JP2005091832A - Development apparatus and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development apparatus for obtaining a stable image quality over a long period by suppressing an image-density irregularity and a degradation in image density regardless of a use state on an image area and multi-sheet continuous output, and also to provide an image forming apparatus using it. <P>SOLUTION: In the development apparatus using a two-component developer consisting of toner and a magnetic carrier, an electrification amount of the developer 3 is 30 (-μC/g) to 60 (-μC/g), a ratio (Dv/Dn) of a weight average particle diameter Dv and a number average particle diameter Dn of the toner is 1.20 or less, a relation of a peripheral speed Vs of a development sleeve 54 and a peripheral speed Vk of agitating members 55 and 56 is Vk>Vs, 100 (mm/s)<Vs and Vk<400 (mm/s), and a carrying amount of the developer per unit area on the development sleeve 54 just after regulation by a developer regulation member is 30 (mg/cm<SP>2</SP>) to 80 (mg/cm<SP>2</SP>). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device using a two-component developer containing toner and a magnetic carrier, and an image forming apparatus using the developing device.

  Conventionally, developing devices using a two-component developer containing toner and a magnetic carrier have been widely used. This developing device carries a two-component developer on a developer carrying member and conveys it to a region facing an image carrier such as a photosensitive drum. Then, while applying an alternating electric field between the image carrier and the developer carrier, the electrostatic latent image formed on the image carrier is developed and visualized according to the image information.

  In the magnetic brush developing method used in the above developing device, the developer carrying member has a plurality of magnets as magnetic field generating means inside thereof, and the two-component developer is so-called magnetic on the surface of the developer carrying member by the magnetic force. Transport while directly supporting as a brush. Then, development is performed by bringing the magnetic brush into contact with or close to the surface of the latent image carrier. For example, the development is performed by repeatedly performing transition and reverse transition from the developer carrier side to the image carrier side between the developer carrier and the image carrier to which an alternating electric field is continuously applied.

  In addition, the developing device includes a developer container that stores a two-component developer obtained by mixing toner and a magnetic carrier. The mixing ratio of the toner and the magnetic carrier in the two-component developer in the developing container changes as the toner is consumed by development. Specifically, the toner density, which is the ratio of the toner weight for the total weight, is reduced. For this reason, normally, toner corresponding to the amount of consumption is supplied from the toner tank containing the toner into the developer accommodating portion, and the toner concentration of the two-component developer accommodated in the developer accommodating portion is reduced. It is kept almost constant.

  This maintenance of toner density is very important for image stabilization, and various methods have been proposed as toner density detection means and maintenance means. For example, a detection unit provided around the image carrier such as a photosensitive drum irradiates the developed toner image on the image carrier with light, detects the toner density from the transmitted light or reflected light, and adjusts the toner replenishment amount. There is a method. There is also a method in which toner density is detected from reflected light when light is irradiated to the developer carried on the developer carrying member by a detecting means provided near the developer carrying member such as a developing sleeve. There is also a method of detecting the toner density by detecting a change in the apparent permeability of the developer in a certain volume near the sensor provided in the developing container by using the inductance of the coil.

  On the other hand, in recent years, colorization of an electrophotographic system has progressed, and the demand for high image quality and high reproducibility has increased. For full-color electrophotographic toner, toners colored yellow, magenta, and cyan are used. Black toner is also used as necessary. Further, in order to obtain a high resolving power and a clear image, it is desirable that the toner has a small particle size. However, as the particle size of the toner is reduced, the surface area per unit weight increases and the charge amount of the agent tends to be too high, and a blurred image is likely to occur due to a decrease in image density. In addition, so-called carrier contamination that causes the carrier to be contaminated due to excessive toner adhering to the carrier is likely to occur, and a side effect of reducing the life of the developer is likely to occur. In particular, when a large number of images are output by an electrophotographic apparatus using a two-component developer, fogging and background smearing may occur, or an edge-enhanced image may be formed with a blurred image, resulting in gradation and The image will be poor in clarity. There is a concern that these are fatal defects particularly in color images.

  In general, when a black and white image is output, the image area is 10% or less. However, when a color image is output, a solid image having continuous tone characteristics is often used, and the image area is increased. It is said to be over 20%. When a large number of images with a large image area are output in succession, a clear and good image can be obtained in the initial stage, but toner replenishment cannot catch up, and there is a high possibility that the image quality will be deteriorated due to a decrease in image density or blurring. Become. Further, as the toner has a smaller particle size, it becomes more difficult to ensure the stability of the charge amount of the agent and the toner concentration, and the above-described tendency becomes remarkable. This is considered to be caused mainly by a decrease in the fluidity of the developer accompanying the reduction in the toner particle size. In the developer whose fluidity is lowered at the time of toner replenishment, the replenishment toner hardly adheres to the carrier and a desired charging performance cannot be obtained. The deterioration of the charging performance of the developer not only impairs the image quality due to soiling or the like, but also the toner is supplied to the developer carrier in a state where the toner does not sufficiently adhere to the carrier, so-called toner scattering in which the toner is ejected from the developing portion. Is also likely to occur.

  As a method for improving the developing device itself against the problems of image density reduction and image blurring, the peripheral speed of the developer carrier is increased and the outer diameter of the developer carrier is increased for the purpose of improving the developing ability. It is possible. However, it has been confirmed that when the peripheral speed of the developer carrying member is increased, the stress applied to the developer in the vicinity of the developer regulating means increases and the additive is embedded in the toner surface. Due to such an embedding phenomenon, density unevenness is generated in the solid image portion, and a so-called blurred image is generated. In addition, when the outer diameter of the agent carrier is increased, it is predicted that the cost increases with the increase in the size of the apparatus and the load on the driving unit increases, thereby reducing the life of the apparatus.

  Another side effect associated with a decrease in developer fluidity is a left-right deviation in image density. In particular, in a color image, there is a high possibility that not only the image density deviation but also the color tone will change, leading to a serious defect. Originally, it is ideal that the toner density and the charge amount are the same level at any location on the surface of the agent carrier facing the image carrier. However, when the flowability of the developer is reduced, or when the agent conveyance capability of the stirring member in the developing device is low, the toner concentration tends to decrease from the upstream side to the downstream side in the conveyance direction of the stirring member. Along with this tendency, the toner density on the developer carrier also varies in the longitudinal direction, and the toner density on the agent carrier adjacent to the downstream side in the transport direction of the agitating member decreases, causing a decrease in image density. It becomes like this. With respect to such a problem of toner density deviation, a means for setting the number of rotations of the stirring member to be high can be considered in order to ensure the developer conveyance capability. However, if the number of revolutions of the stirring member is too high, a deviation of the agent occurs in the developer container, and a deviation in the amount carried on the developer carrier occurs, which also adversely affects the image quality.

  In order to improve the fluidity of the developer by reducing the toner particle size, a method of adding a large amount of additive (fluidity imparting agent) can be considered for the purpose of improving the fluidity of the toner. However, if too much additive is added, the surface of the image carrier is likely to be worn, causing a decrease in surface potential and sensitivity of the image carrier, and there is a concern that abnormal images such as background stains and vertical stripes may be generated. Therefore, there is a limit to the amount of additive added.

In the two-component developing device, proposals relating to the developing conditions of the developing device and toners and carriers constituting the developer have been made for the problems described above.
(1) Proposal concerning development conditions of developing device In Patent Document 1, a method is proposed in which the amount of developer staying on the upstream side in the agent transport direction beside the developer regulating member is 1/3 or less of the total amount of developer. Has been. In this proposal, consideration is given to the effect of pressurization on the other developer by the staying developer, the replacement of the staying developer with another developer, and the like. However, the uniformity of the toner concentration in the developer and the developer carrying amount on the downstream side of the developer regulating member are not taken into consideration, and stable image quality cannot be obtained over the intended long term.
Patent Document 2 proposes a developing device in which a wall that covers the upper side of the developer stirring member along the axial direction thereof is provided. In this proposal, the deviation of the developer in the developer accommodating portion is forcibly suppressed, but no substantial improvement is intended. In the place where the deviation of the agent occurs, the developer is locally stressed with the wall, and side effects such as a decrease in the agent life and a decrease in the agent charging performance become apparent. After all, unless the development conditions of the developing device and the fluidity of the developer are taken into consideration, the improvement is not essential.
Further, in Patent Document 3, a first agitating member and a second agitating member provided at a position farther from the image carrier than the first agitating member are provided in the developer accommodating portion, and the upper part of the second agitating member is provided with the first agitating member. A developing device has been proposed that is made higher than the upper part of the member. In this proposal, the second stirring member is prevented from being buried in the developer, thereby suppressing the deterioration of the stirring performance of the stirring member and stably circulating the developer. However, in the initial image output, the stability of the agent circulation is ensured, but when the bulk density of the developer changes due to changes in usage conditions or usage environments, it cannot be fully handled. It is not an essential improvement.

