JP2010217769A - Positive charging type electrophotographic photoreceptor and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor and an image forming apparatus using the same, wherein even if the toner having insufficient frictional charge is about to adhere to a non-electrostatic latent image forming part on a photoreceptor layer, the toner is in a state of being efficiently prevented from adhering on the non-electrostatic latent image forming part, by improving frictional charging properties of the toner and the photoreceptor layer to stably suppress generation of fogging. <P>SOLUTION: The positive charging type electrophotographic photoreceptor includes at least the photoreceptor layer including a charge generation agent, a charge transport agent, and a binder resin on a support; and the image forming apparatus uses the same, and the photoreceptor layer further includes an electron-donating charge control agent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a positively charged electrophotographic photosensitive member and an image forming apparatus. In particular, the present invention relates to a positively charged electrophotographic photosensitive member capable of stably suppressing the occurrence of fog regardless of the charged state of toner and an image forming apparatus using the positively charged electrophotographic photosensitive member.

Conventionally, in an electrophotographic machine such as a copying machine or a laser printer, after developing an electrostatic latent image formed on an electrophotographic photosensitive member with toner supplied from a developing unit, the developed toner image is Image formation is performed by transferring and fixing to a recording medium (for example, Patent Document 1).
The development of the electrostatic latent image with toner described above is performed by adhering the frictionally charged toner in the developing means to the electrostatic latent image by electrostatic force.

However, in recent years, since the speed of image formation is increasing, there is a problem that the frictional charging of the toner in the developing unit tends to be insufficient.
As a result, the accuracy with which the toner is selectively attached to the electrostatic latent image formed on the electrophotographic photosensitive member is reduced, and the toner is likely to adhere to portions other than the electrostatic latent image. In the formed image, there is a problem that so-called “fogging” tends to occur.

Thus, an electrophotographic photosensitive member that attempts to suppress the occurrence of fog by improving electrical characteristics such as sensitivity characteristics and charging characteristics has been disclosed (for example, Patent Document 1).
That is, Patent Document 1 discloses an electron using an arylidene derivative represented by the following general formula (9) as an electron transporting agent in order to improve the electrical characteristics such as sensitivity characteristics and charging characteristics and suppress the occurrence of fogging. A photographic photoreceptor is disclosed.

(In the general formula (9), R ¹ is a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, an alkylthio group or a residue for forming a ring, R ² is a hydrogen atom, an alkyl group or an aryl group, R ³ and R ⁴ represent a cyano group or an alkoxycarbonyl group, X represents a condensed polycyclic hydrocarbon, m represents an integer of 0 to 5, and when m is 2 or more, a plurality of R ¹ may be the same or different. .)

JP 2003-270819 A (Claims)

  However, even when the electrical characteristics of the electrophotographic photosensitive member are improved as described above, there is a problem that it is difficult to sufficiently suppress the occurrence of fog due to insufficient charge amount of the toner. It is done.

Accordingly, as a result of intensive investigations, the present inventors have found that a toner with insufficient frictional charge can be formed on the photosensitive layer by adding an electron donating charge control agent to the photosensitive layer of the positively charged electrophotographic photosensitive member. Even if the toner is likely to adhere to the non-electrostatic latent image forming portion, the triboelectric chargeability between the toner and the photosensitive layer is improved, and the toner is directly applied to the non-electrostatic latent image forming portion. It has been found that the adhesion can be effectively suppressed.
As a result, it has been found that the occurrence of fogging can be stably suppressed regardless of the charged state of the toner.
That is, an object of the present invention is to provide a positively charged electrophotographic photosensitive member capable of stably suppressing the occurrence of fog regardless of the charged state of toner and an image forming apparatus using the positively charged electrophotographic photosensitive member.

According to the present invention, there is provided a positively charged electrophotographic photosensitive member in which a photosensitive layer containing at least a charge generating agent, a charge transporting agent and a binder resin is provided on a substrate, wherein the photosensitive layer is further charged with an electron donating charge. A positively charged electrophotographic photosensitive member comprising a control agent is provided, and the above-described problems can be solved.
That is, even if the photosensitive layer contains an electron donating charge control agent, the toner with insufficient frictional charging is likely to adhere to the non-electrostatic latent image forming portion on the photosensitive layer. And the photosensitive layer, the triboelectric chargeability can be improved, and the toner can be effectively prevented from adhering to the non-electrostatic latent image forming portion as it is.
Therefore, it is possible to stably suppress the occurrence of fog regardless of the charged state of the toner.

In constituting the positively charged electrophotographic photosensitive member of the present invention, the electron donating charge control agent is selected from the group consisting of azo metal charge control agents, oxycarboxylic acid charge control agents, and boron complex charge control agents. It is preferable that it is at least one selected.
With this configuration, the triboelectric chargeability between the toner and the photosensitive layer can be adjusted to a more suitable range, while the charging characteristics and sensitivity characteristics of the positively charged electrophotographic photosensitive member are effective. Can be held in.

