JP2009015112A - Electrophotographic photoreceptor, and image forming method and image forming apparatus using the photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which has improved stability of a coating liquid for an intermediate layer, and consequently has improved charging characteristics, suppresses an increase in a residual potential, has improved stability for repeated image formation, and causes neither fogging nor image defects such as black spots, environmental memory and moire; and to provide an image forming method and an image forming apparatus using the photoreceptor. <P>SOLUTION: The electrophotographic photoreceptor includes an intermediate layer and a photosensitive layer, sequentially layered on an electrically conductive support, wherein the intermediate layer contains metal oxide particles and particles having vacancies inside. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member, an image forming method using the same, and an image forming apparatus.

  An electrophotographic photoreceptor (hereinafter sometimes simply referred to as a photoreceptor) has a basic structure in which a photosensitive layer is coated on a conductive support. However, in practical use, the adhesion of the photosensitive layer is improved, the coating property of the photosensitive layer is improved, the charge injection from the photosensitive layer to the support is controlled, the electrical breakdown of the photosensitive layer is prevented, and the defects on the support are covered. For the purpose, for example, an intermediate layer (resin layer) is generally provided between the support and the photosensitive layer. However, it is difficult to solve the above-described problems simply by providing a resin layer.

  In order to solve the above-mentioned problems in the resin layer, an intermediate layer using an inorganic particle-dispersed resin layer in which inorganic particles having lower electric resistance than the resin is dispersed in the resin layer has been studied.

  Examples of the inorganic particles used in the inorganic particle-dispersed resin layer include metal powders such as nickel, copper, silver and aluminum, and metal oxide particles such as tin oxide, zinc oxide, aluminum oxide and titanium oxide. The intermediate layer made of the inorganic particle-dispersed resin layer can be adjusted in volume resistivity depending on the composition ratio of the inorganic particles, and the intermediate layer can be formed by applying the inorganic particle dispersion, resulting in good productivity. It is. Furthermore, it has an effect of preventing the occurrence of moiré that becomes a problem when using coherent light as a light source in a laser printer or the like.

  In addition, for electrophotographic photoreceptors that have been compatible with high image quality and high potential stability, proposals have been made to improve image quality by reducing black spots, memory, moire, etc. by using an intermediate layer containing metal oxide particles, and potential stabilization. Proposals have been made. However, even when metal oxide particles are used, there is a problem in that high image quality and high potential stability are not sufficiently ensured due to poor dispersion of the intermediate layer coating liquid and sedimentation after dispersion. Furthermore, there is a problem that the effect of preventing moire becomes insufficient when improving dispersibility or preventing sedimentation.

  Conventionally used inorganic particles have an irregular shape, so they are dispersed in a dispersion medium containing a binder resin and have poor dispersibility when formed into a paint, and the fluidity of the resulting coating liquid Is low, a good coating film could not be obtained. Furthermore, since the inorganic particles generally have a higher density than the dispersion medium, the dispersion stability is low, and when the obtained coating liquid is allowed to stand, the inorganic particles separate and settle, and the pot life is short. A photoreceptor having an intermediate layer obtained from such a coating solution causes a reduction in resolution and image defects such as so-called “black spots” and “white spots” in image characteristics. In order to improve such drawbacks, it has been proposed to use a dispersant such as a surfactant in the preparation of the coating liquid (for example, Patent Document 1), but when used as an electrophotographic photoreceptor, this dispersant is used. In fact, there are new problems that obstruct the flow of electric charge or adsorb moisture and make the electrophotographic characteristics unstable.

  Thus, a technique has been developed in which particles having voids are contained in the intermediate layer of the photoreceptor (see Patent Document 2). However, even if particles having voids inside are added, failures such as moire, memory, and black spots cannot be completely prevented, and the stability of the charged potential cannot be said to be perfect.

Accordingly, in today's electrophotographic technology field, when extremely high image quality is required as in today's world, the problem is becoming apparent again.
Japanese Examined Patent Publication No. 3-38587 JP-A-6-175385

  The present invention has been made to solve the above problems.

  That is, the object of the present invention is to improve the stability of the intermediate layer coating solution, to suppress the charging characteristics of the photoreceptor and the increase in residual potential, to improve the stability in repeated image formation, without fogging, It is an object to provide an electrophotographic photosensitive member, an image forming method and an image forming apparatus using the same without occurrence of image defects such as black spots, environmental memory, and moire.

  As a result of diligent investigations to solve the above problems, the present inventor has found that coating liquid stability and charging of the photoreceptor can be achieved by using particles having voids in the interior in combination with metal oxide particles in addition to the intermediate layer. The present invention has been completed by discovering that the rise in characteristics and residual potential is suppressed to improve the stability in repeated image formation, fog does not occur, and image defects such as black spots, environmental memory, and moire can be prevented.

  That is, it has been found that the object of the present invention is achieved by adopting the following configuration.

  In particular, the effect on moire was remarkable, and a moire resistance effect that could not be achieved by the metal oxide particles having a conventional structure alone and particles having voids therein could be obtained. The reason for this is not clear at this stage, but the presence of metal oxide particles around the particles with voids in the interior causes the surface to be scattered in addition to light scattering in the voids inside the particles with voids inside. It is considered that high light quality can be achieved with high moire resistance.

