WO2016088753A1

WO2016088753A1 - Flake graphite, graphite material, and flake graphite dispersion

Info

Publication number: WO2016088753A1
Application number: PCT/JP2015/083749
Authority: WO
Inventors: 誠司武
Original assignee: 大日本印刷株式会社
Priority date: 2014-12-02
Filing date: 2015-12-01
Publication date: 2016-06-09
Also published as: JP6565641B2; JP2016108234A

Abstract

Provided are flake graphite having excellent conductivity and a flake graphite dispersion and flake graphite material including the flake graphite. The flake graphite has a percentage of counts of fluorine (-) ions to the total count of all (-) ions measured using Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) of 0.5% or more, an average spacing (d002) between (002) planes according to X-ray diffraction of 0.336 nm or less, and an average thickness of 50 nm or less.

Description

Flaky graphite, graphite material, and flaky graphite dispersion

The present invention relates to flaky graphite, graphite material, and flaky graphite dispersion.

Graphene, which has a single layer structure of graphite (graphite), is a two-dimensional planar crystal in which carbon six-membered rings are connected in a planar direction, and has excellent conductivity, thermal conductivity, and the like. In order to draw out the excellent conductivity and thermal conductivity of graphene, it is required to use single-layer graphene or graphene multi-layered in the range of 50 nm or less (hereinafter referred to as flake graphite).
Attempts have been made to obtain a high-performance conductive film or heat conductive film by depositing such flaky graphite.

As a method for depositing flaky graphite, a chemical vapor deposition method (CVD method), a solution coating method, and the like are known. Among these, a solution coating method is attracting attention because it can be formed at a low cost.
When flaky graphite is formed by a solution coating method, it is necessary to disperse the flaky graphite in the solution.

As a method of exfoliating from graphite to obtain flaky graphite, a method is known in which graphite is oxidized and subjected to exfoliation treatment as graphite oxide that can be easily exfoliated, and then the graphite oxide is reduced (for example, Patent Document 1). However, in this method, there is a problem that even if the graphite oxide is reduced, the graphite oxide remains or does not return to the original graphene structure after the reduction. Since graphite oxide has insulating properties, and electrons do not move unless the sp2 structure has two-dimensionally spread π electrons, it is said that the conductivity is low even when the flaky graphite obtained by this method is formed. There was a problem.

As a method for exfoliating graphite without oxidization to obtain flaky graphite, a method is known in which graphite is added in a polar solvent such as water and dispersed using ultrasonic waves (for example, non-patent literature). 1, 2). However, these methods have a problem in that the thickness distribution of the exfoliated graphite is widened, and graphite that is not sufficiently flaked remains so that it cannot be ignored.
Further, as another method for exfoliating graphite without oxidization to obtain flake graphite, Patent Document 2 discloses a thin-layer graphite having a high-pressure emulsification treatment step for exfoliating graphite or a graphite compound layer by a high-pressure emulsification method. A method for producing a thin graphite compound is disclosed. However, in the method of Patent Document 2, the graphite exfoliates during the emulsification process, and the exfoliated graphite also aggregates, and the thickness distribution of the exfoliated graphite is widened similarly to the ultrasonic method, and is sufficiently thinned. There was a problem that untreated graphite remained so much that it could not be ignored.
As described above, in the conventional manufacturing method, graphite oxide remains or many graphites that are not sufficiently flaked remain, so that it has been difficult to obtain flaky graphite having excellent conductivity.
In the conventional manufacturing method, in order to form a film having excellent electrical conductivity and thermal conductivity, it is necessary to perform a treatment such as classification in order to remove graphite that has not been sufficiently exfoliated. The yield of flaky graphite that can be used to obtain the properties was low.

Japanese Translation of PCT International Publication No. 2011-500488 JP 2014-9151 A

The present invention has been made in view of the above circumstances, and provides a flaky graphite and a graphite material excellent in conductivity and thermal conductivity, and a flaky graphite dispersion containing the flaky graphite. Objective.
Another object of the present invention is to provide a method for producing the flaky graphite, a method for producing the graphite material, and a method for producing the flaky graphite dispersion excellent in conductivity and thermal conductivity.
Further, a method for producing flaky graphite capable of obtaining flaky graphite in a high yield, a method for producing a flaky graphite dispersion with little residual graphite that is insufficiently flaked, and conductivity and thermal conductivity A third object is to provide a method for producing an excellent graphite material.

The flaky graphite according to the first aspect of the present invention for solving the first object is a total count of all (−) ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The ratio of the number of fluorine (−) ions to the number is 0.5% or more, the average (002) plane spacing (d002) by X-ray diffraction is 0.336 nm or less, and the average thickness is 50 nm. It is characterized by the following.
The graphite material according to the first present invention for solving the first object is characterized in that the flaky graphite according to the present invention is laminated.
The flaky graphite dispersion according to the first aspect of the present invention for solving the first object is characterized in that the flaky graphite according to the present invention is dispersed in a solvent.

The method for producing flaky graphite according to at least some embodiments of the second present invention for solving the second object is obtained by adding graphite to a fluorine-based solvent having a surface tension at a use temperature of 20 mN / m or less. And a dispersant having a solubility in the solvent of less than 0.1 (g / 100 g solvent) and a dispersion treatment.

The method for producing a flaky graphite dispersion according to at least some embodiments of the second present invention for solving the second object is applied to a fluorine-based solvent having a surface tension at a use temperature of 20 mN / m or less. Mixing graphite with a dispersant having a solubility in the solvent of less than 0.1 (g / 100 g solvent), and carrying out a dispersion treatment;
(I) or (ii) below:
(I) removing a fluorine-based solvent having a surface tension at the use temperature of 20 mN / m or less from the mixed solution after the dispersion treatment;
(Ii) adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more to the mixture from which the solvent has been removed; g / 100 g solvent) or higher step,
It has any one of the processes of removing the fluorine-type solvent whose surface tension in the said use temperature is 20 mN / m or less from the liquid mixture after the said solvent addition.

In order to solve the second object, a method for producing a graphite material according to at least some embodiments of the present invention includes: a fluorine-based solvent having a surface tension at a use temperature of 20 mN / m or less; Mixing with a dispersant having a solubility in the solvent of less than 0.1 (g / 100 g solvent), and carrying out a dispersion treatment;
(I) or (ii) below:
(I) removing a fluorine-based solvent having a surface tension at the use temperature of 20 mN / m or less from the mixed solution after the dispersion treatment;
(Ii) adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more to the mixture from which the solvent has been removed; g / 100 g solvent) or higher step,
A step of making a flaky graphite dispersion by any step of removing a fluorine-based solvent having a surface tension at the use temperature of 20 mN / m or less from the mixed solution after the addition of the solvent;
And a step of forming or molding the flaky graphite dispersion.

The method for producing flaky graphite according to at least some embodiments of the third aspect of the present invention for solving the third object includes, in a solvent having a surface tension at a use temperature of 20 mN / m or less, graphite, It has the process of mixing with the dispersing agent whose solubility with respect to the said solvent is less than 0.1 (g / 100g solvent), and carrying out a dispersion process.

The method for producing a flaky graphite dispersion according to at least some embodiments of the third aspect of the present invention for solving the third object is characterized in that graphite is used in a solvent having a surface tension at a use temperature of 20 mN / m or less. Mixing with a dispersant having a solubility in the solvent of less than 0.1 (g / 100 g solvent), and a dispersion treatment;
(I) or (ii) below:
(I) removing a solvent having a surface tension of 20 mN / m or less from the mixed solution after the dispersion treatment;
(Ii) adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more to the mixture from which the solvent has been removed; g / 100 g solvent) or higher step,
It has one of the processes of removing the solvent whose surface tension at the said use temperature is 20 mN / m or less from the liquid mixture after the said solvent addition.

A method for producing a graphite material according to at least some embodiments of the third aspect of the present invention for solving the third object includes: a solvent having a surface tension at a use temperature of 20 mN / m or less, graphite, Mixing with a dispersant having a solubility in a solvent of less than 0.1 (g / 100 g solvent), and carrying out a dispersion treatment;
(I) or (ii) below:
(I) removing a solvent having a surface tension of 20 mN / m or less from the mixed solution after the dispersion treatment;
(Ii) adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more to the mixture from which the solvent has been removed; g / 100 g solvent) or higher step,
A step of making a flaky graphite dispersion by any one of steps of removing a solvent having a surface tension of 20 mN / m or less from the mixed solution after addition of the solvent;
And a step of forming or molding the flaky graphite dispersion.

According to the first aspect of the present invention, it is possible to provide flaky graphite and a graphite material excellent in conductivity and thermal conductivity, and a flaky graphite dispersion containing the flaky graphite.
In addition, according to the second aspect of the present invention, a method for producing flaky graphite capable of obtaining flaky graphite excellent in conductivity and thermal conductivity in a high yield, and there is little residual graphite that is insufficiently flaked. A method for producing a flaky graphite dispersion and a method for producing a graphite material excellent in conductivity and thermal conductivity can be provided.
Furthermore, according to the third aspect of the present invention, a method for producing flaky graphite capable of obtaining flaky graphite excellent in conductivity and thermal conductivity in a high yield, and there is little residual graphite that is insufficiently flaked. A method for producing a flaky graphite dispersion and a method for producing a graphite material excellent in conductivity and thermal conductivity can be provided.

FIG. 6 shows the measurement results of the graphite film 1 according to the present invention obtained in Example 1-3 by the X-ray diffraction method. FIG. 3 is a SEM photograph of the graphite film 1 according to the present invention obtained in Example 1-3. 4 is an SEM photograph of comparative graphite film 1 obtained in Comparative Example 1-3. 9 is one of AFM photographs of flaky graphite 1 according to the present invention obtained in Example 8. FIG. 7 is a measurement result of the graphite film 8 according to the present invention obtained in Example 8 by X-ray photoelectron spectroscopy. It is an enlarged view of the peak of a carbon atom among the measurement results by X-ray photoelectron spectroscopy of the graphite film 8 according to the present invention obtained in Example 8. It is one of the measurement results by the Raman spectroscopy of the graphite film 8 according to the present invention obtained in Example 8.

Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the spirit thereof. Further, in the description of the embodiments of the present invention, the description “according to the present invention” means “according to at least some embodiments of the present invention”.
I. First and second inventions Hereinafter, flaky graphite according to the first invention, flaky graphite dispersion, and graphite material, and suitable for producing these products of the first invention, A method for producing flaky graphite, a method for producing a flaky graphite dispersion, and a method for producing a graphite material according to the second aspect of the present invention will be described in order.
In the present invention, flaky graphite includes single-layer graphene and graphene that is multilayered in a thickness range of 50 nm or less.
Further, in the present invention, the surface tension is defined as free energy per unit area surplus compared to the inside of the liquid, which the liquid surface has.

1. Flake-like graphite The flaky graphite according to the present invention is a fluorine (-) ion count relative to a total count of all (-) ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The ratio is 0.5% or more, the average interplanar spacing (d002) of (002) planes by an X-ray diffraction method is 0.336 nm or less, and the average thickness is 50 nm or less.

The flaky graphite according to the present invention is a flaky graphite containing at least one of single-layer graphene and multi-layer graphene, wherein the average thickness of the flakes is in the range of 50 nm or less, and is a time-of-flight secondary ion mass spectrometry The ratio of the number of fluorine (−) ions to the total number of all (−) ions measured using the method (TOF-SIMS) is 0.5% or more, and (002) by the X-ray diffraction method. ) Surface average surface spacing (d002) is 0.336 nm or less.
The flaky graphite of the present invention is a small amount of fluorine that is adsorbed or bound to promote exfoliation between the graphite flakes, so that the single-layer graphene or the average interplanar spacing (d002) is graphite. The graphene is multilayered at 0.336 nm or less, and has an average thickness of 50 nm or less, and has excellent conductivity and thermal conductivity. As flaky graphite (graphene) bonded with fluorine, fluorinated graphite having a composition represented by (C _m F) _n (m = 1 to 20) is known (by Shingo Watanabe, “Graphite Intercalation Compound”). Modern Editor, (1986)). However, since the fluorinated graphite has an average interplanar spacing (d002) of 0.809 nm, which is much wider than that of graphite and is insulative, the flaky graphite of the present invention has the above-mentioned fluorinated graphite and Are clearly distinguished. The above document also describes a carbon material obtained by doping graphite with hydrogen fluoride. However, since the carbon material has an average interplanar spacing (d002) of 0.55 nm to 1.28 nm, which is much wider than that of graphite, the flake graphite of the present invention is clearly different from the carbon material. It is a distinction. Although the carbon material is conductive, it is poor in stability because it is doped with gas, and there is a problem in workability.
On the other hand, the flaky graphite adsorbed or bound by a small amount of fluorine of the present invention is excellent in stability, and the exfoliated flaky graphite is more difficult to reagglomerate and is excellent in workability. According to the present invention, the flaky graphite can be laminated as it is without being re-agglomerated, and a laminated body such as an integrated film can be arbitrarily formed. Therefore, a graphite material having excellent conductivity and thermal conductivity can be obtained. Obtainable.

Since the amount of fluorine adsorbed or bonded to the flaky graphite of the present invention is very small, it has been proved effective to use time-of-flight secondary ion mass spectrometry. Time-of-flight secondary ion mass spectrometry is an apparatus for examining what components (atoms and molecules) exist on the outermost surface of a solid sample. According to time-of-flight secondary ion mass spectrometry, it is possible to detect a trace amount component that cannot be detected by X-ray photoelectron spectroscopy described later.
The time-of-flight secondary ion mass spectrometry (TOF-SIMS) is detected by irradiating 69 Ga ⁺ using a time-of-flight secondary ion mass spectrometer (for example, Physical Electronics, model name: TRIFT II). NEGATIVE secondary ions are detected as secondary ion mass spectra. The total count number of all (−) ions and the count number of fluorine (−) ions, measured by the time-of-flight secondary ion mass spectrometry, are measured. The ratio of the number of fluorine (−) ions can be calculated.
In the flaky graphite of the present invention, the ratio of the fluorine (−) ion count to the total count of all ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0.00. Although it is 5% or more, the ratio is preferably 10% or less, more preferably 5% or less, from the viewpoint of making the graphite material or flaky graphite superior in conductivity and thermal conductivity. Further, it is preferably 3% or less. Since the ratio of the count number of fluorine (−) ions that can be regarded as noise may be about 0.2%, it is set to 0.5% or more from the viewpoint of excluding noise. Among them, the ratio of the fluorine (−) ion count is preferably 0.8% or more, and more preferably 1% or more.

In addition, the flake graphite of the present invention reduces graphene oxide because, as will be described later, fluorine is adsorbed or bonded to promote the exfoliation between flakes of graphite (graphite). As compared with the flaky graphite produced in this way, the number of oxygen atoms is reduced, the proportion of bonds forming sp2 bonds between carbon atoms can be increased, and the conductivity and thermal conductivity are high. is there.
In the flaky graphite of the present invention, the composition of carbon atoms is preferably 80% or more, more preferably 90% or more, and even more preferably 92% or more as measured by X-ray photoelectron spectroscopy. Preferably, it is still more preferably 95% or more. The composition of carbon atoms may be 100% as measured by X-ray photoelectron spectroscopy, but usually it is preferably 99% or less because some oxygen atoms are contained.
In the flaky graphite of the present invention, the composition of oxygen atoms is preferably 10% or less, more preferably less than 10%, more preferably 7% or less, as measured by X-ray photoelectron spectroscopy. More preferably, it is 5% or less.

