Touch screen and touch input display device for privacy display

Abstract

To provide touch input for display devices with control of angular illumination for use in privacy display and low stray light displays.SOLUTION: A display comprises a polarized output spatial light modulator, a switchable liquid crystal retarder, an absorbing polarizer, and touch panel electrodes. Electrodes of the switchable liquid crystal retarder shield the touch panel electrodes from electrical noise of the spatial light modulator addressing. The touch panel control and sensing may be synchronized with a driving signal of the switchable liquid crystal retarder. The touch panel may be operated independently of the timing of the data addressing of the spatial light modulator.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to display devices with control of angular illumination for use in privacy displays and touch input with low stray light displays. [Background technology]

[0002] Privacy displays provide image visibility to the primary user (usually in an on-axis position) and reduced visibility of the image content to peepers, typically in off-axis positions. The privacy function may be provided by microlouver optical films that transmit high brightness from the display in the on-axis direction and reduce brightness in off-axis positions, but such films are not electrically switchable, limiting the display to a privacy-only function.

[0003] Controlling the off-axis light output may provide a switchable privacy display.

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

[0005] Further control can be provided by off-axis brightness reduction, which can be achieved by a switchable backlight for a liquid crystal display (LCD) spatial light modulator (SLM). Off-axis brightness reduction can also be provided by switchable liquid crystal retarders, polarizers, and compensation retarders arranged to modulate the input and / or output directional brightness profile of the SLM.

[0006] The touchscreen is arranged to receive input locations from an observer's finger or stylus and may comprise capacitive touch sensing technology, resistive touch sensing technology, electromagnetic induction sensing technology, and other known touch sensing technologies. Summary of the Invention

[0007] According to a first aspect of the present disclosure, there is provided a touch input display device comprising: a spatial light modulator (SLM) arranged to output light; a display polarizer arranged at an output side of the SLM, wherein the display polarizer is a linear polarizer; an additional polarizer arranged at the output side of the display polarizer, wherein the additional polarizer is a linear polarizer; and a switchable liquid crystal retarder comprising a layer of liquid crystal material arranged between the display polarizer and the additional polarizer, wherein the switchable liquid crystal retarder is a polarity controlled retarder, a switchable liquid crystal retarder arranged so that, in its switchable state, it simultaneously introduces no net relative phase shift to orthogonally polarized components of light passing through the display polarizer along an axis normal to the plane of the switchable liquid crystal retarder and introduces a relative phase shift to orthogonally polarized components of light passing through the display polarizer along an axis tilted relative to the normal to the plane of the switchable liquid crystal retarder; a switchable retarder control electrode arranged to apply a voltage to control the state of the switchable liquid crystal retarder; and at least one touch electrode array disposed in a layer to the output side of the switchable retarder control electrode. Advantageously, touch sensing can be provided for a switchable directional display that can have a first mode with high contrast and brightness for a wide range of viewing positions and a second mode with high contrast and brightness for a frontal user and low brightness for off-axis positions. Such a display can provide switchable privacy operation or can provide switchable stray light, for example for use in nighttime operation.

[0008] The touch input display device may further comprise at least one passive retarder disposed between the switchable liquid crystal retarder and the additional polarizer. The at least one passive retarder may be a polarity-controlled retarder that simultaneously introduces no net relative phase shift to orthogonally polarized components of light passed through the display polarizer along an axis normal to the plane of the switchable liquid crystal retarder, and introduces a relative phase shift to orthogonally polarized components of light passed through the display polarizer along an axis tilted relative to the normal to the plane of the switchable liquid crystal retarder. Advantageously, the polar angle range over which high image visibility is achieved in the first mode can be increased, and the polar angle range over which a high level of visual security is achieved in the second mode can be increased.

[0009] The touch electrode array may be formed on a surface of the passive retarder if the display device includes one touch electrode array, or on a surface of one of the passive retarders if the display device includes two or more touch electrode arrays. The touch sensing structure may be formed in a single electrode conductor deposition process, may add little or no thickness to the directional display, and may be advantageously low cost.

[0010] The at least one touch electrode array may include touch electrode array pairs disposed on layers separated by at least one dielectric layer. Advantageously, the electrode routing topology can be simplified compared to touch electrode pairs disposed on a single layer, reducing complexity and improving precision performance of the touch electrode array.

[0011] Each pair of touch electrode arrays may be formed on a respective surface of the passive retarder if the display device includes one passive retarder, or on a respective surface of one of the passive retarders if the display device includes two or more passive retarders. Advantageously, a low-cost manufacturing method for forming the electrode arrays can be provided. The passive retarder can be flexible to accommodate curved, bendable, or foldable displays. Little or no additional thickness is introduced, minimizing costs.

[0012] The at least one dielectric layer may comprise a passive retarder if the display device comprises one passive retarder, or at least one of the passive retarders if the display device comprises two or more passive retarders, thereby reducing the number of layers and advantageously reducing thickness, complexity, and cost.

[0013] The display device may include two or more passive retarders, and the at least one dielectric layer may include at least two passive retarders. The passive retarder can be conveniently formed on the A-plate retarder, which advantageously reduces costs. Furthermore, the passive retarder can be provided by a material that is suitable for forming an electrode thereon.

[0014] The at least one dielectric layer may comprise at least one additional layer that is not a retarder. Advantageously, the dielectric layer can be tailored to provide suitable electrical properties independent of the choice of retarder material and thickness.

[0015] The at least one passive retarder may comprise a passive uniaxial retarder having an optical axis perpendicular to the plane of the passive uniaxial retarder, which allows for a reduced number of retarders and advantageously reduces thickness.

[0016] The at least one passive retarder may include a pair of passive uniaxial retarders having intersecting optical axes in the plane of the passive uniaxial retarders. An electrode array may be formed on one side of each of the retarders, reducing the complexity of electrode formation. Advantageously, this may reduce manufacturing costs.

[0017] The at least one touch electrode array may include a pair of touch electrode arrays formed on opposing surfaces of the passive uniaxial retarders of the passive uniaxial retarder pair, and the at least one dielectric layer may include at least one additional layer disposed between the passive uniaxial retarder pair. The at least one dielectric layer may include an adhesive layer disposed between the touch electrode array pair. Advantageously, a low-cost structure can be provided. To achieve improved touch sensing sensitivity, dielectric properties can be selected by selecting the additional layer material and thickness.

[0018] The at least one touch electrode array may include a pair of touch electrode arrays formed on an outer surface of each passive uniaxial retarder of the passive uniaxial retarder pair, and the at least one dielectric layer may comprise the passive uniaxial retarder pair. The retarder pair may be solvent bonded, advantageously reducing surface reflection and thickness.

[0019] The touch input display device may further comprise an input transparent support substrate and an output transparent support substrate, the liquid crystal material layer being disposed between the input transparent support substrate and the output transparent support substrate, and the at least one touch electrode array being disposed on an output side of the output transparent support substrate. The touch input display device may further comprise an input transparent support substrate and an output transparent support substrate, the liquid crystal material layer being disposed between the input transparent support substrate and the output transparent support substrate, and the at least one touch electrode array being disposed between the switchable retarder control electrodes and the output transparent support substrate. The touch sensing structure may be shielded from the control of the SLM, advantageously increasing sensitivity.

[0020] At least one touch electrode array may be disposed between the switchable retarder control electrodes and the additional polarizer. Advantageously, the visibility of reflections from the touch electrode array can be reduced. Furthermore, the touch electrode array can be integrated with the retarder structure, advantageously reducing thickness and cost.

[0021] The at least one touch electrode array may be separate from the switchable retarder control electrodes. The switchable retarder control electrodes may be disposed on either side of the liquid crystal material layer. Advantageously, the switchable retarder may be switched independently of the control of the touch electrode array.

[0022] The touch input display device may further comprise a control system, which may be arranged to apply drive voltages to the switchable retarder control electrodes to control the switchable liquid crystal retarder, and which may be arranged to address the at least one touch electrode array for capacitive touch sensing. Advantageously, control of the switchable directional display and touch control may be achieved in the same device.

[0023] The drive voltage may have a waveform that includes periods during which the drive voltage is constant, and the control system may be arranged to address the at least one touch electrode array during at least one of the periods during which the drive voltage is constant. Advantageously, the signal-to-noise ratio of the touch signal is increased, improving the sensitivity of the touch system.

[0024] The drive voltage may have a waveform including periods during which the drive voltage is constant but at different levels, and the control system may be arranged to address the at least one touch electrode array during at least one of the periods during which the drive voltage is constant and at the same level, thereby increasing the signal-to-noise ratio of the touch signal and advantageously improving the sensitivity of the touch system.

[0025] The drive voltage waveform may include a positive addressing phase including at least one pulse of positive polarity and a negative addressing phase including at least one pulse of negative polarity, with the peak of the at least one pulse of positive polarity and the peak of the at least one pulse of negative polarity occurring during the period during which the drive voltage is constant. The average voltage across the switchable liquid crystal retarder is maintained at zero, i.e., there is no net DC voltage across the switchable liquid crystal retarder, increasing the number of sampling periods over which a touch signal is acquired. Advantageously, the delay and accuracy of touch location determination are improved.

[0026] The drive voltage waveform may include a positive addressing phase including at least one pulse of positive polarity and at least one additional period, and a negative addressing phase including at least one pulse of negative polarity and at least one additional period, wherein the at least one additional period of the positive addressing phase and the at least one additional period of the negative addressing phase are periods in which the drive voltage is constant and has a level intermediate between the maximum level of the at least one pulse of positive polarity and the minimum level of the at least one pulse of negative polarity. The number of sampling periods is increased, and the common-mode voltage range of the touch signal processing circuit is reduced. Advantageously, the cost and performance of the touch signal processing circuit are improved.

[0027] At least one additional period of the positive addressing phase and at least one additional period of the negative addressing phase may have a zero volt level. This increases the number of sampling periods and further reduces the common-mode voltage range of the touch signal processing circuit. Advantageously, this improves the cost and performance of the touch signal processing circuit.

[0028] At least one additional period of the positive addressing phase and at least one additional period of the negative addressing phase may have a non-zero magnitude level. This increases the number of sampling periods and reduces the common-mode voltage range of the touch signal processing circuitry. Advantageously, this reduces touch signal position delay and improves the cost of the touch signal processing circuitry.

[0029] The drive voltage may have a waveform with a root-mean-square value that provides a constant liquid crystal optical alignment state of the liquid crystal retarder and an arithmetic mean of zero. There is no average net DC voltage across the liquid crystal retarder. The liquid crystal material does not electrochemically degrade, advantageously improving the operating life of the liquid crystal material.

[0030] The control system may be further arranged to address the SLM. The integration of the control system advantageously reduces cost and complexity.

[0031] The drive voltages that the control system is arranged to apply to the switchable retarder control electrodes may be synchronized with respect to the addressing of the SLM, so that the relative timing of the electric fields generated by the electrodes of the switchable liquid crystal retarder and the SLM is fixed. Advantageously, any appearance of screen artifacts, including but not limited to "slow scan bars," is reduced.

[0032] The control system may be arranged to address the SLM using an addressing scheme that includes a vertical blanking interval, and the control system may be arranged to address at least one touch electrode array during the vertical blanking interval. During the vertical blanking interval, a reduction in high frequency signal transitions on the drive electrodes to the SLM is achieved. Electric field radiation from those transitions is reduced, advantageously improving the touch sensitivity of the screen.

[0033] The drive voltage waveform may include an addressing sequence including a first addressing positive voltage phase having a positive maximum voltage and a second addressing negative voltage phase having a negative minimum voltage. The drive voltage waveform in the first phase may include two or more positive voltage levels, and the drive voltage waveform in the second phase may include two or more negative voltage levels, or the drive voltage waveform in the first phase may include at least one positive voltage level and a zero voltage level, and the drive voltage waveform in the second phase may include at least one negative voltage level and a zero voltage level. The touch input display device may further include a third addressing phase including an intermediate drive voltage level intermediate between the positive maximum voltage and the negative minimum voltage. The intermediate voltage level may be zero. The root mean square value of the drive voltage waveform may be arranged to provide a constant liquid crystal optical alignment state of the liquid crystal retarder, and the arithmetic mean of the drive voltage waveform may be zero. The drive electrode may provide a signal that is applied to and measured from the touch electrode array when the drive electrode is at a constant level. The switchable liquid crystal retarder may be DC balanced so that the operating life of the retarder is extended. Advantageously, noise in the touch measurement system is reduced and improved accuracy can be achieved.

[0034] The signal applied to and measured from the touch electrode array can be provided when the drive voltage is at the same constant level, which can advantageously improve the cost and complexity of the touch sensing device.

[0035] The waveform applied to the switchable liquid crystal retarder may be synchronized to the addressing of the SLM. The addressing of the SLM may include a vertical blanking interval during which signals applied to and measured from the touch electrode array are provided. Advantageously, electrical noise from the SLM in the touch signal detector is minimized, increasing the accuracy and speed of touch measurements.

[0036] The touch input display device may further comprise a control system, the control system may be arranged to apply drive voltages to the switchable retarder control electrodes to control the switchable liquid crystal retarder, and the control system may be arranged to address the at least one touch electrode array for capacitive touch sensing. Advantageously, interference between the touch electrode array and the switchable retarder control electrodes can be reduced.

[0037] The drive voltage may have a waveform including periods during which the drive voltage is constant, and the control system may be arranged to address the at least one touch electrode array during at least one of the periods during which the drive voltage is constant. The drive voltage may have a waveform including periods during which the drive voltage is constant but at different levels, and the control system may be arranged to address the at least one touch electrode array during at least one of the periods during which the drive voltage is constant and at the same level. The drive voltage waveform may include a positive addressing phase including at least one pulse of positive polarity and a negative addressing phase including at least one pulse of negative polarity, and the peak of the at least one pulse of positive polarity and the peak of the at least one pulse of negative polarity may occur during the period during which the drive voltage is constant.

