An electrophotographic photoreceptor includes a conductive substrate, and a lamination type photosensitive layer disposed on the conductive substrate and including a charge generation layer and a charge transport layer in this order, in which the charge transport layer contains at least one resin selected from a polyester resin or a polycarbonate resin, and in a case where a Martens hardness and an indentation hardness, which are acquired by an indentation test performed on the charge transport layer to a depth of 0.5 μm, are respectively defined as HM (N/mm.sup.2) and nIT (N/mm.sup.2), Relational Equation (0) is satisfied, an elastic deformation modulus is 45% or greater and 70% or less, and a tensile elastic modulus of the charge transport layer is 2,300 MPa or greater and 5,000 MPa or less,

nIT=a×HM−b(a=2±0.2,b=100±20).  (0)

An electrophotographic photoreceptor includes a conductive substrate, and a lamination type photosensitive layer disposed on the conductive substrate and including a charge generation layer and a charge transport layer, in which the charge transport layer contains a polyester resin having a structure represented by Formula (1) at a terminal and a charge transport material, and in a case where a weight-average molecular weight Mw of the polyester resin is defined as A (×10,000), a value of a ratio M1/M2 of a mass M1 of the charge transport material to a mass M2 of an entire charge transport layer is defined as Cs, and an average thickness of the charge transport layer is defined as Ds (μm), expressions of 7≤A≤40, 0.28≤Cs≤0.55, 27≤Ds≤50, and 5.0≤(A×Ds)/(Cs×100)≤70 are satisfied,

##STR00001## in Formula (1), nd represents an integer of 0 or greater and 4 or less, nd number of Rd's each independently represent a hydrocarbon group having 1 or more and 4 or less carbon atoms, L represents an ether bond or a —O—C(═O)— group, and * represent a bonding portion.

An electrophotographic photoreceptor includes a conductive substrate, an undercoat layer disposed on the conductive substrate, and a lamination type photosensitive layer disposed on the undercoat layer and including a charge generation layer and a charge transport layer, in which the charge transport layer contains a charge transport material and a polyester resin, and in a case where an average thickness of the charge transport layer is defined as As (μm) and an average thickness of the undercoat layer is defined as Bs (μm), expressions 27≤As≤50, 10≤Bs≤40, and 0.70≤As/Bs≤4.80 are satisfied.

An image forming apparatus includes an image bearing member, a charger, a light exposure device, a development device, a transfer belt, a primary transfer device, a secondary transfer device, and a cleaning member. The cleaning member is pressed against a circumferential surface of the image bearing member and collects residual toner remaining on the circumferential surface of the image bearing member as a result of primary transfer of a toner. The transfer belt has a surface resistivity of at least 6 Log Ω and no greater than 11 Log Ω. A linear pressure of the cleaning member on the circumferential surface of the image bearing member is at least 10 N/m and no greater than 40 N/m. The image bearing member includes a conductive substrate and a photosensitive layer of a single layer. The image bearing member satisfies formula (1): $\begin{array}{cc}0.06\leqq \frac{V}{\left(Q/S\right)\times \left(d/{\epsilon }_r.Math.{\epsilon }_0\right)}.& \left(1\right)\end{array}$

An object of the present invention is to provide an electrophotographic photoreceptor which can prevent an increase in potential even using a fluorine resin in a charge transport layer, and can achieve both electrical properties and abrasion resistance, and present invention relates to a lamination type electrophotographic photoreceptor, in which a charge transport layer of the lamination type electrophotographic photoreceptor contains a compound having an E_homo of −4.550 eV or more based on structure optimization calculation by density functional calculation B3LYP/6-31G (d, p) and fluorine resin particles, and a content of the fluorine resin particles is 3% by weight to 20% by weight based on a total mass of the charge transport layer.

