OLED Thin Film Encapsulation with Convex High Refractive Index Layer
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Solution Overview
Problem
Organic light emitting diode (OLED) display devices suffer from low light emission efficiency due to reflection and total reflection at interfacial surfaces caused by layers with different refractive indices, leading to dissipation of emitted light.
Innovation Solution
The OLED display device incorporates a thin film encapsulation layer with alternating inorganic and organic layers, and a high refractive index layer with a convex surface, along with a light scattering protrusion on the inorganic layers, to minimize reflection and enhance light emission by collimating and scattering light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If multiple layers with different refractive indices are used in OLED display device, then device functionality is achieved, but light emission efficiency decreases due to reflection and total reflection at interfacial surfaces
Solution Approach 1:
A light management layer is introduced as an intermediary component between the OLED and the external environment. This layer includes a light scattering layer with protrusions that have varying refractive indices to reduce reflection at interfaces, and a lens layer with convex surfaces to collimate and extract light effectively, thereby improving light emission efficiency without compromising the necessary multilayer structure
Solution Approach 2:
The refractive index parameter is strategically varied within the light management layer. The light scattering layer contains protrusions with different refractive indices (first refractive index different from second refractive index) to minimize reflection losses at each interface, while the lens layer uses a specific refractive index to achieve light collimation and extraction
2Illumination intensity
If light scattering protrusions are added to inorganic layers, then side visibility is improved, but device structure becomes more complex
Solution Approach 1:
The light scattering protrusions are integrated into the existing inorganic encapsulation layers rather than being added as separate components. The protrusions are formed as part of the thin film encapsulation structure, merging the light scattering function with the protective encapsulation function, thereby improving side visibility without significantly increasing device complexity
Solution Approach 2:
The light scattering protrusions are selectively positioned at specific locations within the encapsulation structure - on the inorganic layers of the thin film encapsulation. This localized approach provides side visibility enhancement only where needed, rather than requiring complex structures throughout the entire device
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 increases front visibility and light emission efficiency, reducing the white angular dependency effect and improving side visibility without compromising light efficiency.
Implementation Method 1
a light scattering protrusion disposed on a surface of the thin film encapsulation layer
Implementation Method 2
a high refractive index layer overlapping the low refractive index layer, the high refractive index layer having a convex surface protruding toward the organic light emitting layer
Implementation Method 3
a thin film encapsulation layer disposed on the OLED, the thin film encapsulation layer including at least one inorganic layer and an organic layer disposed on the at least one inorganic layer
Data Source
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AI summary
An OLED display device includes a substrate. A first electrode is disposed on the substrate (110). An organic light emitting layer (212) is disposed on the first electrode (211). A second electrode (213) is disposed on the organic light emitting layer. A thin film encapsulation layer (310) is disposed on the second electrode. The thin film encapsulation layer includes at least one inorganic layer (310, 330) and at least one organic layer (320) that is disposed alternately with the at least one inorganic layer. The at least one organic layer includes a low refractive index layer overlapping the organic light emitting layer and a high refractive index layer disposed on the low refractive index layer. The high refractive index layer includes a convex surface protruding toward the organic light emitting layer.