JP2006227579A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method and image forming apparatus of stably forming a digital image of high precision for the purpose of forming an electrostatic latent image of the high precision by a short wavelength laser etc., and forming the electrostatic latent image as a toner image of the high precision and high image quality. <P>SOLUTION: The image forming method comprises applying a uniform surface potential by an electrostatic charging means to an organic photoreceptor, then forming the electrostatic latent image by an exposing means using a semiconductor laser of 350 to 500 nm in oscillation wavelength as a write light source, forming a developing brush onto a cylindrical developing sleeve carrying a developer containing toner and carrier by a developing means, and contacting the developing brush with the organic photoreceptor to develop the electrostatic latent image to the toner image, in which the absolute value of the electrostatic charging potential in a non-exposing part of the organic photoreceptor is 250 to 450V in the exposing position of the exposing means and the developing sleeve is rotated in a direction counter to the rotating direction of the organic photoreceptor to develop the electrostatic latent image to the toner image. <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.

  In recent years, there are increasing opportunities to use electrophotographic copying machines and printers in the fields of printing and color printing. In the fields of printing and color printing, there is a strong tendency to demand high-quality digital monochrome images or color images. In response to such a demand, it has been proposed to form a high-definition digital image using a short-wavelength laser beam as an exposure light source (Patent Document 1). However, even if the short-wavelength laser light is used to reduce the dot diameter of the exposure and a fine electrostatic latent image is formed on the electrophotographic photosensitive member, the finally obtained electrophotographic image has sufficient high image quality. The current situation has not been achieved.

  The cause is that the formation of the electrostatic latent image on the electrophotographic photosensitive member and the appropriate development conditions for the electrostatic latent image have not been fully elucidated. This is because an image forming method having both development conditions necessary for formation has not been established.

  In other words, as an electrophotographic photoreceptor, an organic photoreceptor developed for a short wavelength laser (hereinafter simply referred to as a photoreceptor) is used, and even if image exposure with a short wavelength laser is performed, a fine dot electrostatic latent image is obtained. It is not always possible to form an image, and since the development method that can reproduce the latent dot images individually and in high density has not yet been achieved in subsequent development, individual dot images can be reproduced independently. The detailed electrophotographic image has not been sufficiently achieved.

  Further, as a developing method, as a developing method of the latent image on the organic photoconductor, a developing sleeve (a developing sleeve) provided on the organic photoconductor is advanced in the developing region in parallel with the advancing direction of the organic photoconductor (hereinafter, referred to as a developing method) Parallel development method) and development method that advances in the counter direction (hereinafter referred to as counter development method) are known (Patent Document 2), but both of them sufficiently solve the problem when forming a high-density dot image. I haven't done it.

  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.

  Recently, a fine unevenness failure called worm-like unevenness has been a problem. Although the cause of this worm-like unevenness has not been clarified, it is considered that the worm-like unevenness is caused by the fact that the relative speed between the photosensitive member and the developing sleeve is high and the frictional charging between the magnetic brush of the developer and the photosensitive member becomes strong. . For this reason, worm-like unevenness tends to occur more easily in the counter development method than in the parallel development method. Further, the worm-like unevenness has a correlation with the frequency of the developing bias, and the worm-like unevenness is reduced as the frequency is increased. However, when the frequency is increased, the sharpness of the image tends to decrease, and it is difficult to satisfy both the reduction of worm-like unevenness and the sharpness of the image.

  The above phenomenon seems to be difficult to solve by simply improving the photoreceptor and developer, and it is necessary to examine comprehensive image forming conditions including the photoreceptor and developer.

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

  That is, in the counter development method, reversely chargeable toner is easily generated due to contact friction between the photoconductor and the toner, and as a result, fogging and toner scattering occur, leading edge density decrease and worm-like unevenness occur. This makes it difficult to reproduce a high-definition electrostatic latent image 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 2000-250239 A JP 2001-125435 A JP-A-11-202559

  An object of the present invention is to provide a high-quality, high-definition electrophotographic image by solving the above-mentioned problems of the prior art. That is, a high-definition electrostatic latent image is formed by a short wavelength laser or the like, and the electrostatic latent image is formed as a toner image with high definition and high image quality. More specifically, after the formation of a high-definition electrostatic latent image, the occurrence of image unevenness and worm-like unevenness due to a decrease in the density at the tip is prevented, and the image density is increased. Another object is to provide an image forming method and an image forming apparatus capable of producing an electrophotographic image with good color reproducibility.

  The inventors of the present invention, as described above, form a high-definition electrostatic latent image with a short wavelength laser or the like, and form the electrostatic latent image on a toner image with high density and high definition. In this method, the formation of the electrostatic latent image on the organic photoconductor is performed under a low potential condition, and development is performed using a soft developer with a counter development method, thereby producing a high-definition and high-quality toner image. As a result, the present invention was completed.

