Whether used for eye protection or vision correction, spectacles with lenses made of plastic are preferred over glass for their considerably lower weight and better fracture strength. In order to provide the required life-long quality of such lenses a specific scratch-resistance is necessary.
Nowadays, spectacle lenses made of plastic are commonly provided with an anti-scratch, dirt-repellent and anti-reflective surface. They are vacuum coated using a physical vapour deposition (PVD) method with up to 10 protective layers, each only a few nanometres thick, which together ensure very high scratch resistance. Hardness and scratch-resistance of these coatings are directly related: therefore, determining the hardness is a suitable method for quantifying the quality of these protective coatings.
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Where will all the raw materials come from for the manufacturing process? How will they be transported to the factory and what is going to be done with the various scrap and residues?