Anti-reflective surface structures

An article comprising a layer defining an anti-reflective surface extending along an axis, wherein a plane containing the axis defines a cross section of the layer and intersects the surface to define a line describing the surface in two dimensions, the layer comprising:

• a series of micro-structures at least partially defined by the line, the line defining a series of alternating micro-peaks and micro-spaces along the axis, wherein a boundary between each adjacent micro-peak and micro-space includes at least one of a bend or an inflection point of the line;
• and
• a plurality of nano-structures at least partially defined by the line, the line defining at least one series of nano-peaks disposed on at least the micro-spaces along the axis,
• wherein each nano-peak has a height and each corresponding micro-peak has a height at least 10 times the height of the nano-peak, and
• wherein the micro-spaces have a width of at least 50 micrometers.

A method of forming an article comprising a layer defining an anti-reflective surface, the method comprising:

• forming a series of micro-structures on a surface of a layer, the series of micro-structures comprising a series of alternating micro-peaks and micro-spaces along an axis;
• disposing a series of nano-sized masking elements on at least the micro-spaces along the axis, wherein the masking elements define a maximum diameter and the corresponding micro-peaks have a height of at least 10 times the maximum diameter of the masking elements;
• and
• exposing the surface of the layer to reactive ion etching to form a plurality of nano-structures on the surface of the layer including a series of nano-peaks along the axis, each nano-peak comprising the masking element and a column between the masking element and the layer,
• wherein the micro-spaces have a width of at least 50 micrometers.

A method of forming an article comprising a layer defining an anti-reflective surface, the method comprising:

• extruding a hot melt material comprising an ultraviolet-stable material;
• shaping the extruded material with a micro-replication tool comprising a mirror image of a series of micro-structures to form the series of micro-structures on the surface of the layer, the series of micro-structures comprising a series of alternating micro-peaks and micro-spaces along an axis;
• and
• forming a plurality of nano-structures on the surface of the layer on at least the micro-spaces, the plurality of nano-peaks comprising at least one series of nano-peaks along the axis,
• wherein the micro-spaces have a width of at least 50 micrometers.