Study on photocrosslinking self-plasticized polyvinyl alcohol photosensitive film

Flexographic printing has received tremendous attention in the printing field due to the advantages of short preparation processes and high printing efficiency. Its printing quality heavily depends on the preparation of the printing plate. However, plate clarity and plate softness are contradictory. This paper reports the development of a clear and soft self-plasticizing modified polyvinyl alcohol (m-PVA) coating that can be UV-cured at room temperature. Glycidyl methacrylate (GMA) was used to prepare unsaturated m-PVA (m-PVA-GMA) in an aqueous system. Meanwhile, the effects of acidic and alkaline environments on the grafted products have been further investigated, suggesting that they differ from those obtained via the dimethyl sulfoxide system. The structural comparison has demonstrated that the reactivity of GMA and m-PVA is higher in alkaline aqueous than in acidic conditions. When the unsaturation degree increases, the crystallization of PVA chain segments will be effectively destroyed. The photographic film, which can be directly photo-crosslinked, was prepared by m-PVA-GMA and washed away the uncrosslinked portion with water. The glass transition temperature (31.4 °C) of the photographic m-PVA-GMA film prepared under alkaline conditions is close to room temperature, and the crosslink density is as high as 3.01 × 103 mol m−3. More importantly, the elongation at break after water washing and the elastic recovery are 110.8 ± 5.3 % and 99 %, respectively. In addition, irradiating selected areas and then removing the non-irradiated portions with water could produce patterns. The m-PVA-GMA film prepared under alkaline conditions has outstanding development accuracy, much higher than the commercially available product nyloprint®. This direct UV-curable film with water-soluble and water-developable properties enables it to be a promising candidate in the fine flexographic printing industry, such as photoresists, electronic devices, and sensors.