Cholesteric liquid crystal electronic paper display device and display panel

Abstract

The application discloses a kind of cholesteric liquid crystal electronic paper, a kind of cholesteric liquid crystal electronic paper display device and display panel, the display panel sequentially includes first substrate, height compensation spacer, first electrode layer, first orientation layer, cholesteric liquid crystal layer, second orientation layer, second electrode layer, second substrate from bottom to top, the first electrode layer includes a plurality of mutually spaced first electrode, a plurality of long strip-shaped first hollow parts are opened in the first electrode, the second electrode layer is the common electrode of whole surface paving, a plurality of long strip-shaped second hollow parts are opened in the second electrode layer, the first hollow part is perpendicular to the second hollow part on the orthographic projection of first substrate and does not overlap with each other staggered on the orthographic projection of first substrate, the display device includes display panel.The application satisfies the requirement of electronic paper display panel ultra-low power consumption and high refresh, also greatly improves the color saturation of cholesteric liquid crystal by controlling light focusing track.

Description

Technical Field

[0001] This invention belongs to the field of display device technology, specifically relating to a cholesteric liquid crystal electronic paper display device and display panel. Background Technology

[0002] With the popularization of low-carbon and environmentally friendly concepts, electronic paper display panels have been widely used in electronic tags, smart retail, and e-readers due to their unique bistable characteristics and extremely low power consumption.

[0003] For example, Chinese invention patent CN120821130B discloses an electronic paper display panel that uses a first driving barrier and a second driving barrier on an array substrate to drive a light control unit to perform lateral physical displacement between a privacy area and a sharing area, thereby switching between different display modes. However, this conventional electronic paper architecture, which relies on the physical displacement of charged particles or microcapsules in space, has obvious drawbacks. Its physical displacement process has a slow response speed, making it impossible to achieve high frame rate refreshes, and frequent physical friction can easily lead to damage to the microcapsule structure, reducing the panel's lifespan. In addition, the first and second electrode layers of traditional electronic paper are usually in a completely opposite, full-area coverage form, which results in a huge inter-electrode parasitic capacitance between the two electrode layers, greatly slowing down the establishment speed of the driving signal and increasing refresh power consumption.

[0004] The core value of ChLCD full-color electronic paper lies in its near-zero power consumption, full-color visibility, outdoor adaptability, and long-term stability, aligning with the national dual-carbon and green display strategy. For cholesteric liquid crystal electronic paper, which pursues near-zero power consumption and high color gamut full-color display, directly applying traditional full-area front-facing electrodes or laterally moving pixel structures not only fails to overcome the power consumption bottleneck caused by huge parasitic capacitance, but also lacks sufficient creativity due to simple material replacement, making it difficult to fundamentally solve the problems of high-voltage power consumption and low optical utilization during rapid state transitions of cholesteric liquid crystals. Summary of the Invention

[0005] The purpose of this invention is to provide a cholesteric liquid crystal electronic paper display device and display panel, aiming to solve the technical problems of high parasitic capacitance and high power consumption caused by the large area of ​​the upper and lower electrodes facing each other in traditional electronic paper display panels, as well as the low optical utilization of traditional pixel structures. It meets the requirements of ultra-low power consumption and high refresh rate for electronic paper display panels, and also significantly improves the color saturation of cholesteric liquid crystals by controlling the light focusing trajectory.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A cholesteric liquid crystal electronic paper display device, wherein the display panel comprises, from bottom to top, a first substrate, a height compensation spacer layer, a first electrode layer, a first alignment layer, a cholesteric liquid crystal layer, a second alignment layer, a second electrode layer, and a second substrate. The first electrode layer includes a plurality of first electrodes arranged at intervals, and a plurality of elongated first hollow portions are formed on the first electrodes. The second electrode layer is a common electrode laid across the entire surface, and a plurality of elongated second hollow portions are formed on the second electrode layer. The orthographic projections of the first hollow portions on the first substrate and the orthographic projections of the second hollow portions on the first substrate are perpendicular to each other and do not overlap. The first alignment layer and the second alignment layer are respectively attached to the upper and lower surfaces of the cholesteric liquid crystal layer. The surfaces of the first alignment layer and the second alignment layer facing the cholesteric liquid crystal layer are provided with groove alignment structures formed by parallel friction.

