RU2785432C2 - Optical stack for switchable directional display device - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: invention relates to switchable optical stacks for provision of control of illumination, when used in a display, including in a confidential display. The confidential display contains a spatial light modulator and a compensating switchable liquid-crystal slowing layer located between the first and the second polarizers installed in series with the spatial light modulator. In a confidential operational mode, light passes without losses along the main axis from the spatial light modulators, whereas light outside the main axis differs in reduced brightness. Display visibility outside the main axis is reduced for peeping people due to reduction in brightness within a wide polar field. In a wide-angle operational mode, the switchable liquid-crystal slowing layer is adjusted in such a way that brightness outside the main axis remains essentially without changes.

EFFECT: invention allows for an increase in brightness of a display, increase in the efficiency of adjustment of image visibility.

27 cl, 89 dwg, 12 tbl

Description

Technical field

The present description pertains essentially to illumination using light modulation devices, and more particularly to switchable optical stops for providing illumination control for use in a display, including a privacy display.

Prerequisites for the creation of the invention

Privacy displays allow the primary user to view the image, which is typically located on the primary axis, and reduce the visibility of the image content to the viewer, which is typically located off the primary axis. The privacy function can be provided by micro louvre optical films that transmit some light along the main axis and give low brightness off the main axis. At the same time, such films are characterized by high losses of direct brightness, and microlouvers can create interference artifacts due to beats when interacting with pixels of a spatial light modulator. It may be necessary to select the distance between the shutters of the blinds, taking into account the screen resolution, which will lead to the accumulation of unsold products and an increase in costs.

Switchable privacy displays can be achieved by adjusting the output optical radiation off the main axis.

Such control can be achieved by reducing the brightness, for example by switching the backlight of a spatial light modulator of a liquid crystal display (LCD). In directional illumination devices, as a rule, waveguides and end light sources are used. Some directional lighting imaging devices have the additional ability to direct illumination through the display panel into the viewport. The imaging system may be formed between the plurality of sources and the corresponding window images. One example of a directional illumination imaging device is an optical isolator, which may use an optical system with a broken optical axis, and therefore can also be an example of a directional illumination device with a broken optical axis for imaging. Light may pass substantially losslessly in one direction through the optical isolator, but light passing in the opposite direction may be output by reflecting off tilted edges as described in US Pat. No. 9,519,153, which is incorporated herein by reference in its entirety.

Adjustment of the off-major-axis visibility can be further provided by lowering the contrast, for example by correcting for tilt offset of liquid crystals in an in-plane switch LCD.

Brief description of the invention

In accordance with the first aspect of the present description, a display device is provided, comprising: a spatial light modulator; a display polarizer located on the side of the spatial light modulator; an additional polarizer located on the same side of the spatial light modulator as the display polarizer; and a plurality of retardation layers located between the additional polarizer and the display polarizer; wherein the plurality of retardation layers comprise: a switchable liquid crystal retardation layer comprising a layer of liquid crystal material disposed between the display polarizer and the secondary polarizer; and at least one passive compensating retardation layer.

The plurality of retardation layers may be arranged so as not to affect the intensity of light passing through the display polarizer, the secondary polarizer, and the plurality of retardation layers along an axis normal to the plane of the retardation layers, and/or to reduce the intensity of light passing through the display polarizer, the secondary a polarizer and a plurality of retarding layers along an axis located at an angle to the normal to the plane of the retarding layers.

At least one passive compensating retardation layer may be configured to not introduce a phase shift into the polarization components of light passing through one of the display polarizer and an additional polarizer on the input side of the plurality of retardation layers along an axis normal to the plane of at least one passive compensating retardation layer , and/or introducing a phase shift into the polarization components of the light passing through one of the display polarizer and the additional polarizer on the input side of the plurality of retardation layers along an axis located at an angle to the normal to the plane of at least one passive compensating retardation layer.

The switchable liquid crystal retardation layer may be configured to not introduce a phase shift into the polarization components of light passing through one of the display polarizer and the additional polarizer on the input side of the plurality of retardation layers along an axis normal to the plane of the switchable liquid crystal retardation layer, and/or to introduce a phase shift into polarization components of light passing through one of the display polarizer and the additional polarizer on the input side of the plurality of retardation layers along an axis at an angle to the normal to the plane of the switchable liquid crystal retardation layer in the switched state of such a switchable liquid crystal retardation layer.

Advantageously, the switchable privacy display can be designed to switch between a wide-angle mode of operation and a privacy mode of operation. The field of view for privacy mode can be expanded compared to known configurations, and lower off-primary-axis brightness levels can be achieved, which increases the degree of privacy that limits the off-primary-axis peeper. In addition, for primary users located on the main axis, it is possible to maintain the brightness level along the main axis in both wide-angle operation and confidential operation.

Parallel electrical vector transmission directions are possible for the display polarizer and the additional polarizer.

In one alternative embodiment, the switchable liquid crystal retardation layer may comprise two surface alignment layers adjacent to and on opposite sides of the liquid crystal material layer, each configured to provide transverse alignment in the adjacent liquid crystal material. The liquid crystal material layer of the switchable liquid crystal retardation layer may comprise a liquid crystal material with a negative dielectric anisotropy. The liquid crystal material layer can provide a phase shift for 550 nm 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.

When using two surface alignment layers that provide transverse alignment, at least one passive compensating retardation layer may contain a retardation layer with an optical axis perpendicular to the plane of the retardation layer, and at least one passive retardation layer provides a phase shift for light with a wavelength of 550 nm in the range -300 nm to -900 nm, preferably in the range -450 nm to -800 nm, and most preferably in the range -500 nm to -725 nm.

In an alternative embodiment, when using two surface alignment layers providing transverse alignment, at least one passive compensating retardation layer may comprise a pair of retardation layers with intersecting optical axes in the plane of the retardation layers, each retardation layer of the pair of retardation layers providing a phase shift for light with a wavelength of 550 nm in the range from 300 nm to 800 nm, preferably in the range from 500 nm to 700 nm, and most preferably in the range from 550 nm to 675 nm. In this case, the advantage is the ability to provide an extended field of view in wide-angle operation. What's more, zero operating voltage can be achieved for wide-angle operation, which can reduce power consumption.

In another alternative embodiment, the switchable liquid crystal retardation layer may comprise two surface alignment layers adjacent to and on opposite sides of the liquid crystal material layer, each configured to provide longitudinal alignment in the adjacent liquid crystal material. An advantage is the ability to achieve higher stability with respect to visualization of the flow of liquid crystal material under the action of applied pressure compared to transverse ordering.

The liquid crystal material layer of the switchable liquid crystal retardation layer may comprise a liquid crystal material with a positive dielectric anisotropy. The liquid crystal material layer can provide a phase shift for 550 nm 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.

When using two surface alignment layers that provide longitudinal alignment, at least one passive compensating retardation layer may contain a retardation layer with an optical axis perpendicular to the plane of the retardation layer, and at least one passive retardation layer provides a phase shift for light with a wavelength of 550 nm in the range -300 nm to -700 nm, preferably in the range -350 nm to -600 nm, and most preferably in the range -400 nm to -500 nm.

Alternatively, when using two surface alignment layers providing longitudinal alignment, at least one passive compensating retardation layer may comprise a pair of retardation layers with intersecting optical axes in the plane of the retardation layers, each retardation layer of the pair of retardation layers providing a phase shift for light with a wavelength of 550 nm in the range from 300 nm to 800 nm, preferably in the range from 350 nm to 650 nm, and most preferably in the range from 450 nm to 550 nm. The advantage in this case is the ability to achieve a higher stability with respect to the visualization of the flow of liquid crystal material under the action of the applied pressure.

In another alternative embodiment, the switchable liquid crystal retardation layer may comprise two surface alignment layers adjacent to and on opposite sides of the liquid crystal material layer, and one of the surface alignment layers is configured to provide transverse alignment in the adjacent liquid crystal material and the other of the surface alignment layers. layers is configured to provide longitudinal ordering in the adjacent liquid crystal material.

If a surface alignment layer capable of providing longitudinal alignment is located between the liquid crystal material layer and the compensating retardation layer, the liquid crystal material layer can provide a phase shift for light with a wavelength of 550 nm 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 from 1200 nm to 1500 nm.

If a surface alignment layer capable of providing longitudinal alignment is located between the liquid crystal material layer and the compensating retardation layer, at least one passive compensating retardation layer may comprise a retardation layer with an optical axis perpendicular to the plane of the retardation layer, wherein at least one passive retardation the layer provides a phase shift for 550 nm 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.

If a surface alignment layer capable of providing longitudinal alignment is located between the liquid crystal material layer and the compensating retardation layer, at least one passive compensating retardation layer may comprise a pair of retardation layers with intersecting optical axes in the plane of the retardation layers, each retardation layer from a pair The retardation layers provide a phase shift for 550 nm 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.

If a surface alignment layer capable of providing transverse alignment is between the liquid crystal material layer and the compensating retardation layer, the liquid crystal material layer can provide a phase shift for light with a wavelength of 550 nm 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.

If a surface alignment layer capable of providing transverse alignment is located between the liquid crystal material layer and the compensating retardation layer, at least one passive compensating retardation layer may comprise a retardation layer with an optical axis perpendicular to the plane of the retardation layer, at least one passive retardation layer provides a phase shift for 550 nm light in the range -300 nm to -1600 nm, preferably in the range -500 nm to -1300 nm, and most preferably in the range -700 nm to -1150 nm.

If a surface alignment layer capable of providing transverse alignment is located between the liquid crystal material layer and the compensating retardation layer, at least one passive compensating retardation layer may comprise a pair of retardation layers with intersecting optical axes in the plane of the retardation layers, each retardation layer from a pair The retardation layers provide a phase shift for 550 nm 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. The advantage in this case is the ability to achieve a higher stability with respect to the visualization of the flow of liquid crystal material under the action of the applied pressure.

Each alignment layer may have a pretilt, and the direction of such pretilt has a component in the plane of the liquid crystal layer that is parallel, or antiparallel, or orthogonal to the transmission direction of the electric vector of the display polarizer. The advantage is that the display can be provided with a narrow viewing angle in the side direction and a wider viewing area when the display is rotated about the horizontal axis. Such a display may be convenient for viewing by a user directly and makes it difficult for a user to view outside the main axis.

The at least one passive retardation layer may comprise at least two passive retardation layers with at least two different optical axes orientations, the optical axes of which may intersect in the plane of the retardation layers. The field of view for longitudinally ordered liquid crystal retardation layers is increased while providing resistance to visualization of liquid crystal material flow under applied pressure.

The pair of passive retardation layers may have optical axes that extend at 45° and 135°, respectively, with respect to the electrical vector transmission direction, which is parallel to the electrical vector transmission direction of the display polarizer. The advantage is that passive retardation layers can be produced using stretched films to provide low cost and high uniformity.

Between the pair of passive retardation layers, a switchable liquid crystal retardation layer may be disposed. An advantage is the possibility of reducing the thickness and simplifying the complexity of the design of multiple retardation layers.

The transparent electrode and the liquid crystal alignment layer may be formed on the side of each of the pair of passive retardation layers adjacent to the switchable liquid crystal retardation layer; and may further comprise first and second substrates between which a switchable liquid crystal retardation layer is located, wherein each of the first and second substrates contains one of a pair of passive retardation layers, each of the pair of passive retardation layers providing a phase shift for light with a wavelength of 550 nm in in the range from 150 nm to 800 nm, preferably in the range from 200 nm to 700 nm, and most preferably in the range from 250 nm to 600 nm.

In one alternative embodiment, at least one passive compensating retardation layer may comprise a retardation layer with an optical axis perpendicular to the plane of the retardation layer. The advantage is the ability to reduce the thickness and simplify the design complexity of the passive retardation layers.

At least one passive compensating retardation layer may comprise two passive retardation layers with an optical axis perpendicular to the plane of the passive retardation layers, and a switchable liquid crystal retardation layer is placed between the two passive retardation layers. An advantage is the possibility of reducing the thickness and simplifying the complexity of the design of multiple retardation layers. High direct viewing performance can be achieved in both wide and privacy modes, with a wide field of view in wide mode, and peepers will not be able to see image data in a wide range of off-principal-axis viewing positions.

The transparent electrode and the liquid crystal alignment layer may be formed on the side of each of the two passive retardation layers adjacent to the switchable liquid crystal retardation layer. The first and second substrates, between which a switchable liquid crystal retardation layer can be placed, and each of the first and second substrates contains one of two passive retardation layers. The two passive retardation layers can provide a common phase shift for 550 nm 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. nm.

In another alternative embodiment, the at least one passive compensating retardation layer may comprise an optical axis retardation layer with a component perpendicular to the plane of the retardation layer and with a component in the plane of the retardation layer. The advantage is that the fields of view in wide-angle mode may increase and peeps may not be able to see image data in a wide range of off-major axis viewing positions.

The in-plane component of the passive retardation layer may extend at 0° with respect to the electrical vector transmission direction, which is parallel or perpendicular to the electrical vector transmission direction of the display polarizer. At least one passive retardation layer may further comprise a retardation layer with an optical axis perpendicular to the plane of the passive retardation layer, or a pair of passive retardation layers with intersecting optical axes in the plane of the passive retardation layers.

The phase shift of the at least one passive compensating retardation layer may be equal to and opposite to the phase shift of the switchable liquid crystal retardation layer.

The switchable liquid crystal retardation layer may comprise first and second pretilts; and at least one passive compensating retardation layer may comprise a compensating retardation layer with first and second pretilts, wherein the first pretilt of the compensating retardation layer is equal to the first pretilt of the liquid crystal retardation layer, and the second pretilt of the compensating retardation layer is equal to the second pretilt of the liquid crystal retardation layer.

The switchable liquid crystal retardation layer may further comprise electrodes configured to supply a voltage to drive the liquid crystal material layer. The electrodes may be on opposite sides of the layer of liquid crystal material. Advantageously, the display can be switched by driving the liquid crystal layer, which makes it possible to obtain a switchable privacy display or other type of display with reduced stray light brightness off the main axis. The display may further comprise a control system configured to control the voltage applied to the electrodes of the at least one switchable liquid crystal retardation layer.

The electrodes may have an ordered structure to provide at least two structured areas. The advantage is that an increased level of privacy can be achieved at the cost of reduced visibility of the image data. The display can be switched between a wide-angle mode without visualization of the masking structure and a confidential mode with additional masking to provide reduced visibility for an off-principal peeper without significant visibility of the masking structure when viewed directly by the user.

The control system may further comprise means for determining the position of the peeper relative to the display, and the control system is configured to adjust the voltage applied to the electrodes of the at least one switchable liquid crystal retardation layer depending on the peeper's position. Advantageously, the visibility of the image to the detected peep can be minimized for a range of peep positions.

The display device may further comprise at least one additional retardation layer and another additional polarizer, wherein at least one additional retardation layer is located between the first mentioned additional polarizer and another additional polarizer. The advantage is that the off-principal axis brightness can be further reduced to limit the visibility of the image to an off-principal viewer.

In one alternative embodiment of the display device, the spatial light modulator is a transmissive spatial light modulator configured to receive light emitted by the backlight. The advantage is that the backlight can provide a reduced off-axis brightness level compared to emissive displays.

The backlight can provide brightness at polar angles with respect to the normal to the spatial light modulator greater than 45 degrees, which is a maximum of 33% brightness along the normal to the spatial light modulator, preferably a maximum of 20% brightness along the normal to the spatial light modulator, and most preferably a maximum of 10% brightness along the normal to the spatial light modulator. The advantage is that the brightness can be limited for peepers off the main axis.

The backlight may contain: a set of light sources; a directional waveguide comprising: an input end extending laterally along a side of the directional waveguide, wherein the light sources are arranged along the input end and configured to introduce the injected light into the waveguide; and opposite first and second guide surfaces passing along the directional waveguide from the input end to direct the input light at the input end along the waveguide, wherein such a waveguide is configured to refract the input light directed through the directional waveguide to exit through the first guiding surface. The advantage is the ability to provide high efficiency uniform illumination of a large surface area.

The backlight may further comprise a reflective film, and the directional waveguide is a collimating waveguide. The collimating waveguide may include (i) a plurality of elongated lens elements; and (ii) a plurality of inclined light output elements, wherein the plurality of elongate lens elements and the plurality of inclined light output elements are oriented to refract input light guided through the directional waveguide to exit through the first guide surface. Advantageously, the backlight can provide a narrow angle light output.

The directional waveguide may be an imaging waveguide configured to image the light sources in a lateral direction so that the light emitted by the sources is directed to respective optical windows in output directions distributed depending on the input positions of the light sources. The imaging waveguide may include a reflective end for reflecting the input light along the imaging waveguide, the second guide surface being configured to refract the reflected input light through the first guide surface as emitted light, the second guide surface comprising light output elements and intermediate regions between the light output elements wherein the light output members are oriented to refract reflected input light through the first guide surface as output light, and the intermediate regions are configured to guide light through the waveguide without diverting it; and the reflective end may have a positive power in a lateral direction extending between the sides of the waveguide that extends between the first and second guide surfaces. An advantage is the ability to provide switchable directional lighting that can be switched between narrow angle and wide angle illumination.

In one alternative embodiment, in which the spatial light modulator is a transmissive spatial light modulator, the display polarizer may be an input display polarizer located on the input side of the spatial light modulator between the backlight and the spatial light modulator, with an additional polarizer placed between the input polarizer display and backlight. The advantage is an increase in display efficiency. The additional polarizer may be a reflective polarizer.

In this case, the display device may further comprise an output polarizer located on the output side of the spatial light modulator.

In one alternative embodiment, in which the spatial light modulator is a transmissive spatial light modulator, the display polarizer may be an output polarizer located on the output side of the spatial light modulator. The advantage is an increase in display efficiency.

The display device may further comprise an input polarizer located on the input side of the spatial light modulator.

The display device may further comprise an additional polarizer located on the input side of the spatial light modulator, and at least one additional retardation layer located between at least one additional polarizer and the input polarizer. The advantage is that the brightness can be limited for peepers off the main axis.

