PS version of the FAQ analysis

The PS version plays an important role in printing. It consists of a photosensitive layer and a plate base. The photosensitive layer should have good lipophilicity; the plate base is a blank part and should have good hydrophilicity. PS plate should meet the following requirements: flat layout, uniform thickness, stable size, not easily deformed, no dirt on the surface, scratches and flaws, can firmly adhere to the photosensitive layer of glue and chemical changes, after surface treatment Good hydrophilicity and abrasion resistance, high resistance to printing.

It is not easy to achieve the above requirements. Here are some of the issues related to the printing plates and the processing methods that are often found in platemaking and printing, which have been summarized by the author in his many years of practical work, for the reference of his colleagues.

First, the common problems in printing and treatment methods

1. The image is hazy and the space 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 the glass 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. If the blanket is used for a long time, there will be aging, there will be a small amount of leakage in some of the edges, PS version and film will not stick tight, drying out of the graphic will be made false. 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 dots are actually coveted. 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. Cannot 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 problems often appear in the version

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 inevitably 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, the use of liquid for a short time, in addition to dirty liquid failure, in addition to the dirty liquid on the dry surface may cause plate contamination.

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 kind of problem is to: after the dirty liquid is used up, it should be tightly closed; the layout should be fully washed after the dirty area is removed; the glue concentration should be increased when the glue is applied, and the glue should be even; the plate after gluing should be dried completely. After printing.

Third, baking problems often appear in the edition

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 the normal developer can be used again.

In the roasting plate, the high temperature causes the PS plate to be deformed and warped. Scratching and squeezing are often performed during the feeding of the plate. When printing, the plate is dirty, and when the screen is slightly damaged, the dirt removal agent can be removed.

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 means that the baking temperature is too high or the fine plate time 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. Also, when wiping the protective agent, it must be rubbed evenly. If the printing is stopped, there will be no time to wipe off the glue. After turning on the machine, there is no water roller, and the ink roller first causes a large number of layouts. 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 performance of the protective agent used in the PS version is directly affected by the quality of the baked version. Many manufacturers prepare their own products. It is necessary to pay attention to whether the formula is suitable, whether the properties of the used drugs are 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, which will 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, at the same time as belonging to the above problems, it is necessary to pay special attention to the control of the pH value of the fountain solution in the printing process, and to master the ink-water balance.

Fourth, PS version in the printing process prone to problems

The task of the PS version is to transmit the graphic part as accurately as possible to the blanket. Graphic part of the hydrophilic, non-graphic part of the ink. But in reality it is not so ideal. There will be various issues related to the PS version. Let us cite some of them and discuss them.

1. The non-graphic part of the layout is dirty, ie, the non-graphic part is pro-inking. There are the following reasons.

A. The chemical composition of the fountain solution is not properly configured to erode the hydrophilic portion of the blank portion. This is done by replacing the dampening fluid with a dampening fluid that is properly configured according to the manufacturer's instructions. B. The roller sleeve of the reversing water roller is dirty or worn, damaging the blank surface. Treatment method: clean or replace the version of the water roller sleeve, wet wash can protect the printing plate. C. Inking too much during halftone printing causes the ink to spread, which eventually sensitizes the non-graphic area. Treatment method: Use thinner ink film for printing. D. The grit of sandpaper on the rubber cloth is retained and the printing plate is worn. Filling ball measures: clean rubber cloth, change paper; add anti-accumulation agent in fountain solution; adjust the amount of water to the minimum, add more concentrate, gum arabic and/or alcohol or alcohol as needed The product keeps the non-image area of ​​the printing plate clean while reducing the amount of water; in the B-B printing machine, the pressure between the printing plate and the rubber fabric is reduced. If an impression cylinder is present, the pressure between the impression cylinder and the paper should be checked; if the build-up occurs mainly in the first printing unit, the amount of water should be increased to help clarify the debris on the paper. E. Aluminum base plate oxidation. The oxidized dirt looks like a lot of clear dots or doughnut-shaped spots. It often appears in areas that have long been in contact with wet reel water rollers. Plates tend to oxidize if they are too slow to dry, or stored in moist places before development or during two printing runs. If the printing press breaks while the plate is not yet dry, the plate will also oxidize. Action: Follow the recommended plate handling procedure. Store plates in a dry place. During the plate making process, a cheesecloth is used to quickly dry the plate. In the printing process, such as parking, should rely on the printing roller to leave, open the empty car until the plate is dry. F. Incorrect working of the water roller and/or the ink roller in the ink system may cause the print to appear dirty in the circumferential or axial direction. Action: Check the pressure, cleanliness, geometric accuracy, and overall condition of each roller in the ink system. G. Pre-exposure (grayed) occurs in the plate during the prepress. Measure: Store the plate in a light-proof box; install appropriate safety lighting equipment at the plate making site. H. The ink is too soft or too oily. At this time, contact the ink manufacturer. I. Excessive fountain solution causes the imprinting to be snow flakes; black solid appears grey and dark in color; in the magnified state, irregularities in the field are found, filled with tiny white spots. Excessive fountain solution emulsifies in the ink. When the ink film is split, the water droplets are exposed, and these water droplets hinder the transfer of the ink to the paper. At this point to reduce the amount of water supply.

2. Part of the PS layout is worn out. There are two reasons: First, there are too many resins in the fountain solution; second, there is too much acid in the fountain solution. The solution is to re-allocate the fountain solution and check the pH.

3. The plate has white fibers. This is mainly due to the fact that the paper fluff is too much or that the roll fabric is peeled off. The method is to clear the printing plate.

4. The graphic part of the plate cannot be properly inked. There are two reasons: First, the plate map