In the flexible packaging printing process, the printing effect of the apparent ink of the printed matter is the saturation and sales of the ink. According to our summary in the production process, we analyzed and summarized the lack of saturation and poor saturation in the spot color during the printing process. For this reason, we will analyze and discuss this problem for peers to share and encourage .

The concept of ink saturation: mainly refers to the fact that the ink can not show a smooth and full printing effect on the substrate during normal printing.

The state of performance: From the appearance of the printed matter, visual observation shows that it is a dense particle distribution, the ink particles are rough, and the dispersibility of the ink is poor when observed with a microscope. The resin and the pigment are separated.

There is a problem of poor saturation. According to what we have encountered, such problems generally occur in green, pink, purple, etc. We have to analyze why this kind of problem arises. We have to analyze it from the source. The following is the author's analysis and summary.

The following factors affect the saturation of ink printing:

1. Viscosity value. The control of ink viscosity should be within a suitable range, that is to say, the viscosity must be proportional to your vehicle speed and solvent drying speed. The printing machine we are using is a high-speed printing machine. During the high-speed operation, the evaporation rate of the solvent is relatively fast, and the viscosity of the ink is required to be relatively low. The higher the viscosity and the lower the transfer rate of the ink. For example: when our production speed is 150 meters per minute, the spot color viscosity is preferably 16-18 seconds. If this viscosity is controlled well, it will have a very important effect on the ink flower. In the case of faster speed, it can also be produced by reducing the viscosity to 15S.

2. Impression roller. Choosing the right pressure roller is more important. The spot color layout is large, and the transfer rate of the ink on the plate roller is relatively high. If you choose the production of the impression roller with a higher hardness, the ink will not be well leveled and wetted on the entire layout during transfer, which will reduce the ink Transfer rate to the printed substrate. When the soft pressure roller is selected for production, the elastic space between the ink and the pressure roller can effectively transfer the ink to the printing material when the pressure roller and the plate roller are printing at the same pressure and high speed. But the premise is: the pressure value of the soft pressure roller must be in the range of 0.18-0.2MPA, and the impression roller must be kept clean and free of foreign objects, which affects the entire ink transfer. The pressure roller can choose 60-65 degree soft impression roller for printing.

3. Ink. Similar problems are likely to occur when all used inks are used for production. The old ink is mainly stored for a long time. If you do not pay attention to the seal, there may be ink oxidation, the solvent in the ink volatilizes, absorbs the moisture in the air, the resin and the pigment in the ink are relatively reduced, and the gloss of the ink decreases. Therefore, the old ink can not be used for production, and the new and old ink must be used together, and the ratio is about 7: 3. Before the old ink is put on the machine, it must be fully stirred and then filtered on the machine. Secondly, the fineness and type of ink will also affect the ink flower problem! Maintain good rotation with a good agitator roller, which can effectively improve the ink-guiding effect of the agitator roller, improve the leveling of the ink, and have a certain effect on the ink flower. If necessary, it can be produced with polyurethane ink. A small amount of white ink can be added appropriately to adjust, provided that the color must be darker to avoid large fluctuations in the color. A small amount of white ink can be used to add a certain effect.

4. Solvent. The solvent ratio is the key. In high-speed printing, the drying speed of the solvent should not be too fast, and a slow-drying solvent should be produced! Now we are using fat-soluble benzene and ketone-free chlorinated polypropylene ink, n-propyl ester is the main solvent, butyl ester, isopropyl alcohol is the co-solvent. When the main solvent volatilizes faster in the production process, it will cause the solvent system to be unbalanced, and other printing problems will occur, such as knife line and blockage. Note: The principle of diligent addition and less addition is used to add solvent. Add from the ink filter socks and stir, do not add from the ink basin, and the force should not be too large, otherwise it will affect the ink hue.

5. Scraper angle. The spot-color version of the doctor blade should not be too hard. It can be relatively soft. The distance between the doctor blade and the platen roller can be relatively far. This can take into account the problems of ink flowers and dry plates.

6. Production Environment. When we shut down in the early stage, a layer of water mist will appear on the surface of the plate roller. The current relative humidity of our workshop is measured to be 80%, and the normal relative humidity of the printing workshop is 50%. When printing in a high-humidity environment, moisture will penetrate into the ink and the solvent through the air, resulting in poor solubility and leveling transferability of the ink, and the water content of the solvent exceeds the standard, resulting in ink flower phenomenon. In addition, the dust and foreign objects brought in from the raw materials will be attracted to the pressure roller by static electricity, resulting in a very thick layer, which will have a certain effect on the transfer of the pressure roller.

7. Plate roller. If the mesh of the plate roller is deep and the groove of the plate roller is not done well, the ink cannot be leveled normally, and the transfer rate of the ink will be effectively reduced. In addition, if the mesh of the plate roller is clogged, the transfer rate of the ink is reduced, which will also have a certain effect on the ink flower. In particular, the plate roller must be cleaned after getting off the machine, so as to avoid the blockage caused by the ink can not be transferred normally and the hue will also change. Before publishing, it must be washed with solvent and pre-polished with 600 grit sandpaper. If the plate roller is shallow, the amount of ink on the ink is reduced, and it is also affected if the ink cannot be filled up. It is recommended to produce with a mesh angle of 40-45 degrees.

8. Raw materials. The raw material film must have a good corona intensity value before printing. If it is low, the ink cannot be transferred sufficiently, especially in shallow screen printing, there will be a quality problem of poor transfer similar to blocking, this problem is mainly on the surface of the film The corona impact strength is not good, the surface of the film does not form a rough surface, the surface tension energy of the material is greater than the surface tension energy of the ink, the ink cannot form an effective adhesion on the film, and the ink cannot be transferred sufficiently, so that the ink cannot be presented Out effect.

Key points: selection of pressure roller for cleaning, viscosity control, solvent ratio, and blade angle. Production Environment. Ink is used correctly.

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