U.S. patent application number 13/740267 was filed with the patent office on 2013-10-31 for carbon nanotube film.
This patent application is currently assigned to BEIJING FUNATE INNOVATION TECHNOLOGY CO., LTD.. The applicant listed for this patent is BEIJING FUNATE INNOVATION TECHNOLOGY CO., LTD. Invention is credited to CHEN FENG, LIANG LIU, LI QIAN, YU-QUAN WANG.
Application Number | 20130287997 13/740267 |
Document ID | / |
Family ID | 49459619 |
Filed Date | 2013-10-31 |
United States Patent
Application |
20130287997 |
Kind Code |
A1 |
FENG; CHEN ; et al. |
October 31, 2013 |
CARBON NANOTUBE FILM
Abstract
A carbon nanotube film includes a number of carbon nanotube
linear units and a number of carbon nanotube groups. The carbon
nanotube linear units are spaced from each other and extend along a
first direction. The carbon nanotube groups are combined with the
carbon nanotube linear units by van der Waals force on a second
direction. The second direction is intercrossed with the first
direction. The carbon nanotube groups between adjacent carbon
nanotube linear units are spaced from each other in the first
direction.
Inventors: |
FENG; CHEN; (Beijing,
CN) ; QIAN; LI; (Beijing, CN) ; WANG;
YU-QUAN; (Beijing, CN) ; LIU; LIANG; (Beijing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CO., LTD; BEIJING FUNATE INNOVATION TECHNOLOGY |
|
|
US |
|
|
Assignee: |
BEIJING FUNATE INNOVATION
TECHNOLOGY CO., LTD.
Beijing
CN
|
Family ID: |
49459619 |
Appl. No.: |
13/740267 |
Filed: |
January 14, 2013 |
Current U.S.
Class: |
428/131 ;
428/221; 428/338; 442/181; 442/21 |
Current CPC
Class: |
Y02E 10/549 20130101;
Y02P 70/50 20151101; Y02P 70/521 20151101; Y10T 428/249921
20150401; B82Y 30/00 20130101; D03D 15/0061 20130101; H01L 51/444
20130101; Y10T 428/24273 20150115; Y10T 442/134 20150401; D03D 9/00
20130101; Y10T 428/268 20150115; Y10T 442/30 20150401; H01L 31/1884
20130101 |
Class at
Publication: |
428/131 ;
428/221; 442/181; 428/338; 442/21 |
International
Class: |
D03D 9/00 20060101
D03D009/00; D03D 15/00 20060101 D03D015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 25, 2012 |
CN |
201210122626.0 |
Claims
1. A carbon nanotube film, comprising: a plurality of carbon
nanotube linear units spaced from each other and substantially
extending along a first direction; and a plurality of carbon
nanotube groups combined with the plurality of carbon nanotube
linear units by van der Waals force in a second direction
intercrossing with the first direction, wherein the plurality of
carbon nanotube groups between adjacent carbon nanotube linear
units are spaced from each other in the first direction.
2. The carbon nanotube film of claim 1, wherein the plurality of
carbon nanotube linear units are substantially parallel to each
other in the second direction and form a plurality of first
conductive paths along the first direction.
3. The carbon nanotube film of claim 1, wherein the plurality of
carbon nanotube groups are interlacedly arranged in the second
direction.
4. The carbon nanotube film of claim 1, wherein the plurality of
carbon nanotube groups are arranged in columns in the second
direction.
5. The carbon nanotube film of claim 4, wherein the plurality of
carbon nanotube groups combined with the plurality of carbon
nanotube linear units form a plurality of second conductive paths
in the second direction.
6. The carbon nanotube film of claim 1, being a free-standing
structure.
7. The carbon nanotube film of claim 1, wherein each carbon
nanotube linear unit comprises a plurality of carbon nanotubes
substantially joined end-to-end by van der Waals force and oriented
along the first direction.
8. The carbon nanotube film of claim 1, wherein an effective
diameter of each carbon nanotube linear unit is greater than or
equal to 0.1 micrometers, and less than or equal to 100
micrometers.
9. The carbon nanotube film of claim 1, wherein each carbon
nanotube group comprises a plurality of carbon nanotubes
substantially extending along the first direction.
10. The carbon nanotube film of claim 1, wherein each carbon
nanotube group comprises a plurality of carbon nanotubes
intercrossed with each other to form a net structure.
11. The carbon nanotube film of claim 10, wherein the plurality of
carbon nanotubes in each carbon nanotube group substantially extend
along a direction defining an angle with the first direction larger
than or equal to 45 degrees, and less than or equal to 90
degrees.
12. The carbon nanotube film of claim 10, wherein the plurality of
carbon nanotubes in each carbon nanotube group substantially extend
along a direction defining an angle with the first direction, and
the angle is less than or equal to 30 degrees.
13. A carbon nanotube film, comprising a plurality of carbon
nanotubes defining a plurality of apertures, the plurality of
carbon nanotubes being made into a plurality of carbon nanotube
linear units and a plurality of carbon nanotube groups, and a
surface area ratio of the plurality of carbon nanotubes to the
plurality of apertures is less than or equal to 1:19.
14. The carbon nanotube film of claim 13, wherein the surface area
ratio of the plurality of carbon nanotubes to the plurality of
apertures is less than or equal to 1:49.
15. The carbon nanotube film of claim 13, wherein the plurality of
carbon nanotube linear units are combined with the plurality of
carbon nanotube groups by van der Waals force so that the carbon
nanotube film is a free-standing structure.
16. The carbon nanotube film of claim 15, wherein the plurality of
carbon nanotube linear units are spaced from each other.
17. The carbon nanotube film of claim 16, wherein the plurality of
carbon linear units are separated from each other in a second
direction and extend substantially along a first direction
intercrossed with the second direction, and the plurality of carbon
linear units substantially form a plurality of conductive paths in
the first direction.
18. The carbon nanotube film of claim 16, wherein the plurality of
carbon nanotube groups between adjacent carbon nanotube linear
units are separated from each other.
