JP2016190772A - Carbon film, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon film excellent in self-standing properties and electroconductivity, and to provide a method for producing the carbon film.SOLUTION: The carbon film contains such a single-layered fibrous carbon nanostructure and a multilayer fibrous carbon nanostructure that the BET specific surface area thereof is 500 m/g or larger. The method for producing the carbon film comprises the steps of: removing a solvent from a fibrous carbon nanostructure dispersion liquid which contains the single-layered fibrous carbon nanostructure having 500 m/g or larger BET specific surface area, the multilayer fibrous carbon nanostructure, a dispersant and the solvent; and forming the carbon film from the solvent-removed fibrous carbon nanostructure dispersion liquid.SELECTED DRAWING: None

Description

  The present invention relates to a carbon film and a method for producing the same, and more particularly to a carbon film including a single-layer fibrous carbon nanostructure and a multilayer fibrous carbon nanostructure, and a method for producing the carbon film. It is.

  In recent years, carbon nanotubes (hereinafter sometimes referred to as “CNT”) have attracted attention as materials that are excellent in electrical conductivity, thermal conductivity, and mechanical properties.

  However, since a fibrous carbon nanostructure such as CNT is a fine structure having a diameter of nanometers, handling and workability are poor by itself. Therefore, for example, a plurality of CNTs are gathered into a film to form a carbon nanotube film (hereinafter also referred to as “CNT film”) that may be referred to as “bucky paper”, and the CNT film It has been proposed to use as a conductive film. Specifically, a CNT film formed by removing a solvent from a carbon nanotube dispersion containing a solvent and CNTs by using a means such as filtration and drying is a member constituting an electrode such as a solar cell or a touch panel ( For example, use as a conductive film or a catalyst layer has been proposed (see, for example, Patent Document 1).

  Carbon films formed by assembling single-layer or multi-layer fibrous carbon nanostructures such as the above-described CNT films are attracting attention as film-like materials having excellent conductivity, thermal conductivity, and mechanical properties. Yes. In particular, multi-layered fibrous carbon nanostructures such as multi-walled CNTs are widely used as carbon film materials because they are relatively easy to produce and have better thermal and chemical stability than single-walled CNTs. .

JP 2010-105909 A

  However, a carbon film made of only multi-walled CNTs may not have sufficient strength due to insufficient strength or may not have sufficient conductivity.

  Therefore, an object of the present invention is to provide a carbon film excellent in self-supporting property and conductivity and a method for producing the same.

  The present inventors have intensively studied to achieve the above object. Then, the present inventors have formed a carbon film including a single-layer fibrous carbon nanostructure having a predetermined BET specific surface area and a multilayer fibrous carbon nanostructure, thereby achieving self-supporting and conductive properties. The present inventors have found that an excellent carbon film can be obtained and completed the present invention.

That is, this invention aims to solve the above-mentioned problem advantageously, and the carbon film of the present invention includes a single-layer fibrous carbon nanostructure and a multilayer fibrous carbon nanostructure, The single-layer fibrous carbon nanostructure has a BET specific surface area of 500 m ² / g or more. Thus, by including a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and a multilayer fibrous carbon nanostructure, a carbon film excellent in self-supporting property and conductivity is provided. be able to.

  In the carbon film of the present invention, the content ratio of the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure is a mass ratio (single-layer fibrous carbon nanostructure / multi-layer fibrous carbon nanostructure. ) Is preferably 95/5 to 5/95. The content ratio of the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure is 95/5 to 5 / in mass ratio (single-layer fibrous carbon nanostructure / multi-layer fibrous carbon nanostructure). By setting it to 95, the conductivity of the carbon film can be further increased and the film formability of the carbon film can be improved.

  In the carbon film of the present invention, it is preferable that the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure include carbon nanotubes. If a fibrous carbon nanostructure containing carbon nanotubes is used, the strength and self-supporting property of the carbon film can be further increased.

In the method for producing a carbon film of the present invention, a fibrous form containing a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more, a multilayer fibrous carbon nanostructure, a dispersant, and a solvent. The method includes a step of removing the solvent from the carbon nanostructure dispersion liquid to form a carbon film. In this way, by removing the solvent from the fibrous carbon nanostructure dispersion liquid in which the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure are dispersed, the film is self-supporting. In addition, a carbon film having excellent conductivity can be manufactured.

  In the method for producing a carbon film of the present invention, a coarse dispersion formed by adding the single-layer fibrous carbon nanostructure, the multilayer fibrous carbon nanostructure, and the dispersant to the solvent, Prepare a fibrous carbon nanostructure dispersion by dispersing the single-layered fibrous carbon nanostructure and the multilayered fibrous carbon nanostructure in a dispersion treatment that provides a cavitation effect or crushing effect Preferably, the method further includes the step of: By subjecting the coarse dispersion to a dispersion treatment that provides a cavitation effect or a crushing effect, the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure can be uniformly dispersed in the dispersion. In carbon films formed from this homogeneous dispersion, single-layered fibrous carbon nanostructures and multi-layered fibrous carbon nanostructures exist in a more homogeneously dispersed manner, so that self-supporting properties, electrical conductivity, and other characteristics can be achieved. This can be further improved.

  In the carbon film of the present invention, the content ratio of the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure is a mass ratio (single-layer fibrous carbon nanostructure / multi-layer fibrous carbon nanostructure. ) Is preferably 95/5 to 5/95. The content ratio of the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure is 95/5 to 5 / in mass ratio (single-layer fibrous carbon nanostructure / multi-layer fibrous carbon nanostructure). By setting the ratio to 95, a carbon film having higher conductivity and excellent film formability can be produced.

  In the method for producing a carbon film of the present invention, it is preferable that the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure include carbon nanotubes. If a fibrous carbon nanostructure containing carbon nanotubes is used, the strength and self-supporting property of the carbon film can be further increased.

  ADVANTAGE OF THE INVENTION According to this invention, the carbon film excellent in self-supporting property and electroconductivity, and its manufacturing method can be provided.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the carbon film of the present invention includes a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and a multilayer fibrous carbon nanostructure. The carbon film of the present invention can be produced using the method for producing a carbon film of the present invention.

(Carbon film)
The carbon film of the present invention comprises an aggregate of fibrous carbon nanostructures obtained by assembling a plurality of fibrous carbon nanostructures into a film shape. One of the major features of the carbon film of the present invention is that it includes a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more. Further, the carbon film of the present invention includes a multilayer fibrous carbon nanostructure as one of the major features.
In the present invention, the carbon film may be a film (a film with a support) formed on a support such as a substrate, or may be a self-supporting film.

[Single-layer fibrous carbon nanostructure]
A single-layer fibrous carbon nanostructure is sometimes referred to as a carbon nanostructure in which a carbon hexagonal mesh surface of graphite forms one cylindrical shape, that is, a single-walled carbon nanotube (“single-walled CNT”). )including. The single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more used in the present invention may be composed of only single-walled CNTs, or non-walled CNTs other than single-walled CNTs. It may be a mixture with a cylindrical single-layer fibrous carbon nanostructure or a graphene nanotape described later.

