JPH0765745A - Cathode ray tube - Google Patents

Abstract

(57) [Summary] [Object] To provide a cathode ray tube capable of correcting electron beam trajectories, preventing factors such as misconvergence and image distortion, and reducing deterioration of beam spot shape. [Structure] Trajectory correcting means 10 and 11 for an electron beam 6 are arranged at positions on the panel 3 side from the center of the main electron lens of the electrodes forming the main electron lens of an electron gun.

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.
The present invention relates to a cathode ray tube capable of correcting an electron beam trajectory by using a polar magnet.

[0002]

2. Description of the Related Art In a color cathode ray tube (CRT), as shown in FIG. 4, which shows a neck tube portion accommodating an electron gun in a particularly enlarged manner, as an example of a single electron gun three-beam type, its outer tube is made of a phosphor. It is composed of a panel 1, a funnel 2 and a neck tube 3. The electron gun housed inside the neck tube 3 is of the one-beam three-beam type, and as is well known to this electron gun, three colors: R (red), G (green), B (blue). ), Each of which emits an electron beam for K: (KR, KG, K
B), and a first grid electrode G1, a second grid electrode G2, a third grid electrode G3, a fourth grid electrode G4, and a fifth grid electrode G that focus their electron beams.
5. Convergence for deflecting the electron beam (C
V) The plate 4 and the like are provided. Third grid electrode G3, fourth grid electrode G4 and fifth grid electrode G5
Forms the main electron lens. Reference numeral 5 is an aperture grill (AG) as a color selection mechanism.

In a CRT in an ideal state, for example, an electron beam 6 emitted from the cathode KG surface toward the phosphor panel 1 surface goes straight as shown by trajectory I in FIG. 4 when there is no influence of vertical geomagnetism. And pass through the tube axis completely.

[0004]

[Problems to be Solved by the Invention] However, a CRT
Under normal use conditions, the vertical magnetic field varies depending on the place of use. In general, an electron moving in a uniform magnetic field receives a force according to Fleming's left-hand rule and draws a circular orbit. Therefore, inside the CRT in the ideal state, the electron beam 6 is similarly P, Q, R, S, T as shown in FIG.
A circular orbit II passing through each point will be drawn, and it will be separated (off axis) from the tube axis (in Fig. 4, the off axis distance is e). A point P among points P, Q, R, S, T forming the circular orbit is an intersection of the electron beam 6 and the center A of the fourth grid electrode G4,
The point Q is the intersection of the electron beam 6 and the convergence (CV) center B of the convergence plate 5, the point R is the intersection of the electron beam 6 and the center line C of the neck seal portion, and the point S is the electron beam 6 and the deflection center D. And the point T indicate the intersection with the phosphor panel 1.

Using the conventional cathode ray tube shown in FIG. 4, points P, Q, R and S on the electron circular orbit II from the tube axis.
And distance to T (off-axis amount) a, b, c, d, e (mm)
Were measured respectively. The results are shown in Table 1.

[0006]

[Table 1]

In Table 1, the approximate radius of curvature is P,
This is the radius of curvature when the orbit II of the electron beam passing through the points Q, R, and T is assumed to be a circular orbit, and the off-axis amount (d) at the deflection center is based on the obtained approximate radius of curvature. It is calculated in.

It can be seen from Table 1 that the panel is displaced by about 7 mm due to vertical geomagnetism under normal use. The off-axis from the center of convergence gives aberration to the electron beam,
This causes deterioration of the beam spot shape on the phosphor screen.
Further, the off-axis (d) at the deflection center line D causes misconvergence and image distortion.

Further, since a thin steel plate is used for the aperture grille (AG) 5 as a color selecting mechanism of the CRT, it is magnetized by the geomagnetism when the set is moved. as a result,
The orbit of the electron beam is disturbed near the aperture grille 5,
Color purity (purity) deteriorates. In order to eliminate this adverse effect, an automatic degaussing coil is usually provided.

Such a degaussing coil alone cannot solve the problem of off-axis due to the vertical geomagnetism shown by the electron beam trajectories P, Q, R, S and T.

Therefore, the present invention corrects the electron beam trajectory to prevent factors such as misconvergence and image distortion,
Another object of the present invention is to provide a cathode ray tube capable of reducing the deterioration of the beam spot shape.

[0012]

According to the present invention, the above object is to dispose the electron beam trajectory correcting means on the panel side from the center of the main electron lens of the electrodes constituting the main electron lens of the electron gun. Is solved by the cathode ray tube.

In the present invention, it is preferable that the orbit correction means is two two-pole magnets capable of adjusting the direction of magnetic force lines, from the viewpoint of ease of arrangement and cost.

In the present invention, it is preferable that the magnet adjusts the trajectory of the electron beam so as to pass through the convergence center or its vicinity and the deflection center or its vicinity.

Further, in the present invention, the intersection of the electron beam curve trajectory before the trajectory correction and the electron beam curve trajectory after the trajectory correction passing through the convergence center or its vicinity and the deflection center or its vicinity is the trajectory correction means. It is preferable to dispose the trajectory correcting means so as to be at the center.