[0038] The waveform of the drive voltage may include a positive addressing phase including at least one pulse of positive polarity and at least one additional period, and a negative addressing phase including at least one pulse of negative polarity and at least one additional period, wherein the at least one additional period of the positive addressing phase and the at least one additional period of the negative addressing phase are periods during which the drive voltage is constant and has a level intermediate between the maximum level of the at least one pulse of positive polarity and the minimum level of the at least one pulse of negative polarity.

[0039] At least one additional period of the positive addressing phase and at least one additional period of the negative addressing phase may have a zero volt level. At least one additional period of the positive addressing phase and at least one additional period of the negative addressing phase may have a non-zero magnitude level. The drive voltage may have a root-mean-square value that provides a constant liquid crystal optical alignment state of the liquid crystal retarder and a waveform with an arithmetic mean of zero. The control system may be further arranged to address the SLM. The drive voltages that the control system is arranged to apply to the switchable retarder control electrodes may be synchronized with respect to the addressing of the SLM. The control system may be arranged to address the SLM using an addressing scheme that includes a vertical blanking interval, and the control system may be arranged to address the at least one touch electrode array during the vertical blanking interval.

[0040] The touch input display device may further comprise a reflective polarizer disposed between the display polarizer and the switchable liquid crystal retarder. Advantageously, when used as a privacy display in ambient light, increased off-axis reflectance can be provided to achieve reduced off-image contrast to peeping observers. In the public mode, reduced reflectance can be achieved to provide a high-contrast public mode for a wide field of view.

[0041] According to a second aspect of the present disclosure, there is provided a touch input display device comprising: an SLM; a display polarizer disposed on an output side of the SLM, wherein the display polarizer is a linear polarizer; an additional polarizer disposed on the output side of the display polarizer, wherein the additional polarizer is a linear polarizer; and a plurality of retarders disposed between the display polarizer and the additional polarizer, wherein the plurality of retarders comprise a switchable liquid crystal retarder disposed between an input transparent support substrate and an output transparent support substrate, and at least one passive polarity-controlled retarder disposed between the switchable liquid crystal retarder and the additional polarizer; and further comprising a first touch input electrode array and a second touch input electrode array disposed between the output transparent support substrate and the additional polarizer.

[0042] The first and second input electrode arrays may be provided on at least one surface of at least one passive polarity-controlled retarder. The at least one passive polarity-controlled retarder may include a retarder pair arranged in series, each having a touch electrode array arranged on one surface, the touch electrode arrays facing each other, and a dielectric material disposed between the touch electrode arrays. The retarder pair may include a passive uniaxial retarder pair, each having its optical axis perpendicular to the plane of the retarder, or a passive uniaxial retarder pair having its optical axis intersecting within the plane of the retarder. The dielectric material may include an adhesive material.

[0043] The touch input display device may further comprise a control system, which may be arranged to control drive voltages applied to the switchable liquid crystal retarder and to control signals applied to and measured from the touch electrode array. Advantageously, touch position measurement can be provided with a small thickness, low cost, high accuracy, and high speed.

[0044] According to a third aspect of the present disclosure, there is provided a method of controlling a touch input display device comprising: an SLM arranged to output light; a display polarizer arranged on an output side of the SLM; an additional polarizer arranged on the output side of the display polarizer; a switchable liquid crystal retarder comprising a liquid crystal material layer arranged between the display polarizer and the additional polarizer; at least one passive retarder arranged between the switchable liquid crystal retarder and the additional polarizer; a switchable retarder control electrode arranged to apply a voltage to control the switchable liquid crystal retarder; and at least one touch electrode array arranged in a layer on the output side of the switchable retarder control electrode, the method comprising: applying a drive voltage to the switchable retarder control electrode to control the switchable liquid crystal retarder, the drive voltage having a waveform that includes a period during which the drive voltage is constant; and addressing the at least one touch electrode array for capacitive touch sensing during at least one of the periods during which the drive voltage is constant. Advantageously, the switchable directional display can provide touch sensing with high sensitivity, high accuracy, and low latency. A small thickness and low cost can be achieved.

[0045] Embodiments of the present disclosure can be used in a wide variety of optical systems. Embodiments may include or operate in conjunction with various 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 in virtually any apparatus related to optical and electrical devices, optical systems, presentation systems, or any apparatus that may incorporate any type of optical system. Thus, embodiments of the present disclosure may be used in optical systems, optical devices used in visual and / or optical presentations, visual peripherals, and the like, as well as in numerous computer environments.

[0046] Before proceeding to the disclosed embodiments in detail, it should be understood that the present disclosure is not limited to the details of the particular arrangements shown in application or construction, as other example embodiments are possible. Moreover, aspects of the present disclosure may be described in various combinations and arrangements to define unique embodiments. Also, the terminology used herein is for purposes of description and not of limitation.

[0047] Directional backlights provide control over illumination emanating from substantially the entire output surface, typically controlled by modulation of independent LED light sources disposed on the input aperture side of the light guide. By controlling the directional distribution of emitted light, it is possible to achieve single-viewing for security features, where only a single viewer can view the display from a limited angular range; illumination provided primarily with a small angular distribution; high electrical efficiency; alternating left-eye and right-eye viewing for time-sequential stereoscopic and autostereoscopic displays; and low cost.

[0048] These and other advantages and features of the present disclosure will become apparent to those skilled in the art upon reading this disclosure in its entirety. [Brief explanation of the drawings]

[0049] By way of example, embodiments are illustrated in the accompanying drawings in which like reference symbols indicate similar parts and in which: [Figure 1A] FIG. 1 illustrates a perspective side view of a touch input display device comprising an SLM, a reflective polarizer, and a switchable liquid crystal retarder, with touch electrode arrays provided on opposing surfaces of a first passive polarity-controlled retarder and a second passive polarity-controlled retarder. [Figure 1B] 1B illustrates, in a front view, the alignment of the optical layers and electrode layers in the optical stack of FIG. 1A. FIG. [Figure 2A] 1B illustrates a perspective side view of the touch input display device of FIG. 1A in a privacy mode. [Figure 2B] 1B illustrates a perspective side view of the touch input display device of FIG. 1A in a public mode. [Figure 3A] 1B is a graph illustrating the variation of output luminance with polarity direction for the transmitted light of FIG. 1A in privacy mode. [Figure 3B] 1B is a graph illustrating the change in reflectance with polar direction for the reflected light beam of FIG. 1A in privacy mode. [Figure 3C] 1B is a graph illustrating the variation of output brightness with polarity direction for the transmitted light of FIG. 1A in public mode. [Figure 3D] 1B is a graph illustrating the change in reflectance with polarity direction for the reflected light beam of FIG. 1A in public mode. [Figure 4A] FIG. 1B illustrates, in a front perspective view, observation of reflected ambient light from the interface surface for the display of FIG. 1A in public mode. [Figure 4B] FIG. 1B illustrates, in a front perspective view, the observation of reflected ambient light for the display of FIG. 1A in privacy mode. [Figure 4C]FIG. 1 illustrates a side view of an automobile having a switchable directional display disposed within the vehicle for both entertainment and sharing modes. [Figure 4D] FIG. 1 illustrates a top view of an automobile having a switchable directional display disposed within the vehicle in an entertainment mode. [Figure 4E] FIG. 1 illustrates a top view of an automobile having a switchable directional display disposed within the vehicle in a shared mode. [Figure 5] FIG. 1B illustrates a side view of the touch input display device of FIG. 1A. [Figure 6A] FIG. 1 illustrates in perspective front view the electrode and control system of a touch input display device in which electrodes are disposed on each side of a dielectric layer. [Figure 6B] 1 illustrates in perspective front view electrodes of a touch input display device where the electrodes are disposed on the same side of a dielectric layer. [Figure 6C] FIG. 10 illustrates in perspective front view electrodes of a further arrangement for a touch input display device. [Figure 6D] FIG. 6D illustrates an arrangement corresponding to FIG. 6C in a side cross-sectional view. [Figure 7] FIG. 1 illustrates a circuit diagram for control of a touch input device. [Figure 8] FIG. 10 illustrates in a perspective front view the driving of a switchable liquid crystal retarder by a voltage waveform. [Figure 9A] 10 is a graph illustrating a drive waveform for driving a switchable liquid electrode. [Figure 9B] 10 is a graph showing drive waveforms for driving a switchable liquid crystal retarder with two opposite-phase drive electrodes. [Figure 10] 9C is a graph illustrating a composite voltage waveform provided across a liquid crystal retarder for the drive waveforms and touch control signals of FIGS. 9A-9B. [Figure 11A]10A-10C are graphs illustrating a composite voltage waveform provided across a liquid crystal retarder and the corresponding timing of control signals for application to and measurement from a touch electrode array, respectively. [Figure 11B] 10A-10C are graphs illustrating a composite voltage waveform provided across a liquid crystal retarder and the corresponding timing of control signals for application to and measurement from a touch electrode array, respectively. [Figure 11C] 10A-10C are graphs illustrating a composite voltage waveform provided across a liquid crystal retarder and the corresponding timing of control signals for application to and measurement from a touch electrode array, respectively. [Figure 11D] 10A-10C are graphs illustrating a composite voltage waveform provided across a liquid crystal retarder and the corresponding timing of control signals for application to and measurement from a touch electrode array, respectively. [Figure 12A] 10 is a graph illustrating exemplary drive waveforms for driving a switchable liquid crystal retarder with zero volt drive electrodes and alternating voltage waveform drive electrodes. [Figure 12B] 12B is a graph illustrating the resultant voltage waveform provided across the liquid crystal retarder for the drive waveform of FIG. 12A. [Figure 13A] 10 is a graph illustrating a composite voltage waveform provided across a liquid crystal retarder having three drive voltage levels. [Figure 13B] 10 is a graph illustrating a composite voltage waveform provided across a liquid crystal retarder having four drive voltage levels. [Figure 14] 10 is a graph illustrating a composite voltage waveform provided across a liquid crystal retarder, the corresponding timing of control signals for application to and measurement from a touch electrode array, and synchronization with the vertical blanking interval of the SLM. [Figure 15] 10 is a graph illustrating a composite voltage waveform provided across a liquid crystal retarder, asynchronously with driving the SLM, and the corresponding timing of control signals for application to and measurement from the touch electrode array. [Figure 16A] 1 illustrates a side view of a touch input display device in which the dielectric layer is provided by a crossed A-plate pair. [Figure 16B] 1 illustrates a perspective side view of a touch input display device in which the dielectric layer is provided by a crossed A-plate pair. [Figure 16C] 1 illustrates a perspective side view of a touch input display device in which the dielectric layer is provided by one of a pair of crossed A-plates. [Figure 17] 1 illustrates a perspective side view of a touch input display device having a dielectric layer disposed between two C-plates. [Figure 18A] 1 illustrates a perspective side view of a touch input display device in which the dielectric layer is provided by a C-plate. [Figure 18B] 18B illustrates the touch input display device of FIG. 18A in a side view. [Figure 19A] FIG. 1 illustrates a perspective side view of a touch-input non-switchable privacy display device with a dielectric layer disposed between two A-plates. [Figure 19B] 19B is a graph illustrating the change in output transmittance of a plurality of passive polar-controlled retarders having polar directions for the transmitted light beam of FIG. 19A. [Figure 20] 1 illustrates a side view of a touch input display device in which a dielectric layer between the touch electrode array is provided between the passive retarder and the output surface of the switchable liquid crystal retarder. [Figure 21A] 10 illustrates a side view of a touch input display device in which a dielectric layer between the touch electrode arrays is provided by an output transparent support substrate and an adhesive layer. FIG. [Figure 21B] FIG. 1 illustrates a side view of a touch input display device in which a touch electrode array is provided between one of the liquid crystal control electrodes and the output transparent support substrate of the switchable liquid crystal retarder. [Figure 21C]1 illustrates a perspective side view of a touch input display device in which a dielectric layer between the touch electrode arrays is provided by an output transparent support substrate of a switchable liquid crystal retarder. [Figure 22] 1 illustrates a perspective side view of a touch-input switchable privacy display device in which a touch electrode array is provided between a liquid crystal polarity-controlled retarder and an additional polarizer. [Figure 23A] FIG. 10 illustrates, in a perspective view, illumination of a retarder layer with off-axis light. [Figure 23B] FIG. 10 illustrates in a perspective view illumination of a retarder layer with off-axis light of a first linear polarization state at 0°. [Figure 23C] FIG. 10 illustrates in a perspective view illumination of a retarder layer with off-axis light of a first linear polarization state at 90°. [Figure 23D] FIG. 10 illustrates in a perspective view illumination of a retarder layer with off-axis light of a first linear polarization state at 45°. [Figure 24A] FIG. 1 illustrates, in a perspective view, illumination of a C-plate retarder with off-axis polarized light with a positive elevation angle. [Figure 24B] FIG. 10 illustrates, in a perspective view, illumination of a C-plate retarder with off-axis polarized light having a negative transverse angle. [Figure 24C] FIG. 1 illustrates, in a perspective view, illumination of a C-plate retarder with off-axis polarized light having a positive elevation angle and a negative lateral angle. [Figure 24D] FIG. 1 illustrates, in a perspective view, illumination of a C-plate retarder with off-axis polarized light having a positive elevation angle and a positive lateral angle. [Figure 24E] 24A to 24D. FIG. 24B is a graph illustrating the change in output transmittance depending on the polarity direction for the transmitted light beams of FIGS. 24A to 24D. FIG. [Figure 25A] FIG. 10 illustrates, in a perspective view, illumination of a crossed A-plate retarder layer with off-axis polarized light having a positive elevation angle. [Figure 25B] FIG. 10 illustrates, in a perspective view, illumination of a crossed A-plate retarder layer with off-axis polarized light having a negative transverse angle. [Figure 25C]FIG. 10 illustrates, in a perspective view, illumination of a crossed A-plate retarder layer with off-axis polarized light having a positive elevation angle and a negative lateral angle. [Figure 25D] FIG. 10 illustrates, in a perspective view, illumination of a crossed A-plate retarder layer with off-axis polarized light having a positive elevation angle and a positive lateral angle. [Figure 25E] 25A to 25D. FIG. 25B is a graph illustrating the change in output transmittance depending on the polarity direction for the transmitted light beams of FIGS. 25A to 25D. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0050] We now describe the terminology related to optical retarders for the purposes of this disclosure.