In the flaky graphite of the present invention, since only a very small amount of fluorine atoms is present, the composition of fluorine atoms may be measured as 0% in the measurement by X-ray photoelectron spectroscopy.
Further, the flaky graphite of the present invention contains atoms different from carbon atoms and oxygen atoms, for example, sulfur atoms, nitrogen atoms, etc., as measured by X-ray photoelectron spectroscopy due to the influence of the dispersant described later. May be. The total composition of atoms different from carbon atoms and oxygen atoms is preferably 5% or less, more preferably 3% or less, and more preferably 2% or less, as measured by X-ray photoelectron spectroscopy. Further preferred.
That is, in the flaky graphite of the present invention, the sum of the carbon atom composition and the oxygen atom composition is preferably 95% or more, more preferably 97% or more, as measured by X-ray photoelectron spectroscopy. 98% or more is even more preferable.

In the flaky graphite of the present invention, among the bonds of the carbon atoms, the ratio of the bonds forming sp2 bonds between the carbon atoms is determined by X-ray photoelectron spectroscopy from the viewpoint of excellent conductivity and thermal conductivity. Is preferably 60% or more, more preferably 70% or more, and even more preferably 75% or more. The higher the ratio of bonds that form sp2 bonds between carbon atoms, the better. The upper limit of the ratio of bonds that form sp2 bonds between carbon atoms is 100%. is there.

In the flaky graphite of the present invention, the ratio of oxygen atoms bonded to carbon atoms out of all carbon atoms measured by X-ray photoelectron spectroscopy (number of oxygen atoms bonded to carbon atoms / total number of carbon atoms) ) Is preferably 0.2 or less, more preferably 0.15 or less, and even more preferably 0.1 or less.
Here, the measurement by X-ray photoelectron spectroscopy is performed by irradiating the sample with X-rays using an X-ray photoelectron spectrometer such as Thermo Fisher Scientific (VG Theta Probe) or ULVAC-PHI (PHI5000 Versa Probe). This can be done by analyzing the spectrum of secondary electrons detected. The percentage represents an atomic percentage.
In addition, the ratio of bonds that form sp2 bonds between carbon atoms is such that the peak of carbon atoms is expanded, and the bonds that form sp2 bonds between carbon atoms (binding energy about 284.6 eV) and carbon atoms The peak separation is performed on the bonds that form sp3 bonds in (bond energy of about 285.5 eV), so that the ratio of the bonds that form sp2 bonds between the carbon atoms among the bonds of the carbon atoms is determined. Can be calculated. Similarly, by expanding the peak of the oxygen atom and performing peak separation into the bond between the oxygen atom and the carbon atom and, for example, the bond between the oxygen atom and the sulfur atom, the oxygen atom is bonded to the carbon atom. The calculated oxygen atomic ratio can be calculated. For the peak shift due to the binding of oxygen atoms to other molecules and the binding energy, reference can be made to the books (for example, edited by Someno Dan, “Surface Analysis”, Kodansha (1976) p274).

In addition, since the flaky graphite of the present invention has good crystallinity, the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and 1580 to 1620 cm ⁻¹ measured by a Raman spectrum are used. The intensity ratio I _D / I _G to the peak intensity (I _G ) in the range is preferably 0.3 or less, more preferably 0.15 or less, and even more preferably 0.10 or less. preferable. The intensity ratio I _D / I _G is usually 0 in the case of raw material graphite, and is 0 or more.
Further, _'the intensity ratio I _G of the peak intensity _{(I G)} in the range of 1580 ~ 1620cm ^-1 / I peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 measured by Raman spectroscopy _G is preferably 0.1 or more, more preferably 0.2 or more, and still more preferably 0.3 or more. The intensity ratio I _{G ′} / I _G usually increases as the thickness of the flaky graphite decreases, and becomes 2 when the thickness is about 0.34 nm (graphene monoatomic layer).
The spectrum in the range of 1300 to 1400 cm ⁻¹ measured by the Raman spectroscopic spectrum is a band (D band) that appears when there is a crystal defect, and the spectrum in the range of 1580 to 1620 cm ⁻¹ is sp2 This is a band (G band) that is commonly observed in the case of a hybrid orbit (the number of C—C bonding hands is three). A spectrum in the range of 2600 to 2800 cm ⁻¹ is also a band (G ′ band) that is commonly observed in the case of sp2 hybrid orbitals.

The flaky graphite of the present invention has a thickness of 1 atom or more of carbon, and has an average thickness of about 0.34 nm to 50 nm. The average thickness of the flaky graphite of the present invention is preferably from about 0.34 nm to about 40 nm, more preferably from about 0.34 nm to about 30 nm, and even more preferably from about 0.34 nm to about 15 nm. desirable. In addition, the thickness of the flaky graphite of the present invention refers to the maximum dimension of the flaky graphite in a direction orthogonal to the surface of the flaky graphite when viewed from the direction in which the area of the flaky graphite is maximized.
The thickness of the flaky graphite of the present invention can be measured using an atomic force microscope (AFM).
The average thickness of the flaky graphite of the present invention is obtained by measuring the thickness with AFM in a state where the flaky graphite is independently dispersed on the substrate, and calculating the average value of the measured values of the thickness of 200 flaky graphites. Can be sought.

More specifically, the average thickness can be obtained as follows.
A membrane having a pore size of 0.02 μm or less after sampling a flake graphite, a mixed liquid containing flake graphite, or a flake graphite dispersion, diluting with a solvent 20 to 2000 times without dispersing flakes The solvent is filtered off by coating on a filter, and the flake graphite is placed on the membrane filter in an independent state without agglomerating. When the dispersant is adhered, the dispersant may be removed by washing the flaky graphite with a solvent having a solubility of 5 (g / 100 g solvent) or more. The flaky graphite is transferred onto the silicon wafer by pressing and removing the washed silicon wafer against the flaky graphite arranged in an independent state without agglomerating on the membrane filter. The flake graphite adhering to the silicon wafer in an independently dispersed state is measured by AFM, and the thickness of the flake is measured. The AFM measurement uses the scanning probe microscope (SPM) function of the Shimadzu Nano Search Microscope SFT-3500, and the scanning range is set to 10 μm × 10 μm in the contact mode, that is, AFM (Atomic Force Microscope). Measurements can be made. The difference in height between the silicon wafer and the flaky graphite in the flaky graphite adhering to the silicon wafer is defined as the thickness of the flaky graphite.
The average thickness of flaky graphite is calculated by repeating the above operation until a total of 200 pieces of flaky graphite can be observed by AFM, and calculating the average value of the measured thickness of 200 pieces of flaky graphite observed by AFM. Can be obtained.

In the flaky graphite of the present invention, the content ratio of the flaky graphite having a flake thickness of 50 nm or less to the whole flaky graphite is preferably 70% by number or more. From the viewpoint of excellent electrical conductivity and thermal conductivity, the content ratio of the flake graphite having a flake thickness of 50 nm or less to the whole flake graphite is preferably as large as possible, more preferably 80% by number or more, and 90% by number. It is still more preferable that it is above. Among them, the content ratio of the flake graphite having a thickness of 0.34 nm or more and less than 10 nm to the whole flake graphite is preferably 10% by number or more, and more preferably 20% by number or more.
The number% represents the ratio of the number of flake graphite having the corresponding thickness to the total number of flake graphite. The number% can be calculated by obtaining the number of flake graphite having a corresponding thickness out of 200 observed by AFM, and obtaining the number ratio in the 200 pieces.

The plane direction size of the flaky graphite of the present invention refers to the size of the surface of the flaky graphite when viewed from the direction in which the area of the flaky graphite is maximized, and the maximum diameter is 0.05 μm or more and 100 μm or less. It is preferably within the range, more preferably within the range of 0.1 μm to 50 μm, and even more preferably within the range of 0.5 μm to 30 μm. The size in the plane direction can be measured by direct observation with an optical microscope, an electron microscope, an atomic force microscope, or the like. Similarly to the average thickness, the average maximum diameter can be obtained by calculating the average value of the maximum diameters of 200 flake graphite measured with a microscope.
Each of the flaky graphites of the present invention preferably has an aspect ratio (maximum diameter / thickness) of 3 or more, more preferably 10 or more. The average aspect ratio (average maximum diameter / average thickness) of the flaky graphite of the present invention is preferably 3 or more, and more preferably 10 or more.

The flaky graphite of the present invention can be produced, for example, by the method for producing flaky graphite of the second invention described later.

[Method for producing flaky graphite]
The method for producing flaky graphite according to the second aspect of the present invention comprises a fluorine-based solvent having a surface tension at a working temperature of 20 mN / m or less, graphite and a solubility in the solvent of less than 0.1 (g / 100 g solvent). It is characterized by having a step of mixing with a dispersant and performing a dispersion treatment (hereinafter sometimes referred to as a dispersion treatment step).

The flaky graphite obtained by the method for producing flaky graphite has a high ratio of single-layer graphene and graphene multi-layered in a range of 50 nm or less, and is not oxidized. Also have excellent electrical and thermal conductivity. In addition, since graphite that has not been sufficiently flaked does not remain, the weight of graphite is hardly reduced even after classification, and flaky graphite can be obtained with a high recovery rate. When the method for producing flaky graphite is used, the ratio of single-layer graphene and graphene multi-layered in a range of 50 nm or less is a yield of 20% by mass or more, more preferably a yield of 50% by mass or more. It is possible to obtain flaky graphite with a yield of 70% by mass or more, more preferably with a yield of 75% by mass or more, and obtain flaky graphite with a yield of 100% by mass. It is also possible.

According to the method for producing flaky graphite, exfoliation between graphite flakes easily proceeds to produce flaky graphite, and the flaky graphite is less likely to re-aggregate, so that it has excellent conductivity and thermal conductivity. The flake graphite can be obtained with high yield.
Graphite (graphite) has a structure in which graphene having a two-dimensional structure is laminated in multiple layers. In the graphite, van der Waals force is generated between the respective layers, and it is estimated that the graphite is bonded with a relatively weak force.
A fluorine-based solvent having a surface tension at a use temperature of 20 mN / m or less is presumed to easily enter between the graphite layers because of its relatively low polarity and low surface tension. By performing a dispersion treatment using such a solvent, it is presumed that the exfoliation of graphite is promoted and flaky graphite is easily generated.
In the method for producing flaky graphite, a dispersant having a solubility in a fluorinated solvent having a surface tension of 20 mN / m or less at the use temperature is less than 0.1 (g / 100 g solvent) is used in combination. Thus, by selecting and using a dispersant having low solubility in the fluorinated solvent, when the dispersant is a liquid, the mixed solution at the time of the dispersion treatment is divided into two phases: the solvent phase and the dispersant phase. Thus, graphite and flaky graphite tend to be present in the dispersant phase having a close polarity.
In such a non-uniform liquid, since a dispersing agent exists around the flaky graphite produced by the dispersion treatment, the flaky graphite is prevented from agglomerating immediately. Moreover, if a dispersing agent is highly viscous, the contact between flake graphite will be suppressed by that amount, and as a result, aggregation of flake graphite will be suppressed. Furthermore, in such a production method, since the dispersant phase is separated from the solvent phase, the flake graphite adsorbed by the dispersant moves to the dispersant phase, and reagglomeration is more easily suppressed. It is estimated to be.
When the dispersant is a solid, the mixed solution at the time of the dispersion treatment is a heterogeneous system containing solid graphite and a solid dispersant in the solvent phase, and both the graphite and the dispersant are contained in the solvent. Since the affinity for graphite is relatively high in the solvent phase and the dispersant is present around the flake graphite produced by the dispersion treatment, the flake graphite is It is estimated that aggregation is suppressed and dispersibility is improved.
From the above, according to the method for producing flaky graphite, a small amount of fluorine is adsorbed or bonded, and peeling of the graphite easily proceeds to produce flaky graphite. Aggregation hardly occurs, and the flaky graphite according to the present invention can be obtained in a high yield.

The method for producing the flaky graphite has at least a dispersion treatment step, and may further include other steps as needed within the range not impairing the effects of the present invention. Hereinafter, a method for producing such flaky graphite will be described in detail in order.

<Graphite>
Examples of the graphite used as a raw material in the present invention include natural graphite, artificial graphite, quiche graphite, and highly oriented pyrolytic graphite, and natural graphite is particularly preferable. Natural graphite is classified into earthy graphite and scaly graphite, but scaly graphite is particularly preferable. This is because scaly graphite has little ash and high purity. Graphene flakes obtained by pulverizing graphite have recently been commercialized by XGscience and can be used as a raw material. Further, expanded graphite in which the interlayer of these graphites is expanded in advance can also be used. The size of the graphite is not particularly limited, but is selected according to the size of the flaky graphite to be finally obtained.
The particle diameter of the graphite before the dispersion treatment is not particularly limited as long as it is a size that enables the dispersion treatment, but those having a maximum diameter of 100 μm or less are preferably used.

<Fluorine-based solvent with surface tension at operating temperature of 20 mN / m or less>
In the present invention, it is preferable to use a fluorine-based solvent having a surface tension at the use temperature of 20 mN / m or less as the solvent during the dispersion treatment. Since the specific solvent easily enters the graphite layer, the exfoliation of the graphite is likely to proceed. In addition, the use temperature here means the solvent temperature at the start of the dispersion treatment.

Specific examples of the fluorinated solvent having a surface tension at a use temperature of 20 mN / m or less include a fluorinated solvent having a fluorinated alkyl group, a fluorinated alkyl ether group or the like having a surface tension of 20 mN / m or less at 25 ° C. Is mentioned. For example, perfluorocarbon (for example, C _X F _{(2X + 2)} : about 16 mN / m when x = 12), hydrofluoroether (for example, C ₄ F ₉ OCH ₃ : 13.6 mN / m, C ₄ F ₉ OC ₂ H ₅ : 13.6 mN / m, C ₃ F ₇ OCH ₃ : 12.4 mN / m, C ₂ F ₅ CF (OCH ₃ ) C ₃ F ₇ : 15 mN / m, and hydrofluorocarbon (eg, C _X A solvent having a surface tension of 20 mN / m or less at the working temperature can be appropriately selected from H _y F _{(2X + 2−y)} : about 16 mN / m when x = 12, y = 1 to 12. In the present invention, it is preferable to use a fluorinated solvent having at least one of a fluorinated alkyl group and a fluorinated alkyl ether group, from the viewpoint of easily entering between graphite layers and facilitating peeling of the graphite.
In addition, the solvent is preferably a fluorine-based solvent having a surface tension of 15 mN / m or less at the working temperature because it easily enters the graphite layer and the peeling of the graphite easily proceeds.
In the present invention, the fluorine-based solvent having a surface tension at the use temperature of 20 mN / m or less can be used alone or in combination of two or more.

<Dispersant>
In the present invention, it is preferable to use a dispersant having a solubility in a fluorinated solvent having a surface tension of 20 mN / m or less at a use temperature of less than 0.1 (g / 100 g solvent).
By selecting and using such a dispersant, re-aggregation of the flaky graphite can be suppressed and the flaky graphite can be obtained in a high yield.

The dispersant may be appropriately selected and used from conventionally known dispersants capable of dispersing flaky graphite having a solubility in the solvent of less than 0.1 (g / 100 g solvent).
Examples of the dispersant include a compound having a hydrophobic group having a high affinity for flaky graphite and a hydrophilic group in one molecule. Examples of the hydrophobic group include a hydrocarbon group having 3 or more carbon atoms, more preferably 6 or more. Examples of the hydrophilic group include a hydroxyl group, a carboxy group, a sulfonic acid group, an amino group, and salts thereof. Is mentioned. As such a dispersant, for example, cationic, anionic, nonionic, amphoteric surfactants can be used. Further, as the dispersant, a polymer surfactant (polymer dispersant) may be used.

