Electric lamp and discharge devices – Cathode ray tube – Screen
Patent
1996-06-25
1998-06-02
O'Shea, Sandra L.
Electric lamp and discharge devices
Cathode ray tube
Screen
313463, 313477R, H01J 2910
Patent
active
057605394
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a color cathode-ray tube, and particularly to a color cathode-ray tube having a novel structure and a method appropriate for manufacturing the same.
BACKGROUND ART
A color cathode-ray tube is an apparatus for displaying a color image, in which three red, green, blue (R,G,B) phosphors are respectively arranged in a prescribed pattern to form a screen, and each phosphor selectively emits light by means of an electron beam.
Referring to FIG. 1, there is depicted a typical structure of the screen of a color picture tube. On the inner surface of a panel P, black matrix B is applied for enhancing the contrast excluding windows in the form of stripes or dots, and each phosphor R,G,B is successively applied in windows of the black matrix B. Remaining symbol A designates the metal back for forming a mirror surface, and I is an intermediate layer.
As the above described screen should be formed in a fine pitch, photo lithography is generally adopted as described in FIG. 2.
Referring to FIG. 2, a slurry of black matrix B or phosphor R,G,B, including photo resist, is applied on the inner surface of a panel P in a thin layer. The panel P is placed on an exposing table, with a mask frame MF mounted in the inner side thereof as an exposure mask. The mask frame MF is formed by supporting a shadow mask M, the color selecting, means, to a frame F. Light emitted from a light source S is compensated by a compensating lens L and exposes the applied layer of the inner surface of the panel P in a prescribed pattern determined by the shadow mask M. And the finished panel P is developed to form functional layers as in the above pattern.
These procedures are repeated four times for the black matrix B and each of phosphors R,G,B to complete the panel as shown in FIG. 3. In FIG. 3, the screen of the panel P can be divided into a non-effective area Pn only with the black matrix B, and an effective area having phosphor R,G,B between the black matrix B to form an image.
To compensate for the difference in distances from the center of emission of the electron beam to the central part and the circumferential part, the panel P is formed in a shape of a curved surface having prescribed curvatures respectively to the horizontal, vertical and the diagonal axis. And the shadow mask M also formed in a curved surface to maintain a prescribed gap, namely the Q value, with the screen of the panel P.
The shadow mask M can be divided into an apertured area having color selecting apertures to form the effective area Pe of the panel P, and a non-apertured area having no apertures to correspond to the non-effective area Pn of the panel P.
As the shadow mask M has the curved surface, the outline O of the effective area Pe projected on the panel P, forms the outwardly convex curved line even in the case of the outline, of the apertured area to be straight. As the result, the shape of the effective area Pe is defined by four lines O and four corner portions C, each of outlines O meeting together thereat and being rounded for continuity's sake.
Referring to FIG. 4, there is depicted a tube mounted in the casing of a television set or a monitor. As the outline O' of the bezzel cover Z of the casing is nearly straight, a part of the non-effective area Pn is exposed at the corner portion C,C' and the outline O of the panel P is covered by the outline O' ot the bezzel cover Z at the intermediate part of the screen, thereby extremely exposing the effective area Pe in the bezzel cover Z.
As the result, a appearance of the finished display is not good, and the screen cannot be extremely utilized. Moreover, excessive heat is radiated and severe doming occurs, as the electron beam exposes the whole effective area Pe, which is larger than the area to actualy display the image.
This screen structure deteriorates the accuracy and reliability of data, especially in the CDP which takes data through the screen. To prevent these problems the outline of the shadow mask M is generally formed to be inwardly concave for the
REFERENCES:
patent: 4675571 (1987-06-01), Bakker et al.
O'Shea Sandra L.
Orion Electric Co. Ltd.
Patel Vip
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