JP5320879B2 - Toner density control method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner concentration control method by which toner concentration is always controlled at an appropriate value over a long term, without making the toner yield deteriorate, even when the target value of the toner concentration is changed, and the toner concentration in a developing means is required to be low in an image forming apparatus equipped with a two-component developing type developing means. <P>SOLUTION: In the toner concentration control method, the output value Vt of a toner concentration detection means (S1) for detecting the toner concentration in the two-component developing type developing means (Y2) is compared with a control target value Vtref, and toner is supplied, according to the difference between them, when the toner concentration corresponding to the control target value Vtref lowers and the toner concentration in the developing means is higher than the toner concentration, showing the control target value as a result obtained by comparing the output value of the toner concentration detection means with the control target value, the toner is collected from the developer carried on a developer carrier (Y21), after passing through a developing area by a toner-collecting mechanism (Yb). <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, a printer, and a composite machine of these, and more specifically, in an image forming apparatus provided with a developing unit of a two-component developing system composed of a toner and a carrier. The present invention relates to a toner concentration control method for controlling toner concentration using a toner recovery mechanism.

  In recent electrophotographic image forming apparatuses such as copying machines and laser printers, high image quality is required, and at the same time, high durability and high stability are also desired. In other words, there is a demand for an image forming apparatus that can reduce image quality changes due to changes in usage environment (including changes in usage status such as continuous image output and intermittent image output) and can always stably form images even over time. Yes. Conventionally, a two-component developer composed of a non-magnetic toner and a magnetic carrier is carried on a developing roller, and the developer is transported to the developing area as the developing roller rotates, and the magnetic field lines of the magnetic poles contained therein approach the developing area. Along the track, a large number of magnetic carriers in the developer gather together with the toner to form a magnetic brush, and a developing bias is applied to the developing roller in the developing region facing the photosensitive drum, whereby the toner on the developing roller 2. Description of the Related Art Two-component developing type developing means for transferring a toner to an electrostatic latent image on a photosensitive drum for development is widely known.

  In an image forming apparatus equipped with such a two-component development system, unlike the one-component development system, controlling the weight ratio of the toner and the carrier, that is, the toner density with high accuracy improves the stability. Is very important above. For example, if the toner concentration is too high, background stains may occur on the image and the detail resolution may be reduced. If the toner concentration is low, problems such as insufficient density in the solid image portion and carrier adhesion may occur. For this reason, it is necessary to control the toner replenishment amount according to the use environment and use situation of the image forming apparatus, and to always adjust the toner concentration in the developer to an appropriate range.

  In general, the toner density control is performed by comparing the output value Vt of the toner density detection means with the control target value Vtref of the toner density and determining the toner replenishment amount according to the difference. And the toner is replenished to the developing means by the toner replenishing means. As this toner concentration detecting means, a device using a magnetic permeability sensor is generally used, and the magnetic permeability sensor system converts the change in the magnetic permeability of the developer due to the change in the toner concentration into a change in the toner concentration. The concentration is detected.

  As another toner density detecting means, there is one using an optical sensor. This optical sensor method creates a patch pattern consisting of solid images with different densities on an image carrier such as a photosensitive drum or an intermediate transfer belt, and irradiates the patch pattern with laser light from an LED or the like. The reflected light is read with an optical sensor such as a photodiode or phototransistor (the type that measures specularly reflected light and the type that measures irregularly reflected light), and the toner density (toner adhesion amount) is detected based on the result. To do.

  In addition, by combining these two methods, a patch pattern is formed on the image carrier at every predetermined control time between the transfer sheets being printed (the time or distance between the end of the previous image formation and the start of the current image formation). A toner density control method that reduces the influence of the measurement error by the magnetic permeability sensor by changing and setting the toner density control target value: Vtref in the developing means by feeding back the detected density of the patch pattern by the optical sensor. Are known. For example, in Patent Document 1 and Patent Document 2, a patch pattern is created in a non-image portion, the density of the created patch pattern is read by a pattern density sensor such as an optical sensor, and the density of the read patch pattern is determined. By changing the toner density control target value: Vtref in a toner density sensor such as a magnetic permeability sensor that detects the toner density in the developing means, it is possible to respond to the judgment of the user and service staff and the potential fluctuation of the photosensitive drum over time. In addition, a toner density control device and an image forming apparatus capable of controlling the toner density are disclosed.

  According to the toner density control method including the toner density control apparatus and the image forming apparatus described in Patent Documents 1 and 2, the image density is stabilized according to the density of the actually output image. Although the toner density target value can be provided, as a means for actually adjusting the toner density, the toner may be replenished when the toner density is raised, but when the toner density is lowered, the toner is developed. Therefore, there is a problem that toner yield (toner yield, productivity) is deteriorated. Further, if the toner is not discharged from the developing unit in consideration of the toner yield, there is a problem that the toner density cannot be quickly stabilized to the target value. In other words, the two problems of improving the toner yield and maintaining the appropriate image density according to the usage situation such as the change in the charged state of the developer cannot be solved simultaneously.

JP-A-57-136667 JP-A-2-34877

  Therefore, in order to solve the above-described problems of the prior art, the present invention reduces the toner density in the developing means by changing the target value of the toner density in the image forming apparatus provided with the developing means of the two-component developing system. A toner concentration control method capable of controlling the toner concentration to an appropriate value for a long period of time without deteriorating the toner yield even when necessary, and the toner concentration controlled by the toner concentration control method An object is to provide a possible image forming apparatus.

In order to solve the above-mentioned problem, the invention according to claim 1 compares the output value of the toner density detecting means for detecting the toner density in the developing means of the two-component developer system with its control target value, In the toner density control method for replenishing toner according to the difference, the toner density corresponding to the control target value decreases, and the output value of the toner density detection means is compared with the control target value to compare the control target value. When the toner concentration of the toner becomes higher than the toner concentration of the control target value, it is carried on the developer carrying member after passing through the development region by a toner collecting mechanism for collecting toner from the developer carried on the developer carrying member. The toner is collected from the developer, and the output value of the toner density detecting means is compared with the control target value. If the toner density in the developing means is lower than the toner density of the control target value , the collected toner is collected. The collected toner collected by the toner collecting mechanism is supplied in preference to the supply of new toner, except when the sky is detected by an empty detection sensor for detecting the empty of the toner.

According to a second aspect of the present invention, there is provided a latent image carrying member carrying an electrostatic latent image on a surface, and a latent image carrying member in a developing region carrying a developer containing toner and a carrier and facing the latent image carrying member. A developer carrying member for supplying toner to the body, developing means of a two-component developing system for developing the electrostatic latent image with toner contained in the developer, and new toner for supplying new toner to the developing means In the image forming apparatus provided with the supply unit, the developing unit includes a toner collecting mechanism for collecting toner from the developer carried on the developer carrying member even after passing through the developing region, and the new toner supply unit. In addition to the new toner supply operation, the recovered toner supply means capable of supplying the toner collected by the toner recovery mechanism to the developer carrying member, and the toner concentration detection means for detecting the toner density in the development means, An empty detection sensor for detecting the empty of the collected toner, and the toner density set as a toner density control target in the developing means decreases, and the determination is made based on the output value of the toner density detecting means When the toner concentration in the developing means becomes higher than the control target toner concentration, the toner concentration of the developer recovered by the toner recovery mechanism and supplied to the developer carrier is brought close to the control target, If the toner density in the developing means by comparing the output value and the control target value of the toner concentration detection means is lower than the toner concentration of the control target value, except when it is detected air by the air detection sensor, The recovered toner is supplied by the recovered toner supply means in preference to the supply of new toner by the new toner supply means .

The present invention is as described above. According to the first aspect of the present invention, the output value of the toner density detecting means for detecting the toner density in the developing means of the two-component developer system, and the control target value thereof. In the toner density control method for replenishing toner according to the difference, the toner density corresponding to the control target value decreases, and the output value of the toner density detection means is compared with the control target value. Then, when the toner concentration in the developing means becomes higher than the toner concentration of the control target value, the developer after passing through the development region by the toner recovery mechanism that recovers the toner from the developer carried on the developer carrier. When toner is collected from the developer carried on the carrier and the output value of the toner density detecting means is compared with the control target value, and the toner density in the developing means is lower than the toner density of the control target value In this case, the collected toner collected by the toner collecting mechanism is supplied prior to the supply of new toner except when the empty detection sensor for detecting the empty of the collected toner is detected. Even if it is necessary to lower the toner density in the developing unit by changing the toner density, the toner density can always be controlled to an appropriate value over a long period without deteriorating the toner yield. That is, for example, if the same image with a high image rate is continuously output and the toner of the same color continues to be used, the developer in the developing unit of the toner color is used for development without being charged so much. Under such circumstances, the toner is more easily transferred to the electrostatic latent image as compared with the normal case, so that it is necessary to reduce the toner concentration of the developer supplied from the developing carrier. In such a case, in the prior art, the toner is discharged / discarded from the developing means, which contributes to the deterioration of the toner yield. In the present invention, only the toner is temporarily isolated by the toner recovery mechanism. In addition, since the collected toner that has been collected can be re-supplied as necessary, the toner yield can be improved. In addition, the developer that quickly collects the toner and supplies it to the developer carrying member can be lowered to an appropriate toner concentration, and the toner concentration can always be controlled to an appropriate value.
In addition to the above effects, the collected toner can be preferentially used for development when toner replenishment is required. That is, the toner having deteriorated can be used preferentially. For this reason, it is possible to prevent problems such as a decrease in transfer efficiency during transfer due to toner deterioration, a decrease in the amount of pumping by the developing roller, and the like, and the image density of the output image cannot be kept constant.

