U.S. patent application number 10/542785 was filed with the patent office on 2006-11-16 for articles with dispersed conductive coatings.
Invention is credited to Paul J. Glatkowski, Hidemi Ito, Joseph W. Piche, Masato Sakai.
Application Number | 20060257638 10/542785 |
Document ID | / |
Family ID | 37419463 |
Filed Date | 2006-11-16 |
United States Patent
Application |
20060257638 |
Kind Code |
A1 |
Glatkowski; Paul J. ; et
al. |
November 16, 2006 |
Articles with dispersed conductive coatings
Abstract
A conductive article includes a substrate made of a
thermoplastic resin, and a transparent and conductive layer
comprising carbon nanotubes and formed on at least one face of the
substrate. The carbon nanotubes are electrical in contact with each
other and dispersed so that each of the carbon nanotubes is
separated form other carbon nanotubes, or that each of bundles of
the carbon nanotubes is separated from other bundles.
Inventors: |
Glatkowski; Paul J.;
(Littleton, MA) ; Piche; Joseph W.; (Raynham,
MA) ; Sakai; Masato; (Osaka, JP) ; Ito;
Hidemi; (Osaka, JP) |
Correspondence
Address: |
NOVAK DRUCE & QUIGG, LLP
1300 EYE STREET NW
400 EAST TOWER
WASHINGTON
DC
20005
US
|
Family ID: |
37419463 |
Appl. No.: |
10/542785 |
Filed: |
January 29, 2004 |
PCT Filed: |
January 29, 2004 |
PCT NO: |
PCT/US04/02320 |
371 Date: |
July 21, 2006 |
Current U.S.
Class: |
428/292.1 |
Current CPC
Class: |
H01B 1/24 20130101; C09D
5/24 20130101; Y10T 428/249924 20150401 |
Class at
Publication: |
428/292.1 |
International
Class: |
D04H 1/00 20060101
D04H001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 30, 2003 |
JP |
2003-21538 |
Claims
1. A conductive article comprising: a substrate; and a transparent
and conductive layer comprising fine conductive fibers and formed
on at least one face of the substrate, wherein the fibers are
electrically in contact with each other and dispersed so as not to
form agglomerates of said fibers.
2. The conductive article of claim 1, wherein the fibers are
electrically in contact with each other and dispersed so that each
of the fibers is separated from other fibers, or that each of
bundles of the fibers is separated from other bundles.
3. The conductive article of claim 1, wherein the fibers are carbon
fibers.
4. The conductive article of claim 1, wherein carbon fibers are
carbon nanotubes.
5. The conductive article of claim 1, wherein the fibers are
multi-wall carbon nanotubes, and each of the carbon nanotubes is
separated from other carbon nanotubes while maintaining electrical
contact between the nanotubes.
6. The conductive article of claim 1, wherein the fibers are
single-wall carbon nanotubes that form bundles of the carbon
nanotubes, and each of the bundles is separated from other bundles
while maintaining electrical contact between the bundles.
7. The conductive article of claim 1, wherein the fibers are
double-wall or triple-wall carbon nanotubes that form bundles of
the carbon nanotubes, and each of the bundles is separated from
other bundles while maintaining electrical contact between the
bundles.
8. The conductive article of claim 1, wherein the conductive
article has a surface resistivity of from 10.sup.0 to 10.sup.11
/.quadrature..
9. The conductive article of claim 1, wherein the transparent and
conductive layer has a surface resistivity of from 10.sup.0 to
10.sup.1 /.quadrature. and a 550 nm light transmittance of at least
50%.
10. The conductive article of claim 1, wherein the transparent and
conductive layer has a surface resistivity of from 10.sup.2 to
10.sup.3 /.quadrature. and a 550 nm light transmittance of at least
75%.
11. The conductive article of claim 1, wherein the transparent and
conductive layer has a surface resistivity of from 10.sup.4 to
10.sup.6 /.quadrature. and a 550 nm light transmittance of at least
90%.
12. The conductive article of claim 1, wherein the transparent and
conductive layer has a surface resistivity of from 10.sup.7 to
10.sup.11 /.quadrature. and a 550 nm light transmittance of at
least 93%.
13. The conductive article of claim 1, wherein the substrate is
formed of a transparent synthetic resin.
14. A conductive article comprising: a substrate made of a
thermoplastic resin; and a transparent and conductive layer
comprising carbon nanotubes and formed on at least one face of the
substrate, wherein the carbon nanotubes are electrically in contact
with each other and dispersed so that each of the carbon nanotubes
is separated form other carbon nanotubes, or that each of bundles
of the carbon nanotubes is separated from other bundles.
15. A method for manufacture of a conductive article comprising:
applying a layer of fine conductive fibers to a surface of a
substrate, wherein the fibers are electrically in contact with each
other and dispersed so as not to form agglomerates of said
fibers.
16. The method of claim 15, wherein the fine conductive fibers are
carbon nanotubes.
17. The method of claim 15, wherein the conductive article has a
surface resistivity of from 10.sup.0 to 10.sup.11
/.quadrature..
18. The method of claim 15, wherein the conductive article has a
surface resistivity of from 10.sup.0 to 10.sup.1 /.quadrature. and
a 550 nm light transmittance of at least 50%.
19. The method of claim 15, wherein the conductive article has a
surface resistivity of from 10.sup.2 to 10.sup.3 /.quadrature. and
a 550 nm light transmittance of at least 75%.
20. The method of claim 15, wherein the conductive article has a
surface resistivity of from 10.sup.4 to 10.sup.6 /.quadrature. and
a 550 nm light transmittance of at least 90%.
21. The method of claim 15, wherein the substrate is formed of a
transparent synthetic resin.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to an articles that have a conductive
layer and optionally a light transmittance, and to methods for
producing such articles.
