JP2011075851A - Electrophotographic photoreceptor, and image forming apparatus having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoreceptor of high durability that excels in mechanical/electric durability and does not cause an image abnormality such as image blurring even if it is used repeatedly for a long term, and allows stable image output for a long term, and to provide an image forming apparatus including the photoreceptor. <P>SOLUTION: This electrophotographic photoreceptor includes a layer containing pyrrolo-quinoline quinone expressed by the formula as an antioxidant to ozone and nitrogen oxide which are generated by discharge in an exposure operation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member used for electrophotographic image formation and an image forming apparatus including the same.

2. Description of the Related Art An electrophotographic image forming apparatus (also referred to as “electrophotographic apparatus”) that forms an image using electrophotographic technology is widely used in copying machines, printers, facsimile machines, and the like.
An electrophotographic photosensitive member (also referred to as “photosensitive member”) used in an electrophotographic process is configured by laminating a photosensitive layer containing a photoconductive material on a conductive support.
Conventionally, a photoconductor (also referred to as “inorganic photoconductor”) having a photosensitive layer mainly composed of an inorganic photoconductive material has been widely used. However, it is resistant to heat resistance, storage stability, human body and environment. It has defects in any of the aspects of toxicity, sensitivity, durability, occurrence of image defects, productivity, manufacturing cost, etc., and satisfactory products are not obtained in all points.

On the other hand, research and development of a photoreceptor (also referred to as “organic photoreceptor”) having a photosensitive layer mainly composed of an organic photoconductive material has progressed, and now it occupies the mainstream of photoreceptors.
Organic photoreceptors have some problems in sensitivity, durability, and environmental stability, but have many advantages over inorganic photoreceptors in terms of toxicity, manufacturing cost, and freedom of material design. Have. For example, an organic photoreceptor can form a photosensitive layer by an easy and inexpensive method typified by a dip coating method.

As an organic photoconductor, a structure in which a single layer type photosensitive layer in which a charge generating material and a charge transporting material are dispersed in a binder resin (also referred to as “binder resin”) is laminated on a conductive support, a charge generating material is used. A laminated photosensitive layer or a reverse laminated photosensitive layer in which a charge generation layer dispersed in a binder resin and a charge transport layer in which a charge transport material is dispersed in a binder resin are formed in this order or in reverse order on a conductive support. Layered configurations have been proposed. Among these, the function-separated type photoconductor having a laminated type photosensitive layer and a reverse laminated type photosensitive layer is excellent in electrophotographic characteristics and durability, has a high degree of freedom in material selection, and can be designed in various ways. Widely used.
Further, in order to prevent charge injection from the conductive support to the single-layer type photosensitive layer or the laminated type photosensitive layer, and to form these photosensitive layers uniformly and uniformly on the conductive support, the conductive support is provided. A technique of providing an intermediate layer (also referred to as “undercoat layer”) between the photosensitive member and the photosensitive layer is also known.

On the other hand, the photoconductor incorporated in the image forming apparatus is repeatedly charged, exposed, developed, transferred, cleaned, and neutralized in various environments, so that the photoconductor has high sensitivity and photoresponsiveness. In addition to being excellent, environmental stability, electrical stability, and durability against mechanical external forces (printing durability) are required.
In particular, with respect to physical properties such as decomposition and deterioration of the charge transport material contained in the surface layer of the photosensitive member due to the oxidizing gas such as ozone and nitrogen oxide (NOx) generated by the discharge in the above operation and exposure light. Durability is a problem.

In recent years, in image forming apparatuses of the tandem method (developing method that superimposes images using a plurality of photoconductors), which has become the mainstream due to demands for colorization and high-speed output images, in addition to black (black toner) Since a plurality of peripheral processes are mounted on a plurality of photoreceptors each having toners such as cyan, magenta, and yellow, the concentration of the oxidizing gas increases dramatically, and defects such as image blurring are caused. It tends to be encouraged.
In order to solve such a problem, a technique for adding various antioxidants to a layer constituting the photoreceptor has been proposed.

Examples of such an antioxidant include dibutylhydroxytoluene (BHT) (see JP-A-57-122444: Patent Document 1) which is a hindered phenol-based antioxidant and a hindered amine-based antioxidant (see Sho 63-18355: see Patent Document 2).
However, depending on the amount of antioxidant used, the residual potential increases remarkably, and the antioxidant itself is altered by reaction with nitrogen oxides during long-term use, losing its effect, and charge generating materials and charge transport materials. However, there is a problem that the original characteristics cannot be maintained and charging and sensitivity are remarkably lowered, and the current situation is not sufficient.
In addition, while the recognition of safety for industrial materials is increasing, there is a concern that the above BHT may adversely affect the human body due to the volatile substances.

On the other hand, as a highly safe antioxidant, a material used as a vitamin or supplement, for example, a tocopherol compound (vitamin E) has been proposed (see JP-A-8-152728: Patent Document 3). The effect is not enough.
In recent years, ubiquinones have attracted attention as materials having a strong antioxidant action, and various substances have been synthesized. Ubiquinones are known to have an anti-aging effect such as preventing cell damage caused by active oxygen, and supplements and cosmetics containing the same have been commercialized.
The applicant of the present application has proposed a technique for preventing deterioration due to ozone or nitrogen oxide as a charged product by including the ubiquinones in the charge transport layer of the photoreceptor (Japanese Patent No. 4076885). 4), however, further effects are required.

In addition, a technique has been proposed in which an aliphatic tricarboxylic acid having a similar structure is contained in the intermediate layer of the photoconductor to suppress a decrease in charge at the first rotation of the photoconductor (JP 2007-34274 A). However, the durability against ozone is unknown.
The pyrroloquinoline quinone used in the present invention has been proposed as an agent that imparts environmental stress resistance to plants (see Japanese Patent Application Laid-Open No. 2006-151881: Patent Document 6), but is not applicable to a photoreceptor.

JP 57-122444 A JP-A-63-18355 JP-A-8-152728 Japanese Patent No. 4076865 JP 2007-34274 A JP 2006-151881 A

  That is, the prior art as described above has not yet achieved a sufficient ozone resistance effect, and is insufficient in practice to deteriorate electrophotographic characteristics such as sensitivity and residual potential by adding an antioxidant or the like. At present, there are still some negative effects. Therefore, there is an awaited proposal for a new material with high safety that improves ozone resistance and has no adverse effects on electrophotographic characteristics.

  The present invention is a highly durable photoconductor that is excellent in mechanical / electrical durability even when used repeatedly for a long period of time, does not generate abnormal images such as image blurring, and can stably output images over a long period of time. It is another object of the present invention to provide an image forming apparatus including the same.

  As a result of intensive studies on improving the printing durability and ozone resistance of the photoreceptor, the inventor has a layer containing pyrroloquinoline quinone, so that the printing durability is remarkably improved and the ozone resistance is excellent. As a result, the inventors have found that a photosensitive member can be obtained.

  Thus, according to the present invention, as an antioxidant for ozone and nitrogen oxides generated by discharge in a photosensitive operation, the formula:

で表されるピロロキノリンキノン（「ＰＱＱ」と略称する）を含有する層を有することを特徴とする感光体が提供される。

A photoreceptor comprising a layer containing pyrroloquinoline quinone (abbreviated as “PQQ”) represented by the formula:

  According to the present invention, the photosensitive member is formed by the exposure, the charging unit for charging the photosensitive member, the exposure unit for exposing the charged photosensitive member to form an electrostatic latent image, and the exposure. Developing means for developing the electrostatic latent image to form a toner image, transfer means for transferring the toner image formed by development onto a recording medium, and fixing the transferred toner image on the recording medium The image forming apparatus includes at least a fixing unit that forms an image, a cleaning unit that removes and collects toner remaining on the photoconductor, and a neutralizing unit that neutralizes surface charge remaining on the photoconductor. An apparatus is provided.

