Stabilization of privacy display

Abstract

A display includes a polarized output spatial light modulator, a switchable liquid crystal retarder, an absorbing polarizer, and a touch panel electrode. During the application of an applied voltage, the switchable liquid crystal layer is stabilized by a cured reactive mesogen material. Light scattering in a privacy mode is reduced and the level of visual safety is increased. During the application of pressure, such as from a finger on the touch screen, the visibility of disclination is minimized.

Description

Technical Field

[0001] The present disclosure generally relates to touch input for display devices with angular illumination control for use in privacy displays and low stray light displays. Background Art

[0002] Privacy displays provide image visibility to the primary user (usually located at an on-axis position) and reduced visibility of image content to a snooper (usually located at an off-axis position). Privacy functionality can be provided by micro-louver optical films that transmit higher brightness from the display in an on-axis direction and lower brightness in an off-axis position, however such films are not electrically switchable and therefore the display is limited to privacy functionality only.

[0003] A switchable privacy display may be provided by controlling the off-axis optical output.

[0004] Control of off-axis privacy can be provided by reducing contrast, for example by adjusting the out-of-plane tilt of the liquid crystal in an in-plane switching LCD.

[0005] Control may be further provided by reducing off-axis brightness. Brightness reduction may be achieved by a switchable backlight for a liquid crystal display (LCD) spatial light modulator. Off-axis brightness reduction may also be provided by a switchable liquid crystal retarder, polarizer, and compensating retarder arranged to modulate the input and / or output directional brightness profile of the spatial light modulator.

[0006] The touch screen is arranged to receive an input position from a viewer's finger or a stylus, and may include capacitive touch, resistive touch, electromagnetic resonance, and other known touch sensing technologies. Summary of the invention

[0007] According to a first aspect of the present disclosure, a display device is provided, the display device comprising: a spatial light modulator; a display polarizer, the display polarizer is arranged on one side of the spatial light modulator, the display polarizer is a linear polarizer; an additional polarizer, the additional polarizer is arranged on the same side of the spatial light modulator as the display polarizer, the additional polarizer is a linear polarizer; and at least one polarity control retarder, the at least one polarity control retarder is arranged between the additional polarizer and the display polarizer, wherein at least one polarity control retarder comprises a switchable liquid crystal retarder, the switchable liquid crystal retarder comprises: a first supporting substrate and a second supporting substrate; a liquid crystal layer, the liquid crystal layer is arranged between a first transparent supporting substrate and a second transparent supporting substrate, the liquid crystal layer comprises a non-curable liquid crystal material and a curable polymer material; an electrode, the electrode is arranged to apply a voltage for controlling the liquid crystal layer; and a corresponding liquid crystal alignment layer, the liquid crystal alignment layer is supported on the first supporting substrate and the second supporting substrate adjacent to the liquid crystal layer for aligning the non-curable liquid crystal material. The curable polymer material may comprise an acrylate or a thiol material. A cross-linked network may be conveniently provided in the liquid crystal layer. Advantageously, brightness and reflection artifacts caused by liquid crystal cell thickness variations and liquid crystal flow variations during applied mechanical forces may be reduced.

[0008] The cured polymer material may include a cured liquid crystal material. The cured liquid crystal material may include a reactive mesogen. In a state where a predetermined voltage is applied to the electrodes, the cured liquid crystal material may have an alignment that is aligned with an alignment of the non-curable liquid crystal material. Advantageously, light scattering in one operating mode may be reduced. The relaxation time of artifacts may be reduced. Low artifact visibility may be provided to a thin flexible device during folding.

[0009] The predetermined voltage is capable of causing the layers of the solidified liquid crystal material and the non-solidified liquid crystal material to simultaneously operate to not introduce a net relative phase shift to an orthogonal polarization component of light that passes through the display polarizer along an axis that is normal to the plane of the at least one polarity control retarder, and to introduce a net relative phase shift to an orthogonal polarization component of light that passes through the additional polarizer along an axis that is oblique to the normal to the plane of the at least one polarity control retarder. Advantageously, scattering can be reduced in a privacy mode of operation, thereby achieving an increased level of visual security. Scattering can be increased in a public mode of operation, thereby achieving increased uniformity.

[0010] The solidified liquid crystal material may be arranged in a network extending between two supporting substrates. The solidified liquid crystal material may be a reactive mesogen. The ratio of the volume of the solidified liquid crystal material to the volume of the non-solidified liquid crystal material may be less than 5%. The network may be attached to each of the two supporting substrates. Electrodes may be arranged on opposite sides of the liquid crystal layer. A solidified network may be provided, which provides a mechanical connection between the substrates across the area of ​​the device. The optical properties of the switchable liquid crystal layer may be substantially determined by the properties of the non-solidified liquid crystal material. Advantageously, a stable liquid crystal layer with high resistance to image artifacts caused by applied mechanical forces is provided.

[0011] The display device may further comprise a control system arranged to control a voltage applied to the electrodes of the switchable liquid crystal retarder.Advantageously, the display is switchable between a private mode of operation and a public mode of operation.

[0012] The at least one polarity controlled retarder may further comprise at least one passive compensating retarder.Advantageously, a polarity region is provided in which a high level of visual security against off-axis snoopers is extended.

[0013] The switchable liquid crystal retarder may include two surface alignment layers, the two surface alignment layers being arranged adjacent to the liquid crystal material on opposite sides of the liquid crystal material and each being configured to provide a homeotropic alignment at the adjacent liquid crystal material. The liquid crystal material layer of the switchable liquid crystal retarder may include a liquid crystal material having a negative dielectric anisotropy. The liquid crystal material layer may have a retardation for light of a wavelength of 550 nm 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. At least one passive retarder may include at least one passive retarder having an optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a total delay for light of 550nm wavelength in the range of -300nm to -900nm, preferably in the range of -450nm to -800nm, and most preferably in the range of -500nm to -725nm; or at least one passive retarder includes a pair of passive retarders having optical axes crossing in the plane of the retarder, each of the pair of passive retarders having a delay for light of 550nm wavelength in the range of 300nm to 800nm, preferably in the range of 500nm to 700nm, and most preferably in the range of 550nm to 675nm. Advantageously, the common mode can provide high image visibility over a wide polarity region. The power consumption of operating in the common mode can be reduced.

[0014] The switchable liquid crystal retarder may include two surface alignment layers, the two surface alignment layers being arranged adjacent to the liquid crystal material layer and on opposite sides thereof, and each being configured to provide homogeneous alignment in the adjacent liquid crystal material. The liquid crystal material layer of the switchable liquid crystal retarder includes a liquid crystal material having positive dielectric anisotropy. The liquid crystal material layer may have a delay in the following range for light of a wavelength of 550 nm: 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. At least one passive retarder may include at least one passive retarder having an optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a total delay for light of 550nm wavelength in the range of -300nm to -700nm, preferably in the range of -350nm to -600nm, and most preferably in the range of -700nm to -500nm; or at least one passive retarder includes a pair of passive retarders having optical axes crossing in the plane of the retarder, each of the pair of passive retarders having a delay for light of 550nm wavelength in the range of 300nm to 800nm, preferably in the range of 350nm to 650nm, and most preferably in the range of 450nm to 550nm. Advantageously, the applied mechanical force can achieve increased stability compared to the homeotropic alignment. In privacy mode, a large polarity area with a high level of visual security can be achieved. The thin flexible switchable retarder can have high resilience to the applied mechanical force.

[0015] According to a second aspect of the present disclosure, there is provided a method for manufacturing a switchable liquid crystal retarder, which is a polarity control retarder for a display device, the method comprising: providing a first supporting substrate and a second supporting substrate, the first supporting substrate and the second supporting substrate having electrodes for controlling a liquid crystal layer, and having a first liquid crystal alignment layer and a second liquid crystal alignment layer supported thereon for aligning a liquid crystal material of the liquid crystal layer; providing a liquid crystal layer disposed between a first transparent supporting substrate and a second transparent supporting substrate, wherein the first liquid crystal alignment layer and the second liquid crystal alignment layer are adjacent to the liquid crystal layer, the liquid crystal layer comprising a non-curable liquid crystal material and a curable liquid crystal material; curing the curable liquid crystal material when a predetermined voltage is applied to the electrodes. Advantageously, in operation, low image scattering can be achieved in at least one operating mode while achieving high resilience to applied mechanical forces.

[0016] The predetermined voltage may be capable of causing the layers of solidified liquid crystal material and non-solidified liquid crystal material to simultaneously: not introduce a net relative phase shift to an orthogonal polarization component of light that passes through the additional polarizer along an axis that is normal to the plane of at least one polarity control retarder, and introduce a net relative phase shift to an orthogonal polarization component of light that passes through the additional polarizer along an axis that is inclined to the normal to the plane of at least one polarity control retarder. The predetermined voltage may be non-zero. Advantageously, the mode with low image scattering may be a privacy mode, so that the level of visual security for off-axis snoopers is increased. Public mode image uniformity may be increased.

[0017] The curable liquid crystal material may be a reactive mesogen. Advantageously, the reactive mesogen may be aligned by an applied voltage and an alignment layer of the liquid crystal retarder.

[0018] The liquid crystal layer may further comprise a polymerising photoinitiator and the step of curing the curable liquid crystal material is performed by applying light radiation, preferably UV radiation, to the liquid crystal layer. Advantageously, a homogeneous liquid crystal layer may be provided.

[0019] Embodiments of the present disclosure may be used in a variety of optical systems. Embodiments may include or be used with a variety of projectors, projection systems, optical components, displays, microdisplays, computer systems, processors, self-contained projector systems, visual and / or audiovisual systems, and electrical and / or optical devices. Aspects of the present disclosure may 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. Thus, embodiments of the present disclosure may be employed in optical systems, devices used in visual and / or optical presentations, visual peripherals, and the like, as well as in a variety of computing environments.

[0020] Before proceeding to the disclosed embodiments in detail, it should be understood that the disclosure is not limited in its application or creation to the details of the particular arrangement shown, as the disclosure can be used in other embodiments. Moreover, aspects of the disclosure may be described in different combinations and arrangements to define their own unique embodiments. Likewise, the terms used herein are for descriptive purposes only and are not intended to be limiting.

[0021] Directional backlighting provides control of illumination emitted from substantially the entire output surface, typically by modulating separate LED light sources arranged at the input aperture side of the light guide. Controlling the directional distribution of the emitted light enables: single-person viewing safety features, where the display can only be viewed from a limited range of angles by a single observer; high electrical efficiency, where illumination is provided primarily over a smaller angular directional distribution; alternating left and right eye viewing for time-sequential stereoscopic and autostereoscopic displays; and low cost.

