Non-stationary cholesteric displays, non-stationary hybrid cholesteric displays and devices

Abstract

The invention relates to a non-stationary cholesteric display, a non-stationary hybrid cholesteric display and device, a non-stationary cholesteric display, using field-induced nematic vertical alignment texture and field-induced vortex alignment texture as video non-stationary, and using cholesteric planar texture and focal conic texture as zero-field bistable. Thus, the display provides not only video speed animation with infinite gray levels, but also excellent static images.

Description

Technical Field

[0001] This invention relates to the field of thin-film transistor (TFT) liquid crystal displays, and more specifically, to astable cholesteric displays, astable hybrid cholesteric displays, and devices thereof, which employ field-induced nematic vertical alignment texture and field-induced eddy current alignment texture as video astable states, and employ cholesteric phase planar texture and focal conic texture as zero-field bistable states. Therefore, the display not only provides video motion with infinite grayscale levels, but also provides excellent still images. Background Technology

[0002] Cholesteric liquid crystal displays (LCDs) are characterized by the fact that the image remains on the display even when the driving voltage is disconnected. Bistableness and multistableness ensure a completely flicker-free static display and offer the potential for unlimited multiplexing to produce giant displays and / or ultra-high resolution displays. In cholesteric liquid crystals, molecules are oriented in a helical pattern characteristic of the material's periodicity. In the planar state, the axis of this helix is ​​perpendicular to the display plane, and light with a wavelength matching the pitch of the helix is ​​reflected, making the display appear bright. When an alternating current (AC) voltage is applied, the liquid crystal structure changes from a planar texture to a focal conic texture. The main characteristic of the focal conic state is its highly diffuse light scattering appearance caused by the distribution of small birefringent domains, where the refractive index changes abruptly at the boundaries between these domains. This texture lacks a single optical axis and is typically milky white (i.e., white light scattering). Planar and focal conic textures can coexist in the same panel or solid, a crucial characteristic for display applications that enables grayscale levels.

[0003] Current cholesteric displays utilize one of the inherent properties of the cholesteric phase: Bragg reflection. In Bragg reflection, only a portion of the incident light with the same circular polarization chirality and within a specific wavelength band is reflected to the observer, producing a monochrome display. However, the remaining spectrum of the incident light, including 50% of the circularly polarized and outward-bragg-reflected bands with opposite chirality, passes through the display and is absorbed by the black coating material on the display's back substrate to ensure contrast. Overall light utilization efficiency is quite low. Bragg reflection gives the impression that monochrome display is one of the unique characteristics of cholesteric liquid crystal displays (CLCDs).

[0004] U.S. Patent No. 5,796,454 discloses a monochrome backlit cholesteric liquid crystal (ChLC) display. It includes a controllable cholesteric liquid crystal (ChLC) structure, a first circular polarizer laminated to a first substrate with units having the same circular polarity as the liquid crystal, a second circular polarizer laminated to a second substrate with units having the opposite circular polarity to the liquid crystal, and a light source. The monochrome backlit display is preferably illuminated by a light source that produces natural "white" light; therefore, when the display is illuminated by incident light, the circular polarizer transmits 50% of the circularly polarized incident light. When the cholesteric liquid crystal (ChLC) is in the ON state, the light reflected by the cholesteric liquid crystal (ChLC) is the portion of incident light having wavelength and the same chirality within its inherent spectral bandwidth. The portion of light transmitted through the cholesteric liquid crystal (ChLC) is the complementary color of the cholesteric liquid crystal (ChLC)'s inherent color. The transmitted light has right circular polarization; however, it is therefore blocked by the left circular polarizer, so the observer will perceive that area of ​​the display as predominantly black. When the display is in the OFF state, the light transmitted through the polarizer is scattered by the cholesteric liquid crystal (ChLC). The forward-scattered incident light portion is emitted as depolarized light from the controllable cholesteric liquid crystal (ChLC) structure. The left circularly polarized portion of the forward-scattered light is transmitted through the left circular polarizer and is thus perceived by the observer. In the '454 patent, the monochrome display is generated by a backlight component, and there is no ambient light except for noise.

