U.S. patent application number 11/354845 was filed with the patent office on 2007-08-16 for method for fabricating nanotube electron emission source by scanning-matrix type electrophoresis deposition.
This patent application is currently assigned to Teco Electric & Machinery Co., Ltd.. Invention is credited to Kuei-Wen Cheng, Chun-Yen Hsiao, Shie-Heng Lee, Yu-An Li, Jin-Lung Tsai.
Application Number | 20070187245 11/354845 |
Document ID | / |
Family ID | 38367215 |
Filed Date | 2007-08-16 |
United States Patent
Application |
20070187245 |
Kind Code |
A1 |
Cheng; Kuei-Wen ; et
al. |
August 16, 2007 |
Method for fabricating nanotube electron emission source by
scanning-matrix type electrophoresis deposition
Abstract
A scanning-matrix type electrophoresis deposition method
fabricates nanotube electron emission source. During the
electrophoresis deposition process, the electrical field is applied
to a single pixel to localize the electrophoresis deposition. The
cathode strips on the cathode plate are vertical to the anode
strips of the anode plate. A sequential pulse voltage signal is
applied to the cathode strips and the anode strips. Therefore only
one electrical field is present for one pixel defined by the
cathode strip cross with the anode strip at one time and nanotube
is formed at that pixel.
Inventors: |
Cheng; Kuei-Wen; (Guanyin
Township, TW) ; Tsai; Jin-Lung; (Guanyin Township,
TW) ; Lee; Shie-Heng; (Guanyin Township, TW) ;
Li; Yu-An; (Guanyin Township, TW) ; Hsiao;
Chun-Yen; (Guanyin Township, TW) |
Correspondence
Address: |
HDSL
4331 STEVENS BATTLE LANE
FAIRFAX
VA
22033
US
|
Assignee: |
Teco Electric & Machinery Co.,
Ltd.
|
Family ID: |
38367215 |
Appl. No.: |
11/354845 |
Filed: |
February 16, 2006 |
Current U.S.
Class: |
204/471 |
Current CPC
Class: |
C25B 7/00 20130101 |
Class at
Publication: |
204/471 |
International
Class: |
C25B 7/00 20060101
C25B007/00 |
Claims
1. A method for fabricating nanotube electron emission source by
scanning-matrix type electrophoresis deposition, comprising:
connecting anode ends of a power source to anode strips of an anode
plate, connecting cathode ends of the power source to one input
ends of signal amplifiers, connecting output ends of the signal
amplifiers to a plurality of cathode strips of a cathode plate,
placing the anode strips vertical to the cathode strips, connecting
a signal generator to another input ends of the signal amplifiers;
providing an electrophoresis tank with electrophoresis solution
therein and placing the anode plate and the cathode plate parallel
in the electrophoresis tank; outputting voltages from anode ends of
the power source to the anode strips, the signal generator sending
pulse voltage signal to one of the signal amplifiers and amplified
by the one of the signal amplifiers such that one of the cathode
strip is conducted while the remaining cathode strips are not
conducted, whereby only one electrical field is present for one
pixel at one time and nanotube is formed at that pixel; and
conducting next cathode strip successively and keeping the
remaining cathode strips being non-conducted to fabricate nanotube
electron emission source in scanning-matrix manner.
2. The method as in claim 1, wherein the power source is a scanning
power source to provide sequential voltage signals to complete
global area electrophoresis in a period of time, wherein the pulse
voltage provided by anode end is 120V.
3. The method as in claim 1, wherein the anode strips are formed
conversely on an insulating plate.
4. The method as in claim 3, wherein the insulating plate is a
glass plate and the anode strips are formed by screen-printing or
lithography.
5. The method as in claim 1, wherein the cathode strips are formed
longitudinally on the cathode plate.
6. The method as in claim 1, wherein the cathode strip is a
semi-finished product with gate and sacrifice layer.
7. The method as in claim 6, wherein the sacrifice layer is
functioned to prevent unwanted deposition such as gate and
dielectric layer.
8. The method as in claim 6, further comprising a step of removing
the sacrifice layer.