[0022] These and other advantages and features of the present disclosure will become apparent to those of ordinary skill in the art from a reading of the entire disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Embodiments are illustrated by way of example in the accompanying drawings, in which like reference numerals indicate similar parts, and in which:

[0024] Figure 1A is a schematic diagram illustrating in perspective side view a touch input display device including a spatial light modulator, a reflective polarizer, and a switchable liquid crystal retarder including a stabilized liquid crystal layer;

[0025] Figure 1B The previous view shows Figure 1A Schematic diagram of aligning optical layers in an optical stack;

[0026] Figure 2A and Figure 2B Different perspective side views are used to illustrate the privacy operation mode and wide-angle operation mode respectively. Figure 1A -B is a schematic diagram of a touch input display device;

[0027] Figure 3A It means that in the privacy operation mode Figure 2A Schematic diagram of the transmission brightness of the transmitted light in the image changing with the polarity direction;

[0028] Figure 3B It means that in the privacy operation mode Figure 2A Schematic diagram showing how the reflectivity of reflected light varies with polarity direction;

[0029] Figure 3C It means that in the public operation mode Figure 2B Schematic diagram of the transmission brightness of the transmitted light in the image changing with the polarity direction;

[0030] Figure 3D It means that in the public operation mode Figure 2B Schematic diagram showing how the reflectivity of reflected light varies with polarity direction;

[0031] Figure 4 It is the liquid crystal director angle relative to the different applied Figure 2A -B and Figure 3A -D is a schematic diagram of a graph of fractional positions of a voltage switchable liquid crystal retarder unit;

[0032] Figure 5A , Figure 5B , Figure 5C and Figure 5Dis a schematic diagram illustrating a method of providing a liquid crystal polymer stabilized switchable liquid crystal retarder for a privacy display including a planar alignment layer in a perspective side view;

[0033] Fig. 6A is a schematic diagram illustrating, in a perspective side view, an arrangement of a switchable compensating retarder including a planar-aligned switchable liquid crystal retarder and a negative C-plate in a privacy mode of operation;

[0034] Figure 6B is a schematic diagram illustrating in perspective side view an arrangement of a switchable compensating retarder including a planar aligned switchable liquid crystal retarder and a negative C-plate providing operation for different applied voltages in a common operating mode;

[0035] Figure 6C is a schematic diagram illustrating, in perspective side view, an arrangement of a switchable compensating retarder and a negative C-plate comprising a switchable liquid crystal retarder aligned in a plane for no applied voltage;

[0036] Fig. 7A It means that in the public operation mode Figure 6B Schematic diagram of the transmission brightness of the transmitted light in the image changing with the polarity direction;

[0037] Figure 7B It means that in the privacy operation mode Fig. 6A Schematic diagram of the transmission brightness of the transmitted light in the image changing with the polarity direction;

[0038] Figure 7C It means that in the privacy operation mode Fig. 6A Schematic diagram showing how the reflectivity of reflected light varies with polarity direction;

[0039] Fig. 8A The previous perspective diagram illustrates the Figure 1A Schematic diagram of observation of reflected ambient light on the interface surface of a display;

[0040] Figure 8B The previous perspective illustrates the operation in private mode. Figure 1A Schematic diagram of observation of reflected ambient light of a display;

[0041] Fig. 9A is a photograph showing the appearance of disclination in a nematic liquid crystal layer not including the cured liquid crystal material of this embodiment during application of pressure;

[0042] Fig. 9B is a photograph showing the appearance of disclinations in a nematic liquid crystal layer not including the cured liquid crystal material of the present embodiment after pressure release and shortly before complete annealing of the disclinations;

[0043] Fig. 10Ais a schematic diagram illustrating, in a perspective side view, an arrangement of a switchable compensating retarder including a homeotropically aligned switchable liquid crystal retarder and a negative C-plate in a privacy mode of operation;

[0044] Fig. 10B is a diagram illustrating the liquid crystal director angle relative to the common operation mode provided by no applied voltage across the pair. Fig. 10A A schematic diagram of a graph of fractional positions of a switchable liquid crystal retarder unit;

[0045] Fig.11A It means that in the privacy operation mode Fig. 10A Schematic diagram of the output brightness of the transmitted light changing with the polarity direction;

[0046] Fig. 11B It means that in the privacy operation mode Fig. 10A Schematic diagram showing how the reflectivity of reflected light changes with polarity direction;

[0047] Fig. 11C It means that in the public operation mode Fig. 10B Schematic diagram of the output brightness of the transmitted light changing with the polarity direction;

[0048] Fig.11D It means that in the public operation mode Fig. 10B Schematic diagram showing how the reflectivity of reflected light changes with polarity direction;

[0049] Fig.11E It is the liquid crystal director angle relative to the applied voltage for different Fig. 10A -B is a schematic diagram of a graph of fractional positions of a switchable liquid crystal retarder unit;

[0050] Fig. 12A , Fig. 12B , Fig. 12C and Fig.12D is a schematic diagram illustrating a method of providing a liquid crystal polymer stabilized switchable liquid crystal retarder for a privacy display including a homeotropic alignment layer in a perspective side view;

[0051] Fig.13A is a diagram illustrating in perspective view the illumination of a retarder layer by off-axis light;

[0052] Fig. 13B is a diagram illustrating, in perspective view, illumination of a retarder layer by off-axis light in a first linear polarization state of 0 degrees;

[0053] Fig. 13C is a diagram illustrating, in perspective view, illumination of a retarder layer by off-axis light in a first linear polarization state at 90 degrees;

[0054] Fig.13Da diagram illustrating in perspective view illumination of a retarder layer by off-axis light in a first linear polarization state at 45 degrees;

[0055] Fig.14A is a diagram illustrating in perspective the illumination of a C-plate retarder by off-axis polarized light having a positive elevation angle;

[0056] Fig. 14B is a diagram illustrating, in perspective, illumination of a C-plate retarder by off-axis polarized light having a negative side angle;

[0057] Fig. 14C is a diagram illustrating, in perspective, illumination of a C-plate retarder by off-axis polarized light having a positive elevation angle and a negative lateral angle;

[0058] Fig.14D is a diagram illustrating, in perspective, illumination of a C-plate retarder by off-axis polarized light having a positive elevation angle and a positive side angle;

[0059] Fig.14E It is explained in Fig.14A -D is a graph showing the output transmittance of the transmitted light rays as a function of polarity direction;

[0060] Fig.15A is a diagram illustrating, in perspective, illumination of crossed A-plate retarder layers by off-axis polarized light having a positive elevation angle;

[0061] Fig. 15B is a diagram illustrating, in perspective, illumination of crossed A-plate retarder layers by off-axis polarized light having a negative side angle;

[0062] Fig. 15C is a diagram illustrating in perspective view illumination of crossed A-plate retarder layers by off-axis polarized light having positive elevation angles and negative lateral angles;

[0063] Fig.15D is a diagram illustrating, in perspective, illumination of crossed A-plate retarder layers by off-axis polarized light having positive elevation and positive side angles; and

[0064] Fig.15E It is explained in Fig.15A -D is a graph of the output transmittance of the transmitted light as a function of polarity direction. DETAILED DESCRIPTION

[0065]

[0046] The terminology associated with optical retarders for the purposes of the present disclosure will now be described.

[0066] In a layer comprising a uniaxial birefringent material, there is a direction that controls the optical anisotropy, while all directions perpendicular to this direction (or at a given angle thereto) have equivalent birefringence.

[0067] The optical axis of an optical retarder refers to the direction of propagation of light in a uniaxial birefringent material that does not experience birefringence. This is different from the optical axis of an optical system, which may be, for example, parallel to a line of symmetry or perpendicular to a display surface along which a chief ray propagates.

[0068] For light propagating in a direction orthogonal to the optical axis, when linearly polarized light with an electric vector direction parallel to the slow axis travels at the lowest speed, the optical axis is the slow axis. The slow axis direction is the direction with the highest refractive index at the design wavelength. Similarly, the fast axis direction is the direction with the lowest refractive index at the design wavelength.

[0069] For a uniaxial birefringent material with positive dielectric anisotropy, the slow axis direction is the extraordinary axis of the birefringent material. For a uniaxial birefringent material with negative dielectric anisotropy, the fast axis direction is the extraordinary axis of the birefringent material.

[0070] The terms half wavelength and quarter wavelength refer to the 0 Operation of the retarder for a design wavelength between 500 nm and 570 nm is generally possible. In this illustrative embodiment, exemplary retardation values ​​are provided for a wavelength of 550 nm unless otherwise specified.

[0071] A retarder provides a relative phase shift between two orthogonal polarization components of a light wave incident thereon and is characterized by the relative phase amount Γ imparted by the retarder to the two polarization components. In some cases, the term "phase shift" is used without the word "relative", but still means a relative phase shift. The relative phase shift is related to the birefringence Δn and the thickness d of the retarder:

[0072] Γ=2.π.Δn.d / λ 0 Equation 1

[0073] In Equation 1, Δn is defined as the difference between the extraordinary refractive index and the ordinary refractive index, that is,

[0074] Δn = n e -n o Equation 2

[0075] For a half-wave retarder, choose d, Δn, and λ 0 The relationship between d, Δn and λ makes the phase shift between polarization components Γ = π. For a quarter-wave retarder, d, Δn and λ are selected. 0 The relationship between makes the phase shift between the polarization components Γ=π / 2.

[0076] The term half-wave retarder herein generally refers to light propagating perpendicular to the retarder and perpendicular to the spatial light modulator.

[0077] Some aspects of the propagation of light through a transparent retarder between a pair of polarizers will now be described.

[0078] The state of polarization (SOP) of light is described by the relative amplitude and phase shift between any two orthogonal polarization components. A transparent retarder does not change the relative amplitude of these orthogonal polarization components, but only acts on their relative phase. Providing a net phase shift between orthogonal polarization components changes the SOP, while maintaining the net relative phase preserves the SOP.

[0079] A linear SOP has a polarization component of non-zero amplitude and an orthogonal polarization component of zero amplitude.

[0080] A linear polarizer transmits a unique linear SOP whose linear polarization component is parallel to the electric vector transmission direction of the linear polarizer and attenuates light at a different SOP.

[0081] An absorbing polarizer is a polarizer that absorbs one polarization component of incident light and transmits a second, orthogonal polarization component. An example of an absorbing linear polarizer is a dichroic polarizer.

[0082] A reflective polarizer is a polarizer that reflects one polarization component of incident light and transmits a second, orthogonal polarization component. An example of a reflective linear polarizer is a multilayer polymer film stack, such as DBEF from 3M. TM or APF TM , or a wire grid polarizer such as the ProFlux from Moxtek TM .

[0083] A retarder placed between a linear polarizer and a parallel linear analyzing polarizer that introduces no relative net phase shift provides complete transmission of light except for residual absorption within the linear polarizer.

[0084] A retarder that provides a relative net phase shift between the orthogonal polarization components changes the SOP and provides attenuation at the analyzing polarizer.

[0085] In this disclosure, "A-plate" refers to an optical retarder that utilizes a layer of birefringent material with its optical axis parallel to the plane of the layer.

[0086] “Positive A-plate” refers to a positive birefringent A-plate, that is, an A-plate having positive Δn.

[0087] In the present disclosure, "C-plate" refers to an optical retarder utilizing a layer of birefringent material whose optical axis is perpendicular to the plane of the layer. "Positive C-plate" refers to a positive birefringent C-plate, i.e., a C-plate with positive Δn. "Negative C-plate" refers to a negative birefringent C-plate, i.e., a C-plate with negative Δn.

[0088] "O-plate" refers to an optical retarder utilizing a layer of birefringent material whose optical axis has a component parallel to the plane of the layer and a component perpendicular to the plane of the layer. "Positive O-plate" refers to a positive birefringent O-plate, i.e., an O-plate with positive Δn.

[0089] An achromatic retarder may be provided, wherein the material of the retarder provides a retardation Δn.d that varies with wavelength λ as

[0090] Δn . d / λ = κ Equation 3

[0091] where κ is essentially a constant.

[0092] Examples of suitable materials include modified polycarbonates from Teijin Films.An achromatic retarder may be provided in this embodiment to advantageously minimize color changes between polarization angle viewing directions with low brightness reduction and polarization angle viewing directions with increased brightness reduction, as will be described below.

[0093] Various other terms related to retarders and liquid crystals used in the present disclosure will now be described.

