Preparation method of flexible conductive film and flexible conductive film

Abstract

The invention discloses a preparation method of a flexible conducting film and the flexible conducting film, and relates to the field of conducting films, the preparation method of the flexible conducting film comprises the steps that a carrier film is provided, the carrier film comprises a first surface and a second surface which are oppositely arranged, a conducting layer is formed on the first surface of the carrier film, and the conducting layer comprises a conducting nanometer material; a polymer adhesive film is laid on the side, away from the carrier film, of the conducting layer, and the polymer adhesive film is made of thermoplastic materials; laying a flexible substrate on one side, far away from the conductive layer, of the polymer adhesive film; performing hot-pressing compounding on a laminated structure of the carrier film, the conductive layer, the polymer adhesive film and the flexible substrate, so that the conductive nano material is embedded into the polymer adhesive film; and removing the carrier film. According to the flexible conductive thin film and the preparation method thereof, hot-pressing compounding is carried out on a laminated structure of the carrier film, the conductive layer, the polymer adhesive film and the flexible substrate, so that the conductive nano material in the conductive layer is embedded into the polymer adhesive film, and the flexible conductive thin film with mechanical flexibility, excellent electrical properties and device reliability is prepared.

Description

Technical Field

[0001] The present application relates to the technical field of conductive films, and in particular to a method for preparing a flexible conductive film and the flexible conductive film. Background Art

[0002] With the rapid development of flexible electronics, wearable devices, transparent displays, flexible solar cells, and other fields, the demand for flexible transparent conductive materials is growing. Currently, the mainstream transparent conductive material on the market is mainly indium tin oxide (ITO) film. ITO film has excellent conductivity and transparency, but it has significant limitations. First, ITO film is an inherently brittle ceramic material. Even at the nanoscale, its mechanical properties are still poor. It is prone to cracking under mechanical stress such as bending and folding, resulting in reduced conductivity and even failure.

[0003] In addition to ITO, other transparent conductive materials such as fluorine-doped tin oxide (FTO) and aluminum-doped zinc oxide (AZO) also face similar challenges, or struggle to simultaneously meet the demands of high-performance flexible electronic devices in terms of conductivity and mechanical flexibility. In recent years, nanocarbon materials and metal nanomaterials, such as silver nanowires (AgNWs), carbon nanotubes (CNTs), and graphene, have attracted considerable attention due to their excellent conductivity, mechanical flexibility, and solution processability. However, the efficient and stable integration of these nanoconductive materials onto flexible substrates while maintaining their excellent electrical properties and imparting superior mechanical reliability remains a current technical challenge. Summary of the Invention

[0004] In view of the above problems, the present application provides a method for preparing a flexible conductive film and a flexible conductive film, so as to achieve the purpose of preparing a flexible conductive film with mechanical flexibility, excellent electrical properties and device reliability.

[0005] The specific scheme is as follows: On the one hand, the present application provides a method for preparing a flexible conductive film, comprising:

[0006] Providing a carrier film, the carrier film comprising a first surface and a second surface disposed opposite to each other, forming a conductive layer on the first surface of the carrier film, the conductive layer comprising a conductive nanomaterial;

[0007] Laying a polymer film on the side of the conductive layer away from the carrier film, wherein the polymer film is a thermoplastic material;

[0008] Laying a flexible substrate on the side of the polymer film away from the conductive layer;

[0009] Hot pressing and laminating the laminated structure of the carrier film, the conductive layer, the polymer adhesive film and the flexible substrate so that the conductive nanomaterial is embedded in the polymer adhesive film to form a composite conductive layer;

[0010] Remove the carrier film.

[0011] In this application, the high temperature of the hot pressing composite process causes the thermoplastic polymer film to be in a molten state, so that the conductive nanomaterials in the conductive layer are embedded in the polymer film, forming a composite conductive layer with a molecular-level or nano-level interlocking structure. The conductive nanomaterials contained in the conductive layer not only have excellent conductivity, but also, by virtue of their unique nanoscale effect, effectively disperse the stress concentration generated by the flexible substrate layer during bending, folding or stretching, significantly improving the mechanical tolerance of the flexible conductive film and ensuring the stability of the conductive performance under deformation.

[0012] The conductive layer is completely covered by the polymer film, forming a dense isolation barrier, which significantly reduces its direct contact with the external environment, thereby significantly enhancing the material's resistance to oxidation, moisture and chemical corrosion. At the same time, the polymer film acts as an outer layer to physically protect the conductive layer, reducing the risk of surface wear on the conductive layer, greatly extending the product's service life and improving the reliability of the device.

[0013] In some embodiments, the adhesive properties of the first surface of the carrier film are less than the adhesive properties of the second surface.

