflection of electron beams are satisfied. However, it is especially important that the three electron beams converge on one point of the phosphor film. FIG. 1 shows an example of a general electron gun provided with means for converging three electron beams. This is the cathode 11, the control electrode 12, and the screen electrode 1 which form the front triode.
3 and first, second, third, fourth, fifth, which form a plurality of auxiliary lenses
Focus electrodes 14, 15, 16, 17, 18 and a final accelerating electrode 19, which is provided adjacent to the fifth focus electrode 18 and forms a main lens, are provided, and each electrode emits from the cathode 11. Three electron beam passage holes through which the generated electron beam passes are formed in an in-line type. The fifth focus electrode 1 forming the main lens
8 and the final accelerating electrode 19 are external electrodes 1 each having a large-diameter electron beam passage hole through which three electron beams pass.
8a and 19a, and internal electrodes 18b and 19b which are inserted into the external electrodes 18a and 19a and in which three independent small diameter electron beam passage holes are formed. A predetermined electric potential is applied to each electrode forming the electron gun, which will be described in detail as follows. A predetermined focus voltage VF is applied to the first and fourth focus electrodes 14 and 17, and the third and fifth focus electrodes 1 and
A dynamic focus voltage VD, which is variable in synchronization with the output signal of the deflection yoke, is applied to 6 and 18 with the focus voltage VF as a base voltage. Then, a static voltage VS lower than the focus voltage VF is applied to the second focus electrode 15, and a high anode voltage VE is applied to the final acceleration electrode 19. In the conventional electron gun for a color cathode ray tube configured as described above, a predetermined potential is applied to each electrode and an electron lens is formed between the electrodes, so that the electron beam emitted from the cathode 11 is The state of being focused and accelerated by each electron lens and landing on the fluorescent film will be described below with reference to a state where each electron beam scans the fluorescent film. As a predetermined potential is applied to each electrode, the fifth focus electrode 1
The main lens formed between the lens 8 and the final acceleration electrode 19 includes a common large-diameter lens L1 and a focus lens L2. The common large-diameter lens L1 and the focus lens L2 have a variable dynamic focus voltage VD synchronized with a deflection signal. By doing so, the magnification becomes different. Therefore, when the dynamic focus voltage VD is low, the orbit of the electron beam in FIG.
Assuming that the electron beams of the blue and green signals are converged on one point of the phosphor screen, when the dynamic focus voltage VD is relatively high, the common large-diameter lens L1 and the focus lens are as shown by the dotted line in FIG. There is a problem that the magnification of L2 becomes relatively small and the three electron beams are not landed at one point. As described above, since the convergence amount of the three electron beams is changed by the change of the dynamic focus voltage VD, each electron beam is not accurately landed on the fluorescent point of the fluorescent film, and a high resolution image is formed when the image is reproduced. There was a problem that I could not do it.

SUMMARY OF THE INVENTION The present invention was created to solve the above-mentioned problems, and its purpose is to correct the change in the convergence amount due to the fluctuation of the dynamic focus voltage, and adopt the cathode ray tube employing this. It is an object of the present invention to provide an electron gun for a color cathode ray tube capable of improving the resolution of.

To achieve the above object, the present invention comprises a cathode forming a front triode, a control electrode and a screen electrode, and a plurality of focus electrodes forming an electron lens, In a color cathode ray tube electron gun to which a dynamic focus voltage is applied that is varied in synchronization with at least one deflection signal in the focus electrode, a cathode side is provided so as to face the focus electrode to which the dynamic focus voltage is applied. An auxiliary electrode having three electron beam passage holes is provided, and the center of each electron beam passage hole located outside the auxiliary electrodes passes through the electron beams on both sides formed on the incident side surface of the focus electrode facing the electron beam passage hole. It is characterized in that it is formed off the center of the hole. Another feature of the present invention comprises a cathode forming a front triode, a control electrode and a screen electrode, a plurality of focus electrodes forming an electron lens, and a final accelerating electrode, and at least two of the focus electrodes. In a color cathode ray tube electron gun to which a dynamic focus voltage that is changed in synchronization with a deflection signal is applied to one focus electrode, three electron guns are provided so as to oppose the focus electrode located on the cathode side to which the dynamic focus voltage is applied. An auxiliary electrode having an electron beam passage hole is provided, and the center of each electron beam passage hole located outside the auxiliary electrode is located on both sides of the electron beam passage hole formed on the incident side surface of the focus electrode facing the auxiliary electrode. The focus formed on the side of the final accelerating electrode and displaced from the center of the Center of the electron beam passage holes formed in the incidence side surface of the electrode, and is formed shifted from the outer electron beam passage holes formed in the exit surface of this and opposing cathode side of the focusing electrode. Another feature of the present invention is to provide a cathode forming a front triode, a control electrode and a screen electrode, and a plurality of focus electrodes forming an electron lens, wherein at least one deflection signal of the focus electrodes is provided. In an electron gun for a color cathode ray tube to which a dynamic focus voltage that is changed in synchronization is applied, an auxiliary electrode having three electron beam passage holes formed on the cathode side so as to face the focus electrode to which the dynamic focus voltage is applied. Is provided, and an electrode member having a large-diameter electron beam passage hole through which three electron beams pass is attached to the emission side surface of the auxiliary electrode.

