Table 4.
Optical properties of CPI films.
| Samples | λcut
a (nm) |
T400
a (%) |
T450
a (%) |
nTE a | nTM a | nav a | Δn a | Rth
a (nm) |
L* a | a* a | b* a | Haze (%) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| CPI-Ia | 303 | 82.1 | 84.5 | 1.6296 | 1.6298 | 1.6296 | 0.0002 | 2 | 95.24 | 0.01 | 1.01 | 1.3 |
| CPI-IIa | 304 | 81.0 | 83.2 | 1.6306 | 1.6315 | 1.6309 | 0.0009 | 9 | 95.27 | −0.02 | 0.86 | 2.8 |
| CPI-Ib | 298 | 84.6 | 86.4 | 1.6091 | 1.6100 | 1.6094 | 0.0009 | 9 | 95.56 | −0.01 | 0.76 | 1.2 |
| CPI-IIb | 299 | 82.2 | 84.0 | 1.6119 | 1.6127 | 1.6122 | 0.0008 | 8 | 95.52 | 0.01 | 0.67 | 2.1 |
| CPI-ref1 | 287 | 84.9 | 86.7 | 1.5419 | 1.5382 | 1.5407 | 0.0037 | 37 | 96.28 | −0.01 | 0.60 | 1.8 |
| CPI-ref2 | 293 | 86.3 | 87.9 | 1.5432 | 1.5371 | 1.5412 | 0.0061 | 61 | 96.26 | −0.01 | 0.65 | 0.6 |
a λcut: Cutoff wavelength. T400, T450: Transmittance at the wavelengths of 400 nm and 450 nm with a thickness of 20 μm, respectively. nTE, nTM: In-plane and out-of-plane refractive indices of the CPI films, respectively. nav: Average refractive indices of the CPI films. Δn: Birefringence, Δn = nTE − nTM. Rth: Optical retardation, Rth = Δn × d, d = 10 μm. L*, a*, b*, see Measurements part.