Optical stack for switchable directional display
First Claim
Patent Images
1. A display device comprising:
- a spatial light modulator;
a display polariser arranged on a side of the spatial light modulator;
an additional polariser arranged on the same side of the spatial light modulator as the display polariser; and
plural retarders arranged between the additional polariser and the display polariser, there being no further polarisers arranged between the plural retarders;
wherein the plural retarders comprise;
a switchable liquid crystal retarder comprising either;
a layer of liquid crystal material and two surface alignment layers disposed adjacent to the layer of liquid crystal material and on opposite sides thereof, each of the surface alignment layers being arranged to provide homeotropic 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 a plane of the layer of liquid crystal material that is parallel or anti-parallel or orthogonal to an electric vector transmission direction of the display polariser, the layer of liquid crystal material having a negative dielectric anisotropy and having a retardance for light of a wavelength of 550 nm in a range from 500 nm to 1000 nm;
ora layer of liquid crystal material and two surface alignment layers disposed adjacent to the layer of liquid crystal material and on opposite sides thereof, each 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 a plane of the layer of liquid crystal material that is parallel or anti-parallel or orthogonal to an electric vector transmission direction of the display polariser, the layer of liquid crystal material having a positive dielectric anisotropy and having a retardance for light of a wavelength of 550 nm in a range from 500 nm to 1000 nm; and
plural passive compensation retarders, each passive compensation retarder having its optical axis perpendicular to a plane of the retarder, the plural passive compensation retarders having a total retardance for light of a wavelength of 550 nm in a range from −
300 nm to −
900 nm in the case that the two surface alignment layers are arranged to provide homeotropic alignment in the adjacent liquid crystal material or in a range from −
300 nm to −
700 nm in the case that the two surface alignment layers are arranged to provide homogeneous alignment in the adjacent liquid crystal material.
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Abstract
A privacy display comprises a spatial light modulator and a compensated switchable liquid crystal retarder arranged between first and second polarisers arranged in series with the spatial light modulator. 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. The visibility of the display to off-axis snoopers is reduced by means of luminance reduction over a wide polar field. In a wide angle mode of operation, the switchable liquid crystal retardance is adjusted so that off-axis luminance is substantially unmodified.
127 Citations
27 Claims
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1. A display device comprising:
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a spatial light modulator; a display polariser arranged on a side of the spatial light modulator; an additional polariser arranged on the same side of the spatial light modulator as the display polariser; and plural retarders arranged between the additional polariser and the display polariser, there being no further polarisers arranged between the plural retarders; wherein the plural retarders comprise; a switchable liquid crystal retarder comprising either; a layer of liquid crystal material and two surface alignment layers disposed adjacent to the layer of liquid crystal material and on opposite sides thereof, each of the surface alignment layers being arranged to provide homeotropic 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 a plane of the layer of liquid crystal material that is parallel or anti-parallel or orthogonal to an electric vector transmission direction of the display polariser, the layer of liquid crystal material having a negative dielectric anisotropy and having a retardance for light of a wavelength of 550 nm in a range from 500 nm to 1000 nm;
ora layer of liquid crystal material and two surface alignment layers disposed adjacent to the layer of liquid crystal material and on opposite sides thereof, each 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 a plane of the layer of liquid crystal material that is parallel or anti-parallel or orthogonal to an electric vector transmission direction of the display polariser, the layer of liquid crystal material having a positive dielectric anisotropy and having a retardance for light of a wavelength of 550 nm in a range from 500 nm to 1000 nm; and plural passive compensation retarders, each passive compensation retarder having its optical axis perpendicular to a plane of the retarder, the plural passive compensation retarders having a total retardance for light of a wavelength of 550 nm in a range from −
300 nm to −
900 nm in the case that the two surface alignment layers are arranged to provide homeotropic alignment in the adjacent liquid crystal material or in a range from −
300 nm to −
700 nm in the case that the two surface alignment layers are arranged to provide homogeneous alignment in the adjacent liquid crystal material. - 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)
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Specification