AMOLED Sub-pixel Coupling Capacitors for Luminance Uniformity
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Solution Overview
Problem
Organic light emitting display devices face issues with luminance uniformity and color balance when displaying low-luminance/low-grayscale images due to differences in emission efficiencies of red, blue, and green sub-pixels, leading to a greenish hue defect.
Innovation Solution
The design includes sub-pixels with coupling capacitors of varying capacitances, where the capacitances of the first and second sub-pixels are greater than the third sub-pixel, allowing the coupling capacitors to adjust voltages and luminance during AMOLED impulsive driving dimming, thereby reducing color and luminance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If AMOLED impulsive driving dimming method is used to display low luminance images, then power consumption is reduced, but luminance uniformity and color balance deteriorate due to different emission efficiencies of sub-pixels
Solution Approach 1:
The patent applies local quality by configuring different coupling capacitor values for different sub-pixel types. Specifically, red and blue sub-pixels are equipped with larger coupling capacitors (first and second capacitors) while green sub-pixels have smaller coupling capacitors (third capacitor), matching the different emission efficiencies of each color to achieve uniform luminance output across all sub-pixels during low luminance operation
Solution Approach 2:
The patent changes the capacitance parameter of coupling capacitors based on sub-pixel type and emission characteristics. By adjusting the capacitor values to compensate for differences in emission efficiency, the system maintains consistent luminance output across red, green, and blue sub-pixels when operating at low luminance levels with impulsive driving
2Use of energy by stationary object
If AID dimming is performed to display low luminance image, then power consumption decreases, but luminance of green sub-pixel increases while red and blue sub-pixels decrease, causing greenish hue defect
Solution Approach 1:
The patent implements local quality by assigning different coupling capacitor values to different color sub-pixels. Red and blue sub-pixels receive larger capacitance values to boost their luminance output, while green sub-pixels receive smaller capacitance values to prevent excessive luminance increase, thereby eliminating the greenish hue defect during low luminance display
Solution Approach 2:
The patent applies preliminary anti-action by pre-configuring coupling capacitors with specific capacitance values that counteract the expected luminance deviations of different sub-pixels during impulsive driving. The larger capacitors for red and blue sub-pixels preemptively compensate for their lower emission efficiency, preventing the greenish hue before it occurs
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 solution enhances luminance uniformity and reduces the greenish hue defect in low-luminance/low-grayscale images by increasing the luminance of sub-pixels with lower emission efficiency, ensuring better color balance.
Implementation Method 1
coupling capacitor including a first electrode including a portion of the emission control line, and a second electrode including an anode of the organic light emitting diode overlapping the portion of the emission control line
Data Source
AI summary
An organic light emitting display panel includes a first sub-pixel, a second sub-pixel, and a third sub-pixel for respectively emitting differently colored lights, each of the sub-pixels including a switching transistor connected to a data line, and having a gate electrode configured to receive a scan signal, a driving transistor connected to the switching transistor, an emission control transistor connected to the driving transistor, and having a gate electrode configured to receive an emission control signal, an emission control line connected to the gate electrode of the emission control transistor, an organic light emitting diode connected the emission control transistor, and coupling capacitor including a first electrode including a portion of the emission control line, and a second electrode including an anode of the organic light emitting diode overlapping the portion of the emission control line, wherein capacitances of a first capacitor including the coupling capacitor of the first sub-pixel and a second capacitor including the coupling capacitor of the second sub-pixel are greater than a capacitance of a third capacitor including the coupling capacitor of the third sub-pixel.