Interference Coating Thickness Ratio for Abrasion-Resistant Optical Articles
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Solution Overview
Problem
Existing optical articles, such as ophthalmic lenses, lack sufficient abrasion resistance and thermal stability while maintaining optical and mechanical performance, and existing manufacturing methods often require heating the substrate, which can be detrimental to heat-sensitive materials.
Innovation Solution
A multilayer interferential coating with a specific ratio of outermost low refractive index layer thickness to outermost high refractive index layer thickness (R D ) is applied, enhancing abrasion resistance and thermal stability without compromising optical properties, and the coating process is conducted without heating the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the total thickness of the anti-reflection coating is increased to improve abrasion resistance, then the coating durability is improved, but the coating complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the thickness parameter ratio between low and high refractive index layers (specifically setting the ratio of sum of low index layer thickness to sum of high index layer thickness between 2.0-3.0) to achieve optimal abrasion resistance without increasing total coating thickness excessively. This parameter optimization resolves the contradiction by finding the right balance point.
Solution Approach 2:
The patent uses composite multilayer structure combining materials with different refractive indices (low index: SiO2, MgF2; high index: TiO2, Ta2O5, ZrO2) to achieve both protective and optical functions. The composite structure allows each layer to contribute differently to abrasion resistance and optical performance.
2Strength
If ion-assisted vapor deposition is used to increase compressive stress and improve coating properties, then the coating hardness is improved, but delamination may occur
Solution Approach 1:
The patent carefully controls the compressive stress parameter within an optimal range by adjusting deposition conditions and layer thickness ratios, avoiding excessive stress that causes delamination while maintaining sufficient hardness. The stress is kept below critical thresholds through parameter optimization.
Solution Approach 2:
Different layers are designed with different local properties - some layers have higher compressive stress for hardness, while others have lower stress for adhesion. The stress distribution is optimized locally in each layer to prevent delamination while achieving overall hardness improvement.
3Reliability
If the substrate is heated during coating deposition to improve coating quality, then the coating adhesion is improved, but heat-sensitive substrates may be damaged
Solution Approach 1:
The patent replaces thermal adhesion improvement methods with mechanical/physical deposition control methods. By optimizing deposition parameters (ion assistance, thickness ratios, deposition speed), good adhesion is achieved without relying on substrate heating, thus avoiding thermal damage to heat-sensitive substrates.
4Reliability
If the ratio of low refractive index layer thickness to high refractive index layer thickness is increased to improve abrasion resistance, then the coating durability is improved, but the optical performance may be affected
Solution Approach 1:
The patent identifies and optimizes the thickness ratio parameter (low index layer total thickness / high index layer total thickness) within the range of 2.0-3.0, which simultaneously achieves good abrasion resistance and maintains optical performance. This parameter optimization resolves the contradiction by finding the optimal balance point.
Solution Approach 2:
The patent uses a slightly excessive thickness of low refractive index layers (ratio 2.0-3.0) to ensure sufficient abrasion resistance, while the optical design compensates for any potential optical performance deviation, achieving both mechanical and optical requirements.
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 coating achieves improved abrasion resistance and high critical temperature without affecting optical performance, and the process is compatible with standard manufacturing processes.
Implementation Method 1
multilayer transparent interferential coating
Implementation Method 2
deposited by ion assistance
Data Source
AI summary
The invention relates toan optical article comprising a substrate having at least one main face successively coated with a monolayer sub-layer having a thickness higher than or equal to 100 nm,a multilayer interferential coating comprising a stack of at least one high refractive index layer having a refractive index higher than 1.55 and at least one low refractive index layer having a refractive index of 1.55 or less, wherein the ratio is higher than or equal to 2, the outermost high refractive index layer(s) of the interferential coating do(es) not comprise TiO2, and the outermost low refractive index layer(s) of the interferential coating is (are) deposited without ionic assistance.