JP6717004B2 - Electrophotographic photoreceptor and image forming apparatus using the same - Google Patents

Description

The present invention relates to an electrophotographic photosensitive member used in an electrophotographic image forming apparatus and an image forming apparatus using the same.

The electrophotographic photosensitive member used in the electrophotographic image forming apparatus is required to have high reliability, long life, and stable image quality from the viewpoints of environmental load reduction and cost reduction. For example, an electrophotographic photosensitive member (hereinafter, also simply referred to as a photosensitive member) having a negatively-charged laminated structure which has been widely used in recent years is usually formed on a conductive support, an intermediate layer and a charge generating layer. It is laminated with a photosensitive layer formed with a charge transport layer. In the electrophotographic photosensitive member having such a negative charging type laminated structure, when the surface thereof is negatively charged and then exposed, charges are generated in the charge generation layer, of which negative charges (electrons) are While moving to the conductive support through the intermediate layer, holes move to the surface of the electrophotographic photosensitive member through the charge transporting layer and cancel the negative charge on the surface to form an electrostatic latent image. .. Therefore, the intermediate layer has an electron-transporting property (moves electrons generated in the charge generation layer to a conductive support rapidly) and a hole-blocking property (from the conductive support to the photosensitive layer). Suppressing the injection of holes) is required.

A technique is known in which specific metal oxide particles are contained in such an intermediate layer. For example, in Patent Document 1, as an attempt to improve the function of the intermediate layer in this way, a photoreceptor in which particles obtained by surface-treating titanium oxide particles with methylhydrogenpolysiloxane as metal oxide particles are contained in the intermediate layer is disclosed. Has been done. Further, Patent Document 2 discloses a photoconductor in which an intermediate layer contains metal oxide particles such as titanium oxide surface-treated with a coupling agent having an amino group.

Japanese Unexamined Patent Publication No. 8-328283 JP, 9-96916, A

However, when the electrophotographic photoreceptor is used in a high temperature and high humidity environment, the resistance of the photosensitive layer becomes low, and charges are injected from the conductive support to the photosensitive layer, resulting in poor charging of minute portions during charging. Image defects such as minute spots (black spots) occur when an image is displayed.

Further, in recent years, it has been required to use the photoconductor with a long life. However, when the photoconductor is used for a long time, black spots become remarkable, and the residual potential after the transfer and before the charge removal are eliminated. Will also increase.

Further, in the future, as the cost of the electrophotographic apparatus is required to be reduced, there is a need for a technique for achieving the cost reduction by eliminating the pre-charging static eliminating means that constitutes the electrophotographic process. However, if there is no charge elimination means before charging, a difference in post-exposure potential occurs between the non-exposed area and the exposed area, and the post-exposure potential increases during repeated electrophotographic processes. There may occur a problem that an image density difference occurs in the photoconductor cycle. Therefore, an electrophotographic photoreceptor having more excellent potential stability is required.

The above Patent Documents 1 and 2 show that stability and environmental characteristics can be improved by containing specific metal oxide particles in the intermediate layer. However, in the methods of Patent Documents 1 and 2, durability is improved. It was found that it was difficult to maintain good hole blocking property and potential stability when the time and the temperature and humidity environment changed.

The present invention has been made in view of the above problems, and provides an electrophotographic photosensitive member capable of maintaining good hole blocking property and potential stability even at the time of durability and when the temperature and humidity environment is changed. The purpose is to

In order to solve the above problems, the present inventors, in the process of examining the cause of the above problems, in the electrophotographic photoreceptor, to contain a conductive metal oxide particles carrying a multi-electron reduction catalyst in the intermediate layer As a result, they have found that good hole blocking property and potential stability are maintained even when they are durable and when the temperature and humidity environment is changed.

That is, the above-mentioned subject concerning the present invention is solved by the following means.

1. An electrophotographic photoreceptor in which an intermediate layer and a photosensitive layer are sequentially laminated on a conductive support,
An electrophotographic photoreceptor, wherein the intermediate layer contains conductive metal oxide particles carrying a multi-electron reduction catalyst.

2. 2. The electrophotographic photosensitive member according to 1 above, wherein the conductive metal oxide particles contain at least one of titanium oxide and tungsten oxide.

3. The electrophotography according to 1 or 2 above, wherein the multi-electron reduction catalyst contains one or more elements selected from the group consisting of platinum, palladium, copper, iron, rhodium, gold, chromium, nickel, cerium, and tungsten. Photoconductor.

4. 4. The electrophotographic photosensitive member according to any one of 1 to 3, wherein the conductive metal oxide particles have a number average primary particle diameter of 10 to 1000 nm.

5. 5. The electrophotographic photosensitive member according to any one of 1 to 4 above, wherein the multi-electron reduction catalyst is supported at a rate of 0.0001 to 40 mass% with respect to the conductive metal oxide particles.

6. The intermediate layer further contains a binder resin, and contains conductive metal oxide particles carrying the multi-electron reduction catalyst in a ratio of 20 to 300 parts by mass with respect to 100 parts by mass of the binder resin. 6. The electrophotographic photosensitive member according to any one of items 1 to 5.

7. An electrophotographic photosensitive member according to any one of 1 to 6,
Charging means for charging the surface of the electrophotographic photosensitive member,
Exposure means for performing latent image formation by performing image exposure on the surface of the electrophotographic photosensitive member charged by the charging means;
Developing means for forming a toner image by visualizing the latent image formed by the exposing means,
Transfer means for transferring the toner image formed on the surface of the electrophotographic photosensitive member by the developing means onto a transfer medium such as paper or a transfer belt;
An image forming apparatus having:

8. 8. The image forming apparatus as described in 7 above, which does not include a discharging unit that discharges residual charges on the surface of the electrophotographic photosensitive member after transfer and before charging.

According to the present invention, there is provided an electrophotographic photosensitive member which maintains good hole blocking property and potential stability even when it is durable and when the temperature and humidity environment is changed.

1 is a cross-sectional configuration diagram of a full-color electrophotographic image forming apparatus showing an embodiment of the present invention.

The present invention is an electrophotographic photoreceptor in which an intermediate layer and a photosensitive layer are sequentially laminated on a conductive support, wherein the intermediate layer contains conductive metal oxide particles carrying a multi-electron reduction catalyst. Is an electrophotographic photoconductor.

Hereinafter, the components of the present invention and modes and modes for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning including the numerical value described before and after that as a lower limit and an upper limit.

[Electrophotographic photoreceptor]
The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor in which an intermediate layer and a photosensitive layer are sequentially laminated on a conductive support, and the intermediate layer is a conductive metal oxide carrying a multi-electron reduction catalyst. It is characterized by containing particles.

The photosensitive layer has both a function of absorbing light to generate charges and a function of transporting charges, and the layer structure of the photosensitive layer is a single layer structure containing a charge generating substance and a charge transporting substance. Alternatively, it may have a laminated structure of a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance.

Further, if necessary, a protective layer (surface protective layer) may be provided on the photosensitive layer.

The photosensitive layer is not particularly limited in its layer structure, and as a specific layer structure including an intermediate layer, for example, in the case of a negatively chargeable photoreceptor, there are the following (1) to (4):
(1) Layer structure in which an intermediate layer, a charge generation layer and a charge transport layer are sequentially laminated on a conductive support (2) An intermediate layer, a charge transport substance and a charge generation substance are contained on the conductive support Layer structure in which a single photosensitive layer is sequentially laminated (3) Layer structure in which an intermediate layer, a charge generation layer, a charge transport layer and a protective layer are sequentially laminated on a conductive support (4) On a conductive support, A layer structure in which an intermediate layer, a single photosensitive layer containing a charge transport substance and a charge generating substance, and a protective layer are sequentially laminated.

The negatively chargeable photoreceptor preferably has a structure in which a charge generation layer (CGL) is provided on an intermediate layer and a charge transport layer (CTL) is provided thereon, and the positively chargeable photoreceptor is preferably an intermediate layer. A structure is provided in which a charge transport layer (CTL) is provided thereon and a charge generation layer (CGL) is provided thereon.

Therefore, the positively chargeable photoreceptor may have the following (1′) and (3′) as preferred layer configurations in addition to the above (2) and (4):
(1') A layer structure in which an intermediate layer, a charge transport layer, and a charge generation layer are sequentially laminated on a conductive support. (3') An intermediate layer, a charge transport layer, a charge generation layer, on the conductive support. And a layer structure in which a protective layer is sequentially laminated.

The photoconductor of the present invention may have any of the layer constitutions of (1) to (4), (1′) and (3′) above. Among these, the preferable layer constitution of the photosensitive layer is the functional separation. A negatively charged photoreceptor having a structure, having a layer structure of the above (1) prepared by sequentially providing an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support, and a conductive support. Particularly preferred is the layer structure of (3) above, which is prepared by sequentially providing an intermediate layer, a charge generation layer, a charge transport layer and a protective layer on top.

Next, the configurations of the intermediate layer, the conductive support, the photosensitive layer (charge generation layer and charge transport layer), and the protective layer that constitute the photoreceptor of the present invention will be described in order.

<Middle layer>
The electrophotographic photoreceptor of the present invention has an intermediate layer between the conductive support and the photosensitive layer. The intermediate layer has a barrier function and an adhesive function. The intermediate layer in the electrophotographic photosensitive member of the present invention contains conductive metal oxide particles carrying a multi-electron reduction catalyst. By having such a constitution, the electrophotographic photosensitive member of the present invention maintains good hole blocking property and potential stability even during durability and when the temperature and humidity environment changes.

In the electrophotographic photoconductor, from the viewpoint of environmental load reduction, productivity improvement, and cost reduction, it is required to extend the life of the photoconductor and improve image quality stability. As an electrophotographic photoreceptor, a laminated photoreceptor in which an intermediate layer and a photosensitive layer are sequentially laminated on a conductive support has been put into practical use, but when used in a high temperature and high humidity environment, the photosensitive layer has a low resistance and a conductive property. There is a problem that image defects such as black spots (small spots) occur at the time of solid white image output due to charge injection from the flexible support to the photosensitive layer, resulting in poor charging of minute portions during charging. ..

The intermediate layer is provided for the purpose of preventing charge injection from the conductive support to the photosensitive layer (hole blocking property). However, if the charge transporting property of the intermediate layer is poor, the charge generated in the charge generating layer is a side effect. It is trapped at the interface between the photosensitive layer and the intermediate layer or at the intermediate layer. As a result, there arises a problem that the residual potential increases after erasing.

As disclosed in the above-mentioned Patent Documents 1 and 2, there is known a method in which conductive metal oxide particles such as titanium oxide are dispersed and added to the intermediate layer to improve the residual potential and prolong the life of the photoreceptor. Has been. At this time, it is considered that the carrier mobility of the conductive metal oxide facilitates the adjustment of the potential on the surface of the photoconductor, so that the stability can be improved.

However, in recent years, it has been required to use the photoconductor with a long life, and when the photoconductor is used for a long time, minute spots are conspicuously generated, and the increase in residual potential after static elimination becomes large. In the methods of Patent Documents 1 and 2, the effect of improving the residual potential after repeated exposure is not sufficient, and it is difficult to perform stable image formation.

