Polyvinyl alcohol-based transparent composite conductive material capable of being precisely patterned through water-based development

Abstract

The invention belongs to the field of compositions of high-molecular compounds for photoetching patterning, and discloses a water-based developing polyvinyl alcohol-based transparent composite conductive material capable of being precisely patterned. The composite conductive material is prepared from polyvinyl alcohol, a diazonium salt photosensitive material, PEDOT: PSS, ethylene glycol, N-methyldiethanolamine, isophorone diisocyanate, lauryl sodium sulfate and butyl acrylate. According to the composite conductive material with the polyvinyl alcohol and the diazonium salt photosensitive material as the main body, PEDOT: PSS is introduced to serve as conductive filler, ethylene glycol, N-methyldiethanolamine, isophorone diisocyanate, lauryl sodium sulfate and butyl acrylate are introduced to improve the material performance, and the obtained composite conductive material is good in film-forming property, high in conductivity, long in storage time and high in conductivity. And the prepared film has high patterning precision, strong flexibility and good adhesion, and can be prepared into a flexible electrode or a conductive functional layer to be used in a flexible electronic device.

Description

Technical Field

[0001] The invention relates to the field of compositions of polymer compounds used for photolithographic patterning, and in particular to a polyvinyl alcohol-based transparent composite conductive material that can be precisely patterned by water-based development. Background Art

[0002] In the fields of flexible electronics, transparent electrodes, and micro-nano devices, precision patterned conductive films are key to achieving high-performance devices. Among mainstream patterning technologies, laser direct writing suffers from low efficiency and high cost, uncontrollable printing processes, and limited resolution. Mask-guided photolithography patterning technology, however, has attracted significant attention due to its ultra-high resolution and simple steps. However, most photosensitive material systems contain toxic components, resulting in low biocompatibility and environmental friendliness of the photosensitive adhesives they produce, as well as a lack of electrical conductivity. This significantly limits the practical application of patterned films produced using this type of photolithography process.

[0003] Patent CN111171488A discloses a visible light-curable photosensitive resin-based silver conductive material for 3D printing and products prepared therefrom. Based on a polymerizable monomer, a silver precursor, and a photoinitiator, visible light-curable 3D printing is combined with in-situ metal generation to prepare standard specimens, solving the problems of safety and process simplification in scenarios requiring medium conductivity and customized structures. However, the introduction of silver particles in this solution will lead to a decrease in the toughness of the matrix, and a specific visible light-responsive initiator is required, which will leave residual photoinitiator byproducts affecting long-term stability.

[0004] Patent CN102161816A discloses a method for preparing polythiophene-carbon nanotube composite photosensitive film materials using click chemistry. The method successfully solves the dispersion and stability problems of polythiophene / carbon nanotube physical blends through click chemistry, and prepares a composite photosensitive film material. However, the complex process, high cost and potential performance loss limit its industrialization potential.

[0005] Patent CN117511183A discloses a polyurethane-epoxy light-heat dual-curing photosensitive resin composition and its preparation method. The light-heat dual-curing design effectively balances the contradictions in material properties and solves the problems of large curing shrinkage, poor aging resistance, and insufficient toughness of traditional photosensitive materials. However, the addition of metal conductive fillers to epoxy photosensitive materials will cause the curing rate to decrease, and the addition of acidic conductive fillers will cause a significant inhibition effect, which greatly limits the electrical modification of the photosensitive material and limits its actual application scenarios.

[0006] Patent CN109270792A discloses a polyimide / photosensitive epoxy acrylic resin composition with high toughness, high heat resistance, and weak alkaline water developability. By modifying the polyimide / epoxy acrylic resin with an alkoxy oligomer, it successfully solves the dilemma of achieving both flexibility and heat resistance in flexible printed circuit board (FPC) cover films, while also achieving the environmentally friendly goal of weak alkaline water developability. However, the raw material cost is high, the process is complex, and the nitrogen-free initiator may contain residual benzoyl groups, posing a migration risk.

[0007] The paper "Preparation and electrical conductivity of metal andphotosensitive polymer composite film" (Shu Min Hsiao, Wen Tung Cheng. Progress in Organic Coatings, 2019, 132:86-94.) successfully prepared a low-silver-content, highly conductive photosensitive polymer composite film through a photopolymerization-heat treatment synergistic strategy. However, this process requires precise control of the UV light intensity and heat treatment time, otherwise the continuity of the conductive layer will be destroyed, and the material has low applicability on flexible substrates or complex curved electronic devices.

