Development of a Novel Transcription Molding Process to Fabricate Sophisticated Polymer Products with Precise Microstructure and High Transparency Applicable to Display Devices and Bio-chips

Abstract

Abstract In this study, we developed a novel transcription-molding process and experimentally discussed its validity for fabricating polymer products having the precise microstructure on the surface. The process was named “Melt-Transcription Process” which consists of two characteristic stages; coating and compression. In the coating stage, a molten polymer is coated on the surface of a metal mold having the precise microstructure by a coating device specially designed in this study. The thickness of the coated polymer melt is typically 100 μm or more. Immediately after coating, the coated polymer is compressed against the mold surface so as to make the polymer flow into the microstructure cavities engraved on the mold, and to fabricate the 3-dimensional structure of polymer products. The pressure required for compression is quite lower than that in conventional nano-imprinting process, because the molten polymer of high temperature is distributed in advance over the mold surface in the coating stage. The “Melt-Transcription Process” was applied to fabricate polymer products with the size of 150 mm in length, 150 mm in width and 1 mm in thickness, having the microstructure of tens micrometers on their surface. Cyclo-olefin polymer (COP) and Polymethyl methacrylate (PMMA) were used as the polymer materials, and the dimensions and transcription ratios (the ratio of the height of the transcribed microstructure to the depth of the microstructure on the mold) of the molded microstructure were experimentally evaluated. As a result, by the Melt-Transcription Process, the microstructure was sufficiently transcribed on a very thin substrate of large surface area with high transcription ratios, typically 95% or more, under relatively low compression pressure of less than 10 MPa. The process was also applied for fabricating products with a range of thicknesses and we could experimentally verify that products composed of a membrane of 80 μm thickness and a surrounding frame with 1.95 mm thickness were successfully molded. Furthermore, we fabricated a micro-lens array product by using film grade PMMA with relatively higher viscosity in a product having 125 μm in thickness and a size of 102 mm × 102 mm.