Pigment for Inks - Pigment ink Uses in 2024

Colorants are divided into pigments and dyes. Pigment inks are dispersed in the form of granular suspension in ink. Dye inks are dispersed in the molecular form in ink. Pigment inks are usually attached on surfaces through binders. Dye inks can make objects colored inside. Colorants largely determines the hue, coloring power, covering power, fineness and density of ink.

Pigment inks are divided into inorganic pigments and organic pigments. Inorganic pigments are composed of simple elements, metal oxides, inorganic salts and their complexes. They feature long history, lower price and many varieties. They also have high covering power and excellent resistance. Organic pigments are mostly unsaturated organic matters. They are usually derivatives of heterocyclic benzene, naphthalene and other aromatic compounds. They have bright color, strong coloring power, high light and heat resistance, chemical stability, etc.

Dye inks have high solubility. They can be dissolved in water, oil or other organic solvents. Dyes can be divided into 11 types according to their properties and applications. In terms of the pH, dyes are divided into acid dyes, alkaline dyes and neutral dyes. By the dyeing method, dyes are divided into direct dyes, disperse dyes, reactive dyes, sulfide dyes, ice dyes, VAT dyes and cationic dyes. There are also dedicated non-toxic food dyes.

Common pigments for ink:

1. 1. Yellow mono pigments, commonly known as Hansa Yellow pigments. They are also called fast yellow pigment because of their outstanding fastness to light.
2. 2. Mono azo red pigments: naphthol AS series. They feature simple synthesis, bright color, and good fastness, water resistance and alkali resistance. They are especially suitable for water-based ink and solvent-based ink. They are more expensive than azo lake pigments.
3. Bisazo yellow pigments. They feature high coloring power, equivalent to 3 times that of fast yellow pigment. They have good transparency, solvent resistance and printing performance. They are mainly for production of yellow ink among four color inks.
4. Condensation type azo pigments, maintaining the color of azo pigments (generally slightly darker than monoazo pigments). They have higher resistance to solvents, heat and migration.
5. Benzimidazolone pigments. They have excellent resistance to high temperature (200-300°C), migration and solvent. DAHE ink contains pigments from Japan. They have stable performance and quality. More importantly, DAHE Ink has very strict environmental requirements for pigments. It attaches great importance to the environmental quality of ink.

Color shifting inks are special inks. They have different colors in different environments. They are suitable for secure printing, watermarking, special signs, etc.

Methods/Steps

1. Pigment selection: pigments are critical for color shifting inks. In general, heat sensitive pigments, light sensitive pigments or acid and alkali sensitive pigments are suitable for color shifting inks. Different pigments have different response mechanisms, It is important to choose pigments according to needs.
2. Solvent selection: solvents are for mixing of pigments and other additives. Different solvents are suitable for different pigments. It is necessary to choose solvents according to the response mechanisms and application conditions of pigments.
3. Diluent adding: Diluent can adjust the viscosity of ink, improve the fluidity of ink and thus facilitate printing. It is necessary to choose diluent according to pigments and application conditions.
4. Additive adding: additives can improve the adhesion, scratch resistance and light resistance of ink, such as hydrophilic agents, leveling agents,tackifiers, etc.
5. Ink preparation: color shifting inks are made by mixing pigments, solvents, diluents and additives according to appropriate proportions.

Note

It is critical to choose pigments. Different pigments have different response mechanisms. It is necessary to choose pigments according to needs.

Inkjet printing has certain requirements for the nanoparticle size. In practical applications, ink in printers is subject to fine treatment, to ensure that the pigment particle size meets the requirements. Special methods are suitable for preparation of nanoparticle pigments, such as the sol-gel method and vapor deposition method. These methods can control the particle size of pigments at a nanoscale level, to meet the requirements of inkjet printing.

The pigment particle size used to manufacture pigment ink is divided into nano-scale and micron-scale, where the average nano-scale particle size (LD50) is in the range of 40-125 nanometers, and the maximum particle size (LD90) shall not exceed 180 nanometers, and the micron-scale particle size is in the range of 0.125-0.300 microns.

The smaller the nanoparticle size, the clearer the printed image, and the better the color performance. Ink of smaller particle size flow faster in the inkjet head, thus accelerating spraying onto paper. Therefore, the moderate particle size of pigments can increase the printing speed while ensuring the image quality.

Electron beam curing ink (eb ink) can quickly change from liquid to solid in the irradiation of a high-energy electron beam. It is completely dried in a few milliseconds in the radiation of the electron beam. It has good printing gloss, film feeling and friction resistance. But the ink and corresponding radiation-drying device are expensive. Promotion of the ink is still difficult. But the ink is promising as it can save the drying time and ensure the product quality without causing environmental pollution.

1. Electron beam curing ink (eb ink): electron beam curing is common for printing in the food and beverage packaging industry, namely, offset printing. The eb ink is adaptive to the development of high-speed and multi-color one-time printing in the printing industry. As electron beam curing ink can save energy and contains no solvents, it will not cause pollution to the environment and packages. It has the advantages of short curing time, high processing speed, large output, small dot expansion rate, good print brightness, and resistance to wear and chemical erosion. This technology has been rapidly promoted and applied. It is especially promising in the field of food packaging.
2. Digital printing ink: the digital printing technology has also been applied in the food package printing industry. It can achieve high image resolution and perfectly reproduce image details.

The environmental friendliness of pigment inks involves the selection of raw materials. The conventional ink production often requires organic solvents. Among them, volatile organic compounds (VOCS) may cause air pollution. According to the environmental protection requirements, ink production enterprises should use water-based or curing inks to reduce the consumption of organic solvents. Water-based ink is a kind of ink with water as the medium. It is harmless, non-toxic and easy to clean, greatly reducing the pollution to the environment. Curing ink changes into a film through light curing or thermal curing, to avoid the release of organic solvents.