Optical Hard Coating Composition With Controlled Alkoxysilane Hydrolysis
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Solution Overview
Problem
Existing radiation-curable hard coating compositions for optical articles require full or partial hydrolysis of epoxy-functional alkoxysilanes to achieve acceptable performance, leading to unstable silanol groups that spontaneously condense, limiting the formation of improved properties.
Innovation Solution
A curable composition comprising unhydrolyzed and partially hydrolyzed alkoxysilanes, along with an ethylenically unsaturated monomer, is formulated to minimize spontaneous condensation, with controlled hydrolysis conditions and separate addition of components to maintain a high monomeric content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy-functional alkoxysilanes are fully or partially hydrolyzed to achieve hard coating adhesion, then adhesion to ophthalmic lens materials is improved, but silanol groups become unstable and spontaneously condense, limiting performance
Solution Approach 1:
The patent changes the hydrolysis parameter from complete or partial hydrolysis (prior art) to controlled partial hydrolysis maintaining 5-45% hydrolyzed content. This parameter optimization resolves the contradiction by achieving sufficient adhesion through controlled silanol formation while preventing excessive condensation that would compromise stability and performance.
Solution Approach 2:
Instead of complete hydrolysis (excessive action) which causes instability, the patent applies partial hydrolysis (5-45% hydrolyzed alkoxysilane content) - just enough to achieve adhesion without triggering spontaneous condensation. This partial action resolves the contradiction between adhesion improvement and composition stability.
2Strength
If alkoxysilane is reacted with stoichiometrically sufficient water to hydrolyze at least 50% of alkoxy groups, then adhesion is achieved, but spontaneous condensation occurs yielding primarily oligomeric and polymeric products, limiting improved properties
Solution Approach 1:
The patent deliberately limits hydrolysis to 5-45% of alkoxy groups rather than the conventional 50% or complete hydrolysis. This partial action prevents the formation of complex oligomeric and polymeric structures while maintaining sufficient adhesion, thereby resolving the contradiction between achieving adhesion and avoiding molecular structure complexity.
Solution Approach 2:
The patent optimizes the hydrolysis parameter by maintaining unhydrolyzed and partially hydrolyzed alkoxysilanes (5-45% hydrolyzed) rather than complete hydrolysis. This parameter change prevents spontaneous condensation into complex oligomeric/polymeric products while achieving acceptable adhesion, resolving the contradiction between adhesion and molecular structure simplicity.
3Reliability
If conventional hydrolysis methods are used to achieve adhesion, then coating performance is acceptable, but the level of unhydrolyzed epoxy-functional alkoxysilane must be below 50 weight percent, limiting improved properties
Solution Approach 1:
The patent applies partial hydrolysis maintaining 5-45% hydrolyzed alkoxysilane content, which is less than the conventional requirement of below 50% unhydrolyzed content. This partial action achieves acceptable performance while preserving higher monomeric content (55-95% unhydrolyzed), thereby resolving the contradiction between performance reliability and monomeric quantity.
Solution Approach 2:
The patent optimizes the hydrolysis parameter by controlling the degree of hydrolysis to 5-45%, which maintains both acceptable performance reliability and high monomeric content (55-95% unhydrolyzed). This parameter optimization resolves the contradiction between performance requirements and monomeric substance quantity.
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 composition achieves improved properties by maintaining a significant monomeric alkoxysilane fraction, enhancing scratch resistance and stability in optical coatings.
Implementation Method 1
Radiation-curable hard coating products, such as those curable by exposure to ultraviolet radiation
Implementation Method 2
Hydrolysis of the alkoxy groups liberates the associated alcohol to form silanol groups
Data Source
AI summary
A curable composition is provided comprising the following components: (i) a first alkoxysilane which is unhydrolyzed; (ii) a second alkoxysilane which is 5 to 45 percent hydrolyzed; and (iii) an ethylenically unsaturated monomer. The invention also provides coatings formed from the curable composition and articles coated with the curable composition, as well as methods of making the articles.