JPS61173256A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body having high sensitivity and showing very low residual potential even after a durability test by incorporating a specified polycyclic quinone pigment as a photoconductive substance into a photosensitive layer. CONSTITUTION:A polycyclic quinone pigment represented by the formula as a photoconductive substance is incorporated into a photosensitive layer. The charge generating layer contains a charge generating material to the utmost limit so as to obtain sufficient absorbance, and the layer is formed as a thin layer of <=10mum, preferably 0.01-1mum thickness so as to implant efficiently charge carriers generated in the layer into the charge transferring layer. Most of incident light is absorbed in the charge generating layer, generating many charge carriers, and the generated charge carriers are implanted into the charge transferring layer without causing deactivation by recombination or trapping.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a useful low-molecular organic photoconductor used in electrophotographic photoreceptors, and particularly to a laminated type photoconductor with functionally separated charge generation layer and charge transport layer. Related to electrophotographic photoreceptors.

[Prior art]

Electrophotographic photoreceptors containing inorganic photoconductors such as selenium, cadmium sulfide, and zinc oxide in the photosensitive layer are well known. On the other hand, organic photoconductive polymers such as polJ, -N-vinylcarbazole, and polyvinylanthracene; low-molecular organic photoconductors such as carbazole, anthracene, pyrazolines, oxadiazoles, and hydrazones; phthalocyanine pigments; and azo pigments. Organic photoconductors such as , indico dyes, thioindico dyes, and squaric acid methine dyes have been developed. Furthermore, for example, US Pat. No. 4,123,270, US Pat.
As disclosed in No. 51613 and No. 4256821, electrophotographic photoreceptors are known that use a photoconductive cis-sazo pigment as a charge generation substance in a photosensitive layer that is functionally separated into a charge generation layer and a charge transport layer. . Electrophotographic photoreceptors using such organic photoconductors can be produced using a coating method using υ dip coating by appropriately selecting a binder, making it possible to provide photoreceptors with extremely high productivity and low cost. Although it has the advantage of being able to select an organic pigment that exhibits photoconductivity in an appropriate wavelength range, it still does not have satisfactory performance in terms of sensitivity and increase in residual potential after durability tests.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and provide an electrophotographic photoreceptor that is highly sensitive and has extremely low residual potential even after a durability test.

[Means for solving problems]

According to the present invention, there is provided an electrophotographic photoreceptor characterized in that a photosensitive layer provided on a conductive substrate contains a polycyclic quinone pigment having the following structural formula I as a photoconductive substance.

Further, according to the present invention, the photosensitive layer is a laminated type consisting of a charge generation layer and a charge transport layer, the charge generation layer contains a polycyclic quinone pigment represented by the following formula (2), and the charge transport layer to the following general formula (1), (wherein R,, R2, R3 and R4 are hydrogen atoms or halodan atoms, R5 is a hydrogen atom, halodan atom, alkyl group or alkoxy group, and R6 and R7 are substituted It is characterized by containing a hydrazone compound represented by the alkyl group, aralkyl group, phenyl group that may have a group, or a residue that forms a 5- to 6-membered ring together with a nitrogen atom. An electrophotographic photoreceptor is provided.

In the electrophotographic photoreceptor of the present invention, a photosensitive layer containing the polycyclic quinone pigment of formula (1) above as a photoconductive substance can be used as a single layer, but it is also possible to use a photosensitive layer containing the polycyclic quinone pigment of formula (I) above as a photoconductive substance. It is also possible to use a single layer containing a mixture of hydrazone compounds of formula (1).

Furthermore, in a preferred embodiment of the present invention, in a laminated photosensitive layer comprising a charge generation layer and a charge transport layer, a mixture of a polycyclic quinone pigment of formula I and a hydrazone compound of formula (II) is used in the charge generation layer. Remarkable effects can be achieved.