[0005] U.S. Patent No. 6,344,887 discloses a method for manufacturing a full-spectrum reflective cholesteric display, which is incorporated herein by reference. This patent discloses a cholesteric display employing a polarizer having the same polarity as a liquid crystal. The display utilizes two reflections: Bragg reflection (reflection) and metallic reflection (second reflection). The display uses a circular polarizer and a metallic reflector film located on the back of the display to guide the second component of the incident light back to the observer.

[0006] U.S. Patent No. 6,873,393 discloses a method for manufacturing a monochrome or color cholesteric display without using Bragg reflection, which is incorporated herein by reference. This patent discloses a cholesteric display employing a front polarizer with the opposite polarity to that of liquid crystal, wherein the display unit structure functions solely as an optical shutter to switch the incident light on (ON) and off (OFF). In monochrome mode, a white state is achieved by metallic reflection from the cholesteric phase planar texture region; a black state is obtained by the cholesteric phase depolarization effect from the cholesteric phase focal conic texture region and the filtering effect of the polarizer. In panchromatic mode, a panchromatic state is generated by the metallic reflector and micro-filter from the cholesteric phase planar texture region; a black state is achieved by the cholesteric phase focal conic texture region.

[0007] U.S. Patent No. 7,564,518 discloses a reflective cholesteric display employing two circular polarizers. The front circular polarizer has a predetermined polarity opposite to that of the Bragg reflective and back reflective circular polarizers of the display. The display system utilizes a weakly absorbing polarizer with high transmittance. In monochrome mode, a white state is achieved by the cholesteric phase focal conic texture region; a black state is achieved by the cholesteric phase planar texture region. In panchromatic mode, a panchromatic state is generated by a micro-filter in the cholesteric phase focal conic texture region; a black state is achieved by the cholesteric phase planar texture region.

[0008] US20200233254A1 describes a cholesteric display using a substrate with a mirror, wherein the monostable liquid crystal structure includes a field-induced nematic vertical alignment texture and a cholesteric phase focal cone texture, which is incorporated herein by reference. Summary of the Invention

[0009] The main objective of this invention is to realize a high frame rate TFT cholesteric liquid crystal display.

[0010] Another object of the present invention is to create an astable display during video display.

[0011] Another object of the present invention is to utilize a bistable display during power-free static display.

[0012] Another objective of this invention is to create field-induced nematic eddy current orientation texture as a video optical ON and grayscale state.

[0013] Another object of the present invention is to create a field-induced nematic vertical orientation texture as a video optics off (OFF) state.

[0014] Another objective of this invention is to realize a field-induced vertical orientation (FVA) display using a linear polarizer.

[0015] Another object of the present invention is to create a statically closed (OFF) state in the cholesteric phase planar texture.

[0016] Another object of the present invention is to obtain a statically ON state in the cholesteric phase focal cone texture.

[0017] Another objective of this invention is to achieve a true full-color display.

[0018] The ultimate goal of this invention is to convert non-steady-state video animation into bistable images. Attached Figure Description

[0019] Figure 1 A schematic structure of a prior art monostable black-and-white cholesteric display is shown;

[0020] Figure 2A schematic structure of an astable backlight transmissive full-color TFT cholesteric display is shown.

[0021] Figure 3 The electro-optic response and driving principle of the non-steady-state and bistable dual-mode cholesteric display are shown;

[0022] Figure 4 The electro-optic response curve of a reflective monochrome cholesteric display is shown;

[0023] Figure 5 Images of grayscale levels of an actively addressed, non-steady-state panchromatic cholesteric display are shown.

