JP6086023B2 - Electrophotographic photosensitive member, electrophotographic image forming method, and electrophotographic image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member, an electrophotographic image forming method, and an electrophotographic image forming apparatus. More specifically, the present invention provides a high-quality image that has high durability and does not cause fogging due to toner scattering even when used in a high-speed machine. The present invention relates to an electrophotographic photosensitive member that can be obtained, an electrophotographic image forming method using the electrophotographic photosensitive member, and an electrophotographic image forming apparatus.

  In recent years, the use of digital electrophotographic image forming apparatuses not only for office use but also in the light printing field of the print-on-demand system (POD system) The demand is growing. To obtain a high-definition and high-quality image, the toner tends to have a smaller particle size.

  However, these toners having a small particle diameter have a large adhesion force to the surface of an electrophotographic photoreceptor (hereinafter also simply referred to as “photoreceptor”), and it is difficult to remove residual toner adhered to the photoreceptor surface after the transfer process. It tends to be enough. In the cleaning method using a rubber blade, a phenomenon such as "toner slipping" where the toner passes through the blade, "blade curl" where the blade is reversed, or generation of scratching noise between the photosensitive member and the blade, so-called "blade squealing" occurs. Cheap.

  In order to solve the “toner slip-through” described above, it is necessary to increase the contact pressure of the blade to the photosensitive member. However, the repeated use causes a problem that the surface of the photosensitive member is worn and durability is insufficient. Occur. Further, it is required to have sufficient durability against deterioration caused by ozone and nitrogen oxides generated during charging.

  For this reason, a technique has been proposed in which a surface protective layer (hereinafter also simply referred to as “protective layer”) is provided on the surface of the photoreceptor to improve the wear resistance (see, for example, Patent Document 1).

  On the other hand, there is a demand for an increase in print speed (number of prints per hour) while maintaining high-definition and high-quality images.

  In order to increase the printing speed, it is necessary to increase the line speed of the image forming apparatus. For this reason, the rotational speed of the photosensitive member is increased, and at the same time, the rotational speed of the developing sleeve of the developing device is increased to ensure developability. Need arises. However, if the rotational speed of the photosensitive member or the developing sleeve is increased, if toner with a small particle diameter is used, the toner inevitably tends to scatter, so a part of the scattered toner is exposed to light. It adheres to the surface of the body, and as a result, fog (background fog) occurs in the image. For this reason, it has been extremely difficult to achieve both high speed and high image quality. This phenomenon was remarkable when styrene-acrylic resin was used for the toner and acrylic resin was contained in the surface protective layer of the photoreceptor.

JP 2012-247474 A

  The present invention has been made in view of the above-described problems and circumstances, and the solution is to obtain a high-quality image that has high durability and does not cause fogging due to toner scattering even when used in a high-speed machine. An electrophotographic photoreceptor, an electrophotographic image forming method and an electrophotographic image forming apparatus using the electrophotographic photoreceptor are provided.

  In order to solve the above problems, the present inventors have found that the above problems can be solved by including organic particles in the surface protective layer of the photoreceptor in the process of examining the cause of the above problems, etc. .

  That is, the said subject which concerns on this invention is solved by the following means.

1. An electrophotographic photoreceptor in which at least a photosensitive layer and a surface protective layer are sequentially laminated on a conductive support, and the surface protective layer contains metal oxide particles, a binder resin, and organic particles,
The binder resin contains a resin obtained by polymerizing a crosslinkable polymerizable compound,
The organic particles, styrene - electrophotographic photoreceptor, characterized in that an acrylic resin particles or polystyrene resin particles child.
2. 2. The electrophotographic photosensitive member according to item 1, wherein the organic particles are styrene-acrylic resin particles.

3 . 3. The electrophotographic photosensitive member according to item 1 or 2, wherein the organic particles have a number average primary particle size in the range of 0.01 to 5.00 μm.
4). 4. The electrophotographic photosensitive member according to any one of items 1 to 3, wherein the number average primary particle size of the organic particles is in a range of 0.01 to 1.00 μm.

5 . The organic particles are mixed with a magnetic powder-dispersed carrier, and when measured by a blow-off method, the charge amount of the organic particles is in the range of −400 to −20 μC / g . The electrophotographic photosensitive member according to any one of Items 4 to 4 .

6 . The electrophotographic photosensitive member according to any one of items 1 to 5 , wherein the organic particles contain a crosslinked resin.

7 . The crosslinkable polymerizable compound is a polymerizable compound having two or more polymerizable functional groups, and the polymerizable functional group having at least one selected from an acryloyl group and a methacryloyl group. The electrophotographic photosensitive member according to any one of items 1 to 6 .

8 . The electrophotographic photosensitive material according to any one of items 1 to 7, wherein the metal oxide particles are any of tin oxide particles, titanium oxide particles, alumina particles, and zinc oxide particles. body.

9 . The electrophotographic photosensitive member according to any one of items 1 to 8, wherein the metal oxide particles are surface-treated with a surface treating agent having a reactive organic group.

10 . Any one of Items 1 to 9 , wherein the surface protective layer contains the organic particles in a range of 5 to 100 parts by mass with respect to 100 parts by mass of the crosslinkable polymerizable compound. The electrophotographic photosensitive member according to claim 1.

11 . An electrophotographic image forming method using the electrophotographic photosensitive member according to any one of items 1 to 10 , comprising at least a charging step, an exposure step, a development step, and a transfer step, An electrophotographic image forming method, wherein the toner for developing an electrostatic latent image used in the developing step contains a styrene-acrylic resin.

12 . An electrophotographic image forming apparatus using the electrophotographic photosensitive member according to any one of items 1 to 10 , comprising at least a charging unit, an exposure unit, a developing unit, and a transfer unit, An electrophotographic image forming apparatus, wherein the electrostatic latent image developing toner used in the developing means contains a styrene-acrylic resin.

  By the above means of the present invention, an electrophotographic photosensitive member capable of obtaining a high-quality image having high durability and no occurrence of fogging due to toner scattering even when used in a high-speed machine, and an electron using the electrophotographic photosensitive member A photographic image forming method and an electrophotographic image forming apparatus can be provided.

  The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

In a digital electrophotographic image forming apparatus using a negatively charged organic photoreceptor, a negatively charged toner is used, and the surface potential (V ₀ ) is reduced (decreased as an absolute value) by image exposure. The negatively charged toner adheres to the portion and is visualized (developed).

In a high-speed electrophotographic image forming apparatus, since the rotational speed of the photosensitive member and the developing sleeve is increased, the rubbing force between the surface of the photosensitive member and the toner is increased, and the toner and the photosensitive member are frictionally charged. At this time, the surface of the photoconductor is positively charged, that is, the surface potential (V ₀ ) of the photoconductor slightly decreases (decreases as an absolute value). Due to the decrease in the surface potential, it is estimated that the negatively charged toner adheres to the surface of the photoreceptor.

  That is, a resin obtained by polymerizing a crosslinkable polymerizable compound having an acryloyl group or a methacryloyl group as a binder resin for a surface protective layer of a photoreceptor using a styrene-acrylic resin as a binder resin for a negatively chargeable toner. When used, the binder resin of the surface protective layer of the photoreceptor becomes positively chargeable with respect to the toner binder resin. Therefore, when the photoconductor and toner are triboelectrically charged, the surface of the photoconductor is charged in the positive direction. Therefore, the surface potential of the photoconductor is lower than the surface potential when charged in the charging process (image exposure). Even in the absence of). Since the surface potential of the photoconductor is lower than a predetermined surface potential, negatively charged toner is likely to adhere to the surface of the photoconductor. Particularly in a high-speed machine, since the rubbing force between the surface of the photoreceptor and the toner becomes large, it is considered that the effect of frictional charging due to rubbing becomes large and fogging increases.

However, when the above-mentioned organic particles are added to the surface protective layer of the photoreceptor, the organic particles are exposed on the surface of the surface protective layer, and the organic particles and the toner are rubbed to reduce the photoreceptor surface potential (V ₀ ). Therefore, it is considered that the occurrence of fogging can be suppressed.

The figure explaining the layer structure of the electrophotographic photosensitive member of this invention Schematic illustrating an example of the configuration of the electrophotographic image forming apparatus of the present invention

  The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor in which a photosensitive layer and a surface protective layer are sequentially laminated on a conductive support, and the surface protective layer comprises metal oxide particles, a binder resin, and organic particles. The binder resin contains a resin obtained by polymerizing a crosslinkable polymerizable compound, and the organic particles are either styrene-acrylic resin particles, polystyrene resin particles, or silicone resin particles. It is characterized by being. This feature is a technical feature common to the inventions according to claims 1 to 10.