[0014] In some embodiments, the melting temperature of the polymer film is lower than that of the carrier film and lower than that of the flexible substrate. The melting temperature of the conductive layer is lower than that of the carrier film and lower than that of the flexible substrate.

[0015] In some embodiments, the melting temperature of the polymer adhesive film increases in a direction from the carrier film toward the flexible substrate.

[0016] In some embodiments, in the direction from the carrier film to the flexible substrate, the polymer adhesive film includes a plurality of sub-adhesive films stacked sequentially, and the melting temperatures of the sub-adhesive films increase sequentially.

[0017] In some embodiments, the conductive layer includes at least conductive rod-shaped nanomaterials, and the length direction of at least part of the rod-shaped nanomaterials forms an angle greater than 0° with the plane where the polymer film is located.

[0018] In some embodiments, the thickness of the polymer film is greater than the thickness of the conductive layer.

[0019] In some embodiments, forming a conductive layer on the first surface of the carrier film includes:

[0020] dispersing the conductive nanomaterial in a solvent to form a dispersion;

[0021] forming a coating of the dispersion on a first surface of the carrier film;

[0022] The coating of the dispersion is cured to form a conductive layer.

[0023] On the other hand, the present application also provides a flexible conductive film, comprising:

[0024] A flexible substrate and a composite conductive layer are sequentially arranged, wherein the composite conductive layer comprises a polymer film and a conductive nanomaterial embedded in the polymer film, wherein the conductive nanomaterial is embedded in the polymer film by hot pressing and melting.

[0025] In some embodiments, the depth of the conductive nanomaterial embedded in the polymer film is no less than 2 / 3 of the thickness of the polymer film, and / or the conductive nanomaterial includes a rod-like structure and a granular structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without any creative work.

[0027] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which this application can be implemented, and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size, without affecting the efficacy and objectives that can be achieved by this application, should still fall within the scope of the technical contents disclosed in this application.

[0028] Figure 1 A flow chart of a method for preparing a flexible conductive film provided in an embodiment of the present application;

[0029] Figure 2 A schematic flow chart of a method for preparing a conductive layer provided in an embodiment of the present application;

[0030] Figures 3 to 7 A product structure diagram of the flexible conductive film preparation method provided in an embodiment of the present application at different process steps;

[0031] Reference numerals:

[0032] 101 - carrier film; 102 - conductive layer; 103 - polymer film; 104 - flexible substrate; 105 - composite conductive layer; 10 - flexible conductive film; P1 - first surface; P2 - second surface. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the embodiments of the present application. Those skilled in the art will know that with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0034] Based on the content in the background technology, the existing technology still has other shortcomings and deficiencies:

[0035] The production of most high-performance transparent conductive films relies on energy-intensive, high-vacuum, and high-cost physical vapor deposition (PVD) or chemical vapor deposition (CVD) technologies, such as vacuum sputtering and atomic layer deposition (ALD). These asset-heavy equipment not only requires significant investment but also has relatively low production efficiency, making it difficult to achieve large-scale, continuous, and low-cost production of flexible devices.

[0036] Indium, as the main component of ITO, has low abundance in the earth's crust and limited reserves, resulting in large price fluctuations and continued increases, which greatly increases the production cost of flexible electronic products using ITO and is not conducive to its large-scale commercial application.

[0037] Nanoconductive material films prepared by the solution method, if directly exposed to the air, are easily affected by environmental factors such as oxidation and sulfurization, resulting in a decrease in conductivity; at the same time, the film is also easily damaged by external friction or mechanical impact, affecting long-term stability.

[0038] The present application provides a method for preparing a flexible conductive film, comprising:

[0039] Providing a carrier film, the carrier film comprising a first surface and a second surface disposed opposite to each other, forming a conductive layer on the first surface of the carrier film, the conductive layer comprising a conductive nanomaterial;

[0040] Laying a polymer adhesive film on the side of the conductive layer away from the carrier film, the polymer adhesive film being a thermoplastic material;

[0041] Laying a flexible substrate on the side of the polymer film away from the conductive layer;

[0042] Hot pressing and laminating the laminated structure of the carrier film, the conductive layer, the polymer adhesive film and the flexible substrate so that the conductive nanomaterial is embedded in the polymer adhesive film to form a composite conductive layer;

[0043] Remove the carrier film.

[0044] The high temperature of the hot pressing composite process causes the thermoplastic polymer film to be in a molten state, so that the conductive nanomaterials in the conductive layer are embedded in the polymer film, forming a composite conductive layer with a molecular-level or nano-level interlocking structure. The conductive nanomaterials contained in the conductive layer not only have excellent conductivity, but also, with their unique nanoscale effect, effectively disperse the stress concentration generated by the flexible substrate layer during bending, folding or stretching, significantly improving the mechanical tolerance of the flexible conductive film and ensuring the stability of the conductive performance under deformation.

