Backlighting system including a specular partial reflector and a circular-mode reflective polarizer
Assignee3M Innovative Properties Company
InventorsMark B. O'Neill, Philip E. Watson
Life of this patent
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Abstract
In a display backlight (120, 220, 420) a specular partial reflector (250, 450) is placed between a circular-mode reflective polarizer (242, 442) and an illumination device (230, 430). The specular partial reflector (450) recycles otherwise unused polarized light (468L) reflected from the circular-mode reflective polarizer (442) which results in an optimized backlight brightness. The main application of the backlight (120) is in liquid crystal displays (100).
Claims14
A backlight, comprising:
- an illumination device comprising at least one light source;
- a circular-mode reflective polarizer;
- and
- a specular partial reflector disposed between the illumination device and the circular-mode reflective polarizer, wherein the specular partial reflector has an orthogonal reflection fraction value of at least 2%;
- wherein the specular partial reflector is in substantially direct polarization communication with the circular-mode reflective polarizer.
A display comprising a liquid crystal panel and a backlight that provides light to the liquid crystal panel, wherein the backlight comprises:
- an illumination device comprising at least one light source;
- a circular-mode reflective polarizer disposed between the liquid crystal panel and the illumination device;
- and
- a specular partial reflector disposed between the illumination device and the circular-mode reflective polarizer, wherein the specular partial reflector has an orthogonal reflection fraction value of at least 2%;
- wherein the specular partial reflector is in substantially direct polarization communication with the circular-mode reflective polarizer.
A backlight for providing polarized light, comprising:
- an illumination device comprising at least one light source;
- a circular-mode reflective polarizer configured to transmit a first portion of light having a first circular polarization and reflect a second portion of light having a second circular polarization orthogonal to the first circular polarization;
- and
- a specular partial reflector disposed between the illumination device and the circular-mode reflective polarizer, the specular partial reflector suitable for receiving the second portion of light from the circular-mode reflective polarizer and returning a third portion of light to the circular-mode reflective polarizer, the third portion of light being a fraction of the second portion of light and having the first circular polarization that is transmittable by the circular-mode reflective polarizer.
Dependencies are inferred from the claim text.