Further, in the future, as the cost of the electrophotographic apparatus is required to be reduced, there is a need for a technique for achieving the cost reduction by eliminating the pre-charging static eliminating means that constitutes the electrophotographic process. If there is no charge elimination means before charging, a difference in post-exposure potential between the non-exposed area and the exposed area will occur in the conventional photoconductor, and the post-exposure potential will increase during repeated electrophotographic processes. There is a problem that an image density difference occurs in the photoconductor cycle when an image is displayed. Therefore, there is a demand for a photoconductor that exhibits sufficient potential stability even when there is no pre-charge erase.

As a result of intensive studies on such a problem, it was revealed that the above problem can be solved by introducing a conductive metal oxide carrying a multi-electron reduction catalyst into the intermediate layer.

As disclosed in the above-mentioned Patent Documents 1 and 2, there is known a method in which conductive metal oxide particles such as titanium oxide are dispersed and added to the intermediate layer to improve the residual potential and prolong the life of the photoreceptor. Has been. At this time, it is considered that the carrier mobility of the conductive metal oxide facilitates the adjustment of the potential on the surface of the photoconductor, so that the stability can be improved.

However, with this method, the effect of improving the residual potential after repeated exposure is not sufficient, and stable image formation is difficult. This is because the conductive metal oxide particles that act as an n-type semiconductor, such as titanium oxide, prevent charge injection from the conductive support to the photosensitive layer, but the charge generated in the charge transport layer in the photosensitive layer is prevented. Due to insufficient transportability, it is considered that the charge is trapped at the interface between the photosensitive layer and the intermediate layer or the metal oxide particle interface in the intermediate layer, and the negative charge on the surface of the photoconductor cannot be canceled effectively. To be Furthermore, when the photoconductor is used for a long time, the increase in residual potential becomes large.

To obtain a sufficient potential stability improvement, it is necessary to add a large amount of conductive metal oxide particles, but since it easily absorbs moisture, the resistance of the photosensitive layer decreases due to moisture absorption in a high humidity environment. Then, electric charges are injected from the conductive support to the photosensitive layer, and a charging failure occurs in a minute portion at the time of charging, which causes minute spots (black spots) at the time of displaying a solid white image. Further, when the photoconductor is used for a long period of time, black spots are significantly generated.

On the other hand, when the multi-electron reduction catalyst is supported on the conductive metal oxide particles, the multi-electron reduction catalyst and the conductive metal oxide form a Schottky junction, and the electrons in the conductive metal oxide particles become multi-electron. It becomes easy to transfer to the reduction catalyst. As a result, it is considered that the probability of trapping charges can be reduced and the carrier mobility of the conductive metal oxide particles can be further improved. Therefore, it is considered that the potential stability on the surface of the photoconductor can be significantly improved and the stability of the obtained image can be improved.

Furthermore, since the conductive metal oxide particles supporting the multi-electron reduction catalyst can ensure the potential stability with a small amount of addition, compared with the case where the multi-electron reduction catalyst is not supported, the required conductivity The amount of metal oxide particles is small. Therefore, by adding a large amount of conductive metal oxide particles, it is possible to prevent the conductive metal oxide particles from becoming a hole injection portion from the conductive support and decreasing the hole blocking property. In addition, charging failure due to low resistance due to moisture absorption in a high humidity environment is unlikely to occur. Note that this mechanism is speculative, and the present invention is not limited to the above mechanism.

(Conductive metal oxide particles)
As the conductive metal oxide in the conductive metal oxide particles supporting the multi-electron reduction catalyst, for example, titanium oxide, tungsten oxide, zinc oxide, tin oxide or the like can be used. These conductive metal oxide particles can be used alone or in combination of two or more. When two or more kinds are mixed and used, they may be in the form of solid solution or fusion. In the photoreceptor of the present invention, it is preferable to use at least one of titanium oxide and tungsten oxide from the viewpoint of carrier transfer ability and chemical stability.

[Titanium oxide]
The titanium oxide is not particularly limited, but titanium oxide obtained by a gas phase method (a method of obtaining titanium oxide by a gas phase reaction of titanium tetrachloride and oxygen) is preferable, using titanium tetrachloride as a raw material. Titanium oxide obtained by the vapor phase method has a uniform particle size and, at the same time, undergoes a high temperature process during production, so that it has high crystallinity, and as a result, the resulting titanium oxide or multi-electron reduction catalyst is obtained. The carrier mobility of the titanium oxide carrying is excellent.

As the titanium oxide, it is advantageous to use commercially available titanium oxide as it is, considering the step of catalyst preparation. Commercially available titanium oxide includes those produced by the liquid phase method and those produced by the gas phase method.However, those produced by the liquid phase method have low crystallinity, and therefore, firing etc. It is preferably carried out to obtain titanium oxide having an optimum specific surface area and crystallinity. From the viewpoint of avoiding labor and cost due to such a firing step, coloring at the time of firing, etc., when a commercially available product is used, it has a suitable crystallinity and a specific surface area, It is preferable to use a commercially available product (for example, titanium oxide manufactured by Showa Denko Ceramics Co., Ltd.) as it is.

[Tungsten oxide (WO ₃ )]
There is no particular limitation on tungsten oxide, and a commercially available product (for example, manufactured by Kojundo Chemical Laboratory Co., Ltd.) can be appropriately used. Since a part of the tungsten oxide may be reduced to the V value, it is preferable to use it after firing it at a high temperature to oxidize it to the VI value. The crystal structure of tungsten oxide is not particularly limited, but a monoclinic system is preferable.

The average primary particle diameter (number average primary particle diameter) of the conductive metal oxide particles is preferably 8 to 1100 nm, more preferably 10 to 1000 nm, and further preferably 20 to 500 nm. If the average primary particle size is 8 nm or more, the cohesive force of the conductive metal oxide particles supporting the multi-electron reduction catalyst does not become too strong, and excellent dispersibility is obtained, and as a result, minute spots are less likely to occur. Become. Further, when the average primary particle diameter is 1100 nm or less, it is possible to suppress the generation of minute spots from the portion of the conductive metal oxide particles serving as a hole injection portion from the conductive support, which is preferable.

The number average primary particle diameter of the conductive metal oxide particles is a photograph in which a scanning electron microscope (for example, JSM-7500F manufactured by JEOL Ltd.) is used to take a 100,000-fold magnified photograph, and 300 particles are randomly captured by a scanner. The number average primary particle size is calculated from the image (excluding the agglomerated particles) using an automatic image processing analyzer “LUZEX (registered trademark) AP (software version Ver.1.32)” (manufactured by Nireco).

(Multi-electron reduction catalyst)
The multi-electron reduction catalyst serves as an acceptor of photo-induced electrons (a substance capable of receiving electrons), stores multiple electrons, and efficiently performs a reduction reaction.

The multi-electron reduction catalyst preferably contains at least one element selected from platinum, palladium, ruthenium, copper, iron, rhodium, gold, chromium, nickel, cerium and tungsten. Specifically, a metal, a metal compound, or the like containing at least one of the above elements can be used. Among these, it is preferable to contain platinum, palladium, ruthenium, copper, iron and tungsten. Moreover, copper and iron are more preferable from the viewpoint of being inexpensive and having high versatility. The element contained in the multi-electron reduction catalyst is preferably a metal element different from the metal element contained in the conductive metal oxide particles. If it is a multi-electron reduction catalyst containing a metal different from the metal element contained in the conductive metal oxide particles, by supporting it on the conductive metal oxide particles, a Schottky junction that connects the respective valence bodies occurs, resulting in multi-electron The carrier is easily transported through the conductive metal oxide particles via the reduction catalyst, which is preferable.

The above-mentioned multi-electron reduction catalyst may be supported on the conductive metal oxide particles in the state of a simple metal, or may be supported on the conductive metal oxide particles in the state of a metal compound. Examples of the metal compound include halides such as chlorides, bromides and iodides of the above metals; salts such as acetates, nitrates and sulfates; hydroxides and oxides. Carbides such as tungsten carbide can also be preferably used. Preferred are simple metals, metal hydroxides or oxides.

The multi-electron reduction catalyst is supported at a ratio of 0.00001 to 45 mass% with respect to the conductive metal oxide particles, although it depends on the number average primary particle diameter and the specific surface area of the conductive metal oxide particles. Is preferable, and it is more preferable that the carrier is supported in a proportion of 0.0001 to 40% by mass. The content is more preferably 0.001 to 30% by mass, still more preferably 0.002 to 10% by mass, and particularly preferably 0.003 to 1% by mass, based on the conductive metal oxide particles. When the amount of the multi-electron reduction catalyst supported is 0.00001% by mass or more based on the conductive metal oxide particles, sufficient sensitivity improvement can be obtained. On the other hand, when the supported amount of the multi-electron reduction catalyst is 45% by mass or less with respect to the conductive metal oxide particles, excellent dispersibility can be maintained and cost can be suppressed, which is preferable. Further, the effect of supporting the multi-electron reduction catalyst can be more remarkably obtained. When the multi-electron reduction catalyst contains the above metal element, it is preferable to control the supported amount of the metal to be in the above range with respect to the conductive metal oxide particles.

The conductive metal oxide particles carrying the multi-electron reduction catalyst are preferably contained in a proportion of 15 to 320 parts by mass, more preferably 20 to 300 parts by mass, relative to 100 parts by mass of the binder resin described below. , More preferably 50 to 200 parts by mass, still more preferably 50 to 150 parts by mass. When the amount is 15 parts by mass or more, the residual potential hardly rises, and the image stability can be effectively obtained. Further, when the amount is 320 parts by mass or less, the potential stability is excellent and, at the same time, the excellent hole blocking performance is maintained, so that minute spots are less likely to occur when a white solid image is printed. The ratio of the conductive metal oxide particles supporting the multi-electron reduction catalyst to the binder resin is the multi-electron reduction catalyst relative to 100 parts by mass of the total mass (solid content) of the polymerizable compounds such as the curable compound forming the binder resin. It may be determined as the mass ratio of the conductive metal oxide particles carrying.

(Method for preparing conductive metal oxide particles supporting multi-electron reduction catalyst)
The electroconductive metal oxide particles supporting the multi-electron reduction catalyst can be prepared by a known method by appropriately selecting the material and appropriately setting the preparation conditions.

For example, a multi-electron reduction catalyst to be supported is attached to the surface of the conductive metal oxide particles in an aqueous medium, filtered, dried, and then calcined by heating to convert the particles to support the multi-electron reduction catalyst. Conductive metal oxide particles can be obtained.

For example, the multi-electron reduction catalyst is bound to the multi-electron reduction catalyst by stirring the mixture containing the feedstock of the multi-electron reduction catalyst, the conductive metal oxide particles, the aqueous solvent, and the alkaline substance if necessary, or Adsorb and support.