In constituting the positively charged electrophotographic photosensitive member of the present invention, the content of the electron donating charge control agent is in the range of 0.01 to 20 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. It is preferable to set the value within the range.
With this configuration, the triboelectric chargeability between the toner and the photosensitive layer can be adjusted to a more suitable range, while the charging characteristics and sensitivity characteristics of the positively charged electrophotographic photosensitive member can be adjusted. It can be held more effectively.

In constituting the positively charged electrophotographic photosensitive member of the present invention, the binder resin is preferably a polycarbonate resin.
With this configuration, the triboelectric charging property between the toner and the photosensitive layer can be adjusted to a more preferable range.

In constituting the positively charged electrophotographic photosensitive member of the present invention, the photosensitive layer is preferably a single layer type photosensitive layer.
With this configuration, it is easy to configure as a positively charged electrophotographic photosensitive member.

Another aspect of the present invention is an image forming apparatus on which any of the positively charged electrophotographic photosensitive members described above is mounted.
That is, since the image forming apparatus of the present invention is equipped with the above-described specific positively charged electrophotographic photosensitive member, it is possible to stably suppress the occurrence of fog regardless of the charged state of the toner. it can.

In constituting the image forming apparatus of the present invention, it is preferable that the developing system is a reversal developing system.
By comprising in this way, the triboelectric charging property between a toner and a photosensitive layer can be exhibited more effectively.

FIGS. 1A to 1B are views for explaining the configuration of a single-layer electrophotographic photosensitive member. FIG. 2 is a diagram for explaining the relationship between the content of the electron donating charge control agent, the occurrence of fogging, and the charging characteristics. FIGS. 3A to 3C are views for explaining the configuration of the multilayer electrophotographic photosensitive member. FIG. 4 is a diagram for explaining the configuration of the image forming apparatus.

[First Embodiment]
The first embodiment is a positively charged electrophotographic photosensitive member in which a photosensitive layer containing at least a charge generating agent, a charge transporting agent, and a binder resin is provided on a substrate, and the photosensitive layer further has an electron donating property. A positively charged electrophotographic photosensitive member comprising a charge control agent.
Hereinafter, the positively charged electrophotographic photosensitive member as the first embodiment will be specifically described for each constituent element mainly by taking a single layer type electrophotographic photosensitive member as an example.

1. Basic Structure A positively charged electrophotographic photosensitive member 10 of the present invention comprises, as shown in FIG. 1 (a), on a substrate 12, a charge generating agent, a charge transporting agent, and an electron donating charge controlling agent. A single-layer electrophotographic photosensitive member 10 provided with a single-layer photosensitive layer 14 made of a resin is preferable.
This is because a single-layer electrophotographic photosensitive member can be easily configured as a positively charged electrophotographic photosensitive member.
That is, it is because it is not easy to construct a positively charged laminated electrophotographic photosensitive member because an electron transfer agent having sufficient electron mobility has not yet been found.
On the other hand, in the case of a single-layer type electrophotographic photoreceptor, generally, since both a hole transport agent and an electron transport agent are added to the photosensitive layer, it is easily configured as a positively charged electrophotographic photoreceptor. Because it can.
In addition, by configuring as a positively charged electrophotographic photosensitive member, it is possible to effectively suppress the generation of oxidizing gas such as ozone in the charging process as compared with the case of configuring as a negatively charged type electrophotographic photosensitive member. As a result, the oxidative deterioration of the photosensitive layer can be effectively suppressed.
In addition, as illustrated in FIG. 1B, the electrophotographic photoreceptor of the present invention is a single-layer electrophotographic photoreceptor 10 ′ in which an intermediate layer 16 is formed between the photosensitive layer 14 and the substrate 12. It can also be.

2. Substrate Moreover, various materials can be used as the constituent material of the substrate.
For example, a substrate formed of a metal such as iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass, or the above-described metal is deposited or deposited. Examples include a substrate made of a laminated plastic material, or a glass substrate coated with aluminum iodide, alumite, tin oxide, indium oxide, or the like.
That is, it is sufficient that the substrate itself has conductivity, or the surface of the substrate has conductivity, and it is sufficient that the substrate has sufficient mechanical strength when used.

3. Intermediate Layer Further, as shown in FIG. 1B, an intermediate layer 16 may be provided on the substrate 12.
This is because the adhesion between the substrate and the photosensitive layer is improved, and by adding a predetermined fine powder in the intermediate layer, the incident light is scattered, the generation of interference fringes is suppressed, and the fogging is further suppressed. This is because it is possible to suppress charge injection from the substrate to the photosensitive layer during non-exposure causing black spots. The fine powder is not particularly limited as long as it has light scattering properties and dispersibility. For example, a white pigment such as titanium oxide, zinc oxide, zinc sulfide, white lead, lithopone, alumina, Inorganic pigments such as extender pigments such as calcium carbonate and barium sulfate, fluorine resin particles, benzoguanamine resin particles, and styrene resin particles can be used.

