JP2006343358A - Process unit and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress development density unevenness caused by an impact when teeth of gears in a drive system come into contact with each other, and further, image quality such as white spots generated as a side effect under development conditions for improving development ability. A process unit and an image forming apparatus that suppress a decrease in image quality are provided. A photosensitive member that carries a latent image on a moving surface, and a developer carried on the moving surface of a developing sleeve, a latent image on the photosensitive member 2. In an image forming apparatus having a developing device 40 that develops an image and a drive source that rotationally drives the developing sleeve 42, the developing device 40 relays the rotational driving force transmitted from the drive source to the developing sleeve 42. A drive transmission gear train having a plurality of gears for transmission is provided, and the photosensitive member 2 is on the rotation path of each gear in the drive transmission gear train while the surface of the photosensitive member 2 moves 1 mm. The number of mobile teeth is 0.72 or more teeth.
[Selection] Figure 1

Description

  The present invention relates to a process unit and an image forming apparatus used for image formation by an electrostatic copying process such as a copying machine, a facsimile machine, and a printer.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile machine, a latent image is formed on a charged image carrier, and the latent image is developed by a developer stored in a developing device. Visualization with toner forms a toner image (see, for example, Patent Document 1). In this developing process, a two-component developer that can be used stably is used because of the charging stability and charging ability of the toner and the developing ability in the image forming process. This two-component developer uses a carrier and toner to charge the toner by friction with the carrier. Further, the developer carrying member of the developing device includes a non-magnetic developing sleeve and a magnet roller fixedly disposed therein, and a two-component developer is raised on the developing sleeve to form a magnetic brush state. . In particular, a large magnetic brush is formed in the developing region by making it stand along the magnetic field lines of the main magnetic pole included in the developer carrier. The development process is performed by sliding the latent image on the image carrier with the magnetic brush and moving the toner to the image carrier. Further, by rotating the developing sleeve and / or the magnet roller, the developer on the surface of the developing sleeve moves while forming a magnetic brush, and continues to supply toner to the latent image.

Conventionally, in a full-color image forming apparatus, a method of developing with a DC bias by a DC voltage (DC voltage developing method) and a method of developing by superimposing an AC bias with an AC voltage (superimposed developing method) are used. The AC bias can vibrate the toner in the space in the development area and improve the reproducibility of fine lines and the gradation reproducibility. There was a recognition that this superimposed development method (AC + DC application method) has higher image quality than the DC voltage development method (DC application method) (see, for example, Patent Document 2).
Moreover, the DC voltage application method has a lower developing ability, which is the toner adhesion performance to the image carrier, than the method of superimposing the AC voltage on the DC voltage. However, with respect to the background stain characteristics of the image carrier, the DC voltage development method is more susceptible to background stain than the superimposed development method even when the potential difference between the DC voltage developing bias and the non-image area (= background portion potential difference) is small. The degree is much better. This is because toner is scattered while reciprocating between the developer carrier and the image carrier due to the superposition of AC voltage, whereas the DC application method is one-way from the developer carrier to the image carrier. This is because the chance of scattering by the action of the electric field is much lower.
Further, in recent years, in place of pulverized toner, a polymerized toner produced by a polymerization method having high image quality and high transfer efficiency has been used because the particle size distribution is narrow and the shape is uniform. In an image forming apparatus using polymerized toner, the DC voltage developing method sometimes has higher reproducibility of details than the superimposed developing method, and the superimposed developing method is not necessarily advantageous in terms of overall image quality. In addition, the development method using only the DC bias without using the AC bias can reduce the cost because the AC bias power source is not required, and has a great user merit. As a result, it is conceivable that an image forming apparatus that employs a DC voltage developing system and that uses a polymerized toner will become the mainstream in the future in terms of both image quality and cost.