Examples of the feedstock for the multi-electron reduction catalyst include metal chlorides, bromides, iodides, and other halides that make up the multi-electron reduction catalyst; acetates, nitrates, sulfates, and other acid conjugate bases; hydroxides, and the like. Can be mentioned. The feedstock for the multi-electron reduction catalyst may be anhydrous or hydrated. For example, cupric chloride (CuCl ₂ .2H ₂ O) or the like can be used as the feedstock for the divalent copper salt. Further, ferric chloride (FeCl ₃ ) or the like can be used as a feed material for the trivalent iron salt. The feed material for the multi-electron reduction catalyst is not particularly limited, but it is preferable to set the amount of the metal to be 0.002 to 800 mass% with respect to the conductive metal oxide particles.

Water is used as the aqueous solvent, but it may further contain a polar solvent other than water. As the polar solvent other than water, a material that dissolves the feedstock of the multi-electron reduction catalyst, water and an alkaline substance is used, and examples thereof include alcohols, ketones, and mixed solutions thereof. Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, dimethylformamide, tetrahydrofuran, or a mixture thereof.

Examples of the alkaline substance added as necessary include sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, triethylamine, trimethylamine, ammonia, and a basic surfactant.

The order of mixing and stirring the conductive metal oxide particles, the feedstock for the multi-electron reduction catalyst, the aqueous solvent, and, if necessary, the alkaline substance is not particularly limited. For example, it is preferable to first mix the conductive metal oxide particles with an aqueous solvent and, if necessary, agitate them, then mix the feed materials for the multi-electron reduction catalyst, and agitate them. However, first, the feedstock of the multi-electron reduction catalyst may be mixed with the aqueous solvent and stirred if necessary, and then the conductive metal oxide particles may be mixed and stirred. Further, the conductive metal oxide particles and the multi-electron reduction catalyst may be mixed in the solvent at the same time and stirred.

When the alkaline substance is added, it may be added at least at one of the three timings before, during, and after mixing the conductive metal oxide particles and/or the multi-electron reduction catalyst with the aqueous solvent. It is preferable that the conductive metal oxide particles and the multi-electron reduction catalyst are mixed with a solvent and sufficiently stirred before addition.

The stirring time is not particularly limited and is, for example, 5 to 120 minutes, preferably 10 to 90 minutes. The stirring temperature is not particularly limited, but is, for example, room temperature to about 120°C.

The conductive metal oxide particles to which the multi-electron reducing catalyst obtained as described above is attached can be separated as a solid content from the mixed liquid. This separation method is not particularly limited, and examples thereof include filtration, sedimentation separation, centrifugation, evaporation to dryness and the like.

The separated electroconductive metal oxide particles supporting the multi-electron reduction catalyst are washed with water and dried if necessary. The drying temperature is not particularly limited, but is, for example, 90 to 150°C.

If necessary, the conductive metal oxide particles carrying the multi-electron reduction catalyst can be obtained by drying and then heating and baking at 100 to 600° C. to convert into metal particles.

In addition, a commercially available product can be appropriately used (for example, copper-supported titanium oxide or copper-supported tungsten oxide manufactured by Showa Denko Ceramics Co., Ltd.: trade name Lumiresh (registered trademark)), or a commercially available product may be used as it is.

The specific forms of the multi-electron reduction catalyst and the conductive metal oxide carrying the multi-electron reduction catalyst are, for example, WO 2008/149889, JP 2013-184100 A, JP 2011-72961 A. Reference may be made to JP-A-2013-15669, JP-A-2009-226299, JP-A-2011-101876, JP-A-2012-114350, and JP-A-2011-20009.

Further, in order to improve the dispersibility, the hydrophobic treatment, and the adhesion between the particles and the resin, the conductive metal oxide particles may be surface-treated either before or after supporting the multi-electron reducing catalyst.

Examples of the surface treatment include a method of treating the conductive metal oxide particles with a surface modifier.

(Surface modifier)
The surface modifier is preferably a surface modifier that reacts with a hydroxy group or the like present on the surface of the conductive metal oxide particles, and examples of the surface modifier include a silane coupling agent and a titanium coupling agent. ..

Further, as the surface modifier, for example, a surface modifier having a reactive organic group is used, and as the surface modifier having a reactive organic group, a surface modifier having a radical polymerizable reactive group can be mentioned.

As the surface modifier having a radically polymerizable reactive group, a vinyl group, a silane coupling agent having a radically polymerizable reactive group such as an acryloyl group is preferable, and as the surface modifier having such a radically polymerizable reactive group, Known compounds as described below are exemplified.

_{S-1: CH 2 = CHSi} (CH 3) (OCH 3) 2
_{S-2: CH 2 = CHSi} (OCH 3) 3
_{S-3: CH 2 = CHSiCl} 3
_{S-4: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-5: CH 2 = CHCOO} (CH 2) 2 Si (OCH 3) 3
_{S-6: CH 2 = CHCOO} (CH 2) 2 Si (OC 2 H 5) (OCH 3) 2
_{S-7: CH 2 = CHCOO} (CH 2) 3 Si (OCH 3) 3
_{S-8: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) Cl 2
_{S-9: CH 2 = CHCOO} (CH 2) 2 SiCl 3
_{S-10: CH 2 = CHCOO} (CH 2) 3 Si (CH 3) Cl 2
_{S-11: CH 2 = CHCOO} (CH 2) 3 SiCl 3
_{S-12: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-13: CH 2 = C} (CH 3) COO (CH 2) 2 Si (OCH 3) 3
_{S-14: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-15: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OCH 3) 3
_{S-16: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) Cl 2
_{S-17: CH 2 = C} (CH 3) COO (CH 2) 2 SiCl 3
_{S-18: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) Cl 2
_{S-19: CH 2 = C} (CH 3) COO (CH 2) 3 SiCl 3
_{S-20: CH 2 = CHSi} (C 2 H 5) (OCH 3) 2
_{S-21: CH 2 = C} (CH 3) Si (OCH 3) 3
_{S-22: CH 2 = C} (CH 3) Si (OC 2 H 5) 3
_{S-23: CH 2 = CHSi} (OCH 3) 3
_{S-24: CH 2 = C} (CH 3) Si (CH 3) (OCH 3) 2
_{S-25: CH 2 = CHSi} (CH 3) Cl 2
_{S-26: CH 2 = CHCOOSi} (OCH 3) 3
_{S-27: CH 2 = CHCOOSi} (OC 2 H 5) 3
_{S-28: CH 2 = C} (CH 3) COOSi (OCH 3) 3
_{S-29: CH 2 = C} (CH 3) COOSi (OC 2 H 5) 3
_{S-30: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OC 2 H 5) 3
_{S-31: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) 2 (OCH 3)
_{S-32: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OCOCH 3) 2
_{S-33: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (ONHCH 3) 2
_{S-34: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OC 6 H 5) 2
_{S-35: CH 2 = CHCOO} (CH 2) 2 Si (C 10 H 21) (OCH 3) 2
_{S-36: CH 2 = CHCOO} (CH 2) 2 Si (CH 2 C 6 H 5) (OCH 3) 2
As the surface modifier, a silane compound having a radically polymerizable reactive organic group other than S-1 to S-36 may be used. These surface modifiers can be used alone or in admixture of two or more.

(Method for producing surface-modified conductive metal oxide particles)
When the surface is modified, treatment is carried out using a wet media dispersion type apparatus with a surface modifier of 0.1 to 100 parts by mass and a solvent of 50 to 5000 parts by mass with respect to 100 parts by mass of the particles. Is preferred. It can also be processed by a dry method.

Hereinafter, a method for uniformly modifying the surface with the surface modifier will be described.

That is, by wet-milling a slurry (suspension of solid particles) containing conductive metal oxide particles and a surface modifier, the conductive metal oxide particles are miniaturized and at the same time surface modification of the particles proceeds. Then, the solvent is removed and the powder is made into powder, whereby conductive metal oxide particles whose surface is uniformly modified with a surface modifier can be obtained.

A wet media dispersion type device, which is a surface modification device used in the present invention, is a conductive metal oxidation device that is prepared by filling beads in a container as media and rotating a stirring disk mounted perpendicular to the rotation axis at high speed. It is an apparatus having a process of crushing aggregated particles of a product and pulverizing and dispersing. As its configuration, when the surface modification is performed on the conductive metal oxide particles, there is no problem as long as the conductive metal oxide particles are sufficiently dispersed and the surface can be modified, for example, vertical type/horizontal type, continuous type. Various modes such as a formula and a batch system can be adopted.

Specifically, a sand mill, ultra visco mill, pearl mill, grain mill, dyno mill, agitator mill, dynamic mill and the like can be used. These dispersion type devices perform fine pulverization and dispersion by impact crushing, friction, shearing, shear stress, etc. using a pulverizing medium (media) such as balls and beads.

As the beads used in the wet media dispersion type apparatus, balls made of glass, alumina, zircon, zirconia, steel, flint stone, etc. can be used, but those made of zirconia or zircon are particularly preferable.

The size of the beads is usually about 1 to 2 mm in diameter, but in the present invention, it is preferably about 0.1 to 1.0 mm.

Although various materials such as stainless steel, nylon, and ceramics can be used for the disk and the inner wall of the container used in the wet media dispersion type device, in the present invention, especially the disk and the inner wall of the ceramic such as zirconia or silicon carbide are used. Is preferred.

By the wet treatment as described above, the conductive metal oxide particles surface-modified with the surface modifier can be obtained.

(Binder resin)
The photoreceptor of the present invention preferably contains a binder resin in the intermediate layer as described above.

The binder resin is not particularly limited, but binder resins such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane and gelatin can be used. The intermediate layer can be formed by dispersing and dissolving electrically conductive metal oxide particles carrying a multi-electron reduction catalyst and a binder resin in a known solvent and dipping and coating. Among the binder resins, alcohol-soluble polyamide resin is preferable.

As a solvent that can be used for forming the intermediate layer, a solvent that satisfactorily disperses the conductive metal oxide particles supporting the above-mentioned multi-electron reduction catalyst and dissolves a binder resin such as a polyamide resin is preferable. Specifically, alcohols having 2 to 4 carbon atoms, such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol, etc., are preferable as the binder resin for the polyamide resin. It is preferable because it exhibits good solubility and coating performance.

Further, in order to improve the storage stability and the dispersibility of the inorganic particles, a cosolvent can be used in combination with the solvent, and examples of the cosolvent having a preferable effect include benzyl alcohol, toluene, cyclohexanone, and tetrahydrofuran. Etc.

The binder resin concentration at the time of forming the coating liquid can be appropriately selected according to the film thickness of the intermediate layer and the coating method. Further, when the conductive metal oxide particles supporting the multi-electron reducing catalyst described above are dispersed, the mixing ratio of the conductive metal oxide particles supporting the multi-electron reducing catalyst to the binder resin is 100 parts by mass of the binder resin. On the other hand, the conductive metal oxide particles supporting the multi-electron reduction catalyst can be used, for example, in the range of 15 to 320 parts by mass, preferably in the range of 20 to 300 parts by mass, and 50 to 200 parts by mass. It is more preferably within the range of parts, and even more preferably within the range of 50 to 150 parts by mass.

An ultrasonic disperser, a ball mill, a bead mill, a sand grinder, a homomixer, or the like can be used as a dispersing means for the conductive metal oxide particles carrying the multi-electron reducing catalyst, but the dispersing means is not limited thereto. Further, the coating liquid for the intermediate layer can prevent the occurrence of image defects by filtering foreign matters and aggregates before coating.