That is, the present invention is achieved by having the following configuration.
1. An electrostatic latent image is formed on an organic photoconductor on a conductive substrate using an exposure unit using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source after applying a uniform surface potential by a charging unit. Forming a developing brush with a developer containing toner on a cylindrical developing sleeve carrying a developer containing toner and carrier by a developing means, contacting the developing brush with an organic photoreceptor, In the image forming method of developing an electrostatic latent image into a toner image, the absolute value of the charged potential of the non-exposed portion of the organic photoreceptor is 250 to 450 V at the exposure position of the exposure unit, and the developing sleeve is An image forming method comprising: rotating an electrostatic latent image into a toner image by rotating the photoconductor in a counter direction.
2. A charging means for providing a uniform surface potential on an organic photoreceptor, an exposure means for forming an electrostatic latent image using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source, a developer containing toner and carrier Development means for forming a developing brush with a developer containing toner on a cylindrical developing sleeve carrying toner, and bringing the developing brush into contact with an organic photoreceptor to visualize the electrostatic latent image into a toner image And a plurality of image forming units having transfer means for transferring a toner image formed on the organic photoconductor to a transfer medium, and the toner on the organic photoconductor is changed in color for each of the plurality of image forming units. In the image forming method of forming a color image by forming each color toner image and transferring the color toner image from an organic photoreceptor to a transfer medium, an organic material is formed at the exposure position of the exposure means. The absolute value of the charged potential of the non-exposed portion of the photoconductor is 250 to 450 V, and the developing sleeve is rotated in the counter direction with respect to the rotation direction of the organic photoconductor to visualize the electrostatic latent image into a toner image. An image forming method.
3. 3. The image forming method according to 1 or 2, wherein the carrier has a volume-based median diameter D50 of 10 to 60 μm and a saturation magnetic value of 20 to 80 emu / g.
4). The image forming method according to any one of 1 to 3, wherein the carrier is a ferrite carrier.
5. 5. The image forming method according to any one of 1 to 4, wherein the carrier is a resin-coated carrier.
6). 6. The image forming method according to any one of 1 to 5, wherein the surface layer of the organic photoreceptor contains lubricating particles.
7). 7. The image forming method as described in 6 above, wherein the lubricating particles are fluorine resin particles.
8). 8. The image forming method according to any one of 1 to 7, wherein the surface layer of the organic photoreceptor contains an antioxidant.
9. 9. The image forming method as described in 8 above, wherein the antioxidant is a hindered phenol antioxidant.
10. 9. The image forming method as described in 8 above, wherein the antioxidant is a hindered amine antioxidant.
11. 10. The image forming method according to any one of 1 to 9, 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.
12 12. The image forming method according to any one of 1 to 11, wherein the toner is a polymerized toner.
13. On the organic photoreceptor, a charging means for applying a uniform surface potential, an exposure means for forming an electrostatic latent image using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source, development containing toner and carrier Developing a developing brush with a developer containing toner on a cylindrical developing sleeve carrying an agent, bringing the developing brush into contact with an organic photoreceptor, and developing the electrostatic latent image into a toner image In the image forming apparatus having the means, the absolute value of the charging potential of the non-exposed portion of the organic photoreceptor is 250 to 450 V at the exposure position of the exposure means, and the developing sleeve is countered with respect to the rotation direction of the organic photoreceptor. An image forming apparatus that visualizes an electrostatic latent image into a toner image by rotating in a direction.
14 A charging means for providing a uniform surface potential on an organic photoreceptor, an exposure means for forming an electrostatic latent image using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source, a developer containing toner and carrier Development means for forming a developing brush with a developer containing toner on a cylindrical developing sleeve carrying toner, and bringing the developing brush into contact with an organic photoreceptor to visualize the electrostatic latent image into a toner image And a plurality of image forming units having transfer means for transferring a toner image formed on the organic photoconductor to a transfer medium, and the toner on the organic photoconductor is changed in color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by forming each color toner image on the surface and transferring the color toner image from an organic photoreceptor to a transfer medium, The absolute value of the charged potential of the non-exposed portion of the photoconductor is 250 to 450 V, and the developing sleeve is rotated in the counter direction with respect to the rotation direction of the organic photoconductor to visualize the electrostatic latent image into a toner image. An image forming apparatus.

  By using the image forming method and the image forming apparatus of the present invention, it is possible to form a high-definition, high-quality electrophotographic image using a short wavelength exposure light source, and the occurrence of fogging or the tip which is likely to occur in the counter development system. In addition, it is possible to prevent a density defect in a portion, and to eliminate fine unevenness called worm-like unevenness, and to provide an electrophotographic image having good dot reproducibility and color reproducibility.

  Hereinafter, the present invention will be described in detail.

  The image forming method of the present invention comprises an exposure unit using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source after applying a uniform surface potential on an organic photoreceptor on an electric substrate by a charging unit. An electrostatic latent image is formed using a developing means, and a developing brush with a developer containing toner is formed on a cylindrical developing sleeve carrying a developer containing toner and carrier by developing means, and the developing brush is organically An image forming method in which the electrostatic latent image is visualized into a toner image by bringing it into contact with a photoconductor, and an absolute value of a charging potential of an unexposed portion of the organic photoconductor is 250 to 250 at an exposure position of the exposure unit. The developing sleeve is rotated in the counter direction with respect to the rotation direction of the organic photoconductor to visualize the electrostatic latent image into a toner image.

  The image forming method of the present invention also comprises a charging means for applying a uniform surface potential on an organic photoconductor, an exposure for forming an electrostatic latent image using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source. A developing brush made of a developer containing toner is formed on a cylindrical developing sleeve carrying a developer containing toner and a carrier, and the developing brush is brought into contact with an organic photoconductor to thereby form the electrostatic latent image A plurality of image forming units each having a developing unit that visualizes the toner image into a toner image and a transfer unit that transfers the toner image formed on the organic photosensitive member to a transfer medium, and coloring each of the plurality of image forming units. An image forming method in which each color toner image is formed on an organic photoreceptor using the changed toner, and each color toner image is transferred from the organic photoreceptor to a transfer medium to form a color image. The absolute value of the charged potential of the non-exposed portion of the organic photoreceptor is 250 to 450 V at the exposure position of the light means, and the electrostatic latent image is obtained by rotating the developing sleeve in the counter direction with respect to the rotational direction of the organic photoreceptor. The toner is visualized as a toner image.

  Since the image forming method of the present invention has the above-described configuration, an electrostatic latent image of a high-definition dot image (digital image) can be formed using a short wavelength laser. A high-quality toner image can be visualized, and a high-quality digital image or color image can be provided.

  The image forming method of the present invention forms an electrostatic latent image on an organic photoreceptor using a writing light source with a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm under the condition that the absolute value of the surface potential is 250 to 450 V. A developing brush made of a developer containing toner is formed on a cylindrical developing sleeve carrying a developer containing toner and a carrier, and the developing brush is brought into contact with an organic photoreceptor to thereby form the electrostatic latent image. Is formed into a toner image by a counter development method.