Moreover, it is preferable to make the film thickness of this intermediate | middle layer into the value within the range of 0.1-50 micrometers. This is because if the intermediate layer is too thick, a residual potential is likely to be generated on the surface of the photoreceptor, which may cause a decrease in electrical characteristics. On the other hand, if the thickness of the intermediate layer becomes too thin, the unevenness of the surface of the substrate cannot be sufficiently relaxed, and the adhesion between the substrate and the photosensitive layer may not be obtained.
Therefore, the thickness of the intermediate layer is preferably set to a value within the range of 0.2 to 40 μm, and more preferably set to a value within the range of 0.5 to 30 μm.

4). Photosensitive layer (1) Electron donating charge control agent The positively chargeable electrophotographic photosensitive member of the present invention is characterized in that the photosensitive layer contains an electron donating charge control agent.
The reason for this is that even if the photosensitive layer contains an electron donating charge control agent, toner with insufficient triboelectric charge tends to adhere to the non-electrostatic latent image forming portion on the photosensitive layer. This is because the triboelectric chargeability between the toner and the photosensitive layer can be improved and the toner can be effectively prevented from adhering to the non-electrostatic latent image forming portion as it is.
Therefore, it is possible to stably suppress the occurrence of fog regardless of the charged state of the toner.
That is, generally, when the triboelectric charging of the toner in the developing unit becomes insufficient due to high-speed image formation or the like, even for a non-electrostatic latent image forming unit that is not developed originally, Toner tends to adhere, and as a result, fog is likely to occur.
For example, in the case of the reversal development method, since the charging polarity of the electrophotographic photosensitive member and the frictional charging polarity of the toner are the same, the charge on the surface of the photosensitive layer is not erased by exposure, The toner repels electrically.
Therefore, basically, toner does not adhere to the non-electrostatic latent image forming portion.
However, if the toner is insufficiently triboelectrically charged, the electrical repulsion is weakened, and the toner is likely to adhere to the non-electrostatic latent image forming portion, which in turn tends to cause fogging. turn into.
In this regard, in the positively charged electrophotographic photosensitive member of the present invention, the photosensitive layer contains an electron donating charge control agent. The microscopic electrostatic attraction between the toner that is extremely positively charged, so-called reversely charged toner, and the non-electrostatic latent image forming portion on the photosensitive layer is reduced, and the reversely charged toner is non-static. Adhesion to the electrostatic latent image forming unit can be effectively suppressed.
Therefore, the positively charged electrophotographic photosensitive member of the present invention can stably suppress the occurrence of fog regardless of the charged state of the toner.

(1) -1 Type As the type of the electron donating charge control agent, a conventionally known compound used as a charge control agent for toner can be used.
For example, azo metal charge control agent, oxycarboxylic acid charge control agent, boron complex charge control agent, iron complex charge control agent, zinc complex charge control agent, alkylsalicylic acid complex salt charge control agent, sulfonic acid pendant Examples thereof include resin charge control agents.

Of the above, it is particularly preferable to use at least one selected from the group consisting of azo metal charge control agents, oxycarboxylic acid charge control agents, and boron complex charge control agents.
The reason for this is that with these electron donating charge control agents, the triboelectric chargeability between the toner and the photosensitive layer can be adjusted to a more suitable range, while the charging characteristics of the electrophotographic photosensitive member and This is because the sensitivity characteristic can be effectively maintained.

  Specific examples of the electron donating charge control agent are shown in the following formulas (1) to (4) (CCA-1 to 4).

(1) -2 Content The content of the electron donating charge control agent is preferably set to a value within the range of 0.01 to 20 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. .
The reason for this is that by setting the content of the electron donating charge control agent in such a range, the triboelectric chargeability between the toner and the photosensitive layer is adjusted to a more suitable range, and the positively charged electrophotographic This is because the charging characteristics and sensitivity characteristics of the photoreceptor can be more effectively maintained.
That is, when the content of the electron donating charge control agent is less than 0.01 parts by weight, it may be difficult to improve the triboelectric chargeability between the toner and the photosensitive layer. . On the other hand, when the content of the electron donating charge control agent exceeds 20 parts by weight, the charging characteristics and sensitivity characteristics of the positively charged electrophotographic photosensitive member may be excessively deteriorated.
Therefore, the content of the electron donating charge control agent is more preferably set to a value within the range of 0.05 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. More preferably, the value is within the range of parts by weight.