  As an embodiment of the present invention, it is preferable that the number average primary particle size of the organic particles is in the range of 0.01 to 5.00 μm because a cleaning effect can be obtained by imparting uneven shapes to the surface of the photoreceptor.

  Further, it is preferable that the charge amount when the organic particles are measured by a magnetic powder dispersion type carrier and the blow-off method is in the range of −400 to −20 μC / g because the effect of suppressing the scattering of toner is obtained and the fog is reduced. .

  Moreover, since the hardness of a surface protective layer is not impaired when the said organic particle contains resin bridge | crosslinked, it is preferable.

  Furthermore, the crosslinkable polymerizable compound is reactive when it has two or more polymerizable functional groups, and the polymerizable functional group is a polymerizable compound having at least one selected from an acryloyl group or a methacryloyl group. Is preferable because it can be a high-hardness surface protective layer.

  Further, it is preferable that the metal oxide particles are any of tin oxide particles, titanium oxide particles, alumina (aluminum oxide) particles, or zinc oxide particles because wear resistance is improved.

  Furthermore, if the metal oxide particles are surface-treated with a surface treatment agent having a reactive organic group, a crosslinkable polymerizable compound and a crosslinked structure are formed, so that a stronger surface protective layer is formed. Is preferable.

  Further, when the surface protective layer contains the organic particles in the range of 5 to 100 parts by mass with respect to 100 parts by mass of the crosslinkable polymerizable compound, an effect of suppressing toner scattering is obtained and fogging is reduced. Since an effect is acquired, it is preferable.

  The electrophotographic photosensitive member of the present invention can be suitably used for an electrophotographic image forming method using an electrostatic latent image developing toner containing a styrene-acrylic resin, and an electrophotographic image forming apparatus. Thereby, even in a high-speed machine, a high-quality image free from fogging due to toner scattering can be obtained.

  Hereinafter, the constituent elements of the present invention, and modes and modes for carrying out the present invention will be described in detail. In the present application, “to” is used in the sense of including the numerical values described before and after the lower limit value and the upper limit value.

≪Electrophotographic photoreceptor≫
The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor in which a photosensitive layer and a surface protective layer are sequentially laminated on a conductive support, and the surface protective layer comprises metal oxide particles, a binder resin, and organic particles. The binder resin contains a resin obtained by polymerizing a crosslinkable polymerizable compound, and the organic particles are either styrene-acrylic resin particles, polystyrene resin particles, or silicone resin particles. It is characterized by being.

The photosensitive layer has both the function of generating light by absorbing light and the function of transporting charge. The layer structure of the photosensitive layer is a single layer structure containing a charge generating material and a charge transporting material. Alternatively, a stacked structure of a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material may be used. Further, an intermediate layer may be provided between the conductive support and the photosensitive layer as necessary. The layer structure of the photosensitive layer is not particularly limited, and examples of specific layer structures including the surface protective layer include the following.
(1) Layer configuration in which a charge generation layer, a charge transport layer, and a surface protective layer are sequentially laminated on a conductive support. (2) A single layer containing a charge transport material and a charge generation material on a conductive support. (3) Layer configuration in which an intermediate layer, a charge generation layer, a charge transport layer, and a surface protection layer are sequentially stacked on a conductive support (4) Conductivity A layer structure in which an intermediate layer, a single-layer photosensitive layer containing a charge transporting substance and a charge generating substance, and a surface protective layer are sequentially laminated on the photosensitive support. ), And among these, a layer structure prepared by sequentially providing an intermediate layer, a charge generation layer, a charge transport layer, and a surface protective layer on a conductive support is particularly preferable. .

  FIG. 1 is a schematic view showing an example of the layer structure of the photoreceptor of the present invention. In FIG. 1, 1 is a conductive support, 2 is a photosensitive layer, 3 is an intermediate layer, 4 is a charge generation layer, 5 is a charge transport layer, 6 is a surface protective layer, 7a is organic particles, and 7b is metal oxide particles. Indicates.

  Next, the structure of the surface protective layer, the conductive support, the intermediate layer, and the photosensitive layer (charge generation layer and charge transport layer) constituting the photoreceptor of the present invention will be described in order.

<Surface protective layer>
The photoreceptor of the present invention has a structure in which at least a photosensitive layer and a surface protective layer are sequentially laminated on a conductive support. The surface protective layer contains metal oxide particles, a binder resin, and organic particles, the binder resin contains a resin obtained by polymerizing a crosslinkable polymerizable compound, and the organic particles are It contains either styrene-acrylic resin particles, polystyrene resin particles, or silicone resin particles.

<Organic particles>
The organic particles that can be used in the surface protective layer according to the present invention are either styrene-acrylic resin particles, polystyrene resin particles, or silicone resin fine particles.

  The number average primary particle size of these organic particles is preferably in the range of 0.01 to 5.00 μm, and more preferably in the range of 0.10 to 3.50 μm. Within this range, when the surface protective layer is formed, the particles are exposed on the surface of the surface protective layer, and the rubbing force with the toner is increased during development, thereby suppressing a decrease in the surface potential of the photoreceptor. .

  These organic particles generally have the same polarity as that of a styrene-acrylic resin used as a binder resin for a negatively charged toner, and when included in a protective layer of the photosensitive member, the surface potential of the negatively charged photosensitive member is obtained. Is not lowered (charged to the positive side), so that occurrence of fogging due to toner scattering can be suppressed.

  In addition, these organic particles preferably have a charge amount measured by the blow-off method under the following conditions with a magnetic powder-dispersed carrier in the range of −400 to −20 μC / g, and more preferably, It is in the range of −350 to −100 μC / g. Within this range, it is possible to effectively suppress the charging of the surface of the photoconductor to the plus side, and thus it is possible to suppress the occurrence of fog due to rubbing with the toner.

(Magnetic powder dispersion type carrier)
The magnetic powder-dispersed carrier (also referred to as a binder-type carrier) according to the present invention is a carrier having a volume average particle diameter of 60 μm in which ferrite particles are dispersed in a polyester resin, and can be produced as follows. it can.

(Method of manufacturing magnetic powder dispersed carrier)
100 parts by mass of a polyester resin (glass transition point (Tg) of 67 ° C., softening point (Tm) of 123 ° C.) manufactured by Kao Corporation, and 500 parts by mass of ferrite particles “MFP-2” (manufactured by TDK) 2 parts by weight of carbon black “Ketjen Black EC” (manufactured by Lion Co., Ltd.) and 1.5 parts by mass of silica “Aerosil # 200” (manufactured by Nippon Aerosil Co., Ltd.) are mixed thoroughly with a Henschel mixer, After melt-kneading with an extrusion kneader, this mixture is cooled, coarsely pulverized, and then pulverized and classified to obtain magnetic particles. The magnetic particles are heat-treated at 300 ° C. for 1 minute to obtain carrier particles having a volume average particle size of 60 μm.

(Measurement method of charge amount)
The charge amount of the organic particles can be measured using a blow-off charge amount measuring device “TB-200” (manufactured by Toshiba Chemical Corporation).

In particular,
(1) In an environment of room temperature and 50% RH, 10 g of a sample (a mixture of 98 parts by mass of a magnetic powder-dispersed carrier carrier and 2 parts by mass of organic particles is placed in a 20 cm ³ glass bottle, and the glass bottle is tapped with a tap denser “tapping” The glass bottle is shaken 10,000 times in “Denser KYT-2000” (manufactured by Seishin Enterprise).
(2) From the glass bottle, 1.0 g of a sample is put in a measurement cell, and the cell is placed on an electronic balance and set to 0 point.
(3) Set the cell in the blow-off charge measuring device “TB-200”, press the measurement button, blow nitrogen gas for 60 seconds at a blow pressure of 9.8 × 10 ⁴ Pa (1 kgf / cm ² ), and display The amount of charge Q (μC) to be recorded is recorded.
(4) Remove the cell from the apparatus, place the cell on the electronic balance described above, measure the mass of the cell, and record the mass m (g) of the flying organic particles.
(5) From the charge amount Q (μC) obtained as described above and the mass m (g) of the blown-off organic particles, the charge amount Q / m (μC / g) is obtained by calculation.

