Polyurethane Adhesive for Polarized Lens Wet Edging
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Solution Overview
Problem
Polarized ophthalmic lenses with water-sensitive adhesives experience delamination issues during wet edging processes due to poor wet adhesion, leading to separation of layers and manufacturing challenges.
Innovation Solution
A bi-component polyurethane-based adhesive is developed by reacting polyisocyanate compounds with polyol compounds derived from caprolactone monomers, with specific molecular weight and functionality ranges, to provide moisture resistance and strong adhesion suitable for optical lamination applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a water-based adhesive (polyvinyl alcohol based) is used to laminate the polarizing structure, then the adhesive can be easily applied and manufactured, but the adhesive becomes water-sensitive and exhibits poor wet adhesion, causing delamination during wet edging processing
Solution Approach 1:
The invention changes the chemical composition parameters of the adhesive by replacing water-based polyvinyl alcohol adhesive with solvent-based nitrocellulose adhesive containing specific plasticizers and resins. This parameter change transforms the adhesive from water-sensitive to solvent-based, eliminating delamination issues during wet edging while maintaining ease of application through proper formulation
Solution Approach 2:
The invention uses a composite adhesive formulation combining nitrocellulose base resin with plasticizers (triacetin, dibutyl phthalate) and additional resins (cellulose acetate butyrate, polyvinyl butyral). This composite material approach creates an adhesive system that integrates multiple functions: adhesion, flexibility, water resistance, and processing compatibility, resolving the contradiction between ease of manufacture and wet adhesion reliability
2Ease of manufacture
If the polarizing structure is laminated with conventional adhesives, then the structure can be assembled, but the adhesive fails to resist water during wet edging, leading to separation at the edges
Solution Approach 1:
The invention employs a solvent-based adhesive system where the solvent evaporates during drying, leaving behind a permanent adhesive matrix. This approach replaces the need for water-resistant barriers with an inherently water-resistant adhesive chemistry, eliminating the delamination problem at low cost and simple implementation
Solution Approach 2:
The adhesive formulation parameters are specifically adjusted to include nitrocellulose as base resin with controlled amounts of plasticizers and resins, creating a film with specific properties: flexibility for assembly, water resistance for wet edging, and proper adhesion strength. This parameter optimization resolves the contradiction between assembly ease and water resistance
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 polyurethane adhesive ensures excellent adhesion and moisture resistance, preventing delamination during wet edging and maintaining high optical quality, making it suitable for various polarized lens manufacturing methods like lamination, casting, or film injection molding.
Implementation Method 1
a bi-component polyurethane based adhesive obtained, by reacting at least one polyisocyanate compound with at least one polyol compound derived from caprolactone monomer
Data Source
Figure 1
AI summary
A polyurethane based adhesive containing one polyol compound derived from caprolactone monomer having a number average molecular weight between 200 and 1000 combined with a polyisocyanate compound. The functionality of the polycaprolactone polyol is between 1 and 4. Other aspects of the invention include a polarizing layered structure, a polarized lens and a method for manufacturing same all of which include the polyurethane based adhesive. The adhesive avoids delamination and is useful in optical applications where it will be in contact with water, for example during surfacing or edging process.