Light Extraction Film for OLED Light Loss Reduction
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Solution Overview
Problem
Conventional organic light emitting devices suffer from significant light loss due to surface plasmon resonance, optical waveguide mode, and total internal reflection, resulting in only about 20% of generated light being effectively utilized, which limits their light-emitting efficiency.
Innovation Solution
A light extraction film comprising a Micro-Lenses Array (MLA) film and an optical film with scattering particles is used, where the MLA film extracts light confined by the substrate mode and the optical film scatters the light to improve light-emitting efficiency, providing uniform light distribution and color stability over a wide viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional organic light emitting device structure is used, then the device construction is simple, but light loss occurs due to surface plasmon resonance, optical waveguide mode, and total internal reflection, resulting in only about 20% of generated light being effectively utilized
Solution Approach 1:
The patent introduces a light extraction film as an intermediary component between the organic light emitting layer and the transparent substrate. This film includes micro-lens arrays and scattering particles that mediate the extraction of guided modes and substrate modes, converting trapped light into extractable light without requiring fundamental changes to the OLED structure
Solution Approach 2:
The light extraction film combines multiple functional elements into a composite structure: micro-lens arrays for extracting waveguide modes, scattering particles for disrupting total internal reflection, and transparent matrix materials. This composite approach enables simultaneous addressing of multiple light loss mechanisms while maintaining optical transparency
2Illumination intensity
If the refractive indices of the organic light emitting layer and transparent electrode layer are greater than that of the transparent substrate, then the optical waveguide mode confines light to the emitting layer, but this causes a loss of about 30 percent of light
Solution Approach 1:
The micro-lens array in the light extraction film acts as an intermediary optical element that intercepts guided modes propagating along the substrate interface. The micro-lenses focus and redirect this confined light at angles that enable extraction through the substrate, converting waveguide-mode light into free-space propagating light
Solution Approach 2:
The patent addresses the two-dimensional confinement of light in the plane parallel to the substrate by introducing a third-dimensional optical structure (micro-lens array) that operates in the vertical dimension. The micro-lenses create three-dimensional light paths that escape the planar waveguide confinement
3Illumination intensity
If the refractive index of the transparent substrate is greater than that of air, then total internal reflection easily occurs at the substrate-air interface, but this results in a loss of about 20 percent of light
Solution Approach 1:
Scattering particles embedded in the light extraction film serve as intermediary elements that intercept light attempting to undergo total internal reflection at the substrate-air interface. These particles scatter the light at various angles, creating extraction paths that bypass the total internal reflection condition and enable light escape
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 enhances light energy gain and color stability, achieving a more uniform light distribution from 0° to 90° viewing angles, thereby improving the overall light-emitting efficiency of the organic light emitting device.
Implementation Method 1
the MLA film has a first surface and a second surface opposite to each other, and has a plurality of micro-lenses disposed on the first surface
Implementation Method 2
When light penetrate toward the optical film, the light confined by the substrate mode can be first extracted by the MLA film
Implementation Method 3
the optical film covers the first surface and includes a plurality of optical particles and a thin film layer, wherein the optical particles are disposed in the thin film layer
Implementation Method 4
about 30 percent of the light generated by the organic light emitting layer 16 will be lost due to the surface plasmon resonance in the interface between the organic light emitting layer 16 and the metal electrode 18
Implementation Method 5
the organic light emitting layer 16 generates light
Data Source
AI summary
The present invention provides a light extraction film including a micro-lens array film and at least one optical film. The micro-lens array film has a first surface and a second surface opposite to each other, and has a plurality of micro-lenses disposed on the first surface. The optical film covers the first surface, and the optical film includes a plurality of optical particles and a thin film layer. The optical particles are disposed in the thin film layer.