Liquid Crystal Display Asymmetric Voltage Control Edge Burning
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Solution Overview
Problem
Conventional liquid crystal display apparatuses experience edge burning when a fixed pattern is changed to a half-tone display over time, due to impurities moving laterally and accumulating at display boundaries, leading to degradation in display quality.
Innovation Solution
A liquid crystal display apparatus and method where voltages with positive and negative polarities are alternately applied to pixels, with effective voltage control shifting the counter electrode voltage or source voltage by 0.3 V or more to create asymmetrical effective voltages, strengthening the electric field and preventing impurity movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If symmetrical effective voltages with positive and negative polarities are applied to pixels, then display quality is maintained, but impurities move laterally and accumulate at display boundaries causing edge burning
Solution Approach 1:
The patent applies asymmetry by intentionally creating different effective voltage values between positive and negative polarity periods. Specifically, when the liquid crystal layer has high molecular orientation (indicating impurity accumulation risk), the effective voltage during the positive polarity period is set differently from that during the negative polarity period. This asymmetric voltage application prevents impurities from accumulating at display boundaries while maintaining acceptable display quality.
Solution Approach 2:
The patent changes the voltage parameter dynamically based on the state of the liquid crystal layer. By monitoring molecular orientation and adjusting the effective voltage values accordingly, the system adapts the electrical parameters to prevent impurity accumulation. The effective voltage values are modified from their conventional symmetrical values to asymmetric values when needed, directly addressing the edge burning problem.
2Force
If voltages are applied to display black regions, then electric field strength increases, but impurities move laterally more easily causing edge burning at boundaries
Solution Approach 1:
The patent applies asymmetry by creating different effective voltage values between positive and negative polarity periods. When the liquid crystal layer has high molecular orientation (indicating impurity accumulation risk), the effective voltage during the positive polarity period is set differently from that during the negative polarity period. This asymmetric voltage application prevents impurities from accumulating at display boundaries while maintaining acceptable display quality.
Solution Approach 2:
The patent utilizes periodic action by alternating between positive and negative polarity periods. During these periodic cycles, the effective voltage is adjusted based on the liquid crystal layer's molecular orientation state. By controlling the voltage application in a periodic manner with asymmetric values, the system prevents continuous impurity migration that would occur with constant symmetrical voltage application.
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 prevents edge burning by maintaining a strong electric field in the cell thickness direction, reducing impurity movement and maintaining display quality when transitioning from a fixed pattern to a half-tone display.
Implementation Method 1
a liquid crystal display apparatus in which a voltage having a positive polarity and a voltage having a negative polarity are alternately applied to a pixel between a counter electrode and a pixel electrode
Data Source
AI summary
A voltage having the positive polarity and a voltage having the negative polarity are alternately applied to a pixel between a counter electrode and a pixel electrode. A counter electrode voltage (Vcom) generating circuit or a source signal generating section is provided each of which controls effective voltages to be applied to the pixel for an identical tone so that an effective voltage having the positive polarity and an effective voltage having the negative polarity are asymmetrically applied to the pixel for all of the tones which can be displayed. The counter electrode voltage (Vcom) generating circuit or the source signal generating section shifts a counter electrode voltage Vcom-A or a source voltage by 0.3 V or more from a voltage causing the effective voltages to be symmetrically applied to the pixel.