Electric lamp and discharge devices – Cathode ray tube – Beam deflecting means
Patent
1983-03-22
1986-02-11
DeMeo, Palmer C.
Electric lamp and discharge devices
Cathode ray tube
Beam deflecting means
H01J 2972
Patent
active
045701008
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to flat-type cathode ray tubes and more particularly is directed to a flat-type cathode ray tube which can reduce power consumption and also can alleviate a circular-arc distortion.
BACKGROUND ART
In an ordinary cathode ray tube such as a television picture tube and so on, an electron gun is opposed to a phosphor screen and is extended backward along the direction substantially perpendicular to the phosphor screen with a result that a depth of a cathode ray tube envelope is considerably large. Whereas, a so-called flat-type cathode ray tube has been proposed that its electron gun is extended along the surface direction of the phosphor screen for making the tube envelope flat.
FIG. 1 schematically illustrates an example of such previously proposed flat-type cathode ray tube. In the figure, reference numeral 1 generally denotes a flat tube envelope, and in this flat tube envelope 1 are provided a target electrode 2 and a back electrode 3. These electrodes 2 and 3 are opposed to each other in the thickness direction of the flat tube envelope 1 (that is, the up-and-down-direction in the drawing). On the target electrode 2 is formed a phosphor screen 4. An electron gun 5 is provided on a plane which is parallel to and remote from the phosphor screen 4. Between the electron gun 5 and the phosphor screen 4 is provided a deflection coil 6 to deflect the electron beam emitted from the electron gun 5.
In such arrangement, to the target electrode 2 is applied a high voltage, for example, 10 KV and to the back electrode 3 is applied a voltage somewhat lower than the former, for example, 6 KV. As a result, the target electrode 2 and the back electrode 3 constitute an auxiliary deflection plate.
In such example, the target electrode 2 is extended to the position near the electron gun 5, surrounding the deflection region by the deflection coil 6, and the potential of the target electrode 2 is high, for example, 10 KV as compared with the potential of the back electrode 3, for example, 6 KV so that as shown in FIG. 2, within the flat tube envelope 1, particularly in the upper portion thereof is formed a diverging lens. Thus, the beam emitted from the electron gun 5 is diverged with a disadvantage that the circular-arc distortion is increased.
Moreover, in such example, since the target electrode 2 forming the auxiliary deflection plate is same in potential as a last grid 5a of the electron gun 5, the beam emitted from the electron gun 5 is never accelerated further. Therefore the power consumption of the cathode ray tube is urged to increase.
DISCLOSURE OF INVENTION
In view of such aspects, it is an object of this invention to provide a flat-type cathode ray tube which reduces power consumption as well as alleviates a circular-arc distortion.
In accordance with this invention, in order to perform such a purpose, in a flat-type cathode ray tube comprising a flat tube envelope in which first and second electrodes are located to face each other in the thickness direction of the envelope to thereby form a first deflection system for performing an electrostatic deflection, a phosphor screen is formed at the side of the first electrode and a second deflection system is formed between the first deflection system and an electron gun for performing an electromagnetic deflection, a third electrode surrounding a region of the second deflection system sufficiently is formed integrally with the second electrode and a voltage lower than that of the first electrode is applied to the second and third electrodes.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1 and 2 are both schematic diagrams useful for the explanation of the present invention,
FIG. 3 is a cross-sectional diagram showing an embodiment of the present invention,
FIGS. 4 to 8 are all schematic diagrams useful for the explanation of the example of FIG. 3,
FIGS. 9a and 9b are a diagram showing a modified examples and
FIG. 10 is a diagram useful for the explanation of the examples of FIGS. 9a and 9b.
BEST MODE FOR CARRYING OUT
REFERENCES:
patent: 4451756 (1984-05-01), Sato et al.
Hatanaka Masato
Ohhoshi Toshio
Sato Hiroki
Tanaka Sakae
DeMeo Palmer C.
O'Shea Sandra L.
Sony Corporation
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