JP7287108B2 - Electrophotographic photoreceptor, process cartridge, and image forming apparatus - Google Patents

Description

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

An electrophotographic photoreceptor is used as an image carrier for an electrophotographic image forming apparatus (for example, a printer or a multifunction machine). An exposure device included in the image forming apparatus exposes the surface of the electrophotographic photosensitive member to form an electrostatic latent image on the surface of the electrophotographic photosensitive member. Patent Document 1 describes an exposure device that exposes the surface of an electrophotographic photosensitive member using a light emitting diode as a light source.

JP 2012-118437 A

However, an exposure apparatus using a light emitting diode as a light source tends to have a lower exposure intensity than a laser scanning type exposure apparatus. The present inventors have found that when an image is formed using an image forming apparatus having an exposure device with a low exposure intensity, the dot reproducibility of the formed image tends to deteriorate.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrophotographic photoreceptor capable of forming an image with excellent dot reproducibility even when the exposure intensity is low and suppressing the occurrence of transfer blur. is to provide Another object of the present invention is to provide a process cartridge and an image forming apparatus capable of forming good images by including such an electrophotographic photoreceptor.

The electrophotographic photoreceptor of the present invention comprises a conductive substrate and a photosensitive layer. The photosensitive layer is a single layer. The photosensitive layer contains a charge generating agent, a hole transporting agent, an electron transporting agent and a binder resin. The hole transport agent is at least one of the compounds represented by formulas (1) to (4). The electron transport agent is at least one of the compounds represented by formulas (10) to (12). However, when the hole transport agent is the compound represented by the general formula (4), the electron transport agent is the compound represented by the general formula (11). The thickness of the photosensitive layer is 27 μm or less. The predetermined potential is 0V or more and +450V or less. The predetermined potential is the potential of the surface of the electrophotographic photosensitive member when 0.1 seconds have passed since the surface of the electrophotographic photosensitive member charged to +750 V was irradiated with predetermined light. The intensity of the predetermined light is 0.1 μJ/cm ² .

In general formula (1), R ¹¹ and R ¹² each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the number of carbon atoms in the group represented by R ¹¹ and the number of carbon atoms in the group represented by R ¹² The sum with the number is 2. R ¹³ and R ¹⁴ each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the sum of the number of carbon atoms in the group represented by R ¹³ and the number of carbon atoms in the group represented by R ¹⁴ is 2 . In general formula (2), R ²¹ and R ²² each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. R ²³ and R ²⁴ are each independently a phenyl group optionally substituted with an alkyl group having 1 to 8 carbon atoms, a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or 1 or more carbon atoms. represents an alkoxy group of 8 or less; R ²⁵ , R ²⁶ , R ²⁷ , R ²⁸ and R ²⁹ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms; show. a1 and a2 each independently represent an integer of 0 or more and 5 or less. In general formula (3), R ³¹ to R ³⁶ each independently represent an alkyl group having 1 to 8 carbon atoms or a phenyl group. R ³⁷ and R ³⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group. b1, b2, b3 and b4 each independently represents an integer of 0 or more and 5 or less. b5 and b6 each independently represent an integer of 0 or more and 4 or less. d and e each independently represent 0 or 1; In general formula (4), R ⁴¹ to R ⁴⁶ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. f1, f2, f4, and f5 each independently represent an integer of 0 or more and 5 or less. f3 and f6 each independently represent an integer of 0 or more and 4 or less.

In general formula (10), ^Q5A and ^Q5B each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. Q ^6A and Q ^6B each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. m ₁ and m ₂ each independently represent an integer of 0 or more and 4 or less. In general formula (11), Q ⁷ and Q ⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. Q ⁹ represents a halogen atom or an alkyl group having 1 to 8 carbon atoms which may be substituted with a halogen atom. m ₃ represents an integer of 1 or more and 4 or less. In general formula (12), Q ¹⁰ and Q ¹¹ each independently represent an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. ^Q12 represents a halogen atom or a hydrogen atom.

A process cartridge of the present invention includes the above electrophotographic photosensitive member.

An image forming apparatus of the present invention includes an image carrier, a charging device, an exposure device, a developing device, and a transfer device. The charging device positively charges the surface of the image carrier. The exposure device exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier. The developing device develops the electrostatic latent image into a toner image. The transfer device transfers the toner image from the image bearing member to a transfer receiving member. The image carrier is the above electrophotographic photoreceptor.

According to the electrophotographic photoreceptor of the present invention, it is possible to form an image with excellent dot reproducibility even when the exposure intensity is low, and it is possible to suppress the occurrence of transfer faintness. Further, according to the process cartridge and the image forming apparatus of the present invention having such an electrophotographic photoreceptor, excellent images can be formed.

1 is a partial cross-sectional view of an electrophotographic photoreceptor according to a first embodiment of the invention; FIG. 1 is a partial cross-sectional view of an electrophotographic photoreceptor according to a first embodiment of the invention; FIG. 1 is a partial cross-sectional view of an electrophotographic photoreceptor according to a first embodiment of the invention; FIG. FIG. 2 shows a measuring machine for measuring a predetermined potential; 1 is a cross-sectional view showing an example of an image forming apparatus; FIG.

A first embodiment of the present invention will be described in detail below. However, the present invention is by no means limited to the following first embodiment. The present invention can be implemented with appropriate modifications within the scope of the purpose of the present invention. It should be noted that descriptions of overlapping descriptions may be omitted as appropriate, but the gist of the invention is not limited. Hereinafter, compounds and derivatives thereof may be collectively referred to by adding "system" to the name of the compound. In addition, when the name of a polymer is expressed by adding "system" to the name of a compound, it means that the repeating unit of the polymer is derived from the compound or its derivative.

First, the substituents used in this specification are described. Halogen atoms (halogen groups) include, for example, fluorine atoms (fluoro groups), chlorine atoms (chloro groups), bromine atoms (bromo groups), and iodine atoms (iodo groups).

An alkyl group having 1 to 8 carbon atoms, an alkyl group having 1 to 6 carbon atoms, and an alkyl group having 1 to 3 carbon atoms are linear or branched unless otherwise specified. is unsubstituted. Examples of alkyl groups having 1 to 8 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 1 -methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-ethylpropyl group, 2-ethylpropyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 1,2-dimethylpropyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1,2-dimethyl butyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1,1,2-trimethylpropyl group, 1,2,2 -trimethylpropyl, 1-ethylbutyl, 2-ethylbutyl, 3-ethylbutyl, linear and branched heptyl groups, and linear and branched octyl groups. Examples of the alkyl group having 1 to 6 carbon atoms and the alkyl group having 1 to 3 carbon atoms are each the corresponding carbon among the groups described as examples of the alkyl group having 1 to 8 carbon atoms It is a group having the number of atoms.

Unless otherwise specified, an alkoxy group having from 1 to 8 carbon atoms may be straight or branched and unsubstituted. Examples of alkoxy groups having 1 to 8 carbon atoms include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, 1-methylbutoxy group, 2-methylbutoxy group, 3-methylbutoxy group, 1-ethylpropoxy group, 2-ethylpropoxy group, 1,1-dimethylpropoxy group, 1,2-dimethylpropoxy group, 2,2- dimethylpropoxy group, 1,2-dimethylpropoxy group, n-hexyloxy group, 1-methylpentyloxy group, 2-methylpentyloxy group, 3-methylpentyloxy group, 4-methylpentyloxy group, 1,1- dimethylbutoxy group, 1,2-dimethylbutoxy group, 1,3-dimethylbutoxy group, 2,2-dimethylbutoxy group, 2,3-dimethylbutoxy group, 3,3-dimethylbutoxy group, 1,1,2- trimethylpropoxy, 1,2,2-trimethylpropoxy, 1-ethylbutoxy, 2-ethylbutoxy, 3-ethylbutoxy, linear and branched heptyloxy groups, and linear and A branched octyloxy group can be mentioned.

