UV Curable Epoxy Acrylate Optical Coatings
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Solution Overview
Problem
Existing UV curable abrasion resistant coatings have poor adhesion and abrasion resistance on thermoset optical elements, while thermally cured coatings are time-consuming and prone to contamination.
Innovation Solution
A UV curable coating composition containing a polymerisable epoxy monomer and a (meth)acrylate monomer, which forms an abrasion resistant coating by ionically polymerising, enhancing adhesion to thermoset materials without compromising abrasion resistance, and includes a cationic initiator and colloidal silica for improved hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a UV curable coating composition is used to form an abrasion resistant coating on thermoset optical elements, then processing time is reduced and contamination is minimized, but adhesion and abrasion resistance are poor
Solution Approach 1:
The patent uses a composite coating composition containing both epoxy monomers and (meth)acrylate monomers. The epoxy component provides adhesion to thermoset substrates through chemical bonding, while the (meth)acrylate component provides abrasion resistance through crosslinked network formation. This composite approach allows simultaneous achievement of good adhesion and abrasion resistance in a UV curable system.
Solution Approach 2:
The patent modifies the chemical composition parameters of the coating by incorporating specific ratios of epoxy monomers (with 2-4 epoxy groups per molecule) and (meth)acrylate monomers (with 2-6 polymerisable double bonds). This parameter optimization enables the coating to achieve both adequate adhesion and abrasion resistance while maintaining UV curability and fast processing.
2Reliability
If a thermal curing process is used to form an abrasion resistant coating, then adhesion and abrasion resistance are improved, but processing time increases and contamination risk increases
Solution Approach 1:
The patent replaces the thermal curing mechanism with a photopolymerisation mechanism using UV light initiation. The coating composition includes photopolymerisable functional groups (epoxy and (meth)acrylate) that undergo crosslinking upon UV irradiation, eliminating the need for thermal curing while maintaining coating performance.
Solution Approach 2:
The UV curing process allows for periodic or controlled irradiation cycles, enabling precise control over the curing process timing and duration. This provides better process control compared to thermal curing, reducing the risk of contamination during extended processing times.
3Strength
If a rigid multifunctional monomer is used in the coating composition, then abrasion resistance is improved, but adhesion to thermoset materials deteriorates
Solution Approach 1:
The patent employs a composite monomer system where rigid multifunctional (meth)acrylate monomers provide abrasion resistance through dense crosslinked networks, while flexible epoxy monomers provide adhesion through chemical bonding to thermoset substrates. The synergistic combination allows both properties to coexist without compromising either.
Solution Approach 2:
The coating composition assigns different functional roles to different monomer components: the (meth)acrylate monomers form the abrasion-resistant surface layer through crosslinking, while the epoxy monomers provide adhesion at the substrate interface. This local differentiation of functionality within the coating structure resolves the contradiction between hardness and adhesion.
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 excellent abrasion resistance, comparable to traditional polyacrylate hard coats, with reduced contamination risks and faster processing times, as demonstrated by high ratings in steel wool and Bayer abrasion resistance tests.
Implementation Method 1
the composition is then cured to form the coating... capable of being UV cured... cationic photopolymerisation
Data Source
AI summary
The invention provides an abrasion resistant coating composition for an optical element. The composition includes a polymerisable epoxy monomer having an average of at least two epoxy groups in the monomer molecule. The composition is capable of forming an abrasion resistant coating on an optical element after ionic polymerisation. The coating composition may also include an ionically polymerisable alkene monomer having an average of at least two polymerisable double bonds in the molecule.