Optical diffusers obtained by melt mixing of incompatible materials

• Main Authors: CLABBURN, ROBIN, ZEIRA, EITAN C
• Format: Patent
• Language: English; French; German
• Published: 26.05.2004
• Edition: 7
• Subjects: ACCESSORIES THEREFOR; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F,C08G; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USINGWAVES OTHER THAN OPTICAL WAVES; APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FORPROJECTING OR VIEWING THEM; CHEMISTRY; CINEMATOGRAPHY; COMPOSITIONS BASED THEREON; ELECTROGRAPHY; GENERAL PROCESSES OF COMPOUNDING; HOLOGRAPHY; METALLURGY; OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; ORGANIC MACROMOLECULAR COMPOUNDS; PERFORMING OPERATIONS; PHOTOGRAPHY; PHYSICS; PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCESIN A PLASTIC STATE; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; THEIR PREPARATION OR CHEMICAL WORKING-UP; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL; WORKING-UP

A process for producing a light diffusing sheet material comprises: (a) selecting a first optically clear material and a second optically clear material, which have different indices, are immiscible in one another, and have a viscosity ratio between 0.05 and 10 measured at the processing temperature; (b) dispersing the first optically clear material in the second optically clear material by mechanical mixing, e.g. by melt mixing or compounding and (c) forming a film from the mixture. The film is caused or allowed to harden to fonn the sheet material. The invention further relates to sheet diffusers made by the process. In preferred embodiments, the material is oriented, e.g. by stretching after extrusion but before it has hardened, or by the extrusion process itself, so as to possess asymmetric diffusing properties.