Three. UV light source
In general, the use of UV ink to print on the general known as UV printing, UV printing is the main principle of ultraviolet radiation, and radiation is a type of electromagnetic wave, different radiation energy, then by the different wavelengths to distinguish, different energy Wavelengths compose Electromagnetic spectrum, which is divided into the following types (from short to long) according to the length of the wavelength: cosmic rays, coffee rays, x-rays, ultraviolet rays, visible spectrum, infrared rays, microwaves, radio waves, etc. .
As mentioned in the preface, the electromagnetic spectrum is divided into (from short to long) according to the long and short wavelength arrangement: cosmic rays, gamma rays, x-rays, ultraviolet rays, visible spectrum, infrared rays, microwaves, and radio waves, among which the ultraviolet rays It is defined by the International Commission on Illumination and can be divided into three categories according to the length of the wavelengths:
(a) UVA:
Ultraviolet light with a wavelength in the electromagnetic spectrum range of 315~400mm is the most harmless and most common ultraviolet light because it has the smallest energy, the fork is called BlackLight, which is near ultraviolet light, and is usually used in relatively harmless and The fluorescent substance emits ultraviolet light, and since it is also called a photochemical line, it represents the energy output that can produce the maximum polymerization hardening efficiency when the UV ink is used, and this point is usually used to measure whether the UV light source has decayed. Point is an important reference point for measurement.
(b) UVB:
Ultraviolet light with a wavelength in the electromagnetic spectrum of 280~315mm is the most typical destructive ultraviolet light. Because it has enough energy to damage biological tissue, he can cause skin cancer, and because the ozone layer has recently been destroyed, shortening the time of exposure to sunlight is very important. This wavelength does not have an effective effect in UV printing inks, and therefore, unless there is a special need, the energy distribution of UV lamps generally used in UV printing in this area is less valued.
(c) UVC:
That is, ultraviolet rays having a wavelength in the electromagnetic spectrum range of 100 to 280 mm are almost completely absorbed in the air. In the use of UV printing, it has the effect of hardening the surface of the ink film. In recent years, there has been a method of performing UV printing by blowing the surface of the printed matter with nitrogen gas. Its purpose is to reduce the chance of ozone generation by UVC, and to make UVC The radiant energy can be fully applied to the polymerization hardening Curing drying. Although this method is more costly, it increases the efficiency of the polymerization hardening and drying to the best level.
IV. Introduction of UV ink
UV inks use ultraviolet radiation of a certain wavelength to achieve ultra-violet curing. The hardening speed can be determined by the type of light initiator, the amount of light used, and the intensity of the UV lamp. Weak, dry speed and UV lamp lamp number to adjust. Because of UV radiation, UV ink has the characteristics of fast connection drying, and this UV characteristic makes it possible to print on non-paper, such as PVC, PET (polyethylene terephtalate), synthetic paper... ... and so on, and because it can be fast-lined to dry so that reprocessing or reversal can be done without waiting, so no need to spray powder when drying, even if printed on paper also have a higher gloss and resistance to friction.
The advantages and disadvantages of UV printing, such as [Table 4]
The composition of the UV ink is mainly composed of a pigment, an oligomer, a monomer, a photoinitiator sensitizer, and a filler, etc. The compositional structure differences of the oxidized inks are shown in Table 5.
Table 5 Comparison of compositional structures of UV inks and traditional oxidized inks
From Table 5, it can be clearly seen that the corresponding component functions between the UV ink and the traditional ink are similar, and the chemical composition structure is completely different.