Electrolysis: processes – compositions used therein – and methods – Electrolytic erosion of a workpiece for shape or surface... – Simple alternating current
Reexamination Certificate
2002-02-12
2004-08-24
Valentine, Donald R. (Department: 1742)
Electrolysis: processes, compositions used therein, and methods
Electrolytic erosion of a workpiece for shape or surface...
Simple alternating current
C205S660000, C205S674000, C205S685000
Reexamination Certificate
active
06780305
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing a support for planographic printing plates, to a support for planographic printing plates, and to a planographic printing plate precursor. In particular, the invention relates to a method for producing a support for planographic printing plates, in which aluminum plates produced from regenerated aluminum ingots such as those from scrapped and recycled aluminum can be used for the material; to a support for planographic printing plates, which is produced according to the method; and to a planographic printing plate precursor, which is fabricated by forming a thermosensitive or photosensitive plate layer on the surface of the support for planographic printing plates.
The invention also relates to an aluminum plate for planographic printing plate supports, which is used as the material in the above-mentioned production method; to a planographic printing plate support formed from the aluminum plate; and to a method for inspecting aluminum plates for planographic printing plate supports. In particular, the invention relates to an aluminum plate for planographic printing plate supports, which is inexpensive and which, when processed into planographic printing plate precursors in a sequential process of roughening its surface followed by forming a plate layer thereon, is almost free from the trouble of feed disorder such as meandering, and which is therefore favorable to the production of planographic printing plate precursors; to a planographic printing plate support formed from the aluminum plate; and to a method for inspecting aluminum plates for planographic printing plate supports, in which a roll of a rolled aluminum plate fed into a device to be processed into planographic printing plate supports is inspected as to whether or not it is likely to encounter the feed disorder as described above by the use of a simple tool in a simplified manner.
2. Description of the Related Art
In general, a planographic printing plate precursor is fabricated in a process that comprises roughening the surface of a pure aluminum or aluminum alloy plate (this is hereinafter referred to as “aluminum plate”), then subjecting the surface thereof to anodic oxidation to thereby form an oxide film thereon to give a planographic printing plate support, and applying a photosensitive or thermosensitive resin onto the surface of the oxide film formed on the planographic printing plate support to thereby form a photosensitive or thermosensitive plate layer thereon. The photosensitive resin layer and the thermosensitive resin layer that are optionally combined with an undercoat layer and a protective layer are known, for example, in JP-A 62333/2000, 101651/1984 and 149491/1985.
Images including letters and pictures are printed on the plate layer of the planographic printing plate precursor, and they are developed thereon to complete a planographic printing plate.
For roughening the surface of an aluminum plate, for example, the plate surface is mechanically processed with a brush roller having nylon hair or the like or with a roughening roller of which the surface is made of an abrasive cloth (mechanical surface roughening); or chemically processed in an alkaline solution (etching); or electrolytically processed in an acidic electrolyte (electrolytic solution) by applying an alternating current to the aluminum plate serving as one electrode therein (AC electrolysis).
For ensuring good water balance in printing, in general, the plate surface is first mechanically roughened, then etched and electrolytically roughened.
After the step of electrolytic surface roughening and the step of chemical surface roughening thereof, the aluminum plate may be optionally desmutted by dipping it in an acid solution to thereby remove oxides, hydroxides and intermetallic compounds of the elements that may be deposited in the aluminum plate as a result of the process of electrolytic surface roughening and chemical surface roughening.
Regenerated aluminum ingots such as those from scrapped and recycled aluminum are more inexpensive than virgin ones, and the energy consumption at the time of production thereof is relatively small. Therefore, producing planographic printing plate precursors from aluminum plates that are prepared from such regenerated aluminum ingots is favorable in point of cost and energy saving and even in point of natural resource saving.
Different from virgin ones, however, adequate control on the alloy components is hardly done for regenerated aluminum ingots (that is, their aluminum purity is no higher than 97% by weight) and the aluminum ingots contain various impurities.
Therefore, various intermetallic compounds and deposits that result from the impurities are exposed out on the surface of the aluminum plates produced from such regenerated aluminum ingots, and the planographic printing plate precursors formed from these aluminum plates often involve defects in the oxide film thereof formed through anodic oxidation. The defects often cause serious ink stains in which ink is attached spotwise on the entire surface of printed matters.
Another problem with aluminum plates that contain many impurities, such as those produced from regenerated aluminum ingots, is that their surfaces are difficult to evenly roughen in an electrochemical process, and, when electrochemically processed, their surfaces are unevenly roughened. Therefore, when such aluminum plates are used in fabricating printing plates and when the thus-fabricated printing plates are used in printing units, ink tends to adhere to and stain the blanket of offset rollers (blanket staining), and then it is transferred onto printed papers to stain them.
In the electrolytic surface-roughening step in the process of producing planographic printing plate supports, used is an alternating current or a direct current. In particular, in case where an alternating current is used in the step, the profile of the roughened surface of the supports often varies greatly, depending on the waveform of the current employed, and when the composition of the aluminum material for the supports is varied, it is often difficult to keep the intended profile of the roughened surface of the supports in a predetermined range. This is one problem with the electrolytic surface-roughing process, and to solve it, the waveform of the current to be employed in the process must be strictly controlled.
In addition, when planographic printing plate precursors are produced from recycled aluminum, scrapped aluminum, and regenerated ingots such as those mentioned above, the mechanical properties thereof greatly vary. When such planographic printing plate precursors are exposed to light, developed and processed into printing plates by the use of an automatic photomechanical device, and when the resulting planographic printing plate is set around the blanket in a planographic offset printer, the planographic printing plate may be involved with various problems. Concretely, the printing plate set in a printer often causes paper feeding disorder such as paper entangling or meandering, and it is often lifted up from the blanket and cannot be well fitted thereto.
Aluminum webs are produced by hot-rolling a cast slab of aluminum and then cold-rolling it to have a predetermined thickness. In general, they are stored and delivered in the form of rolls, after coiled up around roll cores.
In general, aluminum ingots are so rolled into webs that the center part of the resulting webs is thicker than the edges thereof. This is in order that the edges of the aluminum web wound up in coils are prevented from being deformed when roughly contacted with each other.
However, when aluminum ingots are so rolled into webs that the center part of the resulting webs is thicker than the edges thereof, the edges are elongated larger than the center part, and, as a result, the edges are often waved or slacked in the wavy manner (which wavy deformation at the edge portions will be referred to as the “edge strain” he
Masuda Yoshitaka
Nishino Atsuo
Sawada Hirokazu
Uesugi Akio
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