9. The method as in claim 1, wherein the cathode plate and the
anode plate are placed in the electrophoresis tank parallel with
3-5 cm separation therebetween.
10. The method as in claim 1, wherein the electrophoresis solution
used alcohol as solution, the electron emission source uses powder
material made of nanotube formed by arc discharge, the nanotube has
average tube length below 5 .mu.m and average diameter below 100 nm
and has multiple wall, the nanotube has an additive concentration
of 0.1%.about.0.005%.
11. The method as in claim 10, wherein the additive concentration
is preferably 0.02%
12. The method as in claim 1, wherein the solution further
comprises chargers, the charger uses metal salt being conductive
after electrophoresis.
13. The method as in claim 12, wherein the metal salt is one of
InCl and indium nitride or other salt with tin.
14. The method as in claim 12, wherein the charger is InCl salt
with 0.1-0.005% weight concentration and glass power with at 5%
weight concentration to enhance adhesion.
15. The method as in claim 14, wherein the charger is preferably
with 0.01% weight concentration
16. The method as in claim 1, wherein the signal generator
generates a continuous square wave signal.
17. A method for fabricating nanotube electron emission source by
scanning-matrix type electrophoresis deposition, comprising:
connecting anode ends of a power source to anode strips of an anode
plate, connecting cathode ends of the power source to one input
ends of signal amplifiers, connecting output ends of the signal
amplifiers to a plurality of cathode strips of a cathode plate,
placing the anode strips vertical to the cathode strips, connecting
a signal generator to another input ends of the signal amplifiers;
providing an electrophoresis tank with electrophoresis solution
therein and placing the anode plate and the cathode plate parallel
in the electrophoresis tank; outputting voltages from anode ends of
the power source to the anode strips, the signal generator sending
pulse voltage signal to one of the signal amplifiers and amplified
by the one of the signal amplifiers such that one of the signal
amplifiers has not amplification and one cathode strip is at high
level while the remaining cathode strips are at low level, whereby
only one electrical field is present for one pixel defined by the
cathode strip with low level and anode strip with high level at one
time and nanotube is formed at that pixel; and biasing next cathode
strip successively to be low level and keeping the remaining
cathode strips being high level to fabricate nanotube electron
emission source in scanning-matrix manner.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for fabricating a
field emission display, especially to a method for fabricating
nanotube electron emission source by scanning-matrix type
electrophoresis deposition.
[0003] 2. Description of Prior Art
[0004] The field emission display uses cathode electron emitter to
generate electron by electrical field. The emitted electron excites
phosphor on anode plate for illumination. The field emission
display has compact size and flexible viewable area. The field
emission display does not have view angle problem encountered in
LCD.
[0005] Conventional triode field emission display includes an anode
structure and a cathode structure. There is a spacer disposed
between the anode structure and the cathode structure, thereby
providing a space and a support for the vacuum region between the
anode structure and the cathode structure. The anode structure
includes an anode substrate, an anode conducting layer, and a
phosphorus layer. The cathode structure includes a cathode
substrate, a cathode conducting layer, an electron emission layer,
a dielectric layer and a gate layer. The gate layer is provided a
voltage difference to induce the emission of electrons from the
electron emission layer. The conducting layer of the cathode
structure provides a high voltage to accelerate the electron beam,
such that the electron beam can have enough kinetic energy to
impinge and excite the phosphorous layer on the anode structure,
thereby emitting light. Accordingly, in order to maintain the
movement of electrons in the field emission display, a vacuum
apparatus is required to keep the vacuum degree of the display
being below 10.sup.-5 torr. Therefore, the electrons can have
appropriate mean free paths. Meanwhile, the pollution and
toxication of the electron emission source and the phosphorous
layer should be prevented from happening. Furthermore, in order for
the electrons to accumulate enough energy to impinge the
phosphorous powder, a space is required between the two substrates.
Consequently, the electrons can be accelerated to impinge the
phosphorous layer, thereby exciting the phosphorous layer and
emitting light therefrom.
[0006] The electron emission layer is composed of carbon nanotubes.