19. The carbon nanotube film of claim 18, wherein the plurality of
carbon nanotube groups are arranged in columns and rows, and the
plurality of carbon nanotube groups combined with the plurality of
carbon nanotube linear units in a second direction form a plurality
of a second conductive paths, and the second direction is
intercrossed with an extending direction of each carbon nanotube
linear unit.
20. The carbon nanotube film of claim 18, wherein the plurality of
carbon nanotube groups are interlacedly arranged in a second
direction, and the second direction is intercrossed with an
extending direction of each carbon nanotube linear unit.
Description
RELATED APPLICATIONS
[0001] This application claims all benefits accruing under 35
U.S.C. .sctn.119 from China Patent Application No. 201210122626.0,
filed on Apr. 25, 2012 in the China Intellectual Property Office,
the disclosure of which is incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] The present disclosure relates to a carbon nanotube
film.
[0004] 2. Discussion of Related Art
[0005] A transparent conductive film has characteristics of high
electrical conductivity, low electrical resistance, and good light
penetrability. The transparent conductive film is widely used in
liquid crystal display, touch panel, electrochromic devices, and
airplane windows.
[0006] The conventional methods for forming the transparent
conductive film include a vacuum evaporation method and a magnetron
sputtering method. The drawbacks of these methods include
complicated equipment, high cost, and being unsuitable for mass
production. Furthermore, these methods require a high-temperature
annealing process which will damage a substrate on which the
transparent conductive film is formed. The substrate with a low
melting point cannot be used for forming the film. Thus, the
conventional methods have their limitations.
[0007] Carbon nanotubes have excellent electrical conductivity. A
carbon nanotube film made of the carbon nanotubes, which is
prepared by drawing a carbon nanotube array, has good electrical
conductivity and a certain transparence. The spaces between
adjacent carbon nanotubes in the carbon nanotube film are small.
Thus, the transparence of the carbon nanotube film is low, which is
not conducive for wide applications.
[0008] What is needed, therefore, is to provide a method for making
a carbon nanotube film with high transparence, to overcome the
above shortages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Many aspects of the embodiments can be better understood
with references to the following drawings. The components in the
drawings are not necessarily drawn to scale, the emphasis instead
being placed upon clearly illustrating the principles of the
embodiments. Moreover, in the drawings, like reference numerals
designate corresponding parts throughout the several views.
[0010] FIG. 1 is a flow chart of one embodiment of a method for
making a carbon nanotube film.
[0011] FIG. 2 is a scanning electron microscope (SEM) image of an
original carbon nanotube film.
[0012] FIG. 3 is a schematic view of the original carbon nanotube
film shown in FIG. 2 with through holes substantially arranged in a
row.
[0013] FIG. 4 is a schematic view of the original carbon nanotube
film shown in FIG. 2 with through holes substantially arranged in a
number of rows.
[0014] FIG. 5 is a schematic view of one embodiment of a carbon
nanotube film including a number of carbon nanotube groups
substantially arranged in an array.
[0015] FIG. 6 is a schematic view of one embodiment of a carbon
nanotube film including a number of carbon nanotube groups
interlaced with each other.
[0016] FIG. 7 is a flow chart of one embodiment of a method for
making a carbon nanotube film.
[0017] FIG. 8 is a schematic view of the original carbon nanotube
film shown in FIG. 2 including through holes.
[0018] FIG. 9 is an optical microscope image of the original carbon
nanotube film including through holes shown in FIG. 8.
[0019] FIG. 10 is an optical microscope image of a carbon nanotube
film made by the process shown in FIG. 7.
[0020] FIG. 11 shows transparent chart views of different kinds of
films including carbon nanotubes.
[0021] FIG. 12 is a schematic view of another embodiment of a
carbon nanotube film.
[0022] FIG. 13 is an optical microscope image of the carbon
nanotube film shown in FIG. 12.
DETAILED DESCRIPTION
[0023] The disclosure is illustrated by way of example and not by
way of limitation in the figures of the accompanying drawings in
which like references indicate similar elements. It should be noted
that references to "an" or "one" embodiment in this disclosure are
not necessarily to the same embodiment, and such references mean at
least one.
[0024] One embodiment of a carbon nanotube film is provided. The
carbon nanotube film includes a number of carbon nanotube linear
units and a number of carbon nanotube groups. The carbon nanotube
linear units are spaced from each other. The carbon nanotube groups
join with the carbon nanotube linear units by van der Waals force.
The carbon nanotube groups located between adjacent carbon nanotube
linear units are separated from each other.
[0025] The carbon nanotube linear units substantially extend along
a first direction, and are separated from each other along a second
direction crossed with the first direction. A shape of each carbon
nanotube linear unit intersection can be a semi-circle, circle,
ellipse, oblate, or other shapes. In one embodiment, the carbon
nanotube linear units are substantially parallel to each other, and
distances between adjacent carbon nanotube linear units are
substantially equal. The carbon nanotube linear units are
substantially coplanar. An effective diameter of each carbon
nanotube linear unit is larger than or equal to 0.1 micrometers,
and less than or equal to 100 micrometers. In one embodiment, the
effective diameter of each carbon nanotube linear unit is larger
than or equal to 5 micrometers, and less than or equal to 50
micrometers. Distances between adjacent carbon nanotube linear
units are not limited and can be selected as desired. In one
embodiment, the distances between adjacent carbon nanotube linear
units are greater than 0.1 millimeters. Diameters of the carbon
nanotube linear units can be selected as desired. In one
embodiment, the diameters of the carbon nanotube linear units are
substantially equal. Each carbon nanotube linear unit includes a
number of first carbon nanotubes substantially extending along the
first direction. Adjacent first carbon nanotubes extending along
the first direction are joined end to end by Van der Waals
attractive force. In one embodiment, an axis of each carbon
nanotube linear unit is substantially parallel to the axis of first
carbon nanotubes in each carbon nanotube linear unit.