In one alternative embodiment of the display device, the spatial light modulator may comprise an emissive spatial light modulator capable of emitting light. In this case, the display polarizer may be an output display polarizer located on the output side of the ESM. The advantage is the ability to reduce the thickness of the display compared to backlit displays and the ability to easily produce flexible and foldable displays.

The display device may comprise at least one additional retardation layer and another additional polarizer, wherein at least one additional retardation layer is located between the first mentioned additional polarizer and another additional polarizer. The advantage is that the brightness can be limited for peepers off the main axis.

The various optional elements and alternative embodiments set forth above with respect to the first aspect of the present invention may be applied together in any combination.

In accordance with the second aspect of the present description, a viewing angle control optical element for use in a display device containing a spatial light modulator and a display polarizer located on the side of the spatial light modulator, and the optical viewing angle control element contains a control polarizer and a plurality of retardation layers for placement between additional a polarizer and a display polarizer for applying an optical viewing angle control element in the display device, the plurality of retardation layers comprising: a switchable liquid crystal retardation layer containing a layer of liquid crystal material; and at least one passive compensating retardation layer.

Advantageously, the optical viewing angle control element can be offered as an option in the component market and can be installed on display devices by display users. Such an element does not require complex configuration. There is no interference beat between the element and display pixels, and there is no need to select a component based on the pixel pitch. Reduce inventory holding costs.

In an alternative embodiment, the optical viewing angle control may be factory installed in display devices for convenience.

The various elements and alternative embodiments set forth above with respect to the first aspect of the present disclosure may similarly apply to the second aspect of the present disclosure.

Embodiments of the present disclosure can be used in a variety of optical systems. Embodiments may include or operate with a variety of projectors, projection systems, optical components, displays, microdisplays, computer systems, processors, stand-alone projection systems, visual and/or audiovisual systems, and electrical and/or optical devices. Aspects of the present disclosure can be used with virtually any device related to optical and electrical devices, optical systems, presentation systems, or any device that may contain any type of optical system. Accordingly, embodiments of the present disclosure may be used in optical systems, devices used for visual and/or optical presentations, imaging peripherals, and the like in a variety of computing environments.

Before proceeding to a detailed examination of the described embodiments, it should be understood that the description is not limited in its scope or implementation to the details of the specific configurations shown, as the description allows for other embodiments. Moreover, aspects of the description can be presented in various combinations and configurations to define embodiments that are unique in their own right. In addition, the terminology used herein is for purposes of description and is not intended to be limiting.

These and other advantages and elements of the present description will be apparent to those skilled in the art after a full study of this description.

Brief description of graphic materials

Embodiments are shown by way of example in the accompanying figures, in which like numbers indicate like parts, wherein:

Fig. 1A is a circuit diagram illustrating a side perspective view of an optical stack of a directional display device including a front switchable retardation layer;

Fig. 1B is a circuit diagram illustrating a front view of the order of optical layers in the optical stack shown in FIG. 1A;

Fig. 1C is a circuit diagram illustrating a side perspective view of an optical stack of a directional display device having an emission light modulator and a switchable compensating retardation layer disposed on an output side of the emission light light modulator;

Fig. 1D is a circuit diagram illustrating a side perspective view of an optical viewing angle control element comprising a passive compensating retardation layer, a switchable liquid crystal retardation layer, and a control polarizer;

Fig. 2A is a circuit diagram illustrating a side perspective view of an optical stack of a directional display device comprising a backlight, a rear switchable compensating retardation layer, and a transmission spatial light modulator, the additional polarizer comprising a reflective polarizer;

Fig. 2B is a schematic diagram illustrating a front view of the order of optical layers in the optical stack shown in FIG. 2A;

Fig. 2C is a circuit diagram illustrating a side perspective view of an optical stack of a directional display device comprising a backlight, a rear switchable compensating retardation layer, and a transmission spatial light modulator, the additional polarizer comprising a dichroic polarizer;

Fig. 3 is a circuit diagram illustrating a side view of a structure of a compensating switchable liquid crystal retardation layer;

Fig. 4A is a circuit diagram illustrating a side perspective view of a design of a switchable compensating retardation layer including a negative C-plate in wide-angle operation;

Fig. 4B is a circuit diagram illustrating a plot of liquid crystal director angle versus cell passage fraction of a switchable liquid crystal retardation layer;

Fig. 4C is a circuit diagram illustrating a side view of the propagation of emitted light from a spatial light modulator through the optical stack shown in FIG. 4A, in wide-angle operation;

Fig. 4D is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 4C;

Fig. 5A is a circuit diagram illustrating a side perspective view of a design of a switchable compensating retardation layer having a negative C-plate in a confidential mode of operation;

Fig. 5B is a circuit diagram illustrating a side view of the propagation of emitted light from a spatial light modulator through the optical stack shown in FIG. 5A, in confidential mode;

Fig. 5C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 5V;

Fig. 6A is a circuit diagram illustrating a front perspective view of a transmitted light emission for a display operating in the privacy mode;

Fig. 6B is a circuit diagram illustrating a front perspective view of the display shown in FIG. 1A-1C, when operating in confidential mode;

Fig. 6C is a schematic diagram illustrating a side view of a vehicle with a switchable directional display device placed in the interior of the vehicle for entertainment and co-op modes;

Fig. 6D is a circuit diagram illustrating a top view of a vehicle with a switchable directional display device placed in the interior of the vehicle in an entertainment mode;

Fig. 6E is a circuit diagram illustrating a top view of a vehicle with a switchable directional display device placed in the interior of the vehicle, in a co-operation mode;

Fig. 6F is a circuit diagram illustrating a top view of a vehicle with a switchable directional display device placed in the interior of the vehicle for night and day operation;

Fig. 6G is a circuit diagram illustrating a side view of a vehicle with a switchable directional display device placed in the interior of the vehicle during night operation;

Fig. 6H is a circuit diagram illustrating a side view of a vehicle with a switchable directional display device placed in the interior of the vehicle during daytime operation;

Fig. 7A, FIG. 7B, FIG. 7C and FIG. 7D are circuit diagrams illustrating output transmittance versus polar direction at various drive voltages;

Fig. 8 is a flowchart illustrating the control of the private display;

Fig. 9A is a circuit diagram illustrating a side perspective view of a design of a switchable compensating retardation layer in wide-angle operation, comprising passive compensating retardation layers with crossed A-plates and a transversely ordered switchable liquid crystal retardation layer;

Fig. 9B is a circuit diagram illustrating a side perspective view of a construction of a switchable compensating retardation layer in a confidential mode of operation, comprising passive compensating retardation layers with crossed A-plates and a transversely ordered switchable liquid crystal retardation layer;

Fig. 9C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 9A in wide-angle mode;

Fig. 9D is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 9V in confidential mode;

Fig. 10A and FIG. 10B are circuit diagrams illustrating a side perspective view of a design of a switchable compensating retardation layer in wide-angle and confidential modes of operation, respectively, comprising a longitudinally ordered switchable liquid crystal retardation layer and a passive C-plate negative retardation layer;

Fig. 10C is a circuit diagram illustrating a plot of the liquid crystal director angle as a function of the passage fraction through the cell of the switchable liquid crystal retardation layer shown in FIG. 10A, for various applied voltages;

Fig. 11A, FIG. 11B and FIG. 11C are schematic graphs illustrating output transmittance versus polar direction of transmitted light beams of a switchable compensating retardation layer comprising a longitudinally aligned liquid crystal cell and a negative C-plate in confidential mode and two different wide-angle modes, indicating control voltages, respectively;

Fig. 12A is a schematic diagram illustrating a side perspective view of a structure of a switchable compensating retardation layer in a confidential mode of operation, comprising passive compensating retardation layers with crossed A-plates and a longitudinally ordered switchable liquid crystal retardation layer;

Fig. 12B, FIG. 12C and FIG. 12D are schematic graphs illustrating output transmittance versus polar direction of transmitted light beams of a switchable compensating retardation layer comprising a longitudinally aligned liquid crystal cell and crossed A-plates in confidential mode and two different wide-angle modes for different control voltages;

Fig. 13A and FIG. 13B are schematic diagrams illustrating a side view of a portion of a display including a switchable compensating retardation layer and optical coupling layers;

Fig. 14 is a schematic diagram illustrating a side perspective view of a construction of a switchable compensating retardation layer in a confidential mode of operation, comprising passive compensating retardation layers with crossed A-plates and a longitudinally arranged switchable liquid crystal retardation layer, further comprising a passive rotating retardation layer;

Fig. 15A is a schematic diagram illustrating a side perspective view of a switchable compensating retardation layer in a confidential mode of operation, comprising a transversely ordered switchable liquid crystal retardation layer sandwiched between the first and second C-plate passive compensating retardation layers;

Fig. 15B and FIG. 15C are schematic graphs illustrating output transmittance versus polar direction for transmitted light beams in the optical stack shown in FIG. 15A in wide-angle and privacy modes, respectively;

Fig. 16A is a circuit diagram illustrating a side perspective view of a display comprising a switchable liquid crystal retardation layer sandwiched between first and second substrates each comprising C-plate passive compensating retardation layers;

Fig. 16B is a circuit diagram illustrating a side view of a portion of a display comprising a switchable liquid crystal retardation layer sandwiched between first and second substrates each comprising C-plate passive compensating retardation layers;

Fig. 17A is a schematic diagram illustrating a side perspective view of a design of a switchable compensating retardation layer in a wide-angle mode of operation, comprising a longitudinally arranged switchable liquid crystal retardation layer disposed between the first and second passive compensating retardation layers with crossed A-plates;

Fig. 17B and FIG. 17C are schematic graphs illustrating output transmittance versus polar direction for transmitted light beams for the design shown in FIG. 17A in wide-angle and privacy modes, respectively;

Fig. 18A is a schematic diagram illustrating a side perspective view of a construction of a switchable compensating retardation layer in confidential mode, comprising a longitudinally and transversely arranged switchable liquid crystal retardation layer and a passive C-plate negative retardation layer;

Fig. 18B is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 18A in confidential mode;

Fig. 18C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 18A in wide-angle mode;

Fig. 19A is a circuit diagram illustrating a side perspective view of a structure of a longitudinally ordered switchable liquid crystal retardation layer;

Fig. 19B is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 19A for the first applied voltage;

Fig. 19C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 19A for a second applied voltage that is greater than the first applied voltage;

Fig. 19D is a circuit diagram illustrating a side perspective view of a C-plate positioned between parallel polarizers;

Fig. 19E is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 19D;

Fig. 20A is a circuit diagram illustrating a side perspective view of a structure of a longitudinally ordered switchable liquid crystal retardation layer placed between parallel polarizers in series with C-plates placed between parallel polarizers;

Fig. 20B is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 20A for the first applied voltage;

Fig. 20C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 20A for a second applied voltage that is greater than the first applied voltage;

Fig. 21A is a circuit diagram illustrating a side perspective view of a construction of a longitudinally ordered switchable liquid crystal retardation layer arranged in series with a C-plate compensating retardation layer, with a longitudinally ordered switchable liquid crystal retardation layer and a C-plate compensating retardation layer disposed between one pair. parallel polarizers;

Fig. 21B is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 21A for the first applied voltage;

Fig. 21C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 21A for a second applied voltage that is greater than the first applied voltage;

Fig. 22A is a schematic diagram illustrating a side perspective view of a confidential mode switchable compensating retardation layer design comprising a negative C-plate passive compensating retardation layer and a transversely ordered switchable liquid crystal retardation layer disposed between an output polarizer and an additional polarizer; as well as a passive compensating retardation layer with negative C-plates and a transversely ordered switchable liquid crystal retardation layer located between the first mentioned additional polarizer and another additional polarizer, in a confidential mode of operation;

Fig. 22B is a circuit diagram illustrating a side perspective view of the structure of the first switchable compensating retardation layer located at the input of the liquid crystal display and the second switchable compensating retardation layer located at the output of the liquid crystal display;

Fig. 22C is a circuit diagram illustrating a side perspective view of an optical viewing angle control element comprising a first passive compensating retardation layer, a first switchable liquid crystal retardation layer, a first driving polarizer, a second passive compensating retardation layer, a second switchable liquid crystal retardation layer, and a second driving polarizer;

Fig. 22D is a schematic diagram illustrating a plan view of a vehicle with a switchable directional display device placed in the interior of the vehicle for daytime and/or co-operation modes;

Fig. 22E is a schematic diagram illustrating a side view of a vehicle with a switchable directional display placed in the interior of the vehicle for daytime and/or shared modes of operation;

Fig. 22F is a circuit diagram illustrating a top view of a motor vehicle with a switchable directional display placed in the interior of the vehicle for night and/or entertainment operation;

Fig. 22G is a circuit diagram illustrating a side view of a motor vehicle with a switchable directional display placed in the interior of the vehicle for night and/or entertainment operation;

Fig. 23A is a circuit diagram illustrating a side perspective view of the construction of a reflective secondary polarizer and a passive retardation layer located at the input of the liquid crystal display, and a switchable compensating retardation layer and the secondary polarizer located at the output of the liquid crystal display;

Fig. 23B is a circuit diagram illustrating a side perspective view of an optical viewing angle control element comprising a passive retardation layer, a first driving polarizer, a passive compensating retardation layer, a switchable liquid crystal retardation layer, and a second driving polarizer;

Fig. 24A is a schematic diagram illustrating a side perspective view of an optical stack of a passive retardation layer comprising a negative O-plate inclined in a plane orthogonal to the transmission direction of the electric vector of the display polarizer and a negative C-plate, and configured to provide a change in the field of view of the device. display;

Fig. 24B is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams in the passive retardation layer shown in FIG. 24A;

Fig. 24C is a schematic diagram illustrating a side perspective view of an optical stack of a passive retardation layer comprising crossed A-plates and a positive O-plate;

Fig. 24D is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams in the passive retardation layer shown in FIG. 24C;

Fig. 24E is a schematic diagram illustrating a side perspective view of an optical stack of a passive retardation layer comprising two pairs of crossed A-plates;

Fig. 24F is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams in the passive retardation layer shown in FIG. 24E;

Fig. 25A is a schematic diagram illustrating a side perspective view of a construction of a switchable compensating retardation layer in a confidential mode of operation, comprising a passive compensating retardation layer with C-plates and a transversely ordered switchable liquid crystal retardation layer, further comprising a patterned electrode layer;

Fig. 25B is a circuit diagram illustrating lighting (perspective front view) for the main viewer and peeper on a privacy display with masking and brightness control;

Fig. 25C is a circuit diagram illustrating lighting (side perspective view) for a peeper on a privacy display with masking and brightness control;

Fig. 26A is a circuit diagram illustrating a front perspective view of the directional illumination;

Fig. 26B is a circuit diagram illustrating a front perspective view of an omnidirectional backlight;

Fig. 26C is a schematic graph illustrating the change in brightness depending on the lateral viewing angle of displays with different fields of view;

Fig. 27A is a circuit diagram illustrating a side view of a switchable directional display device including an imaging waveguide and a switchable liquid crystal retardation layer;

Fig. 27B is a circuit diagram illustrating a rear perspective view of an imaging waveguide mode of operation in a narrow-angle mode of operation;

Fig. 27C is a schematic graph illustrating a field-of-view luma pattern for the output signal shown in FIG. 27B when used in a display device without a switchable liquid crystal retardation layer;

Fig. 28A is a circuit diagram illustrating a side view of a switchable directional display device comprising a switchable collimating waveguide and a switchable liquid crystal retardation layer in a confidential mode of operation;

Fig. 28B is a circuit diagram illustrating a top view of the output of a collimating waveguide;

Fig. 28C is a schematic graph illustrating the polarity of equal field of view luminance for the display device of FIG. 28A;

Fig. 29A is a circuit diagram illustrating illumination (perspective view) of the retardation layer with light off the main axis;

Fig. 29B is a schematic diagram illustrating illumination (perspective view) of the slow-wave layer with off-principal-axis light for a first linear polarization state at 0 degrees;

Fig. 29C is a schematic diagram illustrating illumination (perspective view) of the slow-wave layer with off-principal-axis light for a first linear polarization state at 90 degrees;

Fig. 29D is a schematic diagram illustrating illumination (perspective view) of the slow-wave layer with off-principal-axis light for a first linear polarization state at 45 degrees;

Fig. 30A is a schematic diagram illustrating the illumination (perspective view) of the C-plate retardation layer with off-principal-axis polarized light with positive elevation;

Fig. 30B is a schematic diagram illustrating the illumination (perspective view) of the C-plate retardation layer with off-major-axis negative side angle polarized light;

Fig. 30C is a schematic diagram illustrating the illumination (perspective view) of the C-plate retardation layer with off-major-axis polarized light with positive elevation and negative side angle;

Fig. 30D is a schematic diagram illustrating the illumination (perspective view) of the C-plate retardation layer with off-major-axis polarized light with positive elevation and positive side angle;

Fig. 30E is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 30A-D;

Fig. 31A is a schematic diagram illustrating the illumination (perspective view) of crossed A-plate retardation layers with off-principal axis positive elevation polarized light;

Fig. 31B is a schematic diagram illustrating the illumination (perspective view) of the retardation layers with crossed A-plates 157 with off-major-axis negative side angle polarized light;

Fig. 31C is a schematic diagram illustrating illumination (perspective view) of crossed A-plate retardation layers with off-major-axis polarized light with positive elevation and negative side angle;

Fig. 31D is a schematic diagram illustrating illumination (perspective view) of crossed A-plate retardation layers with off-major-axis polarized light with positive elevation and positive lateral angle; and

Fig. 31E is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 31A-D.

Detailed description

For the purposes of this description, the following are definitions of terms relating to optical retardation layers.

In a layer containing a uniaxial birefringent material, there is an optical anisotropy defining direction in which all directions perpendicular to it (or at a given angle to that direction) will exhibit the same birefringence.

