At present, a variety of thermal CTP plates have appeared, and the common plates have two types: negative thermal CTP plate and positive thermal CTP plate. The negative CTP plate will partially expose the image and text during infrared scanning, such as TN-type and DIIP-type heat-sensitive plates; while the positive-type ones are exposed to non-image and text parts. The basic principle of heat-sensitive CTP plate imaging is that the infrared light-absorbing dye in the heat-sensitive layer absorbs the infrared laser to generate heat. After reaching a certain temperature, the induced acid-release agent undergoes a thermal decomposition reaction to generate acid. When the plate is heated at 130-140°C for about 30 seconds, the phenolic resin in the exposed area reacts with the acid of the catalyst to undergo bridge curing, insoluble in the developer to form an image area, and the unexposed area dissolves in the developer to expose the aluminum-based sand The target layer becomes a non-image area. Due to the different resins used in thermal plates, the imaging mechanism is also different. Most of them are cross-linked and cured for imaging. The acid is generated by the photothermal acid release agent, and the heat is generated by the infrared absorber.
However, as all over the world attach great importance to environmental protection, these traditional CTP plates can no longer meet the needs of the printing industry, whether it is a negative thermal CTP plate or a positive thermal CTP plate,
After the exposure treatment, these plates still need to go through developing, rinsing, and other processing procedures to generate a large amount of chemical waste liquid, which will inevitably cause a certain degree of impact on the environment. With the continuous advancement of science and technology, chemical-free CTP plates for pre-press and plate-making processes have emerged as the times require, becoming the first choice for CTP green and environment-friendly plates. So far, thermal CTP technology is the only CTP plate technology that can realize no-washing, that is, process-free CTP plate, which will be the development direction of thermal technology in the future. Process-free CTP technology has a broad sense and a narrow sense. In a broad sense, it refers to a plate that can be printed on the machine without any treatment after exposure and imaging on the direct plate-making machine. Any form of chemical waste liquid will be produced; in a narrow sense, it means that the plate does not need to be chemically developed after exposure and imaging, but there will also be non-chemical treatment processes, such as washing with water, coating protective glue, etc.
The development of non-processing technology has experienced several different technologies such as thermal ablation technology, polarity conversion technology, and hot melting technology. Thermal ablation technology refers to the ablation of the non-image and text part of the plate by laser to expose the aluminum plate base, and the image and text will be formed without any change in the image and text part. This kind of plate can be printed directly after exposure. This kind of printing plate is a real process-free printing plate in our concept, but it has not been widely used due to the large amount of dust generated during the imaging process that affects the quality of the printing plate.
Polarity conversion technology refers to the change of hydrophilicity or lipophilicity on the surface of the plate due to physical or chemical changes in the photosensitive layer of the printing plate after exposure, thereby forming graphic printing parts and non-graphic parts. Hot-melt technology is the current true treatment-free plate, and it is also a technology that is currently commercially applied. It refers to the thermal fusion effect of the plastic particles in the surface coating of the plate after exposure and condenses on the surface of the plate base to form Graphics, that is, the ink-friendly layer, can then be printed directly on the machine. Compared with other processing-free technology plates, the biggest feature of this technology is that it uses a hydrophilic aluminum plate base as the hydrophilic layer of the printing plate, and its printability and durability are very good.
CTP technology is the most revolutionary new technology in the printing field. With the development of CTP plate-making technology, a new generation of processing-free thermal plates will create a new situation in the CTP plate industry. Thermal plates that do not require processing such as development have been put into production. , together with the advanced digital printing process, thermal technology will bring digital imaging into a new era and lead the printing industry to digital green printing.