However, the DC voltage developing method may have insufficient developing ability compared to the superimposed developing method. Therefore, it is conceivable to compensate for this from the development process and developer. For example, the linear velocity ratio Vs / Vp between the linear velocity Vs of the developing sleeve and the linear velocity Vp of the image carrier is increased or the toner density is increased. Is required. However, when the linear velocity ratio Vs / Vp is increased, the developing ability is improved, but there is a concern that a so-called edge effect in which the toner adhesion amount at the edge of the latent image is increased becomes remarkable. Specifically, a phenomenon such as white spots in which the periphery of a solid area or a halftone area is emphasized and the outside of the area is white is seen. For example, when a solid area exists in the halftone area, a phenomenon occurs in which the halftone portion around the solid area is whitened without being developed due to the edge effect.
Further, the developing ability can be improved by reducing the developing interval. However, even if the development capability is improved by reducing the development interval, the sliding force with the image carrier by the magnetic brush becomes stronger, the edge effect becomes noticeable as described above, and white spots due to the edge effect occur. End up. Side effects caused by reducing the development area include the occurrence of white spots on the trailing edge, degradation of horizontal line reproducibility, and reduction in developer life due to an increase in developer stress.
Furthermore, reducing the distance between the image carrier and the developing sleeve in the development area improves the developing ability, but increases the rubbing force that presses the magnetic brush against the image carrier. As a result, since the toner held in the spike contributed to the development decreases, reverse development occurs that scrapes off the already developed toner from the image carrier after development. As a result, a white-out image is generated in which the rear end of the image is blurred or the solid image is whitened out. In particular, when the angle between the main magnetic pole for development and the image carrier is 0 degrees, the developer collides with the image carrier in a state where the developer is spiked at the position where the development interval is the narrowest. As a result, the toner scraping force increases, and a white-out image in which the trailing edge of the image is blurred or the solid image is whitened out is generated, and the image quality is greatly reduced.

  Furthermore, in recent years when the development interval, which is the gap between the image carrier and the developer carrier, is further narrowed as the image quality is improved, development density unevenness due to subtle vibration of the developer carrier is more conspicuous. (For example, see Patent Document 3). This is because the degree of change in the development area due to vibration increases with the narrowing, and the rate of change in instantaneous development capacity increases. Even if the axial misalignment of the rotation shaft of the gear is eliminated, uneven development density due to subtle vibration of the developer carrying member due to a cause different from the axial misalignment tends to appear. For example, the developing sleeve slightly vibrates due to an impact when the teeth of the gears for driving the sleeve contact each other. However, in the past, the developing interval was set to be relatively large. Was not so noticeable. However, in recent years when development intervals are becoming narrower, uneven development density due to such vibrations is becoming serious. Furthermore, even if subtle vibrations due to the impact of the teeth of the gears in the drive transmission system of another image forming unit near the image carrier are propagated to the image carrier, uneven development density occurs. There is.

JP 2000-227690 A JP 2004-133178 A JP 2003-240065 A

Therefore, the present invention has been made in view of the above-described problems, and its problem is to suppress development density unevenness caused by an impact when teeth of gears in the drive system of the image forming apparatus and each process apparatus come into contact with each other. The present invention provides a process unit and an image forming apparatus that can perform the above process.
It is another object of the present invention to provide a process unit and an image forming apparatus that suppress deterioration in image quality such as white spots that occur as a side effect under development conditions for improving development capability.

The features of the present invention, which is a means for solving the above problems, are listed below.
1. The process unit of the present invention includes at least an image carrier that carries a latent image on the surface, a developing device that develops the latent image on the image carrier using a developer carried on the surface on which the developer carrier moves, and an image A drive transmission gear train comprising a plurality of gears for relaying a rotational driving force transmitted from the drive source provided in the forming apparatus main body and transmitting it to the developer carrier, and is detachable from the main body. In a certain process unit, the number of moving teeth on the rotation trajectory of each gear constituting the drive transmission gear train during the surface movement of the image carrier by 1 mm is 0.72 or more.
2. The process unit of the present invention is further disposed in the image forming apparatus main body so as to transmit the rotational driving force from the drive source to the drive transmission gear train at a position closer to the driving side than the drive transmission gear train. A drive-side engagement portion that rotates by being abutted and engaged in the rotation axis direction with respect to a drive-side engagement portion formed at an end portion in the rotation axis direction of the drive-side rotation member; Of each gear in the transmission gear train, a first gear to which the rotational driving force from the drive source is first transmitted is formed integrally with the driven side engaging portion, and the driven side engaging portion It is characterized by rotating on the same axis of rotation.
3. In addition, the process unit of the present invention further includes a holding body that holds the driven side engaging portion and the first gear so as to be movable at least within a plane orthogonal to the rotation axis direction thereof. And the first gear move so that their rotation axis approaches the rotation axis of the driving-side rotating member as the driven-side engaging portion and the driving-side engaging portion engage with each other. And
4). The process unit of the present invention is further characterized in that at least the first gear and the downstream gear meshing therewith are negatively displaced.

