POD resin material, POD resin film and preparation method therefor, graphite film and electronic device

Abstract

A POD resin material, a POD resin film and a preparation method therefor, a graphite film and an electronic device. The POD resin film comprises a repeating unit A, a repeating unit B and a repeating unit C, and the structures of the repeating unit A, the repeating unit B and the repeating unit C are as follows: formula (1), formula (2), formula (3). The use of the POD resin material can improve the thermal conductivity of artificial graphite and reduce the particle fall-off amount of artificial graphite.

Description

POD resin material, POD resin film and preparation method thereof, graphite film and electronic device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on July 5, 2023, with application number 202310817704.7 and application name “POD resin material, POD resin film and preparation method thereof, graphite film and electronic device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of thin film materials, and specifically to a POD resin material, a POD resin film and a preparation method thereof, a graphite film and an electronic device. Background Art

[0004] With the improvement of electronic device performance and the continuous miniaturization of products, higher requirements are being placed on heat dissipation. For miniaturized electronic devices, due to the space constraints of their internal electronic components, heat dissipation is generally only possible through the outer casing. Heat conduction between the electronic components and the outer casing is crucial for heat dissipation. Selecting a suitable thermally conductive material for heat conduction between the electronic components and the outer casing can facilitate rapid heat dissipation. Artificial graphite is widely used in various fields due to its high thermal conductivity and scalable production and processing. Existing artificial graphite is often made from polyimide (PI) as a base material, which is obtained by carbonizing and graphitizing PI. However, artificial graphite obtained from PI as a base material has a low thickness, low thermal conductivity, and poor bendability. When used as a thermally conductive film, it is prone to poor thermal conductivity and cracking. To address these issues, the development of new polymer materials for the production of artificial graphite is needed. Aromatic polyoxadiazole (POD) is a high-performance polymer containing benzene and oxadiazole rings in its molecular chain. Artificial graphite can be obtained by carbonizing and graphitizing aromatic polyoxadiazole films. However, the thermal conductivity of artificial graphite obtained using currently disclosed aromatic polyoxadiazole polymer materials has not been significantly improved, and the amount of powder shedding is also high, making it unusable as a thermal conductive material.

[0005] Summary of the Invention

[0006] The present application provides a POD resin material, a POD resin film and a preparation method thereof, a graphite film and an electronic device to improve the thermal conductivity of artificial graphite and reduce the amount of powder loss of artificial graphite.

[0007] In a first aspect, the present application provides a POD resin material, wherein the POD resin film comprises a repeating unit A, a repeating unit B, and a repeating unit C, wherein the structures of the repeating unit A, the repeating unit B, and the repeating unit C are as follows:

[0008] wherein Ar1 is selected from a substituted or unsubstituted aromatic ring group of 6 to 20 carbon atoms;

[0009] Ar2 is a substituted or unsubstituted aromatic ring group containing two benzene rings;

[0010] Ar3 is selected from a substituted or unsubstituted aromatic ring group of 6 to 20 carbon atoms, wherein at least one hydrogen in the aromatic ring group is substituted by a sulfonic acid group;

[0011] The molar ratio of the number of moles of the repeating unit A to the sum of the number of moles of the repeating unit B and the repeating unit C is 99:1 to 70:30;

[0012] The molar ratio of the repeating unit B to the repeating unit C is 1:1 to 2:1.

[0013] The POD resin material of the present application contains repeating units A, B, and C in its molecular structure, and the repeating units A, B, and C satisfy a specific molar ratio. The POD resin having the above molecular structure can increase the compliance of the POD resin and the surface smoothness of the material when forming a POD resin film. After carbonization and graphitization, the obtained graphite film has higher stability, a higher thermal conductivity, and is not easy to fall off. When used as a thermally conductive film, it can effectively protect the heat of electronic equipment from being discharged in time and reduce the pollution of the graphite film to the electronic equipment.

[0014] In an optional implementation, Ar1 is selected from phenyl, biphenyl or naphthyl; Ar2 is selected from biphenyl, naphthyl, Br-substituted biphenyl or Br-substituted naphthyl; Ar3 is selected from phenyl, biphenyl or naphthyl substituted with sulfonic acid.

[0015] In one optional implementation, the POD resin material contains 40% or more C by weight and 10% or less S by weight. A low C content can affect the thermal conductivity of the resulting graphite film. A high C content can yield a higher-quality graphite film from the same POD resin film mass.

