Water-based developing polyvinyl alcohol-based transparent composite conductive materials with precise patterning

Abstract

This invention belongs to the field of compositions of polymeric compounds for photolithographic patterning, and discloses a water-based, precisely patternable polyvinyl alcohol-based transparent composite conductive material. This composite conductive material is prepared from polyvinyl alcohol, a diazonium salt photosensitive material, PEDOT:PSS, ethylene glycol, N-methyldiethanolamine, isophorone diisocyanate, sodium dodecyl sulfate, and butyl acrylate. In the composite conductive material provided by this invention, which is mainly composed of polyvinyl alcohol and a diazonium salt photosensitive material, PEDOT:PSS is introduced as a conductive filler, and ethylene glycol, N-methyldiethanolamine, isophorone diisocyanate, sodium dodecyl sulfate, and butyl acrylate are introduced to improve the material properties. The resulting composite conductive material has good film-forming properties, high conductivity, and long storage time. Furthermore, the thin films prepared from it have high patterning precision, strong flexibility, and good adhesion, and can be used to prepare flexible electrodes or conductive functional layers for use in flexible electronic devices.

Description

Technical Field

[0001] This invention relates to the field of compositions of polymeric compounds for photolithographic patterning, and more particularly to water-based, developable, precisely patternable polyvinyl alcohol-based transparent composite conductive materials. Background Technology

[0002] In the fields of flexible electronics, transparent electrodes, and micro / nano devices, precision-patterned conductive thin films are crucial for realizing high-performance devices. Among the mainstream patterning technologies, laser direct writing suffers from low efficiency and high cost, uncontrollable printing processes, and limited resolution. In contrast, photolithography patterning technology, guided by mask exposure, has attracted considerable attention due to its ultra-high resolution and simple procedures. However, most photosensitive materials contain toxic components, resulting in photosensitive adhesives with low biocompatibility and environmental friendliness, and they also lack conductivity, greatly limiting the practical application of patterned thin films prepared by this type of photolithography process.

[0003] Patent CN111171488A discloses a visible light curable photosensitive resin-based silver conductive material for 3D printing and the products prepared therefrom. Based on polymerizable monomers, silver precursors and photoinitiators, it combines visible light curable 3D printing with in-situ metal generation and prepares standard specimens. This solves the safety and process simplification problems in scenarios requiring moderate conductivity and customized structures. However, the introduction of silver particles in this solution leads to a decrease in matrix toughness and requires a specific visible light responsive initiator, which leaves residual photoinitiator byproducts that affect long-term stability.

[0004] The method for preparing polythiophene-carbon nanotube composite photosensitive film material disclosed in patent CN102161816A by click chemistry successfully solved the dispersion and stability problems of polythiophene / carbon nanotube physical blends and prepared 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 photo-thermal dual-curing photosensitive resin composition and its preparation method. The photo-thermal 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 leads to a decrease in curing rate, and the addition of acidic conductive fillers leads to a significant polymerization inhibition effect. This greatly limits the electrical modification of the photosensitive material and restricts its practical application scenarios.

[0006] Patent CN109270792A discloses a polyimide / photosensitive epoxy acrylate resin composition with high toughness, high heat resistance, and weak alkaline water development capability. By modifying the polyimide / epoxy acrylate resin with alkoxy oligomers, it successfully solves the problem of the incompatibility between flexibility and heat resistance in flexible printed circuit board (FPC) cover films and achieves the environmental goal of weak alkaline water development. However, the raw material cost is high, the process is complex, and the lack of nitrogen initiator may leave benzoyl groups, posing a migration risk.