[0016]

According to the present invention, a deviation (off axis) due to vertical geomagnetism at the center of convergence and the center of deflection, which greatly affects the characteristics of the cathode ray tube, is provided at a predetermined position of the main electron lens portion of the electron gun provided in the cathode ray tube. Since the electron beam trajectory correction means 10 and 11 composed of a two-pole magnet or the like configured so as to make zero is provided, the electron beam trajectory can be moved and corrected to the tube axis side. By substantially canceling the influence of the vertical geomagnetism in this manner, it is possible to suppress the deterioration of the beam spot shape and the characteristic deterioration such as misconvergence and image distortion.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows a schematic plan view of a cathode ray tube having a two-pole magnet according to the present invention. As shown in FIG. 1, in the cathode ray tube of the present embodiment, two pole magnets 10 and 11 are provided between the fourth grid electrode G4, which is the center of the main electron lens, and the panel-side fifth grid electrode G5 adjacent to the fourth grid electrode G4. A cathode ray tube having a structure similar to that of the conventional one shown in FIG. The third grid electrode G3, the fourth grid electrode G4, and the fifth grid electrode G5 constitute a main electron lens, and the fourth grid electrode G4 center A, the convergence (CV) center B, the neck seal portion C, the deflection center D, and the cathode. Those equipped with K (KR, KG, KB), phosphor panel 1, aperture grille (AG) 5, etc. were used.

FIG. 2 shows a schematic side view of an electron gun equipped with the two-pole magnet of this embodiment. 2 shown in FIGS. 1 and 2
As shown in the front view of FIG. 3, the pole magnet includes a circular two-pole magnet 10 having N1 poles and S1 poles locally magnetized, and a circular two-pole magnet 11 having N2 poles and S2 poles ( In FIG. 3, two magnets on the rear side of the bipolar magnet 10 are arranged (stacked).

In FIG. 3, the electron beam 13 passing through the central portion of the two-pole magnet has a magnetic field generated by two pairs of two-pole magnets N2, S1 (two-pole magnet 10) and N2, S2 (two-pole magnet 11). Affected magnet center O
It receives a force in the direction of and moves in that direction. This movement reduces the deviation (off axis) of the electron beam trajectory from the CRT center.

The upper protrusions 10a and 11a of the two-pole magnets 10 and 11 shown in FIG.
It serves as a knob for rotating 0 and 11 along the circumference of the neck tube 3. The magnetic field generated by the two-pole magnet is directed almost evenly upward as shown in Fig. 3 when the N1, S1 axes and the N2, S2 axes intersect at the same angle with respect to the central axis of the perpendicular. is there. Therefore, the two-pole magnet 1
The upper protrusions 10a and 11a of 0 and 11 are symmetrical with respect to the central axis of the perpendicular. As described above, the deviation of the electron beam is corrected by appropriately changing the crossing angle of the magnets to generate an appropriate correction magnetic field.

The mounting positions of the two-pole magnets 10 and 11 are
After correction of the electron beam trajectory, circular orbits Q ', R'through the intersection Q'of the convergence center B and the tube axis or in the vicinity thereof and the intersection S'of the deflection center D and the tube axis or S'in the vicinity thereof. , S ', T', and the intersection M between the circular orbit before correction and the center of the magnet. Therefore, the position of M is the main electron lens portion on the panel 1 side from the center of the fourth grid electrode G4. Of course, the position is set so as not to affect the main electron lens. R'is the intersection of the neck seal portion C and the electron beam trajectory, and T'is the intersection of the phosphor panel 1 and the electron beam trajectory.

A method of determining the mounting position of the two-pole magnet will be described more specifically. As shown in Table 1, for example, in a vertical magnetic field of −50 [μT], the approximate radius of curvature 31
The off-axis of the electron beam that draws a circular orbit of 000 mm is determined by back-calculating the position where the orbit is corrected so that it becomes zero at the convergence center and the deflection center. The two-pole magnets 10 and 11 have the same function of improving the image characteristics as the magnet for adjusting the color purity (purity).

In this embodiment, a single electron gun type cathode ray tube has been described, but a three electron gun type cathode ray tube is also applicable. Also,
The color selection mechanism also uses an aperture grill (AG) in this embodiment, but a shadow mask is also possible.

[0025]

As described above, according to the present invention,
Since the electron beam can be made to pass through substantially the center of the convergence and the deflection, the deterioration of the beam spot shape can be prevented, and the misconvergence and the image distortion can be reduced. Specifically, by correcting the electron beam trajectory, for example, a shift of about 7 mm can be corrected to a shift of about 4 mm, and an image can be improved.

Further, according to the present invention, since it is possible to deal with the situation by only providing the magnet, it is possible to keep the cost low.

[Brief description of drawings]

FIG. 1 is a schematic plan view of an embodiment of a cathode ray tube equipped with a two-pole magnet according to the present invention.

FIG. 2 is a schematic diagram of an electron gun including a two-pole magnet according to the present embodiment.

FIG. 3 is a schematic front view showing a two-pole magnet of this embodiment.

FIG. 4 is a schematic plan view showing a conventional cathode ray tube.

[Explanation of symbols]

 1 Phosphor Panel 2 Funnel 3 Neck Tube 4 Convergence Plate 5 Aperture Grill (AG) 6,13 Electron Beam 10,11 Two-pole Magnet G1-G5 1st-5th Grid Electrodes

Claims (4)

[Claims] 1. A cathode ray tube, wherein the electron beam trajectory correction means is arranged on the panel side from the center of the main electron lens of the electrodes forming the main electron lens of the electron gun. 2. The cathode ray tube according to claim 1, wherein the orbit correction means is two two-pole magnets capable of adjusting the direction of magnetic force lines. 3. The cathode ray tube according to claim 2, wherein the orbit of the electron beam is adjusted by the magnet so as to pass through the convergence center or its vicinity and the deflection center or its vicinity. 4. The intersection of the electron beam curve trajectory before the trajectory correction and the electron beam curve trajectory after the trajectory correction passing through the convergence center or its vicinity and the deflection center or its vicinity becomes the center of the trajectory correction means. 3. The trajectory correcting means is arranged as described above.
The described cathode ray tube.