As the method for drying the intermediate layer, a known drying method can be appropriately selected according to the type of solvent and the film thickness to be formed, and heat drying is particularly preferable. The drying conditions can be, for example, heat drying at 100 to 150° C. for 10 to 60 minutes.

The thickness of the intermediate layer is preferably 0.1 to 15 μm, more preferably 0.3 to 10 μm.

(Conductive support)
The conductive support used in the present invention may be any one as long as it has conductivity, for example, a metal such as aluminum, copper, chromium, nickel, zinc and stainless formed into a drum or a sheet. , A metal foil such as aluminum or copper laminated on a plastic film, aluminum, indium oxide, tin oxide, etc. deposited on a plastic film, a metal on which a conductive substance is applied alone or with a binder resin to form a conductive layer. , Plastic films and paper.

(Photosensitive layer)
As described above, the photosensitive layer constituting the photoconductor of the present invention has a single-layer structure in which a charge generating function and a charge transporting function are provided in one layer, as well as a charge generating layer (CGL) and a charge transporting layer (CGL). More preferably, it has a layer structure in which the function of the photosensitive layer is separated from that of CTL).

In this way, the function-separated type layer structure has a merit that the increase in residual potential due to repeated use can be controlled to be small, and various electrophotographic characteristics can be easily controlled according to the purpose.

Each layer of the photosensitive layer of the function-separated type negative charging photoreceptor will be described below as a specific example of the photosensitive layer.

(Charge generation layer)
The charge generating layer formed in the present invention preferably contains a charge generating substance and a binder resin, and is formed by applying a coating liquid obtained by dispersing the charge generating substance in a binder resin solution. Those are more preferable.

Charge generating substances include azo raw materials such as Sudan Red and Diane Blue, quinone pigments such as pyrenequinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, and polycyclic quinone pigments such as pyranthrone and diphthaloylpyrene. , Phthalocyanine pigments, titanyl phthalocyanine pigments, and the like, but are not limited thereto. Among these, polycyclic quinone pigments and titanyl phthalocyanine pigments are preferable. These charge generating substances can be used alone or in the form of being dispersed in a known binder resin.

As the binder resin forming the charge generation layer, known resins can be used, and examples thereof include polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, and epoxy. Resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and copolymer resin containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resin). , Vinyl chloride-vinyl acetate-maleic anhydride copolymer resin), poly-vinylcarbazole resin, and the like, but are not limited thereto.

The charge generation layer is formed by dispersing a charge generation substance in a solution in which a binder resin is dissolved with a solvent to prepare a coating solution, applying the coating solution with a coating machine to a constant film thickness, and applying the coating solution. It is preferable to make the membrane by drying.

As a solvent for dissolving and coating the binder resin used in the charge generation layer, for example, toluene, xylene, methyl ethyl ketone, cyclohexane, ethyl acetate, t-butyl acetate, methanol, ethanol, propanol, butanol, methyl cellosolve, 4- Examples thereof include, but are not limited to, methoxy-4-methyl-2-pentanone, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine and diethylamine. Further, two or more kinds of solvents may be used in combination.

An ultrasonic disperser, a ball mill, a sand mill, a sand grinder, a homomixer, or the like can be used as the means for dispersing the charge-generating substance, but it is not limited thereto.

The mixing ratio of the charge generating substance to the binder resin is preferably in the range of 1 to 600 parts by mass, more preferably in the range of 50 to 500 parts by mass with respect to 100 parts by mass of the binder resin. The thickness of the charge generation layer varies depending on the characteristics of the charge generation substance, the characteristics of the binder resin, the mixing ratio, etc., but is preferably within the range of 0.01 to 5 μm, more preferably within the range of 0.05 to 3 μm.

The coating liquid for the charge generation layer can prevent the generation of image defects by filtering foreign matters and aggregates before coating. The charge generation layer can also be formed by vacuum-depositing a charge generation substance such as the above pigment.

(Charge transport layer)
The charge transport layer formed in the present invention preferably contains at least a charge transport substance and a binder resin in the layer, and can be formed by dissolving and coating the charge transport substance in a binder resin solution.

A known compound can be used as the charge transport material, and examples thereof include the following. That is, carbazole derivative, oxazole derivative, oxadiazole derivative, thiazole derivative, thiadiazole derivative, triazole derivative, imidazole derivative, imidazolone derivative, imidazolidine derivative, bisimidazolidine derivative, styryl compound, hydrazone compound, pyrazoline compound, oxazolone derivative, benz Imidazole derivative, quinazoline derivative, benzofuran derivative, acridine derivative, phenazine derivative, aminostilbene derivative, triarylamine derivative, phenylenediamine derivative, stilbene derivative, benzidine derivative, poly-N-vinylcarbazole, poly-1-vinylpyrene and poly-9 -Vinyl anthracene and the like. These compounds can be used alone or in combination of two or more.

As the binder resin for the charge transport layer, a known resin can be used, and examples thereof include the following. That is, a polycarbonate resin, a polyacrylate resin, a polyester resin, a polystyrene resin, a styrene-acrylonitrile copolymer resin, a polymethacrylic acid ester resin, a styrene-methacrylic acid ester copolymer resin, etc. may be mentioned. Among these, polycarbonate resins are preferable, and further, polycarbonate resins of the types such as bisphenol A (BPA), bisphenol Z (BPZ), dimethyl BPA, and BPA-dimethyl BPA copolymer have crack resistance, abrasion resistance, and charging characteristics. It is preferable from the viewpoint of.

The charge transport layer can be formed by a known method typified by a coating method. For example, in the coating method, a binder resin and a charge transport substance are dissolved to prepare a coating solution, and the coating solution is kept constant. A desired charge-transporting layer can be formed by applying a coating film having the above thickness and drying it.

Examples of the solvent that dissolves the binder resin and the charge transport material include toluene, xylene, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, tetrahydrofuran, 1,4-dioxane, 1,3. -Dioxolane and the like. The solvent used when preparing the coating liquid for forming the charge transport layer is not limited to the above. Further, two or more kinds of solvents may be used in combination.

The mixing ratio of the binder resin and the charge transport material is preferably in the range of 10 to 500 parts by mass, and more preferably in the range of 20 to 100 parts by mass with respect to 100 parts by mass of the binder resin. More preferable.

The thickness of the charge transport layer varies depending on the characteristics of the charge transport substance and the binder resin, the mixing ratio of these, and the like, but is preferably within the range of 5 to 40 μm, more preferably within the range of 10 to 30 μm.

Known antioxidants, electronic conductive agents, stabilizers, silicone oils and the like may be added to the charge transport layer. The antioxidants described in JP-A-2000-305291 and the electronic conductive agents described in JP-A-50-137543 and JP-A-58-76843 can be preferably used.

(Method of coating each layer constituting the photoconductor)
Each layer such as the intermediate layer, the charge generation layer, the charge transport layer, and the surface protective layer which constitute the photoreceptor of the present invention can be formed by a known coating method.

Specific examples include a dip coating method, a spray coating method, a spin coating method, a bead coating method, a blade coating method, a beam coating method, and a circular amount regulation type coating method.

The circular amount control type coating method is described in, for example, JP-A-58-189061 and JP-A-2005-275373.

(Protective layer)
The electrophotographic photoreceptor of the present invention may further have a protective layer on the photosensitive layer. The protective layer plays a role of protecting the photoconductor from the external environment and impact. When the protective layer is formed, the protective layer preferably contains inorganic particles and a binder resin (hereinafter, also referred to as “binder resin for protective layer”), and if necessary, an antioxidant or a lubricant. Other components may be included.

The inorganic particles contained in the protective layer may be any metal oxide particles including a transition metal, for example, silica (silicon oxide), magnesium oxide, zinc oxide, lead oxide, alumina (aluminum oxide), Examples thereof include metal oxide particles such as zirconium oxide, tin oxide, titania (titanium oxide), niobium oxide, molybdenum oxide, and vanadium oxide. Among them, tin oxide, titanium oxide, zinc oxide, and alumina are preferable.

The method for producing the inorganic particles is not particularly limited, and particles produced by a known production method can be used.

The number average primary particle size of the inorganic particles is preferably in the range of 1 to 300 nm. It is particularly preferably 3 to 100 nm, further preferably 5 to 40 nm.

Regarding the number average primary particle diameter of the above-mentioned inorganic particles, a photographic image obtained by taking a 10,000 times magnified photograph with a scanning electron microscope (manufactured by JEOL Ltd.) and randomly incorporating 300 particles with a scanner (excluding agglomerated particles) Automatic image processing analyzer LUZEX (registered trademark) AP (manufactured by Nireco) software version Ver. The number average primary particle size can be calculated using 1.32.

The inorganic particles are preferably treated with a surface modifier. The specific form of the method for producing the surface modifier and the inorganic particles modified with the surface modifier is the same as the above-mentioned surface modifier for the conductive metal oxide particles and the method for producing the surface modified conductive metal oxide particles. ..

(Binder resin for protective layer)
The binder resin used in the protective layer preferably contains a resin made of a polymer of a polymerizable compound.

The resin that is a polymer obtained by polymerizing a polymerizable compound is preferably a curable resin or a thermoplastic resin that is a cured product obtained by curing a curable compound, and particularly, a high film strength is obtained. Therefore, a curable resin is preferable.

Examples of the thermoplastic resin include resins made of vinyl polymers such as polystyrene resin, polyacrylic resin, polymethacrylic resin, polyvinyl acetate resin, polyvinyl alcohol resin, and polyvinyl butyral resin. Further, a condensation type polymer material such as a polyester resin, a polycarbonate resin, an epoxy resin or a polyurethane resin can be used.

When a curable resin obtained by curing a curable compound is used as the binder resin, the curable compound usable in the protective layer may be a radically polymerizable compound.

As the radically polymerizable compound, a polymerizable monomer having at least one of an acryloyl group and a methacryloyl group as a radically polymerizable reactive group is preferable.

Examples of these polymerizable monomers include the following compounds, but the polymerizable monomers usable in the present invention are not limited thereto.

The above radically polymerizable compounds are known and are available as commercial products. Here, R represents the following acryloyl group and R'represents the following methacryloyl group.

In addition to these, the protective layer of the photoreceptor of the present invention may contain a polymerization initiator, lubricant particles and the like, if necessary.

(Polymerization initiator)
As a method for curing the curable compound usable in the protective layer, a curing reaction can be performed by a method utilizing an electron beam cleavage reaction or a method utilizing light or heat in the presence of a radical polymerization initiator. ..

When performing a curing reaction using a radical polymerization initiator, both a photopolymerization initiator and a thermal polymerization initiator can be used as a polymerization initiator. Further, both light and heat initiators can be used together.

The polymerization initiator that can be used in the present invention includes 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylazobisvaleronitrile) and 2,2'-azobis(2- Azo compounds such as methylbutyronitrile), benzoyl peroxide (BPO), di-tert-butyl hydroperoxide, tert-butyl hydroperoxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide And a thermal polymerization initiator such as a peroxide.