  When fine dot exposure is formed on an organic photoreceptor with a short wavelength laser or the like, the dot latent image tends to be thickened when the surface potential of the organic photoreceptor is high. That is, in a state where the surface potential is high, it is considered that the diffusion of carriers generated by exposure increases and the dot latent image is likely to be thickened. In the present invention, the dot latent image is prevented from being thickened, the dot latent image exposed by a short wavelength laser is thinned, and the dot latent image is clearly formed. Therefore, the absolute value of the charged potential of the organic photoreceptor is 250. An electrostatic latent image of a digital image is formed by using a writing light source with a semiconductor laser or a light emitting diode having an oscillation wavelength of 350 to 500 nm under a condition of ˜450 V (in the present invention, a potential measured in a non-image portion at an exposure position). To do. The resulting fine and clear dot latent image is visualized into a toner image by counter development contact development.

  If the absolute value of the charging potential is less than 250 V, the potential difference required during development (difference between the unexposed portion potential and the exposed portion potential) is small, and a sufficient image density cannot be obtained. On the other hand, if the absolute value of the charging potential exceeds 450 V, the dot latent image tends to be thick as described above, and worm-like unevenness is likely to occur, and the merit of using a short wavelength laser is reduced. Although it is not well understood about the fine unevenness called worm-like unevenness, it is thought that it is likely to occur because the relative speed between the photoconductor and the developing sleeve is fast and the influence of frictional charging between the magnetic brush and the photoconductor is strong. It tends to become more prominent in high-quality images using a short wavelength exposure light source.

  In the present invention, the electrostatic latent image formed as described above is preferably softly developed by a counter method with a developer using a carrier as described below.

  Hereinafter, the developer according to the present invention will be described.

  The developer of the present invention is a two-component developer containing a toner and a carrier, and the volume-based median diameter D50 of the carrier is 10 to 60 μm, the saturation magnetic value is 20 to 80 emu / g, and further 30 to 65 emu / g. Is preferable.

<Career>
The carrier according to the present invention preferably has a volume-based median diameter D50 of 10 to 60 μm and a saturation magnetic value of 20 to 80 emu / g. By using a carrier with a small carrier particle size and a low saturation magnetization value, the magnetic brush on the developing sleeve is softened, and soft-touch development is possible with the counter development method, resulting in reduced fog and tip density. And worm-like unevenness 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 (1).
(MnO) x (MgO) y (Fe 2 O 3) z
In the general formula (1), x + y + z = 100 mol%, and x, y and z are preferably in the range of 5 to 35 mol%, 10 to 45 mol% and 45 to 55 mol%, particularly preferably 7.5 to It is the range of 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 a volume-based median diameter D50 of about 10 to 60 μm, more preferably a volume-based median diameter D50 of 15 to 55 μm. When the volume-based median diameter D50 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-based median diameter D50 is a volume-based median diameter D50 measured by a laser diffraction particle size analyzer “HELOS” (manufactured by Sympatec Corporation) equipped with a wet disperser. Actually, the carrier, water, and a few drops of surfactant are adjusted to the concentration within the measurement in the wet disperser and used for the measurement.

  The magnetization characteristics of the carrier magnetic particles themselves are preferably 20 to 80 emu / g, more preferably 30 to 65 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 a “small fully automatic vibrating sample magnetometer (VSM-C7-10A)” (manufactured by Toei Kogyo Co., Ltd.). Specifically, a cell having a predetermined diameter of 6 mm is filled with 20 to 50 mg of sample and covered. It is obtained by setting the cell in the apparatus, measuring at a maximum magnetic field of 10 kOe, and reading from the magnetization curve.

<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 (2) and (3) are preferable.

In the general formulas (2) and (3), 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 (2) and (3),
(2) :( 3) = 1: 99 to 70:30
Is preferred. More preferably,
(2) :( 3) = 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 (4).

In the general formula (4), 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 diameter of the toner (meaning a volume-based median diameter D ₅₀ in the present invention) 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.

  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.

  Next, the organic photoreceptor according to the present invention will be described.

  The configuration of the organic photoreceptor related to the present invention 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 structure of the photoreceptor according to the present invention is preferably a structure in which a charge generation layer and a charge transport layer are sequentially laminated as a photosensitive layer on a conductive support. Furthermore, it is preferable to provide an intermediate layer between the conductive support and the photosensitive layer. If necessary, a surface protective layer may be further formed on the photosensitive layer.

  Preferable specific examples of the layer structure of the organic photoreceptor according to the present invention are described below.

Conductive Support As the conductive support used in the photoreceptor according to the present invention, a sheet-like or cylindrical conductive support is used.

  The cylindrical conductive support means a cylindrical support necessary to be able to form an endless image by rotating, and the cylindricity is preferably 5 to 40 μm, more preferably 7 to 30 μm.

  This cylindricity is based on JIS standard (B0621-1984). That is, when the cylindrical substrate is sandwiched between two coaxial geometric cylinders, it is represented by the difference in radius at the position where the distance between the two coaxial cylinders is minimum. In the present invention, the difference in radius is represented by μm. The method of measuring the cylindricity is obtained by measuring the roundness of 7 points in total, that is, 2 points 10 mm on both ends of the cylindrical substrate, 4 points of the central part, and 4 points obtained by dividing the distance between the both ends. The measuring device can be measured using a non-contact universal roll diameter measuring machine (manufactured by Mitutoyo Corporation).

As a material for the conductive support, 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.

  As the conductive support used in the present invention, one having an alumite film that has been sealed on the surface thereof may be used. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodizing in sulfuric acid, the sulfuric acid concentration is preferably 100 to 200 g / l, the aluminum ion concentration is 1 to 10 g / l, the liquid temperature is about 20 ° C., and the applied voltage is preferably about 20 V. It is not limited. The average film thickness of the anodized film is usually 20 μm or less, particularly preferably 10 μm or less.

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 agglomerated particles. Likely to happen. 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 image irregularities are likely to occur through these large irregularities. Further, the N-type semiconducting particles having a number average primary particle size of greater than 200 nm are likely to precipitate in the dispersion and easily generate aggregates. As a result, image unevenness is likely to occur.

  The titanium oxide particles include 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 a high-density dot image can be formed. Most preferred.

  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 it is effective in producing a high-density dot image.

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.

  Further, the N-type semiconductive particles may be those surface-treated with a reactive organosilicon compound represented by the following formula.

(R) _n- Si- (X) ₄ - _n
(In the above formula, Si represents a silicon atom, R represents an organic group in which carbon is directly bonded to the silicon atom, X represents a hydrolyzable group, and n represents an integer of 0 to 3).
In the organosilicon compound represented by the above formula, the organic group in which carbon is directly bonded to the silicon represented by R includes alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl and dodecyl, phenyl , Aryl groups such as tolyl, naphthyl and biphenyl, epoxy-containing groups such as γ-glycidoxypropyl and β- (3,4-epoxycyclohexyl) ethyl, γ-acryloxypropyl and γ-methacryloxypropyl ( (Meth) acryloyl group, hydroxyl group such as γ-hydroxypropyl, 2,3-dihydroxypropyloxypropyl, vinyl group such as vinyl and propenyl, mercapto group such as γ-mercaptopropyl, γ-aminopropyl, N-β Amino-containing groups such as (aminoethyl) -γ-aminopropyl, γ-chloropropyl, 1,1, - trifluoride Oro propyl, nonafluorohexyl, halogen-containing groups such as perfluorooctylethyl, other nitro, and cyano-substituted alkyl group. Examples of the hydrolyzable group for X include alkoxy groups such as methoxy and ethoxy, halogen groups, and acyloxy groups.

  Moreover, the organosilicon compound represented by the above formula may be used alone or in combination of two or more.

  Further, in the case of a specific compound of an organosilicon compound represented by the above formula and n is 2 or more, a plurality of R may be the same or different. Similarly, when n is 2 or less, the plurality of Xs may be the same or different. Moreover, when using 2 or more types of organosilicon compounds represented by the above formula, R and X may be the same or different between the respective compounds.

  Further, prior to the surface treatment of the methylhydrogensiloxane copolymer or the reactive organosilicon compound, the N-type semiconductive particles may be subjected to an inorganic surface treatment such as alumina or silica.

  In addition, although the above-mentioned treatment of alumina and silica may be performed simultaneously, it is preferable to perform the alumina treatment first and then the silica treatment. Further, the amount of treatment of alumina and silica when treating alumina and silica is preferably higher than that of alumina.

  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 the N-type semiconductor particles according to the present invention at such a high density in the intermediate layer, the rectification property of the intermediate layer is increased, and the increase in residual potential and transfer memory are generated even when the film thickness is increased. Therefore, it is possible to effectively prevent black spots and to form a good organic photoreceptor with small potential fluctuation. 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, when 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 dot image easily deteriorates. 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 an alcohol-soluble polyamide resin, a copolymerized polyamide resin or a methoxymethylated polyamide resin composed of a chemical structure with few carbon chains between amide bonds such as 6-nylon described above is known. This 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, charging characteristics and sensitivity under high temperature and high humidity and low temperature and low humidity are likely to change. It tends to cause black spots and deterioration of dot reproducibility.

  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 (5), 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 (6), and the number of carbon atoms contained in Y and the number of carbon atoms contained in Z are the number of carbon atoms of the amide bond unit in the repeating unit structure.

In general formula (5), 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 (6), 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, divalent 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 carbon number is less than 7, the hygroscopicity of the polyamide resin is large, the electrophotographic characteristics, particularly the humidity dependency of the potential during repeated use is large, and image defects such as black spots are likely to occur, and the halftone image is Easy 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.

  Preferred polyamide resins include polyamides having a repeating unit structure represented by the following general formula (7).

In General Formula (7), 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 (7), 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 the occurrence of image unevenness in black spots and halftone 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 (7) 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, the aggregated resin is likely to be generated in the intermediate layer, black spots are likely to be generated, and the dot reproducibility is liable to deteriorate.

  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. .

  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 according to the present invention is preferably 0.3 to 10 μm. If the film thickness of the intermediate layer is less than 0.5 μm, image unevenness is likely to occur in black spots and halftone images, and if it exceeds 10 μm, the residual potential is likely to increase and the dot reproducibility 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 according to the present invention is preferably 1 × 10 ⁸ to 10 ¹⁵ Ω · cm, more preferably 1 × 10 ⁹ to 10 ¹⁴ Ω · cm, and still more 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 Charge generating layer In the organic photoreceptor according to the present invention, it is preferable to use a charge generating material having a high sensitivity characteristic in a wavelength region of 350 nm to 500 nm as the charge generating material. As such a charge generation material, pigments such as the following condensed polycyclic compounds are preferably used. These pigments can be used in combination.

  Examples of the charge generating substance of the condensed polycyclic compound include polycyclic quinone pigment compounds represented by the following general formulas (8) to (10), and perylenes represented by the general formulas (11) to (13) and (14). Pigment compounds are preferred.

    These pigment compounds have a large potential attenuation value per unit exposure amount with respect to an exposure light source having a wavelength of 350 to 500 nm, and can form a small dot latent image sharply.

(In the general formulas (8), (9) and (10), X represents a halogen atom, alkyl group, nitro group, cyano group, acyl group or carboxyl group, n is an integer of 0 to 4, and m is 0 to 0. Represents an integer of 6.)
Specific examples of the polycyclic quinone pigment compound represented by the general formula (8) to the general formula (10) are illustrated below.

(In the general formulas (11), (12), and (13), A is a hydrogen atom, an alkyl group, an alkoxy group, or an aromatic hydrocarbon group that may be substituted, and B is a divalent aromatic that may be substituted. Represents a hydrocarbon group or a divalent nitrogen-containing heterocyclic group.)
Specific examples of the perylene pigment compounds of the general formulas (11) to (13) are illustrated below.

(In the general formula (14), R ₁ and R ₂ are hydrogen, substituted or unsubstituted alkyl, and R ₁ and R ₂ may be the same or different. Y is n = 1. ) Is a bridging moiety, substituted or unsubstituted alkylene, and when n = 0, it is a NN direct bond.)
Specific examples of the perylene pigment compound of the general formula (14) are illustrated below.

  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 The charge transport layer contains a charge transport material (CTM) and a binder resin that forms a film by dispersing CTM. Other substances may contain additives such as antioxidants as necessary.