According to the second aspect of the present invention, the latent image carrier that carries the electrostatic latent image on the surface, and the latent image carrier in the development region that is in close proximity to the latent image carrier and carrying the developer containing toner and carrier. A developer carrying member for supplying toner to the image carrier, a developing unit of a two-component developing system that develops the electrostatic latent image with the toner contained in the developer, and a new toner is supplied to the developing unit In the image forming apparatus provided with a new toner supply means, the developing means includes a toner recovery mechanism for recovering toner from the developer carried on the developer carrying member even after passing through the development area, and the new toner Separately from the new toner supply operation of the supply means, the recovered toner supply means capable of supplying the toner collected by the toner recovery mechanism to the developer carrying member, and the toner density detection for detecting the toner density in the developing means And an empty detection sensor for detecting the empty of the collected toner, and the toner density set as a toner density control target in the developing means is lowered and is determined from the output value of the toner density detecting means. When the toner density in the developing unit becomes higher than the control target toner density, the toner density of the developer that is collected by the toner collecting mechanism and supplied to the developer carrier is set as the control target. close, if by comparing the output value and the control target value of the toner concentration detecting means the toner density in the developing unit lower than the toner concentration of the control target value, upon detecting an empty in the air detection sensor except, so to supply the collected toner by the collected toner supplying means in preference to the supply of new toner in the new toner supply means, that is, the developer supplied to the developer carrying member Even when it is necessary to lower the toner concentration, the developer supplied to the developer carrying member by collecting the toner from the developer carried on the developer carrying member even after passing through the developing region by the toner collecting mechanism. The toner density can be quickly brought close to the control target, and the toner density can always be controlled to an appropriate value over a long period without deteriorating the toner yield.
In addition to the above effects, the collected toner can be preferentially used for development when toner replenishment is required. That is, the toner having deteriorated can be used preferentially. For this reason, it is possible to prevent problems such as a decrease in transfer efficiency during transfer due to toner deterioration, a decrease in the amount of pumping by the developing roller, and the like, and the image density of the output image cannot be kept constant.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a configuration explanatory view showing a main part of an image forming apparatus according to an embodiment of the present invention. Reference numeral 1 in the figure denotes a four-tandem type intermediate transfer type color printer exemplified as an embodiment of the image forming apparatus of the present invention. The color printer 1 is mainly formed in a substantially casing shape (not shown). The image forming unit 3, the writing unit 2 disposed substantially in the center of the apparatus main unit, the image forming unit 3 disposed above the writing unit 2, and the transfer disposed above the image forming unit 3. Part 4, a new toner storage part 5 disposed above the transfer part 4 and substantially at the top of the apparatus main body, and a side of the new toner storage part 5 at one side end of the top of the apparatus main body. The fixing unit 6 is arranged. In addition, the color printer 1 includes a sheet feeding unit (not shown) that is disposed in the lower part of the apparatus main body, accommodates a transfer material of a predetermined size, and feeds paper according to a command from a control unit of the apparatus main body, and a fixing unit 6. A paper discharge unit (not shown) that discharges and stacks the transfer material on which the image is fixed is also provided. However, since it is known, a detailed description thereof is omitted. Reference numeral 7 in the figure denotes a registration roller pair that conveys the transfer material conveyed from the paper feeding unit to a secondary transfer nip, which will be described later, and numeral 8 indicated by a broken line conveys it in the direction of the arrow. This is a transfer material conveyance path.

  This writing means 2 scans a toner drum, which has been uniformly charged, by scanning while irradiating a modulated laser beam for each toner color based on color-separated image information inputted from a personal computer or the like. The optical unit has a function as an exposure device that selectively exposes the outer peripheral surface to lower the surface potential of the irradiated portion and forms an electrostatic latent image on the photosensitive drum.

  The image forming unit 3 is mainly composed of four image forming units 3Y, 3C, 3M, and 3K corresponding to toners of four colors of yellow, cyan, magenta, and black. Are arranged in order of yellow, cyan, magenta, and black from the upstream side. The image forming units 3Y, 3C, 3M, and 3K are provided with photosensitive drums Y, C, M, and K, which are latent image carriers, and around the photosensitive drums Y, C, M, and K, respectively. Further, the charging means Y1, C1, M1, K1 for charging the outer peripheral surface of each photosensitive drum to uniformly charge, and the static means formed by the writing means 2 on each photosensitive drum Y, C, M, K. The developing means Y2, C2, M2, and K2 that visualize the electrostatic latent image into a single color toner image with each color toner and the outer peripheral surfaces of the photosensitive drums Y, C, M, and K remain after transfer. Cleaning means Y3, C3, M3, and K3 for cleaning and collecting the transfer residual toner are integrally stored in a unit case (not shown). Note that the arrangement of the image forming units is not limited to the above order, and may be appropriately arranged according to transfer conditions and the like.

  The charging units Y1, C1, M1, and K1 have charging rollers Y10, C10, M10, and K10, and cleaning rollers Y11, C11, M11, and K11 that clean the charging rollers, respectively. The charging rollers Y10, C10, M10, and K10 are rotatably supported by the respective unit cases, abut against the respective photosensitive drums while rotating in the forward direction and the rotational direction of the photosensitive drums, and the surface thereof is negative or It is configured to be charged to a predetermined positive polarity.

  The cleaning units Y3, C3, M3, and K3 are configured to be able to come into contact with and separate from each photosensitive drum, and are cleaning blades that are cleaning members that scrape and collect transfer residual toner that adheres to and remains on each photosensitive drum even after transfer. Y30, C30, M30, K30, and recovered toner storage portions Y31, C31, which are spaces for storing transfer residual toner (hereinafter referred to as recovered toner) recovered from the respective photosensitive drums by the cleaning blades Y30, C30, M30, K30. , M31, K31 and conveying screws Y32, C32, M32, K32, which are conveying means for conveying the collected toner accumulated in the collected toner storage portions Y31, C31, M31, K31 to a waste toner storage portion (not shown). It is configured. The developing units Y2, C2, M2, and K2 will be described in detail later.

  The transfer unit 4 includes an intermediate transfer belt 40 formed of an endless belt made of an elastic resin as an intermediate transfer member, four support rollers 41, 42, 43, 44 that support and stretch the intermediate transfer belt 40, and four It is mainly composed of four primary transfer rollers 45Y, 45C, 45M, and 45K that face the photosensitive drums Y, C, M, and K across the intermediate transfer belt 40, respectively. The support roller 41 is a drive roller connected to a drive unit (not shown), and a secondary transfer roller 46 is provided at a position facing the support roller 41 with the intermediate transfer belt 40 interposed therebetween. A cleaning unit 47 that removes and collects transfer residual toner (including patch patterns formed in the process control process) remaining on the intermediate transfer belt 40 after transfer (secondary transfer) is provided in the vicinity of the support roller 42. Is provided.

  Each of these primary transfer rollers 45Y, 45C, 45M, 45K takes into account defects due to gap discharge, and is in the middle from the directly facing position where the photosensitive drums Y, C, M, K are in contact with the intermediate transfer belt 40 therebetween. This is a contact-type transfer bias (transfer voltage) applying means arranged at a position slightly shifted downstream in the transport direction of the transfer belt 40 (in the direction of the arrow in the figure), and is connected to a bias power source (not shown). The primary transfer bias is applied from the back surface (inner peripheral surface).

  The secondary transfer roller 46 is configured to be pressed against the intermediate transfer belt 40 on the outer periphery of the drive roller 41 by an urging means (not shown) to form a secondary transfer nip. The drive roller 41 is connected to a bias power source (not shown). It is a connected contact-type transfer bias applying means. Further, the secondary transfer roller 46 may be a transfer bias applying unit, and in this case, a transfer bias having a polarity opposite to that of the toner image to be transferred is applied.

  The cleaning unit 47 includes a cleaning blade 47a that can be brought into and out of contact with the intermediate transfer belt 40, a housing portion 47b that stores scraped toner, and the like. The support roller 42 is used as a backup roller to clean the outer peripheral surface of the intermediate transfer belt 40. The transfer residual toner on the intermediate transfer belt 40 is scraped off by contacting the blade 47a, temporarily stored in the storage portion 47b, and transferred residual toner is transported to a waste toner storage portion (not shown) by transport means such as a transport screw. It is configured.

  The new toner storage unit 5 is a space for storing new toner, and is provided for each toner color corresponding to the total four colors of yellow, cyan, magenta, and black, which are the three primary colors of the toner. It is mainly composed of four toner cartridges 5a, 5b, 5c, and 5d that are detachable from each other. Although these arrangements are not particularly limited, in this embodiment, as shown in FIG. 1, the toner cartridge 5a corresponds to yellow, the toner cartridge 5b corresponds to cyan, the toner cartridge 5c corresponds to magenta, and the toner cartridge 5d corresponds to black toner. doing. In addition, the black toner cartridge 5d is made large in consideration of the frequent use of the toner. The toner cartridge will be described later.

  The fixing unit 6 includes a belt-type fixing unit 60 that fixes the transfer material on which the image is transferred by the transfer unit 4 by applying heat and pressure. The fixing unit 6 is made of a heat-insulating material such as resin and other parts in the apparatus main body. And is configured to reduce the adverse effect of heat transmitted to other parts. The fixing unit 60 includes a fixing belt 61 that is an endless belt that can generate heat by a heating unit (not shown), a fixing roller 62 that rotationally drives the fixing belt 61, and a pressure that presses the fixing belt 61 on the fixing roller 62. The pressure roller 63 is urged by an urging means (not shown) and is pressed against the fixing belt 61 on the fixing roller 62 to form a fixing nip. In this fixing nip, the toner transferred to the transfer material in the secondary transfer nip of the transfer unit 4 is applied to the transferred transfer material by the heat of the fixing belt 61 and the pressure by the urging means via the pressure roller 63. The image is fixed on the transfer material.

