JP2014037578A - Copper foil for producing graphene and method for producing graphene using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copper foil for producing grapheme, enabling large area graphene to be produced at low cost, and a method for producing the graphene using the same.SOLUTION: The copper foil for producing graphene has a 60-degree glossiness in both a rolling parallel direction and a rolling orthogonal direction of 500% or more, and has an average crystal grain size after being heated at 400°C for 10 minutes of 30 μm or more.

Description

  The present invention relates to a copper foil base material for producing graphene, and a method for producing graphene using the same.

  Graphite has a layered structure in which a number of flat carbon 6-membered ring layers are stacked, and those having a single atomic layer to several atomic layers are called graphene or graphene sheets. Graphene sheets have unique electrical, optical and mechanical properties, and in particular have a high carrier moving speed. Therefore, graphene sheets are expected to have a wide range of applications in the industry, such as fuel cell separators, transparent electrodes, conductive thin films for display elements, mercury-free fluorescent lamps, composite materials, and drug delivery system (DDS) carriers. ing.

As a method of producing a graphene sheet, a method of peeling graphite with an adhesive tape is known, but the number of layers of the obtained graphene sheet is not constant, it is difficult to obtain a large area graphene sheet, and it is not suitable for mass production There's a problem.
Thus, a technique (chemical vapor deposition (CVD) method) has been developed in which a graphene sheet is grown by bringing a carbon-based material into contact with a sheet-like single crystal graphitized metal catalyst and then performing heat treatment (Patent Literature). 1). As this single crystal graphitized metal catalyst, a metal substrate of Ni, Cu, W or the like is described.
Similarly, a technique for forming graphene by chemical vapor deposition on a copper layer formed on a Ni or Cu metal foil or Si substrate has been reported. Although graphene film formation is generally performed at about 1000 ° C. (Non-patent Document 1), a technique for forming a film at a temperature of about 400 ° C. by using microwave plasma or the like has also been reported. (Patent Documents 2 and 3).

JP 2009-143799 A Japanese Patent No. 4804272 JP2012-020915A

SCIENCE Vol.324 (2009) P1312-1314

However, as in Patent Document 1, it is not easy to manufacture a single crystal metal substrate, which is extremely expensive, and it is difficult to obtain a large-area substrate, and thus it is difficult to obtain a large-area graphene sheet. . On the other hand, Non-Patent Document 1 describes that Cu is used as a substrate, but graphene does not grow in the surface direction in a short time on the Cu foil, and the Cu layer formed on the Si substrate is annealed. The substrate is formed as coarse particles. In this case, the size of graphene is limited by the Si substrate size, and the manufacturing cost is high.
That is, an object of the present invention is to provide a copper foil for producing graphene capable of producing large-area graphene at low cost and a method for producing graphene using the same.

  The copper foil for producing graphene of the present invention has a 60 ° glossiness in both the rolling parallel direction and the perpendicular direction of rolling of 500% or more, and the average crystal grain size after heating at 400 ° C. for 10 minutes is 30 μm or more.

The average crystal grain size is preferably 120 μm or more, and the arithmetic average roughness Ra of the surface is preferably 0.07 μm or less.
Tough pitch copper standardized to JIS-H3100 (alloy number: C1100), oxygen-free copper standardized to JIS-H3510 (alloy number: C1011) or JIS-H3100 (alloy number: C1020), or tough pitch copper or oxygen-free copper On the other hand, it is preferable to contain 0.0001-0.050 mass% of 1 or more types of elements chosen from the group of Sn and Ag.

  The graphene production method of the present invention is performed at 300 ° C. or more and 400 ° C. or less using the graphene production copper foil, the heated copper foil for graphene production is placed in a predetermined chamber, and a carbon-containing gas is supplied. A graphene forming step of forming graphene on the surface of the copper foil for graphene production or the copper plating layer, and a graphene production process while laminating a transfer sheet on the surface of the graphene and transferring the graphene onto the transfer sheet And a graphene transfer step of etching away the copper foil for use.

  ADVANTAGE OF THE INVENTION According to this invention, the copper foil which can produce a large area graphene at low cost is obtained.

