A flexible low-power light-emitting panel of dynamic field emission cathode array and a preparation method thereof

Abstract

The application discloses a flexible low-power light-emitting panel of a dynamic field emission cathode array and a preparation method thereof, and belongs to the technical field of flexible field display. The existing field emission panel has defects such as high driving voltage, inability to bend, no online self-checking of the cathode, poor water-oxygen blocking of the package, and the like. The panel is composed of a flexible PI carbon fiber substrate, a double-layer annular dynamic cathode array, an insulating layer, a quantum dot anode light-emitting layer, a three-layer buffer composite package, and a side-external IGZO driving circuit. A high-temperature-resistant PZT piezoelectric sensor is arranged in a microcavity to collect the deformation of an emitter, and a driving circuit forms a current compensation closed loop through fault diagnosis and dynamic voltage regulation, so that 10-30V low-voltage driving is realized. The preparation process comprises microcavity photoetching, carbon nanotube emitter transfer, layered film plating, flexible packaging and TFT circuit bonding. The panel can withstand 180-degree bending for 10,000 times, the power consumption of the whole machine is reduced by 30%-50%, the service life is doubled, and the panel is suitable for wearable and curved surface vehicle-mounted flexible display devices.

Description

Technical Field Technical Field This invention belongs to the technical field of flat panel display devices and field emission devices, specifically relating to a dynamic field emission cathode array. Flexible low-power light-emitting panels and their fabrication processes are suitable for wearable electronics, curved automotive displays, and portable ultra-thin displays. Low-power flexible display products such as screens. Background Technology

[0002] Field emission displays (FEDs) combine the high response speed and ultra-high contrast of CRTs with the thinness and lightness of flat panel devices. They have no backlight module and theoretically offer better luminous efficiency than LCDs and some OLED products. However, existing commercially available field emission panels have significant technological shortcomings: 1. Traditional FED devices use rigid glass substrates, which cannot be bent and molded, and cannot meet the current application requirements of flexible wearables and curved screens; 2. Conventional single-gate field-emitting cathode driving voltages are generally in the range of 100V to 1000V, resulting in high driving power consumption, making them unsuitable for battery-powered small portable devices; 3. Existing cathode emitters lack online status detection structures, and cannot provide real-time warnings after the emitter tip ages at high temperatures and undergoes mechanical deformation. This leads to a significant reduction in the overall screen lifespan after local pixel failures. 4. Traditional packaging uses a single-layer glass seal, which has poor water and oxygen barrier properties, making the cathode material prone to oxidation and failure. Existing patent CN112701023A discloses a flexible cold cathode fabrication process, but it only achieves a single-layer gate structure, lacking a dynamic voltage regulation circuit and an online cathode detection structure, thus failing to achieve low-power zone control. Foreign patent US20240155877 describes a flexible OLED screen technology route, but its light-emitting principle is completely different from the field emission route of this invention, and it does not have a dual-gate field emission cathode array structure. Currently, there is a lack of a flexible field emission light-emitting panel that can be driven at low voltage, repeatedly bent, and has real-time self-checking of the cathode status. Summary of the Invention

