Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2002-09-10
2004-10-26
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S278100, C148S437000, C148S438000, C148S439000, C148S440000, C101S459000, C420S533000, C420S534000, C420S535000, C420S536000, C420S542000, C420S543000, C420S544000, C420S547000, C420S553000, C420S554000, C428S472200, C428S650000
Reexamination Certificate
active
06808864
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a support for a lithographic printing plate and a presensitized plate, more particularly to a presensitized plate with a high strength where a fatigue fracture does not easily occur, even when the plate is mounted on a plate cylinder of a printing machine with a high tensile force, an anodized layer may not be easily cracked and having an excellent resistance to aggressive ink staining, and a support for a lithographic printing plate used therefor.
In addition, the present invention more particularly relates to a support for a lithographic printing plate where a material cost can be largely reduced, with a very fine crystal grain, excellent surface quality (appearance) and the excellent press life and relates to a presensitized plate using the support.
2. Description of the Related Art
A photosensitive presensitized plate having an aluminum plate as a support is widely used for an offset printing. A presensitized plate is typically manufactured by performing a graining treatment on a surface of an aluminum plate, performing an anodizing treatment, thereafter applying a photosensitive solution and drying the plate so as to form a photosensitive layer (an image recording layer). After the presensitized plate is exposed to an image, it is developed by a plate developer, an exposed portion in case of a positive presensitized plate or a non-exposed portion in case of a negative presensitized plate is removed and plate making is performed, thus a lithographic printing plate is manufactured. In addition, in recent years, a manufacturing method of a presensitized plate using a laser attracts attention and various methods are studied. For example, there is known a photon-system laser lithographic plate using a photopolymerizable composition which is hardened by a visible light laser and a heat mode-system laser lithographic plate using heat or the like generated by a laser light irradiation to record. These systems are very useful since plate making can be performed directly from a digital data in a computer or the like to manufacture a lithographic printing plate.
The lithographic printing plate thus manufactured is then mounted on the plate cylinder of a printing machine, an ink and a fountain solution are supplied to a surface thereof. As they are used for printing, the remaining portion of a photosensitive layer becomes an image area showing an ink affinity, a portion in which a photosensitive layer is removed becomes a non-image area showing a water wettability, thus, it is transcripted on a blanket cylinder and is printed on paper.
As is seen from the foregoing, in a presensitized plate, the physical properties of a photosensitive layer are changed by exposure, and plate making is performed utilizing the changes in the physical properties.
As mentioned above, when a developing processing is performed on a presensitized plate after an image is exposed, there is a case where a surface of a non-image area may be partially eroded by a plate developer, thereby resulting in the deterioration of resistance to aggressive ink staining depending on the conditions of the plate developer. In addition, there is a defect where the level of resistance to aggressive ink staining largely changes depending on whether or not alkali metal silicate is contained in a plate developer. Here “aggressive ink staining” is defined as a defect that inks are attached to a non-image area of a lithographic printing plate in a dotted state or a circular state, thereby resulting in a dotted or a circular scum on paper if printing is intermittently performed many times.
To improve resistance to aggressive ink staining, a number of proposals are presented. Concretely, there are many proposals to specify alloy components contained in an aluminum plate used for a support for a lithographic printing plate. For example, a method by specifying alloy components such as Mg, Mn, Si, Ga, Ti, Cu (JP 5-309964 A, JP 3-177528 A or the like), a method by specifying a ratio of Fe to Si (JP 4-254545 A, JP 7-197162 A or the like), a method by specifying the content of a solid solution of Fe (JP 4-165041 A or the like), a method by specifying a simple Si content (JP 2544215 B, JP 2031725 B or the like), a method by specifying a content, size, distribution or the like of intermetallic compounds (JP 4-165041 A, JP 3-234594 A, JP 2544215 B, JP 4-254545 A or the like) and a method by specifying the characteristics of an anodized layer in combination with specifying alloy components (JP 7-197393 A, JP 7-26393 A or the like) are described.
SUMMARY OF THE INVENTION
Since there has been increasing variety of presensitized plates such as a laser direct recording-type presensitized plate and a conventional analog-type presensitized plate, and the exposure and development have been processed in combination with various plate developers corresponding to image recording layers and the features in their applications, it has been a large problem to control a printing performance which may vary with a plate developer.
In the meantime, efforts to improve various performances of the presensitized plate have been conducted by controlling trace components of aluminum alloys. Since this method is to add only a trace of a certain component to an aluminum alloy, it is advantageous in a point that this addition does not affect the physical properties of a presensitized plate at all.
For example, the inventors of the this application have proposed that the efficiency of electrochemical graining treatment (electrolytic graining treatment) on an aluminum plate may be improved by having the aluminum plate contain, in addition to Fe: 0.05 to 0.5 wt %, Si: 0.03 to 0.15 wt %, Cu: 0.006 to 0.03 wt % and Ti: 0.010 to 0.040 wt %, 1 to 100 ppm of at least one kind element selected from a group consisting of Li, Na, K, Rb, Cs, Ca, Sr, Ba, Sc, Y, Nb, Ta, Mo, W, Tc, Re, Ru, Os, Co, Rh, Ir, Pd, Pt, Ag, Au, C, Ge, P, As, S, Se, Te and Po. (JP 2000-37965 A).
The assignee of this application has proposed that the electrochemical graining characteristic may be further improved by having the aluminum plate contain, in addition to the elements mentioned above, 10 to 200 ppm of Mg, resulting in the improved contact characteristics between the image recording layer and the support in a laser direct-recording type presensitized plate, and in the improved press life of the lithographic printing plate (JP 2001-162958 A).
Moreover, the assignee of this application has proposed to improve the efficiency of electrolytic graining and press life by specifying the concentration of Cu in a depth direction in the vicinity of the surface of an aluminum plate and the relationships between Cu, Si and Ti as well as by adding the foregoing elements (Japanese Patent Application No. 2001-25370).
Since the proposals on the addition of these trace components are, however, not intended to improve resistance to aggressive ink staining, the resistance to aggressive ink staining is not necessarily adequate.
In the meantime, a lithographic printing plate is bent at both ends when it is mounted on a printing machine plate cylinder. Each of the bent portions is fixed in two clamps called gripper portion and gripper edge of printing machine plate cylinder section, after applying tensile force so as to have a lithographic printing plate closely contact with the blanket cylinder, and then the lithographic printing plate is used for printing. Here is a defect that the two bent portions at both ends of the lithographic printing plate are likely to rise out of the plate cylinder due to a reaction force against the bending, therefor, if the plate cylinder is repeatedly pressed to the blanket cylinder under this condition, fatigue fracture is likely to take place since the risen portion is repeatedly bent.
Although this rise may be suppressed by increasing a tensile force applied to the plate when the plate is mounted on the plate cylinder, the lithographic printing plate itself needs a high tensile strength for this purpose.
Sawada Hirokazu
Uesugi Akio
Burns Doane Swecker & Mathis L.L.P.
Fuji Photo Film Co. , Ltd.
Schilling Richard L.
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