Antireflective Polymer Coating With Plasma-Induced Refractive Index Gradient
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Solution Overview
Problem
Conventional antireflective coatings for optical articles, such as ophthalmic lenses, often compromise mechanical properties and are prone to loss of antireflective properties due to mechanical weaknesses, particularly when surface roughening techniques are used.
Innovation Solution
A polymer coating with a refractive index gradient created by plasma treatment using a radio frequency source, resulting in a porosity profile that enhances antireflective properties without compromising mechanical strength, featuring a first superficial layer with a higher refractive index and a second layer with a lower refractive index, both embedded within a polymer coating comprising epoxysilane polymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a stack of inorganic layers is deposited to create antireflective coating, then antireflective properties are achieved, but mechanical properties of the article deteriorate and manufacturing complexity increases
Solution Approach 1:
The patent changes the refractive index parameter within the polymer coating by creating a gradient through plasma treatment. The plasma treatment modifies the polymer structure at different depths, creating layers with different refractive indexes (n1 and n2) without adding separate inorganic material layers, thus maintaining mechanical properties while achieving antireflective functionality
Solution Approach 2:
The patent creates a composite structure within the polymer coating by combining treated and untreated regions. The plasma treatment creates a modified polymer structure with different optical properties while maintaining the polymer matrix, effectively creating a composite material system that achieves antireflective properties without inorganic layers
2Ease of manufacture
If plasma etching is used to control surface roughness for antireflective properties, then antireflective effect is achieved, but mechanical strength decreases and surface becomes vulnerable to mechanical action
Solution Approach 1:
The plasma treatment is applied with controlled depth and intensity to create local modifications only in the subsurface region. The treatment depth is limited to create a specific profile (1-10 nm deep) that affects optical properties while leaving the bulk mechanical properties intact. This localized modification achieves antireflective properties without compromising overall structural integrity
Solution Approach 2:
The plasma treatment creates a porous or microstructured subsurface layer within the polymer coating. This porous structure reduces the refractive index in the treated region, contributing to antireflective properties. The controlled porosity is confined to a thin subsurface layer, maintaining surface hardness and mechanical strength while achieving the desired optical effect
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 achieves effective antireflective properties with improved mechanical strength and durability, maintaining low surface roughness and enhancing the hardness of the polymer coating, thereby maintaining antireflective performance even under external mechanical actions.
Implementation Method 1
This plasma treatment is partially eliminating the organic material of the coating in a subsurface of this coating, creating a porosity that involves a decrease of the refractive index in a certain depth of the coating
Implementation Method 2
said coating comprising a first superficial layer beneath said outer surface having a first refractive index n1 and a second layer beneath said first superficial layer having a second refractive index n2, with n2 < n1
Data Source
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AI summary
The invention concerns an optical article comprising a substrate with two main surfaces, at least one of which is covered by a polymer coating having an outer surface, said coating comprising a first superficial layer beneath the outer surface having a first refractive index n1 and a second layer beneath the first superficial layer having a second refractive index n2, with n2 < n1 and having the lowest refractive index of said polymer coating, and said coating exhibiting antireflective properties due to the difference between refractive indexes n1 and n2, said refractive index difference within the coating resulting from a plasma , corona, and/or an ion beam treatment of an initial polymer coating, through the outer surface. The invention concerns also a method for manufacturing this optical article.