The optical axis refers to the direction of propagation of a light beam in a uniaxial birefringent material in which no birefringence is observed. For light traveling in a direction orthogonal to the optical axis, such an optical axis is the axis of slowest light velocity if linearly polarized light with an electrical vector direction parallel to the axis of slow light travels at the slowest speed. The direction of the axis of slowest light velocity is the direction with the highest refractive index for a given wavelength. Similarly, the direction of the axis of the highest speed of light is the direction with the lowest refractive index for a given wavelength.

In the case of positive dielectric anisotropy in uniaxial birefringent materials, the direction of the axis with the slowest light velocity is the extraordinary axis of the birefringent material. In the case of negative dielectric anisotropy in uniaxial birefringent materials, the direction of the axis with the highest velocity of light is the extraordinary axis of the birefringent material.

The terms "half wavelength" and "quarter wavelength" refer to the function of the slowing layer for a given wavelength λ ₀ , which can typically be between 500 nm and 570 nm. In the present illustrative embodiments, unless otherwise indicated, phase shift values are given for a wavelength of 550 nm.

The retarding layer provides a phase shift between two perpendicular polarization components of the light wave incident on it and differs in the amount of relative phase, Γ, which it imparts to the two polarization components and which is related to the double refraction Δn and the thickness d of the retarding layer by the following relationship:

Γ = 2 . π . Δn. d / λ ₀ eq. one

In eq. 1 Δn is defined as the difference between the extraordinary and ordinary refractive index, i.e.

Δn = n _e - n _o eq. 2

For a half-wave retarding layer, the ratio between d, Δn and λ ₀ is chosen so that the phase shift between the polarization components is Γ = π. For a quarter-wave retarding layer, the ratio between d, Δn and λ ₀ is chosen so that the phase shift between the polarization components is Γ = π / 2.

As used herein, the term "half wave retardation layer" generally refers to light propagating along the normal to the retardation layer and normal to the spatial light modulator.

As used herein, the term "A-plate" refers to an optical retardation layer that uses a layer of birefringent material with an optical axis parallel (x-y) to the plane of the layer.

The term "positive A-plate" refers to A-plates with positive birefringence, that is, A-plates with positive Δn.

In the present description, the term "C-plate" refers to an optical retardation layer that uses a layer of birefringent material with an optical axis perpendicular to the plane of the layer. The term "positive C-plate" refers to a C-plate with positive birefringence, i.e., a C-plate with positive Δn. The term "negative C-plate" refers to a C-plate with negative birefringence, i.e., a C-plate with negative Δn.

The term "O-plate" refers to an optical retardation layer that uses a layer of birefringent material with an optical axis that includes a component parallel to the layer plane and a component perpendicular to the layer plane. The term "positive O-plate" refers to O-plates with positive birefringence, ie O-plates with positive Δn.

Achromatic retardation layers can be provided using a retardation layer material with a phase shift Δn. d, which varies depending on the wavelength λ as follows:

Δn. d / λ = κ eq. 3,

where κ is essentially a constant.

Examples of suitable materials include modified polycarbonates available from Teijin Films. In the illustrated embodiments, achromatic retardation layers can be provided, which have the advantage of minimizing color variations between polar angle viewing directions, where there is little decrease in brightness, and polar angle viewing directions, where there is increased decrease in brightness, as will be described. below.

The following are various other terms used in the present description and related to retardation layers and liquid crystals.

The liquid crystal cell has a phase shift, which is defined as Δn. d, where Δn is the birefringence of the liquid crystal material in the liquid crystal cell, and d denotes the thickness of the liquid crystal cell regardless of the alignment of the liquid crystal material in the liquid crystal cell.

Longitudinal ordering refers to the ordering of liquid crystals in switchable liquid crystal displays in which the molecules are oriented substantially parallel to the substrate. Longitudinal ordering is sometimes called planar ordering. Longitudinal alignment can typically be provided with a slight pretilt, such as 2 degrees, so that the molecules on the surfaces of the alignment layers of the liquid crystal cell will be slightly tilted, as will be described below. The pre-tilt is formed in order to minimize defects when switching cells.

In the present description, the transverse ordering refers to the state in which the rod-shaped liquid crystal molecules are oriented essentially perpendicular to the substrate. In discotic liquid crystals, lateral ordering is defined as a state in which the axis of a columnar structure, which is formed by discoid liquid crystal molecules, is oriented perpendicular to the substrate. In transverse ordering, the pretilt is defined as the angle of inclination of molecules close to the alignment layer and is typically close to 90 degrees and may be 88 degrees for example.

Liquid crystal molecules with positive dielectric anisotropy are switched from longitudinal alignment (eg, A-plate retardation layer orientation) to transverse alignment (eg, C-plate or O-plate retardation layer orientation) by an applied electric field.

Liquid crystal molecules with negative dielectric anisotropy are switched from transverse ordering (eg, retardation layer orientation with C-plates or O-plates) to longitudinal ordering (eg, retardation layer orientation with A-plates) by an applied electric field.

Rod-like molecules have positive birefringence so that n _e > n _o , as described in Equation 2. Discotic molecules have negative birefringence so that _ne < n _o .

Positive retardation layers, such as A-plates, positive O-plates, and positive C-plates, can typically be made from stretched films or rod-shaped liquid crystal molecules. Negative retardation layers, such as negative C-plates, can be made from stretched films or discotic liquid crystal molecules.

Parallel ordering of a liquid crystal cell refers to the parallel or, more commonly, antiparallel direction of ordering of the longitudinal alignment layers. In the case of a pretilted transverse ordering, the alignment layers may include components that are substantially parallel or anti-parallel. The hybrid ordering liquid crystal cells may include one longitudinal alignment layer and one transverse alignment layer. Twisted liquid crystal cells can be formed by alignment layers that do not have a parallel alignment, such as oriented at 90 degrees to each other.

The transmission spatial light modulator may further comprise retardation layers between the input display polarizer and the output display polarizer, for example, as described in US Pat. No. 8,237,876, which is incorporated herein by reference in its entirety. Such retardation layers (not shown) are different from the passive retardation layers of the present embodiments. Such retardation layers compensate for the deterioration in contrast for off-principal-axis viewing positions, and such an effect is different from the decrease in brightness for off-primary-axis viewing positions of the present embodiments.

Optical decoupling retardation layers that are located between the display polarizer and the OLED emissive layer are further described in US Pat. No. 7,067,985. Optical decoupling retardation layers are different from the passive retardation layers of the present embodiments. The retardation decoupling layers reduce the direct reflection from the emissive layer of the OLED display, and such an effect is different from the decrease in brightness for off-principal-axis viewing positions of the present embodiments.

The structure and functions of various switchable display devices will be described below. In this description, the same elements have the same reference numbers. It should be noted that the description that applies to any element is applicable to each device in which the same or a corresponding element is installed. Accordingly, for the sake of brevity, such a description is not repeated.

Fig. 1A is a circuit diagram illustrating a side perspective view of an optical stack of a display device.

The display device 100 includes a spatial light modulator 48 comprising at least one display polarizer, which is an output polarizer 218. The backlight 20 is configured to emit light, and the spatial light modulator 48 includes a transmissive spatial light modulator 48 configured to receive light emitted by the backlight. 20 light. As will be described below, the display device 100 is configured to output light 400 with angular brightness characteristics.

In the present description, the spatial light modulator 48 may include a liquid crystal display comprising substrates 212, 216, and a liquid crystal layer 214 with red, green, and blue pixels 220, 222, 224. The spatial light modulator 48 has an input display polarizer 210 and an output display polarizer 218 on its opposite sides. The display output polarizer 218 is configured to provide a high extinction coefficient for light from pixels 220, 222, 224 of the spatial light modulator 48. Standard polarizers 210, 218 may be absorbing polarizers such as, for example, dichroic polarizers.

A reflective polarizer 208 may optionally be installed between the display dichroic input polarizer 210 and the backlight 210 to provide recirculating light and increase display efficiency. The advantage is the possibility of increasing efficiency.

The backlight 20 may include input light sources 15, a waveguide 1, a rear reflector 3, and an optical stack 5 containing diffusers, reflective films, and other known optical illumination structures. Asymmetric diffusers, which may contain asymmetrical surface features, for example, may be included in the optical stack 5 with increased dispersion in the vertical direction compared to the lateral direction. The advantage is the ability to improve image uniformity.

In the present embodiments, backlight 20 may be configured to provide an angular distribution of light that is characterized by reduced luminance for off-major-axis viewing positions compared to direct luminance, as will be described below in FIG. 26A-28C. The backlight 20 may further comprise a switchable backlight configured to change the output angular luminance characteristics to provide reduced off-principal-axis luminance in confidential mode of operation and higher off-primary-axis luminance in wide-angle mode of operation. Such a switchable backlight 20 may cooperate with the switchable compensating retardation layer 300 of the present embodiments.

An additional polarizer 318 is located on the same output side of the spatial light modulator 48 as the display output polarizer 218, which may be an absorbing dichroic polarizer.

The display polarizer 218 and the additional polarizer 318 are characterized by parallel transmission directions of the electrical vector 219, 319. As will be described below, this parallel arrangement provides high transmission for central viewing positions.

A plurality of retardation layers, collectively referred to herein as a switchable compensating retardation layer 300, is disposed between the secondary polarizer 318 and the display polarizer 218 and includes: (i) a switchable liquid crystal retardation layer 301 comprising a liquid crystal material layer 314 disposed between the display polarizer 218 and additional polarizer 318; and (ii) a passive compensating retardation layer 330.

Fig. 1B is a circuit diagram illustrating a front view of the order of optical layers in the optical stack shown in FIG. 1A. The direction of transmission of the input electrical vector 211 on the input polarizer 210 of the display of the spatial light modulator 48 provides an input polarization component that can be converted by the liquid crystal layer 214 to obtain an output polarization component determined by the direction of transmission of the electrical vector 219 of the output polarizer 218 of the display. The passive compensating retardation layer 330 may comprise a phase shift layer with a birefringent disc material 430, while the switchable liquid crystal retardation layer 301 may comprise a liquid crystal material.

Thus, the switchable liquid crystal retardation layer 300 includes a switchable liquid crystal retardation layer 301, including a switchable liquid crystal retardation layer 301, substrates 312, 316, and a passive compensating retardation layer 330 disposed between the secondary polarizer 318 and the display polarizer 218.

The substrates 312, 316 may be glass substrates or polymer substrates such as polyimide substrates. Flexible substrates can be provided in which transparent electrodes can be easily mounted. The advantage is the ability to obtain curved, curved and foldable displays.

The display device 100 further comprises a control system 352 configured to control the voltage applied by the voltage source 350 to the electrodes of the switchable liquid crystal retardation layer 301.

It may be desirable to provide stray light reduction or privacy control of the emissive display.

Fig. 1C is a circuit diagram illustrating a side perspective view of an optical stack of a directional display device including an emission spatial light modulator 48 and a switchable compensating retardation layer 300 located on the output side of the emission spatial light modulator 48.

The spatial light modulator 48 may alternatively be provided in other types of displays that provide output light 400 by emission, such as organic LED displays (OLEDs) with an output display polarizer 218, substrates 512, 516, and a light emission layer 514. polarizer 218 may provide brightness reduction for light reflected from the OLED pixel plane by one or more retardation layers 518 interposed between the display output polarizer 218 and the OLED pixel plane. One or more retardation layers 518 may be a quarter-wave plate and is different from the compensating retardation layer 330 of the present disclosure.

Thus, in the embodiment shown in FIG. 1C, the spatial light modulator 48 includes an emission spatial light modulator, and the display polarizer is the output display polarizer 218.

In other cases, the directional display device shown in FIG. 1C, identical to that in FIG. 1A as described above.

An optical viewing angle control element 260 for use in a display device will be described below. View-angle control optics 260 can be added to the spatial light modulators containing the display polarizer 210, 218 to enable switching of field of view characteristics.

Fig. 1D is a circuit diagram illustrating a side perspective view of an optical viewing angle control element 260 for use in a display device, comprising a passive compensating retardation layer 330, a switchable liquid crystal retardation layer 301, and a control polarizer 250.

In operation, the viewing angle control optical element 260 may be installed by the user or built into the spatial light modulator 48 with polarized light output at the factory. The viewing angle control optical element 260 may be in the form of a flexible film for curved and curved displays. In an alternative embodiment, the viewing angle control optical element 260 may be fabricated on a rigid substrate, such as a glass substrate.

Advantageously, a commercially available privacy mode control and/or ambient light control can be provided that does not require adjustment depending on the resolution of the pixel plane to avoid interference artifacts. Optical element 260 control angle of view can be optionally built into the spatial light modulator 48 in the factory.

When installing the optical element 260 to control the viewing angle shown in FIG. 1D, on an existing display device, it becomes possible to obtain the display device shown in any of FIGS. 1A-C.

The embodiments shown in FIG. 1A-D provide polar brightness control for light 400 that exits light spatial modulator 48. Thus, the switchable compensating retardation layer 300 (comprising the switchable liquid crystal retardation layer 301 and the passive compensating retardation layer 330) does not affect the brightness of light passing through the display input polarizer 210, the switchable liquid crystal retardation layer 300, and the secondary polarizer 318 along the normal-to-plane axis. of the switchable compensating retardation layer 300, but the switchable compensating retardation layer 300 does dim the light passing through it along an axis inclined to the normal to the plane of the switchable compensating retardation layer 300 in at least one of the switchable states of the switchable compensating retardation layer 300. Principles underlying this effect are described in more detail below with respect to FIGS. 29A-31E and are due to the presence or absence of a phase shift introduced by the switchable liquid crystal retardation layer 301 and the passive compensating retardation layer 330 for light passing along axes that are inclined at different angles with respect to the liquid crystal material of the switchable liquid crystal retardation layer 301 and the passive compensating retardation layer. layer 330. A similar effect is achieved in all devices described below.

Moreover, the use of the passive compensating retardation layer 330 in addition to the switchable liquid crystal retardation layer 301 improves performance, as will be described in more detail below with respect to a number of specific display devices and in comparison with a number of comparative examples described with respect to FIG. 19A-E.

It may be desirable to reduce the number of optical layers between the spatial light modulator 48 and the observer. The construction in which a plurality of retardation layers 300 is installed on the input side of the spatial light modulator 48 will be described below.

Fig. 2A is a schematic diagram illustrating a side perspective view of an optical stack of a directional display device comprising a backlight 20, a rear switchable retardation layer 300, a transmission spatial light modulator 48, the additional polarizer 318 comprising a reflective polarizer; and fig. 2B is a schematic diagram illustrating a front view of the order of optical layers in the optical stack shown in FIG. 2A.

The display device 100 includes a spatial light modulator 48; a display polarizer 210 located on the input side of the spatial light modulator 48 . An additional polarizer 318 is located on the same side of the spatial light modulator 48 as the display polarizer 210. The additional polarizer 318 is a reflective polarizer that functions in conjunction with the illumination 20 to achieve increased efficiency.

A plurality of retardation layers 300 are placed between the additional reflective polarizer 318 and the display polarizer 210. In accordance with FIG. 1A, the plurality of retardation layers 300 comprise: a switchable liquid crystal retardation layer 301 comprising a liquid crystal material layer 314 interposed between the display polarizer 210 and the reflective complementary polarizer 318; and a passive compensating retardation layer 330. Thus, a reflective complementary polarizer 318 is disposed on the input side of the display input polarizer 210 between the display input polarizer 210 and backlight 20, and a plurality of retardation layers 300 are provided between the reflective complementary polarizer 318 and the display input polarizer 210.

As will be described hereinafter, the transmission direction of the electrical vector 319 of the reflective complementary polarizer 318 is parallel to the transmission direction of the electrical vector 211 of the input polarizer 210 to enable the direction parameters to be switched.

In alternative embodiments, the additional polarizer 318 may comprise both a reflective polarizer and an absorbing dichroic polarizer, or may comprise only a dichroic polarizer.

The reflective complementary polarizer 318 may, for example, be a multilayer film, such as DBEF™ available from 3M Corporation, or may be a reticulated polarizer. The advantage is that the display efficiency can be improved by recycling light from the polarized reflection from the polarizer 372. Moreover, cost and thickness can be reduced compared to using an absorptive dichroic polarizer along with a reflective polarizer as an additional polarizer 318.

Compared to the design shown in Fig. 1A, the variant of FIG. 2A can provide improved frontal screen image contrast by reducing the number of layers between pixels 220, 222, 224 and the viewer.

Fig. 2C is a schematic diagram illustrating a side perspective view of an optical stack of a directional display device comprising a backlight 20, a rear switchable compensating retardation layer 300, and a transmissive spatial light modulator 48, with the additional polarizer 318 comprising a dichroic polarizer. Compared to the reflective complementary polarizer 318 shown in FIG. 2A, the dichroic secondary polarizer 318 does not return high-angle light back to the backlight and therefore may reduce off-major-axis brightness compared to the design shown in FIG. 2A. The advantage is the ability to improve privacy performance.

The construction and functions of the switchable compensating retardation layers 300 and the additional polarizer 318 shown in FIG. 1A-1C and FIG. 2A-2B.

Fig. 3 is a schematic diagram illustrating a side view of an exemplary construction of a switchable liquid crystal retardation layer 301 comprising a layer 314 of a negative dielectric anisotropy liquid crystal material 414. The substrates 312, 316 may include transparent electrodes 413, 415 disposed thereon and transverse surface alignment layers 409, 411 located on opposite sides of the switchable liquid crystal retardation layer 301. The transverse alignment layers 409, 411 may provide transverse alignment in the adjacent liquid crystal material 414 with an angle 407 pretilt.

The orientation of the liquid crystal material 414 in the x-y plane is determined by the pretilt direction of the alignment layers, so that there is a pretilt in each alignment layer, and for the pretilt of each alignment layer, there is a pretilt direction with a component 417a, 417b in the plane of the switchable liquid crystal retardation layer 301, which is parallel, or anti-parallel, or orthogonal to the transmission direction of the electrical vector 303 of the output polarizer 218 of the display.

