In the offset printing process, the level of printing plate resistance to printing force is one of the important conditions that determine the quality of the printing. When offset printing is used, it is inevitable that the printing plate (PS plate) will suffer from a decrease in the printing force resistance. There are many studies in the printing industry about the cause of the decline in the printing plate's resistance to printing. I cannot agree with some of the points of view. I only talk about my point of view here. We know that the PS version's resistance to print force refers to the ability of the printing plate to print in a certain amount of quality. This capability plays a decisive role in the printing process. To improve the resistance to printing, the quality of the printed product is good, and the cost is low; if the resistance to printing is reduced, the quality of the printed product is poor, the cost is high, and the extra work is much more (such as human resources, etc.). In view of this phenomenon, I think it is mainly caused by the following factors.
First, the plate-making process can not be standardized operation caused by the decline in printing plate resistance, such as the plate-making process in the plate-making process did not carefully check the density of the film is not uniform; whether in the imposition of "three no" (that is, no glue track, no processing, No pollution); whether the exposure time is properly controlled during the printing, whether the exposure of the printing machine is compact, the control of the development time, and whether the ratio of the developer is reasonable; the temperature of the baking plate and the temperature control of the baking plate are adjusted. Whether it is appropriate and so on.
Whether the density of the film is even or not is a must for the photofinishing staff to know before the printing, and the density of the film plays a significant role in the quality of the dried printing plate. If the printing personnel in the print version of its hearts countless, there will be in the normal exposure time drying out of the printing plate local network is missing or part of the text lines lack of pen strokes, word false is not true, so that the printing plate India The force drops.
Some films are made by the imposition workers themselves during the plate making process. If the imposition workers are not responsible for the imposition, they are not conscientiously engaged in the imposition. The film is dirty, scraps, glue marks, or some films overlap each other ( In particular, this approach is particularly close to graphic sources. The phenomenon of sticking the edge of the paper with graphic tapes and the like causes problems such as false appearance and misprints of printed plates, which causes the printing plate to have a reduced resistance to printing forces.
Correctly controlling the exposure time of a printing plate is an important aspect of improving the printing plate printing force. If the exposure time is too long, that is, overexposure, it will cause the printing plate network to send false, word line is not true; if the exposure time is too short, that is, insufficient exposure, will make the plate surface sand in the development of corrosion incomplete, causing paste plate Characters and other phenomena. Overexposure or underexposure will cause the printing plate's resistance to drop. At the same time, attention should be paid to the situation of the stencil vacuuming during the exposure. If the vacuum is not true, there will be bubbles between the film and the printing plate or between the film and the glass. When the printing plate is exposed, the network points will be lost or misrepresented. Affect the quality of the printing plate, causing the printing plate's resistance to printing force to drop.
When the exposed PS plate is developed, the development time should be properly controlled. Under the condition that the ratio of the developer is reasonable and the temperature is suitable, if the development time is too long, it will cause the printing plate graphic part to be imaginary. The decrease of adhesion of the surface mesh points will also cause the printing plate's resistance to printing force to drop.
After the correct processing, the printing plate should be “thin and uniform†as far as possible when it is coated with a protective rubber (arabino resin). The rag is “clean and cleanâ€. Otherwise, the phenomenon of “peeling†will occur after the glue is dry, and it will also cause printing. The resistance of the printing plate falls.
Baking can improve the printing plate's resistance to printing and make the image part produce chemical resistance, but if the method used in the baking process is not correct, it will also make the printing plate's resistance to printing force drop. For example, if the baking ratio of the baking solution during baking is unreasonable, the coating is not uniform, the baking plate temperature is too high or too low, and the time is too long or too short, etc., the same phenomenon of “soft plate†or “peeling plate†will occur. The Al2O3 film layer of the printing plate is brittle or deteriorates the mechanical strength and chemical stability of the blank portion. Under normal circumstances, we require baking solution should be coated with "thin and uniform", baking temperature control between 200 ~ 230 °C, baking time of 8 ~ 10min is appropriate.
