Application of pearl powder in gravure printing

1. Overview and Characteristics of Pearlescent Pigment Pearlescent powder is a semi-transparent, micro-flaky pigment that produces a pearlescent effect. This type of pigment is divided into natural and artificial two major categories. As early as the 3rd and 40th generations, these pigments were produced. They were originally made from fish scales and were natural products. The use of fish scales to produce pearlescent pigments is expensive and is rarely used. After the extraction of natural pearlescent pigments, they began to develop similar pigments that chemically produce a pearlescent effect and even more brightness than fish scale products. In the early 1950s, research and production of pearlescent layers covered with titanium dioxide and iron oxide on mica sheets began. Pigments, titanium dioxide coated mica wafers are the most widely used pearlescent pigments today. This pearlescent pigment is different from other general pigment pigments. It emits light through the reflection and refraction of light. A piece of transparent mica is powdered by water milling. Each powder is about 3-150 μm in size. After the powders are sorted by size, titanium dioxide is chemically coated on the surface of these powders to form a smooth, Transparent, odorless wafers, which reflect and refract light, pearlescent luster and rainbow illusion, feed into the eye, and are very much related to the thickness of the titanium dioxide coating. If you increase the thickness of the mica wafer, the wafer will produce a variety of color effects, from very soft white to bright rainbow colors.
2. Application of Pearlescent Pigments in Gravure Printing Pearlescent pigments have been available for more than 70 years, and they have a long history in the printing industry. Pearlescent pigments have been widely used in paper printing, and various kinds of printing processes and products have been used all over the world. Above, such as lithography, gravure printing and so on. Products are mainly used in paper printing such as soap packaging paper, cigarette packs, cigarette holders, greeting cards, wallpaper, food packaging paper, etc.; film printing, such as PET, PE, OPP, PS, etc., due to the wide use of pearlescent pigments, now mainly introduces pearlescent The use of pigments in gravure printing. In gravure printing, pearlescent powder can be directly added into the printing dilute to the agent. The amount of pearl powder used can be added with the customer's requirements. Up to 30% (weight ratio) can be added. The printing manufacturer can purchase pearlescent pigments directly and directly mix in the print dilute. Used in the agent.
Pearlescent powder belongs to insoluble pigments, and it needs to rely on a very good diluting agent to make the pearl powder completely wet and dissolved. The effect can be perfect after printing.
1. Pearl powder and dilute agent mixed pearl powder is a kind of crystal powder, when used with diluting agent, if handled improperly, it can easily stick into a ball shape, resulting in the formation of pinholes in the printing, poor printing gloss and other ills. Therefore, it is very important to use a good diluting agent. In order to prevent the pearlescent pigments from sticking to each other and open into small balls, the required pearl powder must be weighed and then gradually added into the diluting agent to adjust evenly to avoid binding of the pearl powder in the diluting agent. For example, the printing viscosity is too high. Add some diluent (such as isopropyl alcohol, ethyl ester) as appropriate.
If you need color pearl effect, you can add 0.5-1% of ordinary color ink in the adjusted pearl powder, you can achieve color pearl effect.
Pearlescent ink sometimes has a deposition phenomenon during its use. It adopts a cyclical operation of the storage tank and uses low-speed stirring to keep the pearl powder flowing. At the same time, the ink is used to guide the ink to the ink tray for printing. The remaining pearl ink is then piped. Return to the ink tank, this device can prevent precipitation of pearl powder, while maintaining color stability. The engraving depth of the plate roll is also related to the printing effect. If anti-settling agent is added to prevent sedimentation, the ink concentration will increase, the fluidity will decrease, and the printing requirements will not be met. This problem is worthy of attention by manufacturers.
2. Selection of pearl powder As mentioned above, the pearl powder particle size has a great relationship with the print engraving depth of the printing plate. If the engraving depth of the plate is not enough, only the ink will be transferred during printing, and the pearl powder Remaining in the ink tank, resulting in more and more serious precipitation and common floating phenomenon.
Before ordering pearlescent pigments, it is necessary to understand the pearlescent effect required by the product in order to determine which type of pearl powder is most suitable.
Third, the pearl powder in gravure printing common problems and countermeasures 1. Print no pearl effect 2. The appearance of pinholes and small bubbles on the printing surface causes bubbles or pinholes in the printing surface, first, may have water in the diluting agent Or there are particles; Second, pearl powder with dilute agent must be allowed to stir all the pearl powder before printing on the machine, such as no mixing, dilute agent in the powder group, such powder group will be printed after drying Cracked and exfoliated to form a small pinhole.

The Causes and Countermeasures of Printed Products without Pearlescent Effect

the reason

Countermeasures 1. Pearlite powder and diluting agent have poor compatibility
2. Diffuse gloss difference
3. Unbalanced print
4. Edition is too shallow
5. Dilution too large
6. If you have added a large amount of pearl powder, but the printing surface pearl effect is still not enough, the problem may appear on the plate roll, because the depth of the plate is not enough, the plate roll is too shallow, only the fine pearl powder transferred and left Under the coarser particles, the result is that the amount of pearlescent powder transferred to the print is insufficient, and the pearlescent effect is deteriorated.
7. There is enough pearl effect on the printing surface, but there is no gloss, because the diluter used is too dry.

Replace diluting agent Replace diluting agent Replace print material Re-engrave roll Reduce dilution

Re-engraved roller

Slow-drying solvents should be added to allow the pearlescent powder to have a good array of time within the printing layer to form a good pearlescent reflective surface.
3. Streaks appear when printed When printing pearl surface in a large area, sometimes there will be vertical stripes, this is due to inappropriate roll caused by, so when printing a large area of ​​pearl surface should use the appropriate depth of mesh sculpture or diamond Patterned surface roll, squeegee should always check and replace.
4. Post-printing pearl powder is severely exfoliated (1) The diluting agent has poor adhesion;
(2) excessive dilution;
(3) too much pearl powder;
(4) It can be protected by a layer of water-based gloss oil;
(5) The dilute agent has poor affinity with pearl powder, which means it is not very compatible.
Fourth, the pearlescent color after printing is not bright, and the non-uniform pearl powder belongs to a translucent and insoluble wafer-like object. The color it displays is affected by the following factors.
1. Paper color The same type of pearl ink is printed on two different papers. The pearl color may not be the same. This is because the color of the paper affects the original color of the pearl powder.
2. The color of the underlying printing will also affect the pearl effect. Before purchasing the pearl powder, it must be clear whether there are other colors affecting the pearl powder. If you need to print pearls on a background pattern, you must first consider the color change of the pearl powder. For example, printing a white pearl powder on a deep red pattern will darken the bottom of the dark red and turn it into a lighter color of the beak, while the white pearl effect will be seen at 45°. If it is replaced with red pearl powder, it will set off each other, but there are still some changes in the red color. Generally, it is advocated to print pearls first on paper, and then to print non-pearlescent patterns on it, the effect will be more vivid and perfect.
3. Add other colors can also change the color of pearl powder In order to save costs, we advocate the use of white pearl powder with color ink to match the required pearl color, for example, the right amount of primary color red ink added to the white pearl powder, will Bright red color appears. This method can also enhance the hiding power of pearlescent ink and reduce the effect of background color on the pearl layer.
4. The color of the diluting agent itself will also affect the pearlescent effect. Some manufacturers produce thinner dilute agents, such as the dilute agent itself, the darker color will affect the effect of the pearl surface. After the printing, the color will turn yellow and the yellow effect will come from the diluting agent. the quality of. (Lu Ronghua)