According to the present invention, even when used repeatedly for a long period of time, it is excellent in mechanical / electrical durability, does not generate abnormal images such as image blurring, and has high durability capable of stable image output over a long period of time. A photoreceptor and an image forming apparatus including the photoreceptor can be provided.
That is, according to the present invention, it is possible to provide a photoreceptor that has improved durability against discharge products such as ozone and nitrogen oxides, and does not deteriorate even with high-concentration ozone. Can be miniaturized.

  PQQ used in the present invention is an additive capable of imparting excellent ozone resistance to a photoreceptor, and at the same time, as it is approved by the FDA (US Food and Drug Administration) as a health food material, it is itself safe for the human body. It is a compound with excellent properties.

  A layered photosensitive layer in which a photoconductor is formed by laminating a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material on a conductive support in this order or reverse order from the conductive support side. And a layer containing pyrroloquinoline quinone is a charge generation layer or charge transport layer of a multilayer photosensitive layer, an intermediate layer formed between a conductive support and the multilayer photosensitive layer, or a multilayer The above effect is particularly exhibited when the surface protective layer is formed on the photosensitive layer.

The above effect is particularly exhibited when PQQ is contained in the charge generation layer or charge transport layer, intermediate layer or surface protective layer of the multilayer photosensitive layer.
When PQQ is contained in the charge transport layer of the laminated photosensitive layer, it is possible to realize a photoreceptor that does not deteriorate particularly even with a high concentration of ozone.
When PQQ is contained in the charge generation layer of the laminated photosensitive layer, it is possible to realize a photoreceptor that can prevent a decrease in charge generation ability and a decrease in sensitivity.
When PQQ is contained in the intermediate layer, it is possible to realize a photoconductor that is in the vicinity of the charge generation layer and prevents a decrease in charge generation capability.
When PQQ is contained in the surface protective layer, it is possible to prevent ozone and nitrogen oxides from penetrating into the photosensitive layer, and to realize a highly durable photoconductor with no deterioration in chargeability.

  PQQ is 1 to 30 parts by weight with respect to 100 parts by weight of the charge generating material, and 1 to 30 parts by weight with respect to 100 parts by weight of the charge transporting material. 1 to 30 parts by weight in the charge transport layer of the layer at a ratio of 1 to 30 parts by weight with respect to 100 parts by weight of the binder resin M contained in the intermediate layer or 1 to 30 parts by weight with respect to 100 parts by weight of the binder resin S contained in the surface protective layer. The above effect is particularly exhibited when it is contained in the surface protective layer in a proportion by weight.

  The above effect is particularly exerted when the layer containing pyrroloquinoline quinone is an intermediate layer and the intermediate layer is a layer formed using an aqueous medium coating solution for an intermediate layer. Since PQQ is water-soluble, it can be dissolved well in an aqueous medium and a good coating film can be obtained.

  When the photoreceptor further has a layer containing a specific ubiquinone as an antioxidant against ozone and nitrogen oxides generated by discharge in the photosensitive operation, the above effect is obtained due to the synergistic effect of PQQ and ubiquinone. Particularly demonstrated.

  The layer containing pyrroloquinoline quinone and the layer containing ubiquinones are the charge generation layer or the charge transport layer of the laminated photosensitive layer, or the layer containing pyrroloquinoline quinone is the intermediate layer and contains the ubiquinones Is a layer on the intermediate layer side of the multilayer photosensitive layer, or a layer containing pyrroloquinoline quinone is a layer on the surface protective layer side of the multilayer photosensitive layer and a layer containing ubiquinones is a surface protective layer In this case, the above-described effect is particularly exhibited.

  The ubiquinones are laminated at a rate of 1 to 30 parts by weight with respect to 100 parts by weight of the charge generation material, and at a rate of 1 to 30 parts by weight with respect to 100 parts by weight of the charge transport material. The charge transport layer of the photosensitive layer is 1 to 30 parts by weight with respect to 100 parts by weight of the binder resin M contained in the intermediate layer, or 1 to 100 parts by weight of the binder resin S contained in the surface protective layer. The above effect is particularly exhibited when it is contained in the surface protective layer in a proportion of 30 parts by weight.

FIG. 2 is a schematic cross-sectional view illustrating a configuration of a main part of the multilayer photoconductor of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a configuration of a main part of the multilayer photoconductor of the present invention. 1 is a schematic side view illustrating a configuration of an image forming apparatus of the present invention.

  The photoreceptor of the present invention is characterized by having a layer containing PQQ represented by the above formula as an antioxidant against ozone and nitrogen oxides generated by discharge in a photosensitive operation.

The layer containing PQQ is formed on the charge generating layer and charge transport layer of the laminated photosensitive layer, an intermediate layer formed between the conductive support and the laminated photosensitive layer, and the laminated photosensitive layer. A surface protective layer may be mentioned.
Among the layers constituting these photoreceptors, the charge generating layer and the charge transport of the laminated photosensitive layer are obtained in that a photoreceptor having excellent characteristics as a photoreceptor and having the better effect of the present invention can be obtained. Particularly preferred are layers, interlayers and surface protective layers.
The PQQ content in each layer will be described in detail in the description of each layer.

The photoreceptor of the present invention has the formula: as an antioxidant against ozone and nitrogen oxides generated by discharge in the photosensitive operation.

(Where n is an integer from 1 to 12)
It is preferable to further have a layer containing ubiquinones represented by:
The photoreceptor of the present invention has the layer containing ubiquinones in addition to the layer containing PQQ, and the effects of the present invention are particularly exhibited by these synergistic effects.

The layer constituting the photoconductor containing ubiquinones is the same as the layer constituting the photoconductor containing PQQ, but has excellent characteristics as a photoconductor and has the better effect of the present invention. In terms of obtaining a photoreceptor, the layer containing PQQ and the layer containing ubiquinones are charge generation layers or charge transport layers of a laminated photosensitive layer, or the layer containing PQQ is an intermediate layer and ubiquinones Is a layer on the intermediate layer side of the laminated photosensitive layer, or a layer containing PQQ is a layer on the surface protective layer side of the laminated photosensitive layer and a layer containing ubiquinones is surface protective. A layer is particularly preferred.
Note that “the layer on the intermediate layer side of the laminated photosensitive layer” refers to the “charge generation layer” in the reverse order when the charge generation layer and the charge transport layer are laminated in this order from the conductive support side. In the case of being laminated, it means “charge transport layer”.
In addition, “the layer on the surface protective layer side of the laminated photosensitive layer” means “charge transport layer” in the reverse order when the charge generation layer and the charge transport layer are laminated in this order from the conductive support side. Means a “charge generation layer”.
The content of ubiquinones in each layer will be described in detail in the description of each layer.

Next, the configuration of the photoreceptor of the present invention will be specifically described.
1 and 2 are schematic cross-sectional views showing the structure of the main part of the multilayer photoreceptor of the present invention.
In the multilayer photoreceptor 20a of FIG. 1, an intermediate layer 14a, a charge generation layer 11a, and a charge transport layer 12a are formed in this order on a conductive support 13a.
In the multilayer photoreceptor 20b of FIG. 2, an intermediate layer 14b, a charge generation layer 11b, a charge transport layer 12b, and a surface protective layer 15b are formed in this order on a conductive support 13b.

The charge generation layer 11a and the charge transport layer 12a in FIG. 1 and the charge generation layer 11b and the charge transport layer 12b in FIG. 2 are collectively referred to as stacked photosensitive layers 16a and 16b, respectively.
The intermediate layers 14a, 14b and 14c and the surface protective layer 15b are arbitrary constituent layers and will be described in detail in the description of each layer.

The photosensitive layer of the photoreceptor of the present invention includes a laminated photosensitive layer in which a charge generation layer and a charge transport layer are formed in this order from the conductive support side as shown in FIGS. 1 and 2, and a charge transport layer from the conductive support side. 1 and 2 are particularly preferred from the viewpoint of wear resistance. However, the layered photosensitive layer shown in FIGS. 1 and 2 is particularly preferable.
In the following description, the laminated photosensitive layer is also simply referred to as “photosensitive layer”.