The single-layer fibrous carbon nanostructure used in the present invention has a BET specific surface area of 500 m ² / g or more, preferably 600 m ² / g or more, more preferably 800 m ² / g or more, It is preferably 2500 m ² / g or less, and more preferably 1200 m ² / g or less. Furthermore, when the single-layer fibrous carbon nanostructure contains single-walled CNTs and the single-walled CNTs are mainly opened, the BET specific surface area is preferably 1300 m ² / g or more. If the BET specific surface area of the single-layer fibrous carbon nanostructure is 500 m ² / g or more, the thermal conductivity and strength of the carbon film can be sufficiently increased. Moreover, if the BET specific surface area of a single layer fibrous carbon nanostructure is 2500 m < ² > / g or less, the aggregation of a single layer fibrous carbon nanostructure will be suppressed and the single layer fibrous carbon nanostructure in a carbon film will be suppressed. Dispersibility can be improved.
In the present invention, the “BET specific surface area” refers to a nitrogen adsorption specific surface area measured using the BET method.

The single-walled carbon nanotubes described above are produced by, for example, supplying a raw material compound and a carrier gas onto a substrate having a catalyst layer for producing carbon nanotubes on the surface, and performing chemical vapor deposition (CVD) to produce CNTs. When a catalyst is synthesized, a method of dramatically improving the catalytic activity of the catalyst layer by making a small amount of an oxidizing agent (catalyst activating substance) present in the system (super growth method; see International Publication No. 2006/011655) ) And can be produced efficiently. Hereinafter, the carbon nanotube obtained by the super growth method may be referred to as “SGCNT”.
In addition, the carbon nanotube manufactured by the super growth method may be comprised only from SGCNT, and may be comprised from SGCNT and the non-cylindrical carbon nanostructure.

  The single-layer fibrous carbon nanostructure of the present invention has a single-layer or multi-layer flat cylindrical carbon nanostructure (hereinafter referred to as “graphene nanotape”) having a tape-like portion whose inner walls are close to or bonded to each other over the entire length. (GNT) ") may be included.

  Here, GNT is presumed to be a substance in which a tape-like portion in which inner walls are close to each other or bonded is formed over the entire length from the synthesis, and a carbon six-membered ring network is formed in a flat cylindrical shape. The And the shape of GNT is a flat cylindrical shape, and the presence of a tape-like part in which the inner walls are close to each other or bonded is present in GNT. For example, GNT and fullerene (C60) are sealed in a quartz tube. When the fullerene insertion GNT obtained by heat treatment (fullerene insertion treatment) under reduced pressure is observed with a transmission electron microscope (TEM), there is a portion (tape-like portion) in which fullerene is not inserted in GNT. Can be confirmed.

And it is preferable that the shape of GNT is a shape which has a tape-shaped part in the center part of the width direction, and the shape of the cross section orthogonal to the extending direction (axial direction) is the cross-sectional length in the vicinity of both ends in the cross-sectional longitudinal direction. It is more preferable that the maximum dimension in the direction orthogonal to the direction is larger than the maximum dimension in the direction orthogonal to the longitudinal direction of the cross section in the vicinity of the central portion in the longitudinal direction of the cross section. preferable.
Here, in the cross-sectional shape of the GNT, “near the central portion in the longitudinal direction of the cross section” means the longitudinal width of the cross section from the longitudinal center line of the cross section (a straight line passing through the longitudinal center of the cross section and perpendicular to the longitudinal direction line). The “near the end in the longitudinal direction of the cross section” means the area outside the longitudinal direction of “near the center in the longitudinal direction of the cross section”.

  Note that a single-layer carbon nanostructure containing GNT as a non-cylindrical carbon nanostructure has a catalyst layer on the surface when a CNT is synthesized by a super-growth method using a substrate having the catalyst layer on the surface. It can be obtained by forming a substrate (hereinafter sometimes referred to as “catalyst substrate”) by a predetermined method. Specifically, the carbon nanostructure containing GNT is obtained by applying a coating liquid A containing an aluminum compound on a substrate, drying the applied coating liquid A, and then forming an aluminum thin film (catalyst supporting layer) on the substrate. ) Is applied on the aluminum thin film, the coating liquid B containing the iron compound is applied, and the applied coating liquid B is dried at a temperature of 50 ° C. or less to form the iron thin film (catalyst layer) on the aluminum thin film. It can be obtained by synthesizing GNT by the super-growth method using the catalyst substrate obtained by forming.

In addition, as the single-layer fibrous carbon nanostructure, the ratio (3σ / Av) of the value (3σ) obtained by multiplying the standard deviation (σ) of the diameter by 3 with respect to the average diameter (Av) is more than 0.20. It is preferable to use a carbon nanostructure of less than 60, more preferably a carbon nanostructure with 3σ / Av exceeding 0.25, and a carbon nanostructure with 3σ / Av exceeding 0.50. Further preferred. If a single-layer fibrous carbon nanostructure having 3σ / Av of more than 0.20 and less than 0.60 is used, the thermal conductivity and strength of the carbon film can be sufficiently obtained even if the amount of the carbon nanostructure is small. Therefore, it is possible to suppress the increase in the hardness of the carbon film (i.e., the decrease in flexibility) by blending the single-layer fibrous carbon nanostructure, and to sufficiently increase the thermal conductivity, flexibility and strength. A carbon film aligned at a high level can be obtained.
“Average diameter (Av) of single-layer fibrous carbon nanostructure” and “standard deviation of diameter of single-layer fibrous carbon nanostructure (σ: sample standard deviation)” are measured with a transmission electron microscope, respectively. The diameter (outer diameter) of 100 single-layered fibrous carbon nanostructures randomly selected by use can be measured and determined. And the average diameter (Av) and standard deviation (σ) of the single-layer fibrous carbon nanostructure may be adjusted by changing the production method and production conditions of the single-layer fibrous carbon nanostructure, You may adjust by combining multiple types of single layer fibrous carbon nanostructure obtained by a different manufacturing method.

  And as a single-layer fibrous carbon nanostructure, when the diameter measured as described above is plotted on the horizontal axis, the frequency is plotted on the vertical axis, and approximated by Gaussian, it takes a normal distribution. Usually used.

  Furthermore, the single-layer fibrous carbon nanostructure preferably has a peak of Radial Breathing Mode (RBM) when evaluated using Raman spectroscopy. Note that there is no RBM in the Raman spectrum of a fibrous carbon nanostructure composed of only three or more multi-walled carbon nanotubes.

  The single-layer fibrous carbon nanostructure preferably has a G-band peak intensity ratio (G / D ratio) of 1 to 20 in the Raman spectrum. If the G / D ratio is 1 or more and 20 or less, the thermal conductivity and strength of the carbon film can be sufficiently increased even if the blending amount of the single-layer fibrous carbon nanostructure is small. Carbon film in which the hardness of the carbon film is increased (that is, the flexibility is lowered) by blending the carbon-like carbon nanostructures, and the heat conductivity, flexibility and strength are juxtaposed at a sufficiently high level. Can be obtained.

  Furthermore, the average diameter (Av) of the single-layer fibrous carbon nanostructure is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, and preferably 10 nm or less. Is more preferable. When the average diameter (Av) of the single-layer fibrous carbon nanostructure is 0.5 nm or more, aggregation of the single-layer fibrous carbon nanostructure can be suppressed and the dispersibility of the carbon nanostructure can be improved. Moreover, if the average diameter (Av) of a single layer fibrous carbon nanostructure is 15 nm or less, the heat conductivity and intensity | strength of a carbon film can fully be improved.

  The single-layer fibrous carbon nanostructure preferably has an average structure length of 100 μm or more and 5000 μm or less at the time of synthesis. Note that, as the length of the structure at the time of synthesis increases, damage such as breakage or cutting occurs more easily at the time of dispersion. Therefore, the average length of the structure at the time of synthesis is preferably 5000 μm or less.

