JP2005181568A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a good color electrophotographic image using an image forming apparatus using an intermediate transfer member and an image forming method. <P>SOLUTION: In the image forming apparatus for forming a color image by forming a color toner image by sequential superposition and transfer onto the intermediate transfer member; retransferring the color toner image at a time onto a recording material; and fixing the retransferred color toner image, at least one of colored toners used in developing devices of a plurality of image forming units contains a particulate external additive having a number average primary particle diameter of 0.1-1.0 μm, and the image forming apparatus has a cleaning device for the intermediate transfer member for removing residual toners after transfer remaining on the intermediate transfer member with a plurality of cleaning blades. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus used as a color copying machine or a color printer, and an image forming method using the image forming apparatus.

  In recent years, color copying machines and color printers have a strong tendency to obtain color images. The color image forming methods with high practical value are roughly classified into commonly used names. There are an intermediate transfer method, a KNC method (a method in which a multi-color superimposed image is formed on a photoconductor and transferred collectively), a tandem method, and the like. .

  Of course, since these are names given from different viewpoints, there are naturally, for example, an intermediate transfer system and a tandem system. A color image forming apparatus of the intermediate transfer system and tandem system (hereinafter, the tandem system is referred to as the intermediate transfer system and the tandem system) is known to obtain a high-quality full-color image. In this method, a toner image is formed on each photoconductor corresponding to yellow, magenta, cyan, and black, and a color superimposed image is formed on the intermediate transfer member, which is collectively transferred to a transfer material.

  In this tandem color image formation, there are two stages of transfer processes, a primary transfer in which the toner image is transferred from each photoconductor to the intermediate transfer body and a secondary transfer in which the toner image is transferred from the intermediate transfer body to the recording paper. Since there are two stages, cleaning of the photoreceptor after the primary transfer and cleaning of the intermediate after the secondary transfer, an image defect due to a transfer failure of the toner image and an image defect due to the cleaning are likely to occur.

  In an image forming apparatus using an intermediate transfer body, in order to avoid an increase in the size of the apparatus, there are many methods that employ a belt-shaped intermediate transfer body that can reduce the size of the apparatus, but the belt-shaped intermediate transfer body In this cleaning, the contact state between the cleaning member and the intermediate transfer member is likely to change, and cleaning defects are likely to occur. In order to solve the cleaning failure of the intermediate transfer member, several proposals have been made so far. For example, there is a method of removing residual toner on the intermediate transfer member using a cleaning device (Patent Document 1) in which a cleaning blade and a metal thin plate member are in close contact, a cleaning device (Patent Document 2) using a cleaning blade and a metal scraper, or the like. Proposed.

  On the other hand, the electrophotographic latent image forming method has shifted from analog type latent image forming using a halogen lamp as a light source to digital type latent image forming using an LED or laser as a light source. Recently, a digital latent image forming method is rapidly becoming mainstream as a printer of a personal computer and also in a normal copying machine because of the ease of image processing and the development to a multifunction device. In this digital color image formation, not only copying but also the use of producing an original image increases, and there is a tendency to require formation of a high-density dot latent image that emphasizes reproducibility of a photographic image or the like. Development of faithfully developing the latent image on the electrophotographic photosensitive member using the polymerized toner having a uniform shape factor and particle size distribution from the high-density dot latent image is under development. When an intermediate transfer body type color image forming apparatus is used, even if a good toner image can be produced on the photoreceptor, the transfer performance of the toner and the cleaning performance of the intermediate transfer body are as effective as originally expected. As regards the cleaning performance of the intermediate transfer member, sufficient polymerization toner cannot be cleaned even if the cleaning device using the cleaning blade and metal scraper described above is used, and the toner easily passes through the cleaning blade. Image defects such as image unevenness are likely to occur.

  Further, defective transfer of toner from the photosensitive member to the intermediate transfer member tends to cause image defects such as a decrease in image density and missing transfer. On the other hand, there have been reports of poor transfer of toner from the intermediate transfer member to recording paper, such as character dust and sharpness deterioration associated with transfer repelling.

  In order to improve the transferability that causes this “transfer omission” and “character dust”, the surface layer of the electrophotographic photosensitive member is made to contain fine particles, the surface is made uneven, and the adhesion force of the toner on the surface of the photosensitive member Techniques such as reducing the friction, improving the transferability, and reducing the frictional force with the blade have been studied. For example, it has been reported that alkylsilsesquioxane resin fine particles are contained in a photosensitive layer (Patent Document 3). However, the alkylsilsesquioxane resin fine particles have a hygroscopic property, and in a high-humidity environment, there arises a problem that the wettability of the surface of the photoreceptor, that is, the surface energy increases, and the transferability tends to decrease. On the other hand, in order to reduce the surface energy of the photoreceptor, an electrophotographic photoreceptor containing a fluororesin powder has been reported. However, the fluororesin powder has a problem that sufficient surface strength cannot be obtained, streak failure due to scratches on the surface of the photoreceptor is likely to occur, and image blurring is likely to occur (Patent Document 4).

  On the other hand, in order to improve the transferability and cleaning performance of the intermediate transfer member, a technique for supplying a solid lubricant to the intermediate transfer member to reduce the surface energy of the intermediate transfer member has been disclosed (Patent Document 5, 6, 7). However, simply controlling the surface of such an intermediate transfer body is still insufficient for improving the total transferability of an image forming system using an intermediate transfer body having two transfer steps, particularly at high temperatures. It has been found that further improvement is necessary for the formation of high humidity and long-term copy images.

In other words, in a tandem color image forming apparatus using an intermediate transfer member, it is important to improve the total toner transferability of both the primary transfer and the secondary transfer, and to improve the cleaning property of the intermediate transfer member. Was found.
JP 2002-162839 A JP 2002-278319 A Japanese Patent Laid-Open No. 5-181291 JP-A 63-56658 JP-A-6-337598 JP-A-6-332324 JP 7-271142 A

  The present invention has been made to solve the above problems. An object of the present invention is to provide a good color electrophotographic image using an image forming apparatus using an intermediate transfer member, and transferability from a photosensitive member to an intermediate transfer member in the formation of a large number of color images. By improving the transferability of the toner image from the intermediate transfer member to the recording material and the removal of the residual toner component on the intermediate transfer member, the transfer defect, character dust, or cleaning failure caused by transfer failure is caused. An object of the present invention is to provide an electrophotographic image forming apparatus and an image forming method capable of preventing image unevenness and the like and reproducing a color image having good sharpness and a vivid hue. Especially when polymerized toner is used, it prevents image unevenness due to poor cleaning that easily occurs on a belt-shaped intermediate transfer body, transfer omission and character dust due to poor transfer, etc. It is an object to provide an electrophotographic image forming apparatus and an image forming method for reproducing a color image.

  In the image forming apparatus for forming a color image using the intermediate transfer member of the present invention, the primary transferability of the color toner image from the photosensitive member to the intermediate transfer member, and the recording of each colored toner image superimposed on the intermediate transfer member As a result of detailed examination of the secondary transfer property to the material and the cleaning property of the toner on the photosensitive member and the intermediate transfer member, the above-mentioned primary transfer property and secondary transfer transfer property of each colored toner are the toner filming on the intermediate transfer member. If the toner filming on the intermediate transfer body increases, the primary transferability and secondary transferability of the toner described above are deteriorated, and transfer omission and character dust due to the transferability defect are likely to occur. . In order to prevent the occurrence of toner filming on the intermediate transfer member, a plurality of cleaning blades capable of more effectively removing residual toner are used as the intermediate transfer member cleaning means, and the toner film generated on the intermediate transfer member is used. The present invention has been completed by finding that it is effective to remove ming at an early stage. That is, the object of the present invention is achieved by adopting one of the following configurations.

(Claim 1)
A plurality of image forming units having at least an electrophotographic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged, and a toner whose color is changed is used for the developing unit for each of the plurality of image forming units. The colored toner images formed on the electrophotographic photosensitive member are sequentially superimposed and transferred onto the intermediate transfer member to form a color toner image, and the color toner image is collectively re-transferred onto the recording material, In an image forming apparatus for fixing a retransferred color toner image to form a color image, at least one of the colored toners used in the developing means of the plurality of image forming units has a number average primary particle size of 0.1 to 0.1. A cleaning means for an intermediate transfer member that contains a 1.0 μm fine particle external additive and removes transfer residual toner remaining on the intermediate transfer member with a plurality of cleaning blades. An image forming apparatus comprising and.

(Claim 2)
A plurality of image forming units are four image forming units, and an image forming unit having a black toner, an image forming unit having a yellow toner, and an image forming unit having a magenta color toner as developing means of each image forming unit The image forming apparatus according to claim 1, further comprising an image forming unit having cyan toner.

(Claim 3)
The image forming apparatus according to claim 2, wherein the fine particle external additive having a number average primary particle size of 0.1 to 1.0 μm is contained in a black toner.

(Claim 4)
3. The fine particle external additive having a number average primary particle size of 0.1 to 1.0 μm is contained in at least one of a yellow toner, a magenta toner, and a cyan toner. The image forming apparatus described.

(Claim 5)
The black toner, yellow toner, magenta toner, and cyan toner contain a fine particle external additive having a number average primary particle size of 5 to 49 nm. The image forming apparatus described in 1.

(Claim 6)
The image forming apparatus according to claim 1, wherein each of the colored toners is a polymerized toner.

(Claim 7)
The image forming apparatus according to claim 1, wherein the number average particle diameter of each of the colored toners is 3.0 to 8.0 μm.

(Claim 8)
The image forming apparatus according to claim 1, wherein at least one of the plurality of cleaning blades is a non-deformable member.

(Claim 9)
The image forming apparatus according to claim 8, wherein the non-deformable member is formed of a metallic scraper.

(Claim 10)
The image forming apparatus according to claim 1, wherein at least one of the plurality of cleaning blades is an elastic blade.

(Claim 11)
The image forming apparatus according to claim 10, wherein the elastic blade is a urethane rubber blade.

(Claim 12)
The image forming apparatus according to claim 1, wherein a contact angle of water on the surface of the electrophotographic photosensitive member is 90 ° or more.