[0003] 2. Description of the Background
[0004] An anti-electrostatic resin plate that is able to release
static electricity and avoid dust adherence has been used for a
clean room partition such as windows used in the clean room. One
such example is described in Japanese Laid Open Patent Publication
2001-62952. The resin material of this invention includes tangled
fibers that would extend at the time of article formation to
provide a good conductivity. A substrate film, where ITO (Indium
Tin Oxide) or ATO (Antimony Tin Oxide) is placed on the surface,
has been known as a transparent conductive film with a surface
resistivity of 10.sup.0 to 10.sup.5.OMEGA./.quadrature.(Japanese
Laid Open Paten Publication 2003-151358).
[0005] In the conventional anti-electrostatic transparent resin
plate (Japanese Laid Open Paten Publication 2001-62952), the carbon
fibers bent and intertwined with each other are buried in an
anti-electrostatic layer. Therefore, the carbon fibers are not well
dispersed. The amount of the carbon fiber in the anti-electrostatic
layer should be increased to a certain level in order to achieve an
adequate surface resistivity of 10.sup.5 to
10.sup.8.OMEGA./.quadrature.. The anti-electrostatic transparent
resin plate (Japanese Laid Open Paten Publication 2001-62952)
mentioned can acquire an electromagnetic shield property when the
amount of the carbon fiber in the anti-electrostatic layer is
further increased and the surface resistivity decreases to
10.sup.4.OMEGA./.quadrature.. However, the transparency of the
anti-electrostatic layer is deteriorated when the amount of the
carbon fiber is increased. Thus, it is difficult to acquire the
practical anti-electrostatic transparent resin plate that has both
good transparency and electromagnetic shield property.
[0006] The transparent conductive film described in the Japanese
Laid Open Paten Publication 2003-1 51358 is formed through a batch
method such as spattering. Therefore, it has a poor productivity
and the high production cost.
SUMMARY OF INVENTION
[0007] The present invention overcomes the problems and
disadvantages associated with current strategies and designs and
provides articles with conductive layers that demonstrate good
conductivity, while acquiring better transparency, and to methods
for forming such articles.
[0008] One embodiment of the invention is directed to articles with
conductive layers that can achieve good conductivity, with the same
amount or less of the ultra fine conductive fiber such as
conventionally available carbon fiber.
[0009] Another embodiment of the invention is directed to methods
for forming articles with the conductive layers that demonstrate a
good conductivity, the thickness of which is reduced to improve the
transparency, which may be by reducing the amount of the ultra fine
conductive fiber.
[0010] Another embodiment of the invention is directed to method
for forming articles with the transparent conductive layer that can
be produced with low production costs.
[0011] Other embodiments and advantages of the invention are set
forth in part in the description, which follows, and in part, may
be obvious from this description, or may be learned from the
practice of the invention.
DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-sectional view of an embodiment of the
conductive article of this invention.
[0013] FIG. 2A is a cross-sectional view showing the dispersion of
the ultra fine conductive fiber in the conductive layer of this
invention, and FIG. 2B is another cross-sectional view showing the
dispersion of the ultra fine conductive fiber in the conductive
layer of this invention.
[0014] FIG. 3 is a plan diagram of the conductive layer showing the
dispersion of the ultra fine conductive fiber in the conductive
layer.
[0015] FIG. 4 is a transmission electron microscopic photograph
showing the dispersion of the ultra fine conductive fiber in the
conductive layer viewing from above.
[0016] FIG. 5 is a scanning electron microscopic photograph showing
the dispersion of the ultra fine conductive fibers in the
conductive layer viewing from above.
[0017] FIG. 6 is an optical microscopic photograph showing the
ultra fine conductive fiber in the conductive layer of the
comparative example viewing from above.
DESCRIPTION OF THE INVENTION
[0018] As embodied and broadly described herein, the present
invention is directed to articles that have conductive coatings,
which may optionally be transparent, and methods of forming such
articles.
[0019] One embodiment of the invention is directed to conductive
articles that have transparent conductive layers comprising ultra
fine conductive fibers on at least one surface of a substrate. A
characteristic of this invention is that the ultra fine conductive
fibers are well dispersed, and yet in contact with each other,
without densely concentrated.
[0020] The conductive article of this invention has a transparent
conductive layer that has the ultra fine conductive fiber on at
least one surface of the substrate. Another characteristic of this
invention is that the ultra fine conductive fibers are in contact
with each other and yet dispersed so that each fiber is separated
from other fibers or each bundle of the fiber, where a plurality of
the fibers make a bundle, is separated from other bundles.
[0021] The carbon fiber, especially carbon nanotube is used as the
ultra fine conductive fiber in this invention. It is preferable
that the fibers or the bundles of the fiber are in contact with
each other and yet dispersed so that each fiber or bundle is
separated from other fibers or bundles. It is also preferable that
the surface resistivity of the article be 10.sup.0 to
10.sup.11.OMEGA./.quadrature.. Also, the surface resistivity of the
conductive layer is 10.sup.0 to 10.sup.1.OMEGA./.quadrature. and
the light transmission of the light with 550 nm wavelength is above
50%. The surface resistivity of the conductive layer is 10.sup.2 to
10.sup.3.OMEGA./.quadrature. and the light transmission of the
light with 550 nm wavelength is above 75%. Or the surface
resistivity of the conductive layer is 10.sup.4 to
10.sup.6.OMEGA./.quadrature. and the light transmission of the
light with 550 nm wavelength is above 88%, or the surface
resistivity of the conductive layer is 10.sup.7 to
10.sup.11.OMEGA./.quadrature. and the light transmission of the
light with 550 nm wavelength is above 93%.
[0022] The conductive article of this invention has a transparent
conductive layer made of thermo-plastic resin that has the carbon
nanotube on at least one surface of the substrate made of a
transparent thermo-plastic resin. Another characteristic of this
invention is that the carbon nanotubes are in contact, yet
dispersed so that each tube is separated from other tubes, and not
densely concentrated.
