Preparation method of biomass-derived electromagnetic shielding carbon plate based on high-conductivity carbon film modification

Abstract

The invention discloses a preparation method of a biomass-derived electromagnetic shielding carbon plate based on high-conductivity carbon film modification, and belongs to the technical field of preparation of carbon paper and electromagnetic shielding materials. The method comprises the following steps: 1, loading the directional binding agent; 2, preparing a carbon film precursor hydrogel; and 3, coating and carbonizing the paper. Controllable preparation of a carbon film precursor hydrogel is chemically and directionally combined with a biomass cellulose raw material, and the preparation of the cellulose-derived carbon surface loaded high-conductivity carbon film is realized through a controllable carbonization technology; the two kinds of carbon with different reaction mechanisms induce generation of efficient electromagnetic attenuation characteristics due to conductivity difference and existence of a heterogeneous interface, so that electromagnetic shielding performance is realized. In the whole preparation process, the product purity is high, and the preparation process is simple. The unique combination of the carbon film precursor hydrogel and the biomass carbon source provides a novel functional design thought and application basis for high-value utilization of biomass materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon paper and electromagnetic shielding material preparation; in particular, it relates to a method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film. Background Art

[0002] With the rapid development of the electronics industry, electromagnetic waves of various frequencies form electromagnetic pollution and interfere with electronic equipment and communications, causing widespread harm. For this reason, various shielding materials have been developed.

[0003] Currently, biomass-based carbon materials for electromagnetic shielding (e.g., cellulose, cotton, and lignin) generally require extremely high temperatures during preparation, resulting in high costs and thick products, which in turn lead to poor electromagnetic shielding effectiveness and limited application. Furthermore, carbon-based electromagnetic shielding materials developed from cellulose require the addition of large amounts of binders during actual use, making the process complex. The introduction of large amounts of binders also compromises electromagnetic shielding effectiveness and increases product thickness. The development of low-cost, ultra-thin biomass-based electromagnetic shielding material preparation methods is a current research priority. Summary of the Invention

[0004] The present invention provides a method for preparing a biomass-derived electromagnetic shielding carbon plate based on modification of a highly conductive carbon film, the purpose of which is to expand the multifunctionality of existing biomass materials and realize the development of ultra-thin electromagnetic shielding carbon materials.

[0005] A method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film is implemented by the following steps: 1. Loading of directional binder: The paper or board made from biomass raw materials is immersed in anhydrous ethanol, and then a directional binder is added and stirred, and then ammonium persulfate is added and stirred continuously, and then taken out, washed and dried to obtain a polymer-treated fiberboard; 2. Preparation of carbon film precursor hydrogel: A glucose precursor is prepared by using hydrogel and soluble polysaccharide, and then a free radical inducing agent is added and stirred uniformly to obtain a carbon film precursor hydrogel; 3. Coating and carbonization of polymer-treated fiberboard: The carbon film precursor hydrogel is spin-coated on the upper and lower surfaces of the fiberboard treated with the polymer, and then dried, and then pre-carbonized and carbonized under inert gas protection to obtain a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film, thereby completing the preparation method.

[0006] Furthermore, the paper or board prepared from the biomass raw material in step 1 is paper or filter paper made from softwood kraft pulp with a thickness of 0.1-0.5 mm, or a plant fiberboard made from softwood kraft pulp with a thickness of 0.8-3 mm.

[0007] Furthermore, the specific process of loading the directional binder in step 1 is as follows: 1g of paper or board prepared from biomass raw materials is immersed in 200~300ml of anhydrous ethanol, then 0.3~0.5ml of directional binder is added and stirred at a rate of 150~1500r / min for 2~3h, then 20~30ml of ammonium persulfate solution with a concentration of 0.5~0.6mmol is added and stirred at a rate of 100~1500r / min for 7~9h, after taking out, it is washed with anhydrous ethanol 3~5 times, and then vacuum dried at 60°C for 24h; wherein the directional binder is polyaniline.

[0008] Furthermore, the hydrogel in step 2 is bisacrylamide and acrylamide; the soluble polysaccharide in step 2 is one or more of glucose, sucrose, fructose, lactose, and sodium carboxymethyl cellulose.

[0009] Furthermore, the free radical inducing agent in step 2 is a triethanolamine aqueous solution and an ammonium persulfate aqueous solution.

[0010] Furthermore, the specific process of preparing the carbon film precursor hydrogel in step 2 is as follows: the soluble polysaccharide, bisacrylamide and deionized water are mixed and completely dissolved at 60°C, acrylamide is added when air-cooled to 40°C to obtain a glucose precursor, and then a triethanolamine aqueous solution and an ammonium persulfate aqueous solution are added and stirred evenly to obtain a carbon film precursor hydrogel.