<Electrophotographic Photoreceptor of First Embodiment>
An electrophotographic photoreceptor (hereinafter sometimes referred to as a photoreceptor) of the first embodiment will be described. The photoreceptor of the first embodiment includes a conductive substrate and a photosensitive layer. The photosensitive layer is a single layer. The photosensitive layer contains a charge generating agent, a hole transporting agent, an electron transporting agent and a binder resin. The hole transport agent is at least one of the compounds represented by formulas (1) to (4). The electron transport agent is at least one compound among compounds represented by general formulas (10) to (12). However, when the hole transport agent is a compound represented by general formula (4), the electron transport agent is a compound represented by general formula (11). The thickness of the photosensitive layer is 27 μm or less. The predetermined potential is 0V or higher and +450V or lower. The predetermined potential is the potential of the surface of the photoreceptor charged to +750 V when 0.1 seconds have passed since the surface of the photoreceptor was irradiated with predetermined light. The predetermined light intensity is 0.1 μJ/cm ² .

The compounds represented by general formulas (1), (2), (3) and (4) are hereinafter referred to as hole transport agents (1), (2), (3) and (4), respectively. may be described. Further, the compounds represented by general formulas (10), (11) and (12) are sometimes referred to as electron transfer agents (10), (11) and (12), respectively. Also, the "thickness of the photosensitive layer" may be described as the "thickness of the photosensitive layer". Details of general formulas (1), (2), (3), (4), (10), (11), and (12) will be described later.

The photoreceptor of the first embodiment can form an image with excellent dot reproducibility even when the exposure intensity (the intensity of the exposure light emitted by the exposure device) is low, and can suppress the occurrence of transfer faintness. The reason for this is presumed as follows.

The exposure intensity of the laser scanning type exposure device is, for example, about 1.5 μJ/cm ² . The exposure intensity of an exposure device using a light emitting diode as a light source is, for example, about 0.35 μJ/cm ² . The exposure intensity of an exposure apparatus using a light emitting diode as a light source tends to be lower than that of a laser scanning type exposure apparatus. When an image is formed using an image forming apparatus having an exposure device with low exposure intensity, the dot reproducibility of the formed image tends to deteriorate. Here, the photosensitive layer included in the photoreceptor of the first embodiment contains at least one compound of the hole transport agents (1) to (4) and one of the electron transport agents (10) to (12). It contains at least one compound. However, when the hole transport agent is hole transport agent (4), the electron transport agent is electron transport agent (11). By containing such a hole transport agent and an electron transport agent, the predetermined potential of the photoreceptor becomes 0 V or more and +450 V or less. When the predetermined potential of the photoreceptor is within such a range, the photoreceptor is not only exposed to high-intensity exposure light, but also exposed to low-intensity exposure light. The surface potential of the exposed areas of the body is preferably lowered. Therefore, the photoreceptor of the first embodiment can form an image with excellent dot reproducibility even when the exposure intensity of the exposure device is low.

Further, during transfer, a negative transfer current flows from the transfer device provided in the image forming apparatus to the photosensitive member. Due to the inflow of negative transfer current, the surface potential of the photosensitive member after transfer (post-transfer potential) may change from a positive value to a negative value. When the post-transfer potential of the photoreceptor becomes a negative value, it becomes difficult for the positively charged toner to electrostatically separate from the surface of the photoreceptor. Then, it becomes difficult to transfer the toner from the photoreceptor to the recording medium, and transfer faintness (fading due to a decrease in potential after transfer) occurs in the formed image. Here, the film thickness of the photosensitive layer included in the photoreceptor of the first embodiment is 27 μm or less. When the film thickness of the photosensitive layer is 27 μm or less, it is possible to prevent the post-transfer potential from changing from a positive value to a negative value, thereby suppressing the occurrence of transfer blurring in the formed image.

Furthermore, since the film thickness of the photosensitive layer is 27 μm or less, the manufacturing cost of the photosensitive layer and, in turn, the manufacturing cost of the photoreceptor can be reduced.

(Structure of photoreceptor)
Next, the structure of the photoreceptor 1 of the first embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 to 3 each show a partial cross-sectional view of photoreceptor 1. FIG. As shown in FIG. 1, the photoreceptor 1 includes, for example, a conductive substrate 2 and a photosensitive layer 3. As shown in FIG. The photosensitive layer 3 is a single layer. The photoreceptor 1 is a single layer electrophotographic photoreceptor having a single photosensitive layer 3 .

As shown in FIG. 2, the photoreceptor 1 may include a conductive substrate 2, a photosensitive layer 3, and an intermediate layer 4 (undercoat layer). An intermediate layer 4 is provided between the conductive substrate 2 and the photosensitive layer 3 . The photosensitive layer 3 may be provided directly on the conductive substrate 2, as shown in FIG. Alternatively, as shown in FIG. 2, the photosensitive layer 3 may be provided on the conductive substrate 2 with an intermediate layer 4 interposed therebetween.

As shown in FIG. 3, the photoreceptor 1 may comprise a conductive substrate 2, a photosensitive layer 3, and a protective layer 5. As shown in FIG. A protective layer 5 is provided on the photosensitive layer 3 . As shown in FIGS. 1 and 2, a photosensitive layer 3 may be provided as the outermost layer of the photoreceptor 1 . Alternatively, as shown in FIG. 3, a protective layer 5 may be provided as the outermost surface layer of the photoreceptor 1 .

As already mentioned, the film thickness of the photosensitive layer 3 is 27 μm or less. The film thickness of the photosensitive layer 3 is preferably 5 μm or more and 27 μm or less, more preferably 10 μm or more and 27 μm or less. The structure of the photoreceptor 1 has been described above with reference to FIGS. 1 to 3. FIG. The photoreceptor will be further described below.

(predetermined potential)
The predetermined potential of the photoreceptor is 0V or more and +450V or less. The predetermined potential is the potential of the surface of the photoreceptor charged to +750 V when 0.1 seconds have passed since the surface of the photoreceptor was irradiated with predetermined light. The predetermined light intensity is 0.1 μJ/cm ² .

Since an image with excellent dot reproducibility can be formed even when the exposure intensity is low, the predetermined potential of the photoreceptor is preferably +430 V or less, more preferably +420 V or less, and +410 V or less. is more preferred. Further, the predetermined potential of the photoreceptor is preferably +350 V or higher, more preferably +390 V or higher.

The predetermined potential of the photoreceptor can be adjusted, for example, by changing one or both of the type of hole transport agent and the type of electron transport agent.