[0023] The expression `not densely concentrated` herein denotes
that there is no significant lump of fibers with the average
diameter of above 0.5 .mu.m when the conductive layer is observed
by an optical microscopy. The word `contact` indicates the
following two states; the carbon nanotubes make an actual contact
with each other, or the carbon nanotubes are located close enough
with a slight space between them that allows the flow of
electricity. The word `conductivity` means that the surface
resistivity falls into the scope of 10.sup.0 to
10.sup.11.OMEGA./.quadrature. when it is measured by JIS K 7194
(ASTM D 991) (when the resistivity is below
10.sup.6.OMEGA./.quadrature.) or JIS K 6911 (ASTM D 257) (when the
resistivity is above 10.sup.6.OMEGA./.quadrature.).
[0024] The ultra fine conductive fibers in the conductive layer of
the first conductive article of this invention are in contact with
each other, and yet well dispersed without being densely
concentrated. The ultra fine conductive fibers are loosely crossing
each other, which allows for the flow of electricity, leading to
the excellent conductivity. Therefore, the same conductivity as
that of the conventional art can be obtained with the smaller
amount of the ultra fine conductive fiber, allowing the improved
transparency and the thinner conductive layer. Since the fibers are
not densely concentrated, the number of the fibers contributing to
the flow of electricity increases when the same amount of the ultra
fine conductive fiber as that of the conventional art is applied,
leading to the improved conductivity. Furthermore, if the carbon
nanotube, which is thin and long, is used as the ultra fine
conductive fiber, the contact between the fibers is further
facilitated, allowing the control of the surface resistivity with
the scope of 10.sup.0 to 10.sup.11.OMEGA./.quadrature.. It is also
possible to obtain a good transparency. The article of this
invention can also have the anti-electrostatic property, the
conductive property, and the electromagnetic shield property.
[0025] The ultra fine conductive fibers or bundles of the fiber in
another conductive article of this invention are in contact with
each other, yet dispersed so that each fiber is separated from
other fibers or each of the bundle of fiber, where a plurality of
the fibers make a bundle, is separated from other bundles. The
frequency of fibers or bundles of fibers that make contact with
each other increases, which allows for the flow of electricity,
leading to excellent conductivity. Therefore, the same conductivity
as that of the conventional art can be obtained with the smaller
amount of the ultra fine conductive fiber, allowing for the
improved transparency and a thinner conductive layer. The improved
conductivity is obtained when the same amount of the ultra fine
conductive fiber as that of the conventional art is applied,
because the frequency for the fibers to make contact with each
other has been increased. Furthermore, if carbon nanotubes are used
as ultra fine conductive fibers, contact between the fibers is
further facilitated. It is also possible to obtain the article with
a good transparency and the article with the improved conductivity.
The article of this invention can also have the anti-electrostatic
property and the electromagnetic shield property.
[0026] Various preferred embodiments of the invention may be
explained by referring to figures. However, this invention is not
limited to those embodiments.
[0027] FIG. 1 is a cross-sectional view of the conductive article
in the plate form of an embodiment of this invention. FIG. 2A is a
cross-sectional view showing the dispersion of the ultra fine
conductive fiber in the conductive layer. FIG. 2B is another
cross-sectional view showing the dispersion of the ultra fine
conductive fiber in the conductive layer. FIG. 3 is a plan diagram
showing the dispersion of the ultra fine conductive fiber in the
conductive layer.
[0028] A conductive article P has a conductive layer 2 with ultra
fine conductive fibers laminated on one (upper) surface of a
substrate 1 that is made of inorganic material such as synthetic
resin, glass or ceramics. The conductive layer 2 can be formed both
upper and bottom surfaces of the substrate 1.
[0029] The substrate 1 is made of thermo-plastic resin, the
hardening resin that is hardened by the application of heat,
ultra-violet ray, electric beam or radioactive ray, glass,
ceramics, or inorganic material. The transparent thermo-plastic
resin, hardening resin, or glass is a desirable material for
acquiring the transparent conductive article P. The transparent
thermo-plastic resin includes, for example, olefin resin such as
polyethylene, polypropylene, and ring polyolefin, vinyl resin such
as polyvinylchloride, polymethylmethacrylate, and polystyrene,
cellulose resin such as nitrocellulose and triacetylcellulose,
ester resin such as polycarbonate, polyethyleneterephtalate,
polydimethylcyclohexeneterephtalate, and aromaticpolyester, ABS
resin, the co-polymer and the mixture of these resins. The
transparent hardening resin includes epoxy resin, polyimid resin
and acrylic resin. The substrate 1 does not necessarily take the
plate form, but may comprise other forms as well.
[0030] The transparent resin with the light transmission of above
75%, preferably above 80%, and the haze of below 5% when the
thickness of the substrate 1 is 3 mm, is especially desirable. Such
resin includes ring polyolefin, polyvinylchloride,
polymethylmethacrylate, polystyrene, triacetylcellulose,
polycarbonate, polyethyleneterephtalate,
polydimethylcyclohexeneterephtalate, co-polymer of these resins,
mixture of these resins and hardening acrylic resin. Since glass
has the excellent light transmission of above 95%, glass is used
frequently for acquiring the transparent conductive article P.
[0031] The ease of forming, the thermo-stability and the durability
against weathering of the substrate 1 made of resin mentioned above
are improved when an adequate amount of plasticizer, stabilizer and
ultra-violet ray absorbent are added. The substrate 1 can also be
made opaque or semi-opaque by adding die or pigment. In this case,
an opaque or a semi-opaque conductive article is acquired. Since
the conductive layer 2 is transparent, the color of the die or
pigment can be kept intact. The thickness of the substrate 1 should
be determined according to the usage, but the thickness of the
substrate is usually about 0.03 to 10 mm.
[0032] The conductive layer 2 formed on one side of the substrate 1
is a transparent layer that has the ultra fine conductive fiber 3.
