Reinforced Optical Films

Abstract

Optical films having structured surfaces are used, inter alia, for managing the propagation of light within a display. As displays become larger, it becomes more important that the film be reinforced so as to maintain rigidity. An optical film of the invention has a first layer comprising inorganic fibers embedded within a polymer matrix. A second layer having a structured surface, for providing an optical function to light passing therethrough, is attached to the first layer. The film may have various beneficial optical properties, for example, light that propagates substantially perpendicularly through the first layer may be subject to no more than a certain level of haze or light incident on the film may be subject to a minimum value of brightness gain. Various methods of manufacturing the films are described.

1 . An optical film, comprising: 
 a first layer comprising inorganic fibers embedded within a polymer matrix; and    a second layer attached to the first layer, the second layer having a structured surface, wherein the optical film provides a brightness gain of at least 10% to light that propagates through the optical film.    
   
   
       2 . An optical film as recited in  claim 1 , wherein the brightness gain is at least 50%.  
   
   
       3 . An optical film as recited in  claim 1 , wherein the brightness gain is at least 100%.  
   
   
       4 . An optical film as recited in  claim 1 , wherein light that propagates substantially perpendicularly through the first layer is subject to a bulk haze of less than 30%.  
   
   
       5 . An optical film as recited in  claim 1 , further comprising at least one of inorganic nanoparticles, light diffusing particles or hollow particles embedded within the polymer matrix.  
   
   
       6 . An optical film as recited in  claim 1 , wherein the structured surface comprises a brightness enhancing layer surface.  
   
   
       7 . An optical film as recited in  claim 1 , wherein the structured surface comprises a plurality of prismatic ribs.  
   
   
       8 . An optical film as recited in  claim 1 , wherein the structured surface comprises a plurality of retroreflecting elements.  
   
   
       9 . An optical film as recited in  claim 1 , wherein the structured surface comprises one or more lenses.  
   
   
       10 . An optical film as recited in  claim 9 , wherein the one or more lenses comprise at least one Fresnel lens.  
   
   
       11 . An optical film as recited in  claim 1 , wherein the structured surface comprises one of a diffractive surface and a light collecting surface.  
   
   
       12 . An optical film as recited in  claim 1 , further comprising a third layer attached to one of the first and second optical layers.  
   
   
       13 . An optical film as recited in  claim 12 , wherein the third layer comprises one of a reflective layer, a transmissive layer, a diffusive layer and a layer having a structured surface.  
   
   
       14 . An optical film as recited in  claim 12 , wherein the third layer comprises a polarizer layer.  
   
   
       15 . An optical film as recited in  claim 14 , wherein the polarizer layer comprises a reflective polarizer layer.  
   
   
       16 . An optical film as recited in  claim 14 , wherein the polarizer layer comprises an absorbing polarizer layer.  
   
   
       17 . An optical film as recited in  claim 12 , wherein the third layer is attached to the structured surface.  
   
   
       18 . An optical film as recited in  claim 12 , wherein the third layer is attached to the first layer.  
   
   
       19 . An optical film as recited in  claim 12 , wherein the third layer is attached to the second layer and the third layer comprises a polymer matrix having inorganic fibers embedded within a polymer matrix.  
   
   
       20 . An optical film as recited in  claim 1 , wherein the polymer matrix comprises a thermosetting polymer.  
   
   
       21 . An optical film as recited in  claim 1 , wherein the polymer matrix comprises a thermoplastic polymer.  
   
   
       22 . An optical film as recited in  claim 1 , wherein the polymer matrix comprises a polymer having a value of T g  less than 120° C.  
   
   
       23 . An optical film as recited in  claim 1 , wherein the single pass transmission through the film for light directed substantially normally to a surface of the film facing away from the structured surface is less than 40%.  
   
   
       24 . An optical film as recited in  claim 23 , wherein the single pass transmission is less than 10%.  
   
   
       25 . An optical film as recited in  claim 1 , wherein light directed to the film having a principal ray at an angle of more 30° to a film normal is transmitted out of the film with the principal ray propagating at an angle of less than 25° to the film normal.  
   