Hereinafter, the measuring device 60 for measuring the predetermined potential of the photoreceptor will be described with reference to FIG. FIG. 4 shows a measuring machine 60 for measuring a given potential. The measuring machine 60 is a drum sensitivity tester (manufactured by Gentec Co., Ltd.). The measuring device 60 includes a corotron charger 62 (“CYNTHIA-30M charger” manufactured by Gentec Co., Ltd.), a halogen lamp 63 (“POLAS-36M” manufactured by Gentec Co., Ltd.), and a bandpass filter 64 (Toshiba Corporation (manufactured by Trek), a probe 65 (“light-passing type probe” manufactured by Trek), and an electrometer 66 (“362A” manufactured by Trek). The photoreceptor 1 to be measured can be set in the measuring machine 60 so as to be rotatable around the rotation axis X of the photoreceptor 1 . Corotron charger 62, halogen lamp 63, and probe 65 are arranged around photoreceptor 1 in the order described from the upstream side in the rotational direction of photoreceptor 1 (clockwise direction in FIG. 4). The bandpass filter 64 is arranged between the halogen lamp 63 and the surface 1 a of the photoreceptor 1 and on the optical path of the light L ₁ emitted from the halogen lamp 63 to the photoreceptor 1 . The probe 65 is arranged so that the distance between the probe 65 and the surface 1a of the photoreceptor 1 is 1 mm. The detection area by probe 65 is 0.238 cm ² . Electrometer 66 is connected to probe 65 .

Next, a method for measuring the predetermined potential of the photoreceptor will be described with continued reference to FIG. The predetermined potential measurement environment is an environment with a temperature of 10° C. and a relative humidity of 15% RH. The photosensitive member 1 to be measured is set on the measuring device 60 . The rotation speed of the photosensitive member ₁ is set so that the time from passing through the exposure position P1 to reaching the potential detection position _P2 is 0.1 second. The exposure position P ₁ is a position where the predetermined light L ₂ emitted from the halogen lamp 63 through the bandpass filter 64 is incident on the surface 1 a of the photoreceptor 1 . The potential detection position P ₂ is a position facing the probe 65 on the surface 1 a of the photoreceptor 1 .

The surface 1a of the photoreceptor 1 is charged to +750 V using the corotron charger 62 while rotating the photoreceptor 1 at the above rotational speed. Next, the light L ₁ is emitted from the halogen lamp 63 , and the predetermined light L ₂ contained in the light L ₁ is selectively transmitted through the bandpass filter 64 . Then, at the exposure position P ₁ , the surface 1 a of the photoreceptor 1 is irradiated with the transmitted predetermined light L ₂ . The light intensity of the predetermined light _L2 is 0.1 μJ/ ^cm2 . The predetermined light _L2 is monochromatic light. The wavelength of the predetermined light _L2 is 780 nm. Since the photoreceptor 1 rotates at the above rotational speed, the predetermined light L ₂ is detected when 0.1 seconds have passed since the surface 1a of the photoreceptor 1 was irradiated with the predetermined light L ₂ at the exposure position P ₁ . reaches the potential detection position _P2 . At the potential detection position _P2 , the probe 65 is used to detect the potential of the surface 1a of the photoreceptor ₁ when 0.1 seconds have elapsed since the surface 1a of the photoreceptor 1 was irradiated with the predetermined light L2. An electrometer 66 obtains the potential of the surface 1a of the photoreceptor 1 based on the potential detected by the probe 65. FIG. The obtained potential of the surface 1a of the photoreceptor 1 is assumed to be a predetermined potential (unit: +V). The apparatus and method for measuring the predetermined potential of the photoreceptor have been described above with reference to FIG.

(Hole transport agent)
The hole transport agent is a compound of at least one (eg, one) of hole transport agents (1) to (4). Hole transport agents (1), (2), (3) and (4) are represented by the following general formulas (1), (2), (3) and (4), respectively.

In general formula (1), R ¹¹ and R ¹² each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the number of carbon atoms in the group represented by R ¹¹ and the number of carbon atoms in the group represented by R ¹² is 2. R ¹³ and R ¹⁴ each independently represent a hydrogen atom, a methyl group, or an ethyl group, and the sum of the number of carbon atoms in the group represented by R ¹³ and the number of carbon atoms in the group represented by R ¹⁴ is 2 .

In general formula (1), it is preferred that one of R ¹¹ and R ¹² represents a hydrogen atom and the other of R ¹¹ and R ¹² represents an ethyl group. Preferably one of R ¹³ and R ¹⁴ represents a hydrogen atom and the other of R ¹³ and R ¹⁴ represents an ethyl group.

In general formula (2), R ²¹ and R ²² each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. R ²³ and R ²⁴ are each independently a phenyl group optionally substituted with an alkyl group having 1 to 8 carbon atoms, a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or 1 or more carbon atoms. represents an alkoxy group of 8 or less; R ²⁵ , R ²⁶ , R ²⁷ , R ²⁸ and R ²⁹ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms; show. a1 and a2 each independently represent an integer of 0 or more and 5 or less.

In general formula (2), when a1 represents an integer of 2 or more and 5 or less, a plurality of R ²¹ may be the same or different. When a2 represents an integer of 2 or more and 5 or less, a plurality of R ²² may be the same or different.

In general formula (2), R ²¹ and R ²² each independently preferably represent an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. , more preferably represents a methyl group. Each of R ²³ and R ²⁴ preferably independently represents a phenyl group optionally substituted with an alkyl group having 1 to 8 carbon atoms, and a phenyl group substituted by an alkyl group having 1 to 8 carbon atoms. group, more preferably a phenyl group substituted with an alkyl group having 1 to 3 carbon atoms, and still more preferably a methylphenyl group. Each of ^R25 , ^R26 , ^R27 , ^R28 and ^R29 preferably independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. The alkyl group having 1 to 8 carbon atoms represented by R ²⁵ , R ²⁶ , R ²⁷ , R ²⁸ and R ²⁹ is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. a1 and a2 preferably represent 1;

In general formula (3), R ³¹ to R ³⁶ each independently represent an alkyl group having 1 to 8 carbon atoms or a phenyl group. R ³⁷ and R ³⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group. b1, b2, b3 and b4 each independently represents an integer of 0 or more and 5 or less. b5 and b6 each independently represent an integer of 0 or more and 4 or less. d and e each independently represent 0 or 1;

In general formula (3), when b1 represents an integer of 2 or more and 5 or less, a plurality of R ³¹ may be the same or different. When b2 represents an integer of 2 or more and 5 or less, a plurality of R ³² may be the same or different. When b3 represents an integer of 2 or more and 5 or less, a plurality of R ³³ may be the same or different. When b4 represents an integer of 2 or more and 5 or less, a plurality of R ³⁴ may be the same or different. When b5 represents an integer of 2 or more and 4 or less, a plurality of R ³⁵ may be the same or different. When b6 represents an integer of 2 or more and 4 or less, a plurality of R ³⁶ may be the same or different.

In general formula (3), each of R ³¹ to R ³⁶ preferably independently represents an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. , a methyl group, or an ethyl group. R ³⁷ and R ³⁸ preferably represent a hydrogen atom. b1, b2, b3, and b4 preferably each independently represent an integer of 0 or more and 2 or less. b5 and b6 preferably represent 0; d and e preferably represent 0;

In general formula (4), R ⁴¹ to R ⁴⁶ each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. f1, f2, f4, and f5 each independently represent an integer of 0 or more and 5 or less. f3 and f6 each independently represent an integer of 0 or more and 4 or less.

In general formula (4), when f1 represents an integer of 2 or more and 5 or less, a plurality of R ⁴¹ may be the same or different. When f2 represents an integer of 2 or more and 5 or less, a plurality of R ⁴² may be the same or different. When f4 represents an integer of 2 or more and 5 or less, a plurality of R ⁴⁴ may be the same or different. When f5 represents an integer of 2 or more and 5 or less, a plurality of R ⁴⁵ may be the same or different. When f3 represents an integer of 2 or more and 4 or less, a plurality of R ⁴³ may be the same or different. When f6 represents an integer of 2 or more and 4 or less, a plurality of R ⁴⁶ may be the same or different.

