With the increasingly fierce market competition, manufacturers are trying hard to improve the function and quality of their products, and on the other hand, improve the packaging quality of their products. Printing with pearl paper occurs under this condition.
First, the basic knowledge of pearl paper
1. The structure of pearl paper
The composition of pearl paper is the same as ordinary whiteboard paper, which consists of three parts: bottom fiber, filler and surface coating. Different from ordinary whiteboard paper, there are pearlescent effect particles in the surface coating. The particles consist of titanium dioxide (or other metal oxides) and mica particles which are formed by the encapsulation of titanium dioxide (or other metal oxides). This structure is in the form of flakes.
2. The characteristics of pearl paper
(1) Low surface energy and poor ink adsorption
Because the surface structure of the sheet structure composed of mica and titanium dioxide (or other metal oxides) is smooth, and the paper surface is relatively smooth during the papermaking process (so that the pearlescent effect can better penetrate the coating into the human eye), the pearlescent paper is superior to the ordinary whiteboard. The surface energy of the paper is much smaller, and the ink is not easily attached and absorbed during printing, and it is not easy to dry.
(2) The surface pearl effect is easily destroyed
3. Problems often caused by pearlescent paper printing
(1) Adhesion and dryness of the ink lead to low density in the printed field, loss of small dots, slow drying, and easy adhesion and scratches on the reverse side.
(2) The pearlescent effect is easily lost, and white spots, flowers, and creases are easily formed in the printing.
Second, pearl paper offset printing
1. Process design
(1) Design and plate making
Since pearlescent paper is mainly a gorgeous effect that embodies the pearl of paper, if the area of printing ink is large, a pearlescent effect of the paper cannot be reflected, and the pearl effect of the second paper has been greatly weakened through the ink layer. Therefore, when designing plates, we should try to avoid large-area field pattern printing according to the characteristics of pearl paper. The general design of some simple lines, patterns, text, can highlight the focus of the contents of the package, but also show the gorgeous effect of paper.
(2) Production process
Since pearlescent particles of pearlescent paper are easily broken, semi-finished products cannot withstand repeated sequence and friction, so the production route should be as short as possible, and some unnecessary technological steps should be eliminated, especially those that involve more manual participation. Can be printed twice at a time, can be printed without offset by screen printing, and can not be glazing even on the machine, and of course it can not be glazing without glazing because glazing can greatly weaken the pearl paper Pearl effect.
At present, there are three types of inks that can be used to print pearlescent papers. According to their printing effects, they are: UV inks, non-absorbent paper printing inks, and common inks. Here are the issues that should be noted when printing each type of ink.
(1) UV ink printing
UV printing uses UV drying, and each printing unit is equipped with an ultraviolet drying device. When the UV ink passes through the drying device, the drying time under the initiation of the photo-initiating group is very short, and it can be said to be instantaneous drying, so that it is completely dry after entering the next printing unit or the receiving portion. We can increase the amount of ink, reduce ink viscosity and other methods to improve the ink on the pearl paper surface of the ink rate, while the ink is also a superimposition of a "dry-dry" overlay, can greatly improve the rate of overprinting.