OLED Pixel Initialization for Black Brightness Uniformity
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Solution Overview
Problem
Organic light emitting display devices face challenges in achieving uniform black brightness and accurately displaying low gray-scale levels without malfunctioning.
Innovation Solution
The device incorporates a specific pixel configuration with initialization transistors and a storage capacitor, where the anode of the organic light emitting diode is initialized to a voltage before light emission, allowing the diode to display brightness corresponding to data signals, including black and low gray-scale levels by charging a voltage in the storage capacitor during a data write-in period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the organic light emitting diode is driven with high current to improve brightness, then the luminance increases, but the black brightness uniformity deteriorates and low gray-scale levels cannot be accurately displayed
Solution Approach 1:
The anode of the organic light emitting diode is initialized to a specific voltage level before the data signal is applied. This preliminary initialization ensures that the OLED starts from a known state, preventing mis-emission and enabling accurate display of low gray-scale levels including black, without requiring high drive currents that would compromise uniformity
2Manufacturing precision
If the initialization voltage is applied too early, then the OLED can display black level accurately, but the data signal cannot be written properly
Solution Approach 1:
The initialization process is segmented into two distinct phases: first, the anode is initialized to a specific voltage level to enable accurate black level display; second, after a controlled time delay, the data signal is written to the pixel. This temporal segmentation allows both black level accuracy and proper data writing to occur without interference
Solution Approach 2:
The pixel operation follows a periodic cycle with distinct time periods: an initialization period where the anode voltage is set to enable black level display, followed by a data write-in period where the data signal is applied. This periodic structure with controlled timing ensures both black accuracy and data integrity
3Productivity
If the scan signal timing is advanced to initialize the first node, then the data writing efficiency improves, but the OLED may malfunction at low gray-scale levels
Solution Approach 1:
The anode initialization is performed as a preliminary action before data writing, but with carefully controlled timing to avoid affecting low gray-scale level display. The initialization voltage is applied early to prepare the OLED for accurate black level display, while the data signal is written at the optimal moment to maintain operational reliability
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 ensures uniform black brightness and accurate display of low gray-scale levels, preventing mis-emission and maintaining proper operation even at black gray-scale levels, thereby enhancing the display quality of the organic light emitting display device.
Implementation Method 1
The organic light emitting diode emits light when a voltage greater than a threshold voltage is applied to the organic light emitting layer
Data Source
AI summary
An organic light emitting display device includes an (i−1)th pixel, an i-th pixel, and an (i+1)th pixel, each including an organic light emitting diode and a driving transistor to control a driving current flowing through the organic light emitting diode. A first node of the i-th pixel, to which a control electrode of the driving transistor of the i-th pixel is connected, is initialized to an initialization voltage in synchronization with an (i−1)th scan signal applied to the i-th pixel, and an anode of the organic light emitting diode of the i-th pixel is initialized to the initialization voltage in synchronization with an i-th scan signal applied to the (i+1)th pixel.