CN110709780B

CN110709780B - Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Info

Publication number: CN110709780B
Application number: CN201880034962.5A
Authority: CN
Inventors: 清水智文; 丸尾敬司
Original assignee: Kyocera Document Solutions Inc
Current assignee: Kyocera Document Solutions Inc
Priority date: 2017-06-12
Filing date: 2018-04-03
Publication date: 2023-05-05
Anticipated expiration: 2038-04-03
Also published as: JP6741156B2; CN110709780A; WO2018230110A1; JPWO2018230110A1

Abstract

An electrophotographic photoreceptor (1) is provided with a conductive substrate (2) and a photosensitive layer (3). The photosensitive layer (3) is a single layer and contains a charge generating agent, a hole transporting agent, an electron transporting agent and a polycarbonate resin. The polycarbonate resin has a repeating unit represented by the general formula (1-1) and a repeating unit represented by the general formula (1-2). In the general formulae (1-1) and (1-2), Q ¹ And Q ² Represents a hydrogen atom and Q ³ And Q ⁴ Represents alkyl, or Q ¹ And Q ² Represents alkyl and Q ³ And Q ⁴ Represents a hydrogen atom. The hole-transporting agent contains compounds represented by the general formulae (HTM 1) to (HTM 7). The scratch-resistant depth of the photosensitive layer (3) is 0.50 μm or less. The Vickers hardness of the photosensitive layer (3) is 17.0HV or more.

Description

Electrophotographic photoreceptor, process cartridge, and image forming apparatus

Technical Field

The invention relates to an electrophotographic photoreceptor, a process cartridge, and an image forming apparatus.

Background

Electrophotographic photoreceptors are used as image bearing bodies in electrophotographic image forming apparatuses (e.g., printers and multifunctional integrated machines). The electrophotographic photoreceptor includes a photosensitive layer. Examples of the electrophotographic photoreceptor include a single-layer electrophotographic photoreceptor and a layered electrophotographic photoreceptor. The photosensitive layer in the single-layer electrophotographic photoreceptor has a function of charge generation and a function of charge transport. The photosensitive layer in the laminated electrophotographic photoreceptor has a charge generation layer having a function of generating electric charges and a charge transport layer having a function of transporting electric charges.

Patent document 1 describes a polycarbonate resin having a repeating unit represented by the following chemical formula (R-a), which is used as a binder resin for an electrophotographic photoreceptor.

[ chemical formula 1 ]

[ patent literature ]

Patent document 1: japanese patent application laid-open No. 2012-51983

Disclosure of Invention

However, the present inventors have found through studies that in an electrophotographic photoreceptor using the polycarbonate resin described in patent document 1, it is insufficient in both of improvement of sensitivity characteristics and anti-fogging properties.

The present invention has been made in view of the above problems, and an object thereof is to provide an electrophotographic photoreceptor having a photosensitive layer excellent in both sensitivity characteristics and anti-fogging properties. Still another object of the present invention is to provide a process cartridge and an image forming apparatus capable of suppressing occurrence of image failure.

An electrophotographic photoreceptor of the present invention includes a conductive substrate and a photosensitive layer. The photosensitive layer is a single layer and contains a charge generating agent, a hole transporting agent, an electron transporting agent and a binder resin. The binder resin contains a polycarbonate resin. The polycarbonate resin has a repeating unit represented by the following general formula (1-1) and a repeating unit represented by the following general formula (1-2). The hole-transporting agent contains a compound represented by the following general formula (HTM 1), general formula (HTM 2), general formula (HTM 3), general formula (HTM 4), general formula (HTM 5), general formula (HTM 6) or general formula (HTM 7). The scratch-resistant depth of the photosensitive layer is 0.50 μm or less. The vickers hardness of the photosensitive layer is 17.0HV or more.

[ chemical formula 2 ]

In the general formulae (1-1) and (1-2), Q ¹ And Q ² Represents a hydrogen atom and Q ³ And Q ⁴ Each independently represents C1-C6 alkyl, or Q ¹ And Q ² Each independently represents C1-C6 alkyl and Q ³ And Q ⁴ Represents a hydrogen atom.

[ chemical 3 ]

In the general formula (HTM 1), R ¹ 、R ² 、R ³ And R is ⁴ Independently of one another, represents C1-C6 alkyl. a1, a2, a3 and a4 each independently represent an integer of 0 to 5. a1 represents an integer of 2 to 5, and R is a number of ¹ The same as or different from each other. a2 represents an integer of 2 to 5, and R is a number of ² The same as or different from each other. a3 represents an integer of 2 to 5, and R is a number of ³ The same as or different from each other. a4 represents an integer of 2 to 5, and R is a number of ⁴ The same as or different from each other.

[ chemical formula 4 ]

In the general formula (HTM 2), R ⁵ 、R ⁶ 、R ⁷ And R is ⁸ Independently of one another, represents a C1-C6-alkyl radical or a hydrogen atom.

[ chemical 5 ]

In the general formula (HTM 3), R ⁹ 、R ¹⁰ 、R ¹¹ And R is ¹² Independently of one another, represents C1-C6 alkyl. b1, b2, b3 and b4 each independently represent an integer of 0 to 5. b1 represents an integer of 2 to 5, and R is a number of ⁹ The same as or different from each other. b2 represents an integer of 2 to 5, and R is a number of ¹⁰ The same as or different from each other. b3 represents an integer of 2 to 5, and R is a number of ¹¹ The same as or different from each other. b4 represents an integer of 2 to 5, and R is a number of ¹² The same as or different from each other.

[ 6 ] A method for producing a polypeptide

In the general formula (HTM 4), R ¹³ 、R ¹⁴ 、R ¹⁵ And R is ¹⁶ Independently of one another, represents C1-C6 alkyl. c1, c2, c3 and c4 each independently represent an integer of 0 to 5. c1 represents an integer of 2 to 5, and R is a number of ¹³ The same as or different from each other. c2 represents an integer of 2 to 5, and R is a number of ¹⁴ The same as or different from each other. c3 represents an integer of 2 to 5, and R is a number of ¹⁵ The same as or different from each other. c4 represents an integer of 2 to 5, and R is a number of ¹⁶ The same as or different from each other.

[ chemical 7 ]

In the general formula (HTM 5), R ¹⁷ 、R ¹⁸ 、R ¹⁹ 、R ²⁰ And R is ²¹ Independently of one another, represents a C1-C6-alkyl radical or a hydrogen atom.

[ chemical formula 8 ]

In the general formula (HTM 6), R ²² 、R ²³ And R is ²⁴ Independently of one another, represents C1-C6 alkyl. d1, d2 and d3 each independently represent an integer of 0 to 5. d1 represents an integer of 2 to 5, and R is a number of ²² The same as or different from each other. d2 represents an integer of 2 to 5, and R is a number of ²³ The same as or different from each other. d3 represents an integer of 2 to 5, and R is a number of ²⁴ The same as or different from each other. R is R ²⁵ Represents a C1-C6 alkyl group or a hydrogen atom.

[ chemical formula 9 ]

/>

In the general formula (HTM 7), R ²⁶ 、R ²⁷ And R is ²⁸ Independently of one another, represents C1-C6 alkyl. e1, e2 and e3 are each independently an integer of 0 to 5. e1 represents an integer of 2 to 5, and R is a number of ²⁶ The same as or different from each other. e2 represents an integer of 2 to 5, and R is a number of ²⁷ The same as or different from each other. e3 represents an integer of 2 to 5, and R is a number of ²⁸ The same as or different from each other. R is R ²⁹ 、R ³⁰ And R is ³¹ Independently of one another, represents a C6-C14 aryl group or a hydrogen atom.

The process cartridge of the present invention includes the above-described electrophotographic photoreceptor.

An image forming apparatus includes an image carrier, a charging unit, an exposing unit, a developing unit, and a transfer unit. The image bearing member is the above-described electrophotographic photoreceptor. The charging unit charges a surface of the image carrier. The charging polarity of the charging unit is positive. The exposure section exposes the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier. The developing section develops the electrostatic latent image into a toner image. The transfer unit transfers the toner image from the image bearing member to the transfer target when the surface of the image bearing member contacts the transfer target.

[ Effect of the invention ]

The electrophotographic photoreceptor of the present invention has excellent sensitivity characteristics and anti-fog properties. Further, the process cartridge and the image forming apparatus of the present invention can suppress occurrence of image failure.

Drawings

Fig. 1 is a partial cross-sectional view of an example of the structure of an electrophotographic photoreceptor according to a first embodiment of the present invention.

Fig. 2 is a partial cross-sectional view of an example of the structure of an electrophotographic photoreceptor according to the first embodiment of the present invention.

Fig. 3 is a partial cross-sectional view of an example of the structure of an electrophotographic photoreceptor according to the first embodiment of the present invention.

Fig. 4 is an example of an image forming apparatus according to a second embodiment of the present invention.

Fig. 5 is an example of the structure of the wiping device.

Fig. 6 is a sectional view taken along line IV-IV of fig. 5.

Fig. 7 is a side view of the fixing table, the scoring pin, and the electrophotographic photoreceptor in fig. 5.

Fig. 8 is a scratch formed on the surface of the photosensitive layer.