(Claim 13)
The image forming apparatus according to claim 1, wherein a surface layer of the electrophotographic photosensitive member contains fluororesin particles.

(Claim 14)
The image forming apparatus according to claim 1, wherein the surface layer of the electrophotographic photosensitive member contains an antioxidant.

(Claim 15)
The image forming apparatus according to claim 1, wherein the intermediate transfer member is a belt-shaped intermediate transfer member.

(Claim 16)
A plurality of image forming units having at least an electrophotographic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged, and a toner whose color is changed is used for the developing unit for each of the plurality of image forming units. The colored toner images formed on the electrophotographic photosensitive member are sequentially superimposed and transferred onto the intermediate transfer member to form a color toner image, and the color toner image is collectively re-transferred onto the recording material, In an image forming apparatus for fixing a retransferred color toner image to form a color image, at least one of the colored toners used in the developing means of the plurality of image forming units has a number average primary particle size of 0.1 to 0.1. An intermediate transfer agent containing 1.0 μm and a fine particle external additive having a number average primary particle size of 5 to 49 nm, and removing residual toner remaining on the intermediate transfer member with a plurality of cleaning blades. An image forming apparatus characterized by having a-body cleaning means.

(Claim 17)
An image forming method, comprising: forming an electrophotographic image using the image forming apparatus according to claim 1.

  By using the present invention, it is possible to achieve improvement in toner transfer characteristics and cleaning performance of an electrophotographic system using an intermediate transfer member, and it is possible to prevent image defects due to transfer omission, character dust and cleaning defects caused by a decrease in toner transfer. In addition, it is possible to provide an electrophotographic image forming apparatus and an image forming method capable of forming a color image with good image density and sharpness.

  The image forming apparatus of the present invention has a plurality of image forming units, and at least one of the colored toners used in the developing means for each of the plurality of image forming units has a number average primary particle size of 0.1 to 1.0 μm. It contains a fine particle external additive. In addition, each color toner image formed on the electrophotographic photosensitive member of each image forming unit is sequentially superimposed and transferred onto the intermediate transfer member to form a color toner image, and the color toner image is collectively collected on the recording material. Then, after the retransfer, there is provided a cleaning means for the intermediate transfer body that removes the transfer residual toner remaining on the intermediate transfer body with a plurality of cleaning blades.

  The image forming apparatus of the present invention has the above-described configuration, thereby preventing the occurrence of toner filming that is easily formed on the intermediate transfer member, improving the primary transfer property and the secondary transfer property of the toner image, and improving the image quality. Occurrence of image defects such as unevenness can be prevented, and a color image with excellent sharpness and vivid hue can be formed.

  First, the toner used for the developing means of the image forming unit of the present invention will be described.

  The image forming apparatus of the present invention has a plurality of image forming units, and at least one of the colored toners used in the developing means for each of the plurality of image forming units has a number average primary particle size of 0.1 to 1.0 μm. It contains a fine particle external additive.

  By using the fine particle external additive having a number average primary particle size of 0.1 to 1.0 μm, toner filming that tends to occur on the intermediate transfer member can be removed at an early stage. To prevent the occurrence of toner filming on the intermediate transfer member and to remove it at the initial stage, the above-described plurality of cleaning blades and a toner added with a fine particle external additive having a number average primary particle size of 0.1 to 1.0 μm are used in combination. By doing so, the effect becomes remarkable. If only the fine particle external additive having a number average primary particle size of less than 0.1 μm is used, the removal of toner film on the intermediate transfer member is less effective. Addition of a fine particle external additive having a number average primary particle size larger than 1.0 μm tends to cause streak-like image defects in the toner image on the intermediate transfer member. The addition of the fine particle external additive is more preferably in the range of the number average primary particle diameter of 0.2 to 0.9 μm.

  As the material for the 0.1 to 1.0 μm fine particle external additive, various inorganic particles, organic fine particles and the like can be mentioned. From the viewpoint of scraping off the toner filming on the intermediate transfer member, the inorganic fine particles and the organic fine particles can be used. Particles are preferred. For example, titanium oxide, strontium titanate, barium titanate, calcium titanate, cerium oxide and the like can be preferably used. These inorganic particles may have a hydrophobic surface.

  The addition amount is preferably 0.1 to 3.0% by mass in the toner (here, the total mass of the toner indicates the total mass including fine particles), more preferably 0.5 to 2.0% by mass. %. If this range is exceeded, the effect of removing the toner filming on the intermediate transfer member increases, but there is a problem that the large-diameter particles themselves are released, and the scattered particles cause contamination of the band electrode and the transfer electrode. This causes image defects such as white streaks. If it is too small, the toner filming removal effect on the intermediate transfer member is small.

  Furthermore, it is preferable that the toner of the developing means of each image forming unit contains a fine particle external additive having a number average primary particle size of 5 to 49 nm. For example, black toner, yellow toner, magenta toner, and cyan toner contain fine particle external additives having a number average primary particle size of 5 to 49 nm, so that they are excellent on the electrophotographic photoreceptor of each image forming unit. A toner image can be formed, the primary transfer property and the secondary transfer property can be improved, and a color image with good sharpness and color reproducibility can be formed.

  Examples of materials that can be preferably used as the material for the 5-49 nm fine particle external additive include silica, alumina, titania, zirconia, and the like. These inorganic particles preferably have a hydrophobic surface.

  The fine particles of 5 to 49 nm are preferably added to the toner in an amount of 0.1 to 3.0% by mass, and more preferably in an amount of 0.3 to 2.5% by mass. If added beyond this range, there is a problem that the fine particles themselves are liberated, and the scattered particles cause contamination of the band electrode and the transfer electrode, leading to image defects such as white stripes.

  The above particle diameter is a number average primary particle diameter, which is magnified 2000 times by observation with a transmission electron microscope, observed 100 particles, and measured by image analysis.

  In addition, the above-mentioned inorganic fine particles are preferably hydrophobized by so-called coupling agents such as various titanium coupling agents and silane coupling agents, silicone oils, and the like. Further, aluminum stearate, zinc stearate, Hydrophobic treatment with a higher fatty acid metal salt such as calcium stearate is also preferably used.

  In addition to the fine particle external additive, a lubricant may be added to the toner of the present invention. For example, zinc stearate, aluminum, copper, magnesium, calcium salt, zinc oleate, manganese, iron, copper, magnesium salt, zinc palmitate, copper, magnesium, calcium salt, linoleic acid Examples include salts of higher fatty acids such as zinc and calcium salts, ricinoleic acid zinc and calcium salts, and the like. The addition amount of these lubricants is preferably about 0.1 to 5% by mass with respect to the toner.

  As a method for adding the external additive to the toner, various known mixing devices such as a Turbuler mixer, a Henschel mixer, a Nauter mixer, and a V-type mixer can be used.

  The toner of the present invention is premised on that a toner prototype (also referred to as colored particles) can be formed before the external additive is added. The colored particles are formed of a colorant (pigment, dye, etc.), a release agent, a binder, and the like, and can be prepared by a pulverization method or a polymerization method. The toner of the present invention is a polymerized toner prepared by a polymerization method. Is more preferable for forming a color image with good sharpness and color reproducibility.

  Hereinafter, the polymerization toner will be described.

  In addition, as a mold release agent in the polymerization method, it is preferable to use various known ones that can be dispersed in water. Specific examples include olefinic waxes such as polypropylene and polyethylene, modified products thereof, natural waxes such as carnauba wax and rice wax, and amide waxes such as fatty acid bisamides. It has already been mentioned that these are added as release agent particles and are preferably salted out / fused together with resin and colorant.

  Similarly, various known charge control agents in the polymerization method and those that can be dispersed in water can be used. Specific examples include nigrosine dyes, naphthenic acid or higher fatty acid metal salts, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts or metal complexes thereof.

  These release agent and charge control agent particles preferably have a number average primary particle size of about 10 to 500 nm in a dispersed state.

  Hereinafter, the toner (colored particles) by the polymerization method preferably used in the present invention will be described.

  As the toner applied to the present invention, a polymerized toner having a relatively uniform particle size distribution and shape of individual toner particles is preferable. Here, the polymerized toner means a toner obtained by forming a binder resin for toner and forming the toner shape by polymerization of a raw material monomer of the binder resin and subsequent chemical treatment. More specifically, it means a toner obtained through a polymerization reaction such as suspension polymerization or emulsion polymerization and, if necessary, a fusing step between particles carried out after the polymerization reaction.

  The polymerized toner used in the present invention is preferably a toner having a specific shape. The polymerized toner that can be preferably used in the present invention will be described below.

  As a preferred polymerized toner applied to the present invention, a toner having 65% by number or more of toner particles having a shape factor in the range of 1.2 to 1.6 and a coefficient of variation of the shape factor of 16% or less is used. It is to be. It has been found that when a polymerized toner having such characteristics is used, the vibration of the cleaning blade can be stabilized and excellent cleaning performance can be exhibited.

  Also, the vibration stability of the cleaning blade varies depending on the particle size of the toner particles. The smaller the particle size, the higher the adhesion force to the image carrier, so that the vibration is likely to be excessive and the toner is contained in the cleaning blade. There is a high probability of passing through. However, when the toner particle diameter is large, such slip-through is reduced, but there is a problem that image quality such as resolution is lowered.

  The shape factor of the toner is expressed by the following formula and indicates the degree of roundness of the toner particles.

Shape factor = ((maximum diameter / 2) ² × π) / projection area Here, the maximum diameter is the distance between the parallel lines when the projected image of toner particles on a plane is sandwiched between two parallel lines. The maximum particle width. The projected area refers to the area of the projected image of the toner particles on the plane.

  This shape factor is obtained by taking a photograph in which toner particles are magnified 2000 times with a scanning electron microscope, and then analyzing a photographic image using “SCANNING IMAGE ANALYZER” (manufactured by JEOL Ltd.) based on this photograph. Was measured. At this time, the shape factor of the present invention was measured by the above formula using 100 toner particles.