Examples of the dispersant include fatty acid salts such as sodium dodecanoate, monoalkyl sulfates such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, polyoxyethylene alkyl ether sulfate, and monoalkyl. Anionic surfactants such as phosphates, cationic surfactants such as alkylammonium salts, polyoxyethylene alkyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, Nonionic surfactants such as polyoxyethylene hydrogenated castor oil; amphoteric surfactants such as alkyldimethylamine oxide and alkylcarboxybetaine. In the case of anionic surfactants, the metal salts mentioned above are fatty acids, sulfonic acids, sulfuric acids, phosphoric acids, etc. without metal ions instead of salts, and in the case of cationic systems, amine structures may be used instead of ammonium salts. It can be used.
Examples of the polymer dispersant include (co) polymers of unsaturated carboxylic acid esters such as polyacrylic acid esters; (partial) amines of (co) polymers of unsaturated carboxylic acid such as polyacrylic acid. Salts, (partially) ammonium salts and (partially) alkylamine salts; (co) polymers of hydroxyl group-containing unsaturated carboxylic acid esters such as hydroxyl group-containing polyacrylates and their modified products; polyurethanes; polyethyleneimine and derivatives thereof Etc. As the polyurethane, a structure in which the main skeleton is polyurethane and the side chain has at least one of polyester and polyether chains and an alkylammonium salt is also preferably used.

In the present invention, a dispersant having a solubility of less than 0.1 (g / 100 g solvent) can be easily determined by the following evaluation method.
Into the sample tube, the solvent to be used in the production method of the present invention and the dispersant to be evaluated are added so as to have a concentration of 0.1 (g / 100 g solvent). After separating the agent, the mass of the remaining dispersant is measured, and the solubility is calculated. When the dispersant is completely dissolved in the solvent, the solubility of the dispersant in the solvent is determined to be 0.1 (g / 100 g solvent) or more.

In the present invention, the dispersant is, among others, flaky graphite described later that the solubility of the dispersant in the solvent used when preparing the flaky graphite dispersion described later is 5 (g / 100 g solvent) or more. It is preferable from the viewpoints of the dispersibility of the dispersion, and the conductivity and thermal conductivity of the flaky graphite and graphite material. When a dispersant having a high solubility as described above is selected and used with respect to the solvent used in preparing the flaky graphite dispersion described later, the dispersant dissolves in the graphite dispersion and is uniform. High dispersion. Furthermore, when preparing a graphite material using a flaky graphite dispersion, the dispersant is easily removed together with the solvent used in the flaky graphite dispersion, and the dispersant remaining in the graphite material is also removed. It can be easily removed by washing with a solvent, and conductivity and thermal conductivity are improved.

Further, in the present invention, the dispersant is solid or liquid at room temperature (25 ° C.), and the produced flake graphite is likely to move to the dispersant phase side, and reagglomeration is easily suppressed. To preferred.
Among them, the viscosity of the dispersant is 10 mPa · s or more at 25 ° C., because the mixed liquid containing the two phases of the solvent and the dispersant becomes a highly viscous liquid and suppresses reaggregation of the flake graphite. Further preferred. The viscosity of the dispersant is more preferably from 100 mPa · s to 50000 mPa · s at 25 ° C., and still more preferably from 100 mPa · s to 3000 mPa · s at 25 ° C.
In addition, the viscosity of the said dispersing agent says what is measured according to ASTM D4440 at 25 degreeC.
In this invention, a dispersing agent can be used individually by 1 type or in combination of 2 or more types.

<Distributed processing>
The flaky graphite is produced by mixing graphite and a dispersant having a solubility in the solvent of less than 0.1 (g / 100 g solvent) in a fluorine-based solvent having a surface tension of 20 mN / m or less at the operating temperature. Then, by dispersing the mixture using a conventionally known disperser, the exfoliation of the graphite easily proceeds to produce flaky graphite, and the flaky graphite is less likely to re-aggregate. Shaped graphite can be obtained with high yield.
Dispersers for performing dispersion processing include ultrasonic dispersers, roll mills such as 2-roll and 3-roll, attritors, Banbury mixers, paint shakers, kneaders, homogenizers, ball mills, sand mills, bead mills, jet mills, and mixers. A mill, mechanical stirring, etc. are mentioned. Among these, it is preferable to select and use a method suitable for dispersing a liquid having a high viscosity, such as a method capable of imparting a shearing force, and a ball mill using a pulverized ball is preferable. The ball shape of the ball mill is not particularly limited, but is preferably 1 mm to 100 mm, more preferably 5 mm to 50 mm.

The content ratio of each component of the mixed solution during the dispersion treatment is not particularly limited, and may be adjusted as appropriate. The content ratio of the graphite in the mixed liquid and the dispersant is preferably 1 part by mass or more and 500 parts by mass or less with respect to 1 part by mass of graphite from the viewpoint of suppressing reaggregation. More preferably, it is at least 100 parts by mass.
Further, the content ratio of graphite in the mixed solution and the solvent is such that the solvent is 10 masses with respect to 1 mass part of graphite from the viewpoint of increasing the separation efficiency from graphite and improving the yield of flaky graphite. Part or more and 100,000 parts by weight or less, more preferably 20 parts by weight or more and 50,000 parts by weight or less.

<Other processes>
The method for producing the flaky graphite may further include other steps as long as the effects of the present invention are not impaired. Examples of such a process include a process of removing a fluorine-based solvent having a surface tension of 20 mN / m or less at a use temperature for taking out flaky graphite, a process of dissolving and removing a dispersant, and the like. . The step of removing the solvent can be performed in the same manner as the solvent removing step of the method for producing the flaky graphite dispersion described later. In addition, the step of dissolving and removing the dispersant is performed by dissolving and washing the dispersant adhering to the surface of the flaky graphite using, for example, a solvent having a solubility of 5 (g / 100 g solvent) or more. This can be done.
It is also preferable to produce a flaky graphite dispersion in the same manner as the method for producing a flaky graphite dispersion described later, and obtain the flaky graphite from the flaky graphite dispersion.
Furthermore, a classification step for removing graphite that has not been sufficiently thinned may be included.
The classification step can be appropriately selected from conventionally known classification methods. On the other hand, the flaky graphite obtained by the production method has almost no graphite that has not been exfoliated sufficiently, so that the flaky graphite of the present invention is excellent in conductivity and thermal conductivity without performing the classification step. Can be obtained.

The flaky graphite of the present invention can be applied in various ways as graphene powder in various modes. Although illustrated below, it is not limited to these.
The flaky graphite of the present invention may be used as a dispersion containing a solvent, or may be used as a paste-like resin composition mixed with a resin or the like. The dispersion containing the flaky graphite can be used for producing a graphite material as described later, and can also be used as a conductive ink. Moreover, the resin composition containing the said flaky graphite can be used as a conductive paint or a conductive adhesive as a conductive resin composition.
Further, the flaky graphite of the present invention may be used as a film or a sheet or a molded body.
Furthermore, the flaky graphite of the present invention may be a polymer composite material, or may be used as a pellet, a wire or the like mixed with a resin.

2. Flaky graphite dispersion The flaky graphite dispersion according to the present invention is characterized in that the flaky graphite according to the present invention is dispersed in a solvent.
As described above, since the flaky graphite according to the present invention is excellent in conductivity and thermal conductivity, the flaky graphite dispersion according to the present invention is a graphite material having excellent conductivity and further excellent thermal conductivity. It is excellent as a pre-preparation for producing.
Further, a resin or the like may be added to the flaky graphite dispersion and used as a resin composition.

Since the flaky graphite according to the present invention has been described above, description thereof is omitted here.
The flaky graphite dispersion according to the present invention preferably contains a dispersant. As the dispersant, a dispersant similar to that described in the method for producing flaky graphite can be appropriately selected and used, and thus description thereof is omitted here.

The solvent contained in the flaky graphite dispersion according to the present invention is not particularly limited as long as it can disperse the flaky graphite according to the present invention. Especially, when the said dispersing agent is contained, it is preferable that the solubility of the said dispersing agent is 5 (g / 100g solvent) or more solvent.
As the solvent in which the solubility of the dispersant is 5 (g / 100 g solvent) or more, from the viewpoint of dispersion stability of the dispersion, a solvent in which the solubility of the dispersant is 10 (g / 100 g solvent) or more is used. It is preferable to select and use, and it is preferable to select and use a solvent that is 20 (g / 100 g solvent) or more.

The solvent having a dispersant solubility of 5 (g / 100 g solvent) or more may be appropriately selected depending on the dispersant. For example, water, methanol, phenol, acetonitrile, isopropyl alcohol, acetone, benzene, ethyl acetate Etc.
In the present invention, the solvent having a solubility of 5 (g / 100 g solvent) or more can be used alone or in combination of two or more.

The flaky graphite dispersion of the present invention can be produced, for example, by the method for producing a flaky graphite dispersion of the second invention described later.

[Method for producing flaky graphite dispersion]
The method for producing a flaky graphite dispersion according to the second aspect of the present invention comprises a fluorine-based solvent having a surface tension at a working temperature of 20 mN / m or less, graphite and a solubility in the solvent of 0.1 (g / 100 g solvent). A step of mixing and dispersing with less than a dispersant,
(I) or (ii) below:
(I) removing a fluorine-based solvent having a surface tension at the use temperature of 20 mN / m or less from the mixed solution after the dispersion treatment;
(Ii) adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more to the mixture from which the solvent has been removed; g / 100 g solvent) or higher step,
It has any one of the processes of removing the fluorine-type solvent whose surface tension in the said use temperature is 20 mN / m or less from the liquid mixture after the said solvent addition.

When the fluorine-based solvent having a surface tension at the use temperature of 20 mN / m or less and the solvent having a solubility of 5 (g / 100 g solvent) or more are phase-separated, the step (ii) is performed. It may be used. However, among these, it is preferable to have the step (i) because it can be easily obtained in a high yield.
The step of removing the fluorine-based solvent having a surface tension of 20 mN / m or less at the use temperature may be hereinafter referred to as a solvent removal step, and the solvent having a solubility of 5 (g / 100 g solvent) or more. Hereinafter, the step of adding may be referred to as a solvent addition step.

The method for producing a flaky graphite dispersion according to the present invention comprises a mixed solution containing flaky graphite obtained by the method for producing flaky graphite according to the present invention, wherein the surface tension at the use temperature is 20 mN / m or less. By removing the fluorinated solvent and adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more, it is possible to produce a flaky graphite dispersion liquid with little residual graphite. . By replacing the fluorine-based solvent having a surface tension of 20 mN / m or less at the use temperature included in the dispersion treatment with a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more, the solvent phase and the A dispersion that is a heterogeneous system including two phases of a dispersant phase can be made into a flaky graphite dispersion having a solvent and a dispersant as one phase.

The method for producing the flaky graphite dispersion has at least a dispersion treatment step, a solvent removal step, and a solvent addition step, and further other steps as necessary within the range not impairing the effects of the present invention. It may have. Hereinafter, the production method of such a flaky graphite dispersion will be described in detail in order, but the dispersion treatment step can be the same as the production method of the flaky graphite, and the description here is omitted. .

<Solvent removal step>
In the step (i), the fluorinated solvent having a surface tension at the use temperature of 20 mN / m or less is removed from the mixed solution obtained by the dispersion treatment step. By removing the solvent, a mixture of a dispersant and flaky graphite can be obtained as a residue.
The method for removing the solvent may be appropriately selected according to the solvent used. As a method for removing the solvent, decantation or filtration is preferable from the viewpoint of easy operation, and the solvent may be removed by appropriate heating or reduced pressure treatment.
In the step (ii), for example, the solvent phase can be removed by liquid separation utilizing the fact that the phases are separated.

<Solvent addition process>
In the step (i), a dispersion of flaky graphite is added to the mixture from which the solvent has been removed by the solvent removal step by adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more. Can be obtained. In the step (ii), a solvent having a solubility of 5 (g / 100 g solvent) or more is added before the solvent removing step.
As the solvent in which the solubility of the dispersant is 5 (g / 100 g solvent) or more, a solvent in which the solubility of the dispersant is 10 (g / 100 g solvent) or more is selected from the viewpoint of dispersion stability of the dispersion. It is preferable to select and use a solvent that is 20 (g / 100 g solvent) or more.
Since the solvent having a solubility of 5 (g / 100 g solvent) or more has been described above, the description thereof is omitted here.

The method for producing a flaky graphite dispersion of the present invention may further include other steps as long as the effects of the present invention are not impaired. Examples of other steps include a step of adding a resin and various additives.
Examples of the additive used in the flaky graphite dispersion include a plasticizer, an antifoaming agent, and a silane coupling agent.

The content ratio of each component in the obtained flaky graphite dispersion is not particularly limited, and may be adjusted as appropriate. The graphite content in the flaky graphite dispersion may be adjusted as appropriate, but from the viewpoint of dispersibility, 0.1 to 20 parts by mass with respect to 100 parts by mass of the total solid content of the flaky graphite dispersion. It is preferably no greater than part by mass, and more preferably no less than 0.5 parts by mass and no greater than 10 parts by mass.
In addition, the content of the solvent in the flaky graphite dispersion is preferably 80% by mass or more and 99% by mass or less, and more preferably 90% by mass or more and 97% by mass or less, based on the total amount of the flaky graphite dispersion. preferable.
Further, the content ratio of the dispersant in the flaky graphite dispersion when the dispersant is contained is 80 parts by mass or more and 99 parts by mass with respect to 100 parts by mass of the total solid content of the flaky graphite dispersion from the viewpoint of dispersibility. Is preferably 9 parts by mass or less, and more preferably 90 parts by mass or more and 99.5 parts by mass or less.
In the present invention, the solid content represents all components other than the solvent. For example, even a liquid dispersant is included in the solid content.

In the flaky graphite dispersion thus obtained, the content ratio of the flaky graphite having a flake thickness of 50 nm or less to the whole flaky graphite is preferably 10% by number or more, and more preferably 50% by number or more. It is preferable that the content is 70% by number or more. From the viewpoint of excellent electrical conductivity and thermal conductivity, the content ratio of the flake graphite having a flake thickness of 50 nm or less to the whole flake graphite is preferably as large as possible, more preferably 80% by number or more, and 90% by number. It is still more preferable that it is above. Among them, the content ratio of the flaky graphite having a thickness of 0.34 nm to 10 nm with respect to the whole flaky graphite is preferably 10% by number or more, and more preferably 20% by number or more.

3. Graphite Material The graphite material according to the present invention is characterized in that the flaky graphite according to the present invention is laminated.
As described above, since the flaky graphite according to the present invention has an average thickness of 50 nm or less and excellent conductivity and thermal conductivity, the graphite material obtained by laminating the flaky graphite according to the present invention is excellent. It has electrical conductivity and also has excellent thermal conductivity.
Since the flaky graphite according to the present invention has been described above, the description thereof is omitted here.

The shape of the graphite material according to the present invention is not limited as long as it is a laminate obtained by laminating the flaky graphite according to the present invention. The graphite material according to the present invention may be laminated so that at least a part of each of the flake graphites of the present invention overlaps each other.
The graphite material according to the present invention may be one in which at least a part of each of the flake graphites of the present invention is in contact with each other. The graphite material according to the present invention may be one in which the flaky graphites of the present invention are in contact with each other in the thickness direction.

The graphite material according to the present invention may be a film or sheet called a graphite film or a graphite sheet, or may be a molded body having a three-dimensional structure.
The graphite film according to the present invention can be a self-supporting film having an area of a circle having a diameter of 18 mm or more depending on the thickness distribution of the flaky graphite constituting the film, but may be in the form of a small piece.
When the graphite material according to the present invention is a film or a sheet, the thickness is not particularly limited. From the viewpoint of having flexibility, the thickness of the graphite material according to the present invention is preferably 1 mm or less, and more preferably 200 μm or less when it is in the form of a film or sheet. Since the graphite film or graphite sheet of the present invention having such a thickness has flexibility, it can be a very thin and light conductor with excellent flexibility.
Moreover, since the graphite material according to the present invention is formed by laminating the flaky graphite according to the present invention, it can follow an adherend having a large number of curved surfaces and irregularities.