  The organic particles according to the present invention preferably contain a crosslinked resin. By containing the crosslinked resin, the hardness of the surface protective layer is not impaired, and the effect of improving the wear resistance can be obtained.

  The organic particles according to the present invention are any of styrene-acrylic resin particles, polystyrene resin particles, and silicone resin particles, and among these, silicone particles and styrene-acrylic resin particles are preferable from the viewpoint of solvent resistance.

  When the content of these organic particles is within the range of 5 to 100 parts by mass with respect to 100 parts by mass of the crosslinkable polymerizable compound, the effect of suppressing toner scattering is obtained and the effect of reducing fogging is obtained. Since it is obtained, it is preferable. Further, it is preferable from the viewpoint of improving the wear resistance of the surface protective layer.

(Measurement method of number average primary particle size)
The number average primary particle size of the organic particles can be measured as follows.

  The above organic particles were photographed with a transmission electron microscope “JEM-2000FX” (manufactured by JEOL Ltd.) at an acceleration voltage of 80 kV at a magnification of 10,000, and photograph images were captured by a scanner, and an image processing analysis apparatus “LUZEX (registered) (Trademark) AP "(manufactured by Nireco Corporation) was used to binarize the organic particles of the photographic image, calculate the horizontal ferret diameter for 100 organic particles, and calculate the average value as the number average primary particle diameter. To do. Here, the horizontal ferret diameter refers to the length of a side parallel to the x-axis of the circumscribed rectangle when the image of the external additive is binarized.

<Binder resin>
The binder resin contained in the surface protective layer according to the present invention contains a resin obtained by polymerizing a crosslinkable polymerizable compound. As the crosslinkable polymerizable compound, a radical polymerizable compound having two or more radical polymerizable reactive groups is preferable, and as the radical polymerizable compound, at least one of an acryloyl group or a methacryloyl group is used as the radical polymerizable reactive group. The radically polymerizable monomer having

  Examples of these radically polymerizable monomers include the following compounds, but the radically polymerizable monomers that can be used in the present invention are not limited to these.

  The above radical polymerizable monomers are known and can be obtained as commercial products.

  Here, R represents the following acryloyl group, and R ′ represents the following methacryloyl group.

  In addition to the resin obtained by polymerizing the crosslinkable polymerizable compound, the binder resin contained in the surface protective layer according to the present invention is a polyester resin, a polycarbonate resin, or the like, as long as the hardness of the surface protective layer is not impaired. Known resins such as polyurethane resins or silicone resins can be used in combination.

<Metal oxide particles>
The surface protective layer according to the present invention preferably contains metal oxide particles because the wear resistance is improved. Examples of the metal oxide particles include silica particles, magnesium oxide particles, zinc oxide particles, alumina (aluminum oxide) particles, zirconium oxide particles, tin oxide particles, titanium oxide particles, niobium oxide particles, molybdenum oxide particles, and vanadium oxide particles. Among them, tin oxide particles, titanium oxide particles, alumina (aluminum oxide) particles, and zinc oxide particles are preferable. The number average primary particle size of the metal oxide particles is preferably in the range of 1 to 300 nm. Especially preferably, it exists in the range of 3-100 nm. It is preferable that the number average primary particle size of the metal oxide particles is in the above range since the transparency of the surface protective layer can be obtained.

(Surface-treated metal oxide particles)
The metal oxide particles contained in the surface protective layer according to the present invention are preferably those treated with a surface treatment agent, and more preferably those treated with a surface treatment agent having a reactive organic group. .

(Surface treatment agent)
As the surface treatment agent according to the present invention, a surface treatment agent that reacts with a hydroxy group or the like present on the surface of the metal oxide particles is preferable, and as these surface treatment agents, a silane coupling agent, a titanium coupling agent, or the like. Can be mentioned. In the present invention, a surface treatment agent having a reactive organic group is preferred for the purpose of further increasing the hardness of the surface protective layer, and the surface treatment agent having a reactive organic group has a radically polymerizable reactive group. A surface treatment agent is preferred. These radical polymerizable reactive groups can react with the crosslinkable polymerizable compound according to the present invention to form a strong protective film. As the surface treatment agent having a radical polymerizable reactive group, a silane coupling agent having a radical polymerizable reactive group such as a vinyl group, acryloyl group or methacryloyl group is preferable, and the surface treatment agent having such a radical polymerizable reactive group. Examples of these include the following known compounds.

_{S-1: CH 2 = CHSi} (CH 3) (OCH 3) 2
_{S-2: CH 2 = CHSi} (OCH 3) 3
S-3: CH ₂ = CHSiCl _{3
S-4: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-5: CH 2 = CHCOO} (CH 2) 2 Si (OCH 3) 3
_{S-6: CH 2 = CHCOO} (CH 2) 2 Si (OC 2 H 5) (OCH 3) 2
_{S-7: CH 2 = CHCOO} (CH 2) 3 Si (OCH 3) 3
_{S-8: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) Cl 2
_{S-9: CH 2 = CHCOO} (CH 2) 2 SiCl 3
_{S-10: CH 2 = CHCOO} (CH 2) 3 Si (CH 3) Cl 2
S-11: CH ₂ = CHCOO (CH ₂ ) ₃ SiCl _{3
S-12: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-13: CH 2 = C} (CH 3) COO (CH 2) 2 Si (OCH 3) 3
_{S-14: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-15: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OCH 3) 3
_{S-16: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) Cl 2
_{S-17: CH 2 = C} (CH 3) COO (CH 2) 2 SiCl 3
_{S-18: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) Cl 2
_{S-19: CH 2 = C} (CH 3) COO (CH 2) 3 SiCl 3
_{S-20: CH 2 = CHSi} (C 2 H 5) (OCH 3) 2
_{S-21: CH 2 = C} (CH 3) Si (OCH 3) 3
_{S-22: CH 2 = C} (CH 3) Si (OC 2 H 5) 3
_{S-23: CH 2 = CHSi} (OCH 3) 3
_{S-24: CH 2 = C} (CH 3) Si (CH 3) (OCH 3) 2
_{S-25: CH 2 = CHSi} (CH 3) Cl 2
_{S-26: CH 2 = CHCOOSi} (OCH 3) 3
_{S-27: CH 2 = CHCOOSi} (OC 2 H 5) 3
_{S-28: CH 2 = C} (CH 3) COOSi (OCH 3) 3
_{S-29: CH 2 = C} (CH 3) COOSi (OC 2 H 5) 3
_{S-30: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OC 2 H 5) 3
_{S-31: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) 2 (OCH 3)
_{S-32: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OCOCH 3) 2
_{S-33: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (ONHCH 3) 2
_{S-34: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OC 6 H 5) 2
_{S-35: CH 2 = CHCOO} (CH 2) 2 Si (C 10 H 21) (OCH 3) 2
_{S-36: CH 2 = CHCOO} (CH 2) 2 Si (CH 2 C 6 H 5) (OCH 3) 2

  Moreover, as a surface treating agent, you may use the silane compound which has the reactive organic group which can be radically polymerized other than said S-1 to S-36. These surface treatment agents can be used alone or in admixture of two or more.

(Method for producing surface-treated metal oxide particles)
In performing the surface treatment, it is preferable to perform treatment using a wet media dispersion type apparatus using 0.1 to 100 parts by mass of a surface treatment agent and 50 to 5000 parts by mass of a solvent with respect to 100 parts by mass of metal oxide particles. Moreover, it can also process by a dry type.

  Below, the surface treatment method which manufactures the metal oxide particle surface-treated uniformly with the surface treating agent is demonstrated.

  That is, by subjecting a slurry (suspension of solid particles) containing metal oxide particles and a surface treatment agent to wet pulverization, the metal oxide particles are refined and the surface treatment of the particles proceeds at the same time. Thereafter, by removing the solvent and pulverizing, metal oxide particles that are uniformly surface-treated with the surface treatment agent can be obtained.

  The wet media dispersion type apparatus which is a surface treatment apparatus used in the present invention is a metal oxide particle by filling beads in a container as a medium and further rotating a stirring disk mounted perpendicularly to a rotation axis at high speed. It is an apparatus which has the process of crushing, crushing and dispersing the aggregated particles. As the configuration, there is no problem if the metal oxide particles are sufficiently dispersed when the surface treatment is performed on the metal oxide particles and the surface treatment can be performed, for example, vertical type / horizontal type, continuous type / batch type, etc. Various modes can be adopted. Specifically, a sand mill, ultra visco mill, pearl mill, glen mill, dyno mill, agitator mill, dynamic mill and the like can be used. These dispersion-type devices are finely pulverized and dispersed by impact crushing, friction, shearing, shear stress, and the like using a grinding medium (media) such as balls or beads.