[1]
An electrophotographic photosensitive member in which an intermediate layer and a photosensitive layer are sequentially laminated on a conductive support, wherein the intermediate layer contains metal oxide particles and particles having voids therein. .

[2]
[1] The electrophotographic photosensitive member according to [1], wherein the metal oxide particles are made of a metal oxide selected from titanium oxide, zinc oxide, and alumina.

[3]
The electrophotographic photosensitive member according to [1] or [2], wherein the number average primary particle size of the particles having voids in the interior is 0.3 μm to 5.0 μm.

[4]
The electrophotographic photosensitive member according to any one of [1] to [3], wherein the particles having voids therein are formed of an inorganic compound.

[5]
[4] The electrophotographic photosensitive member according to [4], wherein the inorganic compound is an inorganic compound selected from at least one of silica, titanium oxide, and alumina.

[6]
The electrophotographic photosensitive member according to any one of [1] to [3], wherein the particles having voids therein are formed of a crosslinked polymer.

[7]
The electrophotographic photosensitive member according to any one of [1] to [6], wherein the metal oxide particles are surface-treated.

[8]
[7] The electron according to [7], wherein the metal oxide particles are subjected to a plurality of surface treatments, and at least one surface treatment is a surface treatment with a compound selected from alumina, silica, or zirconia. Photoconductor.

[9]
An image forming method comprising forming an image using the electrophotographic photosensitive member according to any one of [1] to [8].

[10]
An image forming apparatus that forms an image using the electrophotographic photosensitive member according to any one of [1] to [8].

  According to the present invention, the stability of the intermediate layer coating solution is improved, the charging characteristics of the photoreceptor and the increase in residual potential are suppressed, the stability in repeated image formation is improved, no fog occurs, black spots and the environment It is possible to provide an electrophotographic photosensitive member and an image forming method and an image forming apparatus using the same without causing image defects such as memory and moire.

  Hereinafter, the present invention will be described in more detail.

[Middle layer]
The intermediate layer is formed by applying and drying an intermediate layer coating liquid composed of a binder, a dispersion solvent, and the like.

  Examples of the binder for the intermediate layer include polyamide resins, vinyl chloride resins, vinyl acetate resins, and copolymer resins containing two or more repeating units of these resins. Among these resins, a polyamide resin is preferable because it can reduce a residual potential increase due to repeated use.

  As a solvent for preparing the intermediate layer coating solution, a solvent in which the metal oxide particles are well dispersed and the polyamide resin is dissolved is preferable. Specifically, alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol and the like are excellent in solubility and coating performance of the polyamide resin. These solvents may be used in a total amount of 30 to 100% by mass, preferably 40 to 100% by mass, and more preferably 50 to 100% by mass. Examples of co-solvents that can be used in combination with the above-mentioned solvent to obtain preferable effects include methanol, benzyl alcohol, toluene, methylene chloride, cyclohexanone, and tetrahydrofuran.

  The thickness of the intermediate layer is preferably 0.2 to 40 μm, and more preferably 0.3 to 20 μm.

[Metal oxide particles]
The metal oxide particles are not particularly limited, and examples thereof include those selected from metal oxides such as silica, alumina, titanium oxide, strontium titanate, and zinc oxide. Of these, titanium oxide, zinc oxide, and alumina are preferable.

  The metal oxide particles are preferably surface-treated from the viewpoint of improvement in dispersibility and stability of electrophotographic characteristics. The metal oxide particles are desirably subjected to a plurality of surface treatments, and at least one surface treatment is more preferably performed with alumina, silica, or zirconia.

  As the surface treatment method, a conventionally known method can be appropriately selected and used. For example, metal oxide particles are added to a solution in which a reactive organosilicon compound is dissolved or suspended in an organic solvent or water, and the solution is stirred for several minutes to about 1 hour. And depending on the case, after heat-processing this liquid, it passes through processes, such as filtration, It dries, and the metal oxide particle which coat | covered the surface with the organosilicon compound is obtained. A reactive organosilicon compound may be added to a suspension in which metal oxide particles are dispersed in an organic solvent or water.

  The metal oxide particles used in the present invention have a number average primary particle size of 3 to 500 nm, preferably 10 to 300 nm.

  Here, the number average primary particle size is a value obtained by observing 100 particles as primary particles at random by 10000-fold observation with a transmission electron microscope and image analysis.

  Examples of the transmission electron microscope (TEM) include “H-9000NAR” (manufactured by Hitachi, Ltd.) and “JEM-200FX” (manufactured by JEOL Ltd.).

  The observation method using a transmission electron microscope is performed by a normal method performed when measuring the particle size of particles. For example, the procedure is as follows. First, an observation sample is prepared. After sufficiently dispersing the particles in a room temperature curable epoxy resin, the particles are embedded and cured to produce a block. The prepared block is cut into a thin piece having a thickness of 80 to 200 nm using a microtome equipped with diamond teeth to prepare a measurement sample. Next, the particles are magnified 10,000 times using a transmission electron microscope (TEM), and the particles are photographed. Next, the image information of 100 inorganic particles photographed by the image processing apparatus “Luzex F” (manufactured by Nicole) is arithmetically processed to obtain the number average primary particle size.

