Printing – Planographic – Lithographic printing plates
Reexamination Certificate
2000-01-31
2002-03-12
Funk, Stephen R. (Department: 2854)
Printing
Planographic
Lithographic printing plates
C101S466000
Reexamination Certificate
active
06354207
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
This invention relates to a printing master plate with the use of an ink composition which exists as a solid at ordinary temperature (hereinafter referred to as solid ink) and a device for providing a printing master plate.
2. Description of the Related Art
A photoengraving method is the well-known method for providing printing master plates. In the method, a mask, etc. is formed based on a block copy or a photographic negative (a gathered plate) and then an engraving plate is formed. Based on the engraving plate, proof is performed and a printing master plate (a printing plate) is formed followed by printing.
On the other hand, it is sometimes observed in recent years to employ a DTP (Desk Top Publishing) method wherein the formation of an engraving plate has been digitized. In this method, data including characters, figures images, etc. are output (by laser beam-exposure, etc.) from a computer provided with a built-in memory to form an engraving plate which is then subjected to proof, printing plate-formation and printing as in the conventional case. Use of this method makes it unnecessary to newly form a block copy in the step of proof, thus simplifying the process.
To further simplify the process, there has been developed a method called CTP (Computer to Plate) wherein the printing plate-formation has been digitized. In this method, namely, not only the proof procedures but also various image processing treatments can be efficiently carried out. In this case, it is the most desirable to directly form a printing master plate without resort to any chemical or physical processing.
As printing plate substrates, there have been employed a number of products provided with various photosensitive material layers formed on the surface. Examples thereof include silver halide photosensitive materials (silver salt photographic plates), diazo photosensitive material (PS (Presensitized) plates) and photoconductive materials (electrophotographic plates). In these cases, various chemical and physical post-treatments are needed after exposure for development and fixation. In contrast thereto, there has been also known a processing-free print plating method wherein a surface layer made of silicone rubber is formed and, after exposure, the protective layer is separated to thereby form a printing plate without using water. Although these methods have been already put into practical use over a wide range, complicated processing steps are required in each case. Therefore, it has been urgently required to develop a method whereby a printing plate can be more quickly formed. The above matters are described in detail in, for example, “Insatsu Kogaku Binran (Printing Technology Handbook)”, edited by Japan Society of Printing Science, Gihodo Shuppan (1987).
As methods for the direct formation of printing plates, there have been recently developed the electrophotographic transfer method (xerography method) and the liquid ink jet method. In the electrophotographic transfer method, a toner image formed on a photosensitive drum is transferred onto a printing plate substrate to thereby form a printing plate conveniently and quickly. However, this method suffers from a problem that a large-sized plate highly useful in practice (for example, A2 size or larger) can be hardly formed thereby because of the constitution of the device. Moreover, it is unavoidable from the principle that a small amount of fine toner grains spatter onto the background in the transfer step, which often results in a problem in the actual printing process.
On the other hand, the liquid ink jet system is a convenient method by which a large-sized printing plate can be directly obtained. When an aqueous medium is employed, however, there frequently arises a problem that ink to be printed is repelled by the image of the liquid ink formed on the printing plate upon coating the printing plate with the ink to be printed. This is because resinous components generally have highly hydrophilic nature in many cases. In this case, it is furthermore needed to subject the printing plate substrate to a specific pretreatment so as to prevent the print dots from spreading. Although these problems are somewhat relieved in the case of inks containing organic solvents, there are several serious problems in common to these ink jet systems such that a drying step is needed, that the type and fixation level of resins are limited, and that the printing plate thus obtained has only a short printing life. A number of reports have been made on the application of the ink jet method to engraving or printing plate formation, for example, JP-A-51-84303, JP-A-54-94901, JP-A-56-62157, JP-A-56-113456, JP-A-60-245587, JP-A-62-25081, JP-A-62-62157, JP-A-63-102936, JP-A-63-109052, JP-A-4-69244, JP-A-4-69245, JP-A-4-282249, JP-A-4-317065, JP-A-5-204138, JP-A-5-269958, JP-A-8-324145 and JP-B-58-8991 (the term “JP-A” as used herein means an “unexamined published Japanese patent application, while the term “JP-B” as used herein means an “examined Japanese patent publication”).
To cope with these problems, JP-A-64-27953 discloses a solid ink jet recording method and a device therefor wherein an image forming agent which exists as a solid at room temperature (i.e., a solid ink) prepared from natural wax, etc. is liquefied by heating and then jetted out toward a printing plate substrate followed by solidification, thus forming a printing plate. Since this method can be performed in a solvent-free system, many problems accompanying use of a solvent, as observed in the liquid ink jet system, can be overcome thereby. In addition, natural wax, etc. generally have hydrophobic nature and thus contribute to solve the problem that the ink to be printed is repelled by the image of the liquid ink formed on the printing plate upon coating the printing plate with the ink to be printed. Owing to these characteristics, this method is a highly effective one. In the patent cited above, however, the description is made not in detail but very generally. It is therefore highly difficult based on the description thereof to obtain a highly reliable printing plate having a long life which is to be actually used for forming a printing plate. Thus, experiments should be made in greater detail to improve the abrasion resistance, compatibility with ink, easiness in printing, printing qualities, etc. JP-A-52-20106 discloses a usual printing method with the use of a solid ink.
In general, an ink dot on a printing master plate with the use of a solid ink adheres to a substrate in the form of a hemisphere having a certain thickness just like a lens, which is adequate for uniformly separating the printing plate carrying such ink dots adhering thereto from a paper sheet. With attempts to minimize the ink dot size so as to establish a high clarity and a high resolution of printed images, the contact area between the ink dots and the substrate has been more and more reduced. As a result, there arises a problem that the existing inks are liable to peel off.
When ink dots are located closely to each other or overlap together to form a pattern, the ink cannot be well transferred at grooves between the hemispherical ink dots, thereby giving irregular printing.
In addition, there arises another problem that hemispherical ink dots having a certain thickness are gradually rubbed off from the surface and deformed. In its turn, the printed dot size is changed and the printing life and qualities are damaged.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a solid ink printing plate by which the above-described problems encountered in the conventional art can be overcome and printing qualities can be improved in practice.
The gist of the present invention, which has been made to solve the above-described problems, resides in a solid ink printing master plate constructed by liquefying by heating an ink composition which exists as a solid at room temperature, imparting some jet energy thereto thereby jetting out ink droplets, and th
Kakuta Atsushi
Maekawa Tsutomu
Ouchi Akemi
Funk Stephen R.
Hitachi Koki Co,. Ltd.
McGinn & Gibb PLLC
LandOfFree
Solid ink printing master plate and method for preparing the... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Solid ink printing master plate and method for preparing the..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solid ink printing master plate and method for preparing the... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2882475