WO2020262765A1

WO2020262765A1 - Polyimide film for graphite sheet and manufacturing method therefor

Info

Publication number: WO2020262765A1
Application number: PCT/KR2019/014620
Authority: WO
Inventors: 민재호; 원동영; 최정열
Original assignee: 피아이첨단소재 주식회사
Priority date: 2019-06-28
Filing date: 2019-10-31
Publication date: 2020-12-30
Also published as: KR20210001738A; TW202104373A; KR102286058B1; TWI775102B

Abstract

The present invention relates to a polyimide film for a graphite sheet and a manufacturing method therefor. In an embodiment, the polyimide film for a graphite sheet is formed from a composition for forming a polyimide film, the composition comprising: a polyamic acid; and an imidization catalyst, wherein the polyimide film has a thickness of about 100 ㎛ to about 200 ㎛ and a first surface damage rate, expressed by equation 1, of 0% or about 0.001% to about 0.004%. (Equation 1 is as defined in the detailed description.)

Description

Polyimide film for graphite sheet and its manufacturing method

The present invention relates to a polyimide film for a high-thickness graphite sheet and a method of manufacturing the polyimide film for a graphite sheet.

Graphite is a material with very excellent thermal conductivity and has been in the spotlight as a means of heat dissipation. In particular, the artificial graphite manufactured in the form of a thin sheet has excellent thermal conductivity of about 2 to about 7 times as compared to copper or aluminum, and is therefore preferably used as a heat dissipation means applied to electronic devices.

Recently, electronic devices have a tendency to increase the amount of heat generated per unit volume as their structures are gradually reduced in weight, size, thickness, and high integration. In this case, the performance of the electronic device may be directly adversely affected, such as a reduction in the operation speed of a semiconductor due to a heat load and a shortened lifespan due to deterioration of a battery.

As one of the solutions to this problem, a method of applying a graphite sheet having a relatively thick thickness to an electronic device has been proposed. The high-thickness graphite sheet is advantageous in terms of heat capacity compared to a conventional thin graphite sheet, for example, a graphite sheet having a thickness of 30 μm or less, so that even if the calorific value of an electronic device increases, heat can be efficiently dissipated. There is an advantage.

In general, artificial graphite sheets are manufactured by carbonizing and graphitizing a polyimide film as a precursor. In the manufacture of the high-thickness graphite sheet, a high-thickness polyimide film, for example, a polyimide film having a thickness of 100 μm or more may be used depending on the desired thickness level.

However, even if a graphite sheet is manufactured using a high-thickness polyimide film, it is difficult to obtain a high-quality graphite sheet with a smooth surface and an internal graphite structure in which the graphite structure is not damaged during the heat treatment process, so that the yield is low.

This is, assuming that carbonization and graphitization proceed almost simultaneously in the surface layer and inside of the polyimide film, in the case of a high-thickness polyimide film, the amount of sublimation gas generated from the inside is large, and the graphite structure formed on or during the formation of the surface layer is damaged. It is presumed to be due to the increased possibility of being destroyed. In addition, not only the surface, but also the central portion of the film and the inner side adjacent thereto, the pressure is greatly increased by a relatively large amount of sublimation gas, and the graphite structure formed or formed is destroyed as one cause.

Accordingly, there is a high need for a technology capable of manufacturing a high-quality graphite sheet with a high thickness and intact surface quality and graphite structure.

One object of the present invention is to provide a polyimide film that has low brittleness when applied to a graphite sheet, has excellent surface quality, and can secure a high thickness at the same time, and a method of manufacturing the same.

Another object of the present invention is to provide a method of manufacturing a graphite sheet that has excellent surface quality and thermal conductivity, and is capable of securing a high thickness while having low brittleness.

All of the above and other objects of the present invention can be achieved by the present invention described below.

One embodiment of the present invention is polyamic acid; And an imidation catalyst; formed from a composition for forming a polyimide film, having a thickness of about 100 μm to about 200 μm, and a first surface damage rate of 0% or about 0.001% to about 0.004 represented by Equation 1 below. %. It relates to a polyimide film for graphite sheets.

1st surface damage rate (%) = {(A ₁ / A ₀ ) × 100}

In Equation 1, A ₀ is a polyimide film specimen having a size of 200 mm X 25 mm by heat treatment from about 15° C. to about 1200° C. at a heating rate of about 1° C./min to about 5° C./min to carbonize, First graphitized by heat treatment from about 1200°C to about 2200°C at a temperature rising rate of about 1.5°C/min to about 5°C/min, and from about 2200°C at a temperature rising rate of about 0.4°C/min to about 1.3°C/min Secondary graphitization by heat treatment to about 2500°C, and heat treatment from about 2500°C to about 2800°C at a temperature increase rate of about 8.5°C/min to about 20°C/min to obtain a graphite sheet specimen obtained by tertiary graphitization at 10 magnification. It is the area measured by taking a picture (mm ² ), and A ₁ is the area (mm ² ) of the damaged area measured by taking a picture of the graphite sheet specimen at 10 magnification.

In the above embodiment, the molar ratio of the amic acid group of the polyamic acid: the imidation catalyst in the composition for forming the polyimide film may be about 1:0.15 to about 1:0.20.

In the above embodiment, the composition for forming a polyimide film is 100 parts by weight of polyamic acid; And about 17 parts by weight to about 36 parts by weight of an imidation catalyst.

Another embodiment of the present invention is polyamic acid; And an imidation catalyst; after gelling the composition for forming a polyimide film at about 100° C. to about 200° C., primary imidization at about 200° C. to about 400° C. and secondary at about 300° C. to about 500° C. It is a method for producing a polyimide film for a graphite sheet, comprising imidizing and forming a film to a thickness of about 100 µm to about 200 µm, and the polyimide film has a first surface damage rate represented by Equation 1 above. It relates to a method for producing a polyimide film for a graphite sheet having 0% or about 0.001% to about 0.004%.

Another embodiment of the present invention is a step of preparing a carbonized sheet by heat-treating the above-described polyimide film from about 15°C to about 1200°C; And graphitizing the carbonized sheet from about 1200° C. to about 2800° C. stepwise while changing the temperature increase rate to produce a graphite sheet having a thickness of about 50 μm to about 100 μm. Including, the graphite sheet relates to a method for producing a high-thickness graphite sheet having a second surface damage rate of 0% or about 0.001% to about 0.004% represented by the following Equation 2:

Second surface damage rate (%) = {(B ₁ / B ₀ ) × 100}

In Equation 2, B ₀ is the area measured by photographing the graphite sheet specimen at 10 magnification (mm ² ), and B ₁ is the area of the damaged area measured by photographing the graphite sheet specimen at 10 magnification (mm ² ).