[Particles with gaps inside]
It can be confirmed by TEM or the like that particles having a gap inside (sometimes referred to as hollow particles) have a hollow structure. In the measurement of the primary particle diameter of the hollow particles, a transmission electron microscope (TEM) is used similarly to the measurement of the metal oxide particles described above. The hollow particles preferably have a number average primary particle size of 0.3 μm to 5.0 μm. The hollow particles are roughly classified into organic compound and inorganic compound particles, and any of them can be used in the present invention.

  Inorganic compounds include silica, alumina, titanium oxide, zinc oxide, tin oxide, zirconium oxide, cerium oxide, metal oxides such as iron oxide, tungsten oxide, bismuth oxide, metal carbides such as silicon carbide and titanium carbide, titanic acid Examples thereof include titanates such as strontium, calcium titanate and barium titanate, carbonates such as calcium carbonate, metal nitrides such as aluminum nitride, sulfates such as barium sulfate, copper sulfate and zinc sulfate. Of these, silica, titanium oxide, and alumina are particularly preferable.

  As the organic compound, a crosslinked polymer is preferable. Examples of the crosslinked polymer include SX-866A (primary particle size 0.3 μm) manufactured by JSR Co., Ltd. made of crosslinked styrene-acryl.

  In the present invention, the term “crosslinked polymer” means that the temperature at which the mass reaches 90% by mass or less of the original is 300 ° C. or higher in a nitrogen atmosphere, and for example, the differential scanning calorific value used for measuring the glass transition temperature (Tg), etc. It can be measured by a meter (DSC).

[Photosensitive layer structure]
The photoreceptor of the present invention is obtained by sequentially laminating an intermediate layer, a photosensitive layer, and a protective layer on a conductive support. The layer structure is not particularly limited, and specifically, the following is shown. Such a layer structure can be mentioned.

1) Layer structure in which an intermediate layer and a charge generation layer and a charge transport layer as a photosensitive layer are sequentially laminated on a conductive support.
2) Layer structure in which a single layer containing a charge transport material and a charge generation material is sequentially laminated as an intermediate layer and a photosensitive layer on a conductive support. A protective layer may be provided on the photosensitive layer.

  The photoreceptor of the present invention may have any of the above-described layer structures, but among these, those prepared by providing an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support are preferable.

[Production of photoconductor]
The photoreceptor of the present invention can be prepared by dip coating, circular amount regulation type coating, or a combination of dip coating and round amount regulation type coating to provide a coating film, but is not limited thereto. The circular amount regulation type application is described in detail in, for example, Japanese Patent Application Laid-Open No. 58-189061.

  Next, members and layers constituting the photoreceptor of the present invention will be described.

(Conductive support)
The conductive support is preferably cylindrical and has a specific resistance of 10 ³ Ωcm or less. As a specific example, cylindrical aluminum whose surface has been cleaned after cutting can be mentioned.

(Photosensitive layer)
The photosensitive layer may have a single layer structure in which a charge generation function and a charge transport function are provided in one layer, but more preferably the function of the photosensitive layer is separated into a charge generation layer (CGL) and a charge transport layer (CTL). It is more preferable to take a layer structure. By adopting a configuration in which the functions are separated, an increase in residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoreceptor, a charge generation layer (CGL) is formed on the intermediate layer, and a charge transport layer (CTL) is formed thereon. In the positively charged photoreceptor, the order of the layer configuration is opposite to that in the negatively charged photoreceptor. A preferred layer structure of the photosensitive layer is a negatively charged photoreceptor having the function separation structure.

  Hereinafter, each layer of the photosensitive layer of the function-separated negatively charged photoreceptor will be described.

<Charge generation layer>
The charge generation layer contains a charge generation material (CGM). As other substances, a binder resin and other additives may be contained as necessary.

  A known charge generation material (CGM) can be used as the charge generation material (CGM). For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, the CGM that can minimize the increase in residual potential due to repeated use has a three-dimensional and potential structure that can form a stable aggregate structure among a plurality of molecules. Specifically, a phthalocyanine having a specific crystal structure. CGM of pigments and perylene pigments. For example, CGM such as titanyl phthalocyanine having a Bragg angle 2θ with respect to Cu-Kα ray having a maximum peak at 27.2 °, and benzimidazole perylene having a maximum peak with 2θ at 12.4 ° has little deterioration due to repeated use. The increase in residual potential can be reduced.

  When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably from 0.01 to 2 μm.

<Charge transport layer>
The charge transport layer contains a charge transport material (CTM) and a binder resin. Other substances may contain additives such as antioxidants as necessary.

  The thickness of the charge transport layer is preferably 0.2 to 40 μm, and more preferably 0.3 to 20 μm.

  A known charge transport material (CTM) can be used as the charge transport material (CTM). For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are usually dissolved in a suitable binder resin to form a layer.

  Examples of the resin used for the charge transport layer (CTL) include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, and polycarbonate. Resin, silicone resin, melamine resin, and copolymer resin containing two or more of the repeating units of these resins. In addition to these insulating resins, polymer organic semiconductors such as poly-N-vinylcarbazole can be used.