[0007] The paper “Preparation and electrical conductivity of metal and photosensitive polymer composite film” (Shu Min Hsiao, Wen Tung Cheng. Progress in Organic Coatings, 2019, 132:86-94.) successfully prepared a low-silver-content, high-conductivity photosensitive polymer composite film through a photopolymerization-thermal treatment synergistic strategy. However, this process requires precise control of the intensity of UV light and the time of thermal treatment, 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 high-performance composite conductive photoresist 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, which significantly reduces conductivity. In addition, graphene aggregates may block ultraviolet light 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 integration of photolithography and conductivity by combining low-percolation-threshold carbon black and epoxy photoresist, providing a low-cost solution for medium- and low-precision conductive microstructures. However, its conductivity is too dependent on the concentration of carbon black, and the light scattering and absorption effects of carbon black will lead to an increase in the roughness of the photolithography edge, making it impossible to balance 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 Applied Materials & Interfaces, 2022, 14:25949–25961.) describes how laser pyrolysis carbonizes the photosensitive resin SU8-GO-VB12 to form a porous conductive network, significantly improving the conductivity of the photosensitive resin. However, laser pyrolysis easily leads to structural shrinkage and increased edge roughness. Photolithography and laser pyrolysis require high manufacturing costs and long time, and 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 thin films, it still has the following shortcomings:

[0012] In the patterning process of thin films: screen printing technology suffers from uneven printing thickness and low patterning accuracy due to paste diffusion and screen deformation; transfer printing technology is prone to pattern residue or partial transfer due to stamp deformation and uneven interface adhesion, and its uncontrollable peeling speed limits its high-resolution patterning; while laser direct writing technology has high patterning accuracy, it may damage the flexible substrate during high-temperature sintering, and its expensive system 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 ultraviolet curing and development.

[0013] Among the photosensitive matrix materials used in UV curing, epoxy resins and acrylate resins 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 can produce toxic byproducts during curing through photodegradation. Functional water-soluble photosensitive polymer matrix materials, such as polyvinyl alcohol (PVA), polyethylene glycol (PEG), and methacryloyl hyaluronic acid (HAMA), have a large number of hydrophilic groups in their main chains. Water molecules can insert into the polymer chains to break up molecular entanglement, thus giving them better film-forming properties. PVA is the lowest cost and the only water-soluble photosensitive matrix material that can be stored in dry film form; however, PVA requires different photoinitiators to form a complete photocuring system. Among them, sulfonated thioxanthone derivatives exhibit significant oxygen inhibition polymerization, while cinnamic acid ester photoinitiators show high material volume shrinkage and are prone to producing odors during photocuring. Diazo salt photoinitiators can effectively avoid these problems, but their various properties still need further modification. Summary of the Invention

[0014] To address the aforementioned technical problems, this invention provides a water-based, precisely patternable polyvinyl alcohol-based transparent composite conductive material. This material aims to effectively improve upon the issues of poor conductivity, long curing time, short storage time, poor adhesion, and low flexibility inherent in PVA-based photosensitive composite conductive materials, enabling the prepared patterned conductive film to be widely used in flexible electronic devices.

[0015] To solve the above problems, the present invention adopts the following technical solution:

[0016] This invention first provides a water-based, developable, precisely patternable polyvinyl alcohol-based transparent composite conductive material. The components of the composite conductive material are composed of the following components by mass percentage: 50-65% polyvinyl alcohol (PVA), 5-6.5% diazonium salt photosensitive material, 10-20% PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic 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).

[0017] Preferably, the mass ratio of polyvinyl alcohol to diazonium salt photosensitive material is 10:1.

[0018] Most preferably, the components of the composite conductive material are composed of the following by mass percentage: PVA 60%, diazonium salt photosensitive material 6%, PEDOT:PSS dispersion with a solid content of 2.8%~3% 10%, EG 1%, MDEA 2%, IPDI 10%, SDS 1%, and BA 10%.

