Composite cholesteric liquid crystal display device and driving method

Abstract

This invention discloses a composite cholesteric liquid crystal display device and its driving method, applied in the field of cholesteric liquid crystal display technology. From the observation side to the back side, it comprises: a substrate; a cholesteric liquid crystal display unit; the cholesteric liquid crystal display unit switching between a selective reflection state and a light-transmitting state; an optical adjustment layer disposed between the cholesteric liquid crystal display unit and an electrophoretic display unit, the optical adjustment layer adjusting the optical state of the reflected light after reflection by the electrophoretic display unit, so that at least part of the reflected light passes through the cholesteric liquid crystal display unit and exits from the observation side; and an electrophoretic display unit switching between multiple optical states, including a bright first reflection state, a dark second reflection state, and states between the first and second reflection states, and serving as the reflective background of the cholesteric liquid crystal display unit. This achieves a balance between high brightness, high color saturation, and high black-and-white contrast.

Description

Technical Field

[0001] This invention relates to the field of cholesteric liquid crystal display technology, and in particular to a composite cholesteric liquid crystal display device and a driving method for the composite cholesteric liquid crystal display device. Background Technology

[0002] Color electrophoretic electronic paper typically relies on color filter arrays to achieve color display, but color filters absorb a large amount of incident light, leading to reduced screen brightness, insufficient color saturation, and increased power consumption. Cholesteric liquid crystals can selectively reflect circularly polarized light in specific wavelengths and possess bistable or multistable characteristics, making them suitable for low-power color reflective displays. However, when cholesteric liquid crystals are used alone for high-resolution black and white text display, they often suffer from insufficient dark depth and limited black and white contrast.

[0003] To address this, some studies have proposed a composite display scheme that vertically stacks a cholesteric liquid crystal layer and an electrophoretic display layer. However, when the cholesteric liquid crystal layer and the electrophoretic layer are directly stacked, the light utilization rate is low, and the display brightness and color saturation are insufficient due to polarization mismatch and interlayer interface reflection. The driving electric fields of the two display layers are prone to mutual coupling, resulting in problems such as electric field crosstalk, mis-driving, and image retention. In addition, the shading and scattering of the underlying electrophoretic image by the cholesteric liquid crystal layer weakens the high black-and-white contrast advantage of the electrophoretic display layer in the stacked structure, making it difficult to achieve both black-and-white contrast and color display simultaneously.

[0004] Therefore, how to overcome the above-mentioned defects and design a stacked display scheme that can achieve both color display and maintain high black-and-white contrast has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a composite cholesteric liquid crystal display device and driving method to solve the current technical problem that it is impossible to achieve high black-and-white contrast while realizing color display.

[0006] To address the aforementioned technical problems, this invention provides a composite cholesteric liquid crystal display device, comprising, from the observation side to the back side, the following components: substrate; Cholesteric liquid crystal display unit; the cholesteric liquid crystal display unit switches between a selective reflection state and a light-transmitting state; An optical adjustment layer is disposed between the cholesteric liquid crystal display unit and the electrophoretic display unit. The optical adjustment layer adjusts the optical state of the returned light reflected by the electrophoretic display unit, so that at least part of the returned light passes through the cholesteric liquid crystal display unit and is emitted from the observation side. An electrophoretic display unit that switches between a first reflective state that is bright, a second reflective state that is dark, and multiple optical states between the first reflective state and the second reflective state, and serves as the reflective background of the cholesteric liquid crystal display unit.

[0007] Optionally, it also includes a controller, which includes a first drive terminal and a second drive terminal; The first driving end is connected to the electrode structure of the cholesteric liquid crystal display unit, and the second driving end is connected to the electrode structure of the electrophoretic display unit.

[0008] Optionally, the optical adjustment layer includes any one or any combination of the following: Phase retardation film, polarization conversion film, low haze scattering film, or transparent polymer layer containing anisotropic particles.

[0009] Optionally, the cholesteric liquid crystal display unit covers the entire effective display area of ​​the electrophoretic display unit; And / or, each pixel in the cholesteric liquid crystal display unit corresponds one-to-one with each pixel in the electrophoretic display unit.

[0010] Optionally, the cholesteric liquid crystal display unit includes a first electrode layer, a cholesteric liquid crystal layer, and a second electrode layer stacked sequentially from the observation side to the back side; The electrophoretic display unit includes a third electrode layer, an electrophoretic display layer, and a fourth electrode layer, which are stacked sequentially from the observation side to the back side. The optical adjustment layer is located between the second electrode layer and the third electrode layer; And / or, the cholesteric liquid crystal display unit includes a monochrome cholesteric liquid crystal layer or a multicolor cholesteric liquid crystal layer; And / or, the electrophoretic display layer is any one of a microcapsule electrophoretic display layer, a microcup electrophoretic display layer, or a microcavity electrophoretic display layer.

[0011] Optionally, a drive backplate is provided on the back side of the electrophoretic display unit; And / or, the substrate is a flexible substrate.

[0012] The present invention also provides a driving method for a composite cholesteric liquid crystal display device, for driving the above-mentioned composite cholesteric liquid crystal display device, comprising: During the first time period, a driving signal is applied to the electrophoretic display unit to drive the electrophoretic display unit to switch to a first reflective state that presents a bright state, a second reflective state that presents a dark state, or any optical state between the first reflective state and the second reflective state. During the second time period, a driving signal is applied to the cholesteric liquid crystal display unit to drive the cholesteric liquid crystal display unit to switch to a selective reflection state or a light-transmitting state. The first time period and the second time period do not overlap at least partially.

[0013] Optionally, during the first time period, a driving signal is applied to the electrophoretic display unit to drive the electrophoretic display unit to switch to a first reflective state that presents a bright state or a second reflective state that presents a dark state; During the second time period, a driving signal is applied to the cholesteric liquid crystal display unit to drive the cholesteric liquid crystal display unit to switch to the light-transmitting state; so as to achieve black and white display. Alternatively, during the first time period, a driving signal is applied to the electrophoretic display unit to drive at least a portion of the electrophoretic display unit to switch to a first reflective state that presents a bright state as the underlying optical background of the display device; During the second time period, a driving signal is applied to the cholesteric liquid crystal display unit to drive the corresponding area of ​​the cholesteric liquid crystal display unit to switch to the selective reflection state in order to reflect colored light and achieve color display. Alternatively, during the first time period, a driving signal is applied to the electrophoretic display unit to drive the first region and the second region of the electrophoretic display unit to switch to a first reflective state that is bright or a second reflective state that is dark, respectively. During the second time period, a driving signal is applied to the cholesteric liquid crystal display unit to drive the region corresponding to the first region in the cholesteric liquid crystal display unit to switch to the selective reflection state and the region corresponding to the second region to switch to the light-transmitting state, so as to achieve composite display.

[0014] Optionally, a controller may also be included; The controller controls the electrophoresis display unit to complete state switching; After the electrophoresis display unit completes the state switching, the driving signal applied to the electrophoresis display unit is stopped; After stopping the application of the driving signal to the electrophoretic display unit, the cholesteric liquid crystal display unit is controlled to complete the state switching; After both the cholesteric phase liquid crystal display unit and the electrophoretic display unit have completed their state switching, they enter the holding phase.

[0015] Optionally, when a driving signal is applied to the cholesteric liquid crystal display unit, the electrode structure driving the electrophoretic display unit is in a high-resistivity state, a fixed potential, or an electric field shielding state. And / or, when a driving signal is applied to the electrophoretic display unit, the electrode structure of the cholesteric liquid crystal display unit is driven to be in a high-resistivity state, a fixed potential, or an electric field shielding state; And / or, during the holding phase, the cholesteric liquid crystal display unit maintains the light-transmitting state or the selective reflection state by maintaining a maintaining voltage or periodic maintaining pulses.

[0016] The composite cholesteric liquid crystal display device provided by the present invention comprises, from the observation side to the back side: a substrate; a cholesteric liquid crystal display unit; the cholesteric liquid crystal display unit switching between a selective reflection state and a light-transmitting state; an optical adjustment layer disposed between the cholesteric liquid crystal display unit and an electrophoretic display unit, the optical adjustment layer adjusting the optical state of the reflected light after being reflected by the electrophoretic display unit, so that at least part of the reflected light passes through the cholesteric liquid crystal display unit and is emitted from the observation side; and an electrophoretic display unit switching between a first reflection state exhibiting a bright state, a second reflection state exhibiting a dark state, and multiple optical states between the first reflection state and the second reflection state, and serving as the reflective background of the cholesteric liquid crystal display unit.

