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The standard layering technique employed in crafting top-quality sunglassesMirrored sunglasses typically feature a reflective appearance. These lenses are coated with a thin, sparse reflective layer, often referred to as a half-silvered surface. This term originates from the molecular structure, where reflective particles are evenly dispersed across the glass, covering only half of its surface. This layer reflects approximately half of the incoming light while allowing the rest to pass through.
Frequently, the mirror coating is applied in a gradient pattern, transitioning in shade from top to bottom. This design offers extra shielding from overhead light while permitting more light to enter from below or directly ahead. For instance, while driving, it blocks sunlight while ensuring clear visibility of the dashboard. In some cases, the coating is bi-gradient, with mirrored sections at the top and bottom and a clear middle section.
The primary drawback of reflective sunglasses is the susceptibility of the coating to scratches. Although glass is inherently scratch-resistant, the coatings on glass and most plastic lenses are not. To address this, manufacturers have developed methods to apply optically clear, durable films to lenses. These films are composed of materials like diamond-like carbon (DLC) and polycrystalline diamond. Using ionization, a thin yet highly resilient film is formed on the lens surface. Refer to Patent #5,268,217 for more information.
In most situations, this scratch-resistant layer performs effectively. However, manufacturers of sunglasses have yet to achieve the successful application of a scratch-resistant coating over the reflective layer found on mirrored sunglasses. As a result, the scratch-resistant coating is applied initially to safeguard the lenses, followed by the reflective coating on top.
