Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Forming nonmetal coating
Reexamination Certificate
2001-07-05
2003-10-14
King, Roy (Department: 1742)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Forming nonmetal coating
C205S133000, C205S134000, C205S148000, C205S305000, C205S101000
Reexamination Certificate
active
06632346
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for electrodepositing a zinc oxide film which can be applied as a functional film to electronic devices such as a solar cell, and specifically to improvement of an electrodeposition process for obtaining an uniform zinc oxide film having no defect.
2. Related Background Art
U.S. Pat. No. 5,804,466 (“Process for production of zinc oxide thin film, and process for production of semiconductor device substrate and process for production of photoelectric conversion device using the same film”, filed by Canon Kabushiki Kaisha on Sep. 8, 1998) discloses a process for forming a zinc oxide thin film, which comprises immersing a substrate and a counter electrode in an electrodeposition bath containing zinc nitrate maintained at a temperature of 50° C. or more and applying current between the substrate and the counter electrode to form a zinc oxide thin film on the substrate.
The above-described process is different from a sputtering process and a vacuum process, for example, a vacuum heating vapor deposition or chemical vapor deposition (CVD) method and makes it possible to form a zinc oxide film having at a low cost. The above-described process can form a film having an uneven surface with good controllability, and therefore when this process can be applied to formation of a reflection layer of a solar cell or an intermediate layer thereof, it is possible to utilize the optical confinement effect, thereby improving the efficiency of the solar cell. Further, this process makes it possible to produce a production apparatus of for a long substrate made of a metal at a low cost, and therefore this process can provide, for example, an excellent reflection layer in formation of a sola cell device.
On the basis of the idea as described above, the present inventors actually attempted to deposit a zinc oxide film on a long substrate such as of stainless steel (SUS) which was wound off from the substrate wound in a coil-like state.
FIG. 2
is a schematic view for showing a general structure of an apparatus for depositing an oxide film by an electrodepositing method on the basis of the idea as described above. Its dividedly enlarged views are also given in
FIGS. 3
to
9
. In FIG.
2
and
FIGS. 3
to
9
, names and reference numerals of respective members are common. A procedure for forming or depositing an electrodeposited film on a long substrate by means of this apparatus is described below with reference to these drawings.
Roughly sectioned, the apparatus consists of a wind-off unit
2012
from which a long substrate wound in a coil-like state is wound off, a first electrodeposition tank
2066
in which a first electrodeposition film is deposited or treated, a second electrodeposition tank
2166
in which a second electrodeposition film is deposited or treated, a first circulation tank
2120
from which a heated electrodeposition bath is circulatingly fed to the first electrodeposition tank, a second circulation tank
2222
from which a heated electrodeposition bath is circulatingly fed to the second electrodeposition tank, a first waste-solution tank
2172
in which the electrodeposition bath is temporarily stored before the electrodeposition bath of the first electrodeposition tank is discharged, a second waste-solution tank
2274
in which the electrodeposition bath is temporarily stored before the electrodeposition bath of the second electrodeposition tank is discharged, a filter circulation system for removing particles in the electrodeposition bath held in the first electrodeposition tank to make the bath clean (a piping system connected to a first electrodeposition tank filter circulation filter
2161
), a filter circulation system for removing particles in the electrodeposition bath held in the second electrodeposition tank to make the bath clean (a piping system connected to a second electrodeposition tank filter circulation filter
2263
), a piping system for sending bath-stirring compressed air to both the first electrodeposition tank and the second electrodeposition tank (a piping system extending from a compressed air feed inlet
2182
), a pure-water shower tank
2360
in which the long substrate on which the electrodeposition film has been deposited is washed with a pure-water shower, a first hot-water tank (which here is called “hot water” since hot water is used for the pure water of a rinsing tank)
2361
in which first pure-water rinsing is carried out, a second hot-water tank
2362
in which second pure-water rinsing is carried out, a pure-water heating tank
2339
from which necessary hot pure-water is fed to these hot-water tanks, a drying section
2363
which dries the long substrate having a film formed thereon (film-deposited substrate) after it has been washed, a wind-up unit
2296
for winding again in a coil-like state the long substrate on which film deposition has been completed, and an exhaust system for discharging water vapor generated at the stage of heating the electrodeposition bath or pure water and at the stage of drying (an exhaust system constituted of an electrodeposition water washing system exhaust duct
2020
or a drying system exhaust duct
2370
).
The long substrate is transported from the left to the right as viewed in the drawing, that is, in the order of the wind-off unit
2012
, the first electrodeposition tank
2066
, the second electrodeposition tank
2116
, the pure-water shower tank
2360
, the first hot-water tank
2361
, the second hot-water tank
2362
, the drying section
2363
and the wind-up unit
2296
, so that a predetermined electrodeposition film is deposited.
As shown in
FIG. 3
, a long substrate
2006
wound on a long substrate bobbin
2001
in a coil-like state is set in the wind-off unit
2012
, and the long substrate
2006
is wound off through a feed control roller
2003
, a direction-changing roller
2004
and a delivery roller
2005
in this order. Especially when a subbing layer is previously deposited on the long substrate to be wound in a coil-like state, the substrate is supplied in the form where an interleaf (interleaving paper) has been rolled up together with the substrate so that the substrate or the previously formed layer can be protected. Accordingly, in the case where the interleaf has been rolled up, an interleaf
2007
is wound up on an interleaf wind-up bobbin
2002
while the long substrate is wound off. The direction in which the long substrate
2006
is transported is shown by an arrow
2010
, the direction in which the long substrate bobbin
2001
is rotated is shown by an arrow
2009
, and the direction in which the interleaf wind-up bobbin
2002
is wound up is shown by an arrow
2008
.
FIG. 3
shows that the long substrate delivered from the long substrate bobbin
2001
and the interleaf wound up on the interleaf wind-up bobbin
2002
are not interfered with each other at the transport-starting position and the transport-ending position. For the purpose of dust-proofing, the whole wind-off unit is so structured as to be covered with a wind-off unit clean booth
2011
making use of a HEPA (high-frequency particulate air) filter and a down flow.
The first electrodeposition tank
2066
comprises, as shown in
FIG. 4
, a first electrodeposition bath holder tank
2065
which is not corrosive against the electrodeposition bath and can keep the temperature of the electrodeposition bath, and in that tank a temperature-controlled electrodeposition bath is so held as to have a first electrodeposition bath surface
2025
. The position of this bath surface is realized by an over flow attributable to a partition plate provided inside the first electrodeposition bath holder tank
2065
. The partition plate (not shown) is so installed that the electrodeposition bath is let fall toward the inner-part side by the whole first electrodeposition bath holder tank
2065
. The overflowed electrodeposition bath collected in tub structure in a first electrodeposition tank overflow return opening
2024
comes through a first electr
Arao Kozo
Miyamoto Yusuke
Sonoda Yuichi
Toyama Noboru
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
King Roy
Nicolas Wesley A.
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