[0008] The paper "Preparation and electrochemical application of an AgNW / graphene / SU-8 composite conductive photoresist" (Mengyi Xu, Qian Wu, Wei Wei, et al. Journal of Applied Polymer Science, 2021, 138:51205.) prepared a composite conductive photoresist with excellent performance by adding graphene nanosheets and Ag nanowires as conductive fillers to epoxy resin. However, the exposed silver nanowires are easily oxidized in humid, acidic or high-temperature environments, causing significant attenuation of conductivity, and graphene agglomerates may block ultraviolet penetration and affect the deep curing of photosensitive resin.

[0009] The paper "Carbon based conductive photoresist" (Nina Hauptman, Maša Žveglič, Marijan Maček, et al. Journal of Materials Science, 2009, 44:4625-4632.) achieved the first "photolithography-conductivity" integration by combining low percolation threshold carbon black with epoxy photoresist, providing a low-cost solution for low- and medium-precision conductive microstructures. However, its conductivity is too dependent on the carbon black concentration, and the light scattering and absorption effects of carbon black will increase the roughness of the photolithography edge, making it impossible to strike a balance between photolithography accuracy and conductivity.

[0010] The paper "In planta nitrate sensor using a photosensitive epoxy bioresin" (Hussam Ibrahim, Shihao Yin, Satyanarayana Moru, et al. ACS AppliedMaterials& Interfaces, 2022, 14:25949–25961.) uses laser high temperature to carbonize the photosensitive resin SU8-GO-VB12 to form a porous conductive network, which significantly improves the conductivity of the photosensitive resin. However, laser pyrolysis can easily lead to structural shrinkage and increased edge roughness. Photolithography and laser pyrolysis require high manufacturing costs and a long time. Pyrolysis requires precise control of laser power and scanning speed. Therefore, the conductivity modification and photolithography of this material are both difficult and inefficient, making it unsuitable for large-scale applications.

[0011] In summary, although the UV curing method has made some progress in the research of preparing patterned conductive films, it still has the following shortcomings: In the film patterning process, screen printing can lead to uneven printing thickness and low patterning accuracy due to slurry diffusion and screen deformation. Transfer printing is prone to pattern residue or partial transfer due to stamp deformation and uneven interface adhesion, and its uncontrollable peel speed limits its high resolution. Although laser direct writing technology has high patterning accuracy, it may damage the flexible substrate during the high-temperature sintering process. Its high cost and low efficiency make it difficult to achieve large-scale application. Mask exposure-guided development patterning technology can achieve high-resolution patterning through simple steps such as UV curing and development.

[0012] Among the photosensitive matrix materials used in UV curing, epoxy resins and acrylate resins both suffer from severe intermolecular entanglement due to their long-chain structures, resulting in extremely high viscosity and difficulty in film formation. Therefore, reactive diluents must be added to reduce intermolecular hydrogen bonding and van der Waals forces. However, reactive diluents have poor biocompatibility and photolysis during the curing process produces toxic byproducts. Functional water-soluble photosensitive polymer matrix materials, such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), and methacryloylated hyaluronic acid (HAMA), contain a large number of hydrophilic groups in their main chains. Water molecules can insert between polymer chains to disassemble molecular entanglements, thus imparting better film-forming properties. PVA is relatively low-cost and is the only water-soluble photosensitive matrix material that can be stored as a dry film. However, PVA requires the use of different photoinitiators to form a complete photocuring system. Among them, sulfonated thioxanthone derivatives have obvious oxygen inhibition phenomenon, cinnamate photoinitiators have high material volume shrinkage rate and are prone to produce odor during photocuring, while diazonium salt photoinitiators can well circumvent these problems, but their performance in various aspects still needs further improvement. Summary of the Invention

[0013] In order to solve the above technical problems, the present invention provides a polyvinyl alcohol-based transparent composite conductive material that can be precisely patterned by water-based development, aiming to effectively improve the problems of poor conductivity, long photocuring time, short storage time, poor adhesion, and low flexibility existing in photosensitive composite conductive materials with PVA as the main body, so that the prepared patterned conductive film can be widely used in flexible electronic devices.

