Reflective optical stack for privacy display devices

Abstract

The present invention relates to a reflective optical stack for a privacy display device. The present invention provides a privacy display device comprising a polarized output spatial light modulator, a reflective polarizer, a plurality of polarity control retarders and a polarizer. In a privacy mode of operation, on-axis light from the spatial light modulator is transmitted without loss, however off-axis light has reduced brightness. Furthermore, the display device reflectivity is reduced for on-axis reflection of ambient light, while the reflectivity is increased for off-axis light. By reducing the brightness and increasing the front reflectivity to ambient light, the visibility of the display device to off-axis snoopers is reduced. In a public mode of operation the liquid crystal phase retardation is adjusted, thus the off-axis brightness and reflectivity are not modified.

Description

[0001] This application is a divisional application of Chinese patent application No. 201980020303.0, entitled "Reflective Optical Stack for Privacy Display Device", which was filed on January 24, 2019, under the PCT international application PCT / US2019 / 014889 and entered the Chinese national phase on September 18, 2020. Technical Field

[0002] The present invention generally relates to illumination from a light modulation device, and more particularly to reflective optical stacks for a display device including a privacy display device. Background Technology

[0003] A privacy display provides image visibility to the primary user, typically positioned coaxially, and reduces image visibility to a spy, typically positioned off-axis. Privacy can be provided by a miniature light-shielding optical film transmitting high brightness (low brightness in the off-axis position) from the display device in the coaxial direction; however, such a film is not switchable, thus limiting the display device to privacy functionality.

[0004] A switchable privacy display device can be provided by controlling the off-axis optical output.

[0005] Brightness control can be provided, for example, by using a switchable backlight for a spatial light modulator (SLM) in a liquid crystal display (LCD). Display backlights typically employ a waveguide and a light source positioned along at least one input edge of the waveguide. Some imaging-directional backlights have the additional capability of transmitting the illumination through the display panel to the viewing window. An imaging system can be formed between multiple sources and the corresponding window image. An example of an imaging-directional backlight is an optical valve employing a folded optical system, and therefore, can also be an example of a folded imaging-directional backlight. Light can be transmitted substantially without loss in one direction through the optical valve, while the back-transmitted light can be extracted by reflection from an off-slope surface as described in U.S. Patent No. 9,519,153, which is incorporated herein by reference in its entirety.

[0006] Further control over off-axis privacy can be provided by reducing the contrast, for example by adjusting the liquid crystal bias tilt in an in-plane-switching LCD. Summary of the Invention

[0007] According to a first aspect of the present invention, a display device for ambient lighting is provided, comprising: an SLM configured to output light; wherein the SLM includes an output polarizer disposed on the output side of the SLM, the output polarizer being a linear polarizer; an additional polarizer disposed on the output side of the output polarizer, the additional polarizer being a linear polarizer; a reflective polarizer disposed between the output polarizer and the additional polarizer, the reflective polarizer being a linear polarizer; and at least one polarity control delay unit disposed between the reflective polarizer and the additional polarizer, wherein the at least one polarity control delay unit is capable of simultaneously not referencing the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis normal to the plane of the at least one polarity control delay unit, but referencing the relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis biased towards the plane of the at least one polarity control delay unit.

[0008] The at least one polarity control retarder may be configured to not reference the phase shift to the polarization component of light passing through the reflective polarizer along the axis normal to the plane of the at least one polarity control retarder, and / or to reference the phase shift to the polarization component of light passing through the reflective polarizer along the axis biased towards the plane of the at least one polarity control retarder.

[0009] Preferably, a directional display device is provided, offering high reflectivity and low brightness for off-axis viewing positions and low reflectivity and high brightness for coaxial viewing positions. This increased reflectivity and reduced brightness provide enhanced privacy protection, including an improved visual security level (VSL) for off-axis viewers in ambient lighting conditions. The privacy display device provides low image visibility for off-axis viewers viewing the display device under ambient conditions. Coaxial viewers can observe a largely unmodified display device. The low stray light display device provides low image visibility for some viewers and high image visibility for others. The display device can be used in automotive vehicles to prevent visibility to passengers or drivers.

[0010] The at least one polarity control retarder may include a switchable liquid crystal (LC) retarder comprising an LC material layer, wherein the at least one polarity control retarder may be simultaneously configured in a switchable state of the switchable LC retarder to not reference the pure relative phase shift to the orthogonal polarization component of light passing through the axis of the reflective polarizer along the normal to the plane of the at least one polarity control retarder, but to reference the pure relative phase shift to the orthogonal polarization component of light passing through the axis of the reflective polarizer along the axis biased towards the plane of the at least one polarity control retarder.

[0011] Most preferably, the display device can be switched between a privacy or low-spurious mode with high reflectivity and low brightness for peeping toes, and a wide-viewing-angle mode with increased brightness and reduced reflectivity for off-axis users who require high-contrast images for multiple display device users. The primary user can observe that the display device has substantially the same high brightness and low reflectivity in both operating modes.

[0012] The at least one polarity-controlled retarder may further include at least one passive retarder configured not to reference the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis normal to the plane of the at least one passive retarder, but to reference the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis biased towards the plane of the at least one passive retarder.

[0013] Most preferably, compared to a display device with a switchable LC polarity control delay but no passive polarity control delay, it can substantially increase the polarity area above which a high VSL can be achieved.

[0014] A switchable liquid crystal retarder includes two surface alignment layers arranged adjacent to liquid crystal material layers on their opposite sides, each configured to provide a vertical alignment at the adjacent liquid crystal material layers. In an alternative embodiment where the at least one polarity-controlled retarder includes a switchable LC retarder, the switchable LC retarder may include two surface alignment layers arranged adjacent to LC material layers on their opposite sides, each configured to provide a vertical alignment at the adjacent LC material layers. The LC material layer of the switchable LC retarder may include an LC material having negative dielectric anisotropy. The LC material layer may have a phase retardation of 550 nm wavelength light in the range of 500 nm to 1000 nm, preferably in the range of 600 nm to 900 nm, and most preferably in the range of 700 nm to 850 nm.

[0015] When two surface alignment layers (which provide a vertical alignment) are provided, the at least one polarity-controlled retarder may further include a passive retarder having an optical axis perpendicular to the plane of the retarder, the passive retarder having a phase delay of 550 nm wavelength light in the range of -300 nm to -900 nm, preferably in the range of -450 nm to -800 nm, and most preferably in the range of -500 nm to -725 nm.

[0016] Alternatively, in the case of providing two surface alignment layers (which provide a vertical alignment), the at least one polarity-controlled retarder further comprises a pair of passive retarders having intersecting optical axes in the plane of the retarders, each passive retarder having a phase delay of 550 nm wavelength light in the range of 300 nm to 800 nm, preferably in the range of 500 nm to 700 nm, and most preferably in the range of 550 nm to 675 nm. Most preferably, in this case, a wide field of view, high transmittance, and low reflectivity can be provided without applying voltage. Furthermore, a narrow lateral field of view can be provided with low power consumption in privacy-protected operation mode.

[0017] In the case where the at least one polarity control delayer includes a switchable LC delayer, in another alternative embodiment, the switchable LC delayer may include two surface-aligned layers disposed adjacent to the LC material layer and on opposite sides thereof, each configured to provide a surface alignment in the adjacent LC material. Most preferably, a restoring force that enhances the visibility of the LC material flow during pressure application is achieved compared to a vertical alignment on the opposite sides of the LC.

[0018] The LC material layer of the switchable LC retarder may include an LC material with positive permittivity. The LC material layer may have a phase delay of 550 nm wavelength light in the range of 500 nm to 900 nm, preferably in the range of 600 nm to 850 nm, and most preferably in the range of 700 nm to 800 nm.

[0019] When two surface alignment layers are provided (which provide surface alignment), the at least one polarity-controlled retarder may further include a passive retarder having an optical axis perpendicular to the plane of the retarder, the passive retarder having a phase delay of 550 nm wavelength light in the range of -300 nm to -700 nm, preferably in the range of -350 nm to -600 nm, and most preferably in the range of -400 nm to -500 nm.

[0020] Alternatively, when providing the two surface alignment layers (which provide surface alignment), the at least one polarity-controlled retarder may further include a pair of passive retarders having intersecting optical axes in the plane of the retarder, each passive retarder having a phase delay of 550 nm wavelength light in the range of 300 nm to 800 nm, preferably in the range of 350 nm to 650 nm, and most preferably in the range of 450 nm to 550 nm.

[0021] The field of view using a passive retarder pair with intersecting optical axes in the plane of the retarder can have improved brightness reduction and increased reflectivity in privacy operation mode.

[0022] In the case where the at least one polarity control delayer includes a switchable LC delayer, in another alternative, the switchable LC delayer may include two surface arrangement layers arranged adjacent to the LC material layer and on opposite sides thereof, one of the surface arrangement layers being configured to provide a vertical arrangement in the adjacent LC material, and the other of the surface arrangement layers being configured to provide a surface arrangement in the adjacent LC material.

[0023] When the surface alignment layer is configured to be arranged along the surface between the LC material layer and the polarity control retarder, the LC material layer may have a phase delay of 550 nm wavelength light in the range of 700 nm to 2000 nm, preferably in the range of 1000 nm to 1500 nm, and most preferably in the range of 1200 nm to 1500 nm.

[0024] When the surface alignment layer is configured to be arranged along the surface between the LC material layer and the polarity control retarder, the at least one polarity control retarder may further include a passive retarder with its optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a phase delay of 550 nm wavelength light in the range of -400 nm to -1800 nm, preferably in the range of -700 nm to -1500 nm, and most preferably in the range of -900 nm to -1300 nm.

[0025] When the surface alignment layer is positioned between the LC material layer and the polarity-controlled retarder, the at least one polarity-controlled retarder may further comprise a pair of passive retarders having intersecting optical axes in the plane of the retarder, each retarder having a phase delay of 550 nm wavelength light in the range of 400 nm to 1800 nm, preferably in the range of 700 nm to 1500 nm, and most preferably in the range of 900 nm to 1300 nm. Most preferably, this achieves a restoring force that enhances the visibility of the LC material flow during the application of pressure.

[0026] When a surface alignment layer arranged in a vertical plane is located between the liquid crystal material layer and the polarity control retarder; the liquid crystal material layer has a phase retardation of 550 nm wavelength light in the range of 500 nm to 1800 nm, preferably in the range of 700 nm to 1500 nm, and most preferably in the range of 900 nm to 1350 nm; and the at least one passive retarder includes a passive retarder whose optical axis is perpendicular to the plane of the retarder, the at least one passive retarder having a phase retardation in the range of -300 nm to -1600 nm. The phase delay of 550nm wavelength light is preferably in the range of -500nm to -1300nm and most preferably in the range of -700nm to -1150nm; or the at least one passive retarder comprises a pair of passive retarders having intersecting optical axes in the plane of the retarder, each of the retarders having a phase delay of 550nm wavelength light in the range of 400nm to 1600nm, preferably in the range of 600nm to 1400nm and most preferably in the range of 800nm ​​to 1300nm.

[0027] When the surface arrangement layer configured to provide a vertical alignment is located between the LC material layer and the polarity control retarder, the LC material layer may have a phase delay of 500 nm wavelength light in the range of 500 nm to 1800 nm, preferably in the range of 700 nm to 1500 nm, and most preferably in the range of 900 nm to 1350 nm.

[0028] When the surface alignment layer is configured to provide a vertical arrangement between the LC material layer and the polarity control retarder, the at least one polarity control retarder may further include a passive retarder with its optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a phase delay of 550 nm wavelength light in the range of -300 nm to -1600 nm, preferably in the range of -500 nm to -1300 nm, and most preferably in the range of -700 nm to -1150 nm.

[0029] When a surface arrangement layer configured to provide a vertical alignment is located between the LC material layer and the polarity-controlled retarder, the at least one polarity-controlled retarder may further comprise a pair of passive retarders having intersecting optical axes in the plane of the retarder, each retarder in the pair having a phase delay of 550 nm wavelength light in the range of 400 nm to 1600 nm, preferably in the range of 600 nm to 1400 nm, and most preferably in the range of 800 nm to 1300 nm. Most preferably, the vertical alignment on opposite sides of the LC allows for improved visibility of the LC material flow during pressure application, resulting in a restoring force.

[0030] Each layer has a pre-tilt, which has a component in the plane of the liquid crystal material layer in a pre-tilt direction that is parallel, antiparallel, or orthogonal to the electric vector transmission direction of the reflective polarizer.

[0031] Each layer may have a pretilt, the component of which in the plane of the LC material layer is parallel, antiparallel, or orthogonal to the electric vector propagation direction of the reflective polarizer. Most preferably, high brightness can be achieved for a head-on viewing position.

[0032] In the case where the at least one polarity-controlled retarder includes a switchable LC retarder, the at least one passive retarder may further include two passive retarders, with the switchable LC retarder provided between the two passive retarders. The display device may further include a transport electrode and an LC surface alignment layer formed on one side of each of the two passive retarders immediately adjacent to the switchable LC retarder. The display device may further include first and second substrates, with the switchable LC retarder provided therebetween, each of the first and second substrates including one of the two passive retarders. Each of the two passive retarders may include a passive retarder having an optical axis perpendicular to the plane of the retarder, having a total phase delay of 550 nm wavelength light in the range of -300 nm to -700 nm, preferably in the range of -350 nm to -600 nm, and most preferably in the range of -400 nm to -500 nm. Each of the two passive retarders may have an optical axis in the plane of the passive retarder, wherein the optical axes intersect, and each passive retarder in the pair has a phase delay of 550 nm wavelength light in the range of 150 nm to 800 nm, preferably in the range of 200 nm to 700 nm, and most preferably in the range of 250 nm to 600 nm. Most preferably, this reduces thickness, cost, and complexity.

[0033] The switchable LC delay may further include a transmission electrode configured to apply a voltage to control the LC material layer. The transmission electrode may be located on opposite sides of the LC material layer. The display device may further include a control system configured to control the voltage applied to the electrodes across the switchable LC delay. Most preferably, the display device can be controlled to switch between a privacy mode and a public operation mode.

[0034] The electrodes can be patterned to provide at least two patterned areas. Most preferably, a camouflage pattern can be applied in privacy mode for brightness and reflectivity, and the forward-viewing brightness and reflectivity can be substantially unmodified.

[0035] The at least one polarity-controlled retarder may include at least one passive retarder configured not to reference the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis normal to the plane of the at least one passive retarder, but to reference the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis biased towards the plane of the at least one passive retarder. Most preferably, if a switchable LC polarity-controlled retarder is not provided, thickness and cost can be reduced and efficiency can be improved.

[0036] The at least one polarity control delayer may include at least one passive delayer. The at least one passive delayer may include at least two passive delayers having at least two different orientations of the optical axis. Most preferably, this provides a low-cost privacy display device and a low stray light display device.

[0037] In an alternative embodiment, the at least one passive retarder may comprise a retarder having an optical axis perpendicular to the plane of the retarder. Most preferably, the thickness can be reduced.

[0038] In another alternative, the at least one passive retarder may comprise a pair of passive retarders having intersecting optical axes in the plane of the retarder. Most preferably, the cost of the passive retarder can be reduced, and a highly uniform stretched film can be used for the passive retarder.

[0039] The delay unit has optical axes that extend at 45° and 135° respectively relative to the electrical vector propagation direction of the output polarizer.

[0040] The display device may further include an additional pair of passive retarders arranged between the aforementioned passive retarder pairs, and having intersecting optical axes in the plane of the passive retarders. Most preferably, a privacy display device or a low stray light display device can be provided for both lateral and vertical orientations. In automotive vehicles, this reduces reflections from windshields and other glass surfaces.

[0041] The at least one passive retarder further includes an additional passive retarder pair arranged between the first mentioned passive retarder pair, and having intersecting optical axes in the plane of the passive retarder.

[0042] The additional passive delay pair may have optical axes that extend at 0° and 90° respectively relative to the electric vector transmission direction parallel to the output polarizer. Most preferably, high VSL can be provided in polar regions with some rotational symmetry.

[0043] In another alternative, the at least one passive polarity-controlled retarder may include a retarder having an optical axis oriented with a component perpendicular to the plane of the retarder and a component in the plane of the retarder. The component in the plane of the passive retarder may extend at 0° relative to an electrical vector transmission direction parallel or perpendicular to the electrical vector transmission of the display polarizer. The at least one passive polarity-controlled retarder may further include a passive retarder having an optical axis perpendicular to the plane of the passive retarder; or a pair of passive retarders having intersecting optical axes in the plane of the passive retarder.

[0044] Most preferably, a privacy display device can be provided that achieves reduced brightness and increased reflectivity in the lateral direction at low cost and with minimal complexity. The movable display device can be rotated about a horizontal axis while achieving image visibility comfortable for the primary user.

[0045] The display device may further include at least one additional polarity control delay unit disposed between the output polarizer and the reflective polarizer. Most preferably, it can provide further modification of the field of view profile for the transmitted light. The brightness can be reduced for eavesdroppers while the primary user can observe approximately the same brightness.

[0046] An additional polarizer may be placed between the at least one additional polarity control delay unit and the reflective polarizer.

[0047] The display device may further include a backlight configured to output light, wherein the SLM is a transmission SLM configured to receive the output light from the backlight, wherein the backlight provides brightness at a polar angle greater than 45 degrees relative to the normal of the SLM, which is at most 30% of the brightness along the normal of the SLM, preferably at most 20% of the brightness along the normal of the SLM, and most preferably at most 10% of the brightness along the normal of the SLM. Most preferably, a high VSL can be provided with low thickness and low cost. Furthermore, the VSL can be very high in environments with reduced ambient illuminance.

[0048] An additional polarizer can be disposed between the additional polarity control delay unit and the reflective polarizer. The display device may further include at least one additional polarity control delay unit and an additional polarizer, wherein the at least one additional polarity control delay unit is disposed between the first-mentioned additional polarizer and the additional polarizer. Most preferably, the brightness can be reduced to prevent prying eyes.

[0049] The at least one additional polarity control delay unit may include at least one additional passive delay unit. Preferably, the increase in thickness and cost can be minimal.

[0050] The at least one polarity-controlled retarder mentioned above may include a first switchable LC retarder comprising a first layer of LC material, and the at least one additional polarity-controlled retarder may include a second switchable LC retarder comprising a second layer of LC material. The additional switchable LC retarder may include at least one surface alignment layer disposed adjacent to the LC material, having a pre-tilt direction having a component in the plane of the LC material layer, and being arranged parallel, antiparallel, or orthogonal to the reflective polarizer.

[0051] Preferably, the field of view in the public operating mode remains largely unchanged, while further modification of the field of view profile is provided for the transmitted light in the privacy operating mode. Brightness can be reduced for eavesdroppers, while the primary user can observe substantially the same brightness. The first and second LC delayers can have different phase delays. Chromaticity variations with viewing angle can be reduced.

[0052] The electric vector transmission direction of the reflective polarizer may be parallel to the electric vector transmission direction of the auxiliary polarizer, and / or parallel to the electric vector transmission direction of the output polarizer.

[0053] The LC material layer of each of the first and second switchable LC retarders may have a phase delay of 550 nm wavelength light in the range of 450 nm to 850 nm, preferably in the range of 500 nm to 750 nm, and most preferably in the range of 550 nm to 650 nm. This can improve the VSL at high polarity viewing angles.

[0054] The at least one polarity-controlled retarder mentioned first further includes a pair of passive retarders having intersecting optical axes in the plane of the retarder, wherein the first of the passive retarders has optical axes extending at 45° and 135° relative to the electric vector propagation direction of the output polarizer, respectively, and the second of the passive retarders has an optical axis extending at 135° relative to the electric vector propagation direction of the output polarizer; and the at least one additional polarity-controlled retarder includes another pair of passive retarders having intersecting optical axes in the plane of the retarder, wherein the first of the additional passive retarders has optical axes extending at 45° and 135° relative to the electric vector propagation direction of the output polarizer, respectively; and the optical axes of the closest pair of the first mentioned passive retarders and the additional passive retarders extend in the same direction.

[0055] Ideally, the color presentation of reflected and transmitted light for an off-axis observer should be symmetrical for both positive and negative lateral viewing angles. This can improve the minimum VSL.

[0056] Each passive retarder in the first mentioned passive retarder pair and each passive retarder in the other passive retarder pair have a phase delay of 550 nm wavelength light in the range of 300 nm to 800 nm, preferably in the range of 350 nm to 650 nm, and most preferably in the range of 400 nm to 550 nm. This can improve VSL at high polarity viewing angles.

[0057] The display device may further include: a backlight configured to output light, wherein the SLM is a transmission SLM configured to receive the output light from the backlight, and the SLM further includes an input polarizer disposed on the input side of the SLM, the input polarizer being a linear polarizer; and an additional polarizer disposed on the input side of the input polarizer, the additional polarizer being a linear polarizer; and at least one additional polarity control delay unit disposed between the additional polarizer and the input polarizer. Most preferably, this reduces the increase in thickness between the SLM and the viewer. This can provide improved image fidelity and increase diffuse to reduce the presentation of mirrored front surface reflections on the front-viewing user. It can reduce the number of stacking steps and improve VSL. A wide viewing angle can be provided for the open mode.

[0058] The SLM is a transmitting SLM, and the display polarizer is an output polarizer disposed on the output side of the SLM.

[0059] The reflective polarizer and the output polarizer have parallel electric vector propagation directions. The reflective polarizer and the auxiliary polarizer have parallel electric vector propagation directions.

[0060] The reflective polarizer and the additional polarizer have non-parallel electric vector transmission directions, and the display device further includes a rotor retarder disposed between the reflective polarizer and the additional polarizer, which is configured to rotate the polarization direction of the polarized light incident thereon between the electric vector transmission directions of the display polarizer and the additional polarizer.

[0061] The first mentioned at least one polarity-controlled delay device includes a first switchable liquid crystal delay device comprising a first layer of liquid crystal material, and the at least one additional polarity-controlled delay device includes a second switchable liquid crystal delay device comprising a second layer of liquid crystal material. The first and second liquid crystal delay devices have different phase delays.

[0062] The display device may further include a control system configured to control the application of a common voltage across the first and second switchable LC delays, wherein the LC material of the first LC delay is different from the LC material of the second LC delay. Most preferably, this reduces the cost of the control system. It also reduces chromaticity variations with viewing angle.

[0063] The liquid crystal material layer of each of the first and second switchable liquid crystal delayers has a phase delay of 550 nm wavelength light in the range of 450 nm to 850 nm, preferably in the range of 500 nm to 750 nm, and most preferably in the range of 550 nm to 650 nm.

[0064] The first mentioned at least one polarity-controlled retarder further includes a pair of passive retarders having intersecting optical axes in the plane of the retarder that extend at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer; the first additional polarity-controlled retarder includes another pair of passive retarders having intersecting optical axes in the plane of the retarder that extend at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer; and the optical axes of the closest pair of the first mentioned passive retarders and the other pair of passive retarders extend in the same direction.

