Display Panel Encapsulation Structure for Higher Front Light Extraction
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Solution Overview
Problem
Display devices such as micro-LED and mini-LED suffer from low light exit efficiency due to the divergence of light shapes, with reduced intensity at the front viewing angle and increased intensity at the side viewing angle, attributed to the encapsulation layer's higher refractive index causing total reflection of large-angle light.
Innovation Solution
A display panel design featuring a first encapsulation layer with a first dielectric layer having a lower refractive index, where the distances and structures of these layers are strategically arranged to optimize light exit efficiency, with specific overlaps and distances (H1a < H1b) to reduce total reflection and enhance light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an encapsulation layer with a larger refractive index is provided at one side of the light exit surface, then light can be guided and contained within the device, but light exit efficiency is reduced due to total reflection at the interface between the encapsulation layer and air
Solution Approach 1:
The encapsulation layer is divided into a first encapsulation layer with a first refractive index and a second encapsulation layer with a second refractive index, where the first refractive index is smaller than the second refractive index. This segmentation creates a gradient structure that gradually transitions the refractive index from the high-index region to the low-index region, reducing total internal reflection at the interface and improving light extraction efficiency.
Solution Approach 2:
The refractive index parameter is changed by introducing a gradient structure through the two-layer encapsulation design. The first encapsulation layer has a lower refractive index than the second encapsulation layer, creating a gradual transition that modifies the optical parameters at the interface and reduces total reflection for large-angle light.
2Illumination intensity
If light emitted by the LED enters air through the encapsulation layer, then light can exit the device, but light intensity under the front viewing angle is reduced while light intensity under large viewing angle increases
Solution Approach 1:
The encapsulation structure is segmented into two layers with different refractive indices to control light propagation. The first encapsulation layer with lower refractive index and the second encapsulation layer with higher refractive index work together to reshape the light distribution, concentrating more light intensity in the front viewing angle direction and reducing the butterfly effect.
Solution Approach 2:
By changing the refractive index parameter distribution through the gradient encapsulation structure, the light intensity distribution is modified. The transition from higher to lower refractive index across the layers redirects large-angle light toward the normal direction, improving front viewing angle intensity and correcting the light shape divergence.
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 design improves light exit efficiency by reducing the amount of light reflected at the interface, increasing the amount of light emitted near the light exit surface, thereby enhancing the light shapes and brightness at the front viewing angle.
Implementation Method 1
The low light exit efficiency of the display device lies in: The encapsulation layer has the larger refractive index than air. Large-angle light emitted by the LED is totally reflected at an interface between the encapsulation layer and the air, and cannot be utilized.
Implementation Method 2
A refractive index of the first dielectric layer is smaller than a refractive index of the first encapsulation layer
Data Source
AI summary
A display panel includes a substrate, a plurality of light-emitting devices, a first encapsulation layer, and a first dielectric layer. The first encapsulation layer includes a first portion and a second portion at least partially surrounding the first portion. The first dielectric layer is located between the first encapsulation layer and the plurality of light-emitting devices. Along the direction perpendicular to the plane of the display panel, a distance between a surface of the first portion away from at least one light-emitting device of the plurality of light emitting devices and a surface of the third portion away from the at least one light-emitting device is smaller than a distance between a surface of the second portion away from the at least one light-emitting device and a surface of the fourth portion away from the at least one light-emitting device.