Gradient-Tinted Polycarbonate Lens via Injection Molding
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Solution Overview
Problem
Current methods for creating gradient-tinted polycarbonate ophthalmic lenses face challenges such as poor dye absorption, dye instability, and adhesion issues between different materials, leading to manufacturing complexities and inefficiencies, especially during the injection molding process.
Innovation Solution
A method involving a multilayer wafer with a gradient-tinted inner layer and a transparent outer layer, where the molten polycarbonate is injected and fused directly to the inner tinted surface during molding, ensuring the tint is embedded within the lens and protected from subsequent processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polycarbonate lenses are dipped in dye tanks to achieve gradient tinting, then the lenses can be colored, but the dye absorption is poor and the process is complex
Solution Approach 1:
The patent applies preliminary action by incorporating the dye into the polycarbonate resin before injection molding. The dye is mixed with the polycarbonate pellets in advance, so that the coloring occurs during the molding process itself rather than requiring a separate post-processing dyeing step. This resolves the contradiction by achieving reliable dye absorption through pre-mixing while eliminating the complexity of separate dyeing equipment and procedures.
Solution Approach 2:
The patent merges the coloring operation with the injection molding process. Instead of treating dyeing as a separate step, the dye incorporation is combined with the resin preparation and molding operations. The dye-resin mixture is injected directly into the mold, merging two previously separate processes (dyeing and molding) into one integrated operation, thereby reducing overall process complexity while ensuring uniform dye absorption.
2Reliability
If additives such as surfactants are used to improve dye absorption in polycarbonate, then dye uptake increases, but the process becomes more complex and costly
Solution Approach 1:
The patent extracts and eliminates the need for surfactant additives by using a dye formulation that is inherently compatible with polycarbonate. Instead of adding complex surfactant systems to improve absorption, the invention selects or modifies the dye to work effectively with the hydrophobic polycarbonate matrix on its own. This removes the need for additional chemical additives, simplifying the manufacturing process while maintaining reliable dye absorption.
3Manufacturing precision
If pre-tinted wafers are used in injection molding, then gradient tints can be achieved, but the heat degrades the dyes and adhesion problems occur
Solution Approach 1:
The patent applies preliminary action in a different way - preparing the dye-resin mixture beforehand but placing it inside the mold cavity rather than using pre-tinted wafers. The dyed polycarbonate resin is injected directly into the mold where it forms the lens with the gradient tint pattern. This approach allows the dye to be protected from degradation because it is incorporated into the resin matrix before molding, and the gradient is achieved through the injection process itself rather than relying on pre-colored materials that would be exposed to degrading conditions.
Solution Approach 2:
The patent uses composite materials by creating a dyed polycarbonate resin system where the dye is uniformly distributed within the polycarbonate matrix. This composite approach ensures the dye is protected by the resin during the high-temperature molding process, preventing degradation while maintaining adhesion. The gradient tint is achieved through controlled injection of this composite material, combining the benefits of dye stability with manufacturing precision.
4Reliability
If excess dye is used to ensure sufficient color remains after processing, then color intensity is maintained, but the coating process becomes contaminated
Solution Approach 1:
The patent applies preliminary action by precisely controlling the dye concentration in the resin mixture before injection molding. The correct amount of dye is incorporated into the polycarbonate pellets in advance, ensuring that sufficient color intensity is achieved within the lens material itself. This eliminates the need to add excess dye that would later need to be removed or would contaminate subsequent coating processes. The gradient tint is formed during molding, so no additional dye is needed afterward.
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
This approach results in consistently reproducible, stable gradient tints that are not affected by the injection molding process, reducing manufacturing costs and complexities while maintaining optical quality and adhesion, allowing for a variety of lens configurations and improved durability.
Implementation Method 1
injecting molten polycarbonate against the inner surface to form the inner lens portion that will be positioned closest to the eye. The injection-molded polycarbonate is fused directly to the inner layer of the wafer during the injection-molding process.
Implementation Method 2
tint the inner layer of a multilayer wafer with a gradient tint
Data Source
AI summary
The present invention describes ophthalmic lens products comprising a multilayer wafer and an injection-molded polycarbonate inner portion. The multilayer wafer includes a dyed, photochromic or polarized layer between a tinted inner layer and an outer polymeric layer. The inner layer may be solid or gradient-tinted. The polycarbonate inner portion of the lens product is directly fused to the tinted inner layer of the multilayer wafer during injection molding. The invention further describes a method to produce a gradient-tinted polarized polycarbonate eyewear lens product by obtaining a multilayer wafer having an outer layer, an inner polycarbonate layer, and a polarized layer between the inner and outer layers, applying a gradient tint to the wafer's inner layer, placing the gradient tinted wafer within an injection-molding cavity, and injecting molten polycarbonate directly against the wafer's gradient-tinted layer to form the inner portion of the lens product and to fuse it to the wafer.