The step of preparing the carbonized sheet may include thermally decomposing the polyimide film while heating at a rate of about 1°C/min to about 5°C/min.

In the graphitization, the carbonized sheet is first graphitized while raising the temperature from about 1200° C. to about 2200° C., followed by secondary graphitization while increasing the temperature from about 2200° C. to about 2500° C., and then from about 2500° C. to about 2800° C. To the tertiary graphitization.

The temperature increase rate of the primary graphitization is from about 1.5° C./min to about 5° C./min, the temperature increase rate of the secondary graphitization is from about 0.4° C./min to about 1.3° C./min, and The heating rate may be about 8.5 °C/min to about 20 °C/min.

In the above embodiment, the composition for forming a polyimide film further comprises an inorganic filler of about 1,500 ppm to about 2,500 ppm based on 100 parts by weight of polyamic acid, and the inorganic filler is calcium carbonate, dicalcium phosphate, phosphoric acid. It may include one or more of calcium hydrogen, barium sulfate, silica, titanium oxide, alumina, silicon nitride, and boron nitride.

The present invention is a polyimide film that has low brittleness when applied to a graphite sheet, has excellent surface quality, and can secure a high thickness at the same time, a method for manufacturing the same, and excellent surface quality and thermal conductivity using the same, and low brittleness and high thickness. It provides a graphite sheet manufacturing method that can secure the degree.

1 shows the results of evaluating the surface quality of Example 1 of the present invention.

2 shows the results of evaluating the surface quality of Comparative Example 7 of the present invention.

3 shows the results of evaluating the surface quality of Comparative Example 5 of the present invention.

4 is an exemplary illustration of a method of measuring an area when measuring the first surface damage rate of the present invention.

In describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

When'include','have','consists of' and the like mentioned in the present specification are used, other parts may be added unless'only' is used. In the case of expressing the constituent elements in the singular, it includes the case of including the plural unless specifically stated otherwise.

In addition, in interpreting the constituent elements, it is interpreted as including an error range even if there is no explicit description.

Terms such as first and second used in the present specification may be used to describe various components, but the components should not be limited by terms. The terms are only used for the purpose of distinguishing one component from another component.

In "a to b" representing a numerical range in the present specification, "to" is defined as ≥a and ≤b.

Polyimide film

One embodiment of the present invention relates to a polyimide film for a high-thickness graphite sheet. The polyimide film for a graphite sheet of the present invention includes polyamic acid; And an imidation catalyst; It is formed from a composition for forming a polyimide film comprising, and is a gelled and imidized product of the composition for forming a polyimide film.

The polyimide film for a graphite sheet of the present invention has a thickness of about 100 µm to about 200 µm (for example, about 100 µm, about 110 µm, about 120 µm, about 130 µm, about 140 µm, about 150 µm, about 160 µm Μm, about 170 µm, about 180 µm, about 190 µm, or about 200 µm) is formed to have a thicker thickness than the conventional one, so that the thickness is about 50 µm to about 100 µm (for example, about 50 µm, after carbonization and graphitization). A graphite sheet having a high thickness of about 60 μm, about 70 μm, about 80 μm, about 90 μm, or about 100 μm) is provided.

In addition, the polyimide film for a graphite sheet of the present invention has a thickness of about 50 µm to about 100 µm (e.g., about 50 µm, about 60 µm, about 70 µm, about 80 µm, about 90 µm) when applied as a graphite sheet. Or about 100 μm), and the first surface damage rate represented by the following equation 1 is 0% to about 0.004% (e.g., 0%, about 0.001%, about 0.002%, about 0.003% or about 0.004%, other For example, 0% or about 0.001% to about 0.004%) to achieve excellent surface quality.

1st surface damage rate (%) = {(A ₁ / A ₀ ) × 100}

In Equation 1, A ₀ is a polyimide film specimen having a size of 200 mm × 25 mm from about 1°C/min to about 5°C/min (eg, about 1°C/min, about 2°C/min, about After heat treatment and carbonization from about 15° C. to about 1,200° C. at a heating rate of 3° C./min, about 4° C./min, or about 5° C./min, about 1.5° C./min to about 5° C./min (for example, , About 1.5℃/min, about 2℃/min, about 2.5℃/min, about 3℃/min, about 3.5℃/min, about 4℃/min, about 4.5℃/min, or about 5℃/min) First graphitized by heat treatment from about 1,200°C to about 2,200°C at a heating rate, and then about 0.4°C/min to about 1.3°C/min (e.g., about 0.4°C/min, about 0.5°C/min, about 0.6°C /min, about 0.7℃/min, about 0.8℃/min, about 0.9℃/min, about 1℃/min, about 1.1℃/min, about 1.2℃/min or about 1.3℃/min) Heat treatment from 2,200°C to about 2,500°C for secondary graphitization, and from about 8.5°C/min to about 20°C/min (for example, about 8.5°C/min, about 9°C/min, about 9.5°C/min, about 10℃/min, about 10.5℃/min, about 11℃/min, about 11.5℃/min, about 12℃/min, about 12.5℃/min, about 13℃/min, about 13.5℃/min, about 14℃ /min, about 14.5℃/min, about 15℃/min, about 15.5℃/min, about 16℃/min, about 16.5℃/min, about 17℃/min, about 17.5℃/min, about 18℃/min , About 18.5℃/min, about 19℃/min, about 19.5℃/min, or about 20℃/min). It is the area measured by taking a picture with a magnification (mm ² ), and A ₁ is the damaged area measured by taking a picture of the graphite sheet specimen at 10 magnification Is the area of (mm ² ).

Specifically, the first surface damage rate is a polyimide film specimen having a size of 200 mm X 25 mm and a thickness of about 100 µm to about 200 µm from about 1°C/min to about 5°C/min. After heat-treating from about 15°C to about 1,200°C at one heating rate to carbonize, heat treatment from about 1,200°C to about 2,200°C at any one of about 1.5°C/min to about 5°C/min And secondary graphitization by heat treatment from about 2,200° C. to about 2,500° C. at a temperature rising rate of about 0.4° C./min to about 1.3° C./min, and about 8.5° C./min to about 20° C./min. It may mean the rate of surface damage occurring to the graphite sheet when the graphite sheet specimen is manufactured by third graphitization by heat treatment from about 2,500°C to about 2,800°C at one heating rate.

