The performance of substrates, printing inks and other materials that match printing conditions and are suitable for printing operations is called printability. The printability of the ink refers to the performance of the ink that matches the printing conditions and is suitable for printing operations, mainly including viscosity, adhesion, thixotropy, dryness, etc.
Viscosity:
The internal friction characteristics of the ink shown in the flow is called the viscosity of the ink, and the physical quantity that measures the viscosity of the ink is called the viscosity of the ink. The faster the speed of the printing press, the greater the fluidity of the ink is required, the smaller the viscosity. The viscosity of the ink can be adjusted by mixing ink oil or ink thinner.
Adhesion:
When the ink is transferred from the ink hopper to the ink roller, plate, substrate (or blanket) surface, the ink film first splits and then transfers, and the ability of the ink film to prevent the ink film from breaking in this dynamic process is called the adhesive property of the ink. In the printing process, if the adhesive property of the ink and the performance of the substrate and the printing conditions do not match, the paper will drop powder and hair, the ink overprint is poor, and the printing plate is dirty. The adhesive properties of the ink can be adjusted with adhesives or ZY ink additives.
thixotropy
At a certain temperature, the fluidity of the ink is improved and the viscosity decreases after stirring or applying mechanical external force. After standing, the fluidity becomes bad and the viscosity rises, which is called the thixotropy of the ink. In the printing process, if the thixotropy of the ink is poor, it will occur under the ink is not smooth, the ink is not uniform, and the dot is seriously expanded. In order to prevent the occurrence of the above faults, it is necessary to use an ink shovel to stir the ink in the ink fountain or install an ink stirrer in the ink fountain to stir the ink from time to time.
Dry:
There are three main forms of ink drying
Osmotic drying: The bonding material in the ink, some of it permeates into the substrate, and the other part is fixed on the surface of the substrate with the pigment and dried. The non-thermosetting rotary inks used in high-speed web printing presses are generally based on osmotic drying, mainly printing newspapers and periodicals.
Oxidative polymerization drying: the binder in the ink polymerizes under the action of oxygen in the air, forming a film on the surface of the substrate and drying. Offset printing bright resin ink, bright color, good luster, mainly oxidation polymerization drying, used for printing high-grade fine offset printing products.
Volatilization drying: Some of the binder in the ink evaporates into the air, and the remaining binder and pigment are fixed on the surface of the substrate and dry. Intaglio printing ink is made of volatile solvent as a binder, and the binder used is benzene and xylene which are harmful to human body. Volatile inks are particularly suitable for printing non-absorbent film materials, such as plastic films, metal foils, etc.
In addition, the drying of ink also has ultraviolet, infrared, thermal curing and other forms. The drying of many inks is often a combination of two drying forms to complete the drying of ink film.
In the printing process of ink manufacturers, if the drying of ink is poor, it will cause the back of the paper to rub, sticky pages, dull ink film, ink crystallization and other printing faults. In order to speed up the drying speed of the ink, a drier can be added to the ink. Commonly used drying agents are cobalt drying oil, manganese drying oil, lead drying oil and so on. In order to reduce the drying speed of the ink, a drying inhibitor can be added to the ink.