5. The image forming apparatus according to the present invention includes at least an image carrier that carries a latent image on a moving surface, and a developer that develops the latent image on the image carrier using a developer carried on the moving surface of the developer carrier. In the image forming apparatus having the apparatus and a drive source for rotationally driving the developer carrier, the developing device relays a rotational driving force transmitted from the drive source to transmit to the developer carrier. And the number of moving teeth on the rotation trajectory of each gear in the drive transmission gear train during the surface movement of the image carrier by 1 mm is 0.72 or more. It is characterized by that.
6). The image forming apparatus of the present invention is further disposed in the image forming apparatus main body so as to transmit the rotational driving force from the drive source to the drive transmission gear train at a position closer to the driving side than the drive transmission gear train. And a developing device that is detachably supported by the image forming apparatus main body rotates with respect to a driving side engaging portion formed at an end of the driving side rotating member in the rotation axis direction. A driven side engaging portion that rotates by being abutted and engaged in the axial direction, and among the gears in the drive transmission gear train, a rotational driving force from the drive source is transmitted first. The gear is formed integrally with the driven side engaging portion, and rotates on the same rotational axis as the driven side engaging portion.
7). In the image forming apparatus of the present invention, the developing device further includes a holder that holds the driven side engaging portion and the first gear so as to be movable at least in a plane orthogonal to the rotational axis direction thereof. The driven-side engaging portion and the first gear bring their rotational axis closer to the rotational axis of the driving-side rotating member as the driven-side engaging portion and the driving-side engaging portion are engaged. It is characterized by moving to.
8). The image forming apparatus of the present invention is further characterized in that at least the first gear and the downstream gear meshing with the first gear are negatively shifted.

9. The image forming apparatus according to the present invention includes at least an image carrier that carries a latent image on a moving surface, and a developer that develops the latent image on the image carrier using a developer carried on the moving surface of the developer carrier. An apparatus, a transfer device for transferring a visible image on the image carrier to a surface moving member that moves the surface at a position facing the image carrier, or a recording member held on the surface of the surface moving member, and the surface moving member In the image forming apparatus including the driving source for applying a driving force to the image forming apparatus, the transfer device relays the rotational driving force transmitted from the driving source disposed in the image forming apparatus main body and moves the surface. A drive transmission gear train composed of a plurality of gears that transmit to the body, and the number of moving teeth on the rotation path of each gear in the drive transmission gear train during the surface movement of the image carrier by 1 mm is 0.72; It is more than a tooth To.
10. The image forming apparatus of the present invention is further disposed in the image forming apparatus main body so as to transmit the rotational driving force from the drive source to the drive transmission gear train at a position closer to the driving side than the drive transmission gear train. A transfer device that includes the driven-side rotating member and is detachably supported by the image forming apparatus main body with respect to the driving-side engaging portion formed at an end of the driving-side rotating member in the rotation axis direction. The driven-side engaging portion that rotates by abutting and engaging in the direction of the rotational axis is provided, and among the gears in the drive transmission gear train, the rotational drive force from the drive source is transmitted first. The first gear is formed integrally with the driven side engaging portion and rotates around the same rotation axis as the driven side engaging portion.
11. In the image forming apparatus according to the aspect of the invention, the transfer device may further include a holding body that holds the driven-side engaging portion and the first gear so as to be movable at least in a plane orthogonal to the rotation axis direction. The driven-side engaging portion and the first gear bring their rotational axis closer to the rotational axis of the driving-side rotating member as the driven-side engaging portion and the driving-side engaging portion are engaged. It is characterized by moving to.
12 The image forming apparatus of the present invention is further characterized in that at least the first gear and the downstream gear meshing with the first gear are negatively shifted.