(2) Proposal regarding toner and carrier constituting developer In Patent Document 4, a method of using a low-fluidity developer having an aggregation degree of 30% or more is proposed. As a result of studies by the present inventor, it has been clarified that a developer having lower fluidity tends to cause a deviation of the agent in the developing device, and an image density deviation is more likely to occur. Further, it has been clarified that the amount of developer carried on the downstream side of the developer regulating member tends to decrease from the initial stage of image output, and a fatal defect becomes apparent in order to obtain stable image quality. It was also confirmed that the lower the developer fluidity, the more difficult the toner density uniformity is to be secured, and the tendency for a blurred image to occur when an image with a large image area such as a solid image is output.
In Patent Document 5, the weight average particle diameter and resistance of the carrier, the weight average particle diameter of the toner and the external additive are defined, and the developer carrier is rotated at a position downstream of the developing region in the rotation direction. A method of providing an electrode plate has been proposed. In this proposal, not only the characteristics of the developer but also the development conditions are stipulated. However, the development conditions are intended to suppress toner scattering and have little effect on the image quality. Further, although the characteristics of the toner and the carrier are defined, the developer in the developer accommodating portion is not taken into consideration, and satisfactory image quality cannot be obtained.
Patent Document 6 proposes a developer using a carrier having a narrow particle size distribution that defines the abundance of fine powder and the abundance of coarse powder. In this proposal, by narrowing the carrier particle size distribution, the fluidity of the developer is improved and the toner density is made uniform. However, the effect is slight. The developer has a configuration in which toner is coated on the carrier surface, and the contribution of the toner particle size distribution is overwhelmingly dominant for the flowability of the developer. For this reason, the effect on image density stabilization does not reach the expected level.

  As described above, none of the proposals can sufficiently secure a stable image quality over a long period of time, and a satisfactory quality improvement effect has not yet been proposed.

Japanese Patent Laid-Open No. 5-188767 Japanese Patent Laid-Open No. 2002-229317 JP 2000-347488 A JP-A-6-274017 JP 7-271133 A Japanese Patent Laid-Open No. 2-281280

  The present invention has been made in view of the above problems. The object is to develop a developing device capable of suppressing image density unevenness and a decrease in image density and obtaining stable image quality over a long period of time regardless of the use situation such as whether the image area or the continuous output of a large number of sheets. It is an object of the present invention to provide an image forming apparatus using the above.

In order to achieve the above object, an invention according to claim 1 is directed to an image carrier, a developer container that contains a two-component developer composed of a toner and a magnetic carrier, and a static image formed on the image carrier. In order to develop the electrostatic latent image into a visible image, a developer carrier that carries the developer supplied from the developer container on the surface by a built-in magnetic field generation unit, and a developer carrier that is carried on the developer carrier. A developer regulating member that regulates the amount of developer transported and conveyed, toner concentration detecting means for detecting the toner concentration of the developer in the developer accommodating portion, and stirring for agitating the developer in the developer accommodating portion In the developing device including the member, the charge amount of the developer is 30 (−μC / g) or more and 60 (−μC / g) or less, and the ratio of the weight average particle diameter Dv to the number average particle diameter Dn ( Dv / Dn) is 1.20 or less, and the peripheral speed of the developer carrying member The relationship between the degree Vs and the peripheral speed Vk of the stirring member is Vk> Vs, 100 (mm / s) <Vs, Vk <400 (mm / s), and the developer carrying immediately after regulation by the developer regulating member The developer carrying amount per unit area on the body is 30 (mg / cm ² ) or more and 80 (mg / cm ² ) or less.
According to a second aspect of the present invention, in the developing device of the first aspect, the developer has a toner concentration of 5.0 (wt%) or more and 9.0 (wt%) or less. .
According to a third aspect of the present invention, in the developing device of the first or second aspect, the toner has a weight average particle diameter of 4.5 (μm) or more and 8.0 (μm) or less, and the magnetic carrier has a weight average. A particle size of 30 (μm) or more and 60 (μm) or less is used.
According to a fourth aspect of the present invention, in the developing device of the first, second, or third aspect, the toner includes a toner particle having a toner particle diameter of 3 (μm) or less and a particle number ratio of 5% or less. It is a feature.
According to a fifth aspect of the present invention, in the developing device according to the first, second, third, or fourth aspect, as the developer, a toner and a carrier are stirred and mixed for 10 minutes under conditions of normal temperature and humidity and a toner concentration of 5% or less. If the charge amount Q ₂₀ obtained when stirring and mixing for 20 seconds under the same conditions with respect to the charge amount Q ₆₀₀ obtained sometimes, the charge calculated as Z (%) = (Q ₂₀ / Q ₆₀₀ ) × 100 A toner and a carrier with a rising ratio Z (%) of 70 (%) or more are used.
According to a sixth aspect of the present invention, in the developing device of the first aspect, the relationship between the peripheral speed Vs of the developer carrier and the peripheral speed Vp of the image carrier is 1.5 ≦ (Vs / Vp) ≦ 2.5. It is characterized by satisfying the relationship.
According to a seventh aspect of the present invention, there is provided an image carrier that carries a latent image, latent image forming means that forms a latent image on the surface of the image carrier, and development that develops the latent image formed on the surface of the image carrier. In the image forming apparatus having the above-described means, the developing device according to claim 1, 2, 3, 4, 5, or 6 is used as the developing means.