[0065] Each passive retarder in the first mentioned passive retarder pair and each passive retarder in the additional passive retarder pair have a phase delay of 550 nm wavelength light in the range of 300 nm to 800 nm, preferably in the range of 350 nm to 650 nm, and most preferably in the range of 400 nm to 550 nm. The at least one additional polarization control retarder includes at least one additional passive retarder. The reflective polarizer and the output polarizer may have parallel electric vector propagation directions. The reflective polarizer and the additional polarizer may have parallel electric vector propagation directions. The reflective polarizer and the additional polarizer may have non-parallel electric vector propagation directions, and the display device may further include a rotor retarder disposed between the reflective polarizer and the additional polarizer, which is configured to rotate the polarization direction of the polarized light incident thereon between the electric vector propagation directions of the display polarizer and the additional polarizer. Most preferably, high efficiency can be provided. The additional polarizer can be aligned with the electric vector propagation direction to direct light transmission through polarized sunglasses for general users. SLMs with non-parallel output electrical vector transmission directions, such as TN-LCDs, can be used.

[0066] According to a second aspect of the invention, a viewing angle control optical element is provided for the output side of a display device for ambient lighting, comprising an SLM configured to output light; wherein the SLM includes an output polarizer disposed on the output side of the SLM; the viewing angle control optical element includes an additional polarizer; a reflective polarizer disposed between the output polarizer and the additional polarizer when the viewing angle control optical element is applied to the display device; and at least one polarity control delay unit disposed between the reflective polarizer and the additional polarizer, wherein the at least one polarity control delay unit is capable of simultaneously not referencing the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis normal to the plane of the at least one polarity control delay unit, but referencing the relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis biased towards the plane of the at least one polarity control delay unit.

[0067] Preferably, display device users can attach after-market components to the display device. These components do not require complex arrangement. There is no moiré beating between the components and the pixels of the display device, and there is no need to select the components based on pixel pitch. This reduces inventory costs. Alternatively, the viewing angle control optics can be easily assembled into the display device module at the factory.

[0068] Similarly, the various features and alternatives described above with respect to the first aspect of the invention can be applied to the second aspect of the invention.

[0069] According to a third aspect of the present invention, a display device is provided, comprising: an SLM; a display polarizer disposed on at least one side of the SLM, the display polarizer being a linear polarizer; and a first additional polarizer disposed on the same side of the SLM as one of the at least one display polarizer, the first additional polarizer being a linear polarizer; and a first plurality of polarization-controlled retarders disposed between the first additional polarizer and one of the at least one display polarizer; a further additional polarizer disposed on the same side of the SLM as one of the aforementioned at least one display polarizer, outside the first additional polarizer, the further additional polarizer being a linear polarizer; and a further plurality of polarization-controlled retarders disposed between the further first additional polarizer and one of the at least one display polarizer and the further additional polarizers; wherein the firstly mentioned plurality of polarization-controlled retarders comprises a passive retarder pair having intersecting optical axes in the plane of the retarder, wherein the first of the passive retarder pair... The passive retarder pair has an optical axis extending at 45° relative to the electrical vector transmission direction of the output polarizer, and the second of the passive retarder pair has an optical axis extending at 135° relative to the electrical vector transmission direction of the display polarizer (which is the output polarizer and extends at 45° and 135° relative to the electrical vector transmission direction of the output polarizer, respectively), and wherein the additional plurality of polarity control retarders include additional passive retarder pairs having intersecting optical axes in the plane of the retarder, wherein the first of the additional passive retarder pairs has an optical axis extending at 135° relative to the electrical vector transmission direction of the output polarizer, and the second of the additional passive retarder pairs has an optical axis extending at 45° relative to the electrical vector transmission direction of the display polarizer (which is the output polarizer and extends at 45° and 135° relative to the electrical vector transmission direction of the output polarizer, respectively), and the optical axes of the closest one in the first passive polarity control retarder pair and the one of the additional passive polarity control retarder pairs extend in the same direction.

[0070] The display device includes a spatial light modulator (SLM); a display polarizer disposed on at least one side of the SLM, the display polarizer being a linear polarizer; a first additional polarizer disposed on the same side of the SLM as one of the at least one display polarizer, the first additional polarizer being a linear polarizer; and a first polarization control delay unit disposed between the first additional polarizer and one of the at least one display polarizer; a further additional polarizer disposed on the same side of the SLM as one of the aforementioned at least one display polarizer, outside the first additional polarizer, the further additional polarizer being a linear polarizer; and a further polarization control delay unit. A retarder is disposed between the first additional polarizer and the other additional polarizer, wherein the first polarity-controlled retarder includes a pair of passive retarders having intersecting optical axes in the plane of the retarder that extend at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer; the other polarity-controlled retarder includes another pair of passive retarders having intersecting optical axes in the plane of the retarder that extend at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer; and the optical axes of the closest pair of the first passive polarity-controlled retarders and the other passive polarity-controlled retarders extend in the same direction.

[0071] Each of the first polarity control delay and the other polarity control delay further includes a switchable liquid crystal delay, which includes a liquid crystal material layer. In a switchable state of the switchable liquid crystal delay, each of the first polarity control delay and the other polarity control delay is simultaneously configured such that the pure relative phase shift is not referenced to the orthogonal polarization component of light passing along the axis normal to the plane of the polarity control delay in the at least one of the aforementioned display polarizers, but is referenced to the orthogonal polarization component of light passing along the axis biased towards the plane of the polarity control delay in the at least one of the aforementioned display polarizers.

[0072] The display device further includes a backlight configured to output light, the SLM being a transmission SLM configured to receive the output light from the backlight, and the display device including a display polarizer, which is an input polarizer disposed on the input side of the SLM and an output polarizer disposed on the output side of the SLM.

[0073] A display device includes: a backlight configured to output light; a transmission spatial light modulator (SLM) configured to receive the output light from the backlight; an input polarizer disposed on the input side of the SLM; and an output polarizer disposed on the output side of the SLM, the input polarizer and the output polarizer being linear polarizers; a first additional polarizer disposed on the output side of the output polarizer, the first additional polarizer being a linear polarizer; a first polarization control delay unit disposed between the first additional polarizer and the output polarizer; a further additional polarizer disposed between the backlight and the input polarizer, the further additional polarizer being a linear polarizer; and a further... An external polarization control retarder is disposed between the first additional polarizer and the input polarizer; wherein the first polarization control retarder includes a pair of passive retarders having intersecting optical axes in the plane of the retarder that extend at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer; the additional polarization control retarder includes another pair of passive retarders having intersecting optical axes in the plane of the retarder that extend at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer; and the optical axes of the closest pair of the first passive polarization control retarders and the other pair of passive polarization control retarders extend in the same direction.

[0074] Each of the first polarity control delay and the other polarity control delay further includes a switchable liquid crystal delay, which includes a liquid crystal material layer. In a switchable state of the switchable liquid crystal delay, each of the first polarity control delay and the other polarity control delay is simultaneously configured such that the pure relative phase shift is not referenced to the orthogonal polarization component of light passing along the axis normal to the plane of the polarity control delay in the at least one of the aforementioned display polarizers, but is referenced to the orthogonal polarization component of light passing along the axis biased towards the plane of the polarity control delay in the at least one of the aforementioned display polarizers.

[0075] Preferably, the switchable privacy display provides high image visibility over a wide field of view in open operation mode. A wide-angle backlight, which is less costly and more durable than a collimated backlight, can be provided. In privacy operation mode, a high VSL (Visible Level Sight) over a wide field of view can be achieved, allowing for the location of off-axis eavesdroppers with low display reflectivity. The retarder and additional polarizer can be positioned between the backlight and the SLM (Surface Mount Technology), allowing a diffuser with surface roughness to be placed on the front surface of the display device to minimize the visibility of frontal reflections while achieving high pixel fidelity. Chromaticity and luminance roll-off can be symmetrical.

[0076] According to a fourth aspect of the invention, a transmission SLM is provided, configured to receive output light from the backlight source; an input polarizer disposed on the input side of the SLM; and an output polarizer disposed on the output side of the SLM, the input polarizer and the output polarizer being linear polarizers; a first additional polarizer disposed on the output side of the output polarizer, the first additional polarizer being a linear polarizer; and a first polarization control delay disposed between the first additional polarizer and the output polarizer; a further additional polarizer disposed between the backlight source and the input polarizer, the further additional polarizer being a linear polarizer; and a further polarization control delay. The device is disposed between the first additional polarizer and the input polarizer; wherein the first polarity control delay includes a pair of passive delayers having intersecting optical axes in the plane of the delay and extending at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer; the additional polarity control delay includes another pair of passive delayers having intersecting optical axes in the plane of the delay and extending at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer; and the optical axes of the closest pair of the first passive polarity control delayers and the additional pair of passive polarity control delayers extend in the same direction.

[0077] Preferably, the switchable privacy display provides high image visibility over a wide field of view in open operation mode. A wide-angle backlight, which is less costly and more durable than a collimated backlight, can be provided. In privacy operation mode, a high VSL (Visibility Level Sight) over a wide field of view can be achieved, allowing for the location of off-axis eavesdroppers with low display reflectivity. Some of the retarder and additional polarizer can be positioned between the backlight and the SLM (Self-Lens Display), thus allowing a diffuser with surface roughness to be positioned on the front surface of the display device to minimize the visibility of frontal reflections while achieving high pixel fidelity and high image contrast. Chromaticity and luminance roll-offs can be symmetrical. Scattering from the SLM does not affect light transmitted through one of the retarders and the additional polarizer, thus improving VSL.

[0078] Various embodiments of the present invention can be used in a variety of optical systems. These embodiments may include or be used in conjunction with various projectors, projection systems, optical components, display devices, microdisplay devices, computer systems, processors, stand-alone projector systems, visual and / or audiovisual systems, and electrical and / or optical devices. In fact, aspects of the present invention can be used with any device relating to optical and electrical devices, optical systems, presentation systems, or any device that may contain any type of optical system. Therefore, various embodiments of the present invention can be employed in optical systems, devices for visual and / or optical displays, visual peripherals, and various computing environments.

[0079] Before proceeding with a detailed description of the specific embodiments disclosed herein, it should be understood that, since the disclosed content can have other specific embodiments, it is not limited to the details of the specific settings shown in its application or creation. Furthermore, various aspects of the disclosed content can be described in different combinations and settings to define specific embodiments unique to their own claims. In addition, the terminology used in this specification is for illustrative purposes and not for limitation.

[0080] These and other advantages and features of the present invention will become more apparent to those skilled in the art upon their full reading of the invention. Attached Figure Description

[0081] Various specific embodiments are illustrated by way of example in the accompanying drawings, wherein the same reference numerals denote similar parts, and wherein:

[0082] Figure 1A This is a side perspective view illustrating a switchable privacy display device for ambient lighting, including a transmissive SLM, a reflective polarizer, and a compensated switchable delay unit.

[0083] Figure 1B This is a side perspective view illustrating a switchable privacy display device for ambient lighting, including an emissive SLM and a compensated switchable delay unit;

[0084] Figure 2A This is a previous view example. Figure 1A A diagram showing the arrangement of optical layers in an optical stack;

[0085] Figure 2B This is a side perspective view illustrating a view control element including a reflective polarizer, a passive polarity-controlled retarder, a switchable LC retarder, and an additional polarizer.

[0086] Figure 3 This is a perspective view illustrating the setup of a switchable LC delayer including a passive negative C-plate polarity control delayer in privacy mode;

[0087] Figure 4A The side view is an example of how to pass through privacy mode. Figure 1A A pattern of output light transmission from the SLM in an optical stack;

[0088] Figure 4B It is aimed at Figure 4A The transmitted light beam described herein is illustrated as a graph showing the change in output brightness with polarity direction;

[0089] Figure 5A The example shown is a top-down view illustrating how to pass through privacy mode. Figure 1AA pattern of ambient lighting light transmission in optical stacks;

[0090] Figure 5B It is aimed at Figure 5A The reflected light rays described herein are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0091] Figure 5C It is aimed at Figure 5A The reflected light rays described herein are illustrated in a graph showing the variation of reflectivity with lateral direction.

[0092] Figure 6A This is a perspective illustration of the observation of the output light transmitted by a display device in privacy mode;

[0093] Figure 6B It is a previous perspective diagram illustrating the observation of ambient light reflected from the interface surface of the display device;

[0094] Figure 6C The previous perspective example was for use in privacy mode. Figure 1A and Figure 1B A diagram showing the observation of ambient light reflected from the display device;

[0095] Figure 7A This is a previous perspective example in privacy mode. Figure 1A and Figure 1B The display device presents the pattern;

[0096] Figure 7B This illustrates the privacy mode for setups with and without the aforementioned reflective polarizer. Figure 1A and Figure 1B A graph showing the change in dynamic range perceived by an off-axis spy on a switchable privacy display device relative to ambient illuminance.

[0097] Figure 7C It is for collimated backlights. Figure 1A The display device, for example, shows a graph of VSL changing with polarity direction;

[0098] Figure 7D This is an example of a graph showing how the VSL changes with polarity for a display device that does not include multiple delay units;

[0099] Figure 8A This is a side view illustration of a car vehicle with a switchable directional display device located in the vehicle cabin for both entertainment and sharing modes.

[0100] Figure 8B This is a top view illustrating a car vehicle in entertainment mode with a switchable directional display device located in the vehicle's cabin.

[0101] Figure 8C This is a top view illustrating a car vehicle with a switchable directional display device located in the vehicle cabin in sharing mode.

[0102] Figure 8D This is a top-view illustration of an automobile vehicle with a switchable directional display device located in the vehicle cabin for both nighttime and daytime modes.

[0103] Figure 8E This is a side view illustrating a car vehicle with a switchable directional display device installed in the vehicle cabin in night mode.

[0104] Figure 8F This is a side view illustrating a car vehicle with a switchable directional display device installed in the vehicle cabin in daytime mode.

[0105] Figure 9A This is a perspective view illustrating the setup of a switchable delayer in an open mode, wherein the switchable delayer includes a switchable LC layer arranged vertically and a passive C-plate polarity control delayer.

[0106] Figure 9B The side view is illustrated in the public mode. Figure 1A A pattern of the transmission of output light from the SLM in an optical stack;

[0107] Figure 9C This is an example targeting Figure 9B The curve showing the change in output brightness of the transmitted light as a function of polarity direction;

[0108] Figure 9D The top view is used as an example in public mode. Figure 1A A pattern for the transmission of ambient lighting light in optical stacks;

[0109] Figure 9E It is aimed at Figure 9D The reflected light rays described herein are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0110] Figure 10A This is a perspective view illustrating the observation of the transmitted output light of a display device in open mode;

[0111] Figure 10B This is a previous perspective example shown in public mode. Figure 1A A diagram showing the observation of reflected ambient light from a switchable display device;

[0112] Figure 10CThis is a previous perspective instance in public mode. Figure 1A The display device presents the pattern;

[0113] Figure 11A This is a perspective view illustrating the setup of a switchable delayer in an open mode, wherein the switchable delayer includes a switchable LC layer arranged along the surface and an intersecting A-plate polarity control delayer.

[0114] Figure 11B It is for use in privacy mode. Figure 11A The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0115] Figure 11C It is for use in privacy mode. Figure 11A The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0116] Figure 11D It is for use in public mode. Figure 11A The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0117] Figure 11E It is for use in public mode. Figure 11A The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0118] Figure 11F The diagram illustrates the setup of a switchable compensated delay unit in privacy mode using a perspective view, which includes the cross-shaped A-plate passive polarity controlled delay unit and the surface-arranged switchable LC delay unit, further including a passive rotation delay unit.

[0119] Figure 12A This is a perspective view illustrating the configuration of a switchable delay unit in privacy mode, which includes a switchable LC delay unit arranged along the surface; and a passive negative C-plate delay unit driven by a first voltage.

[0120] Figure 12B This is a perspective view illustrating the configuration of a switchable delay unit in privacy mode, which includes a switchable LC delay unit arranged along the surface; and a passive negative C-plate delay unit driven by a second voltage different from the first voltage.

[0121] Figure 12C It is for use in privacy mode. Figure 12A The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0122] Figure 12D It is for use in privacy mode. Figure 12AThe reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0123] Figure 12E It is for use in public mode. Figure 12B The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0124] Figure 12F It is for use in public mode. Figure 12B The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0125] Figure 13A This is a perspective view illustrating the setup of a switchable delay unit in privacy mode, which includes switchable LC delay units arranged along the surface.

[0126] Figure 13B It is for use in privacy mode. Figure 13A The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0127] Figure 13C It is for use in privacy mode. Figure 13A The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0128] Figure 13D It is for use in public mode. Figure 13A The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0129] Figure 13E It is for use in public mode. Figure 13A The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0130] Figure 13F This is a side perspective view illustrating the view control elements, which include a reflective polarizer, a switchable LC retarder, and an additional polarizer.

[0131] Figure 14A This is a perspective view illustrating the setup of a switchable delayer in privacy mode, which includes a cross-shaped A-plate passive delayer and a vertically arranged switchable LC delayer.

[0132] Figure 14B It is for use in privacy mode. Figure 14A The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0133] Figure 14C It is for use in privacy mode. Figure 14A The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0134] Figure 14D This is a perspective view illustrating the setup of a switchable delay unit in open mode, which includes a cross-shaped A-plate passive delay unit and a vertically arranged switchable LC delay unit.

[0135] Figure 14E It is for use in public mode. Figure 14D The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0136] Figure 14F It is for use in privacy mode. Figure 14D The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0137] Figure 15A This is a perspective view illustrating the setup of a switchable retarder in privacy mode, which includes a switchable LC retarder and a passive negative C-plate retarder arranged along the plane and vertically.

[0138] Figure 15B It is for use in privacy mode. Figure 15A The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0139] Figure 15C It is for use in privacy mode. Figure 15A The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0140] Figure 15D It is for use in public mode. Figure 15A The transmitted light beam in the image is illustrated with a graph showing how the output brightness changes with the polarity direction.

[0141] Figure 15E It is for use in public mode. Figure 15A The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0142] Figure 16 This is a side perspective view illustrating a switchable privacy display device for ambient lighting, which includes a non-collimated backlight; a passive delayer disposed between a reflective recirculating polarizer and a transmissive SLM; a reflective polarizer; a compensated switchable delayer; and an additional polarizer.

[0143] Figure 17A This is a side perspective view illustrating a switchable privacy display device for ambient lighting, which includes an emissive SLM, a passive control delay unit, an additional polarizer, a reflective polarizer, a compensated switchable delay unit, and an additional polarizer.

[0144] Figure 17B This is a side perspective view illustrating a view control element, which includes a passive control retarder, a first additional polarizer, a reflective polarizer, a passive polarity control retarder, a switchable LC retarder, and a second additional polarizer.

[0145] Figure 18A The diagram illustrates a switchable privacy display device for ambient lighting using a side perspective view, which includes a wide-angle backlight, wherein a first plurality of delay units are disposed between the backlight and the SLM, and a further plurality of delay units are configured to receive light from the SLM;

[0146] Figure 18B The previous view illustrates the arrangement of optical layers in an optical stack, which includes multiple retarders disposed between a reflective polarizer and an additional polarizer; and multiple additional retarders disposed between the input polarizer and an additional additional polarizer of the transmission SLM, wherein each of the multiple retarders and the multiple additional retarders includes a cross A-plate.

[0147] Figure 18C This is a graph illustrating the change in logarithmic output brightness with polarity for the transmitted light from multiple delayers (including cross-shaped passive A-plates and surface-aligned switchable LC delayers).

[0148] Figure 18D This is a graph illustrating the change in logarithmic output brightness as a function of the lateral viewing angle for the transmitted light from multiple delayers (including cross-shaped passive A-plates and switchable LC delayers arranged along the surface).

[0149] Figure 18E The diagram is a side perspective view illustrating a switchable privacy display device for ambient lighting, which includes an emissive SLM, a first compensated switchable LC delayer, a first additional polarizer, a reflective polarizer, a second compensated switchable LC delayer, and a second additional polarizer.

[0150] Figure 18F The previous view illustrates the arrangement of optical layers in an optical stack, which includes a plurality of retarders disposed between a reflective polarizer and an additional polarizer; and a further plurality of retarders disposed between the output polarizer and a further additional polarizer for the reflective polarizer, wherein each of the plurality of retarders and the further plurality of retarders includes a cross A-plate.

[0151] Figure 18GThis is a previous view illustrating the arrangement of optical layers in an optical stack, which includes multiple retarders disposed between additional light-absorbing polarizers and additional polarizers; and multiple additional retarders disposed between the output polarizer and the additional additional polarizers, wherein each of the multiple retarders and the multiple additional retarders includes a cross A-plate.

[0152] Figure 18H The previous view illustrates the arrangement of optical layers in an optical stack for a transmission SLM, which includes a plurality of retarders disposed between an additional additional light-absorbing polarizer and an additional polarizer; and a plurality of additional retarders disposed between the input polarizer and the additional additional polarizer, wherein each of the plurality of retarders and the plurality of additional retarders includes a cross A-plate.

[0153] Figure 18I The previous view illustrates the arrangement of optical layers in an optical stack for a transmission SLM, which includes multiple retarders disposed between an additional polarizer and the input polarizer of the transmission SLM; and multiple retarders disposed between the output polarizer and the additional polarizer, wherein each of the multiple retarders and the multiple additional retarders includes a cross A-plate.

[0154] Figure 18J This is a perspective view illustrating the setup of a switchable retarder in privacy mode, which includes a first negative C-plate passive retarder and a first surface-aligned switchable LC retarder disposed between the output polarizer and the reflective polarizer; and a second negative C-plate passive retarder and a second surface-aligned switchable LC retarder disposed between the reflective polarizer and an additional polarizer.

[0155] Figure 18K The diagram illustrates a view control element in a side perspective view, which includes a first compensated switchable LC delay, a first additional polarizer, a reflective polarizer, a second compensated switchable LC delay, and a second additional polarizer.

[0156] Figure 19A This is a top view illustration of an automobile vehicle with a switchable directional display device located in the vehicle cabin for daytime and / or sharing modes.

[0157] Figure 19B This is a side view illustration of an automobile vehicle with a switchable directional display device located in the vehicle cabin for daytime and / or sharing modes.

[0158] Figure 19CThis is a top view illustration of an automobile vehicle with a switchable directional display device located in the vehicle cabin for night and / or entertainment modes.

[0159] Figure 19D This is a side view illustration of an automobile vehicle with a switchable directional display device located in the vehicle cabin for night and / or entertainment modes.

[0160] Figure 20A This is a side perspective view illustrating a privacy display device for ambient lighting, which includes a backlight, a transmission SLM, a reflective polarizer, a delay stack, and an additional polarizer.

[0161] Figure 20B This is a side perspective view illustrating the view control elements, which include a reflective polarizer, a stack of retarders, and an additional polarizer.

[0162] Figure 20C This is a side perspective view illustrating a view control element, which includes a first retarder stack and an additional polarizer; a reflective polarizer; a second retarder stack and another additional polarizer;

[0163] Figure 20D This is a side perspective view illustrating a privacy display device for ambient lighting, which includes a backlight, a reflective recirculating polarizer, an input delay stack, a transmission SLM, a reflective polarizer, a delay stack, and an additional polarizer.

[0164] Figure 21A This is a side perspective view illustrating an optical stack of a passive retarder, which includes a negative C-sheet and is configured to provide a field-of-view modification for a display device;

[0165] Figure 21B It is aimed at Figure 21A The transmitted light in the passive delayer is illustrated by a graph showing the output transmission as a function of polarity.

[0166] Figure 21C This is a side perspective view illustrating an optical stack of a passive retarder, including a negative O-sheet tilted in a plane orthogonal to the electric vector transmission direction of the display polarizer; and a negative C-sheet configured to provide field-of-view modification for the display device;

[0167] Figure 21D It is aimed at Figure 21C The transmitted light in the passive delayer is illustrated by a graph showing the output transmission as a function of polarity.