  Most preferred as a binder for these CTLs is a polycarbonate resin. The polycarbonate resin is most preferable in improving the dispersibility and electrophotographic characteristics of CTM. The ratio of the binder resin to the charge transport material is preferably 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. The thickness of the charge transport layer is preferably 10 to 40 μm.

〔Antioxidant〕
When an antioxidant is applied to the constituent layers of the photoconductor, the influence of an attack of an active gas such as NOx can be reduced, so that the occurrence of image flow in a high temperature and high humidity environment can be suppressed.

Typical examples of the antioxidant used in the present invention are light, heat, and discharge with respect to an auto-oxidizing substance present in the electrophotographic photoreceptor (hereinafter also referred to as photoreceptor) or on the photoreceptor surface. It is a substance having the property of preventing or suppressing the action of oxygen under the above conditions. Specifically, the following compound groups can be mentioned.
(1) Radical chain inhibitor ・ Phenol-based antioxidants Hindered phenol-based antioxidants ・ Amine-based antioxidants Hindered amine-based antioxidants Diallyldiamine-based antioxidants Diallylamine-based antioxidants ・ Hydroquinone-based antioxidants (2 ) Peroxide decomposer ・ Sulfur-based antioxidants Thioethers ・ Phosphoric-based antioxidants Phosphite esters Note that hindered phenol-based antioxidants (antioxidants with a hindered phenol structure) are phenolic OH A compound having a bulky organic group at the ortho position of the alkoxy group of a phenolic OH, and a hindered amine antioxidant (an antioxidant having a hindered amine structure) having a bulky organic group in the vicinity of the N atom It is. The bulky organic group includes a branched alkyl group, for example, a t-butyl group is preferable.

  Among the above antioxidants, the radical chain inhibitor (1) is good. Among them, the antioxidant having a hindered phenol structure or a hindered amine structure reacts with the radical active species generated from the polymerization initiator and oxygen. In order to prevent this, the generated radical active species can be effectively contributed to the reaction, which is preferable.

  Two or more types may be used in combination, for example, a combination of (1) a hindered phenol antioxidant and (2) a thioether antioxidant.

  In the present invention, more preferably, those having the hindered amine structure in the molecule are good for image quality improvement such as image blur prevention and black spot countermeasures, and in another aspect, the hindered phenol structural unit and the hindered amine structural unit are molecular molecules. Those contained therein are also preferred.

[Image forming apparatus]
Next, an image forming apparatus using the photoreceptor of the present invention will be described.

  FIG. 1 is a cross-sectional configuration diagram showing an example of an image forming apparatus using the photoreceptor of the present invention.

  An image forming apparatus 1 shown in FIG. 1 is a digital image forming apparatus, and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer paper transport unit D as a transfer paper transport unit. Yes.

  The upper part of the image reading unit A is provided with automatic document feeding means for automatically conveying the document. The document placed on the document placing table 11 is separated and conveyed by the document conveying roller 12 to the reading position 13a. The image is read. The document after the document reading is completed is discharged onto the document discharge tray 14 by the document transport roller 12.

  On the other hand, the image of the original when placed on the platen glass 13 is read at a speed v of the first mirror unit 15 including the illumination lamp and the first mirror constituting the scanning optical system, and the V-shaped first image is located. Reading is performed by the movement of the second mirror unit 16 including the two mirrors and the third mirror in the same direction at the speed v / 2.

  The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (luminance signal) and then A / D converted, and the image processing unit B performs processing such as density conversion and filter processing. Then, the image data is temporarily stored in the memory.

  In the image forming unit C, as an image forming unit, a drum-shaped photoconductor 21 as an image carrier, a charging means (charging step) 22 for charging the photoconductor 21 on the outer periphery thereof, and a surface potential of the charged photoconductor. Potential detecting means 220 for detecting the toner, developing means (developing process) 23, transfer conveying belt device 45 as a transferring means (transfer process), cleaning device (cleaning process) 26 for the photosensitive member 21, and light neutralizing means (light slow charge). PCL (precharge lamp) 27 as a process is arranged in the order of operation. Further, on the downstream side of the developing means 23, a reflection density detecting means 222 for measuring the reflection density of the patch image developed on the photosensitive member 21 is provided. As the photosensitive member 21, the photosensitive member according to the present invention is used, and the photosensitive member 21 is driven and rotated in the clockwise direction shown in the drawing.

  After the rotating photosensitive member 21 is uniformly charged by the charging unit 22, an image based on an image signal called from the memory of the image processing unit B by an exposure optical system as an image exposure unit (image exposure step) 30 is used. Exposure is performed. The exposure optical system as the image exposure means 30 as the writing means uses a laser diode (not shown) as a light source, and the optical path is bent by the reflection mirror 32 via the rotating polygon mirror 31, the fθ lens 34, and the cylindrical lens 35, and main scanning is performed. Therefore, image exposure is performed on the photoconductor 21 at the position Ao, and an electrostatic latent image is formed by rotation (sub-scanning) of the photoconductor 21. In one example of the present embodiment, the character portion is exposed to form an electrostatic latent image.

  In an image forming apparatus, a semiconductor laser or a light emitting diode can be used as an image exposure light source when forming an electrostatic latent image on a photoreceptor. By using these image exposure light sources, the exposure dot diameter in the writing principal direction is narrowed down to 10 to 80 μm, and digital exposure is performed on the photosensitive member, whereby from 400 dpi (dpi: the number of dots per 2.54 cm) to 2500 dpi. High-resolution electrophotographic images can be obtained.

