Hot Embossing for Transcription of Micro-Features onto Large Thermoplastic Films
Sen-Yeu Yang, Jer-Haur Chang
Department of Mechanical Engineering, No. 1 Sec. 4, Roosevelt Road, Taipei, Taiwan, R.O.C
Taiwan Republic Of China
Keywords: hot embossing, thin film, transcription
Most studies on hot embossing are limited to plastic plate substrates. This study is devoted to hot embossing of thin films, which can be for optical applications. A series of hot embossing experiments were conducted to transcript the micro U-groove features in a stamper onto large thin thermoplastic films. Two thermoplastic films, i.e. PC (amorphopus) and PET (semicrystalline), were investigated in this study. Film embossing is found different from plate embossing in applying slight pressure during heating and backing the stamps with cushion pads. The effects of processing on transcription quality were investigated. The temperatures for effective replication of micro-features for two type of polymer are found different. The micro-features can be successfully embossed onto the amorphous PC films at just above its glass transition temperature (Tg), while onto the semicrystalline PET films only at near its melting temperature (Tm). This research further investigates the formability of hot embossing for replications of micro-features onto large thin films. The formability is defined as the operation window in the plane of embossing pressure and embossing temperature to make successful replication of micro-features. The formability of amorphous PC films was found to be much larger than that of the semicrystalline PET films.