13. An image forming apparatus according to the present invention includes an image carrier that carries a latent image on a moving surface, and a developing device that develops the latent image on the image carrier by a developer carried on the moving surface of the developer carrier. In the image forming apparatus, the developing bias applied to the developer carrier is a direct current voltage (DC voltage), and the linear velocity ratio Vs between the linear velocity Vp of the image carrier and the linear velocity Vs of the developer carrier. / Vp is in the range of 1.7 to 2.0, and the development interval Gp between the image carrier and the developer carrier is in the range of 0.1 to 0.45 mm.
14 An image forming apparatus according to the present invention includes: a developing device that develops a latent image on an image carrier with a developer carried on a moving surface of the developer carrier. A magnetic roller including a main magnetic pole that forms a magnetic brush that slidably rubs the developer onto the image bearing member, the half-width center of the magnetic field by the main magnetic pole, and the developer An angle R formed by a line connecting the rotation center of the carrier with respect to a line connecting the rotation center of the image carrier and the rotation center of the developer carrier rotates the developer carrier. It is in the range of 2 ° to 8.5 ° with respect to the upstream direction.
15. Further, the image forming apparatus of the present invention is the image forming apparatus according to any one of the above 1 to 12, wherein the developing bias applied to the developer carrying member is a direct current voltage (DC voltage), and the image carrying device. The linear velocity ratio Vs / Vp between the linear velocity Vp of the body and the linear velocity Vs of the developer carrier is in the range of 1.7 to 2.0, and the development interval between the image carrier and the developer carrier Gp is in the range of 0.1 to 0.45 mm.
16. Further, the image forming apparatus of the present invention is the image forming apparatus according to the above 13 or 15, wherein the developer carrier includes a magnet roller having a plurality of magnetic poles, and the magnet roller is the image carrier. A magnetic pole that forms a magnetic brush that slidably rubs the developer, and a line connecting the center of the half-value width of the magnetic field by the main magnetic pole and the rotation center of the developer carrier is the rotation of the image carrier. The angle R formed with respect to the line connecting the center and the rotation center of the developer carrier is in the range of 2 ° to 8.5 ° with respect to the upstream direction in which the developer carrier rotates. Characterize

17. The image forming apparatus of the present invention is further characterized in that a two-component developer that mixes a carrier and a toner is used as the developer.
18. In the image forming apparatus of the present invention, the toner further has a volume average particle diameter of 3 to 8 μm and a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn). It exists in the range of 1.00-1.40.
19. The image forming apparatus of the present invention is further characterized in that the toner has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180.
20. In the image forming apparatus of the present invention, the toner further includes a 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. Is a toner obtained by crosslinking and / or elongation reaction in an aqueous medium.
21. The image forming apparatus of the present invention is further characterized in that the toner has a substantially spherical shape.
22. Further, in the image forming apparatus of the present invention, the shape of the toner is defined by a major axis r1, a minor axis r2, and a thickness r3 (provided that r1 ≧ r2 ≧ r3), and the major axis r1. The ratio (r2 / r1) to the minor axis r2 is in the range of 0.5 to 1.0, and the ratio (r3 / r2) of the thickness r3 to the minor axis r2 is in the range of 0.7 to 1.0. It is characterized by being.
23. The image forming apparatus of the present invention is further characterized in that the carrier has a magnetic particle surface coated with a resin and has a volume average particle size in the range of 30 to 80 μm.
24. The image forming apparatus of the present invention is further characterized in that the carrier has an electric resistance in the range of 6 to 10 LogΩ · cm.

