Reflective optical stack for privacy display
First Claim
1. A display device for use in ambient illumination comprising:
- a spatial light modulator;
an output polariser arranged on the output side of the spatial light modulator, the output polariser being a linear polariser;
an additional polariser arranged on the output side of the output polariser, the additional polariser being a linear polariser;
a reflective polariser arranged between the output polariser and the additional polariser, the reflective polariser being a linear polariser having an electric vector transmission direction; and
plural polar control retarders arranged between the reflective polariser and the additional polariser, wherein the plural polar control retarders comprise;
a switchable liquid crystal retarder comprising a layer of liquid crystal material having a retardance for light of a wavelength of 550 nm in a range from 500 nm to 1800 nm, and two surface alignment layers disposed adjacent to the layer of liquid crystal material and on opposite sides thereof, one of the surface alignment layers being between the layer of liquid crystal material and a passive retarder and being arranged to provide homeotropic alignment in the adjacent liquid crystal material and the other of the surface alignment layers being arranged to provide homogeneous alignment in the adjacent liquid crystal material, and each of the surface alignment layers having a pretilt having a pretilt direction with a component in the plane of the layer of liquid crystal material that is parallel or anti-parallel or orthogonal to the electric vector transmission direction of the reflective polariser; and
at least one passive retarder comprising either;
a passive retarder having its optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a retardance for light of a wavelength of 550 nm in a range from −
300 nm to −
1600 nm;
ora pair of passive retarders which have optical axes in the plane of the retarders that are crossed, each retarder of the pair of passive retarders having a retardance for light of a wavelength of 550 nm in a range from 400 nm to 1600 nm.
1 Assignment
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Accused Products
Abstract
A privacy display comprises a polarised output spatial light modulator, reflective polariser, plural polar control retarders and a polariser. In a privacy mode of operation, on-axis light from the spatial light modulator is directed without loss, whereas off-axis light has reduced luminance. Further, display reflectivity is reduced for on-axis reflections of ambient light, while reflectivity is increased for off-axis light. The visibility of the display to off-axis snoopers is reduced by means of luminance reduction and increased frontal reflectivity to ambient light. In a public mode of operation, the liquid crystal retardance is adjusted so that off-axis luminance and reflectivity are unmodified.
246 Citations
30 Claims
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1. A display device for use in ambient illumination comprising:
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a spatial light modulator; an output polariser arranged on the output side of the spatial light modulator, the output polariser being a linear polariser; an additional polariser arranged on the output side of the output polariser, the additional polariser being a linear polariser; a reflective polariser arranged between the output polariser and the additional polariser, the reflective polariser being a linear polariser having an electric vector transmission direction; and plural polar control retarders arranged between the reflective polariser and the additional polariser, wherein the plural polar control retarders comprise; a switchable liquid crystal retarder comprising a layer of liquid crystal material having a retardance for light of a wavelength of 550 nm in a range from 500 nm to 1800 nm, and two surface alignment layers disposed adjacent to the layer of liquid crystal material and on opposite sides thereof, one of the surface alignment layers being between the layer of liquid crystal material and a passive retarder and being arranged to provide homeotropic alignment in the adjacent liquid crystal material and the other of the surface alignment layers being arranged to provide homogeneous alignment in the adjacent liquid crystal material, and each of the surface alignment layers having a pretilt having a pretilt direction with a component in the plane of the layer of liquid crystal material that is parallel or anti-parallel or orthogonal to the electric vector transmission direction of the reflective polariser; and at least one passive retarder comprising either; a passive retarder having its optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a retardance for light of a wavelength of 550 nm in a range from −
300 nm to −
1600 nm;
ora pair of passive retarders which have optical axes in the plane of the retarders that are crossed, each retarder of the pair of passive retarders having a retardance for light of a wavelength of 550 nm in a range from 400 nm to 1600 nm. - 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)
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24. A display device for use in ambient illumination comprising:
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a spatial light modulator; an output polariser arranged on the output side of the spatial light modulator, the output polariser being a linear polariser; an additional polariser arranged on the output side of the output polariser, the additional polariser being a linear polariser; a reflective polariser arranged between the output polariser and the additional polariser, the reflective polariser being a linear polariser having an electric vector transmission direction; and plural polar control retarders arranged between the reflective polariser and the additional polariser, wherein the plural polar control retarders comprise; a switchable liquid crystal retarder comprising a layer of liquid crystal material having a retardance for light of a wavelength of 550 nm in a range from 700 nm to 2000 nm, and two surface alignment layers disposed adjacent to the layer of liquid crystal material and on opposite sides thereof, one of the surface alignment layers being arranged to provide homeotropic alignment in the adjacent liquid crystal material and the other of the surface alignment layers being between the layer of liquid crystal material and a passive retarder and being arranged to provide homogeneous alignment in the adjacent liquid crystal material, and each of the surface alignment layers having a pretilt having a pretilt direction with a component in the plane of the layer of liquid crystal material that is parallel or anti-parallel or orthogonal to the electric vector transmission direction of the reflective polariser; and at least one passive retarder comprising either; a passive retarder having its optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a retardance for light of a wavelength of 550 nm in a range from −
400 nm to −
1800 nm;
ora pair of passive retarders which have optical axes in the plane of the retarders that are crossed, each retarder of the pair of passive retarders having a retardance for light of a wavelength of 550 nm in a range from 400 nm to 1800 nm. - View Dependent Claims (25, 26, 27, 28, 29, 30)
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Specification