[0017] As can be seen, this composite cholesteric liquid crystal display device has an optical adjustment layer between the cholesteric liquid crystal display unit and the electrophoretic display unit. This layer adjusts the optical state of the reflected light from the electrophoretic display unit, allowing at least a portion of the reflected light to pass through the cholesteric liquid crystal display unit and exit from the observation side. Compared with the color filter solution, this avoids the absorption loss of incident light by the filter and overcomes the problem of reduced light utilization caused by polarization mismatch in the direct stacking solution. This improves the utilization of reflected light, thereby enhancing the brightness and color saturation of the display device. Furthermore, the electrophoretic display unit can switch between bright, dark, and multiple grayscale states. It can serve as a high-contrast black and white display layer and as a switchable bottom reflective background for the cholesteric liquid crystal display unit. This allows the display device to achieve a balance of high brightness, high color saturation, and high black and white contrast without the need for a color filter.

[0018] The present invention also provides a driving method for a composite cholesteric liquid crystal display device, which has the same beneficial effects as the composite cholesteric liquid crystal display device described above, and will not be described in detail here. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the structure of a composite cholesteric liquid crystal display device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another composite cholesteric liquid crystal display device provided in an embodiment of the present invention; Figure 3 A schematic diagram of the optical adjustment layer provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of pixel registration in a composite cholesteric liquid crystal display device provided in an embodiment of the present invention; Figure 5a This is a schematic diagram of the structure of a microcapsule electrophoretic display layer provided in an embodiment of the present invention; Figure 5b This is a schematic diagram of the structure of a microcup electrophoretic display layer provided in an embodiment of the present invention; Figure 5c This is a schematic diagram of the structure of a microcavity electrophoretic display layer provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the optical path of the composite cholesteric liquid crystal display device in black and white display mode according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the optical path of the color display mode of the composite cholesteric liquid crystal display device provided in an embodiment of the present invention; Figure 8 A process flow diagram of a driving method for a composite cholesteric liquid crystal display device provided in an embodiment of the present invention; Figure 9 Timing diagram for time-division driving of the composite cholesteric liquid crystal display device provided in an embodiment of the present invention; In the figure: 100. Display device, 110. Substrate, 120. First electrode layer, 130. Cholesteric liquid crystal layer, 140. Second electrode layer, 150. Optical adjustment layer, 160. Third electrode layer, 170. Electrophoretic display layer, 171. Electrophoretic display microcell, 171a. Microcapsule, 171b. Microcup, 171c. Microcavity, 180. Fourth electrode layer, 190. Driving backplane, 200. Controller, 210. Effective display area. Detailed Implementation

[0021] The core of this invention is to provide a composite cholesteric liquid crystal display device. When a cholesteric liquid crystal layer and an electrophoretic layer are directly stacked, the light utilization rate is low, and the display brightness and color saturation are insufficient due to polarization mismatch and interlayer interface reflection. The driving electric fields of the two display layers are prone to mutual coupling, resulting in problems such as electric field crosstalk, mis-driving, and image retention. In addition, the cholesteric liquid crystal layer blocks and scatters the underlying electrophoretic image, which weakens the high black-and-white contrast advantage of the electrophoretic display layer in the stacked structure, making it difficult to achieve both black-and-white contrast and color display simultaneously.

[0022] This application provides a composite cholesteric liquid crystal display device, comprising, from the observation side to the back side: a substrate; a cholesteric liquid crystal display unit; the cholesteric liquid crystal display unit switching between a selective reflection state and a light-transmitting state; an optical adjustment layer disposed between the cholesteric liquid crystal display unit and an electrophoretic display unit, the optical adjustment layer adjusting the optical state of the reflected light after being reflected by the electrophoretic display unit, so that at least part of the reflected light passes through the cholesteric liquid crystal display unit and is emitted from the observation side; and an electrophoretic display unit switching between a first reflection state exhibiting a bright state, a second reflection state exhibiting a dark state, and multiple optical states between the first reflection state and the second reflection state, and serving as the reflective background of the cholesteric liquid crystal display unit.

[0023] This composite cholesteric liquid crystal display device incorporates an optical adjustment layer between the cholesteric liquid crystal display unit and the electrophoretic display unit. This layer adjusts the optical state of the reflected light from the electrophoretic display unit, allowing at least a portion of the reflected light to pass through the cholesteric liquid crystal display unit and exit from the observation side. Compared to color filter solutions, this avoids the absorption loss of incident light by the filter and overcomes the problem of reduced light utilization caused by polarization mismatch in direct stacking solutions. This improves the utilization rate of reflected light, thereby enhancing the brightness and color saturation of the display device. Furthermore, the electrophoretic display unit can switch between bright, dark, and multiple grayscale states, serving as both a high-contrast monochrome display layer and a switchable bottom reflective background for the cholesteric liquid crystal display unit. This allows the display device to achieve a balance of high brightness, high color saturation, and high monochrome contrast without the need for a color filter.

[0024] To enable those skilled in the art to better understand the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The structure of the composite cholesteric liquid crystal display device provided by this invention will be described in detail in the following embodiments.

[0026] Example 1

[0027] Please refer to Figures 1 to 7 , Figure 1 This is a schematic diagram of the structure of a composite cholesteric liquid crystal display device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of another composite cholesteric liquid crystal display device provided in an embodiment of the present invention; Figure 3 A schematic diagram of the optical adjustment layer provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of pixel registration in a composite cholesteric liquid crystal display device provided in an embodiment of the present invention; Figure 5a This is a schematic diagram of the structure of a microcapsule electrophoretic display layer provided in an embodiment of the present invention; Figure 5b This is a schematic diagram of the structure of a microcup electrophoretic display layer provided in an embodiment of the present invention; Figure 5c This is a schematic diagram of the structure of a microcavity electrophoretic display layer provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the optical path of the composite cholesteric liquid crystal display device in black and white display mode according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the optical path for the color display mode of the composite cholesteric liquid crystal display device provided in an embodiment of the present invention.

[0028] See Figure 1 This invention provides a composite cholesteric liquid crystal display device (hereinafter referred to as display device 100), which includes, from the observation side to the back side: a substrate 110; a cholesteric liquid crystal display unit; the cholesteric liquid crystal display unit switching between a selective reflection state and a light-transmitting state; an optical adjustment layer 150 disposed between the cholesteric liquid crystal display unit and an electrophoretic display unit, the optical adjustment layer 150 adjusting the optical state of the reflected light after reflection by the electrophoretic display unit, so that at least part of the reflected light passes through the cholesteric liquid crystal display unit and is emitted from the observation side; and an electrophoretic display unit switching between a first reflection state exhibiting a bright state, a second reflection state exhibiting a dark state, and multiple optical states between the first reflection state and the second reflection state, and serving as the reflective background of the cholesteric liquid crystal display unit.

[0029] The display device 100 in this embodiment is a reflective display device, which does not require a backlight. The ambient light is modulated by the cholesteric liquid crystal display unit, the optical adjustment layer 150 and the electrophoretic display unit to achieve image display. The display device 100 provided in this embodiment can realize black and white display, color display and composite display. For relevant content on black and white display, color display and composite display, please refer to the following content, which will not be repeated here.

[0030] In this embodiment, the substrate 110 serves as the support and protection carrier for the entire display device 100, providing physical support for the cholesteric liquid crystal display unit, the optical adjustment layer 150, and the electrophoretic display unit. The substrate 110 is located on the outer layer of the display device 100 (and closest to the observation side), serving as a common channel for incident and outgoing light. Specifically, when incident light enters from the observation side, ambient light must pass through the substrate 110 to reach the internal cholesteric liquid crystal display unit and electrophoretic display unit. When outgoing light propagates outward from the device, the colored light selectively reflected by the cholesteric liquid crystal display unit, and the return light reflected by the electrophoretic display unit and sequentially passing through the optical adjustment layer 150 and the cholesteric liquid crystal display unit, all ultimately need to pass through the substrate 110 and exit from the observation side into the human eye. In this embodiment, the substrate 110 is a transparent substrate. The substrate 110 in this embodiment can be a flexible substrate or a rigid substrate. For details regarding the material and thickness of the substrate 110, please refer to relevant technologies; further details will not be elaborated here.

[0031] In one feasible embodiment, the substrate 110 is a flexible substrate, which enables the display device 100 to have bendable and rollable characteristics, making it easy to apply to products such as flexible electronic paper and wearable devices.

[0032] Specifically, cholesteric liquid crystal display units utilize the selective reflectivity of cholesteric liquid crystal materials to produce Bragg reflection of circularly polarized light in a specific wavelength band of incident light, thereby displaying corresponding colors. Simultaneously, cholesteric liquid crystal materials possess bistable or multistable characteristics, maintaining their current optical state even after the driving signal is stopped. Therefore, cholesteric liquid crystal display units can be used to achieve low-power color reflective displays. This embodiment does not impose specific limitations on the reflection center wavelength of the cholesteric liquid crystal or the thickness of the cholesteric liquid crystal layer, which can be adjusted according to actual production needs. In this embodiment, the reflection center wavelength range of the cholesteric liquid crystal is 400 nm to 750 nm, and the thickness of the cholesteric liquid crystal layer is 3 μm to 20 μm.

