OLED Pixel Structure for Flexible Substrates
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Solution Overview
Problem
Image sticking in organic light emitting display devices occurs due to shifts in threshold voltages of thin-film transistors caused by electric fields generated within the substrate, affecting the quality and duration of image display.
Innovation Solution
A new pixel structure is implemented with a specific configuration of scan lines and signal lines on a flexible substrate, where components receiving high-level and low-level signals are grouped on opposite sides of each pixel, minimizing the shift in threshold voltages and reducing electric field effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel structure is used with mixed signal lines, then device complexity is reduced, but threshold voltage shifts occur due to electric fields generated by water molecules in the substrate
Solution Approach 1:
The pixel structure is segmented into distinct regions: a first region containing scan lines (first scan line and second scan line) and a second region containing signal lines (emission signal line and Vdd voltage supply line). This spatial segmentation separates components subjected to different voltage levels, preventing electric field interactions that cause threshold voltage shifts while maintaining overall structural organization.
Solution Approach 2:
The emission signal line and Vdd voltage supply line are extracted from the mixed signal line configuration and placed in a separate second region. This extraction removes the source of high-level electric fields from proximity to the thin-film transistor, eliminating the harmful electric field effects caused by water molecules in the substrate without requiring complete structural redesign.
2Loss of time
If image sticking removal time is reduced, then display quality improves, but threshold voltage shifts cause prolonged image sticking
Solution Approach 1:
The pixel structure is designed with preliminary anti-action by pre-positioning the scan lines and signal lines in separate regions before operation. This preventive configuration eliminates the generation of electric fields that would otherwise cause threshold voltage shifts and image sticking, allowing for rapid image sticking removal without compromising display quality.
3Area of stationary object
If scan lines and signal lines are closely positioned to reduce pixel area, then area efficiency improves, but electric field generation increases causing threshold voltage shifts
Solution Approach 1:
The first region containing scan lines and the second region containing signal lines are positioned to maintain equipotentiality by grouping components with similar voltage characteristics together. This reduces potential differences and minimizes electric field generation between adjacent lines, allowing compact pixel design without sacrificing threshold voltage stability.
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 configuration effectively suppresses the generation of electric fields, minimizes threshold voltage shifts, and rapidly removes image sticking, improving image quality and reducing the time image sticking is maintained.
Implementation Method 1
when a substrate on which various types of driving elements including thin-film transistors are disposed holds water as a polar molecule, so that an electric field is generated within the substrate due to a potential difference around the driving elements including the thin-film transistors
Data Source
AI summary
When using a flexible substrate to protect and support various components of an organic light emitting display device, among components including driving elements disposed on each of pixels of the organic light emitting display device, components where a high-level signal is applied during an emission period are grouped and are disposed on one side of the pixels. Further, components where a low-level signal is applied during the emission period are grouped and are disposed on the other side of the pixels. Accordingly, an electric field occurring due to a potential difference in the flexible substrate is minimized and shifting of a threshold voltage Vth of a thin-film transistor may be minimized. Thus, an OLED without an after-image can be provided.