Enhanced Light Guide
A light guide containing substantially aligned non-spherical particles provides more efficient control of light scattering. One or more regions containing ellipsoidal particles may be used and the particle sizes may vary between 2 and 100 microns in the smaller dimension. The light scattering regions may be substantially orthogonal in their axis of alignment. Alternatively, one or more asymmetrically scattering films can be used in combination with a backlight light guide and a reflector to produce an efficient backlight system. The light guides may be manufactured by embossing, stamping, or compression molding a light guide in a suitable light guide material containing asymmetric particles substantially aligned in one direction. The light scattering light guide or non-scattering light guide may be used with one or more light sources, collimating films or symmetric or asymmetric scattering films.
1 . A light guide comprising:
a) a first input surface suitable for receiving light from a light source, and
b) a first output surface comprising first and second mutually orthogonal viewing axes whereby incident light exits the light guide when the total internal reflection condition at the first output surface is not satisfied, and
c) a first light scattering region disposed along an optical path between the first input surface and the first output surface capable of providing improved luminance uniformity along the second viewing axis, comprising a continuous phase of a first material of refractive index n x1 and at least one first dispersed phase domain comprising a second material of refractive index n x2 wherein |n x1 −n x2 |>0.001 and the first dispersed phase domain is non-spherical in shape and aligned substantially parallel to the first output surface with the major axes of the domain parallel to the first viewing axis, and
d) a first boundary surface and a second boundary surface defining opposite surface boundaries of the first light scattering region, and
e) light redirecting features disposed along an optical path between the first input surface and the first output surface capable of providing improved luminance uniformity along the first viewing axis, and
f) wherein the light redirecting features are arranged to have at least one predetermined non-constant dimension or spacing along the first viewing axis.
2 . The light guide of claim 1 wherein the light redirecting features are surface relief features.
3 . The light guide of claim 1 wherein the light redirecting features are printed light scattering patterns.
4 . The light guide of claim 2 wherein the light redirecting features are linear along the second viewing axis.
5 . A light guide comprising:
a) a first input surface suitable for receiving light from a light source, and
b) a first output surface comprising first and second mutually orthogonal viewing axes whereby incident light exits the light guide when the total internal reflection condition at the first output surface is not satisfied, and
c) a first light scattering region disposed along an optical path between the first input surface and the first output surface capable of providing improved luminance uniformity along the second viewing axis, comprising a continuous phase of a first material of refractive index n x1 and at least one first dispersed phase domain comprising a second material of refractive index n x2 wherein |n x1 −n x2 |>0.001 and the first dispersed phase domain is non-spherical in shape and aligned substantially parallel to the first output surface with the major axes of the domain parallel to the first viewing axis, and
d) a first boundary surface and a second boundary surface defining opposite surface boundaries of the first light scattering region, and
e) Light redirecting features disposed along an optical path between the first input surface and the first output surface capable of providing improved luminance uniformity along the first viewing axis, and
f) wherein the light redirecting features are arranged to have at least one predetermined non-constant dimension or spacing in a plane orthogonal to the first output surface.
6 . The light guide of claim 1 wherein the input surface is substantially orthogonal to the output surface and comprises the first boundary surface.
7 . The light guide of claim 6 wherein the input surface contains the first boundary surface.
8 . The light guide of claim 1 wherein the first boundary surface comprises the light redirecting features;
9 . The light guide of claim 1 , wherein the light scattering region is an optical film and the light guide further comprises a substantially non-scattering region that is optically coupled to the optical film.
10 . The light guide of claim 9 wherein the optical film comprises the light redirecting features.
11 . The light guide of claim 1 , further comprising a second light scattering region comprising a second dispersed phase domain of a third material of refractive index n x3 wherein the second dispersed phase domain is non-spherical in shape and aligned substantially parallel to the first output surface with the major axis of the second dispersed phase parallel to the first viewing axis;
12 . The light guide of claim 11 , wherein the first light scattering region is separated from the second light scattering region by a region substantially free of light scattering domains.
13 . The light guide of claim 1 , wherein the thickness of the first light scattering region varies spatially.
14 . The light guide of claim 1 , wherein the first dispersed phase domain is a fiber.
15 . The light guide of claim 1 , further comprising a low refractive index region of a fourth material of refractive index n x4 disposed along an optical path between the first input surface and the first output surface whereby the low refractive index region increases the number of reflections occurring within the light guide relative to a similar light guide without the region.
16 . The light guide of claim 15 wherein n x4 <1.52.
17 . A light emitting assembly comprising:
a) a housing, and
b) at least one light emitting source, and
c) the light guide of claim 1 .
18 . The assembly of claim 17 wherein the light emitting source comprises a light emitting diode with a second output surface through which light is emitted.
19 . The assembly of claim 18 , wherein the first input surface is substantially conformal and optically coupled to the second output surface.
20 . The assembly of claim 18 , wherein the light emitting source comprises a linear array of light emitting diodes.
21 . The assembly of claim 17 , wherein the light source comprises a fluorescent bulb.
22 . A backlight comprising the light emitting assembly of claim 17 .
23 . The light emitting assembly of claim 17 further comprising at least one region selected from the group consisting of light diffusing region, light collimating region, reflective region, absorptive polarizing region, or polarization dependant reflective region.
24 . A display comprising the backlight of claim 22 .
25 . An electroluminescent sign comprising the light emitting assembly of claim 17 .
26 . A device for providing illumination comprising the light emitting assembly of claim 17.