[0019] The photosensitive composite conductive material based on PVA provided by this invention uses diazonium salt photosensitive material as a photoinitiator. In photosensitive adhesives based on PVA / diazonium salt photosensitive materials, the decomposition products of both the PVA matrix and the diazonium salt photosensitive material are insulating, thus the prepared patterned film lacks conductivity and cannot be used as a conductive functional layer for electrodes or devices. Furthermore, common conductive fillers such as graphene, carbon black, and carbon nanotubes, when incorporated into the photosensitive adhesive, severely affect its transparency, preventing the underlying photosensitive material from cross-linking during photocuring and thus hindering precise patterning. To address this issue, this 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 within the PVA matrix. Hydrogen bonds are formed between the hydroxyl groups of PVA and the sulfonic acid groups of PSS, inducing the PEDOT chains to change from a coiled to an extended conformation, lowering the carrier migration barrier and enabling the insulating PVA to become conductive. The introduced ethylene glycol and N-methyldiethanolamine can penetrate into PEDOT:PSS, further extending the PEDOT chains and enhancing their conductivity. The continuity of the conjugated network can further enhance the conductivity of PEDOT:PSS; and PVA, as the main component of the composite material, has high transparency, while PEDOT:PSS is also a transparent conductive material. Therefore, the composite material has both good transparency and conductivity.

[0020] In PEDOT:PSS, due to the thiophene ring in the poly(3,4-ethylenedioxythiophene) (PEDOT) chain passing through... Electron transitions absorb ultraviolet light, with absorption peaks typically located at 300-350 nm. The benzene rings and sulfonic acid groups in polystyrene sulfonic acid (PSS) also absorb ultraviolet light. These factors cause PEDOT:PSS to compete with photosensitive materials for ultraviolet light, affecting the effective excitation of the diazonium salt photosensitive material and thus reducing the efficiency of ultraviolet curing. This necessitates significantly extended curing times or drastically increased equipment power to complete film patterning. However, prolonged or high-power ultraviolet irradiation can easily cause the edges of the pattern to be incorrectly cured during film patterning, affecting the pattern accuracy. To address this issue, this invention incorporates ethylene glycol into the system. This weakens the electrostatic interaction between PEDOT and PSS, promotes the dissociation of PSS chains, and reduces the Coulombic repulsion between PEDOT chains, causing it to transform from a benzene conformation to a quinone conformation. This further enhances conductivity while reducing... Electronic transitions reduce the absorption intensity of ultraviolet light, thereby reducing the interference of PEDOT:PSS on the ultraviolet curing reaction of PVA / diazo salt photosensitive material photosensitive adhesive, resulting in higher precision in the final patterned film.

[0021] The composite conductive material based on PVA / diazonium salt photosensitive material / PEDOT:PSS suffers from a very short storage time after the addition of PEDOT:PSS, as the PEDOT:PSS dispersion is highly acidic. This significantly accelerates the decomposition of the diazonium salt photosensitive material, leading to its rapid failure and the resulting rapid decomposition of the composite conductive material. Furthermore, the use of common alkaline materials such as sodium bicarbonate and disodium hydrogen phosphate introduces small-sized inorganic cations that migrate rapidly to the PSS. - Nearby and strongly attract PSS - The fragmentation of the conductive network due to the presence of sulfonic acid chains significantly reduces its conductivity. To address this issue, this invention incorporates N-methyldiethanolamine into the system. Its amino groups can neutralize the sulfonic acid groups of PSS, reducing the overall acidity of the solution and preventing the rapid decomposition of the diazonium salt photosensitive material. This extends the storage time of the photosensitive composite conductive material. Furthermore, it can selectively remove free PSS chains, further reducing the absorption of ultraviolet light by PEDOT:PSS and improving the efficiency of the photocuring reaction.

[0022] The PVA-based composite conductive material system lacks high-viscosity components, resulting in patterned conductive films with low adhesion and peel strength significantly lower than other photosensitive materials. This prevents stable interfacial bonding with substrates or other functional layers when used in flexible device fabrication, severely limiting the film's application scope. To address this issue, this invention incorporates isophorone diisocyanate and butyl acrylate into the system to enhance adhesion. The isocyanate groups of isophorone diisocyanate react with the hydroxyl groups of PVA to form urethane bonds and a three-dimensional cross-linked network. These urethane bonds strengthen the van der Waals forces between the material and various substrates. The addition of a small amount of sodium dodecyl sulfate ensures uniform dispersion of IPDI. The butyl groups of butyl acrylate can also form hydrogen bonds or van der Waals forces with some substrates, further improving the overall adhesion of the material.

