JP2014203010A - Image forming apparatus, image forming method, and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can suppress image trouble due to a residual potential on an electrophotographic photoreceptor represented by ghost images, while maintaining constant charge potential of the electrophotographic photoreceptor, so as to stably form high-quality images.SOLUTION: An image forming apparatus includes an electrophotographic photoreceptor, a charging member arranged on the electrophotographic photoreceptor, and an application member applying either voltage or current to the charging member so that the charging potential of the electrophotographic photoreceptor after charging and before exposure becomes a saturated charging potential. The image forming apparatus further includes at least charging means for charging the surface of the electrophotographic photoreceptor, exposing means for exposing the charged surface of the electrophotographic photoreceptor to form an electrostatic latent image, developing means for developing the electrostatic latent image using toner to form a visible image, and transfer means for transferring the visible image to a recording medium.

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and a plotter, an image forming method, and a process cartridge.

In an electrophotographic image forming method, an electrostatic latent image is formed on an electrophotographic photosensitive member, and a charged toner is attached to the electrostatic latent image to form a visible image. After the image is finally transferred to a recording medium such as paper, it is fixed on the recording medium by heat or pressure to form an output image.
The electrophotographic image forming method uses a two-component development method using frictional charging generated by stirring and mixing the toner and the carrier by a method of charging the toner for visualization, and a carrier. In other words, it is roughly divided into a one-component development system that applies charge to the toner.
The one-component development method is classified into a magnetic one-component development method and a non-magnetic one-component development method depending on whether magnetic force is used for holding toner particles on the developing roller.
Conventionally, copiers, printers, multifunction devices, etc. that require high speed and image reproducibility have adopted a two-component development system that can meet the requirements of toner charging stability, start-up stability, and long-term image quality stability. Therefore, the one-component development method is often used in small printers, facsimiles, and the like, which have great demands for space saving and cost reduction.

Recently, the colorization of output images has progressed, and the demand for higher image quality and stabilization of image quality has become stronger than ever. Usually, the latent image is formed on the electrophotographic photosensitive member after the electrophotographic photosensitive member is uniformly charged, or the electrophotographic photosensitive member is charged and a target image pattern is formed by a writing device using a laser beam. A latent image pattern corresponding to the above is formed.
Therefore, in order to obtain a stable image, the latent image is formed and the latent image is visualized, that is, the development is stabilized. It is important to maintain uniform charging and to suppress variation in charging potential in the latent image forming portion.

In order to solve these problems, non-contact charging devices using corona discharge such as corotron and scorotron, comb electrodes, and the like have been proposed. Among these, a charging device using corona discharge is an effective method for charging uniformity, and is used in many electrophotographic image forming apparatuses.
On the other hand, in a charging device using corona discharge, a large amount of ozone generated due to discharge is unavoidable, and for the purpose of reducing ozone generation, a contact charging method using a charging member such as a charging roller or a charging brush, Proximity charging methods have been proposed.

  Further, the charging potential of the electrophotographic photosensitive member is controlled to a constant value by detecting the time-dependent deviation of the charging potential and the deviation due to use from the viewpoint of improving the image quality, particularly the reproducibility of the halftone portion. For this reason, the charging potential is controlled and used in a region where the amount of charge applied to the electrophotographic photosensitive member and the charging potential of the electrophotographic photosensitive member are in a substantially proportional relationship.

For example, it has a detection means and a correction means for detecting the occurrence of a ghost image on the electrophotographic photosensitive member, and obtains at least one of the surface potential difference and the toner adhesion amount difference of the electrophotographic photosensitive member by the detection means, A method of correcting the image forming condition of the electrophotographic photosensitive member based on the image forming result of the pattern for detecting the occurrence of the ghost image and confirming the occurrence of the ghost image has been proposed (see Patent Document 1). If the image forming conditions of the electrophotographic photosensitive member are corrected as in this proposal, the generation of ghost images can be suppressed.
However, this proposed technique requires detection means and correction means for detecting the occurrence of a ghost image on the electrophotographic photosensitive member. For this reason, there is a concern that not only the cost is disadvantageous, but also the image forming process becomes complicated and hinders the speeding up of the image output.

  Further, the residual potential of the image on the surface of the electrophotographic photosensitive member is detected by the residual potential detecting means on the downstream side in the rotation direction of the electrophotographic photosensitive member from the transfer means and upstream from the auxiliary charging means, and based on the detection result. There has been proposed a method of erasing the residual history of an image by controlling a bias application condition to the auxiliary charging means (see Patent Document 2). According to this proposed method, the generation of a ghost image can be suppressed, but a residual potential detecting means for the image on the surface of the electrophotographic photosensitive member is required, which is disadvantageous in terms of cost.

  Further, it is generated by pre-transfer exposure using a pre-charging bias unit that applies a pre-charging bias potential having the same polarity as the charging polarity of the charging unit and greater than the charging start voltage to the electrophotographic photosensitive member between application of the lubricant and charging. A method of deleting the residual history of an image has been proposed (see Patent Document 3). According to this proposed method, generation of a ghost image can be suppressed, but a pre-charging bias unit is required, which is disadvantageous in terms of cost.

  Therefore, while maintaining the charging potential of the electrophotographic photosensitive member uniformly, it is possible to suppress image defects caused by the residual potential on the electrophotographic photosensitive member typified by a ghost image, and to stably produce a high-quality image. It is desired to provide an image forming apparatus that can form images.

  An object of the present invention is to solve the above-described problems and achieve the following objects. That is, the present invention can suppress image defects caused by the residual potential on the electrophotographic photosensitive member typified by a ghost image, while maintaining the charging potential of the electrophotographic photosensitive member uniformly, and has high quality. An object is to provide an image forming apparatus capable of stably forming an image.

The image forming apparatus of the present invention as a means for solving the problems includes an electrophotographic photosensitive member, a charging member disposed on the electrophotographic photosensitive member, and charging of the electrophotographic photosensitive member before post-charging exposure. An application member that applies either voltage or current to the charging member so that the potential becomes a saturated charging potential, and charging means for charging the surface of the electrophotographic photosensitive member;
Exposure means for exposing the charged electrophotographic photosensitive member surface to form an electrostatic latent image; and
Developing means for developing the electrostatic latent image with toner to form a visible image;
Transfer means for transferring the visible image to a recording medium;
At least.

  According to the present invention, the conventional problems can be solved, the object can be achieved, and the electrophotographic photoreceptor represented by a ghost image can be maintained while maintaining the charged potential of the electrophotographic photoreceptor uniformly. It is possible to provide an image forming apparatus that can suppress image defects caused by the residual potential and can stably form a high-quality image.

FIG. 1 is a schematic diagram showing the relationship between the amount of charge applied to the electrophotographic photosensitive member and the charging potential. FIG. 2 is a schematic view showing an example of the image forming apparatus of the present invention. FIG. 3 is a schematic view showing an example of the process cartridge of the present invention. FIG. 4 is a schematic view showing an example of the layer structure of the electrophotographic photosensitive member. FIG. 5 is a schematic view of an apparatus for measuring the capacitance of the electrophotographic photosensitive member.

(Image forming apparatus and image forming method)
The image forming apparatus of the present invention includes at least an electrophotographic photosensitive member, a charging unit, an exposure unit, a developing unit, and a transfer unit, and further includes other units as necessary. .
The image forming method of the present invention includes at least a charging step, an exposure step, a development step, and a transfer step, and further includes other steps as necessary.

  The image forming method of the present invention can be preferably carried out by the image forming apparatus of the present invention, the charging step can be performed by the charging unit, the exposure step can be performed by the exposing unit, The developing step can be performed by the developing unit, the transferring step can be performed by the transferring unit, and the other steps can be performed by the other unit.

  In an electrophotographic image forming apparatus, it is important to obtain a constant image quality evenly in an image area. Therefore, it is preferable to make the charging potential on the electrophotographic photosensitive member as constant as possible, and various proposals have been made to achieve this point. However, in these proposals, in order to make the charged potential of the electrophotographic photosensitive member uniform, some additional members and mechanisms are required, which causes a problem of increasing costs.

  As a result of intensive studies by the present inventors in order to solve the above problems, the charging potential of the electrophotographic photosensitive member used in the image forming process is substantially reduced to the charging potential (saturated charging potential) that can be maintained by the electrophotographic photosensitive member. By matching, it is possible to stably form a uniform latent image potential without adding other members or mechanisms, and by forming an image with this latent image potential, stable image quality can be obtained as a final image. I found out.

Here, FIG. 1 is a schematic view showing the relationship between the applied charge amount of the electrophotographic photosensitive member and the charging potential. In FIG. 1, the horizontal axis represents the amount of charge applied to the electrophotographic photosensitive member, and the vertical axis represents the value of the charging potential of the electrophotographic photosensitive member with respect to the amount of charge applied. In a range smaller than the amount of charge that can be held by the electrophotographic photosensitive member, the charging potential of the electrophotographic photosensitive member increases in proportion to the amount of applied charge applied to the electrophotographic photosensitive member. Charges cannot be held in the body, and excess charges leak and show a constant charging potential.
V0 in FIG. 1 is a charging potential (saturated charging potential) that can be maintained by the electrophotographic photosensitive member. Further, the minimum applied charge amount for obtaining the saturated charging potential is Q0. The applied charge amount (coulomb = ampere second) is expressed in units using the charging current amount (ampere) of the electrophotographic photosensitive member, the charging width (meter), and the moving speed of the electrophotographic photosensitive member (meter per second). It can also be calculated as a value per area.

  Usually, the charging potential of the electrophotographic photosensitive member is controlled within a range in which a proportional relationship between the applied charge amount and the charging potential is established (generally B range in FIG. 1). In this control range, a constant charging potential can be finely controlled, which is advantageous when multi-value control of the latent image potential is performed by controlling the exposure intensity to express the halftone of the image. However, the control range is easily affected by the residual potential, which is a problem to be solved by the present invention, and an incidental mechanism as described in the prior art is necessary to suppress image defects such as ghost images. It becomes.

  At present, the digitization of image forming apparatuses has progressed, and the above-described multi-value control of the latent image potential does not necessarily have to be performed, and so-called area gradation image formation in which the density of an image is adjusted by the area of the latent image is widely used. It has been broken. In this case, it is not always necessary to express halftone by multi-value control of the latent image potential. Therefore, it has been found that the influence of the residual potential can be avoided by using the charging potential that can be maintained by the electrophotographic photosensitive member as the potential before exposure.

