Analysis of Transfer and Transfer of Offset Printing Inks

The printing process is the process of ink transfer and transfer. How can the ink be properly transferred according to the production process? What are the factors that affect the ink transfer effect? How to match between them?

First, the transfer of offset printing ink

1. Transfer from ink fountain to ink fountain roller. The ink in the ink fountain is always in good contact with the ink fountain roller so that the ink can be evenly conveyed by the ink fountain. This mainly depends on the rheological properties of the ink: thixotropic can not be too large, the yield value can not be too high, the viscosity can not be too small, the wire head can not be too short, rheology is better and so on. If the ink in the ink fountain has a high yield value and a low viscosity, the ink is poor in ink, because it lacks the necessary adhesion to the ink fountain roller, so the ink fountain must be raked in order to ensure good contact between the ink and the ink fountain roller. Otherwise, the front and back of the printed product will be faded due to the ink and the ink fountain roller gradually disengaging. Also note that the ink reserves in ink fountains must be kept within a certain range, and strive to uniform ink.

2. Transfer from ink fountain roller to ink roller. Since the ink fountain roller of the offset printing press rotates intermittently, the ink output from the ink fountain roller is always an arc-shaped strip-like ink strip, and the width of the ink strip can be adjusted. In the printing process, the thin ink layer and the wide ink stick have better transfer modes than the thick ink layer and the narrow ink stick, and the ink can be evenly beaten as quickly as possible. After the ink is transferred from the ink fountain roller to the ink roller, it can be pressed, sheared, stretched, and fractured in several seconds by several uniform ink rollers. Whether the ink can be quickly evened or not depends on the uniform ink roller. Whether the number of roots and diameters of each other is a prime number, whether the ink transfer route is reasonable, whether the ink is balanced, and whether the ink roller surface has good adsorption power. Offset printing ink inking devices, mostly long ink devices, use more than ten ink rollers to complete ink transfer. In addition, the radial runout of the ink roller and the axial movement of the ink roller will cause the ink to be subjected to a certain radial and axial shear stress. In the transfer process, the ink is squeezed by the ink roller to release a lot of heat, so that the temperature of the ink rises. For example, when the temperature of the shop is 25, after the machine runs continuously for half an hour, the ink temperature on the ink roller will reach 40-50.
3, from the ink roller to the printing plate transfer. In the offset printing process, the printing plate is first wetted by a water roller, and then the printing roller is in full contact with the printing roller to supply ink to the graphic portion of the printing plate. When the general printing plate water film is 1mm, it can block the ink on the ink roller in the blank part. If the water film in the blank part of the printing plate is too thin, it will be dirty and the water film will be too thick, and the ink emulsification will be excessive. Therefore, water supply over the General Assembly damages the ink transfer effect of the ink roller to the printing plate graphic portion, so it is necessary to control the ink and ink balance.

Second, the transfer of offset printing ink 1, from the printing plate to the blanket conversion. Since offset printing is indirect printing, the ink in the graphic part of the plate must pass through the blanket to be transferred to the surface of the substrate. Therefore, the surface of the blanket must have good oleophilic and hydrophobic properties, and the blanket and printing plate must be reasonably balanced. With uniform pressure, when the printing plate graphic part is transferred to the blanket, part of the ink in the printing plate graphic part must also be preserved, so that the protective effect cannot be underestimated and is indispensable.
2, the transfer of blanket material. When the imprinted ink layer is transferred from the blanket to the printed product, the pressure between the blanket and the substrate should be uniform. The ink-receiving properties of the substrate itself should also be good, and should have sufficient strength, the surface should be smooth, the thickness should be even to print a good product. The transfer of the imprinted ink to the surface of the substrate can generally be divided into three steps: the imprinted ink layer and the substrate are in contact with the initial stage of transfer. The imprinted ink layer is subjected to a squeezing force. Under the pressure of the printing plate, the ink is pressed into the fluctuating pores on the surface of the substrate. - Cavitation and breakage of the imprinted ink layer. At this time, the ink layer undergoes tensile fracture due to the occurrence of centrifugal force and vacuole phenomenon, but due to the ink has a good wetting property on the surface of the substrate, a part of the ink layer is transferred to the surface of the substrate. After the imprinted ink layer is divided into two, the imprinted ink transferred on the surface of the substrate is absorbed into the paper through the capillary pores. For a substrate with a smooth surface and little absorption, whether the imprinted ink layer can be adsorbed on the surface of the substrate is faster than the affinity of the surface of the substrate for the ink, and faster than the intermolecular function of the ink and the substrate. force.
3. Imprinting or retransfer of the imprinted ink layer on the substrate. Offset printing ink is an ink in which the oxidized polymeric conjunctiva is the main dry form. The drying process is roughly divided into two stages: fixing. The ink changes from a liquid to a semi-solid state and no longer transfers. It is also called the initial drying stage of the ink. - Dry conjunctiva. The physical and chemical changes occur in the binder in the semi-solid ink, allowing the ink to completely dry and conjunctiva. This is the phase in which the ink is completely dried. However, in the imprinted ink transferred on the surface of the substrate, defects such as blemishes, powdering, strike-through, and crystallization may occur during the printing process due to various reasons. Therefore, it is necessary to adequately estimate the possible faults in advance and take necessary measures. Preventive measures.

Elastic transparent transfer ink

The elastic transparent transfer ink is a high elasticity transfer ink developed by Shenyang Lexi Company based on the original transparent transfer ink. It is not only suitable for ordinary fabrics such as cotton and hemp, but also suitable for high elasticity fabrics such as swimwear. The ink has the characteristics of fast drying speed, easy use, excellent printability, and strong recovery ability. The most remarkable feature of the ink is that after the ink layer is dried and cured, the stretch elasticity is obviously improved, along with the fabric's The amount of tensile deformation increases. Compared with ordinary transparent transfer inks, the elastic transparent ink has a smooth surface, a high gloss, and a bright color after printing. The ink does not contain harmful components to the human body and can be touched after the transfer.

Reprinted from: International Screen Printing