Offset printing ink (on)

The first impression given by prints is the true reproducibility of color, which is manifested by ink. So ink is the most important printing material. As an offset printing operator, it is necessary to fully understand the composition and printability of the offset ink so that the ink can be selectively used properly.

Composition and classification of an offset ink

Offset inks are mainly composed of a homogeneous mixture of colored pigments (dye, etc.), binders, fillers and additives.

Pigments are solid, powdered substances that are insoluble in water, or in oil or binders, and have a certain color. It is not only the main solid component in the ink, but also the part of the color body that is visible on the object. To a large extent determines the ink's color, thick, light and other properties.

The linking material is the heart of the ink, a gluey fluid that, as the name implies, plays a linking role. In the ink, powdery pigments and other substances are mixed and linked to form a sticky body with a certain degree of fluidity and viscosity after being ground and dispersed. The binder is the main fluid component in the ink and determines the flow, viscosity, dryness, and printability of the ink.

The filler is a white, transparent, translucent, or opaque powdery substance that is also a solid part of the ink and acts primarily as a filling. Appropriate selection of fillers, in addition to reducing the amount of pigment, reducing the cost, it can also adjust the ink properties, such as thin, fluidity.

Additives are additional parts of the ink and can also be used as an add-on to the finished ink. As a printing aid to change or improve certain properties of the ink, such as: dryness, abrasion resistance, etc.

Ink Sheet Paper Inks Luminous Quick-drying Ink Four-color Ink Common Ink Ink Paper Ink Four-color Ink General Ink Specialty Ink Offset Gold and Silver Ink Offset Ink Epoxy Ink Offset Pearly Ink Offset Ink-Offset Anti-counterfeit Ink Friction Offset Offset Ink Offset Offset Infrared Drying Ink (IR Series) Offset UV Drying Ink (UV Series) Offset Synthetic Paper Ink Offset Waterless Offset Offset Transfer Ink Thermoset Offset Transfer Ink Non-Hotset Offset Transfer Ink

The most commonly used offset inks are:

(I) Offset Bright Ink

Offset bright ink is a colloidal ink composed of synthetic resin, dry vegetable oil, high-boiling paraffin oil, high-quality pigments and additives. For monochrome, two-color or multi-color offset printing machine on the coated paper printing pictures, pictures and other sophisticated fine prints. The gloss of the ink is mainly caused by the conjunctiva after drying of the linking material. In order to improve the gloss of the ink, the leveling of the ink film is required to be good, and the surface of the substrate should be able to form a flat surface and reflect the incident light directionally, that is, have a mirror effect. This requires that the binder stays on the surface of the substrate as much as possible. Printing on a low-absorption coated paper makes it easy to obtain a good gloss and has a good film-forming property. At the same time, components such as pigments and fillers in the ink do not affect the mirror effect of film formation of the binder.

The proportion of binders such as resin and dry oil in offset inks is large, the proportion of solvents is small, and the types of resins are many. The softening point of the resin with low softening point is better, and the leveling property is also better. The bright ink has also requirements for the pigment. To make the proportion of the ink binder higher, the coloring power of the pigment should be as large as possible, and the dispersibility And not flocculation is better. The gloss of the pigment itself also plays a significant role in the gloss of the printed product, but the pigment is required to have no metallic luster, the transparency should be as strong as possible, the pigment particles are smaller, and the wettability in the binder is better. Similarly, offset inks require fillers that are as small as possible, and often use ultra-fine colloidal calcium carbonate as a filler.

Domestic offset inks are available in six colors in six colors: white, yellow, green, blue, red, and black. Among them: P01233 (medium yellow) P01234 (transparent yellow ink) P01422 (sky blue ink) P01412 (peacock blue ink) P01655 (pink ink) P01656 (pink ink) P01808 (black ink) can be used as a four-color printing.

(B) offset printing ink

Offset resin inks use synthetic resins, dry vegetable oils, mineral oils, high-quality pigments and fillers, and are formulated and ground. It is used by offset presses for printing various graphics and trademarks.
Offset resin inks are characterized by less vegetable oil content and a high proportion of solvents (15-25%), usually high-boiling alkane, which acts as a viscosity-reducing agent in the ink. When the ink is transferred to the paper, this part of the solvent quickly penetrates into the paper fibers under the action of the capillary, which speeds up the drying of the ink and reduces the breakdown of the printed product. Due to the high content of solvent in the ink, the roller and blanket have a destructive effect, thus affecting the quality of the printed matter. The drying of the fast-fixing ink is ultimately based on the dry form of the oxidized conjunctiva. Therefore, it is necessary to add a small amount of lead or cobalt desiccant in the ink, and the drying speed is fast, but the residual viscosity is large.

(C) UV offset printing ink

Printing with UV inks in offset printing is commonly referred to as UV offset printing. UV offset printing ink is a type of ink that uses ultraviolet (UV) radiation energy to cure liquid chemicals by rapid cross-linking to form an ink film. It is one of the energy-curable inks.

UV offset ink as a kind of offset ink, it must first be able to print by offset printing, so UV offset ink should also have some characteristics of ordinary offset ink to meet printability requirements. These performance requirements include fluidity, dispersibility, demulsibility, tackiness, low flying ink, good transferability, and drying and post-printing properties.

1, UV light curing ink characteristics

Ultraviolet light is an electromagnetic wave with a shorter wavelength than visible light, and different wavelengths have different energies. In general, UV light curing inks use UV light wavelengths of 250-400 nm. The ultraviolet light sources commonly used in the industry are high-pressure mercury lamps and metal halide lamps, and both have the highest efficiency in the range of 200 to 300 nm and 300 to 400 nm, respectively. Therefore, colorless UV curable inks are commonly used as high pressure mercury lamps, while colored UV curable inks are commonly used as metal halide lamps.

The fundamental feature of UV light-curable inks is different from other types of inks in that the ink layer is cured and formed into a film that is irradiated with strong ultraviolet light. The film-forming substance is initiated by a photoinitiator and a rapid polymerization reaction takes place within several seconds to several tens of seconds. Completed. Without exposure to strong UV light, even when heated, the ink will remain in a viscous state for a long time and will not cure. The main advantages of UV light-curable inks are:
(1) It can make the thicker ink layer cured once, and the thickness can reach 100-150um..
(2) Short curing time, less energy consumption, saving printing space and space, and high production efficiency.
(3) No organic solvent, almost 100% cured film, no organic solvent volatilization, reducing environmental pollution.
(4) Suitable for printing on substrates with large heat capacity.
(5) Exquisite prints, good quality, high grade, cured ink film heat resistance, solvent resistance and scratch resistance are all good.