  As beads used in the wet media dispersion type apparatus, balls made of glass, alumina, zircon, zirconia, steel, flint stone, or the like can be used, and those made of zirconia or zircon are particularly preferable. Further, as the size of the beads, those having a diameter of about 1 to 2 mm are usually used, but in the present invention, those having a diameter of about 0.1 to 1.0 mm are preferably used.

  Various materials such as stainless steel, nylon and ceramic can be used for the disk and container inner wall used in the wet media dispersion type apparatus. In the present invention, the disk and container inner wall made of ceramic such as zirconia or silicon carbide are particularly used. Is preferred.

  The metal oxide particles surface-treated with the surface treatment agent can be obtained by the wet treatment as described above. The surface-treated metal oxide particles described above are preferably contained within a range of 30 to 250 parts by mass with respect to 100 parts by mass of the crosslinkable polymerizable compound from the viewpoint of improving the wear resistance of the surface protective layer. .

  In addition to these, the surface protective layer according to the present invention may contain lubricant particles and the like as necessary.

<Lubricant particles>
As the lubricant particles contained in the surface protective layer according to the present invention, for example, fluorine atom-containing resin particles can be added. Fluorine atom-containing resin particles include tetrafluoroethylene resin, trifluorinated ethylene chloride resin, hexafluoroethylene chloride propylene resin, vinyl fluoride resin, vinylidene fluoride resin, ethylene difluoride dichloride resin, and their co-polymers. Examples thereof include polymers, and it is preferable to appropriately select one or two or more of these, and tetrafluoroethylene resin and vinylidene fluoride resin are particularly preferable.

<Formation of surface protective layer>
The surface protective layer is prepared by adding a coating solution prepared by adding organic particles, crosslinkable polymerizable compounds, metal oxide particles, and other binder resins, polymerization initiators, lubricant particles, and the like, as required. Can be applied to the surface of the photosensitive layer by natural drying or heat drying and curing. The thickness of the surface protective layer is preferably in the range of 0.2 to 10 μm, and more preferably in the range of 0.5 to 6 μm.

(solvent)
Solvents used for forming the surface protective layer include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, benzyl alcohol, methyl isopropyl ketone, and methyl isobutyl. Ketone, methyl ethyl ketone, cyclohexane, toluene, xylene, methylene chloride, ethyl acetate, butyl acetate, 2-methoxyethanol, 2-ethoxyethanol, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, diethylamine, and the like. It is not limited to these.

(Polymerization initiator)
Examples of a method for polymerizing a crosslinkable polymerizable compound that can be used in the surface protective layer according to the present invention include a method using an electron beam cleavage reaction and a method using light and heat in the presence of a radical polymerization initiator. A polymerization reaction can be performed. When performing a polymerization reaction using a radical polymerization initiator, both a photopolymerization initiator and a thermal polymerization initiator can be used as the polymerization initiator. Further, both light and heat initiators can be used in combination.

  Examples of the polymerization initiator that can be used in the surface protective layer according to the present invention include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylazobisvaleronyl), and 2,2. Azo compounds such as 2'-azobis (2-methylbutyronitrile), benzoyl peroxide (BPO), di-tert-butyl hydroperoxide, tert-butyl hydroperoxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, peroxide And thermal polymerization initiators such as peroxides such as bromomethylbenzoyl and lauroyl peroxide.

  Examples of the photopolymerization initiator include diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1 (Irgacure 369: manufactured by BASF Japan Ltd.), 2-hydroxy-2-methyl- Such as 1-phenylpropan-1-one, 2-methyl-2-morpholino (4-methylthiophenyl) propan-1-one and 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime Acetophenone or ketal photoinitiator, benzoin, benzoin methyl ether, benzo Benzoin ether photopolymerization initiators such as ethyl ether, benzoin isobutyl ether and benzoin isopropyl ether, benzophenone, 4-hydroxybenzophenone, methyl o-benzoylbenzoate, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoylphenyl ether Benzophenone photopolymerization initiators such as acrylated benzophenone and 1,4-benzoylbenzene, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone and 2,4-dichlorothioxanthone And thioxanthone-based photopolymerization initiators.

  Other photopolymerization initiators include ethyl anthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine Oxide (Irgacure 819: manufactured by BASF Japan), bis (2,4-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10-phenanthrene, acridine compound, triazine And imidazole compounds. Moreover, what has a photopolymerization acceleration effect can also be used individually or in combination with the said photoinitiator. Examples include triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, ethyl (2-dimethylamino) benzoate, and 4,4′-dimethylaminobenzophenone.

  The polymerization initiator used in the surface protective layer according to the present invention is preferably a photopolymerization initiator, preferably an alkylphenone compound and a phosphine oxide compound, and more preferably an α-hydroxyacetophenone structure or an acylphosphine oxide structure. Initiators having are preferred.

  These polymerization initiators may be used alone or in combination of two or more. Content of a polymerization initiator is 0.1-40 mass parts with respect to 100 mass parts of a crosslinkable polymeric compound, Preferably it is the range of 0.5-20 mass parts.

(Surface protection layer curing method)
In the present invention, the polymerization reaction of the surface protective layer is performed by irradiating the coating film with active rays to generate radicals, polymerize, and cure by forming a cross-linking bond between the molecules and within the molecule by a cross-linking reaction. Is preferably generated. The actinic rays are preferably light such as ultraviolet rays and visible light and electron beams, and ultraviolet rays are particularly preferred from the viewpoint of ease of use.

As the ultraviolet light source, any light source that generates ultraviolet light can be used without limitation. For example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, a flash (pulse) xenon, an ultraviolet LED, or the like can be used. Irradiation conditions differ depending on each lamp, but the irradiation amount of active rays is usually in the range of 1 to ²⁰ mJ / cm ² , preferably in the range of 5 to 15 mJ / cm ² . The output voltage of the light source is preferably in the range of 0.1 to 5 kW, more preferably in the range of 0.5 to 3 kW.

  As an electron beam source, there is no particular limitation on the electron beam irradiation apparatus, and generally, an electron beam accelerator for electron beam irradiation is a curtain beam type that is relatively inexpensive and can provide a large output. Used. The acceleration voltage during electron beam irradiation is preferably in the range of 100 to 300 kV. The absorbed dose is preferably in the range of 0.005 Gy to 100 kGy (0.5 rad to 10 Mrad).

  The irradiation time of the active ray is a time for obtaining the necessary irradiation amount of the active ray, specifically, preferably in the range of 0.1 second to 10 minutes, and from the viewpoint of polymerization efficiency or work efficiency, 1 second to 5 minutes. A range is more preferred.

  In the present invention, the surface protective layer can be dried before and after irradiation with actinic radiation and during irradiation with actinic radiation, and the timing of drying can be appropriately selected in combination with the irradiation conditions of actinic radiation. The drying conditions for the surface protective layer can be appropriately selected depending on the type of solvent used in the coating solution, the film thickness of the surface protective layer, and the like. The drying temperature is preferably in the range of room temperature to 180 ° C, particularly preferably in the range of 80 to 140 ° C. The drying time is preferably in the range of 1 to 200 minutes, particularly preferably in the range of 5 to 100 minutes. In the present invention, the amount of the solvent contained in the surface protective layer can be controlled in the range of 20 ppm to 75 ppm by drying the surface protective layer under the above drying conditions.

  By providing the surface protective layer on the photosensitive layer as described above, it is possible to increase the hardness of the surface of the photoreceptor, improve the wear resistance, and improve the durability.

<Conductive support>
The support used in the photoconductor of the present invention may be any one as long as it has conductivity. For example, a metal such as aluminum, copper, chromium, nickel, zinc and stainless steel is formed into a drum or a sheet. , Metal foil such as aluminum or copper laminated on plastic film, aluminum, indium oxide and tin oxide deposited on plastic film, conductive material applied alone or with binder resin to provide conductive layer Examples include metals, plastic films, and paper.

《Middle layer》
In the photoreceptor of the present invention, an intermediate layer having a barrier function and an adhesive function can be provided between the conductive support and the photosensitive layer. The intermediate layer can be formed by dip coating or the like by dissolving a binder resin such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane and gelatin in a known solvent. Among the binder resins, an alcohol-soluble polyamide resin is preferable.