  As the charge transport material (CTM), a compound having low absorption of laser light in the region of 350 to 500 nm and high charge transport ability is preferable. As such a compound, the compound of the following general formula (15)-general formula (18) is preferable.

(In the general formula (15), R ₁ and R ₁ ′ each represent a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom, and R ₂ , R ₂ ′, R ₃ and R ₃ ′ each represent a hydrogen atom, Represents an alkyl group, an alkoxy group, a halogen atom or a substituted amino group, and m, m ′, n and n ′ each represent an integer of 1 or 2.)
Specific examples of the compound of the general formula (15) are shown below.

(In General Formula (16), R ₄ represents a hydrogen atom or a methyl group, and Ar ₁ and Ar ₂ are each an aryl group optionally having a halogen atom, an alkyl group, an alkoxy group or a substituted amino group, or Represents a thienyl group, and k represents an integer of 1 or 2.)
Specific examples of the compound of general formula (16) are shown below.

(In the general formula (17), R ₁ represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom, and R ₂ and R ₃ represent an alkyl group, a substituted or unsubstituted aralkyl group or a substituted or unsubstituted aryl group. R ₂ and R ₃ may be the same or different, R ₄ and R _{5 each} represent a hydrogen atom, a lower alkyl group or a substituted or unsubstituted aryl group, and Ar represents a substituted or unsubstituted aryl group And Ar and R ₅ may combine to form a ring.)
Specific examples of the compound of general formula (17) are shown below.

(In General Formula (18), Ar ₁ and Ar ₂ represent a substituted or unsubstituted aromatic ring group, R ₁ and R ₂ represent a hydrogen atom or an alkyl group, and R ₃ represents a hydrogen atom, an alkyl group, or a halogen atom. Represents an atom.)
Specific examples of the compound of general formula (18) are shown below.

  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 20 μm or less, and more preferably 10 to 16 μm. When the film thickness exceeds 20 μm, the absorption and scattering of the short wavelength laser in the charge transport layer increase, and the sharpness tends to decrease and the residual potential tends to increase.

  The surface layer of the photoreceptor of the present invention (a second charge transport layer or a protective layer may be formed on the charge transport layer to form a surface layer) contains lubricating particles, and the surface of the organic photoreceptor The contact angle with respect to water is preferably 90 ° to 130 °. Here, the lubricating particles refer to substances that lower the surface energy of the electrophotographic photosensitive member when added to the surface layer of the electrophotographic photosensitive member. A material that increases the contact angle (contact angle against pure water).

  The lubricating particles are not particularly limited as long as they are materials that increase the contact angle (contact angle with respect to pure water) of the electrophotographic photosensitive member. A preferable material is a material that increases the contact angle by 1 ° or more, and examples thereof include fatty acid metal salts and fluorine-containing resins.

As such lubricating particles, the most preferable materials include fluororesin particles such as polyvinylidene fluoride and polytetrafluoroethylene. In particular, (meaning a median diameter D ₅₀ of the number-based) number average particle diameter fluororesin particles is preferably excellent in releasability containing fluorine atoms 0.01 to 2.0 m. 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.

  The average average primary particle size of the fluorine-containing resin particles is measured from a photograph obtained by photographing the cross-sectional layer of the photosensitive layer with a transmission electron microscope (acceleration voltage 200 kV). As a transmission electron microscope, a model well known to those skilled in the art is usually sufficiently observed. For example, LEM-2000 type (Topcon Corporation), JEM-2000FX (JEOL Ltd.) and the like are used. Specifically, first a sliced sample was cut out using a microtome with diamond teeth as a photosensitive layer, and a tomographic image was taken at a magnification of 10,000 times using a transmission electron microscope (TEM), and the ferret diameter was measured from this. To do. At least 100 particles are selected at random for TEM imaging.

  The fluororesin fine particles preferably have an average primary particle size of 0.02 μm or more and less than 0.20 μm and a crystallinity of 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 (19);

(In General Formula (19), at least one of R ^{4 to} R ⁷ is a fluorine atom, and the remaining groups are each independently a hydrogen atom, a chlorine atom, a methyl group, a monofluoromethyl group, a 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 number 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 in general, 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 viscosity average molecular weight is preferably 10,000 to 100,000.

  In order to form a surface layer in order to make the contact angle with water 90 ° to 130 ° using the fluorine-containing resin fine particles, it is preferable to increase the ratio of the fluorine-containing resin fine particles in the surface layer. It is preferably used in an amount of at least 20 parts by mass and 200 parts by mass with respect to 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 particle 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 lubricating particles in the surface layer, and the contact angle of the photoreceptor with pure water is preferably 90 ° to 130 °, more 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 with a contact angle meter (CA-DT • A type: manufactured by Kyowa Interface Science Co., Ltd.) in an environment of 20 ° C. and 50% RH.

  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 organic photoreceptor according to the present invention preferably contains an antioxidant together with the lubricating particles. By incorporating lubricating particles 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 method can be improved, and the decrease in the concentration at the tip can be 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 by general formula: RO-P (OR) -OR, for example. 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 by general formula: R-S-R, for example. 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.

  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.

  A developing device (developing means) of the counter developing system will be described with reference to FIG. The developing device in FIG. 1 is a contact type two-component type developing device, but the present invention is not limited to this contact type two-component type developing device. For example, a non-contact type one-component type developing device is also employed. it can. In the developing device 102, a developing sleeve 120 (developer carrying member) in which a cylindrical magnet 121 is non-rotatably disposed in an opening of a developing container 110 containing a two-component developer is an organic photoreceptor (image carrier). The developing sleeve 120 is arranged to face the organic photosensitive member 101 rotating in the direction of the arrow, and the developing sleeve 120 rotates counterclockwise so that the developer adsorbed and held on the surface of the developing sleeve 120 and the organic photosensitive member 101 is It is transported to the opposite developing unit. 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 (developer layer thickness regulating means), the developing part is reached, and a magnetic brush (developing brush) is formed by the action of the developing magnetic pole N1 in the developing part. Develop.

  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.