[Conductive supports 13a, 13b, 13c]
The conductive support has a function as an electrode of the photoreceptor and a function as a support member, and the constituent material thereof is not particularly limited as long as it is a material used in the technical field.
Specifically, metallic materials such as aluminum, aluminum alloys, copper, zinc, stainless steel, and titanium: supports made of polymer materials such as polyethylene terephthalate, polyamide, polyester, polyoxymethylene, polystyrene, hard paper, glass, etc. Examples include those obtained by laminating a metal foil on the surface, those obtained by vapor-depositing a metal material, and those obtained by evaporating or applying a layer of a conductive compound such as a conductive polymer, tin oxide, or indium oxide.

The shape of the conductive support is not limited to a cylindrical shape (drum shape) as shown in FIG. 3, and may be a sheet shape, a columnar shape, an endless belt shape, or the like.
If necessary, the surface of the conductive support is subjected to irregular reflection treatment such as anodizing film treatment, surface treatment with chemicals, hot water, coloring treatment, and surface roughening within a range that does not affect the image quality. May be given.

  The irregular reflection treatment is particularly effective when the photoreceptor according to the present invention is used in an electrophotographic process using a laser as an exposure light source. That is, in the electrophotographic process using a laser as an exposure light source, the wavelength of the laser beam is uniform, so the laser beam reflected on the surface of the photoconductor and the laser beam reflected inside the photoconductor cause interference, Interference fringes due to this interference may appear in the image and cause image defects. Therefore, by performing irregular reflection processing on the surface of the conductive support, it is possible to prevent image defects due to interference of laser light having a uniform wavelength.

[Intermediate layers (also referred to as “undercoat layers”) 14a, 14b, 14c]
As shown in FIGS. 1 to 3, the photoreceptor of the present invention may have an intermediate layer on a conductive support.
The intermediate layer has a function of preventing charge injection from the conductive support to the photosensitive layer. That is, a decrease in chargeability of the photosensitive layer is suppressed, a decrease in surface charge other than that which should be erased by exposure is suppressed, and image defects such as fog are prevented from occurring. In particular, during image formation by the reversal development process, it is possible to prevent the occurrence of image fogging called black spots in which minute black dots made of toner are formed on a white background portion.
In addition, the intermediate layer covering the surface of the conductive support reduces the degree of unevenness, which is a defect on the surface of the conductive support, makes the surface uniform, and improves the film formability of the photosensitive layer. Adhesiveness (adhesiveness) between the photosensitive layer and the photosensitive layer can be improved.

The intermediate layer contains the binder resin M and, if necessary, PQQ and other additives as additives.
The binder resin M is not particularly limited as long as it is a material used in the technical field, and examples thereof include thermoplastic resins such as polyamide resins and polyvinyl butyral resins, and thermosetting resins such as polyurethane resins.

The photoreceptor of the present invention is characterized by having a layer containing PQQ as an antioxidant, and the intermediate layer is one of the layers containing PQQ.
In the intermediate layer, PQQ is preferably 1 to 30 with respect to 100 parts by weight of binder resin M.
It is preferably contained in a proportion of 2 parts by weight, more preferably 2 to 20 parts by weight, particularly preferably 2 to 10 parts by weight.
When PQQ is less than 1 part by weight, a sufficient antioxidant effect may not be obtained. On the other hand, when PQQ exceeds 30 parts by weight, the adhesion to the support may be lowered.

The photoreceptor of the present invention preferably further has a layer containing ubiquinones as an antioxidant, and the intermediate layer is one of the layers containing ubiquinones.
In the intermediate layer, the ubiquinones are preferably contained in an amount of 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and particularly preferably 2 to 10 parts by weight with respect to 100 parts by weight of the binder resin M. .
When the amount of ubiquinones is less than 1 part by weight, a sufficient antioxidant effect may not be obtained. On the other hand, when the amount of ubiquinones exceeds 30 parts by weight, the adhesion with the support may be lowered.

Examples of other additives include metal oxide fine particles, an antioxidant, and a conductive agent.
The metal oxide fine particles can easily adjust the volume resistance value of the intermediate layer, can further suppress charge injection into the photosensitive layer, and can maintain the electrical characteristics of the photoreceptor in various environments.
Examples of the metal oxide particles include titanium oxide, aluminum oxide, aluminum hydroxide, and tin oxide. Among these, titanium oxide is particularly preferable.
Titanium oxide may be any crystalline type such as anatase type, rutile type, and amorphous type, or may be a mixture of two or more types, but the rutile type is particularly preferred in terms of stability of physical properties.

The titanium oxide fine particles may have any shape such as a dendritic shape, a needle shape, and a granular shape, but the needle shape is particularly preferable from the viewpoint of achieving both the film strength and the electric characteristics of the intermediate layer.
The number average primary particle size of the titanium oxide fine particles is preferably 30 to 50 nm.
If the number average primary particle diameter of the titanium oxide fine particles is less than 30 nm, the dispersion efficiency of titanium oxide is lowered, and minute black spots are likely to occur in an image. Moreover, even if the number average primary particle diameter of the titanium oxide particles exceeds 50 nm, the dispersibility of the titanium oxide decreases, and the initial sensitivity tends to decrease in a low temperature and low humidity environment.
Even if the surface of titanium oxide fine particles is coated with alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), silica (SiO ₂ ), etc., in order to improve the dispersion stability in the intermediate layer coating solution. Good.

Examples of such titanium oxide fine particles include granular fine particles (average primary particle size: 10 to 30 nm, manufactured by Ishihara Sangyo Co., Ltd., product name: TTO-55A), alumina (Al ₂ O ₃ ), and zirconia (ZrO ₂ ). And dendritic fine particles (average primary particle size: minor axis 40-70 nm, major axis 200-300 nm, manufactured by Ishihara Sangyo Co., Ltd., product name: TTO-D-1), granular fine particles (average primary particle size) Particle diameter: 15 nm, manufactured by Teika Corporation, product name: MT-100T) and granular fine particles (average primary particle diameter: 35 nm, manufactured by Teica Corporation, product name: MT-500SA).

The content of the metal oxide particles in the intermediate layer is preferably 50 to 1000 parts by weight, more preferably 70 to 800 parts by weight, particularly preferably 100 to 100 parts by weight with respect to 100 parts by weight of the binder resin M (for example, polyamide resin). 500 parts by weight.
If the content of titanium oxide is within the above range, the balance between the dispersibility of titanium oxide and the electrical insulation becomes good, and the generation of fog under high temperature and high humidity can be further suppressed.

For the intermediate layer, for example, the binder resin M and additives are dissolved or dispersed in an appropriate solvent to prepare a coating solution for the intermediate layer, this coating solution is applied to the surface of the conductive support, and the solvent is removed by drying. Can be formed.
Specifically, the intermediate layer coating solution can be prepared by dissolving the binder resin M and the additive in a solvent, and adding and dispersing the metal oxide fine particles to the obtained solution.
In order to disperse the metal oxide fine particles in the coating solution, a dispersion treatment may be performed using a known device such as a ball mill, a sand mill, a roll mill, a paint shaker, an attritor, or an ultrasonic disperser.

Examples of the solvent include water; lower alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, tert-butanol and sec-butanol; glymes such as methyl carbitol and butyl carbitol, and the like. And a mixed solvent in which two or more of these solvents are mixed.
The solvent may be appropriately selected depending on the kind of the binder resin M and additives. For example, when the binder resin M is a polyamide resin, methanol and ethanol are used in terms of solubility and applicability of the prepared coating liquid. Is particularly preferred.
Moreover, since PQQ is water-soluble, dissolves well in an aqueous solvent, and an excellent coating film is obtained, the intermediate layer is preferably a layer formed using a coating solution for an intermediate layer of an aqueous solvent.

