Image forming apparatus

Abstract

To provide an image forming apparatus that prevents fogging.SOLUTION: An image forming apparatus comprises: an electrophotographic photoreceptor that has a conductive substrate, an undercoat layer provided on the conductive substrate, including a binder resin and an electron transport material, and satisfying the formula 1-1: 0.20≤EF1-ELUMO1≤0.60 (in the above formula 1-1, EF1 represents the Fermi level of the undercoat layer, and ELUMO1 represents the energy level of the LUMO of the undercoat layer), and a photosensitive layer provided on the undercoat layer; a charging device that electrostatically charges a surface of the electrophotographic photoreceptor; an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with developer including toner to form a toner image; and a transfer device that transfers the toner image to a surface of a recording medium. The time of movement of an outer peripheral surface of the electrophotographic photoreceptor required from the charging performed by the charging device to the development performed by the developing device is 90 msec or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses a negatively charged organic laminated electrophotographic photoreceptor, characterized in that in the laminated photoreceptor in which an undercoat layer, a charge generating layer, and a charge transport layer are laminated in this order on a conductive support, the work function of the conductive support is Wsub, the work function of the undercoat layer is WUCL, and the work function of the charge generating layer is WCGL, the relationship (WUCL-Wsub)>0.6 or (WCGL-WUCL)>0.6 is satisfied, and the film thickness of the undercoat layer is configured to be 2 μm or more and 20 μm or less.

[0003] Patent Document 2 describes an electrophotographic photoreceptor including a conductive substrate and a photosensitive layer provided on the conductive substrate, the photosensitive layer including a charge transport layer and a charge generation layer sequentially laminated on the conductive substrate, the charge transport layer including a first hole transport material and a resin binder, the charge generation layer including a charge generation material, a second hole transport material, an electron transport material and a resin binder, the charge generation material being metal-free phthalocyanine or titanyl phthalocyanine, the electron transport material being a charge-generating material having a charge transport layer and a charge generation layer, the charge generation ... The present invention discloses an electrophotographic photoreceptor comprising a electron transport material, wherein a difference between a LUMO energy of the first electron transport material and a LUMO energy of the charge generating material is in a range of 1.0 to 1.5 eV, a difference between a LUMO energy of the second electron transport material and a LUMO energy of the charge generating material is in a range of 0.6 to 0.9 eV, and a ratio of the content of the second electron transport material to the contents of the first electron transport material and the second electron transport material is in a range of 3 to 40 mass %.

[0004] Patent Document 3 describes a conductive support, metal oxide particles, and an electron-accepting compound having an anthraquinone structure, and has a volume resistivity of 3.5×10 measured by an AC impedance method. 8 Ωm or more 1.0×10 9The present invention discloses an electrophotographic photoreceptor which has, in this order, an undercoat layer having a resistivity in the range of Ωm or less, and a photosensitive layer, and in which the difference (|EfP|-|EfU|) between the Fermi energy (EfP) of the layer of the photosensitive layer closest to the undercoat layer and the Fermi energy (EfU) of the undercoat layer is 0.55 eV or more and 0.75 eV or less. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 05-088393 [Patent Document 2] Patent No. 7004011 [Patent Document 3] JP2014-066755A Summary of the Invention [Problem to be solved by the invention]

[0006] When an image is formed on cardboard using a conventional image forming apparatus, the cardboard has a tendency to require a long time for image fixing due to its slow thermal conductivity. This tends to slow down the rotation speed of the electrophotographic photoreceptor, and the time required from charging to development tends to be long. As a result, the charge retention force decreases, and a phenomenon in which toner adheres to non-image areas of the recording medium (hereinafter referred to as "fogging") may occur. Therefore, in this embodiment, an image forming apparatus is provided with an electrophotographic photoreceptor having a conductive substrate, an undercoat layer containing a binder resin and an electron transport material, and a photosensitive layer, and the moving speed of the outer peripheral surface of the electrophotographic photoreceptor required from charging by the charging device to development by the developing device is 90 msec or more, in which the undercoat layer does not satisfy the following formula 1-1 (i.e., E F1 -E LUMO1 The object of the present invention is to provide an image forming apparatus which suppresses fogging as compared with a case where the value of is less than 0.20 or exceeds 0.60. Formula 1-1: 0.20≦E F1 -E LUMO1 ≦0.60 (In the above formula 1-1, E F1represents the Fermi level of the underlayer, and E LUMO1 represents the LUMO energy level of the undercoat layer.) [Means for solving the problem]

[0007] Specific means for solving the above problems include the following aspects.

[0008] <1> an electrophotographic photoreceptor comprising: a conductive substrate; an undercoat layer provided on the conductive substrate, the undercoat layer containing a binder resin and an electron transport material and satisfying the following formula 1-1; and a photosensitive layer provided on the undercoat layer; a charging device for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and a transfer device for transferring the toner image onto a surface of a recording medium; wherein the time required for the outer peripheral surface of the electrophotographic photosensitive member to move from charging by the charging device to development by the developing device is 90 msec or more. Formula 1-1: 0.20≦E F1 -E LUMO1 ≦0.60 (In the above formula 1-1, E F1 represents the Fermi level of the undercoat layer, E LUMO1 represents the LUMO energy level of the undercoat layer. <2> The undercoat layer further satisfies the following formula 1-2: <1> 2. The image forming apparatus according to claim 1 . Equation 1-2: 0.40≦E F1 -E LUMO1 ≦0.58 (In the above formula 1-2, E LUMO1 represents the LUMO energy level of the undercoat layer, E F1 represents the Fermi level of the undercoat layer. <3> The undercoat layer has a Fermi level E F1 is 4.2 eV or more and 5.0 eV or less, <1> 2. The image forming apparatus according to claim 1 . <4> The undercoat layer has an energy level E LUMO1 is 3.5 eV or more and 4.2 eV or less, <3> 2. The image forming apparatus according to claim 1 . <5> the photosensitive layer is a laminated type photosensitive layer including a charge generating layer provided on the undercoat layer and a charge transport layer provided on the charge generating layer, The charge generating layer satisfies the following formula 2-1: <1> 2. The image forming apparatus according to claim 1 . Equation 2-1: 0.90≦E F2 -E LUMO2 ≦1.40 (In the above formula 2-1, E F2 represents the Fermi level of the charge generating layer, E LUMO2 represents the LUMO energy level of the charge generating layer. <6> The electron transport material has an average primary particle size of 80 nm or more and 400 nm or less. <1> 2. The image forming apparatus according to claim 1 . <7> The electron transport material has an aspect ratio of 1.0 or more and 4.2 or less. <1> 2. The image forming apparatus according to claim 1 . <8> The electron transport material is at least one selected from the group consisting of compounds represented by the following general formulas (1) to (8): <1> 2. The image forming apparatus according to claim 1 . [ka] (In the above general formula (1), R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 and R 18 R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. 11 and R 12 , R 12 and R 13 and R 13 and R 14may each independently be linked to each other to form a ring. 15 and R 16 , R 16 and R 17 and R 17 and R 18 may each independently be linked to each other to form a ring. In general formula (2), R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 and R 28 R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. 21 and R 22 , R 22 and R 23 and R 23 and R 24 may each independently be linked to each other to form a ring. 25 and R 26 , R 26 and R 27 and R 27 and R 28 may each independently be linked to each other to form a ring. In general formula (3), R 31 , R 32 , R 33 , R 34 , R 35 and R 36 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (4), R 41 , R 42 , R 43 , R 44 , R 45 , R 46 , R 47 , R 48 , R 49 and R 50each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (5), R 51 , R 52 , R 53 , R 54 , R 55 , R 56 , R 57 and R 58 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (6), R 61 , R 62 , R 63 and R 64 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (7), R 71 , R 72 , R 73 , R 74 , R 75 , R 76 , R 77 and R 78 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom, and Z represents an oxygen atom or a dicyanomethylene group (=C(CN)2). In general formula (8), R 81 , R 82 , R 83 , R 84 , R 85 , R 86 , R 87 and R 88 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom, and Z represents an oxygen atom or a dicyanomethylene group (=C(CN)2). <9> The electron transport material is at least one of the compounds represented by the general formulas (1) and (2). <8> 2. The image forming apparatus according to claim 1 . <10> The content of the electron transport material is 60% by mass or more and 80% by mass or less based on the total amount of the binder resin component of the undercoat layer and the electron transport material. <1> 2. The image forming apparatus according to claim 1 . Effect of the Invention

[0009] <1> , <8> or <9> According to the invention, in an image forming apparatus having an electrophotographic photoreceptor having a conductive substrate, an undercoat layer containing a binder resin and an electron transport material, and a photosensitive layer, and in which the moving speed of the outer peripheral surface of the electrophotographic photoreceptor required from charging by a charging device to development by a developing device is 90 msec or more, the undercoat layer does not satisfy the above formula 1-1 (i.e., E F1 -E LUMO1 In comparison with the case where the value is less than 0.20 or more than 0.60, an image forming apparatus is provided which suppresses fogging. <2> According to the present invention, the E F1 -E LUMO1 As a result, an image forming apparatus is provided which suppresses fogging, as compared with the case where the fogging rate is less than 0.40 or exceeds 0.58. <3> According to the present invention, the Fermi level E F1 As a result, an image forming apparatus is provided in which fogging is suppressed compared to when the photosensitivity is less than 4.2 eV or exceeds 5.0 eV. <4> According to the present invention, the LUMO energy level E LUMO1 As a result, an image forming apparatus is provided in which fogging is suppressed compared to when the photosensitivity is less than 3.5 eV or exceeds 4.2 eV. <5> According to the present invention, the photosensitive layer is a laminated type photosensitive layer including a charge generating layer provided on the undercoat layer and a charge transport layer provided on the charge generating layer, and E F2 -E LUMO2 As a result, an image forming apparatus is provided which suppresses fogging as compared with the case where the fogging rate is less than 0.90 or exceeds 1.40. <6> According to the present invention, there is provided an image forming apparatus which suppresses fogging as compared with the case where the average primary particle diameter of the electron transport material is less than 80 nm or exceeds 400 nm. <7> According to the present invention, there is provided an image-forming apparatus in which fogging is suppressed compared to when the aspect ratio of the electron transport material is less than 1.0 or exceeds 4.2. <10> According to the invention, there is provided an image forming apparatus which suppresses fogging, compared to when the content of the electron transport material is less than 60 mass % or more than 80 mass % with respect to the total of all binder resin components in the undercoat layer and the electron transport material. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic partial cross-sectional view showing an example of a layer structure of the electrophotographic photoreceptor according to the present embodiment. [Diagram 2] 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an embodiment of the present invention. [Diagram 3] FIG. 4 is a schematic configuration diagram illustrating another example of an image forming apparatus according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described. These descriptions and examples are merely illustrative of the embodiments, and are not intended to limit the scope of the embodiments.

[0012] In the present disclosure, a numerical range indicated using "~" indicates a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively.

[0013] In the numerical ranges described in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in the present disclosure. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples.

[0014] In the present disclosure, the term "step" includes not only an independent step, but also a step that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved.

[0015] In the present disclosure, each component may contain multiple types of corresponding substances. When referring to the amount of each component in a composition in the present disclosure, if multiple substances corresponding to each component are present in the composition, the total amount of the multiple substances present in the composition is meant unless otherwise specified.

[0016] In the present disclosure, the term "main component" refers to a major component, for example, a component that accounts for 30% by mass or more of the total mass of a mixture of multiple components.

[0017] In this disclosure, the electrophotographic photoreceptor is also simply referred to as a photoreceptor.

[0018] <Electrophotographic photoreceptor> The image forming apparatus according to the present embodiment is an image forming apparatus including an electrophotographic photoreceptor having a conductive substrate, an undercoat layer provided on the conductive substrate, which contains a binder resin and an electron transport material and satisfies the following formula 1-1, and a photosensitive layer provided on the undercoat layer, a charging device that charges the surface of the electrophotographic photoreceptor, an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the electrophotographic photoreceptor, a developing device that develops the electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image, and a transfer device that transfers the toner image to a surface of a recording medium, and the movement time of the outer circumferential surface of the electrophotographic photoreceptor required from charging by the charging device to development by the developing device is 90 msec or more. Formula 1-1: 0.20≦E F1 -E LUMO1 ≦0.60 (In the above formula 1-1, E F1 represents the Fermi level of the underlayer, and E LUMO1 represents the LUMO energy level of the undercoat layer.)

[0019] Fig. 1 shows a schematic example of a layer structure of an electrophotographic photoreceptor included in an image forming apparatus according to the present embodiment. Photoreceptor 7A shown in Fig. 1 has a structure in which an undercoat layer 1, a charge generation layer 2, and a charge transport layer 3 are laminated in this order on a conductive substrate 4. The charge generation layer 2 and the charge transport layer 3 constitute a photosensitive layer 5. Photoreceptor 7A may have a layer structure in which a protective layer is further provided on the charge transport layer 3.

[0020] In the photoreceptor according to this embodiment, the photosensitive layer may be a functionally separated type photosensitive layer in which a charge generation layer 2 and a charge transport layer 3 are separated, as in the photoreceptor 7A shown in FIG. 1, or may be a single-layer type photosensitive layer having a charge generation function and a charge transport function, instead of the charge generation layer 2 and the charge transport layer 3.

[0021] In recent years, the demand for electrophotographic printing has increased not only on plain paper but also on thick paper such as postcards and paper used as advertising media. When forming an image on thick paper using an electrophotographic photoreceptor, heat tends to be transferred more slowly than on plain paper. Therefore, fixing tends to require more time. As a result, in the case of a conventional electrophotographic photoreceptor, the rotation speed of the electrophotographic photoreceptor needs to be set slower as the fixing time increases. On the other hand, when the rotation speed of the electrophotographic photoreceptor is slowed (specifically, the movement time of the outer peripheral surface of the electrophotographic photoreceptor required from charging by the charging device to development by the developing device is 90 msec or more), the time required from charging to development becomes longer, and the charge retention force is likely to decrease. As a result, in the case of a conventional electrophotographic photoreceptor, when the rotation speed is slow, image defects such as fogging may occur.

[0022] On the other hand, in the electrophotographic photoreceptor provided in the image forming apparatus according to the present embodiment, the undercoat layer satisfies the formula 1-1: 0.20≦E F1 -E LUMO1 ≦0.60 (in formula 1-1, E F1 represents the Fermi level of the underlayer, and E LUMO1 represents the LUMO energy level of the undercoat layer. F1 -E LUMO1is appropriately small. Therefore, the accumulation of an energy barrier at the interface between the undercoat layer and the charge generating layer is easily suppressed. As a result, it is considered that image fogging can be suppressed even when the rotation speed of the electrophotographic photoreceptor is slow.