In the general formula (2), examples of the alkyl group include methyl, ethyl, propyl, and butyl, and examples of the alkoxy group include methoxy, ethoxy, propoxy, and butoxy. Examples of the 5- to 6-membered ring include pyrrolidino, piperidino, and morpholino. Furthermore, these substituents include alkyl groups such as methyl, ethyl, propyl, and butyl, alkoxy groups such as methoxyethoxy, propoxy, and butoxy, halodane atoms such as chlorine, bromine, and iodine, dimethylamino, and diethylamino groups. , dialkylamino groups such as dipropylamino group and dibutylamino group.

For example, the hydrazone compound of the general formula (1) is JP-A-58-6
It is easily synthesized by the method described in 5261.

Representative compounds of the general formula (1) used in the present invention are illustrated below.

Table 1 The photosensitive layer according to the present invention can be prepared by coating a polycyclic quinone pigment of formula (1) or a mixture of this and a hydrazone compound of formula (2) on a substrate, if necessary, together with a suitable binder. It can be obtained by forming a deposited film using a vacuum deposition apparatus.

In the laminated electrophotographic photoreceptor according to a preferred embodiment of the present invention, the charge generation layer contains as much of the above charge generation material as possible in order to obtain sufficient absorbance, and efficiently charges the generated charge carriers. To inject into the transport layer,
A thin film layer, for example a thin film layer having a thickness of 10 microns or less, preferably 0.01 micron to 1 micron, is desirable.

This means that most of the incident light is absorbed by the charge generation layer, generating many charge carriers, and that the generated charge carriers are not deactivated by recombination or trapping, but are transferred to the charge transport layer. This is due to the need for injection.

In addition to the polycyclic quinone pigment of formula I in the charge generation layer,
When a hydrazone compound is used in combination, the latter is suitably 10 times or less (weight ratio) of the former, preferably 0.01 to 1 times.

The binder that can be used to form the charge generating layer by coating can be selected from a wide variety of insulating resins, and can be selected from organic photoconductive polymers such as Matabori-N-vinylcarbazole, I-rivinylanthracene, and polyvinylpyrene. . Preferably, polyvinyl butyral, -realylate (condensation polymer of bisphenol A and heptalic acid, etc.), polycarnate, polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide resin,
Polyamide, polyvinyl lysine, cellulose resin,
Examples include insulating resins such as urethane resin, epoxy resin, casein, polyvinyl alcohol, and I-rivinylpyrrolidone. The resin contained in the charge generation layer is 80
Less than 40% by weight, preferably less than 40% by weight, is suitable.

The solvent that dissolves these resins varies depending on the type of resin, and is preferably selected from those that do not dissolve the charge transport layer and undercoat layer described below. Specific organic solvents include alcohols such as methanol, ethanol, and isopronoenol, keto/groups such as acetone, methyl ethyl ketone, and cyclohexanone, amides such as N,N-methylformamide, N,N-dimethylacetamide, etc. Sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halodanes such as chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, and trichlorethylene. Hydrocarbons or aromatic compounds such as benzene, toluene, xylene, ligroin, monochlorobenzene, and dichlorobenzenato can be used.

Coating methods include dip coating method, spray coach ink method, spinner coating method, bead coach ink method,
This can be carried out using a coating method such as a Mayer-Per coating method, a blade coating method, a roller coach ink method, or a curtain coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying can be carried out at a temperature of 30° C. to 200° C. for a period of time ranging from 5 minutes to 2 hours, either stationary or under ventilation.

The charge transport layer is electrically connected to the charge generation layer described above, and has the function of receiving and taking charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. have. At this time, this charge transport layer may be laminated on or under the charge generation layer. However, it is desirable that the charge transport layer is laminated on the charge generation layer.

The substance that transports charge carriers in the charge transport layer (hereinafter simply referred to as charge transport substance) is preferably substantially insensitive to the wavelength range of electromagnetic waves to which the charge generation layer is sensitive. The term "electromagnetic waves" used herein includes a broad definition of "light rays" including r-rays, X-rays, ultraviolet rays, visible light, near-infrared rays, infrared rays, far-infrared rays, and the like. When the photosensitive wavelength range of the charge transport layer coincides with or overlaps that of the charge generation layer, charge carriers generated in both layers trap each other, resulting in a decrease in sensitivity.