As described above, in the process unit and the image forming apparatus of the present invention, the larger the number of teeth, the smaller the vibration caused by the impact when the teeth come into contact with each other, and the impulse of impact at the time of contact per tooth. By reducing the size, it was possible to obtain a high-quality image to such an extent that the uneven development density due to vibration caused by the meshing of the gears could not be visually recognized.
Further, the white spot phenomenon occurring at the boundary between the high density image area and the low density image area can be reduced by a combination of relatively simple development conditions without degrading the developing ability.
Further, it was possible to reduce the occurrence of white spots due to the scattering of the developer and the edge effect, which occur as a side effect under the developing conditions for improving the developing ability.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic tandem image forming apparatus as an image forming apparatus will be described.
FIG. 1 is a schematic diagram showing the configuration of the image forming apparatus of the present invention. This image forming apparatus includes four sets of image forming units 1Y, 1M, 1C, and 1K for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). Thus, a full color image can be formed. Y, M, C, and K added after the numerals of each symbol indicate that the members are for yellow, magenta, cyan, and black (the same applies hereinafter, unless otherwise specified, The symbols Y, M, C, and K are omitted). In addition to the image forming units 1Y, 1M, 1C, and 1K, an optical writing unit 10, a transfer device 11, a resist roller pair 19, three paper feed cassettes 20, a fixing device 21, and the like are disposed.
The optical writing unit 10 includes four optical writers. Each optical writer includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates a laser beam on the surface of a photoconductor described later based on image data.

FIG. 2 is an enlarged view showing a schematic configuration of the image forming unit. In FIG. 1, an image forming unit 1 includes a drum-shaped photoreceptor 2 as an image carrier, a charging device 30, a developing device 40, a drum cleaning device 48, and the like.
The charging device 30 charges the drum surface uniformly by sliding the charging roller to which the AC voltage is applied against the photoreceptor 2. The surface of the photosensitive member 2 subjected to the charging process is irradiated with the laser beam modulated and deflected by the optical writing unit 10 while being scanned. Then, an electrostatic latent image is formed on the drum surface. The formed electrostatic latent image is developed by the developing device 40 to become a toner image.
The developing device 40 has a developing sleeve 42 as a developer carrying member disposed so as to be partially exposed from the opening of the casing. Further, it also includes a first conveying screw 43, a second conveying screw 44, a developing doctor 45, a toner concentration sensor (hereinafter referred to as T sensor) 46, and the like.
A two-component developer containing a magnetic carrier and a negatively chargeable toner is accommodated in the casing. The two-component developer is frictionally charged while being agitated and conveyed by the first conveying screw 43 and the second conveying screw 44 and then carried on the surface of the developing sleeve 42. Then, after the layer thickness is regulated by the developing doctor 45, the developer is conveyed to a developing region facing the photoreceptor 2, where toner is attached to the electrostatic latent image on the photoreceptor 2. Due to this adhesion, a toner image is formed on the photoreceptor 2. The two-component developer that has consumed toner by development is returned to the casing as the developing sleeve 42 rotates.
A partition wall 47 is provided between the first conveying screw 43 and the second conveying screw 44. The partition wall 47 divides the first housing portion for housing the developing sleeve 42 and the first transport screw 43 and the second housing portion for housing the second transport screw 44 in the casing. The first conveying screw 43 is driven to rotate by a driving means (not shown), and supplies the two-component developer in the first accommodating portion to the developing sleeve 42 while conveying the two-component developer from the near side to the far side in the drawing. The two-component developer transported to the vicinity of the end portion of the first storage portion by the first transport screw 43 enters the second storage portion through an opening (not shown) provided in the partition wall 47. In the second accommodating portion, the second conveying screw 44 is driven to rotate by a driving means (not shown), and conveys the two-component developer sent from the first accommodating portion in the direction opposite to the first conveying screw 43. . The two-component developer transported to the vicinity of the end of the second storage portion by the second transport screw 44 returns to the first storage portion through the other opening (not shown) provided in the partition wall 47. .

The T sensor 46 composed of a magnetic permeability sensor is provided on the bottom wall near the center of the second housing portion, and outputs a voltage having a value corresponding to the magnetic permeability of the two-component developer passing therethrough. Since the magnetic permeability of the two-component developer shows a certain degree of correlation with the toner concentration, the T sensor 66 outputs a voltage corresponding to the toner concentration. This output voltage value is sent to a control unit (not shown). The control unit includes data storage means such as a RAM, and stores therein a Y Vtref that is a target value of the output voltage from the T sensor 46. In addition, data of M Vtref, C Vtref, and K Vtref, which are target values of output voltages from a T sensor (not shown) mounted on the developing device for other colors, is also stored. The Y Vtref is used for driving control of a toner conveying device (not shown). Specifically, the control unit drives and controls a toner conveyance device (not shown) so that the value of the output voltage from the T sensor 46 approaches the V Vref for Y, and replenishes toner in the second storage unit 49. By this replenishment, the toner concentration of the two-component developer in the developing device 40 is maintained within a predetermined range. Similar toner replenishment control is performed for the developing devices of other process units.
The toner image formed on the Y photoconductor 2 is transferred onto a transfer paper P that is transported to a paper transport belt described later. After the transfer, the surface of the photoreceptor 2 is neutralized by a static eliminator (not shown) after the transfer residual toner is cleaned by the drum cleaning device 48. Then, it is uniformly charged by the charging device 30 and prepared for the next image formation. The same applies to the image forming units for other colors.

