The influence of static electricity in label printing and its solution

In daily production and life, all kinds of objects are likely to generate static electricity due to movement or friction. Similarly, the label printing process involves frequent impacts, friction, and contact and separation steps, which causes almost all of the objects involved in the label printing process to carry static electricity, which causes a lot of trouble for the label printing process. This will not only seriously affect the quality of label printing, but also cause safety production accidents, causing unnecessary losses to label printing companies. Therefore, eliminating static electricity in printing has become one of the important topics in the domestic label printing industry . The author below details the impact of static electricity on the label printing process and how label printing companies should solve the static problem.

The effect of static electricity

1. Static electricity on the surface of the substrate can easily affect the printing quality and printing efficiency.

Label printing often uses various types of substrates such as paper and film. After rubbing or colliding, the surface often accumulates a certain amount of static electricity. These static electricity will adsorb paper dust and dust and impurities floating in the air, thereby affecting the normal transfer of the ink, causing quality problems such as "spotted spots" on the printed matter. For some prints with high surface cleanliness, if there are any dirty spots formed by paper dust, dust and impurities, a large number of non-conforming products will be produced, which will bring huge losses to the label printing enterprises.

In addition, in the process of printing a single sheet of paper, due to the influence of static electricity, several sheets or even a stack of paper are firmly stuck together, which is difficult to separate and stack neatly, which often causes two or even more to be sucked during printing. Sheets of paper, or the phenomenon of absorbing paper, seriously affect printing efficiency.

However, for roll label printing, the substrate is passed from the unwinding to the winding. During the printing process, the printing material is spread over a large area. If there is static electricity on the surface of the printing material, the dust particles in the air will adhere to it, especially for the label of the protective film, which will seriously affect the quality of the printed matter.

2. Ink with static electricity affects printing quality

When performing screen printing, if the electrostatically charged ink is discharged during transfer, "electrostatic ink spots" may form on the printed matter, which looks like the ink has poor fluidity and uneven ink loading. When printing in the field, the phenomenon that the electrostatically charged ink is discharged at the edge of the printed matter often occurs, and the edge of the printed edge is prone to burr-like "ink whiskers", resulting in overprint deviation.

3. Static electricity can cause damage to equipment

Since a large amount of electrostatic charge is accumulated on the surface of the printed matter, in the subsequent striping and rewinding, the electrostatic discharge of the printed matter may damage the photoelectric correction system and the electromagnetic control system of the device, thereby affecting the quality of the final label finished product.

4. Static electricity can cause fires and even cause casualties

High-speed, repeated friction and peeling during label printing cause static electricity on the surface of the substrate. As the static electricity continues to accumulate, the final voltage can reach tens of thousands of volts, and tens of thousands of volts can easily penetrate the air, causing an electric shock or Get angry. In addition, when the electrostatic voltage of the ink is high, it may also ignite the ink and the organic solvent to cause a fire, and the charged ink may also shock the operator and directly threaten the safety of the operator. Every year, there are many safety accidents caused by static electricity in China's label printing industry, causing huge losses.

How to eliminate static electricity

In the label printing process, static electrodes are easy to produce, and ubiquitous, how should label printing companies avoid and eliminate static electricity? The author believes that the following points are worthy of reference and reference.

1. Printing machine grounding

The easiest way to eliminate static electricity is to ground, that is, the printer is in contact with the earth through a wire to make it equipotential with the earth, and the static charge leaks through the earth.

2. Control the temperature and humidity of the printing workshop

Controlling the temperature and humidity of the printing shop is a simple and effective way to prevent and eliminate static electricity. By adjusting the temperature of the printing shop and increasing the relative humidity of the air, the conductivity of the surface of the substrate can be improved and the leakage of electric charge can be accelerated. The temperature of the label printing workshop is preferably 18 to 25 ° C, and the relative humidity is 60% to 70%. If the temperature is too high and the relative humidity is too low, the workshop environment will be too dry and can not eliminate the static electricity; if the temperature is too low and the relative humidity is too high, it may cause the substrate to absorb water and deform, which will affect the final overprint. Therefore, the printing workshop should be equipped with a temperature and humidity control system or a humidifier to monitor the temperature and humidity of the printing workshop at all times. Only by controlling it within a reasonable range can the static electricity be effectively eliminated.

3. Add antistatic agent or isopropanol to the ink

An antistatic agent or isopropyl alcohol is added to the ink to reduce the generation and accumulation of static electricity in the ink. I recommend using an antistatic agent because too much isopropyl alcohol will cause the ink to “anti-slag”. In many professional books, the amount of isopropyl alcohol added should not exceed 2%, but it has been proved that the addition amount far exceeds this amount will really play an antistatic effect.

4. Antistatic treatment of the substrate

The antistatic agent treatment technology mainly applies an antistatic agent (surfactant) to a surface of a charged body such as a substrate to absorb water by using an additive technique or a coating technique to make it hydrophilic. The substrate absorbs moisture in the air, reduces electrical resistance, increases conductivity, and makes static charge less likely to accumulate. Among them, the additive type treatment technology is to mix the additive antistatic agent with a thermoplastic resin in a certain ratio, and add various auxiliary agents, and melt, knead, granulate and the like to obtain an antistatic concentrated masterbatch. Dilute the antistatic concentrated masterbatch to the desired concentration during use. The coating type antistatic agent treatment technology is to make the ionic surfactant into an antistatic coating and apply it on the surface of the plastic film to prevent the accumulation of static charge. In short, the antistatic agent treatment technology is a method for modifying a resin or a substrate, and is a well-recognized and comprehensive antistatic technology.

5. Install the static eliminator

The ions generated by the static eliminator neutralize the charge on the charged body to eliminate static electricity. The static eliminator has three types: external voltage static eliminator, self-discharge static eliminator and radioactive element remover. In the label printing, an external voltage static eliminator is often used to eliminate static electricity by applying a high voltage to a needle-shaped or thin-line electrode and generating a corona discharge to generate ions.

All in all, label printing companies should always pay attention to and prevent the harm caused by static electricity, and do a good job of prevention and control of static electricity according to the actual situation, and be checked by special personnel to prevent the quality problems caused by static electricity and the threat to safety production.