Special glossy printing technology (3)

1 The print has no pearl effect (Table 2-30)

2 Pinholes and small bubbles appear on the printed surface

Bubbles or pinholes appear on the printing surface. First, there may be moisture or particles in the diluting agent. Second, when diluting the pearl powder with the diluting agent, the pearl powder must be thoroughly mixed before printing on the machine. There is a powder group in the diluting agent. Such powder group will break and fall off after the printing is dried to form a tiny pinhole phenomenon.

3 Streaks appear when printing

When the pearl surface is printed on a large area, vertical stripes sometimes appear. This is due to improper roll printing. Therefore, when printing a large area of ​​pearl surface, appropriate depth of mesh engraving or diamond-shaped engraving surface rolling should be used. The squeegee should be checked and replaced frequently.

4 post-print pearl powder falls off

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 diluting agent has poor affinity with pearl powder, that is, it is not very compatible.

Pearlescent color is not bright and uneven after printing.

Pearlescent powder belongs to a translucent and insoluble wafer-like object, and its color is affected by the following factors.

1 paper color

The same pearlescent ink is printed on two different papers, and 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 buying pearl powder, it must be clear whether there are other background colors affect the pearl powder, you must first consider the color change of pearl powder. For example, printing a white pearl powder on a deep red pattern will fade the dark red background to a lighter shade, while at 45° you will see a white pearl effect. 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.

3Add other colors can also change the color of pearl powder

For the sake of cost savings, we advocate the use of white pearl powder combined with color inks to blend the desired pearlescent colors. For example, adding a suitable amount of primary red ink to white pearl powder will result in a bright light red color. This method can also enhance pearlescence. The hiding power of ink reduces the influence of the background on the pearl layer.

4 The color of the diluting agent itself also affects the pearlescent effect

Some manufacturers dilute the color is relatively deep, such as the dilute agent itself, the color will be deeper affect the effect of pearl surface, after printing, the color turns yellow, the effect of yellow comes from the quality of the diluting agent.

screen printing. The size of the pearlescent pigments used in screen printing determines the size of the screen aperture. For the smooth passage of 300 to 800 mesh pearlescent pigments, 200 mesh screen mesh can be used. The addition ratio in the ink is about 5 to 20%. The viscosity of the formulated pearl ink must be moderate and have a certain degree of fluidity.

(3) Pearlescent printing method

Various methods of pearl printing are the same as those of conventional printing methods. However, in order to fully display the glittering pearlescent effect of pearl ink, the following methods should be noted:

Mix pearlescent and translucent printing inks. According to this method, only one printing process is required. The pearlescent effect and the color of the translucent ink appear at the same time, but since the pearlescent effect of the pearlescent ink is easily concealed by the deep color of the translucent ink, it is only suitable for the lighter translucent. The ink color, and the pearlescent pigment addition ratio is between about 15% to 35%.

The first color is printed with pearlescent ink and a semi-transparent ink color is printed on the surface. This method can be applied to deeper color effects, but the hiding power of the printed translucent ink color must not be too high, otherwise it will completely cover the pearl effect.

The first layer is printed with ordinary color inks and a layer of pearlescent ink is printed on the surface. This method will achieve a softer pearlescent effect. The pearlescent pigment in the pearlescent ink can be added to the transparent linking material (such as varnish) at a ratio of 3% to 7%, but the first layer of ink should be printed deeper. , otherwise it will be affected by lightening of the surface layer of pearl ink layer.

(4) Pearlescent printing process

The corresponding model should be selected according to the size of the printed graphic area and the size of the printing plate. If the small version is printed on a web press, due to the large size of the ink tray and the lack of ink absorption, poor ink transfer may occur, and if the amount of ink is increased, the phenomenon of stacking and pasting will occur.

The ink transfer roller used for pearlescent printing is soft and elastic to facilitate the uniform coating and transfer of the pearlescent ink.

The pressure required for printing in the field is large, and the soft lining of the lining is preferred. If you do not meet the requirements at a time, you can print the second time.

In the preparation of pearlescent inks, titanium dioxide, sulphide pigments, chromium salt pigments and other high-shielding pigments should not be added to prevent the pearlescent pigments from being covered and losing the pearlescent effect.

If metallic pearlescent pigments are used instead of gold powder in multicolor printing, golden pearlescent ink can be placed in the first color sequence before printing other colors on it. (to be continued)