In the two-component developing device, the toner in the developer is consumed by the image output, and the cycle is repeated in which the toner is replenished into the developing container and the image is further output according to the consumption amount. In such a two-component developing device, it is important that the toner is uniformly adhered to the surface of the carrier in a short time and the developer is uniformly mixed during toner replenishment. It is important to secure a predetermined amount of toner on the developer carrier and to supply toner faithfully to the latent image on the image carrier. Therefore, the present inventors pay attention to the following characteristics (1), (2), (3), and (4) and define them, and if any of these characteristics is out of the definition, It was found that the improvement effect cannot be obtained.
(1) Regarding the charging characteristics of the developer The charge amount of the developer is 30 to 60 (-μC / g). In a developer having a charge amount higher than 60 (−μC / g), in order to obtain a desired image density, it is necessary to further increase the electric field formed between the developer carrier and the image carrier. When such a large electric field is formed, the tendency of the carrier to move to the image carrier becomes obvious, and when the toner image is electrostatically transferred to the transfer material, the carrier is also transferred, and a blank portion is generated on the image. This increases the possibility of an abnormal image. In addition, the adhesion force between the toner and the carrier is too strong, which adversely impairs the fluidity of the developer and acts in a disadvantageous direction for ensuring the uniformity of the toner concentration. On the other hand, when the charge amount is lower than 30 (-μC / g), the adhesion between the toner and the carrier is too weak, and a background stain that stains the non-image area with the toner tends to occur. Further, in the case of a system that controls the toner density using a toner density sensor that detects a change in the permeability of the developer, if the charge amount is low, the toner density is detected to be lower than the actual toner density. Tend to be. In this case, the possibility of inducing toner scattering is increased.
(2) Uniformity of toner particle size distribution The ratio Dv / Dn between the weight average particle diameter Dv and the number average particle diameter Dn of the toner is 1.20 or less. In order for the developer concentration to be uniform, i.e., to have the same toner concentration in the entire region of the developer, it is required that the toner particle size distribution be uniform. That is, it is desirable that the weight average and number average particle diameter ratio Dv / Dn of the toner is close to 1, and the toner density uniformity can be obtained by setting it to 1.20 or less.
(3) Regarding the stirring state of the developer in the developer container, the relationship between the peripheral speed Vs of the developer carrier and the peripheral speed Vk of the stirring member is Vk> Vs, 100 (mm / s) <Vs, Vk <400. (Mm / s). Here, the peripheral speeds Vs and Vk of the developer carrying member and the stirring member can be calculated from the respective rotation speeds and outer diameters. As the stirring member, for example, a screw member or a blade member can be used. In order to uniformly mix the toner and the carrier in a short time, it is necessary to set the stirring member to an appropriate condition. At that time, the relationship between the peripheral speed of the developer carrier and the peripheral speed of the stirring member is an important factor. First, the peripheral speed of the stirring member needs to be set larger than the peripheral speed of the developer carrier. When the peripheral speed of the agitating member is smaller than the peripheral speed of the developer carrying member, the toner supply to the developer carrying member cannot catch up. Then, by setting the peripheral speed of the stirring member to 100 (mm / s) or more, the replenished toner starts to adhere to the carrier at a short distance from the point where it reaches the developer, and is uniformly mixed in a short time. Is obtained. However, when the peripheral speed of the stirring member exceeds 400 (mm / s), excessive stirring stress is applied to the developer, and carrier contamination and agent deterioration are promoted. Furthermore, the phenomenon that the additive is buried in the toner has become apparent, the fluidity of the developer is lowered, and further the deviation of the agent occurs. There is a risk.
(4) About the developer carrying amount on the developer carrying member The carrying amount of the developer per unit area on the developer carrying member immediately after regulation by the developer regulating member is 30 to 80 (mg / cm ² ). When the carrying amount is less than 30 (mg / cm ² ), it is necessary to increase the electric field applied between the developer carrying member and the image carrying member, which is disadvantageous for carrier adhesion. Further, when the carrying amount is more than 80 (mg / cm ² ), the agent dropping is more likely to occur on the downstream side of the developer carrying member in the developer conveying direction than the developer regulating member. Further, in the space between the image carrier and the developer carrier, the developer filling density tends to increase, and the fluidity of the developer in this space tends to decrease. Along with this decrease in fluidity, toner is not smoothly supplied to the electrostatic latent image on the image carrier, and image density reduction and density unevenness tend to occur.
As described above, by defining the developer charging characteristics, the toner particle size distribution, the agitation state in the developer container, and the developer carrying amount on the developer carrying member within the above ranges, a high area image can be obtained. The quality improvement effect is remarkable even when is continuously output. That is, when a large area image is output, toner is replenished more actively than when a low area image is output. However, with the present invention, the developer after toner replenishment is contaminated with carriers. And uniform mixing in a short time. In addition, it is possible to supply toner uniformly at any location on the developer carrier, and it is possible to develop the toner faithfully with respect to the latent image on the image carrier. As a result, the replenishment toner can be uniformly supplied onto the developer carrier in a short time, and even when a large area image is continuously output, density unevenness and density reduction are suppressed, and stable image quality can be obtained over a long period of time. Can be secured. Further, according to the present invention, even if the charge amount of the developer in the developer accommodating portion varies depending on the usage environment such as temperature and humidity, the density variation is suppressed and stable image quality is ensured over a long period of time. Can do.

  In the present invention, the toner concentration of the developer is preferably in the range of 5.0 to 9.0 (wt%). When the toner concentration is lower than 5.0 (wt%), the charge amount Q / M of the developer increases, and an alternating electric field for developing the electrostatic latent image on the image carrier is applied higher. There is a need. In this case, so-called carrier adhesion also occurs, which may impair image quality. Furthermore, when the charge amount Q / M of the developer is too high, the image density is lowered. Further, when the toner concentration is higher than 9.0 (wt%), toner scattering is likely to occur, and as the level of toner scattering deteriorates, so-called background soiling occurs in which the image background is soiled with toner. Incurs quality degradation.

  In the present invention, the toner preferably has a weight average particle diameter of 4.5 to 8.0 (μm) and the carrier has a weight average particle diameter of 30 to 60 (μm). The reduction in toner particle size is indispensable for increasing the resolution, but as a side effect, fluidity and storage stability tend to deteriorate. When the toner particle size is less than 4.5 (μm), the fluidity of the developer is extremely deteriorated, and it is difficult to ensure a uniform toner concentration in the developer. Further, the reduction in the toner particle diameter is a direction in which the coverage with respect to the carrier increases. When the coverage is excessively high, there is a concern that the carrier contamination is accelerated and the toner is scattered. This mechanism is also applied to the carrier, and the reduction in the particle size of the carrier causes a decrease in fluidity as in the case of the toner, and carrier adhesion occurs particularly when the weight average particle size is less than 30 (μm). Further, when the carrier is increased in particle size, the carrier coverage is increased and there is still a problem. That is, by setting the weight average particle diameter of the toner to 4.5 to 8.0 (μm) and the weight average particle diameter of the carrier to 30 to 60 (μm), the resolution can be improved in addition to the stability of the image density. And higher quality images can be obtained.

  In the present invention, the ratio of the number of particles of 3 (μm) or less in the toner particle size distribution is desirably 5% or less. The effect of improving the quality in the fluidity and storage stability is remarkable, and a good level is obtained in the toner replenishment property and the toner charge rising property in the developing device.

  In the present invention, it is desirable that the charge rising ratio of the developer is 70% or more. The charge rising characteristic of the developer is an important characteristic for how efficiently the replenished toner adheres uniformly to the carrier to form a uniform mixed state. In particular, the excellent charge rise characteristic means that the electrostatic force and van der Waals force act on the carrier in a short time and a desired charge amount can be obtained. Therefore, by using a developer having a charge rising ratio of 70% or more, the effect of suppressing toner scattering and background contamination is great.

  In the present invention, it is more desirable that the peripheral speed (Vs / Vp) of the image carrier relative to the peripheral speed of the developer carrier is in the range of 1.5 to 2.5. Therefore, it is possible to obtain a high quality image. When Vs / Vp is lower than 1.5, the developer passing time through the electrostatic latent image is shortened, so that the developing ability is reduced and an image having a large area is output. The decrease in image density becomes remarkable. Further, it is known that when Vs / Vp is higher than 2.5, that is, when the contact time between the developer and the electrostatic latent image is increased, an abnormal image is generated. The abnormal image referred to here is a decrease in image density at the rear end of the solid image portion, image omission, particularly image omission that is noticeable at the rear end of the halftone image, and image density at the boundary between the solid image and the halftone image. It means change. All of these appear at locations where the latent image potentials are different and at the boundary portions of the image density where the latent image potentials change rapidly and discontinuously. In other words, the toner in the developer moves while the developer passes through the development nip, and a transient phenomenon occurs when a developer layer having a capacitance as a derivative passes through different discontinuous development electric fields. It is thought to be caused. Therefore, it is possible to obtain a high-quality image by adjusting the peripheral speed (Vs / Vp) of the image carrier relative to the peripheral speed of the developer carrier to be in the range of 1.5 to 2.5. It becomes.

  According to the present invention, a developing device capable of suppressing density unevenness and density reduction and obtaining stable image quality over a long period of time regardless of usage conditions such as image area and whether or not a large number of sheets are continuously output, and image formation using the same There is an excellent effect that an apparatus can be provided.

