Multicolor flexible wearable electroluminescent devices and methods of making the same

Abstract

The present application belongs to the technical field of flexible wearable electronic devices, and particularly relates to a multi-color flexible wearable electroluminescent device and a preparation method thereof, which comprises the following steps: (1) fabric planarization, mask production, and preparation of a patterned bottom electrode; (2) spray printing of a white light conversion dielectric layer; (3) spray printing of a light-emitting layer; (4) spray printing of a silver nanowire top electrode; (5) preparation of a color transparent TPU interlayer; and (6) TPU encapsulation. The preparation method is simple and efficient, and can impart the device with planar flexibility and color, and wearable display function.

Description

Technical Field

[0001] This invention belongs to the field of flexible wearable electronic device technology, specifically relating to a multi-color flexible wearable electroluminescent device and its preparation method. Background Technology

[0002] Flexible AC electroluminescent devices have broad application prospects in fields such as bionic electronics, smart wearables, and human-computer interaction. Their colors can change in real time, which is of great significance for their applications in displays and communications. Electroluminescence (EL) refers to the process of directly converting electrical energy into light energy. This device consists of electrodes, an emitting layer, and one or more layers of insulating material. It does not require high bandgap matching and is suitable for large-size displays, flexible electronics, and other fields.

[0003] Full-color electroluminescent (ACEL) displays have broad application prospects in the field of full-color television displays, especially white ACEL. To achieve this, various methods have been used to realize white ACEL devices. Among them, zinc sulfide (ZnS), doped with transition or rare metals, is a high-performance luminescent material, and ACEL devices using zinc sulfide as the electroluminescent material have been widely used. Currently, the most efficient colors of ZnS luminescent materials are blue-green and orange-yellow. Materials that achieve white ACEL by changing the ZnS dopant ions also exist, but their disadvantages include spectrum variations with applied voltage and frequency, and relatively low white light brightness. Alternatively, positive and negative alternating current voltages can be used to drive stacked blue-green and orange-yellow luminescent layers respectively, realizing color-tunable ACEL devices; however, its device structure and driving circuit are relatively complex, hindering widespread application.

[0004] Furthermore, by stacking blue-green and orange-yellow pigments in a single device to achieve white light, brightness can be improved. Their unique properties, such as high color purity, high efficiency, and ultra-thin profile, indicate the enormous potential of multi-color flexible electroluminescent devices. Moreover, with the latest developments in white ACEL, multi-color flexible electroluminescent devices show broad potential in healthcare monitoring, wearable electronics, and self-powered communication in the Internet of Things. Summary of the Invention

[0005] This invention provides a method for fabricating a multi-color flexible wearable electroluminescent device. This method is simple and efficient, and while giving the device planar flexibility, it can also realize color and wearable display functions.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A method for fabricating a multi-color flexible wearable electroluminescent device, the method comprising the following steps:

[0008] (1) Fabric planarization, mask fabrication, and patterned bottom electrode preparation: A TPU film is hot-pressed onto the fabric surface to form a flat layer. This flat layer provides a smooth fabric surface, which makes subsequent layers more uniform than coating or printing directly on the fabric.

[0009] Design luminescent patterns on a computer and cut them using a cutting machine to obtain masks for coating and printing various functional layers;

[0010] A mask is attached to a TPU film, and a bottom electrode is coated on the TPU film surface not covered by the mask to form a fabric device with a patterned liquid metal bottom electrode.

[0011] (2) Spraying white light dielectric layer: Spray white light dielectric ink onto the liquid metal bottom electrode of the fabric device to form a white light dielectric layer on the surface of the bottom electrode. After coating the white light dielectric ink, dry at 70-90℃ for 8-15 minutes.

[0012] The whitening dielectric ink is a mixed solution of whitening pigment, nano barium titanate, PVDF-HFP and isophorone in a weight ratio of 0.12:3:1:8;

[0013] (3) Spraying the luminescent layer: Spray luminescent ink onto the dielectric layer and dry it at 60-100℃ for 15-20 minutes. After the solvent in the luminescent layer has completely evaporated, spray it a second time, remove the mask, and dry it at 60-100℃ for 15-20 minutes to form the luminescent layer.

[0014] (4) Spraying silver nanowire top electrode: Spraying silver nanowire dispersion onto the light-emitting layer and drying at room temperature to form a transparent top electrode.

