How to replace flexo UV ink with flexo ink

As an environmentally friendly ink, water-based inks contain little organic solvent and contain no VOC emissions. However, in order to replace the flexo-printed UV ink with high-grade labels , especially on the film self-adhesive labels, the industry colleagues are not doubtful. Then, in order to replace flexo UV inks, what kind of market demand must be achieved in printing performance? Here, the label will organize a prescription for your flexo ink, and it looks fine~~

Stable pH

The pH of the aqueous ink is actually as unstable as the sawtooth curve. To be stable, it is necessary to shorten the time for measuring the pH and adding the stabilizer, that is, increasing the pH and the frequency of adding the stabilizer. Therefore, foreign label printing companies often use pH real-time control devices in water-based ink applications to measure pH values ​​at any time and add stabilizers at any time to maintain the stability of water-based inks.

The pH-stabilized aqueous ink has a pH of between 8.25 and 8.5 with little fluctuation. Such aqueous ink has stable transferability and stable viscosity (due to the latent heat of evaporation of water, the probability of the viscosity of the ink being increased due to evaporation of water in the aqueous ink is extremely low, and the viscosity of the aqueous ink is often increased by the volatilization of ammonia. Therefore, the color density is stable.

Reasonable viscosity

In order to ensure that the ink stored in the anilox roll cell is smoothly transferred to the printing plate, a low viscosity ink similar to the gravure process must be used, otherwise it is difficult to suck the ink in the cell. However, since the characteristics of the flexographic anilox roller mesh are very different from those of the chamfered tapered mesh of the electroglossogravure, the viscosity of the flexographic UV ink does not have to be as low as that of the gravure ink.

When developing flexographic UV inks abroad, it was the choice of a lower viscosity monomer resin that made the flexo UV ink reach the realm of today. In the same way, the reasonable viscosity of the flexo-printing ink can be similar to that of the UV ink, without having to deliberately pursue low viscosity. Imagine that the ink transfer mechanism of the flexo press is the same, only the drying mechanism is different. In this case, what is the need to reduce the viscosity of the flexographic ink?

Properly increase the color density of water-based inks

The quality of flexographic printing is subject to the anilox roller technology. In order to achieve the high number of printing plates, the anilox roller must also adopt a high number of lines, and according to the optimum ratio of the depth of the cell to the opening of the cell in the anilox roll technology. When the anilox roller is high in number, the amount of ink stored will decrease accordingly, and the BCM value will be lower. At this time, if both the high line number and the high color density are to be pursued on the same printing plate, it is necessary to increase the color density of the ink. In short, it is necessary to increase the pigment ratio of the ink.

It is now known that the pigment ratio of flexo UV ink is generally 25%, the pigment ratio of flexo ink is generally 20%, and the pigment ratio of flexo solvent ink is also about 20%. Since the surface tension of flexographic solvent-based inks is generally lower than that of flexographic inks, the transfer rate from the printing plate is slightly worse. The solvent density of the solvent-based inks of the same pigment ratio is slightly lower than that of the aqueous inks. . Therefore, compared with flexo UV inks, the requirement for color density of flexo-printed inks is only to increase the pigment ratio.

Adjust the surface tension of the ink according to the characteristics of the printing plate

According to the data we have now, the surface tension of the flexo ink and the surface energy of the printing plate (also called the surface tension of the printing plate) should be as close as possible, that is, the difference should be as small as possible. There are generally two ways to do this: one is to adjust the printing plate, and the other is to adjust the ink. Since the plate is basically controlled by foreign manufacturers, the possibility of achieving the first method is negligible. What we can do at this stage is to require the surface energy of the plate to be stable and then to match by adjusting the surface tension of the ink.

The surface tension of aqueous inks is related to the following materials: aqueous solutions, aqueous emulsions, cosolvents, auxiliaries, and the like. Unlike solvent-based inks, the surface tension design of aqueous inks is more difficult than solvent-based inks. Therefore, a large amount of laboratory calculations and experimental work are required. Conventional market applications are often based on a large number of experiments and Based on the trial. The author advocates that certain data measurement and analysis work needs to be done before the trial to avoid the loss of a large amount of materials caused by blind trials.

Adhesion to non-absorbent materials such as films

The ink should adhere to the surface of the film, and the surface tension of the film is required to be above 38 mN/m. If the surface tension of the film is not up to standard, the film must be corona treated or primed to change the surface properties of the film. When printing aqueous ink on the surface of a treated film, if the adhesion of the aqueous ink to the surface is high, the following prerequisites must be met:

(1) The resin characteristics of the aqueous ink must be similar to those of the film. At the moment when the aqueous ink is transferred to the film, the film should have a slightly soluble phase. The micro-dissolving stage is actually the establishment of an anchor point on the surface of the film by the ink, and the foundation of the surface on which the ink film can adhere is established.

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