U.S. patent application number 09/251300 was filed with the patent office on 2002-01-31 for electrodeposition tank, electrodeposition apparatus, and electrodeposition method.
Invention is credited to ARAO, KOZO, MIYAMOTO, YUSUKE, SONODA, YUICHI, TOYAMA, NOBORU.
Application Number | 20020011419 09/251300 |
Document ID | / |
Family ID | 27288420 |
Filed Date | 2002-01-31 |
United States Patent
Application |
20020011419 |
Kind Code |
A1 |
ARAO, KOZO ; et al. |
January 31, 2002 |
ELECTRODEPOSITION TANK, ELECTRODEPOSITION APPARATUS, AND
ELECTRODEPOSITION METHOD
Abstract
The present invention provides an electrodeposition apparatus
for continuously forming a film of an oxide on a substrate by
electrodeposition, wherein an electrodeposition tank for retaining
an electrodeposition bath is formed of a metal and the inside of
the electrodeposition tank is kept electrically floating. This can
form a uniform oxide film without irregularities on the
substrate.
Inventors: |
ARAO, KOZO; (NARA-KEN,
JP) ; TOYAMA, NOBORU; (HIRAKATA-SHI, JP) ;
SONODA, YUICHI; (NARA-KEN, JP) ; MIYAMOTO,
YUSUKE; (KYOTO, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Family ID: |
27288420 |
Appl. No.: |
09/251300 |
Filed: |
February 17, 1999 |
Current U.S.
Class: |
205/333 ;
204/206; 204/279; 205/96 |
Current CPC
Class: |
C25D 9/08 20130101; C25D
7/0621 20130101 |
Class at
Publication: |
205/333 ; 205/96;
204/206; 204/279 |
International
Class: |
C25D 009/00; C25D
005/00; C25D 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 1998 |
JP |
10-034444 |
Jun 30, 1998 |
JP |
10-183883 |
Jul 29, 1998 |
JP |
10-213607 |
Claims
What is claimed is:
1. An electrodeposition tank for forming a film of an oxide on a
substrate with energizing the substrate and an electrode in an
electrodeposition bath, the electrodeposition tank being formed of
a dielectric material.
2. The electrodeposition tank according to claim 1, wherein the
dielectric is reinforced with a metal material.
3. The electrodeposition tank according to claim 1, wherein the
dielectric is a fluororesin.
4. The electrodeposition tank according to claim 1, wherein the
dielectric is a fiber-reinforced plastic.
5. The electrodeposition tank according to claim 1, wherein the
substrate is a long substrate.
6. The electrodeposition tank according to claim 1, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
7. An electrodeposition tank for forming a film of an oxide on a
substrate with energizing the substrate and an electrode in an
electrodeposition bath, comprising an outside wall formed of a
metal material and an inside surface thereof covered with a lining
formed of a dielectric material.
8. The electrodeposition tank according to claim 7, wherein the
dielectric: is a fluororesin.
9. The electrodeposition tank according to claim 7, wherein the
dielectric is a fiber-reinforced plastic.
10. The electrodeposition tank according to claim 7, wherein a
clearance at a seam of the lining is so set that an electric
resistance of the bath from the electrode to the metal part of the
outside wall is greater than an electric resistance of the bath
from the electrode to the substrate.
11. The electrodeposition tank according to claim 7, wherein the
metal part of the outside wall and the substrate are set at an
equal potential.
12. The electrodeposition tank according to claim 7, wherein the
substrate is a long substrate.
13. The electrodeposition tank according to claim 7, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
14. An electrodeposition tank for forming a film of an oxide on a
substrate with energizing the substrate and an electrode in an
electrodeposition bath, comprising an outside tank formed of a
metal material and an inside tank formed of a dielectric material
for housing the electrode inside thereof.
15. The electrodeposition tank according to claim 14, wherein the
dielectric inside tank is reinforced with a metal material.
16. The electrodeposition tank according to claim 14, wherein the
inside tank is provided with an opening to permit inflow and
outflow of the bath solution inside thereof and the bath solution
outside thereof.
17. The electrodeposition tank according to claim 16, wherein the
size of the opening is so set that an electric resistance of the
bath from the electrode in the inside tank to the metal outside
tank is greater than an electric resistance of the bath from the
electrode to the substrate.
18. The electrodeposition tank according to claim 14, wherein the
inside tank is provided with a bath exchanging means for effecting
exchange of the bath solution inside thereof and the bath solution
outside thereof.
19. The electrodeposition tank according to claim 18, wherein the
bath exchanging means comprises a bath outlet system for guiding
the inside bath solution out of the inside tank, a bath inlet
system for guiding the outside bath solution into the inside tank,
and a pump for circulating the bath solution from the outlet system
to the inlet system.
20. The electrodeposition tank according to claim 18, wherein an
electric resistance of the bath from the electrode through the bath
exchanging means to the substrate is greater than an electric
resistance of the bath from the electrode to the substrate in the
inside tank.
21. The electrodeposition tank according to claim 14, wherein the
dielectric is a fluororesin.
22. The electrodeposition tank according to claim 14, wherein the
dielectric is a fiber-reinforced plastic.
23. The electrodeposition tank according to claim 14, wherein the
metal outside tank and the substrate are set at an equal
potential.
24. The electrodeposition tank according to claim 14, wherein the
substrate is a long substrate.
25. The electrodeposition tank according to claim 14, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
26. An electrodeposition apparatus comprising an electrodeposition
tank for forming a film of an oxide on a substrate with energizing
the substrate and an electrode in an electrodeposition bath, a
washing means for washing the substrate after passage through the
electrodeposition tank, and a drying means for forcedly drying the
substrate after passage through the washing means, wherein the
electrodeposition tank is formed of a dielectric material.
27. The electrodeposition apparatus according to claim 26, wherein
the dielectric electrodeposition tank is reinforced with a metal
material.
28. The electrodeposition apparatus according to claim 26, wherein
the dielectric is a fluororesin.
29. The electrodeposition apparatus according to claim 26, wherein
the dielectric is a fiber-reinforced plastic.
30. The electrodeposition apparatus according to claim 26, wherein
the substrate is a long substrate.
31. The electrodeposition apparatus according to claim 26, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
32. An electrodeposition apparatus comprising an electrodeposition
tank for forming a film of an oxide on a substrate with energizing
the substrate and an electrode in an electrodeposition bath, a
washing means for washing the substrate after passage through the
electrodeposition tank, and a drying means for forcedly drying the
substrate after passage through the washing means, wherein the
electrodeposition tank is formed of a metal material and an inside
surface thereof is covered with a lining formed of a dielectric
material.
33. The electrodeposition apparatus according to claim 32, wherein
the dielectric is a fluororesin.
34. The electrodeposition apparatus according to claim 32, wherein
the dielectric is a fiber-reinforced plastic.
35. The electrodeposition apparatus according to claim 32, wherein
a clearance at a seam of the lining is so set that an electric
resistance of the bath from the electrode to the metal part of the
electrodeposition tank is greater than an electric resistance of
the bath from the electrode to the substrate.
36. The electrodeposition apparatus according to claim 32, wherein
the metal part of the electrodeposition tank and the substrate are
set at an equal potential.
37. The electrodeposition apparatus according to claim 32, wherein
the substrate is a long substrate.
38. The electrodeposition apparatus according to claim 32, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
39. An electrodeposition apparatus comprising an electrodeposition
tank for forming a film of an oxide on a substrate with energizing
the substrate and an electrode in an electrodeposition bath, a
washing means for washing the substrate, after passage through the
electrodeposition tank, and a drying means for forcedly drying the
substrate after passage through the washing means, wherein the
electrodeposition tank comprises an outside tank formed of a metal
material and an inside tank formed of a dielectric material for
housing the electrode inside thereof.
40. The electrodeposition apparatus according to claim 39, wherein
the dielectric inside tank is reinforced with a metal material.
41. The electrodeposition apparatus according to claim 39, wherein
the inside tank is provided an opening to permit inflow and outflow
of the bath solution inside thereof and the bath solution outside
thereof.
42. The electrodeposition apparatus according to claim 41, wherein
the size of the opening is so set that an electric resistance of
the bath from the electrode in the inside tank to the metal outside
tank is greater than an electric resistance of the bath from the
electrode to the substrate.
43. The electrodeposition apparatus according to claim 39, wherein
the inside tank comprises a bath exchanging means for effecting
exchange of the bath solution inside thereof and the bath solution
outside thereof.
44. The electrodeposition apparatus according to claim 43, wherein
the bath exchanging means comprises a bath outlet system for
guiding the inside bath solution out of the inside tank, a bath
inlet system for guiding the outside bath solution into the inside
tank, and a pump for circulating the bath solution from the outlet
system to the inlet system.
45. The electrodeposition apparatus according to claim 43, wherein
an electric resistance of the bath from the electrode through the
bath exchanging means to the substrate is greater than an electric
resistance of the bath from the electrode to the substrate in the
inside tank.
46. The electrodeposition apparatus according to claim 39, wherein
the dielectric is a fluororesin.
47. The electrodeposition apparatus according to claim 39, wherein
the dielectric is a fiber-reinforced plastic.
48. The electrodeposition apparatus according to claim 39, wherein
the metal outside tank and the substrate are set at an equal
potential.
49. The electrodeposition apparatus according to claim 39, wherein
the substrate is a long substrate.
50. The electrodeposition apparatus according to claim 39, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
51. An electrodeposition method comprising forming a film of an
oxide on a substrate by the use of the electrodeposition apparatus
as set forth in claim 26.
52. An electrodeposition method comprising forming a film of an
oxide on a substrate by the use of the electrodeposition apparatus
as set forth in claim 32.
53. An electrodeposition method comprising forming a film of an
oxide on a substrate by the use of the electrodeposition apparatus
as set forth in claim 39.
54. An electrodeposition tank for forming a film of an oxide on a
substrate with energizing the substrate and an electrode in an
electrodeposition bath, wherein all or part of a piping system
connected to the tank and a piping system disposed in the tank is
formed of a dielectric.
55. The electrodeposition tank according to claim 54, wherein the
piping system disposed in the tank is electrically insulated from
the tank.
56. The electrodeposition tank according to claim 54, wherein the
dielectric is a fluororesin.
57. The electrodeposition tank according to claim 54, wherein the
dielectric is a fiber-reinforced plastic.
58. The electrodeposition tank according to claim 54, wherein the
substrate is a long substrate.
59. The electrodeposition tank according to claim 54, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
60. An electrodeposition tank for forming a film of an oxide on a
substrate with energizing the substrate and an electrode in an
electrodeposition bath, wherein the inside and outside surfaces of
all or part of a piping system connected to the tank and a piping
system disposed in the tank are coated with a dielectric.
61. The electrodeposition tank according to claim 60, wherein the
piping system disposed in the tank is electrically insulated from
the tank.
62. The electrodeposition tank according to claim 60, wherein the
coating dielectric is a fluororesin.
63. The electrodeposition tank according to claim 60, wherein the
coating dielectric is a fiber-reinforced plastic.
64. The electrodeposition tank according to claim 60, wherein the
substrate is a long substrate.
65. The electrodeposition tank according to claim 60, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
66. An electrodeposition apparatus comprising an electrodeposition
tank for forming a film of an oxide on a substrate with energizing
the substrate and an electrode in an electrodeposition bath, a
washing means for washing the substrate after passage through the
electrodeposition tank, and a drying means for forcedly drying the
substrate after passage through the washing means, wherein all or
part of a piping system connected to the electrodeposition tank and
a piping system disposed in the electrodeposition tank is formed of
a dielectric.
67. The electrodeposition apparatus according to claim 66, wherein
the piping system disposed in the electrodeposition tank is
electrically insulated from the electrodeposition tank.
68. The electrodeposition apparatus according to claim 66, wherein
the dielectric is a fluororesin.
69. The electrodeposition apparatus according to claim 66, wherein
the dielectric is a fiber-reinforced plastic.
70. The electrodeposition apparatus according to claim 66, wherein
the substrate is a long substrate.
71. The electrodeposition apparatus according to claim 66, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
72. An electrodeposition apparatus comprising an electrodeposition
tank for forming a film of an oxide on a substrate with energizing
the substrate and an electrode in an electrodeposition bath, a
washing means for washing the substrate after passage through the
electrodeposition tank, and a drying means for forcedly drying the
substrate after passage through the washing means, wherein the
inside and outside surfaces of all or part of a piping system
connected to the electrodeposition tank and a piping system
disposed in the electrodeposition tank are coated with a
dielectric.
73. The electrodeposition apparatus according to claim 72, wherein
the piping system disposed in the electrodeposition tank is
electrically insulated from the electrodeposition tank.
74. The electrodeposition apparatus according to claim 72, wherein
the coating dielectric is a fluororesin.
75. The electrodeposition apparatus according to claim 72, wherein
the coating dielectric is a fiber-reinforced plastic.
76. The electrodeposition apparatus according to claim 72, wherein
the substrate is a long substrate.
77. The electrodeposition apparatus according to claim 72, which is
mounted in a roll-to-roll apparatus for conveying a long substrate
as stretched between rolls.
78. An electrodeposition method comprising forming a film of an
oxide on a substrate by use of the electrodeposition apparatus as
set forth in claim 66.
79. An electrodeposition method comprising forming a film of an
oxide on a substrate by the use of the electrodeposition apparatus
as set forth in claim 72.
80. An electrodeposition apparatus for continuously forming a film
of an oxide on a substrate by electrodeposition, comprising an
electrodeposition tank for retaining an electrodeposition bath,
wherein the electrodeposition bath is formed of a metal, and
wherein the inside of the electrodeposition tank is kept
electrically floating.
