UV Varnish Printing Technology and Its Curing Technology

Uv printing technology uv low temperature drying


UV (Uitra Violet, or UV) technology is used in the traditional offset printing of paper and metal, waterless offset printing, letterpress flexo printing, and screen printing.

1, UV ink

The UV type lithographic offset printing ink used for metal printing uses UV irradiation for instantaneous drying, which not only accelerates the drying of the ink, but also contributes to environmental protection.

Since the metal surface is a non-absorbent surface, the post-printing drying problem is one of the main technical problems in metal printing. A UV drying device is disposed between the printing cylinders of the offset lithographic printing machine of the metal plate, and a UV type ink is used to realize high-speed and multi-color printing. Since the single base and cleaning agent in the UV ink will have a swell effect on the rubber roller and the blanket, a rubber stick and a rubber blanket dedicated to the UV ink should be used for this purpose.

2. UV Varnish and Curing Technology

(1) Composition: The main component of UV varnish (also called photocuring varnish) consists of photosensitive resin, reactive diluent, photoinitiator and auxiliary agent.

(2) UV curing mechanism

UV curing, that is, the irradiation process energy of the ultraviolet ray irradiates the free-radical-polymerized acrylic coating film into a glazing process. Photoinitiators in the components of this type of coating absorb the light energy of the ultraviolet light and generate free radicals in the excited state, which leads to a polymerization reaction.

(3) UV curing elements:

- UV curing light sources generally use high-pressure mercury lamps or metal halide lamps. For different UV light sources, the wavelength range of the emitted light is different, and the spectral energy distribution in the waveband is also different.

- The power of the UV lamp (ie, the amount of UV lamp radiation) should be controlled at 80-120W/cm to ensure the UV coating curing speed

- UV Varnish should match UV light source. Solving the problem of matching the UV varnish with the UV light source will help speed up the curing speed of the varnish, increase the energy efficiency, and reduce the production cost of the enterprise.

(4) advantages and disadvantages:

Advantages: UV curing has the characteristics of rapid curing and low temperature curing; the film layer is bright and smooth; the refractive effect produces a strong sense of character in the graphic text; the color is more vivid; it helps to maintain the same color and solves the temperature problem of solvent-based glazing coatings. Adhesion caused by changes in humidity, firm film surface after drying, good heat resistance, cold resistance, water resistance, abrasion resistance, and protection; short printing time, high production efficiency, and small occupied space; favorable for environmental protection and improvement of operations surroundings.

Insufficient: due to the high degree of polymerization of UV coating itself, the formation of surface molecules of poor polarity, and no hair pores, so the UV film layer affinity is poor. For example, UV inks have poor affinity with metal surfaces. Therefore, the surface of the metal plate needs to be pre-primed.

The use of UV drying is the development trend of foreign metal printing, the development of low-temperature drying UV printing ink and coating (coating) oil, in order to achieve the purpose of saving energy and improving productivity. With the development of can making technology, the amount of coating required for can bodies should be reduced as much as possible. This will not only reduce the restrictions on storage and transportation and the difficulty of circulation, but also reduce production costs and improve the production environment.