It is process drawing which shows the manufacturing method of the graphene which concerns on embodiment of this invention.

  Hereinafter, the copper foil for graphene manufacture which concerns on embodiment of this invention is demonstrated. In the present invention, “%” means “% by mass” unless otherwise specified.

<Composition>
The copper foil for producing graphene is tough pitch copper (TPC) standardized to JIS-H3100 (alloy number: C1100), or JIS-H3510 (alloy number: C1011) or JIS-H3100 (alloy number: C1020). Oxygen copper (OFC) can be used.
Moreover, the composition containing 0.0001-0.050 mass% of 1 or more types of elements chosen from the group of Sn and Ag with respect to these tough pitch copper or oxygen-free copper can also be used. When the above elements are contained, the strength of the copper foil is improved, the film has an appropriate elongation, and the crystal grain size can be increased. When the content ratio of the element is less than 0.0001% by mass, it may be difficult to control the content ratio because the content ratio is small. When the content of the above elements exceeds 0.050% by mass, the strength is further improved, but the elongation is lowered and the workability is deteriorated and the growth of the crystal grain size is suppressed, and the average after heating at 400 ° C. described later for 10 minutes. The crystal grain size is less than 30 μm. More preferably, the content ratio of the element is 0.040% by mass or less.
In addition, as the copper foil for producing graphene, Sn, Ag, in a content ratio (for example, 0.050% by mass or less) in a range that does not greatly affect the crystal grain size with respect to tough pitch copper or oxygen-free copper. One or more elements selected from the group of In, Ti, Zn, Zr, Fe, P, Ni, Si, Te, Cr, Nb, B, and V may be added, but the additive elements are not limited to these. Absent.

<Thickness>
The thickness of the graphene-producing copper foil is not particularly limited, but is generally 5 to 150 μm. Furthermore, it is preferable to set the thickness of the copper foil to 12 to 50 μm in order to easily perform the etching removal described later while ensuring the handleability. When the thickness of the copper foil for producing graphene is less than 12 μm, it is easy to break and the handling property is inferior, and when the thickness exceeds 50 μm, it may be difficult to remove by etching.

<60 degree gloss>
Both the 60-degree glossiness (JIS Z 8741) in the rolling parallel direction and the perpendicular direction of rolling of the copper foil for producing graphene is 500% or more.
As will be described later, after producing graphene using the copper foil for producing graphene of the present invention, it is necessary to transfer the graphene from the copper foil to the transfer sheet. However, if the surface of the copper foil is rough, transfer is difficult. Was found to be damaged. Therefore, 60 degree glossiness is defined as an index representing the surface roughness of the copper foil.
If any of the 60 ° gloss in the direction parallel to rolling and the direction perpendicular to rolling is less than 500%, the graphene is damaged during transfer. The upper limit of the 60 degree glossiness in the rolling parallel direction and the direction perpendicular to the rolling direction is not particularly limited, but about 900% is practically the upper limit.
In order to facilitate the transfer of graphene to the transfer sheet as described above, the arithmetic average roughness Ra of the surface of the copper foil for producing graphene specified in JIS B0601 is preferably 0.05 μm or less.

<Average crystal grain size>
The average crystal grain size after heating the graphene-producing copper foil at 400 ° C. for 10 minutes is 30 μm or more.
When the average crystal grain size of the graphene-producing copper foil is smaller than 30 μm, it becomes an obstacle to growing graphene on the surface of the graphene-producing copper foil, and the graphene is difficult to grow in the plane direction. This is presumably because the crystal grain boundaries hinder the growth of graphene. In particular, the average crystal grain size of the copper foil for producing graphene is preferably 120 μm or more. The upper limit of the average crystal grain size of the copper foil is not particularly limited, but is, for example, 500 μm or less, preferably 450 μm or less, more preferably 400 μm or less, and most preferably 300 μm or less.
Note that the heating at 400 ° C. for 10 minutes simulates the conditions of heating by the plasma-assisted CVD method when producing graphene.
In addition, the average crystal grain size is measured for a graphene-producing copper foil by the cutting method of JIS H0501.