Since carbon nanotubes, proposed by Iijima in 1991 (Nature, 354, 56
(1991)), comprises very good electronic properties that can be used
to build a variety of devices. The carbon nanotubes also has a very
large aspect ratio, mostly larger than 500, and a very high
rigidity of Young moduli larger than 1000 GPn. In addition, the
tips or defects of the carbon nanotubes are of atomic scale. The
properties described above are considered an ideal material for
building electron field emitter, such as an electron emission
source of a cathode structure of a field emission display. Since
the carbon nanotubes comprise the physical properties described
above, a variety of manufacturing process can be developed, e.g.
screen printing, or thin film processing.
[0007] However, the art of manufacturing the cathode structure
employs carbon nanotubes as an electron emission material, which is
fabricated on the cathode conducting layer. The manufacturing
process can employ chemical vapor deposition (CVD) process, or any
kind of process that can pattern the photosensitive carbon nanotube
solution on any pixel of the cathode conducting layer. Moreover,
the cathode structure can also be manufactured by coating the
carbon nanotubes solution while incorporating with a mask, or
depositing the carbon nanotubes on the cathode conducting layer by
an electrophoresis method. However, it is still difficult to
fabricate nanotube in the cathode electrode in each pixel by
above-mentioned processes. Especially for large-size FED
display.
[0008] Recently, an electrophoresis deposition process is proposed,
for example, US pre-grant publication No. 2003/0102222 discloses an
electrophoresis deposition process. An alcohol suspension for
nanotube is prepared and charger such as Mg, La, Y and Al is used
to form an electrophoresis solution. The cathode electrode
substrate to be deposited is connected to an electrode in the
electrophoresis solution. A DC or AC voltage is applied to provide
electrical field in the electrophoresis solution. The charger is
dissolved in the electrophoresis solution and attached to the
nanotube powder. The electrical field will facilitate the nanotube
powder to deposit on an electrode. This electrophoresis deposition
process can easily deposit the nanotube on the electrode layer
without the limit of forming triode field emission display on
electrode. Therefore, the electrophoresis deposition process is
extensively used on the fabrication of cathode plate.
[0009] However, in prior art electrophoresis deposition process, a
sacrifice layer (or protection layer) is formed for the gate
electrode and dielectric layer to expose the patterned cathode
area. whereby the nanotube is only deposited on the cathode
electrode instead of gate electrode to prevent short circuit
between the cathode electrode and the gate electrode. The sacrifice
layer is removed after electrophoresis deposition process to
removed unwanted nanotube. Moreover, Japan Patent No. 2001020093
discloses an electrophoresis deposition process, where bumps are
formed in specific area of cathode and electrical field is provided
between the bump and the anode. Therefore, the nanotube can be
formed in the specific area and tends to concentrate on the
electrode area. The applicant also provides an anode structure for
ease patterning and the electrophoresis deposition can be
concentrated.
[0010] The above-mentioned prior art provide anode (cathode) to
form electrical field to confine the electrophoresis deposition
area. However, precise calculation is needed. This will influence
reliability of the electrophoresis deposition process. For
high-resolution display panel, the unit electrophoresis area is
smaller. The point-to-point electrical field is influenced by
adjacent electrical field. The point-to-point electrical field in a
matrix is difficult to achieve in electrophoresis deposition
process.
SUMMARY OF THE INVENTION
[0011] The present invention is to provide a method for fabricating
nanotube electron emission source by scanning-matrix type
electrophoresis deposition. The electrophoresis deposition is
performed in interleaving manner such that the electrophoresis
deposition can be localized and the anode plate design can be
simplified.
[0012] Accordingly, the present invention provides a method for
fabricating nanotube electron emission source by scanning-matrix
type electrophoresis deposition.
[0013] The anode ends of a power source are connected to anode
strips of an anode plate. The cathode ends of the power source are
connected to one input ends of signal amplifiers. The output ends
of the signal amplifiers are connected to a plurality of cathode
strips of a cathode plate. The anode strips are placed vertical to
the cathode strips. A signal generator is connected to another
input ends of the signal amplifiers. The anode plate and the
cathode plate are placed parallel in the electrophoresis tank.
