CN1125479C - Cathode ray tube with electron beam shield to prevent halation - Google Patents

Abstract

A cathode ray tube is over-scanned. In order to prevent halation in a dark room, a beam shielding plate is shaped so that the front end surface of the beam shielding plate is substantially parallel to a path (E) of the electron beam or so that it is swept back from the path (E) of the electron beam to thereby prevent the electron beam from striking the front end surface of the beam shielding plate, prevent the reflection of the electron beam at the front end surface, and prevent halation.

Description

Cathode ray tube with electron beam shield to prevent halation

                      

The present invention relates to a cathode ray tube which prevents halation when used for overscanning.

Background technique

As shown in FIG. 1, in a color cathode ray tube, a phosphor screen 4 is formed on the inner surface of a face plate 3 of a tube envelope 2. As shown in FIG. Facing the fluorescent screen 4, a color selection electrode system 10 called an aperture grid or shadow mask is arranged. The electron beam E emitted from the electron gun 5 disposed in the neck 2a of the envelope 2 is deflected by the deflection yoke 6 so as to scan the phosphor screen 4 .

Fig. 2 is a schematic top view showing the color selection mechanism in a cathode ray tube. As shown in Fig. 2, when a cathode ray tube is used as a TV monitor in a broadcasting station, etc., the cathode ray tube is sometimes used in an overscanning manner, even if the electron beam E scans The outside of the normal active area defined by the most distal slit of the color selection electrode system 10. When the cathode ray tube is used with overscanning, the overscanned electron beams are deflected irregularly at the frame 11 of the color selection electrode system. The frame halo is caused when the irregularly deflected electrons reach the phosphor screen 4 . For this reason, in a TV monitor for a broadcasting station etc., a long and thin electron beam shielding plate 12 made of metal is provided between the frame 11 and the deflection center DC of the electron beams, and the shielding plate 12 is attached to the inside. The electron beam shielding plate 13 prevents the electron beam from colliding with the frame 11. Usually, this electron beam shielding plate 12 is made of iron or stainless steel with a thickness of about 0.2mm. When a high voltage is applied, it absorbs electrons, or reflects electrons to the electron gun side, so that the frame 11 is separated from the electron beams, preventing irregular reflections. halo caused.

However, depending on the application of TV monitors by broadcasting stations, it is sometimes in a low current state in a dark room. When using this method, a slight halo can be seen. Therefore, it is desired to suppress such halos.

Contents of invention

An object of the present invention is to provide a cathode ray tube applicable to overscan, which prevents the generation of halos even when used in a dark room or the like.

The present invention provides the following cathode ray tube.

(1) A cathode ray tube capable of scanning an electron beam outside an effective screen, the cathode ray tube having an electron beam shielding plate provided between the frame of the color selection electrode system and the deflection center of the electron beam so that the When the electron beam is scanned on the outside of the effective screen, the electron beam is prevented from hitting the frame, and it is characterized in that the electron beam shielding plate is formed so that the front end surface of the shielding plate on the inside of the screen is substantially parallel to the path of the electron beam, or from the electron beam path extend back.

(2) The cathode ray tube as described in (1), wherein the electron beam shielding plate has a front end portion bent toward the color selection electrode system side, and a front end surface substantially parallel to the electron beam path.

(3) In the cathode ray tube described in (1), the front end surface of the electron beam shielding plate is formed into a tapered surface.

(4) In the cathode ray tube described in (1), the electron beam shielding plate is formed so that the front end portion is bent toward the color selection electrode system side, and the front end surface is formed into a tapered surface.

The present invention is based on the discovery that since the electron beam shielding plate has a certain thickness, its front end surface faces the emission direction of the electron beams in an inclined state, and the electron beams are irregularly reflected on the front end surface, and the reflected electrons bombard the fluorescent screen side. This fact causes halos when overscanning.

