Cholesteric liquid crystal microcapsule reflective display device and driving method thereof

Abstract

This invention relates to the field of cholesteric liquid crystal displays, and particularly to a cholesteric liquid crystal microcapsule reflective display device and its driving method. The device includes a first transparent substrate and a second transparent substrate disposed opposite to each other; a transparent heating electrode array and a display layer are stacked between the first and second transparent substrates; the transparent heating electrode array includes a plurality of heated pixel electrodes arranged in an array; the display layer includes cholesteric liquid crystal microcapsules dispersed in a transparent polymer adhesive matrix; a black light-absorbing layer is also disposed on the surface of the first transparent substrate away from the second transparent substrate; the heated pixel electrodes are used to apply a thermal field to the cholesteric liquid crystal microcapsules, causing the reflection peak of the cholesteric liquid crystal in the microcapsules to shift out of the visible light band and become transparent. This invention allows incident ambient light to pass through the display layer and be absorbed by the black light-absorbing layer on the back side of the first transparent substrate, making flexibility safe and feasible, and avoiding color bleeding during liquid crystal flow when bent.

Description

Technical Field

[0001] This invention relates to the field of cholesteric liquid crystal displays, and in particular to a cholesteric liquid crystal microcapsule reflective display device and its driving method. Background Technology

[0002] Cholesteric liquid crystals have a periodic helical structure and can selectively reflect circularly polarized light of a specific wavelength according to Bragg's law of reflection. Traditional cholesteric liquid crystal display devices use an electric field to switch between a planar reflection state and a focal cone scattering state to achieve bright and dark states. They do not require a backlight or polarizer and have bistable and low power consumption characteristics. Therefore, they are receiving increasing attention in the field of reflective displays such as electronic paper.

[0003] To overcome the problem of color bleeding caused by liquid crystal flowing when bent and compressed, related technologies have proposed a scheme to microencapsulate cholesteric liquid crystals. This involves using a polymer shell to encapsulate the liquid crystal to form microcapsules, and then dispersing the microcapsules in an adhesive matrix to form a display layer, thereby improving the flexibility and reliability of the device.

[0004] However, after microencapsulating cholesteric liquid crystals, there are obvious shortcomings in their driving mechanism. The dielectric constant of the microcapsule shell is much lower than that of the liquid crystal, and most of the applied electric field is distributed on the shell. The actual electric field experienced by the liquid crystal inside is very weak. Therefore, it is often necessary to apply a very high voltage to drive the liquid crystal to switch between the planar reflection state and the focal cone scattering state. This makes it difficult to apply to flexible, low-power devices, and often results in low contrast and poor display effect.

[0005] Therefore, how to provide a cholesteric liquid crystal microcapsule reflective display device that can get rid of the electric field-driven switching between planar reflection state and focal cone scattering state, thereby avoiding the shielding of the electric field by the microcapsule shell, and can improve the display contrast is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a cholesteric liquid crystal microcapsule reflective display device and its driving method, so as to solve the problems in the related art where cholesteric liquid crystal microcapsule systems are difficult to drive by electric field and difficult to achieve high-contrast black and white display.

[0007] To solve the above-mentioned technical problems, the present invention provides a cholesteric liquid crystal microcapsule reflective display device, comprising a first transparent substrate and a second transparent substrate disposed opposite to each other;

[0008] A transparent heating electrode array and a display layer are stacked between the first transparent substrate and the second transparent substrate;

[0009] The transparent heating electrode array includes multiple heating pixel electrodes arranged in an array;

[0010] The display layer comprises cholesteric liquid crystal microcapsules dispersed in a transparent polymer adhesive matrix;

[0011] A black light-absorbing layer is also provided on the surface of the first transparent substrate away from the second transparent substrate;

[0012] The heated pixel electrode is used to apply a thermal field to the cholesteric liquid crystal microcapsule, causing the reflection peak of the cholesteric liquid crystal in the cholesteric liquid crystal microcapsule to shift out of the visible light band and become transparent.

[0013] Optionally, in the cholesteric liquid crystal microcapsule reflective display device, the cholesteric liquid crystal microcapsule includes a first cholesteric liquid crystal microcapsule and a second cholesteric liquid crystal microcapsule.

[0014] The first cholesteric liquid crystal microcapsule contains cholesteric liquid crystal with a left-handed helical structure, and the second cholesteric liquid crystal microcapsule contains cholesteric liquid crystal with a right-handed helical structure.

