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
2001-09-06
2003-12-30
Zimmerman, John J. (Department: 1775)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C205S640000, C101S459000
Reexamination Certificate
active
06670099
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a support for a lithographic printing plate and a method of manufacturing the same, more particularly, to a support for a lithographic printing plate showing an excellent printing performance in which no unevenness in the form of streaks and the like occurs on a surface thereof, and in which uniform electrolytically grained pits are formed efficiently by an electrochemical graining treatment. The present invention also relates to a method of manufacturing the same.
2. Description of the Related Arts
Heretofore, an aluminum alloy plate has been used as a support for a lithographic printing plate. The aluminum alloy plate undergoes a graining treatment in order to acquire adhesion to a photosensitive layer and water receptivity in non-image areas.
Methods of graining that are known heretofore include: a mechanical graining method such as ball graining and brush graining; an electrochemical graining method in which a surface of an aluminum alloy plate undergoes electrolytic graining by using an electrolytic solution mainly containing hydrochloric acid, nitric acid or the like; and a chemical graining method in which a surface of an aluminum alloy plate undergoes etching by an acid solution or an alkaline solution. In recent years, graining by using a combination of the electrochemical graining method and the other graining methods has been becoming the mainstream, since a grained surface obtained by the electrochemical graining method has homogeneous pits and an excellent printing performance.
However, there have been cases where an, appearance defect such as unevenness in the form of streaks occurs on the surface after the electrochemical graining treatment and also homogeneity of pits on the surface after the electrochemical graining treatment is damaged.
Unevenness in the form of streaks is a streak-like unevenness that appears on the surface after the electrochemical graining treatment. Although it has no adverse effect on the printing performance, it makes a plate checking operation difficult during the course of printing and thus the supports with unevenness in the form of streaks are screened out for their appearance defect.
Also, poor homogeneity of the pits has an adverse effect on the printing performance; therefore, homogeneity of pits is required for the supports.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a support for a lithographic printing plate which has no appearance defect such as unevenness in the form of streaks and is excellent in pit homogeneity, and to provide a method of manufacturing the same.
As a result of diligent studies in an attempt to achieve the foregoing object, no features were found regarding element segregation in portions of the support where the unevenness in the form of streaks occurred. When an aluminum surface of the backside of the support for a lithographic printing plate with the unevenness in the form of streaks was investigated, it was found that there was a large degree of dispersion in content of certain elements. Then, the outermost surface layer portion of the aluminum alloy plate before performing a surface treatment was investigated again. As a result, it was found that the dispersion of element contents in the outermost surface layer portion has an influence on uniformity of the surface (about 2 mm to 5 mm from the surface layer) that has been subjected to alkaline etching treatment and the electrochemical graining treatment. Thus, the present invention was accomplished.
Therefore, the present invention provides a support for a lithographic printing plate obtained by subjecting a surface of an aluminum alloy plate to a surface treatment including alkali etching and an electrochemical graining treatment,
wherein the aluminum alloy plate shows dispersion of 50% or lower for each element, the dispersion being defined by an equation (1) below with regard to contents of Fe, Si, Mn, Mg and Sn in a surface layer portion thereof which is from the surface to a depth of 1 &mgr;m:
dispersion(%)=(maximum value−minimum value)/average value×100(%) (1),
where the maximum, minimum and average values are determined based on eight pieces of element content data resulting from excluding the largest and smallest values from ten pieces of element content data obtained by performing an elemental analysis at ten locations.
Preferably, said aluminum alloy plate shows dispersion of 30% or lower for each element, the dispersion being defined by the equation (1) below with regard to the contents of Fe, Si, Mn, Mg and Sn in a portion thereof located at a depth of 2 &mgr;m to 5 &mgr;m from the surface:
dispersion(%)=(maximum value−minimum value)/average value×100(%) (1),
where the maximum, minimum and average values are determined based on eight pieces of element content data resulting from excluding the largest and smallest values from ten pieces of element content data obtained by performing an element analysis at ten locations.
The present invention also provides a method of manufacturing a support for a lithographic printing plate, comprising subjecting the surface of said aluminum alloy plate to alkali etching followed by an electrochemical graining treatment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the present invention will be described in detail.
An aluminum alloy plate used for a support for a lithographic printing plate of the present invention has dispersion of 50% or lower, preferably 40% or lower, for each element, the dispersion being defined by equation (1) below with regard to contents of Fe, Si, Mn, Mg and Sn in a surface layer portion which is from the surface to a depth of 1 &mgr;m:
dispersion(%)=(maximum value−minimum value)/average value×100(%) (1),
where the maximum, minimum and average values are determined based on eight pieces of element content data resulting from excluding the largest and smallest values from ten pieces of element content data obtained by performing an element analysis at ten locations. Herein, the elementary analysis is carried out as follows, for example. First, the aluminum alloy plate is sequentially subjected to alkali etching, rinsing and a desmutting treatment so as to expose a surface at a certain depth from the surface thereof. The exposed surface is rinsed in acetone and dried. The analysis is then performed by using a solid state light emission analyzer at ten locations, the measurement locations being separated from each other by a distance of no less than 2 cm.
When the dispersion of contents of Fe, Si, Mn, Mg and Sn in the surface layer portion from the surface to the depth of 1 &mgr;m is in the above-described range, there will be no occurrence of appearance defect such as unevenness in the form of streaks on the surface by the electrochemical graining treatment conducted thereafter or damage of homogeneity of the pits by the electrochemical graining treatment, since unevenness is not likely to occur during alkali etching.
The present inventors found the cause of dispersion of the contents of these elements. The dispersion occurs due to intermetallic compounds consisting of each of the elements, for example, &agr;-AlFeSi, &agr;-AlFeMnSi, Mg
2
Si, Al
3
Fe and Al
6
Fe, being large-sized and uneven distribution of the intermetallic compounds. To make the intermetallic compounds uniform and fine, it is effective to raise a rolling depressing rate to crush and disperse the large-sized intermetallic compounds. With regard to Sn, although it has not been clarified yet, the same cause is assumed. That is, the specified elements of the present invention are considered to be Fe, Si, Mn, Mg and Sn present in the intermetallic compounds.
Particularly, the effect of Fe, Si, Mn and Mg is distinct in JIS 3000 series materials, and the effect of Sn is distinct in JIS 1050 series materials.
In the present invention, the occurrence of unevenness in alkaline etching is pr
Nishino Atsuo
Sawada Hirokazu
Uesugi Akio
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Zimmerman John J.
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