[0024] Figure 6 An image of a video speed-unsteady TFT cholesteric display is shown. Detailed Implementation

[0025] First refer to Figure 1 This illustrates the structure of a prior art monostable black-and-white cholesteric display. (Example:) Figure 1 As shown, the liquid crystal layer 110 includes at least one stable focal cone textured region 111 and at least one unstable field-induced nematic vertical alignment textured region 112. The liquid crystal layer 110 is located between a transparent front substrate 101 having a transparent common electrode 103 and a translucent back substrate 102 having a mirror pixel electrode 104 to form a cell structure with a thickness in the range of 2-10 micrometers, more preferably, the cell structure is 2.5-3.5 micrometers. The front substrate 101 can be made of glass or plastic with a thickness in the range of 0.1-1.1 millimeters, while the back substrate 102 can be made of glass, plastic, or metal with the same thickness range as the front substrate 101.

[0026] When the liquid crystal layer 110 is addressed in the focal cone texture region 111, the display operates in the optically ON state. The obliquely incident light 140 passing through the transparent front substrate 101 is scattered into diffuse light, with approximately 5% backscattered to the observer and 95% becoming forward-scattered light. When the forward-scattered light component strikes the mirror pixel electrode 104, over 90% of the light is effectively reflected back to the observer. As a result, the backscattered and forward-scattered light ultimately appears in front of the observer 150 as natural light 141.

[0027] Therefore, when the liquid crystal layer 110 is addressed in the field-induced nematic vertical alignment texture region 112, the display operates in an optically off (OFF) state. This texture is non-steady-state because if the field is abruptly turned off, the cholesteric liquid crystal (ChLC) will revert to the planar texture; on the other hand, if the field is slowly turned off, the cholesteric liquid crystal (ChLC) will revert to the focal conic texture. Figure 1As shown, obliquely incident light 140 passing through the field-induced nematic vertically oriented texture region 112 of the uniaxial liquid crystal will be significantly reflected off the mirror surface to form light 142. Based on the law of specular reflection, where the angle of reflection equals the angle of incidence, if the observer 150 views the display normally, there will be no perceptible light. Therefore, the display presents sufficient black in the field-induced nematic texture region.

[0028] Due to the monostable mode, the volatility of the field-induced nematic texture as the optically off (OFF) state and the stability of the focal cone texture as the optically on (ON) state constitute the video speed of the monochrome cholesteric display.

[0029] It is important to note that the video speed displays described above do not possess the inherent grayscale levels currently available for use in cartoon videos because there is an optically ON state for the cholesteric focal conus texture or an optically OFF state for the field-induced vertical orientation texture within a single pixel. In other words, no intermediate brightness changes are involved within a single pixel. Therefore, to achieve a certain grayscale level, image resolution must be sacrificed through spatial blending or the frame rate must be reduced through temporal blending.

[0030] On the other hand, the response time from the cholesteric focicon to the field-induced nematic is typically 5 milliseconds, while the relaxation time of the phase transition from the field-induced nematic back to the cholesteric phase is quite long, which determines the maximum frame rate of the TFT monostable display.

[0031] Now go to Figure 2 , Figure 2 A schematic structure of an astable backlight transmissive full-color TFT cholesteric display is shown, such as... Figure 2 The cross-sectional structure of the full-color display is shown, in which an absorption color filter 230 is deposited on a front transparent conductive substrate 201, and a common ITO (Indium Tin Oxides) electrode 203 is sputtered on top of the color filter layer. The micro-color filter array has a pattern of red pixel regions 231, green pixel regions 232, and blue pixel regions 233. The thickness of the color filter is typically 0.4-1.2 micrometers, more preferably 0.8-1.0 micrometers. An ultrathin polyimide alignment layer is deposited on top of the color filter layer. Furthermore, a front polarizer layer is included, such as a first linear polarizer 221 located outside the front transparent conductive substrate 201, a TFT active matrix 204 fabricated on the inner side of a back active matrix substrate 202, and a back polarizer layer, such as a second linear polarizer 222 fabricated on the outer side of the back active matrix substrate 202. The optical axes of the first linear polarizer 221 and the second linear polarizer 222 are designed to be 90° apart. o Or they may intersect.

