Reflection-Reducing Layer System for Curved Substrates

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Solution Overview

Problem

Conventional antireflection layer systems on curved substrates with low refractive indices face challenges in achieving broadband antireflection over a wide range of angles due to thickness variations and light scattering issues, particularly on surfaces with refractive indices less than 1.7, where existing methods like plasma etching and vacuum deposition struggle to maintain effective refractive index gradients.

Innovation Solution

A reflection-reducing layer system is developed by depositing a refractive index gradient layer through coevaporation of inorganic and organic materials, followed by a nanostructured organic layer produced via plasma etching, which decreases refractive index from the substrate to the surface, achieving a continuous refractive index gradient with low light scattering and improved adhesion on curved substrates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If plasma etching is used to produce nanostructures for antireflection, then reflection is reduced over a wide angle range, but the layer depth is limited to 100-200 nm which is insufficient for broadband antireflection on curved surfaces

Engineering Contradiction:

Improveangle rangeVSAvoidlayer depth

Core Design Contradiction:

Adaptability or versatilityVSLength of stationary object

Solution Approach 1:

The antireflection function is divided into two segments: a plasma-etched nanostructured layer (100-200 nm deep) for angular independence and a subsequent porous gradient layer for broadband coverage. This segmentation allows each layer to optimize for its specific function while working together to solve the overall problem of broadband antireflection on curved surfaces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution transitions from a single-dimensional approach (either plasma etching or gradient layer) to a two-dimensional layered structure where the first layer provides angular independence and the second layer adds broadband capability through refractive index gradient, achieving both requirements simultaneously.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If vacuum deposition is used to create porous gradient layers at oblique angles, then broadband antireflection is achieved, but additional shading effects occur on curved surfaces making the method unsuitable for curved lenses

Engineering Contradiction:

Improvebroadband coverageVSAvoidsuitability for curved surfaces

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The plasma etching step is performed first to create the nanostructured foundation layer before applying the gradient layer. This preliminary action ensures that the subsequent gradient layer deposition occurs on a pre-structured surface that maintains its properties even on curved substrates, avoiding the shading effects problem.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The nanostructured layer acts as an intermediary between the substrate and the gradient layer, providing a foundation that enables broadband antireflection without requiring oblique deposition angles, thus making the overall structure suitable for curved surfaces.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If conventional interference layer systems are used with alternating high and low refractive index materials, then antireflection is achieved, but the residual reflection is approximately 1% which is not sufficient for broadband applications

Engineering Contradiction:

Improveresidual reflectionVSAvoidbroadband range

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent changes the refractive index parameter continuously through the gradient layer instead of using discrete alternating layers. This continuous variation of the refractive index parameter from the substrate interface to the outer surface enables broadband antireflection with lower residual reflection across a wider spectral and angular range.

Inventive Principle:

Principle #35Parameter changes

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 system provides a broadband and angle-independent antireflection arrangement with low residual reflection, even on curved surfaces, maintaining effectiveness across varying thicknesses and angles, while reducing light scattering and enhancing adhesion by matching the refractive index gradient to the substrate material.

Implementation Method 1

a nanostructure is produced at the surface of a plastics substrate by means of a plasma etching process

Methodology Applied

Scientific EffectPlasma etching: Plasma

Implementation Method 2

depositing a refractive index gradient layer through coevaporation of inorganic and organic materials

Methodology Applied

Scientific EffectCoevaporation: Evaporation

Data Source

PatentUS10539716B2Method for producing a reflection-reducing layer system and reflection-reducing layer system

Publication Date: 2020.01.21 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV

AI summary

A reflection-reducing layer system is disclosed. In an embodiment, the system includes a refractive index gradient layer including an inorganic material and an organic material in a spatially varying composition, wherein the refractive index gradient layer has a refractive index which decreases in a growth direction and an organic layer arranged above the refractive index gradient layer, the organic layer having a surface including a nanostructure.