Liquid Crystal Display Common Voltage Control for Ion Polarization
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Solution Overview
Problem
Liquid crystal display devices suffer from image blur due to ion polarization and accumulation when DC voltage is applied for an extended period, leading to deteriorated orientation characteristics and inconsistent display quality across panels.
Innovation Solution
A liquid crystal display device that varies the common voltage applied to the liquid crystal layer at specific frame intervals and adjusts the gamma reference voltage for black gray levels in synchronization with the common voltage changes, using a multistep common voltage generator and adder to generate a variable common voltage that is longitudinally symmetrical with respect to a DC common voltage, thereby preventing ion polarization and accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC voltage is applied to the liquid crystal layer for a long time, then the liquid crystal display device can maintain stable operation, but ion polarization and accumulation occur causing image blur and deteriorated orientation characteristics
Solution Approach 1:
The patent applies periodic polarity inversion to the common voltage signal, switching between positive and negative DC voltages at predetermined intervals. This periodic action prevents ions from accumulating in one direction by reversing the electric field direction, thereby eliminating image blur while maintaining stable liquid crystal operation.
Solution Approach 2:
The patent changes the parameter of common voltage from a fixed DC level to a dynamically switching DC level with alternating polarity. By modifying the voltage parameter to include time-dependent polarity inversion, the system prevents ion polarization while maintaining the stability needed for reliable display operation.
2Object-affected harmful factors
If the common voltage level is varied to suppress ion polarization, then image quality improves, but black luminance differences may occur between positive and negative polarity voltages
Solution Approach 1:
The patent introduces a feedback mechanism where the common voltage generator monitors the polarity state and dynamically adjusts the voltage level to maintain longitudinal symmetry. When polarity switches, the system compensates for luminance differences by adjusting the voltage magnitude, ensuring consistent black level display across both positive and negative polarity cycles.
Solution Approach 2:
The patent deliberately introduces asymmetric voltage adjustment based on polarity state. By applying different voltage levels for positive and negative polarity while maintaining overall longitudinal symmetry, the system compensates for inherent luminance differences and achieves consistent black level performance across polarity transitions.
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 approach effectively suppresses the blur phenomenon, enhances display grade by dispersing the electric field vector, and ensures consistent image quality by preventing ion polarization and accumulation, while also eliminating black luminance differences between positive and negative polarity voltages.
Implementation Method 1
controls the light transmittance of a liquid crystal layer by an electric field applied to the liquid crystal layer
Implementation Method 2
the liquid crystal molecules of the liquid crystal cell Clc are changed in arrangement by the electric field
Implementation Method 3
ions having negative charges are moved in the same motion vector direction and ions having positive charges are moved in the opposite motion vector direction in accordance with the polarity of an electric field applied to the liquid crystal, and polarized
Implementation Method 4
in accordance with the polarity of an electric field applied to the liquid crystal
Data Source
AI summary
A liquid crystal display device and a driving method thereof are provided which can increase a display grade by removing a DC residual image. The liquid crystal display device comprises: a liquid crystal display panel for displaying gray levels by a potential difference between a common electrode for applying a common voltage and pixel electrodes for applying data voltages; a common voltage regulating circuit for generating a variable common voltage which is longitudinally symmetrical with respect to a DC common voltage of a predetermined level and whose voltage level is stepwisely varied at predetermined intervals; and a black gamma reference voltage regulating circuit for adding the variable common voltage to an offset voltage set as a gamma reference voltage of a black gray level to generate a variable gamma reference voltage varying with respect to the gamma reference voltage of the black gray level, the variable gamma reference voltage of the black gray level being varied in synchronization with the variable common voltage.