  The intermediate layer can contain various conductive fine particles and metal oxide particles for the purpose of adjusting the resistance. For example, various metal oxide particles such as alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, and bismuth oxide. Ultrafine particles such as indium oxide doped with tin, tin oxide doped with antimony, and zirconium oxide can be used. These metal oxide particles can be used alone or in combination. When two or more kinds are mixed and used, they may take the form of a solid solution or fusion. Such metal oxide particles preferably have a number average primary particle size of 0.3 μm or less, more preferably 0.1 μm or less.

  As the solvent that can be used for forming the intermediate layer, a solvent in which inorganic fine particles such as the metal oxide particles described above are well dispersed and a binder resin such as a polyamide resin is dissolved is preferable. Specifically, with respect to the polyamide resin in which alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol and sec-butanol are preferred as the binder resin. It is preferable because good solubility and coating performance are exhibited. In order to improve the storage stability and the dispersibility of the inorganic fine particles, the following cosolvent can be used in combination with the solvent. Examples of the co-solvent that can provide a preferable effect include methanol, benzyl alcohol, toluene, cyclohexanone, and tetrahydrofuran.

  The binder resin concentration at the time of forming the coating solution can be appropriately selected according to the film thickness of the intermediate layer and the coating method. Moreover, when inorganic fine particles etc. are disperse | distributed, it is preferable that the mixing ratio of the inorganic fine particles with respect to binder resin shall be 20-400 mass parts with respect to 100 mass parts of binder resin, and is 50-200 mass parts. It is more preferable.

  Examples of the means for dispersing the inorganic fine particles include, but are not limited to, an ultrasonic disperser, a ball mill, a sand grinder, and a homomixer.

  Moreover, the drying method of an intermediate | middle layer can select suitably a well-known drying method according to the kind of solvent and the film thickness to form, and heat drying is especially preferable.

  The thickness of the intermediate layer is preferably in the range of 0.1 to 15 μm, and more preferably in the range of 0.3 to 10 μm.

<< Photosensitive layer >>
As described above, the photosensitive layer constituting the photoreceptor of the present invention has a charge generation layer (CGL) and a charge transport layer (CTL) in addition to a single layer configuration in which a charge generation function and a charge transport function are provided in one layer. And a layer structure in which the functions of the photosensitive layer are separated from each other. As described above, the function-separated layer structure has a merit that it is easy to control various electrophotographic characteristics according to the purpose, in addition to being able to control the increase in residual potential with repeated use. The negatively chargeable photoreceptor has a structure in which a charge generation layer (CGL) is provided on an intermediate layer and a charge transport layer (CTL) is provided thereon. The positively chargeable photoreceptor is a charge transport layer (CTL) provided on the intermediate layer. The charge generation layer (CGL) is provided thereon. A preferred layer structure of the photosensitive layer is a negatively charged photoreceptor having the function separation structure.

  Below, each layer of the photosensitive layer of the function-separated negatively charged photosensitive member will be described as a specific example of the photosensitive layer.

<Charge generation layer>
The charge generation layer contains a charge generation material (CGM) and a binder resin, and is preferably formed by applying a coating solution in which the charge generation material is dispersed in a binder resin solution.

  Examples of the charge generation material include azo raw materials such as Sudan Red and Diane Blue, quinone pigments such as pyrenequinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, and phthalocyanine pigments. Of these, phthalocyanine pigments having a sensitivity of 700 nm or more are preferable, and titanyl phthalocyanine pigments are particularly preferable. However, charge generating materials that can be used in the photoreceptor of the present invention are not limited thereto.

  These charge generation materials can be used alone or in a form dispersed in a known binder resin.

  As the binder resin contained in the charge generation layer, known resins can be used, for example, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, Epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and copolymer resin containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer) Resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin), and poly-vinyl carbazole resin, but are not limited thereto.

  The charge generation layer is formed by dispersing the charge generation material in a solution obtained by dissolving the binder resin in a solvent using a disperser to prepare a coating solution, and applying the coating solution to a certain film thickness using a coating device. It is preferable to prepare the film by drying.

  Solvents for dissolving and coating the binder resin used in the charge generation layer include, for example, toluene, xylene, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran , 1-dioxane, 1,3-dioxolane, pyridine, diethylamine and the like, but are not limited thereto.

  As a means for dispersing the charge generating material, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

  The mixing ratio of the charge generating material to the binder resin is preferably 1 to 600 parts by mass, more preferably 50 to 500 parts by mass with respect to 100 parts by mass of the binder resin. The thickness of the charge generation layer varies depending on the characteristics of the charge generation material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 0.01 to 5 μm, and more preferably 0.05 to 3 μm. It should be noted that the coating solution for the charge generation layer can prevent the occurrence of image defects by filtering foreign matter and aggregates before coating. It can also be formed by vacuum deposition of the pigment.

<Charge transport layer>
The charge transport layer contains at least a charge transport material (CTM) and a binder resin in the layer, and is formed by dissolving and applying the charge transport material in a binder resin solution.

  As the charge transport material, known compounds can be used, for example, carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidines. Derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly -N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene and the like. These compounds can be used alone or in admixture of two or more.

  In addition, a known resin can be used as the binder resin contained in the charge transport layer. For example, polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylate ester Resin, styrene-methacrylate copolymer resin, and the like. Of these, polycarbonate resins are preferred. Furthermore, polycarbonate resins of a type such as bisphenol A (BPA), bisphenol Z (BPZ), dimethyl BPA type polycarbonate resin and BPA-dimethyl BPA copolymer are crack resistant and abrasion resistant. From the viewpoint of charging characteristics, it is preferable.

  The charge transport layer can be formed by a known method typified by a coating method. For example, in the coating method, a binder resin and a charge transport material are dissolved to prepare a coating solution, and the coating solution is formed into a certain film. A desired charge transport layer can be formed by drying after coating with a thickness.

  Examples of the solvent for dissolving the binder resin and the charge transport material include toluene, xylene, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, tetrahydrofuran, 1,4-dioxane, and 1,3- And dioxolane. The solvent used when preparing the coating liquid for forming the charge transport layer is not limited to the above.

  The mixing ratio of the binder resin and the charge transport material is preferably 10 to 500 parts by weight, and more preferably 20 to 100 parts by weight with respect to 100 parts by weight of the binder resin.

  The thickness of the charge transport layer varies depending on the characteristics of the charge transport material and the binder resin, the mixing ratio thereof, and the like, but is preferably 5 to 40 μm, and more preferably 10 to 30 μm.

  In the charge transport layer, a known antioxidant can be added. For example, an antioxidant described in JP-A-2000-305291 can be used.

《Photoconductor application method》
Each layer such as an intermediate layer, a charge generation layer, a charge transport layer, and a surface protective layer constituting the photoreceptor of the present invention can be formed by a known coating method. Specific examples include a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method, and a circular amount regulating coating method (circular slide hopper coating method). The circular amount regulation type coating method is described in, for example, Japanese Patent Application Laid-Open Nos. 58-189061 and 2005-275373.

≪Electrophotographic image forming method≫
The photoreceptor of the present invention can be used in various well-known electrophotographic image forming methods. For example, it can be used in a monochrome image forming method or a full color image forming method. In the full-color image forming method, a four-cycle type image forming method including four types of color developing devices for each of yellow, magenta, cyan, and black and one photoconductor, and a color developing device for each color In addition, any image forming method such as a tandem image forming method in which image forming units having a photosensitive member and a photoconductor are mounted for each color can be used.

  The electrophotographic image forming method of the present invention is an image forming method using the photoreceptor of the present invention, and includes at least a charging step, an exposure step, a developing step, and a transfer step. Further, the toner image transferred onto the transfer belt or the like is transferred onto the copy paper, and the toner image transferred onto the copy paper is fixed on the copy paper in a fixing process such as a contact heating method, thereby obtaining a visible image. Can do.

  In the present invention, the toner used in the development step is a toner containing a styrene-acrylic resin. When the toner contains a styrene-acrylic resin, the toner is rubbed with organic particles contained in the surface protective layer. A decrease in the surface potential of the surface can be suppressed.

≪Electrophotographic image forming device≫
The electrophotographic image forming apparatus of the present invention will be described.

