WO2023162643A1

WO2023162643A1 - Polyimide film for graphite sheet, graphite sheet, and production methods therefor

Info

Publication number: WO2023162643A1
Application number: PCT/JP2023/003690
Authority: WO
Inventors: 幹明小林; 啓介稲葉; 晃男松谷
Original assignee: 株式会社カネカ
Priority date: 2022-02-25
Filing date: 2023-02-06
Publication date: 2023-08-31

Abstract

The present invention addresses the problem of providing a polyimide film capable of providing a high-density graphite sheet with good productivity. This problem is solved by a polyimide film for a graphite sheet, said polyimide film having a dianhydride component and a diamine component as starting materials. The polyimide film for a graphite sheet has a total BTDA, ODPA, and BAPP content of 1-50 mol% with respect to a total of 200 mol% of the dianhydride component and the diamine component, and contains a prescribed amount of an organophosphorous compound.

Description

Polyimide film for graphite sheet, graphite sheet and manufacturing method thereof

The present invention relates to polyimide films for graphite sheets, graphite sheets, and methods for producing them.

Graphite sheets have excellent thermal conductivity, so they are used as heat dissipation materials in various electronic devices such as computers, semiconductor elements mounted in electrical devices, and other heat-generating parts.

As a method for producing such a graphite sheet, for example, Patent Documents 1 to 3 describe a technique for producing a graphite sheet by heat-treating (graphitizing) a polyimide film.

Japanese Patent Publication "2003-165714" Japanese Patent Publication "2016-17169" Japanese Patent Publication "JP 2020-164611" Japanese Patent Publication "JP 2014-136721"

However, the above technology has problems with the density and productivity of the resulting graphite sheets.

An object of one embodiment of the present invention is to provide a polyimide film that can produce a high-density graphite sheet with good productivity.

The present inventors have completed the present invention as a result of intensive research aimed at solving the above problems.

That is, one embodiment of the present invention includes the following.

A polyimide film made from an acid dianhydride component and a diamine component,
The acid dianhydride component contains 50 to 100 mol% of pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic acid in 100 mol% of the total amount of the dianhydride component. At least one of acid dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA) is contained in 0 to 50 mol%, and the diamine component is 4 in 100 mol% of the total amount of the diamine component. , 4'-diaminodiphenyl ether (ODA) in an amount of 50 to 100 mol% and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) in an amount of 0 to 50 mol%, and the acid dianhydride component The 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), the 4,4′-oxydiphthalic dianhydride (ODPA) and The total content of the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 1 to 50 mol%, and the total amount of the polyimide film is 100% by weight. 0.1 to 5.0% by weight of a polyimide film for a graphite sheet.

A step of mixing an acid dianhydride component and a diamine component to obtain a polyamic acid, and a step of adding 0.1 to 5.0 wt% of an organic phosphorus compound with respect to 100 wt% of the polyamic acid. A method for producing a polyimide film, wherein the acid dianhydride component is 50 to 100 mol% of pyromellitic dianhydride (PMDA) in a total amount of 100 mol% of the acid dianhydride component, 3, 0 to 50 mol% of at least one of 3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA), and the diamine component is 50 to 100 mol% of 4,4'-diaminodiphenyl ether (ODA) and 0 to 100 mol% of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) in the total amount of 100 mol% of the diamine component The 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), the 4,4 The total content of '-oxydiphthalic dianhydride (ODPA) and the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 1 to 50 mol% of the polyimide film. Production method.

A method for producing a graphite sheet, comprising a step of heat-treating a polyimide film for a graphite sheet at 2400° C. or higher, wherein the polyimide film for the graphite sheet is made from an acid dianhydride component and a diamine component. A polyimide film, wherein the acid dianhydride component contains 50 to 100 mol% of pyromellitic dianhydride (PMDA) in 100 mol% of the total amount of the acid dianhydride component, 3,3',4, At least one of 4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA) is contained in an amount of 0 to 50 mol%, and the diamine component is the total amount of the diamine component. In 100 mol%, 4,4'-diaminodiphenyl ether (ODA) is 50 to 100 mol%, 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 0 to 50 mol%, The 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and the 4,4′-oxydiphthalic acid dianhydride with respect to 200 mol % of the total amount of the acid dianhydride component and the diamine component The total content of anhydride (ODPA) and the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 1 to 50 mol%, and the total amount of the polyimide film is 100% by weight. A method for producing a graphite sheet containing 0.1 to 5.0% by weight of an organic phosphorus compound.

According to one embodiment of the present invention, it is possible to provide a polyimide film that can provide a high-density graphite sheet with good productivity.

An embodiment of the present invention will be described below, but the present invention is not limited to this. The present invention is not limited to each configuration described below, and various modifications are possible within the scope of the claims, and technical means disclosed in different embodiments and examples can be used. Embodiments and examples obtained by appropriate combinations are also included in the technical scope of the present invention. Also, all scientific and patent documents mentioned in this specification are incorporated herein by reference. In addition, unless otherwise specified in this specification, "A to B" representing a numerical range intends "A or more and B or less".

<1. Technical idea of the present invention>
2. Description of the Related Art In recent years, as the performance of electronic devices has improved, there has been a demand for thick graphite sheets (thick graphite sheets) having better heat dissipation performance. A thick graphite sheet can be produced by heat-treating (graphitizing) a polyimide film having a large thickness (for example, 80 μm or more). However, when the thickness of a conventional polyimide film is simply increased, the surface of the graphite sheet containing the polyimide film as a raw material (made by heat treatment) is greatly foamed and the thermal conductivity is lowered. The present inventors have found that problems such as poor appearance occur.

The inventors of the present invention focused on the outgassing generated in the graphite sheet during the heat treatment of the polyimide film as the cause of the problem that occurs in such a thick graphite sheet.

When a conventional relatively thin graphite sheet is produced, the orientation of the graphite (graphite layer) in the resulting graphite sheet has the effect of increasing the orientation of the polyimide film for the purpose of improving interlaminar strength, etc. Acid anhydrides (PMDA, BPDA, etc.) and/or diamines (ODA, PDA, etc.) with enhancing properties have been employed as raw materials for polyimide films. However, in a thick graphite sheet, since the number of graphite layers increases, when acid anhydride and/or diamine, which have the effect of increasing the orientation of the polyimide film, are used as raw materials for the polyimide film. , The outgas generated in the graphite sheet (between the graphite layers) due to the heat treatment of the polyimide film is blocked by a large number of highly oriented graphite layers, is not discharged from the inside of the graphite sheet, and fills between the graphite layers. Then, as the heating progresses, the amount of the outgas increases and the volume of the outgas increases, pushing up the surface of the graphite layer. It was thought that this outgas push-up of the graphite layer was the cause of problems such as foaming (raising) on the surface of the graphite sheet.

In order to suppress the generation of outgassing when heat-treating a polyimide film, it is necessary to reduce the rate of temperature increase during heat-treatment (for example, less than 0.1°C/min). That is, in conventional polyimide films, in order to suppress the occurrence of problems caused by outgassing, it was necessary to reduce the rate of temperature rise to such an extent that the occurrence of outgassing can be suppressed. However, when the heating rate is reduced to such an extent that the generation of outgas can be suppressed, the time required for the heat treatment of the polyimide film increases, and the productivity of the graphite sheet greatly decreases. That is, the conventional polyimide film has a problem that the productivity of the graphite sheet is greatly reduced when manufacturing a thick graphite sheet.

