JP2006154071A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method and an image forming apparatus in which fogging liable to occur in a counter developing system and occurrence of image unevenness due to density lowering of a peripheral part are prevented, and by which an electrophotographic image having high image density and good color reproducibility can be produced. <P>SOLUTION: The image forming method comprises: forming an electrostatic latent image on a cylindrical organic photoreceptor; and bringing a cylindrical developing sleeve which bears a developing agent comprising a toner and carrier thereon in contact with the organic photoreceptor so as to visualize the electrostatic latent image into a toner image, wherein a contact angle of a surface of the organic photoreceptor to deionized water (20°C, 50% RH) is 90-130°, the carrier has a volume average particle diameter of 10-60 μm and a saturation magnetization of 20-80 emu/g, and the electrostatic latent image is visualized into the toner image while rotating the developing sleeve in a direction counter to the rotating direction of the organic photoreceptor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming method and an image forming apparatus used for electrophotographic image formation, and more particularly to an image forming method and an image forming apparatus used for electrophotographic image formation used in the field of copying machines and printers. Is.

  Electrophotographic photoconductors move from inorganic photoconductors such as Se, arsenic, arsenic / Se alloys, CdS, ZnO, etc. to organic photoconductors with excellent advantages such as pollution and ease of manufacture, and various materials are used. Organic photoreceptors (hereinafter also simply referred to as photoreceptors) have been developed.

  In recent years, function-separated type photoconductors, in which charge generation and charge transport functions are assigned to different materials, have become mainstream. For example, a surface layer contains a lubricating substance on a conductive support to reduce surface energy. The photoconductor used is widely used (Patent Document 1).

  Turning to the electrophotographic process, latent image forming methods are roughly classified into analog image formation using a halogen lamp as a light source and digital image formation using an LED or laser as a light source. Recently, as a hard copy printer for a personal computer, and in an ordinary copying machine, a digital latent image forming method has been rapidly becoming mainstream because of the ease of image processing and the development of a multifunction device.

  In the digital image forming method, an opportunity to produce an original print image is increased, and a demand for high image quality is increasing. In order to improve the image quality of the electrophotographic image, a technique for forming a fine dot image on a toner image by forming a fine latent image on an organic photoreceptor using an exposure light source having a small spot diameter has been developed. .

  That is, as a developing method of the latent image on the organic photoreceptor, a developing method (hereinafter referred to as a parallel developing method) in which a developing sleeve provided on the organic photoreceptor is advanced in the developing region in parallel with the traveling direction of the organic photoreceptor. A developing method that advances in the counter direction (hereinafter referred to as a counter developing method) is known (Patent Document 2), but neither of them can sufficiently solve the problem in forming a high-density dot image.

  In the development system in which the developing sleeve provided on the organic photoreceptor is advanced in parallel with the traveling direction of the organic photoreceptor, the developability of the periphery of the high density image is deteriorated, the density tends to be insufficient, and the photograph has high contrast. The image quality is likely to deteriorate in an image or the like.

  On the other hand, the developing method that proceeds in the counter direction has high developability and can form a high-density dot image, but often the image is fogged or the density is insufficient at the tip.

  It has been found that the above-described phenomena are not sufficiently solved by merely improving the developer, and these phenomena are emphasized or improved by the characteristics of the organic photoreceptor.

  That is, it is presumed to be related to the contrast of the electrostatic latent image formed on the organic photoreceptor and the production of reversely charged toner due to the friction between the organic photoreceptor and the developer.

  That is, in the counter development method, reversely chargeable toner is likely to be generated due to contact friction between the photoconductor and the toner, and as a result, fogging and toner scattering are likely to occur, and the tip portion density is likely to be reduced. A fine electrostatic latent image cannot be reproduced as a toner image.

In addition, a ferrite carrier that uses a low-saturation magnetization carrier and softens the development of a latent image on a photoconductor in a developing system using a two-component developer has been proposed (Patent Document 3). However, a technique for effectively applying these soft developers to the counter development system has not been proposed yet.
JP-A-6-75416 JP 2001-125435 A JP-A-11-202559

  The present invention relates to an image forming method that solves the problems of the prior art as described above, that is, solves the problems that easily occur in the counter development method, and stably forms a high-definition digital image. More specifically, it prevents fogging and toner scattering that tend to occur in the counter development method, prevents image unevenness due to a decrease in the density at the tip, and produces an electrophotographic image with high image density and good color reproducibility. An image forming method and an image forming apparatus that can be manufactured are provided.

  In order to obtain the uniform and high-definition electrophotographic image, the problem as described above of the present invention, that is, the occurrence of fog and the toner scattering, which are likely to occur in the counter development method, is prevented, the partial density shortage is solved. As a result of investigating the relationship between developer composition, organic photoreceptor structure and development method, to prevent fogging and toner scattering in the counter system with excellent developability, and to prevent density defects at the leading edge of the image It is effective to reduce the surface energy of the organic photoreceptor and at the same time to make the developer a soft developer to prevent an increase in reverse chargeable toner that is likely to occur when the developer and the organic photoreceptor are in contact with each other. As a result, the present invention has been completed.

That is, the present invention is achieved by having the following configuration.
(Claim 1)
An electrostatic latent image is formed on a cylindrical organic photosensitive member, and a cylindrical developing sleeve carrying a developer containing toner and carrier is brought into contact with the organic photosensitive member to convert the electrostatic latent image into a toner image. In the image forming method for visualizing, the contact angle (20 ° C., 50% RH) of pure water on the surface of the organic photoreceptor is 90 ° to 130 °, the volume average particle size of the carrier is 10 to 60 μm, and saturation An image forming method characterized in that an electrostatic latent image is visualized as a toner image while rotating a developing sleeve in a counter direction with respect to a rotation direction of an organic photoreceptor, and having a magnetization value of 20 to 80 emu / g.
(Claim 2)
An electrostatic latent image is formed on a cylindrical organic photoreceptor, and a cylindrical developing sleeve carrying a developer containing toner and carrier is disposed in contact with the organic photoreceptor, and the electrostatic latent image is converted into a toner image. A plurality of image forming units having developing means for visualizing and a transfer means for transferring a toner image formed on an organic photoreceptor to a transfer medium are arranged, and a toner whose color is changed for each of the plurality of image forming units is provided. The contact angle of pure water on the surface of the organic photoconductor in an image forming method in which each color toner image is formed on the organic photoconductor and the color toner image is transferred from the organic photoconductor to a transfer medium to form a color image. (20 ° C. and 50% RH) is 90 ° to 130 °, the carrier has a volume average particle size of 10 to 60 μm, a saturation magnetization value of 20 to 80 emu / g, and the developing sleeve in the rotational direction of the organic photoreceptor. And an image forming method, characterized in that to the electrostatic latent image into a toner image while rotating in the counter direction.
(Claim 3)
The image forming method according to claim 1, wherein the carrier is a ferrite carrier.
(Claim 4)
The image forming method according to claim 1, wherein the carrier is a resin-coated carrier.
(Claim 5)
The image forming method according to claim 1, wherein the surface layer of the organophotoreceptor contains a lubricating substance.
(Claim 6)
3. The image forming method according to claim 1, wherein the lubricating substance is fluorine-containing resin fine particles.
(Claim 7)
The image forming method according to claim 1, wherein the surface layer of the organophotoreceptor contains an antioxidant.
(Claim 8)
The image forming method according to claim 7, wherein the antioxidant is a hindered phenol-based antioxidant.
(Claim 9)
The image forming method according to claim 7, wherein the antioxidant is a hindered amine antioxidant.
(Claim 10)
The image forming method according to claim 1, wherein the organic photoreceptor is a laminated organic photoreceptor in which at least a charge generation layer and a charge transport layer are provided on a conductive substrate.
(Claim 11)
The image forming method according to claim 1, wherein the toner is a polymerized toner.
(Claim 12)
An electrostatic latent image is formed on a cylindrical organic photosensitive member, and a cylindrical developing sleeve carrying a developer containing toner and carrier is brought into contact with the organic photosensitive member to convert the electrostatic latent image into a toner image. In the image forming apparatus to be visualized, the contact angle (20 ° C. and 50% RH) of pure water on the surface of the organic photoreceptor is 90 ° to 130 °, the volume average particle size of the carrier is 10 to 60 μm, and saturation An image forming apparatus having a magnetization value of 20 to 80 emu / g and developing an electrostatic latent image into a toner image while rotating a developing sleeve in a counter direction with respect to a rotation direction of an organic photoreceptor.
(Claim 13)
An electrostatic latent image is formed on a cylindrical organic photoreceptor, and a cylindrical developing sleeve carrying a developer containing toner and carrier is disposed in contact with the organic photoreceptor, and the electrostatic latent image is converted into a toner image. A plurality of image forming units having developing means for visualizing and a transfer means for transferring a toner image formed on an organic photoreceptor to a transfer medium are arranged, and a toner whose color is changed for each of the plurality of image forming units is provided. In the image forming apparatus for forming a color image by forming each color toner image on the organic photoconductor and transferring the color toner image from the organic photoconductor to a transfer medium, the surface of the organic photoconductor is in contact with pure water. The angle (20 ° C., 50% RH) is 90 ° to 130 °, the volume average particle diameter of the carrier is 10 to 60 μm, the saturation magnetization value is 20 to 80 emu / g, and the developing sleeve is rotated in the direction of rotation of the organic photoreceptor. Contrast, the image forming apparatus, characterized in that to visualize the toner image an electrostatic latent image while rotating in the counter direction.

  By using the image forming method and the image forming apparatus of the present invention, it is possible to prevent the occurrence of fog, density defect at the tip, toner scattering and carrier adhesion that are likely to occur in the counter development method, and an electrophotographic image with good color reproducibility. Can be provided.

  Hereinafter, the present invention will be described in detail.

  In the image forming method of the present invention, an electrostatic latent image is formed on a cylindrical organic photoreceptor, a cylindrical developing sleeve carrying a developer containing a toner and a carrier is brought into contact with the organic photoreceptor, In the image forming method of developing an electrostatic latent image into a toner image, the contact angle (20 ° C. and 50% RH) of pure water on the surface of the organic photoreceptor is 90 ° to 130 °, and the volume average of the carrier The particle diameter is 10 to 60 μm, the saturation magnetization value is 20 to 80 emu / g, and the electrostatic latent image is visualized as a toner image while rotating the developing sleeve in the counter direction with respect to the rotation direction of the organic photoreceptor. It is characterized by.

  In the image forming method of the present invention, an electrostatic latent image is formed on a cylindrical organic photosensitive member, and a cylindrical developing sleeve carrying a developer containing toner is disposed in contact with the organic photosensitive member. A plurality of image forming units provided with a plurality of image forming units each having a developing unit that visualizes an electrostatic latent image into a toner image and a transfer unit that transfers a toner image formed on an organic photoreceptor onto a transfer medium. In the image forming method, each color toner image is formed on an organic photoreceptor using a toner whose color is changed every time, and each color toner image is transferred from the organic photoreceptor to a transfer medium to form a color image. The contact angle (20 ° C., 50% RH) with respect to pure water on the surface of the toner is 90 ° to 130 °, the volume average particle size of the carrier is 10 to 60 μm, the saturation magnetization value is 20 to 80 emu / g, and the developing sleeve The organic feeling With respect to the rotation direction of the body, and characterized in that the electrostatic latent image while rotating in the counter direction is visualized into a toner image.