[0023] The composite conductive material based on PVA / diazonium salt photosensitive material / PEDOT:PSS suffers from high rigidity in the dried film. This is due to the high-density hydrogen bond network formed by the hydroxyl groups of PVA, the tightly packed rigid molecular chains, and the rigid PEDOT molecular chains in the introduced conductive filler PEDOT:PSS, which restrict the movement of other molecular chains. Consequently, the film prepared from the dried composite conductive material typically exhibits high rigidity. When bonded to a flexible substrate or functional layer, the significant difference in elastic modulus and low elongation at break make it prone to internal stress during mechanical bending, leading to film cracking or separation from the flexible layer. To address this issue, the addition of butyl acrylate to the system further enhances the overall flexibility of the composite conductive material. The butyl acrylate group of BA is a flexible long chain with low polarity and minimal steric hindrance. Its addition allows it to insert between PVA molecular chains, weakening hydrogen bond forces, counteracting the rigidity of the IPDI-PVA network, significantly enhancing the mobility of the molecular chains, and thus improving the overall flexibility of the material.

[0024] This invention further provides a method for preparing the water-based, precisely patternable polyvinyl alcohol-based transparent composite conductive material, comprising the following steps:

[0025] Step 1: Mix polyvinyl alcohol and water at a mass ratio of 1:5~15, and stir at 50℃~60℃ for 2~3 hours to obtain a polyvinyl alcohol aqueous solution; mix diazonium salt photosensitive material and water at a mass ratio of 1:15~30, and stir at room temperature for 20~40 minutes to obtain a diazonium salt aqueous solution; add the diazonium salt aqueous solution to the polyvinyl alcohol aqueous solution, and stir at room temperature for 1~3 hours to obtain solution A;

[0026] Step 2: Add ethylene glycol and N-methyldiethanolamine to a PEDOT:PSS dispersion with a solid content of 2.8%~3%, then stir at room temperature for 1~2 hours, and then place under vacuum for 1~3 hours to obtain solution B;

[0027] Step 3: Add solution B to solution A and stir at room temperature for 1-2 hours to obtain solution C;

[0028] Step 4: Add isophorone diisocyanate and sodium dodecyl sulfate to solution C, and stir at 25℃~50℃ for 1~2 hours to obtain solution D;

[0029] Step 5: Add butyl acrylate to solution D and stir at room temperature for 1-2 hours to obtain polyvinyl alcohol-based transparent composite conductive material.

[0030] The method for preparing patterned conductive films using the polyvinyl alcohol-based transparent composite conductive material of the present invention is as follows: the polyvinyl alcohol-based transparent composite conductive material is poured onto a plasma-treated substrate material (including but not limited to glass, silicon wafer, polyimide PI, polyethylene PE, polyethylene terephthalate PET, etc.), and then fixed on a spin coater. The material is pre-spinned at 1000 rpm for 10-15 seconds to spread the material, and then mainly spinned at 1500 rpm for 15-20 seconds to spread the material evenly. The material is then placed in a constant temperature oven at 80°C for 1-2 hours to evaporate the solvent and form a uniform film layer. A film with a flexible electrode pattern is used to cover the film layer and irradiated with a 20W LED ultraviolet lamp for 1-3 minutes. The film layer is then rinsed with water for 3-5 minutes to obtain a film layer with the corresponding pattern adhering to the substrate. Finally, the film layer and the substrate are separated using a peel tester or a tensile tester to obtain a film or flexible electrode with the corresponding pattern.

[0031] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0032] 1. The mask exposure-guided development patterning technology proposed in this invention breaks through the resolution limit of traditional wet printing process patterning by curing the mask with ultraviolet light after drying and forming the film. Then, ultra-precise and controllable pattern transfer is achieved through development. This series of simple steps not only avoids the problems of low efficiency and expensive equipment of laser direct writing technology, but also achieves high-precision patterning of thin films that is far superior to screen printing and transfer printing. Furthermore, it relies on the high stability of the mask and the natural advantages of the small wavelength and high resolution of ultraviolet light to achieve high consistency and yield of patterned thin films.

