Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-09-15
2003-05-06
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031580, C106S031600, C106S031860
Reexamination Certificate
active
06558458
ABSTRACT:
FIELD OF THE INVENTION
The systems and methods described herein relate to a process for fabricating a lithographic printing plate using ink jet technology.
BACKGROUND OF THE INVENTION
Lithography and offset printing methods have long been combined in a compatible marriage of great convenience for the printing industry for economical, high speed, high quality image duplication in small runs and large. Known art available to the industry for image transfer to a lithographic plate is voluminous but dominated by the photographic process wherein a hydrophilic plate is treated with a photosensitive coating, exposed via a film image and developed to produce a printable, oleophilic image on the plate.
While preparing lithographic plates by photographic image transfer is relatively efficient and efficacious, it is a multi-step, indirect process of constrained flexibility. Typically, a photographically presensitized (PS) plate is prepared from a hydrophilically surface-treated aluminum. A positive or negative film image of an original hard copy is prepared and the PS plate exposed to the film image, developed, washed and made ready for print operations. Any desired changes in the film image must be made by first changing the original hard copy and repeating the photographic process; hence, the constrained flexibility. As sophisticated and useful as it is to prepare plates by photographic image transfer, the need for a lithographic plate fabricating process that obviates the above problems associated with the photographic process has long been recognized. Clearly, it would be highly beneficial to the printing industry to directly produce a quality printable image on a plate without proceeding through a multi-step photographic process. It would also be highly efficacious if a process were developed whereby changes could be made in an original image in some predetermined manner without incurring the need to correct hard copy and repeat the photography, particularly if those changes could be made “on-line”.
Digital computer-aided design of graphical material or text is well known. Electronically derived images of words or graphics presented on the CRT of a digital computer system can be edited and converted to final hard copy by direct printing with impact printers, laser printers or ink jet printers. This manner of printing or producing hard copy is extremely flexible and useful when print runs of no more than a few thousand are required but the print process is not feasible for large runs measured in the tens or hundreds of thousands of pieces. For large runs, printing by lithographic plate is still the preferred process with such plates prepared by the process of photographic image transfer.
It is known that digitized image information can be used in plate making wherein a film is made to express the image according to the image information digitization and an image is formed on the plate by exposure and development. While this method augments flexibility by permitting editing of a digitized image, the method does not overcome the problems associated with the photographic image transfer method of plate fabrication.
Recently, fabrication of lithographic plates by ink jet techniques has been proposed. One such technique is disclosed in Japanese patent application, Kokai 62-25081. This application describes the use of an ink jet system for applying an oleophilic liquid to form an image on the hydrophilic aluminum surface of a lithographic plate. This approach retains the materials and processing of conventional lithographic printing plates and only uses ink jet printing as an alternative in the photomask through which the conventional plates are exposed. U.S. Pat. No. 5,495,803 describes a solid or phase change type of ink jet printing to form a photomask for a printing plate. Thus, these approaches simply are variants of the above platemaking process and do not utilize the ink jet ink image as the hydrophobic image of the plate.
U.S. Pat. No. 4,833,486 discloses the use of an ink jet head to deposit a hot wax upon the surface of a lithographic plate. The hot wax solidifies upon contact with the plate, thus providing an instantaneous printing pattern. Plates prepared by this method are useful for very limited print runs of a few thousand pieces.
There are several advantages for fabricating printing plates by ink jet printers. One advantage is that such processes are environmentally friendly. The complex and potentially polluting chemical preparations and solvents ordinarily used in masking and stripping away photoresist areas of the plates are not always required with ink jet techniques.
The ink jet technology, however, is in its infancy with respect to commercial lithography. Present ink jet techniques cannot produce large or commercially acceptable offset plates. That is, the plates produced by present ink jet techniques have very low plate runs by commercial lithographic standards. Furthermore, there is no ink jet apparatus or process presently available for fabricating large offset plates having a plurality of pages disposed thereon. Indeed, U.S. Pat. No. 4,833,486 teaches that ink jet materials are inexpensive, and therefore, the printing plate may be used a minimum number of times and then discarded. Moreover, in one embodiment of the '486 patent, it is indicated that the system is designed for non-commercial plate production, inasmuch as an office processor system is proposed. Office processing systems ordinarily are not capable of providing the large amounts of digital information required to produce large, commercial lithographic plates.
A further drawback of the apparatus disclosed in the '486 patent is that it makes use of an ink jet medium which may be a wax. Wax is a soft material and will abrade with use under the conditions present for commercial offset printing. Even the so-called hard waxes will not provide the durability required for commercial printing runs of the order of 100,000 cycles. Moreover, waxes do not strongly bond to the printing plate surface, i.e., they prefer to remain on the surface, rather than to actively bond to the substrate.
A liquid ink amenable to ink jet technology that provides a stable, durable image on a lithographic plate would simplify and reduce the costs of applying ink jet technology to lithographic printing techniques.
SUMMARY OF THE INVENTION
The systems and methods disclosed herein provide inks, liquid at room temperature, which comprise a chromium complex, such as a Werner complex. These inks give rise to durable, hydrophobic layers where they are applied to lithographic plates.
Thus, in one aspect, the systems and methods described herein relate to an ink formulation including about 5-90 weight percent water, up to about 75 weight percent of alcohol, up to about 90 weight percent of ether, and a chromium complex. The alcohol may include one or more of ethanol, isopropanol, isobutanol, trifluoroethanol, and 2-butanol. The ether may include one or more of glyme, diglyme, dioxane, and tetrahydrofuran. In certain embodiments, the ink formulation also includes 0.5-5 weight percent N-methylpyrrolidine. In certain embodiments, the chromium complex comprises a Werner complex, such as pentahydroxy(tetradecanato)dichromium. In certain embodiments, the ink formulation also includes a colored dye. In certain embodiments, the ink formulation includes at least 5 weight percent of ether.
In another embodiment, the systems and methods relate to an ink formulation including about 30-70 weight percent water, up to about 50 weight percent of alcohol, up to about 55 weight percent of ether, and a chromium complex. The alcohol may include one or more of ethanol, isopropanol, isobutanol, trifluoroethanol, and 2-butanol. The ether may include one or more of glyme, diglyme, dioxane, and tetrahydrofuran. In certain embodiments, the ink formulation also includes 0.5-5 weight percent N-methylpyrrolidine. In certain embodiments, the chromium complex comprises a Werner complex, such as pentahydroxy(tetradecanato)dichromium. In certain embodiments, the in
American Ink Jet Corporation
Foley & Hoag LLP
Klemanski Helene
LandOfFree
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