[0051] In a layer containing a uniaxially birefringent material, there is a direction that dominates the optical anisotropy, while all directions perpendicular to it (or at a given angle to it) have equivalent birefringence.

[0052] The optic axis of an optical retarder refers to the direction of propagation of light rays in a uniaxially birefringent material where no birefringence occurs, which is distinct from the optic axis of an optical system, which may be, for example, parallel to the axis of symmetry along which the chief ray propagates or the normal to the display surface.

[0053] For light propagating perpendicular to the optic axis, the optic axis is the slow axis when linearly polarized light with its electric vector direction parallel to the slow axis travels at the slowest speed. The slow axis direction is the direction with the highest refractive index at the design wavelength. Similarly, the fast axis direction is the direction with the lowest refractive index at the design wavelength.

[0054] For uniaxial birefringent materials with positive dielectric anisotropy, the slow axis direction is the extraordinary axis of the birefringent material, and for uniaxial birefringent materials with negative dielectric anisotropy, the fast axis direction is the extraordinary axis of the birefringent material.

[0055] The terms half wave and quarter wave refer to the behavior of the retarder relative to a design wavelength λ, which may typically be between 500 nm and 570 nm. In exemplary embodiments of the invention, exemplary retardance values ​​are provided at a wavelength of 550 nm unless otherwise specified.

[0056] A retarder provides a relative phase shift between two orthogonally polarized components of a light wave incident on the retarder and is characterized by the amount of relative phase Γ it imparts to the two polarization components. In some contexts, the term "phase shift" is used without the word "relative," but still refers to a relative phase shift. The relative phase shift is related to the birefringence Δn and thickness d of the retarder by: Γ=2.π.Δn.d / λ0 Equation 1

[0057] In Equation 1, Δn is defined as the difference between the extraordinary and ordinary refractive indices, i.e., Δn=n e -n o formula 2

[0058] For a half-wave retarder, the relationship between d, Δn, and λ is chosen so that the phase shift between the polarization components is Γ = π. For a quarter-wave retarder, the relationship between d, Δn, and λ is chosen so that the phase shift between the polarization components is Γ = π / 2.

[0059] The term half-wave retarder in this specification generally refers to light propagating normal to the retarder and normal to the spatial light modulator (SLM).

[0060] We now describe some aspects of the propagation of light rays through a transparent retarder between a polarizer pair.

[0061] The state of polarization (SOP) of a ray of light is described by the relative amplitude and relative phase shift between two orthogonally polarized components. A transparent retarder affects only the relative phase of these orthogonally polarized components without changing their relative amplitude. Providing a net phase shift between the orthogonally polarized components alters the SOP, while maintaining the net relative phase preserves the SOP.

[0062] A linear SOP has a polarization component with a non-zero amplitude and an orthogonal polarization component with zero amplitude.

[0063] A linear polarizer transmits a unique linear SOP that has a linear polarization component parallel to the electric vector transmission direction of the linear polarizer and attenuates light of a different SOP.

[0064] An absorptive polarizer is one that absorbs one polarization component of incident light and transmits a second, orthogonal polarization component. An example of an absorptive linear polarizer is a dichroic polarizer.

[0065] 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 the DBEF manufactured by 3M Corporation. TM or APF TM or Moxtek's ProFlux TM and other wire grid polarizers.

[0066] A retarder disposed between a linear polarizer and a parallel linear analyzing polarizer that introduces no net relative phase shift provides complete transmission of light except for residual absorption in the linear polarizer.

[0067] A retarder that provides a net relative phase shift between the orthogonal polarization components alters the SOP and provides attenuation in the analyzing polarizer.

[0068] In this disclosure, "A-plate" refers to an optical retarder that utilizes a layer of birefringent material with its optic axis parallel to the plane of the layer.

[0069] "Positive A-plate" refers to a positively birefringent A-plate, ie, an A-plate that has a positive Δn.

[0070] In this disclosure, "C-plate" refers to an optical retarder utilizing a layer of birefringent material with its optic axis perpendicular to the plane of the layer. "Positive C-plate" refers to a positively birefringent C-plate, i.e., a C-plate with a positive Δn. "Negative C-plate" refers to a negatively birefringent C-plate, i.e., a C-plate with a negative Δn.

[0071] "O-plate" refers to an optical retarder utilizing a layer of birefringent material with an optic axis having 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 positively birefringent O-plate, i.e., an O-plate with a positive Δn.

[0072] The retarder material may be provided with an achromatic retarder with retardance Δn.d that varies with wavelength λ as follows: Δn .d / λ =κ Equation 3

[0073] where κ is substantially constant.

[0074] An example of a suitable material is modified polycarbonate manufactured by Teijin Films. In this embodiment, a colorless retarder may be provided to advantageously minimize color exchange between polar angle viewing directions with low luminance degradation and polar angle viewing directions with increased luminance degradation, as described below.

[0075] Various other terms used in this disclosure in connection with retarders and liquid crystals will now be explained.

[0076] The liquid crystal cell has a retardance given by Δn.d, where Δn is the birefringence of the liquid crystal material within the liquid crystal cell and d is the thickness of the liquid crystal cell independent of the alignment of the liquid crystal material within the liquid crystal cell.

[0077] Homogeneous alignment refers to the alignment of liquid crystals in a switchable liquid crystal display where the molecules are aligned substantially parallel to the substrates. Homogeneous alignment is sometimes referred to as planar alignment. Homogeneous alignment may typically have a small pretilt, such as 2 degrees, whereby the molecules at the surface of the alignment layer of the liquid crystal cell are slightly tilted, as explained below. The pretilt is arranged to minimize degradation of the cell's switching.

[0078] In this disclosure, homeotropic alignment is the state in which rod-shaped liquid crystal molecules are aligned substantially perpendicular to the substrate. For discotic liquid crystals, homeotropic alignment is defined as the state in which the axes of the columnar structures formed by the discotic liquid crystal molecules are aligned perpendicular to the surface. In homeotropic alignment, the pretilt is the tilt angle of the molecules close to the alignment layer, which is usually close to 90 degrees, for example, 88 degrees.

[0079] Twisted liquid crystal layers provide a twisted configuration (also known as a helix or spiral) of nematic liquid crystal molecules. The twist can be achieved by non-parallel alignment of the alignment layers. Additionally, cholesteric dopants can be added to the liquid crystal material to resolve any misalignment of the twist direction (clockwise or counterclockwise) and further control the twist pitch in the relaxed (usually undriven) state. Supertwisted liquid crystal layers have a twist greater than 180 degrees. Twisted nematic layers used in SLMs typically have a twist of 90 degrees.

[0080] Liquid crystal molecules with positive dielectric anisotropy can be switched from a homogeneous alignment (such as an A-plate retarder alignment) to a homeotropic alignment (such as a C-plate or O-plate retarder alignment) by an applied electric field.

[0081] Liquid crystal molecules with negative dielectric anisotropy can be switched from a homeotropic alignment (such as the alignment of a C-plate or O-plate retarder) to a homogeneous alignment (such as the alignment of an A-plate retarder) by an applied electric field.

[0082] The rod-shaped molecule is represented by n e >n o The discotic molecule has positive birefringence, such that n e <n o , and has negative birefringence.

[0083] Positive retarders, such as A-plates, positive O-plates, and positive C-plates, can usually be provided by stretched films or rod-like liquid crystal molecules, while negative retarders, such as negative C-plates, can be provided by stretched films or disc-like liquid crystal molecules.

[0084] Parallel liquid crystal cell alignment refers to the alignment directions of the homogeneous alignment layers being parallel, or more typically antiparallel. In the case of pretilted homeotropic alignment, the alignment layers can have components that are substantially parallel or antiparallel. Hybrid aligned liquid crystal cells can have one homogeneous alignment layer and one homeotropic alignment layer. Twisted liquid crystal cells can be provided, for example, by alignment layers that are oriented 90 degrees to each other and do not have parallel alignment.

[0085] The transmissive SLM may further comprise a retarder between the input and output display polarizers, as disclosed, for example, in U.S. Patent No. 8,237,876, which is incorporated herein by reference in its entirety. Such a retarder (not shown) would be at a different location than the passive retarder in this embodiment. Such a retarder compensates for contrast degradation at off-axis viewing locations, which has a different effect on the brightness reduction at off-axis viewing locations in this embodiment.

[0086] A display's private operating mode is one in which the observer experiences a low contrast sensitivity such that the image does not appear sharp. Contrast sensitivity is a measure of the ability to distinguish between different levels of luminance in a static image. Inverse contrast sensitivity can be used as a measure of visual security, in that a high visual security level (VSL) corresponds to low image visibility.

[0087] For a privacy display that provides an image to an observer, the visual security can be given as: VSL=(Y+R) / (YK) Equation 4

[0088] where VSL is the visual security level, Y is the luminance of the white state of the display at the peeper's viewing angle, K is the luminance of the black state of the display at the peeper's viewing angle, and R is the luminance of the reflected light from the display.

[0089] The contrast ratio of the panel is given by: C=Y / K formula 5

[0090] For high-contrast optical LCD modes, the white state transmittance remains substantially constant with viewing angle. For the reduced-contrast LCD modes of the present embodiment, the white state transmittance typically decreases as the black state transmittance increases, as follows: Y+K~PL Equation 6

[0091] The visual security level can then be further given as follows:

number

[0092] Here, the off-axis relative luminance P is usually defined as a percentage of the frontal luminance L at the viewer angle, the display may have an image contrast ratio C, and the surface reflectance is ρ.

[0093] The off-axis relative luminance P is sometimes referred to as the privacy level, although such privacy level P represents the relative luminance of the display at a given polar angle compared to the frontal luminance and is not a measure of the appearance of privacy.

[0094] A display may be illuminated with an ambient illuminance, I, in Lamberts. Thus, in a completely dark environment, a high-contrast display has a VSL of approximately 1.0. As ambient illuminance increases, the perceived image contrast decreases, the VSL increases, and a private image is perceived.

[0095] For a typical LCD display, the panel contrast C exceeds 100:1 at almost all viewing angles, so the visual security level can be approximated as follows: VSL=1+l.ρ / (π.PL) Equation 8

[0096] Compared to privacy displays, it is desirable for wide-angle displays to be easily observed in standard ambient lighting conditions. One measure of image visibility is given by contrast sensitivity, such as the Michelson contrast, given by: M=(I max -I min ) / (I max +I min ) Equation 9

[0097] therefore, M=((Y+R)-(K+R)) / ((Y+R)+(K+R))=(YK) / (Y+K+2.R) Equation 10

[0098] Therefore, the visual security level (VSL) is equivalent to (but not identical with) 1 / M. In this study, for a given off-axis relative luminance P, the visibility W of a wide-angle image is approximated as follows: W=1 / VSL=1 / (1+I.ρ / (π.PL)) Equation 11

[0099] It is desirable to provide touch panel functionality in a switchable directional display device comprising a switchable liquid crystal retarder disposed between a display output polarizer and an additional polarizer for use in displays such as privacy displays and also in low stray light displays such as displays for nighttime use.

[0100] FIG. 1A illustrates a perspective side view of a touch input display device 100 including a spatial light modulator (SLM) 48, a reflective polarizer 302, and a switchable liquid crystal retarder 301, with touch electrode arrays 500, 502 provided on opposing surfaces of a first passive polarity-controlled retarder 330A and a second passive polarity-controlled retarder 330B, and FIG. 1B illustrates a front view of the alignment of the optical layers and electrode layers in the optical stack of FIG. 1A.

[0101] In the present disclosure, the location of the finger 25 is detected by the touch electrode array 500, 502 and the control system 400, 450, 250, 350, as further described below.

[0102] The touch input display device 100 comprises an SLM 48 arranged to output light 400, a display polarizer 218 arranged on the output side of the SLM 48, an additional polarizer 318 arranged on the output side of the display polarizer 218, a switchable liquid crystal retarder 301 comprising a layer 314 of liquid crystal material 414 arranged between the display polarizer 218 and the additional polarizer 318, passive polarity-controlled retarders 330A, 330B arranged between the switchable liquid crystal retarder 301 and the additional polarizer 318, switchable retarder control electrodes 413, 415 arranged to apply a voltage V to control the switchable liquid crystal retarder 301, and touch electrode arrays 500, 502 arranged in layers on the output side of the switchable retarder control electrodes 413, 415.

[0103] The display polarizer 218, the reflective polarizer 302, and the additional polarizer 318 are linear polarizers with electric vector transmission directions 219, 303, 319, respectively.

[0104] The switchable liquid crystal retarder 301 comprises transparent support substrates 312, 316. Electrodes 413, 415 and matching layers (not shown) are disposed on opposing surfaces of the support substrates 312, 316, respectively, to provide matching and electrical control for the layer 314 of liquid crystal material 414. The switchable retarder control electrodes 413, 415 are disposed on either side of the layer 314 of liquid crystal material 414.

[0105] 1A-1B, where the display device includes two or more passive retarders, each of the pair of touch electrode arrays 500, 502 is formed on a respective surface of one of the passive polarity-controlled retarders 330A, 330B. The touch electrode array 500 is formed on the surface of the passive polarity-controlled retarder 330A, and the touch electrode array 502 is formed on the surface of the passive polarity-controlled retarder 330B.