Detailed Description

The embodiments of the present invention will be described in detail below, but the present invention is not limited to the following embodiments, and may be implemented after being appropriately modified within the scope of the object of the present invention. In addition, although the overlapping description is omitted appropriately, the gist of the present invention is not limited thereto. In the present specification, the term "class" is sometimes added to the name of a compound to collectively refer to the compound and its derivative. In the case where a compound name is followed by a "class" to indicate a polymer name, it is meant that the repeating unit of the polymer originates from the compound or derivative thereof.

In the following, C1-C6 alkyl, C1-C3 alkyl and C6-C14 aryl each have the following meanings.

The C1-C6 alkyl group is linear or branched and is unsubstituted. Examples of the C1-C6 alkyl group include: methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl and hexyl.

The C1-C3 alkyl group is linear or branched and is unsubstituted. Examples of the C1-C3 alkyl group include: methyl, ethyl, propyl and isopropyl.

C6-C14 aryl is unsubstituted. Examples of the C6-C14 aryl group include: C6-C14 unsubstituted aromatic monocyclic hydrocarbon group, C6-C14 unsubstituted aromatic condensed bicyclic hydrocarbon group and C6-C14 unsubstituted aromatic condensed tricyclic hydrocarbon group. More specifically, C6-C14 aryl is, for example: phenyl, naphthyl, anthryl and phenanthryl.

< first embodiment: electrophotographic photoreceptor >

The structure of an electrophotographic photoreceptor (hereinafter, may be referred to as a photoreceptor) according to a first embodiment of the present invention will be described. Fig. 1, 2 and 3 are partial sectional views of the structure of a photoconductor 1 as an example of the first embodiment. As shown in fig. 1, a photoreceptor 1 includes a conductive substrate 2 and a photosensitive layer 3. The photosensitive layer 3 is a single layer. As shown in fig. 1, the photosensitive layer 3 may be directly provided on the conductive substrate 2. As shown in fig. 2, the photoreceptor 1 may include, for example, a conductive substrate 2, an intermediate layer 4 (for example, an undercoat layer), and a photosensitive layer 3. In the example of fig. 2, the photosensitive layer 3 is indirectly provided on the conductive substrate 2 via the intermediate layer 4. As shown in fig. 3, the photoreceptor 1 may be provided with a protective layer 5 as an outermost surface layer.

Hereinafter, elements of the photoreceptor 1 (the conductive substrate 2, the photosensitive layer 3, and the intermediate layer 4) will be described. A method for manufacturing the photoreceptor 1 will also be described.

[1. Conductive matrix ]

The conductive substrate 2 is not particularly limited as long as it can be used as the conductive substrate of the photoreceptor 1. As the conductive base 2, a conductive base having at least a surface portion made of a conductive material can be used. The conductive substrate 2 includes, for example: a conductive substrate made of a material having conductivity (conductive material) and a conductive substrate coated with a conductive material. Examples of the conductive material include: aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, and indium. One kind of these conductive materials may be used alone, or two or more kinds may be used in combination. The combination of two or more kinds is, for example: alloys (more specifically, aluminum alloys, stainless steel, brass, etc.). Among these conductive materials, aluminum or an aluminum alloy is preferable in terms of good movement of charges from the photosensitive layer 3 to the conductive base 2.

The shape of the conductive base 2 can be appropriately selected according to the structure of the image forming apparatus to be used. The shape of the conductive base 2 is, for example: sheet-like and drum-like. The thickness of the conductive base 2 may be appropriately selected according to the shape of the conductive base 2.

[2. Photosensitive layer ]

The photosensitive layer 3 contains a charge generating agent, a hole transporting agent, an electron transporting agent, and a binder resin. The photosensitive layer 3 may further contain an additive. The thickness of the photosensitive layer 3 is not particularly limited as long as the photosensitive layer can sufficiently function. Specifically, the thickness of the photosensitive layer 3 may be 5 μm or more and 100 μm or less, and preferably 10 μm or more and 50 μm or less.

The vickers hardness of the photosensitive layer 3 was measured according to the method of Japanese Industrial Standard (JIS) Z2244. In the measurement of vickers hardness, a durometer (for example, matsuzawa co., ltd, manufactured by "micro vickers durometer type DMH-1") is used. The measurement of the vickers hardness can be performed, for example, under the conditions of a temperature of 23 ℃, a load (test force) of the diamond indenter of 10gf, a time required to reach the test force of 5 seconds, an approach speed of the diamond indenter of 2 mm/sec, and a test force holding time of 1 sec.

The vickers hardness of the photosensitive layer 3 is 17.0HV or more, preferably 17.8HV or more, and more preferably 18.2HV or more, from the viewpoint of further improving the anti-fogging property. The upper limit of the vickers hardness of the photosensitive layer 3 is not particularly limited as long as the photosensitive layer of the photosensitive body 1 can function, but is preferably 25.0HV from the viewpoint of manufacturing cost.

The vickers hardness can be controlled by adjusting the type of the polycarbonate resin (1) described later and the type and content of the hole transporting agent described later.

The scratch resistance depth (hereinafter, may be referred to as scratch depth) of the photosensitive layer 3 is 0.50 μm or less. The scratch depth of the photosensitive layer 3 is: the depth of the scratch formed by scratching the photosensitive layer 3 was set under the following specific conditions. The following first, second, third and fourth steps were performed using a scratching device prescribed in JIS K5600-5-5, whereby the scratch depth of the photosensitive layer 3 was measured. The scratching device is provided with a fixing table and a scratching needle. The scoring needle has a hemispherical sapphire tip 1mm in diameter.

In the first step, the photoconductor 1 is fixed to the top surface of the fixing base so that the longitudinal direction of the photoconductor 1 is parallel to the longitudinal direction of the fixing base. In the second step, the scribing needle is vertically abutted against the surface of the photosensitive layer 3. In the third step, the scratch applies a load of 10g to the photosensitive layer 3, and moves the fixing table and the photosensitive body 1 fixed on the top surface of the fixing table at a speed of 30 mm/min along the longitudinal direction of the fixing table by 30mm. Through the above-described third step, scratches are formed on the surface of the photosensitive layer 3. In the fourth step, the maximum depth of the scratch, i.e., the scratch depth, is measured.

As described above, the scratch depth measurement method is schematically described. The method of measuring the scratch depth is described in more detail in the examples.

The scratch depth of the photosensitive layer 3 is 0.50 μm or less, preferably 0.46 μm or less, more preferably 0.44 μm or less, from the viewpoint of further improving the anti-fogging property. The lower limit of the scratch depth of the photosensitive layer 3 is not particularly limited as long as the photosensitive layer of the photosensitive body 1 can function, and may be, for example, 0.00 μm, but is preferably 0.09 μm from the viewpoint of manufacturing cost.

The scratch depth can be controlled by adjusting the type of the polycarbonate resin (1) described later and the type and content of the hole transporting agent described later.

Hereinafter, a charge generating agent, a hole transporting agent, an electron transporting agent, a binder resin, and an additive as optional components will be described.

(Charge generating agent)

The charge generating agent is not particularly limited as long as it is a charge generating agent for a photoreceptor. Examples of the charge generating agent include: phthalocyanine pigments, perylene pigments, disazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, gan Julan pigments, cyanine pigments, powders of inorganic photoconductive materials (e.g., selenium-tellurium, selenium-arsenic, cadmium sulfide and amorphous silicon), pyran salts, anthanthrone pigments, triphenylmethane pigments, vaseline pigments, toluamide pigments, pyrazoline pigments and quinacridone pigments. The charge generating agent may be used alone or in combination of two or more. Examples of the phthalocyanine pigment include: no metal phthalocyanine and no metal phthalocyanine. Examples of the metal phthalocyanine include: oxytitanium phthalocyanine, hydroxygallium phthalocyanine and chlorogallium phthalocyanine. The phthalocyanine pigment may be crystalline or amorphous. The crystal shape (for example, α -type, β -type, X-type, Y-type, V-type, and II-type) of the phthalocyanine pigment is not particularly limited, and various crystal shapes of the phthalocyanine pigment can be used.

Examples of the metal-free phthalocyanine crystal include: x-type crystals of metal-free phthalocyanine (hereinafter, may be referred to as X-type metal-free phthalocyanine). Examples of the crystal of oxytitanium phthalocyanine include: alpha, beta and Y-type crystals of oxytitanium phthalocyanine (hereinafter, sometimes referred to as alpha, beta and Y-type oxytitanium phthalocyanine, respectively). Examples of the crystal of hydroxygallium phthalocyanine include V-type crystal of hydroxygallium phthalocyanine.

In the case where the photoreceptor 1 is applied to a digital optical image forming apparatus, it is preferable to use a charge generating agent having photosensitivity in a wavelength region of 700nm or more. Examples of the charge generating agent having sensitivity in a wavelength region of 700nm or more include phthalocyanine pigments, and from the viewpoint of efficient charge generation, X-type metal-free phthalocyanine is preferable. Further, examples of the digital optical image forming apparatus include: laser printers and facsimile machines using a light source such as a semiconductor laser.

In the case where the photoreceptor 1 is applied to an image forming apparatus using a short wavelength laser light source, it is preferable to use an anthracene-based pigment or a perylene-based pigment as a charge generating agent. The wavelength of the short wavelength laser is, for example, 350nm to 550 nm.