Second, improper adjustment of printing pressure, improper use of fountain solution can also cause the printing plate to withstand the force of force...
Printing pressure refers to the force of interaction between embossed bodies during the printing process. It is indispensable for printing with platen pressure, which inevitably brings about compression deformation, speed difference and friction. There are mainly the following reasons that the printing pressure causes the printing plate to have decreased printing resistance.
The first is that the drum pressure is improperly adjusted, that is, improper pressure adjustment between the plate cylinder and the blanket cylinder. If there is excessive pressure, the friction between the printing plate and the eraser will be exacerbated, and the dots of the graphic part of the printing plate will be damaged, and the resistance force will drop.
Followed by the improper adjustment of the pressure between the ink roller and the water roller, especially the printing roller (usually four diameters are not equal) and the roller (usually two equal diameters), if they are with the printing plate. Excessive pressure adjustment will also increase the friction and cause the printing plate's outlets to suffer losses, resulting in "off edition" and other phenomena, which will cause the printing plate's resistance to printing force to drop.
Of course, whether it is the rubber directly in contact with the printing plate or the printing roller or water roller, the quality of their own (especially the rubber surface) will also affect the printing force of the printing plate, such as the rubber roller. The eraser appears to be aged, crystallized, and forms a glass surface; the softening and aging of the printing roller, and the hardening of the fleece sleeve of the printing roller will also make the printing plate less resistant to printing forces. Of course, these conditions are all put forward under the premise of rationalization of packing linings (the types of packing materials include soft linings, neutral linings, and rigid linings. We do not do research here).
In the lithography process, the purpose of using the fountain solution is to maintain the balance between the blank portion and the graphic portion, and to protect the blank portion of the printing plate from ink invasion. If the fountain solution is used improperly in the printing process, the pH of the fountain solution will be too high or too low, which will cause the printing plate to have a reduced resistance to printing forces. Too low a pH of the fountain solution will seriously corrode the printing plate base (will also make the printing ink layer dry slowly) because the main component of the plate base of the PS plate used in plate offset printing is aluminum. This metal is very lively. , is not stable in strong acid or alkali solution; the pH value of the fountain solution is too high, it will make the graphic part of the printing plate (photo-decomposition type PS plate) - the graphic part of the positive chart type PS is not exposed to heavy Nitrogen compounds are dissolved, resulting in incomplete graphics, weakening their strength and lipophilicity, and reducing the life of the printing plate. It is generally believed that it is appropriate to control the pH of the PS plate at a pH of 5.0 to 6.5. The fountain solution is slightly weakly acidic, because in the weakly acidic fountain solution, the aluminum-based plate will be slightly corroded to form a hydrophilic inorganic salt layer. If a hydrophilic colloid is added to the fountain solution to supplement the depleted hydrophilic colloid layer, it will not cause the reduction of the printing plate's resistance force.
In the lithographic printing process, the balance between water and ink should also be as far as possible. The so-called offset ink balance of lithographic offset printing refers to ensuring the color reproduction, gray balance, color density, and order of the graphic printing under certain printing speed and printing pressure. Adjust the value to meet the requirements of the customer, use the least amount of ink supply and make the blank part within the area of ​​the specified limit, use the minimum amount of water supply, in order to ensure the quality of the print, if during the printing process Failure to achieve ink-water balance will also affect the printing plate's resistance to printing. When water is big, the ink is emulsified, and the density of blotting ink cannot meet the requirements. The printing plate base is affected by the invasion and the corrosion degree is deepened. When the water is small, the plate is “glued†or “stacked with inkâ€, which affects the quality of the printed product and reduces the printing quality. Edition life.