By changing the dynamic focus voltage VD, it is possible to prevent the magnification of the main lens from changing and the convergence characteristics of the three electron beams from being relatively lowered.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An electron gun for a color cathode ray tube according to the present invention is shown in FIG.
As shown in FIG. 3, the cathode 21, the control electrode 22, and the screen electrode 23 that form the front triode, and the plurality of focus electrodes that form the auxiliary lens, that is, the first, second, third, and fourth focus electrodes 24, 25, 26 and 27, and a final accelerating electrode 28 which is provided adjacent to the fourth focus electrode 27 and forms a main lens, the fourth focus electrode 27 and the final accelerating electrode 28 are respectively formed into three parts. External electrodes 27a and 28a having large-diameter electron beam passage holes 27H and 28H through which two beams pass, and the external electrode 2
Three independent electron beam passage holes 27R, 27G, 27B, 28R, 28G, 2 located inside 7a, 28a.
8B is formed of internal electrodes 27b and 28b. Then, the first and second focus electrodes 24, 25
According to the features of the present invention, three electron beam passage holes R are provided between them.
An auxiliary electrode 30 formed by arranging H, GH, and BH is provided. Here, as shown in FIGS. 2 and 3, the electron beam passage holes RH and B located outside the auxiliary electrode 30.
Electron beam passage holes 25R, 25 formed on the center of H and the incident side surface of the second focus electrode 25 and formed on the outside.
B is formed by horizontally staggering the center of the electron beam passage hole 25G located at the center. The fact that these electron beam passage holes are formed in a staggered manner means that the centers of the outer electron beam passage holes RH and BH formed in the auxiliary electrode 30 are second.
The outer electron beam passage holes 25R and 25B formed on the incident side surface of the focus electrode 25 are decentered toward the central electron beam passage hole side or the outer electron beam passage formed on the incident side surface of the second focus electrode 25. The eccentric distance between the central axes of the holes is larger than that of the cathode 21. Then, as described above, a predetermined voltage is applied to each electrode constituting the electron gun, which will be described below. The first and third focus electrodes 24, 2
A predetermined focus voltage VF is applied to 6
The focus voltage VF is applied to the focus electrodes 25 and 27.
Is applied as a base voltage, and a dynamic focus voltage VD that is varied in synchronization with the deflection signal is applied. Then, a static voltage VS lower than the focus voltage VF is applied to the auxiliary electrode 30, and an anode voltage VE higher than the voltage is applied to the final acceleration electrode 28. The static voltage V
It is desirable that S is applied at the same potential as the screen electrode 23. As shown in FIG. 4, another embodiment according to the present invention has the same basic structure as the above-described electron gun shown in FIG. 2, but the auxiliary electrode 30 'is a rim electrode, and the auxiliary electrode 30' is formed on the emitting side surface of the electrode. As shown in FIG. 5, the electrode piece 40 having the large-diameter electron beam passage hole 41 through which the three electron beams pass is attached. The fourth embodiment of the present invention has the same basic structure as the electron gun shown in FIG. 2 as shown in FIG. 6, but the fourth focus electrode 27 to which the dynamic focus voltage VD is applied. Electron beam passage holes 27R ', 27 formed on the incident side surface of the
Outer electron beam passage hole 27R 'of G'and 27B',
The center of 27B 'is the third on the cathode 21 side opposite to this.
Of the three electron beam passage holes 26R, 26G, and 26B formed on the emission side surface of the focus electrode 26, the outer electron beam passage holes 26R and 26B are displaced from the center.