[0014] In order to solve the above problems, the present invention adopts the following technical solutions: The present invention first provides a polyvinyl alcohol-based transparent composite conductive material that can be precisely patterned by water-based development. The components of the composite conductive material are composed of the following components in percentage by mass: 50-65% polyvinyl alcohol (PVA), 5-6.5% diazonium salt photosensitive material, 10-20% PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid) dispersion with a solid content of 2.8%-3%, 0.5-1% ethylene glycol (EG), 0.5-3% N-methyldiethanolamine (MDEA), 5-15% isophorone diisocyanate (IPDI), 0.5-1% sodium dodecyl sulfate (SDS), and 5-15% butyl acrylate (BA).

[0015] Preferably, the mass ratio of polyvinyl alcohol to diazonium salt photosensitive material is 10:1.

[0016] Most preferably, the components of the composite conductive material are composed of: PVA 60%, diazonium salt photosensitive material 6%, PEDOT:PSS dispersion with a solid content of 2.8% to 3% 10%, EG 1%, MDEA 2%, IPDI 10%, SDS 1%, and BA 10%.

[0017] The photosensitive composite conductive material based on PVA provided by the present invention uses a diazonium salt photosensitive material as a photoinitiator. Because both the PVA matrix and the decomposition products of the diazonium salt photosensitive material are insulating, the resulting patterned film lacks conductivity and cannot be used as a conductive functional layer in electrodes or devices. Common conductive fillers such as graphene, carbon black, and carbon nanotubes, when incorporated into the photosensitive adhesive, can severely affect its transparency, preventing crosslinking of the underlying photosensitive material during photocuring and leading to the inability to achieve precise patterning. To solve this problem, the present invention introduces PEDOT:PSS as a conductive filler and uses ethylene glycol and N-methyldiethanolamine to improve the performance of PEDOT:PSS. PEDOT:PSS forms a continuous conductive network in the PVA matrix. The hydroxyl groups of PVA form hydrogen bonds with the sulfonic acid groups of PSS, inducing the PEDOT chain to change from a curled conformation to an extended conformation, reducing the carrier migration barrier and making the insulating PVA conductive. The introduced ethylene glycol and N-methyldiethanolamine can penetrate into the PEDOT:PSS to further extend the PEDOT chain, thereby enhancing the conductivity of the PVA. The continuity of the conjugated network can further enhance the conductivity of PEDOT:PSS. PVA, as the main component of the composite material, has high transparency, and PEDOT:PSS is also a transparent conductive material. Therefore, the composite material has both good transparency and conductivity.

[0018] In PEDOT:PSS, the thiophene ring in the poly(3,4-ethylenedioxythiophene) (PEDOT) chain is Electronic transition absorbs ultraviolet light, and its absorption peak is usually located at 300-350nm. The benzene ring and sulfonic acid group in polystyrene sulfonic acid (PSS) also absorb ultraviolet light. These factors make PEDOT:PSS compete with photosensitive materials for ultraviolet light, affecting the effective excitation of diazonium salt photosensitive materials, thereby reducing the efficiency of ultraviolet light curing, resulting in the need to greatly extend the photocuring time or significantly increase the power of the equipment to complete the patterning of the film. However, long-term or high-power ultraviolet light irradiation can easily cause the edges of the pattern to be mistakenly cured during film patterning, affecting the accuracy of the pattern. To solve this problem, the ethylene glycol added to the system of the present invention will weaken the electrostatic interaction between PEDOT and PSS, promote the dissociation of PSS chains, and reduce the Coulomb repulsion between PEDOT chains, causing it to transform from a benzene conformation to a quinone conformation, reducing the conductivity while further enhancing the conductivity. The electron transition reduces the absorption intensity of ultraviolet light, thereby reducing the interference of PEDOT:PSS on the ultraviolet curing reaction of PVA / diazonium salt photosensitive material photosensitive adhesive, making the final patterned film have higher precision.

[0019] Composite conductive materials based on PVA / diazonium salt photosensitive material / PEDOT:PSS, after adding the conductive filler PEDOT:PSS, the PEDOT:PSS dispersion is strongly acidic, which greatly accelerates the decomposition of the diazonium salt photosensitive material, causing the diazonium salt photosensitive material to quickly fail, resulting in an extremely short storage time of the composite conductive material. The use of common alkaline materials such as sodium bicarbonate and disodium hydrogen phosphate will introduce small-sized inorganic cations that migrate to PSS at a high speed. - Nearby and strongly attracts PSS - To address this issue, the present invention adds N-methyldiethanolamine to the system. Its amino group can neutralize the sulfonic acid group of PSS, reducing the overall acidity of the solution. This can prevent the rapid decomposition of the diazonium salt photosensitive material, extending the storage time of the photosensitive composite conductive material. It can also selectively remove free PSS chains, further reducing the absorption of ultraviolet light by PEDOT:PSS and improving the efficiency of the material's photocuring reaction.