   
       26 . An optical film as recited in  claim 1 , wherein when light is incident on the optical film, the light having a principal ray propagating in a first direction when incident on the optical film, the light is transmitted out of the film with the principal ray propagating in a second direction different from the first direction by at least 5°.  
   
   
       27 . An optical film, comprising: 
 a first layer, comprising inorganic fibers embedded within a polymer matrix; and    a second layer attached to the first layer, the second layer having a structured surface wherein single pass transmission for light, substantially normally incident on a side of the optical film facing away from the structured surface, is less than 40%.    
   
   
       28 . An optical film as recited in  claim 27 , wherein the single pass transmission is less than 10%.  
   
   
       29 . An optical film as recited in  claim 27 , wherein the single pass transmission is less than 5%.  
   
   
       30 . An optical film as recited in  claim 27 , wherein light that propagates substantially perpendicularly through the first layer is subject to a bulk haze of less than 30%.  
   
   
       31 . An optical film as recited in  claim 27 , further comprising at least one of inorganic nanoparticles, light diffusing particles or hollow particles embedded within the polymer matrix.  
   
   
       32 . An optical film as recited in  claim 27 , wherein the structured surface comprises a brightness enhancing layer surface.  
   
   
       33 . An optical film as recited in  claim 27 , wherein the structured surface comprises a plurality of prismatic ribs.  
   
   
       34 . An optical film as recited in  claim 27 , wherein the structured surface comprises a plurality of retroreflecting elements.  
   
   
       35 . An optical film as recited in  claim 27 , wherein the structured surface comprises one or more lenses.  
   
   
       36 . An optical film as recited in  claim 35 , wherein the one or more lenses comprise at least one Fresnel lens.  
   
   
       37 . An optical film as recited in  claim 27 , wherein the structured surface comprises one of a diffractive surface and a light collecting surface.  
   
   
       38 . An optical film as recited in  claim 27 , further comprising a third layer attached to one of the first and second layers.  
   
   
       39 . An optical film as recited in  claim 38 , wherein the third layer comprises one of a reflective layer, a transmissive layer, a diffusive layer and a layer having a structured surface.  
   
   
       40 . An optical film as recited in  claim 38 , wherein the third layer comprises a polarizer layer.  
   
   
       41 . An optical film as recited in  claim 40 , wherein the polarizer layer comprises at least one of a reflective polarizer layer and an absorbing polarizer layer.  
   
   
       42 . An optical film as recited in  claim 38 , wherein the third layer is attached to the structured surface.  
   
   
       43 . An optical film as recited in  claim 38 , wherein the third layer is attached to the second optical layer and the third optical layer comprises a polymer matrix having inorganic fibers embedded within the polymer matrix.  
   
   
       44 . An optical film as recited in  claim 27 , wherein the polymer matrix comprises a thermosetting polymer.  
   
   
       45 . An optical film as recited in  claim 27 , wherein the polymer matrix comprises a thermoplastic polymer.  
   
   
       46 . An optical film as recited in  claim 27 , wherein the polymer matrix comprises a polymer having a value of T g  less than 120° C.  
   
   
       47 . An optical film as recited in  claim 27 , wherein light directed to the film, having a principal ray at an angle of more 30° to a film normal, is transmitted out of the film with the principal ray propagating at an angle of less than 25° to the film normal.  
   
   
       48 . An optical film as recited in  claim 27 , wherein when light is incident on the optical film, the light having a principal ray propagating in a first direction when incident on the optical film, the light is transmitted out of the film with the principal ray propagating in a second direction different from the first direction by at least 5°.  
   
   
       49 . A display system, comprising: 
 a display unit;    a backlight; and    an optical film as recited in  claim 1  disposed between the display unit and the backlight.    
   
   
       50 . A display system, comprising: 
 a display unit;    a backlight; and    an optical film as recited in  claim 27  disposed between the display unit and the backlight.