Stock material or miscellaneous articles – All metal or with adjacent metals – Having composition – density – or hardness gradient
Reexamination Certificate
2001-07-09
2003-04-29
Koehler, Robert R. (Department: 1775)
Stock material or miscellaneous articles
All metal or with adjacent metals
Having composition, density, or hardness gradient
C101S395000, C101S459000, C148S438000, C148S439000, C148S440000, C148S902000, C205S069000, C428S654000, C428S687000, C428S926000
Reexamination Certificate
active
06555247
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an aluminum alloy plate for A planographic printing plate which includes a lithographic printing plate, and more particularly to an aluminum alloy plate for a planographic printing plate which is used for a PS(presensitized) printing plate having a photosensitive layer previously formed thereon and subjected to either a developing treatment or both the developing treatment and a printing treatment of the photosensitive layer.
In planography, a PS printing plate which has a photosensitive layer previously formed thereon and is subjected to either a developing treatment or both developing and printing treatments has been widely used. The PS printing plate has a rough surface on which a photosensitive agent is coated. The PS printing plate is generally made of JIS 1050-type aluminum alloy increased in electrolytic etching properties.
The PS printing plate is manufactured by subjecting the aluminum alloy to predetermined steps, during which the printing plate is subjected to a surface treatment prior to coating of the above-described photosensitive agent thereon. The surface treatment is carried out by subjecting the printing plate to a surface roughing treatment by electrolytic etching and then forming an oxide film on the thus-roughed surface of the printing plate by anodizing. Also, in the manufacturing, washing by a caustic treatment or the like takes place on the printing plate for degreasing of the plate or the like prior to the surface roughing treatment.
The surface roughing treatment is carried out in order to ensure that the photosensitive agent is securely fixed onto the printing plate during formation of the photosensitive layer while being adhered therewith. Such adhesion significantly affects performance of the printing plate.
Unfortunately, the surface roughing treatment described above which has been conventionally practiced causes unetching to occur on the roughed surface of the plate or causes pits formed by the surface roughing treatment to be non-uniformly distributed on the roughed surface, leading to a deterioration in performance of the printing plate. Thus, it is desired to develop techniques of providing a roughed surface free from such defects as described above.
In the past, improvements have been proposed from a viewpoint of a material for the plate in order to eliminate the above-described disadvantages. One of the improvements is adding specific elements to the material. For example, techniques of adding a predetermined amount of Ni to the material to promote formation of pits, to thereby enhance etching properties of the material are proposed, as disclosed in Japanese Patent Application Laid-Open Publication No. 115333/1999 by way of example. Another proposal of adding Sn, In and Ga to the material to form it with fine pits, leading to an improvement in etching properties of the material is disclosed in Japanese Patent Application Laid-Open Publication No. 210144/1983.
However, such addition of specific elements to the material as proposed fails to satisfactorily solve the above-described problems encountered in the prior art. Also, it causes an increase in manufacturing cost of the printing plate and is an obstacle to recycling of the material.
Techniques of controlling a size of intermetallic compounds in the material and density thereof to improve etching properties of the material without adding any specific element thereto are proposed as well (Japanese Patent Application Laid-Open Publication No. 151870/1999). In the techniques proposed, it is considered that the intermetallic compounds act as a starting point in etching of a printing plate, to thereby permit fine pits to be uniformly formed on the printing plate. However, the techniques likewise fail to satisfactorily improve etching properties of the printing plate, resulting in failing to meet the above-described demand.
As a result of careful study by the inventor, it was found that the reasons why control of a size of the intermetallic compounds and density thereof described above fails to provide the printing plate with satisfactory etching properties are due to the fact that chemical solubility of the intermetallic compounds is increased as compared with expectation, to thereby be readily vanished due to dissolution thereof in an electrolyte, resulting in failing to sufficiently function as a starting point for formation of the etching pits. Also, as a result of a further advance of the study, it was also found that suitable dispersion of particles of an AlFe-based intermetallic compound which has a metastable phase contrary to the above-described compound which has a stable phase in the printing plate permits etching properties thereof to be substantially improved to a degree sufficient to meet the above-described demand.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing disadvantages of the prior art, while taking notice of the above-described facts.
Accordingly, it is an object of the present invention to provide an aluminum alloy plate for a planographic printing plate which is capable of eliminating addition of any special element thereto during a surface roughing treatment.
It is another object of the present invention to provide an aluminum alloy plate for a planographic printing plate which is capable of being provided with a roughed surface reduced in formation of an unetched portion thereon and uniformly formed thereon with pits.
It is a further object of the present invention to provide an aluminum alloy plate for a planographic printing plate which is capable of providing a PS printing plate exhibiting enhanced performance.
The term “percent, ppm” and the like as used herein in connection with a content of ingredients and the like will refer to “percentage, ppm” and the like in a mass ratio unless otherwise specified.
In accordance with the present invention, an aluminum alloy plate for a planographic printing plate is provided. The aluminum alloy plate contains, in a mass ratio, 0.1 to 0.6% of Fe, 0.01 to 0.2% of Si, 5 ppm to 150 ppm of Cu, and balance of Al and unavoidable impurities. Also, the aluminum alloy plate has a surface layer portion formed of a dispersion layer of a metastable phase in which AlFe-based intermetallic compound particles of a metastable phase are dispersed.
In a preferred embodiment of the present invention, the dispersion layer contains, in a plane direction, the metastable phase AlFe-based intermetallic compound particles in a ratio of 5/100 or more to the number of AlFe-based intermetallic compound particles of a stable phase.
In a preferred embodiment of the present invention, the dispersion layer is constructed in a plane direction so that of the intermetallic compound particles, particles (a in number) satisfying the following expression A and those (b in number) satisfying the following expression B have relationship therebetween which satisfies the following expression C:
Al quantity/Fe quantity≦1.6 . . . A
Al quantity/Fe quantity>1.6 . . . B
b/a≧0.05 . . . C
In a preferred embodiment of the present invention, the dispersion layer has a depth extending by 2 to 50 &mgr;m from a surface thereof.
In a preferred embodiment of the present invention, the dispersion layer is so constructed that the intermetallic compound particles of 0.1 &mgr;m or more in particle diameter corresponding to a circle have an average particle diameter within a range of from 0.2 to 2.0 &mgr;m.
In a preferred embodiment of the present invention, the dispersion layer has the intermetallic compound dispersed at density of 3000 to 30000 in number per mm
2
in a plane direction.
In a preferred embodiment of the present invention, Cu is contained in an amount of 10 ppm to 40 ppm in a mass ratio.
In a preferred embodiment of the present invention, the aluminum alloy plate further contains, in a mass ratio, 0.004 to 0.1% of Zr and 0.004 to 0.1% of at least one selected from the group consisting of Sn, In and Zn in total.
In a preferred embodiment of the present invention, Zr and
Anderson Kill & Olick
Koehler Robert R.
Lieberstein Eugene
Meller Michael N.
Mitsubishi Aluminum Kabushiki Kaisha
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