JP2014106365A - Electrophotographic photoreceptor and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positively-charged single-layered electrophotographic photoreceptor capable of suppressing a transfer memory to suppress occurrence of image defects in an image forming apparatus including a DC voltage application-type charging unit employing a contact charging system and using a positively-charged single-layered electrophotographic photoreceptor; and to provide an image forming apparatus including the positively-charged single-layered electrophotographic photoreceptor as an image carrier.SOLUTION: A positively-charged single-layered electrophotographic photoreceptor has a photosensitive layer having a single layer structure formed on a conductive substrate, and is used in an image forming apparatus including a DC voltage application-type charging unit employing a contact charging system. An ene-conjugate-type quinone derivative having a specific structure is incorporated in the photosensitive layer as an electron transport material.

Description

  The present invention relates to a positively charged single layer type electrophotographic photosensitive member using an ene-conjugated quinone derivative as an electron transport material, and an image forming apparatus including the above-described electrophotographic photosensitive member as an image carrier.

  As an electrophotographic photoreceptor provided in an electrophotographic image forming apparatus, an inorganic photoreceptor having a photosensitive layer made of an inorganic material such as selenium or amorphous silicon, and mainly a binder resin, a charge generating material, a charge transporting material, etc. And an organic photoreceptor having a photosensitive layer made of any of the above organic materials. Among these photoreceptors, organic photoreceptors are widely used because they are easier to manufacture than inorganic photoreceptors, and the material of the photosensitive layer can be selected from a wide range of materials, and the degree of freedom in design is high. Yes.

  Examples of such an organic photoreceptor include a single layer type organic photoreceptor having a photosensitive layer containing a charge generation material and a charge transport material in the same layer. The single layer type organic photoconductor has a simple structure compared to a multilayer type organic photoconductor in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are laminated on a conductive substrate. It is known that production is easy and generation of film defects can be suppressed.

Further, an image forming process including the following steps 1) to 5) is performed using such an electrophotographic photosensitive member.
1) Step of charging the surface of the electrophotographic photosensitive member 2) Step of exposing the charged surface of the electrophotographic photosensitive member to form an electrostatic latent image 3) The electrostatic latent image with the developing bias voltage applied Step of developing toner 4) Step of transferring the formed toner image to the transfer member by the reverse development method 5) Step of heating and fixing the toner image transferred to the transfer member

  However, in such an image forming process, since the electrophotographic photosensitive member is rotated and used, the potential (bright potential) of the portion exposed in the previous round remains and the charging process in the next round is performed. In such a portion, a phenomenon (transfer memory) in which a desired charging potential (dark potential) cannot be obtained was observed. In addition, there is a problem that it is difficult to obtain a good image because the image density changes between a portion where the transfer memory is generated and a portion where the transfer memory is not generated.

  In addition, single-layer type electrophotographic photosensitive members are classified into a positive charging type and a negative charging type, and there are a contact charging method and a non-contact charging method as a charging method of the electrophotographic photosensitive member. When charging the battery, it generates almost no oxidizing gas such as ozone, which adversely affects the life of the electrophotographic photosensitive member and the office environment. Use a combination of the contact charging method and the positively charged single-layer type electrophotographic photosensitive member. It is preferable to do.

  In the contact charging method, since the discharge region is narrow, the charging ability is poorer than that in the non-contact charging method, and it is difficult to uniformly charge the surface of the electrophotographic photosensitive member. Therefore, in the contact charging method, an AC voltage or a superimposed voltage obtained by superimposing an AC voltage on a DC voltage is applied to the electrophotographic photosensitive member in order to increase the charging uniformity of the surface of the electrophotographic photosensitive member. In such a case, the problem of charging uniformity is solved, but there is a problem that the charged potential on the surface of the electrophotographic photosensitive member is lowered by the negative component of the AC voltage.

  For this reason, from the viewpoint of charging the surface of the electrophotographic photosensitive member to a desired potential, a DC voltage is often applied in the contact charging method. However, with such a charging method, even if the surface of the electrophotographic photosensitive member can be charged to a desired potential, the potential of the surface of the electrophotographic photosensitive member is still difficult to stabilize, so that there is a problem that a transfer memory is likely to occur. .

  For this reason, when a positively charged single layer type electrophotographic photosensitive member is used in an image forming apparatus including a charging unit that applies a DC voltage by a contact charging method, a transfer memory is very easily generated. As it occurs, image defects such as ghosts are likely to occur.

  In order to suppress the generation of the transfer memory, it is effective to use a charge transport material excellent in charge transport ability. Specific examples of such a charge transport material having excellent charge transport ability include, for example, 1,4-naphthoquinone derivatives represented by the following formula, which are used as an electron transport material (for example, paragraph of Patent Document 1). [0056] ETM-3).

JP 2006-031048 A

  Certainly, the 1,4-naphthoquinone derivative described in Patent Document 1 is a charge transport material excellent in charge transport ability. However, the transfer memory is generated due to various factors. For this reason, the use of an electron transport material having an excellent charge transport capability is an effective means for suppressing the generation of a transfer memory, but this alone does not necessarily suppress the generation of a transfer memory.

  The present invention has been made in view of such circumstances, and suppresses transfer memory in an image forming apparatus that includes a contact charging type DC voltage application type charging unit and uses a positively charged single layer type electrophotographic photosensitive member. It is an object of the present invention to provide a positively charged single layer type electrophotographic photosensitive member that can suppress the occurrence of image defects. Another object of the present invention is to provide an image forming apparatus provided with the above positively charged single layer type electrophotographic photosensitive member as an image carrier.

  In the positively charged single layer type electrophotographic photosensitive member in which a photosensitive layer is formed on a conductive substrate, the present inventors use a ene conjugated quinone derivative having a specific structure as an electron transporting material, thereby providing a contact charging method. When a positively charged single layer type electrophotographic photosensitive member is used in an image forming apparatus having a direct current voltage application type charging unit, it has been found that the occurrence of image defects can be suppressed by suppressing the transfer memory, and the present invention has been completed. It was. More specifically, the present invention provides the following.