[0094] The liquid crystal cell has a retardation given by Δn.d, where Δn is the birefringence of the liquid crystal material in the liquid crystal cell and d is the thickness of the liquid crystal cell, independently of the alignment of the liquid crystal material in the liquid crystal cell.

[0095] Alignment along the plane refers to the alignment of the liquid crystal in a switchable liquid crystal display, wherein the molecules are aligned substantially parallel to the substrate. Alignment along the plane is sometimes referred to as planar alignment. Alignment along the plane can typically be provided with a small pre-tilt, for example 2 degrees, so that the molecules on the surface of the alignment layer of the liquid crystal cell are slightly tilted, as will be described below. The pre-tilt is arranged to minimize degeneracy in cell switching.

[0096] In the present disclosure, homeotropic alignment is a state in which rod-like liquid crystal molecules are aligned substantially perpendicular to the substrate. In discotic liquid crystals, homeotropic alignment is defined as a state in which the axis of the columnar structure formed by the discotic liquid crystal molecules is aligned perpendicular to the surface. In homeotropic alignment, pretilt is a tilt angle of the molecules close to the alignment layer and is generally close to 90 degrees and may be, for example, 88 degrees.

[0097] In a twisted liquid crystal layer, a twisted configuration (also referred to as a helical structure or helix) of nematic liquid crystal molecules is provided. The twist can be achieved by non-parallel alignment of the alignment layer. In addition, cholesteric dopants can be added to the liquid crystal material to destroy the degeneracy of the twist direction (clockwise or counterclockwise) and further control the pitch of the twist in the relaxed (usually undriven) state. Super twisted liquid crystal layers have a twist greater than 180 degrees. Twisted nematic layers used in spatial light modulators typically have a twist of 90 degrees.

[0098] Liquid crystal molecules with positive dielectric anisotropy are switched from a planar alignment (eg, an A-plate retarder alignment) to a homeotropic alignment (eg, a C-plate or O-plate retarder alignment) by an applied electric field.

[0099] Liquid crystal molecules with negative dielectric anisotropy are switched from homeotropic alignment (eg, C-plate or O-plate retarder alignment) to planar alignment (eg, A-plate retarder alignment) by an applied electric field.

[0100] Rod-shaped molecules have positive birefringence, so that n e >n o , as described in Equation 2. The discotic molecule has negative birefringence, so that n e <n o .

[0101] Positive retarders such as A-plate, positive O-plate and positive C-plate can generally be provided by stretched films or rod-like liquid crystal molecules. Negative retarders such as negative C-plate can be provided by stretched films or disc-like liquid crystal molecules.

[0102] A parallel liquid crystal cell alignment refers to an alignment direction that is parallel or more typically antiparallel along the plane alignment layer. In the case of a pre-tilted homeotropic alignment, the alignment layer may have substantially parallel or antiparallel components. A hybrid aligned liquid crystal cell may have one along the plane alignment layer and one homeotropic alignment layer. A twisted liquid crystal cell may be provided by alignment layers that do not have a parallel alignment (e.g., oriented at 90 degrees to each other).

[0103] The transmissive spatial light modulator may further include a retarder between the input display polarizer and the output display polarizer, for example, as disclosed in U.S. Pat. No. 8,237,876, which is incorporated herein by reference in its entirety. Such a retarder (not shown) is in a different position than the passive retarder of the present embodiment. Such a retarder compensates for the contrast drop at off-axis viewing positions, which has a different effect than the brightness drop at off-axis viewing positions of the present embodiment.

[0104] The privacy mode of operation of a display is one in which an observer sees low contrast sensitivity such that the image is not clearly visible. Contrast sensitivity is a measure of the ability to distinguish between different brightness levels in a static image. Inverted contrast sensitivity can be used as a measure of visual safety, as a high visual safety level (VSL) corresponds to low image visibility.

[0105] For a privacy display that presents an image to an observer, visual safety can be given as:

[0106] VSL = (Y + R) / (Y – K) Equation 4

[0107] Where VSL is the Visual Safety Level, Y is the luminance of the white state of the display from the perspective of a snooper, K is the luminance of the black state of the display from the perspective of a snooper, and R is the luminance of the reflected light from the display.

[0108] The panel contrast is given by:

[0109] C = Y / K Equation 5

[0110] For high contrast optical LCD modes, the white state transmittance remains substantially constant with viewing angle. In the reduced contrast LCD mode of the present embodiment, the white state transmittance generally decreases as the black state transmittance increases, such that

[0111] Y+K~PL Equation 6

[0112] Then the visual safety level can be further given as:

[0113]

[0114] Where off-axis relative brightness P is typically defined as a percentage of the front brightness, L is at the peeper angle, and the display may have an image contrast ratio C, and the surface reflectivity is ρ.

[0115] The off-axis relative brightness P is sometimes referred to as the privacy level. However, such a privacy level P describes the relative brightness of the display at a given polarization angle compared to the front brightness, rather than being a measure of the privacy profile.

[0116] The display may be illuminated by a Lambertian ambient illumination I. Thus, in a completely dark environment, the VSL of a high contrast display is about 1.0. As the ambient illumination increases, the perceived image contrast decreases, the VSL increases, and a privacy image is perceived.

[0117] For a typical LCD, the panel contrast C is above 100:1 for almost all viewing angles, giving a visual safety level of approximately:

[0118] VSL = 1 + I.ρ / (π.PL) Equation 8

[0119] Compared to privacy displays, the desired wide-angle display is easily observable under standard ambient lighting conditions. One measure of image visibility is given by contrast sensitivity, such as the Michelson contrast given by:

[0120] M = (I max -I min ) / (I max + I min ) Equation 9

[0121] And therefore:

[0122] M=(((Y+R)-(K+R)) / ((Y+R)+(K+R))=(YK) / (Y+K+2.R) Equation 10

[0123] Therefore, the visual safety level (VSL) is equal to (but different from) 1 / M. In this discussion, for a given off-axis relative brightness P, the wide-angle image visibility W is approximated by

[0124] W = 1 / VSL = 1 / (1 + I.ρ / (π. PL)) Equation 11

[0125] A switchable directional display device used in, for example, a privacy display and including a plurality of retarders arranged between a display polarizer and an additional polarizer is described in U.S. Pat. No. 10,126,575 and in U.S. Pat. No. 2019-0086706, both of which are incorporated herein by reference in their entirety. A directional display device further including a reflective polarizer arranged between a display polarizer and a retarder is described in U.S. Pat. No. 10,303,030 and in U.S. Patent Application No. 16 / 256,120 filed on January 24, 2019 (Agent Docket No. 413101), both of which are incorporated herein by reference in their entirety. A directional display polarizer including a passive retarder arranged between a display polarizer and an additional polarizer is described in U.S. Pat. No. 2018-0321553, both of which are incorporated herein by reference in their entirety. Also incorporated herein by reference in its entirety is U.S. patent application Ser. No. 16 / 256,754, filed on Jan. 24, 2019 (Attorney Docket No. 420001).

[0126] The structure and operation of various switchable display devices will now be described. In this specification, common elements have common reference numerals. Note that the disclosure related to any element applies to each device in which the same or corresponding element is provided. Therefore, for the sake of brevity, such disclosure will not be repeated.

[0127] It would be desirable to provide high image quality during touch input for a switchable directional display device comprising a switchable liquid crystal retarder arranged between a display output polarizer and an additional polarizer for use in displays such as privacy displays.

[0128] Figure 1Ais a schematic diagram illustrating a touch input display device 100 including a spatial light modulator 48, a reflective polarizer 302 and a switchable liquid crystal retarder 300 in a perspective side view, wherein touch electrode arrays 500, 502 are provided on facing surfaces of a first passive compensating retarder 330A and a second passive compensating retarder 330B; and Figure 1B The previous view shows Figure 1A Schematic diagram of the alignment of optical layers and electrode layers in an optical stack.

[0129] The position of the finger 25 is detected by detecting deformations of the field lines 570, 572 provided by the touch electrode arrays 500, 502 and a control system including touch drivers 452, 454, touch controller 450 and system controller 460. At least one dielectric layer 504 is arranged between the switchable liquid crystal layer 314 and the additional polarizer 318. The first touch electrode array 500 and the second touch electrode array 502 are arranged on opposite sides of the dielectric layer 504.

[0130] exist Figure 1A , the spatial light modulator 48 is a transmissive spatial light modulator such as a liquid crystal display and further includes a backlight 20. In other embodiments (not shown), an emissive display such as an OLED or micro-LED display may be provided, wherein the display 100 does not include the input polarizer 210 and the backlight 20.

[0131] The spatial light modulator 48 is arranged to output light 700 and includes: a display polarizer 218, which is arranged on the output side of the spatial light modulator 48; an additional polarizer 318, which is arranged on the output side of the display polarizer 218; a reflective polarizer 302, which is arranged between the display polarizer 218 and the additional polarizer 318; and at least one retarder 300, which is arranged between the reflective polarizer 302 and the additional polarizer 318. The display polarizer 218 and the additional polarizer 318 are linear polarizers.

[0132] The display 100 is typically operated in an environment with external lighting 604. When the display is operated in a privacy mode, the reflection of such lighting is used to provide an increased level of visual security to snoopers, as will be further described below.

[0133] The plurality of retarders 300 comprises a switchable liquid crystal retarder 301 comprising a layer 314 of a non-curable liquid crystal material 414 and a cured liquid crystal material 420. The layer 314 is arranged between transparent support substrates 312, 316 and between the display polarizer 218 and the additional polarizer 318.

[0134] Electrodes 413, 415 and alignment layers 418A, 418B are arranged on facing surfaces of the support substrates 312, 316 respectively to provide electrical control and alignment to the layer 314 of non-curable liquid crystal material 414, respectively.

[0135] The control system includes a system controller 460, which is arranged to (i) provide image data to the spatial light modulator 48 via the spatial light modulator controller 250, (ii) provide control to the voltage driver 350 to control the drive voltage V applied to the switchable liquid crystal retarder, and (iii) control the signals applied to and measured from the touch electrode arrays 500, 502 via the touch controller 450 and touch drivers 452, 454.

[0136] The reflective polarizer 302 is arranged between the display polarizer 218 and the plurality of retarders 300. The electric vector transmission direction 303 of the reflective polarizer 302 is parallel to the electric vector transmission direction 219 of the display polarizer 218 and the electric vector transmission direction 319 of the additional polarizer 318.

[0137] The plurality of retarders 300 are arranged between the display polarizer 218 and the additional polarizer 318. The plurality of retarders 300 include: a switchable liquid crystal retarder 301, wherein a liquid crystal layer 314 is arranged between an input transparent support substrate 312 and an output transparent support substrate 316; and two passive compensating retarders 330A, 330B, which are arranged between the switchable liquid crystal retarder 301 and the additional polarizer 318. At least one passive compensating retarder 330 includes a pair of passive uniaxial retarders 330A, 330B, the optical axes of which cross in the plane of the retarders.

[0138] More generally, the display polarizer 218 is arranged on the side of the spatial light modulator 48, which is a linear polarizer. The additional polarizer 318 is arranged on the same side of the spatial light modulator 48 as the display polarizer 218, which is a linear polarizer. In the case where the spatial light modulator is a transmissive spatial light modulator 48, the additional polarizer 318 may alternatively or additionally be arranged between the backlight 20 and the input polarizer 210 of the spatial light modulator. In the case where the spatial light modulator 48 is an emissive spatial light modulator, the plurality of retarders 300 and the additional polarizer 318 are arranged on the output side of the output polarizer 218.