[0007] As an improvement of the present invention, the display panel further includes an optical focusing microstructure layer, which is disposed on the side surface of the second substrate away from the second electrode layer. The optical focusing microstructure layer includes a plurality of nanoimprinted microlenses, and the orthogonal projection of the nanoimprinted microlenses on the first substrate covers the non-hollowed-out solid overlapping portion of the first electrode and the second electrode layer.

[0008] As an improvement of the present invention, the cholesteric liquid crystal layer includes a plurality of microcapsules arranged in a matrix, the microcapsules are filled with cholesteric liquid crystal molecules, and four adjacent microcapsules together form a capsule gap. The area where the orthographic projection of the first hollow part on the first substrate and the orthographic projection of the second hollow part on the first substrate overlap is an electric field-free region, and the orthographic projection of the capsule gap on the first substrate falls completely into the electric field-free region.

[0009] As an improvement of the present invention, the height compensation spacer layer is sandwiched between the first substrate and the first electrode layer. The height compensation spacer layer is made of insulating resin material and includes a plurality of insulating spacer blocks spaced apart from each other.

[0010] As an improvement of the present invention, the region in which the orthographic projection of the non-hollowed-out solid portion of the first electrode on the first substrate overlaps with the orthographic projection of the second hollow portion on the first substrate is a single-electrode weak field region. The orthographic projection of the insulating spacer block on the first substrate coincides with the single-electrode weak field region. The insulating spacer block lifts the first electrode in the single-electrode weak field region toward the second electrode layer, thereby shortening the distance between the first electrode and the second electrode layer at that location and compensating for the electric field strength.

[0011] As an improvement of the present invention, a plurality of first hollow portions are arranged parallel to each other and at equal intervals in the first electrode, and a plurality of second hollow portions are arranged parallel to each other and at equal intervals in the second electrode layer.

[0012] As an improvement of the present invention, both the first substrate and the second substrate are flexible resin thin film substrates.

[0013] As an improvement of the present invention, both the first orientation layer and the second orientation layer are polyimide film layers.

[0014] The present invention also provides a cholesteric liquid crystal electronic paper display device, including any of the above-mentioned cholesteric liquid crystal electronic paper display panels. The display device further includes a driving circuit board and a flexible printed circuit board. The driving circuit board is electrically connected to the first electrode layer and the second electrode layer respectively through the flexible printed circuit board. A waveform modulation chip is integrated on the driving circuit board. The waveform modulation chip is electrically connected to the output terminal of the driving circuit board. The waveform modulation chip is used to output a driving waveform containing a multi-pulse high voltage signal and a frequency modulation signal to the first electrode layer and the second electrode layer to control the cholesteric liquid crystal layer to switch between planar texture and focal conic texture.

[0015] The beneficial effects of this invention are as follows: This invention significantly reduces the physical area between the first and second electrode layers by creating long, non-overlapping, vertically intersecting, spatially projected hollow sections on the upper and lower electrode layers. This reduces the inter-electrode parasitic capacitance by more than 50%, thereby greatly reducing the capacitive load that the driving circuit needs to overcome when refreshing the screen and significantly reducing the display update power consumption.

[0016] This invention combines the trench orientation structure of the first and second orientation layers with the bistable texture characteristics of cholesteric liquid crystals, enabling liquid crystal molecules to maintain excellent planar texture in the absence of an electric field. This, in conjunction with the multi-pulse and frequency-modulated waveforms output by the waveform modulation chip, achieves high-response-speed state transitions.

[0017] This invention directly introduces an optical focusing microstructure layer into a double-sided hollow electrode panel. By using nanoimprinted microlenses, it precisely refracts and focuses external incident light onto the strong electric field effective working area where the upper and lower solid electrodes overlap, avoiding the hollow electrode-free area. This not only makes up for the defect of reduced effective reflection area caused by electrode hollowing, but also significantly improves the reflectivity and color saturation of full-color cholesteric liquid crystal, making the overall structure highly innovative. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a cholesteric liquid crystal electronic paper display panel.

