Optical film

An optical film comprising a structured surface and an opposing surface, said structured surface having a plurality of structures thereon, said structures having a nominal height and an actual height, said actual heights of at least some of said structures having a random variation of at least 2% of said nominal height.

An optical film comprising a structured surface and an opposing surface, said structured surface having a plurality of structures thereon, said structures having a nominal height and an actual height, said actual height of at least some of said structures varying by an amount and with a nominal period sufficient to substantially mask small cosmetic defects in said optical film.

An optical film comprising a structured surface and an opposing surface said opposing surface having a plane associated therewith, said structured surface having a plurality of structures thereon said structures having a nominal height, said structures varying in distance from said plane with a nominal period of less than forty times said nominal height.

An optical film comprising a structured surface and an opposing surface said opposing surface having a plane associated therewith, said structured surface having a plurality of structures thereon, said structures lying a distance from said plane where said distance continuously varies with a varying period.

An optical film comprising a structured surface and an opposing surface, said opposing surface having a plane associated therewith, said structured surface having thereon a plurality of structures, said structures reflecting light entering said film through said opposing surface while making an angle in a first predetermined group of angles with a normal to said plane associated with said opposing surface and refracting light entering said optical film while making an angle in a second predetermined group of angles to said normal to said plane associated with said opposing surface such that a majority of the light exiting said optical film through said structured surface will exit in an output wedge that is smaller than the input wedge and said structures have a nominal height and an actual height, said actual height of at least some of said structures continuously varying with a nominal period of variation less than forty times said nominal height.

An optical film comprising a structured surface and an opposing surface, said opposing surface having a plane associated therewith, said structured surface having thereon a plurality of structures, said structures reflecting light entering said film through said opposing surface while making an angle in a first predetermined group of angles with a normal to said plane associated with said opposing surface and refracting light entering said optical film while making an angle in a second predetermined group of angles to said normal to said plane associated with said opposing surface such that a majority of the light exiting said optical film through said structured surface will exit in an output wedge that is smaller than the input wedge and said structures have a nominal height and an actual height, said structures having a nominal height and an actual height, said actual height of at least some of said structures varying by an amount and with a period sufficient to substantially mask cosmetic defects having maximum dimensions equal to or less than eight times said nominal height in said optical film.

A method of making a tool for manufacturing an optical film, said method comprising the step of thread cutting a groove having a nominal depth and an actual depth in a metal roll with a diamond tool wherein said diamond tool is supported by a fast tool servo actuator and said fast tool servo actuator is stimulated by a random signal such that the actual depth varies continuously.