In addition, due to the recent miniaturization of electronic devices, graphite sheets are required to have a high density from the viewpoint of realizing efficient heat dissipation because they are placed in limited spaces in small electronic devices. It's like

Under such circumstances, the present inventors have found that a high-density graphite sheet can be made into a polyimide film that can be provided with good productivity, in particular, a thick polyimide film that can provide a thick graphite sheet. However, the present inventors have made intensive studies to provide a polyimide film that can produce a high-density graphite sheet with good productivity. As a result, the following findings were newly discovered, leading to the completion of the present invention:
(1) Acid anhydrides (BTDA, ODPA, etc.) and/or diamines (BAPP, etc.), which have the effect of disturbing (lowering) the orientation of the polyimide film, are used as raw materials for the polyimide film in an appropriate amount. The orientation of the resulting polyimide film can be moderately disturbed. When such a polyimide film having moderately disturbed orientation is heat treated, the orientation of the graphite layer can be moderately disturbed in the resulting graphite sheet. By appropriately disturbing the orientation of the graphite layers in the graphite sheet, the outgassing generated in the graphite sheet can be removed appropriately. The graphite sheet can be provided with good productivity because problems such as foaming on the surface of the graphite sheet caused by
(2) A graphite sheet having a high density can be provided by heat-treating a polyimide film containing an appropriate proportion of an organic phosphorus compound.

The polyimide film according to one embodiment of the present invention contains an appropriate amount of an acid anhydride and / or diamine that has the effect of disturbing the orientation of the polyimide film, and contains an appropriate proportion of an organic phosphorus compound, so that it has a high density. can be provided with high productivity. Therefore, it can be suitably used for manufacturing graphite sheets, particularly thick graphite sheets. Such a polyimide film has not been known in the past and can be said to be a surprising discovery.

<2. Polyimide film>
A polyimide film according to one embodiment of the present invention (hereinafter sometimes referred to as the present polyimide film) will be described in detail below. This polyimide film is a polyimide film made from an acid dianhydride component and a diamine component as raw materials, and the acid dianhydride component contains 50 PMDA in the total amount of 100 mol% of the acid dianhydride component. ~100 mol%, and at least one of BTDA and ODPA in an amount of 0 to 50 mol%, and the diamine component contains 50 to 100 mol% of ODA and 0 to 50 mol% of BAPP in the total amount of 100 mol% of the diamine component. %, the total content of the BTDA, the ODPA and the BAPP with respect to the total amount of 200 mol% of the acid dianhydride component and the diamine component is 1 to 50 mol% or less, and an organic phosphorus compound 0.1% by weight to 5.0% by weight.

Since the present polyimide film has the above structure, by using the present polyimide film as a raw material, a graphite sheet having a high density can be provided with good productivity. That is, the present polyimide film can be suitably used for producing graphite sheets. Therefore, the present polyimide film can also be called a polyimide film for graphite sheets.

(Acid dianhydride component)
The acid dianhydride component, which is the raw material of the present polyimide film, contains 50 to 100 mol% of pyromellitic dianhydride (PMDA) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride. (BTDA) and at least one of 4,4'-oxydiphthalic dianhydride (ODPA) from 0 to 50 mol%. The acid dianhydride component may contain only one of BTDA and ODPA, or both of them. In addition, when the present polyimide film uses 1 mol% or more of BAPP as a raw material as a diamine component described later, the acid dianhydride component may contain BTDA and / or ODPA, and does not contain either BTDA or ODPA. It's good.

In one embodiment of the present invention, the amount of PMDA contained in the acid dianhydride component is 50 mol% or more, preferably 60 mol% or more, relative to 100 mol% of the total amount of the acid dianhydride component, More preferably, it is 70 mol % or more. When the present polyimide film contains 50 mol % or more of PMDA, it is possible to provide a polyimide film (and a carbonaceous film) having moderate orientation. The amount of PMDA contained in the acid dianhydride component may be 80 mol% or more, 90 mol% or more, 95 mol% or more, or 100 mol%. .

Above all, it is preferable that 100 mol% of PMDA is included as the acid dianhydride component, and in this case, it is preferable that 50 to 99 mol% of ODA and 1 to 50 mol% of BAPP are included as the diamine component. With such a configuration, the obtained graphite sheet has good thermal diffusivity and flexibility.

In one embodiment of the present invention, when the acid dianhydride component contains at least one of BTDA and ODPA, the content of BTDA and ODPA (the total amount of BTDA and ODPA) is 100% of the total amount of the acid dianhydride component. Based on mol %, it is 1 mol % or more, preferably 5 mol % or more, more preferably 10 mol % or more, and still more preferably 20 mol % or more. The upper limit of the content of BTDA and ODPA is 50 mol% or less, preferably 40 mol% or less, more preferably 30 mol% or less. When the acid dianhydride component contains at least one of BTDA and ODPA in an amount of 1 mol % or more, the orientation of the resulting polyimide film (and carbonaceous film) can be moderately disturbed. Thereby, a graphite sheet can be provided with good productivity. Further, when the content (total amount) of at least one of BTDA and ODPA in the acid dianhydride component is 50 mol% or less, there is no fear that the orientation of the resulting graphite sheet will be excessively disturbed. Good thermal diffusivity and flexibility of the sheet. In other words, when the content (total amount) of BTDA and ODPA exceeds 50 mol%, the orientation of the graphite layers in the resulting graphite sheet is excessively disturbed, and the thermal conductivity and flexibility of the graphite sheet are poor. tend to become

The present polyimide film may contain other acid dianhydrides in addition to the PMDA, the BTDA and the ODPA as acid dianhydride components. Other acid dianhydrides include, for example, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2′,3, 3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride , 3,4,9,10-perylenetetracarboxylic dianhydride, 1,1-(3,4-dicarboxyphenyl)ethane 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)methane dianhydride anhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, p-phenylene bis (trimellitic monoester dianhydride), ethylene bis (trimellitic monoester dianhydride), bisphenol A Mention may be made of bis(trimellitic monoester dianhydride) and their analogues. As other acid dianhydrides, these acid dianhydrides may be used singly, or multiple types of these acid dianhydrides may be mixed in an arbitrary ratio.

The content of the other acid dianhydride in the acid dianhydride component which is the raw material of the present polyimide film is 50 mol% or less, preferably 40 mol, in 100 mol% of the total amount of the acid dianhydride component. %, more preferably 30 mol % or less, still more preferably 20 mol % or less, even more preferably 10 mol % or less, and particularly preferably 0 mol %. That is, it is particularly preferable that the acid dianhydride component, which is the raw material of the present polyimide film, does not contain other acid dianhydrides.

(Diamine component)
The diamine component, which is the raw material of the present polyimide film, contains 4,4'-diaminodiphenyl ether (ODA) in an amount of 50 to 100 mol%, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP ) in an amount of 0 to 50 mol %. When the present polyimide film is made from 1 mol % or more of BTDA or ODPA as the acid dianhydride component, the diamine component may or may not contain BAPP.

In one embodiment of the present invention, the amount of ODA contained in the diamine component is 50 mol% or more, preferably 60 mol% or more, more preferably 70 mol%, based on 100 mol% of the total amount of the diamine component. % or more. By including 50 mol % or more of ODA in the present polyimide film, it is possible to provide a polyimide film (and a carbonaceous film) having an appropriate orientation. The amount of ODA contained in the diamine component may be 80 mol % or more, 90 mol % or more, 95 mol % or more, or 100 mol %.

Among them, it is preferable that the diamine component contains 100 mol % of ODA. In this case, the dianhydride component contains 50 to 99 mol % of PMDA and 1 to 50 mol of at least one of BTDA and ODPA. % is preferred. With such a configuration, the obtained graphite sheet has good thermal diffusivity and flexibility.

In one embodiment of the present invention, when the diamine component contains BAPP, the content of BAPP is 1 mol% or more, preferably 5 mol% or more, relative to 100 mol% of the total amount of the diamine component. It is preferably 10 mol % or more, more preferably 20 mol % or more. The upper limit of the BAPP content is 50 mol % or less, preferably 40 mol % or less, and more preferably 30 mol % or less. When the diamine component contains 1 mol % or more of BAPP, the orientation of the resulting polyimide film (and carbonaceous film) can be moderately disturbed. Thereby, a graphite sheet can be provided with good productivity. Further, when the content of BAPP in the diamine component is 50 mol% or less, there is no possibility that the orientation of the graphite layers in the graphite sheet is excessively disturbed, and the resulting graphite sheet has good thermal diffusivity and flexibility. .