In general formula (4), each of R ⁴¹ to R ⁴⁶ preferably independently represents an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. , a methyl group, or an ethyl group. f1, f2, f4, and f5 preferably each independently represent an integer of 0 or more and 2 or less. f3 and f6 each preferably represent 0; The diphenylaminophenylethenyl group having R ⁴⁴ , R ⁴⁵ and R ⁴⁶ is bonded to the diphenylaminophenylethenyl group having R ⁴¹ , R ⁴² and R ⁴³ at the ortho or para position of the phenyl group. is preferred, and binding at the para position is more preferred.

The hole transport agent is at least one (eg, one) compound among the compounds represented by the chemical formulas (1-HT6), (2-HT4), (3-HT3), and (4-HT1). is preferred. Compounds represented by the chemical formulas (1-HT6), (2-HT4), (3-HT3), and (4-HT1) are used as hole transport agents (1-HT6) and (2-HT4), respectively. ), (3-HT3), and (4-HT1).

The hole transport agent (1-HT6) is a preferred example of the hole transport agent (1). Hole transport agent (2-HT4) is a suitable example of hole transport agent (2). A hole transport agent (3-HT3) is a suitable example of a hole transport agent (3). A hole transport agent (4-HT1) is a suitable example of a hole transport agent (4).

The content of the hole transport agent is preferably 10 parts by mass or more, more preferably 40 parts by mass or more, relative to 100 parts by mass of the binder resin. The content of the hole transport agent is preferably 300 parts by mass or less, more preferably 80 parts by mass or less, relative to 100 parts by mass of the binder resin.

The photosensitive layer may contain only one compound selected from the hole transport agents (1) to (4) as the hole transport agent, or may contain two or more compounds. In addition, the photosensitive layer contains at least one compound selected from the hole transport agents (1) to (4) as a hole transport agent, in addition to hole transport agents other than the hole transport agents (1) to (4). A transport agent (hereinafter sometimes referred to as another hole transport agent) may be further contained.

Other hole transport agents include, for example, oxadiazole compounds (eg, 2,5-di(4-methylaminophenyl)-1,3,4-oxadiazole), styryl compounds (eg, 9- (4-diethylaminostyryl)anthracene), carbazole compounds (e.g., polyvinylcarbazole), organic polysilane compounds, pyrazoline compounds (e.g., 1-phenyl-3-(p-dimethylaminophenyl)pyrazoline), hydrazone compounds, indole compounds , oxazole compounds, isoxazole compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

(Electron transport agent)
The electron transport agent is a compound of at least one (eg, one) of electron transport agents (10) to (12). However, when the hole transport agent is hole transport agent (4), the electron transport agent is electron transport agent (11). That is, when the hole transport agent is hole transport agent (4), the electron transport agents are not electron transport agents (10) and (12). Electron transport agents (10), (11) and (12) are represented by general formulas (10), (11) and (12), respectively.

In general formula (10), ^Q5A and ^Q5B each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. Q ^6A and Q ^6B each independently represent an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. m ₁ and m ₂ each independently represent an integer of 0 or more and 4 or less.

In general formula (10), when m ₁ represents an integer of 2 or more and 4 or less, multiple Q ^6A may be the same or different. When m ₂ represents an integer of 2 or more and 4 or less, multiple Q ^6Bs may be the same or different.

In general formula (10), Q ^5A and Q ^5B each independently preferably represent an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms. , more preferably represents a 1,1-dimethylpropyl group. m ₁ and m ₂ preferably represent zero.

In general formula (11), ^Q7 and ^Q8 each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, a phenyl group, or an alkoxy group having 1 to 8 carbon atoms. Q ⁹ represents a halogen atom or an alkyl group having 1 to 8 carbon atoms which may be substituted with a halogen atom. m ₃ represents an integer of 1 or more and 4 or less.

In general formula (11), when m ₃ represents an integer of 2 or more and 4 or less, multiple Q ^9s may be the same or different.

In general formula (11), Q ⁷ and Q ⁸ each independently preferably represent an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms. , more preferably represents a tert-butyl group. Q ⁹ preferably represents an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and still more preferably a methyl group. m ₃ preferably represents 1;

In general formula (12), Q ¹⁰ and Q ¹¹ each independently represent an alkyl group having 1 to 6 carbon atoms or a hydrogen atom. ^Q12 represents a halogen atom or a hydrogen atom.

In general formula (12), Q ¹⁰ and Q ¹¹ preferably each independently represent an alkyl group having 1 to 6 carbon atoms, more preferably a tert-butyl group. Q ¹² preferably represents a halogen atom, more preferably a chlorine atom.

The electron transport agent is preferably at least one (eg, one) of the compounds represented by the chemical formulas (10-ET2), (11-ET1), and (12-ET5). However, when the hole transport agent is the hole transport agent (4-HT1), the electron transport agent is the compound represented by the chemical formula (11-ET1). That is, when the hole transport agent is the hole transport agent (4-HT1), the electron transport agents are not the compounds represented by the chemical formulas (10-ET2) and (12-ET5). Hereinafter, the compounds represented by the chemical formulas (10-ET2), (11-ET1), and (12-ET5) were prepared as electron transport agents (10-ET2), (11-ET1), and (12-ET5), respectively. ) may be described.

The electron transport agent (10-ET2) is a preferred example of the electron transport agent (10). Electron transport agent (11-ET1) is a preferred example of electron transport agent (11). Electron transport agent (12-ET5) is a suitable example of electron transport agent (12).

Even when the exposure intensity is low, an image with excellent dot reproducibility can be formed and the occurrence of transfer blurring can be suppressed. It is preferable to contain an electron transport agent (10) as a transport agent. For the same reason, the photosensitive layer more preferably contains a hole transporting agent (1-HT6) as a hole transporting agent and an electron transporting agent (10-ET2) as an electron transporting agent.

The photosensitive layer preferably contains the electron transport agent (11) as an electron transport agent because an image with excellent dot reproducibility can be formed even when the exposure intensity is low, and the occurrence of transfer faintness can be suppressed. , more preferably contains an electron transport agent (11-ET1).

The content of the electron transport agent is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, relative to 100 parts by mass of the binder resin. Also, the content of the electron transport agent is preferably 150 parts by mass or less, more preferably 40 parts by mass or less.

The photosensitive layer may contain only one compound selected from the electron transport agents (10) to (12) as the electron transport agent, or may contain two or more compounds. In addition, the photosensitive layer contains at least one compound among the electron transport agents (10) to (12) as an electron transport agent, and an electron transport agent other than the electron transport agents (10) to (12) (hereinafter , which may be described as other electron transport agents).

Other electron transport agents include, for example, quinone-based compounds, diimide-based compounds, hydrazone-based compounds, malononitrile-based compounds, thiopyran-based compounds, trinitrothioxanthone-based compounds, and 3,4,5,7-tetranitro-9-fluorenone-based compounds. compounds, dinitroanthracene-based compounds, dinitroacridine-based compounds, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroacridine, succinic anhydride, maleic anhydride, and dibromomaleic anhydride. Examples of quinone compounds include diphenoquinone compounds, azoquinone compounds, anthraquinone compounds, naphthoquinone compounds, nitroanthraquinone compounds, and dinitroanthraquinone compounds.

(binder resin)
Examples of binder resins include thermoplastic resins (more specifically, polycarbonate resins, polyarylate resins, styrene resins, styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, Styrene-acrylic acid copolymer, acrylic copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer, vinyl chloride-vinyl acetate copolymer, polyester resin , alkyd resins, polyamide resins, polyurethane resins, polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, and polyether resins), thermosetting resins (more specifically, silicone resins, epoxy resins, phenolic resins, urea resins, melamine resins, and other crosslinkable thermosetting resins), and photocurable resins (more specifically, epoxy-acrylic acid-based resins and urethane-acrylic acid-based copolymers). .