When lower alcohols are used as the solvent, the content is preferably 30 to 100% by weight, more preferably 40 to 100% by weight, and particularly preferably 50 to 100% by weight.
Further, a co-solvent such as toluene, methylene chloride, cyclohexanone or tetrahydrofuran may be used in combination for adjusting the evaporation rate of the solvent in the intermediate layer coating solution. Its content is about 5 to 50% by weight of the lower alcohol.

The coating method for the intermediate layer coating solution may be appropriately selected in consideration of the physical properties and productivity of the coating solution. For example, dip coating method, spray method, nozzle method, bar coating method, roll Examples thereof include a coating method, a blade method, a ring method, and a dip coating method.
Among these coating methods, the dip coating method is a method of forming a layer on the surface of the substrate by immersing the substrate in a coating tank filled with a coating solution and then pulling it up at a constant speed or a speed that changes sequentially. Since it is relatively simple and excellent in terms of productivity and cost, it can be suitably used for the production of a photoreceptor. In order to stabilize the dispersibility of the coating liquid, the apparatus used for the dip coating method may be provided with a coating liquid dispersing apparatus represented by an ultrasonic generator.

Although it will not specifically limit if the temperature in the drying process of a coating film is the temperature which can remove the used organic solvent, 50-140 degreeC is suitable and 80-130 degreeC is especially preferable.
When the drying temperature is less than 50 ° C., the drying time may be long. On the other hand, if the drying temperature exceeds 140 ° C., the electrical characteristics during repeated use of the photoreceptor may deteriorate and the resulting image may deteriorate.
The temperature conditions in the production of such a photosensitive layer are common not only in the intermediate layer but also in the formation of layers such as a photosensitive layer described later and other processes.

Although the film thickness of an intermediate | middle layer is not specifically limited, Preferably it is 0.1-10 micrometers, More preferably, it is 0.3-5 micrometers.
If the thickness of the intermediate layer is less than 0.1 μm, the effect on local charging failure may not be sufficient. On the other hand, when the film thickness of the intermediate layer exceeds 10 μm, the residual potential may increase or the adhesive strength between the conductive support and the photosensitive layer may decrease.

[Laminated Photosensitive Layers 16a, 16b]
The laminated photosensitive layer is composed of a charge generation layer and a charge transport layer. As described above, by assigning the charge generation function and the charge transport function to separate layers, the optimum material constituting each layer can be independently selected.

[Charge generation layers 11a and 11b]
The charge generation layer has a function of generating charges by absorbing irradiated light such as a semiconductor laser beam in an image forming apparatus, etc., and has a charge generation material as a main component, and PQQ and additives as necessary. Contains other additives.

  Examples of charge generation materials include azo pigments such as monoazo pigments, bisazo pigments, and trisazo pigments; indigo pigments such as indigo and thioindigo; perylene pigments such as peryleneimide and perylene anhydride; and a large number such as anthraquinone and pyrenequinone. Ring quinone pigments; metal phthalocyanines such as oxotitanium phthalocyanine and phthalocyanine pigments such as metal-free phthalocyanine; organic photoconductive materials such as squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes; and selenium and amorphous Examples thereof include inorganic photoconductive materials such as silicon, and those having sensitivity in the exposure wavelength region can be appropriately selected and used. These charge generation materials can be used alone or in combination of two or more.

In order to improve the function of the charge generation material, triphenylmethane dyes such as methyl violet, crystal violet, knight blue and victoria blue, erythrosine, rhodamine B, rhodamine 3R, acridine orange and frappeosin Sensitizing dyes such as acridine dyes, thiazine dyes typified by methylene blue and methylene green, oxazine dyes typified by capri blue and meldra blue, cyanine dyes, styryl dyes, pyrylium salt dyes or thiopyrylium salt dyes They can be used in combination.
The ratio of use of the sensitizing dye is not particularly limited, but is preferably 10 parts by weight or less, particularly preferably 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the charge generating material.

The charge generation layer may contain a binder resin for the purpose of improving the binding property.
As the binder resin, a resin having a binding property used in this field can be used, and a binder resin having excellent compatibility with the charge generation material is preferable.
Specifically, polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, acrylic resin, methacrylic resin, polycarbonate resin, polyarylate resin, phenoxy resin, polyvinyl butyral resin, polyvinyl Formal resins, copolymer resins containing two or more of the repeating units constituting these resins, and the like can be mentioned. Examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. The binder resin is not limited to these, and a resin generally used in this field can be used as the binder resin. These binder resins can be used alone or in combination of two or more.
The use ratio of the binder resin is not particularly limited, but is about 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the charge generation material.

The photoreceptor of the present invention is characterized by having a layer containing PQQ as an antioxidant, and the charge generation layer is one of the layers containing PQQ.
In the charge generation layer, PQQ is preferably contained in an amount of 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and particularly preferably 2 to 10 parts by weight with respect to 100 parts by weight of the charge generation material. preferable.
When PQQ is less than 1 part by weight, a sufficient antioxidant effect may not be obtained. On the other hand, when PQQ exceeds 30 parts by weight, the sensitivity may decrease.

The photoreceptor of the present invention preferably further has a layer containing ubiquinones as an antioxidant, and the charge generation layer is one of the layers containing ubiquinones.
In the charge generation layer, the ubiquinones are contained in an amount of preferably 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and particularly preferably 2 to 10 parts by weight with respect to 100 parts by weight of the charge generation material. Is preferred.
When the amount of ubiquinones is less than 1 part by weight, a sufficient antioxidant effect may not be obtained. On the other hand, when ubiquinones exceed 30 parts by weight, the sensitivity may be lowered.

  Other additives include hole transport materials, electron transport materials, antioxidants, ultraviolet absorbers, dispersion stabilizers, sensitizers, leveling agents, plasticizers, fine particles of inorganic compounds or organic compounds, etc. You may use together 1 type, or 2 or more types.

The charge generation layer can be formed by a known dry method and wet method.
Examples of the dry method include a method of vacuum-depositing a charge generating material on the surface of an intermediate layer formed on a conductive support.
As a wet method, for example, a charge generating material, PQQ as an additive, other additives and, if necessary, a binder resin are dissolved or dispersed in an appropriate organic solvent to prepare a coating solution for a charge generating layer. There is a method in which the liquid is applied on the conductive support or the surface of the intermediate layer formed on the conductive support and then dried to remove the solvent.

  Examples of the solvent include halogenated hydrocarbons such as dichloromethane and dichloroethane; ketones such as acetone, methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as tetrahydrofuran (THF) and dioxane; -Alkyl ethers of ethylene glycol such as dimethoxyethane; aromatic hydrocarbons such as benzene, toluene and xylene; aprotic polar solvents such as N, N-dimethylformamide and N, N-dimethylacetamide. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment. These solvents can be used alone or in combination of two or more.

Prior to dissolving or dispersing the charge generation material, PQQ as an additive, and other additives as required, in the solvent, the charge generation material may be previously pulverized by a pulverizer. Examples of the pulverizer used for the pulverization treatment include a ball mill, a sand mill, an attritor, a vibration mill, and an ultrasonic disperser.
Dispersers such as paint shakers, ball mills and sand mills can be used to dissolve or disperse the charge generating material, PQQ as an additive, and optionally other additives in a solvent. At this time, it is preferable to appropriately set the dispersion condition so that impurities are generated from the container and the members constituting the disperser due to wear and the like and are not mixed into the coating liquid.
Other steps and conditions are in accordance with the formation of the intermediate layer.

The thickness of the charge generation layer is not particularly limited, but is preferably 0.05 to 5 μm, more preferably 0.1 to 1 μm.
When the thickness of the charge generation layer is less than 0.05 μm, the light absorption efficiency is lowered, and the sensitivity of the photoreceptor may be lowered. When the thickness of the charge generation layer exceeds 5 μm, the charge transfer inside the charge generation layer becomes a rate-determining step in the process of erasing the charge on the surface of the photosensitive layer, and the sensitivity of the photoreceptor may be lowered.

