PS version printing and quality control

After the 1960s, the PS version was increasingly used in the world. At present, it has become an indispensable important material for offset printing. The application of the PS version of the new technology is to improve the work efficiency of the offset printing, the quality of printed products, and to accelerate the development of offset printing technology. The quality of the print version of the PS plate is the most direct factor that affects the quality of the printed product. Therefore, the scientific choice of plate making process and strict operation is the key to PS version quality control. The following is from the development, removal of dirty, revision and other aspects of the printing process is always easy to appear and its influencing factors, and propose a reasonable solution.
First, the development and development is to remove the visible light decomposing part together with the alkali-soluble resin under the action of the alkaline solution, and the exposed aluminum plate-base sand becomes the hydrophilic non-image part of the printing plate, and the unexposed part is insoluble due to the development. The liquid remains and becomes part of the printed image.
1. Positive PS version development principle 2,1,5 photosensitive agent see light decomposition, release the atmosphere, causing the ring to open, rearrangement of the molecular structure, the formation of fluorene ketone, with water to produce hydrazine carboxylic acid, insoluble in water; case of alkali generated The sodium salt dissolves in water. The dissolution rate of sodium salt is related to the temperature and concentration of the developer. The higher the development temperature, the faster the dissolution rate; the higher the developer concentration, the faster the development speed, and vice versa.
2. Positive PS version of the developer design positive picture PS version of the main developer used sodium hydroxide, potassium hydroxide, sodium silicate, etc., mainly used to dissolve the visible light after the photosensitizer and photosensitive resin; due to sodium hydroxide Or potassium hydroxide is easy to react with the carbon dioxide in the air to produce sodium carbonate, so that the development of alkali in the north, the PH value is unstable, difficult to grasp, so to increase the amount of the main (3% -7%) inhibitor sodium or silicon Sodium, which hydrolyzes to form hydrazine-depleted hydrogen, stabilizes the PG value of the developer within a certain range. If the PS plate has not been sealed, sodium silicate must be used because it can act as a post-sealing hole. The caustic soda is then used to adjust the alkali action of the developer. Alkali forces should be controlled to a minimum (to avoid 5% or so), so the design is both real and cheap. Developers can also add some surfactants, such as sodium dodecyl benzene sulphonate, detergent, so that the developer is evenly filled with layout, to achieve the purpose of uniform development, and increase the blank part of the water.
The temperature of the developer is proportional to the speed of development, especially manual development (the temperature is generally controlled at about 25 degrees Celsius), but also pay attention to the temperature change of the developer at any time.
As the positive photo-sensitive layer of the PS plate of the positive picture is decomposed by light, the alkaline action force of the developer in the developing solution is gradually weakened due to alkali dissolution, so the new solution should be added at any time in the developing process, and it should be replaced after a certain period of time. Liquid, so that the alkali effect in a stable range to ensure the quality of development.
Yang Tu PS version of the developer formula example:
Sodium hydroxide 40-60 grams Potassium chloride 20-30 grams Sodium phosphate 5-15 grams
Sodium dodecylbenzene sulfonate 20-30 grams of water 10 liters 3. The negative-stainless-stainless-plate version of the PS principle and the design of the developing solution are examples of a negative-working PS plate made of a photosensitive resin with a diazonium salt group. In this PS daylight process, a light decomposition reaction occurs in the light-receiving part to make the diazo resin. Water insolubility becomes insoluble and then developed with water to remove the water-miscible, non-visible light portion, leaving a water-insoluble light visible portion.
An example of a negative PS version developer formulation is as follows:
Formula I Benzyl alcohol 15 g Isopropyl naphthalene sulfonate 5 g Sodium silicate (40%) Aqueous solution 5 g Water 95 g Formula Diphenylmethanol 10 g Sodium silicate (40%) Aqueous solution 20 g Isopropyl naphthalene sulfonic acid Sodium 5g Sodium nitrate 10g Water 95g 4. Development Operation The PS plate development methods include manual development, semi-mechanical spray development and mechanical development.
Manual development is generally performed in shallow polyvinyl chloride baths. Put the sunlight PS plate into the developing tank, so that the developer is completely immersed in the plate, gently brushing with a soft brush, especially the PS plate version of the negative should be scrubbed, until the developed part is completely dissolved and detached, the plate is removed. Out, rinse the remaining developer on the plate with water, and then use it for neutralization with the aqueous solution of % acid. Due to prolonged exposure to air, the sodium hydroxide in the developer is easily neutralized by pens in the air. The developing solution in the tank undergoes several times of development and dissolves the photosensitive layer containing the dye, which has been decomposed by visible light, and changes from colorless, transparent, to green or dark green, which affects the observation of the development effect, and therefore the quality is not good enough to grasp.
Second, in addition to the dirty dirty is mainly to rule on the layout of the many lines, negative film blots, adhesive tape with blots, ideas, etc. removed. The removal method of the PS plate is relatively simple. It is painted on the excess photosensitive layer with a pen or a painter. The dirt remover immediately dissolves the excess light layer, and then the residual dirt remover is removed with clean water. The dissolved substance is washed away.
Examples of decontamination formulations are as follows:
Diethylene glycol 14-18 parts Butanone 5-10 parts Dimethylformamide 5-10 parts Cyclohexanone 10-14 parts Silica powder 2-6 parts Hydrofluoric acid 0.12-0.18 parts Dyes 0.5-2 copies III. Revisions In the PS plate making and printing process, if the disadvantages of people's layout graphics are found due to the defects of the negative film, PS photosensitive layer or other methods, few lines or broken lines can be carried out. repair.
1. When it is found in the plate making process that it needs to be repaired, after the plate is developed, the place to be repaired should be blown with hot air, covered with a brush or repaired with a repair ballpoint pen, and then dried with hot air of 60-70 degrees Celsius. You can.
2. When it is found in the printing process that it needs to be repaired, because it has been coated with hydrophilic substances such as gum liquid and water medicine, it is not firm to apply the repair liquid directly. The surface of the printing plate must be surface-treated. The spring treatment method is first to remove the cotton wool. The place where the developing solution is scrubbed is to be repaired. The developer solution is wiped off with a wet hair paste, neutralized with 3% phosphoric acid, and then washed with water and dried with hot air to perform repair. After repairing, use hot air to dry the machine.
3. The correction recipe is as follows:
M-toluene-formaldehyde resin (softening point of 118 degrees Celsius or more) 7 grams Ethylene glycol ether 15 ml Basic brilliant blue traces Now, PS plate recycling has made gratifying research results, and has been widely used, this is PS plate making and The development of the offset printing industry has opened up broad prospects.