  Since the image forming method of the present invention has the above-described configuration, it is possible to prevent the occurrence of fogging and the density defect at the tip portion, which are easily generated by the counter development method, and provide a high-quality digital image or color image.

  Hereinafter, the constitution of the organic photoreceptor according to the present invention will be described.

  The contact angle (20 ° C., 50% RH) with respect to pure water on the surface of the organic photoreceptor according to the present invention is 90 ° to 130 °. An electrostatic latent image formed with a photoreceptor having such a surface contact angle is developed on a toner image with a developer using a carrier having a volume average particle size of 10 to 60 μm and a saturation magnetization value of 20 to 80 emu / g. By forming an image, it is possible to prevent the occurrence of reversely chargeable toner due to contact friction between the photoconductor and the toner, which is likely to occur in the counter development method, and it is possible to prevent image unevenness due to fogging or a decrease in the density of the tip, and to prevent toner scattering, etc. Therefore, an electrophotographic image having a high density and good color reproducibility can be formed.

  In order for the contact angle (20 ° C. and 50% RH) of pure water on the surface of the organic photoreceptor to be 90 ° to 130 °, it is preferable that the surface layer of the photoreceptor contains a lubricating substance. Here, the lubricating substance refers to a substance that reduces the surface energy of the electrophotographic photosensitive member when added to the surface layer of the electrophotographic photosensitive member. Specifically, by adding it to the surface layer, A material that increases the contact angle (contact angle with respect to pure water), preferably a material that increases the contact angle by 1 ° or more.

  The lubricating substance is not limited to a material such as a fatty acid metal salt or a fluorine-containing resin as long as it is a material that increases the contact angle (contact angle with respect to pure water) of the electrophotographic photosensitive member.

  Such a lubricating substance is a material that is contained in the surface layer of the photoreceptor and, as a result, increases the contact angle. As the most preferable surface energy reducing agent, fluororesin particles such as polyvinylidene fluoride and polytetrafluoroethylene are preferable. In particular, fluorine-containing resin fine particles having an average particle size of 0.01 to 2.0 μm and containing fluorine atoms and excellent in releasability are preferable. Further, the fluororesin fine particles preferably have an average primary particle size of 0.02 μm or more and less than 0.20 μm. Fluorine-containing resin fine particles having an average primary particle size of 0.02 μm or more and less than 0.20 μm have good dispersion stability and can reduce variations in contact angle.

In this specification, the average primary particle diameter is a value measured by DLS-6000 (manufactured by Otsuka Electronics Co., Ltd.) using a dynamic light scattering method. However, it does not have to be measured by the above apparatus, and may be measured by any apparatus as long as it can be measured by the same principle as that of the above apparatus or by laser diffraction method and centrifugal sedimentation method. In addition, if the same measurement as that of the above apparatus is possible, the measurement may be performed by observing the cross section of the photosensitive layer. The degree is preferably less than 90%. When the crystallinity is less than 90%, the spreadability of the fluororesin fine particles themselves is good, and the variation in the contact angle can be reduced. The lower limit of the crystallinity is not particularly limited as long as the object of the present invention is achieved, but if the crystallinity of the fluororesin fine particles is too small, the extensibility becomes excessive and the dispersibility is low. From the viewpoint of easy deterioration, fluorine-containing resin fine particles having a crystallinity of 40% or more are preferable.

  The crystallinity of the fluororesin fine particles is measured by wide-angle X-ray diffraction measurement. The generated diffraction peak is separated into crystalline and amorphous, and after correcting the baseline, the crystalline and amorphous total X It is expressed as a percentage (%) of the X-ray integral intensity (numerator) of the crystalline with respect to the line integral intensity (denominator).

  In the present invention, the wide-angle X-ray diffraction measurement device and the measurement conditions were measured as follows, but other measurement devices and the like may be used as long as the same result is obtained.

X-ray generator: Rigaku RU-200B
Output: 50kV, 150mA
Monochromator: Graphite Radiation source: CuKα (0.154184 nm)
Scanning range: 3 ° ≦ 2θ ≦ 60 °
Scanning method: θ-2θ
Scanning speed: 2 ° / min
The constituent material of the fluorine-containing resin fine particles is a homopolymer or copolymer of a fluorine-containing polymerizable monomer, or a copolymer of a fluorine-containing polymerizable monomer and a fluorine-free polymerizable monomer. The fluorine-containing polymerizable monomer has the general formula (1);

(In general formula (1), at least one group of R ^{4 to} R ⁷ is a fluorine atom, and the remaining groups are each independently a hydrogen atom, chlorine atom, methyl group, monofluoromethyl group, difluoromethyl group. Or a trifluoromethyl group). Preferable fluorine-containing polymerizable monomers include ethylene tetrafluoride, ethylene trifluoride, ethylene trifluoride chloride, propylene hexafluoride, vinyl fluoride, vinylidene fluoride, ethylene difluoride dichloride and the like. Two or more types of monomers may be used as the fluorine-containing polymerizable monomer.

  Examples of the fluorine-free polymerizable monomer include vinyl chloride. Two or more types of monomers may be used as the fluorine-free polymerizable monomer.

  All of the fluororesin fine particles are preferably made of a homopolymer or copolymer of a fluoropolymerizable monomer among the above-mentioned constituent materials, more preferably polytetrafluoroethylene (PTFE) or polytrifluoride. Ethylene, ethylene tetrafluoride-hexafluoropropylene copolymer, polyvinylidene fluoride, especially polytetrafluoroethylene.

  The average molecular weight of the polymer constituting the fluorine-containing resin fine particles is not particularly limited as long as the object of the present invention can be achieved, but usually the range of 10,000 to 1,000,000 is preferable.

  The crystallinity of the fluororesin fine particles of the present invention varies depending on the constituent material of the fluororesin fine particles, but can also be changed by heat-treating the fluororesin fine particles. For example, when PTFE fine particles (polyethylene terephthalate fine particles) having an average primary particle size of 0.12 μm and a crystallinity of 91.3 are heat-treated at 250 ° C. for 65 minutes, the crystallinity can be reduced to 82.8. The heat treatment means is not particularly limited, and a known dryer or heating furnace can be used.

  As the binder resin in the surface layer, it is preferable to use a resin having a surface active group that assists the dispersibility of the fluorine-containing resin fine particles in the resin partial structure. For example, a polycarbonate or polyarylate having a siloxane group in the partial structure is used. preferable. In particular, a siloxane-modified polycarbonate having a siloxane group shown below in a partial structure is preferable.

  The molecular weight is preferably 10,000 to 100,000.

  In order to form a surface layer when the contact angle (20 ° C., 50% RH) to pure water is 90 ° to 130 ° using the fluorine-containing resin fine particles, the ratio of the fluorine-containing resin fine particles in the surface layer is It is preferable to use at least 20 parts by mass and 200 parts by mass or less based on 100 parts by mass of the binder resin. It is preferable that the variation in the contact angle of the surface is ± 2.0 or less. By satisfying the contact angle and the contact angle variation at the same time, it is possible to improve the fog and the lowering of the tip portion density that are likely to occur in the development of the counter system.

  Other lubricating materials are preferably fatty acid metal salts. The fatty acid metal salt is preferably a metal salt of a saturated or unsaturated fatty acid having 10 or more carbon atoms. For example, aluminum stearate, indium stearate, gallium stearate, zinc stearate, lithium stearate, magnesium stearate, sodium stearate, aluminum palmitate, aluminum oleate and the like, more preferably metal stearate and palmitic acid Sun metal salt.

  The photoreceptor according to the present invention preferably contains a lubricating substance in the surface layer, and the contact angle of the photoreceptor is 90 ° to 130 °, preferably 95 ° to 120 °.

  In the present invention, the variation in the contact angle of the photosensitive member is preferably ± 2 ° of the average value. By setting the variation in the contact angle within a range of ± 2 ° of the average value, it is possible to prevent the tip portion density decrease in the counter development method.

Measurement of Contact Angle and Contact Angle Variation The contact angle of the present invention refers to the contact angle of pure water on the surface of the photoreceptor. The contact angle of the photoreceptor is measured by using a contact angle meter (CA-DT • A type: manufactured by Kyowa Interface Science Co., Ltd.) in an environment of 20 ° C. and 50% RH (relative humidity).

  The contact angle variation is measured in an environment of 20 ° C. and 50% RH. The measurement is performed when the photoreceptor is sufficiently familiar with image formation (after forming at least several printed images). When the photoconductor is cylindrical, measure the four locations at 90 ° in the circumferential direction at three locations, 5 cm from the center and the left and right ends, for a total of 12 locations. The contact angle according to the present invention was used, and the value that was the largest or most negative from this average value was determined as the variation value. In the case where the photosensitive member is a sheet, similarly, at the three positions of 5 cm from the central portion and the left and right end portions, four locations are measured at equal intervals, and a total of 12 locations are measured. The contact angle was defined as the variation value, which was the largest deviation from the average value in the positive or negative direction.

  The organophotoreceptor according to the present invention preferably contains an antioxidant together with the lubricating substance. By including a lubricating substance and an antioxidant in the surface layer, the variation in the contact angle of the surface layer can be reduced, the developability in the counter development system can be improved, and the decrease in the density of the tip is prevented. be able to.

  Antioxidants are substances that have the property of preventing or suppressing the action of oxygen on auto-oxidizing substances present in the photoreceptor or on the photoreceptor surface under conditions such as light, heat, and discharge. Specifically, the following compound groups can be mentioned.

(1) Radical chain inhibitor ・ Phenol antioxidant (hindered phenol)
・ Amine antioxidants (hindered amines, diallyldiamines, diallylamines)
・ Hydroquinone antioxidant (2) Peroxide decomposer ・ Sulfur antioxidant (thioethers)
・ Phosphoric antioxidants (phosphites)
Among the above antioxidants, the radical chain inhibitor (1) is good, and a hindered phenol-based or hindered amine-based antioxidant is particularly 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. Furthermore, the above-mentioned structural unit, for example, a hindered phenol structural unit and a hindered amine structural unit may be included in the molecule.

  Among the antioxidants, particularly hindered phenol-based and hindered amine-based antioxidants are particularly effective in preventing fogging at high temperature and high humidity and preventing a decrease in tip concentration.

  The content of the hindered phenol-based or hindered amine-based antioxidant in the surface layer is preferably 0.01 to 20% by mass. If it is less than 0.01% by mass, fog and spots are likely to occur, and if the content is more than 20% by mass, the charge transport ability in the surface layer is lowered, the residual potential is likely to increase, and the image density is lowered. In addition, the film strength is reduced and muscle scars are likely to occur.