81. The electrodeposition apparatus according to claim 80, wherein
the inside of the electrodeposition tank is kept electrically
floating by interposing a dielectric spacer between the
electrodeposition tank and a frame of the electrodeposition tank or
between the frame of the electrodeposition tank and a ground
surface.
82. The electrodeposition apparatus according to claim 80, wherein
the electrodeposition tank is covered with a dielectric lining.
83. The electrodeposition apparatus according to claim 80, wherein
the electrodeposition tank comprises an inside tank of a dish shape
formed of a dielectric and having an electrode provided inside
thereof.
84. The electrodeposition apparatus according to claim 80, wherein
the substrate is kept electrically floating.
85. The electrodeposition apparatus according to claim 84, wherein
the substrate is kept electrically floating by covering surfaces of
all rollers in contact with the substrate or bearing surfaces of
rotational shafts thereof with a dielectric or by forming all the
rollers in contact with the substrate or the bearings of the
rotational shafts thereof of a dielectric.
86. An electrodeposition method comprising forming a film of an
oxide on a substrate by the use of the electrodeposition apparatus
as set forth in claim 80.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electrodeposition tank,
an electrodeposition apparatus, and an electrodeposition method for
forming an oxide film on a substrate such as a long substrate or
the like comprised of a stainless steel belt sheet or the like by
electrodeposition (having the same meaning as electroplating or
electrolytic deposition) and, more particularly, to an
electrodeposition tank and an electrodeposition apparatus for
forming a zinc oxide film uniformly on a long substrate by use of
an electrodeposition bath with high electric conduction.
[0003] 2. Related Background Art
[0004] The technology for forming an oxide film on a substrate by
making use of electrochemical reaction of aqueous solution
(hereinafter referred to as "electrodeposition method") is recently
drawing attention, in place of vacuum processes, in production of
photovoltaic elements.
[0005] Use of this electrodeposition method presents the following
advantages.
[0006] First, formation of film is extremely simple, different from
that by vacuum apparatus such as sputtering apparatus and the like.
An expensive vacuum pump does not have to be used and no special
care is necessary for design of components around power supplies
and electrodes for use of a plasma.
[0007] The second advantage is low running cost in most cases. The
sputtering apparatus necessitates labor and apparatus for
production of a target to raise the cost and the efficiency of
utilization of the target is approximately 20% or less. Therefore,
if the throughput of apparatus is high or if the thickness of film
is large, a percentage of work for target exchange will be
considerably high.
[0008] The electrodeposition method is also advantageous in the
apparatus and running cost, as compared with CVD and vacuum
evaporation except for sputtering.
[0009] Films made by electrodeposition are of polycrystalline
particles in many cases and demonstrate electroconductivity and
optical characteristics that are by no means inferior to those by
the vacuum processes. Therefore, the electrodeposition method is
superior to the sol-gel process, coating methods using organic
substances, spray pyrolysis, and so on.
[0010] Further, these are also the case with formation of oxide. In
addition, waste liquid can be disposed of readily, so that the
impact is small on environments. Therefore, the cost is also low
for prevention of environmental pollution.
[0011] Meanwhile, we found out the following issues when carrying
out formation of film by the electrodeposition method.
[0012] Specifically, after completion of deposition for a long
period, we found the following adverse effects; an oxide film was
deposited on a piping system (i.e., pipes and joints) connected to
the electrodeposition bath and on a piping system installed in the
electrodeposition tank and film peel-off therefrom occurred to
produce powder, film chips, etc. in the bath, thereby causing
clogging of a circulation system.
[0013] Anodes placed under the substrate in the electrodeposition
tank exhibited greatly different forming rates, depending upon
their locations, whereby hazy irregularities became apt to appear
on the film-forming surface. The hazy irregularities remained, for
example, even after formation of a semiconductor photovoltaic layer
comprising amorphous silicon as a major component by CVD and
formation of a transparent electroconductive layer of ITO or the
like in order to form a solar cell, posing a problem that they
resulted in remaining as nonuniformity of characteristics.
[0014] This phenomenon was more prominent with increasing
concentration of the electrodeposition bath and became more
prominent as the current was increased to raise the deposition
rates. These hindered fully enjoying the advantage of the low
running cost described above. An object of the present invention
is, therefore, to provide an inexpensive electrodeposition tank,
electrodeposition apparatus, and electrodeposition method that can
prevent the oxide film from being deposited on the piping system
connected to the electrodeposition tank and on the piping system
installed in the electrodeposition tank during formation of the
oxide film on the substrate, thereby inhibiting generation of
powder, film chips, etc. in the bath and that can produce a uniform
oxide film evenly without occurrence of the hazy irregularities on
the substrate.
SUMMARY OF THE INVENTION
[0015] The present invention provides an electrodeposition tank for
forming a film of an oxide on a substrate with energizing the
substrate and an electrode in an electrodeposition bath, the
electrodeposition tank being formed of a dielectric material.
[0016] The present invention also provides an electrodeposition
tank for forming a film of an oxide on a substrate with energizing
the substrate and an electrode in an electrodeposition bath,
comprising an outside wall formed of a metal material and an inside
surface thereof covered with a lining formed of a dielectric
material.
[0017] Further, the present; invention provides an
electrodeposition tank for forming a film of an oxide on a
substrate with energizing the substrate and an electrode in an
electrodeposition bath, comprising an outside tank formed of a
metal material and an inside tank formed of a dielectric material
for housing the electrode inside thereof.
[0018] The present invention also provides an electrodeposition
apparatus comprising an electrodeposition tank for forming a film
of an oxide on a substrate with energizing the substrate and an
electrode in an electrodeposition bath, a washing means for washing
the substrate after passage through the electrodeposition tank, and
a drying means for forcedly drying the substrate after passage
through the washing means, wherein the electrodeposition tank is
formed of a dielectric material.
[0019] Further, the present invention provides an electrodeposition
apparatus comprising an electrodeposition tank for forming a film
of an oxide on a substrate with energizing the substrate and an
electrode in an electrodeposition bath, a washing means for washing
the substrate after passage through the electrodeposition tank, and
a drying means for forcedly drying the substrate after passage
through the washing means, wherein the electrodeposition tank is
formed of a metal material and an inside surface thereof is covered
with a lining formed of a dielectric material.
[0020] The present invention also provides an electrodeposition
apparatus comprising an electrodeposition tank for forming a film
of an oxide on a substrate with energizing the substrate and an
electrode in an electrodeposition bath, a washing means for washing
the substrate after passage through the electrodeposition tank, and
a drying means for forcedly drying the substrate after passage
through the washing means, wherein the electrodeposition tank
comprises an outside tank formed of a metal material and an inside
tank formed of a dielectric material for housing the electrode
inside thereof.
[0021] Further, the present invention provides an electrodeposition
tank for forming a film of an oxide on a substrate with energizing
the substrate and an electrode in an electrodeposition bath,
wherein all or part of a piping system connected to the tank and a
piping system disposed in the tank is formed of a dielectric.
[0022] The present invention also provides an electrodeposition
tank for forming a film of an oxide on a substrate with energizing
the substrate and an electrode in an electrodeposition bath,
wherein the inside and outside surfaces of all or part of a piping
system connected to the tank and a piping system disposed in the
tank are coated with a dielectric.
[0023] Further, the present invention provides an electrodeposition
apparatus for continuously forming a film of an oxide on a
substrate by electrodeposition, comprising an electrodeposition
tank for retaining an electrodeposition bath, wherein the
electrodeposition tank is formed of a metal, and wherein the inside
of the electrodeposition tank is kept electrically floating.
[0024] In addition, the present invention provides
electrodeposition methods comprising forming a film of an oxide on
a substrate by the use of each electrodeposition apparatus stated
above.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a schematic sectional view showing an example of
the electrodeposition tank according to the present invention;
[0026] FIG. 2 is a schematic sectional view showing an example of
the electrodeposition apparatus according to the present
invention;
[0027] FIG. 3 is a schematic sectional view showing another example
of the electrodeposition tank according to the present
invention;
[0028] FIG. 4 is a schematic sectional view showing another example
of the electrodeposition tank according to the present
invention;
[0029] FIG. 5 is a schematic sectional view showing an example of
the inside tank of the electrodeposition tank according to the
present invention;
[0030] FIG. 6 is a schematic sectional view showing another example
of the inside tank of the electrodeposition tank according to the
present invention;
[0031] FIG. 7 is a schematic sectional view showing another example
of the electrodeposition tank according to the present
invention;
[0032] FIG. 8 is a schematic sectional view showing another example
of the electrodeposition tank according to the present invention;
and
[0033] FIG. 9 is a schematic sectional view showing another example
of the electrodeposition tank according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] The present invention has been accomplished based on the
following experiments conducted by the inventors.
[0035] First, as illustrated in FIG. 7, electrodeposition was
carried out with keeping the inside of SUS electrodeposition tank
7009 electrically floating by interposing a dielectric spacer 7067
between the electrodeposition tank 7009 and a frame 7066 thereof.
This proved that there appeared little difference among the
deposition rates depending upon the locations of anodes 7017 and a
uniform film was able to be deposited at high deposition rates. At
this time, long substrate 7001 was grounded.
[0036] Next, as illustrated in FIG. 8, electrodeposition was
carried out while a lining 7068 of a 10 mm-thick
polytetrafluoroethylene (Teflon) sheet was provided inside the SUS
electrodeposition tank 7009. This proved that there appeared little
difference among the deposition rates depending upon the locations
of anodes 7017 and a uniform film was able to be deposited at high
deposition rates. Further, electrodeposition was carried out with
keeping the long substrate 7001 electrically floating and it was
proved that deposition was able to be achieved with still higher
uniformity.
[0037] Moreover, as illustrated in FIG. 9, the electrodeposition
apparatus was arranged in such structure that the inside of the
electrodeposition tank 7009 was kept electrically floating, six
open-box-like inside tanks 7069 of PFA were placed inside the
electrodeposition tank 7009, three anodes 7017 were set in each
inside tank 7069, and the long substrate 7001 covered openings of
the inside tanks 7069. Electrodeposition was carried out in this
structure and it was proved that in the case of deposition at a
standstill, the shape of the anodes 7017 was projected slightly but
there appeared little difference among the deposition rates
depending upon the locations of the anodes 7017 and that in the
case of the long substrate 7001 being conveyed continuously, a
uniform film was able to be deposited at high deposition rates.
Further, electrodeposition was carried out with keeping the long
substrate 7001 electrically floating and it was proved that
deposition was able to be achieved with still higher
uniformity.
[0038] The present invention has been accomplished based on the
results of the above experiments and provides the electrodeposition
apparatus for forming a film of an oxide on the long substrate 7001
by electrodeposition, wherein the electrodeposition tank 7009 for
retaining the electrodeposition bath 7016 is formed of a metal and
the inside of the electrodeposition tank 7009 is kept electrically
floating.
[0039] An electrodeposition tank of the present invention is an
electrodeposition tank for forming a film of an oxide on a
substrate with energizing the substrate and an electrode in an
electrodeposition bath, the electrodeposition tank being formed of
a dielectric material.
[0040] This dielectric is preferably reinforced with a metal
material.
[0041] The dielectric is preferably a fluororesin or a
fiber-reinforced plastic.
[0042] Further, the substrate is preferably a long substrate and
more preferably, the tank is mounted in a roll-to-roll apparatus
for conveying the long substrate as stretched between rolls.
[0043] Another electrodeposition tank of the present invention is
an electrodeposition tank for forming a film of an oxide on a long
substrate with energizing the long substrate and an electrode in an
electrodeposition bath, wherein an outside wall is formed of a
metal material and an inside surface thereof is covered with a
lining formed of a dielectric material.
[0044] This dielectric is preferably a fluororesin or a
fiber-reinforced plastic.
[0045] It is also preferable that a clearance at a seam of the
lining be so set that an electric resistance of the bath from the
anode to the metal part of the outside wall is greater than an
electric resistance of the bath from the anode to the
substrate.
[0046] Further, the metal part of the outside wall and the
substrate are preferably set at an equal potential.
[0047] The substrate is preferably a long substrate and the tank is
preferably mounted in a roll-to-roll apparatus for conveying the
long substrate as stretched between rolls.
[0048] Another electrodeposition tank of the present invention is
an electrodeposition tank for forming a film of an oxide on a long
substrate with energizing the long substrate and an electrode in an
electrodeposition bath, comprising an outside tank formed of a
metal material and an inside tank formed of a dielectric material
for housing an anode electrode inside thereof.
[0049] This inside tank of the dielectric is preferably reinforced
with a metal material.
[0050] The inside tank is preferably provided with an opening
adapted to permit inflow and outflow of the bath inside thereof and
the bath outside thereof.
[0051] Further, the size of the opening is preferably so set that
an electric resistance of the bath from the anode inside the inside
tank to the metal outside tank is greater than an electric
resistance of the bath from the anode to the substrate.
[0052] The inside tank is preferably provided with bath
exchanging/moving means for effecting exchange of the bath inside
thereof and the bath outside thereof.
[0053] This bath exchanging means is preferably provided with a
bath outlet system for leading the inside bath solution out of the
inside tank, a bath inlet system for leading the outside bath
solution into the inside tank, and a pump for circulating the bath
solution from the outlet system to the inlet system.
[0054] Further, an electric resistance of the bath from the anode
through the bath exchanging means to the substrate is preferably
greater than an electric resistance of the bath from the anode to
the substrate inside the inside tank.
[0055] The dielectric is preferably a fluororesin or a
fiber-reinforced plastic.
[0056] Further, the metal outside tank and the substrate are
preferably set at an equal potential.
