1. Field of the Invention
The present invention relates to an electrophotographic photoconductor containing a new specifically structured azo compound, electrophotography, an electrophotographic apparatus, a process cartridge for the electrophotographic apparatus, a new azo compound, a method for manufacturing the azo compound and a photoconductive layer material.
2. Description of the Related Art
Largely classified, various inorganic and organic photoconductors are conventionally known as the photoconductors of photoconductors used in electrophotography. “Electrophotography” referred to herein is an image formation process, which is the so-called Carlson process that generally, a photoconductor having a photoconductive property is first electrically charged, for example, by performing corona discharge in a dark place, then an image is exposed, the electric charge of only an exposed section is selectively dispersed to obtain a latent electrostatic image, which is visualized to form an image. Then this latent electrostatic image was developed by a toner which is formed of coloring agents such as dyes and pigments, high-molecular materials or the like, namely, was visualized to form an image. Since a photoconductor which, uses an organic electrophotographic photoconductor has more advantageous aspects such as degree of freedom in photoconductive wavelength area, layer deposition property, flexibility, transparency of layer, productivity, toxicity and cost than those of an inorganic photoconductor, an organic electrophotographic photoconductor is now used for almost all photoconductors. The photoconductor repeatedly used in the electrophtography and similar processes requires excellency in electrostatic properties representing sensitivity, receptible potential, potential retainability, potential stability, residual electric potential, spectral-response property and the like.
In light of the foregoing, there are known an azo compound (see Japanese Patent Application Laid-Open (JP-A) No. 54-22834 and Japanese Patent Application Laid-Open (JP-A) No. 61-151659), a phthalocyanine compounds (see Japanese Patent Application Laid-Open (JP-A) No. 48-34189 and Japanese Patent Application Laid-Open (JP-A) No. 57-14874), perylene compounds (see Japanese Patent Application Laid-Open (JP-A) No. 53-98825 and Japanese Patent Application Laid-Open (JP-A) No. 63-266457), polycyclic quinone compounds (see Japanese Patent Application Laid-Open (JP-A) No. 61-48861), squarylium compounds (see Japanese Patent Application Laid-Open (JP-A) No. 49-105536 and Japanese Patent Application Laid-Open (JP-A) No. 58-21416) and the like as the organic photoconductors that have been so far proposed and actually used in the industry.
Above all, the azo compounds can be easily synthesized, since the electrophotographic properties and spectral sensitivity area are largely different due to the facts that the degree of freedom of for molecular design is big and the molecular structures such as azo components, coupler components and bonding types are different, they have been eagerly studied as not only an analogue recording photoconductor but also a digital recording photoconductor. Azo compounds that have been known up to now as the azo compounds showing a good sensitivity include an azo compound having a carbazole skeleton (see Japanese Patent Application Laid-Open (JP-A) No. 53-95033), an azo compound having a distyryl benzene skeleton (see Japanese Patent Application Laid-Open (JP-A) No. 53-133445), an azo compound having a triphenylamine skeleton (see Japanese Patent Application Laid-Open (JP-A) No. 53-132347), an azo compound having a dibenzothiophene (see Japanese Patent Application Laid-Open (JP-A) No. 54-21728), an azo compound having an oxadiazole skeleton (see Japanese Patent Application Laid-Open (JP-A) No. 54-12742), an azo compound having a fluorenone skeleton (see Japanese Patent Application Laid-Open (JP-A) No. 54-22834), an azo compound having a bisstilbene skeleton (see Japanese Patent Application Laid-Open (JP-A) No. 54-17733), an azo compound having a distyrloxadiazole skeleton (see Japanese Patent Application Laid-Open (JP-A) No. 54-2129), and an azo compound having a distyrylcarbazole skeleton (see Japanese Patent Application Laid-Open (JP-A) No. 54-14967).
Also known are a benzidine bisazo compound (see Japanese Patent Application Laid-Open (JP-A) No. 47-37543 and Japanese Patent Application Laid-Open (JP-A) No. 52-55643), a stylbenzene bisazo compound (see Japanese Patent Application Laid-Open (JP-A) No. 52-8832), a diphenylhexatriene bisazo compound (see Japanese Patent Application Laid-Open (JP-A) No. 58-222152), a diphenylbutadiene bisazo compound (see Japanese Patent Application Laid-Open (JP-A) No. 58-222153) and the like.
In addition, already known as the coupler compounds used for the afore-mentioned compounds are a naphthol coupler (see Japanese Patent Application Laid-Open (JP-A) No. 47-37543), a benzcarbazole coupler (see Japanese Patent Application Laid-Open (JP-A) No. 58-122967), a naphthalimide coupler (see Japanese Patent Application Laid-Open (JP-A) No. 54-79632), a perinone coupler (see Japanese Patent Application Laid-Open (JP-A) No. 57-176055), an azulene coupler (see Japanese Patent Application Laid-Open (JP-A) No. 60-10256), an anthracene coupler (see Japanese Patent Application Laid-Open (JP-A) No. 61-257953) or the like.
However, when a conventional azo compound is used for a laminated stacked type photoconductor, which is one embodiment of an electrophotographic photoconductor, it is not enough in practical use since sensitivity and durability are generally low, and it is desirable that sensitivity and durability should be further improved to satisfy various needs, which are required for an electrophotographic process.
In addition, from the viewpoint of the simplification of a manufacturing process and the like, a single laminar constitution is also advantageous as a photoconductor, which uses an organic material.
Conventionally, known as single laminar photoconductors are (i) a charge transport complexes type photoconductor comprising polyvinyl carbazole (PVK) and trinitrofluorene (see Specification of the United States Patent (US-B) No. 3489237), (ii) since a eutectic mixture comprising a thiapyrrylium dye and polycarbonate (see J. Appl. Phys., 49, 5555 (1978)), and (iii) a photoconductor where a perylene pigment and a hydrazone compound are dispersed in a resin (see Japanese Patent Application Laid Open (JP-A) No. 02-37354). Of these, for items (i) and (ii), since the sensitivities of the photoconductors are low, and the electrostatic and mechanical durability is low, they have a problem in the repeated use. For item (iii), since the sensitivity of the photoconductor is low, a high-speed copying process caused inappropriate defects. Further, electrification potentional and sensitivity were low in a system where the components of the laminated type photoconductor that was industrially used were merely dispersed, particularly, since weatherability and electrostatic and mechanical durability were low, there was a defect that electrostatic property largely varied with the repeated use of the photoconductor.
Thus, for the single laminar photoconductor, a difficult task lies in the development of a high-sensitivity and high-durability organic material, particularly, for a charge-generating material, since a charge-generating point is located on the surface side of the photoconductive layer, which is different from the laminated type photoconductor, more weatherability and durability used for the laminated type photoconductor are required.