超音波の射出成形への応用(その2)

転写性の検討

抄録

We have developed the Ultrasonic Injection Molding (UIM) system as a precision injection molding technology, in which the ultrasonic vibration has been applied to injection molding. In general, a certain shape in minute scale is often transcribed on the surface of products in order to invest the polymer products with an optical function. In consideration of these applications, effectiveness of the UIM system for improving the degree of transcription of a minute shape (triangular pyramid of 70μm in height) was experimentally investigated in this paper under various mold temperature conditions. The results showed that the degree of transcription of the minute shape is improved markedly by the UIM system in comparison with the conventional molding at the same mold temperature, and that the mold temperature in UIM could be reduced about 20K in order to obtain the same transcription as in the conventional molding. The mechanism of the improvement of transcription in UIM could be attributed to the inertia force acting on the polymer melt due to ultrasonic vibration during the melt filling process. Namely, the inertia force due to ultrasonic vibration would stuff the resin into the minute part of mold surface. Furthermore the local heating of resin due to absorption of the ultrasonic vibration was considered to be another mechanism of the transcription improvement during the packing-holding process. Heating due to absorption of ultrasonic vibration, which is evident especially in the region between molten- and solidified-layers would result in reduction of deformation resistance of the solidified layer, and thus the transcription due to packing-holding pressure would be helped by the UIM.