The preslope 407a, 407b may, for example, be 88 degrees so that the component 417 is small in size to achieve disclination reduction in the rarefied (zero voltage) alignment state of the layer 314 of the liquid crystal material 414. Thus, the layer 314 is formed substantially by positive C -plates in zero stress design. In practice, the liquid crystal layer further has a slight O-plate characteristic provided by the pretilt of the transverse alignment layer at 407a and the residual component 417.

The switchable liquid crystal retardation layer 301 includes electrodes 413, 415 located near the retardation layer, the switchable liquid crystal retardation layer 301 and on opposite sides of the switchable liquid crystal retardation layer 301. The layer 314 of the liquid crystal material 414 can be switched by a voltage applied to the electrodes 413, 415.

In the off state, the liquid crystal material 414 is aligned such that component 418 is perpendicular to the plane of the retardation layer 301 and component 417 is in the plane of the retardation layer.

The retardation layer 330 in the figure is a negative passive O-plate containing a birefringent disc material 430. The phase shift of the passive compensating retardation layer 330 may be equal and opposite to the phase shift of the switchable liquid crystal retardation layer 301. The switchable liquid crystal retardation layer 301 may comprise first and second pretilts 407a, 407b; and the passive compensating retardation layer 330 comprises a compensating retardation layer with first and second pretilts 405a, 405b, wherein the first pretilt 405a of the compensating retardation layer 330 is equal to the first pretilt 407a of the liquid crystal retardation layer 301, and the second pretilt 405b of the compensating retardation layer 330 is equal to the second pretilt 307b of the liquid crystal retardation layer 330 layer 301.

Passive O-plates may contain, for example, cured reactive mesogen layers, which may be discotic reactive mesogens. The pretilt of the compensating retardation layer can be provided by curing the reactive mesogenic materials after alignment with a suitable alignment layer. The O-plates can also comprise double stretched polymer films, such as polycarbonate.

During operation, the switchable liquid crystal retardation layer 301 is configured to switch between two orientation states. The first state may provide an overview of the display for multiple viewers. The second state can provide a narrow angle mode for confidential work, or a reduction in stray light, for example, for night work. As will be described below, such elements can provide high transmission over a wide range of polar angles in wide-angle mode of operation, and limited brightness at the edges of the field of view in confidential mode of operation.

The operation of the display shown in FIG. 1A in wide mode representing the first state.

Fig. 4A is a schematic diagram illustrating a side perspective view of the design of the switchable compensating retardation layer 300 in wide-angle operation. The switchable liquid crystal retardation layer 301 is not energized. In FIG. 4A and the other schematic diagrams below, some layers of the optical stack have been omitted for clarity. For example, switchable liquid crystal retardation layer 301 is shown without substrates 312, 316.

The switchable liquid crystal retardation layer 301 includes two surface alignment layers adjacent to the liquid crystal material 414 on opposite sides thereof and configured to provide lateral alignment in the adjacent liquid crystal material 414. As described above, the liquid crystal material 414 may be provided with a pretilt of, for example, 88 degrees from the horizontal to correct alignment defects of the liquid crystal material 414.

The passive compensating retardation layer 330 comprises a negative C-plate retardation layer with an optical axis, which is the axis with the highest light velocity perpendicular to the plane of the retardation layer. Thus, the C-lamellar material 430 may have a negative dielectric anisotropy. The C-plates may contain transparent birefringent materials such as: polycarbonates or reactive mesogens, which are supported on a cross-aligning support such as: Zeonex™ cycloolefin polymer (COP); discotic polymers; and Nitto Denko™ double stretched polycarbonates.

Fig. 4B is a schematic diagram illustrating a graph of liquid crystal director angle 407 versus cell transmission fraction 440 of the switchable liquid crystal retardation layer, where the transmission fraction 440 varies from 0 for the position on the surface of the layer 409 to 1 for the position on the surface alignment layer 411.

For the vertically ordered mode with no applied voltage, as shown in FIG. 4A, the liquid crystal directors are tilted 407 by 88 degrees through the cell thickness as shown by the tilt profile 442. The slope profile for layer 314 may be the same as profile 442. The compensating retardation layer 330 may provide correction for the pretilt direction of the switchable liquid crystal retardation layer 301. with a pretilt of the liquid crystal layer provides only a small difference in the viewing characteristics off the main axis.

Thus, the off-major-axis phase shift for the compensating retardation layer 330 is substantially equal to and opposite to the off-major-axis phase shift for the switchable liquid crystal retardation layer 301 in the absence of an applied voltage.

Fig. 4C is a circuit diagram illustrating a side view of the propagation of emitted light from the spatial light modulator 48 through the optical stack shown in FIG. 1A, in wide-angle mode; and fig. 4D is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 4C in wide-angle mode.

An ideal compensating switchable retardation layer 300 comprises a compensating retardation layer 330 in combination with a changeable switchable liquid crystal retardation layer 301, wherein the dielectric constants, anisotropy, and anisotropy variance of the compensating retardation layer 330 have equal and opposite dielectric constants compared to the anisotropy and anisotropy variance of layer 314. The phase shift of the passive compensating retardation layer 330 is equal to and opposite to that of the switchable liquid crystal retardation layer 301.

Such an ideal compensating switchable retardation layer provides compensation for transmitted light in the first wide-angle mode of the layer 314 of the liquid crystal material 414 for all polar angles; and a narrow field of view in the side direction in the second privacy mode of the switchable liquid crystal retardation layer 301.

In addition, the direction of the optical axis of the compensating retardation layer 330 matches the direction of the optical axis of the liquid crystal retardation layer 301 in its wide-angle state. Such a compensating retardation layer 330 compensates for the phase shift of the liquid crystal retardation layer for all viewing angles and provides an ideal view in a wide-angle state without loss of brightness for all viewing directions.

The wide-angle transmission polar profile for non-ideal material selections will be described below.

In exemplary embodiments of the present disclosure, compensating retardation layers 330 are discussed, which may not fully compensate for the phase shift of the switchable liquid crystal retardation layer 301 due to small differences in material properties that are characteristic of the retardation layers 330, 301. However, such deviations are predominantly small, and with such deviations, it is possible to provide high performance for the wide-angle and narrow-angle conditions, which can be close to ideal performance.

Thus, if the switchable liquid crystal retardation layer 301 is in the first state of these two states, the switchable liquid crystal retardation layer 300 ensures that the polarization component 360, 361 is not converted at all to output light rays 400 passing through it perpendicular to the plane of the switchable retardation layer or under the sharp an angle to the perpendicular to the plane of the switchable retarding layer, such as light beams 402.

The polarization component 362 substantially coincides with the polarization component 360, and the polarization component 364 substantially coincides with the polarization component 361. Therefore, the angular transmission profile in FIG. 4D is essentially uniformly transmissive over the entire wide polar region.

In other words, if the liquid crystal material layer 414 is in the first orientation state of the two orientation states, the plurality of retardation layers 330, 301 provide no phase shift for light passing through them perpendicular to the plane of the retardation layers or at an acute angle to perpendicular to the plane of the retardation layers. 330, 301.

The advantage is that the different brightness levels of the viewing angle display in the first state remain substantially unchanged. Many users can easily see the display in a wide range of viewing angles.

Below will be described the functions of the compensating retardation layer 300 and the additional polarizer 318 in narrow-angle mode, for example, for use in the confidential mode of operation.

Fig. 5A is a schematic diagram illustrating a side perspective view of a construction of a switchable compensating retardation layer 300 in a confidential mode of operation, comprising a passive compensating retardation layer 330 with negative C-plates and a transversely ordered switchable liquid crystal retardation layer 301 in a confidential mode of operation.

The liquid crystal retardation layer 301 further comprises transparent electrodes 413, 415, such as ITO electrodes, passing through the switchable liquid crystal retardation layer 301. The electrodes 413, 415 control the switchable liquid crystal retardation layer 301 by adjusting the voltage applied to the electrodes 413, 415.

The control system 352 is configured to control the voltage applied by the voltage source 350 to the electrodes 413, 415 of the switchable liquid crystal retardation layer 301.

As shown in FIG. 4B, if a voltage is applied, the switchable liquid crystal retardation layer 301 exhibits a sloped slope profile 444 such that a phase shift change occurs for the layer 314 of the liquid crystal material 414.

By controlling the control voltage, the direction can be adjusted to obtain optimal privacy performance depending on the position of the observer. In another application, or to provide controlled brightness to off-axis viewers, such as in a car ride, if a passenger or driver may wish to set a particular visibility of the displayed image without total blackout, this can be achieved by intermediate voltage levels.

Fig. 5B is a circuit diagram illustrating a side view of the propagation of emitted light from the spatial light modulator 48 through the optical stack shown in FIG. 1A in the confidential mode of operation, wherein the switchable liquid crystal retardation layer 301 is oriented by the applied voltage.

In the present embodiments, the compensating switchable liquid crystal retardation layer 330 may be made in combination with the display polarizer 210, 218, 316 and the additional polarizer 318 to achieve an effect in which the output light brightness from the display device at an acute angle to the optical axis (outside the main axis) ) decreases, namely in comparison with the situation of the absence of a slowing layer. The compensating switchable liquid crystal retardation layer 330 may also be combined with the display polarizer 210, 218, 316 and the additional polarizer 318 to achieve the effect that the output light from the display device along the optical axis (main axis) is not reduced in brightness, namely compared to the situation where there is no slowing down layer.

The polarization component 360 from the output display polarizer 218 is transmitted by the output display polarizer 218 and enters the switchable compensating retardation layer 300. Principal axis light contains a polarization component 362 that is no different from component 360, while off-principal axis light contains a polarization component 364 that is is converted by the retarding layers of the switchable compensating retarding layer 300. The polarization component 361 is at least converted to a linear polarization component 364 and absorbed by the additional polarizer 318. More generally, the polarization component 361 is converted to a circular polarization component, which is partially absorbed by the additional polarizer 318.

Thus, if the retardation layer of the switchable liquid crystal retardation layer 301 is in the second orientation state of the two orientation states, the plurality of retardation layers 301, 330 provide no phase shift for light passing through them along an axis perpendicular to the plane of the retardation layers, and provide a non-zero total a phase shift for light passing through them at certain polar angles 363, which are at an acute angle to the perpendicular to the plane of the retardation layers 301, 330.

In other words, if the switchable liquid crystal retardation layer 301 is in the second state of these two states, the switchable liquid crystal retardation layer 330 does not fully convert the polarization component 360 of the light beams 400 passing through it along an axis perpendicular to the plane of the switchable retardation layer 301, but does the transformation of the polarization component 361 in the beams 402 of light passing through it at certain polar angles, which are at an acute angle to the perpendicular to the plane of the retardation layers 301, 330.

For narrow angle operation, below is an example of a material system.

Fig. 5C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 5V with the parameters described in Table 1.

Table 1

FIGURE Mode Passive(s) compensating
(s) slowing down
layer(s) Active LC retardation layer Type of Δn. d
/nm Orientation layers pretilt
/ deg. Δn. d
/nm Δε Voltage
/AT 4A and 4D Wide-
carbonic Negative-
body C-plate -700 transverse
transverse 88
88 810 -4.3 0 5A and 5C Confidential
social 2.2

In the present embodiments, the desired ranges for phase shifts and voltages have been determined by simulating retardation layer stops and experimenting with optical display stops.

The switchable liquid crystal retardation layer 300 includes a first surface alignment layer 409 located on the first side of the liquid crystal material layer 414, and a second surface alignment layer 411 located on the second side of the liquid crystal material layer 414, which is opposite the first side; wherein the first surface alignment layer 409 is a transverse alignment layer and the second surface alignment layer 411 is a transverse alignment layer, wherein the liquid crystal material layer provides a phase shift for light with a wavelength of 550 nm from 500 nm to 1000 nm, preferably from 600 nm up to 900 nm and most preferably from 700 nm to 850 nm.

If the passive compensating retardation layer 330 comprises a retardation layer with an optical axis perpendicular to the plane of the retardation layer, then the passive retardation layer provides a phase shift for light with a wavelength of 550 nm from -300 nm to -900 nm, preferably from -450 nm to -800 nm and most preferably -500 nm to -725 nm.

The polar distribution of light transmission shown in FIG. 5C results in a change in the polarity distribution of brightness for the light exiting from the spatial light modulator substrate 48 and, where appropriate, from the backlight 20.

The advantage is the ability to provide a low-brightness privacy display for a peeper off the main axis while maintaining high brightness for a main-axis viewer. A large polar area is provided, within which the display brightness is reduced for a peeper outside the main axis. Moreover, in the privacy mode of operation, the primary axis brightness remains substantially unchanged for the primary user of the display.

The voltage applied to the electrodes is zero for the first orientation state and is non-zero for the second orientation state. It is advantageous that in the wide-angle operation mode, additional power consumption can be dispensed with, and in the wide-angle operation mode, a failure mode is used to drive the switchable liquid crystal retardation layer 301.

The following is a description of the operation of the private display mode shown in FIG. 1A.

Fig. 6A is a circuit diagram illustrating a front perspective view of a transmitted light emission for a display operating in the privacy mode. The display device 100 may include white areas 603 and black areas 601. A viewer can see an image on the display if the difference in brightness between the visible areas 601, 603 can be sensed. view, which may be optical directional display windows. The peeper 47 sees dimmed beams 402 at viewing positions 27, which may be optical directional display windows. Regions 26, 27 also correspond to the regions on the main axis and outside the main axis shown in FIG. 5C.

Fig. 6B is a circuit diagram illustrating a front perspective view of the display shown in FIG. 1A when operating in confidential mode 1 with brightness changes as shown in FIG. 5C. Thus, the top view quadrants 530, 532, the bottom view quadrants 534, 536, and the side view positions 526, 528 provide reduced brightness, while the central top/bottom view areas 522, 520 and forward view provide much higher brightness.

It may be desirable to provide a dimmable display in a motor vehicle.

Fig. 6C is a schematic diagram illustrating a side view of a vehicle with a switchable directional display device 100 housed in a passenger compartment 602 of the vehicle 600 for entertainment and co-operation modes. The light cone 610 (for example, a cone of light within which the brightness is greater than 50% of the peak brightness) can be formed by distributing the brightness in the display 100 in the vertical direction, and is not switchable.

Fig. 6D is a schematic diagram illustrating a top view of a motor vehicle with a switchable directional display device 100 housed in the interior 602 of the vehicle and functioning like a privacy display in an entertainment mode of operation. The light cone 612 is formed with a narrow angular range so that the passenger 606 can see the display 100 while the driver 604 cannot see the image on the display 100. The advantage is that entertainment images can be displayed to the passenger 606 without distracting the driver 604.

Fig. 6E is a schematic diagram illustrating a top view of a motor vehicle with a switchable directional display device 100 housed in a vehicle interior 602 in a co-operation mode. The light cone 614 is formed with a wide angle range so that everyone in the passenger compartment can see the image on the display 100, for example, if the display is not working or if non-distracting images are displayed on the display.

Fig. 6F is a schematic diagram illustrating a top view of a vehicle with a switchable directional display device 100 housed in a vehicle interior 602 for night and day operation. Compared to the structures shown in Fig. 6C-E, the optical output rotates so that the vertical direction of the display is axially between driver 604 and passenger 606. Light cone 620 provides brightness for both driver 604 and passenger 606.

Fig. 6G is a schematic diagram illustrating a side view of a vehicle with a switchable directional display device 100 housed in a vehicle interior 602 in a night mode. In this case, the display may form a light cone 622 with a narrow angle output. The advantage is the ability to significantly reduce the brightness of ambient light that illuminates interior surfaces and occupants of the vehicle 602 and distracts the driver 604. The advantage is that both driver 604 and passenger 606 can view the displayed images.

Fig. 6H is a schematic diagram illustrating a side view of a vehicle with a switchable directional display device 100 housed in a vehicle interior 602 during daytime operation. In this case, the display may form a light cone 624 with a narrow angle output. The advantage is that everyone in the cabin 602 can easily see the display.

The displays 100 shown in FIG. 6C-H can be installed in other positions in the vehicle interior, such as driver instrument displays, center console displays, and seat back displays.

Fig. 7A-D are circuit diagrams illustrating output transmittance versus polar direction for four different control voltages from 2.05V to 2.35V in 0.1V steps. Thus, an applied voltage can control the positions of the dimming minima. field of view in confidential mode. Moreover, brightness minima can be controlled from elevations of zero or less to elevations that are in the upper quadrants of the polar profile.

Fig. 8 is a block diagram illustrating the control of the privacy display by the control system. Each of the devices described in this document can be controlled.

In the first step 870, the user may activate the private mode of operation.

If the first and additional compensating switchable liquid crystal retardation layers 300B are provided (as, for example, in the device shown in Fig. 22A, which is described below), the control system is in the second orientation state to control the voltage applied to the electrodes 413, 415 of the first mentioned switchable liquid crystal retardation layer 314A, and to control the voltage applied to the electrodes of the additional switchable liquid crystal retardation layer 314B; moreover, the total phase shift for light passing through the first mentioned switchable liquid crystal retardation layer 314A and the first mentioned passive compensating retardation layer 330A at certain polar angles at an acute angle to the perpendicular to the plane of the retardation layers 31A, 330A is different from the total phase shift for light passing through through an additional switchable liquid crystal retardation layer 314B and an additional passive compensating retardation layer 330B at the same polar angles.

Such confidential mode parameters can be entered manually (for example, using a keyboard) or through automatic detection using a sensor to detect the presence of a peeping person, as described, for example, in US Patent Publication No. 2017-0236494, which is hereby incorporated by reference in its entirety. . Optionally, the orientation of the display relative to the peeper can be further determined using the detector 873.

In the second step 872, the position of the peep can be determined, for example, using a camera, or setting parameters from the keyboard, or in another way. In an illustrative example, an "OFFICE" setting may be provided where it may be desirable to optimize privacy for peeps who move around the general office space and thus optimize performance for view quadrants viewed from above. By comparison, in the FLIGHT setting, it may be desirable to optimize the privacy level for seated peeps, while increasing the privacy level for lower elevations than was desirable for the OFFICE setting.

In the third step 876, the voltage applied to the switchable liquid crystal retardation layer 301 may be corrected, and in the fourth step 878, the LED profile may be adjusted by the control system.

