Crosslinked Photochromic Polyurethane Laminate for Uniform Lens Molding
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Solution Overview
Problem
Existing methods for incorporating photochromic properties into plastic lenses, such as polycarbonate, suffer from issues like slow activation and fading rates, low activation intensity, and poor replication of segment lines due to polyurethane bleeding and thickness non-uniformity, especially in injection molding processes.
Innovation Solution
A photochromic polyurethane laminate is developed with a crosslinked structure using a crosslinking agent with three or more functional groups, enhancing mechanical strength, adhesion, heat resistance, and bleeding resistance, allowing for improved manufacturing of lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating containing dissolved photochromic compounds is applied to the surface of a lens, then photochromic properties are incorporated into the lens, but the coating thickness must be about 25 μm or more to provide sufficient light blocking quality, which causes unacceptable segment line nonuniformity and affects surface smoothness
Solution Approach 1:
The patent changes the concentration parameter of photochromic compounds in the coating solution to achieve sufficient light blocking quality with a thinner coating layer. By optimizing the compound concentration, the patent reduces coating thickness from 25 μm or more to a thinner layer that maintains adequate photochromic performance while eliminating segment line nonuniformity issues
Solution Approach 2:
The patent uses a composite coating system comprising a base coating material and dissolved photochromic compounds, creating a multi-component material system that provides both structural integrity and photochromic functionality in a single thin layer, avoiding the need for thick coatings
2Ease of manufacture
If polyurethane is used as the base coating material for photochromic lenses, then the material provides good coating properties, but polyurethane bleeding occurs during injection molding, causing poor replication of segment lines and thickness non-uniformity
Solution Approach 1:
The patent extracts the problematic polyurethane base coating material from the formulation and replaces it with alternative materials that do not exhibit bleeding behavior during injection molding, thereby eliminating segment line replication issues while maintaining coating applicability
Solution Approach 2:
The patent changes the material composition parameters by selecting base materials with different thermal and rheological properties that resist bleeding at injection molding temperatures, thus maintaining manufacturing ease while improving segment line precision
3Reliability
If a thicker coating is used to provide sufficient photochromic compound quantity, then light blocking quality improves, but surface smoothness and segment line uniformity deteriorate
Solution Approach 1:
The patent changes the concentration parameter of photochromic compounds in the coating solution to achieve sufficient light blocking quality with a thinner coating layer. By optimizing the compound concentration, the patent reduces coating thickness from 25 μm or more to a thinner layer that maintains adequate photochromic performance while eliminating segment line nonuniformity issues
Solution Approach 2:
The patent optimizes the local distribution and concentration of photochromic compounds within the coating layer to ensure uniform light blocking performance across the entire lens surface, including segment areas, thereby maintaining surface smoothness while achieving adequate photochromic effect
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 crosslinked polyurethane laminate improves mechanical strength, adhesion, and resistance to bleeding, resulting in more uniform and robust photochromic lenses with enhanced performance.
Implementation Method 1
a photochromic polyurethane laminate that includes a first resin layer, a second resin layer and a polyurethane layer having photochromic properties interposed between the first and second resin layer
Data Source
AI summary
A photochromic polyurethane laminate wherein the photochromic polyurethane layer of the laminate has been crosslinked with an isocyanate-active prepolymer using a crosslinking agent. The crosslinking agent is formulated to have at least three functional groups that are reactive with functional groups of the polyurethane or of the isocyanate-active prepolymer. A method of making the photochromic polyurethane laminate includes steps of causing the crosslinking.