[0014] The voltage of the power source is output from anode ends of
the power source to the anode strips. The signal generator sends
pulse voltage signal to one of the signal amplifiers and amplified
by the one of the signal amplifiers such that one of the cathode
strip is conducted while the remaining cathode strips are not
conducted, whereby only one electrical field is present for one
pixel at one time and nanotube is formed at that pixel.
[0015] The next cathode strip is conducted successively and keeping
the remaining cathode strips being non-conducted to fabricate
nanotube electron emission source in scanning-matrix manner.
BRIEF DESCRIPTION OF DRAWING
[0016] The features of the invention believed to be novel are set
forth with particularity in the appended claims. The invention
itself however may be best understood by reference to the following
detailed description of the invention, which describes certain
exemplary embodiments of the invention, taken in conjunction with
the accompanying drawings in which:
[0017] FIG. 1 shows a schematic diagram of the anode plate and
cathode plate according to a preferred embodiment of the present
invention.
[0018] FIG. 2 shows the schematic diagram of connection of the
anode plate and cathode plate to the electrophoresis deposition
equipment.
[0019] FIG. 3 shows the schematic diagram of connection of the
anode plate and cathode plate to the electrophoresis deposition
equipment during fabrication.
[0020] FIG. 4 shows a simplified schematic diagram of connection of
the anode plate and cathode plate to the electrophoresis deposition
equipment.
[0021] FIG. 5 shows a simplified schematic diagram of connection of
the anode plate and cathode plate to the electrophoresis deposition
equipment according to another preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0022] With reference to FIGS. 1 and 2, in the method for
fabricating nanotube electron emission source by scanning-matrix
type electrophoresis deposition according to the present invention,
cross-scanning electrophoresis deposition localizes current to a
single pixel to fabricate nanotube electron emission source.
Therefore, the peak current can be reduced and the method can be
applied to manufacture of large display.
[0023] According to the method of the present invention, a cathode
plate 1 is prepared with a rows (or 32 rows) of cathode strips 11
in longitudinal direction. The cathode strips 11 are already formed
with gate and semi-finished sacrifice layer. The sacrifice layer is
used to prevent unwanted deposition (such as gate, dielectric) on
the non-electrophoresis deposition area. The sacrifice layer is
removed after electrophoresis deposition process, Therefore,
a.times.b (or 32.times.32) pixels can be provided on the
semi-finished cathode plate 1.
[0024] Afterward, an anode plate 2 is provided, where a plurality
of anode strips 21 is formed on an insulating plate in transverse
direction and vertical to the cathode strips 11. Therefore, b
columns (or 32 columns) of anode strips 21 can be provided for the
cathode plate 1. The insulating plate can be a glass plate and the
anode strips 21 can be formed by screen-printing or
lithography.
[0025] A plurality of anode ends 31 of a scanning power source 3 is
connected to each of the anode strips 21 to provide pulse voltage
sequentially to the anode strips 21. A plurality of cathode ends 32
of a scanning power source 3 is connected to one end of signal
amplifiers 4, and the signal amplifiers 4 are connected to the
cathode strips 11. Another end of the signal amplifier 4 is
connected to a signal generator 5. The scanning power source 3
provides sequential pulse voltage to the anode strips 21 and the
signal generator 5 provides sequential signals to the cathode
strips 11. The signal amplifier 4 provides signal amplification for
the sequential signals of the signal generator 5.
[0026] With reference to FIGS. 3 and 4, after the connection for
the cathode plate 1, the anode plate 2, the scanning power source
3, the signal amplifier 4 and the signal generator 5 is completed,
an electrophoresis solution is prepared for the electrophoresis
tank 6. Alcohol is used for solution and nanotube is used for
electron emission source and manufactured by arc discharge. The
nanotube has average length below 5 .mu.m and average diameter
below 100 nm. The nanotube has multiple wall, the nanotube has an
additive concentration of 0.1%.about.0.005% (preferably 0.02%). The
charger uses metal salt is conductive after electrophoresis, for
example, the metal salt is one of InCl and indium nitride or other
salt with tin. The charger is with 0.1-0.005% weight concentration
and glass power with at 5% weight concentration to enhance
adhesion. Preferably the charger is with 0.01% weight
concentration.