[0023] In the image forming apparatus according to the present embodiment, the moving time of the outer peripheral surface of the electrophotographic photosensitive member required from charging by the charging device to development by the developing device is 90 msec or more, and may be 95 msec or more and 300 msec or less, or 95 msec or more and 250 msec or less. F1 -E LUMO1 is appropriately suppressed, and the accumulation of an energy barrier at the interface between the undercoat layer and the charge generating layer is suppressed, thereby suppressing image fog.

[0024] The above-mentioned "from charging by the charging device to development by the developing device" refers to the period from the start of charging by the charging device to the formation of a toner image in the developing device when the image forming apparatus has the configuration shown in ★Figure 2.

[0025] The undercoat layer satisfies the following formula 1-1, preferably satisfies the following formula 1-2, and more preferably satisfies the following formula 1-3. F1 -E LUMO1 is appropriately small. Therefore, the accumulation of an energy barrier is easily suppressed at the interface between the undercoat layer and the charge generating layer. As a result, even when the rotation speed of the electrophotographic photoreceptor is slow, image fog is further suppressed. Formula 1-1: 0.20≦E F1 -E LUMO1 ≦0.60 Equation 1-2: 0.40≦E F1 -E LUMO1 ≦0.58 Equation 1-3: 0.45≦E F1 -E LUMO1 ≦0.58 In the above formulas 1-1, 1-2 and 1-3, E F1represents the Fermi level of the underlayer, and E LUMO1 represents the LUMO energy level of the undercoat layer.

[0026] The undercoat layer is at the Fermi level E F1 is preferably 4.20 eV or more and 5.00 eV or less, more preferably 4.20 eV or more and 4.70 eV or less, and further preferably 4.30 eV or more and 4.50 eV or less. F1 is within the above range, E F1 -E LUMO1 The gap can be kept reasonably small. ★↑The digits have been corrected to match the significant figures in the examples.

[0027] Fermi level E of the underlayer F1 is measured as follows: After cutting the electrophotographic photoreceptor into 2 cm squares, the charge generation layer and charge transport layer are removed using a solvent such as THF to leave only the conductive substrate and undercoat layer. Next, the outer peripheral surface of the undercoat layer is measured by the Kelvin probe method using a Fermi level measurement device (FAC-2) manufactured by Riken Keiki Co., Ltd.

[0028] The undercoat layer has a LUMO energy level E LUMO1 is preferably 3.50 eV or more and 4.20 eV or less, more preferably 3.60 eV or more and 4.10 eV or less, and even more preferably 3.70 eV or more and 4.00 eV or less. LUMO1 is within the above range, E F1 -E LUMO1 The gap can be kept reasonably small. ★↑The digits have been corrected to match the significant figures in the examples.

[0029] Energy level E of the LUMO of the undercoat layer LUMO1 is measured as follows: After cutting the electrophotographic photoreceptor into 2 cm squares, the charge generation layer and charge transport layer are removed using a solvent such as THF, leaving only the conductive substrate and undercoat layer. Next, this is measured using a photoelectron yield spectrometer (AC-2) manufactured by Riken Keiki Co., Ltd. in the range of 4.00 eV to 6.20 eV at a measurement light intensity of 500 nm, and the horizontal axis is the energy of the irradiated light, and the vertical axis is the electron coefficient rate. The intersection point between the baseline and the straight line drawn at the rising part of the plot is taken as HOMO1. Next, the single film of the undercoat layer peeled off from the substrate is measured by the transmission method in the wavelength range of 200 nm to 800 nm using an ultraviolet-visible near-infrared (UV-Vis-NIR) spectrophotometer (model number: Cary5000, manufactured by Agilent Technologies), and the absorption edge at wavelengths of 400 nm to 700 nm is calculated, and this is taken as the energy gap ΔE (=HOMO-LUMO). Since the energy gap ΔE is the value obtained by subtracting LUMO from HOMO (ΔE=HOMO−LUMO), the LUMO energy (LUMO1) is calculated by the following formula. Formula: LUMO1 = HOMO1 - ΔE

[0030] Above E F1 -E LUMO1 , E F1 and E LUMO1 The method for adjusting the above is not particularly limited, and examples thereof include a method for adjusting the dispersion state of the electron transport material in the undercoat layer (specifically, adjusting the compounding ratio of the binder resin and the electron transport material in the vicinity of the surface of the undercoat layer on the photosensitive layer side; adjusting the type, particle size, aspect ratio, etc. of the electron transport material; and adjusting the energy level by compounding a plurality of electron transport materials having different energy levels).

[0031] In the image forming apparatus according to the present embodiment, the photosensitive layer may be a laminated type photosensitive layer consisting of a charge generating layer provided on an undercoat layer and a charge transport layer provided on the charge generating layer, or may be a single-layer type photosensitive layer, but a laminated type photosensitive layer is preferred.

[0032] The charge generating layer preferably satisfies the following formula 2-1, more preferably satisfies the following formula 2-2, and further preferably satisfies the following formula 2-3. F2 -E LUMO2 is appropriately small. Therefore, the accumulation of an energy barrier is easily suppressed at the interface between the undercoat layer and the charge generating layer. As a result, even when the rotation speed of the electrophotographic photoreceptor is slow, image fog is further suppressed. Equation 2-1: 0.90≦E F2 -E LUMO2 ≦1.40 Equation 2-2: 1.00≦E F2 -E LUMO2 ≦1.35 Equation 2-3: 1.10≦E F2 -E LUMO2 ≦1.30 In the above formulas 2-1, 2-2 and 2-3, E F2 represents the Fermi level of the charge generating layer, E LUMO2 represents the LUMO energy level of the charge generating layer.

[0033] The charge generation layer is at the Fermi level E F2 is preferably 4.50 eV or more and 5.50 eV or less, more preferably 4.70 eV or more and 5.30 eV or less, and further preferably 4.90 eV or more and 5.20 eV or less. F2 is within the above range, E F2 -E LUMO2 The gap can be kept reasonably small. ★↑The digits have been corrected to match the significant figures in the examples.

[0034] The charge generating layer has a LUMO energy level E LUMO2 is preferably 3.50 eV or more and 4.50 eV or less, more preferably 3.60 eV or more and 4.30 eV or less, and even more preferably 3.80 eV or more and 4.10 eV or less. LUMO2 is within the above range, E F2 -E LUMO2 The gap can be kept reasonably small. ★↑The digits have been corrected to match the significant figures in the examples.

[0035] Fermi level E of the charge generation layer F2 is measured as follows: After cutting the electrophotographic photoreceptor into 2 cm squares, an incision is made in the charge transport layer (CT layer) and only the CT layer is peeled off with tweezers. After that, only the charge generation layer (CG layer) is dissolved in a solvent such as THF to prepare a CG solution. The resulting CG solution is applied to a 2 cm square Au-plated plate and the solvent is dried to prepare a measurement sample. The Fermi level of the outer surface of the undercoat layer of this measurement sample is measured by the Kelvin probe method using a Fermi level measurement device (FAC-2) manufactured by the Institute of Physical and Chemical Research.

[0036] Energy level E of the LUMO of the charge generating layer LUMO2 is measured as follows: After cutting the electrophotographic photoreceptor into 2 cm squares, only the charge transport layer (CT layer) is peeled off with tweezers. Next, the outer peripheral surface of the exposed charge generation layer is measured with a photoelectron yield spectrometer (AC-2) manufactured by Riken Keiki Co., Ltd. in the range of 4.00 eV to 6.20 eV at a measurement light intensity of 500 nm. When the energy of the irradiated light is plotted on the horizontal axis and the electron coefficient rate on the vertical axis, the intersection point between the baseline and the straight line drawn at the rising part of the plot is taken as HOMO2. Next, a CG solution in which only the charge generation layer (CG layer) is dissolved in a solvent such as THF is measured by the ultraviolet-visible-near infrared (UV-Vis-NIR) spectrophotometer (model number: Cary5000, manufactured by Agilent Technologies) using the transmission method up to the wavelength range of 200 nm to 800 nm, and the absorption edge at wavelengths of 400 nm to 700 nm is calculated and taken as the energy gap ΔE (= HOMO-LUMO). Since the energy gap ΔE is the value obtained by subtracting LUMO from HOMO (ΔE=HOMO−LUMO), the LUMO energy (LUMO2) is calculated by the following formula. Formula: LUMO2 = HOMO2 - ΔE

[0037] Above EF2 -E LUMO2 , E F2 and E LUMO2 The method for adjusting the charge generation layer is not particularly limited, but examples thereof include adjusting the type of charge generation material, adjusting the type of binder resin in the charge generation layer, and the like.

[0038] Hereinafter, each layer of the electrophotographic photoreceptor according to the present embodiment will be described in detail, with the reference numerals omitted.

[0039] (subbing layer) The undercoat layer contains a binder resin and an electron transport material, and satisfies the following formula 1-1. Formula 1-1: 0.20≦E F1 -E LUMO1 ≦0.60 In the above formula 1-1, E F1 represents the Fermi level of the underlayer, and E LUMO1 represents the LUMO energy level of the undercoat layer.

[0040] Examples of the binder resin include known polymer compounds such as acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea resins, phenolic resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, and epoxy resins; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; and silane coupling agents. Examples of the binder resin used in the undercoat layer include charge transporting resins having charge transporting groups, conductive resins (such as polyaniline, etc.), and the like.

[0041] Among these, the binder resin used in the undercoat layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and in particular, a resin obtained by reacting at least one resin selected from the group consisting of thermosetting resins such as urea resins, phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, unsaturated polyester resins, alkyd resins, and epoxy resins, with a curing agent is preferred. When two or more of these binder resins are used in combination, the mixing ratio is set as necessary.

[0042] Examples of the electron transport material include electron transporting compounds such as perinone compounds, naphthalenetetracarboxydiimide compounds, perylenetetracarboxydiimide compounds, quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone, tetracyanoquinodimethane compounds, fluorenone compounds such as 2,4,7-trinitrofluorenone, dinaphthoquinone compounds, diphenoquinone compounds, xanthone compounds, benzophenone compounds, cyanovinyl compounds, and ethylene compounds. The electron transport material may be used alone or in combination of two or more.

[0043] The average primary particle size of the electron transport material is preferably 80 nm or more and 400 nm or less, more preferably 150 nm or more and 340 nm or less, and even more preferably 180 nm or more and 280 nm or less. When the average primary particle diameter is 80 nm or more, the E F1 It is possible to prevent E from becoming too high. LUMO1 This prevents E from becoming too low. F1 -E LUMO1 When the average primary particle size is 400 nm or less, the E F1 is prevented from becoming too high, and E F1 -E LUMO1 can be easily adjusted to a suitable range.

[0044] The average primary particle size of the electron transport material is determined as follows. After cutting the electrophotographic photoreceptor into 2 cm squares, the charge generation layer and charge transport layer are removed using a solvent such as THF, leaving only the conductive substrate and undercoat layer. Then, using a field emission electron microscope, the surface of the undercoat layer is observed with a secondary electron detector, with the acceleration voltage optimized to transmit through the resin layer on the surface of the undercoat layer. With the field emission electron microscope at a magnification of 20,000 times, the long sides of 100 random particles of the electron transport material are measured, and the arithmetic average value is taken as the average particle diameter.

[0045] The aspect ratio of the electron transport material is preferably 1.0 or more and 4.2 or less, more preferably 1.0 or more and 3.7 or less, and even more preferably 1.0 or more and 3.2 or less. When the aspect ratio is 1.0 or more, the E F1 It is possible to prevent E from becoming too high. LUMO1 This prevents E from becoming too low. F1 -E LUMO1 When the aspect ratio is 4.2 or less, the E F1 is prevented from becoming too high, and E F1 -E LUMO1 can be easily adjusted to a suitable range.

[0046] The aspect ratio of an electron transport material refers to the ratio (long side / short side) of the length of the electron transport material in the longitudinal direction, which is perpendicular to the long side (hereinafter also referred to as the long side), to the length of the electron transport material in the short side direction (hereinafter also referred to as the short side). The aspect ratio of the electron transport material is calculated as follows. After cutting the electrophotographic photoreceptor into 2 cm squares, the charge generation layer and charge transport layer are removed using a solvent such as THF, leaving only the conductive substrate and undercoat layer. The surface is then observed using an electron microscope with an accelerating voltage optimized to transmit the resin layer on the surface. At a magnification of 20,000 times, the long and short sides of any 100 particles of the electron transport material are measured, and the aspect ratio (long side / short side) of each particle is calculated. The arithmetic average of the aspect ratios obtained is taken as the aspect ratio of the electron transport material.

[0047] The electron transport material preferably contains at least one electron transport material selected from the group consisting of compounds represented by the following general formulas (1), (2), (3), (4), (5), (6), (7), and (8), and more preferably contains at least one electron transport material selected from the group consisting of compounds represented by the following general formulas (1) and (2).

[0048] The electron transport material is represented by the following general formulas (1) to (8) (more preferably the compounds represented by general formulas (1) and (2)) in accordance with the above-mentioned E F1 -E LUMO1 It is easy to adjust the value to a suitable range, and fogging is more easily suppressed.

[0049] [ka]

[0050] In general formula (1), R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 and R 18R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. 11 and R 12 , R 12 and R 13 and R 13 and R 14 may each independently be linked to each other to form a ring. 15 and R 16 , R 16 and R 17 and R 17 and R 18 may each independently be linked to each other to form a ring. In general formula (2), R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 and R 28 R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. 21 and R 22 , R 22 and R 23 and R 23 and R 24 may each independently be linked to each other to form a ring. 25 and R 26 , R 26 and R 27 and R 27 and R 28 may each independently be linked to each other to form a ring. In general formula (3), R 31 , R 32 , R 33 , R 34 , R 35 and R 36each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (4), R 41 , R 42 , R 43 , R 44 , R 45 , R 46 , R 47 , R 48 , R 49 and R 50 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (5), R 51 , R 52 , R 53 , R 54 , R 55 , R 56 , R 57 and R 58 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (6), R 61 , R 62 , R 63 and R 64 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (7), R 71 , R 72 , R 73 , R 74 , R 75 , R 76 , R 77 and R 78 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an acyl group, an alkoxycarbonyl group, or a halogen atom, and Z represents an oxygen atom or a dicyanomethylene group (=C(CN)2). In general formula (8), R 81 , R 82 , R 83 , R 84 , R 85 , R 86, R 87 and R 88 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an acyl group, an alkoxycarbonyl group, or a halogen atom, and Z represents an oxygen atom or a dicyanomethylene group (=C(CN)2).

[0051] <Compounds represented by general formula (1) and general formula (2)> The compounds represented by general formula (1) and general formula (2) will be described below.