Next, the relationship between the content of the electron donating charge control agent, the occurrence of fogging, and the charging characteristics will be described with reference to FIG.
That is, in FIG. 2, the content (parts by weight) of the electron donating charge control agent relative to 100 parts by weight of the binder resin of the photosensitive layer is taken on the horizontal axis, and the electrophotographic photoreceptor is used on the left vertical axis. A characteristic curve A in which the fog density (−) in the case of image formation is taken, and a characteristic curve B in which the charging potential (V) in the electrophotographic photosensitive member is taken on the right vertical axis.
The measurement conditions of the fog density and the charging potential are described in the examples.

First, it can be seen from the characteristic curve A that the fog density value decreases as the content of the electron donating charge control agent is increased.
More specifically, as the electron donating charge control agent is increased from 0 parts by weight to 0.1 parts by weight, the fog density value is rapidly decreased from 0.015 to 0.007. Can do. It can be seen that when the content of the electron donating charge control agent is further increased, the value of the fog density continues to decrease very slowly.

Next, from the characteristic curve B, it can be seen that the value of the charging potential decreases as the content of the electron donating charge control agent is increased.
However, it can be seen that the degree of decrease is almost constant as a whole and very moderate.
More specifically, the charge potential is 600 V when the content of the electron donating charge control agent is 0 part by weight, whereas the charge when the content of the electron donating charge control agent is 5 parts by weight. The amount is 585V.
Therefore, it is understood that even when an electron donating charge control agent is contained, the decrease in charging characteristics is at a level that does not cause a problem in practice.

As described above, when the explanations of the characteristic curves A and B are combined, by containing an electron donating charge control agent in the photosensitive layer, it is possible to effectively generate fog while stably maintaining practical charging characteristics. It turns out that it can suppress.
In the characteristic curve shown in FIG. 2, the upper limit of the content of the electron donating charge control agent is up to 5 parts by weight. It has been confirmed that a level that does not cause a problem in practical use can be maintained.
Furthermore, it has been confirmed that not only charging characteristics but also sensitivity characteristics can be maintained at a level that does not cause a problem in practice (see Examples).

(2) Charge generator (2) -1 type Examples of the charge generator usable in the positively charged electrophotographic photosensitive member of the present invention include, for example, phthalocyanine pigments; disazo pigments; disazo condensation pigments, monoazo pigments, Perylene pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azulenium pigments, cyanine pigments, pyrylium salts, ansanthrone pigments, triphenylmethane pigments, selenium pigments, toluidine One kind of conventionally known charge generating agents such as a pigment, a pyrazoline pigment, a quinacridone pigment, or a combination of two or more thereof may be mentioned.

(2) -2 Content Further, it is preferable that the amount of addition of the charge generator is set to a value within the range of 0.2 to 40 parts by weight with respect to 100 parts by weight of the binder resin.
The reason for this is that when the amount of the charge generator added is less than 0.2 parts by weight, the effect of increasing the quantum yield becomes insufficient, and the sensitivity characteristics, electrical characteristics, stability, etc. of the positively charged electrophotographic photosensitive member It is because it becomes impossible to improve. On the other hand, when the amount of the charge generator added exceeds 40 parts by weight, the effect of increasing the extinction coefficient for light having a wavelength in the red region, near infrared region, or infrared region in visible light becomes insufficient. This is because the sensitivity characteristics, electrical characteristics, stability, and the like of the photoconductor may not be improved.
Therefore, the amount of the charge generator added is more preferably in the range of 0.5 to 20 parts by weight, and still more preferably in the range of 1 to 10 parts by weight.

(3) Charge transport agent (3) -1 type As the charge transport agent (hole transport agent and electron transport agent) used in the charge transport layer, 2,5-bis (p-diethylaminophenyl) -1,3 Oxadiazole derivatives such as 1,4-oxadiazole, 1,3,5-triphenyl-pyrazoline, 1- [pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) ) Aromatic tertiary amino such as pyrazoline derivatives such as pyrazoline, triphenylamine, tri (p-methyl) phenylamine, N, N-bis (3,4-dimethylphenyl) biphenyl-4-amine, dibenzylaniline Aromatic tertiary diamino compounds such as compounds, N, N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,1-biphenyl] -4,4'-diamine 1,2,4-triazine derivatives such as 3- (4′-dimethylaminophenyl) -5,6-di- (4′-methoxyphenyl) -1,2,4-triazine, 4-diethylaminobenzaldehyde-1 , Hydrazone derivatives such as 1-diphenylhydrazone, quinazoline derivatives such as 2-phenyl-4-styryl-quinazoline, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) -benzofuran, p- (2 , 2-diphenylvinyl) -N, N-diphenylaniline and other α-stilbene derivatives, enamine derivatives, carbazole derivatives such as N-ethylcarbazole, hole transport materials such as poly-N-vinylcarbazole and derivatives thereof; chloranil, Quinone compounds such as bromoanil and anthraquinone, tetracyanoquinodimethane , Fluorenone compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, xanthone compounds, thiophene compounds, diphenoquinone compounds and other electron transport materials; One kind or a combination of two or more kinds of polymers having a group to be formed in the main chain or side chain can be mentioned.

