Film gravure ink and matters needing attention
The color difference control is one of the important contents of the attention of all the ink. Based on the experience, the color difference of the film gravure ink during use is 3, but the film packaging for special use should be changed according to the actual situation. Color difference of ink. The color difference control of the film gravure ink is affected by many factors such as the flowability and transparency of the ink, the type of printing film, and the like. Among them, the ink flow on the color of the most obvious impact, in order to achieve the true reduction of ink color, we must fully ensure that the flow of ink in a certain range.
Thin film gravure ink viscosity control is the application process needs to break the focus, but also difficult. Under normal circumstances, the film gravure ink viscosity should be controlled at 0.15 ~ 0.30s (25 ℃). If the viscosity is too high, there will be ink transfer is poor, uneven ink and other conditions, and even dirty version or paste plate and other serious consequences; if the viscosity is too low, it will cause the network increased, the edge of the product burr or color too shallow , The edge is not real and other issues.
Thin film gravure ink thixotropy thixotropy to be controlled within a reasonable range, too large or too small will have a negative impact on printing. If the thixotropy is too large, will make the ink thin consistency of a significant change, resulting in not normal, smooth ink, even when the ink can even cause interruption, causing blocking ink, paste version of the fault; if the thixotropy is too small, its mobility Will also become smaller, is not conducive to uniform ink and ink, resulting in ink more and more light ink.
The pH of the film gravure ink should generally be controlled at 8.5 to 9.5. It should be noted that the pH value of the ink will change with the ambient temperature and humidity changes, and when the pH changes, its viscosity and transfer will also change, resulting in color problems. Therefore, in the printing process, it is necessary to regularly monitor and adjust the pH value of the ink, once the pH value changes, by adding the right amount of stabilizer to adjust.
Problems and programs
Poor ink transfer
Poor ink transfer is caused by a variety of factors, the film surface tension is large, water as the main solvent of the ink is difficult to better in its surface wetting, leveling; ink surface dry speed is too fast, easy to occur pH Variety. In addition, the intaglio angle and depth will have a certain impact on the transfer of ink. In this regard, ink suppliers need to continue to improve the performance of ink, gravure plate manufacturers have to cooperate with the application of thin film gravure ink on the gravure plate making appropriate adjustments, such as the use of laser engraving plate to improve the number of lines and so on.
Pinhole, also known as white spots, sometimes full version appears, sometimes local appear. If the recurrence of fixed parts, known as the mechanical pinhole, usually by the plate or guide roller dirty, aging defects caused by; if the non-fixed parts of the occasional, known as the chemical pinhole, The quality of the film gravure ink itself is due to the fact that the defoamer is added in excess. For the pinhole failure, the former can be used to clean the printing plate or guide roller (or replace the plate or guide roller) method to remedy; the latter, for the flexible packaging business, on the one hand need to carefully screen thin film gravure ink products, another In the printing process can also be added to the amount of neutralizer to be eliminated, but should not add too much.
The registration is not ideal
For a long time, this problem is always troubled by us, and thus dare not take the application of film gravure ink. Because the ink tension, in the non-absorbent, non-polar plastic flexible packaging application is even more difficult. Ink suppliers have long been constantly studying, and constantly improve the structure of ink to adapt to the film gravure registration, but there is still no complete and solvent ink overprint quality of the same film gravure ink. High light, dark tone level contrast is weak
If the transfer of ink is good, the performance of the shallow mesh will be more prominent, gravure hole in the ink by the scraper transferred to the roll period, if the ink viscosity change is not obvious, the network is easy to complete reproduction. However, due to the existence of ink and solvent ink is essentially different, if the gravure engraving parameters are still according to the traditional solvent ink gravure engraving parameters to set, it is easy to cause high light, dark parts of the level of contrast greatly weakened. In the production of ink with gravure, may wish to steep gradient gradient some, darker parts slightly deeper, the middle to the high-profile parts slightly shallow, taking into account these points, high light, dark tone can be perfect reproduction.
Thin film gravure ink ink consumption is low, especially in the lines, text, dot part of the ink for a long time the cycle will make the solvent more volatile, resulting in slight changes in the performance of ink, such as rheological deterioration, Wait. Therefore, the operator should be as much as possible, "less tune, less, plus ground," the three points, that is less tune the new ink, less solvent, ground plus a good tune of ink. In addition, the ink composition and the amount of ink should be done in detail the record, in order to stub arch, as a reference for printing comparison.
As the drying problem has always been the biggest problem facing the film gravure ink, so in order to apply a good film gravure ink, the effective adjustment of the oven is the most critical, which is all flexible packaging enterprises using thin film gravure ink should do an important prerequisite work. Mainly should be adjusted according to reasonable conditions, oven inlet should be in a state of micro-pressure, can be slightly inside the gas, should not let the air leakage. In the printing process, the printing film to stay in the oven for the appropriate time to achieve the desired drying effect. After the exploration, the author found that if the oven is properly adjusted, the printing speed can do the following match: Oven length of 1.4 ~ 1.6m, the printing speed can reach 100 ~ 150m / min; oven length of 1.6 ~ 1.8m, the printing speed can To 150 ~ 200m / min; oven length of 1.8 ~ 2.0m, the printing speed can reach 200 ~ 250m / min.
Thin film gravure ink is difficult to dry after drying, in order to prevent blocking, short time downtime, the operator should release the scraper, stop non-stop version, so that the plate has been dipped in ink operation; if long downtime, Edition roll clean, to prevent the ink after drying again boot when the phenomenon of blocking plate.
After the printing stops, first drop the ink tray, rinse the roll with a good diluent, and then release the scraper, clean with a clean cloth once, in the thinner completely dry, then the plate wrapped to save.