  By using the graphene-producing copper foil defined as described above, large-area graphene can be produced at a low cost and with a high yield.

<Manufacture of copper foil for graphene production>
The copper foil for producing graphene according to the embodiment of the present invention can be produced, for example, as follows. First, after manufacturing the copper ingot of a predetermined composition and performing hot rolling, annealing and cold rolling are repeated and a rolled sheet is obtained. The rolled sheet is annealed and recrystallized, and finally cold-rolled to a predetermined thickness of 80 to 99.9% (preferably 85 to 99.9%, more preferably 90 to 99.9%). To obtain copper foil.

Here, it is important to control the 60 degree gloss of the copper foil for producing graphene to 500% or more. As the method, both oil film equivalents of the final pass of the final cold rolling and the pass before the final pass of the final cold rolling are set to 18000 or less.
The rolled copper foil is generally processed at high speed under oil lubrication, but the shear band deformation tends to become dominant as the lubricating oil film becomes thinner. This is a phenomenon common to metals in general. Note that the presence of a shear band is not preferable for the growth of crystal grains when annealed. And the some or short depth of a shear band can be represented by the glossiness of the copper foil surface. Specifically, as a phenomenon during rolling, if the oil film introduced between the roll and the material is thick, oil pits (unevenness) are formed on the rolled surface, but if the oil film is thin, it contacts the rolling roll on the material surface. The area increases and free deformation is limited, oil pits do not develop, the smooth surface profile of the rolling roll is transferred, and a smooth surface is formed. Therefore, the oil film equivalent is set to 18000 or less as an index for thinning the oil film. If the oil film equivalent exceeds 18000, the 60 degree glossiness of the copper foil surface will be less than 500%.

The oil film equivalent is represented by the following formula.
(Oil film equivalent) = {(rolling oil viscosity, kinematic viscosity at 40 ° C .; cSt) × (rolling speed; m / min)} / {(yield stress of material; kg / mm ² ) × (roll biting angle; rad )}
In order to set the oil film equivalent to 18000 or less, a known method such as using a low-viscosity rolling oil or slowing the sheet passing speed may be used.

By the above method, the 60 degree glossiness of the copper foil for producing graphene can be controlled to 500% or more. Further, it has been found that when the 60 ° glossiness of the copper foil is 500% or more, the crystal grain size after annealing tends to increase. This is presumably because crystal growth after annealing is promoted by controlling the oil film equivalent and the material temperature during the final cold rolling to make shear band deformation difficult to occur.
In addition, the method of controlling the 60 degree glossiness of the copper foil for producing graphene to 500% or more is not limited to the above.

<Graphene production method>
Next, with reference to FIG. 1, a method for producing graphene according to an embodiment of the present invention will be described.
First, the graphene producing copper foil 10 of the present invention described above is placed in a chamber (vacuum chamber or the like) 100, the rolled copper foil 10 for producing graphene is heated by the heater 104, and the inside of the chamber 100 is decompressed or evacuated. To do. Then, a carbon-containing gas G is supplied from the gas inlet 102 into the chamber 100 (FIG. 1 (a)). Examples of the carbon-containing gas G include carbon monoxide, methane, ethane, propane, ethylene, acetylene, and the like. However, the carbon-containing gas G is not limited to these, and may be one or two or more mixed gases. The plasma generator 106 excites (decomposes) the carbon-containing gas G. Moreover, the heating temperature of the copper foil 10 for graphene production can be about 300 ° C. or more and about 400 ° C.
Thereby, decomposition gas (carbon gas) forms the graphene 20 on the surface of the copper foil 10 for graphene manufacture (FIG.1 (b)).

And the copper foil 10 for graphene manufacture is cooled to normal temperature, the transfer sheet 30 is laminated | stacked on the surface of the graphene 20, and the graphene 20 is transcribe | transferred on the transfer sheet 30. FIG. Next, this laminated body is continuously immersed in the etching tank 110 through the sink roll 120, and the copper foil 10 for graphene production is removed by etching (FIG. 1C). Thus, the graphene 20 laminated on the predetermined transfer sheet 30 can be manufactured.
Furthermore, when the laminated body from which the copper foil 10 for producing graphene is removed is pulled up, the substrate 40 is laminated on the surface of the graphene 20, and the transfer sheet 30 is peeled off while transferring the graphene 20 onto the substrate 40, The stacked graphene 20 can be manufactured.

