How to choose screen printing ink?
When choosing screen printing ink, we should consider the matching of product material and ink properties, and combine the process characteristics of screen printing:
1. Choose according to the substrate material
1） Paper
Paper products are absorbent materials, and it is easy to find corresponding inks. Generally, solvent-based inks, water-based inks, and UV inks can be used. In the screen printing industry, local UV processes and various decorative UV screen printing processes are the most common.
2). Plastics (PVC, PET, PP, etc.)
There are many types of plastics, and different factories will manufacture a variety of plastic inks to meet the complex plastic materials. We generally divide plastics into absorbent materials such as ABS, non-absorbent materials such as polyolefin materials, and other plastic materials. ABS materials choose common ABS type inks, which do not require pre-press processing, while polyolefin materials require pre-press processing; and other materials require special inks.
3). Metal/glass/ceramics
These materials are non-absorbent materials, and usually require inks made of special resins or adding hardeners for baking to achieve good adhesion. Due to technological advances, UV type inks have also made great progress in recent years. Metal baking ink is cured at high temperature after printing, and has strong adhesion. It is used for aluminum signs and stainless steel products. Glass/ceramic ink: contains inorganic pigments, which are combined with the surface after sintering and are suitable for handicraft printing.
4). Fabric (cotton, polyester)
Textiles are products with loose structures and require special textile inks. The inks for fabrics mainly belong to various glues and thermosetting inks, and UV inks are rarely used. The inks established by printing technology are mainly weak solvent inks and UV-based inks.
2. Select by drying process
The drying method of ink is an issue that must be paid attention to when selecting ink. Different drying methods not only have different requirements for the suitability and parameters of inks, but also define the basic framework for the selection of machines in the subsequent process.
There are two main ways to dry ink: volatile drying and UV drying. Volatile drying means that the solvent in the ink evaporates into the air, and the pigment and the binder are dried on the surface of the product. The volatilization process can be done by natural drying or by using a tunnel drying oven with hot air circulation. The drying efficiency of the tunnel drying oven will be increased several times, so it is often used in large-scale silk-screen printing orders.
UV drying is a special process for UV ink. Only when UV ink is used will a UV curing machine that can emit ultraviolet light be selected for drying. Compared with volatile drying, UV drying has always been highly praised by the market for its environmental protection and the glossiness of the ink itself. Silk-screen printing technology combined with UV drying has become the most mature and reliable process for packaging printing.
Although UV drying has obvious advantages, it also has obvious disadvantages, that is, high voltage is required when the machine is started, the safety is poor, and the light emitted by the metal halide lamp has a high thermal effect, which can easily cause unnecessary deformation of the product, especially for some heat-sensitive materials. UV drying will have many side effects. UVLED is the latest technology that controls the UV light source to produce more concentrated UV light based on UV drying. It effectively controls the thermal effect, keeps the product at a low temperature under UV irradiation, ensures the dimensional stability of the product, and rapidly expands its market share.