[0003] Technical issues The purpose of this invention is to address the shortcomings of existing rigid field emission screens, such as high voltage, inflexibility, inability to monitor cathode failure, and high power consumption, by providing a flexible low-power light-emitting panel with a dynamic field emission cathode array and its fabrication method. To achieve the above objective, this invention provides the following technical solution: A flexible low-power light-emitting panel with a dynamic field emission cathode array, comprising a flexible substrate, a dynamic field emission cathode array insulating layer, an anode light-emitting layer, a flexible encapsulation layer, and an intelligent driving circuit, sequentially combined. The dynamic field emission cathode array is formed on the flexible substrate, the insulating layer covers the surface of the dynamic field emission cathode array, the anode light-emitting layer is laid on top of the insulating layer, the flexible encapsulation layer fully covers the top surface of the anode light-emitting layer and the sides of the panel, and the intelligent driving circuit is a flexible IGZO-TFT thin film array, directly fabricated in the peripheral non-display area of ​​the flexible substrate. The dynamic field emission cathode array comprises several cathode units arranged in a matrix array. Each cathode unit includes a nano-cone emitter, a dynamic gate, a microcavity structure, and a piezoelectric sensor. The microcavity structure is formed on a flexible substrate, and the piezoelectric sensor is embedded and fixed at the bottom of the microcavity structure. The nano-cone emitter is vertically positioned at the center of the microcavity, with its root in contact with the upper surface of the piezoelectric sensor. The dynamic gate is a coaxial double-layer ring structure surrounding the nano-cone emitter. The anode emitting layer consists of an electron blocking layer, a luminescent material layer, and a transparent conductive anode, arranged sequentially from bottom to top. The intelligent driving circuit includes a dynamic bias control module, a fault self-diagnosis module, and a low-power sleep module. The fault self-diagnosis module is electrically connected to each piezoelectric sensor, and the dynamic bias control module is electrically connected to the dynamic gate and the transparent conductive anode, respectively. During operation, the piezoelectric sensor collects real-time nanoscale vibration and deformation data of the nano-cone emitter and transmits it to the fault self-diagnosis module for analysis. When structural attenuation or abnormal deformation of the emitter is detected, the dynamic bias control module adaptively adjusts the inner and outer gate voltages based on the feedback signal to compensate for the attenuation of the emission current, achieving closed-loop active maintenance of the cathode lifetime. Further, the flexible substrate is a polyimide-carbon fiber composite board with a thickness of 50μm to 150μm and a minimum bending radius ≤5mm. The nano-cone emitter is a composite structure of carbon nanotubes and graphene, with a carbon nanotube to graphene mass ratio of 3:1 to 5:1. The emitter tip curvature radius is ≤10nm, and the overall height is 1μm to 5μm. The tip is plasma-etched to form a multi-level sharpened morphology. The dynamic gate consists of an inner gate and an outer gate. The distance between the inner gate and the sidewall of the nano-cone emitter is 0.5μm to 1μm, and the radial distance between the outer gate and the inner gate is 1μm to 2μm. The inner gate controls the electron emission threshold voltage, and the outer gate focuses the electron beam trajectory. The insulating layer is made of parylene C material, with a thickness of 1μm to 3μm, a dielectric constant ≥3.0, and a breakdown field strength greater than 1×10⁻⁶. 6V / cm. The transparent conductive anode is a silver nanowire / ITO composite conductive film with a light transmittance ≥90% and a sheet resistance ≤10Ω / □; the luminescent material layer uses RGB graded quantum dot-doped organic fluorescent composite material, with red quantum dots of 6-8nm, green quantum dots of 4-6nm, and blue quantum dots of 2-4nm, and an intrinsic quantum efficiency ≥80%; the electron blocking layer is a molybdenum oxide film with a thickness of 50nm-100nm. The flexible encapsulation layer is an Al2O3 / SiO2 / polyimide three-layer composite film with a total thickness of 5μm-10μm and a water and oxygen permeability ≤1×10⁻. 6 The panel has a strength of g / (m²·day) and can withstand 10,000 180° bends without structural damage. The dynamic bias control module employs PWM+PFM dual-mode collaborative voltage regulation control, adjusting the cathode and gate drive voltages in real-time according to the grayscale zones of the image. The static display area automatically reduces voltage and enters sleep mode, resulting in a 30%–50% reduction in overall power consumption. The intelligent drive circuit is fabricated using a flexible IGZO-TFT thin-film array, with an overall device drive voltage of 10V–30V. The microcavity structure has a cavity depth of 2μm–5μm and a cavity diameter of 5μm–10μm, and an embedded piezoelectric sensor with a detection sensitivity of 10⁻⁻⁴. 9 N-level. This invention also provides a method for fabricating a flexible low-power light-emitting