CTP plate quality is good and bad pk
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Looking at the current development trend of the CTP market, technology competition is inevitable. Taking the plate as an example, there are four types: silver salt type, photopolymerization type, heat sensitive type (thermal imaging type), and free processing CTP plate material. It is said that each has its own merits and a hundred schools of thought contend.
1. Silver salt type CTP plate material
The silver salt type CTP plate mainly includes two types of silver salt diffusion transfer plate and silver salt and PS plate composite plate.
The silver salt diffusion transfer plate is mainly composed of a plate base, a silver salt emulsion layer and a physical development core layer. The diffusion transfer imaging technology is adopted. The principle is a silver salt plate exposed by laser scanning. In a developer containing a silver halide solvent, Ag+ and a silver halide solvent are complexed and diffused to the image receiving layer to catalyze the physical development nucleus. It is reduced to metallic silver by the action and deposited on the surface of the body to form a silver image. After the development is completed, the silver halide emulsion layer on the surface is removed by water washing to expose the hydrophilic sand and image areas of the non-image area, and in the sensitizing liquid, the long-chain organic molecules with sulfhydryl groups are selectively adsorbed on the deposited silver surface. Make the image area lipophilic. As a result, the deposited silver image begins to accept the ink and repels the water, while the non-image portion (without silver deposition) still rejects the ink, thereby achieving the purpose of direct computer plate making.
The silver salt and PS plate composite plates are mainly composed of a high-sensitivity silver salt emulsion layer and a PS plate with a wide sensitivity range. A pre-photosensitive photosensitive polymer layer, a tie layer, and a silver halide emulsion layer are sequentially coated on the roughened and anodized aluminum base. The imaging principle is that the silver salt layer is first exposed by laser to form a graphic silver image on the resin layer, so that the underlying photosensitive layer can be protected from being photosensitive during the double exposure. After one development, the emulsion layer of the non-exposed portion was dissolved, and then double exposure was performed, that is, the entire layout was exposed with UV light. Since the image image layer blocks the light, the UV light only exposes the photo-decomposable photosensitive resin layer in the non-image portion, and the resin layer which is subjected to secondary development and double exposure is dissolved to expose the alumina plate base. Finally, the silver image layer can be subjected to a lipidation treatment with a fixing solution.
Silver salt type CTP plate features
(1) Silver salt type CTP plate material has high sensitivity.
It can reach 1~3μJ/cm2, which means high-speed plate output can be realized by using laser with low output power, low energy and low intensity. Moreover, the silver salt type CTP plate has a fast photospeed, and is the fastest plate in the current CTP plate.
(2) Silver salt type CTP plate has a wide range of applications.
Red laser, green laser, and violet laser systems can be used. The rinsing method and post-processing process are the same as the conventional method, and the CTP plates of different manufacturers are compatible with the formulation of the chemical solution.
(3) The silver salt type CTP plate has the characteristics of high resolution, wide spectral response and good dot reproducibility.
The number of screen lines can reach 300 lines/inch, the coverage of the dot can reach 1% to 99%, the quality of the printing plate is excellent, and the printing durability is up to 250,000 printing or more, which is suitable for large printing and high quality printing.
(4) Since the silver salt type CTP plate material is made of expensive silver as a raw material.
The production cost is increased to a certain extent, and the silver salt type CTP plate cannot be operated under the bright room, which brings certain limitations to the preservation of the plate material.
2. Photopolymeric CTP plate
The photopolymerization type CTP plate is mainly composed of a sand-imprinted aluminum plate base, a photosensitive layer and a protective layer. The photosensitive layer is mainly composed of a film-forming resin, a sensitizing dye, a photoinitiator, a monomer or an oligomer, and is stable. Composition of agents and other additives. The protective layer is a polyvinyl alcohol oxygen barrier layer, which is mainly used for blocking the inhibition of oxygen on monomers or oligomers. The imaging principle is that after the plate material is scanned by the laser light source, the sensitizing material in the photosensitive layer of the light portion first absorbs the photon energy into an excited state, and then transfers the energy to the photoinitiator, and the photoinitiator decomposes to form a free radical, freely. The base initiating monomer or oligomer polymerizes and solidifies to form a graphic portion. The portion where no light was observed was removed by development to form a blank portion. It should be noted that before the development, the protective layer of the unvisited portion should be washed off, and the high-sensitivity polymer layer is dissolved by the alkaline developing solution. After the development is completed, the protective layer is completely removed with a brush. Finally, the plate is washed with a synthetic resin solution, and the synthetic resin not only improves the hydrophilicity of the blank portion, but also enhances the lipophilicity of the image portion, and can be printed after drying.
