Tips for pearl powder in decorative paper printing

In the decorative paper printing, the pearl powder is expressed in a luxurious and bright atmosphere, which can push up the grade of decorative paper. Among them, the unique metal texture of pearl powder is more and more favored by customers. However, in decorative paper printing, it is not easy to print an ink containing pearl powder. This paper aims to start from the composition of pearl powder ink, combing its characteristics, discussing its adaptability in decorative paper printing, and combining with the practice of Xiaobian for more than ten years, put forward some good ideas and good methods when printing pearl powder ink. And the precautions for the majority of the industry engaged in decorative paper printing reference.

Pearl powder ink composition characteristics

Pearl powder ink is a printing ink prepared by using copper powder (commonly known as gold powder) or aluminum powder (commonly known as silver powder) with an appropriate amount of binder (tempering oil, pearlescent agent) and a small amount of additives, usually called metal powder ink. Among them, a powder made of copper powder is called a gold powder ink, and a powder made of aluminum powder is called a silver powder ink.

Gold powder

Gold powder is a very fine scaly metal powder prepared by mechanically grinding, dispersing, and polishing a plurality of metal particles such as copper, zinc, and a trace amount of aluminum by mechanical means together with stearic acid. The particles of the gold powder have a smooth scale shape, each scale having a diameter of about 50 to 100 μm, a thickness of about 0.10 to 1.80 μm, and a water surface coverage of generally 4000 cm 2 /g. Due to the difference in the amount of zinc in the gold powder, the gold powder has different color. It is generally considered that the zinc containing less than 10% of the zinc is red gold powder, and the zinc containing more than 20% is the glaucomous gold powder, and the between the two is called blue red. Gold powder.

2. Silver powder

Here, silver powder is aluminum powder, usually containing 93.0% aluminum, 0.5% iron and an appropriate amount of grease. Aluminum powder has a small specific gravity, is easy to float in liquid, and has strong light resistance and is less affected by climate change. Therefore, it has good hiding power, strong stability, and good reflection performance against light and heat. Aluminum powder usually has a silver-white metallic luster, and like gold powder, its particles are also scaly.

3. Pearl powder (usually referred to as gold and silver) ink binder

Pearl powder ink binder is a kind of adhesive fluid, which is an important basis for the quality of pearl powder ink. At present, synthetic materials are often used for the connecting materials. The resin used for decorative paper printing pearl powder ink binders, in addition to the properties of general decorative paper printing ink binders, requires low acid value and special stability to pearl powder.

4. Accessories

Excipients mostly refer to other viscous materials and driers added in the amount of pearl powder ink. Sometimes, for special needs, metal powders such as pure gold powder, sterling silver powder, and stainless copper powder are used to prepare a metal ink for use as a metal ink; however, this is not universal.

At present, the pearl powder ink used by decorative paper printing enterprises is an imported brand. This ink has good ink transfer properties, and it can be printed on both the ground and small patterns, but it is expensive. The other type is domestic brands, which are less effective than imported brands. The main performance is that the particles are thicker and the viscosity is not enough. The printed products are slightly less metallic, but the price is cheaper.

Printing adaptability and operation requirements of pearl powder ink

The special preparation of pearl powder ink determines its printing adaptability has its own characteristics.

Dampening solution

First of all, in the water-based decorative paper printing, there is very little additional dampening solution. However, in other printings, the printing of pearl powder ink conforms to the printing principle of the hydrophilic part of the printing plate and the printing of the graphic part. The correct selection and use of the dampening solution is particularly important. Most printing companies now use alcohol and isopropyl alcohol-based alcohol fountain solutions, which have the advantages of small surface tension, good wetting performance, reduced water consumption of printing plates, high volatility, and reduced layout. The temperature improves the printing durability of the printing plate under the premise of ensuring that the blank portion is not dirty, and is particularly suitable for the special ink which is easy to be dirty and emulsified by the pearl powder. However, in the process of use, we must pay attention to control the concentration of alcohol, not the bigger the better.

2. Paper

The quality of paper quality also affects the quality of pearl powder ink printing.

(1) Smoothness

The smoothness of the paper is high, the printability is good, and the gold and silver inks are particularly bright and eye-catching, and the dots are clear and the color is bright. It is usually required that the smoothness of domestic coated paper is above 600s and that of imported coated paper is above 1000s.