[0026] The carbon nanotube groups are separated from each other and
combined with adjacent carbon nanotube linear units by van der
Waals force along the second direction. The carbon nanotube film
can be a free-standing structure. "Free-standing structure" means
than the carbon nanotube film can sustain its sheet-shaped
structure without any support. In one embodiment, the carbon
nanotube groups arranged along the second direction are separated
from each other by the carbon nanotube linear units. The carbon
nanotube groups arranged along the second direction also connect
with the carbon nanotube linear units.
[0027] In one embodiment, the carbon nanotube groups can be
interlacedly located in the second direction and disorderly
arranged in the second direction. As such, the carbon nanotube
groups in the second direction form non-linear conductive paths. In
one embodiment, the carbon nanotube groups are arranged into
columns in the second direction, thus the carbon nanotube groups
form consecutive and linear conductive paths in the second
direction. In one embodiment, the carbon nanotube groups in the
carbon nanotube film are arranged in an array. A length of each
carbon nanotube group in the second direction is substantially
equal to the distance between its adjacent carbon nanotube linear
units. The length of each carbon nanotube group on the second
direction is greater than 0.1 millimeters. The carbon nanotube
groups are also spaced from each other along the first direction.
Spaces between adjacent carbon nanotube groups in the first
direction are greater than or equal to 1 millimeter.
[0028] The carbon nanotube group includes a number of second carbon
nanotubes joined by van der Waals force. Axes of the second carbon
nanotubes can be substantially parallel to the first direction or
the carbon nanotube linear units. The axis of the second carbon
nanotubes can also be crossed with the first direction or the
carbon nanotube linear units such that the second carbon nanotubes
in each carbon nanotube group are crossed into a network
structure.
[0029] The carbon nanotube film includes a number of carbon
nanotubes. The carbon nanotubes can be made into carbon nanotube
linear units and carbon nanotube groups. In one embodiment, the
carbon nanotube film consists of the carbon nanotubes. The carbon
nanotube film defines a number of apertures. Specifically, the
apertures are mainly defined by the separate carbon nanotube linear
units and the spaced carbon nanotube groups. The arrangement of the
apertures is similar to the arrangement of the carbon nanotube
groups. In the carbon nanotube film, if the carbon nanotube linear
units and the carbon nanotube groups are orderly arranged, the
apertures are also orderly arranged. In one embodiment, the carbon
nanotube linear units and the carbon nanotube groups are
substantially arranged as an array, the apertures are also arranged
as an array. A ratio of an area sum of the carbon nanotube linear
units and the carbon nanotube groups to an area of the apertures is
less than or equal to 1:19. In other words, in the carbon nanotube
film, a ratio of the area of the carbon nanotubes to the area of
the apertures is less than or equal to 1:19. In one embodiment, in
the carbon nanotube film, the ratio of the total sum area of the
carbon nanotube linear units and the carbon nanotube groups to the
area of the apertures is less than or equal to 1:49. Therefore, a
transparence of the carbon nanotube film is greater than or equal
to 95%. In one embodiment, the transparence of the carbon nanotube
film is greater than or equal to 98%.
[0030] The carbon nanotube film is an anisotropic conductive film.
The carbon nanotube linear units form first conductive paths along
the first direction, as the carbon nanotube linear units extend
along the first direction. The carbon nanotube groups form second
conductive paths along the second direction. Therefore, a
resistance of the carbon nanotube film along the first direction is
different from a resistance of the carbon nanotube film along the
second direction. The resistance of the carbon nanotube film along
the second direction is over 10 times greater than the resistance
of the carbon nanotube film along the first direction. In one
embodiment, the resistance of the carbon nanotube film along the
second direction is over 20 times greater than the resistance of
the carbon nanotube film along the first direction. In one
embodiment, the resistance of the carbon nanotube film along the
second direction is about 50 times greater than the resistance of
the carbon nanotube film along the first direction. In the carbon
nanotube film, the carbon nanotube linear units are joined by the
carbon nanotube groups on the second direction, which makes the
carbon nanotube film strong and stable.
[0031] It is noted that there can be a few carbon nanotubes
surrounding the carbon nanotube linear units and the carbon
nanotube groups in the carbon nanotube film. However, these few
carbon nanotubes have a small and negligible effect on the carbon
nanotube film properties.
[0032] Referring to FIG. 1, one embodiment of a method for making
the carbon nanotube film includes the following steps:
[0033] S10, providing an original carbon nanotube film including a
number of carbon nanotubes joined end to end by van der Waals
attractive force and substantially extending along a first
direction;
[0034] S20, forming a patterned carbon nanotube film by patterning
the original carbon nanotube film to define at least one row of
through holes arranged in the original carbon nanotube film along
the first direction, each row of the through holes including at
least two spaced though holes; and
[0035] S30, treating the patterned carbon nanotube film with a
solvent such that the patterned carbon nanotube film is shrunk into
the carbon nanotube film.
[0036] In step S10, the original carbon nanotube film can be shown
in FIG. 2. The original carbon nanotube film can be obtained by
drawing from a carbon nanotube array substantially along the first
direction. Specifically, the original carbon nanotube film can be
made by the steps of: providing the carbon nanotube array including
a number of substantially parallel carbon nanotubes; and selecting
carbon nanotubes from the carbon nanotube array and pulling the
selected carbon nanotubes substantially along the first direction,
thereby forming the original carbon nanotube film.
[0037] In one embodiment, the carbon nanotube array is formed on a
substrate, and the carbon nanotubes in the carbon nanotube array
are substantially perpendicular to the substrate. During the
pulling process, as the initial carbon nanotubes are drawn out and
separated from the substrate, other carbon nanotubes are also drawn
out end to end due to van der Waals force between ends of adjacent
carbon nanotubes. This process of pulling produces the original
carbon nanotube film with a certain width. The extending direction
of the carbon nanotubes in the original carbon nanotube film is
substantially parallel to the pulling direction of the original
carbon nanotube film. Therefore, the original carbon nanotube film
consists of carbon nanotubes, and the carbon nanotubes are combined
by van der Waals force. The carbon nanotube film is a free-standing
structure. The carbon nanotubes in the original carbon nanotube
film define a number of micropores, and effective diameters of the
micropores are less than 100 nanometers.
