CTP pros and cons

Looking at the current development trend of the ctp market, technology competition is inevitable. Taking the plate as an example, there have been four types: silver salt type, photopolymerization type, thermal type (thermal imaging type), and CTP plate-free processing. As the saying goes, each has its own merits and contends.

1. Silver salt type CTP plate

Silver salt type CTP plates mainly include silver salt diffusion transfer plates and silver plates and PS plate plates.

The silver salt diffusion transfer plate is mainly composed of a base plate, a silver salt emulsion layer and a physical development core layer. It uses diffusion transfer imaging technology. The principle is the silver salt version exposed by laser scanning. In a developing solution containing a silver halide solvent, Ag+ complexes with the silver halide solvent and diffuses to the image receiving layer, catalyzing the physical development of the core. Under the effect of reduction into metal silver, deposited on the body surface to form a silver image. After the development is completed, the surface of the silver halide emulsion layer is removed by washing to expose the hydrophilic sand and image areas in the non-image area, and is selectively adsorbed on the surface of the deposited silver by a long-chain fatty molecule with a mercapto group in the sensory fat solution. Make the image area oleophilic. As a result, the deposited silver image begins to accept the ink and repel the water, while the non-image part (without silver deposition) still repels the ink, thereby achieving the purpose of direct computer platemaking.

The composite plate of silver salt and PS plate is mainly composed of a high-sensitivity silver salt emulsion layer and a PS plate with a wide color sensing range. A presensitized photosensitive polymer layer, an adhesive layer, and a silver halide emulsion layer were sequentially coated on the roughened and anodized aluminum substrates. The principle of imaging is to first expose the silver salt layer with a laser to form a graphic silver image on the resin layer, so that in the second exposure, the underlying photosensitive layer can be protected from light. After one development, the non-exposed parts of the emulsion layer are dissolved and then exposed twice, that is, the entire plate is exposed with UV light. Since the image and image layer blocks the light, the UV light only exposes the photo-degradable photosensitive resin layer that is not the image portion, and the second-developed and double-exposed resin layer is dissolved to expose the aluminum oxide substrate. Finally, the silver image layer can be treated with a solid solution.

Characteristics of Silver Salt CTP Plate

(1) Silver salt type CTP plate has higher sensitivity.

Can achieve 1 ~ 3μJ/cm2, that is, the use of low output power, low energy, low intensity laser, but also to achieve high-speed plate output. Moreover, the silver salt type CTP plate has a fast photospeed and is the fastest plate material in the CTP plate.

(2) The silver salt type CTP plate has a wide range of applications.

Red laser, green laser, and violet laser systems can all be used. The rinsing methods and post-treatment processes are the same as the traditional methods, and the different manufacturer's CTP plates are compatible with the chemical solution formulation.

(3) The silver salt type CTP plate has the characteristics of high resolution, wide spectral response, and good dot reproducibility.

The number of screens can reach 300 lines/inch. The coverage of network points can reach 1% to 99%. The quality of the printing plate is excellent, and the printing resistance is as high as 250,000 or more. It is more suitable for large printing and high-quality printing.

(4) As silver salt type CTP plates use expensive silver as raw material.

To a certain extent, the production cost is increased, and the silver salt type CTP plate material cannot be operated under the light room, which brings certain limitations to the preservation of the plate material.

2. Photopolymerized CTP Plate

The photopolymerization CTP plate is mainly composed of a three-part aluminum plate, 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 a stable film. Agents and other additives. The protective layer is a polyvinyl alcohol oxygen barrier layer, which is mainly used to block the oxygen blocking effect of monomers or oligomers. The imaging principle is that after scanning of the plate material by the laser light source, the sensitizing dye in the photosensitive layer of the visible part first absorbs the photon energy into an excited state, and then transfers the energy to the photoinitiator, and the photoinitiator decomposes to form free radicals. The base initiates the polymerization of monomers or oligomers and cures to form a graphic portion. The portion where no light was seen was removed by development to form a blank portion. It should be noted that before the development, the protective layer of the non-visible part should be washed away, and then the high-sensitivity polymer layer should be dissolved with an alkaline developer. After the development is completed, the protective layer is completely removed with a brush. Finally, the plate is washed with a synthetic resin solution. The synthetic resin can not only improve the hydrophilicity of the blank part, but also enhance the lipophilicity of the graphic part, and can be printed after drying.

Photopolymerization CTP Plate Features

(1) The photosensitive layer of the photopolymerizable CTP plate is very thin, and the graphic part and the blank part are basically in the same plane, which belongs to the traditional offset printing type, and has a high sensitivity, and the plate making speed is fast.

