Graphene film transfer method

Abstract

The present invention discloses a universal method for non-destructively and cleanly transferring a high-quality graphene film grown on the surface of a metal copper foil to a variety of functional substrates. This method does not require the use of organic solvents such as acetone to remove the transfer medium, thereby achieving efficient, clean, and non-destructive transfer of the graphene film. This method regulates the interfacial bonding force between the graphene and the target substrate so that the bonding force between the transfer medium layer and the graphene film is less than the bonding force between the transfer medium layer and the stripping film, thereby achieving direct stripping of the transfer medium layer from the surface of the graphene film. Without the participation of organic reagents such as acetone, the non-destructive and clean transfer of the graphene film can be successfully achieved. The graphene film obtained by this method has an integrity of up to 99% and a high cleanliness. In addition, the entire transfer process does not require the use of organic solvents. The process is simple and environmentally friendly, and is expected to be used for large-scale production.

Description

Technical Field

[0001] The invention belongs to the field of carbon materials, and in particular relates to a method for transferring a graphene film. Background Art

[0002] Graphene is a novel nanocarbon material with a unique two-dimensional honeycomb crystal structure and excellent electrical, thermal, optical, and mechanical properties. Its applicability on a variety of functional substrates paves the way for its large-scale applications in applications such as touch screens, flexible electronics, heat dissipation, sensors, lithium-ion batteries, and supercapacitors. However, graphene films are typically grown on metal substrates via chemical vapor deposition, necessitating reliable post-growth transfer techniques to achieve crack-free, contaminant-free, and large-area transfer of graphene to any substrate. Summary of the Invention

[0003] To solve the above problems, the present invention provides a clean transfer method for graphene films. The transfer process does not require the use of organic solvents to remove the glue, and the glue layer is directly peeled off. The method includes the following steps: forming a transfer medium layer on the surface of the graphene film directly grown on a metal substrate; removing the metal substrate, attaching the graphene film surface to the target substrate, adhering a peeling film to the transfer medium layer, and directly peeling off the transfer medium layer using the peeling film; the process of removing the transfer medium layer does not require the use of organic solvents.

[0004] According to one embodiment of the present invention, the number of layers of the graphene film is 1 to 10.

[0005] According to one embodiment of the present invention, the transfer method includes the following steps:

[0006] S1. forming a transfer medium layer on the surface of the graphene film directly grown on the metal substrate to obtain a transfer medium layer / graphene film / metal substrate composite;

[0007] S2, adhering a thermal release tape (TRT) layer to the surface of the transfer medium layer;

[0008] S3, removing the metal substrate to obtain a TRT layer / transfer medium layer / graphene film composite;

[0009] S4, laminating the graphene film surface of the TRT layer / transfer medium layer / graphene film composite to a target substrate;

[0010] S5, heating to remove the TRT layer;

[0011] S6. Adhere a release film to the surface of the transfer medium layer of the transfer medium layer / graphene film / target substrate composite, and heat at a certain temperature for a certain time.

[0012] S7, directly peeling off the transfer medium layer using a peeling film;

[0013] Preferably, the lamination method in step S4 is roller lamination;

[0014] Preferably, in step S6, the heating temperature is higher than the glass transition temperature of the transfer medium, and the heating time is 1 hour to 10 hours;

[0015] Further preferably, in step S6, the heating temperature is 5 degrees higher than the glass transition temperature of the transfer medium, and the heating time is 2 hours.

[0016] Preferably, the lamination method in step S4 is roller lamination.

[0017] According to one embodiment of the present invention, in the above step S5, the heating temperature is 100°C to 140°C, preferably, 130°C to 135°C.

[0018] According to one embodiment of the present invention, the transfer medium layer includes one or more of polypropylene carbonate (PPC), polymethyl methacrylate (PMMA), rosin, epoxy resin, ethylene-vinyl acetate copolymer (EVA), and polystyrene (PS); preferably polymethyl methacrylate (PMMA).

[0019] According to one embodiment of the present invention, the thickness of the transfer medium layer is 100 nm to 20 μm; preferably, the thickness of the transfer medium layer is 500 nm to 5 μm.

[0020] According to one embodiment of the present invention, the release film is one or more of a silicone resin film, an acrylic film, and a UV adhesive tape; preferably, the release film is a silicone resin film.