[0015] (5) Preparation of colored transparent TPU interlayer:

[0016] Prepare colored transparent TPU material, design a pattern on a cutting machine that is the same size as the white light dielectric layer printed on the fabric, and cut it to obtain colored transparent TPU for covering the top electrode obtained in (4);

[0017] The cut colored transparent TPU is placed above the top electrode of the fabric device and aligned with the white light dielectric layer to obtain a colored transparent TPU interlayer located above the top electrode of the silver nanowire.

[0018] (6) TPU encapsulation: A transparent TPU film is hot-pressed onto the top of the colored transparent TPU interlayer of the fabric device for hot-press encapsulation, resulting in a multi-color flexible wearable electroluminescent device.

[0019] Preferably, in step (1), the inkjet gun used for printing is a graphic inkjet gun with a nozzle diameter of 0.3-1mm and a printing time of 3min-10min.

[0020] The bottom electrode is selected from one or more of conductive polymer layers, carbon nanotubes, or graphene.

[0021] Preferably, in step (5), the colored transparent TPU material is monochromatic or dichromatic, with a thickness of 0.1-0.5 mm. This material is transparent, has good drape, is resistant to bending, and has high support.

[0022] Preferably, in step (6), the thickness of the transparent TPU film used for encapsulation is 0.2-1mm, and the pattern is designed using digital devices, making it easy to cut.

[0023] Preferably, in step (6), the hot pressing temperature is 120-190℃ and the hot pressing time is 15-30s.

[0024] Preferably, in step (1), the TPU film thickness is 0.05-0.15 mm, the hot pressing temperature is 140-210℃, and the hot pressing time is 5-20 s;

[0025] The mask is a removable adhesive label that can be repeatedly pasted and used after the release paper is removed.

[0026] The liquid metal is one or more of gallium-indium alloy, gallium-tin alloy, gallium-indium-tin alloy, gallium-zinc alloy, gallium-rubidium alloy, or gallium-cesium alloy, or a dispersion of the liquid metal.

[0027] Preferably, in step (3), the luminescent ink is a mixed solution of luminescent powder, PVDF-HFP and isophorone, with a weight ratio of 5:2:9 for each component. The luminescent powder is selected from one of the metal sulfide luminescent powders ZnS, CaS, SrS, CaGa2S4 and SrGa2S4.

[0028] In step (4), the silver nanowire dispersion is a dispersion with a concentration of 2 mg / mL prepared by dispersing silver nanowires in a mixture of isopropanol and ethanol with a volume ratio of 1:10.

[0029] A multi-color flexible wearable electroluminescent device prepared by the preparation method described in this invention comprises, in sequence, a flexible fabric substrate, a polyurethane film substrate, a bottom electrode, a white light-converting dielectric layer, a light-emitting layer, a silver nanowire top electrode, a colored transparent TPU interlayer, and a TPU encapsulation layer.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] 1. The colored transparent TPU interlayer is transparent, has good drape, is not easy to wrinkle, is resistant to bending, has high support, a strong sense of weight, and is crystal clear under light. In the prior art, color paste is added to organosilicon, which can slightly change the color of the device. The present invention uses colored transparent TPU interlayer as the encapsulation material for electroluminescent devices, which eliminates the need for solution preparation and drying steps, avoids damage to the device, and simplifies the process.

[0032] 2. Adding white light-converting pigment to the dielectric layer can change the original color of the device to white light emission with sufficient brightness. Placing a colored transparent TPU interlayer on the device can display the color of the TPU, and images can be displayed under indoor lighting conditions. The white light-converting pigment added to the dielectric ink is an electronic grade pigment, which has been experimentally proven to be able to convert the color to white.

[0033] 3. Cutting can perfectly engrave fine patterns that overlap with the device pattern to form pattern units, and can form patterns of various colors. Colored transparent TPU is easy to cut through and the excess parts are easy to tear off. The process is simple, easy to operate, and the pattern is controllable. Attached Figure Description

[0034] Figure 1 These are the lighting effects of the colored transparent electroluminescent device with added white light-converting pigment in Example 1: (a) red, (b) purple, (c) green, and (d) yellow.

[0035] Figure 2 This is a diagram showing the lighting effect of the silicone-encapsulated electroluminescent device in Comparative Example 1.

[0036] Figure 3 The following are the lighting effects of the colored transparent electroluminescent device without white light conversion pigment in Comparative Example 2: (a) red, (b) purple, (c) green, and (d) yellow.

[0037] Figure 4 These are the lighting effects of the patterned colored transparent electroluminescent device with added white light-converting pigment in Example 2: (a) red, (b) purple, (c) green, and (d) yellow.