[0106] The touch electrode array includes a pair of touch electrode arrays 500, 502 formed on opposing surfaces of the passive polarity-controlled retarders of the passive uniaxial retarder pair, the passive polarity-controlled retarders 330A, 330B, and at least one additional dielectric layer 504 disposed between the passive uniaxial retarder pair. The pair of touch electrode arrays 500, 502 are disposed on layers separated by the dielectric layer 504. The dielectric layer 504 is disposed 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 disposed on and on each side of the dielectric layer 504.

[0107] The touch electrode arrays 500 , 502 are disposed between the switchable retarder control electrodes 413 , 415 and the additional polarizer 318 and are separated from the switchable retarder control electrodes 413 , 415 .

[0108] The touch input display device 100 further comprises a control system 400 arranged to apply a drive voltage V to the switchable voltage retarder control electrodes 413, 415 to control the switchable voltage retarder 301 by the driver 350. The control system 400 is further arranged to address the touch electrode arrays 500, 502 for capacitive touch sensing.

[0109] An optional reflective polarizer 302 is disposed between the display polarizer 218 and the polarity-controlled retarder 300. The polarity-controlled retarder 300 is disposed between the reflective polarizer 302 (or the output polarizer 218 if the reflective polarizer 302 is omitted) and an additional polarizer 318. 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.

[0110] In the embodiment of Figures 1A-1B, the polarity-controlled retarder 300 comprises a passive polarity-controlled retarder 330 and a switchable liquid crystal retarder 301, but may generally be replaced by other configurations of at least one retarder, some examples of which are present in the devices described below.

[0111] This embodiment provides a switchable privacy display that can be switched between a privacy mode with a wide polarity range in which a high level of visual security is achieved, and a public operation mode with a wide polarity range in which high image visibility is achieved. The operation of the privacy display is provided by the polarity-controlled retarder 300, as will now be described.

[0112] The at least one polarity-controlled retarder 300 comprises a switchable liquid crystal retarder 301 arranged so as to simultaneously introduce no net relative phase shift to orthogonally polarized components of light passing through the reflective polarizer 302 along an axis normal to the plane of the at least one polarity-controlled retarder 300, and to introduce a net relative phase shift to orthogonally polarized components of light passing through the reflective polarizer 302 along an axis tilted relative to the normal to the plane of the at least one polarity-controlled retarder 300, in a switchable state of the switchable liquid crystal retarder 301.

[0113] 1A-1B comprises a pair of passive uniaxial retarders 330A, 330B having intersecting optical axes in the plane of the passive uniaxial retarder. The passive polar-controlled retarders 330A, 330B simultaneously provide the polar-controlled retarder 300 with a function of introducing no net relative phase shift to the orthogonal polarization components of light passing through the display polarizer 218 and the reflective polarizer 302 along the normal to the plane 301 of the switchable liquid crystal retarder, and a function of introducing a relative phase shift to the orthogonal polarization components of light passing through the display polarizer 218 along an axis tilted relative to the normal to the plane of the switchable liquid crystal retarder.

[0114] The polar-controlled retarder 300 does not affect the intensity of light passing through the reflective polarizer 302, the polar-controlled retarder 300, and the additional polarizer 318 along an axis normal to the plane of the polar-controlled retarder 300, but the polar-controlled retarder 300, in at least one of the switchable states of the switchable retarder 301, reduces the intensity of light passing therethrough along an axis tilted relative to the normal to the plane of the polar-controlled retarder 300. The principles leading to this effect are described in more detail below with reference to Figures 23A-25E and result from the presence or absence of a phase shift introduced by the polar-controlled retarder 300 to light along axes that are at different angles to the crystalline material of the polar-controlled retarder 300. A similar effect is achieved in all of the devices described below.

[0115] A control system 400 is further arranged to accommodate the SLM 48. The control system comprises a system controller 400 arranged to (i) provide image data to the SLM 48 via an SLM controller 250, (ii) provide control of a voltage driver 350 to control the drive voltages applied to the switchable liquid crystal retarders, and (iii) control the signals applied to and measured from the touch electrode arrays 500, 502 via a touch controller 450 and touch drivers 452, 454.

[0116] The operation of the polarity-controlled retarder 300 will now be further described.

[0117] 2A-2B are schematic diagrams illustrating the touch input display device of FIG. 1A in different perspective side views for operation in a privacy mode of operation and a public mode of operation, respectively. Features of the embodiments of FIGS. 2A-2B that are not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0118] The touch electrode arrays are disposed on the opposing surfaces of the pair of passive uniaxial retarders 330A, 330B. A dielectric layer 504 comprises an adhesive layer provided between the touch electrode arrays disposed on the opposing surfaces of the pair of passive uniaxial retarders. 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.

[0119] The touch finger 25 may be near or in contact with the substrate 320, which may be a glass cover with an oleophobic hard coating to achieve mechanical robustness and resistance to finger grease. Touch control may also be provided by a pen or stylus.

[0120] In operation, the layer 314 of liquid crystal material 414 is driven by the voltage driver 350 with a first voltage waveform Va to provide a first liquid crystal alignment for the privacy operation of FIG. 2A, and is driven by the voltage driver 350 with a second voltage waveform Vb to provide a second liquid crystal alignment for the wide angle operation of FIG. 2B.

[0121] At least one passive polarity-controlled retarder 330 includes a pair of retarders 330A, 330B arranged in series, and each passive polarity-controlled retarder 330A, 330B includes a touch electrode array 500 or a touch electrode array 502 arranged on one surface, the touch electrode arrays 500, 502 facing each other, and a dielectric material 504 arranged between the touch electrode arrays 500, 502.

[0122] The touch electrode arrays 500, 502 may include transparent conductors such as ITO, silver nanowires, or conductive polymers. They may be formed by known techniques, including physical vapor deposition, sputtering, evaporation, inkjet printing, or contact printing. They may be patterned by the use of a mask or photoresist and etching. When the electrodes are formed on a flexible retarder substrate, such as PC or COC / COP, the type and temperature of the electrode deposition process may be controlled to avoid melting or damaging the substrate. Inherently low-temperature processes, such as inkjet and contact printing, can produce electrode layers without exceeding the glass transition temperature of the substrate.

[0123] The routing topology of the touch electrode arrays 500, 502 formed on separate substrates has more options and may be simpler than routing topologies when the electrodes are provided on a single surface of the retarder. When formed as a single layer, the two electrode arrays cannot have crossing electrode traces (without a special processing step to add an intermediate insulating bridge or intermediate dielectric layer). For example, an intermediate dielectric layer may be provided between the electrode layers 500, 502 when the electrode arrays 500, 502 are formed on a single surface. Fabrication of such arrays requires alignment during the electrode array formation process, which increases costs. Advantageously, the cost of forming the electrode arrays 500, 502 can be reduced when the electrode arrays 500, 502 are formed on a different substrate than the retarders 300A, 300B.

[0124] Next, the viewing aspects of an exemplary embodiment similar to the embodiment shown in Figures 2A-2B will be described.

[0125] 3A is a schematic graph illustrating the change in output luminance with the polarity direction of the transmitted light beam of FIGS. 1A and 2A in a privacy mode of operation; FIG. 3B is a schematic graph illustrating the change in reflectance with the polarity direction of the reflected light beam of FIGS. 1A and 2A in a privacy mode of operation; FIG. 3C is a schematic graph illustrating the change in output luminance with the polarity direction of the transmitted light beam of FIGS. 1A and 2B in a public mode of operation; and FIG. 3D is a schematic graph illustrating the change in reflectance with the polarity direction of the reflected light beam of FIGS. 1A and 2B in a public mode, including the embodiments illustrated in Table 1. [Table 1]

[0126] In this embodiment, the switchable liquid crystal retarder 301 comprises two surface matching layers (not shown) disposed adjacent to and on either side of the layer 314 of liquid crystal material 414. Each matching layer is arranged to provide homogeneous matching across the adjacent liquid crystal material 414. The layer 314 of liquid crystal material 414 of the switchable liquid crystal retarder 301 comprises a liquid crystal material 414 having positive dielectric anisotropy. The layer of liquid crystal material 414 has a retardance 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. The at least one retarder 330 further includes a pair of passive retarders 308A, 308B having intersecting optical axes in the plane of the retarder, each passive retarder of the passive retarder pair having a retardance for light of a wavelength of 550 nm in the range of 300 nm to 800 nm, preferably in the range of 350 nm to 650 nm, and most preferably in the range of 450 nm to 550 nm.

[0127] In this embodiment, "crossed" refers to a substantially 90° angle between the optical axes of the two retarders in the plane of the retarders. Passive retarders may be provided using stretched films to advantageously achieve low cost and high uniformity. To reduce the cost of the retarder material, it is desirable to provide the material with some variation in retarder orientation due, for example, to stretching errors during film manufacturing.

[0128] Thus, in the public operating mode as illustrated in Figures 3C and 3D, essentially high brightness output and low reflectance are provided over a wide viewing latitude, whereas in comparison, brightness increases and reflectance decreases for observers located at off-axis viewing positions as illustrated in Figures 3A and 3B.

[0129] Switchable directional display devices, for example for use in privacy displays, comprising multiple retarders disposed between a display polarizer and an additional polarizer are further described in U.S. Pat. No. 10,126,575 and U.S. patent application Ser. No. 16 / 131,419, filed Sep. 14, 2018, entitled "Optical stack for switchable directional display" (Attorney Docket No. 412101), both of which are incorporated herein by reference in their entireties. Directional display devices further comprising a reflective polarizer disposed between the display polarizer and the retarder are described in U.S. Patent Publication No. 2018 / 0329245, which is incorporated herein by reference in its entirety. Directional display polarizers comprising a passive retarder disposed between the display polarizer and an additional polarizer are described in U.S. Patent Publication No. 2018 / 0321553, which is incorporated herein by reference in its entirety.

[0130] Advantageously, the switchable privacy display can have a large polar area that provides a high level of visual security in a privacy mode of operation and a large polar area that provides high image visibility in a public mode of operation. The touch electrode array can be provided at low cost and with minimal additional thickness. High image contrast can be provided for a frontal display user in the privacy mode and for multiple display users in the public mode.

[0131] The operation of the privacy mode of the displays of Figures 1A and 2A-2B will now be further described.

[0132] FIG. 4A is a schematic diagram illustrating, in a front perspective view, the observation of reflected ambient light from interface surfaces of a display operating in public mode. Some light rays 404 may be reflected by the front surface of the additional polarizer 318, or by the cover glass and other surfaces of the display. Typically, such reflectance may be 4% for a combined optical stack at normal incidence and approximately 5% for a combined optical stack at 45-degree incidence due to Fresnel reflections at the air-polarizer or air-glass interfaces. Thus, a low-brightness reflected image 605 of source 604 may be observed by a peeping eye in front of the display 100. Furthermore, dark image data 601 and bright image data 603 are viewed at high brightness by observer 47 so that the image data can be clearly observed. Display output light 400 provides light to both observers 45, 47 so that both can see the image data, advantageously providing a public mode.

[0133] 4B is a schematic diagram illustrating the observation of reflected ambient light in a front perspective view for the display of FIG. 1A operating in privacy mode. Compared to FIG. 4A, a substantially higher reflected brightness is observed from the reflection 606 of the light source 604 due to the off-axis polarization being reflected from the reflective polarizer 302.

[0134] The additional image brightness in area 27 occupied by peeper 47 is substantially reduced compared to the light to observer 45 in area 26. Thus, the image is less visible to peeper 47, advantageously providing a private image.

[0135] The shape and distribution of the reflected image 606 is determined by the spatial distribution of the ambient light source 604 , but may further be determined by the diffusing layer, especially at the output surface of the additional polarizer 318 .

[0136] It may further be desirable to provide controllable display lighting in an automobile.

[0137] 4C is a schematic diagram illustrating a side view of a vehicle having a switchable directional display 100 disposed within a passenger compartment 602 of the vehicle 600 for both entertainment and shared modes of operation. A light cone 610 (e.g., representing a cone of light whose brightness is greater than 50% of its peak brightness) may be provided by the brightness distribution of the display 100 in the elevation direction and is not switchable. Furthermore, the display reflectivity may be increased compared to the frontal reflectivity outside of this light cone 610.

[0138] 4D is a schematic diagram illustrating a top view of a vehicle having a switchable directional display 100 disposed within a vehicle interior 602 in an entertainment mode of operation and operating similarly to a privacy display. The light cone 612 has a narrow angular range, which allows a passenger 606 to see the display 100, but the driver 604 to not see the image on the display 100 as a result of reduced brightness and increased reflectance. Advantageously, entertainment images can be displayed to the passenger 606 without disturbing the driver 604.

[0139] 4E is a schematic diagram illustrating a top view of a vehicle having a switchable directional display 100 disposed within a vehicle cabin 602 in a shared mode of operation. The light cone 614 has a wide angular range so that all occupants can perceive the image on the display 100, for example, when the display is not moving or provides an unobtrusive image.

[0140] Additionally, stray light during nighttime operation can be reduced, thereby reducing distracting interior light within the vehicle cabin and advantageously improving the driver's visibility of objects near the vehicle. The displays of Figures 4A-4E can advantageously be provided with touch-sensing capabilities with high sensitivity and high image quality.

[0141] The operation of the touch input structure will now be further described.

[0142] Figure 5 is a schematic diagram illustrating the touch input display device of Figure 1A in a side view. Features of the embodiment of Figure 5 not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0143] In the touch mode of operation, signals applied to and measured from the touch electrode arrays 500, 502 produce a projected electrostatic field 570 with an effective capacitance 571. The finger 25 produces some distortion of the field lines 572, modifying the capacitance measured from the touch electrode arrays 500, 502.