  As the transfer sheet 30, various resin sheets (polymer sheets such as polyethylene and polyurethane) can be used. As an etching solution for etching and removing the copper foil 10 for producing graphene, for example, a sulfuric acid solution, a sodium persulfate solution, hydrogen peroxide, a sodium persulfate solution, or a solution obtained by adding sulfuric acid to hydrogen peroxide can be used. As the substrate 40, for example, Si, SiC, Ni, or Ni alloy can be used.

<Preparation of sample>
A copper ingot having the composition shown in Tables 1 and 2 was manufactured, hot-rolled, and then cold-rolled. Then, after annealing in an annealing furnace set to a temperature of 300 to 800 ° C., cold rolling was performed to obtain a rolled sheet having a thickness of 1 to 2 mm. This rolled sheet is annealed in an annealing furnace set to a temperature of 300 to 800 ° C. and recrystallized, and finally cold-rolled to a thickness (foil thickness) shown in Tables 1 and 2 with a reduction ratio of 95.0 to 99.8%. The copper foil of Examples 1-27 and Comparative Examples 1-10 was obtained.

Here, the oil film equivalents of both the final pass of the final cold rolling and the pass before the final pass of the final cold rolling were adjusted to the values shown in Tables 1 and 2.
The oil film equivalent is represented by the following formula.
(Oil film equivalent) = {(rolling oil viscosity, kinematic viscosity at 40 ° C .; cSt) × (rolling speed; m / min)} / {(yield stress of material; kg / mm ² ) × (roll biting angle; rad )}

<Measurement of 60 degree glossiness>
About the copper foil of Examples 1-27 and Comparative Examples 1-10, the 60 degree glossiness of the surface after the last cold rolling and after heating for 10 minutes at 400 degreeC was measured.
The 60 degree glossiness was measured using a gloss meter (trade name “PG-1M” manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS-Z8741.

<Measurement of surface roughness (Ra, Rz, Sm)>
About the copper foils of Examples 1 to 27 and Comparative Examples 1 to 10, the surface roughness after final cold rolling and after heating at 400 ° C. for 10 minutes was measured.
Using a contact roughness meter (trade name “SE-3400”, manufactured by Kosaka Laboratories), the arithmetic average roughness (Ra; μm) based on JIS-B0601 was measured, and the oil pit depth Rz was JIS B0601-. Ten-point average roughness was measured according to 1994. The measurement position is changed 10 times in parallel with the rolling direction under the conditions of a measurement standard length of 0.8 mm, an evaluation length of 4 mm, a cut-off value of 0.8 mm, and a feed rate of 0.1 mm / second, and 10 times in each direction. The value in the measurement was obtained. In addition, the average interval of unevenness (Sm; mm) is a measurement position parallel to the rolling direction under the conditions of a measurement reference length of 0.8 mm, an evaluation length of 4 mm, a cut-off value of 0.8 mm, and a feed rate of 0.1 mm / second. The measurement was repeated 10 times, and the values for 10 measurements were obtained. Note that Sm is defined as “average interval of unevenness” in JIS B0601-2001 (conforms to ISO 4287-1997) in which the surface property is expressed by a contour curve method, and the contour length of each unevenness within the reference length. The average of

<Measurement of average crystal grain size>
About the copper foil of Examples 1-27 and Comparative Examples 1-10, after heating for 10 minutes at 400 degreeC after the last cold rolling, the average crystal grain diameter of the surface was measured by the cutting method of JISH0501.