[0033] The electrophoretic display unit achieves optical state switching through the migration of charged pigment particles under the influence of an electric field. Specifically, when a driving voltage is applied between the electrode structures of the electrophoretic display unit, the charged pigment particles migrate towards the electrode with the opposite charge under the influence of the electric field force, causing the electrophoretic display unit to switch to a first reflective state (white state) that is bright, a second reflective state (black state) that is dark, a grayscale state between white and black, or other color states. After the driving signal is stopped, the distribution state of its charged pigment particles can be maintained, thereby achieving low-power static display. This embodiment does not impose specific limitations on the thickness of the electrophoretic display layer or the type of electrophoretic display layer 170, which can be adjusted according to actual production needs. In this embodiment, the thickness of the electrophoretic display layer 170 is 20 micrometers to 150 micrometers.

[0034] In this embodiment, an optical adjustment layer 150 is disposed between the cholesteric liquid crystal display unit and the electrophoretic display unit. The optical adjustment layer 150 serves two purposes: firstly, it adjusts the optical state of the reflected light from the electrophoretic display unit, allowing at least a portion of the reflected light to pass through the cholesteric liquid crystal display unit and exit from the observation side; secondly, it reduces light loss caused by interface reflection and refractive index differences between the cholesteric liquid crystal display unit and the electrophoretic display unit, thereby improving light utilization.

[0035] In the display device 100 of this embodiment, incident light enters from the observation side and sequentially passes through the substrate 110, the cholesteric liquid crystal display unit, and the optical adjustment layer 150 before reaching the electrophoretic display unit. The selectively reflective regions of the cholesteric liquid crystal display unit directly reflect incident light of a specific wavelength back to the observation side, forming colored light. The electrophoretic display unit reflects incident light that is not reflected by the cholesteric liquid crystal display unit, forming returned light. When this returned light passes through the optical adjustment layer 150, its optical state (especially its polarization state) is adjusted so that at least a portion of the returned light satisfies the transmission conditions of the cholesteric liquid crystal display unit, thereby passing through the cholesteric liquid crystal display unit and the substrate 110 and exiting from the observation side. Thus, the selectively reflected light from the cholesteric liquid crystal display unit and the returned light from the electrophoretic display unit are superimposed on the observation side, achieving high-brightness, high-saturation color display, black-and-white display, and composite display.

[0036] In this embodiment, in black and white display mode, the cholesteric liquid crystal layer 130 is in a low-reflection or light-transmitting working state, and the electrophoretic display layer 170 forms a black and white or grayscale image; in color display mode, the electrophoretic display layer 170 provides a high-reflection background, and the cholesteric liquid crystal layer 130 forms selective color reflection; in composite display mode, the two display layers work together to form color, black and white, grayscale or brightness superposition information.

[0037] In black-and-white display mode, the cholesteric liquid crystal layer 130 can operate in a low-reflection, transparent, or weak-reflection state, allowing users to observe black-and-white text, patterns, or grayscale images formed by the electrophoretic display layer 170, thereby achieving high black-and-white display contrast. In color display mode, the electrophoretic display layer 170 can serve as a switchable bottom reflective background. Its white or high-reflection state can enhance the brightness of the color display, while its black, low-reflection, or grayscale state can adjust the brightness levels, thereby improving the contrast, saturation, and visual depth of the color image. This invention utilizes the cholesteric liquid crystal layer to form selectively reflective colors, eliminating the need for an absorptive color filter, reducing light absorption, and improving reflective brightness and light utilization.

[0038] The display device 100 provided in this embodiment also includes a controller 200, which includes a first driving end and a second driving end; the first driving end is connected to the electrode structure of the cholesteric liquid crystal display unit, and the second driving end is connected to the electrode structure of the electrophoretic display unit.

[0039] In this embodiment, the controller 200 is connected to the electrode structures of the cholesteric liquid crystal display unit and the electrophoretic display unit, respectively, for independently controlling the optical state switching of the cholesteric liquid crystal display unit and the electrophoretic display unit. The controller 200 should be able to drive the cholesteric liquid crystal layer 130 and the electrophoretic display layer 170 respectively, enabling them to switch between black-and-white display, color display, and composite display modes, and reducing continuous power consumption during the static display stage. The display device 100 in this embodiment, through independent control and time-division driving by the controller 200, can avoid electric field crosstalk and mis-driving between the two display units. For a detailed description of the time-division driving of the display device 100 provided in this embodiment, please refer to the content in Embodiment 2, which will not be repeated here.

[0040] See Figure 2 The controller 200 includes a first driving terminal and a second driving terminal. The first driving terminal is connected to the first electrode layer 120 and the second electrode layer 140 of the cholesteric liquid crystal display unit and is used to apply a driving voltage. The second driving terminal is connected to the third electrode layer 160 and the fourth electrode layer 180 of the electrophoretic display unit and is used to apply a driving voltage. An optical adjustment layer 150 is disposed between the second electrode layer 140 and the third electrode layer 160, forming an electrical isolation layer between the cholesteric liquid crystal display unit and the electrophoretic display unit. During time-division driving, when one display unit is driven, the electrodes of the other display unit are in a high-resistivity state, a fixed potential, or an electric field shielding state. The optical adjustment layer 150 further blocks the mutual penetration of the driving electric field, achieving electric field isolation.

[0041] In this embodiment, independent electrodes and a controller 200 are used to control the cholesteric liquid crystal layer 130 and the electrophoretic display layer 170 respectively, effectively reducing electric field crosstalk, misdrive, and image retention between the two display layers, and ensuring that each display layer operates independently and stably. Correspondingly, the controller 200 includes a first driving terminal and a second driving terminal, which are respectively connected to the electrode structure of the cholesteric liquid crystal display unit and the electrode structure of the electrophoretic display unit; the first time period and the second time period do not overlap at least partially; when driving one display unit, the electrodes of the other display unit are in a high-resistivity state, a fixed potential, or an electric field shielding state.

[0042] In this embodiment, the cholesteric liquid crystal display unit includes a first electrode structure and a second electrode structure for forming a driving electric field on the cholesteric liquid crystal layer; the electrophoretic display unit includes a third electrode structure and a fourth electrode structure for forming a driving electric field on the electrophoretic display layer 170. This embodiment does not impose specific limitations on the placement of the first, second, third, and fourth electrode structures, as long as they can form a driving electric field on the corresponding display layers.

[0043] In one specific embodiment of this invention, the first electrode structure and the second electrode structure can be respectively disposed on both sides of the cholesteric liquid crystal layer, and the third electrode structure and the fourth electrode structure can be respectively disposed on both sides of the electrophoretic display layer 170. Specifically, the cholesteric liquid crystal display unit includes a first electrode layer 120, a cholesteric liquid crystal layer, and a second electrode layer 140 stacked sequentially from the observation side to the back side; the electrophoretic display unit includes a third electrode layer 160, an electrophoretic display layer 170, and a fourth electrode layer 180 stacked sequentially from the observation side to the back side; the optical adjustment layer 150 is located between the second electrode layer 140 and the third electrode layer 160. Specifically, the first electrode layer 120 and the second electrode layer 140 form a vertical electric field on the cholesteric liquid crystal layer, driving the cholesteric liquid crystal molecules to switch states. The third electrode layer 160 and the fourth electrode layer 180 form a vertical electric field on the electrophoretic display layer 170, driving charged pigment particles to migrate in the dispersion medium.

[0044] In another specific implementation of this embodiment, the first electrode structure and the second electrode structure are disposed on the same side of the cholesteric liquid crystal layer, for example, using a comb-shaped electrode or an interleaved electrode structure, and the cholesteric liquid crystal molecules are driven to switch states by an in-plane electric field. The third electrode structure and the fourth electrode structure are disposed on the same side of the electrophoretic display layer 170, for example, using mutually insulated pixel electrodes and opposing electrodes disposed on the same substrate, and the migration of charged pigment particles is driven by an in-plane electric field, which can also realize the switching between white, black and grayscale states.

[0045] In this embodiment, the first electrode layer 120, the second electrode layer 140, the third electrode layer 160, and the fourth electrode layer 180 are all transparent electrode layers. This embodiment does not impose specific limitations on the materials and film thicknesses of the first electrode layer 120, the second electrode layer 140, the third electrode layer 160, and the fourth electrode layer 180; these can be adjusted according to actual conditions. The materials and parameters of the first electrode layer 120, the second electrode layer 140, the third electrode layer 160, and the fourth electrode layer 180 can be the same or different. In this embodiment, the fourth electrode layer 180 is a pixel electrode layer.

[0046] In this specific embodiment, the first electrode layer 120 and the second electrode layer 140 are respectively connected to the first driving terminal of the controller 200. The controller 200 applies a driving voltage to the first electrode layer 120 and the second electrode layer 140 through the first driving terminal, thereby forming an electric field on the cholesteric liquid crystal layer and driving the cholesteric liquid crystal molecules to switch between different states. The third electrode layer 160 and the fourth electrode layer 180 are respectively connected to the second driving terminal of the controller 200. The controller 200 applies a driving voltage to the third electrode layer 160 and the fourth electrode layer 180 through the second driving terminal, thereby forming an electric field on the electrophoretic display layer 170 and driving charged pigment particles to migrate in the dispersion medium.

