Conductive paste, conductive film and preparation method thereof

Abstract

The embodiment of the invention relates to the technical field of new materials, and discloses conductive paste, a conductive film and a preparation method thereof, and the conductive paste comprises matrix resin, composite silver powder, carbon nanotubes and a curing agent. Wherein the composite silver powder comprises flaky silver powder with D50 being 0.7-2.0 microns and spherical silver powder with D50 being 0.4-0.8 microns, and the mass ratio of the composite silver powder to the matrix resin is (8: 2)-(16: 1). The mass of the carbon nanotube is 0.01-0.1% of the mass of the matrix resin, and the mass of the curing agent is 0.1-0.5% of the mass of the matrix resin. In the embodiment, after being cured, the conductive paste has a multi-scale composite network structure, so that deformation can be responded in time, crack propagation is prevented, the bending and tensile resistance is improved, and good electrical properties are still kept under deformation response. Therefore, the conductive film prepared from the conductive slurry has good bending and tensile resistance, and still keeps good electrical properties under response deformation.

Description

Conductive paste, conductive film and preparation method thereof Technical Field

[0001] The embodiments of the present application relate to the field of new material technology, and in particular to a conductive paste, a conductive film, and a preparation method thereof. Background Art

[0002] Transparent conductive films, which possess both high conductivity and transparency, have seen widespread application in recent years in touch screens, e-paper, smart windows, electronic skin, transparent electric heaters, flexible sensors, electromagnetic shielding, and wearable devices. Common transparent conductive films include ITO (tin-doped indium trioxide) and AZO (aluminum-doped zinc oxide). However, with the increasing demand for larger and more affordable touch panels, traditional ITO films are no longer sufficient. Conductive films such as metal meshes and silver nanowires are now widely used.

[0003] New electronic devices are beginning to develop towards flexibility and even stretchability. However, some conductive pastes known to the inventors of this application have poor ductility after curing, which makes the metal grid have poor toughness, that is, poor bending and stretching resistance, thereby restricting the application of conductive films in the electronic field.

[0004] Summary of the Invention

[0005] In light of this, some embodiments of the present application provide a conductive paste, a conductive film, and a method for preparing the same. The conductive wires formed by curing the conductive paste exhibit a multi-scale composite network structure, capable of timely responding to deformation and preventing crack propagation, thereby improving their flexural and tensile properties, and maintaining good electrical properties despite responsive deformation. Consequently, the conductive film prepared using the conductive paste exhibits excellent flexural and tensile properties, maintaining good electrical properties despite responsive deformation.

[0006] In a first aspect, some embodiments of the present application provide a conductive paste comprising a base resin, composite silver powder, carbon nanotubes, and a curing agent;

[0007] The composite silver powder includes flake silver powder with a D50 of 0.7-2.0 μm and spherical silver powder with a D50 of 0.4-0.8 μm, and the mass ratio between the composite silver powder and the matrix resin is 8:2-16:1;

[0008] The mass of the carbon nanotubes is 0.01-0.1% of the mass of the matrix resin; the mass of the curing agent is 0.1-0.5% of the mass of the matrix resin.

[0009] In some embodiments, the mass ratio of the flaky silver powder to the spherical silver powder is 10:1-1:10.

[0010] In some embodiments, the particle size of the flaky silver powder satisfies D99≤3 μm, and the particle size of the spherical silver powder satisfies D99≤1 μm.

[0011] In some embodiments, the curing agent includes a latent isocyanate.

[0012] In some embodiments, the conductive paste further includes an organic coupling agent, and the mass of the organic coupling agent is 0.1-0.3% of the mass of the composite silver powder.

[0013] In some embodiments, one terminal of the organic coupling auxiliary comprises an amino group and an epoxy group.

[0014] In some embodiments, the conductive paste has a viscosity of 2000-20000 cps, and / or a solid content of 65%-85%.

[0015] In some embodiments, the elongation of the base resin is greater than or equal to 100%.

[0016] In some embodiments, the carbon nanotubes have a length of 0.5 μm to 2 μm.

[0017] In a second aspect, some embodiments of the present application provide a conductive film, including:

[0018] substrate,

[0019] An optical adhesive layer is provided on the substrate, and a side of the optical adhesive layer away from the substrate is provided with grid-shaped grooves;

[0020] The conductive grid is formed by filling the conductive paste of the first aspect into grid-shaped grooves and solidifying the resulting conductive paste.

[0021] In a third aspect, some embodiments of the present application provide a method for preparing a conductive film, comprising:

[0022] Imprinting the optical adhesive coated on the substrate using an imprint template, and separating the imprint template after curing to form an optical adhesive layer with grid-shaped grooves on the substrate;

[0023] The conductive paste of the first aspect is filled in the grid-shaped grooves and cured to obtain a conductive film.

[0024] In some embodiments, before applying the optical adhesive to the substrate, the method further comprises:

[0025] The coated surface of the substrate is surface treated to increase the adhesion between the substrate and the optical adhesive.

[0026] In some embodiments, the surface treatment is performed in the following manner:

[0027] Applying hydrogen peroxide to the coating surface of the substrate and then performing plasma treatment to hydroxylate the coating surface;

[0028] The hydroxylated coating surface is treated with a silane coupling agent having a carbon-carbon double bond to introduce a carbon-carbon double bond for reacting with the optical adhesive.

[0029] In some embodiments, the conductive paste is filled into the grid-shaped grooves in the following manner:

[0030] The grid-shaped grooves are filled once with conductive slurry, and after the surface is dry, the grid-shaped grooves are filled twice with conductive slurry.

[0031] In some embodiments, after the secondary filling and before curing, the method further comprises:

[0032] After surface drying, the carbon nanotube dispersion is filled on the surface of the conductive paste in the grid-shaped grooves.

[0033] In a fourth aspect, some embodiments of the present application further provide a touch panel comprising the conductive film of the second aspect, or a conductive film prepared by the method of the third aspect.

[0034] In a fifth aspect, some embodiments of the present application further provide a display device comprising the touch panel of the fourth aspect.

[0035] In a sixth aspect, some embodiments of the present application further provide an electronic device comprising the display device of the fifth aspect.

[0036] The beneficial effects of the embodiments of the present application: Unlike the prior art, the conductive paste provided by the embodiments of the present application includes a matrix resin, composite silver powder, carbon nanotubes, and a curing agent. The composite silver powder includes flake silver powder with a D50 of 0.7-2.0 μm and spherical silver powder with a D50 of 0.4-0.8 μm, with the mass ratio of the composite silver powder to the matrix resin being 8:2-16:1. The mass of the carbon nanotubes accounts for 0.01-0.1% of the mass of the matrix resin, and the mass of the curing agent accounts for 0.1-0.5% of the mass of the matrix resin.