[0045] The conductive layer is completely covered by the polymer film, forming a dense isolation barrier, which significantly reduces its direct contact with the external environment, thereby significantly enhancing the material's resistance to oxidation, moisture and chemical corrosion. At the same time, the polymer film acts as an outer layer to physically protect the conductive layer, reducing the risk of surface wear on the conductive layer, greatly extending the product's service life and improving the reliability of the device.

[0046] Alternatively, the present application can produce flexible conductive films through coating, lamination, and other processes, which are not only simple but also allow for large-area production. Compared to the prior art method of producing ITO thin films by vacuum evaporation, the present application can effectively reduce production costs. Alternatively, the present application uses a nanoscale conductive material and a polymer film for melt-compounding to form a composite conductive layer. Compared to the indium element required to produce ITO conductive films in the prior art, this material selection can significantly reduce costs.

[0047] Optionally, in this application, the conductive layer is completely coated with a polymer film, forming a dense isolation barrier that significantly reduces direct contact with the external environment, thereby significantly enhancing the material's resistance to oxidation, moisture, and chemical corrosion. Furthermore, the polymer film, as an outer layer, provides physical protection for the conductive layer, reducing the risk of surface wear, thereby significantly extending the product's service life and improving device reliability.

[0048] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] On the one hand, the present invention provides a method for preparing a flexible conductive film. Figure 1-Figure 7 shown.

[0050] refer to Figure 1-Figure 7 , Figure 1 This is a flow chart of a method for preparing a flexible conductive film provided in an embodiment of the present application. Figure 2 A schematic flow chart of a method for preparing a conductive layer provided in an embodiment of the present application is provided. Figures 3 to 7The product structure diagram of the method for preparing a flexible conductive film provided in the embodiment of the present application at different process steps. The method for preparing a flexible conductive film includes the following steps S10 to S50:

[0051] Step S10: Figure 3 As shown, a carrier film 101 is provided. The carrier film 101 includes a first surface P1 and a second surface P2 that are opposite to each other. A conductive layer 102 is formed on the first surface P1 of the carrier film 101. The conductive layer 102 includes a conductive nanomaterial.

[0052] For example, refer to Figure 3 The carrier film 101 can be made of a polymer film, such as polyethylene terephthalate (PET) and polyimide (PI). PET offers low cost and high light transmittance, while PI exhibits excellent temperature resistance. Furthermore, the first surface P1 of the carrier film 101 undergoes a special surface treatment, resulting in a smooth surface with precisely controlled low surface energy. This smooth surface P1 provides an ideal, defect-free substrate for the subsequent dispersion film formation. During the dispersion coating process, the smooth first surface P1 reduces the flow resistance of the dispersion on the carrier film 101, allowing for more uniform spreading of the dispersion and avoiding localized accumulation or uneven leveling. This ensures that the resulting conductive layer 102 is highly uniform. By precisely controlling the low surface energy of the first surface P1 of the carrier film 101, this precisely controlled low surface energy ensures excellent separability between the conductive layer 102 and the carrier film 101 after formation, enabling seamless peeling and ensuring the integrity of the conductive layer 102 during the subsequent peeling process.

[0053] The method of forming the conductive layer 102 on the first surface P1 of the carrier film 101 in step S10 is as follows: Figure 2 As shown, the following steps S101-S103 are included:

[0054] Step S101: dispersing the conductive nanomaterial in a solvent to form a dispersion.

[0055] For example, nanoscale conductive materials with high electrical conductivity and excellent dispersion characteristics are selected, including high-crystallinity silver nanowires (AgNWs), high-purity single-walled or multi-walled carbon nanotubes (SWCNTs / MWCNTs), highly reduced graphene oxide (rGO), ultra-thin layered graphene, and carbon fiber (CF) micro-short fibers with a high aspect ratio.

[0056] Among them, highly crystalline silver nanowires (AgNWs) possess extremely high electrical conductivity and can form a good conductive network at low loadings. Their nanoscale size also imparts excellent flexibility and transparency to the resulting conductive layer. High-purity SWCNTs exhibit unique quantum effects and excellent electrical and mechanical properties, while high-purity MWCNTs offer higher mechanical strength and improved dispersibility. They can be used to prepare high-strength, high-conductivity composites. rGO, derived from the reduction of graphene oxide, retains some of graphene's excellent properties, such as high conductivity and large specific surface area. Ultrathin layered graphene possesses extremely high carrier mobility and excellent electrical properties. Its two-dimensional structure provides unique advantages for constructing conductive networks, enabling the formation of efficient conductive pathways. High-aspect-ratio carbon fiber (CF) microfibers have a high aspect ratio, meaning they can form a good conductive pathway even with a low loading. Furthermore, carbon fiber's high strength and high modulus enhance the mechanical properties of the conductive layer.