The present polyimide film may contain other diamines in addition to the ODA and BAPP as diamine components. Other diamines include, for example, p-phenylenediamine (PDA), 4,4'-diaminodiphenylmethane, benzidine, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl Sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diamino Diphenylsilane, 4,4'-diminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-phenylamine, 1,3-diaminobenzene, 1,2- Mention may be made of diaminobenzenes and their analogues. As other diamines, these diamines may be used alone, or multiple types of these diamines may be mixed in an arbitrary ratio.

The content of the other diamine in the diamine component, which is the raw material of the present polyimide film, is 50 mol% or less, preferably 40 mol% or less, more preferably 30%, based on the total amount of 100 mol% of the diamine component. It is mol % or less, more preferably 20 mol % or less, even more preferably 10 mol % or less, and particularly preferably 0 mol %. That is, it is particularly preferable that the diamine component, which is the raw material of the present polyimide film, does not contain other diamines.

(Total content of BTDA, ODPA and BAPP)
The present polyimide film contains 1 to 50 mol % of the BTDA, the ODPA and the BAPP in total with respect to 200 mol % of the total amount of the acid dianhydride component and the diamine component. In the present polyimide film, the orientation of the present polyimide film (and the carbonaceous film) can be moderately disturbed by setting the amounts of the BTDA, the ODPA and the BAPP used within the above ranges. Therefore, a graphite sheet containing the present polyimide film as a raw material can be produced at a high rate of temperature rise and is highly productive.

In the present polyimide film, the lower limit of the total content of the BTDA, the ODPA and the BAPP with respect to the total amount of 200 mol% of the acid dianhydride component and the diamine component is 1 mol% or more, preferably It is 5 mol % or more, more preferably 10 mol % or more, and still more preferably 20 mol % or more. The upper limit of the total content of BTDA, ODPA and BAPP is 50 mol % or less, preferably 40 mol % or less, and more preferably 30 mol % or less.

This polyimide film is a polyimide film made from substantially equimolar amounts of the acid dianhydride component and the diamine component as raw materials. In this specification, substantially equimolar amounts means that the ratio of molar amounts of two or more different substances (for example, an acid dianhydride component and a diamine component) is from 100:98 to 100:102. It is intended to be within the range, preferably 100:100. That is, in the present specification, "containing 0 to 50 mol% of at least one of BTDA and ODPA in the total amount of 100 mol% of the acid dianhydride component" means "the acid dianhydride component and the diamine component It can also be said that at least one of BTDA and ODPA is contained in an amount of 0 to 50 mol% relative to the total amount of 200 mol%. It can also be said that "0 to 50 mol % of BAPP is contained with respect to 200 mol % of the total amount of the acid dianhydride component and the diamine component". That is, "the total content of the BTDA, the ODPA and the BAPP with respect to 200 mol% of the total amount of the acid dianhydride component and the diamine component" is the content of BTDA and ODPA in the acid dianhydride component and the content of BAPP in the diamine component.

(organophosphorus compound)
This polyimide film contains 0.1 to 5.0% by weight of an organophosphorus compound in 100% by weight of the total amount of this polyimide film.

The content of the organic phosphorus compound in the polyimide film is 0.1 to 5.0% by weight, preferably 0.2 to 3.0% by weight, based on 100% by weight of the total amount of the polyimide film. More preferably 0.3 to 1.5% by weight. When the content of the organic phosphorus compound in the present polyimide film is 0.1% by weight or more, a graphite sheet with high density can be provided, and when it is 5.0% by weight or less, the foaming rate during graphitization is reduced. , has the advantage of being able to provide graphite sheets with higher productivity. In addition, the present polyimide film contains an organic phosphorus compound within the above range, so that (1) it can provide a graphite sheet with excellent peelability from a slightly adhesive film, and (2) the carbonaceous film in the graphitization process. Since fusion can be prevented, it also has the advantage of being able to provide graphite sheets with higher productivity.

Examples of organic phosphorous compounds that the present polyimide film may contain include phosphates, phosphine oxides, phosphites, phosphines, phosphonates, phosphinates, and the like. Only one type of these organophosphorus compounds may be contained, or two or more types may be contained. Among the exemplified organophosphorus compounds, phosphate esters are preferred, and triphenyl phosphate is particularly preferred, since they have the advantage of being stable in air.

From the viewpoint of stability, the organic phosphorus compound contained in the present polyimide film is preferably an organic phosphorus compound in which the valence of phosphorus is pentavalent. That is, the present polyimide film preferably contains, as the organic phosphorus compound, an organic phosphorus compound in which the valence of phosphorus is pentavalent, and may contain only an organic phosphorus compound in which the valence of phosphorus is pentavalent. more preferred.

Examples of organic phosphorus compounds in which the valence of phosphorus is pentavalent include triphenyl phosphate and trimethyl phosphate.

As the organic phosphorus compound that can be contained in the present polyimide film, the temperature at which the weight loss rate is 5% in TG-DTA measurement is preferably 200 ° C. or higher, more preferably 250 ° C. or higher. It is more preferably 300° C. or higher. If the temperature at which the weight reduction rate of the organic phosphorus compound contained in the present polyimide film is 5% in TG-DTA measurement is 200° C. or higher, contamination of the furnace for forming the polyimide film can be reduced.

Examples of organophosphorus compounds whose temperature at which the weight loss rate reaches 5% in TG-DTA measurement is 200°C or higher include triphenyl phosphate and triphenylphosphine oxide.

(Inorganic particles)
The present polyimide film may contain inorganic particles (filler). When the present polyimide film contains inorganic particles, the present polyimide film becomes a polyimide film having excellent slipperiness. Such a polyimide film having excellent lubricity can suppress the occurrence of scratches during transport of the polyimide film, and can prevent fusion of the carbonaceous film in the graphitization process.

Inorganic particles that the present polyimide film may contain include calcium carbonate (CaCO ₃ ), silica, calcium hydrogen phosphate (CaHPO ₄ ), calcium phosphate (Ca ₂ P ₂ O ₇ ), and the like. Among these inorganic particles, phosphorus-containing inorganic particles such as calcium hydrogen phosphate and calcium phosphate are preferred.

The upper limit of the average particle size of the inorganic particles that can be contained in the present polyimide film is not particularly limited, but is preferably 2.5 μm or less, preferably 2.0 μm or less, and preferably 1.5 μm or less. , is preferably 1.0 μm or less. When the average particle size of the inorganic particles is 2.5 μm or less, voids generated inside the film after graphitization can be reduced, so that a graphite sheet having an excellent density after compression can be obtained. Thus, a graphite sheet with even better density can be provided. In addition, the lower limit of the average particle size of the inorganic particles is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.3 μm or more, further preferably 0.5 μm or more, and 0 0.7 μm or more is even more preferable.

In the present specification, the average particle size of inorganic particles is intended to be the volume average particle size, and the inorganic particles dispersed in dimethylformamide are measured using a microtrac particle size distribution analyzer MT3000II. is.

When the polyimide film contains inorganic particles, the lower limit of the content of the inorganic particles in the polyimide film is not particularly limited, but is preferably 0.01% by weight or more, more preferably 0.02% by weight. It is preferably 0.03% by weight or more, and more preferably 0.03% by weight or more. The upper limit of the content of the inorganic particles is not particularly limited, but is preferably 0.30% by weight or less, more preferably 0.20% by weight or less, and further preferably 0.15% by weight or less. It is preferably 0.10% by weight or less, and more preferably 0.10% by weight or less.

(Thickness of polyimide film)
The thickness of the present polyimide film is preferably 80 μm to 200 μm, more preferably more than 80 μm and 200 μm or less, even more preferably 90 μm to 180 μm, even more preferably 100 μm to 170 μm, and 110 μm. ~150 µm is particularly preferred, and 115 µm to 140 µm is most preferred. If the thickness of the polyimide film is within the above range, it is possible to provide a graphite sheet having a more excellent thermal diffusivity.