In the graphite material according to the present invention, the direction in which at least a part of each of the flake graphites of the present invention overlaps each other is usually the thickness direction of the flakes.
Also in the graphite material according to the present invention, it is preferable that an average interplanar spacing (d002) of (002) planes by an X-ray diffraction method is 0.336 nm or less.

Also, in the graphite material according to the present invention, the total count of all (−) ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS), as in the flaky graphite of the present invention. The ratio of the number of fluorine (−) ions to the hydrogen atom is preferably 0.5% or more, more preferably 0.8% or more, and even more preferably 1% or more. Also in the graphite material according to the present invention, the ratio of the fluorine (−) ion count is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less. Is preferred.

Further, in the graphite material according to the present invention, as in the flaky graphite of the present invention, the composition of carbon atoms is preferably 80% or more as measured by X-ray photoelectron spectroscopy, and 90% or more. Is more preferably 92% or more, and still more preferably 95% or more. The composition of carbon atoms may be 100% as measured by X-ray photoelectron spectroscopy, but usually it is preferably 99% or less because some oxygen atoms are contained.
Further, also in the graphite material according to the present invention, like the flaky graphite of the present invention, the composition of oxygen atoms is preferably 10% or less as measured by X-ray photoelectron spectroscopy, and less than 10%. Is more preferable, 7% or less is more preferable, and 5% or less is even more preferable.
Also, in the graphite material according to the present invention, as in the flaky graphite of the present invention, only a very small amount of fluorine atoms is present, and therefore the composition of fluorine atoms is measured as 0% in the measurement by X-ray photoelectron spectroscopy. good.

Further, in the graphite material according to the present invention, as in the flaky graphite of the present invention, among the bonds of the carbon atoms, the ratio of the bonds forming sp2 bonds between the carbon atoms is excellent in conductivity. From the viewpoint of thermal conductivity, it is preferably 60% or more, more preferably 70% or more, and even more preferably 75% or more as measured by X-ray photoelectron spectroscopy. The higher the ratio of bonds that form sp2 bonds between carbon atoms, the better. The upper limit of the ratio of bonds that form sp2 bonds between carbon atoms is 100%. is there.

Also, the graphite material according to the present invention has good crystallinity as in the flaky graphite of the present invention, and therefore has a peak intensity in the range of 1300 to 1400 cm ⁻¹ measured by Raman spectroscopy. The intensity ratio I _D / I _G between (I _D ) and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is preferably 0.3 or less, more preferably 0.15 or less. Further, it is preferably 0.10 or less. The intensity ratio I _D / I _G is usually 0 in the case of raw material graphite, and is 0 or more.
Further, _'the intensity ratio I _G of the peak intensity _{(I G)} in the range of 1580 ~ 1620cm ^-1 / I peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 measured by Raman spectroscopy _G is preferably 0.1 or more, more preferably 0.2 or more, and still more preferably 0.3 or more. The intensity ratio I _{G ′} / I _G usually increases as the thickness of the flaky graphite decreases, and becomes 2 when the thickness is about 0.34 nm (graphene monoatomic layer).

The graphite material according to the present invention has excellent conductivity, but the surface resistance value is preferably 200Ω / □ or less, more preferably 100Ω / □ or less. The surface resistance value here can be measured with a resistivity meter (for example, manufactured by Mitsubishi Chemical Analytech Co., Ltd., model name: Loresta GP MCP-T610).

Moreover, although the graphite material which concerns on this invention has the outstanding heat conductivity, when the thickness is 200 micrometers or less, for example, the thermal diffusivity measured in the surface direction in the surface whose thickness is 200 micrometers or less is 1. It is preferably 0 × 10 ⁻⁶ m ² / s or more, and more preferably 1.0 × 10 ⁻⁵ m ² / s or more.
The thermal diffusivity can be measured using a periodic heating radiation temperature measuring method, and for example, can be measured using a thermowave analyzer TA3 manufactured by Bethel Co., Ltd.

The graphite material according to the present invention is a laminate formed by laminating the flaky graphite according to the present invention, but a flaky graphite having a flake thickness exceeding 50 nm is formed on a part of the flaky graphite constituting the laminate. It may be included.
In the graphite material according to the present invention, the thickness of the flakes on a part of the flake graphite constituting the laminate is preferably within a range where the surface resistance value is 200Ω / □ or less, more preferably 100Ω / □ or less. Flaky graphite exceeding 50 nm may be contained.

The graphite material of the present invention can be produced, for example, by the method for producing a graphite material of the second invention described later.

[Method for producing graphite material]
The method for producing a graphite material according to the second aspect of the present invention is the dispersion of graphite and a solubility in the solvent of less than 0.1 (g / 100 g solvent) in a fluorine-based solvent having a surface tension of 20 mN / m or less at the operating temperature. Mixing the agent and dispersing,
(I) or (ii) below:
(I) removing a fluorine-based solvent having a surface tension at the use temperature of 20 mN / m or less from the mixed solution after the dispersion treatment;
(Ii) adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more to the mixture from which the solvent has been removed; g / 100 g solvent) or higher step,
A step of making a flaky graphite dispersion by any step of removing a fluorine-based solvent having a surface tension at the use temperature of 20 mN / m or less from the mixed solution after the addition of the solvent;
And a step of forming or molding the flaky graphite dispersion.

The method for producing the graphite material includes at least a dispersion treatment step, a solvent removal step, a solvent addition step, and a film formation or molding step, and as necessary, within a range not impairing the effects of the present invention. Furthermore, it may have another process. Hereinafter, the method for producing such a graphite material will be described in detail in order, but the dispersion treatment step, the solvent removal step, and the solvent addition step can be the same as the method for producing the flaky graphite dispersion. Explanation here is omitted.

<Film formation or molding process>
A method for producing a graphite material using the flaky graphite dispersion can be appropriately selected from conventionally known film forming methods or molding methods.
As a suitable film forming method of the graphite material, there is a method in which the flaky graphite dispersion liquid is dropped on a porous substrate such as a filter paper or a membrane filter and filtered to remove the solvent to form a film. Further, as a suitable molding method of the graphite material, for example, a method such as casting molding, in which the flaky graphite dispersion liquid is dropped into a porous mold and the solvent is removed by filtration to mold, is used. . According to these methods, since the dispersant can be removed together with the solvent, it is suitable for making a graphite material excellent in conductivity and thermal conductivity.
In the method, it is preferable to further wash the graphite material with a solvent that dissolves the dispersant. By washing with a solvent that dissolves the dispersant, the dispersant can be removed and a high-purity graphite material can be obtained. Therefore, a graphite material having excellent conductivity and thermal conductivity can be obtained. As a solvent for dissolving the dispersant, it is preferable to select and use a solvent having a solubility of 5 (g / 100 g solvent) or more, and further 10 (g / 100 g solvent) or more.
The graphite material thus obtained may be peeled off from the porous substrate or the liquid-permeable mold and used as a single substance, or transferred to another substrate such as a glass substrate or a resin substrate. May be.
Furthermore, the electrical conductivity and the thermal conductivity can be enhanced by compressing the graphite material using a press or a roll press.

Further, as another film forming method of the graphite material, the flaky graphite dispersion is applied onto a substrate by a known coating method to form a coating film, and the solvent is removed to form the graphite material. And the like. According to this method, since the graphite material can be directly formed on the desired substrate, it is possible to form a graphite material having excellent adhesion to the substrate.

Since the flaky graphite and the graphite material according to the present invention are excellent in conductivity and thermal conductivity, the flaky graphite, the flaky graphite dispersion, and the graphite material according to the present invention include nanoelectronics and nanocomposites. , Transparent conductive films, electrodes, batteries, capacitors, hydrogen storage, application to living bodies, heat dissipation sheets, aerospace industry, sensors, transistors, and the like.

II. Third Invention Hereinafter, a method for producing flaky graphite, a method for producing a flaky graphite dispersion, and a method for producing a graphite material according to the third invention will be described in order.
1. Method for producing flaky graphite A method for producing flaky graphite according to the third aspect of the present invention comprises a solvent having a surface tension at a working temperature of 20 mN / m or less, graphite and a solubility in the solvent of 0.1 (g / g). It is characterized by having a step of mixing with a dispersant (less than 100 g solvent) and carrying out a dispersion treatment (hereinafter sometimes referred to as a dispersion treatment step).

A solvent having a surface tension of 20 mN / m or less at the use temperature has a relatively low polarity and a small surface tension, and therefore easily enters between the graphite layers. Dispersion treatment using such a solvent facilitates the exfoliation of graphite and facilitates the production of flaky graphite, as in the method for producing flaky graphite according to the second aspect of the present invention.
In the production method of the third aspect of the present invention, a solvent having a surface tension of 20 mN / m or less at the use temperature is combined with a dispersant having a solubility in the solvent of less than 0.1 (g / 100 g solvent). Use. By dispersing such a specific dispersant in combination with a specific solvent, graphite or flaky graphite is similar in polarity to the dispersant, as in the method for producing flaky graphite according to the second aspect of the present invention. It becomes easy to exist in the phase, and since the dispersant exists around the flaky graphite produced by the dispersion treatment, it is possible to suppress the flaky graphite from being immediately aggregated. Furthermore, in the present invention, since the dispersant phase is separated from the solvent phase, it is estimated that the flake graphite adsorbed by the dispersant moves to the dispersant phase, and reagglomeration is more likely to be suppressed. The
From the above, according to the method for producing flaky graphite of the third aspect of the present invention, the exfoliation of graphite easily proceeds to produce flaky graphite, and the flaky graphite hardly re-aggregates. Flake graphite excellent in heat conductivity and heat conductivity can be obtained in high yield.

The method for producing flaky graphite according to the third aspect of the present invention has at least a dispersion treatment step, and is within the range not impairing the effects of the present invention, if necessary, the flaky shape according to the second aspect of the present invention. Similar to the method for producing graphite, it may have other steps. Hereinafter, the method for producing the flaky graphite of the third aspect of the present invention will be described in detail in order.

[Distributed processing step]
In the dispersion treatment step, the graphite, the dispersant having a solubility in the solvent of less than 0.1 (g / 100 g solvent), and the dispersion treatment method are as follows. Since it may be the same as the method, description here is abbreviate | omitted.

<Solvent having a surface tension at a working temperature of 20 mN / m or less>
In the present invention, a solvent having a surface tension at the use temperature of 20 mN / m or less is used as the solvent during the dispersion treatment. Since the specific solvent easily enters the graphite layer, the exfoliation of the graphite is likely to proceed. In addition, the use temperature here means the solvent temperature at the start of the dispersion treatment.

Specific examples of the solvent having a surface tension at a working temperature of 20 mN / m or less include hexane (17.9 mN / m, unit omitted), heptane (19. 7), hydrocarbons such as 2,4-dimethylpentane (17.7), alkyl ethers such as diethyl ether (for example, diethyl ether: 16.7), compounds containing a dimethylsiloxane chain (for example, hexamethyldisiloxane: 15 .1, polydimethylsiloxane: 16 to 20 (varies depending on the degree of polymerization, etc.), fluorinated solvents having a fluorinated alkyl group, a fluorinated alkyl ether group, etc. as described above (for example, hydrofluoroether (for example, C ₄ _{_{F 9 OCH 3: 13.6mN / m}} , C 4 F 9 OC 2 H 5: 13.6mN / m, C 3 F 7 OCH 3 _{_{_{12.4mN / m, C 2 F 5}}} CF (OCH 3) C 3 F 7: 15mN / m , etc.), and hydrofluorocarbons), and the like. In the present invention, it is preferable to use a fluorinated solvent because it is easy to enter between graphite layers and the exfoliation of graphite easily proceeds, and at least one of a fluorinated alkyl group and a fluorinated alkyl ether group is preferred. It is preferable to use a fluorine-based solvent having
In addition, the solvent is preferably a solvent having a surface tension of 15 mN / m or less at the use temperature because it easily enters the graphite layer and the peeling of the graphite easily proceeds.
In the third aspect of the present invention, the solvent having a surface tension at the use temperature of 20 mN / m or less can be used alone or in combination of two or more.

The flaky graphite obtained by the method for producing flaky graphite of the third aspect of the invention has a high proportion of single-layer graphene and graphene multi-layered in a range of 50 nm or less, and is not oxidized. Excellent electrical and thermal conductivity without having to In addition, since graphite that has not been sufficiently flaked does not remain, the weight of graphite is hardly reduced even after classification, and flaky graphite can be obtained with a high recovery rate. When the method for producing flaky graphite of the third aspect of the present invention is used, the ratio of the single-layer graphene and the graphene multi-layered in the range of 50 nm or less is a yield of 20% by mass or more, more preferably 50 masses It is possible to obtain flaky graphite with a yield of 100% by mass or more, more preferably with a yield of 70% by mass or more, and even more preferably with a yield of 75% by mass or more. It is also possible to obtain flaky graphite.

In addition, the flake graphite obtained by the method for producing flake graphite according to the third aspect of the present invention is, as described above, peeled between the flakes of the flakes of graphite by using a solvent having a surface tension at the operating temperature of 20 mN / m or less. Therefore, oxygen atoms are reduced as compared with flaky graphite produced by reducing graphene oxide, and the proportion of bonds forming sp2 bonds between carbon atoms is increased. It is possible to have high conductivity and heat conductivity.
The flaky graphite obtained by the method for producing flaky graphite according to the third aspect of the present invention is the same as the flaky graphite according to the first aspect of the present invention. Becomes 0.336 nm or less.

Further, the flaky graphite obtained by the method for producing flaky graphite of the third aspect of the present invention comprises a carbon atom composition, an oxygen atom composition, an atom different from the carbon atom and the oxygen atom as measured by X-ray photoelectron spectroscopy. The composition of the carbon atoms, the sum of the carbon atom composition and the oxygen atom composition, and the ratio of the bonds forming sp2 bonds between the carbon atoms out of the bonds of the carbon atoms is the same as that of the first aspect of the present invention. Similar to those of flaky graphite.

In addition, the flake graphite obtained by the method for producing flake graphite according to the third aspect of the present invention is, as described above, peeled between the flakes of the flakes of graphite by using a solvent having a surface tension at the operating temperature of 20 mN / m or less. Therefore, the I _D / I _G and the I _{G ′} / I _G measured by Raman measurement are the same as those of the flaky graphite of the first invention described above.
In the method for producing flaky graphite according to the third aspect of the present invention, the flaky graphite obtained when the solvent having a surface tension at the operating temperature of 20 mN / m or less contains fluorine is adsorbed by a small amount of fluorine. Or, since it is bonded and promoted to exfoliate between the flakes, fluorine relative to the total count of all (−) ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS) The ratio of the (−) ion count number is the same as that of the flaky graphite of the first invention described above.
Further, the thickness and the surface direction size of the flaky graphite obtained by the method for producing the flaky graphite of the third invention are the same as those of the flaky graphite of the first invention described above.

The flaky graphite obtained by the method for producing the flaky graphite of the third aspect of the present invention can also be applied in various forms and in various forms as graphene powder, like the flaky graphite of the first aspect of the present invention. it can.

2. Method for Producing Flaky Graphite Dispersion A method for producing a flaky graphite dispersion according to the third aspect of the present invention comprises a solvent having a surface tension of 20 mN / m or less at the operating temperature, graphite and a solubility in the solvent of 0.00. A step (dispersion treatment step) of mixing and dispersing a dispersant less than 1 (g / 100 g solvent);
(I) or (ii) below:
(I) a step of removing a solvent having a surface tension at the use temperature of 20 mN / m or less from the mixed solution after the dispersion treatment (hereinafter sometimes referred to as a solvent removal step);
A step of adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more to the mixture from which the solvent has been removed (hereinafter sometimes referred to as a solvent addition step).
(Ii) adding a solvent having a solubility of 5 (g / 100 g solvent) or more to the mixed solution after the dispersion treatment (solvent addition step);
The process of removing the solvent whose surface tension at the said use temperature is 20 mN / m or less from the liquid mixture after the said solvent addition (solvent removal process)
It has any one of these processes.