A preferred configuration of the counter development method will be described. Here, the gap between the photosensitive member 101 and the developing sleeve 120 in the developing portion near the developing magnetic pole N1 in FIG. 1 is a developing gap (Dsd), and the height of the magnetic brush formed on the developing sleeve 120 by the developing magnetic pole N1. Is called the developing brush height (h).
(1) Development gap (Dsd): 0.2 to 0.6 mm
When Dsd is set to 0.2 to 0.6 mm, development is performed in a strong developing electric field, the binding force of the magnetic carrier to the developing sleeve is increased, and the magnetic carrier is prevented from being transferred to and adhered to the photoconductor. it can. In addition, since the developing electric field at the developing gap is increased, the edge effect is reduced and the developing ability is improved. Accordingly, it is possible to prevent the occurrence of thinning of the horizontal line image and white-out at the rear end (deterioration at the rear end), and improve the developability of the solid image.
(2) Depth of penetration of magnetic brush (Bsd): 0 to 0.8 mm, Depth of penetration of magnetic brush (Bsd) = Development brush height (h) −Development gap (Dsd)
By setting the magnetic brush biting depth to 0 to 0.8 mm, the pressure contact with the developer at the developing portion is reduced, and the developer is prevented from slipping through the gap between the developing sleeve 120 and the developing blade 122. Further, it is possible to prevent the development failure of the isolated dot image and the increase in the rough feeling of the halftone image caused by the non-uniform contact of the magnetic brush. When the magnetic brush bite depth is 0 or less, that is, in a non-contact state, the density tends to decrease. When the depth is larger than 0.8 mm, the developer overflows from the nip portion, and uniform image formation cannot be expected.
(3) Peripheral speed ratio (Vs / Vopc) between the developing sleeve and the photoreceptor: 1.2 to 3.0
By setting the peripheral speed ratio of the developing sleeve to the photoreceptor to 1.2 to 3.0, high developability can be obtained. If the peripheral speed ratio is increased too much, the contact frequency of the magnetic brush on the developing sleeve with respect to the photosensitive member increases too much, and the contact state of the magnetic brush with respect to the latent photosensitive member, that is, the mechanical force becomes excessively large. Are likely to fall off, and the carrier is likely to adhere to the photoreceptor, and as a result, the brush image of the magnetic brush is formed on the toner image on the photoreceptor. On the other hand, if the peripheral speed ratio is lowered too much, the chance of contact of the magnetic brush with the photoreceptor is reduced too much, and the developability is lowered. Accordingly, when the peripheral speed ratio is smaller than 1.2, the density is lowered, and when it is larger than 3.0, there is a problem in toner scattering, carrier adhesion, or developing sleeve durability. On the other hand, by setting the peripheral speed ratio within the above range, it is possible to prevent brush eyes. Furthermore, it has the function of preventing the developing effect from becoming excessively high and enhancing the edge effect.
(4) Development bias conditions The difference | V0−Vb | between the surface potential V0 of the photosensitive member and the DC component Vdc of the development bias is 50 to 200 V, the DC component Vdc of the development bias is −250 V to −400 V, and the AC component Vac of the development bias. Is preferably 0.5 to 1.5 kV, a frequency of 3 to 9 kHz, a duty of 45 to 70% (time ratio on the development side with a rectangular wave), and a rectangular wave. That is, in a small two-component developing device having an outer diameter of the developing sleeve of φ30 mm or less and an outer diameter of the photosensitive member of φ60 mm or less, the developing nip width is reduced and the developing ability is reduced by making the developing sleeve small. The development bias condition can be improved by the development bias condition.

  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 at a predetermined positive or negative potential on its peripheral surface by a charging means (charging process) 2 and then exposed to exposure means (exposure process) such as slit exposure or laser beam scanning exposure. : Exposure light 3 (exposure means) subjected to emphasis modulation corresponding to the time-series electric digital image signal of the target image information output from (not shown). 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 (developing process) 4, and the organic photosensitive member 1 is transferred between the organic photoreceptor 1 and the transferring means (transfer process) 5 from a paper supply unit (not shown). The toner images formed and supported on the surface of the organic photoreceptor 1 are sequentially transferred by the transfer means 5 onto the transfer material P taken out and fed in synchronization with the rotation.

  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.

  The image forming apparatus of the present invention is premised on the use of a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as an image exposure light source when forming an electrostatic latent image on a photoreceptor. By using these image exposure light sources, the exposure diameter in the main direction of writing is narrowed down to 10 to 50 μm, and digital exposure is performed on the organic photoreceptor, whereby 600 dpi (dpi: the number of dots per 2.54 cm) or more and 2500 dpi. High-resolution electrophotographic images can be obtained.

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

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

  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 of the toner image from the photosensitive member of the toner image such as an intermediate transfer member or a transfer material is collectively referred to as a transfer medium.

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

  During the image forming process, the primary transfer roller 5Bk is always in 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>
Intermediate layer 1
On the conductive support, the following intermediate layer coating solution was applied by a dip coating method and dried at 120 ° C. for 30 minutes to form an intermediate layer 1 having a dry film thickness of 1.0 μm.

  The following intermediate layer dispersion is diluted twice with the same mixed solvent, and is allowed to stand overnight and then filtered (filter; rigesh mesh filter made by Nippon Pole Co., Ltd., nominal filtration accuracy: 5 microns, pressure: 50 kPa). Produced.

(Preparation of intermediate layer dispersion)
Binder resin: (Exemplary polyamide N-1) 1 part (1.00 volume part)
N-type semiconductive particles: rutile titanium oxide A1 (primary particle size 35 nm; copolymer of methylhydrogensiloxane and dimethylsiloxane (molar ratio 1: 1), in an amount of 5% by mass of the total mass of titanium oxide. Surface treatment) 3.5 parts (1.0 part by volume)
Ethanol / n-propyl alcohol / THF (= 45/20/30 mass ratio) 10 parts The above components were mixed and dispersed in a batch system for 10 hours using a sand mill disperser to prepare an intermediate layer dispersion. .