The lower limit of the thickness of the polyimide film according to one embodiment of the present invention is preferably 80 μm or more, more preferably more than 80 μm, even more preferably 90 μm or more, and even more preferably 100 μm or more. It is preferably 110 μm or more, particularly preferably 115 μm or more, and most preferably 115 μm or more. Further, the upper limit of the thickness of the polyimide film is preferably 200 μm or less, more preferably 180 μm or less, even more preferably 160 μm or less, even more preferably 140 μm or less, and 150 μm or less. It is particularly preferred to have A polyimide film having a thickness of 80 μm or more can be said to be a polyimide film having a large thickness, and can be said to be a polyimide film capable of providing a thick graphite sheet.

Conventional polyimide films have a problem that when the thickness of the polyimide film is increased (e.g., 80 μm or more) in order to provide a thick graphite sheet, the productivity of the resulting graphite sheet becomes poor. However, the polyimide film of the present invention can provide a thick graphite sheet with good productivity even when the polyimide film is thick, and the resulting graphite sheet has a high density. That is, the present polyimide film can be suitably used as a thick polyimide film.

<3. Method for producing polyimide film>
The method for producing a polyimide film according to one embodiment of the present invention (hereinafter sometimes referred to as the method for producing the present polyimide film) is not particularly limited, but for example, a method having the following steps i) to iv) is preferable. ;
i) reacting an acid dianhydride component and a diamine component in an organic solvent to obtain a polyamic acid solution;
ii) applying the polyamic acid solution onto a support to form a mixed solution layer;
iii) drying (heating) the mixed solution layer on the support to form a self-supporting gel film, and then peeling off the gel film from the support;
iv) further heating the peeled gel film to imidize the remaining amic acid, and drying the gel film to obtain a polyimide film.

It can also be said that the acid dianhydride component and the diamine component are monomer units that constitute polyamic acid, which is a copolymer. In this specification, the acid dianhydride component and the diamine component may be collectively referred to as the monomer component.

In the method for producing the present polyimide film, as the step i), the above <2. Polyimide film> The acid dianhydride component and the diamine component detailed in the section are polymerized (as raw materials), and are not particularly limited as long as polyamic acid can be obtained, for example, the following polymerization methods (1) to (5) Either can be preferably used.

(1) A method of dissolving a diamine component in an organic solvent (organic polar solvent) and reacting the diamine component with a substantially equimolar amount of an acid dianhydride component for polymerization.

(2) An acid dianhydride component and an excessively small amount of diamine component are reacted in an organic solvent to obtain a prepolymer having acid dianhydride groups at both ends. Subsequently, the prepolymer is polymerized with a diamine component so that the total amount used in the entire polymerization process is substantially equimolar with respect to the acid dianhydride component.

A specific example of the method (2) is to synthesize a prepolymer having the acid dianhydride at both ends using a diamine component and an acid dianhydride component, and add the diamine component used in the synthesis of the prepolymer to the prepolymer. A method of synthesizing a polyamic acid by reacting a diamine component having the same composition as or a diamine component having a different composition. Also in method (2), the diamine component to be reacted with the prepolymer may have the same composition as the diamine component used to synthesize the prepolymer, or may have a different composition.

(3) An acid dianhydride component and an excess molar amount of a diamine component are reacted in an organic solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after adding the diamine component to the prepolymer, the acid dianhydride component is added so that the total amount of the acid dianhydride component and the diamine component used in the entire polymerization process is substantially equimolar. , a method of polymerizing a prepolymer and a dianhydride component.

(4) After dissolving and/or dispersing an acid dianhydride component in an organic solvent, a diamine component is added in an amount substantially equimolar to the acid dianhydride component to obtain an acid dianhydride. A method of polymerizing a substance component and a diamine component.

(5) A method of polymerizing by reacting a mixture of an acid dianhydride component and a diamine component in substantially equimolar amounts in an organic solvent.

The i) step preferably includes an addition step of adding (mixing) an organophosphorus compound to the polyamic acid solution obtained by polymerizing the acid dianhydride component and the diamine component. The amount of the organophosphorus compound added to the solid content (polyamic acid) of the polyamic acid solution in the addition step is the content of the organophosphorus compound in the resulting polyimide film. In other words, by adjusting the addition amount of the organic phosphorus compound in the adding step, the content of the organic phosphorus compound in the resulting polyimide film can be adjusted.

The acid dianhydride component and the diamine component to be reacted (subjected to polymerization) in the i) step become the acid dianhydride component and the diamine component which are raw materials of the resulting polyimide film, and the polyamide in the i) step (addition step) The amount of the organophosphorus compound added to the acid can be the content of the organophosphorus compound in the resulting polyimide film. Therefore, step i) in the present method for producing a polyimide film can be expressed as follows: a step of mixing an acid dianhydride component and a diamine component to obtain a polyamic acid, and 100 weight of the polyamic acid %, and the acid dianhydride component is pyromellitic acid in the total amount of 100 mol% of the acid dianhydride component. 50 to 100 mol% of dianhydride (PMDA), at least 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′-oxydiphthalic dianhydride (ODPA) 0 to 50 mol% of either, and the diamine component includes 50 to 100 mol% of 4,4'-diaminodiphenyl ether (ODA), 2,2-bis[4- (4-Aminophenoxy)phenyl]propane (BAPP) is contained in an amount of 0 to 50 mol%, and the 3,3′,4,4′- total of benzophenonetetracarboxylic dianhydride (BTDA), the 4,4′-oxydiphthalic dianhydride (ODPA) and the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) The content is 1 to 50 mol %.

A preferred method for producing the present polyimide film can be expressed as follows: a step of mixing an acid dianhydride component and a diamine component to obtain a polyamic acid; and adding 0.1 to 5.0% by weight of an organic phosphorus compound, wherein the acid dianhydride component is pyromellitic dianhydride in the total amount of 100 mol% of the acid dianhydride component 50 to 100 mol% of (PMDA), at least one of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′-oxydiphthalic dianhydride (ODPA) The diamine component contains 50 to 100 mol% of 4,4′-diaminodiphenyl ether (ODA), 2,2-bis[4-(4- containing 0 to 50 mol% of aminophenoxy)phenyl]propane (BAPP), and the 3,3',4,4'-benzophenonetetracarboxylic acid relative to the total amount of 200 mol% of the acid dianhydride component and the diamine component; The total content of acid dianhydride (BTDA), the 4,4′-oxydiphthalic dianhydride (ODPA) and the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is , 1 to 50 mol %.

The acid dianhydride component and the diamine component to be reacted (to be subjected to polymerization) in step i) in the method for producing the present polyimide film, and the organic phosphorus compound to be added to the polyamic acid are described in <2. Polyimide film> section can be incorporated as appropriate.

It can also be said that the steps ii) to iv) in the present method for producing a polyimide film are steps of imidizing the polyamic acid solution to obtain a polyimide film. In the steps ii) to iv), the method for imidizing the polyamic acid includes, for example, (I) a thermal imidization method in which a polyamic acid solution is heated to imidize without using an imidization accelerator, or , (II) polyamic acid, a dehydrating agent (dehydration ring-closing agent) typified by acid dianhydrides such as acetic anhydride, and/or tertiary amines typified by picoline, quinoline, isoquinoline, pyridine, etc. A chemical imidization method of imidizing polyamic acid by adding an imidization accelerator such as a catalyst and heating a polyamic acid solution containing the imidization accelerator can be used.

In particular, the resulting polyimide film has a small coefficient of linear expansion, a high elastic modulus, a tendency to increase birefringence, and can be rapidly graphitized at a relatively low temperature, so that a high-quality graphite sheet can be obtained. Therefore, the chemical imidization method is preferred. In particular, it is preferable to use a dehydrating agent and an imidization accelerator in combination, because the resulting polyimide film can have a smaller linear expansion coefficient, a larger elastic modulus, and a larger birefringence. In addition, since the imidization reaction proceeds more rapidly in the chemical imidization method, the imidization reaction can be completed in a short time in the heat treatment, and is an industrially advantageous method with excellent productivity.

