JP2892046B2 - Color picture tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a color picture tube having a magnetic shield.

(Prior Art) FIG. 4 shows a general color picture tube. A glass envelope 1 has a funnel 3 integrally joined to a panel 2 and a neck portion 4 is provided on the funnel 3. .
An electron gun 6 for emitting and converging a plurality of electron beams 5 is provided in the neck portion 4 of the envelope 1. The electron gun 6 faces the electron gun 6 on the inner surface of the panel 2 of the envelope 1. A phosphor screen 7 is formed. This phosphor screen 7
Has a stripe-like or dot-like phosphor layer that emits each color of red, green, and blue.

A shadow mask structure 8 is provided inside the phosphor screen 7. The shadow mask structure 8 has a rectangular shadow mask 10 having a large number of electron beam passage holes 9 through which the electron beam 5 from the electron gun 6 passes. A frame-shaped mask frame 11 is fixed to the front surface of the mask frame 11, and frame supports 12 are fixed to the outside of the four sides of the mask frame 11.

Further, the frame support 12 engages with pins (not shown) protruding from the inner wall of the panel 2 to support the mask frame 11 in the envelope 1 and to oppose the shadow mask 10 to the phosphor screen 7. Further, the shadow mask 10 and the phosphor screen 7 are held so as to keep a predetermined interval.

A substantially truncated pyramid-shaped magnetic shield 13 is fixed to the mask frame 11 along the inner surface of the funnel 3.

Although not shown, a deflection yoke for deflecting and scanning the electron beam 5 from the funnel 3 to the outer wall of the neck portion 4 is mounted.

After the electron beam 5 emitted from the electron gun 6 passes through the electron beam passage hole 9 formed in the shadow mask 10, the phosphor screen 7 on the inner surface of the panel 2 opposed to the shadow mask 10, ie, the red phosphor screen 7, , And illuminates the phosphor layers that emit the respective colors of green and blue, and emits light from each of the phosphor layers to project an image.

In this type of color picture tube, the relative positions of a large number of electron beam passage holes 9 of the shadow mask 10 and the three color phosphor layers corresponding to each of these electron beam passage holes 9 in order to reproduce colors well. A predetermined matching relationship is maintained so that the electron beam 5 that has passed through the electron beam passage hole 9 accurately land on a predetermined phosphor layer.

Here, if the landing of the electron beam 5 is affected by an external magnetic field such as terrestrial magnetism, the color purity of the reproduced image is degraded. For this purpose, a magnetic shield 13 made of a magnetic metal plate extending along the inner surface of the funnel 3 is attached to the shadow mask structure 8.

As the magnetic shield 13, for example, a configuration described in Japanese Patent Publication No. 63-67307 is known. That is, since it is difficult to completely shield the external magnetic field, mislanding due to the external magnetic field is prevented by the shape and material of the magnetic shield 13 and the shadow mask structure 8.

However, in recent color picture tubes, higher image quality,
Along with higher quality, higher resolution characteristics are required. For this reason, it is necessary to reduce the pitch of many phosphor layers in the phosphor screen 7, and a landing error is likely to occur. In particular, in the peripheral portion of the screen, the landing movement amount due to the external magnetic field is large as the beam deflection angle increases.

As described above, in a color picture tube in which the pitch of the phosphor layer is small for high image quality and high quality, the landing movement amount due to the external magnetic field is large particularly in the peripheral portion of the screen, and the conventional magnetic shield body 13 can completely eliminate the movement. It is difficult to improve.

There are several causes of the landing error due to the external magnetic field in the peripheral portion of the screen. One of the main causes is a disturbance of the magnetic field at the periphery of the opening 14 of the magnetic shield 13 on the electron gun 6 side. is there. That is, FIG. 5 shows the magnetic flux 16 of the external magnetic field in a direction perpendicular to the tube axis 15 serving as the central axis, and FIG. 6 shows the magnetic flux 17 of the external magnetic field in a direction parallel to the tube axis 15. Since the shield body 13 is formed of a magnetic metal plate, near the periphery of the opening 14 on the electron gun 6 side, the magnetic fluxes 16 and 17 of the external magnetic field concentrate, causing a phenomenon that the magnetic field is disturbed. . Therefore, in particular, the electron beam 5 having a large deflection angle passing near the periphery of the opening 14 receives a relatively large Lorentz force due to the disturbance of the magnetic field, and the beam trajectory changes. As a result, a large landing error occurs locally particularly at the periphery of the screen.

The opening 14 on the electron gun 6 side of such a magnetic shield 13
In order to eliminate the disturbance of the magnetic field at the periphery of the image and to reduce the landing error at the periphery of the screen, it is only necessary to enlarge the opening 14 and move the periphery of the opening 14 away from the position where the electron beam 5 passes. In this case, the effect of shielding the external magnetic field by the magnetic shield 13 decreases, and a landing error in the entire screen increases, which is not preferable.

(Problems to be Solved by the Invention) As described above, in the conventional magnetic shield, there is a problem that a landing error is large particularly in the peripheral portion of the screen due to disturbance of the external magnetic field generated near the periphery of the opening on the electron gun side. have.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a high-quality color picture tube with excellent color purity characteristics, in which a landing error due to an external magnetic field in a peripheral portion of a screen is reduced.

