1. Field Of The Invention
The present invention relates generally to liquid crystal display devices, and more particularly to a liquid crystal display device mounted behind a glass cover plate.
2. Description Of The Prior Art
In a liquid crystal cell which serves as an indicator element, the liquid crystal layer is located between two transparent cell plates provided with specific electrode structures. A polarization foil is arranged on both sides of the liquid crystal cell. The rear side of the liquid crystal indicator is provided with a reflector.
In appliances with liquid crystal indicator, e.g. measuring instruments, computers, clocks or watches, the liquid crystal display element is conventionally placed in a housing which consists, on the front side, of a cover glass or transparent plastic panel or a glass sheet or sapphire glass. Behind this the liquid crystal display is placed at a distance of some tenths of a millimeter. Even where the liquid crystal display is intended to be in contact with the front glass, a very thin air gap is present between the liquid crystal indicator and the front glass.
The use of a front glass in an instrument with a liquid crystal display has the disadvantage, even where the glass possesses good transparency, that reflections and refractions occur at the two surfaces of the front glass and at the surface of the display element, which under unfavorable conditions of illumination, e.g. with weak illumination or with light falling at right angles onto the front glass and dark surroundings, render the reading of the indicated information difficult and reduce the contrast of the indication. With anti-reflection coatings, such as are used for improving optical instruments, it would be possible to eliminate the reflections from the front and rear sides of the cover plate and the surface of the liquid crystal display. This, however, is an expensive and questionable process, especially on the surface of the polarization foil. To make the housing terminate with the liquid crystal display on the front side has the disadvantage that the surface of the liquid crystal display, which is sensitive to scratching, shock and moisture, or the surface of the polarization foil stuck onto the latter, is unprotected.