In the method for producing a polyimide film of the present invention, the support used in step ii) is not dissolved by the solution containing the polyimide, and is particularly a support that can withstand the heating required for drying the laminate. Without limitation, for example, a glass plate, an aluminum foil, an endless stainless steel belt, a stainless steel drum, etc. can be suitably used.

In the iii) step, more specifically, the thickness of the finally obtained polyimide film and the heating conditions are set according to the production rate, and the mixed solution layer (polyamic acid solution) coated on the support is subjected to After performing at least one of partial imidization and drying, this is a step of obtaining (peeling) a gel film from the support.

In step iv), more specifically, the gel film (the gel film obtained in step iii) is fixed at its ends and heat-treated while avoiding shrinkage during curing. This is a step of removing water, residual solvent, imidization accelerator, etc., and completely imidizing the remaining amic acid (non-imidized amic acid) to obtain a polyimide-containing film (polyimide film). The heating conditions in the iv) step may be appropriately set according to the thickness of the film to be finally obtained and the production rate.

In addition, the method for drying the mixed solution layer and the gel film in the iii) step and the iv) step is not particularly limited. A method of heating by treatment can be mentioned. The drying temperature (heating temperature) in the drying step is not particularly limited as long as a gel film or polyimide film can be obtained. It may be 400°C to 500°C.

<4. Graphite sheet>
In one embodiment of the invention, there is provided a graphite sheet comprising the polyimide film as a raw material. It can also be said that the graphite sheet according to one embodiment of the present invention (hereinafter referred to as the present graphite sheet) is a graphite sheet obtained by heat-treating the present polyimide film. Since the present graphite sheet contains the present polyimide film as a raw material, it has a high density and can be provided with good productivity. In this specification, the graphite sheet refers to both a graphite sheet before being subjected to the rolling process described later (graphite sheet before rolling) and a graphite sheet after being subjected to the rolling process (graphite sheet after rolling). is intended, unless otherwise specified, graphite sheets after rolling are intended.

The density of the present graphite sheet (graphite sheet after rolling) is preferably more than 2.00 g/cm ³ , more preferably 2.02 g/cm ³ or more, and more preferably 2.04 g/cm ³ or more. more preferably 2.06 g/cm ³ or more. Although the upper limit of the density is not particularly limited, the density of the graphite sheet is usually 2.26 g/cm ³ or less. A graphite sheet with a density of 2.00 g/cm ³ or more can be said to be a graphite sheet with a high density, and can achieve efficient heat dissipation, and is used in fields such as electronic devices that require excellent heat dissipation. , can be suitably used as a heat radiating member. The method for measuring the density of the graphite sheet is as described in Examples below.

(Thermal conductivity)
In this specification, the thermal conductivity of the graphite sheet can be evaluated by the thermal diffusivity of the graphite sheet (graphite sheet after rolling). The thermal diffusivity of the present graphite sheet is preferably 7.0 cm ² /s or more, more preferably 8.0 cm ² /s or more, further preferably 9.0 m ² /s or more, More preferably, it is 9.5 cm ² /s or more. A graphite sheet having a thermal diffusivity of 7.0 cm ² /s or more has excellent thermal conductivity. In other words, it is excellent in heat dissipation, and can be suitably used as a heat dissipation member in fields such as electronic equipment that require excellent heat dissipation. The method for measuring the thermal diffusivity of the graphite sheet is as described in Examples below.

(Productivity)
In this specification, the productivity of the graphite sheet is defined as the ratio of the thickness of the raw material polyimide film to the thickness of the resulting graphite sheet (graphite sheet before rolling) (thickness of graphite sheet before rolling/thickness of polyimide film). It can be evaluated based on the thickness (hereinafter referred to as "GS thickness/PI thickness"). If the GS thickness/PI thickness is greater than a certain value (for example, greater than 3.0), it means that the graphite sheet surface is foamed due to outgassing during heat treatment, and the heat treatment is performed at a substantially high temperature increase rate. It can also be said that the graphite sheet is a graphite sheet with poor productivity. On the other hand, the smaller the GS thickness/PI thickness, the more the graphite sheet is suppressed from foaming due to outgassing during heat treatment, and the graphite sheet can be heat-treated at a high heating rate and has excellent productivity. I can say there is. Specifically, if the GS thickness/PI thickness is 3.0 or less, it can be evaluated that the graphite sheet has excellent productivity. The GS thickness/PI thickness is preferably 2.5 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and even more preferably 1.0 or less.

The lower limit of the thickness of the present graphite sheet (graphite sheet after rolling) is preferably 45 μm or more, more preferably 50 μm or more, and even more preferably 55 μm or more. The upper limit of the thickness of the graphite sheet after rolling is preferably 110 μm or less, more preferably 105 μm or less. If the thickness of the graphite sheet after rolling is 45 μm or more, it can be said that the graphite sheet has a sufficient thickness, and efficient heat dissipation is possible. Moreover, if the thickness is 110 μm or less, there is an advantage that it can be mounted in a thin electronic device with little space.

<5. Manufacturing method of graphite sheet>
The method for producing a graphite sheet according to an embodiment of the present invention (hereinafter sometimes referred to as the present graphite sheet producing method) is particularly Although not limited, it includes a step of heat-treating a polyimide film for a graphite sheet to 2400 ° C. or higher, and the polyimide film for the graphite sheet is a polyimide film made from an acid dianhydride component and a diamine component. , the acid dianhydride component includes 50 to 100 mol% of pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenone tetra At least one of carboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA) is contained in 0 to 50 mol%, and the diamine component contains 100 mol% of the total amount of the diamine component, 50 to 100 mol% of 4,4'-diaminodiphenyl ether (ODA) and 0 to 50 mol% of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), the acid dianhydride The 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and the 4,4′-oxydiphthalic dianhydride (ODPA) based on 200 mol % of the total amount of the component and the diamine component and the total content of the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 1 to 50 mol%, and the total amount of the polyimide film is 100% by weight. The method is a polyimide film containing 0.1 to 5.0% by weight of the compound. It can also be said that the present graphite sheet manufacturing method includes a step of heat-treating the present polyimide film at 2400° C. or higher.

According to this graphite sheet manufacturing method, a high-density graphite sheet can be provided with good productivity.

The method for producing the present graphite sheet will be described in detail below, taking as an example a method including a step of heat-treating a specific polyimide film at 2400°C or higher. In the following description, specific aspects of the polyimide film are described in <2. Polyimide Film> section is incorporated as appropriate.

The method for producing the present graphite sheet is not particularly limited as long as it includes a step of heat-treating a specific polyimide film (the present polyimide film) at 2400 ° C. or higher, but the polyimide film is heat-treated in an inert gas atmosphere or under reduced pressure. It is preferably a so-called polymer thermal decomposition method. Specifically, the present graphite sheet manufacturing method includes a carbonization step of preheating a polyimide film at a temperature of about 1000° C. to obtain a carbonized polyimide film, and a carbonized polyimide film produced in the carbonization step. is heat-treated (heated) at a temperature of 2400° C. or higher to graphitize, and a rolling step of rolling this. In the present graphite sheet manufacturing method, the carbonization step and the graphitization step may be performed continuously, or after the carbonization step is completed, the graphitization step alone may be performed separately.

Below, the carbonization process, graphitization process, and rolling process that can be included in the present graphite sheet manufacturing method will be described in detail.

(Carbonization process)
The carbonization step is a step of heat-treating the polyimide film to a temperature of about 1000° C. to carbonize (carbonize) the polyimide film. The carbonization method of the polyimide film in the carbonization step is not particularly limited. For example, a rectangular polyimide film may be carbonized while being laminated with a graphite sheet, or a roll-shaped polyimide film may be carbonized as it is in a roll. Alternatively, the film may be unwound from a roll-shaped polyimide film and carbonized continuously. The carbonization step is preferably performed under a vacuum atmosphere, under reduced pressure, or in an inert gas, and nitrogen is preferably used as the inert gas. In addition, in this specification, the carbonized polyimide film obtained by the carbonization process may be called a carbonaceous film.

