Special Screen Printing - Pearl Printing

With the improvement of technology and development of signage technology, the use of special printing to deal with the bottom layer of signage panels has become a common means, and colorful, beautiful and moving, not only increased the decorative nature, but also obtained more prominent results. The following will introduce several common special screen printing technology and issues to pay attention to.

First, pearl printing

Pearlescent printing is a new type of printing that is popular in packaging printing and security printing in recent years. It mainly uses pearl ink. Pearlescent ink is a pearl glossy ink. When the print pattern changes the angle, the color of the ink will change, which can identify the authenticity. The printing process of pearlescent printing is basically the same as the traditional printing process. The key lies in the preparation of pearlescent ink. It is generally composed of a binder, a thickener, a pearlescent pigment, a solvent and an auxiliary agent. In the preparation of pearlescent ink, the glittering effect of pearlescent pigments is passive luminescence, that is, its glittering effect can only be manifested under the condition of receiving light. In order to give full play to this feature of pearlescent pigments, it is necessary to pay attention to the following three major relationships when selecting pearlescent pigments for ink formulation:

1. The relationship between the size of the pearlescent pigment and the flash effect. Pearlescent pigments used in packaging and printing are all in the form of flakes. Usually, the distance between the flash sources is large and the flash effect is dispersed. On the other hand, with small diameters and small flash source spacing, the flash effect is concentrated.

2. The relationship between the size of the pearlescent pigment and the flash intensity. The larger the diameter of the pearlescent pigment, the greater the chance of multiple reflections and refractions on the surface of the pearlescent pigment, and the stronger the intensity of the flash; on the contrary, the intensity of the flash is weak.

3. The relationship between the size of pearlescent pigments and the cohesiveness and suspension settling in the binder. Generally, the smaller the diameter of the pearlescent pigment is, the easier it is to agglomerate, and the smaller the aspect ratio of the particles, so that sedimentation is more likely to occur in the binder. Otherwise, it tends to be suspended.

In order to disperse the pigment evenly in the binder, it is necessary to select the pearl pigment with the appropriate diameter and aspect ratio based on the density of the binder in order to grasp the three major relationships. In the ink formulation, it is also possible to prevent the sedimentation of the pearlescent pigment by adding a thickening agent; or to allow the pearlescent pigment to be wetted before being dispersed in the binder, so that the problem of sedimentation and agglomeration of the particles can also be avoided.

The preparation method of pearlescent ink is: 1 In general, add 10~20g of pearlescent pigment per 100g of ink; 2 Mix the pearlescent pigment with the binder in a 1:1 ratio to make the ink fluidity conform to printing requirements; 3 Deploy color Pearlescent inks can also be added with trace organic pigments to reduce costs. White pearlescent pigments are generally used in combination with other pigments. For example, adding 1% carbon black to a white pearlescent pigment can produce an ancient silver effect.

In general, the pearl color deployment should be based on light colors, because the deployment of dark colors when the amount of dark pigment added too much, will cover part of the pearl luster. In addition, it is not possible to mix colored pearlescent ink series products. Unlike general-purpose inks, two or more inks can be mixed into another color. When two or more pearlescent inks are used in combination, complementary colors appear between them. Phenomenon, but will reduce the pearl effect.

Pearlescent ink printing is mainly used in the packaging and printing of goods, such as paper printing soap packaging paper, cigarette cases, cigarette holders, greeting cards, wallpaper, food packaging paper, etc.; film printing: PET, PE, OPP, PS and so on. In the printing process, pearlescent printing is almost suitable for all kinds of printing, but due to different printing processes, its mechanical properties, technical indicators and operations are all different, and the proportion of pearlescent ink is also different. In screen printing, the general ratio of pearlescent ink is: 10% to 45% of the linking material, 0.5% to 1.5% of thickener, 5% to 30% of pearlescent pigment, 15% to 35% of solvent, and appropriate amount of auxiliary agent.


Source: Screen Printing Industry 2005.8 Qi Cheng