Original edition for lithographic printing and lithographic platemaking method

Abstract

The present invention provides an original plate for positive pattern panographic plate which has good developing latitude when the image is formed, can inhibit the production of defects due to partial damage of image, can be used for directly making plate for implementing uniform image reproducibility and can use infrared laser and its plate-making method for planographic plate. On the hydrophilic supporting body are successively formed the following superimposed layers; lower layer containing water-in soluble and alkali-soluble resin, infrared absorption dyes containing water-insoluble and alkali-soluble resin and upper heat-sensing layer capable of raising alkaline aqueous solution dissolvability by means of heating, and the upper heat-sensing layer at least contains two kinds of surfactant or lower layer and upper heat-sensing layer respectively contain different surfactants. After the image is exposed, it uses alkaline developing solution to make development.

Description

technical field [0001] The present invention relates to an original plate for lithographic printing plates that can be used as an offset printing master plate and a plate-making method for lithographic printing plates, and in particular to a so-called direct plate-making, positive-working type for infrared laser that can be directly plate-making by digital signals from a computer or the like. A master plate for lithographic printing plates and a plate-making method for lithographic printing plates. Background technique [0002] The situation in recent years is that with the development of lasers, especially solid-state lasers and semiconductor lasers with near-infrared to infrared light-emitting regions, high-output and compact objects can be easily obtained. These lasers are very useful as exposure light sources for direct plate making from digital data such as computers. [0003] The material of the positive-working lithographic printing plate for infrared laser is a bind...

AI Technical Summary

Problems solved by technology

[0004] However, in the original plate for positive-working lithographic printing plates using such an infrared laser, the resistance to dissolution of the developer of the unexposed portion (image portion) and the solubility of the exposed portion (non-image portion) under various conditions The difference between them cannot be said to be sufficient. Due to changes in use conditions, it is easy to cause problems of excessive development and poor development.

The imaging ability of the original plate for lithographic printing plates depends on the heat generated by the infrared laser on the surface of the recording layer. In the vicinity of the support, due to heat diffusion, the heat used for imaging, that is, melting the recording layer is reduced, and the difference between exposure and unexposed is also very large. Small, so there is a problem of insufficient highlight reproducibility

[0005] For example, with regard to the latitude of development, an original plate material for positive-working lithography for plate making by UV exposure, that is, onium salts and quinoid diazide compounds containing binder resins soluble in alkaline solutions, This onium salt and quinone diazide compound, in the unexposed part (image part), interacts with the binder resin to act as a solvent repellant, and, in the exposed part (non-image part), , is decomposed by light to generate acid, and functions as a dissolution accelerator. There is almost no problem in the original material for lithographic printing plates in the past. However, when UV exposure is carried out through the image of the stone plate, it is easy to cause light to spread , there is also the problem of highlight reproducibility

[0006] On the other hand, in the original material for a positive-working lithographic printing plate using an infrared laser, the infrared absorber or the like only acts as a solvent repellant in the unexposed portion (image portion), and acts as a solvent repellant in the exposed portion (non-image portion). does not promote dissolution

Therefore, in the original material for a positive-working lithographic printing plate using an infrared laser, in order to make a difference in solubility between the unexposed part and the exposed part, a binder resin having high solubility in an alkaline developer has to be used in advance. However, the problems brought about are poor damage resistance, unstable state before development, etc.