(Graphitization process)
The graphitization step is a step of heat-treating the carbonaceous film obtained in the carbonization step at a temperature of 2400° C. or higher to graphitize the carbonaceous film. The graphitization step can also be said to be a step of heat-treating a carbonaceous film to obtain a graphite sheet (graphite sheet before rolling). In the graphitization step, the temperature (maximum temperature) at which the carbonaceous film obtained in the carbonization step is heat-treated is preferably, for example, 2400° C. or higher, 2600° C. or higher, 2800° C. or higher, 2900° C. or higher, or 3000° C. or higher. . Although the upper limit of the maximum temperature is not particularly limited, it is preferably 3300° C. or lower, more preferably 3200° C. or lower. In the graphitization step, if the temperature (maximum temperature) when heat-treating the carbonaceous film obtained in the carbonization step is 2400°C or higher, there is an advantage that the obtained graphite sheet has a good thermal diffusivity. If it is below, there is an advantage that the sublimation of the graphite member in the graphitization furnace can be suppressed. The graphitization step is performed under reduced pressure or in an inert gas, and argon or helium can be suitably used as the inert gas.

In the graphitization step, a rectangular carbonaceous film may be graphitized in a state of being laminated with a graphite sheet, or a roll-shaped carbonaceous film may be graphitized as it is in a roll. may be drawn out and graphitized continuously.

In the graphitization step, the temperature rise rate when heating the carbonaceous film to the maximum temperature is not particularly limited, but from the viewpoint of providing a graphite sheet with good productivity, it is preferably 0.2 ° C./min or more, and 0.3 ° C. /min or more, more preferably 0.4°C/min or more, and even more preferably 0.5°C/min or more. A carbonaceous film in which excessive foaming does not occur in the resulting graphite sheet when heat-treated (graphitized) at a rate of temperature increase of 0.2° C./min or more can be said to be a carbonaceous film with excellent productivity. A polyimide film that can provide such a carbonaceous film can be said to be a polyimide film with excellent productivity.

A carbonaceous film obtained by carbonizing the present polyimide film has a somewhat disturbed orientation, similar to the present polyimide film. Such a carbonaceous film having a somewhat disturbed orientation is outgassed even when the carbonaceous film is heat-treated (graphitized) at a high temperature increase rate of 0.2 ° C./min or more in the graphitization process. It is easy to come off, and it is possible to suppress the foaming of the obtained graphite sheet, so that the graphite sheet can be provided with good productivity.

(rolling process)
The rolling step is a step of rolling the graphite sheet obtained by the graphitization step (graphite sheet before rolling). The rolling process can be said to be a process of obtaining a graphite sheet after rolling, and can also be said to be a compression process. The graphite sheet before rolling is in a foamed state due to the influence of outgassing generated in the graphitization process, and may have an excessive thickness unsuitable for practical use. The thickness can be adjusted and flexibility can be imparted. In the rolling step, the method of rolling the graphite sheet is not particularly limited, and examples thereof include a method of rolling using metal rolls or the like. The rolling step may be performed while the manufactured graphite sheet is cooled to room temperature, or may be performed continuously with the graphitization step.

An embodiment of the present invention may include the following configuration.

[1] A polyimide film made from an acid dianhydride component and a diamine component, wherein the acid dianhydride component is pyromellitic dianhydride in the total amount of 100 mol% of the acid dianhydride component at least one of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′-oxydiphthalic dianhydride (ODPA) The diamine component contains 50 to 100 mol% of 4,4′-diaminodiphenyl ether (ODA), 2,2-bis[4-(4 -Aminophenoxy)phenyl]propane (BAPP) in an amount of 0 to 50 mol%, and the 3,3′,4,4′-benzophenone tetra Total content of carboxylic dianhydride (BTDA), 4,4'-oxydiphthalic dianhydride (ODPA) and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 1 to 50 mol %, and a polyimide film for a graphite sheet containing 0.1 to 5.0 wt % of an organophosphorus compound in 100 wt % of the total amount of the polyimide film.

[2] containing 100 mol% of pyromellitic dianhydride (PMDA) as the acid dianhydride component, and 50 to 99 mol% of 4,4'-diaminodiphenyl ether (ODA) as the diamine component; The polyimide film for a graphite sheet according to [1], containing 1 to 50 mol% of 2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP).

[3] containing 100 mol% of 4,4'-diaminodiphenyl ether (ODA) as the diamine component, and 50 to 99 mol% of pyromellitic dianhydride (PMDA) as the acid dianhydride component; [1], containing 1 to 50 mol% of at least one of 3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA) polyimide film for graphite sheets. [4] The polyimide film for graphite sheets according to any one of [1] to [3], which has a thickness of 80 to 200 μm.

[5] The polyimide film for a graphite sheet according to any one of [1] to [4], containing an organic phosphorus compound in which the valence of phosphorus is pentavalent as the organic phosphorus compound.

[6] The graphite sheet according to any one of [1] to [5], wherein the organophosphorus compound has a temperature of 200° C. or higher at which the weight loss rate becomes 5% in TG-DTA measurement. polyimide film for

[7] A graphite sheet containing, as a raw material, the polyimide film for a graphite sheet according to any one of [1] to [6].

[8] a step of mixing an acid dianhydride component and a diamine component to obtain a polyamic acid;
A method for producing a polyimide film, comprising the step of adding 0.1 to 5.0% by weight of an organic phosphorus compound with respect to 100% by weight of the polyamic acid, wherein the acid dianhydride component is the acid 50 to 100 mol% of pyromellitic dianhydride (PMDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4, At least one of 4'-oxydiphthalic dianhydride (ODPA) is contained in 0 to 50 mol%, and the diamine component contains 4,4'-diaminodiphenyl ether (ODA) in the total amount of 100 mol% of the diamine component. 50 to 100 mol%, containing 0 to 50 mol% of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), the total amount of the acid dianhydride component and the diamine component being 200 mol % of the 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), the 4,4′-oxydiphthalic dianhydride (ODPA) and the 2,2-bis[4-( the total content of 4-aminophenoxy)phenyl]propane (BAPP) is 1-50 mol%;
A method for producing a polyimide film.

[9] A method for producing a graphite sheet, comprising a step of heat-treating a polyimide film for a graphite sheet at 2400° C. or higher, wherein the polyimide film for a graphite sheet comprises an acid dianhydride component and a diamine component. A polyimide film as a raw material, wherein the acid dianhydride component is 50 to 100 mol% of pyromellitic dianhydride (PMDA) in the total amount of 100 mol% of the acid dianhydride component, 3,3' , 4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA) containing 0 to 50 mol% of at least one, and the diamine component is the diamine 50 to 100 mol% of 4,4'-diaminodiphenyl ether (ODA) and 0 to 50 mol of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) in 100 mol% of the total amount of components %, the 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), the 4,4′- The total content of oxydiphthalic dianhydride (ODPA) and the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 1 to 50 mol%, and the total amount of the polyimide film A method for producing a graphite sheet containing 0.1 to 5.0% by weight of an organophosphorus compound in 100% by weight.

[10] The polyimide film for the graphite sheet contains 100 mol% of pyromellitic dianhydride (PMDA) as the acid dianhydride component, and 4,4'-diaminodiphenyl ether (ODA) as the diamine component. and 1 to 50 mol% of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP).

[11] The polyimide film for the graphite sheet contains 100 mol% of 4,4'-diaminodiphenyl ether (ODA) as the diamine component, and pyromellitic dianhydride (PMDA) as the acid dianhydride component. 50 to 99 mol%, at least one of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA) from 1 to 50 mol %, the method for producing a graphite sheet according to [9].

[12] The method for producing a graphite sheet according to any one of [9] to [11], wherein the polyimide film for the graphite sheet has a thickness of 80 to 200 μm.

[13] The polyimide film for a graphite sheet according to any one of [9] to [12], wherein the organic phosphorus compound contains an organic phosphorus compound in which the valence of phosphorus is pentavalent. A method of manufacturing a graphite sheet.

[14] The temperature at which the weight loss rate of the organic phosphorus compound contained in the polyimide film for the graphite sheet is 5% in TG-DTA measurement is 200 ° C. or higher, [9] to [13] A method for producing a graphite sheet according to any one of the above.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited only to the following examples.

