JPH09219162A - Cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of halation despite using a cathode-ray tube in a dark room, by forming the cathode-ray tube so that a tip surface, on the picture surface inner side of a beam shielding plate, can be parallel or shaded to the track of an electron beam. SOLUTION: A frame 11 is fitted to a color sorting electrode 10, and an inside magnetic shield 1MS via a temperature compensation plate 14. Also, a spring 15 is fitted to the frame 11 via a spring holder 16, to attach a color sorting machine body structure to a phosphor panel. A slender rectangular beam shielding plate 1 is nipped between the shield 13 and the compensation plate 14 to be arranged in a vertical direction to a cathode-ray tube. The shielding plate 1 is folded on the electrode 10 side to be formed so that the tip surface 1a of the shielding plate 1 can be nearly parallel or shaped to the track E of an electron beam. This makes the electron beam unabutting to the tip surface 1a, and makes an electron, abutting on the shielding plate 1, reflect to a polarizing center side, or, be adsorbed into the shielding plate 1, thereby making the electron unreflected to a fluorescent surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode ray tube which prevents halation when used in overscan.

[0002]

2. Description of the Related Art A color cathode ray tube, as shown in FIG.
A fluorescent screen 4 is formed on the inner surface of the panel surface 3 of the tubular body 2, and a color selection electrode 10 called an aperture grill or a shadow mask is arranged facing the fluorescent screen 4. The electron beam E emitted from the electron gun 5 arranged on the neck portion 2a of the tube body 2 is deflected by the deflection yoke 6 to scan a predetermined fluorescent surface 4.

In a cathode ray tube used for a monitor for a broadcasting station or the like, as shown in FIG. 6 which is a schematic view of the color selecting mechanism in the cathode ray tube as seen from above, an effective screen (in the drawing, the color selecting electrode 10 It may be used in overscan in which the electron beam E is scanned outside the edge slit). When used in such overscan, the overscanned electron beam is diffusely reflected by the frame 11 of the color selection mechanism, and when the diffusely reflected electrons reach the fluorescent screen, frame halation occurs. Therefore, in a broadcast station monitor or the like, a metal elongated plate-shaped beam shield plate 12 is provided between the frame 11 and the electron beam deflection center DC so as not to hit the frame 11 with the electron beam. It is attached to the plate 13 and arranged. The beam shield 12 is usually made of iron or stainless steel having a thickness of about 0.2 mm, and absorbs electrons by applying a high voltage, or reflects electrons to the electron gun side to shield the frame 11 from the electron beam. However, halation due to diffuse reflection is prevented.

[0004]

However, depending on the application of the broadcast station monitor, it may be used in a dark room in a low current state. When used in such a usage method, it is observed that a slight halation occurs,
The suppression of this halation was requested.

The present invention has been made in view of the above demands, and an object of the present invention is to provide a cathode ray tube capable of preventing halation even when used in overscan and used in a dark room.

[0006]

In order to achieve the above object, the present invention provides the following cathode ray tube. (1) A cathode ray tube that scans an electron beam outside the effective screen, and prevents the frame of the color selection electrode from being irradiated with the electron beam when scanning the electron beam outside the effective screen. In order to achieve this, in a cathode ray tube having a beam shield plate disposed between the frame and the deflection center of the electron beam, the tip surface of the beam shield plate on the inner side of the screen is substantially aligned with the trajectory of the electron beam. A cathode ray tube having a beam shield plate formed so as to be parallel or shaded with respect to an electron beam trajectory. (2) The cathode ray tube according to the above (1), wherein the tip portion is bent toward the color selection electrode side, and the tip surface has a beam shield plate which is substantially parallel to the trajectory of the electron beam. (3) The cathode ray tube according to the above (1), which has a beam shield plate having a tapered tip surface. (4) The cathode ray tube according to (1) above, which has a beam shield plate formed by bending the tip portion toward the color selection electrode and forming the tip surface in a tapered shape.

