Screen printing ink status quo and market development trend (3)

(2) Electron beam curing ink

Electron beam curing ink, like UV ink, is one of the most promising "green" inks in screen printing. Since the energy of the electron beam radiation is stronger than the ultraviolet radiation, the electron beam curing ink is not limited by the thickness of the ink layer and is safer to operate than the ultraviolet light curing ink. The Chicago home appliance printing company has used this ink to produce membrane switches. The thick-film screen-printed prints are placed in an electron beam radiation drying device. The ink is fully dried in a few milliseconds under the irradiation of the electron beam. The print has a good gloss, and the film has a strong touch and is resistant to rubbing. Very satisfied. However, the ink and its radiation drying device are very expensive. At present, there are still difficulties in its promotion, but because it can save drying time, ensure product quality, and do not pollute the environment, it has a promising future.

4, UV light solid ink and light solid drying technology to create the future of screen printing

UV screen printing ink (abbreviated as UV ink) English name is Ultraviolet screen printing ink. Invented UV inks have a history of more than 50 years. One of the earliest UV ink patents in the world was published in 1946. UV inks were first used for offset printing, and web four-color offset printing was used for some time, but it has not been popularized. Since 1970, however, the introduction of UV inks into screen printing has shown promising prospects.

(1) Composition of screen printing UV photocurable ink

Screen-printed UV inks are radical photopolymers that excite rapidly through UV radiation and cause radical changes in the polymerization reaction. This characteristic requires the ink to have a special structure that adapts to this reaction mode. The composition of UV ink and ordinary ink is compared as follows:
UV Ink Composition Ordinary Ink Composition
Pigments
Prepolymer or homogeneous polymer
Monomer Dry oil, mineral oil Photosensitizers Driers
Additives Additives

Ultraviolet light-cured inks, although their composition, appearance, and rheological properties are similar to ordinary inks, their components must contain materials that are compatible with UV light curing drying conditions. For example, pigments, its chemical composition and surface treatment affect the ability of UV radiation and the curing and drying of inks. The ultraviolet transmission spectra of the four pigments used in the European color standard range from 200 to 400 mm. According to the curve analysis of the spectrum, it can be determined that each pigment maintains its fixed spectral range. But only the carbon black pigment is the exception, it absorbs almost all of the UV spectrum. Spectral measurements were performed on dispersion sheets of aqueous pigments with a depth of 10 mm.

(2) Photocuring drying characteristics of screen printing UV inks

As previously described, UV inks consist of binders: prepolymers and monomers, as well as photosensitizers and pigments of a certain composition. A photosensitizer is a compound that can change under the influence of ultraviolet light to form an atomic group. This compound can promote polymerization of monomers and prepolymerized reactive groups, and at the same time, the ink is cured and dried. The speed of curing and drying depends on the correct choice of pigments and the choice of photosensitizers that enable the inks to produce the desired photocuring under UV conditions. Unlike solvent-based inks, the use of UV solid dry ink does not lose the fine level of printed images due to drying. Because the ink is not irradiated with ultraviolet light, it is always in a stable state without drying characteristics. When the printed product passes through the ultraviolet irradiating device for about 1 to 2 seconds, the ink is cured and dried, and the printed product can be directly stacked together. When the UV ink is cured, there is actually no loss of ink, and the resulting ink film is much thicker than the solvent ink. When the solvent ink is dried, evaporation of the solvent causes a loss of approximately 60% of the thickness of the ink film. At present, the UV ink curing and drying apparatus cannot transmit ink layers that are too thick, and the ink layer can only be surface-cured, thus affecting the adhesion and durability of the ink to the substrate.

(3) Screen printing UV ink characteristics and print quality

The use of screen printing UV ink has achieved good printability and print quality so far. 1 Stability: UV inks cure and dry only when exposed to UV radiation. It does not crust in the air. Therefore, it is absolutely stable on the screen plate, and fully meets the requirements of screen printing. 2 gloss issues: UV ink under ultraviolet radiation can instantly dry the ink layer, so compared with traditional inks, without relying on the nature of printing materials can get a better ink gloss. When using traditional inks, what happens most often is: After drying, the ink gloss appears to be reduced, and this phenomenon has been eliminated when using UV inks. 3 Abrasion resistance and chemical resistance: The three-dimensional photocrosslinker produced by the photopolymerization of the ink structural unit by ultraviolet rays promotes the ink to have a wear-resistance that meets professional requirements, as well as resistance to acids, alkalis, and chemicals. performance. UV prints In any case, no need to add printing oil. 4 screen cleaning and ozone problems: UV ink to use different screen cleaning agent and ordinary ink, its composition has outstanding solubility of UV ink, but will not etch the screen photosensitive film and squeegee. The ozone produced by the UV ink in the drying process is an allotrope of oxygen, which is caused by ultraviolet radiation having a wavelength of 220 mm or less. The generated ozone can be discharged to the outside by the exhaust fan of the cooling lamp. In the air, ozone is immediately decomposed into oxygen. When mass-produced, the ozone content per cubic meter of air around the machine does not exceed 0.1 mg. This content complies with today's permitted ozone content around the working environment. 5 Printing quality: Ink does not occur in the printing process. Ink penetration changes the color tone of printed products. Because no solvent volatilizes, it can be printed on poorly absorbent substrates with good adhesion. The photocured and dried ink film has a good handle quality, and the ink taste is extremely small.

(4) European screen printing UV ink market

In summary, due to the characteristics of screen printing UV inks with low solvent content and no pollution of the environment, “green” inks have increasingly attracted the attention of the screen printing industry in various countries in the world, and they have invested a lot of manpower and material resources one after another. Develop research and production of UV inks. Especially in Europe, since the European Economic Community strictly implemented environmental protection laws that restricted the use of organic solvent inks in 1992, the range of applications and the amount of UV inks used by screen printers in various countries have been expanding and increasing year by year. According to the FESPA European Screen Printing Association's internal magazine article, the first European ink production company, the Sericol Group ink company, has doubled its UV ink production in the last six years and has become the world's ink sales volume. The largest company, and this trend continues. The UV ink market is also evolving. For example, some screen printers established in Eastern Europe no longer use traditional solvent-based ink screen printing methods, but instead use UV inks to process screen prints. According to the introduction of the French general manager of Dubuit (Dubuit) at the 2004 Guangzhou International Network Printing Exhibition Technology Exchange Conference, in recent years, in the European screen printing industry, the production volume and sales volume of UV inks have increased significantly, and Product varieties are moving in the direction of UV water-based inks. In particular, in 2003, the amount of UV ink used by the European screen printing factory has reached more than 90%.

Source of information: pack.cn