Areas of Application for Organic Pigments

The considerable increase in demand for colored pigments over the last three decades is in response to a number of external factors, primarily of a psychological nature. Advertising effectiveness and product promotion have become increasingly dependent on the public attention value of colored materials. On the other hand, both industry and the private sector show an ever increasing tendency to color products for identification and differentiation purposes. 

Organic pigments are used to color a variety of media. It is useful to distinguish between three primary fields of application the coatings and paints industry, the printing inks industry, and the plastics and fibers industry. Besides, organic pigments are used for special purposes, for instance in office materials and in the mass coloration of paper. 

It is useful in this context to focus on the performance of entire pigmented systems rather than to reflect upon the properties of individual components. The properties of a pigment powder, for instance, bear very little resemblance to its ultimate property in use. 

As an example, a given pigment, incorporated in one medium, may match grade 8 on the Blue Scale for lightfastness, which is an excellent value while a change of application medium may render the same pigment sensitive enough to reach only 

The technical requirements for pigments are subject to constant change because of the development and introduction of new vehicle systems fostered by the proliferation of materials to be colored. The recurring necessity to replace traditional pigments that are not usable with the newer vehicle systems is a permanent incentive for the development of new products. 

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Typically the chromophores used are pH sensitive, i.e. acidochromic or ionochromic (see section 1.4), and the medium is one whose pH varies with temperature. A variety of pH sensitive chromophores are known that are readily synthesised and can be modified to provide a wide range of shades. Application of these pH sensitive dyes in pressure and thermally sensitive papers for digital printing, e.g. fax papers, where the whole object is for the process to be irreversible, will be covered under ionochromism. The main area of application for reversible indirect thermochromic materials is as thermochromic organic pigments, as will be described below (section 1.3.4.1). 

Figures 32 and 33 show how many different areas of application there are for inorganic [30] and organic pigments.

The initial objective of this series of books has been to establish a coherent body of explanatory information on the principles and application technology of relevance for students preparing to take the Associateship examinations of the Society. This particular book has been directed specifically to the subject areas covered by Section A of Paper B the organic chemistry and application of dyes and pigments and of the auxiliaries used with them in textile coloration processes. However, many qualified chemists and colourists interested in the properties of colorants and their auxiliaries have found the First Edition useful as a work of reference. For several reasons it has been convenient to divide the material into two separate volumes 1. Colorants, 2. Auxiliaries. Although fluorescent brighteners share some features in common with colorants, they have been treated as auxiliary products in this book. 

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