Conductive film, method for producing the same, and electronic device

Abstract

This application provides a conductive film, its preparation method, and an electronic device. The conductive film comprises modified graphene and modified polymeric particles. The modified graphene is graphene with surface carboxyl functionalization treatment, and the modified polymeric particles include polymeric particles and conductive polymers grafted onto the surface of the polymeric particles. This application uses a combination of modified graphene and modified polymeric particles to give the conductive film high mechanical strength and low sheet resistance.

Description

Technical Field

[0001] This invention relates to the field of conductive film technology, and in particular to a conductive film, its preparation method, and an electronic device thereof. Background Technology

[0002] The conductivity of graphene as a filler in polymers stems from the fact that initially isolated, dispersed filler particles form continuous conductive pathways once a certain critical volume dispersion is achieved. Therefore, the more graphene added to the polymer and the more uniformly it is dispersed, the better the conductivity of the conductive film and the lower its sheet resistance. However, as the amount of graphene filler increases, the bonding force between polymer molecules weakens, leading to a decrease in the tensile strength of the conductive film. When the mechanical strength of the conductive film falls below 10 MPa, its application in flexible wearable devices will be affected.

[0003] Therefore, how to prepare a conductive composite film with high mechanical strength and low sheet resistance has become an urgent technical problem to be solved. Summary of the Invention

[0004] Therefore, it is necessary to provide a conductive film with both high mechanical strength and low sheet resistance, as well as its preparation method and electronic device.

[0005] In a first aspect, this application provides a conductive film comprising modified graphene and modified polymeric colloidal material;

[0006] The modified graphene is graphene that has undergone surface carboxyl functionalization modification, and the modified polymeric particle material includes polymeric particle material and conductive polymer grafted onto the surface of the polymeric particle material.

[0007] In some embodiments, the sheet resistance of the conductive film is 1Ω / □ to 10Ω / □.

[0008] In some embodiments, the tensile strength of the conductive film is 10 MPa to 15 MPa.

[0009] In some embodiments, the polymeric granule material includes at least one of waterborne polyurethane, waterborne acrylic, waterborne epoxy resin, and waterborne phenolic resin.

[0010] In some embodiments, the conductive polymer includes at least one of polypyrrole, polythiophene, and polyaniline.

[0011] Secondly, this application provides a method for preparing a conductive film as described in the first aspect, the method comprising:

[0012] Graphene was modified by surface carboxyl functionalization to obtain a modified graphene solution.

[0013] A conductive polymer is grafted onto the surface of a polymeric colloidal material to obtain a modified polymeric colloidal material solution;

[0014] The conductive film is prepared using a slurry containing the modified graphene solution and the modified polymer colloidal material solution.

[0015] In some embodiments, the method for preparing the modified graphene solution includes:

[0016] An activator is added to a graphene solution to induce a ring-opening reaction of the epoxy groups in the graphene. Then, oxalic acid is added, and the mixture is heated and stirred to obtain the modified graphene solution.

[0017] In some embodiments, the modified graphene solution also contains polyvinylpyrrolidone.

[0018] Optionally, the mass ratio of the polyvinylpyrrolidone to the graphene contained in the graphene solution is 1:(4~6).

[0019] In some embodiments, the graphene solution contains graphene in a mass ratio of 1:(10~50) to oxalic acid.

[0020] In some embodiments, the graphene solution is obtained by ultrasonic dispersion.

[0021] In some embodiments, the heating method includes water bath heating.

[0022] In some embodiments, the heating temperature is 50°C to 70°C.

[0023] In some embodiments, the heating time is 0.5h to 1.5h.

[0024] In some embodiments, the modified graphene solution has a mass content of 1% to 10%.

[0025] In some embodiments, the activator includes at least one of HBr and HF.

[0026] In some embodiments, the method for preparing the modified polymer colloidal material solution includes:

[0027] A conductive polymer monomer is added to a solution containing the polymeric granules to adjust the solution to an acidic system. An oxidant is added while stirring. The conductive polymer monomer is grafted onto the surface of the polymeric granules to form the conductive polymer, thus obtaining the modified polymeric granule solution.

[0028] In some embodiments, the mass ratio of the polymeric granules to the conductive polymer monomer is (5~20):1.

[0029] In some embodiments, the molar ratio of the oxidant to the conductive polymer monomer is (1~3):1.

[0030] In some embodiments, the mass content of the solution containing the polymeric colloidal material is 30% to 35%.

[0031] In some embodiments, the pH of the acidic system is 1 to 3.

[0032] In some embodiments, the oxidant includes at least one of FeCl3, CuCl2, H2O2, and I2.

[0033] In some embodiments, the conductive polymer monomer includes at least one of pyrrole monomer, thiophene monomer, and aniline monomer.

[0034] In some embodiments, the slurry comprises, by weight parts: 100 to 300 parts of the modified graphene solution; and 50 to 70 parts of the modified polymer colloidal material solution.

[0035] In some embodiments, the slurry also includes additives.

[0036] Optionally, the additive includes at least one of an adjuvant, a dispersant, an antifoamer, and a thickener.

[0037] In some embodiments, the viscosity of the slurry is 500 mPa·s to 1500 mPa·s.

[0038] In some embodiments, the adjuvant includes at least one selected from ethylene glycol, dipropylene glycol methyl ether, glycerin, N-methylpyrrolidone, and acetone.

[0039] In some embodiments, the slurry includes 10 to 50 parts of the additive by weight.

[0040] In some embodiments, the dispersant includes at least one of polyethylene glycol octylphenyl ether, sodium dodecyl sulfate, polyoxyethylene lauryl ether, and gum arabic powder.

[0041] In some embodiments, the slurry includes 1 to 3 parts of the dispersant by weight.

[0042] In some embodiments, the defoamer includes at least one of polyether defoamers, polyvinyl alcohol defoamers, and fatty acid amide defoamers.

[0043] In some embodiments, the slurry includes 0.2 to 1 part of the defoamer by weight.

[0044] In some embodiments, the thickener includes at least one of carboxymethyl cellulose, propylene glycol alginate, methyl cellulose, and polyoxyethylene.

[0045] In some embodiments, the slurry includes 1 to 2 parts of the thickener by weight.

[0046] Thirdly, this application provides an electronic device comprising the conductive film as described in the first aspect.

[0047] Compared with traditional technologies, this application has at least the following beneficial effects:

[0048] This application achieves the connection between graphene and polymeric particles via hydrogen bonds or chemical bonds by modifying the surface of graphene with carboxyl functional groups and by grafting conductive polymers onto the surface of polymeric particles. This not only enables graphene to form a highly efficient conductive pathway, but also makes the fusion of graphene and polymeric particles more robust, increasing the mechanical strength of the conductive film and reducing its sheet resistance. Detailed Implementation

[0049] To facilitate understanding of the present invention, a more complete description will be given below with reference to relevant embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0051] In this application, when numerical intervals (i.e., numerical ranges) are mentioned, unless otherwise specified, the distribution of selectable numerical values ​​within the numerical interval is considered continuous, and includes the two endpoints of the numerical interval (i.e., the minimum and maximum values), as well as every numerical value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that numerical interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints, which is equivalent to directly listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. The term "numerical interval" can be broadly included to include percentage intervals, ratio intervals, proportion intervals, etc.

[0052] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0053] In this application, the terms "first aspect," "second aspect," "third aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0054] Traditional methods for preparing low sheet resistance conductive films include: 1. Chemical vapor deposition (CVD) to prepare pure graphene conductive films. This method utilizes a carbon source to form single or multiple layers of graphene on a copper or nickel substrate, where carbon atoms are arranged in a specific configuration. The graphene is then transferred to other substrates. However, this method is costly, requires stringent preparation conditions, and is difficult to transfer. 2. Graphene conductive films are prepared using graphene oxide slurry through coating, high-temperature calcination, and calendering processes. However, the conductive films obtained by this method are brittle and not resistant to bending. 3. Composite conductive films are prepared using graphene as a filler and polymer materials as a binder. However, polymer materials have insulating properties, resulting in conductive films with high sheet resistance. However, this application modifies the surfaces of graphene and polymeric particles separately, and integrates graphene and polymeric particles through hydrogen bonding, thereby increasing the interfacial compatibility and conductive channels between the polymeric particles and graphene. In addition, after surface modification, the mass content of graphene in aqueous solution is increased, and the resulting conductive film has high mechanical strength and low sheet resistance, expanding the application of conductive films in the field of flexible wearable heating.

[0055] The first aspect of this application provides a conductive film comprising modified graphene and modified polymeric colloidal material;

[0056] The modified graphene is graphene that has undergone surface carboxyl functionalization modification, and the modified polymeric particle material includes polymeric particle material and conductive polymer grafted onto the surface of the polymeric particle material.

[0057] This application modifies the surface of graphene by carboxyl functionalization, introducing active hydrogen atoms through carboxyl grafting, making graphene easier and more uniformly dispersed in aqueous solution. Furthermore, conductive polymers are grafted onto the surface of the polymeric granules, improving the conductivity of the polymeric granules and providing a bonding point for the modified graphene, enabling hydrogen bonding between the modified graphene and the conductive polymer. This not only improves the bonding strength between graphene and the polymeric granules but also provides a highly efficient conductive pathway for graphene, effectively improving the mechanical strength of the conductive film and reducing sheet resistance.

[0058] It should be noted that, in this application, conductive polymer refers to a polymer material that is conductive, such as polypyrrole.

[0059] In some embodiments, the sheet resistance of the conductive film is 1Ω / □ to 10Ω / □, for example, it can be 1Ω / □, 2Ω / □, 3Ω / □, 4Ω / □, 5Ω / □, 6Ω / □, 7Ω / □, 8Ω / □, 9Ω / □ or 10Ω / □.

[0060] In some embodiments, the tensile strength of the conductive film is 10 MPa to 15 MPa, for example, it can be 10.0 MPa, 10.5 MPa, 11.0 MPa, 11.5 MPa, 12.0 MPa, 12.5 MPa, 13.0 MPa, 13.5 MPa, 14.0 MPa, 14.5 MPa or 15.0 MPa.

[0061] In some embodiments, the thickness of the conductive film is 30μm to 100μm, for example, it can be 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm.

[0062] In some embodiments, the polymeric granule material includes at least one of waterborne polyurethane, waterborne acrylic, waterborne epoxy resin, and waterborne phenolic resin.

[0063] In some embodiments, the conductive polymer includes at least one of polypyrrole, polythiophene, and polyaniline. Polypyrrole is preferred.

[0064] A second aspect of this application provides a method for preparing a conductive film as described in the first aspect, the method comprising:

[0065] Graphene was modified by surface carboxyl functionalization to obtain a modified graphene solution.