[0021] According to one embodiment of the present invention, the silicone resin film is composed of a silicone resin layer + a PET layer, has a viscosity of 8 to 50 g, and a thickness of the silicone resin layer is 5 to 50 μm, preferably, the viscosity is 10 to 20 g; the acrylic film is composed of an acrylic (PMMA) layer + a PET layer, has a viscosity of 5 to 30 g, and a thickness of the acrylic layer is 5 to 50 μm, preferably, the viscosity is 10 to 20 g.

[0022] According to one embodiment of the present invention, the method for removing the metal substrate is an etching method or an electrochemical bubbling method; preferably, the etching method.

[0023] According to one embodiment of the present invention, the metal substrate is one of Cu, Ni, Pt, Ru or an alloy thereof; preferably copper foil.

[0024] According to one embodiment of the present invention, the stripping method is manual stripping or mechanical stripping at a speed of 1 to 10 mm / s.

[0025] Beneficial effects:

[0026] The graphene film transfer method of the present invention can trigger the deformation of the transfer medium at high temperature by adding polymer molecules with a low glass transition temperature to PMMA, thereby achieving controllable conformal contact between the transfer medium and graphene, and further realizing large-scale transfer of high-quality graphene film without cracks, pollution and wrinkles. The transfer medium can be directly peeled off from the graphene through a peeling film, thereby providing an ultra-clean surface and extremely high carrier mobility. This method can be applied to the batch processing of large-area two-dimensional materials in the future and has good efficiency. At the same time, it avoids the disadvantages of traditional degumming methods such as the need for acetone fumigation and immersion, and the high cost of waste liquid treatment.

[0027] The graphene film transfer method of the present invention regulates the interfacial bonding force, making the bonding force between the transfer medium layer and the graphene smaller than the bonding force between the transfer medium layer and the stripping film, thereby directly stripping the transfer medium layer from the graphene surface. Compared with organic solvent debonding, this method produces less residual graphene adhesive, achieves up to 99% graphene film integrity, and offers high cleanliness, effectively preventing uneven water and oxygen doping. Furthermore, the entire transfer process does not require the use of organic solvents, resulting in a simple and environmentally friendly process that facilitates mechanization and large-scale production.

[0028] The method of the present invention has simple process and can easily realize the lossless and clean transfer of graphene films in batches, and is expected to become the preferred solution for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings.

[0030] Figure 1 It is a schematic flow chart of the graphene film transfer method of the present invention.

[0031] Figure 2 This is an optical microscope photograph of the graphene transferred in Example 1.

[0032] Figure 3 This is an atomic force microscope photograph of the graphene transferred in Example 1.

[0033] Figure 4 This is an optical microscope photograph of the transferred graphene in Comparative Example 1.

[0034] Figure 5 This is an atomic force microscope photograph of the transferred graphene in Comparative Example 1.

[0035] Figure 6 This is a photograph of the height change of the transfer medium before and after heating in Example 1. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to specific embodiments.

[0037] The numbers S1 to S7 of the steps described herein are for the purpose of distinguishing different steps and are not intended to limit the order and continuity of the steps. That is, other auxiliary steps such as cleaning and drying may be included between any of the steps.

[0038] like Figure 1 As shown, the graphene film transfer method of the present invention includes:

[0039] S1. forming a transfer medium layer on the surface of the graphene film directly grown on the metal substrate to obtain a transfer medium layer / graphene film / metal substrate composite;

[0040] S2, adhering a thermal release tape (TRT) layer to the surface of the transfer medium layer;

[0041] S3, removing the metal substrate to obtain a TRT layer / transfer medium layer / graphene film composite;

[0042] S4, laminating the graphene film surface of the TRT layer / transfer medium layer / graphene film composite to a target substrate;

[0043] S5, heating to remove the TRT layer;

[0044] S6, adhering a release film to the surface of the transfer medium layer / graphene film / target substrate composite, and heating at a temperature 5 degrees higher than the glass transition temperature of the transfer medium for 2 hours;

[0045] S7. Use a peeling film to directly peel off the transfer medium layer.

