Flexographic UV Varnish Performance Introduction and Problem Analysis

What are the characteristics of the flexographic UV varnish?

(1) Contains no volatile solvents to prevent air pollution and improve the operating environment.

(2) Fast photocuring (curing speed can reach 100-200 meters/minute), improving production efficiency.

(3) Save energy and apply to automatic production lines. UV Varnish passes through an instant photochemical reaction even if the liquid UV coating becomes a solid film.

(4) The surface of the film after photocuring does not adhere and the product can be stacked immediately.

(5) Polished by UV Varnish has high gloss, abrasion resistance, water resistance, and chemical resistance.

(6) Due to the absence of solvents, the viscosity is relatively stable, so the printability is good.

(7) The thermal substrate can be coated.

(8) The UV-coated paper can be recycled to reduce environmental pollution.

What are the effects of oligomers in UV Varnish? What are the commonly used oligomers?

Oligomer is the main film-forming substance of UV varnish, and its properties are related to the viscosity of UV varnish. The curing speed and the nature of the film after curing play an important role. The oligomers all contain C=C unsaturated double bonds. The currently commonly used oligomers are generally acrylic resins.

What are the active monomers in UV Varnish? What are the commonly used reactive monomers?

The reactive monomer is a macromolecular compound whose molecular structure also contains a C=C unsaturated double bond, which on the one hand participates in the cross-linking reaction of the oligomer and on the other hand acts as a reactive diluent for the adjustment of the UV varnish. The viscosity of the currently used active monomers is acrylates.

What are the photoinitiators in UV Varnish? What are the commonly used photoinitiators?

Photoinitiators are the main components in UV coatings. Although the oligomers and reactive monomers in the formulation are themselves capable of polymerization upon exposure to ultraviolet light, they are inefficient and cannot meet the requirements of practical applications. A photoinitiator is a compound capable of generating free radicals or cations upon exposure to ultraviolet light. After absorbing the radiant energy of ultraviolet light, the photoinitiator initiates a cross-linking reaction between the oligomer and the monomer, so that the UV coating oil is cured and salted. membrane. Common photoinitiators are ketones, ethers and sulphides.

UV varnish gloss is not good. What are the reasons for the lack of brightness? How to solve it?

(1) UV varnish viscosity is too small and the coating is too thin.

(2) There are too many non-reactive dilution solvents such as ethanol.

(3) The paper surface is rough and its absorption is too strong.

(4) The anilox roller is too thin and the fuel supply is too small.

(5) Coating is uneven.

Solution: Appropriately increase the viscosity and coating amount of UV varnish according to different conditions of the paper, and apply a primer to the paper with strong permeability.

How to solve the problem of incomplete UV curing, surface stickiness, and large residual odor?

UV lamp aging, UV varnish storage time is too long, UV curing agent in the non-reactive diluent added too much, etc. will lead to the above failure, so the timely replacement of a new lamp, add a certain amount of UV varnish Curing accelerator to enhance drying and ventilation conditions before curing.

How to solve the UV coating on the surface of flowers. Can't paint, poor adhesion problems?

Excessive anti-sticking material on the surface of the ink, inadequate auxiliary materials in the ink, and improper photo-curing conditions all contribute to the above phenomenon. Therefore, when printing, it is required that the used ink should meet the light conditions, and if necessary, it can also be solved by applying primer or replacing the special UV coating.