Recycling backlights with semi-specular components
First Claim
1. A backlight, comprising:
- a front and back reflector forming a hollow light recycling cavity, the front reflector being partially transmissive to provide an output illumination area, and wherein the front reflector has a reflectivity for p-polarized light that is;
(1) constant, or (2) increases, with angle of incidence, and a transmission that generally decreases with angle of incidence;
a component that provides the cavity with a desired balance of specular and diffuse characteristics, the component being characterized by a transport ratio greater than 15% at a 15 degree incidence angle and less than 95% at a 45 degree incidence angle, wherein the front or back reflectors can be or include the component, or the component can be distinct from the front and back reflectors; and
one or more light source members disposed to emit light into the light recycling cavity over a limited angular distribution;
wherein the front reflector has a hemispherical reflectivity for unpolarized visible light of Rfhemi, and the back reflector has a hemispherical reflectivity for unpolarized visible light of Rbhemi, and Rfhemi*Rbhemi is at least 0.70.
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Accused Products
Abstract
A hollow light-recycling backlight has a “semi-specular” component providing a balance of specularly and diffusely reflected light improving the uniformity of the light output. The component may be arranged on the reflectors (1021), (1014) or inside the cavity (1016). This balance is achieved by designing the component'"'"'s “transport ratio” defined by (F−B)/(F+B), (F and B are the amounts of incident light scattered forwards and backwards respectively by the component in the plane of the cavity) to lie in a certain range. Furthermore, the product of the front and back reflector “hemispherical” reflectivities should also lie in a given range. Alternatively, the “cavity transport value”, a measure of how well the cavity can spread injected light from the injection point to distant points in the cavity should lie in a further range and the “hemispherical” reflectivity of the back reflector should be >0.7.
187 Citations
11 Claims
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1. A backlight, comprising:
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a front and back reflector forming a hollow light recycling cavity, the front reflector being partially transmissive to provide an output illumination area, and wherein the front reflector has a reflectivity for p-polarized light that is;
(1) constant, or (2) increases, with angle of incidence, and a transmission that generally decreases with angle of incidence;a component that provides the cavity with a desired balance of specular and diffuse characteristics, the component being characterized by a transport ratio greater than 15% at a 15 degree incidence angle and less than 95% at a 45 degree incidence angle, wherein the front or back reflectors can be or include the component, or the component can be distinct from the front and back reflectors; and one or more light source members disposed to emit light into the light recycling cavity over a limited angular distribution; wherein the front reflector has a hemispherical reflectivity for unpolarized visible light of Rfhemi, and the back reflector has a hemispherical reflectivity for unpolarized visible light of Rbhemi, and Rfhemi*Rbhemi is at least 0.70. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification