Extrusion International 5-2019

24 Extrusion International 5/2019 FILM EXTRUSION The automotive as well as mobil phone market offers good opportunities for the application of optical films. Almost every illuminated button is made by this flexible technology. By IMD technology 3D design combined with brilliant optic and high haptic quality becomes possible. Not only one monitor is used in cars for e.g. the on board computer or navigation systems. Also video monitors in the backside of the seats are installed. Also the interior decorating styles high demand in Quality. These applications have always represented enormously high demands with respect to optical quality of the extruded film with a too high birefringence. The using for optical applications of that film is not anymore possible. So, the production of ultra-thin, low-tension films of high optical quality in particular, is quickly sepa- rating the men from the boys. With the BREYER OptiFlex line producers of Polycarbonate and PMMA (as single layer or coextruded multilay- er) film are staying always flexible and ahead. Both side polished, mat and struc- tured filmwith optical properties can be produced on a single line. BREYER film extrusion systems today offer es- pecially for the thickness range of 50 to 1000 µm with excellent achievable tolerances. Producing transparent film that is as smooth and thin as possible is the desire of many processing companies whose film is used for the mentioned optical applications. However, most extrusion systems and their integrat- ed calender machines run into prob- lems when it comes to thicknesses of less than 500 microns. The bending of the calender rolls and thus the thickness tolerances do not allow for a thinner produc- tion in closed roll gap mode. On top, another challenge arises: when pressing the film between the cal- ender rolls too much, tensions are stored inside the film which are releases in the later process as too much shrinkage and further more, To keep the film flat Especially flat applications require a well flatness of the film. By the BREY- ER calender with its slewable third calender roll is not anymore a matter of many minutes. By this feature the residential time of the film around the center calender roll is influenced. During running condition the posi- tion of the third roll in relation to the center roll can be changed,resp ad- justed exactly to this position where top and lower side cooling is bal- anced and the film becomes flat. Changing quick from one thickness to another The BREYER gap control system in- cludes an automatic film thickness OptiFlex Line – How Adjusting Thickness and Flatness of Film Becomes Fast&Easy