Erasing Electrodes for LCOS Switching Speed
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Solution Overview
Problem
In-plane switching liquid crystal displays face limitations in switching speed due to weak restoring forces, particularly when operating in color sequential mode, where rapid image changes are required to display partial images at a higher rate.
Innovation Solution
The introduction of erasing electrodes that apply an erasing electric field to bring liquid crystal molecules back to their rest orientation, combined with a configuration where erasing electrodes are shared between adjacent pixels and made of non-transparent conductive metals like copper or aluminum, allowing for efficient reorientation without the need for indium-tin oxide.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If in-plane switching is used to eliminate indium-tin oxide, then manufacturing cost is reduced, but switching speed becomes too slow for color sequential mode
Solution Approach 1:
The patent applies a preliminary erasing action by introducing erasing electrodes that actively reset liquid crystal molecules to their initial orientation before the next image frame is displayed. This preliminary action (erasing) enables faster switching speeds required for color sequential mode while maintaining the in-plane switching architecture that eliminates expensive indium-tin oxide materials.
2Productivity
If erasing electrodes are added to enhance switching speed, then productivity is improved, but device complexity increases
Solution Approach 1:
The patent merges the erasing electrode structure with the existing pixel electrode structure by placing erasing electrodes on the same substrate and integrating them into the same electrical control system. This combining approach enables enhanced switching speed through active erasing while minimizing the increase in device complexity by reusing existing structural elements and control circuits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the switching speed of liquid crystal displays, particularly in color sequential mode, while reducing manufacturing costs and eliminating the need for indium-tin oxide, thereby improving viewing angle performance and eliminating the requirement for angle-of-view compensation films.
Implementation Method 1
the introduction of erasing electrodes that apply an erasing electric field to bring liquid crystal molecules back to their rest orientation
Implementation Method 2
The voltage applied between the pixel electrode and the common electrode produces an electric field which orients the molecules of the liquid crystal according to the modulus of the field
Data Source
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AI summary
The invention relates to active-matrix liquid crystal displays. The invention mainly relates to small screens made, for example, from silicon substrates (Liquid Crystal on Silicon technology, LCOS). In particular, the invention relates to colour sequential mode display. The pixel comprises a pixel electrode (Ep) controlled by a control transistor (Q) and counter-electrodes (CE) disposed on the same side of the liquid crystal as the pixel electrode and arranged in parallel to the pixel electrode. The liquid crystal is formed by molecules having a natural rest orientation in the absence of voltage between the pixel electrode and the counter-electrodes and a different orientation in the presence of an electric field created between the pixel electrode and the counter-electrodes. Erase electrodes (EF) are located on each side of the pixel transversely to the counter-electrodes and, during an erase phase, said electrodes can produce an electric erase field that returns the molecules of the liquid crystal to their rest orientation.