Plastic Lens Materials Flashcards
1
Q
CR39 (Essilor Orma)
A
N Value = 1.498 V Value = 58 Specific Gravity = 1.32 CVF = 1.05 Reflectance = 3.97% UV cut off = 355nm
2
Q
Key features and benefits of CR39
A
- Excellent Optics
- Low cost
- Easy to tint
- Lowest reflectance so doesnt need MAR
3
Q
Disadvantages of CR39
A
- Thickness
- Shatters under high impact into hooked shards
- Not very scratch resistant
4
Q
Trivex
A
N value = 1.53 V value = 45 Specific Gravity = 1.11 CVF = 0.99 Reflectance = 4.39% UV Cut off = 400nm
5
Q
Key features and Benefits of Trivex
A
- High impact resistance
- Blocks 100% of UVA & UVB
- Higher V value than polycarbonate
- Lightest lens material available
- Good chem resistance
6
Q
Disadvantages of Trivex
A
- Tinting not possible
- Slightly thicker than polycarbonate
- Scratches easily
- Difficult to glaze
7
Q
Polycarbonate (Essilor airwear)
A
N = 1.59 V Value = 30 Specific Gravity = 1.21 CVF = 0.89 Reflectance - 5.19% UV Cut off = 385nm
8
Q
Key features and Benefits of Polycarbonate
A
- High impact resistance
- Lighter than high index plastic lenses
- Thinner than trivex
- Good UV protection
- Thermoplastic - can be remoulded
- Good for Supra and Rimless as you can drill into it and cut grooves
9
Q
Disavantages of Polycarbonate
A
- Not good for chem resistance - if used with acetone, lens goes milky
- Low V value means more dispersion
- Not very scratch resistant
- Difficult to tint
10
Q
1.6 Plastic (Essilor Ormix)
A
N = 1.60 V Value = 42 Specific Gravity = 1.30 CVF = 0.87 Reflectance = 5.33% UV Cut off = 395nm
11
Q
Key features and Benefits of 1.6 Plastic
A
- Thin and lightweight
- Less costly than 1.74 plastic
- Good UV protection
12
Q
Disadvantages of 1.6 Plastic
A
- Low V value
- Difficult to tint
- Flatter so more reflections (MAR coated)
13
Q
1.67 Plastic (Essilor Stylis)
A
N = 1.67 V Value = 32 Specific Gravity = 1.36 CVF = 0.78 Reflectance = 6.29% UV Cut off = 395nm
14
Q
Key features and Benefits of 1.67 Plastic
A
- Cheaper than 1.74
- Good UV protection
- Thin
15
Q
Disadvantages of 1.67 Plastic
A
- Low V value
- Diff to tint
- Flatter so more reflections (MAR coated)