JPH02281538A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To compensate axial dislocation caused by dispersion of parts accuracy and assembly accuracy, and prevent deterioration of focus characteristic and convergence characteristic by providing purity convergence magnets. CONSTITUTION:An electron gun 22 in a neck part 21 of a cathode ray tube consists of a cathode 11, a control electrode 12, an accelerating electrode 13, a focusing electrode 14, a final accelerating electrode 15 and a shielding cap 23. A prefocus lens 16 consists of the electrode 12-14, and a main lens 17 consists of the electrodes 14-15. A purity convergence magnet 30 is located between the lenses 16 and 17. When axial dislocation of three electron beams out from the lens 16 is generated by parts error or assembly error, orbit correction is performed by a compensating magnetic field so that the beams enter to the center of the lens 17 accurately in parallel with each other. A purity convergence magnet 40 is located between the lens 17 and a deflecting yoke. Consequently, orbit correction of axial dislocation is performed by a compensating magnetic field.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention can prevent deterioration of focus characteristics and convergence characteristics due to variations in precision of electron gun components, deflection yoke, envelope, etc. Regarding cathode ray tubes.

[Conventional technology]

Generally, a cathode ray tube consists of an envelope l whose inside is evacuated to a high vacuum, and a plurality of red, green, and blue phosphor stripes arranged on the inner face of the envelope l, as shown in Figure 3. Alternatively, a phosphor film 2 made of phosphor dots and a shadow mask 3 having a color selection function for causing the phosphor of an arbitrary color contained in the phosphor film 2 to emit light are arranged side by side in the same horizontal plane. three in-line electron guns 4, a deflection yoke 6 for deflecting the three electron beams 5 emitted from the in-line electron guns 4, variations in assembly of the electron guns, and axes of the electron guns and deflection yokes 2-pole and 4-pole to correct color misalignment and static convergence caused by various factors such as axis misalignment between the two or shadow mask variations.

It has a utility magnet 7 that generates a six-pole magnetic field.

Figure 4 shows the purity convergence magnet 7.
This is an example of a two-pole magnet 8, a four-pole magnet 9,
Six-pole magnets 10 are provided in sequence. Each magnet is formed by two ring-shaped magnets,
Two rings that generate two-pole magnetic field distribution, four-pole magnetic field distribution, and six-pole magnetic field distribution as shown in Fig. 5(a), Fig. 5(b), and Fig. 5(c) are combined, and each By setting the angle appropriately, the strength and direction of the magnetic field can be set arbitrarily.
By changing the direction of the three electron beams, color shift and static convergence are corrected.

[Problem to be solved by the invention]

The focus characteristics and convergence characteristics of an electron gun are greatly influenced by variations in the accuracy of parts and assembly accuracy of the electron gun. FIG. 6 is a cross-sectional view of a pi-potential type electron gun, in which an electron beam emitted from a cathode 11 serving as an electron source is transmitted through a prefocus lens 16 formed by a control electrode 12, an accelerating electrode 13, and a focusing electrode 14. Focusing electrode 14
The main lens 1 formed between the main lens 1 and the final accelerating electrode 15
7 and reaches the display surface. If the parts and assembly of this pi-potential type electron gun are formed completely as designed, the electron beam will naturally deviate from the central axis of the electron gun, as shown in the beam trajectory 18. The object then passes straight through the center of the main lens 17 and continues straight until it enters the deflection magnetic field. However, in an actual electron gun, parts and assemblies cannot exist completely as designed, and errors (or tolerances) within a certain range cannot be avoided. For example, the control electrode 12, the accelerating electrode 13
If the prefocus lens 16 formed by the focusing electrode 14 has an axis misalignment of the electron beam passing hole due to the above-mentioned error, the electron beam will be prefocused as shown by the beam trajectory 19 in FIG. It is refracted by the focus lens 16 and deviates from the center axis of the electron gun, and as a result, the main lens 1
Pass through a position off the center of 7. However, after passing through the main lens 17, the main lens receives refractive power, so the angle with the electron gun axis decreases, and the axis deviation on the screen is as large as the ratio of the axis deviation at the main lens position. On the contrary, the axial deviation at the main lens position will be large, and since this is the location where the spherical aberration of the main lens is large, the focus level will deteriorate.

Next, if the prefocus lens 16 is completely as designed, but there is an error in the main lens 17, the sixth
As shown by the beam trajectory 20 in the figure, the beam is refracted by the main lens and deviates from the axis of the electron gun, which appears as a deviation on the screen.

In this case, it appears as a positional shift, but since the light passes through the center of the main lens, there is little deterioration in focus. However, if we use a purity convergence magnet to change the trajectory of the electron beam in order to correct this positional deviation, the deviation on the screen will be reduced.

Since it passes through a position off the center of the main lens, it ends up degrading the forgas level.

In this way, if the precision of either the prefocus lens or the main lens is poor, the focus level of the electron gun will deteriorate, making it impossible to obtain sufficient resolution. Even if there is a misalignment between the axis and the axis of the deflection yoke or the axis of the phosphor film, focus deterioration will occur because the purity convergence magnet changes the trajectory of the electron beam in the same way as described above. At the same time, dynamic convergence also deteriorates.

[Means to solve the problem]

The cathode ray tube of the present invention uses two purity convergence magnets, and the first purity convergence magnet is provided at the prefocus lens position of the electron gun or between the prefocus lens and the main lens, and To correct the axis deviation of the electron beam, a second purity convergence magnet is provided at the main lens position of the electron gun or between the main lens and the deflection yoke, and the main lens, the deflection yoke,
Alternatively, it is possible to correct the axis misalignment of the fluorescent film and to correct errors in components and assembly of the cathode ray tube without deteriorating the focus characteristics and convergence characteristics of the electron gun.