[0019] List of reference numerals in the attached diagram: 1. First substrate; 2. Insulating spacer block; 3. First electrode layer; 4. Cholesteric liquid crystal layer; 5. Second electrode layer; 6. Second substrate; 7. Nanoimprinted microlens. Detailed Implementation

[0020] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0021] Example 1 This embodiment provides a cholesteric liquid crystal electronic paper display panel. The display panel includes, from bottom to top, a first substrate 1, a height compensation spacer layer, a first electrode layer 3, a first alignment layer, a cholesteric liquid crystal layer 4, a second alignment layer, a second electrode layer 5, and a second substrate 6.

[0022] Both the first substrate 1 and the second substrate 6 are made of flexible polyimide resin film substrates with a thickness of 50 μm. A height compensation spacer layer is provided on the upper surface of the first substrate 1. The height compensation spacer layer is composed of multiple insulating spacer blocks 2 formed by UV curing of photosensitive resin material. The height of the insulating spacer blocks 2 is 0.6 μm, and their shape is a truncated cone. Their orthogonal projection on the first substrate 1 is arranged in a matrix at intervals.

[0023] A first electrode layer 3 is sputtered on the side of the high-compensation spacer layer away from the first substrate 1. The material of the first electrode layer 3 is an indium tin oxide conductive film with a sheet resistance of 30 Ω / □. The first electrode layer 3 is formed by laser etching to create multiple strip-shaped first electrodes arranged at intervals. Each first electrode has multiple elongated first hollow portions inside, which are parallel to each other and arranged at equal intervals.

[0024] In this embodiment, the width of the first hollow portion is 15μm, the width of the solid indium tin oxide between adjacent first hollow portions is 25μm, and the hollowness rate of its electrode surface is set to 37.5%.

[0025] A second electrode layer 5 is deposited on the side of the second substrate 6 near the cholesteric liquid crystal layer 4. This second electrode layer 5 serves as a common electrode for the entire substrate and is also made of indium tin oxide. Multiple elongated second cutouts are also formed on the second electrode layer 5. The second cutouts are parallel to each other and equally spaced, with a width of 15 μm and a solid width of 25 μm between adjacent second cutouts.

[0026] In terms of spatial projection, the length extension direction of the first cutout portion intersects the length extension direction of the second cutout portion at a 90° angle. When viewed perpendicularly to the panel direction, the orthographic projections of the first cutout portion and the second cutout portion on the first substrate 1 are completely offset in space and do not overlap.

[0027] The first and second orientation layers are respectively attached to the upper and lower surfaces of the cholesteric liquid crystal layer 4, both of which are made of polyimide thin film with a thickness of 80 nm. The surfaces of the first and second orientation layers facing the cholesteric liquid crystal layer 4 are provided with micro-groove orientation structures formed by parallel friction. The friction alignment directions of the two orientation layers are parallel to each other, which is used to apply micro-anchoring and confinement forces to the liquid crystal molecules.

[0028] The cholesteric liquid crystal layer 4, sandwiched between the first and second orientation layers, comprises multiple microcapsules arranged in a monolayer matrix. The average particle size of the microcapsules is 10 μm, and they are filled with full-color cholesteric liquid crystal molecules with bistable phase transition properties. Due to the close packing of the microcapsules in the plane, the outer walls of four adjacent microcapsules together form a tiny rhomboid capsule gap in space.

[0029] In this embodiment, through precise alignment, the electric field-free region formed by the overlapping orthographic projections of the first and second hollow portions on the first substrate 1 perfectly coincides with the orthographic projection of the capsule gap on the first substrate 1. The region where the orthographic projection of the non-hollowed-out solid portion of the first electrode on the first substrate 1 overlaps with the orthographic projection of the second hollow portion on the first substrate 1 is defined as the single-electrode weak-field region, and the orthographic projection of the aforementioned insulating spacer 2 on the first substrate 1 completely coincides with this single-electrode weak-field region. During assembly, the insulating spacer 2 located below lifts the first electrode in this region by 0.6 μm along the vertical direction, forcibly shortening the physical distance between the first electrode solid and the upper second electrode layer 5, thereby compensating for the electric field weakening caused by the hollowing out of the common electrode.