(3) -2 Content The content of the hole transport agent is preferably set to a value in the range of 10 to 100 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. A value within the range of parts by weight is preferred.
Further, the content of the electron transport agent is preferably a value within the range of 10 to 100 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer, and a value within the range of 20 to 70. Is more preferable.

(4) Additives In addition, for the purpose of preventing deterioration of the photoreceptor due to ozone, oxidizing gas, or light and heat generated in the electrophotographic apparatus, an antioxidant, a light stabilizer, and heat stability in the photoreceptor layer. It is preferable to add an agent or the like.
For example, as the antioxidant, hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, organic phosphorus compounds, and the like are used. Examples of the light stabilizer include derivatives such as benzophenone, benzotriazole, dithiocarbamate, and tetramethylpiperidine.

(5) Binder resin The type of the binder resin is not particularly limited. For example, a polycarbonate resin, a polyester resin, a polyarylate resin, a styrene-butadiene copolymer, and a styrene-acrylonitrile copolymer are used. , Styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, ionomer, vinyl chloride-vinyl acetate copolymer Polymers, alkyd resins, polyamides, polyurethanes, polysulfones, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyether resins, and other thermoplastic resins, silicone resins, epoxy resins, phenol resins, urea resins, melamine resins, and other crosslinks Heat hardening Resins such as photocurable resins such as curable resins, epoxy acrylates and urethane acrylates can be used.

Moreover, among the above-mentioned, it is particularly preferable to use a polycarbonate resin.
This is because, with a polycarbonate resin, the triboelectric chargeability between the toner and the photosensitive layer can be adjusted to a more suitable range.
In addition, as a number average molecular weight of polycarbonate resin, it is preferable to set it as the value within the range of 5000-100000, and it is more preferable to set it as the value within the range of 10000-70000.

(6) Film thickness The film thickness of the photosensitive layer is preferably set to a value in the range of 5 to 100 μm.
The reason for this is that when the thickness of the photosensitive layer is less than 5 μm, the mechanical strength of the photosensitive member may be insufficient. On the other hand, when the thickness of the photosensitive layer exceeds 100 μm, it may be easily peeled off from the substrate or the intermediate layer or may be difficult to form uniformly. Accordingly, the thickness of the photosensitive layer is more preferably set to a value within the range of 10 to 80 μm, and further preferably set to a value within the range of 20 to 40 μm.

5). Method for forming photosensitive layer In forming a single-layer type photosensitive layer, a binder resin, a charge generating agent, an electron transporting agent, a hole transporting agent, and an electron donating charge control agent are added to a solvent. Preferably, the method includes a step of preparing a photosensitive layer coating solution, a step of applying the prepared photosensitive layer coating solution onto a substrate, and a step of drying the substrate coated with the photosensitive layer coating solution.
Hereinafter, each process will be described.

(1) Coating liquid preparation process A binder resin, a charge generator, an electron transport agent, a hole transport agent, and an electron donating charge control agent are added to a solvent, for example, a roll mill, a ball mill, an attritor, a paint. It is preferable to disperse and mix using a shaker, an ultrasonic disperser or the like to obtain a coating solution.
More specifically, it is preferable to prepare a coating solution having a solid content concentration of 10 to 30% by weight.

Moreover, various organic solvents can be used as the solvent for preparing the coating liquid. For example, 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, chloroform and tetrachloride Halogenated hydrocarbons such as carbon and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dioxane and dioxolane; ketones such as acetone, methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and methyl acetate Class, dimethylformaldehyde, dimethylformamide, dimethylsulfoxide, etc., alone or in combination of two or more. That.
Furthermore, in order to improve the dispersibility of the electron transporting agent, the charge generating agent and the like and the smoothness on the surface of the photoreceptor layer, it is also preferable to add a surfactant, a leveling agent or the like when preparing the coating solution.

(2) Coating process Moreover, when performing a coating process, it is also preferable to apply | coat a coating liquid directly on a base | substrate, or to apply indirectly through an intermediate | middle layer.
As a coating method, it is preferable to use, for example, a spin coater, an applicator, a spray coater, a bar coater, a dip coater, a doctor blade or the like in order to form a photosensitive layer having a uniform thickness.

(3) Drying process Moreover, after an application | coating process, it is preferable to make it dry at the drying temperature of 60 to 150 degreeC, for example using a high temperature dryer, a vacuum dryer, etc. in a drying process.