Of course, there are many external and internal factors that will also cause the printing plate to suffer from a decrease in the printing capacity, such as the quality of the PS plate, the correct access to the printing plate, and the responsibility of the printer when printing. Whether or not it has achieved a series of problems such as "Sanping," "Three-Diligence," and "Three Littles," and so on, there have been many discussions in this area, and no analysis or research has been done here.
I think that whether it is a plate-making process or a printing process, as long as we carefully deal with several issues mentioned above, it will improve the printing plate's resistance to printing, and it will print high-quality, high-quality prints.
First, the plate-making process can not be standardized operation caused by the decline in printing plate resistance, such as the plate-making process in the plate-making process did not carefully check the density of the film is not uniform; whether in the imposition of "three no" (that is, no glue track, no processing, No pollution); whether the exposure time is properly controlled during the printing, whether the exposure of the printing machine is compact, the control of the development time, and whether the ratio of the developer is reasonable; the temperature of the baking plate and the temperature control of the baking plate are adjusted. Whether it is appropriate and so on.
Whether the density of the film is even or not is a must for the photofinishing staff to know before the printing, and the density of the film plays a significant role in the quality of the dried printing plate. If the printing personnel in the print version of its hearts countless, there will be in the normal exposure time drying out of the printing plate local network is missing or part of the text lines lack of pen strokes, word false is not true, so that the printing plate India The force drops.
Some films are made by the imposition workers themselves during the plate making process. If the imposition workers are not responsible for the imposition, they are not conscientiously engaged in the imposition. The film is dirty, scraps, glue marks, or some films overlap each other ( In particular, this approach is particularly close to graphic sources. The phenomenon of sticking the edge of the paper with graphic tapes and the like causes problems such as false appearance and misprints of printed plates, which causes the printing plate to have a reduced resistance to printing forces.
Correctly controlling the exposure time of a printing plate is an important aspect of improving the printing plate printing force. If the exposure time is too long, that is, overexposure, it will cause the printing plate network to send false, word line is not true; if the exposure time is too short, that is, insufficient exposure, will make the plate surface sand in the development of corrosion incomplete, causing paste plate Characters and other phenomena. Overexposure or underexposure will cause the printing plate's resistance to drop. At the same time, attention should be paid to the situation of the stencil vacuuming during the exposure. If the vacuum is not true, there will be bubbles between the film and the printing plate or between the film and the glass. When the printing plate is exposed, the network points will be lost or misrepresented. Affect the quality of the printing plate, causing the printing plate's resistance to printing force to drop.
When the exposed PS plate is developed, the development time should be properly controlled. Under the condition that the ratio of the developer is reasonable and the temperature is suitable, if the development time is too long, it will cause the printing plate graphic part to be imaginary. The decrease of adhesion of the surface mesh points will also cause the printing plate's resistance to printing force to drop.
After the correct processing, the printing plate should be “thin and uniform†as far as possible when it is coated with a protective rubber (arabino resin). The rag is “clean and cleanâ€. Otherwise, the phenomenon of “peeling†will occur after the glue is dry, and it will also cause printing. The resistance of the printing plate falls.
Baking can improve the printing plate's resistance to printing and make the image part produce chemical resistance, but if the method used in the baking process is not correct, it will also make the printing plate's resistance to printing force drop. For example, if the baking ratio of the baking solution during baking is unreasonable, the coating is not uniform, the baking plate temperature is too high or too low, and the time is too long or too short, etc., the same phenomenon of “soft plate†or “peeling plate†will occur. The Al2O3 film layer of the printing plate is brittle or deteriorates the mechanical strength and chemical stability of the blank portion. Under normal circumstances, we require baking solution should be coated with "thin and uniform", baking temperature control between 200 ~ 230 °C, baking time of 8 ~ 10min is appropriate.
Second, improper adjustment of printing pressure, improper use of fountain solution can also cause the printing plate to withstand the force of force...
Printing pressure refers to the force of interaction between embossed bodies during the printing process. It is indispensable for printing with platen pressure, which inevitably brings about compression deformation, speed difference and friction. There are mainly the following reasons that the printing pressure causes the printing plate to have decreased printing resistance.
