Discussion on Quality Problems of PS Plate Printing Plates

Shaiban is a "bridge" process in platemaking and printing. Its status is very important. The quality of the printing plate not only directly affects the quality of the printed matter, but also directly involves the production cost. Here only on the personal work experience, the PS version of the printing quality problems specific analysis and discussion, exchange of experience in order to improve the quality of the PS version of the printing version, improve the PS version utilization.

one. The image is imaginary and dirty

1. The adhesive tape on the film is too close to the image, the image pad is imaginary, and the tape paper is dirty; when the imposition is over, the image pad is imaginary and there are also dirty marks. Solution: Keep the tape or imposition base as far as possible to avoid imagining. The dirt on the tape can be removed with a dirt remover or removed with a double exposure of a scattering film.

2. Dust, sand, and other dirt are deposited on the PS plate, causing the image to become dirty on the pad. The team must carefully check the layout, remove all the dust, and do a good job of indoor hygiene. The ideal is to print in a dust-free environment.

3. The glass is unclean during printing, and there are glue points to dirty the image pad. According to the operating process requirements, the glass must be wiped clean before printing, otherwise it is not allowed to print.

4. Shaiban vacuum pump performance is poor, lack of vacuum, plate material and film contact is not true, causing sun drying. The treatment method is to overhaul the vacuum pump, and the vacuum degree must be 0.08 MPa.

5. Slab printing machine airtight is not good, there are leaks, making inhalation is not true. Printing plate blemishes, often due to the aging of rubber teeth, should be replaced or stick.

6. The bottom of the printing machine is uneven, inhaling unevenly, and the partial film is in poor contact with the PS plate. There are three ways to solve this problem. One is to check whether the bottom of the drying rack is uneven and to be flattened when uneven. The other is to choose a porous wool liner to promote contact between the PS plate and the film. Third, use the second suction method, ie the first suction. The gas stops releasing some of the gas, and then inhales again, which can promote even and close contact between the PS plate and the film.

7. The film image is not dense enough to protect the image from being absorbed by the light when it is printed and the image is exposed. In principle, printing cannot be done when the image density is less than the standard, and it must be re-plated. Sometimes you can try to pull the light far away, so you can reduce or avoid sun drying to a certain extent.

Second, the blank part of the printing plate is dirty

1. Insufficient exposure resulted in incomplete decomposition of the sensitizer and incomplete removal of the development, causing the blank part of the printing plate to become dirty. If the printing plate is not printed on the machine, it can be rescued by the second development method, but this rescue is only applicable to the case where the exposure is slightly insufficient. In severe cases, it cannot be saved. Determine the appropriate exposure time is the key to determine the quality of the printing plate, you can use a continuous ash scale test, so that the density of O.45 does not absorb ink, you can effectively solve the problem caused by the exposure of the plate dirty.

2. Insufficient development, non-image sensitive film removed, resulting in dirty plates. The reasons are as follows: 1 The concentration of the developer is insufficient; 2 The development time is insufficient; 3 The temperature of the developer is low, and the ideal developer temperature is (22±2)°C.

3. PS photosensitive layer coating is uneven, the thickness is inconsistent, the degree of decomposition of the photosensitive resin when the printing plate is different, causing the upper dirt. For example, the emulsion coated with a centrifugal baking machine often appears radiating, and the four sides are easy to get dirty. This situation can be rescued by local exposure or partial development.

4. The ink is improperly smeared. You can use turpentine to wash away the ink and refresh the ink.

5. Brown protective glue is improper, there is leakage of glue. Dirty.

6. In addition to the dirty method caused by the blank part of the dirty, the reasons are: 1 less than the amount of dirty agent; 2 repair time is not sufficient; 3 remove the dirty agent on the printing plate is not timely rinse and wipe.

7. The layout is blue and green. This version can be used to identify the dirty agent, can be removed when the dirt removal agent, it shows insufficient development or underexposure; if you can not afford to remove, then the PS version is not completely sealed, belongs to the PS version of the body quality problems, and the sun The version is irrelevant and cannot be salvaged. Contact with the manufacturer for resolution.

