OLED Capping Layer Stack for Sealing and Directional Light Output
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Solution Overview
Problem
Display devices face challenges in achieving improved sealing properties and increased light emission in the display direction, particularly in organic light emitting display (OLED) technology, where existing solutions fail to effectively manage moisture ingress and optimize light distribution.
Innovation Solution
A display device design incorporating a capping layer with alternately stacked inorganic layers of different refractive indices, including low and high refractive layers, to enhance sealing and direct light emission, where the thickness of the low refractive layers is greater than the high refractive layers, and the capping layer covers the electrode and light emitting elements to improve reliability and luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer capping structure is used, then the device structure is simple, but the sealing property and light emission control are insufficient
Solution Approach 1:
The capping layer is constructed as a composite structure with alternating high refractive index layers (first, second, and third high refractive index layers) and low refractive index layers (first and second low refractive index layers). This composite material approach enables simultaneous achievement of effective sealing and controlled light emission by utilizing the different optical properties of materials with varying refractive indices, resolving the contradiction between simple structure and functional performance.
Solution Approach 2:
The capping layer is segmented into multiple distinct sub-layers with different refractive indices and thicknesses. The first low refractive index layer has a greater thickness than the second low refractive index layer, creating an asymmetric segmented structure. This segmentation allows independent optimization of each layer's function for both sealing and light emission control, addressing the limitation of single-layer structures.
2Illumination intensity
If the thickness of low refractive index layers is increased, then light emission in display direction is enhanced, but the structural symmetry is reduced
Solution Approach 1:
The patent deliberately introduces asymmetry by making the first low refractive index layer have a greater thickness than the second low refractive index layer. This asymmetric thickness distribution is strategically designed to optimize light emission in the display direction while maintaining the overall functional balance of the capping layer structure, effectively resolving the contradiction between enhanced light emission and structural symmetry.
Solution Approach 2:
Different thicknesses are assigned to different low refractive index layers based on their local functional requirements. The first low refractive index layer, positioned closer to the light emitting element, has greater thickness to maximize light emission control in the display direction, while the second low refractive index layer has smaller thickness. This local quality differentiation optimizes overall performance.
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 effectively improves the sealing properties and light emission in the display direction, enhancing the reliability and performance of the display device by efficiently guiding light and preventing moisture ingress.
Implementation Method 1
a capping layer disposed on the light emitting element and including at least one low refractive layer and at least one high refractive layer that are alternately disposed
Implementation Method 2
The capping layer may comprise a first low refractive layer on the electrode layer and the light emitting element, a first high refractive layer on the first low refractive layer, and a second low refractive layer on the first high refractive layer
Data Source
AI summary
A display device includes an electrode layer including a first electrode and a second electrode that are spaced apart from each other and disposed on a substrate, a light emitting element between the first electrode and the second electrode, and a capping layer disposed on the light emitting element and including at least one low refractive layer and at least one high refractive layer that are alternately disposed. The capping layer includes a first low refractive layer on the electrode layer and the light emitting element, a first high refractive layer on the first low refractive layer, and a second low refractive layer on the first high refractive layer. A thickness of the first low refractive layer is greater than a thickness of the second low refractive layer.