[0016] In an optional implementation, the molar ratio of the benzene ring to the oxadiazole ring is 1:1.1 to 1:1.5. This molar ratio of oxadiazole rings can form a stable pyrrole structure during heat treatment. The formed pyrrole structure can facilitate the formation of a stable C6-ring structure during graphitization, thereby improving the thermal conductivity of the graphite thermal conductive film.

[0017] In one optional implementation, the POD resin material contains graphene, wherein the graphene accounts for 0.5% to 50% by weight of the POD resin material. Graphene has a high thermal conductivity. Therefore, by adding graphene to the POD resin, a graphite film with even higher thermal conductivity can be obtained after the POD resin material is carbonized.

[0018] In a second aspect, the present application provides a POD resin film, which is prepared from the POD resin material of the present application.

[0019] In a third aspect, the present application provides a method for preparing a POD resin film, the preparation method comprising:

[0020] placing reaction raw materials comprising an aromatic diacid monomer, an aromatic diformic acid sulfonate, and a hydrazine salt monomer in a fuming sulfuric acid solution for polymerization reaction to obtain a resin solution; and subjecting the resin solution to a film-forming treatment to obtain the POD resin film;

[0021] The aromatic diacid monomers include at least a portion of diphenyl ring aromatic diacid monomers, and the ratio of the total molar number of the aromatic diacid monomers and the aromatic diformic acid sulfonate to the molar number of the hydrazine salt is 1:1.01 to 1:1.1.

[0022] Part of the aromatic diacid monomers reacts with the hydrazine salt to form repeating unit A, the diphenyl ring aromatic diacid monomer in the aromatic diacid monomer reacts with the hydrazine salt to form repeating unit B, and the aromatic diformic acid sulfonate reacts with the hydrazine salt to form repeating unit C.

[0023] In one optional implementation, the resin solution has a viscosity greater than 100 Pa.s and a solids content of 5-20%. The viscosity and solids content of the resin solution affect the film forming quality. If the viscosity of the resin solution is too low, sticking to the roller will be severe, resulting in a rough film surface. The solids content also affects the viscosity of the POD resin solution. If the solids content is too low, the solvent content will be high, resulting in poor economic efficiency.

[0024] In one optional implementation, the aromatic diacid monomer includes at least two of terephthalic acid, 1,4-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 3,3-biphenyl dicarboxylic acid, terephthalic acid, 2,4-biphenyl dicarboxylic acid, 3,3-diphenyl ether dicarboxylic acid, isophthalic acid, biphenyl dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, or 1,4-naphthalene dicarboxylic acid; at least one of the two is a diphenyl ring aromatic diacid monomer. The diphenyl ring aromatic diacid monomer can be selected from at least one of biphenyl dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, or 1,4-naphthalene dicarboxylic acid.

[0025] In an optional implementation, the aromatic dicarboxylic acid sulfonate includes a combination of isophthalic acid-5-sulfonate.

[0026] In one optional implementation, the polymerization reaction includes prepolymerization at 80-110°C for 2-5 hours, followed by polymerization at 110-170°C for 2-5 hours. This polymerization process can help form a stable network structure, which helps improve the integrity and stability of the graphite film structure during subsequent carbonization and graphitization processes.

[0027] In a fourth aspect, the present application provides a graphite film, and the POD resin film of the present application is obtained by carbonization and graphitization treatment; the thickness of the graphite film is 0.01mm~100mm, the thermal conductivity coefficient is ≥1300W / m*k, and the surface powder loss is ≤2mg.

[0028] In one optional implementation, the carbonization temperature is 800-1400°C, with a heating rate of 0.1-1°C / min. In another implementation, the carbonization temperature is 800-1000°C at a heating rate of 0.4-0.8°C / min, and 1000-1400°C at a heating rate of 0.1-0.4°C / min. This process helps reduce cracks on the resin film and effectively reduces surface powder loss on the graphite film.

[0029] In a fifth aspect, the present application provides an electronic device, which includes a housing, a heating device and a graphite film as described in the present application, wherein the graphite film is arranged between the housing and the heating device.

[0030] The technical effects that can be achieved in the above-mentioned second to fifth aspects can be described with reference to the corresponding effects in the above-mentioned first aspect, and will not be repeated here.