[0037] In this embodiment, after the conductive paste with the above components is cured, under the action of external tensile force or bending force, the spherical silver powder can migrate in response to bending and tensile deformation, and the flake silver powder forms a bridge connection between the spherical silver powders. The two cooperate with each other, so that the cured conductive paste (such as a wire or a metal grid) can still have good conductive properties under elastic deformation. The flake silver powder with a D50 of 0.7-2.0um and the spherical silver powder with a D50 of 0.4-0.8um make the composite silver powder adapt to each other after stacking, and can be filled as tightly as possible, reducing local bridging to form structural defects such as holes, thereby improving mechanical properties, reducing resistance, and improving conductive properties. In addition, the carbon nanotubes further form a bridge connection between the composite silver powders, forming a multi-scale composite network structure with the composite silver powder, thereby being able to respond to deformation in a timely manner and prevent crack propagation, improving its anti-bending and tensile properties, and still maintaining good electrical properties under response deformation. Therefore, the conductive film prepared by using the conductive paste has good bending and tensile properties and still maintains good electrical properties under response deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0039] FIG1 is a schematic diagram of the microstructure of the conductive paste after curing in some embodiments of the present application;

[0040] FIG2 is a schematic flow chart of a method for preparing a conductive film in some embodiments of the present application. DETAILED DESCRIPTION

[0041] The present application is described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present application, but are not intended to limit the present application in any form. It should be noted that those skilled in the art may make several variations and improvements without departing from the scope of the present application. These all fall within the scope of protection of the present application.

[0042] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0043] It should be noted that, if there is no conflict, the various features in the embodiments of the present application can be combined with each other and are all within the scope of protection of the present application. In addition, although the functional modules are divided in the device schematic and the logical order is shown in the flow chart, in some cases, the steps shown or described can be performed in a different order than the module division in the device or the order in the flow chart. In addition, the words "first", "second", "third", etc. used herein do not limit the data and execution order, but only distinguish between the same items or similar items with basically the same functions and effects.

[0044] Unless otherwise defined, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which this application belongs. The terms used in this specification and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" as used in this specification includes any and all combinations of one or more of the relevant listed items.

[0045] In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0046] Currently, the commonly used transparent conductive films are transparent metal oxides such as ITO (tin-doped indium trioxide), but they are inherently brittle and have high resistance. In actual applications, the voltage requirements of touch driver chips are relatively high, and special chips are needed. The chip cost is high, which to some extent limits their application in the field of flexible transparent conductive films.

[0047] Domestic and international researchers have proposed several materials to replace traditional ITO (indium tin oxide), such as graphene, carbon nanotubes, and metal meshes. However, carbon nanotubes (with a square resistance of 60 to 300 Ω / sq) and graphene (with a square resistance of 50 to 500 Ω / sq) have high electrical resistances, and their synthesis requires complex processes and equipment, such as chemical vapor deposition, which limits their application in production.

[0048] The metal mesh conductive film is made by using conductive paste to prepare patterned wires on the surface or inside of a flexible and highly transmittance substrate to form a metal mesh with high conductivity. The mesh area without patterns is a transparent substrate, and light can pass through normally.

[0049] Metal mesh conductive films, due to their high transparency, conductivity, and flexibility, have great application value in capacitive touch and flexible display applications. In particular, combining metal mesh conductive films with in-mold electronics (IME) technology can be used to create curved touch panels, serving as intelligent skins for electronic devices such as robots and electric vehicles.

[0050] During the in-mold forming process, the conductive film needs to withstand a certain degree of bending and stretching, so it is necessary to develop a corresponding bendable and stretchable metal grid. For example, in the in-mold electronic process to produce curved touch displays, the metal grid in the conductive film often needs to withstand 20% or even 100% stretching. For another example, in flexible touch displays (such as foldable screens), the conductive film often needs to be repeatedly bent tens of thousands or even millions of times.

[0051] It's understood that the metal grid is formed by curing a conductive paste. Conductive paste is typically a viscous paste composed of silver powder, a binder, a solvent, and a curing agent. Once the paste cures and dries, the solvent evaporates and the curing agent shrinks, reducing the distance between the silver particles and allowing them to contact each other, thus forming a conductive path.

[0052] However, some conductive pastes known to the inventors of the present application, such as those whose main conductive components are nano-silver powder or nano-copper powder, lack the ability to form a network structure when the conductive film is stretched or bent, resulting in insufficient stability in the conductive performance of the metal grid when bent or stretched, and large resistance fluctuations.

[0053] Based on this, this application proposes the following technical solutions:

[0054] Some embodiments of the present application provide a conductive paste comprising a matrix resin, composite silver powder, carbon nanotubes, and a curing agent. The composite silver powder comprises flake silver powder with a D50 of 0.7-2.0 μm and spherical silver powder with a D50 of 0.4-0.8 μm, with the mass ratio of the composite silver powder to the matrix resin being 8:2-16:1. The mass of the carbon nanotubes accounts for 0.01-0.1% of the mass of the matrix resin, and the mass of the curing agent accounts for 0.1-0.5% of the mass of the matrix resin.

[0055] In this embodiment, after the conductive paste having the above components is cured, under the action of external tensile force or bending force, the spherical silver powder can migrate in response to bending and tensile deformation, and the flake silver powder forms a bridge connection between the spherical silver powders. The two cooperate with each other, so that the cured conductive paste (such as a wire or a metal grid) can still have good conductive properties under elastic deformation. The flake silver powder with a D50 of 0.7-2.0um and the spherical silver powder with a D50 of 0.4-0.8um make the composite silver powder particle size adapted, which can be filled as tightly as possible, reducing local bridging to form structural defects such as holes, thereby improving mechanical properties, reducing resistance, and improving conductive properties. In addition, the carbon nanotubes further form a bridge connection between the composite silver powders, forming a multi-scale composite network structure with the composite silver powder, thereby being able to respond to deformation in a timely manner and prevent crack propagation, improving its anti-bending and tensile properties, and still maintaining good electrical properties under response deformation. Therefore, the conductive film prepared by using the conductive paste has good bending and tensile properties and still maintains good electrical properties under response deformation.

[0056] The following describes the conductive paste provided by some embodiments of the present application. The conductive paste includes a matrix resin, composite silver powder, carbon nanotubes, and a curing agent. The composite silver powder includes flake silver powder with a D50 of 0.7-2.0 μm and spherical silver powder with a D50 of 0.4-0.8 μm. The mass ratio of the composite silver powder to the matrix resin is 8:2-16:1. The mass of the carbon nanotubes is 0.01-0.1% of the mass of the matrix resin, and the mass of the curing agent is 0.1-0.5% of the mass of the matrix resin.

[0057] The matrix resin serves as a carrier for conductive materials such as silver powder and carbon nanotubes. Upon curing, the matrix resin also acts as a bond between the silver powder and carbon nanotubes. In some embodiments, the matrix resin can be made of a polyurethane with high elongation. In some embodiments, the matrix resin can be made of other polyesters, polyacrylates, or other resins with elongations ≥100% or ≥500%. These high-elongation resins exhibit high elongation upon curing, thereby enhancing the conductor's resistance to bending and tensile forces.

[0058] In some embodiments, the glass transition temperature of the matrix resin is lower than the operating temperature of the in-mold process. For example, the glass transition temperature of the matrix resin is at least 20°C lower than the operating temperature of the in-mold process. In other words, during the in-mold process, the cured matrix resin in the metal mesh of the conductive film is in a highly elastic or viscous state, capable of promptly deforming in response to stretching or bending, thereby reducing brittle fracture and increasing the metal mesh's resistance to bending and stretching.

[0059] Among them, the composite silver powder includes two different forms of silver particles, namely spherical silver powder and flaky silver powder. It can be understood that spherical silver powder is silver particles with roughly spherical particles, the contact area between particles is small, and it has good migration ability under the action of force. Flake silver powder is silver particles with roughly flaky particles, the contact area between particles is large, and it is relatively stable under the action of force. Based on the fact that the composite silver powder includes spherical silver powder and flaky silver powder, after the conductive paste is cured, under the action of external tensile force or bending force, the spherical silver powder can respond to bending and tensile deformation and migrate, and the flaky silver powder forms a bridge connection between the spherical silver powders, and the two cooperate with each other, so that the cured conductive paste (such as a wire or a metal grid) can still have good conductivity under elastic deformation.