[0020] Composite conductive material systems based on PVA lack high-viscosity components, resulting in low adhesion and peel strength for the resulting patterned conductive films. This makes it impossible to form a stable interfacial bond with substrates or other functional layers when used to prepare flexible devices, significantly limiting the film's potential applications. To address this issue, the present invention incorporates isophorone diisocyanate and butyl acrylate into the system to enhance the material's viscosity. The isocyanate groups of isophorone diisocyanate react with the hydroxyl groups of PVA to form carbamate bonds and a three-dimensional crosslinked network. The carbamate bonds enhance the van der Waals forces between the material and various substrates. Adding a small amount of sodium lauryl sulfate during the process ensures uniform dispersion of IPDI. The butyl acrylate groups can also form hydrogen bonds or generate van der Waals forces with some substrates, further enhancing the overall viscosity of the material.

[0021] Based on the composite conductive material of PVA / diazonium salt photosensitive material / PEDOT:PSS, the hydroxyl groups of PVA form a high-density hydrogen bond network, and the high crystallinity causes the rigid molecular chains to be closely arranged, and the introduced conductive filler PEDOT:PSS contains rigid molecular chains PEDOT, which will limit the movement of other molecular chains, causing the film prepared after the composite conductive material is dried to generally exhibit high rigidity. After being combined with a flexible substrate or functional layer, due to the large difference in elastic modulus and the low elongation at break, it is easy to generate internal stress during mechanical bending, causing the film to crack or separate from the flexible layer. To solve this problem, the butyl acrylate added to the system of the present invention can further improve the overall flexibility of the composite conductive material. The butyl ester group of BA is a flexible long chain with low polarity and low steric hindrance. After addition, it can be inserted between the PVA molecular chains, weakening the hydrogen bond force, offsetting the rigidity of the IPDI-PVA network, significantly enhancing the mobility of the molecular chains, and thus improving the overall flexibility of the material.

[0022] The present invention further provides a method for preparing the polyvinyl alcohol-based transparent composite conductive material capable of precise patterning by water-based development, comprising the following steps: Step 1, polyvinyl alcohol and water are mixed in a mass ratio of 1:5-15, and stirred at 50°C-60°C for 2-3 hours to obtain a polyvinyl alcohol aqueous solution; a diazonium salt photosensitive material is mixed with water in a mass ratio of 1:15-30, and stirred at room temperature for 20-40 minutes to obtain a diazonium salt aqueous solution; the diazonium salt aqueous solution is added to the polyvinyl alcohol aqueous solution, and stirred at room temperature for 1-3 hours to obtain solution A; Step 2: Add ethylene glycol and N-methyldiethanolamine to a PEDOT:PSS dispersion having a solid content of 2.8% to 3%, stir at room temperature for 1 to 2 hours, and then place under vacuum for 1 to 3 hours to obtain a solution B; Step 3, adding solution B to solution A and stirring at room temperature for 1 to 2 hours to obtain solution C; Step 4: adding isophorone diisocyanate and sodium lauryl sulfate to solution C, and stirring at 25° C. to 50° C. for 1 to 2 hours to obtain solution D; Step 5: Add butyl acrylate to solution D and stir at room temperature for 1 to 2 hours to obtain a polyvinyl alcohol-based transparent composite conductive material.

[0023] The method for preparing a patterned conductive film using the polyvinyl alcohol-based transparent composite conductive material of the present invention is as follows: pouring the polyvinyl alcohol-based transparent composite conductive material on a plasma-treated substrate material (including but not limited to glass, silicon wafer, polyimide PI, polyethylene PE, polyethylene terephthalate PET, etc.), then fixing it on a spin coater, pre-spinning it at a speed of 1000 rpm for 10-15 seconds to spread the material, then main spinning it at a speed of 1500 rpm for 15-20 seconds to spread the material evenly, and then placing it in an 80°C constant temperature oven to dry for 1-2 hours to volatilize the solvent to form a uniform film layer, covering the film layer with a film having a flexible electrode pattern, and irradiating it with a 20W LED ultraviolet lamp for 1-3 minutes, and then rinsing it with water for 3-5 minutes to obtain a film layer with a corresponding pattern adhered to the substrate, and finally using a peel tester or a tensile press to separate the film layer and the substrate to obtain a film or flexible electrode with a corresponding pattern.