Examples of the charge generating agent include: phthalocyanine pigments represented by the following chemical formulas (CGM-1) to (CGM-4) (hereinafter, sometimes referred to as charge generators (CGM-1) to (CGM-4), respectively).

[ chemical formula 10 ]

[ chemical formula 11 ]

[ chemical formula 12 ]

[ chemical formula 13 ]

From the viewpoint of efficient generation of electric charges, the content of the charge generating agent is preferably 0.1 part by mass or more and 50 parts by mass or less, more preferably 0.5 part by mass or more and 30 parts by mass or less, and particularly preferably 0.5 part by mass or more and 4.5 parts by mass or less, relative to 100 parts by mass of the binder resin.

(hole transporting agent)

The hole transporting agent contains a compound represented by the following general formula (HTM 1), general formula (HTM 2), general formula (HTM 3), general formula (HTM 4), general formula (HTM 5), general formula (HTM 6), or general formula (HTM 7). Hereinafter, these hole-transporting agents are sometimes referred to as hole-transporting agents (HTM 1) to (HTM 7), respectively. The photosensitive layer 3 may contain one kind of the hole transporting agent, or two or more kinds thereof.

[ chemical formula 14 ]

[ 15 ] A method of producing a polypeptide

[ 16 ] the preparation method

In the general formula (HTM 3), R ⁹ 、R ¹⁰ 、R ¹¹ And R is ¹² Independently of one another, represents C1-C6 alkyl. b1, b2, b3 and b4 each independently represent an integer of 0 to 5. b1 represents an integer of 2 to 5, and R is a number of ⁹ The same as or different from each other. b2 represents an integer of 2 to 5, and R is a number of ¹⁰ The same as or different from each other. b3 represents an integer of 2 to 5, and R is a number of ¹¹ The same as or different from each other. b4 represents an integer of 2 to 5, and R is a number of ¹² Identical or different from each otherAnd the same is true.

[ chemical formula 17 ]

[ chemical formula 18 ]

[ chemical formula 19 ]

[ chemical formula 20 ]

From the viewpoint of further improving the sensitivity characteristics and the anti-fogging property, a1 and a3 in the general formula (HTM 1) are preferably represented by 1. From the same point of view, R is preferred ¹ And R is ³ Each independently represents a C1-C3 alkyl group, more preferably represents a methyl group. From the same point of view, a2 and a4 preferably represent 0. The hole-transporting agent (HTM 1) represented by the general formula (HTM 1) is, for example, a hole-transporting agent represented by the following chemical formula (HTM 1-1) (hereinafter, sometimes referred to as a hole-transporting agent (HTM 1-1)).

[ chemical formula 21 ]

From the viewpoint of further improving the sensitivity characteristics and the anti-fogging property, R in the general formula (HTM 2) ⁵ And R is ⁶ Preferably each independently represents a C1-C6 alkyl group, more preferably a C1-C3 alkyl group, and even more preferably a methyl group. From the same point of view, R ⁷ And R is ⁸ Preferably represents a hydrogen atom. The hole-transporting agent (HTM 2) represented by the general formula (HTM 2) is, for example, a hole-transporting agent represented by the following chemical formula (HTM 2-1) (hereinafter, sometimes referred to as a hole-transporting agent (HTM 2-1)).

[ chemical formula 22 ]

In the general formula (HTM 3), b1 and b3 are preferably represented by 1 from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property. From the same point of view, R is preferred ⁹ And R is ¹¹ Each independently represents a C1-C3 alkyl group, more preferably represents a methyl group. From the same point of view, b2 and b4 preferably represent 0. The hole-transporting agent (HTM 3) represented by the general formula (HTM 3) is, for example, a hole-transporting agent represented by the following chemical formula (HTM 3-1) (hereinafter, sometimes referred to as a hole-transporting agent (HTM 3-1)).

[ chemical formula 23 ]

In the general formula (HTM 4), c1 and c2 are preferably represented by 1 from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property. From the same point of view, R is preferred ¹³ And R is ¹⁴ Each independently represents a C1-C3 alkyl group, more preferably represents a methyl group. From the same point of view, c3 and c4 preferably represent 0. The hole-transporting agent (HTM 4) represented by the general formula (HTM 4) is, for example, a hole-transporting agent represented by the following chemical formula (HTM 4-1) (hereinafter, sometimes referred to as a hole-transporting agent (HTM 4-1)).

[ chemical 24 ]

In the general formula (HTM 5), R is preferable from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property ¹⁷ 、R ¹⁸ 、R ¹⁹ 、R ²⁰ And R is ²¹ Each independently represents a C1-C6 alkyl group, more preferably a C1-C3 alkyl group, and even more preferably a methyl group. The hole-transporting agent (HTM 5) represented by the general formula (HTM 5) is, for example, a hole-transporting agent represented by the following chemical formula (HTM 5-1) (hereinafter, sometimes referred to as a hole-transporting agent (HTM 5-1)).

[ chemical 25 ]

In the general formula (HTM 6), d1, d2, and d3 are preferably 0 from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property. From the same point of view, R ²⁵ Preferably represents a hydrogen atom. The hole-transporting agent (HTM 6) represented by the general formula (HTM 6) is, for example, a hole-transporting agent represented by the following chemical formula (HTM 6-1) (hereinafter, sometimes referred to as a hole-transporting agent (HTM 6-1)).

[ chemical 26 ]

In the general formula (HTM 7), from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property, it is preferable that each of e1, e2, and e3 independently represents 0 or 1. In the case where e1, e2 and e3 represent 0, R is preferable from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property ²⁹ 、R ³⁰ And R is ³¹ Each independently represents a C6-C14 aryl group, more preferably a phenyl group. In the case where e1, e2 and e3 represent 1, R is preferable from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property ²⁹ 、R ³⁰ And R is ³¹ Represents a hydrogen atom. In the case where e1, e2 and e3 represent 1, R is preferable from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property ²⁶ 、R ²⁷ And R is ²⁸ Represents a C1-C3 alkyl group, more preferably a methyl group. The hole-transporting agent (HTM 7) represented by the general formula (HTM 7) is, for example, a hole-transporting agent represented by the following chemical formula (HTM 7-1) (hereinafter, sometimes referred to as a hole-transporting agent (HTM 7-1)) and a hole-transporting agent represented by the chemical formula (HTM 7-2) (hereinafter, sometimes referred to as a hole-transporting agent (HTM 7-2)).

[ chemical formula 27 ]

[ chemical 28 ]

Among these hole-transporting agents, the hole-transporting agent (HTM 1), the hole-transporting agent (HTM 2) and the hole-transporting agent (HTM 6) are preferable, and the hole-transporting agent (HTM 1-1), the hole-transporting agent (HTM 2-1) and the hole-transporting agent (HTM 6-1) are more preferable from the viewpoint of further improving the anti-fogging property. From the viewpoint of further improving the sensitivity characteristics, the hole transporting agents (HTM 1), HTM3, HTM5, and HTM7 are preferable, and the hole transporting agents (HTM 1-1), HTM3-1, HTM5-1, HTM7-1, and HTM7-2 are more preferable.

From the viewpoint of efficient hole transport, the content of the hole transporting agent is preferably 10 parts by mass or more and 200 parts by mass or less, more preferably 10 parts by mass or more and 100 parts by mass or less, relative to 100 parts by mass of the binder resin. Further, from the viewpoint of further improving the sensitivity characteristics and suppressing crystallization by the combination with the polycarbonate resin (1) described later, the content of the hole transporting agent is preferably 10 parts by mass or more and 90 parts by mass or less, more preferably 10 parts by mass or more and 80 parts by mass or less, with respect to 100 parts by mass of the polycarbonate resin (1).

The photosensitive layer 3 may contain other hole transporting agents in addition to the hole transporting agents (HTM 1) to (HTM 7). Other hole-transporting agents are, for example: diamine derivatives (more specifically, N, N, N ', N' -tetraphenylphenylenediamine derivatives, N, N, N ', N' -tetraphenylnaphthylenediamine derivatives, N, N, N ', N' -tetraphenylphenanthrylenediamine (N, N, N ', N' -tetraphenyl phenanthrylene diamine) derivatives and the like), oxadiazoles (more specifically, 2, 5-bis (4-methylaminophenyl) -1,3, 4-oxadiazole and the like), styrenes (more specifically, 9- (4-diethylaminostyryl) anthracene and the like), carbazoles (more specifically, polyvinylcarbazole, etc.), an organic polysilane compound, a pyrazoline compound (more specifically, 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline, etc.), a hydrazone compound, an indole compound, an oxazole compound, an isoxazole compound, a thiazole compound, a thiadiazole compound, an imidazole compound, a pyrazole compound, and a triazole compound, which are structurally different from the hole transporting agents (HTM 1) to (HTM 7). The total content of the hole-transporting agents (HTM 1) to (HTM 7) is preferably 80 mass% or more, more preferably 90 mass% or more, and particularly preferably 100 mass% relative to the total mass of the hole-transporting agents.

(electron transporting agent)

Examples of the electron transport agent include: quinone compounds, diimide compounds, hydrazone compounds, malononitrile compounds, thiopyran compounds, trinitrothioxanthone compounds, 3,4,5, 7-tetranitro-9-fluorenone compounds, dinitroanthracene compounds, dinitroacridine compounds, tetracyanoethylene, 2,4, 8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride and dibromomaleic anhydride. Examples of the quinone compound include: diphenoquinone compounds, azo quinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds and dinitroanthraquinone compounds. These electron transport agents may be used singly or in combination of two or more.