The ultra fine conductive fibers 3 are in contact with each other,
and yet dispersed without being densely concentrated. That is, the
fibers or bundles of the fiber, where a plurality of the fibers
makes a bundle, are in contact with each other and yet dispersed so
that each fiber is separated from other fibers or each bundle is
separated from other bundles. The fibers will be in one of the
following three states when the conductive layer 2 is formed with
the ultra fine conductive fiber 3 and a binder; the ultra fine
conductive fibers are dispersed as described above in the binder,
as shown in FIG. 2A; the ultra fine conductive fibers are dispersed
as described above, with a part of the fiber is in the binder and
other part of the fiber protrudes or exposes itself from the
binder, as shown in FIG. 2B; or the combination of the two. That
is, the ultra fine conductive fibers are dispersed as described
above, where some fibers are buried in the binder as shown in FIG.
2A and a part of other fibers protrudes or exposes itself from the
binder as shown in FIG. 2B.
[0033] The dispersion of the ultra fine conductive fiber 3 viewing
from above is shown in FIG. 3. The ultra fine conductive fibers 3
or bundles of the fiber are in contact with each other and yet
dispersed so that each fiber or each bundle is separated from other
fibers or other bundles. The fibers are not intensely intertwined
so that they are not densely concentrated. The fibers are simply
crossing each other, making contact with each other in or on the
conductive layer 2. Since the fibers are loosely crossing,
spreading in a broader area compared to the case where the fibers
are densely concentrated, the frequency for the ultra fine
conductive fiber to make contact with each other is greater,
achieving the excellent conductivity. The same frequency of the
fiber contact (the density of the flow of electricity) should be
acquired to achieve the same conductivity of 10.sup.5 to
10.sup.8.OMEGA./.quadrature. as that of the conventional art. Since
the fibers are dispersed as described above, the smaller amount of
the ultra fine conductive fiber allows the same frequency of the
fiber contact, leading the better transparency. It is also possible
to make the conductive layer thinner, achieving the even better
transparency.
[0034] It is not necessary for the ultra fine conductive fibers 3
or bundles of the fiber to be completely separated from other
fibers or bundles. Small lumps of fibers with diameters of less
than 0.5 .mu.m is acceptable.
[0035] The frequency of the fiber contact is higher in this
invention than that of the conventional art when the same amount of
the ultra fine conductive fiber 3 is applied to the conductive
layer 2, leading to the improved conductivity.
[0036] Additionally, the conductivity can be improved even if the
thickness of the conductive layer 2, which has the ultra fine
conductive fiber 3, is reduced to 5 to 500 nm. Therefore, it is
desirable to reduce the thickness of the conductive layer 2 to 5 to
500 nm, preferably to 5 to 200 nm.
[0037] Ultra fine carbon fiber such as carbon nanotube, carbon
nanohorn, carbon nanowire, carbon nanofiber, and graphite fibril,
ultra fine metal fiber such as metal nanotube and metal nanowire
made of platinum, gold, silver, nickel, and silicon, and ultra fine
metal oxide fiber such as metal oxide nanotube or metal oxide
nanowire made of zinc oxide are used for the ultra fine conductive
fiber 3 in the conductive layer 2. The fiber with the diameter of
0.3 to 100 nm and the length of 0.1 to 20 .mu.m, especially 0.1 to
10 .mu.m is preferably used. Since the ultra fine conductive fibers
3 are dispersed, without being densely concentrated, so that each
fiber or bundle of the fibers is separated from other fibers or
bundles, it is possible to acquire the article with the light
transmission of above 50% when the surface resistivity of the
conductive layer 2 is 10.sup.0 to 10.sup.1.OMEGA./.quadrature. and,
the light transmission of above 75%, when surface resistivity is
10.sup.2 to 10.sup.3.OMEGA./.quadrature., and the light
transmission of above 88% when the surface resistivity is 10.sup.4
to 10.sup.6.OMEGA./.quadrature., and the light transmission of
above 93% when the surface resistivity is 10.sup.7 to
10.sup.11.OMEGA./.quadrature.. The light transmission indicates the
transmission rate of the light with 550 nm wavelength measured by a
spectrometer.
[0038] Carbon nanotube has a very small diameter of 0.3 to 80 .mu.m
among the ultra fine conductive fibers 3. Since the carbon
nanotubes or bundles of the tube are separated from other tubes or
bundles, there are very few obstacles for light transmission,
achieving the transparent conductive layer 2 with the light
transmission of above 50%. The ultra fine conductive fibers 3 in
the conductive layer 2 are in contact with each other, and yet
dispersed well, without being densely concentrated, so that each
fiber or bundle of the fiber is separated from other fibers or
bundles, allowing the flow of electricity. Therefore, it is
possible to control the surface resistivity with the scope of
10.sup.0 to 10.sup.11.OMEGA./.quadrature., when the estimated
content of the ultra fine conductive fiber 3 in the conductive
layer 2 is 1.0 to 450 mg/m.sup.2. The value of the estimated
content of the fiber can be obtained by following the steps
described below. First, observe the conductive layer 2 by an
electron microscopy, measuring the area occupied with the ultra
fine conductive fiber in the plan area. Then, measure the thickness
of the conductive layer. Then, multiply the value of the fiber area
by the thickness of the conductive layer acquired from the electro
microscopic observation and the specific gravity of ultra fine
conductive fiber (value 2.2, the average of 2.1-2.3, reported as
the specific gravity of graphite is used when the ultra fine
conductive fiber is made of carbon nanotube).
[0039] Here, the expression `not densely concentrated` denotes that
there is no lump of fibers with the average diameter, which is the
average of the longer diameter and the shorter diameter, of above
0.5 .mu.m when the conductive layer is observed by an optical
microscopy.
[0040] The carbon nanotube described above includes multi-layered
carbon nanotube, which has a plurality of tubes made of carbon
walls with different diameters enclosed around the shared center
axis and single-layered carbon nanotube, which has a single
enclosed carbon wall around the center axis.