[0024] Compared with the prior art, the beneficial effects of the present invention are embodied in: 1. The mask exposure-guided development patterning technology proposed in the present invention breaks through the resolution limit of traditional wet printing process patterning through UV curing of the mask after drying and film formation, and then realizes ultra-precise controllable pattern transfer through development. This series of simple steps not only circumvents the problems of low efficiency and expensive equipment of laser direct writing technology, but also realizes high-precision patterning of thin films that is far superior to screen printing and transfer printing. It also relies on the high stability of the mask and the natural advantages of small wavelength and high resolution of ultraviolet light to achieve high consistency and yield of patterned thin films.

[0025] 2. The composite conductive material containing PVA / diazonium salt photosensitive material proposed in the present invention allows water molecules to intervene through the hydrophilic groups in PVA, thereby achieving natural disentanglement and obtaining uniform film-forming properties without the need for active diluents, thus avoiding the biocompatibility issues caused by active diluents. The PVA-based photosensitive material can be stored in the form of a dry film, solving the problems of on-site coating and difficult thickness control of hydrogel materials. The diazonium salt photosensitive material is adapted to PVA as the preferred photoinitiator, achieving a low curing shrinkage rate far superior to other functional water-soluble photosensitive polymer material systems at a lower cost, thereby avoiding the oxygen inhibition problem of most photoinitiators.

[0026] 3. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in the present invention makes the prepared patterned film have conductive properties by adding PEDOT:PSS. Due to the inherent good light transmittance of PEDOT:PSS, the transparency of the film is guaranteed while achieving adjustable conductivity, thereby being compatible with the photolithographic patterning function of the composite conductive material.

[0027] 4. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in the present invention, after adding ethylene glycol, will weaken the electrostatic interaction between PEDOT and PSS, promote the dissociation of PSS chains, and reduce the Coulomb repulsion between PEDOT chains, so that it transforms from a benzene conformation to a quinone conformation, forming a continuous conjugated network while further enhancing the conductivity, thereby enhancing the Stacking causes the energy absorption peak of the material to red-shift to the visible light region, reducing the absorption intensity of ultraviolet light, thereby reducing the negative impact of the introduction of PEDOT:PSS conductive filler on the photocuring process and improving the efficiency of ultraviolet curing.

[0028] 5. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in the present invention can selectively dissolve and remove free insulating PSS chains by adding N-methyldiethanolamine, under the premise that ethylene glycol weakens the electrostatic interaction between PEDOT and PSS, thereby further reducing the absorption of ultraviolet light by PEDOT:PSS. The amino group of N-methyldiethanolamine can react with the sulfonic acid group of PSS to neutralize the solution, thereby reducing the acidity of the solution and reasonably solving the problem of decomposition of the diazonium salt photosensitive material caused by the acidic environment. N-methyldiethanolamine is an organic weak base and has less effect on the conductivity of PEDOT:PSS than inorganic bases.

[0029] 6. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in the present invention enhances the adhesion of the material by adding isophorone diisocyanate (IPDI). The isocyanate group of IPDI can react with the hydroxyl group of PVA to form carbamate bonds and form a three-dimensional cross-linked network, wherein the carbamate bonds can form hydrogen bonds or generate van der Waals forces with various substrate materials, so that the prepared film has good adhesion. When used to prepare flexible devices, it can form a stable interface bond with the substrate or other functional layers, so that it can maintain good stability in different application scenarios.

[0030] 7. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in the present invention enhances the flexibility of the material by introducing butyl acrylate (BA). Since the butyl ester group of BA can also form hydrogen bonds or generate van der Waals forces with most substrate materials, it can further synergize with IPDI to enhance the overall viscosity of the material. The butyl ester group of BA is a flexible chain with low polarity and low steric hindrance, which can be inserted between PVA molecular chains to weaken the hydrogen bonding force and effectively reduce its hydrogen bond density. At the same time, BA can combine with PEDOT through van der Waals forces, and its hydrophobic chain will combine with the sulfonic acid group of PSS through dipole action. In addition, under the influence of PEDOT:PSS, the acryloyl group of BA will undergo esterification and cross-linking with the hydroxyl group of PVA to form a network structure. Therefore, the introduction of BA not only reduces the interference between PVA chains, but also promotes the interfacial bonding between PVA and PEDOT:PSS, ultimately significantly improving the overall flexibility and viscosity of the material, so that the patterned conductive film prepared from the composite conductive material has both strong flexibility and good adhesion, reducing the generation of cracks during mechanical bending, and maintaining good interface stability when used in flexible devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the reaction mechanism of UV curing of PVA and diazonium salt photosensitive material in an embodiment of the present invention.