[0066] A conductive polymer is grafted onto the surface of a polymeric colloidal material to obtain a modified polymeric colloidal material solution;

[0067] The conductive film is prepared using a slurry containing the modified graphene solution and the modified polymer colloidal material solution.

[0068] In some embodiments, the method for preparing the modified graphene solution includes:

[0069] An activator is added to a graphene solution to induce a ring-opening reaction of the epoxy groups in the graphene. Then, oxalic acid is added, and the mixture is heated and stirred to obtain the modified graphene solution.

[0070] In some embodiments, the stirring speed of the stirring process is 600 rpm to 1000 rpm, for example, it can be 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm, 950 rpm or 1000 rpm.

[0071] In some embodiments, the modified graphene solution further comprises polyvinylpyrrolidone. The addition of polyvinylpyrrolidone in this application improves the dispersibility of graphene in water.

[0072] Optionally, the mass ratio of the polyvinylpyrrolidone to the graphene contained in the graphene solution is 1:(4~6), for example, it can be 1:4.0, 1:4.2, 1:4.4, 1:4.6, 1:4.8, 1:5.0, 1:5.2, 1:5.4, 1:5.6, 1:5.8 or 1:6.0.

[0073] In some embodiments, the graphene solution contains a graphene to oxalic acid mass ratio of 1:(10~50), for example, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45 or 1:50.

[0074] This application controls the mass ratio of graphene to oxalic acid to ensure the functionalization of carboxyl groups on the graphene surface, thereby improving the dispersibility of graphene in solvents without affecting its conductivity. If the graphene content is relatively low, the modified graphene surface may have more carboxyl groups, thus reducing its conductivity and resulting in a high sheet resistance of the conductive film. Conversely, if the graphene content is relatively high, the graphene surface may have fewer carboxyl groups or some graphene may not be carboxylated, thus reducing the dispersibility of the modified graphene in solvents. Furthermore, the presence of fewer activated hydrogens on the graphene surface reduces the bonding force between the modified graphene and the polymer material, leading to a decrease in the mechanical properties of the conductive film.

[0075] In some embodiments, the graphene solution is obtained by ultrasonic dispersion.

[0076] Optionally, the power of the ultrasonic dispersion is 200W to 400W, for example, 200W, 220W, 240W, 260W, 280W, 300W, 320W, 340W, 360W, 380W, or 400W. Further optionally, the frequency of the ultrasonic dispersion is 40kHz to 60kHz, for example, 40kHz, 42kHz, 44kHz, 46kHz, 48kHz, 50kHz, 52kHz, 54kHz, 56kHz, 58kHz, or 60kHz. Even more optionally, the duration of the ultrasonic dispersion is 1h to 3h, for example, 1.0h, 1.2h, 1.4h, 1.6h, 1.8h, 2.0h, 2.2h, 2.4h, 2.6h, 2.8h, or 3.0h.

[0077] In some embodiments, the heating method includes water bath heating.

[0078] In some embodiments, the heating temperature is 50°C to 70°C, for example, it can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C or 70°C.

[0079] This application controls the temperature during the graphene modification process to make the modified graphene have both conductivity and dispersibility. If the temperature is relatively low, the rate of grafting carboxyl functional groups onto the graphene may be slow; if the temperature is relatively high, too many carboxyl functional groups may be grafted onto the graphene surface, affecting the conductivity of the graphene.

[0080] In some embodiments, the heating time is 0.5h to 1.5h, for example, it can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1.0h, 1.1h, 1.2h, 1.3h, 1.4h or 1.5h.

[0081] In some embodiments, the mass content of the modified graphene solution is 1% to 10%, for example, it can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0082] In some embodiments, the activator includes at least one of HBr and HF.

[0083] Optionally, the mass concentration of the active ingredient in the activator is 30% to 50%, for example, it can be 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48% or 50%.

[0084] Optionally, the mass ratio of the active ingredient in the activator to the graphene contained in the graphene solution is (5~15):1, for example, it can be 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1 or 15:1.

[0085] In some embodiments, the method for preparing the modified polymer colloidal material solution includes:

[0086] A conductive polymer monomer is added to a solution containing the polymeric granules to adjust the solution to an acidic system. An oxidant is added while stirring. The conductive polymer monomer is grafted onto the surface of the polymeric granules to form the conductive polymer, thus obtaining the modified polymeric granule solution.

[0087] This application forms conductive polymer monomers in situ on the surface of polymeric granules under an acidic system, so that the conductive polymer covers the entire surface of the polymeric granules, providing a landing point for modified graphene. Furthermore, since the polymeric granules have hydrophilic groups, the polymer-modified polymeric granules have good dispersibility in water.

[0088] Optionally, the temperature during the reaction process is 0℃~40℃, for example, it can be 0℃, 4℃, 8℃, 12℃, 16℃, 20℃, 24℃, 28℃, 32℃, 36℃ or 40℃.

[0089] In some embodiments, the stirring speed is 1000 rpm to 2000 rpm, for example, it can be 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm or 2000 rpm.

[0090] In some embodiments, the mass ratio of the polymeric granules to the conductive polymer monomer is (5~20):1, for example, it can be 5:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1 or 20:1.

