A container component is made from microcellular foam material, no more than approximately 30 mils thick, having a core of very small uniformity distributed cells to provide uniform opacity that is locally eliminated by the application of heat and pressure to create window areas at least 60% as thick...http://www.google.es/patents/US4728559?utm_source=gb-gplus-sharePatente US4728559 - Thermoformed plastic containers with transparent windows and method of making same
Thermoformed plastic containers with transparent windows and method of ...