[0047] In this embodiment, an optical adjustment layer 150 is disposed between the cholesteric liquid crystal display unit and the electrophoretic display unit. The optical adjustment layer 150 is used to adjust the polarization state of the light reflected by the electrophoretic display unit, so that at least part of the light reflected by the electrophoretic display layer 170 is converted into a polarization component that can be transmitted through the cholesteric liquid crystal layer 130, thereby passing through the cholesteric liquid crystal display unit and exiting from the observation side, improving light utilization. At the same time, the optical adjustment layer 150 is also used to reduce light loss caused by interlayer interface reflection, scattering and refractive index difference between the cholesteric liquid crystal display unit and the electrophoretic display unit, improving display brightness and image clarity. In addition, the optical adjustment layer 150 is also used to form electrical insulation between the cholesteric liquid crystal display unit and the electrophoretic display unit, reducing electric field crosstalk between the two display units.

[0048] See Figure 3 The reflected light from the electrophoretic display unit passes through the third electrode layer 160 and enters the optical adjustment layer 150. The optical adjustment layer 150 adjusts the polarization state of the reflected light, generating adjusted reflected light. The polarization state of the adjusted reflected light matches the transmission conditions of the cholesteric liquid crystal layer, allowing it to pass sequentially through the second electrode layer 140, the cholesteric liquid crystal layer, the first electrode layer 120, and the substrate 110 before exiting from the observation side. Without adjustment, polarization components in the reflected light that do not match the transmission polarization state of the cholesteric liquid crystal layer are blocked by the cholesteric liquid crystal layer and cannot exit, resulting in light loss. After adjustment by the optical adjustment layer 150, at least a portion of the reflected light is converted into adjusted reflected light, improving the light utilization and display brightness of the display device 100.

[0049] In this embodiment, the optical adjustment layer 150 can be a single-layer structure or a multi-layer structure. The optical adjustment layer 150 adjusts the optical state of the reflected light after being reflected by the electrophoretic display unit, so that at least part of the reflected light passes through the cholesteric liquid crystal display unit and is emitted from the observation side. In this embodiment, the visible light transmittance of the optical adjustment layer 150 is not less than 80%, the thickness of the optical adjustment layer 150 is 1 micrometer to 100 micrometers, and the refractive index difference between the optical adjustment layer 150 and the adjacent electrode layer is not greater than 0.10.

[0050] In this embodiment, the optical adjustment layer 150 includes any one or any combination of the following: a phase retardation film, a polarization conversion film, a low-haze scattering film, or a transparent polymer layer containing anisotropic particles. It should be noted that the optical adjustment layer 150 provided in this embodiment can also be a refractive index matching adhesive layer or a composite film layer that combines polarization adjustment and electrical insulation functions.

[0051] Specifically, a phase retardation film is used to introduce a phase delay into the returned light to change its polarization state. The phase retardation film is a λ / 2 waveplate, where λ is the center wavelength of visible light. A polarization conversion film is used to reverse the polarization direction of the returned light. A low-haze scattering film is used to depolarize the returned light. A refractive index matching adhesive layer is used to reduce interface reflection between adjacent layers. A transparent polymer layer containing anisotropic particles utilizes the birefringence effect to adjust the polarization state of the returned light. A composite film layer, which combines polarization adjustment and electrical insulation functions, adjusts the polarization state of the returned light while simultaneously forming electrical insulation between the two display units.

[0052] In one feasible embodiment, an insulating layer is provided between the optical adjustment layer 150 and the cholesteric liquid crystal layer, or between the optical adjustment layer 150 and the electrophoretic display layer 170, to isolate the driving electric field between the two display units and reduce electric field crosstalk.

[0053] This embodiment does not impose specific restrictions on the correspondence between the pixels of the cholesteric liquid crystal display unit and the pixels of the electrophoretic display unit. The relationship between the pixels of the cholesteric liquid crystal display unit and the pixels of the electrophoretic display unit can be one-to-one, many-to-one, or one-to-many, as long as the display content of the two display units can be correctly superimposed on the observation side.

[0054] In this embodiment, the cholesteric liquid crystal display unit covers the entire effective display area 210 of the electrophoretic display unit; and / or, each pixel in the cholesteric liquid crystal display unit corresponds one-to-one with each pixel in the electrophoretic display unit. In this embodiment, the cholesteric liquid crystal layer 130 covers the entire effective display area 210 of the electrophoretic display layer 170, and can utilize its selective reflective properties to form a full-screen color display effect without the need to set up local overlay areas without display function, thereby realizing full-screen color reflective display.

[0055] Specifically, the cholesteric liquid crystal display unit covers the entire effective display area 210 of the electrophoretic display unit. That is, the cholesteric liquid crystal display unit completely covers the visible display area of ​​the electrophoretic display unit in space, rather than only covering a partial area. In this embodiment, the cholesteric liquid crystal display unit covers the entire effective display area 210 of the electrophoretic display unit, enabling the display device 100 to achieve color display across the entire screen, thereby achieving full-screen color display.

[0056] Each pixel in the cholesteric liquid crystal display unit corresponds one-to-one with each pixel in the electrophoretic display unit. That is, each pixel in the cholesteric liquid crystal display unit is precisely aligned spatially with a pixel in the electrophoretic display unit, allowing the display content of the two display units to be superimposed on the viewing side.

[0057] In one specific implementation of this embodiment, the cholesteric liquid crystal display unit covers the entire effective display area 210 of the electrophoretic display unit. In this case, the display device 100 can achieve color display across the entire screen area.

[0058] In one specific implementation of this embodiment, each pixel in the cholesteric liquid crystal display unit corresponds one-to-one with each pixel in the electrophoretic display unit. In this case, the display content of the two display units can be superimposed on the viewing side, allowing for precise spatial matching of color modulation information and black-and-white information.

[0059] As one specific implementation method of this embodiment, see Figure 4 The cholesteric liquid crystal display unit covers the entire effective display area 210 of the electrophoretic display unit, and each pixel in the cholesteric liquid crystal display unit corresponds one-to-one with each pixel in the electrophoretic display unit. Through full-screen coverage and pixel-level one-to-one registration, accurate matching of color modulation information and black-and-white information can be ensured across the entire screen.

[0060] In this embodiment, a driving backplate 190 is provided on the back side of the electrophoretic display unit; and / or, the substrate 110 is a flexible substrate. As a specific implementation of this embodiment, a driving backplate 190 is provided on the back side of the electrophoretic display unit. In this specific implementation, the driving backplate 190 is an active driving backplate, and the active driving backplate is in contact with the fourth electrode layer 180. As a specific implementation of this embodiment, the substrate 110 is a flexible substrate. As a specific implementation of this embodiment, a driving backplate 190 is provided on the back side of the electrophoretic display unit. And the substrate 110 is a flexible substrate. In this specific implementation, the driving backplate 190 is an active driving backplate, and the active driving backplate is in contact with the fourth electrode layer 180.

[0061] In this embodiment, the cholesteric phase liquid crystal display unit includes a monochrome cholesteric phase liquid crystal layer or a multicolor cholesteric phase liquid crystal layer; and / or, the electrophoretic display layer 170 is any one of a microcapsule electrophoretic display layer, a microcup electrophoretic display layer, or a microcavity electrophoretic display layer. The "and / or" in this embodiment includes the following three scenarios: the cholesteric phase liquid crystal display unit includes a monochrome cholesteric phase liquid crystal layer or a multicolor cholesteric phase liquid crystal layer; the electrophoretic display layer 170 is any one of a microcapsule electrophoretic display layer, a microcup electrophoretic display layer, or a microcavity electrophoretic display layer; the cholesteric phase liquid crystal display unit includes a monochrome cholesteric phase liquid crystal layer or a multicolor cholesteric phase liquid crystal layer, and the electrophoretic display layer 170 is any one of a microcapsule electrophoretic display layer, a microcup electrophoretic display layer, or a microcavity electrophoretic display layer.

[0062] Specifically, a monochromatic cholesteric liquid crystal layer has a single reflective center wavelength, used to achieve monochromatic reflective displays. A multicolor cholesteric liquid crystal layer has multiple different reflective center wavelengths, used to achieve multicolor or full-color displays.

[0063] In one specific embodiment of this invention, the cholesteric liquid crystal display unit includes a monochromatic cholesteric liquid crystal layer. The monochromatic cholesteric liquid crystal layer has a single reflective center wavelength and can reflect light of any color from the red, green, or blue bands, thereby achieving monochromatic reflective display.

[0064] In one specific implementation of this embodiment, the multicolor cholesteric liquid crystal layer is a single-layer multicolor cholesteric liquid crystal layer. That is, within the same cholesteric liquid crystal layer, different regions have different reflection center wavelengths. A black matrix or isolation structure can be provided between adjacent reflective regions to reduce color crosstalk.