  Here, hindered phenol refers to compounds having a branched alkyl group at the ortho position relative to the hydroxyl group of the phenol compound and derivatives thereof (however, the hydroxyl group may be converted to alkoxy).

  The hindered amine system is a compound having a bulky organic group near the N atom. The bulky organic group includes a branched alkyl group, for example, a t-butyl group is preferable. For example, compounds having an organic group represented by the following structural formula are preferred.

In the formula, R ₁₃ represents a hydrogen atom or a monovalent organic group, R ₁₄ , R ₁₅ , R ₁₆ and R ₁₇ represent an alkyl group, and R ₁₈ represents a hydrogen atom, a hydroxyl group or a monovalent organic group.

  Examples of the antioxidant having a hindered phenol partial structure include compounds described in JP-A-1-118137 (P7 to P14), but the present invention is not limited thereto.

  Examples of the antioxidant having a hindered amine partial structure include compounds described in JP-A-1-118138 (P7 to P9), but the present invention is not limited thereto.

  As an organic phosphorus compound, there exist the following as a typical thing with the compound represented, for example by General formula (2): RO-P (OR) -OR. Here, R represents a hydrogen atom, each substituted or unsubstituted alkyl group, alkenyl group or aryl group.

  As an organic sulfur type compound, there exist the following as a typical thing with the compound represented, for example by General formula (2): RSR. Here, R represents a hydrogen atom, each substituted or unsubstituted alkyl group, alkenyl group or aryl group.

  The following are examples of typical antioxidant compounds.

  Further, as the antioxidants that have been commercialized, the following compounds, for example, “Irganox 1076”, “Irganox 1010”, “Irganox 1098”, “Irganox 245”, “Irganox” as hindered phenols, are used. Knox 1330 "," Irganox 3114 "," Irganox 1076 "," 3,5-di-t-butyl-4-hydroxybiphenyl ", hindered amine series" Sanol LS2626 "," Sanol LS765 "," Sanol LS770 " , “Sanol LS744”, “Tinuvin 144”, “Tinuvin 622LD”, “Mark LA57”, “Mark LA67”, “Mark LA62”, “Mark LA68”, “Mark LA63”. TPS "," Sumi Iser TP-D ", and the phosphite system is" Mark 2112 "," Mark PEP-8 "," Mark PEP-24G "," Mark PEP-36 "," Mark 329K "," Mark HP-10 " Is mentioned.

  The surface layer according to the present invention preferably contains a charge transport material. As the charge transport material (CTM), a known hole transport property (P-type) charge transport material (CTM) is preferably used. 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.

  The mass ratio of the binder resin and the charge transport material in the surface layer is preferably 30 to 200 parts by mass, and more preferably 50 to 150 parts by mass with respect to 100 parts by mass of the binder.

  The present invention is an organic photoreceptor having a surface layer as described above. The constitution of the organic photoreceptor other than the surface layer will be described below.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function essential to the configuration of the electrophotographic photoconductor. All known organic photoconductors such as a photoconductor composed of an organic charge generating material or an organic charge transport material, a photoconductor composed of a polymer complex with a charge generating function and a charge transport function are contained.

The constitution of the organophotoreceptor according to the present invention is not particularly limited as long as it has the surface layer described in the above-mentioned claim (1) or (2), and examples thereof include the following constitutions;
1) A structure in which a charge generation layer and a charge transport layer are sequentially laminated as a photosensitive layer on a conductive support. 2) A charge generation layer, a first charge transport layer and a second charge transport layer are formed as a photosensitive layer on a conductive support. Sequentially stacked configuration;
3) A structure in which a single layer containing a charge transport material and a charge generation material is formed as a photosensitive layer on a conductive support;
4) A structure in which a charge transport layer and a charge generation layer are sequentially laminated as a photosensitive layer on a conductive support;
5) A structure in which a surface protective layer is further formed on the photosensitive layer of the photoreceptors 1) to 5) above.

  The photoconductor may have any of the above configurations. The surface layer of the photoreceptor is a layer in contact with the air interface. When only a single-layer photosensitive layer is formed on the conductive support, the photosensitive layer is the surface layer, and the conductive layer In the case where a single-layered or laminated photosensitive layer and a surface protective layer are laminated on the conductive support, the surface protective layer is the outermost surface layer. In the present invention, the configuration 2) is most preferably used. Note that, even if the photoreceptor according to the present invention has any configuration, an undercoat layer (intermediate layer) may be formed on the conductive support prior to the formation of the photosensitive layer.

  The charge transport layer means a layer having a function of transporting charge carriers generated in the charge generation layer by photoexposure to the surface of the organic photoreceptor, and the specific detection of the charge transport function is carried out between the charge generation layer and the charge transport layer. It can be confirmed by laminating a transport layer on a conductive support and detecting optical conductivity.

  Next, the layer structure of the organic photoreceptor will be described focusing on the structure of 2) above.

Conductive Support The conductive support used for the photoreceptor may be either a sheet or a cylinder, but a cylindrical conductive support is preferred for designing an image forming apparatus compactly. .

  Cylindrical conductive support means a cylindrical support necessary for forming an endless image by rotating. Conductivity is within a range of 0.1 mm or less in straightness and 0.1 mm or less in deflection. A support is preferred. Exceeding the range of straightness and shake makes it difficult to form a good image.

As the conductive material, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ωcm or less at room temperature. The conductive support according to the present invention is most preferably an aluminum support. As the aluminum support, one in which components such as manganese, zinc, magnesium and the like are mixed in addition to the main component aluminum is also used.

Intermediate layer In the present invention, an intermediate layer is preferably provided between the conductive support and the photosensitive layer.

  The intermediate layer used in the present invention preferably contains N-type semiconductor particles. The N-type semiconductive particle means a particle whose main charge carrier is an electron. That is, since the main charge carriers are electrons, the intermediate layer containing the N-type semiconductive particles in the insulating binder effectively blocks hole injection from the substrate, and the electrons from the photosensitive layer. In contrast, it has a property of low blocking.

  Here, a method for discriminating N-type semiconductor particles will be described.

  An intermediate layer having a thickness of 5 μm is formed on the conductive support (the intermediate layer is formed using a dispersion in which 50% by mass of particles are dispersed in the binder resin constituting the intermediate layer). The intermediate layer is negatively charged and the light attenuation characteristics are evaluated. In addition, the light attenuation characteristics are similarly evaluated by charging to positive polarity.

  N-type semiconductive particles are particles that are dispersed in the intermediate layer in the above evaluation when the light attenuation when charged negatively is greater than the light attenuation when charged positively. It is called semiconductive particle.

As the N-type semiconductor particles, titanium oxide (TiO ₂ ) and zinc oxide (ZnO) are preferable, and titanium oxide is particularly preferably used.

  As the N-type semiconductor particles, fine particles having a number average primary particle diameter in the range of 3.0 to 200 nm are used. Particularly, 5 nm to 100 nm is preferable. The number average primary particle diameter is a measured value as the average diameter in the ferret direction by image analysis by magnifying fine particles 10,000 times by transmission electron microscope observation, randomly observing 100 particles as primary particles. N-type semiconducting particles having a number average primary particle size of less than 3.0 nm are difficult to uniformly disperse in the intermediate layer binder, and easily form aggregated particles. Is likely to occur. On the other hand, N-type semiconducting particles having a number average primary particle size larger than 200 nm tend to make large irregularities on the surface of the intermediate layer, and the reproducibility of dot images tends to deteriorate through these large irregularities. In addition, the N-type semiconductive particles having a number average primary particle size larger than 200 nm are likely to precipitate in the dispersion and easily generate aggregates. As a result, the reproducibility of the dot image tends to deteriorate.

  The titanium oxide particles have anatase, rutile, brookite, and amorphous forms as crystal forms. Among them, the rutile form titanium oxide pigment or the anatase form titanium oxide pigment has a rectifying property of charge passing through the intermediate layer. In other words, the electron mobility is increased, the charging potential is stabilized, the residual potential is prevented from increasing, and the dot image is prevented from deteriorating.

  N-type semiconductive particles are preferably surface-treated with a polymer containing methylhydrogensiloxane units. The molecular weight of the polymer containing the methyl hydrogen siloxane unit is 1000 to 20000, and the surface treatment effect is high. As a result, the rectifying property of the N-type semiconductor particles is improved, and the N-type semiconductor particles are contained. By using the intermediate layer, the occurrence of black spots is prevented and there is an effect on the reproducibility of good dot images.

The polymer containing a methylhydrogensiloxane unit is preferably a copolymer of a structural unit of-(HSi (CH ₃ ) O)-and a structural unit other than this (other siloxane unit). As other siloxane units, dimethylsiloxane units, methylethylsiloxane units, methylphenylsiloxane units, diethylsiloxane units, and the like are preferable, and dimethylsiloxane is particularly preferable. The proportion of methylhydrogensiloxane units in the copolymer is 10 to 99 mol%, preferably 20 to 90 mol%.

  The methylhydrogensiloxane copolymer may be any of a random copolymer, a block copolymer, a graft copolymer, etc., but a random copolymer and a block copolymer are preferred. In addition to methylhydrogensiloxane, the copolymerization component may be one component or two or more components.

  The intermediate layer coating solution prepared for forming the intermediate layer used in the present invention is composed of a binder resin, a dispersion solvent and the like in addition to the N-type semiconductive particles such as the surface-treated titanium oxide.

  The ratio of the N-type semiconductive particles in the intermediate layer is preferably 1.0 to 2.0 times in terms of the volume ratio of the intermediate layer to the binder resin (when the volume of the binder resin is 1). By using such high-density N-type semiconductor particles in the intermediate layer, the rectification of the intermediate layer is enhanced, and the increase in residual potential and dot image degradation are effectively prevented even when the film thickness is increased. And a good organic photoreceptor can be formed. Further, such an intermediate layer preferably uses 100 to 200 parts by volume of N-type semiconductive particles with respect to 100 parts by volume of the binder resin.

  On the other hand, the binder resin in which these particles are dispersed to form the layer structure of the intermediate layer is preferably a polyamide resin in order to obtain good dispersibility of the particles, but the polyamide resin shown below is particularly preferable.

  That is, a polyamide resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less is preferable for the intermediate layer. The heat of fusion is more preferably 0 to 30 J / g, and most preferably 0 to 20 J / g. On the other hand, if the water absorption exceeds 5% by mass, the water content in the intermediate layer increases, the rectification property of the intermediate layer decreases, black spots tend to occur, and the reproducibility of the dot image tends to deteriorate. The water absorption is more preferably 4% by mass or less.

  The heat of fusion of the resin is measured by DSC (Differential Scanning Calorimetry). However, if the same measurement value as the DSC measurement value is obtained, the DSC measurement method is not particular. The heat of fusion is determined from the endothermic peak area when the DSC temperature rises.

  On the other hand, the water absorption rate of the resin is determined by mass change by the water immersion method or by the Karl Fischer method.