[Configuration of the invention]

(Means for Solving the Problems) The present invention provides an envelope provided with a funnel having a panel and a neck, an electron gun arranged in the neck of the envelope and emitting a plurality of electron beams, A phosphor screen formed on an inner surface of a panel of the envelope, a shadow mask assembly having a shadow frame disposed inside the phosphor screen and having a number of electron beam passage holes mounted on a mask frame; A magnetic shield along the inner surface of the funnel fixed to a mask frame of the shadow mask structure, having a curl-shaped portion bent outward without protruding inward at the periphery of the opening on the gun side; It is provided with.

(Function) The present invention prevents the inside of the magnetic field from being disturbed by preventing the curled portion at the periphery of the opening on the electron gun side of the magnetic shield from projecting inward, and opening the curl-shaped portion by projecting outward. The external magnetic field near the periphery of the part has a gentle distribution, and the influence of the disturbance of the magnetic field near the periphery of the opening on the electron beam can be substantially neglected. It is greatly improved.

(Embodiment) An embodiment of the present invention will be described below with reference to FIG. 1 to FIG.

The color picture tube also has the same configuration as that of the color picture tube of FIG. 4 except for the magnetic shield, and therefore, the corresponding portions are denoted by the same reference numerals and detailed description thereof will be omitted. I do.

In FIG. 1, a magnetic shield body 13 is formed in a substantially truncated pyramid shape by a magnetic metal plate, and has a frame-shaped mounting side portion engaged with the inner surface side of the mask frame 11 of the shadow mask structure 8. An outer edge 22 parallel to the tube axis 15 serving as a central axis is formed by bending outside the mounting side 21, and a slope 23 along the inner surface of the funnel 3 is connected to the edge 22. A curl-shaped portion 24 is provided in which the periphery of the opening 14 on the side of the electron gun 6 of the inclined portion 23 is bent outward in an arc shape. The radius of curvature of the curled portion 24 varies depending on the size and the deflection angle of the color picture tube.
For a color picture tube with a deflection of about 2 mm or more is appropriate.

Then, the magnetic shield body 13 is attached by a clip or the like with the mounting side 21 abutting against the edge piece of the mask frame 11, and the slope 23 is formed along the inner surface of the funnel 3 of the envelope 1 by the electron gun 6. Direction.

In the color picture tube of FIG. 1, FIG. 2 shows a magnetic flux 16 of an external magnetic field in a direction perpendicular to the tube axis 15, and FIG. 3 shows a magnetic flux 17 of an external magnetic field in a direction parallel to the tube axis 15. However, due to the outward curl-shaped portion 24 at the periphery of the opening 14 on the electron gun 6 side of the magnetic shield 13, the magnetic fluxes 16 and 17 of the external magnetic field near the periphery of the opening 14 have a gentle distribution. The disturbance of the magnetic field near the periphery of the opening 14 as shown in FIGS. 5 and 6 does not occur. Therefore, the influence of the disturbance of the magnetic field near the periphery of the opening 14 on the electron beam 5 becomes substantially negligible, and the electron beam 5 having a large deflection angle reaching the peripheral portion of the screen is also affected by the disturbance of the external magnetic field. And landing errors are greatly reduced.

As shown in FIGS. 2 and 3, the improvement of the landing error due to the external magnetic field can be made with respect to either the external magnetic field perpendicular to the tube axis 15 or the external magnetic field parallel to the tube axis 15. Is also effective.

In addition, since the curled portion 24 is bent at the periphery of the opening 14 on the electron gun 6 side of the magnetic shield 13, the magnetic shield 13 has a reinforcing effect, and manufacturing variations are reduced.

〔The invention's effect〕

According to the color picture tube of the present invention, since the curled portion of the magnetic shield body does not protrude inward but protrudes outward, the external magnetic field near the periphery at the opening on the electron gun side of the magnetic shield body is obtained. Can be almost eliminated, a landing error at the peripheral portion of the screen due to an external magnetic field can be significantly improved, and high image quality with excellent color purity characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of a color picture tube according to the present invention, FIGS. 2 and 3 are explanatory views showing the flow of magnetic flux in the magnetic shield of FIG. 1, and FIG. FIGS. 5 and 6 are cross-sectional views of a color picture tube, and are explanatory views showing the flow of magnetic flux in the magnetic shield of FIG. 1 ... envelope, 2 ... panel, 3 ... funnel, 4 ...
... Neck part, 5 ... Electron beam, 6 ... Electron gun, 7 ...
Phosphor screen, 8 ... Shadow mask structure, 9 ...
Electron beam passage hole, 10 Shadow mask, 11 Mask frame, 13 Magnetic shield, 14 Opening, 24
...... Curl-shaped part.

Claims (1)

(57) [Claims] 1. An envelope provided with a funnel having a panel and a neck, an electron gun disposed in the neck of the envelope to emit a plurality of electron beams, and an inner surface of a panel of the envelope. A shadow mask structure in which a shadow mask having a large number of electron beam passage holes disposed on the inside of the phosphor screen is attached to a mask frame; and a peripheral edge of an opening on the electron gun side. A magnetic shield that has a curled portion bent outward without protruding inward, and is fixed to a mask frame of the shadow mask structure and along an inner surface of the funnel. Color picture tube.