The main components of the UV ink are a polymerizable prepolymer, a photosensitive monomer, a photoinitiator, an auxiliary component, a coloring pigment, a filler, an additive (leveling agent, a polymerization inhibitor), and the like.


1. Polymeric prepolymer
The polymerizable prepolymer is an important component determining the performance of the UV varnish coating. It is the most basic component in the UV ink and is a film-forming substance. The performance plays an important role in the curing process and the properties of the ink film after curing. Generally classified according to the skeleton structure. The skeleton structure affects coating hardness, abrasion resistance, adhesion, light resistance, chemical resistance, and water resistance.
The prepolymer is structurally a low molecular weight resin containing a "C=C" unsaturated double bond, such as an acryloyl group, a methyl acrylate group, a vinyl group, an allyl group or the like. There are mainly resin types such as epoxy acrylate resin, urethane acrylate resin, polyester acrylate resin, polyether acrylic resin, polypropyl acrylate, and unsaturated polyester resin. Under the same conditions, the photocuring speed is the fastest, so the oligomers are mostly acrylic resins.
UV ink and UV varnish need to have the viscosity of the coating machine when coating, generally by adding 20% to 80% of the monomer to reduce the viscosity of the prepolymer, and the monomer itself polymerizes to become a cured film. portion.
Reactive diluent, also known as cross-linking monomer, is a functional monomer whose role in the ink is to adjust the viscosity, cure speed and cured film properties of the ink. The reactive diluent also structurally also contains a "C=C" unsaturated double bond which may be an acryloyl group, a methyl propyl acyl group, a vinyl group and an allyl group. In view of the fact that the acryloyl photocuring rate is the fastest, most of the reactive diluents currently used are acrylate monomers. Due to the different amounts of acryloyl groups, they can be divided into three types: monofunctional groups and difunctional groups. The release effect and curing speed of various functional group reactive diluents are different. In general, the more the functionality, the faster the cure, but the worse the dilution.
Traditional reactive diluents, such as styrene, first-generation acrylate monomers, etc., are highly toxic, and some acrylate monomers have a strong irritating effect on the skin. In order to reduce the skin irritation of reactive diluents, there are usually two methods: one is to use ethylene oxide, propylene oxide and hexyl ester ring-opening polymerization to increase the molecular weight of the monomer; the second is to change the monomer ester structure; The species is a change in the previously used alcohol esterification process. When alcohol is added to the acryloyl group, the skin irritation of the polyfunctional monomer is greatly reduced. For example, when the neopentyl glycol diacrylate is esterified, the pH value (skin irritation index) is 4.96, and When synthesized, the pH drops to 0.3.
Recently, some well-performing monomers have been developed, such as: alkoxy acrylates, carbonic acid monoacrylates, imidazolyl monoacrylates, cyclic carbonate monoacrylates, epoxy silicone monomers, silicone acrylics. Ester and vinyl ether monomers. When selecting a monomer, follow these guidelines:
a, low viscosity, good dilution effect;
b, curing fast;
c, good adhesion on the material;
d. It is less irritating to the skin and less toxic;
e. No odor is left in the coating.