  The electrophotographic image forming apparatus of the present invention is an image forming method using the photoreceptor of the present invention, and includes at least a charging unit, an exposure unit, a developing unit, and a transfer unit. Further, the toner image transferred onto a transfer belt or the like is transferred onto a copy sheet, and a visible image can be obtained by fixing the toner image transferred onto the copy sheet onto the sheet with fixing means such as a contact heating method. it can.

  In the present invention, the toner used in the developing means is a toner containing a styrene-acrylic resin. When the toner contains a styrene-acrylic resin, the toner is rubbed with organic particles contained in the surface protective layer. A decrease in the surface potential of the surface can be suppressed.

  Note that a non-contact charging device is preferably used as the charging means for charging the electrophotographic photosensitive member. Examples of the non-contact charging device include a corona charging device, a corotron charging device, and a scorotron charging device.

  FIG. 2 is a schematic cross-sectional view illustrating an example of a color image forming apparatus showing one embodiment of the present invention.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes four sets of image forming units (image forming units) 10Y, 10M, 10C, and 10Bk, an endless belt-shaped intermediate transfer body unit 7, and a feeding unit. It comprises a paper conveying means 21 and a fixing means 24. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  The image forming unit 10Y that forms a yellow image includes a charging unit (charging step) 2Y, an exposure unit (exposure step) 3Y, and a developing unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. A unit (developing step) 4Y, a primary transfer roller 5Y as a primary transfer unit (primary transfer step), and a cleaning unit 6Y. The image forming unit 10M that forms a magenta image includes a drum-shaped photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, and It has a cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer roller 5C as a primary transfer unit, And cleaning means 6C. The image forming unit 10Bk that forms a black image includes a drum-shaped photoreceptor 1Bk as a first image carrier, a charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk as a primary transfer unit, and a cleaning unit. 6Bk.

  The four sets of image forming units 10Y, 10M, 10C, and 10Bk are centered around the photosensitive drum 1Y, 1M, 1C, or 1Bk, and charging means 2Y, 2M, 2C, or 2Bk, and exposure means 3Y, 3M, 3C, or 3Bk. And developing means 4Y, 4M, 4C or 4Bk, and cleaning means 6Y, 6M, 6C or 6Bk for cleaning the photosensitive drums 1Y, 1M, 1C or 1Bk.

  The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the colors of the toner images to be formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are different, and the image forming unit 10Y is taken as an example in detail. Explained.

  The image forming unit 10Y has a charging unit 2Y (hereinafter simply referred to as a charging unit 2Y or a charger 2Y), an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 6Y (around a photosensitive drum 1Y as an image forming body). Hereinafter, the cleaning unit 6Y or the cleaning blade 6Y) is simply disposed, and a yellow (Y) toner image is formed on the photosensitive drum 1Y. In the present embodiment, in the image forming unit 10Y, at least the photosensitive drum 1Y, the charging unit 2Y, the developing unit 4Y, and the cleaning unit 6Y are provided so as to be integrated.

  The charging unit 2Y is a unit that applies a uniform potential to the photosensitive drum 1Y. In the present embodiment, a corona discharge type charger 2Y is used for the photosensitive drum 1Y.

  The exposure means 3Y performs exposure based on the image signal (yellow) on the photosensitive drum 1Y given a uniform potential by the charger 2Y, and forms an electrostatic latent image corresponding to the yellow image. The exposure unit 3Y includes an LED having light emitting elements arranged in an array in the axial direction of the photosensitive drum 1Y and an imaging element (trade name; SELFOC (registered trademark) lens). Alternatively, a laser optical system or the like is used.

  The developing means 4Y includes, for example, a developing sleeve that contains a magnet and rotates while holding the developer, and a voltage applying device that applies a DC and / or AC bias voltage between the organic photosensitive member and the developing sleeve. .

  The cleaning unit 6Y includes a cleaning blade and a brush roller provided on the upstream side of the cleaning blade.

  The image forming apparatus of the present invention is configured by integrally combining the above-described photosensitive member and components such as a developing device and a cleaning device as a process cartridge (image forming unit), and this image forming unit is connected to the apparatus main body. It may be configured to be detachable. Further, at least one of a charger, an image exposure device, a developing device, a transfer or separation device, and a cleaning device is integrally supported together with a photosensitive member to form a process cartridge (image forming unit), which is detachable from the apparatus main body. A single image forming unit may be detachable using guide means such as a rail of the apparatus main body.

  The endless belt-shaped intermediate transfer body unit 7 has an endless belt-shaped intermediate transfer body 70 as a second image carrier having a semiconductive endless belt shape that is wound around a plurality of rollers and is rotatably supported.

  The fixing unit 24 is, for example, a heat roller fixing formed by a heating roller having a heating source therein and a pressure roller provided in pressure contact with the heating roller so as to form a fixing nip portion. One of the methods is mentioned.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10Bk is sequentially transferred onto a rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5Bk as primary transfer means. Thus, a synthesized color image is formed. A transfer material P as a transfer material (a support for carrying a fixed final image: for example, plain paper, a transparent sheet, etc.) housed in the paper feed cassette 20 is fed by a paper feed means 21 and a plurality of intermediates. After passing through the rollers 22A, 22B, 22C, 22D and the registration roller 23, they are conveyed to a secondary transfer roller 5b as a secondary transfer means, and are secondarily transferred onto the transfer material P, and the color images are collectively transferred. The transfer material P onto which the color image has been transferred is fixed by the fixing means 24, is sandwiched between the paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus. Here, a toner image transfer support formed on a photosensitive member such as an intermediate transfer member or a transfer material is collectively referred to as a transfer medium.

  On the other hand, after the color image is transferred to the transfer material P by the secondary transfer roller 5b as the secondary transfer means, the residual toner is removed by the cleaning means 6b from the endless belt-shaped intermediate transfer body 70 in which the transfer material P is separated by curvature. The

  During the image forming process, the primary transfer roller 5Bk is always in contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C are in contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5b contacts the endless belt-shaped intermediate transfer body 70 only when the transfer material P passes through the secondary transfer roller 5b.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10Bk, and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10Bk are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1Bk in the drawing. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, and 74, primary transfer rollers 5Y, 5M, 5C, and 5Bk, and a cleaning unit 6b. Become.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

≪Preparation of surface-treated metal oxide particles≫
(Preparation of surface-treated metal oxide particles 1)
100 parts by mass of “tin oxide” having a number average primary particle size of 20 nm as metal oxide particles, 30 parts by mass of “Exemplary Compound S-13” as a polymerizable surface treatment agent, and 1000 parts by mass of methyl ethyl ketone were mixed with a wet sand mill (diameter of 0.5 mm). Alumina beads) and mixed at 30 ° C. for 6 hours, and then methyl ethyl ketone and alumina beads were separated by filtration and dried at 60 ° C. to produce “surface-treated metal oxide particles 1”.

(Preparation of surface-treated metal oxide particles 2 to 6)
Surface-treated metal oxide particles 2 to 6 were produced in the same manner as in the preparation of the surface-treated metal oxide particles 1 except that the metal oxide particles and the surface treatment agent were changed as shown in Table 1.

<< Production of photoconductor >>
<Preparation of Photoreceptor 1>
Photoreceptor 1 was produced as follows.

  The surface of a cylindrical aluminum support having a diameter of 100 mm was cut to prepare a conductive support.

<Intermediate layer>
A dispersion having the following composition was diluted twice with the same solvent, and allowed to stand overnight, followed by filtration (filter; using a lime mesh 5 μm filter manufactured by Nihon Pall) to prepare an intermediate layer coating solution.

Polyamide resin: “CM8000” (manufactured by Toray Industries, Inc.) 1 part by mass Titanium oxide: “SMT500SAS” (manufactured by Teica) 3 parts by mass Methanol 10 parts by mass Using a sand mill as a disperser, dispersion was carried out for 10 hours in a batch system. .

  It apply | coated by the dip coating method so that it might become a dry film thickness of 2 micrometers on the said support body using the said coating liquid.

<Charge generation layer>
Charge generation material: Y-TiPh (Titanyl phthalocyanine pigment (titanyl phthalocyanine pigment having a maximum diffraction peak at a position of at least 27.3 ° by Cu-Kα characteristic X-ray diffraction spectrum measurement)) 20 parts by mass Polyvinyl butyral resin: “# 6000-C "(manufactured by Denki Kagaku Kogyo Co., Ltd.) 10 parts by mass t-butyl acetate 700 parts by mass 4-methoxy-4-methyl-2-pentanone 300 parts by mass are mixed and dispersed for 10 hours using a sand mill to generate charge. A layer coating solution was prepared. This coating solution was applied onto the intermediate layer by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm.