[0032] Figure 2 Schematic diagram of the reaction mechanism of PEDOT:PSS and ethylene glycol in an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the microscopic reaction after PEDOT:PSS, IPDI, and BA are sequentially added to PVA in an embodiment of the present invention.

[0034] Figure 4 This is a graph showing how the transmittance of a transparent conductive film prepared from a composite conductive material with different PEDOT:PSS dosages and the resistance of a flexible electrode change with the PEDOT:PSS dosage in an embodiment of the present invention.

[0035] Figure 5 This is a graph showing the change in resistance value of the flexible electrode prepared from the composite conductive material with different EG dosages according to the embodiment of the present invention.

[0036] Figure 6 This is a graph showing the change in the size deviation rate of the film prepared from the final composite conductive material in an embodiment of the present invention as the mask size decreases.

[0037] Figure 7 3 is a comparison chart of the change in the photocuring activity retention rate of the composite conductive material containing or not containing the MDEA component over time in the embodiment of the present invention.

[0038] Figure 8 This is a comparison chart of the peel strengths of flexible films of the same size prepared from solution C, solution D, and the final composite conductive material on different substrates in an embodiment of the present invention, measured using a 180° peel tester.

[0039] Figure 9 Graph showing the stress-strain curve of the flexible film prepared from the solution D and the final composite conductive material in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following embodiments are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific operating procedures. However, the protection scope of the present invention is not limited to the following embodiments.

[0041] Example 1 The polyvinyl alcohol-based transparent composite conductive material provided in this embodiment, which can be precisely patterned by water-based development, comprises the following components by mass percentage: PVA 60%, diazonium salt photosensitive material (whose structural formula is as follows: Figure 1 The following preparation steps are used: Step 1: 6 g of PVA was mixed with 60 g of water, and the mixture was stirred at 50° C. for 3 hours to obtain a PVA aqueous solution; 0.6 g of a diazonium salt photosensitive material was mixed with 12 g of water, and the mixture was stirred at room temperature for 30 minutes to obtain a diazonium salt aqueous solution; the diazonium salt aqueous solution was added to a polyvinyl alcohol aqueous solution, and the mixture was stirred at room temperature for 2 hours to obtain a solution A.

[0042] Step 2: Add 0.1 g of ethylene glycol and 0.2 g of N-methyldiethanolamine to 1 g of a PEDOT:PSS dispersion with a solid content of 2.8% to 3%, then stir at room temperature for 2 hours and place under vacuum for 2 hours to obtain solution B.

[0043] Step 3: Add solution B to solution A and stir at room temperature for 2 hours to obtain solution C.

[0044] Step 4: Add 1 g of IPDI and 0.1 g of SDS to solution C, and stir at 50° C. for 2 hours to obtain solution D.

[0045] Step 5: Add 1 g of butyl acrylate to solution D and stir at room temperature for 2 hours to obtain the final polyvinyl alcohol-based transparent composite conductive material.

[0046] The prepared composite conductive materials were poured onto plasma-treated substrates (glass, silicon wafer, polyimide (PI), polyethylene (PE), and polyethylene terephthalate (PET). The substrates were then mounted on a spin coater and pre-spun at 1000 rpm for 10 seconds to spread the material. The spin coaters were then spun at 1500 rpm for 15 seconds to evenly spread the material. The coatings were then dried in an incubator at 80°C for 1 hour to evaporate the solvent and form a uniform film. A film sheet with a flexible electrode pattern was placed over the film layer and irradiated with a 20W LED UV lamp for 2 minutes. The film layer was then rinsed with water for 3 minutes to obtain a film layer with the corresponding pattern adhered to the substrate. Finally, the film layer was separated from the substrate using a 180° peel tester to obtain a film or flexible electrode with the corresponding pattern. A dot-line film ruler was placed over the film layer to test the development accuracy of the composite conductive material.