[0011] Furthermore, the mass ratio of the soluble polysaccharide, bisacrylamide, deionized water and acrylamide is 35:(0.1-0.5):(15-50):(1-10).

[0012] Furthermore, the concentration of the triethanolamine aqueous solution is 5 wt %; the concentration of the ammonium persulfate aqueous solution is 10 wt %; and the mass volume ratio of the triethanolamine aqueous solution, the ammonium persulfate aqueous solution, and the precursor in glucose is 10 μL:5 μL:(1-10) g.

[0013] Furthermore, the drying treatment in step 3 is: vacuum drying at 60° C. for 24 h.

[0014] Furthermore, the pre-carbonization and carbonization treatment in step three: under the protection of inert gas, the temperature is raised to 150-250°C at a rate of 1-5°C / min and kept warm for 3-6 hours to complete the pre-carbonization, and then the temperature is raised to 1200-1400°C at a rate of 1-10°C / min and kept warm for 2-6 hours to complete the carbonization treatment; the inert gas is nitrogen or argon.

[0015] Furthermore, the amount of spin coating in step 3 is 0.25 g / cm 2 ; Spin coating uses a coater.

[0016] Starting from the design and preparation of ultra-thin biomass carbon materials, the present invention develops the orderly construction of multi-layered composite ultra-thin materials, loads a highly conductive carbon film on the surface of biomass-derived carbon materials, and realizes the preparation of ultra-thin carbon plates, which helps to open up the functionalization and high-value utilization of biomass materials and expand their application in the field of electromagnetic shielding functions. The highly conductive carbon film is set on the outermost layer, combined with the porous structure of the cellulose layered inside the paper and board prepared from biomass raw materials to realize the construction of a multi-layer structure, promote the "absorption-reflection-reabsorption" process of electromagnetic wave reflection, which can effectively enhance the electromagnetic attenuation characteristics, and finally realize the design and preparation of biomass-derived electromagnetic shielding carbon plates modified with highly conductive carbon films with orderly and controllable structures.

[0017] The reaction principle of the present invention is as follows: a polysaccharide solution and a hydrogel film are used to prepare a uniformly dispersed carbon film precursor hydrogel, and the hydrogel is controlled and carbonized in a limited area under the induction of free radicals to prepare an anisotropically oriented hydrogel carbon film. Directed grafting is achieved by combining the polymer on the surface of the biomass material with the free radicals of the carbon film precursor hydrogel, and the carbon film precursor hydrogel is evenly coated on the surface of the biomass material by coating. Finally, a highly conductive carbon material is obtained by pre-carbonization, high-temperature carbonization, and step-by-step carbonization treatment. High-efficiency electromagnetic shielding performance is achieved through the synergistic effect of the carbonization of the biomass material itself and the high conductivity of the carbon film on its surface.

[0018] The beneficial effects of the present invention are: the controllable preparation of carbon film precursor hydrogel is used to chemically and directional combine with biomass cellulose raw materials, and the preparation of highly conductive carbon film loaded on the surface of cellulose-derived carbon is achieved through controllable carbonization technology. The two carbons with different reaction mechanisms induce the generation of efficient electromagnetic attenuation characteristics due to the difference in conductivity and the existence of heterogeneous interfaces, thereby achieving electromagnetic shielding performance. The overall preparation process of the present invention has high product purity, simple preparation technology, and excellent performance, and can achieve ultra-strong electromagnetic shielding effectiveness in ultra-thin thicknesses of tens of microns to two millimeters. The unique combination of carbon film precursor hydrogel and biomass carbon source in the present invention provides a new functional design concept and application basis for the high-value utilization of biomass materials.

[0019] The present invention is applicable to the preparation of biomass-derived electromagnetic shielding carbon plates modified based on highly conductive carbon films. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a SEM spectrum of the biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film prepared in Example 1; Figure 2 1 is a graph showing the electromagnetic shielding performance of the biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film prepared in Example 1; Figure 3 is a SEM spectrum of the biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film prepared in Example 2; Figure 4 This is a diagram of the electromagnetic shielding performance of the biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film prepared in Example 2. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0022] Specific embodiment 1: This embodiment is a method for preparing a biomass-derived electromagnetic shielding carbon plate based on a highly conductive carbon film modification, which is achieved by the following steps: 1. Loading of directional binder: The paper or board made from biomass raw materials is immersed in anhydrous ethanol, and then a directional binder is added and stirred, and then ammonium persulfate is added and stirred continuously, and then taken out, washed and dried to obtain a polymer-treated fiberboard; 2. Preparation of carbon film precursor hydrogel: A glucose precursor is prepared by using hydrogel and soluble polysaccharide, and then a free radical inducing agent is added and stirred uniformly to obtain a carbon film precursor hydrogel; 3. Coating and carbonization of polymer-treated fiberboard: The carbon film precursor hydrogel is spin-coated on the upper and lower surfaces of the fiberboard treated with the polymer, and then dried, and then pre-carbonized and carbonized under inert gas protection to obtain a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film, thereby completing the preparation method.