(Image forming operation)
Next, the image forming operation of the color printer 1 will be described with reference to FIG.
In the case of forming a color image, first, when an image forming operation is started in the color printer 1, the photosensitive drums Y, C, M, and K are rotationally driven in the directions of the arrows in the figure. The outer peripheral surfaces of the photosensitive drums Y, C, M, and K are uniformly charged to a predetermined polarity (for example, minus) by the means Y1, C1, M1, and K1. Next, the charging surface is irradiated with laser light that is light-modulated based on the image information separated into predetermined colors from the writing means 2, whereby the outer circumference of each photosensitive drum Y, C, M, K is irradiated. An electrostatic latent image is formed on the surface. This electrostatic latent image is visualized as a single-color toner image by each developing means Y2, C2, M2, and K2, and each color toner image is converted to 1 by the corresponding primary transfer rollers 45Y, 45C, 45M, and 45K. A next transfer bias is applied and sequentially superposed on the intermediate transfer belt 40 to form a color toner image. When a single color image is formed, the above operation is performed only with a predetermined single color photosensitive drum such as the black photosensitive drum K.

  On the other hand, the transfer material transported from the paper feed section along the transport path 8 is sent to the secondary transfer nip after the transfer timing is adjusted by the resist roller pair 7. Therefore, a secondary transfer bias is applied by the driving roller 41, and the full-color toner image on the intermediate transfer belt 40 is transferred to the transfer material. Next, the transfer material carrying the toner image is sent to the fixing nip of the fixing unit 6, and heat and pressure are applied by the fixing means 60, and the unfixed toner image carried on the transfer material is fixed to the transfer material. The As described above, after the toner image is fixed on the transfer material, the toner image is discharged and stacked on the paper discharge unit. Transfer residual toner adhering to the surface of the intermediate transfer belt 40 after the secondary transfer is removed by the cleaning unit 47 together with the removal toner of the patch pattern for process control, and is transferred to each of the photosensitive drums Y, C, M, and K. The transfer residual toner that adheres after the transfer is removed by the cleaning means Y3, C3, M3, and K3, and is prepared for another image forming operation. The transfer residual toner removed by the cleaning unit 47 and the cleaning units Y3, C3, M3, and K3 is carried to a waste toner container (not shown) and discarded.

(Toner cartridge)
Next, a toner cartridge which is a new toner supply unit of the color printer 1 will be described with reference to FIG.
FIG. 2 is a plan view showing a schematic configuration of the toner cartridge according to the present embodiment. The toner cartridge 5a corresponding to the yellow toner will be described as an example, but the toner cartridges 5b, 5c and 5d corresponding to the other color toners have the same configuration.
The toner cartridge 5a stores a yellow new toner, closes an opening of one end of the container body 50a having a spiral toner conveyance groove on the inner wall, and rotates the container body 50a. It is mainly composed of a cap portion 51a that is freely held.
The container main body 50a is integrally formed with a container gear 52a exposed from a part of the slit opening of the cap 51a, and is rotationally driven in response to drive transmission from the image forming apparatus main body. The cap portion 51a is provided with a cap portion opening 53a indicated by a broken line provided with a shutter mechanism (not shown), and yellow new toner can be discharged to the outside through the cap portion opening 53a. .

(New toner supply operation)
Next, a new toner replenishing operation of the color printer 1 will be described with reference to FIGS.
The toner cartridges 5a, 5b, 5c and 5d and the developing means Y2, C2, M2 and K2 of the color printer 1 are replenished with new toner which is a new toner supply means through cap opening 53a (53b, 53c and 53d). Connected by paths 9a, 9b, 9c, and 9d, each color new toner filled in the toner cartridge can be supplied to each developing means through the new toner supply path. The new toner supply paths 9a, 9b, 9c, and 9d are connected to a control means (not shown), and a new toner supply capable of controlling the amount of new toner supplied by controlling the ON / OFF time per predetermined control time. A replenishing screw 90a as a means and a toner remaining amount detecting sensor (not shown) for detecting whether or not toner is present in the replenishing path are provided. The container main body 50a and the replenishing screw 90a of 5a are rotated, and a predetermined amount of new toner is replenished to each developing means through each new toner replenishment path. Also, in the color printer 1, when the toner remaining amount detection sensor detects that there is no toner in the new toner replenishment path, the corresponding toner cartridge is requested to replenish toner, and the remaining toner amount is detected even after a predetermined time has elapsed. If the sensor does not detect the presence of toner, it is determined that there is no toner in the toner cartridge.

(Development means)
Next, the developing means Y2, C2, M2, and K2 of the color printer 1 will be described in detail with reference to FIGS. 3, 4 (a), and 4 (b).
FIG. 3 is a vertical sectional view showing a schematic configuration of the developing unit of the image forming apparatus according to the present embodiment, and FIG. 4 is a perspective view when the schematic configuration of the developing unit of FIG. 3 is cut along a horizontal line. It is sectional drawing, (a) is the sectional view on the aa line of FIG. 3, (b) is sectional drawing on the bb line. Reference numeral Y2 shown in FIG. 3 is a yellow toner developing unit which is cited as an embodiment of the developing unit of the color printer 1. Reference numeral Y denotes the above-described photosensitive drum Y.

  The developing unit Y2 is a dry two-component developing type biaxial transport type developing unit, and includes a developing case Y20 that is a housing of the entire developing unit Y2 and contains a two-component developer composed of toner and a magnetic carrier. The developing case Y20 is pivotally supported by the developing case Y20 in parallel with the photosensitive drum Y, and is a predetermined distance from the photosensitive drum Y at the closest position of the developing region in FIG. , About 0.2 to 0.4 mm), a developing roller Y21 is provided. The developing roller Y21 is composed of a sleeve having a cylindrical outer peripheral surface made of a non-magnetic material such as aluminum, and a magnet roller in which a plurality of magnetic poles fitted in the sleeve are magnetized. A developing bias that is connected to a bias power source and moves toner in the two-component developer carried on the sleeve surface to the image carrier side can be applied.

  In the developing case Y20, a new toner supply port 10a indicated by a broken line to which new toner is supplied by the new toner supply means, and the new toner supplied through the new toner supply port 10a are fed to the shaft of the developing roller Y21. There is provided a developer supply path Ya for supplying along the direction. That is, yellow new toner is supplied from the toner cartridge 5a to the developer supply path Ya through the new toner supply path 9a, and the new carrier and the magnetic carrier accommodated in the developing case Y20 in the developer supply path Ya. Are charged with stirring and conveyed to the developing roller Y21. The developer supply path Ya is rotatably supported in parallel with the developing roller Y21, charged while stirring the developer, transported in opposite directions to circulate the developer, and the developing roller. Two stirring screws Y22 and Y23, which are stirring and conveying means for supplying the developer to Y21, are provided. In the present embodiment, the developing roller Y21 has an outer diameter of φ18 mm, a roller length of 326 mm (the range where the developer is present is 303 mm), and a rotation speed of 315 rpm. The stirring screws Y22 and Y23 each have a pitch of 20 mm, a screw blade diameter of φ14 (shaft diameter φ6), a screw range length of 330 mm, and a rotational speed of 350 rpm.

  Further, the developer supply path Ya is provided with a toner concentration sensor S1 including a magnetic permeability sensor as a toner concentration detecting means near the bottom, and an output value of the toner concentration sensor S1: Vt and a control target value: Vtref. The toner replenishment amount is calculated according to a predetermined arithmetic expression according to the difference, and the new toner is supplied to the developing unit by the new toner supply unit or the recovered toner is supplied by the recovery toner supply unit described later. To do.

  In addition, the developing case Y20 is provided with an aluminum doctor blade Y24 that projects from the developing roller Y21 so as to be spaced apart by a predetermined distance and is a regulating member that regulates the thickness of the developer carried on the developing roller Y21. The toner recovery mechanism Yb that recovers the toner from the developer carried on the developing roller Y21 even after passing through the development area, and the toner that is separated from the developer supply path Ya as the recovery toner supply means and is recovered by the toner recovery mechanism Yb A recovered toner transport path Yc for transporting the toner to the vicinity of the new toner supply port 10a is also provided. As shown in FIG. 4A, the developer supply path Ya and the recovered toner transport path are located on the bottom surface of the recovered toner transport path Yc on the most upstream side in the transport direction and below the new toner supply port 10a. A new toner drop opening 10a ′ communicating with Yc is provided, and the new toner conveyed in the new toner supply path 9a is supplied to the developer supply path Ya through the new toner drop opening 10a ′. It is like that.

  The toner recovery mechanism Yb is connected to a bias power source and can apply a voltage to a toner recovery roller Y25, and a toner recovery member that contacts the outer peripheral surface of the toner recovery roller Y25 and scrapes off the toner carried by the toner recovery roller Y25. And a recovery blade Y26. The toner recovery operation of the toner recovery mechanism Yb is controlled by turning on or off the solenoid clutch CL1 provided in the drive gear train of the toner recovery roller Y25 according to a command from a CPU that is a control unit of the image forming apparatus main body. Then, the rotation of the toner collecting roller Y25 is controlled by transmitting or cutting the driving from the motor M as the driving means to the toner collecting roller Y25.

