Ink fineness affects image transfer and clarity

First, the proportion

The ratio of the weight (g) of a 1 cm 3 ink to its volume at 20°C is called the specific gravity of the ink.

The specific gravity of the ink is a physical quantity for estimating the amount of ink and evaluating its process characteristics. At present, the specific gravity of a commercially available offset ink is generally about 1 to 3 g/cm3.

In the adjustment process, the proportion of the selected ink or auxiliary material should generally be considered. For example, when the ratio is large and the proportion is small, the delamination phenomenon is not only prone to occur, but also causes the floating color to appear on the surface with a small specific color. For example, when the same color ink is used for dispensing, the specific weight is smaller than the specific weight. In the printing process, the ink with a large specific gravity not only consumes a large amount of ink, but also easily accumulates on the ink roller, printing plate, and blanket, causing problems such as stacker rollers, stack plates, blankets, or stencils. This is especially true in high-speed printing conditions when the uniformity of the ink layer transfer is disrupted.

Second, fineness

Fineness refers to the maximum particle size of pigments, fillers, etc. in the ink, and the uniformity of distribution in the binder.

The fineness of the ink, to some extent, the liquidity and color intensity of the ink, has a great influence on the printing process and printing quality.

In the printing process, the fineness of the ink affects the transfer and sharpness of the image because it maintains a certain relationship with the dot area on the printing plate (as listed in Table B-1). If the ratio is relatively close, defects such as network deficiency, enlargement, poor spotting, and lack of cleanliness are prone to occur. The fineness of the ink is fine, the dots of the blot are full and strong, and the coloring power is also strong. If it is too thick, it is not only easy to cause destruction, stencil printing, stacking of ink (heap version, heap blanket), but also is not conducive to the integrity of small outlets.

At present, the fineness of domestic offset printing ink is generally 15 to 20 μm. Most of the products in the factory are below 15 μm, but the fineness of various accessories is generally 20 to 35 μm.

Third, transparency

Transparency refers to the extent to which the ink film covers the printing material or overlaps the surface of another ink layer, and it can be visualized by the covering. It is an indicator of the size of the hiding power of the ink film on the covered surface. It is usually called For the hiding power of ink.

Ink transparency. For the three- or four-color printing color sequence design and printed color effects, it is of great significance. In three- or four-color printing, the transparency of the ink is the key to achieving a color reduction effect. The use of high transparency inks, in addition to considering the original and process factors, the color sequence design is more flexible. In some multi-color overprinting, if it is necessary to cover the background color, it is required to use ink with low transparency so as to achieve the purpose of not revealing the background color.

The transparency of ink is generally classified into three types: transparent (non-hidden), translucent (half-masked), and opaque (covered).