  As the polymerized toner, the number of toner particles having a shape factor in the range of 1.2 to 1.6 is preferably 65% by number or more, more preferably 70% by number or more.

  When the number of toner particles having a shape factor in the range of 1.2 to 1.6 is 65% by number or more, the triboelectric chargeability on the developer conveying member and the like becomes more uniform, and excessively charged toner is accumulated. In addition, since it becomes easier to replace the toner from the surface of the developer conveying member, problems such as development ghost are less likely to occur. Further, the toner particles are less likely to be crushed, the contamination of the charging member is reduced, and the chargeability of the toner is stabilized.

  The method for controlling the shape factor is not particularly limited. For example, a method in which toner particles are sprayed into a hot air stream, a method in which toner particles are repeatedly applied with mechanical energy due to impact force in a gas phase, or a method in which a toner is not dissolved in a solvent and a swirl flow is applied. There is a method in which a toner having a shape factor of 1.2 to 1.6 is prepared and added to a normal toner so as to fall within the scope of the present invention. In addition, the overall shape is controlled at the stage of preparing a so-called polymerization method toner, and a toner prepared with a shape factor of 1.0 to 1.6 or 1.2 to 1.6 is similarly added to a normal toner. There is a method to prepare.

  In order to control the shape factor of the toner uniformly without any lot variation, the characteristics of the toner particles (colored particles) that are being formed in the process of polymerizing, fusing and controlling the shape of the resin particles (polymer particles) Appropriate process end time may be determined while monitoring.

  Monitoring means that a measuring device is incorporated in-line, and process conditions are controlled based on the measurement result. In other words, in the case of a polymerization method toner that is formed by incorporating measurement such as shape in-line, for example, by associating or fusing resin particles in an aqueous medium, the shape and particle size are measured while performing sequential sampling in the fusing step. The reaction is stopped when the desired shape is obtained.

  Although it does not specifically limit as a monitoring method, The flow type particle image analyzer FPIA-2000 (made by Toa Medical Electronics Co., Ltd.) can be used. This apparatus is suitable because the shape can be monitored by performing image processing in real time while passing the sample liquid. That is, a pump or the like is used from the reaction field and is constantly monitored to measure the shape and the like, and the reaction is stopped when the desired shape is obtained.

  The number particle size distribution and the number variation coefficient of the toner are measured by a Coulter Counter TA-II or Coulter Multisizer (manufactured by Coulter). In the present invention, a Coulter Multisizer is used, and an interface (manufactured by Nikkaki Co., Ltd.) that outputs a particle size distribution and a personal computer are connected. The aperture used in the Coulter Multisizer was 100 μm, and the volume and number of toners of 2 μm or more were measured to calculate the particle size distribution and average particle size. The number particle size distribution represents the relative frequency of the toner particles with respect to the particle size, and the number average particle size represents the median diameter in the number particle size distribution.

  The number variation coefficient in the toner number particle size distribution is calculated from the following equation.

Number variation coefficient = [S / Dn] × 100 (%)
[In the formula, S represents the standard deviation in the number particle size distribution, and Dn represents the number average particle size (μm). ]
The number variation coefficient of the toner is preferably 27% or less, and more preferably 25% or less. When the number variation coefficient is 27% or less, voids in the transferred toner layer are reduced, fixing properties are improved, and offset is less likely to occur. In addition, the charge amount distribution becomes sharp, the transfer efficiency is increased, and the image quality is improved.

  The method for controlling the number variation coefficient is not particularly limited. For example, a method of classifying toner particles by wind force can be used, but classification in a liquid is effective for reducing the number variation coefficient. As a method of classifying in this liquid, there is a method of separating and collecting toner particles according to a difference in sedimentation speed caused by a difference in toner particle diameter by using a centrifuge and controlling the rotation speed.

  In particular, when a toner is produced by a suspension polymerization method, a classification operation is indispensable in order to make the number variation coefficient in the number particle size distribution 27% or less. In the suspension polymerization method, it is necessary to disperse a polymerizable monomer in an oil droplet having a desired size as a toner in an aqueous medium before polymerization. That is, mechanical shearing with a homomixer or homogenizer is repeated for large oil droplets of a polymerizable monomer to reduce the oil droplets to the size of toner particles. In the method using shearing, the number particle size distribution of the obtained oil droplets is wide, and therefore the particle size distribution of the toner obtained by polymerizing the oil droplets is also wide. For this reason, classification operation is essential.

  Further, in the polymerization toner formed by associating or fusing the resin particles, the fusing particle surface has many irregularities at the fusing stop stage, and the surface is not smooth, but the temperature in the shape control step, By making the conditions such as the number of revolutions of the stirring blade and the stirring time appropriate, a toner having no corners can be obtained. These conditions vary depending on the physical properties of the resin particles. For example, by setting the rotational speed to be higher than the glass transition temperature of the resin particles, the toner can be formed with a smooth surface and no corners.

  The toner of the present invention preferably has a number average particle diameter of 3 to 8 μm. When the toner particles are formed by a polymerization method, the particle size can be controlled by the concentration of the aggregating agent, the amount of the organic solvent added, the fusing time, and further the composition of the polymer itself.

  When the number average particle diameter is 3 to 8 μm, it is possible to reduce the presence of excessively adhering toner or low adhering toner on the developer conveying member in the fixing step, and developability over a long period of time. And the transfer efficiency is increased, the image quality of halftone is improved, and the image quality of fine lines and dots is improved.

  Among the methods for controlling the shape factor, the polymerization toner is preferable because it is simple as a production method and has excellent surface uniformity as compared with the pulverized toner.

  The polymerized toner is produced by emulsion polymerization of monomers in a suspension polymerization method or in a solution to which an emulsion of necessary additives is added to produce fine polymer particles, and then an organic solvent, an aggregating agent, etc. It can manufacture by the method of adding and associating. A method of preparing by mixing with a dispersion liquid such as a release agent and a colorant necessary for the composition of the toner at the time of association, and a toner component such as a release agent and a colorant dispersed in the monomer And a method of emulsion polymerization. Here, the association means that a plurality of resin particles and colorant particles are fused.

  That is, various constituent materials such as a colorant and, if necessary, a release agent, a charge control agent, and a polymerization initiator are added to the polymerizable monomer, and a homogenizer, a sand mill, a sand grinder, an ultrasonic disperser, etc. Various constituent materials are dissolved or dispersed in the polymerizable monomer. The polymerizable monomer in which these various constituent materials are dissolved or dispersed is dispersed in oil droplets having a desired size as a toner in an aqueous medium containing a dispersion stabilizer using a homomixer or a homogenizer. Thereafter, the stirring mechanism is transferred to a reaction apparatus which is a stirring blade described later, and the polymerization reaction is advanced by heating. After completion of the reaction, the dispersion stabilizer is removed, filtered, washed, and dried to prepare a toner.

  Further, as a method for producing the toner of the present invention, a method of preparing by associating or fusing resin particles in an aqueous medium can also be mentioned. The method is not particularly limited, and examples thereof include methods disclosed in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904. That is, a method of associating a plurality of fine particles composed of resin particles and colorants, etc., or particles composed of resin and colorant, in particular, after dispersing them in water using an emulsifier, the critical aggregation concentration The above flocculant is added for salting out, and at the same time, the formed polymer itself is heated and fused at a temperature higher than the glass transition temperature to gradually grow the particle size while forming fused particles. Then, a large amount of water was added to stop the particle size growth, and the particle surface was smoothed while heating and stirring to control the shape, and the particles were heated and dried in a fluidized state while containing water, whereby a toner was obtained. Can be formed. Here, an organic solvent that is infinitely soluble in water may be added simultaneously with the flocculant.

  In addition, the aqueous medium as used in the field of this invention shows what contained 50 mass% or more of water at least.

  As the polymerizable monomer constituting the resin, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decyl Styrene, styrene or styrene derivatives such as pn-dodecylstyrene, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, Methacrylic acid ester derivatives such as lauryl tacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, acrylic Acrylates such as isobutyl acid, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, olefins such as ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, Halogenated vinyls such as vinyl bromide, vinyl fluoride, vinylidene fluoride, vinyl esters such as vinyl propionate, vinyl acetate, vinyl benzoate, vinyl methyl ether, vinyl ethyl ether Vinyl ethers such as tellurium, vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone, N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, vinyl naphthalene, vinyl pyridine, etc. There are acrylic acid or methacrylic acid derivatives such as vinyl compounds, acrylonitrile, methacrylonitrile, acrylamide and the like. These vinyl monomers can be used alone or in combination.

  Further, it is more preferable to use a combination of monomers having an ionic dissociation group as the polymerizable monomer constituting the resin. For example, it has a substituent such as a carboxyl group, a sulfonic acid group, a phosphoric acid group as a constituent group of the monomer, specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumar Acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxy And propyl methacrylate.

  Furthermore, polyfunctionality such as divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, etc. It is also possible to use a crosslinkable resin by using a functional vinyl.

  These polymerizable monomers can be polymerized using a radical polymerization initiator. In this case, an oil-soluble polymerization initiator can be used in the suspension polymerization method. Examples of the oil-soluble polymerization initiator include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carboxyl). Nitriles), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo- or diazo-based polymerization initiators such as azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate , Cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4,4- t-butylperoxycyclohexyl) propane, tris The (t-butylperoxy) triazine peroxide polymerization initiator or a peroxide, such as and the like polymeric initiator having a side chain.

  Moreover, when using an emulsion polymerization method, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like.

  Dispersion stabilizers include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate , Bentonite, silica, alumina and the like. Furthermore, those generally used as surfactants such as polyvinyl alcohol, gelatin, methylcellulose, sodium dodecylbenzenesulfonate, ethylene oxide adduct, and higher alcohol sodium sulfate can be used as the dispersion stabilizer.

  As the resin excellent in the present invention, those having a glass transition point of 20 to 90 ° C. are preferred, and those having a softening point of 80 to 220 ° C. are preferred. The glass transition point is measured by a differential calorimetric analysis method, and the softening point can be measured by a Koka flow tester. Further, these resins preferably have a molecular weight measured by gel permeation chromatography of 1,000 to 100,000 in terms of number average molecular weight (Mn) and 2000 to 1,000,000 in terms of weight average molecular weight (Mw). Further, the molecular weight distribution is preferably such that Mw / Mn is 1.5 to 100, particularly 1.8 to 70.