  The binder resin for the intermediate layer is preferably an alcohol-soluble polyamide resin. As the binder resin for the intermediate layer of the organic photoreceptor, a resin having excellent solvent solubility is required in order to form the intermediate layer with a uniform film thickness. As such alcohol-soluble polyamide resins, copolymerized polyamide resins and methoxymethylated polyamide resins composed of a chemical structure with few carbon chains between amide bonds such as 6-nylon described above are known. The resin has a high water absorption rate, and the intermediate layer using such a polyamide tends to be highly environment-dependent. As a result, for example, the charging characteristics and sensitivity under high temperature and high humidity and low temperature and low humidity are likely to change. Dot image is likely to deteriorate.

  Alcohol-soluble polyamide resin improves the above-mentioned drawbacks and improves the disadvantages of conventional alcohol-soluble polyamide resins by giving the characteristics of heat of fusion 0-40 J / g and water absorption of 5% by mass or less. Even if the external environment changes or even if the organic photoreceptor is used continuously for a long time, a good electrophotographic image can be obtained.

  Hereinafter, the alcohol-soluble polyamide resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less will be described.

  The alcohol-soluble polyamide resin is preferably a polyamide resin containing a repeating unit structure having 7 to 30 carbon atoms between amide bonds in an amount of 40 to 100 mol% of the entire repeating unit structure.

  Here, a repeating unit structure having 7 to 30 carbon atoms between amide bonds will be described. The repeating unit structure means an amide bond unit forming a polyamide resin. This is because a polyamide resin (type A) formed by condensation of a compound having a repeating unit structure having both an amino group and a carboxylic acid group, and a polyamide resin (type B) formed by condensation of a diamino compound and a dicarboxylic acid compound. ) In both examples.

  That is, the repeating unit structure of type A is represented by the general formula (3), and the carbon number contained in X is the carbon number of the amide bond unit in the repeating unit structure. On the other hand, the repeating unit structure of type B is represented by the general formula (4), and the number of carbons contained in Y and the number of carbons contained in Z are respectively the number of carbons of the amide bond unit in the repeating unit structure.

In general formula (3), R ₁ is a hydrogen atom, a substituted or unsubstituted alkyl group, X is a substituted or unsubstituted alkylene group, a group containing a divalent cycloalkane, a divalent aromatic group, and these A mixed structure is shown, and l is a natural number.

In general formula (4), R ₂ and R ₃ are each hydrogen atom, a substituted or unsubstituted alkyl group, Y and Z are each substituted or unsubstituted alkylene group, a group containing a divalent cycloalkane, and a divalent group. And m and n are natural numbers.

  As described above, the repeating unit structure having 7 to 30 carbon atoms includes a substituted or unsubstituted alkylene group, a group containing a divalent cycloalkane, a divalent aromatic group, and a chemical structure having a mixed structure thereof. Among them, a chemical structure having a group containing a divalent cycloalkane is preferable.

  The polyamide resin has 7 to 30 carbon atoms between amide bonds in the repeating unit structure, preferably 9 to 25, more preferably 11 to 20. The proportion of the repeating unit structure having 7 to 30 carbon atoms between amide bonds in the entire repeating unit structure is 40 to 100 mol%, preferably 60 to 100 mol%, more preferably 80 to 100 mol%.

  When the number of carbon atoms is less than 7, the hygroscopicity of the polyamide resin is large, electrophotographic characteristics, particularly the humidity dependence of the potential during repeated use is large, and image defects such as black spots are more likely to occur. Reproducibility tends to deteriorate. If it is larger than 30, the dissolution of the polyamide resin in the coating solvent becomes worse, and it is not suitable for forming a coating film of the intermediate layer.

  Further, when the ratio of the repeating unit structure having 7 to 30 carbon atoms between amide bonds to the entire repeating unit structure is smaller than 40 mol%, the above effect is reduced.

  Preferable polyamide resin includes polyamide having a repeating unit structure represented by the following general formula (5).

In General Formula (5), Y ₁ represents a group containing a divalent alkyl-substituted cycloalkane, Z ₁ represents a methylene group, m represents 1 to 3, and n represents 3 to 20.

In the general formula (5), the group containing a divalent alkyl-substituted cycloalkane of Y ₁ preferably has the following chemical structure. That is, the polyamide resin in which Y ₁ has the following chemical structure has a remarkable effect of preventing deterioration of black spots and dot images.

In the above chemical structure, A represents a single bond and an alkylene group having 1 to 4 carbon atoms, R ₄ represents a substituent, represents an alkyl group, and p represents a natural number of 1 to 5. However, the plurality of R ₄ may be the same or different.

  Specific examples of the polyamide resin include the following examples.

  In the above specific examples, “%” in parentheses indicates the ratio (mol%) of the repeating unit structure having 7 or more carbon atoms between amide bonds in the repeating unit structure.

  Among the above specific examples, N-1 to N-4 polyamide resins having a repeating unit structure of the general formula (5) are particularly preferable.

  The molecular weight of the polyamide resin is preferably 5,000 to 80,000, more preferably 10,000 to 60,000 in terms of number average molecular weight. When the number average molecular weight is 5,000 or less, the uniformity of the film thickness of the intermediate layer is deteriorated, and the effects of the present invention are not sufficiently exhibited. On the other hand, if it is larger than 80,000, the solvent solubility of the resin is likely to be lowered, and the aggregated resin is likely to be generated in the intermediate layer, so that fog is likely to occur.

  A part of the polyamide resin is already available on the market. For example, the polyamide resin is sold under the trade names such as Vestamelt X1010 and X4685 manufactured by Daicel Degussa Co., Ltd., and can be produced by a general synthesis method of polyamide. However, an example of a synthesis example is given below.

Synthesis of exemplified polyamide resin (N-1) 215 parts by mass of lauryl lactam, 3-aminomethyl-3,5,5-trimethylcyclohexylamine in a polymerization kettle equipped with a stirrer, nitrogen, nitrogen introduction tube, thermometer, dehydration tube, etc. 112 parts by mass, 153 parts by mass of 1,12-dodecanedicarboxylic acid and 2 parts by mass of water were mixed and reacted for 9 hours while distilling water under heating and pressure. When the polymer was taken out and the copolymer composition was determined by C ¹³ -NMR, it coincided with the composition of N-1. The melt flow index (MFI) of the synthesized copolymer was 5 g / 10 min under the condition of (230 ° C./2.16 kg).

As the solvent for dissolving the polyamide resin and preparing the coating solution, alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol are preferable, It is excellent in the solubility of polyamide and the coating property of the prepared coating solution. These solvents are 30 to 100% by mass, preferably 40 to 100% by mass, and more preferably 50 to 100% by mass in the total solvent. 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 0.3 to 10 μm. If the thickness of the intermediate layer is less than 0.5 μm, black spot is likely to occur and the dot image is likely to deteriorate. If it exceeds 10 μm, the residual potential is likely to increase, and the reproducibility of the dot image tends to deteriorate. As for the film thickness of an intermediate | middle layer, 0.5-5 micrometers is more preferable.

Moreover, it is preferable that the said intermediate | middle layer is an insulating layer substantially. Here, the insulating layer has a volume resistance of 1 × 10 ⁸ or more. The volume resistance of the intermediate layer and the protective layer is preferably 1 × 10 ⁸ to 10 ¹⁵ Ω · cm, more preferably 1 × 10 ⁹ to 10 ¹⁴ Ω · cm, and further preferably 2 × 10 ⁹ to 1 × 10 ¹³ Ω. -Cm. The volume resistance can be measured as follows.

  Measurement conditions: According to JIS: C2318-1975.

Measuring instrument: Hiresta IP manufactured by Mitsubishi Yuka
Measurement conditions: Measurement probe HRS
Applied voltage: 500V
Measurement environment: 30 ± 2 ℃, 80 ± 5RH%
If the volume resistance is less than 1 × 10 ⁸ , the charge blocking property of the intermediate layer decreases, the occurrence of black spots increases, the potential holding property of the organic photoreceptor deteriorates, and good image quality cannot be obtained. On the other hand, if it is greater than 10 ¹⁵ Ω · cm, the residual potential tends to increase in repeated image formation, and good image quality cannot be obtained.

Photosensitive layer The photosensitive layer configuration of the photoconductor according to the present invention may be a single-layer photosensitive layer configuration in which a charge generation function and a charge transport function are provided on one layer on the intermediate layer. It is preferable that the function is separated into a charge generation layer (CGL) and a charge transport layer (CTL). By adopting a configuration in which the functions are separated, an increase in the 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 photoconductor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer, and a charge transport layer (CTL) is formed thereon.

  The structure of the photosensitive layer of the function-separated negatively charged photoreceptor will be described below.

Charge generation layer In the organic photoreceptor according to the present invention, the above-mentioned titanyl phthalocyanine adduct pigment is used as a charge generation material. it can.

  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 0.3 μm to 2 μm.

Charge Transport Layer As described above, in the present invention, the charge transport layer is composed of a plurality of charge transport layers, and the uppermost charge transport layer contains a lubricating substance or the like so that the contact angle is 90 ° to 130 °. .

  The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses and forms a CTM.

  As the charge transport material (CTM), a known hole transport property (P-type) charge transport material (CTM) is preferably used. 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.

  The binder resin used for the charge transport layer (CTL) may be either a thermoplastic resin or a thermosetting resin. For example, polystyrene, 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 these resins A copolymer resin containing two or more of the repeating unit structures. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used. Of these, polycarbonate resins are most preferred because of their low water absorption and good CTM dispersibility and electrophotographic characteristics.

  The ratio of the binder resin to the charge transport material is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.

  The total thickness of the charge transport layer is preferably 10 to 40 μm. If the total film thickness is less than 10 μm, the concentration at the tip end tends to decrease, and if it exceeds 40 μm, the residual power tends to increase, and the sharpness tends to deteriorate. Further, the thickness of the charge transport layer serving as the surface layer is preferably 0.5 to 10 μm.

  Solvents or dispersion media used to form layers such as intermediate layers, charge generation layers, and charge transport layers include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone , Methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, Tetrachloroethane, tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cello Lube, and the like. Although this invention is not limited to these, Dichloromethane, 1, 2- dichloroethane, methyl ethyl ketone, etc. are used preferably. These solvents may be used alone or as a mixed solvent of two or more.

  Further, the coating solution for each layer is preferably filtered with a metal filter, a membrane filter or the like in order to remove foreign matters and aggregates in the coating solution before entering the coating step. For example, it is preferable to select a pleat type (HDC), a depth type (profile), a semi-depth type (profile star), etc., manufactured by Nippon Pole Co., Ltd. according to the characteristics of the coating solution and perform filtration.

  Next, as a coating processing method for producing the organic photoreceptor, a coating processing method such as dip coating or spray coating is used in addition to the ride hopper type coating apparatus. For forming the surface layer according to the present invention, it is most preferable to use a circular slide hopper type coating apparatus.