Polycarbonate resin is preferable as the binder resin because it is possible to form an image with excellent dot reproducibility even when the exposure intensity is low and the occurrence of transfer blur can be suppressed, and the repeating unit represented by the chemical formula (Z) is More preferred is a polycarbonate resin having Hereinafter, a polycarbonate resin having a repeating unit represented by the chemical formula (Z) may be referred to as a polycarbonate resin (Z).

The viscosity-average molecular weight of the binder resin is preferably 20,000 or more. When the viscosity-average molecular weight of the binder resin is 20,000 or more, the photosensitive layer becomes difficult to wear. Also, the viscosity average molecular weight of the binder resin is preferably 80,000 or less, more preferably 60,000 or less, and even more preferably 40,000 or less. When the viscosity-average molecular weight of the binder resin is 80,000 or less, the binder resin is easily dissolved in the solvent, and the formation of the photosensitive layer is facilitated.

(Charge generating agent)
Examples of charge generating agents include phthalocyanine pigments, perylene pigments, bisazo pigments, trisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaline pigments, indigo pigments, azulenium pigments, cyanine pigments, Pigments, powders of inorganic photoconductive materials (e.g. selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, or amorphous silicon), pyrylium pigments, anthanthrone-based pigments, triphenylmethane-based pigments, threne-based pigments, toluidine-based pigments , pyrazoline-based pigments, and quinacridone-based pigments. The photosensitive layer may contain only one charge-generating agent, or may contain two or more charge-generating agents.

Examples of phthalocyanine pigments include metal-free phthalocyanine, titanyl phthalocyanine, and chloroindium phthalocyanine. Titanyl phthalocyanine is represented by the chemical formula (CGM-1). A metal-free phthalocyanine is represented by the chemical formula (CGM-2).

Titanyl phthalocyanine may have a crystalline structure. Examples of titanyl phthalocyanine crystals include α-type, β-type and Y-type crystals of titanyl phthalocyanine (hereinafter sometimes referred to as α-type, β-type and Y-type titanyl phthalocyanine).

As the charge generating agent, titanyl phthalocyanine is preferred, and Y-type titanyl phthalocyanine is more preferred. Y-type titanyl phthalocyanine has a main peak at, for example, a Bragg angle (2θ±0.2°) of 27.2° in its CuKα characteristic X-ray diffraction spectrum. The main peak in the CuKα characteristic X-ray diffraction spectrum is the peak having the first or second highest intensity in the range where the Bragg angle (2θ±0.2°) is 3° or more and 40° or less.

An example of the method for measuring the CuKα characteristic X-ray diffraction spectrum will be described. A sample (titanyl phthalocyanine) is filled in a sample holder of an X-ray diffraction device (for example, "RINT (registered trademark) 1100" manufactured by Rigaku Co., Ltd.), and an X-ray tube Cu, tube voltage 40 kV, tube current 30 mA, and CuKα An X-ray diffraction spectrum is measured under the condition of a characteristic X-ray wavelength of 1.542 Å. The measurement range (2θ) is, for example, 3° or more and 40° or less (start angle: 3°, stop angle: 40°), and the scanning speed is, for example, 10°/min.

Y-type titanyl phthalocyanines are classified into, for example, the following three types (I) to (III) according to their thermal properties in differential scanning calorimetry (DSC) spectra.
(I) A Y-type titanyl phthalocyanine having a differential scanning calorimetry spectrum having peaks in the range of 50° C. or higher and 270° C. or lower in addition to peaks associated with vaporization of adsorbed water.
(II) A Y-type titanyl phthalocyanine having no peaks in the range of 50° C. to 400° C. other than peaks associated with vaporization of adsorbed water in differential scanning calorimetry spectra.
(III) Y-type titanyl phthalocyanine having no peak in the range of 50° C. or higher and 270° C. or lower in the differential scanning calorimetry spectrum other than the peak associated with vaporization of adsorbed water, and having a peak in the range of higher than 270° C. and 400° C. or lower .

The Y-type titanyl phthalocyanine has no peak in the range of 50° C. or higher and 270° C. or lower other than the peak associated with vaporization of adsorbed water in the differential scanning calorimetry spectrum, and has a peak in the range of 270° C. or higher and 400° C. or lower. is more preferred. As the Y-type titanyl phthalocyanine having such a DSC peak, one having one peak in the range of more than 270°C and not more than 400°C is preferable, and one having one peak at 296°C is more preferable.

An example of a method for measuring a differential scanning calorimetry spectrum will be described. A sample (titanyl phthalocyanine) is placed on a sample pan, and a differential scanning calorimetry spectrum is measured using a differential scanning calorimeter (eg, "TAS-200 model DSC8230D" manufactured by Rigaku Corporation). The measurement range is, for example, 40° C. or higher and 400° C. or lower. The heating rate is, for example, 20° C./min.

The content of the charge generating agent is preferably 0.1 parts by mass or more and 50 parts by mass or less, more preferably 0.5 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the binder resin.

(Additive)
The photosensitive layer may contain additives as required. Examples of additives include radical scavengers, singlet quenchers, softeners, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, donors, surfactants, plasticizers, and sensitizers. , electron acceptor compounds, dispersants, and leveling agents. In addition, the photosensitive layer may not contain an antioxidant. Also, the photosensitive layer may not contain a dispersant.

(combination of materials)
Even when the exposure intensity is low, an image with excellent dot reproducibility can be formed and the occurrence of transfer faintness can be suppressed. Each of C1 to C20 is preferred. For the same reason, the combination of the hole transport agent and the electron transport agent is the combination No. 1 shown in Table 1. Each of C1 to C20, and the binder resin is preferably a polycarbonate resin (Z). For the same reason, the combination of the hole transport agent and the electron transport agent is the combination No. 1 shown in Table 1. It is preferably each of C1 to C20 and the charge generating agent is Y-type titanyl phthalocyanine. For the same reason, the combination of the hole transport agent and the electron transport agent is the combination No. 1 shown in Table 1. Each of C1 to C20, the binder resin is polycarbonate resin (Z), and the charge generating agent is preferably Y-type titanyl phthalocyanine.

In Table 1, "No." indicates "Combination No.", "HTM" indicates "hole transport agent", and "ETM" indicates "electron transport agent". The numbers shown in the "HTM" and "ETM" columns are general formula numbers or chemical formula numbers.

(Conductive substrate)
The conductive substrate is not particularly limited as long as it can be used as the conductive substrate of the photoreceptor. At least the surface portion of the conductive substrate may be made of a conductive material. An example of the conductive substrate is a conductive substrate made of a conductive material. Another example of a conductive substrate is a conductive substrate coated with a material having electrical conductivity. Conductive materials include, for example, aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass. These conductive materials may be used alone, or two or more of them may be used in combination (for example, as an alloy). Among these electrically conductive materials, aluminum and aluminum alloys are preferred because of good charge transfer from the photosensitive layer to the conductive substrate.

The shape of the conductive substrate is appropriately selected according to the structure of the image forming apparatus. Examples of the shape of the conductive substrate include a sheet shape and a drum shape. Moreover, the thickness of the conductive substrate is appropriately selected according to the shape of the conductive substrate.