  In FIG. 1 described above, the image forming units 1Y, 1M, 1C, and 1K are arranged in a horizontal direction, and a transfer device 11 is arranged below them. The transfer device 11 includes a paper transport belt 12, a drive roller 13, a stretching roller 14, four transfer bias rollers 17Y, M, C, and K. The endless paper transport belt 12 is tension-stretched by a driving roller 13 and stretching rollers 14 and 15 in a horizontally long posture that takes a space in the horizontal direction rather than the vertical direction. Then, it is endlessly moved counterclockwise in the figure by a driving roller 13 rotated by a driving system (not shown). A transfer bias is applied to each of the four transfer bias rollers 17, M, C, and K from a power source (not shown). Then, the paper conveying belt 12 is pressed from the back surface thereof toward the photoreceptors 2Y, 2M, 2C, and 2K to form transfer nips. In each transfer nip, a transfer electric field is formed between the photoreceptor 2 and the transfer bias roller due to the influence of the transfer bias. The above-described toner image formed on the photoreceptor 2 is transferred onto the transfer paper P that is transported onto the paper transport belt 12 due to the influence of the transfer electric field and nip pressure. On this toner image, the M, C, K toner images formed on the photoreceptors 2M, 2C, 2K are sequentially superimposed and transferred. By such superposition transfer, a full-color toner image combined with the white color of the paper is formed on the transfer paper P that is conveyed from the right side to the left side in the drawing while being held on the surface of the paper conveyance belt 12.

Below the transfer device 11, three paper feed cassettes 20 that accommodate a plurality of transfer papers P in an overlapping manner are arranged in multiple stages so as to overlap in the vertical direction, and each cassette is the top transfer paper. A paper feed roller is pressed against P. When the paper feed roller is driven to rotate at a predetermined timing, the uppermost transfer paper P is fed to the paper transport path.
The transfer paper P fed from the paper feed cassette 20 to the paper transport path is sandwiched between the rollers of the registration roller pair 19. The registration roller pair 19 sends out the transfer paper P sandwiched between the rollers at a timing at which toner images can be superimposed at each transfer nip. As a result, the toner image is superimposed and transferred onto the transfer paper P at each transfer nip. The transfer paper P on which the full color image is formed is sent to the fixing device 21.
The fixing device 21 forms a fixing nip with a heating roller 21a having a heat source such as a halogen lamp inside and a pressure roller 21b brought into pressure contact therewith. The full color image is fixed on the surface of the transfer paper P while being sandwiched in the fixing nip. The transfer sheet P that has passed through the fixing device 21 is discharged out of the apparatus through a pair of discharge rollers (not shown).

  FIG. 3 is an enlarged configuration diagram showing the developing device and the side plate of the main body in the image forming apparatus of the present invention. The developing device 40 includes a developing sleeve 42 that is partially exposed from an opening (not shown) of the casing 41, a conveying screw (not shown), a developing doctor, and the like. The developing sleeve shaft 50 extends from the inside of the casing 41 from the upper side surface of the casing 41 in the drawing. Outside the casing 41, a roller gear 51, which is a downstream gear, is fixed to the developing sleeve shaft 50 and rotates integrally with the developing sleeve shaft 50. The roller gear 51 meshes with a first gear 52 of a driven side rotating member disposed on the right side in the drawing. The driven-side rotating member is rotatably held by a holding shaft 54 that is a holding body protruding from the side surface of the casing 41, and includes a convex portion 55 and a claw 53 that are driven-side engaging portions, and a first gear 52. have.