[0060] In this embodiment, both the spherical and flake silver powders have relatively small particle sizes. The D50 of the spherical silver powder is 0.4-0.8 μm, while that of the flake silver powder is 0.7-2.0 μm. It is understood that D50 refers to the particle size at which the cumulative particle size distribution percentage of a sample reaches 50%, and can be used to represent the average particle size of the powder.

[0061] It can be understood that smaller-sized spherical silver powder and flake silver powder, when stacked, adapt to each other and can be filled as tightly as possible, reducing structural defects such as local bridging to form holes, thereby improving mechanical properties, reducing resistance, and improving conductivity.

[0062] If the composite silver powder has local bridging or loose filling within the metal mesh, forming structural defects such as holes, this can cause the metal mesh to crack or break during bending and stretching, resulting in increased resistance or short circuits. In some embodiments, the particle size of the flaky silver powder satisfies D99 ≤ 3 μm, and the particle size of the spherical silver powder satisfies D99 ≤ 1 μm. It is understood that D99 refers to the particle size corresponding to the 99th percentile of the cumulative particle size distribution of a sample. In this embodiment, the particle size of the flaky silver powder is less than 3 μm, and the particle size of the spherical silver powder is less than 1 μm, further enabling the composite silver powder to be tightly packed, improving its bending and tensile resistance.

[0063] Considering the high activity of nano-scale powders, which are prone to sintering and form larger particles, which are not conducive to responding to bending and tensile deformation, in some implementations, air flow separation can be used to remove silver particles with a diameter of less than 100nm from the composite silver powder. This ensures that the particle size of the flaky silver powder in the composite powder meets the requirements of 100nm≤D99≤3um, and the particle size of the spherical silver powder meets the requirements of 100nm≤D99≤1um, which facilitates dense packing, reduces structural defects, and improves bending and tensile resistance.

[0064] In some embodiments, the mass ratio of the flaky silver powder to the spherical silver powder is 10:1 to 1:10. The composite silver powder formulated with this ratio can balance the responsive deformation capability of the spherical silver powder with the bridging conductivity of the flaky silver powder, improving its flexural tensile strength and electrical conductivity.

[0065] The carbon nanotubes are fibrous, flexible, conductive materials that can bridge spherical and flake silver particles. In some embodiments, the carbon nanotubes are 0.5 μm to 2 μm in length and 0.01 to 0.1% of the mass of the matrix resin.

[0066] When the conductive paste solidifies, a small amount of carbon nanotubes further form bridge conduction between the composite silver powders, forming a multi-scale composite network structure with the composite silver powders. This can respond to deformation in a timely manner and prevent crack propagation, thereby improving its bending and tensile properties and maintaining good electrical properties under response deformation.

[0067] A curing agent is a substance used to accelerate or control the curing reaction of a resin. Under the influence of the curing agent and temperature, the matrix resin in the conductive paste undergoes chemical reactions such as condensation, ring closure, addition, or catalysis, transforming into a solid. This solid then bonds with the composite silver powder and carbon nanotubes, forming a conductive wire with a multi-scale composite network structure.

[0068] In some embodiments, the curing agent includes latent isocyanate, and the mass of the latent isocyanate is 0.1-0.5% of the mass of the matrix resin, which is beneficial to improving the bending tensile properties of the conductive paste after curing and the conductive properties after deformation response.

[0069] In some embodiments, the conductive paste further includes an organic coupling agent, and the mass of the organic coupling agent is 0.1-0.3% of the mass of the composite silver powder.

[0070] The organic coupling agent can improve the interface interaction between different materials such as composite silver powder and resin, thereby improving the bending tensile properties of the conductive paste after curing and the conductive performance after response to deformation.

[0071] In some embodiments, the organic coupling aid can be a silane coupling agent with a molecular weight of 200-4000 and having amino or epoxy groups at the end, an acrylate oligomer with a molecular weight of 200-4000 and having amino or epoxy groups at the end, or a polyether with a molecular weight of 200-4000 and having amino or epoxy groups at the end, and copolymers thereof. In some embodiments, the organic coupling aid can be a polyurethane oligomer with a molecular weight of 200-4000 and having amino or epoxy groups at the end, a polyester oligomer with a molecular weight of 200-4000 and having amino or epoxy groups at the end, or a low molecular weight polysiloxane with a molecular weight of 200-4000 and having amino or epoxy groups at the end, and copolymers thereof.

[0072] The amino and epoxy groups at one end of the organic coupling agent are easy to react with the surface of the composite silver powder, while the other end can be cross-linked with the matrix resin under the action of the latent isocyanate curing agent, thereby effectively enhancing the interaction between the filler interfaces and the mechanical properties, which is beneficial to improving the bending tensile properties of the conductive paste after curing and the conductive properties after response to deformation.

[0073] In some embodiments, the conductive paste has a viscosity of 2000-20000 cps, and / or a solid content of 65%-85%.

[0074] It is understood that by adding solvent to adjust the viscosity of the conductive paste to 2,000-20,000 cps, it can meet the requirements of multiple subsequent coating and filling processes. Compared to high-viscosity conductive pastes that form thicker conductive fillers through a single coating and filling, low-viscosity conductive pastes have better coating properties and can form denser, less defective conductive circuits through multiple coating and filling processes. This can effectively improve the conductive paste's anti-flexural tensile properties after curing, as well as its conductivity after deformation response.

[0075] In some embodiments, viscosity adjustment can be performed by mixing a high-boiling point solvent with a medium-boiling point solvent. For example, the mass ratio of the high-boiling point solvent to the medium-boiling point solvent is 1:9-9:1. In some embodiments, the boiling point of the high-boiling point solvent is greater than or equal to 180°C, such as isophorone, DBE, diethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, ethylene glycol diacetate, or diethyl adipate. In some embodiments, the boiling point of the medium-boiling point solvent is between 100°C and 180°C, such as ethylene glycol ethyl ether acetate, MIBK, diacetone alcohol, or ethylene glycol diethyl ether.

[0076] It is understood that the base resin, composite silver powder, carbon nanotubes, curing agent, and organic coupling agent are uniformly dispersed in a solvent at a certain mass ratio to obtain the conductive paste. In some embodiments, the conductive paste can be prepared using the following preparation method, which includes but is not limited to the following steps:

[0077] (1) A certain amount of base resin is dissolved in a high boiling point solvent and stirred at 80°C for 4-12 hours to form a solution with a solid content of 30-40%.

[0078] (2) Add carbon nanotubes to the solution in step (1), with the mass of the carbon nanotubes being 0.01-0.1% of the mass of the matrix resin. First, use a low-speed agitator to disperse and wet the solution, stirring at 50-300 rpm for 0.5-2 hours; then, use a high-speed agitator to disperse the solution, stirring at 1000-3000 rpm for 10-30 minutes; finally, place the solution in a ball mill and mill for 8-24 hours.

[0079] (3) Add a high boiling point solvent to the carbon nanotube dispersion obtained in step (2), dilute to 20%, and ultrasonically vibrate for 15-60 minutes. Then, filter through a filter membrane with a pore size of 3 μm to remove undispersed carbon nanotube agglomerates.