[0033] 2. The composite conductive material containing PVA / diazonium salt photosensitive material proposed in this invention allows water molecules to intervene through the hydrophilic groups in PVA, achieving natural deentanglement. It can achieve uniform film formation without reactive diluents, avoiding the biocompatibility problems caused by reactive diluents. The PVA-based photosensitive material can be stored in the form of a dry film, solving the problems of on-site coating and thickness control of hydrogel materials. The diazonium salt photosensitive material is a preferred photoinitiator adapted to PVA, achieving a much lower curing shrinkage rate than other functional water-soluble photosensitive polymer material systems at a lower cost, and avoiding the oxygen inhibition polymerization problem of most photoinitiators.

[0034] 3. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in this invention enables the patterned film to have conductive properties by adding PEDOT:PSS. Furthermore, due to the inherent good light transmittance of PEDOT:PSS, the film maintains its transparency while achieving adjustable conductivity, thus compatibility with the photolithographic patterning function of the composite conductive material.

[0035] 4. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in this invention, upon the addition of ethylene glycol, weakens the electrostatic interaction between PEDOT and PSS, promotes the dissociation of PSS chains, and reduces the Coulombic repulsion between PEDOT chains, causing it to transform from a benzene conformation to a quinone conformation. This forms a continuous conjugated network while further enhancing conductivity, thus strengthening the material's properties. Stacking causes the energy absorption peak of the material to redshift to the visible light region, reducing the absorption intensity of ultraviolet light. This reduces the negative impact of introducing PEDOT:PSS conductive filler on the photocuring process and improves the efficiency of ultraviolet curing.

[0036] 5. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in this invention, by adding N-methyldiethanolamine, can selectively dissolve and remove free insulating PSS chains while weakening the electrostatic interaction between PEDOT and PSS with ethylene glycol, further reducing the absorption of ultraviolet light by PEDOT:PSS. Moreover, the amino group of N-methyldiethanolamine can neutralize the sulfonic acid group of PSS, reducing the acidity of the solution, thus reasonably solving the problem of decomposition of diazonium salt photosensitive material caused by acidic environment. Furthermore, N-methyldiethanolamine is a weak organic base, which has a smaller impact on the conductivity of PEDOT:PSS compared to inorganic bases.

[0037] 6. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in this invention enhances the adhesion of the material by adding isophorone diisocyanate (IPDI). The isocyanate groups of IPDI can react with the hydroxyl groups of PVA to generate urethane bonds and form a three-dimensional cross-linked network. The urethane 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.

[0038] 7. The composite conductive material containing PVA / diazonium salt photosensitive material / PEDOT:PSS proposed in this invention enhances the flexibility of the material by introducing butyl acrylate (BA). Since the butyl acrylate group of BA can also form hydrogen bonds or generate van der Waals forces with most substrate materials, it can further synergistically enhance the overall adhesion of the material with IPDI. Moreover, the butyl acrylate group of BA is a flexible chain with low polarity and small 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 be combined with PEDOT through van der Waals forces, and its hydrophobic chain will combine with the sulfonic acid group of PSS through dipole interaction. In addition, under the influence of PEDOT:PSS, the acryloyl group of BA will undergo esterification crosslinking with the hydroxyl group of PVA to form a network structure. Therefore, the introduction of BA not only reduces interference between PVA chains, but also promotes the interfacial bonding between PVA and PEDOT:PSS, ultimately significantly improving the overall flexibility and adhesion of the material. This allows the patterned conductive film prepared from the composite conductive material to have both strong flexibility and good adhesion, reducing crack generation during mechanical bending and maintaining good interfacial stability when applied to flexible devices. Attached Figure Description

[0039] Figure 1 This is a schematic diagram illustrating the reaction mechanism of PVA and diazonium salt photosensitive material under ultraviolet light curing in an embodiment of the present invention.

[0040] Figure 2 This is a schematic diagram of the reaction mechanism between PEDOT:PSS and ethylene glycol in an embodiment of the present invention.

