Optical stack for privacy display
First Claim
Patent Images
1. A switchable display device comprising:
- a backlight arranged to output light;
a transmissive spatial light modulator arranged to receive the light output from the backlight,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,wherein the plural retarders comprise;
a switchable liquid crystal retarder comprising;
a 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
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 the 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; and
at least one passive compensation retarder that comprises either;
a passive uniaxial retarder having its optical axis perpendicular to the plane of the retarder and having a retardance for light of a wavelength of 550 nm in a range from −
300 nm to −
700 nm;
ora pair of passive uniaxial retarders having optical axes in the plane of the retarders that are crossed and each having a retardance for light of a wavelength of 550 nm in a range from +300 nm to +800 nm.
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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 polarizers 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.
180 Citations
26 Claims
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1. A switchable display device comprising:
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a backlight arranged to output light; a transmissive spatial light modulator arranged to receive the light output from the backlight, 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, wherein the plural retarders comprise; a switchable liquid crystal retarder comprising;
a 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
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 the 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; andat least one passive compensation retarder that comprises either; a passive uniaxial retarder having its optical axis perpendicular to the plane of the retarder and having a retardance for light of a wavelength of 550 nm in a range from −
300 nm to −
700 nm;
ora pair of passive uniaxial retarders having optical axes in the plane of the retarders that are crossed and each having a retardance for light of a wavelength of 550 nm in a range from +300 nm to +800 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, 24, 25, 26)
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Specification