Thus, the control system may further comprise means 872 for determining the position of the peeper 47 relative to the display device 100, and the control system is configured to adjust the voltage applied by the source 350 to the electrodes 413, 415 of the switchable liquid crystal retardation layer 314, depending on the position of the peeper 47 set.

The advantage is that the privacy mode of the display can be controlled to be optimized based on the viewer's viewing geometry.

Returning to the discussion of the present embodiments, additional designs for compensating switchable retardation layers 300 will be described below.

Fig. 9A is a schematic diagram illustrating a side perspective view of a construction of a switchable retardation layer in a private mode, comprising passive compensating retardation layers 308A, 308B with crossed A-plates and a transversely ordered switchable liquid crystal retardation layer 301; and fig. 9B is a schematic diagram illustrating a side perspective view of a structure of a switchable compensating retardation layer in a confidential mode, comprising passive compensating retardation layers with crossed A-plates and a transversely ordered switchable liquid crystal retardation layer.

Compared to the structures shown in Fig. 4A and FIG. 5A, compensating retardation layer 330 may alternatively comprise a pair of retardation layers 308A, 308B with optical axes in the plane of the retardation layers that intersect. Thus, the compensating retardation layer 330 comprises a pair of retardation layers 308A, 308B, each containing one A-plate.

Each of the pair of retardation layers 308A, 308B comprises a plurality of A-plates with respective optical axes 309A, 309B extending at different angles relative to each other. Each of the optical axes 309A, 309B of the retardation layer pair extend at 45° with respect to the electrical vector transmission direction, which is parallel to the electrical vector transmission direction 211 of the input display polarizer 210 in case the additional polarizer 318 is placed on the input side of the input display polarizer, or parallel direction 219 transmission of the electric vector of the output polarizer 218 display in case the additional polarizer 318 is placed on the output side of the input polarizer 218 display.

Fig. 9C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 9A in wide-angle mode; and fig. 9D is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 9B in the confidential mode of operation as shown in the exemplary embodiment of Table 2.

table 2

FIGURE Mode Passive(s) compensating
(s) slowing down
layer(s) Active LC retardation layer Type of Δn. d
/nm Orientation layers Prednac-lon
/ deg. Δn. d
/nm Δε Voltage
/AT 9A and 9C Wide-
carbonic Cross-
A-inserts +650 at 45°
+650 at 135° transverse
transverse 88
88 810 -4.3 0 9B and 9D Confidential
social 2.3

If the passive compensating retardation layer 330 comprises a pair of retardation layers with intersecting optical axes in the plane of the retardation layer, then each retardation layer of the pair of retardation layers provides a phase shift for light with a wavelength of 550 nm from 300 nm to 800 nm, preferably from 500 nm to 700 nm and most preferably from 550 nm to 675 nm.

The advantage is that it is possible to simplify the production of the A-plates and reduce costs compared to the C-plate retardation layer shown in FIG. 4A and FIG. 5A. Moreover, a zero-voltage state can be provided for the wide-angle operation, which minimizes power consumption in the wide-angle operation.

In the present embodiments, the term "cross" refers to an angle of substantially 90° between the optical axes of two retardation layers in the plane of the retardation layers. In order to reduce the cost of retardation layer materials, it is desirable to provide materials with a certain degree of deviation in the orientation of the retardation layer due to stretching errors, such as during film production. Deviations from the preferred directions in the orientation of the retardation layer can reduce forward luminance and increase minimum transmission. Angle 310A is preferably at least 35° and at most 55°, more preferably at least 40° and at most 50°, and most preferably at least 42.5° and at most 47.5°. Angle 310B is preferably at least 125° and at most 145°, more preferably at least 130° and at most 135°, and most preferably at least 132.5° and at most 137.5°.

At the moment of mechanical deformation, such as when a display is touched, the transversely ordered liquid crystal retardation layers 301 shown in FIG. 9A-9B may have undesirably long recovery times, creating visible mismatch artifacts. It would be desirable to provide a fast recovery after mechanical deformation.

Fig. 10A-10B are schematic diagrams illustrating a side perspective view of a design of a switchable retardation layer in wide-angle and confidential modes of operation, respectively, comprising a longitudinally ordered switchable liquid crystal retardation layer comprising a liquid crystal material 414 with positive dielectric anisotropy and a passive retardation layer 330 with negative C- plates for the first and second control voltages, respectively.

The switchable liquid crystal retardation layer further comprises surface alignment layers 431, 433 adjacent to the liquid crystal material layer 414, and each of them is configured to provide longitudinal alignment in the adjacent liquid crystal material. In other words, the switchable liquid crystal retardation layer comprises two surface alignment layers 431, 433 adjacent to and on opposite sides of the liquid crystal material layer 414, and each of them is configured to provide longitudinal alignment in the adjacent liquid crystal material 414.

Fig. 10C is a schematic diagram illustrating a plot of the liquid crystal director angle 407 as a function of the passage fraction 440 through the switchable liquid crystal retardation layer 301 shown in FIG. 10A for a number of different applied voltages. Fig. 10C differs from FIG. 4B with a smaller pretilt angle and its growth depending on the applied voltage. Profile 441 illustrates the tilt angle for liquid crystal material 414 at an applied voltage of 0 V, and tilt profile 443 illustrates director orientations for 2.5 V, and tilt profile 445 illustrates director orientations for 5 V. Thus, liquid crystal layers in desired switching states are typically beveled and compensation is provided by compensating retardation layers 330. Increasing the voltage from 2.5 V to 10 V gradually reduces the thickness of the retardation layer 301 in which the skewing occurs and advantageously increases the polar field of view within which transmission is maximized.

The resulting liquid crystal tilt component 419a, 419b is substantially larger than the components 417a, 417b shown in FIG. 5A compared to a direction perpendicular to the plane of the retardation layer.

The increased amplitude of the resulting component 419a, 419b may provide an increased recovery force after mechanical deformation compared to, for example, FIG. 9A. The advantage is the ability to reduce the sensitivity to mechanical deformations, for example when touching the display.

The operating voltage can be reduced below 10V for an acceptable wide-angle field of view, resulting in reduced power consumption; reduces costs and simplifies electrical control.

Fig. 11A-11C are schematic graphs illustrating the change in output transmission for the polar direction of transmitted light beams in a switchable compensating retardation layer comprising a longitudinally aligned liquid crystal retardation layer 301 and a negative C-lamella passive compensating retardation layer 330, similar to the display device shown in FIG. . 10A and 10B, in privacy mode and two wide angle modes for various drive voltages, including the embodiments shown in Table 3.

Table 3

FIGURE Mode Passive(s) compensating
(s) slowing down (s)
layer(s) Active LC retardation layer Type of Δn. d
/nm Orientation layers Prednac-lon
/ deg. Δn. d
/nm Δε Voltage
/AT 11A Confidential Negative C-plate -500 Longitudinal Longitudinal 2
2 750 +13.2 2.3 11B wide-angle-
ny 5.0 wide-angle-
ny 10.0

Desirable optical phase shift ranges for an active LC retardation layer 301 comprising longitudinal alignment layers 431, 433 on both substrates and a passive compensating retardation layer 330 with negative C-plates are described in Table 4 below.

Table 4

Active LCD layer
phase shift /nm Minimum negative phase shift
C-plates /nm Standard negative C-plate phase shift /nm Maximum negative phase shift
C-plates /nm 600 -300 -400 -500 750 -350 -450 -600 900 -400 -500 -700

The switchable liquid crystal retardation layer 300 thus comprises a first surface alignment layer 431 located on the first side of the liquid crystal material layer 414, and a second surface alignment layer 433 located on the second side of the liquid crystal material layer 414, which is opposite the first side; wherein the first surface alignment layer 409 is a longitudinal alignment layer and the second surface alignment layer is a longitudinal alignment layer; wherein the liquid crystal material layer provides a phase shift for 550 nm light in the range of 500 nm to 1000 nm, preferably in the range of 600 nm to 850 nm, and most preferably in the range of 700 nm to 800 nm. Thus, if the first and second alignment layers are in each case longitudinal alignment layers, and if the passive compensating retardation layer 330 comprises a retardation layer with an optical axis perpendicular to the plane of the retardation layer, then the passive retardation layer provides a phase shift for light with a wavelength of 550 nm 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.

The advantage is the ability to provide privacy off the main axis by reducing the brightness and increasing the level of privacy in the wide polar regions. In addition, compared to transverse ordering, resistance to visual artifacts caused by the flow of liquid crystal material in layer 314 can be improved.

A number of other optical structure and control configurations will be described below as shown in FIG. 10A.

The 5V mode provides lower power consumption and allows the use of cheaper electronics while still achieving an acceptable brightness sweep in wide-angle mode. The field of view in wide-angle mode can be further extended in 10 V mode.

Fig. 12A is a schematic diagram illustrating a side perspective view of a switchable compensating retardation layer structure in a confidential mode of operation, the structure comprising passive compensating retardation layers 308A, 308B with crossed A-plates and a longitudinally ordered switchable liquid crystal retardation layer 301; and fig. 12B-D are schematic graphs illustrating the change in polar direction output transmittance for transmitted light beams in a switchable compensating retardation layer 301 comprising longitudinally aligned liquid crystal material 414 and cross-A-plate passive retardation layers 308A, 308B, in confidential mode and wide angle. mode for various control voltages, including the corresponding embodiments shown in Table 5.

Table 5

FIGURE Mode Passive(s) Compensating(s) Slowing(s)
layer(s) Active LC retardation layer Type of Δn. d
/nm Orientation
rubbing layers Predna-
clone
/ deg. Δn. d
/nm Δε Voltage
/AT 12B Confi-den-
social Cross-
A-inserts +500 at 45°
+500 at 135° Longitudinal
Longitudinal 2
2 750 +13.2 2.3 Wide-
carbonic 5 12D Wide-
carbonic ten

Desirable optical phase shift ranges for an active LC retardation layer 301 comprising longitudinal alignment layers 409, 411 on both substrates and cross-positive A-plate retardation layers 308A, 308B are described in Table 6 below.

Table 6

Active LCD layer
phase shift /nm Minimum positive
phase shift
A-plates /nm standard positive
phase shift
A-plates /nm Maximum positive
phase shift
A-plates /nm 600 +300 +400 +600 750 +350 +500 +700 900 +400 +600 +800

Thus, if each of the first and second alignment layers is a longitudinal alignment layer; the liquid crystal material layer provides a phase shift for 550 nm light in the range of 500 nm to 1000 nm, preferably in the range of 600 nm to 850 nm, and most preferably in the range of 700 nm to 800 nm; and the passive compensating retardation layer 330 comprises a pair of retardation layers with intersecting optical axes in the plane of the retardation layer, then each retardation layer of the pair of retardation layers provides a phase shift for light with a wavelength of 550 nm from 300 nm to 800 nm, preferably from 350 nm to 650 nm and most preferably from 450 nm to 550 nm.

Moreover, cross A-plates can be easily made from cheap materials.

By way of example, a number of other optical structure and control configurations will be described below as shown in FIG. 12A. fig. 12C and FIG. 12D further show that by correcting for applied voltage and phase shifts, various wide-angle fields of view can be achieved, which is advantageous.

The structures of the optical stack structures will be further described below.

Fig. 13A and FIG. 13B are schematic diagrams illustrating side views of a portion of a display comprising a switchable compensating retardation layer and optical bonding layers 380. Optical bonding layers 380 may be provided for laminating films and substrates, achieving increased efficiency and reduced brightness at large viewing angles in confidential mode. Moreover, an air gap 384 can be provided between the spatial light modulator 48 and the switchable compensating retardation layer 300. modulator 48 light.

A passive compensating retardation layer 330 may be provided between the switchable liquid crystal retardation layer 301 and the spatial light modulator 48 as shown in FIG. 13A, or may be provided between the additional polarizer 318 and the switchable liquid crystal retardation layer 301 as shown in FIG. 13b. Both systems provide substantially the same optical performance.

In FIG. 13A shows that the optical layers are bonded to the outer sides of the substrates 312, 316. The advantage is that the substrates 312, 316 can be reduced in bending due to the accumulated stresses in the lamination process of the substrates 312, 316, as well as maintaining the plane parallelism of the display.

Similarly, a switchable compensating retardation layer 300 may be formed in which the output polarizer 218 is a display polarizer. The scatter that spatial light modulator 48 can provide, such as from phase structures at pixels 220, 222, 224, does not degrade the output luminance profile compared to designs in which a switchable compensating retardation layer 301 is located behind spatial light modulator 48.

It may be desirable to install an additional polarizer with an electrical vector transmission direction that is different from the electrical vector transmission direction of the display polarizer.

Fig. 14A is a schematic diagram illustrating a side perspective view of the construction of a switchable compensating retardation layer in a confidential mode of operation, comprising passive compensating retardation layers 308A, 308B with crossed A-plates and a longitudinally ordered switchable liquid crystal retardation layer 301 as described above, but additionally comprising passive rotating retardation layer 460.

The display polarizer 218 may provide an electrical vector transmission direction 219, which may extend, for example, at an angle 317 equal to 45 degrees in the case of an LCD display with twisted nematic liquid crystals. The additional polarizer 318 may be configured to provide vertically polarized light to a wearer who may be wearing polarized sunglasses that typically transmit vertically polarized light.

The passive rotating retardation layer 460 is different from the compensating retardation layer 330 of the present embodiments, and the principle of its operation is given below.

The passive rotating retardation layer 460 may comprise a birefringent material 462 and be a half-wave plate with a phase shift at a wavelength of 550 nm, such as 275 nm.

The passive rotational retardation layer 460 is characterized by such an orientation 464 of the axis with the highest light velocity, inclined at an angle 466, which can be 22.5 degrees to the direction of transmission 319 of the electric vector of the additional polarizer 318. Thus, the passive rotational retardation layer 460 rotates the polarization after the exit polarizer 218 so that the direction of polarization of the light incident on the compensating retardation layer 308B is parallel to the direction 319.

The passive rotational retardation layer 460 changes the polarization state along the main axis, providing an angular rotation of the polarization component after the display polarizer 218. In contrast, the compensating retardation layers 308A, 308B together do not change the polarization state along the main axis.

Moreover, the passive rotating retardation layer 460 induces a polarization rotation that may be substantially independent of the viewing angle. In contrast, compensating retardation layers 308A, 308B result in significant output brightness variations depending on the viewing angle.

Advantageously, a display can be provided with an output polarization direction 319 that is different from the polarization direction 219 of the display polarizer, for example to allow viewing with polarizing sunglasses.

In an alternative embodiment, the independent retardation layer 460 may be omitted, and the phase shift of the retardation layer 308B shown in FIG. 11A will increase to provide additional half-wave rotation over the phase shift of the retardation layer 308A. Continuing with the exemplary embodiment, the phase shift of the retardation layer 308B at 550 nm may be 275 nm greater than the phase shift of the retardation layer 308A. The advantage is the ability to reduce the number of layers, reduce complexity and cost.

It would be desirable to achieve a reduction in thickness and a reduction in the total number of optical components.

Fig. 15A is a schematic diagram illustrating a side perspective view of a construction of a switchable compensating retardation layer in a confidential mode of operation, comprising a longitudinally ordered switchable liquid crystal retardation layer 301 disposed between the first and second C-plate passive compensating retardation layers 330A, 330B, shown below in table 7.

Table 7

FIGURE Mode Passive (s) compensating (s) slowing down (s) layer (s) Active LC retardation layer Type of Δn. d
/nm Orientation layers Pre-tilt
/ deg. Δn. d
/nm Δε Voltage
ing
/AT 15B Wide-
carbonic negative
C-plate, 330A
negative
C-plate, 330B -275
-275 Longitudinal
Longitudinal 2
2 750 13.2 5.0 15A and 15C Confidential
social 2.6 17A and 17B Wide-
carbonic A-plate, 330A
A-plate, 330B 575
575 Longitudinal
Longitudinal 2
2 750 13.2 5.0 Confidential
social 2.6

Fig. 15B and FIG. 15C are schematic graphs illustrating output transmittance versus polar direction for transmitted light beams in the optical stack shown in FIG. 15A in wide-angle and privacy modes, respectively.

The passive compensating retarding layer 330 includes first and second C-plates 330A, 330B; and the switchable liquid crystal layer 301 is between the first and second C-plates 330A, 330B.

The passive compensating retardation layer 330A, 330B comprises two passive retardation layers with an optical axis perpendicular to the plane of the passive retardation layers, and a switchable liquid crystal retardation layer 301 is disposed between such two passive retardation layers. Thus, each of the first and second substrates 312, 316 in FIG. . 1A contains one of two passive retardation layers 330A, 330B.

The combination of two passive retardation layers 330A, 330B provides an overall phase shift for 550 nm light in the range of -300 nm to -800 nm, preferably in the range of -350 nm to -700 nm, and most preferably in the range of -400 nm up to -600 nm.

Fig. 16A contains a circuit diagram illustrating a side perspective view of a display comprising a switchable liquid crystal retardation layer 301 disposed between first and second substrates, each of which includes C-lamella passive compensating retardation layers 330A, 330B; and fig. 16B is a circuit diagram illustrating a side view of a display portion comprising a switchable liquid crystal retardation layer 301 disposed between first and second substrates each including C-plate passive compensating retardation layers 330A, 330B.

The first C-plate 330A includes a transparent electrode layer 415 and a liquid crystal alignment layer 411 formed on one side, and a second C-plate 330B includes a transparent electrode layer 413 and a liquid crystal alignment layer 409 formed on one side.

The liquid crystal material layer 314 is disposed between the first and second substrates 312, 316, and each of the first and second substrates 312, 316 includes one of the first and second C-plates 330A, 330B. The C-plates can be made from double stretched COP films that are coated with ITO to form the electrodes 413, 415 and have liquid crystal alignment layers 409, 411 deposited thereon.

The advantage is that the number of layers can be reduced compared to the design shown in FIG. 1, resulting in reduced thickness, cost, and manufacturing complexity. Moreover, the C-plates 330A, 330B may be flexible substrates and may provide a flexible privacy display.