6). Laminated electrophotographic photoreceptor The positively charged electrophotographic photoreceptor of the present invention may be configured as a laminated electrophotographic photoreceptor.
That is, as shown in FIG. 3A, the positively charged electrophotographic photosensitive member of the present invention is a laminated photosensitive layer in which a charge generation layer 24 and a charge transport layer 22 are sequentially laminated on a substrate 12. The laminated electrophotographic photosensitive member 20 provided with 26 may be configured.
Further, as shown in FIG. 2B, a laminated electrophotographic photosensitive member 20 provided with a laminated photosensitive layer 26 'formed by sequentially laminating a charge transport layer 22 and a charge generating layer 24 on the substrate 12. You may comprise as'.
As shown in FIG. 2C, the multilayer electrophotographic photoreceptor is a laminate in which an intermediate layer 16 is formed between the substrate 12 and the charge generation layer 24 as long as the characteristics of the photoreceptor are not impaired. It may be a type electrophotographic photoreceptor 20 ″.

The substrate and organic material used in the multilayer electrophotographic photosensitive member can be basically the same as in the case of the single-layer electrophotographic photosensitive member.
Further, the content of the electron donating charge control agent is preferably set to a value in the range of 0.01 to 20 parts by weight with respect to 100 parts by weight of the binder resin in the surface layer of the laminated photosensitive layer. More preferably, the value is within the range of 1 to 5 parts by weight.
In addition, the content of the charge transport agent in the charge transport layer is preferably set to a value in the range of 30 to 100 parts by weight with respect to 100 parts by weight of the binder resin in the charge transport layer.
The content of the charge generation agent in the charge generation layer is preferably set to a value within the range of 5 to 1000 parts by weight with respect to 100 parts by weight of the binder resin of the charge generation layer.
Furthermore, the film thickness of the charge transport layer is preferably a value in the range of 5 to 50 μm, and the film thickness of the charge generation layer is preferably a value in the range of 0.1 to 5 μm.
As a method for forming a laminated photosensitive layer, an intermediate layer, a charge generation layer, and a charge transport layer may be sequentially formed on a substrate in the same manner as in the case of forming a single-layer photosensitive layer.

[Second Embodiment]
The second embodiment is an image forming apparatus on which the positively charged electrophotographic photosensitive member described as the first embodiment is mounted.
Hereinafter, the second embodiment will be specifically described focusing on differences from the contents described in the first embodiment.

  As the image forming apparatus of the present invention, a copying machine 30 as shown in FIG. 4 can be preferably used. The copying machine 30 includes an image forming unit 31, a paper discharge unit 32, an image reading unit 33, and a document feeding unit 34. The image forming unit 31 further includes an image forming unit 31a and a paper feeding unit 31b. In the illustrated example, the document feeding unit 34 includes a document placing tray 34a, a document feeding mechanism 34b, and a document discharge tray 34c, and the document placed on the document placing tray 34a. Is fed to the image reading position P by the document feeding mechanism 34b and then discharged to the document discharge tray 34c.

Then, when the original is sent to the original reading position P, the image reading unit 33 reads the image on the original using the light from the light source 33a. That is, an image signal corresponding to the image on the document is formed using an optical element 33b such as a CCD.
On the other hand, recording sheets (hereinafter simply referred to as “sheets”) S stacked on the sheet feeding unit 31b are sent one by one to the image forming unit 31a. The image forming unit 31a is provided with an electrophotographic photosensitive member 41 as an image carrier. Further, around the electrophotographic photosensitive member 41, a charging unit 42, an exposing unit 43, a developing unit 44, and The transfer roller 45 and the cleaning unit 46 are arranged along the rotation direction of the electrophotographic photosensitive member 41.

Among these components, the electrophotographic photoreceptor 41 is rotationally driven in the direction indicated by the solid line arrow in the figure, and the surface thereof is uniformly charged by the charging means 42. Thereafter, an exposure process is performed on the electrophotographic photosensitive member 41 by the exposure unit 43 based on the above-described image signal, and an electrostatic latent image is formed on the surface of the electrophotographic photosensitive member 41.
Based on the electrostatic latent image, the developing means 44 attaches toner and develops it to form a toner image on the surface of the electrophotographic photoreceptor 41. The toner image is transferred as a transfer image onto the sheet S conveyed to the nip portion between the electrophotographic photosensitive member 41 and the transfer roller 45. Next, the sheet S to which the transferred image is transferred is conveyed to the fixing unit 47 and a fixing process is performed.