[0015] The first cholesteric phase liquid crystal microcapsule and the second cholesteric phase liquid crystal microcapsule are mixed and arranged in the display layer.

[0016] Optionally, the cholesteric liquid crystal microcapsule reflective display device further includes a common transparent electrode;

[0017] The common transparent electrode is disposed on the surface of the second transparent substrate facing the first transparent substrate.

[0018] Optionally, in the cholesteric liquid crystal microcapsule reflective display device, the transparent heating electrode array is disposed on the surface of the first transparent substrate facing the second transparent substrate.

[0019] Optionally, the cholesteric liquid crystal microcapsule reflective display device further includes an insulating planarization layer;

[0020] The insulating planarization layer is disposed between the transparent heating electrode array and the first transparent substrate.

[0021] Optionally, in the cholesteric liquid crystal microcapsule reflective display device, each of the heated pixel electrodes includes a first electrode region and a second electrode region;

[0022] The first electrode region and the second electrode region can be subjected to different heating voltages to form a temperature gradient within the pixel corresponding to the heated pixel electrode, so that the reflection peak of the cholesteric liquid crystal in the cholesteric liquid crystal microcapsule at different temperatures is located at different color positions.

[0023] Optionally, in the cholesteric liquid crystal microcapsule reflective display device, the first electrode region and the second electrode region are interlocking interdigitated structures.

[0024] A driving method for a cholesteric liquid crystal microcapsule reflective display device, the driving method for driving the cholesteric liquid crystal microcapsule reflective display device as described above, comprising:

[0025] In the black state display step, a heating voltage is applied to the heated pixel electrode of the target pixel, causing the cholesteric liquid crystal microcapsules in the target pixel to heat up until their reflection peak shifts out of the visible light band and becomes transparent. The incident ambient light passes through the display layer and is absorbed by the black light-absorbing layer, so the target pixel displays black.

[0026] Optionally, the driving method for the cholesteric liquid crystal microcapsule reflective display device further includes:

[0027] In the white state display step, the first electrode region of the heated pixel electrode of the target pixel is heated to a first temperature, and the second electrode region of the heated pixel electrode is heated to a second temperature lower than the first temperature, so that a temperature gradient from the first temperature to the second temperature is formed in the target pixel; the temperature gradient causes different temperature zones in the target pixel to reflect blue, green and red light respectively, and the target pixel displays white after spatial color mixing of the light reflected from different temperature zones.

[0028] Optionally, the driving method for the cholesteric liquid crystal microcapsule reflective display device further includes:

[0029] In the grayscale display step, the black state driving waveform corresponding to the black state display step and the white state driving waveform corresponding to the white state display step are alternately applied within one frame period; by adjusting the duty cycle of the white state driving waveform within one frame period, the target pixel displays grayscale corresponding to the duty cycle.

[0030] The cholesteric liquid crystal microcapsule reflective display device provided by the present invention includes a first transparent substrate and a second transparent substrate disposed opposite to each other; a transparent heating electrode array and a display layer are stacked between the first transparent substrate and the second transparent substrate; the transparent heating electrode array includes a plurality of heating pixel electrodes arranged in an array; the display layer includes cholesteric liquid crystal microcapsules dispersed in a transparent polymer adhesive matrix; a black light-absorbing layer is also disposed on the surface of the first transparent substrate away from the second transparent substrate; the heating pixel electrodes are used to apply a thermal field to the cholesteric liquid crystal microcapsules, causing the reflection peak of the cholesteric liquid crystal in the cholesteric liquid crystal microcapsules to shift out of the visible light band and become transparent. This invention applies a thermal field to microencapsulated cholesteric liquid crystal in the display layer using a transparent heating electrode array. This causes the pitch to shorten with increasing temperature, the reflection peak to blue-shift until it moves out of the visible light band, becoming transparent. Ambient light passing through the display layer is absorbed by the black light-absorbing layer on the back of the first transparent substrate, resulting in a pure, scatter-free black state. This black state is completely independent of the electric field-driven switching between planar reflection and focal conic scattering states, physically avoiding the problem of shielding the electric field by the microcapsule shell. This results in a low required driving voltage, flexible and safe operation. Furthermore, the microcapsules confine the liquid crystal within independent microcavities, preventing color bleeding during bending and achieving a fully solid-state flexible display. Additionally, the black state created by the black light-absorbing layer is deeper than the black state created by the focal conic scattering state of the cholesteric liquid crystal, thus improving the contrast of the black and white display. This invention also provides a driving method for a cholesteric liquid crystal microcapsule reflective display device with the above-mentioned beneficial effects. Attached Figure Description

[0031] 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.