[0041] Figure 3 This is a schematic diagram of the microscopic reaction after PEDOT:PSS, IPDI, and BA are added to PVA in sequence in an embodiment of the present invention.

[0042] Figure 4 The graph shows the changes in light transmittance and resistance of flexible electrodes of transparent conductive films prepared with composite conductive materials of different PEDOT:PSS dosages in the embodiments of the present invention, as a function of PEDOT:PSS dosage.

[0043] Figure 5 The graph shows the change in resistance of flexible electrodes made of composite conductive materials with different EG dosages in the embodiments of the present invention as a function of EG dosage.

[0044] Figure 6 This is a graph showing the change in dimensional deviation rate of the thin film prepared from the final composite conductive material in this embodiment of the invention as the mask size decreases.

[0045] Figure 7 This is a comparison chart showing the change in photocurability retention rate over time for composite conductive materials containing or without MDEA components in the embodiments of the present invention.

[0046] Figure 8 This is a comparison chart showing the peel strength of flexible films of the same size prepared on different substrates using a 180° peel tester for solutions C, D, and the final composite conductive material in the embodiments of the present invention.

[0047] Figure 9 This is a stress-strain curve of the flexible thin film prepared by solution D and the final composite conductive material in an embodiment of the present invention. Detailed Implementation

[0048] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0049] Example 1

[0050] The water-based, precisely patternable polyvinyl alcohol-based transparent composite conductive material provided in this embodiment has the following composition by mass percentage: PVA 60%, diazonium salt photosensitive material (its structural formula is as follows). Figure 1 The composition includes 6% PEDOT:PSS dispersion (2.8%~3% solids), 10% EG, 1% MDEA, 2% IPDI, 1% SDS, and 10% BA. The specific preparation steps are as follows:

[0051] Step 1: Mix 6g PVA with 60g water and stir at 50℃ for 3 hours to obtain a PVA aqueous solution; mix 0.6g diazonium salt photosensitive material with 12g water and stir at room temperature for 30 minutes to obtain a diazonium salt aqueous solution; add the diazonium salt aqueous solution to a polyvinyl alcohol aqueous solution and stir at room temperature for 2 hours to obtain solution A.

[0052] Step 2: Add 0.1g of ethylene glycol and 0.2g of N-methyldiethanolamine to 1g of PEDOT:PSS dispersion with a solid content of 2.8%~3%, stir at room temperature for 2 hours, and then place under vacuum for 2 hours to obtain solution B.

[0053] Step 3: Add solution B to solution A and stir at room temperature for 2 hours to obtain solution C.

[0054] Step 4: Add 1g IPDI and 0.1g SDS to solution C and stir at 50℃ for 2 hours to obtain solution D.

[0055] Step 5: Add 1g 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.

[0056] The prepared composite conductive materials were poured onto plasma-treated substrates (glass, silicon wafers, polyimide (PI), polyethylene (PE), and polyethylene terephthalate (PET), respectively), and then fixed on a spin coater. The material was pre-spread at 1000 rpm for 10 seconds, followed by a main spin at 1500 rpm for 15 seconds to ensure uniform spreading. The material was then dried in an 80°C oven for 1 hour to evaporate the solvent and form a uniform film. A film with a flexible electrode pattern was placed over the film and irradiated with a 20W LED UV lamp for 2 minutes, followed by rinsing with water for 3 minutes to obtain a film with the corresponding pattern adhered to the substrate. Finally, a 180° peel tester was used to separate the film from the substrate to obtain a thin film or flexible electrode with the corresponding pattern. The development accuracy of the composite conductive material can be tested by covering the film with a dotted line gauge.

[0057] Figure 1 This is a schematic diagram illustrating the reaction mechanism of PVA and diazonium salt photosensitive material under ultraviolet light curing in an embodiment of the present invention. As shown in the figure, when the composite conductive material based on PVA and diazonium salt photosensitive material is exposed to ultraviolet light, the diazonium molecules rapidly decompose to generate active molecular groups. These active groups further crosslink with the hydroxyl groups of PVA to produce substances insoluble in water.

