Aluminum film printing transparency and abrasion resistance

In current high-end packaging cartons, in order to improve the effect of packaging printing, the surface brightness of the packaging box is often increased. One of the common practices is to use specialty papers, such as gold and silver cardboard, to print on such paper in order to obtain For higher gloss, transparent ink is often used for printing. Next, the author discusses the printability of clear ink.

Transparent ink features: Clear ink is a colorant made entirely or mostly using dye inks, its hiding power is very low, very high transparency.

Hue: Due to the high transparency of the transparent ink, after the printing is generally composite aluminum film, so that the luster of the aluminum film and the gloss of the ink combine with each other, reflecting a more vivid color. Moreover, products printed with clear ink, from different angles of view, there will be more obvious changes in the hue, the difference observed under different light sources will be greater. Therefore, in the deployment of this type of ink, we must understand what the customer compound material, in order to deploy the same process ink, and in a similar environment to observe the hue of the ink. For example, the hue of some inks before compounding is very close to that of standard ones, but the hue after compounding may be very different. Conversely, some hue after ink printing has a certain gap with the standard, but the hue after compounding is closer to the standard. The hue of transparent ink is very laborious, so it is very important to understand the customer's process.

Transparency: The transparency of clear ink is determined by the two parts of dye (pigment) and binder (containing adjuvant), and the former plays a major role, while the latter has little effect. For polyurethanes, polyamides, and chlorinated polypropylenes, inks made from these common types of resins have higher transparency. In general, inks with dyes as colorants have higher transparency than those with pigments as colorants. Sometimes due to other needs, some pigments will be mixed in the dye, and the transparency of the ink will be reduced.

Residual solvents and odors: Attentive operators will notice that the drying speed of clear inks is significantly slower because of the low solids content of the clear inks (due to the dye's higher color concentration than the pigments, so the amount does not need to be much) and the solvent content is high. Therefore, it is necessary to control the drying conditions, otherwise it is easy to cause excessive residual solvents and produce odors. In severe cases, after compounding, the solvent will slowly penetrate into and spread around, causing discoloration of other colors. Therefore, when using such a transparent ink, it is necessary to pay attention to the control of the solvent ratio and the printing speed, and then put it into a curing chamber at about 40° C. for aging for more than 10 hours.

Dissolution of clear ink by adhesive: The dye used in the clear ink is completely soluble in organic solvents, so when the print comes into contact with the compounding adhesive, the solvent in the adhesive removes the clear ink from the print. Dissolved more or less. Increasing the compounding speed or increasing the viscosity of the adhesive can alleviate this problem to some extent, but it is only a temporary solution. In addition, if the transparency is allowed to be properly reduced, a part of the pigment may be added to the dye to make a transparent ink, which also has a certain improvement on the problem of the dissolution of the clear ink. In addition, in response to the above difficulties, some ink factories have developed transparent inks that are completely insoluble in alcohol-soluble adhesives and have been applied to some printing materials. It is believed that insoluble ester-soluble adhesives will be developed in the future. Adhesive transparent ink.