Furthermore, according to the super-growth method, the single-layer fibrous carbon nanostructure is an aggregate (orientated assembly) oriented in a direction substantially perpendicular to the substrate on the substrate having a catalyst layer for carbon nanotube growth on the surface. The mass density of the fibrous carbon nanostructure as the aggregate is preferably 0.002 g / cm ³ or more and 0.2 g / cm ³ or less. If the mass density is 0.2 g / cm ³ or less, the connection between the single-layer fibrous carbon nanostructures is weakened, so that the single-layer fibrous carbon nanostructures can be uniformly dispersed in the carbon film. . Moreover, if the mass density is 0.002 g / cm ³ or more, the integrity of the single-layer fibrous carbon nanostructure can be improved, and the handling can be facilitated because it can be prevented from being broken.

Furthermore, the single-layer fibrous carbon nanostructure preferably has a plurality of micropores. In particular, the single-layer fibrous carbon nanostructure preferably has micropores having a pore diameter smaller than 2 nm, and the abundance thereof is a micropore volume determined by the following method, preferably 0.40 mL / g or more. More preferably, it is 0.43 mL / g or more, More preferably, it is 0.45 mL / g or more, and as an upper limit, it is about 0.65 mL / g normally. Since the single-layer fibrous carbon nanostructure has the micropores as described above, the aggregation of the single-layer fibrous carbon nanostructure is suppressed, and a carbon film in which the single-layer fibrous carbon nanostructure is highly dispersed is formed. Can be obtained. The micropore volume can be adjusted, for example, by appropriately changing the preparation method and preparation conditions of the single-layer fibrous carbon nanostructure.
Here, “micropore volume (Vp)” is a nitrogen adsorption / desorption isotherm at a liquid nitrogen temperature (77 K) of a single-layer fibrous carbon nanostructure, and nitrogen at a relative pressure P / P0 = 0.19. Assuming that the adsorption amount is V, it can be calculated from the formula (I): Vp = (V / 22414) × (M / ρ). Here, P is a measurement pressure at the time of adsorption equilibrium, P0 is a saturated vapor pressure of liquid nitrogen at the time of measurement, and in formula (I), M is an adsorbate (nitrogen) molecular weight of 28.010, and ρ is an adsorbate (nitrogen). ) At 77K with a density of 0.808 g / cm ³ . The micropore volume can be determined using, for example, “BELSORP (registered trademark) -mini” (manufactured by Nippon Bell Co., Ltd.).

  Moreover, it is preferable that the t-plot obtained from the adsorption isotherm of the single-layer fibrous carbon nanostructure has a convex shape. Among them, it is more preferable that the opening process is not performed and the t-plot shows a convex shape upward. The “t-plot” is obtained by converting the relative pressure to the average thickness t (nm) of the nitrogen gas adsorption layer in the adsorption isotherm of the single-layer fibrous carbon nanostructure measured by the nitrogen gas adsorption method. Can be obtained. That is, the average thickness t of the nitrogen gas adsorption layer is plotted against the relative pressure P / P0, and the average thickness t of the nitrogen gas adsorption layer corresponding to the relative pressure is obtained from the known standard isotherm to perform the above conversion. Gives a t-plot of the single-layer fibrous carbon nanostructure (t-plot method by de Boer et al.).

Here, in the substance having pores on the surface, the growth of the nitrogen gas adsorption layer is classified into the following processes (1) to (3). Then, the inclination of the t-plot is changed by the following processes (1) to (3).
(1) Monomolecular adsorption layer formation process of nitrogen molecules on the entire surface (2) Multimolecular adsorption layer formation and capillary condensation filling process in the pores accompanying it (3) Apparent filling of the pores with nitrogen Formation process of multimolecular adsorption layer on non-porous surface

  The t-plot showing an upwardly convex shape is located on a straight line passing through the origin in a region where the average thickness t of the nitrogen gas adsorption layer is small, whereas when t becomes large, the plot becomes the straight line. The position will be shifted downward. The single-layer fibrous carbon nanostructure having such a t-plot shape has a large ratio of the internal specific surface area to the total specific surface area of the single-layer fibrous carbon nanostructure, and constitutes a single-layer fibrous carbon nanostructure. It shows that a large number of openings are formed in the carbon nanostructure.

The inflection point of the t-plot of the single-layer fibrous carbon nanostructure is preferably in a range satisfying 0.2 ≦ t (nm) ≦ 1.5, and 0.45 ≦ t (nm) ≦ 1. Is more preferably in the range of 0.5, more preferably in the range of 0.55 ≦ t (nm) ≦ 1.0.
The “position of the bending point” is an intersection of the approximate line A in the process (1) described above and the approximate line B in the process (3) described above.

Further, the single-layer fibrous carbon nanostructure preferably has a ratio (S2 / S1) of the internal specific surface area S2 to the total specific surface area S1 obtained from the t-plot of 0.05 or more and 0.30 or less.
Further, the total specific surface area S1 and the internal specific surface area S2 of the single-layer fibrous carbon nanostructure are not particularly limited, but individually, S1 is preferably 600 m ² / g or more and 1400 m ² / g or less, more preferably not more than 800 m ² / g or more 1200 m ² / g. On the other hand, S2 is preferably 30 m ² / g or more and 540 m ² / g or less.
Here, the total specific surface area S1 and the internal specific surface area S2 of the single-layer fibrous carbon nanostructure can be obtained from the t-plot. Specifically, first, the total specific surface area S1 can be obtained from the slope of the approximate line in the process (1), and the external specific surface area S3 can be obtained from the slope of the approximate line in the process (3). Then, the internal specific surface area S2 can be calculated by subtracting the external specific surface area S3 from the total specific surface area S1.

  Incidentally, measurement of adsorption isotherm of single-layer fibrous carbon nanostructure, creation of t-plot, and calculation of total specific surface area S1 and internal specific surface area S2 based on analysis of t-plot are, for example, commercially available The measurement can be performed using “BELSORP (registered trademark) -mini” (manufactured by Nippon Bell Co., Ltd.).

[Multilayer fibrous carbon nanostructure]
The multi-layer fibrous carbon nanostructure is a carbon nanostructure in which a plurality of graphite carbon hexagonal mesh layers are stacked concentrically to form a single cylindrical shape, that is, a multi-wall carbon nanotube (referred to as “multi-wall CNT”). May be included). The multilayer fibrous carbon nanostructure used in the present invention may be composed of only multilayer CNT, or a mixture of multilayer CNT and a non-cylindrical multilayer fibrous carbon nanostructure other than multilayer CNT. There may be. The multi-walled CNT is not particularly limited, but is preferably a carbon nanostructure in which two to eight layers are stacked concentrically to form a single cylindrical shape, that is, a carbon nanotube having two to eight layers. This is because if two to eight carbon nanotubes are used, the thermal conductivity and strength of the thermal conductive sheet can be further improved as compared with the case of using nine or more carbon nanotubes.

  The multi-layered fibrous carbon nanostructure can generally be manufactured by a laser ablation method, an arc discharge method, a thermal CVD method, a plasma CVD method, a combustion method, or the like, but may be manufactured by any method. . In particular, multi-walled CNTs manufactured by thermal CVD using acetylene as a catalyst carrier with zeolite as a catalyst carrier do not need to be purified, and although they have some amorphous carbon coating due to thermal decomposition, they are highly pure and well graphitized. Is preferable. Examples of commercially available products are “NC7000” manufactured by Nanocy, “VGCF-X” manufactured by Showa Denko KK, “baytubes C150P” and “baytubes C70P” manufactured by Bayer Holding Co., Ltd., “NT” manufactured by Hodogaya Chemical Co., Ltd. -7 "and the like.