panel of the above-mentioned dynamic field emission cathode array, comprising the following steps: S1. Flexible substrate pretreatment: Take a polyimide / carbon fiber composite substrate and activate it by oxygen plasma surface cleaning. S2. Fabrication of microcavities and piezoelectric sensors: Photolithography and dry etching are used to form an array of microcavity grooves on the substrate surface. At the bottom of the microcavities, a piezoelectric sensor film is fabricated by sputtering and photolithography patterning. S3. Cathode Emitter Transfer and Integration: A nickel-iron bicomponent catalyst layer is sputtered onto an independent high-temperature resistant temporary substrate. A carbon nanotube-graphene composite emitter is grown in an environment of 600–800℃ using CVD chemical vapor deposition. The resulting emitter array is then separated from the temporary substrate by laser or mechanical exfoliation. It is then aligned and transferred to the bottom of a flexible substrate microcavity using a precision alignment system and fixed to the upper surface of the piezoelectric sensor by conductive bonding. The transfer alignment accuracy is controlled within ±0.5μm. S4. Dynamic gate forming: A double-layer ring dynamic gate is formed around the microcavity by metal sputtering and pattern photolithography. S5. Insulating layer deposition: Deposit parylene C insulating film by CVD method, and prepare gate external contact points by photolithography dry opening method; S6. Preparation of the anode light-emitting layer: sequentially thermally evaporate a molybdenum oxide electron blocking layer, spin-coat a quantum dot composite light-emitting layer, and magnetron sputter a silver nanowire composite transparent anode; S7. Composite Encapsulation: An Al2O3 / SiO2 inorganic water-barrier layer is prepared by atomic layer deposition, and a polyimide organic protective layer is coated on the surface to form an integral composite encapsulation layer; S8. Circuit Integration: The flexible TFT driving circuit is bonded to the cathode array contacts through ACF anisotropic conductive adhesive, and aging test is performed under power-on conditions. The finished light-emitting panel is obtained. Preferably, in step S3, the thickness of the nickel-iron catalyst film is 1 nm to 5 nm, and the CVD growth time of the carbon nanotube-graphene composite emitter is 30 to 60 min. Beneficial effects Compared with the prior art, the present invention has the following significant advantages: 1. Low voltage and low power consumption: The dual-gate collaborative regulation of electron emission threshold and beam current, combined with dynamic bias partition voltage regulation, reduces the operating voltage to 10-30V, and the power consumption of the whole machine is reduced by 30%-50% compared with traditional FED, making it suitable for portable devices powered by lithium batteries. 2. Excellent bending performance and long life closed-loop protection: The microcavity-embedded piezoelectric sensor collects the nanoscale deformation and vibration signals of the emitter in real time. After being processed by the fault self-diagnosis module, the signals are fed back to the dynamic bias control module, which dynamically adjusts the inner and outer gate voltages to compensate for emission attenuation. This achieves 180° 10,000 bends without mechanical failure, while actively delaying emitter aging and effectively avoiding screen scrapping caused by local pixel failure, thus increasing the overall lifespan by more than 2 times. 3. High-quality light emission: The graded particle size RGB quantum dot composite light emission layer has high color purity and high luminous efficiency. The dual-gate focused electron beam significantly improves the uniformity of pixel light emission. 4. Mature and controllable processes: Photolithography, CVD, atomic layer deposition, ACF bonding and emitter transfer are all existing mature mass production processes, raw materials are readily available, and industrialization is easy. Figure 1 is a schematic diagram of the overall cross-sectional structure of the flexible low-power light-emitting panel of the dynamic field emission cathode array of the present invention; Figure 2 is a schematic diagram of the three-dimensional structure of a single cathode unit of the present invention; Figure 3 is a block diagram of the internal modules of the intelligent driving circuit of the present invention; Figure 4 is a flowchart of the overall fabrication process of the flexible light-emitting panel of the present invention. In the diagram: 100-Flexible substrate, 200-Dynamic field emission cathode array, 210-Cathode unit, 211-Nano-tip emitter, 212-Dynamic gate, 213-Microcavity structure, 214-Piezoelectric sensor, 300-Insulating layer, 400-Anode light-emitting layer, 410-Transparent conductive anode, 420-Light-emitting material layer, 430-Electron blocking layer, 500-Flexible encapsulation layer, 600-Intelligent driving circuit, 610-Dynamic bias control module, 620-Fault self-diagnosis module, 630-Low power sleep module. Detailed Implementation The present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited to the content described. Example 1 (Optimal Example) 1. Flexible substrate: PI and carbon fiber composite sheet, 100μm thick, bending radius 3mm, tensile strength ≥200MPa; 2. Cathode