(middle layer)
The intermediate layer (undercoat layer) contains, for example, inorganic particles and a resin used for the intermediate layer (intermediate layer resin). The presence of the intermediate layer makes it possible to maintain an insulating state to the extent that leakage can be suppressed, and to smooth the flow of current generated when the photosensitive member is exposed to light, thereby suppressing an increase in resistance.

Examples of inorganic particles include particles of metals (e.g., aluminum, iron, and copper), particles of metal oxides (e.g., titanium oxide, alumina, zirconium oxide, tin oxide, and zinc oxide), and non-metal oxides. (eg, silica) particles. One of these inorganic particles may be used alone, or two or more thereof may be used in combination.

Examples of the resin for the intermediate layer are the same as the examples of the binder resin described above. In order to form the intermediate layer and the photosensitive layer satisfactorily, the resin for the intermediate layer is preferably different from the binder resin contained in the photosensitive layer. The intermediate layer may contain additives. Examples of additives contained in the intermediate layer are the same as examples of additives contained in the photosensitive layer.

(Manufacturing method of photoreceptor)
Next, an example of a method for manufacturing a photoreceptor will be described. A photoreceptor manufacturing method includes a photosensitive layer forming step. In the photosensitive layer forming step, a coating liquid for forming a photosensitive layer (hereinafter sometimes referred to as a photosensitive layer coating liquid) is prepared. A coating solution for a photosensitive layer is applied onto a conductive substrate. Next, at least part of the solvent contained in the coated photosensitive layer coating liquid is removed to form a photosensitive layer. The photosensitive layer coating liquid contains, for example, a charge generating agent, a hole transporting agent, an electron transporting agent, a binder resin, and a solvent. The photosensitive layer coating liquid is prepared by dissolving or dispersing a charge generating agent, a hole transporting agent, an electron transporting agent and a binder resin in a solvent.

The solvent contained in the coating liquid for photosensitive layer is not particularly limited as long as it can dissolve or disperse each component contained in the coating liquid for photosensitive layer. Examples of solvents include alcohols (more specifically, methanol, ethanol, isopropanol, butanol, etc.), aliphatic hydrocarbons (more specifically, n-hexane, octane, cyclohexane, etc.), aromatic hydrocarbons, etc. Hydrogen (more specifically, benzene, toluene, xylene, etc.), halogenated hydrocarbons (more specifically, dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, etc.), ethers (more specifically, dimethyl ether , diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether), ketones (more specifically, acetone, methyl ethyl ketone, cyclohexanone, etc.), esters (more specifically, ethyl acetate, methyl acetate, etc.), Dimethylformaldehyde, dimethylformamide, and dimethylsulfoxide. These solvents may be used singly or in combination of two or more.

The coating liquid for the photosensitive layer is prepared by mixing each component and dispersing it in a solvent. For mixing or dispersing, for example, a bead mill, roll mill, ball mill, attritor, paint shaker, or ultrasonic disperser can be used.

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

Methods for removing at least part of the solvent contained in the photosensitive layer coating solution include, for example, heating, reduced pressure, or combined use of heating and reduced pressure. More specifically, a method of heat-treating (hot-air drying) using a high-temperature dryer or a reduced-pressure dryer is exemplified. The heat treatment temperature is, for example, 40° C. or higher and 150° C. or lower. The heat treatment time is, for example, 3 minutes or more and 120 minutes or less.

Incidentally, the method for manufacturing a photoreceptor may further include a step of forming an intermediate layer, if necessary. A known method can be appropriately selected for the step of forming the intermediate layer.

<Image forming apparatus>
Next, an image forming apparatus including the photoreceptor 1 of the first embodiment will be described. A tandem color image forming apparatus will be described below as an example with reference to FIG. FIG. 5 is a cross-sectional view showing an example of an image forming apparatus.

The image forming apparatus 110 shown in FIG. 5 includes image forming units 40a, 40b, 40c, and 40d, a transfer belt 50, and a fixing device 52. Hereinafter, each of the image forming units 40a, 40b, 40c, and 40d will be referred to as the image forming unit 40 when there is no need to distinguish between them.

The image forming unit 40 includes an image carrier 100 , a charging device 42 , an exposure device 44 , a developing device 46 , a transfer device 48 and a cleaning device 54 . The image carrier 100 is the photoreceptor 1 of the first embodiment.

As already described, according to the photoreceptor 1 of the first embodiment, even when the exposure intensity is low, an image with excellent dot reproducibility can be formed, and the occurrence of transfer faintness can be suppressed. Therefore, the image forming apparatus 110 can form a good image on the recording medium P by including the photoreceptor 1 as the image carrier 100 .

An image carrier 100 is provided at a central position of the image forming unit 40 . The image carrier 100 is rotatable in the arrow direction (counterclockwise). Around the image carrier 100, there are a charging device 42, an exposure device 44, a developing device 46, a transfer device 48, and a cleaning device 54 in the order described from the upstream side in the rotational direction of the image carrier 100. be provided.

Each of the image forming units 40a to 40d sequentially superimposes toner images of a plurality of colors (for example, four colors of black, cyan, magenta, and yellow) on the recording medium P on the transfer belt 50. FIG.

The charging device 42 positively charges the surface (for example, the peripheral surface) of the image carrier 100 . The charging device 42 is, for example, a scorotron charger.

The exposure device 44 exposes the charged surface of the image carrier 100 . Thereby, an electrostatic latent image is formed on the surface of the image carrier 100 . The electrostatic latent image is formed based on image data input to image forming apparatus 110 . A light source 441 of the exposure device 44 includes a light emitting diode. As already mentioned, the exposure intensity of the exposure device 44 having the light source 441 including the light-emitting diode tends to be lower than that of the laser scanning exposure device. The photoreceptor 1 of the first embodiment can be exposed not only when the photoreceptor 1 is irradiated with high-intensity exposure light, but also when the photoreceptor 1 is irradiated with low-intensity exposure light. The surface potential of the region is favorably lowered. Therefore, the image forming apparatus 110 having such a photoreceptor 1 can form an image with excellent dot reproducibility even when the exposure device 44 has a light source 441 including a light emitting diode. The intensity of the light (exposure light) with which the exposure device 44 irradiates the surface of the image carrier 100 is, for example, 0.1 μJ/cm ² or more and 1.0 μJ/cm ² or less.

The developing device 46 supplies toner to the surface of the image carrier 100 and develops the electrostatic latent image into a toner image. The developing device 46 is, for example, a developing roller. When the developer is a one-component developer, the developing device 46 supplies toner, which is a one-component developer, to the electrostatic latent image formed on the image carrier 100 . When the developer is a two-component developer, the developing device 46 supplies the electrostatic latent image formed on the image carrier 100 with the toner, which is contained in the two-component developer, and the carrier. Thus, the image carrier 100 carries a toner image.

The transfer belt 50 conveys the recording medium P between the image carrier 100 and the transfer device 48 . The transfer belt 50 is an endless belt. The transfer belt 50 is rotatable in the arrow direction (clockwise).

The transfer device 48 transfers the toner image developed by the developing device 46 from the surface of the image carrier 100 to the recording medium P which is a transfer target. Specifically, the transfer device 48 transfers the toner image from the surface of the image carrier 100 to the recording medium P while the surface of the image carrier 100 and the recording medium P are in contact with each other. That is, the image forming apparatus 110 employs a direct transfer method. The transfer device 48 is, for example, a transfer roller.

The cleaning device 54 collects toner adhering to the surface of the image carrier 100 .

