PS version of the pre-printed sensitized photosensitive lithography (also known as PS version) from the 50's has been applied so far, with its high resolution, bright spot, high resistance to force and other characteristics, and gradually replace the protein plate, multi-layer metal plate and other plates , has become a new type of modern fast printing plate. At present, under normal circumstances, the PS version of the print resistance is generally about 100,000 prints, after baking the PS version of the print force can be increased by 3-5 times to reach 30 million to 500,000 prints, but now there are many manufacturers reflect the PS The print resistance of the print is not high, generally only 210,000 prints, or even thousands of prints. Here, I only personal experience, in accordance with the PS version of the production process, on the PS version of the printing force plate production and plate-making process of rough discussion and analysis.
First, the edition plate material choice PS version base is aluminum. The aluminum material used for the PS plate belongs to general industrial grade pure aluminum, and its thickness is generally 0.3mm and its content is 99.5%. The main impurities are iron and silicon, followed by copper, magnesium, zinc, manganese and titanium. The presence of a small amount of impurities in the aluminum plate can increase the tensile strength and hardness of the pure aluminum, reduce the elongation, and reduce the conductive properties of the aluminum.
Second, the composition of sensitizers and sensitizers for coating PS plates are composed of photosensitive materials, film-forming polymer resins, dyes, and organic solvents. For a photosensitive layer coated with a photosensitive agent formulated with a photosensitizer alone, its alkali resistance is strong, the film forming property is poor, and development is difficult; an appropriate amount of phenolic resin is added to the photosensitizer. Although the alkali resistance is poor, the film forming property and the adsorptivity are improved, and the ratio of the two is 0.5:1 or 0.62:1. If the amount of the photosensitizer is small and the film-forming resin is large, the alkali resistance is reduced and the dots are easily lost. The low residual film rate directly reduces the printing plate's resistance to printing force.
The application of the PS version of the sensitizer requires the use of a special coating machine to ensure that the thickness of the photosensitive layer after coating is uniform. Coating machines are generally divided into two types, single-sheet and roll-type. In coating methods, there are paving, roller coating, extrusion and electrostatic coating. We do not recommend the use of centrifugal coating. China's commonly used roller coating type, in order to ensure the coating quality, the general negative picture type photosensitive layer solid content of about 1g/m2. The positive pattern is 2-2.5 g/m2, and the thickness is generally (20±1.0) mg/dm2. When the coating produces lateral stripes and other faults should be promptly removed.
Third, the PS version of the plate-making version of the PS plate is the key to maximize the reproduction of the film's network and tone, in the printing plate surface to form a solid lipophilic basis and stable hydrophilic basis. Otherwise, it not only wastes time, but also seriously reduces the printing plate's resistance to printing and wastes the plate. A series of factors that directly affect the quality of platemaking include dot reproducibility of the original plate version of the plate making, plate making equipment and conditions. Platemaking process and operation, especially exposure, development conditions, and the like.
1. The original positive or negative version of the original version of the PS version can be made using traditional methods such as photolithography, electronic color separation and photocopying. In addition to the adjustment of the tone reproduction curve, it is also necessary to pay attention to the original density contrast and dot finish. Because the original Y value is too low, exposure, underdevelopment, or excessive thinning are the causes. It is easy to form soft dots with low density or active dots with high density and low edge density. The printing stability of these two types of outlets is poor, and the exposure and development are slightly changed, which will cause the printing plates to have different shades, which will directly affect the printing plate's resistance to printing forces. The original version of the hard dot, due to its high density and clean dots, has a large exposure and development latitude. So the quality is stable. Therefore, the original printing pattern used in the printing must be clear and have a high density and contrast. Take Huaguang brand YZ-600 11 film as an example. The original maximum density should be above 4.0. The minimum density is below 0.05, the gamma ratio is above 8.0, and the layout clean reduces haze and collage.
2. Shaiban light source for the printing plate light source. The sensitization of the sensitizer is a redox reaction. Only the sensitizer fully absorbs enough light energy of T to occur, and its degree of decomposition, cross-linking, and bonding are directly proportional to the required light intensity and the illumination time. Therefore, the emission spectrum of the printing plate light source and the photosensitizer photosensitive curve Sensitive areas should try to match. Experiments have shown that the photosensitivity of the positive photosensitive thorn is within 300nm-460nm, and the figure is within 200nm-500nm. Take into account the effects of the printing plate and the printing plate. Spectral design is suitable in the 350nm-460nm region. Therefore, the ideal light source for printing PS plates is iodine lamp. (To be continued)
A Preliminary Study on the Resistance of PS Plate to India (Part One)
January 05 18:10:34, 2024
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