Each evaluation method in Examples and Comparative Examples will be described below.

<Thickness of graphite sheet before rolling>
The thickness of the graphite sheet before rolling was measured by the following method. In the graphite sheet before rolling, the thickness of the graphite sheet was measured at four corners and one central point using a Mitutoyo micrometer. Here, the "central point" refers to the position of the intersection of diagonal lines drawn from the four measurement points at each corner of the obtained graphite sheet to the diagonal measurement points. Then, the average value of the thickness measurement values obtained at a total of five locations (four corner locations and one center location) was taken as the thickness of the graphite sheet before rolling. Note that the four corners mean the vertices of a rectangular graphite sheet before rolling, which is the object of measurement.

<Thickness of graphite sheet after rolling>
The thickness of the graphite sheet after rolling was measured by the following method. In the rolled graphite sheet, the thickness of the graphite sheet was measured at four corners and one central point using a Mitutoyo micrometer. Here, the "central point" refers to the position of the intersection of diagonal lines drawn from the four measurement points at each corner of the obtained graphite sheet to the diagonal measurement points. Then, the average value of the thickness measurement values obtained at a total of five locations (four locations at the corners and one location at the center) was taken as the thickness of the graphite sheet after rolling. It should be noted that the four corners are intended to be the vertices when the rolled graphite sheet to be measured is rectangular.

<Thermal diffusivity of graphite sheet after rolling>
The thermal diffusivity of the graphite sheet after rolling was measured by the following method. A sample of a graphite sheet after rolling cut into a square of 30 mm × 30 mm was measured using a "Thermo Wave Analyzer TA3" manufactured by Bethel Co., Ltd. under the conditions of an atmosphere of 25 ° C. and a frequency of 75 Hz to determine the thermal diffusivity. was obtained by measuring The sample was prepared by punching out the center portion of the graphite sheet after rolling, which is the object of measurement, with a Thomson blade. Here, the “central portion” means the central portion of the rolled graphite sheet in the width direction and also in the longitudinal direction.

<Density of graphite sheet after rolling>
The density of the graphite sheet after rolling was measured by the following method. A square of 30 mm×30 mm was punched out from the center of the rolled graphite sheet to obtain a sample. The samples were then weighed. Based on the measured weight and the thickness of the sample measured according to the method described in <Thickness of graphite sheet after rolling>, the density of the graphite sheet after rolling was calculated by the following formula:
Density of graphite sheet after rolling (g/cm ³ )=weight of graphite sheet after rolling (g)/(area of graphite sheet after rolling (cm ² )×thickness of graphite sheet after rolling (cm)).

(Example 1)
<Production of polyimide film>
90 mol% of pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic acid di 10 mol % of anhydride (BTDA) was dissolved to obtain a polyamic acid solution containing 18.5% by weight of polyamic acid. To the obtained polyamic acid solution, triphenyl phosphate (TPP, pentavalence of phosphorus, temperature 220 ° C. at which the weight loss rate becomes 5% in the measurement of TG-DTA), which is an organic phosphorus compound, was added. Triphenyl phosphate was added so that the concentration of triphenyl phosphate was 0.3% by weight with respect to 100% by weight of the solid content (polyamic acid) of the polyamic acid solution, and calcium hydrogen phosphate having an average particle size of 2.2 μm ( Inorganic particles) were added so that the concentration of the calcium hydrogen phosphate was 0.08% by weight with respect to 100% by weight of the solid content (polyamic acid) in the polyamic acid solution. While cooling the polyamic acid solution, an imidization catalyst containing 1 equivalent of acetic anhydride, 1 equivalent of isoquinoline and 1 equivalent of dimethylformamide is added to the carboxylic acid groups contained in the polyamic acid, and defoaming. Thus, a polyamic acid solution (mixed solution) containing an imidization catalyst was obtained.

Next, the mixed solution was applied onto an aluminum foil so that the thickness after drying was 135 μm to obtain a mixed solution layer. The mixed solution layer on the aluminum foil was dried using a hot air oven and a far infrared heater. The drying conditions are as follows. First, the mixed solution layer on the aluminum foil was dried in a hot air oven at 120° C. for 440 seconds to form a self-supporting gel film. The gel film was peeled off from the aluminum foil and fixed to the frame. Further, the gel film was heated stepwise in a hot air oven at 120°C for 60 seconds, 275°C for 72 seconds, 400°C for 77 seconds, 450°C for 93 seconds, and a far infrared heater at 460°C for 40 seconds. and dried to produce a polyimide film (A) having a thickness of 135 μm.

<Manufacture of graphite sheet>
A polyimide film (A) cut into a size of 200 mm×200 mm was sandwiched between graphite sheets of size 220 mm×220 mm (one polyimide film and one graphite sheet were alternately laminated) to obtain a laminate. The laminate was placed in a carbonization device (a carbonization device manufactured by Kurata Giken Co., Ltd.) (inside a heating space). In a vacuum atmosphere, the heating space in the carbonization apparatus in which the laminate was installed was heated to 600° C. at a heating rate of 0.4° C./min, and then held at 600° C. for 1 hour. After that, the heating space in the carbonization device is heated to 1000° C. at a heating rate of 0.4° C./min, and then the laminate (polyimide film in the laminate) is heat-treated (carbonized) at 1000° C. for 30 minutes. to obtain a carbonaceous film.

The obtained carbonaceous film was cooled to room temperature (23°C) and formed into a roll having an inner diameter of 100 mm to obtain a roll of carbonaceous film. The carbonaceous film roll is placed on the hearth of a graphitization furnace (graphitization furnace manufactured by Kurata Giken Co., Ltd.) so that the width direction is vertical. In the high temperature range, under an argon atmosphere, the temperature was raised to 2900 ° C. (maximum graphitization temperature) at a heating rate of 0.5 ° C./min, and then held at 2900 ° C. for 30 minutes to obtain a graphitized film (graphite before rolling). sheet) was prepared. Table 1 shows the measurement results of the thickness of the obtained graphite sheet before rolling.

The resulting graphitized film was cooled to room temperature and rolled by a 2-ton precision roll press (clearance type) manufactured by Thank Metal Co., Ltd. to obtain a graphite sheet (graphite sheet after rolling). The thickness, thermal diffusivity and density of the obtained graphite sheet after rolling were measured and evaluated. Table 1 shows the results.

(Examples 2-3, Comparative Example 1)
A polyimide film was prepared and heat-treated in the same manner as in Example 1, except that the amount of the organic phosphorus compound added and/or the average particle size of the inorganic particles was changed as shown in Table 1. to obtain a graphite sheet. Each physical property of the obtained graphite sheet was measured and evaluated. Table 1 shows the results.

(Example 4)
In the production of polyimide film, 4,4'-diaminodiphenyl ether (ODA) 85 mol% and 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) 15 mol% dissolved in dimethyl 100 mol % of pyromellitic dianhydride (PMDA) was dissolved in a formamide solution to obtain a polyamic acid solution containing 18.5% by weight of polyamic acid. Triphenyl phosphate (TPP), which is an organic phosphorous compound, was added to the obtained polyamic acid solution so that the concentration of the triphenyl phosphate was 0.00% relative to 100% by weight of the solid content (polyamic acid) in the polyamic acid solution. Add so as to be 3% by weight, further calcium hydrogen phosphate (inorganic particles) with an average particle size of 2.2 μm, the concentration of the calcium hydrogen phosphate is the solid content of the polyamic acid solution (polyamic acid) 100 weight % to 0.08% by weight.

(Examples 5-6, Comparative Example 2)
A polyimide film was prepared and heat-treated in the same manner as in Example 4, except that the amount of the organic phosphorus compound added and/or the average particle size of the inorganic particles was changed as shown in Table 2. to obtain a graphite sheet. Each physical property of the obtained graphite sheet was measured and evaluated. Table 1 shows the results.

