Polymeric Interference Filters combined with Optical Elements
Publication Date: 2003-Apr-24
The IP.com Prior Art Database
Multilayer optical interference filters can now be manufactured with all-polymer components. Such filters can be combined with bulk optical elements such as lenses, prisms, and the like, many of which are made by injection molding. The polymeric filters can be manufactured before the bulk element to which it will be attached is made. The film stack can even serve as a substrate for the bulk element. This opens new opportunities in manufacturing, particularly in simplifying the manufacturing processes of polymeric articles.
Interference Filters combined with Optical Elements
Multilayer optical interference filters can now be manufactured with all-polymer components (1). Such filters can be combined with bulk optical elements such as lenses, prisms, rods, slabs or optical elements of various shapes. Many lenses are now made by injection molding of polymers. In contrast to vacuum deposited thin film filters, the polymeric filters can be manufactured before the bulk element to which it will be attached is made. The film stack can even serve as a substrate for the bulk element in some cases. In general, this opens new opportunities in manufacturing, particularly in simplifying the manufacturing processes of polymeric articles, which need the combined properties of a thin film stack and a bulk optical element.
Typically, polymeric thin film filters are made by coextruding all layers simultaneously with no substrate and are freestanding film stacks having anywhere from 10 to 1000 layers. For added toughness or other functionalities an outer skin layer is usually included in the coextruded film stack, the two skin layers typically accounting for 10% to 50% of the thickness of the entire film. This skin layer can consist of one of the polymers in the optical layers in the film stack or can be a different material. Multiple skin layers can be coextruded or post laminated after the film making process. The skin material may be specially chosen in anticipation of providing improved adhesion of the film to another material, or may contain additives with optical functionalities such as dyes or pigments, or light diffusing properties. Examples of polymeric interference filters include color balancing filters, IR or UV cutoff filters, broadband mirrors, cold mirrors, color shifting mirrors, iridescent films and anti-reflection films.
Film/optical element combinations
Laminating is a process in which previously formed films or sheets are bonded to other objects such that they are sufficiently adhered to each other. Typically this process refers to articles wherein both of the elements are initially in solid form. If one element is not flat and must retain its shape, the other element to be bonded to it must either first be converted to the shape of the optical element to which it is being joined, or it must be shaped during the process of combining the two elements. Cold shaping of polymer multilayer film is possible for shapes of large radius of curvature such as, for example, automobile windscreens.
Shaping the film to a 3D form that departs significantly from a flat surface can be done via thermoforming, which uses a combination of heat and pressure to conform the film to the shape of a pre-made mold. In this case, the mold would first be shaped to that of the surface of the optical element to which the optical film is to be laminated. Once thermoformed, common optical adhesives can then be employed to join the fi...