Card – picture – or sign exhibiting – Illuminated sign – Luminescent
Patent
1984-12-07
1986-07-15
Peshock, Robert
Card, picture, or sign exhibiting
Illuminated sign
Luminescent
362 25, G09F 1322
Patent
active
045998167
DESCRIPTION:
BRIEF SUMMARY
The invention relates to an apparatus for illuminating passive liquid crystal displays.
BACKGROUND
In a known liquid crystal display for a motor vehicle, the light striking the LCD cell from the internal lighting means is passed through only in the triggered areas of the cell. In the non-triggered areas, however, the light is predominantly absorbed, so that the information is presented in negative contrast. Bright characters appear against a dark background. Since the two glass plates of the LCD cell, located one immediately above the other, have a plurality of support points, and since furthermore the electrodes vapor-deposited onto the glass plates partly intersect one another, the appearance of the dark background of the display is not uniform. If a plurality of LCD cells, guided on struts, are disposed beside one another, then these struts between the individual displays must be appropriately colored to match the dark background, or like the support points and electrode crossings they must be masked by colored masks. Such colored masks, because of the various transmission properties of the materials in the areas to be masked, must be black, or in other words must have a high refractive index. On the other hand, however, since the LCD cells in the optically blocked, non-triggered areas have a not inconsiderable amount of afterglow, the background in these areas appears variously bright, depending on the brightness of the internal lighting means; and so depending on this variable brightness of the background, the masked areas of the LCD displays and the guide struts are variably prominent in appearance.
With the present invention, the object is to match the masked areas optically to the non-triggered areas of the LCD cell such that regardless of the internal lighting means they present a homogeneous appearance for the liquid crystal displays.
THE INVENTION
Briefly, the apparatus according to the invention, has photoconductor means for lighting the masked areas of the liquid crystal display, in which output of the internal light takes place, the order of magnitude of which is selected to match the afterglow in the blocked areas of the liquid crystal display. As a result, the brightness in the area of the masks when the illumination is variable varies in the same manner as that of the blocked areas of the liquid crystal display, so that the display assures a homogeneous appearance for all light conditions.
By suitable configuration of the photoconductor and use of a common light source, advantageous further embodiments of and improvements to the basic invention are possible. For instance, to avoid parallax it is advantageous if the surface areas of the photoconductor that output the light toward the front are located on the side of the photoconductor facing the LCD cell. In the simplest possible manner, the surface of the photoconductor is roughened in the surface regions giving out, or outputting the light.
DRAWING
An exemplary embodiment of the invention is shown in the drawing and explained in further detail in the ensuing description. The drawing shows a liquid crystal display, having a photoconductor in accordance with the invention, in cross section.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT
The drawing shows a liquid crystal display 10 in the dashboard of a motor vehicle, which comprises two LCD cells 11 and 12 disposed beside one another. The LCD cells 11 and 12 are inserted into a transparent plastic frame 13, behind which two light sources in the form of incandescent bulbs 14 and 15 are disposed. The liquid crystal substance of the LCD cells 11 and 12 is located between two respective glass plates 16 and 17, which are spaced apart from one another by the desired distance by means of support points 18. For the individual display elements of the LCD cells 11 and 12. electrodes are vapor-deposited on the inside of each glass plate 16 and 17, which are bonded in a manner not visible via conductor tracks on two opposing sides of the LCD cells 11 and 12. The LCD cells 11 and 12 are g
REFERENCES:
patent: 2858632 (1958-11-01), Caserio et al.
patent: 3038271 (1962-06-01), MacHutchin et al.
patent: 3182415 (1965-05-01), Brooks
patent: 3978599 (1976-09-01), Berger
Petermann Hans
Ziegler Wolfgang
Contreras Wenceslao J.
Peshock Robert
Robert & Bosch GmbH
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