[0041] There is a plurality of tubes made of carbon walls with
different diameters enclosed around the shared center axis in the
multi-layered carbon nanotube. The carbon walls are configured as
hexagonal stacking structure. Some multi-layered carbon nanotube
has a carbon wall spiral that makes a plurality of layers. The
desirable multi-layered carbon nanotube has 2 to 30 carbon wall
layers. An excellent light transmission is acquired when the
multi-layered carbon nanotube described above is dispersed as
described above in the conductive layer. The more desirable carbon
nanotube has 2 to 15 carbon wall layers. Usually, the multi-layered
carbon nanotube is dispersed with each piece of the carbon nanotube
separated from other pieces. However, in some cases, the 2 to 3
layered carbon nanotubes form bundles, which are dispersed as
described above.
[0042] The single-layered carbon nanotube has a single enclosed
carbon wall around the center axis. The carbon wall is configured
as hexagonal stacking structure. The single-layered carbon nanotube
is not easily dispersed piece by piece. Two or more tubes form a
bundle. The bundles are not densely concentrated or intensely
intertwined with each other. The bundles are simply crossing each
other, making contact with each other, dispersed in or on the
conductive layer. The preferable bundle of the single-layered
carbon nanotube has 10 to 50 tubes.
[0043] The surface resistivity of 10.sup.0 to
10.sup.11.OMEGA./.quadrature. of the conductive article P with the
conductive layer 2, where the ultra fine conductive fibers 3 are
loosely crossing each other, is obtained with the excellent
conductivity and the anti-electrostatic property, because the ultra
fine conductive fiber 3 are loosely crossing each other, allowing
the enough flow of electricity, even with the reduced thickness of
5 to 500 nm for the conductive layer 2 when the estimated content
of the ultra fine conductive fiber 3 in the conductive layer 2 is
1.0 to 450 mg/m.sup.2. Since the ultra fine conductive fiber is
separated from other fibers and there is no lump, there are very
few obstacles for light transmission, achieving the good
transparency. The transparency is also improved, because the
estimated content of the ultra fine conductive fiber 3 is reduced,
as the thickness of the conductive layer 2 gets thinner.
[0044] The surface resistivity of 10.sup.4 to
10.sup.11.OMEGA./.quadrature. of the conductive layer 2 can be
obtained even if the estimated content of the ultra fine conductive
fiber 3 is reduced to 1.0 to 30 mg/m.sup.2. Also, the conductive
layer 2 with the excellent transparency (the light transmission of
above 88%) is acquired. Therefore, the transparent article can be
acquired when transparent resin or glass is used for the substrate
1. The transparent conductive polycarbonate resin plate with the
light transmission of above 78%, the haze of below 2%, and the
anti-electrostatic property is obtained when the transparent
polycarbonate resin with the thickness of about 3 mm is used as the
substrate 1.
[0045] The surface resistivity of 10.sup.2 to
10.sup.3.OMEGA./.quadrature. of the conductive layer 2 is obtained
when the estimated content of the ultra fine conductive fiber 3 in
the conductive layer 2 is increased to 30 to 250 mg/m.sup.2. Also,
the transparent conductive layer 2 is acquired (the light
transmission of above 75%). Therefore, the transparent article with
the low resistively can be acquired when transparent resin or glass
is used for the substrate 1. The transparent conductive
polycarbonate resin plate with the excellent conductive property,
which has the light transmission of above 65% and the haze of below
4%, is obtained when the transparent polycarbonate resin with the
thickness of about 3 mm is used as the substrate 1. This resin
plate also has the electromagnetic shield property.
[0046] The surface resistivity of 10.sup.0 to
10.sup.1.OMEGA./.quadrature. of the conductive layer 2 is obtained
when the estimated content of the ultra fine conductive fiber 3 in
the conductive layer 2 is increased to 250 to 450 mg/m.sup.2, while
keeping the transparency of the conductive layer 2 (the light
transmission of above 50%). Therefore, the transparent conductive
article can be acquired when transparent resin is used for the
substrate 1. The transparent conductive polycarbonate resin plate
with the excellent conductive property, which has the light
transmission of above 45% and the haze of below 5%, is obtained
when the transparent polycarbonate resin with the thickness of
about 3 mm is used as the substrate 1. This resin plate also has
the electromagnetic shield property. The light transmission of the
conductive layer 2 can be obtained by correcting the light
transmission of the light with 550 nm wavelength of the article
using the light transmission of the substrate. A spectrometer is
used for measuring. The transmission and the haze are measured
according to ASTM D 1003.
[0047] The improvement of the dispersion of the ultra fine
conductive fiber 3 is important to achieve the better conductivity
and transparency of the conductive layer 2 by adding a large amount
of the ultra fine conductive fiber 3 to the conductive layer 2. It
is also important to form the thinner conductive layer 2 by
reducing the viscosity of the coating solution. Therefore, the
disperser should be used for the better dispersion. Macromolecule
disperser and coupling agent such as alkylammonate solution of acid
polymer, tertiary amine modified alkyl co-polymer, and co-polymer
between polyoxyethyllene and polyoxypropylene are used as the
disperser. Additive such as ultra-violet ray absorbent, surface
modifier, and stabilizer can be added to the conductive layer 2 in
order to achieve the durability against weathering and other
properties.
[0048] The transparent thermo-plastic resin, especially
polyvinylchloride, co-polymer between vinylchloride and vinyl
acetate, polymethylmethacrylate, nitrocellulose, chlorinated
polyethylene, chlorinated polypropylene, and fluorovinylidene and
the transparent hardening resin that is hardened by the application
of heat, ultra-violet ray, electric beam or radioactive ray,
especially melamine acrylate, urethane acrylate, epoxy resin,
polyimid resin, and silicon resin such as acryl-transformer
silicate are used as a binder. Therefore, the conductive layer 2,
which is made of the transparent binder and the ultra fine
conductive fiber, is a transparent layer. Also, inorganic material
such as colloidal silica can be added to the binder. When the
substrate 1 is made of a transparent thermo-plastic resin, the same
transparent thermo-plastic resin or the different transparent
thermo-plastic resin with the mutual-solubility is preferably used
as the binder for acquiring the transparent conductive article. The
article P with the durability against wearing can be obtained when
the binder with a hardening resin or colloidal silica is used.
