Liquid Crystal Refresh Mode for Image Retention
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Solution Overview
Problem
Liquid crystal display devices experience image retention issues due to differences in positive and negative voltage effective values during alternating current-drive, especially when displaying still images for extended periods, which existing solutions like JP-A-2002-182622 and JP-A-2012-252062 do not fully mitigate.
Innovation Solution
An electro-optical device with a display panel set to a predefined temperature higher than ordinary temperature but lower than the liquid crystal's Ni point, where the light valves are energized in a specific 'refresh mode' to reduce image retention, using a drive voltage that minimizes light transmittance variation and incorporating a timer for energization control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alternating current-drive is used to prevent liquid crystal material deterioration, then device reliability is improved, but display quality deteriorates due to image retention and flicker caused by voltage effective value differences
Solution Approach 1:
The patent applies parameter changes by adjusting the temperature of the liquid crystal layer to a specific range (20°C to 40°C) and controlling the drive voltage characteristics. This temperature parameter change modifies the liquid crystal material properties to reduce the difference between positive and negative voltage effective values, thereby reducing image retention and flicker while maintaining the benefits of alternating current-drive for material durability.
Solution Approach 2:
The patent employs periodic action through alternating current-drive with polarity reversal at constant cycles (horizontal period or field period). This periodic voltage application prevents direct current damage to liquid crystal materials while the specific temperature control ensures that the periodic action does not cause image retention or flicker, resolving the contradiction between reliability and display quality.
2Reliability
If standard alternating current-drive is applied, then device reliability is maintained, but image retention occurs when displaying still images for long periods
Solution Approach 1:
The patent changes the temperature parameter of the liquid crystal layer to a specific range (20°C to 40°C) which modifies the material's response characteristics. This parameter change enables the liquid crystal to maintain uniform adsorption states during prolonged display periods, preventing image retention while preserving the operational stability provided by alternating current-drive.
Solution Approach 2:
The patent applies preliminary action by pre-heating or pre-cooling the liquid crystal layer to the optimal temperature range before displaying still images for extended periods. This preliminary temperature adjustment prepares the liquid crystal material to maintain uniform properties throughout the display duration, preventing image retention from developing over time.
3Manufacturing precision
If voltage is applied to correct image retention, then display quality is improved, but liquid crystal material deterioration accelerates
Solution Approach 1:
The patent uses parameter changes by controlling the liquid crystal layer temperature to a specific range (20°C to 40°C) and applying alternating current-drive with controlled voltage effective values. This approach corrects display uniformity issues through temperature-controlled voltage application rather than high-voltage correction methods, thereby improving display quality without accelerating material deterioration.
Solution Approach 2:
The patent replaces direct high-voltage correction methods with a temperature-controlled electrical field approach. By adjusting the temperature parameter, the system modifies the liquid crystal's electrical characteristics to achieve uniform display without requiring excessive correction voltages that would damage the material, thus substituting a gentler, more material-friendly correction mechanism.
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 mitigates image retention and flicker by uniformizing the adsorption state of ionic substances, maintaining display quality and appearance, with the refresh mode reducing image retention by up to 70% within a few hours.
Implementation Method 1
A liquid crystal device serving as an electro-optical device includes a liquid crystal layer serving as an electro-optical element interposed between a pair of substrates
Implementation Method 2
light from a light source is caused to be incident on the display panel, and the display panel is set to have the predefined temperature
Data Source
AI summary
An electro-optical device includes a display panel including a liquid crystal layer interposed between a pair of substrates, and in the electro-optical device, a normal display mode and a refresh mode serving as a specific display mode in which the display panel is set to have a predefined temperature higher than ordinary temperature and lower than an Ni point of the liquid crystal layer and is energized in display where brightness becomes homogeneous in a screen are selectable.