[0038] The step S20 is mainly used to form spaced through holes
arranged along the first direction in the original carbon nanotube
film. The original carbon nanotube film can be patterned by using
laser beams or electron beams irradiating the original carbon
nanotube film.
[0039] In one embodiment, the original carbon nanotube film is
patterned by laser beams, and the step S20 includes the following
sub-steps. A laser is provided. An irradiating path of a laser beam
emitted from the laser can be controlled by a computer. A shape of
the original carbon nanotube film having the though holes are
inputted into the computer, which controls the irradiating path of
the laser beam. The laser irradiates the original carbon nanotube
film to form the through holes. A power density of the laser beam
ranges from about 10000 watts per square meter to about 100000
watts per square meter and a moving speed of the laser beam ranges
from about 800 millimeters per second (mm/s) to about 1500 mm/s. In
one embodiment, the power density is in a range from about 70000
watts per square meter to about 80000 watts per square meter, and
the moving speed is in a range from about 1000 mm/s to about 1200
mm/s.
[0040] In step S20, a shape of each through hole can be a circle,
ellipse, triangle, quadrangle, or other shapes. The quadrangle
shape can have at least one pair of parallel sides, such as a
parallelogram, trapezia, rectangle, square, or rhombus. In one
embodiment, the shape of each through hole is rectangular. In
another embodiment, the shape of the through hole is a straight
line, which can be considered as a rectangle with a narrow width.
An effective diameter of the through hole is larger than the
effective diameter of the micropore in the original carbon nanotube
film. In one embodiment, the effective diameter of the through hole
is larger than or equal to 0.1 millimeters. A space between
adjacent through holes is larger than the effective diameter of the
micropore in the original carbon nanotube film. In one embodiment,
the space between adjacent through holes is larger than or equal to
0.1 millimeters. The shape and effective diameter of the through
hole and the space between adjacent through holes can be selected
as desired.
[0041] In step S20, the patterned carbon nanotube film can be
divided into a number of connecting parts and at least two
extending parts by the through holes. The connecting parts are
located between adjacent through holes in each row. The connecting
parts are separated from each other along the first direction by
the through holes. The at least two extending parts substantially
extend along the first direction. The at least two extending parts
are connected with each other on the second direction by the
connecting parts. Therefore, the at least two extending parts and
the connecting parts are an integrated structure. Specifically,
structures of the patterned carbon nanotube films can be described
as follow:
[0042] (1) Referring to FIG. 3, a number of through holes 122 are
separately formed in an original carbon nanotube film 120. The
through holes 122 are arranged into only one row along a first
direction X. The first direction X is substantially parallel to the
extending direction of the carbon nanotubes in the original carbon
nanotube film 120. The original carbon nanotube film 120 can be
divided into a number of connecting parts 124 and two extending
parts 126 by the through holes 122. The connecting parts 124 are
parts of the original carbon nanotube film 120 between adjacent
through holes 122 in the same row. The two extending parts 126 are
parts of the original carbon nanotube film 120 except the
connecting parts 124.
[0043] The connecting parts 124 are separated from each other by
the though holes 122. The connecting parts 124 and the though holes
122 in the same row are alternately arranged. The two extending
parts 126 are located on opposite sides of the connecting parts
124. The extending parts 126 are divided by the connecting parts
124 along a second direction Y crossed with the first direction X.
In one embodiment, the second direction Y is substantially
perpendicular to the first direction X. Each extending part 126
extends along the first direction X.
[0044] (2) Referring to FIG. 4, a number of through holes 122 are
arranged into a number of rows in the original carbon nanotube film
120. The through holes 122 in the same row are spaced from each
other along the first direction X. The through holes 122 are
interlaced with each other along the second direction Y. That is,
the through holes 122 in the second direction Y are not arranged in
a straight line. The through holes 122 in the second direction Y
can also be arranged in columns, and the through holes 122 in the
same column are spaced from each other. The through holes 122 can
be arranged as an array.
[0045] The original carbon nanotube film 120 is divided into a
number of connecting parts 124 and a number of extending parts 126
by the through holes 122. Every adjacent connecting parts 124 in
the same row are separated by the through hole 122. A length of
each connecting part 124 is equal to a space between adjacent
through holes 122 in the same row along the first direction Y. Each
extending part 126 is a connective structure along the first
direction X. Each extending part 126 is sandwiched between adjacent
connecting parts 126 in the second direction Y. A width of each
extending part 126 in the second direction Y is equal to a space
between adjacent through holes 122 in the second direction Y. The
extending parts 126 connect with adjacent connecting parts 124
arranged along the second direction Y. In one embodiment, an
effective length of each through hole 122 in the first direction X
is larger than a space between adjacent through holes 122 along the
second direction Y.
[0046] The shapes of the through holes or the space between
adjacent through holes arranged in the same row or in the same
column can be different. In the patterned carbon nanotube film, the
arrangement of the connecting parts 124 is similar to the
arrangement of the through holes 122. There are a few carbon
nanotubes protruding around edges of each through holes 122, which
is a result of the manufacturing process of the carbon nanotube
film.
[0047] In step S30, the patterned carbon nanotube film is
suspended. The step S30 can include dropping or spraying the
solvent on the suspended patterned carbon nanotube film, and
further shrinking the patterned carbon nanotube film into the
carbon nanotube film. Because the carbon nanotubes in each
extending part of the original carbon nanotube film are
substantially joined end-to-end and substantially oriented along
the first direction, and each extending part of the original carbon
nanotube film is a consecutive structure on the first direction,
the extending parts in the original carbon nanotube film are shrunk
into the carbon nanotube linear units of the carbon nanotube film
under interfacial tension. During the treating process with the
solvent, each extending part of the patterned carbon nanotube film
is substantially shrunk toward its center in the second direction
and formed into the carbon nanotube linear unit, a space between
adjacent extending parts will be increased. Therefore, the carbon
nanotube linear units are spaced from each other in the carbon
nanotube film. A space between adjacent carbon nanotube linear
units in the carbon nanotube film is larger than the effective
diameter of the through holes connected with the extending part or
larger than the effective diameter of the through holes defined by
the original carbon nanotube film in the second direction.
