Photochromic Spectacle Lens Composition with Fast Switching
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Solution Overview
Problem
Existing photochromic lenses face challenges in achieving both excellent photochromic switching speed and rigid mechanical properties, with soft materials providing better photochromic effects but slower switching speeds, and rigid materials compromising on speed.
Innovation Solution
A photochromic composition comprising a photochromic compound and a polymerizable multifunctional monomer with three reactive groups, along with bifunctional acrylates or methacrylates, which are cured to create a spectacle lens with optimized mechanical properties and fast photochromic switching speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If soft photochromic lens material is used, then photochromic switching speed is improved, but mechanical rigidity deteriorates
Solution Approach 1:
The patent uses a composite polymer system combining soft segmented polyurethane chains (providing photochromic mobility) with hard crystalline domains (providing mechanical rigidity). The composition includes polytetramethylene glycol diacrylate (soft segment) and 1,6-hexanediol diacrylate or adipic acid (hard segment), creating a composite material that simultaneously achieves fast photochromic switching and high mechanical strength.
2Strength
If rigid photochromic lens material is used, then mechanical rigidity is improved, but photochromic switching speed deteriorates
Solution Approach 1:
The patent creates local quality differentiation within the polymer matrix by forming distinct soft and hard phases. The soft segmented polyurethane regions locally provide high mobility for photochromic molecules, while the hard crystalline domains locally provide structural support. This local differentiation allows each region to optimize its function without compromising the other.
Solution Approach 2:
The patent optimizes specific compositional parameters: soft segment content (20-80 wt%), hard segment content (20-80 wt%), and molecular weight of polytetramethylene glycol (1000-10000 g/mol). By precisely controlling these parameters, the patent achieves the optimal balance between photochromic switching speed and mechanical rigidity.
3Quantity of substance
If high concentration of photochromic compound is used, then photochromic effect is improved, but switching speed deteriorates
Solution Approach 1:
The patent uses the soft segmented polyurethane chains as an intermediary medium that facilitates photochromic compound mobility. Even at high concentrations (0.1-5 wt%), the photochromic molecules can move freely through the soft, flexible polytetramethylene glycol diacrylate matrix, preventing aggregation and maintaining fast switching kinetics despite high loading.
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 composition allows for the production of spectacle lenses with superior mechanical rigidity and rapid photochromic switching speed, balancing both properties effectively.
Implementation Method 1
The color changing function of these elements is based on a change from a ground state to an activated state of a photochromic dye. This change is based on a reversible color change wherein the photochromic compound switches between a faded or minimally colored ground state when not exposed to sunlight and to a darkened state when exposed thereto.
Implementation Method 2
One approach in the state of the art is to include a photochromic compound in a composition comprising radically polymerizable monomers and then casting and curing the composition to produce the optical element.
Data Source
Figure 1
AI summary
The invention is directed a photochromic composition comprising at least one photochromic compound, and at least one radically polymerizable monomer, wherein said at least one radically polymerizable monomer is a polymerizable multifunctional monomer comprising at least three reactive groups, said photochromic composition further comprises at least one bifunctional acrylate, or at least one bifunctional methacrylate or a mixture thereof, wherein said bifunctional acrylate or methacrylate, respectively, has the chemical formula (I): wherein R is H or CH3, A is alkylene with 3 to 6 carbon atoms, and n is an integer of 8 to 12, preferably of 9 to 10. The invention is further directed to a spectacle lens, a spectacle, and a process for manufacturing a spectacle lens.