JPS60198549A - electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body superior in photosensitivity by forming an electrostatic charge generating layer composed of at least 2 constituents of a charge generating material and an electron acceptor by vapor deposition, and a charge transfer layer on a conductive substrate. CONSTITUTION:An electrophotographic sensitive body is obtained by forming a charge generating layer composed of at least 2 constituents of a charge generating material, such as metal-free phthalocyanine or phthalocyanine compds., and an electron acceptor, such as acid anhydrides, e.g., phthalic anhydride, by the vapor deposition method, and further, a charge transfer layer on a conductive substrate made of brass, aluminum, gold, or the like. It is preferred to form the charge generating layer by vapor codeposition, and also to deposit the charge generating material and the electron acceptor alternately on each other each in thickness of <=30nm to form the charge generating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electrophotographic photoreceptor, more specifically, an electrophotographic photoreceptor comprising a layer made of a photocharge generating substance and a layer made of a charge transporting substance on a conductive support. Regarding the body.

[Technical background of the invention and its problems]

Generally, an electrophotographic photoreceptor based on the Carlson method is required to have a high electric resistance value in a dark state and excellent charging properties. However, even though photoreceptors in the early stages of development, in which a single layer of photoconductor is laminated on a conductive support, have high sensitivity in the visible region, they often have low electrical resistance values in the dark state. It was difficult to apply this method to electrophotography using the Carlson method.

For this reason, photoreceptors are now being used in which the chargeability of the photoreceptor is improved by separating the charge generation layer and the charge transport layer, thereby increasing the sensitivity. This photoreceptor has the advantage that since the charge transport layer does not need to generate charges, a material having excellent charge retention ability and charge transport can be selected as the charge transport material for the layer. In a photoreceptor having such a laminated structure, excitons generated in the charge generation layer by light irradiation dissociate within the charge generation layer or near the boundary between the charge generation layer and the charge transport layer to generate carriers. It is believed that these carriers (holes or electrons) are transported into the Iff charge transport layer and neutralize the charges on the surface of the photoreceptor, thereby forming an electrostatic latent image.

In the above laminated photoreceptor, the charge generation layer is usually thinner and has weaker mechanical strength than the charge transport layer.
The charge transport layer is the upper layer and the charge generation layer is the lower layer.

When a vapor-deposited film of a charge-generating substance is used for the charge-generating layer, especially when a vapor-deposited film of a phthalocyanine compound such as copper phthalocyanine is used, the receptive charge potential is low and the sensitivity is lower than that of PVK-TNF. The problem is that it is not as high as or lower than that.

Since the difference between the work function of the conductive substrate and the work function of the charge generating material is small, the Schottky barrier formed between the two is small, and therefore the efficiency of carrier generation using this barrier is low. This is thought to be the cause of these problems.

[Purpose of the invention]

The present invention eliminates the drawbacks of electrophotographic photoreceptors using a vapor-deposited film of a charge-generating substance, typified by the above-described vapor-deposited film of a phthalocyanine compound, as a charge-generating substance layer, and provides an electrophotographic photoreceptor with excellent photosensitivity. It is something to do.

[Summary of the invention]

The present invention has been completed based on the discovery that the above object can be achieved by using a vapor deposited film in which a charge generating substance and an electron-accepting material are dispersed as a charge generating layer.

The photoreceptor of the present invention is the same as a conventional photoreceptor in which a photoconductor is separated into two layers, except that an electron-accepting substance is added as a charge generation layer.

As the charge-generating substance that can be used in the present invention, any charge-generating substance that can be vapor-deposited can be used, and examples thereof include metal-free phthalocyanine, phthalocyanine compounds represented by the following general formula, derivatives thereof, merocyanine, Examples include cyanine pigments and penylene pigments.

As the electron-accepting compound used in the present invention, (1) acid anhydrides such as phthalic anhydride, tetrachlorophthalic anhydride, mellitic anhydride, and pyromellitic anhydride;

■Tricyanobenzene, tetracyanobenzene, dinitrobenzene, trinitrobenzene, tetranitrobenzene, dinitrochlorobenzene, dinitrobromobenzene% Trinitroanisole, nitroanilinol, dinitro-r-nisole, trinitroanisole, nitrotoluene, dinitrotoluene, trinitrotoluene%lJ Benzene and benzene derivatives having strong electron-withdrawing substituents such as halogen, Schiff/group, and nitro group, such as chlortrinitrotoluene, dichlordinitrotoluene, and cyfromodinitrotoluene.

(2) Condensed polycyclic compounds having strong electron-withdrawing substituents such as dichloroanthracene, dibromoanthracene, dicyanoanthracene, and tetracyanobile 7, and derivatives thereof.

■Chloranil, bromoanil, dichlordicyano-p-
Quinones and quinones having strong electron-withdrawing substituents and their derivatives, such as benzoquinone, anthraquinone, dichloroanthraquinone, and dinitroanthraquinone.

■Fluorenone and its derivatives having strong electron-withdrawing substituents such as trinitrofluorenone, dicyanomethylene fluorenone, dicyanomethylene trinitrofluorenone, and tetranitrofluorenone.

■Tetracyanoquinodimethane and its derivatives.

■Tetracyanoethylene and its derivatives.

(2) Bis-di, thiolate complexes such as bis(1,2-dimethyldithiolate)nickel and derivatives thereof.

■Halogens such as iodine and bromine.

[Phase] Other compounds having strong electron-withdrawing substituents such as nitro, cyano, and carboxyl groups.