[0139] At least one polarity control retarder 300 is arranged between the additional polarizer 318 and the display polarizer 218, wherein the at least one polarity control retarder 300 comprises a switchable liquid crystal retarder 301, the switchable liquid crystal retarder comprising: a first support substrate 312 and a second support substrate 316; a liquid crystal layer 314 disposed between the first transparent support substrate 312 and the second transparent support substrate 316, the liquid crystal layer 314 comprising a non-curable liquid crystal material 414 and a curable liquid crystal material 420. The curable liquid crystal material may be a reactive mesogen, as will be further described below.

[0140] The electrodes 413 , 415 are arranged to apply voltages for controlling the liquid crystal layer 314 ; and respective liquid crystal alignment layers 418A, 418B are supported adjacent to the liquid crystal layer 314 on the first and second support substrates 312 , 316 for aligning the non-curable liquid crystal material 414 .

[0141] The dielectric layer 504 is arranged between the passive delayers 330A, 330B. The first touch electrode array 500 and the second touch electrode array 502 may be provided on at least one surface of at least one passive compensation delayer 330. The touch electrode arrays may be arranged on the opposing surfaces of a pair of passive uniaxial delayers 330A, 330B. The dielectric layer 504 may include an adhesive layer provided between the touch electrode arrays 500, 502 arranged on the opposing surfaces of a pair of passive uniaxial delayers 330A, 330B. The dielectric layer 504 may include, for example, an optically clear adhesive (OCA) or a pressure sensitive adhesive (PSA), or may be provided by another dielectric material.

[0142] The touch finger 25 may be brought close to or in contact with a substrate 320, which may be a glass cover or a hard-coated polymer layer with an oleophobic hard coating for mechanical robustness and resistance to finger oils. Touch control may also be provided by a pen or stylus.

[0143] As will be further described herein, layer 314 includes a solidified liquid crystal material 420 provided as a network 424 including cross-links 422 between molecules of the solidified liquid crystal material 420 .

[0144] Spacers 370 may be provided that include adhesive spacer balls and / or polymer walls. Advantageously, some resistance to applied mechanical forces may be provided. Visibility of flow of the non-curable liquid crystal material 414 may be reduced.

[0145] Figure 1BThe arrangement of the orientations of the various components is further illustrated. The polarizers 218, 302, 318 are aligned with parallel electric vector transmission directions 219, 303, 319, respectively. The passive retarders 330A, 330B are provided with optical axis directions 331A, 331B at 135 degrees and 45 degrees, respectively. The shapes and orientations of the electrodes 500, 502 are illustrated as orthogonal strips, however other shapes and orientations may be provided.

[0146] The structure and operation of an arrangement of multiple retarders will now be described.

[0147] Figure 2A is a schematic diagram illustrating an arrangement of a switchable retarder 300 in a privacy operation mode in a perspective side view, wherein the switchable retarder 301 comprises a switchable liquid crystal layer 314 having a planar alignment and crossed A-plate polarity-controlled passive retarders 330A, 330B; and Figure 2B It means that in the public operation mode Figure 2A Schematic diagram of how the output brightness of the transmitted light changes with the polarity direction.

[0148] The passive delay elements 330A, 330B are composed of non-switching molecules 408A, 408B, respectively.

[0149] The switchable liquid crystal retarder 301 comprises two surface alignment layers 418A, 418B which are arranged adjacent to and on opposite sides of the layer 314 of non-curable liquid crystal material 414 and are each configured to provide a planar alignment in the adjacent non-curable liquid crystal material 414. Advantageously, the planar alignment provides a high restoring force for the molecules of the non-curable liquid crystal material 414 compared to the homeotropic alignment.

[0150] The switchable liquid crystal retarder 301 and the passive retarder 330 may be replaced by any of those described in U.S. Patent No. 10,126,575, U.S. Patent Publication No. 2019-0086706, U.S. Patent No. 10,303,030, U.S. Patent Application No. 16 / 256,120 filed on January 24, 2019 (Agent Docket No. 413101), U.S. Provisional Patent Application No. 62 / 756,902 filed on November 7, 2018 (Agent Docket No. 426000), and U.S. Provisional Patent Application No. 62 / 844,980 filed on May 8, 2019 (Agent Docket No. 426000A), the entire contents of which are incorporated herein by reference in their entirety.

[0151] In the privacy mode, the switchable liquid crystal layer 314 is driven by a first voltage V1. The molecules of the non-curable liquid crystal material 414 and the cured liquid crystal material 420 are aligned in the same alignment, i.e. the variation of the tilt of the molecules through the thickness of the layer 314 is the same for the cured liquid crystal material 420 and the non-curable liquid crystal material 414.

[0152] In the common mode, the switchable liquid crystal layer 314 is driven by a second voltage V2. The molecules of the non-curable liquid crystal material 414 and the cured liquid crystal material 420 are aligned in different orientations, i.e. the change in the tilt across the layer 314 is different for the non-curable liquid crystal material 414 and the cured liquid crystal material 420. Figure 4 The alignment of the liquid crystal in layer 314 is described.

[0153] Some of the cured liquid crystal material 420A may be arranged in a network 424 that extends between and is attached to each of the two support substrates 312, 316. Some of the cured liquid crystal material 420B may be arranged to be attached to the support substrates 312, 316.

[0154] In the privacy mode, the predetermined voltage V1 of the switchable liquid crystal layer 314 causes the layer 314 of the solidified liquid crystal material 420 and the non-solidified liquid crystal material 414 to simultaneously: not introduce a net relative phase shift to the orthogonal polarization component of light passing through the additional polarizer 318 along the axis 199 along the normal to the plane of the at least one polarity-controlled retarder 300, and to introduce a net relative phase shift to the orthogonal polarization component of light passing through the additional polarizer along the axis 197 tilted to the normal to the plane of the at least one polarity-controlled retarder 300. Such phase shift changes, when combined with the passive retarder 330 and analyzed by the polarizers 218, 302, and 318, provide polarity changes in transmittance and reflectance, for example. Figure 3A -Those described in B.

[0155] In the common mode, the switchable liquid crystal layer 314 is driven by V2 which is different from the predetermined voltage V1. The voltage V2 causes the layer 314 of the non-curable liquid crystal material 414 to simultaneously: not introduce a net relative phase shift to the orthogonal polarization component of light passing through the additional polarizer 318 along the axis 199 along the normal to the plane of the at least one polarity-controlled retarder 300, and to introduce a net relative phase shift to the orthogonal polarization component of light passing through the additional polarizer along the axis 197 tilted to the normal to the plane of the at least one polarity-controlled retarder 300. Such phase shift changes, when combined with the passive retarder 330 and analyzed by the polarizers 218, 302 and 318, provide polarity changes in transmittance and reflectance, for example Figure 3C -D as described in.

[0156] A network 424 of solidified liquid crystal material 414 is attached to substrates 312, 316. Deformation of the thickness of layer 314 during applied mechanical force is reduced. The retardation of layer 314 is substantially maintained and the net relative phase shift introduced by the applied mechanical force is maintained for both privacy and public modes of operation. Advantageously, brightness in the area of ​​applied mechanical force is reduced and reflection artifacts are reduced. In other words, during the applied force, the thickness of the liquid crystal layer 314 may vary, thereby producing an undesirable retardation profile in the layer 314. The network 424 of aligned solidified liquid crystal molecules 420 provides resistance to cell gap variations, thereby achieving a uniform retardation profile across the display area. Advantageously, the visibility of artifacts due to variations in the thickness of layer 314 is reduced.

[0157] The molecules 420B arranged near the substrates 312, 316 may be arranged to increase the restoring force of the molecules 414 after a mechanical force is applied. Advantageously, the visibility of artifacts may be reduced.

[0158] During the application of mechanical force, the non-curable liquid crystal material 414 may flow within the layer 314. Such flow may provide disclination that adjusts the retardation characteristics of the layer 314 and changes the net relative phase shift. Fig. 9A Such undesirable disclination is illustrated in FIG. 4B in a layer that does not include the cured liquid crystal material 420 .

[0159] The solidified liquid crystal material 420 provides an increased restoring force to the non-solidified liquid crystal material 414, preventing the formation of large area disclinations, and can reduce the relaxation time of disclinations after flow. Advantageously, the time that brightness and reflection artifacts are visible in the area of ​​applied mechanical force can be reduced, and the size of the artifacts can be reduced.

[0160] In privacy mode, light scattering in layer 314 undesirably directs image data to the location of the snooper and reduces the level of visual security. The molecules of the non-curable liquid crystal material 414 and the cured liquid crystal material 420 are aligned in a common alignment. Light scattering is reduced and the privacy mode visual security level is advantageously increased.

[0161] In common mode, light scattering may be provided in layer 314 due to alignment disorder between molecules of non-curable liquid crystal material 414 and cured liquid crystal material 420. Advantageously, such scattering provides increased angular brightness uniformity in common mode, thereby increasing image visibility for off-axis users.

[0162] During the applied force, flow of the non-curable liquid crystal material 414 may occur in the liquid crystal layer 314. The flow may cause undesirable liquid crystal alignment disturbances and dislocations, which may provide visual artifacts. The network 424 of aligned cured liquid crystal molecules 420 provides resistance to the flow of the non-curable liquid crystal material 414. The amount of retardation variation and disclination in the layer 314 due to the flow is reduced, and the visibility of artifacts due to the flow of the material is advantageously reduced.

[0163] In the privacy mode, the driving voltage V1 may be lower than the driving voltage V2 for the public mode, as shown in Table 1 below for Figure 3A -D. A high drive voltage increases the restoring force and reduces the relaxation time after flow, thereby reducing the time of artifact visibility. It is desirable to provide increased restoring force in layer 314 at a lower drive voltage.

[0164] In this embodiment, the molecules of the non-curable liquid crystal material 414 and the cured liquid crystal material 420 are aligned in the driving state of a given voltage V1, and the restoring force provided by the molecules of the cured liquid crystal material 420 provides the same energy minimum as the energy provided by the driving voltage V1. The total restoring force on the molecule 414 is increased, thereby reducing the size and decay time of the disclination. Advantageously, the visibility of artifacts is reduced.

[0165] In public mode, the time of visibility of artifacts has been reduced due to the resilience provided by the high drive voltage. Advantageously, the time of visibility and the size of flow artifacts are reduced in both private and public modes of operation.

[0166] In the common mode, voltage V2 provides a phase structure with a slow polarity variation of brightness and reflectivity with polar angle, as will be shown in Figure 3C -D, while in privacy mode the polarity roll-off is faster, as will be Figure 3A -B. Retardation changes in layer 314 due to material flow in the area of ​​applied force are visible as local brightness and reflectivity changes that depend on polar angle and deform the polar brightness and reflectivity profiles. The aligned solidified liquid crystal material 420 provides increased restoring force in the privacy mode of operation, thereby reducing the range of polar angles where artifacts exist. Advantageously, polarity changes in the visibility of material 414 flow and disclination artifacts are reduced in both the privacy mode and the public mode.

[0167] It can be assumed that Figure 2A The features of the arrangement of -B correspond to the features with equivalent reference numerals as discussed above, including any potential variations in the features.

[0168] The optical output of the exemplary embodiment will now be described.

[0169] Figure 3A It means that in the privacy operation mode Figure 2A A schematic diagram showing how the transmittance of the transmitted light varies with the polarity direction; and Figure 3B It means that in the privacy operation mode Figure 2A Schematic diagram showing how the reflectivity of reflected light varies with polarity direction; Figure 3C It means that in the public operation mode Figure 2B A schematic diagram showing how the transmittance of the transmitted light varies with the polarity direction; and Figure 3D It means that in the public operation mode Figure 2B A schematic diagram showing how the reflectivity of reflected light varies with polarity direction, including the embodiments shown in Table 1.