  The toner collecting roller Y25 is installed in the vicinity of the developing roller Y21 including a magnet roller, and is in contact with a magnetic carrier carried on the developing roller Y21. Therefore, the toner collecting roller Y25 is made of a nonmagnetic material (for example, an aluminum tube or a nonmagnetic stainless roller). It is preferable to configure. This is because the carrier is prevented from being collected by being influenced by the magnetic flux density of the developing roller 21 and the toner is mainly adsorbed electrostatically. Further, the installation interval between the toner recovery roller Y25 and the developing roller Y21 is preferably equal to the interval between the developing roller Y21 and the photosensitive drum Y (in this embodiment, about 0.2 to 0.4 mm). In the present embodiment, the toner collection roller Y25 is a hollow tube having a diameter of φ16, a roller length of 336 mm, and a material made of aluminum. The shaft is rotatably supported at 100 rpm.

  In the present embodiment, the collection blade Y26 is made of polyurethane rubber, has a thickness of 1.8 mm, a protruding length of 7.6 mm, and a contact pressure of 0.2 (N / cm). Further, the toner recovery operation may be controlled by the contact / separation operation of the recovery blade Y26 instead of the rotation / non-rotation control of the toner recovery roller Y25. This blade contacting / separating mechanism can be realized with a general configuration in which the collecting blade Y26 is always separated by a spring that pressurizes the collecting blade Y26 in the contact direction and a cam clutch. As described above, if the control of the toner collecting operation is the blade contact / separation method, the toner can be collected by the peeling action when the collecting blade Y26 contacts the toner collecting roller Y25, and the toner collecting roller Y25 is separated when separated. It is possible to make the collection impossible by simply carrying around the adhered toner. Further, at the time of recovery, the blade contact / separation method requires a clutch having a relatively larger power than the above-described roller rotation control method because the recovery blade Y26 is separated from the spring pressure. Since the collecting blade Y26 remains separated from the toner collecting roller Y25, effects such as prevention of sticking of the toner collecting roller Y25 and the collecting blade Y26 and prevention of settling due to long-term contact of the blade can be expected.

The collected toner transport path Yc is rotated by a motor M that is a driving unit, and is a collected toner transport screw that is a collected toner transport unit that transports the toner collected by the toner recovery mechanism Yb in the direction indicated by the arrow shown in FIG. Y27 is provided, and a communication port Y28 communicating with the developer supply path Ya is provided in the vicinity of the downstream end in the transport direction of the collected toner transport screw Y27, and constitutes a recovered toner supply means.
The collected toner conveying screw Y27 is connected to a motor M as a driving means via a solenoid clutch CL2 and a gear train, and controls the amount of rotation by controlling the ON / OFF time of the clutch CL2 per predetermined time. In addition, the supply amount (conveyance amount) of the collected toner collected by the toner collecting mechanism Yb can be controlled. In the collected toner conveying screw Y27 of the present embodiment, the screw pitch is 15 mm, the screw blade diameter is φ10 (shaft diameter φ3), the screw range length is 300 mm, and the rotational speed is 100 rpm (min ⁻¹ ). The supply amount is controlled by adjusting the ON / OFF time of the clutch CL2.

  The collected toner conveyance path Yc is provided with a piezoelectric fullness detection sensor S2 for detecting the fullness of the collected toner and a piezoelectric empty detection sensor S3 for detecting the emptyness, and these fullness detection sensors S2 The empty detection sensor S3 is electrically connected to the CPU of the main body of the image forming apparatus. The CPU detects whether the collected toner accumulated in the collected toner transport path Yc is full or empty, and detects by the CPU. It is possible to judge. As shown in FIG. 4A, the fullness detection sensor S2 is in the vicinity of the communication port Y28 on the downstream side in the transport direction of the collected toner transport screw Y27 and above the axial center of the recovered toner transport screw Y27. Opposed to each other. The reason why it is arranged at such a position is that the downstream side in the transport direction of the recovered toner transport screw Y27 is the position where the volume of the recovered toner is cumulatively high, and is the optimal position for detecting fullness. Further, the empty detection sensor S3 is disposed in the vicinity of the upstream end portion in the transport direction of the collected toner transport screw Y27, and opposed to a portion below the axial center of the recovered toner transport screw Y27. The reason why it is arranged at such a position is that the upstream end of the collected toner conveying screw Y27 in the conveying direction is the position where the volume of collected toner is the lowest, and is the optimal position for detecting the empty state. Note that these sensors (S2, S3) are not piezoelectric sensors but optical sensors (there are locations where light is projected and received at all times within the sensor, and the energization state of the sensors changes depending on the presence or absence of toner. And a method for detecting the presence or absence of toner). Whether full or empty is judged is based on whether or not there is a hindrance to the transport of the collected toner transport screw Y27, and an allowance is provided by considering a safety factor from a continuous image formation experiment with an assumed average image area. I have it. As an example of a continuous image formation experiment, it can be evaluated by forming 1000 images by A4 landscape, 5% image area, or 50% images, 10% images, and 3% images mixed at a predetermined ratio. . The full detection sensor S2 is arranged in the vicinity of the upper end of the outer periphery of the screw blade of the opposing collection toner conveyance screw Y27, and the empty detection sensor S3 is arranged in the vicinity of the lower end of the outer periphery of the screw blade of the opposite collection toner conveyance screw Y27. The detailed installation height, sensitivity, and the like are adjusted based on the results of the image formation experiment described above (see FIG. 3).

  As described above, the configuration of the developing unit according to the present embodiment has been described by taking the yellow toner developing unit Y2 as an example, but other toner color developing units (C2, M2, and K2) are similar. It has a configuration. Further, as the toner collecting member, the blade-type collecting blade Y26 that scrapes by contacting the edge has been described as an example, but there is also a method of scraping the two rollers with a speed difference in the forward direction. Alternatively, a brush roller may be applied to the toner collecting roller Y25, and the toner may be finally collected by a flicker member that has been entrapped in the brush roller. The toner collecting mechanism itself applies a bias applied to the toner collecting roller. A method may be used in which the electrostatic attraction force is changed and the toner is peeled off and collected from the toner collecting roller. Further, as an example of the new toner conveying means and the collected toner conveying means, a screw type that is rotationally driven by the driving means has been described, but the uniaxial deviation proposed by the applicant in Japanese Patent Laid-Open No. 10-333412 and the like. You may use as a conveyance means of the system which mixes and conveys the airflow and toner using powder pumps, such as a core screw pump and a diaphragm pump. By doing so, it is possible to simplify the apparatus and save space. The term “new toner” used in the present invention includes not only new toners stored in the toner cartridges 5a, 5b, 5c, and 5d of the new toner storage unit 5, but also the developer from the new toner storage unit. This refers to the toner that has been supplied to the supply path and is carried on the developing roller, and “collected toner” refers to the toner that has been collected by the toner collecting mechanism.

(Operation of developing means)
Next, the operation of the developing means of the color printer 1 will be described with reference to FIGS. 3, 4 (a) and 4 (b).
First, the new toner supplied by the new toner supply means through the new toner supply port 10a of the developing case Y20 and the new toner dropping port 10a 'of the recovered toner transport path Yc is accommodated in the developing case Y20 by the stirring screws Y22 and Y23. The magnetic carrier is charged while being mixed and stirred, and is conveyed toward the developing roller Y21 in the direction shown in FIG. 4B. Next, the developer reaching the vicinity of the developing roller Y21 is magnetically attracted and carried by the magnetic force of the magnet roller in the developing roller Y21, and is conveyed to the vicinity of the doctor blade Y24 as the developing roller Y21 rotates. Therefore, the thickness of the developer is made uniform by the doctor blade Y24, and the developer carried on the developing roller Y21 is regulated to a certain amount. As the developing roller Y21 further rotates, the developing roller Y21 reaches a position facing the photosensitive drum Y, that is, the developing region shown in FIG. 3, and a developing bias is applied. Therefore, only the toner at the position corresponding to the latent image is transferred to the electrostatic latent image carried on the photosensitive drum Y by the electrostatic force, so that a single color toner image is developed. Therefore, the toner that has not been developed and the carrier that has transported the toner reach a position facing the toner collecting roller Y25 as the developing roller Y21 rotates. At a predetermined timing, a voltage is applied to the toner collecting roller Y25, and only the toner from the developer carried on the developing roller Y21 is electrostatically transferred to the toner collecting roller Y25. Then, the toner that has not been collected by the toner collection roller Y25 and the carrier that has conveyed the toner are conveyed to the front of the developer agitating screws Y22 and Y23 (the part away from the agent in FIG. 3) as the development roller Y21 further rotates. Then, it is peeled off from the surface of the developing roller Y21 by the repulsive pole of the magnet roller, falls on the stirring screws Y22 and Y23, and is stirred. The toner transferred onto the toner recovery roller Y25 is scraped off from the toner recovery roller Y25 by the recovery blade Y26 as the toner recovery roller Y25 rotates, and is carried to the recovery toner transport path Yc. The collected toner is conveyed to the collected toner conveyance path Yc or is conveyed by the collected toner conveyance screw Y27 and returned to the developer supply path Ya from the communication port Y28.

