Pigment plays a role of coloring agent in ink, and it directly affects some of the characteristics of ink. Pigment is a highly dispersed powder that is colored, black or white and insoluble in water and organic solvents. According to its source and chemical composition, it can be divided into two categories: organic pigments and inorganic pigments.
(1) Inorganic pigments are metal oxides of colored metals or some insoluble metal salts. Inorganic pigments can be divided into natural inorganic pigments and synthetic inorganic pigments, and natural inorganic pigments are mineral pigments.
(2) Organic pigments are colored organic compounds, which can also be divided into natural and synthetic categories. Synthetic organic pigments are commonly used now. They have a wide range of colors and better performance than inorganic pigments.
Dyes are organic compounds that are water-soluble and sometimes dissolve in organic solvents. From some dyes, insoluble colored precipitates can be prepared, called lake pigments, which are used to make printing inks.
The requirements for pigments used in printing inks are quite high, especially for color, dispersion, lightfastness, transparency, etc. The color of color pigments should be close to the spectral color. The saturation should be as high as possible. The transparency of the pigments used in primary color ink should be high. All pigments should not only have water resistance but also combine quickly and evenly with the connecting material. The pigment should not have a too strong oil absorption capacity, and it is best to have properties such as alkali resistance, acid resistance, alcohol resistance, and heat resistance.
Connecting material is the main component of ink. It plays a role in dispersing pigments, giving ink appropriate viscosity, fluidity, and transfer performance, and solidifying pigments on the surface of printed matter after printing by film formation. Connecting material is commonly known as ink varnish.
Connecting material can be made from various substances, such as various dry vegetable oils, which can be used to make ink varnish. Mineral oil can also be used to make ink varnish. Solvents and water, as well as various synthetic resins, can be used to make ink varnish.
Rheological properties, viscosity, neutrality, acid value, color, water resistance, and printing performance of ink mainly depend on the connecting material. Using different connecting materials for the same pigment can produce different types of ink. Using different pigments with the same connecting material still produces the same type of ink, because it cannot change the fundamental properties of ink. Therefore, the quality of ink, apart from being related to pigments, mainly depends on the connecting material.
The filler is a white, transparent, translucent, or opaque powdery substance. It mainly plays a filling role and fills part of the pigment. By using some fillers appropriately, the amount of pigment can be reduced, the cost can be reduced, the properties of ink can be adjusted, such as its viscosity and flowability, and the flexibility of formula design can be improved.
Additives are materials added to improve the performance of ink during ink production and printing use. Ink formulated based on basic composition still cannot meet certain requirements in some aspects, or it may be different from ink due to changes in conditions.