Optical films, method of making and method of using
An optical film including a plurality of structures formed from a material with each structure having a base, a first side wall that forms an acute angle with the base, and a second side wall that forms an obtuse angle with the base. The optical film efficiently couples light out of a light source or other structure. The optical film may be fabricated with a photolithographic process.
1 . An optical film comprising:
a plurality of structures formed from a material with each structure including:
a base;
a first side wall that forms an acute angle with the base; and
a second side wall that forms an obtuse angle with the base.
2 . The film of claim 1 , further comprising a substrate having a top surface,
wherein the plurality of structures are on or adjacent the top surface.
3 . The film of claim 1 , wherein the acute angle is equal to about (90+δ)/2, where δ is the angle of light coming into the plurality of structures.
4 . The film of claim 1 , wherein h is equal to about a tan δ, tan θ/(tan θ−tan δ), where h is the height of the structures, a is the width of the base of each structure, δ is the angle of light coming into the plurality of structures, and θ is the acute angle.
5 . The film of claim 1 , wherein each structure includes a top such that the first side, the second side, the base and the top form a quadrilateral.
6 . The film of claim 5 , wherein each top is flat.
7 . The film of claim 5 , wherein each top is textured.
8 . The film of claim 1 , wherein the material is a photopolymerized material.
9 . The film of claim 1 ,
wherein another material is between adjacent structures of the plurality of structures; and
wherein the another material has a lower refractive index than the material of the plurality of structures.
10 . The film of claim 9 , wherein the another material includes scattering particles.
11 . The film of claim 9 , wherein the another material is air.
12 . The film of claim 9 , further comprising a diffusing material that covers the another material and a surface of each structure opposite the base.
13 . The film of claim 1 , wherein each first side wall is coated with a reflective coating.
14 . The film of claim 13 , wherein the reflective coating is a metal coating.
15 . The film of claim 13 , wherein the reflective coating is a dielectric material coating.
16 . The film of claim 1 , wherein another material is between adjacent structures of the plurality of structures and covers a surface of each structure opposite the base.
17 . An optical film comprising:
a substrate;
a plurality of structures on or adjacent the substrate and formed from a photopolymerized material with each structure including:
a base;
a first side wall that forms an acute angle with the base;
a second side wall that forms an obtuse angle with the base; and
a top, the top being substantially parallel to the base, forming an acute angle with the second side wall, and forming an obtuse angle with the first side wall; and
another material having a lower refractive index than the material of the plurality of quadrilateral structures, the another material being located between adjacent first and second side walls.
18 . The film of claim 17 , wherein the another material covers the tops of the plurality of structures.
19 . A method of making an optical film comprising:
depositing a photopolymerizable material on a surface;
selectively polymerizing part of the photopolymerizable material such that a plurality of polymerized structures is formed in the photopolymerizable material, each polymerized structure having:
a first side wall that forms an acute angle with the surface; and
a second side wall that forms an obtuse angle with the surface; and
removing the photopolymerizable material not polymerized.
20 . The method of claim 19 , wherein the selectively polymerizing is performed by illuminating a photomask with collimated light that is incident on the surface at a non-normal angle.
21 . The method of claim 19 , further comprising depositing an optically clear filler material between the plurality of polymerized structures subsequent to the step of removing the photopolymerizable material not polymerized.
22 . An optical film for use in a light source comprising:
a substrate; and
a plurality of structures formed from a photopolymerized material with each structure including:
a base;
a first side wall that forms an acute angle with the base; and
a second side wall that forms an obtuse angle with the base,
wherein h is equal to about a tan δ tan θ (tan θ−tan δ), where h is a height of the structures, a is a width of the base of each structure, δ is an angle of light coming into the
plurality of structures from a light source, and θ is the acute angle.