Light redirecting films including intersecting optical elements with flat and curved surfaces
View Patent ↗Light redirecting film including a thin optically transparent substrate having a pattern of individual optical elements of well-defined shape on at least one surface that are quite small relative to the length and width of the surface. At least some of the optical elements have at least one flat surface and at least one curved surface, and intersecting each other over an intersection volume of the intersecting optical elements.
1. A light redirecting film comprising a thin optically transparent substrate having a light entrance surface for receiving light from a light source and an opposite light exit surface, at least one of the surfaces having a pattern of individual optical elements of well defined shape having at least one flat surface and at least one curved surface and being quite small relative to the length and width of the substrate to redistribute light passing through the substrate in a predetermined angular distribution, wherein at least some of the optical elements intersect each other over an intersection volume of the intersecting optical elements.
2. The film of claim 1 wherein at least some of the optical elements intersect each other only on the curved surface of the optical elements to increase the relative percentage of flat surface area to curved surface area of the optical elements to increase on axis gain of light passing through the substrate.
3. The film of claim 1 wherein the predetermined angular distribution of the light passing through the substrate is in a direction approximately normal to the substrate.
4. The film of claim 1 wherein the predetermined angular distribution of the light passing through the substrate has a peak angular distribution that is normal to the substrate.
5. The film of claim 1 wherein the position or placement of the optical elements on at least one of the surfaces is randomized.
6. The film of claim 1 wherein at least some of the optical elements intersect each other to a greater extent on the curved surface of the optical elements than on the flat surface to increase the relative percentage of flat surface area to curved surface area of the optical elements to increase on axis gain of light passing through the substrate.
7. The film of claim 6 wherein the relative percentage of the remaining flat surface area to the remaining curved surface area of the optical elements that intersect each other is greater than 60%.
8. The film of claim 6 wherein the relative percentage of the remaining flat surface area to the remaining curved surface area of the optical elements that intersect each other is greater than 75%.
9. A light redirecting film comprising a thin optically transparent substrate having a light entrance surface for receiving light from a light source and an opposite light exit surface, at least one of the surfaces having a pattern of individual optical elements of well defined shape having at least two sloping surfaces and being quite small relative to the length and width of the substrate to redistribute light passing through the substrate in a predetermined angular distribution, wherein at least some of the optical elements intersect each other to achieve substantially complete surface coverage of at least one of the surfaces of the substrate within the pattern of optical elements, wherein at least one of the sloping surfaces is flat and at least one other of the sloping surfaces is curved, and at least some of the optical elements intersect each other over an intersection volume of the curved surface of the intersecting optical elements.
10. A light redirecting film comprising a thin optically transparent substrate having a light entrance surface for receiving light from a light source, and an opposite light exit surface, at least one of the surfaces having a pattern of individual optical elements of well defined shape and quite small relative to the length and width of the substrate to redistribute light passing through the substrate in a predetermined angular distribution, said optical elements having only two sides or surfaces, one of the sides being flat and the other side being curved, the two sides coming together to form a ridge, said ridge having a misshaped ridge peak, wherein:
1
-
(
2
-
ξ
)
·
sin
(
a
cos
(
ξ
)
)
+
(
1
-
2
·
ξ
)
·
a
cos
(
ξ
)
(
2
-
β
)
·
sin
(
a
cos
(
β
)
)
+
(
1
-
2
·
β
)
·
a
cos
(
β
)
≥
0.9
where
:
ξ
=
1
-
γ
2
·
R
·
cos
(
θ
)
β
=
1
-
D
R
·
cos
(
θ
)
R=Radius of curvature of the curved side,
D=Peak depth or height of the optical element,
θ=Interior angle of the flat side to the surface of the substrate, and
γ=Width of the misshaped ridge peak when viewed from above and normal to the substrate.
11. The film of claim 10 wherein the predetermined angular distribution of the light passing through the substrate is in a direction approximately normal to the substrate.