[0052] [ka]

[0053] In general formula (1), R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 and R 18 (Hereafter, simply "R 11 ~R 18 Each of R independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. 11 and R 12 , R 12 and R 13 and R 13 and R 14 may each independently be linked to each other to form a ring. 15 and R 16 , R 16 and R 17 and R 17 and R 18 may each independently be linked to each other to form a ring.

[0054] In general formula (2), R 21 , R 22 , R 23 , R24 , R 25 , R 26 , R 27 and R 28 (Hereafter, simply "R 21 ~R 28 Each of the groups independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxy ... R represents an aryl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. 21 and R 22 , R 22 and R 23 and R 23 and R 24 may each independently be linked to each other to form a ring. 25 and R 26 , R 26 and R 27 and R 27 and R 28 may each independently be linked to each other to form a ring.

[0055] In general formula (1), R 11 ~R 18 The alkyl group represented by the formula (I) may be a substituted or unsubstituted alkyl group.

[0056] In general formula (1), R 11 ~R 18 Examples of the unsubstituted alkyl group represented by the formula (I) include a linear alkyl group having 1 to 20 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms), a branched alkyl group having 3 to 20 carbon atoms (preferably 3 to 10 carbon atoms), and a cyclic alkyl group having 3 to 20 carbon atoms (preferably 3 to 10 carbon atoms).

[0057] Examples of the linear alkyl group having 1 to 20 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, a tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, and an n-icosyl group.

[0058] Examples of the branched alkyl group having 3 to 20 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, an isododecyl group, a sec-dodecyl group, a tert-dodecyl group, a tert-tetradecyl group, and a tert-pentadecyl group.

[0059] Examples of the cyclic alkyl group having 3 to 20 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, and polycyclic (e.g., bicyclic, tricyclic, spirocyclic) alkyl groups formed by linking these monocyclic alkyl groups.

[0060] Among the above, as the unsubstituted alkyl group, a straight-chain alkyl group such as a methyl group or an ethyl group is preferable.

[0061] Substituents in the alkyl group include an alkoxy group, a hydroxy group, a carboxy group, a nitro group, and a halogen atom (such as a fluorine atom, a bromine atom, or an iodine atom). The alkoxy group that replaces the hydrogen atom in the alkyl group is R 11 ~R 18 Examples of the alkoxy group include the same as the unsubstituted alkoxy group represented by the following formula:

[0062] In general formula (1), R 11 ~R 18 The alkoxy group represented by the following formula (I) includes a substituted or unsubstituted alkoxy group.

[0063] In general formula (1), R 11 ~R 18 Examples of the unsubstituted alkoxy group represented by the formula (I) include linear, branched or cyclic alkoxy groups having 1 to 10 carbon atoms (preferably 1 to 6, more preferably 1 to 4).

[0064] Specific examples of linear alkoxy groups include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, an n-octyloxy group, an n-nonyloxy group, and an n-decyloxy group. Specific examples of branched alkoxy groups include an isopropoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, an isopentyloxy group, a neopentyloxy group, a tert-pentyloxy group, an isohexyloxy group, a sec-hexyloxy group, a tert-hexyloxy group, an isoheptyloxy group, a sec-heptyloxy group, a tert-heptyloxy group, an isooctyloxy group, a sec-octyloxy group, a tert-octyloxy group, an isononyloxy group, a sec-nonyloxy group, a tert-nonyloxy group, an isodecyloxy group, a sec-decyloxy group, and a tert-decyloxy group. Specific examples of the cyclic alkoxy group include a cyclopropoxy group, a cyclobutoxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, a cyclooctyloxy group, a cyclononyloxy group, and a cyclodecyloxy group. Among these, the unsubstituted alkoxy group is preferably a linear alkoxy group.

[0065] Substituents in the alkoxy group include an aryl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a hydroxyl group, a carboxy group, a nitro group and a halogen atom (such as a fluorine atom, a bromine atom or an iodine atom). The aryl group that substitutes the hydrogen atom in the alkoxy group is, for example, R 11 ~R 18 Examples of the unsubstituted aryl group include the same groups as the unsubstituted aryl group represented by the following formula: The alkoxycarbonyl group that replaces the hydrogen atom in the alkoxy group is, for example, 11 ~R 18 Examples of the alkoxycarbonyl group include the unsubstituted alkoxycarbonyl group represented by the following formula: The aryloxycarbonyl group that replaces the hydrogen atom in the alkoxy group is, for example, 11 ~R 18 Examples of the aryloxycarbonyl group include the unsubstituted aryloxycarbonyl group represented by the following formula:

[0066] In general formula (1), R 11 ~R 18 The aralkyl group represented by the following formula (I) includes a substituted or unsubstituted aralkyl group.

[0067] In general formula (1), R 11 ~R 18 The unsubstituted aralkyl group represented by the following formula is preferably an aralkyl group having 7 to 30 carbon atoms, more preferably an aralkyl group having 7 to 16 carbon atoms, and even more preferably an aralkyl group having 7 to 12 carbon atoms.

[0068] Examples of the unsubstituted aralkyl group having 7 to 30 carbon atoms include a benzyl group, a phenylethyl group, a phenylpropyl group, a 4-phenylbutyl group, a phenylpentyl group, a phenylhexyl group, a phenylheptyl group, a phenyloctyl group, a phenylnonyl group, a naphthylmethyl group, a naphthylethyl group, an anthracylmethyl group, and a phenyl-cyclopentylmethyl group.

[0069] Substituents in the aralkyl group include an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a halogen atom (such as a fluorine atom, a bromine atom, an iodine atom, etc.). The alkoxy group that substitutes the hydrogen atom in the aralkyl group is, for example, R 11 ~R 18 Examples of the alkoxy group include the same as the unsubstituted alkoxy group represented by the following formula: The alkoxycarbonyl group that replaces the hydrogen atom in the aralkyl group is, for example, 11 ~R 18 Examples of the alkoxycarbonyl group include the unsubstituted alkoxycarbonyl group represented by the following formula: The aryloxycarbonyl group that replaces the hydrogen atom in the aralkyl group is, for example, 11 ~R 18 Examples of the aryloxycarbonyl group include the unsubstituted aryloxycarbonyl group represented by the following formula:

[0070] In general formula (1), R 11 ~R 18 The aryl group represented by the formula (I) may be a substituted or unsubstituted aryl group.

[0071] In general formula (1), R 11 ~R 18 The unsubstituted aryl group represented by the following formula is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 14 carbon atoms, and even more preferably an aryl group having 6 to 10 carbon atoms.

[0072] Examples of the aryl group having 6 to 30 carbon atoms include a phenyl group, a biphenyl group, a 1-naphthyl group, a 2-naphthyl group, a 9-anthryl group, a 9-phenanthryl group, a 1-pyrenyl group, a 5-naphthacenyl group, a 1-indenyl group, a 2-azulenyl group, a 9-fluorenyl group, a biphenylenyl group, an indacenyl group, a fluoranthenyl group, an acenaphthylenyl group, an aceanthryllenyl group, a phenalenyl group, and a fluorenyl group. Examples of the anthryl group include anthryl, bianthracenyl, teranthracenyl, quaternary anthracenyl, anthraquinolyl, phenanthryl, triphenylenyl, pyrenyl, chrysenyl, naphthacenyl, pleiadenyl, picenyl, perylenyl, pentaphenyl, pentacenyl, tetraphenylenyl, hexaphenyl, hexacenyl, rubicenyl, and coronenyl groups. Of the above, the phenyl group is preferred.

[0073] Substituents in the aryl group include an alkyl group, an alkoxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a halogen atom (such as a fluorine atom, a bromine atom, or an iodine atom). The alkyl group that substitutes the hydrogen atom in the aryl group is, for example, R 11 ~R 18 Examples of the unsubstituted alkyl group include the same groups as the unsubstituted alkyl group represented by the following formula: The alkoxy group that substitutes the hydrogen atom in the aryl group is, in general formula (1), R 11 ~R 18 Examples of the alkoxy group include the same as the unsubstituted alkoxy group represented by the following formula: The alkoxycarbonyl group that replaces the hydrogen atom in the aryl group is, for example, 11 ~R 18 Examples of the alkoxycarbonyl group include the unsubstituted alkoxycarbonyl group represented by the following formula: The aryloxycarbonyl group that replaces the hydrogen atom in the aryl group is, for example, 11 ~R 18 Examples of the aryloxycarbonyl group include the unsubstituted aryloxycarbonyl group represented by the following formula:

[0074] In general formula (1), R11 ~R 18 The aryloxy group represented by the following formula (-O-Ar, Ar represents an aryl group) includes a substituted or unsubstituted aryloxy group.

[0075] In general formula (1), R 11 ~R 18 The unsubstituted aryloxy group represented by the following formula is preferably an aryloxy group having 6 to 30 carbon atoms, more preferably an aryloxy group having 6 to 14 carbon atoms, and even more preferably an aryloxy group having 6 to 10 carbon atoms.

[0076] Examples of the aryloxy group having 6 to 30 carbon atoms include a phenyloxy group (phenoxy group), a biphenyloxy group, a 1-naphthyloxy group, a 2-naphthyloxy group, a 9-anthryloxy group, a 9-phenanthryloxy group, a 1-pyrenyloxy group, a 5-naphthacenyloxy group, a 1-indenyloxy group, a 2-azulenyloxy group, a 9-fluorenyloxy group, a biphenylenyloxy group, an indacenyloxy group, a fluoranthenyloxy group, an acenaphthylenyloxy group, an aceanthryllenyloxy group, a phenalenyloxy group, a fluorenyloxy group, an anthryloxy group, a bianthracenyloxy group, a teranthracenyloxy group, a quateranthracenyloxy group, an anthraquinolyloxy group, a phenanthryloxy group, and a phenyloxy group. Examples of the aryloxy group include an oxy group, a triphenylenyloxy group, a pyrenyloxy group, a chrysenyloxy group, a naphthacenyloxy group, a pleiadenyloxy group, a picenyloxy group, a perylenyloxy group, a pentaphenyloxy group, a pentacenyloxy group, a tetraphenylenyloxy group, a hexaphenyloxy group, a hexacenyloxy group, a rubicenyloxy group, and a coronenyloxy group. Among the above, a phenyloxy group (phenoxy group) is preferable.

[0077] Substituents in the aryloxy group include an alkyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, and a halogen atom (such as a fluorine atom, a bromine atom, an iodine atom, etc.). The alkyl group that substitutes the hydrogen atom in the aryloxy group is, for example,11 ~R 18 Examples of the unsubstituted alkyl group include the same groups as the unsubstituted alkyl group represented by the following formula: The alkoxycarbonyl group that replaces the hydrogen atom in the aryloxy group is, for example, 11 ~R 18 Examples of the alkoxycarbonyl group include the unsubstituted alkoxycarbonyl group represented by the following formula: The aryloxycarbonyl group that replaces the hydrogen atom in the aryloxy group is, for example, 11 ~R 18 Examples of the aryloxycarbonyl group include the unsubstituted aryloxycarbonyl group represented by the following formula:

[0078] In general formula (1), R 11 ~R 18 The alkoxycarbonyl group represented by the following formula (-CO-OR, where R represents an alkyl group) includes a substituted or unsubstituted alkoxycarbonyl group.

[0079] In general formula (1), R 11 ~R 18 The number of carbon atoms in the alkyl chain in the unsubstituted alkoxycarbonyl group represented by the following formula is preferably 1 or more and 20 or less, more preferably 1 or more and 15 or less, and even more preferably 1 or more and 10 or less.

[0080] Examples of the alkoxycarbonyl group having an alkyl chain carbon number of 1 to 20 include a methoxycarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, an isopropoxycarbonyl group, an n-butoxycarbonyl group, a sec-butoxybutylcarbonyl group, a tert-butoxycarbonyl group, a pentaoxycarbonyl group, a hexaoxycarbonyl group, a heptoxycarbonyl group, an octaoxycarbonyl group, a nonaoxycarbonyl group, a decaoxycarbonyl group, a dodecaoxycarbonyl group, a tridecaoxycarbonyl group, a tetradecaoxycarbonyl group, a pentadecaoxycarbonyl group, a hexadecaoxycarbonyl group, a heptadecaoxycarbonyl group, an octadecaoxycarbonyl group, a nonadecaoxycarbonyl group, and an icosaoxycarbonyl group.

[0081] Substituents in the alkoxycarbonyl group include an aryl group, a hydroxy group and a halogen atom (such as a fluorine atom, a bromine atom, an iodine atom, etc.). The aryl group that replaces the hydrogen atom in the alkoxycarbonyl group is, for example, R 11 ~R 18 Examples of the unsubstituted aryl group include the same groups as the unsubstituted aryl group represented by the following formula:

[0082] In general formula (1), R 11 ~R 18 The aryloxycarbonyl group represented by the following formula (-CO-OAr, Ar represents an aryl group) includes a substituted or unsubstituted aryloxycarbonyl group.

[0083] In general formula (1), R 11 ~R 18 The number of carbon atoms in the aryl group in the unsubstituted aryloxycarbonyl group represented by the following formula is preferably 6 or more and 30 or less, more preferably 6 or more and 14 or less, and further preferably 6 or more and 10 or less.

[0084] The aryloxycarbonyl group having an aryl group having 6 to 30 carbon atoms is phenyloxycarbonyl group, biphenyloxycarbonyl group, 1-naphthyloxycarbonyl group, 2-naphthyloxycarbonyl group, 9-anthryloxycarbonyl group, 9-phenanthryloxycarbonyl group, 1-pyrenyloxycarbonyl group, 5-naphthacenyloxycarbonyl group, 1-indenyloxycarbonyl group, 2-azulenyloxycarbonyl group, 9-fluorenyloxycarbonyl group, biphenylenyloxycarbonyl group, indacenyloxycarbonyl group, fluoranthenyloxycarbonyl group, acenaphthylenyloxycarbonyl group, aceanthryloxycarbonyl group, phenalenyloxycarbonyl group, fluorenyloxycarbonyl group, anthryloxycarbonyl group, bianthracenyloxycarbonyl group, Examples of the anthracenyloxycarbonyl group include anthracenyloxycarbonyl group, teranthracenyloxycarbonyl group, quaternanthracenyloxycarbonyl group, anthraquinolyloxycarbonyl group, phenanthryloxycarbonyl group, triphenylenyloxycarbonyl group, pyrenyloxycarbonyl group, chrysenyloxycarbonyl group, naphthacenyloxycarbonyl group, pleiadenyloxycarbonyl group, picenyloxycarbonyl group, perylenyloxycarbonyl group, pentaphenyloxycarbonyl group, pentacenyloxycarbonyl group, tetraphenylenyloxycarbonyl group, hexaphenyloxycarbonyl group, hexacenyloxycarbonyl group, rubicenyloxycarbonyl group, and coronenyloxycarbonyl group. Among the above, the phenoxycarbonyl group is preferred.

