Organic EL Display Drive Units for Luminance Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Organic EL display devices experience luminance unevenness due to coupling between pixels, which is exacerbated by changes in the I-V characteristic of organic EL elements and the threshold voltage and mobility of drive transistors over time, leading to fluctuations in voltage and current, resulting in inconsistent light emission.
Innovation Solution
A display device configuration where pixel circuits are grouped into drive units with shared power supply lines and write scanning lines, allowing for sequential threshold correction and signal writing operations that synchronize the voltage between gate sources of drive transistors across pixels, minimizing the impact of coupling and maintaining consistent luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If pixels share constant voltage lines for auxiliary capacitors to reduce device complexity, then wiring complexity is reduced, but voltage fluctuation between pixels occurs causing luminance unevenness
Solution Approach 1:
The patent divides the display panel into multiple drive units, where each drive unit contains a plurality of pixels and is independently controlled. This segmentation isolates the voltage fluctuation effects within each drive unit, preventing propagation between different drive units and maintaining luminance uniformity across the display.
Solution Approach 2:
The patent performs threshold voltage correction (Vth correction) for each drive unit before signal writing. By preliminarily correcting the threshold voltage differences among drive units, the system compensates for manufacturing variations and ensures uniform voltage distribution across all pixels before they are driven, preventing luminance unevenness.
2Manufacturing precision
If sequential driving of drive units is used to reduce coupling effects, then luminance unevenness is reduced, but driving time increases
Solution Approach 1:
The patent segments the display into multiple drive units that can be driven sequentially. Each drive unit is processed in a time slot, allowing the system to complete Vth correction and signal writing for each unit before moving to the next unit. This segmentation enables sequential processing that maintains luminance uniformity while managing the overall driving time efficiently.
Solution Approach 2:
The patent implements a periodic driving sequence where drive units are activated in alternating time slots. By using periodic action to switch between different drive units, the system can perform necessary corrections and signal writing operations without simultaneous operation, thereby reducing coupling effects and maintaining luminance uniformity across the display.
3Manufacturing precision
If Vth correction is performed for all pixels simultaneously to improve manufacturing precision, then luminance uniformity is improved, but coupling effects between pixels worsen voltage fluctuations
Solution Approach 1:
The patent segments the pixel array into multiple drive units, where Vth correction is performed independently for each drive unit. This segmentation prevents coupling effects from propagating across the entire display, as each drive unit is corrected and driven separately. The independent correction of each drive unit maintains luminance uniformity while minimizing harmful coupling effects between adjacent pixels.
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 reduces luminance unevenness by ensuring consistent voltage and current across pixels, maintaining uniform light emission despite temporal changes in organic EL elements and drive transistors, thereby enhancing display quality.
Implementation Method 1
current driving type light emitting elements, for example, organic EL (Electro Luminescence) elements of which luminance of emitted light changes according to values of running currents
Implementation Method 2
an auxiliary capacitor connected to a source of the drive transistor
Data Source
AI summary
A color display unit includes subpixels arranged in matrix form. Display pixels are formed from multiple subpixels, one for each of the display colors, grouped together across multiple subpixel rows. Drive units are formed including multiple rows of display pixels that are connected to a common power supply line. Common write scanning lines are provided, where the number of common write scanning lines per drive unit equals the number of rows of subpixels that are included in a display pixel. Each common write scanning line is connected to every pixel of at least one given color in its respective drive unit. The drive units are driven sequentially in a drive-unit-scanning direction. Within each individual drive unit, the write scanning lines thereof are scanned for the signal writing operation sequentially in a scanning direction opposite to the drive-unit-scanning direction.