[0047] Figure 1 This figure illustrates the reaction mechanism for UV curing of PVA and a diazonium salt photosensitive material in an embodiment of the present invention. As shown, when the composite conductive material based on PVA and a diazonium salt photosensitive material is exposed to ultraviolet light, the diazonium molecules rapidly decompose to produce reactive molecular groups, which further cross-link with the hydroxyl groups of the PVA to produce a water-insoluble substance.

[0048] Figure 2 Schematic diagram of the reaction mechanism of PEDOT:PSS and ethylene glycol in the embodiment of the present invention. of Form hydrogen bonds, weakening and electrostatic interaction, and hydrogen bonding The group hydration layer is destroyed, the local dielectric constant is reduced, and the conductivity is increased; hydrogen bonds also make Intrachain conjugation is enhanced, The accumulation of N-methyldiethanolamine can red-shift the energy absorption peak from the ultraviolet light segment to the visible light segment; N-methyldiethanolamine can remove some of the free By reducing the scattering cross section, lowering the apparent absorbance, and reducing the number of benzene rings in the system, proton transfer induces acid-base neutralization, and the synergistic effect of ion pair recombination reduces the acidity of the PEDOT:PSS solution. Therefore, the addition of ethylene glycol and N-methyldiethanolamine has the following advantages: improving the overall conductivity of the material; reducing the UV absorbance of PEDOT:PSS, thereby reducing its interference with the photocuring reaction; and extending the storage life of the material.

[0049] Figure 3This is a schematic diagram of the microscopic reaction after EG-modified PEDOT:PSS, IPDI, and BA are sequentially added to PVA in an embodiment of the present invention. As can be seen from the figure, PVA first undergoes multi-level physical assembly with EG-modified PEDOT:PSS through hydrogen bonding and phase separation. Then the hydroxyl groups of PVA react with the isocyanate groups of IPDI to form carbamate bonds. The carbamate bonds can form hydrogen bonds with various substrate materials or generate van der Waals forces to form a stable interface bond. Finally, BA will bind to PEDOT through van der Waals forces, and its hydrophobic chain will bind to the sulfonic acid group of PSS through dipole action. In addition, the acryloyl group of BA will undergo an esterification reaction with the hydroxyl groups of PVA to form a copolymer. The adhesion and flexibility of the final material are significantly improved.

[0050] To verify the effect of PEDOT:PSS dosage on conductivity and transmittance, the amounts of all other materials except PEDOT:PSS in the above preparation steps remained unchanged, and the amount of PEDOT:PSS was gradually increased from 0g to 2g in increments of 0.25g. Using plasma-treated polyimide (PI) as a substrate, the composite conductive materials with varying PEDOT:PSS dosages were fabricated into transparent conductive films. These films were then patterned using masks to form flexible electrodes of the same size. Figure 4 The transmittance of transparent conductive films and the resistance of flexible electrodes prepared from composite conductive materials with different PEDOT:PSS dosages are plotted as a function of PEDOT:PSS dosage. As can be seen from the figure, the transmittance of the film and the resistance of the flexible electrode will show a downward trend with the increase of PEDOT:PSS dosage, but when the dosage increases to 1g, the resistance value will no longer show a significant decrease, and the transmittance will show a rapid downward trend.

[0051] To verify the effect of ethylene glycol dosage on conductivity, the amounts of all other materials except ethylene glycol in the above preparation steps remained unchanged, while the amount of EG was increased stepwise from 0g to 0.2g in increments of 0.025g. Using plasma-treated polyimide (PI) as a substrate, the composite conductive materials with different EG dosages were fabricated into patterned flexible electrodes of the same size. Figure 5 The resistance value of the flexible electrode prepared from the composite conductive material with different EG dosage changes with the EG dosage. It can be seen that as the ethylene glycol dosage in the system increases, the resistance of the prepared flexible electrode will decrease. When the ethylene glycol dosage increases to 0.1g, the resistance value no longer decreases significantly with the increase of ethylene glycol dosage.

[0052] Figure 6The graph shows the change in the size deviation rate of the film prepared from the composite conductive material in the embodiment of the present invention as the mask size decreases. The mask plate uses a film. The size deviation rate is defined as: the absolute value of the difference between the mask size and the actual pattern size at the corresponding position as a percentage of the mask size. It can be seen that as the mask size decreases, the size deviation rate will slowly increase, but 100 The size deviation rate of the above mask pattern sizes is less than 1%.

