EvoClear^™ 1.56 High Index Lenses
Including SV 70 & 74, FT 28/74, FT 35/74, Tri 7x28/74
Product Specifications & Processing Guide

 

Lens Characteristics
Refractive Index	1.557
Dispersion Value (Abbe)	36.0
Density	1.240
Visible Light	91%
UV Transmission Cutoff	392nm
Chemical Resistance	Excellent
Machinability	Excellent
Rear Surface Coating	Optional
Blank Size	70mm (SV only) and 74mm diameter blanks
Bifocal segment placement	In - 5mm, Down - 5mm
Trifocal segment placement	In - 4.75mm, Down - 4mm
Base Curves	0.50, 2.00, 4.12, 6.12, 8.50, 10.00
Power range	-10.00 to +8.00
Add ranges
FT 28 Bifocal	1.00 to 3.50 in .25 Diopter steps.
FT 35 Bifocal	1.00 to 3.00 in .25 Diopter steps.
FT 7x28 Trifocal	1.50 to 3.00 in .25 Diopter steps.

 

Lens Specifications
Nominal Base Curve	Actual Base Curve	Radius mm	Sphere Sag 50mm	Concave Curve	Thicknesses for 70mm and 74mm Edge    Center
0.50	0.45	1177.775	0.27	3.00	70 74	15.5      12.7 15.2      11.8
2.00	1.88	281.914	1.11	3.00	70 74	15.8      14.4 15.3      13.7
4.12	3.97	133.501	2.36	6.00	70 74	16.0      13.4 15.4      12.2
6.12	5.97	88.777	3.59	6.00	70 74	8.0       14.0 13.9      13.6
8.50	8.43	62.871	5.18	6.00	70 74	10.0      13.3 10.3      13.9
10.00	10.11	52.423	6.34	6.00	70 74	9.7      16.1 Not available

General: These high index material lenses have a refractive index of 1.557. Standard pads and polish materials used for surfacing CR-39^® lenses can be applied to the EvoClear Lenses. If you have questions, please contact Technical Services at 1-800-759-0075.

Abrasion Resistance Coatings: The front surface has the superior protection of the RLXPlus^® non-tintable coating. The uncoated rear surface of the lens provides adequate durability for normal use. Backside coating is recommended if the lens will be worn in a highly abrasive environment. Using a backside coating after surfacing is always recommended when the lens will be anti-reflection coated. However, be sure to verify the impact resistance is maintained, particularly when using a non-tintable coating. Please call Technical Services for the latest test results with various backside coatings.

Tinting and Neutralizing: When using a tintable backside coating, the tinting performance and compatibility with specific neutralizers is coating dependent. We recommend against tinting prior to using a non-tintable coating. Coating applications can change the color or density of tinted surfaces. Special care must be taken when clamping EvoClear single vision and flat-top 28 lenses. The combination of edge pressure and high temperatures will cause warpage. You should position the clamp with only enough pressure to keep the lens from falling out. If the lens does warp during the tinting process, remove the warpage by baking the lens on a flat tray in a 175-200º F oven for 5 minutes.

AR Coating: Confirm the compatibility of AR coatings with the backside coating. Include impact testing. Using a backside coating after surfacing is always recommended when the lens will be anti-reflection coated. Please call Technical Services for the latest test results with various AR coatings.

Computer Calculation of Rx:The easiest, most efficient method to calculate and process values for an Rx is to use an existing computer software package that includes EvoClear lens design data. If your software company has not included this data in its package, our Technical Services group will be happy to provide the necessary specifications. Please forward us the contact name and phone number of your software vendor. If you need a software program for processing lenses, Signet Armorlite has developed a computer program to calculate surfacing data. This program is available through Signet Armorlite's Technical Services Department

Thermal Stability: The new EvoClear Lens material has a similar level of heat sensitivity as other high index materials. The lens can flex if heated under pressure. To prevent warpage, avoid heating the lens over 130º F while it is under pressure from frame or clamping. Warpage can cause a plastic lens to fit loosely in the frame. If the lens should become warped, heat without pressure and allow the lens to return to its original shape.

For More Information: Call Technical Services at (800) 759-0075 for more processing information or technical data. Current customers may also visit our web site at http://www.signetarmorlite.com/ to access other technical information and TIPS.