The liquid crystal material layer 314 is desirably placed between the first and second A-plate substrates.

Fig. 17A is a schematic diagram illustrating a side perspective view of the design of the switchable compensating retardation layer 300 in wide-angle operation, comprising a longitudinally arranged switchable liquid crystal retardation layer 301 interposed between the first and second passive compensating retardation layers 330A, 330B with crossed A-plates, as described above; and fig. 17B and FIG. 17C are schematic graphs illustrating output transmittance versus polar direction for transmitted light beams for the structure shown in FIG. 17A, when switched to wide-angle and confidential mode of operation, respectively, containing additional exemplary embodiments shown in Table 7.

In contrast to the design shown in Fig. 15A, the advantage is that A-plates can be manufactured at a lower cost than C-plates.

Hybrid ordered structures containing longitudinal and transverse alignment layers will be described below.

Fig. 18A is a schematic diagram illustrating a side perspective view of a construction of a switchable retardation layer in a private mode, comprising a longitudinally and transversely ordered switchable liquid crystal retardation layer 301, containing a liquid crystal material 423 and a passive C-plate negative retardation layer 330.

Fig. 18B-18C are schematic graphs illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 18A in wide-angle and privacy modes, respectively, which are provided by the design shown in Table 8.

Table 8

FIGURE Mode Passive (s) compensating (s) slowing down (s) layer (s) Active LC retardation layer Type of Δn. d
/nm Orientation layers Pre-tilt
/ deg. Δn. d
/nm Δε Voltage
/AT Wide-
carbonic negative
C-plate -1100 Longitudinal Transverse 2
88 1300 +4.3 15.0 18A Confidential 2.8 Not shown Wide-
carbonic Cross
A-plates +1100
at 45°
+1100
at 135° transverse
Longitudinal 2
88 1300 +4.3 15.0 Not shown Confidential 2.8

The hybrid ordered switchable liquid crystal retardation layer 301 has a variable slope so that effective birefringence is reduced for a given cell material and cell thickness. Therefore, the structure of the retardation layer must be adjusted in order to provide compensation compared to structures with the same alignment layers. The switchable liquid crystal retardation layer 330 includes a first surface alignment layer 441 located on the first side of the liquid crystal material layer 423, and a second surface alignment layer 443 located on the second side of the liquid crystal material layer 423, which is opposite the first side. The first surface alignment layer 441 is a transverse alignment layer capable of providing transverse alignment in the adjacent liquid crystal material 423, and the second surface alignment layer 443 is a longitudinal alignment layer configured to provide longitudinal alignment in the adjacent liquid crystal material 423.

Moreover, the optimal designs of the retardation layers are related to the relative position of the passive compensating retardation layer 330 with respect to the transverse and longitudinal alignment layers.

If the surface alignment layer 443, configured to provide longitudinal alignment, is between the liquid crystal material layer 423 and the compensating retardation layer 330, then the liquid crystal material layer 423 provides a phase shift for light with a wavelength of 550 nm in the range from 500 nm to 1800 nm, preferably in the range from 700 nm to 1500 nm, and most preferably in the range from 900 nm to 1350 nm. If a surface alignment layer 443 configured to provide longitudinal alignment is between the liquid crystal material layer 423 and the compensating retardation layer 330, the passive compensating retardation layer may comprise a retardation layer 330 with an optical axis perpendicular to the plane of the retardation layer, as shown in FIG. 18A, wherein the passive retardation layer 330 provides a phase shift for 550 nm light in the range -300 nm to -1600 nm, preferably in the range -500 nm to -1300 nm, and most preferably in the range -700 nm to - 1150 nm; or in an alternative embodiment, the passive compensating retardation layer may comprise a pair of retardation layers (not shown) with intersecting optical axes in the plane of the retardation layers, each retardation layer of the pair of retardation layers providing a phase shift for light with a wavelength of 550 nm 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.

If the surface alignment layer 441, configured to provide transverse ordering, is between the liquid crystal material layer 423 and the compensating retardation layer 330, then the liquid crystal material layer 423 provides a phase shift for light with a wavelength of 550 nm in the range from 700 nm to 2000 nm, preferably in the range from 1000 nm to 1700 nm, and most preferably in the range from 1200 nm to 1500 nm. If a surface alignment layer 441 capable of providing lateral alignment is between the liquid crystal material layer 423 and the compensating retardation layer 330, the passive compensating retardation layer may comprise a retardation layer 330 with an optical axis perpendicular to the plane of the phase plate, as shown in FIG. 18A, wherein the passive retardation layer provides a phase shift for 550 nm light in the range -400 nm to -1800 nm, preferably in the range -700 nm to -1500 nm, and most preferably in the range -900 nm to -1300 nm; or in an alternative embodiment, the passive compensating retardation layer may comprise a pair of retardation layers (not shown) with intersecting optical axes in the plane of the retardation layers, each retardation layer of the pair of retardation layers providing a phase shift for light with a wavelength of 550 nm 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.

Compared to the design shown in Fig. 5A, the confidential mode of operation can advantageously provide increased resistance to material flow visualization when the liquid crystal retardation layer is pressed.

For comparison with the present embodiments, the characteristics of retardation layers placed between parallel polarizers in serial placement will be described below. First of all, the field of view of the longitudinally ordered liquid crystal retardation layer 301 for two different driving voltages will be described below.

Fig. 19A is a schematic diagram illustrating a side perspective view of a structure of a longitudinally ordered switchable liquid crystal retardation layer 390; fig. 19B is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 19A for the first applied voltage; and fig. 19C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 19A for a second applied voltage that is larger than the first applied voltage, comprising the structure shown in Table 9. The longitudinally ordered switchable liquid crystal retardation layer 390 corresponds to the switchable liquid crystal retardation layer 330 described above, and can be applied as a switchable liquid crystal retardation layer in any of devices described in this document.

Fig. 19D is a schematic diagram illustrating a side perspective view of a passive C-plate retardation layer 392 positioned between parallel polarizers; and fig. 19E is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 19D containing the structure shown in Table 9. The C-laminated passive retardation layer 392 corresponds to the passive compensating retardation layer 330 and can be applied as at least one passive compensating retardation layer in any of the devices described herein.

Table 9

FIGURE Passive (s) compensating (s) slowing down (s) layer (s) Central polarizer Active LC retardation layer Type of Δn. d
/nm Orientation layers Pre-
incline
/ deg. Δn. d
/nm Δε Voltage
ing
/AT 19A and 19B - - - Longitudinal
Longitudinal one 900 +15 2.4 20.0 19D and 19E Negative
C-plate -700 - - - - - - 20A and 20B Negative
C-plate -700 Yes Longitudinal
Longitudinal one 900 +15 2.4 20.0 21A and 21B Negative
C-plate -700 Not Longitudinal
Longitudinal one 900 +15 2.4 20.0

Fig. 20A is a schematic diagram illustrating a side perspective view of the construction of a longitudinally ordered switchable liquid crystal retardation layer 390 disposed between parallel polarizers 394, 396 in series with a field-of-view controlling passive retardation layer comprising a C-plate retardation layer 392 disposed between the parallel polarizers. 396, 398; fig. 20B is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 20A for the first applied voltage; fig. 20C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 20A for a second applied voltage that is greater than the first applied voltage, containing the structure shown in Table 9.

Fig. 21A is a schematic diagram illustrating a side perspective view of the structure of the longitudinally ordered switchable liquid crystal retardation layer 301 in series with the C-plate compensating retardation layer 330, with the longitudinally ordered switchable liquid crystal material 712 and the C-plate compensating retardation layer 330 interposed between one a pair of parallel polarizers; fig. 21B is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 21A for the first applied voltage; and fig. 21C is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 21A for a second applied voltage that is greater than the first applied voltage, containing the structure shown in Table 9.

Surprisingly, optimal conditions for operating at maximum field of view provide equal and opposite net phase shifts for the compensating retardation layer 330 compared to the switchable liquid crystal retardation layer 301 in its off state. An ideal compensating retardation layer 330 and a switchable liquid crystal retardation layer 301 can provide (i) no change in input light characteristics in wide-angle mode of operation and (ii) an optimal side-angle reduction for off-major-axis positions for all elevations if they are capable of providing narrow state. This concept can be applied to all display devices described in this document.

It may be desirable to increase brightness reduction for off-major-axis viewing positions. In particular, it would be desirable to provide a greater privacy reduction for a wide-angle backlit liquid crystal display.

Fig. 22A is a circuit diagram illustrating a side perspective view (and note, an inverted view where the z-axis along which the emitted light is directed downwards) of a switchable compensating retardation layer structure in a private mode of operation, comprising: a first switchable compensating retardation layer 300A ( in this case, a passive compensating retardation layer 330A with negative C-plates and a transversely ordered switchable liquid crystal retardation layer 301A, but this is only an example, they can be replaced by any designs of the plurality of retardation layers described herein), located between the display output polarizer 218 and an additional polarizer 318A; and an additional switchable compensating retardation layer 300B (in this case, a passive compensating retardation layer 330B with negative C-plates and a transversely ordered switchable liquid crystal retardation layer 301B, but this is only an example, they can be replaced by any of the multiple retardation layer designs described herein), located between the first mentioned additional polarizer 318A and another additional polarizer 318B with the electric vector transmission direction 319B.

In an alternative embodiment, the first mentioned additional polarizer 318A may be located on the input side of the input display polarizer 210, in which case another additional polarizer 318B may be located on the input side of the input display polarizer 210 between the first mentioned additional display polarizer 318A and the backlight 20, and the additional switchable the compensating retardation layer 300B may be located between another additional polarizer 318B and the first mentioned additional polarizer 318A.

In these two alternative embodiments, each of the first plurality of retardation layers 300A and the additional plurality of retardation layers 300B is positioned between a respective pair of polarizers and therefore acts like the respective structure in the devices described above.

The pretilt directions 307A, 309AA of the alignment layers 307A, 309AA of the additional switchable liquid crystal retardation layer 301A may include a component in the plane of the liquid crystal layer that is ordered parallel, or antiparallel, or orthogonal to the pretilt directions of the alignment layers 307B, 309AB of the first switchable liquid crystal retardation layer 301B. In the wide-angle operation mode, both switchable liquid crystal retardation layers 301A, 301B are activated to provide a wide viewing angle. In the confidential mode of operation, the switchable liquid crystal retardation layers 301B, 301A can cooperate with each other to achieve a more significant dimming and thereby improve privacy on a single axis, which is advantageous.

The phase shifts provided by the first switchable liquid crystal retardation layer 301B and the additional liquid crystal retardation layers 301A may be different from each other. The switchable liquid crystal retardation layer 301B and the additional switchable liquid crystal retardation layer 301A may be activated by a common voltage, and the liquid crystal material 408B in the first switchable liquid crystal retardation layer 301B may be different from the liquid crystal material 408A in the additional switchable liquid crystal retardation layer 301A. Thus, chromatic changes in polar brightness profiles can be reduced, as shown elsewhere in this document, in order to advantageously improve off-major-axis color rendering.

In an alternative embodiment, the switchable liquid crystal retardation layers 301B, 301A may have orthogonal ordering such that both horizontal and vertical dimming is achieved to advantageously provide privacy in landscape and portrait.

In an alternative embodiment, layers 301A, 301B may provide different control voltages. The advantage is the ability to more effectively control the sweep of the brightness profile or switch between landscape and confidential mode.

The phase shift control layer 330B may include a passive compensating retardation layer 330A located between the first additional polarizer 318A and another additional polarizer 318B. More generally, the switchable liquid crystal retardation layer 301A can be eliminated and a fixed dimming can be provided by passive compensating retardation layers 330A. For example, a decrease in brightness in the view quadrants can be achieved by layer 330A alone. The advantage is the ability to provide an expansion of the area of the polar region to reduce the brightness. In addition, a backlight with a wider brightness output angle than a collimating backlight can be used, increasing the visibility of the display in wide angle mode.

Fig. 22B is a circuit diagram illustrating a side perspective view of the construction of the first switchable compensating retardation layer located at the input of the liquid crystal display and the second switchable compensating retardation layer located at the output of the liquid crystal display.

The first mentioned additional polarizer 318A is located on the input side of the display input polarizer 210 between the display input polarizer 210 and the backlight 20, and the display device further comprises: another additional polarizer 318B located on the output side of the display output polarizer 218; and additional retardation layers 301B, 330B located between another additional polarizer 318B and the display output polarizer 218. The additional retardation layers comprise an additional switchable liquid crystal retardation layer 301B with a liquid crystal material layer 414B and electrodes 413B, 415B on opposite sides of the liquid crystal material layer 414B, wherein the liquid crystal material layer 414B can be switched between two orientation states by a voltage applied to the electrodes 413B, 415B .

Fig. 22C is a circuit diagram illustrating a side perspective view of an optical viewing angle control element comprising a first passive compensating retardation layer, a first switchable liquid crystal retardation layer, a first driving polarizer 250, a second passive compensating retardation layer, a second switchable liquid crystal retardation layer, and a second driving polarizer. 250. Such an element may provide similar performance to the design shown in FIG. 22B when used with a display device 100 comprising a spatial light modulator 48 .

It may be desirable to provide entertainment and nighttime modes of operation in a motor vehicle.

Fig. 22D is a circuit diagram illustrating a top view of a motor vehicle with a switchable directional display device such as that shown in FIG. 22B housed in vehicle interior 602 for daytime and/or shared modes of operation; and fig. 22E is a schematic diagram illustrating a side view of a vehicle with a switchable directional display placed in a vehicle interior 602 for daytime and/or shared modes of operation. The light cone 630, 632 is formed with a wide field of view, and therefore the display is predominantly visible to many in the cabin.

Fig. 22F is a circuit diagram illustrating a top view of a motor vehicle with a switchable directional display device such as that shown in FIG. 22B placed in the interior 602 of the vehicle for night and/or entertainment modes of operation; and fig. 22G is a schematic diagram illustrating a side view of a vehicle with a switchable directional display placed in the interior 602 of the vehicle for night and/or entertainment operation. The light cone 634, 636 is formed with a narrow field of view, and therefore the display is predominantly visible to only one person in the cabin. The advantage is the ability to limit the intensity of stray light during night operation, which increases driver safety. Moreover, the reflection of the display on the windshield 601 is reduced, minimizing the chance of driver 604 being distracted.

It would be desirable to provide a limited field of view for the light cones that wide-angle illumination and emissive light modulators provide, and at low cost.

Fig. 23A is a schematic diagram illustrating a side perspective view of the structure of the reflective complementary polarizer 318A and the passive retardation layer 270 located at the input of the spatial light modulator 48. At the output of the spatial light modulator 48 are a plurality of retardation layers 300, similar to those used in the device shown in FIG. 22V. Compared to the design shown in Fig. 22B, a passive retardation layer 270 is provided in place of the rear compensating switchable liquid crystal retardation layer 300A. The advantage is cost savings and thickness reduction while maintaining low off-axis brightness in privacy mode and acceptable viewing angle in wide angle mode.

Fig. 23B is a circuit diagram illustrating a side perspective view of an optical viewing angle control element comprising a passive retardation layer 270, a first driving polarizer 250A, a passive compensating retardation layer 330, a switchable liquid crystal retardation layer 301, and a second driving polarizer 250B. An optical element is located in front of the spatial light modulator 48 to provide a display device.

The following is a description of various passive retardation layers 270, any of which may be applied to any of the devices described above.

Fig. 24A is a schematic diagram illustrating a side perspective view of an optical stack of a passive retardation layer 270 comprising a retardation layer 272A with negative O-plates inclined in a plane orthogonal to the transmission direction of the electric vector of the display polarizer and a retardation layer 272B with negative C-plates, and configured to provide a change in the field of view of the display device; and fig. 24B is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams in the passive retardation layer according to FIG. 24A containing the structure shown in Table 10.

Table 10

FIGURES Passive slow layer Layer Type of Angle out of plane /° Angle in plane /° Δn. d
/nm 24A and 24B 272A Negative O-plate 65 90 -550 272B Positive C-plate 90 0 +500

Thus, the passive retardation layer 270 comprises a passive retardation layer 272A, which is an optical axis negative O-plate with an in-plane component of the passive retardation layer 272A and a component perpendicular to the plane of the passive retardation layer 272A. Moreover, the in-plane component of the passive retarding layer extends at a 90° angle with respect to the electrical vector transmission direction, which is parallel to the electrical vector transmission direction 219 of the display polarizer 218. The passive retardation layer 272B comprises a passive retardation layer with an optical axis perpendicular to the plane of the passive retardation layer.

The advantage is the ability to reduce the brightness for lateral viewing directions. The mobile display can be easily rotated around a horizontal axis, while maintaining privacy in case of peepers outside the main axis in the lateral direction.

Fig. 24C is a schematic diagram illustrating a side perspective view of an optical stack of a passive retardation layer 270 comprising crossed A-plates and a positive O-plate; and fig. 24D is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams in the passive retardation layer according to FIG. 24C containing the structure shown in Table 11.

Table 11

FIGURES Passive slow layer Layer Type of Angle out of plane /° Angle in plane /° Δn. d
/nm 24C and 24D 272A Positive A-plate 0 45 +500 272B Positive A-plate 0 135 +500 Positive O-plate 65 90 +550

Thus, the passive retardation layer 270 comprises passive retardation layers 272A, 272B, which are crossed A-plates, and an optical axis retardation layer 272C with an in-plane component of the passive retardation layer 272C and a component perpendicular to the plane of the passive retardation layer 272C. The in-plane component of the passive retarding layer extends at a 90° angle with respect to the electrical vector transmission direction, which is parallel to the electrical vector transmission direction 219 of the display polarizer 218. The advantage is the ability to reduce the brightness for lateral viewing directions. The mobile display can be easily rotated around a horizontal axis, while maintaining privacy in case of peepers outside the main axis in the lateral direction.

It may be desirable to provide brightness reduction in both the lateral and vertical directions.