The recording medium P onto which the toner image has been transferred by the transfer device 48 is conveyed to the fixing device 52 by the transfer belt 50 . The fixing device 52 is, for example, a heating roller and/or a pressure roller. The unfixed toner image transferred by the transfer device 48 is heated and/or pressed by the fixing device 52 . The toner image is fixed on the recording medium P by heating and/or pressing the toner image. As a result, an image is formed on the recording medium P. FIG.

An example of the image forming apparatus has been described above, but the image forming apparatus is not limited to the image forming apparatus 110 described above. Although the image forming apparatus 110 is a color image forming apparatus, the image forming apparatus may be a monochrome image forming apparatus. In this case, the image forming apparatus may have, for example, only one image forming unit. Further, although the image forming apparatus 110 employs a tandem system, the image forming apparatus may employ, for example, a rotary system. Although the scorotron charger has been described as an example of the charging device 42, the charging device may be a charging device other than the scorotron charger (for example, a charging roller, a charging brush, or a corotron charger). Although the exposure device 44 including the light source 441 including the light emitting diode has been described as an example, the exposure device may be another exposure device (for example, a laser scanning type exposure device). Although the image forming apparatus 110 employs a contact developing method, the image forming apparatus may employ a non-contact developing method. Although the image forming apparatus 110 employs a direct transfer method, the image forming apparatus may employ an intermediate transfer method. When the image forming apparatus employs an intermediate transfer method, the transfer target corresponds to an intermediate transfer belt. Although the image forming unit 40 does not include a static eliminating device, the image forming unit may further comprise a static eliminating device.

<Process cartridge>
Next, with continued reference to FIG. 5, an example of a process cartridge including the photoreceptor 1 of the first embodiment will be described. A process cartridge corresponds to each of the image forming units 40a to 40d. A process cartridge includes an image carrier 100 . The image carrier 100 is the photoreceptor 1 of the first embodiment. As already described, according to the photoreceptor 1 of the first embodiment, even when the exposure intensity is low, an image with excellent dot reproducibility can be formed, and the occurrence of transfer faintness can be suppressed. Therefore, by providing the photoreceptor 1 as the image carrier 100, the process cartridge can form a good image on the recording medium P. FIG.

The process cartridge may further include at least one of the charging device 42 , the exposure device 44 , the developing device 46 , the transfer device 48 and the cleaning device 54 in addition to the image carrier 100 . The process cartridge may further include a static eliminator (not shown). The process cartridge is designed to be detachable from the image forming apparatus 110 . Therefore, the process cartridge is easy to handle, and when the sensitivity characteristics of the image carrier 100 deteriorate, the process cartridge including the image carrier 100 can be easily and quickly replaced. The process cartridge including the photoreceptor 1 of the first embodiment has been described above with reference to FIG.

<Photoreceptor of Second Embodiment>
Next, the photoreceptor of the second embodiment will be described. The photoreceptor of the second embodiment includes a conductive substrate and a photosensitive layer. The photosensitive layer is a single layer. The photosensitive layer contains a charge generating agent, a hole transporting agent, an electron transporting agent and a binder resin. The hole transport agent is at least one compound selected from hole transport agents (1) to (4). The electron transport agent is at least one compound selected from electron transport agents (10) to (12). However, when the hole transport agent is hole transport agent (4), the electron transport agent is electron transport agent (11). The thickness of the photosensitive layer is 27 μm or less. The predetermined potential of the photoreceptor of the second embodiment is not particularly limited. The photoreceptor of the second embodiment is the same as the photoreceptor of the first embodiment except that the predetermined potential is not limited. The photoreceptor of the second embodiment can form an image with excellent dot reproducibility even when the exposure intensity is low, and can suppress the occurrence of transfer faintness. Another example of the process cartridge is a process cartridge including the photoreceptor of the second embodiment instead of the photoreceptor of the first embodiment. Another example of the image forming apparatus is an image forming apparatus including the photoreceptor of the second embodiment instead of the photoreceptor of the first embodiment.

EXAMPLES Hereinafter, the present invention will be described more specifically using examples. However, the present invention is in no way limited to the scope of the examples.

First, as materials for forming the photosensitive layer of the photoreceptor, the following charge-generating agent, electron-transporting agent, hole-transporting agent, and binder resin were prepared.

(Charge generating agent)
Y-type titanyl phthalocyanine described in the first embodiment was prepared as a charge generating agent. This Y-type titanyl phthalocyanine had a maximum peak at a Bragg angle (2θ±0.2°) of 27.2° and no peak at 26.2° in the CuKα characteristic X-ray diffraction spectrum. In the differential scanning calorimetry spectrum, this Y-type titanyl phthalocyanine has no peaks in the range of 50° C. or higher and 270° C. or lower other than the peak associated with vaporization of adsorbed water, and one peak in the range of 270° C. or higher and 400° C. or lower. (Specifically, one peak at 296°C).

(Electron transport agent)
As electron transport agents, the electron transport agents (10-ET2), (11-ET1), and (12-ET5) described in the first embodiment were prepared. Further, as electron transport agents used in Comparative Examples, compounds represented by the following chemical formulas (ETa) and (ETb) (hereinafter sometimes referred to as electron transport agents (ETa) and (ETb), respectively) were prepared. bottom.

(Hole transport agent)
As hole transport agents, the hole transport agents (1-HT6), (2-HT4), (3-HT3), and (4-HT1) described in the first embodiment were prepared. In addition, a compound represented by the following chemical formula (HTa) (hereinafter sometimes referred to as a hole transport agent (HTa)) was prepared as a hole transport agent used in Comparative Examples.

(binder resin)
As a binder resin, the polycarbonate resin (Z) described in the first embodiment was prepared. The viscosity average molecular weight of the polycarbonate resin (Z) was 30,000.

<Production of Photoreceptor>
Photoreceptors (A-1) to (A-6) and (B-1) to (B-5) were produced using the charge generating agent, electron transport agent, hole transport agent, and binder resin.

(Production of photoreceptor (A-1))
3.5 parts by mass of Y-type titanyl phthalocyanine as a charge generating agent, 60.0 parts by mass of a hole transport agent (4-HT1), 30.0 parts by mass of an electron transport agent (11-ET1), polycarbonate resin as a binder resin 100.0 parts by mass of (Z) and 800.0 parts by mass of tetrahydrofuran as a solvent were mixed for 20 hours using a ball mill to obtain a coating liquid for a photosensitive layer. A coating liquid for a photosensitive layer was applied onto a conductive substrate (a drum-shaped support made of aluminum) by a dip coating method. The coated photosensitive layer coating solution was dried with hot air at 100° C. for 60 minutes. Thus, a photosensitive layer (thickness: 27 μm) was formed on the conductive substrate to obtain a photosensitive member (A-1). In the photoreceptor (A-1), a single layer of photoreceptor layer was provided directly on the conductive substrate.

(Production of photoreceptors (A-2) to (A-6) and (B-3) to (B-5))
Photoreceptors (A-2) to (A-6) and (A-2) to (A-6) and ( Each of B-3) to (B-5) was produced.

(Production of photoreceptors (B-1) to (B-2))
Manufacture of photoreceptor (A-1) except that the types of hole transport agent and electron transport agent shown in Table 2 were used, and the film thickness of the photosensitive layer was changed from 27 μm to 30 μm by the method shown below. Photoreceptors (B-1) to (B-2) were each produced in the same manner as above. The film thickness of the photosensitive layer was increased (specifically, changed from 27 μm to 30 μm) by increasing the coating speed (lifting speed of the conductive substrate) when applying the coating liquid for the photosensitive layer by dip coating.