[0057] One or more of the selected conductive nanomaterials are mixed in a specific mass or volume ratio. Different ratios affect the properties of the final conductive layer. For example, increasing the proportion of silver nanowires may improve conductivity but reduce transparency, while increasing the proportion of carbon nanotubes may enhance the mechanical strength of the conductive layer. Therefore, the appropriate ratio can be determined based on specific application requirements.

[0058] Then, advanced dispersion technology is used to achieve highly uniform and stable dispersion of the conductive nanomaterials in the selected solvent system.

[0059] For example, high-energy ultrasonic treatment uses the high pressure and high temperature generated by the cavitation effect of ultrasound to destroy the agglomeration between conductive nanomaterials and disperse them into single particles or small agglomerates. Shear-assisted dispersion generates strong shear force through high-speed stirring, grinding and other equipment to disperse the conductive nanomaterials in the solvent. The shear force can effectively break up the agglomerates and evenly disperse the materials. Mechanical grinding places the conductive nanomaterials and solvents together in the grinding equipment, and the rolling and impact of the grinding balls crushes and disperses the materials. Chemical surface modification-assisted dispersion introduces specific chemical groups or polymer chains on the surface of the conductive nanomaterial to change its surface properties and enhance its compatibility with the solvent, thereby achieving better dispersion.

[0060] At the same time, the above-mentioned solvent system needs to have good volatility and wettability for nanomaterials. The good volatility of the solvent system allows the solvent to evaporate quickly during the subsequent film formation process to form a uniform and dense conductive layer; the wettability for nanomaterials can fully wet the surface of the conductive nanomaterial, allowing it to be better dispersed in the solvent. The solvent can be a low-boiling point alcohol, such as isopropyl alcohol and ethanol, which have the advantages of fast volatility and good wettability for many nanomaterials; aqueous solvents are low-cost and environmentally friendly; high-boiling point aprotic polar solvents, such as N-methylpyrrolidone and dimethylformamide, have good solubility and wettability for a variety of nanomaterials.

[0061] In order to further optimize the long-term stability of the dispersion and the density of the subsequent film formation, a specific type of dispersing aid, surfactant or polymer binder can be introduced in an appropriate amount.

[0062] Step S102 : forming a coating layer of the dispersion on the first surface P1 of the carrier film 101 .

[0063] Exemplarily, the dispersion containing the conductive nanomaterial prepared in step 101 is coated on the first surface P1 of the carrier film 101 with high uniformity through advanced precision coating technology, such as high-precision atomization spraying, spin coating, micro-gravure coating, slit extrusion coating or continuous dip coating, to avoid conductivity differences due to uneven thickness.

[0064] Step S103 : curing the dispersion coating to form a conductive layer 102 .

[0065] Exemplarily, after coating is completed, the coating of the dispersion is cured, that is, a precise solvent removal process is performed. This process can be achieved by optimizing the thermal field, for example, convection drying, infrared heating, vacuum degassing or combining dynamic airflow assisted evaporation to ensure that the solvent is completely volatilized. As the solvent gradually evaporates, the spacing between the nano-conductive materials continues to decrease, and the interaction force between them gradually increases. Under appropriate curing conditions, the nano-conductive materials will be orderly stacked or networked by means of van der Waals forces, electrostatic effects or chemical bonding to form a continuous conductive path. This orderly structural arrangement can improve the transmission efficiency of electrons and reduce the resistance of the conductive layer 102, thereby giving the conductive layer 102 good conductive properties. At the same time, the conductive layer 102 formed by orderly stacking or networking is more compact, which can effectively block the intrusion of external environmental factors and improve the stability and durability of the conductive layer 102. By precisely controlling various parameters in the curing process, such as heating temperature, time, thermal field distribution and initial thickness of the coating, the thickness of the conductive layer 102 can be precisely controlled within the range of 50nm-500nm. At the same time, the conductive layer 102 still maintains inherent flexibility after curing.

[0066] In the above steps, the process of preparing the dispersion by solution method, coating the dispersion on the first surface of the carrier film and curing the dispersion coating to form a conductive layer are all mature low-cost processes, which can effectively reduce production costs compared with vacuum evaporation to prepare ITO thin films.

[0067] Step S20: Figure 4 As shown, a polymer adhesive film 103 is applied on the side of the conductive layer 102 away from the carrier film 101 , and the polymer adhesive film 103 is a thermoplastic material.