  Among the above coating liquid supply type coating apparatuses, the coating method using a slide hopper type coating apparatus is most suitable when the above-described dispersion using a low boiling point solvent is used as the coating liquid, and is a cylindrical photoconductor. In this case, the coating is preferably performed using a circular slide hopper type coating apparatus described in detail in JP-A No. 58-189061 and the like.

<Career>
The carrier according to the present invention has a volume average particle size of 10 to 60 μm and a saturation magnetization value of 20 to 80 emu / g. By using a carrier having a small carrier particle size and a low saturation magnetization value, the magnetic brush on the developing sleeve is softened, and the soft development can be performed by the counter development method, and the fog and the tip density are lowered. Can be prevented.

  As the magnetic particles of the carrier used in the present invention, iron powder, magnetite, various ferrites and the like can be used, and magnetite and various ferrites are preferable.

The ferrite carrier has the following general formula (6).
(MnO) x (MgO) y (Fe 2 O 3) z
In the above general formula (6), x + y + z = 100 mol%, and in order to obtain a ferrite carrier with a saturation magnetization value of 20 to 80 emu / g, x, y and z are 5 to 35 mol% and 10 to 45 mol%, respectively, as basic compositions. And the range of 45-55 mol% is preferable, Especially preferably, it is the range of 7.5-12.5 mol%, 35-45 mol%, and 45-55 mol%.

Further, a part of MnO, MgO and Fe ₂ O ₃ is substituted with SnO ₂ . The substitution amount of SnO ₂ is preferably 0.5 to 5.0 mol%, particularly preferably 0.5 to 3.0 mol%. When the substitution amount of SnO ₂ is less than 0.5 mol%, sufficient carrier surface uniformity cannot be obtained. On the other hand, when the substitution amount of SnO ₂ exceeds 5.0 mol%, the saturation magnetization tends to decrease. As described above, if the substitution amount of SnO ₂ is in the range of 0.5 to 5.0 mol%, the low saturation magnetization carrier can be stably obtained, and the ear on the magnetic brush becomes soft, so that soft development is achieved. Can be obtained and the surface properties are uniform, so that the characteristics after resin coating can be stabilized, and the image quality and durability are excellent. A ferrite carrier having excellent stability can be obtained.

  The carrier according to the present invention preferably has an average particle size of about 10 to 60 μm, more preferably an average particle size of 15 to 55 μm.

  When the average particle size is less than 10, carriers are likely to be scattered and carrier adhesion to the photoreceptor is likely to occur. If it exceeds 60 μm, the ears on the magnetic brush are likely to be rough, making it difficult to adapt to the soft development method.

  The volume average particle diameter is a volume-based average particle diameter measured by a laser diffraction particle size analyzer “HELOS” (manufactured by Sympatec Corporation) equipped with a wet disperser.

  The magnetization characteristics of the carrier magnetic particles themselves are preferably 20 to 80 emu / g in saturation magnetization. When the saturation magnetization is less than 20 emu / g, the magnetic binding force to the developing sleeve is small, so that the carrier adheres to the image forming member and the magnetic brush becomes small, so that a high density image cannot be obtained. On the other hand, if it exceeds 80 emu / g, the magnetic brush becomes stiff, and the counter development method tends to cause a decrease in the density at the tip.

  The saturation magnetization is measured by “DC magnetization characteristic automatic recording device 3257-35” (manufactured by Yokogawa Electric Corporation).

<Carrier resin coating>
The carrier according to the present invention preferably comprises magnetic particles as a core (core) and the surface thereof is coated with a resin. The resin used for coating the carrier core material is not particularly limited, and various resins can be used. For the positively chargeable toner, for example, a fluorine-based resin, a fluorine-acrylic resin, a silicone-based resin, a modified silicone-based resin, or the like can be used, and a condensation-type silicone resin is preferable. Conversely, for negatively chargeable toners, for example, acrylic-styrene resins, mixed resins of acrylic-styrene resins and melamine resins, and cured resins thereof, silicone resins, modified silicone resins, epoxy resins. , Polyester resins, urethane resins, polyethylene resins, and the like. Preferred are mixed resins of acrylic-styrene resins and melamine resins, cured resins thereof, and condensation type silicone resins. Moreover, you may add a charge control agent, an adhesive improvement agent, a primer processing agent, a resistance control agent, etc. as needed.

  As the coating resin, a siloxane-based resin is preferably used, and a resin having a crosslinked structure is preferable. Examples of the siloxane-based resin include a silicone resin. As the structure of the silicone resin, those represented by the following general formulas (7) and (8) are preferable.

In the general formulas (7) and (8), R _{5 to} R ₈ each represent a substituent selected from a methyl group, an ethyl group, a phenyl group, a vinyl group, a hydroxyl group, and the like. In particular, in the combination of R ₅ and R _6, a mixture of a combination of a hydroxyl group and a methyl group and a combination of a methyl group and a methyl group is preferable from the viewpoint of adhesiveness. Furthermore, the use of the resin having this configuration is preferable because a crosslinked film can be formed by using the curing agent described below. Moreover, you may use modification types, such as alkyl modification, phenol modification, and urethane modification. Regarding the ratio of the above general formulas (7) and (8),
(7) :( 8) = 1: 99 to 70:30
Is preferred. More preferably,
(7) :( 8) = 5: 95-50: 50
It is.

  Further, the charge amount and the like can be adjusted by adding a silane coupling agent to the silicone resin. In order to adjust the charge amount, 5 to 50 parts by mass, preferably 7 to 45 parts by mass of the silane coupling agent is added to 100 parts by mass of the silicone resin. If the added amount is excessive, there is a problem that the hardness of the resin is lowered. If the added amount is too small, the chargeability-imparting ability is lowered and the object cannot be achieved.

  Examples of the silane coupling agent include alkoxysilanes having an amino group or an amine at the terminal, and those having the following structure can be given.

  Among the above silane coupling agents, those having an amine group at the end as shown in the structures of the exemplary compounds (1), (2), (3), (5) and (6) are preferable. I can list them. The reason for this is not clear, but it is presumed that it can be taken into the resin more easily due to the effect of the active hydrogen of the amine present at the terminal, and the chargeability can be stabilized. Furthermore, by using the one having an amine group at the terminal, the crosslinking point can be increased, and a denser crosslinked structure can be provided.

  Further, it is preferable to use a curing agent in order to form a crosslinked structure in the resin. Examples of the curing agent include an oxime type curing agent having a structure represented by the following general formula (9).

In the general formula (9), R ₉ represents a substituent selected from the group consisting of a methyl group, an ethyl group, a propyl group, a phenyl group and derivatives thereof, and R ₁₀ and R ₁₁ are a methyl group, an ethyl group, The substituent selected from the group which consists of a propyl group and those derivatives is shown.

  Specifically, the following structures can be mentioned.

  In this invention, the addition amount of the said oxime type hardening | curing agent is 0.1-10 mass parts with respect to 100 mass parts of resin, Preferably it is good to add 0.5-8 mass parts. When the amount is within this range, a dense cross-linked structure can be formed, and thus a dense film can be formed. When the addition amount is excessive, a reaction residue remains on the contrary, so that the degree of cross-linking is lowered, and the density of the film is reduced, so that a problem that durability is lowered is likely to occur.

<Carrier manufacturing method>
The carrier can be manufactured by coating a magnetic particle with a silicone resin or the like a plurality of times and performing a heat treatment.

  The coating method is not particularly limited, and a coating method such as a dipping method or a spray drying method is used. Also, the heat treatment method is not particularly limited, and for example, a dryer or the like in which a coated carrier is put in a bucket and heated to dry can be used.

  The multiple times of coating and heat treatment means that the magnetic particles are coated with a silicone resin, and after the heat treatment, the silicone resin is further coated and the heat treatment step is repeated. It is preferable that the heat treatment is sufficiently performed each time to cause a crosslinking reaction. The heating temperature is preferably 180 ° C. ≦ first heating temperature ≦ nth heating temperature ≦ 300 ° C. If the temperature is lower than 180 ° C., sufficient crosslinking reaction does not proceed, so that film wear occurs and sufficient durability cannot be obtained. Further, the first heating temperature ≦ the nth heating temperature is preferable because the low crosslinking component can be eliminated.

  The resin coating amount of the first coating is preferably 40 to 95% by mass of the entire resin coating amount. More preferably, it is 45-90 mass%. On the other hand, the resin coating amount in the second and subsequent final coatings is preferably 5% by mass to 60% by mass, and more preferably 10% by mass to 55% by mass with respect to the entire resin coating amount. That is, when the resin coating amount is less than 5% by mass, the final coating cannot be made uniform, and unevenness occurs in the resin layer on the surface, which is not preferable.

  The number of times of coating is not problematic in terms of properties even if the number of times of coating is repeated. However, if the number of times of coating is twice, this property can be satisfied.

  The apparatus for applying mechanical stress to the carrier is not particularly limited, and for example, a stirring mixer such as a Nauter mixer, a tumbler mixer, a V-type mixer and a W-corn type mixer can be used. A device with low impact energy per unit time, such as a Nauter mixer, takes a long time to obtain a carrier that satisfies the performance. Therefore, a Turbler mixer, a V-type mixer, and a W cone type having a high impact force per unit time. It is preferable to use a stirring mixer such as a mixer.

  The coating resin film thickness of the silicone resin on the magnetic particles is preferably 0.2 to 2.0 μm, more preferably 0.3 to 1.5 μm.

  If the coating resin film thickness is thicker than 2.0 μm, the image density is low and a good image cannot be obtained. If the coating resin film thickness is thinner than 0.2 μm, sufficient durability cannot be obtained, and charge is injected from the developing sleeve. Then, the carrier easily adheres to the surface of the image forming body, which is not preferable.

  The film thickness of the coating resin was measured by cutting the center of the carrier particles, observing the cut surface with a scanning electron microscope, and extracting several points at random, and taking the average value as the coating resin film thickness.

  The amount of the silicone resin coating resin on the magnetic particles is preferably 0.3 to 15% by mass and more preferably 0.4 to 10% by mass with respect to the magnetic particles. If the amount of the coating resin is less than 0.3% by mass, a uniform coating layer cannot be formed on the surface of the magnetic particles, and if it exceeds 15% by mass, the coating layer becomes too thick and the magnetic particles are not formed. Particles are generated, which is not preferable because the carrier particles are uneven and have poor fluidity. Further, if the coating resin amount is outside the preferred range, sufficient chargeability and charge rise characteristics cannot be obtained, which is not preferred.

  The amount of the coating resin was measured with a quantitative carbon analyzer “EMAIA-500” (manufactured by Horiba Seisakusho).

<toner>
The toner is preferably obtained by mixing inorganic fine particles with colored particles containing a binder resin, a colorant and other additives. The volume average particle size of the toner is preferably 3 to 20 μm, and more preferably 5 to 12 μm. The method for producing the colored particles is not particularly limited, and those produced by a pulverization method or a polymerization method can be used. However, in the present invention, a polymer toner produced by a polymerization method capable of obtaining a uniform particle size distribution is more preferable. preferable. Here, the polymerized toner means a toner in which a toner binder resin is formed and a toner shape is formed by polymerization of a raw material monomer of the binder resin and, if necessary, subsequent chemical treatment. More specifically, it means a toner formed through a polymerization reaction such as suspension polymerization or emulsion polymerization, and if necessary, a step of fusing particles between them. Since the polymerized toner is produced by uniformly dispersing the raw material monomers in an aqueous system and then producing the toner, a toner having a uniform toner particle size distribution and shape can be obtained.

