The structure of highly drawn PET film with transverse lines and its polarized light scattering.

When the PET film is drawn to about 4 times at first stage, the transverse line structure is observed under the polarized optical microscope (POM) and the scanning electron microscope (SEM). These transverse lines extended and slightly undulated perpendicular to the draw direction. Consequently, the transverse lines are distributed perpendicular to the draw direction.From the observation of the POM and the SEM and the results of the S-S curve and of the birefringence of PET films, it can be considered that the transverse line structure is composed of the “squeezed structure” and the relaxed craze-like structure.PET film with the transverse line structure shows the unique polarized light scattering patterns when the incident beam has the component perpendicular to the draw direction, and that the light in this pattern oscillates in the draw direction.The “polarized pattern” shows four leaf-shaped patterns not only in the front but also in the back. The intensity of the “polarized pattern” in the negative direction is weak.Such “polarized pattern” can be observed when the transverse line structure extends perpendicular to the draw direction. When the transverse lines are inclined perpendicular at 3.8°, the “polarized pattern” is changed into the pair of two leaf-shaped patterns.The incident beam reflects and transmits repeatedly at the boundary between two layers which have different densities and refractive indices. Consequently it is considered that polarized light vibrating in the horizontal plane is observed.Such optical property of the PET film is similar to a half-wave plate or an optically active substance, which is, however, substantially different from the PET film. This is because the “polarized pattern” in this paper does not depend on the thickness of the sample films and light vibrating perpendicularly to the draw direction is changed into the one vibrating in parallel to the draw direction and not vice versa. There is a possibility of applying the PET film to an optical element, such as an optical isolator and an opto electric integrated circuits.