[0091] This application controls the mass ratio of polymeric colloid material to conductive polymer monomers, thereby enabling the modified polymeric colloid material to possess a certain degree of conductivity while also dispersing better in the solvent. If the amount of polymeric colloid material added is relatively high, some polymeric colloid material may not be grafted onto the conductive polymer or there may be too little conductive polymer, resulting in low conductivity of the modified polymeric colloid material and a high sheet resistance of the prepared conductive film. If the amount of polymeric colloid material added is relatively low, the conductive polymer may undergo self-polymerization due to too few grafting points, thereby affecting the uniformity of the conductive polymer grafting on the surface of the polymeric colloid material and causing poor sheet resistance uniformity of the conductive film.

[0092] In some embodiments, the molar ratio of the oxidant to the conductive polymer monomer is (1~3):1, for example, it can be 1.0:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1 or 3.0:1.

[0093] In some embodiments, the oxidant is added as an oxidant solution with a concentration of 0.1 mol / L to 0.5 mol / L, for example, 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, or 0.5 mol / L. Further optionally, the oxidant is added at a rate of 1 ml / min to 1.5 ml / min.

[0094] In some embodiments, the mass content of the solution containing the polymeric colloidal material is 30% to 35%, for example, it can be 30%, 31%, 32%, 33%, 34% or 35%.

[0095] In some embodiments, the pH of the acidic system is 1 to 3, for example, it can be 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, or 3.0. Optionally, the acidic system is adjusted using an acidic material, such as hydrochloric acid.

[0096] This application controls the pH of the acidic system, resulting in conductive polymers grafted onto the surface of the polymer particles having better conjugated conductivity. If the pH is relatively high, it may lead to a longer polymerization time, a lower molecular weight of the conductive polymer, and thus a shorter electron conjugation system, affecting the conductivity of the conductive polymer.

[0097] In some embodiments, the oxidant includes at least one of FeCl3, CuCl2, H2O2, and I2.

[0098] In some embodiments, the conductive polymer monomer includes at least one selected from pyrrole monomer, thiophene monomer, and aniline monomer. Pyrrole monomer is preferred.

[0099] This application uses pyrrole monomer conductive polymer monomers. The polypyrrole formed by polymerization has hydrophilic groups, which can improve the dispersibility of polymer granules in aqueous solution, and thus facilitate their bonding with graphene materials.

[0100] In some embodiments, the slurry comprises, by weight parts: 100 to 300 parts of the modified graphene solution; and 50 to 70 parts of the modified polymer colloidal material solution. The number of parts of the modified graphene solution can be 100, 120, 140, 160, 180, 200, 220, 240, 260, 280, or 300 parts; the number of parts of the modified polymer colloidal material solution can be 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, or 70 parts.

[0101] This application controls the amount of modified graphene solution and modified polymer colloidal material solution added to ensure that the prepared conductive film has advantages such as good conductivity, low sheet resistance, and high tensile strength. If the amount of modified graphene solution added is relatively low, the conductive film may have a high sheet resistance; if the amount of modified graphene solution added is relatively high, the conductive film may have a lower tensile strength due to the high filler content.

[0102] In some embodiments, the slurry also includes additives.

[0103] Optionally, the additive includes at least one of an adjuvant, a dispersant, an antifoamer, and a thickener.

[0104] In some embodiments, the viscosity of the slurry is 500 mPa·s to 1500 mPa·s, for example, it can be 500 mPa·s, 600 mPa·s, 700 mPa·s, 800 mPa·s, 900 mPa·s, 1000 mPa·s, 1100 mPa·s, 1200 mPa·s, 1300 mPa·s, 1400 mPa·s or 1500 mPa·s.

[0105] This application controls the viscosity of the slurry to make it more suitable for the coating process, thereby producing a conductive film with uniform thickness and good sheet resistance. If the viscosity is relatively low, the slurry may flow and fail to coat during the coating process, or the uniformity after coating may be poor. If the viscosity is relatively high, there may be problems such as high coating resistance or clogging of the doctor blade gap, making coating difficult or impossible.

[0106] In some embodiments, the adjuvant includes at least one selected from ethylene glycol, dipropylene glycol methyl ether, glycerin, N-methylpyrrolidone, and acetone. Optionally, the adjuvant is a combination of ethylene glycol, dipropylene glycol methyl ether, and glycerin, wherein the mass ratio of ethylene glycol, dipropylene glycol methyl ether, and glycerin is 1:1:1.

[0107] In some embodiments, the slurry includes 10 to 50 parts of the additive by weight, for example, 10, 15, 20, 25, 30, 35, 40, 45 or 50 parts.

[0108] In some embodiments, the dispersant includes at least one of polyethylene glycol octylphenyl ether (Trappon X-100), sodium dodecyl sulfate, polyoxyethylene lauryl ether, and gum arabic powder.

[0109] In some embodiments, the slurry contains 1 to 3 parts of the dispersant by weight, for example, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, or 3.0 parts.

[0110] In some embodiments, the defoamer includes at least one of polyether defoamers, polyvinyl alcohol defoamers, and fatty acid amide defoamers.

[0111] In some embodiments, the slurry includes 0.2 to 1 part of the defoamer by weight, for example, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.0 parts.

[0112] In some embodiments, the thickener includes at least one of carboxymethyl cellulose, propylene glycol alginate, methyl cellulose, and polyoxyethylene.

[0113] In some embodiments, the slurry contains 1 to 2 parts of the thickener by weight, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0 parts.