  The average diameter (Av) of the multilayer fibrous carbon nanostructure is preferably 4 nm or more, more preferably 6 nm or more, preferably 15 nm or less, and more preferably 10 nm or less. When the average diameter (Av) of the multilayer fibrous carbon nanostructure is 4 nm or more, aggregation of the multilayer fibrous carbon nanostructure can be suppressed and dispersibility in the carbon film can be enhanced. Moreover, if the average diameter (Av) of a multilayer fibrous carbon nanostructure is 15 nm or less, the heat conductivity and intensity | strength of a carbon film can fully be improved.

  The average length of the multilayer fibrous carbon nanostructure is preferably 0.01 μm or more and 100 μm or less, and more preferably 1 μm or more and 10 μm or less. When the average length of the multilayer fibrous carbon nanostructure is 0.01 μm or more, the thermal conductivity and strength of the carbon film can be sufficiently increased. When the average length of the multilayer fibrous carbon nanostructure is 100 μm or less, aggregation of the multilayer fibrous carbon nanostructure can be suppressed and dispersibility in the carbon film can be enhanced.

The BET specific surface area of the multilayer fibrous carbon nanostructure is preferably 10 m ² / g or more and 500 m ² / g or less, more preferably 100 m ² / g or more and 350 m ² / g or less, and 150 m ² / g. More preferably, it is 300 m ² / g or less. When the BET specific surface area of the multilayer fibrous carbon nanostructure is 10 m ² / g or more, the thermal conductivity and strength of the carbon film can be sufficiently increased. Moreover, if the BET specific surface area of a multilayer fibrous carbon nanostructure is 500 m < ² > / g or less, aggregation of a multilayer fibrous carbon nanostructure can be suppressed and the dispersibility in a carbon film can be improved.

[Content ratio of single-layer fibrous carbon nanostructure and multilayer fibrous carbon nanostructure]
The carbon film of the present invention contains a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and a multilayer fibrous carbon nanostructure. Furthermore, the carbon film of the present invention has a mass ratio (single-layer fibrous carbon) of the content ratio of the single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and the multilayer fibrous carbon nanostructure. Nanostructure / multi-layer fibrous carbon nanostructure) is preferably 95/5 to 5/95, and more preferably 90/10 to 10/90. If the content ratio of the single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and the multilayer fibrous carbon nanostructure in the carbon film is within the above range, the conductivity of the carbon film is increased. In addition to the further improvement, the film formability of the carbon film can be improved.

<Characteristics of carbon film>
As described above, the carbon film of the present invention contains a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and a multi-layer fibrous carbon nanostructure. Excellent in properties.
The reason why the carbon film is excellent in self-supporting property and conductivity by including a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and a multilayer fibrous carbon nanostructure is not clear. However, it is presumed that a porous structure having a highly developed network can be obtained by containing such a single-layer fibrous carbon nanostructure and a multilayer fibrous carbon nanostructure.
The carbon film of the present invention preferably further has the following properties.

[Conductivity]
The carbon film of the present invention preferably has conductivity that can be used as a conductive film in a solar cell or a touch panel. Specifically, the volume conductivity is preferably 50 S / cm or more, more preferably 100 S / cm or more, and even more preferably 150 S / cm or more. This is because if the volume conductivity is 50 S / cm or more, it has sufficient conductivity to be used as a conductive film in a solar cell or a touch panel.
The volume conductivity of the carbon film can be measured by a four-terminal four-probe method. The volume conductivity of the carbon film is determined by the BET specific surface area and amount of the single-layer fibrous carbon nanostructure used for forming the carbon film, the type of the multilayer fibrous carbon nanostructure, and the single-layer fibrous carbon. It can be adjusted by adjusting the content ratio of the nanostructure and the multilayer fibrous carbon nanostructure.

[Content of single-layer and multilayer fibrous carbon nanostructures]
The carbon film of the present invention is preferably composed of 75% by mass or more of single-layer and multilayer fibrous carbon nanostructures, and more preferably does not contain components other than impurities inevitably mixed during production. This is because if the content of the single-layer and multi-layer fibrous carbon nanostructures is 75% by mass or more, characteristics such as conductivity, thermal conductivity, and mechanical characteristics can be sufficiently improved.

[Glossiness]
In the carbon film of the present invention, the glossiness of the film surface at 60 degrees is preferably 5 or more, more preferably 10 or more, and preferably 50 or less.
The glossiness of the carbon film can be measured under the condition of an incident angle of 60 degrees according to JIS Z8741. In addition, the glossiness of the carbon film is adjusted by adjusting the type and amount of fibrous carbon nanostructures used to form the carbon film, and the method for preparing the fibrous carbon nanostructure dispersion liquid used to form the carbon film. Can be adjusted.

[density]
Furthermore, the density of the carbon film of the present invention is preferably 0.4 g / cm ³ or more, more preferably 0.6 g / cm ³ or more, and 1.0 g / cm ³ or less. Is preferred.
In the present invention, the density of the carbon film can be obtained by measuring the mass, area and thickness of the carbon film and dividing the mass of the carbon film by the volume.

[Autonomy]
Furthermore, the carbon film of the present invention is preferably a self-supporting film that can maintain its shape as a film even when no support is present. Specifically, the carbon film of the present invention more preferably maintains the shape as a film without a support in a size of 10 nm to 3 μm in thickness and an area of 1 mm ^{2 to} 100 cm ² .

(Method for producing carbon film)
The carbon film manufacturing method of the present invention can be used when manufacturing the above-described carbon film of the present invention. And the manufacturing method of the carbon film of this invention contains a single layer fibrous carbon nanostructure with a BET specific surface area of 500 m < ² > / g or more, a multilayer fibrous carbon nanostructure, a dispersing agent, and a solvent. It includes a step of forming a carbon film by removing the solvent from the fibrous carbon nanostructure dispersion liquid (film formation step). The method for producing a carbon film of the present invention includes a fibrous carbon nanostructure obtained by subjecting a crude dispersion containing such a single-layer fibrous carbon nanostructure, a multilayer fibrous carbon nanostructure, a dispersant and a solvent to dispersion treatment. A step of preparing a dispersion (dispersion preparation step) may be included before the film formation step.
And the carbon film obtained using the manufacturing method of the carbon film of the present invention includes a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and a multilayer fibrous carbon nanostructure. Therefore, it is excellent in independence and conductivity.

<Dispersion preparation process>
Here, in the dispersion preparation step, a coarse dispersion formed by adding a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more, a multilayer fibrous carbon nanostructure, and a dispersant in a solvent. It is preferable to prepare a fibrous carbon nanostructure dispersion by dispersing the single-layer and multilayer fibrous carbon nanostructures in a dispersion treatment in which a cavitation effect or a crushing effect is obtained. This is because a fibrous carbon nanostructure dispersion liquid in which single-layer and multilayer fibrous carbon nanostructures are well dispersed can be obtained by using a dispersion treatment capable of obtaining a cavitation effect or a crushing effect. If a carbon film is prepared using a fibrous carbon nanostructure dispersion liquid in which single-layer and multilayer fibrous carbon nanostructures are well dispersed, the single-layer and multilayer fibrous carbon nanostructures are homogeneously assembled. Thus, a carbon film having excellent properties such as conductivity, thermal conductivity and mechanical properties can be obtained.
The fibrous carbon nanostructure dispersion used in the method for producing a carbon film of the present invention is obtained by dispersing single-layer and multilayer fibrous carbon nanostructures in a solvent using a known dispersion treatment method other than the above. May be prepared. In addition, the fibrous carbon nanostructure dispersion liquid may be blended with known additives such as fillers, stabilizers, colorants, charge control agents, and lubricants, depending on the use of the carbon film to be produced. .

