Composite Optical Material for Scratch-Resistant Sunglasses
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Solution Overview
Problem
Current thermoplastic materials for high-end sunglasses, such as polycarbonate and polyamide, face challenges like stress-cracking, compatibility issues with frame materials, and inadequate impact resistance, while newly developed cycloaliphatic copolyesters like Tritan lack inherent scratch resistance and require specific processing conditions.
Innovation Solution
A composite material using a cycloaliphatic copolyester with a glass transition temperature around 115°C, treated with a compatible anti-scratch varnish and bonding primer, applied within a precise temperature range to ensure adhesion and prevent deformation, allowing for the creation of scratch-resistant, versatile, and aesthetically customizable optical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polycarbonate is used as the substrate material, then impact resistance is improved, but stress-cracking sensitivity increases
Solution Approach 1:
The patent uses a composite material consisting of a polycarbonate substrate combined with a silane-based anti-scratch varnish coating. This composite structure allows the polycarbonate to provide impact resistance while the coating layer protects against stress-cracking and surface scratches, resolving the contradiction between impact resistance and stress-cracking sensitivity.
2Reliability
If polyamide is used as the substrate material, then stress-cracking resistance and frame compatibility are improved, but impact resistance decreases
Solution Approach 1:
The patent employs a composite structure with a polyamide substrate that provides stress-cracking resistance and frame compatibility, combined with a silane-based anti-scratch varnish coating that enhances surface hardness and scratch resistance, thereby compensating for polyamide's lower impact resistance compared to polycarbonate.
3Strength
If a silane-based anti-scratch varnish is applied to the copolyester substrate, then scratch resistance is improved, but adhesion difficulty increases
Solution Approach 1:
The patent applies a silane-based bonding primer to the copolyester substrate before applying the anti-scratch varnish. This preliminary action prepares the substrate surface by creating a suitable adhesion layer, ensuring that the subsequent varnish coating adheres properly and achieves the desired scratch resistance without adhesion problems.
Solution Approach 2:
The silane-based bonding primer acts as an intermediary layer between the copolyester substrate and the anti-scratch varnish. This intermediate layer facilitates adhesion by chemically or physically bonding to both the substrate and the varnish, resolving the adhesion difficulty while maintaining scratch resistance.
4Ease of manufacture
If the copolyester glass transition temperature is lowered to improve processing ease, then processing becomes easier, but thermal stability decreases
Solution Approach 1:
The patent selects a copolyester with a specific glass transition temperature range (around 115°C) that balances processing ease and thermal stability. By carefully controlling the copolymer composition and molecular structure, the material achieves suitable melt flow characteristics for injection molding while maintaining adequate thermal stability for the intended application.
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 composite material achieves improved scratch resistance, processing ease, and compatibility with various frame materials, while maintaining optical clarity and allowing for tinting and surface treatments, addressing the limitations of previous materials.
Implementation Method 1
a layer of bonding primer made of polyurethane and a layer of silicone anti-scratch varnish
Implementation Method 2
a copolyester substrate, in particular a copolyester marketed under the trademark "Tritan" and having a glass transition temperature around 115°C
Data Source
AI summary
The invention relates to a composite material for optical use and to the method for obtaining same. This material comprises: a substrate made from thermoplastic copolyester, an adhesion primer layer made from polyurethane, and an anti-scratch silicone varnish which advantageously includes hydroxyl groups, aliphatic CH groups, ester groups and siloxane groups without methyl groups. This material can be use to produce optical parts, in particular spectacle lenses, especially for sunglasses, as well as visors for helmets or masks.