Complex Inorganic Color Pigments: An Overview

2 сентября, 2015

Pokraskin

James White

An important family of high performance pigments is termed complex inorganic color pigments, or CICPs. Chemically, these pigments are synthetic crystalline metal oxides that have structures identical to those of naturally occurring minerals. They are called complex because they contain two or more different metals [1]. Complexity provides a range of metal combinations and in practice gives a wide range of colors for this class of pigments.

CICPs are used when outstanding color stability is required. Resistant to attack and dissolution by chemical agents and solvents, they do not bleed or migrate in application. They have heat stabilities hundreds of degrees higher than organic pigments, and are not discolored by exposure to ultraviolet (UV) light. The fact that these pigments absorb UV light without decomposition makes them good

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Ті

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La’

Та

ІГ

Ac*

104

10b

106

107

108

109

110

111

112

114

116

118

100

101

102

103

Figure 5.1 Elements commonly found in elements are colorless and are present to

CICPs. Light shaded elements are those balance charge and to modify color hues.

responsible for the primary color. Dark shaded

UV absorbers and opacifiers in their own right. They are the most stable and durable type of colorants commercially available — truly high performance products.

The elements typically found in CICPs are listed in Figure 5.1. Of these metal ions, only seven, all transition metals, are responsible for producing color [2]. Other metal ions in the pigments are colorless, and are added as modifiers to balance the charge of the crystal lattice, or to slightly modify the shade that the coloring ions produce.

Transition metal compounds are generally quite colorful, and CICPs are no exception. Color in CICPs is generated by electronic d-d transitions on the coloring metal ions in the crystal lattice, or from metal-to-conduction band transitions within the solids. These metal-based electronic transitions are spectroscopically unfavorable, resulting in relatively poor light absorption [3]. This means that CICPs have relatively weak coloring power when compared to other pigments. However, metal oxides are very stable entities and their color is very durable.

5.2