[Charge transport layers 12a, 12b]
The charge transport layer has a function of transporting charges generated in the charge generation layer to the surface of the photoreceptor, and contains a charge transport material and a binder resin, and optionally PQQ and other additives as additives.
As the charge transport material, high molecular compounds such as polyvinyl carbazole, polyvinyl pyrene, and polyacenaphthylene, or low molecular compounds such as various pyrazoline derivatives, oxazole derivatives, hydrazone derivatives, stilbene derivatives, and arylamine derivatives can be used.
Binder resins include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylic ester, methacrylic ester, vinyl alcohol, ethyl vinyl ether, polyvinyl acetal, polycarbonate, polyester, polyamide, polyurethane, cellulose Examples include ether, phenoxy resin, silicon resin, and epoxy resin.

As the binder resin, a transparent resin that does not absorb the light from the exposure light source of the image forming apparatus can be used among the resins having binding properties used in this field, and a resin similar to that contained in the charge generation layer can be used. One kind can be used alone or two or more kinds can be used in combination.
Among these, polystyrene, polycarbonate, polyarylate, and polyphenylene oxide are preferable because they have a volume resistance of 10 ¹³ Ω or more, excellent electrical insulation, and excellent film formability, potential characteristics, and the like, and polycarbonate is particularly preferable. .
The use ratio of the binder resin is not particularly limited, but is about 50 to 300 parts by weight with respect to 100 parts by weight of the charge transport material.

The photoreceptor of the present invention is characterized by having a layer containing PQQ as an antioxidant, and the charge transport layer is one of the layers containing PQQ.
In the charge transport layer, PQQ is preferably contained in an amount of 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and particularly preferably 2 to 10 parts by weight with respect to 100 parts by weight of the charge transport material. preferable.
When PQQ is less than 1 part by weight, a sufficient antioxidant effect may not be obtained. On the other hand, when PQQ exceeds 30 parts by weight, the strength of the coating film may be lowered.

The photoreceptor of the present invention preferably further has a layer containing ubiquinones as an antioxidant, and the charge transport layer is one of the layers containing ubiquinones.
In the charge transport layer, ubiquinones are preferably contained in an amount of 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and particularly preferably 2 to 10 parts by weight with respect to 100 parts by weight of the charge transport material. Is preferred.
When the amount of ubiquinones is less than 1 part by weight, a sufficient antioxidant effect may not be obtained. On the other hand, when the amount of ubiquinones exceeds 30 parts by weight, the strength of the coating film may be reduced.

Other additives include hole transport materials, electron transport materials, antioxidants, ultraviolet absorbers, dispersion stabilizers, sensitizers, leveling agents, plasticizers, fine particles of inorganic compounds or organic compounds, etc. You may use together 1 type, or 2 or more types.
Similarly to the charge generation layer, the charge transport layer can be formed by preparing a coating solution for a charge transport layer and using a wet method, particularly a dip coating method.
As the solvent used for the preparation of the charge transport layer coating solution, one of the same solvents as those used for the preparation of the charge generation layer coating solution may be used alone or in combination of two or more.

Examples of the solvent include alcohols such as methanol, ethanol, isopropanol and butanol; aliphatic hydrocarbons such as n-hexane, octane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene; dichloromethane, dichloroethane and tetrachloride. Halogenated hydrocarbons such as carbon and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, propylene glycol monomethyl ether, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone and cyclohexanone; ethyl acetate, Esters such as methyl acetate; dimethylformaldehyde, dimethylformamide, dimethylsulfoxy Among these, it is particularly preferable to use tetrahydrofuran and 1,3-dioxolane alone.
Other processes and conditions are in accordance with the formation of the intermediate layer and the charge generation layer.

[Surface protective layer 15a]
As shown in FIG. 2, the photoreceptor of the present invention may have a surface protective layer on the photosensitive layer.
The surface protective layer has a function of improving the durability of the photoreceptor, and is composed of the binder resin S and, if necessary, PQQ and other additives as additives, and the same charge transport as that contained in the charge transport layer. You may contain the 1 type (s) or 2 or more types of a substance.
Examples of the binder resin S include the same binders as those contained in the charge transport layer and the charge transport layer.

The photoreceptor of the present invention is characterized by having a layer containing PQQ as an antioxidant, and the surface protective layer is one of the layers containing PQQ.
In the surface protective layer, PQQ is preferably contained in an amount of 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and particularly preferably 2 to 10 parts by weight with respect to 100 parts by weight of the binder resin S. .
When PQQ is less than 1 part by weight, a sufficient antioxidant effect may not be obtained. On the other hand, when PQQ exceeds 30 parts by weight, the strength of the coating film may be reduced, and scratches may easily occur.

The photoreceptor of the present invention preferably further has a layer containing ubiquinones as an antioxidant, and the surface protective layer is one of the layers containing ubiquinones.
The content of ubiquinones in the surface protective layer is preferably 1 to 30 parts by weight, more preferably 2 to 20 parts by weight, and particularly preferably 2 to 10 parts by weight with respect to 100 parts by weight of the binder resin S. It is preferable.
When the amount of ubiquinones is less than 1 part by weight, a sufficient antioxidant effect may not be obtained. On the other hand, when the amount of ubiquinones exceeds 30 parts by weight, the strength of the coating film may be reduced and scratches may be easily generated.

The surface protective layer can be formed by, for example, preparing a coating solution for forming a protective layer by dissolving a binder resin in an appropriate solvent, applying the coating solution to the surface of the photosensitive layer, and removing the organic solvent by drying. .
Other steps and conditions thereof are in accordance with the formation of the intermediate layer, the charge transport layer, and the charge transport layer.

The thickness of the protective layer is not particularly limited, but is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.
When the thickness of the protective layer is less than 0.5 μm, the surface resistance of the photoreceptor is inferior and the durability may be insufficient. Further, when the thickness of the protective layer exceeds 10 μm, the resolution of the photoreceptor may be lowered.

[Image forming apparatus]
The image forming apparatus of the present invention includes a photosensitive member of the present invention, a charging unit for charging the photosensitive member, an exposure unit for exposing the charged photosensitive member to form an electrostatic latent image, and a static formed by exposure. Developing means for developing an electrostatic latent image to form a toner image, transfer means for transferring the toner image formed by development onto a recording medium, and fixing the transferred toner image on the recording medium to form an image A fixing unit for removing the toner remaining on the photosensitive member, and a discharging unit for removing the surface charge remaining on the photosensitive member.
The image forming apparatus of the present invention and the operation thereof will be described with reference to the drawings, but are not limited to the following description.

FIG. 3 is a schematic side view showing the configuration of the image forming apparatus of the present invention.
An image forming apparatus (laser printer) 100 in FIG. 3 includes a photoreceptor 1 of the present invention, an exposure unit (semiconductor laser) 31, a charging unit (charging unit) 32, a developing unit (developing unit) 33, and a transfer unit. The image forming apparatus includes a (transfer charger) 34, a conveyance belt (not shown), a fixing unit (fixing unit) 35, and a cleaning unit (cleaner) 36. Reference numeral 51 denotes a recording medium (recording paper or transfer paper).

  The photosensitive member 1 is rotatably supported by the main body of the image forming apparatus 100 (not shown), and is driven to rotate in the direction of the arrow 41 around the rotation axis 44 by a driving unit (not shown). The drive means includes, for example, an electric motor and a reduction gear, and transmits the driving force to a conductive support constituting the core of the photoconductor 1 to drive the photoconductor 1 to rotate at a predetermined peripheral speed. . The charging unit (charging unit) 32, the exposure unit 31, the developing unit (developing unit) 33, the transfer unit (transfer charging unit) 34, and the cleaning unit (cleaner) 36 are arranged in this order along the outer peripheral surface of the photoreceptor 1. The photosensitive member 1 indicated by the arrow 41 is provided from the upstream side to the downstream side in the rotation direction.