Among these electron transport agents, the compound represented by the following general formula (ETM 1) is preferable from the viewpoint of efficient electron transport, and the compound represented by the following chemical formula (ETM 1-1) (hereinafter, sometimes referred to as an electron transport agent (ETM 1-1)) is more preferable.

[ chemical 29 ]

In the general formula (ETM 1), R ⁴¹ And R is ⁴⁴ Independently of one another, represents a C1-C6-alkyl radical or a hydrogen atom. R is R ⁴² And R is ⁴³ Independently of one another, represents C1-C6 alkyl. f1 and f2 are each independently an integer of 0 to 4. f1 represents an integer of 2 to 4, and R is a number of ⁴² The same as or different from each other. f2 represents an integer of 2 to 4, and R is a number of ⁴³ The same as or different from each other.

[ chemical formula 30 ]

/>

From the viewpoint of efficient electron transport, the content of the electron transporting agent is preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 10 parts by mass or more and 80 parts by mass or less, relative to 100 parts by mass of the binder resin. Further, from the viewpoint of further improving the sensitivity characteristics and suppressing crystallization by the combination with the polycarbonate resin (1) described later, the content of the electron mediator is preferably 10 parts by mass or more and 70 parts by mass or less, more preferably 10 parts by mass or more and 60 parts by mass or less, and still more preferably 10 parts by mass or more and 50 parts by mass or less, with respect to 100 parts by mass of the polycarbonate resin (1).

(adhesive resin)

The binder resin contains a polycarbonate resin having a repeating unit represented by the following general formula (1-1) and a repeating unit represented by the following general formula (1-2) (hereinafter, may be referred to as a polycarbonate resin (1)). The photosensitive layer 3 may contain one or two or more kinds of polycarbonate resins (1).

[ chemical 31 ]

In the general formulae (1-1) and (1-2), Q is from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property ¹ 、Q ² 、Q ³ And Q ⁴ The C1-C6 alkyl group represented is preferably a C1-C3 alkyl group, more preferably a methyl group. From the same point of view, it is further preferable that: q (Q) ¹ And Q ² Represents methyl and Q ³ And Q ⁴ Represents a hydrogen atom, or Q ¹ And Q ² Represents a hydrogen atom and Q ³ And Q ⁴ Represents methyl. From the viewpoint of improving sensitivity characteristics, Q is particularly preferred ¹ And Q ² Represents a hydrogen atom and Q ³ And Q ⁴ Represents methyl.

Preferred examples of the repeating unit represented by the general formula (1-1) (hereinafter, sometimes referred to as the repeating unit (1-1)) include repeating units represented by the following chemical formulas (11-1) and (11-2).

[ chemical formula 32 ]

Preferred examples of the repeating unit represented by the general formula (1-2) (hereinafter, sometimes referred to as the repeating unit (1-2)) include repeating units represented by the following chemical formulas (12-1) and (12-2).

[ chemical formula 33 ]

Examples of the polycarbonate resin (1) include: a polycarbonate resin represented by the following general formula (1).

[ chemical 34 ]

Q in the general formula (1) ¹ And Q ² Respectively with Q in the general formula (1-1) ¹ And Q ² Has the same meaning. Q in the general formula (1) ³ And Q ⁴ Respectively with Q in the general formula (1-2) ³ And Q ⁴ Has the same meaning. Further, r in the general formula (1) represents: in the polycarbonate resin (1), the repeating unit (1)-a percentage of the number of 1) relative to the sum of the number of repeating units (1-1) and the number of repeating units (1-2). s represents: in the polycarbonate resin (1), the number of the repeating units (1-2) is a percentage of the total of the number of the repeating units (1-1) and the number of the repeating units (1-2). In addition, r and s are not values obtained from 1 resin chain, but are arithmetic average values obtained from the whole (a plurality of resin chains) of the polycarbonate resin (1) contained in the photosensitive layer 3.

In the general formula (1), r is preferably a number of 50 to 70 and s is preferably a number of 30 to 50, more preferably r is a number of 55 to 65 and s is preferably a number of 35 to 45 from the viewpoint of further improving the sensitivity characteristics and the anti-fogging property and the formation property of the photosensitive layer 3.

In the polycarbonate resin (1), the arrangement of the repeating units (1-1) and (1-2) is not particularly limited. That is, the polycarbonate resin (1) may be any of random copolymer, alternating copolymer, periodic copolymer, block copolymer, and the like. Examples of random copolymers include: a copolymer comprising repeating units (1-1) and repeating units (1-2) arranged in a random manner. Examples of the alternating copolymer include: a copolymer comprising repeating units (1-1) and repeating units (1-2) alternately arranged. The periodic copolymer is, for example: 1 or a plurality of repeating units (1-1) and 1 or a plurality of repeating units (1-2) are periodically arranged. Examples of the block copolymer include: a copolymer comprising a block of a plurality of repeating units (1-1) and a block of a plurality of repeating units (1-2).

The polycarbonate resin (1) may contain repeating units other than the repeating units (1-1) and (1-2). The total ratio (mole fraction) of the amounts of the repeating units (1-1) and (1-2) relative to the total amount of the repeating units in the polycarbonate resin (1) is preferably 0.80 or more, more preferably 0.90 or more, and still more preferably 1.00.

In order to obtain a photoreceptor 1 having more excellent photosensitivity and anti-fogging properties by improving the compatibility of the polycarbonate resin (1) with the hole transporting agent and the electron transporting agent, the polycarbonate resin (1) preferably contains no repeating unit having a fluorine atom and no terminal group having a fluorine atom. From the same viewpoint, the polycarbonate resin (1) is preferably not subjected to terminal modification.

The method for producing the binder resin may be any method as long as the polycarbonate resin (1) can be produced. The present invention is not particularly limited. Examples of the method for producing the binder resin include: a method for performing interfacial polycondensation of a diol compound constituting a repeating unit of the polycarbonate resin (1) with phosgene (i.e., phosgene method); and a method of transesterification of a diol compound with diphenyl carbonate. Specific examples of phosgene processes are: a method in which a diol compound represented by the following general formula (1-1-1) and a diol compound represented by the following general formula (1-2-1) are mixed at a content ratio corresponding to a molar fraction (r/(r+s) of the general formula (1)) to obtain a mixture, and the mixture is subjected to interfacial polycondensation with phosgene. In addition, Q in the following general formula (1-1-1) ¹ And Q ² Respectively with Q in the general formula (1-1) ¹ And Q ² Has the same meaning. Q in the following general formula (1-2-1) ³ And Q ⁴ Respectively with Q in the general formula (1-2) ³ And Q ⁴ Has the same meaning.

[ 35 ]

Specific examples of the polycarbonate resin (1) are polycarbonate resins represented by the following chemical formulas (R-1) and (R-2) (hereinafter, sometimes referred to as polycarbonate resins (R-1) and (R-2), respectively).

[ chemical formula 36 ]

The binder resin may be used alone or in combination with a resin (other than the polycarbonate resin (1). Examples of other resins include: thermoplastic resins (polycarbonate resins other than the polycarbonate resin (1), polyarylate resins, styrene-based resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, styrene-acrylic acid copolymers, polyethylene resins, ethylene-vinyl acetate copolymers, chlorinated polyethylene resins, polyvinyl chloride resins, polypropylene resins, ionomers, vinyl chloride-vinyl acetate copolymers, polyester resins, alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyether resins, polyester resins, and the like), thermosetting resins (silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, other crosslinkable thermosetting resins, and the like), and photocurable resins (epoxy-acrylic resins, polyurethane-acrylic copolymers, and the like). These resins may be used alone or in combination of two or more. The content of the polycarbonate resin (1) is preferably 80 mass% or more, more preferably 90 mass% or more, and still more preferably 100 mass% relative to the total amount of the binder resin.

The viscosity average molecular weight of the binder resin is preferably 20,000 or more, more preferably 25,000 or more, and still more preferably 30,000 or more. The viscosity average molecular weight of the binder resin is preferably 70,000 or less, more preferably 50,000 or less, and still more preferably 40,000 or less. When the viscosity average molecular weight of the binder resin is 30,000 or more, the abrasion resistance of the binder resin can be improved, and the photosensitive layer 3 becomes less likely to be abraded. On the other hand, when the viscosity average molecular weight of the binder resin is 40,000 or less, the binder resin is easily dissolved in a solvent at the time of forming the photosensitive layer 3, and thus the photosensitive layer 3 is often easily formed.

(additive)

Additives as optional ingredients are, for example: degradation inhibitors (more specifically, antioxidants, radical scavengers, quenchers, ultraviolet absorbers, and the like), softeners, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, donors, surfactants, and leveling agents. When the additives are added, one of these additives may be used alone or two or more of them may be used in combination.

Examples of antioxidants include: hindered phenol compounds, hindered amine compounds, thioether compounds, and phosphite compounds. Among these antioxidants, hindered phenol compounds and hindered amine compounds are preferable.