[0065] In one specific embodiment of this invention, the multicolor cholesteric liquid crystal layer is a multicolor cholesteric liquid crystal layer stacked together. That is, the cholesteric liquid crystal display unit includes multiple cholesteric liquid crystal sublayers stacked along the viewing side to the back side, each sublayer having a different reflection center wavelength. For example, it could be a red reflective cholesteric liquid crystal sublayer, a green reflective cholesteric liquid crystal sublayer, and a blue reflective cholesteric liquid crystal sublayer stacked sequentially, each sublayer selectively reflecting light of different wavelengths, thereby achieving full-color display.

[0066] As one specific implementation method of this embodiment, see Figure 5a The electrophoretic display layer 170 is a microcapsule electrophoretic display layer. The electrophoretic display microunit 171 includes multiple microcapsules 171a, each microcapsule 171a encapsulating a dispersion medium and charged pigment particles.

[0067] As one specific implementation method of this embodiment, see Figure 5bThe electrophoretic display layer 170 is a microcup electrophoretic display layer. The electrophoretic display microunit 171 includes multiple compartments formed by the structure of microcup 171b, and each compartment is filled with a dispersion medium and charged pigment particles.

[0068] As one specific implementation method of this embodiment, see Figure 5c The electrophoretic display layer 170 is a microcavity electrophoretic display layer. The electrophoretic display microunit 171 includes multiple microcavities 171c formed by polymer walls, and each microcavity 171c is filled with a dispersion medium and charged pigment particles.

[0069] The optical path propagation process and working principle of the display device 100 of this embodiment will be described in detail below with reference to the accompanying drawings.

[0070] See Figure 6 In the diagram, hollow arrows represent incident light, dashed lines represent transmitted light, and dashed lines represent reflected light. The cholesteric liquid crystal layer is in a transparent state, and the electrophoretic display layer 170 forms a high-contrast black and white image. In black and white display mode, the cholesteric liquid crystal display unit is driven to a transparent state. Incident light enters from the observation side, passes through the substrate 110, and sequentially passes through the first electrode layer 120, the cholesteric liquid crystal layer, the second electrode layer 140, the optical adjustment layer 150, and the third electrode layer 160 before reaching the electrophoretic display layer 170. In the white region of the electrophoretic display unit, the incident light is reflected by the electrophoretic display layer 170 to form reflected light. The reflected light sequentially passes through the third electrode layer 160, the optical adjustment layer 150, the second electrode layer 140, the cholesteric liquid crystal layer, the first electrode layer 120, and the substrate 110 before exiting from the observation side, appearing white. In the black region of the electrophoretic display unit, the incident light is absorbed, and the reflected light intensity is extremely low, appearing black. In the region where the electrophoretic display unit is in a grayscale state, the intensity of the returned light is between the white and black states, thus presenting the corresponding grayscale.

[0071] See Figure 7In the diagram, the thick solid lines represent the target wavelength light selectively reflected directly by the cholesteric liquid crystal layer, the dashed lines represent transmitted light, the dashed lines represent light returned from the electrophoretic white background after transmission, and the thin solid lines represent the returned light after being adjusted by the optical adjustment layer 150. It should be noted that the tilt direction of the thin solid lines in the diagram is schematic and does not necessarily indicate that polarization adjustment causes a change in the propagation direction of the light. In a real display device 100, if the incident light is approximately normal and the light returns to its original position, the light can still propagate approximately perpendicularly. The diagonal thin solid lines in the diagram are mainly used to distinguish between ordinary returned light and returned light adjusted by the optical adjustment layer 150, avoiding the misunderstanding that they follow the same ordinary reflection path. In color display mode, at least a portion of the cholesteric liquid crystal display unit is driven to a selective reflection state, and the corresponding area of ​​the electrophoretic display unit is driven to a white or highly reflective state as the underlying reflective background. Incident light enters from the observation side and reaches the cholesteric liquid crystal layer. Regions in the cholesteric liquid crystal layer that are in a selectively reflective state selectively reflect incident light of a specific wavelength, forming colored light. This colored light propagates along its original path, passing through the first electrode layer 120 and the substrate 110, and exits from the observation side. Incident light not selectively reflected by the cholesteric liquid crystal layer continues to propagate, passing through the second electrode layer 140, the optical adjustment layer 150, and the third electrode layer 160, reaching the electrophoretic display layer 170. Regions in the electrophoretic display layer 170 that are in a white or highly reflective state reflect the incident light, forming reflected light. The reflected light passes through the third electrode layer 160 and enters the optical adjustment layer 150. The polarization state of the reflected light is adjusted by the optical adjustment layer 150, causing at least a portion of the reflected light to be converted into adjusted reflected light. This adjusted reflected light sequentially passes through the second electrode layer 140, the cholesteric liquid crystal layer 130, the first electrode layer 120, and the substrate 110, and exits from the observation side. The total light emitted from the observation side consists of colored light directly reflected by the cholesteric liquid crystal layer 130 and adjusted return light transmitted after being reflected by the electrophoretic display layer 170.

[0072] The display device 100 of this embodiment can be fabricated using the following method: a substrate 110 is provided, and a first electrode layer 120, a cholesteric liquid crystal layer 130, and a second electrode layer 140 are sequentially formed on the substrate 110; an optical adjustment layer 150 is formed on the second electrode layer 140; an electrophoretic display unit is provided, the electrophoretic display unit including a third electrode layer 160, an electrophoretic display layer 170, and a fourth electrode layer 180; the optical adjustment layer 150 and the third electrode layer 160 are laminated or bonded according to a full-screen coverage relationship, and spatial registration and electrode connection are performed. The manufacturing method is applicable to flexible substrates, roll-to-roll coating, low-temperature lamination, and various electrophoretic display layer structures. This invention is compatible with cholesteric liquid crystal coating, encapsulation, microcapsule electrophoresis, microcup electrophoresis, microcavity electrophoresis, lamination bonding, and flexible substrate manufacturing processes. It has a reliable structure and is suitable for large-area, flexible, and low-power display product applications.

[0073] The display device 100 provided in this embodiment has an optical adjustment layer 150 between the cholesteric liquid crystal display unit and the electrophoretic display unit. This layer adjusts the optical state of the reflected light from the electrophoretic display unit, allowing at least a portion of the reflected light to pass through the cholesteric liquid crystal display unit and exit from the observation side. Compared with the color filter scheme, this avoids the absorption loss of incident light by the filter and overcomes the problem of reduced light utilization caused by polarization mismatch in the direct stacking scheme, thus improving the utilization rate of the reflected light and enhancing the brightness and color saturation of the display device 100. At the same time, the electrophoretic display unit can switch between bright, dark, and multiple grayscale states, serving as both a high-contrast black and white display layer and a switchable bottom reflective background for the cholesteric liquid crystal display unit. This allows the display device 100 to achieve a balance of high brightness, high color saturation, and high black and white contrast without the need for a color filter. The display device 100 of this application improves the utilization rate of returned light and reduces stacked optical loss and drive crosstalk through the coordinated design of cholesteric liquid crystal layer 130, electrophoretic display layer 170, optical adjustment layer 150 and time-division driving mode. This enables the two display layers to display separately or in tandem, thereby realizing an electronic paper display device with high brightness, high contrast, full-screen color display and low power consumption.

[0074] The specific details of the driving method for a composite cholesteric liquid crystal display device provided by this invention will be described in detail in the following embodiments.

[0075] Example 2

[0076] Please refer to Figures 8 to 9 , Figure 8 A process flow diagram of a driving method for a composite cholesteric liquid crystal display device provided in an embodiment of the present invention; Figure 9 Timing diagram for time-division driving of a composite cholesteric liquid crystal display device provided in an embodiment of the present invention.

[0077] See Figure 8 In this embodiment of the invention, the driving method for the composite cholesteric liquid crystal display device includes: S101: In the first time period, a driving signal is applied to the electrophoretic display unit to drive the electrophoretic display unit to switch to a first reflective state that presents a bright state, a second reflective state that presents a dark state, or any optical state between the first reflective state and the second reflective state.

[0078] In this step, the first time period is the driving period of the electrophoretic display unit. During the first time period, a driving signal is applied to the electrode structure of the electrophoretic display unit. Under the action of the driving signal, the charged pigment particles in the electrophoretic display layer 170 migrate in the electric field, causing the electrophoretic display unit to switch from the current optical state to the target optical state. The target optical state is a first reflective state (white state) that presents a bright state, a second reflective state (black state) that presents a dark state, or a grayscale state between the first reflective state and the second reflective state.

[0079] For a detailed explanation of the working principle of the electrophoretic display unit, please refer to the aforementioned content; it will not be repeated here.

[0080] S102: In the second time period, a driving signal is applied to the cholesteric liquid crystal display unit to drive the cholesteric liquid crystal display unit to switch to a selective reflection state or a light-transmitting state; the time periods of the first time period and the second time period do not overlap at least partially.

