Roll-to-Roll Embossing of Sunlight Guide Film with Wide Outgoing Angle

Abstract

Artificial lighting consumes over 20% of the total energy used by commercial buildings. Sunlight guides used in windows guide sunlight to the ceilings of indoor rooms. Microstructure film designed and fabricated by roll-to-roll embossing improves solar energy use. A roller mold was fabricated with a diamond turning lathe and used for UltraViolet (UV) cured embossing. After embossing, sunlight guide film 400 mm wide was fabricated. The film microstructure prism and curved surfaces 21 µm high and spaced at 18 µm intervals. When sunlight illuminates the inclined or curved surface, incoming rays are reflected from the outgoing surface in total internal reflection. Specimen performance wasmeasured using measurement installation including a light source, photodetector, and a rotating table. These produced sunlight guide film able to adopt elevation angles of 40°-70°. The outgoing angle exceeded a 30° average above the transom’s outgoing horizontal 90° angle, which is defined by full width at half maximum of outgoing light intensity. Experimental results showed of the microstructure film had high energy efficiency and a broad range of outgoing angles, reducing energy consumption by 19% in artificial building lighting for an ideal room model.