1. Why do some uv inks cure faster than others?
is generally prepared according to the characteristics of some substrates and the special requirements of some applications. From a chemical point of view, the faster the curing speed of ink, the worse the flexibility after curing. Imagine that after the ink is cured, all the ink molecules will undergo cross-linking reaction. If these molecules have many molecular chains and branches, the curing speed of ink will be very fast, but the curing speed of flexible ink may be slow, but it will be very flexible.
Most inks are designed according to application requirements. For example, for the ink specially designed for producing membrane switches, the cured ink film must be compatible with the composite adhesive and flexible enough to adapt to subsequent processing, such as die cutting and embossing. It is worth noting that the chemical raw materials used in the ink can not react with the substrate surface, otherwise it will cause cracking, damage or delamination. The curing speed of this kind of polymeric ink is usually very slow. However, those inks specially designed to produce cards or hard plastic display panels do not need to have such high flexibility, and their drying speed is faster according to the application requirements.
Whether the drying speed of ink is fast or slow, the final application should be the starting point. Another noteworthy problem is the fixed line equipment. Some inks can cure quickly, but inefficient curing equipment may also slow down the curing speed of inks or lead to incomplete curing.
2. What is the relationship between the setting parameters on the UV curing lamp?
Watt/inch is the unit of curing lamp power, which is obtained according to Ohm's law: Volt (voltage) * Ampere (current) = Watt (power); Watt/cm2 or milliwatt/cm2 represents the peak illuminance (ultraviolet energy) per unit area when the radiometer passes under the curing lamp.
Peak illumination mainly depends on curing power, etc. The reason why we use watt to measure the peak reading is mainly because it represents the electric energy consumed by the curing lamp. Besides the amount of electricity received by the curing unit, other factors that affect the peak illuminance include the condition and geometry of the reflector, the service life of the curing lamp and the distance between the curing lamp and the curing surface.
3. How can we ensure the proper curing of UV ink?
The curing of the ink when it first passes through the curing unit is very important. Proper curing can avoid the problems of substrate deformation, over curing, rewetting and insufficient curing, and optimize the viscosity between ink and body fluid or paint and paint.
4. What is the dyne level?
Dyne/cm is a unit for measuring surface tension. This tension is caused by the intermolecular attraction of a specific liquid (surface tension) or solid (surface energy). In practical application, we usually call this parameter dyne level. The dyne level or surface energy of a specific substrate represents its wettability and ink adhesion. Surface energy is a physical property of matter. Many films and substrates used in printing have low printing level, such as 31 dynes/cm polyethylene and 29 dynes/cm polypropylene, so they need special treatment. Proper treatment can improve the dyne level of some substrates, but this is only temporary. When you are ready to print, there are other factors that will affect the dyne level of the substrate, such as processing time and times, storage conditions, environmental humidity, dust and so on. Because dyne level will change with time, most printing houses think it is necessary to process or reprocess these films before printing.
5. How does plasticizer affect the adhesion of ink on PVC?
Plasticizer is a chemical substance that can make printing materials softer and more flexible. Widely used in PVC. The types and quantities of plasticizers added to flexible PVC or other plastics mainly depend on people's requirements for mechanical, heat dissipation and electrical properties of printing materials. Plasticizer may migrate to the surface of substrate, affecting the adhesion of ink. The plasticizer remaining on the substrate surface is a kind of pollution, which will reduce the surface energy of the substrate. The more surface pollution, the lower surface energy and the less adhesion to ink. In order to avoid this situation, people can clean the substrate with mild cleaning solvent before printing to improve its printability.
6. What are the factors that affect the stability or shelf life of UV ink?
An important factor affecting the stability of ink is the storage of ink. UV ink is usually stored in plastic ink cartridges, not metal ink cartridges, because plastic containers have certain oxygen permeability, which can ensure a certain air gap between the ink surface and the container cover. This air gap, especially the oxygen in the air, helps to minimize the premature crosslinking of ink. Besides packaging, the temperature of the ink container also plays an important role in maintaining its stability. High temperature will cause early reaction and crosslinking of ink. The adjustment of the original ink formula may also affect the stability of the ink on the shelf. Additives, especially catalysts and photoinitiators, may shorten the shelf life of ink.
7. What happens if the color UV ink is cured with a nitrogen curing device?
The curing system for curing printed matter with nitrogen gas appeared ten years ago. These systems are mainly used in the curing process of textiles and membrane switches. People use nitrogen instead of oxygen, mainly because oxygen will inhibit the curing of ink. However, due to the limited illumination of bulb in this system, the curing effect of pigment or color ink is not very good.