[0032] Figure 1 A schematic diagram of a specific embodiment of the cholesteric phase liquid crystal microcapsule reflective display device provided by the present invention;

[0033] Figure 2 This is a partial structural schematic diagram of another specific embodiment of the cholesteric liquid crystal microcapsule reflective display device provided by the present invention;

[0034] Figure 3 This is a partial structural schematic diagram of another specific embodiment of the cholesteric liquid crystal microcapsule reflective display device provided by the present invention;

[0035] Figure 4This is a driving timing diagram for a specific embodiment of the cholesteric liquid crystal microcapsule reflective display device provided by the present invention.

[0036] Figure label:

[0037] 101-First transparent substrate; 102-Black light-absorbing layer; 103-Insulating planarization layer; 104-Transparent heating electrode array; 105-Display layer; 105a-First cholesteric liquid crystal microcapsule; 105b-Second cholesteric liquid crystal microcapsule; 105c-Transparent polymer adhesive matrix; 106-Second transparent substrate; 107-Common transparent electrode; 201-First electrode region; 202-Second electrode region; 203-Thin film transistor switching element. Detailed Implementation

[0038] 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.

[0039] The core of this invention is to provide a cholesteric liquid crystal microcapsule reflective display device, the specific embodiment of which is shown in the schematic cross-sectional view of its stacked structure as follows. Figure 1 As shown, this is referred to as Specific Embodiment 1, which includes a first transparent substrate 101 and a second transparent substrate 106 disposed opposite to each other;

[0040] A transparent heating electrode array 104 and a display layer 105 are stacked between the first transparent substrate 101 and the second transparent substrate 106;

[0041] The transparent heating electrode array 104 includes a plurality of heating pixel electrodes arranged in an array;

[0042] The display layer 105 includes cholesteric liquid crystal microcapsules dispersed in a transparent polymer adhesive matrix 105c;

[0043] A black light-absorbing layer 102 is also provided on the surface of the first transparent substrate 101 away from the second transparent substrate 106;

[0044] The heated pixel electrode is used to apply a thermal field to the cholesteric liquid crystal microcapsule, causing the reflection peak of the cholesteric liquid crystal in the cholesteric liquid crystal microcapsule to shift out of the visible light band and become transparent.

[0045] In one specific embodiment, both the first transparent substrate 101 and the second transparent substrate 106 are made of a transparent flexible polymer material, with a thickness preferably between 50 micrometers and 200 micrometers, including the endpoints. The material can be selected from at least one of polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyimide, and transparent polyamide film, and the visible light transmittance is preferably greater than 85%. This arrangement ensures that ambient light can pass smoothly through the substrate to reach the black light-absorbing layer 102, and also gives the device good flexibility and bending resistance. Of course, other transparent substrates can also be selected according to actual conditions, and this invention is not limited thereto.

[0046] In one specific embodiment, the black light-absorbing layer 102 has an absorption rate of more than 90%, preferably more than 95%, for visible light in the 400 nm to 700 nm range. Its material can be selected from at least one of a carbon black-doped polymer resin layer, a black chromium oxide film, and an organic black photoresist, or it can be a black ink layer and / or black tape. The black light-absorbing layer 102 sufficiently absorbs ambient light transmitted through the display layer 105, thereby providing a pure black background for the device when the display layer 105 is transparent. The black ink layer offers greater flexibility and stability, while the black tape is easy to install and improves production efficiency. These can be selected according to actual needs, and the present invention is not limited thereto.

[0047] In one specific embodiment, the display layer 105 is disposed on the side of the transparent heating electrode array 104 facing the second transparent substrate 106, and its thickness is preferably 5 micrometers to 50 micrometers. The wall material of the cholesteric liquid crystal microcapsules in the display layer 105 is selected from at least one of melamine-formaldehyde resin, urea-formaldehyde resin, polyurea, polyurethane, gelatin-gum arabic composite system, and polymethyl methacrylate, and its wall thickness is preferably 50 nanometers to 500 nanometers, and the microcapsule particle size is preferably 1 micrometer to 20 micrometers; the transparent polymer adhesive matrix 105c is selected from at least one of polyvinyl alcohol, aqueous polyurethane, gelatin, acrylic emulsion, and transparent silicone, and its refractive index is preferably close to that of the microcapsule wall material to reduce interface scattering. The microcapsules confine the liquid crystal within independent microcavities, avoiding color bleeding of the liquid crystal flow when bent and compressed.