The first aspect of the present invention is:
A photosensitive layer having a single layer structure including at least a charge generation material, a hole transport material, an electron transport material, and a binder resin is formed on a conductive substrate, and includes a contact charging type DC voltage application type charging unit. A positively charged single layer type electrophotographic photosensitive member used as an image carrier in an image forming apparatus,
It is a positively charged single layer type electrophotographic photoreceptor, wherein the electron transport material is one or more compounds selected from ene conjugated quinone derivatives represented by the following general formulas (1) to (3).

（一般式（１）〜（３）中、Ｒ^１〜Ｒ^４は、それぞれ、水素原子、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルコキシ基、置換基を有していてもよいアラルキル基、置換基を有していてもよい芳香族炭化水素基、及び置換基を有していてもより複素環基からなる群より選択される基である。）

(In General Formulas (1) to (3), R ^{1 to} R ⁴ are each a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a substituent. An alkoxy group which may have a substituent, an aralkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, and a heterocyclic group which may have a substituent A group selected from the group consisting of

The second aspect of the present invention is:
An image carrier;
A contact charging type DC voltage application type charging unit for charging the surface of the image carrier;
An exposure unit for exposing a surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier;
A developing unit for developing the electrostatic latent image as a toner image;
A transfer portion for transferring the toner image from the image carrier to a transfer target, wherein the image carrier is a positively charged single layer type electrophotographic photosensitive member according to the first aspect. An image forming apparatus.

  According to the present invention, in an image forming apparatus that includes a contact charging type DC voltage application type charging unit and uses a positively charged single layer type electrophotographic photosensitive member, positive charging that can suppress the occurrence of image defects by suppressing transfer memory. A single layer type electrophotographic photosensitive member can be provided. In addition, according to the present invention, it is possible to provide an image forming apparatus that includes the above-described positively charged single-layer type electrophotographic photosensitive member as an image carrier and can suppress the occurrence of image defects by suppressing a transfer memory.

1 is a schematic cross-sectional view showing the structure of a positively charged single layer type electrophotographic photosensitive member according to an embodiment of the present invention. 1 is a schematic diagram illustrating a configuration of an image forming apparatus including a positively charged single layer type electrophotographic photosensitive member according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. . In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the summary of invention is not limited.
[First Embodiment]
In the first embodiment, a photosensitive layer having a single layer structure including at least a charge generating material, a hole transporting material, an electron transporting material, and a binder resin is formed on a conductive substrate. A positively charged single layer type electrophotographic photosensitive member (hereinafter sometimes referred to as a single layer type photosensitive member or a photosensitive member) used as an image carrier in an image forming apparatus including an application type charging unit, The present invention relates to a positively charged single layer type electrophotographic photoreceptor, in which the transport material is one or more compounds selected from ene conjugated quinone derivatives represented by the following general formulas (1) to (3).

（一般式（１）〜（３）中、Ｒ^１〜Ｒ^４は、それぞれ、水素原子、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルコキシ基、置換基を有していてもよいアラルキル基、置換基を有していてもよい芳香族炭化水素基、及び置換基を有していてもより複素環基からなる群より選択される基である。）

(In General Formulas (1) to (3), R ^{1 to} R ⁴ are each a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a substituent. An alkoxy group which may have a substituent, an aralkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, and a heterocyclic group which may have a substituent A group selected from the group consisting of

  As shown in FIG. 1, a positively charged single layer type electrophotographic photoreceptor 10 according to the first embodiment includes a conductive substrate 12 and a charge generation material and a hole transport material formed on the conductive substrate 12. , An electron transport material, and a single photosensitive layer 14 containing a binder resin. The positively charged single layer type electrophotographic photoreceptor 10 is not particularly limited as long as it includes the conductive substrate 12 and the photosensitive layer 14. Specifically, for example, as shown in FIG. 1A, the photosensitive layer 14 may be directly provided on the conductive substrate 12, or the positively charged single layer type electrophotographic photosensitive shown in FIG. 1B. Like the body 10, an intermediate layer 16 may be provided between the conductive substrate 12 and the photosensitive layer 14. Further, as shown in FIGS. 1A and 1B, the photosensitive layer 14 may be exposed as an outermost layer, or the positively charged single layer type electrophotographic photosensitive shown in FIG. 1C. Like the body 10, a protective layer 18 may be provided on the photosensitive layer 14.

  Hereinafter, the conductive substrate and the photosensitive layer will be described in order.

[Conductive substrate]
The conductive substrate is not particularly limited as long as it can be used as a conductive substrate of a positively charged single layer type electrophotographic photosensitive member. Specifically, for example, a material having at least a surface portion made of a conductive material can be used. Specifically, for example, it may be made of a conductive material, or may be a plastic material or the like whose surface is covered with a conductive material. Examples of the conductive material include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass. Moreover, as a material which has electroconductivity, the material which has electroconductivity may be used by 1 type, and may be used as an alloy etc., for example, combining 2 or more types. Further, among the above, the conductive substrate is preferably made of aluminum or an aluminum alloy. By doing so, a positively charged single layer type electrophotographic photosensitive member capable of forming a more suitable image can be provided. This is considered to be due to good charge transfer from the photosensitive layer to the conductive substrate.

  The shape of the conductive substrate can be appropriately selected according to the structure of the image forming apparatus to be used. For example, a sheet-like or drum-like substrate can be suitably used. Further, the thickness of the conductive substrate can be appropriately selected according to the shape.

(Photosensitive layer)
The photosensitive layer provided in the positively charged single-layer type electrophotographic photoreceptor is a photosensitive layer having a single layer structure including at least a charge generation material, a hole transport material, an electron transport material, and a binder resin. There is no particular limitation as long as it is one or more compounds selected from ene conjugated quinone derivatives represented by the general formulas (1) to (3).