[0080] (4) Add the composite silver powder to the solution obtained in step (3), wherein the mass ratio between the composite silver powder and the matrix resin is 8:2-16:1. Add a high-boiling point solvent and a medium-boiling point solvent according to the required viscosity or solid content, and use a stirrer to stir at a low speed (50-100 rpm for 1-2 hours) to disperse the composite silver powder. Then, add an organic coupling agent and a curing agent, and then stir at a high speed of 1000-3000 rpm for 10-30 minutes.

[0081] (5) The slurry in step (4) is rolled using a three-roll mill to obtain a uniformly dispersed slurry.

[0082] (6) The slurry in step (5) is filtered through a filter membrane with a pore size of 3 μm to obtain a conductive slurry.

[0083] The conductive paste prepared by the above steps has a conductive material with multi-scale morphology. Compared with a single conductive material, it has better anti-bending and tensile properties and can still maintain good electrical properties under response deformation.

[0084] Please refer to Figure 1. After the conductive paste containing only flaky silver powder is cured, it responds slowly when subjected to tensile or bending forces, which easily causes brittle fracture, resulting in large resistance fluctuations. After the conductive paste containing only spherical silver powder is cured, it responds quickly when subjected to tensile or bending forces. However, due to the heterogeneity of the conductive paste, microcracks will be generated. At this time, there is a lack of flaky or fibrous fillers for bridging, resulting in large resistance fluctuations. When the conductive paste includes spherical silver powder, flaky silver powder and carbon nanotubes, the carbon nanotubes and spherical silver powder network bridges the flaky silver powder to form a multi-scale composite network structure. The spherical silver powder can migrate in response to bending and tensile deformation, and the flaky silver powder and carbon nanotubes form a bridge connection between the spherical silver powder. As a result, it can respond to deformation in a timely manner and prevent crack expansion, improve its anti-bending and tensile properties, and still maintain good electrical properties under response deformation.

[0085] In summary, the conductive paste provided in the embodiments of the present application includes a matrix resin, composite silver powder, carbon nanotubes, and a curing agent. The composite silver powder includes flake silver powder with a D50 of 0.7-2.0 μm and spherical silver powder with a D50 of 0.4-0.8 μm. The mass ratio of the composite silver powder to the matrix resin is 8:2-16:1. The mass of the carbon nanotubes accounts for 0.01-0.1% of the mass of the matrix resin.

[0086] In this embodiment, after the conductive paste with the above components is cured, under the action of external tensile force or bending force, the spherical silver powder can migrate in response to bending and tensile deformation, and the flake silver powder forms a bridge connection between the spherical silver powders. The two cooperate with each other, so that the cured conductive paste (such as a wire or a metal grid) can still have good conductive properties under elastic deformation. The flake silver powder with a D50 of 0.7-2.0um and the spherical silver powder with a D50 of 0.4-0.8um make the composite silver powder adapt to each other after stacking, and can be filled as tightly as possible, reducing local bridging to form structural defects such as holes, thereby improving mechanical properties, reducing resistance, and improving conductive properties. In addition, the carbon nanotubes further form a bridge connection between the composite silver powders, forming a multi-scale composite network structure with the composite silver powder, thereby being able to respond to deformation in a timely manner and prevent crack propagation, improving its anti-bending and tensile properties, and still maintaining good electrical properties under response deformation. Therefore, the conductive film prepared by using the conductive paste has good bending and tensile properties and still maintains good electrical properties under response deformation.

[0087] Some embodiments of the present application also provide a conductive film comprising a substrate, an optical adhesive layer, and a conductive mesh. The optical adhesive layer is disposed on the substrate, and a surface of the optical adhesive layer facing away from the substrate is provided with a grid-like groove. The conductive mesh is formed by curing the conductive paste described in any of the aforementioned embodiments into the grid-like grooves.

[0088] The substrate can be a copolyester with a ductility greater than or equal to 100%, or a high-molecular-weight polycarbonate. These substrates possess ductility and can meet the bending and stretching deformation requirements of the in-mold process. It is understood that the substrate is transparent and has high light transmittance.

[0089] The optical adhesive is one having a ductility greater than or equal to 100% after curing. That is, the ductility of the optical adhesive layer is greater than or equal to 100%. In some embodiments, the glass transition temperature (Tg) of the optical adhesive layer is lower than the operating temperature of the in-mold process, for example, at least 20°C lower than the operating temperature of the in-mold process. Consequently, during the in-mold process, the optical adhesive layer is in a highly elastic or viscous state, easily deformed by stretching and bending, and thus can meet the deformation requirements of the in-mold process for stretching and bending.

[0090] In some embodiments, after the optical adhesive is coated on the substrate, an embossing template may be used to emboss the optical adhesive, and after curing, an optical adhesive layer having grid-like grooves is formed. In some embodiments, the diameter of the grid-like grooves is 3-20 μm.

[0091] The conductive paste in any one of the aforementioned embodiments is filled in the grid-shaped grooves and solidified to form the conductive grid.

[0092] This conductive paste has the same components and functions as the conductive paste in any of the above-mentioned embodiments, and will not be further described here. The conductive wire formed by curing the conductive paste has a multi-scale composite network structure that can promptly respond to deformation and prevent crack propagation, thereby improving its bending and tensile properties, and maintaining good electrical properties under responsive deformation. As a result, the conductive film including the metal mesh formed by curing the conductive paste has good bending and tensile properties and maintains good electrical properties under responsive deformation.

[0093] Some embodiments of the present application further provide a method for preparing a conductive film. Referring to FIG. 2 , the method S100 includes but is not limited to the following steps:

[0094] S10: Imprinting the optical adhesive coated on the substrate using an imprint template, and separating the imprint template after curing to form an optical adhesive layer with grid-shaped grooves on the substrate.

[0095] The substrate can be a copolyester with a ductility greater than or equal to 100%, or a high-molecular-weight polycarbonate. These substrates possess ductility and can meet the bending and stretching deformation requirements of the in-mold process. It is understood that the substrate is transparent and has high light transmittance.

[0096] The optical adhesive is one having a ductility greater than or equal to 100% after curing. That is, the ductility of the optical adhesive layer is greater than or equal to 100%. In some embodiments, the glass transition temperature (Tg) of the optical adhesive layer is lower than the operating temperature of the in-mold process, for example, at least 20°C lower than the operating temperature of the in-mold process. Consequently, during the in-mold process, the optical adhesive layer is in a highly elastic or viscous state, easily deformed by stretching and bending, and thus can meet the deformation requirements of the in-mold process for stretching and bending.

[0097] In some embodiments, the coating thickness of the optical adhesive is 20-50 μm. It is understood that the optical adhesive is coated on one surface of the sheet substrate. After the coating is completed, the optical adhesive is embossed using an embossing template. It is understood that the embossing template has a structure complementary to the grid-like grooves. In some embodiments, the embossing depth is 10-20 μm. UV light is used for curing, and the embossing template is separated after curing to obtain an optical adhesive layer, and the surface of the optical adhesive layer away from the substrate has a grid-like groove. In some embodiments, the diameter width of the grid-like groove is 3-20 μm.

[0098] S20: Filling the grid-shaped grooves with the conductive paste of any one of the aforementioned embodiments, and curing the mixture to obtain a conductive film.

[0099] In some embodiments, the conductive paste can be applied to the surface of the optical adhesive layer. Because the surface of the optical adhesive layer facing away from the substrate has a grid of grooves, the conductive paste can fill the grid of grooves. The conductive paste is then scraped from areas outside the grooves, completing a single filling. It should be understood that the number of fillings is unlimited; after one or more fillings, the conductive paste will completely fill the grooves.

