Application of UV ink in screen printing

The dryness of the ink has a great influence on the printing, especially in the screen printing, the longer the ink stagnation time will make the ink layer thicker. Therefore, the good dryness of the ink is more important for screen printing.

First, the effect of ink drying on screen printing

Dryness of ink refers to the speed of ink drying. It depends on the nature of the binder in the ink. It is also related to the nature of the pigment and auxiliary materials in the ink and the ratio of the ingredients. The effect of ink drying speed on screen printing is mainly as follows:

1. Dry too quickly. The viscosity of the ink increases, the particles become thicker, and the blot becomes lighter and weaker, which can easily cause blocking of the mesh. 2. Dry too slowly. Imprint gloss is poor, and the printed products are easily dirty, which is particularly unfavorable to the post-print operations (overprinting time interval is too long, cutting waiting time is too long, etc.), thereby reducing production efficiency.

From the above analysis, it can be seen that drying too fast mainly has a great influence on the printing adaptability, while drying too slowly has an effect on post-printing. At the same time, this also reflects the irreversible requirement for ink drying after printing and printing. That is, the slower the drying speed of the ink is, the better the printing ink is. This ensures good ink flowability and stable rheology; after printing, the ink The faster the drying speed, the better, in order to facilitate the post-printing operations. However, most of the inks used today are dried by means of oxidized conjunctiva, permeation, and volatilization. Therefore, it is difficult to adjust the dryness of the ink in consideration of the requirements for printing and drying of the ink after printing.

Second, the basic principles and characteristics of UV ink

UV inks, with its unique drying method, fundamentally solve the different requirements of printing and printing on the drying properties of inks. The basic principle of drying is: through ultraviolet radiation on the ink, causing the photochemical reaction of the ink, so that the ink reaches The purpose of curing. In the drying process of UV inks, there are two main chemical reactions:

1. Photochemical reaction: The photopolymerization initiator contained in the ink, under ultraviolet radiation, undergoes a photochemical reaction to generate free radicals (forming fragments or other reactions).

2. Chain reaction: The photochemical reaction generates free radicals with the ability to initiate chain reaction, so that unsaturated multi-functional prepolymers, multi-functional crosslinking agents, and reactive diluents in the ink undergo chain reaction and cross-linked with each other. There is a three-dimensional structure of photocured product dried ink film. Therefore, the drying of the UV ink depends mainly on its photocuring drying characteristics, so that the ink has different drying properties under light (UV light) and light-free conditions, ie, the ink is not affected by light during printing, and the ink maintains a stable rheology. Characteristics, with a good printing state; printed by UV radiation, rapid drying, to meet the post-process operations, greatly improving the production efficiency. This fundamentally solves the different requirements on the drying properties of the ink after printing and printing, and greatly improves the drying adaptability of the ink.

Third, screen printing UV ink type and characteristics

UV inks have different types according to their purposes. At present, there are mainly the following types of screen printing UV inks in China:

1. UV curable plastic ink

Applicable to all kinds of plastic film, such as PET, PC, PVC, artificial leather, nylon cloth, etc., also applies to all kinds of metal sheets, such as copper, aluminum, stainless steel and other substrates. Can resist scrubbing with various solvents, no net blocking when printing, fast curing, good curing toughness, excellent adhesion fastness, and bright colors.

2.UV UV curing etching ink

The product's screen-printed merchandise, inserts, covers, and high-grade packaging boxes are etched with copper and silver plates, with distinct layers. The patterns are more expensive and clear, with excellent results.

3. UV curing anti-etching ink

The use of UV-curing anti-etching inks, solvent-free dispensing and contamination problems, simple printing, bright lines, strong etch resistance, but also according to different types need acid or alkali and so on.

Fourth, the use of UV ink should pay attention to the problem

Although UV inks have many advantages, they should have better performance and good printing quality. In screen printing, the following issues must also be noted:

1. Select a UV curing machine that matches the UV ink power and spectrum used to ensure curing efficiency and effectiveness.

2. According to different inks, use different meshes to match with the screen, otherwise it will also have a greater impact on the printing effect. 3. UV inks should not be diluted in general, so as not to affect its photocuring properties. If dilution is required, special diluents must be used to adjust.

4. UV inks should be stored at low temperatures and protected from light to ensure the stability of their photo-curing properties.

In summary, UV inks show their unique advantages in terms of their unique drying methods. They fundamentally solve the different requirements for printing and drying of inks after printing. Created conditions for the improvement of printing quality. With the constant recognition of the nature of UV inks and the further improvement of the performance of UV inks, UV inks will surely find wider application in screen printing.

Author/Wei Gongyuan Source: Screen Printing Industry-2006 No.9