Here, the centers of the outer electron beam passage holes 27R 'and 27B' formed on the incident side surface of the fourth focus electrode 27 are at the centers of the outer electron beam passage holes 26R and 26B formed on the emission side surface of the second focus electrode 26. Located outside the center of. The operation of the electron gun for a color cathode ray tube according to the present invention constructed as described above will be described below.
First, when a predetermined potential is applied to each of the electrodes forming the electron gun according to the present invention, an electron lens is formed between the electrodes, but the second and fourth focus electrodes 25 and 27 are relatively low. When the dynamic focus voltage VD is applied, the auxiliary electron lens formed between the auxiliary electrode 30 and the second focus electrode 25 is relatively weak, and the trajectory of the electron beam emitted from the cathode 21 is as shown in FIG. As indicated by the solid line 2 in FIG. 2, the light passes through the auxiliary lens, the common lens L1 of the main lens and the focus lens L2, and is converged to one point on the phosphor screen. When a relatively high dynamic focus voltage VD that is variable in synchronization with a deflection signal is applied to the second and fourth focus electrodes 25 and 27, the auxiliary electrode 30 and the second focus electrode
The auxiliary electron lens formed between the focus electrodes 25 is strongly formed. The auxiliary electron lens has an electron beam passage hole 25 in which the centers of the electron beam passage holes RH and BH on both sides of the auxiliary electrode 30 are formed on both sides of the second focus electrode 25.
It is formed so as to stagger in the horizontal direction with respect to the centers of R and 25B. Therefore, the electron beams on both outer sides emitted from the cathode 21 are transmitted through the outer electron beam passage holes RH, 25R,
While passing through the auxiliary lens formed by BH and 25B, it is focused from the outer electron beam passage holes RH and BH of the auxiliary electrode 30 to the electron beam passage hole GH side located in the center, and passes through the outer electron beam of the second focus electrode 25. Hole 25R,
After further focusing from 25B and applying a dynamic focus voltage VF, the light passes through the relatively weakened outlines of the common large-diameter lens L1 and the focus lens L2. Therefore, the electron beams on both sides passing through the common large-diameter lens L1 and the focus lens L2 are strongly focused by the electron beam passage holes 25R and 25B, and are converged to the central electron beam side. Therefore, by changing the dynamic focus voltage VD, it is possible to prevent the magnification of the main lens from changing and the convergence characteristics of the three electron beams from being relatively lowered. As another embodiment of the present invention, when an electrode member 40 having a large-diameter electron beam passage hole 41 is attached to the emission side surface of the auxiliary electrode 30 ', a large-diameter electron beam that requires a high focus voltage VF is applied. By decentering the electron beams on both sides toward the central electron beam passage hole by the passage hole 41, it is possible to prevent the convergence characteristic from being deteriorated in accordance with the voltage variation as in the above-described embodiment. Then, in the electron gun of the embodiment as shown in FIG. 6, when a high dynamic focus voltage which is variable in synchronization with the deflection signal is applied, as described above, it is between the auxiliary electrode 30 and the second focus electrode 25. The electron beams on both outer sides, which are primarily converged by the auxiliary electron lens formed, are on both outer electron beam passage holes 26R, 26B, 27R ', 27 of the third and fourth focus electrodes 26, 27.
An asymmetric auxiliary lens formed by shifting the center of B'is converged to the central electron beam side. Therefore, the electron beam emitted from the cathode 21 is converged in multiple stages and is incident on the main lens, so that the overall convergence characteristic of the electron gun can be improved.