When the phase tension of the solvent having a surface tension at the use temperature of 20 mN / m or less and the solvent having the solubility of the dispersant of 5 (g / 100 g solvent) or more is used, the step (ii) is used. Also good. However, among these, it is preferable to have the step (i) because it is easy to obtain flaky graphite with high yield.

A method for producing a flaky graphite dispersion according to the third aspect of the present invention comprises a mixed liquid containing flaky graphite obtained by the method for producing flaky graphite according to the present invention, wherein the surface tension at the use temperature is 20 mN / It is possible to produce a flaky graphite dispersion with little residual graphite that has not been exfoliated by removing a solvent of m or less and adding a solvent having a solubility of 5 (g / 100 g solvent) or more. it can. By replacing the solvent having a surface tension of 20 mN / m or less at the use temperature included in the dispersion treatment with a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more, the solvent phase and the dispersant A dispersion that is a heterogeneous system including two phases can be made into a flaky graphite dispersion having a solvent and a dispersant as one phase.

The method for producing a flaky graphite dispersion according to the third aspect of the present invention includes at least a dispersion treatment step, a solvent removal step, and a solvent addition step, and as necessary without impairing the effects of the present invention. In addition, other steps may be included. Regarding the dispersion treatment step, the solvent removal step, and the solvent addition step in the method for producing a flaky graphite dispersion of the third invention, the method for producing the flaky graphite of the second invention described above, the second Since it can be the same as that of the manufacturing method of the flaky graphite dispersion liquid of this invention of this invention, description here is abbreviate | omitted.

The content ratio of each component in the flaky graphite dispersion obtained by the method for producing a flaky graphite dispersion of the third invention is not particularly limited, and may be appropriately adjusted. The content of graphite and solvent in the flaky graphite dispersion, and the content of the dispersant when a dispersant is included are the same as those of the flaky graphite dispersion of the first invention described above. Preferably there is.

The flaky graphite dispersion obtained by the production method of the third aspect of the present invention has a high ratio of single-layer graphene and multi-layer graphene within a range of 50 nm or less, and is not oxidized. It is excellent as a preparatory preparation for producing a graphite material having heat conductivity and heat conductivity. Further, a resin or the like can be added to the flaky graphite dispersion obtained by the production method of the third present invention and used as a resin composition.

3. Method for Producing Graphite Material A method for producing a graphite material according to the third aspect of the present invention comprises a solvent having a surface tension of 20 mN / m or less at the operating temperature, a graphite and a solubility in the solvent of 0.1 (g / 100 g solvent). ) Less than the dispersant, and a dispersion process (dispersion process);
(I) or (ii) below:
(I) a step of removing a solvent having a surface tension of 20 mN / m or less at the use temperature from the mixed solution after the dispersion treatment (solvent removal step);
A step of adding a solvent having a solubility of the dispersant of 5 (g / 100 g solvent) or more to the mixture from which the solvent has been removed (solvent addition step)
(Ii) adding a solvent having a solubility of 5 (g / 100 g solvent) or more to the mixed solution after the dispersion treatment (solvent addition step);
The process of removing the solvent whose surface tension at the said use temperature is 20 mN / m or less from the liquid mixture after the said solvent addition (solvent removal process)
A step of making a flaky graphite dispersion by any of the steps,
And a step of forming or forming the flaky graphite dispersion (film formation or forming step).

A method for producing a graphite material according to a third aspect of the present invention comprises forming or molding a graphite material using the flaky graphite dispersion obtained by the method for producing a flaky graphite dispersion according to the third aspect of the present invention. Therefore, the graphite material excellent in electroconductivity and heat conductivity can be manufactured.

The method for producing a graphite material according to the third aspect of the present invention includes at least a dispersion treatment step, a solvent removal step, a solvent addition step, and a film formation or molding step, and within a range not impairing the effects of the present invention. Further, other steps may be provided as necessary. Regarding the dispersion treatment step, the solvent removal step, the solvent addition step, and the film formation or molding step in the method for producing a graphite material of the third invention, the production of the flake graphite of the second invention described above Since it can be the same as the method, the method for producing the flaky graphite dispersion of the second invention, and the method for producing the graphite material of the second invention, description thereof is omitted here.

The graphite material obtained by the method for producing a graphite material of the third aspect of the present invention can also be applied in various ways in the same manner as the graphite material of the first aspect of the present invention.

Hereinafter, the present invention will be specifically described with reference to examples. These descriptions do not limit the present invention. Moreover, it implemented at 25 degreeC unless there was particular description.
[Evaluation methods]
<Fluorine detection by TOF-SIMS>
NEGATIVE secondary ions detected by irradiating 69Ga ⁺ on flaky graphite or graphite film using TOF-SIMS (time-of-flight secondary ion mass spectrometry, Physical Electronics, model name: TRIFT II) Was detected as a secondary ion mass spectrum.
When the influence of molecular adsorption on the flaky graphite surface is considered, such as when 6 months or more have passed after the flaky graphite is produced, the outermost surface is converted to SiO ₂ using a primary ion beam (69Ga ⁺ ). After about 1 nm etching, the measurement was performed.

<Measurement of average spacing (d002) of (002) planes by X-ray diffraction method>
Using XRD (powder X-ray diffraction, manufactured by Rigaku Corporation, model name: Miniflex II) for flake graphite or graphite material, the peak position 2θ is determined from the diffraction pattern by CuKα ray (λ = 0.15418 nm). The average distance between planes: d was calculated from Bragg diffraction formula: λ = 2d · sin θ. Usually, the average interplanar spacing (d002) of graphite is 0.3356 nm.

<Thickness of flaky graphite>
A mixed liquid containing flaky graphite or a flaky graphite dispersion is sampled, diluted 20 to 2000 times with a solvent having a solubility of 5 (g / 100 g solvent) or more, and a membrane having a pore size of 0.02 μm The solvent was filtered off by coating on the filter, and the flakes were placed on the membrane filter in an independent state without agglomeration. Further, the dispersant is washed with a solvent having a solubility of 5 (g / 100 g solvent) or more (in each example, the solvent used as the dispersion solvent, and only Comparative Examples 2 and 5 are water instead of toluene). Was removed. The flaky graphite was transferred onto the silicon wafer by pressing and removing the washed silicon wafer on the membrane filter with the flaky graphite placed on the membrane filter. The flake graphite adhering to the silicon wafer in an independently dispersed state was measured by AFM, and the thickness of the flake was measured. The AFM measurement uses the function of the scanning probe microscope (SPM) in the Shimadzu Corporation nanosearch microscope SFT-3500, and the scanning range is 10 μm × 10 μm in the contact mode, that is, AFM (Atomic Force Microscope). The measurement was performed. The difference in height between the silicon wafer and the flaky graphite in the flaky graphite adhering on the silicon wafer was defined as the thickness of the flaky graphite.
The average thickness of flaky graphite is calculated by repeating the above operation until a total of 200 pieces of flaky graphite can be observed by AFM, and calculating the average value of the measured thickness of 200 pieces of flaky graphite observed by AFM. I asked for it.

<Composition analysis by X-ray photoelectron spectroscopy>
Measurement by X-ray photoelectron spectroscopy was carried out using an X-ray photoelectron spectrometer (Examples 1 to 7 and Comparative Examples 1 to 3 manufactured by Thermo Fisher Scientific, product name VG Theta Probe, Examples 8 to 18 and Comparative Examples 4 to 6). Using a product name PHI5000 Versa Probe manufactured by ULVAC-PHI, Inc. and analyzing the spectrum of secondary electrons detected by irradiating the sample with X-rays.
As the irradiation X-ray, a single crystal spectral AlKα ray was used, and a neutralizing electron gun was used.
A bond in which sp2 bonds are formed between carbon atoms (bond energy: about 284.6 eV) and a bond in which sp3 bonds are formed between carbon atoms (bond energy: about 285.5 eV); By performing peak separation, it is possible to calculate the proportion of bonds that form sp2 bonds between carbon atoms among the bonds of the carbon atoms (see FIG. 6).

<Analysis by Raman spectroscopy>
Analysis by Raman spectroscopy was performed using a Raman spectroscopy analyzer (model name: XploRA) manufactured by Horiba. A 532 nm laser was used as the light source. After the baseline correction of the obtained chart, the peak intensities of 1300 to 1400 cm ⁻¹ (I _D ), 1580 to 1620 cm ⁻¹ (I _G ), and 2600 to 2800 cm ⁻¹ (I _{G ′} ) are calculated. The peak intensity ratios I _D / I _G and I _{G ′} / I _G were determined. The Raman measurement was performed 10 times while changing the position of the graphite film to be measured, and the peak intensity described later showed an average value thereof.
Detailed measurement conditions were as follows.
Spectrometer: Czerny Turner type detector with focal length = 200 mm: Resolution (100 μm slit width) 2 to 15 cm −1
Laser power: 20-25mW

<Conductivity>
The surface resistance of the graphite film was measured with a resistivity meter (model name: Loresta GP MCP-T610, manufactured by Mitsubishi Chemical Analytech Co., Ltd.) using a four-probe method.

<Thermal conductivity>
The graphite film was peeled off from the membrane filter used for the filtration, and an attempt was made to form a graphite free-standing film having an area of a circle having a diameter of 18 mm or more. Some were able to form a self-supporting film, while others were not able to form a self-supporting film by being divided into a plurality of small pieces. About the thing in which the self-supporting film | membrane was able to be formed, the thermal diffusivity of the surface direction of the film | membrane was measured using the thermowave analyzer TA3 (period heating radiation temperature measuring method) of Bethel.

1. Example I series (first and second inventions)
(Example 1-1: Production of flaky graphite)
Fluorine-based solvent (hydrofluoroether (C ₄ F ₉ OC ₂ H ₅ ), 3M Novec7200, surface tension 13.6 mN / m) 10 mL (14.3 g) and graphite (Nippon Graphite Co., Ltd. ACB-100) 2 mg Dispersant (Tokyo Chemical Industry Co., Ltd. dodecylbenzenesulfonic acid; solubility in fluorine-based solvent less than 0.1 (g / 100 g solvent), solubility in water 25 (g / 100 g solvent), viscosity at 25 ° C. 1200 mPa · s) 50 mg was mixed, and flaky graphite 1 was obtained by processing with a stainless steel ball at 10 Hz for 30 minutes in a ball mill (mixer mill manufactured by Lecce).
Sample a small amount from the mixture containing flaky graphite 1 and filter the fluorine-based solvent with a membrane filter with a pore size of 0.02 microns (GE Healthcare Japan, Anodisco, material: alumina, unless otherwise stated). Separately, fluorine was detected by TOF-SIMS measurement for the flake graphite 1 from which the dispersant was removed by washing with water, and the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was It was 1.4%. Further, when the average interplanar spacing (d002) of the (002) plane of the flaky graphite 1 by the X-ray diffraction method was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.

(Example 1-2: Production of flaky graphite dispersion)
The fluorine-based solvent was removed from the mixed solution containing flaky graphite 1 obtained in Example 1-1, and 10 mL of water (solubility of the dispersing agent 25 (g / 100 g solvent)) was added to thereby precipitate. A flaky graphite dispersion 1 was obtained (yield of flaky graphite 100% dispersed in the dispersion).
The yield was determined to be 100% because the flaky graphite dispersion was allowed to stand for 1 hour and it was confirmed that precipitation did not occur.
In addition, a small amount of flaky graphite dispersion 1 is sampled and applied onto a membrane filter having a pore size of 0.02 micron, so that the fluorinated solvent is filtered and placed in an independent state without agglomerating the flakes on the membrane filter. It was. Further, when fluorine was detected by TOF-SIMS measurement for the flake graphite 1 from which the dispersant was removed by washing with water, the ratio of the number of fluorine (−) ions to the total number of (−) ions was 1. 4%. Further, when the average interplanar spacing (d002) of the (002) plane of the flaky graphite by the X-ray diffraction method was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, the flaky graphite 1 was transferred onto the silicon wafer by pressing and removing the washed silicon wafer on the membrane filter with the flaky graphite 1 placed thereon. The flaky graphite 1 existing in an independently dispersed state on this silicon wafer was measured by AFM, and the thickness of the flakes was measured. there were.

(Example 1-3: Production of graphite film)
The flaky graphite dispersion 1 obtained in Example 1-2 was filtered and washed with water to obtain a circular graphite film 1 having a diameter of 18 mm and a thickness of 30 μm.
When fluorine was detected by TOF-SIMS measurement on the graphite film 1, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%. Further, the average interplanar spacing (d002) of the (002) plane of the graphite film 1 was measured by the X-ray diffraction method. In FIG. 1, the measurement result by the X-ray-diffraction method of the graphite film 1 is shown. The peak of graphite film 1 was located at 2θ = 26.56 °, and the average interplanar spacing (d002) was calculated to be 0.3356 nm, which was the same as that of ACB-100 of raw material graphite.
Further, when the graphite film 1 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 96% and the oxygen atom composition was 4%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 81%.
FIG. 2 shows an SEM photograph of the graphite film 1 according to the present invention.

(Example 2-1: Production of flaky graphite)
In Example 1-1, the dispersant was tween 20 (polyoxyethylene (20) sorbitan monolaurate manufactured by Tokyo Chemical Industry Co., Ltd., solubility in the fluorine-based solvent was less than 0.1 (g / 100 g solvent), solubility in water 50 Except that (g / 100 g solvent) was exceeded and the viscosity at 25 ° C. was changed to 370 mPa · s, flaky graphite 2 was obtained in the same manner as in Example 1-1.

(Example 2-2: Production of flaky graphite dispersion)
The fluorinated solvent was removed from the mixed liquid containing flaky graphite 2 obtained in Example 2-1, and 10 mL of water was added to obtain flaky graphite dispersion 2 without precipitation (into the dispersion). (Yield of dispersed flaky graphite 100%). Using the flaky graphite dispersion 2, the flaky graphite 2 existing in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 1-2, and the thickness of the flaky graphite 2 was measured by AFM. The range was from 3 nm to 12 nm, and the average thickness was 8 nm.

(Example 2-3: Production of graphite film)
The flaky graphite dispersion 2 obtained in Example 2-2 was filtered and washed with water to obtain a graphite film 2.
When the fluorine was detected in the graphite film 2 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.3%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 2 was measured by the X-ray diffraction method, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 2 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 96% and the oxygen atom composition was 4%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 78%.

(Example 3-1: Production of flaky graphite)
In Example 1-1, the dispersant was span20 (Sorbitan monolaurate, a solubility in the fluorine-based solvent of less than 0.1 (g / 100 g solvent) manufactured by Tokyo Chemical Industry Co., Ltd., and a solubility in isopropyl alcohol of 10 (g / 100 g solvent). Except that the viscosity at 25 ° C. was changed to 4200 mPa · s), flaky graphite 3 was obtained in the same manner as in Example 1-1.

(Example 3-2: Production of flaky graphite dispersion)
The fluorinated solvent was removed from the mixed liquid containing the flaky graphite 3 obtained in Example 3-1, and 10 mL of isopropyl alcohol was added to obtain a flaky graphite dispersion 3 without precipitation (dispersion liquid). The yield of flaky graphite dispersed in 100%). Using the flaky graphite dispersion 3, the flaky graphite 3 existing in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 1-2, and the thickness of the flaky graphite 3 was measured by AFM. The range was 5 nm to 41 nm, and the average thickness was 33 nm.

(Example 3-3: Production of graphite film)
The flaky graphite dispersion 3 obtained in Example 3-2 was filtered and washed with isopropyl alcohol to obtain a graphite film 3.
When fluorine was detected in the graphite film 3 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 3 was measured by X-ray diffraction, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 3 was measured by X-ray photoelectron spectroscopy, the composition of carbon atoms was 95% and the composition of oxygen atoms was 5%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 76%.