In order to set the charging potential of the electrophotographic photosensitive member before exposure to a charging potential (saturated charging potential) that can be maintained by the electrophotographic photosensitive member, a charge exceeding Q0 may be applied to the electrophotographic photosensitive member. If the amount of applied charge per unit area (that is, the amount of current) is too large, electrostatic damage to the electrophotographic photosensitive member is increased, and the durability life may be reduced. For this reason, in the present invention, it is preferable to provide a surface layer containing a cross-linked product obtained by cross-linking the surface layer composition on the outermost surface of the electrophotographic photoconductor so that the electrophotographic photoconductor is resistant to electrostatic damage. It was found that stress properties can be ensured, the charging potential can be made uniform in the entire region, and an image with high image quality without image unevenness can be obtained.
This simplifies the configuration of the image forming apparatus and reduces the cost, thereby providing a high-quality image at low cost. The effect is particularly significant in an image forming apparatus that is reduced in size and cost.

In the present invention, the charging means includes a charging member disposed on the electrophotographic photosensitive member, and the charging member so that a charging potential of the electrophotographic photosensitive member before exposure after charging becomes a saturated charging potential. And an application member for applying either voltage or current. As a result, the electrophotographic photosensitive member can be stably and uniformly charged, the occurrence of a ghost image due to the residual image potential of the electrophotographic photosensitive member can be prevented, and an image forming apparatus capable of obtaining good image quality can be provided at a low cost. Cost can be reduced.
Here, the saturated charging potential means the surface potential when the maximum amount of charge that can be held by the electrophotographic photosensitive member is held.
Whether the charging potential of the electrophotographic photosensitive member is a saturated charging potential is determined by measuring the surface potential while applying an electric charge to the electrophotographic photosensitive member until an excessive amount of electric charge is obtained. This can be confirmed by plotting the surface potential and ascertaining whether the surface potential remains unchanged. Further, the saturation charging potential can be measured, for example, by the surface potential that has not changed (becomes in an equilibrium state) at this time.

The electrostatic capacity of the electrophotographic photosensitive member is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1 nF / cm ^{2 to} 0.2 nF / cm ² .
The capacitance of the electrophotographic photosensitive member can be measured, for example, by the method described in JP-A-2008-216704. That is, it can be measured by using the electrostatic capacity measuring device of the electrophotographic photosensitive member shown in FIG. 5 includes an exposure lamp 111 for exposing the photosensitive drum 101, a surface potential meter probe 103 for measuring the potential of the photosensitive drum 101, a corona charger 106 for charging the photosensitive drum 101, A power source 107 for supplying a voltage to the corona charger 106, a switch 113 of the power source 107, a light source 108 for neutralizing the photosensitive drum 101, a lamp box 110 for covering the exposure lamp 111, and an electrophotographic photosensitive member for exposing the exposed light. The exposure guide box 102 guides to the irradiation surface, and the stop 112 for adjusting the illuminance.
In this electrophotographic photoreceptor electrostatic capacity measuring device, the photoreceptor drum 101 is rotated by a motor 114 and rotates in the direction of the arrow in FIG. At this time, a high voltage is output from the power source 107, and the photosensitive drum 101 is charged by the corona charger 106. The current (passing current) passing through the photosensitive drum 101 at the time of charging is measured and sent to the signal processing circuit 105. A smoothing circuit (not shown) is incorporated in the signal processing circuit 105, and the passing current is smoothed by the smoothing circuit. Thereafter, it is converted into a digital signal by the A / D converter 116 and sent to the controller 115, where the digital signal is processed.

  Further, the surface potential of the photosensitive drum 101 is sent from the surface potential meter probe 103 to the surface potential meter 104 as a monitor unit, monitored, and sent to the signal processing circuit 109. Thereafter, the data is converted by the A / D converter 116, and then sent to the controller 115 for arithmetic processing. The controller 115 is connected to a motor driver in a motor 114 that rotates the photosensitive drum 101. In the motor driver, a function for outputting the rotation speed and a function for remotely controlling the rotation speed are added, so that the rotation speed control and the rotation speed recognition are possible.

  The units around the photosensitive drum 101 are ON / OFF controlled by a digital relay output. Further, the post-exposure potential of the photosensitive drum 101 can be measured by using the exposure lamp 111, and when removing the surface potential of the photosensitive drum 101, it can be removed by using the static elimination light source 108. In addition, it is possible to evaluate characteristics such as charging characteristics and light attenuation characteristics of the photosensitive drum 101.

As the exposure means (exposure lamp 111), for example, a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), electroluminescence (EL), or the like can be used. .
In order to irradiate only light in a desired wavelength range, various filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used. A neutral density filter can also be used to lower the value. The diaphragm 112 for adjusting the illuminance may be a neutral density filter that can adjust the illuminance without using the diaphragm.
By using the apparatus for measuring the electrostatic capacitance of the electrophotographic photosensitive member shown in FIG. 5, the drum rotation speed, the surface potential / passing current sampling interval are adjusted, and the set discharge current is changed. The electric capacity can be calculated.

The absolute value of the charging potential of the electrophotographic photosensitive member is not particularly limited and can be appropriately selected according to the purpose, but is preferably 200V to 400V. If the absolute value of the charging potential is less than 200V, the potential difference required for development cannot be sufficiently ensured, and the image density may be lowered. Part may be easily contaminated.
The charging potential of the electrophotographic photosensitive member can be measured using, for example, a surface potentiometer (manufactured by Trek, MODEL 344) separately incorporated in an image forming apparatus.

The absolute value of the applied charge amount of the electrophotographic photosensitive member is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 25 nC / cm ^{2 to} 55 nC / cm ² .
The applied charge amount of the electrophotographic photosensitive member is, for example, a digital multimeter (AD 7451A manufactured by Advantest Corporation) in which the current value between the conductive support of the electrophotographic photosensitive member and the ground point is separately incorporated in the image forming apparatus. It can be calculated by measuring and dividing by the passage area calculated from the charging width and linear velocity of the electrophotographic photosensitive member.

<Electrophotographic photoreceptor>
The electrophotographic photoreceptor is not particularly limited and may be appropriately selected depending on the intended purpose.The electrophotographic photoreceptor has a support, an undercoat layer on the support, a photosensitive layer, and a surface layer. It is preferable to have other layers as required.

  In general electrophotographic photoreceptors, materials and layer configurations are selected so that more charged charges can be retained. The electrophotographic photosensitive member used in the image forming apparatus of the present invention also needs to maintain a charged charge, but the existing electrophotographic photosensitive member may maintain a charged potential that is too high. In addition to the electrostatic capacity of the electrophotographic photoreceptor, the dark potential and the withstand voltage contribute to the charge potential that can be maintained, so that a surplus charge can be stably released from the surface of the electrophotographic photoreceptor. It is preferable to do.

<< Support >>
Examples of the support include those having a volume resistivity of 10 ¹⁰ Ω · cm or less, for example, metals such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, tin oxide, indium oxide, etc. The metal oxide of the above is coated by film or cylindrical plastic or paper by vapor deposition or sputtering, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc. After the conversion, a tube subjected to surface treatment such as cutting, superfinishing or polishing can be used. An endless nickel belt or an endless stainless steel belt can also be used as a support.

In addition, what coated and disperse | distributed electroconductive powder to the suitable binder resin on a support body can also be used as said support body.
Examples of the conductive powder include carbon black, acetylene black; metal powder such as aluminum, nickel, iron, nichrome, copper, zinc, and silver; metal oxide powder such as conductive tin oxide and ITO. Can be mentioned.
Examples of the binder resin include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, and polyacetic acid. Vinyl, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate, ethyl cellulose, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin , Phenol resin, alkyd resin, and the like. These may be used individually by 1 type and may use 2 or more types together.
The conductive layer can be formed by applying a coating solution in which the conductive powder and the binder resin are dispersed in a solvent. Examples of the solvent include tetrahydrofuran, dichloromethane, methyl ethyl ketone, toluene, and the like.
Furthermore, by a heat shrinkable tube in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, polytetrafluoroethylene-based fluororesin on a cylindrical substrate. Those provided with a conductive layer can also be used favorably as the support.
Among these, from the viewpoints of alignment accuracy during image formation, dimensional stability, and the like, the support is preferably a hard circular tube or a thin tube with sufficient tensile strength.

  There is no restriction | limiting in particular as a diameter of the said support body, Although it can select suitably according to the objective, 20 mm-150 mm are preferable, 24 mm-100 mm are more preferable, 28 mm-70 mm are especially preferable. If the diameter is less than 20 mm, it may be physically difficult to arrange the charging, exposure, development, transfer, and cleaning steps around the electrophotographic photosensitive member. If the diameter exceeds 150 mm, image formation is performed. The device can become large and take up space.

<< undercoat layer >>
The undercoat layer is formed between the support and the photosensitive layer, and may be a single layer or a plurality of layers.
The undercoat layer includes a resin as a main component, a material including an electron-accepting material, N-type semiconductive particles, and a resin as main components, and a metal oxide obtained by chemically or electrochemically oxidizing a support surface. Membrane, etc. Among these, those containing an electron accepting material, N-type semiconductor particles, and a resin are preferable.

The electron-accepting material is not particularly limited and may be appropriately selected depending on the intended purpose. However, a material having high affinity with N-type semiconductor particles is used. For example, an anthraquinone structure having a hydroxyl group is used as a basic skeleton. And a fullerene derivative.
Examples of the compound having a hydroxyl group-containing anthraquinone structure as a basic skeleton include hydroxyanthraquinone compounds and aminohydroxyanthraquinone compounds. Specifically, 1,2-dihydroxy-9,10-anthraquinone, 1,4 -Dihydroxy-9,10-anthraquinone, 1,5-dihydroxy-9,10-anthraquinone, 1,2,4-trihydroxy-9,10-anthraquinone, 1-hydroxyanthraquinone, 2-amino-3-hydroxyanthraquinone, 1-amino-4-hydroxyanthraquinone and the like. These may be used individually by 1 type and may use 2 or more types together.
Examples of the fullerene derivative include phenyl C61 butyric acid methyl ester, phenyl C61 butyric acid butyl ester, phenyl C61 butyric acid isobutyl ester, and the like. These may be used individually by 1 type and may use 2 or more types together.

As the N-type semiconductor particles is not particularly limited and may be appropriately selected depending on the purpose, for example, zinc oxide, tin dioxide, indium oxide, ITO _{(e.g., In 2 O 3: SnO 2} = 90: 10 (Mass%)) or other metal oxides, particles in which these metal oxides are coated on the surface of inorganic oxide particles, those in which these metal oxides are aluminum-doped (aluminum-doped zinc oxide), etc. Can be mentioned.

  There is no restriction | limiting in particular as said resin, According to the objective, it can select suitably, For example, thermoplastic resins, such as polyamide, polyvinyl alcohol, casein, methylcellulose; Acrylic, phenol, melamine, alkyd, unsaturated polyester, epoxy And thermosetting resins. These may be used individually by 1 type and may use 2 or more types together.