<Measurement>
The following measurements were performed for each of the photoreceptors (A-1) to (A-6) and (B-1) to (B-5), which are measurement objects.

(Measurement of film thickness of photosensitive layer)
The film thickness of the photosensitive layer was measured by an eddy current film thickness meter (“LH-373” manufactured by Ketto Kagaku Kenkyusho Co., Ltd.). Table 2 shows the measured film thickness of the photosensitive layer.

(Measurement of prescribed potential)
The predetermined potential (unit: +V) of the photoreceptor was measured according to the measuring method described in the above (Predetermined potential) of <Electrophotographic photoreceptor of the first embodiment>. Table 2 shows the measured predetermined potentials.

<Evaluation>
The following evaluations were performed for each of the photoreceptors (A-1) to (A-6) and (B-1) to (B-5) to be evaluated. The evaluation machine used for each evaluation was a modified monochrome printer ("FS-1300D" manufactured by Kyocera Document Solutions Co., Ltd.). The modification points of the remodeled machine were to remove the cleaning blade and to change the light source of the exposure device to a light emitting diode.

(Evaluation of dot reproducibility)
The evaluation environment for dot reproducibility was an environment with a temperature of 23° C. and a relative humidity of 60% RH. The intensity of the exposure light emitted from the exposure device of the evaluation machine was 0.35 μJ/cm ² . Using the evaluation machine, image I (a dot image with a print rate of 20%) was printed on one sheet of paper (“High Quality PPC Paper” manufactured by Fuji Xerox Co., Ltd., A4 size). The printed image I was observed with the naked eye, and the dot reproducibility of the photoreceptor was evaluated according to the following criteria. Table 2 shows the evaluation results of dot reproducibility.
[Evaluation Criteria for Dot Reproducibility]
Evaluation A: In the printed image I, a print area of 50% or more of the dot area of the input image I is ensured.
Evaluation B: In the printed image I, only less than 50% of the dot area of the input image I is secured.

(Evaluation of Post-transfer Potential and Evaluation of Suppression of Occurrence of Blurred Transfer)
The evaluation environment for the post-transfer potential and the suppression of the occurrence of transfer faintness was an environment with a temperature of 32° C. and a relative humidity of 80% RH. The charging device of the evaluation machine was set so that the charging potential of the photoreceptor was +750V. The transfer current of the transfer device of the evaluation machine was set to -18 μA. Using the evaluation machine, an image II (entirely solid image) was printed on one sheet of paper (Fuji Xerox Co., Ltd., "high-quality PPC paper", A4 size). The printed image II was observed with the naked eye to confirm the presence or absence of faint transfer. Then, based on the following criteria, it was evaluated whether or not the occurrence of transfer faintness in the formed image was suppressed. Table 2 shows the results of the evaluation of suppression of occurrence of transfer faintness.
[Evaluation Criteria for Suppression of Scratches in Transfer]
Evaluation A: No transfer faintness is observed in the formed image.
Evaluation B: Transfer faintness is observed in the formed image.

During the printing of Image II, the surface potential of the photoreceptor was measured after the image was transferred by the transfer device of the evaluation machine and before the charge was removed by the charge removing device. The measured surface potential was taken as the post-transfer potential (unit: V). Table 2 shows the measured post-transfer potentials.

The meanings of the terms in Table 2 are as follows. "HTM" indicates hole transport agent. "ETM" indicates an electron transport agent. "Thickness" indicates the thickness of the photosensitive layer. "Dot Reproducibility" indicates the evaluation of dot reproducibility. “Transfer faint” indicates evaluation of suppression of occurrence of transfer faint.

As shown in Table 2, the photosensitive layers of photoreceptors (A-1) to (A-6) contain hole transport agents (1) to (4) (more specifically, hole transport agents ( 1-HT6), (2-HT4), (3-HT3), and (4-HT1)). The photosensitive layers of photoreceptors (A-1) to (A-6) contain electron transport agents (10) to (12) (more specifically, electron transport agents (10-ET2), (11-ET1 ), and (12-ET5)). When the photosensitive layers of the photoreceptors (A-1) to (A-6) contain the hole transport agent (4) (more specifically, the hole transport agent (4-HT1)), the electron transport agent is It was electron transport agent (11) (more specifically, electron transport agent (11-ET1)). The thickness of the photosensitive layer of each of the photoreceptors (A-1) to (A-6) was 27 μm or less. The predetermined potential of each of the photosensitive members (A-1) to (A-6) was 0 V or more and +450 V or less.

As shown in Table 2, the evaluation result of the dot reproducibility of the photoreceptors (A-1) to (A-6) was A, and images excellent in dot reproducibility were formed by using these photoreceptors. did it. Further, the post-transfer potentials of the photosensitive members (A-1) to (A-6) were positive values. For this reason, the evaluation result of suppression of the occurrence of transfer blurring of the photoreceptors (A-1) to (A-6) is A, and the use of these photoreceptors reduces the transfer blurring caused by the decrease in the post-transfer potential. I was able to suppress the occurrence. In addition, since the thickness of the photosensitive layer of each of the photoreceptors (A-1) to (A-6) is 27 μm or less, the amount of material used for forming the photoreceptor can be reduced, and these photoreceptors can be manufactured at low cost. could be reduced.

From the above, it was shown that the photoreceptor according to the present invention can form an image with excellent dot reproducibility even when the exposure intensity is low, and can suppress the occurrence of transfer blurring. Since such a photoreceptor is provided, the process cartridge and the image forming apparatus according to the present invention can form good images.

A photoreceptor and a process cartridge according to the present invention can be used in an image forming apparatus. The image forming apparatus according to the present invention can be used to form an image on a recording medium.

1: photoreceptor (electrophotographic photoreceptor)
1a : Surface 2 : Conductive substrate 3 : Photosensitive layer 4 : Intermediate layer 5 : Protective layer 42 : Charging device 44 : Exposure device 46 : Developing device 48 : Transfer device 100 : Image carrier 110 : Image forming device 441 : Light source L2 : Predetermined light P : Recording medium (transfer target)

Claims (5)

An electrophotographic photoreceptor comprising a conductive substrate and a photosensitive layer,
The photosensitive layer is a single layer,
The photosensitive layer contains a charge generating agent, a hole transport agent, an electron transport agent and a binder resin,
The hole transport agent is at least one compound selected from compounds represented by chemical formulas (1-HT6), (2-HT4), (3-HT3), and (4-HT1),
The electron transport agent is a compound represented by the chemical formula (11-ET1),
The thickness of the photosensitive layer is 27 μm or less,
The predetermined potential is 0 V or more and +450 V or less, and the predetermined potential is the electrophotographic photosensitive member when 0.1 seconds have elapsed since the surface of the electrophotographic photosensitive member charged to +750 V was irradiated with predetermined light. and the intensity of the predetermined light is 0.1 μJ/cm ² .

2. The electrophotographic photoreceptor according to claim 1 , wherein said binder resin is a polycarbonate resin having a repeating unit represented by chemical formula (Z).

A process cartridge comprising the electrophotographic photoreceptor according to claim 1 . an image carrier;
a charging device that positively charges the surface of the image carrier;
an exposure device that exposes the charged surface of the image carrier to form an electrostatic latent image on the surface of the image carrier;
a developing device that develops the electrostatic latent image as a toner image;
a transfer device for transferring the toner image from the image carrier to a transfer target;
An image forming apparatus, wherein the image carrier is the electrophotographic photosensitive member according to claim 1 or 2 . 5. The image forming apparatus according to claim 4 , wherein the light source of said exposure device includes a light emitting diode.

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