Further, the sheet S after fixing is sent to the paper discharge unit 32. However, when performing post-processing (for example, stapling processing), the paper S is sent to the intermediate tray 32a and then post-processed. Is done. Thereafter, the sheet S is discharged to a discharge tray portion (not shown) provided on the side surface of the image forming apparatus. On the other hand, when no post-processing is performed, the sheet S is discharged to a discharge tray 32b provided below the intermediate tray 32a. The intermediate tray 32a and the paper discharge tray 32b are configured as a so-called in-body paper discharge unit.
Next, after the transfer is performed as described above, residual toner (and paper dust) remaining on the electrophotographic photosensitive member 41 is removed by the cleaning unit 46. That is, while the electrophotographic photosensitive member 41 is cleaned, the residual toner is collected in a waste toner container (not shown).

In the image forming apparatus of the present invention, a positively charged electrophotographic photosensitive member having a photosensitive layer containing an electron donating charge control agent is mounted as the electrophotographic photosensitive member. A quality image can be formed stably.
Here, in the image forming apparatus of the present invention, it is preferable that the developing system is a reversal developing system.
This is because, with the reverse development method, the triboelectric charging property between the toner and the photosensitive layer can be more effectively exhibited.
That is, since the electrophotographic photosensitive member of the present invention is a positively charged electrophotographic photosensitive member, the charging polarity of the non-electrostatic latent image forming portion is positive in the reverse development method.
Further, the toner charging polarity is also positive.
On the other hand, since the photosensitive layer of the positively charged electrophotographic photosensitive member of the present invention contains an electron donating charge control agent, the toner in contact with the non-electrostatic latent image forming portion in the photosensitive layer is more positive. Will be charged.
As a result, the electric repulsion between the non-electrostatic latent image forming portion and the toner can be increased more effectively, and as a result, the occurrence of fog is stably suppressed regardless of the charged state of the toner. This is because it can be done.

  Hereinafter, the present invention will be described in detail with reference to examples and comparative examples.

[Example 1]
1. Production of an electrophotographic photoreceptor In a container, 3 parts by weight of an X-type metal-free phthalocyanine crystal represented by the following formula (5) as a charge generator, and stilbene amine represented by the following formula (6) as a hole transport agent 50 parts by weight of a compound, 30 parts by weight of a naphthoquinone compound represented by the following formula (7) as an electron transport agent, and a bisphenol Z-type polycarbonate resin represented by the following formula (8) having a number average molecular weight of 30000 as a binder resin 100 parts by weight, 0.1 part by weight of an azo metal-based charge control agent (CCA-3) represented by the formula (3) as an electron donating charge control agent, and 700 parts by weight of tetrahydrofuran as a solvent were accommodated. .
Subsequently, the material accommodated in the container was mixed and dispersed for 50 hours using a ball mill to obtain a photosensitive layer coating solution.
Next, the obtained photosensitive layer coating solution was applied to a substrate having a diameter of 30 mm made of an aluminum tube by a dip coating method, and then dried with hot air at 130 ° C. for 45 minutes to obtain a film thickness of 30 μm. A single-layer type electrosensitive layer was formed.
Next, in the substrate, the photosensitive layer formed in the lower end region when the dip coating method is performed is immersed in tetrahydrofuran to reduce the film thickness to a predetermined thickness, thereby forming a portion where the gap regulating roller contacts. The final single-layer electrophotographic photosensitive member was obtained.

2. Evaluation (1) Evaluation of fog density An image was formed using the obtained single layer type electrophotographic photosensitive member, and the fog density was evaluated.
That is, the obtained single-layer type electrophotographic photosensitive member was assembled in a printer (FS-1300D modified machine manufactured by Kyocera Mita Corporation), and 10 blank paper images were obtained at a temperature of 20 ° C. and a relative humidity of 50% RH. Formed.
Subsequently, using a spectrophotometer (SpectagEye, manufactured by Gretag Macbeth Co., Ltd.), the fog density (−) in the white paper portion of the obtained formed image was measured and evaluated according to the following criteria. The obtained results are shown in Table 1.
A: The fog density value is 0.01 or less.
A: The fog density value is more than 0.01 and not more than 0.012.
(Triangle | delta): The value of fog density exceeds 0.012, and is a value below 0.02.
X: The value of the fog density exceeds 0.02.

Details of the image forming apparatus will be described below.
Linear speed of electrophotographic photosensitive member 168mm / sec
Charging method Scorotron charging (charging potential: + 600V)
Exposure system Laser scanner (wavelength: 780nm)
Development method Two-component development method, reversal development method Transfer method Intermediate transfer method Cleaning method Counter blade method Charge removal method LED light discharge (wavelength: 630nm)

(2) Charging potential The charging potential of the obtained single-layer type electrophotographic photosensitive member was evaluated.
That is, a surface potential of an electrophotographic photosensitive member (corresponding to Comparative Example 1) that does not contain an electron donating charge control agent is set to 600 V by setting a potential measuring jig equipped with a potential probe at a development position for the electrophotographic photosensitive member. Thus, charging conditions were set.
Next, without changing this setting, the electrophotographic photosensitive member was replaced with the electrophotographic photosensitive member of Example 1, charged, and the surface potential after performing a printing operation corresponding to a blank original was measured. And evaluated according to the following criteria. The obtained results are shown in Table 1.
A: The value of the charging potential is a value in the range of 580 to 620V.
X: The value of the charging potential is less than 580V or more than 620V.