[0057] The substrate is preferably a long substrate and more
preferably, the tank is mounted in a roll-to-roll apparatus for
conveying the long substrate as stretched between rolls.
[0058] Further, an electrodeposition apparatus of the present
invention is an electrodeposition apparatus comprising an
electrodeposition tank for forming a film of an oxide on a
substrate with energizing the substrate and an electrode in an
electrodeposition bath, a washing means for washing the substrate
after passage through the electrodeposition tank, and a drying
means for forcedly drying the substrate after passage through the
washing means, wherein the electrodeposition tank is formed of a
dielectric material.
[0059] This electrodeposition tank of the dielectric is preferably
reinforced with a metal material.
[0060] The dielectric is preferably a fluororesin or a
fiber-reinforced plastic.
[0061] Further, the substrate is preferably a long substrate and
more preferably, the tank is mounted in a roll-to-roll apparatus
for conveying the long substrate as stretched between rolls.
[0062] Another electrodeposition apparatus of the present invention
is an electrodeposition apparatus comprising an electrodeposition
tank for forming a film of an oxide on a long substrate with
energizing the long substrate and an electrode in an
electrodeposition bath, a washing means for washing the substrate
after passage through the electrodeposition tank, and a drying
means for forcedly drying the substrate after passage through the
washing means, wherein the electrodeposition tank is formed of a
metal material and an inside surface thereof is covered with a
lining formed of a dielectric material.
[0063] The dielectric is preferably a fluororesin or a
fiber-reinforced plastic.
[0064] A clearance at a seam of the lining is preferably so set
that an electric resistance of the bath from the anode to the metal
part of the electrodeposition tank is greater than an electric
resistance of the bath from the anode to the substrate.
[0065] Further, the metal part of the electrodeposition tank, and
the substrate are preferably set at an equal potential.
[0066] The substrate is preferably a long substrate and more
preferably, the apparatus is mounted in a roll-to-roll apparatus
for conveying the long substrate as stretched between rolls.
[0067] Another electrodeposition apparatus of the present invention
is an electrodeposition apparatus comprising an electrodeposition
tank for forming a film of an oxide on a long substrate with
energizing the long substrate and an electrode in an
electrodeposition bath, a washing means for washing the substrate
after passage through the electrodeposition tank, and a drying
means for forcedly drying the substrate after passage through the
washing means, wherein the electrodeposition tank comprises an
outside tank formed of a metal material and an inside tank formed
of a dielectric material for housing an anode electrode inside
thereof.
[0068] The inside tank of the dielectric is preferably reinforced
with a metal material.
[0069] The inside tank is preferably provided with an opening
adapted to permit inflow and outflow of the bath inside thereof and
the bath outside.
[0070] Further, the size of the opening is preferably so set that
an electric resistance of the bath from the anode in the inside
tank to the metal outside tank is greater than an electric
resistance of the bath from the anode to the substrate.
[0071] The inside tank is preferably provided with bath
exchanging/moving means for effecting exchange of the bath inside
thereof and the bath outside.
[0072] This bath exchanging means is preferably provided with a
bath outlet system for leading the inside bath solution out of the
inside tank, a bath inlet system for leading the outside bath
solution into the inside tank, and a pump for circulating the bath
solution from the outlet system to the inlet system.
[0073] Further, an electric resistance of the bath from the anode
through the bath exchanging means to the substrate is preferably
greater than an electric resistance of the bath from the anode to
the substrate inside the inside tank.
[0074] The dielectric is preferably a fluororesin or a
fiber-reinforced plastic.
[0075] Further, the metal outside tank and the substrate are
preferably set at an equal potential.
[0076] The substrate is preferably a long substrate and more
preferably, the apparatus is mounted in a roll-to-roll apparatus
for conveying the long substrate as stretched between rolls.
[0077] Next described are the constitution and operation of the
present invention, together with the details of how we have
accomplished the present invention. The inventors conducted studies
on the hazy irregularities appearing on the long substrate by the
following experiments.
[0078] The electrodeposition tank 2009 illustrated in FIG. 2 is
normally formed of stainless steel (SUS), whereas we employed FRP
as a material replacing it. This verified that there appeared
little difference among the deposition rates depending upon the
locations of the anodes 2017 and a uniform film was able to be
formed at high deposition rates.
[0079] Next, a lining of 10 mm-thick polytetrafluoroethylene
(Teflon) sheets was provided inside the electrodeposition tank 2009
of stainless steel. There was some clearance at seams between the
sheets and part of electrodeposition bath 2016 stayed in this
clearance, whereby the substrate 2001 was electrically connected
via the electrodeposition bath 2016 to the stainless steel
electrodeposition tank 2009.
[0080] The clearance at the seams of the Teflon sheets was not so
large, however, so that this electrical connection had a large
resistance of several ten .OMEGA. or more. The electric resistance
between the anode 2017 and the substrate 2001 was 0.3 .OMEGA..
[0081] When electrodeposition was carried out using the
electrodeposition tank 2009 lined with the Teflon sheets as
described above, there appeared little difference among the
deposition rates depending upon the locations of the anodes 2017
and a uniform film was able to be formed at high deposition rates,
as in the case of the FRP electrodeposition tank being used. When
electrodeposition was carried out in such a configuration that the
stainless steel electrodeposition tank 2009 and the substrate 2001
were connected by a copper wire having the sectional area of 22
mM.sup.2 so as to be kept at an equal potential, the uniformity of
deposition was further improved.
[0082] Further, instead of the Teflon sheets, ETFE films 50 .mu.m
thick were placed as a lining inside the stainless steel
electrodeposition tank 2009. In this case, part of the
electrodeposition bath 2016 also leaked, whereby the anodes 2017
and the electrodeposition tank 2009 were electrically connected via
the resistance of the bath. This resistance, however, was greater
than 50 .OMEGA.. On the other hand, the electric resistance between
the anodes 2017 and the substrate 2001 was 0.2 .OMEGA..
[0083] When electrodeposition was carried out using the
electrodeposition tank 2009 lined with the ETFE films as described
above, there appeared little difference among the deposition rates
depending upon the locations of the anodes 2017 and a uniform film
was able to be formed at high deposition rates, as in the case the
FRP electrodeposition tank being used.
[0084] Six dish vats of PFA were placed in the stainless steel
electrodeposition tank 2009, three anodes 2017 were set in each
vat, and the substrate 2001 was arranged to cover the openings of
the vats. When electrodeposition was carried out using the
electrodeposition tank provided with the vats as described above,
it was verified that in the case of deposition at a standstill,
there appeared little difference among the deposition rates
depending upon the locations of the anodes 2017, though the shape
of the anodes was projected slightly, and in the case of the
substrate being conveyed, a uniform film was able to be produced at
high deposition rates.
[0085] Subsequently, eight openings having the diameter of 5 mm
were bored in the lower part of each of the dish vats so as to let
bubbling air go into the vats, whereby agitation of the bath was
also effected in the vats. When electrodeposition was carried out
with the substrate 2001 being conveyed, using the electrodeposition
tank capable of bubbling in the stated arrangement of the vats,
further improvement in uniformity was verified at high deposition
rates.
[0086] Further, an opening of 8 mm was bored in the lower part of
the dish vat, a Teflon tube was put into this opening, it was
connected to an exhaust port of a circulation pump, and another
Teflon tube was also drawn similarly from the lower part of the
electrodeposition tank 2009 to be connected to an inlet port of the
circulation pump. When electrodeposition was carried out with the
substrate 2001 being conveyed in this configuration to form a bath
circulation system of 400 ml/min while agitating the bath below the
substrate, improvement in uniformity was verified at high
deposition rates, as in the case of the bubbling air being
introduced into the vats. The resistance of the circulation system
between the anodes 2017 and the substrate 2001 was over 1
k.OMEGA..
[0087] The dish vats were replaced by stainless steel vats and the
inside of the vats was lined with Teflon sheets. When
electrodeposition was carried out with the substrate 2001 being
conveyed in this configuration, a uniform film was able to be
formed.
[0088] For accomplishing the above object, an electrodeposition
tank of the present invention is an electrodeposition tank for
forming an oxide on a substrate with energizing the substrate and
an electrode in an electrodeposition bath, wherein all or part of a
piping system connected to this tank and a piping system placed in
the tank is formed of a dielectric.
[0089] In the above configuration of the electrodeposition tank,
the piping system placed in this tank is preferably electrically
insulated from the tank.
[0090] The above dielectric is preferably a fluororesin.
[0091] The dielectric is also preferably a fiber-reinforced
plastic.
[0092] Further, the substrate is preferably a long substrate and
more preferably, the tank is mounted in a roll-to-roll apparatus
for conveying the long substrate as stretched between rolls.
[0093] Another electrodeposition tank of the present invention is
an electrodeposition tank for forming an oxide on a substrate with
energizing the substrate and an electrode in an electrodeposition
bath, wherein the inside and outside surfaces of all or part of a
piping system connected to this tank and a piping system placed in
the tank are coated with a dielectric.
[0094] In the above configuration of another electrodeposition
tank, the piping system placed in this tank is preferably
electrically insulated from the tank.
[0095] The above coating dielectric is preferably a
fluororesin.
[0096] The coating dielectric is also preferably a fiber-reinforced
plastic.
[0097] Further, the substrate is preferably a long substrate and
more preferably, the tank is set in a roll-to-roll apparatus for
conveying the long substrate as stretched between rolls.
[0098] On the other hand, an electrodeposition apparatus of the
present invention is an electrodeposition apparatus comprising an
electrodeposition tank for forming an oxide on a substrate with
energizing the substrate and an electrode in an electrodeposition
bath, a washing means for washing the substrate after passage
through the electrodeposition tank, and a drying means for drying
the substrate after passage through the washing means, wherein all
or part of a piping system connected to the electrodeposition tank
and a piping system placed in the electrodeposition tank is formed
of a dielectric.
[0099] In the above configuration of the electrodeposition
apparatus, the piping system placed in the electrodeposition tank
is preferably electrically insulated from the electrodeposition
tank.
[0100] The above dielectric is preferably a fluororesin.
[0101] The dielectric is also preferably a fiber-reinforced
plastic.
[0102] Further, the substrate is preferably a long substrate and
more preferably, the apparatus is set in a roll-to-roll apparatus
for conveying the long substrate as stretched between rolls.
[0103] Another electrodeposition apparatus of the present invention
is an electrodeposition apparatus comprising an electrodeposition
tank for forming a film of an oxide on a substrate with energizing
the substrate and an electrode in an electrodeposition bath, a
washing means for washing the substrate after passage through the
electrodeposition tank, and a drying means for drying the substrate
after passage through the washing means, wherein the inside and
outside surfaces of all or part of a piping system connected to the
electrodeposition tank and a piping system placed in the
electrodeposition tank are coated with a dielectric.
[0104] In the above configuration of another electrodeposition
apparatus, the piping system placed in the electrodeposition tank
is preferably electrically insulated from the electrodeposition
tank.
[0105] The above coating dielectric is preferably a
fluororesin.
[0106] The coating dielectric is also preferably a fiber-reinforced
plastic.
[0107] Further, the substrate is preferably a long substrate and
more preferably, the apparatus is set in a roll-to-roll apparatus
for conveying the long substrate as stretched between rolls.
[0108] The operation of the present invention will be described
below, together with the details of how the inventors have
accomplished the present invention. Specifically, the inventors
conducted studies on the powder and film chips appearing in the
bath and on the hazy irregularities by the following
experiments.
[0109] In the electrodeposition apparatus illustrated in FIG. 2,
the whole piping system connected to the electrodeposition tank
2009 and the whole piping system placed in the electrodeposition
tank 2009 are normally formed of stainless steel (SUS). The
inventors employed FRP as a material replacing it and found out
that a uniform film was able to be formed at high deposition rates
with little clogging of the circulation system due to the powder
and film chips and with little difference among the deposition
rates depending upon the locations of the anodes 2017.
[0110] Next, the whole piping system connected to the
electrodeposition tank 2009 and the whole piping system placed in
the electrodeposition tank were replaced by those obtained by
laying a Teflon coating on inside and outside surfaces of stainless
steel pipes. Electrodeposition was carried out using the pipes with
this coating and it was verified that a uniform film was able to be
formed at high deposition rates with little clogging of the
circulation system due to the powder and film chips and with little
difference among the deposition rates depending upon the locations
of the anodes 2017, as in the case of the FRP piping systems being
used.
[0111] Heat-resistant vinyl chloride was used as a material for the
piping system 3011, 3012, 3013 disposed in the electrodeposition
tank 3000 and for the piping system 3014, 3015, 3016, 3017
connected to the electrodeposition tank 3,000, as illustrated in
FIG. 3. Electrodeposition was carried out using the piping systems
of heat-resistant vinyl chloride in part and it was verified that a
uniform film was able to be formed at high deposition rates with
little clogging of the circulation system due to the powder and
film chips and with little difference among the deposition rates
depending upon the locations of the anodes, as in the case of the
FRP piping systems being used.
[0112] Preferred embodiments of the electrodeposition apparatus
according to the present invention will be described below, but it
should be noted that the present invention is by no means intended
to be limited to the following embodiments.
[0113] FIG. 2 is a schematic diagram showing an example of the
apparatus for producing the oxide film by electrodeposition, which
is simplified to only the function to form a zinc oxide film by
electrodeposition.
[0114] In FIG. 2, reference numeral 2001 designates a long
substrate such as a stainless steel belt sheet or the like wound in
a roll form, which is generally called a roll substrate, a web, a
hoop, a coil, a tape, a reel, or the like. Namely, the long
substrate is a thin sheet having a belt-like shape of an elongate
rectangle, which can be rolled up in the longitudinal direction to
be held in the roll shape. Since deposition can be carried out
continuously, the long substrate is extremely advantageous from the
industrial aspect, for example, in capability of decreasing the
availability and running cost. The long substrate 2001 is carried
in the form of the cylindrical substrate rolled in a coil shape
around a bobbin, to this apparatus.
[0115] In this apparatus, the long substrate of the coil shape is
set on a substrate feed roller 2002, and the substrate fed
therefrom in the direction of the arrow 2004 is conveyed to a
substrate winding roller 2062 to be wound thereon while an
interleaf (e.g., interleaving paper) for protection of the surface
is unwound by an interleaf winding roller 2003.
[0116] In more detail, the substrate 2001 is guided via a tension
detecting roller 2005 and a power-supply roller 2006 in its
conveyance path to enter the electrodeposition tank 2009. Inside
the electrodeposition tank 2009, the substrate 2001 is positioned
by support rollers 2013, 2014 and an oxide film is formed thereon
by electrodeposition.
[0117] Next, the substrate 2001 having passed the electrodeposition
tank 2009 is guided into a washing tank 2030 to be washed with
water. Positioning inside the washing tank 2030 is effected by
support rollers 2031, 2066. The substrate 2001 having passed the
washing tank 2030 is guided into a hot air drying furnace 2051 to
be dried.
[0118] The substrate 2001 having passed the hot air drying furnace
2051 is guided via a support roller 2057 and lateral deviation
thereof is corrected by a skew correcting roller 2059. While a new
interleaf fed from an interleaf feeding roller 2060 is interleaved
for protection of the surface of deposited film, the substrate is
wound up on the substrate winding roller 2062 and then is carried
to the next step if necessary.
[0119] The tension detecting roller 2005 is arranged to detect
dynamic winding tension of the substrate 2001 and feed the
detection result back to an unrepresented brake means, such as a
powder clutch, linked to a shaft of the substrate feeding roller
2002, thereby maintaining the tension constant. Based on this, the
conveyance path of the substrate 2001 is designed to be a
predetermined value between the support rollers.
[0120] Particularly, since this apparatus is constructed so that
the rollers do not touch the film-forming surface, weak tension
will pose issues; for example, the substrate 2001 slips off the
support rollers, the substrate 2001 is suspended down at the exit
or entrance of the electrodeposition tank 2009 or the washing tank
2030 so as to scratch the film-forming surface, and so on.
[0121] The structure of the apparatus that prevents the contact of
the film-forming surface has such advantages as capability of
protecting the film-forming surface from damage and pollution etc.
and is preferably employed for use where asperities of the micron
size have to be formed on a thin film, particularly, such as a
reflecting film of a solar cell or the like.
[0122] The power-supply roller 2006 is provided for applying a
cathode-side potential to the long substrate, is set as close to
the electrodeposition bath as possible, and is connected to the
negative electrode of power supply 2008.
[0123] The electrodeposition tank 2009 retains the
electrodeposition bath 2016 and defines the path of the substrate
2001. The anodes 2017 are set with respect to the path and an anode
potential is applied from the power supply 2008 via a supply bar
2015 to the anodes 2017. This permits an electrochemical,
electrolytic deposition process to proceed with the substrate 2001
being negative and the anodes 2017 being positive in the
electrodeposition bath.
[0124] If the electrodeposition bath 2016 is maintained at high
temperature, a considerable amount of water vapor will evolve.
Thus, the water vapor is discharged through vapor exhaust ducts
2010, 2011, 2012.
[0125] For agitating the electrodeposition bath 2016, air is
introduced through an agitating air inlet pipe 2019 and the air is
subject to bubbling from an air blow pipe 2018 in the
electrodeposition tank 2009.
[0126] For replenishing the high-temperature bath to the
electrodeposition tank 2009, an electrodeposition circulation tank
2025 is provided, a heater 2024 is set therein to heat the bath,
and the bath is supplied from a bath circulation pump 2023 through
an electrodeposition bath supply pipe 2020 to the electrodeposition
tank. The bath overflowing out of the electrodeposition tank 2009
and the bath positively fed back in part is guided through an
unrepresented feedback path back to the electrodeposition
circulation tank 2025 to be heated again.
[0127] When the discharge of the pump is constant, the bath supply
amount from the electrodeposition circulation tank 2025 to the
electrodeposition tank 2009 can be controlled by valve 2021 and
valve 2022. Specifically, for increasing the supply amount, the
valve 2021 is opened more while the valve 2022 is closed more; for
decreasing the supply amount, the reverse operation is carried out.
The level of the electrodeposition bath 2016 is retained by
adjusting the supply amount and the feedback amount not
illustrated.
[0128] The electrodeposition circulation tank 2025 is provided with
a filter circulation system comprised of a circulation pump 2027
and a filter, so as to remove particles from the electrodeposition
circulation tank 2025. If the supply and feedback of the bath are
sufficiently large between the electrodeposition circulation tank
2025 and the electrodeposition tank 2009, the adequate particle
removing effect can be achieved by this configuration in which only
the electrodeposition circulation tank 2025 is provided with the
filter, as described above.
[0129] In this apparatus, the electrodeposition circulation tank
2025 is also provided with a vapor exhaust duct 2026 to exhaust
water vapor. Particularly, since the electrodeposition circulation
tank 2025 is provided with the heater 2024 as a heating source, the
exhaust system is extremely effective where evolution of water
vapor is considerable and unintentional discharge or dew
condensation of the water vapor evolved is not preferred.
[0130] An electrodeposition reserve tank 2029 is provided for
preventing the heated bath from being discharged into an existing
waste liquid system at once to damage a disposal system and is;
thus adapted to retain the electrodeposition bath 2016 of the
electrodeposition tank 2009 once and increase efficiency of work by
making the electrodeposition tank 2009 vacant. Reference numeral
2028 designates a valve.
[0131] After completion of electrodeposition in the
electrodeposition tank 2009, the substrate 2001 is then guided to
the washing tank 2030 to be washed with water. In the washing tank
2030 the substrate 2001 is positioned by the support rollers 2031
and 2066 and passes a first washing tank 2032, a second washing
tank 2033, and a third washing tank 2034 in the stated order.
[0132] In a washing circulation tank portion 2050, each of the
washing tanks is provided with a washing circulation tank 2047 to
2049 and a water circulating pump 2044 to 2046 and a water supply
amount to the washing tank 2030 is determined by two valves, i.e.,
by valve 2038 and valve 2041, or by valve 2039 and valve 2042, or
by valve 2040 and valve 2043. Cleaning water is supplied through a
supply pipe 2035, or through a supply pipe 2036, or through a
supply pipe 2037 to the washing tank 2032 to 2034.
[0133] The control method of supply amount by the two valves is the
same as the control in the electrodeposition tank 2009. Just as in
the electrodeposition tank 2009, overflowing water and
unrepresented feedback water positively fed back in part can also
be led back to each washing circulation tank 2047 to 2049.
[0134] In the three-stage washing system as illustrated in FIG. 2,
the purity of the cleaning water normally increases from the
upstream washing tank to the downstream washing tank in the
substrate conveying direction, i.e., from the first washing tank
2032 toward the third washing tank 2034. This means that
cleanliness of the substrate 2001 increases toward the end of the
process as the substrate 2001 is conveyed.
[0135] This allows the use amount of water to be decreased greatly,
by first replenishing the third washing circulation tank 2049 with
the cleaning water, then replenishing the second washing
circulation tank 2048 with the cleaning water overflowing out of
the third washing circulation tank 2049, and further replenishing
the first washing circulation tank 2047 with the cleaning water
overflowing from the second washing circulation tank 2048.
[0136] After completion of washing, the substrate 2001 is subjected
to a draining step with air knife 2065 provided in part of the
washing tank 2030 and then is conveyed to the hot air drying
furnace 2051. In this furnace, the substrate is dried by convective
air at a temperature enough to evaporate water fully. The
convective air is supplied by leading hot air generated by a hot
air generator 2055 through a filter 2054 to remove dust and blowing
the hot air from hot air blow pipe 2052.
[0137] Overflowing air is collected again by hot air collecting
pipe 2053 and is mixed with external air from external air inlet
pipe 2056 to be sent to the hot air generator.
[0138] The conveyance path of the substrate 2001 in the hot air
drier is positioned by support roller 2066 and support roller
2057.
[0139] The skew correcting roller 2059 is adapted to correct
widthwise deviation of the substrate 2001 and wind the substrate
onto the substrate winding roller 2062 in the direction of the
arrow 2061. An unrepresented sensor detects a deviation amount and
the deviation is controlled by rotating the skew correcting roller
2059 about a fulcrum at an unrepresented arm. Normally, deviation
amounts detected by the sensor and operating amounts of the skew
correcting roller 2059 both are very small and they are designed
within 1 mm.
[0140] On the occasion of winding the substrate 2001, a new
interleaf is supplied from the interleaf feeding roller 2060 in
order to protect the surface of the substrate.
[0141] Stopper 2007 and stopper 2058 are members adapted to be
actuated simultaneously to keep the substrate 2001 at a standstill
with the conveying tension thereon. This improves operability
during exchange of substrate 2001 and during maintenance of the
apparatus.
[0142] Use of the electrodeposition apparatus as illustrated in
FIG. 2 presents the following advantages.
[0143] First, formation of film is extremely simple, different from
the vacuum apparatus such as the sputtering apparatus or the like.
An expensive vacuum pump does not have to be used and no care is
necessary for the design of components around the power supply and
electrode for use of the plasma.
[0144] Next, the running cost is low in most cases. This is for the
following reason; the sputtering apparatus necessitates the labor
and apparatus for production of the target to raise the cost and
the utilization efficiency of the target is approximately 20% or
less. Therefore, if the throughput of the apparatus is high or if
the thickness of film is large, the percentage of the work for
target exchange will be considerably high.
[0145] The electrodeposition method of the present invention is
also superior in the apparatus and running cost to CVD and vacuum
evaporation except for sputtering.
[0146] In many cases, the films are of polycrystalline particles
and demonstrate the electroconductive and optical characteristics
comparable to those of films made by the vacuum methods. Therefore,
the electrodeposition method of the present invention is superior
to the sol-gel process, the coating method using the organic
substance, the spray pyrolysis method, and so on.
[0147] Further, these also hold in formation of oxide and the waste
liquid can be disposed of easily. Therefore, the impact is small on
environments, so that the cost is low for prevention of
environmental pollution.
[0148] Namely, an example of the electrodeposition apparatus of the
present invention is an apparatus for continuously forming a
uniform oxide film on the long substrate 2001, the apparatus
comprising the electrodeposition tank 2009 for forming the oxide
film on the substrate 2001, the washing means such as the washing
tank 2030 or the like for washing the substrate 2001 having passed
the electrodeposition tank 2009, and the drying means such as the
hot air drying furnace 2051 or the like for forcedly drying the
substrate 2001 having passed the washing means, the apparatus being
improved, particularly, in the structure of the piping system
(pipes and joints) connected to the electrodeposition tank and the
piping system placed in the electrodeposition tank.
[0149] The present invention is also characterized in that the
inside of the electrodeposition tank 2009 (7009) is kept
electrically floating in the electrodeposition apparatus described
above. The electrically floating state of the inside of the
electrodeposition tank 7009 can be realized by interposing the
dielectric spacer 7067 between the electrodeposition tank 7009 and
the frame 7066 thereof, as illustrated in FIG. 7. A more preferable
result can be achieved by providing the electrodeposition tank 7009
with the dielectric lining 7068 and electrically floating the long
substrate 7001 as well, as illustrated in FIG. 8.
[0150] Another preferred configuration is such that the inside of
the electrodeposition tank 7009 is kept electrically floating as
described above, the inside tanks 7069 of the open-box shape formed
of the dielectric, inside of which the anodes 7017 are disposed,
are set in the electrodeposition tank 7009, and the conveyance path
of the long substrate 7001 is set so as to cover the openings of
the inside tanks 7069, as illustrated in FIG. 9. In this case, a
more preferable result can also be achieved by further electrically
floating the long substrate 7001 as well.
[0151] Another electrodeposition apparatus of the present invention
is an apparatus for continuously forming a uniform oxide on the
long substrate 2001, the apparatus comprising the electrodeposition
tank 2009 for forming the oxide on the substrate 2001 with
energizing the long substrate 2001 and anodes 2017 in the
electrodeposition bath 2016, the washing means such as the washing
tank 2030 or the like for washing the substrate 2001 having passed
the electrodeposition tank 2009, and the drying means such as the
hot air drying furnace 2051 or the like for forcedly drying the
substrate 2001 having passed the washing means 2030, in which,
particularly, the electrodeposition tank 2009 is improved or the
electrodeposition tank 2009 is used as an outside tank while a
separate inside tank is provided. Each of the components will be
described below in detail.
[0152] [Substrate]
[0153] A material for the substrate 2001 used in the present
invention is any material that permits electrical conduction at the
film-forming surface and that is not corroded with the
electrodeposition bath 2016, and is selected from metals such as
stainless steel (SUS), Al, Cu, Fe, Cr, and so on, and alloys
thereof. The substrate can also be a PET film coated with a metal
or the like.
[0154] Among these, where an element forming process is carried out
in a succeeding step, stainless steel is suitable for the long
substrate, because it is relatively inexpensive and excellent in
anticorrosion.
[0155] The surface of the substrate may be either flat or rough. In
the case of rough surfaces not less than 1 .mu.m, even if a film is
formed with good wettability, dry irregularities are apt to take
place between the electrodeposition tank 2009 and the washing tank
2003 and thus the present invention is effective.
