What are the properties of printing inks?
The nature of the ink is very complex, different ink with different light resistance, heat resistance, uniformity, resistance, thixotropy, acid and alkali resistance, water resistance, plasticity, fluidity, viscosity, drying and adhesion etc.. Here are only the most closely related to printability, liquidity, adhesiveness, stickiness and dryness.
Drying refers to the ink in a variety of solvents out of ink or change, and make the ink fixation, drying characteristics. The drying of ink is no more than three ways: the ink binder is absorbed into the paper, absorbed by the paper, the solvent in the ink layer is volatilized, and the material is oxidized into the conjunctiva in the air. Therefore, when printing, the drying speed of the ink is determined by the consistency of the ink, the kind of solvent in the ink, the absorption properties of the paper and the conditions at the time of printing (including temperature, humidity, ventilation, etc.). Of course, add dry oil in ink, drying can be accelerated to a certain extent, but the dryness of the oil ink if you add too much, the surface of the ink quickly drying to form the closed state, the internal dry more slowly, the printing surface slightly squeezed friction will be dirty job. In particular, "eat" large amount of ink on the ground printing, dry oil use more caution.
Viscosity refers to the resistance of an ink when it is split by tension. The magnitude of the viscosity depends on its internal friction coefficient. Viscosity is closely related to adhesiveness. Generally, substances with large viscosity have great adhesiveness. But adhesion emphasizes on the amount of transfer in the instant of contact between the plate and the paper, while the stickiness emphasizes the ease of separation between the plate and the paper. Ink viscosity is too large or too small, are detrimental to printing. Excessive viscosity will cause hair loss and powder loss, which will lead to uneven ink transmission. And viscosity is too small, easy to cause ink emulsification, imprinting is not strong, printing luster is not high. Unlike adhesion, as the printing speed increases, the viscosity of the ink increases during printing.
Adhesion refers to the physical properties of an ink that can adhere to the material in contact with it. The adhesion of the ink depends first on the adhesion of the binder. Secondly, depending on the concentration of the pigment in the ink, the greater the adhesiveness of the bonding material to manufacture the ink, the greater the concentration of the pigment and the greater the adhesiveness. Ink on the printing plate or blanket adhesion and adhesion of the paper determines the relationship between the ink transfer rate, also affect the ink on the paper firmly fixed degree. The higher the printing speed, the worse the adhesion of the ink.
Flowability is the index of the flow (diffusion) of ink on printed paper. Liquidity is soft ink, small is hard ink. Obviously, the greater the ink consistency, the smaller the liquidity. Liquidity is also related to temperature, when the temperature is high, the liquidity is large, when the temperature is low, it is smaller. Ink flow too large or too small will have adverse effects on printing.