  The binder resin used for the toner is not particularly limited, and various conventionally known resins are used. Specific examples include styrene resins, acrylic resins, styrene / acrylic resins, and polyester resins. The colorant is not particularly limited, and a conventionally known material is used. Specific examples include carbon black, nigrosine dye, aniline blue, calcoin blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate and rose bengal. Examples of other additives include charge control agents such as salicylic acid derivatives and azo metal complexes, fixing improvers such as low molecular weight polyolefins and carnauba wax.

  The magnetic toner can be obtained by using magnetic fine particles as a colorant. As the magnetic fine particles, particles such as ferrite and magnetite having an average primary particle diameter of 0.1 to 2.0 μm are used. The addition amount of the magnetic fine particles is preferably 20 to 70% by mass in the toner.

  Further, from the viewpoint of imparting fluidity, it is preferable to mix inorganic fine particles with colored particles. As the inorganic fine particles, inorganic oxide particles such as silica, titania and alumina are preferable, and these inorganic fine particles are more preferably hydrophobized with a silane coupling agent or a titanium coupling agent.

<Developer>
The developer can be prepared by mixing toner and carrier. The mixing amount of the toner with respect to the carrier is preferably 2 to 10% by mass.

  The mixing apparatus is not particularly limited, and a Nauter mixer, a W cone, a V-type mixer, or the like can be used.

  A developing device of the counter direction developing system will be described with reference to FIG. In the developing device 102, a developing sleeve 120 in which a cylindrical magnet 121 is disposed in a non-rotating manner is disposed in an opening portion of a developing container 110 containing a two-component developer so as to face the organic photoreceptor 101. 120 rotates in the counter direction with respect to the organic photosensitive member 101 rotating in the direction of the arrow, and conveys the developer adsorbed and held on the surface to the developing unit facing the organic photosensitive member 101. The magnet 121 has a developing magnetic pole N1 on the organic photoreceptor 101 side, and the first conveying magnetic pole S3, the second conveying magnetic pole N2, the third conveying magnetic pole S2, and the second conveying magnetic pole S2 are arranged in the rotational direction of the developing sleeve 120 from the developing magnetic pole N1. 3. It has a pumping magnetic pole S1 constituting a conveying magnetic pole and a separating magnetic pole.

  The developer in the developing container 110 is attracted and held on the developing sleeve 120 by the action of the pumping pole S1 at the position (pumping position) Q on the surface of the developing sleeve 120 corresponding to the pumping magnetic pole S1 of the magnet 121, and the developing blade After the layer thickness is regulated by 122, the developing unit is reached, and a magnetic brush is formed by the action of the developing magnetic pole N 1 in the developing unit to develop the latent image on the organic photoreceptor 101.

  The developer whose toner density is reduced by the development is held on the developing sleeve 120 and returned to the inside of the developing container 110 by the action of the first and second transport magnetic poles S3 and N2, and the third transport magnetic pole S2 and the pumping magnetic pole S1. At the position (developer dropping position) P on the surface of the developing sleeve 120 where the intermediate magnetic flux density is the smallest, it peels off from the developing sleeve 120 and falls. The developing sleeve 120 from which the developer has been peeled is adsorbed and held by the new developer at the pumping position Q as described above.

  A first agitating and conveying member 123 is installed below the developing sleeve 120 in the developing container 110, and a second agitating and conveying member 124 is further installed via a partition wall 140. These first and second agitating / conveying members 123 and 124 are of a screw type and have a helical screw blade 128 and a plate-like protrusion 130 between the blades.

  The developer having a low toner concentration peeled off from the developing sleeve 120 falls on the first stirring / conveying member 123 and is stirred and conveyed in the axial direction by the first stirring / conveying member 123 in the axial direction. This is passed to the second agitating and conveying member 124 through an opening (not shown). The second agitating / conveying member 124 conveys the developer and the toner replenished from the replenishing port 118 of the developing container 110 in a reverse rotation to the above while agitating, and an opening (not shown) at the other end of the partition wall 140. And return to the first stirring and conveying member 123 side.

Next, the process cartridge and the electrophotographic apparatus according to the present invention will be described.
FIG. 2 shows a schematic configuration of an electrophotographic apparatus having a process cartridge including an organic photoreceptor.

  In FIG. 2, reference numeral 1 denotes a drum-shaped organic photoconductor (photoconductor), which is driven to rotate about a shaft C in the direction of an arrow at a predetermined peripheral speed. In the rotation process, the organic photoreceptor 1 is uniformly charged with a positive or negative predetermined potential on its peripheral surface by the charging means 2 and then output from an exposure means (not shown) such as slit exposure or laser beam scanning exposure. Exposure light 3 (exposure means) that has been emphasized and modulated in response to a time-series electrical digital image signal of target image information. In this way, electrostatic latent images corresponding to the target image information are sequentially formed on the peripheral surface of the organic photoreceptor 1.

  The formed electrostatic latent image is then developed with toner by the developing means 4 and taken out from a paper feed unit (not shown) between the organic photoreceptor 1 and the transfer means 5 in synchronization with the rotation of the organic photoreceptor 1. The toner images formed and supported on the surface of the organic photoreceptor 1 are sequentially transferred by the transfer means 5 to the fed transfer material P.

  The transfer material P that has received the transfer of the toner image is separated from the surface of the organic photoreceptor, introduced into the image fixing means 24, and subjected to image fixing to be printed out as an image formed product (print, copy).

  After the image transfer, the surface of the organic photoreceptor 1 is cleaned by removing the transfer residual toner by the cleaning unit 6, and is further subjected to a static elimination process with pre-exposure light Pex from a pre-exposure unit (not shown). Used repeatedly for image formation. When the charging unit 2 is a contact charging unit using a charging roller or the like, pre-exposure is not always necessary.

  In the present invention, among the above-mentioned components such as the organic photoreceptor 1, the charging unit 2, the developing unit 4 and the cleaning unit 6, a plurality of components are housed in a container PC and integrally combined as a process cartridge. The process cartridge may be configured to be detachable from an electrophotographic apparatus main body such as a copying machine or a laser beam printer. For example, at least one of the charging unit 2, the developing unit 4 and the cleaning unit 6 is integrally supported together with the organic photoreceptor 1 to form a cartridge, which can be attached to and detached from the apparatus body using a guide unit AN such as a rail of the apparatus body. It can be a process cartridge.

  An embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described as a full-color image forming apparatus to which the present invention is applied.

  FIG. 3 is a cross-sectional configuration diagram of a color image forming apparatus showing an 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.

  An image forming unit 10Y that forms a yellow image has a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a primary transfer unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. A primary transfer roller 5Y and a cleaning means 6Y are provided. An image forming unit 10M that forms a magenta image includes a drum-shaped photoconductor 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 photoconductor 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, 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 10K include charging means 2Y, 2M, 2C, and 2K that rotate around the photosensitive drums 1Y, 1M, 1C, and 1K, and image exposure means 3Y, 3M, 3C and 3K, rotating developing means 4Y, 4M, 4C and 4K, and cleaning means 5Y, 5M, 5C and 5K for cleaning the photosensitive drums 1Y, 1M, 1C and 1K.

  The image forming units 10Y, 10M, 10C, and 10K have the same configuration except that the colors of the 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.

In the image forming method of the present invention, when an electrostatic latent image is formed on a photoreceptor, it is preferable to perform image exposure using an exposure beam having a spot area of 2000 μm ² or less. Even when such small-diameter beam exposure is performed, the organic photoreceptor of the present invention can faithfully form an image corresponding to the spot area. A more preferable spot area is 100 to 1000 μm ² . As a result, an electrophotographic image having a gradation of not less than 800 dpi (dpi is the number of dots per 2.54 cm) can be achieved.

The spot area of the exposure beam is a light intensity distribution plane appearing on the cut surface when the exposure beam is cut along a plane perpendicular to the beam, and in a region where the light intensity is 1 / e ² or more of the maximum peak intensity. It means the corresponding area.

Examples of the light beam used include a scanning optical system using a semiconductor laser, and a solid state scanner such as an LED or a liquid crystal shutter. The light intensity distribution includes a Gaussian distribution and a Lorentz distribution, but 1 / e of each peak intensity. ^The area up to ² is the spot area.

  The endless belt-shaped intermediate transfer body unit 7 is an endless belt-shaped intermediate transfer body 70 (transfer medium) as a semiconductive endless belt-shaped second image carrier that is wound around a plurality of rollers and 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, the transfer medium refers to a transfer medium for a toner image on a photosensitive member such as an intermediate transfer member or a transfer material.

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

  The secondary transfer roller 5b is brought into pressure contact with 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.

  Next, FIG. 4 shows a color image forming apparatus using the organic photoreceptor of the present invention (a copying machine having at least a charging means, an exposure means, a plurality of developing means, a transfer means, a cleaning means and an intermediate transfer body around the organic photoreceptor. 1 is a sectional view of the configuration of a laser beam printer). The belt-shaped intermediate transfer body 70 uses an elastic body having a medium resistance.

  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.

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

  Next, the electrostatic latent image is developed with yellow toner as the first color by yellow (Y) developing means (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 not activated and do not act on the photoreceptor 1. The yellow toner image of the first color is not affected by the second to fourth developing devices.

  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 first color yellow toner image 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 photoreceptor 1 after the transfer of the first color yellow toner image corresponding to the intermediate transfer body 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. is there.

  When the superimposed color toner image transferred onto the belt-shaped intermediate transfer member 70 is transferred to 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 paper 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 heated and fixed.

  The organophotoreceptor of the present invention is generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers, but also displays, recordings, light printing, plate making and facsimiles using electrophotographic technology. The present invention can be widely applied to such devices.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. In the following text, “part” means “part by mass”.

Production of Photoreceptor 1 Photoreceptor 1 was produced as follows.

The surface of the cylindrical aluminum support was cut to prepare a conductive support having a ten-point surface roughness Rz = 1.5 (μm).
<Intermediate layer>
The following intermediate layer dispersion was diluted twice with the same mixed solvent, and allowed to stand overnight, followed by filtration (filter; rigesh 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 Inorganic particles: Titanium oxide (Number average primary particle size 35 nm: Titanium oxide treated with silica / alumina and methylhydrogenpolysiloxane) 3 parts Methanol 10 parts are mixed as a disperser Using a sand mill, batch dispersion was performed for 10 hours to prepare an intermediate layer dispersion.

  It apply | coated so that it might become a dry film thickness of 1.0 micrometer on the said support body using the said coating liquid.