Fig. 24E is a schematic diagram illustrating a side perspective view of an optical stack of passive retardation layers 272A-D comprising two pairs of crossed A-plates; and fig. 24F is a graph illustrating output transmittance versus polar direction for transmitted light beams in the passive retardation layer according to FIG. 24E containing the structure shown in Table 12.

Table 12

FIGURES Passive Control Slow Layer Layer Type of Angle out of plane /° Angle in
plane /° Δn. d
/nm 24E, 24F 272A Positive A-plate 0 45 700 272B 90 0 272D 135

Thus, retardation layer 270 comprises a pair of passive retardation layers 272A, 272D with intersecting optical axes in the plane of the retardation layers. Each of the pair of retardation layers contains a plurality of A-plates with respective optical axes extending at different angles relative to each other. The pair of passive retardation layers 272B, 272C has optical axes that extend at 90° and 0°, respectively, with respect to the electrical vector transmission direction, which is parallel to the electrical vector transmission direction 211 of the display polarizer 210.

The pair of passive retardation layers 272A, 272D has optical axes that extend at angles of 45° and 135°, respectively, with respect to the electrical vector transmission direction 211, which is parallel to the electrical vector transmission direction of the display polarizer 218.

The display further comprises another pair of passive retardation layers 272B, 272C located between the first mentioned pair of passive retardation layers 272A, 272D with intersecting optical axes in the plane of the retardation layers. The additional pair of passive retardation layers 272B, 272C has optical axes that extend at 0° and 90°, respectively, with respect to the electrical vector transmission direction 211, 317, which is parallel to the electrical vector transmission direction of the display polarizer 210, 316.

The phase shift of each A-plate for 550 nm light may be in the range of 600 nm to 850 nm, preferably in the range of 650 nm to 730 nm, and most preferably in the range of 670 nm to 710 nm. An advantage is the ability to reduce the change in color of the absorbed light from the central viewing position to the viewing position off the main axis.

In further exemplary embodiments, angle 273A is preferably at least 40° and at most 50°, more preferably at least 42.5° and at most 47.5°, and most preferably at least 44° and at most 46°. Angle 273D is preferably at least 130° and at most 140°, more preferably at least 132.5° and at most 137.5°, and most preferably at least 134° and at most 136°.

In additional exemplary embodiments, the inner pair of retardation layers 272B, 272C may be manufactured to less stringent tolerances than the outer pair of retardation layers 272A, 272D. Angle 273B is preferably at least -10° and at most 10°, more preferably -5° and at most 5°, and most preferably at least -2° and at most 2°. The angle 273C is preferably at least 80° and at most 100°, more preferably at least 85° and at most 95°, and most preferably at least 88° and at most 92°.

In the present embodiment, a transmission profile is provided that has a certain rotational symmetry. The advantage is the ability to provide a confidential display with reduced visibility of the image with a wide field of view for lateral or vertical viewing positions of the peeping. In addition, such a design can be used to provide an improved privacy mode of operation for landscape and portrait orientations of a mobile display. Such a structure can be installed in a vehicle in order to reduce the intensity of stray light for passengers outside the main axis, as well as to reduce the intensity of light falling on the windshield and other glass surfaces of the vehicle.

It would be desirable to provide improved image rendering by adding masking to the confidential image seen by the peeping 47 in the confidential mode of operation.

Fig. 25A is a schematic diagram illustrating a side perspective view of a construction of a switchable retardation layer in a confidential mode of operation, comprising a passive compensating retardation layer with negative C-plates and a transversely ordered switchable liquid crystal retardation layer, further comprising a structured electrode layer 415. Thus, the electrodes 415a , 415b, 415c are structured to provide at least two structured regions.

At least one of the electrodes 413, 415 may be patterned, in this example, patterned is electrode 415 with regions 415a, 415b, 415c controlled by respective voltage sources 350a, 350b, 350c with voltage values Va, Vb, Vc. Gaps 417 may be provided between the electrode regions 415a, 415b, 415c. Thus, the slope of the material 414a, 414b, 414c can be independently adjusted to render the masking structure at different brightness levels when viewed off the main axis.

Thus, the switchable liquid crystal retardation layer located between the display polarizer 218 and the additional absorptive polarizer 318 is controlled by the address electrodes 415a, 415b, 415c and the common electrode 413. The address electrodes may be structured to provide at least two structured regions containing the electrode 415a and gap 417.

Fig. 25B is a circuit diagram illustrating illumination (front perspective view) for the main viewer and peeper on a privacy display with masking and brightness control. The display device 100 may include dark image data 601 and white background data 603 visible to the main viewer 45 in the 26p viewport. In comparison, the peeping 47 can see the masked image as shown in FIG. 25C, which is a schematic diagram illustrating lighting (side perspective view) for a peeper on a privacy masking display with brightness control. Thus, in the white background areas 603, a masking structure can be provided that creates mixed brightness in the white area 603. Thus, the patterned areas of the electrodes 415a, 415b, 415c are masking structures. At least one of the structured areas is independently addressable and configured to operate in a private mode.

The structured regions may be configured to provide masking for a plurality of spatial frequencies by controlling the structures that are activated in the confidential mode of operation. In an illustrative example, a presentation with text 20 mm high may be presented. A masking pattern with a similar pattern size can be displayed using the first electrode pattern control. In the second example, a large area photograph can be presented that is best seen by a peeper 47 . lower spatial frequency.

Advantageously, by adjusting the voltages Va, Vb, Vc in layer 892, a controllable masking structure can be provided. When operating in live view mode, the masking structure may remain substantially invisible. Moreover, the masking image can be removed by applying the same Va, Vb and Vc.

It would be desirable to provide such an off-principal-axis luminosity to the peeper that is, for example, less than 1%. The off-major-axis low-brightness directional backlight devices that can be used with the compensating switchable liquid crystal retardation layers of the present embodiments will be described below. Directional illumination devices will be further described below.

Similar structuring can be applied to any of the devices described herein.

It would be desirable to provide additional brightness reduction off the main axis due to directional illumination from the spatial light modulator 48 . Directional illumination from a spatial light modulator 48 through the use of directional illumination devices 20 will be described below.

Fig. 26A is a circuit diagram illustrating a front perspective view of the directional illumination 20, and FIG. 26B is a schematic diagram illustrating a front perspective view of an omnidirectional backlight 20, any of which may be used in any of the devices described herein. Thus, the directional illumination 20, as shown in FIG. 26A forms a narrow cone 450 while non-directional illumination 20 as shown in FIG. 26B forms a cone 452 with a wide-angle distribution of outgoing light beams.

Fig. 26C is a schematic diagram illustrating brightness variation with side viewing angle for a number of different backlight designs. The graph shown in Fig. 26C may be a cross section of the polar field profiles described herein.

The Lambert emitter backlight features an 846 brightness profile that is independent of the viewing angle.

Conventional wide-angle backlights are characterized by sweeping at large angles such that the full width at half maximum 866 relative brightness may be greater than 40°, preferably greater than 60°, and most preferably greater than 80°. In addition, the relative brightness 864 at +/-45° is preferably greater than 7.5%, more preferably greater than 10%, and most preferably greater than 20%.

In comparison, directional illumination 20 is characterized by sweeping at high angles such that the full width at half maximum 862 relative brightness may be less than 60°, preferably less than 40°, and most preferably less than 20°. Moreover, the backlight 20 can provide brightness at polar angles with respect to the normal to the spatial light modulator 48 greater than 45 degrees, which is a maximum of 33% of the brightness along the normal to the spatial light modulator 48, preferably a maximum of 20% of the brightness along the normal to the spatial light modulator 48 light and most preferably a maximum of 10% brightness along the normal to the spatial modulator 48 light.

Scattering and diffraction of the spatial light modulator 48 can reduce the effectiveness of the confidential mode of operation if the switchable retardation layer 300 is located between the display input polarizer 210 and the additional polarizer 318. Brightness at polar angles with respect to the normal to the spatial light modulator in excess of 45 degrees can be increased in those designs. , in which the switchable retardation layer 300 is located between the output display polarizer 218 and the additional polarizer 318, compared with designs in which the switchable retardation layer 300 is located between the input display polarizer 210 and the additional polarizer 318.

An advantage is the ability to provide reduced brightness off the main axis for the design shown in FIG. 1A compared to FIG. 2A with the same illumination 20.

In the exemplary embodiment shown in FIG. 1A, brightness at polar angles with respect to the normal to the spatial light modulator 48 greater than 45 degrees can be as high as 18%, while in the exemplary embodiment shown in FIG. 2A, the brightness at polar angles with respect to the normal to the spatial light modulator 48 exceeding 45 degrees can be at most 10%. The advantage is that the embodiment shown in FIG. 1A can provide a wider viewing area in a wide-angle mode of operation while providing a viewing area in a privacy mode of operation similar to the embodiment shown in FIG. 2A.

Such brightness profiles may be provided by the directional illuminations 20 described below, or may also be provided by wide angle illuminations in combination with yet another additional polarizer 318B and passive retardation layers 270 or an additional compensating switchable liquid crystal retardation layer 300B.

Fig. 27A is a circuit diagram illustrating a side view of a switchable directional display device 100 including a switchable liquid crystal retardation layer 300 and a backlight 20. The backlight 20 shown in FIG. 27A can be applied to any of the devices described herein comprising an imaging waveguide 1 illuminated by a set of light sources 15 through an input end 2. FIG. 27B is a circuit diagram illustrating a rear perspective view of the mode of operation of the imaging waveguide 1 shown in FIG. 27A in the narrow angle mode of operation.

The imaging waveguides 1 are of the same type as those described in US Pat. No. 9,519,153, which is incorporated herein by reference in its entirety. The waveguide 1 has an input end 2 extending laterally along the waveguide 1. A set of light sources 15 is located along the input end 2 and supplies light to the waveguide 1.

[409] The waveguide 1 also has opposing first and second guide surfaces 6, 8 extending through the waveguide 1 from the input end 2 to the reflective end 4 to guide the input light at the input end 2 back and forth along the waveguide 1. The second guide surface 8 has a plurality light output elements 12 facing the reflective end 4 and configured to reflect at least a portion of the light directed back through the waveguide 1 from the reflective end 4 from various input positions along the input end 2 in various directions, which depend on the position of the input, through the first guide surface 6.

In operation, the light rays pass from the set of light sources 15 through the input end and are directed to the reflective end 4 between the first and second guide surfaces 6, 8 without loss. The reflected rays fall on the facets 12 and exit when reflected as light rays 230 or when transmitted as light rays 232 . The transmitted light beams 232 are directed back through the waveguide 1 by the faces 803, 805 of the rear reflector 800. The operation of the rear reflectors is further described in US Pat. No. 10,054,732, which is incorporated herein by reference in its entirety.

As shown in FIG. 27B, the optical power of the curved reflective end 4 and facets 12 forms an optical window 26 that is passed through the spatial light modulator 48, and it contains an axis 197 that generally extends along the optical axis 199 of the waveguide 1. A similar optical window 26 forms the transmitted rays. 232 lights that the rear reflector 800 reflects.

Fig. 27C is a schematic graph illustrating a field-of-view luma pattern for the output signal shown in FIG. 27B when used in a display device without a switchable liquid crystal retardation layer.

Thus, for an off-major-axis viewing position, those observed by peepers 47 may have a reduced brightness, such as 1% to 3% of the center peak brightness at 0 degrees elevation and +/-45 degrees lateral angle. Further off-major-axis brightness reduction is achieved by the plurality of retardation layers 301, 330 of the present embodiments.

Below, another type of directional backlight with low brightness outside the main axis will be described.

Fig. 28A is a circuit diagram illustrating a side view of a switchable directional display device including a backlight 20 including a switchable collimating waveguide 901 and a switchable liquid crystal retardation layer 300 and an additional polarizer 318. The backlight 20 shown in FIG. 28A can be used in any of the devices described herein and has the following structure.

Waveguide 901 has an input end 902 extending laterally along waveguide 901. A set of light sources 915 is located along input end 902 and supplies light to waveguide 1. Waveguide 901 also has opposing first and second guide surfaces 906, 908 extending through waveguide 1 from from the input end 2 to the reflective end 4 to guide the input light at the input end 2 back and forth along the waveguide 1. In operation, the light is directed between the first and second guide surfaces 906, 908.

The first guide surface 906 may be provided with a lens structure 904 comprising a plurality of elongated lens elements 905, and the second guide surface 908 may be provided with prism structures 912 that are tilted and act as light output elements. The plurality of elongated lens elements 905 of the lens structure 904 and the plurality of inclined light output elements reflect the input light directed through the waveguide 901 to exit through the first guide surface 906.

A rear reflector 903, which may be a flat reflector, is provided in order to direct the light that is passed through the surface 908 back through the waveguide 901.

The output light rays that are incident on both the prismatic structures 912 and the lens elements 905 of the lens structure 904 exit at angles close to being incident at a low angle to the surface 906. The prismatic reflective film 926 containing the facets 927 is configured to redirect the output rays 234 light by total internal reflection through a spatial light modulator 48 and a compensating switchable liquid crystal retardation layer 300.

Fig. 28B is a schematic diagram illustrating a plan view of the output of a collimating waveguide 901. The prismatic structures 912 are configured to direct light at angles of incidence onto the lens structure 904, and such beams pass at an angle below the critical angle and therefore may be deflected. When falling on the edges of the lens surface, the slope of the surface provides light reflection for the deflected rays and creates a collimating effect. Light beam 234 may be formed by light beams 188a-c and light beams 189a-c incident at positions 185 in lens structure 904 of collimating waveguide 901.

Fig. 28C is a schematic graph illustrating the polarity of equal field of view luminance for the display device of FIG. 28A. In this way, a narrow exit light cone can be provided, the size of which is determined by the structures 904, 912 and the reflective film 926.

The advantage is that in areas with side angles, such as 45 degrees or more, where peepers may be present, the display output brightness will be negligible, typically less than 2%. It would be desirable to achieve an additional reduction in the output brightness. This additional reduction is provided by a compensating switchable liquid crystal retardation layer 300 and an additional polarizer 318, as shown in FIG. 28A. The advantage is that a high-performance, low-brightness privacy display can be provided off the main axis within a wide field of view.

Directional illuminations, such as the types of illuminations shown in FIG. 27A and FIG. 28A, together with the plurality of retardation layers 301, 330 of the present embodiments, can provide an off-major-axis luminance of less than 1.5%, preferably less than 0.75%, and most preferably less than 0.5% for the characteristic positions of the peeper 47. In addition, for the main observer 45 can be provided with high brightness and uniformity of light along the main axis. Advantageously, a high-performance, off-primary-axis, low-brightness privacy display within a wide field of view can be provided, which can be switched to wide-angle mode by controlling the switchable retardation layer 301 with the control system 352 shown in FIG. 1A.

Below is a further description of the function of the retardation layers located between parallel polarizers for brightness off the main axis. In the various devices described above, retardation layers are placed between a pair of polarizers (typically an additional polarizer 318 and either an input polarizer 210 and an output polarizer 218) in a number of different configurations. In each case, the retardation layers are configured to avoid affecting brightness for light passing through a pair of polarizers and a plurality of retardation layers along an axis normal to the plane of the retardation layers, but they do not reduce brightness for light passing through a pair of polarizers and a plurality of retardation layers tilted normal to the plane of the retardation layers, in at least one of the switchable states of the compensating switchable retardation layer 300. Below is a more detailed description of this effect, the principles of which can be applied generally to all devices described above.

Fig. 29A is a circuit diagram illustrating the illumination (perspective view) of the retardation layer with light off the main axis. The correction retardation layer 630 may comprise a birefringent material represented by a refractive index ellipsoid 632 with an optical axis direction 634 at 0 degrees to the x-axis, having a thickness 631. Conventional light rays 636 propagate in such a way that the path length in the material matches the thickness 631. Rays 637 of light are in the y-z plane with an increased path length; however, the material birefringence is essentially the same as for beams 636. In comparison, light beams 638 that are in the x-z plane have an increased path length in the birefringent material, and furthermore, the birefringence is different from conventional rays 636.

Thus, the phase shift of the retardation layer 630 depends on the angle of incidence of the respective ray, and also the plane of incidence, i.e. the rays 638 in the x-z plane, will have a phase shift different from the conventional rays 636 and the rays 637 in the y-z plane.

The interaction of polarized light with the retardation layer 630 will be described below. In order to highlight the differences between the first and second polarization components during operation in the directional illumination 101, the third and fourth polarization components will be discussed in the following explanation.

Fig. 29B is a schematic diagram illustrating illumination (perspective view) of the slow-wave layer with off-principal-axis light for a third linear polarization state at 90 degrees to the x-axis, and FIG. 29C is a schematic diagram illustrating illumination (perspective view) of the slow-wave layer with off-principal-axis light for a fourth linear polarization state at 0 degrees to the x-axis. In such designs, the linear polarization states of the incident light are aligned with the optical axes of the birefringent material represented by the 632 ellipse. each beam 636, 637, 638. Thus, the retardation layer 630 does not introduce a phase shift in the polarization components of the light passing through the polarizer on the input side of the retardation layer 630 along an axis normal to the plane of the retardation layer 630. Accordingly, the retardation layer 630 does not affect the brightness of light passing through retardation layer 630 and polarizers (not shown) on each side of retardation layer 630. Although FIG. 29A-C refer exclusively to the retardation layer 630, which is passive, a similar effect is achieved by using a switchable liquid crystal retardation layer and a plurality of retardation layers in the devices described above.

Fig. 29D is a schematic diagram illustrating illumination (perspective view) of the retardation layer 630 with off-major-axis light for a 45-degree linear polarization state. The linear polarization state can be decomposed into third and fourth polarization components that are orthogonal and parallel to the direction of optical axis 634, respectively. The thickness of the retarding layer 631 and the phase shift of the material, represented by the refractive index ellipsoid 632, can provide the net effect of a relative phase shift of the third and fourth polarization components incident on the layer by half a wavelength for a given wavelength in the normal direction represented by beam 636. A given wavelength can be in the range, for example, from 500 to 550 nm.