  The undercoat layer is formed by applying an undercoat layer coating solution in which the electron-accepting material, the N-type semiconductor particles, the resin, and other components, if necessary, are dissolved or dispersed in a solvent on a support and drying. Can be formed. You may add additives, such as a plasticizer, a leveling agent, antioxidant, a lubricant, to the said charge transport layer coating liquid as needed.

  The solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, and acetone. These may be used individually by 1 type and may use 2 or more types together. Among these, non-halogen solvents are preferable from the intention of reducing environmental burdens, and cyclic ethers such as tetrahydrofuran, dioxolane, and dioxane; aromatic hydrocarbons such as toluene and xylene, or derivatives thereof are particularly preferable.

  The average thickness of the undercoat layer is not particularly limited and can be appropriately selected according to the purpose. However, it is preferably 0.5 μm to 20 μm, and charge generation from the support is more reliably prevented. From the viewpoint of quickly decaying the charge generated in the layer and the surplus charge at the time of charging, 2 μm to 15 μm is more preferable.

The photosensitive layer is not particularly limited and may be appropriately selected depending on the purpose. For example, a photosensitive layer having a single layer structure including a charge generation material, a charge transport material, and a binder resin, a charge generation layer, And a photosensitive layer having a multilayer structure having a charge transport layer.
The photosensitive layer having the laminated structure includes a forward layer type having a charge transport layer containing a charge transport material and a binder resin on a charge generation layer containing a charge generation material and a binder resin, and a charge transport layer And a reverse layer type having a charge generation layer thereon.

<< Photosensitive layer of laminated structure >>
-Charge generation layer-
The charge generation layer preferably contains at least a charge generation material, preferably contains a binder resin, and further contains other components as necessary.

-Charge generation material-
The charge generation material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include compounds having a tetrabenzoporphyrin skeleton.
As the compound having the tetrabenzoporphyrin skeleton, for example, unsubstituted tetrabenzoporphyrin, and copper, silver, gold, platinum, nickel, calcium, strontium, barium, titanium, manganese, iron, cobalt, nickel, as the central metal, Examples thereof include complexes into which aluminum, gallium and the like are introduced, and compounds having an alkyl group, phenyl group, halogen group, hydroxy group, amino group, nitro group, carboxyl group and the like as characteristic groups. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the charge generating substance include azo pigments such as monoazo pigments, bisazo pigments, trisazo pigments, and tetrakisazo pigments; triarylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, cyanine Organic dyes, styryl dyes, pyrylium dyes, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indanthrone pigments, squarylium pigments, phthalocyanine pigments, etc. Pigments or dyes; inorganic materials such as cadmium sulfide, zinc oxide, and titanium oxide. These may be used individually by 1 type and may use 2 or more types together.

--Binder resin--
Examples of the binder resin are moderately electrically insulating and include known thermoplastic resins, thermosetting resins, photocurable resins, and photoconductive resins.
Examples of the binder resin include polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, ethylene-vinyl acetate copolymer, polyvinyl butyral, polyvinyl Thermoplastic resins such as acetal, polyester, phenoxy resin, (meth) acrylic resin, polystyrene, polycarbonate, polyarylate, polysulfone, polyethersulfone, ABS resin, phenol resin, epoxy resin, urethane resin, melamine resin, isocyanate resin , Alkyd resins, silicone resins, thermosetting resins such as thermosetting acrylic resins, polyvinyl carbazole, polyvinyl anthracene, polyvinyl pyrene, and the like. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, antioxidant, a plasticizer, a leveling agent, etc. are mentioned.

-Antioxidant-
Examples of the antioxidant include phenolic compounds, paraphenylenediamines, hydroquinones, organic sulfur compounds, and organic phosphorus compounds.

  Examples of the phenol compound include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-ethyl- 6-t-butylphenol), 4,4′-thiobis- (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1,3 Tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxy Benzyl) benzene, tetrakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, bis [3,3′-bis (4′-hydroxy-3 ′) -T-butylphenyl) butyric acid] cricol ester, tocopherols, and the like.

  Examples of the paraphenylenediamines include N-phenyl-N′-isopropyl-p-phenylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl- p-phenylenediamine, N, N′-di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine, and the like.

Examples of the hydroquinones include 2,5-di-t-octyl hydroquinone, 2,6-didodecyl hydroquinone, 2-dodecyl hydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methyl. And hydroquinone and 2- (2-octadecenyl) -5-methylhydroquinone.
Examples of the organic sulfur compounds include dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate, and the like. It is done.
Examples of the organic phosphorus compounds include triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine, and the like.

  These compounds are known as antioxidants such as rubbers, plastics and fats and oils, and commercially available products can be easily obtained. The content of the antioxidant is preferably 0.01% by mass to 10% by mass with respect to the total mass of the charge generation layer.

  As said plasticizer, what is used as a plasticizer of common resins, such as dibutyl phthalate and dioctyl phthalate, can be used as it is, for example. The content of the plasticizer is preferably 0% by mass to 30% by mass with respect to the total mass of the charge generation layer.

Examples of the leveling agent include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil; polymers having a perfluoroalkyl group in the side chain, and oligomers.
The content of the leveling agent is preferably 0% by mass to 1% by mass with respect to the total mass of the charge generation layer.

  In the charge generation layer, the support includes a charge generation layer coating solution in which the charge generation material is dispersed in a solvent together with a binder resin and other components as necessary using a ball mill, an attritor, a sand mill, an ultrasonic wave, or the like. Or it can form by apply | coating on the said undercoat and drying.

  The solvent is not particularly limited and may be appropriately selected depending on the intended purpose.For example, isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, mono Examples include chlorobenzene, cyclohexane, toluene, xylene, ligroin, and the like. These may be used individually by 1 type and may use 2 or more types together.

A method for forming the charge generation layer using the charge generation layer coating liquid is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a dip coating method, a spray coating method, a bead coating method, a nozzle Examples thereof include a coating method, a spinner coating method, and a ring coating method. After application, it is dried by heating in an oven or the like. There is no restriction | limiting in particular as said drying temperature, Although it can select suitably according to the objective, 50 to 60 degreeC is preferable.
There is no restriction | limiting in particular in the average thickness of the said charge generation layer, Although it can select suitably according to the objective, 0.01 micrometer-5 micrometers are preferable, and 0.1 micrometer-2 micrometers are more preferable.

-Charge transport layer-
The charge transport layer contains a charge transport material and a binder resin, and further contains other components as necessary.

-Charge transport material-
The charge transport material is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include anthracene derivatives, pyrene derivatives, carbazole derivatives, tetrazole derivatives, metallocene derivatives, phenothiazine derivatives, pyrazoline compounds, hydrazone compounds, styryl. Compounds, styrylhydrazone compounds, enamine compounds, butadiene compounds, distyryl compounds, oxazole compounds, oxadiazole compounds, thiazole compounds, imidazole compounds, triphenylamine derivatives, phenylenediamine derivatives, aminostilbene derivatives, triphenylmethane derivatives, etc. It is done. These may be used individually by 1 type and may use 2 or more types together.

-Binder resin-
The binder resin is not particularly limited and may be appropriately selected depending on the intended purpose. For example, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester , Polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy resin, polycarbonate, cellulose acetate, ethyl cellulose, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly (N-vinyl carbazole) ), Acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin, alkyd resin, and the like. These may be used individually by 1 type and may use 2 or more types together.

  There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, antioxidant, a plasticizer, a leveling agent, etc. are mentioned. Examples of the antioxidant, the plasticizer, and the leveling agent include the same as those in the charge generation layer.

  The charge transport layer comprises a charge transport layer coating solution prepared by dissolving or dispersing the charge transport material, the binder resin, and other components in a solvent, if necessary, the charge generation layer, the support, or the undercoat layer. It can be formed by coating on top and drying.

  The solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, and acetone. These may be used individually by 1 type and may use 2 or more types together. Among these, non-halogen solvents are preferable from the intention of reducing environmental burdens, and cyclic ethers such as tetrahydrofuran, dioxolane, and dioxane; aromatic hydrocarbons such as toluene and xylene, or derivatives thereof are particularly preferable.

  The average thickness of the charge transport layer is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 5 μm to 40 μm and more preferably 15 μm to 35 μm from the viewpoint of resolution and responsiveness.

<< Photosensitive layer with a single layer structure >>
The photosensitive layer having a single layer structure is a photosensitive layer in which a charge generation material and a charge transport material are dispersed or dissolved in a binder resin to realize a charge generation function and a charge transport function in one layer.
For the charge generation material, charge transport material, binder resin, solvent, and various additives used for the single layer photosensitive layer, any material contained in the charge generation layer and the charge transport layer is used. It is possible.
As the binder resin, in addition to the binder resin mentioned in the charge transport layer, the binder resin mentioned in the charge generation layer may be mixed and used. The content of the charge generation material with respect to 100 parts by mass of the binder resin is not particularly limited and can be appropriately selected according to the purpose, but is preferably 5 parts by mass to 40 parts by mass, and 10 parts by mass to 30 parts by mass. Is more preferable. The content of the charge transport material is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0 part by mass to 190 parts by mass, and more preferably 50 parts by mass to 150 parts by mass.

The photosensitive layer having the single layer structure is a coating solution in which the charge generation material, the charge transport material, and the binder resin are dissolved or dispersed in a solvent such as tetrahydrofuran, dioxane, dichloroethane, methyl ethyl ketone, cyclohexane, cyclohexanone, toluene, xylene, or the like. Can be formed by coating using a method such as dip coating, spray coating, bead coating, or ring coating.
There is no restriction | limiting in particular as average thickness of the photosensitive layer of the said single layer structure, According to the objective, it can select suitably, 10 micrometers-50 micrometers are preferable.

There is no restriction | limiting in particular as total thickness of the said undercoat layer and a photosensitive layer, Although it can select suitably according to the objective, 20 micrometers-60 micrometers are preferable.
When the total thickness of the undercoat layer and the photosensitive layer is within the numerical range, it is possible to form a uniform visible image over a long period of time, and therefore, it is possible to provide a stable image forming apparatus with little temporal variation. it can. If the average thickness is less than 20 μm, it may be difficult to ensure electrical uniformity as an electrophotographic photosensitive member, and if it exceeds 60 μm, the resolution of the electrostatic latent image may be reduced. is there.

<< surface layer >>
The surface layer contains a crosslinked product obtained by crosslinking the surface layer composition, and is provided on the outermost surface of the electrophotographic photosensitive member.
The surface layer composition contains a polymer having higher mechanical strength than the photosensitive layer, and further contains other components as necessary.
The polymer is not particularly limited as long as it contains a crosslinking component, and may be either a thermoplastic resin or a thermosetting resin, but has high mechanical strength and the ability to suppress wear due to friction with the cleaning blade. A thermosetting resin is preferable because of its extremely high point.