[0100] Based on the curing temperature of the matrix resin in the conductive paste, the product filled with the conductive paste is baked and cured at the curing temperature, for example, at 80°C-120°C for 15-30 minutes, so that the surface of the substrate has a metal grid, thereby obtaining a conductive film.

[0101] In this embodiment, the conductive paste has the same components and functions as the conductive paste in any of the above embodiments, and will not be described in detail here. The conductive wire formed by curing the conductive paste has a multi-scale composite network structure that can promptly respond to deformation and prevent crack propagation, thereby improving its bending and tensile properties and maintaining good electrical properties under responsive deformation. As a result, the conductive film including the metal mesh formed by curing the conductive paste has good bending and tensile properties and maintains good electrical properties under responsive deformation.

[0102] In some embodiments, before applying the optical adhesive to the substrate, the method S100 further includes:

[0103] S30: performing surface treatment on the coating surface of the substrate to increase the adhesion between the substrate and the optical adhesive.

[0104] It is understood that when the adhesion between the substrate and the optical adhesive is enhanced, the substrate and the optical adhesive layer have a stronger bonding force. When the conductive film is bent, it is not easy to cause interface peeling, which is conducive to maintaining its electrical properties.

[0105] In some embodiments, the surface treatment is performed in the following manner:

[0106] (1) After applying hydrogen peroxide to the coating surface of the substrate, plasma treatment is performed to hydroxylate the coating surface.

[0107] (2) Treating the hydroxylated coating surface with a silane coupling agent having a carbon-carbon double bond to introduce a carbon-carbon double bond for reacting with the optical adhesive.

[0108] Plasma treatment involves using a plasma surface treatment machine to physically and chemically modify the surface of a material, improving its adhesion. Plasma treatment of a substrate coated with hydrogen peroxide generates more hydroxyl groups on the coated surface.

[0109] Then, the hydroxylated coating surface is treated with a silane coupling agent having a carbon-carbon double bond. The silane coupling agent reacts with the hydroxyl group to produce a chemical bond, while the carbon-carbon double bond remains, which is equivalent to introducing a carbon-carbon double bond on the substrate surface. Silane coupling agents having a carbon-carbon double bond may include vinyltrichlorosilane, vinyltriethoxysilane, vinyltrimethoxysilane, or γ-methacryloxypropyltrimethoxysilane.

[0110] It is understood that the optical adhesive is an acrylate containing double bonds, and the carbon-carbon double bonds on the surface of the substrate react with the acrylate containing double bonds, thereby forming a strong bond.

[0111] In this embodiment, the surface treatment method can effectively increase the bonding strength between the substrate and the optical adhesive layer, thereby effectively improving the bending and tensile properties. When the conductive film is bent, it is less likely to cause interface peeling, which is conducive to maintaining its electrical properties.

[0112] In some embodiments, the conductive paste is filled into the grid-shaped grooves in the following manner:

[0113] The grid-shaped grooves are filled once with conductive slurry, and after the surface is dry, the grid-shaped grooves are filled twice with conductive slurry.

[0114] For example, the conductive paste is applied to the groove surfaces of the optical adhesive layer, filling the grid-like grooves. The conductive paste is then scraped off from areas not containing grooves, completing the filling process. Next, the surface is dried at 60-120°C for 2-5 minutes. It is important to note that the surface drying temperature should not exceed the glass transition temperature of the substrate.

[0115] After the surface is dry, continue applying conductive paste to the groove surface of the optical adhesive layer. This allows the conductive paste to fill the grid-like grooves a second time. Scrape the conductive paste from areas other than the grooves to complete the secondary filling. Next, dry at 60-120°C for 2-5 minutes.

[0116] In this embodiment, by applying the conductive paste multiple times and then drying it, the filler in the grid-shaped groove can be made denser and have fewer defects, which can effectively improve the bending and tensile properties of the conductive metal grid and the conductive performance after deformation.

[0117] In some embodiments, after the secondary filling and before curing, the method S100 further includes:

[0118] S40: After surface drying, the carbon nanotube dispersion is filled on the surface of the conductive paste in the grid-shaped grooves.

[0119] The carbon nanotube dispersion is a solution of carbon nanotubes and a matrix resin dispersed in a solvent. After the secondary filling with the conductive paste, the carbon nanotube dispersion is applied to the surface of the grooves to further cover the conductive paste in the grooves. The carbon nanotube dispersion is then scraped off from areas outside the grooves to complete the filling.

[0120] It's understood that due to the conductivity of carbon nanotubes and the viscosity of the matrix resin, the carbon nanotube dispersion effectively covers and fills surface defects in the filler within the grooves, thereby effectively reducing cracks caused by surface defects and ensuring that the metal mesh maintains good electrical properties despite bending and stretching deformation. Furthermore, it effectively masks the metallic luster imparted by the silver powder, improving environmental stability.

[0121] In summary, the conductive film prepared by the above-mentioned method for preparing a conductive film has the composition and performance of the conductive paste in the above-mentioned embodiment. That is, the metal grid formed by curing the conductive paste has a multi-scale composite network structure, which can respond to deformation in time and prevent crack propagation, thereby improving its anti-bending and tensile properties, and still maintaining good electrical properties under the response deformation. On the other hand, by introducing carbon-carbon double bonds by hydroxylation on the surface of the substrate, the adhesion between the substrate and the optical adhesive layer can be effectively increased. When the conductive film is bent, interface peeling is not likely to occur, which is conducive to maintaining its electrical properties. In addition, the use of a low-viscosity conductive paste for secondary filling can make the filler in the grid-shaped groove denser and less defective, and can effectively improve the anti-bending and tensile properties of the conductive metal grid and the conductive properties after the response deformation.

[0122] In order to further illustrate the technical solution of the present application, several examples and comparative examples of the prepared conductive films are provided below for verification purposes.

[0123] Example 1:

[0124] Provide conductive paste: The conductive paste includes the following components and weight content:

[0125] Polyurethane is used as the base resin;

[0126] The composite silver powder has a mass ratio of 9:1 to the matrix resin, wherein the mass ratio of the flaky silver powder to the spherical silver powder is 7:3, the D50 of the flaky silver powder is 0.7 μm, and the D50 of the spherical silver powder is 0.4 μm;

[0127] carbon nanotubes, 0.03% of the matrix resin mass;

[0128] Latent isocyanate is used as curing agent, accounting for 0.2% of the mass of the base resin;

[0129] A silane coupling agent with a molecular weight of 2000 and an amino group and an epoxy group at the end is used as an organic coupling auxiliary agent, and the amount is 0.2% of the mass of the base resin.

[0130] Substrate surface treatment: Hydrogen peroxide is applied to the coated surface of the substrate and then plasma treated to hydroxylate the coated surface. The hydroxylated coated surface is treated with a silane coupling agent containing carbon-carbon double bonds to introduce carbon-carbon double bonds for reaction with the optical adhesive.

[0131] Apply optical adhesive: Apply optical adhesive to one surface of the substrate with a coating thickness of 20-50um.

[0132] Imprint curing: The optical adhesive is imprinted using an imprint template with an imprint depth of 10-20 μm. UV light is used for curing. After curing, the imprint template is separated to obtain an optical adhesive layer with grid-like grooves.

[0133] Filling with conductive paste: The grid-shaped grooves are filled with conductive paste for the first time. After the surface is dry, the grid-shaped grooves are filled with conductive paste for the second time. After the surface is dry, the carbon nanotube dispersion is filled on the surface of the conductive paste in the grid-shaped grooves.