[0156] Further, another electroconductive material may also be
deposited on the substrate 2001 and it is selected according to the
purpose of electrodeposition.
[0157] When the long substrate is of stainless steel, it has the
electric resistance greater than the other metals; therefore,
particularly, if the thickness of the substrate is not more than
about 0.1 mm the electric resistance of the substrate will often be
greater than the electric resistance between the anodes 2017 and
the substrate 2001 through the electrodeposition bath 2016,
described hereinafter.
[0158] In such cases, control of the anode potential to the
substrate 2001 is not easy and the electric current expected to
flow between the substrate 2001 and the anodes 2017 leaks through
other members, for example, through the electrodeposition tank
itself and the pipes, posing difficulties of the control thereof.
The difficulties of the control of the anode potential often result
in an issue of the above-stated irregularities and, therefore, the
present invention is effective particularly in such cases.
[0159] [Oxide Film]
[0160] Oxide films that can be formed by the present invention
include a polycrystal film of zinc oxide aligned along the c-axis,
a polycrystal film of zinc oxide having the c-axis inclined, and so
on.
[0161] (Electrodeposition Bath)
[0162] The electrodeposit:ion bath 2016 retained in the
electrodeposition tank 2009 can be selected from wellknown baths
for plating of metal and those comprising zinc nitrate for
deposition of zinc oxide (available in the form of hexahydrate) as
a major ingredient. A saccharide such as sucrose, dextrin, or the
like can also be added in order to enhance uniformity of film.
[0163] The electric conductivity of the electrodeposition bath 2016
used in the present invention is preferably not less than 1 mS/cm
and the effect appears prominent, particularly, if the conductivity
is not less than 10 mS/cm. This is for the reason that as the
electric conductivity of the electrodeposition bath 2016 increases,
other current paths than those from the anodes 2017 to the
substrate 2001 are established, including current paths from the
anodes 2017 to the electrodeposition tank 2009 and current paths
toward the pipes and other members.
[0164] In other words, though the increase per se of the current
other than the current paths flowing from the anodes 2017 to the
substrate 2001 simply means just loss of current (which is not
always preferable, because the current sometimes becomes over
several times the original current paths), potentials are often
instable at flow end sites in the case of the current other than
the current paths flowing from the anodes 2017 to the substrate
2001 in almost all practical systems, so that fluctuations of the
current flowing from the anodes 2017 to the substrate 2001 become
very large.
[0165] It was verified in fact by experiments conducted by the
inventors that to make the potential of the electrodeposition tank
2009 equal to the potential of the substrate 2001 was able to make
steady the current flowing from the anodes 2017 to the substrate
2001, subject to the fluctuations, i.e., the original current for
deposition of oxide.
[0166] The essence of deposition of uniform oxide in the
electrodeposition bath 2016 with high conductivity according to the
present invention is to stabilize or make more efficient the
current flowing from the anodes 2017 to the substrate 2001 by
making steady or decreasing the current other than the current
paths flowing from the anodes 2017 to the substrate 2001.
[0167] Particularly, for forming a film of zinc oxide with surface
roughness approximately equal to the wavelengths of light,
effective as an optical confinement reflecting layer of a solar
cell, the concentration of zinc nitrate is preferably not less than
0.1 mol/l. For obtaining the zinc oxide film aligned along the
c-axis, the concentration of zinc nitrate is preferably not more
than 0.05 mol/l in general, though depending upon the
substrate.
[0168] In either case, the saccharide added is preferably 3 g/l or
more of sucrose or 0.001 g/l or more of dextrin. In these cases,
the temperature of the bath is preferably not less than 60.degree.
C., because deposition of metal does not take place. Particularly,
the temperature is preferably not less than 80.degree. C. for
improvement in uniformity of film. This temperature makes the
effect of the present invention more prominent, because the
electric conductivity is increased remarkably at; this
temperature.
[0169] [Electrodeposition Tank]
[0170] For the electrodeposition tank 2009, metals applicable are
stainless steel (SUS), Fe, Al, Cu, Cr, brass, and so on because of
their excellent heat resistance and workability, among which
stainless steel is preferably used in consideration to corrosion
resistance. The stainless steel can be either ferritic,
martensitic, or austenitic stainless steel.
[0171] When the electrodeposition tank is required to have a heat
retaining property, the electrodeposition tank can be constructed
in dual structure and complemented by a heat insulator between tank
walls. Examples of the heat insulator include air, oil, glass wool,
urethane, and so on, taking the temperature and simplicity into
consideration.
[0172] Particularly, the present invention employs the dielectric
for the electrodeposition tank itself or for the inside tanks
disposed in the electrodeposition tank 2009. The electrodeposition
tank or the inside tanks formed of the dielectric can be molded
members of resins described below or members formed of the
fiber-reinforced plastics.
[0173] (Dielectrics used for the Electrodeposition Tank etc.)
[0174] The dielectric materials applicable for formation of the
electrodeposition tank or the inside tanks described above include
ceramics including alumina, magnesia, calcia, silicon nitride,
silicon carbide, and so on, glasses such as lead-potassium glass,
lead-potassium-sodium glass, zinc borosilicate, aluminosilicate,
borosilicate, barium borosilicate, alkali-barium glass, and so on,
and styrene-based resins such as AAS (acrylonitrile acrylate
styrene), ABS (acrylonitrile butadiene styrene), ACS (acrylonitrile
polyethylene chloride styrene), AES (acrylonitrile ethylene
styrene), AS (acrylonitrile styrene), and so on.
[0175] Other dielectric materials applicable are vinyl resins such
as EVC (ethylene vinyl chloride), EVA (ethylene vinyl acetate), PVC
(polyvinyl chloride), VP (vinyl propionate), PVB (polyvinyl
butyral), PVF (polyvinyl formal), and so on, fluororesins such as
PTFE (polytetrafluoroethylene), FEP (fluoroethylene polypropylene),
PFA (tetrafluoroethylene perfluoroalkyl vinyl ether), ETFE
(ethylene tetrafluoroethylene), CTFE (polychlorotrifluoroethylene),
PVDF (polyvinylidene fluoride), ECTFE (ethylene
chlorotrifluoroethylene), PVF (polyvinyl fluoride), and so on,
polyacetal resins, polyamide resins including nylon etc.,
polyamide-imide resins, polyarylate resins, and polyimide
resins.
[0176] Further dielectric materials applicable are polyethylene
resins such as LDPE (low density polyethylene), LLDPE (linear low
density polyethylene), HDPE (high density polyethylene), UHMWPE
(ultra-high molecular weight polyethylene), and so on, polyester
resins such as PET (polyethylene terephthalate), PBT (polybutylene
terephthalate), polycarbonate, and so on, styrol resins such as
polystyrene, polyparamethylstyrene, and so on, propylene resins
such as polypropylene and the like, acrylic resins such as PMMA
(polymethyl methacrylate) and the like, epoxy resins such as BPA
(bisphenol A) and the like, allyl resins such as DAP (diallyl
phthalate) and the like, phenol resins such as bakelite and the
like, unsaturated polyester resins, furan resins such as furfuryl
alcohol polymer, furfuryl alcohol furfural copolymer, furfural
phenol copolymer, furfural ketone copolymer, and so on, urethane
resins, and urea resins.
[0177] Other dielectric materials can be mixtures of these
materials and composite materials with fibers. Among the resins,
the fluororesins are preferably used, particularly, where the
operating temperature of the electrodeposition bath is high and
high corrosion resistance is expected.
[0178] The form of the dielectric used for the electrodeposition
tank or the inside tanks can be either one selected from molded
products of the ceramics, glasses, and resins described above by
use of a hollow box die or a cylindrical die, sheets, films, foamed
products, fabric of fibers, etc. thereof, and molded products of
combinations thereof. When the tank cannot stand alone, it can also
be constructed with a framework of metal or other thermosetting
resin.
[0179] (Inside Tank)
[0180] Those described above in the sections of [electrodeposition
tank] and [dielectrics used for the electrodeposition tank etc.]
can also be applied similarly to the inside tank used in the
present invention. Materials inferior in strength can also be
applied to the inside tank, however, because the inside tank does
not have to support the entire weight of the electrodeposition
tank, different from the outside tank. Therefore, a material can be
selected with focus on characteristics, price, etc. as a
dielectric. An example conceivable is a box formed of PFA sheets 5
mm thick and stainless steel fasteners.
[0181] The electrodeposition tank itself cannot be constructed of
only PFA, because it is required to prevent the bath from leaking
and to be capable of supporting the entire weight of the
electrodeposition bath. It needs to be constructed using a metal
box of stainless steel or the like as a support.
[0182] On the other hand, in the case of the inside tank, the leak
of the bath is not problematic and there are little restrictions on
the strength. When the inside tank is formed of the dielectric so
as to prevent the leak of current, however, electrical insulation
has to be maintained at the operating temperatures of the
electrodeposition bath and PFA meets that condition. In this case,
if the operating temperatures are about 70.degree. C., PV can also
be used instead of PFA, whereby the production cost can be
decreased.
[0183] (Glass Fiber-reinforced Plastics)
[0184] Fiber-reinforced plastics (FRP) that can be used for the
electrodeposition tank of the present invention include those using
glass fibers as reinforcing fibers (GRP), those using carbor fibers
(CRP), those using boron fibers (BRP), and so on.
[0185] Resins suitably applicable for the FRPs are unsaturated
polyester resins, epoxy resins, urethane resins, vinyl ester
resirs, phenol resins, and diallyl phthalate resins.
[0186] When only the fiber-reinforced plastic is used for the
dielectric electrodeposition tank in the present invention, it is
not preferable to increase the electrical conductivity by a metal
coating on the reinforcing fibers. Preferred FRPs are those having
the resistivity of not less than 100 .OMEGA.cm.
[0187] Since there are possibilities that the FRPs are deformed
after long-term use in the high-temperature bath, they are
preferably reinforced by a support of metal angles or the like.
[0188] (Bath Exchanging Means)
[0189] In the present invention, where the inside tank is disposed
in the electrodeposition tank 2009, this inside tank is provided
with the bath exchanging means. The bath exchanging means used in
the present invention can be either one selected from a single
opening or plural openings bored in the bottom or a side wall of
the inside tank, a circulation system for circulating part of the
bath, comprised of a pump and a tube or pipe, and so on.
[0190] The openings have advantages of basically simple structure
and capability of being made at low cost. Preferred openings are
those permitting free replacement of the bath and having a large
electric resistance due to the bath. For achieving this, the
openings can be formed in a large diameter and the openings can be
provided with a cover or be formed in a maze shape so as to prevent
a linear current path from the anode 2017 from being created to the
electrodeposition tank 2009. The opening may also be provided with
a fan for the bath so as to promote the replacement of the bath
positively.
[0191] The circulation system of the bath is superior to the simple
openings in that the current path from the anode 2017 can be made
electrically narrow. Further, the circulation system has an
advantage of easiness to control the degree of replacement of the
bath.
[0192] In cases where a plurality of anodes 2017 and a
corresponding number of inside tanks are disposed in the
electrodeposition tank 2009, there is also freedom of arrangement;
for example, a configuration in which there are one suction pipe of
the bath and a plurality of return pipes to the inside tanks.
[0193] If there are possibilities that the operating temperatures
of the bath are decreased greatly in the above circulation system,
temperature retaining means or heating means can also be provided
midway of the circulation system. It is also possible to perform
management of the bath by measuring the concentration of the bath
or particles therein in the circulation system.
[0194] [Piping Systems (Pipes and Joints)]
[0195] For the piping systems applicable to the present invention,
metals applicable are stainless steel (SUS), Fe, Cu, Cr, brass, and
so on because of their excellent heat resistance and workability,
among which stainless steel is preferably used in consideration to
corrosion resistance. The stainless steel can be either ferritic,
martensitic, or austenitic stainless steel.
[0196] When the piping systems are formed of a dielectric, they can
be molded of the resins described below, they can be metal pipes
with a coating on inside and outside surfaces, and they can be
formed of the fiber-reinforced plastics described below.
[0197] The structure of the piping systems can be selected from
dielectric piping systems, metal piping systems coated with the
dielectric, or combinations of these with metal piping systems.
[0198] (Dielectrics used for the Piping Systems (Pipes and
Joints))
[0199] The dielectric materials that can be used for the above
piping systems are styrene-based resins such as AAS (acrylonitrile
acrylate styrene), ABS (acrylonitrile butadiene styrene), ACS
(acrylonitrile polyethylene chloride styrene), AES (acrylonitrile
ethylene styrene), AS (acrylonitrile styrene), and so on.
[0200] Other dielectric materials applicable are vinyl resins such
as EVC (ethylene vinyl chloride), EVA (ethylene vinyl acetate), PVC
(polyvinyl chloride), VP (vinyl propionate), PVB (polyvinyl
butyral), PVF (polyvinyl formal), and so on, fluororesins such as
PTFE (polytetrafluoroethylene), FEP (fluoroethylene polypropylene),
PFA (tetrafluoroethylene perfluoroalkyl vinyl ether), ETFE
(ethylene tetrafluoroethylene), CTFE (polychlorotrifluoroethylene),
PVDF (polyvinylidene fluoride), ECTFE (ethylene
chlorotrifluoroethylene), PVF (polyvinyl fluoride), and so on,
polyacetal resins, polyamide resins including nylon etc.,
polyamide-imide resins, polyarylate resins, and polyimide
resins.