The polymer is preferably transparent to writing light at the time of image formation, and preferably excellent in insulation, mechanical strength, and adhesiveness. For example, ABS resin, ACS resin, olefin-vinyl monomer copolymer, Chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylbenten , Polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, polyvinylidene chloride, epoxy resin, etc. It is. These may be used individually by 1 type and may use 2 or more types together.
The polymer preferably has at least a main component cross-linked, and a cross-linking agent having a polyfunctional acryloyl group, carboxyl group, hydroxyl group, amino group or the like in order to increase the electrical strength or mechanical strength of the polymer. More preferably, it contains a cross-linked product cross-linked by. Thereby, the electrical strength and mechanical strength of the surface layer are increased, and the stress applied to the electrophotographic photosensitive member during charging can be greatly reduced.
There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, a charge transport substance, antioxidant, a plasticizer, a leveling agent, etc. are mentioned.

  The method for forming the surface layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the surface layer coating solution containing the polymer and other components may be used as the surface of the photosensitive layer in the electrophotographic photoreceptor. Examples of the method include forming by heating and drying after coating.

  The coating method for the surface layer coating solution is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a dip coating method, a spray coating method, a bead coating method, and a ring coating method. .

There is no restriction | limiting in particular in the average thickness of the said surface layer, Although it can select suitably according to the objective, 0.5 micrometer-10 micrometers are preferable and 1 micrometer-8 micrometers are more preferable.
When the average thickness is less than 0.5 μm, the thickness of the surface layer is too thin, and the electrical strength and mechanical strength may decrease. When the average thickness exceeds 10 μm, the charge transport material is contained in the surface layer. If a polymer having a charge transport capability is not used as a polymer used for the surface layer, problems such as a decrease in sensitivity of the photoreceptor, an increase in potential after exposure, and an increase in residual potential may occur.

<< Other layers >>
There is no restriction | limiting in particular as said other layer, According to the objective, it can select suitably, For example, an intermediate | middle layer etc. are mentioned.

  Here, FIG. 4 is a schematic sectional view showing an example of the electrophotographic photosensitive member. 4 includes a support 110, an undercoat layer 111, a photosensitive layer 114, and a surface layer 115. The photosensitive layer 114 includes a charge generation layer 112, a charge transport layer, and the like. 113.

<Charging step and charging means>
The charging step is a step of charging the surface of the electrophotographic photosensitive member, and is performed by the exposure unit.
The charging means is not particularly limited as long as it can apply a voltage to the surface of the electrophotographic photosensitive member to be uniformly charged, and can be appropriately selected according to the purpose. It is roughly divided into a contact type charging means for charging by contact with the electrophotographic photosensitive member, and (2) a non-contact type charging means for charging in a non-contact manner with the electrophotographic photosensitive member.

Examples of the contact type charging means (1) include a conductive or semiconductive charging roller, a magnetic brush, a fur brush, a film, and a rubber blade. Among these, the charging roller can significantly reduce the amount of ozone generated compared to corona discharge, and is excellent in stability during repeated use of the electrophotographic photosensitive member, and is effective in preventing image quality deterioration. .
The magnetic brush includes, for example, a non-magnetic conductive sleeve that supports various ferrite particles such as Zn—Cu ferrite, and a magnet roll included in the sleeve. The fur brush is formed, for example, by winding or pasting a fur conductively treated with carbon, copper sulfide, metal, metal oxide, or the like around a metal or a conductive metal core.
Examples of the non-contact charging means (2) include, for example, a non-contact charger using a corona discharge, a needle electrode device, a solid discharge element; a conductive material disposed with a small gap with respect to the electrophotographic photosensitive member. Alternatively, a semiconductive charging roller can be used.

  Among these, the charging unit preferably includes a roller-shaped charging member disposed in contact with the electrophotographic photosensitive member and a voltage applying member that applies a DC voltage to the roller-shaped charging member. Thereby, the power supply cost of the charging voltage applied to the roller-shaped charging member can be reduced.

<Exposure process and exposure means>
The exposure can be performed, for example, by exposing the surface of the electrophotographic photosensitive member imagewise using the exposure unit.
The optical system in the exposure is roughly classified into an analog optical system and a digital optical system. The analog optical system is an optical system that projects an original directly onto an electrophotographic photosensitive member by an optical system, and the digital optical system receives image information as an electrical signal, converts this into an optical signal, and converts it into an electrophotographic photosensitive device. It is an optical system that exposes and forms a body.
The exposure unit is not particularly limited as long as the surface of the pre-electrophotographic photosensitive member charged by the charging unit can be exposed like an image to be formed, and can be appropriately selected according to the purpose. However, various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, a liquid crystal shutter optical system, and an LED optical system can be used.
It is preferable that the electrostatic latent image potential on the electrophotographic photosensitive member is a binary electrostatic latent image potential of an exposed portion and a non-exposed portion by an exposure unit. Thereby, since an intermediate value is not taken as the latent image potential, an image with stable quality can be obtained.
In the present invention, an optical backside system that performs imagewise exposure from the backside of the electrophotographic photosensitive member may be employed.

<Development process and development means>
The developing step is a step of developing the electrostatic latent image using a toner or a developer to form a visible image.
The visible image can be formed, for example, by developing the electrostatic latent image using the toner or the developer, and can be performed by the developing unit.
The developing means is not particularly limited as long as it can be developed using toner or developer, for example, and can be appropriately selected from known ones. For example, the toner or developer is accommodated, and Preferable examples include those having at least developing means capable of bringing the toner or developer into contact or non-contact with the electrostatic latent image.
The developing unit is not particularly limited as long as it has these configurations, and can be appropriately selected from known ones. For example, the developer is accommodated, and the developer is contained in the electrostatic latent image. Those having at least a developing device which can be applied in a contact or non-contact manner are preferable.
As the developing device, a magnetic one-component developing device using magnetic toner or a non-magnetic one-component developing device using non-magnetic toner may be used.

  The developer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a two-component developer composed of a toner and a carrier, a magnetic one-component developer, and a non-magnetic one-component developer.

<< Toner >>
The toner is not particularly limited and may be appropriately selected depending on the intended purpose. However, it preferably contains a binder resin and a colorant, and further contains other components as necessary.
The shape of the toner is not particularly limited and may be appropriately selected depending on the intended purpose. The toner may be indefinite or spherical. Further, it may be a magnetic toner or a non-magnetic toner.

-Binder resin-
There is no restriction | limiting in particular as said binder resin, According to the objective, it can select suitably, For example, as a styrene-type binder resin, styrene, such as polystyrene and polyvinyltoluene, or the homopolymer of its substituted, styrene-p- Chlorstyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene- Methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethacrylate methyl copolymer, styrene-acrylonitrile copolymer, styrene- Vinyl methyl ether copolymer, styrene-vinyl methyl Styrene copolymers such as ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-maleic acid copolymers, styrene-maleic acid ester copolymers; polymethyl as an acrylic binder Methacrylate, polybutyl methacrylate; polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic hydrocarbon resin, Aromatic petroleum resins, chlorinated paraffin, paraffin wax, and the like can be mentioned. These may be used alone or in combination of two or more.

  Among these, as the binder resin, a polyester resin is preferable from the viewpoint that the melt viscosity can be further lowered while ensuring the stability during storage of the toner. In addition, the polyester resin is preferable in that the melt viscosity can be further lowered while ensuring the stability during storage of the toner, as compared with the styrene resin or the acrylic resin.

  There is no restriction | limiting in particular as said polyester resin, According to the objective, it can select suitably, For example, it can obtain by the polycondensation reaction of an alcohol component and a carboxylic acid component.

  There is no restriction | limiting in particular as said alcohol component, According to the objective, it can select suitably, For example, polyethyleneglycol, diethyleneglycol, triethyleneglycol, 1,2-propyleneglycol, 1,3-propyleneglycol, 1,4 -Diols such as propylene glycol, neopentyl glycol, 1,4-butenediol; 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol Etherified bisphenols such as A; divalent alcohol units in which these are substituted with saturated or unsaturated hydrocarbon groups having 3 to 22 carbon atoms; other divalent alcohol units; sorbitol, 1, 2, 3 , 6-Hexane Trol, 1,4-sorbitan, pentaesitol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methyl Examples thereof include trihydric or higher alcohol monomers such as propanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane and 1,3,5-trihydroxymethylbenzene. These may be used alone or in combination of two or more.

  The carboxylic acid component is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include monocarboxylic acids such as palmitic acid, stearic acid, and oleic acid, maleic acid, fumaric acid, mesaconic acid, and citraconic acid. Terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, divalent organic acid monomers in which these are substituted with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, these Acid anhydride, lower alkyl ester and dimer acid from linolenic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1 , 2,4-Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-di Trivalent or higher polyvalent polycarboxylic acids such as ruboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid embol trimer acid, anhydrides of these acids, etc. Examples thereof include carboxylic acid monomers. These may be used alone or in combination of two or more.

There is no restriction | limiting in particular as an epoxy resin, According to the objective, it can select suitably, For example, the polycondensate etc. of bisphenol A and epochlorhydrin etc. are mentioned.
As the epoxy resin, a commercially available product can be used, and specific examples thereof include, under the trade name, EPOMIC R362, EPOMIC R364, EPOMIC R365, EPOMIC R366, EPOMIC R367, EPOMIC R369 (above, manufactured by Mitsui Petrochemical Industries Ltd. ), Epototo YD-011, Epototo YD-012, Epototo YD-014, Epototo YD-904, Epotot YD-017 (above, manufactured by Tohto Kasei Co., Ltd.), Epocoat 1002, Epocoat 1004, Epocoat 1007 (above, Shell Chemical Stock) Company-made).

-Colorant-
The colorant is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, Hansa Yellow G, rhodamine 6G lake. , Calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallylmethane dye, monoazo, disazo, and the like. These may be used alone or in combination of two or more.

  The black toner can also be made into a magnetic toner by containing a magnetic material. There is no restriction | limiting in particular as a magnetic body, According to the objective, it can select suitably, For example, ferromagnetic materials, such as iron and cobalt, magnetite, hematite, Li system ferrite, Mn-Zn system ferrite, Cu-Zn system Examples thereof include fine powders such as ferrite, Ni-Zn ferrite and Ba ferrite.

-Charge control agent-
The charge control agent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, metal complexes of monoazo dyes, nitrohumic acid or salts thereof, salicylic acid, naphthoic salts, dicarboxylic acid Co, Cr, Fe And metal complex amino compounds, quaternary ammonium compounds, organic dyes, and the like. These may be used alone or in combination of two or more.
For color toners other than black, white metal salts of salicylic acid derivatives are preferred.
It is preferable that the toner contains a charge control agent in that the triboelectric chargeability can be sufficiently controlled.