  Hereinafter, embodiments of a developing device to which the invention is applied and an image forming apparatus including the developing device will be described. FIG. 1 shows an electrophotographic full-color printer as an image forming apparatus according to the present invention. In FIG. 1, in the apparatus main body 1, there are photoconductor units 2Y, 2M, 2C, and 2K for forming images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K). The developing devices 3Y, 3M, 3C, and 3K are detachably mounted. Here, the subscripts Y, M, C, and K of the respective symbols indicate members for yellow, magenta, cyan, and black, respectively. The photoreceptor units 2Y, 2M, 2C, and 2K include drum-shaped photoreceptors 4Y, 4M, 4C, and 4K as image carriers. The developing devices 3Y, 3M, 3C, and 3K apply yellow toner (Y), magenta toner (M), cyan toner (C), and black toner (K) to the electrostatic latent images on the photoreceptors 4Y, 4M, 4C, and 4K. ) Supply and develop each electrostatic latent image. Further, below the photosensitive unit 2, a transfer belt 5 to which a toner image formed by each photosensitive unit 2 is transferred is disposed obliquely in the diagonal direction of the apparatus main body 1. The transfer belt 5 is provided around a plurality of rollers to which a rotational driving force is transmitted so as to be rotationally driven in a direction indicated by an arrow A. Further, a writing device 6 as a latent image forming unit for irradiating each photoconductor 4 with laser light and forming a latent image on each photoconductor 4 is disposed above the photoconductor unit 2. A fixing device 7 for fixing the toner image transferred onto the transfer material P is disposed in the apparatus main body 1 at a position downstream of the transfer belt 5 in the transfer material moving direction. Here, the photoreceptor units 2Y, 2M, 2C, and 2K are arranged in this order from the upstream side in the transfer material moving direction. As the photoconductors 4Y, 4M, 4C, and 4K, belt-like photoconductors or the like may be used.

  Further, below the apparatus main body 1, paper feed units 8 and 9 that can store transfer materials P of different sizes are disposed. A manual feed tray 10 that can be manually fed from the outside is disposed at the right end of the apparatus main body 1 in FIG. A duplex unit 11 serving as a transfer path for the transfer material is disposed at the center of the apparatus main body 1. On the left side of the apparatus main body 1, a reversing unit 12 and a reversing conveyance path 13 that are also used as a conveyance path for a transfer material are branched. A paper discharge tray 14 is disposed at the top of the apparatus main body 1.

  Since the photoconductor units 2Y, 2M, 2C, and 2K have the same configuration except for the portion arranged in the apparatus main body 1, the photoconductor unit 2Y will be described, and the photoconductor units 2M, 2C, and 2K are configured. Description of is omitted. FIG. 2 is a schematic configuration diagram of the photoreceptor unit. As shown in FIG. 2, the photosensitive unit 2Y is a unit comprising a photosensitive member 4Y, a charging roller 15Y that contacts the photosensitive member, and a cleaning device 16Y. The photosensitive unit 2Y is detachably attached to the apparatus main body 1. It has been. The cleaning device 16Y cleans the toner remaining on the surface of the photoreceptor 4Y with the brush roller 17Y and the cleaning blade 18Y.

  The writing device 6 is configured to irradiate the surface of each photoconductor 4 while scanning with laser light based on image data. FIG. 3 is a schematic configuration diagram of the writing device. As shown in FIG. 3, the writing device 6 includes a light source (not shown), rotary polygon mirrors 20 and 21, f-θ lenses 23 and 32, a reflection mirror, and the like. Two rotary polygon mirrors 20 and 21 arranged on the same axis are rotated by a polygon motor 22 and modulated by Y, M, C, and K image data from laser diodes as two light sources. , K laser light is distributed to the left and right and reflected.

  Specifically, the Y laser light and the M laser light from the rotary polygon mirrors 20 and 21 pass through the two layers of the fθ lens 23. The Y laser light from the fθ lens 23 is reflected by the mirror 24, passes through the long WTL 25, and then irradiates the photoreceptor 4Y of the photoreceptor unit 2Y via the mirrors 26 and 27. The M laser light from the fθ lens 23 is reflected by the mirror 28, passes through the long WTL 29, and then is reflected by the photoconductor 4M of the photoconductor unit 2M via the mirrors 30 and 31. The C laser light and the K laser light from the rotary polygon mirrors 20 and 21 pass through the two layers of the fθ lens 32. The C laser light from the fθ lens 32 is reflected by the mirror 33, passes through the long WTL 34, and then irradiates the photoreceptor 4C of the photoreceptor unit 2C through the mirrors 35 and 36. The K laser light from the fθ lens 32 is reflected by the mirror 37 and passes through the long WTL 38, and then is irradiated to the photoconductor 4K of the photoconductor unit 2K through the mirrors 39 and 40.

  In the printer configured as described above, when image formation is instructed by an operation unit (not shown), the photoconductors 4Y, 4M, 4C, and 4K in FIG. 1 are rotated by a drive source (not shown) to rotate clockwise. . The charging rollers 15 (Y, M, C, K) of the photoconductor unit 2 (Y, M, C, K) are applied with a charging bias from a power source (not shown), and the photoconductor 4 (Y, M, C, K). ) Are uniformly charged. The photoreceptor 4 (Y, M, C, K) is uniformly charged by the charging roller 15 (Y, M, C, K), respectively, and then the Y, M, C, K color of each color is written by the writing device 6. An electrostatic latent image is formed on each surface by exposure with laser light modulated with image data. The electrostatic latent images on these photoconductors 4 (Y, M, C, K) are developed by the developing device 3 (Y, M, C, K), and Y, M, C, K toner images are obtained. Become.

  One transfer material is separated from the selected one of the paper feed cassettes 8 and 9 by paper feed rollers 41 and 42, and the resist disposed on the paper feed side with respect to the photosensitive unit 2Y. Paper is fed to the roller 43. In the printer having the above-described configuration, the manual feed tray 9 is disposed on the right side portion of the apparatus main body 1, and the transfer material can be fed from the manual feed tray 9 to the registration roller 43. The registration roller 43 sends each transfer material onto the transfer belt 5 at a timing when the leading edge of each transfer material coincides with the toner image on the photoreceptors 4Y, 4M, 4C, and 4K. The transferred transfer material is electrostatically attracted to the transfer belt 5 charged by the paper suction roller 43 and conveyed to each transfer unit.

  When the transfer material conveyed by the transfer belt 5 passes through each transfer portion in turn, the transfer brushes 44, 45, 46, 47 use Y, M, C, K on the photoreceptors 4Y, 4M, 4C, 4K. The toner images of each color are sequentially superimposed and transferred. The full color toner image is fixed by the fixing device 7 on the transfer material on which the four-color full color toner image is formed. The transfer material that has passed through the fixing device 7 is discharged to the discharge tray 14 through a predetermined transport path of the reversing unit 11, the duplex unit 12, and the reverse transport path 13 according to the designated mode.

  The above-described image forming operation is an operation when the full-color mode for superimposing four colors is selected by an operation unit (not shown). When the three-color superposition full-color mode is selected by the operation unit, the formation of the K toner image is omitted, and a full-color image is formed on the transfer material by superposing the Y, M, and C three-color toner images. When the monochrome image forming mode is selected on the operation unit, only the K toner image is formed and a monochrome image is formed on the transfer material.

  Next, the developing device 3 will be described. Since the developing devices 3Y, 3M, 3C, and 3K have the same configuration except that the toner colors are different, the configuration of the developing device 3Y will be described as a representative. FIG. 4 is a configuration diagram illustrating a schematic configuration of the developing device. FIG. 5 is a plan view showing the configuration of the developing device. As shown in FIGS. 4 and 5, the developing device 3Y accommodates a two-component developer having Y toner and a carrier in a developing case 53 serving as a developer accommodating portion. Further, in the developing case 53, a developing sleeve 54 as a developer carrying member disposed so as to face the photoconductor 4Y through the opening 53a of the developing case 53, and stirring for conveying the developer while stirring the developer. Screw members 55 and 56 as members are provided.

  The developing case 53 is divided by a partition wall 57 into a first space portion 65 located on the developer supply side to the photoreceptor 4Y and a second space portion 64 side receiving supply of replenishing toner from the supply port 62. It is divided. The screw member 56 is disposed in the space portion 65, and the screw member 55 is disposed in the space portion 64, and is rotatably supported by a bearing member (not shown) provided in the developing case 53. Of course, the developing sleeve 54 is also rotatably supported by the developing case 53 via a bearing member (not shown). The developing sleeve 54 rotates when a rotational driving force is transmitted from a driving unit (not shown).

  As shown in FIG. 5, the screw members 55 and 56 extend in the width direction of the transfer material and are arranged in parallel to each other. One ends of the screw members 55 and 56 are mounted so as to mesh with the gears 66 and 68 having the same number of teeth. In this embodiment, the rotational driving force from the drive motor 69 is transmitted to the gear 66, so that the screw members 55 and 56 are rotationally driven in directions opposite to each other. In FIG. 5, the screw member 55 rotates in a direction to convey the developer from left to right, and the screw member 56 rotates in a direction to convey the developer from right to left.

  Between the one end of the partition wall 57 and the inner side surface of the developing case 53, a delivery portion 58 for feeding the developer from the space portion 65 to the space portion 64 is formed. Between the other end of the partition wall 57 and the inner surface of the developing case 53, a delivery portion 59 for sending the developer from the space portion 64 to the space portion 65 is formed. The width W of the delivery part 58 is formed to be narrower than the width W1 of the delivery part 59. The end portion of the developing case 53 where the transfer portion 58 is formed protrudes outward from the image forming area L of the photosensitive member 4 formed between both end faces of the developing sleeve 54, and the transferring portion 59 is the image forming area L. It is formed so that it may be located outside.

  The developing case 53 is equipped with a toner concentration sensor 63 as toner concentration detecting means for detecting and outputting the toner concentration in the developer. As shown in FIG. 4, the toner density sensor 63 has a detection surface facing the inside of the space 65, and is disposed closer to the transfer unit 58 than the transfer unit 59 with respect to the center line of the image forming region L. ing.

  The operation of the developing device 5Y having such a configuration will be described with respect to developer conveyance. When the screw members 55 and 56 rotate at a constant speed, the two-component developer in the developing case 53 is conveyed from the left to the right in FIG. 5 while being stirred, and is a space in which the conveying screw 56 is disposed from the transfer unit 59. Sent to part 65. The two-component developer sent from the transfer section 59 to the space section 65 is stirred by the transport screw 56 and simultaneously transported to the left in FIG. 5, and then sent from the transfer section 58 to the space section 64 side, and again. While being agitated by the conveying screw 55, it is conveyed rightward. By transporting the developer while stirring, the Y toner and the carrier are frictionally charged by stirring while the developer circulates in the developing device 3Y.

  The conveying screw 56 supplies a part of the developer to the developing sleeve 54, and the developing sleeve 54 carries the developer magnetically and conveys it. As shown in FIG. 5, the developer on the developing sleeve 54 is regulated in height (carrying amount) by a developer regulating member 61 arranged in the developing case 53. The electrostatic latent image on the photoreceptor 4Y is developed with Y toner on the developing sleeve 54 to become a Y toner image. When the toner concentration of the developer in the developing case 53 reaches a predetermined value, Y toner is supplied from the toner supply port 62 to the space 64 side in the developing case 53. The Y toner is mixed with the developer by stirring by the screw member 55.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Here, the part is based on weight. The main characteristics of each example and comparative example are summarized in Table 13 at the end, and the results of evaluation are summarized in Table 14.

[Example 1]
* Example of toner production (master batch pigment component)
Pigment Quinacridone-based magenta pigment (CI Pigment Red122) 50 parts Binder resin Epoxy resin 50 parts Water 30 parts The above raw materials were mixed in a Henschel mixer to obtain a mixture in which pigment aggregates were soaked with water. This was kneaded for 45 minutes with two rolls set at a roll surface temperature of 130 ° C. to obtain a master batch pigment A. Next, using this master batch pigment A, a toner was prepared by the following method.
(Toner component)
Binder resin Epoxy resin (R-304, Mitsui Chemicals) 100 parts Colorant Masterbatch pigment A 13 parts Charge control agent Zinc salicylate (Bontron E84, Orient Chemistry) The kneaded product was melt-kneaded and finely pulverized so as to have an average particle diameter of 12 μm by a jet mill pulverizer equipped with a flat plate-type collision plate in the pulverization part. This was subjected to surface treatment using a turbo mill connected to a DS type airflow classifier, and the average particle size was 11.5 μm. Furthermore, fine powder classification was performed to obtain fine particles having a weight average particle diameter of 12.1 μm and a particle number ratio of 3 μm or less of 0%. To 20 kg of the fine particles, 100 g of hydrophobic silica fine particles having an average particle diameter of 0.3 μm and 100 g of hydrophobic titanium oxide fine particles having an average particle diameter of 0.3 μm were added and stirred to obtain a magenta electrophotographic toner. .
* Carrier Production Example Silicone resin (SR2411 manufactured by Toray Dow Corning Silicone) was diluted to obtain a silicone resin solution (solid content: 5%). Using a fluidized bed coating apparatus, the silicon resin solution is applied at a rate of about 40 g / min in an atmosphere of 100 ° C. on the surface of 5 kg of carrier core material particles (MnMgSr ferrite) having a weight average particle diameter of 70 μm. did. Further, this was heated at 240 ° C. for 2 hours to obtain a carrier A having a true specific gravity of 5.0 g / cm ³ .

A developer having a toner concentration of TC 4.5 wt% was prepared using the color toner and carrier obtained by the above method, and an IPSiO color 8100 machine manufactured by Ricoh was modified to the development conditions shown in Table 1 to output an image. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V, and this is set as a reference value. A high area image having an image area of 20% was output while maintaining this reference value. The toner density transition, toner scattering, and image quality were evaluated for 20000 sheets.

[Example 2]
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 1 above had a weight average particle diameter of 8.4 μm and a particle number ratio of 3 μm or less adjusted to 2%. Then, using the same carrier A as in Example 1, an image was output under the same development conditions as in Example 1 for evaluation.

Example 3
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 1 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 15%. Further, the carrier B obtained by the same method as in Example 1 was used except that carrier core particles (MnMgSr ferrite) having a weight average particle diameter of 35 μm were used as the carrier, and image output was performed under the same development conditions as in Example 1. And evaluated.

Example 4
* Production Example of Polymerized Toner 710 g of ion-exchanged water was charged with 450 g of a 0.1 M Na ₃ PO ₃ aqueous solution, heated to 60 ° C., and then 12000 rpm using a TK homomixer (manufactured by Special Machine Industries). Was stirred. To this, 68 g of 1.0M CaCl ₃ aqueous solution was gradually added to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .
(Toner component)
170g of styrene
30g of n-butyl acrylate
Quinacridone magenta pigment 10g
Di-t-butylsalicylic acid metal compound 2g
Polyester resin 10g
The above formulation was heated to 60 ° C., and uniformly dissolved and dispersed at 12000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo). In this, 10 g of polymerization initiators 2,2′-azobis (2,4-dimethylvaleronitrile) were dissolved to prepare a polymerizable monomer composition. The polymerizable monomer composition is charged into the aqueous medium and stirred at 10,000 rpm for 20 minutes in a TK homomixer at 60 ° C. in an N ₂ atmosphere to granulate the polymerizable monomer composition. did. Then, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C. and reacted for 10 hours. After completion of the polymerization reaction, a part of the aqueous medium is distilled off under reduced pressure and cooled, and after adding hydrochloric acid to dissolve calcium phosphate, filtration, washing and drying are performed, and the weight average particle size is 8.2 μm, 3 μm or less. Colored suspension particles having a particle number ratio of 2% were obtained. To 20 kg of the fine particles, 100 g of hydrophobic silica fine particles having an average particle diameter of 0.3 μm and 100 g of hydrophobic titanium fine particles having an average particle diameter of 0.3 μm were added and stirred to obtain a magenta electrophotographic toner. Then, using the same carrier A as in Example 1, an image was output under the same development conditions as in Example 1 for evaluation.

Example 5
Carrier C was obtained in the same manner as in Example 1, except that carrier core particles (MnMgSr ferrite) having a weight average particle diameter of 50 μm were used for the carrier. Then, using the same magenta toner as in Example 2, the developer was adjusted under the same conditions as in Example 1, and an image was output under the same development conditions as in Example 1 for evaluation.

Example 6
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 4 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 13%. A developer having a toner concentration of TC 7.0 wt% was prepared using the same carrier B as in Example 3, and an image was output by modifying a Ricoh IPSiO color 8100 machine. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 2.50 V and set as a reference value. While maintaining this reference value, an image having an image area of 20% was output and evaluated.

Example 7
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 4 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 13%. A developer having a toner concentration of TC 7.0 wt% was prepared using the same carrier B as in Example 3, and an image was output by modifying a Ricoh IPSiO color 8100 machine. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 2.50 V and set as a reference value. While maintaining this reference value, an image having an image area of 10% was output and evaluated.

Example 8
A magenta electrophotographic toner was obtained in the same manner as in Example 4 except that the toner in Example 4 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 13%. A developer having a toner concentration of TC 10.0 wt% was prepared using the same carrier B as in Example 3, and an image was output by modifying a Ricoh IPSiO color 8100 machine. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 2.00 V and set as a reference value. While maintaining this reference value, an image having an image area of 20% was output and evaluated.

[Example 9] (Increased peripheral speed of stirring member)
A magenta electrophotographic toner was obtained in the same manner as in Example 4 except that the toner in Example 4 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 13%. Then, a developer having a toner concentration of 4.5% was prepared using the same carrier B as in Example 3, and an Ricoh IPSiO color 8100 machine was modified to the development conditions shown in Table 2 to output an image. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. While maintaining this reference value, an image having an image area of 20% was output and evaluated.

[Example 10] (Reduce developer carrying amount)
A magenta electrophotographic toner was obtained in the same manner as in Example 4 except that the toner in Example 4 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 13%. Then, a developer having a toner concentration of 4.5% was prepared using the same carrier B as in Example 3, and an Ricoh IPSiO color 8100 machine was modified to the development conditions shown in Table 3 to output an image. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. While maintaining this reference value, an image having an image area of 20% was output and evaluated.

[Example 11] (Upper peripheral speed of photoconductor)
A magenta electrophotographic toner was obtained in the same manner as in Example 4 except that the toner in Example 4 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 13%. A developer having a toner concentration of 4.5% was prepared using the same carrier B as in Example 3, and an Ricoh IPSiO color 8100 machine was modified to the development conditions shown in Table 4 to output an image. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. While maintaining this reference value, an image having an image area of 20% was output and evaluated.

[Example 12] (Increasing developer carrying amount)
A magenta electrophotographic toner was obtained in the same manner as in Example 4 except that the toner in Example 4 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 13%. A developer having a toner concentration of 4.5% was prepared using the same carrier B as in Example 3, and the quality was evaluated by modifying a Ricoh IPSiO color 8100 machine to the development conditions shown in Table 5. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. While maintaining this reference value, an image having an image area of 20% was output and evaluated.

[Example 13] (Linear speed ratio of developing sleeve to photoreceptor increased)
A magenta electrophotographic toner was obtained in the same manner as in Example 4 except that the toner in Example 4 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 13%. Then, a developer having a toner concentration of 4.5% was prepared using the same carrier B as in Example 3, and an image was output by modifying the Ricoh IPSiO color 8100 machine to the development conditions shown in Table 6. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. While maintaining this reference value, an image having an image area of 20% was output and evaluated.

(Further increase in the ratio of OPC line speed)
[Embodiment 14] (The linear velocity ratio of the developing sleeve to the photosensitive member is further increased)
A magenta electrophotographic toner was obtained in the same manner as in Example 4 except that the toner in Example 1 above had a weight average particle size of 5.1 μm and a particle number ratio of 3 μm or less adjusted to 13%. A developer having a toner concentration of 4.5% was prepared using the same carrier B as in Example 3, and an Ricoh IPSiO color 8100 machine was modified to the development conditions shown in Table 7 to output an image. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. While maintaining this reference value, an image having an image area of 20% was output and evaluated.

[Comparative Example 1]
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 1 above had a weight average particle diameter of 5.1 μm and a particle number ratio of 3 μm or less adjusted to 22%. The same carrier B (weight average particle size 35 μm) as in Example 3 was used. Except for this, an image was output under the same conditions as in Example 1 for evaluation.

[Comparative Example 2]
With the toner in Example 1, fine particles having a weight average particle diameter of 8.4 μm and 3 μm or less and a particle number ratio of 0% were obtained. To 20 kg of the fine particles, 200 g of hydrophobic titanium oxide fine particles having an average particle diameter of 0.3 μm were added and mixed by stirring to obtain a magenta electrophotographic toner having a true specific gravity of 1.20 g / cm ³ . The same carrier A (weight average particle diameter 70 μm) as in Example 1 was used as the carrier. Except for this, an image was output under the same conditions as in Example 1 for evaluation.

[Comparative Example 3]
With the toner in Example 1, fine particles having a weight average particle diameter of 5.1 μm and 3 μm or less and a particle number ratio of 15% were obtained. To 20 kg of the fine particles, 200 g of hydrophobic silica fine particles having an average particle diameter of 0.015 μm were added and stirred to obtain a magenta electrophotographic toner. The carrier used was the same carrier B (weight average particle size 35 μm) as in Example 1. Except for this, an image was output under the same conditions as in Example 1 for evaluation.

[Comparative Example 4] (The peripheral speed of the developing sleeve is larger than the peripheral speed of the stirring member)
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 1 above had a weight average particle size of 5.1 μm and a particle number ratio of 3 μm or less adjusted to 15%. Further, the carrier B obtained by the same method as in Example 1 was used except that carrier core particles (MnMgSr ferrite) having a weight average particle diameter of 35 μm were used as the carrier. Then, a developer having a toner concentration of 4.5% was prepared, and an Ricoh IPSiO color 8100 machine was modified to the development conditions shown in Table 8 to output an image. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. An image was output in a state where the reference value was maintained, and evaluation was performed.

[Comparative Example 5] (The peripheral speed of the stirring member and the developing sleeve is 100 (mm / s) or less)
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 1 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 15%. Further, the carrier B obtained by the same method as in Example 1 was used except that carrier core particles (MnMgSr ferrite) having a weight average particle diameter of 35 μm were used as the carrier. Then, a developer having a toner concentration of 4.5% was prepared, and the Ricoh IPSiO color 8100 machine was modified to the development conditions shown in Table 9 to output an image. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. An image was output in a state where the reference value was maintained, and evaluation was performed.

[Comparative Example 6] (The peripheral speed of the stirring member and the developing sleeve is 400 (mm / s) or more)
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 1 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 15%. Further, the carrier B obtained by the same method as in Example 1 was used except that carrier core particles (MnMgSr ferrite) having a weight average particle diameter of 35 μm were used as the carrier. Then, a developer having a toner concentration of 4.5% was prepared, and the quality evaluation was performed by modifying the Ricoh IPSiO color 8100 machine to the development conditions shown in Table 10. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. An image was output in a state where the reference value was maintained, and evaluation was performed.

[Comparative Example 7] (developer carrying amount is 30 (mg · cm ² ) or less)
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 1 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 15%. Further, the carrier B obtained by the same method as in Example 1 was used except that carrier core particles (MnMgSr ferrite) having a weight average particle diameter of 35 μm were used. Then, a developer having a toner concentration of 4.5% was prepared, and a Ricoh IPSiO color 8100 machine was modified to the development conditions shown in Table 11 to output an image. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. An image was output in a state where the reference value was maintained, and evaluation was performed.

[Comparative Example 8] (Developer carrying amount is 80 (mg · cm ² ) or more)
A magenta electrophotographic toner was obtained in the same manner as in Example 1 except that the toner in Example 1 was prepared such that the ratio of the number of particles having a weight average particle size of 5.1 μm and 3 μm or less was 15%. Further, the carrier B obtained by the same method as in Example 1 was used except that carrier core particles (MnMgSr ferrite) having a weight average particle diameter of 35 μm were used. Then, a developer having a toner concentration of 4.5% was prepared, and the quality evaluation was performed by modifying the Ricoh IPSiO color 8100 machine to the development conditions shown in Table 12. As an initial setting of the developer, the toner density sensor output Vt is adjusted to 3.00 V and set as a reference value. An image was output in a state where the reference value was maintained, and evaluation was performed.

The method for measuring the developer charge amounts Q ₆₀₀ and Q ₂₀ is as follows. A developer by mixing 50 g of a carrier and a toner corresponding to a toner concentration of 5% under normal temperature and humidity for a predetermined time (device name: ball mill mount S4-2, manufactured by Ito Manufacturing Co., Ltd., rotation speed: 280 rpm). Create 3 g of this developer was placed in a measurement gauge set with a mesh of 635 mesh (manufactured by Toyo Corporation, SUS316) and blow-off for 60 seconds (blow-off device: TB-200, manufactured by Toshiba Chemical Co., Ltd.), blow gas: nitrogen air, Blow pressure: 1.5 ± 0.1 (kg / cm ² )), and then the charge amount Q (μC) and mass M (g) of the scattered powder were measured, and the charge amount Q / M (−μC / g) can be obtained. The developer charge amount Q / M in Table 14 is measured by the same procedure described above after 3 g of developer is placed in the measurement gauge.

  The particle size distribution of the toner can be measured by various methods. In this embodiment, the toner particle size distribution is measured by a small hole passage method (Coulter counter method). A COULTER COUNTER MODEL TA2 (manufactured by Coulter, Inc.) was used as a measuring device, an interface for outputting the number distribution and volume distribution was connected, and an aperture (pore) of 100 μm was used. As a measuring method, first, a toner measurement sample is dispersed in a surfactant added to an electrolytic aqueous solution. This sample is injected into another 1% NaCl field solution, and an electric current is passed between the electrodes through the electrolytic solution in which the electrodes are placed on both sides of the aperture tube. The particle size distribution of 2 to 40 μm particles is measured from this resistance change, and the number average particle size and weight average particle size are determined from the average distribution. The carrier particle size distribution was measured in the range of 0.7 to 125 μm using a Microtrac particle size distribution meter (model SRA, manufactured by Nikkiso Co., Ltd.).

  For evaluation of image density unevenness, the L portion (left side of the image), the M portion (center of the image), and the R portion (right side of the image) of the solid portion of 290 mm in the main scanning direction × 30 mm in the sub-scanning direction are X-rite 938 spectral densitometers. Measure with An allowable level is a range in which the difference between the maximum and minimum image density at each measurement location is 0.050.

  For the evaluation of the image density variation, the average value of the LMR portion in the image sample is calculated, and the range in which the image density variation from the initial range is ± 0.120 is set as the allowable level.

Regarding the evaluation of the toner scattering amount, the toner scattered around the developing sleeve is collected with an adhesive tape, and the toner weight is evaluated. The following levels 4 are acceptable levels.
Rank 5: 10 mg or less Rank 4: 11-30 mg
Rank 3: 31-60mg
Rank 2: 61-150 mg
Rank 1: 151 mg or more

  The toner density stability was evaluated as follows. The series of evaluations described above is performed after setting the reference value of the toner density sensor before outputting the image and controlling the toner density sensor to indicate the reference value and outputting the image. Therefore, it can be determined that the smaller the fluctuation range of the toner density from the initial stage, the better the stability. A range in which the toner density TC variation from the initial stage is within a range of ± 0.30 wt% is set as an allowable level.

  The toner density TC deviation was evaluated as follows. The developer was sampled from the upstream portion, the central portion, and the downstream portion in the conveying direction of the stirring member on the developer carrying member, and measurement was performed by the blow-off method. An allowable level is a range in which the difference between the maximum and minimum toner density at each measurement location is 0.15 wt%.

As can be seen from Tables 1 to 13, in Examples 1 to 14, the charge amount Q / M as a developer is in the range of 30 to 60 (−μC / g), and the toner weight and the number average particle diameter. The ratio (Dv / Dn) is 1.20 or less. Further, at the peripheral speed Vs of the developing sleeve and the peripheral speed Vk of the stirring member, the relationship of Vk> Vs is satisfied, and 100 (mm / s) <Vs, Vk <400 (mm / s), The body weight is adjusted to be in the range of 30 to 80 (mg / cm ² ). As a result, in Examples 1 to 14, as shown in Table 14, the same level of toner density was obtained at any location on the developing sleeve, and stable image quality without density unevenness or density reduction over a long period of time was obtained. It can be seen that Furthermore, the toner concentration of the developer is 5.0 to 9.0 wt%, the toner weight average particle size is 4.5 to 8.0 μm, and the carrier weight average particle size is 30 to 60 μm, so that the toner concentration control is stable. In addition to the characteristics, the resolution was improved and it was confirmed that a higher quality image could be obtained. Also, by setting the particle number ratio of 3 μm or less to 5% or less and the charge rising ratio to 70% or more, the fluidity of the toner is improved and the toner concentration in the developer is made more uniform, resulting in a quality improvement effect. It was confirmed that becomes more prominent. Also, by adjusting the ratio of the peripheral speed of the developer carrier and the peripheral speed of the image carrier to be 1.5 to 2.5, in addition to stabilizing the image density, abnormal image generation such as image omission is generated. It was confirmed that it was suppressed.

  Hereinafter, the developer material used in the developing device of the present invention will be described. The toner includes at least a binder resin, a colorant, a release agent, and a charge control agent. As the binder resin used for the toner, all those conventionally used as the binder resin for toner are applied. Specifically, homopolymers of styrene such as polystyrene, polychlorostyrene, and polyvinyltoluene, and substituted products thereof; styrene / p-chlorostyrene copolymer, styrene / propylene copolymer, styrene / vinyltoluene copolymer, styrene / Vinyl naphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer, styrene / octyl acrylate copolymer, styrene / methyl methacrylate copolymer Styrene / ethyl methacrylate copolymer, styrene / butyl methacrylate copolymer, styrene / α-chloromethyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / vinyl ethyl ether copolymer, styrene / Vinyl methyl ketone copolymer, steel Styrene copolymers such as styrene / butadiene copolymer, styrene / isoprene copolymer, styrene / acrylonitrile / indene copolymer, styrene / maleic acid copolymer, styrene / maleic acid ester copolymer; polymethyl methacrylate , Polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyvinyl butyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic A group petroleum resin, chlorinated paraffin, paraffin wax and the like can be mentioned, and these are used alone or in admixture of two or more.

  As the colorant used in the toner, dyes and pigments capable of obtaining toners of yellow, magenta, cyan, and black colors can be used, and all of the pigments and dyes conventionally used as toner colorants are used. Applied. Specifically, nigrosine dye, aniline blue, calco oil blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, phthalocyanine green, Hansa Yellow G rhodamine 6C lake, chrome yellow, quinacridone, benzidine yellow, malachite green, malachite Examples thereof include green hexalate, rose bengal, monoazo dye / pigment, disazo dye / pigment, and trisazo dye / pigment. The amount of these colorants to be used is generally 1-30 wt%, preferably 3-20 wt%, relative to the binder resin.

  As the charge control agent used for the toner, either a positive charge control agent or a negative charge control agent can be used, but in the case of color toner, a transparent to white one that does not impair the color tone. Is preferably used. For example, quaternary ammonium salts, imidazole metal complexes, salts, and the like are used as positive polarity, and salicylic acid complexes, salts, organic boron salts, calixarene compounds, and the like are listed as negative polarity.

  In addition, the toner used in the developing device of the present invention is made of synthetic waxes such as low molecular weight polyethylene and polypropylene, candelilla wax, carnauba wax, rice wax, wax, Plant waxes such as jojoba oil; animal waxes such as beeswax, lanolin and whale wax; mineral waxes such as montan wax and ozokerite; fats and oils such as hardened castor oil, hydroxystearic acid, fatty acid amide, phenol fatty acid ester System waxes can be contained, and these are used alone or in admixture of two or more.

  Furthermore, in the toner used in the developing device of the present invention, various plasticizers (dibutyl phthalate, It is also possible to add auxiliary agents such as dioctyl phthalate) and resistance adjusting agents (tin oxide, lead oxide, antimony oxide, etc.). Furthermore, fluidity-imparting agents other than the above-mentioned mold release agents, auxiliaries and the like can be mixed as necessary. Examples of the fluidity imparting agent include silica fine particles, titanium oxide fine particles, aluminum oxide fine particles, magnesium fluoride fine particles, silicon carbide fine particles, boron carbide fine particles, titanium carbide fine particles, zirconium carbide fine particles, boron nitride fine particles, titanium nitride fine particles, zirconium nitride. Fine particles, magnetite fine particles, molybdenum disulfide fine particles, aluminum stearate fine particles, magnesium stearate fine particles, zinc stearate fine particles, fluororesin fine particles, acrylic resin fine particles, etc. may be mentioned, and these may be used alone or in combination of two or more. Is possible. As the fluidity-imparting agent, those having a primary particle size of less than 0.1 μm, a surface hydrophobized with a silane coupling agent, silicon oil or the like, and a hydrophobization degree of 40 or more are preferable.