Further, as the photopolymerization initiator, diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 4-(2-hydroxyethoxy)phenyl- (2-hydroxy-2-propyl)ketone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone (Irgacure (registered trademark) 369: manufactured by BASF Japan Ltd.), 2-hydroxy. 2-Methyl-1-phenylpropan-1-one, 2-methyl-2-morpholino(4-methylthiophenyl)propan-1-one, 1-phenyl-1,2-propanedione-2-(o-ethoxy Carbonyl) oxime and other acetophenone or ketal photoinitiators, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, benzoin ether photoinitiators such as benzoin isopropyl ether, benzophenone, 4-hydroxybenzophenone, o -Methyl benzoylbenzoate, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoylphenyl ether, acrylated benzophenone, benzophenone-based photopolymerization initiators such as 1,4-benzoylbenzene, 2-isopropylthioxanthone, 2-chlorothioxanthone , 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, and other thioxanthone-based photopolymerization initiators.

Other photopolymerization initiators include ethylanthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine. Oxide (Irgacure (registered trademark) 819: manufactured by BASF Japan Ltd.), bis(2,4-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10-phenanthrene, acridine-based Examples thereof include compounds, triazine compounds, and imidazole compounds.

Further, those having a photopolymerization promoting effect can be used alone or in combination with the above photopolymerization initiator. For example, triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino)ethyl benzoate, 4,4'-dimethylaminobenzophenone and the like can be mentioned.

The polymerization initiator used in the present invention is preferably a photopolymerization initiator, preferably an alkylphenone compound, a phosphine oxide compound, more preferably an α-hydroxyacetophenone structure or an initiator having an acylphosphine oxide structure. preferable.

You may use these polymerization initiators individually or in mixture of 2 or more types. The content of the polymerization initiator is within the range of 0.1 to 40 parts by mass, preferably within the range of 0.5 to 20 parts by mass with respect to 100 parts by mass of the polymerizable compound.

(Lubricant particles)
It is also possible to incorporate various lubricant particles in the protective layer. For example, fluorine atom-containing resin particles can be added.

The fluorine atom-containing resin particles include tetrafluoroethylene resin, trifluorochloroethylene resin, hexafluorochloroethylene propylene resin, vinyl fluoride resin, vinylidene fluoride resin, difluorodichloroethylene resin, and these It is preferable to appropriately select one kind or two or more kinds from the copolymer, and a tetrafluoroethylene resin and a vinylidene fluoride resin are particularly preferable.

(solvent)
As the solvent used for forming the protective layer, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, benzyl alcohol, methyl isopropyl ketone, methyl isobutyl ketone. , Methyl ethyl ketone, cyclohexane, toluene, xylene, methylene chloride, ethyl acetate, butyl acetate, 2-methoxyethanol, 2-ethoxyethanol, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine and diethylamine. It is not limited to.

(Formation of protective layer)
The protective layer is a binder resin (or a polymerizable compound such as a radically polymerizable curable compound), and conductive oxide particles carrying the above-mentioned multi-electron reduction catalyst, a known resin if necessary, and a polymerization initiator. A coating solution prepared by adding lubricant particles, antioxidants, etc. can be applied to the surface of the photosensitive layer by a known method, naturally dried or heat-dried, and then cured to prepare.

The thickness of the protective layer is preferably in the range of 0.2 to 10 μm, more preferably in the range of 0.5 to 6 μm.

In the present invention, the protective layer is cured by irradiating the coating film with actinic rays to generate radicals and polymerizing, and by forming a cross-linking bond due to a cross-linking reaction between the molecules to cure the curable resin. It is preferable to generate. As the actinic rays, light such as ultraviolet rays and visible light and electron rays are preferable, and ultraviolet rays are particularly preferable from the viewpoint of ease of use.

As the ultraviolet light source, any light source that emits ultraviolet light can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, a flash (pulse) xenon, an ultraviolet LED, etc. can be used.

Irradiation conditions differ depending on the respective lamps, but the irradiation dose of actinic radiation is usually in the range of 1 to ²⁰ mJ/cm ² , and preferably in the range of 5 to 15 mJ/cm ² . The output voltage of the light source is preferably in the range of 0.1 to 5 kW, particularly preferably in the range of 0.5 to 3 kW.

As the electron beam source, there is no particular limitation on the electron beam irradiation apparatus, and generally, as such an electron beam accelerator for electron beam irradiation, a curtain beam system that can obtain a large output at a relatively low cost is effective. Used.

The acceleration voltage at the time of electron beam irradiation is preferably in the range of 100 to 300 kV. The absorbed dose is preferably in the range of 0.005 Gy to 100 kGy (0.5 to 10 Mrad).

The irradiation time of the actinic ray is a time at which the required irradiation amount of the actinic ray is obtained, and specifically, it is preferably in the range of 0.1 seconds to 10 minutes, and from the viewpoint of curing efficiency or work efficiency, 1 second to 5 minutes. It is considered that the range is more preferable.

In the present invention, the surface protective layer can be dried before and after irradiation with actinic rays and during irradiation with actinic rays, and the timing of drying can be appropriately selected in combination with the irradiation conditions of actinic rays.

The conditions for drying the protective layer can be appropriately selected depending on the type of solvent used in the coating liquid, the film thickness of the protective layer, and the like. Further, the drying temperature is preferably in the range of room temperature to 180°C, particularly preferably in the range of 80 to 140°C. The drying time is preferably within the range of 1 to 200 minutes, particularly preferably within the range of 5 to 100 minutes.

[Image forming apparatus and image forming method]
The photoconductor of the present invention can be provided in a general electrophotographic image forming apparatus. Further, the photoconductor of the present invention can be preferably used in an image forming method using the image forming apparatus.

The image forming method will be described below together with the image forming apparatus.

An image forming apparatus that achieves the effects of the present invention is preferably (1) an electrophotographic photosensitive member of the present embodiment, (2) a charging unit that charges the surface of the electrophotographic photosensitive member described above, and (3) a charging unit. By exposing means for exposing the surface of the formed electrophotographic photosensitive member to form a latent image, (4) developing means for visualizing the latent image formed by the exposing means to form a toner image, and (5) developing means. And a transfer means for transferring the toner image formed on the surface of the electrophotographic photosensitive member onto a transfer medium such as paper or a transfer belt.

A non-contact charging device is preferably used as the charging means for charging the electrophotographic photosensitive member. Examples of the non-contact charging device include a corona charging device, a corotron charging device, and a scorotron charging device.

FIG. 1 is a cross-sectional configuration diagram illustrating an example of a color image forming apparatus according to an embodiment of the present invention.

This color image forming apparatus is called a tandem type color image forming apparatus, and it includes four sets of image forming units (image forming units) 10Y, 10M, 10C and 10Bk, an endless belt-shaped intermediate transfer body unit 7, and a sheet feeding unit. It has a paper conveying means 21 and a fixing means 24. A document image reading device SC is arranged above the main body A of the image forming apparatus.

The image forming unit 10Y that forms a yellow image includes a charging unit (charging process) 2Y and an exposure unit (exposure process) 3Y that are arranged around a drum-shaped electrophotographic photosensitive member 1Y as a first image carrier. It has a developing means (developing step) 4Y, a primary transfer roller 5Y as a primary transfer means (primary transfer step), and a cleaning means 6Y.

The image forming unit 10M that forms a magenta image includes a drum-shaped electrophotographic photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a primary transfer roller as a primary transfer unit. 5M, cleaning means 6M.

The image forming unit 10C that forms a cyan image is a drum-shaped electrophotographic photosensitive member 1C as a first image carrier, a charging unit 2C, an exposing unit 3C, a developing unit 4C, and a primary transfer roller as a primary transfer unit. 5C and cleaning means 6C.

The image forming unit 10Bk that forms a black image includes a drum-shaped electrophotographic photosensitive member 1Bk as a first image carrier, a charging unit 2Bk, an exposing unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk as a primary transfer unit, It has a cleaning means 6Bk.

The four sets of image forming units 10Y, 10M, 10C, and 10Bk are mainly composed of the electrophotographic photoconductors 1Y, 1M, 1C, and 1Bk, and charging means 2Y, 2M, 2C, 2Bk, image exposing means 3Y, 3M, and 3C. 3Bk, developing means 4Y, 4M, 4C, 4Bk, and cleaning means 6Y, 6M, 6C, 6Bk for cleaning the electrophotographic photoconductors 1Y, 1M, 1C, 1Bk.

The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the toner images formed on the electrophotographic photoconductors 1Y, 1M, 1C, and 1Bk are different, and the image forming unit 10Y is used as an example. Will be described in detail.

The image forming unit 10Y has a charging unit 2Y (hereinafter simply referred to as a charging unit 2Y or a charger 2Y), an exposing unit 3Y, a developing unit 4Y, and a cleaning unit 6Y around an electrophotographic photosensitive member 1Y which is an image forming body. Hereinafter, the cleaning unit 6Y or the cleaning blade 6Y) is simply arranged to form a yellow (Y) toner image on the electrophotographic photosensitive member 1Y. Further, in the present embodiment, at least the electrophotographic photosensitive member 1Y, the charging unit 2Y, the developing unit 4Y, and the cleaning unit 6Y of the image forming unit 10Y are provided so as to be integrated.

The charging unit 2Y is a unit that applies a uniform potential to the electrophotographic photosensitive member 1Y, and in the present embodiment, a corona discharge type charger 2Y is used for the electrophotographic photosensitive member 1Y.

The exposure unit 3Y forms an electrostatic latent image corresponding to a yellow image by performing exposure based on the image signal (yellow) on the electrophotographic photosensitive member 1Y to which a uniform potential is applied by the charger 2Y. As the exposing means 3Y, as the exposing means 3Y, LEDs and image forming elements (trade name: SELFOC (registered trademark) lens; manufactured by Nippon Sheet Glass Co., Ltd., which are arranged in an array form in the axial direction of the electrophotographic photosensitive member 1Y ) And a laser optical system or the like.

The developing unit 4Y is configured to supply toner to the electrophotographic photosensitive member 1Y and develop the electrostatic latent image formed on the surface of the electrophotographic photosensitive member 1Y.

The cleaning unit 6Y may have a roller or a blade that comes into pressure contact with the surface of the electrophotographic photosensitive member 1Y.

The endless belt-shaped intermediate transfer member unit 7 is provided so as to be able to contact the electrophotographic photosensitive members 1Y, 1M, 1C, and 1Bk. The endless belt-shaped intermediate transfer member unit 7 includes an endless belt-shaped intermediate transfer member 70 which is a second image carrier, and primary transfer rollers 5Y, 5M, 5C arranged in contact with the endless belt-shaped intermediate transfer member 70. 5Bk, and a cleaning means 6b for the endless belt-shaped intermediate transfer member 70.

The endless belt-shaped intermediate transfer member 70 is wound by a plurality of rollers 71, 72, 73, 74 and is rotatably supported.

The image forming apparatus of the present invention is configured by integrally combining the above-described photoconductor and the constituent elements such as a developing unit and a cleaning unit as a process cartridge (image forming unit), and this image forming unit with respect to the apparatus main body. It may be configured to be removable.