(2) Ink absorption

Ink absorption refers to the instantaneous absorption and total absorption of the paper in the ink. The ink absorption of the base paper used for printing pearl powder ink should be fast and moderate. If the absorption starts too much (large amount), specular reflection cannot be formed; on the contrary, it is prone to stickiness. It is required that the ink absorption of the low pressure paper is about 40 to 50 s, and the high pressure paper is about 150 s.

(3) Glossiness

The gloss of the base paper is of course higher, and the normal requirement is about 30% to 40%.

(4) Surface strength

The surface of the base paper used for printing pearl powder ink is high in strength. It is required to be able to rotate at a line speed of (80 to 200) m/s. The paper surface is not pulled or powdered, that is, it is suitable for normal printing under high speed operation of decorative paper printing machine. .

In short, the most suitable paper for pearlescent ink printing should be compact, smooth and bright, so as to fully reflect the distinctive characteristics of ink.

3. Printing pressure

When printing pearl powder ink, the imprint is often faint and false, and the printing pressure required is larger than that of the general ink. This is because the pearlescent powder has coarser particles, is difficult to mix well with the binder, and has poor transfer performance. It is necessary to increase the printing pressure to achieve good transfer of the ink layer from the plate to the paper, especially in the case of rough paper.

4. Printing speed

When the pearl powder ink is printed, the printing speed should not be too fast, otherwise the phenomenon of pulling and pasting may occur. In addition, if the printing speed is too fast and the temperature rises, the pearl powder ink is easily oxidized and blackened, which affects the quality of the printed product.

Pearlescent powder ink common printing failures and solutions

1. Large area is not printed

Numerous practices have proved that pearlescent powder ink printing, printing a group is difficult to achieve results, even if the printing pressure, ink volume is adjusted a lot, the ink is not piled up, the printing is not flat, but it is easy to cause dirt, adhesion and other defects.

Solution: Do the same version again. The first set of ink layers will be thinner and the bottom layer will be used. The amount of ink after pressing will be larger and the standard will be achieved. The pearl powder ink printed in this way is thick and flat in the field, and the effect is good, and there is no bad phenomenon such as ink sticks and sticky. Need to be reminded: the contents of the two units of pearl powder printing plates are exactly the same, which will bring some trouble to the overprinting, especially the clear texture, the overprinting between the two units must be accurate.

2. Imprinting, paste

The fault is mainly caused by the excessive amount of ink and the small amount of water, and the paper imprinted portion cannot receive excess pearl powder ink and expands to the edge of the blot.

Solution: Properly reduce the amount of ink, increase the amount of water and connecting materials, and operate according to the requirements of water balance. In the pearl powder ink, the captain and assistant must be vigilant, diligently sample and observe, and find that the paste is processed in time, otherwise it will not pay attention, and the blank part will be dirty.

3. Stacking ink

This is also a problem that is easy to happen. Due to the poor rheology of the pearl powder ink, the transferability is lower than that of the general ink, and it is easy to accumulate on the surface of the printing plate or the glue stick, which causes the print to be unclear.

Solution: wash the glue stick, diligent version. After printing a certain quantity, it is necessary to clean the printing plate and the glue stick once, and remove the excess ink accumulated on the top to ensure the perfect transfer of the pearl powder ink. In addition, in order to keep the ink in a smooth and uniform manner, the pearl powder ink in the ink fountain should be added less, diligently and frequently stirred to avoid the phenomenon of “empty”.

4. The back is dirty

There are three reasons for this failure: First, the paper has limited ink absorption, the ink volume is too large, and the ink layer is too thick; secondly, the material is too tight; third, the dampening solution and water are used improperly, causing the ink to be emulsified. .

Solution: First, strictly control the concentration and dosage. Two printing can be considered when printing; secondly, reduce the amount of powder appropriately; third, adjust the receiving tension reasonably; fourth, try to increase the drying temperature. Minimize the risk of sticking according to the actual situation

The printing failures that occur when printing the pearl powder inks above are small series or may be encountered by you. Try the solutions we have summarized. In short, in order to improve the printing quality of pearl powder ink and perfect the decorative paper printing effect, it is necessary to fully realize that pearl powder ink is very different from ordinary ink, regardless of the particle size, size, weight, physical properties, and chemistry of the pigment. The nature is not the same, and then accurately grasp the printing adaptability and focus of pearl powder ink, develop the habit of more observation, diligent thinking, and good summary in the work, so that it can print the decorative paper of customer satisfaction and peer praise. Boutique.