Since the conductive layer 2 is formed on the surface of the
substrate 1, adequate binder should be chosen to improve the
particular property such as the durability against weathering,
surface strength, and durability against wearing.
[0049] When the estimated content of the ultra fine conductive
fiber 3 in the conductive layer 2 is 1.0-450 mg/m.sup.2, and when
the thickness of the conductive layer 2 is reduced to 5-500 nm, the
surface resistivity of 10.sup.0 to 10.sup.11.OMEGA./.quadrature.
with the excellent conductivity, the anti-electrostatic property,
and transparency is obtained, because the ultra fine conductive
fibers 3 or the bundle of the fiber are dispersed so that each
fiber or bundle is separated from other fibers or bundles. The
preferable estimated content of the ultra fine conductive fiber 3
is 1.0 to 200 mg/m.sup.2 and the preferable thickness of the
conductive layer 2 is 5 to 200 nm. The powdered conductive metal
oxide of 30 to 50 weight % can be added beside the ultra fine
conductive fiber to the conductive layer 2.
[0050] The conductive article P described above can be efficiently
produced, for example, by the following methods. First, the binder
for forming the conductive layer is solved into a volatile solvent.
The ultra fine conductive fiber 3 is equally dispersed in this
solution, making a coating solution, which is then applied to one
surface of the substrate 1. The conductive layer 2 is obtained by
drying the coating solution on the substrate 1, forming the
conductive article P. In the second method, the coating solution is
applied to the surface of the thermoplastic resin film, which is
the same thermoplastic resin film as that the substrate 1 or the
different thermo-plastic resin film with the mutual-solubility.
Then, the coating solution is dried on the conductive film, forming
the conductive film with the conductive layer 2. The conductive
film is placed to one surface of the substrate 1 through thermal
pressing or roll pressing, forming the conductive article P. In the
third method, the coating solution is applied to and dried on a
peeling-off film made of polyethyleneterephtalate, forming the
conductive layer 2. Then, if necessary, an adhesive layer is formed
on the conductive layer 2, forming a transfer film. The transfer
film is pressed on one surface of the substrate 1, transferring the
conductive layer 2 or the both adhesive layer and the conductive
layer 2. The conductive article P is obtained. Also, the article of
this invention can be produced by any conventional methods.
[0051] When the article P is formed through the first method, it is
important to apply the thermal pressing at the final stage of the
forming, because the thermal pressing can shrink the conductive
layer 2 in the vertical direction. The frequency of contact between
the ultra fine conductive fibers, which are dispersed in the
conductive layer 2, increases and the space between the fibers is
reduced, promoting the better flow of electricity, when the
conductive layer 2 is pressed down in the vertical direction. This
method has an effect to further reduce the surface resistivity. If
the latter methods, the laminating method or transfer method is
employed, the thermal pressing at the final stage of the production
is not necessarily required, because the conductive layer has
already been pressed down during the thermal pressing or the
transferring process. Also, the final thermal pressing is not
required if the desirable conductivity for the particular use of
the conductive article has already been achieved before its
application.
[0052] The following examples illustrate embodiments of the
invention, but should not be viewed as limiting the scope of the
invention.
EXAMPLES
Comparative Example 1 and Example 1
[0053] Powdered vinylchloride resin as the binder is solved into
cyclohexanon used as a solvent. The multi-layered carbon nanotube
(product of Tsinghua-Nafine Nano-Powder Commercialization
Engineering Center, with the average outer diameter of 10 nm) is
added to the solution described above with the content percentage
shown in the Table 1. Also, alkylammonate solution of acid polymer,
of 10 weight % of the multi-layered carbon nanotube is added to and
equally dispersed in the solution as the disperser. Two kinds of
coating solution with the different content percentage of the
multi-layered carbon nanotube and the binder are acquired.
[0054] Vinylchloride resin film with the thickness of 0.1 mm is
used as the substrate. The coating solution is applied to the
surface of the substrate with the variety of thickness. Then, the
substrate is placed on the vinylchloride resin sheet with the
thickness of 0.5 mm after the solution is dried and hardened. Then,
the substrate is pressed in temperature of 160.degree. C. with the
pressure of 30 kg/cm.sup.2. Six kinds of transparent conductive
vinylchloride resin sheets a-f, each of which has the conductive
layer with the different content percentage of the multi-layered
carbon nanotube and the different thickness, are acquired. Also,
the vinylchloride resin sheet g for the comparative example 1 is
prepared by pressing the vinylchloride resin film as the substrate
and the vinylchloride resin sheet together.
[0055] The light transmission, the haze and the surface resistivity
are measured for each of the transparent conductive vinylchloride
resin sheets a-f and for the vinylchloride resin sheet g for
comparison. The results are listed in the Table 1. The estimated
content of the carbon nanotube of each of the resin sheets and the
light transmission of the light with 550 nm wavelength of the
conductive layer of each of the sheets are also listed in the Table
1.
[0056] The light transmission and the haze are measured by a direct
reading haze computer HGM-2DP, a product of Suga Shikenki according
to ASTM D1003. The surface resistivity is measured by a Highlester
produced by Mitsubishi Kagaku, according to ASTM D 257 or measured
by a Rollester produced by Mitsubishi Kagaku, according to ASTM
D991. The light transmission is measured by a Shimazu
auto-recording spectrometer UV-3100PC produced by Shimazu
Seisakusho. The difference in the light transmission of the light
with 550 nm wavelength between the transparent conductive
vinylchloride resin sheets and the vinylchloride resin sheet for
comparison is recorded. Table 1
[0057] The content percentage of the multi-layered carbon nanotube
and the thickness are different between the resin sheets c and e,
or the resin sheets d and f. However, each pair shows about the
same surface resistivity, because each pair has about the same
estimated content of the multi-layered carbon nanotube, as seen
from the Table 1. As to the resin sheets a, b, c, and d, as the
content percentage of the multi-layered carbon nanotube increases
from 3 mg/m.sup.2 to 20 mg/m.sup.2, the surface resistivity
decreases from 10.sup.7.OMEGA./.quadrature. to
10.sup.4.OMEGA./.quadrature., showing the improving
anti-electrostatic property, and the light transmission decreases
from 88% to 80%, while keeping the good transparency of above 80%.