In addition, at least one of the charging unit, the exposing unit, the developing unit, the primary transfer roller, and the cleaning unit is integrally supported with the photoconductor to form a process cartridge (image forming unit), which is detachably attached to the main body of the apparatus. The image forming unit may be detachable by using guide means such as a rail of the apparatus main body.

The process cartridge 8 includes a casing, an electrophotographic photosensitive member 1Y, a charging unit 2Y, a developing unit 4Y, a cleaning unit 6Y, and an endless belt-shaped intermediate transfer unit 7, which are housed in the casing. Support rails 82L and 82R are provided in the apparatus body as means for guiding the process cartridge 8 into the apparatus body. As a result, the process cartridge 8 can be attached to and detached from the apparatus main body. These process cartridges 8 can be a single image forming unit detachably attached to the apparatus main body.

The sheet feeding/conveying means 21 is provided so that the transfer material P in the sheet feeding cassette 20 can be conveyed to the secondary transfer roller 5b via the plurality of intermediate rollers 22A, 22B, 22C, 22D and the registration roller 23.

The fixing unit 24 fixes the color image transferred by the secondary transfer roller 5b. The paper discharge roller 25 is provided so as to sandwich the transfer material P, which has been subjected to the fixing process, and can be placed on a paper discharge tray 26 provided outside the image forming apparatus.

In the image forming apparatus A thus configured, the image is formed by the image forming units 10Y, 10M, 10C and 10Bk. Specifically, the charging means 2Y, 2M, 2C, and 2Bk charge the surfaces of the electrophotographic photosensitive members 1Y, 1M, 1C, and 1Bk by corona discharge to negatively charge them. Next, the surfaces of the electrophotographic photoconductors 1Y, 1M, 1C and 1Bk are exposed by the exposing means 3Y, 3M, 3C and 3Bk based on the image signal to form an electrostatic latent image. Next, the developing means 4Y, 4M, 4C, and 4Bk apply toner to the surfaces of the electrophotographic photoconductors 1Y, 1M, 1C, and 1Bk to develop.

Next, the primary transfer rollers (primary transfer means) 5Y, 5M, 5C, and 5Bk are brought into contact with the rotating endless belt-shaped intermediate transfer member 70. As a result, the images of the respective colors formed on the electrophotographic photoconductors 1Y, 1M, 1C, and 1Bk are sequentially transferred onto the rotating endless belt-shaped intermediate transfer member 70 to transfer the color image (primary transfer). ). During the image forming process, the primary transfer roller 5Bk constantly contacts the electrophotographic photosensitive member 1Bk. On the other hand, the other primary transfer rollers 5Y, 5M, and 5C contact the corresponding electrophotographic photoconductors 1Y, 1M, and 1C only when forming a color image.

Then, after separating the primary transfer rollers 5Y, 5M, 5C, 5Bk and the endless belt-shaped intermediate transfer body 70, the toner remaining on the surfaces of the electrophotographic photoconductors 1Y, 1M, 1C, 1Bk is cleaned by the cleaning means 6Y. Remove with 6M, 6C, 6Bk. Then, in preparation for the next image formation, the surface of the electrophotographic photosensitive member 1Y, 1M, 1C, 1Bk is neutralized by a neutralizing unit (not shown) as necessary, and then negatively charged by the charging unit 2Y, 2M, 2C, 2Bk. To charge.

On the other hand, a transfer material P (for example, a support member carrying a final image such as plain paper or a transparent sheet) housed in the paper feed cassette 20 is fed by the paper feed/conveyance means 21 and a plurality of intermediate rollers 22A, 22B. , 22C, 22D, and the resist roller 23, and is conveyed to the secondary transfer roller (secondary transfer means) 5b. Then, the secondary transfer roller 5b is brought into contact with the rotating endless belt-shaped intermediate transfer member 70 to collectively transfer the color image onto the transfer material P (secondary transfer). The secondary transfer roller 5b contacts the endless belt-shaped intermediate transfer member 70 only when performing the secondary transfer on the transfer material P. After that, the transfer material P to which the color images are collectively transferred is separated at a portion of the endless belt-shaped intermediate transfer body 70 having a high curvature.

The transfer material P on which the color images are collectively transferred in this manner is fixed by the fixing means 24, and then is sandwiched by the paper discharge rollers 25 and placed on the paper discharge tray 26 outside the apparatus. Here, a transfer support for a toner image formed on a photoconductor such as an intermediate transfer body or a transfer material is generically called a transfer medium. Further, after the transfer material P to which the color images are collectively transferred is separated from the endless belt-shaped intermediate transfer body 70, the residual toner on the endless belt-shaped intermediate transfer body 70 is removed by the cleaning means 6b.

In the image forming apparatus of the present invention, the toner image formed on the surface of the electrophotographic photosensitive member by the developing unit is transferred onto a transfer medium such as paper or a transfer belt, and then the surface of the electrophotographic photosensitive member is charged by the charging unit. Before charging, it is preferable not to have a charge eliminating means for eliminating residual charges on the surface of the electrophotographic photosensitive member. If the intermediate layer does not have sufficient charge transportability without a charge eliminating means, a difference in post-exposure potential between the non-exposed portion and the exposed portion occurs, so that the post-exposure potential increases during the repetition of the electrophotographic process, resulting in blackening. When a solid image is printed, an image density difference occurs in the photoconductor cycle. However, since the electrophotographic photosensitive member of the present invention is excellent in the charge transport property of the intermediate layer, a difference in post-exposure potential is unlikely to occur even when a charge eliminating means such as a charge eliminating lamp or a precharge lamp is not used. Therefore, a stable image is formed. Therefore, the cost of the image forming apparatus can be reduced by not using the charge removing unit.

For example, in the image forming apparatus shown in FIG. 1, the toner image formed on the surface of the electrophotographic photosensitive member by the developing unit is transferred onto the endless belt-shaped intermediate transfer member 70 (transfer belt), and the electrophotographic photosensitive members 1Y and 1M are transferred. After removing the residual toner by cleaning the surfaces of 1C, 1Bk, and before the next charging, a charge removing means for removing the residual charge on the surfaces of the electrophotographic photosensitive members 1Y, 1M, 1C, 1Bk is provided. It can have no form.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, “parts” or “%” is used, but unless otherwise specified, “parts by mass” or “% by mass” is indicated.

[Example 1]
<Production of Photoreceptor 1>
An intermediate layer, a charge generation layer, and a charge transport layer were sequentially laminated on a conductive support shown below to prepare a photoconductor 1.

(Conductive support)
A conductive support of a cylindrical aluminum support having a diameter of 30 mm was prepared.

(Middle layer)
Preparation of TiO ₂ /Cu ²⁺ Compound 1 Rutile TiO ₂ powder (MT-150A, number average primary particle size 100 nm, manufactured by Teika Co., Ltd.) was used as conductive metal oxide particles, and fine particles of TiO ₂ were used in distilled water. And TiO ₂ is suspended in water at a concentration of 10% by mass, and then CuCl ₂ .2H ₂ O (manufactured by Wako Pure Chemical Industries, Ltd.) is added to Cu(II) with respect to TiO ₂ . It was added in an amount of 0.1% by mass, heated to 90° C. with stirring and held for 1 hour. Next, the obtained suspension was filtered by suction filtration, the residue was washed with distilled water and further dried by heating at 110° C. to obtain TiO ₂ fine particles carrying a divalent copper salt.

The obtained copper divalent salt-supporting TiO ₂ fine particles were subjected to inductively coupled plasma emission spectrometry (ICP-AES, P-4010, HITACHI) and polarized Zeeman atomic absorption spectrometry (Polarized Zeeman AAS, Z-2000, HITACHI) to form Cu(II ) When the carried amount was evaluated, 0.0050 mass% (5 mass% of the charged amount) was carried with respect to TiO ₂ .

100 parts by mass of a polyamide resin (CM8000 manufactured by Toray Industries, Inc.) as a binder resin was added to 1700 parts by mass of a mixed solvent of ethanol/n-propyl alcohol/tetrahydrofuran (volume ratio 45/20/35), and mixed by stirring at 20°C. did. 100 parts by mass of the copper divalent salt-supporting TiO ₂ fine particles prepared above were added to this solution and dispersed by a bead mill at a mill residence time of 5 hours. Then, this solution was allowed to stand for a whole day and night and then filtered to obtain an intermediate layer coating solution. Filtration was performed under a pressure of 50 kPa using a Rigimesh filter (manufactured by Nippon Pall Ltd.) having a nominal filtration accuracy of 5 μm as a filtration filter. The intermediate layer coating solution thus obtained was applied to the outer periphery after washing the above-mentioned support by a dip coating method and dried at 120° C. for 30 minutes to form an intermediate layer having a dry film thickness of 2 μm.

(Charge generation layer)
Charge generating substance: Titanyl phthalocyanine pigment (Cu-Kα characteristic X-ray diffraction spectrum measurement, titanyl phthalocyanine pigment having a maximum diffraction peak at a position of at least 27.3°) 20 parts by mass Polyvinyl butyral resin (#6000-C: electrochemical (Manufactured by Kogyo Co., Ltd.) 10 parts by mass t-butyl acetate 700 parts by mass 4-methoxy-4-methyl-2-pentanone 300 parts by mass were mixed and dispersed for 10 hours using a sand mill to prepare a charge generation layer coating liquid. This coating solution was applied onto the intermediate layer by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm.

(Charge transport layer)
Charge transport material (4,4′-dimethyl-4″-(β-phenylstyryl)triphenylamine) 225 parts by mass Binder resin: Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 300 parts by mass Antioxidant (dibutylhydroxytoluene) , BHT) 6 parts by mass Tetrahydrofuran (THF) 1600 parts by mass Toluene 400 parts by mass Silicone oil (KF-96: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part by mass was mixed and dissolved to prepare a charge transport layer coating liquid. The coating liquid was applied onto the charge generation layer by a dip coating method and dried at 120° C. for 70 minutes to form a charge transport layer having a dry film thickness of 20 μm.

[Example 2]
<Production of Photoreceptor 2>
Preparation of TiO ₂ /Fe ³⁺ Compound In the above “Preparation of TiO ₂ /Cu ²⁺ compound 1,” instead of CuCl ₂ .2H ₂ O, iron(III) chloride hexahydrate (FeCl ₃ ·6H ₂ O, Kanto Chemical Co., Ltd., purity 99.9 mass%) was added in the same procedure except that Fe(III) was added in an amount of 0.1 mass% with respect to TiO ₂ . Thus, TiO ₂ fine particles carrying Y were obtained.

When the Fe(III) loading amount of the obtained iron trivalent salt-supporting TiO ₂ fine particles was evaluated in the same manner as above, 0.0050% by mass (5% by mass of the charged amount) was supported with respect to TiO ₂ . ..

Photoreceptor 2 was prepared in the same procedure as in Example 1 (intermediate layer), except that TiO ₂ /Cu ²⁺ -based compound 1 was replaced with the TiO ₂ /Fe ³⁺ -based compound prepared above.

[Example 3]
<Production of Photoreceptor 3>
Preparation of TiO ₂ /Pt In the above “Preparation of TiO ₂ /Cu ²⁺ system compound 1”, instead of CuCl ₂ ·2H ₂ O, platinum chloride (4) acid (manufactured by Kishida Chemical Co., Ltd.) was added to TiO _2. Then, Pt-supported TiO ₂ fine particles were obtained by the same procedure except that platinum was added in an amount of 0.1% by mass.