[0031] Among them, the data in the above-mentioned possible implementation methods of the present application, such as the molar ratio of each repeating unit, the molar ratio of each raw material, and the temperature, time, heating rate and performance parameters in the preparation method, when measured, the values ​​within the scope of engineering measurement error should be understood to be within the range specified in the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of this application clearer, this application will be further described in detail below with reference to the accompanying drawings.

[0033] The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and appended claims of this application, the singular expressions "a", "an", "above", "the", and "this" are intended to also include expressions such as "one or more", unless the context clearly indicates otherwise.

[0034] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in yet other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0035] The POD resin material of the present embodiment contains a specific ratio of repeating units A, B, and C in its molecular structure. Carbonization and graphitization of the POD resin material of the present embodiment can produce a graphite film with excellent thermal conductivity and low flaking properties. The following describes the POD resin material of the present embodiment in further detail.

[0036] A POD resin material according to an embodiment of the present application includes a repeating unit A, a repeating unit B, and a repeating unit C. The structures of the repeating unit A, the repeating unit B, and the repeating unit C are as follows:

[0037] In one embodiment, the molecular formula of the POD resin material can be expressed by the following chemical formula:

[0038] The ratio n1:(n2+n3) of the number of moles n1 of repeating unit A to the sum of the number of moles of repeating unit B and repeating unit C is in the range of 99:1 to 70:30. For example, the ratio n1:(n2+n3) can be 99:1, 95:5, 90:10, 88:12, 85:15, 80:20, 78:22, 75:25, 70:30, or a value between any two of the above ratios.

[0039] The ratio of the number of moles n2 of repeating unit B to the number of moles n3 of repeating unit C is 1:1 to 2:1. For example, the ratio of n2:n3 can be 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, or a value between any two of the above ratios.

[0040] It is understood that the above molecular formula is only used to characterize the repeating units A, B and C in the molecular structure containing the above molar numbers, and does not mean that the repeating units A, B and C are connected and arranged according to the above structure.

[0041] In the molecular structure of the POD resin material, Ar1 is selected from a substituted or unsubstituted aromatic ring group having 6 to 20 carbon atoms, for example, phenyl, biphenyl or naphthyl.

[0042] Ar2 is a substituted or unsubstituted aromatic ring group containing two benzene rings, and Ar1 and Ar2 are different. For example, Ar2 can be selected from biphenyl or naphthyl, or Br-substituted biphenyl or Br-substituted naphthyl.

[0043] Ar3 is selected from a substituted or unsubstituted aromatic ring group having 6 to 20 carbon atoms and at least one hydrogen in the aromatic ring group is substituted by a sulfonic acid group. For example, Ar3 can be selected from a phenyl group, a biphenyl group or a naphthyl group substituted by a sulfonic acid group.

[0044] In the POD resin material of the embodiments of the present application, the mass proportion of the C element is ≥ 40%. For example, the mass proportion of the C element can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%, or a value between any two of the above values. The mass proportion of the S element is ≤ 10%. For example, the mass proportion of the S element can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, or a value between any two of the above values.

[0045] In the POD resin material of the present embodiment, the molar ratio of benzene rings to oxadiazole rings in its molecular structure is 1:1.1 to 1:1.5. For example, the molar ratio of benzene rings to oxadiazole rings can be 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5, or any value between these two values.

[0046] To improve the thermal conductivity of the graphite film formed after graphitization of the POD resin material, graphene may be added to the POD resin material. The graphene may comprise 0.5% to 50% by weight of the POD resin material. For example, the graphene may comprise 0.5%, 1%, 2%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50% by weight of the POD resin material, or any value between these two values.

[0047] Based on the same technical purpose, an embodiment of the present application provides a POD resin film, which is prepared from the POD resin material of the present application.

[0048] Among them, the preparation method of the POD resin film of the embodiment of the present application includes the following steps: placing reaction raw materials containing aromatic diacid monomers, aromatic diformic acid sulfonate and hydrazine salt monomers in a fuming sulfuric acid solution for polymerization reaction to obtain a resin solution; the resin solution is subjected to film-forming treatment to obtain the POD resin film; wherein the aromatic diacid monomers include at least a portion of diphenyl ring aromatic diacid monomers, and the ratio of the total molar number of the aromatic diacid monomers and the aromatic diformic acid sulfonate to the molar number of the hydrazine salt is 1:1.01 to 1:1.1.