[0081] In this step, after the electrophoretic display unit completes its state switching, the driving signal applied to the electrophoretic display unit is stopped. Subsequently, during the second time period, a driving signal is applied to the electrode structure of the cholesteric liquid crystal display unit. Under the action of the driving signal, the cholesteric liquid crystal molecules switch from the current optical state to the target optical state, thereby causing the cholesteric liquid crystal display unit to switch to a selective reflection state (displaying color) or a light-transmitting state (displaying transparency or low scattering).

[0082] For a detailed explanation of the working principle of cholesteric liquid crystal display units, please refer to the aforementioned content; it will not be repeated here.

[0083] In the driving method of the display device 100 provided in this embodiment, the time periods of the first time period and the second time period do not overlap at least partially, that is, the two display layers are not driven at the same time, so as to avoid electric field crosstalk and mis-driving problems caused when the two display layers are driven at the same time.

[0084] In this embodiment, the driving processes of the cholesteric liquid crystal display unit and the electrophoretic display unit employ non-overlapping or partially non-overlapping time intervals. That is, the cholesteric liquid crystal display unit and the electrophoretic display unit are driven separately according to different time intervals, avoiding electric field crosstalk caused by simultaneous driving of the two display units. If the two display units are driven simultaneously, the driving electric fields of the two display units may couple with each other, generating electric field crosstalk, mis-driving, and image retention, affecting display stability. Therefore, this invention, through the coordinated design of the cholesteric liquid crystal display unit, the electrophoretic display unit, the optical adjustment layer 150, and the time-division driving method, improves the utilization rate of returned light, reduces stacked optical losses and driving crosstalk, enabling the two display layers to display separately or collaboratively, thereby achieving an electronic paper display device that combines high brightness, high contrast, full-screen color display, and low power consumption.

[0085] The display device 100 provided in this embodiment also includes a controller 200; the controller 200 controls the electrophoretic display unit to complete the state switching; after the electrophoretic display unit completes the state switching, it stops applying the driving signal to the electrophoretic display unit; after stopping applying the driving signal to the electrophoretic display unit, it controls the cholesteric liquid crystal display unit to complete the state switching; after both the cholesteric liquid crystal display unit and the electrophoretic display unit complete the state switching, it enters the holding phase.

[0086] For details, see Figure 9 During the first time period T1, the controller 200 applies a driving signal to the electrophoretic display layer 170 through the electrode structure of the electrophoretic display unit. Under the action of the driving signal, the electrophoretic display layer 170 switches to the target reflection state. After the first time period ends, the driving waveform returns to zero, and the application of the driving signal to the electrophoretic display layer 170 stops, entering the electric field release stage T2. During the electric field release stage T2, the controller 200 controls the electrode structures of the electrophoretic display unit and the cholesteric liquid crystal display unit to be in a high-resistivity state, a fixed potential, or an electric field shielding state, and does not apply an effective driving signal to either display layer, so as to release the residual charge and induced electric field remaining in the electrode structure and display layer during the previous driving process, and prevent the residual electric field from interfering with the subsequent optical state switching of the cholesteric liquid crystal layer. Subsequently, during the second time period T3, the controller 200 applies a driving signal to the cholesteric liquid crystal layer 130 through the electrode structure of the cholesteric liquid crystal display unit. Under the action of the driving signal, the cholesteric liquid crystal layer 130 switches to the target optical state. After the second time period ends, the driving waveform returns to zero or switches to the sustaining waveform, entering the sustaining phase T4. During the sustaining phase, the electrophoretic display layer 170 maintains its current reflection state based on its bistable characteristics, without the need for continuous application of a driving signal; the cholesteric liquid crystal layer 130 maintains its current optical state through a sustaining voltage or periodic sustaining pulses. Through the above time-division control, electric field crosstalk caused by simultaneous driving of the two display layers can be effectively avoided, while reducing static display power consumption.

[0087] The driving method of the display device 100 provided in this embodiment effectively reduces the problems of electric field crosstalk and misdrive between two display units by setting independent electrodes and time-division driving. In this embodiment, when a driving signal is applied to the cholesteric liquid crystal display unit, the electrode structure of the driving electrophoretic display unit is in a high-resistivity state, a fixed potential, or an electric field shielding state; and / or, when a driving signal is applied to the electrophoretic display unit, the electrode structure of the driving cholesteric liquid crystal display unit is in a high-resistivity state, a fixed potential, or an electric field shielding state; and / or, during the holding phase, the cholesteric liquid crystal display unit maintains a light-transmitting state or a selectively reflective state by maintaining a holding voltage or periodic holding pulses.

[0088] In one specific implementation of this embodiment, when a driving signal is applied to the cholesteric liquid crystal display unit, the electrode structure of the driving electrophoretic display unit is in a high-resistivity state, a fixed potential, or an electric field shielded state. At this time, when the cholesteric liquid crystal display unit is driven, the electrodes of the electrophoretic display unit are in a high-resistivity state, a fixed potential, or an electric field shielded state, preventing the driving electric field of the cholesteric liquid crystal display unit from causing erroneous driving of the electrophoretic display unit and ensuring that the electrophoretic display unit maintains the switched reflection state.

[0089] In one specific implementation of this embodiment, when a driving signal is applied to the electrophoretic display unit, the electrode structure driving the cholesteric liquid crystal display unit is in a high-resistivity state, a fixed potential, or an electric field shielding state. At this time, when the electrophoretic display unit is driven, the electrodes of the cholesteric liquid crystal display unit are in a high-resistivity state, a fixed potential, or an electric field shielding state, preventing the driving electric field of the electrophoretic display unit from causing mis-driving of the cholesteric liquid crystal display unit and ensuring that the cholesteric liquid crystal display unit maintains its original optical state.

[0090] In one specific implementation of this embodiment, when a driving signal is applied to the cholesteric liquid crystal display unit, the electrode structure driving the electrophoretic display unit is in a high-resistivity state, a fixed potential, or an electric field shielded state. Similarly, when a driving signal is applied to the electrophoretic display unit, the electrode structure driving the cholesteric liquid crystal display unit is in a high-resistivity state, a fixed potential, or an electric field shielded state. In this case, regardless of which display unit is driven, the electrodes of the other display unit are in a high-resistivity state, a fixed potential, or an electric field shielded state. This reduces electric field crosstalk and mis-driving issues between the two display units, ensuring that the electrophoretic display unit and the cholesteric liquid crystal display unit operate independently.

[0091] In one specific implementation of this embodiment, the cholesteric liquid crystal display unit maintains a transparent or selectively reflective state during the holding phase by maintaining a holding voltage or periodic holding pulses. This improves the optical stability of the cholesteric liquid crystal layer 130 during the holding phase, preventing optical state drift. Simultaneously, the holding voltage is much lower than the driving voltage, resulting in lower power consumption and not affecting the device's low-power characteristics. It is understood that a low-reflection or transparent operating state can be achieved through a holding voltage, periodic holding pulses, or the material's own weak scattering state; this embodiment does not require that the state be a non-electrically maintained steady state.

[0092] This embodiment uses independent electrodes, an electric field isolation structure, and a time-division driving method to control the cholesteric liquid crystal layer 130 and the electrophoretic display layer 170 separately, effectively reducing electric field crosstalk, misdrive, and image retention between the two display layers, ensuring that each display layer operates independently and stably. Correspondingly, the controller 200 includes a first driving terminal and a second driving terminal, which are respectively connected to the electrode structure of the cholesteric liquid crystal display unit and the electrode structure of the electrophoretic display unit; the first time period and the second time period do not overlap at least partially; when driving one display unit, the electrodes of the other display unit are in a high-resistivity state, a fixed potential, or an electric field shielded state.

[0093] The electrophoretic display layer 170 can maintain a black-and-white, grayscale, or reflective background state after the driving signal is stopped; the cholesteric liquid crystal layer 130 can maintain a selective reflective state according to the display mode, or maintain a low-reflection or light-transmitting working state by maintaining a sustaining voltage or periodic sustaining pulses, thereby reducing the overall static power consumption. Correspondingly, the electrophoretic display unit has bistable characteristics and maintains the current reflective state after the driving signal is stopped; the cholesteric liquid crystal material has bistable or multistable characteristics; the cholesteric liquid crystal display unit maintains a light-transmitting state or a selective reflective state during the holding phase by maintaining a sustaining voltage or periodic sustaining pulses.

[0094] The driving method for the display device 100 provided in this embodiment drives the display device 100 to achieve black-and-white display mode, color display mode, and composite display mode. The controller 200 can drive the cholesteric liquid crystal layer 130 and the electrophoretic display layer 170 respectively, enabling them to switch between black-and-white display, color display, and composite display modes, and reducing continuous power consumption during the static display stage. Correspondingly, the controller 200 independently controls the optical state switching of the cholesteric liquid crystal display unit and the electrophoretic display unit, enabling the display device 100 to flexibly switch between black-and-white display mode, color display mode, and composite display mode.