When the amount of Pt supported on the obtained Pt-supported TiO ₂ fine particles was evaluated in the same manner as above, 0.0050 mass% (5 mass% of the charged amount) was supported on TiO ₂ .

In the (intermediate layer) of Example 1, a photoconductor 3 was produced by the same procedure except that the TiO ₂ /Cu ²⁺ compound 1 was replaced by the TiO ₂ /Pt prepared above.

[Example 4]
<Production of Photoreceptor 4>
Preparation of TiO ₂ /Pd In the above “Preparation of TiO ₂ /Cu ²⁺ system compound 1”, instead of CuCl ₂ ·2H ₂ O, palladium chloride was added in an amount of 0.1% by mass of palladium based on TiO ₂ . TiO ₂ fine particles carrying Pd were obtained by the same procedure except that the addition was made in step 1.

When the amount of Pd supported on the obtained Pd-supported TiO ₂ fine particles was evaluated in the same manner as above, 0.0050% by mass (5% by mass of the charged amount) was supported on TiO ₂ .

A photoreceptor 4 was prepared in the same procedure as in Example 1 (intermediate layer), except that the TiO ₂ /Cu ²⁺ compound 1 was replaced by the TiO ₂ /Pd prepared above.

[Example 5]
<Production of Photoreceptor 5>
Preparation of TiO ₂ /Ni In the above-mentioned “Preparation of TiO ₂ /Cu ²⁺ system compound 1,” instead of CuCl ₂ ·2H ₂ O, a nickel oxide reagent (first-class) was used, and nickel was added to TiO _{2 in} an amount of 0.1 Ni-supported TiO ₂ fine particles were obtained by the same procedure except that the addition was performed in an amount of mass%.

When the Ni-supported amount of the obtained Ni-supported TiO ₂ fine particles was evaluated in the same manner as above, 0.0050 mass% (5 mass% of the charged amount) was supported with respect to TiO ₂ .

In the (protective layer) of Example 1, a photoconductor 5 was prepared by the same procedure except that the TiO ₂ /Cu ²⁺ compound 1 was replaced with the TiO ₂ /Ni prepared above.

[Example 6]
<Production of Photoreceptor 6>
Preparation of WO ₃ /Cu ²⁺ Compound WO ₃ powder (number average primary particle size 90 nm, manufactured by Kojundo Chemical Laboratory Co., Ltd.) is passed through a filter to remove particles having a particle size of 1 μm or more, and baked at 650° C. for 3 hours. By performing a pre-treatment, the tungsten trioxide fine particles were obtained.

In the preparation of _"TiO 2 / ^{Cu 2+} system the preparation of compounds 1" above, instead of TiO ₂ particles, with tungsten trioxide microparticles prepared above, and _"TiO 2 / ^{Cu 2+} systems Preparation of Compound 1" By supporting a copper divalent salt in the same manner, tungsten trioxide fine particles carrying a copper divalent salt were obtained.

The copper divalent salt-supported tungsten trioxide fine particles were subjected to inductively coupled plasma emission spectrometry (ICP-AES, P-4010, HITACHI) and polarized Zeeman atomic absorption spectrometry (Polarized Zeeman AAS, Z-2000, HITACHI) to form Cu(II). When the loading amount was evaluated, 0.0050% by mass (5% by mass of the charged amount) was loaded on WO ₃ .

In the (intermediate layer) of Example 1, the TiO ₂ /Cu ²⁺ compound 1 was prepared as described above in WO.
Photoreceptor 6 was produced in the same procedure except that the ₃ /Cu ²⁺ compound was used instead.

[Example 7]
<Production of Photoreceptor 7>
Preparation of WO ₃ /Pd In the above “Preparation of WO ₃ /Cu ²⁺ compound”, instead of CuCl ₂ ·2H ₂ O, palladium chloride is added in an amount such that palladium is 0.1% by mass with respect to WO ₃ . WO ₃ microparticles supporting Pd were obtained by the same procedure except that the addition was performed.

When the amount of Pd supported on the obtained Pd-loaded WO ₃ fine particles was evaluated in the same manner as above, 0.0050% by mass (5% by mass of the charged amount) was supported on WO ₃ .

In the (intermediate layer) of Example 1, a photoconductor 7 was prepared by the same procedure except that the TiO ₂ /Cu ²⁺ compound 1 was replaced with WO ₃ /Pd prepared above.

[Example 8]
<Production of Photoreceptor 8>
Preparation of TiO ₂ /Cu ²⁺ system compound _{2 In} “Preparation of TiO ₂ /Cu ²⁺ system compound 1” of Example 1, CuCl ₂ ·2H ₂ O (manufactured by Wako Pure Chemical Industries, Ltd.) was replaced with Cu(II). TiO ₂ fine particles supporting a divalent copper salt (TiO ₂ /Cu ²⁺ compound 2) were obtained by the same procedure except that the addition amount was 0.002 mass% with respect to ₂ .

About the obtained TiO ₂ /Cu ²⁺ compound 2, Cu(II) was measured by inductively coupled plasma emission spectrometry (ICP-AES, P-4010, HITACHI) and polarized Zeeman atomic absorption spectrometry (Polarized Zeeman AAS, Z-2000, HITACHI). ) When the carried amount was evaluated, 0.0001 mass% (5 mass% of the charged amount) was carried with respect to TiO ₂ .

In Example 1 (intermediate _layer), a TiO 2 / ^{Cu 2+} compound 1 In a similar procedure, except that instead of the _TiO 2 / ^{Cu 2+} compound 2 prepared above, to prepare a photoreceptor 8 ..

[Example 9]
<Production of Photoreceptor 9>
In _"TiO 2 / ^{Cu 2+} system the preparation of compounds 1" of Example 1 TiO ₂ / ^{Cu 2+} compounds _3, CuCl 2 · _2H 2 O (manufactured by Wako Pure Chemical Industries, Ltd.) Cu (II) is TiO TiO ₂ fine particles (TiO ₂ /Cu ²⁺ compound 3) supporting a copper divalent salt were obtained by the same procedure except that the amount was 800 mass% with respect to ₂ .

Regarding the obtained TiO ₂ /Cu ²⁺ system compound 3, Cu(II) was obtained by inductively coupled plasma emission spectrometry (ICP-AES, P-4010, HITACHI) and polarized Zeeman atomic absorption spectrometry (Polarized Zeeman AAS, Z-2000, HITACHI). ) When the carried amount was evaluated, 40 mass% (5 mass% of the charged amount) was carried with respect to TiO ₂ .

In Example 1 (intermediate _layer), a TiO 2 / ^{Cu 2+} compound 1 In a similar procedure, except that instead of the _TiO 2 / ^{Cu 2+} compound 3 prepared above, to prepare a photosensitive member 9 ..

[Example 10]
<Production of Photoreceptor 10>
In _"TiO 2 / ^{Cu 2+} system the preparation of compounds 1" of Example 1 TiO ₂ / ^{Cu 2+} compounds _4, CuCl 2 · _2H 2 O (manufactured by Wako Pure Chemical Industries, Ltd.) Cu (II) is TiO TiO ₂ fine particles (TiO ₂ /Cu ²⁺ compound 4) supporting a divalent copper salt were obtained by the same procedure except that the addition amount was 0.0016 mass% with respect to ₂ .

For _TiO 2 / ^{Cu 2+} compound 4 obtained, ICP (ICP-AES, P-4010 , HITACHI) and polarization Zeeman atomic absorption spectrometry (Polarized Zeeman AAS, Z-2000 , HITACHI) at Cu (II ) When the carried amount was evaluated, 0.00008 mass% (5 mass% of the charged amount) was carried with respect to TiO ₂ .

In the (intermediate layer) of Example 1, a photoconductor 10 was produced by the same procedure except that the TiO ₂ /Cu ²⁺ type compound 1 was replaced with the TiO ₂ /Cu ²⁺ type compound 4 prepared above. ..

[Example 11]
<Production of Photoreceptor 11>
In _"TiO 2 / ^{Cu 2+} system the preparation of compounds 1" of Example 1 TiO ₂ / ^{Cu 2+} compounds _5, CuCl 2 · _2H 2 O (manufactured by Wako Pure Chemical Industries, Ltd.) Cu (II) is TiO TiO ₂ fine particles (TiO ₂ /Cu ²⁺ system compound 5) supporting a divalent copper salt were obtained by the same procedure except that the addition amount was 840 mass% with respect to ₂ .

For _TiO 2 / ^{Cu 2+} compound 5 obtained, ICP (ICP-AES, P-4010 , HITACHI) and polarization Zeeman atomic absorption spectrometry (Polarized Zeeman AAS, Z-2000 , HITACHI) at Cu (II ) When the carried amount was evaluated, 42 mass% (5 mass% of the charged amount) was carried with respect to TiO ₂ .

In Example 1 (intermediate _layer), a TiO 2 / ^{Cu 2+} compound 1 In a similar procedure, except that instead of the _TiO 2 / ^{Cu 2+} compound 5 prepared above, to prepare a photoreceptor 11 ..

[Example 12]
<Production of Photoreceptor 12>
Of Example 1 TiO ₂ / ^{Cu 2+} compound 6 in _"TiO 2 / ^{Cu 2+} system the preparation of compound 1" is an electrically conductive metal oxide rutile TiO ₂ powder (MT-150A, the number average primary particle size 100 nm, the Tayca Corporation), the same procedure was changed to rutile TiO ₂ powder (number average primary particle diameter of 10 _nm), was prepared TiO 2 / ^{Cu 2+} compound 6.

In Example 1 (intermediate _layer), a TiO 2 / ^{Cu 2+} compound 1 In a similar procedure, except that instead of the _TiO 2 / ^{Cu 2+} compound 6 prepared above, to prepare a photoreceptor 12 ..

[Example 13]
<Production of Photoreceptor 13>
Of Example 1 TiO ₂ / ^{Cu 2+} compound 7 in _"TiO 2 / ^{Cu 2+} system the preparation of compound 1" is an electrically conductive metal oxide rutile TiO ₂ powder (MT-150A, the number average primary particle size TiO ₂ /Cu ²⁺ compound 7 was prepared by the same procedure except that rutile type TiO ₂ powder (number average primary particle size 1000 nm) was used instead of 100 nm, manufactured by Teika Co., Ltd.

In the (intermediate layer) of Example 1, a photoreceptor 13 was prepared by the same procedure except that the TiO ₂ /Cu ²⁺ compound 1 was replaced by the TiO ₂ /Cu ²⁺ compound 7 prepared above. ..

[Example 14]
<Production of Photoreceptor 14>
Of Example 1 TiO ₂ / ^{Cu 2+} compound 8 in _"TiO 2 / ^{Cu 2+} system the preparation of compound 1" is an electrically conductive metal oxide rutile TiO ₂ powder (MT-150A, the number average primary particle size TiO ₂ /Cu ²⁺ -based compound 8 was prepared by the same procedure except that rutile type TiO ₂ powder (number average primary particle size 9 nm) was used instead of 100 nm, manufactured by Teika Co., Ltd.).