(Comparative Example 3)
Except for using 100 mol% of PMDA instead of 90 mol% of pyromellitic dianhydride (PMDA) and not using 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) A polyimide film was prepared in the same manner as in Example 2 and heat-treated to obtain a graphite sheet. Each physical property of the obtained graphite sheet was measured and evaluated. Table 1 shows the results.

〔summary〕
Table 1 clearly shows the following.

From Examples 1 to 3, the polyimide film contains 90 mol% (within the range of 50 to 100 mol%) of PMDA and 10 mol% (within the range of 0 to 50 mol%) of BTDA as the acid dianhydride component. and 100 mol% (within the range of 50 to 100 mol%) of ODA as a diamine component, and 0.3 to 1.1% by weight (0.1 to 5.0 The graphite sheet obtained by heat-treating a polyimide film containing 135 μm in thickness before heat treatment has a thickness of 135 μm before heat treatment. It can be seen that the graphite sheet is excellent in Also, from a comparison between Examples 1 to 3 and Comparative Example 1, it can be seen that a graphite sheet having a higher density can be provided by including an organophosphorus compound in the polyimide film.

From Examples 4 to 6, the polyimide film contains 100 mol% PMDA (within the range of 50 to 100 mol%) as the acid dianhydride component and 85 mol% ODA as the diamine component (50 to 100 mol% ), 15 mol% (within the range of 0 to 50 mol%) of BAPP, and 0.3 to 1.1% by weight (0.1 to 5.0 The graphite sheet obtained by heat-treating the polyimide film containing 135 μm in thickness before the heat treatment was heat-treated at a relatively high heating rate of 0.5° C./min. The thickness of the graphite sheet obtained by rolling is sufficiently thin. That is, it can be seen that the graphite sheet is excellent in productivity, in which excessive foaming does not occur even when heat-treated at a relatively high rate of temperature rise. Further, from a comparison between Examples 4 to 6 and Comparative Example 2, it can be seen that a graphite sheet having a higher density can be provided by including an organophosphorus compound in the polyimide film.

Further, from Comparative Example 3, a polyimide film that did not use, as a raw material, a monomer that disturbs the orientation of the polyimide film, such as BTDA, ODPA, or BAPP, was heated at a relatively high heating rate of 0.5° C./min. When the temperature is raised, the surface of the graphite sheet to be obtained is greatly foamed, and the thickness before rolling is excessively large. I understand. Moreover, the density of the resulting graphite sheet is also low, and it can be seen that a graphite sheet having a high density cannot be provided.

From the above results, it was shown that the polyimide film according to one embodiment of the present invention can provide a high-density graphite sheet, particularly a high-density thick graphite sheet, with good productivity.

According to the polyimide film according to one embodiment of the present invention, a graphite sheet with high density can be provided with good productivity. A graphite sheet with such a high density can be suitably used as a heat dissipation member for electronic devices, particularly thin electronic devices.

Claims

A polyimide film made from an acid dianhydride component and a diamine component,
The acid dianhydride component contains 50 to 100 mol% of pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic acid in 100 mol% of the total amount of the dianhydride component. 0 to 50 mol% of at least one of acid dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA),
The diamine component contains 50 to 100 mol% of 4,4′-diaminodiphenyl ether (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane ( BAPP) containing 0 to 50 mol%,
The 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and the 4,4′-oxydiphthalic acid dianhydride with respect to 200 mol % of the total amount of the acid dianhydride component and the diamine component The total content of anhydride (ODPA) and the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 1 to 50 mol%,
A polyimide film for a graphite sheet, containing 0.1 to 5.0% by weight of an organic phosphorus compound in 100% by weight of the total amount of the polyimide film.
The acid dianhydride component contains 100 mol% pyromellitic dianhydride (PMDA), and the diamine component contains 4,4′-diaminodiphenyl ether (ODA) in an amount of 50 to 99 mol%, 2,2-bis The polyimide film for a graphite sheet according to claim 1, containing 1 to 50 mol% of [4-(4-aminophenoxy)phenyl]propane (BAPP).
As the diamine component, 4,4'-diaminodiphenyl ether (ODA) is contained in an amount of 100 mol%, and as the acid dianhydride component, pyromellitic dianhydride (PMDA) is contained in an amount of 50 to 99 mol%, 3,3', The graphite sheet according to claim 1, containing 1 to 50 mol% of at least one of 4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA). polyimide film for
The polyimide film for graphite sheets according to claim 1, which has a thickness of 80 to 200 μm.
The polyimide film for a graphite sheet according to claim 1, wherein the organophosphorus compound contains an organophosphorus compound in which the valence of phosphorus is pentavalent.
The polyimide film for a graphite sheet according to claim 1, wherein the organophosphorus compound has a temperature of 200°C or higher at which the weight loss rate becomes 5% in TG-DTA measurement.
A graphite sheet containing the polyimide film for a graphite sheet according to any one of claims 1 to 6 as a raw material.
A step of mixing an acid dianhydride component and a diamine component to obtain a polyamic acid, and
A method for producing a polyimide film, comprising a step of adding 0.1 to 5.0% by weight of an organic phosphorus compound with respect to 100% by weight of the polyamic acid,
The acid dianhydride component contains 50 to 100 mol% of pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic acid in 100 mol% of the total amount of the dianhydride component. 0 to 50 mol% of at least one of acid dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA),
The diamine component contains 50 to 100 mol% of 4,4′-diaminodiphenyl ether (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane ( BAPP) containing 0 to 50 mol%,
The 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and the 4,4′-oxydiphthalic acid dianhydride with respect to 200 mol % of the total amount of the acid dianhydride component and the diamine component the total content of anhydride (ODPA) and the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 1 to 50 mol%;
A method for producing a polyimide film.
A method for producing a graphite sheet, comprising a step of heat-treating a polyimide film for a graphite sheet at 2400° C. or higher,
The polyimide film for the graphite sheet is a polyimide film made from an acid dianhydride component and a diamine component,
The acid dianhydride component contains 50 to 100 mol% of pyromellitic dianhydride (PMDA) and 3,3′,4,4′-benzophenonetetracarboxylic acid in 100 mol% of the total amount of the dianhydride component. 0 to 50 mol% of at least one of acid dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA),
The diamine component contains 50 to 100 mol% of 4,4′-diaminodiphenyl ether (ODA), 2,2-bis[4-(4-aminophenoxy)phenyl]propane ( BAPP) containing 0 to 50 mol%,
The 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and the 4,4′-oxydiphthalic acid dianhydride with respect to 200 mol % of the total amount of the acid dianhydride component and the diamine component The total content of anhydride (ODPA) and the 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) is 1 to 50 mol%,
A method for producing a graphite sheet, which is a polyimide film containing 0.1 to 5.0% by weight of an organic phosphorus compound in 100% by weight of the total amount of the polyimide film.
The polyimide film for the graphite sheet contains 100 mol% of pyromellitic dianhydride (PMDA) as the acid dianhydride component, and 50 to 4,4'-diaminodiphenyl ether (ODA) as the diamine component. 10. The method for producing a graphite sheet according to claim 9, comprising 99 mol% and 1 to 50 mol% of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP).
The polyimide film for the graphite sheet contains 100 mol% of 4,4'-diaminodiphenyl ether (ODA) as the diamine component, and pyromellitic dianhydride (PMDA) as the acid dianhydride component from 50 to 99 mol%, containing 1 to 50 mol% of at least one of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4'-oxydiphthalic dianhydride (ODPA) 10. The method for producing a graphite sheet according to claim 9.
The method for producing a graphite sheet according to claim 9, wherein the polyimide film for the graphite sheet has a thickness of 80 to 200 µm.
The method for producing a graphite sheet according to claim 9, wherein the polyimide film for the graphite sheet contains, as the organic phosphorus compound, an organic phosphorus compound in which the valence of phosphorus is pentavalent.
10. The method for producing a graphite sheet according to claim 9, wherein the organophosphorus compound contained in the polyimide film for the graphite sheet has a temperature of 200° C. or higher at which the weight loss rate is 5% in TG-DTA measurement. .