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
1999-12-22
2001-12-11
Baxter, Janet (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
C430S302000
Reexamination Certificate
active
06329122
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the preparation of a photosensitive lithographic printing plate.
BACKGROUND OF THE INVENTION
In general, an aluminum support to be incorporated in lithographic printing plate is required to exhibit excellent water wettability and water receptivity. Thus, it is well known that an aluminum support is finely roughened by a mechanical, chemical or electrochemical process so that it is grained. It is further known that the surface of the aluminum support thus grained is anodized to enhance the mechanical strength and even the water receptivity thereof. The aluminum support which has thus been anodized is then rinsed. During this procedure, aluminum ions contained in the anodizing solution and dissolved upon anodization are retained on the aluminum support. During rinsing, these aluminum ions form aluminum hydroxide which is then attached to the aluminum support to mar the external appearance. In order to eliminate this defect, it has been heretofore practiced to intensify rinsing. However, this approach is disadvantageous in that the required amount of rinsing water is increased, adding to the production cost.
SUMMARY OF THE INVENTION
It is therefore an abject of the present invention to provide a process for the preparation of an aluminum support for photosensitive lithographic printing plate which allows little production of aluminum hydroxide without increasing the amount of rinsing water to be used in rinsing after anodization and allows little attachment of aluminum hydroxide to the aluminum support to prevent defective external appearance.
The inventors made extensive studies of the accomplishment of the foregoing object of the present invention As a result, it was found that when an aluminum substrate which has been anodized is treated with an aqueous solution having a pH value of 15 to 5 before rinsed, the production of aluminum hydroxide during rinsing can be inhibited, making it possible to prevent defects caused by aluminum hydroxide. The present invention has thus been worked out.
The present invention concerns a process for the preparation of a photosensitive lithographic printing plate which comprises providing a photosensitive layer on an aluminum support obtained by treating an anodized aluminum substrate with an aqueous solution having a pH value of from 1.5 to 5.
Another embodiment of the present invention is a process for the preparation of a photosensitive lithographic printing plate which comprises treating an anodized aluminum substrate with an aqueous solution having a pH value of from 1.5 to 5, treating said anodized aluminum substrate with a silicate of alkaline metal so that the amount of Si atom attached to the aluminum support thus obtained reached from 0.1 to 8 mg/m
2
, and then providing a positive-working photosensitive layer on said aluminum support.
DETAILED DESCRIPTION OF THE INVENTION
The photosensitive lithographic printing plate according to the present invention will be further described with reference to support, interlayer, positive-working photosensitive layer and development process in this order.
Firstly, the support to be incorporated in the photosensitive lithographic printing plate of the present invention and its treatment will be described hereinafter.
(Aluminum Plate)
The aluminum plate to be used in the present invention is a plate-like body made of pure aluminum or aluminum alloy comprising aluminum as a main component and a slight amount of foreign elements. Examples of these foreign elements include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The aluminum alloy preferably comprises such foreign elements in an amount of not greater than 10% by weight. Aluminum suitable for the present invention is pure aluminum. However, since completely pure aluminum can hardly be produced from the standpoint of refining technique, aluminum comprising foreign elements in an amount as little as possible may be used. Any aluminum alloy comprising foreign elements in the above defined amount may be used in the present invention. The aluminum plate to be used in the present invention is not specifically limited in its formulation. Any known commonly used material may be properly used. Preferred examples of such a known include those according to JIS A1050, JIS A1100, JIS A1200, JIS A3003, JIS A3103 and JIS A3005. The thickness of the aluminum plate to be used in the present invention is from about 0.1 mm to 0.6 mm. Prior to being roughened, the aluminum plate is optionally subjected to degreasing, i.e., treatment with a surface active agent or alkaline aqueous solution to remove rolling oil from the surface thereof.
(Roughening and Anodization)
In general, the foregoing aluminum plate is firstly roughened on the surface thereof. The surface roughening of the aluminum plate can be accomplished by mechanical roughening method, electrochemical dissolution-roughening method or chemical selective dissolution method. As the mechanical roughening method there may be used any known method such as ball abrasion method, brush abrasion method, blast abrasion method and buffing. The electrochemical roughening method may be carried out using alternating current or direct current in a hydrochloric acid or nitric acid as an electrolyte. A combination of the mechanical roughening method and the electrochemical roughening method as disclosed in JP-A-54-63902 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”) may be used.
The aluminum plate which has thus been roughened is optionally alkalinically etched and neutralized, and then anodized to enhance its water receptivity or abrasion resistance. As the electrolyte to be used in the anodization of aluminum plate there may be used any electrolyte with which a porous oxide layer can be formed. In general, sulfuric acid, phosphoric acid, oxalic acid, chromic acid or mixture thereof may be used. The concentration of such an electrolyte may be properly predetermined according to the kind of the electrolyte.
The anodization conditions vary with the kind of the electrolyte used and thus cannot be unequivocally predetermined. In general, it is preferred that the concentration of the electrolyte be from 1 to 80% by volume, the liquid temperature be from 5 to 70° C., the current density be from 5 to 60 A/cm
2
, the voltage be from 1 to 100 V and the electrolysis time be from 10 seconds to 5 minutes.
The amount of anodized layer is preferably not less than 1.0 g/m
2
, more preferably from 2.0 to 6.0 g/m
2
. If the amount of anodized layer falls below 1.0 g/m
2
, the resulting printing durability is insufficient. Further, the resulting lithographic printing plate can be easily scratched on the non-image area, occasionally causing so-called “scratch scumming”, i.e., attachment with ink on scratched area during printing.
The anodization is made on the support of lithographic printing plate at the surface to be used for printing- Since lines of electric force reach the other surface of the support, it is usual that an anodized layer is formed on the other surface of the support in an amount of from 0.01 to 3 g/m
2
.
(Treatment with Acidic Aqueous Solution)
In the present invention, the aluminum support which has thus been anodized is treated with an acidic aqueous solution having a pH value of from 1.5 to 5, preferably from 2 to 4 to inhibit the formation of aluminum hydroxide and the attachment of aluminum hydroxide to the aluminum support, making it possible to eliminate defective external appearance. If the pH value of the electrolyte is lower than 1.5, the anodized layer is dissolved in the electrolyte, increasing the diameter of pores in the anodized layer that can render the aluminum support more stainable. On the contrary, if the pH value of the electrolyte is higher than 5,, the formation of oxide layer cannot be prevented, making it impossible to inhibit the occurrence of defective external appearance caused by aluminum oxide.
The treatment temperature is from 10° C.
Hotta Hisashi
Uesugi Akio
Baxter Janet
Fuji Photo Film Co. , Ltd.
Lee Sin J.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Process for the preparation of photosensitive lithographic... 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 the preparation of photosensitive lithographic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of photosensitive lithographic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2588664