That is, the cathode ray tube of the present invention has a cleverly shaped electron beam shield whose front surface is substantially parallel to the electron beam path, or extends backward from the electron beam path, thereby preventing the electron beam from hitting the electron beam. The front surface of the beam shielding plate, and the reflection of the electron beams at the front surface, can prevent halation.

The electron beam shielding in this way can be formed by bending the front end of the electron beam shielding plate toward the side of the color selection electrode system, so that the front end surface is basically parallel to the electron beam path, or the front end surface of the electron beam shielding plate is a tapered surface. the front surface of the board.

Description of drawings

The above and other objects and features of the present invention will be described in detail below with reference to the accompanying drawings, in which:

Figure 1 is a sectional view of the general structure of a cathode ray tube;

Fig. 2 is a plan view of a color selection mechanism of a cathode ray tube;

Fig. 3 is a view illustrating generation of halos with a conventional electron beam reflector;

4 is a plan view of a color selection mechanism in a cathode ray tube according to an embodiment of the present invention;

Fig. 5 is a view of a front end portion of an example of an electron beam reflecting plate of the present invention;

Fig. 6 is a view of another example of the electron beam reflecting plate of the present invention; and

Fig. 7 is a view showing still another example of the electron beam reflecting plate of the present invention.

Detailed ways

Next, examples of the present invention will be described. Fig. 4 is a plan view of the color selection mechanism in the cathode ray tube of the present invention. The cathode ray tube of the present invention is the same as the conventional cathode ray tube shown in FIG. 1 except for the electron beam shielding plate 1, so that the same reference numerals are used in FIG. 4 to designate the same structural parts as those in FIG.

In Figure 4, a frame 11 is attached to a color selection electrode system 10 called a shadow mask or aperture grid. An internal magnetic shield (IMS) 13 is attached to the frame by a standard temperature compensation plate (STC plate) 14 . The spring 15 is attached to the frame 11 through the spring holder 16, and the spring 15 is used to attach the color selection mechanism to the fluorescent screen 4 shown in FIG. 1 . Also, a long and thin rectangular electron beam shielding plate 1 is provided in the vertical direction of the cathode ray tube and sandwiched between the inner magnetic shield 13 and the standard temperature compensation plate 14 . The front end side of the electron beam shielding plate 1 protrudes toward the central axis C side of the color selection electrode system 10, and prevents the electron beam E from colliding with the frame 11 arranged in the vertical direction.

The electron beam path E shown in FIG. 4 reaches from the deflection center DC to the farthest narrow slit ES of the color selection electrode system (the end of the fluorescent screen, that is, the end corresponding to the effective screen area). Usually, a cathode ray tube is used for an area within this point (called underscanning), but in a TV monitor used in a broadcasting station, etc., electron beams are used to scan a portion other than this point (called overscanning). When the electron beam is made to sweep the deflection angle of the normal full-scan half-angle α of the electron beam path E shown in FIG. Front surface side (deflection center side). The electron beams are reflected in a direction different from that of the fluorescent screen 4 shown in FIG. 1 or absorbed. Thereby, the electron beams are prevented from striking the frame 11 and halation to the phosphor screen due to irregular reflection.

As shown in FIG. 3, the electron beam shielding plate 12 is arranged perpendicular to the central axis C. As shown in FIG. In this state, since the plate has a certain thickness, when the front end surface 12a of the plate is oriented in the electron beam emission direction, the electron beam hits the front end surface 12a and is reflected toward the fluorescent screen 4. This is the cause of the halo.

In the embodiment of the present invention, the shape of the electron beam shielding plate 1 is very ingenious. Fig. 5 shows an enlarged view of its front end side. The front end portion of the electron beam shielding plate 1 is bent toward the color selection electrode system side such that its front end surface 1a is substantially parallel to the path E of the electron beams. As a result, the electron beams no longer hit the front end surface 1 a , and the electrons hitting the electron beam shielding plate 1 are reflected toward the deflection center side or absorbed by the electron beam shielding plate 1 . Therefore, there are no electrons reflected toward the phosphor screen 4 . Therefore, even if the cathode ray tube is used in a dark room with a low current, halo will not be caused.

