Tinting Optical Substrates with Polyoxyalkylene Coatings
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Solution Overview
Problem
Optical substrates, particularly polycarbonate and thermoset substrates, face challenges with poor abrasion resistance and the lack of tintable abrasion-resistant coatings, as existing hard coatings are either non-tintable or offer poor abrasion resistance when tintable.
Innovation Solution
A method and composition involving a polymerizable monomer with a polyoxyalkylene backbone, an abrasion-resistant agent, and a high crosslinking monomer are applied to form a tintable and abrasion-resistant coating layer on optical substrates, allowing for the introduction of tinting compounds, with specific ratios of these components optimizing tintability and abrasion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If abrasion resistant hard coatings are applied to optical substrates, then abrasion resistance is improved, but tintability deteriorates
Solution Approach 1:
The patent applies composite materials by combining polyoxyalkylene monomers with abrasion-resistant agents (such as colloidal silica, aluminum oxide, or titanium dioxide) and high crosslinking monomers to create a multi-component coating system. This composite formulation enables the coating to simultaneously achieve high abrasion resistance through the abrasion-resistant agent and good tintability through the polyoxyalkylene matrix that can incorporate dye molecules, thus resolving the contradiction between these two properties.
Solution Approach 2:
The patent utilizes parameter changes by controlling the molecular structure of polyoxyalkylene monomers (specifically those with at least four contiguous oxyalkylene units) and adjusting the ratio of monomers to abrasion-resistant agents. By optimizing these parameters, the coating achieves a balance where the polyoxyalkylene chains provide sufficient flexibility and dye uptake capability while the abrasion-resistant agent provides hardness, thereby resolving the tintability-abrasion resistance trade-off.
2Strength
If organosiloxane hard coatings are used to improve abrasion resistance, then abrasion resistance is improved, but the coating becomes non-tintable
Solution Approach 1:
The patent extracts the tintability function from the organosiloxane coating system by removing the organosiloxane resin and replacing it with polyoxyalkylene monomers that inherently possess dye uptake capability. The abrasion resistance function is maintained through the inclusion of abrasion-resistant agents, thus separating and independently optimizing the two functions that were conflicting in the organosiloxane system.
Solution Approach 2:
The patent changes the chemical composition parameters by substituting organosiloxane resins with polyoxyalkylene monomers having specific structural characteristics (at least four contiguous oxyalkylene units). This parameter change fundamentally alters the coating's chemical nature to enable dye incorporation while maintaining abrasion resistance through the abrasion-resistant agent component.
3Strength
If acrylate based hard coatings are applied to thermoplastics, then abrasion resistance is improved, but the coatings are generally not tintable
Solution Approach 1:
The patent creates a composite coating system that replaces conventional acrylate resins with polyoxyalkylene monomers combined with abrasion-resistant agents. This composite approach allows the coating to achieve abrasion resistance from the inorganic abrasion-resistant agent while the polyoxyalkylene component provides the organic matrix necessary for dye incorporation, thus resolving the tintability issue inherent in acrylate-based hard coatings.
4Ease of manufacture
If in-mould coating is used to apply coatings to substrates, then manufacturing cost is reduced, but no known systems provide tintable in-mould coatings
Solution Approach 1:
The patent achieves universality by formulating a multi-functional coating composition that can be applied via in-mould coating processes while simultaneously providing abrasion resistance and tintability. The coating system is designed to perform multiple functions (adhesion, abrasion resistance, and dye uptake) within a single formulation, enabling cost-effective manufacturing through in-mould application while overcoming the limitation of non-tintable coatings.
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 provides a coating that is up to 3 times more abrasion-resistant than uncoated CR-39 in standard tests and up to 20 times more resistant in steel wool tests, while maintaining tintability, effectively addressing the limitations of existing coatings.
Implementation Method 1
polymerising the coating composition to form an abrasion resistant coating layer
Implementation Method 2
introducing a tinting compound into the coating layer to thereby tint the optical substrate
Data Source
AI summary
The present invention provides a method for tinting an optical substrate. The method includes the steps of applying a coating composition containing: • a polymerisable monomer having a polyoxyalkylene backbone containing at least four contiguous oxyalkylene units, and • an abrasion resistant agent and/or a high crosslinking polymerisable monomer to the optical substrate, polymerizing the coating composition to form an abrasion resistant coating layer, and introducing a tinting compound into the coating layer to thereby tint the optical substrate. The invention also provides a coating composition and an optical substrate that is tinted according to the method of the invention.