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
2000-12-07
2003-10-28
Hamilton, Cynthia (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
C430S944000, C430S945000, C430S964000, C430S947000
Reexamination Certificate
active
06638686
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a planographic printing plate precursor, and more particularly, to a planographic printing plate for laser plate production.
2. Description of the Related Art
Recently, with development of image forming technologies, attention has been focused on technologies for forming letter manuscripts, images and the like directly on the surface of a plate, while scanning the plate with laser beams restricted narrowly, to produce a plate directly without using a film.
As such an image forming material, there are listed a so-called thermal type positive type planographic printing plate in which an infrared absorbing agent present in a photosensitive layer generates heat upon exposure by exhibiting its light-heat converting action, and exposed portions of the photosensitive layer are solubilized by the generated heat to form positive images, and a thermal type negative type planographic printing plate of in which a radical generator and an acid generator generate a radical and an acid due to heat, and a radical polymerization reaction and an acid crosslinking reaction occur, causing insolubilization of exposed portions of the photosensitive layer, to form negative images. In such thermal type image formation, laser light irradiation causes a light-heat converting substance in a photosensitive layer to generate heat which causes an image formation reaction.
A planographic printing plate precursor which enables laser plate printing (direct type planographic printing plate precursor) is generally manufactured by roughening the surface of an aluminum plate which is in the form of a wave, carrying out an anodizing treatment on the surface, and then applying thereon a photosensitive layer coating solution and drying it, to form a photosensitive layer. Then, the planographic printing plate precursor in the form of a wave is cut into a sheet of desired size, and a plurality of such sheet are stacked and then packed. Alternatively, after being stored in a state of being wound in roll form, the plate is cut into desired sizes. The packed and delivered planographic printing plate precursors are subjected to image printing by laser exposure and to developing processing, and are then set at a printer.
However, an aluminum substrate which has been roughened and on which an anodized film has been formed essentially has the problem of low sensitivity for the following reason. Because the substrate has heat conductivity which is extremely high as compared with that of the photosensitive layer, heat generated in a vicinity of the interface between the photosensitive layer and the substrate is diffused into the substrate before being used for forming images sufficiently, resultantly. As a result, the decomposition reaction of the positive photosensitive layer is insufficient at the interface between the photosensitive layer and the substrate, and a film remains at the non-image parts.
Further, there is also the problem that although such a thermal type recording layer must contain an infrared absorbing agent having light-heat converting ability, such agents have poor solubility due to their relatively large molecular weight, and adhere to micro openings in the anodized substrate and are difficult to be removed therefrom. Therefore, a film tends to remain in a developing process using an alkali developing solution.
For coping with this problem, various primers have been studied, for improving the developing property of the photosensitive layer at the interface between the substrate and the photosensitive layer, in the case of a positive photosensitive layer. However, a sufficiently satisfactory level has not been attained in any case.
When roughening of a substrate is non-uniform, the tight contact between the photosensitive layer and the substrate also decreases. When the close fit between the photosensitive layer and the substrate decreases, the ability to withstand repeated printings of a planographic printing plate after plate production is lowered. Particularly, with a photosensitive layer of a direct writing type planographic printing plate, it is difficult to ensure close contact with a substrate as compared with a photosensitive layer of a planographic printing plate requiring a plate production film in the production thereof. Thus, an improvement in the ability to withstand repeated printings is desired.
Further, recently, sensitive materials which are activated by a shorter wavelength as compared with conventional products which are activated by wavelengths around 500 nm have been studied for enabling work under a safe light of a bright red color. However, in the photosensitive printing plate which is activated by a short wavelength of 450 nm or less and is described in Japanese Patent Application No. 11-209822 and has been newly developed recently, light absorption of an anodized film at an exposure wavelength of 450 nm or less is low as compared with the absorption at wavelengths around 500 nm. Therefore, in conducting laser image writing on a printing plate, the plate tends to be affected by light diffusion, and a thin image portion called a fringe is formed around each halftone dot. Consequently, a problem occurs that the halftone dot on the whole becomes bolder, and the halftone dot area ratio increases.
In this case, it is advisable to further increase the light absorption of the anodized film, and to this end, it is necessary to raise the volume proportion of the anodized film itself by decreasing the pore diameter of fine pores called micropores existing in the anodized film, or by decreasing the number of pores per unit area. However, on the other hand, since the micropores of an anodized film of aluminum result in close contact by holding the photosensitive layer by an anchor effect, a decrease in the size of the micropores or a decrease in the number of micropores per unit area thus deteriorates the close contact with the photosensitive layer, such that the structure cannot be used in actual practice. Therefore, for obtaining close contact by the substrate, the presence of a certain amount of micropores is necessary. Until now, there has been no way other than sacrificing halftone dot quality and reproducibility in order to form an image and using it as a printing plate.
In addition, in the above-described packaging of direct writing type planographic printing plate precursors, it is necessary to precisely stack the plurality of planographic printing plate precursors cut to the same given size. To this end, it is necessary to precisely convey the plurality of planographic printing plate precursors cut into the same given size. For the conveying, a belt conveyer is usually used. However, there is the problem that a planographic printing plate precursor may slip, and accurate conveying and stacking are difficult. Further, though conveying belts and conveying rollers are used for laser image writing, development, printing and the like conducted by users, and also for the transfer of the planographic printing plate precursor to various processes, there is a problem that the planographic printing plate precursor may slip and accurate conveying and stacking are difficult with these conveying belts and conveying rollers as well. Particularly in laser exposure, extremely high positioning accuracy is required, and therefore, poor conveying invites not only a reduction in productivity but also a reduction in the quality of formed images. Also, in developing processing, a automatic conveying type developing machine are used in almost all cases, and there is a great demand to overcome the problem of poor conveying during the developing process as well.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a direct writing type planographic printing plate precursor which can overcome the above-described various problems.
The present inventors conducted intensive studies, and found that the above-described object can be attained by using an aluminum substrate having specific properties, and thus a
Endo Tadashi
Hotta Hisashi
Sasaki Hirokazu
Sawada Hirokazu
Uesugi Akio
Burns Doane , Swecker, Mathis LLP
Fuji Photo Film Co. , Ltd.
Hamilton Cynthia
LandOfFree
Planographic printing plate does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Planographic printing plate, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Planographic printing plate will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3175350