an ordinary refractive index or an extraordinary refractive index as a function of the applied field being either on or off, respectively. In the instance where the ordinary refractive index of the liquid crystal droplets is matched closely with the refractive index of the surrounding polymer matrix, light incident on a film comprising liquid crystal droplets and polymer is not refracted and the film is substantially transparent. In the instance where the extraordinary refractive index of the liquid crystal droplets does not match the refractive index of the surrounding polymer matrix, and the LC droplets are provided with the correct size and geometry, light incident on a film comprising liquid crystal droplets and polymer is refracted and the film is substantially opaque.
The size of the LC droplets, oralternatively referred to herein as LC domains, also has a profound effect upon the electro-optical characteristics of PDLC films. When LC and surrounding polymeric matrix have the same refractive index, the film will be transparent regardless of the size of the domains. When the refractive indecies of the LC droplets and the polymer matrix are not matched, however, domain size, domain size distribution, and number of domains determine the extent to which light is scattered. Ideally, the polymeric matrix of a PDLC is chosen such that its index of refraction matches the ordinary index of refraction of the LC domain
As described hereinabove, when both LC and polymer have the same refractive index, transparency is achieved. The closeness of the matching of the indices, or the "index matching", may