FIG. 4 is an enlarged configuration diagram showing the developing device being mounted on the image forming apparatus of the present invention and the side plate of the image forming apparatus main body. The developing device 40 is detachable from the image forming apparatus main body. In the image forming apparatus main body, the developing device 40 is detachably mounted by sliding the developing device 40 in the vertical direction on the paper surface in the drawing. The side plate 70 of the image forming apparatus main body is provided with a shaft hole 71 for inserting the developing sleeve shaft 50 of the developing device 40. When the end of the developing sleeve shaft 50 protruding from the casing side surface of the developing device 40 is inserted into the shaft hole 71 when the developing device 40 is mounted on the image forming device main body, the developing device 40 is positioned relative to the image forming apparatus main body. Is made. By this positioning, the developing sleeve 42 and the surface of the photoreceptor 2 are made to face each other at a predetermined developing interval.
On the right side of the developing sleeve shaft 50 in the figure, a driven side rotating member is rotatably held by a holding shaft 54 protruding from the side surface of the casing of the developing device 40. The driven-side rotating member is integrally formed to rotate with the driven-side engaging portion including the convex portion 55 and the two claws 53 formed at the end portion in the rotation axis direction, and the same rotation axis. And a first gear 52. The first gear 52 of the driven side rotating member meshes with a roller gear 51 fixed to the developing sleeve shaft 50.
A drive shaft 68 that receives drive from a drive motor is attached to an outer surface (upper surface in the drawing) of the side plate 70 of the image forming apparatus main body. A drive gear 69 is rotatably attached to the drive shaft 68. A driving side rotating member 60 having a shaft 61, a driving side engaging portion 62, a driving output gear 66 and the like is rotatably supported by the side plate 70 on the left side of the driving shaft 67 having such a configuration. The shaft 61 of the driving side rotation member 60 is attached so as to penetrate the side plate 70 from the outside (upper side in the figure) to the inner side (lower side in the figure). A drive output gear 66 is fixed to the shaft 61 outside the image forming apparatus and meshes with the drive gear 69 described above. Further, a drive-side engaging portion having a cup portion 65 having a brown tube-like concave portion and two claws 53 erected on the inner bottom surface of the shaft 61 inside the image forming apparatus. 62 is provided. When a driving motor (not shown) rotates, the rotational driving force is transmitted from the driving gear 69 to the driving output gear 66, and the driving side engaging portion 62 rotates.

As shown in the figure, the developing device 40 is configured such that the driven side engaging portions 53 and 55 face the driving side engaging portion 62 that is rotatably supported by the side plate of the image forming device main body. It is attached to. At the time of mounting, the convex portion 55 of the driven side engaging portion enters the cup portion 65 of the driving side engaging portion 62 on the image forming apparatus main body side, and both engage with each other. When the driving side engaging portion 62 rotates in this state, the two claws 63 provided on the bottom surface of the cup portion 65 are individually hooked on the two claws provided on the end surface of the driven side engaging portion. As a result, the driven side rotation members 52, 53, and 55 of the developing device 40 rotate. Then, the rotational driving force is transmitted to the developing sleeve 42 via the first gear 52 and the downstream gear further than this, and the developing sleeve 42 rotates.
As for the surface of the developing sleeve 42, it is desirable to stabilize the pumping amount of the two-component developer by the roller by carving a groove such as a V-groove or roughening by sandblasting. By doing so, uneven development density due to fluctuations in the pumping amount can be suppressed. In general, the developing sleeve 42 that has been subjected to groove processing such as a V-groove is more preferable than the developing sleeve 42 that has been sandblasted, because it can be stably conveyed with no wear even when used for a long period of time. .
As shown in FIG. 3, when the developing device 40 is mounted on the image forming apparatus main body, a spring material fixed to the side plate 70 of the image forming apparatus main body contacts the one end surface of the developing sleeve shaft 50. It is supposed to do. A developing bias is applied as a spring material main electrode from a power source (not shown).

