SUNLENSIS - MATERIALI E SPESSORI

$CR39 or poly ally diglycol carbonate (PADC) is the most used plastic polymer for making sun lenses and for ophthalmic use. The name originates from the thirty-ninth compound studied as part of a project for the research of transparent resins, by a division of PPG Industries; this project was called “Columbia Resins”. CR39 has a refractive index of (1.498) and a low chromatic dispersion, Abbe number (57.8). Compared to glass it has about half the specific weight and is thinner. It offers impact resistance that exceeds FDA (American regulatory body) requirements but is still not unbreakable and is not recommended for use on eyewear used for certain sporting activities. The CR39 lenses offer high quality vision and transparency, guaranteeing protection from UV rays up to 360nm.$

$Polycarbonate is a thermoplastic polymer obtained from carbonic acid. It has a rather high refractive index (1.587), a low specific weight and high impact resistance, but a low Abbe number (29) which leads to a higher dispersion than materials such as CR39 or glass. It is used to make children’s sunglasses, sports and safety frames. Polycarbonate also offers ultraviolet protection, ensuring a UV protection up to 380 nm as well as good vision quality and transparency.$

INylon, or polyamide, is a new high performance material, because it combines the advantages of polycarbonate and those of CR39 lenses. Nylon lenses have considerable impact resistance and do not break when drilled (making them perfect clip-ons and rimless). It is compatible with all the materials used for frames, lightweight and easy to work with, coated with a hard coating it has a good resistance to impact and scratches. It is recommended for coatings including mirror.

Polarized lenses made of a material called Tri-acetate of cellulose (TAC) have many advantages including a natural abrasion resistance. The TAC lens is lighter and thinner than other lenses. The polarizing filter with which it is fitted allows shielding the reflections created by highly reflective surfaces such as water or asphalt, reducing glare, improving comfort, the perception of contrast and thee vision if the wearer.

$A high optical quality and a remarkable scratch resistance characterize the mineral glass lenses. The most widespread glass in optics is Crown glass which, having a low chromatic dispersion, Abbe number (~60) and a low refractive index (~1.52) ensures clear, comfortable and contrast-rich vision. Crown glass is characterized by a high percentage of silica, variable percentages of lime and soda. The greater specific weight and fragility limit the use in the case of sports and dynamic activities. If various metals are added to the chemical compound of Crown glass, other types of glass with higher refractive index and higher optical qualities can be obtained: for example by adding lead to the glass components we obtain Flint glass with Abbe number (50-55) and refractive index (~1.7).$

Triacetate material (TAC) with increased thickness dedicated to the creation of filters for magnetic clip-ons with "U" groove and for traditional clip-ons. The 1.10 mm thickness makes the lens more resistant, less deformable and more stable in the frame

Polycarbonate Material Low thickness polycarbonate material that allows for less weight and good impact resistance. The BASE 8 does not need to be decentralized due to its low thickness. Shapeable with traditional "V" groove.

Material CR39 in increased thickness for mounting lenses on nylor frames for greater safety of sealing of the side walls to the groove. It can also be used for traditional assemblies with a "V" groove