Eyeglass Lens Hard Coat Layer Crack Suppression
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Solution Overview
Problem
Spectacle lenses with hard coat layers face issues of crack generation and poor weather resistance, despite improved abrasion resistance.
Innovation Solution
A spectacle lens with a polyurethane-based substrate and a hard coat layer formed by curing a composition containing inorganic oxide particles, a silane coupling agent, and a polyfunctional epoxy compound, where the epoxy compound constitutes 45-60 mass% of the matrix component, and the hard coat layer has an average thickness of 10-50 µm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coat layer is formed on spectacle lenses to improve abrasion resistance, then scratch resistance is improved, but cracks are likely to be generated and weather resistance deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the hard coat layer by incorporating specific components: a silane coupling agent (γ-glycidoxypropyltrimethoxysilane), a polyfunctional epoxy compound (trimethylolpropane polyglycidyl ether), and inorganic oxide particles (silicon oxide). The epoxy compound content is controlled at 45-60 mass% of the matrix component. These parameter changes create a crosslinked network structure that provides both abrasion resistance and crack suppression, resolving the contradiction between hardness and weather resistance.
Solution Approach 2:
The patent creates a composite hard coat layer combining organic components (silane coupling agent, epoxy compound) with inorganic components (silicon oxide particles). This composite structure integrates the benefits of both material types: the organic matrix provides flexibility and adhesion to prevent cracking, while the inorganic particles contribute to hardness and abrasion resistance. The resulting composite material achieves both improved scratch resistance and enhanced weather resistance.
2Strength
If the hard coat layer thickness is increased to improve scratch resistance, then abrasion resistance is improved, but initial cracks and peeling are more likely to occur
Solution Approach 1:
The patent optimizes the thickness parameter of the hard coat layer to 10-50 µm, avoiding excessive thickness that would cause internal stresses and cracking. Simultaneously, the chemical composition is adjusted with 45-60 mass% epoxy compound content to create a flexible crosslinked network. This dual parameter optimization allows the film to maintain integrity while providing sufficient scratch resistance.
Solution Approach 2:
The patent creates local quality variations within the hard coat layer through the distribution of inorganic oxide particles (silicon oxide) throughout the organic matrix. This heterogeneous structure provides localized reinforcement against scratching while the continuous organic phase maintains overall film flexibility and adhesion. The silane coupling agent further enhances local bonding at the interface between organic and inorganic phases, preventing peeling.
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 effectively suppresses crack generation and enhances weather resistance, providing high scratch resistance and maintaining the hardness of the hard coat film while preventing initial cracks and peeling.
Implementation Method 1
a silane coupling agent (B) and a polyfunctional epoxy compound (C). The curable composition is applied to the lens substrate and cured to form the hard coat layer
Implementation Method 2
the epoxy compound constitutes 45-60 mass% of the matrix component, and the hard coat layer has an average thickness of 10-50 µm
Implementation Method 3
a curable composition containing inorganic oxide particles (A), a silane coupling agent (B), and a polyfunctional epoxy compound (C)
Data Source
AI summary
Provided is a spectacle lens which can suppress the generation of cracks at the time of manufacture. The spectacle lens is a spectacle lens which includes a lens substrate and a hard coat layer and in which the hard coat layer is obtained by curing a curable composition containing inorganic oxide particles, a silane coupling agent, and a polyfunctional epoxy compound contained at more than 40% by mass and 60% by mass or less in a matrix component.