[0032] Within the TFT active matrix 204, gate lines for transmitting scan signals from the outside, gate electrodes as branches of the gate lines, and storage capacitor electrodes parallel to the gate lines are formed on a transparent insulating back substrate 202, such as glass. A gate insulating layer is formed thereon, and data lines perpendicular to the gate lines and transmitting display signals from the outside are formed on a portion of the gate insulating layer. Semiconductor and N+ layers are formed on the gate insulating layer and gate electrodes, and source and drain electrodes are formed on layers with ohmic contacts, with the source electrode electrically connected to the data line. In this embodiment, the gate electrode, source, drain, gate insulating layer, semiconductor, and N+ layer form the TFT 204, and a TFT channel is generated in a portion of the a-Si layer between the source and drain. When a scan signal is applied to the gate electrode through the gate line, the TFT turns on, and the display signal reaches the source through the data line and then flows into the drain through the channel in the a-Si layer.

[0033] like Figure 2 As shown, sealing rings 207 are printed around the four sides of the display to form liquid crystal cell junctions, and conductive silver dots 208 serve as common electrodes to connect the front substrate and the back substrate. Finally, the data and power input flexible printed circuit board (FPC) 206 is interconnected to the display's driver IC chip (X driver and Y driver of the chip on glass (COG)) via anisotropic conductive adhesive 205.

[0034] When the driving voltage is V0, the liquid crystal layer 210 is addressed in the field vertical alignment (FVA) texture 211 by the driving voltage V0, and the display operates in an optically off state in the red pixel region 231. The backlight beam 241 emanating from the backlight panel 240 reaches the linear polarizer 222 and is converted to plane polarization. The beam continues to pass through the liquid crystal FVA texture without attenuation or phase transition. Finally, a large portion of the light component is absorbed by the front polarizer layer, therefore, there is no red light perceptible to the observer.

[0035] Similarly, when the liquid crystal layer 210 is addressed in the field-induced eddy alignment (FEA) textures 212, 213, and 214, the display operates in an optically ON state with different gray levels in the green pixel region 232 and the blue pixel region 233. It should be noted that, as... Figure 2As shown, 212, 213, and 214 are all FEA textures, corresponding to different pixel regions. 212 and 213 correspond to the green pixel region, and 214 corresponds to the blue pixel region, but they are not specifically distinguished in name and are all named FEA texture. When the driving voltage value is V1, under the same driving voltage, FEA textures 212 and 213 have the same tilt angle θ1 relative to the normal direction, but have different domain orientations. There are many domains in the FEA, among which the tilt angle θ1 relative to the normal direction of the display is the same (e.g., Figure 2 (as shown), but the azimuth angle can be between 0 and 180 degrees. o The tilt angle θ varies within a range of 0 to 90°. It is inversely proportional to the driving voltage. o The range varies. Therefore, compared to FEA texture 212 and FEA texture 213, FEV texture 214 has a larger tilt angle θ2 addressed by a lower voltage V2. Liquid crystal eddies can form between domains, and the size and shape of the eddies depend on the driving voltage and the elastic properties of the surface alignment material and the liquid crystal. Light scattering and depolarization are typical phenomena of the eddy current effect. It should be noted that both FVA texture and FEA texture belong to electrically driven or field-induced nematic states. Figure 1 As shown, they can be interchanged simultaneously and instantaneously without any delay or relaxation process, which is the principle of the astable display of the present invention.

[0036] The backlight 241 emanating from the backlight panel 240 reaches the linear polarizer 222, and over 40% of the beam is converted to plane polarization, which diffuses and depolarizes to some extent as it passes through the liquid crystal FEA texture. Finally, the components pass through the front polarizer in large quantities with controllable intensity and color. Generally, the larger the tilt angle and the lower the voltage applied, the brighter the emitted light becomes; for example, blue light 243 is brighter than green light 242. This creates grayscale levels between the red pixel region 231, the green pixel region 232, and the blue pixel region 233. Ultimately, a color image that can be recognized by an observer is achieved.

[0037] Similarly, monochrome displays can also be manufactured using the aforementioned display structure without employing a color filter layer in the front substrate. In this case, the total resolution of monochrome will be three times higher than that of the full-color version of the same size, making it particularly suitable for applications in projection displays.

[0038] In the field of cholesteric displays, it is easy to understand that if the helical pitch of the cholesteric liquid crystal material is selected in the visible wavelength, then the first linear polarizer 221 and the second linear polarizer 222 can be replaced by circular polarizers with opposite polarities.

[0039] and Figure 1Compared with the prior art monostable display mode shown, in which there is a relaxation time from the nematic phase to the cholesteric phase between the optical on (ON) and off (OFF) states, the prior art display of the present invention provides a true video speed display with infinite gray levels.

[0040] Now turning to Figure 3 , Figure 3 shows the electro-optical response and driving principle of the non-stable and bistable dual-mode cholesteric display, as Figure 3 shown, presenting the electro-optical (Electro-Optical, EO) curve of the transmissive TFT display as Figure 2 shown. The vertical axis represents the transmittance of the display, while the horizontal axis represents the voltage level V of the driving waveform applied to the display. The specific descriptions of the meanings and functions are as follows:

[0041] 1. Cholesteric planar state 301

[0042] When the display is just manufactured from the LCD production line, the initial state will be the cholesteric planar texture or the optically dark state. When the driving voltage level rises from zero to the level V1 (V < V1), the display remains in the steady-state planar state.

[0043] 2. Cholesteric planar to focal cone transition 302

[0044] In the rising part of curve 302 where the voltage level is between V1 and V2 (V1 < V ≤ V2), a cholesteric phase transition from the planar state to the focal cone state occurs. Within this part, the helical pitch of the cholesteric phase structure remains the same, but its helical axis becomes more random with the increase in voltage, and at this time it is a state of coexistence of the planar and focal cone. The transmittance of the curve allows for arranging many gray levels for a static display, which can be called the multistability of the cholesteric display. The rising part of curve 302 (referred to as γ1 in this article) has a positive slope.

[0045] 3. Saturated cholesteric focal cone state 303

[0046] In the voltage range V2 < V < V3, the display presents a saturated cholesteric focal cone state and has the brightest brightness. The voltage V3 can also be expressed as V th , which is the threshold voltage from the cholesteric phase state to the field-induced nematic state.

[0047] 4. Field-induced vortex state 304

[0048] When the increasing voltage crosses V th , the EO curve gradually descends from the optical on (ON) state to the optical off (OFF) state. This is a dynamic turbulent state excited by the voltage V, where V3 < V ≤ V4, and the brightness of the display decreases with the increase in voltage. As Figure 2As shown, the tilt angle θ of the liquid crystal molecules varies from 0 to π as a function of the driving voltage. In this invention, the transmission of the descending curve 304 can be allowed to arrange many gray levels of the astable display; this portion of the descending curve can be defined as γ2 with a negative slope.

[0049] 5. Field-induced vertical orientation state 305

[0050] When the voltage exceeds V4 (V≥V4), the field-induced vertical alignment state can also be simplified to the "H" state in the field. In the "H" state, the liquid crystal molecules are vertically aligned (VA) with the substrate of the display, causing the display to exhibit minimum transmittance or optical off (OFF) state.

[0051] 6. Phase splitter 306

[0052] like Figure 3 The EO curve shown can be divided into two parts by phase break line 306. To its right is the field-induced nematic phase, where an astable display mode with video rate and multiple gray levels can be achieved. To its left is the cholesteric phase, where a bistable or multistable gray-level display mode can be obtained. The astable and bistable modes can be interchanged via a fast path through phase break line 306. The fast path represents the relaxation mechanism from the vertically aligned portion 301 to the planar portion 305; the molecular relaxation of the liquid crystal is the bridge connecting these two display modes. The relaxation process can be divided into four stages: first, the delay time while the vertically aligned structure still exists in the cell; second, the fast relaxation period when a transient planar structure is formed; third, when the equilibrium pitch is reached; and finally, the slow relaxation period when the final planar structure is formed. Initially, by changing the polar angle of the directional orientation (the angle between the directional orientation and the normal to the cell surface) from 0 to π / 2 (approximately 1.25 milliseconds), the liquid crystal transitions from vertical alignment through the intermediate conical structure to a quasi-equilibrium transient planar state. The fact that relaxation to the equilibrium wavelength is completed in about 10 milliseconds means that the equilibrium cholesteric phase pitch has been reached, and the next relaxation process is merely a macroscopic structural change. After the electric field is removed, the relaxation time interval is 0.5 milliseconds to 10 milliseconds.

[0053] Based on the above EO curve, the driving device for an astable video display can be described as follows:

[0054] 1. Start

[0055] Whether it's a brand-new monitor from the monitor manufacturer or a monitor in a power-off, idle state, a voltage pulse with a sufficient pulse width (above V4) will be applied to all pixels of the monitor panel to set the monitor to a black field vertical orientation. Startup time does not affect the video frame rate because it is part of the pipeline waveform.

[0056] 2. Frame Addressing

[0057] All levels of the analog signal with voltage levels within the range of curve γ2 (V3 < V ≤ V4) are sorted by line-to-line scanning controlled by the TFT gate signal and latched to each individual TFT source of the sub-pixel. The liquid crystal molecules in the TFT array will be instantaneously addressed to a predetermined optical on (ON), off (OFF), and / or gray level, where the gray level or total color is determined by a hardware ladder circuit and pulse width modulation (PWM). For example, if a ladder circuit including a series of resistors and operational amplifier ICs generates 64 voltages: v0, v1, v2, v i …v 63 and PWM provides 4 levels of Vrms, the combined gray level for each color is 256. There are three primary colors, red, green, and blue, for color reproduction, so the total number of colors in the display will exceed 16 million. The bias voltage v i (i = 0 to 63) represents the gray level voltage according to curve γ2, and the values of the resistors are determined by γ2 correction to achieve a linear gray level for the human eye.

[0058] 3. Frame Sorting

[0059] When displaying the current image, the next frame data is restored in the frame buffer transferred from the shift register and DA (Digital-to-Analog) converter. To cancel the DC (Direct Current) component, frame-to-frame or line-to-line inversion can be used in the driving scheme, and the frame rate can be in the range of 30 to 140 frames per second (FPS), and most preferably the frame rate is 60 to 100 FPS. It should be noted that this driving device operates in the field-induced nematic state without phase changes and relaxations as in the prior art monostable displays.

[0060] 4. Bistable Mode Conversion

[0061] When the non-steady-state video display switches to the bistable display, a control signal is sent to the frame buffer to lock a predetermined image, the ladder circuit is switched from curve γ2 (V3 < V ≤ V4) to curve γ1 (V1 < V ≤ V2), and all liquid crystal pixels are simultaneously set from the field-induced nematic state to the cholesteric planar state via a fast path, and the display will be ready to address the specified static image.

[0062] Therefore, all levels of the analog signal with voltage levels within the range of curve γ1 (V1 < V ≤ V2) are sorted by line-to-line scanning controlled by the TFT gate signal and latched to each individual TFT source of the sub-pixel. Instantaneously, the liquid crystal and / or gray level, and the gray level or total color are determined by a hardware ladder circuit and PWM. For example, if a ladder circuit including a series of resistors and operational amplifier ICs generates 64 voltages: v'0, v'1, v'2, v'i …v' 63 With PWM providing 4 levels of Vrms, the total number of colors will exceed 16 million. The bias voltage v' of the ladder circuit... i (i=0~63) indicates that the resistor value is determined by γ1 correction based on the gray level voltage of curve γ1 to achieve linear gray levels for the human eye. Once the data addressing of the final row is completed, the image is fixed by suddenly and simultaneously switching all sub-pixels to zero voltage. Finally, the zero-field bistable image will be recognized by the observer.

[0063] from Figure 3 It is understandable that curves γ1 and γ2 are different (v' i ≠v i The former is positive and the latter is negative. For example, given a certain display transmittance T... 50 There exist separate ladder circuits V γ2 and V γ1 The two voltages are used for video speed non-steady-state addressing and static bistable image addressing.

[0064] Dual-mode displays allow for a wide range of frame rate modulation from 0 to 140 FPS, superior to any other currently available display, including e-ink, OLED, and LCD displays. Zero-FPS full-color displays are ideal for new e-books, where low power consumption, flicker-free operation, and low eye strain are key parameters for end-users. Furthermore, 140 FPS displays meet the standards for gaming and ultra-high-speed video displays, marking a watershed moment in advanced display technology and representing a new trend in the information industry.

[0065] Now go to Figure 4 , Figure 4 The electro-optic response curve of a reflective monochrome cholesteric display is shown, illustrating the use of, for example... Figure 2 The illustrated display structure shows the EO curve of a monochrome display made by placing a reflective polarizer in the back substrate instead of a color filter layer in the front substrate. Therefore, the vertical axis of the curve represents the reflectivity of the display, and in this structure, backlighting is not involved. However, in addition to reflective polarizers, commercially available transflective and reflective polarizers can be attached to the back substrate to achieve a so-called transflective monochrome display. Similarly, a transflective full-color display mode can also be achieved using the same transflective and reflective polarizer arrangement, which is beneficial for astable and bistable display modes visible in sunlight.

[0066] Now go to Figure 5Images of grayscale levels of an actively addressed, non-steady-state, full-color cholesteric display are shown. The display, an a-Si TFT panel with a 4.6” diagonal, 640×150 resolution, and full color, was manufactured on a TFT LCD production line and optically tested in an optical laboratory.

[0067] Now go to Figure 6 The image shown is from a video speed-unsteady TFT cholesteric display. The quality of the display is comparable to currently available SVA (super-vertical alignment) LCD monitors or TVs. Typically, the optical performance of SVA is almost identical to that of the FVA of this invention in terms of contrast and viewing angle; however, the difference lies in the fact that the former LCD contains a nematic material with negative dielectric anisotropy, while the latter is a cholesteric phase material with positive dielectric anisotropy.

[0068] Although the invention and its advantages have been described in detail, those skilled in the art will understand that various changes, substitutions and modifications can be made to the invention without departing from the spirit and scope of the most extensive form of the invention.

Claims

1. A non-steady state cholesteric display comprising: a. a front transparent conductive substrate, and b. a front polarizer layer, and c. a cholesteric phase liquid crystal layer having at least one field-induced homeotropic alignment region and one field-induced vortex alignment region, and d. a back active matrix substrate, and e. a back polarizer layer, and f. a back light panel, wherein the front transparent conductive substrate with the front polarizer layer, the cholesteric phase liquid crystal layer, and the back active matrix substrate with the back polarizer layer are juxtaposed to form a display structure.

2. The non-steady state cholesteric display of claim 1, wherein a light beam from the back light panel that passes through the field-induced vortex alignment region is modulated into polarized light to form an optical ON state with at least one gray scale; wherein the light that passes through the field-induced homeotropic alignment region is substantially absorbed by the front polarizer layer and the back polarizer layer to form an optical OFF state, wherein the field-induced homeotropic alignment region and the field-induced vortex alignment region are instantaneously interchangeable at video frequencies, whereby an observer will observe a high frame rate black and white animation.

3. The non-steady state cholesteric display of claim 1, wherein the front polarizer layer and the back polarizer layer are linear polarizers with their polarization axes crossed to each other.

4. The non-steady state cholesteric display of claim 1, wherein the front polarizer and the back polarizer are circular polarizers with opposite handedness.

5. The non-steady state cholesteric display of claim 1, wherein the field-induced homeotropic alignment region is in a nematic homeotropic phase.