[0068] For example, refer to Figure 4 , a polymer adhesive film 103 is applied to the side of the conductive layer 102 away from the carrier film 101, for example, by laminating or coating a thermoplastic polymer adhesive film 103 with excellent optical transparency, excellent adhesion, outstanding weather resistance and efficient packaging performance, or by directly applying the polymer adhesive film 103 in the form of an adhesive film to the surface of the conductive layer 102. The thermoplastic material softens and melts when heated, forming a fluid gel state, which facilitates the subsequent embedding of the conductive nanomaterial. The polymer adhesive film 103 can be made of industry-standard high-performance materials, such as high-transmittance ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), high-strength ethylene-propylene-ethylene copolymer (EPE), or high-adhesion polyvinyl butyral (PVB), etc., either as a single component or in a composite formulation. Its thickness can be optimized according to the target application requirements, for example, the thickness can be 200μm-500μm.

[0069] Step S30: Figure 5 As shown, a flexible substrate 104 is applied on the side of the polymer film 103 away from the conductive layer 102 .

[0070] For example, refer to Figure 5 A flexible substrate 104 is applied to the side of the polymer film 103 facing away from the conductive layer 102. This application requires appropriate processing methods, with lamination and coating being common. Flexible substrate 104 must exhibit high light transmittance, excellent mechanical bending fatigue life, dimensional stability, and good resistance to thermal deformation. Typical materials include, but are not limited to, polyethylene terephthalate (PET), polyethersulfone (PES), polypropylene (PP), polycarbonate (PC), or polyimide (PI) films. Flexible substrate 104 provides physical support for the entire flexible conductive film.

[0071] Step S40: Figure 6 As shown, the laminated structure of the carrier film 101 , the conductive layer 102 , the polymer adhesive film 103 and the flexible substrate 104 is composited by hot pressing, so that the conductive nanomaterial is embedded in the polymer adhesive film 103 to form a composite conductive layer 105 .

[0072] For example, refer to Figure 6 , the laminated structure of the carrier film 101, the conductive layer 102, the polymer film 103 and the flexible substrate 104 is introduced into an advanced vacuum lamination device. Hot pressing and laminating are carried out under precisely controlled packaging parameters. The hot pressing and laminating process can choose to be constant or step-by-step temperature rise, for example, 130℃-160℃. Within this temperature range, the polymer film 103 can be fully melted and softened, while avoiding excessive temperature that causes material decomposition or performance degradation. The conductive layer 102 material can also be well integrated with the polymer film 103 at this temperature to achieve effective embedding of the conductive nanomaterial; the isostatic pressure range, for example, 0.5bar-1.5bar, can provide sufficient force to enable the molten polymer film 103 to fully infiltrate, fill and wrap the conductive layer 102 under pressure drive. And precise timing control, for example, 5 minutes to 20 minutes. This time range is to ensure that the polymer film 103 has enough time to fully interact with the conductive layer 102 in the molten state, so that the conductive nanomaterial can be evenly dispersed and embedded in the polymer film 103 to form a composite conductive layer 105 and construct a stable molecular-level or nano-level interlocking structure.

[0073] During this process, the thermoplastic polymer film 103 undergoes melting, softening, and controlled flow under the combined effects of temperature and pressure, allowing its molecular chains to fully move, enabling it to thoroughly wet, fill, and encapsulate the conductive layer 102. This process eliminates the need for simple surface attachment of the conductive layer 102, but rather allows it to be dynamically "in situ embedded" or "implanted" into the superficial surface layer or even deeper within the polymer film 103, forming a molecular- or nano-scale interlocking structure with the polymer film 103 matrix, thereby forming a composite conductive layer 105. This unique embedded encapsulation mechanism provides the composite conductive layer 105 with excellent mechanical protection, structural integrity, and stable electrical properties.

[0074] Step S50: Figure 7 As shown, the carrier film 101 is removed.

[0075] For example, refer to Figure 7 After the encapsulation is completed and the film is cooled and solidified, the inherent low adhesion properties of the first surface P1 of the carrier film 101 are utilized to perform a precise, smooth, and residue-free peeling operation. This peeling process must ensure that the laminated structure is not mechanically damaged. After peeling, the flexible conductive film 10 constructed by the present invention is finally obtained. The flexible conductive film 10 is presented from bottom to top as a flexible substrate 104 and a composite conductive layer 105. In this final structure, the conductive layer 102 has been perfectly encapsulated by the polymer film 103, achieving an integrated thin film with ultra-high conductivity, excellent optical transparency, and extreme surface flatness. Its visible light transmittance can be stably maintained at above 80% at a specific wavelength, such as 550nm.

[0076] In this application, the high temperature during the hot-pressing lamination process melts the thermoplastic polymer film 103, causing the conductive nanomaterials in the conductive layer 102 to embed within it, forming a composite conductive layer 105 and constructing a molecular- or nano-scale interlocking structure. This tightly interlocked structure provides a continuous and stable channel for electron transmission, significantly reducing scattering and obstruction during electron transmission, and ensuring that the flexible conductive film 10 maintains excellent conductive properties in a variety of usage scenarios.

