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  Diffuser for flat panel displayThe Patent Description & Claims data below is from USPTO Patent Application 20070274092. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application claims is related to and claims priority from U.S. provisional application 60/451,632 filed on Feb. 28, 2003, the entire contents of which are incorporated by reference. BACKGROUND OF THE INVENTION [0002] This invention relates to optical sheet material and, more specifically, to such sheet material characterized by light diffusion properties. This invention also relates to back light displaying using the optical sheet, and to processes for making the sheet material. [0003] In many current displays systems, for example in Liquid Crystal Displays (LCD), it is desirable to have diffusing components. Examples of the utility of diffusing components include (but are not limited to) masking artifacts, such as seeing electronic components located behind the diffuser film and/or hiding injection molded patterns or printing on the light guide pipe of the display, improved uniformity in illumination and increased viewing angle. In a typical LCD display, diffusion of light is introduced into the backlight assembly by adding separate films (i.e., a stack) that are comprised of a non-diffusing substrate to which a highly irregular, diffusing surface treatment is applied or attached. It is thus desirable to generate diffuse light without the added cost of separate films. [0004] In backlight computer displays or other display systems, optical films or sheet material are commonly used to direct, diffuse or polarize light. For example, in backlight displays, brightness enhancement films (BEFs) use prismatic structures on the surfaces thereof to direct light along a viewing axis (i.e., an axis normal to the display). This enhances the brightness of the light viewed by the user of the display and allows the system to consume less power in creating a desired level of on-axis illumination. Such films can also be used in a wide range of other optical designs, such as in projection displays, traffic signals, and illuminated signs. [0005] In current displays systems, for example in Liquid Crystal Displays (LCD), it is desirable to have diffusing components. Examples of the utility of diffusing components include (but are not limited to) masking artifacts, such as seeing electronic components located behind the diffuser film and/or hiding injection molded patterns or printing on the light guide pipe, improved uniformity in illumination and increased viewing angle. In a typical LCD display, diffusion of light is introduced into the backlight assembly by adding separate films (i.e., a stack) that are comprised of a non-diffusing substrate to which a highly irregular, diffusing surface treatment is applied or attached. It is thus desirable to generate diffuse light without the added cost of separate films. [0006] Some of undesirable features of diffuser films are a lack of dimensional stability during high temperature and humidity testing due to mismatched material properties between the substrate and coating, coating defects due to lack of coating process robustness, defect generation during material conversion due to scratches in the coatings, impressions or texture non-uniformities due to tooling and/or web handling rollers, dust attraction and film stickage due to static charge creation, and reduced luminance and luminance uniformity. The first four of the above undesirable features may reduce the yield during the various cutting and assembly processes. It is desirable that diffusers minimize the above undesirable features while enhancing the desirable features of high brightness and brightness uniformity. SUMMARY OF THE INVENTION [0007] An embodiment of the invention features a light diffusing film with a low scattering power hereinafter referred to as a top diffuser film or a light diffusing film with a high scattering power hereafter referred to as a bottom diffuser film. Desirably both films are unitary or monolithic films characterized by the absence of coatings and include a uniformly dispersed anti-static material comprising a fluorinated phosphonium sulfonate in an amount sufficient to impart anti-static properties to the film. The films may also contain at least one UV stabilizer to prevent discoloration due to the short wavelength light coming out of the light source. The top diffuser film consists essentially of polycarbonate material and the anti-static material and has a texture on at least one surface thereof for obtaining a low scattering of light. The bottom diffuser film consists essentially of polycarbonate, the anti-static material, possibly a UV stabilizer, and a uniformly dispersed acrylic bulk scattering additive having a particle size of from about 3 to about 10 microns in an amount from about 2 to about 7 percent by weight percent for the high scattering of light. [0008] In another aspect of the invention, a backlight display device comprises an optical source for generating light; a light guide for guiding the light therealong including a reflective surface for reflecting the light out of the light guide; and an arrangement of optical films including at least one of a top or bottom diffuser film as set forth above. A preferred device utilizes both the top and bottom diffuser film. [0009] In another aspect of the invention, a light diffusing film for a back light display is provided. The film comprises: a unitary film consisting essentially of polycarbonate and a uniformly dispersed anti-static material