First, common problems and solutions in printing
First of all, let's talk about the correct operation of the graphic point transferred from the film to the PS version:
Commonly used in China is a positive-type PS plate. This type of plate is prepared by coating a prepared photosensitive liquid onto a surface-treated aluminum plate, which is heated and dried to form a photosensitive layer. The pre-coated plate is used for storage and use. During the printing, the sensitized plate and the positive plate coated with a photosensitive layer are closely exposed to light, and the photosensitizer in the light part is decomposed to release nitrogen, causing cracking of the ring, rearrangement of the molecular structure, formation of an fluorenone compound, and formation of tannic acid in water. The compound is subjected to a development treatment to remove the photo-decomposed photosensitive layer, and a non-photosensitive region, that is, a graphic portion of the plate, is stored to make a printing plate. We know that the contact between the film and the photosensitive layer of the PS plate is an important factor affecting the quality of the plate. The contact state is different, and the dot change rule is also different. Good contact is a prerequisite for adjusting the controlled transfer of the dot. Operation should be strictly relative to the surface of the drug film, suction tightly, to ensure good transfer of graphic network points. However, the production of drug film surface is still the case back, due to the thickness of the film base will cause light scattering, uneven transfer of dots, the change can not be controlled, should be strictly avoided. In daily production, there are many problems in this area, as described below.
1. The image is hazy and blank is not clean. To solve this problem, the platen glass must first be kept clean. Wipe clean with alcohol and rub both sides. The transparency of work is not enough, the penetration of light will be affected, and the printed version will be blurred. If the film plate and glass plate are not tightly adhered to each other, it will also cause sun exposure.
Sometimes a film base is used for a long time. There are a lot of residual rubber left on the tape, the transparency will be affected, and the film and film base will not be attached so tightly. Therefore, the film base will need to be replaced after a long time. . In the case of imposition, if the two images overlap, the image will also be shammy. For example, if the leather cloth is used for a long time, aging will occur, and there will be a small amount of air leaks in some marginal areas. The PS version and the film will not stick tightly, and the printed images will also become empty. If the machine takes a long time, it is necessary to check if the vacuum of the air pump is not enough.
If the lamp is used for too long, the cutting rate will decrease and the exposure will be insufficient. When inhaling, if you can't go from the middle to the surroundings, there will be local bubbles, and the PS plate will have a partial blur. This is to check the bottom plate.
2, PS version outlets are not true. To solve this problem, check on the film. The dots on the film used in the printing shall have sufficient darkness, and the dot structure on the printing plate shall be transferred to the printing plate, and the covered portion (net point) must not pass through the light, causing the photosensitive layer of the printing plate to be sensitive. Otherwise, the dots on the printing plate will not be solid, and the dots will fall when printing. The dot faints. We know that the dots are absolutely clear. The transition between the transparent plane and the cladding with high blackness is very steep. It is a sudden change, and the edges of the dots are actually rising. The darkness of the dot is the opposite, and the blackness increases slowly from the edge. So the dot produces an edge with a large or small slope.
Dizzy dots on printing plates cause color deviations due to their unstable performance, and it is often possible to see "small dots missing" on the printing plate. To solve this problem, the film before printing should undergo a rigorous inspection, and the dots should have sufficient darkness and sufficient clear edges.
3, can not reflect the subtle part of the work. For example, a hair filament, which is on the photo, becomes blurred on the plate. This is mainly due to the lack of exposure or the concentration of the syrup in the process of washing out the small part of the wash.
Second, the common problems in the version and solution
After the print version, it will be processed. If the temperature of the developer in the plate processor is too low, the processing speed of the plate processor is too fast, the development time will be shortened, the development will be insufficient, and the plate will not be washed cleanly. If the concentration of the developer is not enough, the time for replenishing the developer is adjusted too long and the plate will be insufficiently developed.
The method to eliminate the above failure is to check the developer temperature and development time and adjust to reasonable data. When using the developer, the manufacturer will provide the proportion of the recipe and it will be done according to the proportion. But sometimes it can be thickened. The stencil machine should be repaired in time, replace the rubber roller, and regularly clean the crystals in the tank and the pipe wall. The specific method is: using oxalic acid to circulate the water in the plate processor and effectively remove the dirt, and at the same time, the brush roller on the machine must be cleaned and replaced if necessary. In addition, in addition to the dirty process, the operation is not careful, in addition to the lack of dirty fluid consumption, short liquid use time, in addition to dirty injection failure, in addition to dirty liquid used in the layout will cause the printing plate dirty.
