Electrolysis: processes – compositions used therein – and methods – Electrolytic erosion of a workpiece for shape or surface... – Simple alternating current
Reexamination Certificate
1999-06-24
2001-04-24
Gorgos, Kathryn (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic erosion of a workpiece for shape or surface...
Simple alternating current
C205S658000, C204S211000, C204S230600, C204S242000, C204SDIG009
Reexamination Certificate
active
06221236
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an apparatus and method for electrolytic treatment which comprises etching a metal web electrolytically using alternating waveform current continuously, and particularly, relates to an apparatus and method for electrolytic treatment suitable for electrolytic etching of aluminum web during manufacturing a support for planographic printing plate.
Electrolytic etching of a surface of aluminum, iron or the like is widely utilized, and alternating waveform current is generally used due to required quality and the improvement in reaction efficiency. For example, Japanese Patent KOKOKU 56-19280 discloses an electrolytic etching treatment which can provide excellent roughening as a support for an offset printing plate by using an alternating waveform current impressed to that the electric voltage at anode is made greater than the electric voltage at cathode in electrolytic roughening of an aluminum plate.
In general, electrolytic etching is carried out at a current density of 10 to 100 A/dm
2
in an acidic electrolytic solution, such as 1 to 5% nitric acid or hydrochloric acid. Upon treating electrolytically an aluminum plate as the metal web, Al→Al
3+
+3e dissolution reaction occurs at an anode period, and H
+
|e; (½)H
2
↑ hydrogen gas generation reaction and Al
3+
+3OH→Al(OH)
3
aluminum hydroxide smut formation reaction occur simultaneously at a cathode period on the aluminum plate.
These reactions occur alternately according to the frequency of power supply, and, in general, it is possible to obtain a required roughened surface by adjusting these fundamental reactions by controlling electrolytic conditions, such as the type and concentration of electrolytic solution, temperature conditions, current density and charged quantity of electricity.
Hereupon, in the case of using alternating waveform current, there are necessarily differences between the treatment initiating part by the dissolution reaction and the terminating part caused by the current cycle on entering a metal web into an electrolytic bath and on going out of the bath. These differences generate according to the frequency of a power supply. For example, in the case of a treating speed of 50 m/min and a frequency of power supply of 60 Hz, the differences generate at an interval (pitch) of 1.39 cm in the longitudinal direction of the metal web. In view of massproduction, a higher treating speed and a higher current density treating speed and a higher current density treatment are desired. In the case of high strength aluminum support containing manganese or the like which recently increases, there is a tendency to manufacture a high quality support for planographic printing plate by lowering frequency.
On the other hand, the degree of the above mentioned ununiformity according to the frequency of power supply becomes stronger by higher treating speed, higher current density or lower frequency due to its generation mechanism.
In this regard, Japanese Patent KOKAI 1-230800 discloses an electrolytic apparatus provided with low current density zones at the entrance and exit, i.e. the front end and rear end of an electrode, and Japanese Paten KOKAI 4-289200 discloses a roughening method using a power supply frequency of 1 to 30 Hz.
However, according to the conventional methods mentioned above, the ununiformity according to the frequency cannot be removed entirely in the case of high treating speed, high current density or variation of electrolytic solution conditions.
SUMMARY OF THE INVENTION
An object of the invention is to provide an electrolytic treatment apparatus and an electrolytic treatment method which remove the ununiformity according to the frequency and can achieve high treating speed and high current density treatment.
The inventors investigated eagerly as to the nonuniformity of metal web according to the frequency, and as a result, they found that there is a special frequency capable of reducing the ununiformity under prescribed conditions, such as treating speed and current density.
That is, as mentioned previously, electrolytic conditions, i.e. the type, concentration and temperature of the electrolytic solution used, current density, charged quantity of electricity, electrolytic treatment period, frequency and the like are set so as to obtain a required roughened surface. Heretofore, the frequency was set usually by a unit of 10 Hz, such as 40 Hz, 50 Hz or 60 Hz. The inventors found that there is an optimum frequency which is slipped from the above magnification of 10 Hz or the like.
Thus, the present invention provides an apparatus for electrolytic treatment which comprises etching a metal web electrolytically using alternating waveform current continuously, wherein a frequency-variable means having an ability to vary frequency of an electric power supply of said alternating waveform current arbitrarily is provided, and a method for electrolytic treatment which comprise etching a metal web electrolytically using alternating waveform current continuously, wherein frequency of said alternating waveform current is other than a magnification of 10 Hz but produces optimum ununiformity.
REFERENCES:
patent: 4315806 (1982-02-01), Arora
patent: 4482434 (1984-11-01), Pliefke
patent: 5082537 (1992-01-01), Stroszynski et al.
patent: 5755949 (1998-05-01), Amor
patent: 0 390 033 (1990-10-01), None
patent: 0 585 586 (1994-03-01), None
Hirokawa Tsuyoshi
Matsuura Atsushi
Yamazaki Toru
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Gorgos Kathryn
Keehan Christopher M.
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