Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Patent
1989-11-29
1992-03-10
O'Shea, Sandra L.
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
313497, H01J 196
Patent
active
050952447
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a fluorescent display tube and, particularly, to a fluorescent display tube adaptable to constitute a display device having a large size display screen with a plurality of the fluorescent display tubes by arranging them in horizontal and vertical directions.
2. Background Art
In order to provide a large size display screen, for example, a large size color display screen, a display device has been proposed, whose front view and side view are shown in FIGS. 1 and 2, respectively. As shown, the display device includes a plurality of fluorescent display tubes 1 arranged in rows and columns (i.e., in vertical direction Y and horizontal direction X), each fluorescent display tube having a fluorescent surface on which 16 fluorescent segment trios, each including, for example, red, green and blue fluorescent segments R, G and B, that is, 48 fluorescent segments R, G and B, are arranged in two lines (rows) and 8 columns to form a large size display screen, and provides a color image display on the large size display screen by selectively exciting the respective fluorescent segments thereon according to a display information.
In this case, an interval De between adjacent fluorescent segments, for example, trios of adjacent fluorescent display tubes 1 tends to be large due to the thickness of the peripheral wall and the thickness of the portion accommodating the lead wires 2 as shown in FIG. 2. Since, in order to perform a uniform display in a large display screen, an interval Ds between the fluorescent trios in each fluorescent display tube is also selected necessarily to be substantially the same as the interval De between the trios of adjacent fluorescent display tubes, it is desired to make the interval De between the trios in the adjacent display tubes as small as possible, in order to obtain a higher resolution on such large display screen. Therefore, it is required to arrange the fluorescent segment trios in the respective fluorescent display tubes as close to a glass wall surface of the tube horizontally as possible. When the fluorescent segments are arranged in the vicinity of the glass tube surface, an electron beam path directed thereto is necessarily close to the glass wall surface and thus the electron beam tends to be influenced by an unstable electric field produced by electric charges accumulated on the glass wall surface, i.e., insulating wall surface and, further, the possibility of collision of the electron beam with the wall surface is increased causing the unstability of electric field therearound to be increased.
This problem is enhanced for fluorescent segments located at outermost ends in a horizontal direction when the respective fluorescent segments take the form of vertically entending stripes.
In fluorescent display tubes used in such display device, since the respective fluorescent segments are fine, it is preferable, in view of simplicity of construction, to arrange a common line-shaped cathode to a plurality of fluorescent segments, for example, each trio of fluorescent segments. In such case, the line-shaped cathode is supported under tension by fixing both ends thereof to a stationary portion. Therefore, a temperature distribution on the cathode when it is heated exhibits high temperature around a center portion thereof and low temperature around the end portions due to heat dissipation in the connecting portions of the ends to the stationary portion, making electron emission density in the center portion large while that in the opposite end portions low. Consequently, even if a heating condition is set such that the temperature in the center portion of the cathode during operation reaches a value at which electron emission thereof is saturated, it does not become saturated at the opposite ends thereof, resulting in a difference in luminance of fluorescent segments at the center portion from those at the end portions. Further, in the opposite end portions which are easily influenced by current supply to the cathode (heat
REFERENCES:
patent: 4608518 (1986-08-01), Fukuda et al.
patent: 4857800 (1989-08-01), Ohkoshi et al.
Hayashi Masatake
Maeda Makoto
O'Shea Sandra L.
Sony Corporation
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