<Charge transport layer>
Charge transport material: 4,4′-dimethyl-4 ″-(β-phenylstyryl) triphenylamine 225 parts by mass Binder: Polycarbonate Z “Z300” (manufactured by Mitsubishi Gas Chemical) 300 parts by mass Antioxidant: “Irganox 1010” (Manufactured by BASF Japan) 6 parts by mass Tetrahydrofuran 1600 parts by mass Toluene 400 parts by mass Silicone oil: “KF-54” (manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part by mass was mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied onto the charge generation layer by a dip coating method to form a charge transport layer having a dry film thickness of 20 μm.

<Surface protective layer>
Organic particles: Silicone resin particles (number average primary particle size 0.8 μm) “X-52-854” (manufactured by Shin-Etsu Chemical Co., Ltd.) 30 parts by mass Surface-treated metal oxide particles 1 150 parts by mass Polymerizable compound (Exemplary compound) M1) 100 parts by weight Polymerization initiator: “Irgacure 819” (manufactured by BASF Japan) 12.5 parts by weight 2-butanol 510 parts by weight The above components are mixed and stirred, sufficiently dissolved and dispersed, and a surface protective layer coating solution Was prepared. A surface protective layer was applied to the photoreceptor having the coating solution prepared up to the charge transport layer using a circular slide hopper coating machine. After coating, the surface protective layer having a dry film thickness of 2.0 μm was obtained by irradiating with an ultraviolet ray for 1 minute using a xenon lamp. In this way, “Photoreceptor 1” was produced.

<Preparation of photoconductors 2-18>
Photoconductors 2 to 18 were prepared in the same manner as Photoconductor 1, except that the surface protective layer was configured as shown in Table 2.

≪Development of developer≫
The developer used for the evaluation was produced as follows.

<Preparation of Toner 1>
(1) Preparation of core part resin fine particles [1] Core part resin fine particles [1] having a multilayer structure were prepared through the following first stage polymerization, second stage polymerization and third stage polymerization.

(A) First stage polymerization (preparation of resin fine particle [A1] dispersion)
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction device, a surfactant solution in which 4 parts by mass of sodium polyoxyethylene-2-dodecyl ether sulfate was dissolved in 3040 parts by mass of ion-exchanged water was charged. The internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. To this surfactant solution, a polymerization initiator solution in which 10 parts by mass of a polymerization initiator (potassium persulfate: KPS) was dissolved in 400 parts by mass of ion-exchanged water was added to a temperature of 75 ° C., and then 532 masses of styrene. A monomer mixed solution consisting of 1 part by weight, 200 parts by weight of n-butyl acrylate, 68 parts by weight of methacrylic acid, and 16.4 parts by weight of n-octyl mercaptan was added dropwise over 1 hour, and the reaction system was heated at 75 ° C. for 2 hours. Polymerization (first stage polymerization) was carried out by heating and stirring to prepare a dispersion of resin fine particles [A1]. The resin fine particles [A1] produced by the first stage polymerization had a mass average molecular weight (Mw) of 16,500.

The mass average molecular weight (Mw) was measured using “HLC-8220” (manufactured by Tosoh Corporation) and the column “TSKguardcolumn + TSKgelSuperHZM-M3 series” (manufactured by Tosoh Corporation) while maintaining the column temperature at 40 ° C. and tetrahydrofuran as a carrier solvent. (THF) was allowed to flow at a flow rate of 0.2 ml / min, and the measurement sample was dissolved in tetrahydrofuran to a concentration of 1 mg / ml under a dissolution condition in which treatment was performed for 5 minutes using an ultrasonic disperser at room temperature. A sample solution is obtained by processing with a 2 μm membrane filter, and 10 μl of this sample solution is injected into the apparatus together with the above carrier solvent, detected using a refractive index detector (RI detector), and the molecular weight of the measurement sample Use a calibration curve whose distribution was measured using monodisperse polystyrene standard particles. And calculate. As a standard polystyrene sample for calibration curve measurement, the molecular weights manufactured by Pressure Chemical are 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1 .1 × 10 ⁵ , 3.9 × 10 ⁶ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ⁶ , and at least about 10 standard polystyrene samples were measured, and a calibration curve It was created. A refractive index detector was used as the detector.

(B) Second stage polymerization (preparation of resin fine particle [A2] dispersion: formation of intermediate layer)
In a flask equipped with a stirrer, a monomer mixture comprising 101.1 parts by mass of styrene, 62.2 parts by mass of n-butyl acrylate, 12.3 parts by mass of methacrylic acid, and 1.75 parts by mass of n-octyl mercaptan As a release agent, 93.8 parts by mass of paraffin wax “HNP-57” (manufactured by Nippon Seiwa Co., Ltd.) was added and heated to 90 ° C. for dissolution.

  On the other hand, a surfactant solution in which 3 parts by mass of sodium polyoxyethylene-2-dodecyl ether sulfate was dissolved in 1560 parts by mass of ion-exchanged water was heated to 98 ° C., and the resin fine particles [A1 32.8 parts by mass (in terms of solid content) was added, and the monomer solution containing the paraffin wax was added by a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. A dispersion liquid containing emulsified particles having a dispersed particle diameter of 340 nm was prepared by mixing and dispersing for a time. Next, a polymerization initiator solution in which 6 parts by mass of potassium persulfate was dissolved in 200 parts by mass of ion-exchanged water was added to this emulsified particle dispersion, and this reaction system was heated and stirred at 98 ° C. for 12 hours for polymerization. (Second-stage polymerization) was performed to prepare a dispersion of resin fine particles [A2]. The Mw of the resin fine particles [A2] prepared by the second stage polymerization was 23000.

(C) Third stage polymerization (preparation of resin fine particle [1] dispersion for core part: formation of outer layer)
A polymerization initiator solution prepared by dissolving 5.45 parts by mass of potassium persulfate in 220 parts by mass of ion-exchanged water is added to the dispersion of the resin fine particles [A2], and styrene 293.8 is used at a temperature of 80 ° C. A monomer mixed solution consisting of parts by mass, n-butyl acrylate 154.1 parts by mass, and n-octyl mercaptan 7.08 parts by mass was added dropwise over 1 hour. After completion of the dropwise addition, polymerization (third stage polymerization) was performed by heating and stirring for 2 hours, and then the mixture was cooled to 28 ° C. to prepare a dispersion of core part resin fine particles [1]. The Mw of the resin fine particles [1] for the core part was 26800. The volume average particle diameter of the resin fine particles [1] for core portion was 125 nm. Furthermore, the glass transition point (Tg) of the resin fine particles [1] for the core portion was 28.1 ° C.

(2) Preparation of dispersion of resin fine particles for shell layer [1] In the first stage polymerization of the resin fine particles for core [1], 548 parts by mass of styrene, 156 parts by mass of 2-ethylhexyl acrylate, methacrylic acid In the same manner except that a monomer mixed solution in which n-octyl mercaptan was changed to 16.5 parts by mass was subjected to a polymerization reaction and post-reaction treatment, and resin particles for shell layer [1] A dispersion was prepared. The Tg of the resin fine particles for shell layer [1] was 53.0 ° C.

(3) Preparation of Colorant Fine Particle Dispersion [1] 90 parts by mass of sodium dodecyl sulfate was added to 1600 parts by mass of ion-exchanged water, and while stirring this solution, carbon black “Regal 330R” (manufactured by Cabot Corporation) 420 parts by mass The colorant fine particle dispersion liquid [1] in which the colorant fine particles are dispersed was prepared by performing a dispersion treatment using a stirrer “Clearmix” (manufactured by M Technique Co., Ltd.). .

  The particle diameter of the colorant fine particles in this colorant fine particle dispersion [1] was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.) and found to be 110 nm.

(4) Preparation of Toner 1 (a) Formation of Core Part [1] 420 parts by mass (in terms of solid content) of dispersion of resin fine particles [1] for core part, 900 parts by mass of ion-exchanged water, and colorant fine particle dispersion 100 parts by mass of the liquid [1] was stirred in a reaction vessel equipped with a temperature sensor, a cooling pipe, a nitrogen introducing device, and a stirring device. After adjusting the temperature in the reaction vessel to 30 ° C., 5 mol / liter sodium hydroxide aqueous solution was added to this solution to adjust the pH to 8-11.