（一般式（１）〜（３）中、Ｒ^１〜Ｒ^４は、それぞれ、水素原子、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルコキシ基、置換基を有していてもよいアラルキル基、置換基を有していてもよい芳香族炭化水素基、及び置換基を有していてもより複素環基からなる群より選択される基である。）

(In General Formulas (1) to (3), R ^{1 to} R ⁴ are each a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a substituent. An alkoxy group which may have a substituent, an aralkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, and a heterocyclic group which may have a substituent A group selected from the group consisting of

  The photosensitive layer of the positively charged single-layer type electrophotographic photosensitive member according to the first embodiment is an ene conjugate represented by any one of the general formulas (1) to (3) among electron transporting materials excellent in charge transporting ability. Since the quinone derivative is contained as an electron transport material, transfer memory generated in the transfer process of the image forming process can be suppressed. Hereinafter, the transfer memory generated in the image forming process will be described.

  In general, an image forming process using an electrophotographic system includes a charging process, an exposure process, a developing process, a transfer process, a charge eliminating process, and the like. In the charging step, which is the first step, the surface of the positively charged single-layer type electrophotographic photosensitive member, which is the surface of the image bearing member, has a positive charge by being uniformly charged to a constant potential. Next, in the exposure step, the surface of the positively charged single-layer type electrophotographic photosensitive member charged to a constant potential is exposed to form an electrostatic latent image.

  Further, in the developing step, toner is applied to the exposed portion, thereby forming a toner image and visualizing the electrostatic latent image. In the transfer step, the toner image formed on the surface of the positively charged single layer type electrophotographic photosensitive member is transferred to the intermediate transfer member. Here, in the step of transferring the toner image to the intermediate transfer member, a negative polarity bias having a polarity opposite to the charge of the positively charged single layer type electrophotographic photosensitive member is applied to the intermediate transfer member.

  When a negative polarity bias is applied to the intermediate transfer member, the exposed portion has toner that forms a toner image on the surface thereof, so that the polarity at the time of charging is maintained even when the negative polarity bias is applied. (Positive polarity) is maintained. However, the portion that has not been exposed does not have the toner constituting the toner image on the surface thereof, and therefore has a negative polarity (negative polarity) charge due to the negative polarity bias. As a result, the exposed portion and the unexposed portion on the positively charged single-layer electrophotographic photosensitive member have different polar potentials, and this potential difference causes the generation of transfer memory during subsequent image formation. Cause.

  Therefore, in the present invention, the negatively charged portion of the unexposed portion, which is a cause of the transfer memory, is represented by any one of the general formulas (1) to (3) included in the photosensitive layer. The potential difference is eliminated by the action of the electron transport material which is a conjugated quinone derivative, and the transfer memory generated in the transfer process is suppressed.

  Hereinafter, a method for producing a charge generating material, a hole transport material, an electron transport material, a binder resin, an additive, and a positively charged single layer type electrophotographic photoreceptor, which are components constituting the photosensitive layer, will be described.

(Charge generation material)
The charge generation material is not particularly limited as long as it can be used as a charge generation material for a positively charged single layer type electrophotographic photosensitive member. Specifically, for example, X-type metal-free phthalocyanine (x-H2Pc), Y-type oxotitanyl phthalocyanine (Y-TiOPc) represented by the following formula (I), perylene pigment, bisazo pigment, dithioketopyrrolopyrrole pigment, Powders of inorganic photoconductive materials such as metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azurenium pigments, cyanine pigments, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon , Pyrylium salts, ansanthrone pigments, triphenylmethane pigments, selenium pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments, and the like.

  Further, the charge generation material may be used alone or in combination of two or more kinds so as to have an absorption wavelength in a desired region. Further, among the above-described charge generating materials, in particular, in a digital optical image forming apparatus such as a laser beam printer or a facsimile using a light source such as a semiconductor laser, a positively charged single layer having sensitivity in a wavelength region of 700 nm or more Since a type electrophotographic photoreceptor is required, for example, phthalocyanine pigments such as metal-free phthalocyanine and oxotitanyl phthalocyanine are preferably used. The crystal form of the phthalocyanine pigment is not particularly limited, and various types are used. In addition, an image forming apparatus of an analog optical system such as an electrostatic copying machine using a white light source such as a halogen lamp needs a positively charged single layer type electrophotographic photosensitive member having sensitivity in the visible region. For example, perylene pigments and bisazo pigments are preferably used.

(Hole transport material)
The hole transport material is not particularly limited as long as it can be used as a hole transport material contained in the photosensitive layer of the positively charged single layer type electrophotographic photoreceptor. Specific examples of the hole transport material include benzidine derivatives, oxadiazole compounds such as 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole, 9- (4-diethylaminostyryl). ) Styryl compounds such as anthracene, carbazole compounds such as polyvinyl carbazole, organic polysilane compounds, pyrazoline compounds such as 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline, hydrazone compounds, triphenylamine compounds, Examples thereof include nitrogen-containing cyclic compounds such as indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, triazole compounds, and condensed polycyclic compounds. Among these hole transport materials, triphenylamine compounds having one or more triphenylamine skeletons in the molecule are more preferable. These hole transport materials may be used alone or in combination of two or more.

(Electron transport material)
The electron transport material is one or more compounds selected from ene conjugated quinone derivatives represented by the following general formulas (1) to (3).