[0144] The SLM 48 includes pixel drive electrodes 202. It is desirable that signals provided to the pixels of the SLM 48 are not interfered with by signals for the touch control system, and that the sensitivity of the touch control system is not interfered with by signals provided to the SLM 48. In this embodiment, electrodes 413, 415 provide shielding between the pixel drive electrodes 202 and the touch sensing system. The above-described electrical signal shielding increases the signal-to-noise ratio of touch signal detection. Advantageously, touch sensitivity is increased and image stability is not degraded. Furthermore, this embodiment eliminates the need to use touch sensing methods at inter-pixel locations within the SLM 48, thereby increasing the aperture ratio of the pixels. Advantageously, the increased aperture ratio allows for more light transmission through the display panel. Further advantageously, the resolution of the display is not reduced by integrating touch sensing circuitry at the pixel locations of the SLM 48.

[0145] Some known displays use the interaction of a finger or touch stylus with light emitted from the display. If the light output angle is different in public and private modes, the sensitivity and performance of the touch system may vary depending on the display mode. In the described embodiment, in which the touch electrodes 500, 502 are not located in the pixel plane of the SLM 48, the operation and sensitivity of touch sensing is independent of whether the display is operating in public or privacy mode.

[0146] Next, the arrangement of the touch electrode arrays 500, 502 will be described.

[0147] 6A is a schematic diagram illustrating, in a perspective front view, electrode and control systems for touch input display devices 400, 450, 350, 250. Features of the embodiments of FIG. 6A that are not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0148] The touch electrode arrays 500, 502 are disposed on either side of a dielectric layer 504. The system controller 400 synchronizes the voltage driver 350 and the touch controller 450 so that driving and measuring signals from the touch controller can occur during times when the drive voltage of the switchable liquid crystal retarder is constant, e.g., zero. This can improve the signal-to-noise ratio (SNR) of the measurement process, increasing touch sensitivity and immunity to electrical interference. The measured or detected capacitance fluctuations can be on the order of femtofarads. The measurement circuitry may include capacitance-to-voltage converter circuitry and may further include analog signal processing circuitry. Alternatively or additionally, a capacitance-to-digital circuitry can be used and may further include digital signal processing capabilities. The measurement circuitry may be gated with a waveform 436 to improve the SNR. The measurement circuitry may include frequency filtering to prioritize and distinguish frequency bands of the touch panel signal drive from other frequencies to improve the SNR. Electrodes 415 and 413 can screen high frequency drive signals from touch electrode arrays 500, 502 to SLM 48, thereby improving the SNR of the measurement process without having to synchronize to the vertical blanking interval (VBI) of SLM 48. However, system controller 400 may also synchronize touch controller 450 and SLM 48, for example, so that driving and measuring the touch controller signals occurs during the VBI of SLM 48 addressing, further improving the SNR of the touch measurement.

[0149] The drive voltages that the control system 400 is arranged to apply to the switchable retarder control electrodes 413 , 415 are synchronized with respect to the addressing of the SLM 48 .

[0150] In operation, it is desirable to provide (i) driving of image data, (ii) control of a switchable liquid crystal layer for both wide and privacy modes of operation, and (iii) touch input.

[0151] Some types of displays provide in-cell touch, i.e., the electrodes 202 can further provide touch input functionality. Compared to the present embodiment, if the in-cell touch protruding force lines 570 were provided by some of the electrodes 202 of the SLM 48, the liquid crystal retarder electrodes 413, 415 could shield the protruding fields from such in-cell electrodes and reduce the signal-to-noise ratio of measurements of signals from the touch electrode array 202. Therefore, such an in-cell touch electrode array 202 may be ineffective at providing touch functionality in the presence of the switchable liquid crystal retarder 314. During operation, the liquid crystal retarder electrodes 413, 415 may generate additional electric field lines such that the protruding fields 570 from the touch electrode arrays 500, 502 may reduce the signal-to-noise ratio of measurements of signals from the touch electrode arrays 500, 502. It would be desirable to provide a high signal-to-noise ratio for a touch control system comprising the touch drivers 452, 454 and the touch control system 450.

[0152] It would be desirable to achieve touch input without masking of the touch signal by the electrodes 413, 415 of the switchable liquid crystal layer 314.

[0153] 6B is a schematic diagram illustrating a further electrode arrangement for a touch input display device in a perspective front view. Compared to the arrangement in FIG. 6A, the touch electrode array is a single array 503 arranged on a single surface of the compensation retarder 330. Advantageously, a simpler structure can be provided. The touch electrode array 503 is formed on one surface of at least one passive polarity-controlled retarder 330.

[0154] Figure 6C is a schematic diagram illustrating a transparent front view of electrode arrays 500, 502 in a further arrangement of a touch input display device. Compared to Figure 6B, electrodes on the same surface are isolated from each other by small insulating bridges (not shown) at the intersections between electrode arrays 500, 502. This arrangement increases the fringe field between electrode sets, thus increasing the SNR of detection and measurement.

[0155] Figure 6D is a schematic diagram illustrating the arrangement of section A-A' of Figure 6C in a side cross-sectional view, where the insulating bridge has been replaced by a continuous dielectric layer 504. Features of the embodiments of Figures 6C-6D that are not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features.

[0156] Next, a control circuit for driving and measuring signals from the touch sensor will be described.

[0157] FIG. 7 is a schematic diagram illustrating an equivalent circuit for controlling a touch input device. The touch panel system can generate a voltage Vsource relative to a reference potential Vref_1, which can be a complex waveform, as described below. Vsource is applied to a first array of touch panel electrodes, as described below. The first electrode array, together with elements of a second electrode array, forms a spatial matrix of capacitors, e.g., Cmatrix. The second electrode arrays may be on the same side of the substrate, on each side of the substrate, or on two separate substrates. When a pulse Vsource is applied to the first electrode array, a signal, e.g., a voltage Vdetect, can be detected at the second electrode array. The voltage Vsource and the detection voltage Vdetect can be sequentially scanned or connected to one or more of the electrodes comprising the first and second electrode arrays, respectively, to measure the spatial array of capacitances across the display surface. When the panel surface is touched, the presence of a finger distorts the electric field in its vicinity, which can be detected as a change in capacitance and measured as a change in voltage Vdetect at each of the associated capacitance matrices. This change in capacitance is illustrated by Cfinger. For mains connected equipment, Vref_1 and Vref_2 can be considered to be at ground potential. For battery powered equipment, Vref_1 can be considered to be at floating potential.

[0158] In the figures herein, a single finger 25 is shown for clarity, but the touch panel of this embodiment is capable of resolving multiple touches from one or more fingers. The finger (or fingers) creates a dielectric change that can be applied to one or more elements of Cmatrix, which can be detected as a change in capacitance at Vdetect.

[0159] The second electrode array may include electrodes of different shapes, particularly shapes designed to more easily distinguish between the desired signal voltage change to Vdetect caused by the presence of a finger and injected noise voltages picked up, for example, by the finger acting as an antenna.

[0160] Figure 8 is a schematic diagram illustrating in a perspective front view the driving of a switchable liquid crystal retarder with voltage waveforms 430, 432 driven by connecting wires 427, 429 to electrodes 413, 415 of the switchable retarder containing a liquid crystal layer 314 that includes a liquid crystal material 414. Features of the embodiment of Figure 8 that are not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features.

[0161] Next, the drive waveforms for the switchable liquid crystal retarder and touch controller 450 are described.

[0162] 9A is a schematic graph illustrating drive waveforms for driving a switchable liquid crystal retarder, including a first voltage waveform 430 provided to electrode 413 that is zero volts and a second voltage waveform 432 provided to electrode 415 that is an AC voltage waveform when a dual-rail power supply is provided. Voltage waveform 430 may be at ground potential or a reference potential for battery-powered devices. Voltage waveform 432 may have a first addressing positive voltage phase with a positive maximum +V1 and a second addressing negative voltage phase with a negative minimum voltage −V1. Using this arrangement, the switchable liquid crystal retarder may be driven by a single drive amplifier. Advantageously, the complexity of the drive circuitry is reduced.

[0163] 9B is a schematic graph illustrating alternative drive voltage waveforms 430, 432 for driving a switchable liquid crystal retarder when only a single rail power supply has voltage rail V1. Features of the embodiment of FIG. 9B that are not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features.

[0164] The waveforms 430, 432 are shown driven in antiphase. Using this arrangement, the switchable liquid crystal retarder can be driven by two drive amplifiers. Advantageously, the power supply can be a single rail type, thus reducing complexity and cost.

[0165] 10 is a schematic graph illustrating a composite voltage waveform 434 provided across liquid crystal retarder 301 for the drive waveforms of FIGS. 9A-9B and a waveform 436 for the control signal of touch controller 450. Features of the embodiment of FIG. 10 not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0166] The drive voltage waveform 434 includes an addressing sequence including a first addressing positive voltage phase 431 having a positive maximum voltage level 435 and a second addressing negative voltage phase 433 having a negative minimum voltage level 437. In the drive voltage waveform 434 across the layer of liquid crystal material 314 in FIG. 10 , the voltage transition is shown as being essentially instantaneous. In reality, some transition time exists. The drive voltage across the layer of liquid crystal material 314 has a waveform 434 including periods 451, 453 during which the drive voltage is constant, and the control system 400 is arranged to address the at least one touch electrode array 500, 502 during at least one of the periods 451, 453 during which the drive voltage is constant. Thus, the waveform 436 is provided during period 451. In another embodiment, the waveform 436 may be provided during period 453.

[0167] The arithmetic mean of the drive voltage waveform 434 is zero. In other words, the arithmetic mean potential across the switchable liquid crystal layer 314 between the electrodes 413, 415 is zero. Advantageously, the liquid crystal material 414 within the liquid crystal retarder layer 314 is DC balanced. This minimizes the effects of charge transfer and optimizes cell lifetime and performance.

[0168] 10 further illustrates the touch control waveform 436 applied to the touch controller 450. When the touch control waveform 436 is in a first low state, no signal is provided to the controller 450 and no touch sensing is provided. When the touch control waveform 436 is in a second high state, a signal is provided to the controller 450 and the signal is applied by the touch drivers 452, 454 to and measured from the touch electrode arrays 500, 502.

[0169] Thus, when the drive voltage of the composite voltage waveform 434 is at a constant level, it provides the signal that is applied to and measured from the touch electrode arrays 500, 502.

[0170] The active state of the touch control waveform 436 is provided for a period of time that is less than or equal to the length of the constant voltage level of the waveform 434, e.g., period 431. Furthermore, the signal applied to and measured from the touch electrode arrays 500, 502 is provided when the drive voltage of the voltage waveform 434 is at the same constant level 435 each time the signal is applied and measured in the waveform 434.

[0171] The signal-to-noise ratio of touch location detection is increased due to reduced fringe field fluctuations seen by the touch electrode arrays 500, 502 due to interference from the changing electric fields on the switchable liquid crystal retarder electrodes 413, 415, and therefore contributions to capacitance fluctuations from the vicinity of the finger are easier to distinguish. Advantageously, this can increase the sensitivity and improve the accuracy of touch detection.

[0172] It is desirable to increase the signal-to-noise ratio of the touch measurement system.Further voltage waveforms 434 and corresponding touch control waveforms 436 are now described.

[0173] 11A-11D are schematic graphs illustrating the composite voltage waveform 434 provided across the liquid crystal retarder layer 314 and the corresponding timing of touch control signals 436 for application to and measurement from the touch electrode arrays 500, 502. Features of the embodiments of FIGS. 11A-11D that are not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0174] Thus, the drive voltage waveform 434 in the first phase includes at least one positive voltage level and a zero voltage level, and the drive voltage waveform in the second phase includes at least one negative voltage level and a zero voltage level.

[0175] 11A , the drive voltage across the layer 314 of liquid crystal material 414 has a waveform 434 including periods 451, 453, 455 during which the drive voltage is constant, and the control system 400 is arranged to address at least one touch electrode array 500, 502 during at least one of the periods 451, 455 during which the drive voltage is constant. The drive voltage waveform 434 includes a positive addressing phase 431 including at least one pulse 461 of positive polarity having a level V2, and a negative addressing phase 433 including at least one pulse 463 of negative polarity having a level −V2.

[0176] Waveform 436 is provided during periods 451, 455. The drive voltage has a waveform 434 including periods 451, 453, 455 in which the drive voltage is constant but at different levels +V2, 0, -V2, respectively, and control system 400 is arranged to address at least one touch electrode array 500, 502 during at least one of periods 451, 455 in which the drive voltage is constant and at the same level, zero volts.

[0177] In other words, the drive voltage waveform 434 includes a positive addressing phase 431 including at least one pulse 461 of positive polarity and at least one additional period 465, and a negative addressing phase 433 including at least one pulse 463 of negative polarity and at least one additional period 467, wherein the at least one additional period 465 of the positive addressing phase 431 and the at least one additional period 467 of the negative addressing phase 433 have constant drive voltage levels intermediate between the maximum level of the at least one pulse 461 of positive polarity and the minimum level of the at least one pulse 463 of negative polarity, as described above for periods 451, 455. The at least one additional period 465 of the positive addressing phase 431 and the at least one additional period 467 of the negative addressing phase 433 have zero volt levels.

[0178] The drive voltage has a root mean square value that provides a constant liquid crystal optical alignment state of the liquid crystal retarder 301 and has a waveform 434 that has an arithmetic mean of zero.

[0179] 11A illustrates that touch control signals are applied to and measured from the touch electrode array and are provided during times below Ts when the drive voltage waveform 434 is at a constant level and when the voltage waveform 434 is at zero volts. The voltage drive waveform 434 may be non-zero at other times, such as shown during time Td.

[0180] 10 , the signal-to-noise ratio of touch location detection is increased due to a reduction in the absolute level of fringe fields seen by the touch electrode arrays 500, 502 due to interference from the electric fields on the switchable liquid crystal retarder electrodes 413, 415, and therefore contributions to capacitance fluctuations from the vicinity of the finger 25 are easier to distinguish. Advantageously, touch detection sensitivity can be increased and accuracy can be improved.

[0181] High frequency detection reduces the perceived delay at the recorded position of finger 25. The entire slot Ts or a portion within Ts may be used for signals applied to and measured from the touch electrode array.