(2) The developer used in the photopolymerizable CTP plate is alkaline, and the film-forming resin and monomer or oligomer in the photosensitive layer have a certain degree of acidity, can be dissolved in the alkali solution and removed by development, and alkali The developer has little pollution and is environmentally friendly.

(3) Photopolymerization type CTP plate can use violet laser diode (410nm), argon ion laser (488nm), FDYAG laser (532nm), infrared laser diode (830nm) and other plate photosensitive light sources, and its cost is lower. And the photopolymerized CTP plate can withstand printing force of more than 1 million Indians after baking.

3. Thermal type CTP plate

There are many types of thermal-type CTP plates, but there are mainly two types that are relatively mature at present, namely, hot-melt type and thermal cross-link type.

Thermally melted CTP plate is mainly composed of three parts: aluminum plate, ink-receptive layer and PVA layer (used in conventional offset printing) or silica gel (used in waterless offset printing) without roughening. The imaging principle is to use semiconductor laser diode exposure. The thermosensitive coating (ie, the ink receptive layer) on the plate is ink-receptive and insoluble in alkaline potions. After exposure, the coating absorbs energy, increases solubility, and can be dissolved in alkaline solutions. During development, the exposed portion is dissolved in alkaline solution to form a blank portion of the printing plate. The non-exposed portion is insoluble and forms the graphic portion of the printing plate. After development, it is generally cleaned and glued before printing on the machine.

The thermal cross-linked CTP plate mainly consists of a roughened aluminum plate and a single-layer PS photosensitive layer. Its imaging principle is through infrared exposure. When exposed, the photothermal conversion material converts the light energy of the infrared laser into thermal energy, which causes a thermal cross-linking reaction of some of the polymers in the photosensitive layer to form a latent image; and further heating, the cross-linking reaction of the molecular compound in the graphic part further occurs. So that the graphic part is not dissolved in the alkaline developer. It should be noted that when the preheating is performed, a part of the reaction occurs in the blank portion, so that the image of the blank portion is removed during the development. If the temperature is too high, a hot mist will form on the plate; if the temperature is too low, the graphic part will be lightened or weakened.

Thermal CTP Plate Features

(1) The thermal CTP plate has a low natural light sensitivity and is exposed by infrared laser light, so it can be operated under bright room conditions.

(2) For thermal plates to generate images, the initial thermal threshold must be reached, and thermal energy above the initial threshold will not change the dot shape. It is the only technology that can control the predicted results, the quality is easy to control, the publishing quality is stable, and the exposure is stable. The printing plate can be extended to 6 months after the development, the quality of the plate will not have the slightest impact.

(3) The heat-sensitive CTP plate has good dot reproducibility, high resolution, sharp and clear edges, easy ink balance during printing, good printing applicability, and plate-resistance after printing. More than 1 million impressions.

In addition to the above-mentioned three major CTP plates, the elimination of CTP plates in recent years has become a hot topic of discussion.

4 free processing CTP plate

The processing-free CTP plate was first introduced by Japan's Asahi Chemicals. Broadly speaking, it means that after the plate is exposed and imaged on the plate-making equipment, it can be printed on the machine without any follow-up processing procedures. Of course, it does not require chemical development and rinsing. It is a real sense-free plate. In a narrow sense, it means that the plates do not require chemical development after being exposed and imaged on the plate-making machine. However, there are still some non-chemical processing processes, such as the removal of the ablation waste from the plates, and the application of protective glue. From the aspect of the plate making method, the free-handling plates can be divided into two types: plate-free plates for DI (printing machine direct imaging) printers and plates that are exposed and imaged on a CTP plate-setter.

Free handling of the characteristics of media

(1) Compared with the traditional CTP plates, the process-free plate eliminates the steps of developing, fixing, cleaning, gluing, and drying, shortens the platemaking cycle, reduces the amount of energy consumed during exposure, and reduces the overall plate making cost. Improves production efficiency and simplifies production processes.

(2) Since the plate-free processing does not require chemical development, rinsing, etc., the chemical-free liquid waste, exhaust gas, and waste residue that will destroy the environment will not be generated in the plate-free plate processing process. This will reduce the environmental pollution, and the operator It is helpful.

(3) The change of the processing conditions of the plate, the change of the laser energy, the concentration of the processing liquid, and the treatment-free plate which does not need to be rinsed can make it have higher quality stability.

(4) Free-handling plates do not require chemical development processing devices, which saves plant space, which is a big advantage for small companies, but the free-handling plates are more expensive than conventional CTP plates.

The CTP market war has entered the warring days of war. We have no fear of war. Only in this way can we push the wheel of history and create a better future.