(Applied voltage of toner recovery roller)
Next, the bias voltage applied to the toner recovery roller of the color printer 1 will be described. FIG. 5 is a graph showing the relationship between the toner adhesion amount of two types of developer and the development bias.
This graph shows the toner adhesion amount when the bias applied to the toner collecting roller is −50 V, the toner collecting roller is rotated in the forward direction at about twice the peripheral speed of the developing roller, and the developing bias is changed. Showing the relationship. The slope of the graph of FIG. 5 can take various values depending on the combination of the type of carrier and the type of toner. The amount of toner attached to the toner collection roller per area depends on the bias applied to the toner collection roller and the developing roller. It can be seen that the voltage increases in proportion to the difference from the developing bias applied to. That is, when the image area ratio to be collected is set, the toner adhesion amount is determined, and the bias applied to the toner collection roller can be determined from the toner adhesion amount using FIG. In the developing unit according to the present embodiment, the developer to be used is developer A shown in FIG. 5, and the bias applied to the toner recovery roller is set to the developing bias +100 V or more. For example, when the developing bias is −500 V, 0 to −400 V is applied to the toner collecting roller. In this embodiment, the two rollers, the toner collecting roller and the developing roller, are collected with a speed difference in the forward direction. However, the toner collecting roller may be collected by rotating in the counter direction. . In this way, by controlling the bias applied to the toner recovery roller by the control means, the toner recovery amount that can be recovered by the toner recovery roller (toner recovery mechanism) can be controlled.

  As will be described later in the description of the toner, electrostatic toner recovery from the developing roller by the toner recovery roller has a particle size produced by a toner manufacturing method as described below rather than pulverized toner having a variation in particle size. A toner having a small variation, that is, a toner having a substantially uniform capacitance is preferable. That is, it is a toner of a true spherical shape, a substantially spherical shape, a rugby ball shape, and a plum dried shape, which will be described later. In these toners, the charge amount of each toner that remains unused on the developing roller is much smaller than that of the pulverized toner, and the electrostatic toner adsorbed and collected by the toner collecting roller thereafter. This is because a margin can be given to the setting range of the bias voltage. Toner with a large variation in particle size has a variation in the charge amount of each toner, and it is necessary to set a bias voltage having a polarity different from that of the toner charge according to the toner with a large charge amount, but it is too large. As a result, a charge injection phenomenon occurs in the toner having a small charge amount and the polarity is reversed. As a result, the polarity becomes the same as that of the bias voltage and the adsorption action cannot be generated. Therefore, if the bias voltage is too large or too small, suction recovery cannot be performed, and it is not possible to provide a sufficient setting. In that case, when the variation of the temperature and humidity environment is taken into consideration, the setting that can be used in the entire environment is further freed up. On the other hand, if the above-described toner having a substantially uniform capacitance studied in the present invention is used, a range in which the charge injection phenomenon does not occur can be widened, and only the setting for environmental fluctuations needs to be considered.

(Optical sensor)
Next, the optical sensor will be described with reference to FIG.
In the color printer 1 described above, the color optical sensor S4 is downstream in the moving direction of the intermediate transfer belt 40 of the magenta image forming unit 3M, and the black optical sensor S4 ′ is downstream of the black image forming unit 3K. Are disposed toward the outer surface of the intermediate transfer belt 40 (see FIG. 1). That is, the optical sensor S4 (S4 ′) indicated by a one-dot chain line (an overhead line) in FIG. 3 is not installed downstream of the yellow image forming unit 3Y, but is installed downstream of the image forming units 3M and 3K. Has been. The optical sensor S4 is a diffuse reflection type sensor composed of a light emitting element such as an LED and a light receiving element such as a photodiode, and the optical sensor S4 ′ for black is a light emitting element such as an LED and a light receiving element such as a photodiode. It is a regular reflection type sensor consisting of This is because the specular reflection type has a more severe mounting accuracy and is likely to cause a failure due to misalignment, but the diffuse reflection type cannot measure a black toner image. Of course, one of the regular reflection type may be provided downstream of the black image forming unit 3K as a shared color and black, or a total of four may be provided in each image forming unit. These optical sensors S4 (S4 ′) irradiate a patch pattern composed of solid images with different densities formed on the intermediate transfer belt 40 at a predetermined time other than the time of image formation, and reflect the reflected light. A voltage corresponding to the amount of received light is read and the output value is sent to a control means (not shown) for processing. Based on the result, the amount of toner attached to the intermediate transfer belt 40 is determined. The color toner images are used for position adjustment of each color toner image and control of image forming conditions (image forming timing, developing bias, charging potential, exposure potential (exposure amount), toner density, etc.) on the photosensitive drum, so-called process control.

[Toner density control]
Next, toner density control, which is a feature of the present invention, will be described.
In the toner density control according to the present embodiment, first, the control unit of the color printer 1 compares the output value Vt of the toner density sensor S1, which is a toner density detection unit, with its control target value Vtref, and the developing unit (Y2 , C2, M2, K2) to determine whether or not the toner density is lower than the target, and the toner replenishment amount (supply amount per predetermined control time: rotation amount, motor driving ON time, etc.) is determined by a predetermined arithmetic expression. calculate. When it is determined that the toner density in the developing unit is lower than the target, in principle, the collected toner is supplied to the developer supply path (Ya, Ca, Ma, Ka) by the collected toner supply unit. That is, the collected toner conveying screw (Y27, C27, M27, K27) of the collected toner conveying path (Yc, Cc, Mc, Kc) is driven to collect the collected toner from the communication port (Y28, C28, M28, K28). Supply to the supply path. When the output value Vt of the toner density sensor S1 is within a predetermined range compared with the control target value Vtref, the supply of the collected toner is stopped. However, when empty detection is performed by the empty detection sensor S3 indicating that it is difficult to convey with the collected toner conveying screw (Y27, C27, M27, K27), the collected toner supply means does not supply the collected toner. Only new toner is supplied by the new toner supply means. At this time, for example, when an instruction to output multiple copies of the same image with a high image area ratio is given, when the toner consumption amount exceeding the supply capability of the collected toner supply unit of the developing unit is expected, Depending on the judgment of the control means of the color printer 1, both the collected toner supply means and the new toner supply means may be operated to supply both the new toner and the collected toner. By controlling in this way, the toner having deteriorated can be used preferentially, causing a decrease in transfer efficiency during transfer due to toner deterioration, a decrease in the amount of pumping by the developing roller, and the like. The problem that the density cannot be kept constant can be prevented. In addition, since the toner density can be quickly adjusted to an appropriate value, the image quality of the output image can always be improved.

  In the color printer 1 according to the present embodiment, the actual toner adhesion amount to the intermediate transfer belt 40 is determined based on the information from the optical sensor S4 (S4 ′), and the adhesion amount is larger than the target value. In this case, the amount of adhesion information is fed back to lower the toner density control target in the developing means by a predetermined value (the control target value Vtref corresponds to the voltage output from the toner density sensor S1. As will be described later, when this value increases, it indicates that the toner density has decreased, so the control target value Vtref is increased by a predetermined value). Control is performed so that the image density of the output image becomes appropriate. In such a case, the actual toner density in the developing unit may be higher than the control target toner density. Therefore, in the toner density control according to the present embodiment, the output value Vt of the toner density sensor S1 is compared with the control target value Vtref, and when it is determined that the toner density in the developing unit is high, the toner recovery is performed. The mechanism (Yb, Cb, Mb, Kb) collects only the toner from the developing roller (Y21, C21, M21, K21), stores it in the collected toner conveyance path (Yc, Cc, Mc, Kc), and develops it. The toner density of the developer in the inside is lowered. By controlling the toner density in this way, even when the toner density in the developing means becomes higher than the target, the developer can be quickly lowered to an appropriate toner density, and therefore the image density of the output image can be reduced. Can always be appropriate. In addition, since the collected toner can be re-supplied, the toner yield is not deteriorated.

  Note that the control target value Vtref (the toner density corresponding to the control target value) is not limited to the case where the information from the optical sensor is fed back and changed, and the toner of a specific developing unit is not used. When the color toner is consumed, the developer in the developing unit is continuously stirred, and the charge amount of the developer (toner) is increased, the toner adhesion amount of the output image increases. Therefore, it is necessary to increase the control target value Vtref and decrease the corresponding toner density. In addition, it is desirable to change and set the control target value Vtref as necessary, such as changes in the surrounding environment of the printer 1 such as humidity and temperature, and changes in the trend of the image area ratio of the output image.

<Effect confirmation experiment>
Next, the following experiment was conducted to confirm the above-described effects and the like.
FIG. 6 is a graph showing the change with time of the output value Vt of the toner concentration detection sensor of the embodiment, and FIG. 7 is a graph showing the change with time of the output value Vt ′ of the toner concentration detection sensor of the comparative example. The horizontal axis in the figure is the elapsed time (seconds), and the vertical axis is the output voltage of the toner density sensor S1. The lower the output value, the higher the toner density. Also, the solid line in the figure shows the change over time of the output value Vt ′ of the toner density sensor of the example and the output value Vt ′ of the toner density sensor of the comparative example, and the alternate long and short dash line is the control target of the toner density sensor. The value Vtref.
In the example of FIG. 6, the color printer 1 according to the above-described embodiment is used so that the toner density exceeds the control target, that is, the output value Vt from the toner density detection sensor S1 is the control target value Vtref (= -0.2V), and the output value of the toner density sensor S1 when the toner is collected by the toner collecting mechanism Yb according to the toner density control described above is plotted for each elapsed time. In the comparative example of FIG. 7, the output value Vt ′ of the toner concentration sensor S1 is plotted for each elapsed time without controlling the toner collection mechanism Yb after controlling the toner concentration to exceed the control target. It is. As is apparent from FIGS. 6 and 7, in this embodiment, even if the toner density exceeds the target value, that is, the toner density becomes too high, the toner density is set to the target value by 30 seconds by the toner recovery mechanism Yb. Although it can be quickly returned in about 50 seconds, it can be seen that in the comparative example, the toner cannot be collected, and thus it has a steady deviation with respect to the target value. In other words, once the toner density of the developing unit becomes higher than the control target by changing the control target in accordance with the usage state such as a change in charging state, the toner in which the actual toner density in the developing unit does not reach the control target. Image formation is performed in a state where the density is too high. That is, it can be seen that it is difficult to maintain an appropriate image density.