[0182] Alternatively, some of the zero voltage time slots in waveform 434 may not be used for touch measurement, i.e., some of waveform 436 may be removed. This allows the operating frequency of the switchable liquid crystal retarder to be set at a higher level while achieving a lower processing load on controller 450 for measuring the touch signal. Advantageously, the operating frequency of the switchable liquid crystal retarder can be freely set to suit the material and optical system.

[0183] It may be desirable to increase the length of time that touch measurements are provided.

[0184] As shown in FIG. 11B, the zero voltage time of waveform 434 may be increased. To maintain the desired liquid crystal matching, the negative minimum voltage −V3 and the positive maximum voltage +V3 may have a larger magnitude than V2 shown in FIG. 11A. The same overall root mean square (RMS) drive to switchable liquid crystal layer 314 may be provided. The increased detection time allows more electrodes to be measured, thereby increasing the accuracy of touch location measurements. A directional output may be advantageously maintained, and the detection time may be increased to advantageously achieve sensitivity, response time, and accuracy.

[0185] It may be desirable to reduce high frequency temporal signals in the electric field from the switchable liquid crystal retarder electrodes 413, 415.

[0186] 11C, the waveform of the drive voltage can be other than a square wave. For example, using a waveform 434 with a trapezoidal waveform profile 439 reduces high frequency Fourier components and reduces electrical interference from driving the liquid crystal retarder 301. Advantageously, the signal-to-noise ratio of the touch measurement can be improved.

[0187] Compared with FIG. 11A, FIG. 11D illustrates that the peak of at least one pulse 461 of positive polarity and the peak of at least one pulse 463 of negative polarity are periods 451, 453 in which the driving voltage is constant.

[0188] Thus, a method of controlling a touch input display device 100 includes a switchable liquid crystal retarder 301 comprising an SLM 48 arranged to output light 400, a display polarizer 218 arranged at the output side of the SLM 48, an additional polarizer 318 arranged at the output side of the display polarizer 218, a switchable liquid crystal retarder 301 comprising a layer 314 of liquid crystal material 414 arranged between the display polarizer 218 and the additional polarizer 318, at least one passive polarity-controlled retarder 330 arranged between the switchable liquid crystal retarder 301 and the additional polarizer 318, and a switchable retarder 330 arranged to apply a voltage to control the switchable liquid crystal retarder 301. and at least one touch electrode array 500, 502 disposed in at least one layer on an output side of the switchable retarder control electrodes 413, 415, and the method includes applying a drive voltage to the switchable retarder control electrodes 413, 415 to control the switchable liquid crystal retarder 301, the drive voltage having a waveform 434 including periods 451, 453, 455 during which the drive voltage is constant; and addressing the at least one touch electrode array 413, 415 for capacitive touch sensing during at least one of the periods 451, 453, 455 during which the drive voltage is constant.

[0189] It may be desirable to further increase the frequency of touch location measurements.

[0190] Figure 12A is a schematic graph illustrating two further exemplary drive voltage waveforms 430, 432, and Figure 12B is a schematic graph illustrating a composite voltage waveform 434. Features of the embodiments of Figures 12A-12B that are not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0191] Each of the first addressing phase 431 and the second addressing phase 433 includes a drive voltage level 441 intermediate between a positive maximum voltage 435 and a negative minimum voltage 437. The intermediate voltage level 441 is zero volts. In other words, the voltage waveform 434 in the first phase 431 includes at least one positive voltage level 435 and a zero voltage level 441, and the composite drive voltage waveform 434 in the second phase 433 includes at least one negative voltage level 437 and a zero voltage level 441.

[0192] The root mean square (RMS) value of the drive voltage waveform 434 is arranged to provide a constant liquid crystal optical alignment state of the liquid crystal retarder, and the arithmetic mean of the drive voltage waveform 434 is zero.

[0193] As illustrated, an increased density or frequency of time slots Ts at which signals applied to and measured from the touch electrode array may be provided may be provided. Increasing the density of measurement time slots Ts may reduce the delay in touch signal measurement, thereby improving the reliability of touch interaction when the finger 25 or multiple fingers are moving. Providing signals applied to and measured from the touch electrode arrays 500, 502 while the voltage of the switchable liquid crystal retarder is the same constant value improves the signal-to-noise ratio of the touch measurement system, advantageously improving reliability.

[0194] In some situations, it may be desirable to measure the touch signal at a voltage other than ground.

[0195] 13A-13B are schematic graphs illustrating composite voltage waveforms provided across a liquid crystal retarder having three and four drive voltage levels, respectively. Features of the embodiments of FIGS. 13A-13B that are not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0196] At least one additional period 465 of the positive addressing phase 431 and at least one additional period 467 of the negative addressing phase 433 have a non-zero magnitude level V1.

[0197] In FIG. 13A, the voltage waveform 434 in the first phase 431 includes a first positive voltage level 435 and a second voltage level 442, and the composite waveform 434 of the drive voltage in the second phase 433 includes at least one negative voltage level 437 and a second voltage level 442.

[0198] In FIG. 13B, the drive voltage waveform 434 in the first phase 431 includes multiple positive voltage levels 435, 443, and the drive voltage waveform 434 in the second phase 433 includes two or more negative voltage levels 444, 437.

[0199] If the ground signal has a lot of high frequency electrical noise, the touch signal measurement can be taken while the composite voltage waveform 434 is away from ground, which can advantageously improve the reliability of touch signal detection.

[0200] 14 is a schematic graph illustrating the composite voltage waveform 434 across the liquid crystal retarder, the corresponding timing of the control signal waveform 436 for application to and measurement from the touch electrode arrays 500, 502, and synchronization with the vertical blanking interval (VBI) of the SLM 48. Features of the embodiment of FIG. 14 not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0201] Compared to the biphasic addressing waveforms 434 of other embodiments herein, the voltage waveform 434 includes a third addressing phase 425 that includes an intermediate drive voltage level 446 midway between the positive maximum voltage 435 and the negative minimum voltage 437. The intermediate voltage level 446 is illustrated as zero.

[0202] The control system 400 is arranged to address the SLM 48 using an addressing scheme that includes a vertical blanking interval VBI, and the control system 400 is arranged to address at least one touch electrode array 500, 502 during the vertical blanking interval VBI.

[0203] Thus, the waveform 436 applied to the switchable liquid crystal retarder is synchronous with the addressing of the SLM 48. The addressing waveform 438 of the SLM 48 includes a vertical blanking interval (VBI), and the waveform 436 applied to and measured from the touch electrode arrays 500, 502 is provided during the vertical blanking interval (VBI). Advantageously, the signal-to-noise ratio of touch detection can be improved because interference from high frequency signals, including data addressing of the SLM 48, is reduced.

[0204] When the switchable liquid crystal retarder is located between the SLM 48 and the touch electrode array, the electrodes of the switchable liquid crystal retarder can substantially shield the electrical noise effects of the high frequency SLM data phase 438 from the touch detection circuitry, which may not provide synchronization to the SLM. Synchronization with the VBI of the SLM 48 reduces the frequency of position updates from the touch electrode system, thus increasing position lag errors of a moving finger. This is particularly problematic when the addressing frequency of the SLM is reduced below 60 Hz, for example to save power.

[0205] For example, due to high speed movement of finger 25, it may be desirable to provide a touch measurement update rate that differs from the addressing of SLM 48.

[0206] 15 is a schematic graph illustrating a composite voltage waveform 434 provided across the liquid crystal retarder, asynchronous with the drive waveform 438 of the SLM 48, and corresponding timing of control signal waveforms 436 for application to and measurement from the touch electrode arrays 500, 502. Features of the embodiment of FIG. 15 not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0207] Advantageously, increased response speed and reduced latency can be provided by the touch system. Additionally, the drive signals to the SLM 48 can operate independently of the touch panel and can be provided by a separate supplier without the need for electrical integration thereof. Shielding the electrical noise of the SLM 48 from the touch electrode array 500 means that the touch panel update frequency is not limited to the VBI period of the SLM 48 addressing, preserving the signal-to-noise ratio, allowing these components to be operated independently without synchronization. In particular, the touch panel control and measurement signals can be independent of, and compatible with, the variable addressing refresh rate of the SLM 48, for example, as used in SLMs compatible with "Freesync™" technology.

[0208] Next, other structures of switchable directional displays with touch electrode arrays are described.

[0209] 16A is a schematic diagram illustrating a side view of a touch input display device in which the dielectric layer 504 is provided by a pair of crossed A-plates, and FIG. 16B is a schematic diagram illustrating a side view of a touch input display device in which the dielectric layer is provided by a pair of crossed A-plates 330A, 330B. The dielectric layer 504 thus comprises at least one passive polarity-controlled retarder. Features of the embodiments of FIGS. 16A-16B that are not discussed in further detail can correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0210] The display device 100 comprises two or more passive polarity-controlled retarders 330A, 330B, and at least one dielectric layer 504 comprises all of the passive polarity-controlled retarders 330A, 330B. The touch electrode array includes a pair of touch electrode arrays 500, 502 formed on an outer surface of each passive uniaxial retarder of the pair of passive uniaxial retarders 330A, and at least one dielectric layer 504 comprises the pair of passive uniaxial retarders 330A, 330B.

[0211] Advantageously, the crossed A-plate retarders 330A, 330B can achieve a wide field of view for a high level of visibility security. Electrodes can be conveniently provided on one side of the A-plate retarders 330A, 330B using low-cost, roll-to-roll manufacturing techniques. The retarders 330A, 330B may be attached by solvent bonding to reduce thickness and complexity and increase robustness against environmental and mechanical stress.

[0212] 16A-16B further illustrate that the reflective polarizer 302 can be omitted to provide a display with off-axis brightness control. Off-axis reflections are reduced in arrangements where lateral reflections are deemed undesirable. Advantageously, thickness and cost can be reduced.

[0213] 16C is a schematic diagram illustrating a side view of a touch input display device in which the dielectric layer is provided by one of a pair of crossed A-plate passive polarity-controlled retarders 330A. Thus, the dielectric layer 504 comprises at least one passive polarity-controlled retarder. Features of the embodiment of FIG. 16C that are not discussed in further detail may correspond to features having equivalent reference numbers discussed above, including any potential variations of the features.

[0214] The at least one passive retarder comprises a pair of passive uniaxial retarders 330A, 330B having intersecting optical axes in the plane of the passive uniaxial retarders. The at least one dielectric layer 504 comprises a passive polarity-controlled retarder 330A, and the display device 100 comprises two passive polarity-controlled retarders 330A, 330B.

[0215] Compared to the arrangements of FIGS. 1A and 2A, the dielectric layer 504 includes crossed A-plate passive polarity-controlled retarders 330A, 330B. The A-plates may be bonded in contact, for example, by solvent bonding, which advantageously provides a thin structure. Advantageously, thickness can be reduced. Compared to the arrangement of FIG. 16B, the electrode arrays 500, 502 are formed on a single substrate, and only a single element is provided with an electrode, thereby reducing manufacturing costs. Furthermore, the reduced dielectric thickness can improve the operational characteristics of capacitive sensing in the touchscreen. Advantageously, at least one of the electrode arrays 500 can be protected by the other passive polarity-controlled retarder 330B.

[0216] It may be desirable to provide a compensating retarder 330 that is not an A-plate.

[0217] 17 is a schematic diagram illustrating a touch input display device in a perspective side view, with a dielectric layer disposed between a pair of C-plates 330A, 330B, which are passive uniaxial retarder pairs, each having an optical axis perpendicular to the plane of the retarder. Features of the embodiment of FIG. 17 not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features. The pair of retarders 330A, 330B comprises a passive uniaxial retarder pair, each having an optical axis perpendicular to the plane of the retarder. A dielectric material 507 may be disposed in the dielectric layer 504 between the electrode arrays 500, 502, and may be, for example, an adhesive material.

[0218] Compared to Figure 16B, the polarity regions for high image visibility in Figures 3A-3D can be improved to provide greater viewing freedom in public operating modes, for example. Furthermore, the material or materials of the C-plate can be different from that of the A-plate in Figure 2A to provide different adhesion of the transparent electrode, such as ITO. Furthermore, the orientation of the electrodes is preferably not aligned with the in-plane stretch direction of the retarder, reducing cost and complexity.

[0219] 18A is a schematic diagram illustrating a touch input display device in a perspective side view in which the dielectric layer 504 is provided by a single C-plate 330 having an optical axis perpendicular to the plane of the retarder, and FIG. 18B is a schematic diagram illustrating the touch input display device of FIG. 18A in a side view. Exemplary embodiments are provided in Table 2. Features of the embodiments of FIGS. 18A-18B that are not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features. [Table 2]

[0220] The passive polarity-controlled retarder 330 comprises a passive uniaxial retarder having an optical axis perpendicular to the plane of the passive uniaxial retarder 330. A dielectric layer 504 comprises the passive polarity-controlled retarder 330. Touch electrode arrays 500, 502 are disposed on each side of the passive polarity-controlled retarder 330. Advantageously, the number of films can be reduced, reducing thickness, cost, and complexity.

[0221] The single passive polarity-controlled retarder 330 provides the dielectric layer 504. Advantageously, the thickness, cost, and complexity of the display device are reduced. The use of a C-plate can increase the field of view for high image visibility in public mode and for high visibility security level in privacy operation mode.

[0222] It may be desirable to provide brightness reduction in both the lateral and elevational directions.

[0223] Figure 19A is a schematic diagram illustrating an optical stack of passive polarity-controlled retarders 330A-D comprising two crossed A-plate pairs in a side perspective view, and Figure 19B is a schematic graph illustrating the variation of output transmittance with polarity direction for a transmitted ray in the passive retarder of Figure 19A comprising the structure illustrated in Table 3. Features of the embodiments of Figures 19A-19B that are not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features. [Table 3]

[0224] The retarder thus includes passive polarity-controlled retarders 330A, 330D with intersecting optic axes in the plane of the retarder. Each retarder pair comprises multiple A-plates with their respective optic axes aligned at different angles to each other. The pair of passive polarity-controlled retarders 330B, 330C have their optic axes extending at 90° and 0°, respectively, with respect to the electric vector transmission direction, which is parallel to the electric vector transmission 211 of the display polarizer 210.