unit parameters: carbon nanotube to graphene mass ratio 4:1; emitter height 3μm, tip curvature 5nm; inner grid distance from emitter 0.8μm, inner and outer grid spacing 1.5μm; microcavity depth 3μm, diameter 8μm; piezoelectric sensor sensitivity 5×10⁻ 9 N; The dynamic gate is made of molybdenum metal with a film thickness of 200nm; 3. Insulating layer: Parylene C, thickness 2μm, dielectric constant 3.2, breakdown field strength 1.2×10⁻⁶ 6 V / cm; 4. Anode light-emitting layer: 80nm molybdenum oxide electron blocking layer; 7nm red quantum dots, 5nm green light, and 3nm blue light composite light-emitting layer with a quantum efficiency of 85%; silver nanowire / ITO composite anode with a transmittance of 92% and a sheet resistance of 8Ω / □; 5. Encapsulation layer: Al2O3 / SiO2 total film thickness 2μm, outer PI protective layer 6μm, total encapsulation thickness 8μm, water and oxygen permeability 5×10⁻ 7 g / (m²·day); 6. Driving circuit: IGZO flexible TFT array, rated operating voltage 20V, overall power consumption reduced by 40% after dynamic voltage adjustment. Example 2 (Panel fabrication process) S1. Substrate pretreatment: The PI carbon fiber substrate is placed in a plasma cleaner and cleaned for 5 minutes in an oxygen atmosphere at 100W power. S2. Fabrication of the microcavity and piezoelectric sensor: A microcavity groove with a depth of 3 μm and a diameter of 8 μm was formed by photolithography and dry etching; a piezoelectric sensor thin film was sputtered and photolithographically formed at the bottom of the microcavity, with a sensitivity of 5 × 10⁻⁻⁻⁶. 9 N; S3. Cathode Emitter Transfer: A 3nm nickel-iron composite catalyst layer was sputtered onto a silicon temporary substrate and placed in a CVD furnace at 650℃ for 45 min to grow a carbon nanotube-graphene composite emitter (carbon nanotube to graphene mass ratio 4:1, height 3μm). The emitter array was then laser-assisted lift-off and aligned and transferred to the bottom of the flexible substrate microcavity using a double-sided alignment photolithography system with an alignment accuracy of ±0.3μm. It was then bonded and fixed to the surface of the piezoelectric sensor using conductive silver paste. S4. Dynamic gate forming: 200nm of metallic molybdenum is sputtered, and a double-layer ring dynamic gate with an inner gate (0.8μm from the emitter) and an outer gate (1.5μm from the inner gate) is formed by pattern photolithography. S5. Insulating layer deposition: CVD deposition of 2μm parylene C insulating film, photolithography dry opening to expose the gate and subsequent anode contact points; S6. Preparation of the anodic light-emitting layer: thermally evaporated 80nm molybdenum oxide electron blocking layer; spin-coated composite light-emitting layer containing RGB graded quantum dots (7nm for red light, 5nm for green light, and 3nm for blue light); magnetron sputtered silver nanowire / ITO composite transparent anode with 92% transmittance and 8Ω / □ sheet resistance; S7. Composite Encapsulation: An Al2O3 / SiO2 inorganic water- and oxygen-barrier stack (total thickness 2μm) is prepared by atomic layer deposition, coated with a 6μm polyimide organic protective layer, resulting in a total encapsulation thickness of 8μm and a water and oxygen permeability of 5×10⁻⁻⁻⁶. 7 g / (m²·day); S8. Circuit Integration: Using ACF anisotropic conductive adhesive, the flexible IGZO-TFT driving circuit with dynamic bias, fault self-diagnosis, and low-power sleep module is press-bonded with the cathode array and anode contacts. After power-on aging test, the finished product is screened. Example 3 The difference between this embodiment and Embodiment 1 is as follows: the mass ratio of carbon nanotubes to graphene in the nano-cone emitter is adjusted to 3:1, the emitter height is 1 μm, and the tip curvature radius is 8 nm; the inner gate spacing of the dynamic gate is 0.5 μm, and the outer gate spacing is 2 μm; the thickness of the insulating layer (parylene C) is 1.5 μm; the total thickness of the encapsulation layer (Al2O3 / SiO2) is 1.5 μm, and the outer PI protective layer is 3.5 μm. Everything else is the same as in Embodiment 1. The resulting panel exhibits uniform light emission under a 20V driving voltage and passes 10,000 bending tests without failure. Example 4 The difference between this embodiment and Embodiment 1 is that: the mass ratio of carbon nanotubes to graphene is 5:1; the emitter height is 5 μm; the tip curvature radius is 10 nm; the microcavity depth is 5 μm and the diameter is 10 μm; and the piezoelectric sensor sensitivity is 1 × 10⁻⁻⁻⁶. 9 N; The driving voltage is 12V. In low-voltage mode, power consumption is further reduced by 10% compared to Example 1, making it suitable for ultra-low power electronic tag applications. Summary of Invention Effects This invention overcomes the shortcomings of traditional field emission screens, such as high voltage, rigidity, and easy failure, through four core innovations: dual-gate dynamic emission control, piezoelectric real-time online monitoring and closed-loop feedback, flexible composite substrate, and dynamic partitioning low-power drive. The product combines flexible bending, ultra-low power consumption, long life and high display quality, and has extremely high industrialization value in the fields of smart wearables, curved electronics and ultra-thin portable displays.