[0170]

[0171] Table 1

[0172] The layer 314 of the non-curable liquid crystal material 414 of the switchable liquid crystal retarder 301 comprises a non-curable liquid crystal material 414 having a positive dielectric anisotropy.

[0173] In this example, desirable retardation and voltage ranges have been established by simulating retarder stacks and experimenting with display optical stacks.Retardation ranges providing design configurations for various optical layers will now be described.

[0174] The predetermined voltage is not zero. The layer 314 of non-curable liquid crystal material 414 and cured liquid crystal material 420 has a retardation for light of 550 nm wavelength 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.

[0175] At least one passive delay 330 includes a pair of passive delays 330A, 330B having optical axes crossing in the plane of the delays, each passive delay 330A, 330B in the pair of passive delays has a delay in the following range for light of 550nm wavelength: in the range of 300nm to 800nm, preferably in the range of 350nm to 650nm, and most preferably in the range of 450nm to 550nm.

[0176] In another embodiment (not shown), the at least one passive retarder 330 may include at least one passive retarder 330 having an optical axis perpendicular to the plane of the retarder 330, the at least one passive retarder 330 having a total retardation for light of 550 nm wavelength 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 passive retarder may be provided using a stretched film to advantageously achieve low cost and high uniformity.

[0177] The passive polarity controlled retarder 330 is provided by a pair of A plates 330A, 330B having crossed axes. In this embodiment, "crossed" refers to an angle of substantially 90° between the optical axes of the two retarders in the plane of the retarders. In order to reduce the cost of the retarder material, it is desirable to provide a material that has some variation in the orientation of the retarder, for example due to stretching errors during film manufacturing. Variations in the orientation of the retarder away from the preferred direction can reduce the front brightness and increase the minimum transmittance. Preferably, the angle between the optical axes in the plane of the retarder is 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°.

[0178] Figure 3A -D illustrates that high brightness and low reflectivity are achieved in a direction parallel to axis 199. Advantageously, front users see high image visibility for both private and public modes of operation.

[0179] Figure 3A -B illustrates low brightness and high reflectivity achieved in a direction along axis 197 that is oblique to axis 199 in the lateral direction for privacy operation. Advantageously, a high level of visual security is presented to off-axis snoopers during the privacy mode of operation. Figure 3C -D illustrates that high brightness and low reflectivity are achieved in a direction along axis 197 that is oblique to axis 199 in the lateral direction for public operation. Advantageously, high image visibility is presented to off-axis users during the public operation mode.

[0180] Figure 4 It is the liquid crystal director angle relative to the applied voltage for different Figure 2A -B and Figure 3A Schematic diagram of a graph of fractional positions of a switchable liquid crystal retarder unit of FIG.

[0181] Profile 441 illustrates the tilt angle of the non-curable liquid crystal material 414 for an applied voltage of 0V; tilt profile 443 illustrates the director orientation for the privacy mode for an applied voltage V1 of, for example, 2.5V; and tilt profile 445 illustrates the director orientation for the public mode for an applied voltage V2 of, for example, 5V. Thus, the directors are distributed across the thickness of the cell for both privacy and wide-angle modes. The cured liquid crystal material 420 of this embodiment has a profile 443 for both the privacy mode and the public mode. In contrast, the non-curable liquid crystal material 414 switches between profile 445 in the public mode and profile 443 in the privacy mode.

[0182] In operation, applied pressure may deform contours 443, 445. Deformation of contour 443 is more visible than contour 445. Advantageously, this embodiment achieves increased resistance to deviation of the non-curable liquid crystal material from contour 443. Image artifacts are reduced during applied pressure.

[0183] A method of manufacturing a stable liquid crystal retarder for a switchable privacy display with low artifact visibility during applied mechanical forces will now be presented.

[0184] Figure 5A -D is a schematic diagram illustrating a method for providing a reactive mesogen polymer stabilized switchable liquid crystal retarder for a privacy display in a perspective side view. It may be assumed that Figure 5A The features of the arrangement of -D correspond to the features with equivalent reference numerals as discussed above, including any potential variations in the features.

[0185] A method for manufacturing a switchable liquid crystal retarder 301, wherein the switchable liquid crystal retarder is a polarity control retarder for a display device 100, the method comprising: Figure 5A In the first step shown in the embodiment, a first supporting substrate 312 and a second supporting substrate 316 are provided, wherein the first supporting substrate and the second supporting substrate have electrodes 413, 415 for controlling a liquid crystal layer 314 and have a first liquid crystal alignment layer 418A and a second liquid crystal alignment layer 418B supported thereon for aligning the liquid crystal material of the liquid crystal layer 314, and a liquid crystal layer 314 disposed between the first transparent supporting substrate 312 and the second transparent supporting substrate 316 is disposed, wherein the first liquid crystal alignment layer 418A and the second liquid crystal alignment layer 418B are adjacent to the liquid crystal layer 314, and the liquid crystal layer 314 includes a non-curable liquid crystal material 414 and a curable liquid crystal material 420. The liquid crystal layer may include the optical properties described in Table 1 or other tables herein.

[0186] The curable liquid crystal material 420 may be a reactive mesogen. Reactive mesogens (RMs) are low molecular weight liquid crystal materials containing reactive end groups that can be polymerized by visible or UV light. RMs have the inherent characteristics of liquid crystals, including self-organization, anisotropic optical and dielectric properties, and controlled alignment defined by a surface alignment layer (e.g., rubbed polyimide); at the same time, RMs can be polymerized into a network structure or solid material and retain their liquid crystal alignment and anisotropic properties. By way of example and not limitation, example reactive mesogen materials include RM257 and RM488 sold by Merck Ltd. Example photoinitiators include Irgacure 651 sold by Ciba.

[0187] The ratio of the volume of the curable liquid crystal material 420 to the volume of the non-curable liquid crystal material 414 may be less than 5%. Advantageously, light scattering may be reduced and the level of visual security in the privacy mode may be increased.

[0188] Figure 5A The liquid crystal layer 314 is further illustrated as including an isotropic curable polymer material 421. Prior to curing, the curable polymer material may include a monomer material. The curable polymer materials 420, 421 may include a material including an acrylate or a thiol.

[0189] Figure 5B It is described that a predetermined voltage V1 is applied to the electrodes 413 and 415 . Figure 5C The curable liquid crystal material 420 is illustrated to be cured when a predetermined voltage V1 is applied. The liquid crystal material may further include a polymerization photoinitiator. The step of curing the curable liquid crystal material is performed by applying light radiation 720 from a light source 722 , and preferably ultraviolet radiation, to the liquid crystal layer 314 .

[0190] Figure 5D The liquid crystal retarder 301 is illustrated after the curable liquid crystal material 420 has been cured to the provided network 424 and the voltage V1 has been removed. The non-curable liquid crystal molecules 414 are provided with a tilt and orientation provided by the pre-tilt and alignment direction of the alignment layers 418A, 418B. Figure 5C At the curing step, the solidified liquid crystal material 420 is provided by applying a voltage V1 and the alignment directions of the alignment layers 418A, 418B.

[0191] The network 424 may include a network of cured liquid crystal material 420 and cured isotropic material 421. Crosslinking may be provided between the cured polymer materials 420, 421 by bonding between the liquid crystal material 420, between the isotropic material 421, or between the liquid crystal material 420 and the isotropic material 421. Advantageously, increased resistance to applied mechanical forces may be achieved.

[0192] In other words, a method of manufacturing a liquid crystal retarder for a privacy display device 100 includes the following steps: (i) providing a first transparent support substrate 312 and a second transparent support substrate 316, wherein electrodes 413, 415 are on at least one side of each of the first transparent support substrate 312 and the second transparent support substrate 316; (ii) forming liquid crystal alignment layers 418A, 418B on the electrodes 413, 415 of each of the first transparent support substrate 312 and the second transparent support substrate 316; (iii) providing a liquid crystal layer 314 between the alignment layers; wherein the liquid crystal layer 314 includes (a) a non-curable liquid crystal material 414 and (b) a curable liquid crystal material 420; (iv) applying a curing step voltage across the electrodes; and (v) curing the curable liquid crystal material 420. The curing step voltage V1 is the voltage at which the liquid crystal retarder is driven to provide a privacy operation mode of the display device (e.g., Figure 2A The curable liquid crystal material 420 includes a photoinitiator, and the step of curing the curable liquid crystal material includes illumination by ultraviolet radiation 720.

[0193] like Figure 5D As illustrated in , after curing, the light source 722 and voltage driver are removed and the molecules of the non-curable liquid crystal material 414 relax while the molecules of the cured liquid crystal material 420 remain in the cured liquid crystal network 424 including the molecular orientation of the driven state.

[0194] Advantageously, a switchable liquid crystal retarder 301 may be provided for use in a switchable privacy display 100 having low artifact visibility due to applied pressure during touch operation.

[0195] It would be desirable to reduce the thickness of the polarity control retarder 300 while achieving high image quality during a touch operation.

[0196] Fig. 6A is a schematic diagram illustrating, in a perspective side view, an arrangement of a switchable compensating retarder including a planar-aligned switchable liquid crystal retarder and a negative C-plate in a privacy mode of operation; Figure 6B is a schematic diagram illustrating in perspective side view an arrangement of a switchable compensating retarder including a planar aligned switchable liquid crystal retarder and a negative C-plate providing operation for different applied voltages in a common operating mode; and Figure 6C is a schematic diagram illustrating an arrangement of a switchable compensating retarder and a negative C-plate in a perspective side view for no applied voltage including a switchable liquid crystal retarder aligned in a plane. Fig. 6A The features of the arrangement of -C correspond to the features with equivalent reference numerals as discussed above, including any potential variations in the features.

[0197] and Figure 1Aand Figure 2A -B, the first support substrate 312 and the second support substrate 316 may be provided by passive compensating delays 330A, 330B.

[0198] The passive compensating retarder 330 comprises a negative C-plate retarder having an optical axis which is a fast axis perpendicular to the plane of the retarder. Thus, the material 430 of the C-plate retarder may have a negative dielectric anisotropy. The C-plate may comprise a transparent birefringent material such as polycarbonate or a reactive mesogen cast onto a substrate providing homeotropic alignment, such as Zeonex TM Cyclic olefin polymer (COP); discotic polymer; and Nitto Denko TM Bi-stretch polycarbonate.

[0199] Fig. 6A -C further comprises surface alignment layers 418A, 418B, the two surface alignment layers being arranged adjacent to the layer of the non-curable liquid crystal material 414 and each being configured to provide a planar alignment in the adjacent liquid crystal layer 314. In other words, the switchable liquid crystal retarder comprises two surface alignment layers 418A, 418B, the two surface alignment layers being arranged adjacent to and on opposite sides of the layer of the non-curable liquid crystal material 414 and each being configured to provide a planar alignment in the adjacent non-curable liquid crystal material 414. For example, a material such as glass can be used. Figure 1A The substrate provided by the passive compensating delay 330A, 330B may have a reduced thickness and stiffness compared to a substrate of a display having a plurality of layers 314 and a plurality of layers 314 disposed thereon. Advantageously, this embodiment provides for increased resilience of the layer 314 to applied mechanical forces during touch operation. Such displays may also be foldable or bendable. Advantageously, increased resilience to folding or bending of the display may be achieved. A very small thickness may be achieved.