[0053] To verify the effect of MDEA on the photocuring activity retention rate of composite conductive materials, a control group without MDEA was prepared. Its components, by mass percentage, were: PVA 62%, diazonium salt photosensitive material 6%, PEDOT:PSS dispersion with a solid content of 2.8% to 3% 10%, EG 1%, IPDI 10%, SDS 1%, and BA 10%. The comparison of the photocuring activity retention rate of composite conductive materials with and without MDEA components over time is shown in the figure below. Figure 7 As shown in the figure, it can be seen that the addition of 2% by mass of MEDA can significantly improve the photocuring activity retention rate of the composite conductive material. The photocuring activity retention rate is defined as the percentage of the effective reaction amount after storage to the initial effective reaction amount, where the effective reaction amount is measured by UV-Vis spectroscopy to determine the photosensitive material of the diazonium salt. The characteristic absorption peak of the group at a wavelength of 365 nm was directly quantified.

[0054] Figure 8 This chart compares the peel strengths of flexible films of identical dimensions prepared using Solution C, Solution D, and the final composite conductive material according to the present invention, measured using a 180° peel tester, on different substrates. As can be seen, the peel strength of the conductive film prepared using Solution D is higher than that of the conductive film prepared using Solution C, and the peel strength of the conductive film prepared using the final polyvinyl alcohol-based transparent composite conductive material is also higher than that of the conductive film prepared using Solution D.

[0055] Figure 9 These are stress-strain curves for flexible films prepared from Solution D and the final composite conductive material in this example. When the elongation of the flexible film prepared from Solution D reaches 34%, the stress peaks at approximately 29 MPa (corresponding to the elongation at break). At this point, the film breaks instantly, and the stress decreases to zero in a very short time. When the elongation of the flexible film prepared from the final composite conductive material reaches 110%, the stress peaks at approximately 23 MPa (corresponding to the elongation at break), followed by a gradual decrease in stress, demonstrating that the material maintains strong toughness within a deformation range of 110%.

[0056] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A polyvinyl alcohol-based transparent composite conductive material capable of precise patterning by water-based development, characterized in that: The components of the composite conductive material are composed of 50-65% polyvinyl alcohol, 5-6.5% diazonium salt photosensitive material, 10-20% PEDOT:PSS dispersion with a solid content of 2.8%-3%, 0.5-1% ethylene glycol, 0.5-3% N-methyldiethanolamine, 5-15% isophorone diisocyanate, 0.5-1% sodium lauryl sulfate, and 5-15% butyl acrylate.

2. The polyvinyl alcohol-based transparent composite conductive material capable of being precisely patterned by water-based development according to claim 1, characterized in that: The mass ratio of polyvinyl alcohol to diazonium salt photosensitive material is 10:

1.

3. The polyvinyl alcohol-based transparent composite conductive material capable of precise patterning by water-based development according to claim 1 or 2, characterized in that: The components of the composite conductive material are composed of 60% polyvinyl alcohol, 6% diazonium salt photosensitive material, 10% PEDOT:PSS dispersion with a solid content of 2.8% to 3%, 1% ethylene glycol, 2% N-methyldiethanolamine, 10% isophorone diisocyanate, 1% sodium lauryl sulfate, and 10% butyl acrylate.

4. A method for preparing a polyvinyl alcohol-based transparent composite conductive material capable of precise patterning by water-based development according to any one of claims 1 to 3, characterized in that: The steps include: Step 1, polyvinyl alcohol and water are mixed in a mass ratio of 1:5-15, and stirred at 50°C-60°C for 2-3 hours to obtain a polyvinyl alcohol aqueous solution; a diazonium salt photosensitive material is mixed with water in a mass ratio of 1:15-30, and stirred at room temperature for 20-40 minutes to obtain a diazonium salt aqueous solution; the diazonium salt aqueous solution is added to the polyvinyl alcohol aqueous solution, and stirred at room temperature for 1-3 hours to obtain solution A; Step 2: Add ethylene glycol and N-methyldiethanolamine to a PEDOT:PSS dispersion having a solid content of 2.8% to 3%, stir at room temperature for 1 to 2 hours, and then place under vacuum for 1 to 3 hours to obtain a solution B; Step 3, adding solution B to solution A and stirring at room temperature for 1 to 2 hours to obtain solution C; Step 4: adding isophorone diisocyanate and sodium lauryl sulfate to solution C, and stirring at 25° C. to 50° C. for 1 to 2 hours to obtain solution D; Step 5: Add butyl acrylate to solution D and stir at room temperature for 1 to 2 hours to obtain a polyvinyl alcohol-based transparent composite conductive material.

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