Graphite film with high thermal diffusion coefficient
By using inorganic particles to modify the polyimide film and controlling the heat treatment process, the problem of excessive foaming of the polyimide film during graphitization is solved, and a graphite film with a high thermal diffusion coefficient is realized, which is suitable for the heat dissipation layer of electronic equipment.
Patent Information
- Application Number
- CN202410023172.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-08
- Publication Date
- 2025-07-08
AI Technical Summary
The existing polyimide films are prone to excessive foaming during graphitization, resulting in too low density of graphite films and inability to effectively increase the thermal diffusion coefficient, especially when the thickness is greater than 150μm or more, the problem is more significant.
Polyimide films with inorganic fine particles are used to prepare polyamic acid by chemical cyclization, and a dehydrating agent and a catalyst are added during carbonization and graphitization to control the heat treatment temperature to form a graphite film with high thermal diffusion coefficient.
The thermal diffusion coefficient of the graphite film is improved to ensure that heat dissipation can be effectively dissipated when the thickness is large, and to meet the heat dissipation needs of electronic equipment.
Smart Images
Figure BDA0004653418980000121 
Figure BDA0004653418980000131
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of polyimide films, and particularly to a graphite film with a high thermal diffusion coefficient. Background Art
[0002] The rapid growth of mobile devices has made thinning a trend in electronic products. In order to reduce the volume of electronic components, components need to be closely packed. When components are overly closely packed, a large amount of heat is generated during the operation of the components. Therefore, the heat dissipation problem has become an important issue. When the requirements for heat conduction and heat dissipation performance become increasingly severe, the emergence of artificial graphite films has provided solutions to these problems. Artificial graphite films have excellent flexibility and a heat conduction efficiency four times that of copper, making graphite films widely used in mobile devices.
[0003] Artificial graphite films are produced by subjecting polyimide films to a series of high-temperature pyrolysis reactions and atomic rearrangement processes to generate pure carbon elements. These high-temperature treatment processes are called carbonization and graphitization. The main function of the carbonization process is to pyrolyze non-carbon elements, and the treatment temperature is about between 800 - 1300 °C; the function of the graphitization process is to drive carbon atoms through high temperature to rearrange the carbon atoms to form a continuous and ordered layered structure. During the process, foaming will occur, forming a foamed graphite film, and its operating temperature occurs at 1500 - 3000 °C. After calendering the obtained foamed graphite film, a flexible graphite film can be obtained, which is suitable for use as a heat dissipation layer in electronic devices.
[0004] Graphite films fired from known general polyimide films tend to have the problem of excessive foaming during the graphitization process. This phenomenon results in too low a density of the calendered graphite film, making it impossible to effectively improve the thermal diffusion coefficient. Especially when the thickness of the polyimide film is greater than 150 μm, the problem of excessive foaming is even more obvious. Summary of the Invention
[0005] In order to solve the above deficiencies in the art, the present application aims to provide a graphite film with a high thermal diffusion coefficient, which is fired from a polyimide film with inorganic particles. After being formulated, the polyimide film undergoes carbonization and graphitization processes, and then after calendering, a graphite film with excellent thermal diffusion coefficient is obtained.
[0006] A graphite film with a high thermal diffusion coefficient is fired from a polyimide film with inorganic particles, and the inorganic particles account for 0.50 wt% or less of the total weight of the film;
[0007] And the polyimide film is obtained by chemical cyclization of polyamic acid, and the polyamic acid is polymerized from diamine monomers and dianhydride monomers.