<Charge generation layer: CGL>
Charge generation material (CGM): oxytitanyl phthalocyanine (a titanyl phthalosine pigment having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° in an X-ray diffraction spectrum by Cu-Kα characteristic X-ray) 24 parts polyvinyl butyral resin “S-LEC BL-1” (manufactured by Sekisui Chemical Co., Ltd.) 12 parts 2-butanone / cyclohexanone = 4/1 (v / v) 300 parts The above composition is mixed, dispersed using a sand mill, and charged. A generation layer coating solution was prepared. This coating solution was applied by a dip coating method to form a charge generation layer having a dry film thickness of 0.5 μm on the intermediate layer.

<Charge transport layer 1 (CTL1)>
Charge transport material (4,4′-dimethyl-4 ″-(α-phenylstyryl)
Triphenylamine) 225 parts Polycarbonate (Z300: Mitsubishi Gas Chemical Co., Ltd.) 300 parts Antioxidant (Irganox 1010: Nihon Ciba Geigy Co., Ltd.) 6 parts Dichloromethane 2000 parts Silicon oil (KF-54: Shin-Etsu Chemical Co., Ltd.) 1 part mixed And dissolved to prepare a charge transport layer coating solution 1. This coating solution was applied onto the charge generation layer by a dip coating method and dried at 110 ° C. for 70 minutes to form a charge transport layer 1 having a dry film thickness of 18.0 μm.

<Preparation of polytetrafluoroethylene resin particle (PTFE particle) dispersion>
PTFE particles (PTFE particles having an average primary particle size of 0.12 μm and a crystallinity of 91.3) were heat-treated at 250 ° C. for 40 minutes, and PTFE particles having a crystallinity of 82.8 were used. A liquid was prepared.

PTFE particles (PT1: average primary particle size 0.12 μm, crystallinity 82.8) 200 parts Toluene 600 parts Fluorine comb type graft polymer (trade name GF300, manufactured by Toagosei Co., Ltd.) 15 parts were mixed. After that, a PTFE particle dispersion was prepared by dispersing with a sand grinder (made by Amex Co., Ltd.) using glass beads.

<Charge transport layer 2 (CTL2)>
815 parts of PTFE particle dispersion (4,4′-dimethyl-4 ″-(α-phenylstyryl)
Triphenylamine) 150 parts Siloxane-modified polycarbonate resin (PC-1) 150 parts Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 150 parts Antioxidant (Exemplary Compound 1-1) 12 parts THF: Tetrahydrofuran 2800 parts Silicon oil (KF) -54: manufactured by Shin-Etsu Chemical Co., Ltd.) 4 parts were mixed and dissolved to prepare a charge transport layer coating solution 2. This coating solution is applied onto the charge transport layer 1 with a circular slide hopper coater, dried at 110 ° C. for 70 minutes to form a charge transport layer 2 having a dry film thickness of 2.0 μm, and the photoreceptor 1 is formed. Produced.

Production of photoconductors 2 to 8 Photoconductor 1 was produced in the same manner as in photoconductor 1 except that the types and addition amounts of the fluorine-containing resin fine particles and the antioxidant in charge transport layer 2 (CTL2) were changed as shown in Table 1. In the same manner, photoconductors 2 to 8 were produced.

In Table 1,
PTFE and H represent the following fluororesin fine particles.

PTFE: Polyethylene terephthalate resin particles H: Copolymer resin particles of ethylene trifluoride-tetrafluoroethylene Further, the contact angle and the variation in the contact angle in Table 1 were measured by the above-described method and expressed as absolute values.

Preparation MnO Preparation Carrier 1-5 Carrier: 10mol%, MgO: 39mol% , Fe 2 O 3: 50mol% and SnO _2: using 1 mol%, 5 hours pulverized into a wet ball mill, and mixed and dried Then, it hold | maintained at 850 degreeC for 1 hour, and calcination was performed. This was pulverized with a wet ball mill for 7 hours to 3 μm or less. Appropriate amounts of a dispersant and a binder were added to this slurry, and granulated and dried by a spray dryer to obtain a granulated product.

This granulated material was held at 1200 ° C. for 4 hours in an electric furnace in an air atmosphere and subjected to main firing. Thereafter, it was pulverized and further classified under different classification conditions to obtain ferrite carriers having average particle diameters of 8 μm, 12 μm, 35 μm, 58 μm, and 65 μm. These are used as a core material, and a mixture of a silicone resin in which the combination of R ₅ and R ₆ in the general formula (7) is a methyl group and a hydroxyl group and a general formula (8) in which the substituents are all methyl groups (mass ratio = ( 7): (8) = 40: 60) 100 parts of silane coupling agent (Exemplary Compound (1)) 10 parts, oxime type curing agent (Exemplary Compound (15)) 5 parts are mixed, and the solid content concentration is A 15% by weight toluene solution was prepared. Subsequently, the first coating was performed on one magnetic substance particle by a spray drying method so that the coating amount was 1.5% by mass, and a curing treatment was performed at a heating temperature of 200 ° C. for 3 hours. The second coating is performed by spray drying so that the coating amount is 0.8% by mass, cured at a heating temperature of 250 ° C. for 3 hours, and coated with a silicone resin, with an average particle size of 8 μm, 12 μm, and 35 μm. 1 to 5 obtained resin-coated ferrite carriers corresponding to 58 μm and 65 μm.

Production of Carriers 6 to 9 As shown in Table 2, except that the compositions of MnO, MgO, Fe ₂ O ₃ and SnO ₂ were changed, the Mn—Mg—Sn system having an average particle size of 35 μm was used in the same manner as in Example 1. Ferrite carriers 6 to 9 were obtained.

  For the ferrite carriers 1 to 9, saturation magnetization was measured.

Preparation of Toner * Preparation of Toner Bk, Toner Y, Toner M, and Toner C Add sodium n-dodecyl sulfate = 0.90 kg and 10.0 L of pure water to dissolve with stirring. While stirring, 1.20 kg of Legal 330R (carbon black manufactured by Cabot) was gradually added to this liquid, and then continuously dispersed for 20 hours using a sand grinder (medium type disperser). After dispersion, the particle size of the dispersion was measured using an electrophoretic light scattering photometer ELS-800 manufactured by Otsuka Electronics Co., Ltd. As a result, the weight average particle size was 122 nm. Moreover, the solid content concentration of the dispersion measured by a mass method by standing drying was 16.6% by mass. This dispersion is referred to as “colorant dispersion 1”.

  0.055 kg of sodium dodecylbenzenesulfonate is mixed with 4.0 L of ion-exchanged water and dissolved by stirring at room temperature. This is referred to as an anionic surfactant solution A.

  0.014 kg of nonylphenyl alkyl ether is mixed with 4.0 L of ion-exchanged water and dissolved by stirring at room temperature. This is designated as a nonionic surfactant solution A.

  Potassium persulfate = 223.8 g is mixed with 12.0 L of ion-exchanged water and dissolved with stirring at room temperature. This is referred to as initiator solution A.

  In a 100 L reaction kettle equipped with a temperature sensor, a cooling pipe, and a nitrogen introducing device, 3.41 kg of a polypropylene emulsion having a number average molecular weight (Mn) of 3500, an anionic surfactant solution A, and a nonionic surfactant solution A were added. Start agitation. Then, 44.0 L of ion exchange water is added.

  When heating is started and the liquid temperature reaches 75 ° C., the initiator solution A is added in its entirety. Thereafter, while controlling the liquid temperature at 75 ° C. ± 1 ° C., 14.3 kg of styrene, 2.88 kg of n-butyl acrylate, 0.8 kg of methacrylic acid, and 548 g of t-dodecyl mercaptan are added.

  Furthermore, the liquid temperature was raised to 80 ° C. ± 1 ° C., and stirring was performed for 6 hours. Cool the liquid temperature below 40 ° C and stop stirring. It filtered with the pole filter and this was set as latex A1.

  The glass transition temperature of the resin particles in the latex A1 was 59 ° C., the softening point was 116 ° C., the molecular weight distribution was weight average molecular weight = 13.4 million, and the weight average particle size was 125 nm.

  Potassium persulfate = 200.7 g is mixed with 12.0 L of ion-exchanged water, and dissolved with stirring at room temperature. This is designated initiator solution B.

  The nonionic surfactant solution A is put into a 100 L reaction kettle equipped with a temperature sensor, a cooling pipe, a nitrogen introducing device, and a comb-shaped baffle, and stirring is started. Next, 44.0 L of ion exchange water is added.

  Heating is started, and when the liquid temperature reaches 70 ° C., the initiator solution B is added. At this time, a solution prepared by previously mixing 11.0 kg of styrene, 4.00 kg of n-butyl acrylate, 1.04 kg of methacrylic acid, and 9.02 g of t-dodecyl mercaptan is added.

  Thereafter, the liquid temperature was controlled to 72 ° C. ± 2 ° C., and the mixture was heated and stirred for 6 hours. Furthermore, the liquid temperature was raised to 80 ° C. ± 2 ° C., and the mixture was heated and stirred for 12 hours.

  Cool the liquid temperature below 40 ° C and stop stirring. It filtered with the pole filter and this filtrate was set to latex B1.

  The glass transition temperature of the resin particles in the latex B1 was 58 ° C., the softening point was 132 ° C., the molecular weight distribution was weight average molecular weight = 245,000, and the weight average particle size was 110 nm.

  Sodium chloride = 5.36 kg as salting-out agent and 20.0 L of ion-exchanged water are added and dissolved by stirring. This is designated as sodium chloride solution A.

  In a 100 L SUS reaction kettle (stirring blade is an anchor blade) equipped with a temperature sensor, a cooling pipe, a nitrogen introducing device, and a comb-shaped baffle, latex A1 = 20.0 kg and latex B1 = 5.2 kg prepared above and a coloring agent are dispersed. Liquid 1 = 0.4 kg and ion-exchanged water 20.0 kg are added and stirred. Then warm to 35 ° C. and add sodium chloride solution A. Then, after leaving for 5 minutes, the temperature rise is started, and the temperature is raised to 85 ° C. in 5 minutes (temperature rise rate = 10 ° C./min). The mixture is heated and stirred at a liquid temperature of 85 ° C. ± 2 ° C. for 6 hours to cause salting out / fusion. Then, it cools to 30 degrees C or less and stops stirring. The mixture is filtered through a sieve having an opening of 45 μm, and this filtrate is used as an association liquid. Subsequently, using a centrifuge, wet cake-like non-spherical particles were collected from the associated liquid by filtration. Thereafter, it was washed with ion exchange water.

  The wet cake-like colored particles that had been washed as described above were dried with hot air at 40 ° C. to obtain colored particles. Further, careful classification was performed with an air classifier to obtain colored particles having a 50% volume particle diameter (Dv50) of 4.2 μm. Furthermore, 1.0% by mass of hydrophobic silica (hydrophobic degree = 70, number average primary particle size = 12 nm) was added to the colored particles to obtain “Toner Bk”.

  In the production of toner Bk, C.I. I. “Toner Y” was obtained in the same manner except that 8 parts of Pigment Yellow 185 were used.

