Enhancement of Photosensitivity and Its Mechanism in an Extrinsic-Photocarrier-Generation-Type Organic Photoreceptor

UMEDA Minoru

doi:10.1246/nikkashi.1997.799

Enhancement of photosensitivity in a laser-beam sensitive layered photoreceptor consisting of a triphenylamine trisazo pigment has been performed. We focused an investigation on increasing a number of electron transfer sites for the extrinsic photocarrier generation between a carrier generation material (CGM) and a carrier transport material (CTM). To increase the number of CGMs at the surface of the CGM particle, we designed to control the particle size of the trisazo pigment for the CGM. As a result, quantum efficiency of a layered photoreceptor, of which carrier generation layer (CGL) was formed using the CGM dispersion ball-milled at 40°Cfor 258 hours, was proven to be 2.1 times larger than that ball-milled at room temperature. The magnitude of quantum efficiency was 0.8 at 3×10⁷Vm^-1. This value is equal to that using titanyl phthalocyanine, which currently exhibits the highest ph otosensitivity for a laser-diode beam. X-ray diffraction, absorption spectrum, electroabsorption spectrum and TEM observations of the high-sensitive trisazo pigment revealed that the secondary particle has a large vacant space which originates in a randomness of the primary particle size. In the layered photoreceptor, CTM penetrates not only into the CGL but also into such secondary particle after an overcoating of the carrier transport layer. This results in an increased density of photocarrier generation site in the CGL. Consequently, the layered photoreceptor using the trisazo pigment has achieved the highest photosensitivity resulting from an increase in number of the extrinsic electron transfer site.

Enhancement of Photosensitivity and Its Mechanism in an Extrinsic-Photocarrier-Generation-Type Organic Photoreceptor

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