[0030] An optical focusing microstructure layer is attached to the surface of the second substrate 6 on the side opposite to the second electrode layer 5. This layer is formed with a high-density array of nanoimprinted microlenses 7 using a roll-to-roll nanoimprinting process, with the microlenses having a radius of curvature of 12 μm. The orthogonal projection of the microlenses onto the first substrate 1 precisely covers the non-perforated solid overlap portion of the first electrode and the second electrode layer 5, thereby focusing and guiding external incident light to the strong electric field working region.

[0031] The display panel is electrically connected to an external driving circuit board via flexible printed circuit cables. The driving circuit board integrates a high-voltage waveform modulation chip, which outputs a specially designed multi-pulse high-voltage signal and a frequency modulation signal to the first electrode layer 3 and the second electrode layer 5. The multi-pulse high-voltage signal has a driving voltage amplitude of ±35V and includes a preparation pulse, a selection pulse, and a sustain pulse. The frequency modulation signal dynamically switches between 60Hz and 240Hz during screen refresh to drive and control the cholesteric liquid crystal molecules to rapidly switch between a planar texture state that reflects specific full-color light and a focal conic texture state that transmits light completely.

[0032] Example 2 This embodiment is basically the same as Embodiment 1, except that the width of the electrode layer cutouts and the electrode perforation rate are changed. In this embodiment, the width of the first and second cutouts of the first and second electrode layers is 20 μm, and the width of the solid indium tin oxide between adjacent cutouts is 20 μm. Under these parameters, the perforation rate of the electrode surface is increased to 50.0%. Since the solid overlap area is further reduced, the inter-electrode parasitic capacitance of the panel will theoretically be further reduced, but the corresponding effective working area of ​​the strong electric field is also narrowed.

[0033] Example 3 This embodiment is basically the same as Embodiment 1, except that the height of the insulating spacer block in the height compensation spacer layer is changed. In this embodiment, the height of the insulating spacer block is 0.2 μm. Under this height parameter, the first electrode in the weak field region of the single electrode is pushed up towards the second electrode layer by a height of 0.2 μm. Since the reduction in the physical spacing of the weak field region of the single electrode is small, its physical compensation effect on the electric field strength in this region is significantly weakened compared with Embodiment 1.

[0034] Example 4 This embodiment is basically the same as Embodiment 1, except that the frequency modulation parameters of the waveform modulation chip in the driver circuit board are changed. In this embodiment, when refreshing the screen, the waveform modulation chip cancels the dynamic switching mode of the frequency modulation signal and instead outputs a single-frequency multi-pulse high-voltage drive waveform with a fixed frequency of 60Hz to the first electrode layer and the second electrode layer. This embodiment is mainly used to evaluate the specific impact of the frequency modulation function on the fast flip-flop efficiency and refresh power consumption of cholesteric liquid crystal.

[0035] Comparative Example 1 This comparative example uses the conventional manufacturing process of a standard electronic paper display panel as a reference. Both the first and second electrode layers are made of a fully covered indium tin oxide conductive film, with no cutouts on the electrodes. The two electrode layers are spatially aligned and cover each other in a conventional, full-area manner. No height compensation spacer layer is used inside the panel; only conventionally distributed spherical gap support particles are used to maintain the cell thickness. The surfaces of the first and second electrode layers are not coated with a polyimide alignment layer, nor are there any parallel friction trench structures. The liquid crystal molecules are in a disordered, naturally random arrangement when no external electric field is applied. The outer surface of the second substrate is flat and does not have any optical focusing microstructure layer. The external driving circuit uses a conventional single-pulse fixed high-voltage (±35V, fixed 50Hz) driving waveform and does not have multi-pulse or frequency modulation capabilities.

[0036] Comparative Example 2 This comparative example is the same as Comparative Example 1, except that the conventional electrophoretic display material in Comparative Example 1 is simply replaced with the same cholesteric liquid crystal microcapsule layer as in Example 1, in order to verify the actual display effect of simply replacing the material without making overall structural improvements.

