OLED Overcoating Layer Convex Concave Light Extraction

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Solution Overview

Problem

Organic light emitting diode (OLED) display devices suffer from low light extraction efficiency and deteriorated black color visibility due to high reflectance when microlens arrays are used to enhance light emission.

Innovation Solution

The OLED display device incorporates a substrate with an overcoating layer featuring convex and concave portions, a light emitting layer with varying thicknesses in these portions, and electrodes, where the emitting material layers are positioned to maximize light extraction and minimize reflectance, utilizing specific distance and angle relationships to optimize light emission and black color visibility.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a microlens array is attached to the outer surface of the substrate or a microlens is formed in an overcoating layer, then light extraction efficiency is improved, but visibility of black color is deteriorated due to relatively high reflectance

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidvisibility of black color

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating different surface regions (convex and concave portions) with different optical properties. The convex portions have a first refractive index and the concave portions have a second refractive index, allowing each region to perform different functions: convex portions extract light while concave portions reduce reflectance to improve black color visibility.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining regions with different refractive indices within the overcoating layer. The convex portions are formed with a first refractive index material and concave portions with a second refractive index material, creating a composite structure that simultaneously achieves light extraction and reflectance reduction.

Inventive Principle:

Principle #40Composite materials

2Illumination intensity

If more currents are applied to the light emitting layer, then luminance of the OLED display device is increased, but power consumption is increased and lifetime is reduced

Engineering Contradiction:

ImproveluminanceVSAvoidpower consumption

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

The patent converts the harmful effect of light loss (which occurs naturally in OLEDs) into a benefit by using the microlens structure to redirect and extract more light. This allows the device to achieve higher luminance efficiency without requiring additional current, thereby reducing power consumption and extending lifetime.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Illumination intensity

If more currents are applied to the light emitting layer, then luminance of the OLED display device is increased, but lifetime of the OLED display device is reduced

Engineering Contradiction:

ImproveluminanceVSAvoidlifetime

Core Design Contradiction:

Illumination intensityVSDuration of action of stationary object

Solution Approach 1:

The patent converts the harmful effect of light loss into a beneficial light extraction mechanism. By using the microlens array structure with different refractive indices, more light is extracted from the OLED without increasing drive current, thereby maintaining luminance while extending device lifetime through reduced electrical stress.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 significantly improves light extraction efficiency and enhances the visibility of black colors by reducing reflectance, thereby increasing the overall performance of the OLED display device.

Implementation Method 1

an overcoating layer on the substrate and including a plurality of convex portions and a plurality of concave portions

Methodology Applied

Scientific EffectRefraction: Refraction

Implementation Method 2

a light emitting layer on the first electrode and including a first emitting material layer... the first emitting material layer in the plurality of convex portions is separated from the second electrode by a first distance, and wherein the first emitting material layer in the plurality of concave portions is separated from the second electrode by a second distance different from the first distance

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS11108023B2Organic light emitting diode display device

Publication Date: 2021.08.31 LG DISPLAY CO LTD

AI summary

An organic light emitting diode display device includes a substrate, an overcoating layer on the substrate and including a plurality of convex portions and a plurality of concave portions, a first electrode on the overcoating layer, a light emitting layer on the first electrode and including a first emitting material layer, and a second electrode on the light emitting layer, wherein the first emitting material layer in the plurality of convex portions is separated from the second electrode by a first distance, and the first emitting material layer in the plurality of concave portions is separated from the second electrode by a second distance different from the first distance.