[0058] Figure 2 This is a schematic diagram illustrating the reaction mechanism of PEDOT:PSS with ethylene glycol in an embodiment of the present invention. The hydroxyl groups of ethylene glycol react with... of Forming hydrogen bonds, weakening and The electrostatic interaction, and hydrogen bonding makes The disruption of the hydration layer of the functional groups reduces the local dielectric constant and increases the conductivity; hydrogen bonds also... Intrachain conjugation enhancement, enhancement Accumulation causes the energy absorption peak to shift from the ultraviolet region to the visible region; N-methyldiethanolamine can remove some free... By reducing the scattering cross-section, lowering the apparent absorbance, and decreasing the number of benzene rings in the system, acid-base neutralization is induced through proton transfer, and the acidity of the PEDOT:PSS solution is reduced through the synergistic effect of ion pair recombination. Therefore, the addition of ethylene glycol and N-methyldiethanolamine has the following advantages: improved overall material conductivity; reduced UV absorbance of PEDOT:PSS, thus reducing its interference with the photocuring reaction; and extended material storage time.

[0059] Figure 3This diagram illustrates the microscopic reaction after sequentially adding EG-modified PEDOT:PSS, IPDI, and BA to PVA in an embodiment of the present invention. As shown in the diagram, 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 urethane bonds. These urethane bonds can form hydrogen bonds or generate van der Waals forces with various substrate materials, creating stable interfacial bonds. Finally, BA binds to PEDOT through van der Waals forces, and its hydrophobic chains bind to the sulfonic acid groups of PSS through dipole interactions. Furthermore, the acryloyl groups of BA undergo esterification with the hydroxyl groups of PVA to form a copolymer. Ultimately, the adhesion and flexibility of the material are significantly improved.

[0060] To verify the effect of PEDOT:PSS dosage on conductivity and transmittance, the dosages of all materials except PEDOT:PSS in the above preparation steps were kept constant, and the dosage of PEDOT:PSS was increased incrementally in increments of 0.25g up to 2g, starting from 0g. Using plasma-treated polyimide (PI) as a substrate, transparent conductive films were fabricated from composite conductive materials with different PEDOT:PSS dosages, and then further fabricated into patterned flexible electrodes of the same size using a mask. Figure 4 The graph shows the changes in transmittance and resistance of flexible electrodes of transparent conductive films prepared with composite conductive materials of different PEDOT:PSS dosages as a function of PEDOT:PSS dosage. As can be seen from the graph, the transmittance of the film and the resistance of the flexible electrode both show a decreasing trend with the increase of PEDOT:PSS dosage. However, when the dosage is increased to 1g, the resistance no longer shows a significant decrease, and the transmittance shows a rapid decreasing trend.

[0061] To verify the effect of ethylene glycol dosage on conductivity, the dosages of all materials except ethylene glycol in the above preparation steps were kept constant, while the dosage of EG was increased incrementally in increments of 0.025g up to 0.2g, starting from 0g. Using plasma-treated polyimide (PI) as a substrate, patterned flexible electrodes of the same size were fabricated from composite conductive materials with different EG dosages. Figure 5 The graph shows the change in resistance of flexible electrodes prepared with composite conductive materials of different EG dosages as a function of EG dosage. It can be seen that as the amount of ethylene glycol in the system increases, the resistance of the prepared flexible electrodes decreases. When the amount of ethylene glycol increases to 0.1g, the resistance no longer decreases significantly with the increase of ethylene glycol dosage.

[0062] Figure 6This diagram illustrates the change in dimensional deviation rate of the thin film prepared from the composite conductive material in this invention as the mask size decreases. The mask is a film sheet, and the dimensional deviation rate is defined as the percentage of the absolute value of the difference between the mask size and the actual pattern size at the corresponding position relative to the mask size. It can be seen that as the mask size decreases, the dimensional deviation rate increases slowly, but remains relatively constant at 100%. The dimensional deviation rate of the above mask patterns is less than 1%.