[0049] Part of the aromatic diacid monomers reacts with the hydrazine salt monomer to form repeating unit A, the diphenyl ring aromatic diacid monomer in the aromatic diacid monomer reacts with the hydrazine salt monomer to form repeating unit B, and the aromatic diformic acid sulfonate reacts with the hydrazine salt monomer to form repeating unit C.

[0050] The aromatic diacid monomer includes at least two of terephthalic acid, 1,4-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 3,3-biphenyl dicarboxylic acid, terephthalic acid, 2,4-biphenyl dicarboxylic acid, 3,3-diphenyl ether dicarboxylic acid, isophthalic acid, biphenyl dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, or 1,4-naphthalene dicarboxylic acid; at least one of the monomers is a diphenyl ring aromatic diacid monomer. The diphenyl ring aromatic diacid monomer can be selected from at least one of biphenyl dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, or 1,4-naphthalene dicarboxylic acid. The aromatic dicarboxylic acid sulfonate includes isophthalic acid-5-sulfonate. For example, isophthalic acid-5-sulfonate can be calcium isophthalic acid-5-sulfonate.

[0051] The polymerization reaction of the raw materials in fuming sulfuric acid includes the following steps: prepolymerization at 80-110°C for 2-5 hours, followed by polymerization at 110-170°C for 2-5 hours. The resulting resin solution has a viscosity greater than 100 Pa·s and a solids content of 5-20%.

[0052] The resin solution is subjected to a film-forming treatment to obtain a POD resin film, wherein the film-forming treatment may include the following steps: degassing, casting, stretching, drying and shaping.

[0053] The embodiment of the present application also provides a graphite film, which uses the POD resin film of the present application as a raw material, and the POD resin film is obtained by carbonization treatment and graphitization treatment. Among them, the carbonization temperature in the carbonization treatment can be 800-1400°C, and the heating rate can be 0.1-1°C / min. In a specific embodiment, in the carbonization treatment, when the temperature is raised to the range of 800-1000°C, the heating rate can be 0.4-0.8°C / min; when the temperature is raised to the range of 1000-1400°C, the heating rate can be 0.1-0.4°C / min. In the graphitization treatment, when the temperature is raised to the range of 1400-2000°C, the heating rate can be 2-5°C / min; when the temperature is in the range of 2000-2800°C, the heating rate can be 3-8°C / min. This process is conducive to reducing the film surface cracks of the resin film and effectively reducing the surface powder loss of the graphite film.

[0054] The thickness of the graphite film of the embodiment of the present application can be 0.01mm to 100mm. The thickness of the graphite film obtained by the method of the present application can be adjusted over a relatively large range, and both micron-level films and millimeter-level films can be obtained. The thermal conductivity of the obtained graphite film can be ≥1300W / m*k, and the surface powder loss can be ≤2mg. Therefore, the graphite film of the embodiment of the present application can have the advantages of both high thermal conductivity and low powder loss.

[0055] The present application also provides an electronic device, which may include a housing, a heating device, and a graphite film according to the present application. The graphite film is disposed between the housing and the heating device to conduct heat from the heating device. For example, the graphite film may be attached to the surface of the heating device, attached to the inner wall of the housing, or filled in the gap between the heating device and the housing to promptly conduct heat generated by the heating device.

[0056] The POD resin film of the present application will be further described in detail below with reference to specific embodiments.

[0057] Examples 1-5 and Comparative Examples 1-5

[0058] The preparation process of POD resin film includes the following steps:

[0059] S1. Using aromatic diacid monomer, diphenyl ring aromatic diacid monomer, aromatic diformic acid sulfonate and hydrazine salt monomer as reaction raw materials, a polycondensation reaction is carried out in fuming sulfuric acid to obtain a resin solution; the viscosity of the resin solution is greater than 100 Pa.S, and the solid content is 5-20%.

[0060] S2. The resin solution is extruded through a coat-hanger-type die and then sequentially conveyed to a first-stage coagulation bath (reaction temperature of 90-130°C, reaction time of 3-5h), a second-stage coagulation bath (reaction temperature of 140-170°C, reaction time of 2-6h) and a third-stage coagulation bath (reaction temperature of 150-180°C, reaction time of 3-6h) for coagulation molding to obtain a coagulated acid-containing wet primary cast film. The coagulation baths at each stage include sulfuric acid and water.