[0037] To verify the technical effects of the embodiments of the present invention, key performance indicators were tested on the display panels and devices of Embodiments 1 to 4, as well as Comparative Examples 1 and 2. The test indicators mainly included inter-electrode parasitic capacitance (to measure power reduction potential), white field reflectivity and color saturation (to measure optical utilization and full-color effect), refresh power consumption, full-screen response time (to measure dynamic screen refresh rate), and root mean square error of display uniformity in weak-field areas (to measure the completeness of liquid crystal flipping). The relevant test data are shown in Table 1 below.

[0038] Table 1. Key performance indicator test data for each embodiment and comparative example.

[0039] Analysis of the experimental data reveals that the staggered, hollowed-out electrode structure significantly reduces capacitance and power consumption. Comparative Examples 1 and 2, which use traditional, non-hollow, full-area, face-to-face electrodes, exhibit an inter-electrode parasitic capacitance as high as 88.6 pF / cm². 2 and 89.2pF / cm 2 In contrast, Embodiment 1, by introducing long, non-overlapping, vertically intersecting, spatially projected hollow sections, significantly reduced the area directly opposite the electrodes, resulting in a substantial decrease in parasitic capacitance to 32.5 pF / cm². 2 In Example 2, due to the increased permeability to 50.0%, the parasitic capacitance is further reduced to 21.8 pF / cm². 2 Regarding refresh power consumption, in Comparative Example 2, the cholesteric liquid crystal material driven by high voltage was directly replaced. Frequent charging and discharging under extremely high parasitic capacitance caused the refresh power consumption to surge to 6.80 μW / cm². 2 Conversely, in Examples 1 and 2, due to the significant reduction in capacitive load, the refresh power consumption was reduced to 0.45 μW / cm². 2 and 0.32 μW / cm 2 This fully demonstrates that the interlaced hollow electrode structure has fundamentally broken through the bottleneck of capacitor power consumption.

[0040] Regarding the improvement of visual effects by the optical focusing microstructure layer, Comparative Example 2, due to its fully covered electrodes and lack of optical optimization, has a white-field reflectivity of only 22.4% and low color saturation. Although Example 1 has a 37.5% electrode cutout area, the outermost nanoimprinted microlens array precisely focuses the incident light onto the strong electric field display area where the physical electrodes overlap, perfectly avoiding the ineffective cutout area. Its white-field reflectivity not only did not decrease but actually increased to 46.2%, and its color saturation reached 73.5% NTSC. Example 2, due to its larger electrode cutout ratio, has a smaller effective reflective entity, resulting in a slight decrease in reflectivity and saturation compared to Example 1. This indicates that the optical focusing layer and the cutout electrodes in Example 1 achieved optimal photoelectric coupling in spatial scale.

[0041] Regarding the coupling effect of alignment structure, electric field compensation, and waveform modulation, Comparative Example 2, due to the absence of an alignment layer providing initial anchoring force and the use of conventional single-pulse driving, achieved a full-screen response time as high as 620ms. Example 1, by setting first and second alignment layers with parallel friction grooves, induced liquid crystal molecules to establish an initial planar texture with high response sensitivity. Combined with multi-pulse and frequency modulation signals, the full-screen response time was significantly shortened to 210ms. Example 4, after eliminating frequency modulation, extended the response time to 380ms, and the refresh power consumption increased due to reduced conversion efficiency, verifying the necessity of synergy between specific driving waveforms and panel structure. Furthermore, for the single-electrode weak field region caused by electrode cutouts, Example 1 used an insulating spacer block with a height-compensated spacer layer to lift the electrode, successfully shortening the cell thickness to compensate for the electric field, resulting in excellent display uniformity in the weak field region. However, in Example 3, after reducing the height of the insulating spacer block to 0.2μm, insufficient electric field compensation led to incomplete flipping of liquid crystal molecules in the weak field region, resulting in a longer response time and a drastically increased root mean square error in display uniformity, exhibiting significant display non-uniformity. This comparison fully demonstrates the technical contribution of the high-compensation septum layer to ensuring the display quality of large-area perforated panels.