[Single-layer fibrous carbon nanostructure]
As the single-layer fibrous carbon nanostructure used for preparing the fibrous carbon nanostructure dispersion liquid, the single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more can be used. Such a single-layer fibrous carbon nanostructure may consist of only single-walled CNTs, or may be composed of single-walled CNTs and non-cylindrical single-layered fibrous carbon nanostructures or GNTs other than single-walled CNTs. It may be a mixture of

[Multilayer fibrous carbon nanostructure]
As the multilayer fibrous carbon nanostructure used for preparing the fibrous carbon nanostructure dispersion liquid, the multilayer fibrous carbon nanostructure described above can be used. Such a multilayer fibrous carbon nanostructure may consist of only multilayer CNT, or may be a mixture of multilayer CNT and a non-cylindrical multilayer fibrous carbon nanostructure other than multilayer CNT. .

[Content of monolayer and multilayer fibrous carbon nanostructures in the dispersion]
The fibrous carbon nanostructure dispersion liquid contains a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and a multilayer fibrous carbon nanostructure. Furthermore, the carbon film of the present invention has a mass ratio (single-layer fibrous carbon) of the content ratio of the single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and the multilayer fibrous carbon nanostructure. Nanostructure / multi-layer fibrous carbon nanostructure) is preferably 95/5 to 5/95, and more preferably 90/10 to 10/90. In the fibrous carbon nanostructure dispersion liquid, if the content ratio of the single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more and the multilayer fibrous carbon nanostructure is within the above range, A carbon film having higher conductivity and excellent film formability can be produced.

[Dispersant]
Further, the dispersant used for the preparation of the fibrous carbon nanostructure dispersion liquid is not particularly limited as long as it can disperse single-layer and multilayer fibrous carbon nanostructures and can be dissolved in a solvent described later. Activators, synthetic polymers or natural polymers can be used.

Here, examples of the surfactant include sodium dodecylsulfonate, sodium deoxycholate, sodium cholate, sodium dodecylbenzenesulfonate, and the like.
Examples of the synthetic polymer include polyether diol, polyester diol, polycarbonate diol, polyvinyl alcohol, partially saponified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, acetal group-modified polyvinyl alcohol, butyral group-modified polyvinyl alcohol, and silanol group-modified. Polyvinyl alcohol, ethylene-vinyl alcohol copolymer, ethylene-vinyl alcohol-vinyl acetate copolymer resin, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, acrylic resin, epoxy resin, modified epoxy resin, phenoxy resin, modified phenoxy system Resin, phenoxy ether resin, phenoxy ester resin, fluorine resin, melamine resin, alkyd resin, phenol resin, Polyacrylamide, polyacrylic acid, polystyrene sulfonic acid, polyethylene glycol, and polyvinylpyrrolidone.
Furthermore, examples of natural polymers include polysaccharides such as starch, pullulan, dextran, dextrin, guar gum, xanthan gum, amylose, amylopectin, alginic acid, gum arabic, carrageenan, chondroitin sulfate, hyaluronic acid, curdlan, chitin, chitosan, Examples thereof include cellulose and salts or derivatives thereof. The derivative means a conventionally known compound such as ester or ether.

  These dispersants can be used alone or in combination of two or more. Among these, as the dispersant, a surfactant is preferable, and sodium deoxycholate is particularly preferable because of excellent dispersibility of the single-layer and multilayer fibrous carbon nanostructures.

[solvent]
The solvent for the fibrous carbon nanostructure dispersion liquid is not particularly limited. For example, water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, Alcohols such as heptanol, octanol, nonanol, decanol, amyl alcohol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as diethyl ether, dioxane and tetrahydrofuran, N, N- Amide polar organic solvents such as dimethylformamide and N-methylpyrrolidone, and aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene and paradichlorobenzene These may be used alone or in combination of two or more.

[Distributed processing]
In the dispersion preparation step, the single-layer fibrous carbon nanostructure, the multilayer fibrous carbon nanostructure, and the dispersing agent described above are added to the solvent, and the single-layer and multilayer fibrous carbon nanostructure are added. Is dispersed to prepare a fibrous carbon nanostructure dispersion liquid. For this dispersion treatment, a known mixing method and dispersion method described later can be used. Although not particularly limited, in the production method of the present invention, a fibrous carbon nanostructure dispersion liquid is prepared by subjecting it to a dispersion treatment for obtaining a cavitation effect or a dispersion treatment for obtaining a crushing effect, which will be described in detail below. It is preferable to do. A fibrous carbon nanostructure dispersion liquid in which single-layer and multilayer fibrous carbon nanostructures are more uniformly dispersed can be prepared. In carbon films formed from this homogeneous dispersion, single-layered fibrous carbon nanostructures and multi-layered fibrous carbon nanostructures exist in a more homogeneously dispersed manner, so that they are self-supporting, conductive, and other properties. Can be further improved.

[[Distributed processing with cavitation effect]]
The dispersion treatment that provides a cavitation effect is a dispersion method that uses a shock wave that is generated when a vacuum bubble generated in water bursts when high energy is applied to a liquid. By using this dispersion method, the single-layer and multilayer fibrous carbon nanostructures can be favorably dispersed.

  Here, specific examples of the dispersion treatment that can provide a cavitation effect include dispersion treatment using ultrasonic waves, dispersion treatment using a jet mill, and dispersion treatment using high shear stirring. Only one of these distributed processes may be performed, or a plurality of distributed processes may be combined. More specifically, for example, an ultrasonic homogenizer, a jet mill, and a high shear stirring device are preferably used. These devices may be conventionally known devices.

  When an ultrasonic homogenizer is used to disperse single-layer and multilayer fibrous carbon nanostructures, the coarse dispersion may be irradiated with ultrasonic waves using an ultrasonic homogenizer. The irradiation time may be appropriately set depending on the amount of single-layer and multilayer fibrous carbon nanostructures, and is preferably, for example, 3 minutes or more, more preferably 30 minutes or more, and preferably 5 hours or less, 2 hours The following is more preferable. For example, the output is preferably 20 W or more and 500 W or less, more preferably 100 W or more and 500 W or less, and the temperature is preferably 15 ° C. or more and 50 ° C. or less.

  In the case of using a jet mill, the number of treatments may be set as appropriate depending on the amount of single-layer and multilayer fibrous carbon nanostructures, for example, preferably 2 times or more, more preferably 5 times or more, and 100 times or less. Is preferable, and 50 times or less is more preferable. For example, the pressure is preferably 20 MPa or more and 250 MPa or less, and the temperature is preferably 15 ° C. or more and 50 ° C. or less.

  Furthermore, when high shear stirring is used, stirring and shearing may be applied to the coarse dispersion with a high shear stirring device. The faster the turning speed, the better. For example, the operation time (time during which the machine is rotating) is preferably 3 minutes or more and 4 hours or less, the peripheral speed is preferably 5 m / second or more and 50 m / second or less, and the temperature is preferably 15 ° C. or more and 50 ° C. or less.

  In addition, it is more preferable to perform the dispersion treatment for obtaining the above-described cavitation effect at a temperature of 50 ° C. or lower. This is because a change in concentration due to the volatilization of the solvent is suppressed.

