Microstructured Spectacle Lenses via Segmented Casting Mold
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Solution Overview
Problem
The manufacturing of lenses with diffractive microstructures is complex, especially for thermosetting materials like Perfalit 1.67, where subsequent machining or lithographic processing is difficult, leading to high costs and long cycle times for conventional microstructured casting molds.
Innovation Solution
A method involving a structure carrier layer with a microstructure that is cast onto a lens main body, using a support substrate as a casting mold, allowing for faster curing and reduced tool cycle times, and potentially remaining as a protective layer to prevent damage and soiling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional microstructured casting molds are used for thermosetting materials, then the lens can be produced with diffractive microstructure, but the manufacturing complexity and cycle time increase significantly
Solution Approach 1:
The casting mold is segmented into two separate components: a support substrate that provides mechanical strength and a structure carrier layer that carries the microstructure. This segmentation allows the structure carrier layer to be thin and flexible, enabling rapid curing and easy removal, thus reducing the overall cycle time while maintaining microstructure quality.
Solution Approach 2:
The structure carrier layer acts as an intermediary between the support substrate and the lens material. It transfers the microstructure to the lens during casting and then can be removed or left as a protective layer. This intermediary approach allows the use of thin, flexible structures that cure rapidly without requiring long cycle times.
2Manufacturing precision
If material-removing machining methods are used to create microstructures, then rotationally symmetrical structures can be achieved, but the manufacturing complexity and cost increase
Solution Approach 1:
The microstructure is created in advance on the structure carrier layer using simple casting or embossing techniques before the lens manufacturing process. This preliminary action avoids the need for complex material-removing machining during lens production, significantly reducing manufacturing complexity and cost while maintaining the required rotational symmetry.
Solution Approach 2:
Instead of directly machining the microstructure into the lens material, a negative of the desired microstructure is first created on the structure carrier layer. This copy is then transferred to the lens during casting, replacing complex machining operations with simpler copying and casting processes.
3Ease of manufacture
If the structure carrier layer is made thin and flexible for easy microstructuring, then manufacturing simplicity improves, but the layer requires support during processing
Solution Approach 1:
The system is segmented into a thin structure carrier layer for microstructuring and a separate support substrate for mechanical strength. This segmentation allows each component to be optimized independently: the structure carrier layer remains thin and flexible for easy microstructuring, while the support substrate provides necessary support during processing.
Solution Approach 2:
The support substrate serves multiple functions: it provides mechanical support to the thin structure carrier layer, acts as a casting mold surface, and can be reused for multiple lens productions. This multi-functionality justifies the added complexity by simplifying the overall manufacturing process.
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 method simplifies and cost-effectively produces lenses with diffractive microstructures by reducing cycle times and tool costs, while protecting the microstructure during processing and use, ensuring optical effectiveness and durability.
Implementation Method 1
A lens main body, in particular the lens actually to be produced, or a lens blank which later is further processed to form the actual lens, is then cast on the microstructure of the structure carrier layer
Implementation Method 2
For this purpose, the initially liquid (or viscous) volume material has to be cured (e.g., by polymerization of monomers)
Implementation Method 3
The microstructure serves in particular as a diffractive grating for visible light, preferably for color fringe correction in a spectacle lens
Data Source
AI summary
A method for producing a spectacle lens having in particular a diffractive microstructure on at least one lens surface. To this end, a thin structural support layer is initially made available, which on a surface has a microstructure. A lens main body is then cast to the microstructure of the structural support layer.