(combination of materials)

In order to further improve the sensitivity characteristics and the anti-fog property, it is preferable to: the photosensitive layer 3 contains one or more of a hole transporting agent (HTM 1-1), a hole transporting agent (HTM 2-1), and a hole transporting agent (HTM 6-1), and contains one or more of a polycarbonate resin (R-1) and a polycarbonate resin (R-2) as a binder resin. For the same reason, more preferable are: the photosensitive layer 3 contains one of a hole transporting agent (HTM 1-1), a hole transporting agent (HTM 2-1), and a hole transporting agent (HTM 6-1), and contains a polycarbonate resin (R-2) as a binder resin.

[3. Intermediate layer ]

The photoreceptor 1 of the present embodiment described above may have an intermediate layer 4 (for example, an undercoat layer). The intermediate layer 4 contains, for example, inorganic particles and a resin (resin for intermediate layer) used in the intermediate layer. By providing the intermediate layer 4, it is possible to smoothly flow a current generated when exposing the photoreceptor 1 while maintaining an insulating state to such an extent that occurrence of electric leakage can be suppressed, and to suppress an increase in resistance.

Examples of the inorganic particles include: particles of metals (more specifically, aluminum, iron, copper, etc.), particles of metal oxides (more specifically, titanium dioxide, aluminum oxide, zirconium oxide, tin oxide, zinc oxide, etc.), and particles of non-metal oxides (more specifically, silicon dioxide, etc.). These inorganic particles may be used singly or in combination of two or more. In addition, the inorganic particles may be subjected to surface treatment.

The resin for the intermediate layer is not particularly limited as long as it is a resin capable of forming the intermediate layer.

[4 ] Process for producing photoreceptor ]

A method for manufacturing the photoreceptor 1 will be described. The method for manufacturing the photoreceptor 1 includes, for example, a photosensitive layer forming step. In the photosensitive layer forming step, a coating liquid (hereinafter, may be referred to as a coating liquid for a photosensitive layer) for forming the photosensitive layer 3 is prepared. Then, the photosensitive layer coating liquid is coated on the conductive substrate 2. Then, drying is performed by an appropriate method, and at least part of the solvent contained in the applied coating liquid for the photosensitive layer is removed, thereby forming the photosensitive layer 3. The coating liquid for a photosensitive layer contains, for example, a charge generating agent, a hole transporting agent, an electron transporting agent, a polycarbonate resin (1) as a binder resin, and a solvent. The above-mentioned coating liquid for a photosensitive layer is prepared by dissolving or dispersing a charge generating agent, a hole transporting agent, an electron transporting agent and a polycarbonate resin (1) as a binder resin in a solvent. Various additives may be added to the coating liquid for a photosensitive layer as required.

Hereinafter, the photosensitive layer forming process will be described in detail. The solvent contained in the coating liquid for a photosensitive layer is not particularly limited as long as it can dissolve or disperse each component contained in the coating liquid. Examples of the solvent include: alcohols (more specifically, methanol, ethanol, isopropanol, butanol, etc.), aliphatic hydrocarbons (more specifically, n-hexane, octane, cyclohexane, etc.), aromatic hydrocarbons (more specifically, benzene, toluene, xylene, etc.), halogenated hydrocarbons (more specifically, methylene chloride, dichloroethane, carbon tetrachloride, chlorobenzene, etc.), ethers (more specifically, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, etc.), ketones (more specifically, acetone, methyl ethyl ketone, cyclohexanone, etc.), esters (more specifically, ethyl acetate, methyl acetate, etc.), dimethyl formaldehyde, dimethyl formamide, and dimethyl sulfoxide. These solvents may be used alone or in combination of two or more. Among these solvents, a non-halogenated solvent is preferable.

The respective components are mixed and dispersed in a solvent, whereby a coating liquid for a photosensitive layer is prepared. In the mixing or dispersing operation, for example, a bead mill, a roller mill, a ball mill, an attritor, a paint shaker, and an ultrasonic disperser may be used.

In order to improve the dispersibility of each component, the coating liquid for the photosensitive layer may contain, for example, a surfactant.

The method of coating with the coating liquid for a photosensitive layer is not particularly limited as long as it is a method capable of uniformly coating the coating liquid for a photosensitive layer. Examples of the coating method include: dip coating, spray coating, spin coating and bar coating.

The method for removing at least a part of the solvent contained in the coating liquid for a photosensitive layer is not particularly limited as long as it is a method capable of evaporating at least a part of the solvent in the coating liquid. The removal method includes: heating, depressurizing, or a combination of heating and depressurizing. More specifically, a method of performing heat treatment (hot air drying) using a high-temperature dryer, a reduced-pressure dryer, or the like. The heat treatment conditions are, for example, a temperature of 40 ℃ to 150 ℃ and a time of 3 minutes to 120 minutes.

The method for producing the photoreceptor 1 may further include a step of forming the intermediate layer 4, if necessary. In the step of forming the intermediate layer 4, a known method can be appropriately selected.

The photoreceptor of the present embodiment described above has excellent sensitivity characteristics and anti-fogging properties, and therefore can be applied to various image forming apparatuses.

< second embodiment: image Forming apparatus-

An image forming apparatus according to a second embodiment will be described below. An image forming apparatus according to a second embodiment includes an image carrier, a charging unit, an exposure unit, a developing unit, and a transfer unit. The image bearing member is the photoreceptor according to the first embodiment. The charging unit charges a surface of the image carrier. The charging polarity of the charging unit is positive. The exposure section exposes the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier. The developing section develops the electrostatic latent image into a toner image. The transfer unit transfers the toner image from the image bearing member to the transfer target when the surface of the image bearing member contacts the transfer target.

The image forming apparatus according to the second embodiment can suppress occurrence of image failure. The reason for this is presumed as follows. An image forming apparatus according to a second embodiment includes the photoreceptor according to the first embodiment as an image carrier. The photoreceptor according to the first embodiment has excellent sensitivity characteristics and anti-fogging properties. Thus, the image forming apparatus according to the second embodiment can suppress image failure (more specifically, fog or the like).

An embodiment of an image forming apparatus according to a second embodiment will be described below with reference to fig. 4 by taking a tandem color image forming apparatus as an example.

The image forming apparatus 100 in fig. 4 is a direct transfer type image forming apparatus. In general, in an image forming apparatus employing a direct transfer method, an image bearing member is in contact with a recording medium as a transfer target, and therefore, fine components are easily attached to the surface of the image bearing member, and image failure is easily generated. However, the image forming apparatus 100 as an example of the second embodiment includes the photoreceptor according to the first embodiment as the image carrier 30. The photoreceptor according to the first embodiment has excellent sensitivity characteristics and anti-fogging properties. Therefore, when the photoreceptor according to the first embodiment is provided as the image carrier 30, occurrence of image failure can be suppressed even in the image forming apparatus 100 employing the direct transfer method.

The image forming apparatus 100 includes

image forming units

40a, 40b, 40c, and 40d, a transfer belt 50, and a fixing portion 52. Hereinafter, the

image forming units

40a, 40b, 40c, and 40d are all described as the image forming unit 40, unless distinction is required.

The image forming unit 40 includes an image carrier 30, a charging portion 42, an exposing portion 44, a developing portion 46, and a transfer portion 48. The image carrier 30 is provided at a central position of the image forming unit 40. The image carrier 30 is provided rotatably in the arrow direction (counterclockwise rotation). Around the image carrier 30, a charging portion 42, an exposure portion 44, a developing portion 46, and a transfer portion 48 are provided in this order from the upstream side in the rotation direction of the image carrier 30, with reference to the charging portion 42. The image forming unit 40 may further include one or both of a cleaning portion (not shown) and a neutralizing portion (not shown).

Toner images of several colors (for example, four colors of black, cyan, magenta, and yellow) are sequentially superimposed on the recording medium P on the transfer belt 50 by each of the image forming units 40a to 40 d.

The charging unit 42 is a charging roller. The charging roller charges the surface of the image carrier 30 when coming into contact with the surface of the image carrier 30. In general, in an image forming apparatus including a charging roller, image failure is likely to occur. However, the image forming apparatus 100 includes the photoreceptor according to the first embodiment as the image carrier 30. The photoreceptor according to the first embodiment has excellent sensitivity characteristics and anti-fogging properties. Thus, even in the image forming apparatus 100 including the charging roller as the charging portion 42, occurrence of image failure can be suppressed. The image forming apparatus 100 as an example of the second embodiment adopts a contact charging method. The charging portion of the other contact charging system includes, for example, a charging brush. The charging unit may be a noncontact type. Examples of the charging unit of the noncontact method include: corona tube charging portion and gate control type corona charging portion.

The voltage applied by the charging unit 42 is not particularly limited. The voltage applied by the charging unit 42 is, for example, a dc voltage, an ac voltage, or a superimposed voltage (a voltage in which the ac voltage is superimposed on the dc voltage), and is preferably a dc voltage. The dc voltage has the following advantages over the ac voltage and the superimposed voltage. When only a direct current voltage is applied to the charging unit 42, the voltage applied to the image carrier 30 is constant, and therefore it is easy to uniformly charge the surface of the image carrier 30 to a constant potential. When only a dc voltage is applied to the charging portion 42, the abrasion amount of the photosensitive layer tends to be reduced. As a result, a high-quality image can be formed.

The exposure unit 44 exposes the surface of the charged image carrier 30. Thereby, an electrostatic latent image is formed on the surface of the image carrier 30. Based on the image data input to the image forming apparatus 100, an electrostatic latent image is formed.