[[Dispersed treatment that can produce a crushing effect]]
Dispersion treatment that provides a crushing effect can uniformly disperse single-layer and multi-layered fibrous carbon nanostructures in a solvent, as well as shock waves when bubbles disappear, compared to the dispersion treatment that provides the cavitation effect described above. This is more advantageous in that damage to single-layer and multi-layered fibrous carbon nanostructures due to can be suppressed.

In the dispersion treatment in which this crushing effect is obtained, a shear force is applied to the coarse dispersion to break up and disperse aggregates of single-layer and multi-layer fibrous carbon nanostructures, and a back pressure is applied to the coarse dispersion. In addition, if necessary, by cooling the coarse dispersion, it is possible to uniformly disperse the monolayer and multilayer fibrous carbon nanostructures in the solvent while suppressing the generation of bubbles.
When a back pressure is applied to the coarse dispersion, the back pressure applied to the coarse dispersion may be reduced to atmospheric pressure all at once, but is preferably reduced in multiple stages.

Here, in order to further disperse the single-layer and multi-layer fibrous carbon nanostructures by applying a shearing force to the coarse dispersion, for example, a dispersion system having a disperser having the following structure may be used.
In other words, the disperser has a disperser orifice having an inner diameter d1, a dispersion space having an inner diameter d2, and a terminal portion having an inner diameter d3 from the inflow side to the outflow side of the coarse dispersion liquid (where d2>d3> d1)).
In this disperser, the inflowing high-pressure (for example, 10 to 400 MPa, preferably 50 to 250 MPa) coarse dispersion passes through the disperser orifice, and becomes a high flow rate fluid with a decrease in pressure. Into the dispersed space. Thereafter, the high-velocity coarse dispersion liquid flowing into the dispersion space flows at high speed in the dispersion space and receives a shearing force at that time. As a result, the flow rate of the coarse dispersion decreases, and the monolayer and multilayer fibrous carbon nanostructures are well dispersed. Then, a fluid having a pressure (back pressure) lower than the pressure of the inflowing coarse dispersion flows out from the terminal portion as the fibrous carbon nanostructure dispersion liquid.

Note that the back pressure of the coarse dispersion can be applied to the coarse dispersion by applying a load to the flow of the coarse dispersion. For example, a rough pressure can be obtained by disposing a multistage step-down device downstream of the disperser. A desired back pressure can be applied to the dispersion.
Then, by reducing the back pressure of the coarse dispersion in multiple stages using a multistage pressure reducer, when the fibrous carbon nanostructure dispersion is finally released to atmospheric pressure, the fibrous carbon nanostructure dispersion The generation of bubbles can be suppressed.

Further, the disperser may include a heat exchanger for cooling the coarse dispersion and a cooling liquid supply mechanism. This is because the generation of bubbles in the coarse dispersion can be further suppressed by cooling the coarse dispersion that has been heated to a high temperature by applying a shearing force with the disperser.
In addition, it can suppress that a bubble generate | occur | produces in the solvent containing a single | mono layer and a multilayer fibrous carbon nanostructure also by cooling a rough dispersion liquid beforehand instead of arrangement | positioning of a heat exchanger etc.

  As described above, in the dispersion treatment in which this crushing effect is obtained, the occurrence of cavitation can be suppressed, so damage to single-layer and multi-layer fibrous carbon nanostructures caused by cavitation, which is sometimes a concern, in particular, bubbles are generated. Damage to the single-layer and multi-layer fibrous carbon nanostructures due to the shock wave when disappearing can be suppressed. In addition, it is possible to uniformly and efficiently disperse single-layer and multilayer fibrous carbon nanostructures by suppressing the adhesion of bubbles to single-layer and multilayer fibrous carbon nanostructures and energy loss due to the generation of bubbles. Can do.

  As a distributed system having the above configuration, for example, there is a product name “BERYU SYSTEM PRO” (manufactured by Miki Co., Ltd.). And the dispersion | distribution process from which a crushing effect is acquired can be implemented by controlling a dispersion | distribution condition appropriately using such a dispersion | distribution system.

[Viscosity of fibrous carbon nanostructure dispersion]
The viscosity of the fibrous carbon nanostructure dispersion liquid is preferably 0.001 Pa · s or more, more preferably 0.01 Pa · s or more, and 0.8 Pa · s or less. Is more preferable, and 0.6 Pa · s or less is more preferable. If the viscosity of the fibrous carbon nanostructure dispersion liquid is 0.001 Pa · s or more and 0.8 Pa · s or less, a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more in a film forming step described later. The film and the multi-layered fibrous carbon nanostructure can be formed well, and the resulting carbon film can be sufficiently enhanced in properties such as conductivity, thermal conductivity and mechanical properties, and the carbon film can be easily manufactured. Because it can be done. The viscosity of the fibrous carbon nanostructure dispersion liquid can be adjusted, for example, by changing the blending amount and type of the single-layer and multilayer fibrous carbon nanostructures and the dispersant.
Here, in the present invention, the viscosity of the fibrous carbon nanostructure dispersion liquid is a B-type viscometer, and in accordance with JIS K7117-1, the temperature is 23 ° C., the rotor is M4, and the rotation speed is 60 rpm. It can be measured under conditions.

<Film formation process>
In the film forming step, the solvent is removed from the fibrous carbon nanostructure dispersion described above to form a carbon film. Specifically, in the film forming step, for example, the solvent is removed from the fibrous carbon nanostructure dispersion liquid using any one of the following methods (A) and (B) to form a carbon film.
(A) A method of drying the applied fibrous carbon nanostructure dispersion liquid after applying the fibrous carbon nanostructure dispersion liquid on the film-forming substrate.
(B) A method of filtering a fibrous carbon nanostructure dispersion liquid using a porous film-forming substrate and drying the obtained filtrate.

In addition, in the manufacturing method of the carbon film of this invention, it developed highly by forming into a film the single-layer fibrous carbon nanostructure with a BET specific surface area of 500 m < ² > / g or more, and a multilayer fibrous carbon nanostructure. Since a porous structure having a network can be obtained, it is presumed that a carbon film excellent in self-supporting property and conductivity can be obtained.

[Deposition substrate]
Here, the film-forming substrate is not particularly limited, and a known substrate can be used according to the application of the carbon film to be produced.
Specifically, examples of the film formation substrate on which the fibrous carbon nanostructure dispersion liquid is applied in the method (A) include a resin substrate and a glass substrate. Here, as the resin base material, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetrafluoroethylene (PTFE), polyimide, polyphenylene sulfide, aramid, polypropylene, polyethylene, polylactic acid, polyvinyl chloride, polycarbonate, The base material which consists of polymethyl methacrylate, an alicyclic acrylic resin, a cycloolefin resin, a triacetyl cellulose etc. can be mentioned. Moreover, as a glass base material, the base material which consists of normal soda glass can be mentioned.
Moreover, as a film-forming base material which filters the fibrous carbon nanostructure dispersion liquid in the said method (B), the porous sheet | seat which consists of filter paper, a cellulose, a nitrocellulose, an alumina etc. can be mentioned.

[Application]
As a method of applying the fibrous carbon nanostructure dispersion liquid on the film-forming substrate in the method (A), a known coating method can be employed. Specifically, the coating method includes dipping method, roll coating method, gravure coating method, knife coating method, air knife coating method, roll knife coating method, die coating method, screen printing method, spray coating method, gravure offset method, etc. Can be used.