  In the production of toner Bk, C.I. I. “Toner M” was obtained in the same manner except that 10 parts of Pigment Red 122 was used.

  In the production of toner Bk, C.I. I. “Toner C” was obtained in the same manner except that 5 parts of Pigment Blue 15: 3 was used.

The volume average particle diameters of Toner Bk, Toner Y, Toner M, and Toner C were 4.5 μm, 4.3 μm, 4.6 μm, and 4.7 μm, respectively. Production Production of Developer Groups 1-9 100 parts by mass of “Carriers 1-9” and 4 parts by mass of “Toner Bk, Toner Y, Toner M, Toner C” (for each type of carrier and toner) V “Developer group 1 (1Bk, 1Y, 1M, 1C) to developer group 9 (9Bk, 9Y, 9M, 9C)” were produced by mixing with a mold stirrer.

Evaluation 1 (Evaluation by counter development method)
The obtained photoreceptor is mounted on a commercially available full-color multifunction device 8050 (a tandem-type full-color multifunction device 8050 using an intermediate transfer member (made by Konica Minolta Business Technologies Co., Ltd.) modified to a counter developing system), Y, Color image evaluation using each color toner of M, C, and Br was performed. Using an original image having a white background portion, a solid portion solid image portion, a halftone image portion, and a character image portion, it was continuously copied and evaluated on A4 paper. Specifically, evaluation images were taken out at the start and every 5000 sheets, and a total of 300,000 sheets were printed and evaluated. Evaluation items and evaluation criteria are shown below.

Evaluation condition Photoconductor linear velocity: 220 mm / sec
Line speed of developing sleeve: 400mm / sec
Development: Counter development method, reversal development method (1) Image evaluation At the start of image density, a density meter “RD-918” (manufactured by Macbeth) was used for the 300,000th sheet, and the printer paper density was set to 0.0. The relative concentration was measured.

◎: 1.3 or more / good ○: 1.0 or more to less than 1.3 / practical problem level ×: less than 1.0 / practical problem fogging 918 "(manufactured by Macbeth) was used, and the fog density was measured at a relative density where the reflection density of A4 paper was 0.000.
A: Less than 0.010 (very good)
○: 0.010 or more and less than 0.020 (a level that causes no problem in practice)
×: 0.020 or more (problematic problems)
Reduction in tip density A halftone image of 300,000 sheets was produced and evaluated.

  (Double-circle): Generation | occurrence | production of density | concentration fall of a front-end | tip part is not seen, but a halftone image is reproduced clearly (very good).

  ○: The halftone image is clearly reproduced, but there is a drop in the tip density of less than 0.04 in reflection density (no problem in practical use).

  X: The half-tone image has a drop in tip density of 0.04 or more in reflection density (practically problematic).

Toner scattering ◎: Very little toner scattering and good sharpness of character image (good)
○: There is a slight toner scattering, but it is possible to judge up to three-point character images (practical)
X: Toner scattering is large and part of the 3-point character image cannot be determined. (Not practical)
Carrier adhesion A: There is almost no carrier adhesion to the organic photoreceptor, and no scratches or image defects are observed due to carrier adhesion. (Good)
◯: Slight carrier adhesion is observed, but no photoconductor scratches or image defects are observed due to carrier adhesion. (Practical acceptable)
X: There are many carrier adhesions, and the generation | occurrence | production of the generation | occurrence | production of the damage | wound of a photoreceptor and image defect by carrier adhesion is seen. (Not practical)
Color reproducibility The color of the solid image portion of the secondary color (red, blue, green) in each of the Y, M, and C toners of the first image and the 100th image is measured by “Macbeth Color-Eye 7000”, and CMC The color difference between the first and 100th sheets of each solid image was calculated using the (2: 1) color difference formula.

A: Color difference is 3 or less (good)
×: Color difference is greater than 3 (practical problem and impractical)
The results are shown in Table 3.

  As apparent from Table 3, in the image evaluation produced by the counter development method, an organic photoreceptor having a contact angle (20 ° C., 50% RH) with respect to pure water of the surface in the range of 90 ° to 130 ° was used, and the developer Combination No. using a carrier having a volume average particle diameter of 10 to 60 μm and a saturation magnetization value of 20 to 80 emu / g is used as the carrier. Nos. 2 to 4, 7, 8, 10 to 12, and 14 to 16 show good characteristics in all evaluation items such as image density, fogging, tip density reduction, toner scattering, carrier adhesion, and color reproducibility. On the other hand, the combination No. in which the volume average particle diameter of the carrier is 8 μm is used. In No. 1, fogging, toner scattering, and carrier adhesion occur, and color reproducibility is deteriorated. In addition, the combination No. in which the volume average particle diameter of the carrier is 65 μm is used. In No. 5, the density of the tip portion is reduced, and the color reproducibility is deteriorated. In addition, combination No. using a carrier having a carrier saturation value of 15 emu / g. No. 6 has fogging, toner scattering, and carrier adhesion, and color reproducibility is deteriorated. In addition, combination No. using a carrier having a carrier saturation value of 85 emu / g. In No. 9, the density of the tip portion is lowered, and the color reproducibility is deteriorated. Also, combination No. using an organic photoreceptor having a contact angle of 88 on the surface. 13 also has fogging and a decrease in density at the tip, and color reproducibility is deteriorated.

Evaluation 2 (Evaluation using the parallel development method)
The evaluation performed in Evaluation 1 was evaluated by a parallel development system in which the traveling directions of the photosensitive member and the developing sleeve proceed in parallel.

Evaluation condition Photoconductor linear velocity: 220 mm / sec
Line speed of developing sleeve: 400mm / sec
Development: Parallel development method, reversal development method As a result, the difference between the invention of evaluation 1 and the comparative example does not appear clearly, and no reduction in tip density or occurrence of fog is observed in all of the invention and comparative examples. However, as compared with the counter development method, the image density was lowered and an electrophotographic image with insufficient density was obtained.

It is a figure which shows the cross section of the developing device of the counter direction developing method. 1 is a diagram illustrating an example of a schematic configuration of an electrophotographic apparatus having a process cartridge including an organic photoreceptor. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention. 1 is a cross-sectional view of a color image forming apparatus using an organic photoreceptor of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Organic photoreceptor C axis | shaft 2 Charging means 3 Exposure light 4 Developing means 5 Transfer means P Transfer material 24 Fixing means 6 Cleaning means Pex Pre-exposure means PC Process cartridge container AN Guide means 101 Organic photoreceptor 102 Developing apparatus 110 Developing container 118 Replenishment Port 120 Developing sleeve 121 Magnet 122 Developing blade 123 First conveying member 124 Second conveying member 128 Screw blade 130 Plate-like protrusion 140 Partition N1 Developing magnetic pole N2 Second developing magnetic pole S1 Pumping magnetic pole S2 Third conveying magnetic pole S3 First conveying magnetic pole P Developer drop position Q Pumping position

Claims (13)

An electrostatic latent image is formed on a cylindrical organic photosensitive member, and a cylindrical developing sleeve carrying a developer containing toner and carrier is brought into contact with the organic photosensitive member to convert the electrostatic latent image into a toner image. In the image forming method for visualizing, the contact angle (20 ° C., 50% RH) of pure water on the surface of the organic photoreceptor is 90 ° to 130 °, the volume average particle size of the carrier is 10 to 60 μm, and saturation An image forming method characterized in that an electrostatic latent image is visualized as a toner image while rotating a developing sleeve in a counter direction with respect to a rotation direction of an organic photoreceptor, and having a magnetization value of 20 to 80 emu / g. An electrostatic latent image is formed on a cylindrical organic photoreceptor, and a cylindrical developing sleeve carrying a developer containing toner and carrier is disposed in contact with the organic photoreceptor, and the electrostatic latent image is converted into a toner image. A plurality of image forming units having developing means for visualizing and a transfer means for transferring a toner image formed on an organic photoreceptor to a transfer medium are arranged, and a toner whose color is changed for each of the plurality of image forming units is provided. The contact angle of pure water on the surface of the organic photoconductor in an image forming method in which each color toner image is formed on the organic photoconductor and the color toner image is transferred from the organic photoconductor to a transfer medium to form a color image. (20 ° C. and 50% RH) is 90 ° to 130 °, the carrier has a volume average particle size of 10 to 60 μm, a saturation magnetization value of 20 to 80 emu / g, and the developing sleeve in the rotational direction of the organic photoreceptor. And an image forming method, characterized in that to the electrostatic latent image into a toner image while rotating in the counter direction. The image forming method according to claim 1, wherein the carrier is a ferrite carrier. The image forming method according to claim 1, wherein the carrier is a resin-coated carrier. The image forming method according to claim 1, wherein the surface layer of the organophotoreceptor contains a lubricating substance. 3. The image forming method according to claim 1, wherein the lubricating substance is fluorine-containing resin fine particles. The image forming method according to claim 1, wherein the surface layer of the organophotoreceptor contains an antioxidant. The image forming method according to claim 7, wherein the antioxidant is a hindered phenol-based antioxidant. The image forming method according to claim 7, wherein the antioxidant is a hindered amine antioxidant. The image forming method according to claim 1, wherein the organic photoreceptor is a laminated organic photoreceptor in which at least a charge generation layer and a charge transport layer are provided on a conductive substrate. The image forming method according to claim 1, wherein the toner is a polymerized toner. An electrostatic latent image is formed on a cylindrical organic photosensitive member, and a cylindrical developing sleeve carrying a developer containing toner and carrier is brought into contact with the organic photosensitive member to convert the electrostatic latent image into a toner image. In the image forming apparatus to be visualized, the contact angle (20 ° C. and 50% RH) of pure water on the surface of the organic photoreceptor is 90 ° to 130 °, the volume average particle size of the carrier is 10 to 60 μm, and saturation An image forming apparatus having a magnetization value of 20 to 80 emu / g and developing an electrostatic latent image into a toner image while rotating a developing sleeve in a counter direction with respect to a rotation direction of an organic photoreceptor. An electrostatic latent image is formed on a cylindrical organic photoreceptor, and a cylindrical developing sleeve carrying a developer containing toner and carrier is disposed in contact with the organic photoreceptor, and the electrostatic latent image is converted into a toner image. A plurality of image forming units having developing means for visualizing and a transfer means for transferring a toner image formed on an organic photoreceptor to a transfer medium are arranged, and a toner whose color is changed for each of the plurality of image forming units is provided. In the image forming apparatus for forming a color image by forming each color toner image on the organic photoconductor and transferring the color toner image from the organic photoconductor to a transfer medium, the surface of the organic photoconductor is in contact with pure water. The angle (20 ° C., 50% RH) is 90 ° to 130 °, the volume average particle diameter of the carrier is 10 to 60 μm, the saturation magnetization value is 20 to 80 emu / g, and the developing sleeve is rotated in the direction of rotation of the organic photoreceptor. Contrast, the image forming apparatus, characterized in that to visualize the toner image an electrostatic latent image while rotating in the counter direction.

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