[0048] In another specific embodiment, the cholesteric phase liquid crystal microcapsule includes a first cholesteric phase liquid crystal microcapsule 105a and a second cholesteric phase liquid crystal microcapsule 105b.

[0049] The first cholesteric liquid crystal microcapsule 105a contains a cholesteric liquid crystal with a left-handed helical structure, and the second cholesteric liquid crystal microcapsule 105b contains a cholesteric liquid crystal with a right-handed helical structure.

[0050] The first cholesteric phase liquid crystal microcapsule 105a and the second cholesteric phase liquid crystal microcapsule 105b are mixed and arranged in the display layer 105.

[0051] For unpolarized natural light, its left-handed and right-handed circularly polarized components each account for approximately half of the energy. A single-chiral cholesteric liquid crystal can only reflect one type of circularly polarized component, with a theoretical upper limit of reflectivity of only about 50%. In this preferred embodiment, since the first cholesteric liquid crystal microcapsule 105a and the second cholesteric liquid crystal microcapsule 105b are mixed and arranged, both left-handed and right-handed microcapsules are present at each location, so that the reflected light in each wavelength band contains both left-handed and right-handed circularly polarized components. The total reflectivity can approach 100% of the incident natural light energy, theoretically reaching twice that of using only a single chiral liquid crystal, thereby significantly improving the white state brightness. Of course, the specific materials of the first cholesteric liquid crystal microcapsule 105a and the second cholesteric liquid crystal microcapsule 105b can be adjusted according to actual conditions, which is not limited here. The structural schematic diagram of the display layer 105 is shown below. Figure 2 As shown.

[0052] In one specific embodiment, the ratio of the first cholesteric liquid crystal microcapsule 105a to the second cholesteric liquid crystal microcapsule 105b is from 1:0.8 to 1:1.2, including the endpoint values, with approximately 1:1 being optimal. Within the above ratio range, the distribution of left- and right-handed microcapsules in the display layer 105 is more balanced, and the recycling of the two circular polarization components is more efficient, further ensuring the brightness of the white state and the purity of the black state. Of course, the specific ratio can be adjusted according to actual conditions, and this invention does not limit it.

[0053] In one specific embodiment, the transparent heating electrode array 104 is disposed on the surface of the first transparent substrate 101 facing the second transparent substrate 106.

[0054] Multiple row scan lines and multiple column data lines intersect to define multiple pixel units corresponding to the transparent heating electrode array, and each pixel unit corresponds to a heating pixel electrode that can be independently addressed and driven. The material of the transparent heating electrode array 104 is selected from at least one of indium tin oxide, indium zinc oxide, silver nanowire network, graphene film and conductive polymer, with a visible light transmittance preferably greater than 80% and a sheet resistance preferably between 10 ohms per square and 200 ohms per square. This configuration allows the transparent heating electrode array 104 to generate Joule heat when powered on to drive the display layer 105, while ensuring that ambient light can pass through the electrode array smoothly.

[0055] In one specific embodiment, the left-handed cholesteric liquid crystal in the first cholesteric liquid crystal microcapsule 105a is prepared by mixing a nematic liquid crystal host with a first chiral dopant, and the right-handed cholesteric liquid crystal in the second cholesteric liquid crystal microcapsule 105b is prepared by mixing the same nematic liquid crystal host with a second chiral dopant. The clearing point of the nematic liquid crystal host is preferably between 60°C and 120°C. The first chiral dopant has left-handed helical induction ability, and the second chiral dopant has right-handed helical induction ability. The doping concentration of both chiral dopants is preferably between 15% and 45% of the mass of the corresponding nematic liquid crystal host, so that the reflection peak of the microcapsule at room temperature is located in the visible light band, and the helical temperature coefficient is preferably between 0.5 nm / °C and 5 nm / °C. Preferably, the absolute values ​​of the helical torsion force constants of the first chiral dopant and the second chiral dopant are basically the same, so as to ensure that the reflection peaks of the left-handed microcapsules and the right-handed microcapsules are consistent at room temperature and that the helical temperature response is matched, thereby ensuring that the two types of microcapsules respond synchronously in the black and white states and improving the uniformity of the display.