For a given wavelength, and for light propagating normally along beam 636, the output polarization can be rotated 90 degrees from the linear polarization state 640 at -45 degrees. Light propagating along beam 637 may experience a phase difference that is close to but not the same as the phase difference along beam 637 due to changes in thickness, and therefore the output may experience an elliptical polarization state 639 with a major axis similar to that of linear polarization. output light for beam 636.

On the contrary, the phase difference for the state of linear polarization along the beam 638 may differ significantly, in particular, a smaller value of the phase difference can be achieved. Such a phase difference can provide an output polarization state 644 that, at a given tilt angle 642, is substantially circular. Thus, retardation layer 630 introduces a phase shift in the polarization components of light passing through the polarizer on the input side of retardation layer 630 along an axis corresponding to beam 638 that is inclined relative to the normal to the plane of retardation layer 630. Although FIG. 29D refers to the retardation layer 630 which is passive, a similar effect is achieved by using the switchable liquid crystal retardation layer and the plurality of retardation layers described above in the switched state of the switchable liquid crystal retardation layer corresponding to the confidential mode.

To illustrate an example of off-major axis stop retardation layer characteristics, the angular luminance control for the C-plates 308A, 308B located between the sub-polarizer 318 and the display output polarizer 218 will be described below for different off-major-axis illumination scenarios considering the functions of the C-plate 560. located between parallel polarizers 500, 210.

Fig. 30A is a schematic diagram illustrating the illumination (perspective view) of the C-plate layer with polarized light off the main axis with positive elevation. The incident linear polarization component 704 hits the birefringent material 632 of the retardation layer 560, which is a C-plate with an optical axis direction 507 that is perpendicular to the plane of the retardation layer 560. No net phase difference is observed for the polarization component 704 as it passes through the liquid crystal molecule , and therefore the output polarization component is identical to component 704. Thus, when passing through the polarizer 210, maximum transmission is noted. Thus, the retardation layer comprises a retardation layer 560 with an optical axis 561 perpendicular to the plane of the retardation layer 560, which is the x-y plane. The retardation layer 560 with an optical axis perpendicular to the plane of the retardation layer comprises a C-plate.

Fig. 30B is a schematic diagram illustrating illumination (perspective view) of a C-plate layer with off-major-axis negative side angle polarized light. As in the design shown in Fig. 30A, no resulting phase difference is observed in the polarization state 704, and transmission occurs at maximum brightness. Thus, the retardation layer 560 does not introduce a phase shift in the polarization components of the light passing through the polarizer on the input side of the retardation layer 560 along an axis normal to the plane of the retardation layer 560. Accordingly, the retardation layer 560 does not affect the brightness of the light passing through the retardation layer 560 and polarizers (not shown) on each side of retardation layer 560. Although FIG. 29A-C refer exclusively to the retardation layer 560, which is passive, a similar effect is achieved by using a switchable liquid crystal retardation layer and a plurality of retardation layers in the devices described above.

Fig. 30C is a schematic diagram illustrating illumination (perspective view) of a C-plate layer with off-major-axis polarized light with positive elevation and negative side angle. Compared to the design shown in Fig. 30A-B, the polarization state 704 is separated into eigenstates 703, 705 with respect to the birefringent material 632, which provides a net phase difference when passed through the retardation layer 560. The resulting elliptical polarization component 656 is passed through the polarizer 210 with reduced brightness compared to rays shown in Fig. 30A-B.

Fig. 30D is a schematic diagram illustrating illumination (perspective view) of a C-plate layer with off-major-axis polarized light with positive elevation and positive lateral angle. Similarly, as shown in FIG. 30C, the polarization component 704 is separated into eigenstates 703, 705 which are subjected to the resulting phase difference, and an elliptical polarization component 660 is provided, which, after passing through the polarizer, is noted to decrease in brightness of the corresponding beam off the main axis. Thus, the retardation layer 560 introduces a phase shift in the polarization components of the light passing through the polarizer on the input side of the retardation layer 560 along an axis that is tilted relative to the normal to the plane of the retardation layer 560. Although FIG. 29D refers to the retardation layer 560, which is passive, a similar effect is achieved by using the switchable liquid crystal retardation layer and the plurality of retardation layers described above in the switched state of the switchable liquid crystal retardation layer corresponding to the confidential mode.

Fig. 30E is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 30A-D. Thus, the C-plate can provide brightness reduction in the polar quadrants. In combination with the switchable liquid crystal retardation layer 301 described elsewhere herein, (i) in the first state of the wide-angle mode of operation, the dimming of the C-plate can be eliminated, and (ii) in the second state of the narrow-angle mode of operation, the dimming of the wide-angle mode can be achieved. polar region.

To illustrate an example of the characteristics of stop retardation layers off the main axis, the corner brightness control for cross A-plates 308A, 308B located between the additional polarizer 318 and the output polarizer 218 of the display will be described below for various off-axis lighting conditions.

Fig. 31A is a schematic diagram illustrating the illumination (perspective view) of crossed A-plate retardation layers with off-principal-axis polarized light with positive elevation. A linear polarizer 218 with an electric vector transmission direction 219 is used to provide a linear polarization state 704 that is parallel to the lateral direction for the first A-plate 308A of the crossed A-plates 308A, 308B. The optical axis direction 309A is inclined at +45 degrees with respect to the lateral direction. The phase shift of the retardation layer 308A for an angle θ ₁ off the main axis in the direction of positive elevation results in a resulting polarization component 650 that is typically elliptical at the output. The polarization component 650 hits the second A-plate 308B of crossed A-plates 308A, 308B with an optical axis direction 309B that is orthogonal to the optical axis direction 309A of the first A-plate 308A. In the plane of incidence shown in Fig. 31A, the phase shift of the second A-plate 308B for an angle θ ₁ outside the main axis is equal to and opposite to the phase shift of the first A-plate 308A. Thus, for the incident polarization component 704, a resultant zero phase shift is provided, and the output polarization component is identical to the input polarization component 704.

The output polarization component coincides with the direction of transmission of the electric vector of the additional polarizer 318, and therefore its transmission is efficient. An advantage is the ability to provide substantially no loss for light beams that contain a corner component with zero side angle, thus achieving full transmission efficiency.

Fig. 31B is a schematic diagram illustrating the illumination (perspective view) of the layers of a crossed A-plate phase plate with off-major-axis polarized light with a negative side angle. Thus, the first A-plate 308A converts the input polarization component to an intermediate polarization component 652, which is typically an elliptical polarization state. The second A-plate 308B again generates a phase shift equal in magnitude and opposite to that of the first A-plate so that the output polarization component is identical to the input polarization component 704 and light is effectively passed through the polarizer 318.

Thus, the retardation layer comprises a pair of retardation layers 308A, 308B with intersecting axes in the plane of the retardation layers 308A, 308B, which form the x-y plane in the present embodiments. The pair of retardation layers 308A, 308B has optical axes 309A, 309B that extend at a 45° angle with respect to the electrical vector transmission direction, which is parallel to the electrical vector transmission direction of the polarizer 318.

An advantage is the ability to provide substantially no loss for light beams that contain a zero elevation corner component, therefore achieving full transmission efficiency.

Fig. 31C is a schematic diagram illustrating illumination (perspective view) of crossed A-plate retardation layers with off-major-axis polarized light with positive elevation and negative side angle. The first A-plate 308A converts the polarization component 704 to an elliptical polarization component 654. The resulting elliptical component 656 emerges from the second A-plate 308B. An input polarizer 318 analyzes an elliptical component 656 with reduced brightness compared to the input brightness of the first polarization component 704.

Fig. 31D is a schematic diagram illustrating illumination (perspective view) of crossed A-plate retardation layers with off-major-axis polarized light with positive elevation and positive lateral angle. The first and second A-plates 308A, 308B form the polarization components 658 and 660 because the resulting phase shift of the first and second retardation layers does not compensate.

Thus, the brightness is reduced for light rays with non-zero side angle and non-zero elevation components. The advantage is the ability to increase the level of privacy of the display for peeps who find themselves in the viewing quadrants of the display, while not significantly reducing the effectiveness of brightness for the main users of the display.

Fig. 31E is a schematic graph illustrating output transmittance versus polar direction for transmitted light beams according to FIG. 31A-D. Compared to the design shown in Fig. 30E, for off-major-axis viewing, the dimming region is expanded. However, the switchable liquid crystal retardation layer 301 can provide reduced uniformity compared to C-plate designs for off-major-axis viewing in the first wide-angle operating state.

As used herein, the terms "substantially" and "approximately" express degrees of tolerance generally accepted in the industry for the respective terms and/or degrees of relativity between elements. Such industry-accepted degrees of tolerance are from zero percent to ten percent, and are consistent with component values, angle values, and the like, without limitation. Such interdependence between elements ranges from about zero percent to ten percent.

While various embodiments have been described above in accordance with the principles described herein, it should be understood that they are presented by way of example only and not by way of limitation. Thus, the breadth and scope of the present description should not be limited by any of the exemplary embodiments described above, but should only be determined in accordance with any of the claims and their equivalents following from this description. In addition, the above advantages and elements are presented in the described embodiments, but should not limit the scope of such published claims in relation to processes and structures implemented using any or all of the above advantages.

In addition, section headings in this document are proposed for consistency in accordance with 37 CFR 1.77 (Code of Federal Regulations) or otherwise to provide text organization. These headings are not intended to limit or characterize the embodiment(s) set forth in any claims that may follow from the present description. In particular and by way of example, although the headings refer to the "field of technology", the claims should not be limited to the language chosen in this heading to describe the so-called field. In addition, the description of technology in the Background of the Invention section should not be construed as an admission that a particular technology is prior art to any embodiment(s) of this disclosure. In addition, the "Summary" section should not be considered as characterization of the embodiment(s) set forth in the published claims. Additionally, in this description, any reference to "invention" in the singular should not be used as an argument for asserting that only one new element is present in this description. A variety of inventions may be included within the scope of the many embodiments flowing from this specification, and accordingly, such claims claim(s) the invention(s) protected by them and its (their) equivalents. In all cases, the scope of such claims is considered on their merits in light of the present description and should not be limited by the section headings given herein.

Claims (52)

1. A switchable confidential display device, comprising: a backlight capable of emitting light; a transmission spatial light modulator configured to receive light emitted by the backlight; a display polarizer located on the side of the spatial light modulator; an additional polarizer located on the same side of the spatial light modulator as the display polarizer; and a plurality of retardation layers located between the additional polarizer and the display polarizer, wherein there are no additional polarizers between said plurality of retardation layers; in this case, a plurality of slowing layers contain: a switchable liquid crystal retardation layer comprising a layer of liquid crystal material with positive dielectric anisotropy and providing a phase shift for light with a wavelength of 550 nm in the range from 500 nm to 1000 nm; two surface alignment layers adjacent to and on opposite sides of the liquid crystal material layer, and each of them is configured to provide longitudinal alignment in the adjacent liquid crystal material; and each alignment layer has a pretilt, and the direction of such pretilt has a component in the plane of the liquid crystal layer that is parallel or antiparallel or orthogonal to the transmission direction of the electric vector of the display polarizer; and at least one passive compensating retardation layer, which contains: a retarding layer with an optical axis perpendicular to the plane of the retarding layer, and providing a phase shift for light with a wavelength of 550 nm in the range from -300 nm to -700 nm; or a pair of retarding layers with intersecting optical axes in the plane of the retarding layers, wherein each retarding layer of the pair of retarding layers provides a phase shift for light with a wavelength of 550 nm in the range from 300 nm to 800 nm. 2. The switchable privacy display device of claim 1, wherein the transmission directions of the electrical vector of the display polarizer and the additional polarizer are parallel. 3. The switchable privacy display device according to claim 1 or 2, wherein the liquid crystal material layer provides a phase shift for 550 nm light in the range of 600 nm to 850 nm. 4. The switchable privacy display device of claim 3, wherein: at least one passive compensating retardation layer contains: a retarding layer with an optical axis perpendicular to the plane of the retarding layer, wherein at least one passive retarding layer provides a phase shift for light with a wavelength of 550 nm in the range from -350 nm to -600 nm; or a pair of retardation layers with intersecting optical axes in the plane of the retardation layers, wherein each retardation layer of the pair of retardation layers provides a phase shift for light with a wavelength of 550 nm in the range from 350 nm to 650 nm. 5. The switchable confidential display device of claim 1, wherein the plurality of retardation layers are configured to not affect the brightness of light passing through the display polarizer, the additional polarizer, and the plurality of retardation layers along an axis normal to the plane of the retardation layers. 6. The switchable confidential display device of claim 1, wherein the plurality of retardation layers are configured to reduce the brightness of light passing through the display polarizer, the additional polarizer, and the plurality of retardation layers along an axis inclined relative to the normal to the plane of the retardation layers. 7. The switchable privacy display device of claim 1, wherein the switchable liquid crystal retardation layer further comprises electrodes configured to apply voltage to drive the liquid crystal material layer. 8. The switchable privacy display device of claim 7, wherein the electrodes are located on opposite sides of the layer of liquid crystal material. 9. The switchable privacy display device of claim 7 or 8, wherein the electrodes are structured to provide at least two structured areas. 10. The switchable private display device of claim 7, further comprising a control system configured to control the voltage applied to the electrodes of the at least one switchable liquid crystal retardation layer. 11. The switchable private display device according to claim 10, wherein the control system further comprises means for determining the position of the peeker relative to the display, and the control system is configured to adjust the voltage applied to the electrodes of the at least one switchable liquid crystal retardation layer, depending on the position of the peeker . 12. The switchable privacy display device of claim 1, further comprising a second retardation layer and a second polarizer, the second retardation layer being positioned between the additional polarizer and the second polarizer. 13. The switchable privacy display device of claim 1, further comprising a backlight capable of emitting light, wherein the spatial light modulator is a transmissive spatial light modulator capable of receiving light emitted by the backlight. 14. The switchable privacy display device of claim 13, wherein the backlight provides brightness at polar angles with respect to the normal to the spatial light modulator greater than 45 degrees, which is a maximum of 33% brightness along the normal to the spatial light modulator. 15. The switchable privacy display device of claim 13, wherein the backlight comprises: a set of light sources; directional waveguide, comprising: an input end extending laterally along a side of the directional waveguide, wherein the light sources are located along the input end and configured to introduce the input light into the waveguide; and opposite first and second guide surfaces passing along the directional waveguide from the input end to direct the input light at the input end along the waveguide, wherein such a waveguide is configured to refract the input light directed through the directional waveguide to exit through the first guiding surface. 16. The switchable privacy display device of claim 15, wherein the backlight further comprises a reflective film and the directional waveguide is a collimating waveguide. 17. The switchable privacy display device of claim 16, wherein the collimating waveguide comprises (i) a plurality of elongated lens elements; and (ii) a plurality of inclined light output members, wherein the plurality of elongated lens elements and the plurality of inclined light output elements are oriented to refract input light guided through the directional waveguide to exit through the first guide surface. 18. The switchable privacy display device of claim. 15, wherein the directional waveguide is an imaging waveguide configured to image light sources in a lateral direction such that emitted light from the light sources is directed to respective optical windows in output directions distributed in depending on the input positions of the light sources. 19. The switchable confidential display device of claim 18, wherein the imaging waveguide comprises a reflective end for reflecting input light along the imaging waveguide, the second guide surface being configured to refract the reflected input light through the first guide surface as output light, the second guide surface the surface comprises light output elements and intermediate regions between the light output elements, wherein the light output elements are oriented so as to refract the reflected input light through the first guiding surface as output light, and the intermediate regions are configured to guide light through the waveguide without diverting it; and the reflective end has a positive power in a lateral direction extending between the sides of the waveguide that extends between the first and second guide surfaces. 20. The switchable privacy display device of claim 1, wherein the display polarizer is an input display polarizer located on the input side of the spatial light modulator between the backlight and the spatial light modulator, and the additional polarizer is located between the input display polarizer and the backlight. 21. The switchable privacy display device of claim 20, wherein the additional polarizer is a reflective polarizer. 22. The switchable privacy display device of claim 20 or 21, which further comprises an output polarizer located on the output side of the spatial light modulator. 23. The switchable privacy display device of claim 1, wherein the display polarizer is an output polarizer located on the output side of the spatial light modulator. 24. The switchable privacy display device of claim 23, further comprising an input polarizer located on the input side of the spatial light modulator. 25. The switchable privacy display device of claim 24, further comprising a second additional polarizer located on the input side of the spatial light modulator and a second retardation layer located between the second additional polarizer and the input polarizer. 26. The switchable confidential display device of claim 1, wherein the spatial light modulator comprises an emissive spatial light modulator capable of emitting light, and the display polarizer is an output display polarizer disposed on an output side of the emissive spatial light modulator. 27. An optical viewing angle control element for use in a switchable confidential display device containing a spatial light modulator and a display polarizer located on the side of the spatial light modulator, and the optical viewing angle control element contains a control polarizer and a plurality of retardation layers for placement between an additional polarizer and a polarizer display for applying an optical viewing angle control in a switchable confidential display device, and between the plurality of retardation layers there are no additional polarizers, while the plurality of retardation layers comprise: a switchable liquid crystal retardation layer comprising a layer of liquid crystal material; and two surface alignment layers adjacent to and on opposite sides of the liquid crystal material layer, each configured to provide longitudinal alignment in the adjacent liquid crystal material; and each of the surface alignment layers has a pretilt, and the direction of such pretilt has a component in the plane of the liquid crystal layer that is parallel, or antiparallel, or orthogonal to the transmission direction of the electrical vector of the display polarizer; wherein the liquid crystal material layer of the switchable liquid crystal retardation layer has a positive dielectric anisotropy and provides a phase shift for light with a wavelength of 550 nm in the range of 500 nm to 1000 nm; and at least one passive compensating retardation layer, which contains: a retarding layer with an optical axis perpendicular to the plane of the retarding layer, and providing a phase shift for light with a wavelength of 550 nm in the range from -300 nm to -700 nm; or a pair of retarding layers with intersecting optical axes in the plane of the retarding layers, with each retarding layer providing a phase shift for light with a wavelength of 550 nm in the range from 300 nm to 800 nm.

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