（一般式（１）〜（３）中、Ｒ^１〜Ｒ^４は、それぞれ、水素原子、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルコキシ基、置換基を有していてもよいアラルキル基、置換基を有していてもよい芳香族炭化水素基、及び置換基を有していてもより複素環基からなる群より選択される基である。）

(In General Formulas (1) to (3), R ^{1 to} R ⁴ are each a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a substituent. An alkoxy group which may have a substituent, an aralkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, and a heterocyclic group which may have a substituent A group selected from the group consisting of

In the general formulas (1) to (3), when R ^{1 to} R ⁴ are an alkyl group which may have a substituent, the number of carbon atoms of the alkyl group is particularly limited within a range not hindering the object of the present invention. It is not limited. As for carbon number of an alkyl group, 1-10 are typically preferable, 1-6 are more preferable, and 1-4 are especially preferable. The structure of the alkyl group may be any of linear, branched, cyclic, and a combination thereof. Examples of the substituent that the alkyl group may have include a halogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, a cyano group, and the like. The number of substituents that the alkyl group may have is not particularly limited as long as the object of the present invention is not impaired. The number of substituents that the alkyl group may have is typically preferably 3 or less.

  Specific examples of the alkyl group which may have a substituent include methyl, ethyl, n-propyl, cyclopropyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert- Butyl group, cyclobutyl group, n-pentyl group, cyclopentyl group, n-hexyl group, cyclohexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, chloromethyl group, dichloromethyl group, Examples thereof include a trichloromethyl group, a cyanomethyl group, a hydroxymethyl group, and a hydroxyethyl group. Among these groups, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group are preferable, and a methyl group and an ethyl group are more preferable. A methyl group is particularly preferred.

In the general formulas (1) to (3), when R ^{1 to} R ⁴ are an alkenyl group which may have a substituent, the number of carbon atoms of the alkenyl group is particularly limited within a range that does not impair the object of the present invention. It is not limited. As for carbon number of an alkyl group, 2-10 are typically preferable, 2-6 are more preferable, and 2-4 are especially preferable. The structure of the alkyl group may be any of linear, branched, cyclic, and a combination thereof. Examples of the substituent that the alkenyl group may have include a halogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, and a cyano group. The number of substituents that the alkenyl group may have is not particularly limited as long as the object of the present invention is not impaired. Typically, the number of substituents that the alkenyl group may have is preferably 3 or less.

  Specific examples of the alkenyl group which may have a substituent include a vinyl group, 1-propenyl group, 2-propenyl group (allyl group), 1-butenyl group, 2-butenyl group, 3-butenyl group, 2 -Cyanovinyl group, 2-chlorovinyl group, 3-chloroallyl group, etc. are mentioned. Among these groups, a vinyl group and a 2-propenyl group (allyl group) are preferable.

In the general formulas (1) to (3), when R ^{1 to} R ⁴ are an alkoxy group which may have a substituent, the number of carbon atoms of the alkoxy group is particularly limited within a range not hindering the object of the present invention. It is not limited. As for carbon number of an alkoxy group, 1-10 are typically preferred, 1-6 are more preferred, and 1-4 are especially preferred. The structure of the alkoxy group may be any of linear, branched, cyclic, and a combination thereof. Examples of the substituent that the alkoxy group may have include a halogen atom, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, a cyano group, and the like. The number of substituents that the alkoxy group may have is not particularly limited as long as the object of the present invention is not impaired. Typically, the number of substituents that the alkoxy group may have is preferably 3 or less.

  Specific examples of the alkoxy group which may have a substituent include methoxy group, ethoxy group, n-propyloxy group, cyclopropyloxy group, isopropyloxy group, n-butyloxy group, isobutyloxy group, sec-butyloxy group. Group, tert-butyloxy group, cyclobutyloxy group, n-pentyloxy group, cyclopentyloxy group, n-hexyloxy group, cyclohexyloxy group, n-heptyloxy group, n-octyloxy group, n-nonyloxy group, n -Decyloxy group, chloromethyloxy group, dichloromethyloxy group, trichloromethyloxy group, cyanomethyloxy group, hydroxymethyloxy group, hydroxyethyloxy group, and the like. Among these groups, methoxy group, ethoxy group, n-propyloxy group, isopropyloxy group, n-butyloxy group, isobutyloxy group, sec-butyloxy group, and tert-butyloxy group are preferable, and methoxy group, ethoxy group Are more preferable, and a methoxy group is particularly preferable.

In the general formulas (1) to (3), when R ^{1 to} R ⁴ are an aralkyl group which may have a substituent, the carbon number of the aralkyl group is particularly limited within a range not inhibiting the purpose of the present invention. It is not limited. The carbon number of the aralkyl group is typically preferably 1-15, more preferably 1-13, and particularly preferably 1-12. Examples of the substituent that the aralkyl group may have include a halogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a nitro group, a cyano group, and 2 to 4 carbon atoms. An aliphatic acyl group, a benzoyl group, a phenoxy group, an alkoxycarbonyl group containing an alkoxy group having 1 to 4 carbon atoms, a phenoxycarbonyl group, and the like. The number of substituents that the aralkyl group may have is not particularly limited as long as the object of the present invention is not impaired. The number of substituents that the aralkyl group may have is typically preferably 5 or less, and more preferably 3 or less.

  Specific examples of the aralkyl group which may have a substituent include a benzyl group, 2-methylbenzyl group, 3-methylbenzyl group, 4-methylbenzyl group, 2-chlorobenzyl group, 3-chlorobenzyl group, Examples include 4-chlorobenzyl group, phenethyl group, α-naphthylmethyl group, β-naphthylmethyl group, α-naphthylethyl group, β-naphthylethyl group, and the like. Among these groups, a benzyl group, a phenethyl group, an α-naphthylmethyl group, and a β-naphthylmethyl group are preferable, and a benzyl group and a phenethyl group are more preferable.

In the general formulas (1) to (3), when R ^{1 to} R ⁴ are an aromatic hydrocarbon group which may have a substituent, an aromatic hydrocarbon group which may have a substituent Is not particularly limited as long as the object of the present invention is not impaired. Typically, the aromatic hydrocarbon group is preferably a phenyl group or a group formed by condensing two or three benzene rings or connecting them by a single bond. The number of benzene rings contained in the aromatic hydrocarbon group is 1 to 3, and 1 or 2 is preferable. Examples of the substituent that the aromatic hydrocarbon group may have include a halogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a nitro group, a cyano group, and a carbon number. Examples thereof include a 2 to 4 aliphatic acyl group, a benzoyl group, a phenoxy group, an alkoxycarbonyl group containing an alkoxy group having 1 to 4 carbon atoms, and a phenoxycarbonyl group.