[0056] Furthermore, the cholesteric liquid crystal microcapsule reflective display device also includes an insulating planarization layer 103;

[0057] The insulating planarization layer 103 is disposed between the transparent heating electrode array 104 and the first transparent substrate 101.

[0058] The insulating planarization layer 103 provides electrical insulation and forms a flat surface. Its material is selected from at least one of photosensitive polyimide, benzocyclobutene, and inorganic insulating layers, and its thickness is preferably 0.5 micrometers to 3 micrometers. This arrangement provides a flat growth surface for the transparent heating electrode array 104 while further improving the insulation reliability of the device.

[0059] Please continue to refer to this. Figure 1 In this specific embodiment, the second transparent substrate 106 is the light-facing surface of the display assembly. Ambient light enters from one side of the second transparent substrate 106, passes sequentially through the display layer 105 and the transparent heating electrode array 104, and then passes through the first transparent substrate 101 to reach the black light-absorbing layer 102. This invention utilizes the transparent heating electrode array 104 to apply a thermal field to the cholesteric liquid crystal microcapsules in the display layer 105. According to Bragg's law of reflection, the reflection center wavelength of the cholesteric liquid crystal is proportional to its pitch, and the pitch shortens as the temperature increases. Therefore, by controlling the heating temperature, the reflection wavelength of the microcapsules can be adjusted, even shifting its reflection peak out of the visible light band to achieve a transparent state. Combined with the absorption of transmitted light by the black light-absorbing layer 102, a pure black state can be obtained. With this configuration, the black state of this invention is not achieved through liquid crystal scattering, but through thermal transparency combined with background absorption, completely avoiding the problem of shielding the electric field by the microcapsule shell.

[0060] In a preferred embodiment, each of the heated pixel electrodes includes a first electrode region 201 and a second electrode region 202;

[0061] The first electrode region 201 and the second electrode region 202 can be subjected to different heating voltages to form a temperature gradient within the pixel corresponding to the heated pixel electrode, so that the reflection peak of the cholesteric liquid crystal in the cholesteric liquid crystal microcapsule at different temperatures is located at different color positions.

[0062] The schematic diagram of the planar partitioning corresponding to this specific implementation method can be referred to. Figure 3 This configuration allows different temperature regions to coexist within the same pixel, and according to Bragg's law of reflection, different temperature regions exhibit different reflection wavelengths, providing a structural basis for broadband reflection synthesis within the pixel.

[0063] Furthermore, the first electrode region 201 and the second electrode region 202 are interlocking interdigitated structures.

[0064] You can continue to refer to this. Figure 3 The first electrode region 201 and the second electrode region 202 are set as interlaced interdigitated structures, so that they are alternately distributed and close to each other in the pixel plane. This is beneficial to form a smooth and continuous temperature gradient between the first electrode region 201 and the second electrode region 202 through thermal diffusion, thereby continuously covering the red, green and blue reflection bands in the pixel and improving the uniformity of white state synthesis.

[0065] Furthermore, the first electrode region 201 and the second electrode region 202 are respectively connected to different data signal lines through independent thin-film transistor switching elements 203, or different voltages are fed in through a single thin-film transistor switching element 203 in conjunction with a voltage divider circuit within the pixel, thereby generating a controllable temperature gradient within the same pixel. This arrangement allows the heating voltage of the first electrode region 201 and the second electrode region 202 to be independently and precisely controlled, further improving the controllability of the temperature gradient. Of course, the specific driving methods of the first electrode region 201 and the second electrode region 202 can be adjusted according to actual conditions, and this invention does not limit them here.

[0066] In a preferred embodiment, a common transparent electrode 107 is also included;

[0067] The common transparent electrode 107 is disposed on the surface of the second transparent substrate 106 facing the first transparent substrate.

[0068] The common transparent electrode 107 serves as a reference potential surface, which helps to shield external electromagnetic interference. Its material is also selected from transparent conductive materials such as indium tin oxide and indium zinc oxide. The second transparent substrate 106 and the first transparent substrate 101 are sealed with edge encapsulant to form a fully solid-state flexible display unit. Of course, the common transparent electrode 107 can also be omitted according to actual needs, and this invention does not limit it.