[0085] Substituents in the aryloxycarbonyl group include an alkyl group, a hydroxy group and a halogen atom (such as a fluorine atom, a bromine atom, an iodine atom, etc.). The alkyl group that substitutes the hydrogen atom of the aryloxycarbonyl group is, in general formula (1), R 11 ~R 18 Examples of the unsubstituted alkyl group include the same groups as the unsubstituted alkyl group represented by the following formula:

[0086] In general formula (1), R 11 ~R 18 An alkoxycarbonylalkyl group represented by (-(C n H 2n ) -CO-OR, R represents an alkyl group, and n represents an integer of 1 or more. and substituted or unsubstituted alkoxycarbonylalkyl groups.

[0087] In general formula (1), R 11 ~R 18 The alkoxycarbonyl group (-CO-OR) in the unsubstituted alkoxycarbonylalkyl group represented by the formula (1) is, for example, 11 ~R 18 Examples of the alkoxycarbonyl group include the same groups as the alkoxycarbonyl group represented by the following formula:

[0088] In general formula (1), R 11 ~R 18 The alkylene chain (-C n H 2n -) includes a linear alkylene chain having 1 to 20 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms), a branched alkylene chain having 3 to 20 carbon atoms (preferably 3 to 10 carbon atoms), and a cyclic alkylene chain having 3 to 20 carbon atoms (preferably 3 to 10 carbon atoms).

[0089] Examples of the linear alkylene chain having 1 to 20 carbon atoms include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, an n-pentylene group, an n-hexylene group, an n-heptylene group, an n-octylene group, an n-nonylene group, an n-decylene group, an n-undecylene group, an n-dodecylene group, a tridecylene group, an n-tetradecylene group, an n-pentadecylene group, an n-heptadecylene group, an n-octadecylene group, an n-nonadecylene group, and an n-icosylene group.

[0090] Examples of branched alkylene chains having 3 to 20 carbon atoms include isopropylene, isobutylene, sec-butylene, tert-butylene, isopentylene, neopentylene, tert-pentylene, isohexylene, sec-hexylene, tert-hexylene, isoheptylene, sec-heptylene, tert-heptylene, isooctylene, sec-octylene, tert-octylene, isononylene, s Examples of the alkyl group include an ec-nonylene group, a tert-nonylene group, an isodecylene group, a sec-decylene group, a tert-decylene group, an isododecylene group, a sec-dodecylene group, a tert-dodecylene group, a tert-tetradecylene group, and a tert-pentadecylene group.

[0091] Examples of the cyclic alkylene chain having 3 to 20 carbon atoms include a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, a cycloheptylene group, a cyclooctylene group, a cyclononylene group, and a cyclodecylene group.

[0092] Substituents in the alkoxycarbonylalkyl group include an aryl group, a hydroxy group and a halogen atom (such as a fluorine atom, a bromine atom, an iodine atom, etc.). The aryl group that substitutes the hydrogen atom of the alkoxycarbonylalkyl group is, in general formula (1), R 11 ~R 18 Examples of the unsubstituted aryl group include the same groups as the unsubstituted aryl group represented by the following formula:

[0093] In general formula (1), R 11 ~R 18 An aryloxycarbonylalkyl group represented by (-(C n H 2n ) -CO-OAr, Ar represents an aryl group, and n represents an integer of 1 or more. Examples of the aryloxycarbonyl group include a substituted or unsubstituted aryloxycarbonylalkyl group.

[0094] In general formula (1), R 11 ~R 18The aryloxycarbonyl group (-CO-OAr, Ar represents an aryl group) in the unsubstituted aryloxycarbonylalkyl group represented by the general formula (1) is 11 ~R 18 Examples of the aryloxycarbonyl group include the same groups as the aryloxycarbonyl group represented by the following formula:

[0095] In general formula (1), R 11 ~R 18 The alkylene chain (-C n H 2n -) is R in the general formula (1). 11 ~R 18 Examples of the alkoxycarbonylalkyl group include the alkylene chain of the alkoxycarbonylalkyl group represented by the following formula:

[0096] Substituents in the aryloxycarbonylalkyl group include an alkyl group, a hydroxy group and a halogen atom (such as a fluorine atom, a bromine atom or an iodine atom). The alkyl group that substitutes the hydrogen atom of the aryloxycarbonylalkyl group is, in the general formula (1), R 11 ~R 18 Examples of the unsubstituted alkyl group include the same groups as the unsubstituted alkyl group represented by the following formula:

[0097] In general formula (1), R 11 ~R 18 Examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0098] In general formula (1), R 11 and R 12 , R 12 and R 13 , R 13 and R 14 , R 15 and R 16 , R 16 and R 17 or R 17 and R 18However, examples of the ring structure formed by linking together include a benzene ring, a condensed ring having 10 to 18 carbon atoms (a naphthalene ring, anthracene ring, phenanthrene ring, chrysene ring (benzo[α]phenanthrene ring), tetracene ring, tetraphene ring (benzo[α]anthracene ring), triphenylene ring, etc.). Among the above, the ring structure formed is preferably a benzene ring.

[0099] In general formula (2), R 21 ~R 28 As the alkyl group represented by the formula (1), R 11 ~R 18 Examples of the alkyl group include the same groups as those represented by the following formula: In general formula (2), R 21 ~R 28 As the alkoxy group represented by the formula (1), R 11 ~R 18 Examples of the alkoxy group include the same groups as the alkoxy group represented by the following formula: In general formula (2), R 21 ~R 28 As the aralkyl group represented by the formula (1), R 11 ~R 18 Examples of the aralkyl group include the same groups as those represented by the following formula: In general formula (2), R 21 ~R 28 As the aryl group represented by the formula (1), R 11 ~R 18 The aryl group may be the same as the aryl group represented by the following formula: In general formula (2), R 21 ~R 28 As the aryloxy group represented by the formula (1), R 11 ~R 18 Examples of the aryloxy group include the same groups as the aryloxy group represented by the following formula: In general formula (2), R 21 ~R 28 As the alkoxycarbonyl group represented by the formula (1), R 11 ~R 18 Examples of the alkoxycarbonyl group include the same groups as the alkoxycarbonyl group represented by the following formula: In general formula (2), R 21 ~R28 As the aryloxycarbonyl group represented by the formula (1), R 11 ~R 18 Examples of the aryloxycarbonyl group include the same groups as the aryloxycarbonyl group represented by the following formula: In general formula (2), R 21 ~R 28 As the alkoxycarbonylalkyl group represented by the formula (1), R 11 ~R 18 Examples of the alkoxycarbonylalkyl group include the same groups as those represented by the following formula: In general formula (2), R 21 ~R 28 As the aryloxycarbonylalkyl group represented by the formula (1), R 11 ~R 18 The aryloxycarbonylalkyl group may be the same as that represented by the following formula: In general formula (2), R 21 ~R 28 As the halogen atom represented by the formula (1), R 11 ~R 18 Examples of the halogen atom include those represented by the following formula:

[0100] In general formula (2), R 21 and R 22 , R 22 and R 23 , R 23 and R 24 , R 25 and R 26 , R 26 and R 27 or R 27 and R 28 However, examples of the ring structure formed by linking together include a benzene ring, a condensed ring having 10 to 18 carbon atoms (a naphthalene ring, anthracene ring, phenanthrene ring, chrysene ring (benzo[α]phenanthrene ring), tetracene ring, tetraphene ring (benzo[α]anthracene ring), triphenylene ring, etc.). Among the above, the ring structure formed is preferably a benzene ring.

[0101] In general formula (1), R 11 , R 12 , R13 , R 14 , R 15 , R 16 , R 17 and R 18 are preferably each independently a hydrogen atom, an alkyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, or an aryloxycarbonylalkyl group.

[0102] In general formula (2), R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 and R 28 are preferably each independently a hydrogen atom, an alkyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, or an aryloxycarbonylalkyl group.

[0103] Specific examples of the compound represented by formula (1) or (2) are shown below, but the present embodiment is not limited thereto.

[0104] [ka]

[0105] [ka]

[0106] [ka]

[0107] [ka]

[0108] [ka]

[0109] [ka]

[0110] The compound represented by general formula (1) and the compound represented by general formula (2) are in an isomeric relationship (i.e., a cis-trans isomer relationship). In a general synthesis method, 2 moles of an orthophenylenediamine compound and 1 mole of a naphthalenetetracarboxylic acid compound are heated and condensed to obtain a mixture of cis and trans isomers, and the mixture ratio of the cis isomer is usually higher than that of the trans isomer. The cis and trans isomers can be separated, for example, by heating and washing with an alcohol solution of potassium hydroxide to separate the soluble cis isomer from the poorly soluble trans isomer.

[0111] <Compound represented by general formula (3)> The compound represented by formula (3) will be described below.

[0112] [ka]

[0113] In general formula (3), R 31 , R 32 , R 33 , R 34 , R 35 and R 36 (Hereafter, simply "R 31 ~R 36 ") each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom.

[0114] In general formula (3), R 31 ~R 36 The alkyl group, alkoxy group, aralkyl group, aryl group, alkoxycarbonyl group, and halogen atom represented by the formula (1) are 11 ~R 18Examples of the alkyl group, alkoxy group, aralkyl group, aryl group, alkoxycarbonyl group, and halogen atom represented by the following formula are mentioned.

[0115] In general formula (3), R 31 ~R 36 The alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by R 11 ~R 18 These groups may have the same substituents as those exemplified for the alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by the following formula:

[0116] Below, exemplary compounds of the compound represented by general formula (3) are shown, but the present embodiment is not limited thereto. The following exemplary compound numbers are hereinafter written as exemplary compound (3-number). Specifically, for example, exemplary compound 5 is hereinafter written as "exemplary compound (3-5)".

[0117] [ka]

[0118] The abbreviations and the like in the above exemplary compounds have the following meanings. Pr: n-propyl group c-C6H 11 : Cyclohexyl group C6H5: Phenyl group p-Cl-C6H4: parachlorophenyl group CH2C6H5: Benzyl group CH2CH2C6H5: Phenethyl group

[0119] <Compound represented by general formula (4)> The compound represented by formula (4) will be described below.

[0120] [ka]

[0121] In general formula (4), R 41 , R 42 , R 43 , R 44 , R 45 , R 46 , R 47 , R 48 , R 49 and R 50 (Hereafter, simply "R 41 ~R 50 ") each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom.

[0122] In general formula (4), R 41 ~R 50 The alkyl group, alkoxy group, aralkyl group, aryl group, alkoxycarbonyl group, and halogen atom represented by the formula (1) are 11 ~R 18 Examples of the alkyl group, alkoxy group, aralkyl group, aryl group, alkoxycarbonyl group, and halogen atom represented by the following formula are mentioned.

[0123] In general formula (4), R 41 ~R 50 The alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by R 11 ~R 18 These groups may have the same substituents as those exemplified for the alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by the following formula:

[0124] Below, exemplary compounds of the compound represented by general formula (4) are shown, but the present embodiment is not limited thereto. The following exemplary compound numbers are hereinafter written as exemplary compound (4-number). Specifically, for example, exemplary compound 5 is hereinafter written as "exemplary compound (4-5)".

[0125] [ka]

[0126] The abbreviations and the like in the above exemplary compounds have the following meanings. ·Bu: n-butyl group c-C6H 11 : Cyclohexyl group p-CH3-C6H4: para-tolyl group C6H5: Phenyl group p-Cl-C6H4: parachlorophenyl group o-Cl-C6H4: ortho-chlorophenyl group CH2C6H5: Benzyl group 3,5-(CH3)2-C6H3: 3,5-dimethylphenyl group 3,5-Cl2-C6H3: 3,5-dichlorophenyl group

[0127] <Compound represented by general formula (5)> The compound represented by formula (5) will be described below.

[0128] [ka]

[0129] In general formula (5), R 51 , R 52 , R 53 , R 54 , R 55 , R 56 , R 57 and R 58 (Hereinafter referred to as “R 51 ~R 58 ") each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom.

[0130] In general formula (5), R 51 ~R 58 The alkyl group, alkoxy group, aralkyl group, aryl group, alkoxycarbonyl group, and halogen atom represented by the formula (1) are 11 ~R 18Examples of the alkyl group, alkoxy group, aralkyl group, aryl group, alkoxycarbonyl group, and halogen atom represented by the following formula are mentioned.

[0131] In general formula (5), R 51 ~R 58 The alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by R 11 ~R 18 These groups may have the same substituents as those exemplified for the alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by the following formula:

[0132] In general formula (5), R 51 ~R 58 may each independently be represented by a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group.

[0133] In general formula (5), R 51 and R 58 are each independently preferably an alkyl group having 3 to 12 carbon atoms, an alkoxy group having 3 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group, from the viewpoint of further suppressing the residual potential, and more preferably a branched alkyl group having 3 to 12 carbon atoms, a branched alkoxy group having 3 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group. A branched alkyl group having 3 to 8 carbon atoms or a branched alkoxy group having 3 to 8 carbon atoms is more preferable, and a t-butyl group is particularly preferable.

[0134] In general formula (5), R 52 and R 57are each independently, from the viewpoint of further suppressing the residual potential, preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a linear alkoxy group having 1 to 4 carbon atoms, even more preferably a linear alkyl group having 1 to 3 carbon atoms or a linear alkoxy group having 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0135] In general formula (5), R 53 , R 54 , R 55 and R 56 preferably represents a hydrogen atom. In general formula (5), R 51 and R 58 are preferably the same group from the viewpoint of further suppressing the residual potential. In general formula (5), R 52 and R 57 are preferably the same group from the viewpoint of further suppressing the residual potential. In general formula (5), R 51 and R 52 are preferably different groups from the viewpoint of further suppressing the residual potential. In general formula (5), R 57 and R 58 are preferably different groups from the viewpoint of further suppressing the residual potential.

[0136] Below, exemplary compounds of the compound represented by general formula (5) are shown, but the present embodiment is not limited thereto. The following exemplary compound numbers are hereinafter written as exemplary compound (5-number). Specifically, for example, exemplary compound 5 is hereinafter written as "exemplary compound (5-5)".

[0137] [ka]

[0138] The abbreviations and the like in the above exemplary compounds have the following meanings. t-C4H9: t-butyl group OCH3: Methoxy group t-C4H9O: t-butoxy group c-C6H 11 : Cyclohexyl group C6H5: Phenyl group CH2C6H5: Benzyl group

[0139] <Compound represented by general formula (6)> The compound represented by formula (6) will be described below.

[0140] [ka] In general formula (6), R 61 , R 62 , R 63 and R 64 (Hereafter, simply "R 61 ~R 64 ") each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom.