[0023] Specific Embodiment 2: This embodiment differs from Specific Embodiment 1 in that the paper or board made from the biomass raw material in Step 1 is paper or filter paper made from softwood kraft pulp with a thickness of 0.1-0.5 mm, or plant fiberboard made from softwood kraft pulp with a thickness of 0.8-3 mm. Other steps and parameters are the same as those in Specific Embodiment 1.

[0024] Specific embodiment three: This embodiment differs from specific embodiment one in that the specific process for loading the directional binding agent in step one is as follows: 1g of paper or board made from biomass raw materials is immersed in 200-300ml of anhydrous ethanol, followed by the addition of 0.3-0.5ml of the directional binding agent and stirring at 150-1500 r / min for 2-3 hours. Then, 20-30ml of a 0.5-0.6mmol ammonium persulfate solution is added and stirred at 100-1500 r / min for 7-9 hours. After removal, the paper or board is washed with anhydrous ethanol 3-5 times and then vacuum-dried at 60°C for 24 hours. The directional binding agent is polyaniline. Other steps and parameters are the same as those in specific embodiment one.

[0025] Specific embodiment 4: This embodiment differs from specific embodiment 1 in that the hydrogel in step 2 is bisacrylamide and acrylamide; and the soluble polysaccharide in step 2 is one or more of glucose, sucrose, fructose, lactose, and sodium carboxymethyl cellulose. Other steps and parameters are the same as those in specific embodiment 1.

[0026] In this embodiment, when the soluble polysaccharide is a composition, the components are mixed in any ratio.

[0027] Specific embodiment 5: This embodiment differs from specific embodiment 1 in that the free radical inducing agent in step 2 is a triethanolamine aqueous solution and an ammonium persulfate aqueous solution. The other steps and parameters are the same as those in specific embodiment 1.

[0028] Specific Embodiment 6: This embodiment differs from Specific Embodiment 1 in that the specific process for preparing the carbon membrane precursor hydrogel in step 2 is as follows: soluble polysaccharide, bisacrylamide, and deionized water are mixed and completely dissolved at 60°C. After air cooling to 40°C, acrylamide is added to obtain a glucose precursor. A triethanolamine aqueous solution and an ammonium persulfate aqueous solution are then added and stirred to obtain the carbon membrane precursor hydrogel. Other steps and parameters are the same as those in Specific Embodiment 1.

[0029] Specific embodiment 7: This embodiment differs from specific embodiment 6 in that the mass ratio of the soluble polysaccharide, bisacrylamide, deionized water, and acrylamide is 35:(0.1-0.5):(15-50):(1-10). Other steps and parameters are the same as those of specific embodiment 6.

[0030] Specific Embodiment 8: This embodiment differs from Specific Embodiment 6 in that the concentration of the triethanolamine aqueous solution is 5 wt %; the concentration of the ammonium persulfate aqueous solution is 10 wt %; and the mass volume ratio of the triethanolamine aqueous solution, ammonium persulfate aqueous solution, and glucose precursor is 10 μL:5 μL:(1-10) g. Other steps and parameters are the same as Specific Embodiment 6.

[0031] Specific embodiment 9: This embodiment differs from specific embodiment 1 in that the drying process in step 3 is performed under vacuum at 60° C. for 24 hours. Other steps and parameters are the same as those in specific embodiment 1.

[0032] Specific Embodiment 10: This embodiment differs from Specific Embodiment 1 in that, in step 3, the pre-carbonization and carbonization treatments are performed by heating the temperature to 150-250°C at a rate of 1-5°C / min and holding for 3-6 hours under an inert gas atmosphere, followed by heating the temperature to 1200-1400°C at a rate of 1-10°C / min and holding for 2-6 hours to complete the carbonization treatment. The inert gas is nitrogen or argon. Other steps and parameters are the same as those in Specific Embodiment 1.

[0033] In this embodiment, the pre-carbonization and carbonization treatments are performed in a vacuum oven.

[0034] Specific embodiment 11: This embodiment differs from the specific embodiment 1 in that the amount of spin coating in step 3 is 0.25 g / cm 2 The other steps and parameters are the same as those in the first embodiment.