[0095] In black and white display mode, the cholesteric liquid crystal display unit is driven to a light-transmitting state, and the electrophoretic display unit displays a black and white image. Specifically, in the first time period, a driving signal is applied to the electrophoretic display unit, driving it to switch to a first reflective state that is bright or a second reflective state that is dark, so as to form black and white text, patterns or grayscale images; in the second time period, a driving signal is applied to the cholesteric liquid crystal display unit, driving it to switch to a light-transmitting state, so that incident light from the observation side can pass through the cholesteric liquid crystal display unit to reach the electrophoretic display unit; thus achieving black and white display.

[0096] In monochrome display mode, a sustaining voltage or periodic sustaining pulses are applied to the cholesteric liquid crystal display unit, or it is kept in a low-reflection, weak-scattering state to reduce the occlusion of the underlying electrophoretic image by the cholesteric liquid crystal display unit. After the electrophoretic layer driving is stopped, the electrophoretic display unit maintains the current monochrome image; the cholesteric liquid crystal display unit can remain in a transparent state or switch to other states as needed for the display mode.

[0097] In color display mode, the electrophoretic display unit is driven to a white state or a high-reflectivity state as the underlying reflective background, and the cholesteric liquid crystal display unit displays color. Specifically, in the first time period, a driving signal is applied to the electrophoretic display unit, driving at least a portion of the electrophoretic display unit to switch to a bright first reflective state as the underlying optical background of the display device 100; in the second time period, a driving signal is applied to the cholesteric liquid crystal display unit, driving the corresponding area of ​​the cholesteric liquid crystal display unit to switch to a selective reflective state to reflect colored light, thereby achieving color display. The light reflected back by the electrophoretic display unit is polarized and adjusted by the optical adjustment layer 150, and at least a portion of it passes through the cholesteric liquid crystal display unit and exits towards the observation side, forming a color display effect together with the selectively reflected light of the cholesteric liquid crystal display unit itself. By adjusting the reflective state of the electrophoretic display unit and the selective reflective state of the cholesteric liquid crystal display unit, the brightness, saturation, and visual contrast of the color display can be improved.

[0098] In composite display mode, the displayed content is decomposed into color modulation information and black-and-white / grayscale information, which are displayed collaboratively by two display layers. Specifically, in the first time period, a driving signal is applied to the electrophoretic display unit, causing the first and second regions of the electrophoretic display unit to switch to a bright first reflective state or a dark second reflective state, respectively, to form black-and-white text, grayscale images, or bright and dark background information. In the second time period, a driving signal is applied to the cholesteric liquid crystal display unit, causing the region corresponding to the first region of the cholesteric liquid crystal display unit to switch to a selective reflective state and the region corresponding to the second region to switch to a transparent state, thereby achieving composite display. In this composite display mode, the two display layers perform spatial registration and temporal coordination according to a preset image mapping relationship, so that the color modulation effect of the cholesteric liquid crystal display unit is superimposed with the black-and-white / grayscale information of the electrophoretic display unit, thereby forming a composite display effect.

[0099] In this embodiment, in black-and-white display mode, the cholesteric liquid crystal display unit is in a low-reflection or light-transmitting state, and the electrophoretic display unit forms a black-and-white or grayscale image; in color display mode, the electrophoretic display unit provides a high-reflection background, and the cholesteric liquid crystal display unit forms selective color reflection; in composite display mode, the two display units work together to form color, black-and-white, grayscale, or overlay information. Correspondingly, a driving signal is applied to the electrophoretic display unit in a first time period to drive the electrophoretic display unit to switch to the target reflection state; a driving signal is applied to the cholesteric liquid crystal display unit in a second time period to drive the cholesteric liquid crystal display unit to switch to the selective reflection state or the light-transmitting state; through time-division driving where the first and second time periods are at least partially non-overlapping, the display device 100 can switch between different display modes.

[0100] The driving method for the display device provided in this embodiment controls the cholesteric liquid crystal layer and the electrophoretic display layer separately through independent electrodes, an electric field isolation structure, and a time-division driving method. This effectively reduces electric field crosstalk, misdrive, and image retention between the two display layers, ensuring that each display layer operates independently and stably. Simultaneously, the electrophoretic display layer can maintain a black-and-white, grayscale, or reflective background state after driving stops, while the cholesteric liquid crystal layer can maintain a selective reflective state or a low-reflection or light-transmitting state by maintaining a sustaining voltage and periodic sustaining pulses, thereby reducing overall static power consumption. The controller can drive the cholesteric liquid crystal layer and the electrophoretic display layer separately, enabling them to switch between black-and-white display mode, color display mode, and composite display mode, and reducing continuous power consumption during the static display phase. In black-and-white display mode, the cholesteric liquid crystal layer is in a low-reflection or light-transmitting state, and the electrophoretic display layer forms a black-and-white or grayscale image. In color display mode, the electrophoretic display layer provides a high-reflection background, and the cholesteric liquid crystal layer forms selective color reflection. In composite display mode, the two display layers work together to form color, black-and-white, grayscale, or overlay information. Correspondingly, the controller includes a first driving terminal and a second driving terminal, respectively connected to the electrode structure of the cholesteric liquid crystal display unit and the electrode structure of the electrophoretic display unit; the first time period and the second time period do not overlap at least partially, and when driving one display unit, the electrodes of the other display unit are in a high-resistivity state, a fixed potential, or an electric field shielding state; the optical adjustment layer has an electrical insulation function, further blocking the mutual penetration of the driving electric field; the electrophoretic display unit has bistable characteristics, and the cholesteric liquid crystal material has bistable or multistable characteristics; both do not require continuous application of driving signals or only require extremely low maintenance power to maintain their current state during the holding phase. Thus, this invention, through the synergistic design of the cholesteric liquid crystal layer, the electrophoretic display layer, the optical adjustment layer, and the time-division driving method, enables the two display layers to display separately or collaboratively, realizing an electronic paper display device with high brightness, high contrast, full-screen color display, and low power consumption maintenance characteristics.

[0101] The display device and its fabrication method of this application are described below through specific embodiments (specific embodiment 1, specific embodiment 2 and specific embodiment 3). Specific Implementation Example 1

[0103] A first transparent electrode layer, a monochromatic cholesteric liquid crystal layer, and a second transparent electrode layer are sequentially formed on a transparent substrate. The cholesteric liquid crystal layer can switch between a selective reflection state, a low reflection state, or a light-transmitting / weak reflection operating state.

[0104] An optical compensation layer or polarization state adjustment layer (i.e., the optical adjustment layer in this embodiment) is disposed below the second transparent electrode layer, and a third transparent electrode layer, an electrophoretic display layer, a pixel electrode layer, and a driving backplate are disposed therebelow in sequence. The electrophoretic display layer can be a microcapsule electrophoretic display layer, a microcup electrophoretic display layer, a microcavity electrophoretic display layer, or other electrophoretic display structures.

[0105] When displaying black and white text, the cholesteric liquid crystal layer is driven to a low-reflection or light-transmitting operating state, and a sustaining voltage or periodic sustaining pulses can be applied as needed; simultaneously, the electrophoretic display layer is driven to form a black, white, or grayscale image. After the electrophoretic layer driving is stopped, the electrophoretic display layer retains the black and white image.

[0106] When displaying monochrome color prompts, the corresponding area of ​​the electrophoretic display layer is driven to a white state or a high-reflectivity state, and the corresponding area of ​​the cholesteric liquid crystal layer is driven to a selective reflection state, thereby forming a high-brightness monochrome color pattern. The light reflected back from the electrophoretic display layer is polarized by the optical compensation layer and then at least partially passes through the cholesteric liquid crystal layer and exits towards the observation side to improve display brightness. Specific Implementation Example 2

[0108] The monolayer cholesteric liquid crystal layer is divided into red, green, and blue selective reflective regions, each corresponding to one or more pixel regions in the electrophoretic display layer. The electrophoretic display layer serves as the bottom reflective background with adjustable brightness.

[0109] When displaying a color image, the corresponding area of ​​the electrophoretic display layer is first driven to a white state, a high reflectivity state, a black state, or a predetermined grayscale state. Then, the corresponding cholesteric liquid crystal reflective area is driven according to the color image data, so that it is in a selective reflectivity state, a low reflectivity state, or a light-transmitting / weak reflectivity working state.

[0110] When the electrophoretic display layer is in a white or high-reflectivity state, a high-brightness color display is formed in the corresponding cholesteric liquid crystal region; when the electrophoretic display layer is in a black or low-reflectivity state, the reflected light in the corresponding region decreases, thus forming a darker color or black region. By combining the brightness modulation of the electrophoretic display layer with the selective reflection of the cholesteric liquid crystal layer, comprehensive adjustment of color brightness, saturation, and contrast is achieved.