[0061] S3, washing the acid-containing wet nascent cast film to obtain a nascent cast film free of sulfuric acid;

[0062] S4. After biaxially stretching the raw cast film that does not contain sulfuric acid, heat-setting it at 300-450° C., trimming it, and winding it to obtain a POD resin film.

[0063] The raw materials used in Examples 1-5 and Comparative Examples 1-5 and the molar amounts of the raw materials are listed in Table 1.

[0064] Table 1

[0065] Examples 6-10 and Comparative Examples 6-10

[0066] The POD resin films of Examples 1-5 and Comparative Examples 1-5 were subjected to carbonization and graphitization to obtain graphite films. The POD resin films corresponding to Examples 1-5 and Comparative Examples 1-5 were subjected to the following processes to obtain graphite films, which are respectively designated as Examples 6-10 and Comparative Examples 6-10.

[0067] Carbonization treatment process: When the room temperature is raised to 800°C, the heating rate is controlled at 0.8-1°C / min; in the range of 800-1000°C, the heating rate is controlled at 0.4-0.8°C / min; when the temperature is raised to the range of 1000-1400°C, the heating rate can be 0.1-0.4°C / min.

[0068] Graphitization treatment process: when the temperature is in the range of 1400-2000°C, the heating rate can be 2-5°C / min; when the temperature is in the range of 2000-2800°C, the heating rate can be 3-5°C / min.

[0069] Example 11

[0070] The POD resin material of Example 1 is subjected to the following carbonization and graphitization processes to form a graphite film.

[0071] Carbonization treatment process: When the room temperature is raised to 800℃, the heating rate is controlled at 5℃ / min; in the range of 800-1000℃, the heating rate is controlled at 3℃ / min; when the temperature is raised to the range of 1000-1400℃, the heating rate can be 2℃ / min.

[0072] Graphitization treatment process: when the temperature is in the range of 1400-2000°C, the heating rate can be 2-5°C / min; when the temperature is in the range of 2000-2800°C, the heating rate can be 3-5°C / min.

[0073] The thermal conductivity of the graphite films of each embodiment and comparative example and the amount of powder loss of the graphite films corresponding to embodiments 6-10 and comparative examples 6-10 were tested respectively. The test results are listed in Table 2.

[0074] The thermal conductivity test method includes: using a heat flow sensor to measure the heat flow through the sample to obtain the thermal conductivity of the sample.

[0075] The test method for powder loss includes: selecting a protective film with a thickness of 1-2gf / 25mm and a size of 50*130mm; the size of the sample graphite film is 50*100mm. Remove the transparent release film from the test protective film and weigh it, and record the weight t1. A single-sided tape is attached to each end of the graphite film and fixed to the stainless steel plate, with the overlapping width of the single-sided tape and the graphite film being 5mm. Use a 2Kg roller to roll 3 times at a rolling speed of (600±10)mm / min; let it stand for 10 minutes; peel the protective film in the opposite direction at an angle of 180°, with a stretching speed of 300±10mm / min, to peel the protective film off the surface of the graphite film; weigh the peeled protective film, and record the weight t2. The mass change △t is the powder loss weight, △t=t2-t1.

[0076] Table 2

[0077] It can be seen from the relevant test data in Table 2 that when the graphite film is prepared using the POD resin film of the embodiment of the present application, its thermal conductivity and powder loss are better than those of the comparative example. Among them, in comparative example 1, when the Ar2 group in the formed POD resin film is benzene, the corresponding graphite film has a higher powder loss. In comparative example 2, when the molecular structure of the POD resin film contains only Ar1 groups, the corresponding graphite film has a lower thermal conductivity and a higher powder loss. In comparative examples 3-4, when the ratio of Ar1, Ar2, and Ar3 in the molecular structure of the POD resin film is not within the range specified in the present application, its thermal conductivity and powder loss are inferior to those of the embodiment of the present application. It can be seen that the graphite film obtained using the embodiment of the present application has better thermal conductivity and powder loss performance. In addition, it can be seen from the relevant test data of Examples 6 and 11 that when the carbonization and graphitization processes of the embodiment of the present application are adopted, a graphite film with better performance can be obtained. It is shown that the carbonization and graphitization processes of the embodiments of the present application can help form a graphite film with a more complete structure.