According to the present invention, since the beam shielding plate has a thickness in the halation at the time of the above-mentioned overscan, the tip surface faces with an inclination in the electron beam incident direction, and the electron beam is reflected by this tip surface. This is based on the finding that the cause is that reflected electrons are incident on the phosphor screen side.

That is, in the cathode ray tube of the present invention, the shape of the beam shield plate is devised so that the tip end surface of the beam shield plate is substantially parallel to the trajectory of the electron beam or is shaded with respect to the trajectory of the electron beam. The formation prevents the electron beam from striking the tip surface of the beam shield plate, prevents the electron beam from being reflected on the tip surface, and prevents halation.

In order to form the tip end surface of the beam shield plate in this way, the tip end portion of the beam shield plate should be bent toward the color selection electrode side so that the tip end surface is substantially parallel to the trajectory of the electron beam. Alternatively, it can be achieved by tapering the tip surface of the shielding plate.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. FIG. 1 is a schematic view of a color selection mechanism in a cathode ray tube according to the present invention as seen from above. The cathode ray tube of the present invention is similar to the ordinary cathode ray tube as shown in FIG. 5 except for the beam shield plate, and therefore, the same components are designated by the same reference numerals.

In FIG. 1, a frame 11 is attached to a color selection electrode 10 called a shadow mask or an aperture grill, and a temperature compensation plate (STC) is attached to this frame.
Internal magnetic shield (IMS) 1 via plate 14
3 is attached. A spring 15 for attaching the color selection mechanism to the phosphor panel is attached to the frame 11 via a spring holder 16. Further, an elongated rectangular beam shield plate 1 is sandwiched between an inner magnetic shield 13 and a temperature compensation plate 14 and arranged in the vertical direction of the cathode ray tube. The tip side of the beam shielding plate 1 projects toward the central axis C of the color selection electrode 10 to prevent the electron beam E from hitting the frame 11 arranged in the vertical direction.

The trajectory E of the electron beam shown in FIG. 1 extends from the deflection center DC to the extreme end slit ES (corresponding to the edge of the fluorescent screen, that is, the effective screen edge) ES of the color selection electrode. Usually used inside this (called underscan)
It is normal, but in monitors for broadcast stations, etc., scanning is performed to the outside of this (called overscan). When the electron beam is swung larger than the deflection angle α of the trajectory E of the electron beam shown in FIG. 1, the electron beam hits the beam shield plate 1 on the front side (deflection center side) of the frame to which a high voltage is applied. The electron beam is reflected or absorbed in a direction other than the fluorescent screen. As a result, the electron beam hits the frame 11 to prevent halation due to diffused reflection on the phosphor screen.

As shown in FIG. 7, the conventional beam shield plate 12 is in a state in which a flat plate is oriented in a direction perpendicular to the central axis C. In this state, since the flat plate has a thickness, its front end face 12a is oriented in the incident direction of the electron beam, and when the front end face 1a is hit with the electron beam, it is reflected on the fluorescent screen,
It caused halation.

In the present invention, the shape of this beam shield plate is devised, and an enlarged view of the tip side thereof is shown in FIG. The beam shield plate 1 is formed such that its tip end is bent toward the color selection electrode and its tip end surface 1a is substantially parallel to the electron beam trajectory E. As a result, this tip surface 1
The electron beam does not hit a, and the electrons hit the beam shield 1 are reflected to the deflection center side,
Electrons are not reflected on the phosphor screen because they are absorbed by the beam shield plate 1. Therefore, halation does not occur even when used in a dark room in a low current state.

Bending angle θ of the beam shield plate 1 shown in FIG.
In order to make the tip surface 1a substantially parallel to the trajectory of the electron beam, the trajectory E of the electron beam is set to the beam shield plate 1.
It is preferable that the deflection angle α is substantially the same as the deflection angle α at the time of striking the tip edge of, but it can be changed within a range of about 5 °. If the bending angle is shallower than this, the tip surface 1a will face in the incident direction of the electron beam, and the electron beam will move toward the tip surface 1a.
Upon hitting a, electrons are reflected to the fluorescent surface and halation occurs. On the other hand, if the bending angle is larger than this,
There is a possibility that the electrons reflected by the curved surface 1b may reach the fluorescent screen. Further, it is preferable that the bending position is a portion as close to the tip edge as possible in order to easily position the tip surface.