[Filtration]
As a method of filtering the fibrous carbon nanostructure dispersion liquid using the film-forming substrate in the method (B), a known filtration method can be employed. Specifically, natural filtration, vacuum filtration, pressure filtration, centrifugal filtration, or the like can be used as a filtration method.

[Dry]
As a method for drying the fibrous carbon nanostructure dispersion liquid applied on the film forming substrate in the method (A) or the filtrate obtained in the method (B), a known drying method can be employed. Examples of the drying method include a hot air drying method, a vacuum drying method, a hot roll drying method, and an infrared irradiation method. The drying temperature is not particularly limited, but is usually room temperature to 200 ° C., and the drying time is not particularly limited, but is usually 0.1 to 150 minutes.

<Post-treatment of carbon film>
Here, the carbon film formed as described above is usually contained in a fibrous carbon nanostructure dispersion liquid such as a single-layer fibrous carbon nanostructure, a multilayer fibrous carbon nanostructure, and a dispersant. The components are contained in the same ratio as the fibrous carbon nanostructure dispersion liquid. Therefore, in the carbon film manufacturing method of the present invention, the carbon film formed in the film forming step may optionally be washed to remove the dispersant from the carbon film. If the dispersant is removed from the carbon film, characteristics such as conductivity of the carbon film can be further enhanced.

  The carbon film can be washed by bringing the dispersant into contact with a soluble solvent and eluting the dispersant in the carbon film into the solvent. The solvent capable of dissolving the dispersant in the carbon film is not particularly limited, and can be used as a solvent for the fibrous carbon nanostructure dispersion liquid, preferably the fibrous carbon nanostructure dispersion. The same solvent as the liquid can be used. Further, the contact between the carbon film and the solvent can be performed by immersing the carbon film in the solvent or by applying the solvent to the carbon film. Furthermore, the carbon film after washing can be dried using a known method.

  In the carbon film manufacturing method of the present invention, the carbon film formed in the film forming step may optionally be pressed to further increase the density. From the viewpoint of suppressing deterioration in characteristics due to damage or destruction of the fibrous carbon nanostructure, the pressing pressure at the time of pressing is preferably less than 3 MPa, and more preferably not pressing.

(Use of carbon film)
The carbon film of the present invention can be particularly suitably used as a conductive film for solar cells, touch panels and the like.
Note that the carbon film of the present invention can be used as it is formed on the film-forming substrate or after being peeled from the film-forming substrate. In addition, the carbon film of the present invention can be used for various products after arbitrarily laminating a known functional layer such as an overcoat layer. Here, the lamination of the functional layer such as the overcoat layer on the carbon film can be performed using a known method.

<Touch panel>
Specifically, the carbon film of the present invention can be suitably used as a conductive layer that is formed on a transparent substrate and constitutes a touch sensor of a touch panel such as a capacitive touch panel.

<Solar cell>
The carbon film of the present invention can be used as a conductive layer or a catalyst layer that constitutes an electrode of a solar cell such as a dye-sensitized solar cell. More specifically, the carbon film of the present invention comprises a conductive layer constituting a photoelectrode of a dye-sensitized solar cell, a conductive layer constituting a counter electrode (catalyst electrode) of the dye-sensitized solar cell, and / or It can be used as a catalyst layer.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

<Synthesis of single-layer fibrous carbon nanostructure 1>
Carbon nanotubes obtained by the super growth method described in International Publication No. 2006/011655 were used. Specifically, the single-layer fibrous carbon nanostructure 1 was grown under the following conditions.
Carbon compound: ethylene; supply rate 50 sccm
Atmosphere (gas) (Pa): Helium, hydrogen mixed gas; supply rate 1000 sccm
Pressure 1 atmospheric pressure water vapor addition amount (ppm): 300 ppm
Reaction temperature (° C): 750 ° C
Reaction time (min): 10 minutes Metal catalyst (abundance): Iron thin film; thickness 1 nm
Substrate: silicon wafer.
The obtained single-walled fibrous carbon nanostructure 1 has a BET specific surface area of 1,050 m ² / g and a low-frequency region of 100 to 300 cm ⁻¹ , which is characteristic of single-walled carbon nanotubes when measured with a Raman spectrophotometer. A radial breathing mode (RBM) spectrum was observed. Moreover, as a result of measuring the diameter of 100 single-layer fibrous carbon nanostructures 1 at random using a transmission electron microscope, the average diameter (Av) was 3.3 nm, and the diameter distribution (3σ) was 1.9. , (3σ / Av) was 0.58.

<Synthesis of single-layer fibrous carbon nanostructure 2>
A single-layer fibrous carbon nanostructure 2 was obtained by the same method except that the thickness of the iron thin film layer of the metal catalyst of Production Example 1 was changed to 5 nm. The obtained single-walled fibrous carbon nanostructure 2 has a BET specific surface area of 620 m ² / g and has a radial characteristic in a low-frequency region of 100 to 300 cm ⁻¹ , which is characteristic of single-walled carbon nanotubes when measured with a Raman spectrophotometer A breathing mode (RBM) spectrum was observed. Moreover, as a result of measuring the diameter of 100 single-layer fibrous carbon nanostructures 2 randomly using a transmission electron microscope, the average diameter (Av) was 5.9 nm, and the diameter distribution (3σ) was 3.3. , (3σ / Av) was 0.56.

<Preparation of single-layer fibrous carbon nanostructure dispersion liquid 1>
1.0 g of the above-mentioned single-layer fibrous carbon nanostructure 1 is added to 500 mL of a 2% by weight aqueous solution of sodium deoxycholate (DOC) as a solvent containing a dispersant to obtain a crude dispersion containing DOC as a dispersant. It was. A high-pressure homogenizer having a multi-stage pressure control device (multi-stage pressure reducer) that applies a back pressure during dispersion of the coarse dispersion containing the single-layer fibrous carbon nanostructure 1 (product name “BERYU SYSTEM PRO” )) And the dispersion of the crude dispersion was performed at a pressure of 100 MPa. Specifically, the single-layer fibrous carbon nanostructure dispersion liquid 1 was obtained by applying a shearing force to the coarse dispersion liquid while applying a back pressure to disperse the single-layer fibrous carbon nanostructure structure. The dispersion treatment was carried out for 10 minutes while returning the dispersion liquid flowing out from the high-pressure homogenizer to the high-pressure homogenizer again.

<Preparation of single-layer fibrous carbon nanostructure dispersion liquid 2>
The single-layer fibrous carbon nanostructure 1 was used in the same manner except that the single-layer fibrous carbon nanostructure 1 used in the single-layer fibrous carbon nanostructure dispersion liquid 1 was changed to a single-layer fibrous carbon nanostructure 2 A body dispersion 2 was obtained.

<Preparation of multi-layer fibrous carbon nanostructure dispersion>
The single-layer fibrous carbon nanostructure 1 used in the single-layer fibrous carbon nanostructure dispersion liquid 1 was manufactured by Nanocyl NC7000 (BET specific surface area: 270 m ² / g, average diameter: 9.5 nm, average length: 1). A multilayer fibrous carbon nanostructure dispersion was obtained in the same manner except that the thickness was changed to 0.5 μm and the average number of layers: 7).