  As a method for producing the toner used in the developing device of the present invention, a known method is used. For example, after fully mixing binder resin, colorant and pigment, charge control agent, if necessary, release agent, etc. at an appropriate ratio using a mixer such as a Henschel mixer or a ball mill, screw type extrusion continuous Melt-kneading is performed using a kneading machine, a two-roll mill, a three-roll mill, and a pressure heating kneader. In the case of a color toner, a masterbatch pigment obtained by previously melt-kneading a part of the binder resin and the pigment for the purpose of improving the dispersibility of the pigment is generally used as the colorant.

  The kneaded product obtained by the above method is cooled and solidified, and then coarsely pulverized using a collision pulverizer such as a hammer mill. Further, the coarsely pulverized product is pulverized by a jet mill pulverizer and then subjected to surface treatment using a rotor pulverizer connected to an airflow classifier or the like. Examples of the collision type pulverizer include a hammer mill, a ball mill, a tube mill, a vibration mill, and the like. As a jet type pulverizer including a compressed air and a collision plate as main components, type I and IDS type. A collision type pulverizer (manufactured by Nippon Pneumatic Industry Co., Ltd.) can be preferably used. Examples of the rotor pulverizer include a roll mill, a pin mill, a fluidized bed jet mill and the like, and in particular, a fixed container as an outer wall and a rotating piece having the same central axis as the fixed container are provided as main components. As such a rotor-type pulverizer, a turbo mill (manufactured by Turbo Industry Co., Ltd.), a kryptron (manufactured by Kawasaki Heavy Industries Ltd.), a fine mill (manufactured by Nippon Pneumatic Industry Co., Ltd.) and the like can be used. As the connected airflow classifier, for example, a dispersion separator (DS) classifier (manufactured by Nippon Pneumatic Kogyo Co., Ltd.), a multi-division classifier (Elbow Jet; manufactured by Nittetsu Mining Co., Ltd.) and the like can be used. Furthermore, fine powder classification can be performed using an airflow classifier or a mechanical classifier to obtain fine particles.

  Furthermore, when adding and mixing a fluidity-imparting agent to the fine particles obtained by the above method, known equipment such as a Henschel mixer, a super mixer, and a ball mill can be used. Alternatively, a toner may be directly produced from a monomer, a colorant and a fluidity imparting agent by a suspension polymerization method or a non-aqueous dispersion polymerization method.

  The carrier used in the developing device of the present invention is composed of at least a core material and a binder resin. As the core material, a material having a weight average particle size of 20 μm or less is used from the viewpoint of preventing carrier adhesion to the photosensitive drum, and a material of 100 μm or less is used from the viewpoint of preventing the occurrence of carrier streaks or the like. . Specific materials may be appropriately selected according to the use and purpose of use of a carrier known as a two-component carrier for an electrophotographic developer, for example, ferrite, magnetite, iron, nickel and the like.

  As the carrier coating resin used in the developing device of the present invention, those conventionally used generally as carrier coating resins can be used. For example, acrylic resins, amino resins, polystyrene resins, (Meth) acrylic resin, polyolefin resin, polyamide resin, polycarbonate resin, polyether resin, polysulfinic acid resin, polyester resin, epoxy resin, polypropylene resin, urea resin, urethane / urea Various thermoplastic resins such as resins, silicone resins, polyethylene resins, Teflon (registered trademark) resins, thermosetting resins and mixtures thereof, and copolymers, block polymers, graft polymers and polymers of these resins Although it is a blend etc., it is not restricted to these.

  The film thickness of the binder resin in the carrier is suitably 0.05 to 1.00 μm, preferably 0.1 to 0.8 μm. When the film thickness is less than 0.05 μm, the film is too thin, and the film coated when the toner and the carrier are stirred and mixed in the developing device is liable to be scraped, so that sufficient durability cannot be obtained. On the other hand, when the film thickness is 1.00 μm or more, the carrier resistance becomes too high and the carrier adhesion tends to deteriorate. Further, the fluidity of the developer tends to deteriorate, which is not preferable from the viewpoint of controlling the toner density sensor.

Further, a resistance adjusting agent can be used for the carrier as necessary. Any electrically conductive material may be used as long as it is known in the art, but carbon black is preferably used from the viewpoint of an inexpensive electrically conductive material. Moreover, it is most preferable to use carbon black having a BET specific surface area of 800 m ² / g, preferably 1000 m ² / g or more and a DBP oil absorption of 200 ml / 100 g, preferably 250 ml / 100 g or more. Further, when color stains are a problem with a color carrier or the like, it is preferable to use a white metal oxide. Examples of the white metal oxide include titanium oxide, zinc oxide, and tin oxide particles.

1 is a schematic configuration diagram illustrating a configuration of a printer according to an embodiment. FIG. 2 is a configuration diagram showing a configuration of a photoconductor unit of the printer. FIG. 2 is a configuration diagram illustrating a configuration of a writing device of the printer. FIG. 2 is a configuration diagram illustrating a configuration of a developing device of the printer. FIG. 2 is a plan view showing a configuration of a developing device of the printer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Device main body 2 Photoconductor unit 3Y, 3M, 3C, 3K Developing device 4Y, 4M, 4C, 4K Photoconductor 53 Developing case 54 Developing sleeve 55, 56 Screw member 58, 59 Delivery portion 61 Developer regulating member 62 Toner supply port 63 Toner density sensor

Claims (7)

An image carrier;
A developer accommodating portion for accommodating a two-component developer comprising toner and a magnetic carrier;
In order to develop the electrostatic latent image formed on the image carrier into a visible image, a developer carrier that carries the developer supplied from the developer container on the surface by a built-in magnetic field generating means and conveys it. Body,
A developer regulating member that regulates the amount of developer carried and conveyed on the developer carrying member;
Toner concentration detecting means for detecting the toner concentration of the developer in the developer accommodating portion;
In a developing device comprising a stirring member that stirs the developer in the developer storage section,
The charge amount of the developer is 30 (−μC / g) or more and 60 (−μC / g) or less,
The ratio of the weight average particle diameter Dv to the number average particle diameter Dn (Dv / Dn) of the toner is 1.20 or less,
The relationship between the peripheral speed Vs of the developer carrying member and the peripheral speed Vk of the stirring member is Vk> Vs, 100 (mm / s) <Vs, Vk <400 (mm / s),
Development in which the developer carrying amount per unit area on the developer carrying member immediately after regulation by the developer regulating member is 30 (mg / cm ² ) or more and 80 (mg / cm ² ) or less. apparatus. The developing device according to claim 1.
The developing device, wherein the developer has a toner concentration of 5.0 (wt%) or more and 9.0 (wt%) or less. The developing device according to claim 1 or 2,
The toner has a weight average particle size of 4.5 (μm) or more and 8.0 (μm) or less, and the magnetic carrier has a weight average particle size of 30 (μm) or more and 60 (μm) or less. A developing device characterized by using The developing device according to claim 1, 2 or 3,
A developing device comprising a toner particle having a toner particle diameter of 3 (μm) or less and having a particle number ratio of 5% or less. The developing device according to claim 1, 2, 3 or 4,
The developer was stirred and mixed for 20 seconds under the same conditions with respect to the charge amount Q ₆₀₀ obtained when the toner and the carrier were stirred and mixed for 10 minutes under a condition of normal temperature and humidity and a toner concentration of 5% or less. If the charge amount Q ₂₀ obtained sometimes is
Z (%) = (Q ₂₀ / Q ₆₀₀ ) × 100
A developing device using a toner and a carrier that can obtain a charge rising ratio Z (%) calculated by (1) of 70 (%) or more. The developing device according to claim 1.
A developing device characterized in that the relationship between the peripheral velocity Vs of the developer carrier and the peripheral velocity Vp of the image carrier satisfies a relationship of 1.5 ≦ (Vs / Vp) ≦ 2.5. Image forming apparatus comprising: an image carrier that carries a latent image; a latent image forming unit that forms a latent image on the surface of the image carrier; and a developing unit that develops the latent image formed on the surface of the image carrier. In
An image forming apparatus using the developing device according to claim 1, 2, 3, 4, 5, or 6 as the developing means.

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