Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
1999-02-05
2002-05-14
Wyszomierski, George (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
C148S552000
Reexamination Certificate
active
06387198
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing an aluminum alloy substrate for a lithographic printing plate which has a necessary strength and a uniform grainable surface, and which shows, after graining, substantially no streak patterns formed by streaks, etc., and a uniform appearance.
2. Description of the Related Art
Generally, an aluminum alloy sheet 0.1 to 0.5 mm thick (JIS 1050, etc.) has been used as an aluminum alloy substrate for a lithographic printing plate. Such an aluminum alloy sheet has usually been produced by scalping an ingot obtained by semicontinuous casting so that the surface portion is removed, homogenizing the scalped ingot, hot-rolling the homogenized ingot, cold-rolling the hot-rolled plate, intermediate-annealing the cold-rolled plate, and finally cold-rolling the annealed plate.
The aluminum alloy substrate for a lithographic printing plate thus produced is grained by either one of or a combination of at least two of the following steps: a mechanical step, a chemical step and an electrochemical step. The grained aluminum alloy substrate is further anodized, and optionally subjected to hydrophilic treatment to give a lithographic printing plate support. The substrate is further coated with a photosensitive material to form a photosensitive layer, and is optionally subjected to a heating-burning treatment so that the photosensitive layer is strengthened, to give a photosensitive lithographic printing plate.
The lithographic printing plate is then successively subjected to treatment for producing a printing plate such as image exposure, development, water washing and lacquering to give a printing original plate. The photosensitive layer remaining still undissolved after the development is water repellent, and forms image areas as an ink-accepting portion which selectively accepts ink alone; the surface of the aluminum alloy support under the photosensitive layer is exposed in the portion where the photosensitive layer is dissolved, and the portion forms nonimage areas as a water-accepting portion due to its hydrophilic property. In development, the quality of the development is judged by visually observing the developed surface. Accordingly, an aluminum alloy substrate having a highly uniform surface which does not hinder the visual judgment is required.
When printing is to be carried out, both end portions of the printing original plate are bent, gripped in the original plate fixtures of the printing drum of a printer, and fixed. Accordingly, the substrate for a lithographic printing plate must be excellent in bendability and mountability on a printing drum, and hardly forms cracks in the bent portion during printing.
When dampening water is supplied to the original plate which is fixed as explained above, the water is held in nonimage areas alone where the photosensitive layer is removed and a hydrophilic alloy substrate surface is exposed, and it is not held in image areas where a water repellent photosensitive layer surface remains. When ink is supplied to the original plate surface in such a state, the ink adheres to the image areas alone, and is held there. The ink adhering to and being held in the image areas is further transferred to a bracket drum, and then it is transferred to a surface to be printed such as a paper sheet surface from the bracket drum, whereby printing is conducted.
Sometimes the number of prints is as many as 100,000, for example. The lithographic printing plate support must have a property of resisting transferring as many times as mentioned above, namely, resistance to printing. At the same time, the original plate must not form cracks in a bent portion as explained above, and the original plate used after burning must have a high proof stress and must not be shifted from a printing drum. Moreover, the original plate must have a water retention property for sufficiently holding dampening water so that ink does not adhere to nonimage areas. Furthermore, when pitting corrosion is produced in nonimage areas with dampening water, ink adheres to the nonimage areas during printing, which results in scumming or tinting of printed materials. Accordingly, in order to prevent scumming or tinting during printing, it is important to ensure corrosion resistance as well as water retention of the original plate. In order to ensure these properties, it is necessary to obtain an excellent uniformity of the grained surface, by graining treatment such as electrochemical treatment, and resistance to corrosion and a defectless anodic oxide film of the support.
Japanese Examined Patent Publication (Kokoku) No. 5-28197 discloses a process for producing an aluminum alloy substrate for a lithographic printing plate which shows less scumming or tinting, comprising the steps of: holding an ingot, as a homogenizing treatment, at temperature of 460 to 600° C., desirably 520 to 600° C. for at least 1 hour, hot-rolling the ingot with at least several rolling passes so that recrystallization and precipitation are repeated, the hot rolling being completed at temperatures of at least 300° C., and cold-rolling the hot-rolled plate while the cold-rolled plate is intermediate-annealed during cold rolling by heating the plate to a selected temperature of 400 to 600° C. and rapidly cooling the plate at a rate of at least 500° C./sec so that precipitation of metallic Si is inhibited.
Japanese Unexamined Patent Publication (Kokai) No. 8-179496 discloses a process for producing an aluminum alloy substrate for a lithographic printing plate excellent in visible image formability in exposure and development, wherein homogenizing is conducted at temperatures of 500 to 600° C., rough hot-rolling is started at a temperature of 430 to 480° C., hot rolling is repeated with a plurality of passes so that dynamic recrystallization is caused, rough hot rolling is finished at a temperature of 380 to 430° C. to give a plate having a thickness of 10 to 35 mm, and finish hot-rolling is completed at a temperature of 260 to 350° C. to form a fine recrystallized structure.
Japanese Unexamined Patent Publication (Kokai) No. 62-148295 discloses a process for producing an aluminum alloy substrate for a lithographic printing plate, comprising the following procedures: an aluminum alloy is homogenized at temperatures of 500 to 600° C. for at least 3 hours, and cooled to a temperature up to 430° C. at a rate up to 50° C./h or the alloy is held at temperatures of 350 to 450° C. for at least 30 minutes, so that precipitation of metallic Si is inhibited by precipitating Si contained in the alloy as Al—Fe—Si compounds and the occurrence of scumming or tinting is decreased; the alloy is hot-rolled at temperatures of 450 to 200° C. to prevent the recrystallized grains from becoming as coarse as at least 100 &mgr;m among passes and to inhibit the formation of streak patterns. In addition, the intermediate annealing subsequent to hot rolling is conducted by holding the plate at temperatures of 350 to 500° C. for 2 to 5 hours, or passing the plate through a temperature region of 400 to 550° C. in a continuous annealing furnace for a time up to 120 sec.
Japanese Unexamined Patent Publication (Kokai) No. 61-201747 discloses a process for producing an aluminum alloy substrate for a lithographic printing plate wherein the core region of the substrate is made a stripe-like rolled structure to decrease the strength lowering of the photosensitive layer subsequent to burning, by starting hot rolling at a temperature of 480 to 550° C., and finishing hot rolling at a temperature of at least 320° C. so that the hot-rolled plate has a thickness of 2.5 to 3.5 mm.
Any of the conventional technologies mentioned above form a fine and uniform grain structure in the substrate by repeating recrystallization during hot rolling.
In particular, the support for a lithographic printing plate has been required to have uniformity in appearance where no streak patterns such as streaks are substantially observed, so that a uniform grained surface can be obtai
Mizushima Kazumitsu
Nishikawa Yasuhisa
Sakaki Hirokazu
Sawada Hirokazu
Suzuki Hideki
Combs-Morillo Janelle
Lackenback Siegel LLP
Nippon Light Metal Co. Ltd.
Nissen J. Harold
Wyszomierski George
LandOfFree
Process for producing aluminum alloy substrate for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing aluminum alloy substrate for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing aluminum alloy substrate for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2816776