| This thesis is devoted to the research and development a new system and process of polymer extrusion roller embossing process for replication of microstructures. Precise single-screw extrusion molding is used to fabricate the optical polymer plate and then the polymer thin plate is directly fed into the roller micro-embossing facility before it cools down. Rollers with microstructures on the surface transfer the patterns onto the hot polymer thin plate while the plate is rolled through. A new set of extrusion roller embossing system can be set up by designing and developing the polymer extrusion die and roller micro-embossing facility. Finally, the extrusion roller embossing system is confirmed that it can be applied to transfer microstructures large and continuously. The advantage of this technology is the simplicity of craft process, high efficient and replication on a large area. This is the kind of potential technology to fabricate polymer microstructure.A roller micro-embossing facility is setup, consisting of a driving roller and a roller with microstructures. The diameter of the two roller is 64mm, the length is 125mm, and the range of the driving roller is from 0～30rpm. The metal rollers with microstructures are prepared by coating the slab mould, and microstructure are the periodical distribution of micro-pore. An extrusion machine with a coat-hanger die is used to extruding thin plates, and polymer plate with width of 120mm and thickness of 1mm can be extruded.The extrusion roller embossing system is used to do experiment. The polymer plate from the extrusion die is fed horizontal directly into the rollers. It is found that the surface temperature of polypropylene (PP) thin plate is still closed to its melting point before the plate get through the roller, and it is suitable for extrusion roller embossing microstructure process. Under the proper processing parameters, through the observation and measurement of the optical microscope and 3D image determination, it is proved that three kinds of microstructure can replicate onto the polymer thin plate successfully.In this study, the influence of microstructure replication on the temperature of coat-hanger die, the rotation speed of driving roller and the pressure of roller is discussed. It is found that as the rotation speed of driving roller is increasing, the replication of microstructure on polymer plate's surface is poor. However, increasing the pressure of roller and the temperature of coat-hanger die, the replication of microstructure on polymer thin plate's surface improves. The best replication results are obtained with the die temperature of 210℃, a rotation speed of 1.5rpm and the roller pressure of 8200N. At this time, uniformity of diameter and transfer rate of height for the replicated polymer micro-lens is very excellent.Two kinds of polymer materials, such as polycarbonate (PC) and polypropylene (PP), are used to discuss the influence of optical properties for the fabricated polymer thin plate on different materials and microstructure. It is found that the diffuser prepared by the two materials can made the light diffused, but the diffusion of polycarbonate (PC) is better than polypropylene (PP). And the diffuser with surface microstructures can scatter the light more uniformly and effectively. However, the haze of the diffuser increases with its transmittance declining. Moreover, the optical properties of diffuser are related with not only the size of microstructures, but also the distribution of microstructures. |
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