Several models were proposed to elucidate the phenomenon of ink release in waterless lithography. The WFBL model, which considers the weak boundary layer composed of diffusable liquid in the ink, can explain the ink release to some extent and, however, several experimental results cannot be understood by the model. In an adhesion system, the mechanical strength is well correlated with some of the wettability of the adherent surface, the adhesion energy between the adhesives and the adherent, or the fracture energy of the weak boundary layer.
The main purpose of this study is to re-examine the correlation between ink release and surface-chemical parameters concerning wettability and adhesion which are estimated from contact angle. Ink release tests and contact angle measurements were extensively carried out on the material candidates for non-image area (silicone elastomer, ethylenepropylene rubber, butyl rubber, polyfluoroalkyl acrylate, polytetrafluoroethylene, and so on).
Though the ink release was not found to have any correlation with the parameters, work of adhesion decreases remarkably when the ink polymer on the material is surrounded by n-decane or silicone oil. The decrease in the work of adhesion should be the driving force of ink release. Swelling with organic liquid and time-dependence of contact angle were observed on the materials which showed ink release, and, therefore, the swelling must be necessary to the ink release.

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Photochemical properties of poly (p-vinyl phenethyl trans-cinnamate) (PPVPhC) were compared with those of poly (vinyl trans-cinnamate) (PVC), a typical photosensitive polymer with cinnamoyl group.
Following photochemical behaviors were found from the investigation.
1) Disappearance rate of traps double bond of PPVPhC was faster than that of PVC upon the UV-irradiation.
2) Blue shift of absorption band at 278nm was observed during the irradiation to PPVPhC. This seems to be caused by photoisomerization and crosslinking reaction.
3) Triplet life time of PPVPhC was thought to be longer than that of PVC from the phosphorescence life times of their model compounds at 77K.
4) Initial quantum yields of photocrosslinking were approximately the same for the two polymers. With further irradiation the quantum yield for PVC was decreased but that for PPVPhC was not.
5) Sensitivity of PPVPhC measured by gray-scale method was much better than that of PVC.
Phenethyl group of PPVPhC introduced between main chain and cinnamoyl group was considered to relax the undesirable steric hindrance which was responsible for the unreactive cinnamoyl group of PVC.
It was then concluded that the steric factor caused the different behaviors found as described above between PPVPhC and PVC.

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