360 degree privacy film
Light control films are provided that confine light transmitted therethrough to be within a 360° view region and block light outside of this view region. The light control films can provide security in all directions including right-and-left and up-and-down of the films, without compromising light transmittance compared to one-dimensional light control films. The light control films include an array of light transmissive, tapered posts and absorptive regions disposed between the posts.
1. A light control film, comprising:
a first major surface and a second major surface opposite the first major surface;
a view axis generally perpendicular to at least one of the first and second major surfaces;
an array of posts comprising a light transmissive material, the array of posts being arranged in two dimensions with columns and rows, and extending along respective longitudinal axes from the first major surface to the second major surface; and
absorptive regions comprising a polymerizable composition containing one or more optically absorptive materials continuously disposed between the array of posts, the one or more optically absorptive materials only filling gaps in fluid communication between the posts and extending between a first end surface and a second end surface along the view axis,
wherein at least one of the posts has a tapered shape along the respective longitudinal axis, and
wherein the array of posts and the absorptive regions are arranged to confine light transmitted out of the first or second major surface to be within a 360° view cone around the view axis.
2. The light control film of claim 1 , further comprising an optically transparent carrier layer disposed adjacent at least one of the first and second major surfaces to support respective ends of the array of posts.
3. The light control film of claim 1 , further comprises an adhesive layer configured to couple the light control film to a substrate.
4. The light control film of claim 1 , further comprising land regions at the first or second major surface configured to connect respective ends of the array of posts, the land regions comprising the light transmissive material.
5. The light control film of claim 1 , wherein the array of posts comprise a transparent polymeric material, optionally the transparent polymeric material comprises at least one of polyurethane, acrylate, and polycarbonate.
6. The light control film of claim 1 , wherein the one or more optically absorptive materials comprise at least one of pigment and dye.
7. The light control film of claim 1 , wherein the absorptive regions further comprise a radiation cured resin or a thermally cured resin.
8. The light control film of claim 1 , wherein at least one of the posts have a cross sectional shape of polygon, optionally, the posts each have a cross sectional shape of hexagon, the hexagons are arranged in a close packed layout, and the absorptive regions therebetween form a honeycomb pattern.
9. The light control film of claim 8 , wherein the posts have a depth D along the view axis, the hexagons adjacent the first major surface have a side width W 1 , the hexagons adjacent the second major surface have a side width W 2 , the honeycomb pattern of the absorptive regions has a wall thickness T 1 adjacent the first major surface, and the honey comb pattern of the absorptive regions has a wall thickness T 2 adjacent the second major surface, the ratio D/((W 1 +W 2 )/2) is between 2 and 8, and the ratio (W 1 +W 2 )/(T 1 +T 2 ) is between 2 and 30.
10. The light control film of claim 1 , wherein an area ratio of the array of posts and the absorptive regions adjacent the first major surface is 3:2 or more, and an area ratio of the array of posts and the absorptive regions adjacent the second major surface is 4:1 or more.
11. The light control film of claim 1 , wherein the tapered shape of the at least one of the posts has a draft angle of about 5° or less.
12. The light control film of claim 1 , wherein the 360° view cone has a transmission cutoff angle with respect to the view axis of about 45° or less.
13. The light control film of claim 1 , wherein within the 360° view cone, a normalized light transmittance is about 50% or more.
14. The light control film of claim 13 , wherein the normalized light transmittance is about 63% or more.
15. A display device comprising the light control film of claim 1 .
16. A method of making a light control film having a first major surface and a second major surface opposite the first major surface, and a view axis generally perpendicular to at least one of the first and second major surfaces, the method comprising:
providing an array of posts comprising a light transmissive material, the array of posts being supported by an optically transparent carrier layer, the array of posts being arranged in two dimensions with columns and rows, and extending along respective longitudinal axis from a first major surface to a second major surface; and
filling gaps between the posts by flowing a polymerizable composition containing one or more optically absorptive materials to continuously dispose between the array of posts to form absorptive regions, the gaps being in fluid communication with each other to provide fluid channels through which the one or more optically absorptive materials can flow around the columns and rows of posts,
wherein at least one of the posts has a tapered shape along the respective longitudinal axis, and
wherein the array of posts and the absorptive regions are arranged to confine light transmitted out of the first or second major surface to be within a 360° view cone around the view axis.
17. The method of claim 16 , wherein the posts each have a cross sectional shape of hexagon, the hexagons are arranged in a close packed layout, and the absorptive regions therebetween form a honeycomb pattern.
18. The method of claim 17 , wherein the posts have a depth D along the view axis, the hexagons adjacent the first major surface have a side width W1, the hexagons adjacent the second major surface have a side width W2, the honeycomb pattern of the absorptive regions has a wall thickness T1 adjacent the first major surface, and the honey comb pattern of the absorptive regions has a wall thickness T2 adjacent the second major surface, the ratio D/((W1+W2)/2) is between 2 and 8, and the ratio (W1+W2)/(T1+T2) is between 2 and 30.
19. The method of claim 16 , wherein providing the array of posts comprises (i) preparing a polymerizable composition; (ii) depositing the polymerizable composition onto a master negative micro-structured molding surface having hexagonal pockets which are negative replica of the array of posts; and (iii) curing the polymerizable composition to create the array of posts.