As it is obvious from this result, the surface resistivity and the
light transmission decrease in proportion to the increase of the
estimated content of the multi-layered carbon nanotube, even though
the content percentage of the multi-layered carbon nanotube and the
thickness of the layer are different among the resin sheets, if the
carbon nanotube is dispersed without being densely concentrated.
Therefore, the estimated content of the carbon nanotube should be 3
to 20 mg/ m.sup.2 in order to obtain the surface resistivity of
10.sup.4.OMEGA./.quadrature. to 10.sup.7.OMEGA./.quadrature.. If
the lower surface resistivity is desired, the estimated content of
the multi-layered carbon nanotube should be further increased. The
estimated content of the multi-layered carbon nanotube can be
increased either by increasing the content percentage of the carbon
nanotube or increasing the thickness of the conductive layer.
[0058] There is no big difference in haze among the transparent
conductive vinylchloride resin sheets a-f. The light transmission
of the resin sheets a-f is lower than that of the light
transmission of the resin sheet g of the comparative example, by 3
to 10%. But they have the enough light transmission of above 80%
for the practical use of the transparent resin sheet.
Example 2
[0059] The multi-layered carbon nanotube (product of
Tsinghua-Nafine Nano-Powder Commercialization Engineering Center,
with the average outer diameter of 10 nm) and tertiary amine
modified alkyl co-polymer as the disperser are added to and equally
dispersed in ethanol solvent. This coating solution is prepared
such that it has 0.007 weight % of the multi-layered carbon
nanotube and the 0.155 weight % of the disperser.
[0060] This coating solution is applied to the surface of a
polycarbonate plate, which is a product of Takiron Co. Ltd., with
the thickness of 3 mm, the light transmission of 90.2%, and the
haze of 0.40%. The transparent conductive polycarbonate resin plate
with the conductive layer of the thickness of 29 nm and the
estimated content of the multi-layered carbon nanotube of 2.5
mg/m.sup.2 is obtained after the solution is dried. The surface
resistivity and the light transmission of the conductive layer of
the resin plate are measured by the same way as that of the example
1. The surface resistivity is
3.2.times.10.sup.10.OMEGA./.quadrature., and the light transmission
is 95.0%. The light transmission and the haze of the transparent
conductive polycarbonate are measured by the same way as that of
the example 1. The light transmission is 83.8% and the haze is
1.0%.
Example 3
[0061] 1.7 weight % of the powdered vinylchloride resin as the
binder is solved into cyclohexanon solvent. The single-layered
carbon nanotube (product of Carbon Nano Technology, with the
diameter of 0.7-2 nm) and alkylammonate solution of acid polymer,
as a disperser are added to and equally dispersed in the solution.
This coating solution has 0.3 weight % of single-layered carbon
nanotube and 0.18 weight % of disperser. This coating solution is
applied to and dried on the surface of acryl film with the
thickness of 100 .mu.m, acquiring the conductive laminate film. The
transparent conductive vinylchloride resin plate is obtained by
pressing the laminate film described above to the vinylchloride
resin plate with the thickness of 3 mm in the temperature of
160.degree. C. with the pressure of 30 Kg/cm.sup.2.
[0062] The conductive layer of this resin plate is observed by a
transmission electron microscopy (a product of Nihon Denshi Kogyo
Corp., JEM-2010), measuring the area ratio of the single-layered
carbon nanotube. The area ratio of the single-layered carbon
nanotube is 11.1%. The thiclcess of the conductive layer is 65 nm.
Therefore, the estimated content of the single-layered carbon
nanotube is 15.9 mg/m.sup.2, acquired by multiplying the area
ration 11.1% by the thickness of 65 nm and the specific gravity
(2.2). The surface resistivity and the light transmission of the
conductive layer of the resin plate are measured by the same manner
as that of the example 1. The surface resistivity is
3.3.times.10.sup.7.OMEGA./.quadrature., and the light transmission
is 92.8%. The light transmission and the haze of the transparent
conductive vinylchloride resin plate are measured by the same way
as that of the example 1. The light transmission is 80.1% and the
haze is 1.6%.
[0063] Additionally, the conductive layer of the transparent
conductive vinylchloride resin plate is observed by an optical
microscopy (a product of Nikon Corp., OPTIPHOTO 2-POL). No lump
with the size of 0.5 .mu.m is observed. Then, the conductive layer
of the resin plate is observed by a transmission electron
microscopy. As it is seen from FIG. 4, the single layered carbon
nanotube is dispersed well, with no lump with the size of 0.5
.mu.m. Although the single layered carbon nanotubes are somewhat
bent, the bundles are equally dispersed so that each bundle is
separated from other bundles, and yet in contact, simply crossing
each other.
Example 4
[0064] The coating solution is prepared by the following procedure.
Single-layered Carbon nanotube (synthesized by referring to
Chemical Physics Letters, 323 (2000) P 580-585, with the diameter
of 1.3-1.8 nm) and the co-polymer between poly oxy-ethylene and
poly oxy-propylene as the disperser are added to and dispersed in
the mixture of isopropylene alcohol and water (with the compound
ratio of 3:1) as a solvent. This coating solution is prepared such
that it has 0.003 weight % of single-layered carbon nanotube and
0.05 weight % of disperser. This coating solution is applied to the
surface of a polyethyleneterephtalate film with the thickness of
100 .mu.m (with the light transmission of 94.5%, and the haze of
1.5%). After drying the solution, the film is coated with the
urethane acrylate solution diluted to 1-600.sup.th with methyl
isobutyl ketone, and then dried. The transparent conductive
polyethyleneterephtalate film is obtained.