The developing portion 46 supplies toner to the surface of the image carrier 30, thereby developing the electrostatic latent image into a toner image. The developing unit 46 can adopt a contact developing method, that is, a method of developing an electrostatic latent image into a toner image when the electrostatic latent image contacts the surface of the image carrier 30. In general, in the image forming apparatus employed, image failure due to fog is likely to occur. However, the image forming apparatus 100 includes the photoreceptor according to the first embodiment as the image carrier 30. The photoreceptor according to the first embodiment has excellent anti-fogging property. Thus, even if the contact development method is adopted in the image forming apparatus 100 including such a photoreceptor, image failure due to fog can be suppressed.

The developing unit 46 can clean the surface of the image carrier 30. That is, the image forming apparatus 100 can employ a so-called cleanerless system. In this case, the developing portion 46 can remove the residual component on the surface of the image carrier 30. In general, in an image forming apparatus provided with a cleaning portion (e.g., a cleaning blade), residual components on the surface of an image bearing member are scraped off by the cleaning portion. However, in the image forming apparatus of the no-blade cleaner system, the residual components on the surface of the image bearing member cannot be scraped off. Therefore, in an image forming apparatus using a blade-less cleaner, generally, residual components are likely to remain on the surface of an image bearing member. However, the image forming apparatus 100 includes the photoreceptor of the first embodiment, which is excellent in sensitivity characteristics and anti-fogging property, as the image carrier 30. Therefore, even if the cleaner-less system is adopted in the image forming apparatus 100 including the photoreceptor, the residual components (particularly, the minute components of the recording medium P such as paper dust) are less likely to remain on the surface of the photoreceptor. As a result, the image forming apparatus 100 can suppress occurrence of image failure (for example, fog).

In order to efficiently clean the surface of the image carrier 30 even during development, the following conditions (a) and (b) are preferably satisfied.

Condition (a): a difference in rotational speed (rotational speed) is provided between the image carrier 30 and the developing portion 46 by the contact development method.

Condition (b): the surface potential of the image carrier 30 and the potential of the developing bias satisfy the following expressions (b-1) and (b-2).

0 (V) < potential of developing bias (V) < surface potential of unexposed area (V) … … (b-1) of image bearing member 30

Potential of developing bias (V) > surface potential of exposed area of image bearing member 30 (V) > 0 (V) … … (b-2)

As shown in condition (a), if a rotational speed difference is provided between the image bearing member 30 and the developing unit 46 by the contact development method, the surface of the image bearing member 30 contacts the developing unit 46, and the adhering component on the surface of the image bearing member 30 is removed by friction with the developing unit 46. The rotation speed of the developing portion 46 is preferably faster than the rotation speed of the image carrier 30.

In the condition (b), the development system is assumed to be the reversal development system. In order to improve the electrical characteristics of the image carrier 30 having the positive charging polarity, it is preferable that the charging polarity of the toner, the surface potential of the unexposed region of the image carrier 30, the surface potential of the exposed region of the image carrier 30, and the potential of the developing bias are positive. After the transfer unit 48 transfers the toner image from the image carrier 30 to the recording medium P, the surface potential of the unexposed area and the surface potential of the exposed area of the image carrier 30 are measured before the charging unit 42 charges the surface of the image carrier 30.

When the expression (b-1) of the condition (b) is satisfied, an electrostatic repulsive force acting between the residual toner (hereinafter, sometimes referred to as residual toner) on the image carrier 30 and the unexposed area of the image carrier 30 is larger than an electrostatic repulsive force acting between the residual toner and the developing portion 46. Accordingly, the residual toner in the unexposed area of the image carrier 30 moves from the surface of the image carrier 30 to the developing unit 46 and is then collected.

When the expression (b-2) of the condition (b) is satisfied, the electrostatic repulsive force acting between the residual toner and the exposed region of the image carrier 30 is smaller than the electrostatic repulsive force acting between the residual toner and the developing portion 46. Accordingly, the residual toner in the exposed area of the image carrier 30 is held on the surface of the image carrier 30. The toner held on the exposed area of the image carrier 30 is directly used in the subsequent image formation.

The transfer belt 50 conveys the recording medium P between the image carrier 30 and the transfer portion 48. The transfer belt 50 is an endless belt. The transfer belt 50 is provided rotatably in the arrow direction (clockwise direction).

The transfer portion 48 transfers the toner image developed by the developing portion 46 from the surface of the image carrier 30 to the recording medium P. When the toner image is transferred from the image carrier 30 to the recording medium P, the image carrier 30 contacts the recording medium P. The transfer portion 48 includes, for example: and a transfer roller.

After the transfer portion 48 transfers the unfixed toner image onto the recording medium P, the fixing portion 52 heats and/or pressurizes the unfixed toner image. The fixing portion 52 is, for example, a heat roller and/or a pressure roller. The toner image is fixed on the recording medium P by heating and/or pressurizing the toner image. As a result, an image is formed on the recording medium P.

As described above, an example of the image forming apparatus according to the second embodiment is described, but the image forming apparatus according to the second embodiment is not limited to the image forming apparatus 100 described above. For example, although the image forming apparatus 100 described above is a tandem type image forming apparatus, the image forming apparatus according to the second embodiment is not limited thereto, and a swing type (rotation type) or the like may be employed. The image forming apparatus according to the second embodiment may be a monochrome image forming apparatus. In this case, the image forming apparatus may include, for example, only 1 image forming unit. The image forming apparatus according to the second embodiment may adopt an intermediate transfer method. In the case where the image forming apparatus according to the second embodiment employs an intermediate transfer system, the intermediate transfer belt corresponds to the transfer target.

< third embodiment: process cartridge >

The process cartridge according to the third embodiment includes the photoreceptor according to the first embodiment as an image bearing member. Next, an example of a process cartridge according to a third embodiment will be described with reference to fig. 4.

For example, each of the image forming units 40a to 40d (fig. 4) corresponds to the process cartridge according to the third embodiment. These process cartridges contain integrated parts. The integrated portion contains the image carrier 30. The integrated portion may include at least one of a charging portion 42, an exposing portion 44, a developing portion 46, and a transferring portion 48, in addition to the image bearing member 30. The process cartridge may further include one or both of a cleaning portion (not shown) and a neutralizing portion (not shown). The process cartridge is, for example, designed to be freely detachable with respect to the image forming apparatus 100. Such a process cartridge is easy to handle, and when the sensitivity characteristics of the image bearing member 30 are degraded, the process cartridge including the image bearing member 30 can be replaced easily and quickly.

The process cartridge according to the third embodiment described above is provided with the photoconductor according to the first embodiment as an image bearing member, and therefore occurrence of image failure can be suppressed.

[ example ]

Hereinafter, the present invention will be described more specifically by using examples. In addition, the present invention is not limited in any way to the scope of the embodiments.

< materials used in examples and comparative examples >

The following charge generating agent, hole transporting agent, electron transporting agent, and binder resin were prepared as materials for producing a single-layer photoreceptor.

[ Charge generating agent ]

The charge generating agent (CGM-1) described in the first embodiment was prepared. The charge generating agent (CGM-1) is a metal-free phthalocyanine represented by the chemical formula (CGM-1), and its crystal structure is X-type. That is, the charge generating agent (CGM-1) used is X-type metal-free phthalocyanine.

[ hole-transporting agent ]

The hole-transporting agents (HTM 1-1), (HTM 2-1), (HTM 3-1), (HTM 4-1), (HTM 5-1), (HTM 6-1), (HTM 7-1) and (HTM 7-2) described in the first embodiment were prepared. Hole transporting agents (HTM 8-1) and (HTM 9-1) were also prepared. The hole transporting agents (HTM 8-1) and (HTM 9-1) are hole transporting agents represented by the following chemical formulas (HTM 8-1) and (HTM 9-1), respectively.

[ FORMS 37 ]

[ Electron transporting agent ]

The electron mediator (ETM 1-1) described in the first embodiment was prepared.

[ binding resin ]

The polycarbonate resins (R-1) and (R-2) described in the first embodiment and the polycarbonate resins (R-10) to (R-14) were prepared as the binder resin. The polycarbonate resins (R-10) to (R-14) are each represented by the following chemical formulas (R-10) to (R-14). Wherein the polycarbonate resin (R-14) comprises a terminal group having a fluorine atom (a terminal group having a fluorine atom) as shown in the chemical formula (R-14). In addition, none of the polycarbonate resins (R-1), (R-2) and (R-10) to (R-13) contains an end group having a fluorine atom.

[ chemical 38 ]

[ chemical formula 39 ]

< production of photoreceptor >

[ photoreceptor (A-1) ]

Hereinafter, a method for producing the photoreceptor (a-1) according to example 1 will be described. 2 parts by mass of a charge generating agent (CGM-1), 65 parts by mass of a hole transporting agent (HTM 1-1), 35 parts by mass of an electron transporting agent (ETM 1-1), 100 parts by mass of a polycarbonate resin (R-1) as a binder resin, and 300 parts by mass of tetrahydrofuran as a solvent were placed in a container. The material in the vessel and the solvent were mixed for 2 minutes using a rod-shaped ultrasonic vibrator, and the material was dispersed in the solvent. Further, the material in the vessel and the solvent were mixed for 50 hours using a ball mill, and the material was dispersed in the solvent. Thus, a coating liquid for a photosensitive layer was obtained. The coating liquid for a photosensitive layer was coated on an aluminum drum support as a conductive base using a dip coating method. The coated photosensitive layer was hot air dried at 100℃for 40 minutes with a coating liquid. Thus, a photosensitive layer (film thickness 25 μm) was formed on the conductive substrate. As a result, a single-layer photoreceptor, namely, photoreceptor (A-1), was obtained. The surface of the obtained photoreceptor (A-1) was visually observed, and it was confirmed that crystallization did not occur.

