Pigment Blue 15:3

Pigment Blue 15:3 (molecular formula: C32H16CuN8) also called copper phthalocyanine, is a blue, odorless solid, a chemical complex compound between copper and phthalocyanine, which is in the form of a powder or metallic shiny needles. Pigment blue 15:3 is the most important blue pigment in industry. It is used in many ways for coatings, plastics and printing inks. Furthermore, it has been used as a tattoo dye.

In principle, copper phthalocyanine pigments have high temperature resistance and excellent fastness properties against light, weather and chemical influences.

Preparation: Copper phthalocyanine is technically prepared by reacting phthalic anhydride with copper(I) chloride and urea and ammonium heptamolybdate as catalyst under heating. An alternative process is the thermal reaction of phthalic acid dinitrile with metallic copper or copper salts in the presence of ammonia or urea. The substance counts it among the chemical substances produced in large quantities ("High Production Volume Chemical", HPVC).

Properties: Copper phthalocyanine exists in eleven modifications, three of which are of economic importance. These are the thermally less stable red-tinted α-form (C.I. Pigment Blue 15:0, 15:1 and 15:2), the stable green-tinted β-form (C.I. Pigment Blue 15:3 and 15:4), and the strongly red-tinted ε-form (C.I. Pigment Blue 15:6).

The predominant part of copper phthalocyanine is used as a high-fastness pigment. It is the most common pigment in terms of quantity for the blue color range in paints and coatings, plastics and printing inks. For example, the blue recycling garbage cans for paper waste are colored with this pigment. Various specially quality-controlled brands are approved as colorants for consumer products, for use in care products, stamping inks, cosmetics such as toothpaste (Regulation (EU) 2020/2081 and for foodstuffs.

Pigment Blue 15:3 was used on a large scale as a tattoo ink mainly for color blends. In 2020, the European Union planned to ban the pigments Pigment Blue 15:3 and "Pigment Green 7" for tattoo inks because of health risks, as their documentation did not meet the requirements of the EU chemicals regulation REACH (Erk P et al. (2003). The ban was finally imposed on January 4, 2023 (EU Commission (2021).

Copper phthalocyanine is one of the most commonly used donor materials in organic solar cells, where it is also responsible for much of the absorption due to its blue color. Thus, the first organic solar cell was already based on copper phthalocyanine (Yu-Sheng Hsiao et al. (2008).

The reversibly water-soluble CuPc derivative alcian blue is used in biochemistry and histopathology for staining and labeling.

1. Erk P et al. (2003) Phthalocyanine dyes and pigments in Porphyrin Handbook 19: 105-149.
2. EU Commission (2021) Possible end to tattoo dyes blue 15 and green 7. Retrieved May 13, 2021.
3. Commission Regulation (EU) 2020/2081 of 14 December 2020 amending Annex XVII to Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) as regards substances in tattoo inks or permanent make-up.
4. Yu-Sheng Hsiao et al. (2008) Morphological control of CuPc and its application in organic solar cells. In: Nanotechnology 19: 415603
5. Tang CW (1985) Twolayer organic photovoltaic cell. In: Appl. Phys. Lett. vol. 48:183-185.