6. The non-steady state cholesteric display of claim 1, wherein the field-induced vortex alignment region is in a nematic tilted phase.

7. The non-steady state cholesteric display of claim 1, wherein the field-induced vortex alignment region has a plurality of liquid crystal domains.

8. The un-stable cholesteric display of claim 7, wherein the plurality of domains each have a tilt angle θ that varies in a range of 0 to 90 o and an azimuthal angle that varies in a range of 0 to 180 o degrees.

9. The non-steady state cholesteric display of claim 1, wherein the display is a transmissive display.

10. The non-steady state cholesteric display of claim 1, wherein the display is a transflective display.

11. The non-steady state cholesteric display of claim 1, wherein the display is a reflective display.

12. The non-steady state cholesteric display of claim 1, further comprising a color filter at the front transparent conductive substrate to enable a full color display.

13. The non-steady state cholesteric display of claim 1, wherein the video speed of the display is in the range of 30 to 140 FPS.

14. A non-steady state hybrid cholesteric display comprising: a. a front conductive color filter substrate, and b. a front polarizer layer, and c. a cholesteric phase liquid crystal layer having at least one field-induced homeotropic alignment region and one field-induced vortex alignment region in a non-steady state mode and at least one cholesteric phase planar region and one cholesteric phase focal conic region in a bistable mode, and d. a back active matrix substrate, and e. a back polarizer layer, and f. a back light panel, wherein the front conductive color filter substrate with the front polarizer layer, the cholesteric phase liquid crystal layer, and the back active matrix substrate with the back polarizer layer are juxtaposed to form a display structure. wherein the front conductive color filter substrate with the front polarizer layer, the cholesteric liquid crystal layer and the back active matrix substrate with the back polarizer layer are juxtaposed to form a display structure.

15. The non-steady state hybrid cholesteric display of claim 14, wherein the light beams from the backlight panel that pass through the field-induced vortex orientation region and / or through the field-free focal conic region are modulated to polarized light to form an optical ON state; wherein the light that passes through the field-induced homeotropic orientation region and / or the field-free planar region is substantially absorbed by the front and back polarizer layers to form an optical OFF state, whereby an observer will see a video display and a static display, respectively.

16. The non-steady state hybrid cholesteric display of claim 14, wherein the video display and the static display are dual-mode cholesteric displays.

17. A driving apparatus for a non-steady state cholesteric display, comprising: a. an initiation phase, and b. a frame addressing phase, and c. a frame sequencing phase, and d. a dual-mode switching phase, wherein an initiation pulse is applied to all pixels of the display panel to set the display to a black field-induced homeotropic state; wherein all levels of addressing analog signals are latched to each individual TFT source of a sub-pixel in a line-to-line scan sequencing controlled by TFT gate signals to drive the display into a field-induced homeotropic region and a field-induced vortex orientation region; wherein the frame sequencing data is restored into a frame buffer while displaying a current image; wherein a dual-mode switching signal is sent to the frame buffer, locking a predetermined image, switching a ramp circuit from a curve γ2 to a curve γ1, setting all liquid crystal pixels from the field-induced nematic state to a cholesteric state; whereby the display exhibits non-steady state images and dual-steady state images with infinite gray levels.

18. The driving apparatus of claim 17, wherein the field-induced homeotropic region is addressed by analog signals with voltage levels V≥V4.

19. The driving apparatus of claim 17, wherein the field-induced vortex orientation region is addressed by analog signals with voltage levels in the range of curve γ2 (V3 20. The driving apparatus of claim 17, wherein the gray levels of the non-steady state images are determined by a γ2 correction.

21. The driving apparatus of claim 17, wherein the switching phase from a non-steady state display to a dual-steady state display switches the ramp circuit from curve γ2 (V3 22. The driving apparatus of claim 17, wherein the gray levels of the dual-steady state images are determined by a γ1 correction and are fixed by instantaneously switching all sub-pixels to zero voltage.

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