[0114] In some embodiments, the slurry comprises, by weight parts:

[0115] The modified graphene solution comprises 100 to 300 parts; the modified polymer colloidal material solution comprises 50 to 70 parts; the additives comprise 10 to 50 parts; the dispersant comprises 1 to 3 parts; the defoamer comprises 0.2 to 1 part; and the thickener comprises 1 to 2 parts.

[0116] In some embodiments, the stirring speed during slurry preparation is 1000 rpm to 2000 rpm, and the time is 2 h to 4 h.

[0117] In some embodiments, the method of preparing the conductive film using the slurry includes at least one of blade coating and roller coating.

[0118] In some embodiments, a method for preparing a conductive film using the slurry includes:

[0119] The slurry is coated onto a substrate to obtain a slurry layer, and the slurry layer is dried to obtain the conductive film.

[0120] Optionally, during the drying process, gradient heating and gradient cooling are used sequentially. The starting temperature of the gradient heating is 50℃~70℃, the ending temperature of the gradient heating is 80℃~100℃, and the ending temperature of the gradient cooling is room temperature (e.g., room temperature is 20℃~30℃). The heating gradient during the gradient heating process is 4℃ / min~6℃ / min, and the cooling gradient during the gradient cooling process is 4℃ / min~6℃ / min.

[0121] Optionally, the substrate includes a PET release film.

[0122] Exemplarily, a method for preparing the above-mentioned conductive film is provided, comprising:

[0123] An activator solution with a mass concentration of 30%~50% was added to a graphene solution, with the mass ratio of activator to graphene being (5~15):1. After stirring and reacting, the epoxy groups in the graphene were opened, and then oxalic acid was added, with the mass ratio of graphene to oxalic acid being 1:(10~50). The mixture was stirred at 600rpm~1000rpm for 0.5h~1.5h under water bath heating conditions of 50℃~70℃. After washing with deionized water and drying, the carboxyl functionalized modified graphene powder was obtained.

[0124] The carboxyl-functionalized graphene powder and polyvinylpyrrolidone were added to deionized water, with a mass ratio of polyvinylpyrrolidone to graphene of 1:(4~6). The mixture was ultrasonically dispersed for 1h~3h at 200W~400W and 40kHz~60kHz to obtain a modified graphene solution with a mass content of 1%~10%.

[0125] A conductive polymer monomer is added to a solution containing 30%~35% of the polymer granules, with a mass ratio of polymer granules to conductive polymer monomer of (5~20):1. The solution is adjusted to an acidic system with a pH of 1~3. An oxidant is added while stirring at 1000rpm~2000rpm, with a molar ratio of oxidant to conductive polymer monomer of (1~3):1. The conductive polymer monomer is grafted onto the surface of the polymer granules to form a conductive polymer, thus obtaining the modified polymer granule solution.

[0126] The slurry is prepared according to the following mass percentages: 100-300 parts of the modified graphene solution; 50-70 parts of the modified polymer colloidal material solution; 10-50 parts of additives; 1-3 parts of dispersant; 0.2-1 part of defoamer; and 1-2 parts of thickener. After mixing at 1000-2000 rpm for 2-4 hours, a slurry with a viscosity of 500 mPa·s-1500 mPa·s is obtained.

[0127] The slurry is coated onto a substrate and then placed in a drying apparatus. The substrate coated with the slurry is subjected to a gradient heating and gradient cooling process. The initial temperature of the gradient heating is 50℃~70℃, the final temperature of the gradient heating is 80℃~100℃, and the final temperature of the gradient cooling is room temperature (e.g., room temperature is 20℃~30℃). The heating gradient during the gradient heating process is 4℃ / min~6℃ / min, and the cooling gradient during the gradient cooling process is 4℃ / min~6℃ / min. After drying, the conductive film is obtained.

[0128] A third aspect of this application provides an electronic device comprising the conductive film described in the first aspect.

[0129] In some embodiments, the electronic device includes a flexible wearable device.

[0130] The embodiments of the present invention will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this invention, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0131] Example 1

[0132] Graphene was dispersed in deionized water, and then a 40% HBr solution was added. The mixture was stirred at 800 rpm for 10 h, with a HBr to graphene mass ratio of 10:1. After stirring, oxalic acid was added, with a graphene to oxalic acid mass ratio of 1:20. The mixture was stirred at 800 rpm for 1 h under a 60°C water bath heating condition. After washing with deionized water and drying at 60°C, modified graphene powder with surface carboxyl functionalization was obtained.

[0133] The modified graphene powder and polyvinylpyrrolidone were added to deionized water and ultrasonically dispersed for 3 hours at 300W and 50kHz to obtain a modified graphene solution with a mass content of 3% and a mass ratio of polyvinylpyrrolidone to graphene of 1:5.

[0134] Pyrrole monomer was added to an aqueous solution containing 35% waterborne polyurethane at a mass ratio of 10:1. The solution was adjusted to an acidic system with a pH of 1.5. FeCl3 solution was added while stirring at 1500 rpm at a molar ratio of 2:1 to FeCl3. The pyrrole monomer was grafted onto the surface of the waterborne polyurethane to form polypyrrole, thus obtaining the modified polymer colloid material solution.

[0135] The slurry was prepared according to the following mass percentages: 200 parts of the modified graphene solution; 50 parts of the modified polymer granule material solution; 25 parts of additives; 2.5 parts of Triton-100; 0.5 parts of polyether defoamer; and 1 part of methylcellulose. After mixing at 1500 rpm for 3 hours, a slurry with a viscosity of 1000 mPa·s was obtained. The additives used were ethylene glycol, dipropylene glycol methyl ether, and glycerol in a mass ratio of 1:1:1.