Next, an aqueous solution obtained by dissolving 60 parts by mass of magnesium chloride hexahydrate in 60 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, temperature increase was started, and the temperature of the reaction system was increased to 80 ° C. (core part formation temperature) over 80 minutes. In this state, the particle diameter of the particles was measured with “Coulter Multisizer 3” (manufactured by Coulter Inc.). When the median diameter (D ₅₀ ) on the volume basis of the particles became 5.8 μm, sodium chloride 40.2 An aqueous solution in which 1000 parts by mass of ion-exchanged water is dissolved is added to stop the particle size growth, and further, as an aging treatment, fusion is performed by heating and stirring at a liquid temperature of 80 ° C. (core aging temperature) for 1 hour. The core part [1] was formed. In addition, it was 0.930 when the circularity of core part [1] was measured with the flow type particle image analyzer "FPIA2100" (made by Sysmex Corporation).

(B) Formation of shell layer (production of toner base particles [1])
Subsequently, 46.8 parts by mass (in terms of solid content) of a dispersion of resin fine particles for shell layer [1] is added at 65 ° C., and 2 parts by mass of magnesium chloride hexahydrate is dissolved in 60 parts by mass of ion-exchanged water. After the added aqueous solution was added over 10 minutes, the temperature was raised to 80 ° C. (shelling temperature), and stirring was continued for 1 hour, and fine particles of the resin fine particles [1] for shell layer were formed on the surface of the core part [1]. Then, aging treatment was performed to a predetermined circularity at 80 ° C. (shell aging temperature) to form a shell layer. Here, an aqueous solution in which 40.2 parts by mass of sodium chloride was dissolved in 1000 parts by mass of ion-exchanged water was added, and the mixture was cooled to 30 ° C. at 8 ° C./min. The toner base material having a shell layer on the surface of the core part and having a shell layer on the surface of the core part and having a median diameter (D ₅₀ ) of 5.9 μm and Tg of 31 ° C. by repeatedly washing with exchange water and then drying with hot air of 40 ° C. Particles [1] were obtained.

(C) Addition of external additive (preparation of toner 1)
To 100 parts by mass of the dried toner base particles [1], 0.75 part by mass of silica “RX-200” (HMDS treatment, number average primary particle size 12 nm; manufactured by Nippon Aerosil Co., Ltd.), hydrophobic titanium dioxide (number average) 0.5 parts by mass of the primary particle size 20 nm) was added, and the stirring blade peripheral speed was 40 m / sec and mixed at a treatment temperature of 30 ° C. for 15 minutes using a Henschel mixer “FM10B” (manufactured by Mitsui Miike Chemical Co., Ltd.), and then Toner 1 was produced by removing coarse particles using a sieve having an opening of 90 μm.

<Creation of carrier>
100 parts by mass of ferrite core and 5 parts by mass of copolymer resin particles of cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5/5) are put into a high-speed mixer equipped with stirring blades, and stirred and mixed at 120 ° C. for 30 minutes. By forming a resin coat layer on the surface of the ferrite core by the action of mechanical impact force, a carrier having a volume-based median diameter of 50 μm was obtained.

  The volume-based median diameter of the carrier was measured by a laser diffraction particle size distribution analyzer “HELOS & RODOS” (manufactured by Sympathic) equipped with a wet disperser.

<Production of developer>
The above carrier is added to the toner 1 so that the toner concentration becomes 6%, and development is performed by mixing for 30 minutes at a rotation speed of 45 rpm with a micro type V type mixer (manufactured by Tsutsui Rika Kikai Co., Ltd.). Agent 1 was produced.

≪Evaluation≫
The photoreceptors 1 to 18 produced as described above were evaluated as follows.

<Evaluation method>
The obtained photoreceptor was mounted on a digital printing system “bizhub PRESS 1250” manufactured by Konica Minolta Co., Ltd. and evaluated. The evaluation was carried out by using an A4 document with a printing area ratio of 5% and making a real copy of 300,000 copies at an apparatus line speed of 600 mm / sec. The environment was room temperature and 50% RH environment.

(Evaluation of fogging)
Regarding the evaluation of fogging, 20 white solid images were printed at the room temperature and 50% RH at the initial stage and after the above durability test, and the 20th image was scanned with a scanner. This scanned image was captured by an image editing software “Photoshop CS6” (manufactured by Adobe Systems) and converted to a monochrome image. Thereafter, the black rate of the scanned image was calculated with the same software. This black rate was evaluated as the black rate. The average value of 10 points was adopted. Here, the portion where the toner is covered with the white background is recognized as black. The blackening ratio represents the area ratio of the black spot portion of the image. The solid black image has a blackening ratio of 100% and the blank paper has 0%.

(Cover judgment criteria)
◎: Less than 0.05% ○: 0.05% or more and less than 0.15% △: 0.15% or more and less than 0.3% ×: 0.3% or more <Result>
The results of evaluation as described above are shown in Table 3.

  As is apparent from the results in Table 3, the photoconductors 1 to 15 of the present invention were able to obtain high-quality images without fogging due to toner scattering even after 300,000 copies were actually taken. On the other hand, the photoconductors 16 to 18 for comparison were not practically resistant to fogging after 300,000 copies.

DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Photosensitive layer 3 Intermediate | middle layer 4 Charge generation layer 5 Charge transport layer 6 Surface protective layer 7a Organic particle 7b Metal oxide particle 1Y, 1M, 1C, 1Bk Photosensitive drum 2Y, 2M, 2C, 2Bk Charging means 3Y, 3M, 3C, 3Bk Exposure means 4Y, 4M, 4C, 4Bk Developing means 6Y, 6M, 6C, 6Bk Cleaning means 10Y, 10M, 10C, 10Bk Image forming unit

Claims (12)

An electrophotographic photoreceptor in which at least a photosensitive layer and a surface protective layer are sequentially laminated on a conductive support, and the surface protective layer contains metal oxide particles, a binder resin, and organic particles,
The binder resin contains a resin obtained by polymerizing a crosslinkable polymerizable compound,
The organic particles, styrene - electrophotographic photoreceptor, characterized in that an acrylic resin particles or polystyrene resin particles child.   The electrophotographic photosensitive member according to claim 1, wherein the organic particles are styrene-acrylic resin particles. 3. The electrophotographic photosensitive member according to claim 1, wherein the number average primary particle size of the organic particles is in a range of 0.01 to 5.00 μm.   4. The electrophotographic photosensitive member according to claim 1, wherein the number average primary particle size of the organic particles is in a range of 0.01 to 1.00 μm. 5. The organic particles mixed with a magnetic powder-dispersed carrier, when measured by the blow-off method, wherein the charge amount of the organic particles from claim 1, characterized in that in the range of -400 to-20 [mu] C / g Item 5. The electrophotographic photosensitive member according to any one of Items 4 to 4 . Wherein the organic particles, an electrophotographic photosensitive member according to any one of claims 1 to 5, characterized by containing a crosslinked resin. The crosslinkable polymerizable compound is a polymerizable compound having two or more polymerizable functional groups, and the polymerizable functional group having at least one selected from an acryloyl group and a methacryloyl group. The electrophotographic photosensitive member according to any one of claims 1 to 6 . The electrophotographic photosensitive member according to any one of claims 1 to 7, wherein the metal oxide particles are any one of tin oxide particles, titanium oxide particles, alumina particles, and zinc oxide particles. body. The electrophotographic photoreceptor according to any one of claims 1 to 8, wherein the metal oxide particles are surface-treated with a surface treatment agent having a reactive organic group. Any surface protective layer is, with respect to the crosslinkable polymerizable compound to 100 parts by mass, the preceding claims, characterized in that it contains in the range of the organic particles 5 to 100 parts by weight to claim 9 The electrophotographic photosensitive member according to claim 1. An electrophotographic image forming method using the electrophotographic photosensitive member according to any one of claims 1 to 10 , comprising at least a charging step, an exposure step, a development step, and a transfer step, An electrophotographic image forming method, wherein the toner for developing an electrostatic latent image used in the developing step contains a styrene-acrylic resin. An electrophotographic image forming apparatus using the electrophotographic photosensitive member according to any one of claims 1 to 10 , comprising at least a charging unit, an exposure unit, a developing unit, and a transfer unit, An electrophotographic image forming apparatus, wherein the electrostatic latent image developing toner used in the developing means contains a styrene-acrylic resin.

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