Electrophoretic Display Storage Capacitor Line Potential Control
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Solution Overview
Problem
Electrophoretic display devices suffer from image persistence and contrast deterioration due to insufficient reset and diffusion of charged particles, especially when a potential difference of 0V is maintained between the common electrode and pixel electrode after image resetting.
Innovation Solution
The implementation of a storage capacitor and thin film transistor (TFT) in each pixel, allowing for controlled electric potential levels on the storage capacitor line to set the electric field between the pixel and common electrodes, preventing luminance level shifts and contrast deterioration by managing the reset state and promoting electrophoretic material migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the potential difference between the common electrode and pixel electrode is set to 0V after resetting the image, then the device structure is simple, but the charged particles diffuse and cause contrast deterioration and image persistence
Solution Approach 1:
The patent applies preliminary action by setting the electric potential of the storage capacitor line to a specific level (higher than the capacitor line low select signal level) before the image is displayed. This preliminary electric field configuration prevents charged particle diffusion during image retention, thereby avoiding contrast deterioration and image persistence without requiring complex additional control structures.
Solution Approach 2:
The patent changes the electric potential parameter of the storage capacitor line from a conventional 0V state to a higher potential level. This parameter change creates an electric field that actively prevents charged particle diffusion, solving the contrast deterioration problem while maintaining a relatively simple device structure.
2Ease of operation
If the reset is performed insufficiently due to the state of the displayed image before reset, then the reset operation is simple, but image persistence occurs
Solution Approach 1:
The patent implements feedback by using the storage capacitor line electric potential to continuously monitor and adjust the charged particle distribution state. By maintaining a specific electric potential level on the storage capacitor line, the system provides continuous feedback control that ensures complete reset of charged particles, preventing image persistence regardless of the previous display state.
3Use of energy by moving object
If the white particles diffuse when the image is retained with 0V potential difference, then the energy consumption is low, but the white level turns to gray and contrast deteriorates
Solution Approach 1:
The patent applies equipotentiality by setting the storage capacitor line to a specific electric potential level that creates a balanced electric field configuration. This equipotential configuration prevents charged particle diffusion during image retention, maintaining the white level brightness without requiring excessive energy consumption.
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 ensures a vivid color tone after reset, prevents particle diffusion, and maintains image contrast, effectively addressing the issues of image persistence and contrast deterioration in electrophoretic display devices.
Implementation Method 1
the charged electrophoretic particle is drawn to either one of the electrodes depending on the direction of the electric field
Implementation Method 2
the electric field between the pixel electrode and the common electrode is externally set by controlling high and low (level) of the electric potential of the storage capacitor line
Implementation Method 3
a thin film transistor (TFT) provided in the pixel, a source electrode of the TFT being coupled to a first electrode of the storage capacitor and the pixel electrode, a drain electrode of the TFT being coupled to the signal line, and a gate electrode of the TFT being coupled to the scan line
Implementation Method 4
a storage capacitor provided in the pixel... A capacitor line high select signal VSH, a capacitor line non-select signal VSC or a capacitor line low select signal VSL is supplied to the storage capacitor line
Data Source
AI summary
An electrophoretic display device including a first substrate, a second substrate, an electrophoretic material interposed between the first substrate and the second substrate, the electrophoretic material including a positively charged particle and a negatively charged particle, a common electrode provided on the second substrate, a pixel provided at an intersection of a signal line and a scan line, the pixel provided in a plural number and arranged in matrix on the first substrate. The electrophoretic display device further including a pixel electrode provided in the pixel, a capacitor line provided in the pixel, a storage capacitor provided in the pixel, and a second electrode of the storage capacitor being coupled to a storage capacitor line and a thin film transistor (TFT) provided in the pixel, a source electrode of the TFT being coupled to a first electrode of the storage capacitor and the pixel electrode, a drain electrode of the TFT being coupled to the signal line, and a gate electrode of the TFT being coupled to the scan line. A capacitor line low select signal VSL or a capacitor line non-select signal VSC having a higher electric potential than an electric potential of the capacitor line low select signal VSL is supplied to the storage capacitor line.