(3) Evaluation of sensitivity potential Further, the sensitivity potential of the obtained single-layer electrophotographic photosensitive member was evaluated.
That is, the surface potential after the printing operation corresponding to the solid image was measured under the same conditions as the charging potential measurement conditions, and the sensitivity potential was measured, and evaluated according to the following criteria. The obtained results are shown in Table 1.
○: The value of the sensitivity potential is 65V or less.
X: The value of the sensitivity potential exceeds 65V.

[Examples 2-3]
In Examples 2-3, a single-layer electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the addition amount of the electron donating charge control agent was changed to 1 part by weight and 5 parts by weight, respectively. evaluated. The obtained results are shown in Table 1.

[Examples 4 to 6]
In Examples 4 to 6, a single layer was used in the same manner as in Examples 1 to 3 except that the oxycarboxylic acid type charge control agent (CCA-4) represented by the formula (4) was used as the electron donating charge control agent. A type electrophotographic photosensitive member was produced and evaluated. The obtained results are shown in Table 1.

[Examples 7 to 9]
In Examples 7 to 9, a single layer type was used as in Examples 1 to 3 except that the azo metal-based charge control agent (CCA-1) represented by the formula (1) was used as the electron donating charge control agent. An electrophotographic photoreceptor was produced and evaluated. The obtained results are shown in Table 1.

[Examples 10 to 12]
In Examples 10 to 12, a single-layer type was used as in Examples 1 to 3, except that the boron-complex charge control agent (CCA-2) represented by the formula (2) was used as the electron donating charge control agent. An electrophotographic photoreceptor was produced and evaluated. The obtained results are shown in Table 1.

[Comparative Example 1]
In Comparative Example 1, a single-layer electrophotographic photosensitive member was produced and evaluated in the same manner as in Example 1 except that the electron donating charge control agent was not added. The obtained results are shown in Table 1.

According to the positively chargeable electrophotographic photosensitive member and the image forming apparatus according to the present invention, the toner having insufficient frictional charge can be formed on the photosensitive layer by adding an electron donating charge control agent to the photosensitive layer. Even when it is likely to adhere to the electrostatic latent image forming portion, the triboelectric chargeability between the toner and the photosensitive layer is improved, and the toner adheres directly to the non-electrostatic latent image forming portion. This can be effectively suppressed.
As a result, the occurrence of fog can be stably suppressed regardless of the charged state of the toner.
Therefore, the positively charged electrophotographic photosensitive member and the image forming apparatus using the same according to the present invention are expected to significantly contribute to the improvement in quality and cost in image forming apparatuses such as copying machines and printers.

10: Single layer type electrophotographic photosensitive member, 10 ': Single layer type electrophotographic photosensitive member having an intermediate layer, 12: Base, 14: Single layer type photosensitive layer, 16: Intermediate layer, 20: Multilayer type electrophotographic photosensitive member , 20 ′: laminated electrophotographic photosensitive member having an intermediate layer, 22: charge transporting layer, 24: charge generating layer, 26: laminated photosensitive layer, 30: copying machine, 31: image forming unit, 31a: image forming Part 31b: paper feeding unit 32: paper discharge unit 33: image reading unit 33a: light source 33b: optical element 34: document feeding unit 34a: document tray, 34b: document feeding mechanism 34c: Document discharge tray, 41: Photoconductor drum, 42: Charger, 43: Exposure source, 44: Developer, 45: Transfer roller, 46: Cleaning device

Claims (7)

A positively charged electrophotographic photosensitive member provided with a photosensitive layer containing at least a charge generating agent, a charge transporting agent and a binder resin on a substrate,
The positively charged electrophotographic photosensitive member, wherein the photosensitive layer further contains an electron donating charge control agent.   The electron donating charge control agent is at least one selected from the group consisting of an azo metal charge control agent, an oxycarboxylic acid charge control agent and a boron complex charge control agent. The positively charged electrophotographic photosensitive member as described.   The content of the electron donating charge control agent is set to a value within a range of 0.01 to 20 parts by weight with respect to 100 parts by weight of the binder resin of the photosensitive layer. The positively charged electrophotographic photosensitive member as described.   The positively charged electrophotographic photosensitive member according to claim 1, wherein the binder resin is a polycarbonate resin.   The positively charged electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is a single layer type photosensitive layer.   An image forming apparatus comprising the positively charged electrophotographic photosensitive member according to claim 1.   The image forming apparatus according to claim 6, wherein the developing system is a reversal developing system.