Next, the toner suitably used in the image forming apparatus of the present invention will be described.
In order to reproduce minute dots of 600 dpi or more, the toner preferably has a volume average particle diameter of 3 to 8 μm. The ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is preferably in the range of 1.00 to 1.40. The closer (Dv / Dn) is to 1.00, the sharper the particle size distribution. With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do.

The toner shape factor SF-1 is preferably in the range of 100 to 180, and the shape factor SF-2 is preferably in the range of 100 to 180. 8 and 9 are explanatory diagrams schematically showing the shape of the toner in order to explain the shape factor SF-1 and the shape factor SF-2, respectively. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (A). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) Expression (A)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.
The shape factor SF-2 indicates the ratio of the unevenness of the toner shape and is represented by the following formula (B). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) ² / AREA} × (100π / 4) Expression (B)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.
Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated.
When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered, which is not preferable.

  The toner suitably used in the image forming apparatus of the present invention is a water-based toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, a polyester, a colorant, and a release agent are dispersed in an organic solvent. A toner obtained by crosslinking and / or elongation reaction in a solvent. Hereinafter, the constituent material and the manufacturing method of the toner will be described.

(polyester)
The polyester is obtained by a polycondensation reaction between a polyhydric alcohol compound and a polycarboxylic acid compound.
Examples of the polyhydric alcohol compound (PO) include dihydric alcohol (DIO) and trihydric or higher polyhydric alcohol (TO). (DIO) alone or a mixture of (DIO) and a small amount of (TO) preferable. Examples of the dihydric alcohol (DIO) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (diethylene glycol) , Triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); bisphenols (bisphenol A, bisphenol) F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol; Alkylene oxide bisphenol (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among them, preferred are alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms. It is a combined use. The trihydric or higher polyhydric alcohol (TO) includes 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); trihydric or higher phenols (Trisphenol PA, phenol novolak, cresol novolak, etc.); and alkylene oxide adducts of the above trivalent or higher polyphenols.

  Examples of the polyvalent carboxylic acid (PC) include divalent carboxylic acid (DIC) and trivalent or higher polyvalent carboxylic acid (TC). (DIC) alone and (DIC) with a small amount of (TC) Mixtures are preferred. Divalent carboxylic acids (DIC) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid) And naphthalenedicarboxylic acid). Of these, preferred are alkenylene dicarboxylic acids having 4 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms. Examples of the trivalent or higher polyvalent carboxylic acid (TC) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polyhydric carboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the acid anhydride or lower alkyl ester (methyl ester, ethyl ester, isopropyl ester, etc.) of the above-mentioned thing.

The ratio of the polyhydric alcohol (PO) to the polycarboxylic acid (PC) is usually 2/1 to 1/1, preferably as the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. Is 1.5 / 1 to 1/1, more preferably 1.3 / 1 to 1.02 / 1.
The polycondensation reaction between a polyhydric alcohol (PO) and a polycarboxylic acid (PC) is carried out in the presence of a known esterification catalyst such as tetrabutoxytitanate or dibutyltin oxide, and heated to 150 to 280 ° C. while reducing the pressure as necessary. The produced water is distilled off to obtain a polyester having a hydroxyl group. The hydroxyl value of the polyester is preferably 5 or more, and the acid value of the polyester is usually 1 to 30, preferably 5 to 20. By giving an acid value, it tends to be negatively charged, and furthermore, when fixing to a recording paper, the affinity between the recording paper and the toner is good and the low-temperature fixability is improved. However, when the acid value exceeds 30, there is a tendency to deteriorate with respect to the stability of charging, particularly environmental fluctuation.
The weight average molecular weight is 10,000 to 400,000, preferably 20,000 to 200,000. A weight average molecular weight of less than 10,000 is not preferable because offset resistance deteriorates. On the other hand, if it exceeds 400,000, the low-temperature fixability is deteriorated.

In addition to the unmodified polyester obtained by the above polycondensation reaction, the polyester preferably contains a urea-modified polyester. The urea-modified polyester is obtained by reacting a terminal carboxyl group or hydroxyl group of the polyester obtained by the above polycondensation reaction with a polyvalent isocyanate compound (PIC) to obtain a polyester prepolymer (A) having an isocyanate group. It is obtained by cross-linking and / or extending the molecular chain by the reaction of the amine with amines.
Examples of the polyvalent isocyanate compound (PIC) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) ); Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; Those blocked with caprolactam or the like; and combinations of two or more of these.
The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably as an equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 4/1 to 1.2 / 1, more preferably 2.5 / 1 to 1.5 / 1. When [NCO] / [OH] exceeds 5, low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1, when a urea-modified polyester is used, the urea content in the ester is lowered and hot offset resistance is deteriorated.
The content of the polyvalent isocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40 wt%, preferably 1 to 30 wt%, more preferably 2 to 20 wt%. . If it is less than 0.5 wt%, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. On the other hand, if it exceeds 40 wt%, the low-temperature fixability deteriorates.
The number of isocyanate groups contained per molecule in the polyester prepolymer (A) having an isocyanate group is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2 on average. Five. If it is less than 1 per molecule, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance is deteriorated.

Next, as amines (B) to be reacted with the polyester prepolymer (A), a divalent amine compound (B1), a trivalent or higher polyvalent amine compound (B2), an amino alcohol (B3), an amino mercaptan (B4) ), Amino acid (B5), and amino acid block of B1 to B5 (B6).
Examples of the divalent amine compound (B1) include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′-diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′-dimethyldicyclohexyl). Methane, diamine cyclohexane, isophorone diamine, etc.); and aliphatic diamines (ethylene diamine, tetramethylene diamine, hexamethylene diamine, etc.) and the like. Examples of the trivalent or higher polyvalent amine compound (B2) include diethylenetriamine and triethylenetetramine. Examples of amino alcohol (B3) include ethanolamine and hydroxyethylaniline. Examples of amino mercaptan (B4) include aminoethyl mercaptan and aminopropyl mercaptan. Examples of the amino acid (B5) include aminopropionic acid and aminocaproic acid. Examples of the compound (B6) obtained by blocking the amino group of B1 to B5 include ketimine compounds and oxazolidine compounds obtained from the amines of B1 to B5 and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

The ratio of amines (B) is equivalent to the equivalent ratio [NCO] / [NHx] of isocyanate groups [NCO] in the polyester prepolymer (A) having isocyanate groups and amino groups [NHx] in amines (B). Is usually 1/2 to 2/1, preferably 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2. When [NCO] / [NHx] exceeds 2 or less than 1/2, the molecular weight of the urea-modified polyester becomes low, and the hot offset resistance deteriorates.
The urea-modified polyester may contain a urethane bond together with a urea bond. The molar ratio of the urea bond content to the urethane bond content is usually 100/0 to 10/90, preferably 80/20 to 20/80, and more preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance is deteriorated.

  The urea-modified polyester is produced by a one-shot method or the like. Polyhydric alcohol (PO) and polyvalent carboxylic acid (PC) are heated to 150-280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate, dibutyltin oxide, etc., and water generated while reducing the pressure as necessary. Distill off to obtain a polyester having a hydroxyl group. Subsequently, at 40-140 degreeC, this is made to react with polyvalent isocyanate (PIC), and the polyester prepolymer (A) which has an isocyanate group is obtained. Further, this (A) is reacted with amines (B) at 0 to 140 ° C. to obtain a urea-modified polyester.

When reacting (PIC) and when reacting (A) and (B), a solvent may be used if necessary. Usable solvents include aromatic solvents (toluene, xylene, etc.); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.); esters (ethyl acetate, etc.); amides (dimethylformamide, dimethylacetamide, etc.) and ethers And those inert to isocyanates (PIC), such as tetrahydrofuran (such as tetrahydrofuran).
In addition, in the crosslinking and / or extension reaction between the polyester prepolymer (A) and the amines (B), a reaction terminator can be used as necessary to adjust the molecular weight of the resulting urea-modified polyester. Examples of the reaction terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), and those obtained by blocking them (ketimine compounds).
The weight average molecular weight of the urea-modified polyester is usually 10,000 or more, preferably 20,000 to 10,000,000, and more preferably 30,000 to 1,000,000. If it is less than 10,000, the hot offset resistance deteriorates. The number average molecular weight of the urea-modified polyester or the like is not particularly limited when the above-mentioned unmodified polyester is used, and may be a number average molecular weight that can be easily obtained to obtain the weight average molecular weight. When the urea-modified polyester is used alone, its number average molecular weight is usually 2000-15000, preferably 2000-10000, more preferably 2000-8000. When it exceeds 20000, the low-temperature fixability and the glossiness when used in a full-color apparatus are deteriorated.

By using the unmodified polyester and the urea-modified polyester in combination, the low-temperature fixability and the glossiness when used in a full-color image forming apparatus are improved. Therefore, it is preferable to use the urea-modified polyester alone. The unmodified polyester may include a polyester modified with a chemical bond other than a urea bond.
The unmodified polyester and the urea-modified polyester are preferably at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance. Therefore, it is preferable that the unmodified polyester and the urea-modified polyester have a similar composition.
The weight ratio of unmodified polyester to urea-modified polyester is usually 20/80 to 95/5, preferably 70/30 to 95/5, more preferably 75/25 to 95/5, and particularly preferably 80 /. 20-93 / 7. When the weight ratio of the urea-modified polyester is less than 5%, the hot offset resistance is deteriorated, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.

