Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Making printing plates
Reexamination Certificate
2001-07-03
2004-04-06
Huff, Mark F. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Making printing plates
C205S214000
Reexamination Certificate
active
06716569
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a preparation method for a lithographic printing plate from a photosensitive or thermosensitive presensitized plate. The properties of the plate such as remaining of colors and remaining of films in the non-image area, contamination of the printed matters at the portion corresponding to the non-image area and printing durability are improved.
Conventional presensitized plate for the preparation of a lithographic printing plate has an ink-receptive photosensitive layer formed on a hydrophilic substrate. When such photosensitive layer of the presensitized plate is image-wise exposed followed by development of the exposed photosensitive layer with a developer, the area of the photosensitive layer exposed to light is removed to expose hydrophilic surface of the substrate. On the other hand, the area of the photosensitive layer that is not exposed to light remains on the surface of the substrate to form an ink-receptive image portion to thus provide a lithographic printing plate. In such printing plate, in order to prevent contamination of the printed matter caused by adhesion of ink to the non-image area, it is necessary to make the non-image area more hydrophilic. Conventionally, by using a developer containing alkaline metal silicate to develop such plate, non-image area of the plate may be hydrophilized to reduce the contamination. However, when such developer containing alkaline metal silicate is used, the following problems were observed; a solid precipitate resulted from SiO
2
is easily produced, and gel resulted from SiO
2
was produced when wastewater from the developer is neutralized. Also, such developer may cause a problem such as re-absorption of lipophilic component such as dye and resin dissolved in the developer on the alkaline metal silicate that is absorbed during the development to result in deterioration of the properties such as remaining of color or remaining of film in the non-image area.
In order to solve these problems, a developer comprising at least 0.01 mol/L of at least one compound selected from saccharides, oximes, phenols and fluorinated alcohols as a developing stabilizer and an alkaline agent (that is, silicate-free developer) may be utilized. However, when such developer is used for the conventional presensitized plate for a lithographic printing plate, anodized film on an aluminum substrate was dissolved by the developer to result in accumulating of the dissolved material in the developer. Thus produced mud or sludge deteriorates the detergency of the automatic developing machine and chokes the spray nozzles. Further, if a printing plate developed by such developer was left during developing process, it would be difficult to remove ink that is adhered to (that is so-called “Hochi-yogore” (contamination after being left)).
In order to solve these problems, there has been proposed a various methods for treating anodized film on the substrate. But steam treatment that was known as a method to prevent dissolution of the film during development, can not solve the problem of contamination after being left although it prevents remaining of color in the non-image area or remaining of film. Although the treatment of anodized film with a silicate can solve the problem of contamination after being left, problems as to printing durability, deterioration of property of remaining of color or film can not be solved.
The above problems are likewise caused when a presensitized plate having a thermosensitive layer that can be directly made up from the data of letter or image using laser light is used.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide a preparation method for a lithographic printing plate, having good properties with regard to remaining of colors, remaining of films, printing durability and contamination as well as prevention of a formation of mud or sludge in a developer.
The inventors of the present invention have conducted various studies to accomplish the foregoing objects and have found that the foregoing problems can be solved by a lithographic printing plate prepared by treating a surface of an anodized aluminum substrate with an aqueous solution comprising at least one compound selected from the group consisting of nitrite group-containing compound, fluorine atom-containing compound and phosphorous atom-containing compound, coating the treated substrate with a photosensitive layer or thermosensitive layer, image-wise exposing to light and developing it with a developer comprising no silicate. Such lithographic printing plate has good properties with regard to remaining of colors, remaining of film, printing durability and contamination as well as prevention of the formation of mud or sludge in the developer.
That is, the present invention provides a preparation method for a lithographic printing plate, which comprises forming a presensitized plate by coating a photosensitive layer or thermosensitive layer on an anodized aluminum substrate treated with an aqueous solution and developing the presensitized plate with a developer comprising no silicate, wherein the aqueous solution comprises at least one compound selected from the group consisting of nitrite group-containing compound, fluorine atom-containing compound and phosphorous atom-containing compound, with the proviso that when the at least one compound is fluorine atom-containing compound, the treated aluminum substrate has a surface which satisfies the formula: 0.30≦A/(A+B)≦0.90 wherein, A represents peak area of fluorine atom (1S) (count·eV/sec) determined by X ray Electron Spectroscopy for Chemical Analysis (ESCA), and B represents peak area of aluminum atom (2P) (counts ·eV/sec) determined by X ray ESCA, and when the at least one compound is phosphorous atom-containing compound, the treated aluminum substrate has a surface which satisfies the formula: 0.05≦A/(A+B)≦0.70 wherein, A represents peak area of phosphorous atom (2P) (count·eV/sec) determined by X ray ESCA, and B represents peak area of aluminum atom (2P) (count·eV/sec) determined by X ray ESCA.
Generally, a thermal conductivity of an aluminum substrate of a presensitized plate with a thermosensitive layer is rather high than that of the thermosensitive layer. Therefore, heat around the interface between the thermosensitive layer and the substrate easily transfers to the inside of the substrate before substantial progress of an image-forming reaction. As the result, some portion of the positive-working thermosensitive layer, which the portion normally should be non-image area, would remain and some portion of the negative-working thermosensitive layer, which normally should be image area, may not be formed as an image due to insufficient polymerization reaction (low sensitivity). However, it is found that the sensitivity of the presensitized plate with the thermosensitive layer prepared by the method of the present invention is higher than that of the conventional ones. The reason for the fact is not clear but the following reason can be considered. For example, when the anodized substrate was treated with an aqueous solution comprising at least one compound selected from the group consisting of nitrite group-containing compound, fluorine atom-containing compound and phosphorous atom-containing compound, the anodized film is sealed hydrophilically to form an airspace which shows low thermal conductivity. It is considered that such airspace may inhibit the transfer of the heat caused by irradiation of laser light to the thermosensitive layer.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The method of the present invention will be explained in detail below.
Aluminum Substrate
In the present invention, the aluminum substrate, which has been anodized by the after-mentioned method, should be treated with an aqueous solution comprising at least one compound selected from the group consisting of nitrite group-containing compound, fluorine atom-containing compound and phosphorous atom-containing compound.
Treatment of Substrat
Hotta Hisashi
Sakamoto Atsushi
Burns Doane Swecker & Mathis L.L.P.
Fuji Photo Film Co. , Ltd.
Huff Mark F.
Walke Amanda C.
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