Multilayer Insulating Stack for Display Light Extraction
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Solution Overview
Problem
Existing display devices suffer from reduced light outputting efficiency and display quality due to light being reflected at interlayer interfaces within the multilayered structure, rather than being discharged outside.
Innovation Solution
A display device configuration that includes a substrate with a transistor, a light-emitting device connected to the transistor, an encapsulation layer, a sensing electrode, and multiple insulating layers with specific refractive indices and thicknesses, where the second insulating layer has a higher refractive index than the first insulating layer, and a third insulating layer made of inorganic material like silicon nitride is included between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a multilayered structure is used in the display device, then the device can integrate multiple functional layers (light-emitting device, touch sensor, encapsulation layer), but light reflection occurs at interlayer interfaces reducing light outputting efficiency
Solution Approach 1:
An intermediate layer with refractive index 1.60-1.90 is introduced between the encapsulation layer (refractive index ~1.50) and the air interface. This intermediate layer acts as an optical mediator that reduces the refractive index mismatch and minimizes light reflection at the interface, allowing more light to escape to the front while maintaining the protective function of the encapsulation layer.
Solution Approach 2:
The refractive index parameter of the intermediate layer is specifically optimized to be between 1.60 and 1.90, which is higher than the encapsulation layer but lower than air. This parameter change creates a gradual refractive index transition that reduces optical impedance mismatch and minimizes reflection loss at the interface.
2Productivity
If the refractive index of the second insulating layer is increased to reduce light reflection, then light outputting efficiency improves, but the layer thickness and overall device structure become more complex
Solution Approach 1:
The refractive index of the second insulating layer is optimized to a specific range (1.60-1.90) rather than maximizing it indefinitely. This parameter optimization achieves sufficient light extraction improvement while avoiding excessive complexity. The thickness is controlled at 5-15 μm to balance optical performance with structural simplicity.
Solution Approach 2:
The patent employs a composite insulating layer structure with multiple layers having different refractive indices (first insulating layer with lower refractive index, second insulating layer with higher refractive index of 1.60-1.90, and optional third insulating layer). This composite structure achieves superior light extraction compared to single-layer structures while maintaining reasonable device complexity.
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 enhances light outputting efficiency and display quality by minimizing light reflection and maximizing light discharge to the front, resulting in improved frontal visibility and luminance.
Implementation Method 1
a refractive index of the second insulating layer is greater than a refractive index of the first insulating layer
Implementation Method 2
some of the light generated by the light-emitting device may be reflected on an interlayer interface, so it may not be discharged to the outside but may become extinct
Data Source
AI summary
A display device includes: a substrate; a transistor on the substrate; a light-emitting device connected to the transistor; an encapsulation layer on the light-emitting device; a sensing electrode on the encapsulation layer; a first insulating layer on the sensing electrode and including an opening; a second insulating layer on the encapsulation layer and the first insulating layer; and a third insulating layer between the first insulating layer and the second insulating layer, wherein a refractive index of the second insulating layer is greater than a refractive index of the first insulating layer.