JPS5939853B2 - Shadow mask type color picture tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shadow mask type color picture tube, and more particularly to an improvement of a shadow mask structure built into the picture tube.

The shadow mask type color picture tube is as shown in Figure 1.
A funnel 1, a panel 2 sealed to the open end of the funnel 1, a fluorescent surface 3 coated on the inner surface of the panel 2, and a plurality of pins 4 provided on the side wall of the panel 2.
and a shadow mask structure supported by pins 4 facing the fluorescent surface 3.

As shown in FIGS. 2 and 3, the shadow mask structure consists of an effective surface having a large number of openings through which electron beams selectively pass, and an ineffective surface formed around the periphery of the effective surface.

A mask portion 7 having a spherical surface substantially equal to the spherical face of the panel 2, a mask skirt portion 8 bent to attach the mask portion 7 to a frame to be described later, and a A frame 9 welded at ~20 points, a bimetal 10 welded to the frame 9 to compensate for thermal expansion of the shadow mask structure 5 that occurs during operation of the color cathode ray tube, and a bimetal 10 welded to the bimetal 10 and the pin 4 A spring 11 is fitted to hold the shadow mask structure at a position relative to the panel 2.

In the shadow mask type color cathode ray tube having such a structure, the electron beam emitted from the electron gun 6 passes through the opening of the mask portion 7 and is applied to the red, green, and
The total area of the openings of the mask section 7 is usually 1 of the surface area of the mask section 7.
5%, most of the electron beam collides with the non-opening portion and heats the mask portion 7.

For example, as a result of measurement with a 20-inch color picture tube, the high pressure 24
Under the conditions of KV and beam current of 1000 μA, the temperature at the center of the mask part 7 increases significantly during the first 10 minutes.
It reaches saturation in 0 minutes and the temperature rises by about 40°C.

However, the temperature of the frame 9 gradually increased and reached a saturated state in about 1 hour.

Due to such a temperature rise, the mask portion 7 thermally expands and protrudes in the direction of the fluorescent surface 3, thereby causing color shift.

That is, in FIG. 4, the mask portion 7 which was in the state before the start of operation (G) moves to the state B) where thermal expansion occurs due to the temperature rise.

Therefore, on the phosphor surface 3, as shown in FIGS. 5A and 5B, the electron beam passing through the aperture 12 moves toward the center, causing the adjacent phosphors of other colors to emit light and producing a normal color image. becomes impossible to reproduce.

This phenomenon appears over the entire screen.

When this was measured using a color picture tube with a deflection angle of 110°, it appeared most prominently on the circumference 100 mm from the center of the face of panel 2, and at a high voltage of 24 KV and a beam current of 10
At 00 μA, the electron beam moves 0.07 to 0.1 mm,
This is causing a color shift phenomenon.

In addition, in order to correct the expansion of the mask part 7, the bimetal 1
0 is set, but for the first 10 minutes, frame 9
Since the temperature rise is small, the effect is hardly noticeable.

Next, when the temperature of the frame 9 rises, the mask portion 7 is deformed so as to approach the face surface of the panel 2, resulting in an effect opposite to that of correcting the initial thermal expansion.

The present invention was made to eliminate the above-mentioned drawbacks, and by increasing the temperature rise of the mask skirt portion, the temperature difference between the center and corner of the mask portion is reduced, thereby reducing color shift due to thermal expansion. A shadow mask type color picture tube having a shadow mask structure is provided.

A shadow mask structure adapted to an embodiment of the present invention will be explained below with reference to FIG.

That is, in FIG. 16, one end of the frame 19
It has a bent part 19□ that covers the ineffective surface of 7,
The skirt portion 18 of the mask portion is welded to the inner wall of the frame 19 directly or via a protrusion 20 to form a shadow mask structure 15.

By having the structure as in the embodiment of the invention, the frame 19 welded to the outside of the mask skirt portion 18 retains the heat generated by the electron beam hitting the mask skirt portion 18 among the deflected electron beams. Since the temperature of the mask skirt portion 18 can be increased by blocking the heat radiation, it is possible to reduce the temperature difference between the center and corner of the mask portion 17 and reduce color shift due to thermal expansion. It became.

Further, the bent portion 191 of the frame 19 that covers the ineffective portion of the mask portion 17 also serves to prevent mask deformation due to external force.

By configuring as above, the mask skirt portion 18
The temperature of the mask increases, and color shift due to thermal expansion of the mask portion that occurs after the start of operation can be reduced.

Actually incorporated into a 20 inch 110° deflection color cathode ray tube,
When operated at a high voltage of 24 KV and a beam current of 1000 μA, the initial electron beam movement was reduced by about 50% compared to a conventional color cathode ray tube.

Shadow mask structure 1J adapted to other embodiments of the present invention
As shown in FIG. 7, a white plating layer 12 is provided on the inner surface of the frame 19 facing the mask skirt portion 18.

Therefore, the deflected electron beam is transmitted to the mask skirt portion 18.
The heat generated by the mask is reflected by the frame 19 when it is radiated, increasing the temperature of the mask skirt portion 18 and having the effect of further reducing color shift due to thermal expansion.

In a shadow mask structure l adapted to still another embodiment of the present invention, as shown in FIG. At the same time, it can prevent overscanning of electron beams coming around from the outside of the frame 19, and can also serve as an electron shield plate.

In the above three embodiments, the thickness of the frame, the mask part,
Although the shape of the mask skirt was not specified, it is possible to make the frame thicker or thinner, or to provide an opening on the non-effective surface of the mask, so that the electron beam passing through the opening can be used to form the frame. It goes without saying that the frame 19 may be heated by heating the bent portion 191 of the frame 19, or that the protrusions may be interposed in the form of bands or dots when welding the inner wall of the frame and the mask skirt via the protrusions. do not have.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway side view of a shadow mask type color picture tube, Fig. 2 is a simplified sectional view taken along the line nn' in Fig. 1, and Fig. 3 is a color picture tube of the color picture tube shown in Fig. 1. FIG. 4 is an explanatory cross-sectional view showing the initial thermal expansion phenomenon of the mask portion, and FIG. 5 shows the relative position of the fluorescent surface and the electron beam accompanying the phenomenon shown in FIG. FIG. 6 is a cross-sectional view of a main part of a shadow mask structure adapted to one embodiment of the present invention, and FIGS. 7 and 8 are cross-sections of a main part of a shadow mask structure adapted to other embodiments of the present invention. It is a diagram. 5, 'j5...Shadow mask structure, 7.17
...Mask part, 8,18...Mask skirt part, 9゜19...Frame, 13...
... Reinforcement part, 191 ... Bending part of the frame.

Claims (1)

[Claims] 1. A mask portion consisting of an effective surface in which a large number of openings through which electron beams selectively pass and an ineffective surface provided at the periphery of the effective surface; A shadow mask structure including a mask skirt portion bent with respect to a surface, and a frame having a bent portion that holds the mask skirt portion on an inner wall and covers at least a part of the ineffective surface. A shadow mask type color picture tube.