[0078] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A POD resin material, characterized in that: It comprises a repeating unit A, a repeating unit B and a repeating unit C, and the structures of the repeating unit A, the repeating unit B and the repeating unit C are as follows: Wherein, Ar1 is selected from a substituted or unsubstituted aromatic ring group of 6 to 20 carbon atoms; Ar2 is a substituted or unsubstituted aromatic ring group containing two benzene rings, and Ar1 and Ar2 are different; Ar3 is selected from a substituted or unsubstituted aromatic ring group of 6 to 20 carbon atoms, and at least one hydrogen in the aromatic ring group is substituted by a sulfonic acid group; The molar ratio of the number of moles of the repeating unit A to the sum of the number of moles of the repeating unit B and the repeating unit C is 99:1 to 70:30; The molar ratio of the repeating unit B to the repeating unit C is 1:1 to 2:

1.

2. The POD resin material according to claim 1, characterized in that: The Ar1 is selected from phenyl, biphenyl or naphthyl; the Ar2 is selected from biphenyl, naphthyl, Br-substituted biphenyl or Br-substituted naphthyl; the Ar3 is selected from phenyl, biphenyl or naphthyl substituted with sulfonic acid.

3. The POD resin material according to claim 1 or 2, characterized in that: In the POD resin material, the mass proportion of the C element is ≥40%, and the mass proportion of the S element is ≤10%.

4. The POD resin material according to any one of claims 1 to 3, characterized in that: The molar ratio of the benzene ring to the oxadiazole ring is 1:1.1 to 1:1.

5.

5. The POD resin material according to any one of claims 1 to 4, characterized in that: The POD resin material contains graphene; the mass proportion of the graphene in the POD resin material is 0.5%-50%.

6. A POD resin film, characterized in that: The POD resin film is prepared from the POD resin material according to any one of claims 1 to 5.

7. A method for preparing a POD resin film as claimed in claim 6, characterized in that: include: placing a reaction raw material including an aromatic diacid monomer, an aromatic diformic acid sulfonate and a hydrazine salt monomer in a fuming sulfuric acid solution for polymerization reaction to obtain a resin solution; The resin solution is subjected to film-forming treatment to obtain the POD resin film; The aromatic diacid monomers include at least some diphenyl ring aromatic diacid monomers, and the ratio of the total molar number of the aromatic diacid monomers and the aromatic diformic acid sulfonate to the molar number of the hydrazine salt is 1:1.01 to 1:1.

1.

8. The preparation method according to claim 7, characterized in that: The viscosity of the resin solution is greater than 100 Pa.S, and the solid content is 5-20%.

9. The preparation method according to claim 7 or 8, characterized in that: The aromatic diacid monomers include at least two of terephthalic acid, 1,4-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 3,3-biphenyl dicarboxylic acid, terephthalic acid, 2,4-biphenyl dicarboxylic acid, 3,3-diphenyl ether dicarboxylic acid, isophthalic acid, biphenyl dicarboxylic acid, 2,6-naphthalene dicarboxylic acid or 1,4-naphthalene dicarboxylic acid; at least one of which is selected from biphenyl dicarboxylic acid, 2,6-naphthalene dicarboxylic acid or 1,4-naphthalene dicarboxylic acid; The aromatic dicarboxylic acid sulfonate includes isophthalic acid-5-sulfonate.

10. The preparation method according to any one of claims 7 to 9, characterized in that: The polymerization reaction comprises: Prepolymerize at 80-110°C for 2-5 hours, then heat to 110-170°C for polymerization for 2-5 hours.

11. A graphite film, characterized in that: The POD resin film according to claim 6 is obtained by carbonization and graphitization; the thickness of the graphite film is 0.01 mm to 100 mm, the thermal conductivity is ≥1300 W / m*k, and the surface powder loss is ≤2 mg.

12. The graphite film according to claim 11, characterized in that The carbonization temperature in the carbonization treatment is 800-1400° C., and the heating rate is 0.1-1° C. / min.

13. The graphite film according to claim 12, characterized in that: In the carbonization treatment, the heating rate is 0.4-0.8°C / min in the range of 800-1000°C; and the heating rate is 0.1-0.4°C / min in the range of 1000-1400°C.

14. An electronic device, characterized in that: It comprises a shell, a heating device and a graphite film as described in any one of claims 11 to 13, wherein the graphite film is arranged between the shell and the heating device.

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