Generally speaking, UV is not specifically applied to lithography. It is a “radiation hardening technology” that irradiates a chemical with a UV light source, and the scale “photoinitiator” contained in the chemical is stimulated by the UV light source to glue and harden the “polymer” contained in the chemical in a very short time (less than 1 second) , commonly known as UV curing. Internationally, “electronic beam hardening technology” is classified into the same category, collectively known as UV / EBcuring.UV Printing Technology

       UV hardening can be used in various traditional printing formats, including relief, flexo, lithography, screen printing, etc. as long as UV ink is used and UV light source is used to complete the main part. Lithographic UV printing is based on the structure of lithographic printing, using UV ink and UV light source. UV Printing Technology

      Of course, some very important matching conditions need to be reached at the same time. In addition to printing, UV glazing with transparent materials is also a widely used glazing method in the market.UV Printing Technology

1、 Characteristics of lithographic UV printing  UV Printing Technology

In general, the advantages of UV printing are:UV Printing Technology

1. High color saturation and good color effect. Compared with traditional lithography, lithography UV printing can obtain higher color effect, and more satisfactory results can be obtained for prints with strict color requirements.UV Printing Technology

2. The image has high gloss and beautiful vision. Matching with the matting background color can obtain an exciting visual contrast, which is very helpful to strengthen the high-quality image of the product (Tolliver, 1998).UV Printing Technology

3. It is applicable to many types of printed objects with completely different physical and chemical properties, including paper, paperboard, plastic, sirol, PVC, PE, etc. This feature can print more product types than traditional lithography, and has a broader market future.

4. It can be dried immediately while printing, which can greatly improve the production efficiency (RadTech, 1998). Because there is no need to wait for the ink drying time, the production time can be greatly shortened, and the printing company can also save a lot of space for storing the parts to be dried, which is helpful to cost saving.UV Printing Technology

5. Since the printing is immediately dry, powder spraying is not required, which can improve the quality problems caused by powder spraying and can be avoided.UV Printing Technology

6. Due to the immediate drying during printing, color changes will not occur within 48 hours after printing, as in traditional lithography (ehrlitzer, 1998).UV Printing Technology.UV Printing Technology

7. The light resistance of the image is better.UV Printing Technology

8. The abrasion resistance of the image is better.UV Printing Technology

9. More friendly to the environment (RadTech, 1998).UV Printing Technology

In addition to the above advantages, does lithographic UV printing have no disadvantages? The answer is that it certainly has some disadvantages:UV Printing Technology

1. The machine investment cost of lithographic UV printing is higher than that of traditional lithographic printing equipment, and the investment decision needs to be more careful.UV Printing Technology

2. The market types that can use lithographic UV printing are wider and more scattered than the traditional lithographic printing market. Therefore, if manufacturers want to invest in the development of this technology, they should first conduct market analysis and research to avoid the risk of not finding orders after investing in equipment.UV Printing Technology

3. The ink cost of lithographic UV printing is about 3-4 times that of traditional lithographic printing, and the material cost is high. The production management technology, process technology and cost control in printing production need to be more rigorous, otherwise the proportion of cost loss will be higher than that of traditional lithography.UV Printing Technology

4. The ink storage area needs strict temperature control, which needs to be kept below 20 ℃, and the storage cost is high (hostmann Steinberg, 1992).UV Printing Technology

5. If the ultraviolet ray is leaked, it will have a health impact on personnel.UV Printing Technology

6. Lithographic UV printing is not as popular as traditional lithographic printing. The manpower supply familiar with operation technology needs to rely on their own training.UV Printing Technology

In general, the types of technologies that UV printing will be applied to are briefly described below:UV Printing Technology

1. UV light source equipment: including lamp tube, reflector, energy control device and temperature control device (or cooling device).UV Printing Technology

(1) Lamp tube: the lamp tube used by UV light source. The most commonly used type is the mercury lamp tube filled with mercury

      Sometimes, other metals, such as gallium, are added. In addition, metal halogen lamps and quartz lamps are also commonly used. At present, it mostly depends on imports. The electromagnetic wave length emitted by UV lamp must be between 200-400nm.UV Printing Technology

(2) Reflector: the main function of reflector is to reflect the UV electromagnetic wave back to increase the efficiency of UV light source (UV tech publications, 1991). UV Printing Technology

      Another important function is to maintain the working temperature of the lamp tube. The reflector surface is usually aluminum, and the reflectivity requirement is usually as high as 90%.UV Printing Technology

      There are two basic types of reflector, one is focusing type and the other is defocusing type. With the development of manufacturers, there are other extended types.UV Printing Technology

(3) Energy control device: the main energy supply of this device is to control the UV energy emitted by the UV lamp to be stable, so as to maintain the efficiency and stability of hardening and meet the needs of different printing speeds. There are electronic design and microcomputer control.