More specifically, the first surface damage rate is a polyimide film specimen having a size of 200 mm × 25 mm and a thickness of 125 µm is carbonized by heat treatment from 15° C. to 1,200° C. at a heating rate of 1° C./min, Heat treatment from 1,200℃ to 2,200℃ at a rate of 1.5℃/min for primary graphitization, heat treatment at a rate of 0.4℃/min from 2,200℃ to 2,500℃ for secondary graphitization, and a temperature increase of 8.5℃/min When prepared as a graphite sheet specimen by tertiary graphitization by heat treatment from 2,500°C to 2,800°C at a rate, it may mean the rate of surface damage occurring to the graphite sheet.

In the first surface damage rate, A ₀ is the area of the graphite sheet specimen in mm ² measured after photographing the graphite sheet specimen at 10 magnification using a digital camera, and A ₁ is the graphite sheet specimen using a digital camera. It is the area of the damaged area in mm ² measured after taking a picture at 10 magnification.

At this time, each area is measured by applying a filter with a grid drawn at intervals of 1 mm in width and 1 mm in height to a digital image photograph taken at 10 magnification and visually checking the number of squares (mm ² ) included in the area. It can be done by counting and measuring.

4 illustrates a method of measuring an area when measuring the first surface damage rate represented by Equation 1. Referring to FIG. 4, when measuring the first surface damage rate represented by Equation 1, a digital image photograph taken at 10 magnification was prepared for the graphite sheet prepared as in (a), and 1 mm in width and 1 mm in length. Apply a filter with a grid drawn at intervals of. At this time, the area of one space formed by the grid is 1 mm ² . In the first surface damage rate, A ₀ is measured by counting the case where the graphite sheet occupies 50% or more of the area of one space formed by the grid as in (b). Since A ₀ measured in FIG. 4B is a total of 200, it can be measured as 200 mm ² . In the first surface damage rate, A ₁ is measured by counting the cases where the visually visible damage occupies 50% or more of the portion occupied by the graphite sheet in the area of one space formed by the grid as in (c). Since A ₁ measured in FIG. 4C is 159 in total, it may be measured as 159 mm ² . Substituting the A ₀ value and A ₁ in this example for the surface damage rate of Equation 1, the damage rate in the exemplary 20 mm x 10 mm sized graphite specimen of FIG. 4 is 79.5%.

Unlike the conventional polyimide film, which was difficult to achieve both thickness and surface quality due to high surface damage rate when applied as a high-thickness graphite sheet in the range of about 50 μm to about 100 μm, the polyimide film of the present invention is applied to a graphite sheet. It has low brittleness, has excellent surface quality, and can secure a high thickness at the same time.

The composition for forming a polyimide film includes a polyamic acid and an imidization catalyst as follows.

(Polyamic acid)

In the composition for forming a polyimide film, polyamic acid serves as a precursor to be converted to polyimide by an imidization catalyst. The polyamic acid is not particularly limited as long as it is obtained by polymerizing a dianhydride monomer and a diamine monomer.

For example, dianhydride monomers that can be used as raw materials for the polyamic acid are pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3',4, 4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylene tetra Carboxylic dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4 -Dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic anhydride, bis (3 ,4-dicarboxyphenyl) sulfone dianhydride, p-phenylenebis (trimelitic monoester acid anhydride), ethylenebis (trimelitic monoester acid anhydride), bisphenol Abis (trimelitic Monoester acid anhydride) and derivatives thereof. When using the dianhydride monomer of the above example, it is possible to obtain a polyamic acid having excellent imidization efficiency and improved uniformity. In addition, the dianhydride monomer of the above example may be used alone or in combination of two or more.

For example, diamines that can be used as a raw material for the polyamic acid are 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, benzidine, 3,3'-dichlorobenzidine, 4 ,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl ether (4,4'-oxy Cydianiline), 3,3'-diaminodiphenyl ether (3,3'-oxydianiline), 3,4'-diaminodiphenyl ether (3,4'-oxydianiline), 1,5- Diaminonaphthalene, 4,4'-diaminodiphenyl diethyl silane, 4,4'-diaminodiphenyl silane, 4,4'-diaminodiphenyl ethylphosphine oxide, 4,4'-diaminodi Phenyl N-methylamine, 4,4'-diaminodiphenyl N-phenyl amine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene And it may be one or more of these derivatives. When the diamine monomer of the above example is used, it is possible to obtain a polyamic acid having improved uniformity while having excellent imidization efficiency. In addition, the monomers of the above example may be used alone or in combination of two or more.

For example, the dianhydride monomer and diamine monomer that can be used as raw materials for the polyamic acid are about 1:0.9 to about 1:1.1 (e.g., about 1:0.9, about 1:1, or about 1:1.1 ) Can be used in the polymerization of polyamic acid. Within the above range, it is possible to obtain a polyamic acid having excellent imidization efficiency and improved uniformity.

The weight average molecular weight of the polyamic acid is not particularly limited, but about 150,000 g/mole or more to about 1,000,000 g/mole or less (e.g., about 150,000 g/mole, about 200,000 g/mole, about 250,000 g/mole, about 300,000 g/mole, about 350,000 g/mole, about 400,000 g/mole, about 450,000 g/mole, about 500,000 g/mole, about 550,000 g/mole, about 600,000 g/mole, about 650,000 g/mole, about 700,000 g /mole, about 750,000 g/mole, about 800,000 g/mole, about 850,000 g/mole, about 900,000 g/mole, about 950,000 g/mole or about 1,000,000 g/mole), specifically about 170,000 g/mole or more to about It may be 700,000 g/mole or less, more specifically about 190,000 g/mole or more to about 500,000 g/mole or less. Within the above range, the polyamic acid may further improve the heat resistance and mechanical properties of the polyimide film of the present invention.

The viscosity of the polyamic acid is not particularly limited, but about 90,000 cP or more and about 500,000 cP or less (e.g., about 90,000 cP, about 100,000 cP, about 110,000 cP, about 120,000 cP, about 130,000 cP, about 140,000 cP, about 150,000 cP, about 160,000 cP, about 170,000 cP, about 180,000 cP, about 190,000 cP, about 200,000 cP, about 210,000 cP, about 220,000 cP, about 230,000 cP, about 240,000 cP, about 250,000 cP, about 260,000 cP, about 270,000 cP , About 280,000 cP, about 290,000 cP, about 300,000 cP, about 310,000 cP, about 320,000 cP, about 330,000 cP, about 340,000 cP, about 350,000 cP, about 360,000 cP, about 370,000 cP, about 380,000 cP, about 390,000 cP, about 400,000 cP, about 410,000 cP, about 420,000 cP, about 430,000 cP, about 440,000 cP, about 450,000 cP, about 460,000 cP, about 470,000 cP, about 480,000 cP, about 490,000 cP or about 500,000 cP), specifically about 150,000 cP or more To about 400,000 cP, more specifically about 180,000 cP or more to about 300,000 cP. Within the above range, the polyamic acid may further improve the heat resistance and mechanical properties of the polyimide film of the present invention.