  Specific examples of the aromatic hydrocarbon group which may have a substituent include a phenyl group, o-tolyl group, m-tolyl group, p-tolyl group, o-chlorophenyl group, m-chlorophenyl group, p- Examples include chlorophenyl group, o-nitrophenyl group, m-nitrophenyl group, p-nitrophenyl group, α-naphthyl group, β-naphthyl group, biphenylyl group, anthryl group, and phenanthryl group. Among these, a phenyl group, an α-naphthyl group, and a β-naphthyl group are preferable, and a phenyl group is more preferable.

In the general formulas (1) to (3), when R ^{1 to} R ⁴ are a heterocyclic group which may have a substituent, the heterocyclic group which may have a substituent is represented by the present invention. There is no particular limitation as long as it does not impede the purpose. Typically, the heterocyclic group is a 5- or 6-membered monocycle containing one or more heteroatoms selected from the group consisting of N, S, and O, such monocycles, or such A heterocyclic group in which a single ring and a 5- or 6-membered hydrocarbon ring are condensed. When the heterocyclic group is a condensed ring, the number of rings contained in the condensed ring is preferably 3 or less. Examples of the substituent that the heterocyclic group may have include a halogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a nitro group, a cyano group, and 2 to 2 carbon atoms. 4 aliphatic acyl group, benzoyl group, phenoxy group, alkoxycarbonyl group including an alkoxy group having 1 to 4 carbon atoms, and phenoxycarbonyl group.

  Examples of suitable heterocyclic rings constituting the heterocyclic group which may have a substituent include thiophene, furan, pyrrole, imidazole, pyrazole, isothiazole, isoxazole, pyridine, pyrazine, pyrimidine, pyridazine, triazole, Tetrazole, indole, 1H-indazole, purine, 4H-quinolidine, isoquinoline, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, benzofuran, 1,3-benzodioxole, benzoxazole, benzothiazole, benzimidazole, Examples include benzimidazolone, phthalimide, piperidine, piperazine, morpholine, and thiomorpholine.

  Specific examples of suitable compounds among the ene conjugated quinone derivatives represented by any one of the general formulas (1) to (3) include the following compounds.

  In addition to the ene conjugated quinone derivative represented by any one of the general formulas (1) to (3), the electron transport material has conventionally been a positively charged single-layer type electrophotographic photosensitive member as long as the object of the present invention is not impaired. It may contain an electron transport material used in the photosensitive layer of the body. Specific examples of the electron transport material that can be used together with the ene-conjugated quinone derivative represented by any one of the general formulas (1) to (3) include a naphthoquinone derivative, a diphenoquinone derivative, an anthraquinone derivative, an azoquinone derivative, and a nitroantone. Quinone derivatives such as araquinone derivatives, dinitroanthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, trinitrothioxanthone derivatives, 3,4,5,7-tetranitro-9-fluorenone derivatives, dinitroanthracene derivatives, dinitroacridine derivatives, tetracyanoethylene, Examples include 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride.

  The ene conjugated quinone derivative represented by any one of the general formulas (1) to (3) together with the ene conjugated quinone derivative represented by any one of the general formulas (1) to (3). When other compounds are included, the ratio of the mass of the ene conjugated quinone derivative represented by any one of the general formulas (1) to (3) to the total mass of the electron transport material is preferably 80% by mass or more, and 90% by mass. % Or more is more preferable, and 100 mass% is particularly preferable.

(Binder resin)
The binder resin is not particularly limited as long as it can be used as a binder resin contained in the photosensitive layer of the positively charged single layer type electrophotographic photosensitive member. Specific examples of the resin suitably used as the binder resin include polycarbonate resin, styrene resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, styrene-acrylic acid copolymer. Polymer, acrylic copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, polyurethane resin , Polycarbonate resins, polyarylate resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyether resins, polyester resins, etc .; silicone resins, epoxy resins, phenol resins, Fluororesin, melamine resin, thermosetting resin such other crosslinking thermosetting resins, epoxy acrylate resins, urethane - include photocurable resins such as acrylate copolymer resin. These resins may be used alone or in combination of two or more.

  Among these resins, a photosensitive layer having a good balance of processability, mechanical properties, optical properties, and abrasion resistance can be obtained. Therefore, bisphenol Z-type polycarbonate resins, bisphenol ZC-type polycarbonate resins, and bisphenol C-type polycarbonates are obtained. A resin and a polycarbonate resin such as a bisphenol A type polycarbonate resin are more preferable.

(Additive)
The photosensitive layer of the positively charged single layer type electrophotographic photosensitive member contains various additives in addition to the charge generating material, the hole transporting material, the electron transporting material, and the binder resin as long as the electrophotographic characteristics are not adversely affected. You may go out. Additives that can be incorporated into the photosensitive layer include, for example, antioxidants, radical scavengers, singlet quenchers, UV absorbers and other deterioration inhibitors, softeners, plasticizers, surface modifiers, extenders, Examples thereof include a sticking agent, a dispersion stabilizer, a wax, an acceptor, a donor, a surfactant, and a leveling agent.

(Method for producing positively charged single layer type electrophotographic photoreceptor)
The method for producing the positively charged single layer type electrophotographic photosensitive member is not particularly limited as long as the object of the present invention is not impaired. A preferred example of a method for producing a positively charged single layer type electrophotographic photosensitive member includes a method of forming a photosensitive layer by applying a coating solution for a photosensitive layer on a conductive substrate. Specifically, a charge generation material, a hole transport material, an electron transport material, a binder resin, and, if necessary, a coating solution in which various additives are dissolved or dispersed in a solvent are coated on a conductive substrate and dried. By doing so, a photosensitive layer can be produced. The application method is not particularly limited, and examples thereof include a method using a spin coater, applicator, spray coater, bar coater, dip coater, doctor blade and the like. Moreover, as a drying method of the coating film formed on the electroconductive base | substrate, the method of hot-air drying etc. on the conditions for 15 to 120 minutes at 80-150 degreeC are mentioned, for example.

