The Characteristics and Application of Screen Printing in Packaging and Decorating

With the increasing demand in the packaging and printing market, packaging and printing in various countries has developed rapidly. At present, the packaging and printing industry has gradually become the sunrise industry of China's national economy. In the field of packaging and printing, offset printing, flexo printing, gravure printing, and screen printing coexist and develop each other. As far as the current situation is concerned, screen printing has shown a strong momentum of development with its wide range of printing materials, flexible printing layers, thick ink layers, good color-forming properties, and strong ink adhesion. It can be predicted that in future packaging and decoration printing industry, The application scope of screen printing will be more extensive and the market potential will be even greater.

1 Characteristics of screen printing 1) Thick ink layers From the four printing methods of plain printing, embossing, gravure printing and screen printing, the ink layer thicknesses that lithographic and letterpress printing can achieve are only a few μm, and gravure printing can reach 8~18 μm. The screen printing ink layer thickness can reach 30~100μm. Nowadays packaging products often contain signs and patterns that need to be highlighted, and screen printing can meet this demand for packaging products. Its thick ink layer can enhance the three-dimensional sense of printing graphics, this feature is unmatched by other printing methods.

2) Not limited by the size and shape of the printing format The maximum area that can be printed by the general printing method is full sheet, screen printing can reach 3 × 8m, or even larger printing format, so it meets the needs of many outdoor advertising signs. And the screen printing ink has strong light resistance, it can make the printed matter not affected by the temperature and sunlight, and keep it shiny and beautiful. Screen printing not only accommodates large-format printing, but also prints on ultra-small items such as buttons. In addition, screen printing can also be printed on special moldings and curved surfaces. Containers such as bottles and boxes can be printed by screen printing.

3) Low printing pressure Screen printing plates are soft and the printing pressure is small, so not only can be printed on paper and plastic packaging products, but also can be printed on various fragile glass and ceramic substrates.

4) Wide printability Screen printing can use a variety of inks for printing, such as water, oil and other inks. And screen printing can achieve many special effects through the selected ink, such as swelling, ice, pearl, fragrance and so on.

5) Flexible printing methods Diversified screen printing can use high-end equipment such as roller screen printers or rotary screen printers to achieve large-scale industrial production. At the same time, due to its flexible printing methods and simple processes, it can also be used in small batches with simple tools. Manual production.

2 Application of screen printing in the field of packaging and decoration

1) Plastic screen printing

Plastic screen printing often recognizes high-density polyethylene (containers, pipes), ABS (auto parts, telephones), polypropylene (logos, trunks), and cellulose resins (commodities, toys) as substrates. Because some plastics have small polarity, low surface tension, poor wettability, and smooth surfaces, it is difficult to achieve a clear print and secure adhesion. Therefore, the surface needs to be pretreated to improve the screen printing effect. The pretreatment methods include annealing, dust removal, plasma, degreasing, hot air treatment, and the like.

Plastic screen printing does not use thermosetting inks, because curing at high temperatures can cause plastic deformation, so most of them are based on the melting properties of plastics. When printing, choose the appropriate ink based on the properties of the plastic and the use of the finished product.

2) Metal screen printing

Metal screens are printed with hard materials such as metal plates, metal molded products (beverage cans, etc.), and metal foils. As metal printing products are often an integral part of various containers, building materials, household appliances, and brand names, this imposes higher requirements on their surface decoration and durability. Therefore, surface treatment such as polishing, drawing and spinning is required before printing. Patterns, sandblasting, sand surface treatment, spray paint, etc. Then according to the surface properties of the substrate to choose the right ink, the current metal screen printing ink types are mainly solvent evaporation type, oxidation drying type, UV curing type. The direct printing method is usually used in printing, taking care to remove the oil on the metal surface and keep it clean. It is also possible to subject the prints to high-gloss treatments as needed to produce a high-gloss finish to enhance their decorative effect.

3) Glass Screen Printing

Glass screen printing objects are all kinds of beverages and wine glass bottles, decorative glass products and so on. Glass screen printing mainly uses glass glaze as the ink, and the printed glass products are fired at a high temperature of 520° C. to 600° C., so that the glaze can be cured on the glass. In this temperature range, glass glazes are classified into three types: low temperature (520°C), medium temperature (560°C), and high temperature (600°C). Low-temperature glazes are used in thin glass products, medium-temperature glazes are used in tableware, cosmetics, and other glass products, and high-temperature glazes are suitable for printing beverage bottles.

In recent years, with the development of screen printing UV inks, UV glass inks have emerged, which have excellent wear resistance, fast curing speed, and are gradually used in glass screen printing.

4) Ceramic Screen Printing

As the screen printing has the characteristics of strong three-dimensional image, bright color and durable wear, it has been widely used in the field of ceramic decoration technology.

Ceramic screen printing process can be divided into two major categories: direct and indirect methods. The direct method is a kind of technological method that directly prints the graphic on the surface of the embryo and then burns it into porcelain. It can also be directly printed on the porcelain surface. The direct method is suitable for ceramic products with flat surfaces (eg, tiled surfaces) and is generally not used for ceramicware. The indirect method refers to the printing of the decals on the decals and the transfer of the decals to ceramics. The indirect method results in higher accuracy.

In a word, screen printing has a great deal of flexibility and wide applicability, showing a steady growth in the field of packaging and printing, and it occupies an important position. However, there are also problems and deficiencies in screen printing. In the future, improvements and research and development in terms of printing speed, accuracy, ink environmental protection, etc. must be strengthened.

Source: "Printing World"