OLED Light Extraction Pattern with Concave Convex Structures
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Solution Overview
Problem
Organic light emitting display apparatuses face reduced light extraction efficiency and brightness due to total reflection at interfaces, leading to increased power consumption and issues like black visibility and Mura phenomena.
Innovation Solution
Incorporating a light extraction pattern with concave and convex portions on a substrate and a color filter layer with different thickness regions to enhance light extraction efficiency and reduce external light reflection, thereby minimizing rainbow and circular ring Mura.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional planar light extraction structure is used, then the device structure is simple, but light extraction efficiency is reduced due to total reflection at interfaces
Solution Approach 1:
The patent introduces a light extraction pattern with convex and concave portions on the planarization layer surface. The convex portions have curved surfaces that act as microlenses to refract and extract light, while the concave portions trap and redirect light that would otherwise be totally reflected. This curvature-based structure resolves the contradiction by maintaining manufacturing feasibility through standard photolithography while dramatically improving light extraction efficiency.
2Illumination intensity
If external light reflection is reduced to improve black visibility, then black color quality improves, but light extraction efficiency may be affected
Solution Approach 1:
The color filter layer is designed with different thicknesses at different locations: a first thickness in the light separation portion and a second thickness in other regions. This local variation allows the filter to selectively absorb reflected external light in specific areas to improve black visibility, while maintaining optimal light extraction properties in emission areas. The light extraction pattern's convex and concave portions also create local optical field variations that enhance this selective control.
3Ease of manufacture
If uniform color filter thickness is used, then manufacturing is simple, but rainbow Mura and circular ring Mura phenomena occur due to light interference
Solution Approach 1:
The color filter layer deliberately breaks uniformity by having different thicknesses in different regions. The first thickness in the light separation portion and the second thickness in emission portions create asymmetric optical paths that disrupt the formation of interference patterns. This asymmetric design eliminates rainbow Mura and circular ring Mura phenomena while remaining compatible with standard manufacturing processes.
4Illumination intensity
If light extraction efficiency is improved to increase brightness, then luminance increases, but power consumption increases
Solution Approach 1:
The patent converts the harmful effect of total internal reflection at the planarization layer surface into a beneficial light extraction mechanism. The concave portions of the light extraction pattern are specifically designed to trap light that would normally be totally reflected and redirect it toward extraction angles. This transforms energy loss into useful light output, improving brightness without increasing power consumption.
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
Improves light extraction efficiency, reduces power consumption, and achieves real black visibility by minimizing rainbow and circular ring Mura, resulting in higher luminance and extended emission layer lifespan.
Implementation Method 1
a planarization layer including a light extraction pattern which is at the emission area of each of the plurality of color subpixels and the white subpixel and includes a plurality of concave portions and a convex portion
Implementation Method 2
the color filter layer comprises a first filter region and a second filter region having different thicknesses at the light separation portion
Data Source
AI summary
An organic light emitting display apparatus includes a plurality of pixels each including a plurality of color subpixels and a white subpixel, where each pixel includes an emission area disposed on a substrate. The display apparatus further includes a planarization layer including a light extraction pattern which is at the emission area of each of the plurality of color subpixels and the white subpixel and includes a plurality of concave portions and a convex portion, a light emitting device layer on the light extraction pattern, a color filter layer disposed between the substrate and the light extraction pattern to overlap the emission area of each of the plurality of color subpixels, and a light separation portion disposed between the substrate and the light extraction pattern to overlap the emission area of each of the plurality of color subpixels.