What is the principle of ultraviolet curing equipment?

In recent years, UV-curable inks are increasingly used in screen printing and offset printing industries. As we all know, compared with the traditional solvent-based ink, UV curing ink has the advantages of good gloss, strong three-dimensional effect and no harmful solvent volatilization. Especially in ink drying, ultraviolet curing ink can be cured instantly under ultraviolet irradiation, which avoids the shortcomings of traditional solvent-based ink such as long drying cycle and large occupied area, and greatly improves work efficiency and quality. After printing, UV curing ink needs to be cured instantly with UV curing equipment. The main factors affecting the curing quality are the wavelength and energy of UV lamp, the speed of conveyor belt and the cooling system of UV machine.

I. UV curing principle, UV lamp and related technical parameters:

1, UV curing principle: adding photoinitiator (or photosensitizer) to the resin with special formula, after absorbing high-intensity UV light in the UV curing equipment, active free radicals are generated, thus initiating polymerization, cross-linking and grafting reactions, and making the resin change from liquid to solid in a few seconds.

2.UV curing lamp: At present, the light source of UV equipment used in industry is mainly gas discharge lamp (mercury lamp). According to the pressure of gas in the lamp cavity, it can be divided into low pressure, medium pressure, high pressure and ultra-high pressure. High pressure mercury lamps are usually used in industrial production and curing. High-pressure mercury lamp can produce characteristic ultraviolet (UV), visible light and infrared light (IR) with strong radiation of 3 10nm, 365nm and 4 10nm, among which the wavelength with 365nm as the main peak is the common wave band for curing and drying in all countries of the world (hereinafter referred to as UV lamp refers to 365nm high-pressure mercury lamp).

Second, the influence of related parameters on curing quality

1、

UV machine wavelength: the spectrum of 365nm band is suitable for general photocurable inks (not suitable for inks with special spectral requirements such as icing and wrinkling). Too much stray light of UV lamp will affect the curing effect. It is suggested that the customer conduct a light curing test before selecting the ultraviolet curing equipment to check whether the wavelength of the UV machine meets the light curing requirements.

2. Power of UV machine: Generally, the power required for UV curing ink is 80- 120w/cm. Too high light curing energy will cause ink embrittlement, and too low light curing energy will not achieve light curing effect.

3. Air suction device: the UV lamp emits ultraviolet rays, and at the same time, it also generates a lot of heat, so that the temperature inside the machine keeps rising. In light curing machine, an exhaust device is installed above the ultraviolet lamp, and the ozone generated in the curing process is discharged out of the room through the exhaust pipe to achieve the purpose of cooling. When the substrate is too thin or the temperature resistance requirement is very low, it is necessary to determine whether it can meet the requirements through photocuring test. For substrates with high temperature requirements, we can carry out special treatment, and install timely glass plates under the lamp to cool down and further filter stray light.

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