Liquid crystal display device

Patent

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Details

350339F, 350345, G02F 113

Patent

active

045196796

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device in which the legibility and a liquid crystal display element are more easily made by combining the filter for displaying in color, a display unit and plates for effecting the transflection of light with one another.
2. Description of the Prior Art
Liquid crystal display devices are composed of the liquid crystal display element and polarizer, the liquid crystal display element having a liquid crystal material sandwiched between two glass plates. Those two glass plates are thinly coated with transparent electrodes. If a voltage used as a displaying signal, is applied across those electrodes, then the optical axis of the liquid crystal material has the property that it becomes parallel to an electric field generated by that voltage. Also in the absence of an electrical signal, the optical axis of the liquid crystal material is parallel to the two transparent electrodes and its axial direction is twisted just through 90 degrees between the two electrodes. Such a liquid crystal display element is normally called a TN(Twisted Nematic) type liquid crystal. By providing polarizers outside of said two glass plates, light can only transmit through (or be intercepted by), those display pattern portions desired to effect the display.
The liquid crystal display device is possible to effect various displays for the reasons that the transmission or interception of light is selectively effected and still with an external electrical signal. Since the legibility of a pattern to be displayed is due to external light, it is called a light receiving type display element. The light receiving type display element requires necessarily external light. To this end, the display element is used by disposing an illuminant adjacent thereto or by effectively utilizing surrounding light. With reference to conventional examples shown in FIG. 1 through FIG. 3, the respective operations thereof will be described hereinafter. FIG. 1 is a sectional view illustrating the passage of light with a liquid crystal display device used in the reflection mode. (1) is a liquid crystal display element, (2) and (3) are polarizers, and (4) is a reflector from which light is well reflected. Upon incident light L.sub.1 falling on the polarizer (2), that portion of light capable of passing therethrough has only a constant component of polarized light while the other component of polarized light is absorbed by the polarizer (2). Light passed through this polarizer (2) travels while it retains its direction of polarization identical to the optical axis of the liquid crystal in the process in which it passes through the liquid crystal display element (1) and on that portion of the liquid crystal not applied with an electric field. In the TN type liquid crystal, the optical axis of the liquid crystal is twisted just through 90 degrees between the two electrodes. Thus, when light incident upon the liquid crystal display element (1) leaves the latter, it changes to light having a direction of polarization twisted through 90 degrees with respect to the incident light. Assuming now that the polarizer (3) has an absorption axis orthogonal to that of the polarizer (2), the abovementioned incident light L.sub.1 passes through the polarizer (3) as it is left intact and reaches the reflector (4). Light reflected from the reflector (4) again passes through the polarizer (3), the liquid crystal display element (1) and the polarizer (2) and can be observed as reflected light L.sub.2 resulting in our eyes viewing the surface of the reflector (4) as being light. With an electric field applied to the liquid crystal display element (1), that portion of the liquid crystal having the electric field existing thereon has the optical axis parallel to the electric field. That is, the optical axis of the liquid crystal changes from its state in which it is parallel to the transparent electrodes to its direction perp

REFERENCES:
patent: 3799647 (1974-03-01), Luft
patent: 3840695 (1974-10-01), Fischer
patent: 3984176 (1976-10-01), Hirai et al.
patent: 4227777 (1980-10-01), Murakami
patent: 4371870 (1983-02-01), Biferno
"An Automotive Instrument Panel Employing Liquid Crystal Displays," Paper No. 770274, Int'l Automotive Engineering Congress and Exposition, Feb. 28-Mar. 4, 1977 of Society of Automotive Engineers.

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