Abstract
Effects of the coating-process conditions on the structure and mechanical properties of pressure-sensitive adhesive layers composed of block copolymers have been revealed using neat triblock copolymer and triblock/ diblock copolymer blend. For this purpose, atomic force microscope （AFM） observation, two-dimensional small-angle X-ray scattering （2D-SAXS） measurement and stress-strain measurement were performed. The coated layers of the block copolymer were prepared by the solution coating and the hot-melt coating process at various conditions. As for the solution coating process, it was found that the ordering regularity of spheres and d spacing of body-centered cubic （BCC） lattice exhibited very complicated behaviors as a function of the drying temperature. The effect of structure freezing during the solvent evaporation was taken into account and such complicated behaviors of experimental results could be almost perfectly explained. It was also found that the degree of clarity of the reflection planes in the uniaxial stretching direction is enhanced with stretching and the rate of improvement in the degree of clarity along the uniaxial stretching depends on the drying temperature. We could correlate the fracture of the block copolymer film having spherical microdomains with the completion of the stretching-induced ordering of spheres in the stretching direction. As for the hot-melt coating process, the coated layer had the anisotropic distribution of the spheres where the d spacing of the reflection plane in the machine direction （MD） is longer and the regularity of the ordering of the reflection planes is lower in the MD as compared to that in the directly solidified specimen by quenching from 190 ºC to room temperature without application of shear. These facts are ascribed to shear and elongational deformation during the hot-melt coating process. Furthermore, it was found that the effects of the coating rate and the extent of the remained strain were increased with the coating rate when the discharge rate （the flux of materials provided onto the substrate through the die lip） was kept constant. On the contrary, no effects were confirmed when the discharge rate was so controlled to maintain the thickness of the as-coated layer constant. Regarding the effects of the cooling-roll temperature, it was found that the extent of the remained strain was decreased with an increase in the cooling-roll temperature.
