Liquid Crystal Display Polarity Inversion for DC Image Sticking
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Solution Overview
Problem
Liquid crystal displays suffer from direct current (DC) image sticking, flicker, and nonuniform stains due to prolonged application of DC voltage, which degrade display quality and are difficult to address with existing materials or methods.
Innovation Solution
A liquid crystal display and driving method that inverts the polarity of the data voltage every frame period, divides liquid crystal cells into groups charged with the same or opposite polarity, and adjusts the polarity control signal phase to prevent DC image sticking and flicker, while suppressing DC drive to reduce nonuniform stains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If data voltage is supplied to liquid crystal cells in an interlaced manner with polarity inversion every frame period, then power consumption is reduced and basic display function is maintained, but DC image sticking occurs due to dominant supply of same-polarity voltage to specific horizontal lines
Solution Approach 1:
The liquid crystal cells are divided into two groups: odd-numbered horizontal line cells and even-numbered horizontal line cells. Each group receives data voltage with a different polarity pattern, allowing independent polarity control for each segment to prevent DC accumulation while maintaining power efficiency
Solution Approach 2:
Instead of inverting polarity every frame period for all cells (which causes DC image sticking), the patent inverts the polarity pattern between the two groups of cells. Odd-line cells and even-line cells receive opposite polarity sequences, effectively canceling out DC components while maintaining the interlaced scanning benefit
2Object-generated harmful factors
If polarity is inverted every frame period for all liquid crystal cells, then DC offset components are reduced, but DC image sticking occurs due to cumulative effect of same-polarity voltage on specific lines
Solution Approach 1:
The display is segmented into odd-line cells and even-line cells with independent polarity control. This segmentation allows each group to experience balanced polarity exposure over time, preventing the cumulative DC effect that occurs when all cells follow the same inversion pattern
Solution Approach 2:
The patent introduces asymmetry in the polarity inversion pattern by treating odd-line and even-line cells differently. While both groups maintain overall polarity balance, their instantaneous polarity states are opposite, creating an asymmetric control scheme that eliminates DC image sticking
3Productivity
If data voltage with dominant same-polarity supply is applied to odd-numbered horizontal lines during odd-numbered frame periods, then interlaced scanning is maintained, but DC image sticking appears due to prolonged exposure to same polarity
Solution Approach 1:
The patent segments the display into two independently controlled groups (odd-lines and even-lines), allowing each group to maintain interlaced scanning benefits while experiencing balanced polarity exposure. This segmentation enables both groups to scan efficiently without suffering from DC accumulation
Solution Approach 2:
The patent implements periodic polarity inversion with a modified pattern: odd-line cells and even-line cells invert polarity in opposite phases. This periodic action with opposite phases ensures that over time, both groups experience equal exposure to positive and negative polarities, eliminating DC image sticking while maintaining interlaced scanning productivity
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
Effectively prevents DC image sticking, flicker, and nonuniform stains by ensuring alternating polarities and adjusting data drive frequencies, thereby enhancing display quality and reducing the accumulation of ions that cause these issues.
Implementation Method 1
A liquid crystal display switches a data voltage supplied to liquid crystal cells Clc using a thin film transistor (TFT) formed in each liquid crystal cell Clc to actively control data
Implementation Method 2
The liquid crystal display is driven in an inversion manner in which a polarity of the liquid crystal cells Clc is inverted between the neighboring liquid crystal cells Clc and the polarity is inverted every one frame period, so as to reduce direct current (DC) offset components
Data Source
AI summary
A liquid crystal display and a method of driving the same are disclosed. A timing controller of the liquid crystal display controls a polarity control signal to have a different phase in each frame and allows liquid crystal cells to be divided into a first liquid crystal cell group charged to a data voltage of a same polarity during two frame periods and a second liquid crystal cell group charged during a current frame period to the data voltage with a polarity opposite a polarity of the data voltage charged during a previous frame period. The liquid crystal cells belonging to the first liquid crystal cell group are successively charged to the data voltage of the same polarity during three or more frame periods at intervals of a predetermined time equal to or longer than two frame periods.