[ photoreceptors (A-2) to (A-11) and photoreceptors (B-1) to (B-7) ]

The photoreceptors (A-2) to (A-11) and the photoreceptors (B-1) to (B-7) were obtained by the above-described method for producing the photoreceptor (A-1) except that the binder resin and the hole-transporting agent shown in Table 1 were used. The surfaces of the obtained photoreceptors (A-2) to (A-11), (B-1) and (B-3) to (B-7) were visually observed, and it was confirmed that crystallization did not occur. On the other hand, the surface of the photoreceptor (B-2) was visually observed, and it was confirmed that crystallization occurred. In Table 1, R-2 and R-10 to R-14 of the "kind" of the column "binder resin" represent polycarbonate resins (R-1), (R-2) and (R-10) to (R-14), respectively. The column "molecular weight" of the binder resin "indicates the viscosity average molecular weight of the binder resin.

< evaluation method >

[ measurement of scratch depth ]

The scratch depths of the photosensitive layers were measured for each of the obtained photoreceptors (A-1) to (A-11) and photoreceptors (B-1) to (B-7), respectively. The scratch depth was measured by using a scratch device 200 (see FIG. 5) defined in JIS K5600-5-5 (Japanese Industrial Standard K5600: general test method for paints; fifth section: mechanical properties of coating film; fifth section: scratch hardness (load needle method)), according to the method described later.

Hereinafter, the scratching device 200 defined in JIS K5600-5-5 will be described with reference to FIG. 5. Fig. 5 is an example of the structure of the scratching device 200. The scratching device 200 comprises: a fixing base 201, a fixing tool 202, a scoring pin 203, a

support arm

204, 2 shaft support portions 205, a

base

206, 2 rail portions 207, a weight pan 208, and a constant speed motor (not shown). A weight 209 is placed on the weight dish 208.

In fig. 5, the X-axis direction and the Y-axis direction are horizontal directions, and the Z-axis direction is vertical direction. The X-axis direction indicates the longitudinal direction of the stationary stage 201. The Y-axis direction indicates a direction orthogonal to the X-axis direction in a plane parallel to the top surface 201a (placement surface) of the stationary stage 201. The X-axis direction, Y-axis direction, and Z-axis direction in fig. 6 to 8 described later are also as defined in fig. 5.

The stationary table 201 corresponds to the test board stationary table in JIS K5600-5-5. The stationary stage 201 has a top surface 201a, one end 201b, and the other end 201c. The top surface 201a of the stationary stage 201 is a horizontal surface. One end 201b is opposite to the 2 shaft support portions 205.

The fixing member 202 is provided on the other end 201c side on the top surface 201a of the fixing table 201. The fixing member 202 fixes the measurement object (photoreceptor 1) on the top surface 201a of the fixing table 201.

The scoring needle 203 has a needle tip 203b (see fig. 6). The structure of the needle tip 203b is a hemispherical shape having a diameter of 1 mm. The material of the tip 203b is sapphire.

The support arm 204 supports the scoring needle 203. The support arm 204 rotates about the support shaft 204a in the direction in which the scoring needle 203 approaches and separates from the photoconductor 1.

The 2 shaft support portions 205 rotatably support the support arm portion 204.

The base 206 has a top surface 206a. On one end side of the

top surface

206a, 2 shaft support portions 205 are provided.

The 2 rail portions 207 are provided on the other end side of the top surface 206a. The 2 rail portions 207 are disposed to oppose each other in parallel. Each of the 2 rail portions 207 is provided in parallel with the longitudinal direction (X-axis direction) of the stationary table 201. The stationary table 201 is mounted between 2 rail portions 207. The stationary table 201 is horizontally movable along the guide rail portion 207 in the longitudinal direction (X-axis direction) of the stationary table 201.

The weight pan 208 is disposed above the scoring pin 203 via the support arm 204. A weight 209 is placed on the weight dish 208.

The fixed stage 201 is moved along the rail portion 207 in the X-axis direction of the fixed stage 201 by the constant speed motor.

Hereinafter, a method for measuring the scratch depth will be described. The scratch depth measuring method includes the following first, second, third and fourth steps. A surface property meter ("HEIDON TYPE14" manufactured by new eastern science co.) was used as the scratching device 200. The scratch depth was measured at a temperature of 23℃and a relative humidity of 50% RH. The photoreceptor 1 has a drum shape (cylindrical shape).

(first step)

In the first step, the photoconductor 1 is fixed to the top surface 201a of the fixed stage 201 such that the longitudinal direction of the photoconductor 1 is parallel to the longitudinal direction of the fixed stage 201. At this time, the photoconductor 1 is mounted as the center axis L of the photoconductor 1 ₂ The (rotation axis) direction is parallel to the longitudinal direction of the stationary stage 201.

(second step)

In the second step, the scribing needle 203 is vertically abutted against the surface 3a of the photosensitive layer 3. With reference to fig. 5, a method of vertically abutting the scribing needle 203 against the surface 3a of the photosensitive layer 3 of the drum-shaped photosensitive body 1 will be described with reference to fig. 6 and 7.

Fig. 6 is a sectional view taken along line IV-IV of fig. 5, and is a sectional view when the scoring needle 203 is brought into contact with the photoreceptor 1. Fig. 7 is a side view of the fixing table 201, the scoring pin 203, and the photoconductor 1 in fig. 5.

With the central axis A of the scoring needle 203 ₁ The scoring pin 203 is brought close to the photosensitive body 1 in such a manner that the extension line of (a) is perpendicular to the top surface 201a of the fixing stage 201. Then, the tip 203b of the scribing needle 203 is brought into contact with a point (contact point P) farthest from the top surface 201a of the stationary stage 201 in the vertical direction (Z-axis direction) on the surface 3a of the photosensitive layer 3 of the photosensitive body 1 ₂ ). Thereby, the central axis A of the scoring needle 203 is used ₁ And tangent A ₂ The tip 203b of the scoring needle 203 is brought into contact with the photoreceptor 1 in a vertical manner. At this time, the contact point P of the top surface 201a ₁ Contact point P with tip 203b ₂ The connecting line segment is perpendicular to the central axis L of the photoreceptor 1 ₂ . In addition, tangent A ₂ Is perpendicular to the central axis L in the photoreceptor 1 ₂ An outer circumference formed by a cross section of (a) is at the contact point P ₂ Is a tangent to (a) the line of (b).

(third step)

Next, a third step is described with reference to fig. 5 and 6. In the third step, the scoring needle is used for the following steps203 to the surface 3a of the photosensitive layer 3, and a load W of 10g was applied to the photosensitive layer 3 by the scoring pin. Specifically, a 10g weight 209 was placed on the weight pan 208. In this state, the stationary stage 201 is moved. Specifically, the fixed-speed motor is driven to horizontally move the stationary table 201 along the rail portion 207 in the X-axis direction. That is, one end 201b of the stationary stage 201 is moved from the first position N ₁ To a second position N ₂ . In addition, the second position N ₂ Is positioned at a first position N ₁ Downstream side of (a). The downstream side refers to: in the longitudinal direction of the fixed stage 201, the fixed stage 201 is located on one side in the direction away from the 2 shaft support portions 205. As the stationary table 201 moves in the longitudinal direction, the photosensitive body 1 also moves horizontally in the longitudinal direction of the stationary table 201. The moving speed of the stationary stage 201 and the photoconductive body 1 was 30 mm/min. The moving distance between the stationary table 201 and the photoconductive body 1 is 30mm. The moving distance of the stationary table 201 and the photoconductive body 1 corresponds to the first position N ₁ And a second position N ₂ Distance D between _1-2 . As a result of the movement of the stationary stage 201 and the photosensitive body 1, a scratch S is formed on the surface 3a of the photosensitive layer 3 of the photosensitive body 1 by the scratch pin 203.

The scratch S will be described with reference to fig. 8 in addition to fig. 5 to 7. Fig. 8 is a scratch S formed on the surface 3a of the photosensitive layer 3. The scratch S is opposite to the top surface 201a and the tangent line a of the fixing table 201 ₂ Are all vertical. Also, the scratch S passes through a line L in fig. 7 ₃ . Line L ₃ Is composed of several contact points P ₂ A wire is formed. Line L ₃ With the top surface 201a of the stationary table 201 and the central axis L of the photoreceptor 1 ₂ Are all parallel. Line L ₃ Perpendicular to the central axis A of the scoring needle 203 ₁ 。

(fourth step)

In the fourth step, the maximum value of the depth Ds of the scratch S, i.e., the scratch depth, is measured. Specifically, the photoconductor 1 is removed from the stationary stage 201. The scratch S formed on the photosensitive layer 3 of the photosensitive body 1 was observed at a magnification of 5 times using a three-dimensional interference microscope (Bruker corporation "WYKO NT-1100"), and the depth Ds of the scratch S was measured. The depth Ds of the scratch S is from the tangent A ₂ Go to scratchDistance of bottom of mark S. The maximum value of the depth Ds of the scratch S serves as the scratch depth. The scratch depths measured are shown in table 1.

