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
Due to the smooth surface of the sheet structure composed of mica and titanium dioxide (or other metal oxides), and the relatively smooth paper surface during the papermaking process (so that the pearlescent effect can better penetrate the coating into the human eye), the pearlescent paper is more than normal The surface energy of whiteboard paper is much smaller. In printing, the ink is not easy to adhere and absorb, and it is not easy to dry.
(2) The surface pearl effect is easily destroyed
Since the structure of flakes composed of mica and titanium dioxide (or other metal oxides) is easily broken during the printing process or peeled off by the ink, the pearlescent effect is easily lost or white spots are easily formed during printing.
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, easy sticking on the back surface, and easy scratches.
(2) The pearlescent effect is easily lost, and white spots, flowers, and creases are easily formed in 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 pearl effect of paper cannot be reflected, and the pearl effect of the second paper is greatly weakened by 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 not be printed twice at once, can be printed with offset printing without screen printing, and can be applied offline without polishing, but of course it can not be glossless, because the coating will greatly weaken the pearlescent paper. Pearl effect.
2. Printing
At present, there are three kinds of inks that can be used for printing 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 ink, reduce the ink viscosity and other methods to improve the ink on the pearl paper surface of the ink, while the ink is also a superimposition of a "dry-dry" overlay method, can greatly improve the overprint rate. Therefore, UV ink printing is generally not affected by dry, anti-sticking, pearl paper off powder, etc.; at the same time it will not produce scratches, ink skin and other phenomena. However, due to the limited function of the printing press, there are not many enterprises that can print with UV ink, and the printing cost is relatively high, which is suitable for printing in larger batches.
(2) Non-absorbent paper printing ink printing
Such inks, such as Hangzhou Hanhua's JP ink, are used exclusively for printing papers with a variety of non-absorbent surfaces. This type of ink is tailor-made for papers with low surface energy and poor absorption properties. The printing conditions are the same as those of ordinary printing, which can effectively improve the adhesion and drying performance of the printed ink layer. However, the printing speed cannot be too fast, preventing the amount of ink from drying and causing the back surface to become dirty.
(3) Ordinary ink printing
For the low-quality pearl paper printing products with low quality requirements, most companies use ordinary inks for printing, which not only meets the requirements of customers, but also provides economic benefits. However, special attention should be paid to the precautions mentioned in the above process design, in particular to avoid large-area printing, which will not be described here.
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
Due to the smooth surface of the sheet structure composed of mica and titanium dioxide (or other metal oxides), and the relatively smooth paper surface during the papermaking process (so that the pearlescent effect can better penetrate the coating into the human eye), the pearlescent paper is more than normal The surface energy of whiteboard paper is much smaller. In printing, the ink is not easy to adhere and absorb, and it is not easy to dry.
(2) The surface pearl effect is easily destroyed
Since the structure of flakes composed of mica and titanium dioxide (or other metal oxides) is easily broken during the printing process or peeled off by the ink, the pearlescent effect is easily lost or white spots are easily formed during printing.
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, easy sticking on the back surface, and easy scratches.
(2) The pearlescent effect is easily lost, and white spots, flowers, and creases are easily formed in 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 pearl effect of paper cannot be reflected, and the pearl effect of the second paper is greatly weakened by 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 not be printed twice at once, can be printed with offset printing without screen printing, and can be applied offline without polishing, but of course it can not be glossless, because the coating will greatly weaken the pearlescent paper. Pearl effect.
2. Printing
At present, there are three kinds of inks that can be used for printing 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 ink, reduce the ink viscosity and other methods to improve the ink on the pearl paper surface of the ink, while the ink is also a superimposition of a "dry-dry" overlay method, can greatly improve the overprint rate. Therefore, UV ink printing is generally not affected by dry, anti-sticking, pearl paper off powder, etc.; at the same time it will not produce scratches, ink skin and other phenomena. However, due to the limited function of the printing press, there are not many enterprises that can print with UV ink, and the printing cost is relatively high, which is suitable for printing in larger batches.
(2) Non-absorbent paper printing ink printing
Such inks, such as Hangzhou Hanhua's JP ink, are used exclusively for printing papers with a variety of non-absorbent surfaces. This type of ink is tailor-made for papers with low surface energy and poor absorption properties. The printing conditions are the same as those of ordinary printing, which can effectively improve the adhesion and drying performance of the printed ink layer. However, the printing speed cannot be too fast, preventing the amount of ink from drying and causing the back surface to become dirty.
(3) Ordinary ink printing
For the low-quality pearl paper printing products with low quality requirements, most companies use ordinary inks for printing, which not only meets the requirements of customers, but also provides economic benefits. However, special attention should be paid to the precautions mentioned in the above process design, in particular to avoid large-area printing, which will not be described here.
Reprinted from: Print Magazine
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