〔Example〕

Next, the present invention will be explained in detail using the drawings. FIG. 1 shows a first embodiment of the cathode ray tube of the present invention. There is an electron gun 22 in the neck part 21 of the cathode ray tube.
is the cathode 11. Control electrode 12, acceleration electrode 13. Focusing electrode 14. It is composed of a final acceleration electrode 15 and a shield cup 23. Control ring f! 12, the acceleration electrode 13, and the focusing electrode 14 form a prefocus lens 16, and the focusing electrode 14 and the final acceleration electrode 15 form a main lens 17.
is formed. The first purity convergence magnet 30 is installed at the pre-focus lens position or between the pre-focus lens 16 and the main lens 17, and is made of 2fi, 4-pole and 6-pole magnets, and is placed at the pre-focus lens position or between the pre-focus lens 16 and the main lens 17. If the three electron beams are axially misaligned due to component or assembly errors, their orbits can be corrected using a correction magnetic field so that they can be incident parallel to the center of the main lens 17 as accurately as possible. In addition, a second lens is provided at the main lens position or between the main lens 17 and the deflection yoke (not shown).
A purity convergence magnet 40 is provided, which is made of 2-pole, 4-fi, and 6-pole magnets, and the three electron beams exiting the main lens 17 may be misaligned due to parts of the main lens or assembly errors, or may be caused by the electron gun. If there is an axis misalignment between the axis of the deflection yoke or the fluorescent film, the trajectory can be corrected using the correction magnetic field.

FIG. 2 shows a second embodiment of the cathode ray tube of the present invention, in which the first purity convergence magnet 31 provided between the prefocus lens or the prefocus lens and the main lens is an integrated magnet. Therefore, it is only necessary to magnetize the integrated magnet with a magnetic field distribution that corrects the axis deviation of the three electron beams exiting the prefocus lens 16. This can be done by detecting the optimum amount of magnetization when testing the characteristics of the cathode ray tube, magnetizing the magnet by that amount when magnetizing the magnet, and attaching the magnet to the cathode ray tube. The main lens 17 or between the main lens and the deflection yoke has two poles, four poles, and six poles similar to the first embodiment.
A second purity convergence magnet 40 consisting of a polar magnet is provided.

As understood from the first and second embodiments above, the axis deviation of the electron beam at the prefocus lens is corrected by the first purity convergence magnet, and the main lens, deflection yoke, and fluorescent film correct the axis deviation of the electron beam. By correcting the axis misalignment with the second purity convergence magnet, the electron beam passes through the center of the main lens and the electron beam trajectory is as designed, so that the focusing characteristics and convergence characteristics are not deteriorated. .

Although the above embodiment has been explained using a pi-potential type electron gun, it can also be applied to cathode ray tubes of other focusing type electron guns.

〔Effect of the invention〕

As explained above, the present invention provides a first purity convergence magnet at the pre-focus lens position or at a position between the pre-focus lens and the main lens, and improves component accuracy and assembly accuracy of the electrodes forming the pre-focus lens. It is possible to correct the axis misalignment of the electron beams due to variations in the electron beams, allow three electron beams to pass through the center of the main lens, and to install a second purity filter at the main lens position or between the main lens and the deflection yoke.・Convergence magnet is installed, and electrode parts forming the main lens have a variation in assembly accuracy.
Since it is possible to correct the axis misalignment between the electron gun, the deflection yoke, and the fluorescent film, it is possible to prevent deterioration of focus characteristics and convergence characteristics caused by these variations. In addition, with the present invention, it becomes possible to further loosen the precision of parts precision and assembly precision, which has been extremely strictly controlled up to now, and improve display quality such as output and convergence, as well as reduce costs. It has the great effect of being able to do the following.

Furthermore, when changing the focus voltage, the movement of the beam spot on the screen can be made as designed, and adjustment can be made easily.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a first embodiment of the cathode ray tube of the present invention, FIG. 2 is a sectional view of a second embodiment of the invention, FIG. 3 is an explanatory diagram of a conventional cathode ray tube, and FIG. 4 are cross-sectional views of the purity convergence magnet, Fig. 5 (a>, (b), (
c) are respectively 2M magnet and 48i! Magnet and 6g! The magnetic field distribution diagram of the magnet, FIG. 6, is an explanatory diagram of the beam trajectory when there is a partial error or an assembly error. DESCRIPTION OF SYMBOLS 1... Envelope, 2... Fluorescent film, 3... Shadow mask, 4... In-line electron gun, 5... Electron beam, 6... Deflection yoke, 7... Purity. Convergence magnet, 8... 2-pole magnet, 9...
...4 pole magnet, 10...6 [i magnet, 1
DESCRIPTION OF SYMBOLS 1... Cathode, 12... Control electrode, 13... Acceleration electrode, 14... Focusing electrode, 15... Final acceleration electrode, 1
6... Prefocus lens, 17... Main lens, 18.19° 20... Beam trajectory, 30.31.
...First purity convergence magnet, 40...Second purity convergence magnet.

Claims (1)

[Claims] In a cathode ray tube that has at least an in-line electron gun, a deflection yoke that deflects the electron beam, and a fluorescent film that produces an image, the prefocus of the electron gun is placed outside the envelope in which the in-line electron gun is sealed. A first purity convergence magnet is provided at the lens position or a position corresponding to between the prefocus lens and the main lens, and a second purity convergence magnet is provided at the main lens position or a position corresponding to between the main lens and the deflection yoke. Purity
A cathode ray tube characterized by being equipped with a convergence magnet.