[0111] An optical adjustment layer is disposed between the cholesteric liquid crystal layer and the electrophoretic display layer to adjust the polarization state of the light returned by the electrophoretic display layer, so that at least part of the returned light matches the transmission conditions of the cholesteric liquid crystal layer and is emitted toward the observation side. Specific Implementation Example 3

[0113] A flexible transparent polymer substrate is used as the substrate on the observation side, and a flexible active driving backplane is used as the substrate on the back side. From the observation side to the back side, the following are sequentially arranged: a flexible transparent polymer substrate, a first transparent electrode layer, a cholesteric liquid crystal layer, a second transparent electrode layer, an optical adjustment layer, a third transparent electrode layer, an electrophoretic display layer, a pixel electrode layer (i.e., a fourth electrode layer), and a driving backplane.

[0114] The cholesteric liquid crystal layer is driven by a first transparent electrode layer and a second transparent electrode layer; the electrophoretic display layer is driven by a third transparent electrode layer and a pixel electrode layer. An optical adjustment layer is located between the second and third transparent electrode layers to reduce electric field crosstalk between the two display layers and to adjust the polarization state of the light returning from the electrophoretic display layer.

[0115] The controller operates in a time-division multiplexing manner, following the sequence of "electrophoretic display layer update, electric field release, cholesteric liquid crystal layer update, and state maintenance." During the electrophoretic display layer update, the relevant electrodes of the cholesteric liquid crystal layer can be in a fixed potential, a high-resistivity state, or a shielded state; during the cholesteric liquid crystal layer update, the relevant electrodes of the electrophoretic display layer can be in a fixed potential or a high-resistivity state.

[0116] In the static display stage, the electrophoretic display layer maintains its black-and-white, grayscale, or reflective background state; the cholesteric liquid crystal layer maintains a selective reflective state according to the display mode, or maintains a low-reflection / transmittance working state by maintaining a signal, thereby realizing a low-power composite display.

[0117] The display device and its driving method provided by this invention break through the limitations of traditional color filter schemes and partial stacking schemes. It performs pixel-level full-screen composite of a cholesteric liquid crystal layer covering the entire effective display area and a high-contrast electrophoretic display layer, achieving precise pixel-level global alignment and stacking. This allows the cholesteric liquid crystal layer to perform color selective reflection, while the electrophoretic display layer not only presents high-contrast black and white images but also serves as a dynamically switchable bottom reflective background, enhancing the brightness, saturation, and visual contrast of the color display from the underlying optical modulation principle. Simultaneously, an optical adjustment layer is further provided between the two display layers to perform polarization conversion and optical matching on the returned light from the electrophoretic display layer, allowing at least a portion of the returned light to pass through the cholesteric liquid crystal layer and exit from the observation side, thereby reducing stacking light loss and improving light utilization. Furthermore, through independent electrodes, an electric field isolation structure, and a time-division driving method, electric field crosstalk between the two display layers is reduced, enabling the device to switch between color display, black and white display, and composite display modes according to the displayed content. Therefore, while solving the problems of light transmission loss, electric field crosstalk, and reduced black-and-white contrast caused by simple stacking, the present invention achieves full-screen color display, high black-and-white contrast, high reflective brightness, and bistable low power consumption without relying on absorptive color filters or significantly increasing static power consumption.

[0118] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section.

[0119] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0120] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0121] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0122] The composite cholesteric liquid crystal display device and driving method provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A composite cholesteric liquid crystal display device, characterized in that, From the observation side to the dorsal side, the following are included in sequence: substrate; Cholesteric liquid crystal display unit; the cholesteric liquid crystal display unit switches between a selective reflection state and a light-transmitting state; An optical adjustment layer is disposed between the cholesteric liquid crystal display unit and the electrophoretic display unit. The optical adjustment layer adjusts the optical state of the returned light reflected by the electrophoretic display unit, so that at least part of the returned light passes through the cholesteric liquid crystal display unit and is emitted from the observation side. An electrophoretic display unit that switches between a first reflective state that is bright, a second reflective state that is dark, and multiple optical states between the first reflective state and the second reflective state, and serves as the reflective background of the cholesteric liquid crystal display unit.

2. The composite cholesteric liquid crystal display device according to claim 1, characterized in that, It also includes a controller, which includes a first drive terminal and a second drive terminal; The first driving end is connected to the electrode structure of the cholesteric liquid crystal display unit, and the second driving end is connected to the electrode structure of the electrophoretic display unit.

3. The composite cholesteric liquid crystal display device according to claim 1, characterized in that, The optical adjustment layer includes any one or any combination of the following: Phase retardation film, polarization conversion film, low haze scattering film, or transparent polymer layer containing anisotropic particles.

4. The composite cholesteric liquid crystal display device according to claim 1, characterized in that, The cholesteric phase liquid crystal display unit covers the entire effective display area of ​​the electrophoretic display unit; And / or, each pixel in the cholesteric liquid crystal display unit corresponds one-to-one with each pixel in the electrophoretic display unit.

5. The composite cholesteric liquid crystal display device according to claim 1, characterized in that, The cholesteric liquid crystal display unit includes a first electrode layer, a cholesteric liquid crystal layer, and a second electrode layer stacked sequentially from the observation side to the back side. The electrophoretic display unit includes a third electrode layer, an electrophoretic display layer, and a fourth electrode layer, which are stacked sequentially from the observation side to the back side. The optical adjustment layer is located between the second electrode layer and the third electrode layer; And / or, the cholesteric liquid crystal display unit includes a monochrome cholesteric liquid crystal layer or a multicolor cholesteric liquid crystal layer; And / or, the electrophoretic display layer is any one of a microcapsule electrophoretic display layer, a microcup electrophoretic display layer, or a microcavity electrophoretic display layer.

6. The composite cholesteric liquid crystal display device according to claim 1, characterized in that, A drive backplate is provided on the back side of the electrophoresis display unit; And / or, the substrate is a flexible substrate.

7. A driving method for a composite cholesteric liquid crystal display device, used to drive the composite cholesteric liquid crystal display device as described in any one of claims 1 to 6, characterized in that, include: During the first time period, a driving signal is applied to the electrophoretic display unit to drive the electrophoretic display unit to switch to a first reflective state that presents a bright state, a second reflective state that presents a dark state, or any optical state between the first reflective state and the second reflective state. During the second time period, a driving signal is applied to the cholesteric liquid crystal display unit to drive the cholesteric liquid crystal display unit to switch to a selective reflection state or a light-transmitting state. The first time period and the second time period do not overlap at least partially.

8. The driving method for the composite cholesteric liquid crystal display device according to claim 7, characterized in that, During the first time period, a driving signal is applied to the electrophoretic display unit to drive the electrophoretic display unit to switch to a first reflective state that presents a bright state or a second reflective state that presents a dark state; During the second time period, a driving signal is applied to the cholesteric liquid crystal display unit to drive the cholesteric liquid crystal display unit to switch to the light-transmitting state; To achieve black and white display; Alternatively, during the first time period, a driving signal is applied to the electrophoretic display unit to drive at least a portion of the electrophoretic display unit to switch to a first reflective state that presents a bright state as the underlying optical background of the display device; During the second time period, a driving signal is applied to the cholesteric liquid crystal display unit to drive the corresponding area of ​​the cholesteric liquid crystal display unit to switch to the selective reflection state in order to reflect colored light and achieve color display. Alternatively, during the first time period, a driving signal is applied to the electrophoretic display unit to drive the first region and the second region of the electrophoretic display unit to switch to a first reflective state that is bright or a second reflective state that is dark, respectively. During the second time period, a driving signal is applied to the cholesteric liquid crystal display unit to drive the region corresponding to the first region in the cholesteric liquid crystal display unit to switch to the selective reflection state and the region corresponding to the second region to switch to the light-transmitting state, so as to achieve composite display.

9. The driving method for the composite cholesteric liquid crystal display device according to claim 7, characterized in that, It also includes the controller; The controller controls the electrophoresis display unit to complete state switching; After the electrophoresis display unit completes the state switching, the driving signal applied to the electrophoresis display unit is stopped; After stopping the application of the driving signal to the electrophoretic display unit, the cholesteric liquid crystal display unit is controlled to complete the state switching; After both the cholesteric phase liquid crystal display unit and the electrophoretic display unit have completed their state switching, they enter the holding phase.

10. The driving method for the composite cholesteric liquid crystal display device according to claim 7, characterized in that, When a driving signal is applied to the cholesteric liquid crystal display unit, the electrode structure driving the electrophoretic display unit is in a high-resistivity state, a fixed potential, or an electric field shielding state. And / or, when a driving signal is applied to the electrophoretic display unit, the electrode structure of the cholesteric liquid crystal display unit is driven to be in a high-resistivity state, a fixed potential, or an electric field shielding state; And / or, during the holding phase, the cholesteric liquid crystal display unit maintains the light-transmitting state or the selective reflection state by maintaining a maintaining voltage or periodic maintaining pulses.

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