JPH0524607B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing a miniature cathode ray tube, particularly a microcathode ray tube having a function of electrostatically and magnetically focusing an electron beam.

Conventional configuration and its problems As a video camera viewfinder, the diagonal length of the screen surface is 1.5 inches, 1 inch or 1 inch.
Ultra-compact cathode ray tubes of about 0.5 inches are used. Since such cathode ray tubes are often powered by batteries, it is especially desirable that they operate with low power consumption and high efficiency.

Since the deflection power in the above-mentioned ultra-small cathode ray tube occupies a considerable proportion of the total power consumption, reducing the deflection power greatly contributes to power saving. Since the deflection power is proportional to the anode voltage, lowering the anode voltage can reduce the deflection power, but simply lowering the anode voltage makes it difficult to obtain the necessary brightness on the phosphor screen surface. In cathode ray tubes that do not have a metal back on the phosphor screen surface, the required screen surface brightness can be obtained with a relatively low anode voltage, but so-called ion burn occurs on the phosphor screen surface. Also, the anode voltage can be lowered by reducing the thickness of the aluminum vapor-deposited film constituting the metal back; The screen surface brightness is approximately half that of the case without the screen (anode voltage 2KV), which cannot be said to be sufficient.

Furthermore, when the film thickness is reduced, wrinkles are formed on the film surface in a pattern. When viewing the phosphor screen surface through an optical lens as in a viewfinder, the wrinkles become very unsightly.

OBJECTS OF THE INVENTION An object of the present invention is to provide a manufacturing method suitable for obtaining a high-efficiency, high-quality compact cathode ray tube that does not include a metal bag and hardly causes ion burnout.

Structure of the Invention According to the manufacturing method of the present invention, the magnetic ring that is disposed between the cathode and the deflection yoke of an electrostatic focusing electron gun and generates an electron beam focusing magnetic field is magnetized after the tube is evacuated. This will be explained in detail below along with the embodiments shown in the drawings.

In FIG. 1, an electrostatic focusing electron gun 3 enclosed in a neck portion 2 of a glass bulb 1 has a cathode 4,
It comprises a control electrode 5, an acceleration electrode 6, a focusing electrode 7, and an anode 8, and a ferromagnetic ring 9 is attached to the inner peripheral surface of the focusing electrode 7. The ferromagnetic ring 9 is arranged coaxially with the gun axis,
By being magnetized so that S and N poles are generated in the direction of the gun axis, a magnetic field for electron beam focusing coaxial with the gun axis is generated.

On the other hand, the face panel portion 10 of the glass bulb 1
The phosphor screen 11 attached to the inner surface of the phosphor screen 11 does not have a metal back and faces the electron gun 3 without a metal back. 1
2 is an internal conductive film held at the same potential as the anode 8;
3 indicates a deflection yoke.

The modulated electron beam emitted from the electron gun 3 is deflected by the horizontal and vertical deflection magnetic fields produced by the deflection yoke 13, and a monochrome image is projected on the surface of the phosphor screen 11. The modulated electron beam incident on 7 is prefocused by a focusing magnetic field produced by a magnetized ferromagnetic ring 9, and then finally focused by a main electron lens generated between the focusing electrode 7 and anode 8. Receives a focusing effect. That is, the modulated electron beam incident on the focusing electrode 7 is focused in two stages by the focusing magnetic field and the main electron lens.

On the other hand, negative ions generated near the crossover between the control electrode 5 and the accelerating electrode 6 are focused by the main lens in the same way as the electron beam, but since they have a large mass compared to the electrons, they are made of ferromagnetic material. It is hardly affected by the focusing magnetic field by the ring 9 and the deflection magnetic field by the deflection yoke 13. Therefore, the anions incompletely focused by the main lens impinge on a relatively wide area centered on the center of the phosphor screen 11, causing ion burn only in the center of the phosphor screen. Never.

To explain this in more detail using Figure 2,
The electron beam 14 shown by the solid line in the same figure is focused by the magnetic field lens 15 formed by the ferromagnetic ring 9 and the main electron lens 16 and converges to a point on the surface of the phosphor screen 11, whereas the electron beam 14 is shown by the shadow shown by the broken line. Since the ion beam 17 is mainly focused only by the main electron lens 16, it does not converge to a single point on the surface of the phosphor screen 11, but is dispersed over a relatively wide area. For this reason, the occurrence of ion burn is considerably reduced even though it does not have a metal back.

Although the ferromagnetic ring 9 is attached to the inner circumferential surface of the focusing electrode 7 in the embodiment described above, it may be coaxially provided on the outer circumferential surface of the focusing electrode 7. Further, the ferromagnetic ring 9 does not necessarily need to be attached to the focusing electrode 7, and in short, it is sufficient if it is coaxially installed in the tube near the midpoint between the cathode 4 and the deflection yoke 13.

By the way, the electron gun components including the ferromagnetic ring 9 are used for gas removal during the tube exhaust process.
Heated to a temperature of 400℃. Furthermore, since the temperature distribution of this heating is not necessarily uniform, the coercive force of the ferromagnetic ring 9, which has been magnetized in advance, may change irregularly before and after the pipe evacuation process. If this happens, it becomes difficult to obtain the intended ion dispersion effect and electron beam focusing effect satisfactorily.

Therefore, in the present invention, the magnetization process for the ferromagnetic ring 9 is performed after the tube is evacuated. The magnetization processing device 18 shown in FIG. 3 consists of a U-shaped iron piece 19 and a coil 20 wound around it.
A magnetizing magnetic field 23 is generated between the two. Then, the ferromagnetic ring of the cathode ray tube 24 to be processed after exhaust, which is arranged so that the tube axis is parallel to the magnetic field 23, is exposed to the magnetic field 23.
3, it is magnetized to a predetermined coercive force.

When operating the completed cathode ray tube, if the focused state of the electron beam is not optimal, the device 18 may be used to re-magnetize or demagnetize it.

Effects of the Invention Since the method for manufacturing a small cathode ray tube of the present invention is configured as described above, it is possible to obtain a high efficiency small cathode ray tube that can obtain sufficient brightness with a relatively low anode voltage and has almost no fear of ion burnout. Not only this, but also the uniformity of the magnetization and coercive force of the ferromagnetic ring can be obtained, and a decrease in resolution due to variations and changes in the electron beam focusing magnetic field can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view of a small cathode ray tube to which the present invention is applied, and FIG. 2 is an explanatory diagram of the operation of a magnetic field lens and a main electron lens formed by a ferromagnetic ring of the same cathode ray tube.
FIG. 3 is a perspective view showing an example of a magnetization processing apparatus applied in the manufacturing method of the present invention. 3... Electron gun, 4... Cathode, 7... Focusing electrode,
9... Ferromagnetic ring, 11... Fluorescent screen, 13... Deflection yoke.

Claims (1)

[Claims] 1 An electrostatic focusing electron gun, a phosphor screen that faces the electron gun without intervening a metal bag, and an electron beam disposed in the tube between the cathode and the deflection yoke of the electron gun and arranged approximately parallel to the tube axis. 1. A method of manufacturing a small cathode ray tube comprising a magnetic ring that generates a beam focusing magnetic field, the method comprising magnetizing the magnetic ring after the tube is evacuated.