Light directing film having variable height structured surface and light directing article constructed therefrom

A light directing article comprising:

• a first sheet of light directing film having a first surface and a structured surface opposite said first surface, said structured surface including a linear array of prism elements oriented along a first major axis, said array including a repeating pattern of prism zones, the pattern including at least a first zone that measures less than about 300 microns in width comprising a first prism element having a peak defining a first dihedral angle and disposed at a first distance from a reference plane and a second zone that measures between 200 and 4000 microns in width adjacent said first zone and comprising a second prism element having a peak defining a second dihedral angle substantially equal to the first dihedral angle and disposed at a second distance from the reference plane which is less than said first distance, the reference plane being disposed between the structured surface and the first surface;
• a second sheet of light directing film having a substantially planar surface disposed adjacent said first sheet of light directing film and having a structured surface opposite said substantially planar surface having a linear array of prism elements oriented along a second major axis;
• said first major axis intersecting said second major axis within a predetermined angular range, whereby, optical coupling between said first sheet and said second sheet occurs primarily in said first zone.

An optical display, comprising:

• a light source;
• a viewing screen;
• light transfer means for directing light from said light source to said viewing screen, said light transfer means including at least a first sheet of light directing film, said film including a first surface and a structured surface opposite said first surface and having an array of prism elements, each prism element having opposing facets which intersect at a peak, said array including a repeating pattern of prism zones, said pattern including at least:
• a first zone that measures less than about 300 microns in width and comprising at least a first prism element having a peak defining a first dihedral angle and disposed at a first distance from a reference plane located between the structured surface and the first surface;
• and
• a second zone that measures between 200 and 4000 microns in width adjacent said first zone and comprising at least a second prism element having a peak defining a second dihedral angle substantially equal to the first dihedral angle and disposed at a second distance from the reference plane, said second distance being less than said first distance, whereby, when the structured surface of said light directing film is placed adjacent a planar surface, optical coupling occurs primarily in said first zone.