[0225] The passive polarity-controlled retarders 330A, 330D have optic axes that extend at 45° and 135°, respectively, with respect to the electric vector transmission direction 211, which is parallel to the electric vector transmission of the display polarizer 218.

[0226] The display further includes a pair of passive polarity-controlled retarders 330B, 330C disposed between the first-mentioned passive polarity-controlled retarders 330A, 330D, with intersecting optic axes in the plane of the retarders. The additional pair of passive polarity-controlled retarders 330B, 330C have optic axes each extending at 0° and 90°, respectively, relative to the electric vector transmission directions 211, 317 that are parallel to the electric vector transmission of the display polarizers 210, 316.

[0227] For example, as described with reference to Figures 16B-16C, the electrode arrays 500, 502 may be formed on the surface of one or two of the passive polarity-controlled retarders 330A, 330B, 330C, 330D.

[0228] This embodiment provides a transmittance profile with some rotational symmetry. Advantageously, the privacy display can reduce the visibility of the image from a wide field of view, either to the side or from an elevated viewing position, to a peeping eye. Furthermore, such a configuration can be used to achieve improved privacy operation for both landscape and portrait operation of the mobile display. Such an arrangement may be provided within a vehicle to reduce stray light to off-axis passengers and also to reduce light impinging on the vehicle's windshield and other glass surfaces.

[0229] Compared to the switchable embodiments provided herein, the switchable liquid crystal retarder is omitted. Touch electrode arrays 500, 502 are provided to enable touch control of the passive privacy display. Advantageously, the thickness and cost of the display can be reduced.

[0230] Next, an arrangement will be described in which the touch electrode array is formed on or in the transparent substrates 312, 316 of the switchable liquid crystal retarder.

[0231] 20 is a schematic diagram illustrating a touch input display device 100 in a side view in which a dielectric layer 504 between touch electrode arrays 500, 502 is provided between a passive polarity-controlled retarder 330, which may be a C-plate or crossed A-plates 330A, 330B, and an output surface of an output transparent support substrate 316 of a switchable liquid crystal retarder 301. Features of the embodiment of FIG. 20 that are not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features.

[0232] The touch input display device 100 further comprises an input transparent support substrate 312 and an output transparent support substrate 316, with a layer 314 of liquid crystal material 414 disposed between the input transparent support substrate and the output transparent support substrate, and at least one touch electrode array disposed on the output side of the output transparent support substrate 316. The substrate 316 may have an electrode pattern of a touch electrode array 502 formed on the light output side of the substrate 316, and the passive polarity-controlled retarder 330 may have a touch electrode array 500 formed on the input side of the passive polarity-controlled retarder 330 for output light from the SLM 48. A dielectric material 507, which may be an inorganic material such as silicon dioxide and / or an adhesive, is provided between the touch electrode arrays 500, 502.

[0233] Advantageously, a single retarder can be provided with electrodes on a single surface, reducing thickness, cost and complexity. During fabrication of the switchable liquid crystal retarder 301, additional transparent electrodes can be conveniently formed on the transparent substrate 316.

[0234] It may be desirable to provide the electrode arrays 500, 502, 415 on only one side of the transparent output substrate 316.

[0235] 21A is a schematic diagram illustrating a side view of a touch input display device 100 in which a dielectric layer 504 between touch electrode arrays 500, 502 is provided by an output transparent support substrate 316 and an adhesive layer 322. The electrode array 500 is formed on a passive polarity-controlled retarder 330, and the electrodes 502 are formed on the transparent substrate 316.

[0236] A dielectric material 507, which may be an inorganic material such as silicon dioxide, is provided between the touch electrode array 502 and the liquid crystal control electrode 415. The waveform of this embodiment described above can be used to reduce electrical interference between the two electrodes 502, 415.

[0237] Advantageously, the electrodes 415, 502 are formed on only one side of the transparent support substrate 316, reducing the complexity and cost of manufacturing the substrate 316.

[0238] FIG. 21B is a schematic diagram illustrating a side view of a touch input display device 100 in which touch electrode arrays 500, 502 and a dielectric layer 504 are provided between one of the liquid crystal control electrodes 415 and the output transparent support substrate 316 of the switchable liquid crystal retarder. The waveforms of this embodiment described above can be used to reduce electrical interference between the electrodes 500, 502, 415. Advantageously, all of the electrodes 415, 500, 502 can be formed on one side of the substrate, reducing cost and complexity. Compared to FIG. 21C below, the arrangement of FIGS. 21A-21B allows the support substrate 316 to be processed to have touch electrode arrays 500, 502 on only one side, advantageously reducing complexity and increasing process yield.

[0239] 21C is a schematic diagram illustrating a touch input display device 100 in a perspective side view similar to FIG. 21A, but with electrode array 500 formed on the output side of substrate 316. Advantageously, the electrode structure formed near the liquid crystal layer is simpler than in FIG. 21B. Features of the embodiments of FIGS. 21A-21C that are not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features.

[0240] FIG. 22 is a schematic diagram illustrating a touch-input switchable privacy display device 100 in a perspective side view, in which touch electrode arrays 500, 502 are disposed between the liquid crystal polarity-controlled retarder 301 and the additional polarizer 318. Compared to the above embodiment, a passive polarity-controlled retarder 330 is disposed between the liquid crystal retarder 301 and the display output polarizer 218. Transparent substrates 370, 372 are provided having electrode arrays 500, 502 formed on their respective surfaces, with a dielectric layer 504 formed therebetween. The transparent substrates 370, 372 may have low birefringence, for example, and may have their optical axes aligned parallel or perpendicular to the polarizer 318. The waveforms of this embodiment described above can be used to reduce electrical interference between the electrodes 500, 502, 413, 415. Features of the embodiment of FIG. 22 not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features.

[0241] Advantageously, a passively controlled retarder 330 can be provided that does not have surface characteristics suitable for forming transparent electrodes 500, 502. Furthermore, the electrode structure formed on the transparent substrate 316 is less complex than the arrangement of Figures 21B-21C.

[0242] The operation of the retarder layer between parallel polarizers for off-axis illumination will now be further described. In the various devices described above, at least one polarity-controlled retarder is disposed between the reflective polarizer 318 and the additional polarizer 218 in a variety of different configurations. In each case, the at least one polarity-controlled retarder is configured, at least in one of the switchable states of the compensated switchable polarity-controlled retarder 300, to not affect the intensity of light passing through the reflective polarizer 318, the at least one polarity-controlled retarder, and the additional polarizer 218 along an axis normal to the plane of the polar-controlled retarder(s), but to reduce the intensity of light passing through the reflective polarizer 318, the at least one polarity-controlled retarder, and the additional polarizer 218 along an axis tilted relative to the normal to the plane of the polar-controlled retarder(s). A more detailed explanation of this effect will now be provided, the principles of which may be generally applied to all of the devices described above.

[0243] 23A is a schematic diagram illustrating, in a perspective view, illumination of a polar-controlled retarder layer with off-axis light. The polar-controlled retarder 630 may include a birefringent material represented by an index ellipsoid 632 with an optical axis direction 634 of 0 degrees relative to the x-axis, and has a thickness 631. Features of the embodiments of Figures 23A-25E below that are not discussed in further detail may correspond to features with equivalent reference numbers discussed above, including any potential variations of the features.

[0244] Normal ray 636 propagates such that its path length in the material is the same as thickness 631. Ray 637 is in the yz plane and has an increased path length, but the birefringence of the material is substantially the same as ray 636. Ray 638, which is in the xz plane, has an increased path length in the birefringent material and, furthermore, its birefringence is different from that of normal ray 636.

[0245] Therefore, the retardance of the polar-controlled retarder 630 depends on the angle of incidence of each ray, and ray 638 in the plane of incidence, ie, xz, has a different retardance than ordinary ray 636 and ray 637 in the yz plane.

[0246] We now describe the interaction of polarized light with the polarity-controlled retarder 630. To distinguish between the first and second polarization components during operation in a directional backlight 101, the following description refers to the third and fourth polarization components.

[0247] 23B is a schematic diagram illustrating, in a perspective view, illumination of the polar-controlled retarder layer with off-axis light of a third linear polarization state at 90 degrees relative to the x-axis, and FIG. 23C is a schematic diagram illustrating, in a perspective view, illumination of the polar-controlled retarder layer with off-axis light of a fourth linear polarization state at 0 degrees relative to the x-axis. In such an arrangement, the incident linear polarization state is aligned with the optic axis of the birefringent material, represented by ellipse 632. As a result, no phase difference is provided between the third and fourth orthogonal polarization components, and no change in the polarization state of the linearly polarized input light for each of rays 636, 637, and 638 occurs. Therefore, the polar-controlled retarder 630 does not introduce a phase shift to the polarization components of light passing through the polarizer at the input side of the polar-controlled retarder 630 along an axis normal to the plane of the polar-controlled retarder 630. Thus, the polar-controlled retarder 630 does not affect the brightness of light passing through the polar-controlled retarder 630 and the polarizers (not shown) on either side of the polar-controlled retarder 630. Although Figures 23A-23C relate specifically to a polar-controlled retarder 630 that is passive, a similar effect is achieved by the polar-controlled retarders in the devices described above.

[0248] FIG. 23D is a schematic diagram illustrating, in a perspective view, illumination of a polar-controlled retarder 630 layer with off-axis light of a 45-degree linear polarization state. The linear polarization state may be decomposed into third and fourth polarization components that are orthogonal and parallel, respectively, to the optical axis 634 direction. The polar-controlled retarder thickness 631 and material retardance, represented by index ellipsoid 632, can provide a net effect of shifting the phase of normally incident third and fourth polarization components, represented by light ray 636, by half a wavelength relative to the design wavelength. The design wavelength may be, for example, in the range of 500-550 nm.

[0249] For light propagating normally along ray 636 at the design wavelength, the output polarization may be rotated 90 degrees to a -45 degree linear polarization state 640. Light propagating along ray 637 may see a phase difference similar, but not identical, to the phase difference along ray 637 due to thickness variations, and thus an elliptical polarization state 639 may be output, which may have a major axis similar to the linear polarization axis of the output light in ray 636.

[0250] In contrast, the phase difference of the incident linear polarization state along light ray 638 may be significantly different, and in particular, less phase difference may be provided. Such a phase difference may provide an output polarization state 644 that is substantially circular at a given tilt angle 642. Thus, the polar-controlled retarder 630 introduces a phase shift to the polarization components of light passing through the polarizer at the input side of the polar-controlled retarder 630 along an axis corresponding to light ray 638 that is tilted with respect to the normal to the plane of the polar-controlled retarder 630. While FIG. 23D relates to a passive polar-controlled retarder 630, a similar effect is achieved by the polar-controlled retarders described above in the switchable states of the switchable liquid crystal polar-controlled retarders corresponding to the privacy modes.

[0251] 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 with reference to the operation of the C-plate between parallel polarizers 218, 210 for various off-axis illumination arrangements.

[0252] FIG. 24A is a schematic diagram illustrating, in a perspective view, illumination of a C-plate layer with off-axis polarized light having a positive elevation angle. An incident linearly polarized light component 704 is incident on the birefringent material 632 of the polar-controlled retarder 560, which is a C-plate with an optic axis direction 507 perpendicular to the plane of the polar-controlled retarder 560. Because the polarized light component 704 has no net phase difference in transmission through the liquid crystal molecules, the output polarization component is the same as component 704. Therefore, maximum transmission is seen through the polarizer 210. The polar-controlled retarder 560 therefore has an optic axis 561 perpendicular to the plane of the polar-controlled retarder 560, which is the xy plane. A polar-controlled retarder 560 with an optic axis perpendicular to the plane of the polar-controlled retarder comprises a C-plate.

[0253] FIG. 24B is a schematic diagram illustrating, in a perspective view, illumination of a C-plate layer with off-axis polarized light having a negative transverse angle. Similar to the arrangement of FIG. 24A, polarization state 704 sees no net phase difference and is transmitted with maximum intensity. Thus, the polarized retarder 560 does not introduce a phase shift to the polarization components of light passing through the polarizers (not shown) on the input side of the polarized retarder 560 along an axis normal to the plane of the polarized retarder 560. Therefore, the polarized retarder 560 does not affect the intensity of light passing through the polarized retarder 560 and the polarizers (not shown) on each side of the polarized retarder 560. While FIGS. 24A-24B specifically relate to a passive polarized retarder 560, similar effects are achieved with the polarized retarders in the devices described above.

[0254] 24C is a schematic diagram illustrating, in a perspective view, illumination of a C-plate layer with off-axis polarized light having a positive elevation angle and a negative lateral angle. Compared to the arrangement of FIGS. 24A-24B, polarization state 704 decomposes into eigenstates 703 and 705 for birefringent material 632, providing a net phase difference upon transmission through polarity-controlled retarder 560. The composite elliptically polarized component 656 transmits through polarizer 210 with reduced intensity compared to the light beam shown in FIGS. 24A-24B.

[0255] FIG. 24D is a schematic diagram illustrating, in a perspective view, illumination of a C-plate layer with off-axis polarized light having a positive elevation angle and a positive horizontal angle. Similar to FIG. 24C, polarization component 704 is decomposed into eigenstates 703 and 705 that experience a net phase difference, providing an elliptically polarized component 660 that reduces the intensity of each off-axis ray after transmission through the polarizer. Thus, the polarity-controlled retarder 560 introduces a phase shift to the polarization components of light passing through the polarizer at the input side of the polarity-controlled retarder 560 along an axis tilted relative to the normal to the plane of the polarity-controlled retarder 560. While FIG. 24D relates to a passive polarity-controlled retarder 560, a similar effect is achieved by the polarity-controlled retarder described above in the switchable state of the switchable liquid crystal polarity-controlled retarder corresponding to the privacy mode.