2. Cooling device:UV Printing Technology

      When the UV lamp emits the UV electromagnetic wave, it will also emit IR (infrared wave), so that the UV equipment will operate at high temperature (for example, the temperature of the quartz lamp can reach 600-800 ℃), UV Printing Technology

      which will not only shorten the service life of the equipment, but also easily cause expansion and contraction to the printed matter, resulting in the inability to register the gauge position during printing, so the importance of the cooling device can be seen.UV Printing Technology

3. Ink supply system:UV Printing Technology

        Because UV ink has higher viscosity and greater friction than traditional lithographic ink, and will damage the components of the printing machine (including blanket, ink roller, etc.), in addition to the continuous mixing of the ink in the ink tank during printing, the ink roller and blanket in the ink supply system shall be used, which shall be designed for UV printing.UV Printing Technology

      In order to maintain the stability of UV printing ink and avoid excessive temperature affecting the viscosity of printing ink, the temperature control device of ink roller is also an important equipment.UV Printing Technology

4. Heat dissipation and exhaust device:UV Printing Technology

The main function is to eliminate the excessive heat energy inside the machine and the ozone generated during the polymerization and hardening of printing ink. It is usually composed of exhaust motor and exhaust pipe.UV Printing Technology

5. Printing ink:

      Whether the ink quality is good or not is the most critical factor that directly affects UV printing. In addition to the traditional quality factors such as color performance and color gamut, the printability of printing ink directly affects the adhesion, strength and anti friction of the printed object after printing. The types and characteristics of photoinitiators and polymerized monomers are the key basic materials.UV Printing Technology

       To control the adhesion of UV ink, when wet UV ink contacts the printed object, the surface tension of the printed object (unit: dynes / cm) must be higher than the surface tension of the printed ink (schilstra, 1997), so as to produce good ink adhesion. 

       Therefore, controlling the surface tension of the printed ink and the printed object is an important technology of UV printing.

6. UV energy measuring equipment:UV Printing Technology

       In UV printing, due to the aging of UV lamp, power supply, printing machine speed and other factors, it is necessary to control the UV energy to maintain stability, so the technology of measuring UV energy has become a very important part.UV Printing Technology

7. Foreign technology development trend:UV Printing Technology

(1) Stable growth of the market.

(2) Application of multi-color printing and color separation technology with high fine performance. Including hi fi color and stochastic screening technology.

(3) Cold UV curing (Holland, 1997):

       Heraeus develops the excemer lamp, which will not produce infrared rays, so it will not generate heat. For thin-film printing or printed objects prone to shrinkage effect, it has effective and good positioning control results.UV Printing Technology

       Other advantages are: energy saving, no erosion of printing machine parts, no odor, etc. However, so far, its efficiency can not replace the mercury lamp, and it has great potential for development in the future.UV Printing Technology

       Compared with traditional lithography, the current use of lower plate UV printing in China belongs to a very few types of technology. So far, few manufacturers have installed lithographic printing machines specially designed for the characteristics of lithographic UV printing, and most of them are used to produce magnetic cards, films and high-quality cosmetic packaging boxes.UV Printing Technology

       Domestic printing companies use more lithographic UV applications, most of which are used for glazing. It Z mostly is off-line UV glazing. When the paper printed matter completed by traditional lithography needs high gloss glazing (including full glazing and local glazing), most of them adopt this method.UV Printing Technology

       Its investment is small, and most of it is invested by the polishing factory, so the printing company does not have to invest, and the polishing factory is more cost-effective because the equipment can play an efficiency. UV Printing Technology

      The disadvantages are long production process and unstable quality. Because traditional lithography uses powder spraying, the glazing effect will be affected. This combination is mostly used in commercial advertising printing and packaging boxes.UV Printing Technology

        At present, there are no major problems in the equipment of lithographic UV printing technology in China. As the leading international manufacturers (printing presses such as Heidelberg and Roland; UV equipment: UV Printing Technology

       ist Metz, eltosch, spectral; UV tubes: OSRAM, etc.) have professional and complete equipment, these equipment have also experienced the strict test of foreign printing companies, and there are no major problems in their use efficiency and stability,UV Printing Technology

      except the financial problem of high equipment investment. At present, the problems in the application of lithographic UV printing technology in China mainly focus on material supply and printability.UV Printing Technology