<Charge generation layer: CGL>
Charge generation material (CGM): 24 parts of the above CG1-5 Polyvinyl butyral resin “ESREC BL-1” (manufactured by Sekisui Chemical Co., Ltd.) 12 parts 2-butanone / cyclohexanone = 4/1 (v / v) 300 parts The mixture was mixed and dispersed using a sand mill to prepare a charge generation layer coating solution. 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 (CTL)>
Charge transport material (CTM): CT2-35 225 parts Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 300 parts Antioxidant (Exemplary Compound AO1-3) 6 parts THF / toluene mixture (volume ratio 3/1 mixture) 2000 parts Silicon oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part was 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 16.0 μm.

Production of Photoreceptor 2 Photoreceptor 2 was produced in the same manner as Photoreceptor 1 except that CGM of Photoreceptor 1 was changed from CG1-5 to CG2-17.

Preparation of photoconductor 3 The CGM of photoconductor 1 was changed from CG1-5 to CG3-1 / CG3-2 / CG3-3 (1/2/1 mass ratio) and CTM was changed from CT2-35 to CT1-7. Was the same as Photoreceptor 1, and Photoreceptor 3 was produced.

Preparation of Photoreceptor 4 After preparing the following PTFE dispersion on the charge transport layer 1 of the photoreceptor 1, a protective layer was applied.

<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 (average primary particle size 0.12 μm) 200 parts Toluene 600 parts Fluorine comb-type graft polymer (trade name GF300, manufactured by Toa Gosei Chemical Co., Ltd.) 15 parts, and then a sand grinder using glass beads (( PTFE particle dispersion was prepared by dispersion with Amex Corporation.

<Protective layer>
PTFE particle dispersion 815 parts Charge transport material (CT2-35) 150 parts Siloxane-modified polycarbonate resin (Exemplary compound PC-1) 150 parts Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 150 parts Antioxidant (AO2-1) 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 protective layer coating solution 1. This coating solution is applied onto the charge transport layer of the photoreceptor 1 with a circular slide hopper coater, dried at 110 ° C. for 70 minutes to form a protective layer with a dry film thickness of 2.0 μm, and the photoreceptor 4 is produced. did.

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. Then, it was crushed and further classified by changing the classification conditions to obtain ferrite carriers having a volume-based median diameter D50 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 (2) is a methyl group and a hydroxyl group and a general formula (3) in which the substituents are all methyl groups (mass ratio = ( 2): (3) = 40: 60) 100 parts, 10 parts of a silane coupling agent (Exemplary Compound (1)) and 5 parts of an oxime type curing agent (Exemplary Compound (15)) 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, and the volume-based median diameter D50 is 8 μm. 1 to 5 obtained resin-coated ferrite carriers corresponding to 12 μm, 35 μm, 58 μm and 65 μm.

Production of Carriers 6 to 9 As shown in Table 1, except that the composition of MnO, MgO, Fe ₂ O ₃ and SnO ₂ was changed, Mn − having a volume-based median diameter D50 of 35 μm was the same as in Example 1. Mg-Sn 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 (meaning the volume-based median diameter D ₅₀ in the present invention) are 4.5 μm, 4.3 μm, 4.6 μm, and 4.7 μm, respectively. It was.

Production of Developer Group 1-9 100 parts by mass of “Carriers 1-9” and 4 parts by mass of “Toner Bk, Toner Y, Toner M, Toner C” (each type of carrier and toner) are V-shaped. “Developer group 1 (1Bk, 1Y, 1M, 1C) to developer group 9 (9Bk, 9Y, 9M, 9C)” were produced by mixing with a stirrer.

Evaluation 1 (Evaluation by counter development method)
The resulting photoreceptor is mounted on a commercially available full-color multifunction device 8050 (tandem-type full-color multifunction device 8050 using an intermediate transfer member (made by Konica Minolta Business Technologies Co., Ltd.) with a counter development system), and a charger. After charging the photoconductor to −400 V, a 405 nm short wavelength laser light source is used as the exposure light source, and the exposure diameter (Ld) of spot exposure is set to 30 μm and 0.5 mW on the photoconductor surface. 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 5 sheets were printed and evaluated. Evaluation items and evaluation criteria are shown below.

Evaluation conditions Development: Counter development method, reversal development method Exposure light source: 405 nm short wavelength laser light source Charging condition: Absolute value of the charged potential of the photosensitive member at the exposure position: 400 V
Photoconductor linear velocity: 180 mm / sec
Peripheral speed ratio of developing sleeve to photoreceptor (Vs / Vopc); 2.0
Magnetic brush bite depth D; 0.30mm
Distance between developer carrier (developing sleeve) and photoconductor (Ds); 0.25 mm
AC component Vac of development bias; 1.4 KVp-p
DC component Vdc of development bias; -200V
Difference between the surface potential V0 of the photoreceptor and the DC component Vdc of the developing bias (| V0−Vdc |); 200V
Frequency: 5KHz
Duty: 50% square wave Image evaluation Image density At the start, a density meter “RD-918” (manufactured by Macbeth) was used for the 50,000th sheet, and the density of the printer paper was measured at a relative density of 0.0. .

◎: 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)
Density reduction at the tip portion A halftone image at 50,000 sheets was prepared 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).

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)
Dot reproducibility The dot reproducibility of the toner image was evaluated by looking through a 100x magnifier.

A: Image dot size is reproduced independently (less than ± 30% of the exposure spot area)
○: The size of the image dot is increased or decreased by 30 to 60% of the exposure spot area, and each is reproduced independently (practical level)
X: The size of the image dot increases or decreases beyond 60% of the exposure spot area, and the image dot is partially lost or connected (practical problem level).
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 smaller than 2 (good)
○: Color difference is 2 to 3 (no problem)
×: Color difference is greater than 3 (practical problem and impractical)
The results are shown in Table 3.

  As is apparent from Table 3, in the image evaluation produced by the counter development method, the combination No. was obtained under the condition that the absolute value of the charged potential of the non-exposed portion of the organic photoreceptor was 400V. Good evaluation results have been obtained for all of Nos. 1 to 12. Among them, combination No. 1 using a carrier having a volume average particle diameter of 10 to 60 μm and a saturation magnetic value of 20 to 80 emu / g is used. Nos. 2 to 4, 7, 8, and 10 to 12 show particularly good characteristics in all evaluation items such as image density, fogging, tip density reduction, carrier adhesion, dot reproducibility, and color reproducibility.