In the (intermediate layer) of Example 1, the photoconductor 14 was prepared by the same procedure except that the TiO ₂ /Cu ²⁺ compound 1 was replaced by the TiO ₂ /Cu ²⁺ compound 8 prepared above. ..

[Example 15]
<Production of Photoreceptor 15>
Of Example 1 TiO ₂ / ^{Cu 2+} compound 9 in the _"TiO 2 / ^{Cu 2+} system the preparation of compound 1" is an electrically conductive metal oxide rutile TiO ₂ powder (MT-150A, the number average primary particle size TiO ₂ /Cu ²⁺ compound 9 was prepared by the same procedure except that rutile TiO ₂ powder (number average primary particle size 1003 nm) was used instead of 100 nm, manufactured by Teika Co., Ltd.

In the (intermediate layer) of Example 1, the photoconductor 15 was prepared by the same procedure except that the TiO ₂ /Cu ²⁺ system compound 1 was replaced with the TiO ₂ /Cu ²⁺ system compound 9 prepared above. ..

[Example 16]
<Production of Photoreceptor 16>
In the (intermediate layer) of Example 1, the addition amount of the copper divalent salt-supporting TiO ₂ fine particles (TiO ₂ /Cu ²⁺ compound 1) was 100 parts by mass to 20 parts by mass with respect to 100 parts by mass of the polyamide resin as the binder resin. A photoconductor 16 was manufactured in the same procedure as in Example 1 except that the mass part was changed.

[Example 17]
<Production of Photoreceptor 17>
In the (intermediate layer) of Example 1, the addition amount of the copper divalent salt-supporting TiO ₂ fine particles (TiO ₂ /Cu ²⁺ compound 1) was 100 parts by mass to 300 parts by mass with respect to 100 parts by mass of the polyamide resin as the binder resin. A photoconductor 17 was manufactured in the same procedure as in Example 1 except that the mass part was changed.

[Example 18]
<Production of Photoreceptor 18>
In the (intermediate layer) of Example 1, the addition amount of the copper divalent salt-supporting TiO ₂ fine particles (TiO ₂ /Cu ²⁺ compound 1) was 100 parts by mass to 18 parts by mass with respect to 100 parts by mass of the polyamide resin as the binder resin. A photoconductor 18 was manufactured in the same procedure as in Example 1 except that the mass part was changed.

[Example 19]
<Production of Photoreceptor 19>
In the (intermediate layer) of Example 1, the addition amount of the copper divalent salt-supporting TiO ₂ fine particles (TiO ₂ /Cu ²⁺ system compound 1) was 100 parts by mass to 100 parts by mass with respect to 100 parts by mass of the polyamide resin as the binder resin. A photoconductor 19 was produced in the same procedure as in Example 1 except that the mass part was changed.

[Example 20]
<Production of Photoreceptor 20>
Preparation of TiO ₂ /WO ₃ /Cu ²⁺ Compound In the preparation of “Preparation of TiO ₂ /Cu ²⁺ compound 1” in Example 1, rutile TiO ₂ powder (MT-150A, number average primary particle size 100 nm, taker). (Manufactured by Co., Ltd.) in place of 10% by mass, rutile type TiO ₂ powder (MT-150A, number average primary particle size 100 nm, manufactured by Teika Co., Ltd.) 5% by mass, and tungsten trioxide fine particles (number) prepared in Example 6 An average primary particle size of 90 nm) was used in an amount of 5% by mass, and a copper divalent salt was carried by carrying a copper divalent salt in the same manner as in “Preparation of TiO ₂ /Cu ²⁺ compound 1” above. Titanium oxide/tungsten trioxide fine particles carrying a salt were obtained. At this time, the number average primary particle diameter of the titanium oxide/tungsten trioxide fine particles was 95 nm.

The obtained copper divalent salt-supporting TiO ₂ /WO ₃ fine particles were subjected to inductively coupled plasma emission spectrometry (ICP-AES, P-4010, HITACHI) and polarized Zeeman atomic absorption spectrometry (Polarized Zeeman AAS, Z-2000, HITACHI). When the amount of Cu(II) supported was evaluated, 0.0050 mass% (5 mass% of the charged amount) was supported with respect to TiO ₂ /WO ₃ .

In the same manner as in Example 1 (intermediate layer), except that the TiO ₂ /Cu ²⁺ system compound 1 was replaced with the TiO ₂ /WO ₃ /Cu ²⁺ system compound prepared above, the photoreceptor 20 was prepared. It was made.

[Comparative Example 1]
<Production of Comparative Photoreceptor 1>
In Example 1 (intermediate layer), 100 parts by mass of titanium oxide (SMT500SAS, number average primary particle size 100 nm, manufactured by Teika Co., Ltd.) that does not carry a metal is used in place of 100 parts by mass of the TiO ₂ fine particles supporting a copper divalent salt. Comparative Photoreceptor 1 was prepared in the same procedure except that it was used.

[Comparative example 2]
<Production of Comparative Photoreceptor 2>
In Example 6 (intermediate layer), 100 parts by mass of tungsten trioxide particles supporting no copper divalent salt were added in place of 100 parts by mass of copper divalent salt-supporting tungsten trioxide particles. Comparative Photoreceptor 2 was prepared in the same procedure.

[Comparative Example 3]
<Production of Comparative Photoreceptor 3>
The same procedure as in Comparative Example 1 except that the amount of the conductive metal oxide particles not supporting the multi-electron reduction catalyst was 300 parts by mass with respect to 100 parts by mass of the polyamide resin as the binder resin. A comparative photoconductor 3 was prepared.

[Evaluation method]
(1) Evaluation of Potential Stability At the Bk development position of Bizhub (registered trademark) 554 actual machine manufactured by Konica Minolta Business Technologies Inc., the precharged erase was removed at the Bk development position, and the surface potential meter was installed in the development machine to modify the temperature. In a low-temperature low-humidity environment with a humidity of 15% RH, the change width of the surface potential Vi(V) of the exposed portion before and after the printing of 20 solid A3 black images was measured as ΔVi(V). When the change width ΔVi of the surface potential was less than 10 V, it was evaluated as practical.

(2) Evaluation of hole blocking property In a high-temperature and high-humidity environment of a temperature of 30° C. and a humidity of 80% RH, a Bizhub (registered trademark) 554 actual machine has a photoreceptor surface potential V0 of 600 V and a bias potential Vb of 450 V at a Bk developing position. A white solid image was printed, and the number of black spots (spotted image defects) was counted. When the number of black spots per 100 cm ² was less than 5, it was judged that there was no practical problem.

The obtained results are shown in Table 1 below.

From the results shown in Table 1, it is recognized that the photoconductors of Examples 1 to 20 have excellent potential stability and hole blocking property as compared with the photoconductors of Comparative Examples 1 to 3. Since the photoconductors of Comparative Examples 1 and 2 do not contain a multi-electron reduction catalyst, the carrier transportability of the intermediate layer is not sufficient, and excellent potential stability cannot be obtained without erase before charging. When the content of the conductive metal oxide particles is increased in order to improve the carrier transportability of the intermediate layer, as in Comparative Example 3, when the multielectron reduction catalyst is not included, the conductive metal oxide particles become the carrier injection point. It was found that the hole blocking property was apt to be deteriorated by the above.

As in Examples 1 to 7, metals other than Cu and Fe, such as Pt, Pd, and Ni, are supported on titanium oxide or tungsten oxide as a multi-electron reduction catalyst and introduced into the intermediate layer for excellent potential stability. And to provide hole blocking property.

From the comparison of Examples 1 and 8 to 11, the photoconductors of Examples 1, 8 and 9 in which the supported amount of the multi-electron reduction catalyst was 0.0001 to 40 mass% with respect to the conductive metal oxide were particularly preferable. It was found to show excellent potential stability.

Further, from the comparison of Examples 1 and 12 to 15, the photoconductors of Examples 1, 12 and 13 in which the number average primary particle diameter of the conductive metal oxide is 10 to 1000 nm show more excellent potential stability.

Further, from the comparison of Examples 1 and 16 to 19, Examples 1 and 12 in which the content of the conductive metal oxide supporting the multi-electron reduction catalyst was 20 to 300 parts by mass with respect to 100 parts by mass of the binder resin. It was found that the photoconductors of Nos. 13 and 13 exhibited more excellent potential stability and hole blocking property.

1Y, 1M, 1C, 1Bk Electrophotographic photoreceptor 2Y, 2M, 2C, 2Bk Charging means 3Y, 3M, 3C, 3Bk Exposure means 4Y, 4M, 4C, 4Bk Developing means 5Y, 5M, 5C, 5Bk Primary transfer roller 5b 2 Next transfer roller 6Y, 6M, 6C, 6Bk, 6b Cleaning means 7 Endless belt-shaped intermediate transfer body unit 8 Process cartridge 10Y, 10M, 10C, 10Bk Image forming unit 20 Paper feeding cassette 21 Paper feeding conveying means 22A, 22B, 22C, 22D Intermediate roller 23 Registration roller 24 Fixing means 25 Paper ejection roller 26 Paper ejection tray 70 Endless belt-shaped intermediate transfer body 71, 72, 73, 74 Roller 82L, 82R Support rail A Image forming device P Transfer material SC Original image reading device

Claims (5)

An electrophotographic photoreceptor in which an intermediate layer and a photosensitive layer are sequentially laminated on a conductive support,
The intermediate layer contains conductive metal oxide particles carrying a multi-electron reduction catalyst ,
The conductive metal oxide particles contain at least one of titanium oxide and tungsten oxide,
The multi-electron reduction catalyst contains one or more elements selected from the group consisting of platinum, palladium, copper, iron, rhodium, gold, chromium, nickel, cerium, and tungsten, provided that the multi-electron reduction catalyst is Including a metal element different from the metal element contained in the conductive metal oxide particles,
The electrophotographic photoreceptor, wherein the multi-electron reduction catalyst is supported in a proportion of 0.0001 to 0.005 mass% with respect to the conductive metal oxide particles . The electrophotographic photosensitive member according to claim 1 , wherein the conductive metal oxide particles have a number average primary particle diameter of 10 to 1000 nm. The intermediate layer further contains a binder resin, and contains conductive metal oxide particles carrying the multi-electron reduction catalyst in a ratio of 20 to 300 parts by mass with respect to 100 parts by mass of the binder resin. The electrophotographic photosensitive member according to 1 or 2 . An electrophotographic photosensitive member according to any one of claim 1 to 3
Charging means for charging the surface of the electrophotographic photosensitive member,
Exposure means for performing latent image formation by performing image exposure on the surface of the electrophotographic photosensitive member charged by the charging means;
Developing means for forming a toner image by visualizing the latent image formed by the exposing means,
Transfer means for transferring the toner image formed on the surface of the electrophotographic photosensitive member by the developing means onto a transfer medium such as paper or a transfer belt;
An image forming apparatus having: The image forming apparatus according to claim 4 , wherein the image forming apparatus does not include a charge removing unit that removes residual charges on the surface of the electrophotographic photosensitive member after transfer and before charging.