[0168] Figure 21EThis is a side perspective view illustrating an optical stack of passive retarders, including a positive O-plate tilted in a plane orthogonal to the electric vector transmission direction of the display polarizer; and intersecting A-plates configured to provide field-of-view modification for the display device;

[0169] Figure 21F It is aimed at Figure 21E The transmitted light in the passive delayer is illustrated by a graph showing the output transmission as a function of polarity.

[0170] Figure 22A This is a side perspective view illustrating an optical stack configured to provide a field of view modification for a display device (including two intersecting pairs of A plates);

[0171] Figure 22B It is aimed at Figure 22A The transmitted light in the passive delayer is illustrated by a graph showing the output transmission as a function of polarity.

[0172] Figure 23A and Figure 23B This is a side view illustration of a privacy display device for ambient lighting, which includes a transmission SLM, a reflective polarizer, an LC delayer, a compensation delayer, and an additional polarizer.

[0173] Figure 24A This is a perspective view illustrating the setup of a switchable compensated delay unit in privacy mode, which includes a switchable LC delay unit arranged along a plane and positioned between first and second C-plate passive polarity control delay units.

[0174] Figure 24B and Figure 24C These are examples for public mode and privacy mode respectively. Figure 24A The transmitted light in the optical stack, and the curve of output transmission as a function of polarity direction;

[0175] Figure 24D It is for use in privacy mode. Figure 24A The reflected light rays in the image are illustrated with a graph showing the change in reflectivity as a function of polarity.

[0176] Figure 25A The diagram illustrates a display device in perspective view, which includes a switchable compensated delay disposed between first and second C-plate passive polarity controlled delay substrates.

[0177] Figure 25B This is a side view illustrating a portion of a display device, which includes a switchable compensated retarder disposed between first and second C-plate passive polarity controlled retarder substrates.

[0178] Figure 25CThe diagram illustrates the arrangement of a switchable compensated delay unit in open mode using a perspective view, which includes a switchable LC delay unit arranged along a plane and disposed between first and second intersecting A-plate passive polarity controlled delay units.

[0179] Figure 25D and Figure 25E It is for use in wide-angle and privacy modes respectively. Figure 25C The transmission light is set up, and the output transmission is shown as a curve of the polarity direction.

[0180] Figure 26A The diagram illustrates the setup of a switchable retarder in privacy mode using a perspective view, which includes a negative C-plate passive retarder and a vertically arranged switchable LC retarder, and further includes a patterned electrode layer.

[0181] Figure 26B This is a perspective front view illustrating the lighting of the main viewer and the spy through a concealed, brightness-controlled privacy display device;

[0182] Figure 26C This is a perspective view illustrating the illumination of a spy through a concealed, brightness-controlled privacy display device;

[0183] Figure 27A This is a perspective view illustrating the arrangement of switchable LC delay units arranged along a plane;

[0184] Figure 27B It is for the first applied voltage. Figure 27A The transmitted light beam in the diagram illustrates the curve of output transmission as the polarity direction changes;

[0185] Figure 27C It is for a second applied voltage that is greater than the first applied voltage. Figure 27A The transmitted light beam in the diagram illustrates the curve of output transmission as the polarity direction changes;

[0186] Figure 27D This is a perspective view illustrating a C-plate positioned between parallel polarizers;

[0187] Figure 27E It is aimed at Figure 27D The transmitted light beam in the diagram illustrates the curve of output transmission as the polarity direction changes;

[0188] Figure 28A This is a perspective view illustrating the arrangement of a switchable LC delayer connected in series with a C-plate between parallel polarizers and arranged along the plane between parallel polarizers.

[0189] Figure 28BIt is for the first applied voltage. Figure 28A The transmitted light beam in the diagram illustrates the curve of output transmission as the polarity direction changes;

[0190] Figure 28C It is for a second applied voltage that is greater than the first applied voltage. Figure 28A The transmitted light beam in the diagram illustrates the curve of output transmission as the polarity direction changes;

[0191] Figure 29A This is a perspective view illustrating the arrangement of a switchable LC retarder arranged along a plane in series with a C-plate polarity control retarder, wherein the switchable LC and the C-plate polarity control retarder arranged along the plane are positioned between a single pair of parallel polarizers.

[0192] Figure 29B It is for the first applied voltage. Figure 29A The transmitted light beam in the diagram illustrates the curve of output transmission as the polarity direction changes;

[0193] Figure 29C It is for a second applied voltage that is greater than the first applied voltage. Figure 29A The transmitted light beam in the diagram illustrates the curve of output transmission as the polarity direction changes;

[0194] Figure 30A This is a perspective drawing illustrating a directional backlight;

[0195] Figure 30B This is a perspective drawing illustrating a non-directional backlight;

[0196] Figure 30C This is a graph illustrating the change in brightness with varying lateral viewing angles of display devices with different field of view;

[0197] Figure 31A This is a side view illustration of a switchable directional display device, which includes an imaging waveguide and a switchable LC delayer;

[0198] Figure 31B This is a diagram illustrating the operation of the imaging waveguide in narrow-angle mode, shown in a perspective view later.

[0199] Figure 31C When used in display devices without a switchable LC delay unit, for example... Figure 31B The output field-of-view brightness curve is a graph;

[0200] Figure 32A This is a side view illustration of a switchable directional display device, which includes a switchable collimating waveguide and a switchable LC delayer in privacy mode;

[0201] Figure 32B This is a top view illustrating the output of a collimated waveguide;

[0202] Figure 32C It is aimed at Figure 32A An example of a display device showing the equal brightness field of view polarity curve;

[0203] Figure 33A This is a perspective view illustrating the illumination of a retarder layer through which off-axis light passes;

[0204] Figure 33B This is a perspective view illustrating illumination through a retarder layer of light with a first linear polarization state of 0 degrees.

[0205] Figure 33C This is a perspective view illustrating illumination through a retarder layer of light with a first linear polarization state of 90 degrees.

[0206] Figure 33D This is a perspective view illustrating illumination through a retarder layer of light in a first linear polarization state at 45 degrees.

[0207] Figure 34A This is a perspective view illustrating illumination through a C-plate retarder with off-axis polarized light having a positive elevation angle;

[0208] Figure 34B This is a perspective view illustrating the illumination of a C-plate retarder through which off-axis polarized light with a negative side angle is transmitted.

[0209] Figure 34C This is a perspective view illustrating the illumination of a C-plate retarder through which off-axis polarized light with positive elevation and negative side angles passes;

[0210] Figure 34D This is a perspective view illustrating the illumination of a C-plate retarder through which off-axis polarized light with positive elevation and positive side angles passes;

[0211] Figure 34E It is aimed at Figures 34A to 34D The transmitted light beam in the diagram illustrates the curve of output transmission as the polarity direction changes;

[0212] Figure 35A This is a perspective view illustrating illumination through an A-plate retarder layer of light crossing off-axis polarized light with a positive elevation angle;

[0213] Figure 35B This is a perspective view illustrating the illumination of an A-plate retarder layer through which off-axis polarized light with a negative side angle crosses.

[0214] Figure 35CThis is a perspective view illustrating the illumination of an A-plate retarder layer through which off-axis polarized light with positive elevation and negative side angles crosses.

[0215] Figure 35D This is a perspective view illustrating illumination through an A-plate retarder layer transmitting intersecting off-axis polarized light with positive elevation and positive side angles; and

[0216] Figure 35E It is aimed at Figures 35A to 35D The transmitted light beam in the diagram illustrates the curve of output transmission as the polarity direction changes. Detailed Implementation

[0217] The terminology relating to optical delay devices for the purposes of this invention will now be explained.

[0218] In a layer comprising a uniaxial birefringent material, there are directions that manipulate the optical anisotropy, but all directions perpendicular to it (or at a specific angle) have equal birefringence.

[0219] The optical axis of an optical retarder refers to the direction of light propagation in a uniaxial birefringent material in which light does not undergo birefringence. This is different from the optical axis of an optical system that can propagate along, for example, a line of symmetry or a principal ray perpendicular to the surface of a display device.

[0220] For light propagating in a direction orthogonal to the optical axis, the optical axis is the slow axis when linearly polarized light with an electric vector direction parallel to the slow axis travels at the slowest speed. The slow axis direction is the direction with the highest refractive index at the design wavelength. Similarly, the fast axis direction is the direction with the lowest refractive index at the design wavelength.

[0221] For a positively dielectric anisotropic uniaxial birefringent material, the slow axis direction is the extraordinary axis of the birefringent material. For a negatively dielectric anisotropic uniaxial birefringent material, the fast axis direction is the extraordinary axis of the birefringent material.

[0222] The terms "half-wavelength" and "quarter-wavelength" refer to delayer operation for a design wavelength λ0 that is typically between 500 nm and 570 nm. In exemplary embodiments of the invention, unless otherwise specified, exemplary phase delay values ​​are provided for a wavelength of 550 nm.

[0223] The retarder provides a relative phase shift between two orthogonally polarized components of an incident light wave, and is characterized by imparting a relative phase amount Γ to the two polarization components. In some contexts, the term "phase shift" may be used without the modifier "relative," but it still refers to a relative phase shift. The relative phase shift is expressed by the following equations relating the birefringence Δn and thickness δ of the retarder:

[0224] Equation 1: Γ = 2πΔnd / λ0

[0225] In Equation 1, Δn is defined as the difference between the extraordinary refractive index and the ordinary refractive index, i.e.

[0226] Δn=ne-n o Equation 2

[0227] For a half-wave delayer, choosing the relationship between d, Δn, and λ0, the phase shift between the polarization components is Γ = π. For a quarter-wave delayer, choosing the relationship between d, Δn, and λ0, the phase shift between the polarization components is Γ = π / 2.

[0228] The term "half-wave delayer" as used in this specification generally refers to light transmitted perpendicular to the delayer and perpendicular to the spatial light modulator (SLM).

[0229] The following will explain some aspects of light transmission through the transparent delay between polarizer pairs.

[0230] The state of polarization (SOP) of light is described by the relative amplitude and phase shift between any two orthogonal polarization components. A transparent retarder does not change the relative amplitude of these orthogonal polarization components, but only affects their relative phase. Providing a pure phase shift between the orthogonal polarization components alters the SOP; however, maintaining a pure relative phase preserves the SOP.

[0231] Linear SOP has polarization components with non-zero amplitude and orthogonal polarization components with zero amplitude.

[0232] A linear polarizer transmits a unique linear SOP with a linear polarization component parallel to the direction of electrical vector transmission of the linear polarizer, and attenuates light with different SOPs.

[0233] An absorptive polarizer is a polarizer that absorbs the polarization component of incident light and transmits a second orthogonal polarization component. An example of an absorptive linear polarizer is a dichroic polarizer.

[0234] A reflective polarizer is a polarizer that reflects the polarization component of incident light and transmits a second orthogonal polarization component. Examples of reflective polarizers that are linear polarizers are multilayer polymer film stacks (such as 3MCorporation's DBEFTM or APFTM) or metal wire grating polarizers (such as Moxtek's ProFluxTM). Reflective linear polarizers may further include cholesterol reflective materials and tandemly arranged quarter-wave plates.

[0235] A delay unit positioned between a linear polarizer and a parallel linear analysis polarizer without introducing a relative pure phase shift provides complete transmission of the light, except for the residual absorption within the linear polarizer.

[0236] A delayer that provides a relative pure phase shift between orthogonal polarization components alters the SOP and provides attenuation at the analytical polarizer.

[0237] In this invention, "A-film" refers to an optical retarder that utilizes a birefringent material layer, the optical axis of which is parallel to the plane of the layer.

[0238] "Positive A-film" refers to a positive birefringent A-film, that is, an A-film with positive Δn.

[0239] In this invention, "C-plate" refers to an optical retarder utilizing a birefringent material layer, the optical axis of which is perpendicular to the plane of the layer. "Positive C-plate" refers to a positive birefringent C-plate, i.e., a C-plate with positive Δn. "Negative C-plate" refers to a negative birefringent C-plate, i.e., a C-plate with negative Δn.

[0240] "O-plate" refers to an optical retarder that utilizes a birefringent material layer, whose optical axis has a component parallel to the plane of the layer and a component perpendicular to the plane of the layer. "Positive O-plate" refers to a positive birefringent O-plate, that is, an O-plate with positive Δn.

[0241] Achromatic retarders can be provided, wherein the material of the retarder has a phase delay Δn.d that varies with wavelength λ.

[0242] Equation 3: Δn.d / λ=κ

[0243] Where κ is approximately a constant.

[0244] Examples of suitable materials include modified polycarbonates supplied by Teijin Films. In specific embodiments of the invention, an achromatic retarder may be provided to advantageously reduce color variation between a viewing direction with a low brightness reduction polarity angle and a viewing direction with an increased brightness reduction polarity angle, as described below.

[0245] Various other terms used in this invention relating to delay devices and liquid crystals will now be explained.

[0246] The liquid crystal cell has a phase retardation given by Δn.d, where Δn is the birefringence of the liquid crystal material in the liquid crystal cell, and d is the thickness of the liquid crystal cell, regardless of the arrangement of the liquid crystal material in the liquid crystal cell.

[0247] Planar alignment refers to the arrangement of liquid crystals in a switchable LCD, where the molecules are aligned approximately parallel to the substrate. Sometimes, plane alignment is referred to as planar alignment. Planar alignment typically has a small pre-tilt (e.g., 2 degrees), so that, as will be explained below, the molecules at the surface of the alignment layer of the liquid crystal cell are slightly offset. The pre-tilt is set to minimize fading during cell switching.

[0248] In this invention, vertical alignment refers to a state in which rod-like liquid crystal molecules are aligned substantially perpendicular to the substrate. In discoid liquid crystals, vertical alignment is defined as a state in which the columnar structures formed by discoid liquid crystal molecules are aligned perpendicular to the surface. In vertical alignment, pre-tilt is the tilt angle of the molecules approaching the alignment layer, and is typically close to 90 degrees, for example, 88 degrees.

[0249] In a twisted liquid crystal layer, a twisted structure (also known as a helical structure or spiral) of nematic liquid crystal molecules is provided. This twist can be achieved through a non-parallel arrangement of layers. Furthermore, a cholesterol dopant can be added to the liquid crystal material to disrupt the decay of the twist direction (clockwise or counterclockwise) and further control the spacing of the twist in the relaxed (typically undriven) state. Super-twisted liquid crystal layers have a twist greater than 180 degrees. Twisted nematic layers used in SLMs typically have a twist of 90 degrees.

[0250] By applying an electric field, liquid crystal molecules with positive dielectric anisotropy are switched from planar alignment (such as A-plate retarder alignment) to vertical alignment (such as C-plate or O-plate retarder alignment).

[0251] By applying an electric field, liquid crystal molecules with negative dielectric anisotropy are switched from vertical alignment (such as C-plate or O-plate retarder orientation) to plane alignment (such as A-plate retarder orientation).

[0252] Rod-shaped molecules exhibit positive birefringence, therefore, as explained in Equation 2, n e >n o Disk-shaped molecules exhibit negative birefringence, therefore n e <n o .

[0253] Positive retarders (such as A-plates, positive O-plates, and positive C-plates) can typically be provided by stretching thin films or rod-shaped liquid crystal molecules. Negative retarders (such as negative C-plates) can be provided by stretching thin films or disk-shaped liquid crystal molecules.

[0254] Parallel liquid crystal cell alignment refers to the alignment of surface-aligned layers in a parallel or more commonly antiparallel direction. In the case of pre-tilted vertical alignment, the alignment layers may have generally parallel or antiparallel components. A mixed-alignment liquid crystal cell may have one surface-aligned layer and one vertical alignment layer. Twisted liquid crystal cells can be provided by alignment layers without parallel alignment (e.g., oriented at 90 degrees to each other).

[0255] The transmission SLM may further include a delay unit located between the input display polarizer and the output display polarizer, for example, as disclosed in U.S. Patent No. 8,237,876, which is incorporated herein by reference in its entirety. Such a delay unit (not shown) is located at a different position than the passive delay unit described in the embodiments of the present invention. Such a delay unit compensates for contrast degradation at off-axis viewing positions, and its effect differs from the brightness reduction at off-axis viewing positions in the embodiments of the present invention.

[0256] Private operating modes of a display device are those in which the observer sees a low contrast sensitivity so that the image is not clearly visible. Contrast sensitivity is a measure of the ability to distinguish different levels of brightness in a still image. Inverse contrast sensitivity can be used as a measure of visual safety, as a high visual safety level (VSL) corresponds to low image visibility.

[0257] For privacy display devices that provide images to observers, visual security can be specified as:

[0258] Equation 4: VSL = (Y + R) / (Y – K)

[0259] Where VSL is the visual security level, Y is the brightness of the display device in white state at the spy's viewpoint, K is the brightness of the display device in black state at the spy's viewpoint, and R is the brightness of the reflected light from the display device.

[0260] Set the panel contrast to:

[0261] Equation 5: C = Y / K

[0262] For high-contrast optical LCD modes, the white state transmission remains substantially constant with viewing angle. In the low-contrast liquid crystal mode of a specific embodiment of the invention, the white state transmission typically decreases as the black state transmission increases, such that...

[0263] Y+K~PL Equation 6

[0264] Then, the visual security level can be further specified as:

[0265]

[0266] The off-axis relative brightness P is typically defined as a percentage of the forward-looking brightness, L is at the peeper angle, and the display device may have an image contrast ratio C, and the surface reflectivity is ρ.

[0267] The off-axis relative brightness P is sometimes referred to as the privacy level. However, such a privacy level P describes the relative brightness of the display device at a specific polar angle relative to the forward viewing brightness, and is not a measurement of privacy presentation.

[0268] The display device can be illuminated by a Lambert ambient illuminance of I. Therefore, in a completely dark environment, the high-contrast display device has a VSL of approximately 1.0. As the ambient illuminance increases, the perceived image contrast deteriorates, the VSL increases, and a privacy-protected image is perceived.

[0269] For typical liquid crystal display devices, the panel contrast ratio C is greater than 100:1 for almost all viewing angles, thereby allowing the visual safety level to approach:

[0270] Equation 8: VSL = 1 + I.ρ / (π.PL)

[0271] Compared to privacy displays, wide-angle displays are easily observable under standard ambient lighting conditions. This is achieved through measurements of specific image visibility using contrast sensitivity, for example, via a Michelson contrast equation:

[0272] M = (I max –I min ) / (I max +I min Equation 9

[0273] so:

[0274] M=((Y+R)–(K+R)) / ((Y+R)+(K+R))=(YK) / (Y+K+2.R) Equation 10

[0275] Therefore, the Visual Safety Level (VSL) is equivalent to (but not the same as) 1 / M. In the discussion of this invention, for a specific off-axis relative brightness P, the wide-angle image visibility W is approximately...

[0276] W = 1 / VSL = 1 / (1 + I.ρ / (π.PL)) Equation 11

[0277] U.S. Patent No. 10,126,575, which is incorporated herein by reference in its entirety, and U.S. Patent Application No. 16 / 131,419, filed September 14, 2018, entitled "Optical stack for switchable directional display" (Attorney General's No. 412101), describe a switchable directional display device for, for example, a privacy display device, including a plurality of retarders disposed between a display polarizer and an additional polarizer. U.S. Patent Publication No. 2018-0329245, which is incorporated herein by reference in its entirety, describes a directional display device further including a reflective polarizer disposed between the display polarizer and the retarders. U.S. Patent Publication No. 2018-0321553, which is incorporated herein by reference in its entirety, describes a directional display polarizer including a passive retarder disposed between the display polarizer and the additional polarizer.

[0278] The structure and operation of various switchable display devices will now be described. In this specification, common components are given common reference numerals. It should be noted that the disclosed information regarding any component applies to every device in which the same or corresponding component is provided. Therefore, for the sake of simplicity, such disclosure will not be repeated.

[0279] Figure 1A This is a schematic diagram illustrating an optical stack for a display device used for ambient lighting, shown in a side perspective view. Figure 1B This is a side perspective view illustrating a switchable privacy display device for ambient lighting, which includes an emitting spatial light modulator (SLM) and a compensated switchable delay; and Figure 2A This is a schematic diagram illustrating the arrangement of optical layers in the optical stack shown in the first figure from the previous view.

[0280] The display device 100 for ambient lighting 604 includes: an SLM 48 configured to output light 400; wherein the SLM 48 includes an output polarizer 218 disposed on the output side of the SLM 48, the output polarizer 218 being a linear polarizer; an auxiliary polarizer 318 disposed on the output side of the output polarizer 218, the auxiliary polarizer 318 being a linear polarizer; and a reflective polarizer 302 disposed between the output polarizer 218 and the auxiliary polarizer 318, the reflective polarizer 302 being a linear polarizer. Generally, the polarizers 210, 218, and 318 can be, for example, dichroic polarizers.

[0281] At least one polarization control delay unit 300 is disposed between the reflective polarizer 302 and the auxiliary polarizer 318. The electric vector propagation direction 303 of the reflective polarizer 302 is parallel to the electric vector propagation direction 319 of the auxiliary polarizer 318. The electric vector propagation direction 303 of the reflective polarizer 302 is parallel to the electric vector propagation direction 219 of the output polarizer 218.

[0282] Therefore, the display device for ambient lighting 604 includes an SLM 48 configured to output light 400. In this invention, the SLM 48 may include a liquid crystal display device comprising an input polarizer 210, an output polarizer 218 having substrates 212, 216, a liquid crystal layer 214, and red, green, and blue pixels 220, 222, 224. A backlight 20 may be configured to illuminate the SLM 48 and may include an input light source 15, a waveguide 1, a back reflector 3, and an optical stack 5 comprising a diffuser, a light-directing film, and other known optical backlight structures. An asymmetric diffuser, which may include, for example, asymmetric surface relief features, may be provided in the optical stack 5, which provides increased diffuse in the elevation direction compared to the lateral direction. Most preferably, image uniformity can be improved.

[0283] The following is for reference Figures 30A to 32C The structure and operation of the backlight 20 used in the privacy display device are further explained. Figure 1A In an exemplary embodiment, the brightness at a polar angle greater than 45 degrees to the normal perpendicular to the SLM can be up to 18%.

[0284] The display device may further include a reflective recirculating polarizer 208 disposed between the backlight 20 and the SLM 48. The reflective recirculating polarizer 208 differs from the reflective polarizer 302 of a specific embodiment of the invention. The reflective recirculating polarizer 208 provides reflection of polarized light from a backlight source having polarization (orthogonal to the electric vector propagation direction of the dichroic input polarizer 210). The reflective recirculating polarizer 208 does not reflect ambient light 604 to the observer.

[0285] like Figure 1B As illustrated, an SLM 48 can be provided by other display device types that emit output light 400, such as an organic LED display (OLED), instead of having an output polarizer 218. The output polarizer 218 can provide brightness reduction for light reflected from the OLED pixel plane by inserting one or more delayers 518 between the output polarizer 218 and the OLED pixel plane. The one or more delayers 518 can be quarter-wave plates and differ from the delayer 330 of this invention.

[0286] Therefore, the SLM 48 includes an output polarizer 218 disposed on the output side of the SLM 48. The output polarizer 218 can be configured to provide a high absorption ratio for light from the pixels 220, 222, 224 of the SLM 48 and to prevent back reflection from the reflective polarizer 302 toward the pixels 220, 222, 224.

