What are organic pigments？

Organic pigments are important colorants, ubiquitous in our lives. This article will explain what organic pigments are by dividing them into six key points:

1. Definition of Organic Pigments
2. Characteristics of Organic Pigments
3. Color Properties
4. Classification of Organic Pigments
5. Applications of Organic Pigments
6. Development History and Trends

Definition of Organic Pigments

Organic pigments are a class of colorants made from organic compounds that possess a range of pigmentary properties. Unlike dyes, organic pigments lack affinity for the objects they are intended to color. They require adhesives or film-forming substances to adhere to surfaces or be incorporated into objects to impart color.

Organic pigments are insoluble in water or solvents. However, not all insoluble organic substances can be used as organic pigments. Organic pigments color objects by dispersing fine particles in the medium they are intended to color. Therefore, their performance depends not only on their chemical structure but also on the following factors:

· Pigment particle size and distribution

· Particle surface physical state

· Polarity and crystal form

· Compatibility with the medium

Many pigment manufacturers, while developing new structural varieties, are also dedicated to researching pigment surface properties. They aim to develop products with diverse properties, such as easy dispersion, high transparency, high tinting strength, and excellent flowability, to improve product quality.

Pigment properties include resistance to sunlight, water immersion, acid and alkali resistance, organic solvent resistance, heat resistance, crystal stability, dispersibility, and hiding power.

Characteristics of Organic Pigments

·Production Process: The intermediates, equipment, and synthesis processes required for their production are similar to those used in dye production, so they are often produced within the dye industry.

·Comparison with Inorganic Pigments:

· Advantages: They typically have high tinting strength, are easy to grind and disperse, are less prone to sedimentation, and have vibrant colors.

· Disadvantages: They typically have poor light, heat, and weather resistance.

· Applications: They are commonly used to color materials such as inks, coatings, rubber products, plastics, stationery, and building materials.

Color Properties of Organic Pigments

· Vivid colors and strong tinting strength

· Low density and non-toxicity

· However, some varieties are often not as light-resistant, heat-resistant, solvent-resistant, and migration-resistant as inorganic pigments.

The variety of colors is endless and colorful. Each color can be determined by three parameters:

(1) Hue: The characteristic that distinguishes colors from each other, which can distinguish red, yellow, green, blue, purple, etc.

(2) Lightness (brightness): The characteristic value that indicates the change in the lightness and darkness of the surface of an object

(3) Saturation (chroma): The characteristic value that indicates the intensity of the color on the surface of an object

The colors in nature are ever-changing, but the most basic are the three primary colors of red, yellow, and blue.

Classification of organic pigments

There are many varieties of organic pigments, and there are many classification methods:

• Classification by color spectrum Classification into yellow, orange, red, purple, brown, blue, green pigments, etc.

• Classification by function Classification into ordinary pigments, fluorescent pigments, pearlescent pigments, color-changing pigments, etc.
• Classification by application object Classification into pigments for coatings, pigments for inks, pigments for plastics and rubber, pigments for cosmetics, etc.
• Classification by molecular structure

Azo pigments: Pigments containing an azo group (-N=N-)

Phthalocyanine pigments: such as phthalocyanine blue and phthalocyanine green

Condensed polycyclic pigments

Other structural pigments

Note: Azo pigments and phthalocyanine pigments account for over 90% of all organic pigments and are primarily produced in Western Europe, the United States, and Japan.

Applications of Organic Pigments

Due to their excellent properties, organic pigments are widely used in numerous industries:

· Ink Industry: One of the largest application areas, particularly printing inks (offset, flexographic, and gravure), which require vibrant colors, high tinting strength, fine particles, and excellent dispersibility.

· Coatings Industry: Used in various paints and coatings, particularly automotive, industrial, and exterior paints, where weather and light resistance are critical.

· Plastics Industry: Used to color various plastics, pigments require excellent heat resistance (150°C-280°C), migration resistance, and good dispersibility.

· Textile Fiber: Through pre-slurry coloring, pigments are uniformly mixed into molten polymers and then spun to produce colored fibers.

· Cosmetic Applications: Applications in eye shadow, lipstick, and gel nail polish. Organic pigments offer a wide range of vibrant colors, including red, phthalocyanine blue, and phthalocyanine green. Organic pigments offer excellent tinting strength and color stability, enabling gel nail polish to achieve vibrant colors.

· Other fields: including rubber products, leather, papermaking, ceramics, food packaging, pharmaceutical packaging printing, children’s toys, stationery, etc.

Development history & development trends

The development of organic pigments has roughly gone through three stages:

(1) Early exploration (late 19th century-early 20th century): In 1856, William Perkin synthesized the first organic dye “aniline purple”, marking the beginning of the era of synthetic organic pigments

(2) Rapid development (1920s-1960s): The rise of the color printing industry promoted the development of traditional azo pigments and phthalocyanine pigments

(3) Modernization and diversification (1980s to present): The progress of basic disciplines has promoted the leap of organic pigment technology, and the invention of DPP pigments is a milestone

The future development of organic pigments is mainly reflected in:

· High performance: Developing pigments that can better withstand harsh environments (such as higher temperatures and stronger ultraviolet rays)

· Environmental protection and safety: Developing environmentally friendly organic pigments that are less toxic and do not contain heavy metals and harmful aromatic amines

New material development: For example, exploring organic-inorganic hybrid nanopigments derived from natural plants.

Summary

Organic pigments, as indispensable colorants in modern industry and life, come in a wide variety of types, with diverse properties and a wide range of applications. From everyday plastics and printed materials to demanding automotive coatings, engineering plastics, and cosmetics, they create vibrant colors.