[0042] It should be noted that the accompanying drawings merely illustrate the technical concept of the present invention and should not be used to limit the scope of protection of the present invention. For those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A cholesteric liquid crystal electronic paper display panel, characterized in that, The display panel, from bottom to top, includes a first substrate, a height compensation spacer layer, a first electrode layer, a first alignment layer, a cholesteric liquid crystal layer, a second alignment layer, a second electrode layer, and a second substrate. The first electrode layer includes a plurality of first electrodes arranged at intervals. The first electrodes have a plurality of elongated first hollow portions. The second electrode layer is a common electrode laid across the entire surface. The second electrode layer has a plurality of elongated second hollow portions. The orthographic projections of the first hollow portions on the first substrate and the orthographic projections of the second hollow portions on the first substrate are perpendicular to each other and do not overlap. The first alignment layer and the second alignment layer are respectively attached to the upper and lower surfaces of the cholesteric liquid crystal layer. The surfaces of the first alignment layer and the second alignment layer facing the cholesteric liquid crystal layer are provided with groove alignment structures formed by parallel friction.

2. The cholesteric liquid crystal electronic paper display panel according to claim 1, characterized in that: The display panel further includes an optical focusing microstructure layer, which is disposed on the side surface of the second substrate away from the second electrode layer. The optical focusing microstructure layer includes a plurality of nanoimprinted microlenses, and the orthogonal projection of the nanoimprinted microlenses on the first substrate covers the non-hollowed-out solid overlapping portion of the first electrode and the second electrode layer.

3. The cholesteric liquid crystal electronic paper display panel according to claim 1, characterized in that: The cholesteric liquid crystal layer includes a plurality of microcapsules arranged in a matrix. The microcapsules are filled with cholesteric liquid crystal molecules. Four adjacent microcapsules together form a capsule gap. The area where the orthographic projection of the first hollow part on the first substrate overlaps with the orthographic projection of the second hollow part on the first substrate is a field-free region. The orthographic projection of the capsule gap on the first substrate falls completely into the field-free region.

4. The cholesteric liquid crystal electronic paper display panel according to claim 1, characterized in that: The height compensation diaphragm layer includes a plurality of insulating diaphragm blocks spaced apart from each other.

5. The cholesteric liquid crystal electronic paper display panel according to claim 3, characterized in that: The region where the orthographic projection of the non-hollowed-out solid portion of the first electrode on the first substrate overlaps with the orthographic projection of the second hollow portion on the first substrate is the single-electrode weak field region. The orthographic projection of the insulating spacer block on the first substrate coincides with the single-electrode weak field region. The insulating spacer block lifts the first electrode in the single-electrode weak field region toward the second electrode layer.

6. The cholesteric liquid crystal electronic paper display panel according to claim 1, characterized in that: Multiple first hollow portions are arranged parallel to each other and at equal intervals within the first electrode, and multiple second hollow portions are arranged parallel to each other and at equal intervals within the second electrode layer.

7. The cholesteric liquid crystal electronic paper display panel according to any one of claims 1-6, characterized in that: Both the first substrate and the second substrate are flexible resin thin film substrates.

8. The cholesteric liquid crystal electronic paper display panel according to any one of claims 1-6, characterized in that: Both the first orientation layer and the second orientation layer are polyimide film layers.

9. A cholesteric liquid crystal electronic paper display device, comprising the cholesteric liquid crystal electronic paper display panel according to any one of claims 1-8, characterized in that: The display device further includes a driving circuit board and a flexible printed circuit board. The driving circuit board is electrically connected to the first electrode layer and the second electrode layer through the flexible printed circuit board. A waveform modulation chip is integrated on the driving circuit board. The waveform modulation chip is electrically connected to the output terminal of the driving circuit board. The waveform modulation chip is used to output a driving waveform containing multi-pulse high voltage signal and frequency modulation signal to the first electrode layer and the second electrode layer to control the cholesteric liquid crystal layer to switch between planar texture and focal cone texture.

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