[0038] Figure 5 This is a diagram showing the lighting effect of the electroluminescent device formed by the pattern unit in Comparative Example 2.

[0039] Figure 6 The images shown are from Example 2, illustrating the lighting effect of a colored transparent electroluminescent device formed on a T-shirt using white light-converting pigment: (a) red, (b) purple, (c) green, and (d) yellow.

[0040] Figure 7 This is a schematic diagram of the structure of a multi-color flexible wearable electroluminescent device. Detailed Implementation

[0041] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] The present invention will now be further illustrated with specific examples. The following embodiments are only for explaining the present invention and do not constitute a limitation thereof. The test samples and test procedures used in the following embodiments include the following (if the specific experimental conditions are not specified in the embodiments, they are generally performed according to conventional conditions or the conditions recommended by the reagent company; unless otherwise specified, the reagents, consumables, etc. used in the following embodiments can be obtained commercially).

[0044] White light-converting pigment, purchased from Xin Shuangjian Optoelectronic New Materials R&D Center, model is EL cold light sheet electronic grade pigment;

[0045] PVDF-HFP, Chinese name polyvinylidene fluoride-hexafluoropropylene copolymer, was purchased from Shanghai Aijie Biotechnology Co., Ltd.

[0046] ZnS:Cu luminescent powder, purchased from Shanghai Keyan Optoelectronic Technology Co., Ltd.;

[0047] Silver nanowires were purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd.

[0048] Example 1

[0049] A multi-color flexible wearable electroluminescent device comprises, in sequence, a flexible fabric substrate, a polyurethane film substrate, a bottom electrode, a white light-converting dielectric layer, a light-emitting layer, a silver nanowire top electrode, a colored transparent TPU interlayer, and a TPU encapsulation layer. A schematic diagram is shown below. Figure 7 .

[0050] The fabrication steps of this multi-color flexible wearable electroluminescent device are as follows:

[0051] (1) Fabric planarization, mask fabrication, and patterned liquid metal bottom electrode preparation: A TPU film is hot-pressed onto the fabric surface to form a flat layer on the fabric surface. This flat layer provides a smooth fabric surface, which makes the subsequent layers more uniform than coating or printing directly on the fabric. The hot-pressing temperature is 165℃.

[0052] Design luminescent patterns on a computer and cut them using a cutting machine to obtain masks for coating and printing various functional layers;

[0053] A mask is attached to a TPU film, and liquid metal is coated on the TPU film surface not covered by the mask to form a fabric device with a patterned liquid metal bottom electrode. The coating is done using a craft spray gun with a nozzle diameter of 0.5 mm and a coating time of 10 minutes.

[0054] (2) Spraying white light dielectric layer: Spray white light dielectric ink onto the liquid metal bottom electrode of the fabric device to form a white light dielectric layer on the surface of the bottom electrode. After coating the white light dielectric ink, dry at 80°C for 15 minutes.

[0055] The whitening dielectric ink is a mixed solution of whitening pigment, nano barium titanate, PVDF-HFP and isophorone in a weight ratio of 0.12:3:1:8. The amount of whitening pigment used is 1% of the total weight of nano barium titanate, PVDF-HFP and isophorone.

[0056] (3) Spraying the luminescent layer: Spray luminescent ink onto the dielectric layer and dry it at 80°C for 15 minutes. After the solvent in the luminescent layer has completely evaporated, spray it a second time, remove the mask, and dry it at 80°C for 15 minutes to form the luminescent layer.

[0057] (4) Spraying silver nanowire top electrode: Spraying silver nanowire dispersion onto the light-emitting layer and drying at room temperature to form a transparent top electrode; the silver nanowire dispersion is a dispersion with a concentration of 2 mg / mL prepared by dispersing silver nanowires in a mixture of isopropanol and ethanol with a volume ratio of 1:10.

[0058] (5) Preparation of colored transparent TPU interlayer: Prepare colored transparent TPU material with a thickness of 0.2 mm;

[0059] Design a pattern on a cutting machine that is the same size as the white light dielectric layer printed on the fabric, and cut it to obtain a colored transparent TPU for covering the top electrode obtained in (4);

[0060] The cut colored transparent TPU is placed above the top electrode of the fabric device and aligned with the white light dielectric layer.

[0061] (6) TPU encapsulation: A transparent TPU film is hot-pressed onto the top of the fabric device for hot-press encapsulation to obtain a multi-color flexible wearable electroluminescent device. The hot-pressing temperature is set to 160℃ and the hot-pressing time is 20s.