The charger 32 is a charging unit that uniformly charges the outer peripheral surface of the photoreceptor 1 to a predetermined potential.
For example, the exposure unit 31 includes a blue semiconductor laser as a light source, and is charged by irradiating the surface of the photoreceptor 1 between the charger 32 and the developer 33 with the light of the laser beam output from the light source. The outer peripheral surface of the photoreceptor 1 is exposed according to the image information. The light is repeatedly scanned in the main scanning direction in the direction in which the rotation axis 44 of the photoconductor 1 extends, and these are imaged to form an electrostatic latent image on the surface of the photoconductor 1 in sequence. That is, the charge amount of the photoreceptor 1 uniformly charged by the charger 32 is different depending on whether the laser beam is irradiated or not, and an electrostatic latent image is formed.

  The developing unit 33 is a developing unit that develops an electrostatic latent image formed on the surface of the photoconductor 1 by exposure with a developer (toner), and is provided facing the photoconductor 1. A developing roller 33a for supplying toner to the toner, and a casing 33b for supporting the developing roller 33a so as to be rotatable about a rotation axis parallel to the rotation axis 44 of the photosensitive member 1 and containing a developer containing toner in the internal space thereof. Prepare.

  The transfer charger 34 supplies a toner image, which is a visible image formed on the outer peripheral surface of the photoreceptor 1 by development, between the photoreceptor 1 and the transfer charger 34 from the direction of the arrow 42 by a conveying unit (not shown). It is a transfer means to transfer on the transfer paper 51 which is a recording medium. The transfer charger 34 is, for example, a contact-type transfer unit that includes a charging unit and transfers the toner image onto the transfer paper 51 by applying a charge having a polarity opposite to that of the toner to the transfer paper 51.

  The cleaner 36 is a cleaning unit that removes and collects toner remaining on the outer peripheral surface of the photoconductor 1 after the transfer operation by the transfer charger 34, and a cleaning blade 36 a that peels off toner remaining on the outer peripheral surface of the multilayer photoconductor 1. And a recovery casing 36b for storing the toner separated by the cleaning blade 36a. The cleaner 36 is provided together with a static elimination lamp (not shown).

Further, the image forming apparatus 100 is provided with a fixing device 35 as fixing means for fixing the transferred image on the downstream side where the transfer paper 51 that has passed between the photoreceptor 1 and the transfer charger 34 is conveyed. It is done. The fixing device 35 includes a heating roller 35a having a heating unit (not shown), and a pressure roller 35b that is provided facing the heating roller 35a and is pressed by the heating roller 35a to form a contact portion.
Reference numeral 37 denotes a separating unit that separates the transfer paper and the photosensitive member, and 38 denotes a casing that houses each unit of the image forming apparatus.

The image forming operation by the image forming apparatus 100 is performed as follows.
First, when the photosensitive member 1 is rotationally driven in the direction of the arrow 41 by the driving unit, the photosensitive member 1 is provided by the charger 32 provided on the upstream side in the rotational direction of the photosensitive member 1 with respect to the light imaging point by the exposure unit 31. Are uniformly charged to a predetermined positive potential.

Next, light corresponding to image information is irradiated from the exposure unit 32 to the surface of the photoreceptor 1. In this exposure, the surface charge of the portion irradiated with light is removed by this exposure, and a difference occurs between the surface potential of the portion irradiated with light and the surface potential of the portion not irradiated with light. A latent image is formed.
Toner is supplied to the surface of the photosensitive member 1 on which the electrostatic latent image is formed from a developing device 33 provided on the downstream side in the rotation direction of the photosensitive member 1 with respect to the light image formation point by the exposure means 33, and the electrostatic latent image. Is developed to form a toner image.

In synchronization with the exposure of the photoreceptor 1, the transfer paper 51 is supplied between the photoreceptor 1 and the transfer charger 34. The transfer charger 34 applies a charge having a polarity opposite to that of the toner to the supplied transfer paper 51, and the toner image formed on the surface of the photoreceptor 1 is transferred onto the transfer paper 51.
The transfer paper 51 onto which the toner image has been transferred is conveyed to the fixing device 35 by the conveying means, and is heated and pressurized when passing through the contact portion between the heating roller 35a and the pressure roller 35b of the fixing device 35, and the toner The image is fixed on the transfer paper 51 and becomes a robust image. The transfer paper 51 on which the image is formed in this way is discharged to the outside of the image forming apparatus 100 by the conveying means.

  On the other hand, the toner remaining on the surface of the photoreceptor 1 after the transfer of the toner image by the transfer charger 34 is separated from the surface of the multilayer photoreceptor 1 by the cleaner 36 and collected. The charge on the surface of the photoreceptor 1 from which the toner has been removed in this manner is removed by the light from the static elimination lamp, and the electrostatic latent image on the surface of the photoreceptor 1 disappears. Thereafter, the photosensitive member 1 is further driven to rotate, and a series of operations starting from charging is repeated to form images continuously.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

Example 1
Titanium oxide fine particles (average primary particle size: 10 to 30 nm, manufactured by Ishihara Sangyo Co., Ltd., product name: TTO-55A) as metal oxide fine particles and copolymer nylon resin (manufactured by Toray Industries, Inc., product name) as binder resin : Amilan CM8000) 3 parts by weight was added to a mixed solvent of 60 parts by weight of methanol and 40 parts by weight of 1,3-dioxolane, and dispersed with a paint shaker for 10 hours to prepare an intermediate layer coating solution (total amount 3 kg). .
The obtained coating solution for the intermediate layer is filled in a coating tank, and a cylindrical support made of aluminum having a diameter of 30 mm and a total length of 340 mm is immersed and pulled up as a conductive support, and then the obtained coating film is naturally dried. An intermediate layer having a thickness of 0.9 μm was formed on the conductive support.

Next, 15 parts by weight of titanyl phthalocyanine represented by the following structural formula as a charge generation material (for example, prepared by a known method described in Japanese Patent No. 3567422) and butyral resin (product of Sekisui Chemical Co., Ltd., product) as a binder resin Name: ESREC BM-2) 10 parts by weight was added to 1,400 parts by weight of 1,3-dioxolane solvent, and dispersed for 72 hours with a ball mill to prepare a charge generation layer coating solution (total amount 3 kg).
The obtained charge generation layer coating solution is applied to the surface of the intermediate layer previously provided by the same dip coating method as that for the intermediate layer, and the resulting coating film is naturally dried to generate a charge of 0.2 μm in thickness. A layer was formed on the intermediate layer.

Next, 20 parts by weight of a diamine compound represented by the following structural formula as a charge transport material, 1 part by weight of PQQ (manufactured by Sigma-Aldrich) as an additive, and polycarbonate resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name) as a binder resin 30 parts by weight of PCZ300) was dissolved in a solvent of 300 parts by weight of tetrahydrofuran to prepare a coating solution for charge transport layer (total amount: 3 kg).
The obtained charge transport layer coating solution was applied to the surface of the charge transport layer previously provided by the same dip coating method as that for the intermediate layer, and the resulting coating film was dried at a temperature of 140 ° C. for 1 hour to obtain a film thickness. A 25 μm charge transport layer was formed on the charge generation layer to produce the photoreceptor of Example 1 shown in FIG.

(Example 2)
As an additive for the charge transport layer coating solution, in addition to 1 part by weight of PQQ, 1 part by weight of ubiquinones represented by the following structural formula (n = 10, manufactured by Wako Pure Chemical Industries, Ltd., product name: Coenzyme Q10) A photoconductor of Example 2 shown in FIG. 1 was produced in the same manner as Example 1 except that it was used.

(Comparative Example 1)
A photoconductor of Comparative Example 1 having the same laminated structure as that of FIG. 1 was produced in the same manner as in Example 1 except that PQQ was not used as an additive for the charge transport layer coating solution.

(Comparative Example 2)
As in Example 1, except that 1 part by weight of dibutylhydroxytoluene (BHT, manufactured by Kyodo Yakuhin Co., Ltd.) represented by the following structural formula was used as an additive for the coating solution for the charge transport layer, instead of PQQ. Thus, a photoreceptor of Comparative Example 2 having the same laminated structure as that of FIG. 1 was produced.