Claims

1. A flexible low-power light-emitting panel with a dynamic field emission cathode array, characterized in that, The system includes a flexible substrate (100), a dynamic field emission cathode array (200), an insulating layer (300), an anode light-emitting layer (400), a flexible encapsulation layer (500), and a smart driving circuit (600). The dynamic field emission cathode array (200) is formed on the flexible substrate (100), the insulating layer (300) covers the surface of the dynamic field emission cathode array (200), the anode light-emitting layer (400) is laid on top of the insulating layer (300), and the flexible encapsulation layer (500) fully covers the top surface of the anode light-emitting layer (400) and the sides of the panel. The smart driving circuit (600) is a flexible IGZO-TFT. A thin-film array is directly fabricated on the peripheral non-display area of ​​a flexible substrate (100); the dynamic field emission cathode array (200) includes several cathode units (210) arranged in a matrix array, each cathode unit (210) including a nano-cone emitter (211), a dynamic gate (212), a microcavity structure (213), and a piezoelectric sensor (214); the microcavity structure (213) is formed on the flexible substrate, the piezoelectric sensor (214) is embedded and fixed at the bottom of the microcavity structure (213), the nano-cone emitter (211) is vertically arranged at the center of the microcavity and its root is in contact with the upper surface of the piezoelectric sensor (214), and the dynamic field emission cathode array (200) is formed on the flexible substrate. The gate (212) is a coaxial double-layer ring structure and surrounds the outside of the nano-cone emitter (211); the anode light-emitting layer (400) is provided with an electron blocking layer (430), a light-emitting material layer (420), and a transparent conductive anode (410) from bottom to top; the intelligent driving circuit (600) includes a dynamic bias control module (610), a fault self-diagnosis module (620), and a low-power sleep module (630). The fault self-diagnosis module (620) is electrically connected to each piezoelectric sensor (214), and the dynamic bias control module (610) is electrically connected to the dynamic gate (212) and the transparent conductive anode (410) respectively.

2. The flexible low-power light-emitting panel with a dynamic field emission cathode array according to claim 1, characterized in that: The flexible substrate (100) is a polyimide-carbon fiber composite board with a thickness of 50μm to 150μm and a minimum bending radius of ≤5mm.

3. The flexible low-power light-emitting panel of a dynamic field emission cathode array according to claim 1, characterized in that: The nano-tip emitter (211) is a composite structure of carbon nanotubes and graphene, with a mass ratio of carbon nanotubes to graphene of 3:1 to 5:

1. The radius of curvature of the emitter tip is ≤10nm, and the overall height is 1μm to 5μm. The tip is formed into a multi-level sharpened morphology by plasma etching.

4. A flexible low-power light-emitting panel with a dynamic field emission cathode array according to claim 1, characterized in that: The dynamic gate (212) is divided into an inner gate and an outer gate. The distance between the inner gate and the sidewall of the nano-tip emitter is 0.5μm to 1μm, and the radial distance between the outer gate and the inner gate is 1μm to 2μm. The inner gate controls the electron emission threshold voltage, and the outer gate focuses the electron beam trajectory.

5. A flexible low-power light-emitting panel with a dynamic field emission cathode array according to claim 1, characterized in that: The insulating layer (300) is made of parylene C material, with a thickness of 1μm to 3μm, a dielectric constant ≥3.0, and a breakdown field strength greater than 1×10⁻⁶. 6 V / cm.

