Stabilization for privacy display

Patent metadata

Field	Value
Publication number	US-11809052-B2
Application number	US-202117372059-A
Country	US
Kind code	B2
Filing date	Jul 9, 2021
Priority date	Jun 29, 2018
Publication date	Nov 7, 2023
Grant date	Nov 7, 2023

Abstract

A display comprises a polarised output spatial light modulator, switchable liquid crystal retarder, absorbing polarizer and touch panel electrodes. The switchable liquid crystal layer is stabilised by a cured reactive mesogen material during application of an applied voltage. Light scatter in privacy mode is reduced and visual security level enhanced. Visibility of disclinations during application of applied pressure, for example from a finger on a touch screen is minimised.

First claim

The invention claimed is:

1. A display device comprising:
a spatial light modulator;
a display polariser arranged on a side of the spatial light modulator, the display polariser being a linear polariser;
an additional polariser arranged on the same side of the spatial light modulator as the display polariser, the additional polariser being a linear polariser; and
at least one polar control retarder arranged between the additional polariser and the display polariser,
wherein the at least one polar control retarder comprises a switchable liquid crystal retarder comprising:
first and second support substrates;
a liquid crystal layer disposed between the first and second transparent support substrates, the liquid crystal layer comprising non-curable liquid crystal material and cured polymer material, wherein the cured polymer material comprises a cured liquid crystal material and is arranged to provide resistance to flow of non-curable liquid crystal material during application of applied force;
electrodes arranged to apply a voltage for controlling the liquid crystal layer; and
respective liquid crystal alignment layers supported on the first and second support substrates adjacent the liquid crystal layer for aligning the non-curable liquid crystal material,
wherein
the display device is configured such that application of a predetermined voltage to the electrodes is capable of causing the layer of cured liquid crystal material and non-curable liquid crystal material simultaneously to introduce no net relative phase shift to orthogonal polarisation components of light passed by the display polariser along a first axis and to introduce a net relative phase shift to orthogonal polarisation components of light passed by the additional polariser along a second axis inclined to the first axis, and
the cured liquid crystal material has an alignment that is aligned with the alignment of the non-curable liquid crystal material in a state in which the predetermined voltage is applied to the electrodes.

2. A display device according to claim 1 , wherein the cured liquid crystal material comprises a reactive mesogen.

3. A display device according to claim 1 , wherein the first axis is along a normal to the plane of the at least one polar control retarder.

4. A display device according to claim 1 , wherein the ratio of the volume of the cured polymer material to the volume of the non-curable liquid crystal material is less than 5%.

5. A display device according to claim 1 , wherein the cured polymer material is arranged in a network that extends between the two support substrates.

6. A display device according to claim 5 , wherein the network is attached to each of the two support substrates.

7. A display device according to claim 1 , wherein the electrodes are disposed on opposite sides of the liquid crystal layer.

8. A display device according to claim 1 , further comprising a control system arranged to control the voltage applied to the electrodes of the switchable liquid crystal retarder.

9. A display device according to claim 1 , wherein the at least one polar control retarder further comprises at least one passive compensation retarder.

10. A display device according to claim 1 , wherein the switchable liquid crystal retarder comprises two surface alignment layers disposed adjacent to the liquid crystal material on opposite sides thereof and each arranged to provide homeotropic alignment at the adjacent liquid crystal material.

11. A display device according to claim 10 , wherein the layer of liquid crystal material of the switchable liquid crystal retarder comprises a liquid crystal material with a negative dielectric anisotropy.

12. A display device according to claim 10 , wherein the layer of liquid crystal material has a retardance for light of a wavelength of 550 nm in a range from 500 nm to 1000 nm.

13. A display device according to claim 10 , wherein:
the at least one polar control retarder comprises at least one passive retarder having an optical axis perpendicular to the plane of the at least one passive retarder, the at least one passive retarder having a total retardance for light of a wavelength of 550 nm in a range from −300 nm to −900 nm; or
the at least one polar control retarder comprises a pair of passive retarders which have optical axes in the plane of the passive retarders that are crossed, each passive retarder of the pair of passive retarders having a retardance for light of a wavelength of 550 nm in a range from 300 nm to 800 nm.

14. A display device according to claim 1 , wherein the switchable liquid crystal retarder comprises two surface alignment layers disposed adjacent to the layer of liquid crystal material and on opposite sides thereof and each arranged to provide homogeneous alignment in the adjacent liquid crystal material.

15. A display device according to claim 14 , wherein the layer of liquid crystal material of the switchable liquid crystal retarder comprises a liquid crystal material with a positive dielectric anisotropy.

16. A display device according to claim 14 , wherein the layer of liquid crystal material has a retardance for light of a wavelength of 550 nm in a range from 500 nm to 900 nm.

17. A display device according to claim 14 , wherein:
the at least one polar control retarder comprises at least one passive retarder having an optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a total retardance for light of a wavelength of 550 nm in a range from −300 nm to −700 nm; or
the at least one polar control retarder comprises a pair of passive retarders which have optical axes in the plane of the retarders that are crossed, each passive retarder of the pair of passive retarders having a retardance for light of a wavelength of 550 nm in a range from 300 nm to 800 nm.

Assignees

• Reald Spark Llc

Inventors

• Harrold Jonathan
• Woodgate Graham J
• Ramsey Robert

Classifications

• G02F1/137 Primary

  characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering · CPC title

• G02B6/0038

  Linear indentations or grooves, e.g. arc-shaped grooves or meandering grooves, extending over the full length or width of the light guide · CPC title

• G02B6/0055

  Reflecting element, sheet or layer · CPC title

• G02F1/139

  based on orientation effects in which the liquid crystal remains transparent · CPC title

• G02F1/1323

  Arrangements for providing a switchable viewing angle · CPC title