Characteristics of photopolymeric CTP plate
(1) The photopolymerizable CTP plate has a thin photosensitive layer, and the image portion and the blank portion are substantially on the same plane, which is a conventional offset type, and has high sensitivity and fast plate making speed.
(2) The developer used in the photopolymerizable CTP plate material is alkaline, and the film-forming resin and monomer or oligomer in the photosensitive layer have a certain acidity, can be dissolved in the alkali solution and removed by development, and the alkali The developer has a small pollution and is environmentally friendly.
(3) Photopolymerization type CTP plate material can use different laser light source such as violet laser diode (410nm), argon ion laser (488nm), FDYAG laser (532nm), infrared laser diode (830nm), etc., and the cost is low. And the photopolymerization type CTP plate has a printing durability of more than 1 million impressions after being baked.
3. Thermal CTP plate
There are many types of heat-sensitive CTP plates, but there are two types of mature types, namely, hot-melt type and heat-cross-linked type.
The hot-melt type CTP plate is mainly composed of an aluminum plate, an ink-receiving layer and a PVA layer (used in conventional offset printing) or a silica gel (used in waterless offset printing) which do not require roughening. Its imaging principle is exposure using a semiconductor laser diode. The heat-sensitive coating (ie, the ink-receptive layer) on the substrate is ink-repellent and insoluble in alkaline syrup. After exposure, the coating absorbs energy, increases solubility, and dissolves in alkaline syrup. At the time of development, the exposed portion is dissolved in the alkaline syrup to form a blank portion of the printing plate. The non-exposed portion does not dissolve, forming a graphic portion of the printing plate. After development, it is usually cleaned and glued before it can be printed on the machine.
The thermally crosslinked CTP plate mainly consists of a roughened aluminum plate and a single layer PS photosensitive layer. Its imaging principle is exposed by infrared light. During exposure, the photothermal conversion substance converts the light energy of the infrared laser into heat energy, causing some of the polymer in the photosensitive layer to undergo thermal crosslinking reaction to form a latent image; and reheating to further crosslink the molecular compound in the image portion So that the graphic portion is not dissolved in the alkaline developer. It should be noted that when preheating, the blank portion also partially reacts, so the image of the blank portion is removed during development. If the temperature is too high, a hot mist will form on the plate; if the temperature is too low, the image will be faded or weakened.
Thermal CTP plate features
(1) The thermal CTP plate has a low sensitivity to natural light and is exposed by infrared laser, so it can be operated under bright room conditions.
(2) The thermal plate must generate the image, and the initial thermal energy threshold must be reached. The thermal energy above the initial threshold does not change the shape of the dot. It is the only technology that can control the predicted results. The quality is easy to control, the publishing quality is stable, and after exposure. The plate can be extended to 6 months before development, and there is no slight impact on the quality of the plate.
(3) The thermal CTP plate has good dot reproducibility and high resolution, and the edge of the dot is sharp and clear. It is easy to achieve ink balance during printing, has good printability, and the printing durability of the plate after baking is up to More than 1 million prints.
In addition to the three dominant CTP plates introduced above, the free handling of CTP plates in recent years has become a hot topic of discussion.
4. Free processing of CTP plates
The free-handling CTP plate was first introduced by Asahi Kasei Corporation of Japan. In a broad sense, it means that after the plate is exposed and imaged on the direct plate making equipment, it can be printed on the machine without any subsequent processing steps. Of course, it does not need chemical development, rinsing, etc., and is a true processing-free plate; In a narrow sense, it means that the plate material does not need to be chemically developed after exposure and imaging on the direct plate-making machine, but there are still some non-chemical treatment processes, such as the removal of the plate ablation waste and the application of the protective rubber. In terms of plate making, the process-free plates can be divided into two categories: process-free plates for DI (direct image on-press) presses and plates for exposure imaging on CTP platesetters.
Free handling plate features
(1) Compared with the traditional CTP plate, the process-free plate eliminates the steps of development, fixing, cleaning, gluing, drying, etc., shortens the plate making cycle, reduces the amount of energy consumed during exposure, and reduces the overall plate-making cost. , improve production efficiency and simplify the production process.
(2) Since the chemical-free printing plate does not require chemical development, rinsing, etc., the process-free plate-making process does not cause chemical waste liquid, exhaust gas, waste residue, etc., which reduces environmental pollution, and is also suitable for printing operators. It is beneficial.
(3) Changes in the rinsing conditions of the plate, changes in the laser energy, and thickening of the rinsing solution, which allows for higher quality stability without the need for rinsing of the process-free plate.
(4) The chemical-free processing device is not required for the processing-free plate, which saves space in the factory and is a big advantage for small companies, but the price of the process-free plate is higher than that of the conventional CTP plate.
The CTP market war has entered the era of the Warring States. We are not afraid of war. Only in this way can we promote the wheel of history and create a better future.