[0201] Further dielectric materials applicable are polyethylene
resins such as LDPE (low density polyethylene), LLDPE (linear low
density polyethylene), HDPE (high density polyethylene), UHMWPE
(ultra-high molecular weight polyethylene), and so on, polyester
resins such as PET (polyethylene terephthalate), PBT (polybutylene
terephthalate), polycarbonate, and so on, styrol resins such as
polystyrene, polyparamethylstyrene, and so on, propylene resins
such as polypropylene and the like, acrylic resins such as PMMA
(polymethyl methacrylate) and the like, epoxy resins such as BPA
(bisphLenol A) and the like, allyl resins such as DAP (diallyl
phthalate) and the like, phenol resins such as bakelite and the
like, unsaturated polyester resins, furan resins such as furfuryl
alcohol polymer, furfuryl alcohol furfural copolymer, furfural
phenol copolymer, furfural ketone copolymer, and so on, urethane
resins, urea resins, and ketone resins.
[0202] Other dielectric materials can be mixtures of these
materials and composite materials with fibers. Among the resins,
the fluororesins are preferably used, particularly, where the
operating temperature of the bath is high and high corrosion
resistance is expected.
[0203] The form of the dielectric used for the piping systems
applicable to the present invention can be selected from a molded
form of the above resins by a cylindrical die, fabric of fibers of
the resins, or a combination thereof.
[0204] (Glass Fiber-reinforced Plastics)
[0205] Fiber-reinforced plastics (FRP) that can be applicable to
the piping systems in the present invention include those using
glass fibers as reinforcing fibers (GRP), those using carbon fibers
(CRP), those using boron fibers (BRP), and so on.
[0206] Resins suitably applicable for the FRPs are unsaturated
polyester resins, epoxy resins, urethane resins, vinyl ester
resins, phenol resins, and diallyl phthalate resins.
[0207] When only the fiber-reinforced plastic is used for the
dielectric piping systems in the present invention, it is not
preferable to increase the electrical conductivity by a metal
coating on the reinforcing fibers. Preferred FRPs are those having
the resistivity of not less than 100 .OMEGA.cm.
[0208] [Washing Means]
[0209] The washing means used in the present invention can be a
shower for washing, in addition to the method of letting the
substrate 2001 pass through water reserved in the washing tank 2030
as illustrated in FIG. 2.
[0210] [Drying Means]
[0211] Very effective drying means used in the present invention is
one for first removing water-soluble solutes sufficiently and
thereafter draining water by the air knife as illustrated in FIG.
2. In that case, hot air suffices for subsequent heat drying. If a
vacuum device is used in the succeeding step, an infrared heater or
the like can also be utilized for removing adsorbed water.
[0212] [Conveying Means]
[0213] The conveying means of the substrate used in the present
invention is preferably arranged to exert the tension of not less
than 0.5 kg per cm of the width of the substrate thereon so as to
prevent vertical vibration of the substrate and in turn prevent
occurrence of stepped irregularities between the tanks.
[0214] FIG. 2 shows horizontal conveyance of the substrate by the
roll-to-roll method, but oblique conveyance of the substrate using
a folding roller between the tanks can also be applied.
[0215] [Spacer 7067, Lining 7068, and Inside Tanks 7069]
[0216] The dielectrics used for the spacer 7067, lining 7068, and
inside tanks 7069 in the present invention are ceramics including
alumina, magnesia, calcia, silicon nitride, silicon carbide, and so
on, glasses such as lead-potassium glass, lead-potassium-sodium
glass, zinc borosilicate, aluminosilicate, borosilicate, barium
borosilicate, alkali-barium glass, and so on, styrene-based resins
such as AAS (acrylonitrile acrylate styrene), ABS (acrylonitrile
butadiene styrene), ACS (acrylonitrile polyethylene chloride
styrene), AES (acrylonitrile ethylene styrene), AS (acrylonitrile
styrene), and so on, vinyl resins such as EVC (ethylene vinyl
chloride), EVA (ethylene vinyl acetate), PVC (polyvinyl chloride),
VP (vinyl propionate), PVB (polyvinyl butyral), PVF (polyvinyl
formal), and so on, fluororesins such as PTFE
(polytetrafluoroethylene), FEP (fluoroethylene polypropylene), PFA
(tetrafluoroethylene perfluoroalkyl vinyl ether), ETFE (ethylene
tetrafluoroethylene), CTFE (polychlorotrifluoroethylene), PVDF
(polyvinylidene fluoride), ECTFE (ethylene
chlorotrifluoroethylene), PVF (polyvinyl fluoride), and so on,
polyacetal resins, polyamide resins including nylon etc.,
polyamide-imide resins, polyarylate resins, polyimide resins,
polyethylene resins such as LDPE (low density polyethylene), LLDPE
(linear low density polyethylene), HDPE (high density
polyethylene), UHMWPE (ultra-high molecular weight polyethylene),
and so on, polyester resins such as PET (polyethylene
terephthalate), PBT (polybutylene terephthalate), polycarbonate,
and so on, styrol resins such as polystyrene,
polyparamethylstyrene, arid so on, propylene resins such as
polypropylene and the like, acrylic resins such as PMMA (polymethyl
methacrylate) and the like, epoxy resins such as BPA (bisphenol A)
and the like, allyl resins such as DAP (diallyl phthalate) and the
like, phenol resins such as bakelite and the like, unsaturated
polyester resins, furan resins such as furfuryl alcohol polymer,
furfuryl alcohol furfural copolymer, furfural phenol copolymer,
furfural ketone copolymer, and so on, urethane resins, and urea
resins. Further, the dielectrics can also be mixtures of these
materials and composite materials with fibers. In the case of the
resins being used, the fluororesins are preferably used,
particularly, where the operating temperature of the
electrodeposition bath 7016 is high and high corrosion resistance
is expected.
[0217] The spacer 7067 and the lining 7068 in the present invention
can be made in the form of sheets, films, foamed products, fabric
of fibers, etc. of the above-stated ceramics, glasses, and resins.
Further, the inside tanks 7069 can be made as molded products of
the above-stated ceramics, glasses, and resins, for example, by use
of a box-shape or cylindrical die.
[0218] [Electrical Floating]
[0219] The electrical floating of the inside of the
electrodeposition tank 7009 or the long substrate 7001 means that
the inside surface of the electrodeposition tank 7009 or the long
substrate 7001 is electrically floating with respect to the main
body of the apparatus. Since the main body of the apparatus is
grounded in general, it indicates electrical floating with respect
to the ground.
[0220] The electrical floating of the inside of the
electrodeposition tank 7009 can be achieved by interposing the
spacer 7067 of the dielectric, for example, such as Teflon, Delrin,
or the like, between the frame 7066 supporting the
electrodeposition tank 7009, and the electrodeposition tank 7009,
as illustrated in FIG. 7. If the electrodeposition tank 7009 is
fixed to the frame 7066 by bolts or the like, a necessary measure
will be taken to prevent the electrodeposition tank 7009 from
becoming electrically conductive to the frame 7066 through the
bolts. The electrical floating can also be implemented by
interposing the spacer 7067 of the dielectric, for example, such as
Teflon, Delrin, or the like, between the frame 7066 and the ground
surface, but the way of interposing the spacer 7067 between the
electrodeposition tank 7009 and the frame 7066 as illustrated in
FIG. 8 is simpler. Where the spacer 7067 is interposed between the
frame 7066 and the ground surface and if anchor bolts are screwed
into the ground surface, a necessary measure will be taken to
prevent the frame 7066 from becoming electrical conductive to the
ground surface through the anchor bolts. When the pipes to the
electrodeposition tank 7009 are SUS pipes or the like, it is
preferable to interpose a pipe, a joint, or the like of
heat-resistant polyvinyl chloride midway. Namely, it is preferable
to maintain the electrodeposition tank 7009 at the same potential
as that of the pipes inside the electrodeposition tank 7009.
[0221] The electrical floating of the long substrate 7001 (2001)
can be achieved by covering bearing surfaces of rotational shafts
of all the rollers in contact with the long substrate 7001 (2001)
(for example, the support rollers 2005, 2013, 2014, 2031, 2057,
2066, the skew correcting roller 2059, etc.) except for the
power-supply roller 2006 with the dielectric, for example, such as
Teflon, Delrin, or the like, or by making the bearings of the
rotational shafts of all the rollers in contact with the long
substrate 2001 except for the power-supply roller, of the
dielectric. The electrical floating of the long substrate can also
be realized by covering the surfaces of all the rollers in contact
with the long substrate 2001 except for the power-supply roller
with the dielectric or by making all the rollers in contact with
the long substrate 2001 except for the power-supply roller, of the
dielectric. The covering can be achieved, for example, by attaching
a dielectric film such as a polyimide film or the like to the
surfaces with two sided adhesive tape, by impregnating them with
the dielectric of the resin such as Teflon or the like, and so on,
and may also be achieved by a combination of some of these
methods.
[0222] The electrical floating can be checked by measuring the
electric resistance between the inside surface of the
electrodeposition tank 7009 and the ground surface, the electric
resistance between the long substrate 7001 and the ground surface,
and the electric resistance between the electrodeposition tank 7009
and the long substrate 7001 by a tester with nothing inside the
electrodeposition tank 7009 and confirming that the result is of
the M.OMEGA. order.
EXAMPLES
[0223] Examples based on the present invention will be described
below, but it should be noted that the present invention is by no
means intended to be limited to these examples.
Example 1
[0224] The electrodeposition tank 7009 as illustrated in FIG. 7 was
incorporated as the electrodeposition tank 2009 into the
electrodeposition apparatus as illustrated in FIG. 2, and
deposition was carried out therein.
[0225] In FIG. 7, the electrodeposition tank 7009 is formed of SUS
and in the dual structure in which glass wool is put as a heat
insulator, thus having good heatinsulating and heat-retaining
properties. The long substrate 7001 of SUS430 is conveyed through a
slit formed in the both side walls of this electrodeposition tank
7009. Each of the both side wall portions of the electrodeposition
tank 7009 having the slit is double walls. The electrodeposition
bath 7016 retained in the electrodeposition tank 7009 is arranged
to overflow to drop into between the double walls. The
electrodeposition bath 7016 overflowing to drop into between the
double walls is guided through the unrepresented circulation system
to be used again as the electrodeposition bath 7016 herein. The
circulation amount was controlled so that the height from the
overflowing point to the bath surface became 35 mm.
[0226] The electrodepositicn bath 7016 was zinc nitrate of 0.2
mol/l and was kept at 80.degree. C. Zinc nitrate is for
electrochemically depositing zinc oxide on the surface of the long
substrate 7001 by cooperation of existing zinc ions or complex ions
and nitric ions. The electrodeposition bath 7016 contained dextrin
0.7 g/l in order to enhance uniformity of the zinc oxide film. The
electric conductivity of the electrodeposition bath 7016 was 65
mS/cm.
[0227] Four anodes 7017 were disposed inside the electrodeposition
bath 7016. These anodes 7017 are provided for advancing the
electrochemical reaction when the voltage is placed between the
anodes 7017 and the long substrate 7001. For formation of zinc
oxide, the potential of the anodes 7017 is maintained higher than
the potential of the long substrate 7001.
[0228] The electrodeposition tank 7009 is installed through the
spacer 7067 of an acrylic sheet on the frame 7066. This keeps the
inside of the electrodeposition tank 7009 electrically floating
with respect to the ground, whereby electric lines are prevented
from directly running from the anodes 7017 to the SUS
electrodeposition tank 7009. The anodes 7017 are connected to
respective separate power supplies 7008, so as to be powered
independently of each other. The return of the current is
implemented as a common return from the power-supply roller 7006
driven in contact with the long substrate 7001. Each power supply
7008 was controlled as a constant current source and the
electrodeposition current density toward the long substrate 7001
was arranged to be able to be set in the range of 0.2 mA/cm.sup.2
to 30 mA/cm.sup.2 at each of the anodes 7017.
[0229] While the conveyance of the long substrate 7001 was stopped,
deposition was investigated at a standstill. The deposition rates
approximately proportional to the current, 1 to 200 .ANG./s, were
obtained by the current densities in this range. The present
example employed the current density of about 13 mA/cm.sup.2. The
deposition rate obtained at a standstill was about 100 .ANG./s. The
size of each anode 7017 was 110.times.500 mm in a surface opposed
normally to the long substrate 7001 and the thickness thereof was
20 mm. The anodes were of zinc having the purity of 4 N. A current
set value of each power supply 7008 was about 7 A and the
power-supply voltages indicated 2.5 to 4.0 V.
[0230] The distance between the anodes 7017 and the long substrate
7001 was either of 10 mm and 25 mm and in either case an
electrodeposited zinc oxide film was extremely uniform. Further,
the uniform zinc oxide film 1 .mu.m thick was able to be
continuously formed on the long substrate 7001 at the conveyance
speed of 1200 mm/min of the long substrate 7001.
Comparative Example 1
[0231] The electrodeposition tank 7009 similar to that in Example 1
was electrically grounded and incorporated as the electrodeposition
tank 2009 in the electrodeposition apparatus as illustrated in FIG.
2, and then formation of film was carried out therein.
[0232] The current density of about 180 mA/cm.sup.2 was needed for
obtaining the deposition rate of about 100 .ANG./S. Namely, the
electric current that had to be supplied from the power supplies
was about 100 A, which was close to the capacity limit of the power
supplies. Besides, deposition was very apt to be affected by the
magnitude of the distance between the anodes 7017 and the long
substrate 7001. When the distance between the anodes 7017 and the
long substrate 7001 was set to 15 mm, heavily uneven patterns
appeared in the film, and great variations of characteristics took
place when solar cells were made. When the distance between the
anodes 7017 and the long substrate 7001 was increased to 50 mm in
order to reduce the relative distance differences, the deposition
rates of film were decreased by an order of magnitude or more and
were values not satisfying the demanded specifications of the
present apparatus at all.