The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 45 to 65 ° C, preferably 45 to 60 ° C. If it is less than 45 ° C., the heat resistance of the toner deteriorates, and if it exceeds 65 ° C., the low-temperature fixability becomes insufficient.
In addition, since the urea-modified polyester is likely to be present on the surface of the obtained toner base particles, the heat-resistant storage stability tends to be good even when the glass transition point is low as compared with known polyester-based toners.

(Coloring agent)
As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher , Yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow (G, GR), permanent yellow (NCG), Vulcan fast yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Sayred, Parachlor Ortonito Aniline Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine B, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R , Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thio Indigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red Polyazo Red, Chrome Vermillion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Lid Russian nin green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The content of the colorant is usually 1 to 15% by weight, preferably 3 to 10% by weight, based on the toner.

  The colorant can also be used as a master batch combined with a resin. As a binder resin to be kneaded together with the production of the master batch or the master batch, a polymer of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyl toluene or the like, or a copolymer of these and a vinyl compound, Polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like can be mentioned, and these can be used alone or in combination.

(Charge control agent)
Known charge control agents can be used, such as nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified 4 Secondary ammonium salts or compounds, tungsten simple substances or compounds, fluorine activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives. Specifically, Bontron 03 of a nigrosine dye, Bontron P-51 of a quaternary ammonium salt, Bontron S-34 of a metal-containing azo dye, E-82 of an oxynaphthoic acid metal complex, E-84 of a salicylic acid metal complex , Phenolic condensate E-89 (above, Orient Chemical Industries, Ltd.), quaternary ammonium salt molybdenum complex TP-302, TP-415 (above, Hodogaya Chemical Co., Ltd.), quaternary ammonium salt copy Charge PSY VP2038, copy blue PR of triphenylmethane derivative, copy charge of quaternary ammonium salt NEG VP2036, copy charge NX VP434 (manufactured by Hoechst), LRA-901, LR-147 which is a boron complex (Nippon Carlit) Manufactured), copper phthalocyanine, perylene, quinacridone, azo series Fee, a sulfonic acid group, a carboxyl group, and polymer compounds having a functional group such as quaternary ammonium salts. Of these, substances that control the negative polarity of the toner are particularly preferably used.
The amount of charge control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by weight per 100 parts by weight of the binder resin. The range of 0.2 to 5 parts by weight is preferable. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, the effect of the charge control agent is reduced, the electrostatic attractive force with the developing roller is increased, the developer fluidity is lowered, and the image density is lowered. Invite.

(Release agent)
As a release agent, a low melting point wax having a melting point of 50 to 120 ° C. works more effectively as a release agent in the dispersion with the binder resin between the fixing roller and the toner interface. The effect on high temperature offset is exhibited without applying a release agent such as oil. Examples of such a wax component include the following. Examples of waxes and waxes include plant waxes such as carnauba wax, cotton wax, wood wax, rice wax, animal waxes such as beeswax and lanolin, mineral waxes such as ozokerite and cercin, and paraffin, microcrystalline, And petroleum waxes such as petrolatum.
In addition to these natural waxes, synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax, and synthetic waxes such as esters, ketones, and ethers can be used. Furthermore, fatty acid amides such as 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride imide, chlorinated hydrocarbon, and low molecular weight crystalline polymer resin, poly-n-stearyl methacrylate, poly-n- A crystalline polymer having a long alkyl group in the side chain such as a homopolymer or copolymer of polyacrylate such as lauryl methacrylate (for example, a copolymer of n-stearyl acrylate-ethyl methacrylate, etc.) can also be used. .
The charge control agent and the release agent can be melt-kneaded together with the master batch and the binder resin, or may be added when dissolved and dispersed in an organic solvent.

(External additive)
Inorganic fine particles are preferably used as an external additive for assisting the fluidity, developability and chargeability of the toner particles. The primary particle diameter of the inorganic fine particles is preferably 5 × 10 ^-3 ~2μm, it is particularly preferably 5 × 10 ^-3 ~0.5μm. Moreover, it is preferable that the specific surface area by BET method is 20-500 m < ² > / g. The use ratio of the inorganic fine particles is preferably 0.01 to 5 wt% of the toner, and particularly preferably 0.01 to 2.0 wt%.
Specific examples of the inorganic fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, diatomaceous earth. Examples include soil, chromium oxide, cerium oxide, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. Among these, as the fluidity imparting agent, it is preferable to use hydrophobic silica fine particles and hydrophobic titanium oxide fine particles in combination. In particular, when stirring and mixing are performed using an average particle size of both fine particles of 5 × 10 ⁻² μm or less, the electrostatic force and van der Waals force with the toner are remarkably improved, so that a desired charge level is obtained. Even when stirring and mixing inside the developing device is performed to obtain a good image quality that does not cause the release of the fluidity imparting agent from the toner and does not generate firefly, etc., and further reduces the residual toner. It is done.
Titanium oxide fine particles are excellent in environmental stability and image density stability, but have a tendency to deteriorate the charge rise characteristics. Therefore, if the amount of titanium oxide fine particles added is larger than the amount of silica fine particles added, this side effect is affected. It can be considered large. However, when the added amount of the hydrophobic silica fine particles and the hydrophobic titanium oxide fine particles is in the range of 0.3 to 1.5 wt%, the charge rising characteristics are not greatly impaired, and the desired charge rising characteristics can be obtained, that is, repeated copying. Stable image quality can be obtained even if

Next, a toner manufacturing method will be described. Here, although a preferable manufacturing method is shown, it is not limited to this.
(Toner production method)
(1) A toner material solution is prepared by dispersing a colorant, unmodified polyester, a polyester prepolymer having an isocyanate group, and a release agent in an organic solvent.
The organic solvent is preferably volatile with a boiling point of less than 100 ° C. from the viewpoint of easy removal after toner base particle formation. Specifically, toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, methyl ethyl ketone, Methyl isobutyl ketone and the like can be used alone or in combination of two or more. In particular, aromatic solvents such as toluene and xylene and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform, and carbon tetrachloride are preferable. The usage-amount of an organic solvent is 0-300 weight part normally with respect to 100 weight part of polyester prepolymers, Preferably it is 0-100 weight part, More preferably, it is 25-70 weight part.

(2) The toner material liquid is emulsified in an aqueous medium in the presence of a surfactant and resin fine particles.
The aqueous medium may be water alone or an organic solvent such as alcohol (methanol, isopropyl alcohol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.). It may be included.
The amount of the aqueous medium used relative to 100 parts by weight of the toner material liquid is usually 50 to 2000 parts by weight, preferably 100 to 1000 parts by weight. If the amount is less than 50 parts by weight, the dispersion state of the toner material liquid is poor, and toner particles having a predetermined particle diameter cannot be obtained. If it exceeds 20000 parts by weight, it is not economical.

Further, in order to improve the dispersion in the aqueous medium, a dispersant such as a surfactant and resin fine particles is appropriately added.
As surfactants, anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, alkylamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, Quaternary ammonium salt type cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, benzethonium chloride, fatty acid amide derivatives, polyhydric alcohols Nonionic surfactants such as derivatives, for example, amphoteric surfactants such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine And the like.

Further, by using a surfactant having a fluoroalkyl group, the effect can be obtained in a very small amount. Preferred anionic surfactants having a fluoroalkyl group include fluoroalkyl carboxylic acids having 2 to 10 carbon atoms and metal salts thereof, disodium perfluorooctanesulfonyl glutamate, 3- [ω-fluoroalkyl (C6-C11 ) Oxy] -1-alkyl (C3-C4) sodium sulfonate, 3- [ω-fluoroalkanoyl (C6-C8) -N-ethylamino] -1-propanesulfonic acid sodium, fluoroalkyl (C11-C20) carvone Acids and metal salts, perfluoroalkylcarboxylic acids (C7 to C13) and metal salts thereof, perfluoroalkyl (C4 to C12) sulfonic acids and metal salts thereof, perfluorooctanesulfonic acid diethanolamide, N-propyl-N- ( 2-Hydroxyethyl) Perful Olooctanesulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, etc. Can be mentioned.
Product names include Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.), Florard FC-93, FC-95, FC-98, FC-129 (Sumitomo 3M Co., Ltd.), Unidyne DS-101. DS-102 (manufactured by Daikin Industries, Ltd.), Megafac F-110, F-120, F-113, F-191, F-812, F-833 (manufactured by Dainippon Ink, Inc.), Xtop EF-102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products), and Fgentent F-100, F150 (manufactured by Neos).

  In addition, examples of the cationic surfactant include aliphatic quaternary ammonium salts such as aliphatic primary, secondary or secondary amine acids having a fluoroalkyl group, and perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salts. , Benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (manufactured by Asahi Glass), Florard FC-135 (manufactured by Sumitomo 3M), Unidyne DS-202 (Daikin Industries) Manufactured), MegaFuck F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products), Footgent F-300 (Neos), and the like.

The resin fine particles are added to stabilize the toner base particles formed in the aqueous medium. For this reason, it is preferable to add so that the coverage existing on the surface of the toner base particles is in the range of 10 to 90%. For example, polymethyl methacrylate fine particles 1 μm and 3 μm, polystyrene fine particles 0.5 μm and 2 μm, poly (styrene-acrylonitrile) fine particles 1 μm, trade names are PB-200H (manufactured by Kao Corporation), SGP (manufactured by Soken Co., Ltd.), Techno Examples include polymer SB (manufactured by Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), and micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.).
In addition, inorganic compound dispersants such as tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite can also be used.

