Technology V of the most pyrographic plate imaging

2022-07-27
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Plate imaging technology (V)

thermal crosslinked plate is composed of thermal sensitive coating and hydrophilic plate base. The thermosensitive coating is generally composed of (alkali) water-soluble film-forming resin (such as phenolic resin), thermosensitive crosslinking agent and infrared dye; The hydrophilic plate base can use the same aluminum plate base as the traditional PS plate. The function of infrared dye is to effectively absorb the light energy of infrared laser and convert the absorbed light energy into heat energy, so that the temperature of thermal sensitive coating can reach the reaction temperature of thermal crosslinking agent; The function of thermosensitive cross-linking agent is to react with film-forming resin to form a spatial structure under the action of temperature, so that the thermosensitive coating loses its water solubility. Due to the effect of spatial cross-linking, the thermal coating in the exposed area is still left on the plate to become an oleophilic printing surface after development, while the unexposed area is mainly used by the plastic sliding friction and wear tester to remove the sliding friction and wear of plastics and plastic matrix composites, so that the hydrophilic plate substrate below can be exposed to become a hydrophilic non printing surface. In order to further improve the effect of thermal crosslinking, some plates often need to be preheated after exposure, so as to further deepen the effect of thermal crosslinking (which is also a mechanism to increase the sensitivity). This kind of plate is called the hot cross-linked plate that needs preheating. The graphic area of thermally crosslinked plates is composed of spatially crosslinked polymer resin, so this kind of plates usually have very high mechanical strength and printing resistance, and can generally print hundreds of thousands of copies, which is very suitable for long-term printing. According to the data provided in the announcement, the brush market is calculated

both heat transfer plates and thermally induced phase change plates are processless ctplates that can be printed without chemical post-treatment after imaging, and no ablative debris, steam fog and other wastes will be generated during laser scanning imaging. Therefore, this type of plate is suitable for both offline and on-line direct plate making, which has attracted widespread attention. The heat transfer direct plate is composed of a color band and an image receiving substrate. The image receiving substrate itself has good hydrophilicity (for example, the aluminum plate base of traditional PS plate). Its main function is to accept the hot wax layer transferred by the ribbon and build a hydrophilic non printing surface. The ribbon is composed of a heat-resistant polymer sheet base and a thermal sensitive layer (thermal wax layer), which is composed of a low melting point polymer material and an infrared dye. When imaging, the color band is in close contact with the image receiving substrate, and the laser light energy is absorbed by the dye and converted into heat energy, so that the temperature of the thermal sensitive layer rises, resulting in the melting of the polymer of the thermal wax layer, so that the "liquid" thermal wax layer is transferred to the image receiving substrate to form a printed image surface. In order to improve the mechanical strength of the image area, it is often necessary to cure the hot wax layer transferred on the surface of the image receiving substrate at a higher temperature. The principle is to crosslink the hot wax layer to form a spatial structure

although this kind of plate does not need post-processing after development, the separated color band and image receiving substrate will bring inconvenience to use and control, and increase variable factors. In contrast, the direct plate with thermally induced phase change has more advantages. This plate is composed of a heat sensitive coating and a supporting substrate. The thermal sensitive coating has enough hydrophilicity to become a non printing surface, but it can change into lipophilic under the action of heat energy to become a printed graphic surface. The substrate of this plate is only the support of the thermal sensitive coating and does not participate in the final printing. Therefore, there is no affinity requirement. It can be either a polymer sheet substrate or a metal plate substrate according to different purposes. Agfa company has released a new reusable plate technology, called Litespeed, which is worth mentioning. Litespied is actually a polymer coating liquid, which can be sprayed on the surface of any printing plate or printing plate cylinder to form a polymer film. Therefore, this polymer film is also called spray on polymer. The sprayed polymer film can be printed without post-processing after laser imaging. After printing, the polymer film can be easily cleaned, and the surface of the printing plate or plate cylinder returns to the original state. Because the supporting base material can be reused, spraying polymer film is very suitable for direct plate making on the machine

● inkjet plates

there are two basic types of inkjet plates. One is to coat the photosensitive layer of the traditional PS plate with an image receiving layer that can accept ink, and the other is a substrate with excellent hydrophilic and water retaining properties (such as the aluminum plate base of the traditional PS plate). The ink-jet direct plate uses the computer to control the reciprocating mechanical movement of the nozzle to realize scanning, and directly sprays the ink onto the image receiving layer or hydrophilic substrate on the photosensitive layer surface of the PS plate to form the ink image. For the first type of printing plate, the inkjet printing plate shall be fully exposed to UV light to expose the photosensitive layer of the PS plate that is not sprayed on the ink image, and then the photosensitive layer of the PS plate can be removed after the PS plate development process, so that the hydrophilic plate base below is exposed to become a non printing surface, that is, the inkjet image on the surface of the image receiving layer is only used as the "Mask" image during UV light exposure, Protect the PS plate photosensitive layer below from ultraviolet light. This kind of plate can use the conventional water-based inkjet technology. The image receiving layer should generally have appropriate hydrophilicity and be able to dissolve in alkaline water, so as to meet the requirements that the receiving ink and collection process can be removed when starting PS plate development from the mobilization s (or "seed") of the given starting URL. For the second plate, the ink image formed by inkjet is the final lipophilic printing area, so it is required to use the inkjet imaging technology of special ink

solid inkjet, also known as phase change inkjet, is a good choice. This inkjet technology uses polymer solid inks that do not contain any solvent that is automatically measured at the beginning of printing, and realizes jet imaging by relying on temperature difference. Therefore, the inks sprayed onto hydrophilic substrates have sufficient mechanical strength and become the graphic surface of printing. The advantage of inkjet direct plate is that it can use the mature inkjet technology and the traditional PS plate. The disadvantage is that the resolution is not high (mainly limited by inkjet technology, generally below 1500dpi), and the speed is relatively low (limited by the reciprocating motion of the nozzle). It is suitable for the printing field where the resolution is not high. (end of full text)

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