-Release agent-
The release agent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, low molecular weight polypropylene, low molecular weight polyethylene, carnauba wax, microcrystalline wax, jojoba wax, rice wax, montanic acid wax , Etc. These may be used alone or in combination of two or more.

-Other ingredients-
There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, additives, such as a fluid improvement agent, etc. are mentioned.
In order to obtain a good image, it is important to impart sufficient fluidity to the toner. For this purpose, it is generally effective to externally add hydrophobized metal oxide fine particles or lubricant fine particles as a fluidity improver, and metal oxide, organic resin fine particles, metal soap, etc. as additives. It is possible to use.

Specific examples of the additive include a fluororesin such as polytetrafluoroethylene, a lubricant such as zinc stearate, an abrasive such as cerium oxide and silicon carbide, and an inorganic oxide such as SiO ₂ and TiO ₂ having a hydrophobic surface. And the like, and those known as anti-caking agents and surface treated products thereof. These may be used alone or in combination of two or more.
Among these, hydrophobic silica is particularly preferable in order to improve the fluidity of the toner.

  The method for producing the toner is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a polymerization method such as a suspension polymerization method, an emulsion polymerization dispersion polymerization method, an emulsion aggregation method, and an emulsion association method, and a polymer. Examples thereof include a dissolution suspension method, a granulation method, and a pulverization method.

The toner is not particularly limited and may be appropriately selected depending on the intended purpose. The toner has an average circularity of 0.93 to 1.00, which is an average value of the circularity SR represented by the following formula 1. Is preferable, and 0.95-0.99 is more preferable.
The average circularity is an index of the degree of unevenness of toner particles, and indicates 1.00 when the toner is a perfect sphere, and the average circularity becomes smaller as the surface shape becomes more complicated.
[Formula 1]
Circularity SR = perimeter of circle having area equal to projected area of toner particles / perimeter of toner particles

There is no restriction | limiting in particular as a weight average particle diameter of the said toner, Although it can select suitably according to the objective, 3 micrometers-10 micrometers are preferable, and 4 micrometers-8 micrometers are more preferable. In the numerical range, since the toner particles have a sufficiently small particle size with respect to the minute latent image dots, the dot reproducibility is excellent. If the weight average particle size is less than 3 μm, phenomena such as a decrease in transfer efficiency and a decrease in blade cleaning properties may occur, and if it exceeds 10 μm, it is difficult to suppress scattering of characters and lines. is there.
The weight average particle diameter of the toner can be measured using, for example, Coulter Multisizer II (manufactured by Coulter Counter).

<Transfer process and transfer means>
The transfer step is a step of transferring the visible image onto a recording medium. After the primary transfer of the visible image onto the intermediate transfer member using an intermediate transfer member, the visible image is transferred onto the recording medium. A primary transfer step of forming a composite transfer image by transferring a visible image onto an intermediate transfer body using two or more colors, preferably full color toner as the toner, and a composite transfer image; A mode including a secondary transfer step of transferring the transfer image onto the recording medium is more preferable.
The transfer can be performed, for example, by charging the electrophotographic photosensitive member with the transfer charger using the visible image, and can be performed by the transfer unit. The transfer means includes a primary transfer means for transferring a visible image onto an intermediate transfer member to form a composite transfer image, and a secondary transfer means for transferring the composite transfer image onto a recording medium. Embodiments are preferred.
The intermediate transfer member is not particularly limited and may be appropriately selected from known transfer members according to the purpose. For example, a transfer belt and the like are preferable.

The transfer unit (the primary transfer unit and the secondary transfer unit) includes at least a transfer unit that peels and charges the visible image formed on the electrophotographic photosensitive member toward the recording medium. preferable. There may be one transfer means or two or more transfer means.
Examples of the transfer device include a corona transfer device using corona discharge, a transfer belt, a transfer roller, a pressure transfer roller, and an adhesive transfer device.
There is no restriction | limiting in particular as said recording medium, According to the objective, it can select suitably, For example, paper, a thread | yarn, a fiber, leather, a metal, a plastics, glass, wood, ceramics etc. are mentioned. Among these, paper (recording paper) is particularly preferable.

<Other processes and other means>
Examples of the other processes include a fixing process, a cleaning process, a recycling process, and a control process.
Examples of the other means include a fixing means, a cleaning means, a recycling means, and a control means.
The image forming apparatus does not have a charge eliminating unit for removing a residual potential difference remaining on the electrophotographic photosensitive member after passing through the transfer unit. Thereby, cost and power consumption can be further suppressed, and stress applied to the electrophotographic photosensitive member can be reduced.

<< Fixing process and fixing means >>
The fixing step is a step of fixing the visible image transferred to the recording medium using a fixing unit, and may be performed each time the toner of each color is transferred to the recording medium, or for the toner of each color. You may perform this simultaneously in the state which laminated | stacked this.
There is no restriction | limiting in particular as said fixing device, Although it can select suitably according to the objective, A well-known heating-pressing means is suitable. Examples of the heating and pressing means include a combination of a heating roller and a pressure roller, a combination of a heating roller, a pressure roller, and an endless belt.
The fixing device includes a heating body including a heating element, a film in contact with the heating body, and a pressure member in pressure contact with the heating body through the film, and the film and the pressure member It is preferably a unit that heats and fixes a recording medium on which an unfixed image is formed. The heating in the heating and pressing means is usually preferably 80 ° C to 200 ° C.
In the present invention, for example, a known optical fixing device may be used together with or in place of the fixing step and the fixing unit depending on the purpose.

<< Cleaning process and cleaning means >>
The cleaning step is a step of removing the toner remaining on the electrophotographic photosensitive member, and can be suitably performed by a cleaning unit.
The cleaning means is not particularly limited as long as it can remove the electrophotographic toner remaining on the electrophotographic photosensitive member, and can be appropriately selected from known cleaners. For example, a magnetic brush cleaner , Electrostatic brush cleaner, magnetic roller cleaner, blade cleaner, brush cleaner, web cleaner, and the like.

<< Recycling process and recycling means >>
The recycling step is a step of recycling the toner removed by the cleaning step to the developing unit, and can be suitably performed by the recycling unit.
There is no restriction | limiting in particular as said recycling means, A well-known conveyance means etc. are mentioned.

<< Control process and control means >>
The control step is a step of controlling each of the steps, and can be suitably performed by a control unit.
The control means is not particularly limited as long as the movement of each means can be controlled, and can be appropriately selected according to the purpose. Examples thereof include devices such as sequencers and computers.

(Process cartridge)
The process cartridge of the present invention includes at least an electrophotographic photosensitive member and charging means for charging the surface of the electrophotographic photosensitive member, and further includes other means as necessary.
Examples of the other means include an exposure means, a development means, a transfer means, and a cleaning means.
As the exposure unit, the developing unit, the transfer unit, and the cleaning unit, the same ones as those of the above-described image forming apparatus can be appropriately selected and used.
The process cartridge can be detachably provided in various electrophotographic image forming apparatuses, facsimiles, and printers, and it is particularly preferable that the process cartridge is detachably provided in the image forming apparatus of the present invention.

Here, FIG. 2 is a schematic view showing an example of the image forming apparatus 100 of the present invention. The image forming unit of the image forming apparatus 100 includes electrophotographic photoreceptors 1Y, 1C, 1M, and 1K.
The electrophotographic photoreceptors 1Y, 1C, 1M, and 1K are provided along the conveyance direction of the intermediate transfer belt 5. The electrophotographic photoreceptors 1Y, 1C, 1M, and 1K are collectively referred to as the electrophotographic photoreceptor 1.
The electrophotographic photoreceptors 1Y, 1C, 1M, and 1K are capable of carrying images of toners of various colors (for example, yellow, cyan, magenta, and black) and have a photoconductive layer. The image is written on the electrophotographic photoreceptor 1 by the exposure means 3.
Around the drum-shaped electrophotographic photoreceptors 1Y, 1C, 1M, and 1K, a charging unit 2, an exposing unit 3, a developing unit 4, an intermediate transfer belt 5, and a cleaning unit 6 are arranged, respectively.

  The intermediate transfer belt 5 is wound around rollers 50 and 51. Inside the intermediate transfer belt 5, primary transfer rollers 52 </ b> Y, 52 </ b> C, 52 </ b> M, and 52 </ b> K as primary transfer units are arranged corresponding to the electrophotographic photoreceptors 1. Further, a secondary transfer roller 53 as a secondary transfer unit for collectively transferring the superimposed image on the intermediate transfer belt 5 onto the recording medium is disposed at a position facing the roller 51.

  The electrostatic latent image forming means may be means for forming an electrostatic latent image on the electrophotographic photosensitive member 1 after charging the electrophotographic photosensitive member 1 as defined in the present invention using a charging means 2. If there is no restriction | limiting in particular, according to the objective, it can select suitably.

As a charging method, a voltage can be applied to the surface of the electrophotographic photosensitive member 1 using the following charging means 2.
The charging means 2 is not particularly limited and may be appropriately selected depending on the purpose. For example, the charging means 2 may include a conductive or semiconductive roll, a brush, a film, a rubber blade and the like, which is known per se. And non-contact zone means using corona discharge such as corotron and scorotron. Among these, a charging unit having a charging roller that performs contact charging by bringing a conductive or semiconductive roll to which a DC voltage is applied into contact with the electrophotographic photosensitive member is preferable. In addition, when using a charging means having a contact charging roller, a soft contact charging roller is used and a pressure member is not provided so that a large pressing force is not applied to the contact portion. Is more preferable.

The exposure means 3 can be performed, for example, by exposing the surface of the electrophotographic photosensitive member imagewise using an exposure apparatus.
The exposure means 3 is not particularly limited as long as the surface of the electrophotographic photosensitive member charged by the charging means 2 can be exposed like an image to be formed, and can be appropriately selected according to the purpose. However, various exposure means such as a copying optical system, a rod lens array system, a laser optical system, a liquid crystal shutter optical system, and an LED optical system can be used.
Further, when forming a halftone image, it is preferable to use area gradation performed by changing the exposure area according to the image.

The developing unit 4 is a unit that develops the electrostatic latent image formed on the electrophotographic photosensitive member 1 using a developer to form a visible image, and includes a developing sleeve, a developer stirring and conveying mechanism, Have
The developing sleeve carries a developer and conveys it to a position facing the electrophotographic photosensitive member.
A developing gap defined as a gap is formed between the electrophotographic photosensitive member and the developing sleeve.
The development gap is a substantially uniform gap in consideration of the pumping amount of the developer, the strength of the magnetic field for holding the developer on the development sleeve, the magnetization of the carrier in the developer, the rotation speed of the development sleeve, and the like. Since it adjusts and forms, 0.2 mm-0.4 mm are preferable as an average value.

