Digital printing plates have requirements for CTP performance. As we all know, CTP process can bring many benefits for printing: excellent imaging quality, near perfect calibration, and fast production turnover. However, its various advantages are not only attributed to imaging equipment, but also depend on the quality and performance of CTP plates.
Here, we will focus on exploring several characteristics of the plate material and how they interact to assist CTP equipment in digital plate making, thereby affecting imaging quality. This applies to all CTP plates, but is particularly suitable for thermosensitive plates. At present, the use of global thermal plates is growing rapidly, and has also been recognized as the first choice for high-quality Planographic printing plates.
Requirements for aluminum based materials
In traditional plate making, whether the dot can be accurately positioned on the plate material largely depends on whether the position of the plate assembly and positioning registration device is accurate when using a vacuum pumping device or a continuous copying device. Anyway, this requires the plate to be quite flat when laid flat, but due to the direct contact exposure method used in the imaging process, the entire process can accept changes in the surface flatness of various types of plates, which are caused by the treatment of the aluminum substrate surface during the production of traditional plates. However, because the Digital printing plate is exposed by focusing the energy emitted by the laser light source, the requirements for the flatness of the digital plate, including the surface treatment of the aluminum base, are more stringent.
In addition, using energy focused imaging is different from direct imaging, which means that there will be no visible stripes when imaging on digital plates, as there will be no stripes generated during anodizing and polishing of aluminum plates.
When applying photosensitive emulsion on digital plates, it must be smooth, uniform, and free from defects. Because the dot size generated on the laser Computer to plate is very small, any dust in the air, no matter how small, falling on the plate in the process of reel production will cause this artificial image spot. In fact, irregular images can also be generated due to electrostatic spots, and they are very small and cannot even be seen with a magnifying glass used to inspect traditional printing materials.
The same uniformity requirements are also applied to the photosensitive coating of synthetic materials for Digital printing plates. Generally speaking, when the traditional printing plate is exposed under the ultraviolet light, the energy it receives is about 10000 times the energy transmitted by the laser system to the Digital printing plate coating in the direct plate making equipment. That is to say, in order to accurately meet the physical characteristics mentioned above, the emulsion coating of Digital printing plate must strictly meet the spectral sensitivity characteristics of a specific range, meet the requirements of synthetic substances (especially the molecular structure in the coating), and respond actively to energy. Therefore, factories producing Digital printing plates need special and additional chemicals, as well as special production workflow.
Compared to traditional plates, CTP plates also require different operating methods during transportation. Because many digital plate imaging uses the edge of the plate as a key reference point for calculating the imaging position. Digital plates have very strict requirements for the straightness and uniformity of the edges. Although this is only a minor issue for traditional plates, if the digital plate edge