How to choose and use UV ink ?
Time:2025-05-24
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UV ink is a widely used ink variety in paper printing due to its bright printing colors, high glossiness, water resistance, solvent resistance, wear resistance, and fast curing speed. It is widely used in embossed printing, flexographic printing, offset printing, etc. Choosing and using UV ink well, especially comprehensively grasping the influencing factors, judgment methods, and solution ideas of UV ink curing, is very important for reducing printing failures and improving label printing quality.
The current application status of UV ink
1. The quality of UV ink varies greatly
At present, the quality of UV ink in the domestic paper printing market varies greatly, so people often encounter faults such as dry rollers, ink stacking, ink flying, and dirty plates during the printing process; UV printed products also commonly have problems such as poor ink adhesion, low glossiness, and insufficient coverage, especially the problem of low white ink coverage is more prominent. These are often caused by the use of low-end UV ink, which not only affects printing efficiency, but also significantly fails to meet the quality requirements of the books.
In order to avoid potential issues with UV ink as much as possible and meet the quality requirements of different materials, application fields, printing processes, etc., UV ink suppliers have been continuously improving and launching new products.
2. There is no unified standard for UV light sources to follow
The curing effect of UV ink is directly affected by the UV light source. Due to the lack of a unified standard for the spectral range of UV light sources, the spectral range and power of commercially available UV light sources vary greatly. If the matching between UV light source and ink is not good, it will cause incomplete curing or excessive surface curing of UV ink, ultimately leading to quality problems such as poor ink adhesion.
How to choose UV ink
The curing performance of ink is the most critical factor in determining the quality of UV printing products. Therefore, when choosing UV ink, the main consideration is whether the emission wavelength of the UV lamp used in our printing equipment matches the triggering wavelength of the photoinitiator in the ink. In addition, the key properties such as curing speed and adhesion of different types of UV ink provided by different manufacturers are also not the same. Generally speaking, as long as white ink and black ink can meet the requirements, other color schemes of ink will not have too many problems. Therefore, black ink and white ink should be carefully examined.
1. Performance characteristics of UV light source: The wavelength range of UV light is 200-600nm, but ozone is generated at a wavelength of 254nm, while heat is generated above a wavelength of 400nm. Ozone pollution pollutes the environment and damages the health of workers; Heat not only causes dimensional instability and even severe deformation of printed materials, but also leads to energy waste, both of which we do not want to occur in UV printing. Low energy UV (HUV/LEC) lamps emit wavelengths between 280-600nm, avoiding the ozone band but still containing a significant amount of heat generation. LED lamps perfectly solve this problem. The available wavelengths for single wavelength LED lights are 365nm, 385nm, and 395nm, avoiding the ozone and heat generation bands. Moreover, the light energy of single wavelength light sources is highly concentrated, resulting in high ink curing efficiency and safer use.
2. Choose UV ink based on its compatibility with UV light sources. The prerequisite for UV ink curing is the exposure of UV light, and the photoinitiator in the ink can absorb its energy and generate free radicals. Under the action of free radicals, the resin and single-molecule compounds in the ink can undergo cross-linking reactions, causing the ink to solidify. The triggering wavelength of traditional UV ink photoinitiators is generally 220-580nm, while the triggering wavelength of low-energy UV ink photoinitiators is 280-400nm. LED-UV ink photoinitiators mainly absorb UV light with a wavelength of 365-400nm. When choosing UV ink, the first thing to consider is whether the wavelength range sensitive to the ink corresponds to the emission wavelength range of the UV lamp used by the company. At the same time, the actual curing energy of the UV curing system should also be taken into account to determine the specific model of UV ink.
3. The selection of UV ink color based on the curing performance of black ink and white ink also affects the curing speed of UV ink. Different colors of ink have different curing speeds, mainly because each pigment has different absorption rates for UV light of different wavelengths. Among all color schemes, magenta ink is the easiest to cure, while black ink is the most difficult to cure.
This is because although black theoretically absorbs all light and should have a high curing efficiency, the pigment particles have a blocking effect on light, which hinders the curing of deep ink. Therefore, black UV ink requires high curing energy, and the curing speed of black and various deep color inks is relatively slow. The high energy required for curing white ink is due to the fact that white pigments can achieve total reflection of all visible light, making it difficult and slow to completely cure white UV ink. The curing efficiency of an ink series is directly related to white ink and black ink. As long as there is no problem with white ink and black ink, other color inks can be used with confidence.
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