Pearl printing technology control points
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Pearlescent printing is a new type of printing that has become more popular in packaging printing and anti-counterfeiting printing in recent years. It mainly uses pearlescent ink. Pearlescent ink is a pearlescent ink. When the print pattern changes its angle, the color of the ink changes, so that the authenticity can be recognized. The printing process of pearl printing is basically consistent with the traditional printing process. The key is the preparation of pearlescent ink, which is generally composed of a binder, a thickener, a pearlescent pigment, a solvent, an auxiliary agent and the like. In the blending of pearlescent inks, the glittering effect of pearlescent pigments is passive luminescence, that is, under the condition of receiving light, the glittering effect can be exhibited. In order to give full play to this feature of pearlescent pigments, when choosing pearlescent pigments, you should pay attention to the following three relationships:
1. The relationship between the size of the pearlescent pigment and the glittering effect. The pearlescent pigments used in packaging and printing are all in the form of flakes. Generally, the distance between the flash sources is large when the film diameter is large, and the glittering effect is dispersed. Conversely, the film diameter is small, the pitch of the flash source is small, and the glittering effect is concentrated.
2. The relationship between the size of the pearlescent pigment and the intensity of the flash. The larger the diameter of the pearlescent pigment, the more the surface is exposed to multiple reflections of light, the greater the chance of refraction, 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 the pearlescent pigment and the cohesiveness and the suspension settling property in the binder. Generally, the smaller the particle diameter of the pearlescent pigment, the easier it is to agglomerate, and the smaller the aspect ratio of the particles, so that sedimentation is likely to occur in the binder, otherwise it is liable to be suspended.
In order to uniformly disperse the pigment in the binder, it is necessary to select a suitable pearlite pigment having an aspect diameter and an aspect ratio based on the density of the binder on the basis of mastering the three relationships. In the ink formulation, the precipitation of the pearlescent pigment can also be prevented by adding a thickener; or the pearlescent pigment can be wetted before being dispersed in the binder, thereby avoiding the disadvantage of causing the particles to aggregate and agglomerate.
The method of blending pearlescent inks is as follows: 1 Generally, 10-20 g of pearlescent pigment is added per 100 g of ink; 2 the pearlescent pigment is directly blended with the binder in a ratio of 1:1, so that the ink fluidity meets the printing requirements; Pearlescent inks can also be added with some trace organic pigments to reduce costs. Generally, a white pearlescent pigment is used in combination with other pigments, for example, by adding 1% carbon black to a white pearlescent pigment, an ancient silver effect can be obtained.
In general, pearl color matching should be based on light color, because the amount of dark pigment added when blending dark colors will cover a part of pearlescent luster. In addition, the color pearlescent ink series cannot be mixed. It is different from general-purpose inks. It can be mixed into two colors using two or more inks. When two or more pearlescent inks are mixed, complementary colors appear. The phenomenon will reduce the pearlescent effect.
Pearlescent ink printing is mainly used in commodity packaging printing, such as paper-printed soap packaging paper, cigarette case, cigarette holder, greeting card, wallpaper, food packaging paper, etc.; film printing: PET, PE, OPP, PS, etc. In the printing process, pearl printing is suitable for all kinds of printing, but due to the different mechanical properties, technical indicators and operations of different printing processes, the ratio of pearlescent inks also differs. In screen printing, the general ratio of pearlescent ink is: 10%~45% of binder, 0.5%~1.5% of thickener, 5%~30% of pearlescent pigment, 15%~35% of solvent, and suitable amount of additives.