Passive Matrix OLED Brightness Uniformity via Local Encapsulation
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Solution Overview
Problem
Passive matrix (PM) OLED display devices are sensitive to power loss and exhibit brightness variations due to electrode power loss and organic material property changes, making them difficult to commercialize effectively compared to active matrix devices.
Innovation Solution
A display device using semiconductor light emitting devices with a substrate, first and second electrodes, and a wavelength converting layer, where the semiconductor light emitting devices have varying brightnesses and distances between electrodes, allowing for linear adjustments to compensate for power loss and minimize brightness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive matrix OLED display devices are used, then manufacturing process is simple and manufacturing cost is low, but brightness uniformity deteriorates due to power loss and organic material property changes
Solution Approach 1:
The patent applies local quality by varying the thickness of the third encapsulation layer across different regions of the display device. Specifically, the encapsulation layer is designed to be thicker in regions experiencing greater power loss (typically farther from power supply lines) and thinner in regions with less power loss. This non-uniform thickness distribution compensates for the brightness variations caused by electrode power loss and organic material degradation, thereby improving overall brightness uniformity while maintaining the simple passive matrix manufacturing process.
2Device complexity
If passive matrix OLED display devices are used, then device complexity is reduced, but sensitivity to power loss increases causing brightness variations
Solution Approach 1:
The patent employs parameter changes by modifying the physical dimensions of the encapsulation layer. The third encapsulation layer is designed with variable thickness as a key parameter, where the thickness is adjusted according to the power loss characteristics of different display regions. This parameter modification allows the device to compensate for power loss effects without increasing structural complexity or requiring additional active matrix control circuits, thus maintaining reliability while preserving the simplicity of the passive matrix structure.
3Manufacturing precision
If uniform encapsulation layer thickness is used, then manufacturing precision is improved, but brightness uniformity deteriorates due to power loss variations across the display
Solution Approach 1:
The patent resolves this contradiction by implementing local quality through a non-uniform encapsulation layer design. Rather than applying a uniform thickness across the entire display, the third encapsulation layer is engineered with spatially varying thickness. The thickness distribution is specifically optimized to counteract the power loss gradient across the display device, with thicker regions positioned where power loss is more severe. This approach prioritizes luminance uniformity over manufacturing precision, as the controlled non-uniformity in the encapsulation layer directly compensates for the inherent power loss variations in passive matrix structures.
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 solution reduces brightness variations and load effects in PM structures, allowing for more stable and uniform luminance by using semiconductor light emitting devices with different brightnesses and adjusting line resistances, thereby improving the design and performance of PM display devices.
Implementation Method 1
Light emitting diodes (LEDs) are well-known semiconductor light emitting devices that convert electric current into light
Implementation Method 2
a wavelength converting layer disposed on the semiconductor light emitting devices
Data Source
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AI summary
A display device using semiconductor light emitting devices (300) is disclosed. The display device includes a substrate (100), a plurality of first electrodes (200) disposed on the substrate (100), a light emitting device array comprising a plurality of semiconductor light emitting devices (300) electrically connected to the first electrodes (200), constituting individual pixels, and having different brightnesses increasing from one side of a current input direction of each of the first electrodes (200) to the other side of the current input direction of each of the first electrodes (200) , and a plurality of second electrodes (400) electrically connected to the semiconductor light emitting devices (300). Thus, brightness variation caused by power loss may be reduced in a display device of passive matrix (PM) type using the light emitting device array, thereby reducing load effect that is a problem of a conventional display device of PM type using a conventional light emitting device array.