6. A flexible low-power light-emitting panel with a dynamic field emission cathode array according to claim 1, characterized in that: The transparent conductive anode (410) is a silver nanowire / ITO composite conductive film with a light transmittance ≥90% and a sheet resistance ≤10Ω / □; the luminescent material layer (420) uses RGB graded particle size quantum dot-doped organic fluorescent composite material, with red quantum dot particle size of 6-8nm, green quantum dot size of 4-6nm, and blue quantum dot size of 2-4nm, and intrinsic quantum efficiency of the material ≥80%; the electron blocking layer (430) is a molybdenum oxide film with a thickness of 50nm-100nm.

7. A flexible low-power light-emitting panel with a dynamic field emission cathode array according to claim 1, characterized in that: The flexible encapsulation layer (500) is an Al2O3 / SiO2 / polyimide three-layer composite film with a total thickness of 5μm to 10μm and a water and oxygen permeability of ≤1×10⁻. 6 g / (m²·day), the entire panel can withstand 180° bending 10,000 times without structural damage.

8. A flexible low-power light-emitting panel with a dynamic field emission cathode array according to claim 1, characterized in that: The dynamic bias control module (610) adopts PWM+PFM dual-mode coordinated voltage regulation control, and adjusts the cathode and gate driving voltages in real time according to the grayscale partition of the screen. The static display area automatically reduces voltage and goes into sleep mode, reducing the power consumption of the whole machine by 30% to 50%. The intelligent driving circuit is made of flexible IGZO-TFT thin film array, and the overall driving voltage of the device is 10V to 30V.

9. A flexible low-power light-emitting panel with a dynamic field emission cathode array according to claim 1, characterized in that: The microcavity structure (213) has a cavity depth of 2μm to 5μm and a cavity diameter of 5μm to 10μm, and an embedded piezoelectric sensor (214) with a detection sensitivity of 10⁻. 9 Level N: Real-time acquisition of transmitter vibration and deformation data and transmission back to the fault self-diagnosis module (620); When structural attenuation of the transmitter is detected, the dynamic bias control module (610) adaptively adjusts the dynamic gate voltage to compensate for the emission current.

10. A method for fabricating a flexible low-power light-emitting panel of a dynamic field emission cathode array according to any one of claims 1 to 9, characterized in that, It includes the following steps: S1. Flexible Substrate Pretreatment: A polyimide / carbon fiber composite substrate is taken and activated by oxygen plasma surface cleaning. S2. Microcavity and Piezoelectric Sensor Fabrication: An array of microcavity grooves is formed on the substrate surface using photolithography and dry etching. A piezoelectric sensor film is fabricated at the bottom of the microcavities by sputtering and photolithography patterning. S3. Cathode Emitter Transfer and Integration: A nickel-iron bicomponent catalyst layer is sputtered onto an independent high-temperature resistant temporary substrate. A carbon nanotube-graphene composite emitter is grown at 600–800℃ using CVD chemical vapor deposition. The resulting emitter is then peeled off, aligned, and transferred to the bottom of the microcavities on the flexible substrate and fixedly connected to the upper surface of the piezoelectric sensor. S4. Dynamic Gate Forming: A double-layer annular dynamic gate is formed around the microcavities by metal sputtering and patterned photolithography. S5. Insulating Layer Deposition: Parylene C is deposited using CVD. Insulating film, photolithography dry aperture preparation of gate external contact points; S6, Anode light-emitting layer preparation: sequential thermal evaporation deposition of molybdenum oxide electron blocking layer, spin coating of quantum dot composite light-emitting layer, magnetron sputtering of silver nanowire composite transparent anode; S7, Composite encapsulation: atomic layer deposition preparation of Al2O3 / SiO2 inorganic water-blocking oxygen layer, surface coating of polyimide organic protective layer to form integral composite encapsulation layer; S8, Circuit integration: flexible TFT driving circuit bonded to cathode array contacts through ACF anisotropic conductive adhesive, power-on aging test to obtain finished light-emitting panel.

11. The preparation method according to claim 10, characterized in that: In step S3, the thickness of the nickel-iron catalyst film is 1 nm to 5 nm, the CVD growth time of the carbon nanotube-graphene composite emitter is 30 to 60 min, and the alignment accuracy of the emitter transfer is controlled within ±0.5 μm.

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