[0287] A polarity control delay unit 300 is positioned between the reflective polarizer 302 and the additional polarizer 318. Figures 1A to 1B In a specific embodiment, the polarity control delay 300 includes a passive polarity control delay 330 and a switchable liquid crystal delay 301, but it can generally be replaced by other arrangements of at least one delay, some examples of which are presented in the apparatus described below.

[0288] At least one polarity control retarder 300 is capable of simultaneously not referencing the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer 302 along the axis normal to the plane of the at least one polarity control retarder 300, but instead referencing the relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer 302 along the axis biased towards the plane of the at least one polarity control retarder 300. The polarity control retarder 300 does not affect the brightness of light passing through the reflective polarizer 302, polarity control retarder 300, and additional polarizer 318 along the axis normal to the plane of the polarity control retarder 300, but it does reduce the brightness of light passing through the plane biased towards the plane of the polarity control retarder 300, at least in one of the switchable states of the switchable retarder 301. References below Figures 33A to 35E The principle leading to this effect will be explained in more detail, and the presence or absence of a phase shift introduced by the polarity control retarder 300 causes light to travel at different angles along the axis of the liquid crystal material with respect to the polarity control retarder 300. A similar effect is achieved in all the devices described below.

[0289] The polarity control retarder 300 includes a switchable liquid crystal retarder 301, which includes a liquid crystal material layer 314; and substrates 312 and 316 disposed between the reflective polarizer 302 and the additional polarizer 318. Therefore, at least one polarity control retarder 300 includes a switchable liquid crystal retarder 301, which includes a layer 314 of liquid crystal material 414, wherein at least one polarity control retarder 300 is simultaneously disposed in a switchable state of the switchable liquid crystal retarder 301 to prevent the pure relative phase shift from being applied to the orthogonal polarization component of light passing through the reflective polarizer 302 along the axis normal to the plane of the at least one polarity control retarder 300, while applying the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer 302 along the axis biased towards the plane of the at least one polarity control retarder.

[0290] like Figure 2A As illustrated, when the SLM 48 is a liquid crystal display device, the input electric vector propagation direction 211 at the input polarizer 210 provides the input polarization component, which can be transformed through the liquid crystal layer 214 to provide the output polarization component determined by the electric vector propagation direction 219 of the output polarizer 218. The electric vector propagation direction of the reflective polarizer 302 is parallel to the electric vector propagation direction of the output polarizer 218. Furthermore, the electric vector propagation direction 303 of the reflective polarizer 302 is parallel to the electric vector propagation direction 319 of the auxiliary polarizer 318.

[0291] Switchable LCD delay unit 301 Figure 1A The substrates 312 and 316 illustrated herein include electrodes 413 and 415. Figure 3 (As illustrated in the illustration), it is configured to provide a voltage across layer 314 of liquid crystal material 414. The control system 352 is configured to control the voltage applied across the electrodes of the switchable liquid crystal delay unit 301 via voltage driver 350.

[0292] As will be further explained below, the polarity control delay 300 further includes a passive polarity control delay 330. At least one polarity control delay 300 includes at least one passive delay 330 configured not to reference the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer 302 along the axis normal to the plane of the at least one passive delay, but to reference the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer 302 along the axis biased towards the plane of the at least one passive delay.

[0293] The passive polarity-controlled delayer 330 may include a phase delay layer having a solid birefringent material 430, while the switchable liquid crystal delayer 301 may include a layer 314 of liquid crystal material 414, as will be described below.

[0294] Figure 2B This is a schematic diagram illustrating the viewing angle control element 260 as a side perspective view, which includes a reflective polarizer 302; a polarity control retarder 300, which includes a passive polarity control retarder 330, a switchable liquid crystal retarder 301; and an additional polarizer. (The remaining details may vary.) Figure 2B The features of the setting are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0295] View angle control optics 260 is applied to the output side of a display device for ambient lighting 604, comprising an SLM 48 configured to output light; wherein the SLM 48 includes an output polarizer 218 disposed on the output side of the SLM 48; view angle control optics 260 includes an additional polarizer 318; a reflective polarizer 302 disposed between the output polarizer 218 and the additional polarizer 318 when the view angle control optics 260 is applied to the display device; and at least one polarity control delay 300 disposed between the reflective polarizer 302 and the additional polarizer 318; wherein the at least one polarity control delay 300 is capable of simultaneously not referencing the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer 302 along the axis normal to the plane of the at least one polarity control delay 300, but referencing the relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer 302 along the axis biased towards the plane of the at least one polarity control delay.

[0296] In use, the viewing angle control optics 260 can be attached to the polarized output SLM 48 by the user or factory-assembled. The viewing angle control optics 260 can be provided as a flexible thin film for curved and bent display devices. Alternatively, the viewing angle control optics 260 can be provided on a rigid substrate such as a glass substrate.

[0297] Most preferably, off-the-shelf privacy control elements and / or stray light control elements that do not require matching the panel pixel resolution to avoid moiré artifacts are available. View angle control optics 260 can be further provided for factory assembly to the SLM 48.

[0298] By Figure 2B The viewing angle control optical element 260 is attached to an existing display device to form a viewing angle control optical element 260, which can ... Figures 1A to 2A The display device shown in any of the above.

[0299] The setup and operation of the polarity control delay 300, including the switchable liquid crystal delay 301, will now be discussed.

[0300] Figure 3This is a schematic diagram illustrating the setup of the polarity control delay 300 in privacy operation mode, shown in perspective view. In privacy operation mode, it includes a negative C-plate passive polarity control delay 330 and a vertically arranged switchable liquid crystal delay 301.

[0301] exist Figure 3 In the following other schematic diagrams, some layers of the optical stack are omitted for clarity. For example, substrates 312 and 316 are omitted to show the switchable liquid crystal retarder 301. (The remaining text is incomplete and likely refers to further details.) Figure 3 The features of the setting are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0302] The switchable liquid crystal retarder 301 includes a layer 314 of liquid crystal material 414 having negative dielectric anisotropy. The passive polarity controlled retarder 330 includes a negative C-plate having an optical axis perpendicular to the plane of the retarder 330, schematically illustrated by the orientation of the disk-shaped material 430.

[0303] The liquid crystal retarder 301 further includes transfer electrodes 413 and 415 configured to control the liquid crystal material by adjusting the voltage applied to the electrodes to switch the liquid crystal material layer. The electrodes 413 and 415 may span layer 314 and are configured to apply a voltage for controlling the liquid crystal retarder 301. The transfer electrodes are located on opposite sides of the liquid crystal material layer 414 and may be, for example, through an ITO electrode.

[0304] An alignment layer can be formed between electrodes 413, 415 and the liquid crystal material 414 of layer 314. The orientation of the liquid crystal molecules in the xy plane is determined by the pre-tilt direction of the alignment layer, so each alignment layer has a pre-tilt, wherein the pre-tilt of each alignment layer has components 417a, 417b in the plane of layer 314 with a pre-tilt direction that is parallel, antiparallel, or orthogonal to the electric vector transmission direction 303 of the reflective polarizer 302.

[0305] The driver 350 provides a voltage V to electrodes 413, 415 across layer 314 of the switchable liquid crystal material 414, causing the liquid crystal molecules to tilt at an angle toward the vertical line, thereby forming an O-sheet. The tilted plane is determined by the pre-tilting direction of the arrangement layers formed on the inner surfaces of the substrates 312, 316.

[0306] In typical use, the liquid crystal layer can switch between two states: a first state, open mode, allowing multiple users to use the display device; and a second state, a privacy mode, for the primary user, where visibility to a spy is minimized. This switching is achieved by applying a voltage across the electrodes.

[0307] Generally, such a display device can be considered as having a first wide-angle state and a second reduced off-axis brightness state. Such a display device can provide a privacy display. In another use, or for providing controlled brightness to an off-axis observer, such as in an automotive environment when a passenger or driver may wish to maintain some visibility (not completely obscured) of the displayed image via an intermediate voltage level, stray light can be reduced for nighttime operation.

[0308] The propagation of polarized light from the output polarizer 218 will now be considered in both coaxial and off-axis directions.

[0309] Figure 4A The side view illustrates the operation in privacy mode. Figure 1A A schematic diagram of the transmission of output light from the SLM in the optical stack; and Figure 4B It is aimed at Figure 4A The transmitted light rays described herein are illustrated with a schematic graph showing the change in output brightness with polarity direction. When the liquid crystal material layer 314 is in the second state of the two aforementioned states, the polarity control retarder 300 does not provide an overall transformation of the polarization component 360 to the output light rays 400 passing through it along the axis of the plane of the switchable retarder, but it does provide an overall transformation of the polarization component 361 to the light rays 402 passing through it at some acute angles to the perpendicular to the plane of the retarder. (The remaining text is incomplete and requires further context.) Figure 4A The features of the setting are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0310] The polarization component 360 from the output polarizer 218 is transmitted via a reflective polarizer 302 and incident on the retarder 300. The coaxial light has an unmodified polarization component 362 from component 360, while the off-axis light has a polarization component 364 transformed by the polarity-controlled retarder 300. At least polarization component 361 is transformed into a linear polarization component 364 and absorbed by an additional polarizer 318. More generally, polarization component 361 is transformed into an elliptic polarization component and partially absorbed by the additional polarizer 318.

[0311] Therefore, in the polarity representation of the transmission via the polarity control delay unit 300 and the additional polarizer 318 in the privacy mode, as follows: Figure 4B The examples illustrate areas that provide high transmission and areas that provide low transmission.

[0312] Figure 4BThe polarity distribution of light transmission illustrated herein modifies the polarity distribution of the luminance output of the underlying SLM 48. In the case where the SLM 48 includes a directional backlight 20, the off-axis luminance can then be further reduced as described above.

[0313] The preferred embodiment is a privacy display device that provides low brightness for off-axis viewers and maintains high brightness for coaxial viewers.

[0314] The operation of the reflective polarizer 302 for light from ambient light source 604 will now be described.

[0315] Figure 5A An example of using the privacy mode is shown in a top-down view. Figure 1A A schematic diagram of the transmission of ambient lighting light in an optical stack; Figure 5B It is aimed at Figure 5A The reflected light rays described herein are illustrated with a schematic graph showing the variation of reflectivity with polarity. Further details not discussed in more detail may be included. Figure 5A The features of the setting are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0316] Ambient light source 604 illuminates display device 100 with non-polarized light. Additional polarizer 318 transmits light 410 perpendicular to the surface of the display device with a first polarization component 372 (which is a linear polarization component parallel to the electric vector transmission direction 319 of additional polarizer 318).

[0317] In both operating states, polarization component 372 remains unmodified by polarity control delay 300, so the transmitted polarization component 382 is parallel to the transmission axis of reflective polarizer 302 and output polarizer 218, thus conducting ambient light through SLM48 and causing loss.

[0318] By comparison, for ray 412, the guided off-axis light passes through polarization control retarder 300 such that the polarization component 374 incident on reflective polarizer 302 is reflected. After passing through retarder 300, this polarization component is converted back into component 376 and transmitted through additional polarizer 318.

[0319] Therefore, when the liquid crystal material layer 314 is in the second state of the two aforementioned states, the reflective polarizer 302 does not provide reflected light for the ambient light 410 passing through the additional polarizer 318 and subsequently the polarizer 300 along the axis of the plane perpendicular to the polarization control retarder 300, but provides reflected light 412 for the ambient light passing through the additional polarizer 318 and subsequently the polarization control retarder 300 at some polar angles that are acute to the perpendicular line to the plane perpendicular to the polarization control retarder 300; wherein the reflected light 412 returns through the polarization control retarder 300 and then is transmitted through the additional polarizer 318.

[0320] Therefore, the polarity control delay 300 does not provide an overall transformation of the polarization component 380 along the axis of the plane of the switchable delay via the additional polarizer 318 and subsequently the ambient light 410 of the polarity control delay 300, but it does provide an overall transformation of the polarization component 372 to some polar angles that are acute to the perpendicular line to the plane of the polarity control delay 300 via the absorptive polarizer 318 and subsequently the ambient light 412 of the polarity control delay 300.

[0321] therefore, Figure 5B The polarity distribution of light reflection illustrated herein demonstrates that high reflectivity can be provided at a normal spy's position by controlling the spy-proof state of the retarder 300. Therefore, in the spy-proof operating mode, as... Figure 4B The illustration shows an increase in reflectivity for an off-axis viewing position and a decrease in brightness for off-axis light from the SLM.

[0322] Ideally, a privacy display device should be provided that has high reflectivity for off-axis eavesdroppers and low reflectivity for coaxial observers. As mentioned above, such increased reflectivity can provide an enhanced level of visual security for display devices in ambient lighting environments.

[0323] In another application, such a display device can provide a switchable mirror presentation. This improves the aesthetic appearance of a display device that is not in operation. For example, in a television application in a home environment, the display device can be provided as a mirror for off-axis viewing, thus advantageously providing a sense of expanded living space by reflecting ambient light and concealing the typical "black hole" of a large television screen.

[0324] The explanation is as follows Figure 5A The reflectivity of the setting was measured.

[0325] Figure 5CThis is a schematic graph illustrating the measurement of reflectivity 390 as a function of lateral viewing angle 392 for some reflected light 412. Outline 394 illustrates the reflectivity change of the display device in privacy mode, while outline 396 illustrates the reflectivity change of the display device in public mode.

[0326] Compared to Figure 5B The peak reflectivity is approximately 20%, where 50% represents the reflectivity of the perfectly reflective polarizer 302. This reduction in reflectivity is due to transmission losses from the additional polarizer 318, the polarization reflection efficiency of the reflective polarizer, chromaticity variations at the tuning point of the polarization control delayer 300, and other reflection and scattering losses within the optical stack.

[0327] Further explanation will follow. Figure 1A The operation of the privacy mode on the display device.

[0328] Figure 6A This is a previous perspective view illustrating the observation of the transmitted output light of a display device operating in privacy mode. The display device 100 may have a white area 603 and a black area 601. If a spy can perceive the brightness difference between the observed areas 601 and 603, then an image on the display device can be observed. Operationally, the primary user 45 observes the full-brightness image via ray 400 at a viewing position 26, which may be an optical window of a directional display device. The spy 47 observes the reduced brightness ray 402 at a viewing position 27, which may include, for example, an imaging waveguide of the optical window of a directional display device. Areas 26 and 27 further represent polarity curves. Figure 4B and Figure 5B The coaxial and off-axis regions.

[0329] Figure 6B This is a schematic diagram illustrating the observation of ambient light reflected from the interface surface of the display device, as previously illustrated by a perspective view. Therefore, reflections can occur through the front surface of the additional polarizer 318 and other surfaces of the display device. Figure 5A Some of the light rays 404 are illustrated in the diagram. Typically, due to Fresnel reflection at the air-polarizer interface, such reflectivity can be 4% for a vertically incident coupled optical stack and approximately 5% for a coupled optical stack incident at 45 degrees. Therefore, a low-brightness reflected image 605 of source 604 can be observed by a spy in front of display device 100.

[0330] Figure 6C The previous perspective illustration was for operation in privacy mode. Figure 1A A schematic diagram illustrating the observation of ambient light reflected from the display device. Compared to Figure 6BThe reflected brightness is approximately higher, as can be observed from the reflection of source 604 at 606. This can be further discussed in more detail... Figures 6A to 6C The settings feature is assumed to correspond to features having equivalent reference numbers as discussed above, including any potential variations in the features.

[0331] The shape and distribution of the reflected image 606 are determined by the spatial distribution of the ambient light source 604, but can be further determined by the diffuse layer, particularly at the output surface of the additional polarizer 318.

[0332] Figure 7A The previous perspective view is illustrated in different viewing positions, such as Figure 4B and Figure 5B The privacy mode operation with brightness and reflectivity variations illustrated in the example. Figure 1A The schematic diagram of the display device is shown. Therefore, each of the nine views 520, 522, 524, 526, 528, 530, 532, 534 and 536 corresponds to a view from the relative viewing position, as shown in the perspective view of these views.

[0333] Therefore, the upper viewing quadrant views 530, 532, the lower viewing quadrant views 534, 536, and the side viewing position views 526, 528 provide both reduced brightness of the ambient light source 604 and increased reflections 606, 605. However, the upper / lower center viewing area views 522, 524 and the front view 520 provide a much brighter and low reflectivity area 605 in which there is virtually no visibility of reflections from the reflective polarizer 302.

[0334] Figure 7B This refers to the configuration of profile 624 with reflective polarizer 302 and the configuration of profile 626 without reflective polarizer 302, as well as the exemplary specific embodiments in Table 1, illustrating the privacy operation mode. Figure 1A A schematic diagram illustrating the change in the visual safety level 620 of the off-axis spyware of a switchable privacy display device relative to the ratio 622 of ambient illuminance to forward-looking luminance.

[0335]

[0336] Table 1

[0337] therefore, Figure 7B An example is shown where the level of visual safety can be improved by using a reflective polarizer 302.

[0338] Compared to the specific embodiment of the present invention, omitting the reflective polarizer 302 provides a visual safety level V for general ambient illuminance less than 4.0. Such a visual safety level is insufficient to achieve the desired privacy against a spy 27. The specific embodiment of the present invention achieves a high visual safety level above 4.0 for a lux / nit ratio of 20% or lower. For example, the desired visual safety can be achieved for a forward-looking user 26 observing a 200-nit image in an environment with 40-nit ambient illuminance. The visual safety level increases with increasing ambient illuminance.

[0339] Figure 7C It is for including the collimated backlight 20 Figure 1A The display device, illustrating a schematic diagram of how the visual safety level changes with polarity, will be referenced below. Figures 32A to 32C The ratio of 20% ambient illuminance (lux) to forward luminance (nit) (lux / nit) further illustrates this.

[0340] Figure 7C An example is provided for a first polarity region 690 for viewing by the primary user 26, achieving a visual safety level V of less than 1.2, thereby providing image visibility W greater than 83%. Most preferably, the display device 100 can be easily viewed with high contrast. In a second polarity region 692, the visual safety level V is greater than 4.0, and the eye of a spy positioned in this region will not be easily discernible on the display device. A polarity region 694 is located between regions 690 and 692 and is an area where image visibility is reduced, although not at the desired level of visual safety. Most preferably, embodiments of the invention achieve a large polarity region 690 for the primary user, a large polarity region 692 for the spy, and a small transitional region 694.

[0341] Figure 7D It is for the same as Figure 7C The lux / nit ratio, for a display device that does not include multiple delay units, illustrates a schematic diagram showing the change of visual safety level with polarity direction. Compared to a specific embodiment of the present invention, the polarity region 692 requiring a visual safety level V>4 is significantly reduced, and the polarity region 694 where image visibility is reduced but the visual safety level is insufficient is increased.

[0342] Compared to the present invention, in narrow angular ranges (such as the typical "center" pattern of a single retarder layer, and for example, referring to...) Figures 27A to 27B (Note:) Providing a single retarder with high reflectivity at the top will not achieve high reflectivity over the wide-angle range. In particular, Figure 5AThe double passage of reflected light illustrated provides a very narrow area of ​​high reflectivity. The reflected light must pass through the retarder twice, with the input and output ray directions opposing around the normal of the display device. This multiplies the optical effect and confines the high reflectivity to rays with an elevation angle close to the design angle (e.g., + / - 45 degrees lateral angle and zero degree elevation angle). The extended privacy protection around the horizontal line in this embodiment of the invention creates a larger area (e.g., polar region 692) with high visual security.

[0343] The multiple retarder units of this invention, in specific embodiments, provide high reflectivity over a wide-angle range and achieve the desired privacy against off-axis peeping. Furthermore, the retarder units can be switched to provide low reflectivity and high image visibility in an open operating mode. Most preferably, the multiple retarder units achieve a significant increase in polarity region 692 and a significant decrease in polarity region 694, while achieving comfortable image visibility for the primary user within polarity region 690.

[0344] The aim is to provide controllable lighting for display devices in automobiles.

[0345] Figure 8A This is a side view illustrating a car vehicle having a switchable directional display device 100 (for both entertainment and sharing operation modes) disposed within the vehicle cabin 602 of the car vehicle 600. A light cone 610 (e.g., representing a light cone whose internal brightness is greater than 50% of the peak brightness) provides the brightness distribution of the display device 100 in the elevation direction and is not switchable. Furthermore, the reflectivity of the display device can be increased compared to the forward reflectivity of the area outside this light cone 610.

[0346] Figure 8B This is a top view illustrating a car vehicle with a switchable directional display device 100 (operating in entertainment mode and in a manner similar to a privacy screen) located within the vehicle cabin 602. The light cone 612 has a narrow angle range, such that the passenger 606 can see the display device 100, while the driver 604 may not see the image on the display device 100 due to reduced brightness and increased reflectivity. Preferably, entertainment images can be displayed to the passenger 606 without distracting the driver 604.

[0347] Figure 8C This is a top view illustrating a car vehicle with a switchable directional display device 100 (in shared operation mode) located within the vehicle cabin 602. The light cone 614 has a wide angle range, so that all occupants can see the image on the display device 100, for example, when the display device is in a non-dynamic state or when a non-distracting image is provided.

[0348] Figure 8D This is a top-view illustration of an automobile vehicle equipped with a switchable directional display device 100 (for both night and daytime operation modes) located within the vehicle's cabin 602. Compared to Figures 8A to 8C With the aforementioned configuration, the optical output is rotated so that the elevation direction of the display device is along the axis between the positions of driver 604 and passenger 606. The light cone 620 illuminates both driver 604 and passenger 606 and has a low display device reflectivity.

[0349] Figure 8E This is a side view illustrating a schematic diagram of an automobile vehicle having a switchable directional display device 100 (in nighttime operation mode) disposed within the vehicle cabin 602. Therefore, the display device provides a narrow-angle output light cone 622. This advantageously reduces stray light that illuminates the interior surfaces of the vehicle cabin 602 and the occupants, thus reducing distraction for the driver 604. Both the driver 604 and the passenger 606 can advantageously observe the displayed image.

[0350] Figure 8F This is a side view illustrating a car vehicle with a switchable directional display device 100 (in daytime operation mode) disposed within the vehicle cabin 602. Therefore, the display device can provide a narrow-angle output light cone 624. Most preferably, the display device is easily visible to all occupants of the cabin 602.

[0351] Can Figures 8A to 8F The display device 100 is located in other vehicle cabin locations, such as driver instrument display, center console display, and seatback display.

[0352] The operation of the display device 100 in the open mode, representing the first state, will now be explained, and further details of the polarity control delay unit 300 will be illustrated.

[0353] Figure 9A This is a schematic diagram illustrating the configuration of the polarity control delay unit 300 in the open operating mode, shown as a perspective view. In a specific embodiment of the invention, zero volts are provided across the liquid crystal delay unit 301; Table 2 describes the configuration for... Figure 9A This is an exemplary specific embodiment of the settings. Those not discussed in further detail may be... Figure 9A The features of the setting are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0354]

[0355] Table 2

[0356] The switchable liquid crystal retarder 301 includes two surface-aligned layers disposed on electrodes 413, 415 and adjacent to and on opposite sides of a liquid crystal material 414, each configured to provide a vertical alignment within the adjacent liquid crystal material 414. The liquid crystal material 414 layer of the switchable liquid crystal retarder 301 comprises a liquid crystal material having negative dielectric anisotropy. The liquid crystal molecules 414 may have a pre-tilt of, for example, 88 degrees relative to the horizontal line to eliminate fading during switching.

[0357] In specific embodiments of the present invention, the desired ranges for phase delay and voltage have been established through simulation of delay stacks and experiments with display device optical stacks. The ranges for phase delay provided for various optical layer designs will now be described.