The polyamic acid may be dissolved in an organic solvent and used as a polyamic acid solution. In this case, the polyamic acid solution can further improve processability and ease of operation when manufacturing a polyimide film.

The organic solvent is not particularly limited as long as it is a solvent in which polyamic acid can be dissolved, but may be specifically an aprotic polar solvent.

For example, the aprotic polar solvent is an amide solvent such as N,N'-dimethylformamide (DMF), N,N'-dimethylacetamide (DMAc), p-chlorophenol, o-chlorophenol Phenolic solvents such as N-methyl-pyrrolidone (NMP), gamma butyrolactone (GBL), and Diglyme.

The organic solvent may further use an auxiliary solvent as necessary to adjust the solubility of the polyamic acid. The auxiliary solvent may be, for example, toluene, tetrahydrofuran, acetone, methyl ethyl ketone, methanol, ethanol, water, and the like.

When the polyamic acid is dissolved in an organic solvent and used as a polyamic acid solution, the polyamic acid solution contains about 15% by weight to about 20% by weight (e.g., about 15% by weight, about 16% by weight, About 17% by weight, about 18% by weight, about 19% by weight, or about 20% by weight), and about 80% by weight to about 85% by weight of an organic solvent (e.g., about 80% by weight, about 81% by weight) Weight percent, about 82 weight percent, about 83 weight percent, about 84 weight percent, or about 85 weight percent). Within the above range, it is advantageous to control the weight average molecular weight and viscosity of the total polyamic acid solution, and may be more advantageous in the film formation process.

(Imidation catalyst)

In the composition for forming a polyimide film, the imidation catalyst serves to promote the conversion of polyamic acid to polyimide.

The imidation catalyst may be an imine-based component such as an aliphatic tertiary amine, an aromatic tertiary amine, and a heterocyclic tertiary amine. Among these, a heterocyclic tertiary amine may be preferable from the viewpoint of reactivity as a catalyst. Non-limiting examples of the heterocyclic tertiary amine include quinoline, isoquinoline, β-picoline (BP), pyridine, and the like, and these may be used alone or in combination of two or more.

In one embodiment, the content of the imidation catalyst in the precursor composition for a polyimide film is about 0.15 mol to about 0.2 mol, for example about 0.15 mol, about 0.16 mol, based on 1 mol of the amic acid functional group of the polyamic acid. About 0.17 moles, about 0.18 moles, about 0.19 moles, or about 0.20 moles. Within the above range, the imidation catalyst can further improve crystallinity while allowing the matrix structure of the polyimide film of the present invention to be arranged more regularly than before.

In another embodiment, the content of the imidation catalyst in the precursor composition for the polyimide film is from about 17 parts by weight to about 36 parts by weight based on 100 parts by weight of the amic acid of the polyamic acid (for example, about 17 parts by weight, About 18 parts by weight, about 19 parts by weight, about 20 parts by weight, about 21 parts by weight, about 22 parts by weight, about 23 parts by weight, about 24 parts by weight, about 25 parts by weight, about 26 parts by weight, about 27 parts by weight, About 28 parts by weight, about 29 parts by weight, about 30 parts by weight, about 31 parts by weight, about 32 parts by weight, about 33 parts by weight, about 34 parts by weight, about 35 parts by weight, or about 36 parts by weight). Within the above range, the imidation catalyst can further improve crystallinity while allowing the matrix structure of the polyimide film of the present invention to be arranged more regularly than before.

(Inorganic filler)

In addition to the above-described components, the composition for forming a polyimide film may further include an inorganic filler. In the composition for forming a polyimide film, the inorganic filler may be present in a dispersed state in a matrix in the polyimide film, and then sublimated during carbonization and/or graphitization to induce a predetermined foaming phenomenon. In this case, the polyimide film may form a polyimide spacing with high regularity due to a structure in which inorganic fillers are uniformly dispersed in the polyimide matrix. The predetermined voids formed by such foaming can improve the bending resistance of the graphite sheet, and the inorganic filler is sublimated during carbonization and/or graphitization, and the polyimide is converted into graphite, so that the graphite sheet has excellent regularity and alignment. Can be manufactured. In addition, as the inorganic filler is sublimated, it can itself serve as a passage for gas discharge, thereby preventing surface defects and damage due to foaming.

The inorganic filler is not particularly limited as long as it has sublimability at a temperature of about 1000°C or higher, but specifically, among calcium carbonate, dicalcium phosphate, calcium hydrogen phosphate, barium sulfate, silica, titanium oxide, alumina, silicon nitride, and boron nitride. It may contain one or more. When using the inorganic filler of the above example, the polyimide film can obtain a graphite sheet having further improved bending resistance and structural uniformity. In addition, the inorganic filler of the above example may be used alone or in combination of two or more.

The content of the inorganic filler in the precursor composition for a polyimide film is about 1,500 ppm to about 2,500 ppm (e.g., about 1,500 ppm, about 1,600 ppm, about 1,700 ppm, about 1,800 ppm, about 100 parts by weight of polyamic acid). 1,900 ppm, about 2,000 ppm, about 2,100 ppm, about 2,200 ppm, about 2,300 ppm, about 2,400 ppm, or about 2,500 ppm). Within the above range, when the polyimide film is carbonized and/or graphitized, sublimation gas generated inside the film is smoothly discharged to the outside of the film, further improving the surface quality, and converting the polyimide structure to an artificial graphite structure. It can further improve the efficiency.

The average particle diameter of the inorganic filler is not particularly limited, but about 1.5 µm to about 4.5 µm (eg, about 1.5 µm, about 2 µm, about 2.5 µm, about 3 µm, about 3.5 µm, about 4 µm, or about 4.5 μm). Within the above range, the inorganic filler may further reduce the formation of bright spots due to excessive foaming, while preventing the polyimide film surface from being excessively low in roughness, thereby further improving the surface quality.

(additive)

The composition for forming a polyimide film may further include additives including a dehydrating agent, in addition to the above-described components.

The dehydrating agent promotes a ring closure reaction through a dehydration action on polyamic acid, specifically aliphatic acid anhydride, aromatic acid anhydride, N,N'-dialkylcarbodiimide, halogenated lower aliphatic, halogenated lower fatty acid anhydride, arylphos It may be a fondane dihalide, a thionyl halide, or a mixture of two or more of these.

