Prismatic Microstructured Films for OLED Light Extraction

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Solution Overview

Problem

Current OLED devices face challenges in achieving uniform white light emission due to limited color mixing, primarily caused by inner reflection at the substrate-air boundary, which restricts the out-coupling of generated light from single color sources.

Innovation Solution

A microstructured film with prismatic features is applied externally to the OLED device on the substrate, enhancing light extraction and aiding in uniform luminance distribution by diffusing light from each stripe, allowing it to blend with adjacent stripes and produce a broader emission spectrum.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a transparent substrate is used in bottom-emitting OLED devices, then light can be emitted from the substrate side, but inner reflection at the substrate-air boundary limits light out-coupling efficiency

Engineering Contradiction:

Improvelight out-coupling efficiencyVSAvoidinner reflection at substrate-air boundary

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

A microstructured film is introduced as an intermediary layer between the OLED device and the external environment. This film with prismatic or lens-like features acts as a mediator that modifies light propagation paths, reducing total internal reflection at the substrate-air interface and enhancing light extraction efficiency.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention transitions from a planar substrate surface to a microstructured surface with three-dimensional prismatic or lens-like features. This dimensional change creates multiple light extraction pathways and angles, effectively reducing the impact of total internal reflection and improving overall light out-coupling.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Illumination intensity

If separated elements emitting red, green and blue light are used, then color display is achieved, but uniform white light emission is difficult to obtain due to limited color mixing

Engineering Contradiction:

Improveuniformity of white light emissionVSAvoidcolor mixing capability

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The microstructured film merges the light from separated red, green, and blue emitting elements by redirecting and overlapping their emission paths. This spatial merging enables effective color mixing and produces uniform white light emission across the display area.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The prismatic or lens-like microstructures use curved or angled surfaces to redirect light from discrete color elements. These geometric features facilitate the mixing of different color wavelengths by redirecting them to overlap spatially, achieving uniform white light emission.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Illumination intensity

If microstructured film is applied to enhance light extraction, then luminance uniformity improves, but device complexity increases

Engineering Contradiction:

Improveluminance uniformityVSAvoidstructure complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The invention uses a thin microstructured film applied to the substrate surface rather than integrating complex microstructures directly into the OLED device layers. This approach enhances light extraction and luminance uniformity while minimizing increases in device complexity and manufacturing difficulty.

Inventive Principle:

Principle #30Flexible shells and thin films

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 approach significantly improves luminance uniformity and efficiency, achieving a 29-35% increase in average luminance with more consistent light distribution across the display, enabling effective white lighting and color-tunable applications.

Implementation Method 1

the use of microstructured film splits the emission from each stripe so that it blends with the split emission from adjacent stripes to obtain a broader emission spectrum

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 3

The out-coupling of generated light in single color OLED devices is limited due to inner reflection at the substrate-air-boundary caused by the significant difference in the refractive index

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS7586245B2Using prismatic microstructured films for image blending in OLEDS

Publication Date: 2009.09.08 AMS OSRAM INT GMBH

AI summary

An apparatus such as a light source is disclosed which has an OLED device and a microstructured film disposed on the substrate or transparent electrode of said OLED device and on the exterior of said OLED device. The microstructured film contains features which diffuse light emitted by said OLED device and increase the luminance of the device.