JPS58198830A - Cathode-ray tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improving focus characteristics of an in-line color cathode ray tube, and particularly to improving focus deterioration caused by just focus voltage difference between three guns.

Generally, an electron gun used in a color cathode ray tube has a prefocus type electron lens 1 and a main lens type electron lens 2, as shown in FIG.
The electron beam is shown as being imaged on the screen 4. Note that 5 is one point of crossover.

In addition, in the shadow mask inline type electron gun, as shown in Fig. 2, the electron gun is arranged on one plane, and the electron gun is screened by the offset of the main lens 2, the STC magnetic pole 6, and the deflection yoke magnetic field. 3 electron beams are converged at each point on 4.

Note that 7 is the focal point of the central electron gun, and 8 is the focal point of the side electron guns.

However, in conventional integrated in-line electron guns, all three electron guns are designed with the same dimensions except for the final offset electron lens. Therefore, due to astigmatism caused by the final offset electrode and astigmatism caused by the quadrupole magnetic field that corrects the residual offset design, a difference occurs in the focus voltage between the central electron gun and the electron guns placed on both sides, which affects the focus characteristics. It had some influence. In particular, focus adjustment is delicate in color display tubes for office automation, etc., and this is a major hurdle in improving focus.

The present invention aims to provide a cathode ray tube with easy focus adjustment, and is configured so that a focus voltage difference is corrected by a prefocus lens having a relatively large degree of freedom. That is, as shown in Fig. 2, in the conventional design, when the imaging points of the electron beams on both sides are in front of the imaging point of the central electron beam, that is, when the just focus voltage on both sides is high, By strengthening the prefocus lenses on both sides and placing the virtual object point farther away from the main lens than that of the central electron gun, the imaging point can be made to coincide with the central imaging point. be.

FIG. 3 shows an embodiment of the present invention. Second grid electrode G
Regarding the hole diameter of II, the hole diameters on both sides are made smaller than the center hole diameter to strengthen the prefocus. Note that G8 is a third grid electrode, and 9 is a main lens surface.

The embodiment shown in FIG. 4 is an example in which this is achieved by using a difference in the thickness of the second grid electrode GB. Note that Ls is a side electron lens, and LC is a center electron lens.

In the embodiment shown in FIG. 5, the intensity of the prefocus lens is controlled by deflecting the incident side of the third grid electrode Gs as shown in the figure to change the electrode spacing 11, 12. Furthermore, in this case, the effect of correcting STC deviation due to focus voltage fluctuation is also provided.

In the embodiment shown in FIG. 6, prefocus correction is performed by changing the hole diameters of the third grid electrode G8.

The embodiment shown in FIG. 7 is an example in which pseudo-multistage prefocus lenses are realized. The diameter of the exit hole on the side of the second grid electrode Gll is increased so that a sufficiently strong lens is formed at the small entrance hole. By doing this, the prefocus on both sides is made stronger than that in the center. Also in this case, by making the large holes on both sides eccentric to the outside with respect to the small hole, it is possible to provide a function of correcting the 8TC deviation due to the shift focus voltage difference.

As explained above, according to the present invention, the focus voltages of each electron gun can be matched by prefocus correction, and a cathode ray tube of extremely high quality and good focus can be obtained for terminal displays and the like.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram illustrating the lens system of an electron gun in a general cathode ray tube, Fig. 2 is an explanatory diagram illustrating the focus voltage difference between the electron gun in the center and on both sides, and Fig. 3 is an explanatory diagram illustrating the lens system of the electron gun of a general cathode ray tube. Enlarged sectional views of essential parts of an embodiment of such a cathode ray tube, No. 4 to
FIG. 7 is an enlarged sectional view of a main part of another embodiment. 1. Sleeping focus lens, 2. Main lens, 3-I-.Virtual object point, 4. Meeting, Medium screen, 7.
... Focus of central electron gun, 8... Focus of side electron gun, 9... Fist/main lens surface, GB board... 2nd grid electrode, G8... 3rd grid electrode. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. In an in-line color cathode ray tube, the focal length of the electron lens formed between the second grid electrode and the third grid electrode is different from that of the electron gun located in the center and the electron guns located on both sides. A cathode ray tube characterized by a difference in 2. A cathode ray tube according to claim 1, characterized in that the hole diameter or plate thickness of the second grid electrode is different between the center and both sides. 3. The cathode ray tube according to claim 1, wherein the distance between the second grid electrode and the third grid electrode is different between the center and both sides. 4. The cathode ray tube according to claim 1, wherein the third grid electrode has a hole diameter or plate thickness at the electron beam incident point that is different between the center and both sides. 5. In the cathode ray tube according to claim 1, the second grid electrode has a configuration in which the entrance side and the exit side have different hole diameters, and the hole diameter or depth on the exit side is different between the center and both sides. A cathode ray tube characterized by a difference.