[0062] The transparent TPU film is 0.2mm thick and can be easily cut by designing patterns using digital devices.

[0063] The resulting colored transparent TPU electroluminescent device exhibits a lighting effect as follows: Figure 1 As shown, the device emits light uniformly and can produce different colors. The colored transparent TPU has good light transmittance, revealing the true color of the electroluminescent device covered by the transparent film. The device itself emits white light, and the colored transparent TPU interlayer placed on the device forms the color of the TPU. The illumination effect of the electroluminescent device without the addition of white light-converting pigment is shown in the image. Figure 3 As shown, blue and yellow mixed together form green, blue and green mixed together form indigo, and blue and red mixed together form violet, etc.

[0064] Comparative Example 1

[0065] The difference from Example 1 is as follows: Step (4) Encapsulation layer: Silicone is encapsulated on the fabricated electroluminescent device. Red pigment and silicone are mixed and stirred evenly, and an encapsulation layer is formed on the device by slowly moving a coating tool. The encapsulation layer is a mixed solution of red pigment and silicone, with a weight ratio of 1:2 for each component.

[0066] The measured color of the device showed a slight change, but did not meet the color requirements of a multi-color light-emitting display.

[0067] Comparative Example 2

[0068] Unlike Example 1, in step (1) device fabrication: no whitening pigment was added during the fabrication of the electroluminescent device. The device was dried at 80°C for 15 minutes to form a dielectric layer on the patterned bottom electrode surface. The dielectric ink was a mixed solution of barium titanate, PVDF-HFP and isophorone, with a weight ratio of 3:1:8.

[0069] The lighting effect of a colored transparent electroluminescent device without added white light-converting pigment is shown in the image below. Figure 3 As shown, the measured color of the device is blue, and it forms a mixed color with the colored transparent TPU interlayer, which cannot fully display the original color of the colored transparent TPU interlayer.

[0070] Comparative Example 2: The effect of lighting up a colored transparent electroluminescent device with added white light-converting pigment is shown in the image below. Figure 1As shown, generally speaking, since the white light-converting pigment transforms the original blue light into white light, it contains phosphor, a substance that can absorb external light and emit light of a specific color. It can convert light into other colors, thus achieving the effect of white light. The results show that a red transparent film appears purple when placed on an electroluminescent device without white light-converting pigment, and red when placed on an electroluminescent device with white light-converting pigment. Therefore, it can be inferred that devices with white light-converting pigment can more accurately reproduce the color of the colored transparent film.

[0071] Comparative Example 3

[0072] Unlike Comparative Example 2, step (2) involves printing a whitening dielectric layer: the whitening dielectric ink is a mixed solution of whitening pigment, nano-barium titanate, PVDF-HFP, and isophorone in a weight ratio of 0.06:3:1:8. The amount of whitening pigment is adjusted to 0.5% of the total weight of nano-barium titanate, PVDF-HFP, and isophorone.

[0073] The measured color of the device was still blue, with a small amount of bright white light, and it did not meet the requirement of turning into white light.

[0074] Comparative Example 4

[0075] Unlike Comparative Example 2, step (2) involves printing a whitening dielectric layer: the whitening dielectric ink is a mixed solution of whitening pigment, nano-barium titanate, PVDF-HFP, and isophorone in a weight ratio of 0.3:3:1:8. The amount of whitening pigment is adjusted to 2.5% of the total weight of nano-barium titanate, PVDF-HFP, and isophorone.

[0076] The measured color of the device is converted into white light, but it contains many impurities, including blue light spots, which affects the overall color uniformity of the device and makes it impure.

[0077] Comparative Example 5

[0078] Unlike Comparative Example 2, step (2) involves printing a whitening dielectric layer: the whitening dielectric ink is a mixed solution of whitening pigment, nano-barium titanate, PVDF-HFP, and isophorone in a weight ratio of 0.6:3:1:8. The amount of whitening pigment is adjusted to 5% of the total weight of nano-barium titanate, PVDF-HFP, and isophorone.

[0079] The measured white light from the device did not reach pure white light; it still contained blue light.