[0065] The conductive layer of the film is observed by a scanning
electron microscopy (a product of Hitachi Seisakusho, S-800). The
area ratio of the single-layered carbon nanotube is 70.3%. The
thick ness of the conductive layer is 47 nm. Therefore, the
estimated content of the single-layered carbon nanotube in the
conductive layer is 72.7 mg/m.sup.2, acquired by multiplying the
area ratio of 70.3% by the thickness of 47 nm and the specific
gravity (2.2). The surface resistivity and the light transmission
of the conductive layer of the film are measured by the same method
used in the example 1. The surface resistivity is
5.4.times.10.sup.2.OMEGA./.quadrature. and the light transmission
is 90.5%. The light transmission and the haze of the transparent
conductive polyethyleneterephtalate film are measured by the same
way as that of the example 1. The light transmission is 85.8% and
the haze is 1.8%.
[0066] Additionally, the conductive layer of the transparent
conductive polyethyleneterephtalate film is observed by an optical
microscopy. No lump with the size of 0.5 .mu.m is observed. Then,
the conductive layer of the film is observed by a transmission
electron microscopy. As it is seen from FIG. 5, the single-layered
carbon nanotube is dispersed well, with no lump. The bundles of the
single-layered carbon nanotube are equally dispersed so that each
bundle is separated from other bundles, and yet in contact, simply
crossing each other.
Example 5
[0067] The coating solution, which is used in the Example 4, is
applied to and dried on the surface of a polyethyleneterephtalate
film used in the Example 4, obtaining the transparent conductive
polyethyleneterephtalate film with the estimated content of the
carbon nanotube in the conductive layer of 267.3 mg/m.sup.2. The
surface resistivity and the light transmission of the conductive
layer of the film are measured by the same method used in the
example 1. The surface resistivity is
8.6.times.10.sup.1.OMEGA./.quadrature. and the light transmission
is 60.6%. The light transmission and the haze of the transparent
conductive polyethyleneterephtalate film are measured by the same
way as that of the example 1. The light transmission is 57.1% and
the haze is 5.4%.
Comparative Example 2
[0068] 1.7 weight % of the powdered vinylchloride resin as the
binder is solved into cyclohexanon solvent. The single-layered
carbon nanotube used in the Example 3 and aluminum-coupling agent
as a coupling agent are added to and equally dispersed in the
solution. This coating solution has 0.3 weight % of single-layered
carbon nanotube and 0.12 weight % of coupling agent. This coating
solution is applied to and dried on the surface of acryl film, as
in the Example 3, acquiring the conductive laminate film. The
transparent vinylchloride resin plate is obtained by pressing the
laminate film described above to the surface of the vinylchloride
resin plate.
[0069] The conductive layer of the film is observed by a
transmission electron microscopy. The area ratio of the carbon
nanotube is 12.0%. The thickness of the conductive layer is 62 nm.
Therefore, the estimated content of the carbon nanotube in the
conductive layer is 16.4 mg/m.sup.2, acquired by multiplying the
area ration 12.0% by the thickness of 62 nm and the specific
gravity (2.2). The surface resistivity and the light transmission
of the conductive layer are measured by the same method used in the
example 1. The surface resistivity is
2.2.times.10.sup.10.OMEGA./.quadrature. and the light transmission
is 92.5%. Although the estimated content of the carbon nanotube and
the light transmission are almost the same as those of the Example
3, the surface resistivity is higher by
10.sup.3.OMEGA./.quadrature..
[0070] The conductive layer of the resin plate is observed by an
optical microscopy. As it is seen from FIG. 6, the carbon nanotube
is not dispersed enough and there are pluralities of lumps. The
lumps with the size of 0.5 .mu.m are observed. The biggest size of
the lump reaches 10 .mu.m. The large difference in the surface
resistivity between the Example 3 and the Comparative Example 2 is
due to the presence of the lump of the carbon nanotube. That is,
the Example 3 has the excellent surface resistivity because there
is no lump of the carbon nanotube. The carbon nanotubes or bundle
of the tube are dispersed in the conductive layer or on the surface
of the conductive layer so that each tube or bundle are separated
from other tubes or bundles, and yet simply crossing each other in
the Example 3. The loosely crossing carbon nanotubes are present in
a broader area, increasing the frequency of contact between the
carbon nanotubes. As a result, the improved conductivity is
acquired.
[0071] Other embodiments and uses of the invention will be apparent
to those skilled in the art from consideration of the specification
and practice of the invention disclosed herein. All references
cited herein, including all publications, U.S. and foreign patents
and patent applications, are specifically and entirely incorporated
by reference. It is intended that the specification and examples be
considered exemplary only with the true scope and spirit of the
invention indicated by the following claims. TABLE-US-00001 TABLE 1
resin sheet layer CNT total 550 nm layer components (Wt %)
thickness content registivity transmission hase transmission No CNT
disperser binder (nm) (mg/m.sup.2) (.OMEGA./.quadrature.) (%) (%)
(%) a 20 2 78 11 3.2 1.21 .times. 10.sup.7 87.8 1.0 97.2 b 20 2 78
21 6.5 1.73 .times. 10.sup.6 86.4 0.9 96.0 c 20 2 78 32 9.8 2.89
.times. 10.sup.5 85.2 0.9 -- d 20 2 78 65 20.0 4.51 .times.
10.sup.4 79.5 0.9 88.7 e 60 6 34 9 9.7 1.03 .times. 10.sup.5 85.5
0.8 -- f 60 6 34 19 19.5 7.77 .times. 10.sup.4 80.6 1.0 89.8 g --
-- -- -- -- >10.sup.14 90.8 1.3 -- CNT: Multi-wall carbon
nanotubes
* * * * *