[0200] We will now describe Fig. 6A and 6B The optical output of the arrangement.

[0201] Fig. 7A It means that in the public operation mode Figure 6B Schematic diagram of the transmission brightness of the transmitted light in the image changing with the polarity direction; Figure 7B It means that in the privacy operation mode Fig. 6A Schematic diagram of the transmission brightness of the transmitted light in the image changing with the polarity direction; Figure 7C It means that in the privacy operation mode Fig. 6A Schematic diagram of how the reflectivity of reflected light varies with polarity direction, including the arrangement described in Table 2.

[0202]

[0203] Table 2

[0204] The passive polarity control retarder 330 includes a first C-plate 330A and a second C-plate 330B; and the switchable liquid crystal layer 314 is provided between the first C-plate 330A and the second C-plate 330B. The switchable liquid crystal retarder 301 includes two surface alignment layers 418A, 418B, which are arranged adjacent to the layer 314 of the non-curable liquid crystal material 414 and on opposite sides thereof, and each is configured to provide a planar alignment in the adjacent non-curable liquid crystal material 414. The layer of the non-curable liquid crystal material 414 of the switchable liquid crystal retarder 301 includes a non-curable liquid crystal material 414 having positive dielectric anisotropy.

[0205] In this example, desirable retardation and voltage ranges have been established by simulating retarder stacks and experimenting with display optical stacks.Retardation ranges providing design configurations for various optical layers will now be described.

[0206] The liquid crystal material layer 314 has a retardation for light of 550 nm wavelength in the following range: in the range of 500 nm to 1000 nm, preferably in the range of 600 nm to 900 nm, and most preferably in the range of 700 nm to 850 nm. The two passive retarders 330A, 330B each include a passive retarder having an optical axis perpendicular to the plane of the retarder, and the total retardation of the two passive retarders for light of 550 nm wavelength is in the following range: 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.

[0207] Advantageously, in very low thickness embodiments, high optical performance can be achieved in both private and public modes of operation.

[0208] The operation of the privacy display will now be further described.

[0209] Fig. 8A The previous perspective diagram illustrates the Figure 1A Schematic diagram of the observation of reflected ambient light on the interface surface of the display.

[0210] Display 100 may be provided with white areas 603 and black areas 601. The snooper 47 may observe an image on the display if a brightness difference between the black areas 601 and the white areas 603 is perceived. In operation, primary user 45 observes a full brightness image at observation location 26, which may be an optical window of a directional display, through rays 700. Snooper 47 observes reduced brightness rays 402 at observation location 27, which may be, for example, an optical window of a directional display including an imaging waveguide. Observation locations 26, 27 further indicate Figure 3C -D's polar diagram in the on-axis and off-axis regions.

[0211] Thus, some of the light rays 404 may be reflected by the front surface of the additional polarizer 318 and other surfaces of the display. Typically, such reflectivity may be 4% for a bonded optical stack at normal incidence and about 5% for a bonded optical stack at 45 degree incidence due to Fresnel reflection at the air-polarizer interface. Thus, a low brightness reflected image 605 of the source 604 may be observed by a peeper in front of the display 100.

[0212] Figure 8B The previous perspective illustrates the operation in private mode. Figure 1A Schematic diagram of observation of reflected ambient light of a display. Observation positions 26 and 27 further represent Figure 3A -B's on-axis and off-axis regions of the polar diagram. Fig. 8A By comparison, for the off-axis snooper 47 in the off-axis viewing position 27, the reflection 606 from the source 604 can be observed to have a substantially higher reflected brightness. In contrast, the user 45 in the viewing position 26 sees a low reflectivity image with a high brightness. The shape and distribution of the reflected image 606 is determined by the spatial distribution of the ambient light source 604, but can be further determined by the diffusion layer, particularly at the output surface of the additional polarizer 318.

[0213] Advantageously, the image seen by the user 45 has high brightness and image visibility, while the image seen by the snooper 47 has low brightness and a high visual security level.

[0214] It can be assumed that Fig. 8A The features of the arrangement of -B correspond to the features with equivalent reference numerals as discussed above, including any potential variations in the features.

[0215] The appearance of artifacts due to the applied force applied to the liquid crystal layer without the cured liquid crystal material 420 of the present embodiment will now be described.

[0216] Fig. 9A is a photograph showing the appearance of disclination 600 in the nematic liquid crystal layer 314 not including the cured liquid crystal material of the present embodiment during application of pressure by the finger 25; and Fig. 9B is a photograph showing the appearance of disclinations 600 in a nematic liquid crystal layer not including the cured liquid crystal material of the present embodiment after pressure release and shortly before complete annealing of the disclinations.

[0217] Such disclinations provide undesirable image artifacts over a relatively large area and last for several seconds and are unacceptable for display appearance.

[0218] It would be desirable to provide increased uniformity of common operating modes.

[0219] Fig. 10A is a schematic diagram illustrating, in a perspective side view, an arrangement of a switchable compensating retarder 300 including a homeotropically aligned switchable liquid crystal retarder 301 and a negative C-plate 330 in a privacy mode of operation; and Fig. 10B is a diagram illustrating the liquid crystal director angle relative to the common operation mode provided by no applied voltage across the pair. Fig. 10A Schematic diagram of a graph of fractional positions of a switchable liquid crystal retarder unit.

[0220] Substrate 316 may be provided by retarder 330 to advantageously reduce thickness, while substrate 312 may be provided by a harder substrate material, such as glass, to increase rigidity and advantageously reduce visibility of artifacts resulting from applied forces during touch operations.

[0221] The switchable liquid crystal retarder 301 includes two surface alignment layers 418A, 418B, which are disposed adjacent to and on opposite sides of the non-curable liquid crystal material 414 and are arranged to provide a homeotropic alignment at the adjacent non-curable liquid crystal material 414. The non-curable liquid crystal material 414 may be provided with a pre-tilt of, for example, 88 degrees from the horizontal to remove the degeneracy of the alignment of the non-curable liquid crystal material 414. When driven with the privacy mode voltage V1, the cured liquid crystal material 420 may have the same alignment as the alignment of the non-curable liquid crystal material 420. Therefore, in the public mode, the alignments of the non-curable liquid crystal material 414 and the cured liquid crystal material 420 are different, and advantageously some scattering may be provided to increase uniformity.

[0222] Fig.11A It means that in the privacy operation mode Fig. 10A Schematic diagram of the output brightness of the transmitted light changing with the polarity direction; Fig. 11B It means that in the privacy operation mode Fig. 10A Schematic diagram showing how the reflectivity of reflected light changes with polarity direction; Fig. 11C It means that in the public operation mode Fig. 10B A schematic diagram showing how the output brightness of the transmitted light varies with the polarity direction; and Fig.11D It means that in the public operation mode Fig. 10B Schematic diagram of the variation of the reflectivity of reflected light with polarity direction, including the arrangement described in Table 3.

[0223]

[0224] Table 3

[0225] Compared to the embodiments of Tables 1 and 2, the liquid crystal retarder alignment is provided by homeotropic alignment rather than longitudinal alignment. Figure 3C -D, improved Fig. 11C -D wide angle mode performance. In addition, due to the low driving voltage, the power consumption of the common mode is reduced.

[0226] The liquid crystal material layer of the switchable liquid crystal retarder includes a liquid crystal material having negative dielectric anisotropy.

[0227] The switchable liquid crystal retarder 301 comprises two surface alignment layers 418A, 418B which are arranged adjacent to the non-curable liquid crystal material 414 on opposite sides thereof and are each configured to provide a homeotropic alignment at the adjacent non-curable liquid crystal material 414 .

[0228] In this example, desirable retardation and voltage ranges have been established by simulating retarder stacks and experimenting with display optical stacks.Retardation ranges providing design configurations for various optical layers will now be described.

[0229] The layer of liquid crystal material has a retardation for light of wavelength 550 nm 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.

[0230] At least one passive delay device comprises a passive delay device having an optical axis perpendicular to the plane of the delay device, the passive delay device having a delay within the following range for light at a wavelength of 550nm: within the range of -300nm to -900nm, preferably within the range of -450nm to -800nm, and most preferably within the range of -500nm to -725nm; or (not shown) at least one passive delay device comprises a pair of passive delay devices having optical axes crossing in the plane of the delay device, each passive delay device in the pair of passive delay devices having a delay within the following range for light at a wavelength of 550nm: within the range of 300nm to 800nm, preferably within the range of 500nm to 700nm, and most preferably within the range of 550nm to 675nm.

[0231] The switchable liquid crystal retarder 301 comprises two surface alignment layers, which are arranged on the electrodes 413, 415 and adjacent to and on opposite sides of the layer of non-curable liquid crystal material 414, and each is configured to provide a homeotropic alignment in the adjacent non-curable liquid crystal material 414. The layer of non-curable liquid crystal material 414 of the switchable liquid crystal retarder 301 comprises a liquid crystal material having a negative dielectric anisotropy. The liquid crystal molecules 414 may be provided with a pre-tilt of, for example, 88 degrees from the horizontal to remove degeneracy in switching.

[0232] Fig.11Eis a schematic diagram illustrating a graph of a liquid crystal director angle 407 relative to a fractional position 440 across a switchable liquid crystal retarder unit, wherein the fractional position 440 varies between 0 for a position at the surface alignment layer 409 and 1 for a position at the surface alignment layer 411. Fig.11E Different from Figure 4 , because the pretilt angle is large and decreases with the applied voltage.

[0233] like Fig. 6A , for a homeotropic mode with no voltage applied, the liquid crystal director is at a tilt 407 of 88 degrees through the thickness of the cell, as indicated by tilt profile 442. The tilt profile of layer 314 may be the same as profile 442. Compensating retarder 330 may provide correction to the pre-tilt direction of switchable liquid crystal retarder 301. Compensating retarder 330 may alternatively have a uniform tilt angle of 90 degrees, such a difference from the pre-tilt of the liquid crystal layer providing only a minor difference in off-axis viewing characteristics. The non-curable liquid crystal material 414 switches between profile 442 in the public mode and profile 444 in the privacy mode, while the cured liquid crystal material 420 maintains profile 444 in both operating modes.

[0234] The formation will now be described Fig. 10A -B method for switchable liquid crystal layer.

[0235] Fig. 12A -D is a schematic diagram illustrating, in a perspective side view, a method of providing a liquid crystal polymer stabilized switchable liquid crystal retarder for a privacy display comprising a homeotropic alignment layer. Fig. 12A -D method and Figure 5A The method of -D is similar, except that the liquid crystal materials 414, 420 include negative dielectric anisotropy materials and homeotropic alignment layers 418A, 418B are provided.

[0236] A method for manufacturing a liquid crystal retarder for a privacy display device 100 includes the following steps: (i) providing a first transparent supporting substrate 312 and a second transparent supporting substrate 316, wherein electrodes 413, 415 are on at least one side of each of the first transparent supporting substrate 312 and the second transparent supporting substrate 316; (ii) forming a liquid crystal alignment layer on the electrodes 413, 415 of each of the first transparent supporting substrate 312 and the second transparent supporting substrate 316; (iii) providing a liquid crystal layer 314 between the alignment layers; wherein the liquid crystal layer 314 includes (a) a non-curable liquid crystal material 414 and (b) a curable liquid crystal material 420; and the liquid crystal layer 314 has a delay for light of 550 nm wavelength in the following range: 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; (iv) applying a curing step voltage across the electrodes; and (v) curing the curable liquid crystal material 420. The curing step voltage V1 is at which the liquid crystal retarder is driven to provide a privacy operation mode of the display device (eg Figure 2A The curable liquid crystal material 420 includes a photoinitiator, and the step of curing the curable liquid crystal material includes illumination by ultraviolet radiation 720.