  In the positively charged single layer type electrophotographic photosensitive member, the contents of the charge generation material, the hole transport material, the electron transport material, and the binder resin are appropriately selected and are not particularly limited. Specifically, for example, the content of the charge generation material is preferably 0.1 to 50 parts by mass, and more preferably 0.5 to 30 parts by mass with respect to 100 parts by mass of the binder resin. 5-100 mass parts is preferable with respect to 100 mass parts of binder resin, and, as for content of an electron transport material, 10-80 mass parts is more preferable. The content of the hole transport material is preferably 5 to 500 parts by mass and more preferably 25 to 200 parts by mass with respect to 100 parts by mass of the binder resin. Further, the total amount of the hole transport material and the electron transport material, that is, the content of the charge transport material is preferably 20 to 500 parts by mass, and 30 to 200 parts by mass with respect to 100 parts by mass of the binder resin. More preferably.

  The thickness of the photosensitive layer of the positively charged single layer type electrophotographic photosensitive member is not particularly limited as long as it can sufficiently function as the photosensitive layer. Specifically, for example, 5 to 100 μm is preferable, and 10 to 50 μm is preferable.

  The solvent contained in the coating solution for the photosensitive layer is not particularly limited as long as each component constituting the photosensitive layer can be dissolved or dispersed. Specifically, 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, ethylene glycol dimethyl ether and diethylene glycol dimethyl ether; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; Esters such as ethyl acetate and methyl acetate Aprotic polar organic solvents such as dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide. These solvents may be used alone or in combination of two or more.

  The positively charged single layer type electrophotographic photosensitive member is used as an image carrier of an image forming apparatus including a contact charging type DC voltage application type charging unit, which will be described later. By doing so, the transfer memory is in spite of the condition that the charge polarity of the single-layer electrophotographic photosensitive member is positive and the transfer method is a contact charging method in which a DC voltage is applied. Can be suppressed, and an image forming apparatus capable of forming a high-quality image can be provided.

[Second Embodiment]
In the second embodiment, an image carrier, a contact charging type charging unit that applies a DC voltage for charging the surface of the image carrier, and the surface of the charged image carrier are exposed to expose the image carrier. An exposure unit for forming an electrostatic latent image on the surface of the toner, a developing unit for developing the electrostatic latent image as a toner image, and a transfer unit for transferring the toner image from the image carrier to the transfer target. And an image forming apparatus using the positively charged single layer type electrophotographic photosensitive member according to the first embodiment as an image carrier.

  The image forming apparatus of the present invention can be applied to both a monochrome image forming apparatus and a tandem type color image forming apparatus using a plurality of colors of toner as described later. Here, a tandem type color image forming apparatus is used. The image forming apparatus will be described.

  Note that the tandem type color image forming apparatus including the positively charged single layer type electrophotographic photosensitive member according to the present embodiment is arranged in parallel in a predetermined direction in order to form toner images with different colors of toner on each surface. A plurality of image carriers that are provided, and arranged to face each image carrier, carry and convey toner on the surface, and supply the conveyed toner to the surface of each image carrier, respectively. A positively charged single-layer type electrophotographic photosensitive member according to the first embodiment is used as each image carrier.

  FIG. 2 is a schematic diagram showing a configuration of an image forming apparatus including a positively charged single layer type electrophotographic photosensitive member according to an embodiment of the present invention. Here, the color printer 1 will be described as an example of the image forming apparatus.

  As shown in FIG. 2, the color printer 1 has a box-shaped device main body 1a. In the apparatus main body 1a, a toner image based on image data and the like is transferred to the paper P while feeding the paper P fed from the paper feeding unit 2 and the paper P fed from the paper feeding unit 2. An image forming unit 3 and a fixing unit 4 for performing a fixing process for fixing the unfixed toner image transferred onto the paper P by the image forming unit 3 to the paper P are provided. Further, on the upper surface of the apparatus main body 1a, a paper discharge unit 5 for discharging the paper P subjected to the fixing process by the fixing unit 4 is provided.

  The paper feed unit 2 includes a paper feed cassette 121, a pickup roller 122, paper feed rollers 123, 124 and 125, and a registration roller 126. The paper feed cassette 121 is provided so as to be detachable from the apparatus main body 1a, and stores the paper P of each size. The pickup roller 122 is provided at the upper left position of the paper feed cassette 121 shown in FIG. 2 and takes out the paper P stored in the paper feed cassette 121 one by one. The paper feed rollers 123, 124, and 125 send out the paper P picked up by the pickup roller 122 to the paper transport path. The registration roller 126 temporarily waits for the paper P sent to the paper transport path by the paper feed rollers 123, 124, 125, and then supplies the paper P to the image forming unit 3 at a predetermined timing.

  The paper feeding unit 2 further includes a manual feed tray (not shown) and a pickup roller 127 that are attached to the left side surface of the device main body 1a shown in FIG. The pickup roller 127 takes out the paper P placed on the manual feed tray. The paper P taken out by the pickup roller 127 is sent out to the paper transport path by the paper feed rollers 123 and 125, and is supplied to the image forming unit 3 by the registration roller 126 at a predetermined timing.

  The image forming unit 3 includes an image forming unit 7, an intermediate transfer belt 31 on which a toner image based on image data transmitted from a computer or the like to the surface (contact surface) of the image forming unit 7 is primarily transferred, A secondary transfer roller 32 is provided for secondary transfer of the toner image on the intermediate transfer belt 31 onto the paper P fed from the paper feed cassette 121.