The exposure dot diameter refers to the length of the exposure beam (Ld: measured at the maximum position) along the main scanning direction in a region where the intensity of the exposure beam is 1 / e ² or more of the peak intensity.

The light beams used have a solid scanner such as the scanning optical system and LED using a semiconductor laser, there is a Gaussian distribution and Lorentz distribution, etc. also the light intensity distribution is in each 1 / e ² or more regions of peak intensity The exposure dot diameter according to the present invention is used.

  The electrostatic latent image on the photoconductor 21 is reversely developed by the developing unit 23, and a visible toner image is formed on the surface of the photoconductor 21. In the image forming method according to the present invention, it is preferable to use a polymerized toner as a developer used in the developing unit. By using a polymer toner having a uniform shape and particle size distribution in combination with the photoreceptor of the present invention, an electrophotographic image with better sharpness can be obtained.

  In the transfer paper transport section D, paper feed units 41 (A), 41 (B), and 41 (C) are provided below the image forming unit as transfer paper storage means for storing transfer paper P of different sizes. Further, a manual paper feeding unit 42 for manually feeding paper is provided on the side, and the transfer paper P selected from any of them is fed along the transport path 40 by the guide roller 43 and fed. The transfer paper P is temporarily stopped by a pair of paper feed registration rollers 44 that correct the inclination and bias of the transfer paper P to be transferred, and then fed again. The transport path 40, the pre-transfer roller 43a, and the paper feed path 46 The toner image on the photosensitive member 21 is transferred to the transfer paper P while being transferred to the transfer conveyance belt 454 of the transfer conveyance belt device 45 by the transfer electrode 24 and the separation electrode 25 at the transfer position Bo. Is, transfer sheet P is separated from the photosensitive member 21 surface, it is conveyed to the fixing unit 50 by the transfer conveyor belt device 45.

  The fixing unit 50 includes a fixing roller 51 and a pressure roller 52. By passing the transfer paper P between the fixing roller 51 and the pressure roller 52, the toner is fixed by heating and pressing. After the toner image has been fixed, the transfer paper P is discharged onto the paper discharge tray 64.

  The above describes the state in which image formation is performed on one side of the transfer paper. However, in the case of double-sided copying, the paper discharge switching member 170 is switched, the transfer paper guide 177 is opened, and the transfer paper P is indicated by a broken arrow. Conveyed in the direction.

  Further, the transfer paper P is transported downward by the transport mechanism 178 and is switched back by the transfer paper reversing unit 179, and the rear end portion of the transfer paper P is transported into the duplex copying paper supply unit 130 as the leading end. The

  The transfer paper P is moved in a paper feed direction by a conveyance guide 131 provided in the double-sided copy paper supply unit 130, the transfer paper P is re-fed by the paper supply roller 132, and the transfer paper P is guided to the conveyance path 40. .

  Again, as described above, the transfer paper P is conveyed in the direction of the photosensitive member 21, the toner image is transferred to the back surface of the transfer paper P, fixed by the fixing unit 50, and then discharged onto the paper discharge tray 64.

  As the image forming apparatus, the above-described photosensitive member and components such as a developing unit and a cleaning unit may be integrally coupled as a process cartridge, and this unit may be configured to be detachable from the apparatus main body. In addition, 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, and is a single unit that is detachable from the apparatus main body. It is good also as a structure which can be attached or detached using guide means, such as a rail of an apparatus main body.

  FIG. 2 is a cross-sectional configuration diagram showing an example of a color image forming apparatus using the photoreceptor of the present invention.

  The color image forming apparatus of FIG. 2 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 the like. The paper feeding and conveying means 21 and the fixing means 24 are included. 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. An 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, 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, and a primary transfer roller 5C as a primary transfer unit. It has 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 include charging means 2Y, 2M, 2C, and 2Bk that rotate around the photosensitive drums 1Y, 1M, 1C, and 1Bk, and image exposure means 3Y, 3M, 3C and 3Bk, rotating developing means 4Y, 4M, 4C and 4Bk, and cleaning means 5Y, 5M, 5C and 5Bk for cleaning the photosensitive drums 1Y, 1M, 1C and 1Bk.

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

  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 5Y (around a photosensitive drum 1Y as an image forming body). Hereinafter, the cleaning means 5Y or the cleaning blade 5Y) 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 5Y 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 image 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. As the exposure means 3Y, the exposure means 3Y includes an LED in which light emitting elements are arranged in an array in the axial direction of the photosensitive drum 1Y and an imaging element (trade name; Selfoc lens), or A laser optical system or the like is used.

  The endless belt-like intermediate transfer body unit 7 includes an endless belt-like 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.

  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 rollers 22A, 22B, 22C, 22D and registration roller 23, they are conveyed to a secondary transfer roller 5b as a secondary transfer means, and are secondarily transferred onto a transfer material P to transfer a color image all at once. The transfer material P onto which the color image has been transferred is subjected to fixing processing by the fixing unit 24, is sandwiched between 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, 74, primary transfer rollers 5Y, 5M, 5C, 5Bk, and cleaning means 6b. Consists of.