[0046] In step S1, the graphene film can be grown on a metal substrate by chemical vapor deposition. The metal substrate can be a foil of Cu, Ni, Pt, Ru, or their alloys that catalyze the growth of graphene. The pre-transferred graphene film is a single layer. The material used for the transfer medium layer is one or more of polypropylene carbonate (PPC), polymethyl methacrylate (PMMA), rosin, epoxy resin, ethylene-vinyl acetate copolymer (EVA), and polystyrene (PS). The transfer medium layer can be formed on the graphene film by dissolving the material used for the transfer medium layer in an organic solvent to form a solution, applying the solution to the upper surface of the graphene film, and forming a transfer medium layer / graphene film / metal substrate composite after the solvent evaporates. The coating method can be any appropriate method, such as spin coating, blade coating, spray coating, etc. The appropriate solvent and solution concentration can be selected according to the selected auxiliary transfer and coating method. The specific parameters are not limited here. Those skilled in the art will understand that the purpose of forming the solution is to form the transfer medium layer, as long as the solution can achieve the above purpose.

[0047] In step S2, a TRT layer is adhered to the surface of the transfer medium layer.

[0048] In step S3, the metal substrate is removed to obtain a TRT layer / transfer medium layer / graphene film composite.

[0049] In step S4, the graphene film surface of the TRT layer / transfer medium layer / graphene film composite is bonded to the target substrate.

[0050] In step S5, the heating temperature is 100°C to 140°C, preferably 130°C to 135°C.

[0051] In step S6, a release film is adhered to the surface of the transfer medium layer / graphene film / target substrate composite, and heated at a temperature 5 degrees higher than the glass transition temperature of the transfer medium for 2 hours.

[0052] In step S7, the transfer medium layer is directly peeled off using a peeling film.

[0053] This method modulates the interfacial bonding strength between graphene and the target substrate, making the bonding strength between the transfer medium layer and the graphene film smaller than that between the transfer medium layer and the peeling film. This allows the transfer medium layer to be directly peeled off from the graphene film surface. This method successfully achieves non-destructive and clean transfer of graphene films without the need for organic reagents such as acetone.

[0054] The present invention is further described below by way of specific examples, which are merely exemplary and do not constitute any limitation on the scope of protection of the present invention.

[0055] In the following examples and comparative examples, all reagents, materials and instruments used are commercially available unless otherwise specified.

[0056] Example 1

[0057] A single-layer graphene film grown on a 10 cm × 10 cm copper substrate was selected. PMMA was dissolved in anisole to a PMMA content of 4% by weight. The copper foil / graphene film was placed in a spin coater and the PMMA solution was spin-coated onto the graphene film surface at 1000 rpm. Curing was performed at 170°C for 90 seconds to obtain a PMMA layer / graphene film / copper substrate composite with a PMMA layer thickness of 1 μm. TRT (thinly oxidized polymer) was adhered to the dried PMMA layer to form a TRT layer / PMMA layer / graphene film / copper substrate composite. The composite was immersed in a sodium persulfate etchant. After the metal foil was completely etched, it was rinsed, air-dried, and roller-laminated onto the target substrate (PET). The TRT layer was then removed by heating at 140°C for 5 minutes. A silicone resin film was applied to the PMMA surface and heated at 110°C for 2 hours. The silicone resin film was manually peeled off at a rate of 5 cm / min, completing the graphene transfer process.

[0058] Figure 2 and Figure 3 The optical microscope photos and atomic force microscope photos of the graphene film transferred to the PET substrate are respectively. Figure 2 and Figure 3 It can be seen that the surface of the graphene film transferred to the target substrate is clean and almost damage-free.

[0059] Comparative Example 1

[0060] A single-layer graphene film grown on a 5cm×5cm copper substrate is selected, and PMMA is spin-coated on the graphene film / copper substrate complex (the coating method is the same as in Example 1) to form a PMMA layer / graphene film / copper substrate. The thickness of the PMMA layer is 1μm. TRT is adhered to the surface of the dried PMMA layer to obtain a TRT layer / PMMA layer / graphene film / copper substrate complex. The complex is immersed in ammonium persulfate etching solution, and after the copper is completely etched, it is washed with water, dried, and roller-pressed to the target substrate (PET). Then, the TRT layer is removed by heating at 130°C for 3 minutes. The PMMA layer / graphene film / PET is immersed in acetone vapor for 10 minutes to remove the PMMA layer, thereby completing the graphene transfer process.

