Polyester (OKP Optical Plastic): For injection molding, raw material of the film
OKP is a special polyester for optical use arising from coal chemistry. OKP has a high refractive index of 1.6 or more, extremely low birefringence, and high fluidity. Therefore, it is easy to obtain high performance injection-molded objects and films.
Features
High refractive index
Low birefringence
Low Abbe number
High fluidity
Example of usage
Various optical lens
Various optical films
Other optical elements
Comparison of birefringence
OKP4
PMMA (methyl methacrylate resin)
Polycarbonate resin
COP (cyclo-olefin polymer)
Abbe number
Physical properties
| Properties | Unit,Conditions | OKP4 | OKP4HT | OKP-1 | Reference | |
|---|---|---|---|---|---|---|
| PC (Optical grade) |
COP | |||||
| Physical properties | ||||||
| Glass transition temperature | ℃ | 121 | 142 | 133 | 145 | 139 |
| Heat distortion temperature | ℃,1.80MPa | 103 | 119 | 112 | 123 | 122 |
| Linear expansion coefficient | ×10-5/℃ | 7.4 | 6.3 | 6.5 | 7.0 | 6.0 |
| Optical properties | ||||||
| Refractive index (D line) | - | 1.607 | 1.632 | 1.642 | 1.585 | 1.531 |
| Abbe number | νD | 27 | 23 | 22 | 29 | 56 |
| Birefringence | ×10-4,OGC method | ＜ 5 | 55 | ＜ 5 | 128 | 53 |
∗ Values of other resins indicated for comparison are quoted form catalogs and published documents.
New development product
Optical films (OKP-F)
Optical film can be produced by the melt extrusion method. It's a very low birefringence, orientation birefringence does not occur mostly by stretched.