[0077] The interlocking structure formed by the conductive nanomaterial and the polymer film 103 not only strengthens the bonding between the conductive layer 102 and the polymer film 103, but also enhances the mechanical strength of the entire flexible conductive film 10. When subjected to external forces such as tension, compression, or bending, this interlocking structure effectively transmits and disperses stress, preventing the material from breaking or delamination.

[0078] The conductive layer 102 is completely covered by the polymer film 103, forming a dense isolation barrier, which significantly reduces direct contact with the external environment, thereby significantly enhancing the material's resistance to oxidation, moisture and chemical corrosion. At the same time, the polymer film 103 acts as an outer layer to physically protect the conductive layer 102, reducing the risk of surface wear of the conductive layer 102, greatly extending the product's service life, and improving the reliability of the device.

[0079] In some embodiments, the adhesive property of the first surface P1 of the carrier film 101 is less than the adhesive property of the second surface P2 .

[0080] Specifically, the carrier film 101 exhibits dual-sided heterogeneity. The first surface P1 of the carrier film 101 is mirror-polished and modified with a low-surface-energy coating, resulting in a smooth, precisely controlled low-surface-energy surface. This provides an ideal substrate for the subsequent formation of a conductive nanomaterial dispersion coating on the first surface P1, ensuring ultra-high uniformity and low roughness of the resulting conductive layer 102, facilitating subsequent non-destructive peeling of the conductive layer 102. The second surface P2 can be modified with an adhesive coating to provide controlled adhesion, enabling temporary fixing or connection during specific process stages.

[0081] In some embodiments, the melting temperature of the polymer film 103 is lower than the melting temperature of the carrier film 101 and lower than the melting temperature of the flexible substrate 104. The melting temperature of the conductive layer 102 is lower than the melting temperature of the carrier film 101 and lower than the melting temperature of the flexible substrate 104. During the process of forming a laminated structure with the carrier film 101, the conductive layer 102, the polymer film 103, and the flexible substrate 104 and performing hot pressing and laminating, the conductive nanomaterial needs to be embedded in the polymer film 103. To avoid the carrier film 101 or the flexible substrate 104 melting first during hot pressing and laminating, which could lead to adverse consequences such as material structure damage and performance degradation, thus affecting the quality of the final product, the melting temperatures of the polymer film 103 and the conductive layer 102 are required to be lower than the melting temperature of the carrier film 101 and lower than the melting temperature of the flexible substrate 104. In this way, during hot pressing and laminating, the polymer film 103 and the conductive layer 102 can reach a molten state first, which facilitates the embedding of the conductive nanomaterial into the polymer film 103, while the carrier film 101 and the flexible substrate 104 remain relatively stable, ensuring the smooth progress of the entire laminating process and the quality of the composite conductive layer 105.

[0082] In some embodiments, the melting temperature of the polymer adhesive film 103 increases in a direction from the carrier film 101 to the flexible substrate 104 .

[0083] Specifically, in the direction from the carrier film 101 to the flexible substrate 104, the polymer film 103 includes multiple layers of sub-films stacked in sequence, and the melting temperatures of the sub-films increase in sequence. When hot pressing and laminating, since the side of the polymer film 103 away from the conductive layer 102 has a higher melting temperature, this side is less likely to reach a molten state when the temperature required for the process is reached. This can effectively prevent external water vapor or pollutants from entering the interior of the polymer film 103, thereby avoiding quality problems such as degradation of the polymer film 103 performance and weak bonding with adjacent layers due to the influence of water vapor or pollutants. At the same time, the melting temperature of the side of the polymer film 103 close to the conductive layer 102 is relatively low, and this side can reach a molten state first at the process temperature. The molten polymer film 103 has good fluidity and viscosity. When the conductive layer 102 is heated to a molten state, it can be smoothly embedded in the molten polymer film 103, achieving good bonding and ensuring the stability and conductive performance of the entire composite conductive layer 105.

[0084] In some embodiments, the conductive layer 102 includes at least conductive rod-shaped nanomaterials, and the length direction of at least a portion of the rod-shaped nanomaterials forms an angle greater than 0° with the plane where the polymer film 103 is located.

[0085] Within the single layer of conductive nanomaterials, rod-shaped nanomaterials are present at varying angles. Some rod-shaped nanomaterials have a relatively small angle with the plane of the polymer film 103, such as approximately 10°-20°. These rod-shaped nanomaterials are relatively parallel to the plane of the polymer film 103, but still have a certain inclination. Other rod-shaped nanomaterials, on the other hand, have a larger angle with the plane of the polymer film 103, potentially reaching 30°-40°, making them easier to embed within the polymer film 103.