[0061] The optical microscope photos and atomic force microscope photos of the graphene obtained by the conventional acetone degumming process in Comparative Example 1 are shown in FIG. Figure 4 and Figure 5 As shown in the figure, there is a lot of residual glue on the surface of the graphene film, and the degumming process causes the graphene to be damaged.

[0062] From Example 1 and Comparative Example 1, it can be seen that the preparation method of the present invention improves the integrity and cleanliness of the graphene film, and the entire transfer process does not require the use of organic solutions, and the operation is convenient.

[0063] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the content of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for transferring a graphene film, characterized in that: The following steps are involved: forming a transfer medium layer on the surface of the graphene film directly grown on the metal substrate; The metal substrate is removed, and after the graphene film surface is attached to the target substrate, the transfer medium layer is adhered to a peeling film, and the transfer medium layer is directly peeled off using the peeling film; The process of removing the transfer medium layer does not require the use of organic solvents; The steps include: S1. forming a transfer medium layer on the surface of the graphene film directly grown on the metal substrate to obtain a transfer medium layer / graphene film / metal substrate composite; S2, adhering a thermal release tape TRT layer to the surface of the transfer medium layer; S3, removing the metal substrate to obtain a TRT layer / transfer medium layer / graphene film composite; S4, laminating the graphene film surface of the TRT layer / transfer medium layer / graphene film composite to a target substrate; S5, heating to remove the TRT layer; S6, adhering a release film to the surface of the transfer medium layer of the transfer medium layer / graphene film / target substrate composite, and heating at a certain temperature for a certain time; S7. Use a peeling film to directly peel off the transfer medium layer.

2. The transfer method according to claim 1, wherein The number of layers of the graphene film is 1 to 10.

3. The transfer method according to claim 1, wherein The lamination method in step S4 is roller lamination.

4. The transfer method according to claim 1, wherein: In step S6, the heating temperature is higher than the glass transition temperature of the transfer medium, and the heating time is 1 hour to 10 hours.

5. The transfer method according to claim 1, wherein: In step S6, the heating temperature is 5 degrees higher than the glass transition temperature of the transfer medium, and the heating time is 2 hours.

6. The transfer method according to claim 1, wherein: In step S5, the heating temperature is 100°C to 140°C.

7. The transfer method according to claim 6, characterized in that In step S5, the heating temperature is 130°C to 135°C.

8. The transfer method according to claim 1, wherein: The transfer medium layer includes one or more of polypropylene carbonate (PPC), polymethyl methacrylate (PMMA), rosin, epoxy resin, ethylene-vinyl acetate copolymer (EVA), and polystyrene (PS).

9. The transfer method according to claim 8, characterized in that The transfer medium layer is polymethyl methacrylate (PMMA).

10. The transfer method according to claim 8, characterized in that The thickness of the transfer medium layer is 100 nm to 20 μm.

11. The transfer method according to claim 10, characterized in that The thickness of the transfer medium layer is 500 nm to 5 μm.

12. The transfer method according to claim 1, wherein The release film is one or more of a silicone resin film, an acrylic film, and a UV adhesive tape.

13. The transfer method according to claim 12, characterized in that: The release film is a silicone resin film.

14. The transfer method according to claim 12, wherein: The silicone resin film is composed of a silicone resin layer + a PET layer, has a viscosity of 8 to 50 g, and a thickness of the silicone resin layer of 5 to 50 μm; The acrylic film consists of an acrylic (PMMA) layer and a PET layer, has a viscosity of 5 to 30 g, and a thickness of 5 to 50 μm.

15. The transfer method according to claim 14, characterized in that: The viscosity of the silicone resin film is 10-20 g; the viscosity of the acrylic film is 10-20 g.

16. The transfer method according to claim 1, wherein The method for removing the metal substrate is an etching method or an electrochemical bubbling method.

17. The transfer method according to claim 16, characterized in that: The metal substrate is one of Cu, Ni, Pt, Ru or an alloy thereof.

18. The transfer method according to claim 17, characterized in that: The metal substrate is copper foil.

19. The transfer method according to claim 1, wherein The stripping method is manual stripping or mechanical stripping, and the speed is 1 to 10 mm / s.

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