Organic EL Panel Drive Control for Cost Reduction
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Solution Overview
Problem
Flat self-luminous panels using organic EL devices face high costs compared to liquid crystal displays (LCDs), necessitating a reduction in production costs while maintaining image quality.
Innovation Solution
A panel and drive control method featuring pixel circuits with light-emitting elements, sampling transistors, drive transistors, and holding capacitors, where threshold correction and power supply are managed to reduce costs by controlling source voltage and video signal potentials across multiple rows, allowing for efficient light emission control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If threshold correction is performed on all pixel circuits simultaneously, then production cost is reduced, but image quality uniformity deteriorates due to variations in threshold voltage and mobility
Solution Approach 1:
The patent divides the pixel circuits into multiple groups based on their row positions and performs threshold correction separately on each group. This segmentation allows simultaneous processing of multiple pixel circuits (reducing cost) while maintaining correction accuracy for each group (preserving image quality uniformity). The drive control unit processes pixel circuits in units of multiple rows, applying different correction timings to different groups.
Solution Approach 2:
The patent implements dynamic threshold correction by adjusting the correction timing based on the row position of each pixel circuit. The drive control unit controls the sampling transistors to perform threshold correction at different times for different rows, creating a dynamic correction schedule that adapts to the specific characteristics of each pixel group while maintaining overall efficiency.
2Device complexity
If power supply control is simplified to reduce cost, then device complexity is reduced, but control precision over light emission deteriorates
Solution Approach 1:
The patent applies preliminary action by performing threshold correction before the main light emission period. The drive control unit first corrects the threshold voltage variations in pixel circuits during a preliminary correction phase, then maintains the corrected state during the light emission period. This preliminary correction ensures that subsequent power supply control is simpler while maintaining precise light emission control.
Solution Approach 2:
The patent implements feedback mechanisms where the drive control unit monitors the light emission characteristics and adjusts the power supply accordingly. The sampling transistors and holding capacitors work together to provide feedback on the actual light output, allowing the control unit to make precise adjustments to maintain consistent emission levels across all pixel circuits.
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 method achieves reduced production costs for EL panels by simplifying power control and threshold correction processes, ensuring consistent image quality and reducing variations in threshold voltage and mobility across pixels.
Implementation Method 1
Organic EL devices rely on light emission from an organic thin film when the film is applied with an electric field
Data Source
AI summary
A common power line shared by all the pixels allows threshold correction to be performed simultaneously on all the pixels. Video signal lines are set to a second reference potential higher than a reference potential, followed by multi-step threshold correction and video signal writing which are performed in a line sequential manner. Performing the threshold correction immediately before the video signal writing ensures shorter time from the threshold correction to the video signal writing. This suppresses leak currents, providing improved image quality.