8. After development, the layout is light blue. This is because the storage time of the plate is too long or the temperature is too high when the photosensitive adhesive is applied, resulting in oxidation of the aluminum oxide on the surface of the aluminum plate and the photosensitive layer. It is insoluble in the developer and does not cause dinging under normal conditions. It only appears dirty when using dirt remover. This is because the dirt remover dissolves in a bluish color, accumulates in darker circles, and becomes dirty after drying. The solution is to remove the lysate brown with a damp cloth immediately after it is dirty.

three. Plate printing does not absorb ink

1. Overexposure: 1 The original density is too low, the photo transmission light when printing; 2 exposure time is too long; 3PS version is not properly preserved, light leakage, long shelf life, deterioration, poor ink absorption.

2. Excessive development: 1 developer is too strong, too alkaline; 2 too long development time; 7 developer temperature is too high.

According to the different characteristics of different manufacturers of different grades of the PS version of the sensitizer, the use of a suitable formulation, ratio of the developer, test and control with the test strip, is an effective way to steadily control the development quality.

3. The protective glue changes acid and deteriorates. This is often the case in the summer months of high-temperature plum rain. The glue is not uniform, and the rubber path is produced, resulting in no ink absorption.

four. Too light

1. Excessive exposure should reduce the exposure time;

2. Over development, should reduce the development time;

3. Insufficient density of the original plate, transmission of light during printing, making the outlets smaller;

4. Insufficient pressure or gaskets in the press should be properly adjusted for pressure or padding.

5. The PS version is too coarse and its mesh is damaged and becomes lighter.

Fives. Picture is too deep

The reason why the graphic is too deep is often the opposite of the reason that the graphic is too light, and the solution is the opposite.

1. Insufficient exposure should increase the exposure time;

2. Insufficient development should enhance the development;

3. The original non-graphic part has a high degree of fog, and the transparency is not good, and the exposure time can be appropriately increased.

4. The pressure of the press or the thickness of the pad should be properly reduced pressure or pad.

5. The ink is too thin and too soft. Processing method, update ink.

Sixth, PS version of India's low resistance

The normal PS printing resistance is generally about 100,000 impressions. After the baked PS version, the printing resistance can be increased by 3 to 5 times and reach 300,000 to 500,000 impressions.

At present, there are quite a number of manufacturers who report that the PS version is not very good at printing power. Generally, there are only 20,000 to 30,000 prints. More than 50,000 to 100,000 prints are not printed, and sometimes even a new version is printed on thousands of pages before it starts to fall. The reason is nothing more than two kinds, not the PS version of the quality of the problem, that is, printing manufacturers use problems. Here only the reasons why printing manufacturers use the PS version of improper printing force caused by the decline in the cause of the analysis.

1. When printing PS plate, overexposure or over development will directly reduce the resistance of PS plate.

2. Improper printing pressure and gasket, excessive pressure on the water roller and ink roller will accelerate the wear of the printing plate and accelerate the off-page.

3. The use of rubber blankets is aging for a long time, the elasticity is not good, the capacity of the sense of fat drops, and the ink transfer performance is poor.

4. The printer has a tap, destroys the layout of the sand, and the bar is the fastest.

5. Poor quality of paper, powder, hair loss, dregs, printing adhesion in the blanket and plate, so that the plates wear out version;

6. The layout is exposed to organic solvents or alkaline substances, and the photosensitive film is eroded and dissolved.

7: poor performance of fountain solution, inappropriate pH value, will promote the version;

8. During the printing process or when it is stopped, the printing plate is directly irradiated with strong light, the PS plate photosensitive layer decomposes, the color becomes significantly lighter, and the resistance to printing force is greatly reduced. This is a problem that is often overlooked. The solution is very simple, just hang curtains and block the glare.

Although there are many factors that cause the PS plate to be imprinted in printing and printing, various types of friction are the most frequent and most frequent causes of the decrease in the printing plate strength of the PS plate. Therefore, minimizing various frictions is to increase the printing quality of the PS plate. The most important and effective way is force.