Reflective LCD Flicker Reduction via Isolated Electrode
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Solution Overview
Problem
Reflective and transflective LCDs experience flicker issues when driven at low frequencies, leading to reduced display quality, and existing solutions compromise brightness and contrast by adding additional transparent electrodes, which reduce reflectivity.
Innovation Solution
The LCD design features a reflective layer electrically isolated from the lower electrode, with a capacitive coupling arrangement that eliminates the DC component of the electric field, maintaining high reflectance and contrast by using the same material for both electrodes and incorporating a passivation layer to ensure flicker-free operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the LCD is driven at a lower frequency to reduce power consumption, then power consumption is reduced, but flicker increases and display quality deteriorates
Solution Approach 1:
The patent changes the electrical parameters of the lower electrode by using a transparent conductive material instead of a reflective metallic material. This parameter change allows the lower electrode to be electrically isolated from the reflective layer while maintaining capacitive coupling, which eliminates the DC component of the electric field in the LC layer and eliminates flicker at low drive frequencies.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary between the lower electrode and the reflective layer. This insulating layer electrically isolates the two components while still allowing capacitive coupling, thereby enabling the reflective layer to function as a reflector without creating a DC electric field that causes flicker.
2Reliability
If transparent electrodes are added on the reflective electrode side to address flicker, then flicker is reduced, but reflectivity decreases and brightness and contrast are reduced
Solution Approach 1:
The patent merges the functions of the lower electrode and the reflective layer into a single integrated structure. The lower electrode is made of transparent conductive material that also serves as the reflector, eliminating the need for separate transparent electrodes and maintaining high reflectivity while reducing flicker.
Solution Approach 2:
The patent changes the material parameter of the lower electrode from reflective metallic material to transparent conductive material. This parameter change allows the electrode to be electrically isolated from the reflective layer while maintaining both electrical functionality and optical reflectivity, thereby reducing flicker without sacrificing brightness and contrast.
3Illumination intensity
If the lower electrode is made of reflective metallic material, then reflectivity is improved, but a DC electric field is created in the LC layer causing flicker
Solution Approach 1:
The patent changes the material parameter of the lower electrode from reflective metallic material to transparent conductive material. This parameter change eliminates the DC electric field in the LC layer by creating electrical symmetry, thereby eliminating flicker while maintaining reflectivity through the transparent conductive material's optical properties.
Solution Approach 2:
The patent introduces an insulating layer as an intermediary between the lower electrode and the reflective layer. This insulating layer electrically isolates the two components while allowing capacitive coupling, which eliminates the DC electric field that causes flicker while preserving the reflective function.
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 eliminates or significantly reduces flicker without sacrificing reflectance or contrast, ensuring high display quality and power efficiency, particularly suitable for portable devices.
Implementation Method 1
a reflective layer, configured to at least partly reflect incident light having passed through the liquid crystal layer
Implementation Method 2
The present invention is based on the realization that the amount of flicker in an LCD can be eliminated or, at least, considerably reduced, by eliminating or, at least, substantially reducing the DC-component of an electric field in the LC layer
Implementation Method 3
The upper electrode can be coated with a passivation layer, thereby improving the light stability of the liquid crystal display
Data Source
AI summary
A liquid crystal display having a plurality of pixels (1), comprising an lower electrode layer (21), a transparent upper electrode layer (13), a liquid crystal layer (10) arranged between the upper and lower electrode layers (13, 21) and an at least partly reflective layer (20, 30), for at least partly reflecting incident light having passed through the liquid crystal layer (10). The reflective layer (20, 30) is electrically isolated from the lower electrode layer (21) and positioned between the liquid crystal layer (10) and the lower electrode layer (21). With this arrangement the DC-component of an electric field in the liquid crystal layer can be eliminated or, at least, considerably reduced, and a flicker-free reflective or transflective LCD thereby realized. Furthermore, flicker is eliminated without having to pay the price of reduced reflectance of the reflective layer and the consequent reduction in display brightness and contrast.