Among the above examples, when an aliphatic acid anhydride such as acetic anhydride, propionic anhydride, and lactic acid anhydride, or a mixture of two or more thereof is used, it is possible to realize the effect of ease of obtaining raw materials and reduction of cost.

The addition amount of the dehydrating agent in the composition for forming a polyimide film is about 0.5 mol to about 5 mol (e.g., about 0.5 mol, about 1 mol, about 1.5 mol, about 2 mol, about 1 mol of the amic acid group in the polyamic acid). 2.5 moles, about 3 moles, about 3.5 moles, about 4 moles, about 4.5 moles or about 5 moles). Within the above range, the composition for forming a polyimide film may further improve imidization efficiency due to dehydration.

Manufacturing method of polyimide film

Another embodiment of the present invention is polyamic acid; And an imidation catalyst; A composition for forming a polyimide film comprising a polyimide film of about 100 ℃ to about 200 ℃ (for example, about 100 ℃, about 110 ℃, about 120 ℃, about 130 ℃, about 140 ℃, about 150 ℃, about 160 ℃, After gelation at about 170°C, about 180°C, about 190°C, or about 200°C), about 200°C to about 400°C (eg, about 200°C, about 210°C, about 220°C, about 230°C, about 240℃, about 250℃, about 260℃, about 270℃, about 280℃, about 290℃, about 300℃, about 310℃, about 320℃, about 330℃, about 340℃, about 350℃, about 360℃ , At about 370°C, about 380°C, about 390°C or about 400°C) and about 300°C to about 500°C (for example, about 300°C, about 310°C, about 320°C, about 330°C) , About 340℃, about 350℃, about 360℃, about 370℃, about 380℃, about 390℃, about 400℃, about 410℃, about 420℃, about 430℃, about 440℃, about 450℃, about Secondary imidization at 460° C., about 470° C., about 480° C., about 490° C., or about 500° C.), and from about 100 μm to about 200 μm (eg, about 100 μm, about 110 μm, about 120 μm) , About 130 µm, about 140 µm, about 150 µm, about 160 µm, about 170 µm, about 180 µm, about 190 µm, or about 200 µm), including filming to a thickness of, high-thickness graphite sheet polyimide It relates to a method of manufacturing a film. Through this, the present invention provides an effect of more economically and efficiently manufacturing a polyimide film capable of securing a high thickness while having low brittleness when applied to a graphite sheet.

In addition, the polyimide film prepared by the method for producing a polyimide film for a graphite sheet has a surface damage rate of 0% to about 0.004% (e.g., 0%, about 0.001%, about 0.002) represented by the above formula 1 %, about 0.003% or about 0.004%, for example 0% or about 0.001% to about 0.004%). The description of Equation 1 is as described above.

In addition, the composition for forming the polyimide film and the respective components contained therein, specific examples, and descriptions of the content are as described above.

Specifically, the molar ratio of the amic acid group of the polyamic acid: the imidization catalyst in the composition for forming the polyimide film is about 1:0.15 to about 1:0.20 (eg, about 1:0.15, about 1:0.16, about 1: 0.17, about 1:0.18, about 1:0.19 or about 1:0.20).

Specifically, the composition for forming a polyimide film is 100 parts by weight of polyamic acid; And about 17 parts by weight to about 36 parts by weight of the imidation catalyst (e.g., about 17 parts by weight, about 18 parts by weight, about 19 parts by weight, about 20 parts by weight, about 21 parts by weight, about 22 parts by weight, about 23 parts by weight) Parts by weight, about 24 parts by weight, about 25 parts by weight, about 26 parts by weight, about 27 parts by weight, about 28 parts by weight, about 29 parts by weight, about 30 parts by weight, about 31 parts by weight, about 32 parts by weight, about 33 Parts by weight, about 34 parts by weight, about 35 parts by weight, or about 36 parts by weight); may be included.

Specifically, the composition for forming a polyimide film is about 1,500 ppm to about 2,500 ppm (e.g., about 1,500 ppm, about 1,600 ppm, about 1,700 ppm, about 1,800 ppm, about 1,900 ppm, based on 100 parts by weight of polyamic acid, About 2,000 ppm, about 2,100 ppm, about 2,200 ppm, about 2,300 ppm, about 2,400 ppm or about 2,500 ppm) of an inorganic filler, wherein the inorganic filler is calcium carbonate, dicalcium phosphate, calcium hydrogen phosphate, It may contain at least one of barium sulfate, silica, titanium oxide, alumina, silicon nitride, and boron nitride.

In the method for producing a polyimide film of the present invention, prior to gelling the composition for forming a polyimide film, a step of preparing a polyamic acid may be additionally performed. The step of preparing such a polyamic acid is not particularly limited, and an appropriate method may be employed among methods such as emulsion polymerization, solution polymerization, bulk polymerization, and suspension polymerization.

In the method for producing a polyimide film, when the gelling temperature is less than about 100° C., it is difficult to film the composition for forming a polyimide film into a polyimide film. On the other hand, when the gelling temperature is greater than about 200°C, there is a problem that brittleness occurs when the polyimide film obtained by excessive gelation is applied as a graphite sheet.

Specifically, in the gelling process, the composition for forming a polyimide film may be prepared as a solution, applied to a support, and dried to form a sheet-shaped gel. The support may be a glass plate, an aluminum foil, an endless stainless belt, or a stainless drum, but is not limited thereto. The application method is not particularly limited, and may be, for example, a casting method. At this time, the sheet-shaped gel may be dried and gelled for about 10 minutes to about 20 minutes in the range of the gelling temperature to be prepared as a sheet-shaped gel having self-support.

The sheet-shaped gel prepared in the sheet shape is then peeled off from the support and then from about 200°C to about 400°C (eg, about 200°C, about 210°C, about 220°C, about 230°C, about 240°C , About 250℃, about 260℃, about 270℃, about 280℃, about 290℃, about 300℃, about 310℃, about 320℃, about 330℃, about 340℃, about 350℃, about 360℃, about Primary imidization at 370°C, about 380°C, about 390°C or about 400°C and about 300°C to about 500°C (e.g., about 300°C, about 310°C, about 320°C, about 330°C, about 340℃, about 350℃, about 360℃, about 370℃, about 380℃, about 390℃, about 400℃, about 410℃, about 420℃, about 430℃, about 440℃, about 450℃, about 460℃ , About 470°C, about 480°C, about 490°C, or about 500°C) through a secondary imidization process to form a film. In the case of performing the primary and secondary imidization as described above, amic acid remaining without reaction may be additionally imidized, and the quality of the polyimide film may be further uniformly improved. In addition, within the temperature range, the efficiency of converting the polyamic acid to polyimide may be further improved.