[0134] Curing: Bake and cure at a curing temperature, for example, bake at 80°C-120°C for 15-30 minutes to obtain a conductive film.

[0135] Example 2:

[0136] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0137] Base resin;

[0138] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 8:2;

[0139] carbon nanotubes, 0.03% of the matrix resin mass;

[0140] Curing agent, 0.2% of the base resin mass;

[0141] Organic coupling agent, 0.2% of the base resin mass;

[0142] The rest is the same as Example 1.

[0143] Example 3

[0144] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0145] Base resin;

[0146] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 6:4;

[0147] carbon nanotubes, 0.03% of the matrix resin mass;

[0148] Curing agent, 0.2% of the base resin mass;

[0149] Organic coupling agent, 0.2% of the base resin mass;

[0150] The rest is the same as Example 1.

[0151] Example 4

[0152] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0153] Base resin;

[0154] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 4:6;

[0155] carbon nanotubes, 0.03% of the matrix resin mass;

[0156] Curing agent, 0.2% of the base resin mass;

[0157] Organic coupling agent, 0.2% of the base resin mass;

[0158] The rest is the same as Example 1.

[0159] Example 5

[0160] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0161] Base resin;

[0162] The mass ratio of composite silver powder to matrix resin is 16:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0163] carbon nanotubes, 0.03% of the matrix resin mass;

[0164] Curing agent, 0.2% of the base resin mass;

[0165] Organic coupling agent, 0.2% of the base resin mass;

[0166] The rest is the same as Example 1.

[0167] Example 6

[0168] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0169] Base resin;

[0170] The mass ratio of composite silver powder to matrix resin is 12:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0171] carbon nanotubes, 0.03% of the matrix resin mass;

[0172] Curing agent, 0.2% of the base resin mass;

[0173] Organic coupling agent, 0.2% of the base resin mass;

[0174] The rest is the same as Example 1.

[0175] Example 7

[0176] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0177] Base resin;

[0178] The mass ratio of composite silver powder to matrix resin is 8:2, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0179] carbon nanotubes, 0.03% of the matrix resin mass;

[0180] Curing agent, 0.2% of the base resin mass;

[0181] Organic coupling agent, 0.2% of the base resin mass;

[0182] The rest is the same as Example 1.

[0183] Example 8

[0184] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0185] Base resin;

[0186] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0187] carbon nanotubes, 0.01% of the matrix resin mass;

[0188] Curing agent, 0.2% of the base resin mass;

[0189] Organic coupling agent, 0.2% of the base resin mass;

[0190] The rest is the same as Example 1.

[0191] Example 9

[0192] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0193] Base resin;

[0194] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0195] carbon nanotubes, 0.05% of the matrix resin mass;

[0196] Curing agent, 0.2% of the base resin mass;

[0197] Organic coupling agent, 0.2% of the base resin mass;

[0198] The rest is the same as Example 1.

[0199] Example 10

[0200] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0201] Base resin;

[0202] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0203] carbon nanotubes, 0.1% of the matrix resin mass;

[0204] Curing agent, 0.2% of the base resin mass;

[0205] Organic coupling agent, 0.2% of the base resin mass;

[0206] The rest is the same as Example 1.

[0207] Example 11

[0208] The difference from Example 1 is that the conductive paste 1 includes the following components and weight contents:

[0209] Base resin;

[0210] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0211] carbon nanotubes, 0.1% of the matrix resin mass;

[0212] Curing agent, 0.5% of the mass of the base resin;

[0213] Organic coupling agent, 0.2% of the base resin mass;

[0214] The rest is the same as Example 1.

[0215] Example 12

[0216] The difference from Example 1 is that the D50 of the flaky silver powder is 2 μm, and the D50 of the spherical silver powder is 0.4 μm;

[0217] Example 13

[0218] The difference from Example 1 is that the D50 of the flaky silver powder is 0.7 μm, and the D50 of the spherical silver powder is 0.8 μm;

[0219] Example 14

[0220] The difference from Example 1 is that the D50 of the flake silver powder is 1 μm, and the D50 of the spherical silver powder is 0.6 μm;

[0221] Comparative Example 1

[0222] The difference from Example 1 is that the conductive paste 1 includes the following components and weight contents:

[0223] Base resin;

[0224] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flaky silver powder to spherical silver powder is 10:0;

[0225] carbon nanotubes, 0.03% of the matrix resin mass;

[0226] Curing agent, 0.2% of the base resin mass;

[0227] Organic coupling agent, 0.2% of the base resin mass;

[0228] The rest is the same as Example 1.

[0229] Comparative Example 2

[0230] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0231] Base resin;

[0232] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 0:10;

[0233] carbon nanotubes, 0.03% of the matrix resin mass;

[0234] Curing agent, 0.2% of the base resin mass;

[0235] Organic coupling agent, 0.2% of the base resin mass;

[0236] The rest is the same as Example 1.

[0237] Comparative Example 3

[0238] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0239] Base resin;

[0240] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0241] carbon nanotubes, 0% of the matrix resin mass;

[0242] Curing agent, 0% of the base resin mass;

[0243] Organic coupling agent, 0% of the base resin mass;

[0244] The rest is the same as Example 1.

[0245] Comparative Example 4

[0246] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0247] Base resin;

[0248] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0249] carbon nanotubes, 0.03% of the matrix resin mass;

[0250] Curing agent, 0.2% of the base resin mass;

[0251] Organic coupling agent, 0% of the base resin mass;

[0252] The rest is the same as Example 1.

[0253] Comparative Example 5

[0254] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0255] Base resin;

[0256] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0257] carbon nanotubes, 0.03% of the matrix resin mass;

[0258] Curing agent, 0% of the base resin mass;

[0259] Organic coupling agent, 0.2% of the base resin mass;

[0260] The rest is the same as Example 1.

[0261] Comparative Example 6

[0262] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0263] Base resin;

[0264] The mass ratio of composite silver powder to matrix resin is 9:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0265] carbon nanotubes, 0% of the matrix resin mass;

[0266] Curing agent, 0.2% of the base resin mass;

[0267] Organic coupling agent, 0.2% of the base resin mass;

[0268] The rest is the same as Example 1.

[0269] Comparative Example 7

[0270] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0271] Base resin;

[0272] The mass ratio of composite silver powder to matrix resin is 17:1, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0273] carbon nanotubes, 0.03% of the matrix resin mass;

[0274] Curing agent, 0.2% of the base resin mass;

[0275] Organic coupling agent, 0.2% of the base resin mass;

[0276] The rest is the same as Example 1.

[0277] Comparative Example 8

[0278] The difference from Example 1 is that the conductive paste includes the following components and weight contents:

[0279] Base resin;

[0280] The mass ratio of composite silver powder to matrix resin is 4:2, wherein the mass ratio of flake silver powder to spherical silver powder is 7:3;

[0281] carbon nanotubes, 0.03% of the matrix resin mass;

[0282] Curing agent, 0.2% of the base resin mass;

[0283] Organic coupling agent, 0.2% of the base resin mass;

[0284] The rest is the same as Example 1.

[0285] Comparative Example 9

[0286] The difference from Example 1 is that the substrate is not surface treated.

[0287] Comparative Example 10

[0288] The difference from Example 1 is that the conductive paste is used for one-time filling, and the carbon nanotube dispersion is not filled.

[0289] Comparative Example 11

[0290] The difference from Example 1 is that the conductive paste is used for secondary filling, and the carbon nanotube dispersion is not filled.