  The flocculant used is not particularly limited, but those selected from metal salts are preferably used. Specifically, as a monovalent metal, for example, an alkali metal salt such as sodium, potassium or lithium, as a divalent metal, for example, an alkaline earth metal salt such as calcium or magnesium, or a divalent metal such as manganese or copper. And salts of trivalent metals such as iron and aluminum, and specific salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate, etc. Can be mentioned. These may be used in combination.

  These flocculants are preferably added in an amount equal to or higher than the critical aggregation concentration. The critical flocculation concentration is an index relating to the stability of the aqueous dispersion, and indicates a concentration at which flocculation occurs when a flocculant is added. This critical aggregation concentration varies greatly depending on the emulsified components and the dispersant itself. For example, it is described in Seizo Okamura et al., “Polymer Chemistry 17, 601 (1960) edited by Polymer Society” and the like, and a detailed critical aggregation concentration can be obtained. As another method, a desired salt is added to the target particle dispersion at different concentrations, the ζ (zeta) potential of the dispersion is measured, and the salt concentration at which this value changes is defined as the critical aggregation concentration. You can ask for it.

  The addition amount of the flocculant may be not less than the critical aggregation concentration, but is preferably 1.2 times or more, more preferably 1.5 times or more of the critical aggregation concentration.

  The solvent that dissolves infinitely means a solvent that dissolves infinitely in water, and in the present invention, a solvent that does not dissolve the formed resin is selected. Specific examples include alcohols such as methanol, ethanol, propanol, isopropanol, t-butanol, methoxyethanol, and butoxyethanol, nitriles such as acetonitrile, and ethers such as dioxane. In particular, ethanol, propanol, and isopropanol are preferable.

  The addition amount of the infinitely soluble solvent is preferably 1 to 100% by volume with respect to the polymer-containing dispersion to which the flocculant is added.

  In order to make the shape uniform, it is preferable to fluidly dry a slurry in which 10% by mass or more of water is present after preparing and filtering colored particles. Those having a polar group are preferred. The reason for this is considered to be that it is particularly easy to make the shape uniform in order to exhibit the effect that the existing water slightly swells with respect to the polymer in which the polar group is present.

  The toner of the present invention contains at least a resin and a colorant, but may contain a release agent, a charge control agent, or the like, which is a fixability improving agent, if necessary. Further, an external additive composed of inorganic fine particles or organic fine particles may be added to the toner particles containing the resin and the colorant as main components.

  As the colorant used in the toner, carbon black, magnetic material, dye, pigment and the like can be arbitrarily used. As the carbon black, channel black, furnace black, acetylene black, thermal black, lamp black and the like are used. . Magnetic materials include ferromagnetic metals such as iron, nickel and cobalt, alloys containing these metals, compounds of ferromagnetic metals such as ferrite and magnetite, alloys that do not contain ferromagnetic metals but exhibit ferromagnetism by heat treatment, For example, a kind of alloy called Heusler alloy such as manganese-copper-aluminum, manganese-copper-tin, chromium dioxide, or the like can be used.

  As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95 etc. can be used, and a mixture thereof can also be used. Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 122, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment yellow 14, 17, 93, 94, 138, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 60, etc. can be used, and a mixture thereof can also be used. The number average primary particle diameter varies depending on the type, but is preferably about 10 to 200 nm.

  As a method for adding the colorant, the polymer particles prepared by the emulsion polymerization method are added at the stage of agglomerating by adding an aggregating agent, and the polymer is colored, or at the stage of polymerizing the monomer. The method of adding, polymerizing, and making it a colored particle etc. can be used. In addition, when adding a coloring agent in the step which prepares a polymer, it is preferable to use it, treating the surface with a coupling agent etc. so that radical polymerization property may not be inhibited.

  Further, a low molecular weight polypropylene (number average molecular weight = 1500 to 9000), a low molecular weight polyethylene, or the like as a fixing property improving agent may be added.

  Similarly, various known charge control agents and those that can be dispersed in water can be used. Specific examples include nigrosine dyes, naphthenic acid or higher fatty acid metal salts, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts or metal complexes thereof.

  In addition, it is preferable that the number average primary particle diameter of these charge control agent and fixability improving agent particles is about 10 to 500 nm in a dispersed state.

In a suspension polymerization method toner in which a toner component obtained by dispersing or dissolving a toner component such as a colorant in a so-called polymerizable monomer is suspended in an aqueous medium and then polymerized. The shape of the toner particles can be controlled by controlling the flow of the medium. That is, when a large amount of toner particles having a shape factor of 1.2 or more are formed, the flow of the medium in the reaction vessel is turbulent and the polymerization proceeds to exist in an aqueous medium in a suspended state. When the oil droplets gradually become polymerized, the oil droplets become soft particles. By colliding the particles, particle coalescence is promoted, and particles with an irregular shape are obtained. . When spherical toner particles having a shape factor smaller than 1.2 are formed, spherical particles can be obtained by using a laminar flow of the medium in the reaction vessel to avoid particle collision. By this method, the toner shape distribution can be controlled within the scope of the present invention.
<Developer>
The toner used in the present invention may be a one-component developer or a two-component developer, but is preferably a two-component developer.

  When used as a one-component developer, there is a method in which the toner is used as it is as a non-magnetic one-component developer. Usually, however, the toner particles contain about 0.1 to 5 μm of magnetic particles as a magnetic one-component developer. Use. As a method for its inclusion, it is usually contained in non-spherical particles in the same manner as the colorant.

  Further, it can be mixed with a carrier and used as a two-component developer. In this case, conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead are used as the magnetic particles of the carrier. Ferrite particles are particularly preferable. The magnetic particles preferably have a volume average particle size of 15 to 100 μm, more preferably 25 to 60 μm.

  The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene / acrylic resin, silicone resin, ester resin, or fluorine-containing polymer resin is used. The resin for constituting the resin-dispersed carrier is not particularly limited, and known resins can be used. For example, a styrene acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like can be used. it can.

  Next, the photoconductor used in the present invention will be described in detail.

  The electrophotographic photosensitive member used in the image forming apparatus of the present invention may be either an inorganic photosensitive member or an organic photosensitive member. However, when forming a latent image, color sensitivity to laser light used for image exposure, An organic photoreceptor is preferable from the viewpoint of good productivity.

  Here, the organic photoconductor means an electrophotographic photoconductor formed by giving an organic compound at least one of a charge generation function and a charge transport function indispensable for the configuration of the electrophotographic photoconductor. It contains all known organic electrophotographic photoreceptors such as a photoreceptor composed of an organic charge generating material or an organic charge transport material, a photoreceptor composed of a polymer complex with a charge generating function and a charge transport function.

  In the electrophotographic photoreceptor used in the image forming apparatus of the present invention, it is preferable that the surface of the photoreceptor is made to have low surface energy properties and the transferability of toner from the photoreceptor to the intermediate transfer member is improved. As a measure for this, one is to make the surface layer of the photoreceptor into a surface layer containing fluorine resin particles in the present invention, and the other is to supply a surface energy reducing agent to the surface of the photoreceptor. As a result, the surface energy of the photosensitive member can be reduced, and the transferability of toner from the photosensitive member to the intermediate transfer member can be improved. By combining the reduction of the surface energy of the photoconductor and the use of the toner group having the toner turbidity described above, the primary transferability and secondary transfer of the toner of the image forming apparatus using the intermediate transfer body are used. By combining the transfer efficiency of both the color and the synergistic effect, it is possible to provide a color electrophotographic image having good sharpness and good hue reproduction for both the character image and the color image.

  In the electrophotographic photoreceptor of the present invention, the surface layer preferably has a contact angle with water of 90 ° or more by reducing the surface energy. By making the contact angle with water 90 ° or more, it is possible to improve the cleaning property of the toner and the like and improve the transfer property of the toner from the photosensitive member to the intermediate transfer member.

  Examples of the fluorine resin particles include, for example, polytetrafluoroethylene, polyvinylidene fluoride, polytrifluoroethylene chloride, polyvinyl fluoride, polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polytetrafluoroethylene- Examples include resin particles such as hexafluoropropylene copolymer, polyethylene-trifluoride ethylene copolymer, polytetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer, and volume average particle diameter. The thickness is preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm. The amount of the fluororesin particles contained in the photoreceptor of the present invention is preferably 0.1 to 90% by mass, more preferably 1 to 50% by mass with respect to the binder resin of the surface layer of the photoreceptor. If the amount is less than 0.1%, sufficient photosensitive durability and lubricity cannot be imparted to the photosensitive layer, and the improvement of the primary transfer property of the toner is small, resulting in a decrease in image density, transfer loss, and sharpness. Deterioration is likely to occur. If it exceeds 90% by mass, the formation of the surface layer tends to be difficult.

  The volume average particle diameter of the fluororesin particles is measured by a laser diffraction / scattering particle size distribution measuring apparatus “LA-700” (manufactured by Horiba, Ltd.). The surface contact angle of the photosensitive member is measured by using a contact angle meter (CA-DT-A type: manufactured by Kyowa Interface Science Co., Ltd.) in an environment of 20 ° C. and 50% RH.

  Hereinafter, a specific configuration of the photoreceptor used in the present invention will be described.

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

  The cylindrical conductive support of the present invention means a cylindrical support necessary for forming an endless image by rotating, and the straightness is in the range of 0.1 mm or less and the deflection is 0.1 mm or less. Certain conductive supports are preferred. Exceeding the range of straightness and shake makes it difficult to form a good image.