When the charge transport material does not have film-forming properties, a film can be formed by selecting an appropriate binder. Resins that can be used as binders include, for example, acrylic resins, polyarylates, polyesters, polycarnates,
polystyrene acrylonitrile-styrene copolymer,
Insulating resins such as acrylonitrile-butadiene copolymer, polyvinyl butyral, polyvinyl formal, l+J sulfone, polyacrylamide, polyamide, chlorinated copolymer, or organic photoconductive resins such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, etc. Polymers can be mentioned.

Since the charge transport layer has a limit in its ability to transport charge carriers, it cannot be made thicker than necessary. Typically it is 5 microns to 30 microns, with a preferred range of 8 microns to 20 microns. When forming the charge transport layer by coating, an appropriate coating method as described above can be used.

A photosensitive layer consisting of a laminated structure of various charge generation layers and charge transport layers is provided on a substrate having a conductive layer. Examples of substrates having a conductive layer include those in which the substrate itself is conductive;
For example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium,
Nickel, indium, gold, platinum, etc. can be used, and plastics (e.g. , polyethylene, I-lipropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, polyfluoroethylene, etc.), or conductive particles (e.g.
A substrate in which plastic is coated with carbon black, silver particles, etc.) together with a suitable binder, a substrate in which plastic or paper is impregnated with conductive particles, a plastic having a conductive polymer, etc. can be used.

A subbing layer having barrier and adhesive functions can also be provided between the conductive layer and the photosensitive layer. The subbing layer is casein,
Polyvinyl alcohol, nitrocellulose, ethylene-
It can be formed from acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, nylon 66, nylon 610° copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane gelatin, aluminum oxide, and the like.

The thickness of the undercoat layer is suitably 0.1 micron to 40 micron, preferably 0.1 micron to 3 micron.

When using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, and the charge transport material is an electron transport material, the surface of the charge transport layer must be positively charged, and exposure after charging is required. Then, in the exposed area, electrons generated in the charge generation layer are injected into the charge transport layer, and then reach the surface and neutralize the positive charge, causing a decrease in surface potential and creating an electrostatic contrast with the unexposed area. . A visible image can be obtained by developing the electrostatic latent image thus formed with a negatively charged toner. This can be directly fixed, or the toner image can be transferred to paper or plastic film i and then developed and fixed.

Alternatively, a method may be used in which the electrostatic latent image on the photoreceptor is transferred onto an insulating layer of transfer paper, then developed and fixed. The type of developer, the developing method, and the fixing method may be any known ones or known methods, and are not limited to specific ones.

On the other hand, when the charge transport material consists of a hole transport material, the surface of the charge transport layer tends to be negatively charged. When exposed to light after charging, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area. After that, it reaches the surface and neutralizes the negative charges, resulting in attenuation of the surface potential and an electrostatic contrast between it and the unexposed area.

During development, it is necessary to use a positively charged toner, contrary to the case where an electron transport material is used.

The electrophotographic photoreceptor used in the present invention is subject to deterioration due to ultraviolet rays, ozone, etc., contamination due to oil, etc., damage due to metal cutting powder, and damage to the photoreceptor due to photoreceptor contact members such as developing members, transfer members, and cleaning members. A protective layer may be further provided on the photosensitive layer for the purpose of preventing scratching. In order to form an electrostatic latent image thereon, this protective layer desirably has a surface resistivity of 10 11 Ω or more.

The protective layer is, for example, polyvinyl butyral, moon? Riester, 1? Is the liquor nate, acrylic resin, methacrylic resin, polyamide, polyimide 1,1? It is formed by applying a solution prepared by dissolving a resin such as realylate, polyurethane, styrene-zotanoene copolymer, ethylene-acrylic acid copolymer, or styrene-acrylonitrile codelimer in an organic solvent onto the photosensitive layer and drying it. Additionally, additives such as ultraviolet absorbers may be added to the resin liquid. The thickness of the retention layer is generally 0.05 to 20 microns, preferably 2 to 5 microns.