[0291] Comparative Example 12

[0292] The difference from Example 1 is that the D50 of the flaky silver powder is 0.6 μm, and the D50 of the spherical silver powder is 0.4 μm;

[0293] Comparative Example 13

[0294] The difference from Example 1 is that the D50 of the flaky silver powder is 2.1 μm, and the D50 of the spherical silver powder is 0.4 μm.

[0295] Comparative Example 14

[0296] The difference from Example 1 is that the D50 of the flaky silver powder is 0.7 μm, and the D50 of the spherical silver powder is 0.3 μm;

[0297] Comparative Example 15

[0298] The difference from Example 1 is that the D50 of the flaky silver powder is 0.7 μm, and the D50 of the spherical silver powder is 0.9 μm.

[0299] The conductive films corresponding to Examples 1-14 and Comparative Examples 1-15 were subjected to the following tests:

[0300] (1) Conductivity test

[0301] A test unit was constructed using a 7µm diameter, 100mm long conductor with a 2mm x 2mm conductive film at each end. Ten test units were placed 10mm apart to obtain 10 square resistance values. Before the test unit was subjected to external tension, these 10 square resistance values ​​were relatively close, with minimal fluctuation. Therefore, the average of these 10 square resistance values ​​was used as the corresponding square resistance of the conductive film.

[0302] (2) Bending test

[0303] The national standard GB / T6742-2007 / ISO1519:2002 was purchased for the bending test around the rod, and the rod diameter was set to 2mm.

[0304] (3) Tensile test

[0305] Tensile testing is performed at a temperature 20-100°C above the substrate's glass transition temperature, ensuring the substrate is in a highly elastic state to facilitate stretching and maintain its optical properties. After reaching the desired elongation (generally two reference points, 20% and 100%, are used), the substrate is cooled to room temperature to set, and the sheet resistance of the test unit is then measured. Understandably, since the tensile deformation of each test unit is not exactly the same, the tensile sheet resistance of these ten test units fluctuates within a certain range.

[0306] The measurement results of the above-mentioned Examples 1-9 are shown in Table 1 below, the measurement results of Examples 10-11 and Comparative Examples 1-8 are shown in Table 2 below, the measurement results of Example 1 and Comparative Examples 9-11 are shown in Table 3 below, and the measurement results of Examples 1, 12-14 and Comparative Examples 12-15 are shown in Table 4 below.

[0307] Table 1 Measurement results of Examples 1-9

[0308] Table 2 Measurement results of Examples 10-11 and Comparative Examples 1-8

[0309] Table 3 Measurement results of Example 1 and Comparative Examples 9-11

[0310] Table 4 Measurement results of Examples 1, 12-14, and Comparative Examples 12-15

[0311] Comparative Examples 1 and 2 in Table 2 show that when the composite silver powder contains only flake silver powder, the bending performance is poor and the square resistance fluctuates significantly after high-temperature stretching. This is attributed to the insufficient mobility of the flake silver powder, which causes defects in the conductive film after stretching, affecting the conductive performance. When the composite silver powder contains only spherical silver powder, the bending performance is also poor. Although spherical silver powder has good mobility and can adapt to bending and stretching operations, it lacks the ability to form a network structure and cannot maintain conductive properties during bending.

[0312] As can be seen from Examples 1-9 in Table 1 or Examples 10-11 in Table 2, when the composite silver powder comprises both flaky and spherical silver powder, not only is the electrical conductivity improved, but the bending performance is also significantly enhanced. This is because the flaky and spherical silver powders can form a multi-scale composite network structure, taking into account the migration ability of the spherical silver powder and the bridging ability of the flaky silver powder. This allows for timely response to deformation and prevents crack propagation, improving its flexural tensile properties and maintaining good electrical properties despite deformation response. Furthermore, when the mass ratio of the composite silver powder to the matrix resin is within the range of 8:2-16:1, the mass ratio of the carbon nanotubes to the matrix resin is within the range of 0.01-0.1%, the mass ratio of the curing agent to the matrix resin is within the range of 0.1-0.5%, and the mass ratio of the organic coupling agent to the composite silver powder is within the range of 0.1-0.3%, the flexural tensile properties of the conductive film are improved.

[0313] It is understandable that when the carbon nanotube content is too high, the multi-scale composite network structure will be too strong, which is not conducive to the migration of fillers and is prone to brittle fracture under tensile force, thereby affecting the tensile resistance. When the curing agent is too little, the bonding performance of the conductive layer is affected and the mechanical properties are reduced; when the curing agent is too much, the toughness of the conductive layer is reduced. When the mass ratio between the organic coupling agent and the composite silver powder is too high, it is easy to destroy the interfacial interaction between different materials. When the mass ratio between the organic coupling agent and the composite silver powder is too low, it cannot improve the interfacial interaction between different materials.

[0314] Comparative Example 7 in Table 2 shows that when the composite silver powder / matrix resin ratio is too high, both the bending resistance and the electrical properties after tensile deformation are relatively poor. It is understandable that when the composite silver powder / matrix resin ratio is too high, the conductive paste has a high viscosity and lacks matrix resin, resulting in poor migration of fillers such as the composite silver powder. Consequently, brittle fracture is likely to occur when bending or stretching is applied, affecting the material's bending resistance and electrical conductivity.

[0315] From Comparative Example 8 in Table 2, it can be seen that when the composite silver powder / matrix resin ratio is too low, although a larger amount of matrix resin can provide sufficient lubrication to fillers such as the composite silver powder, excessive matrix resin is prone to slippage during bending, making it difficult to provide sufficient stability to the multi-scale composite network structure. As a result, the bending resistance and electrical properties after tensile deformation are relatively poor.

[0316] As can be seen from Comparative Example 3 in Table 2, when no carbon nanotubes are introduced, the bending resistance is poor. It is understandable that the lack of a multi-scale composite network structure formed by carbon nanotubes is not conducive to the stability of the structure during bending deformation.

[0317] Comparative Examples 1-6 in Table 2 show that even when no curing agent is used, the bending resistance and electrical properties after tensile deformation are slightly reduced. Excessive curing agent is detrimental to these properties because the curing agent makes the resin cross-linked network dense, thereby reducing its ability to respond to deformation. The lack of an organic coupling agent also leads to a slight reduction in the bending resistance and electrical properties after tensile deformation.

[0318] Comparative Example 9 in Table 3 shows that if the substrate is not surface treated to improve adhesion, the conductive film is prone to interfacial delamination under bending, and its bending resistance is reduced. Interfacial delamination is also observed under 100% stretching.

[0319] From the experimental data in Table 3, it can be seen that the filling process has a great influence on the anti-bending performance and the electrical properties after tensile deformation. From Comparative Example 10 in Table 3, it can be seen that when a filling is performed once, due to the thinner conductive paste (generally 3-7um), the thinner heterogeneous coating is prone to produce more defects. These defects are prone to brittle fracture under tensile or bending force, resulting in metal grid short circuit, poor anti-bending performance and electrical properties after tensile deformation.

[0320] The second filling process can fill the defects left by the first filling, thereby improving the bending resistance and electrical properties after tensile deformation. Furthermore, this double filling process allows the use of a relatively low-viscosity conductive paste. Compared to high-viscosity conductive pastes that form a thicker conductive layer through a single application, low-viscosity conductive pastes have better coating properties and can be applied multiple times to form a denser, less defective conductive layer. This effectively improves the bending and tensile properties of the conductive paste after curing, as well as its electrical conductivity after deformation.

