Variable transmittance birefringent device
First Claim
1. A variable reflectance vehicle mirror which can be controlled to adjust reflectivity, comprising:
- a super twisted nematic (STN) liquid crystal cell having a front side and a rear side;
a first polarization filter positioned on the front side of said STN liquid crystal cell;
a second polarization filter positioned on the rear side of said STN liquid crystal cell;
a reflective layer positioned adjacent to said second polarization filter; and
a control circuit connected to said STN liquid crystal cell for controlling the birefringence of the STN liquid crystal cell to adjust the degree of reflection of the mirror.
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Accused Products
Abstract
A variable reflectance mirror employing a super-twisted nematic (STN) liquid crystal cell to control reflectivity. The STN liquid crystal cell includes a layer of STN liquid crystal material formed between a pair of transparent electrodes, where a polymer alignment layer is formed over the electrodes so as to orient the STN liquid crystal material to possess a twist angle between approximately 180° and approximately 270°. A pair of crossed polarizers are respectively positioned on the outer surfaces of the front and rear plates. A layer of reflective material is further formed adjacent to the outer surface of the polarizer adjacent to the rear plate. The transparent electrodes are connected to a voltage source to apply an electrical bias across the STN liquid crystal layer, where the transmitivity of the STN liquid crystal layer to light can be varied by varying the electrical bias applied across the transparent electrodes to vary the birefringence of the STN liquid crystal layer. The degree of reflection provided by the variable reflectance mirror is adjusted by adjusting the electrical bias applied across the STN liquid crystal layer. A stacked IC control circuit is provided for controlling the electrical bias applied across the STN liquid crystal layer.
107 Citations
57 Claims
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1. A variable reflectance vehicle mirror which can be controlled to adjust reflectivity, comprising:
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a super twisted nematic (STN) liquid crystal cell having a front side and a rear side;
a first polarization filter positioned on the front side of said STN liquid crystal cell;
a second polarization filter positioned on the rear side of said STN liquid crystal cell;
a reflective layer positioned adjacent to said second polarization filter; and
a control circuit connected to said STN liquid crystal cell for controlling the birefringence of the STN liquid crystal cell to adjust the degree of reflection of the mirror. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 39, 40, 41, 42, 43)
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38. A variable reflectance vehicle mirror which can be controlled to adjust reflectivity, wherein the variable reflectance is provided by a super twisted nematic (STN) liquid crystal cell having variably controllable transmittance.
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44. A variable reflectance vehicle mirror which can be controlled to adjust reflectivity, comprising:
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a super twisted nematic (STN) liquid crystal cell having a front side and a rear side;
a first polarization filter positioned on the front side of said STN liquid crystal cell;
a second polarization filter positioned on the rear side of said STN liquid crystal cell; and
a reflective layer positioned adjacent to said second polarization filter;
wherein the variable reflectance vehicle mirror is formed to have a rimless outer periphery. - View Dependent Claims (45, 46, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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47. A control device for controlling the reflectivity of a variable reflectance vehicle mirror which utilizes a super twisted nematic (STN) liquid crystal cell to control reflectivity, comprising:
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a light detector for detecting an intensity of light impinging upon the variable reflectance mirror; and
a control circuit responsive to the detected light intensity which is connected to the STN liquid crystal cell for controlling the birefringence of the STN liquid crystal cell to adjust reflectivity of the mirror.
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Specification