(Example 4-1: Production of flaky graphite)
In Example 1-1, the dispersing agent was BYK-9076 manufactured by Big Chemie Japan (polyurethane-containing, alkylammonium salt of high molecular weight copolymer, solubility in fluorine-based solvent was less than 0.1 (g / 100 g solvent), and into water. Exfoliated graphite 4 was obtained in the same manner as in Example 1-1 except that the solubility was 15 (g / 100 g solvent) and the viscosity at 25 ° C. was 1050 mPa · s.

(Example 4-2: Production of flaky graphite dispersion)
The fluorinated solvent was removed from the mixed solution containing the flaky graphite 4 obtained in Example 4-1, and 10 mL of water was added to obtain a flaky graphite dispersion 4 without precipitation (into the dispersion). (Yield of dispersed flaky graphite 100%). Using flaky graphite dispersion 4, flaky graphite 4 existing in a state of being independently dispersed on a silicon wafer was prepared in the same manner as in Example 1-2, and the thickness of flaky graphite 4 was measured by AFM. The range was from 3 nm to 11 nm, and the average thickness was 8 nm.

(Example 4-3: Production of graphite film)
The flaky graphite dispersion 4 obtained in Example 4-2 was filtered and washed with water to obtain a graphite film 4.
When fluorine was detected in the graphite film 4 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 4 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 4 was measured by X-ray photoelectron spectroscopy, the composition of carbon atoms was 96% and the composition of oxygen atoms was 4%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 78%.

(Example 5-1: Production of flaky graphite)
In Example 1-1, the dispersant was a branched polyethyleneimine (number average molecular weight Mn 60000, 50% aqueous solution) manufactured by Sigma-Aldrich (solubility in the fluorine-based solvent was less than 0.1 (g / 100 g solvent), solubility in water 50 ( Except that the viscosity was changed to over 10,000 gPa · s) at 25 ° C., flake graphite 5 was obtained in the same manner as in Example 1-1.

(Example 5-2: Production of flaky graphite dispersion)
The fluorinated solvent was removed from the mixed solution containing the flake graphite 5 obtained in Example 5-1, and 10 mL of water was added to obtain a flake graphite dispersion 5 (the flakes dispersed in the dispersion). Yield of glassy graphite 100%). Using the flaky graphite dispersion 5, the flaky graphite 5 present in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 1-2, and the thickness of the flaky graphite 5 was measured by AFM. The range was 7 nm to 48 nm, and the average thickness was 35 nm.

(Example 5-3: Production of graphite film)
The comparative flaky graphite dispersion 5 obtained in Example 5-2 was filtered and washed with water to obtain a graphite film 5.
When fluorine was detected in the graphite film 5 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 5 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 5 was measured by X-ray photoelectron spectroscopy, the composition of carbon atoms was 95% and the composition of oxygen atoms was 5%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 76%.

(Example 6-1: Production of flaky graphite)
In Example 1-1, a dispersant was sodium dodecylbenzenesulfonate (hard type) manufactured by Tokyo Chemical Industry Co., Ltd. (solubility in the fluorine-based solvent was less than 0.1 (g / 100 g solvent), solubility in water 20 (g / Exfoliated graphite 6 was obtained in the same manner as in Example 1-1 except that it was changed to 100 g solvent) and solid at 25 ° C.

(Example 6-2: Production of flaky graphite dispersion)
The fluorinated solvent was removed from the mixed solution containing the flaky graphite 6 obtained in Example 6-1 and 10 mL of water was added to obtain a flaky graphite dispersion 6 without precipitation (into the dispersion). (Yield of dispersed flaky graphite 100%). Using flaky graphite dispersion 6, flaky graphite 6 existing in a state of being independently dispersed on a silicon wafer was prepared in the same manner as in Example 1-2, and the thickness of flaky graphite 6 was measured by AFM. The range was 3 nm to 11 nm, and the average thickness was 9 nm.

(Example 6-3: Production of graphite film)
The flaky graphite dispersion 6 obtained in Example 6-2 was filtered and washed with water to obtain a graphite film 6.
When fluorine was detected in the graphite film 6 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.5%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 6 was measured by X-ray diffraction, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 6 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 96% and the oxygen atom composition was 4%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 80%.

(Comparative Example 1-1: Production of comparative flaky graphite)
In Example 1-1, the dispersant was Surflon S-420 (surfactant having a perfluoroalkyl group) manufactured by AGC Seimi Chemical (solubility 0.7 (g / 100 g solvent) in the fluorinated solvent, and isopropyl alcohol. Comparative flaky graphite 1 was obtained in the same manner as in Example 1-1 except that the solubility was changed to 10 (g / 100 g solvent) excess and the viscosity at 25 ° C. was 800 mPa · s.

(Comparative Example 1-2: Production of comparative flaky graphite dispersion)
The fluorinated solvent was removed from the mixed liquid containing the comparative flaky graphite 1 obtained in Comparative Example 1-1, and 10 mL of isopropyl alcohol was added to obtain a comparative flaky graphite dispersion 1. The comparative flaky graphite dispersion 1 had a precipitate. Using the supernatant of comparative flaky graphite dispersion 1, comparative flaky graphite 1 existing in a state of being independently dispersed on a silicon wafer was prepared in the same manner as in Example 1-2. When the thickness was measured, it was in the range of 63 nm to 260 nm, and the average thickness was 198 nm. Including precipitation, it is believed that there is actually a thicker flake graphite.

(Comparative Example 1-3: Production of comparative graphite film)
The comparative flaky graphite dispersion liquid 1 obtained in Comparative Example 1-2 was filtered and washed with isopropyl alcohol to obtain a comparative graphite film 1. FIG. 3 shows an SEM photograph of the comparative graphite film 1.
When the fluorine was detected by TOF-SIMS measurement for the comparative graphite film 1, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 0 excluding noise. Further, when the average interplanar spacing (d002) of the (002) plane of the comparative graphite film 1 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.

(Comparative Example 2-2: Production of comparative flaky graphite dispersion)
A comparative flaky graphite dispersion 2 was obtained in the same manner as in Example 1-2, except that toluene (solubility of the dispersant is 1 (g / 100 g solvent)) was used instead of water in Example 1-2. . In the comparative flaky graphite dispersion 2, precipitation occurred. Using the supernatant of the comparative flaky graphite dispersion 2, the comparative flaky graphite 2 existing in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 1-2. When the thickness was measured, it was in the range of 75 to 230 nm, and the average thickness was 177 nm. Including precipitation, it is believed that there is actually a thicker flake graphite.

(Comparative Example 2-3: Production of comparative graphite film)
The comparative flaky graphite dispersion 2 obtained in Comparative Example 2-2 was filtered and washed with water to obtain a comparative graphite film 2.
When the fluorine was detected by TOF-SIMS measurement for the comparative graphite film 2, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 0 excluding noise. Further, when the average interplanar spacing (d002) of the (002) plane of the comparative graphite film 2 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.

(Comparative Example 3-1: Production of comparative flaky graphite)
In Example 1-1, the fluorinated solvent was changed to water (surface tension (25 ° C.) 72 mN / m), and the dispersant was Surflon S-420 (surfactant having a perfluoroalkyl group) manufactured by AGC Seimi Chemical. (Soluble in water less than 0.1 (g / 100 g solvent), solubility in isopropyl alcohol more than 10 (g / 100 g solvent), viscosity at 25 ° C. 800 mPa · s) Comparative flaky graphite 3 was thus obtained.

(Comparative Example 3-2: Production of Comparative Flaky Graphite Dispersion)
Water was removed from the mixed solution containing the comparative flaky graphite 3 obtained in Comparative Example 3-1, and 10 mL of isopropyl alcohol was added to obtain a comparative flaky graphite dispersion 3. The comparative flaky graphite dispersion 3 had a precipitate. Using the supernatant of the comparative flaky graphite dispersion 3, the comparative flaky graphite 3 existing in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 1-2. When the thickness was measured, it was in the range of 70 nm to 250 nm, and the average thickness was 182 nm. Including precipitation, it is believed that there is actually a thicker flake graphite.

(Comparative Example 3-3: Production of comparative graphite film)
The comparative flaky graphite dispersion 3 obtained in Comparative Example 3-2 was filtered and washed with isopropyl alcohol to obtain a comparative graphite film 3.
When fluorine was detected in the comparative graphite film 3 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 0 excluding noise. When the average interplanar spacing (d002) of the (002) plane of the comparative graphite film 3 was measured by the X-ray diffraction method, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.

Table 1 shows the evaluation results of Examples 1 to 6 and Comparative Examples 1 to 3.

From the results of Table 1, in Examples 1 to 6, flaky graphite can be obtained at a high yield of 100%, and a flaky graphite dispersion with little residual graphite that is not flaky is obtained. And a graphite film excellent in conductivity and thermal conductivity could be obtained.
When the thermal diffusivity was measured for the graphite films of Examples 1, 2, 4 and 6 in which a self-supporting film was formed, iron (1.4 × 10 ⁻⁵ m ² / s), SUS304 (stainless steel) (0.4 × 10 ⁻⁵ m ² / s) or the like, which is equal or higher than that, and was confirmed to be excellent in thermal conductivity.
On the other hand, a fluorine-based solvent having a surface tension at a working temperature of 20 mN / m or less was used as a solvent for dispersing graphite. In Comparative Example 1 using a dispersant having high solubility in the solvent, the time-of-flight type 2 No flaky graphite with a ratio of fluorine (-) ion count to 0.5% or more of the total count of all (-) ions measured using secondary ion mass spectrometry (TOF-SIMS) It was. In the dispersion of Comparative Example 1, precipitation occurred, and the yield of flaky graphite having a thickness of 50 nm or less dispersed in the dispersion was 0%. Moreover, it was shown that the obtained comparative graphite film 1 has a high resistance value and is inferior in conductivity.
Also in Comparative Example 2, the ratio of the number of fluorine (−) ions to the total number of (−) ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0. No more than 5% flaky graphite was obtained. In Comparative Example 2, when the dispersion was prepared, the dispersion was prepared by adding a solvent having a dispersant solubility of less than 5 (g / 100 g solvent), so that precipitation occurred and the dispersion was 50 nm or less dispersed in the dispersion. The yield of flaky graphite was 0%. Moreover, it was shown that the obtained comparative graphite film 2 has a high resistance value and is inferior in conductivity.
Also in Comparative Example 3, the ratio of the number of fluorine (−) ions to the total number of (−) ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0. No more than 5% flaky graphite was obtained. In Comparative Example 3 in which a solvent having a surface tension at a working temperature of more than 20 mN / m in combination with a dispersant having low solubility in the solvent was used as a solvent for dispersing the graphite, precipitation occurred in the dispersion, resulting in dispersion. The yield of flaky graphite of 50 nm or less dispersed in the liquid was 0%. Moreover, it was shown that the obtained comparative graphite film 3 has a high resistance value and is inferior in conductivity.

(Example 8-1, 2: Production of flaky graphite and flaky graphite dispersion)
Fluorine solvent (hydrofluoroether (C ₄ F ₉ OC ₂ H ₅ ), 3M Novec 7200, surface tension 13.6 mN / m) 14 mL (20.0 g) and graphite (Nippon Graphite Co., Ltd. ACB-100) 20 mg Dispersant (Tokyo Chemical Industry Co., Ltd. dodecylbenzenesulfonic acid; solubility in fluorine-based solvent less than 0.1 (g / 100 g solvent), solubility in water 25 (g / 100 g solvent), viscosity at 25 ° C. 1200 mPa · s) 100 mg was mixed, and flaky graphite 8 was obtained by processing with a stainless steel ball at 20 Hz for 30 minutes in a ball mill (a mixer mill manufactured by Lecce).

The fluorine solvent was removed from the mixture containing flaky graphite 8 by decantation and reduced pressure treatment, and 20 mL of water was added to prepare flaky graphite dispersion 8 (yield of flaky graphite dispersed in dispersion 100% ). The flake graphite dispersion 8 is diluted 200 times with water and then applied onto a membrane filter having a pore size of 0.02 microns to separate the water and place the flakes on the membrane filter in an independent state without agglomeration. It was. Further, regarding the flaky graphite 8 from which the dispersant was removed by washing with water, fluorine was detected by TOF-SIMS measurement. As a result, the ratio of the number of fluorine (−) ions to the total number of (−) ions was It was 1.4%. Further, when an average interplanar spacing (d002) of the (002) plane of the flaky graphite 8 was measured by X-ray diffraction, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Furthermore, the flaky graphite 8 was transferred onto the silicon wafer by pressing and removing the washed silicon wafer on the membrane filter with the flaky graphite 8 placed thereon. The flake graphite 8 existing in a state of being dispersed independently on the silicon wafer was measured by AFM, and the thickness of the flake was measured. This operation was repeated, and the average thickness of the flaky graphite 8 was determined to be 26 nm. Of the measured flakes, flakes having a thickness of less than 10 nm are 32% by number, flakes having a thickness in the range of 10 nm to 50 nm are 62%, and flakes having a thickness exceeding 50 nm are 6%. It was confirmed.
FIG. 4 shows an AFM photograph of the flaky graphite 8.

(Example 8-3: Production of graphite film)
The flaky graphite dispersion 8 obtained in Example 8-2 was filtered and washed with water to obtain a circular graphite film 8 having a diameter of 36 mm and a thickness of 20 μm.
When fluorine was detected in the graphite film 8 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%.

Further, the average interplanar spacing (d002) of the (002) plane of the graphite film 8 was measured by the X-ray diffraction method. The peak of graphite 8 was located at 2θ = 26.56 °, and the average interplanar spacing (d002) was calculated to be 0.3356 nm, which was the same as that of ACB-100 of raw material graphite.

The graphite film 8 was measured by X-ray photoelectron spectroscopy. In FIG. 5, the measurement result by the X-ray photoelectron spectroscopy of the graphite film 8 is shown. The composition of carbon atoms was 95.2% and the composition of oxygen atoms was 4.2%. FIG. 6 shows an enlarged view of the peak of the carbon atom in the measurement result by X-ray photoelectron spectroscopy. Of the bonds possessed by the carbon atoms, the ratio of the bonds forming sp2 bonds between the carbon atoms was 81%. According to X-ray photoelectron spectroscopy, the composition of fluorine atoms was measured as 0%.

Further, Raman measurement was performed on the graphite film 8. In FIG. 7, an example of the measurement result by the Raman spectroscopy of the graphite film 8 is shown. The Raman measurement was performed 10 times while changing the position of the graphite film to be measured, and the peak intensity described later showed an average value thereof. As a result, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is 0.08, The results confirming that there are few defects were obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.43, The result which proves that the thickness of flaky graphite is thin was obtained.

(Example 9-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Example 8-1, the dispersant was tween 20 (polyoxyethylene (20) sorbitan monolaurate manufactured by Tokyo Chemical Industry Co., Ltd., solubility in the fluorinated solvent was less than 0.1 (g / 100 g solvent), solubility in water 50 Except that (g / 100 g solvent) was exceeded and the viscosity at 25 ° C. was changed to 370 mPa · s, flaky graphite 9 was obtained in the same manner as in Example 8-1.

In the same manner as in Example 8-2, the fluorinated solvent was removed from the mixed solution containing flaky graphite 9 obtained above, and water was added to obtain flaky graphite dispersion 9 without precipitation. (Yield 100% of flaky graphite dispersed in dispersion). Using the flaky graphite dispersion 9, the flaky graphite 9 existing in a state of being independently dispersed on the silicon wafer was prepared in the same manner as in Example 8-2, and the thickness of the flaky graphite 9 was measured by AFM. The average thickness of the flaky graphite 9 was 31 nm. Further, of the measured flakes, the number of flakes having a thickness of less than 10 nm is 28%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 65%, and the number of flakes having a thickness exceeding 50 nm is 7%. confirmed.

