Photoconductive phthalocyanine compounds

Photoconductive phthalocyanine compounds are usually prepared by the photoreceptor makers and their subsidiaries, and are not commercially available. For titanyl phthalocyanine, only crude material, which requires appropriate treatment to fine tune the desirable photosensitivity, is available from Sanyo Color Works, Orient Chemicals, and Toyo Ink Manufacturing. Such products may also cost several thousand dollars a kilogram. 

The semiconductor selenium is an excellent photoconductor however, its photoresponsiveness decreases sharply at wavelengths over 550 nm, which has motivated research on organic photoconductive materials.1550,1551 Many different organic compounds display photoconductive behaviour, such as phthalocyanines (596 M = metal) or squaraines (597) (Figure 6.33) today more than 90% of xerographic photoreceptors are composed of organic photoconductors. 

One restriction however has to be made octacyanosubstituted phthalocyanines most probably always contain a certain amount of sheet polymerized material, which might contribute to the observed photoconductivity [199b]. Tetracyano-phthalocyaninatometal complexes are unable to form sheet polymers and are therefore presently under investigation [203]. The central metal atom also influences the photoconductivities whereby generally larger G and values were observed for the copper compounds. 

---