[0237] In more detail, Fig. 12A As described in , in a first step, a liquid crystal layer is provided, wherein the liquid crystal material comprises non-curable liquid crystal molecules 414 and curable liquid crystal molecules 420. An alignment layer (not shown) is arranged to provide alignment, for example, in-plane alignment at each surface by anti-parallel pre-tilt alignment.

[0238] like Fig. 12B As illustrated in FIG. 4 , a voltage may be applied across the liquid crystal layer 314 via electrodes 413, 415. The voltage may be substantially the same as the voltage V1 provided to achieve the liquid crystal alignment state for privacy operation.

[0239] like Fig. 12C As described in , the cell can be cured while maintaining the applied voltage. The curable liquid crystal material 420 may include, for example, reactive mesogen molecules having a birefringence similar to that of the non-curable liquid crystal material 414 and the photoinitiator.

[0240] like Fig.12D As illustrated in , after curing, the light source 722 and voltage driver are removed and the molecules of the non-curable liquid crystal material 414 relax while the molecules of the cured liquid crystal material 420 remain in the cured liquid crystal network 424 including the molecular orientation of the driven state.

[0241] The operation of the polarity-controlled retarder layer between parallel polarizers for off-axis illumination will now be further described. In the various arrangements described above, at least one polarity-controlled retarder is arranged between the reflective polarizer 318 and the additional polarizer 218 in various different configurations. In each case, the at least one polarity-controlled retarder is configured such that it does not affect the brightness of light passing through the reflective polarizer 318, the at least one polarity-controlled retarder, and the additional polarizer 218 along an axis along the normal to the plane of the one or more polarity-controlled retarders, but does reduce the brightness of light passing through the reflective polarizer 318, the at least one polarity-controlled retarder, and the additional polarizer 218 along an axis tilted to the normal to the plane of the one or more polarity-controlled retarders in at least one of the compensating switchable states of the switchable polarity-controlled polarity-controlled retarder 300. This effect will now be described in more detail, the principles of which are generally applicable to all arrangements described above.

[0242] Fig.13A 630 may include a birefringent material represented by a refractive index ellipsoid 632, the optical axis direction 634 of which is 0 degrees from the x-axis and has a thickness 631. It may be assumed that Figures 13A-15E Features of the arrangements correspond to features with equivalent reference numerals as discussed above, including any potential variations in features.

[0243] Normal ray 636 propagates such that the path length in the material is the same as thickness 631. Ray 637 in the yz plane has an increased path length; however, the birefringence of the material is substantially the same as ray 636. By comparison, ray 638 in the xz plane has an increased path length in the birefringent material, and additionally, the birefringence is different than normal ray 636.

[0244] Therefore, the delay of polarity controlled retarder 630 depends on the angle of incidence of the corresponding ray and also on the plane of incidence, ie, the delay of ray 638 in the xz plane will be different from the delay of normal ray 636 and ray 637 in the yz plane.

[0245] The interaction of polarized light with the polarization controlled retarder 630 will now be described. In order to distinguish the first polarization component from the second polarization component during operation in the directional backlight 101, the following explanation will refer to the third polarization component and the fourth polarization component.

[0246] Fig. 13B is a schematic diagram illustrating in perspective the illumination of the polarization-controlled retarder layer by off-axis light of a third linear polarization state at 90 degrees to the x-axis, and Fig. 13Cis a schematic diagram illustrating, in perspective, the illumination of the polarization-controlled retarder layer by off-axis light of a fourth linear polarization state at 0 degrees to the x-axis. In such an arrangement, the incident linear polarization state is aligned with the optical axis of the birefringent material represented by ellipse 632. Therefore, no phase difference is provided between the third orthogonal polarization component and the fourth orthogonal polarization component, and no change is produced in the polarization state of the linearly polarized input for each ray 636, 637, 638. Therefore, the polarization-controlled retarder 630 does not introduce a phase shift into the polarization component of light that passes through the polarizer on the input side of the polarization-controlled retarder 630 along an axis that is normal to the plane of the polarization-controlled retarder 630. Therefore, the polarization-controlled retarder 630 does not affect the brightness of light that passes through the polarization-controlled retarder 630 and the polarizers (not shown) on each side of the polarization-controlled retarder 630. Although Fig.13A -C specifically relates to a passive polarity-controlled delay 630, but the polarity-controlled delays in the devices described above achieve a similar effect.

[0247] Fig.13D A schematic diagram illustrating illumination of a polarization control retarder 630 layer by off-axis light in a 45 degree linear polarization state is shown in perspective. The linear polarization state can be decomposed into a third polarization component and a fourth polarization component that are orthogonal and parallel to the direction of the optical axis 634, respectively. For a design wavelength, the polarization control retarder thickness 631 and the material retardation represented by the refractive index ellipsoid 632 can provide a net effect of relative phase shifting of the third polarization component and the fourth polarization component incident thereon in a normal direction represented by a half wavelength ray 636. The design wavelength can be, for example, in the range of 500 nm to 550 nm.

[0248] At the design wavelength and for light propagating normally along ray 636, the output polarization at -45 degrees may be rotated 90 degrees to a linear polarization state 640. Due to the change in thickness, light propagating along ray 637 may see a phase difference that is similar, but not identical, to the phase difference of the light along ray 637, and may therefore output an elliptical polarization state 639 whose major axis may be similar to the linear polarization axis of the output light of ray 636.

[0249] By comparison, the phase difference of the incident linear polarization state along ray 638 can be significantly different, and in particular can provide a lower phase difference. Such a phase difference can provide an output polarization state 644 that is substantially circular at a given tilt angle 642. Thus, the polarization-controlled retarder 630 introduces a phase shift to the polarization component of light that passes through the polarizer on the input side of the polarization-controlled retarder 630 along the axis corresponding to the normal to the plane of the polarization-controlled retarder 630. Although Fig.13DA passive polarity-controlled retarder 630 is involved, but a similar effect is achieved to the polarity-controlled retarder described above in the switchable state of the switchable liquid crystal polarity-controlled retarder corresponding to the privacy mode.

[0250] To illustrate the off-axis behavior of the polarity controlled retarder stack, the angular brightness control of the C-plates 330A, 330B between the additional polarizer 318 and the output display polarizer 218 will now be described for various off-axis illumination arrangements with reference to the operation of the C-plate between the parallel polarizers 503, 210.

[0251] Fig.14A Schematic diagram illustrating illumination of a C-plate layer by off-axis polarized light having a positive elevation angle in perspective. An incident linear polarization component 704 is incident on the birefringent material 632 of the polarity control retarder 560, which is a C-plate having an optical axis direction 507 perpendicular to the plane of the polarity control retarder 560. Polarization component 704 sees no net phase difference when transmitted through the liquid crystal molecules, and therefore the output polarization component is the same as component 704. Therefore, maximum transmittance is seen through the polarizer 210. Therefore, the optical axis 561 of the polarity control retarder 560 is perpendicular to the plane of the polarity control retarder 560, i.e., the xy plane. The polarity control retarder 560 having an optical axis perpendicular to the plane of the polarity control retarder includes a C-plate.

[0252] Fig. 14B is a schematic diagram illustrating, in perspective, illumination of a C-plate layer by off-axis polarized light having a negative side angle. As with the arrangement of 14A, polarization state 704 sees no net phase difference and is transmitted at maximum brightness. Therefore, polarization-controlled retarder 560 does not introduce a phase shift to the polarization component of light that passes through the polarizer on the input side of polarization-controlled retarder 560 along an axis that is normal to the plane of polarization-controlled retarder 560. Therefore, polarization-controlled retarder 560 does not affect the brightness of light that passes through polarization-controlled retarder 560 and polarizers (not shown) on each side of polarization-controlled retarder 560. Although Fig.14A -C specifically relates to a passive polarity-controlled delay 560, but the polarity-controlled delays in the devices described above achieve a similar effect.

[0253] Fig. 14C is a schematic diagram illustrating in perspective the illumination of a C-plate layer by off-axis polarized light having a positive elevation angle and a negative lateral angle. Fig.14A Compared to the arrangement of -B, polarization state 704 is decomposed into eigenstates 703, 705 relative to the birefringent material 632, thereby providing a net phase difference when transmitted through the polarization controlled retarder 560. Fig.14A The resulting elliptically polarized component 656 is transmitted through polarizer 210 with reduced brightness compared to the ray illustrated in -B.

[0254] Fig.14D Schematic diagram of the illumination of the C-plate layer by off-axis polarized light with positive elevation angle and positive lateral angle in perspective view. Fig. 14C In a similar manner, polarization component 704 is decomposed into eigenstates 703, 705 that experience a net phase difference and provide an elliptical polarization component 660 that reduces the brightness of the corresponding off-axis ray after transmission through the polarizer. Thus, the polarization-controlled retarder 560 introduces a phase shift to the polarization component of light that passes through the polarizer on the input side of the polarization-controlled retarder 560 along an axis that is tilted to the normal to the plane of the polarization-controlled retarder 560. Although Fig.14D A passive polarity-controlled retarder 560 is involved, but a similar effect is achieved to the polarity-controlled retarder described above in the switchable state of the switchable liquid crystal polarity-controlled retarder corresponding to the privacy mode.

[0255] Fig.14E It is explained in Fig.14A -Schematic diagram of the output transmittance of the transmitted light in D varying with the polarity direction. Therefore, the C-plate can provide reduced brightness in the polarity quadrant. In combination with the switchable liquid crystal layer 314 described elsewhere herein, (i) the brightness reduction of the C-plate can be removed in the first wide-angle operating state, and (ii) an extended polarity region with reduced brightness can be achieved in the second privacy operating state.

[0256] To illustrate the off-axis behavior of the polarity-controlled retarder stack, angular brightness control of the crossed A-plates 330A, 330B between the additional polarizer 318 and the output display polarizer 218 will now be described for various off-axis illumination arrangements.

[0257] Fig.15A Schematic diagram illustrating illumination of crossed A-plate retarder layers by off-axis polarized light having a positive elevation angle in perspective. A linear polarizer 218 having an electric vector transmission direction 219 is used to provide a linear polarization state 704 parallel to the lateral direction on the first A-plate 330A of the crossed A-plates 330A, 330B. The optical axis direction 331A is tilted +45 degrees relative to the lateral direction. The polarity-controlled retarder 330A is oriented to an off-axis angle θ in the positive elevation direction. 1 The delay provides a resulting polarization component 650 that is generally elliptical at output. The polarization component 650 is incident on the second A-plate 330B of the crossed A-plates 330A, 330B, the optical axis direction 331B of the second A-plate being orthogonal to the optical axis direction 331A of the first A-plate 330A. Fig.15A In the incident plane, the second A plate 330B has an off-axis angle θ 1 The retardation of is equal and opposite to the retardation of the first A-plate 330A. Therefore, a net zero retardation is provided for the incident polarization component 704, and the output polarization component is the same as the input polarization component 704.

[0258] The output polarization component is aligned with the electric vector transmission direction of the additional polarizer 318 and is therefore efficiently transmitted. Advantageously, there is substantially no loss for light rays having zero lateral angle components, thereby achieving full transmission efficiency.

[0259] Fig. 15B Schematic diagram illustrating illumination of crossed A-plate retarder layers by off-axis polarized light having a negative side angle in perspective. Thus, the input polarization component is converted by the first A-plate 330A into an intermediate polarization component 652, which is generally an elliptical polarization state. The second A-plate 330B again provides equal and opposite retardation to the first A-plate, so that the output polarization component is the same as the input polarization component 704, and the light is effectively transmitted through the polarizer 318.