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, it is preferable to provide an intermediate layer having a barrier function between the conductive support and the photosensitive layer, and in particular, an intermediate layer in which titanium oxide fine particles are dispersed and contained in a binder resin such as polyamide. preferable. The average particle diameter of the titanium oxide particles is preferably in the range of 10 nm to 400 nm in terms of number average primary particle diameter, and is preferably 15 nm to 200 nm. If it is less than 10 nm, the effect of preventing the occurrence of moire by the intermediate layer is small. On the other hand, if it is larger than 400 nm, the titanium oxide particles in the intermediate layer coating solution are likely to settle, and as a result, the uniform dispersibility of the titanium oxide particles in the intermediate layer is poor, and the black spots are likely to increase. An intermediate layer coating liquid using titanium oxide particles having a number average primary particle size in the above range has good dispersion stability, and the intermediate layer formed from such a coating liquid has an environmental characteristic in addition to the function of preventing the occurrence of black spots. Is good and has cracking resistance.

  The shape of the titanium oxide particles used in the present invention includes a dendritic shape, a needle shape, a granular shape, and the like. The titanium oxide particles having such a shape are, for example, titanium oxide particles, anatase type, rutile as crystal types. There are types, amorphous types, and the like. Any crystal type may be used, or two or more crystal types may be mixed and used. Among them, the rutile type and granular type are the best.

  The titanium oxide particles of the present invention are preferably surface-treated. Among these, it is preferable to perform a plurality of surface treatments, and among the plurality of surface treatments, the last surface treatment is a surface treatment using a reactive organosilicon compound. In addition, at least one of the surface treatments is at least one surface treatment selected from alumina, silica, and zirconia, and finally a surface treatment using a reactive organosilicon compound. It is preferable to carry out.

  Alumina treatment, silica treatment, and zirconia treatment are treatments for precipitating alumina, silica, or zirconia on the surface of titanium oxide particles, and alumina, silica, and zirconia deposited on these surfaces are water of alumina, silica, and zirconia. Japanese products are also included. The surface treatment of the reactive organosilicon compound means using a reactive organosilicon compound in the treatment liquid.

  In this way, when the surface treatment of the titanium oxide particles is performed at least twice, the surface of the titanium oxide particles is uniformly coated (treated), and when the surface-treated titanium oxide particles are used for the intermediate layer, the intermediate layer It is possible to obtain a good photoconductor having good dispersibility of the titanium oxide particles therein and causing no image defects such as black spots.

  Preferable reactive organosilicon compounds used for the surface treatment include various alkoxysilanes such as methyltrimethoxysilane, n-butyltrimethoxysilane, n-hexycyltrimethoxysilane, dimethyldimethoxysilane, and methylhydrogenpolysiloxane.

Photosensitive layer The photosensitive layer configuration of the photoreceptor of the present invention may be a single-layer photosensitive layer configuration in which the intermediate layer has a charge generation function and a charge transport function in one layer, but more preferably the function of the photosensitive layer. The charge generation layer (CGL) and the charge transport layer (CTL) may be separated from each other. By adopting a configuration in which the functions are separated, an increase in the residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoconductor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer and a charge transport layer (CTL) is formed thereon. In the positively charged photoconductor, the order of the layer configuration is the reverse of that in the negatively charged photoconductor. The most preferred photosensitive layer structure of the present invention is a negatively charged photoreceptor structure having the function separation structure.

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

Charge generation layer The charge generation layer contains a charge generation material (CGM). Other substances may contain a binder resin and other additives as necessary.

  In the electrophotographic photoreceptor of the present invention, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used alone or in combination as a charge generating material.

  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 0.1 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.

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

  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 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. The thickness of the charge transport layer is preferably 10 to 40 μm.

  The charge transport layer may be composed of two or more layers. When the charge transport layer is composed of two or more layers, it is preferable that the uppermost charge transport layer contains the above-mentioned fluorine-based resin particles to form a surface layer of the photoreceptor.

  The most preferable layer structure of the photoconductor of the present invention has been exemplified above, but other photoconductor layer configurations may be used in the present invention.

  FIG. 1 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 a plurality of sets of image forming units (image forming units) 10Y, 10M, 10C, and 10Bk, a belt-shaped intermediate transfer body unit 7, and paper feeding It comprises a 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 includes a charging unit 2Y, an exposure 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 photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, It has a cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a primary transfer roller 5C as a primary transfer unit. It has cleaning means 6C. The image forming unit 10Bk that forms a black image includes a drum-shaped photoreceptor 1Bk as a first image carrier, a charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk as a primary transfer unit, and a cleaning unit. 6Bk.

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

  Each colored image formed by the image forming units 10Y, 10M, 10C, and 10Bk is sequentially transferred onto a rotating 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 sheet P as a recording material (a support for carrying a fixed final image: for example, plain paper, transparent sheet, etc.) housed in the sheet feeding cassette 20 is fed by a sheet feeding means 21 and has a plurality of intermediate rollers. After passing through 22A, 22B, 22C, 22D and the registration roller 23, it is conveyed to the secondary transfer roller 5A as the secondary transfer means, and is secondarily transferred onto the paper P, and the color images are collectively transferred. The paper P on which the color image has been transferred is fixed by the fixing unit 24, is sandwiched between the paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus.

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

  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 5A comes into pressure contact with the belt-shaped intermediate transfer member 70 only when the sheet P passes through the secondary transfer roller 5A and secondary transfer is performed.

  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 a belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10Bk are arranged in tandem in the vertical direction. A 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 belt-shaped intermediate transfer body unit 7 includes a belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, and 75, primary transfer rollers 5Y, 5M, 5C, and 5Bk, and a cleaning unit 6A. Consists of.

  The image forming units 10Y, 10M, 10C, and 10Bk and the belt-shaped intermediate transfer body unit 7 are integrally pulled out from the main body A by the drawer operation of the housing 8.

  A support rail 82 </ b> L on the left side of the housing 8 in the figure is disposed on the left side of the belt-shaped intermediate transfer body 70 and in the upper space of the fixing unit 24. The support rail 82R on the right side of the housing 8 in the drawing is disposed near the lower part of the lowermost developing means 4Bk. The support rail 82R is disposed at a position that does not hinder the operation of attaching and detaching the developing units 4Y, 4M, 4C, and 4Bk to the housing 8.

  The right side of the photoconductors 1Y, 1M, 1C, and 1Bk in the housing 8 is surrounded by the developing means 4Y, 4M, 4C, and 4Bk, and the lower side in the figure is the charging means 2Y, 2M, 2C, and 2Bk, and the cleaning means 6Y. , 6M, 6C, 6Bk, etc., and the left side in the figure is surrounded by a belt-like intermediate transfer member 70.

  Among them, the photosensitive member, the cleaning unit, the charging unit and the like form one photosensitive unit, and the developing unit and the toner replenishing device form one developing unit.

  The image forming apparatus of the present invention is characterized in that a plurality of cleaning blades are used as cleaning means for residual toner on the intermediate transfer member. By removing the residual toner on the intermediate transfer member with the plurality of cleaning blades, even if a minute residual toner is attached on the intermediate transfer member, the attached toner can be more effectively removed. Residual toner on the intermediate transfer member, together with the plurality of cleaning blades, remains with strong adhesion due to the effect of rubbing the surface of the intermediate transfer member by the fine particle external additive having the number average primary particle size of 0.1 to 1.0 μm. The toner can be effectively removed.

  FIG. 2 shows an example of the cleaning means for the intermediate transfer member.

  The intermediate transfer member cleaning means of the present invention has a plurality of cleaning blades. In one embodiment of the present invention, the belt-like intermediate transfer member cleaning means 6A is a cleaner that opens to face the toner image carrying surface of the belt-like intermediate transfer member 70, as shown in FIGS. It has a case 61C, facing the opening of the cleaner case 61C, and two cleaning blades in order from the upstream side in the moving direction of the belt-shaped intermediate transfer body 70, that is, an elastic blade 61A such as a urethane rubber blade and a metal such as SUS. A scraper 61B is provided. In the present embodiment, the attachment structure of the elastic blade 61A and the metal scraper 61B is provided such that a swing arm 61D is swingably provided in the cleaner case 61C with one end side as a swing fulcrum 61E. The holder 61F serves as a holder 61F, and the elastic blade 61A and one end of the metal scraper 61B are fixed to the holder 61F, and a return spring 61G is interposed between the free end of the swing arm 61D and the cleaner case 61C. The swing arm 61D is swung between a cleaning position and a retract position by a drive mechanism (not shown). In FIG. 2A, a brush roll 61H is provided at the lower edge of the opening of the cleaner case 61C and collects the toner removed by the elastic blade and the metal scraper. 61I is a flicker that adsorbs the toner adhering to the brush roll 61H, and the toner adhering to the flicker is removed by a 61J scraper and collected by the conveying screw 61K.

  In particular, in the present embodiment, various conditions (free length, contact pressure, thickness, set angle, etc.) of the elastic blade 61A are cleaned without applying unnecessary load to the drive source of the belt-shaped intermediate transfer body 70. It is appropriately selected from the viewpoint of ensuring safety. On the other hand, the various conditions of the metal scraper 61B are also selected as appropriate mainly from the viewpoint of ensuring cleanability. From the viewpoint of further improving the cleanability at the tip of the metal scraper 61B, for example, a belt shape It is preferable to perform an etching process on the leading edge contacting the surface of the intermediate transfer member 70. Further, the distance d between the elastic blade 61A and the metal scraper 61B may be appropriately selected depending on the shape of the cleaner case 61C, the set position, and the like. However, if the distance d between the two sheets is too close, the toner accumulates in the gaps between the two over time, and the cleaning performance may be deteriorated.

  Furthermore, in this embodiment, the elastic blade 61A and the metal scraper 61B are separated from the belt-shaped intermediate transfer body 70 portion corresponding to the roller 75 (backup roller) to the upstream side in the moving direction of the belt-shaped intermediate transfer body 70. It is disposed in the vicinity, and floating toner or dust adheres between the roller 75 and the belt-shaped intermediate transfer body 70, and a minute convex portion is formed on the surface portion of the belt-shaped intermediate transfer body 70 corresponding to the roller 75. Even so, the cleaning performance of the elastic blade 61A and the metal scraper 61B is not affected. However, the elastic blade 61A may be brought into contact with the belt-shaped intermediate transfer member 70 corresponding to the roller 75. In the present embodiment, the cleaning means 6A is disposed corresponding to the portion of the belt-shaped intermediate transfer body 70 located between the roller 75 and the roller 77 (a backup roller corresponding to the brush roller 61H). An elastic blade 61A and a metal scraper 61B are brought into contact with the belt-shaped intermediate transfer member 70.