in an amount sufficient to impart anti-static properties to the film. [0010] In another aspect of the invention, an assembly for an optical film is provided. The film comprises: the light diffusion film described above, a backing film; and a pressure sensitive adhesive adhering the backing film to the light diffusion film. [0011] In another aspect of the invention there is provided a process for making a light diffusing film. The process comprises: texturing a calendaring roll to form a textured calendaring roll; and using the textured calendaring roll to form the light diffusing film described above. [0012] In another aspect of the invention there is provided a process for making a light diffusing film. The process comprises: using a polymeric coated melt calendaring roll to form the light diffusing film described above. [0013] In another aspect of the invention there is provided process for making a light diffusing film. The process comprises: forming an assembly comprising the light diffusion film described above, a backing film, and a pressure sensitive adhesive adhering the backing film to the light diffusion film; and removing the backing film from the light diffusion film. [0014] In another aspect of the invention there is provided a light diffusing film for a back light display. The film comprises: a unitary film consisting essentially of polycarbonate and a uniformly dispersed anti-static material comprising a fluorinated phosphonium sulfonate in an amount sufficient to impart anti-static properties to the film, said film additionally comprising at least one textured surface for the low scattering of light, or said film additionally comprising a uniformly dispersed acrylic bulk scattering additive of particles having a mean particle size of from about 3 to about 10 microns and present in an amount from about 2 to about 7 percent by weight percent for the high scattering of light. [0015] In another aspect of the invention there is provided a backlight display device. The backlight display device comprises: an optical source for generating light; a light guide for guiding the light therealong; a unitary film consisting essentially of polycarbonate and a uniformly dispersed anti-static material in an amount sufficient to impart anti-static properties to the film. [0016] In another aspect of the invention there is provided a backlight display device. The backlight display device comprises: an optical source for generating light; a light guide for guiding the light therealong; a unitary film consisting essentially of polycarbonate and a uniformly dispersed anti-static material comprising a fluorinated phosphonium sulfonate in an amount sufficient to impart anti-static properties to the film, said film additionally comprising at least one textured surface for the low scattering of light, or said film additionally comprising a uniformly dispersed acrylic bulk scattering additive of particles having a particle size of from about 3 to about 10 microns in an amount from about 2 to about 7 percent by weight percent for the high scattering of light. [0017] In another aspect of the invention there is provided a light diffusing film for a back light display. The film comprises: a unitary film consisting essentially of polycarbonate and a uniformly dispersed anti-static material comprising a fluorinated phosphonium sulfonate in an amount sufficient to impart anti-static properties to the film, the surface resistivity of the film being below about 10.sup.15 ohm/square. [0018] In another aspect of the invention there is provided a light diffusing film for a back light display. The film comprises: a unitary film consisting essentially of polycarbonate and a uniformly dispersed anti-static material in an amount sufficient to impart anti-static properties to the film, the unitary film being substantially transparent. [0019] In another aspect of the invention there is provided a process for making a light diffusing film comprising polycarbonate. The process comprises: passing a polymer resin comprising polycarbonate through a 70 micron or less melt filter of porous disks to provide filtered resin; forming pellets from the filtered resin; melting and extruding the pellets to form an extruded melt; and passing the extruded melt through a gap between two calendaring rolls to form the light diffusing film. [0020] In another aspect of the invention there is provided a process for making a light diffusing film comprising polycarbonate. The process comprises: melting and extruding the polymer resin comprising polycarbonate to form an extruded melt; and passing the extruded melt through a gap between two calendaring rolls to form the light diffusing film having a thickness of at least about 0.008 inches, and wherein the light diffusing film does not exhibit any visible waving when viewed at any angle. [0021] In another aspect of the invention there is provided a process for making a light diffusing film comprising polycarbonate. The process comprises: melting and extruding the polymer resin comprising polycarbonate to form an extruded melt; and passing the extruded melt through a gap between two calendaring rolls to form a web of light diffusing film, a web oscillation speed and a web winding tension being sufficient such that the light diffusing film exhibits no visual gauge bands. Continue reading... Full patent description for Diffuser for flat panel display Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Diffuser for flat panel display patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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