This invention relates broadly to photoreceptors for electrophotography and more particularly to improved photoreceptors which are composed of amorphous silicon having a dielectric layer which increases the surface voltage in the dark while reducing residual voltage under illumination.
The photoreceptor utilizing hydrogenated amorphous silicon (a-Si:H) and a dielectric layer described above is an improvement over a photoreceptor described in my co-pending patent application Ser. No. 06/138,699, now U.S. Pat. No. 4,330,182 a continuation-in-part of U.S. Pat. No. 4,226,897 in which blocking layers were disclosed.
In the past, prior art devices described in U.S. Pat. No. 4,225,222 which issued Sept. 30, 1980, to Kempter described p-n junctions in amorphous silicon for electrophotography. Other amorphous photoreceptors were described by Mort et al in Photographic Science and Engineering, Vol. 24, No. 5, pages 241-250. Also, UK patent application No. 2,018,466A filed Mar. 2, 1979 by Misumi et al and U.S. Pat. No. 4,265,991 which issued May 5, 1981 to Hirai, described blocking layers on imaging-forming members. Other blocking layers on amorphous silicon photoreceptors were described by Shimizu, Komatsu and Inoue in Photographic Science & Engineering, Vol. 24, No. 5, September, 1980, in pages 250-254. These blocking layers increased the dark surface voltage (Vs) but retained substantial surface charge under illumination, thereby reducing voltage contrast.
Apparatus suitable for the present invention using asymmetrical electrical fields is described in my above-mentioned U.S. Pat. No. 4,226,897. Suitable apparatus with uniform electrical fields is described in my U.S. Pat. No. 3,069,283. Improved apparatus is described herein.