When the path E of the electron beam reaches the edge of the electron beam shielding plate 1, the bending angle θ of the electron beam shielding plate 1 shown in FIG. 5 is preferably substantially the same as the deflection angle α so that the front end surface 1a is substantially parallel to the electron beam The path, of course, the bending angle θ can be changed in the range of about 5°. If the bending angle is smaller than this value, the front surface 1a will be oriented along the emission direction of the electron beam, and the electron beam will hit the front surface 1a, causing the electrons to reflect to the phosphor screen 4, causing a halo. On the other hand, if the bending angle is larger than this value, there is a possibility that the electrons reflected from the bending surface 1b reach the phosphor screen 4 . Also, from the viewpoint of easy positioning of the front end surface, it is preferable to make the bent portion as close as possible to the edge.

A cathode ray tube of the present invention having an electron beam shielding plate of a given shape shown in FIG. 5, and a cathode ray tube having an electron beam shielding plate 12 before improvement shown in FIG. 3 were used to conduct experiments comparing different overscans A safety margin for halos to appear on the fluorescent screen 4 under the amount (deflection amount from the effective screen edge of the screen to the non-effective screen).

In the conventional cathode ray tube shown in FIG. 2, the halo (state when reflection occurs on the front end surface of the electron beam shielding plate) is caused at about 3 to 4 mm, but in the cathode ray tube of the embodiment of the present invention, the halo is caused at about 15 mm. Causes halo (the state when the electron beam collides with the inner magnetic shield plate). Monitors for broadcast stations typically use an overscan of 105 to 107%. For example, in a 20-inch tube, there is an overscan of about 10 mm on one side, so it was proved that a sufficient margin can be secured with the cathode ray tube of the embodiment of the present invention.

In addition, the electron beam shielding plate 1A shown in FIG. 6 is a flat plate similar to the conventional electron beam shielding plate, but by making the front end surface tapered, the front end surface extends backward from the electron beam path so that the electron beams cannot hit the surface. The angle of the tapered surface can be appropriately selected in consideration of the orientation of the electron beam reflection plate and the like. As for the method of forming the front end surface into a tapered surface, it can be formed by a known etching method.

In addition, in the electron beam reflection plate 1B shown in FIG. 7, since the front end portion is bent and a tapered surface is formed on the front end surface, even if the bending angle is slightly deviated from α shown in FIG. Since the margin is increased by the tapered surface of the front end surface, electron beams can be reliably prevented from colliding with the front end surface.

In the cathode ray tube of the present invention, the electron beam shielding plate is skillfully formed, thereby reliably preventing halation during overscanning.

Claims (4)

1. a cathode ray tube is characterized in that making the effectively outside of screen of electron beam scanning, and this pipe comprises:

Be arranged at the beam shielding plate between the deflection center of the framework of color selecting pole system and electron beam, prevent when electron beam scanning during in effective screen outside electron beam clash into described framework,

Described beam shielding plate is arranged essentially parallel to the path (E) of electron beam that arrives the distal-most end narrow slit (ES) of color selecting pole system from deflection center (DC) towards the front end surface (1a) of central shaft (C), perhaps described front end surface on described electron beam transmit direction gradually away from the path of described electron beam.

2. cathode ray tube as claimed in claim 1, it is characterized in that, described beam shielding plate has a fore-end, and described front end surface is positioned on the described fore-end, and this fore-end bends to the color selecting pole system side so that described front end surface is arranged essentially parallel to described electron beam path.

3. cathode ray tube as claimed in claim 1 is characterized in that the front end surface of described beam shielding plate forms the conical surface.

4. cathode ray tube as claimed in claim 1, the fore-end bending that it is characterized in that described beam shielding plate is to the color selecting pole system side and form the conical surface.

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