Using the cathode ray tube of the present invention having a beam shield plate shaped as shown in FIG. 2 and a conventional cathode ray tube having a beam shield plate as shown in FIG. 7 before improvement,
An experiment was conducted to compare the margin until halation appears on the screen when the amount of overscan (the amount of deflection from the effective screen edge of the panel to the invalid screen side) is varied.

In the conventional cathode ray tube, halation occurs at about 3 to 4 mm (a state where reflection occurs at the tip surface of the beam shield plate), but in the cathode ray tube of the present invention, halation occurs at about 15 mm for the first time. (The electron beam hits the internal magnetic shield). Broadcasting station monitors usually use 105-107% overscan. For example, the 20-inch monitor has an overscan of about 10 mm on one side. On the other hand, the cathode ray tube of the present invention can secure sufficient allowance. Was confirmed.

Further, the beam shield plate 1'shown in FIG. 3 has a flat plate shape like the conventional beam shield plate, but its tip end surface is tapered so that the tip end surface is hidden from the electron beam. Therefore, the electron beam is not hit. This taper angle can be appropriately selected in consideration of the direction of the beam reflector and the like. A method of forming the tip end surface in a tapered shape can be usually formed by known etching.

Further, the beam reflector 1 "shown in FIG. 4 has a bent tip portion and a taper on the tip surface, so that the bending angle may slightly deviate from the deflection angle α shown in FIG. , Even if there is an error in mounting the beam shield plate, the taper of the tip surface expands the allowable range.
It is possible to reliably prevent the electron beam from hitting the tip surface.

[0020]

According to the cathode ray tube of the present invention, by devising the shape of the beam shield plate, it is possible to reliably prevent the occurrence of halation during overscan.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a color selection mechanism in a cathode ray tube of the present invention.

FIG. 2 is a schematic view showing a tip portion of an example of a beam reflector according to the present invention.

FIG. 3 is a schematic view showing another example of the beam reflector according to the present invention.

FIG. 4 is a schematic view showing still another example of the beam reflector according to the present invention.

FIG. 5 is a schematic view showing a general structure of a cathode ray tube.

FIG. 6 is a schematic plan view showing a color selection mechanism of a cathode ray tube.

FIG. 7 is a schematic diagram illustrating generation of halation by a conventional beam reflector.

[Explanation of symbols]

 1,1 ', 1 "Beam shielding plate 1a Tip surface of beam reflecting plate 2 Tubular body 3 Panel surface 4 Fluorescent surface 10 Color selection electrode 11 Frame 13 Internal magnetic shield E Electron beam E Effective screen edge α Deflection angle DC Deflection center C Central axis

Claims (4)

[Claims] 1. A cathode ray tube for scanning an electron beam outside an effective screen, wherein when scanning an electron beam outside the effective screen,
In a cathode ray tube having a beam shield plate arranged between the frame and the deflection center of the electron beam in order to prevent the frame of the color selection electrode from being irradiated with the electron beam, in the screen of the beam shield plate. A cathode ray tube having a beam shielding plate formed such that a front end surface on one side thereof is formed to be substantially parallel to or shadow of an electron beam trajectory. 2. A cathode ray tube according to claim 1, further comprising a beam shield plate whose tip is bent toward the color selection electrode and whose tip surface is substantially parallel to the trajectory of the electron beam. 3. A cathode ray tube according to claim 1, further comprising a beam shield plate having a tapered tip surface. 4. The end portion is bent toward the color selection electrode, and
The cathode ray tube according to claim 1, further comprising a beam shield plate having a tapered tip surface.