Titanyl phthalocyanines

Most phthalocyanines show inferior dark decay to azo pigments, an exception being the titanyl phthalocyanines, where in the best cases, e.g. the a- and Y- forms, they show comparable dark decay coupled with superior photosensitivity. A comparison of the sensitivity of azo pigments and selected polymorphs of phthalocyanines is shown graphically in Figure 4.12. 

Titanyl phthalocyanines are used as the CGMs in commercial organic photoconductors, e.g. in the engines from Canon, Xerox, Konica and other OEMs. 

Brumbach M, Placencia D, Armstrong NR (2008) Titanyl phthalocyanine/Cgo heterojunctions band-edge offsets and photovoltaic device performance. J Phys Chem C 112 3142... 

Placencia D, Wang WN, Shallcross RC, Nebesny KW, Brumbach M, Armstrong NR (2009) Organic photovoltaic cells based on solvent-annealed, textured titanyl phthalocyanine/Ceo heterojunctions. Adv Fund Mater 19 1913... 

Titanyl phthalocyanine (TiOPc) is probably the phthalocyanine most often utilized in eommercial eleetrophotographic photoreeeptors. In a study of the wavelength dependence of photoconductivity in single- and dual-layer photoreceptors it was concluded that the pigment was p-type and that generation occurred in the pigment bulk and was unaffected by the presence of a hole-transport molecule electron donor [34n]. The pigment form was not identified in this study. 

Chlorotitanium(III) phthalocyanine is formed by the reaction of titanium trichloride with dilithium phthalocyanine in boiling quinoline in the absence of air. This d1 complex has a magnetic moment of 1.79 B.M. (see Section VI,D) 341). It is stable to air oxidation in the solid state but is oxidized in solution. The oxidation product is oxytitanium(IV) phthalocyanine (titanyl phthalocyanine). This latter diamagnetic complex may also be prepared by the reaction of titanium tetrachloride dipyridinate and phthalonitrile at 270°C followed by sublimation at 400°C/10 6 mm 213). Titanium tetrachloride reacts with phthalonitrile to yield, after recrystallization from sulfuric acid, dihydroxytitanium(IV) phthalocyanine 820). 

Tsuzuki, T., Shirota, Y, Rostalski, J., and Meissner, D. 2000. The effect of fullerene doping on photoelectric conversion using titanyl phthalocyanine and a perylene pigment. Solar Energy Materials and Solar Cells 61 (l) l-8. 

Klofta, T.J., J. Danziger, P.A. Lee, J. Pankow, K.W. Nebesny, and N.R. Armstrong (1987). Photoelectrochemical and spectroscopic characterization of thin films of titanyl phthalocyanine Comparisons with vanadyl phthalocyanine. J. Phys. Chem. 91,5646-5651. 

Liu CJ, Hsieh JC, Ju YH (1996) Response characteristics of lead phthalocyanine gas sensor effect of operating temperature and deposition annealing. J Vac Sci Technol A 14 753-756 Liu CJ, Peng CH, Ju YH, Hsieh JC (1998) Titanyl phthalocyanine gas sensor for NO detection. Sens Actuators B... 

Quinacridone family color range 300 suggested stabilization mechanism 300 Y-form titanyl phthalocyanine 263... 

For several pigments, the origins of crystallochromy could be derived from accurate structure data in combination with spectroscopic investigations. Primarily, the distortion of the molecule due to packing effects may change the absorption spectrum of the solid. Molecular distortions have been identified to be the reason for the solid state absorption properties in various phthalocyanines, especially in titanyl phthalocyanine ... 

Of these 70 million OPC photoreceptors, 45 million were by Canon, 10 million by Mitsubishi Chemicals, 4 million by Fuji Electric, 3 million each by Yamanashi Electronics and Dainippon Ink and Chemicals, and 5 million by others. The largest fraction of these OPC photoreceptors were based upon titanyl phthalocyanines. 

Although titanyl phthalocyanine is known to have two crystal forms (alpha and beta), in the course of OPC investigations over the past fifteen years, many new crystal modifications were discovered, exhibiting different patterns of X-ray diffraction spectra. 

The shape of the titanyl phthalocyanine molecule is not planar but pyramidal, where the titanium atom is out of the plane of the phthalocyanine macrocycle and the symmetry of the molecule is reduced from D4h to C4h. Accordingly, titanyl phthalocyanines can have more crystal modifications than such planar molecules as copper phthalocyanine or metal-free phthalocyanine. General procedures used in the development of new crystal modifications involve solvent treatment of amorphous titanyl phthalocyanines obtained by acid pasting or milling procedures. 

Among a variety of titanyl phthalocyanines, the Y-form, developed by Konica, is said to be the most sensitive . The quantum efficiency of Y-form titanyl phthalocyanine for photo carrier generation is reported to be almost 1. Y-form titanyl phthalocyanine is also reported to incorporate one water molecule to one titanyl phthalocyanine molecule in the crystal. The location of these water molecules in the crystal is as yet not clear, but they are considered to play an important role in the high sensitivity of the Y-form l On the other hand, the incorporated water molecules are reversibly desorbed, and the sensitivity changes according to the quantity of water in the crystals. Because of such instability in sensitivity, photoreceptors with the Y-form of titanyl phthalocyanine have not yet been commercialized. 

During an investigation to improve the stability of the sensitivity of Y-form titanyl phthaloqfanine, 1+1 adduct compounds of titanyl phthalocyanine and gem-diols were found. Their photosensitivity is comparable to that of the Y-form. ... 

Recently, Fuji Xerox armounced a new series of printers, with hydroxygallium phthalocyanine as the charge generating material. Hydroxygallium phthalocyanine is reported to have several crystal forms, with the V form as the most photosensitive. The photosensitivity of the V form hydroxygallium phthalocyanine is comparable to that of Y form titanyl phthalocyanine, but is independent of the humidity l... 

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. 

Figure 17-6 Transient decay curve of single-layer photoreceptors with X-form metal-free phthalocyanine and Y-form titanyl phthalocyanine.

Generally, pi-pi interaction between stacked molecules is considered to cause the absorption of phthalocyanine compounds in the near infrared region. Mizuguchi et al. have investigated the origin of the absorption of phthalocyanine compounds in the infrared region, and proposed a different mode of interpretation. In addition to pi-pi interaction, they propose consideration of the molecular distortion for titanyl phthalocyanines and molecular distortion and exdton coupling for beta-form metal-free phthalocyanine . 

Evaporated films of chlorogallium phthalocyanine and fluoroaluminum phthalocyanine have been reported to have high third order nonlinear susceptibility . Since that time, phthalocyanine compounds have been extensively investigated in the form of evaporated films, Langmuir-Blodgett films, and spin-coated films. Evaporated films of vanadyl phthalocyanine and titanyl phthalocyanine were also found to have a higher third order nonlinear susceptibility . 

Dainippon Ink and Chemicals markets its photoconductive X-form metal-free phthalocyanines as the Fastogen Blue 8120 series. Products include materials for printers and material for plate making. X-form metal-free phthalocyanine is less sensitive than titanyl phthalocyanine, but is considerably lower in price. The prices are only 2000 to 5000 a kilogram. Figure 17.6 shows a comparison of the transient decay curve of surface potential of single layer photoreceptors with the X-form metal-free phthalocyanine and the Y-form titanyl phthalocyanine. The... 

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