(Example 3)
In the same manner as in Example 1, an intermediate layer having a thickness of 0.9 μm was formed on the conductive support.
Next, the charge generation layer coating solution (total amount: 3 kg) was used in the same manner as in Example 1 except that 0.1 part by weight of PQQ (manufactured by Sigma-Aldrich) was added as an additive to the charge generation layer coating solution. And a charge generation layer having a thickness of 0.2 μm was formed on the intermediate layer.
Next, a charge transport layer having a thickness of 25 μm was formed on the charge generation layer in the same manner as in Example 1 except that PQQ was not used as an additive for the charge transport layer coating solution, as shown in FIG. A photoconductor of Example 3 was produced.

Example 4
In addition to 1 part by weight of PQQ, 0.1 wt. Of ubiquinones represented by the above structural formula (n = 10, manufactured by Wako Pure Chemical Industries, Ltd., product name: Coenzyme Q10) as an additive for the charge generation layer coating solution A photoconductor of Example 4 shown in FIG. 1 was produced in the same manner as in Example 3 except that the above-described parts were used.

(Example 5)
An intermediate layer coating solution (total amount 3 kg) was prepared in the same manner as in Example 1 except that 0.1 part by weight of PQQ (Sigma-Aldrich) was added as an additive for the intermediate layer coating solution. An intermediate layer having a thickness of 0.9 μm was formed on the conductive support.
Next, in the same manner as in Example 1, a charge generation layer having a thickness of 0.2 μm was formed on the intermediate layer.
Next, a charge transport layer having a thickness of 25 μm was formed on the charge generation layer in the same manner as in Example 1 except that PQQ was not used as an additive for the charge transport layer coating solution, as shown in FIG. A photoconductor of Example 5 was produced.

(Example 6)
Dendritic titanium oxide fine particles surface-treated with alumina (Al ₂ O ₃ ) and zirconia (ZrO ₂ ) as metal oxide fine particles (average primary particle size: minor axis 40-70 nm, major axis 200-300 nm, Ishihara Sangyo Co., Ltd., product name: TTO-D-1) 12 parts by weight, aqueous polyacrylic polyol as binder resin (solid content: 45%, OH value: 80, manufactured by DIC Corporation, product name: Burnock WE-300) 8 .4 parts by weight and blocked isocyanate compound (solid content: 40%, NCO content: 5.4%, manufactured by Mitsui Chemicals Polyurethanes, product name: Takenate WB-920 :) 10.5 parts by weight and PQQ as an additive 1 part by weight (manufactured by Sigma-Aldrich) is added to 69 parts by weight of water and dispersed with a paint shaker for 6 hours to prepare an intermediate layer coating solution (total amount of 1 kg). Made.
The obtained coating solution for the intermediate layer is filled in a coating tank, an aluminum cylindrical support having a diameter of 30 mm and a total length of 340 mm is immersed and pulled up as a conductive support, and the resulting coating film is heated at 150 ° C. An intermediate layer having a thickness of 1.0 μm was formed on the conductive support by drying and curing for 30 minutes.
Since PQQ was water-soluble, it dissolved well in the intermediate layer coating solution, and the surface of the intermediate layer coating film was smooth and extremely good.
Next, in the same manner as in Example 1, a charge generation layer having a thickness of 0.2 μm was formed on the intermediate layer.
Next, a charge transport layer having a thickness of 25 μm was formed on the charge generation layer in the same manner as in Example 1 except that PQQ was not used as an additive for the charge transport layer coating solution, as shown in FIG. A photoconductor of Example 6 was produced.

(Example 7)
As in Example 5, except that 1 part by weight of dibutylhydroxytoluene (BHT, manufactured by Kyodo Pharmaceutical Co., Ltd.) represented by the above structural formula was used as an additive for the charge generation layer coating solution, FIG. The photoreceptor of Example 7 shown was produced.

(Comparative Example 3)
In the same manner as in Comparative Example 1, an intermediate layer, a charge generation layer, and a charge transport layer were sequentially formed on the conductive support.
Titanium oxide fine particles as metal oxide fine particles (average primary particle size: 15 nm, manufactured by Teika Co., Ltd., product name: MT-100T) 0.373 parts by weight and polycarbonate resin as binder resin (manufactured by Mitsubishi Gas Chemical Co., Ltd., product name: PCZ400) 0.373 parts by weight was added to 6.714 parts by weight of a solvent, and a dispersion treatment was carried out with a paint shaker for 3 hours to prepare a primary dispersion for the surface protective layer (total amount 80 g).
Next, 10 parts by weight of a diamine compound represented by the above structural formula as a charge transport material, 13.627 parts by weight of a polycarbonate resin (product name: PCZ300, manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a binder resin, and dimethylpolysiloxane as a leveling agent (Product name: KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.0028 parts by weight was added to a solvent of 244.786 parts by weight of tetrahydrofuran and mixed to prepare a charge transport material solution (total amount 2.92 kg). .
The obtained charge transport material solution and the primary dispersion for the surface protective layer were mixed and dispersed for 1 hour with a paint shaker to prepare a secondary dispersion coating liquid for the surface protective layer (total amount of 3 kg).
The obtained secondary dispersion coating liquid for surface protective layer (surface protective layer coating liquid) was applied on the charge transport layer previously provided by the ring coating method, and the resulting coating film was heated at 130 ° C. for 1 hour. A surface protective layer having a thickness of 8 μm was formed on the charge transport layer by drying, and a photoreceptor of Comparative Example 3 having the same laminated structure as that of FIG. 2 was produced.

(Example 8)
As the additive for the primary dispersion for the surface protective layer, a coating solution for the surface protective layer (total amount of 3 kg) was prepared in the same manner as in Comparative Example 3 except that 0.5 part by weight of PQQ (manufactured by Sigma-Aldrich) was added. Then, a surface protective layer having a thickness of 8 μm was formed on the charge transport layer, and a photoconductor of Example 8 shown in FIG. 2 was produced.

Example 9
As an additive for the primary dispersion for the surface protective layer, in addition to 0.5 parts by weight of PQQ, ubiquinones represented by the above structural formula (n = 10, manufactured by Wako Pure Chemical Industries, Ltd., product name: Coenzyme Q10) 0 A photoconductor of Example 9 shown in FIG. 2 was produced in the same manner as in Example 8, except that 0.5 part by weight was used.

(Evaluation)
For each of the photoreceptors of Examples 1 to 9 and Comparative Examples 1 to 3 prepared as described above, the electrical characteristics, electrical durability, and ozone resistance were measured, and the electrical characteristics, image characteristics, and The ozone resistance was evaluated.

(Electrical properties and electrical durability)
Each photoconductor was mounted on a commercially available digital copying machine (manufactured by Sharp Corporation, model: AR-450S) equipped with a corona discharge charger as charging means for the photoconductor.
After confirming the initial image, in order to measure the surface potential of the photoconductor in the image forming process, the developing unit is removed from the digital copying machine, and a surface potential meter (Model: MODEL344 manufactured by Trek Japan Co., Ltd.) is used instead. Installation, initial electrical properties and electrical durability were measured.

The surface of the photoreceptor when this digital copying machine is not exposed to laser light in a normal temperature / normal humidity (N / N) environment at a temperature of 25 ° C. and a relative humidity of 50%. The potential was measured as a charging potential V0 (−V), and the surface potential of the photosensitive member when exposed by laser light was measured as an exposure potential VL (−V).
Further, the surface potential of the photoconductor immediately after being exposed to the laser beam was measured as a residual potential Vr (−V).
These measurement results were used as evaluation indexes for initial electrical characteristics.