[0008] The aforementioned diamine monomers include one or more of 4,4-ODA (4,4'-diaminodiphenyl ether), TPEQ (1,4-bis(4-aminophenoxy)benzene), and MDA (4,4'-methylenedianiline);
[0009] The dianhydride monomers include a first group of dianhydride monomers and a second group of dianhydride monomers. The first group of dianhydride monomers is PMDA (pyromellitic dianhydride), and the second group of dianhydride monomers is selected from one or more of BPDA (3,3',4,4'-biphenyltetracarboxylic dianhydride), HQDPA (4,4'-oxydiphthalic anhydride), BPADA (bisphenol A type diether dianhydride), and ODPA (oxydiphthalic anhydride); and the percentage of the mole number of the second group of dianhydride monomers in the total mole number of the dianhydrides of the polyamic acid is 5-50 mol%. Wherein the graphite film has a thermal diffusivity of greater than or equal to 900 mm 2 / s. Detailed implementation manners
[0010] Next, the technical solutions of the present application will be clearly and completely described in conjunction with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.
[0011] It should be particularly noted that similar substitutions and modifications made to the present application are obvious to those skilled in the art, and they are all regarded as included in the present application. Relevant personnel can obviously make changes or appropriate alterations and combinations to the methods and applications described herein without departing from the content, spirit, and scope of the present application to implement and apply the technology of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.
[0012] If no specific conditions are indicated in the present application, they are all carried out according to conventional conditions or conditions recommended by the manufacturer. The raw materials or auxiliary materials used, as well as the reagents or instruments used without indicating the manufacturer, are all conventional products that can be obtained through commercial purchase.
[0013] Next, the present application will be described in detail.
[0014] The present invention relates to a graphite film with a high thermal diffusion coefficient, which is formed by firing a polyimide film containing inorganic particles; and the polyimide film is obtained by chemically cyclizing polyamic acid, wherein the polyamic acid is polymerized from diamine monomers and dianhydride monomers. The aforementioned diamine monomers include one or a combination of 4,4'-ODA (4,4'-diaminodiphenyl ether), TPEQ (1,4-bis(4-aminophenoxy)benzene), and MDA (4,4'-methylenedianiline). The dianhydride monomers include PMDA (pyromellitic dianhydride) and at least one of BPDA (3,3',4,4'-biphenyltetracarboxylic dianhydride), HQDPA (4,4'-phenylenedioxydiphthalic anhydride), BPADA (bisphenol A type diether dianhydride), and ODPA (oxydiphthalic anhydride), and the molar percentage of one or a combination of BPDA, HQDPA, ODPA, and BPADA in the total molar amount of the dianhydrides of the polyamic acid is 5-50 mol%.
[0015] Among them, the inorganic particles include phosphates, carbonates, metal oxides, silica, titanium dioxide, boron nitride, etc. Phosphates are preferably used, such as calcium dihydrogen phosphate, calcium hydrogen phosphate, and calcium phosphate.
[0016] The addition amount of the inorganic particles is preferably 0.5 wt% or less of the total weight of the film, more preferably 0.2 wt% or less.
[0017] The chemical cyclization method is carried out by adding a dehydrating agent and a catalyst. The dehydrating agent is acetic anhydride, and the catalyst is methylpyridine and isoquinoline.
[0018] The addition amount of the dehydrating agent is at least 2 equivalents or more, and the addition amount of the catalyst is at least 1 equivalent or more.
[0019] Carbonized film: The polyimide film is heat-treated under reduced pressure or in an inert gas environment, or under reduced pressure while introducing an inert gas. The minimum heat treatment temperature in the carbonization step must be 1000 °C or higher, preferably 1100 °C or higher, more preferably 1200 °C or higher.
[0020] Graphite film: The above carbonized film is carried out under reduced pressure or in an inert gas. The maximum heat treatment temperature in the graphitization step is 2400 °C or higher, preferably 2600 °C or higher, more preferably 2800 °C or higher, and then obtained after rolling. A graphite film with a higher thermal diffusivity can be obtained at 2800 °C or higher.
[0021] <Detection method>
[0022] The thermal diffusion coefficient of the graphite film obtained in the following examples was measured by the following method.
[0023] (1) Thickness: Measured using the MiniTest 2100 instrument manufactured by Elektro Physik.