  FIG. 3 is a schematic cross-sectional view showing an example of a color image forming apparatus using the photoreceptor of the present invention.

  The color image forming apparatus of FIG. 3 is a sectional view of a laser beam printer having a charging unit, an exposure unit, a plurality of developing units, a transfer unit, a cleaning unit, and an intermediate transfer body around a photosensitive member. The body 70 uses a medium resistance elastic body.

  In FIG. 3, reference numeral 1 denotes a rotary drum type photoconductor that is repeatedly used as an image forming body, and is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed.

  In the rotation process, the photoreceptor 1 is uniformly charged to a predetermined polarity and potential by a charging means (charging process) 2, and then time-series electric digital of image information by an image exposure means (image exposure process) 3 (not shown). An electrostatic latent image corresponding to the yellow (Y) color component image (color information) of the target color image is formed by receiving image exposure by scanning exposure light or the like by a laser beam modulated in accordance with the pixel signal. The

  Then, the electrostatic latent image is developed with yellow toner as the first color by yellow (Y) developing means: developing step (yellow color developing device) 4Y. At this time, the second to fourth developing means (magenta developer, cyan developer, black developer) 4M, 4C, and 4Bk are turned off and do not act on the photosensitive member 1. The first color yellow toner image is not affected by the second to fourth developing units.

  The intermediate transfer member 70 is stretched by rollers 79a, 79b, 79c, 79d, and 79e, and is driven to rotate in the clockwise direction at the same peripheral speed as the photosensitive member 1.

  The yellow toner image of the first color formed and supported on the photosensitive member 1 is applied to the intermediate transfer member 70 from the primary transfer roller 5a in the process of passing through the nip portion between the photosensitive member 1 and the intermediate transfer member 70. The intermediate transfer (primary transfer) is sequentially performed on the outer peripheral surface of the intermediate transfer body 70 by the electric field formed by the primary transfer bias.

  The surface of the photosensitive member 1 after the transfer of the first color yellow toner image corresponding to the intermediate transfer member 70 is cleaned by the cleaning device 6a.

  Similarly, the second color magenta toner image, the third color cyan toner image, and the fourth color black (black) toner image are sequentially superimposed and transferred onto the intermediate transfer body 70 to correspond to the target color image. A superimposed color toner image is formed.

  The secondary transfer roller 5b is supported in parallel with the secondary transfer counter roller 79b so as to be separated from the lower surface of the intermediate transfer body 70.

  The primary transfer bias for sequentially superimposing and transferring the first to fourth color toner images from the photosensitive member 1 to the intermediate transfer member 70 has a polarity opposite to that of the toner and is applied from a bias power source. The applied voltage is, for example, in the range of +100 V to +2 kV.

  In the primary transfer process of the first to third color toner images from the photosensitive member 1 to the intermediate transfer member 70, the secondary transfer roller 5b and the intermediate transfer member cleaning means 6b can be separated from the intermediate transfer member 70. .

  When the superimposed color toner image transferred onto the belt-shaped intermediate transfer member 70 is transferred onto the transfer material P, which is the second image carrier, the secondary transfer roller 5b is brought into contact with the belt of the intermediate transfer member 70. At the same time, the transfer material P is fed from the pair of paper registration rollers 23 through the transfer sheet guide to the belt of the intermediate transfer body 70 to the contact nip with the secondary transfer roller 5b at a predetermined timing. A secondary transfer bias is applied to the secondary transfer roller 5b from a bias power source. By this secondary transfer bias, the superimposed color toner image is transferred (secondary transfer) from the intermediate transfer body 70 to the transfer material P as the second image carrier. The transfer material P that has received the transfer of the toner image is introduced into the fixing means 24 and fixed by heating.

  Next, embodiments of the present invention will be shown to further explain the present invention.

  In the text, “part” means “part by mass”.

[Production of photoconductor]
Example 1
Preparation of intermediate layer dispersion 1 Metal oxide particles: Titanium oxide with an average particle size of 0.035 μm (primary surface treatment; silica / alumina treatment, secondary surface treatment; methyl hydrogen polysiloxane (MHPS) treatment) 3 parts, hollow Particles: 0.3 parts of hollow silica (God Ball B-6C average particle size 2.3 μm, manufactured by Suzuki Oil & Fat Co., Ltd.) was mixed for 10 minutes with “Henschel Mixer” (manufactured by Mitsui Miike Chemical Co., Ltd.), and then 100 μm openings Coarse particles were removed with a sieve to prepare a “fine particle mixture”.

  Polyamide resin 1 part Isopropyl alcohol 10 parts Polyamide N-1 is heated and dissolved in isopropyl alcohol, and then mixed with the above "fine particle mixture". The mixture is dispersed in a sand mill disperser whose surface is processed with ceramic. Dispersion time 10 hours was dispersed by a batch method to prepare an intermediate layer dispersion 1.

  This dispersion was applied to the intermediate layer of the photoreceptor having the following constitution.

(Conductive support)
The surface of the cylindrical aluminum support was cut to prepare a conductive support having a ten-point surface roughness Rz = 1.5 (μm) and a length of 362 mm.

(Middle layer)
The intermediate layer dispersion was applied onto the conductive support by a dip coating method to form an intermediate layer having a thickness of 10 μm.