[0136] The slurry was coated onto a PET release film and then subjected to gradient heating and gradient cooling in a drying device. The starting temperature of the gradient heating was 60°C and the ending temperature was 90°C. The ending temperature of the gradient cooling was room temperature. The heating gradient was 5°C / min and the cooling gradient was 5°C / min. After drying, a conductive film with a thickness of 50 μm was obtained.

[0137] Example 2

[0138] The modified graphene solution was prepared according to the method of Example 1, except that the mass content of the modified graphene solution was 6%.

[0139] Pyrrole monomer was added to an aqueous solution containing 35% waterborne polyurethane at a mass ratio of 10:1. The solution was adjusted to an acidic system with a pH of 1.5. FeCl3 solution was added while stirring at 1500 rpm at a molar ratio of 2:1 to FeCl3. The pyrrole monomer was grafted onto the surface of the waterborne polyurethane to form polypyrrole, thus obtaining the modified polymer colloid material solution.

[0140] The slurry was prepared according to the following mass percentages: 250 parts of the modified graphene solution; 50 parts of the modified polymer granule material solution; 30 parts of additives; 3 parts of Triton-100; 0.6 parts of polyether defoamer; and 1.5 parts of methylcellulose. After mixing at 1500 rpm for 3 hours, a slurry with a viscosity of 1200 mPa·s was obtained. The additives used were ethylene glycol, dipropylene glycol methyl ether, and glycerol in a mass ratio of 1:1:1.

[0141] The slurry was coated onto a PET release film and then subjected to gradient heating and gradient cooling in a drying device. The starting temperature of the gradient heating was 60°C and the ending temperature was 90°C. The ending temperature of the gradient cooling was room temperature. The heating gradient was 5°C / min and the cooling gradient was 5°C / min. After drying, a conductive film with a thickness of 50 μm was obtained.

[0142] Example 3

[0143] The modified graphene solution was prepared according to the method in Example 1, except that the mass ratio of polyvinylpyrrolidone to graphene was 1:4, the mass ratio of graphene to oxalic acid was 1:10, the water bath heating temperature was 50°C, and the mass content of modified graphene was 9%.

[0144] Pyrrole monomer was added to an aqueous solution containing 30% waterborne polyurethane at a mass ratio of 20:1. The solution was adjusted to an acidic system with a pH of 2. FeCl3 solution was added while stirring at 1500 rpm at a molar ratio of 2:1 to FeCl3. The pyrrole monomer was grafted onto the surface of the waterborne polyurethane to form polypyrrole, thus obtaining the modified polymer granular material solution.

[0145] The slurry was prepared according to the following mass percentages: 100 parts of the modified graphene solution; 60 parts of the modified polymer granule material solution; 10 parts of additives; 1 part of Triton-100; 1 part of polyether defoamer; and 2 parts of methylcellulose. After mixing at 1500 rpm for 3 hours, a slurry with a viscosity of 600 mPa·s was obtained. The additives used were ethylene glycol, dipropylene glycol methyl ether, and glycerol in a mass ratio of 1:1:1.

[0146] The slurry was coated onto a PET release film and then subjected to gradient heating and gradient cooling in a drying device. The starting temperature of the gradient heating was 60°C and the ending temperature was 90°C. The ending temperature of the gradient cooling was room temperature. The heating gradient was 5°C / min and the cooling gradient was 5°C / min. After drying, a conductive film with a thickness of 50 μm was obtained.

[0147] Example 4

[0148] The modified graphene solution was prepared according to the method in Example 1, with the only differences being that the mass ratio of polyvinylpyrrolidone to graphene was 1:6; the mass ratio of graphene to oxalic acid was 1:50; the water bath heating temperature was 70°C; and the mass content of the modified graphene solution was 9%.

[0149] Pyrrole monomer was added to an aqueous solution containing 33% waterborne polyurethane at a mass ratio of 5:1. The solution was adjusted to an acidic system with a pH of 3. FeCl3 solution was added while stirring at 1500 rpm at a molar ratio of 2:1 to FeCl3. The pyrrole monomer was grafted onto the surface of the waterborne polyurethane to form polypyrrole, thus obtaining the modified polymer colloid material solution.

[0150] The slurry was prepared according to the following mass percentages: 300 parts of the modified graphene solution; 70 parts of the modified polymer granule material solution; 50 parts of additives; 2 parts of Triton-100; 1 part of polyether defoamer; and 2 parts of methylcellulose. After mixing at 1500 rpm for 3 hours, a slurry with a viscosity of 1500 mPa·s was obtained. The additives used were ethylene glycol, dipropylene glycol methyl ether, and glycerol in a mass ratio of 1:1:1.

[0151] The slurry was coated onto a PET release film and then subjected to gradient heating and gradient cooling in a drying device. The starting temperature of the gradient heating was 60°C and the ending temperature was 90°C. The ending temperature of the gradient cooling was room temperature. The heating gradient was 5°C / min and the cooling gradient was 5°C / min. After drying, a conductive film with a thickness of 50 μm was obtained.

[0152] Example 5

[0153] The conductive film was prepared according to the method of Example 1, except that the mass ratio of graphene to oxalic acid was 1:5 during the preparation of the modified graphene solution.