During the gluing process, a low concentration of glue is used, and the non-graphical part of the oxidation phenomenon will cause the plate to be dirty. The solution to this problem is: in addition to the dirty note should be used after the cover tight; layout should be fully washed in addition to dirty, glue to increase the concentration of glue, plastic injection should be uniform; after the plastic plate, the layout of the length of the dry After printing.
Third, the baking of common problems and solutions
The film-forming agent of the positive-type PS plate photosensitive layer is made of cresol-home formaldehyde resin, which has been transformed from a linear shape into a bulk structure, which enhances the abrasion resistance of the graphic and text parts. Therefore, the roasting plate can increase the resistance to printing. However, there are often problems with baking in actual work.
The printing plate is not faithfully reflecting the original tone level, but the rubber track. The rubber track is often caused by improper protection of the scratching agent. The rubber track left by the high concentration of the protective agent or uneven grinding will harden on the printing plate after baking and will not dissolve in the developer. Ink absorption. In this case, a slightly thicker alkaline solution than normal developer can be used again.
In the roasting plate, the high temperature causes the PS plate to be deformed and bent. Scratching and squeezing are often performed during the feeding of the plate. When printing, the plate is dirty, and the miscellaneous agent can be removed when the screen is slightly damaged. Light red after baking. This light red color is due to a trace amount of photosensitive layer on the blank part of the plate, which has been changed after baking. If it is treated with developer, it will not get dirty. If the reddish remains on the plate after the treatment, it must be dirty. This condition can be treated with a dirt remover. Dark brown or dark brown after baking. Under normal circumstances, the photosensitive layer is reddish brown after baking. If the color is dark brown or dark brown, it indicates that the baking temperature is excessive or the time of the fine plate is too long. This version is over-baked version, any degree of photosensitive resin layer of carbonization, darkening and brittle, the result will reduce the PS version of the print resistance.
After the baking version was dark green. This type of printing indicates that the baking temperature is low or the time is short, the photosensitive resin is not completely polymerized, and the wear resistance, corrosion resistance, solvent resistance, and ink affinity are not maximized, and the second baking is possible. Edition for best results.
Dirty after PS version baking is a common fault. There are several reasons for this situation. Before the baking plate, the dust, impurities, and the scratches were not completely cleaned. These dirt will be firmly adsorbed on the plate after baking, causing the plate to be dirty; insufficient exposure or incomplete development will result in incomplete decomposition of the non-graphic part of the photosensitive resin, the ink will be dirty when printing; wipe protection agent Improperly dirty. PS version baking protection agent is easy to precipitate, after placing the solute precipitated to the bottom of the bottle, the back of the protective solution is poured out thin, with this kind of protective agent to wipe the version will cause the layout to protect the touch is too thin or have leaks, resulting in PS version Dirty. Therefore, before use, be sure to shake it evenly and throw it out for use. And wipe the protective agent must be rubbed evenly; wipe the middle of the stop and did not wipe the glue in time, after the boot, there is no water roller, and the first ink roller causes the layout to appear. A lot of ink road. If this ink channel is washed with gasoline, the surface is clean, and it will be dirty when it is turned on. In this case, you can use a clean cloth to add some of the pine oil and scrub it slowly. After the ink channel is completely dissolved, wash it clean with clean water. That is to say, the original and the original traces of the traces were not removed; the protective agent was poor in performance and the roasting plate was dirty. The quality of the protective agent used in the PS plate baking plate directly affects the quality of the baking plate. Many manufacturers are required to pay attention to whether the formulation is appropriate or not, whether the performance of the used drug is standard and whether the preparation method is appropriate. No matter which bad book goes wrong, it will lead to the problem of protective agent performance and cause no protective effect of the protective agent. In particular, when certain medicines are not available, and when they are replaced with drugs that are not commonly used, special attention must be paid to the quality of the protective agent. In order to prevent the loss of the plate, it can be tried first, and it can not be used, and it can be put into normal production after no problem. In order to obtain better printing quality, it is always at the same time as mentioned above. In the printing process, special attention must be paid to the control of the pH value of the fountain solution to master the ink-water balance.