Advanced Test Setup for Accelerated Aging of Plastics by Visible LED Radiation

In this article, a newly developed test setup for the aging of optical plastics by visible radiation (450 nm) is presented. In addition to a comprehensive monitoring of the operating parameters and an efficient cooling of the high-power multiple chips on board the LEDs used, the plastic samples can be fully temperature-controlled, independent of the radiant power of the LED, due to fluid driven thermostatization. The sample surface temperatures and irradiance values were verified by in situ measurements and simulations. To validate the test setup, polycarbonate samples with well-known aging behavior were aged for 1896 h. By spectroscopic IR and UV/vis analysis of the samples at different aging times, known optical aging results of polycarbonate could be observed, which proves the intended operationality of the system.

Stain-resistant, superomniphobic flexible optical plastics based on nano-enoki mushroom-like structures

In this paper, we demonstrate the stain-resistance and high pressure stability of superomniphobic flexible optical plastics.

SPECTRAL AND ANGULAR DEPENDENCE OF THE EFFICIENCY OF A TWO-LAYER AND SINGLE-RELIEF SAWTOOTH MICROSTRUCTURE

Spectral and angular dependences of the diffraction efficiency of two-layer single-relief sawtooth microstructures are analyzed. The microstructures are assembled from optical plastics and new brands of special optical glass. This makes it easy to replicate elements with diffraction microrelief by precision casting or stamping. Wide possibilities of weakening the dependence of the diffraction efficiency of such microstructures on the wavelength and the angle of incidence of radiation on the element are demonstrated.

Improved molding of micro structures using PVD-coated mold inserts

Micro structured optical plastics components are intensively used, i.e. in consumer electronics, for optical sensors in metrology, innovative LED-lighting, or laser technology. Injection molding has been proven successful for the large-scale production of these parts. However, the production of these parts still causes difficulties due to challenges in the molding and demolding of plastics parts created with laser-structured mold inserts. A complete molding of the structures often leads to increased demolding forces, which then cause a breaking of the structures and a clogging of the mold. An innovative approach is to combine physical vapor deposition (PVD)-coated, laser-structured inserts and a variothermal molding process to create functional micro structures in a one-step process. Therefore, a PVD coating is applied after the laser-structuring process in order to improve the wear resistance and the anti-adhesive properties against the plastics melt. In a series of molding trials with polycarbonate (PC) and polymethyl methacrylate (PMMA) using different coated molds, the mold temperature during injection was varied in the range of the glass transition and the melt temperature of the polymers. Subsequently, the surface topography of the molded parts was evaluated by digital three-dimensional laser-scanning microscopy. The influence of the molding parameters and the coating of the mold insert on the molding accuracy and the demolding behavior were analyzed. It was shown that micro structures created by ultra-short pulse laser ablation can be successfully replicated in a variothermal molding process. Due to the mold coating, significant improvements could be achieved in producing micro structured optical plastics components.