The polyimide film filmed as described above has a thickness of about 100 μm to about 200 μm (for example, about 100 μm, about 110 μm, about 120 μm, about 130 μm, about 140 μm, about 150 μm, about 160 μm, about 170 μm, about 180 μm, about 190 μm or about 200 μm). When the thickness of the polyimide film is less than about 100 μm, it is difficult to apply it as a high-thick graphite sheet. On the other hand, when the thickness of the polyimide film exceeds about 200 μm, brittleness is excessively high.

그라파이트 시트Graphite sheet

Another embodiment of the present invention relates to a method of manufacturing a high-thickness graphite sheet having a second surface damage rate of 0% or about 0.001% to about 0.004% represented by Equation 2 below. The second surface damage rate may be 0%, about 0.001%, about 0.002%, about 0.003%, or about 0.004%. For another example, it may be 0% or from about 0.001% to about 0.004%.

The high-thickness graphite sheet manufacturing method includes the steps of preparing a carbonized sheet by heat-treating a polyimide film from 15°C to 1200°C; And graphitizing the carbonized sheet from about 1200° C. to about 2800° C. stepwise while changing a temperature increase rate to produce a graphite sheet having a thickness of about 50 μm to about 100 μm. Includes.

Second surface damage rate (%) = {(B ₁ / B ₀ ) × 100}

In this case, a specific method of measuring the second surface damage rate (%) is the same as the method of measuring the first surface damage rate represented by Equation 1 above.

The polyimide film is the polyimide film described above, and includes polyamic acid; And an imidation catalyst; formed from a composition for forming a polyimide film, having a thickness of about 100 µm to about 200 µm, and a first surface damage rate represented by Formula 1 described in the description of the polyimide film is 0 % Or from about 0.001% to about 0.004%.

The polyimide film in the method for producing a high-thickness graphite sheet of the present invention is the same as the polyimide film of the present invention, and is also manufactured by the polyimide film of the present invention, so a description thereof will be omitted.

(Carbonization step)

In the method for producing a high-thickness graphite sheet of the present invention, the step of preparing the carbonized sheet includes the above-described polyimide film of the present invention from about 15°C to about 1200°C, specifically from about 20°C to about 1200°C, more Specifically, it is carbonized by heat treatment at elevated temperature from about 50°C to about 1200°C. Within the above temperature range, the polymer chains of the polyimide film are sufficiently thermally decomposed to produce a carbonized sheet having an amorphous carbon body formed therethrough, and thus can be used for graphitization for the production of a graphite sheet.

Specifically, in the carbonization method, after putting the polyimide film into a high-temperature furnace facility such as an electric furnace, heating the polyimide film in a nitrogen/argon atmosphere from about 15°C to the maximum temperature of about 1200°C over about 12 hours to about 14 hours. It may be thermally decomposed while converting the polyimide film into a carbonized sheet.

In the step of preparing the carbonized sheet, the temperature increase rate during carbonization is about 1°C/min to about 5°C/min (eg, about 1°C/min, about 2°C/min, about 3°C/min, about 4°C/min or about 5°C/min). Within the temperature increase rate range, the polymer chains of the polyimide film are sufficiently thermally decomposed, thereby producing a carbonized sheet in which an amorphous carbon body is formed, and thus can be used for graphitization for producing a graphite sheet.

(Graphitization step)

In the method for producing a high-thickness graphite sheet of the present invention, the step of producing a graphite sheet comprises graphitizing the carbonized sheet obtained in the above and the carbonization step in a temperature range of about 1200°C to about 2800°C while changing the temperature increase rate step by step. Is prepared from about 50 μm to about 100 μm of graphite sheet. Through such a graphitization process, a graphite sheet formed by rearranging carbon in an amorphous carbon body in a carbonized sheet is prepared.

Specifically, the graphitization method is not particularly limited, but after putting the carbonized sheet into a high-temperature furnace facility such as an electric furnace, in a mixed gas atmosphere containing nitrogen, argon, and a small amount of helium, about 1200° C. to about 2800° C. It can be prepared by raising and maintaining the temperature step by step over 10 hours to about 14 hours.

More specifically, in the step of preparing the graphite sheet, the carbonized sheet is primary graphitized while raising the temperature from about 1200°C to about 2200°C, and then secondary graphitized while raising the temperature from about 2200°C to about 2500°C, Then tertiary graphitization from about 2500° C. to about 2800° C. may be included. In such a case, the carbon rearrangement efficiency of the amorphous carbon body in the carbonized sheet is further improved, the brittleness is low even in the high thickness range, and the surface quality may be excellent.

More specifically, the heating rate of the primary graphitization is about 1.5°C/min to about 5°C/min (eg, about 1.5°C/min, about 2°C/min, about 2.5°C/min, about 3°C /min, about 3.5°C/min, about 4°C/min, about 4.5°C/min, or about 5°C/min), and the heating rate of the secondary graphitization is about 0.4°C/min to about 1.3°C/min ( For example, about 0.4°C/min, about 0.5°C/min, about 0.6°C/min, about 0.7°C/min, about 0.8°C/min, about 0.9°C/min, about 1°C/min, about 1.1°C/ min, about 1.2°C/min or about 1.3°C/min), and the rate of temperature increase of the tertiary graphitization is about 8.5°C/min to about 20°C/min (eg, about 8.5°C/min, about 9°C /min, about 9.5℃/min, about 10℃/min, about 10.5℃/min, about 11℃/min, about 11.5℃/min, about 12℃/min, about 12.5℃/min, about 13℃/min , About 13.5℃/min, about 14℃/min, about 14.5℃/min, about 15℃/min, about 15.5℃/min, about 16℃/min, about 16.5℃/min, about 17℃/min, about It may be 17.5° C./min, about 18° C./min, about 18.5° C./min, about 19° C./min, about 19.5° C./min, or about 20° C. In such a case, the amorphous carbon body in the carbonized sheet The carbon rearrangement efficiency is further improved, the brittleness is low even in the high thickness range, and the surface quality may be excellent.

In addition, within the first to third graphitization temperature range and the first to third graphitization heating rate, the gas generated during the production of the graphite sheet proceeds stably, further preventing surface damage, The surface damage rates of the above equations 1 and 2 can be further reduced closer to 0%.

The high-thickness graphite sheet manufacturing method includes, after performing the step of manufacturing the graphite sheet, the graphitized graphite sheet from about 5°C/min to about 10°C/min (eg, about 5°C/min, about 6°C/min). a cooling step of cooling at a rate of min, about 7°C/min, about 8°C/min, about 9°C/min or about 10°C/min); It may additionally include. In such a case, the brittleness of the graphite sheet is further lowered, and the surface quality may be further improved.