Simultaneously, each connecting part will be drawn under the
shrinking of the adjacent extending parts. The connecting part is
formed into the carbon nanotube group in the carbon nanotube film.
Therefore, the carbon nanotube film is formed.
[0048] An interfacial tension is generated between the patterned
carbon nanotube film and the solvent, and the interfacial tension
varies depending on the volatility of the solvent. Pulling tensions
applied to the connecting parts are produced by the shrinking of
the extending parts. The pulling tensions vary depending on the
interfacial tension. The pulling tensions can affect the
arrangement of the carbon nanotubes in the connecting parts, and
further affect the structures of the carbon nanotube groups in the
carbon nanotube film.
[0049] If the solvent is an organic solvent with a high volatility,
such as alcohol, methanol, acetone, dichloroethane, or chloroform,
the interfacial tension generated between the patterned carbon
nanotube film and the solvent is strong. During the process of
shrinking the extending parts, pulling forces are produced. The
pulling forces applied to the connecting parts adjacent to the
extending parts are strong. The carbon nanotubes oriented along the
first direction in the connecting parts will be formed into the
second carbon nanotubes extending along a direction crossing with
the first direction. Simultaneously, under the interfacial tension,
the carbon nanotubes in each connecting part will be shrunk and
each connecting part will be formed into the carbon nanotube group
with a net structure. In one embodiment, a first angle defined by
the second carbon nanotubes and the first direction is greater than
or equal to 45 degrees, and less than or equal to 90 degrees.
[0050] If the solvent is water, or a mixture of water and the
organic solvent, the interfacial force between the patterned carbon
nanotube film and the solvent is relatively weak. The pulling
forces generated by the shrinking of the extending parts are weak,
thus the pulling forces are weakly applied to the connecting parts.
The arrangements of the carbon nanotubes in the connecting parts
will slightly changed by the weak pulling forces. A second angle is
defined by the second carbon nanotubes in the carbon nanotube
groups with the first direction. The second angle is less than or
equal to 30 degrees. In one embodiment, the second angle is less
than or equal to 15 degrees. In one embodiment, the first solvent
is water, and during the process of forming the carbon nanotube
linear units, the arrangements of carbon nanotubes in the
connecting parts are substantially not changed. Therefore, the
second carbon nanotubes in the carbon nanotube groups are
substantially parallel to the carbon nanotube linear units and the
first direction.
[0051] In the step S20, if the through holes are arranged in rows,
the carbon nanotube linear units made from the extending parts of
the original carbon nanotube film, will be substantially parallel
to each other. If the through holes are arranged in rows and
columns, the extending parts will be formed into carbon nanotube
linear units substantially extending along the first direction, and
the carbon nanotube linear units are separately arranged on the
second direction. At the same time, the connecting parts will be
formed into the carbon nanotube groups, and the carbon nanotube
groups will connect with the carbon nanotube linear units on the
second direction and be spaced in the first direction. The carbon
nanotube linear units, which are substantially parallel and
separate on the second direction, form the first conductive paths
substantially extending along the first direction. The carbon
nanotube groups are connected with the carbon nanotube linear units
in the second directions and spaced in the first direction, which
form the second conductive paths extending along the second
direction.
[0052] Therefore, the effective diameters of the carbon nanotube
linear units can be selected by the spaces between adjacent through
holes in the second direction and the shapes of the through holes.
Spaces between adjacent carbon nanotube linear units can be
controlled by the spaces between adjacent through holes in the
second direction and the widths of through holes in the second
direction. In one embodiment, the shape of the through holes is
rectangular, the widths of the through holes in the second
direction are substantially equal, and the spaces between adjacent
though holes in the same rows are substantially equal. Therefore,
the shapes and the effective diameters of the carbon nanotube
linear units are substantially equal. Further, if the lengths of
the through holes in the first directions are substantially equal,
the carbon nanotube groups will be substantially arranged in the
second direction and the shapes of the carbon nanotube groups will
be substantially the same. In conclusion, both the spaces between
adjacent carbon nanotube linear units and the effective diameter of
the carbon nanotube linear units can be effectively and easily
adjusted according to the method for making the carbon nanotube
film provided by the present disclosure.
[0053] Under the same condition, a resistance of the carbon
nanotube film along the first direction is not affected by the
number of the through holes arranged along the first direction. The
more through holes that are arranged along the first direction, the
higher a resistance of the carbon nanotube film along the second
direction. The less through holes that are arranged along the first
direction, the lower the resistance of the carbon nanotube film
along the second direction. Under the same condition, the
resistance of the carbon nanotube film along the second direction
is not affected by the number of the through holes in the original
carbon nanotube film along the second direction. The more through
holes that are arranged along the second direction, the higher a
resistance of the carbon nanotube film along the first direction.
The less through holes that are arranged along the second
direction, the lower the resistance of the carbon nanotube film
along the first direction. Therefore, the resistance of the carbon
nanotube film, especially the electrical anisotropy of the carbon
nanotube film, can be changed by the number of the through holes in
the patterned carbon nanotube film. That is, the step S20 can
affect the resistance of the carbon nanotube film.
[0054] It is noted that, the electrical conductivity of the carbon
nanotube film can be affected by parameters of the through holes.
If the through holes are uniformly distributed in the patterned
carbon nanotube film and each through hole is rectangular, the
length of each through hole in the first direction is marked as
parameter A, the width of each through hole in the second direction
is marked as parameter B, the space between adjacent through holes
in the first direction is marked as parameter C, and the space
between adjacent through holes in the second direction is marked as
parameter D. In one embodiment, the parameter A is smaller than the
parameter D. If compared with the parameter A, the parameter B is
relatively small, the through holes can be considered as straight
lines. The affect of the parameters of the through holes on the
resistance and electrical anisotropy of the carbon nanotube film
can be detailed below:
[0055] (1) If the parameters A and B are constant, the ratio of the
resistance of the carbon nanotube film along the second direction
to the resistance of the carbon nanotube film along the first
direction is increased as the ratio of the parameter A to parameter
B (A/B) increases. The electrical anisotropy of the carbon nanotube
film is proportional to the ratio of the parameter A to parameter
B.