Examples include.

The mixing ratio of the charge-generating substance and the electron-accepting substance is preferably 0.1 to 10 times the molar ratio of the charge-generating substance; below this, the effect of adding the electron-donating substance is not significant. On the other hand, if it is 10 times or more, the carrier mobility in the charge generation layer will be reduced, and the photosensitivity will be reduced.

In the method for forming the 'α charge generation layer of the present invention, mono- or dual-layer deposition can be performed depending on the deposition temperature of the charge-generating material and the electron-accepting material. When the deposition temperatures of the charge-generating material and the electron-accepting material are the same, it is possible to form a uniformly dispersed charge-generating layer with a predetermined quantitative ratio by co-evaporating them from the same boat with mixed evaporation sources.

When there is a difference in the deposition temperature of the charge-generating substance and the electron-accepting substance, there is a co-evaporation (binary evaporation) method in which each is heated to a predetermined temperature from two boats and deposited at the same time, and an extremely thin film is alternately deposited on each. A method of forming by repeating the multiplication f- is effective, and can form a uniformly dispersed charge generation layer in a predetermined ratio. In the method of alternately and repeatedly laminating, each layer is 30
0 A or less button Accordingly, it is possible to form a uniformly dispersed layer in the charge generation layer as a whole by θS.

- Forming by primary vapor deposition is simpler as an apparatus, but forming by binary vapor deposition has the advantage that it is easier to control the quantitative ratio of each component. Furthermore, although the method of forming by the repeating layering method takes some time θS, it is an effective method for uniformly dispersing the charge-generating material and the electron-accepting material when the amount ratio is large. The method for forming the charge generation layer may be selected depending on the combination and quantity ratio of the charge generation substance and the electron accepting material.

The charge transport layer used in the present invention is not particularly limited as long as it is transparent to visible light and has charge transport ability, and examples include polymeric organic semiconductors such as polyvinylcarbazole or derivatives thereof; oxadiazole derivatives. , a triphenylamine conductor, or a low-molecular organic semiconductor such as a pyrazoline derivative dispersed in an organic polymer compound can be used. The type of such polymer compound is not particularly limited, and examples include known binder materials for electrophotographic photoreceptors such as polystyrene, polyvinyl chloride, and vinyl chloride.
Vinyl acetate copolymers, polyvinyl acetates, polyvinyl acetals, phenol resins, epoxy resins, alkyd resins, etc. can be used as appropriate.

Brass, aluminum, gold, silver, etc. are used as the conductive support of the electrophotographic photoreceptor of the present invention, and these are thin sheets of cylindrical shape with appropriate thickness, hardness, or flexibility. It may be coated with a thin layer of plastic. It may also be metallized paper, metallized plastic sheet or glass coated with a conductive layer of aluminum iodide, copper oxide or chromium oxide or tin oxide. It is usually desirable that the support be itself electrically conductive or have an electrically conductive surface and be sufficiently strong to handle.

In the present invention, an electrophotographic photoreceptor with excellent photosensitivity can be obtained by using a vapor-deposited film in which a charge-generating substance and a charge-accepting substance are dispersed as a charge-generating layer. It is presumed that this is due to the remarkable increase in the efficiency of oxidation generation due to sensitization. In addition, the work function of the charge-generating substance increases, the difference in work function with the conductive substrate increases, the shimy barrier formed between the two increases, and the carrier generation efficiency increases accordingly. This is also presumed to be because the probability that the generated carriers (holes) are trapped is also reduced.

〔Effect of the invention〕

As detailed above, the present invention makes it possible to obtain a charge generation layer with high carrier generation efficiency ρ by using a mixed layer of a charge generation substance and an electron accepting substance as a charge generation layer by vapor deposition on a conductive support. Therefore, it has remarkable effects such as being able to obtain an electrophotographic photoreceptor with excellent photosensitivity.

[Embodiments of the invention]

Examples 1 to 5 Using a polyethylene terephthalate resin layer on which M was vapor-deposited as a conductive support, a charge generation layer having a material composition as shown in Table 1 was formed on the M side by vapor deposition.

A polymer solution of a charge transport material as shown in Table 1 was applied thereon by a pulling method and dried at 90° C. for 24 hours. The charging ability and photosensitivity are shown in Table 1.

As a comparative example, Table IK shows the characteristics when the charge generation layer consists of only a charge generation substance.

The following is a continuation with one page of blank space. Inventor: Kimi Mizushima - 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki City
Comprehensive research at Tokyo Shibaura Electric Co., Ltd.

Claims (5)

[Claims] (1) In an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge generation layer consists of at least two components, a charge generation substance and an electron accepting substance, formed by a vacuum deposition method. An electrophotographic photoreceptor characterized by: (2) The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer is a thin film obtained by co-evaporating a charge generation substance and an electron accepting substance. (3) The electron according to claim 1, characterized in that the charge generating layer is obtained by alternately depositing and laminating a charge generating substance and an electron accepting substance in a range of 300X or less. Photographic photoreceptor 0 (4) Electrophotographic photoreceptor O R1 according to claim 1, wherein the charge generating substance is at least one of metal-free phthalocyanine, a phthalocyanine compound represented by the following general formula, and its derivatives. (5) The molar ratio of the charge-generating substance and electron-accepting substance in the charge-generating layer to the charge-generating substance is 0.1 to 1.
Claim 1 characterized in that it is in the range of 0 times
The electrophotographic photoreceptor described in .