[0154] Example 6

[0155] The conductive film was prepared according to the method of Example 1, except that the mass ratio of graphene to oxalic acid was 1:60 during the preparation of the modified graphene solution.

[0156] Example 7

[0157] The conductive film was prepared according to the method of Example 1, except that the water bath heating temperature was 40°C during the preparation of the modified graphene solution.

[0158] Example 8

[0159] The conductive film was prepared according to the method of Example 1, except that the water bath heating temperature was 80°C during the preparation of the modified graphene solution.

[0160] Example 9

[0161] The conductive film was prepared according to the method of Example 1, except that the mass ratio of aqueous polyurethane to pyrrole monomer was 3:1 during the preparation of the modified polymer colloidal material solution.

[0162] Example 10

[0163] The conductive film was prepared according to the method of Example 1, except that the mass ratio of aqueous polyurethane to pyrrole monomer was 25:1 during the preparation of the modified polymer colloidal material solution.

[0164] Example 11

[0165] The conductive film was prepared according to the method of Example 1, except that the pH of the acidic system was 4 during the preparation of the modified polymer colloidal material solution.

[0166] Example 12

[0167] The conductive film was prepared according to the method of Example 1, except that the mass fraction of the modified graphene solution was 80 parts during the preparation of the slurry.

[0168] Example 13

[0169] The conductive film was prepared according to the method of Example 1, except that the mass fraction of the modified graphene solution was 400 parts during the preparation of the slurry.

[0170] Example 14

[0171] The conductive film was prepared according to the method of Example 1, except that the mass fraction of the modified polymer colloidal material solution was 30 parts during the preparation of the slurry.

[0172] Example 15

[0173] The conductive film was prepared according to the method of Example 1, except that the mass fraction of the modified polymer colloidal material solution was 100 parts during the preparation of the slurry.

[0174] Example 16

[0175] The conductive film was prepared according to the method of Example 1, except that the amount of additives added was adjusted during the preparation of the slurry so that the viscosity of the slurry was 500 mPa·s.

[0176] Comparative Example 1

[0177] The conductive film was prepared according to the method of Example 1, except that the graphene was not modified. That is, the step of adding oxalic acid was removed in the preparation of modified graphene in Example 1, and the mass content of the graphene solution was 3%.

[0178] Comparative Example 2

[0179] The conductive film was prepared according to the method of Example 1, except that the waterborne polyurethane was not modified, that is, a 35% waterborne polyurethane aqueous solution was directly used to replace the modified polymer granule material solution.

[0180] Comparative Example 3

[0181] The conductive film was prepared according to the method of Example 1, except that neither graphene nor aqueous polyurethane was modified. That is, the graphene solution in Example 1 was used to replace the modified graphene solution, and the aqueous polyurethane solution was used to replace the modified polymer colloidal material solution.

[0182] The conductive films prepared in the above embodiments and comparative examples were subjected to sheet resistance and tensile strength tests. The test methods included:

[0183] Sheet resistance test: The sheet resistance of the conductive film was tested using a handheld four-probe tester of model M-3 from Suzhou Jingge Electronics Co., Ltd.

[0184] Tensile strength test: According to ISO 527-3:1995 Plastics - Determination of tensile properties - Part 3: Test conditions for films and sheets, the polymer-based thermal interface material was made into dumbbell-shaped samples (Type 5). Then, referring to GB / T 1040.1-2006 Plastics - Determination of tensile properties, the tensile strength of the dumbbell-shaped samples was tested at room temperature and at a tensile rate of 2 mm / min using a KDL5000N universal tensile testing machine.

[0185] The test results are shown in Table 1.

[0186] Table 1

[0187]

[0188] As can be seen from the table above:

[0189] (1) Compared with Examples 5-6, Example 1 shows that the present application controls the mass ratio of graphene to oxalic acid to ensure the functionalization of carboxyl groups on the surface of graphene, improves the dispersibility of graphene in solvent, and maintains the conductivity of graphene.

[0190] (2) Compared with Examples 7-8, Example 1 shows that the present application controls the temperature during the graphene modification process, so that the modified graphene has both conductivity and dispersibility.

[0191] (3) Compared with Examples 9-10, Example 1 shows that the present application controls the mass ratio of polymeric colloid material to conductive polymer monomer, so that the modified polymeric colloid material has a certain conductivity and can be better dispersed in the solvent.

[0192] (4) Compared with Example 11, it can be seen that the conductive polymer grafted on the surface of the polymer granules prepared by controlling the pH of the acidic system in this application has better conjugated conductivity.

[0193] (5) Compared with Examples 12-15, it can be seen that the present application controls the amount of modified graphene solution and modified polymer colloidal material solution added to ensure that the conductive film obtained has the advantages of good conductivity, low sheet resistance and high tensile strength.

[0194] (6) Compared with Example 16, Example 1 shows that the present application controls the viscosity of the slurry so that the slurry can be better suited to the coating process, thereby the prepared conductive film has uniform thickness and good sheet resistance uniformity.

[0195] (7) Compared with Comparative Examples 1-3, it can be seen that this application modifies the surface of graphene by carboxyl functionalization and grafts conductive polymers onto the surface of polymeric granules, thereby connecting graphene and polymeric granules with conductive polymers through hydrogen bonds and chemical bonds. This not only enables graphene to form an efficient conductive pathway, but also makes the graphene and polymeric granules more firmly integrated, increasing the mechanical strength of the conductive film and reducing the sheet resistance.