[0035] The beneficial effects of the present invention are verified by the following examples: Example 1:

[0036] A method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film is implemented by the following steps: 1. Loading of directional binder: The paper or board made from biomass raw materials is immersed in anhydrous ethanol, and then a directional binder is added and stirred, and then ammonium persulfate is added and stirred continuously, and then taken out, washed and dried to obtain a polymer-treated fiberboard; 2. Preparation of carbon film precursor hydrogel: A glucose precursor is prepared by using hydrogel and soluble polysaccharide, and then a free radical inducing agent is added and stirred uniformly to obtain a carbon film precursor hydrogel; 3. Coating and carbonization of polymer-treated fiberboard: The carbon film precursor hydrogel is spin-coated on the upper and lower surfaces of the fiberboard treated with the polymer, and then dried, and then pre-carbonized and carbonized under inert gas protection to obtain a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film, thereby completing the preparation method.

[0037] The paper or board prepared from the biomass raw material in step 1 of this embodiment is paper made from softwood kraft pulp with a thickness of 0.2 mm.

[0038] The specific process of loading the directional binder described in step 1 of this embodiment is as follows: 1 g of paper or board prepared from biomass raw materials is immersed in 200 ml of anhydrous ethanol, then 0.4 ml of the directional binder is added and stirred at a rate of 500 r / min for 2 hours, then 20 ml of ammonium persulfate solution with a concentration of 0.55 mmol is added and stirred at a rate of 500 r / min for 8 hours, and after taking out, it is washed with anhydrous ethanol four times and then vacuum dried at 60°C for 24 hours; wherein the directional binder is polyaniline.

[0039] In step 2 of this embodiment, the hydrogel is bisacrylamide and acrylamide; and the soluble polysaccharide in step 2 is glucose.

[0040] The free radical inducing agents in step 2 of this embodiment are triethanolamine aqueous solution and ammonium persulfate aqueous solution.

[0041] The specific process of preparing the carbon film precursor hydrogel in step 2 of this embodiment is as follows: glucose, bisacrylamide and deionized water are mixed and completely dissolved at 60°C, acrylamide is added when air-cooled to 40°C to obtain a precursor in glucose, and then a triethanolamine aqueous solution and an ammonium persulfate aqueous solution are added and stirred evenly to obtain a carbon film precursor hydrogel; the amount of glucose, bisacrylamide, deionized water and acrylamide is 35g:0.35g:15g:10g; the concentration of the triethanolamine aqueous solution is 5wt%; the concentration of the ammonium persulfate aqueous solution is 10wt%; the mass volume ratio of the triethanolamine aqueous solution, ammonium persulfate aqueous solution and glucose precursor is 10μL:5μL:10g.

[0042] The drying process described in step 3 of this embodiment is as follows: vacuum drying at 60° C. for 24 h.

[0043] The pre-carbonization and carbonization treatment in step 3 of this embodiment are as follows: under the protection of inert gas, the temperature is raised to 200°C at a rate of 2°C / min and kept warm for 3 hours to complete the pre-carbonization, and then the temperature is raised to 1200°C at a rate of 5°C / min and kept warm for 2 hours to complete the carbonization treatment; the inert gas is nitrogen.

[0044] The amount of spin coating in step 3 of this embodiment is 0.25 g / cm 2 ; Spin coating uses a coater.

[0045] The paper or board prepared from biomass raw materials in this embodiment is a commercial product of Shandong Xingangji Co., Ltd.

[0046] In this embodiment, the biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film is subjected to a carbonization treatment at high temperature during the preparation process to carbonize the biomass cellulose into biomass-derived carbon. At the same time, the carbon film precursor hydrogel is controllably carbonized to form a hydrogel carbon film wrapped around the fiber surface. The specific micromorphology SEM image is shown in the figure. Figure 1 As shown in the figure, the hydrogel carbon film forms carbon spheres at high temperatures, which are evenly wrapped on the surface of carbon fibers. It has a porous structure, and the cellulose inside is overlapped layer by layer.

[0047] The electromagnetic shielding effectiveness of the biomass-derived carbon plate modified with a highly conductive carbon film prepared in this embodiment is as follows: Figure 2 As shown, an electromagnetic shielding effectiveness SE of nearly 47dB can be achieved in the X-band T , which shows that the biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film prepared in this embodiment has excellent electromagnetic shielding performance. Example 2:

[0048] The difference between this embodiment and embodiment 1 is that the temperature of the carbonization treatment in step 3 is 1400° C.; the rest is the same as embodiment 1.