[0086] In order to further optimize the performance of the conductive layer, at least two layers of conductive nanomaterials may be used, and each layer may include rod-shaped nanomaterials with different angles. For example, the rod-shaped nanomaterials in the first layer of conductive nanomaterials mainly have an angle of less than 45° relative to the plane where the polymer film 103 is located. These rod-shaped nanomaterials are relatively gently embedded in the polymer film 103. They form a relatively dense conductive network in the shallow area of ​​the polymer film 103, which can quickly conduct current along the plane of the polymer film 103. The rod-shaped nanomaterials in the second layer of conductive nanomaterials mainly have an angle of more than 45° relative to the plane where the polymer film 103 is located. They are vertically or approximately vertically interspersed in the first layer of conductive network, which facilitates the faster embedding of the rod-shaped nanomaterials into the thermoplastic material after the polymer film 103 is melted during the hot pressing composite process, which can increase the melting embedding rate of the conductive nanomaterials in the thermoplastic material. In addition, the two rod-shaped nanomaterials with different angles can connect the conductive areas at different positions, realize the expansion of the conductive path in the direction perpendicular to the plane of the polymer film 103, and can make the final formed Figure 7 The composite conductive layer 105 has relatively uniform conductivity in both horizontal and vertical directions. Through this design of multiple layers with different angles of rod-shaped nanomaterials in each layer, the conductive layer can construct a more three-dimensional, complex and stable three-dimensional network embedded structure.

[0087] In some embodiments, the thickness of the polymer film 103 is greater than the thickness of the conductive layer 102 .

[0088] Specifically, the thicker polymer film 103 provides a wider embedding space for the conductive layer 102. Due to the greater thickness of the polymer film 103, the rod-shaped conductive nanomaterials described in the above embodiment can be embedded at varying depths and angles, forming a complex three-dimensional embedding structure. For example, some conductive nanomaterials may be embedded only on the surface of the polymer film 103, while others may penetrate deep into the interior of the polymer film 103. This multi-layered embedding method helps strengthen the bonding between the conductive layer 102 and the polymer film 103.

[0089] On the other hand, the embodiment of the present application further provides a flexible conductive film 10, such as Figure 7 As shown, Figure 7 This is a schematic structural diagram of a flexible conductive film 10 provided in an embodiment of the present application.

[0090] like Figure 7 As shown, the flexible conductive film 10 includes a flexible substrate 104 and a composite conductive layer 105 arranged in sequence, and the composite conductive layer 105 includes a polymer film 103 and a conductive nanomaterial embedded in the polymer film 103, wherein the conductive nanomaterial is embedded in the polymer film 103 based on hot pressing and melting.

[0091] The flexible conductive film 10 utilizes a layered structure consisting of a flexible substrate 104 and a composite conductive layer 105. The flexible substrate 104 provides flexibility and mechanical support for the entire flexible conductive film 10, while the composite conductive layer 105 imparts its excellent electrical conductivity. The two layers are tightly bonded together by a polymer adhesive film 103, forming a single, integrated structure. When subjected to external forces, they can deform collaboratively and withstand stress together, ensuring the structural stability and reliability of the flexible conductive film 10.

[0092] During the hot-pressing process, the conductive nanomaterials are melted and embedded in the polymer film 103, forming a molecular or nanoscale interlocking structure. Strong interactions exist between the conductive nanomaterials and the polymer film 103, making the bond between them more secure. Compared to traditional simple physical hybrid structures, this interlocking structure significantly improves the interfacial bonding strength between the conductive nanomaterials and the polymer film 103, reduces interfacial defects and voids, and thus enhances the mechanical and electrical properties of the flexible conductive film 10.

[0093] Due to the high conductivity and uniform dispersion of the conductive nanomaterials, as well as the formation of molecular- or nanoscale interlocking structures, the flexible conductive film 10 exhibits excellent electrical conductivity, with a sheet resistance of less than 100Ω / sq. It also has high transmittance. In the visible light band, for example, at 550nm, its transmittance exceeds 80%, and can even reach over 90%, meeting the requirements of transparent applications. Furthermore, the conductive layer 102 is deeply encapsulated by the polymer film 103, effectively preventing physical damage to the conductive material during bending and folding. This allows the flexible conductive film 10 to maintain stable conductivity without significant degradation after undergoing multiple bending cycles, for example, tens to hundreds of thousands of times. Because the polymer film 103 completely encapsulates the conductive layer 102, the surface of the flexible conductive film 10 exhibits its own smoothness, avoiding the roughness issues that may arise from nanomaterial film formation and facilitating subsequent device integration. Furthermore, the polymer film 103 effectively isolates and protects the conductive layer, significantly improving its resistance to oxidation, moisture, chemical corrosion, and wear, thereby extending the product's service life.