The cleaning means 6 is not particularly limited as long as it is a means for cleaning the surface of the electrophotographic photosensitive member, and can be appropriately selected according to the purpose. Examples thereof include a cleaning blade.
As a method for cleaning the electrophotographic photosensitive member, in addition to the method using the cleaning blade, electrostatic cleaning using a brush to which a voltage is applied so as to be opposite in polarity to the toner remaining on the electrophotographic photosensitive member. A method is mentioned.

Next, a series of processes for image formation will be described using a negative-positive process. In the case of contents common to all electrophotographic photosensitive members and developing means, the electrophotographic photosensitive member is simply indicated by reference numeral 1 and the developing means is indicated by reference numeral 4.
The electrophotographic photoreceptor 1 having a photoconductive layer is uniformly charged negatively by a charging means 2 having a charging member.
When the electrophotographic photosensitive member 1 is charged by the charging unit 2, charging of an appropriate size suitable for setting the electrophotographic photosensitive member 1 to the potential of the present invention from a voltage applying unit to be described later to the charging member. A voltage is applied. At this time, a charge is imparted from the charging member to the electrophotographic photosensitive member 1, but excess charge exceeding the charge that can be held by the electrophotographic photosensitive member 1 passes through the electrophotographic photosensitive member and eventually becomes a leakage current. Flows to the ground electrode. As a result, the electrophotographic photosensitive member 1 has a constant charging potential.
The charged electrophotographic photosensitive member 1 forms a latent image with the laser light L irradiated by the exposure means 3 such as a laser optical system (the absolute value of the exposed portion potential is lower than the absolute value of the non-exposed portion potential). ) Is performed.
Laser light is emitted from a semiconductor laser, and the surface of the electrophotographic photosensitive member 1 is scanned in the direction of the rotational axis of the electrophotographic photosensitive member 1 by a polygonal polygonal mirror that rotates at high speed.

The electrostatic latent image formed in this way is developed with a developer made of toner or a mixture of toner and carrier supplied on a developing sleeve 40 as a developer carrying member in the developing means 4 and is visible. An image is formed.
At the time of developing the electrostatic latent image, a developing bias in which an appropriate voltage or an alternating voltage is superimposed on the voltage between the exposed portion and the non-exposed portion of the electrophotographic photosensitive member 1 is applied from the voltage applying unit to the developing sleeve. Applied.
The toner images formed on the electrophotographic photoreceptors 1Y, 1C, 1M, and 1K corresponding to the respective colors are sequentially superimposed on the intermediate transfer belt 5 by primary transfer rollers 52Y, 52C, 52M, and 52K as primary transfer means. Is transcribed. At this time, it is preferable that a potential having a polarity opposite to the toner charging polarity is applied to the primary transfer roller 52 as a transfer bias. Thereafter, the intermediate transfer belt 5 is separated from the electrophotographic photosensitive member 1 to obtain a transfer image.
The superimposed toner images transferred onto the intermediate transfer belt 5 are collectively transferred by a secondary transfer roller 53 onto a recording medium such as paper fed from the paper feeding device 200.

The recording medium fed from the selected paper feeding cassette of the paper feeding device 200 is temporarily stopped by the registration roller pair and the oblique shift is corrected, and then conveyed to the secondary transfer portion of the secondary transfer roller 53 at a predetermined timing. Is done.
The recording medium on which the superimposed images are collectively transferred is sent to the fixing unit 7 where the toner image is fixed by heat and pressure. After the fixing, the recording medium is discharged to a paper discharge tray 8 by a pair of paper discharge rollers and stacked.

After the primary transfer, the toner remaining on the electrophotographic photosensitive member 1 is removed and collected by the cleaning unit 6, and the toner remaining on the intermediate transfer belt 5 after the secondary transfer is removed by the intermediate transfer belt cleaning unit 6. And collected.
In this embodiment, the image forming apparatus is configured to perform secondary transfer using the intermediate transfer belt 5, but the toner images of the plurality of electrophotographic photoreceptors 1 are sequentially recorded while the recording medium is conveyed by the conveyance belt. A configuration may be adopted in which the image is transferred onto the medium.

The electrophotographic photosensitive member 1, the charging unit 2, the developing unit 4 and the like can be integrally configured as a process cartridge that can be attached to and detached from the main body of the image forming apparatus. FIG. 3 shows an example of the process cartridge 300. In FIG. 3, the color-specific codes are omitted.
The charging unit 2 includes a charging roller 20 as a charging member and a charging roller cleaning roller 21.
The developing unit 4 includes a developing sleeve 40 and developer agitating and conveying members 41 and 42 for agitating, conveying, and circulating the developer in the developing casing. A toner replenishing section (not shown) is provided above the developer stirring and conveying members 41 and 42.
The cleaning means 6 has a cleaning blade 60 that contacts the surface of the electrophotographic photoreceptor 1 in the leading direction.

  According to the image forming apparatus, the image forming method, and the process cartridge of the present invention, the charging potential of the electrophotographic photosensitive member is maintained uniformly, and is caused by the residual potential on the electrophotographic photosensitive member represented by a ghost image. Image defects can be suppressed, and high-quality image quality can be stably formed.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Production Example 1)
<Preparation of electrophotographic photoreceptor 1>
An aluminum cylinder having an outer diameter of 40 mm and a wall thickness of 0.8 mm was used as the cylindrical conductive support. On this aluminum cylinder, as shown below, an undercoat layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution are successively applied by dip coating, and after repeated drying, a surface layer coating solution Was spray-coated and dried to form an undercoat layer having an average thickness of 20 μm, a charge generation layer having an average thickness of 0.2 μm, a charge transport layer having an average thickness of 17 μm, and a surface layer having an average thickness of 3 μm. Thus, the electrophotographic photoreceptor 1 was produced.

(Formation of undercoat layer)
An undercoat layer coating solution having the following composition was dip-coated on the aluminum cylinder, and then dried by heating at 120 ° C. for 25 minutes to form an undercoat layer.
-Composition of undercoat layer coating solution-
-Alkyd resin (Beckosol 1307-60-EL, manufactured by DIC Corporation) ... 6 parts by mass-Melamine resin (Super Becamine G-821-60, manufactured by DIC Corporation)-4 parts by mass-N-type semiconductor Aluminum Doped Zinc Oxide (Pazet CK, manufactured by Hakusui Tech Co., Ltd.) ... 25 parts by mass ・ 1,2-Dihydroxy-9,10-anthraquinone as a charge accepting material ... 0.6 parts by mass ・ Titanium oxide (CR -EL, manufactured by Ishihara Sangyo Co., Ltd.) ... 15 parts by mass ・ Methyl ethyl ketone ... 200 parts by mass

(Formation of charge generation layer)
After dip-coating the charge generation layer coating solution having the following composition on the undercoat layer, heating was continued at 120 ° C. for 20 minutes, followed by heating to 180 ° C. at a heating rate of 5 ° C. per minute. By holding for 15 minutes, the tetrabenzoporphyrin precursor was thermally converted to tetrabenzoporphyrin to form a charge generation layer.
-Composition of coating solution for charge generation layer-
-Tetrabenzoporphyrin precursor represented by the following chemical formula (1): 2 parts by mass
・ Polyvinyl butyral (ESREC BM-S, manufactured by Sekisui Chemical Co., Ltd.) 0.1 mass part Tetrahydrofuran 50 mass parts

(Formation of charge transport layer)
A charge transport layer coating solution having the following composition was dip coated on the charge generation layer, and then dried by heating at 135 ° C. for 20 minutes to form a charge transport layer.
-Composition of charge transport layer coating solution-
-Charge transport material (D-1) represented by the following structural formula: 9 parts by mass
-Fullerene derivative represented by the following chemical formula (3): 0.5 part by mass
-Bisphenol Z polycarbonate (Panlite TS-2050, manufactured by Teijin Chemicals Ltd.) ... 9 parts by mass-Silicone oil (KF-50, manufactured by Shin-Etsu Chemical Co., Ltd.) ... 0.002 parts by mass-Tetrahydrofuran・ 100 parts by mass

(Formation of surface layer)
A surface layer coating solution having the following composition was spray-coated on the charge transport layer and then thermally crosslinked at 150 ° C. for 30 minutes to form a surface layer.
-Composition of surface layer coating solution-
Charge transporting polyol represented by the following chemical formula (4): 15 parts by mass
・ Fullerene derivative represented by the following chemical formula (3): 0.8 part by mass
・ Isocyanate (xylene diisocyanate, Takenate 500, manufactured by Mitsui Takeda Chemical Co., Ltd.): 7 parts by mass ・ Polyol (polyester polyol, number average molecular weight 1,000, Sanester No. 22, manufactured by Sanyo Chemical Industries, Ltd.) -25 parts by mass-Cyclohexanone-65 parts by mass-Tetrahydrofuran-215 parts by mass-Mixing conditions for surface layer coating solution-
NCO / OH = 1.0 (molar ratio), charge transporting polyol / polyester polyol = 2/1 (mass ratio), solvent mixing ratio: tetrahydrofuran / cyclohexanone = 10/3 (volume ratio)

The total thickness of the coating layers (undercoat layer, charge generation layer, charge transport layer, and surface layer) of the obtained electrophotographic photoreceptor 1 was 40.2 μm on average.
The electrostatic capacity of the obtained electrophotographic photoreceptor 1 was measured by the method described in JP-A-2008-216704. That is, using the electrostatic capacity measuring device shown in FIG. 5, the drum rotation speed is 1,350 rpm, the surface potential / passing current sampling interval is 0.01 sec, and the set discharge current is changed to change the electrostatic capacity of the electrophotographic photosensitive member. When the capacity was calculated, it was 0.128 nF / cm ² .

(Production Example 2)
<Preparation of electrophotographic photoreceptor 2>
In Production Example 1, the electrophotographic photosensitive member 2 was prepared in the same manner as in Production Example 1, except that the dip coating conditions were changed so that the average thickness of the undercoat layer was 15 μm and the average thickness of the charge transport layer was 27 μm. Produced.
The total thickness of the coating layers (undercoat layer, charge generation layer, charge transport layer, and surface layer) of the obtained electrophotographic photoreceptor 2 was 45.2 μm on average.
The electrostatic capacity of the obtained electrophotographic photoreceptor 2 was measured by the method described in JP-A-2008-216704. That is, using the electrostatic capacity measuring device shown in FIG. 5, the drum rotation speed is 1,350 rpm, the surface potential / passing current sampling interval is 0.01 sec, and the set discharge current is changed to change the electrostatic capacity of the electrophotographic photosensitive member. When the capacity was calculated, it was 0.114 nF / cm ² .