(Charge generation layer)
60 parts of titanyl phthalocyanine Silicone resin solution (KR5240, 15 mass% xylene-butanol solution: manufactured by Shin-Etsu Chemical Co., Ltd.) 700 parts 2-butanone 2000 parts The above components are mixed and dispersed for 10 hours using a sand mill, and the charge generation 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 thickness of 0.2 μm.

(Charge transport layer)
Charge transport material: 4-methoxy-4 ′-(4-methyl-α-phenylstyryl) triphenylamine 200 parts Bisphenol Z-type polycarbonate (Iupilon Z300: manufactured by Mitsubishi Gas Chemical Company)
300 parts Antioxidant: Sanol LS2626 (manufactured by Sankyo Lifetech Co., Ltd.) 1.7 parts THF 2000 parts The above components were 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 thickness of 25 μm.

(Example 2)
A photoconductor similar to that of Example 1 was produced, except that the metal oxide particles of the photoconductor intermediate layer of Example 1 were replaced with titanium oxide SMT100SAM (manufactured by Takeca) having an average particle size of 0.015 μm.

(Example 3)
A photoconductor similar to that of Example 1 was produced, except that the metal oxide particles of Example 1 were replaced with titanium oxide CR-EL (manufactured by Ishihara Sangyo Co., Ltd.) having an average particle size of 0.25 μm.

Example 4
A photoconductor similar to that of Example 1 was produced, except that the hollow particles of the photoconductor intermediate layer of Example 1 were replaced with hollow alumina having an average particle size of 4.5 μm. The hollow alumina was produced by a chemical vapor deposition method (CVD method).

(Example 5)
A photoconductor similar to that of Example 1 was produced, except that the hollow particle of the intermediate layer of Example 1 was replaced with hollow alumina having an average particle diameter of 0.2 μm. The hollow alumina was produced by a chemical vapor deposition method (CVD method).

(Example 6)
A photoconductor similar to that of Example 1 except that instead of the hollow particles of the photoconductor intermediate layer of Example 1, hollow silica having an average particle size of 8.0 μm (God Ball B-25C manufactured by Suzuki Oil & Fats Co., Ltd.) was used. Was made.

(Example 7)
A photoconductor similar to that of Example 1 except that the hollow particles in the intermediate layer of the photoconductor of Example 1 are replaced with hollow polymer particles (SX866 (A) manufactured by JSR) having a primary particle size of 0.3 μm made of crosslinked styrene-acryl. Was made.

(Example 8)
The same photoconductor as in Example 1 except that the hollow particles in the intermediate layer of Example 1 were replaced with hollow polymer particles (MH5055, manufactured by Nippon Zeon Co., Ltd.) having an average particle diameter of 0.5 μm made of modified styrene-acryl. Was made.

Example 9
Example 1 except that the metal oxide particles of the photoreceptor intermediate layer of Example 1 were replaced with zinc oxide having an average particle size of 0.40 μm (primary surface treatment; silica treatment, secondary surface treatment; methylhydrogenpolysiloxane treatment). 1 was prepared.

(Example 10)
Example 1 except that the metal oxide particles of the photoreceptor intermediate layer of Example 1 were replaced with alumina (primary surface treatment; zirconia treatment, secondary surface treatment; methylhydrogenpolysiloxane treatment) having an average particle size of 0.05 μm. A photoconductor similar to that described above was prepared.

Example 11
A photoconductor similar to that of Example 1 was produced, except that the metal oxide particles of the photoconductor intermediate layer of Example 1 were replaced with titanium oxide having an average particle size of 0.1 μm (surface treatment; methylhydrogenpolysiloxane treatment). .

Example 12
A photoconductor similar to that of Example 1 was produced, except that the hollow particles of the photoconductor intermediate layer of Example 1 were replaced with hollow titanium oxide having an average particle size of 5.0 μm. Hollow titanium oxide was produced by chemical vapor deposition (CVD).

(Example 13)
Except that the metal oxide particles in the intermediate layer of Example 1 were replaced with titanium oxide having an average particle size of 0.35 μm (no surface treatment), and the hollow particles were replaced with hollow iron oxide having an average particle size of 5.5 μm. A photoconductor similar to that of Example 1 was produced. The hollow iron oxide was produced by a chemical vapor deposition method (CVD method).

(Comparative Example 1)
A photoconductor similar to that of Example 1 was prepared except that the metal oxide particles of the photoconductor intermediate layer of Example 1 were not added.

(Comparative Example 2)
A photoconductor similar to that of Example 1 was produced, except that the hollow particles of the photoconductor intermediate layer of Example 1 were replaced with silicone having an average particle size of 2.0 μm and Tospearl 120 (manufactured by GE Toshiba Silicone).

(Comparative Example 3)
A photoconductor similar to that of Example 1 was produced except that the metal oxide of the photoconductor intermediate layer of Example 1 was replaced with silicone having an average particle size of 2.0 μm and Tospearl 120 (manufactured by GE Toshiba Silicone).

