the materials




Two types of materials

The material is an essential component of the corrective lenses. It plays a vital role in providing the corrective function and serves as a platform for the application of one or more coatings.

 

There are essentially two types of lens materials: organic glass and mineral glass.

 

 

Organic glass

There are 2 types of organic materials: thermo-hardened and thermoplastic.

 

Thermo-hardened materials: the most widely used

Example: 1.5 index material

Their many qualities make them the most widely used materials in ophthalmic optics.

 

Properties 

  • Irreversible hardening under the action of heat

  • Highly resistant to shocks

  • Excellent transparency

  • Multiple coloring options

 

Thermoplastic materials: increasingly widespread use

Example: Polycarbonate

These materials are experiencing a revival today, namely with the development of polycarbonates.

 

Properties

  • They can be shaped when heated or injection-molded

  • Excellent resistance to shocks

  • Extreme light

  • Effective protection against ultraviolet rays

Polycarbonate is a soft material that must always be protected by an anti-scratch coating.

 

 

Mineral glass

 

Properties

 

  • Robust

  • Hard

  • Breakable at ambient temperature

  • Transmits visible light

  • Surface can be polished to be made transparent and non reflective

 

Towards a new standard

The 1.5-index mineral lens is the most frequently used material at this time. It is made of 60-70% silicon oxide and of other components (calcium, sodium and boric oxides).

However, 1.6-index lenses are tending to become the new standard. This higher index is obtained by adding a significant share of titanium oxide.

 

 

Refractive indexes according to the type of material

 

Material Refractive index
Mineral glass 1.5 to 1.9
Organic glass – low and medium index 1.5 – 1.56
Organic glass – Polycarbonate 1.59
Organic glass – high and very high index 1.6 – 1.67 – 1.74


 
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