[0080] In this invention, the whitening pigment is selected at a ratio of 1% of the total weight of nano-barium titanate, PVDF-HFP, and isophorone to achieve optimal optical effects and color saturation. Barium titanate is a commonly used white pigment with good hiding and reflective properties. PVDF-HFP acts as a binder, firmly adhering barium titanate to the surface of the desired object. Multiple experiments have proven that only a 1% addition of whitening pigment ensures uniform pigment distribution of barium titanate and synergistically achieves optimal optical effects with barium titanate, avoiding problems such as excessive pigment thickness or excessive light reflection. Furthermore, excessively high proportions may lead to pigment precipitation or instability, affecting the quality and durability of the pigment. Insufficient addition will not affect the color transition, resulting in only a small amount of bright white light, or even no transition at all.

[0081] The methods described above may not completely remove blue light because white light is composed of multiple colors, and it's impossible to remove only one color. Complete removal of blue light may require more complex optical equipment or techniques, such as using mirrors, gratings, or optical interference.

[0082] Example 2

[0083] A multi-color patterned flexible wearable electroluminescent device is fabricated using the following steps:

[0084] (1) Fabric planarization, pattern mask fabrication, and patterned liquid metal bottom electrode preparation: A TPU film is hot-pressed onto the fabric surface to form a flat layer on the fabric surface. This flat layer provides a smooth fabric surface, which makes the subsequent layers more uniform than coating or printing directly on the fabric. The hot-pressing temperature is 165℃.

[0085] Design luminescent patterns on a computer and cut them using a cutting machine to obtain masks for coating and printing various functional layers;

[0086] A mask is attached to a TPU film, and liquid metal is coated on the TPU film surface not covered by the mask to form a fabric device with a patterned liquid metal bottom electrode. The coating is done using a craft spray gun with a nozzle diameter of 0.5 mm and a coating time of 10 minutes.

[0087] (2) Spraying white light dielectric layer: Spray white light dielectric ink onto the liquid metal bottom electrode of the fabric device to form a white light dielectric layer on the surface of the bottom electrode. After coating the white light dielectric ink, dry at 80°C for 15 minutes.

[0088] The whitening dielectric ink layer is a mixed solution of whitening pigment, nano barium titanate, PVDF-HFP and isophorone in a weight ratio of 0.12:3:1:8;

[0089] (3) Spraying the luminescent layer: Spray luminescent ink onto the dielectric layer and dry it at 80°C for 15 minutes. After the solvent in the luminescent layer has completely evaporated, spray it a second time, remove the mask, and dry it at 80°C for 15 minutes to form the luminescent layer.

[0090] (4) Spraying silver nanowire top electrode: Spraying silver nanowire dispersion onto the light-emitting layer and drying at room temperature to form a transparent top electrode; the silver nanowire dispersion is a dispersion with a concentration of 2 mg / mL prepared by dispersing silver nanowires in a mixture of isopropanol and ethanol with a volume ratio of 1:10.

[0091] (5) Preparation of colored transparent TPU interlayer: Prepare colored transparent TPU material with a thickness of 0.2mm; First, design a pattern of the same size as the white light dielectric layer printed on the fabric on the engraving machine, and cut it to obtain colored transparent TPU for covering the top electrode device obtained in (4); Place the cut colored transparent TPU on the top electrode of the fabric device and align it with the white light dielectric layer.

[0092] (6) TPU encapsulation: A transparent TPU film is hot-pressed onto the top of the fabric device for hot-press encapsulation to obtain a multi-color flexible wearable electroluminescent device. The hot-pressing temperature is set to 160℃ and the hot-pressing time is 20s.

[0093] The transparent TPU film is 0.2mm thick and can be easily cut using digital designs.

[0094] Patterned colored transparent electroluminescent devices such as Figure 4 As shown, the light transmittance is high and the pattern edges are clear. The effect diagram of the electroluminescent device formed by the pattern units is as follows. Figure 5 As shown, the multi-colored electroluminescent T-shirt produced is as follows: Figure 6 As shown, the luminescent pattern displays well on the T-shirt, and uniform luminescence can be observed under indoor lighting conditions.

[0095] This invention first fabricates a flexible wearable electroluminescent device, then uses a lettering machine to print a colored transparent interlayer TPU and an encapsulating TPU, and finally uses a transparent TPU film to press the colored transparent interlayer TPU underneath for thermo-sealing, completing the fabrication of the multi-color flexible wearable electroluminescent device on fabric. The high light transmittance and bending resistance of the colored transparent TPU ensure the stretchability, flexibility, and high transparency of the fabricated device. The invention utilizes a spray coating technology to achieve the layer-by-layer stacking of the device's functional layers on the fabric, a simple and easy-to-operate process with controllable patterns.

[0096] 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.