Example 1 Ammonia aqueous solution of casein (casein 11.2, 9, 28% ammonia water 1g,
222 ml of water was applied by a dip coating method and dried to form a subbing layer of coating jL 1 , Og/m 2 .

Next, a charge generating material 1' heavy part represented by formula (1), butyral resin (S-LEC BM-2: Sekisui Chemical (Yanagi))
1 part by weight and 30 parts by weight of isozorobyl alcohol were dispersed for 4 hours using a Ga-Lumil disperser. This dispersion was applied onto the previously formed subbing layer by a dip coating method and dried to form a charge generation layer.

The film thickness at this time was 0.3μ.

Next, 1 part by weight of p-diethylaminobenzaldehyde-N-7enyl-N-α-naphthylhydrazone, which is exemplified compound 1 of general formula (1), and polysulfone resin (P1700
: Union Carbide Co., Ltd., 1 part by weight and 6 parts by weight of monochlorobenzene were mixed and dissolved by stirring with a stirrer. This liquid was applied onto the charge generation layer by dip coating and dried to form a charge transport layer. The film thickness at this time was 12μ.

Corona discharge of -5 kV was applied to the photoreceptor thus prepared. The surface potential at this time was measured (initial potential V).

Furthermore, the surface potential of this photoreceptor was measured after it was left in a dark place for 5 seconds (dark decay Vs).

Sensitivity was evaluated by measuring the exposure-fil (EHlux·8ee) required to attenuate the potential vs after dark decay to 1/2. These results were as follows.

Vo knee 590 is ruto vs knee 570 volt EH: 5.71uxHsea Examples 2 to 14 Completely the same as Example 1 except that the compounds shown in Table 1 were used in place of the compound A1 used in Example 1. A photoreceptor was prepared in a similar manner and the characteristics of this photoreceptor were measured. These results are shown in Table 2.

Table 2 2 570 550 5.93 3
585 575 6.04 4 575
550 6.15 5 590 570
6.46 6 605 580 6.9
7 7 600 575 6.78 8
595 570 6.39 9 585
565 6.710 10 585 56
0 6.511 11 585 565
6.412 12 595 580 6.
813 13 600 580 6.814
14 590 570 6.6 Comparative example 1~
6 A photoreceptor was prepared in exactly the same manner as in Example 1, except that the charge transport material shown in Table 3 was used in place of the hydrazone compound used in Example 1. The charging characteristics are shown in Table 4.

Table 3 2H5 Table 4 As is clear from the above results, it can be seen that the laminated photoreceptor of the present invention has extremely high sensitivity compared to the photoreceptors 1 to A6 of the comparative examples. Further, images of the photoreceptors of Examples 1 to 3 were repeatedly printed 20,000 times using a copying machine NP-1502 manufactured by Canon Corporation. As a result, good quality images were obtained for each photoreceptor even after repeating 20,000 times. As a result, it can be seen that the photoreceptor of the present invention has extremely excellent durability.

Claims (2)

[Claims] (1) A photosensitive layer provided on a conductive substrate contains a polycyclic quinone pigment having the following structural formula I, ▲numerical formula, chemical formula, table, etc.▼ as a photoconductive substance. Electrophotographic photoreceptor. (2) The above photosensitive layer is a laminated type consisting of a charge generation layer and a charge transport layer, and the charge generation layer contains a polycyclic quinone pigment represented by the following formula I, ▲numerical formula, chemical formula, table, etc. and the charge transport layer contains the following general formula II, ▲mathematical formula, chemical formula, table, etc. an atom, an alkyl group, or an alkoxy group, and R_6 and R
_7 indicates an alkyl group, an aralkyl group, a phenyl group, which may have a substituent, or a residue that forms a 5- to 6-membered ring together with a nitrogen atom). An electrophotographic photoreceptor according to claim 1, characterized in that: