US 5363470

Patent Overview — US 5,363,470

Title: "Displacing an optical lighting film's linear array of grooves to facilitate emission of light"

Patent number / application: US 5,363,470 A; Application US 08/089,288

Inventor: David L. Wortman

Assignee: Minnesota Mining and Manufacturing Co. (original); 3M Co (current assignee listed)

Key dates: Priority/filing 1993-07-08; granted/publication 1994-11-08; anticipated expiration 2013-07-08 (status: Expired – Lifetime)

Purpose: The patent addresses light conduits for transporting and distributing light. Conventionally, such conduits use optical lighting film — flexible transparent polymeric sheets with a structured surface of side-by-side, substantially right-angled isosceles prisms forming linear grooves — that totally internally reflect light entering below a critical angle. Extracting light conventionally required adding an extractor such as a diffuse scatterer (e.g., a reflective white polymeric tape), which must be physically added and becomes less effective as depleted zones form along longer conduits.

Plain-language scope: Rather than adding a separate extractor, the invention orients the film's linear array of grooves non-parallel to the conduit's longitudinal axis. In an embodiment with a tubular, circular-cross-section conduit, the grooves are helical. This non-parallel disposition causes some or all light that would otherwise be totally internally reflected to fall outside the critical angle, facilitating increased light emission. It also makes light rays travelling through the axis follow non-planar (spiralling) paths within the conduit, spiralling in the same rotational direction as the grooves. A diffuse scatterer may optionally be placed on the interior wall in conjunction with the spiralled grooves to further increase emitted-light intensity along the conduit's length.

Source URL: https://patents.google.com/patent/US5363470/en

What the excerpt does not establish: It provides only the abstract/definitions portion and a figure list (the specification text is truncated after FIG. 8). It does not supply the full claims, the complete written description, exact numerical ranges or angles, detailed embodiments, or the full figures. It also does not independently verify assignee status or legal status beyond what the source page lists.