Next, the surface electrometer was removed from the digital copying machine, and the developing unit was attached again. For each photoconductor, a character test chart (ISO19752) was printed (image formation) on 100,000 sheets of recording paper in an N / N environment. .
After the image formation on 100,000 sheets was completed and the image was confirmed, the developing unit was removed from the digital copying machine and the surface potential meter was attached again. For each photoconductor, the charging potential V0 (V) and exposure were the same as in the initial stage. The potential VL (V) was measured.
Further, the surface potential of the photoconductor immediately after being exposed to the laser beam in the same manner as in the initial stage was measured as a residual potential Vr (−V).
It was evaluated that the smaller the potential fluctuation ΔVL (| V0−VL |), the better the stability of the electrical characteristics, and at the same time, the density and sharpness of the obtained character image were evaluated by visual observation.

(Ozone resistance)
Immediately after the evaluation of electrical characteristics and electrical durability, the digital copying machine was turned off and the photoconductor was left as it was.
After being left for a day, the above character test chart was output again, and the density and clarity of the character image were evaluated by visual observation.
That is, the photoconductor portion left in the vicinity of the charger is left in a state where the ozone atmosphere and the discharge product are attached, and the deterioration of the photoconductor is remarkably accelerated. The degree of deterioration was evaluated.

[Electrical characteristics]
Electrical characteristics were evaluated according to the following criteria.
○: Good ΔVL less than 60V Δ: Slightly poor ΔVL 60V or more and less than 80V ×: Bad ΔVL 80V or more

[Image characteristics]
Image characteristics were evaluated according to the following criteria.
◎: Good ○: No problem in actual use, but there are minute black spots ×: Fog is generated

[Ozone resistance]
The ozone resistance was evaluated according to the following criteria.
A: Good (no change)
○: Although there is no problem in actual use, the character density is slightly reduced. X: Whitening occurs Table 1 shows the obtained results.
“After printing durability test” in Table 1 means “after 100,000 images have been formed”.

From the evaluation results in Table 1, the following can be understood.
(1) Photoreceptors having a layer containing PQQ as an antioxidant (Examples 1 to 9) are more resistant to ozone than photoreceptors having no PQQ-containing layer (Comparative Examples 1 to 3). It is good.
(2) In addition to the layer containing PQQ as an antioxidant, the photoreceptors (Examples 2, 4, 7 and 9) having a layer containing Q10 as an antioxidant have better ozone resistance. .
(3) On the other hand, the photoreceptor (Comparative Example 1) that does not have a layer containing PQQ has the greatest deterioration.
(4) The deterioration of the photoconductor (Comparative Example 2) having a layer containing BHT instead of PQQ as the antioxidant is large. This is presumably because the volatile BHT was vaporized in the heat drying during the production of the photoconductor, and the remaining amount in the photoconductor was reduced.
(5) In the photoreceptor (Comparative Example 3) that does not have a layer containing PQQ but has a surface protective layer, it can be sufficiently predicted that the mechanical strength is improved by the surface protective layer. The durability against is not improved so much.

1, 20a, 20b, 20c Electrophotographic photosensitive member 13a, 13b, 13c Conductive support 11a, 11b Charge transport layer 12a, 12b Charge transport layer 14a, 14b, 14c Intermediate layer 15b Surface protective layer 16a, 16b Multilayer type photosensitive layer

31 Exposure means (semiconductor laser)
32 Charging means (charger)
33 Developing means (developer)
33a Developing roller 33b Casing 34 Transfer means (transfer charger)
35 Fixing means (fixing device)
35a Heating roller 35b Pressure roller 36 Cleaning means (cleaner)
36a Cleaning blade 36b Recovery casing 37 Separating means 38 Housing 41, 42 Arrow 44 Rotating axis 51 Recording medium (recording paper or transfer paper)
100 Image forming device (laser printer)

Claims (15)

As an antioxidant for ozone and nitrogen oxides generated by discharge in photosensitive operation, the formula:

An electrophotographic photoreceptor comprising a layer containing pyrroloquinoline quinone represented by the formula: The electrophotographic photoreceptor is a laminate in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are laminated in this order or reverse order from the conductive support side on a conductive support. And a layer containing the pyrroloquinoline quinone is formed between the charge generation layer or the charge transport layer of the multilayer photosensitive layer, between the conductive support and the multilayer photosensitive layer. The electrophotographic photosensitive member according to claim 1, which is a surface protective layer formed on the intermediate layer or the laminated photosensitive layer.   The electrophotographic photosensitive member according to claim 2, wherein the layer containing pyrroloquinoline quinone is a charge generation layer or a charge transport layer, the intermediate layer, or the surface protective layer of the multilayer photosensitive layer.   The electrophotographic photosensitive member according to claim 2 or 3, wherein the layer containing pyrroloquinoline quinone is the intermediate layer, and the intermediate layer is a layer formed using a coating solution for an intermediate layer of an aqueous medium.   The said pyrroloquinoline quinone is contained in the charge generation layer of the said laminated type photosensitive layer in the ratio of 1-30 weight part with respect to 100 weight part of said charge generation substances. Electrophotographic photoreceptor.   6. The pyrroloquinoline quinone according to claim 2, wherein the pyrroloquinoline quinone is contained in the charge transport layer of the multilayer photosensitive layer in a ratio of 1 to 30 parts by weight with respect to 100 parts by weight of the charge transport material. Electrophotographic photoreceptor.   The electrophotography according to any one of claims 2 to 6, wherein the pyrroloquinoline quinone is contained in the intermediate layer in a ratio of 1 to 30 parts by weight with respect to 100 parts by weight of the binder resin contained in the intermediate layer. Photoconductor.   The said pyrroloquinoline quinone is contained in the said surface protective layer in the ratio of 1-30 weight part with respect to 100 weight part of binder resin which the said surface protective layer contains. Electrophotographic photoreceptor. The electrophotographic photoreceptor is an antioxidant for ozone and nitrogen oxides generated by discharge in a photosensitive operation.

(Where n is an integer from 1 to 12)
The electrophotographic photosensitive member according to claim 1, further comprising a layer containing ubiquinones represented by: Whether the layer containing pyrroloquinoline quinone and the layer containing ubiquinones are a charge generation layer or a charge transport layer of the multilayer photosensitive layer,
The layer containing pyrroloquinoline quinone is the intermediate layer and the layer containing ubiquinones is the layer on the intermediate layer side of the multilayer photosensitive layer, or the layer containing pyrroloquinoline quinone is the layer The electrophotographic photosensitive member according to claim 9, wherein the layer on the surface protective layer side of the multilayer photosensitive layer and the layer containing the ubiquinones are the surface protective layer.   The electrophotographic photoreceptor according to claim 9 or 10, wherein the ubiquinone is contained in the charge generation layer of the multilayer photosensitive layer in a ratio of 1 to 30 parts by weight with respect to 100 parts by weight of the charge generation material.   The electron according to any one of claims 9 to 11, wherein the ubiquinones are contained in the charge transport layer of the multilayer photosensitive layer in a ratio of 1 to 30 parts by weight with respect to 100 parts by weight of the charge transport material. Photoconductor.   The electrophotographic photosensitive member according to any one of claims 9 to 12, wherein the ubiquinones are contained in the intermediate layer in a ratio of 1 to 30 with respect to 100 parts by weight of the binder resin contained in the intermediate layer. The electron according to any one of claims 9 to 13, wherein the ubiquinones are contained in the surface protective layer in a ratio of 1 to 30 parts by weight with respect to 100 parts by weight of the binder resin contained in the surface protective layer. Photoconductor.   The electrophotographic photosensitive member according to any one of claims 1 to 14, a charging unit for charging the electrophotographic photosensitive member, and exposing the charged electrophotographic photosensitive member to form an electrostatic latent image. An exposure unit; a development unit that develops the electrostatic latent image formed by exposure to form a toner image; a transfer unit that transfers the toner image formed by development onto a recording medium; and the transferred unit Fixing means for fixing a toner image on the recording medium to form an image; cleaning means for removing and collecting toner remaining on the electrophotographic photosensitive member; and removing surface charges remaining on the electrophotographic photosensitive member. An image forming apparatus comprising at least a charge eliminating unit.

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