Common Problems with UV Ink on UV and UV DTF Printers

Recently, the popularity of UV DTF printers is increasing, and accordingly, the sale of UV ink as one of the basic consumables continues to grow.

However, customers will have some questions before purchasing, such as:

– What is the level of UV ink resistance to sunlight?

– How to deal with uneven printing?

– Whether environmental protection is used or not, is there harm to the human body?

UV ink has many advantages such as 100% instant curing, resistance to wear, no need to spray powder, resistance to solvents and other advantages that lead to increased productivity.

However, customers still want to understand exactly the characteristics of UV ink before using it.

How UV inks are working

Ultraviolet curing (commonly known as UV curing) is a photochemical process in which high-intensity ultraviolet light is used to instantly cure or “dry” inks, coatings or adhesives.

UV formulations are liquid monomers and oligomers mixed with a small percent of photoinitiators, and then exposed to UV energy.

 In a few seconds, the formulation – inks, coatings or adhesives instantly “harden” or cure, ready for the next processing step. (Source “ Heraeus-UV Curing process”).

What is the difference in sunlight resistance between UV inks and regular inks when printing the same color?

The level of resistance to sunlight is mostly related to the pigment, and the only difference in the resin is the degree of yellowness.

The main difference between the four inks is in the yellow ink.

Yellow UV ink can reach level 5 of sun resistance, while normal yellow ink is only level 3+.

 If you use the same pigment, the sun resistance will be closer.

Of course, with UV ink, water resistance is also better due to hardening, and due to the presence of photosensitizers, it will be slightly better than ordinary offset ink.

Why is UV fluorescent ink not resistant to sunlight?

Fluorescent ink generally has 1-3 levels of sunlight resistance.

Fluorescent powder is unstable, the principle of fluorescence itself is to absorb ultraviolet light that is prone to electronic jump.

Therefore, under high intensity UV radiation, it cannot easily recover after the jump, resulting in decomposition.

Fluorescent pigment also has poor temperature resistance, the general decomposition temperature is lower than 120 ℃, while at the general pigment is at least 150 ℃ or more, and at the sunlight-resistant ink can be more than 180 ℃.

Why is the print darkened when printing with UV ink compared to regular ink? How to improve?

The main reason for dark UV printing is caused by the problem of transferability of printing, but of course, it is also related to the lack of leveling time, the gloss is relatively low, and it will also appear darker.

First of all, the transferability of the ink should be improved, you can choose a relatively slow curing speed, and the roller should not be dry.

Second, the use of special UV printing equipment is just as important as the use of special consumables.

Increased distance from the ink set to the UV lamp, air pressure, varnish oil, etc., these are all factors that affect how to improve printing gloss.

Limitations of UV metallic inks

Gold and silver ink can only show a metallic luster when it floats to the surface, but it will cause problems such as floating silver and copper, and the surface is prone to problems such as wear resistance.

These colors are not suitable for post-processing such as coding, lamination, etc., and the metallic luster will be significantly reduced if varnished.

Currently, the company Sublistar adopts another printing method, which also has a gold and silver metallic effect.

Mostly crystal labels are printed, and print is easy on all kinds of hard surfaces of various sizes.

You can use UV flat printing or UV DTF printing from roll to roll with the help of a laminator.

The operating process will be more complex, but the display effect is good.

The printing process is as follows:

UV printers first print the design on A-film, the roll-to-roll printer will automatically do the lamination.

This time you need to remove the waste film.

Then proceed according to the following:

Laminate the hot foil stamping film, peel off the hot foil stamping film.

Laminate the B film, peel off the A film, attach to the object, press and peel off the film.

Under the same UV drying conditions, why does K ink (black ink) dry less thoroughly or too slowly than other colors?

Black ink with its dark color absorbs UV rays, especially when the ink layer is thicker, so UV rays cannot penetrate through the ink layer or the bottom absorbs very little UV rays.

On-machine improvement methods generally use a higher curing speed as well as a higher concentration of special black products.

The curing system uses the help of LED-UV lamps, since LED-UV lamps have stronger penetration, while ordinary UV lambs have better surface curing performance.

The choice of LED-UV lamps also has an advantage because they are more energy efficient and environmentally friendly.

These are some of the questions that customers have before buying and using equipment, and people from Sublistar are here to answer them and help them in choosing a machine in every way.