[0260] Thus, the polarity-controlled retarder includes a pair of retarders 330A, 330B whose optical axes cross in the plane (in this embodiment, the xy plane) of the retarders 330A, 330B. The pair of retarders 330A, 330B have optical axes 331A, 331B, each extending at 45° relative to the direction of electric vector transmission parallel to the electric vector transmission of the polarizer 318.

[0261] Advantageously, there is substantially no loss for light rays having an angular component at zero elevation, thereby achieving full transmission efficiency.

[0262] Fig. 15C Schematic diagram illustrating illumination of crossed A-plate retarder layers by off-axis polarized light having positive elevation angle and negative lateral angle in perspective. Polarization component 704 is converted by first A-plate 330A into elliptical polarization component 654. Resulting elliptical component 656 is output from second A-plate 330B. Elliptical component 656 is analyzed by input polarizer 318 with reduced brightness compared to the input brightness of first polarization component 704.

[0263] Fig.15D is a schematic diagram illustrating in perspective the illumination of crossed A-plate retarder layers by off-axis polarized light having positive elevation and positive side angles. Polarization components 658 and 660 are provided by first A-plate 330A and second A-plate 330B since the net retardation of the first and second retarders provides no compensation.

[0264] Thus, for light having a non-zero lateral angle component and a non-zero elevation angle component, the brightness is reduced. Advantageously, display privacy may be increased for a snooper disposed in the viewing quadrant without substantially reducing luminous efficiency for the primary display user.

[0265] Fig.15E It is explained in Fig.15A -Schematic diagram of the output transmittance of the transmitted light in D changing with the polarity direction. Fig.14E Compared to the arrangement of , the area of ​​reduced brightness is increased for off-axis viewing. However, compared to the C-plate arrangement for off-axis viewing in the first common operating mode state, the switchable liquid crystal layer 314 may provide reduced uniformity.

[0266] As used herein, the terms "substantially" and "approximately" provide industry-accepted tolerances for their corresponding terms and / or relativity between items. Such industry-accepted tolerances range from zero percent to ten percent and correspond to, but are not limited to, component values, angles, etc. The relativity between such items is between approximately zero percent and ten percent.

[0267] Although various embodiments according to the principles disclosed herein have been described above, it should be understood that the embodiments are presented by way of example only and not limitation. Therefore, the breadth and scope of the present disclosure should not be limited by any of the exemplary embodiments described above, but should only be defined in accordance with any claims issued from this disclosure and their equivalents. In addition, the above advantages and features are provided in the described embodiments, but the application of such issued claims should not be limited to processes and structures that achieve any or all of the above advantages.

[0268] In addition, the section headings provided herein are consistent with the recommendations under 37 CFR 1.77, or otherwise provide organizational cues. These headings should not limit or characterize the embodiments set forth in any claims that may be issued by the present disclosure. Specifically and by way of example, although the title refers to the "technical field", the claims should not be limited by the language selected under this title to describe the so-called field. In addition, the description of the technology in the "background technology" should not be interpreted as admitting that certain technologies are prior art to any embodiment of the present disclosure. "Invention content" is also not considered to be a feature of one or more embodiments set forth in the issued claims. In addition, any reference to "invention" in the singular form in the present disclosure should not be used to demonstrate that there is only a single novel point in the present disclosure. Multiple embodiments can be set forth according to the limitations of multiple claims issued from the present disclosure, and such claims accordingly define multiple embodiments and their equivalents protected by them. In all cases, the scope of such claims should be considered on its own merits in view of the present disclosure, and should not be constrained by the titles set forth herein.

Claims

1. A display device, the display device include: Spatial light modulator; a display polarizer disposed on one side of the spatial light modulator, the display polarizer being a linear polarizer; an additional polarizer disposed on the same side of the spatial light modulator as the display polarizer, the additional polarizer being a linear polarizer; as well as at least one polarity-controlled retarder, the at least one polarity-controlled retarder being arranged between the additional polarizer and the display polarizer, wherein the at least one polarity-controlled retarder comprises a switchable liquid crystal retarder, the switchable liquid crystal retarder comprising: a first transparent supporting substrate and a second transparent supporting substrate; a liquid crystal layer disposed between the first transparent supporting substrate and the second transparent supporting substrate, the liquid crystal layer comprising a non-curable liquid crystal material and a cured polymer material, wherein the cured polymer material comprises a cured liquid crystal material, wherein the cured polymer material is arranged to provide resistance to flow of the non-curable liquid crystal material; an electrode arranged to apply a voltage for controlling the liquid crystal layer, wherein the curable liquid crystal material has an alignment aligned with an alignment of the non-curable liquid crystal material in a state in which a predetermined voltage is applied to the electrode; and a corresponding liquid crystal alignment layer supported on the first transparent supporting substrate and the second transparent supporting substrate adjacent to the liquid crystal layer for aligning the non-curable liquid crystal material, The predetermined voltage is capable of causing the layers of the solidified liquid crystal material and the non-solidified liquid crystal material to simultaneously perform the following operations: not introducing a net relative phase shift into the orthogonal polarization component of light passing through the display polarizer along an axis along the normal to the plane of the at least one polarity-controlled retarder, and introducing a net relative phase shift into the orthogonal polarization component of light passing through the additional polarizer along an axis inclined to the normal to the plane of the at least one polarity-controlled retarder. 2 . The display device according to claim 1 , wherein the curable polymer material comprises an acrylate or thiol material. 3 . The display device according to claim 1 , wherein the solidified liquid crystal material comprises reactive mesogens. 4 . The display device of claim 1 , wherein a ratio of a volume of the curable polymer material to a volume of the non-curable liquid crystal material is less than 5%. 5 . The display device according to claim 1 , wherein the cured polymer material is arranged into a network extending between the two transparent supporting substrates. The display device according to claim 5 , wherein the network is attached to each of the two transparent supporting substrates. 7 . The display device according to claim 1 , wherein the electrodes are provided on opposite sides of the liquid crystal layer.

8. A display device according to claim 1, further comprising a control system arranged to control the voltage applied to the electrodes of the switchable liquid crystal retarder. 9 . The display device of claim 1 , wherein the at least one polarity-controlled retarder further comprises at least one passive compensation retarder.

10. A display device according to claim 9, wherein the switchable liquid crystal retarder comprises two surface alignment layers, which are arranged adjacent to the liquid crystal layer on opposite sides of the liquid crystal layer and are each configured to provide a homeotropic alignment in the non-curable liquid crystal material. The display device according to claim 10 , wherein the liquid crystal layer has negative dielectric anisotropy. 12 . The display device according to claim 10 , wherein the liquid crystal layer has a retardation within the range of 500 nm to 1000 nm for light of a wavelength of 550 nm.

13. The display device according to claim 10, in: The at least one passive compensating retarder comprises at least one passive retarder having an optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a total retardation for light of 550 nm wavelength within the range of: within the range of -300 nm to -900 nm; or The at least one passive compensating delay comprises a pair of passive retarders having optical axes crossing in the plane of the retarders, each of the pair of passive retarders having a delay within the range of 300nm to 800nm ​​for light of a wavelength of 550nm.

14. A display device according to claim 9, wherein the switchable liquid crystal retarder comprises two surface alignment layers, which are arranged adjacent to the liquid crystal layer and on opposite sides thereof, and each is configured to provide a planar alignment in the non-curable liquid crystal material. 15 . The display device according to claim 14 , wherein the liquid crystal layer has positive dielectric anisotropy. 16 . The display device according to claim 14 , wherein the liquid crystal layer has a retardation within the range of 500 nm to 900 nm for light of a wavelength of 550 nm.

17. The display device according to claim 14, in: The at least one passive compensating retarder comprises at least one passive retarder having an optical axis perpendicular to the plane of the retarder, the at least one passive retarder having a total retardation for light of 550 nm wavelength in the range of: -300 nm to -700 nm; or The at least one passive compensating delay comprises a pair of passive retarders having optical axes crossing in the plane of the retarders, each of the pair of passive retarders having a delay within the range of 300nm to 800nm ​​for light of a wavelength of 550nm.

18. A method of manufacturing a switchable liquid crystal retarder, the switchable liquid crystal retarder being a polarity-controlled retarder for a display device, the method include: providing a first transparent supporting substrate and a second transparent supporting substrate, the first transparent supporting substrate and the second transparent supporting substrate having electrodes for controlling a liquid crystal layer, and having a first liquid crystal alignment layer and a second liquid crystal alignment layer supported thereon for aligning liquid crystal materials of the liquid crystal layer; a liquid crystal layer disposed between the first transparent supporting substrate and the second transparent supporting substrate, wherein the first liquid crystal alignment layer and the second liquid crystal alignment layer are adjacent to the liquid crystal layer, and the liquid crystal layer comprises a non-curable liquid crystal material and a curable polymer material; as well as curing the curable polymer material upon application of a predetermined voltage to the electrodes, wherein the cured polymer material is arranged to provide resistance to flow of the non-curable liquid crystal material, The predetermined voltage is capable of causing the layers of solidified polymer material and non-solidified liquid crystal material to simultaneously perform the following operations: not introducing a net relative phase shift into an orthogonal polarization component of light passing through the additional polarizer along an axis along the normal to the plane of at least one polarity-controlled retarder, and introducing a net relative phase shift into an orthogonal polarization component of light passing through the additional polarizer along an axis inclined to the normal to the plane of the at least one polarity-controlled retarder.

19. The method of claim 18, wherein the curable polymer material is a reactive mesogen.

20. The method of claim 18, wherein The liquid crystal layer further includes a polymerization photoinitiator, and The step of curing the curable polymer material is performed by applying ultraviolet radiation to the liquid crystal layer. The method of claim 18 , wherein the predetermined voltage is non-zero.

22. A display device, the display device include: Spatial light modulator; a display polarizer disposed on one side of the spatial light modulator, the display polarizer being a linear polarizer; an additional polarizer disposed on the same side of the spatial light modulator as the display polarizer, the additional polarizer being a linear polarizer; as well as at least one polarity-controlled retarder, the at least one polarity-controlled retarder being arranged between the additional polarizer and the display polarizer, wherein the at least one polarity-controlled retarder comprises a switchable liquid crystal retarder, the switchable liquid crystal retarder comprising: a first support substrate and a second support substrate; a liquid crystal layer disposed between the first supporting substrate and the second supporting substrate, the liquid crystal layer comprising a non-curable liquid crystal material and a curable polymer material, wherein the curable polymer material is arranged to provide resistance to flow of the non-curable liquid crystal material during application of the applied force; electrodes arranged to apply a voltage for controlling the liquid crystal layer; and a corresponding liquid crystal alignment layer supported on the first supporting substrate and the second supporting substrate adjacent to the liquid crystal layer for aligning the non-curable liquid crystal material, in The display device is configured such that application of a predetermined voltage to the electrodes causes the layers of the solidified liquid crystal material and the non-solidified liquid crystal material to simultaneously: introduce no net relative phase shift to an orthogonal polarization component of light that passes through the display polarizer along an axis that is normal to a plane of the at least one polarity-controlled retarder, and introduce a net relative phase shift to an orthogonal polarization component of light that passes through the additional polarizer along an axis that is tilted to the normal to the plane of the at least one polarity-controlled retarder, and The curable liquid crystal material has an alignment aligned with an alignment of the non-curable liquid crystal material in a state in which the predetermined voltage is applied to the electrodes.

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