CR-39 refers to the material that is used to make the majority prescription lenses. It is an optical grade plastic polymer recognised for its light weight, chemical resistance properties and 'tint-ability'. In comparable prescriptions it is approximately half the weight of glass lenses, while being slightly thicker. Its impact resistance is greater than glass but does not rise to the level of polycarbonate and it should not be considered for applications where impacts are prevalent. On this basis, it is not recommended for active sports and motorcycling. It is more scratch resistant than polycarbonate, but will scratch if not properly taken care of.
Polycarbonate is an impact resistant material. It is becoming used more widely in recent times - especially for motorcycling and action sports. It is also used frequently for the glazing of rimless frames because of these properties. Although polycarbonate is impact resistant, it should not be considered indestructible. Polycarbonate is the strongest material available and will have the tendency to break into larger pieces, instead of the CR39's smaller pieces, and is, consequently, less hazardous. Polycarbonate is thinner than standard CR39.
Polycarbonate lenses are ten times more impact resistant than other plastics making them highly suitable for action sports or folk that are a little (shall we say) heavy-handed! They offer UV protection and stop 99.9% of rays from the sun, fluorescent lights and computer screens. Our polycarbonate lenses are supplied with a scratch resistant coating and are thinner than standard lens and therefore more comfortable to wear.
Comparison of Lens Materials & Material Characteristics
Polycarbonate
- Strongest material for impact resistance
- Lightweight
- Can be coated for scratch resistance
- Most have built-in UV radiation protection
Plastic (CR39)
- About one-half the weight of glass
- Resistant to solvents and pitting
- More choices for coatings and tinting
No comments:
Post a Comment