[0256] Figure 24E is a schematic graph illustrating the variation of output transmittance with polar direction for the transmitted light beam of Figures 24A-24D. Thus, the C-plate can provide brightness reduction in the polar quadrants. In combination with the switchable liquid crystal layer 314 described elsewhere herein, (i) elimination of the C-plate brightness reduction may be provided in a first, wide-angle operating state, and (ii) an extended polar region for brightness reduction may be achieved in a second, privacy operating state.

[0257] To illustrate the off-axis behavior of the retarder stack, the angular brightness control of crossed A-plate passive polarity-controlled retarders 330A, 330B between the additional polarizer 318 and the output display polarizer 218 is now described for various off-axis illumination arrangements.

[0258] FIG. 25A is a schematic diagram illustrating illumination of a crossed A-plate retarder layer with off-axis polarized light having a positive elevation angle in a perspective view. A linear polarizer 218 with an electric vector transmission direction 219 is used to provide a linear polarization state 704 parallel to the horizontal direction on the first A-plate 330A of the crossed A-plate passive polarity-controlled retarders 330A, 330B. The optic axis direction 331A is tilted +45 degrees relative to the horizontal direction. The retardance of the polarity-controlled retarder 330A for an off-axis angle θ1 in the positive elevation direction provides a composite polarization component 650 that is approximately elliptical on the output. The polarization component 650 is incident on the second A-plate 330B of the crossed A-plate passive polarity-controlled retarders 330A, 330B, which has an optic axis direction 331B orthogonal to the optic axis direction 331A of the first A-plate 330A. 25A, the retardance of the second A-plate 330B for the off-axis angle θ1 is equal and opposite to the retardance of the first A-plate 330A. Thus, a net zero retardation is provided to the input polarization component 704, and the output polarization component is the same as the input polarization component 704.

[0259] The output polarization component is aligned with the electric vector transmission direction of the additional polarizer 318 and is therefore efficiently transmitted. Advantageously, virtually no loss is incurred for rays with zero transverse angular component, thus achieving perfect transmission efficiency.

[0260] 25B is a schematic diagram illustrating, in a perspective view, illumination of a crossed A-plate retarder layer with off-axis polarized light having a negative transverse angle. Thus, the input polarization component is converted by the first A-plate 330A into an intermediate polarization component 652, which has a roughly elliptical polarization state. Again, the second A-plate 330B provides equal and opposite retardation to the first A-plate, such that the output polarization component is the same as the input polarization component 704, and the light is efficiently transmitted through the polarizer 318.

[0261] The polarity-controlled retarder thus comprises a pair of retarders 330A, 330B having intersecting optic axes in the plane of the retarders 330A, 330B, which in this embodiment lies in the xy plane. The pair of retarders 330A, 330B have optic axes 331A, 331B each extending at 45° to the electric vector transmission direction, which is parallel to the electric vector transmission of the polarizer 318.

[0262] Advantageously, substantially no loss is incurred for rays having an angular component at zero elevation angle so that perfect transmission efficiency is achieved.

[0263] 25C is a schematic diagram illustrating, in a perspective view, illumination of a crossed A-plate retarder layer with off-axis polarized light having a positive elevation angle and a negative lateral angle. Polarized light component 704 is converted by the first A-plate 330A into an elliptically polarized light component 654. The resulting elliptically polarized light component 656 is output from the second A-plate 330B. The elliptically polarized light component 656 is analyzed by the input polarizer 318, which has reduced intensity compared to the input intensity of the first polarized light component 704.

[0264] 25D is a schematic diagram illustrating, in a perspective view, illumination of a crossed A-plate retarder layer with off-axis polarized light having a positive elevation angle and a positive lateral angle. Polarization components 658 and 660 are provided by the first and second A-plate passive polarity-controlled retarders 330A, 330B because the net retardance of the first and second retarders does not provide compensation.

[0265] Thus, brightness is reduced for rays with non-zero lateral and non-zero elevation components. Advantageously, the luminous efficiency of the primary display user is not substantially reduced, while the privacy of the display can be improved for peepers positioned to view the quadrants.

[0266] Figure 25E is a schematic graph illustrating the variation of output transmittance with polarity direction for the transmitted light beam of Figures 25A-25D. Compared to the arrangement of Figure 24E, the area of ​​brightness reduction is increased for off-axis viewing. However, the switchable liquid crystal layer 314 may result in reduced uniformity compared to a C-plate arrangement for off-axis viewing in the first public mode of operation.

[0267] As used herein, the terms "substantially" and "approximately" provide an industry-accepted tolerance for corresponding terms and / or relative values ​​between items. Such industry-accepted tolerances may range from 0 percent to 10 percent, including, but not limited to, component values, angles, etc. Such relative values ​​may range from approximately less than 0 percent to 10 percent.

[0268] While various embodiments in accordance with the principles disclosed herein have been described above, it should be understood that they are presented by way of example only, and not by way of limitation. Thus, the breadth and scope of this disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with any claims and their equivalents derived from this disclosure. Furthermore, while the above-described advantages and features are provided in the described embodiments, this does not limit the application of such derived claims to processes and structures that achieve any or all of the above advantages.

[0269] Furthermore, the section headings herein are provided for consistency with guidance under 37 CFR 1.77 or to otherwise provide organizational guidance. These headings are not intended to limit or characterize the embodiment(s) set forth in any claim(s) that may arise from this disclosure. Specifically, and merely by way of example, there is a heading titled "Technical Field," but the language chosen under this heading to describe the so-called field does not limit the scope of the claims. Furthermore, any description of technology in the "Background" section should not be construed as an admission that a particular technology is prior art to any embodiment(s) of this disclosure. The "Summary of the Invention" section should also not be considered to characterize the embodiment(s) set forth in the published claims. Furthermore, references to the singular "invention" within this disclosure should not be used to assert that only a single novelty exists in this disclosure. Multiple embodiments may be set forth by this disclosure, subject to the limitations of the published claims. Accordingly, such claims define and protect this embodiment(s) and their equivalents. In all instances, the scope of such claims will be considered on their own merits in light of this disclosure, but should not be constrained by the headings set forth herein.

Claims

1. A touch input display device comprising: a spatial light modulator (SLM) arranged to output light; a display polarizer arranged on the output side of the SLM, the display polarizer being a linear polarizer; an additional polarizer arranged on the output side of the display polarizer, the additional polarizer being a linear polarizer; a switchable liquid crystal retarder comprising a liquid crystal material layer arranged between the display polarizer and the additional polarizer, and simultaneously introducing no net relative phase shift to the orthogonal polarization component of the light passing through the display polarizer along the axis along the normal of the plane of the switchable liquid crystal retarder, and introducing a relative phase shift to the orthogonal polarization component of the light passing through the display polarizer along the axis inclined with respect to the normal of the plane of the switchable liquid crystal retarder, a polarization direction control retarder arranged in a switchable state; a switchable retarder control electrode arranged to apply a voltage for controlling the state of the switchable liquid crystal retarder; a first passive retarder arranged between the display polarizer and the additional polarizer; and at least one touch electrode array arranged in a layer on the output side of the switchable retarder control electrode.

2. The touch input display device according to claim 1, further comprising a second passive retarder arranged between the switchable liquid crystal retarder and the additional polarizer.

3. The touch input display device according to claim 2, wherein at least one of the first passive retarder or the second passive retarder is a polarization direction control retarder, and the polarization direction control retarder simultaneously introduces no net relative phase shift to the orthogonal polarization component of the light passing through the display polarizer along the axis along the normal of the plane of the switchable liquid crystal retarder, and introduces a relative phase shift to the orthogonal polarization component of the light passing through the display polarizer along the axis inclined with respect to the normal of the plane of the switchable liquid crystal retarder.

4. When the touch input display device includes one touch electrode array, or when the touch input display device includes two or more touch electrode arrays, one of the touch electrode arrays is formed on the surface of the passive retarder when the touch input display device includes one passive retarder, or on the surface of one of the passive retarders when the touch input display device includes two or more passive retarders. The touch input display device according to claim 2 or 3.

5. The touch input display device according to any one of claims 2 to 4, wherein the at least one touch electrode array includes a pair of touch electrode arrays disposed in layers separated by at least one dielectric layer.

6. The touch input display device according to claim 5, wherein each of the pair of touch electrode arrays is formed on the respective surface of the passive retarder when the touch input display device includes one passive retarder, or on the respective surface of one of the passive retarders when the touch input display device includes two or more passive retarders.

7. The touch input display device according to claim 5 or 6, wherein the at least one dielectric layer includes the passive retarder when the touch input display device includes one passive retarder, or includes at least one of the passive retarders when the touch input display device includes two or more passive retarders.

8. The touch input display device according to any one of claims 5 to 7, wherein the touch input display device includes two or more passive retarders and the at least one dielectric layer includes at least two passive retarders.

9. The touch input display device according to any one of claims 5 to 8, wherein the at least one dielectric layer includes at least one additional layer that is not a retarder. **Claim 10**: The touch input display device according to any one of claims 5 to 9, wherein at least one of the first passive retarder or the second passive retarder is a passive uniaxial retarder, and includes a passive uniaxial retarder having an optical axis perpendicular to the plane of the passive uniaxial retarder. **Claim 11**: The touch input display device according to any one of claims 2 to 9, wherein at least one of the first passive retarder or the second passive retarder is a pair of passive uniaxial retarders, and includes a pair of passive uniaxial retarders having optical axes intersecting in the plane of the passive uniaxial retarder. **Claim 12** The touch input display device according to claim 11, wherein the at least one touch electrode array includes a pair of touch electrode arrays formed on opposing surfaces of respective passive uniaxial retarders of the pair of passive uniaxial retarders. **Claim 13** The touch input display device according to claim 12, wherein the at least one dielectric layer includes an adhesive layer disposed between the pair of touch electrode arrays. **Claim 14** The touch input display device according to claim 11, wherein the at least one touch electrode array includes a pair of touch electrode arrays formed on outer surfaces of respective passive uniaxial retarders of the pair of passive uniaxial retarders, and the at least one dielectric layer includes the pair of passive uniaxial retarders. **Claim 15** The touch input display device according to claim 1, further comprising an input transparent support substrate and an output transparent support substrate, wherein the liquid crystal material layer is disposed between the input transparent support substrate and the output transparent support substrate, and the at least one touch electrode array is disposed on the output side of the output transparent support substrate. **Claim 16** The touch input display device according to claim 1, further comprising an input transparent support substrate and an output transparent support substrate, wherein the liquid crystal material layer is disposed between the input transparent support substrate and the output transparent support substrate, and the at least one touch electrode array is disposed between the switchable retarder control electrode and the output transparent support substrate. **Claim 17** The touch input display device according to claim 1, wherein the at least one touch electrode array is disposed between the switchable retarder control electrode and the additional polarizer. **Claim 18** The touch input display device according to claim 1, wherein the at least one touch electrode array is separated from the switchable retarder control electrode.

19. The touch input display device according to claim 1, wherein the switchable retarder control electrode is disposed on both sides of the liquid crystal material layer.

20. The touch input display device according to claim 1, further comprising a reflective polarizer disposed between the display polarizer and the switchable liquid crystal retarder.

21. The touch input display device according to claim 1, further comprising a control system, wherein the control system is arranged to apply a driving voltage to the switchable retarder control electrode to control the switchable liquid crystal retarder, and the control system is arranged to address the at least one touch electrode array for capacitive touch sensing.

22. The touch input display device according to claim 21, wherein the driving voltage has a waveform including a period during which the driving voltage is constant, and the control system is arranged to address the at least one touch electrode array during at least one of the periods during which the driving voltage is constant.

23. The touch input display device according to claim 22, wherein the driving voltage has a waveform including periods during which the driving voltage is constant but at different levels, and the control system is arranged to address the at least one touch electrode array during at least one of the periods during which the driving voltage is constant and at the same level.

24. The touch input display device according to claim 23, wherein the waveform of the driving voltage includes a positive addressing phase including at least one pulse of positive polarity and a negative addressing phase including at least one pulse of negative polarity, and a peak of the at least one pulse of positive polarity and a peak of the at least one pulse of negative polarity are the periods during which the driving voltage is constant.

25. The waveform of the drive voltage includes a positive addressing phase including at least one pulse of positive polarity and at least one additional period, and a negative addressing phase including at least one pulse of negative polarity and at least one additional period, wherein the at least one additional period of the positive addressing phase and the at least one additional period of the negative addressing phase are periods in which the drive voltage is constant and has a level intermediate between the maximum level of at least one pulse of positive polarity and the minimum level of at least one pulse of negative polarity. The touch input display device according to claim 22 or 23.

26. The touch input display device according to claim 25, wherein the at least one additional period of the positive addressing phase and the at least one additional period of the negative addressing phase have a level of zero volts.

27. The touch input display device according to claim 25, wherein the at least one additional period of the positive addressing phase and the at least one additional period of the negative addressing phase have a level of a non-zero magnitude.

28. The touch input display device according to any one of claims 21 to 27, wherein the drive voltage has a waveform having a root mean square value that provides a constant liquid crystal optical alignment state in the liquid crystal retarder and an arithmetic mean of zero.

29. The touch input display device according to any one of claims 21 to 28, wherein the control system is further arranged to address the SLM.

30. The touch input display device according to claim 29, wherein the drive voltage arranged to be applied by the control system to the switchable retarder control electrode is synchronized with a signal including data for addressing the SLM.

31. The touch input display device according to claim 29 or 30, wherein the control system is arranged to address the SLM using an addressing method including a vertical blanking interval, and the control system is arranged to address the at least one touch electrode array during the vertical blanking interval.

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