  The image forming unit 7 includes a black unit 7K, a yellow unit 7Y, a cyan unit 7C, and a magenta unit 7M which are sequentially arranged from the upstream side (right side in FIG. 2) to the downstream side. ing. Each of the units 7K, 7Y, 7C and 7M has a positively charged single layer type electrophotographic photosensitive member 37 (hereinafter referred to as a photosensitive member 37) as an image carrier capable of rotating in the direction of an arrow (clockwise) at the center position. Has been placed. Around each photoconductor 37, there are a charging unit 39, an exposure unit 38, a developing unit 71, a cleaning unit (not shown), and a static elimination unit (not shown) in order from the upstream side in the rotation direction. Has been placed. As the photoconductor 37, the positively charged single layer type electrophotographic photoconductor according to the first embodiment is used.

  The charging unit 39 uniformly charges the peripheral surface of the photoconductor 37 rotated in the direction of the arrow. As a specific example of the charging unit 39, charging including a contact-type charging roller and a charging brush that charges the peripheral surface (surface) of the photosensitive member 37 while the charging roller and the charging brush are in contact with the photosensitive member 37. The charging unit 39 provided with a charging roller is preferably used.

  A charging unit including a contact-type charging roller charges the peripheral surface (surface) of the photoconductor 37 while the charging roller is in contact with the photoconductor 37. As such a charging roller, for example, a roller that rotates depending on the rotation of the photoconductor 37 while being in contact with the photoconductor 37 can be used. Moreover, as a charging roller, the roller etc. which the surface part was comprised with resin at least are mentioned, for example. More specifically, for example, a core metal that is rotatably supported, a resin layer formed on the metal core, and a voltage application unit that applies a voltage to the metal core may be used. The charging unit including such a charging roller can charge the surface of the photoreceptor 37 that is in contact with the cored bar by applying a voltage to the cored bar by the voltage applying unit.

  The voltage applied to the charging roller by the voltage application unit is not particularly limited, but it is preferable that only the DC voltage is applied rather than the application of the superimposed voltage obtained by superimposing the AC voltage on the AC voltage or DC voltage. There is a tendency that the abrasion amount of the photosensitive layer tends to be smaller when only the DC voltage is applied to the charging roller than when the superimposed voltage obtained by superimposing the AC voltage on the AC voltage or DC voltage is applied to the charging roller. Can be formed. The DC voltage applied to the positively charged single layer type electrophotographic photosensitive member is preferably 1000 to 2000V, more preferably 1200 to 1800V, and particularly preferably 1400 to 1600V.

  When the image forming apparatus includes a charging unit that applies a DC voltage including a charging roller and a positively charged single-layer type electrophotographic photosensitive member as an image carrier, a transfer memory tends to occur. When the positively charged single layer type electrophotographic photosensitive member according to the embodiment is used as an image carrier, the transfer memory can be suppressed and the occurrence of image defects can be suppressed.

  Further, the resin constituting the resin layer of the charging roller is not particularly limited as long as the peripheral surface of the photoreceptor 37 can be charged satisfactorily. Specific examples of the resin used for the resin layer include a silicone resin, a urethane resin, and a silicone-modified resin. Further, the resin layer may contain an inorganic filler.

  The exposure unit 38 is a so-called laser scanning unit, and irradiates the peripheral surface of the photoreceptor 37 uniformly charged by the charging unit 39 with laser light based on image data input from a personal computer (PC) as a host device. Then, an electrostatic latent image based on the image data is formed on the photoreceptor 37. The developing unit 71 supplies toner to the circumferential surface of the photoreceptor 37 on which the electrostatic latent image is formed, thereby forming a toner image based on the image data. The toner image is primarily transferred to the intermediate transfer belt 31. The cleaning unit cleans the toner remaining on the peripheral surface of the photoreceptor 37 after the primary transfer of the toner image to the intermediate transfer belt 31 is completed. The neutralization unit neutralizes the peripheral surface of the photoreceptor 37 after the primary transfer is completed. The peripheral surface of the photoconductor 37 cleaned by the cleaning unit and the charge eliminating unit is directed to the charging unit 39 for a new charging process, and a new charging process is performed.

  The intermediate transfer belt 31 is an endless belt-like rotating body, and includes a driving roller 33, a driven roller 34, a backup roller 35, and 1 so that the surface (contact surface) side is in contact with the circumferential surface of each photoconductor 37. It is stretched over a plurality of rollers such as the next transfer roller 36. The intermediate transfer belt 31 is configured to rotate endlessly by a plurality of rollers in a state where the intermediate transfer belt 31 is pressed against the photoconductor 37 by a primary transfer roller 36 disposed to face each photoconductor 37. The driving roller 33 is rotationally driven by a driving source such as a stepping motor, and provides a driving force for rotating the intermediate transfer belt 31 endlessly. The driven roller 34, the backup roller 35, and the primary transfer roller 36 are rotatably provided, and are driven to rotate with the endless rotation of the intermediate transfer belt 31 by the driving roller 33. These rollers 34, 35, and 36 are driven to rotate via the intermediate transfer belt 31 in accordance with the main rotation of the drive roller 33 and support the intermediate transfer belt 31.

  The primary transfer roller 36 applies a primary transfer bias (a polarity opposite to the toner charging polarity) to the intermediate transfer belt 31. By doing so, the toner image formed on each photoconductor 37 circulates in the direction of the arrow (counterclockwise) by driving the drive roller 33 between each photoconductor 37 and the primary transfer roller 36. The images are sequentially transferred (primary transfer) to the intermediate transfer belt 31 in an overcoated state. Thereafter, if desired, after neutralization is performed by a neutralization unit (not shown) for neutralizing the surface of each photoconductor 37 with neutralizing light, each photoconductor 37 is further rotated to move to the next process. .

  The secondary transfer roller 32 applies a secondary transfer bias having a polarity opposite to that of the toner image to the paper P. By doing so, the toner image primarily transferred onto the intermediate transfer belt 31 is transferred to the paper P between the secondary transfer roller 32 and the backup roller 35, and thereby, a color transfer image ( An unfixed toner image) is transferred.

