Electrophoretic Display Compensation Voltage for Screen Retention
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Solution Overview
Problem
Color electrophoretic display devices face issues with screen retention capability due to unnecessary electric fields applied after power is turned off, leading to particle migration and degradation in display quality.
Innovation Solution
An image display device with a memory that includes a first substrate with switching elements and pixel electrodes, a counter substrate, an electrophoretic layer with charged particles of different colors and threshold voltages, and a voltage application unit that applies a compensation voltage to suppress particle movement during the final screen update period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power is turned off after screen update, then energy consumption is reduced, but particle migration occurs due to potential difference between electrodes causing screen retention degradation
Solution Approach 1:
The patent applies a compensation voltage in the final period of screen update to preemptively counteract the potential difference that would otherwise cause particle migration after power-off. This preliminary anti-action eliminates the harmful electric field before it can affect particle positions, allowing power to be turned off without compromising screen retention
Solution Approach 2:
The patent changes the voltage parameter by applying a specific compensation voltage (different from reference potential) in the final period before power-off. This parameter change equalizes the potential between pixel electrode and counter electrode, preventing the electric field formation that would cause particle migration during the energy-saving idle state
2Reliability
If compensation voltage is applied in final period, then screen retention capability is improved, but device complexity increases due to additional voltage control
Solution Approach 1:
The patent merges the compensation voltage application with the existing screen update process by implementing it as the final period of the same update cycle. This integration avoids creating a separate control system, as the compensation voltage is applied through the existing voltage application unit that already controls the display elements during normal operation
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
The compensation voltage effectively reduces particle movement after power is turned off, improving screen retention capability and maintaining display quality by compensating for potential differences between pixel and counter electrodes.
Implementation Method 1
an electrophoretic layer 40 formed by containing electrophoretic particles 41... a voltage application unit 60 which... applies a voltage to the electrophoretic particles 41
Implementation Method 2
compensating for potential difference between pixel and counter electrodes... suppresses the movement of the charged particles C
Data Source
AI summary
An image display device having improved image retention capability by analyzing the mechanism behind the creation of an unwanted electric field applied to an element after a power supply is turned off, and devising a drive method and so forth for compensating for the same, is provided. Electrophoretic particles contain three types of charged particles, C (cyan), M (magenta), and Y (yellow) that are mutually different in color and threshold voltage for starting electrophoresis. When the threshold voltages of C (cyan), M (magenta) and Y (yellow) are respectively Vth3, Vth2, and Vth3, these satisfy the relationship |Vth3|<|Vth2|<|Vth1|. Further, a voltage application unit applies a voltage (VE) different from a reference potential during the final period of image update period. The voltage (VE) is a compensation voltage that suppresses the movement of charged particles.