[0056] (2) If the parameters A and C are constant, the resistance
of the carbon nanotube film at the first direction is increased as
the ratio of the parameter B to parameter D (B/D) increases.
[0057] (3) If the parameters B and D are constant, the resistance
of the carbon nanotube film along the second direction is increased
as the ratio of the parameter A to parameter C (A/C) increases. In
addition, the electrical anisotropy of the carbon nanotube film can
be improved by decreasing the ratio of the parameter A to the
parameter C.
[0058] The method for making the carbon nanotube film further
includes a step of collecting the carbon nanotube film.
Specifically, one end of the original carbon nanotube film drawn
from the carbon nanotube array is fixed on a collecting unit. The
collecting unit is rotated, the original carbon nanotube film can
be continuously patterned and treated with the solvent in order,
and then the carbon nanotube film is continuously formed and
collected on the collecting unit. Thus, the carbon nanotube film
can be continuously formed as rotating the collecting unit. The
carbon nanotube film can be produced automatically. It can be
understood that the collecting unit also can be a fixing element
used to fix the original carbon nanotube film, such as a bar.
[0059] The carbon nanotube films and the methods for making the
carbon nanotube films can be further described in the following
embodiments.
[0060] Referring to FIG. 5, one embodiment of the carbon nanotube
film 10 is provided. The carbon nanotube film 10 is a free-standing
structure, and includes a number of carbon nanotube linear units 12
and a number of carbon nanotube groups 14. The carbon nanotube
groups 14 are connected with the carbon nanotube linear units 12 by
van der Waals force. The carbon nanotube linear units 12 are
inserted into the carbon nanotube groups 14.
[0061] The carbon nanotube linear units 14 are substantially
parallel to each other and separate from each other along the
second direction Y. The carbon nanotube linear units 14 extend
along the first direction X which is substantially perpendicular to
the second direction Y, to form the first conductive paths. Each
carbon nanotube linear unit 12 consists of carbon nanotubes joined
end-to-end by van der Waals force and substantially extend along
the first direction X. The intersection shape of each carbon
nanotube linear unit 12 is circular. The diameter of the carbon
nanotube linear unit 12 is about 10 micrometers. The space between
adjacent carbon nanotube linear units 12 is wider than 1
millimeter.
[0062] The carbon nanotube groups 14 are arranged in an array.
Specifically, the carbon nanotube groups 14 are spaced from each
other along the first direction X. The carbon nanotube groups 14
are orderly arranged along the second direction Y and connected
with the carbon nanotube linear units 12 to form the second
conductive paths. Each carbon nanotube group 14 includes the carbon
nanotubes crossed to form a network structure. Angles defined by
the extending directions of the carbon nanotube in the carbon
nanotube groups with the first direction X, are greater than or
equal to 60 degrees, and less than or equal to 90 degrees.
[0063] The carbon nanotube film 10 has different structures in the
first direction X and the second direction Y. Therefore, the carbon
nanotube film 10 has different properties in the first and second
direction. The carbon nanotube film 10 is an electrically
anisotropic film. The resistance of the carbon nanotube film 10 in
the second direction Y is about 50 times greater than that in the
first direction X. The transparence of the carbon nanotube film 10
can reach up to 98.43% in the visible light region.
[0064] The carbon nanotube film 10 can also have a structure as
shown in FIG. 6, in which the carbon nanotube groups 14 are in a
staggered arrangement in the second direction Y. Specifically, the
carbon nanotube groups 14 are arranged in rows in the first
direction X, and disorderly arranged in the second direction Y. In
another embodiment, the carbon nanotube groups 14 are in a
staggered arrangement in the first direction X. That is, the carbon
nanotube groups 14 are arranged in columns in the second direction
Y, and disorderly arranged in the first direction X.
[0065] Referring to FIG. 7, one embodiment of the method for making
the carbon nanotube film 10 is provided. The method includes the
following steps.
[0066] A carbon nanotube array 110 is provided. The carbon nanotube
array 10 is grown on a substrate 112. An original carbon nanotube
film 120 is drawn from the carbon nanotube array 110 using an
adhesive tape 114. The original carbon nanotube film 120 includes a
number of carbon nanotubes joined end to end by van der Waals force
and substantially extending along the first direction X.
[0067] The adhesive tape 114 is removed. The end of the original
carbon nanotube film 120 adhered to the adhesive tape 114, is fixed
on a fixing element 128. The fixing element 128 is a bar. The
original carbon nanotube film 120 between the fixing element 128
and the carbon nanotube array 110 is suspended. The suspended
original carbon nanotube film 120 is patterned by a laser with a
power density of about 70000 watts per square millimeter, and a
scanning speed of about 1100 millimeters per seconds. A number of
rectangular through holes 122 are defined in the original carbon
nanotube film 120. Referring to FIGS. 8 and 9, the patterned carbon
nanotube film 120 is divided into a number of connecting parts 124
and a number of extending parts 126 by the through holes 122. The
connecting parts 124 are arranged in an array, which is similar to
the arrangement of the through holes 122. The spaces between
adjacent through holes 122 both in the first direction X and the
second direction Y are about 1 millimeter. The length of the
through hole 122 in the first direction X is about 3 millimeters.
The width of the through hole 122 in the second direction Y is
about 1 millimeter. That is, the parameters A, B, C and D of each
through hole 122 are respectively about 3 millimeters, about 1
millimeter, about 1 millimeter, and about 1 millimeter. Thus, the
lengths of the connecting part 124 in the first direction X and the
second direction Y are about 1 millimeter. The width of the
extending part 126 in the second direction Y is substantially equal
to the parameter D of the through hole 122.