<Example 1>
In a 200 mL beaker, 90 g of the produced single-layer fibrous carbon nanostructure dispersion liquid 1 and 10 g of the multilayer fibrous carbon nanostructure dispersion liquid were added, and the mixture was stirred with a stirrer for 10 minutes. Thereafter, the mixed CNT dispersion was filtered under a condition of 0.09 MPa using a vacuum filtration device equipped with a membrane filter. After completion of the filtration, each of isopropyl alcohol and water was passed through a vacuum filtration device to wash the carbon film formed on the membrane filter, and then air was allowed to pass for 15 minutes. Next, the carbon film 1 was formed by detaching the carbon film after immersing the produced carbon film / membrane filter in ethanol.
The obtained carbon film 1 has the same size as a membrane filter, has excellent film formability, and maintains the state of the film even when peeled off from the filter, and also has excellent self-supporting properties. It was. Further, when the conductivity of the obtained carbon film 1 was measured (product name “Loresta-GX” manufactured by Mitsubishi Chemical Analytech Co., Ltd.), the volume conductivity of the carbon film 1 was 310 S / cm, which was very good conductivity. showed that. As a result of measuring the film density of the obtained carbon film 1, the density was 0.85 g / cm ³ . Next, as a result of measuring the glossiness at 60 degrees for the produced carbon film 1 using a glossmeter (manufactured by Horiba, Ltd., handy glossmeter gloss checker, wavelength (890 nm)), the glossiness was 38. there were.

<Example 2>
A carbon membrane was prepared in the same manner as in Example 1 except that the single-layer fibrous carbon nanostructure dispersion liquid 1 and the multilayer fibrous carbon nanostructure dispersion liquid were mixed so as to achieve the blending ratio shown in Table 1 below. 2 was formed.
The obtained carbon film 2 has the same size as a membrane filter, has excellent film formability, and maintains the film state even when peeled off from the filter, and has excellent self-supporting properties. It was. Further, when the conductivity of the obtained carbon film 2 was measured (product name “Loresta-GX” manufactured by Mitsubishi Chemical Analytech Co., Ltd.), the volume conductivity of the carbon film 2 was 205 S / cm, which was very good conductivity. showed that. As a result of measuring the film density of the obtained carbon film 2, the density was 0.63 g / cm ³ . Further, with respect to the obtained carbon film 2, the glossiness at 60 degrees was 22.

<Example 3>
A carbon membrane was prepared in the same manner as in Example 1 except that the single-layer fibrous carbon nanostructure dispersion liquid 1 and the multilayer fibrous carbon nanostructure dispersion liquid were mixed so as to achieve the blending ratio shown in Table 1 below. 3 was formed.
The obtained carbon film 3 has the same size as a membrane filter, has excellent film formability, and maintains the film state even when peeled off from the filter, and also has excellent self-supporting properties. It was. In addition, when the conductivity of the obtained carbon film 3 was measured (product name “Loresta-GX” manufactured by Mitsubishi Chemical Analytech Co., Ltd.), the volume conductivity of the carbon film 3 showed a favorable conductivity of 76 S / cm. It was. As a result of measuring the film density of the obtained carbon film 3, the density was 0.57 g / cm ³ . Furthermore, the obtained carbon film 3 had a glossiness of 13 at 60 degrees.

<Example 4>
A carbon membrane was prepared in the same manner as in Example 1 except that the single-layer fibrous carbon nanostructure dispersion liquid 2 and the multi-layer fibrous carbon nanostructure dispersion liquid were mixed so as to achieve the blending ratio shown in Table 1 below. 4 was formed.
The obtained carbon film 4 has the same size as a membrane filter, has excellent film formability, and maintains the film state even when peeled off from the filter, and also has excellent self-supporting properties. It was. Further, when the conductivity of the obtained carbon film 4 was measured (product name “Loresta-GX” manufactured by Mitsubishi Chemical Analytech Co., Ltd.), the volume conductivity of the carbon film 4 showed a good conductivity of 64 S / cm. It was. As a result of measuring the film density of the obtained carbon film 4, the density was 0.66 g / cm ³ . Further, the obtained carbon film 4 had a glossiness of 25 at 60 degrees.

<Example 5>
A carbon membrane was prepared in the same manner as in Example 1 except that the single-layer fibrous carbon nanostructure dispersion liquid 1 and the multilayer fibrous carbon nanostructure dispersion liquid were mixed so as to achieve the blending ratio shown in Table 1 below. 5 was formed.
The obtained carbon film 5 maintained the state of the film even after being peeled off from the filter, and had excellent self-supporting property, but contraction of the film was observed. In addition, when the conductivity of the obtained carbon film 5 was measured (product name “Loresta-GX” manufactured by Mitsubishi Chemical Analytech Co., Ltd.), the volume conductivity of the carbon film 5 was as good as 64 S / cm. It was. As a result of measuring the film density of the obtained carbon film 5, the density was 0.51 g / cm ³ . Further, with respect to the obtained carbon film 5, the glossiness at 60 degrees was 10.

<Comparative Example 1>
A comparative example carbon film 1 was formed by the same operation as in Example 1 using only the multilayer fibrous carbon nanostructure dispersion liquid.
In the obtained Comparative Example carbon film 1, the contraction of the film was noticeable, and the film on the membrane filter was also noticeably cracked, and the self-supporting property of the film was not seen at all.

  The results of the above examples and comparative examples are shown in Table 1 below. Regarding the film formability of the obtained carbon film, after peeling from the membrane filter, if the state of the film having the same size as the membrane filter can be maintained, it is evaluated as ◯, and when shrinkage or cracking is observed Was evaluated as x. Regarding the self-supporting property of the obtained carbon film, it is evaluated as ◯ when the state of the film can be maintained even after being peeled off from the filter, and is evaluated as × when the state of the film cannot be maintained after being peeled off from the filter. did. Moreover, it was set as-about the item which evaluation measurement could not be performed.

  From Table 1, it can be seen that the carbon films of the examples are excellent in self-supporting property and conductivity.

  ADVANTAGE OF THE INVENTION According to this invention, the carbon film excellent in self-supporting property and electroconductivity, and its manufacturing method can be provided.

Claims (7)

Including a single-layer fibrous carbon nanostructure and a multilayer fibrous carbon nanostructure,
The carbon film whose BET specific surface area of this single-layer fibrous carbon nanostructure is 500 m < ² > / g or more.   The content ratio of the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure is 95/5 to 5 in mass ratio (single-layer fibrous carbon nanostructure / multi-layer fibrous carbon nanostructure). The carbon film according to claim 1, which is / 95.   The carbon film according to claim 1 or 2, wherein the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure include carbon nanotubes. From the fibrous carbon nanostructure dispersion liquid containing a single-layer fibrous carbon nanostructure having a BET specific surface area of 500 m ² / g or more, a multilayer fibrous carbon nanostructure, a dispersant, and a solvent, the solvent The manufacturing method of a carbon film including the process of removing carbon and forming a carbon film.   A dispersion obtained by adding the single-layered fibrous carbon nanostructure, the multi-layered fibrous carbon nanostructure, and the dispersant in the solvent is a dispersion capable of obtaining a cavitation effect or a crushing effect. The method further comprises a step of preparing the fibrous carbon nanostructure dispersion by dispersing the single-layer fibrous carbon nanostructure and the multi-layer fibrous carbon nanostructure in a treatment. The manufacturing method of the carbon film of description.   The content ratio of the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure in the fibrous carbon nanostructure dispersion is a mass ratio (single-layer fibrous carbon nanostructure / multi-layer fibrous The method for producing a carbon film according to claim 4 or 5, wherein the carbon nanostructure is 95/5 to 5/95.   The method for producing a carbon film according to any one of claims 4 to 6, wherein the single-layer fibrous carbon nanostructure and the multilayer fibrous carbon nanostructure include carbon nanotubes.