[0097] The multi-color flexible wearable electroluminescent device and its fabrication method provided by this invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make several improvements and modifications to this invention without departing from the principles of this invention, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A method for fabricating a multi-color flexible wearable electroluminescent device, characterized in that... The method includes the following steps: (1) Fabric planarization, mask fabrication, and patterned bottom electrode preparation: A TPU film is hot-pressed onto the fabric surface to form a flat layer. This flat layer provides a smooth fabric surface, which makes subsequent layers more uniform than coating or printing directly on the fabric. Design luminescent patterns on a computer and cut them using a cutting machine to obtain masks for coating and printing various functional layers; A mask is attached to a TPU film, and a bottom electrode is sprayed onto the TPU film surface not covered by the mask to form a fabric device with a patterned bottom electrode. (2) Spraying white light dielectric layer: Spray white light dielectric ink onto the liquid metal bottom electrode of the fabric device to form a white light dielectric layer on the surface of the bottom electrode. After spraying the white light dielectric ink, dry at 70-90℃ for 8-15 minutes. The whitening dielectric ink is a mixed solution of whitening pigment, nano barium titanate, PVDF-HFP and isophorone in a weight ratio of 0.12:3:1:8; (3) Spraying the luminescent layer: Spray luminescent ink onto the dielectric layer and dry it at 60-100℃ for 15-20 minutes. After the solvent of the luminescent layer has completely evaporated, spray it a second time, peel off the mask, and dry it at 60-100℃ for 15-20 minutes to form the luminescent layer. (4) Spraying silver nanowire top electrode: Spraying silver nanowire dispersion onto the light-emitting layer and drying at room temperature to form a transparent top electrode; (5) Preparation of colored transparent TPU interlayer: Prepare colored transparent TPU material, design a pattern on a cutting machine that is the same size as the white light dielectric layer printed on the fabric, and cut it to obtain colored transparent TPU for covering the top electrode obtained in step (4); The cut colored transparent TPU is placed above the top electrode of the fabric device and aligned with the white light dielectric layer to obtain a colored transparent TPU interlayer located above the top electrode of the silver nanowire. (6) TPU encapsulation: The transparent TPU film is hot-pressed onto the colored transparent TPU interlayer on the top of the fabric device for hot-press encapsulation, resulting in a multi-color flexible wearable electroluminescent device.

2. The preparation method according to claim 1, characterized in that: In step (1), the printing gun used is a graphic inkjet gun with a nozzle diameter of 0.3-1mm and a printing time of 3min-10min; The bottom electrode is selected from one or more of conductive polymer layers, carbon nanotubes, or graphene.

3. The preparation method according to claim 1, characterized in that: In step (5), the colored transparent TPU material is monochromatic or dichromatic and has a thickness of 0.1-0.5 mm.

4. The preparation method according to claim 1, characterized in that: In step (6), the thickness of the transparent TPU film used for encapsulation is 0.2-1 mm.

5. The preparation method according to claim 1, characterized in that: In step (6), the hot pressing temperature is 120-190℃ and the hot pressing time is 15-30s.

6. The preparation method according to claim 1, characterized in that: In step (1), the TPU film thickness is 0.05-0.15 mm, the hot pressing temperature is 140-210℃, and the hot pressing time is 5-20 s; The mask is a removable adhesive label that can be repeatedly pasted and used after the release paper is removed. The liquid metal is one or more of gallium-indium alloy, gallium-tin alloy, gallium-indium-tin alloy, gallium-zinc alloy, gallium-rubidium alloy, or gallium-cesium alloy, or a dispersion of the liquid metal.

7. The preparation method according to claim 1, characterized in that: In step (3), the luminescent ink is a mixed solution of luminescent powder, PVDF-HFP and isophorone, with a weight ratio of 5:2:9 for each component. The luminescent powder is selected from one of the metal sulfide luminescent powders ZnS, CaS, SrS, CaGa2S4 and SrGa2S4. In step (4), the silver nanowire dispersion is a dispersion with a concentration of 2 mg / mL prepared by dispersing silver nanowires in a mixture of isopropanol and ethanol with a volume ratio of 1:

10.

8. A multi-color flexible wearable electroluminescent device prepared by the method according to claim 1, characterized in that, The multi-color flexible wearable electroluminescent device comprises, in sequence, a flexible fabric substrate, a polyurethane film substrate, a bottom electrode, a white light-converting dielectric layer, a light-emitting layer, a silver nanowire top electrode, a colored transparent TPU interlayer, and a TPU encapsulation layer.

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