[0068] A drop bottle 130 is placed above the patterned carbon
nanotube film 120. Alcohol 132 from the drop bottle 130 is dropped
onto the patterned carbon nanotube film 120. Under interfacial
tension produced between the extending part 126 and the alcohol
132, each extending part 126 is shrunk toward its center to form
the carbon nanotube linear unit 12. Simultaneously, a pulling force
is produced in the process of the shrinking of the extending part
126. Under the pulling force and the interfacial tension produced
between the connecting part 124 and the alcohol 132, extending
directions of most of the carbon nanotubes in the connecting part
124 are shifted into directions intersecting with the first
direction, and the carbon nanotube group 14 is formed. The carbon
nanotube groups 14 are connected with the carbon nanotube linear
units 12 in the second direction, and separated from each other in
the first direction. Thus, the carbon nanotube film 10 is
formed.
[0069] There are some carbon nanotubes protruding from the edges of
the through holes 122 resulting from limitations of the laser.
After the process of treatment with the solvent, there can still be
a few carbon nanotubes shown in FIG. 10 extending from the
peripheries of the carbon nanotube linear units 12 and the carbon
nanotube groups 14.
[0070] If the through holes are arranged in the staggered,
disordered arrangement in the second direction Y as shown in FIG.
4, the carbon nanotube film shown in FIG. 6 obtained by the
above-mentioned method, includes the staggered carbon nanotube
groups.
[0071] The carbon nanotube film 10 is transparent and electrically
conductive. In table 1, the sample "1" represents the original
carbon nanotube film 120, sample "2" represents a patterned carbon
nanotube film formed by using a laser irradiating the original
carbon nanotube film 120 to form a number of through holes in the
original carbon nanotube film, sample "3" represents an alcohol
treated carbon nanotube film made by using alcohol soaking the
original carbon nanotube film 120 to shrink the original carbon
nanotube film, and sample "4" represents the carbon nanotube film
10 formed by the original carbon nanotube film that has been laser
treated and then alcohol treated in sequence. "X" represents the
first direction X, which is the carbon nanotubes in the samples
extending direction, and "Y" represents the second direction Y,
which is substantially perpendicular to the first direction X.
Resistances of the samples 1-4 are measured by adhering the samples
with 3 millimeters.times.3 millimeters to PET sheets. The samples
1-4 are adhered to the PET sheets by a mixture of UV adhesive and
butyl acetate 1:1 by volume. The transparence of the samples 1-4
are measured in suspended state under different wavelengths.
TABLE-US-00001 TABLE 1 Resistance/ K.OMEGA. Transparence under
different wavelengths/% sample X Y 370 nm 450 nm 500 nm 550 nm 600
nm 650 nm 700 nm 750 nm 1 1.245 108.0 76.08 79.17 80.31 81.2 81.88
82.46 82.92 83.32 2 2.00 160.5 80.39 83.03 84.01 84.73 85.27 85.78
86.14 86.51 3 -- -- 84.98 86.33 86.81 87.29 87.62 87.92 88.10 88.29
4 3.23 163.3 98.43 98.42 98.41 98.43 98.40 98.45 98.42 98.38
[0072] From the table 1, the resistance of the carbon nanotube film
10 in every direction is larger than the resistances of the
original carbon nanotube film 120 and the patterned carbon nanotube
film in their corresponding direction. But the carbon nanotube film
10 is still an anisotropic and electrically conductive film, and
the resistance of the carbon nanotube film 10 in the second
direction is over 50 times greater than that in the first direction
X. The transparence of the carbon nanotube film 10 is better than
that of the original carbon nanotube film 120 and the patterned
carbon nanotube film under each wavelength. Further, the
transparence of the carbon nanotube film 10 is higher than 98% in
the visible region.
[0073] Referring to FIGS. 12 and 13, one embodiment of a carbon
nanotube film 20 is provided. The carbon nanotube film 20 includes
a number of the carbon nanotube linear units 12 and a number of
carbon nanotube groups 24 arranged in an array. The structure of
the carbon nanotube film 20 is similar to that of the carbon
nanotube film 10, except that the carbon nanotube groups 24
includes a number of carbon nanotubes substantially extending along
the first direction X. The carbon nanotube linear units extend
along the first direction X. That is, the carbon nanotubes in the
carbon nanotube film 20 are substantially oriented along the same
direction, which is the same as the extending direction of the
carbon nanotube linear units.
[0074] A method for making the carbon nanotube film 20 is similar
to the method for making the carbon nanotube film 10, expect that
in the step S30, water is used as the solvent to treat the
patterned carbon nanotube film having a number of through holes
formed by laser.
[0075] The parameters A, B, C, and D of the through holes affect
the properties of the carbon nanotube film provided by the present
disclosure. The affection can be specifically explained in the
following scenarios. In the following scenarios, the through holes
are uniformly arranged in the original carbon nanotube film as an
array.
[0076] (Scenario I) the parameters of A and C are constant to
determine how parameters B and D affect the carbon nanotube
film.
[0077] First, the original carbon nanotube films have undergone the
different treated conditions shown in table 2 to form the samples.
Secondly, the samples are adhered to the PET sheets. Specifically,
UV adhesive is mixed with butyl acetate in 1:1 by volume forming a
mixture. The mixture is coated on the PET sheets, and the samples
are covered with the mixture to adhere to the PET sheets. The
samples adhered to the PET sheets are made into 3
millimeters.times.3 millimeters sheets, and then used to measure
the resistances of the sample. In table 2, all experiment
conditions are acted on the original carbon nanotube film, the
transparence of the samples is measured under about 550 nanometers
wavelengths, the "parallel resistance" is the resistance of the
samples in the first direction, which is substantially parallel to
the extending directions of the carbon nanotubes in the samples,
and the "perpendicular resistance" is the resistance of the samples
in the second direction, which is substantially perpendicular to
the extending directions of the carbon nanotubes in the samples.
The transparence of the PET sheet adhered solidified UV adhesive is
about 91.40% under the wavelengths of about 550 nanometers.