[0233] On the other hand, when the electrodeposition tank 7009 was
made floating with respect to the ground as in Example 1, the
current to be supplied from the power supply 7008 was 7 A, as
described above, and there was little change of the current with
change in the distance between the anodes 7017 and the long
substrate 7001 to either of 10 mm and 25 mm. In addition, the
electrodeposited zinc oxide film was uniform and the uniform zinc
oxide film 1 .mu.m thick was able to be continuously formed on the
substrate at the conveyance speed of 1200 mm/min of the long
substrate 7001.
Example 2
[0234] As illustrated in FIG. 8, the lining 7068 of the Teflon
sheets 5 mm thick was provided inside the electrodeposition tank
7009 of Example 1, this electrodeposition tank 7009 was
incorporated as the electrodeposition tank 2009 in the
electrodeposition apparatus as illustrated in FIG. 2, and
electrodeposition was carried out therein.
[0235] The deposition rates of about 70 .ANG./s were achieved with
supply of the current of about 5 A from each of the power supplies
7008. The distance between the anodes 7017 and the long substrate
7001 was either of 10 mm and 25 mm and the electrodeposited zinc
oxide film was extremely uniform in either case. Further, the
uniform zinc oxide film 1 .mu.m thick was able to be continuously
formed on the long substrate 7001 at the conveyance speed of 850
mm/min of the long substrate 7001.
Example 3
[0236] Electrodeposition was carried out in similar fashion to that
in Example 2 except that the long substrate 7001 was made
electrically floating with respect to the ground. The electrical
floating of the long substrate 7001 was effected by using Delrin
bearings for the respective rollers.
[0237] The deposition rates of about 70 .ANG./s were obtained with
supply of the current of about 5 A from each of the power supplies
7008. The distance between the anodes and the substrate was either
of 10 mm and 25 mm and the electrodeposited zinc oxide film was
extremely uniform in either case. Further, the extremely uniform
zinc oxide film 1 .mu.m thick was able to be continuously formed on
the long substrate 7001 at the conveyance speed of 850 mm/min of
the long substrate 7001.
Example 4
[0238] The electrodeposition tank 7009 as illustrated in FIG. 9 was
incorporated as the electrodeposition tank 2009 in the
electrodeposition apparatus as illustrated in FIG. 2 and deposition
was carried out therein.
[0239] In FIG. 9, the electrodeposition tank 7009 is formed of SUS
and in the dual structure in which glass wool is put as a heat
insulator, thus having good heat-insulating and heat-retaining
properties. The long substrate 7001 of SUS430 is conveyed through a
slit formed in the both side walls of this electrodeposition tank
7009. Each of the both side wall portions of the electrodeposition
tank 7009 having the slit is double walls. The electrodeposition
bath 7016 retained in the electrodeposition tank 7009 is arranged
to overflow to drop into between the double walls. The
electrodeposition bath 7016 overflowing to drop into between the
double walls is guided through the unrepresented circulation system
to be used again as the electrodeposition bath 7016 herein. The
circulation amount was controlled so that the height from the
overflowing point to the bath surface became 35 mm.
[0240] The electrodeposition tank 7009 and the long substrate 7001
were made each electrically floating with respect to the ground,
independently of each other.
[0241] The electrodeposition bath 7016 was zinc nitrate of 0.2
mol/l and was kept at 80.degree. C. Zinc nitrate is for
electrochemically depositing zinc oxide on the surface of the long
substrate 7001 by cooperation of existing zinc ions or complex ions
and nitric ions. The electrodeposition bath 7016 contained dextrin
0.7 g/l in order to enhance uniformity of the zinc oxide film. The
electric conductivity of the electrodeposition bath 7016 was 65
mS/cm.
[0242] Four anodes 7017 were disposed inside the electrodeposition
bath 7016. These anodes 7017 are provided for advancing the
electrochemical reaction when the voltage is placed between the
anodes 7017 and the long substrate 7001. For formation of zinc
oxide, the potential of the anodes 7017 is maintained higher than
the potential of the long substrate 7001.
[0243] Each anode 7017 is disposed in the inside tank 7069 of PFA
having the thickness of 2 mm and the inside dimensions of 210
mm.times.120 mm. This structure prevents electric lines from
directly running from the anodes 7017 to the SUS electrodeposition
tank 7009. The anodes 7017 are connected to the respective separate
power supplies 7008, so as to be powered independently of each
other. The return of the current is implemented as a common return
from the power supply roller 7006 driven in contact with the long
substrate 7001. Each power supply 7008 was controlled as a constant
current source and the electrodeposition current density toward the
long substrate 7001 was arranged to be able to be set in the range
of 0.2 mA/cm.sup.2 to 30 mA/cm.sup.2 at each of the anodes
7017.
[0244] While the conveyance of the long substrate 7001 was stopped,
deposition was investigated at a standstill. The deposition rates
approximately proportional to the current, 1 to 200 .ANG./s, were
obtained by the current densities in the above range. The present
example employed the current density of about 10 mA/cm.sup.2. The
deposition rate achieved at a standstill was 80 .ANG./s. The size
of each anode 7017 was 110.times.200 mm in a surface opposed
normally to the long substrate 7001 and the thickness thereof was
20 mm. The anodes were of zinc having the purity of 4 N. A current
set value of each, power supply 7008 was about 2 A and the
power-supply voltages indicated 1.5 to 2.5 V.
[0245] The distance between the anodes 7017 and the long substrate
7001 was either of 10 mm and 25 mm and in either case the
electrodeposited zinc oxide film was extremely uniform. Further,
the uniform zinc oxide film 1 .mu.m thick was able to be
continuously formed on the long substrate 7001 at the conveyance
speed of 400 mm/min of the long substrate 7001.
Example 5
[0246] FIG. 4 is a schematic diagram showing an example of the
electrodeposition tank of the present invention. In FIG. 4, the
outside tank 4000 of the electrodeposition tank is formed of
stainless steel (SUS) and in the dual structure in which a heat
insulator of glass wool is interposed, thereby having good
heat-insulating and heat-retaining properties.
[0247] The long substrate 4002 is formed of a stainless steel belt
sheet (SUS430) and this substrate 4002 is conveyed through a slit
formed in each of the both side walls of the outside tank 4000 of
the electrodeposition tank.
[0248] Each of the side walls of the outside tank 4000 having the
slit is double walls and overflows 4007 and 4008 of the
electrodeposition bath 4001 retained in the tank are arranged to
drop into the space between the double walls. The overflowing bath
is returned to the unrepresented circulation system to be used
again as the electrodeposition bath 4001. With consideration to the
circulation amount, the height from the overflowing point to the
bath surface was set to 35 mm.
[0249] The electrodeposition bath 4001 is zinc nitrate of 0.2 mol/l
and is kept at 80.degree. C. Zinc nitrate makes zinc ions or
complex ions present in the bath and also makes nitric ions present
in the bath to electrochemically deposit zinc oxide on the surface
of the substrate by interaction of the ions. The electrodeposition
bath 4001 contains dextrin 0.7 g/l in order to enhance the
uniformity of zinc oxide film. The electric conductivity of the
electrodeposition bath 4001 was 65 mS/cm.
[0250] There are anode A 4003, anode B 4004, anode C 4005, and
anode D 4006 disposed in the electrodeposition bath 4001. The
voltage is placed between these anodes and the long substrate 4002,
whereupon the electrochemical reaction proceeds. For forming a film
of zinc oxide, the potential of the anodes has to be maintained
higher than the potential of the long substrate.
[0251] Each anode is covered by the inside tank of PFA 4011 to 4014
having the thickness of 2 mm and the inside dimensions of 210
mm.times.120 mm. This structure prevents electric lines from
directly running from the anodes to the stainless steel
electrodeposition outside tank 4000.
[0252] The anodes are connected to the respective separate power
supplies 4021 to 4024, so as to permit independent current to flow.
The return of the current is implemented as a common return from
the power-supply roller 4010 driven in contact with the long
substrate.
[0253] Each power supply is controlled as a constant current source
and the electrodeposition current density to the substrate 4002 is
arranged to be able to be set in the range of 0.2 mA/cm.sup.2 to 30
mA/cm.sup.2 at each anode.
[0254] While the conveyance of the long substrate 4002 was stopped,
deposition was investigated at a standstill. The deposition rates
approximately proportional to the current, 1 to 200 .ANG./sec, were
obtained by the current densities in the above range and the
present example employed the current density of about 10
mA/cm.sup.2. The deposition rate obtained in the deposition at a
standstill was 80 .ANG./sec.
[0255] The size of each anode was 100.times.200 mm in a surface
opposed to the long substrate 4002 and the thickness thereof was 20
mm. Each anode was formed of zinc having the purity of 4 N. At this
time, the current set value of each power supply was 2 A and the
power-supply voltages indicated 1.5 to 2.5 V.
[0256] In the present example, the electrodeposition outside tank
4000, together with the return path to the power supplies, was
connected to the common ground 4025. This configuration was
employed because the apparatus would have become expensive if the
apparatus should have been constructed by electrically insulating
all the rollers supporting the long substrate 4002. Insulation of
the large electrodeposition outside tank 4000 would also result in
increasing the cost similarly. If insulated, the tank has to be
constructed so as to be adapted for short-circuits due to water
drops or other contact objects.
Comparative Example 2
[0257] Prior to the investigation of Example 5, deposition was
carried out without the inside tanks 4011 to 4014 in the
electrodeposition bath 4001. As a result, the current density of
350 mA/cm.sup.2 was necessary for obtaining the deposition rate of
200 .ANG./sec. Namely, the current to be supplied from the power
supplies was 40 A, which was close to the capacity limit of the
power supplies.
[0258] Besides, deposition was very sensitive to the magnitude of
the distance between the anodes and the substrate. When the
distance between the anodes and the substrate was set to 10 mm,
heavily uneven patterns appeared in the film and large variations
of characteristics occurred when solar cells were made. When the
distance between the anodes and the substrate was increased to 50
mm in order to decrease the relative distance differences, the
deposition rates of film were decreased by an order of magnitude or
more, and were values not satisfying the required specifications of
the present apparatus at all.
[0259] On the other hand, where the inside tanks were disposed as
in Example 5, the current to be supplied from the power supplies
was 2 A, as described above, and there was little influence
appeared when the distance between the anodes and the substrate was
changed to either of 10 mm and 25 mm. As a result, the zinc oxide
film was uniform with only one interference ring in the deposition
area.
[0260] Further, in this case, the uniform zinc oxide film 1 .mu.m
thick was able to be formed on the substrate at the conveyance
speed 350 mm/sec of the long substrate 4002 and asperities of about
1 .mu.m were formed in this film.
Example 6
[0261] The inside tanks of Example 5 were replaced by the inside
tanks 5011 as illustrated in FIG. 5. In FIG. 5, a plurality of
openings 5038 to 5041 are bored in the bottom of the inside tank
5011. An intermediate control plate 5042 having a plurality of
openings 5035 to 5037 is disposed inside the inside tank 5011 and a
control plate 5043 having a plurality of openings 5031 to 5034 is
spaced above it. The spacing between the intermediate control plate
5042 and the control plate 5043 is set to be so small that the
electric resistance from the unrepresented anode disposed above the
upper control plate 5043 to the electrodeposition outside tank 4000
of such metal as stainless steel or the like is smaller than that
in the case without the inside tank 5011. On the other hand, this
spacing is set to be so large as to permit sufficient inflow and
outflow of the bath as indicated by an arrow in the figure.
[0262] Normally, the openings have the cross-sectional area not
less than the diameter of 2 mm and the spacing between the control
plates is 1 mm to 50 mm. In the present example each control plate
was perforated to have eleven openings of the diameter of 10 mm and
the PFA control plates 2 mm thick were spaced 2 mm apart from each
other.
[0263] Deposition was carried out in the electrodeposition
apparatus of the long substrate illustrated in FIG. 2, the
electrodeposition apparatus incorporating the inside tanks 5011 of
the present example instead of those in Example 5. The deposition
rate of 80 .ANG./sec was obtained with supply of the current of 3 A
from each power supply and the zinc oxide film was extremely
uniform even with change in the distance between the anodes and the
substrate to either of 10 mm and 25 mm.
[0264] Further, in this case, the extremely uniform zinc oxide film
1 .mu.m thick was able to be continuously formed on the substrate
at the conveyance speed 350 mm/sec of the long substrate 2001, and
asperities of about 1 .mu.m were formed in this film. When observed
in detail, the present example did not show fine stains, considered
to be traces of bubbles as seen in Example 1, and the air by air
bubbling was introduced into the inside tanks 5011 to effect
agitation of the bath, thereby implementing further excellent
uniformity of deposition.
Example 7
[0265] The inside tanks of Example 5 were replaced by the inside
tanks 6011 as illustrated in FIG. 6. In FIG. 6, the inside tank
6011 is formed of stainless steel (SUS304) 3 mm thick and in a box
shape opening up and the inside of the inside tank is lined with
sheets of polyvinylidene fluoride which is a fluororesin. The
lining was constructed so that the seams of this lining 6045 became
not more than 0.2 mm.
[0266] Opening 6043 and opening 6044 are formed in the upper part
of the side walls of this inside tank 6011 so as to permit inflow
and outflow of the bath. There is a fan 6046 in the bath outside
the opening 6043, so that the bath outside the inside tank 6011 can
be led into the inside tank 6011.
[0267] The resistance from the anode 6003 placed in the inside tank
6011 to the electrodeposition outside tank of stainless steel 4000
was 20 times greater than that in the case without this inside tank
6011. The flow rate of the bath by the fan 6046 was set to about
100 ml/min.
