text: 1. Field of the Invention
  The present invention relates to a negative-type image recording material on which an infrared laser is capable of writing, and particularly relates to a negative-type image recording material whose strength of an image portion of a recording layer is high, and which is capable of forming a planographic plate having excellent plate life.
  2. Description of the Related Art
  As the development of laser technologies has been significant in recent years, particularly, in a solid state laser and a semiconductor laser having a light emission region from near infrared rays region to infrared rays region, the trends of higher powering and miniaturization of laser devices have been proceeded. Therefore, these lasers are very much useful as a light source for exposure when a plate is engraved directly from digital data of a computer or the like.
  A material for a negative-type planographic plate for infrared-laser for which an infrared laser having a light emission region in the aforementioned infrared rays region is used as a light source for exposure is a material for a planographic plate, which has a photosensitive layer containing an infrared absorbing agent, a polymerization initiator for generating a radical due to the light or heat and a polymerizable compound.
  Usually, such a negative-type image recording material utilizes a recording method in which a polymerization reaction is generated using a radical as an initiator generated due to the light or heat and an image portion is formed by hardening a recording layer of an exposure portion. As for such a negative-type image formation material, the image formation property is lower compared to that of a positive-type image formation material causing the solubilization of a recording layer by an energy of infrared laser irradiation and the negative-type image formation material forms a tight image portion by promoting hardening reaction by polymerization, it is common to carry out a heating process prior to a development process.
  As such a printing plate having a recording layer formed by polymerization system due to the light or heat, technologies employing photopolymeric or thermal polymeric compositions as a photosensitive layer as mentioned in respective publications of Japanese Patent Application Laid-Open No. 8-108621 and JP-A No. 9-34110 are known. Although these photosensitive layers are excellent in high sensitivity image formation property, in the case where a hydrophilization-processed substrate has been used as a substrate, there are problems that adhesion in an interface between the photosensitive layer and the substrate is low and the plate life is inferior.
  Moreover, in order to enhance the sensitivity, it has been also considered to use a high power infrared laser, however, there has been also a problem that the ablation of a photosensitive layer has been generated during laser scanning and the optical system has been polluted.