The object of the present invention is to provide a positive charging electrophotographic photoreceptor having high sensitivity, low residual potential, and excellent chargeability, and relates to a positive charging electrophotographic photoreceptor including a conductive support, a photosensitive layer, and a protective layer in this order, the photosensitive layer containing a charge generation substance, a positive hole transport substance, and an electron transport substance in the same layer, in which the positive hole transport substance includes at least one of the compounds represented by any one of the following formulas (1) to (5), and a binder resin of the protective layer is an alcohol-soluble thermoplastic resin, providing that the symbols in the formula are defined in the specification. ##STR00001##

An image forming method uses an electrophotographic photoreceptor and a toner for developing an electrostatic charge image. The image forming method has a charging step, an exposure step, a developing step, a transfer step and a cleaning step, wherein the charging step uses a contact charging device; the photoreceptor has a universal hardness value (HU) of 170 N/mm.sup.2 or more, and an elastic deformation ratio of 40% or more when a Vickers indenter is used in a predetermined environment and pushed by a maximum load of 2 mN. The toner for developing an electrostatic charge image contains toner base particles of a core-shell structure having a shell layer of 10% by mass or less with respect to a mass of a toner base particle on an outside of a resin constituting a core particle, and a solubility parameter value (SPs) of a resin constituting the shell layer is 10.75 or less.

An image forming apparatus includes an image bearing member, a charger, a light exposure device, and a development device. The charger charges a circumferential surface of the image bearing member to a positive polarity. The light exposure device exposes the charged circumferential surface of the image bearing member to light to form an electrostatic latent image on the circumferential surface of the image bearing member. The development device supplies a toner to the electrostatic latent image through application of a developing bias. The developing bias is a voltage of an alternating current voltage superimposed on a direct current voltage. The alternating current voltage has a frequency of 4 kHz or higher and 10 kHz or lower. The image bearing member includes a conductive substrate and a photosensitive layer of a single layer. The image bearing member satisfies formula (1)

[00001]$\begin{array}{cc}0.60\leqq \frac{V}{\left(Q/S\right)\times \left(d/{\mathrm{.Math.}}_r.Math.{\mathrm{.Math.}}_0\right)}& \left(1\right)\end{array}$

An image forming apparatus includes an image bearing member, a charger, a light exposure device, a development device, a transfer belt, a primary transfer device, a secondary transfer device, and a cleaning member. The cleaning member is pressed against a circumferential surface of the image bearing member and collects residual toner remaining on the circumferential surface of the image bearing member as a result of primary transfer of a toner. The transfer belt has a surface resistivity of at least 6 Log Ω and no greater than 11 Log Ω. A linear pressure of the cleaning member on the circumferential surface of the image bearing member is at least 10 N/m and no greater than 40 N/m. The image bearing member includes a conductive substrate and a photosensitive layer of a single layer. The image bearing member satisfies formula (1):

[00001]$\begin{array}{cc}0.60\leqq \frac{V}{\left(Q/S\right)\times \left(d/{\mathrm{.Math.}}_r.Math.{\mathrm{.Math.}}_0\right)}& \left(1\right)\end{array}$

Provided are an electrophotographic photoconductor being resistant to abrasion even in long-term use, having highly sensitive electric characteristics, being capable of maintaining a high retention rate, and being capable of providing a stable image without filming, a method of manufacturing the same, and an electrophotographic device. The photoconductor includes an electroconductive substrate (1), a charge generation layer (3), and a charge transport layer (4); the charge transport layer contains a hole transport material, a resin binder, an electron transport material, and an inorganic oxide; the charge generation layer contains a charge generation material; the masses of the hole transport material, the resin binder, the electron transport material, and the inorganic oxide in the charge transport layer respectively denoted by a to d satisfy 1.5≤b/a≤5.7, 0.005≤c/a≤0.35, 0.05≤d/a≤0.70, a≥c+d, and c/d≥0.01; the hole transport material contains a compound expressed by formula (A-1); and the charge generation material contains titanyl phthalocyanine having an exothermic peak at 251±5° C., a half-value width of the exothermic peak equal to or less than 15° C., and a heating value equal to or greater than 1.0 mJ/mg when a temperature rise condition is 20° C./min in differential scanning calorimetry, and having an X-ray diffraction peak at 27.2±0.3°.

##STR00001##