[0069] The device of the present invention can be fabricated in the following manner:

[0070] S101: A black light-absorbing layer 102 is formed on one surface of the first transparent substrate 101, and an insulating planarization layer 103 and a transparent heating electrode array 104 are sequentially formed on the other surface of the first transparent substrate 101.

[0071] S102: Prepare first cholesteric phase liquid crystal microcapsules 105a and second cholesteric phase liquid crystal microcapsules 105b respectively, mix them in a preset ratio and disperse them in a transparent polymer adhesive matrix 105c, coat them onto the transparent heating electrode array 104 by slit coating, screen printing or inkjet printing and cure them to form a display layer 105.

[0072] S103: Finally, the second transparent substrate 106, which is provided with a common transparent electrode 107, is aligned and bonded with the first transparent substrate 101 and the edges are sealed to obtain an all-solid-state display device. Of course, the specific manufacturing process can be adjusted according to the actual situation, and this invention does not limit it here.

[0073] The cholesteric liquid crystal microcapsule reflective display device provided by the present invention includes a first transparent substrate 101 and a second transparent substrate 106 disposed opposite to each other; a transparent heating electrode array 104 and a display layer 105 are stacked between the first transparent substrate 101 and the second transparent substrate 106; the transparent heating electrode array 104 includes a plurality of heating pixel electrodes arranged in an array; the display layer 105 includes cholesteric liquid crystal microcapsules dispersed in a transparent polymer adhesive matrix 105c; a black light-absorbing layer 102 is also disposed on the surface of the first transparent substrate 101 away from the second transparent substrate 106; the heating pixel electrodes are used to apply a thermal field to the cholesteric liquid crystal microcapsules, causing the reflection peak of the cholesteric liquid crystal in the cholesteric liquid crystal microcapsules to shift out of the visible light band and become transparent. This invention applies a thermal field to the microencapsulated cholesteric liquid crystal in the display layer 105 using a transparent heating electrode array 104. This causes the pitch of the liquid crystal to shorten as the temperature increases, the reflection peak to shift blue until it moves out of the visible light band and becomes transparent. The incident ambient light passes through the display layer 105 and is absorbed by the black light-absorbing layer 102 on the back of the first transparent substrate 101, thereby obtaining a pure black state without scattering. This black state is completely independent of the electric field driving the switching between the planar reflection state and the focal conic scattering state, thus avoiding the problem of the microcapsule shell shielding the electric field from a physical mechanism perspective. This results in a low required driving voltage, flexible and safe operation. Furthermore, the microcapsules confine the liquid crystal within an independent microcavity, avoiding color bleeding during liquid crystal flow when bending, and realizing a fully solid-state flexible display. In addition, the black state caused by the black light-absorbing layer 102 is deeper in color than the black state caused by the focal conic scattering state of the cholesteric liquid crystal, thereby improving the contrast of the black and white display.

[0074] The present invention also provides a driving method for a cholesteric liquid crystal microcapsule reflective display device, wherein the driving method is used to drive the cholesteric liquid crystal microcapsule reflective display device as described above, and one specific embodiment includes:

[0075] In the black state display step, a heating voltage is applied to the heated pixel electrode of the target pixel, causing the cholesteric liquid crystal microcapsules in the target pixel to heat up until their reflection peak shifts out of the visible light band and becomes transparent. The incident ambient light passes through the display layer 105 and is absorbed by the black light-absorbing layer 102, so the target pixel displays black.

[0076] In this specific embodiment, during black-state display, the same or similar heating voltages are simultaneously applied to the pixel by the first electrode region 201 and the second electrode region 202, causing the two types of microcapsules within the entire pixel area to be uniformly heated to a preset high temperature, such as 60 to 90 degrees Celsius. This shortens the pitch of the microcapsules to a reflection center wavelength of less than 400 nanometers, allowing them to enter the ultraviolet band. At this time, the display layer 105 is transparent to visible light, and the reflectivity of the target pixel can be reduced to below 3%, presenting a pure black without scattering. This black state is achieved through thermochromic transparency combined with background absorption, thus physically avoiding the problem of shielding the electric field by the microcapsule shell.

