Acrylate TPU Coating for Photochromic Lens Adhesion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for manufacturing photochromic bifocal lenses face challenges with adhesion and photochromic performance, as the coating often builds up at segments, leading to undesirable color changes and instability of photochromic dye molecules at high temperatures, which complicates the processing of high-temperature resins and limits control over the coating layer depth and dye gradient.
Innovation Solution
An in-mold coating process using an acrylate-based thermoset composition with a small fraction of polycarbonate-based thermoplastic polyurethane (TPU) is applied to the lens substrate, allowing for a uniform imbibable bifocal surface that maintains adhesion and enables effective photochromic performance by incorporating a photochromic dye solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a coating is applied to the lens substrate using conventional methods, then the lens can be manufactured, but the coating builds up at segments causing undesirable color changes and poor adhesion
Solution Approach 1:
The patent modifies the chemical composition parameters of the coating material by incorporating TPU (thermoplastic polyurethane) into the acrylate-based coating formulation. This compositional parameter change enables the coating to maintain adhesion strength while achieving uniform distribution at segment interfaces, preventing the buildup problems associated with conventional coatings.
Solution Approach 2:
The patent creates a composite coating material by combining TPU with acrylate-based polymers. This composite formulation leverages the adhesive properties of TPU and the optical clarity of acrylate, resulting in a coating that adheres strongly to the lens substrate and maintains uniformity at bifocal segments without undesirable color changes.
2Productivity
If high-temperature resins are processed to manufacture lenses, then the lens substrate can be formed, but photochromic dye molecules become unstable leading to poor photochromic performance
Solution Approach 1:
The patent applies the coating to the lens substrate immediately after lens formation while the substrate is still in the mold and at elevated temperature. This preliminary action ensures the coating is deposited under optimal conditions before the lens is removed and cooled, allowing the photochromic dye to be incorporated into the coating matrix before any potential degradation can occur.
Solution Approach 2:
The patent utilizes the temperature parameter of the freshly formed lens substrate to facilitate coating application and curing. The elevated temperature of the lens immediately after molding accelerates the curing process and ensures proper adhesion, while the TPU-containing coating formulation maintains photochromic dye stability even at these elevated processing temperatures.
3Ease of manufacture
If the coating layer depth and dye gradient are not controlled, then the manufacturing process is simpler, but the optical quality and photochromic performance are compromised
Solution Approach 1:
The patent employs a self-leveling coating formulation that automatically achieves uniform thickness and proper dye distribution during the coating and curing process. The TPU-containing acrylate coating has rheological properties that allow it to self-adjust and level out, eliminating the need for complex external control mechanisms while ensuring consistent coating depth and optical quality.
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 process achieves high adhesion strength and good photochromic performance, with the TPU-enhanced coating resisting deformation and maintaining integrity even after imbibing with a photochromic solution, while allowing for flexible tint modification and improved optical quality.
Implementation Method 1
an acrylate-based thermoset composition which cures to form an imbibable bifocal surface
Implementation Method 2
a photochromic solution is subsequently imbibed by contact with the segmented surface
Implementation Method 3
photochromic performance by incorporating a photochromic dye solution
Data Source
AI summary
A method and coating used to prepare a photochromically-enabled bifocal ophthalmic lens. The coating is a high adhesive strength acrylate-based coating that contains a small quantity of a polycarbonate-based TPU. The coating is applied to produce an intermediate imbibable bifocal surface. A photochromic solution is subsequently imbibed by contact with the bifocal surface.