[Performance evaluation]
(Evaluation of Examples 1 to 13 and Comparative Examples 1 to 3)
The photoconductors of Examples 1 to 13 and Comparative Examples 1 to 3 obtained as described above were converted into a reversal development type digital copying machine “Sitoos 7085” manufactured by Konica Minolta Business Technologies (scorotron charger, semiconductor laser image exposure device). (Wavelength: 680 nm), A4 paper having reversal developing means (85 sheets / minute machine), and the following evaluation items were evaluated. Evaluation was performed by changing environmental conditions (temperature and humidity conditions) for each evaluation item. The evaluation basically consists of an original image in which the character ratio, halftone image, solid white image, and solid black image with a pixel rate of 7% are divided into ¼ equal parts in A4 and 10,000 sheets in intermittent mode. A copy was made and evaluated. The evaluation results are shown in the table.

Evaluation conditions Photoreceptor line speed: 420 mm / sec Travel time from image exposure process to development process; 0.108 sec Charging conditions Charging device; Scorotron charging device (negative charging)
Charging potential: -650V to -750V
Exposure condition: set to an exposure amount at which the solid black image potential is set to −50 V. Exposure beam: Image exposure was performed with a semiconductor laser at a dot density of 400 dpi (number of dots per 2.54 cm).

Transfer conditions: Electrostatic transfer Cleaning conditions: Use a cleaning blade (Evaluation items and methods)
Interference fringes Evaluation of interference fringes (Evaluation was performed with halftone images at the initial stage of actual shooting)
◎: No interference fringe generation: Good ○: Minor interference fringe generation: no problem in practical use △: Remarkable interference fringe generation: practical use ×: Interference fringe generation through 100,000 copies: problem in practical use Black spot etc. (Evaluated with a white image in the early stage of live action.)
Periodic image defects (high temperature and high humidity (30 ° C, 80% RH))
The periodicity coincided with the period of the photoconductor, and the number of visible white defects, black spots, and streak image defects per A4 size was determined.

A: Frequency of image defects of 0.4 mm or more: All copied images are 5 / A4 or less (good)
○: Frequency of image defects of 0.4 mm or more: 6 to 8 / A4 (no problem in practical use)
Δ: Frequency of image defects of 0.4 mm or more: 9 to 10 / A4 (possible for practical use)
×: Frequency of image defects of 0.4 mm or more: 11 / A4 or more occurred (practical problem)
Coating solution stability The sample was allowed to stand for 1 month in a general environment (25 ° C., 60% RH), and the degree of sedimentation of the solution was visually confirmed.

  A: No settling is observed.

  ○: Slight sedimentation is observed, but there is no problem in actual use.

  X: There is much sedimentation of solid content and the function as a coating liquid is not fulfilled.

Residual potential In a low-temperature, low-humidity (10 ° C, 20% RH) environment, an original image with a pixel ratio of 7%, a halftone image, a solid white image, and a solid black image, each divided into 1/4 equals A4. 10,000 sheets were copied in the intermittent sheet mode, and the potential change (| ΔV |) of the solid black image portion at the development position after the initial and 10,000 sheets was evaluated.

A: Potential change in solid black image portion | ΔV | is less than 50 V (good)
○: Potential change in solid black image portion | ΔV | is 50 V to less than 100 V (no problem in practical use)
Δ: The potential change | ΔV | of the solid black image portion is 100 V to less than 150 V (practical use)
×: The potential change | ΔV | of the solid black image portion is larger than 150 V (practically problematic)

  As is clear from Table 1, Examples 1 to 13 in the present invention are all good in properties, but Comparative Examples 1 to 3 outside the present invention are at least one of these properties.

1 is a schematic view in which functions of an image forming apparatus are incorporated. 1 is a cross-sectional configuration diagram of a color image forming apparatus. 1 is a cross-sectional view of a color image forming apparatus using a photoconductor of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 21 Photoconductor 22 Charging means 23 Developing means 24 Transfer pole 25 Separation pole 26 Cleaning device 30 Exposure optical system 45 Transfer conveyance belt apparatus 50 Fixing means 250 Separation claw unit

Claims (10)

An electrophotographic photosensitive member in which an intermediate layer and a photosensitive layer are sequentially laminated on a conductive support, wherein the intermediate layer contains metal oxide particles and particles having voids therein. . 2. The electrophotographic photosensitive member according to claim 1, wherein the metal oxide particles are made of a metal oxide selected from titanium oxide, zinc oxide, and alumina. The electrophotographic photosensitive member according to claim 1 or 2, wherein the number average primary particle size of the particles having voids therein is 0.3 µm to 5.0 µm. The electrophotographic photosensitive member according to claim 1, wherein the particles having voids therein are formed of an inorganic compound. The electrophotographic photosensitive member according to claim 4, wherein the inorganic compound is an inorganic compound selected from at least one of silica, titanium oxide, and alumina. The electrophotographic photosensitive member according to claim 1, wherein the particles having voids therein are formed of a crosslinked polymer. The electrophotographic photosensitive member according to claim 1, wherein the metal oxide particles are surface-treated. 8. The electron according to claim 7, wherein the metal oxide particles are subjected to a plurality of surface treatments, and at least one surface treatment is a surface treatment with a compound selected from alumina, silica, or zirconia. Photoconductor. An image forming method, wherein an image is formed using the electrophotographic photosensitive member according to claim 1. An image forming apparatus that forms an image using the electrophotographic photosensitive member according to claim 1.

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