  As a dispersant that can be used in combination with the resin fine particles and the inorganic compound dispersant, the dispersed droplets may be stabilized by a polymer protective colloid. For example, acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups Bodies such as acrylic acid-β-hydroxyethyl, methacrylic acid-β-hydroxyethyl, acrylic acid-β-hydroxypropyl, methacrylic acid-β-hydroxypropyl, acrylic acid-γ-hydroxypropyl, methacrylic acid-γ-hydroxy Propyl, acrylic acid-3-chloro-2-hydroxypropyl, methacrylic acid-3-chloro-2-hydroxypropyl, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate Luric acid esters, N-methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, or compounds containing vinyl alcohol and a carboxyl group Esters such as vinyl acetate, vinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic acid chloride, methacrylic acid chloride, vinyl pyridine, vinyl pyrrolidone, vinyl Nitrogen compounds such as imidazole and ethyleneimine, or homopolymers or copolymers such as those having a heterocyclic ring thereof, polyoxyethylene, poly Xoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxy Polyoxyethylenes such as ethylene nonylphenyl ester, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.

  The dispersion method is not particularly limited, and known equipment such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied. Among these, the high-speed shearing method is preferable in order to make the particle size of the dispersion 2 to 20 μm. When a high-speed shearing disperser is used, the rotational speed is not particularly limited, but is usually 1000 to 30000 rpm, preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 ° C. (under pressure), preferably 40 to 98 ° C.

(3) At the same time as the preparation of the emulsion, the amines (B) are added to cause a reaction with the polyester prepolymer (A) having an isocyanate group.
This reaction involves molecular chain crosslinking and / or elongation. The reaction time is selected depending on the reactivity between the isocyanate group structure of the polyester prepolymer (A) and the amines (B), but is usually 10 minutes to 40 hours, preferably 2 to 24 hours. The reaction temperature is generally 0 to 150 ° C, preferably 40 to 98 ° C. Moreover, a well-known catalyst can be used as needed. Specific examples include dibutyltin laurate and dioctyltin laurate.

(4) After completion of the reaction, the organic solvent is removed from the emulsified dispersion (reactant), washed and dried to obtain toner base particles.
In order to remove the organic solvent, the temperature of the entire system is gradually raised in a laminar stirring state, and after giving strong stirring in a certain temperature range, a spindle-shaped toner base particle can be produced by removing the solvent. . Further, when an acid such as calcium phosphate salt or an alkali-soluble material is used as the dispersion stabilizer, the calcium phosphate salt is dissolved from the toner base particles by a method such as dissolving the calcium phosphate salt with an acid such as hydrochloric acid and washing with water. Remove. It can also be removed by operations such as enzymatic degradation.

(5) A charge control agent is injected into the toner base particles obtained above, and then inorganic fine particles such as silica fine particles and titanium oxide fine particles are externally added to obtain a toner.
The injection of the charge control agent and the external addition of the inorganic fine particles are performed by a known method using a mixer or the like.
Thereby, a toner having a small particle size and a sharp particle size distribution can be easily obtained. Furthermore, by giving strong agitation in the process of removing the organic solvent, the shape between the true spherical shape and the rugby ball shape can be controlled, and the surface morphology is also controlled between the smooth shape and the umeboshi shape. be able to.

The shape of the toner in the present embodiment is a substantially spherical shape, and can be represented by the following shape rule.
10A to 10C are explanatory views schematically showing the shape of the toner of the present embodiment.
10A to 10C, when a substantially spherical toner is defined by a major axis r ₁ , a minor axis r ₂ , and a thickness r ₃ (where r ₁ ≧ r ₂ ≧ r ₃ ). In the toner of the present invention, the ratio between the major axis and the minor axis (r ₂ / r ₁ ) (see FIG. 10B) is 0.5 to 1.0, and the ratio between the thickness and the minor axis (r ₃ / R ₂ ) (see FIG. 10C) is preferably in the range of 0.7 to 1.0. If the ratio of the major axis to the minor axis (r ₂ / r ₁ ) is less than 0.5, the dot reproducibility and transfer efficiency are inferior because of the separation from the true spherical shape, and high quality image quality cannot be obtained. On the other hand, when the ratio (r ₃ / r ₂ ) between the thickness and the short axis is less than 0.7, it becomes close to a flat shape and a high transfer rate like a spherical toner cannot be obtained. In particular, when the ratio of the thickness to the short axis (r ₃ / r ₂ ) is 1.0, the rotating body has the long axis as the rotation axis, and the fluidity of the toner can be improved.
Note that r ₁ , r ₂ , and r ₃ were measured with a scanning electron microscope (SEM) while changing the angle of field of view and taking pictures.

  As described above, the image forming apparatus according to the embodiment of the present invention has been described by taking the example of the quadruple tandem indirect transfer system, but the present invention is not necessarily limited to such an apparatus. For example, a quadruple tandem direct transfer system or a latent image carrier may be used for one monochrome. Also, toner supply means, recovered toner supply means, transport means, toner density sensor, full detection sensor, empty detection sensor, optical sensor, writing means, image forming part (charging means, cleaning means), transfer part, paper feeding part, The fixing unit, the paper discharge unit, and the like are merely examples, and other known configurations such as devices and means can be employed. Even in such a case, it is clear that the same effect can be obtained with respect to the above-mentioned problem. Note that the shape, structure, and the like of each component shown in the drawings are merely preferable examples, and can be appropriately changed within the scope of the claims.

1 is a configuration explanatory view showing a main part of an image forming apparatus according to an embodiment of the present invention. 2 is a plan view illustrating a schematic configuration of a toner cartridge of the image forming apparatus same as above. FIG. FIG. 2 is a vertical sectional view showing a schematic configuration of a developing unit according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line aa showing a schematic configuration of the developing unit. It is a bb line sectional view showing a schematic structure of a developing means same as the above. 6 is a graph showing the relationship between the toner adhesion amount of two types of developer and the development bias. It is a graph which shows the time-dependent change of the output value Vt of the toner concentration detection sensor of an Example. It is a graph which shows the time-dependent change of the output value Vt 'of the toner concentration detection sensor of a comparative example. FIG. 6 is an explanatory diagram schematically illustrating the shape of a toner for explaining a shape factor SF-1. FIG. 6 is an explanatory diagram schematically showing the shape of a toner for explaining a shape factor SF-2. (A) is a perspective view schematically showing the shape of a toner together with an xyz axis. (B) is a view of the toner of (a) as seen from the y direction. (C) is a view of the toner of (a) as seen from the x direction.

Explanation of symbols

1 Color printer (image forming device)
Y, C, M, K Photosensitive drum (latent image carrier)
Y2, C2, M2, K2 Developing means Ya (Ca, Ma, Ka) Developer supply path Y21 (C21, M21, K21) Developing roller (developer carrier)
Yb (Cb, Mb, Kb) Toner recovery mechanism Yc (Cc, Mc, Kc) Recovery toner transport path (recovered toner supply means)
Y27 (C27, M27, K27) Collected toner conveying screw (collected toner supply means) Y28 (C28, M28, K28) Communication port (collected toner supply means)
5 New toner container 5a, 5b, 5c, 5d Toner cartridge (new toner supply means)
9a, 9b, 9c, 9d New toner supply path (new toner supply means)
90a (90b, 90c, 90d) Supply screw (new toner supply means)
S1 Toner density sensor (toner density detection means)
S2 Full detection sensor S3 Empty detection sensor S4, S4 'Optical sensor

Claims (2)

In a toner concentration control method for comparing an output value of a toner density detecting means for detecting a toner density in a developing means of a two-component developer system with a control target value and replenishing toner according to the difference,
The toner density corresponding to the control target value is decreased, and the toner density in the developing unit is higher than the toner density of the control target value by comparing the output value of the toner density detecting unit with the control target value. In this case, the toner is collected from the developer carried on the developer carrying member after passing through the development region by a toner collecting mechanism for collecting the toner from the developer carried on the developer carrying member ,
When the toner concentration in the developing unit is lower than the toner concentration of the control target value by comparing the output value of the toner concentration detection unit and the control target value, the empty detection sensor detects the empty state of the collected toner. A toner concentration control method, wherein the collected toner recovered by the toner recovery mechanism is supplied in preference to the supply of new toner, except when the toner is detected. A latent image carrier that carries an electrostatic latent image on the surface, and a developer carrier that carries a developer containing toner and a carrier and supplies toner to the latent image carrier in a development area that is in close proximity to the latent image carrier. And a new toner supplying means for supplying new toner to the developing means. The developing means uses a toner contained in the developer to develop the electrostatic latent image. In the forming device,
The developing means includes a toner collecting mechanism for collecting toner from the developer carried on the developer carrying member even after passing through a developing area, and a toner collecting mechanism separately from the new toner supplying operation of the new toner supplying means. A recovered toner supply means capable of supplying the recovered toner recovered to the developer carrying member, a toner concentration detecting means for detecting the toner density in the developing means, and an empty detection sensor for detecting the empty of the recovered toner are provided. And
When the toner density set as the toner density control target in the developing means decreases and the toner density in the developing means becomes higher than the control target toner density as judged from the output value of the toner density detecting means. The toner concentration of the developer that collects the toner by the toner collecting mechanism and supplies it to the developer carrier, close to the control target ,
If the toner density in the developing means by comparing the output value and the control target value of the toner density detecting means is lower than the toner concentration of the control target value, except when it is detected air by the air detection sensor An image forming apparatus, wherein the collected toner is supplied by the collected toner supply means in preference to the supply of new toner by the new toner supply means .

Images