(Example 9-3: Production of graphite film)
The flaky graphite dispersion 9 obtained in Example 9-2 was filtered and washed with water to obtain a graphite film 9.
When fluorine was detected in the graphite film 9 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.3%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 9 was measured by X-ray diffraction, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 9 was measured by X-ray photoelectron spectroscopy, the composition of carbon atoms was 96% and the composition of oxygen atoms was 4%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 79%.
As a result of Raman measurement of the graphite film 9, the intensity ratio I _D / I _G of the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.10, and the result which supports that there are few defects was obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.39, The result which proves that the thickness of flaky graphite is thin was obtained.

(Example 10-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Example 8-1, the dispersant was span 20 (Sorbitan monolaurate, solubility in the fluorine-based solvent less than 0.1 (g / 100 g solvent), Tokyo Chemical Industry Co., Ltd., solubility in isopropyl alcohol 10 (g / 100 g solvent) Except that the viscosity at 25 ° C. was changed to 4200 mPa · s), flaky graphite 10 was obtained in the same manner as in Example 8-1.

The fluorinated solvent is removed from the mixed liquid containing flaky graphite 10 obtained as described above in the same manner as in Example 8-2, and 10 mL of isopropyl alcohol is added, whereby flaky graphite dispersion 10 having no precipitation is added. (100% yield of flaky graphite dispersed in the dispersion). Using the flaky graphite dispersion 10, the flaky graphite 10 existing in a state of being independently dispersed on the silicon wafer was prepared in the same manner as in Example 8-2, and the thickness of the flaky graphite 10 was measured by AFM. The average thickness of the flaky graphite 10 was 43 nm. Of the measured flakes, the number of flakes having a thickness of less than 10 nm is 8%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 76%, and the number of flakes having a thickness exceeding 50 nm is 16%. It was confirmed.

(Example 10-3: Production of graphite film)
The flaky graphite dispersion 10 obtained in Example 10-2 was filtered and washed with isopropyl alcohol to obtain a graphite film 10.
When fluorine was detected in the graphite film 10 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 10 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 10 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 95% and the oxygen atom composition was 5%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 76%.
As a result of the Raman measurement of the graphite film 10, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.15, and a result supporting that there were few defects was obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.33, The result which proves that the thickness of flaky graphite is thin was obtained.

(Example 11-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Example 8-1, the dispersing agent was BYK-9076 manufactured by Big Chemie Japan (polyurethane-containing, alkylammonium salt of high molecular weight copolymer, solubility in fluorine-based solvent was less than 0.1 (g / 100 g solvent), into water. Exfoliated graphite 11 was obtained in the same manner as in Example 8-1, except that the solubility was 15 (g / 100 g solvent) and the viscosity at 25 ° C. was 1050 mPa · s.

By removing the fluorinated solvent from the mixed solution containing flaky graphite 11 obtained in Example 11-1 and adding water in the same manner as in Example 8-2, flaky graphite dispersion without precipitation is added. 11 was obtained (yield of flaky graphite 100% dispersed in the dispersion). Using flaky graphite dispersion 11, flaky graphite 11 existing in a state of being independently dispersed on a silicon wafer was prepared in the same manner as in Example 8-2, and when the thickness of flaky graphite 11 was measured by AFM, The average thickness of the flaky graphite 11 was 34 nm. Of the measured flakes, the number of flakes having a thickness of less than 10 nm is 9%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 86%, and the number of flakes having a thickness exceeding 50 nm is 5%. It was confirmed.

(Example 11-3: Production of graphite film)
The flaky graphite dispersion 11 obtained in Example 11-2 was filtered and washed with water to obtain a graphite film 11.
When fluorine was detected in the graphite film 11 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 11 was measured by X-ray diffraction, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 11 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 96% and the oxygen atom composition was 4%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 79%.
As a result of Raman measurement of the graphite film 11, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.08, and the results supporting the few defects were obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.38, The result which proves that the thickness of flaky graphite is thin was obtained.

(Example 12-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Example 8-1, the dispersant was a branched polyethyleneimine (number average molecular weight Mn 60000, 50% aqueous solution) manufactured by Sigma-Aldrich (solubility in the fluorine-based solvent was less than 0.1 (g / 100 g solvent), solubility in water 50 ( Except that the viscosity was changed to more than g / 100 g solvent) and a viscosity at 25 ° C. (10000 mPa · s), flaky graphite 12 was obtained in the same manner as in Example 8-1.

The fluorinated solvent is removed from the mixed solution containing the flaky graphite 12 obtained in Example 12-1 in the same manner as in Example 8-2, and water is added to obtain a flaky graphite dispersion 12. (Yield of flaky graphite dispersed in dispersion liquid: 100%). Using the flaky graphite dispersion 12, the flaky graphite 12 present in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 1-2, and the thickness of the flaky graphite 12 was measured by AFM. The average thickness of the flaky graphite 12 was 45 nm. Of the measured flakes, the number of flakes having a thickness of less than 10 nm is 4%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 75%, and the number of flakes having a thickness exceeding 50 nm is 21%. It was confirmed.

(Example 12-3: Production of graphite film)
The comparative flaky graphite dispersion 12 obtained in Example 12-2 was filtered and washed with water to obtain a graphite film 12.
When fluorine was detected in the graphite film 12 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 12 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 12 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 95% and the oxygen atom composition was 5%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 78%.
As a result of Raman measurement of the graphite film 12, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.16 and the result which supports that there are few defects was obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.31, The result which proves that the thickness of flaky graphite is thin was obtained.

(Example 13-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Example 8-1, the dispersant was sodium dodecylbenzene sulfonate (hard type) manufactured by Tokyo Chemical Industry Co., Ltd. (solubility in the fluorine-based solvent was less than 0.1 (g / 100 g solvent), and solubility in water was 20 (g / Exfoliated graphite 13 was obtained in the same manner as in Example 8-1, except that it was changed to 100 g solvent) and solid at 25 ° C.

The fluorinated solvent is removed from the mixed solution containing the flaky graphite 13 obtained in Example 13-1 in the same manner as in Example 8-2, and water is added to obtain a flaky graphite dispersion 13. (Yield of flaky graphite dispersed in dispersion liquid: 100%). Using the flaky graphite dispersion 13, the flaky graphite 13 existing in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 8-2, and the thickness of the flaky graphite 13 was measured by AFM. The average thickness of the flaky graphite 12 was 38 nm. Further, of the measured flakes, the number of flakes having a thickness of less than 10 nm is 36%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 58%, and the number of flakes having a thickness exceeding 50 nm is 6%. It was confirmed.

(Example 13-3: Production of graphite film)
The flaky graphite dispersion 13 obtained in Example 13-2 was filtered and washed with water to obtain a graphite film 13.
When fluorine was detected in the graphite film 13 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.5%. Further, when the average interplanar spacing (d002) of the (002) planes of the graphite film 13 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 13 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 96% and the oxygen atom composition was 4%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 82%.
As a result of the Raman measurement of the graphite film 13, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.13 and the result which supports that there are few defects was obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.40, The result which proves that the thickness of flaky graphite is thin was obtained.

(Example 14-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Example 8-1, except that the fluorine-based solvent was changed to 10 mL (18.7 g) of perfluorocarbon (C _x F _{2x + 2,} x = 12), 3M Fluorinert FC-43, surface tension 16 mN / m, In the same manner as in Example 8-1, flaky graphite 14 was obtained. The solubility of the dispersant (Tokyo Chemical Industry Co., Ltd. dodecylbenzenesulfonic acid) in the fluorine-based solvent was less than 0.1 (g / 100 g solvent), and the solubility in water was 25 (g / 100 g solvent).

The fluorinated solvent is removed from the mixed solution containing the flaky graphite 14 obtained in Example 14-1 in the same manner as in Example 8-2, and water is added to obtain a flaky graphite dispersion 14. (Yield of flaky graphite dispersed in dispersion liquid: 100%). Using the flaky graphite dispersion 14, the flaky graphite 14 existing in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 8-2, and the thickness of the flaky graphite 14 was measured by AFM. The average thickness of the flaky graphite 14 was 22 nm. Of the measured flakes, the number of flakes having a thickness of less than 10 nm is 15%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 87%, and the number of flakes having a thickness exceeding 50 nm is 7%. It was confirmed.

(Example 14-3: Production of graphite film)
The flaky graphite dispersion 14 obtained in Example 14-2 was filtered and washed with water to obtain a graphite film 14.
When fluorine was detected in the graphite film 14 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%. Further, when the average interplanar spacing (d002) of the (002) plane of the graphite film 14 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 14 was measured by X-ray photoelectron spectroscopy, the composition of carbon atoms was 96% and the composition of oxygen atoms was 4%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 75%.
As a result of Raman measurement of the graphite film 14, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.09, and a result supporting that there were few defects was obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.35, The result which proves that the thickness of flaky graphite is thin was obtained.

(Example 15-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Examples 8-1, a fluorine-based solvent hydrofluorocarbon _{_{_{(C x H y F (2x}}} + 2-y) x = 12 ( main component)), manufactured by Asahi Glass Company ASAHIKLIN AC-2000, the surface tension 13.4MN / m) Exfoliated graphite 15 was obtained in the same manner as in Example 8-1, except that the volume was changed to 10 mL (16.7 g). The solubility of the dispersant (Tokyo Chemical Industry Co., Ltd. dodecylbenzenesulfonic acid) in the fluorine-based solvent was less than 0.1 (g / 100 g solvent), and the solubility in water was 25 (g / 100 g solvent).

The fluorinated solvent is removed from the mixed solution containing the flaky graphite 15 obtained in Example 15-1 in the same manner as in Example 8-2, and water is added to obtain a flaky graphite dispersion 15. (Yield of flaky graphite dispersed in dispersion liquid: 100%). Using flaky graphite dispersion 15, flaky graphite 15 existing in a state of being independently dispersed on a silicon wafer was prepared in the same manner as in Example 8-2, and the thickness of flaky graphite 15 was measured by AFM. The average uniform thickness of the flaky graphite 15 was 20 nm. Further, of the measured flakes, the number of flakes having a thickness of less than 10 nm is 30%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 64%, and the number of flakes having a thickness exceeding 50 nm is 6%. It was confirmed.

(Example 15-3: Production of graphite film)
The flaky graphite dispersion 15 obtained in Example 15-2 was filtered and washed with water to obtain a graphite film 15.
When fluorine was detected in the graphite film 15 by TOF-SIMS measurement, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 1.4%. Further, when an average interplanar spacing (d002) of (002) planes of the graphite film 15 by X-ray diffraction method was measured, it was 0.3356 nm, which was the same as that of ACB-100 of raw material graphite.
Further, when the graphite film 15 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 96% and the oxygen atom composition was 4%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 80%.
As a result of Raman measurement of the graphite film 15, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.08, and the results supporting the few defects were obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.44, The result which proves that the thickness of flaky graphite is thin was obtained.

(Comparative Examples 4-1 and 2: Production of comparative flaky graphite and comparative flaky graphite dispersion)
In Example 8-1, the dispersant is Surflon S-420 (surfactant having a perfluoroalkyl group) manufactured by AGC Seimi Chemical Co., Ltd. (solubility 0.7 (g / 100 g solvent) in the fluorinated solvent, and isopropyl alcohol. Comparative flaky graphite 4 was obtained in the same manner as in Example 8-1, except that the solubility was increased to 10 (g / 100 g solvent) and the viscosity at 25 ° C. was 800 mPa · s.

A comparative flaky graphite dispersion was prepared by removing the fluorinated solvent from the mixed liquid containing the comparative flaky graphite 4 obtained in Comparative Example 4-1, and adding isopropyl alcohol in the same manner as in Example 8-2. 4 was obtained. The comparative flaky graphite dispersion 4 had a precipitate. After decanting the mixture and removing the supernatant, the precipitate is filtered off with a nylon mesh having a mesh size of 100 μm, dried and dried using a heating vacuum oven, and the mass of the precipitate is 74% by mass with respect to the raw material. there were. Since flaky graphite having a thickness of 50 nm or less does not precipitate, the proportion of flaky graphite having a thickness of 50 nm or less is at least 26% by mass or less. In view of the fact that the flaky graphite having a thickness of 50 nm or less is often the same or smaller in size in the plane direction than the flaky graphite having a thickness exceeding 50 nm, the mass is lighter by the thickness. In the dispersion 4, it can be said that it is at least 26% by number or less.

(Comparative Example 4-3: Production of Comparative Graphite Film)
The comparative flaky graphite dispersion 4 obtained in Comparative Example 4-2 was filtered through a membrane filter having a pore size of 0.02 micron including precipitates, and washed with isopropyl alcohol to obtain a comparative graphite film 4. It was.
When the fluorine was detected by TOF-SIMS measurement for the comparative graphite film 4, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 0 except for noise (0.2%). there were. Further, when the average interplanar spacing (d002) of the (002) plane of the comparative graphite film 4 was measured by X-ray diffraction, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
The comparative graphite film 4 was subjected to Raman measurement. As a result, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is 0.08, The results confirming that there are few defects were obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.18, The result which proves that the thickness of flaky graphite is not so thin was obtained.

(Comparative Example 5-2: Production of Comparative Flaky Graphite Dispersion)
Comparative flaky graphite dispersion 5 was obtained in the same manner as in Example 8-2, except that toluene (solubility of the dispersant is 1 (g / 100 g solvent)) was used instead of water in Example 8-2. . The comparative flaky graphite dispersion 5 had a precipitate. After decanting the mixture and removing the supernatant, the precipitate is filtered through a nylon mesh having a mesh size of 100 μm and dried using a heating vacuum oven to measure the mass. The mass of the precipitate is 80% by mass with respect to the raw material. there were. Since flaky graphite having a thickness of 50 nm or less does not precipitate, the proportion of flaky graphite having a thickness of 50 nm or less is at least 20% by mass or less. In view of the fact that the flaky graphite having a thickness of 50 nm or less is often the same or smaller in size in the plane direction than the flaky graphite having a thickness exceeding 50 nm, the mass is lighter by the thickness. In the dispersion 5, it can be said that it is at least 20% by number or less.

(Comparative Example 5-3: Production of Comparative Graphite Film)
The comparative flaky graphite dispersion 5 obtained in Comparative Example 5-2 was filtered through a membrane filter having a pore size of 0.02 micron including precipitates, and washed with water to obtain a comparative graphite film 5. .
When the fluorine was detected by TOF-SIMS measurement for the comparative graphite film 5, the ratio of the fluorine (−) ion count to the total count of all (−) ions was 0 excluding noise (0.2%). It was. Further, when the average interplanar spacing (d002) of the (002) plane of the comparative graphite film 5 was measured by X-ray diffraction, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
The comparative graphite film 5 was subjected to Raman measurement. As a result, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is 0.17, The results confirming that there are few defects were obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.18, The result which proves that the thickness of flaky graphite is not so thin was obtained.

(Comparative Examples 6-1 and 2: Production of comparative flaky graphite and comparative flaky graphite dispersion)
In Example 8-1, the fluorine-based solvent was changed to water (surface tension (25 ° C.) 72 mN / m), and the dispersant was Surflon S-420 (surfactant having a perfluoroalkyl group) manufactured by AGC Seimi Chemical. (Soluble in water less than 0.1 (g / 100 g solvent), solubility in isopropyl alcohol exceeding 10 (g / 100 g solvent), viscosity at 25 ° C. 800 mPa · s) Comparative flaky graphite 6 was thus obtained.

By removing water from the mixed solution containing the comparative flaky graphite 6 obtained in Comparative Example 6-1 in the same manner as in Example 8-2, and adding isopropyl alcohol, the comparative flaky graphite dispersion 6 was obtained. Obtained. The comparative flaky graphite dispersion 6 had a precipitate. After decanting the mixture and removing the supernatant, the precipitate is filtered through a nylon mesh having a mesh size of 100 μm and dried using a heating vacuum oven to measure the mass. The mass of the precipitate is 80% by mass with respect to the raw material. there were. Since flaky graphite having a thickness of 50 nm or less does not precipitate, the proportion of flaky graphite having a thickness of 50 nm or less is at least 20% by mass or less. Considering that flaky graphite having a thickness of 50 nm or less often has the same or smaller size in the surface direction than flaky graphite having a thickness exceeding 50 nm, the mass is light by the thickness, so at least 20% by number The following can be said.

