Blocking layer with needle shaped particles

Details Blocking layer with needle shaped particles Blocking layer with needle shaped particles

1999-10-12

2001-01-23

Rodee, Christopher D. (Department: 1753)

Radiation imagery chemistry: process, composition, or product th

Electric or magnetic imagery, e.g., xerography,...

Radiation-sensitive composition or product

C430S064000

Reexamination Certificate

active

06177219

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a photoreceptor useful for an electrostatographic printing machine, and particularly to an improved charge blocking layer.
BACKGROUND OF THE INVENTION
A charge blocking layer containing dispersed grain shaped titanium oxide (TiO
2
) particles is known. Such a blocking layer is problematic in certain situations because at low temperatures (e.g., about 10 to 15 degrees C), charge transport through the blocking layer containing the grain shaped titanium oxide particles is not efficient enough and high residual voltage (e.g., around 100 V) is observed. The present inventors have found that this low temperature problem can be reduced by increasing the concentration of the grain shaped titanium oxide particles to a high level such as over about 90% by weight based on the weight of the blocking layer. At such a high concentration, however, the parameters of dispersion quality, particle size distribution, and degree of particle settling become much worse. In fact, such a highly concentrated dispersion of grain shaped titanium oxide particles in a binder generally is unsuitable for use in dip coating the charge blocking dispersion onto a photoreceptor substrate. There is a need, addressed by the present invention, for an improved charge blocking composition that solves the above low temperature problem and that exhibits good dispersion qualities to allow dip coating of the charge blocking composition onto a photoreceptor substrate.
Conventional photoreceptors and their materials are disclosed in Katayama et al., U.S. Pat. No. 5,489,496 (discloses in col. 4, lines 57-58 that “needle-like titanium oxide particles may be used together with titanium oxide having a grain-like shape” in an undercoat layer); Yashiki, U.S. Pat. No. 4,579,801; Yashiki, U.S. Pat. No. 4,518,669; Seki et al., U.S. Pat. No. 4,775,605; Kawahara, U.S. Pat. No. 5,656,407; Markovics et al., U.S. Pat. No. 5,641,599; Monbaliu et al., U.S. Pat. No. 5,344,734; Terrell et al., U.S. Pat. No. 5,721,080; and Yoshihara, U.S. Pat. No. 5,017,449.
Conventional charge blocking layers are also disclosed in U.S. Pat. No. 4,464,450; U.S. Pat. No. 5,449,573; U.S. Pat. No. 5,385,796; and Obinata et al, U.S. Pat. No. 5,928,824.
SUMMARY OF THE INVENTION
The present invention is accomplished in embodiments by providing a photoreceptor comprising:
(a) a substrate;
(b) a charge blocking layer including a binder, a plurality of grain shaped n-type particles, and a plurality of needle shaped n-type particles, wherein the grain shaped particles have a higher concentration in the blocking layer than the needle shaped particles; and
(c) an imaging layer.


REFERENCES:
patent: 4464450 (1984-08-01), Teuscher
patent: 4518669 (1985-05-01), Yashiki
patent: 4579801 (1986-04-01), Yashiki
patent: 4775605 (1988-10-01), Seki et al.
patent: 5017449 (1991-05-01), Yoshihara
patent: 5344734 (1994-09-01), Monbaliu et al.
patent: 5385796 (1995-01-01), Spiewak et al.
patent: 5449573 (1995-09-01), Aoki et al.
patent: 5489496 (1996-02-01), Katayama et al.
patent: 5641599 (1997-06-01), Markovics et al.
patent: 5656407 (1997-08-01), Kawahara
patent: 5721080 (1998-02-01), Terrell et al.
patent: 5928824 (1999-07-01), Obinata et al.
patent: 5958638 (1999-09-01), Katayama et al.
Huoy-Jen Yuh and John S. Chambers, “Charge Generating Layer with Needle Shaped Particles”, Serial No. 09/416,824 (D/97389).

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