[0358] The liquid crystal material layer 314 has a phase retardation of 550 nm light wavelength in the range of 500 nm to 1000 nm, preferably in the range of 600 nm to 900 nm, and most preferably in the range of 700 nm to 850 nm; and the retarder 330 further includes a passive retarder having an optical axis perpendicular to the plane of the retarder, the passive retarder having a phase retardation of 550 nm light wavelength in the range of -300 nm to -900 nm, preferably in the range of -450 nm to -800 nm, and most preferably in the range of -500 nm to -725 nm.

[0359] Alternatively, the passive polarity-controlled retarder 330 may include an O-plate retarder having an optical axis oriented with a component perpendicular to the plane of the retarder and a component in the plane of the retarder. Such a retarder can provide further compensation for any remaining tilt of the liquid crystal material 414.

[0360] Figure 9B The side view is used as an example in the public operation mode. Figure 1A A schematic diagram of the transmission of output light from the SLM in the optical stack; and Figure 9C It is aimed at Figure 9B The transmitted light beam described herein is illustrated with a schematic graph showing the change in output brightness as a function of polarity. Further details not discussed in more detail may be included. Figures 9B to 9C The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0361] Therefore, when the liquid crystal retarder 301 is in the first state of the aforementioned two states, the polarity control retarder 300 does not provide an overall transformation of polarization components 360 and 361 to the output light passing through the plane perpendicular to the switchable retarder 301 or forming an acute angle with the perpendicular line to the plane perpendicular to the switchable retarder 301. That is, polarization component 362 is approximately the same as polarization component 360, and polarization component 364 is approximately the same as polarization component 361. Therefore, Figure 9C The angular transmission profile generally spans a wide polarity region and transmits uniformly. Preferably, the display device can be switched to a wide field of view.

[0362] Figure 9D The top view is used as an example in the public operation mode. Figure 1A A schematic diagram of the transmission of ambient lighting light in an optical stack; and Figure 9E It is aimed at Figure 9D The reflected light rays described herein are illustrated with a schematic graph showing the variation of reflectivity with polarity. Further details not discussed in more detail may be included. Figures 9D to 9E The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0363] Therefore, when the liquid crystal retarder 301 is in the first state of the two aforementioned states, the polarization control retarder 300 will not provide an overall transformation of the polarization component 372 to the ambient light 412 of the polarization control retarder 300 through the additional polarizer 318 or the plane perpendicular to the plane perpendicular to the polarization control retarder 300.

[0364] In the open mode of operation, the input light 412 has a polarization state 372 after passing through the additional polarizer 318. No polarization transformation occurs in either the forward-looking or off-axis directions, therefore the reflectivity of the light 402 from the reflective polarizer 302 is very low. The light 412 is transmitted through the reflective polarizer 302 and at the display polarizers 218, 210, or... Figure 1A Backlight or Figure 1B Losses in optical isolators 218 and 518 in the transmitting SLM 48.

[0365] Ideally, in open operation mode, it provides high brightness and low reflectivity across a wide field of view. Multiple observers can easily view such a display with high contrast.

[0366] The following will explain the public mode for the first state. Figure 1A The presentation of the display device.

[0367] Figure 10AThis is a previous perspective illustration illustrating the observation of the transmitted output light of a display device operating in open mode; Figure 10B This is a previous perspective example shown in public mode. Figure 1A A schematic diagram of the observation of reflected ambient light from a switchable display device; and Figure 10C This is a previous perspective view instance operating in public mode. Figure 1A A schematic diagram of the display device.

[0368] Therefore, high display brightness is achieved for the desired off-axis viewing position of user 45, with virtually no reflection from reflective polarizer 302. High image visibility values ​​are achieved, and multiple users can easily distinguish display information. Fresnel reflection 605 remains as present in conventional display devices and is typically at a low level. A high-performance open mode is provided.

[0369] The further settings for the delay will now be explained.

[0370] Figure 11A This is a schematic diagram illustrating the setup of a switchable retarder in open operating mode, as shown in a perspective view. The switchable retarder includes a switchable liquid crystal layer having a surface-aligned arrangement, and intersecting A-plate polarity control retarders. Figure 11B This is for use in privacy mode. Figure 11A The transmitted light beam in the diagram illustrates the output brightness as a function of polarity. Figure 11C This is for use in privacy mode. Figure 11A The reflected light rays in the image are illustrated with a schematic graph showing how reflectivity changes with polarity. Figure 11D This is for use in the public operating mode. Figure 11A The transmitted light rays in the diagram illustrate the output brightness as a function of polarity; and Figure 11E This is for use in the public operating mode. Figure 11A The reflected light rays are illustrated with schematic graphs showing the variation of reflectivity with polarity, including the specific embodiments illustrated in Table 3A. Those not discussed in further detail may be... Figures 11A to 11E The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0371]

[0372] Table 3A

[0373] The switchable liquid crystal retarder 301 includes two surface-aligned layers 419a and 419b, which are arranged adjacent to and on opposite sides of the liquid crystal material 421, and each is configured to provide surface alignment in the adjacent liquid crystal material 421. The layer 314 of the liquid crystal material 421 of the switchable liquid crystal retarder 301 comprises a liquid crystal material 421 having positive dielectric anisotropy. The layer of liquid crystal material 421 has a phase retardation of 550 nm wavelength light in the range of 500 nm to 900 nm, preferably in the range of 600 nm to 850 nm, and most preferably in the range of 700 nm to 800 nm. The retarder 330 further includes a pair of passive retarders 330A and 330B, which have intersecting optical axes in the plane of the retarder, and each passive retarder of the pair of passive retarders has a phase delay of 550 nm wavelength light in the range of 300 nm to 800 nm, preferably in the range of 350 nm to 650 nm, and most preferably in the range of 450 nm to 550 nm.

[0374] Compared to the specific embodiments described in Table 2, a passive polarity-controlled retarder 330 is provided by a pair of A-plates 330A and 330B with a cross axis. In this specific embodiment of the invention, "cross" refers to an angle of approximately 90° between the optical axes of the two retarders in the plane of the retarder. To reduce the cost of the retarder material, it is necessary to provide a material that has some variation in retarder orientation due to, for example, stretching errors during thin film manufacturing. Variations in retarder orientation away from the preferred orientation can reduce the forward-looking brightness and increase the minimum transmission. Preferably, angle 310A is at least 35° and at most 55°, most preferably at least 40° and at most 50°, and most preferably at least 42.5° and at most 47.5°. Preferably, angle 310B is at least 125° and at most 145°, most preferably at least 130° and at most 135°, and most preferably at least 132.5° and at most 137.5°.

[0375] Compared to the specific embodiments described in Table 2, the liquid crystal retarder arrangement is provided by aligning along a surface rather than perpendicular to it. This aligning along a surface advantageously provides a reduction in recovery time during mechanical deformation, such as when the display device is touched.

[0376] The passive retarder can be provided using an extended thin film to advantageously achieve low cost and high uniformity. Furthermore, it improves the field of view of liquid crystal retarders with planar alignment, while providing restoring force to the visibility of the flow of liquid crystal material during pressure application.

[0377] The required additional polarizer 318 can provide different electric vector transmission directions for the output polarizer 218 and the reflective polarizer 302.

[0378] Figure 11FThis is a schematic diagram illustrating the arrangement of the retarder 300 in privacy mode, shown in a perspective view. It includes the intersecting A-plate passive polarity controlled retarders 330A and 330B and a switchable liquid crystal retarder 301 arranged along the surface, further including a passive rotational retarder 460, which includes the specific embodiments illustrated in Table 3B. (The remaining details may vary.) Figure 11F The features of the setting are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0379]

[0380] Table 3B

[0381] The reflective polarizer 302 and the additional polarizer 318 have non-parallel electric vector transmission directions 303 and 319, and the display device 100 further includes a rotor delayer 460 disposed between the reflective polarizer 302 and the additional polarizer 318, wherein the rotor delayer 460 is configured to rotate between the electric vector transmission directions of the display polarizer 218 and the additional polarizer 318 to the polarization direction of the polarized light incident thereon.

[0382] The output polarizer 218 and the reflective polarizer 302 may have electrical vector transmission directions 219 and 303, which may be at an angle 217 of 45 degrees, for example, in the case of a twisted nematic LCD display device. The additional polarizer 318 may be configured to provide vertically polarized light to a user who is wearing polarized sunglasses that typically transmit vertically polarized light.

[0383] The passive rotating retarder 460 differs from the polarization-controlled retarder 330 of a specific embodiment of the invention, and its operation will now be described. The passive rotating retarder 460 may include a birefringent material 462 and is a half-wave plate, which has a phase delay at, for example, a wavelength of 550 nm at 275 nm. The passive rotating retarder 460 has a fast-axis orientation 464, which is biased at an angle 466, possibly 22.5 degrees, toward the electric vector propagation direction 319 of the additional polarizer 318. Therefore, the passive rotating retarder 460 rotates the polarization from the output polarizer 218 such that the polarization direction of the light incident on the polarization-controlled retarder 330B is parallel to direction 319.

[0384] Operationally, the passive rotation retarder 460 modifies the coaxial polarization state by providing an angular rotation of the polarization component from the output polarizer 218. This contrasts with the polarization control retarders 330A and 330B, which do not modify the coaxial polarization state overall. Furthermore, the passive rotation retarder 460 provides a rotation of polarization, offering only a small change in output brightness with viewing angle in the off-axis direction. In contrast, the polarization control retarders 330A and 330B provide a more general modification of output brightness with viewing angle.

[0385] Most preferably, for example, to provide viewing with polarized sunglasses, the display device may have an output polarization direction 319 that is different from the polarization direction 219 of the display polarizer.

[0386] In an alternative embodiment, the separate delayer 460 may be omitted, and an additional Figure 11A The phase delay of delayer 330B is used to provide the half-wave rotation. Continuing with the exemplary embodiment, the phase delay of delayer 330B at a wavelength of 550 nm can be 275 nm greater than the phase delay of delayer 330A. Most preferably, this reduces the number of layers, complexity, and cost.

[0387] In other embodiments, a passive rotational delay 460 may be provided between the display output polarizer 218 and the reflective polarizer 302, such that the electrical vector transmission directions 303, 319 of the reflective polarizer 302 and the additional polarizer 318 are parallel.

[0388] Figure 12A This is a schematic diagram illustrating the setup of a switchable retarder in privacy mode, shown in a perspective view. It includes a switchable liquid crystal retarder arranged along a surface, comprising a liquid crystal 421; and a passive negative plate retarder 330 driven by a first voltage V1; and Figure 12B This is a schematic diagram illustrating the setup of a switchable retarder in privacy mode, shown in a perspective view. It includes switchable liquid crystal retarders arranged along a surface; and a passive negative C-plate retarder driven by a second voltage V2 different from the first voltage V1. Further details not discussed here are possible. Figures 12A to 12B The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0389] Compared to Figure 12A The driving voltage V2 is increased to provide a tilt increase to the molecules of the liquid crystal material 414 at the center of layer 314 of the liquid crystal retarder. This tilt increase alters the phase delay of the switchable liquid crystal retarder 301 between the privacy and public modes.

[0390] Figure 12CThis is for use in privacy mode. Figure 12A The transmitted light rays in the diagram illustrate the output brightness as a function of polarity; and Figure 12D This is for use in privacy mode. Figure 12A The reflected light rays are illustrated with a schematic graph showing the change in reflectivity as a function of polarity. Figure 12E This is for use in the public operating mode. Figure 12B The transmitted light rays in the diagram illustrate the output brightness as a function of polarity; and Figure 12F This is for use in the public operating mode. Figure 12B The reflected light rays are illustrated with a schematic graph showing the variation of reflectivity with polarity. Table 4A shows an exemplary embodiment of a configuration incorporating a passive retarder arranged along a surface.

[0391]

[0392] Table 4A

[0393] The switchable liquid crystal retarder 301 includes two surface alignment layers disposed adjacent to the liquid crystal material layer and on opposite sides thereof, each configured to provide surface alignment in adjacent liquid crystal material 414. The liquid crystal material layer 314 of the switchable liquid crystal retarder 301 comprises a liquid crystal material 414 having positive dielectric anisotropy. The liquid crystal material layer 414 has a phase retardation of 550 nm wavelength light in the range of 500 nm to 900 nm, preferably in the range of 600 nm to 850 nm, and most preferably in the range of 700 nm to 800 nm. The retarder 330 further includes a passive retarder having an optical axis perpendicular to the plane of the retarder, the passive retarder having a phase retardation of 550 nm wavelength light in the range of -300 nm to -700 nm, preferably in the range of -350 nm to -600 nm, and most preferably in the range of -400 nm to -500 nm.

[0394] Compared to Figure 11A This can reduce the thickness and complexity of the delay unit 330.

[0395] The structure of the passive polarity control delay unit 330 will now be described.

[0396] Figure 13A This is a schematic diagram illustrating the setup of a switchable retarder in privacy mode, shown in perspective view. It includes a switchable liquid crystal retarder 301 arranged along its surface in privacy mode. The switchable liquid crystal retarder 301 includes surface alignment layers 419a and 419b arranged adjacent to liquid crystal material 421 and configured to provide surface alignment at adjacent liquid crystal material 421. Figure 13B This is for use in privacy mode. Figure 13A The transmitted light beam in the diagram illustrates the output brightness as a function of polarity. Figure 13C This is for use in privacy mode. Figure 13A The reflected light rays in the image are illustrated with a schematic graph showing how reflectivity changes with polarity. Figure 13D This is for use in the public operating mode. Figure 13A The transmitted light rays in the diagram illustrate the output brightness as a function of polarity; and Figure 13E This is for use in the public operating mode. Figure 13A The reflected light rays are illustrated with a schematic graph showing the change in reflectivity as a function of polarity.

[0397] Specific in Table 4B Figure 13A Exemplary specific embodiments of the settings.

[0398]

[0399] Table 4B

[0400] The switchable liquid crystal retarder 301 includes two surface alignment layers disposed adjacent to the liquid crystal material layer and on opposite sides thereof, each configured to provide surface alignment in adjacent liquid crystal material 414. The liquid crystal material layer of the switchable liquid crystal retarder comprises a liquid crystal material having positive dielectric anisotropy. The liquid crystal retarder 301 may have a phase delay of 550 nm wavelength light in the range of 500 nm to 1500 nm, preferably in the range of 700 nm to 1200 nm, and most preferably in the range of 800 nm to 1000 nm.

[0401] Since no passive delayer is provided, Figures 13A to 13E The specific embodiments described above advantageously achieve cost and complexity reduction. Furthermore, the disclosure mode can be an undriven state of the liquid crystal material in layer 314, and a relatively low voltage is used in the privacy mode. Additionally, compared to vertical alignment, surface alignment layers advantageously provide reduced visibility due to liquid crystal material flow caused by surface treatment of the display device (e.g., when using a touch panel).

[0402] Figure 13F This is a schematic diagram illustrating a viewing angle control element using a side perspective view, which includes a reflective polarizer, a switchable liquid crystal retarder, and an additional polarizer. A low-cost, switchable component market tier is available, providing privacy protection with a switchable "bullseye" field of view profile.

[0403] Further configuration of the switchable delay unit 300 will now be explained.

[0404] Figure 14AThis is a schematic diagram illustrating the setup of a switchable retarder in privacy operation mode, shown in perspective view. It includes cross-shaped passive retarders 330A and 330B and a vertically arranged switchable liquid crystal retarder 301. Figure 14B This is for use in privacy mode. Figure 14A The transmitted light rays in the diagram illustrate the output brightness as a function of polarity; and Figure 14C This is for use in privacy mode. Figure 14A The reflected light rays are illustrated with a schematic graph showing the change in reflectivity as a function of polarity. Further details not discussed in more detail can be added. Figures 14A to 14C The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0405] Figure 14D This is a schematic diagram illustrating the setup of a switchable retarder in open operation mode, shown in perspective view, which includes a cross-shaped A-plate passive retarder and a vertically arranged switchable liquid crystal retarder. Figure 14E This is for use in the public operating mode. Figure 14D The transmitted light rays in the diagram illustrate the output brightness as a function of polarity; and Figure 14F This is for use in the public operating mode. Figure 14D The reflected light rays are illustrated with a schematic graph showing the change in reflectivity as a function of polarity. Further details not discussed in more detail can be added. Figures 14D to 14F The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0406] Therefore, the passive polarity-controlled retarder 330 includes retarder pairs 330A and 330B, which have intersecting optical axes in the plane of the retarder. The retarder pairs 330A and 330B have optical axes extending at + / -45° relative to each of the electrical vector propagation directions of the output polarizer. Each of the retarder pairs 330A and 330B includes a single A-plate. Exemplary specific embodiments are illustrated in Table 5.

[0407]

[0408] Table 5

[0409] The switchable liquid crystal retarder 301 includes two surface-aligned layers disposed on electrodes 413, 415 and adjacent to and on opposite sides of a liquid crystal material 414, each configured to provide a vertical alignment within the adjacent liquid crystal material 414. The liquid crystal material 414 layer of the switchable liquid crystal retarder 301 comprises a liquid crystal material having negative dielectric anisotropy. The liquid crystal material layer 314 has a phase retardation of 550 nm wavelength light in the range of 500 nm to 1000 nm, preferably in the range of 600 nm to 900 nm, and most preferably in the range of 700 nm to 850 nm. The retarder 301 further includes a pair of passive retarders having intersecting optical axes in the plane of the retarder, each passive retarder in the pair having a phase retardation of 550 nm wavelength light in the range of 300 nm to 800 nm, preferably in the range of 500 nm to 700 nm, and most preferably in the range of 550 nm to 675 nm.

[0410] Ideally, it provides a wide field of view and high reflectivity in privacy mode. It also allows for easier and lower-cost manufacturing of the A-film compared to the C-film retarder.

[0411] The liquid crystal delay unit 301 with mixed arrangement will now be described.

[0412] Figure 15A This is a schematic diagram illustrating the setup of a switchable retarder in privacy operation mode, shown in a perspective view. It includes a switchable liquid crystal retarder 301 arranged along the surface and perpendicular to the surface, which includes liquid crystal material 414; and a passive negative C-plate retarder 330. Figure 15B This is for use in privacy mode. Figure 15A The transmitted light rays in the diagram illustrate the output brightness as a function of polarity; and Figure 15C This is for use in privacy mode. Figure 15A The reflected light rays are illustrated with a schematic graph showing the change in reflectivity as a function of polarity. Figure 15D This is for use in the public operating mode. Figure 15A The transmitted light rays in the diagram illustrate the output brightness as a function of polarity; and Figure 15E This is for use in the public operating mode. Figure 15A The reflected light rays are illustrated with a schematic graph showing the change in reflectivity as a function of polarity. Further details not discussed in more detail can be added. Figures 15A to 15E The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0413] Table 6 illustrates specific embodiments of a configuration that incorporates both vertical and surface-aligned layers of passive delayers.

[0414]

[0415] Table 6

[0416] The switchable liquid crystal delay 301 includes two surface alignment layers 419a and 419b, which are arranged adjacent to the liquid crystal material 414 and on opposite sides thereon. One of the surface alignment layers 419a is configured to provide a vertical alignment in the adjacent liquid crystal material 414, and the other of the surface alignment layers 419b is configured to provide a surface alignment in the adjacent liquid crystal material 414.

[0417] Compared to specific embodiments with two vertical or two lateral arrangement layers, the design of the passive polarity control delay 330 can differ if it is placed on the side of the vertical arrangement layer 419a or on the side of the lateral arrangement layer 419b.

[0418] When the surface alignment layer 419b is configured to be positioned between layer 314 of liquid crystal material 414 and polarity control retarder 330, the liquid crystal retarder 301 has a phase delay of 550 nm wavelength light in the range of 700 nm to 2000 nm, preferably in the range of 1000 nm to 1500 nm, and most preferably in the range of 1200 nm to 1500 nm. The polarity control retarder 300 may further include a passive polarity control retarder 330, whose optical axis is perpendicular to the plane of the retarder, and the passive polarity control retarder 330 has a phase delay of 550 nm wavelength light in the range of -400 nm to -1800 nm, preferably in the range of -700 nm to -1500 nm, and most preferably in the range of -900 nm to -1300 nm.

[0419] Figure 15A The C-plate can be replaced with a cross-shaped A-plate. When the polarity control retarder 300 further includes a pair of passive retarders (which have cross-shaped optical axes in the plane of the retarder), each retarder in the pair has a phase delay of 550 nm wavelength light in the range of 400 nm to 1800 nm, preferably in the range of 700 nm to 1500 nm, and most preferably in the range of 900 nm to 1300 nm.

[0420] When the surface alignment layer 419a is configured to provide a vertically aligned surface arrangement between the liquid crystal material 414 layer 314 and the polarity control retarder 330, the liquid crystal retarder 301 has a phase delay of 550 nm wavelength light in the range of 500 nm to 1800 nm, preferably in the range of 700 nm to 1500 nm, and most preferably in the range of 900 nm to 1350 nm. The polarity-controlled retarder 300 may further include a passive polarity-controlled retarder 330, the optical axis of which is perpendicular to the plane of the retarder 330. The passive polarity-controlled retarder 330 has a phase delay of 550 nm wavelength light in the range of -300 nm to -1600 nm, preferably in the range of -500 nm to -1300 nm, and most preferably in the range of -700 nm to -1150 nm. Alternatively, the retarder 330 may further include a pair of passive retarders having intersecting optical axes in the plane of the retarder. Each retarder in the pair has a phase delay of 550 nm wavelength light in the range of 400 nm to 1600 nm, preferably in the range of 600 nm to 1400 nm, and most preferably in the range of 800 nm to 1300 nm.

[0421] The optimal choice is, Figure 15A The mixed arrangement achieves an increased polarity angle range, and the reflectivity above it from the reflective polarizer 302 is increased.

[0422] An alternative display device structure will now be described, which includes multiple optical stacks to achieve control of the field of view of a privacy or low stray light display device.

[0423] Figure 16 This is a side perspective view illustrating a switchable privacy display device 100 for ambient lighting, which includes a non-collimated backlight 20; a separate passive polarization control delay 300B disposed between a reflective recirculating polarizer 318B and a transmissive SLM; a reflective polarizer 302; a polarization control delay 300A; and an additional polarizer 318A. Therefore, compared to... Figure 1A Display device, Figure 16 Further including an additional passive polarity control delay unit 300B, which is disposed between the input polarizer 210 of the transmission SLM 48 and an additional auxiliary polarizer 318B. This is configured to recycle the light in the backlight 20 and, advantageously, similar to... Figure 1A The reflective polarizer 318B improves efficiency by means of the reflective polarizer 208, and provides an additional auxiliary polarizer 318B.

[0424] Preferably, the field of view of the display device is modified by an additional polarizer 318B to reduce the off-axis brightness from the SLM 48. This reduces stray light and improves visual security for eavesdroppers. The additional polarizer 318B can be a reflective polarizer, unlike the reflective polarizer 302. The additional reflective polarizer 318B provides light recycling in the backlight 20 without increasing forward reflections in privacy mode, thus improving efficiency.

[0425] Figure 17A This is a side perspective view illustrating a switchable privacy display device for ambient lighting, including an emissive SLM 48, a passively controlled delay unit 300B, an additional polarizer 318B, a reflective polarizer 302, multiple delay units 300, and an additional polarizer 318A. The additional polarization control delay unit 300B is positioned between the output polarizer 218 and the reflective polarizer 302. The additional polarizer 318A is positioned between the additional polarization control delay unit 300B and the reflective polarizer 302.