Another embodiment of the present invention relates to a high-thickness graphite sheet manufactured by the above-described high-thickness graphite sheet manufacturing method.

The thick graphite sheet has a thickness of about 50 μm to about 100 μm. In this case, it has excellent heat capacity and is more advantageous for use as a heat dissipation means applied to an electronic device.

The high-thickness graphite sheet is formed from a polyimide film having a thickness of about 100 μm to about 200 μm. In addition, the high-thickness graphite sheet may be a carbonized and graphitized sheet of a polyimide film having a thickness of about 100 μm to about 200 μm. In this case, the high-thickness graphite sheet has a thickness of about 50 µm to about 100 µm, has excellent heat capacity, and is more advantageous for use as a heat dissipation means applied to electronic devices.

The high-thickness graphite sheet implements excellent surface quality as the second surface damage rate represented by Equation 2 is 0% or from about 0.001% to about 0.004%. In this case, it has more advantageous properties to be used as a heat dissipation means applied to an electronic device.

In addition, the high-thickness graphite sheet may have a thermal conductivity of about 800 W/m·K or more in a planar direction, specifically about 800 W/m·K to about 1200 W/m·K. In this case, it has more advantageous properties to be used as a heat dissipation means applied to an electronic device.

실시예 및 비교예Examples and Comparative Examples

실시예 1Example 1

Oxydianiline (ODA, 3,3'-oxydianiline or 4,4'-oxydianiline) and dianhydride monomer as diamine monomer in dimethylformamide (DMF) as an organic solvent in a nitrogen atmosphere in a 0.5 L reactor As a result, pyromellitic dianhydride (PMDA, pyromellitic dianhydride) was added in a weight ratio of 1:1 and then polymerized to prepare a polyamic acid solution. At this time, the weight ratio of the solid content to the solvent in the total reaction product was 20:80.

2,500 ppm of calcium phosphate having an average particle diameter of 3 µm was added to the polyamic acid solution as an inorganic filler, and stirred to obtain a precursor composition.

Subsequently, beta-picoline as an imidation catalyst was added in an amount of 0.17 molar to 1 mol of amic acid group, and then uniformly mixed and degassed to prepare a composition for forming a polyimide film.

The composition for forming a polyimide film was cast on a SUS plate (100SA, Sandvik) as a support at 500 µm using a doctor blade, and dried in a hot air method at a temperature ranging from 100°C to 200°C to prepare a sheet-shaped gel. .

Then, the sheet-shaped gel is peeled off the SUS plate, fixed to the pin frame, transferred to a high-temperature tenter, and subjected to primary imidization for 10 minutes at a temperature of 200°C to 400°C in a high-temperature tenter, and then 300°C to 500°C. First imidization was performed for 10 minutes at a temperature of °C. The polyimide films filmed by the primary and secondary imidization were cooled at 25° C. and separated from the pin frame to obtain a polyimide film having a size of 20 cm x 2.5 cm and a thickness of 125 μm.

실시예 2 내지 실시예 3 Examples 2 to 3

Thickness in the same manner as in Example 1, except that the solvent content of the polyamic acid solution and the molar ratio (content) of the imidation catalyst (beta-picoline) in the composition for forming a polyimide film were changed as shown in Table 1 below. A 125 μm polyimide film was prepared.

실시예 4 Example 4

The polyimide film prepared in Example 1 was subjected to carbonization heat treatment from 50° C. to 1200° C. at a heating rate of 1° C./min to prepare a carbonized sheet.

Subsequently, graphitization heat treatment was performed in which the carbonized sheet was calcined while changing the heating rate in steps of 1 to 3 steps in a temperature range of 1200° C. to 2800° C. to prepare a graphite sheet having a final thickness of 50 μm. At this time, the first graphitization was heated from 1200°C to 2200°C at a rate of 1.5°C/min, the secondary graphitization was heated from 2200°C to 2500°C at a rate of 0.4°C/min, and the third graphitization was 2500°C. The temperature was raised from °C to 2800 °C at a rate of 8.5 °C/min.

실시예 5Example 5

A graphite sheet having a final thickness of 50 μm was prepared in the same manner as in Example 4, except that the polyimide film was changed to the polyimide film prepared in Example 2.

실시예 6 Example 6

A graphite sheet having a final thickness of 50 μm was prepared in the same manner as in Example 4, except that the polyimide film was changed to the polyimide film prepared in Example 3.

비교예 1 (열법)Comparative Example 1 (thermal method)

In a 0.5 L reactor in a nitrogen atmosphere, in dimethylformamide (DMF) as an organic solvent, oxydianiline (ODA, 3,3'-oxydianiline) as a diamine monomer, and pyromellitic dianhydride (PMDA) as a dianhydride monomer. , pyromellitic dianhydride) was added in a weight ratio of 1:1 and then polymerized to prepare a polyamic acid solution. At this time, the weight ratio of solid content: solvent in the total reaction product was 20:80.

Then, the sheet-shaped gel is peeled off the SUS plate, fixed to the pin frame, transferred to a high-temperature tenter, and subjected to primary imidization for 10 minutes at a temperature of 200°C to 400°C in a high-temperature tenter, and then 300°C to 500°C. First imidization was performed for 10 minutes at a temperature of °C. The polyimide films filmed by the first and second imidizations were cooled at 25° C. and separated from the pin frame to obtain a polyimide film having a size of 20 cm x 25 cm and a thickness of 125 μm.

비교예 2 (촉매법 -기존일반 촉매법)Comparative Example 2 (catalyst method-conventional general catalyst method)

비교예 3 내지 4Comparative Examples 3 to 4

비교예 5Comparative Example 5

The polyimide film prepared in Comparative Example 1 was subjected to carbonization heat treatment from 50° C. to 1200° C. at a heating rate of 1° C./min to prepare a carbonized sheet.

비교예 6Comparative Example 6

A graphite sheet having a final thickness of 50 μm was prepared in the same manner as in Example 6, except that the polyimide film of Comparative Example 5 was changed to the polyimide film of Comparative Example 2.

비교예 7Comparative Example 7

A graphite sheet having a final thickness of 50 μm was prepared in the same manner as in Example 6, except that the polyimide film of Comparative Example 5 was changed to the polyimide film of Comparative Example 3.

비교예 8Comparative Example 8

A graphite sheet having a final thickness of 50 μm was prepared in the same manner as in Example 6, except that the polyimide film of Comparative Example 5 was changed to the polyimide film of Comparative Example 4.

