Technology IV of the most pyrographic plate imagin

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Plate imaging technology (IV)

● photopolymer plate

photopolymer plate is usually composed of aluminum plate base, photosensitive layer and surface layer. The photopolymerization layer is mainly composed of polymerized monomer (+ oligomer), initiator, spectral sensitizer and film-forming resin. The initiator generally adopts the multi initiator system with high quantum efficiency. The role of the spectral sensitizer is to effectively extend the photosensitive range of the initiator to the light-emitting wavelength region of the laser. At present, it can be extended to 488nm (sub ion laser) and 532nm (frequency doubled YAG laser). The function of the surface layer is to separate the oxygen molecules in the atmosphere from entering the photosensitive layer, so as to improve the chain growth efficiency of the photosensitive layer and obtain high sensitivity

thanks to these effective measures, the sensitivity of photopolymerized direct plates has been greatly improved, and the minimum imaging exposure has been reduced to 10 μ About j/cm2, it can be used as the heat shield of aircraft, which is second only to the silver salt type direct plate. Moreover, this plate has simple structure, and its resolution, printing resistance and post-processing are similar to or even better than the conventional PS plate. Because the inherent photosensitive range of most high-efficiency initiator systems is to start the UV region of the instrument at a certain speed, and it is very easy to extend the photosensitive range to the light-emitting wavelength range of uv-ld laser, photopolymerized direct plates will become the preferred system for the next generation of UV direct plates, which has a very good development prospect. With the emergence of UV light source plate Imagesetter, many companies began to introduce photopolymerized direct plates suitable for UV light source imaging on the basis of the original visible light polymerized direct plates. Representative ones include lv-1 (suitable for uv-ld laser), La-5 (suitable for Ar + laser), Ly-5 (suitable for fd-yag laser) of MC imaging company, LP series photosensitive polymer plates (suitable for Ar + and fd-yag laser) launched by Fuji company, etc

● infrared thermal plate

up to now, the development prospect of infrared thermal plate has been promising, and it is considered that it may become the main product monopolizing the direct plate market. For this reason, infrared laser thermal plates are the most abundant and diverse. In general, infrared thermal plates can be roughly divided into two types, namely, thermal ablation type direct plates and non thermal ablation type direct plates. Non thermal ablation can be divided into thermal crosslinking, thermal transfer and thermally induced phase change. Among the numerous thermal plates, the non post-processing plates that can be printed without any chemical post-processing after laser scanning imaging are the development direction of thermal plates, which have attracted great attention of major companies. In this competition, Ko promotes the production, trade, steel blending and development. Dak polychrome, Agfa, pressek, Asahi, Fuji and Toray are still important manufacturers and suppliers of thermal sensitive direct plate system

the representative work of heat sensitive plates without post-treatment is the thermal ablative waterless offset direct plate introduced by prestek company. This plate technology has achieved great commercial success in Heidel and the direct imaging printing machine of Berg company, which emphasizes the need to build a new political and business relationship with Qing Dynasty, and in other manufacturers' direct imaging printing machines. Last year, Asahi introduced a non thermal ablative thermally induced phase change/affinity change direct plate without post-treatment at the iGAS exhibition, which attracted widespread attention from peers. Subsequently, at the drupa`2000 Expo held this year, several companies joined the ranks, such as Agfa and Kodak polychrome, which launched prototype products or technology releases one after another. Despite the impact of UV photosensitive direct plate, the development momentum of thermal plate is still very rapid. At present, we can not see who is the final winner

among thermal ablative plates, Presstek's thermal ablative waterless offset plates are worth mentioning. This plate is composed of oil repellent silicone surface layer, photothermal conversion layer (light absorption layer), lipophilic bottom layer and plate base. The silica gel surface layer will form the final non printing surface, which will be removed with the vaporization of the photothermal conversion layer under the action of heat, so that the underlying hydrophilic layer is exposed to become the printing surface receiving ink. The main function of the photothermal conversion layer is to absorb the light energy emitted by the scanning laser, and effectively convert the absorbed light energy into heat energy, so that the temperature of the layout can rise to the vaporization temperature level. The plate base of this plate can be either a metal base (such as aluminum plate base) or a flexible polymer sheet base (such as polyester sheet base), which has a wide adaptability

this kind of plate can be printed after laser scanning and imaging, so it is particularly suitable for in machine direct plate making system, which is the main reason why a considerable number of direct imaging printers are equipped with this kind of plate at present. Although this kind of plate is also a direct plate without post-treatment, it needs to take necessary measures to carry out sewage treatment in order to produce ablation vapor mist and debris during scanning imaging, otherwise it will pollute imaging optics and the environment. It should be noted that waterless offset printing is not the only choice for thermal ablative direct plates. Through appropriate structural changes, thermal ablative direct plates can also be used for conventional watery offset printing. (to be continued)

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