(Production Example 3)
<Preparation of electrophotographic photoreceptor 3>
In Production Example 1, the electrophotographic photosensitive member 3 was produced in the same manner as in Production Example 1 except that the dip coating conditions were changed, the average thickness of the undercoat layer was 17 μm, and the average thickness of the charge transport layer was 37 μm. did.
The total thickness of the coating layers (undercoat layer, charge generation layer, charge transport layer, and surface layer) of the obtained electrophotographic photoreceptor 3 was 57.2 μm on average.
The electrostatic capacity of the obtained electrophotographic photoreceptor 3 was measured by the method described in JP-A-2008-216704. That is, using the electrostatic capacity measuring device shown in FIG. 5, the drum rotation speed is 1,350 rpm, the surface potential / passing current sampling interval is 0.01 sec, and the set discharge current is changed to change the electrostatic capacity of the electrophotographic photosensitive member. When the capacity was calculated, it was 0.090 nF / cm ² .

(Production Example 4)
<Preparation of electrophotographic photoreceptor 4>
In Production Example 1, electrophotographic photosensitive member 4 was produced in the same manner as in Production Example 1 except that the dip coating conditions were changed, the average thickness of the charge transport layer was 20 μm, and the surface layer was not formed. did.
The total thickness of the coating layers (undercoat layer, charge generation layer, and charge transport layer) of the obtained electrophotographic photoreceptor 4 was 40.2 μm on average.
The electrostatic capacity of the obtained electrophotographic photosensitive member 4 was measured by the method described in JP-A-2008-216704. That is, using the electrostatic capacity measuring device shown in FIG. 5, the drum rotation speed is 1,350 rpm, the surface potential / passing current sampling interval is 0.01 sec, and the set discharge current is changed to change the electrostatic capacity of the electrophotographic photosensitive member. When the capacity was calculated, it was 0.132 nF / cm ² .

(Production Example 5)
<Preparation of electrophotographic photoreceptor 5>
An aluminum cylinder having an outer diameter of 40 mm and a wall thickness of 0.8 mm was used as the cylindrical conductive support. On this aluminum cylinder, undercoat coating solution, charge generation layer coating solution, and charge transport layer coating solution having the following composition were sequentially dip coated and dried, and then the surface layer coating solution was added. By spray coating and drying, an undercoat layer having an average thickness of 15 μm, a charge generation layer having an average thickness of 0.2 μm, a charge transport layer having an average thickness of 27 μm, and a surface layer having an average thickness of 3 μm were formed. Thus, an electrophotographic photoreceptor 5 was produced.

(Formation of undercoat layer)
An undercoat layer coating solution having the following composition was dip-coated on the aluminum cylinder, and then dried by heating at 120 ° C. for 25 minutes to form an undercoat layer.
-Composition of undercoat layer coating solution-
-Alkyd resin (Beckosol 1307-60-EL, manufactured by DIC Corporation) ... 6 parts by mass-Melamine resin (Super Becamine G-821-60, manufactured by DIC Corporation)-4 parts by mass-N-type semiconductor Aluminum Doped Zinc Oxide (Pazet CK, manufactured by Hakusuitec Co., Ltd.) ... 25 parts by mass ・ 1,2-Dihydroxy-9,10-anthraquinone as a charge accepting material ... 0.4 parts by mass ・ Titanium oxide (CR -EL, manufactured by Ishihara Sangyo Co., Ltd.) ... 15 parts by mass ・ Methyl ethyl ketone ... 200 parts by mass

(Formation of charge generation layer)
A charge generation layer coating solution having the following composition was dip-coated on the undercoat layer, and then heated and dried at 120 ° C. for 20 minutes to form a charge generation layer.
-Composition of coating solution for charge generation layer-
・ Oxotitanium phthalocyanine pigment ・ ・ ・ 2 parts by mass ・ Polyvinyl butyral (ESREC BM-S, manufactured by Sekisui Chemical Co., Ltd.) ... 0.2 parts by mass ・ Tetrahydrofuran ... 50 parts by mass

(Formation of charge transport layer)
A charge transport layer coating solution having the following composition was dip coated on the charge generation layer, and then dried by heating at 135 ° C. for 20 minutes to form a charge transport layer. In the dip coating, the lifting speed and the surrounding atmosphere were adjusted so that the amount of the coating solution adhered became uniform.
-Composition of charge transport layer coating solution-
-Charge transport material (D-1) represented by the following structural formula: 10 parts by mass
-Bisphenol Z polycarbonate (Panlite TS-2050, manufactured by Teijin Chemicals Ltd.) ... 10 parts by mass-Silicone oil (KF-50, manufactured by Shin-Etsu Chemical Co., Ltd.)-0.002 parts by mass-Tetrahydrofuran・ 100 parts by mass

(Formation of surface layer)
A surface layer coating solution having the following composition was spray-coated on the charge transport layer and then thermally crosslinked at 150 ° C. for 30 minutes to form a surface layer.
-Composition of surface layer coating solution-
Charge transporting polyol represented by the following chemical formula (4): 15 parts by mass
・ Isocyanate (xylene diisocyanate, Takenate 500, manufactured by Mitsui Takeda Chemical Co., Ltd.): 7 parts by mass ・ Polyol (polyester polyol, number average molecular weight 1,000, Sanester No. 22, manufactured by Sanyo Chemical Industries, Ltd.) -25 parts by mass-Cyclohexanone-65 parts by mass-Tetrahydrofuran-215 parts by mass-Mixing conditions for surface layer coating solution-
NCO / OH = 1.0 (molar ratio), charge transporting polyol / polyester polyol = 2/1 (mass ratio), solvent mixing ratio: tetrahydrofuran / cyclohexanone = 10/3 (volume ratio)

The total thickness of the coating layers (undercoat layer, charge generation layer, charge transport layer, and surface layer) of the obtained electrophotographic photoreceptor 5 was 45.2 μm on average.
The electrostatic capacity of the obtained electrophotographic photoreceptor 5 was measured by the method described in JP-A-2008-216704. That is, using the electrostatic capacity measuring device shown in FIG. 5, the drum rotation speed is 1,350 rpm, the surface potential / passing current sampling interval is 0.01 sec, and the set discharge current is changed to change the electrostatic capacity of the electrophotographic photosensitive member. When the capacity was calculated, it was 0.069 nF / cm ² .

(Comparative Example 1)
<Production of process cartridge>
The electrophotographic photoreceptor 1 produced in Production Example 1 was used, and flanges were provided at both ends of the electrophotographic photoreceptor 1.
This electrophotographic photosensitive member 1 with a flange was incorporated into a process cartridge in which an image forming unit of imgio MP C4500 manufactured by Ricoh Co., Ltd. was modified to a contact roller charging system. The toner color of the process cartridge was black.

<Assembly of image forming apparatus and image formation>
Next, the manufactured process cartridge is replaced with a black process cartridge manufactured by Ricoh Co., Ltd., and the charging voltage applied to the electrophotographic photosensitive member from the charging means, that is, the surface potential of the contact charging roller is −150V. The direct current voltage was adjusted so that the developing bias voltage was appropriately adjusted, and image formation was performed. At this time, neutralization of the surface potential after transfer of the electrophotographic photosensitive member was not performed.
As the toner, imgio MP P toner black C4500 (manufactured by Ricoh Co., Ltd.) was used.
Next, measurement of the charging potential and post-exposure potential of the electrophotographic photosensitive member after exposure after charging, measurement of the saturated charging potential of the electrophotographic photosensitive member before exposure after charging, and electron before exposure after charging as follows Measurement of the applied charge amount of the photographic photoreceptor and image evaluation were performed. The results are shown in Table 1.

<Measurement of the charging potential V and the post-exposure potential VL of the electrophotographic photoreceptor after exposure after charging>
The charging potential V and the post-exposure potential VL of the electrophotographic photosensitive member after charging and after exposure are the charging potential of the electrophotographic photosensitive member that is contact-charged by applying a DC voltage of each applied voltage by a charging means provided in the image forming apparatus. V and a surface potential meter (Model 344, manufactured by Trek Co., Ltd.) in which the charged electric potential VL after the entire surface of the charged electrophotographic photosensitive member is exposed by an exposure unit provided in the image forming apparatus is separately incorporated in the image forming apparatus. And measured.

<Measurement of saturation charging potential of electrophotographic photoreceptor after exposure after charging>
The saturation charging potential of the electrophotographic photosensitive member before and after the exposure was measured as the potential at the time when the surface potential was balanced by plotting the amount of applied charge and the surface potential at the time of capacitance measurement.

<Measurement of the imparted charge amount Q of the electrophotographic photoreceptor after exposure after charging>
The applied charge amount Q of the electrophotographic photosensitive member after charging and before exposure is a digital multimeter (manufactured by Advantest, manufactured by separately incorporating the current value between the conductive support of the electrophotographic photosensitive member and the grounding point into the image forming apparatus. AD7451A) and calculated by dividing by the passage area (639.6 cm ² ) calculated from the charging width (312 mm) and linear velocity (205 mm / sec) of the electrophotographic photosensitive member.

<Image evaluation>
The initial image quality and the image quality after outputting 2,000 sheets were evaluated as follows.
The initial image quality refers to the quality of an image formed on the first to tenth sheets.
The image quality after outputting 2,000 sheets means the quality of the image formed on the 2,000th sheet.

<< Initial image quality >>
As for the initial image quality, a 2by2 full-tone image with a pixel density of 25% is formed immediately after a band-like image having a length of 150 mm in the flow direction, formed by repeating a portion with a pixel density of 100% and 0% every 20 mm in the width direction. Using the obtained image pattern, the presence or absence of a ghost image in the entire tone portion was visually observed and evaluated according to the following criteria. In addition, the presence or absence of other image quality defects was visually evaluated.
[Ghost image]
○: Excellent (level at which ghost images cannot be detected over the entire surface)
△: Level that does not cause any problem in practical use (level that can slightly detect a ghost image compared to ○)
×: Unusable (level that can clearly detect ghost images by itself)
In addition, all of the above evaluations were performed in a room adjusted to an environment of temperature 20 ° C. to 23 ° C. and relative humidity 50% to 65% RH.

<< Image quality after outputting 2,000 sheets >>
As for the image quality after outputting 2,000 sheets, the initial image is output after outputting 2,000 band charts in which a portion having a pixel density of 100% and 0% is repeatedly formed every 20 mm in the width direction with respect to the total length in the flow direction. Evaluation similar to quality was performed.

(Examples 1-4)
In Comparative Example 1, the charging voltage applied from the charging means to the electrophotographic photosensitive member was changed to DC voltages of −210V, −250V, −300V, and −350V as shown in Table 1, and the developing bias voltage was adjusted. In the same manner as in Comparative Example 1, the image forming apparatuses of Examples 1 to 4 were assembled and image formation was performed.
For the image forming apparatuses of Examples 1 to 4, as in Comparative Example 1, measurement of the charging potential and post-exposure potential of the electrophotographic photosensitive member, measurement of the saturated charging potential of the electrophotographic photosensitive member before exposure after charging, and electron Measurement of the applied charge amount of the photographic photoreceptor and image evaluation were performed. The results are shown in Table 1.