[0426] Figure 17B This is a schematic diagram illustrating the viewing angle control element 260 for a radiating display device, shown in a side perspective view.

[0427] Operationally, the light from the display output polarizer 218 has a field of view modified by the passive polarization control delay unit 300B and the additional polarizer 318B. Most preferably, the field of view from the emitting display device is reduced. The reflective polarizer 302, the multiple polarization control delay units 300A, and the additional polarizer 318A provide an open mode (determined by the SLM 48, delay unit 300B, and additional polarizer 318B) and a privacy mode (with...). Figure 1B The switching between display devices 100 and those with high off-axis reflectivity and reduced off-axis brightness.

[0428] Compared to Figure 1B Display device, Figure 17A It further includes an additional polarity control delay unit 300B and an additional additional polarizer 318B, wherein the additional polarity control delay unit 300B is disposed between the first-mentioned additional polarizer and the additional additional polarizer 318B.

[0429] The desired outcome is a public mode with high image visibility for off-axis viewing and a privacy mode with a high level of visual security. A specific embodiment of a switchable privacy display device including multiple additional delayers and additional polarizers will now be described.

[0430] Figure 18AThis is a side perspective view illustrating a switchable privacy display device 100 for ambient lighting 604, which includes a wide-angle backlight 20, wherein a first polarity control delay unit 300A is disposed between the backlight 20 and the SLM 48, and a further polarity control delay unit 300B is configured to receive light from the SLM 48. (The remaining details are not discussed further.) Figures 16 to 18B The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0431] Figure 18A With Figure 1A A similar structure is provided, wherein a viewing angle control element 260A is provided to receive light from the output polarizer 218 of the SLM.

[0432] In contrast, as explained elsewhere, the backlight 20 can be provided by a wide-angle backlight 20, rather than a directional backlight. The SLM 48 is a transmissive SLM configured to receive output light 400 from the backlight 20, and the SLM 48 further includes an input polarizer 210 disposed on the input side of the SLM 48; the input polarizer 210 is a linear polarizer. An additional polarizer 318B, also a linear polarizer, is disposed on the input side of the input polarizer 210. At least one additional polarization control delay unit 300B is disposed between the additional polarizer 318B and the input polarizer 210.

[0433] The first mentioned at least one polarity control delay device 300A includes a first switchable liquid crystal delay device 301A, which includes a first layer 314A of liquid crystal material, and at least one additional polarity control delay device 300B includes a second switchable liquid crystal delay device 301B, which includes a second layer 314B of liquid crystal material.

[0434] The polarity control delay unit 300A includes a passive polarity control delay unit 330A and a switchable liquid crystal delay unit 301A. The additional polarity control delay unit 300B includes a passive polarity control delay unit 330B and a switchable liquid crystal delay unit 301B. As described elsewhere in this specification, the polarity control delay unit 300B provides modification of the output transmission polarity luminance profile, and the polarity control delay unit 300A provides modification of the output transmission polarity luminance and reflectance profiles.

[0435] Compared to Figure 16Because the backlight 20 has higher brightness for the off-axis polarity position, the off-axis brightness is increased in open mode. Therefore, image visibility for off-axis users is improved by controlling the two liquid crystal layers 314A and 314B. In privacy mode, the off-axis brightness is reduced by doubling the brightness control polarity control delay units 300A and 300B and corresponding additional polarizers 318A and 318B, thus improving the visual security level for off-axis peepers. Furthermore, high reflectivity is provided for off-axis users.

[0436] The preferred option is to have, as referenced Figure 1A The described operation of the reflective recirculating polarizer (which is functionally different from the reflective polarizer 302) can provide an additional polarizer 318B to further achieve high efficiency and reduced field of view for privacy operations.

[0437] Figure 18A A single viewing angle control element 260A is provided on the front surface of the SLM 48. Most preferably, this reduces the thickness of the front portion of the screen. Furthermore, a diffuser can be positioned on the front surface of the polarizer 318 or between the viewing angle control element 260A and the output polarizer 218. Most preferably, this reduces the visibility of front surface reflections. Additionally, a viewing angle control element 260B can be conveniently provided between the SLM 48 and the backlight 20. This reduces assembly costs and complexity. It also advantageously reduces the number of surfaces between the pixel layer 214 and the display device user 26, thereby achieving improved image contrast.

[0438] The explanation is as follows Figure 18A In a similar configuration, each of the passive delayers 330A and 330B includes a passive multi-delayer pair.

[0439] Figure 18B This is a schematic diagram illustrating the arrangement of optical layers in an optical stack, as shown in the previous view. It includes a polarization control retarder 300A disposed between a reflective polarizer 302 and an additional polarizer 318A; and a further polarization control retarder 300B disposed between an input polarizer 210 and another additional polarizer 318B of a transmission SLM 48, wherein each of the polarization control retarder 300A and the further polarization control retarder 300B includes intersecting A-plates. Exemplary embodiments are provided in Tables 7 and 8A.

[0440]

[0441] Table 7

[0442]

[0443] Table 8A

[0444] Compared to Figure 11A Specific embodiments, Figures 18A to 18F Specific embodiments include a transmitting SLM48 with high brightness over a wide field of view; and a wide-angle backlight 20, or an emitting SLM 48.

[0445] Furthermore, the specific embodiment includes a polarity control delay unit 300A, an additional polarizer 318A, a further polarity control delay unit 300B, and another additional polarizer 318B. This configuration doubles the transmission profile. Therefore, very low brightness can be achieved with design polar angles such as + / -45 degrees side angle and 0 degrees elevation angle. However, high brightness from the backlight or emitting SLM at angles higher than the design polar angle provides increased light levels and reduced reflectivity. This can reduce visual security for high-angle observers. At least one additional polarity control delay unit 300B includes at least one additional passive delay unit, in... Figure 18B In a specific embodiment, two cross-passive polarity control delayers 330BA and 330BB are provided.

[0446] The required design can provide adjustment for a minimum value (which is, for example, greater than 45 degrees at a lateral angle between 50 and 65 degrees). In an arrangement with an additional polarity-controlled retarder 300B, each of the layers 314A, 314B of the liquid crystal material 414 of the switchable liquid crystal retarder 301A, 301B can have a phase delay of 550 nm wavelength light in the range of 450 nm to 850 nm, preferably in the range of 500 nm to 750 nm, and most preferably in the range of 550 nm to 650 nm.

[0447] Each of the plurality of retarders mentioned first and the plurality of other retarders may include a pair of passive retarders having an optical axis in the plane of the retarder, wherein each of the passive retarder pairs 330A and 330B mentioned first has a phase delay of 550 nm wavelength light in the range of 300 nm to 800 nm, preferably in the range of 350 nm to 650 nm, and most preferably in the range of 400 nm to 550 nm.

[0448] Ideally, brightness and reflectivity at high angles should be reduced, thereby improving the visual security level against prying eyes at high viewing angles. The reduction of color asymmetry in switchable privacy displays will now be discussed.

[0449] Figure 18CThis is a schematic graph illustrating the change of logarithmic output brightness with polarity direction for the transmitted light of multiple retarders (including crossed passive A-plates; and switchable liquid crystal retarders arranged along the surface, used for one of the crossed A-plate retarders 330AA, 330AB and polarity-controlled retarder 300B of liquid crystal layer 314A, as shown in Table 8A); and Figure 18D This is a schematic graph illustrating the change of logarithmic output brightness with lateral viewing angle 470A for the transmission of light from multiple retarders (including cross-shaped passive A-plates; and switchable liquid crystal retarders arranged along the surface for one of the polarity-controlled retarders 300B, including retarders 330AA, 330AB, and 314A in Table 8B).

[0450] Figure 18C and Figure 18D Examples illustrate the brightness asymmetry provided by some of the aforementioned intersecting sequences of A-plates 330AA, 330AB. Because the brightness profile is wavelength-dependent, such asymmetry can provide, in operation, a distinct color variation with different presentation on either side of the display device, as illustrated in the corner regions 472L, 472R. Figure 11A In this setup, such color shifts are generally not very visible due to the low brightness of the collimated backlight 20. However, as the brightness of the backlight 20 increases at higher angles, or for an emissive SLM, the asymmetry becomes more noticeable. The desired outcome will be to provide asymmetrical color rendering.

[0451] Please refer to the reference again immediately. Figure 18B The polarity control delay 300A mentioned first includes a pair of passive delayers 330AA and 330AB, which have intersecting optical axes 331AA and 331AB in the plane of the delayers 330AA and 330AB. The first 330AA in the passive delayer pair has an optical axis 331AA that extends at 45° relative to the electric vector transmission direction 219 of the output polarizer 218, and the second 330AB in the passive delayer pair has an optical axis 331AB that extends at 135° relative to the electric vector transmission direction 219 of the output polarizer 218.

[0452] At least one additional polarity-controlled retarder 300B includes additional passive retarder pairs 330BA, 330BB, having intersecting optical axes 331BA, 331BB in the plane of the retarders 330BA, 330BB. The first 330BA of the additional passive retarder pair has an optical axis 331BA extending at 135° relative to the electrical vector propagation direction 219 of the output polarizer 218, and the second 330BB of the additional passive retarder pair has an optical axis 331BB extending at 45° relative to the electrical vector propagation direction 219 of the output polarizer 218. The second retarders 330AB, 330BB of each passive retarder pair are configured to receive light from the first retarders 330AA, 330BA of the corresponding passive polarity-controlled retarder pairs 330A, 330B. Therefore, the first pair of the additional pairs closest to each other and the passive retarder 330AA of the passive retarder 330BB have corresponding optical axes 331AA and 331AB extending in the same direction.

[0453] In this invention, the rotation direction of the optical axis of the passive retarder can be clockwise or counterclockwise, such that any optical axis within each passive retarder pair extends at 45° and 135° respectively. In the exemplary example, the rotation direction is clockwise.

[0454] Please refer to the reference again immediately. Figure 18D The brightness profile of the intersecting A-pieces 330BA, 330BB and liquid crystal retarder 314B is illustrated by profile 470B. Combined, profiles 470A and 470B are multiplied. Figure 18B The delay setting thus achieves an average of the two brightness profiles and further achieves color symmetry. This is beneficial for improving angular uniformity.

[0455] Or, in Figure 18A and Figure 18B In this example, the reflective polarizer 318B can be omitted. In that case, the reflective polarizer 318B can be replaced with a dichroic absorption polarizer (not shown) if necessary.

[0456] Another configuration of polarity control delay 300A and another polarity control delay 300B will now be provided.

[0457] Figure 18E This is a side perspective view illustrating a switchable privacy display device for ambient lighting, including an emissive SLM 48, a first polarity control delay unit 300A, a first auxiliary polarizer 318A, a reflective polarizer 302, a second polarity control delay unit 300B, and a second auxiliary polarizer 318B; and Figure 18FThis is a schematic diagram illustrating the arrangement of optical layers in an optical stack, as shown in the previous view. It includes a polarization control retarder 300A disposed between an additional light-absorbing polarizer 318A and another additional polarizer 318B for a reflective polarizer 302; and another polarization control retarder 300B disposed between an output polarizer 218 and another additional polarizers 318B, 302. Each of the polarization control retarder 300A and the other plurality of retarders 300B includes intersecting A-plates 330AA, 330AB, 330BA and 330BB.

[0458] Exemplary specific embodiments are provided in Table 8B.

[0459]

[0460] Table 8B

[0461] Compared to Figure 18A The setup, since scattering from the SLM 48 does not modify the field of view of the brightness profile from the viewing angle control element 260B, advantageously provides brightness reduction for off-axis viewing positions. Furthermore, a single stack of optical components can be provided for convenient parts market or factory assembly.

[0462] Figures 18E to 18F A further embodiment illustrates that the reflective polarizer 302 may further provide an additional polarizer 318B for the additional plurality of retarder 300Bs. Most preferably, this reduces cost and thickness and improves efficiency.

[0463] A specific embodiment of a brightness control display device with symmetrical color and brightness output will now be described.

[0464] Figure 18G This is a schematic diagram illustrating the arrangement of optical layers in an optical stack, as shown in the previous view. It includes a polarity control retarder 300A disposed between an additional light-absorbing polarizer 318A and another additional polarizer 318B; and another polarity control retarder 300B disposed between an output polarizer 218 and another additional polarizer 318B. Each of the polarity control retarder 300A and the other plurality of retarders 300B includes interleaved A-plate retarders 330AA, 330AB, 330BA, and 330BB.

[0465] The display device therefore includes: an SLM 48; a display polarizer disposed on at least one side of the SLM, the display polarizer being a linear polarizer; a first additional polarizer 318A disposed on the same side of the SLM 48 as one of the at least one display polarizer, the first additional polarizer 318A being a linear polarizer; and a first polarization control delay unit 300A disposed between the first additional polarizer 318A and one of the at least one display polarizer; a further additional polarizer 318B disposed on the same side of the SLM as the at least one display polarizer, outside the first additional polarizer 318A, the further additional polarizer 318B being a linear polarizer; and a further polarization control delay unit 300B disposed between the first additional polarizer 318A and the further additional polarizer 300B. Between oscillators 318B, wherein the first polarity-controlled delayer includes passive delayer pairs 330AA and 330AB, which have intersecting optical axes 331AA and 331AB in the plane of the delayer and extending at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer 218; the other polarity-controlled delayer includes another passive delayer pair 330BA and 330BB, which have intersecting optical axes 331BA and 331BB in the plane of the delayer and extending at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer 218; and the optical axes 331BB and 331AA of one of the first passive polarity-controlled delayer pairs and one of the other passive polarity-controlled delayer pairs that are closest to each other extend in the same direction.

[0466] Each of the first polarity control delay unit 300A and the other polarity control delay unit 300B further includes switchable liquid crystal delay units 301A and 301B, which include layers 314A and 314B of liquid crystal materials 414A and 414B. In the switchable state of the switchable liquid crystal delay units 301A and 301B, each of the first polarity control delay unit 300A and the other polarity control delay unit 300B is simultaneously configured so that the pure relative phase shift is not referenced to the orthogonal polarization component of light passing along the axis normal to the plane of the polarity control delay unit in the at least one display polarizer, but the pure relative phase shift is referenced to the orthogonal polarization component of light passing along the axis biased towards the plane of the polarity control delay unit in the at least one display polarizer.

[0467] In addition to replacing the reflective polarizer 302 with an additional polarizer 318B, Figure 18G Examples and Figure 18E and Figure 18F The example is the same. The preferred option is as follows: Figures 18C to 18DThe same method illustrated achieves a brightness control display device with symmetrical color and brightness output in the lateral direction. Furthermore, for environments where high off-axis reflectivity is undesirable, the reflectivity of the reflective polarizer 302 is eliminated.

[0468] Figure 18H This is a schematic diagram illustrating the arrangement of optical layers in an optical stack for a transmission SLM 48, as illustrated in the previous view. It includes a plurality of additional retarders 300B disposed between additional additional light-absorbing polarizers 318B and additional polarizers 318A; and a plurality of retarders 300A disposed between input polarizer 210 and additional polarizers 318A, wherein each of the plurality of retarders 300A and the plurality of additional retarders 300B includes a cross A-plate.

[0469] In addition to placing the optical stack on the input side of the SLM and between the backlight 20 and the SLM 48, Figure 18H Examples and Figure 18G The example is the same. Most preferably, the thickness of the front portion of the screen is reduced, and an increase in diffusion can be provided on the front surface without blurring pixels. Furthermore, image contrast can be improved.

[0470] Figure 18I This is a schematic diagram illustrating the arrangement of optical layers in an optical stack for a transmission SLM 48, as shown in the previous view. It includes a plurality of additional retarders 300B disposed between an additional auxiliary polarizer 318B and an input polarizer 210; and a plurality of retarders 300A disposed between an output polarizer 218 and an auxiliary polarizer 318A. Each of the plurality of retarders 300A, 300B and the plurality of additional retarders includes intersecting A-plates 330AA, 330AB, 330BA, and 330BB.

[0471] The display device includes: a backlight 20 configured to output light; a transmission SLM 48 configured to receive the output light from the backlight 20; an input polarizer 210 disposed on the input side of the SLM 48; and an output polarizer 218 disposed on the output side of the SLM 48, wherein the input polarizer 210 and the output polarizer 218 are linear polarizers; a first additional polarizer 318A disposed on the output side of the output polarizer 218, wherein the first additional polarizer 318A is a linear polarizer; a first polarization control delay unit 300A disposed between the first additional polarizer 318A and the output polarizer 218; a further additional polarizer 318B disposed between the backlight 20 and the input polarizer 210, wherein the further additional polarizer 318B is a linear polarizer; and a further polarization control delay unit 300B disposed between the input polarizer 210 and the further additional polarizer 318B; wherein the first polarization control delay unit 300A includes a passive delay unit pair. 330AA and 330AB have intersecting optical axes 331AA and 331AB in the plane of the retarder, extending at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer 218. The additional polarity-controlled retarder 300B includes another pair of passive retarders 330BA and 330BB, which have intersecting optical axes 331BA and 331BB in the plane of the retarder, extending at 45° and 135° respectively relative to the electric vector propagation direction of the output polarizer 218. The optical axes 331BB and 331AA of one of the first passive polarity-controlled retarder pairs and one of the additional passive polarity-controlled retarder pairs that are closest to each other extend in the same direction.

[0472] In addition to placing the optical stack on both sides of the SLM 48 and between the backlight 20 and the SLM 48, Figure 18I Examples and Figure 18H The same example applies. Ideally, the scattering from the SLM will not provide stray light to the spy, achieving a high level of visual security.

[0473] Figure 18JThis is a schematic diagram illustrating the arrangement of a switchable retarder in privacy mode, shown in perspective view. It includes a negative C-plate passive polarity controlled retarder 330A and a surface-aligned switchable liquid crystal retarder 301A, disposed between the output polarizer 218 and the reflective polarizer 302; and a negative C-plate passive polarity controlled retarder 330B and a surface-aligned switchable liquid crystal retarder 301B, disposed between the absorptive polarizer 318 and the reflective polarizer 302 in privacy mode. Therefore, the display device may further include a phase retardation control layer 300A disposed between the output polarizer 218 and the reflective polarizer 302. The phase retardation control layer 300A may include another switchable liquid crystal retarder 301A disposed between the output polarizer 218 and the reflective polarizer 302.

[0474] The aforementioned polarity control delay unit 300B includes a first switchable liquid crystal delay unit 301B, which comprises a first layer of liquid crystal material 414B. The additional polarity control delay unit 300A includes a second switchable liquid crystal delay unit 301A, which comprises a second layer of liquid crystal material 414A. The additional switchable liquid crystal delay unit 301A includes a surface alignment layer 307A, which is disposed adjacent to the liquid crystal material 414A. This layer has a pre-tilt direction, which is a component of the pre-tilt direction in the plane of the liquid crystal material layer, and is arranged parallel, antiparallel, or orthogonal to the reflective polarizer.

[0475] The pre-tilt directions 307A and 331A of the arrangement layers of the additional switchable liquid crystal retarder 301A may have components in the plane of the liquid crystal layer 314A, which are parallel, antiparallel, or orthogonal to the pre-tilt directions of the arrangement layers 307B and 331B of the first switchable liquid crystal retarder 301B. In open operation mode, both switchable liquid crystal layers 301B and 301A are driven to provide a wide viewing angle. In privacy operation mode, the switchable liquid crystal retarder 301A and 301B can cooperate to advantageously achieve an improved brightness reduction, thus improving privacy on a single axis.

[0476] The first and second liquid crystal retarder 301A and 301B may have different phase delays. The phase delays provided by the first liquid crystal retarder 301B and the additional liquid crystal layer 314A may be different. The control system 352 may be configured to control the application of a common voltage across the first and second switchable liquid crystal retarder 301A and 301B. The liquid crystal material 414B of the first liquid crystal retarder 301B may be different from the liquid crystal material 414A of the second liquid crystal layer 301A. This can reduce the chromaticity variation of the polar brightness profile illustrated elsewhere in this specification, thus advantageously improving off-axis color reproduction.

[0477] Alternatively, the switchable liquid crystal delay units 301A and 301B can be orthogonally arranged, thus achieving brightness reduction in both the horizontal and vertical directions to facilitate privacy protection in both the horizontal and vertical directions.

[0478] The phase retardation control layer 300A may include a passive polarity control retarder 330A disposed between the output polarizer 218 and the reflective polarizer 302. More generally, the switchable liquid crystal retarder 301A may be omitted, and a fixed brightness reduction may be provided by the passive retarder 330A. For example, brightness reduction in the viewing quadrant may be provided solely by layer 330A. Most preferably, a polarity region for brightness reduction may be achieved.

[0479] Figure 18J As a further example, the reflective polarizer 302 can provide an additional polarizer 318B, and may omit, for example... Figure 18F The dichroic polarizer 318B is preferred. It achieves both increased efficiency and reduced thickness.

[0480] Figure 18K This is a schematic diagram illustrating the viewing angle control element 260 in a side perspective view, which includes a first polarity control retarder 300A, a first additional polarizer 318A, a reflective polarizer 302, a second polarity control retarder 300B, and a second additional polarizer 318B. Most preferably, off-the-shelf privacy control elements and / or stray light control elements that do not require matching the panel pixel resolution to avoid moiré artifacts can be provided. The viewing angle control optics 260 can be further provided for factory assembly to an SLM 48. (The remaining text is not discussed in further detail.) Figures 18E to 18H The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0481] The required features include both entertainment and nighttime operation modes for use in vehicles.

[0482] Figure 19A The top view illustrates a configuration located within the vehicle cabin 602, such as... Figures 19A to 19B The illustration shows a car vehicle with a switchable directional display device (for daytime and / or shared operating modes); and Figure 19B This is a side view illustrating an automobile vehicle with a switchable directional display (for daytime and / or shared operation modes) located within the vehicle cabin 602. The light cones 630 and 632 have a wide field of view, thus facilitating viewing of the low-reflectivity display by multiple passengers.

[0483] Figure 19C The top view illustrates a configuration located within the vehicle cabin 602, such as... Figures 19A to 19BA schematic diagram of a car vehicle with a switchable directional display (for night and / or entertainment operation modes) illustrated herein. Figure 19D This is a side view illustrating a car vehicle with a switchable directional display (for nighttime and / or entertainment operation modes) located within the vehicle cabin 602. Cones 634 and 636 have narrow viewing angles, thus allowing only a single passenger to see the display. Off-center passengers further see increased reflections from the display, reducing visibility. Most preferably, stray light for nighttime operation is reduced, thereby improving driving safety. Furthermore, reducing reflections from the windshield 601 from the display minimizes distraction for the driver 604. (The remaining text is incomplete and requires further context.) Figures 19A to 19D The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0484] The following describes a display device 100 that includes a polarity control delay 30 as a passive delay 272 and includes a reflective polarizer 302 and an additional polarizer 318.

[0485] Figure 20A This is a side perspective view illustrating a privacy display device 100 for ambient lighting 604, which includes a backlight 20, a transmission SLM 48, a reflective polarizer 302, a passive polarization control delay unit 300, including passive delay units 272A, 272B, 272C, and 272D; and an additional polarizer 318; and Figure 20B This is a schematic diagram illustrating the viewing angle control elements in a side perspective view, which includes a reflective polarizer 302, a passive polarity control delay unit 300, and an additional polarizer 318.

[0486] The following is for reference Figures 22A to 22B The operation of such a display device is explained. Preferably, a low-cost privacy or other type of low stray light display device can be provided. Furthermore, compared to the switchable display device 100, the complexity and thickness of the display device are reduced.

[0487] Figure 20C This is a schematic diagram illustrating the viewing angle control element 260 using a side perspective view. It includes a passive polarity control delay unit 300A, comprising passive delay units 272AA, 272AB, 272AC, and 272AD, disposed between the auxiliary polarizer 318A and the reflective polarizer 302; and additional auxiliary polarizer 318B and additional passive polarity control delay units 300B, comprising passive delay units 272BA, 272BB, 272BC, and 272BD, disposed on the input side of the reflective polarizer 302. Compared to... Figure 20BThis can further reduce off-axis brightness, while maintaining forward brightness when attached to the output of an SLM.

[0488] Figure 20D This is a side perspective view illustrating a privacy display device used for ambient lighting. Compared to Figure 20A An additional polarizer 318B, which is a reflective polarizer, and an additional polarization control delay 300B, including delayers 272BA and 272BB, are disposed at the input of the SLM. The additional polarizers 318B and 300B achieve a reduction in the increased brightness for the wide-angle backlight 20. Most preferably, this improves the visual safety level for the wide-angle backlight. Compared to the switchable configuration described elsewhere, this reduces thickness and cost. [Further details not discussed here are possible.] Figures 20A to 20D The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0489] Figures 20A to 20D The specific embodiments described herein illustrate a stack of passive polarity control delayers 300, as follows: Figures 22A to 22B The example shown includes four passive delayers. However, other types of passive delayer stacks will also be described below and may be incorporated therein. Various combinations of polarity-controlled delayers 300, including a passive delayer 272 disposed between a reflective polarizer 302 and an additional polarizer 318, will now be described.

[0490] Figure 21A This is a schematic diagram illustrating a passive retarder optical stack, shown in a side perspective view, which includes a negative C-sheet and is configured to provide field-of-view modification for a display device; and Figure 21B It is aimed at Figure 21A The transmitted light in the passive delayer is illustrated by a schematic curve showing how the output transmission changes with the polarity direction.

[0491] Figure 21C This is a schematic diagram illustrating an optical stack of a passive retarder, shown in a side perspective view. It includes a negative O-sheet tilted in a plane orthogonal to the electric vector propagation direction of the display polarizer; and a negative C-sheet configured to provide field-of-view modification for the display device; and Figure 21D It is aimed at Figure 21C The transmitted light in the passive delayer is illustrated by a schematic graph showing the output transmission as the polarity direction changes, including the structure illustrated in Table 9A.

[0492]

[0493] Table 9A

[0494] The passive polarity control retarder 300B therefore includes a passive retarder 272A, which is a negative O-plate having an optical axis whose component lies in the plane of the passive retarder 272A and is perpendicular to the plane of the passive retarder 272A. Furthermore, the component in the plane of the passive retarder extends at 90° relative to the electric vector propagation direction 219 parallel to the display polarizer 218. The passive retarder 272B includes a passive retarder having an optical axis perpendicular to the plane of the passive retarder.

[0495] Ideally, the brightness can be reduced for side viewing. The movable display device can be comfortably rotated around the horizontal axis, while achieving privacy protection against off-axis peeping from the side.

[0496] Figure 21E This is a schematic diagram illustrating the optical stack of a passive retarder, shown in a side perspective view, including intersecting A-plates and positive O-plates; and Figure 21F It is aimed at Figure 21E The transmitted light in the passive delayer is illustrated by a schematic graph showing the output transmission as the polarity direction changes, including the structure illustrated in Table 9B.

[0497]

[0498] Table 9B

[0499] The passive polarity control retarder 300B therefore includes passive retarders 272A and 272B, which are intersecting A-pieces; and a retarder 272C having a component in the plane of the passive retarder 272C and a component perpendicular to the plane of the passive retarder 272C. The component in the plane of the passive retarder extends at 90° relative to the electric vector propagation direction 219 parallel to the display polarizer 218. Most preferably, brightness can be reduced for side viewing. The portable display device can be comfortably rotated about the horizontal axis while achieving privacy against off-axis peeping in the side.

[0500] The desired effect is to provide brightness reduction in both the lateral and elevation directions.

[0501] Figure 22A This is a schematic diagram illustrating the optical stack of passive retarder 272A-D (including two intersecting pairs of A plates) using a side perspective view; and Figure 22B It is aimed at Figure 22A The transmitted light in the passive delayer is illustrated with a schematic graph showing the output transmission as a function of polarity, including the structures shown in Table 10. (The remaining text is incomplete and requires further context.) Figures 22A to 22B The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0502]

[0503] Table 10

[0504] The retarder therefore includes passive retarder pairs 272A and 272D, which have intersecting optical axes in the plane of the retarder. Each of the retarder pairs includes a plurality of A plates having respective optical axes arranged at different angles to each other. Passive retarder pairs 272B and 272C have optical axes that extend at 90° and 0° respectively relative to the electrical vector propagation direction 211 parallel to the display polarizer 210.

[0505] The passive delayers 272A and 272D have optical axes that extend at 45° and 135° respectively relative to the electric vector transmission direction 211 parallel to the display polarizer 218.

[0506] The display device further includes additional passive retarder pairs 272B and 272C, arranged between the previously mentioned passive retarder pairs 272A and 272D, and having intersecting optical axes in the plane of the retarders. The additional passive retarder pairs 272B and 272C have optical axes extending at 0° and 90° respectively relative to the electrical vector transmission directions 211 and 217 parallel to the display polarizers 210 and 316.

[0507] The phase retardation of each A-plate for light with a wavelength of 550nm can be in the range of 600nm to 850nm, preferably in the range of 650nm to 730nm, and most preferably in the range of 670nm to 710nm. This can advantageously reduce the color change of absorbed light from the center viewing position to the off-axis viewing position.

[0508] In another exemplary embodiment, preferably angle 273A is at least 40° and at most 50°, most preferably at least 42.5° and at most 47.5°, and more preferably at least 44° and at most 46°. Preferably angle 273D is at least 130° and at most 140°, most preferably at least 132.5° and at most 137.5°, and most preferably at least 134° and at most 136°.

[0509] In another exemplary embodiment, the internal delay pairs 272B and 272C may have a looser tolerance than the external delay pairs 272A and 272D. Preferably, angle 273B is at least -10° and at most 10°, most preferably at least -5° and at most 5°, and most preferably at least -2° and at most 2°. Preferably, angle 273C is at least 80° and at most 100°, most preferably at least 85° and at most 95°, and most preferably at least 88° and at most 92°.

[0510] Specific embodiments of the present invention provide a transmission profile with some rotational symmetry. Most preferably, the privacy display device can reduce visibility from a wide field of view for the side or upward viewing position of a spy. Furthermore, such a configuration can be used to enhance privacy operation for both lateral and longitudinal operation of the mobile display device. Such a configuration can be provided in vehicles to reduce stray light to off-axis passengers, and also to reduce light falling on the windshield and other glass surfaces in the vehicle.

[0511] Figures 23A to 23B This is a schematic diagram illustrating a portion of a display device as a side view, including a switchable compensated retarder and an optical bonding layer 380. Further details not discussed here are possible. Figures 23A to 23B The features of the aforementioned configuration are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations in those features. An optical bonding layer 380 may be provided to stack the thin film and substrate, thereby achieving increased efficiency and reduced brightness at high viewing angles in privacy mode. Furthermore, an air gap 384 may be provided between the SLM 48 and the polarity control retarder 300. To reduce wetting of the two surfaces at the air gap 384, an anti-wetting surface 382 may be provided to at least one of the polarity control retarder 300 or the SLM 48.

[0512] Delay unit 330 can be used in, for example Figure 23B As illustrated, it is provided between the switchable liquid crystal layer 314 and the SLM 48, or may be provided as shown in the example. Figure 23A The example shown is provided between the additional polarizer 318 and the switchable liquid crystal layer 314. Generally, the same optical performance is provided in both systems except for the hybrid arrangement described elsewhere in this specification. The desired result is a reduction in the thickness and overall number of optical components.

[0513] Figure 24A This is a schematic diagram illustrating the setup of a switchable compensated retarder in privacy angle operation mode, shown in perspective view. It includes a vertically arranged switchable liquid crystal retarder positioned between the first and second C-plate passive polarity control retarders. Figure 24B and Figure 24C This is for both public mode and privacy mode. Figure 24A The transmitted light rays in the optical stack are illustrated by a schematic graph showing the change in output transmission with polarity; and Figure 24D This is for use in privacy mode. Figure 24A The reflected light rays are illustrated with schematic graphs showing the variation of reflectivity with polarity, including the specific embodiments illustrated in Table 11. Those not discussed in further detail may be... Figures 24A to 24DThe features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0514]

[0515] Table 11

[0516] The passive polarity-controlled retarder 330 includes first and second C-plates 330A and 330B; and a switchable liquid crystal layer 314 is provided between the first and second C-plates 330A and 330B. The switchable liquid crystal retarder includes two surface-aligned layers 419a and 419b, which are arranged adjacent to the liquid crystal material 414 on opposite sides, and each is configured to provide surface alignment in the adjacent liquid crystal material 414. The liquid crystal material 414 layer of the switchable liquid crystal retarder includes liquid crystal material 414 having negative and positive dielectric anisotropy.

[0517] The liquid crystal material layer 314 has a phase delay of 550 nm wavelength light in the range of 500 nm to 1000 nm, preferably in the range of 600 nm to 900 nm, and most preferably in the range of 700 nm to 850 nm. Each of the two passive retarders includes a passive retarder having an optical axis perpendicular to the plane of the retarder, and having a total phase delay of 550 nm wavelength light in the range of -300 nm to -700 nm, preferably in the range of -350 nm to -600 nm, and most preferably in the range of -400 nm to -500 nm.

[0518] Figure 25A This is a schematic diagram of a display device illustrated by a perspective view, which includes a switchable compensated retarder disposed between first and second C-plate passive polarity controlled retarder substrates; and Figure 25B This is a schematic diagram illustrating a portion of a display device in a side view, which includes a switchable compensated delay disposed between first and second C-plate passive polarity controlled delay substrates.

[0519] The polarity-controlled delay unit 300 includes two passive delay units 330A and 330B; and a switchable liquid crystal delay unit 301, which includes a liquid crystal material layer 314 provided between the two passive delay units 330A and 330B. The display device 100 further includes transfer electrodes 413 and 415; and liquid crystal surface alignment layers 409 and 411 formed on one side of each of the two passive delay units 330A and 330B adjacent to the switchable liquid crystal delay unit layer 314. The display device 100 further includes first and second substrates, between which the switchable liquid crystal delay unit layer 314 is provided, each of the first and second substrates including one of the two passive delay units 330A and 330B.

[0520] Therefore, the first C-sheet 330A has a transparent electrode layer 415 and a liquid crystal arrangement layer 411 formed on one side, and the second C-sheet 330B has a transparent electrode layer 413 and a liquid crystal arrangement layer 409 formed on one side.

[0521] A liquid crystal layer 314 is provided between first and second substrates 312 and 316, and each of the first and second substrates 312 and 316 includes one of the first and second C-sheets 330A and 330B. The C-sheets may be provided in an ITO-coated bilayer extended COP film to provide electrodes 413 and 415 and have liquid crystal alignment layers 409 and 411 formed thereon.

[0522] Preferably, compared to the setup in the first figure, the number of layers can be reduced, thereby reducing thickness, cost, and complexity. Furthermore, the C-sheets 330A and 330B can be flexible substrates and can provide a flexible privacy display device.

[0523] The required liquid crystal layer 314 will be provided between the first and second A-film substrates.

[0524] Figure 25C This is a schematic diagram illustrating the arrangement of a switchable compensated retarder in open operating mode, shown in perspective view. It includes switchable liquid crystal retarders arranged along a surface, positioned between first and second intersecting A-plate passive polarity controlled retarders; and Figure 25D and Figure 25E This is for driving in wide-angle and privacy modes respectively. Figure 25C The structure transmits light rays, illustrating a schematic graph of output transmission varying with polarity, including the specific embodiments further illustrated in Table 11. Those not discussed in further detail may be... Figures 25A to 25E The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0525] The switchable liquid crystal retarder includes two surface-aligned layers 419a and 419b, which are arranged adjacent to the liquid crystal material 414 layer 314 on opposite sides thereon, and each is configured to provide surface alignment in the adjacent liquid crystal material 414. The liquid crystal material 414 layer of the switchable liquid crystal retarder includes liquid crystal material 414 having negative and positive dielectric anisotropy.

[0526] The liquid crystal material layer 314 has a phase delay of 550 nm wavelength light in the range of 500 nm to 1000 nm, preferably in the range of 600 nm to 900 nm, and most preferably in the range of 700 nm to 850 nm. Each of the two passive retarders has an optical axis in the plane of the passive retarder, wherein the optical axes intersect, and each passive retarder in the pair has a phase delay of 550 nm wavelength light in the range of 150 nm to 800 nm, preferably in the range of 200 nm to 700 nm, and most preferably in the range of 250 nm to 600 nm.

[0527] Compared to Figure 24A The advantage of this setup is that it reduces the cost of manufacturing adult films compared to adult films.

[0528] The desired improvement will be to enhance the image presentation of the spy image seen by the spy 47 in spy mode by adding a mask.

[0529] Figure 26A This is a schematic diagram illustrating the setup of a switchable retarder in privacy mode, shown in a perspective view. It includes a negative C-sheet passive retarder and a vertically arranged switchable liquid crystal retarder, further comprising a patterned electrode layer 415. At least one of the electrodes 413, 415 can be patterned; in this example, electrode 415 is patterned in regions 415a, 415b, 415c and driven by voltages Va, Vb, Vc via corresponding voltage drivers 350a, 350b, 350c. A gap 417 can be provided between the electrode regions 415a, 415b, 415c. Therefore, the tilt of the molecules 414a, 414b, 414c can be independently adjusted to reveal masking patterns with different brightness levels for off-axis viewing.

[0530] Therefore, the switchable liquid crystal retarder 301, disposed between the reflective polarizer 302 and the additional polarizer 318, is controlled by addressing electrodes 415a, 415b, 415c and uniform electrode 413. The addressing electrodes can be patterned to provide at least two patterned regions including electrode 415a and gap 417.

[0531] Figure 26B This is a schematic diagram illustrating the lighting of a primary viewer and a spy through a concealed, brightness-controlled privacy display device, presented in a perspective front view. The display device 100 may have dark image data 601 and white background data 603, which are visible to the primary viewer 45 in the viewing window 26p. In contrast, the spy 47 can see... Figure 26C The obscured image illustrated in the diagram (which is a perspective view illustrating illumination through an obscured, brightness-controlled privacy display device) is shown. Further details not discussed here may be included. Figures 26A to 26C The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0532] Therefore, a masking structure with mixed brightness of white area 603 can be provided in white background area 603. The patterned areas of electrodes 415a, 415b, 415c are thus masking patterns. At least one of the patterned areas can be individually addressed and configured to operate in a privacy mode.

[0533] The patterned area can be configured to provide masking for multiple spatial frequencies by controlling which patterns are provided during the spying operation mode. In an exemplary example, 20mm high text can be provided. A masking pattern with a similar pattern size can be provided by first control of the electrode pattern. In a second example, a photograph can be provided of the largest area of ​​content most visible to the spy 47. By combining the first and second electrode areas to provide the voltage and achieve the resulting lower spatial frequency pattern, the spatial frequency of the masking pattern can be reduced to hide the larger area structure.

[0534] Preferably, a controllable masking structure can be provided by adjusting the voltages Va, Vb, and Vc across layer 892. Essentially, for forward-looking operations, the masking structure is not visible. Furthermore, the masking image can be removed by providing the same Va, Vb, and Vc.

[0535] Furthermore, to provide masking from the brightness modulation of the privacy image, specific embodiments of the invention provide masked reflections from ambient lighting 604, thereby advantageously achieving further concealment of the privacy image from the spy 47, while achieving unmasked reflections from the primary user 45.

[0536] The performance of the delay unit between parallel polarizers in a series configuration will now be explained. First, the field of view of the surface-aligned liquid crystal delay unit 301 will be explained for two different driving voltages.

[0537] Figure 27A This is a schematic diagram illustrating the arrangement of switchable liquid crystal delay devices arranged along the surface, as shown in a perspective view. Figure 27B It is for the first applied voltage. Figure 27A The transmitted light beam in the diagram illustrates a schematic curve showing how the output transmission changes with polarity; and Figure 27C It is for a second applied voltage that is greater than the first applied voltage. Figure 27A The transmitted light beam in the diagram illustrates a schematic curve showing how the output transmission changes with polarity, including the structures illustrated in Table 12.

[0538] Figure 27D This is a schematic diagram illustrating a C-plate positioned between parallel polarizers, shown in perspective view; and Figure 27E It is aimed at Figure 27D The transmitted light beam in the diagram illustrates a schematic curve showing how the output transmission changes with polarity, including the structures illustrated in Table 12.

[0539]

[0540] Table 12

[0541] Figure 28A This is a schematic diagram illustrating the arrangement of a switchable liquid crystal retarder 390 arranged along the plane between parallel polarizers 394 and 396, which is connected in series with a passive retarder for field of view control, including a C-plate retarder 392 arranged between parallel polarizers 396 and 398. Figure 28B It is for the first applied voltage. Figure 28A The transmitted light beam in the diagram illustrates the change in output transmission polarity.

[0542] Figure 28C It is for a second applied voltage that is greater than the first applied voltage. Figure 28A The transmitted light beam in the diagram illustrates a schematic curve showing how the output transmission changes with polarity, including the structures illustrated in Table 12.

[0543] Figure 29A This is a schematic diagram illustrating the arrangement of a switchable liquid crystal retarder arranged along a surface and connected in series with a C-plate polarization control retarder, wherein the switchable liquid crystal arranged along the surface and the C-plate polarization control retarder are arranged between a single pair of parallel polarizers. Figure 29B It is for the first applied voltage. Figure 29A The transmitted light beam in the diagram illustrates a schematic curve showing how the output transmission changes with polarity; and Figure 29C It is for a second applied voltage that is greater than the first applied voltage. Figure 29A The transmitted light beam in the diagram illustrates a schematic curve showing how the output transmission changes with polarity, including the structures illustrated in Table 12. (The remaining details are not discussed further.) Figures 27A to 29C The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0544] Unexpectedly, the optimal conditions for maximum field-of-view operation are provided by the equal and opposite pure phase delay of the polarity control delay 330, compared to the switchable liquid crystal retarder layer 314 in its undriven state. The ideal polarity control delay 330 and switchable liquid crystal retarder layer 314 achieve (i) unmodified open-mode performance from the input light, and (ii) optimal reduction of lateral viewing angles at off-axis positions for all elevation angles when configured to provide a narrow-angle state. This description can be applied to all display devices disclosed in this specification.

[0545] The desired effect is to provide a further reduction in off-axis brightness for directional illumination from the SLM 48. Directional illumination from the SLM 48 through the directional backlight 20 will now be described.

[0546] Figure 30A This is a previous perspective view illustrating a directional backlight 20 (or a "narrow-angle" or "collimated" backlight), and Figure 30B This is a schematic diagram illustrating a non-directional backlight 20 (or a "wide-angle" backlight or a "non-collimated" backlight), which can be selectively applied to any of the devices described in this specification. Therefore, as Figure 30A The directional backlight 20 shown provides a narrow cone 450, however, as Figure 30B The non-directional backlight 20 shown provides a wide-angle distribution cone 452 for the light output rays.

[0547] Figure 30C It is a schematic graph illustrating the change in brightness with the side viewing angle for various backlight settings. Figure 30C The curve can be a cross-section of the polar field of view profile described in this specification. (The remaining text is incomplete and lacks context.) Figures 30A to 30C The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0548] The Lambertian backlight has a brightness profile 846 independent of viewing angle. In a specific embodiment of the invention, the backlight 20 can be configured to provide an angular light distribution with reduced brightness for off-axis viewing positions compared to forward-looking brightness.

[0549] A typical wide-angle backlight has a roll-off at higher angles, such that the maximum full-width half-height of relative brightness is preferably greater than 40°, most preferably greater than 60°, and most preferably greater than 80°. Similarly, a typical wide-angle backlight has a roll-off at higher angles, such that the maximum full-width half-height 866 of relative brightness is greater than 40°, preferably greater than 60°, and most preferably greater than 80°. Furthermore, the relative brightness 864 at + / -45° is preferably greater than 7.5%, most preferably greater than 10%, and most preferably greater than 20%. Most preferably, a display device achieving a roll-off similar to that of the wide-angle backlight can provide high image visibility for off-axis users.

[0550] A display device that includes a wide-angle backlight 20 and only adds a polarizer 318 and a polarization control delay 330 (excluding the additional polarization control delay 300B and the additional additional polarizer 318B) typically does not achieve the required level of visual security for off-axis users in privacy mode. What is required is that such a display device may have a directional backlight 20 as will now be described.

[0551] The backlight 20 may be a directional backlight that provides brightness in at least one azimuth direction at a polar angle greater than 45 degrees relative to the normal of the SLM, which is at most 30% of the brightness along the normal of the SLM, preferably at most 20% of the brightness along the normal of the SLM, and most preferably at most 10% of the brightness along the normal of the SLM. The directional backlight 20 may have a roll-off at higher angles such that the full-width half-height 862 of the relative brightness is less than 60°, preferably less than 40°, and most preferably less than 20°. In an exemplary example, the brightness 868 at 45 degrees may be 18% of the forward-looking brightness from the backlight 20.

[0552] Such a brightness profile can be provided by the directional backlight 20 described below, or it can also be provided by a wide-angle backlight incorporating an additional polarizer 318B and a polarity control delay unit 300B, as described elsewhere in this specification.

[0553] One type of switchable backlight 20 will now be described.

[0554] Figure 31A This is a side view illustrating a switchable directional display device 100, which includes a switchable liquid crystal polarity control delay unit 300 and a backlight 20. It can... Figure 31A The backlight 20 is used in any of the devices described in this specification, and it includes an imaging waveguide 1 that is illuminated through the light source array 15 via the input terminal 2. Figure 31B This is a perspective view example in narrow-angle operation mode. Figure 31A A schematic diagram of the operation of imaging waveguide 1.

[0555] Imaging waveguide 1 is of the type described in U.S. Patent No. 9,519,153, which is incorporated herein by reference in its entirety. Waveguide 1 has an input end 2 extending laterally along waveguide 1. A light source array 15 is arranged along input end 2 and inputs light into waveguide 1.

[0556] Waveguide 1 also has opposing first and second guiding surfaces 6, 8 extending across waveguide 1 from input end 2 to reflection end 4 for guiding light input forward and backward along waveguide 1. The second guiding surface 8 has a plurality of light extraction features 12 facing reflection end 4 and is configured to deflect at least some of the light guided back from reflection end 4 through waveguide 1 (which comes from different input positions across input end 2 in different directions depending on the input position)

[0557] Operationally, light is guided from the light source array 15 through the input end and guided between the first and second guiding surfaces 6 and 8 without loss to the reflecting end 4. The reflected ray 232 is incident on surface 12 and output as ray 230 or transmitted as ray 232. The transmitted ray 232 is transmitted back through waveguide 1 via surfaces 803 and 805 of the back reflector 800. The operation of the back reflector is further described in U.S. Patent No. 10,054,732, which is incorporated herein by reference throughout.

[0558] like Figure 31B As illustrated, the refractive power of the curved reflective end 4 and surface 12 provides an optical window 26 for transmission via the SLM48 and has an axis 197 that is generally aligned with the optical axis 199 of the waveguide 1. A similar optical window 26 is provided by the transmission ray 232 reflected by the rear reflector 800.

[0559] Figure 31C When used in display devices that do not have a switchable liquid crystal delay unit, for example... Figure 31B A schematic diagram of the output field-of-view brightness curve. This can be used for aspects not discussed in further detail. Figures 31A to 31C The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0560] Therefore, the off-axis viewing position observed by the spy 47 can have reduced brightness, for example, between 1% and 3% of the center peak brightness at an elevation angle of 0 degrees and a lateral angle of + / -45 degrees. Further reduction in off-axis brightness is achieved through the plurality of delayers 301, 330 described in this embodiment of the invention.

[0561] The backlight 20 may therefore further include a switchable backlight configured to switch the output angle brightness profile to provide off-axis brightness reduction in privacy mode and higher off-axis brightness in public mode.

[0562] Another type of directional backlight with low off-axis brightness will now be described.

[0563] Figure 32A This is a side view illustrating a schematic diagram of a switchable directional display device, including a backlight 20, a switchable collimating waveguide 901, a switchable liquid crystal polarity control delay 300, and an additional polarizer 318. It can... Figure 32A The backlight 20 is used in any of the devices described in this specification and is configured as follows.

[0564] Waveguide 901 has an input end 902 extending laterally along waveguide 901. A light source array 915 is arranged along input end 902 and inputs light into waveguide 1. Waveguide 901 also has opposing first and second guiding surfaces 906, 908 extending across waveguide 1 from input end 2 to reflecting end 4 for guiding the light input at input end 2 forward and backward along waveguide 1. Operationally, light is guided between the first and second guiding surfaces 906, 908.

[0565] The first guiding surface 906 may have a biconvex lens structure 904 including a plurality of elongated biconvex lens elements 905, and the second guiding surface 908 may have a prism structure 912 that is deflected and used as a light extraction feature. The plurality of elongated biconvex lens elements 905 and the plurality of deflecting light extraction features of the biconvex lens structure 904 deflect the input light guided by the waveguide 901 so that it exits through the first guiding surface 906.

[0566] A rear reflector 903, which can be a planar reflector, is provided to guide light transmitted through surface 908 back through waveguide 901.

[0567] The output light rays incident on the prism structure 912 and the biconvex lens element 905 of the biconvex lens structure 904 are output to the surface 906 at an angle close to tangential incidence. The prism-directing film 926, including the surface 927, is configured to re-direct the output light rays 234 through total internal reflections from the SLM 48 and the compensated switchable liquid crystal polarity control retarder 300.

[0568] Figure 32BThis is a schematic diagram illustrating the output of the collimating waveguide 901 from a top view. The prism structure 912 is configured to provide light to the biconvex lens structure 904 at an incident angle below the critical angle and thus allowing it to escape. When incident at the edge of the biconvex lens surface, the deflection of the surface provides light deflection for the escaping rays and provides a collimation effect. Ray 234 can be provided by rays 188a-c and 189a-c incident at position 185 of the biconvex lens structure 904 of the collimating waveguide 901.

[0569] Figure 32C It is aimed at Figure 32A The display device is illustrated with a schematic diagram of the isoluminance field-view polarity curve. Therefore, a narrow output light cone can be provided, the size of which is determined by the structures 904, 912 and the steering film 926. (The remaining text is incomplete and requires further context.) Figures 32A to 32C The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0570] Most preferably, in areas where a spy can be positioned at a lateral angle of, for example, 45 degrees or greater, the brightness output from the display device is very low, typically less than 2%. Further reduction in output brightness will be required to achieve this. (The text abruptly ends here, likely due to an incomplete sentence or missing information.) Figure 32A The compensated switchable liquid crystal polarity control delay 300 and additional polarizer 318 illustrated provide such a further reduction. Most preferably, a high-performance privacy display with low off-axis brightness can be provided over a wide field of view.

[0571] Figure 31A and Figure 32A The type of directional backlight described herein, together with the plurality of delay units 301, 330 of the specific embodiments of the present invention, can achieve an off-axis brightness of less than 1.5%, preferably less than 0.75%, and most preferably less than 0.5% for the position of a general spy 47. Furthermore, high coaxial brightness and uniformity can be provided for the primary user 45. Most preferably, a high-performance privacy display device with low off-axis brightness can be provided above a wide field of view, which can be achieved through… Figure 1A The control system 352 illustrated controls the switchable delayer 301 to switch it to open mode.

[0572] The operation of the polarization control retarder layer between parallel polarizers used for off-axis illumination will now be further explained. In the various devices described above, at least one polarization control retarder is disposed between the reflective polarizer 318 and the additional polarizer 218 in various different arrangements. In each case, the arrangement of the at least one polarization control retarder does not affect the brightness of light passing through the reflective polarizer 318, the at least one polarization control retarder, and the additional polarizer 218 along the axis normal to the plane of the polarization control retarder(s), but does reduce the brightness of light passing through the reflective polarizer 318, the at least one polarization control retarder, and the additional polarizer 218 along the axis normal to the plane of the polarization control retarder(s), at least in one of the switchable states of the compensated switchable liquid crystal polarization control retarder 300. A more detailed explanation of this effect will now be given, and in general, the principle described herein can be applied to all the devices described above.

[0573] Figure 33A This is a perspective view illustrating illumination through a polarity-controlled retarder layer of off-axis light. The polarity-controlled retarder 630 may include a birefringent material, represented by a refractive index ellipse 632 with its optical axis 634 at 0 degrees to the x-axis, and having a thickness 631. (The following is not discussed in further detail.) Figures 33A to 35E The features of the settings are assumed to correspond to the features having equivalent reference numbers as discussed above, including any potential variations of the features.

[0574] Ordinary ray 636 propagates, therefore its path length in the material is the same as its thickness 631. Ray 637 has an increased path length in the yz plane; however, the birefringence of the material is substantially the same as that of ray 636. In contrast, ray 638 in the xz plane has an increased path length in the birefringent material, and its birefringence is also different from that of ordinary ray 636.

[0575] The phase delay of the polarity control delayer 630 is therefore determined by the incident angle of the corresponding ray and also by the incident plane, that is, the ray 638 in the xz plane will have a different phase delay than the ordinary ray 636 and the ray 637 in the yz plane.

[0576] The interaction between the polarized light and the polarization control delay unit 630 will now be explained. To distinguish the first and second polarization components during operation in the directional backlight 101, the following explanation will refer to the third and fourth polarization components.

[0577] Figure 33BThis is a perspective view illustrating the illumination of a retarder layer with polarity control based on the polarization of off-axis light in a third linear polarization state at 90 degrees to the x-axis. Figure 33C This is a perspective view illustrating the illumination of a polarization-controlled retarder layer through which off-axis light of a fourth linear polarization state at 0 degrees to the x-axis is transmitted. In this setup, the incident linear polarization state is aligned with the optical axis of the birefringent material represented by ellipse 632. Therefore, no phase difference is provided between the third and fourth orthogonal polarization components, and there is no change in the polarization state of the linearly polarized input resulting from the lack of a phase shift for each ray 636, 637, 638. Therefore, the polarization-controlled retarder 630 does not reference the phase shift of the polarization component of the light passing through the polarizer on the input side of the polarization-controlled retarder 630 along the axis normal to the plane of the polarization-controlled retarder 630. Therefore, the polarization-controlled retarder 630 does not affect the brightness of the light passing through the polarization-controlled retarder 630 and the polarizers (not shown) on the side of each of the polarization-controlled retarder 630. Although Figures 33A to 33C Specifically, it involves a passive polarity control delay 630, but a similar effect is achieved through the polarity control delay in the device described above.

[0578] Figure 33D This is a perspective view illustrating illumination through a polarization-controlled retarder 630 layer of off-axis light with a linear polarization state of 45 degrees. The linear polarization state can be resolved into third and fourth polarization components, respectively orthogonal and parallel to the optical axis direction 634. For a design wavelength, the material phase retardation represented by the polarization-controlled retarder thickness 631 and the refractive index ellipsoid 632 provides a pure effect on the phase of the third and fourth polarization components incident on it in the normal direction represented by ray 636 through a half-wavelength relative shift. The design wavelength can be, for example, in the range of 500 to 550 nm.

[0579] At the designed wavelength and for light propagating perpendicularly along ray 636, the output polarization can then be rotated by 90 degrees to a linear polarization state 640 of -45 degrees. Light propagating along ray 637 can be seen to have a phase difference similar to, but not the same as, the phase difference along ray 637 due to the change in thickness, thus an elliptic polarization state 639 can be output with a principal axis similar to the linear polarization axis of the output light for ray 636.

[0580] By comparison, the phase difference for the incident linear polarization state along ray 638 can vary significantly, particularly providing a low phase difference. Such a phase difference can provide an output polarization state 644 that is approximately circular at a specific deflection angle 642. Therefore, the polarization control retarder 630 references the phase shift to the polarization component of the light passing through the axis of ray 638 along the axis corresponding to the normal to the plane deflected towards the polarization control retarder 630 on the input side of the polarizer of the polarizer 630. Although Figure 33D The passive polarity control delay 630 is involved, but a similar effect is achieved by the polarity control delay described above in the switchable state of the switchable liquid crystal polarity control delay corresponding to the privacy mode.

[0581] Taking the off-axis behavior of the polarity control delay stack as an example, the angle brightness control of the C-plates 330A and 330B between the additional polarizer 318 and the output display polarizer 218 will now be explained with reference to the operation of the C-plate between the parallel polarizers 500 and 210 for various off-axis illumination settings.

[0582] Figure 34A This is a perspective view illustrating illumination through a C-plate of off-axis polarized light with a positive elevation angle. The incident linear polarization component 704 is incident on the birefringent material 632 of the polarization control retarder 560, which is a C-plate having an optical axis direction 507 perpendicular to the plane of the polarization control retarder 560. Since the polarization component 704 does not exhibit pure phase difference during transmission through the liquid crystal molecules, the output polarization component is the same as component 704. Therefore, maximum transmission is observed through the polarizer 210. Thus, the polarization control retarder 560 has an optical axis 561 perpendicular to the plane of the polarization control retarder 560 (i.e., the xy plane). The polarization control retarder 560, having an optical axis perpendicular to the plane of the polarization control retarder, includes a C-plate.

[0583] Figure 34B This is a perspective view illustrating illumination of a C-layer through off-axis polarized light with a negative side angle. (The last sentence appears to be incomplete and possibly refers to a different concept.) Figure 34A With the polarization state 704 set, pure phase difference is not visible, and transmission is at maximum brightness. Therefore, the polarization control delay 560 does not reference the phase shift to the polarization component of light passing through the polarizer on the input side of the polarizer 560 along the axis normal to the plane of the polarization control delay 560. Therefore, the polarization control delay 560 does not affect the brightness of light passing through the polarizer 560 and the polarizers (not shown) on the side of each of the polarization control delay 560. Although Figures 34A to 34C Specifically, it involves a passive polarity control delay 560, but a similar effect is achieved through the polarity control delay in the device described above.

[0584] Figure 34C This is a perspective view illustrating illumination of a C-sheet layer through off-axis polarized light with positive elevation and negative side angles. Compared to Figures 34A to 34B The polarization state 704 is configured such that the birefringent material 632, which provides pure phase difference during transmission through the polarity control retarder 560, resolves the eigenstates 703 and 705. The resulting elliptic polarization component 656, compared to... Figures 34A to 34B The rays illustrated herein are transmitted with a polarizer 210 that reduces brightness.

[0585] Figure 34D This is a perspective view illustrating illumination of a C-sheet layer through which off-axis polarized light with positive elevation and positive side angles is transmitted. (To be continued) Figure 34C Similarly, polarization component 704 is resolved into eigenstates 703 and 705 undergoing pure phase difference, and an elliptically polarized component 660 is provided that reduces the brightness of the corresponding off-axis ray after transmission through the polarizer. Therefore, the polarization control retarder 560 references the phase shift to the polarization component of the light passing through the polarizer on the input side of the polarizer 560 along the axis normal to the plane of the polarization control retarder 560. Although Figure 34D The passive polarity control delay device 560 is involved, but in the switchable state of the switchable liquid crystal polarity control delay device corresponding to the privacy mode, a similar effect is achieved by the polarity control delay device described above.

[0586] Figure 34E It is aimed at Figures 34A to 34D The transmitted light in the image is illustrated by a schematic graph showing the output transmission changing with polarity. Therefore, the C-plate can provide brightness reduction in the polarity quadrant. In conjunction with the switchable liquid crystal layer 314 described elsewhere in this specification, (i) removal of brightness reduction of the C-plate can be provided in a first wide-angle operating state, and (ii) an extended polarity region for brightness reduction can be achieved in a second privacy-protected operating state.

[0587] Taking the off-axis behavior of the polarity control delay stack as an example, the angle brightness control of the A-plates 330A and 330B at the intersection between the auxiliary polarizer 318 and the output display polarizer 218 will now be explained for various off-axis illumination settings.

[0588] Figure 35AThis is a perspective view illustrating illumination through a cross-shaped A-plate retarder layer of light with positive elevation angle and off-axis polarization. A linear polarizer 218 with an electric vector propagation direction 219 is used to provide a linear polarization state 704 parallel to the lateral direction on the first A-plate 330A of the cross-shaped A-plates 330A and 330B. The optical axis direction 331A is offset to the lateral direction at +45 degrees. For the off-axis angle 1 in the positive elevation direction, the phase delay of the polarization-controlled retarder 330A provides a polarization component 650, which is generally elliptical in output. The polarization component 650 is incident on the second A-plate 330B of the cross-shaped A-plates 330A and 330B, which has an optical axis direction 331B orthogonal to the optical axis direction 331A of the first A-plate 330A. Figure 35A In the incident plane, the phase delay of the second A-plate 330B with respect to the off-axis angle 1 is equal to and opposite to the phase delay of the first A-plate 330A. Therefore, a pure zero phase delay is provided for the incident polarization component 704, and the output polarization component is the same as the input polarization component 704.

[0589] The output polarization component is aligned with the electrical vector propagation direction of the additional polarizer 318, thus enabling efficient transmission. Most preferably, there is virtually no loss for light rays with zero lateral angle components, thus achieving full transmission efficiency.

[0590] Figure 35B This is a perspective view illustrating illumination through an A-plate retarder layer transmitting off-axis polarized light with a negative side angle. Therefore, the first A-plate 330A converts the input polarization component into an intermediate polarization component 652, which is generally elliptical polarization. The second A-plate 330B again provides an equal and opposite phase delay to the first A-plate, so the output polarization component is the same as the input polarization component 704, and the light is effectively transmitted through the polarizer 318.

[0591] Therefore, the polarity control retarder includes a pair of retarders 330A and 330B, which have intersecting optical axes in the plane of the retarders 330A and 330B (i.e., the xy plane in a specific embodiment of the invention). The retarder pair 330A and 330B have optical axes 331A and 331B, each extending at 45° relative to the direction of electrical vector propagation parallel to the polarizer 318.

[0592] Ideally, there is virtually no loss for light with a zero elevation angle component, thus achieving full transmission efficiency.

[0593] Figure 35CThis is a perspective view illustrating illumination through an A-plate retarder layer containing intersecting off-axis polarized light with positive elevation and negative side angles. The polarization component 704 is converted into an elliptic polarization component 654 by the first A-plate 330A. The resulting elliptic component 656 is output from the second A-plate 330B. The elliptic component 656 is analyzed by an input polarizer 318 with reduced brightness compared to the input brightness of the first polarization component 704.

[0594] Figure 35D This is a perspective view illustrating illumination through an A-plate retarder layer with cross-polarized light having positive elevation and positive side angles. Since the pure phase delay of the first and second retarders does not provide compensation, polarization components 658 and 660 are provided through the first and second A-plates 330A and 330B.

[0595] Therefore, brightness is reduced for light with non-zero side angle and non-zero elevation components. Most preferably, this improves the privacy of the display device against prying eyes positioned in the viewing quadrant, while largely maintaining luminous efficiency for the primary display device user.

[0596] Figure 35E It is aimed at Figures 35A to 35D The transmitted light beam in the diagram illustrates a schematic curve showing how the output transmission changes with polarity. Compared to... Figure 34E The configuration increases the area of ​​reduced brightness for off-axis viewing. However, compared to the C-plate configuration for off-axis viewing in the first disclosed mode of operation, the switchable liquid crystal layer 314 provides reduced uniformity.

[0597] As used in this specification, the terms "generally" and "approximately" provide an industry-recognized tolerance for their relevance to the application terms and / or items. Such industry-recognized tolerances range from 0% to 10% and correspond to, but are not limited to, component values, angles, etc. The relevance between such items ranges from approximately 0% to 10%.

[0598] While various specific embodiments based on the principles disclosed in this specification have been described above, it should be understood that they are illustrated by way of example only and not as limitations. Therefore, the breadth and scope of the invention should not be limited to any of the exemplary embodiments described above, but should be defined solely by any claim asserted from the invention and its equivalents. Furthermore, while the aforementioned advantages and features are provided in the described embodiments, the application of such claimed claims should not be limited to procedures and structures for achieving any or all of the aforementioned advantages.

[0599] Furthermore, the paragraph headings in this specification are provided for organizational purposes in accordance with the recommendations under 37 CFR 1.77 or otherwise. These headings should not limit the specific embodiments or features set forth in any of the claims asserted by this invention. Specifically, and by way of example, although the headings refer to the “Technical Field,” the claims should not be limited to the terms chosen to describe the so-called technical field under this heading. Furthermore, the description of the technology in the “Background Art” section should not be construed as some technology being considered background art to any specific embodiment of this invention. The “Summary of the Invention” section should also not be construed as the features set forth in the claimed claims. Moreover, any reference to “Invention” in the singular throughout this invention should not be used to assert a single novel feature in this invention. Multiple specific embodiments may be set forth according to the limitations of the multiple claims asserted by this invention, and this claim therefore defines the multiple specific embodiments protected therefrom and their equivalents. In all instances, the scope of this claim should be considered according to the advantages of the invention itself, but should not be limited by the headings set forth in this specification.

Claims

1. A viewing angle control optical element applied to the output side of a display device for ambient lighting, the display device comprising: Spatial light modulator (SLM), configured to output light; The SLM includes an output polarizer disposed on the output side of the SLM; The viewing angle control optical element includes: An additional polarizer is disposed on the output side of the output polarizer when the viewing angle control optical element is applied to the display device; A reflective polarizer, which is a linear polarizer, is disposed between the output polarizer and the additional polarizer when the viewing angle control optical element is applied to the display device; and A plurality of polarity-controlled retarders are disposed between the reflective polarizer and the additional polarizer, wherein there are no other polarizers between the reflective polarizer and the additional polarizer. The plurality of polarity-controlled delayers include a switchable liquid crystal delayer and at least one passive polarity-controlled delayer, wherein the switchable liquid crystal delayer includes a liquid crystal material layer.

2. The viewing angle control optical element according to claim 1, wherein the switchable liquid crystal retarder comprises two surface alignment layers arranged adjacent to liquid crystal material layers on their opposite sides, and each is configured to provide a vertical alignment at the liquid crystal material layers.

3. The viewing angle control optical element according to claim 2, wherein the liquid crystal material layer of the switchable liquid crystal delayer comprises a liquid crystal material with negative dielectric anisotropy.

4. The viewing angle control optical element according to claim 2, wherein the liquid crystal material layer has a phase delay of 550 nm wavelength light in the range of 500 nm to 1000 nm.

5. The viewing angle control optical element according to claim 2, wherein: The at least one passive polarity-controlled retarder includes a passive retarder having an optical axis perpendicular to the plane of the retarder, the passive retarder having a phase delay of 550 nm wavelength light in the range of -300 nm to -900 nm; or The at least one passive polarity-controlled retarder includes a pair of passive retarders having intersecting optical axes in the plane of the retarders, each of the passive retarders having a phase delay of 550 nm wavelength light in the range of 300 nm to 800 nm.

6. The viewing angle control optical element of claim 1, wherein the switchable liquid crystal retarder comprises two surface alignment layers disposed adjacent to the liquid crystal material layer and on opposite sides thereof, and each being configured to provide a surface alignment in the liquid crystal material layer.

7. The viewing angle control optical element according to claim 6, wherein the liquid crystal material layer of the switchable liquid crystal delayer comprises a liquid crystal material having positive dielectric anisotropy.

8. The viewing angle control optical element according to claim 6, wherein the liquid crystal material layer has a phase delay of 550 nm wavelength light in the range of 500 nm to 900 nm.

9. The viewing angle control optical element according to claim 6, wherein: The at least one passive polarity-controlled retarder includes a passive retarder having an optical axis perpendicular to the plane of the retarder, the passive retarder having a phase delay of 550 nm wavelength light in the range of -300 nm to -700 nm; or The at least one passive polarity-controlled retarder includes a pair of passive retarders having intersecting optical axes in the plane of the retarders, each of the passive retarders having a phase delay of 550 nm wavelength light in the range of 300 nm to 800 nm.

10. The viewing angle control optical element of claim 1, wherein the switchable liquid crystal delay further comprises a transmission electrode configured to apply a voltage for controlling the liquid crystal material layer.

11. The viewing angle control optical element according to claim 10, wherein the transmission electrode is located on the opposite side of the liquid crystal material layer.

12. The viewing angle control optical element of claim 10, wherein the transmission electrode is patterned to provide at least two patterned regions.

13. The viewing angle control optical element of claim 1, further comprising at least one additional polarity control delay unit disposed between the output polarizer and the reflective polarizer.

14. The viewing angle control optical element of claim 13, wherein an additional polarizer is disposed between the at least one additional polarity control delay unit and the reflective polarizer.

15. The viewing angle control optical element of claim 13, wherein the at least one passive polarity control delayer comprises a first switchable liquid crystal delayer comprising a first layer of liquid crystal material, and the at least one additional polarity control delayer comprises a second switchable liquid crystal delayer comprising a second layer of liquid crystal material.

16. The viewing angle control optical element of claim 15, wherein the first switchable liquid crystal retarder and the second switchable liquid crystal retarder have different phase delays.

17. The viewing angle control optical element according to claim 1, wherein the SLM is an emission SLM and the output polarizer is a display polarizer.

18. The viewing angle control optical element according to claim 1, wherein the reflective polarizer and the output polarizer have parallel electric vector transmission directions.

19. The viewing angle control optical element according to claim 1, wherein the reflective polarizer and the additional polarizer have parallel electric vector transmission directions.

20. The viewing angle control optical element according to claim 1, wherein: The reflective polarizer and the additional polarizer have non-parallel electric vector propagation directions, and The viewing angle control optical element further includes a rotor retarder disposed between the reflective polarizer and the additional polarizer, which is configured to rotate the polarization direction of the polarized light incident thereon between the electrical vector transmission directions of the output polarizer and the additional polarizer.

21. The viewing angle control optical element of claim 1, wherein at least one polarity control retarder is capable of simultaneously not referencing the pure relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis normal to the plane of the at least one polarity control retarder, but referencing the relative phase shift to the orthogonal polarization component of light passing through the reflective polarizer along the axis biased towards the plane of the at least one polarity control retarder.

Images