(Comparative Example 6-3: Production of comparative graphite film)
The comparative flaky graphite dispersion 6 obtained in Comparative Example 6-2 was filtered through a membrane filter having a pore size of 0.02 micron including precipitates, and washed with isopropyl alcohol to obtain a comparative graphite film 6. It was.
When the fluorine was detected by TOF-SIMS measurement for the comparative graphite film 6, the ratio of the count number of fluorine (−) ions to the total count number of all (−) ions was 0 except for noise (0.2%). It was. Further, when the average interplanar spacing (d002) of the (002) plane of the comparative graphite film 6 was measured by X-ray diffraction, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
The comparative graphite film 6 was subjected to Raman measurement. As a result, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is 0.16, The results confirming that there are few defects were obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.17, The result which proves that the thickness of flaky graphite is not so thin was obtained.

Table 2 shows the evaluation results of Examples 8 to 15 and Comparative Examples 4 to 6.

From the results of Table 2, in Examples 8 to 15, flaky graphite dispersions with an average thickness of 50 nm or less can be obtained in high yield, and there is little residual graphite that is insufficiently flaked. It was possible to obtain a graphite film excellent in conductivity and thermal conductivity.
When the thermal diffusivity was measured for the graphite films of Examples 8, 9, 11, 13, 14 and 15 in which a self-supporting film was formed, iron (1.4 × 10 ⁻⁵ m ² / s), SUS304 (stainless steel) Compared to (0.4 × 10 ⁻⁵ m ² / s) or the like, the value was equal to or higher, and it was confirmed that the thermal conductivity was excellent.
On the other hand, a fluorine-based solvent having a surface tension at a working temperature of 20 mN / m or less was used as a solvent for dispersing graphite. In Comparative Example 4 using a dispersant having high solubility in the solvent, the time-of-flight type 2 No flaky graphite with a ratio of fluorine (-) ion count to 0.5% or more of the total count of all (-) ions measured using secondary ion mass spectrometry (TOF-SIMS) It was. Moreover, it was shown that the obtained comparative graphite film 4 has a high resistance value and is inferior in conductivity.
Also in Comparative Example 5, the ratio of the number of fluorine (−) ions to the total number of (−) ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0. No more than 5% flaky graphite was obtained. In Comparative Example 5, when the dispersion was prepared, precipitation was generated because the dispersion was prepared by adding a solvent having a solubility of the dispersant less than 5 (g / 100 g solvent). Moreover, it was shown that the obtained comparative graphite film 5 has a high resistance value and is inferior in conductivity.
Also in Comparative Example 6, the ratio of the number of fluorine (−) ions to the total number of (−) ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0. No more than 5% flaky graphite was obtained. In Comparative Example 6 in which a solvent having a surface tension at an operating temperature of more than 20 mN / m and a dispersant having a low solubility in the solvent were used in combination as a solvent for dispersing graphite, precipitation occurred in the dispersion. Moreover, it was shown that the obtained comparative graphite film 6 has a high resistance value and is inferior in conductivity.

2. Example II series (third invention)
Examples of the third aspect of the present invention will be described below. Among the examples of the third aspect of the present invention, Examples 1 to 6 and 8 to 15 and Comparative Examples 1 to 6 are the first examples of the Example I series. The same as Examples 1 to 6 and 8 to 15 and Comparative Examples 1 to 6 of the second invention. Therefore, of the third embodiment of the present invention, detailed description of Examples 1 to 6 and 8 to 15 and Comparative Examples 1 to 6 is omitted here.

(Example 7-1: Production of flaky graphite)
In Example 1-1, the fluorine-based solvent was changed to 10 mL (6.8 g) of heptane (surface tension 19.65 mN / m), and the dispersant was tween 20 (polyoxyethylene (20) sorbitan mono) manufactured by Tokyo Chemical Industry Co., Ltd. Example 1-1 with the exception that the solubility in laurate and heptane was less than 0.1 (g / 100 g solvent), the solubility in water was more than 50 (g / 100 g solvent), and the viscosity at 25 ° C. was 370 mPa · s. Similarly, flaky graphite 7 was obtained.

(Example 7-2: Production of flaky graphite dispersion)
Heptane was removed from the mixed solution containing flaky graphite 7 obtained in Example 7-1, and 10 mL of water was added to obtain flaky graphite dispersion 7. (Yield 100% of flaky graphite dispersed in dispersion). Using the flaky graphite dispersion 7, the flaky graphite 7 existing in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 1-2, and the thickness of the flaky graphite 7 was measured by AFM. The range was 4 nm to 37 nm, and the average thickness was 30 nm.

(Example 7-3: Production of graphite film)
The flaky graphite dispersion 7 obtained in Example 7-2 was filtered and washed with water to obtain a graphite film 7. When the average interplanar spacing (d002) of the (002) plane of the graphite film 7 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 7 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 95% and the oxygen atom composition was 5%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 74%.

In Examples 1 to 7, flaky graphite having a thickness of 50 nm or less can be obtained at a high yield of 100%, and a flaky graphite dispersion having little residual graphite that is insufficiently flaked can be obtained. Further, a graphite film excellent in conductivity and thermal conductivity could be obtained.
When the thermal diffusivity was measured for the graphite films of Examples 1, 2, 4 and 6 in which a self-supporting film was formed, iron (1.4 × 10 ⁻⁵ m ² / s), SUS304 (stainless steel) (0.4 × 10 ⁻⁵ m ² / s) or the like, which is equal or higher than that, and was confirmed to be excellent in thermal conductivity.
On the other hand, a solvent having a surface tension at a working temperature of 20 mN / m or less was used as a solvent at the time of graphite dispersion, but the dispersion of Comparative Example 1 using a dispersant having high solubility in the solvent caused precipitation. Thus, the yield of flaky graphite of 50 nm or less dispersed in the dispersion was 0%. Moreover, it was shown that the obtained comparative graphite film 1 has a high resistance value and is inferior in conductivity.
Further, when preparing the dispersion, the dispersion of Comparative Example 2 in which the dispersion was prepared by adding a solvent having a solubility of the dispersant less than 5 (g / 100 g solvent) resulted in precipitation. The yield of flaky graphite having a thickness of 50 nm or less dispersed in was 0%. Moreover, it was shown that the obtained comparative graphite film 2 has a high resistance value and is inferior in conductivity.
In addition, as a solvent for dispersing graphite, precipitation occurred in the dispersion of Comparative Example 3 in which a solvent having a surface tension at the operating temperature exceeding 20 mN / m and a dispersant having a low solubility in the solvent were used in combination. The yield of flaky graphite of 50 nm or less dispersed in the dispersion was 0%. Moreover, it was shown that the obtained comparative graphite film 3 has a high resistance value and is inferior in conductivity.

(Example 16-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Example 8-1, the fluorine-based solvent was changed to 20 mL (13.6 g) of heptane (surface tension 19.65 mN / m), and the dispersant was tween 20 (polyoxyethylene (20) sorbitan mono) manufactured by Tokyo Chemical Industry Co., Ltd. Example 8-1 with the exception that the solubility in laurate and heptane was less than 0.1 (g / 100 g solvent), the solubility in water was more than 50 (g / 100 g solvent), and the viscosity at 25 ° C. was 370 mPa · s. Similarly, flaky graphite 16 was obtained.

Heptane was removed from the mixed solution containing flaky graphite 16 obtained in Example 16-1 in the same manner as in Example 8-2, and water was added to obtain flaky graphite dispersion 16 ( Yield of flaky graphite dispersed in dispersion (100%). Using the flaky graphite dispersion 16, the flaky graphite 16 present in an independently dispersed state on the silicon wafer was prepared in the same manner as in Example 8-2, and the thickness of the flaky graphite 16 was measured by AFM. The average thickness of the flaky graphite 16 was 45 nm. Of the measured flakes, the number of flakes having a thickness of less than 10 nm is 2%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 74%, and the number of flakes having a thickness exceeding 50 nm is 24%. It was confirmed.

(Example 16-3: Production of graphite film)
The flaky graphite dispersion liquid 16 obtained in Example 16-2 was filtered and washed with water to obtain a graphite film 16. When the average interplanar spacing (d002) of the (002) plane of the graphite film 16 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 16 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 95% and the oxygen atom composition was 5%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 70%.
As a result of Raman measurement of the graphite film 16, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.08, and the results supporting the few defects were obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.43, The result which proves that the thickness of flaky graphite is thin was obtained.

(Example 17-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Example 8-1, the fluorine-based solvent was changed to 2,4-dimethylpentane (surface tension 17.7 mN / m) 20 mL (13.4 g), and the dispersant was tween 20 (polyoxyethylene manufactured by Tokyo Chemical Industry Co., Ltd.). (20) Sorbitan monolaurate, solubility in 2,4-dimethylpentane is less than 0.1 (g / 100 g solvent), solubility in water is more than 50 (g / 100 g solvent), viscosity is changed to 370 mPa · s at 25 ° C. Except that, flaky graphite 17 was obtained in the same manner as in Example 8-1.

By removing 2,4-dimethylpentane from the mixed liquid containing flaky graphite 17 obtained in Example 17-1 and adding water in the same manner as in Example 8-2, a flaky graphite dispersion was obtained. 17 was obtained (yield of flaky graphite dispersed in the dispersion, 100%). Using the flaky graphite dispersion 17, the flaky graphite 17 existing in a state of being independently dispersed on the silicon wafer was prepared in the same manner as in Example 8-2, and the thickness of the flaky graphite 17 was measured by AFM. The average thickness of the flaky graphite 17 was 44 nm. Of the measured flakes, the number of flakes having a thickness of less than 10 nm is 4%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 76%, and the number of flakes having a thickness exceeding 50 nm is 20%. It was confirmed.

(Example 17-3: Production of graphite film)
The flaky graphite dispersion liquid 17 obtained in Example 17-2 was filtered and washed with water to obtain a graphite film 17. When the average interplanar spacing (d002) of the (002) plane of the graphite film 17 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 17 was measured by X-ray photoelectron spectroscopy, the carbon atom composition was 95% and the oxygen atom composition was 5%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 73%.
As a result of the Raman measurement of the graphite film 17, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.08, and the results supporting the few defects were obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.43, The result which proves that the thickness of flaky graphite is thin was obtained.

(Example 18-1, 2: Production of flaky graphite and flaky graphite dispersion)
In Example 8-1, the fluorinated solvent was changed to 20 mL (16.4 g) of polydimethylsiloxane (KF-96L-1cs, surface tension 16.9 mN / m, manufactured by Shin-Etsu Chemical Co., Ltd.), and the dispersant was changed to Tokyo Kasei. Industrial tween 20 (polyoxyethylene (20) sorbitan monolaurate, solubility in polydimethylsiloxane less than 0.1 (g / 100 g solvent), solubility in water over 50 (g / 100 g solvent), viscosity at 25 ° C. 370 mPa Except for the change to s), flaky graphite 18 was obtained in the same manner as in Example 8-1.

From the mixed solution containing the flaky graphite 18 obtained in Example 18-1, polydimethylsiloxane was removed in the same manner as in Example 8-2, and water was added to obtain a flaky graphite dispersion 18. (Yield of flaky graphite dispersed in dispersion liquid: 100%). Using flaky graphite dispersion 18, flaky graphite 18 existing in a state of being independently dispersed on a silicon wafer was prepared in the same manner as in Example 8-2, and when the thickness of flaky graphite 18 was measured by AFM, The average thickness of the flaky graphite 18 was 43 nm. Further, of the measured flakes, the number of flakes having a thickness of less than 10 nm is 10%, the number of flakes having a thickness in the range of 10 nm to 50 nm is 69%, and the number of flakes having a thickness exceeding 50 nm is 21%. It was confirmed.

(Example 18-3: Production of graphite film)
The flaky graphite dispersion liquid 18 obtained in Example 18-2 was filtered and washed with water to obtain a graphite film 18. When the average interplanar spacing (d002) of the (002) plane of the graphite film 18 by X-ray diffraction was measured, it was 0.3356 nm, which was the same as that of ACB-100 of the raw graphite.
Further, when the graphite film 18 was measured by X-ray photoelectron spectroscopy, the composition of carbon atoms was 95% and the composition of oxygen atoms was 5%. And the ratio of the bond which has formed the sp2 bond between carbon atoms among the bonds which the said carbon atom has was 73%.
As a result of Raman measurement of the graphite film 18, the intensity ratio I _D / I _G between the peak intensity (I _D ) in the range of 1300 to 1400 cm ⁻¹ and the peak intensity (I _G ) in the range of 1580 to 1620 cm ⁻¹ is It was 0.07, and the result which proves that there are few defects was obtained. The / _{I G} _'intensity ratio I _G of the peak intensity in the range of 1580 ~ 1620cm ^-1 _{(I G)} peak intensity (I _{_G)'} in the range of 2600 ~ 2800 cm ^-1 is 0.46, The result which proves that the thickness of flaky graphite is thin was obtained.

In Examples 8 to 18, it was possible to obtain a flaky graphite dispersion with insufficient residual graphite, and a graphite film excellent in conductivity and thermal conductivity.
When the thermal diffusivity was measured for the graphite films of Examples 8, 9, 11, 13, 14 and 15 in which a self-supporting film was formed, iron (1.4 × 10 ⁻⁵ m ² / s), SUS304 (stainless steel) Compared to (0.4 × 10 ⁻⁵ m ² / s) or the like, the value was equal to or higher, and it was confirmed that the thermal conductivity was excellent.
On the other hand, a solvent having a surface tension at a working temperature of 20 mN / m or less was used as a solvent for dispersing graphite, but the dispersion of Comparative Example 4 using a dispersant having high solubility in the solvent caused precipitation. Thus, the yield of flaky graphite of 50 nm or less dispersed in the dispersion was low. Moreover, it was shown that the obtained comparative graphite film 4 has a high resistance value and is inferior in conductivity.
Further, when preparing the dispersion, the dispersion of Comparative Example 5 in which the dispersion was prepared by adding a solvent having a solubility of the dispersant of less than 5 (g / 100 g solvent) caused precipitation, and the dispersion The yield of flaky graphite of 50 nm or less dispersed in was low. Moreover, it was shown that the obtained comparative graphite film 5 has a high resistance value and is inferior in conductivity.
In addition, as a solvent for dispersing graphite, precipitation occurred in the dispersion of Comparative Example 6 using a combination of a solvent having a surface tension exceeding 20 mN / m at the use temperature and a dispersant having low solubility in the solvent. The yield of flaky graphite of 50 nm or less dispersed in the dispersion was low. Moreover, it was shown that the obtained comparative graphite film 6 has a high resistance value and is inferior in conductivity.

Claims

The ratio of the number of fluorine (−) ions to the total number of (−) ions measured using time-of-flight secondary ion mass spectrometry (TOF-SIMS) is 0.5% or more, and X Flaky graphite having an average interplanar spacing (d002) of (002) planes of 0.336 nm or less and an average thickness of 50 nm or less by line diffraction method.
As measured by X-ray photoelectron spectroscopy, the composition of carbon atoms is 80% or more and 99% or less, the composition of oxygen atoms is 10% or less, and among the bonds of the carbon atoms, sp2 bonds are present between the carbon atoms. The flaky graphite according to claim 1, wherein the proportion of bonds formed is 60% or more.
A graphite material in which the flaky graphite according to claim 1 or 2 is laminated.
A flaky graphite dispersion obtained by dispersing the flaky graphite according to claim 1 or 2 in a solvent.