Evaluation 2 (Evaluation by counter development method)
Combination No. 1 performed in Evaluation 1 Evaluations were made in the same manner except that the charging conditions for evaluation 3 were changed as shown in Table 4. In addition, evaluation items for worm-like unevenness described below were added to the evaluation items for image evaluation in Evaluation 1 for evaluation.

Evaluation conditions Development: Counter development method, reversal development method Exposure light source: 405 nm short wavelength laser light source Photoconductor linear velocity: 180 mm / sec
Peripheral speed ratio of developing sleeve to photoreceptor (Vs / Vopc); 2.0
Magnetic brush bite depth D; 0.30mm
Distance between developer carrier (developing sleeve) and photoconductor (Ds); 0.25 mm
AC component Vac of development bias; 1.4 KVp-p
The difference between the surface potential V0 of the photoreceptor and the DC component Vdc of the developing bias (| V0−Vdc |); 180V
Frequency: 5KHz
Duty: 50% rectangular wave Addition of image evaluation Worm-like unevenness A halftone image of 50,000 sheets was observed with a loupe (× 20), and the presence or absence of worm-like unevenness was observed and evaluated.

A: No occurrence of worm-like unevenness (good)
○: Slightly worm-like unevenness but no problem (practical level)
X: There is worm-like unevenness. Visually wavy irregularity and practically problematic (problematically problematic)

  As a result, the charging condition is the combination No. in the present invention. 14 and 15 show good characteristics in all evaluation items such as image density, fogging, tip density reduction, carrier adhesion, dot reproducibility, color reproducibility, worm-like unevenness, etc. Combination No. whose absolute value is 220V In No. 13, the image density is low, the density of the tip portion is lowered, and the color reproducibility is also degraded. In addition, the combination No. with an absolute value of the charging potential of 500V. In No. 16, the density at the tip portion is lowered, the dot reproducibility is deteriorated, and the worm-like unevenness appears remarkably.

Evaluation 3 (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 Charging condition: Absolute value of the charging potential of the photosensitive member at the exposure position: 400 V
Photoconductor linear velocity: 220 mm / sec
Line speed of developing sleeve: 350 mm / 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 with any combination, and an electrophotographic image with poor color reproducibility due to 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 P1 Developer drop position Q1 Pumping position

Claims (14)

An electrostatic latent image is formed on an organic photoconductor on a conductive substrate using an exposure unit using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source after applying a uniform surface potential by a charging unit. Forming a developing brush with a developer containing toner on a cylindrical developing sleeve carrying a developer containing toner and carrier by a developing means, contacting the developing brush with an organic photoreceptor, In the image forming method of developing an electrostatic latent image into a toner image, the absolute value of the charged potential of the non-exposed portion of the organic photoreceptor is 250 to 450 V at the exposure position of the exposure unit, and the developing sleeve is An image forming method comprising: rotating an electrostatic latent image into a toner image by rotating the photoconductor in a counter direction. A charging means for providing a uniform surface potential on an organic photoreceptor, an exposure means for forming an electrostatic latent image using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source, a developer containing toner and carrier Development means for forming a developing brush with a developer containing toner on a cylindrical developing sleeve carrying toner, and bringing the developing brush into contact with an organic photoreceptor to visualize the electrostatic latent image into a toner image And a plurality of image forming units having transfer means for transferring a toner image formed on the organic photoconductor to a transfer medium, and the toner on the organic photoconductor is changed in color for each of the plurality of image forming units. In the image forming method of forming a color image by forming each color toner image and transferring the color toner image from an organic photoreceptor to a transfer medium, an organic material is formed at the exposure position of the exposure means. The absolute value of the charged potential of the non-exposed portion of the photoconductor is 250 to 450 V, and the developing sleeve is rotated in the counter direction with respect to the rotation direction of the organic photoconductor to visualize the electrostatic latent image into a toner image. An image forming method. 3. The image forming method according to claim 1, wherein a volume-based median diameter D50 of the carrier is 10 to 60 μm and a saturation magnetic value is 20 to 80 emu / g. 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 lubricating particles. The image forming method according to claim 6, wherein the lubricating particles are fluorine-based resin particles. The image forming method according to claim 1, wherein the surface layer of the organic photoreceptor contains an antioxidant. The image forming method according to claim 8, wherein the antioxidant is a hindered phenol-based antioxidant. The image forming method according to claim 8, 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. On the organic photoreceptor, a charging means for applying a uniform surface potential, an exposure means for forming an electrostatic latent image using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source, development containing toner and carrier Developing a developing brush with a developer containing toner on a cylindrical developing sleeve carrying an agent, bringing the developing brush into contact with an organic photoreceptor, and developing the electrostatic latent image into a toner image In the image forming apparatus having the means, the absolute value of the charging potential of the non-exposed portion of the organic photoreceptor is 250 to 450 V at the exposure position of the exposure means, and the developing sleeve is countered with respect to the rotation direction of the organic photoreceptor. An image forming apparatus that visualizes an electrostatic latent image into a toner image by rotating in a direction. A charging means for providing a uniform surface potential on an organic photoreceptor, an exposure means for forming an electrostatic latent image using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm as a writing light source, a developer containing toner and carrier Development means for forming a developing brush with a developer containing toner on a cylindrical developing sleeve carrying toner, and bringing the developing brush into contact with an organic photoreceptor to visualize the electrostatic latent image into a toner image And a plurality of image forming units having transfer means for transferring a toner image formed on the organic photoconductor to a transfer medium, and the toner on the organic photoconductor is changed in color for each of the plurality of image forming units. In the image forming apparatus for forming a color image by forming each color toner image on the surface and transferring the color toner image from an organic photoreceptor to a transfer medium, The absolute value of the charged potential of the non-exposed portion of the photoconductor is 250 to 450 V, and the developing sleeve is rotated in the counter direction with respect to the rotation direction of the organic photoconductor to visualize the electrostatic latent image into a toner image. An image forming apparatus.

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