[0063] To verify the effect of MDEA on the photocurability retention rate of composite conductive materials, a control group without MDEA was prepared. The composition of the control group by mass percentage was: PVA 62%, diazonium salt photosensitive material 6%, PEDOT:PSS dispersion with a solid content of 2.8%–3% 10%, EG 1%, IPDI 10%, SDS 1%, and BA 10%. The comparison graph of the photocurability retention rate of composite conductive materials with and without MDEA over time is shown below. Figure 7 As shown, the addition of 2% MEDA by mass significantly improves the photocuring activity retention rate of the composite conductive material. The photocuring activity retention rate is defined as the percentage of effective reaction amount after storage relative to the initial effective reaction amount. The effective reaction amount is determined by UV-Vis spectroscopy of the diazonium salt photosensitive material. The characteristic absorption peak of the functional group at a wavelength of 365 nm was directly quantified.

[0064] Figure 8 This is a comparison chart showing the peel strength of flexible films of the same size prepared on different substrates using solutions C, D, and the final composite conductive material in this embodiment of the invention, measured using a 180° peel tester. As can be seen from the chart, the peel strength of the conductive film prepared with solution D is higher than that of the conductive film prepared with solution C, and the peel strength of the conductive film prepared with the final polyvinyl alcohol-based transparent composite conductive material is higher than that of the conductive film prepared with solution D.

[0065] Figure 9 The stress-strain curves of the flexible film prepared by solution D and the final composite conductive material in this embodiment of the invention are shown below: When the elongation of the flexible film prepared by solution D reaches 34%, the stress peak is approximately 29 MPa (corresponding to the elongation at break), at which point the film breaks instantaneously, and the stress decreases to zero in a very short time. When the elongation of the flexible film prepared by the final composite conductive material reaches 110%, the stress peak is approximately 23 MPa (corresponding to the elongation at break), and then the stress gradually decreases, indicating that the material maintains strong toughness within 110% deformation.

[0066] 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 should be included within the protection scope of the present invention.

Claims

1. A water-based, developable, precisely patternable polyvinyl alcohol-based transparent composite conductive material, characterized in that, The composite conductive material comprises the following components by mass percentage: 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 dodecyl sulfate, and 5-15% butyl acrylate.

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

1.

3. The water-based, precisely patternable polyvinyl alcohol-based transparent composite conductive material according to claim 1 or 2, characterized in that, The composition of the composite conductive material by mass percentage is as follows: 60% polyvinyl alcohol, 6% diazonium salt photosensitive material, 10% PEDOT:PSS dispersion with a solid content of 2.8%~3%, 1% ethylene glycol, 2% N-methyldiethanolamine, 10% isophorone diisocyanate, 1% sodium dodecyl sulfate, and 10% butyl acrylate.

4. A method for preparing a water-based, developable, precisely patternable polyvinyl alcohol-based transparent composite conductive material according to any one of claims 1 to 3, characterized in that, Includes the following steps: Step 1: Mix polyvinyl alcohol and water at a mass ratio of 1:5~15, and stir at 50℃~60℃ for 2~3 hours to obtain a polyvinyl alcohol aqueous solution; mix diazonium salt photosensitive material and water at a mass ratio of 1:15~30, and stir at room temperature for 20~40 minutes to obtain a diazonium salt aqueous solution; add the diazonium salt aqueous solution to the polyvinyl alcohol aqueous solution, and stir at room temperature for 1~3 hours to obtain solution A; Step 2: Add ethylene glycol and N-methyldiethanolamine to a PEDOT:PSS dispersion with a solid content of 2.8%~3%, then stir at room temperature for 1~2 hours, and then place under vacuum for 1~3 hours to obtain solution B; Step 3: Add solution B to solution A and stir at room temperature for 1-2 hours to obtain solution C; Step 4: Add isophorone diisocyanate and sodium dodecyl sulfate to solution C, and stir at 25℃~50℃ for 1~2 hours to obtain solution D; Step 5: Add butyl acrylate to solution D and stir at room temperature for 1-2 hours to obtain polyvinyl alcohol-based transparent composite conductive material.

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