[0141] In general formula (6), R 61 ~R 64 The alkyl group, alkoxy group, aralkyl group, aryl group, alkoxycarbonyl group, and halogen atom represented by the formula (1) are 11 ~R 18 Examples of the alkyl group include an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, and a halogen atom represented by the following formula:

[0142] In general formula (6), R 61 ~R 64 The alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by R 11 ~R 18These groups may have the same substituents as those exemplified for the alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by the following formula:

[0143] In general formula (6), R 61 ~R 64 may each independently be represented by a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group.

[0144] In general formula (6), R 61 and R 64 are each independently, from the viewpoint of further suppressing the residual potential, preferably an alkyl group having 3 to 12 carbon atoms, an alkoxy group having 3 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group, more preferably a branched alkyl group having 3 to 12 carbon atoms, a branched alkoxy group having 3 to 12 carbon atoms, a cycloalkyl group, an aryl group, or an aralkyl group, further preferably a branched alkyl group having 3 to 8 carbon atoms or a branched alkoxy group having 3 to 8 carbon atoms, and particularly preferably a t-butyl group.

[0145] In general formula (6), R 62 and R 64 are each independently, from the viewpoint of further suppressing the residual potential, preferably a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, more preferably a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms, or a linear alkoxy group having 1 to 4 carbon atoms, even more preferably a linear alkyl group having 1 to 3 carbon atoms or a linear alkoxy group having 1 to 3 carbon atoms, and particularly preferably a methyl group.

[0146] In general formula (6), R 61 and R 64 are preferably the same group. In general formula (6), R 62 and R 63 are preferably the same group. In general formula (6), R 61and R 62 are preferably different groups. In general formula (6), R 63 and R 64 are preferably different groups.

[0147] Exemplary compounds represented by general formula (6) are shown below, but the present embodiment is not limited thereto. It should be noted that the following exemplary compound numbers are hereinafter referred to as exemplary compound (6-number). Specifically, for example, exemplary compound 5 is hereinafter referred to as "exemplified compound (6-5)".

[0148] [ka]

[0149] The abbreviations and the like in the above exemplary compounds have the following meanings. t-C4H9: t-butyl group OCH3: Methoxy group t-C4H9O: t-butoxy group c-C6H 11 : Cyclohexyl group C6H5: Phenyl group CH2C6H5: Benzyl group

[0150] <Compound represented by general formula (7)> The compound represented by formula (7) will be described below.

[0151] [ka]

[0152] In general formula (7), R 71 , R 72 , R 73 , R 74 , R 75 , R 76 , R 77 and R 78 (Hereinafter referred to as “R 71 ~R 78") each independently represent a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an acyl group, an alkoxycarbonyl group, or a halogen atom, and Z represents an oxygen atom or a dicyanomethylene group (=C(CN)2).

[0153] In general formula (7), R 71 ~R 78 Examples of the alkyl group represented by the formula (I) include linear or branched alkyl groups having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms), and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and the like. In general formula (7), R 71 ~R 78 Examples of the alkoxy group represented by the formula (I) include alkoxy groups having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms), and specific examples include a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

[0154] In general formula (7), R 71 ~R 78 The aralkyl group represented by the formula (I) includes a group represented by the formula -L-Ar, where L represents an alkylene group and Ar represents an aryl group. The alkylene group represented by L includes linear or branched alkylene groups having 1 to 12 carbon atoms, such as a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, an n-pentylene group, an isopentylene group, a neopentylene group, and a tert-pentylene group. Examples of the aryl group represented by Ar include a phenyl group, a methylphenyl group, a dimethylphenyl group, and an ethylphenyl group. In general formula (7), R 71 ~R 78 Specific examples of the aralkyl group represented by the formula (I) include a benzyl group, a methylbenzyl group, a dimethylbenzyl group, a phenylethyl group, a methylphenylethyl group, a phenylpropyl group, and a phenylbutyl group.

[0155] In general formula (7), R 71 ~R 78 Examples of the aryl group represented by the formula (I) include a phenyl group, a methylphenyl group, a dimethylphenyl group, an ethylphenyl group, etc. Among these, a phenyl group is preferred.

[0156] In general formula (7), R 71 ~R 78 The acyl group (-C(=O)-R AC , R AC represents a hydrocarbon group.) includes, for example, an acyl group having 1 to 10 carbon atoms (preferably 1 to 6, more preferably 1 to 3), and specific examples thereof include an acetyl group, a propanoyl group, a benzoyl group, and a cyclohexanecarbonyl group.

[0157] In general formula (7), R 71 ~R 78 The alkoxycarbonyl group represented by the formula (1) is 11 ~R 18 Examples of the alkoxycarbonyl group include the same groups as the alkoxycarbonyl group represented by the following formula:

[0158] In general formula (7), R 71 ~R 78 The alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by R in general formula (1) are 11 ~R 18 These groups may have the same substituents as those exemplified for the alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by the following formula: In general formula (7), R 71 ~R 78 The acyl group represented by R in general formula (1) 11 ~R 18 The alkyl group may have the same substituents as those exemplified for the alkyl group represented by the following formula:

[0159] In general formula (7), R 71 ~R 78 Examples of the halogen atom represented by the formula (I) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0160] In general formula (7), R 78 From the viewpoint of further suppressing the residual potential, the group represented by the formula is an alkoxycarbonyl group (-C(=O)-OR 78A ) is preferred. 78A is an alkyl group having 8 or more carbon atoms (long chain alkyl group) or -L 181 -OR 182 Indicates L 181 represents an alkylene group, and R 182 indicates an alkyl group having 8 or more carbon atoms (long-chain alkyl group).

[0161] In general formula (7), R 78 -L 181 -OR 182 The group represented by L 181 represents an alkylene group, and R 182 indicates an alkyl group having 8 or more carbon atoms (long-chain alkyl group).

[0162] L 181 Examples of the alkylene group represented by the formula (I) include linear or branched alkylene groups having 1 to 12 carbon atoms, such as a methylene group, an ethylene group, an n-propylene group, an isopropylene group, an n-butylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, an n-pentylene group, an isopentylene group, a neopentylene group, and a tert-pentylene group.

[0163] R 182 The long-chain alkyl group represented by the formula (I) is not particularly limited as long as it has 8 or more carbon atoms. From the viewpoint of suppressing cracking of the layer, the carbon number is preferably from 8 to 12. Furthermore, the long-chain alkyl group may be linear or branched, and is preferably linear. Examples of the linear alkyl group having 8 to 12 carbon atoms include an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, and an n-dodecyl group. Examples of the branched alkyl group having 8 to 12 carbon atoms include an isooctyl group, a sec-octyl group, a tert-octyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an isodecyl group, a sec-decyl group, and a tert-decyl group.

[0164] The compound represented by formula (7) may have only one long-chain alkyl group in one molecule, or may have two or more long-chain alkyl groups in one molecule. From the viewpoint of suppressing cracking of the photosensitive layer, the number of long-chain alkyl groups in one molecule of the compound represented by formula (7) is preferably 1 to 3, more preferably 1 to 2.

[0165] In one embodiment, the compound represented by the general formula (7) is, from the viewpoint of further suppressing the residual potential, 71 ~R 77 each independently represents a hydrogen atom, a halogen atom, or an alkyl group; R 78 is preferably a linear alkyl group having 8 or less carbon atoms.

[0166] Exemplary compounds of the compound represented by general formula (7) are shown below, but are not limited thereto. The following exemplary compound numbers are hereinafter referred to as exemplary compound (7-number). Specifically, for example, exemplary compound 5 is hereinafter referred to as "exemplary compound (7-5)".

[0167] [ka]

[0168] The abbreviations and the like in the above exemplary compounds have the following meanings. =C(CN)2: dicyanomethylene group

[0169] <Compound represented by general formula (8)> The compound represented by formula (8) will be described below.

[0170] [ka]

[0171] In general formula (8), R 81 , R 82 , R 83 , R 84 , R 85 , R 86 , R 87 and R 88 (Hereafter, simply "R 81 ~R 88 ") are each independently a hydrogen atom, an alkyl group, Z represents an oxygen atom or a dicyanomethylene group (=C(CN)2).

[0172] In general formula (8), R 81 ~R 88 The alkyl group, alkoxy group, aralkyl group, aryl group, acyl group, alkoxycarbonyl group, and halogen atom represented by the formula (7) are R 71 ~R 78 Examples of the alkyl group include an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an acyl group, an alkoxycarbonyl group, and a halogen atom represented by the following formula:

[0173] In general formula (8), R 81 ~R 88 The alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by R 11 ~R 18 These groups may have the same substituents as those exemplified for the alkyl group, alkoxy group, aralkyl group, aryl group and alkoxycarbonyl group represented by the following formula: In general formula (8), R 81 ~R 88 The acyl group represented by R in general formula (1) 11 ~R 18 The alkyl group may have the same substituents as those exemplified for the alkyl group represented by the following formula:

[0174] Exemplary compounds of the compound represented by general formula (8) are shown below, but are not limited thereto. The following exemplary compound numbers are hereinafter referred to as exemplary compound (8-number). Specifically, for example, exemplary compound 5 is hereinafter referred to as "exemplary compound (8-5)".

[0175] [ka]

[0176] The abbreviations and the like in the above exemplary compounds have the following meanings. C(=O)CH3: Acetyl group OCH3: Methoxy group CN: Cyano group CH2C6H5: Benzyl group =C(CN)2: dicyanomethylene group

[0177] The content of the electron transport material is preferably 60% by mass or more and 80% by mass or less, more preferably 65% ​​by mass or more and 75% by mass or less, and even more preferably 68% by mass or more and 72% by mass or less, based on the total of the entire binder resin component and the electron transport material in the undercoat layer. When the content of the electron transport material is 60% by mass or more, the electron transport property of the undercoat layer is easily ensured, and the E F1 -E LUMO1 When the content of the electron transport material is 80% by mass or less, the electron transport material is easily dispersed with high uniformity in the undercoat layer, and E F1 -E LUMO1 can be easily adjusted to a suitable range.

[0178] The undercoat layer may further contain inorganic particles. As inorganic particles, for example, powder resistivity (volume resistivity) of 10 2 Ωcm or more 10 11 Examples of such particles include inorganic particles with a particle size of Ωcm or less. Among these, examples of inorganic particles having the above resistance value include tin oxide particles, tin oxide particles, and the like. Metal oxide particles such as titanium particles, zinc oxide particles, zirconium oxide particles, etc. are preferred, with zinc oxide particles being particularly preferred.

[0179] The specific surface area of ​​inorganic particles by the BET method is, for example, 10 m 2 / g or more is preferable. The specific surface area is 10m 2 When the molecular weight is 1.0 or more, the decrease in electrostatic chargeability tends to be suppressed. The volume average particle size of the inorganic particles is, for example, from 50 nm to 2000 nm (preferably from 60 nm to 1000 nm).

[0180] The content of the inorganic particles is, for example, preferably from 0% by mass to 80% by mass, and more preferably from 0% by mass to 70% by mass, based on the total solid content of the undercoat layer.

[0181] The inorganic particles may be surface-treated. Two or more types of inorganic particles having different surface treatments or different particle sizes may be used in combination.

[0182] Examples of the surface treatment agent include a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, a surfactant, etc. In particular, a silane coupling agent is preferred, and a silane coupling agent having an amino group is more preferred.

[0183] Examples of silane coupling agents having an amino group include, but are not limited to, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0184] Silane coupling agents may be used in combination of two or more kinds. For example, a silane coupling agent having an amino group may be used in combination with another silane coupling agent. Examples of other silane coupling agents include, but are not limited to, vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0185] The surface treatment method using the surface treatment agent may be any known method, and may be either a dry method or a wet method.

[0186] The amount of the surface treatment agent to be used is preferably, for example, 0.5% by mass or more and 10% by mass or less based on the inorganic particles.

[0187] The dry method is, for example, a method in which a surface treatment agent is attached to the surface of inorganic particles by dropping a surface treatment agent directly or dissolved in an organic solvent or spraying it together with dry air or nitrogen gas while stirring inorganic particles with a mixer or the like that exerts a large shearing force. The dropping or spraying of the surface treatment agent is preferably performed at a temperature below the boiling point of the solvent. After dropping or spraying the surface treatment agent, baking may be performed at 100° C. or higher. The temperature and time of baking are not particularly limited as long as electrophotographic properties can be obtained.

[0188] In the wet method, for example, inorganic particles are dispersed in a solvent by stirring, ultrasonic waves, a sand mill, an attritor, a ball mill, or the like, while a surface treatment agent is added, and after stirring or dispersing, the solvent is removed. In the wet method, the surface treatment agent is attached to the surface of the inorganic particles by using a solvent such as filtration or distillation. After the solvent is removed, baking may be performed at 100° C. or higher. The temperature and time for baking are not particularly limited as long as electrophotographic properties can be obtained. In the wet method, moisture contained in the inorganic particles may be removed before the surface treatment agent is added. Examples of such methods include a method of removing the moisture while stirring and heating in a solvent, and a method of removing the moisture by azeotropy with the solvent.

[0189] The undercoat layer may contain various additives for improving electrical properties, environmental stability, and image quality. Examples of the additives include known materials such as polycyclic condensation and azo-based electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, silane coupling agents, etc. As described above, silane coupling agents are used for surface treatment of inorganic particles, and may also be added to the undercoat layer as an additive.

[0190] Examples of silane coupling agents as additives include vinyltrimethoxysilane, 3-methacryloxypropyl-tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, and the like.

[0191] Examples of the zirconium chelate compound include zirconium butoxide, zirconium ethyl acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate zirconium butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octanoate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide.

[0192] Examples of titanium chelate compounds include tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate ethyl ester, titanium triethanolamine, and polyhydroxytitanium stearate.

[0193] Examples of aluminum chelate compounds include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethylacetoacetate aluminum diisopropylate, and aluminum tris(ethylacetoacetate).

[0194] These additives may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0195] The undercoat layer preferably has a Vickers hardness of 35 or more. The surface roughness (ten-point average roughness) of the undercoat layer is preferably adjusted to between 1 / (4n) (n is the refractive index of the upper layer) and 1 / 2 of the wavelength λ of the exposure laser used in order to suppress moire images. Resin particles or the like may be added to the undercoat layer to adjust the surface roughness. Examples of the resin particles include silicone resin particles and crosslinked polymethyl methacrylate resin particles. The surface of the undercoat layer may be polished to adjust the surface roughness. Examples of the polishing method include buffing, sandblasting, wet honing, grinding, and the like.

[0196] The formation of the undercoat layer is not particularly limited, and a well-known formation method can be used. For example, the undercoat layer can be formed by forming a coating film of a coating solution for forming the undercoat layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary.

[0197] Examples of the solvent for preparing the coating liquid for forming the undercoat layer include known organic solvents, such as alcohol-based solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone-based solvents, ketone alcohol-based solvents, ether-based solvents, and ester-based solvents. Specific examples of these solvents include ordinary organic solvents such as methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene.

[0198] Examples of the method for dispersing the inorganic particles when preparing the coating liquid for forming the undercoat layer include known methods such as those using a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0199] Examples of the method for applying the coating liquid for forming the undercoat layer onto the conductive substrate include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0200] The thickness of the undercoat layer is set, for example, preferably at least 15 μm, and more preferably within the range of from 20 μm to 50 μm.

[0201] (Conductive substrate) Examples of conductive substrates include metal plates, metal drums, and metal belts containing metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Examples of conductive substrates include paper, resin films, belts, etc. coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.) or alloys. Here, "conductive" refers to a material having a volume resistivity of 10 13 Less than Ωcm It is said.

[0202] When the electrophotographic photoreceptor is used in a laser printer, the surface of the conductive substrate is preferably roughened to a center line average roughness Ra of 0.04 μm to 0.5 μm in order to suppress interference fringes that occur when irradiating with laser light. When non-interfering light is used as the light source, roughening to prevent interference fringes is not particularly necessary, but it is suitable for extending the life of the conductive substrate since it suppresses the occurrence of defects due to unevenness on the surface.

[0203] Examples of methods for roughening the surface include wet honing, which involves spraying an abrasive suspended in water onto the conductive substrate; centerless grinding, in which the conductive substrate is pressed against a rotating grindstone and continuously ground; and anodizing.

[0204] As a method for roughening the surface, there can be mentioned a method in which, without roughening the surface of the conductive substrate, a conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the surface is roughened by the particles dispersed in the layer.

[0205] In the roughening treatment by anodization, an oxide film is formed on the surface of a conductive substrate made of metal (e.g., aluminum) by anodizing the substrate in an electrolyte solution using the substrate as the anode. Examples of electrolyte solutions include sulfuric acid solution and oxalic acid solution. However, the porous anodic oxide film formed by anodization is chemically active in its original state, easily contaminated, and has a large resistance variation depending on the environment. Therefore, it is preferable to perform a sealing treatment on the porous anodic oxide film, in which the micropores of the oxide film are filled by volume expansion caused by hydration reaction in pressurized steam or boiling water (metal salts such as nickel may be added) to change the film into a more stable hydrated oxide.

[0206] The thickness of the anodic oxide film is preferably, for example, from 0.3 μm to 15 μm. If the thickness is within this range, the film tends to exhibit a barrier property against injection and tends to suppress an increase in residual potential due to repeated use.

[0207] The conductive substrate may be subjected to a treatment with an acidic treatment solution or a boehmite treatment. Treatment with an acid treatment liquid is carried out, for example, as follows. First, an acid treatment liquid containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. The compounding ratios of phosphoric acid, chromic acid, and hydrofluoric acid in the acid treatment liquid are, for example, in the range of 10% by mass to 11% by mass for phosphoric acid, 3% by mass to 5% by mass for chromic acid, and 0.5% by mass to 2% by mass for hydrofluoric acid, and the total concentration of these acids is preferably in the range of 13.5% by mass to 18% by mass. The treatment temperature is preferably, for example, 42° C. to 48° C. The film thickness of the coating is preferably 0.3 μm to 15 μm.

[0208] The boehmite treatment is carried out, for example, by immersing the material in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting the material with heated steam at 90°C to 120°C for 5 to 60 minutes. The thickness of the coating is preferably 0.1 μm to 5 μm. This may be further anodized using an electrolyte solution having low coating solubility, such as adipic acid, boric acid, borates, phosphates, phthalates, maleates, benzoates, tartrates, or citrates.

[0209] (Middle class) Although not shown, an intermediate layer may be further provided between the undercoat layer and the photosensitive layer. The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include acetal resins (e.g., polyvinyl butyral, etc.), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride ... Examples of the polymeric compounds include vinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, and melamine resin. The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used in the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon. The compounds used in the intermediate layer may be used alone or as a mixture or polycondensation product of a plurality of compounds.

[0210] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing zirconium atoms or silicon atoms.

[0211] The formation of the intermediate layer is not particularly limited, and a well-known formation method can be used. For example, the intermediate layer can be formed by forming a coating film of a coating liquid for forming an intermediate layer in which the above components are added to a solvent, drying the coating film, and heating it if necessary. The intermediate layer can be formed by any of the usual coating methods, such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating and curtain coating.

[0212] The thickness of the intermediate layer is preferably set in the range of, for example, 0.1 μm to 3 μm. The intermediate layer may also be used as an undercoat layer.

[0213] (Charge generation layer) The charge generation layer is, for example, a layer containing a charge generation material and a binder resin. The charge generation layer may also be a vapor deposition layer of the charge generation material. The vapor deposition layer of the charge generation material is suitable for use with a non-coherent light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array.

[0214] Examples of the charge generating material include azo pigments such as bisazo and trisazo; condensed aromatic pigments such as dibromoanthanthrone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0215] Among these, in order to correspond to laser exposure in the near infrared region, it is preferable to use a metal phthalocyanine pigment or a metal-free phthalocyanine pigment as the charge generating material. Specifically, for example, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, and titanyl phthalocyanine are more preferable.

[0216] On the other hand, in order to accommodate laser exposure in the near ultraviolet region, preferred charge generating materials include condensed aromatic pigments such as dibromoanthanthrone, thioindigo pigments, porphyrazine compounds, zinc oxide, trigonal selenium, and bisazo pigments.

[0217] The above charge generating materials may be used when using incoherent light sources such as LEDs and organic EL image arrays that emit light at a central wavelength of 450 nm to 780 nm, but from the viewpoint of resolution, when using a thin photosensitive layer of 20 μm or less, the electric field strength in the photosensitive layer becomes high, and a decrease in charging due to charge injection from the substrate, so-called black spots, is likely to occur as an image defect. This becomes more noticeable when using charge generating materials that are p-type semiconductors such as trigonal selenium and phthalocyanine pigments and are prone to generating dark current.

[0218] In contrast, when n-type semiconductors such as fused aromatic pigments, perylene pigments, and azo pigments are used as charge generating materials, dark current is unlikely to occur, and image defects known as black spots are suppressed even in thin films. The n-type is determined by the polarity of the photocurrent that flows using the commonly used time-of-flight method, and those that easily pass electrons as carriers rather than holes are considered to be n-type.

[0219] The binder resin used in the charge generating layer may be selected from a wide range of insulating resins, and may also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, polysilane, and the like. Examples of the binder resin include polyvinyl butyral resin, polyarylate resin (polycondensation product of bisphenols and aromatic dicarboxylic acid, etc.), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinylpyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, polyvinylpyrrolidone resin, etc. Here, "insulating" means a material having a volume resistivity of 10 13 This means that the resistance is Ωcm or more. These binder resins may be used alone or in combination of two or more.

[0220] The compounding ratio of the charge generating material to the binder resin is preferably within a range of 10:1 to 1:10 by mass.

[0221] The charge generating layer may contain other well-known additives.

[0222] The formation of the charge generation layer is not particularly limited, and a known formation method is used, for example, by forming a coating film of a coating solution for forming a charge generation layer in which the above-mentioned components are added to a solvent, drying the coating film, and heating it as necessary. The formation of the charge generation layer may be performed by vapor deposition of a charge generation material. The formation of the charge generation layer by vapor deposition is particularly suitable when a condensed ring aromatic pigment or a perylene pigment is used as the charge generation material.

[0223] Examples of the solvent for preparing the coating liquid for forming the charge generating layer include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene, etc. These solvents may be used alone or in combination of two or more.

[0224] Examples of methods for dispersing particles (e.g., charge generating material) in the coating liquid for forming a charge generating layer include media dispersers such as ball mills, vibration ball mills, attritors, sand mills, and horizontal sand mills, and medialess dispersers such as stirrers, ultrasonic dispersers, roll mills, and high-pressure homogenizers. Examples of high-pressure homogenizers include a collision method in which the dispersion liquid is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion liquid is dispersed by penetrating a fine flow path under high pressure. During this dispersion, it is effective to adjust the average particle size of the charge generating material in the coating liquid for forming the charge generating layer to 0.5 μm or less, preferably 0.3 μm or less, and more preferably 0.15 μm or less.

[0225] Examples of a method for applying the coating liquid for forming the charge generating layer onto the undercoat layer (or onto the intermediate layer) include conventional methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0226] The thickness of the charge generating layer is set, for example, preferably in the range of 0.1 μm or more and 5.0 μm or less, and more preferably in the range of 0.2 μm or more and 2.0 μm or less.

[0227] (charge transport layer) The charge transport layer is, for example, a layer containing a charge transport material and a binder resin, and may be a layer containing a polymer charge transport material.

[0228] Examples of the charge transport material include electron transporting compounds such as quinone compounds such as p-benzoquinone, chloranil, bromanil, and anthraquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and ethylene compounds. Examples of the charge transport material include hole transporting compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination, but are not limited to these.

[0229] As the charge transport material, from the viewpoint of charge mobility, a triarylamine derivative represented by the following structural formula (a-1) and a benzidine derivative represented by the following structural formula (a-2) are preferable.

[0230] [ka]

[0231] In structural formula (a-1), Ar T1 , Ar T2 , and Ar T3 each independently represents a substituted or unsubstituted aryl group, -CH-C(R T4 )=C(R T5 )(R T6 ), or -CH-CH=CH-CH=C(R T7 )(R T8 ) is shown. T4 , R T5 , R T6 , R T7 , and R T8 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Examples of the substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0232] [ka]

[0233] In structural formula (a-2), R T91 and R T92 R each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms. T101 , R T102 , R T111 and R T112 each independently represents a halogen atom, an alkyl group having from 1 to 5 carbon atoms, an alkoxy group having from 1 to 5 carbon atoms, an amino group substituted with an alkyl group having from 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ) and R T12 , R T13 , R T14 , R T15 and R T16 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. Tm1, Tm2, ​​Tn1, and Tn2 each independently represent an integer of 0 or more and 2 or less. Examples of the substituent for each of the above groups include a halogen atom, an alkyl group having from 1 to 5 carbon atoms, and an alkoxy group having from 1 to 5 carbon atoms. Examples of the substituent for each of the above groups also include a substituted amino group substituted with an alkyl group having from 1 to 3 carbon atoms.

[0234] Among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), in particular, "-C6H4-CH=CH-CH=C(R T7 )(R T8 )" and triarylamine derivatives having "-CH=CH-CH=C(R T15 )(R T16 ) is preferable from the viewpoint of charge mobility.

[0235] As the polymer charge transport material, known materials having charge transport properties such as poly-N-vinylcarbazole and polysilane are used. In particular, polyester polymer charge transport materials are particularly preferred. The polymer charge transport material may be used alone or in combination with a binder resin.

[0236] Examples of the binder resin used in the charge transport layer include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polysilane, etc. Among these, polycarbonate resin or polyarylate resin is suitable as the binder resin. These binder resins are used alone or in combination of two or more. The compounding ratio of the charge transport material to the binder resin is preferably from 10:1 to 1:5 by mass.

[0237] The charge transport layer may contain other well-known additives.

[0238] The formation of the charge transport layer is not particularly limited, and a known formation method can be used. For example, the charge transport layer can be formed by forming a coating film of a coating liquid for forming the charge transport layer in which the above components are added to a solvent, drying the coating film, and heating it as necessary.

[0239] Examples of solvents for preparing the coating liquid for forming the charge transport layer include ordinary organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene, ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride, and cyclic or linear ethers such as tetrahydrofuran and ethyl ether. These solvents may be used alone or in combination of two or more.

[0240] Examples of a coating method for coating the coating liquid for forming the charge transport layer on the charge generating layer include ordinary methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating and curtain coating.

[0241] The thickness of the charge transport layer is set, for example, preferably in the range of 5 μm or more and 50 μm or less, and more preferably in the range of 10 μm or more and 30 μm or less.

[0242] (protective layer) A protective layer is provided on the photosensitive layer as necessary for the purpose of, for example, preventing chemical changes in the photosensitive layer when the photosensitive layer is charged and further improving the mechanical strength of the photosensitive layer. Therefore, it is preferable to apply a layer composed of a cured film (crosslinked film) as the protective layer. Examples of such a layer include the following layers 1) and 2).

[0243] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton in the same molecule (i.e., a layer containing a polymer or crosslinked product of the reactive group-containing charge transport material). 2) A layer composed of a cured film of a composition containing a non-reactive charge transport material and a reactive group-containing non-charge transport material that does not have a charge transport skeleton and has a reactive group (i.e., a layer containing a non-reactive charge transport material and a polymer or crosslinked body of the reactive group-containing non-charge transport material).

[0244] The reactive group of the reactive group-containing charge transport material may be a chain polymerizable group, an epoxy group, -OH, -OR (wherein R represents an alkyl group), -NH2, -SH, -COOH, or -SiR. Q1 3-Qn (OR Q2 ) Qn [However, R Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group; R Q2 represents a hydrogen atom, an alkyl group, or a trialkylsilyl group; Qn represents an integer of 1 to 3.

[0245] The chain polymerizable group is not particularly limited as long as it is a functional group capable of radical polymerization, and is, for example, a functional group having a group containing at least a carbon double bond.Specific examples include a group containing at least one selected from a vinyl group, a vinyl ether group, a vinyl thioether group, a styryl group (vinyl phenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof.Among them, the chain polymerizable group is preferably a group containing at least one selected from a vinyl group, a styryl group (vinyl phenyl group), an acryloyl group, a methacryloyl group, and derivatives thereof, because of its excellent reactivity.

[0246] The charge transporting skeleton of the reactive group-containing charge transporting material is not particularly limited as long as it is a known structure in electrophotographic photoreceptors, and examples thereof include a skeleton derived from a nitrogen-containing hole transporting compound such as a triarylamine compound, a benzidine compound, a hydrazone compound, etc., and a structure conjugated with a nitrogen atom. Among these, a triarylamine skeleton is preferred.

[0247] The reactive group-containing charge transport material having a reactive group and a charge transporting skeleton, the non-reactive charge transport material, and the reactive group-containing non-charge transport material may be selected from well-known materials.

[0248] The protective layer may contain other well-known additives.

[0249] The formation of the protective layer is not particularly limited, and a well-known formation method can be used. For example, the protective layer can be formed by forming a coating film of a coating liquid for forming the protective layer in which the above components are added to a solvent, drying the coating film, and, if necessary, subjecting it to a curing treatment such as heating.

[0250] Examples of the solvent for preparing the coating solution for forming the protective layer include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; and tetrahydrofuran and dioxane. Examples of the solvent include ether solvents, cellosolve solvents such as ethylene glycol monomethyl ether, and alcohol solvents such as isopropyl alcohol and butanol. These solvents may be used alone or in combination of two or more. The protective layer-forming coating liquid may be a solvent-free coating liquid.

[0251] Examples of a method for applying the protective layer-forming coating liquid onto a photosensitive layer (e.g., a charge transport layer) include conventional methods such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating.

[0252] The thickness of the protective layer is set, for example, preferably in the range of 1 μm or more and 20 μm or less, and more preferably in the range of 2 μm or more and 10 μm or less.

[0253] (single-layer photosensitive layer) The single-layer type photosensitive layer (charge generation / charge transport layer) is, for example, a layer containing a charge generation material, a charge transport material, and, if necessary, a binder resin and other well-known additives. Note that these materials are the same as those described for the charge generation layer and the charge transport layer. The content of the charge generating material in the single-layer photosensitive layer is preferably 0.1% by mass to 10% by mass, more preferably 0.8% by mass to 5% by mass, based on the total solid content. The content of the charge transport material in the single-layer photosensitive layer is preferably 5% by mass to 50% by mass, based on the total solid content. The method for forming the single-layer type photosensitive layer is the same as the method for forming the charge generating layer and the charge transport layer. The thickness of the single-layer photosensitive layer is, for example, 5 μm or more and 50 μm or less, and preferably 10 μm or more and 40 μm or less.

[0254] [Image forming device (and process cartridge)] The image forming apparatus according to the present embodiment includes an electrophotographic photosensitive member, a charging device which charges the surface of the electrophotographic photosensitive member, an electrostatic latent image forming device which forms an electrostatic latent image on the surface of the charged electrophotographic photosensitive member, a developing device which develops the electrostatic latent image formed on the surface of the electrophotographic photosensitive member with a developer containing toner to form a toner image, and a transfer device which transfers the toner image to the surface of a recording medium, and the movement time of the outer peripheral surface of the electrophotographic photosensitive member required from charging by the charging device to development by the developing device is 90 msec or more.

[0255] The image forming apparatus according to the present embodiment may be any of known image forming apparatuses, such as an apparatus provided with a fixing means for fixing a toner image transferred onto the surface of a recording medium; an apparatus of a direct transfer type for directly transferring a toner image formed on the surface of an electrophotographic photosensitive member onto a recording medium; an apparatus of an intermediate transfer type for primarily transferring a toner image formed on the surface of an electrophotographic photosensitive member onto the surface of an intermediate transfer member, and then secondarily transferring the toner image transferred onto the surface of the intermediate transfer member onto the surface of a recording medium; an apparatus provided with a cleaning means for cleaning the surface of an electrophotographic photosensitive member before charging after the transfer of a toner image; an apparatus provided with a discharging means for irradiating the surface of an electrophotographic photosensitive member with discharging light to discharge the surface before charging after the transfer of a toner image; and an apparatus provided with an electrophotographic photosensitive member heating member for increasing the temperature of the electrophotographic photosensitive member and reducing the relative temperature.

[0256] In the case of an intermediate transfer type device, the transfer means has, for example, an intermediate transfer body onto whose surface a toner image is transferred, a primary transfer means which primarily transfers the toner image formed on the surface of the electrophotographic photosensitive body onto the surface of the intermediate transfer body, and a secondary transfer means which secondarily transfers the toner image transferred onto the surface of the intermediate transfer body onto the surface of a recording medium.

[0257] The image forming apparatus according to the present embodiment may be either a dry development type image forming apparatus or a wet development type image forming apparatus (a development type using a liquid developer).

[0258] In the image forming apparatus according to the present embodiment, for example, a portion including an electrophotographic photosensitive member However, it may be a cartridge structure (process cartridge) that is detachably attached to the image forming apparatus. As the process cartridge, for example, a process cartridge equipped with the electrophotographic photosensitive member according to the present embodiment is preferably used. Note that the process cartridge may be equipped with at least one selected from the group consisting of a charging means, an electrostatic latent image forming means, a developing means, and a transfer means, in addition to the electrophotographic photosensitive member.

[0259] An example of an image forming apparatus according to the present embodiment will be described below, but the present invention is not limited to this. Note that only the main parts shown in the drawings will be described, and descriptions of the rest will be omitted.

[0260] FIG. 2 is a schematic diagram showing an example of the image forming apparatus according to the present embodiment. As shown in FIG. 2, the image forming apparatus 100 according to the present embodiment includes a process cartridge 300 including an electrophotographic photoreceptor 7, an exposure device 9 (an example of an electrostatic latent image forming means), a transfer device 40 (a primary transfer device), and an intermediate transfer body 50. In the image forming apparatus 100, the exposure device 9 is disposed at a position where it can expose the electrophotographic photoreceptor 7 from the opening of the process cartridge 300, the transfer device 40 is disposed at a position facing the electrophotographic photoreceptor 7 via the intermediate transfer body 50, and the intermediate transfer body 50 is disposed with a part of it in contact with the electrophotographic photoreceptor 7. Although not shown, the image forming apparatus 100 also includes a secondary transfer device that transfers the toner image transferred to the intermediate transfer body 50 to a recording medium (e.g., paper). The intermediate transfer body 50, the transfer device 40 (a primary transfer device), and the secondary transfer device (not shown) correspond to an example of a transfer means.

[0261] 2 supports an electrophotographic photoreceptor 7, a charging device 8 (an example of a charging means), a developing device 11 (an example of a developing means), and a cleaning device 13 (an example of a cleaning means) integrally within a housing. The cleaning device 13 has a cleaning blade (an example of a cleaning member) 131, which is disposed so as to come into contact with the surface of the electrophotographic photoreceptor 7. The cleaning member may not be in the form of the cleaning blade 131, but may be a conductive or insulating fibrous member, which may be used alone or in combination with the cleaning blade 131.

[0262] FIG. 2 shows an example of an image forming apparatus equipped with a fibrous member 132 (roll-shaped) that supplies lubricant 14 to the surface of electrophotographic photosensitive member 7, and a fibrous member 133 (flat brush-shaped) that assists in cleaning, which may be arranged as needed.

[0263] Hereinafter, each configuration of the image forming apparatus according to this embodiment will be described.

[0264] -Charging device- As the charging device 8, for example, a contact type charger using a conductive or semiconductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. Also, a non-contact type roller charger, a scorotron charger or corotron charger that utilizes corona discharge, or other chargers known per se, can be used.

[0265] -Exposure equipment- The exposure device 9 may be, for example, an optical device that exposes the surface of the electrophotographic photoreceptor 7 with light such as semiconductor laser light, LED light, or liquid crystal shutter light in a predetermined image. The wavelength of the light source is within the spectral sensitivity range of the electrophotographic photoreceptor. The wavelength of the semiconductor laser is mainly near infrared light having an oscillation wavelength of about 780 nm. However, it is not limited to this wavelength, and a laser having an oscillation wavelength of 600 nm or a blue laser having an oscillation wavelength of 400 nm to 450 nm may also be used. In addition, a surface-emitting laser light source capable of outputting multiple beams is also effective for forming a color image.

[0266] -Developing device- The developing device 11 may be, for example, a general developing device that develops by contacting or non-contacting a developer. The developing device 11 is not particularly limited as long as it has the above-mentioned functions, and may be selected according to the purpose. For example, it may be a known developing device that has a function of attaching a one-component developer or a two-component developer to the electrophotographic photoreceptor 7 using a brush, roller, or the like. Among them, it is preferable to use a developing roller that holds a developer on its surface.

[0267] The developer used in the developing device 11 may be a one-component developer containing only toner, or may be a two-component developer containing toner and a carrier. The developer may be magnetic or non-magnetic. Well-known developers are used.

[0268] -Cleaning device- The cleaning device 13 is a cleaning blade type device equipped with a cleaning blade 131 . In addition to the cleaning blade system, a fur brush cleaning system or a simultaneous development and cleaning system may also be used.

[0269] -Transfer device- Examples of the transfer device 40 include known transfer chargers such as a contact type transfer charger using a belt, roller, film, rubber blade, etc., and a scorotron transfer charger or corotron transfer charger that utilizes corona discharge.

[0270] -Intermediate transfer body- A belt-like intermediate transfer belt containing semiconductive polyimide, polyamideimide, polycarbonate, polyarylate, polyester, rubber, etc. is used as the intermediate transfer body 50. The intermediate transfer body may be in the form of a drum other than a belt.

[0271] FIG. 3 is a schematic diagram showing another example of the image forming apparatus according to the present embodiment. 3 is a tandem-type multi-color image forming apparatus equipped with four process cartridges 300. In the image forming apparatus 120, the four process cartridges 300 are arranged in parallel on the intermediate transfer body 50, and one electrophotographic photosensitive body is used for each color. The image forming apparatus 120 has the same configuration as the image forming apparatus 100, except that it is a tandem type. EXAMPLES

[0272] The electrophotographic photoreceptor of the present disclosure will be described in more detail below with reference to examples. The materials, amounts, ratios, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present disclosure. Therefore, the scope of the electrophotographic photoreceptor of the present disclosure should not be interpreted as being limited by the specific examples shown below. In the following description, unless otherwise specified, "parts" and "%" are by mass. In the following description, unless otherwise specified, synthesis, production, processing, measurement, etc. were carried out at room temperature (25°C ± 3°C).

[0273] -Preparation of electron transport material- Preparation of electron transport material (1) 6.4 g of the exemplary compound (1-1) of the general formula (1), 72 g of zirconia beads having a diameter of 0.3 mm, and 1.0 g of sodium chloride were placed in a zirconia container and ground at a rotation speed of 500 rpm for 2 hours using a planetary mill (Fritsch: P-7 Classic Line). After grinding, the pigment particles were separated by filtration while washing the zirconia beads with 500 ml of distilled water. The resulting aqueous dispersion of pigment particles was centrifuged and the supernatant water was removed by decantation to isolate the pigment. The isolated pigment was washed repeatedly with water until the electrical conductivity was 10 μS / cm or less, and then dried for 48 hours in a freeze dryer. The dried pigment particles were classified using a 1000 mesh sieve to remove coarse particles, and the resulting material was used as the electron transport material (1). Preparation of electron transport material (2) The electron transport material (1) was prepared in the same manner as the electron transport material (1), except that no classification was performed. Preparation of electron transport material (3) The compound of the electron transport material (1) was (1-1) and zinc oxide: (average particle size 70 nm: manufactured by Teika Co., Ltd.: specific surface area value 15 m 2 The electron transport material was prepared in the same manner as in the preparation of the electron transport material (1), except that a 9:1 mixture of 2,3-dichloro-1 ... Preparation of electron transport material (4) Zinc oxide: (average particle size 70 nm: manufactured by Teika Co., Ltd.: specific surface area value 15 m 2 100 parts of zinc oxide (100 parts by weight / g) was mixed with 500 parts of tetrahydrofuran and stirred, and 1.4 parts of a silane coupling agent (KBE503: manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred for 2 hours. Thereafter, the toluene was distilled off by reduced pressure distillation, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with a silane coupling agent. 110 parts of zinc oxide that had been subjected to the surface treatment was mixed with stirring in 500 parts of tetrahydrofuran, and a solution in which 0.6 parts of alizarin was dissolved in 50 parts of tetrahydrofuran was added, followed by stirring for 5 hours at 50° C. Thereafter, the zinc oxide to which alizarin had been added was filtered out by filtration under reduced pressure, and further dried under reduced pressure at 60° C. to obtain zinc oxide to which alizarin had been added.

[0274] <Example 1> (Formation of Undercoat Layer 1) A mixed solution was obtained by mixing 60 parts of the electron transport material (1) as the electron transport material, 13.5 parts of a curing agent (blocked isocyanate Sumidur 3175, manufactured by Sumitomo Bayern Urethane Co., Ltd., curing agent content 75% by mass), 15 parts of a butyral resin (S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.), and 85 parts of methyl ethyl ketone. 38 parts of this mixed solution and 25 parts of methyl ethyl ketone were mixed, and dispersed for 2 hours in a sand mill using 1 mmφ glass beads to obtain a dispersion solution. To the resulting dispersion, 0.005 parts of dioctyltin dilaurate as a catalyst and 30 parts of silicone resin particles (Tospearl 145, Momentive Performance Materials Japan LLC) were added to obtain a coating solution for the undercoat layer. This coating solution was applied onto a cylindrical aluminum substrate by dip coating, and dried and cured at 170°C for 30 minutes to obtain a 25μm thick undercoat layer.

[0275] (Formation of Charge Generation Layer) One part of hydroxygallium phthalocyanine having diffraction peaks at Bragg angles (2θ±0.5°) of at least 7.8° and 28.6° in the X-ray diffraction spectrum using CuKα characteristic X-rays was mixed with one part of polyvinyl butyral (S-LEC BM-5, manufactured by Sekisui Chemical Co., Ltd.) and 80 parts of n-butyl acetate, and the mixture was dispersed together with glass beads in a paint shaker for 1 hour to prepare a coating liquid for a charge generating layer. The resulting coating liquid was dip-coated on a conductive substrate on which an undercoat layer had been formed, and dried by heating at 130°C for 10 minutes to form a charge generating layer with a thickness of 0.15 μm.

[0276] (Formation of charge transport layer) 45 parts of a benzidine compound represented by the following formula (CTM1) as a charge transport material, and 55 parts of a polymer compound (viscosity average molecular weight: 40,000) having a repeating unit represented by the following formula (PCZ1) as a binder resin were dissolved in 350 parts of toluene and 150 parts of tetrahydrofuran, and 8 parts of a tetrafluoroethylene resin (Lubron L5, manufactured by Daikin Industries, Ltd., average particle size 300 nm) were added. Furthermore, 100 ppm of KP340 manufactured by Shin-Etsu Chemical Co., Ltd. was added to this coating liquid, and the coating liquid for the charge transport layer was prepared by processing five times with a high-pressure homogenizer. The obtained coating liquid was applied onto the charge generating layer by dip coating, and heated at 130° C. for 45 minutes to form a charge transport layer having a thickness of 40 μm.

[0277] [ka]

[0278] [ka]

[0279] (Production of image forming device) The electrophotographic photoreceptor obtained above was mounted in a drum cartridge of an image forming apparatus DocuCentre C5570 manufactured by FUJIFILM Business Innovation Co., Ltd. to prepare an image forming apparatus.

[0280] <Examples 2 to 14 and Comparative Examples 1 to 6> Except for changing the type of undercoat layer from undercoat layer (1) to the type of undercoat layer and the type of charge generation layer shown in the table below, electrophotographic photoreceptors of each example were obtained with the same specifications as in Example 1. In addition, in the image forming apparatus, the movement time of the outer peripheral surface of the electrophotographic photoreceptor required from charging by the charging device to development by the developing device was set to the specifications shown in Table 1. The methods for producing the undercoat layers and charge generation layers changed from those in Example 1 are as follows.

[0281] Preparation of undercoat layer (2) The undercoat layer (1) was prepared in the same manner as in the preparation of the undercoat layer (1), except that the electron transporting material was changed to the electron transporting material (2) and the dispersion time by the sand mill was changed to 4 hours.

[0282] Preparation of undercoat layer (3) The undercoat layer (1) was prepared in the same manner as in the preparation of the undercoat layer (1), except that the electron transport material was changed to the electron transport material (3).

[0283] Preparation of undercoat layer (4) The undercoat layer was prepared in the same manner as in the undercoat layer (1), except that the content of the electron transport material was 57 parts based on the total of the binder resin components and the electron transport material in the undercoat layer.

[0284] Preparation of undercoat layer (5) The undercoat layer (1) was prepared in the same manner as in the preparation of the undercoat layer (1), except that the electron transport material was changed to the electron transport material (2).

[0285] Preparation of undercoat layer (6) The undercoat layer (1) was prepared in the same manner as in the undercoat layer (1), except that the electron transporting material was changed to the electron transporting material (4) and the amount added was changed to 24 parts.

[0286] Preparation of undercoat layer (7) The undercoat layer was prepared in the same manner as in the undercoat layer (1), except that the amount of the electron transport material was 83 parts based on the total amount of the binder resin component and the electron transport material in the undercoat layer.

[0287] Preparation of charge generation layer (2) A part of chlorogallium phthalocyanine having diffraction peaks at Bragg angles (2θ±0.5°) of at least 7.9° and 28.8° in the X-ray diffraction spectrum using CuKα characteristic X-rays was mixed with 1 part of polyvinyl butyral (S-LEC BM-5, manufactured by Sekisui Chemical Co., Ltd.) and 80 parts of n-butyl acetate, and the mixture was dispersed together with glass beads in a paint shaker for 1 hour to prepare a coating liquid for a charge generating layer. The resulting coating liquid was dip-coated on a conductive substrate on which an undercoat layer had been formed, and dried by heating at 130°C for 10 minutes to form a charge generating layer with a thickness of 0.15 μm.

[0288] <Reference example 1> An image forming apparatus was obtained with the same specifications as in Example 1, except that the movement time of the outer peripheral surface of the electrophotographic photosensitive member required from charging by the charging device to development by the developing device was set to the specifications shown in Table 1.

[0289] <Evaluation of fogging> Using the image forming apparatus of each example, 1M sheets were printed in a low temperature and low humidity environment (10°C, 5% RH), and then the occurrence of fogging was confirmed with the naked eye and evaluated according to the following criteria. The results are shown in Table 1. A: No image defects. B: A minor image defect occurred, but it did not affect the quality. C: Image defects occurred, but were not serious enough to affect quality. D: Image defects occurred to a certain extent, which caused quality problems.

[0290] [Table 1]

[0291] As shown in each table, it was found that the electrophotographic photoreceptors of Examples had less fogging than the electrophotographic photoreceptors of Comparative Examples.

[0292] The image forming apparatus according to the present embodiment includes the following aspects. (((1))) An electrophotographic photoreceptor comprising: a conductive substrate; an undercoat layer provided on the conductive substrate, the undercoat layer containing a binder resin and an electron transport material and satisfying the following formula 1-1; and a photosensitive layer provided on the undercoat layer; a charging device for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and a transfer device for transferring the toner image onto a surface of a recording medium; wherein the time required for the outer peripheral surface of the electrophotographic photosensitive member to move from charging by the charging device to development by the developing device is 90 msec or more. Formula 1-1: 0.20≦E F1 -E LUMO1 ≦0.60 (In the above formula 1-1, E F1 represents the Fermi level of the undercoat layer, E LUMO1 represents the LUMO energy level of the undercoat layer. (((2))) The image forming apparatus according to (((1))) above, wherein the undercoat layer further satisfies the following formula 1-2: Equation 1-2: 0.40≦E F1 -E LUMO1 ≦0.58 (In the above formula 1-2, E LUMO1 represents the LUMO energy level of the undercoat layer, E F1 represents the Fermi level of the undercoat layer. (((3))) The undercoat layer has a Fermi level E F1 The image forming apparatus according to (((1))) or (((2))), wherein (((4))) The undercoat layer has an energy level E LUMO1 The image forming apparatus according to (((3))) above, wherein the optical density is 3.5 eV or more and 4.2 eV or less. (((5))) the photosensitive layer is a laminated type photosensitive layer including a charge generating layer provided on the undercoat layer and a charge transport layer provided on the charge generating layer, The image forming apparatus according to any one of (((1))) to (((4))) above, wherein the charge generating layer satisfies the following formula 2-1: Equation 2-1: 0.90≦E F2 -E LUMO2 ≦1.40 (In the above formula 2-1, E F2 represents the Fermi level of the charge generating layer, E LUMO2 represents the LUMO energy level of the charge generating layer. (((6))) The image forming apparatus according to any one of (((1))) to (((5))), wherein the electron transport material has an average primary particle diameter of 80 nm or more and 400 nm or less. (((7))) The image forming apparatus according to (((1))), wherein the electron transport material has an aspect ratio of 1.0 or more and 4.2 or less. (((8))) The image forming apparatus according to any one of (((1))) to (((7))), wherein the electron transport material is at least one selected from the group consisting of compounds represented by the following general formulas (1) to (8): [ka] (In the above general formula (1), R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 and R 18 R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. 11 and R 12 , R 12 and R 13 and R 13 and R 14 may each independently be linked to each other to form a ring. 15 and R 16 , R 16 and R 17 and R 17 and R 18 may each independently be linked to each other to form a ring. In general formula (2), R 21 , R 22 , R 23 , R 24 , R 25 , R 26 , R 27 and R 28R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. 21 and R 22 , R 22 and R 23 and R 23 and R 24 may each independently be linked to each other to form a ring. 25 and R 26 , R 26 and R 27 and R 27 and R 28 may each independently be linked to each other to form a ring. In general formula (3), R 31 , R 32 , R 33 , R 34 , R 35 and R 36 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (4), R 41 , R 42 , R 43 , R 44 , R 45 , R 46 , R 47 , R 48 , R 49 and R 50 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (5), R 51 , R 52 , R 53 , R 54 , R 55 , R 56 , R 57 and R 58 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (6), R61 , R 62 , R 63 and R 64 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (7), R 71 , R 72 , R 73 , R 74 , R 75 , R 76 , R 77 and R 78 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom, and Z represents an oxygen atom or a dicyanomethylene group (=C(CN)2). In general formula (8), R 81 , R 82 , R 83 , R 84 , R 85 , R 86 , R 87 and R 88 each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom, and Z represents an oxygen atom or a dicyanomethylene group (=C(CN)2). (((9))) The image forming apparatus according to (((8))), wherein the electron transporting material is at least one of the compounds represented by general formulas (1) and (2). (((10))) The image forming apparatus described in any one of (((1))) to (((9))), wherein the content of the electron transport material is 60% by mass or more and 80% by mass or less with respect to the total of all binder resin components of the undercoat layer and the electron transport material.

[0293] According to the invention of (((1))), (((8))) or (((9)), in an image forming apparatus which is provided with an electrophotographic photoreceptor having a conductive substrate, an undercoat layer containing a binder resin and an electron transport material, and a photosensitive layer, and in which the moving speed of the outer peripheral surface of the electrophotographic photoreceptor required from charging by a charging device to development by a developing device is 90 msec or more, the undercoat layer does not satisfy the above formula 1-1 (i.e., E F1 -E LUMO1 In comparison with the case where the value is less than 0.20 or more than 0.60, an image forming apparatus is provided which suppresses fogging. According to the invention related to (((2))), E F1 -E LUMO1 As a result, an image forming apparatus is provided which suppresses fogging, as compared with the case where the fogging rate is less than 0.40 or exceeds 0.58. According to the invention related to (((3))), the Fermi level E F1 As a result, an image forming apparatus is provided in which fogging is suppressed compared to when the photosensitivity is less than 4.2 eV or exceeds 5.0 eV. According to the invention related to (((4))), the LUMO energy level E LUMO1 As a result, an image forming apparatus is provided in which fogging is suppressed compared to when the photosensitivity is less than 3.5 eV or exceeds 4.2 eV. According to the invention related to (((5))), the photosensitive layer is a laminated type photosensitive layer including a charge generating layer provided on the undercoat layer and a charge transport layer provided on the charge generating layer, and E F2 -E LUMO2 As a result, an image forming apparatus is provided which suppresses fogging as compared with the case where the fogging rate is less than 0.90 or exceeds 1.40. According to the invention related to (((6))), there is provided an image forming apparatus which suppresses fogging as compared with the case where the average primary particle diameter of the electron transport material is less than 80 nm or exceeds 400 nm. According to the invention related to (((7))), there is provided an image-forming apparatus which suppresses fogging as compared with the case where the aspect ratio of the electron transport material is less than 1.0 or exceeds 4.2. According to the invention related to (((10))), there is provided an image forming apparatus which suppresses fogging, as compared with a case in which the content of the electron transport material is less than 60 mass % or more than 80 mass % with respect to the total of all binder resin components in the undercoat layer and the electron transport material. [Explanation of symbols]

[0294] 1 undercoat layer, 2 charge generation layer, 3 charge transport layer, 4 conductive substrate, 5 photosensitive layer, 7A electrophotographic photosensitive member, 7 electrophotographic photosensitive member, 8 charging device, 9 exposure device, 11 developing device, 13 cleaning device, 14 lubricant, 40 transfer device, 50 intermediate transfer body, 100 image forming apparatus, 120 image forming apparatus, 131 cleaning blade, 132 fibrous member (roll-shaped), 133 fibrous member (flat brush-shaped), 300 process cartridge

Claims

1. an electrophotographic photoreceptor comprising: a conductive substrate; an undercoat layer provided on the conductive substrate, the undercoat layer containing a binder resin and an electron transport material and satisfying the following formula 1-1; and a photosensitive layer provided on the undercoat layer; a charging device for charging the surface of the electrophotographic photoreceptor; an electrostatic latent image forming device for forming an electrostatic latent image on the charged surface of the electrophotographic photoreceptor; a developing device for developing an electrostatic latent image formed on the surface of the electrophotographic photoreceptor with a developer containing a toner to form a toner image; and a transfer device for transferring the toner image onto a surface of a recording medium; and a moving time of the outer peripheral surface of the electrophotographic photosensitive member required from charging by the charging device to development by the developing device is 90 msec or more. Formula 1-1: 0.20≦E Ｆ１ -E ＬＵＭＯ１ ≦0.60 (In the above formula 1-1, E Ｆ１ represents the Fermi level of the undercoat layer, E ＬＵＭＯ１ represents the LUMO energy level of the undercoat layer.

2. 2. The image-forming apparatus according to claim 1, wherein the undercoat layer further satisfies the following formula 1-2. Formula 1-2: 0.40≦E Ｆ１ -E ＬＵＭＯ１ ≦0.58 (In the above formula 1-2, E ＬＵＭＯ１ represents the LUMO energy level of the undercoat layer, E Ｆ１ represents the Fermi level of the undercoat layer.

3. The undercoat layer has a Fermi level E Ｆ１ 2. The image forming apparatus according to claim 1, wherein the excitation voltage Vdc is 4.2 eV or more and 5.0 eV or less.

4. The undercoat layer has an energy level E ＬＵＭＯ１ The image forming apparatus according to claim 3 , wherein the energy of the excitation light is 3.5 eV or more and 4.2 eV or less.

5. the photosensitive layer is a laminated type photosensitive layer including a charge generating layer provided on the undercoat layer and a charge transport layer provided on the charge generating layer, 2. The image forming apparatus according to claim 1, wherein the charge generating layer satisfies the following formula 2-1. Formula 2-1: 0.90≦E Ｆ２ -E ＬＵＭＯ２ ≦1.40 (In the above formula 2-1, E Ｆ２ represents the Fermi level of the charge generating layer, E ＬＵＭＯ２ represents the LUMO energy level of the charge generating layer.

6. 2. The image forming apparatus according to claim 1, wherein the electron transport material has an average primary particle diameter of 80 nm or more and 400 nm or less.

7. 2. The image forming apparatus according to claim 1, wherein the electron transport material has an aspect ratio of 1.0 to 4.

2.

8. 2. The image forming apparatus according to claim 1, wherein the electron transporting material is at least one selected from the group consisting of compounds represented by the following general formulas (1) to (8): 【Chemistry 1】 (In the above general formula (1), R １１ , R １２ , R １３ , R １４ , R １５ , R １６ , R １７ and R １８ R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. １１ and R １２ , R １２ and R １３ and R １３ and R １４ may each independently be linked to each other to form a ring. １５ and R １６ , R １６ and R １７ and R １７ and R １８ may each independently be linked to each other to form a ring. In general formula (2), R ２１ , R ２２ , R ２３ , R ２４ , R ２５ , R ２６ , R ２７ and R ２８ R each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkoxycarbonylalkyl group, an aryloxycarbonylalkyl group, or a halogen atom. ２１ and R ２２ , R ２２ and R ２３ and R ２３ and R ２４ may each independently be linked to each other to form a ring. ２５ and R ２６ , R ２６ and R ２７ and R ２７ and R ２８ may each independently be linked to each other to form a ring. In general formula (3), R ３１ , R ３２ , R ３３ , R ３４ , R ３５ and R ３６ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (4), R ４１ , R ４２ , R ４３ , R ４４ , R ４５ , R ４６ , R ４７ , R ４８ , R ４９ and R ５０ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (5), R ５１ , R ５２ , R ５３ , R ５４ , R ５５ , R ５６ , R ５７ and R ５８ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (6), R ６１ , R ６２ , R ６３ and R ６４ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom. In general formula (7), R ７１ , R ７２ , R ７３ , R ７４ , R ７５ , R ７６ , R ７７ and R ７８ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom; Z represents an oxygen atom or a dicyanomethylene group (=C(CN) ２ ) In general formula (8), R ８１ , R ８２ , R ８３ , R ８４ , R ８５ , R ８６ , R ８７ and R ８８ each independently represents a hydrogen atom, an alkyl group, an alkoxy group, an aralkyl group, an aryl group, an alkoxycarbonyl group, or a halogen atom; Z represents an oxygen atom or a dicyanomethylene group (=C(CN) ２ )

9. 9. The image forming apparatus according to claim 8, wherein the electron transporting material is at least one of the compounds represented by the general formulas (1) and (2).

10. 2 . The image forming apparatus according to claim 1 , wherein the content of the electron transport material is 60% by mass or more and 80% by mass or less based on the total of the entire binder resin component of the undercoat layer and the electron transport material.

Images