[0049] In this embodiment, the biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film is subjected to a carbonization treatment at high temperature during the preparation process to carbonize the biomass cellulose into biomass-derived carbon. At the same time, the carbon film precursor hydrogel is controllably carbonized to form a hydrogel carbon film wrapped around the fiber surface. The specific micromorphology SEM image is shown in the figure. Figure 3 As shown in FIG. 1 , the hydrogel carbon film forms carbon spheres at high temperatures and uniformly wraps around the carbon fiber surface. Compared with Example 1, the size of the carbon particles gradually increases as the carbonization temperature increases.

[0050] The electromagnetic shielding effectiveness of the biomass-derived carbon plate modified with a highly conductive carbon film prepared in this embodiment is as follows: Figure 4 As shown, an electromagnetic shielding effectiveness SE of nearly 45dB can be achieved in the X-band T , which shows that the biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film prepared in this embodiment has excellent electromagnetic shielding performance.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film, characterized in that It proceeds as follows:

1. Loading of directional binder: The paper or board made from biomass raw materials is immersed in anhydrous ethanol, and then a directional binder is added and stirred, and then ammonium persulfate is added and stirred continuously, and then taken out, washed and dried to obtain a polymer-treated fiberboard; 2. Preparation of carbon film precursor hydrogel: A glucose precursor is prepared by using hydrogel and soluble polysaccharide, and then a free radical inducing agent is added and stirred uniformly to obtain a carbon film precursor hydrogel; 3. Coating and carbonization of polymer-treated fiberboard: The carbon film precursor hydrogel is spin-coated on the upper and lower surfaces of the fiberboard treated with the polymer, and then dried, and then pre-carbonized and carbonized under inert gas protection to obtain a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film, thereby completing the preparation method.

2. The method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film according to claim 1, characterized in that The paper or board prepared from the biomass raw material in step 1 is paper or filter paper made from softwood kraft pulp with a thickness of 0.1-0.5 mm, or a plant fiberboard made from softwood kraft pulp with a thickness of 0.8-3 mm.

3. The method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film according to claim 1, characterized in that The specific process of loading the directional binder described in step 1 is as follows: 1g of paper or board prepared from biomass raw materials is immersed in 200~300ml of anhydrous ethanol, then 0.3~0.5ml of directional binder is added and stirred at a rate of 150~1500r / min for 2~3h, then 20~30ml of ammonium persulfate solution with a concentration of 0.5~0.6mmol is added and stirred at a rate of 100~1500r / min for 7~9h, after taking out, it is washed with anhydrous ethanol 3~5 times, and then vacuum dried at 60°C for 24h; wherein the directional binder is polyaniline.

4. The method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film according to claim 1, characterized in that The hydrogel in step 2 is bisacrylamide and acrylamide; the soluble polysaccharide in step 2 is one or more of glucose, sucrose, fructose, lactose, and sodium carboxymethyl cellulose.

5. The method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film according to claim 1, characterized in that The free radical inducing agents in step 2 are triethanolamine aqueous solution and ammonium persulfate aqueous solution.

6. The method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film according to claim 1, characterized in that The specific process of preparing the carbon film precursor hydrogel in step 2 is as follows: soluble polysaccharide, bisacrylamide and deionized water are mixed and completely dissolved at 60°C, acrylamide is added when air-cooled to 40°C to obtain a glucose precursor, and then triethanolamine aqueous solution and ammonium persulfate aqueous solution are added and stirred evenly to obtain a carbon film precursor hydrogel.

7. The method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film according to claim 6, characterized in that The mass ratio of the soluble polysaccharide, bisacrylamide, deionized water and acrylamide is 35:(0.1-0.5):(15-50):(1-10).

8. The method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film according to claim 6, characterized in that The concentration of the triethanolamine aqueous solution is 5 wt %; the concentration of the ammonium persulfate aqueous solution is 10 wt %; the mass volume ratio of the triethanolamine aqueous solution, the ammonium persulfate aqueous solution and the precursor in glucose is 10 μL:5 μL:(1-10) g.

9. The method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film according to claim 1, characterized in that The pre-carbonization and carbonization treatment in step 3: under the protection of inert gas, the temperature is raised to 150-250°C at a rate of 1-5°C / min and kept warm for 3-6 hours to complete the pre-carbonization, and then the temperature is raised to 1200-1400°C at a rate of 1-10°C / min and kept warm for 2-6 hours to complete the carbonization treatment; the inert gas is nitrogen or argon.

10. The method for preparing a biomass-derived electromagnetic shielding carbon plate modified with a highly conductive carbon film according to claim 1, characterized in that The amount of spin coating in step 3 is 0.25 g / cm 2 ; Spin coating uses a coater.

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