[0024] (2) The thermal diffusivity of the graphite film was analyzed using a laser flash thermal diffusivity analyzer (Netzsch LFA467), and the test was carried out in the in-plane mode at a voltage of 260 V and a pulse width of 0.050 ms.
[0025] Example 1
[0026] Preparation of polyamic acid
[0027] 100 mole% of diamine 4,4'-ODA was added to N,N-dimethylacetamide (DMAc). After complete dissolution, 5 mole% of dianhydride ODPA was added, and the mixture was stirred until completely dissolved. Then, while maintaining the temperature at 25 °C, 95 mole% of dianhydride PMDA and 0.2 wt% of calcium hydrogen phosphate were slowly added. After stirring for 6 hours until the dianhydride was dissolved and the reaction occurred, and the temperature of the solution was maintained at 25 °C, a copolymer polyamic acid solution with a viscosity of 180,000 cps ± 20,000 cps was finally obtained.
[0028] Preparation of polyimide film
[0029] The above polyamic acid solution was mixed with a dehydrating agent and a catalyst, and the addition ratio was such that the molar ratio of polyamic acid: dehydrating agent: catalyst was 1:2:1. It was coated on a steel belt and placed in an oven at 80 °C to heat and remove most of the solvent. Then, the above polyamic acid colloidal film was peeled off and placed in an oven at 170 °C to 370 °C for heating and biaxial stretching to form a polyimide film. The thickness of the PI film was controlled by the coating head gap, and a polyimide film with a thickness of 170 μm was obtained.
[0030] Preparation of carbonized film
[0031] The polyimide film was cut into a width of 257 mm and a length of 50 m and wound around a graphite inner tube, or the polyimide film was cut into two sample forms of 257 mm * 323 mm and placed in a graphite crucible. It was heated under a reduced pressure environment, and the heating rate was divided into the following sections: from room temperature to 500 °C at 5 °C per minute, from 500 to 800 °C at 0.5 °C per minute, and from 800 to 1300 °C at 1 °C per minute.
[0032] Preparation of graphite film
[0033] The above carbonized film is graphitized by heating under normal pressure with argon gas introduced. The heating rate is as follows: from room temperature to 2000 °C, it is 10 °C per minute; from 2000 to 2200 °C, it is 5 °C per minute; and finally, it is carried out at 1 °C per minute in the range of 2200 °C to 2500 - 3000 °C, and held at a constant temperature for 1 hour in the range of 2500 - 3000 °C. The thermal diffusivity of the finally obtained graphite film is 946 mm 2 / s.
[0034] Example 2
[0035] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine MDA, 5 mole% of dianhydride ODPA, and 95 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. The thickness of the PI film is controlled by the coating head gap, and a polyimide film with a thickness of 172 μm is obtained. The thermal diffusivity of the finally obtained graphite film is 923 mm 2 / s.
[0036] Example 3
[0037] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine TPEQ, 5 mole% of dianhydride ODPA, and 95 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. The thickness of the PI film is controlled by the coating head gap, and a polyimide film with a thickness of 171 μm is obtained. The thermal diffusivity of the finally obtained graphite film is 965 mm 2 / s.
[0038] Example 4
[0039] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 50 mole% of diamine 4,4ODA and 50 mole% of diamine MDA, 5 mole% of dianhydride ODPA, and 95 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. The thickness of the PI film is controlled by the coating head gap, and a polyimide film with a thickness of 170 μm is obtained. The thermal diffusivity of the finally obtained graphite film is 937 mm 2 / s.
[0040] Example 5
[0041] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 50 mole% of diamine MDA and 50 mole% of diamine TPEQ, and 5 mole% of dianhydride ODPA and 95 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. Control the thickness of the PI film using the coating head gap to obtain a polyimide film with a thickness of 173 μm. The thermal diffusivity of the finally measured graphite film is 956 mm 2 / s.
[0042] Example 6
[0043] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 50 mole% of diamine 4,4ODA and 50 mole% of diamine TPEQ, and 5 mole% of dianhydride ODPA and 95 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. Control the thickness of the PI film using the coating head gap to obtain a polyimide film with a thickness of 195 μm. The thermal diffusivity of the finally measured graphite film is 959 mm 2 / s.
[0044] Example 7
[0045] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 33 mole% of diamine 4,4ODA, 33 mole% of diamine MDA, and 34 mole% of diamine TPEQ, and 5 mole% of dianhydride ODPA and 95 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. Control the thickness of the PI film using the coating head gap to obtain a polyimide film with a thickness of 193 μm. The thermal diffusivity of the finally measured graphite film is 948 mm 2 / s.
[0046] Example 8
[0047] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4ODA, and 15 mole% of dianhydride ODPA and 85 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. Control the thickness of the PI film using the coating head gap to obtain a polyimide film with a thickness of 196 μm. The thermal diffusivity of the finally measured graphite film is 1012 mm 2 / s.
[0048] Example 9
[0049] The implementation steps are the same as those in Example 8. By controlling the coating head gap to control the PI film thickness, a polyimide film with a thickness of 55 μm is obtained. Finally, the thermal diffusivity of the graphite film is measured to be 1075 mm 2 / s.
[0050] Example 10
[0051] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 50 mole% of dianhydride ODPA and 50 mole% of dianhydride PMDA. The production of the remaining polyimide films, carbonized films, and graphite films is the same as that in Example 1. By controlling the coating head gap to control the PI film thickness, a polyimide film with a thickness of 243 μm is obtained. Finally, the thermal diffusivity of the graphite film is measured to be 1063 mm 2 / s.
[0052] Example 11
[0053] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 15 mole% of dianhydride HQDPA and 85 mole% of dianhydride PMDA. The production of the remaining polyimide films, carbonized films, and graphite films is the same as that in Example 1. By controlling the coating head gap to control the PI film thickness, a polyimide film with a thickness of 173 μm is obtained. Finally, the thermal diffusivity of the graphite film is measured to be 1021 mm 2 / s.
[0054] Example 12
[0055] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 15 mole% of dianhydride BPDA and 85 mole% of dianhydride PMDA. The production of the remaining polyimide films, carbonized films, and graphite films is the same as that in Example 1. By controlling the coating head gap to control the PI film thickness, a polyimide film with a thickness of 172 μm is obtained. Finally, the thermal diffusivity of the graphite film is measured to be 927 mm 2 / s.
[0056] Example 13
[0057] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 15 mole% of dianhydride BPADA and 85 mole% of dianhydride PMDA. The production of the remaining polyimide films, carbonized films, and graphite films is the same as that in Example 1. By controlling the coating head gap to control the PI film thickness, a polyimide film with a thickness of 172 μm is obtained. Finally, the thermal diffusivity of the graphite film is measured to be 1017 mm 2 / s.
[0058] Example 14
[0059] The implementation steps are the same as those in Example 8. By controlling the gap of the coating head to control the thickness of the PI film, a polyimide film with a thickness of 315 μm is obtained. Finally, the thermal diffusivity of the graphite film is measured to be 1005 mm 2 / s.
[0060] Comparative Example 1
[0061] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine PDA (p-phenylenediamine), 5 mole% of dianhydride ODPA, and 95 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. By controlling the gap of the coating head to control the thickness of the PI film, a polyimide film with a thickness of 160 μm is obtained. Finally, the thermal diffusivity of the graphite film is measured to be 751 mm 2 / s.
[0062] Comparative Example 2
[0063] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine m-PDA (m-phenylenediamine), 5 mole% of dianhydride ODPA, and 95 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. By controlling the gap of the coating head to control the thickness of the PI film, a polyimide film with a thickness of 175 μm is obtained. Finally, the thermal diffusivity of the graphite film is measured to be 783 mm 2 / s.
[0064] Comparative Example 3
[0065] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine BAFL (9,9-bis(4-aminophenyl)fluorene), 5 mole% of dianhydride ODPA, and 95 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film, and graphite film is the same as that in Example 1. By controlling the gap of the coating head to control the thickness of the PI film, a polyimide film with a thickness of 184 μm is obtained. Finally, the thermal diffusivity of the graphite film is measured to be 816 mm 2 / s.
[0066] Comparative Example 4
[0067] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 50 mole% of diamine 4,4'-ODA and 50 mole% of diamine PDA (), and 5 mole% of dianhydride ODPA and 95 mole% of dianhydride PMDA. The production of the remaining polyimide films, carbonized films and graphite films is the same as in Example 1. Control the thickness of the PI film using the coating head gap to obtain a polyimide film with a thickness of 166 μm. The thermal diffusivity of the final measured graphite film is 802 mm 2 / s.
[0068] Comparative Example 5
[0069] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 100 mole% of dianhydride PMDA. The production of the remaining polyimide films, carbonized films and graphite films is the same as in Example 1. Control the thickness of the PI film using the coating head gap to obtain a polyimide film with a thickness of 167 μm. The thermal diffusivity of the final measured graphite film is 650 mm2 / s.
[0070] Comparative Example 6
[0071] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 3 mole% of dianhydride ODPA and 97 mole% of dianhydride PMDA. The production of the remaining polyimide films, carbonized films and graphite films is the same as in Example 1. Control the thickness of the PI film using the coating head gap to obtain a polyimide film with a thickness of 182 μm. The thermal diffusivity of the final measured graphite film is 872 mm 2 / s.
[0072] Comparative Example 7
[0073] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 55 mole% of dianhydride ODPA and 45 mole% of dianhydride PMDA. The production of the remaining polyimide films, carbonized films and graphite films is the same as in Example 1. Control the thickness of the PI film using the coating head gap to obtain a polyimide film with a thickness of 155 μm. The thermal diffusivity of the final measured graphite film is 851 mm 2 / s.
[0074] Comparative Example 8
[0075] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 15 mole% of dianhydride BTDA (benzophenone-3,3',4,4'-tetracarboxylic dianhydride) and 85 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film and graphite film is the same as that of Example 1. The thickness of the PI film is controlled by the coating head gap to obtain a polyimide film with a thickness of 168 μm. The thermal diffusivity of the finally measured graphite film is 706 mm 2 / s.
[0076] Comparative Example 9
[0077] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 15 mole% of dianhydride BPAF (9,9-bis(3,4-dicarboxyphenyl)fluorene) and 85 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film and graphite film is the same as that of Example 1. The thickness of the PI film is controlled by the coating head gap to obtain a polyimide film with a thickness of 153 μm. The thermal diffusivity of the finally measured graphite film is 795 mm 2 / s.
[0078] Comparative Example 10
[0079] Repeat the steps of Example 1, except that the formulation in the polyamic acid step is changed to 100 mole% of diamine 4,4'-ODA, and 15 mole% of dianhydride DSDA (diphenyl-3,3',4,4'-tetracarboxylic dianhydride) and 85 mole% of dianhydride PMDA. The production of the remaining polyimide film, carbonized film and graphite film is the same as that of Example 1. The thickness of the PI film is controlled by the coating head gap to obtain a polyimide film with a thickness of 177 μm. The thermal diffusivity of the finally measured graphite film is 761 mm 2 / s.
[0080] Table of Examples and Comparative Examples:
[0081]
[0082]
[0083] Comparative Example 1: Since the monomer of diamine is selected as 100 mole% of diamine PDA, the thermal diffusivity of its graphite film is less than 900 mm 2 / s.
[0084] Comparative Example 2: Since the monomer of diamine is selected as 100 mole% of diamine m-PDA, the thermal diffusivity of its graphite film is less than 900 mm 2 / s.