[0196] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0197] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A conductive film, characterized in that, The conductive film contains modified graphene and modified polymer colloidal materials; The modified graphene is graphene that has undergone surface carboxyl functionalization modification, and the modified polymeric particle material includes polymeric particle material and conductive polymer grafted onto the surface of the polymeric particle material. The method for preparing the conductive film includes: An activator is added to a graphene solution to induce a ring-opening reaction of the epoxy groups in the graphene, followed by the addition of oxalic acid. The mixture is then heated and stirred to obtain a modified graphene solution. The mass ratio of graphene to oxalic acid in the graphene solution is 1:(10~50), and the solid content of the modified graphene solution is 1%~10%. A conductive polymer monomer is added to a solution containing the aforementioned polymeric colloidal material to adjust the solution to an acidic state. An oxidant is then added while stirring. The conductive polymer monomer is grafted onto the surface of the polymeric colloidal material to form the conductive polymer, resulting in the modified polymeric colloidal material solution. The mass ratio of the polymeric colloidal material to the conductive polymer monomer is (5~20):1, and the mass content of the solution containing the polymeric colloidal material is 30%~35%. The conductive film is prepared using a slurry containing the modified graphene solution and the modified polymer colloidal material solution; the slurry comprises, by mass parts: 100 to 300 parts of the modified graphene solution; 50 to 70 parts of the modified polymer colloidal material solution; and the viscosity of the slurry is 500 mPa·s to 1500 mPa·s.

2. The conductive film as described in claim 1, characterized in that, The conductive film satisfies at least one of the following conditions: (1) The sheet resistance of the conductive film is 1Ω / □~10Ω / □; (2) The tensile strength of the conductive film is 10MPa~15MPa; (3) The polymeric granule material includes at least one of waterborne polyurethane, waterborne acrylic, waterborne epoxy resin and waterborne phenolic resin; (4) The conductive polymer includes at least one of polypyrrole, polythiophene and polyaniline.

3. A method for preparing the conductive film according to claim 1 or 2, characterized in that, The preparation method includes: An activator is added to a graphene solution to induce a ring-opening reaction of the epoxy groups in the graphene, followed by the addition of oxalic acid. The mixture is then heated and stirred to obtain the modified graphene solution. The mass ratio of graphene to oxalic acid in the graphene solution is 1:(10~50), and the solid content of the modified graphene solution is 1%~10%. A conductive polymer monomer is added to a solution containing the aforementioned polymeric colloidal material to adjust the solution to an acidic state. An oxidant is then added while stirring. The conductive polymer monomer is grafted onto the surface of the polymeric colloidal material to form the conductive polymer, resulting in the modified polymeric colloidal material solution. The mass ratio of the polymeric colloidal material to the conductive polymer monomer is (5~20):1, and the mass content of the solution containing the polymeric colloidal material is 30%~35%. The conductive film is prepared using a slurry containing the modified graphene solution and the modified polymer colloidal material solution; the slurry comprises, by mass parts: 100 to 300 parts of the modified graphene solution; 50 to 70 parts of the modified polymer colloidal material solution; and the viscosity of the slurry is 500 mPa·s to 1500 mPa·s.

4. The preparation method according to claim 3, characterized in that, The method for preparing the modified graphene solution satisfies at least one of the following conditions: (1) The modified graphene solution also contains polyvinylpyrrolidone; (2) The graphene solution was obtained by ultrasonic dispersion; (3) The heating method includes water bath heating; (4) The heating temperature is 50℃~70℃; (5) The heating time is 0.5h~1.5h; (6) The activator includes at least one of HBr and HF.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the polyvinylpyrrolidone to the graphene contained in the graphene solution is 1:(4~6).

6. The preparation method according to claim 3, characterized in that, The method for preparing the modified polymer colloidal material solution satisfies at least one of the following conditions: (1) The molar ratio of the oxidant to the conductive polymer monomer is (1~3):1; (2) The pH of the acidic system is 1 to 3; (3) The oxidant includes at least one of FeCl3, CuCl2, H2O2 and I2; (4) The conductive polymer monomer includes at least one of pyrrole monomer, thiophene monomer and aniline monomer.

7. The preparation method according to claim 3, characterized in that, The slurry also includes additives.

8. The preparation method according to claim 7, characterized in that, The additives include at least one of the following: auxiliaries, dispersants, defoamers, and thickeners.

9. The preparation method according to claim 8, characterized in that, The slurry also satisfies at least one of the following conditions: (1) The adjuvant includes at least one of ethylene glycol, dipropylene glycol methyl ether, glycerin, N-methylpyrrolidone and acetone; (2) The slurry contains 10 to 50 parts of the additive by weight; (3) The dispersant includes at least one of polyethylene glycol octylphenyl ether, sodium dodecyl sulfate, polyoxyethylene lauryl ether, and gum arabic powder; (4) The slurry contains 1 to 3 parts of the dispersant by weight; (5) The defoamer includes at least one of polyether defoamers, polyvinyl alcohol defoamers, and fatty acid amide defoamers; (6) The slurry contains 0.2 to 1 part of the defoamer by weight; (7) The thickener includes at least one of carboxymethyl cellulose, propylene glycol alginate, methyl cellulose and polyoxyethylene; (8) The slurry contains 1 to 2 parts of the thickener by mass.

10. An electronic device, characterized in that, The electronic device includes the conductive film as described in claim 1 or 2.

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