Takashi Tomie

Hygroscopic Expansion of Polyester Films

The hygroscopic expansion of polyethylene terephthalate (PET) and polyethylene 2,6-naphthalate (PEN) films was measured by use of a thermomechanical analyzer at 30, 40 or 50°C. Their initial weight increase was proportional to the square root of time after exposure to moisture, obeying Ficks law; the hygroscopic expansion with time showed the same relationship. The equilibrium moisture content was 1.0×10-5/% RH for both films; the hygroscopic expansion at equilibrium was also about the same for these films. However, the diffusion constant for moisture in PEN films was 16×10-9 cm2/s at 30°C in comparison with 48×10-8 for PET, although the activation energies were 45 kJ/mol for PET and 41 for PEN.

The Structure of Co–Cr Films Sputtered onto a Moving Substrate

Transmission electron micrographs, microbeam electron diffraction and X-ray pole figures were employed in order to elucidate the structure of Co–Cr films formed by facing targets sputtering. The c-axes of the hcp structure of the microcrystallites deposited on a static polyethylene terephthalate substrate had a sharp distribution around the normal of the film plane at the center of the deposition area, but were inclined slightly at the edge with respect to the target configuration. For a Co–Cr permalloy double-layered film formed on a moving substrate, the c-axes of individual crystallites scattered considerably, although the average was maintained along the normal of the film plane, with a slight tilt toward the forward-moving direction.

Influence of Injection Molding Process on the Local Fluctuations of Magneto-Optical Signals.

The local fluctuations of magneto-optical (MO) signals were investigated in the vicinity of the preformat pits of polycarbonate (PC) substrates fabricated under different injection molding conditions and also using stampers which had different shapes of grooves and preformat pits. A strong correlation was observed between the substrate birefringence and the fluctuation of the MO signal. The rate-of-change of the fluctuations, as the phase shift of the optical head was varied, was attributed to the shapes of preformat pits and grooves. The fluctuation of the MO signal could be controlled by varying the injection molding conditions and the shapes of preformat pits and grooves.

The Influence of Adjacent Preformat Pits on Magneto-Optical Signals

Fluctuations in magneto-optical (MO) signals have been observed in 3.5-in. 640 MB MO disks which have the zone constant angular velocity (ZCAV) format. They were found to occur at the border of each band (zone) when there were preformat pits in the adjacent band. The fluctuations were observed in those MO disks whose substrates were injection molded polycarbonate (PC). The degree of these MO signal fluctuations depended on the injection molding conditions of the substrates and the phase shift of the optical head. It is thought that such phenomena can be attributed to tilted ellipsoids of substrate birefringence that occur around preformat pits, and which are caused by stresses induced around the preformat pits during the injection molding process.