In the packaging bag printing process, the ink film color of the color printing packaging bag mainly depends on the ink concentration and transfer rate in the printing work. For some specific substrates or specific working inks, the concentration of the working ink is relatively fixed, and the transfer rate depends on the ink viscosity and other factors, as well as the printing speed and other factors. It should be noted here that these elements will have different effects on the highlights, shadows, and midtones of the printed matter when they change.
1. Change of temperature and humidity
If the room temperature and the liquid temperature of the ink change drastically, the migration state will change, and the color tone will change accordingly. This is because the temperature change affects the viscosity of the ink. At the same time, the dry weather of high temperature and low humidity will have a significant impact on the ink transfer rate of the highlight part.
Therefore, the temperature and humidity of the printing workshop must be controlled in any case when printing high-end products. In addition, when using the ink in winter, preheat it in advance to reduce the temperature change of the ink itself.
2. Separation of synthetic colors
This kind of phenomenon is prone to occur in light colors and mixed colors of organic colors and inorganic pigments, which have very different specific gravities. Especially when the ink flow in the ink tray is too slow, the precipitation will promote the separation of the synthetic color, so pay attention to making the ink circulation smooth.
In addition, if the agitation is not sufficient during toning, the density of a certain color will increase as the printing progresses. Therefore, a dissolving machine or other method should be used for sufficient agitation before the formal printing.
3. The ink is deteriorated and the color is deteriorated
Because of long-term printing, the ink solvent composition is changed, or the moisture in the air is mixed into the ink to cause the ink to deteriorate and the color to be deteriorated.
In order to prevent the temperature drop due to the heat of vaporization, a slow-drying solvent can be used together. At high temperature and humidity, a certain amount of water may be mixed into the ink. Therefore, when abnormalities occur, new inks should be added or all replaced. The remaining inks that have been used many times should be filtered or discarded regularly because they are mixed with a lot of dust.
4. The working viscosity and drying speed of the ink have changed
The change of the working viscosity of the ink can directly affect the color of the printed product. When the viscosity is high, the color density is relatively high, and when the viscosity is low, the color density is relatively low. This kind of influence is sometimes obvious and must be paid attention to. Because of the requirements of the printing process, the working viscosity of the ink should be moderate. When the working viscosity of the ink is too large, it is not conducive to the transfer of the ink, and it is easy to produce a paste scene. If the ink is sticky for a small period of time, the color of the printed product is prone to static electricity, which is not conducive to the control of the ink color.
The change of viscosity has a subtle effect on the migration area caused by the ink migration or the flow method of the dots, especially in multi-color printing. Therefore, when the printing speed is certain, the viscosity of the ink is required to be consistent from start to finish, and it is best to use an automatic viscosity control instrument.
When the solvent ratio in the ink is changed, the drying speed of the working ink will change, which in turn affects the ink transfer rate and printing color. Regarding some inks with a small amount, after a period of use in the ink tank, the natural volatilization of the solvent will not only affect the working viscosity of the ink, but also affect the solvent ratio and volatilization speed, so it is necessary to replenish the solvent in time.
Shanghai Duxia Industry and Trade Co., Ltd. is a modern enterprise specializing in the printing of plastic flexible packaging, established in 2008. We have very rich experience in the field of bag making. Any customer who needs professional customized packaging bags, welcome your consultation!