As described above, the electron gun for a color cathode ray tube of the present invention can prevent the convergence characteristic of the electron beam from being deteriorated due to the fluctuation of the focus voltage or the dynamic focus voltage, and the resolution of the cathode ray tube which employs this can be reduced. It has the advantage that it can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a conventional electron gun for a color cathode ray tube.

FIG. 2 is a sectional view of an electron gun for a color cathode ray tube according to the present invention.

3 is a cross-sectional view showing an extract of the auxiliary electrode and the second focus electrode shown in FIG.

FIG. 4 is a sectional view showing another embodiment of the electron gun for a color cathode ray tube according to the present invention.

5 is an exploded perspective view showing a state in which the auxiliary electrode shown in FIG. 4 is provided.

FIG. 6 is a sectional view showing still another embodiment of the electron gun for a color cathode ray tube according to the present invention.

[Explanation of symbols]

 Reference Signs List 11 cathode 12 control electrode 13 screen electrode 14 first focus electrode 15 second focus electrode 16 third focus electrode 17 fourth focus electrode 18 fifth focus electrode 18a external electrode 18b internal electrode 19 final acceleration electrode 19a external electrode 19b internal electrode L1 Common large-diameter lens L2 Focus lens 21 Cathode 22 Control electrode 23 Screen electrode 24 First focus electrode 25 Second focus electrode 25B Electron beam passage hole 25G Electron beam passage hole 25R Electron beam passage hole 26 Third focus electrode 26B, 26G, 26R Electron beam passing hole 27 Fourth focus electrode 27a External electrode 27b Internal electrode 27B, 27B 'Electron beam passing hole 27G, 27G' Electron beam passing hole 27R, 27R 'Electron beam passing hole 2 H Large-diameter electron beam passage hole 28 Final acceleration electrode 28a External electrode 28b Internal electrode 28H Large-diameter electron beam passage hole 28R, 28G, 28B Electron beam passage hole 30, 30 'Auxiliary electrode GH Electron beam passage hole RH, BH Outside electron beam Passage hole 40 Electrode piece 41 Large-diameter electron beam passage hole

Claims (8)

[Claims] 1. A cathode, a control electrode, and a screen electrode that form a front triode, and a plurality of focus electrodes that form an electron lens. At least one of the focus electrodes is synchronized with a deflection signal. In the electron gun for a color cathode ray tube to which a variable dynamic focus voltage is applied, an auxiliary electrode having three electron beam passage holes is formed on the cathode side so as to face the focus electrode to which the dynamic focus voltage is applied. The electron beam passage hole provided outside the auxiliary electrode has a center, and the electron beam passage hole is formed outside the incident side surface of the focus electrode to which a dynamic focus voltage is applied to face the auxiliary electrode. An electron gun for a color cathode ray tube, which is formed so as to deviate from the center of the. 2. The center of the electron beam passage hole located outside the focus electrode to which the dynamic focus voltage is applied is located outside the center of the electron beam passage hole located outside the auxiliary electrode. An electron gun for a color cathode ray tube according to claim 1. 3. The voltage is applied to the auxiliary electrode and the screen electrode at the same potential.
An electron gun for a color cathode ray tube according to the item. 4. A cathode comprising a front triode, a control electrode and a screen electrode, a plurality of focus electrodes forming an electron lens, and a final acceleration electrode, at least two focus electrodes of the focus electrodes. In a color cathode ray tube electron gun to which a dynamic focus voltage that is changed in synchronization with a deflection signal is applied, three electron beam passage holes are provided so as to face the focus electrode located on the cathode side to which the dynamic focus voltage is applied. Is formed, and the center of each electron beam passage hole located outside the auxiliary electrode is formed on the incident side surface of the focus electrode, to which the dynamic focus voltage is applied, facing the auxiliary electrode. It is formed so as to deviate from the center of the electron beam passage hole located on the outer side, and is positioned toward the final acceleration electrode side. The center of the electron beam passage hole, which is formed on the incident side surface of the focus electrode to which the dynamic focus voltage is applied, is located on the outer side formed on the emitting side surface of the focus electrode on the cathode side facing the focus electrode. An electron gun for a color cathode ray tube, which is formed so as to deviate from the center of an electron beam passage hole located therein. 5. The center of the electron beam passage hole located outside the focus electrode located on the cathode side to which the dynamic focus voltage is applied is located outside the center of the electron beam passage hole located outside the auxiliary electrode. The electron gun for a color cathode ray tube according to claim 4, wherein the electron gun is located. 6. The center of an electron beam passage hole, which is formed on the incident side surface of the focus electrode to which the dynamic focus voltage is applied and which is located toward the final acceleration electrode side, is located outside the focus electrode of the focus electrode facing the focus electrode. 5. The electron gun for a color cathode ray tube according to claim 4, wherein the electron gun is located outside the center of the electron beam passage hole formed on the emitting side surface and located outside. 7. A cathode, a control electrode, and a screen electrode that form a front triode, and a plurality of focus electrodes that form an electron lens, and are synchronized with a deflection signal of at least one of the focus electrodes. In the electron gun for a color cathode ray tube to which a variable dynamic focus voltage is applied, an auxiliary electrode having three electron beam passage holes formed on the cathode side so as to face the focus electrode to which the dynamic focus voltage is applied. And an electrode member having a large-diameter electron beam passage hole through which three electron beams pass together is attached to the emission side surface of the auxiliary electrode. 8. The electron gun for a color cathode ray tube according to claim 7, wherein a voltage is applied to the auxiliary electrode and the screen electrode at the same potential.