[0077] As a preferred embodiment, the driving method of the cholesteric liquid crystal microcapsule reflective display device further includes:

[0078] In the white state display step, the first electrode region 201 of the heated pixel electrode of the target pixel is heated to a first temperature, and the second electrode region 202 of the heated pixel electrode is heated to a second temperature lower than the first temperature, so that a temperature gradient from the first temperature to the second temperature is formed in the target pixel; the temperature gradient causes different temperature zones in the target pixel to reflect blue, green and red light respectively, and the target pixel displays white after spatial color mixing of the light reflected from different temperature zones.

[0079] In this preferred embodiment, the first temperature is, for example, 70 to 90 degrees Celsius, and the second temperature is, for example, 30 to 50 degrees Celsius. A continuous temperature gradient is naturally formed between the first electrode region 201 and the second electrode region 202 through thermal diffusion. According to the dependence of pitch on temperature, the region with higher temperature has the shortest pitch and the reflected light is blue-shifted, mainly reflecting the blue band. The region with lower temperature has the longest pitch and the reflected light is red-shifted, mainly reflecting the red band. The intermediate temperature region reflects the green band, thereby generating a reflection spectrum covering the three primary colors of red, green and blue simultaneously within a single pixel.

[0080] Since the first cholesteric liquid crystal microcapsule 105a and the second cholesteric liquid crystal microcapsule 105b are roughly uniformly mixed, each temperature zone reflects both left-handed and right-handed circularly polarized components simultaneously. Moreover, the reflected light of each color is closely arranged in space, and its scale is much smaller than the resolution limit of the human eye. After entering the human eye, spatial color mixing occurs, which is perceived as a high-brightness white. Its reflected brightness can reach more than twice that of the traditional single chiral cholesteric liquid crystal white state.

[0081] As another preferred embodiment, the driving method for the cholesteric liquid crystal microcapsule reflective display device further includes:

[0082] In the grayscale display step, the black state driving waveform corresponding to the black state display step and the white state driving waveform corresponding to the white state display step are alternately applied within one frame period; by adjusting the duty cycle of the white state driving waveform within one frame period, the target pixel displays grayscale corresponding to the duty cycle.

[0083] The driving timing in this preferred embodiment can be referenced. Figure 4 , Figure 4 The CCP displayed three frames of driving signals, the first of which was completely white, with the grayscale level remaining at 255 throughout, and the white state time (T) w This is equal to one frame period (T). f The third frame is completely black, with the grayscale level remaining at 0 throughout, and the black state duration (T) b This is equal to one frame period (T). f The second frame is a gray frame, with a white state duration to black state duration ratio of 3:2, meaning a grayscale of 40%. In this preferred embodiment, a frame period is, for example, 20 milliseconds, corresponding to a 50 Hz refresh rate. The black state driving waveform heats the pixels uniformly to display black, while the white state driving waveform heats the pixels in sections to form a temperature gradient to display white. Utilizing the persistence of vision effect of the human eye, the average reflected brightness perceived by the observer changes linearly with the duty cycle. For example, a duty cycle of 0 corresponds to a completely black state, and a duty cycle of 100% corresponds to a completely white state. The intermediate grayscale corresponds linearly to the intermediate duty cycle. In actual driving, the duration of each subfield needs to be greater than the thermal response time of the cholesteric liquid crystal. The typical value of the thermal response time is 1 to 10 milliseconds, which can be achieved by optimizing the microcapsule particle size, substrate thermal conductivity design, and heating power to meet the grayscale modulation requirements.

[0084] In summary, the cholesteric liquid crystal microcapsule reflective display device and its driving method provided by this invention achieve a black state through thermally induced transparency combined with background absorption, reducing reflectivity to below 3% with no residual scattered light. The white state is synthesized through full-spectrum reflection of red, green, and blue light and utilizes left-handed and right-handed microcapsules to fully recover the two circularly polarized components, achieving a brightness more than twice that of the traditional cholesteric liquid crystal white state. Therefore, it has significantly better contrast and brightness than existing cholesteric liquid crystal displays and electrophoretic displays. Furthermore, this solution relies entirely on thermal field driving, with the electric field only used to generate Joule heat, eliminating the electric field shielding bottleneck. It requires a low driving voltage, perfectly matching the microcapsule system. When the image is statically displayed, it consumes almost zero power due to the inherent bistable state of the cholesteric liquid crystal, requiring only a brief, millisecond-level heating during state refresh, significantly reducing average power consumption. In addition, this invention is a reflective display, providing clear readability under strong ambient light without backlight loss. The spherical surface of the microcapsules helps eliminate specular reflection, providing a paper-like reading experience and a wide viewing angle.