[0321] As shown in Table 3 for Example 1 and Comparative Example 11, a third filling with a carbon nanotube dispersion fills surface defects in the conductive layer, preventing cracks caused by these defects and ensuring that the metal grid maintains good electrical properties despite bending and stretching deformation. Furthermore, this third filling effectively masks the metallic luster imparted by the silver powder, improving environmental stability.

[0322] From the experimental results of Example 1 and Examples 12-14 in Table 4, it can be seen that when the D50 of the flaky silver powder is in the range of 0.7-2.0 μm and the D50 of the spherical silver powder is in the range of 0.4-0.8 μm, the number of bending times is greater than 30,000 times, and the square resistance size and the fluctuation of the 20% and 100% tensile square resistance are all within the ideal range.

[0323] From the experimental results of Example 1 and Comparative Examples 12-13 in Table 4, it can be seen that when the D50 of the flaky silver powder is too small, the flaky silver powder cannot play an effective bridging role and lacks the ability to form a network structure, and the electrical performance deteriorates when bent; when the D50 of the flaky silver powder is too large, the filling effect of the flaky silver powder in the grid-like groove is poor, which also reduces the effective bridging effect.

[0324] From the experimental results of Example 1 and Comparative Examples 14-15 in Table 4, it can be seen that when the D50 of the spherical silver powder is too small, there are too many interfaces between the spherical silver powder, resulting in a decrease in electrical performance during bending; when the D50 of the spherical silver powder is too large, the filling effect of the spherical silver powder in the grid-shaped grooves is also poor, which also reduces the migration effect, thereby resulting in a decrease in electrical performance.

[0325] In summary, the metal grid formed by the curing of the conductive paste has a multi-scale composite network structure, which can respond to deformation in time and prevent crack propagation, thereby improving its anti-bending and tensile properties, and still maintaining good electrical properties under the response deformation. On the other hand, the above-mentioned method of introducing carbon-carbon double bonds by hydroxylation of the substrate surface can effectively increase the adhesion between the substrate and the optical adhesive layer. When the conductive film is bent, interface peeling is not likely to occur, which is conducive to maintaining its electrical properties. In addition, the use of a low-viscosity conductive paste for secondary filling can make the filler in the grid-shaped groove denser and have fewer defects, which can effectively improve the anti-bending and tensile properties of the conductive metal grid and the conductive properties after response deformation.

[0326] Some embodiments of the present application further provide a touch panel, which includes the conductive film in any one of the above embodiments.

[0327] In some embodiments, the touch panel can be a capacitive touch panel, comprising a glass substrate, a conductive film disposed on the glass substrate, and a protective film disposed on the conductive film. Voltage is applied to electrodes at the four corners of the glass substrate, generating a uniform low-voltage electric field across the entire panel. By measuring the change in electrostatic capacitance at the four corners of the panel, the coordinates of the finger touching the screen are determined, thereby enabling touch operation.

[0328] In this embodiment, the conductive film has the same structure and function as the conductive film in any of the above embodiments, which will not be described in detail here. Based on the structure and function of the conductive film, the touch panel can be developed into a curved or flexible touch panel.

[0329] Some embodiments of the present application further provide a display device including the touch panel in the above embodiment. Since the touch panel can be developed into a curved or flexible touch panel, the display device can be developed into a curved or flexible display device.

[0330] Some embodiments of the present application further provide an electronic device, comprising the display device in the above embodiment.

[0331] It is understandable that the electronic device may be a mobile phone, a tablet, a computer or a robot, etc. The curved or flexible display device may be a display device or a smart cover in an electronic device.

[0332] Among them, the touch panel in the display device not only has excellent light transmittance and conductivity, but also has excellent tensile and bending resistance, which can meet the requirements of flexible electronic devices.

[0333] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Based on the concept of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present application as described above. For the sake of simplicity, they are not provided in detail. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A conductive paste, It is characterized in that It includes base resin, composite silver powder, carbon nanotube and curing agent; The composite silver powder includes flaky silver powder with a D50 of 0.7-2.0 um and spherical silver powder with a D50 of 0.4-0.8 um, and the mass ratio between the composite silver powder and the matrix resin is 8:2-16:1; The mass of the carbon nanotubes is 0.01-0.1% of the mass of the matrix resin; the mass of the curing agent is 0.1-0.5% of the mass of the matrix resin.

2. The conductive paste according to claim 1, It is characterized in that The mass ratio of the flaky silver powder to the spherical silver powder is 10:1-1:

10.

3. The conductive paste according to claim 1, It is characterized in that The particle size of the flaky silver powder satisfies D99≤3um, and the particle size of the spherical silver powder satisfies D99≤1um.

4. The conductive paste according to claim 1, It is characterized in that The curing agent includes latent isocyanate.

5. The conductive paste according to claim 1, It is characterized in that The conductive paste further comprises an organic coupling auxiliary agent, and the mass of the organic coupling auxiliary agent is 0.1-0.3% of the mass of the composite silver powder.

6. The conductive paste according to claim 5, It is characterized in that One molecular end of the organic coupling auxiliary agent includes an amino group and an epoxy group.

7. The conductive paste according to claim 1, It is characterized in that The conductive paste has a viscosity of 2000-20000 cps, and / or a solid content of 65%-85%.

8. The conductive paste according to claim 1, It is characterized in that The elongation of the base resin is greater than or equal to 100%.

9. The conductive paste according to claim 1, It is characterized in that The length of the carbon nanotube is 0.5um-2um.

10. A conductive film, It is characterized in that include: Base material, An optical adhesive layer is disposed on the substrate, the optical adhesive layer being away from the substrate A grid-like groove is provided; A conductive grid is formed by filling the conductive paste according to any one of claims 1 to 9 in the grid-shaped grooves and curing the conductive paste.

11. A method for preparing a conductive film, It is characterized in that include: Using an embossing template to emboss the optical adhesive coated on the substrate, and separating the embossing template after curing to form an optical adhesive layer with grid-shaped grooves on the substrate; The conductive paste as described in any one of claims 1 to 9 is filled into the grid-shaped grooves and cured to obtain the conductive film.

12. The method according to claim 11, It is characterized in that Before applying the optical adhesive to the substrate, the method further comprises: The coated surface of the substrate is surface treated to increase the adhesion between the substrate and the optical adhesive.

13. The method according to claim 12, It is characterized in that The surface treatment is carried out in the following manner: Applying hydrogen peroxide to the coating surface of the substrate and then performing plasma treatment to hydroxylate the coating surface; The hydroxylated coating surface is treated with a silane coupling agent having a carbon-carbon double bond to introduce a carbon-carbon double bond for reacting with the optical adhesive.

14. The method according to claim 11, It is characterized in that The conductive paste is filled into the grid-shaped grooves in the following manner: The grid-shaped grooves are filled once with the conductive paste, and after the surface is dried, the grid-shaped grooves are filled twice with the conductive paste.

15. The method according to claim 14, It is characterized in that After the secondary filling and before curing, the method further comprises: After surface drying, the carbon nanotube dispersion is filled on the surface of the conductive paste in the grid-shaped grooves.

16. A touch panel, It is characterized in that It comprises the conductive film as claimed in claim 9, or a conductive film prepared by the method for preparing a conductive film as claimed in any one of claims 11 to 15.

17. A display device, It is characterized in that Comprising the touch panel as claimed in claim 16.

18. An electronic device, It is characterized in that Comprising the display device as claimed in claim 17.

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