<물성 평가><Physical property evaluation>

(1) Surface quality evaluation 1

The surface quality of the high-thickness graphite sheets prepared in Examples 4 to 6 and Comparative Examples 5 to 8 was evaluated visually. Specifically, in the evaluation of the surface quality, the surface of each high-thickness graphite sheet was observed through the naked eye for cracks or cracks.

When no cracks or cracks occur within the observation area (20 cm wide and 2.5 cm long), the surface quality is indicated as "excellent", and when the number of cracks or cracks occurs 1 to 5, the surface quality is indicated as " When the number of cracks or cracks occurred more than 5 or graphitized was not performed, the surface quality was evaluated as "poor". Results are shown in FIGS. 1 to 3 and Table 3 below.

(2) Surface damage rate evaluation

For the high-thickness graphite sheets prepared in Examples 4 to 6 and Comparative Examples 5 to 8, the second surface damage rate represented by Equation 2 was measured, and when the second surface damage rate exceeds 0.004, "unsuitable" Evaluated as. The results are shown in Table 3 below.

Second surface damage rate (%) = {(B ₁ / B ₀ ) × 100}

(3) thermal conductivity

The thermal diffusivity of the graphite sheet specimens of Examples and Comparative Examples in the plane direction was measured by a laser flash method using a thermal diffusivity measuring equipment (model name LFA 467, Netsch), and the density (weight/volume) in the thermal diffusivity measured value And specific heat (a measure of specific heat using DSC) to calculate thermal conductivity. In addition, in the (1) surface quality evaluation, cracks or cracks occurred, or a specimen that was not graphitized could not be measured. The results are shown in Table 3 below.

(4) Bright spot occurrence evaluation

The number of bright spots generated is a factor causing surface defects of the graphite sheet, and the number of protrusions having a size of 0.05 mm or more in the 50 mm X 50 mm square of the sheet was measured. In addition, in the (1) surface quality evaluation, cracks or cracks occurred, or a specimen that was not graphitized could not be measured. The results are shown in Table 3 below.

Although the above has been described with reference to the embodiments of the present invention, a person of ordinary skill in the field to which the present invention belongs will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Simple modifications or changes of the present invention can be easily implemented by those of ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims

Polyamic acid; And an imidation catalyst; is formed from a composition for forming a polyimide film comprising,

A polyimide film for a graphite sheet having a thickness of about 100 µm to about 200 µm and a first surface damage rate of 0% or about 0.001% to about 0.004% represented by Equation 1 below:

<Equation 1>

1st surface damage rate (%) = {(A 1 / A 0 ) × 100}

In Equation 1, A 0 is a polyimide film specimen having a size of 200 mm X 25 mm by heat treatment from about 15° C. to about 1200° C. at a heating rate of about 1° C./min to about 5° C./min to carbonize, First graphitized by heat treatment from about 1200°C to about 2200°C at a temperature rising rate of about 1.5°C/min to about 5°C/min, and from about 2200°C at a temperature rising rate of about 0.4°C/min to about 1.3°C/min Secondary graphitization by heat treatment to about 2500°C, and heat treatment from about 2500°C to about 2800°C at a temperature increase rate of about 8.5°C/min to about 20°C/min to obtain a graphite sheet specimen obtained by tertiary graphitization at 10 magnification. It is the area measured by taking a picture (mm 2 ), and A 1 is the area (mm 2 ) of the damaged area measured by taking a picture of the graphite sheet specimen at 10 magnification.
The method of claim 1,

In the composition for forming a polyimide film, the amic acid group of the polyamic acid: the molar ratio of the imidation catalyst is about 1:0.15 to about 1:0.20, a polyimide film for a graphite sheet.
The method of claim 1,

The composition for forming a polyimide film may include 100 parts by weight of polyamic acid; And about 17 parts by weight to about 36 parts by weight of the imidization catalyst; to a polyimide film for a graphite sheet containing.
The method of claim 1,

The composition for forming a polyimide film further comprises an inorganic filler of about 1,500 ppm to about 2,500 ppm based on 100 parts by weight of polyamic acid,

The inorganic filler is calcium carbonate, dicalcium phosphate, calcium hydrogen phosphate, barium sulfate, silica, titanium oxide, alumina, silicon nitride, and a polyimide film for a graphite sheet containing at least one of boron nitride.
Polyamic acid; And an imidation catalyst; after gelling the composition for forming a polyimide film at about 100° C. to about 200° C., primary imidization at about 200° C. to about 400° C. and secondary at about 300° C. to about 500° C. It is a method for producing a polyimide film for a graphite sheet comprising imidizing and forming a film to a thickness of about 100 μm to about 200 μm,

The polyimide film is a method of manufacturing a polyimide film for a graphite sheet having a first surface damage rate of 0% or about 0.001% to about 0.004% represented by the following formula:

<Equation 1>

1st surface damage rate (%) = {(A 1 / A 0 ) × 100}

In Equation 1, A 0 is a polyimide film specimen having a size of 200 mm X 25 mm by heat treatment from about 15° C. to about 1200° C. at a heating rate of about 1° C./min to about 5° C./min to carbonize, First graphitized by heat treatment from about 1200°C to about 2200°C at a temperature rising rate of about 1.5°C/min to about 5°C/min, and from about 2200°C at a temperature rising rate of about 0.4°C/min to about 1.3°C/min Secondary graphitization by heat treatment to about 2500°C, and heat treatment from about 2500°C to about 2800°C at a temperature increase rate of about 8.5°C/min to about 20°C/min to obtain a graphite sheet specimen obtained by tertiary graphitization at 10 magnification. It is the area measured by taking a picture (mm 2 ), and A 1 is the area (mm 2 ) of the damaged area measured by taking a picture of the graphite sheet specimen at 10 magnification.
The method of claim 5,

In the composition for forming a polyimide film, the amic acid group of the polyamic acid: the molar ratio of the imidation catalyst is about 1:0.15 to about 1:0.20, a method for producing a polyimide film for a graphite sheet.
The method of claim 5,

The composition for forming a polyimide film may include 100 parts by weight of polyamic acid; And about 17 parts by weight to about 36 parts by weight of an imidation catalyst; a method for producing a polyimide film for a graphite sheet.
The method of claim 5,

The composition for forming a polyimide film further comprises an inorganic filler of about 1,500 ppm to about 2,500 ppm based on 100 parts by weight of polyamic acid,

The inorganic filler includes one or more of calcium carbonate, dicalcium phosphate, calcium hydrogen phosphate, barium sulfate, silica, titanium oxide, alumina, silicon nitride, and boron nitride, a method for producing a polyimide film for a graphite sheet .