[0085] 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.

[0086] It should be noted that, in this specification, 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 said element.

[0087] The cholesteric liquid crystal microcapsule reflective display device and its 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 cholesteric liquid crystal microcapsule reflective display device, characterized in that, Includes a first transparent substrate and a second transparent substrate disposed opposite to each other; A transparent heating electrode array and a display layer are stacked between the first transparent substrate and the second transparent substrate; The transparent heating electrode array includes multiple heating pixel electrodes arranged in an array; The display layer comprises cholesteric liquid crystal microcapsules dispersed in a transparent polymer adhesive matrix; A black light-absorbing layer is also provided on the surface of the first transparent substrate away from the second transparent substrate; The heated pixel electrode is used to apply a thermal field to the cholesteric liquid crystal microcapsule, causing the reflection peak of the cholesteric liquid crystal in the cholesteric liquid crystal microcapsule to shift out of the visible light band and become transparent. Each of the heated pixel electrodes includes a first electrode region and a second electrode region, wherein the first electrode region and the second electrode region are interlocking interdigitated structures. The first electrode region and the second electrode region can be subjected to different heating voltages to form a continuous temperature gradient within the pixel corresponding to the heated pixel electrode, so that different temperature zones within the pixel reflect blue, green and red light respectively, and the pixel displays white after spatial color mixing of the light reflected from different temperature zones.

2. The cholesteric liquid crystal microcapsule reflective display device as described in claim 1, characterized in that, The cholesteric phase liquid crystal microcapsule includes a first cholesteric phase liquid crystal microcapsule and a second cholesteric phase liquid crystal microcapsule; The first cholesteric liquid crystal microcapsule contains cholesteric liquid crystal with a left-handed helical structure, and the second cholesteric liquid crystal microcapsule contains cholesteric liquid crystal with a right-handed helical structure. The first cholesteric phase liquid crystal microcapsule and the second cholesteric phase liquid crystal microcapsule are mixed and arranged in the display layer.

3. The cholesteric liquid crystal microcapsule reflective display device as described in claim 1, characterized in that, It also includes a common transparent electrode; The common transparent electrode is disposed on the surface of the second transparent substrate facing the first transparent substrate.

4. The cholesteric liquid crystal microcapsule reflective display device as described in claim 1, characterized in that, The transparent heating electrode array is disposed on the surface of the first transparent substrate facing the second transparent substrate.

5. The cholesteric liquid crystal microcapsule reflective display device as described in claim 4, characterized in that, It also includes an insulating planarization layer; The insulating planarization layer is disposed between the transparent heating electrode array and the first transparent substrate.

6. A driving method for a cholesteric liquid crystal microcapsule reflective display device, characterized in that, The driving method for the cholesteric liquid crystal microcapsule reflective display device is used to drive the cholesteric liquid crystal microcapsule reflective display device as described in any one of claims 1 to 5, comprising: In the black state display step, a heating voltage is applied to the heated pixel electrode of the target pixel, causing the cholesteric liquid crystal microcapsules in the target pixel to heat up until their reflection peak shifts out of the visible light band and becomes transparent. The incident ambient light passes through the display layer and is absorbed by the black light-absorbing layer, so the target pixel displays black.

7. The driving method for the cholesteric liquid crystal microcapsule reflective display device as described in claim 6, characterized in that, Also includes: In the white state display step, the first electrode region of the heated pixel electrode of the target pixel is heated to a first temperature, and the second electrode region of the heated pixel electrode is heated to a second temperature lower than the first temperature, so that a temperature gradient from the first temperature to the second temperature is formed in the target pixel; the temperature gradient causes different temperature zones in the target pixel to reflect blue, green and red light respectively, and the target pixel displays white after spatial color mixing of the light reflected from different temperature zones.

8. The driving method for the cholesteric liquid crystal microcapsule reflective display device as described in claim 7, characterized in that, Also includes: In the grayscale display step, the black state driving waveform corresponding to the black state display step and the white state driving waveform corresponding to the white state display step are alternately applied within one frame period; By adjusting the duty cycle of the white state driving waveform within a frame period, the target pixel displays a grayscale value corresponding to the duty cycle.

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