Patent · US Expired

Method of making color-neutral LCD indicators of low residual transmission

US4541693A · kind A · utility

7Cited by

4References

6Claims

0Family size

Assignee

Robert Bosch GmbH · DE

Inventors

Peter Knoll · Ettlingen, DE
Peter Rapps · Karlsruhe, DE
Wolfgang Ziegler · Waldbronn, DE

Key dates

Filing date	Sep 26, 1983
Grant date	Sep 17, 1985
Priority date	—
Expiry date	Sep 26, 2003

Classification

Technology area (CPC G)Physics
CPC primaryG02F1/133509
WIPO fieldOptics
WIPO sectorInstruments

Abstract

The disturbing residual transmission of a liquid crystal display device which is particularly noticeable in negative contrast devices is reduced by reference to the fact that the residual transmission is colored. The entire display surface of the liquid crystal device is provided with a transparent covering of a color complementary to the residual transmission color when the liquid crystal is not turned on. The transparent colored covering can be applied by printing as well as otherwise. In another embodiment, color shifts between turned-on and not turned-on displays are counteracted by mixing into the liquid crystal material a dichroic coloring material which has much lower absorption when the display is turned on. A light blue dichroic coloring material is suitable for LCDs which have residual transmission in the red region.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.