  Then, during the cleaning cycle, the cleaning means 6A moves the swing arm 61D to a cleaning position (position closer to the belt-shaped intermediate transfer body 70 than the retract position) by a driving mechanism (not shown), so that the belt-shaped intermediate transfer body. While the elastic blade 61A and the tip of the metal scraper 61B are placed in contact with the surface at a predetermined contact pressure, the oscillating arm 61D is returned to the return spring 61G by a drive mechanism (not shown) during an imaging cycle other than the cleaning cycle. The elastic blade 61A and the tip of the metal scraper 61B are spaced apart from the surface of the belt-shaped intermediate transfer body 70 against the retracted position.

  As described above, by using a combination of the elastic blade 61A and the metal scraper 61B, a high rotational torque is not required for the driving source of the belt-shaped intermediate transfer body 70, and the cleaning property of the small-diameter polymerized toner is improved. In addition, stable cleaning performance can be maintained even for the minute convex portions on the belt-shaped intermediate transfer member 70. These effects were confirmed in Examples described later.

  A rubber elastic body is used as the material of the elastic blade, and urethane rubber, silicon rubber, fluorine rubber, chloropyrene rubber, butadiene rubber, and the like are known as the material. Of these, urethane rubber blades are other materials. It is particularly preferable in that it has excellent wear characteristics as compared with the rubber blades.

  It is preferable that at least one of the plurality of cleaning blades used in the cleaning means for the intermediate transfer member of the present invention is a non-deformable member. The non-deformable member means a member that does not cause elastic deformation due to contact with the intermediate transfer member. A metal scraper is preferably used as the non-deformable member.

  The metal scraper is a thin metal plate having a thickness of 0.01 to 2 mm, particularly preferably 0.02 to 0.5 mm. The metal thin plate is made of a flexible and rigid thin metal plate. Any metal material can be used, but a SUS300 series, SUS400 series stainless steel plate, aluminum plate, phosphor bronze plate, or the like is preferably used.

Preferred values of contact angle theta ₂ to the intermediate transfer member contact angle theta ₁ and metal scraper to the intermediate transfer member of the elastic blade, it is neither 5 to 35 °. The free length of the elastic blade and the metal scraper (the length of the leading portion not fixed to the holder 61F) is preferably 6 to 15 mm.

  The biting amount of the elastic blade and the metal scraper with respect to the intermediate transfer member is preferably set to 0.4 to 2.0 mm, more preferably 0.5 to 1.5 mm. This amount of biting means a load applied to the leading portion of the elastic blade or the leading portion of the metal scraper generated by the relative movement of the intermediate transfer member and the elastic blade or metal scraper. From the viewpoint of the intermediate transfer member, this load corresponds to the rubbing force received from the elastic blade or the metal scraper, and defining the range means that the intermediate transfer member needs to be scraped with an appropriate force. means. In addition, the amount of biting is that when the elastic blade or the metal scraper is brought into contact with the intermediate transfer member, the leading portion of the elastic blade or the leading portion of the metal scraper does not bend on the surface of the intermediate transfer member and enters the inside linearly. This is the length of biting into the interior.

  FIG. 3 is an arrangement diagram showing the positional relationship among the photosensitive member, the belt-shaped intermediate transfer member, and the primary transfer roller. The primary transfer rollers 5Y, 5M, 5C, and 5Bk are pressed from the back surface of the belt-like intermediate transfer member 70 as an intermediate transfer member to the photosensitive members 1Y, 1M, 1C, and 1Bk, as shown in the layout diagram of FIG. The primary transfer rollers 5Y, 5M, 5C, and 5Bk are located downstream of the contact point between the belt-like intermediate transfer member 70 as an intermediate transfer member when not pressed and the photosensitive members 1Y, 1M, 1C, and 1Bk in the rotational direction of the photosensitive member. Are arranged and pressed to the photoreceptors 1Y, 1M, 1C, and 1Bk. At this time, the belt-like intermediate transfer member 70 as an intermediate transfer member is bent along the outer periphery of each of the photosensitive members 1Y, 1M, 1C, and 1Bk, and is most downstream in the contact area between the photosensitive member and the belt-like intermediate transfer member 70. The primary transfer rollers 5Y, 5M, 5C, and 5Bk are arranged.

  FIG. 4 is an arrangement diagram showing the positional relationship among the backup roller, the belt-shaped intermediate transfer member, and the secondary transfer roller. As shown in the layout diagram of FIG. 4, the secondary transfer roller 5 </ b> A is more than the contact center portion between the belt-like intermediate transfer body 70 and the backup roller 74 as an intermediate transfer body when not pressed by the secondary transfer roller 5 </ b> A. It is desirable that the backup roller 74 is disposed upstream of the rotation direction.

  As the intermediate transfer member, a polymer film such as polyimide, polycarbonate, PVdF, or a synthetic rubber such as silicone rubber or fluororubber added with a conductive filler such as carbon black is used. Either a belt shape may be used, but a belt shape is preferable from the viewpoint of freedom in device design.

  The surface of the intermediate transfer member is preferably appropriately roughened. By setting the 10-point surface roughness Rz of the intermediate transfer member to 0.5 to 2 μm, the surface energy reducing agent supplied to the photosensitive member is taken into the surface of the intermediate transfer member and the toner adhesion on the intermediate transfer member is reduced. It becomes easy to improve the transfer rate of the secondary transfer of toner from the intermediate transfer member to the recording material. In this case, the effect tends to be greater when the ten-point surface roughness Rz of the intermediate transfer member is larger than the ten-point surface roughness Rz of the photosensitive member.

  On the other hand, the photosensitive member cleaning means is basically the same as the intermediate transfer member cleaning means shown in FIG. 2 except for the metal scraper. The cleaning means is used as a cleaning means such as 6Y, 6M, 6C, 6Bk in FIG.

Next, embodiments of the present invention will be specifically described. However, the configuration of the present invention is not limited to this.
(Development of developer)
(Manufacture of toner 1Bk (black))
0.90 kg of sodium n-dodecyl sulfate and 10.0 liters of pure water were added and dissolved by stirring. To this solution, 1.20 kg of Legal 330R (Cabot Black Carbon Black) was gradually added and stirred well for 1 hour, followed by continuous dispersion for 20 hours using a sand grinder (medium disperser). This is referred to as “colorant dispersion 1”.

  A solution composed of 0.055 kg of sodium dodecylbenzenesulfonate and 4.0 liters of ion-exchanged water is referred to as “anionic surfactant solution A”.

  A solution composed of 0.014 kg of nonylphenol polyethylene oxide 10 mol adduct and 4.0 liters of ion-exchanged water is referred to as “nonionic surfactant solution B”.

  A solution obtained by dissolving 223.8 g of potassium persulfate in 12.0 liters of ion-exchanged water is referred to as “initiator solution C”.

  A GL (glass lining) reaction kettle with a volume of 100 liters equipped with a temperature sensor, a condenser tube, and a nitrogen introducing device was added to a WAX emulsion (a polypropylene emulsion having a number average molecular weight of 3000: number average primary particle size = 120 nm / solid content concentration = 29. 9%) 3.41 kg, the total amount of “anionic surfactant solution A” and the total amount of “nonionic surfactant solution B” were added, and stirring was started. Subsequently, 44.0 liters of ion exchange water was added.

  Heating was started and when the liquid temperature reached 75 ° C., the entire amount of “Initiator Solution C” was added dropwise. Thereafter, while controlling the liquid temperature at 75 ° C. ± 1 ° C., 12.1 kg of styrene, 2.88 kg of n-butyl acrylate, 1.04 kg of methacrylic acid, and 548 g of t-dodecyl mercaptan were added dropwise. After completion of the dropping, the liquid temperature was raised to 86 ° C. ± 1 ° C., and the mixture was heated and stirred for 5 hours to carry out emulsion polymerization. Next, the liquid temperature was cooled to 40 ° C. or less to stop the polymerization reaction, and then the residual monomer was distilled off under reduced pressure (1.33 kPa), followed by filtration through a pole filter to obtain a latex. This is designated as “Latex-A”.

  The glass transition temperature of the resin particles in Latex-A was 57 ° C., the softening point was 121 ° C., the molecular weight distribution was weight average molecular weight = 17,000, and the weight average particle size was 120 nm.

  A solution prepared by dissolving 0.055 kg of sodium dodecylbenzenesulfonate in 4.0 liters of ion-exchanged pure water is referred to as “anionic surfactant solution D”.

  Further, a solution obtained by dissolving 0.014 kg of nonylphenol polyethylene oxide 10 mol adduct in 4.0 liters of ion-exchanged water is referred to as “nonionic surfactant solution E”.

  A solution obtained by dissolving 200.7 g of potassium persulfate (manufactured by Kanto Chemical Co., Ltd.) in 12.0 liters of ion-exchanged water is referred to as “initiator solution F”.

  A WAX emulsion (a polypropylene emulsion with a number average molecular weight of 3000: number average primary particle size = 120 nm / solid content concentration of 29.9%) was added to a 100 liter GL reaction kettle equipped with a temperature sensor, a cooling pipe, a nitrogen introducing device and a comb baffle. 3.41 kg, the total amount of “anionic surfactant solution D” and the total amount of “nonionic surfactant solution E” were added, and stirring was started.

  Next, 44.0 liters of ion exchange water was added. Heating was started, and when the liquid temperature reached 70 ° C., “initiator solution F” was added. Then, 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 was dropped. After completion of the dropping, the liquid temperature was controlled at 80 ° C. ± 2 ° C., and the mixture was heated and stirred for 5 hours to carry out emulsion polymerization. Next, the liquid temperature was cooled to 40 ° C. or less to stop the polymerization reaction, and then the residual monomer was distilled off under reduced pressure (1.33 kPa), followed by filtration through a pole filter to obtain a latex. This is designated as “Latex-B”.

  The glass transition temperature of the resin particles in Latex-B 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.

  A solution obtained by dissolving 5.36 kg of sodium chloride as a salting-out agent in 20.0 liters of ion-exchanged water is referred to as “sodium chloride solution G”.

  A solution obtained by dissolving 1.00 g of a fluorine-based nonionic surfactant in 1.00 liter of ion-exchanged water is referred to as “nonionic surfactant solution H”.

  In a 100 liter SUS reaction kettle equipped with a temperature sensor, a cooling pipe, a nitrogen introduction device, a particle size and shape monitoring device, latex-A = 20.0 kg, latex-B = 5.2 kg, and a colorant prepared above. Dispersion 1 = 0.4 kg and ion-exchanged water 20.0 kg were added and stirred. Next, the mixture was heated to 40 ° C., and sodium chloride solution G, 6.00 kg of isopropanol (manufactured by Kanto Chemical Co., Inc.) and nonionic surfactant solution H were added in this order. Then, after standing for 10 minutes, temperature increase was started, the temperature was raised to 85 ° C. in 60 minutes, and the mixture was heated and stirred at 85 ± 2 ° C. for 0.5 to 3 hours while being salted out / fused. Diameter growth. Next, 2.1 liters of pure water was added to stop the particle size growth, and a fused particle dispersion was prepared (salting out / fusing stage).

In a 5-liter reaction vessel equipped with a temperature sensor, a cooling pipe, a particle size and shape monitoring device, 5.0 kg of the fused particle dispersion prepared above was placed, and the liquid temperature was 85 ° C. ± 2 ° C. The shape was controlled by heating and stirring for 5 to 15 hours (shape control step). Then, it cooled to 40 degrees C or less, and stopped stirring. Next, using a centrifugal separator, classification is performed in the liquid by a centrifugal sedimentation method, followed by filtration through a sieve having an opening of 45 μm, and this filtrate is used as an association liquid. Subsequently, wet cake-like non-spherical particles were collected by filtration from the associating liquid using Nutsche. Thereafter, it was washed with ion exchange water. The non-spherical particles were dried at a suction air temperature of 60 ° C. using a flash jet dryer and then dried at a temperature of 60 ° C. using a fluidized bed dryer. To 100 parts by mass of the obtained colored particles, silica A (particle diameter: 12 nm): 1 part by mass and titania B (particle diameter: 155 nm): 0.6 part by mass are externally added and mixed with a Henschel mixer to obtain an emulsion polymerization society. A legal toner 1Bk was obtained. The number average particle diameter of the toner 1Bk was 5.6 μm, and the shape factor was 1.33.
(Manufacture of toner 1Y (yellow))
In the production of the toner 1Bk, C.I. was used instead of Regal 330R (carbon black manufactured by Cabot) used for the production of “Colorant Dispersion Liquid 1”. I. Toner 1Y was obtained in the same manner except that Pigment Yellow 185 was used and Titania B was removed. The number average particle diameter of the toner 1Y was 5.6 μm, and the shape factor was 1.35.
(Manufacture of toner 1M (magenta))
In the production of the toner 1Bk, C.I. I. Toner 1M was obtained in the same manner except that Pigment Red 122 was used and Titania B was removed. The number average particle diameter of the toner 1M was 5.6 μm, and the shape factor was 1.27.
(Manufacture of toner 1C (cyan))
In the production of the toner 1Bk, C.I. I. Toner 1C was obtained in the same manner except that CI Pigment Blue 15: 3 was used and titania B was removed. The number average particle diameter of the toner 1C was 5.6 μm, and the shape factor was 1.37.
(Manufacture of toner 2Bk to toner 9Bk (black))
In the production of the toner 1Bk, the toner 2Bk was similarly prepared except that silica A (particle diameter: 12 nm): 1 part by mass and titania B (particle diameter: 155 nm): 0.6 part by mass were changed as shown in Tables 1 and 2. Toner 9Bk was obtained. The number average particle diameters and shape factors of the toner 2Bk to the toner 9Bk were almost the same as those of the toner 1Bk.
(Manufacture of toner 2Y to toner 9Y (yellow))
Toner 1Y to Toner 9Y were obtained in the same manner as in the production of toner 1Y, except that silica A (particle diameter: 12 nm): 1 part by mass was changed as shown in Tables 1 and 2. The number average particle diameters and shape factors of the toner 2Y to the toner 9Y were almost the same as those of the toner 1Y.
(Manufacture of toner 2M to toner 9M (magenta))
Toner 1M to Toner 9M were obtained in the same manner as in the production of toner 1M, except that silica A (particle diameter: 12 nm): 1 part by mass was changed as shown in Tables 1 and 2. Number average particle diameters and shape factors of Toner 2M to Toner 9M were almost the same as those of Toner 1M.
(Manufacture of toner 2C to toner 9C (cyan))
Toner 1C to Toner 9C were obtained in the same manner as in the production of Toner 1C, except that silica A (particle diameter: 12 nm): 1 part by mass was changed as shown in Tables 1 and 2. The number average particle diameter and shape factor of toner 2C to toner 9C were almost the same as toner 1C.
[Manufacture of developer]
For evaluation by mixing 10 parts by mass of each of toners 1Bk to 9Bk, toners 1Y to 9Y, toners 1M to 9M, and toners 1C to 9C and 100 parts by mass of a 45 μm ferrite carrier coated with a styrene-methacrylate copolymer. Developers 1Bk to 9Bk, Developers 1Y to 9Y, Developers 1M to 9M, and Developers 1C to 9C were produced, and Developer groups 1 to 9 shown in Tables 1 and 2 were produced.

[Production of photoconductor]
Photoconductors used in the examples were produced as follows (the photoconductors in each example were produced in a total of four or more because each image unit uses the same type of photoconductor).

Preparation of Photoreceptor The following intermediate layer coating solution was prepared and applied onto a washed cylindrical aluminum substrate by a dip coating method to form an intermediate layer having a dry film thickness of 0.3 μm.

<Intermediate layer (UCL) coating solution>
Polyamide resin (Amilan CM-8000: manufactured by Toray Industries, Inc.) 60 g
1600 ml of methanol
The following coating solution components were mixed and dispersed for 10 hours 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 0.2 μm on the intermediate layer.

<Charge generation layer (CGL) coating solution>
Y-type titanyl phthalocyanine (Maximum peak angle of X-ray diffraction by Cu-Kα characteristic X-ray is 27.3 at 2θ) 60 g
700 g of silicone resin solution (KR5240, 15% xylene-butanol solution: manufactured by Shin-Etsu Chemical Co., Ltd.)
2-butanone 2000ml
The following coating solution components were mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied onto the charge generation layer by a dip coating method to form a charge transport layer having a thickness of 20 μm.

<Charge transport layer (CTL) coating solution>
Charge transport material (4-methoxy-4 '-(4-methyl-α-phenylstyryl) triphenylamine) 200 g
Bisphenol Z-type polycarbonate (Iupilon Z300: manufactured by Mitsubishi Gas Chemical Company) 300g
Hindered amine (Sanol LS2626: Sankyosha) 3g
1,2-dichloroethane 2000ml
<Surface protective layer>
Charge transport material (4-methoxy-4 '-(4-methyl-α-phenylstyryl) triphenylamine) 200 g
Bisphenol Z-type polycarbonate (Iupilon Z300: manufactured by Mitsubishi Gas Chemical Company) 300g
Hindered amine (Sanol LS2626: Sankyosha) 3g
100 g of polytetrafluoroethylene resin particles (average particle size 0.5 μm)
1-butanol 50g
Were mixed and dissolved to prepare a surface protective layer coating solution. This coating solution was applied onto the charge transport layer by a dip coating method, followed by heat curing at 100 ° C. for 40 minutes to form a surface protective layer having a dry film thickness of 4 μm, thereby preparing a photoreceptor. The surface contact angle of the photoreceptor with respect to water was 106 °.

<Evaluation>
In each of the image forming units, the photosensitive member and the developing unit include four photosensitive members and Y (yellow), M (magenta), C (cyan), and Bk for each developer group (toner group) shown in Tables 1 and 2. Four sets of developing means each containing (black) developer (toner) are combined, and these photosensitive members and developing means are mounted on a digital copying machine having an intermediate transfer member as shown in FIGS. An A4 image having a solid, solid image portion, character image portion, and halftone image of part, Bk and Y, M, and C was printed and evaluated under normal temperature and humidity (20 ° C., 50% RH). Evaluation items, evaluation methods, and evaluation criteria are described below.

Character dust A character image was formed, and toner dust around the characters was observed visually and with a 20-fold magnifier, and evaluated according to the following criteria.

A: Toner dust around the characters is not observed even with loupe observation (good)
○: Cannot be visually discerned, but toner dust around the characters is observed with a loupe (no problem in practice)
×: Toner dust around the character is visually observed, and the sharpness of the character is inferior (practically problematic)
Transfer missing A halftone image having a density of 0.4 was formed on both sides of a transfer paper (basis weight 200 g / m ² ), and the occurrence of white spots due to transfer missing was visually evaluated.

◎◎: No transfer at all (very good)
A: 1 to 2 transfer omissions exist only on the back surface per 100 images, but it cannot be distinguished without staring (good)
○: Although there are 1 to 4 transfer omissions per 50 images, it cannot be determined without staring (no problem in practical use)
×: 5 or more clear transfer omissions exist for 50 images regardless of the front and back sides (practical problem)
Cleanability of intermediate transfer member A: No toner aggregation on the intermediate transfer member, good cleaning, and no image unevenness (good)
○: Slight aggregation of toner or the like occurs on the intermediate transfer member, but cleaning is good and image unevenness does not occur (no problem in practical use)
X: Aggregation of toner or the like occurs on the intermediate transfer member, toner slips out, and image unevenness occurs. (There are practical problems)
Image Density The image density was measured by using a densitometer “RD-918” (manufactured by Macbeth) for the solid part of each color and measuring the relative reflection density with zero recording paper.

A: Each density of the solid (solid) image portion of Bk and Y, M, C is 1.2 or more (good)
○: Each density of the solid (solid) image portion of Bk and Y, M, C is 0.8 or more (no problem in practical use)
X: Each density of the solid (solid) image part of Bk and Y, M, and C is less than 0.8 (practical problem)
(Sharpness)
The sharpness of the image was evaluated by squeezing the characters in both low temperature and low humidity (10 ° C., 20% RH) and high temperature, high humidity (30 ° C., 80% RH) environments. 3-point and 5-point character images were formed and evaluated according to the following criteria.

◎: 3 points and 5 points are clear and easily readable ○: 3 points are partially unreadable 5 points are clear and easily readable ×: 3 points are almost unreadable Part or all of the image is unreadable Process conditions for a digital copying machine having an intermediate transfer body Image forming line speed L / S: 180 mm / s
Charging condition of the photoconductor (40 mmφ): The potential of the non-image part is detected by a potential sensor and can be feedback controlled. The controllable range is −500 V to −900 V, and the surface of the photoconductor when fully exposed The potential was in the range of −50 to 0V.

Image exposure light: Semiconductor laser (wavelength: 780 nm)
Intermediate transfer member: A seamless belt-like intermediate transfer member 70, a semiconductive resin belt having a volume resistivity of 1 × 10 ⁸ Ω · cm and Rz of 0.9 μm was used.

Primary transfer conditions Primary transfer roller (5Y, 5M, 5C, 5Bk (each 6.05 mmφ) in FIG. 1): Configuration in which elastic rubber is attached to the core: Surface specific resistance 1 × 10 ⁶ Ω, transfer voltage applied Secondary transfer Conditions A belt-like intermediate transfer member 70 as an intermediate transfer member and a backup roller 74 and a secondary transfer roller 5A are disposed so as to sandwich the belt-like intermediate transfer member 70, and the resistance value of the backup roller 74 is 1 × 10 ⁶ Ω. The secondary transfer roller has a resistance value of 1 × 10 ⁶ Ω and constant current control (about 80 μA).

  Fixing is a thermal fixing method using a fixing roller in which a heater is disposed inside the roller.

  The distance Y on the intermediate transfer member from the first contact point between the intermediate transfer member and the photosensitive member to the first contact point with the next photosensitive member was set to 95 mm.

  The outer peripheral length (circumferential length) of the drive roller 71, the guide rollers 72 and 73 and the backup roller 74 for secondary transfer is 31.67 mm (= 95 mm / 3), and the outer peripheral length of the tension roller 76 is 23. .75 mm (= 95 mm / 4).

  The outer peripheral length of the primary transfer roller was 19 mm (= 95 mm / 5).

Cleaning Condition of Photoreceptor Cleaning Blade: A urethane rubber blade (free length: 8 mm) having a JISA hardness of 65 degrees and a rebound resilience of 60 was contacted by a counter method in the rotation direction of the photoreceptor with a contact load of 18 N / m.

Cleaning Condition for Intermediate Transfer Member The cleaning means shown in FIG. 2 was used as the cleaning means 6A.

  Elastic blade 61A: Urethane rubber having a rebound resilience of 35 at a rubber hardness of 75 ° and 23 ° C. was used. The elastic blade 61A has a thickness of 2 mm, a free length of 10 mm, is supported by a support member (swinging arm 61D + holder 61F), and makes an angle with the belt-shaped intermediate transfer body 70 in contact with the intermediate transfer body moving direction in a counter manner. (Angle 16.5 °). The amount of biting into the belt-shaped intermediate transfer member 70 at the tip of the elastic blade 61A was 1.25 mm.

  Metal scraper 61B: SUS304 whose tip was etched was used. The metal scraper 561B has a thickness of 0.15 mm and a free length of 10 mm. The metal scraper 561B is supported by a support member (swinging arm 61D + holder 61f), and an angle formed with the belt-shaped intermediate transfer body 70 is counter-type in the direction of movement of the intermediate transfer body. (Angle 16.5 °). The amount of biting into the belt-shaped intermediate transfer body 70 at the tip of the metal scraper 61B was 1.00 mm. The distance d between the upstream elastic blade 61A and the downstream metal scraper 61B was set to 2 mm.

  The results are shown in Table 3.

  From Table 3 above, the developer group satisfying the requirements of the present invention, that is, at least one of the colored toners used in the developing means of each image forming unit is a fine particle having a number average primary particle size of 0.1 to 1.0 μm. The developer group (Nos. 1 to 7) using toner containing an external additive has achieved good evaluation above the practical range in terms of character dust, transfer omission, intermediate transfer member cleaning properties, image density, and sharpness. On the other hand, in the developer group (No. 8) outside the present invention which does not contain the fine particle external additive having a number average primary particle size of 0.1 to 1.0 μm, the character dust and the intermediate transfer member are cleaned. And sharpness are reduced. Further, in the developer group (No. 9) other than the present invention using the fine particle external additive of 1.2 μm, transfer omission occurs and the sharpness is lowered.

Example 2 (Change of intermediate transfer member cleaning means)
Evaluation of the developer groups 1 and 4 of Example 1 was performed under the condition that the metal scraper of the cleaning means for the intermediate transfer member was removed. Evaluation items, evaluation methods, and evaluation criteria were the same as in Example 1. The evaluation results are shown in Table 4.

  From the results in Table 4, it is found that all the evaluation results are lower than those in Example 1. In particular, the deterioration of the cleaning property of the intermediate transfer member and the sharpness deterioration associated therewith are large. That is, under the condition that the metal scraper is removed from the cleaning means for the intermediate transfer member, the cleaning property of the intermediate transfer member is deteriorated even when a developer group within the scope of the present invention is used, and sufficient image performance cannot be obtained. Found.

1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention. 2 is an example of an intermediate transfer member cleaning unit. FIG. 3 is a layout diagram illustrating a positional relationship among a photosensitive member, a belt-shaped intermediate transfer member, and a primary transfer roller. FIG. 6 is a layout diagram showing a positional relationship among a backup roller, a belt-shaped intermediate transfer member, and a secondary transfer roller.

Explanation of symbols

1Y, 1M, 1C, 1Bk photoconductor 2Y, 2M, 2C, 2Bk charging means 3Y, 3M, 3C, 3Bk exposure means 4Y, 4M, 4C, 4Bk developing means 5A secondary transfer roller (secondary transfer means)
5Y, 5M, 5C, 5Bk Primary transfer roller (primary transfer means)
6Y, 6M, 6C, 6Bk Photoconductor cleaning means 7 Belt-shaped intermediate transfer body unit 10Y, 10M, 10C, 10Bk Image forming unit (image forming unit)
6A Cleaning means for intermediate transfer member 70 Belt-shaped intermediate transfer member

Claims (17)

A plurality of image forming units having at least an electrophotographic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged, and a toner whose color is changed is used for the developing unit for each of the plurality of image forming units. The colored toner images formed on the electrophotographic photosensitive member are sequentially superimposed and transferred onto the intermediate transfer member to form a color toner image, and the color toner image is collectively re-transferred onto the recording material, In an image forming apparatus for fixing a retransferred color toner image to form a color image, at least one of the colored toners used in the developing means of the plurality of image forming units has a number average primary particle size of 0.1 to 0.1. A cleaning means for an intermediate transfer member that contains a 1.0 μm fine particle external additive and removes transfer residual toner remaining on the intermediate transfer member with a plurality of cleaning blades. An image forming apparatus comprising and. A plurality of image forming units are four image forming units, and an image forming unit having a black toner, an image forming unit having a yellow toner, and an image forming unit having a magenta color toner as developing means of each image forming unit The image forming apparatus according to claim 1, further comprising an image forming unit having cyan toner. The image forming apparatus according to claim 2, wherein the fine particle external additive having a number average primary particle size of 0.1 to 1.0 μm is contained in a black toner. 3. The fine particle external additive having a number average primary particle size of 0.1 to 1.0 μm is contained in at least one of a yellow toner, a magenta toner, and a cyan toner. The image forming apparatus described. The black toner, yellow toner, magenta toner, and cyan toner contain a fine particle external additive having a number average primary particle size of 5 to 49 nm. The image forming apparatus described in 1. The image forming apparatus according to claim 1, wherein each of the colored toners is a polymerized toner. The image forming apparatus according to claim 1, wherein the number average particle diameter of each of the colored toners is 3.0 to 8.0 μm. The image forming apparatus according to claim 1, wherein at least one of the plurality of cleaning blades is a non-deformable member. The image forming apparatus according to claim 8, wherein the non-deformable member is formed of a metallic scraper. The image forming apparatus according to claim 1, wherein at least one of the plurality of cleaning blades is an elastic blade. The image forming apparatus according to claim 10, wherein the elastic blade is a urethane rubber blade. The image forming apparatus according to claim 1, wherein a contact angle of water on the surface of the electrophotographic photosensitive member is 90 ° or more. The image forming apparatus according to claim 1, wherein a surface layer of the electrophotographic photosensitive member contains fluororesin particles. The image forming apparatus according to claim 1, wherein the surface layer of the electrophotographic photosensitive member contains an antioxidant. The image forming apparatus according to claim 1, wherein the intermediate transfer member is a belt-shaped intermediate transfer member. A plurality of image forming units having at least an electrophotographic photosensitive member, a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit are arranged, and a toner whose color is changed is used for the developing unit for each of the plurality of image forming units. The colored toner images formed on the electrophotographic photosensitive member are sequentially superimposed and transferred onto the intermediate transfer member to form a color toner image, and the color toner image is collectively re-transferred onto the recording material, In an image forming apparatus for fixing a retransferred color toner image to form a color image, at least one of the colored toners used in the developing means of the plurality of image forming units has a number average primary particle size of 0.1 to 0.1. An intermediate transfer agent containing 1.0 μm and a fine particle external additive having a number average primary particle size of 5 to 49 nm, and removing residual toner remaining on the intermediate transfer member with a plurality of cleaning blades. An image forming apparatus characterized by having a-body cleaning means. An image forming method, comprising: forming an electrophotographic image using the image forming apparatus according to claim 1.

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