Causes of plastic film full-page failure

When gravure printing is performed on plastic films, full-size or large-area solid-printing products often appear. This situation is often due to improper process control or other reasons, it is easy to produce full version failure, and the failure to produce the actual product is not the same. So it must be analyzed in detail and find the best solution. To sum up, the full version of the failure are mainly full version of white ink, full version of color ink, a large area of ​​white ink and a large area of ​​color ink and other situations.

The cause of full version failure

1. When the full version of white ink is used in gravure printing, it can easily cause full-quality failures. The manifestation is mainly that the ink scraper on the printing plate cannot be scraped cleanly, so that the excess ink not in the net hole is also printed on the film as the printing roller runs. Under normal circumstances, the new version is not easy to appear, but the premise is that the pressure and angle of the printing blade must be moderate. Under normal circumstances, the blade pressure can not exceed 3kg, the best angle is 35 degrees. We know that excessive pressure will severely abrade the printing plate and shorten its useful life. Larger angles of the printing squeegee also affect the life of the printing plate, and full angle failure occurs when the angle is small. In addition, the balance of the scraper is also very important, generally requiring the scraper to be parallel. It mainly refers to the distance between the blade and the blade holder and the tangential distance between the blade's throat and the printing plate. If the left side of the blade holder is higher than the right or the right is higher than the left, full plate quality accidents often occur. The extension of the blade is generally no more than 2.5 cm from the tool holder, and the blade's throat is generally at 45 degrees from the tangent of the plate.

The best printing angle and pressure position are the preconditions for uniform inking. A large amount of ink can also cause full-quality accidents. Excessive consideration of the cost of the ink by the manufacturer may also result in a full version of the accident, as some products require that the composite aluminized film cannot have white spots or rough white ink particles. Some manufacturers will use cheap white ink to make up for it. If the quality of the inexpensive white ink is poor, coarse particles may cause the full-plate failure described above. Poor quality white ink particles not only have poor hiding power, but are also more prone to compound white point failures; at the same time, they can lead to the service life of the doctor blade and plate rollers.

In the gravure printing process, white ink production is relatively simple and the price is much lower than other color inks. Poor quality white ink, yellow hue is second, fear is that the fineness of titanium dioxide does not meet the requirements, poor dispersion in the resin resulting in poor printability ink. Titanium dioxide in white ink belongs to inorganic substances, and it does not fuse well with various types of resins belonging to organic polymers because of different polarities. In addition, some manufacturers add titanium dioxide as a filler to the resin when processing white ink. This is the direct cause of the long life of the squeegee and the plate cylinder, and the periodic instability of the print quality. During the printing process, due to the high hardness of titanium dioxide, coarse particles, the influence of static electricity, and the continuous reduction of the resin, they are constantly gathering. Therefore, when cleaning the ink plate, it is often found that the bottom of the plate has a thick layer of white material, which is too much titanium dioxide. Many reasons. Therefore, flexible packaging printers should strictly inspect the products supplied by the ink supplier. Generally, the white ink has a diameter of ≥12 μm. The fineness of the detected ink is called the fineness meter, and the pattern scraping for a certain pressure is called the reading value. This value is the fineness value.

2. Different inks that are not compatible with each other are used for printing, that is, inks of different resin systems are used for mixing. Incompatible printing will cause a lot of printing failures, but in fact, it is impossible for any manufacturer to print with the same resin system ink. This is mainly determined by graphic requirements. In the actual printing process, inks of different resin systems should be avoided as much as possible to ensure product quality. Mixing inks of different resin systems often results in quality accidents such as watermarks and graphic leaks. When the composite aluminum plating film is used, there are obvious defects.

3, full version also has a great relationship with the control viscosity of the ink. The so-called viscosity refers to the extent of liquid or semi-mobility. Viscosity is critical at every stage of ink use and is an important indicator for evaluating ink properties. The viscosity of the printing ink white film is often detected using a 2# viscosity cup, and printing is most suitable in 17 seconds to 19 seconds. The depth of the printing white roll is generally 35 microns to 40 microns. The viscosity of the color ink is often suitable for 14 seconds to 16 seconds. High viscosity and poor cell transfer also produce full-scale quality accidents. The viscosity of the ink is too high, which can easily cause the following problems: (1) The fluidity is correspondingly poor, and it is not easy to fill every mesh point or fill the mesh hole, and the dot cannot be completely transferred to the printing material, and is easy to form. White point and other printing failures. (2) The impact force on the squeegee increases, resulting in difficulty in squeegee squeegee and printing defects such as knife lines. (3) is not conducive to the transfer of ink, easy to produce block printing and other printing failures.

The viscosity of the ink is too low, and its fluidity is so good that watermarks, sharpness reduction, and the like may occur. At the same time, it is prone to static electricity, which is not conducive to the control of ink.

The cause of full-color ink phenomenon

The color ink mainly refers to the blue, red, and yellow primary inks and corresponding spot colors. Such as dark blue, red, orange and so on. The first printing problem that can easily occur with full-color ink is twill. There are many reasons for this phenomenon:

First, the quality of the impression cylinder itself was printed. Mainly reflected in the poor concentricity or the surface is not smooth, low hardness and so on. In addition, because of pressure problems, the pressure is too high, the imbalance between the guide posts and guide bushes, and the guide pillars are loose. The detection method is to align the impression cylinder and carefully observe whether the state of the twill changes or not. The reason can be found based on the result. Second, the cause of ink. Inconsistent stirring of the ink also produces the above situation. If the ink is used for a long time, it is recommended that it be filtered to remove foreign matter and reduce the quality of the twill. Watermarks, nail prints, and circle prints often occur in spot-color inks that incorporate a large amount of white ink, such as light blue, light yellow, and so on. If the original color ink in the printing is also caused by the above situation is mostly due to the quality of the ink itself. Third, the generation of static electricity can also easily cause water lines and nail prints. Fourth, there is a large relationship between printing speed and the speed should reach 100 meters/min or more. Fifth, the printed square roll tension. If the printing tension is too loose, the material cannot be evenly and evenly printed and the twill weave will also occur. The solution is to adjust the tension according to the requirements of the printed product.

Full version failure - "matt"

Intaglio printing on plastic film is prone to pitting. Irregular pockmarks are mainly caused by the high viscosity of the ink. The cause of the viscosity increase is mainly due to the excessive volatilization of the solvent or the difference in the temperature and humidity of the operating environment. The solution is to reduce the viscosity of the ink. Generally, the temperature of the printing operation environment is preferably 21°C, and the relative humidity is preferably controlled at 60%. In addition, the occurrence of pitting irregularities may also be caused by static electricity. The solution is to install a static eliminator. The main type of circled pitting is caused by foreign matter on the pressure roller, such as the accumulation of dirt. It is also possible that due to the damage of the printing blade, it should be carefully observed and combined with the actual situation. Regular line spots are caused by two reasons: there is a defect in the pressure roller, which usually occurs in a thick cycle; or there is damage on the printing plate roller, such as a loophole, etc. The solution is to repair the roller.

Source: China Ink Technology Network