[0027] The cathode plate 1 and the anode plate 2 are placed in the
electrophoresis tank 6 with 3-5 cm separation therebetween. The
scanning power source 3 finishes a global area electrophoresis
within a period of time, for example, within 1 second. Therefore
scanning power source 3 sequentially sends pulse voltage of 120V to
the anode strips 21 in the frequency of b or 32 Hz (duty=1/b or
1/32). The signal generator 5 sends a continuous square-wave signal
to the signal amplifier 4. The signal amplifier 4 amplifies the
continuous square-wave signal and sends the amplified continuous
square-wave signal to the first one of the cathode strips 11, while
the remaining cathode strips 11 are not conducted. Therefore, an
electrical field is established between the first cathode strip 11
and the first anode strip 21 due to a potential difference. A
nanotube can be fabricated on the position to be deposited with
electron emission source on the first cathode strip 11. The
remaining cathode strips 11 are conducted one by one and other
cathode strips 11 are not conducted. In this manner, the electron
emission source can be fabricated. The duty cycle for the cathode
strips 11 are 1/a or 1/32 (frequency a or 32 Hz) or higher
frequency. Therefore, the electrophoresis deposition is performed
at the frequency of a.times.b (or 32.times.32). The electrophoresis
deposition is 15 minutes and an electron emission source with 5-10
um thickness can be formed by one electrophoresis deposition
operation.
[0028] FIG. 5 shows the schematic diagram of electrophoresis
deposition method according to another preferred embodiment of the
present invention. A cathode plate 1a is prepared with a plurality
of cathode strips 11a, an anode plate 2a is prepared with a
plurality of anode strips 21a. A scanning power source 3a comprises
anode ends 31a connected to the plurality of anode strips 21a for
providing sequential pulse voltage to the anode strips 21a. The
scanning power source 3a further comprises a plurality of cathode
ends 32a connected to input ends of a plurality of signal amplifier
4a and the outputs of the signal amplifiers 4a are also connected
to the plurality of cathode strips 11a. A signal generator 5a is
also connected to another inputs of signal amplifiers 4a.
[0029] The cathode strips 11a and the anode strips 21a are placed
in the electrophoresis tank 6 with 3-5 cm separation therebetween
and vertical to each other. The scanning power source 3a sends a
lagged sequential signals to the anode strips 21a, where the
sequential signal is pulse voltage signal of 120V. At the same
time, the signal generator 5a generates a signal for outputting to
the signal amplifiers 4a, where only one of the signal amplifiers
4a does not perform amplification and the remaining signal
amplifiers 4a perform amplification. Therefore, the first cathode
strip 11a is in low level while other cathode strips 11a are in
high level, which level is the same as that of anode strips 21a.
Therefore, nanotube will be formed on the first cathode strip 11a
and can be formed on other cathode strips 11a successively.
[0030] To sum up, the scanning-matrix type electrophoresis
deposition method according to the present invention has following
advantages: [0031] 1. The electrode strips of the anode plate and
the cathode plate are arranged cross to each other. Only one pixel
has electrophoresis deposition at one time to concentrate the
electrophoresis deposition area. [0032] 2. The anode plate used in
the scanning-matrix type electrophoresis deposition method
according to the present invention has simpler structure and the
electrical field in the electrophoresis deposition process is
simplified. [0033] 3. The electrophoresis deposition is localized
and the electrical field intensity can be increased. [0034] 4. The
cost and electrical current consumption can be reduced for
large-size display.
[0035] Although the present invention has been described with
reference to the preferred embodiment thereof, it will be
understood that the invention is not limited to the details
thereof. Various substitutions and modifications have suggested in
the foregoing description, and other will occur to those of
ordinary skill in the art. Therefore, all such substitutions and
modifications are intended to be embraced within the scope of the
invention as defined in the appended claims.
* * * * *