[0094] In some embodiments, the depth to which the conductive nanomaterial is embedded in the polymer film 103 is not less than 2 / 3 of the thickness of the polymer film 103. The deeply embedded conductive nanomaterial is more fully coated by the polymer film 103, reducing direct contact with the external environment. It can effectively prevent the conductive nanomaterial from being oxidized, corroded, or reacting with other chemical substances, thereby improving the chemical stability of the flexible conductive film 10. At the same time, optionally, the conductive nanomaterial includes a rod-like structure and a granular structure. The rod-like structure has a specific aspect ratio. During the hot pressing composite and embedding process, its long axis direction can be arranged in an orderly manner along the melt flow direction of the polymer film 103, reducing the resistance during embedding. The granular structure is relatively small and regular in size, and can be more easily filled into the microscopic gaps of the polymer film 103. This allows the conductive nanomaterial as a whole to be more easily and quickly embedded into the interior of the polymer film 103, improving production efficiency and reducing process costs.

[0095] The various embodiments in the specification of this application are described in a progressive, parallel, or progressive and parallel manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the various embodiments can be referenced to each other. The embodiments provided in the embodiments of this application can be combined with each other if there is no contradiction.

[0096] It should be noted that in the description of this application, it should be understood that the description of the drawings and embodiments is illustrative rather than restrictive. The same figure numbers throughout the embodiments of the specification identify the same structure. In addition, for the purpose of understanding and ease of description, the drawings may exaggerate the thickness of some layers, films, panels, regions, etc. It is also understood that when an element such as a layer, film, region or substrate is referred to as "on" another element, the element may be directly on the other element or there may be an intermediate element. In addition, "on" refers to positioning an element on or below another element, but does not essentially mean positioning on the upper side of another element according to the direction of gravity.

[0097] The terms "upper," "lower," "top," "bottom," "inner," "outer," and the like, indicating positions or locations, are based on the positions or locations shown in the accompanying drawings and are intended solely to facilitate and simplify the description of this application. They are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. When a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally located component.

[0098] It should also be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such article or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the article or device comprising the aforementioned elements.

[0099] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a flexible conductive film, characterized in that: include: Providing a carrier film, the carrier film comprising a first surface and a second surface disposed opposite to each other, forming a conductive layer on the first surface of the carrier film, the conductive layer comprising a conductive nanomaterial; Laying a polymer film on the side of the conductive layer away from the carrier film, wherein the polymer film is a thermoplastic material; Laying a flexible substrate on the side of the polymer film away from the conductive layer; Hot-pressing the laminated structure of the carrier film, the conductive layer, the polymer film, and the flexible substrate so that the conductive nanomaterial is embedded in the polymer film to form a composite conductive layer; The carrier film is removed.

2. The preparation method according to claim 1, characterized in that The adhesive properties of the first surface of the carrier film are lower than the adhesive properties of the second surface.

3. The preparation method according to claim 1, characterized in that The melting temperature of the polymer film is lower than the melting temperature of the carrier film and lower than the melting temperature of the flexible substrate; the melting temperature of the conductive layer is lower than the melting temperature of the carrier film and lower than the melting temperature of the flexible substrate.

4. The preparation method according to claim 1, characterized in that The melting temperature of the polymer adhesive film increases in a direction from the carrier film to the flexible substrate.

5. The preparation method according to claim 4, characterized in that In the direction in which the carrier film points toward the flexible substrate, the polymer adhesive film includes a plurality of sub-adhesive films stacked in sequence, and the melting temperatures of the sub-adhesive films increase in sequence.

6. The preparation method according to claim 1, characterized in that The conductive layer at least includes conductive rod-shaped nanomaterials, and the length direction of at least part of the rod-shaped nanomaterials forms an angle greater than 0° with the plane where the polymer film is located.

7. The preparation method according to claim 1, characterized in that The thickness of the polymer film is greater than the thickness of the conductive layer.

8. The preparation method according to claim 1, characterized in that Forming a conductive layer on the first surface of the carrier film, comprising: dispersing the conductive nanomaterial in a solvent to form a dispersion; forming a coating of the dispersion on a first surface of the carrier film; The coating layer of the dispersion is cured to form the conductive layer.

9. A flexible conductive film, characterized in that: include: A flexible substrate and a composite conductive layer are sequentially arranged, wherein the composite conductive layer comprises a polymer film and a conductive nanomaterial embedded in the polymer film, wherein the conductive nanomaterial is embedded in the polymer film based on hot pressing and melting.

10. The flexible conductive film according to claim 9, characterized in that: The depth of the conductive nanomaterial embedded in the polymer film is not less than 2 / 3 of the thickness of the polymer film; And / or, the conductive nanomaterial includes a rod-like structure and a granular structure.

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