  The fixing unit 4 performs a fixing process on the transfer image transferred to the paper P by the image forming unit 3. The fixing unit 4 is disposed opposite to the heating roller 41 heated by the energized heating element and the heating roller 41. Is provided with a pressure roller 42 that is pressed against the peripheral surface of the heating roller 41.

  The transferred image transferred to the paper P by the secondary transfer roller 32 in the image forming unit 3 is subjected to a fixing process by heating when the paper P passes between the heating roller 41 and the pressure roller 42. To be established. The paper P subjected to the fixing process is discharged to the paper discharge unit 5. Further, in the color printer 1 of the present embodiment, the transport roller 6 is disposed at an appropriate position between the fixing unit 4 and the paper discharge unit 5.

  The paper discharge unit 5 is formed by recessing the top of the device main body 1a of the color printer 1, and a paper discharge tray 51 for receiving the discharged paper P is formed at the bottom of the concave portion. .

  The color printer 1 forms an image on the paper P by the image forming operation as described above. In the tandem type image forming apparatus as described above, the positively charged single-layer type electrophotographic photosensitive member according to the first embodiment is provided as the image carrier. Even if it is a charging method to be applied and a transfer memory in which the image carrier is a positively charged single-layer type electrophotographic photosensitive member is likely to be generated, a transfer memory is hardly generated, so that a suitable image can be formed. An image forming apparatus is obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

  In the examples and comparative examples, the following electron transport materials (ETM-1 to 8) and the electron transport material (HTM-1) were used.

<ETM-1-8>

<HTM-1>

[Examples 1 to 6, Comparative Example 1 and Comparative Example 2]
5 parts by mass of metal-free phthalocyanine, 50 parts by mass of a hole transport material (HTM-1), 35 parts by mass of an electron transport material of the type shown in Table 1, 100 parts by mass of a bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of 50,000, Then, 800 parts by mass of tetrahydrofuran was added to a ball mill and mixed and dispersed for 50 hours to prepare a coating solution for the photosensitive layer. The obtained coating solution is applied on a conductive substrate by a dip coating method, treated at 100 ° C. for 40 minutes to remove tetrahydrofuran from the coating film, and a positively charged single layer electrophotographic photosensitive member having a photosensitive layer with a thickness of 30 μm. Got the body.

  The positively charged single layer type electrophotographic photosensitive member obtained in Examples and Comparative Examples is mounted on a printer (FS-5300DN, manufactured by Kyocera Document Solutions Co., Ltd.) in which the charging unit is replaced with a charging roller that applies a DC voltage. The difference between the blank part potential when the transfer bias was turned off and the blank part potential when the transfer bias was turned on was evaluated as a transfer memory. After endurance printing for 1 hour, the printed image was observed and the occurrence of image defects The presence or absence was evaluated. In the evaluation of the image, ◎ indicates that no image defect is observed, ◯ indicates that a solid patch with a side of 10 mm appears as a ghost in the halftone portion, the above-mentioned solid patch appears as a ghost, and an alphabet with a side of 3 mm appears as a ghost. However, a state where the character cannot be clearly read is indicated by Δ, and the solid patch appears as a ghost, and an alphabet with a side of 3 mm appears as a ghost, and a state where the character can be clearly read is indicated by ×. Table 1 shows the evaluation results of the transfer memory and the image.

  According to the first to sixth embodiments, there is an image forming apparatus that includes a contact charging type charging unit that applies a DC voltage and includes a positively charged single-layer type electrophotographic photosensitive member as an image carrier, and easily generates a transfer memory. A positively charged single layer type electrophotographic photoreceptor comprising a photosensitive layer containing an ene conjugated quinone derivative (ETM-1 to ETM-6) represented by any one of the general formulas (1) to (3) as an electron transport material It can be seen that a transfer image can be suppressed and a suitable image can be formed by using.

  On the other hand, according to Comparative Examples 1 and 2, a positively charged single layer type electrophotographic photosensitive member containing an electron transfer agent material having a structure not corresponding to any of the general formulas (1) to (3) in the photosensitive layer is image-bearing. In the case of an image forming apparatus having a contact charging type charging unit for applying a DC voltage and having a positively charged single layer type electrophotographic photosensitive member as an image carrier, the transfer memory cannot be suppressed and an image defect occurs. I understand that it is easy.

DESCRIPTION OF SYMBOLS 10 Positively charged single layer type electrophotographic photosensitive member 12 Conductive substrate 14 Photosensitive layer 16 Intermediate layer 18 Protective layer

Claims (2)

A photosensitive layer having a single layer structure including at least a charge generation material, a hole transport material, an electron transport material, and a binder resin is formed on a conductive substrate, and includes a contact charging type DC voltage application type charging unit. A positively charged single layer type electrophotographic photosensitive member used as an image carrier in an image forming apparatus,
A positively charged single layer type electrophotographic photoreceptor, wherein the electron transport material is one or more compounds selected from ene conjugated quinone derivatives represented by the following general formulas (1) to (3).

(In General Formulas (1) to (3), R ^{1 to} R ⁴ are each a hydrogen atom, an alkyl group which may have a substituent, an alkenyl group which may have a substituent, or a substituent. An alkoxy group which may have a substituent, an aralkyl group which may have a substituent, an aromatic hydrocarbon group which may have a substituent, and a heterocyclic group which may have a substituent A group selected from the group consisting of An image carrier;
A contact charging type DC voltage application type charging unit for charging the surface of the image carrier;
An exposure unit for exposing a surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier;
A developing unit for developing the electrostatic latent image as a toner image;
And a transfer portion for transferring the toner image from the image carrier to a transfer target, wherein the image carrier is the positively charged single layer type electrophotographic photosensitive member according to claim 1. Image forming apparatus.

Images