[ measurement of Vickers hardness ]

For each of the obtained photoreceptors (A-1) to (A-11) and photoreceptors (B-1) to (B-7), the Vickers hardness of the photosensitive layer was measured. The vickers hardness of the photosensitive layer was measured according to the method of Japanese Industrial Standard (JIS) Z2244. In the measurement of vickers hardness, a durometer (Matsuzawa co., ltd "microscopic vickers durometer type DMH-1") was used. The measurement of vickers hardness was performed under conditions of a temperature of 23 ℃, a load (test force) of the diamond indenter of 10gf, a time required to reach the test force of 5 seconds, an approach speed of the diamond indenter of 2 mm/second, and a test force holding time of 1 second. The measured vickers hardness is shown in table 1.

[ evaluation of sensitivity characteristics ]

The sensitivity characteristics of each of the obtained photoreceptors (A-1) to (A-11) and photoreceptors (B-1) to (B-7) were evaluated. The sensitivity characteristics were evaluated in an environment of a temperature of 23℃and a humidity of 50% RH. First, the surface of the photoreceptor was charged to +700V using a drum sensitivity tester (manufactured by GENTEC corporation). Then, monochromatic light (wavelength 780nm, half-width 20nm, light intensity 1.5. Mu.J/m) was extracted from the white light of the halogen lamp using a band-pass filter ² ). The extracted monochromatic light is irradiated to the surface of the photoreceptor. When 0.5 seconds passed from the start of irradiation, the surface potential of the photoreceptor was measured. Measured surface potential as post-exposure potential V _L (unit V). Measured post-exposure potential V of photoreceptor _L Shown in table 1. In addition, post-exposure potential V _L The smaller the absolute value of (c), the more excellent the photosensitivity characteristic of the photoreceptor.

[ evaluation of anti-fog Property ]

The resulting photoreceptors (A-1) to (A-11) and photoreceptors (B-1) to (B-7) were each evaluated for anti-fogging properties of the formed images. An image forming apparatus (a refitted machine of "monochrome printer FS-1300D" manufactured by kyo porcelain office information systems corporation) was used as an evaluation machine. The image forming apparatus adopts a direct transfer method, a contact developing method, and a cleanerless method. In this image forming apparatus, the developing unit cleans toner remaining on the photoreceptor. The charging unit of the image forming apparatus is a charging roller. "Beijing ceramic office information System brand paper VM-A4" (A4) sold by Beijing ceramic office information System Co., ltd.) was used as the printing paper. In the evaluation using the evaluator, a one-component developer (test production sample) was used.

Images I were continuously printed on 12,000 sheets of paper using an evaluation machine at a photoreceptor rotational speed of 168 mm/sec and a charging potential of +600V. Image I is an image with a print coverage of 1%. Next, a blank image was printed on 1 sheet of paper. The printing was performed at a temperature of 32.5℃and a humidity of 80% RH. For the obtained blank image, the image density at 3 in the blank image was measured using a reflection densitometer (manufactured by X-rite corporation, "RD 914"). The sum of the image densities at 3 of the blank image divided by the number of measurement positions. Thus, an arithmetic average of the image density of the blank image is obtained. The image density of the reference paper is subtracted from the arithmetic average value of the image density of the blank image to obtain a value as the fog density. The measured haze density was determined according to the following evaluation criteria. The photoreceptor judged to be a or B was evaluated as having good anti-fogging property. The photoreceptor judged to be C was evaluated as having poor anti-fogging property. The haze density (FD value) and the determination result are shown in table 1. In table 1, the haze density (FD value) and the determination result "-" of comparative example 2 are shown as follows: since the photosensitive property of the photoreceptor (B-2) used in comparative example 2 was particularly poor with respect to other photoreceptors, the evaluation of the anti-fogging property was not performed under the same conditions.

(criterion for determining anti-fog Property)

And (3) judging A: the haze density is 0.010 or less.

And (3) judging B: the haze density is greater than 0.010 and less than 0.020.

And C, judging: the haze density is greater than 0.020.

[ Table 1 ]

As shown in Table 1, the photoreceptors (A-1) to (A-11) contain one of the polycarbonate resins (R-1) and (R-2) contained in the general formula (1). The photoreceptor (A-1) to (A-11) contains one of the hole transporting agents (HTM 1-1) to (HTM 7-1) and (HTM 7-2) contained in the general formula (HTM 1), the general formula (HTM 2), the general formula (HTM 3), the general formula (HTM 4), the general formula (HTM 5), the general formula (HTM 6) or the general formula (HTM 7). In the photoreceptors (A-1) to (A-11), the scratch depth of the photosensitive layer is 0.28 μm or more and 0.46 μm or less. In the photoreceptors (A-1) to (A-11), the Vickers hardness of the photosensitive layer is 17.8HV or more and 20.2HV or less. In the photoreceptors (A-1) to (A-11), the post-exposure potential V _L Is +112V to +137V. Among the photoreceptors (A-1) to (A-11), A (good) was the result of the determination of the anti-fogging property.

As shown in Table 1, the photoreceptors (B-1) to (B-4) contain one of the polycarbonate resins (R-10) to (R-13), and the polycarbonate resins (R-10) to (R-13) are not contained in the general formula (1). The photoreceptors (B-5) and (B-6) contain one of the hole-transporting agents (HTM 8-1) and (HTM 9-1), and the hole-transporting agents (HTM 8-1) and (HTM 9-1) are not contained in the general formula (HTM 1), the general formula (HTM 2), the general formula (HTM 3), the general formula (HTM 4), the general formula (HTM 5), the general formula (HTM 6) and the general formula (HTM 7). In the photoreceptors (B-1), (B-3), (B-4) and (B-7), the scratch depth of the photosensitive layer exceeds 0.50. Mu.m. In the photoreceptors (B-3) to (B-6), the Vickers hardness of the photosensitive layer is less than 17.0HV. In the photoreceptor (B-2), the potential V after exposure _L Is +193V. The determination result of the anti-fogging property of the photoreceptors (B-1) and (B-3) to (B-7) was C (poor).

As is clear from Table 1, the photoreceptors (A-1) to (A-11) are excellent in sensitivity characteristics as compared with the photoreceptor (B-2). The photoreceptors (A-1) to (A-11) are excellent in anti-fogging property as compared with the photoreceptors (B-1) and (B-3) to (B-7).

[ Industrial availability ]

The electrophotographic photoreceptor according to the present invention can be used in an image forming apparatus such as a multifunctional integrated machine.

Claims

1. An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer, characterized in that,

the photosensitive layer is a single layer and contains a charge generating agent, a hole transporting agent, an electron transporting agent and a binder resin,

the binder resin comprises a polycarbonate resin and,

the polycarbonate resin has a repeating unit represented by the following general formula (1-1) and a repeating unit represented by the following general formula (1-2),

the hole-transporting agent contains one of the compounds represented by the following chemical formulas (HTM 2-1) and (HTM 6-1),

the scratch-resistant depth of the photosensitive layer is 0.50 μm or less,

the vickers hardness of the photosensitive layer is 17.0HV or more,

in the general formulae (1-1) and (1-2),

Q ¹ and Q ² Represents a hydrogen atom and Q ³ And Q ⁴ Represents a methyl group, and is preferably a methyl group,

or Q ¹ And Q ² Represents methyl and Q ³ And Q ⁴ Represents a hydrogen atom and is represented by the formula,

2. the electrophotographic photoreceptor as claimed in claim 1, wherein,

in the general formulae (1-1) and (1-2), Q ¹ And Q ² Represents a hydrogen atom and Q ³ And Q ⁴ Represents methyl.

3. The electrophotographic photoreceptor as claimed in claim 1, wherein,

the content of the hole transporting agent is 10 parts by mass or more and 90 parts by mass or less relative to 100 parts by mass of the polycarbonate resin represented by the general formula (1).

4. The electrophotographic photoreceptor as claimed in claim 1, wherein,

the polycarbonate resin is a polycarbonate resin represented by the following chemical formula (R-2),

5. a process cartridge comprising a housing, a plurality of fixing members,

an electrophotographic photoreceptor comprising the composition of claim 1.

6. An image forming apparatus includes:

an image bearing body;

a charging unit that charges a surface of the image carrier;

an exposure unit that exposes the surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier;

a developing section that develops the electrostatic latent image into a toner image; and

a transfer unit for transferring the toner image from the image bearing member to a transfer object,

The image forming apparatus is characterized in that,

the image bearing member is the electrophotographic photoreceptor according to claim 1,

the charging polarity of the charging section is positive,

the transfer unit transfers the toner image from the image bearing member to the transfer target when the surface of the image bearing member contacts the transfer target.

7. The image forming apparatus according to claim 6, wherein,

the transferred body is a recording medium.

8. The image forming apparatus according to claim 6, wherein,

the developing unit develops the electrostatic latent image into the toner image when the developing unit makes contact with the surface of the image bearing member.

9. The image forming apparatus according to claim 6, wherein,

the developing unit cleans the surface of the image bearing member.

10. The image forming apparatus according to claim 6, wherein,

the charging section is a charging roller.