TABLE-US-00002 TABLE 2 parameter/ millimeter parallel perpendicular
sample A B C D treated condition resistance resistance
transparence/% 1 3 0.9 1 0.6 laser treated 3.2 K.OMEGA. 118.5
K.OMEGA. 80.84 81.51 2 laser treated and then 2.07 K.OMEGA. 46.9
K.OMEGA. 89.68 89.11 alcohol treated 3 3 0.7 1 0.8 laser treated
2.1 K.OMEGA. 90.4 K.OMEGA. 79.47 79.43 4 laser treated and then
1648 .OMEGA. 50.1 K.OMEGA. 90.11 89.86 alcohol treated 5 3 0.5 1 1
laser treated 1862 .OMEGA. 92.6 K.OMEGA. 78.63 77.97 6 laser
treated and then 1712 .OMEGA. 74.9 K.OMEGA. 89.35 90.33 alcohol
treated 7 3 0.3 1 1.2 laser treated 1510 .OMEGA. 103.6 K.OMEGA.
78.48 79 8 laser treated and then 1283 .OMEGA. -- 89.79 90.1
alcohol treated 9 -- original carbon 964 .OMEGA. 33.8 K.OMEGA. 75
73.41 nanotube film
[0078] It can be seen from the table 2 that when the original
carbon nanotube film has undergone the laser treatment and then the
alcohol treatment to form the carbon nanotube film, the
transparence of the carbon nanotube film is close to the
transparence of the PET sheet with solidified UV adhesive.
Therefore, the carbon nanotube film is excellent in transparence.
Having the parameters A and C constant, the parallel resistances of
the samples increase as the ratio of the parameter B to parameter D
(BID) increases, and the parallel resistances of the samples are
not affected whether the original carbon nanotube films have
undergone the shrinking process from the solvent treatment.
[0079] In one embodiment, the ratio of the parameter B to the
parameter D is less than or equal to 2, and the parallel
resistances are greater than or equal to 1 K.OMEGA.. The shrinking
process from the solvent treatment, under the same through hole
parameters results in the perpendicular resistances of the carbon
nanotube films being greatly lower than the perpendicular
resistances of the patterned carbon nanotube films, and the
electrical anisotropy of the carbon nanotube film is increased. The
transparence of the carbon nanotube film can be improved, and the
resistance can be minimally increased.
[0080] (Scenario II) the parameters of B and D are constant to
determine how the parameters A and C affect the carbon nanotube
film
[0081] Samples shown in table 3 are made by the similar methods to
the samples shown in table 2. The differences are the parameters of
the through holes for forming the samples.
TABLE-US-00003 TABLE 3 parameter/ millimeter parallel perpendicular
sample A B C D treated condition resistance resistance
transparence/% 1 3 0.5 1 1 laser treated 1774 .OMEGA. 118.4
K.OMEGA. 79.39 79.34 2 laser treated and then 1656 .OMEGA. 88.8
K.OMEGA. 90.01 90.10 alcohol treated 3 2.5 0.5 1.5 1 laser treated
1692 .OMEGA. 80 K.OMEGA. 78.43 77.80 4 laser treated and then 1600
.OMEGA. 53.3 K.OMEGA. 89.72 89.95 alcohol treated 5 2.0 0.5 2.0 1
laser treated 1653 .OMEGA. 62.1 K.OMEGA. 77.63 77.39 6 laser
treated and then 1666 .OMEGA. 48.4 K.OMEGA. 89.55 89.59 alcohol
treated 7 1.5 0.5 2.5 1 laser treated 1502 .OMEGA. 46.3 K.OMEGA.
76.37 76.66 8 laser treated and then 1406 .OMEGA. 34.0 K.OMEGA.
89.40 89.25 alcohol treated 9 -- original carbon 909 .OMEGA. 42.6
K.OMEGA. 73.06 73.56 nanotube film
[0082] It can be seen from the table 2 that when the parameters B
and D are constant, the perpendicular resistances of the carbon
nanotube film increase as the ratio of the parameter A to parameter
C (A/C) increases. The perpendicular resistances of the samples are
not affected whether the original carbon nanotube films have
undergone the shrinking process from the solvent treatment. In one
embodiment, the ratio of the parameter A to the parameter C is
great than or equal to 0.5, and the perpendicular resistances are
greater than 30 K.OMEGA.. The electrical anisotropy of the carbon
nanotube film can be improved as the ratio of the parameter A to
parameter C increases. The solvent treatment process is not
conducive to improving the electrical anisotropy of the carbon
nanotube film.
[0083] Tension of the Carbon Nanotube Film
[0084] The term "tension" in the text means that minimal pulling
tensions applied to various portions of the carbon nanotube
structures. The carbon nanotube structures include an original
carbon nanotube film, a patterned carbon nanotube film, and a
carbon nanotube film provided by the present disclosure. In one
embodiment, a width of the original carbon nanotube film is about
15 millimeters, and a tension of the original carbon nanotube film
is about 150 milli-Newtons. A width of the patterned carbon
nanotube film is about 15 millimeters, and a tension of the
patterned carbon nanotube film is about 47 milli-Newtons, wherein
the patterned carbon nanotube film includes a number of uniformly
dispersed through holes, and the parameters A, B, C and D of the
through holes are respectively 3 millimeters, 0.35 millimeters, 0.8
millimeters, and 0.35 millimeters. A tension of the carbon nanotube
film is about 105 milli-Newtons. The carbon nanotube film is made
from the patterned original carbon nanotube film with a width about
15 millimeters. In one embodiment, the tension of the carbon
nanotube film is greater than or equal to 90 milli-Newtons.
[0085] It is to be understood that the above-described embodiment
is intended to illustrate rather than limit the disclosure.
Variations may be made to the embodiment without departing from the
spirit of the disclosure as claimed. The above-described
embodiments are intended to illustrate the scope of the disclosure
and not restricted to the scope of the disclosure.
[0086] It is also to be understood that the above description and
the claims drawn to a method may include some indication in
reference to certain steps. However, the indication used is only to
be viewed for identification purposes and not as a suggestion as to
an order for the steps.
* * * * *