The first is that the drum pressure is improperly adjusted, that is, improper pressure adjustment between the plate cylinder and the blanket cylinder. If there is excessive pressure, the friction between the printing plate and the eraser will be exacerbated, and the dots of the graphic part of the printing plate will be damaged, and the resistance force will drop.
Followed by the improper adjustment of the pressure between the ink roller and the water roller, especially the printing roller (usually four diameters are not equal) and the roller (usually two equal diameters), if they are with the printing plate. Excessive pressure adjustment will also increase the friction and cause the printing plate's outlets to suffer losses, resulting in "off edition" and other phenomena, which will cause the printing plate's resistance to printing force to drop.
Of course, whether it is the rubber directly in contact with the printing plate or the printing roller or water roller, the quality of their own (especially the rubber surface) will also affect the printing force of the printing plate, such as the rubber roller. The eraser appears to be aged, crystallized, and forms a glass surface; the softening and aging of the printing roller, and the hardening of the fleece sleeve of the printing roller will also make the printing plate less resistant to printing forces. Of course, these conditions are all put forward under the premise of rationalization of packing linings (the types of packing materials include soft linings, neutral linings, and rigid linings. We do not do research here).
In the lithography process, the purpose of using the fountain solution is to maintain the balance between the blank portion and the graphic portion, and to protect the blank portion of the printing plate from ink invasion. If the fountain solution is used improperly in the printing process, the pH of the fountain solution will be too high or too low, which will cause the printing plate to have a reduced resistance to printing forces. Too low a pH of the fountain solution will seriously corrode the printing plate base (will also make the printing ink layer dry slowly) because the main component of the plate base of the PS plate used in plate offset printing is aluminum. This metal is very lively. , is not stable in strong acid or alkali solution; the pH value of the fountain solution is too high, it will make the graphic part of the printing plate (photo-decomposition type PS plate) - the graphic part of the positive chart type PS is not exposed to heavy Nitrogen compounds are dissolved, resulting in incomplete graphics, weakening their strength and lipophilicity, and reducing the life of the printing plate. It is generally believed that it is appropriate to control the pH of the PS plate at a pH of 5.0 to 6.5. The fountain solution is slightly weakly acidic, because in the weakly acidic fountain solution, the aluminum-based plate will be slightly corroded to form a hydrophilic inorganic salt layer. If a hydrophilic colloid is added to the fountain solution to supplement the depleted hydrophilic colloid layer, it will not cause the reduction of the printing plate's resistance force.
In the lithographic printing process, the balance between water and ink should also be as far as possible. The so-called offset ink balance of lithographic offset printing refers to ensuring the color reproduction, gray balance, color density, and order of the graphic printing under certain printing speed and printing pressure. Adjust the value to meet the requirements of the customer, use the least amount of ink supply and make the blank part within the area of ​​the specified limit, use the minimum amount of water supply, in order to ensure the quality of the print, if during the printing process Failure to achieve ink-water balance will also affect the printing plate's resistance to printing. When water is big, the ink is emulsified, and the density of blotting ink cannot meet the requirements. The printing plate base is affected by the invasion and the corrosion degree is deepened. When the water is small, the plate is “glued†or “stacked with inkâ€, which affects the quality of the printed product and reduces the printing quality. Edition life.
Of course, there are many external and internal factors that will also cause the printing plate to suffer from a decrease in the printing capacity, such as the quality of the PS plate, the correct access to the printing plate, and the responsibility of the printer when printing. Whether or not it has achieved a series of problems such as "Sanping," "Three-Diligence," and "Three Littles," and so on, there have been many discussions in this area, and no analysis or research has been done here.
I think that whether it is a plate-making process or a printing process, as long as we carefully deal with several issues mentioned above, it will improve the printing plate's resistance to printing, and it will print high-quality, high-quality prints.
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