[0268] Deposition was carried out in the electrodeposition
apparatus of the long substrate illustrated in FIG. 2, the
electrodeposition apparatus incorporating the inside tanks of the
present example instead of those in Example 5. The deposition rate
of 80 .ANG./sec was obtained with supply of the current of 2.1 A
from each power supply and the extremely uniform zinc oxide film 1
.mu.m thick was able to be continuously formed on the substrate at
the conveyance speed 350 mm/sec of the long substrate 2001, as in
Example 6. Asperities of about 1 .mu.m were formed in this
film.
[0269] Since the electrodeposition tank 2009 of FIG. 2 is provided
with the active bath exchanging means, use of this
electrodeposition tank 2009 permits temperature irregularities and
concentration irregularities of the electrodeposition bath to be
decreased remarkably and permits replenishment of new bath and
removal of byproducts to take place effectively on the film-forming
interface, thereby greatly enhancing microscopic uniformity of
deposition.
Example 8
[0270] The electrodeposition tank formed of FRP was used in place
of the outside tank of the electrodeposition tank of Example 5. The
electrodeposition tank of FRP was formed of SMC (sheet molding
compound) containing glass fibers and unsaturated polyester. The
inside tanks all were removed.
[0271] This electrodeposition tank was incorporated into the
electrodeposition apparatus of the long substrate illustrated in
FIG. 2 and deposition was carried out in the electrodeposition
apparatus. The deposition rate of 70 .ANG./sec was obtained with
supply of the current of 2.3 A from each power supply and the
extremely uniform zinc oxide film 1 .mu.m thick was able to be
continuously formed on the substrate at the conveyance speed 300
mm/sec of the long substrate 2001, as in Example 6. Asperities of
about 1 .mu.m were formed in this film.
[0272] Use of the electrodeposition tank of the present example
permits us to employ the configuration without the inside tanks.
Particularly, in cases where the deposition rates are slow and some
film thickness is required, the total length of the
electrodeposition tank has to be set long; but many inside tanks do
not have to be installed in such cases and thus the total cost of
the electrodeposition apparatus can be decreased. Further, this
electrodeposition tank also has the industrial merits of easier
maintenance and easier action to an unforeseen accident by the
degree of simplicity of the structure.
Example 9
[0273] The outside tank 4000 of the electrodeposition tank of
Example 5 was equipped with the lining of ETFE film. The ETFE used
had the thickness of 50 .mu.m. Although the covering of ETFE was
not perfect only in part because of formation of air holes for the
air bubbling or the like, the electrical insulation of ETFE itself
was sufficient and the electric field from the anode to the
stainless steel electrodeposition tank was effectively intercepted
in most part. It was verified that 70% or more of the current
flowing to the anode without the inside tanks being disposed,
flowed toward the substrate. Measurement of current was carried out
by measuring the return current at the power supply part, using a
clamp ammeter.
[0274] On the occasion of incorporation of the tank into the
electrodeposition apparatus, all the inside tanks were removed, as
in Example 8.
[0275] The electrodeposition tank provided with this lining of ETFE
film was incorporated into the electrodeposition apparatus of the
long substrate illustrated in FIG. 2 and deposition was carried out
in the electrodeposition apparatus. The deposition rate of 60
.ANG./sec was obtained with supply of the current of 3 A from each
power supply and the extremely uniform zinc oxide film 2 .mu.m
thick was able to be continuously formed on the substrate at the
conveyance speed 200 mm/sec of the long substrate 2001, as in
Example 6. Asperities of about 1 .mu.m were formed in this
film.
[0276] Since the present example permits stainless steel to be used
for the outside tank 4000 of the electrodeposition tank, the tank
will experience little mechanical and chemical change with a lapse
of time and is extremely tough. The ETFE is readily available,
strong against high temperatures, and excellent in chemical
resistance as well, so that stable characteristics can be expected
over a long period. Further, the structure can be simple, because
the inside tanks do not have to be set, as in Example 8. Therefore,
the production cost can be decreased and the maintenance cost can
also be decreased.
Example 10
[0277] FIG. 1 is a schematic diagram showing an example of the
electrodeposition tank of the present invention.
[0278] In FIG. 1, the electrodeposition tank 1000 is formed of
stainless steel (SUS) and in the dual structure in which a heat
insulator of glass wool is interposed, thereby having good
heat-insulating and heat-retaining properties.
[0279] The long substrate 1002 is formed of a stainless steel belt
sheet (SUS430) and this substrate 1002 is conveyed through a slit
formed in each of the both side walls of the electrodeposition tank
1000.
[0280] Each of the side walls of the electrodeposition tank 1000
having the slit is double walls and overflows 1007 and 1008 of the
electrodeposition bath 1001 retained in the tank are arranged to
drop into the space between the double walls. The overflowing bath
returns through an unrepresented return path to electrodeposition
bath circulation tank 1025 and then is supplied again from bath
circulating pump 1024 through bath supply pipe 1023 to the
electrodeposition tank 1000. With consideration to the circulation
amount, the height from the overflowing point to the bath surface
was set to 35 mm.
[0281] For agitating the electrodeposition bath 1001, air is
introduced from agitating air inlet pipe 1022 to effect bubbling of
air from air blow pipe 1021 in the electrodeposition tank 1000.
[0282] All the piping systems connected to the electrodeposition
tank 1000 and placed in the electrodeposition tank 1000 are formed
of heat-resistant vinyl chloride to be electrically insulated from
the electrodeposition tank.
[0283] The electrodeposition bath 1001 is zinc nitrate of 0.2 mol/l
and is kept at 70.degree. C. Zinc nitrate makes zinc ions or
complex ions present in the bath and also makes nitric ions present
in the bath to electrochemically deposit zinc oxide on the surface
of the substrate by the substrate by interaction of the ions. The
electrodeposition bath 1001 further contains dextrin 0.7 g/l in
order to enhance the uniformity of zinc oxide film. The electric
conductivity of the electrodeposition bath 1001 was 65 mS/cm.
[0284] There are anode A 1003, anode B 1004, anode C 1005, and
anode D 1006 disposed in the electrodeposition tank 1000. The
voltage is placed between these anodes and the long substrate 1002,
whereupon the electrochemical reaction proceeds. For forming a film
of zinc oxide, the potential of the anodes has to be maintained
higher than the potential of the long substrate.
[0285] The anodes are connected to the respective separate power
supplies 1011 to 1014, so as to permit independent current to flow.
The return of the current is implemented as a common return from
the power-supply roller 1010 driven in contact with the long
substrate.
[0286] Each power supply is controlled as a constant current source
and the electrodeposition current density to the substrate 1002 is
arranged to be able to be set in the range of 0.2 mA/cm.sup.2 to
150 mA/cm.sup.2 at each anode.
[0287] While the conveyance of the long substrate 1002 was stopped,
deposition was investigated at a standstill. There appeared little
clogging of the circulation system due to the powder and film chips
and little difference among the deposition rates depending upon the
locations of the, anodes, and the deposition rates approximately
proportional to the current, 1 to 200 .ANG./sec, were obtained in
the above range of the current densities. The present example
employed the current density of about 60 mA/cm.sup.2. The
deposition rate obtained in the deposition at a standstill was 80
.ANG./sec.
[0288] The size of each anode was 100.times.200 mm in the surface
opposed to the long substrate 1002 and the thickness thereof was 20
mm. Each anode was made of zinc having the purity of 4 N. At this
time, the current set value of each power supply was 12 A and the
power-supply voltages indicated 2.5 to 3.5 V.
[0289] In the present example, the electrodeposition tank 1000,
together with the return path to the power supplies, is connected
to the common ground. This configuration was employed because the
apparatus would have become expensive if the apparatus should have
been constructed by insulating all the rollers supporting the long
substrate 1002. If insulated, the tank has to be constructed so as
to be adapted for short-circuits due to water drops or other
contact objects.
Comparative Example 3
[0290] Prior to the investigation of Example 10, deposition was
carried out by employing stainless steel piping systems as all the
piping systems connected to the electrodeposition tank 1000 and
disposed in the electrodeposition tank 1000. Since these piping
systems were made of stainless steel, they were grounded through
the electrodeposition tank. The current density of 300 mA/cm.sup.2
was necessary for obtaining the deposition rate of 200
.ANG./sec.
[0291] Namely, the current to be supplied from the power supplies
was 60 A, which was close to the capacity limit of the power
supplies. Besides, oxide films were deposited on the piping system
connected to the electrodeposition tank 1000 and on the piping
system placed inside the electrodeposition tank 1000, and there
appeared the powder, film chips, etc. due to peel-off of film
therefrom, thereby adversely affecting the system by clogging of
the circulation system or the like.
[0292] Deposition was very sensitive to the magnitude of the
distance between the anodes and the substrate. When the distance
between the anodes and the substrate was set to 10 mm, heavily
uneven patterns appeared in the film, and large variations of
characteristics occurred when solar cells were made. When the
distance between the anodes and the substrate was increased to 50
mm in order to decrease the relative distance differences, the
deposition rates of film were decreased by an order of magnitude or
more, and were values not satisfying the required specifications of
the present apparatus at all.
[0293] On the other hand, where the electrodeposition bath supply
pipe and air blow pipe were made as in the above example, the
current to be supplied from the power supplies was 12 A, as
described above, and there was little influence appeared when the
distance between the anodes and the substrate was changed to either
of 10 mm and 25 mm. As a result, the zinc oxide film was uniform
with only one interference ring in the deposition area.
[0294] Further, in this case, the uniform zinc oxide film with
asperities about 1 .mu.m thick was able to be continuously formed
in the thickness of 1 .mu.m on the substrate at the conveyance
speed 350 mm/sec of the long substrate 1002.
Example 11
[0295] All the piping systems connected to the electrodeposition
tank 1000 and disposed in the electrodeposition tank 1000 were FRP
piping systems, instead of the piping systems of Example 10.
[0296] The piping systems were incorporated into the
electrodeposition apparatus illustrated in FIG. 2 and deposition
was carried out in the electrodeposition apparatus. There appeared
little clogging of the circulation system due to the powder and
film chips and little difference among the deposition rates
depending upon the locations of the anodes. In addition, the
deposition rate of 60 .ANG./sec was obtained with supply of the
current of 10 A from each power supply and the uniform zinc oxide
film with asperities about 1 .mu.m thick was able to be
continuously formed in the thickness of 1 .mu.m on the substrate at
the conveyance speed 300 mm/sec of the long substrate 2001, as in
Example 10.
Example 12
[0297] The piping systems of Example 10 were replaced by piping
systems obtained by coating inside and outside surfaces of
stainless steel pipes or the like with Teflon.
[0298] The piping systems were incorporated into the
electrodeposition apparatus illustrated in FIG. 2 and deposition
was carried out in the electrodeposition apparatus. There appeared
little clogging of the circulation system due to the powder and
film chips and little difference among the deposition rates
depending upon the locations of the anodes. In addition, the
deposition rate of 70 .ANG./sec was obtained with supply of the
current of 15 A from each power supply and the uniform zinc oxide
film with asperities about 1 .mu.m thick was able to be
continuously formed in the thickness of 1 .mu.m on the substrate at
the conveyance speed 200 mm/sec of the long substrate 2001, as in
Example 11.
[0299] Since the present example can employ the metal material such
as stainless steel or the like for the piping systems, they can be
extremely tough against mechanical and chemical change with a lapse
of time.
Example 13
[0300] The piping systems of Example 10 were modified into the
structure as illustrated in FIG. 3, in which air blow pipe 3011,
agitating air inlet pipe B 3015, and electrodeposition bath supply
pipe 3016 in the figure were made of stainless steel whereas air
blow pipe joint 3012, agitating air inlet pipe A 3013, agitating
air inlet pipe joint 3014, and electrodeposition bath supply pipe
3017 were made of heat-resistant vinyl chloride. In FIG. 3,
reference numeral 3000 designates the deposition tank, 3001 the
deposition bath, 3021 the bath circulation pump, and 3022 the
electrodeposition circulation tank.
[0301] The piping systems of this configuration were incorporated
into the electrodeposition apparatus illustrated in FIG. 2 and
deposition was carried out in the electrodeposition apparatus.
There appeared little clogging of the circulation system due to the
powder and film chips and little difference among the deposition
rates depending upon the locations of the anodes. In addition, the
deposition rate of 72 .ANG./sec was obtained with supply of the
current of 17 A from each power supply and the uniform zinc oxide
film with asperities about 1 .mu.m thick was able to be
continuously formed in the thickness of 1 .mu.m on the substrate at
the conveyance speed 200 mm/sec of the long substrate 2001, as in
Example 11.
[0302] Since the present example can employ the metal material such
as stainless steel or the like for part of the piping systems, they
can be extremely touch against mechanical and chemical change with
a lapse of time.
[0303] As detailed above, the present invention can provide the
inexpensive electrodeposition tank and electrodeposition apparatus
that can prevent the oxide film to be deposited on the piping
system connected to the electrodeposition tank and on the piping
system disposed in the electrodeposition tank during formation of
the oxide film on the substrate, so as to suppress appearance of
the powder, film chips, etc. in the bath and that can evenly form
the uniform oxide film without irregularities on the substrate.
[0304] The electrodeposition apparatus according to the present
invention can be obtained readily by making use of the existing
apparatus.
[0305] The present invention permits formation of the oxide film
suitable for the reflecting layer of the solar cell or the like.
Particularly, the invention can provide the inexpensive
electrodeposition tank that can remarkably enhance the uniformity
of film and the film characteristics in the formation of zinc oxide
on the long substrate, and also provide the inexpensive
electrodeposition apparatus provided with the tank. Further, it can
facilitate the maintenance of the tank and apparatus.
* * * * *