<Manufacture of graphene>
The copper foil (100 × 100 mm) in each example and each comparative example was placed in a vacuum chamber, methane gas was supplied to this chamber (supply gas flow rate: 10 to 100 cc / min), and the plasma generator was operated. Then, after heating up copper foil to 400 degreeC in 10 minutes, it hold | maintained for 10 minutes and made the graphene grow on the copper foil surface.
For each example, graphene was produced 10 times under the above conditions, and after the graphene on the surface of the copper foil was transferred to a PET film, the resistance value of the graphene (sheet resistance: Ω / sq) was measured by a four-terminal method. A sheet resistance exceeding 1000Ω / sq was regarded as defective, and the yield was evaluated according to the following criteria based on the number of times exceeding 1000Ω / sq out of 10 productions. If the evaluation is ◎ or ○, there is no practical problem.
A: The number of times exceeding 1000 Ω / sq is 10 times or less in 10 times of manufacture. ○: The number of times exceeding 1000 Ω / sq is 2 times or more and 4 times or less in 10 times of manufacturing. Of which, the number of times exceeding 1000Ω / sq is 5 times or more

The obtained results are shown in Tables 1 and 2. In Tables 1 and 2, G60 _RD and G60 _TD indicate 60 degree glossiness in the rolling parallel direction and the rolling perpendicular direction, respectively. GS represents an average crystal grain size.

As is apparent from Tables 1 and 2, the 60 degree glossiness of the surface of the copper foil is 500% or more, and the average crystal grain size after heating at 400 ° C. for 10 minutes is 30 μm or more. In the case, the production yield of graphene was excellent.
In particular, Examples 3, 6, 7, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22 having an average crystal grain size of 120 μm or more after heating at 400 ° C. for 10 minutes. , 23, 24, 26, and 27, the graphene production yield was the best.

On the other hand, the oil film equivalent of both the final cold rolling final pass and the pass immediately before the final cold rolling pass exceeded 18000, and the 60-degree glossiness of the surface of the copper foil itself was less than 500%. In Comparative Examples 1, 2, 4 to 10, the production yield of graphene was inferior. In the case of Comparative Examples 1, 2, 4 to 10, the average grain size after heating at 400 ° C. for 10 minutes was less than 30 μm. This is because the oil film equivalent of the final cold rolling is too much, and the shear band This is considered to be because the growth of crystal grains was suppressed.
In the case of Comparative Example 3 containing Ag in excess of 0.050 mass%, the average crystal grain size after heating at 400 ° C. for 10 minutes was less than 30 μm, and the graphene production yield was poor. In the case of Comparative Example 3, the oil film equivalent of both the final pass of the final cold rolling and the pass immediately before the final pass of the final cold rolling was set to 18000 or less, so the 60 degree glossiness of the surface of the copper foil However, the glossiness was 500% or more.

2 Copper foil base material 4 Copper plating layer 10 Copper foil for graphene production 20 Graphene 30 Transfer sheet

Claims (5)

  A copper foil for producing graphene having a 60 ° gloss in the direction parallel to and perpendicular to the rolling direction of 500% or more and an average crystal grain size of 30 μm or more after heating at 400 ° C. for 10 minutes.   The graphene-producing copper foil according to claim 1, wherein the average crystal grain size is 120 μm or more.   The copper foil for producing graphene according to claim 1 or 2, wherein the arithmetic average roughness Ra of the surface is 0.07 µm or less.   Tough pitch copper standardized to JIS-H3100 (alloy number: C1100), oxygen free copper standardized to JIS-H3510 (alloy number: C1011) or JIS-H3100 (alloy number: C1100), or tough pitch copper or oxygen free copper On the other hand, the copper foil for graphene manufacture in any one of Claims 1-3 which contains 0.0001-0.050 mass% of 1 or more types of elements chosen from the group of Sn and Ag. It is a manufacturing method of graphene in 300 ° C or more and 400 ° C or less using the copper foil for graphene manufacture in any one of Claims 1-4,
A graphene forming step of arranging the heated copper foil for producing graphene in a predetermined chamber and supplying a carbon-containing gas, and forming graphene on the surface of the copper foil for producing graphene or the copper plating layer,
A graphene transfer process comprising: laminating a transfer sheet on the surface of the graphene; and transferring the graphene onto the transfer sheet while etching and removing the copper foil for producing graphene.