Variable Index Light Extraction Layer for Transparent Displays

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Solution Overview

Problem

Traditional light extraction layers in optical stacks, such as those used in displays and lighting applications, often suffer from being non-transparent and distorting, making it difficult to view images or objects clearly due to scattered light.

Innovation Solution

A variable index light extraction layer is introduced, comprising microreplicated posts with distinct regions of different refractive indices, where one region has a lower effective index of refraction than the other, allowing for selective extraction of light at supercritical angles without significant scattering of subcritical light, thus maintaining image clarity and resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If traditional light scattering features (diffusely reflective printed extraction dots or structures) are used in light extraction layers, then light extraction capability is improved, but optical transparency and image clarity deteriorate

Engineering Contradiction:

Improvelight extraction capabilityVSAvoidimage clarity

Core Design Contradiction:

Illumination intensityVSLoss of information

Solution Approach 1:

The patent applies local quality by creating distinct first and second regions with different refractive indices within the light extraction layer. The first region (with lower effective index) and second region (with higher effective index) are spatially separated and do not overlap, allowing each region to perform specialized optical functions. This local differentiation enables selective light extraction in specific areas while maintaining transparency in other areas, thus resolving the contradiction between light extraction capability and image clarity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining multiple substances with different refractive indices within a single light extraction layer. The layer comprises a first substance in the first region and a second substance in the second region, creating a composite structure that simultaneously achieves light extraction functionality and optical transparency. This composite approach allows the layer to extract light effectively while minimizing distortion and maintaining image quality.

Inventive Principle:

Principle #40Composite materials

2Productivity

If light scattering features are added to extract light from the lightguide, then light extraction efficiency is improved, but light scattering increases causing distortion

Engineering Contradiction:

Improvelight extraction efficiencyVSAvoidlight scattering

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by systematically varying the refractive index parameter across different regions of the light extraction layer. The first region has a lower effective refractive index while the second region has a higher effective refractive index. This parameter differentiation allows the structure to control light propagation and extraction without relying on traditional scattering mechanisms, thereby improving light extraction efficiency while minimizing harmful light scattering and distortion.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a uniform light extraction layer is used, then manufacturing is simplified, but selective light extraction at different angles is limited

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidselective light extraction capability

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent applies segmentation by dividing the light extraction layer into distinct first and second regions with different refractive indices. This segmentation allows each region to be optimized for specific light extraction functions - the first region for extracting light at certain angles and the second region for extracting light at different angles. Despite this functional segmentation, the regions are arranged to not overlap from plan view, which simplifies the manufacturing process compared to more complex three-dimensional structured designs.

Inventive Principle:

Principle #1Segmentation

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 variable index light extraction layer effectively extracts light at supercritical angles while minimizing light scattering, resulting in a transparent and non-distorting layer that enhances image clarity and contrast in reflective displays and lighting applications.

Implementation Method 1

The first region has a lower effective index of refraction than the second region... selectively extraction of light at supercritical angles without significant scattering of subcritical light

Methodology Applied

Scientific EffectRefraction: Refraction

Data Source

PatentUS9651728B2Variable index light extraction layer with microreplicated posts and methods of making the same

Publication Date: 2017.05.16 3M INNOVATIVE PROPERTIES CO

AI summary

Variable index light extraction layers (100) that contain a plurality of microreplicated posts (120) are described. The variable index light extraction layers contain a plurality of microreplicated posts (120), a first region including a first lower-index substance (130) and a second region including a second higher-index substance (140). Optical films can use the variable index light extraction layers (100) in front lit or back lit display devices.