[0085] Comparative Example 3: Since the diamine monomer was selected as 100 mole% of diamine BAFL, the thermal diffusivity of its graphite film was less than 900 mm 2 / s.
[0086] Comparative Example 4: Since the diamine monomer contained 50 mole% of diamine PDA, the thermal diffusivity of its graphite film was less than 900 mm 2 / s.
[0087] Comparative Example 5: Since the dianhydride monomer was selected as 100 mole% of dianhydride PMDA, the thermal diffusivity of its graphite film was less than 900 mm 2 / s.
[0088] Comparative Example 6: Since the dianhydride monomer was selected as 3 mole% of dianhydride ODPA and 97 mole% of dianhydride PMDA, the thermal diffusivity of its graphite film was less than 900 mm 2 / s.
[0089] Comparative Example 7: Since the dianhydride monomer was selected as 55 mole% of dianhydride ODPA and 45 mole% of dianhydride PMDA, the thermal diffusivity of its graphite film was less than 900 mm 2 / s.
[0090] Comparative Example 8: Since the dianhydride monomer was selected as 15 mole% of dianhydride BTDA and 85 mole% of dianhydride PMDA, the thermal diffusivity of its graphite film was less than 900 mm 2 / s.
[0091] Comparative Example 9: Since the dianhydride monomer was selected as 15 mole% of dianhydride BAPF and 85 mole% of dianhydride PMDA, the thermal diffusivity of its graphite film was less than 900 mm 2 / s.
[0092] Comparative Example 10: Since the dianhydride monomer was selected as 15 mole% of dianhydride DSDA and 85 mole% of dianhydride PMDA, the thermal diffusivity of its graphite film was less than 900 mm 2 / s
[0093] The description of the above embodiments is only used to help understand the method and its core idea of the present application. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.
Claims
1. A graphite film with a high thermal diffusion coefficient, characterized in that, It is fired from a polyimide film having inorganic fine particles, and the inorganic fine particles account for 0.50 wt% or less of the total weight of the polyimide film; and The polyimide film is obtained by chemical cyclization of polyamic acid, and the polyamic acid is polymerized from a diamine monomer and a dianhydride monomer; The diamine monomer includes one or more of 4,4'-diaminodiphenyl ether, 1,4-bis(4-aminophenoxy)benzene, and 4,4'-methylenedianiline; The dianhydride monomer includes a first group of dianhydride monomers and a second group of dianhydride monomers. The first group of dianhydride monomers is pyromellitic dianhydride, and the second group of dianhydride monomers is selected from one or more of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-phenylenedioxydiphthalic anhydride, bisphenol A type diether dianhydride, and oxydiphthalic anhydride. The percentage of the molar number of the second group of dianhydride monomers in the total molar number of the dianhydride monomers of the polyamic acid is 5-50 mol%.
2. The graphite film with a high thermal diffusion coefficient according to claim 1, wherein The thickness of the polyimide film is 30-350 μm.
3. The graphite film with a high thermal diffusion coefficient according to claim 1, wherein The inorganic fine particles include: phosphates, carbonates, metal oxides, silica, titanium dioxide, boron nitride, and zinc oxide; preferably phosphates; Preferably, the phosphates include: calcium dihydrogen phosphate, calcium hydrogen phosphate, and calcium phosphate.
4. The graphite film with a high thermal diffusion coefficient according to claim 1, wherein The addition amount of the inorganic fine particles accounts for 0.2 wt% or less of the total weight of the polyimide film.
5. The graphite film with high thermal diffusivity according to claim 1, characterized in that, The firing temperature of the graphite film is 2500 °C or higher, preferably 2800 °C or higher.
6. The graphite film with a high thermal diffusion coefficient according to claim 1, wherein The thermal diffusivity of the graphite film is greater than or equal to 900 mm 2 / s.