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  Method for subdividing multilayer optical film cleanly and rapidlyUSPTO Application #: 20060191630Title: Method for subdividing multilayer optical film cleanly and rapidly Abstract: Polymeric multilayer optical films, and laminate bodies that include such films, are cut or subdivided into one or more discrete pieces by removably applying a first and second liner to opposed major surfaces of the multilayer optical film. Laser radiation is then directed at the multilayer optical film through the first liner in such a way as to produce cut lines that define a plurality of pieces of the first liner and of the multilayer optical film. Thereafter, the plurality of pieces of the first liner are removed from the plurality of pieces of the multilayer optical film while the pieces of multilayer optical film are supported by the second liner. Application of the first liner to the multilayer optical film can be accomplished with electrostatics. (end of abstract) Agent: 3m Innovative Properties Company - St. Paul, MN, US Inventors: Bruce E. Tait, John A. Wheatley, Steven J. Dobrzynski, David K. Mortenson USPTO Applicaton #: 20060191630 - Class: 156272800 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20060191630. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a continuation of U.S. application Ser. No. 10/268,118, filed Oct. 10, 2002, which is a continuation-in-part of U.S. application Ser. No. 10/152,412, filed May 21, 2002, now abandoned and claims priority thereto. FIELD OF THE INVENTION [0002] The present invention relates to methods of cutting or subdividing an optical body comprising a multilayer optical film into a plurality of smaller pieces. BACKGROUND [0003] Multilayer optical films, i.e., films that provide desirable transmission and/or reflection properties at least partially by an arrangement of microlayers of differing refractive index, are known. It has long been known to make such multilayer optical films by depositing a sequence of inorganic materials in optically thin layers ("microlayers") on a substrate in a vacuum chamber. Typically, the substrate is a relatively thick piece of glass, limited in size due to constraints on the vacuum chamber volume and/or the degree of uniformity possible by the deposition process. [0004] More recently, multilayer optical films have been demonstrated by coextrusion of alternating polymer layers, See, e.g., U.S. Pat. No. 3,610,729 (Rogers), U.S. Pat. No. 4,446,305 (Rogers et al.), U.S. Pat. No. 4,540,623 (Im et al.), U.S. Pat. No. 5,448,404 (Schrenk et al.), and U.S. Pat. No. 5,882,774 (Jonza et al.), the disclosures of which are incorporated herein by reference in their entireties. In these polymeric multilayer optical films, polymer materials are used predominantly or exclusively in the makeup of the individual layers. Such films are compatible with high volume manufacturing processes, and can be made in large sheets and roll goods. [0005] Many product applications, however, require relatively small and numerous pieces of film. Filters for individual photodiode detectors is one such application. Windows, reflectors, and/or filters for fiber optic devices and other small-scale photonics devices are additional applications. For these applications, small pieces of multilayer optical film can be obtained from a larger sheet of such film by subdividing the sheet by mechanical means, such as by cutting the sheet with a shearing device (e.g., a scissors), or slitting the sheet with a blade. However, the forces exerted on the film by the cutting mechanism can produce layer delamination in a region along the cut line or edge of the film. This is particularly true for many polymeric multilayer optical films. The delamination region is often discernable by a discoloration relative to intact areas of the film. Because the multilayer optical film relies on intimate contact of the individual layers to produce the desired reflection/transmission characteristics, the delamination region fails to provide those desired characteristics. [0006] In some product applications, the delamination may not be problematic or even noticeable. In others--particularly where it is important for substantially the entire piece of film from edge to edge to exhibit the desired reflection or transmission characteristics, or where the film can be subjected to mechanical stresses and/or wide temperature variations that could cause the delamination to propagate in the film over time--the delamination can be highly detrimental. [0007] There exists, therefore, a need for an improved method for subdividing multilayer optical film and articles comprising such film. Preferably, the method would not produce delamination at the cut lines or film edges, would cut the film cleanly without substantial debris accumulation on the film, and would be compatible with automated and/or continuous manufacturing processes. BRIEF SUMMARY [0008] The present application discloses methods of subdividing or cutting a multilayer optical film body comprising a multilayer optical film into one or more discrete pieces. In a simple case, the multilayer optical film body consists essentially of a multilayer optical film. In other cases the multilayer optical film body can also comprise one or more additional layers laminated to the multilayer optical film. A first and second liner are removably applied to opposed major surfaces of the multilayer optical film body. Preferably, laser radiation is then directed at the film body through one of the liners (arbitrarily designated the first liner), the laser radiation being adapted to produce cut lines that define a plurality of pieces of the first liner and of the film body. Typically, the laser radiation produces a plume of smoke and debris that deposits on the workpiece--in this case, on the first liner. Thereafter, the plurality of pieces of the first liner (with accompanying debris) are removed from the plurality of pieces of the multilayer optical film body while the pieces of multilayer optical film body are supported by the second liner. The removal can be accomplished by contacting the first liner with an adhesive tape and pulling the tape away from the multilayer optical film body. [0009] Preferably, at least the first liner is applied to the film body using electrostatics. After the cut lines are formed with the laser radiation and before removal of the pieces of the first liner from the pieces of multilayer optical film body, a neutralizer member can be used to reduce the electrostatic attraction between the first liner and the multilayer optical film body. [0010] Although laser radiation is a preferred technique for cutting the film body, alternative approaches such as rotary die cutting and ultrasonic cutting may also be suitable in some cases. BRIEF DESCRIPTION OF THE DRAWINGS [0011] Throughout the specification reference is made to the appended drawings, where like reference numerals designate like elements, and wherein: [0012] FIG. 1 is a greatly magnified perspective view of a multilayer optical film body; [0013] FIG. 2 is a plan view of a sheet of multilayer optical film body, with broken cut lines indicating how it is to be subdivided; [0014] FIG. 3 is a sectional view of a multilayer optical film body disposed between an upper and lower liner, the figure further depicting electromagnetic radiation forming gaps at cut lines that define discrete pieces of the multilayer optical film body and of the upper liner; [0015] FIG. 4 is a sectional view similar to FIG. 3, but where an adhesive film has been applied to the upper liner so that it can remove the pieces of upper liner from the pieces of multilayer optical film body; [0016] FIGS. 3a and 4a are similar to FIGS. 3 and 4 respectively except that the former figures include cut lines that extend completely through the microlayers of the multilayer optical film(s) in the film body but do not extend completely through an optically thick tearable outer layer the film body; [0017] FIG. 5 is a plan view of a piece of multilayer optical film body cut from a larger sheet; [0018] FIG. 6 is a sectional view through the piece of multilayer optical film body of FIG. 5 with a plurality of filter frames attached thereto; [0019] FIG. 7 depicts a continuous process for subdividing a multilayer optical film body; and Continue reading... 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