(Comparative Example 2)
In Comparative Example 1, Comparative Example 2 was performed in the same manner as Comparative Example 1, except that the electrophotographic photosensitive member 2 produced in Production Example 2 was used and the charging voltage applied from the charging means to the electrophotographic photosensitive member was -200V. The image forming apparatus was assembled and image formation was performed.
For the image forming apparatus of Comparative Example 2, as in Comparative Example 1, measurement of the charging potential and post-exposure potential of the electrophotographic photosensitive member, measurement of the saturated charging potential of the electrophotographic photosensitive member before exposure after charging, and electrophotographic photosensitive Measurement of the amount of charge applied to the body and image evaluation were performed. The results are shown in Table 1.

(Examples 5 to 8)
In Comparative Example 2, the charging voltage applied from the charging means to the electrophotographic photosensitive member was changed to DC voltages of −360V, −400V, −450V, and −500V as shown in Table 1, and the developing bias voltage was adjusted. In the same manner as in Comparative Example 2, the image forming apparatuses of Examples 5 to 8 were assembled and image formation was performed.
For the image forming apparatuses of Examples 5 to 8, as in Comparative Example 1, measurement of the charging potential and post-exposure potential of the electrophotographic photosensitive member, measurement of the saturation charging potential of the electrophotographic photosensitive member before exposure after charging, and electron Measurement of the applied charge amount of the photographic photoreceptor and image evaluation were performed. The results are shown in Table 1.

(Comparative Example 3)
In Comparative Example 1, Comparative Example 3 was performed in the same manner as Comparative Example 1 except that the electrophotographic photosensitive member 3 produced in Production Example 3 was used and the charging voltage applied from the charging means to the electrophotographic photosensitive member was -350 V. The image forming apparatus was assembled and image formation was performed.
For the image forming apparatus of Comparative Example 3, as in Comparative Example 1, measurement of the charging potential and post-exposure potential of the electrophotographic photosensitive member, measurement of the saturated charging potential of the electrophotographic photosensitive member before exposure after charging, and electrophotographic photosensitivity Measurement of the amount of charge applied to the body and image evaluation were performed. The results are shown in Table 1.

(Examples 9 to 11)
In Comparative Example 3, the charging voltage applied from the charging means to the electrophotographic photosensitive member was −510V, −600V, and −700V as shown in Table 1 except that the development bias voltage was adjusted. In the same manner as in Example 3, the image forming apparatuses of Examples 9 to 11 were assembled and image formation was performed.
For the image forming apparatuses of Examples 9 to 11, in the same manner as in Comparative Example 1, measurement of the charging potential and post-exposure potential of the electrophotographic photosensitive member, measurement of the saturation charging potential of the electrophotographic photosensitive member before exposure after charging, and electron Measurement of the applied charge amount of the photographic photoreceptor and image evaluation were performed. The results are shown in Table 1.

(Examples 12 to 15)
In Examples 1 to 4, the image forming apparatuses of Examples 12 to 15 were the same as Examples 1 to 4 except that the electrophotographic photoreceptor 1 was replaced with the electrophotographic photoreceptor 4 produced in Production Example 4. Were assembled and image formation was performed.
For the image forming apparatuses of Examples 12 to 15, as in Comparative Example 1, measurement of the charging potential and post-exposure potential of the electrophotographic photosensitive member, measurement of the saturation charging potential of the electrophotographic photosensitive member before exposure after charging, and electron Measurement of the applied charge amount of the photographic photoreceptor and image evaluation were performed. The results are shown in Table 1.

(Comparative Example 4)
In Comparative Example 1, the image forming apparatus of Comparative Example 4 was assembled and image formation was performed in the same manner as Comparative Example 1 except that the electrophotographic photosensitive member 5 produced in Production Example 5 was used.
For the image forming apparatus of Comparative Example 4, as in Comparative Example 1, measurement of the charging potential and post-exposure potential of the electrophotographic photosensitive member, measurement of the saturated charging potential of the electrophotographic photosensitive member before exposure after charging, and electrophotographic photosensitivity Measurement of the amount of charge applied to the body and image evaluation were performed. The results are shown in Table 1.

(Comparative Examples 5-6)
In Comparative Example 4, the charging voltage applied from the charging means to the electrophotographic photosensitive member was −400 V and −700 V DC voltage as shown in Table 1, except that the developing bias voltage was adjusted, and Comparative Example 4 and Similarly, the image forming apparatuses of Comparative Examples 5 to 6 were assembled and image formation was performed.
For the image forming apparatuses of Comparative Examples 5 to 6, as in Comparative Example 1, measurement of the charging potential and post-exposure potential of the electrophotographic photosensitive member, measurement of the saturated charging potential of the electrophotographic photosensitive member before post-exposure, Measurement of the applied charge amount of the photographic photoreceptor and image evaluation were performed. The results are shown in Table 1.

From the results shown in Table 1-1 and Table 1-2, the following is recognized.
<Comparison of Examples 1-15 and Comparative Examples 1-6>
In contrast to Examples 1 to 15, in Comparative Examples 1 to 6, the occurrence of a ghost image due to the afterimage potential of the electrophotographic photosensitive member was observed, and the deterioration of the image quality became remarkable.
Therefore, the usefulness of image formation was shown in the range where the charge potential of the electrophotographic photosensitive member after the post-charge exposure before the saturation charge potential (range A in FIG. 1).

<Comparison of Examples 1-11>
In Examples 1, 2, 3, 9, 10, and 11, which are upper and lower limits of the preferable range (200 V to 400 V) as the absolute value of the charging potential V of the electrophotographic photosensitive member, Examples 5, 6, and 7 near the center are used. As compared with, a slight tendency of deterioration was observed in the image after continuous paper feeding.

  From these results, the charging potential of the electrophotographic photosensitive member after exposure after charging is within a range (range A in FIG. 1), preferably the surface layer composition on the outermost surface. The superiority of the image quality of the image forming apparatus having a surface layer containing a cross-linked product obtained by cross-linking is shown.

Examples of the aspect of the present invention include the following.
<1> an electrophotographic photoreceptor;
Application of applying either voltage or current to the charging member so that the charging potential of the charging member arranged on the electrophotographic photosensitive member and the electrophotographic photosensitive member before exposure after charging becomes a saturated charging potential. A charging means for charging the surface of the electrophotographic photosensitive member,
Exposure means for exposing the charged electrophotographic photosensitive member surface to form an electrostatic latent image; and
Developing means for developing the electrostatic latent image with toner to form a visible image;
Transfer means for transferring the visible image to a recording medium;
The image forming apparatus is characterized by having at least.
<2> The image forming apparatus according to <1>, wherein the electrophotographic photosensitive member has a surface layer containing a crosslinked product obtained by crosslinking the surface layer composition on the outermost surface.
<3> The image forming apparatus according to any one of <1> to <2>, wherein the absolute value of the charging potential of the electrophotographic photosensitive member is 200V to 500V.
<4> The charging device according to <1> to <3>, wherein the charging unit includes a roller-shaped charging member disposed in contact with the electrophotographic photosensitive member, and a voltage applying member that applies a DC voltage to the roller-shaped charging member. The image forming apparatus according to any one of the above.
<5> The image forming apparatus according to any one of <1> to <4>, wherein the latent image potential on the electrophotographic photosensitive member is a binary latent image potential of an exposed portion and a non-exposed portion by an exposure unit. .
<6> The image forming apparatus according to any one of <1> to <5>, wherein the image forming apparatus does not have a charge eliminating unit for removing a residual potential difference remaining on the electrophotographic photosensitive member after passing through the transfer unit. .
<7> an electrophotographic photoreceptor;
Application of applying either voltage or current to the charging member so that the charging potential of the charging member arranged on the electrophotographic photosensitive member and the electrophotographic photosensitive member before exposure after charging becomes a saturated charging potential. And a charging means for charging the surface of the electrophotographic photosensitive member.
<8> Either a voltage or a current is applied to the charging member such that the charging member disposed on the electrophotographic photosensitive member and the charging potential of the electrophotographic photosensitive member before exposure after charging become a saturated charging potential. A charging step for charging the surface of the electrophotographic photosensitive member,
Exposing the charged electrophotographic photoreceptor surface to form an electrostatic latent image; and
A developing step of developing the electrostatic latent image with toner to form a visible image;
A transfer step of transferring the visible image to a recording medium;
Is an image forming method characterized by including at least.

DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 2 Charging means 3 Exposure means 4 Developing means 100 Image forming apparatus 300 Process cartridge

JP 2008-122440 A JP 2005-189319 A JP 2010-134153 A

Claims (8)

An electrophotographic photoreceptor;
Application of applying either voltage or current to the charging member so that the charging potential of the charging member arranged on the electrophotographic photosensitive member and the electrophotographic photosensitive member before exposure after charging becomes a saturated charging potential. A charging means for charging the surface of the electrophotographic photosensitive member,
Exposure means for exposing the charged electrophotographic photosensitive member surface to form an electrostatic latent image; and
Developing means for developing the electrostatic latent image with toner to form a visible image;
Transfer means for transferring the visible image to a recording medium;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the electrophotographic photoreceptor has a surface layer containing a crosslinked product obtained by crosslinking the surface layer composition on the outermost surface.   The image forming apparatus according to claim 1, wherein an absolute value of a charging potential of the electrophotographic photosensitive member is 200 V to 500 V.   The image according to any one of claims 1 to 3, wherein the charging means includes a roller-shaped charging member disposed in contact with the electrophotographic photosensitive member, and a voltage applying member that applies a DC voltage to the roller-shaped charging member. Forming equipment.   5. The image forming apparatus according to claim 1, wherein the latent image potential on the electrophotographic photosensitive member is a binary latent image potential of an exposed portion and a non-exposed portion by an exposure unit.   6. The image forming apparatus according to claim 1, wherein the image forming apparatus does not have a charge eliminating unit for removing a residual potential difference remaining on the electrophotographic photosensitive member after passing through the transfer unit. An electrophotographic photoreceptor;
Application of applying either voltage or current to the charging member so that the charging potential of the charging member arranged on the electrophotographic photosensitive member and the electrophotographic photosensitive member before exposure after charging becomes a saturated charging potential. And a charging means for charging the surface of the electrophotographic photosensitive member. A charging member disposed on the electrophotographic photosensitive member, and an application member that applies either a voltage or a current to the charging member so that the charging potential of the electrophotographic photosensitive member before exposure after charging becomes a saturated charging potential. A charging step for charging the surface of the electrophotographic photosensitive member,
Exposing the charged electrophotographic photoreceptor surface to form an electrostatic latent image; and
A developing step of developing the electrostatic latent image with toner to form a visible image;
A transfer step of transferring the visible image to a recording medium;
An image forming method comprising: