A photosensitive layer of an electrophotographic photosensitive member is a single layer and contains a charge generating material, a binder resin, a first electron transport material, a second electron transport material, and a hole transport material. The binder resin includes a polyarylate resin. The polyarylate resin includes repeating units represented by formulas (1), (2), (3), and (4).

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The repeating unit (3) has a percentage content of greater than 0% and less than 50% to a total number of repeats of the repeating units (1) and (3). The repeating unit (4) has a percentage content of at least 35% and less than 70% to a total number of repeats of the repeating units (2) and (4).

An electrophotographic photosensitive member includes a conductive substrate and a photosensitive layer. The photosensitive layer is a single-layer photosensitive layer and contains a charge generating material, a hole transport material, an electron transport material, and a binder resin. The binder resin has a viscosity average molecular weight of at least 25,000 and no greater than 50,000. A strain at break of the photosensitive layer is at least 4.9% and no greater than 13.0%. A scratch resistant depth of the photosensitive layer is no greater than 0.50 m.

The present invention is to provide a charge transport substance having high resistance to stress within electrophotographic processes, an electrophotographic photoreceptor which has excellent high-speed responsiveness, shows a sufficient residual potential, and has high resistance to stress within electrophotographic processes, an electrophotographic cartridge, and an image-forming apparatus. The invention provides a charge transport substance having a specific structure. The invention further provides an electrophotographic photoreceptor including a photosensitive layer which contains the charge transport substance having a specific structure, an electrophotographic cartridge, and an image-forming apparatus, equipped with this electrophotographic photoreceptor.

An electrophotographic photosensitive member includes at least one photosensitive layer on which a first photosensitive layer disposed on an outermost side thereof. The first photosensitive layer contains a charge generating material, a binder resin including a polyarylate resin with repeating units (1), (2), (3), and (4), an electron transport material, and a hole transport material.

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The electron transport material includes a compound represented by formula (10), (11), or (12). The hole transport material includes compounds represented by formulas (21) and (22):

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A percentage content of a number of repeats of the repeating unit (3) to the total number of repeats of the repeating units (1) and (3) is greater than 0% and less than 50%. A percentage content of a number of repeats of the repeating unit (4) to the total number of repeats of the repeating units (2) and (4) is at least 35% and less than 70%.

An electrophotographic photosensitive member with suppressed potential variation even in the case that a protective layer including a cured material of a composition having a polymerizable functional group is used is provided. An electrophotographic photosensitive member including a support, a charge generation layer, a charge transport layer containing a charge transporting material, and a protective layer, in the order presented, wherein the charge transport layer contains a polycarbonate resin having a structure selected from a group A and a structure selected from a group B, and the protective layer includes a cured material of a composition containing a compound having at least a functional group selected from chain-polymerizable functional groups and sequential polymerizable functional groups.

An electrophotographic photoreceptor comprising at least a photosensitive layer on a conductive substrate, wherein the photosensitive layer is a laminate having a charge transport layer and a charge generation layer, the charge transport layer contains four or more types of compounds each having a maximum absorption wavelength falling within a wavelength range of from 300 nm to 600 nm in a tetrahydrofuran solution at 25? C., and maximum absorption wavelengths falling within the wavelength range of at least four types of the compounds of said four or more types of the compounds are separated from each other by 10 nm or more.

The present invention is to provide a charge transport substance having high resistance to stress within electrophotographic processes, an electrophotographic photoreceptor which has excellent high-speed responsiveness, shows a sufficient residual potential, and has high resistance to stress within electrophotographic processes, an electrophotographic cartridge, and an image-forming apparatus. The invention provides a charge transport substance having a specific structure. The invention further provides an electrophotographic photoreceptor including a photosensitive layer which contains the charge transport substance having a specific structure, an electrophotographic cartridge, and an image-forming apparatus, equipped with this electrophotographic photoreceptor.

An electrophotographic photosensitive member includes a support, an undercoat layer formed directly on the support, and a photosensitive layer formed on the undercoat layer, wherein when an ionization potential of the undercoat layer is represented by IPu, the IPu is 6.0 eV or higher, when an ionization potential of the support is represented by IPs, the IPs is lower than the IPu, the undercoat layer contains a compound (), when an ionization potential of the compound () is represented by IP, the IP is 5.0 eV or higher and 5.4 eV or lower, and the IPs and the IP satisfy the following relational expression (1):

[00001]$\begin{array}{cc}\mathrm{IPs}\mathrm{IP}-1..& \left(1\right)\end{array}$

An electrophotographic photosensitive member including: a support, a charge generating layer, and a charge transporting layer in this order, wherein the charge transporting layer contains: a compound represented by the formula (A-1), and at least one selected from the group consisting of a compound represented by the formula (A-2) and a compound represented by the formula (A-3).