Electric lamp and discharge devices – Cathode ray tube – Envelope
Patent
1988-08-17
1990-05-15
DeMeo, Palmer C.
Electric lamp and discharge devices
Cathode ray tube
Envelope
313479, 358247, 358252, H01J 2989
Patent
active
049260901
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a television picture tube having a composite frontal pane which includes viewing screen which is spherically or aspherically convexly curved relative to the viewer, a convexly curved supplementary pane spaced from the viewing screen, and a transparent cast resin layer inserted between the viewing screen and the supplementary pane for gluing the screen to the pane.
TECHNOLOGY REVIEW
As is known, the viewing screen of a television picture tube has a more or less considerably spherically convex curvature relative to the viewer Moreover, in the course of the further development of television picture tubes, aspherical, so-called FST (flat square tube) tubes have been developed which have a very large radius of curvature in the central region of the viewing screen and a somewhat reduced radius of curvature in its edge regions For example, the two radii are approximately 1.6 m and 1.4 m with a viewing screen diagonal measure of about 0.6 m. With such a viewing screen configuration, distortion in the television image at excessively acute viewing angles is reduced but the viewing screen is still discerned as a curved surface. Moreover, in these flat picture tubes the viewing screen surface is a closer approximation to a planar rectangular surface which, for reasons of image and viewing quality from acute angles and for purposes of design, is considered to be the best.
Additionally, for example DE-AS No. 2,247,337 or U.S. Pat. No. 3,879,627 disclose providing the television tube with a composite frontal pane. The latter is composed of the tube bottom itself--i.e. the viewing screen--, a supplementary pane placed in front of the viewing screen at a distance therefrom and a transparent cast resin layer applied in a form locking manner between the viewing screen and the supplementary pane. This layer firmly connects the viewing screen and the supplementary pane to one another by way of adhesion. The supplementary pane here extends parallel to the frontal face of the viewing screen. This is to avoid distortions and lens effects due to different spaces between these two components Instead of the cast resin layer, a prefabricated plastic molded body with matching refraction index can also be employed whose front or rear surface is completely connected with the supplementary pane and the viewing screen.
The composite frontal pane serves various purposes. On the one hand, it is provided to prevent damage to the picture tube and protect the viewer against shards of glass and other flying parts if the tube should implode. On the other hand, a special configuration of the composite frontal pane may improve the television image. This involves, in particular, the suppression of reflections and double images due to multiple reflections. In principle, the following interfering effects, which adversely influence the television image, are possible: supplementary pane, the viewing screen and its fluorescent coating; above-mentioned faces; region of the viewing screen.
Picture tubes now have a typical reflection coefficient from 5.5 to 6% which is the sum of the reflections occurring at the two viewing screen faces and at its fluorescent coating. The reflection coefficient of the two faces of a clear-glass supplementary pane lies at about 8%.
The total reflection coefficient of about 12% resulting under consideration of the absorption in glass (transmittance of clear glass is about 90%) can be reduced by means of various measures. If both interfaces of the supplementary pane are made non-reflective, a reflection coefficient of 1% can typically be realized By reducing the transmittance of the supplementary pane, the light beams not reflected by its frontal face are additionally attenuated once during passage to the interior reflecting faces of the supplementary pane or of the viewing screen The intensity of the reflected light component of these beams is again weakened during its passage through the supplementary pane whose transmittance has been reduced to, for example, 60%. Thus, th
REFERENCES:
patent: 2517774 (1950-08-01), Epstein
patent: 3952152 (1976-04-01), Lill et al.
patent: 4563612 (1986-01-01), Deal et al.
patent: 4804883 (1989-02-01), Muller et al.
Kazuo Oomae; Patents Abstracts of Japan, Apr. 26, 1986, vol. 10, #11.
DeMeo Palmer C.
Flabeg GmbH
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