  In such a drive transmission system, the combination of the driving side engaging portion 62 and the driven side engaging portions 53 and 55 is widely known under the name of a so-called coupling joint. In the drive transmission by the coupling joint, the driving-side rotating shaft member and the driven-side rotating shaft member can be arranged on substantially the same axis. However, it is very difficult to arrange these two rotating shaft members on the same axis line due to factors such as errors in assembly accuracy, and both rotating shaft members rotate at positions slightly displaced from each other. However, the drive is transmitted. For example, in the illustrated image forming apparatus, as described above, since the developing device 40 is positioned by inserting the developing sleeve shaft 50 into the shaft hole 71 of the side plate 70, the image forming apparatus main body side performs the development. The positioning reference position of the device 40 is the center of the shaft hole 71 of the side plate 70. In the side plate 70, a distance error due to an assembly error or the like is inevitably generated between the center of the shaft hole 71 and the shaft 61 of the driving side rotation member 60. On the other hand, in the developing device 40, the positioning reference with respect to the image forming apparatus main body is the center of the developing sleeve shaft 50. The distance between this center and the shaft of the driven side rotating member is also caused by an assembly error or the like. An error will inevitably occur. Due to these distance errors, a slight misalignment between the driving side rotating member 60 and the driven side rotating members 52, 53, and 55 inevitably occurs. Such axial misalignment causes fluctuations in the rotational speed of the developing sleeve 42 and causes uneven development density.

In the conventional coupling joint, the rotational speed fluctuation of the developing sleeve 42 due to the axial misalignment is caused by the fact that the drive transmission amount from the driving side engaging portion to the driven side engaging portion is changed due to the axial misalignment. It is in. Specifically, if there is an axial misalignment, the drive transmission amount to the driven side engaging portion per unit rotation amount varies depending on the rotation position during one rotation of the driving side engaging portion. . In general, when there is a shaft misalignment, until the driving side engaging portion rotates 180 ° from a predetermined rotation reference position, the rotation amount increases to the driven side engaging portion per unit rotation amount. The drive transmission amount of gradually increases. On the other hand, during the period from 180 ° to 360 ° rotation, the drive transmission amount to the driven side engaging portion per unit rotation amount gradually decreases as the rotation amount increases. As described above, the amount of drive transmission to the driven side engaging portion varies depending on the difference in the rotational position of the driving side engaging portion, resulting in speed fluctuations in the rotating body.
In a conventional coupling joint, an Oldham joint is known as one that can rotate two engaging portions even if the two engaging portions are largely misaligned. In this Oldham joint, even if the two engaging portions are largely misaligned, they are forced to rotate. Therefore, fluctuations in the drive transmission speed due to misalignment of the shaft are inevitable. Furthermore, in the Oldham coupling, a groove-shaped recess is provided at one end of the two engaging portions, and the other end can be slid in the groove longitudinal direction with respect to the groove-shaped recess. The convex part engaged with is provided. Then, in accordance with the rotation of the driving side engaging portion, the convex portion is slid in the groove longitudinal direction within the concave portion, thereby forming a state in which no axial misalignment occurs. As a result, even if there is an axial misalignment between both engaging portions, both engaging portions are forcibly rotated. In such a configuration, a rotational position where the frictional force between the convex portion and the groove-shaped concave portion increases and a rotational position where the frictional force decreases are generated during one rotation of the driving side engaging portion. At the rotational position where the frictional force becomes large, a strong force acts to bend the rotational axis of the driving side engaging portion in the direction perpendicular to the axial direction, but the convex portion is slid using this force. Thus, both engaging portions are managed to be rotated. As a result, the load on the rotational drive source such as a motor varies depending on the rotational position of the driving side engaging portion, and the amount of drive transmission from the driving side to the driven side varies. As described above, the conventional Oldham coupling is to force both the engaging portions that are misaligned to each other by the sliding movement of the convex portion, and to rotate both engaging portions without the misalignment of the shaft center. It wasn't something to do.
Therefore, in the image forming apparatus of the present invention, a new configuration (to be described later) which has not been conventionally used is adopted for the driven-side rotating members 52, 53 and 55, thereby eliminating the axial misalignment of both engaging portions. It is like that.

FIG. 5A is an enlarged perspective view showing the driven side rotating member, and FIG. 5B is an enlarged perspective view showing the driving side engaging portion of the driving side rotating member. FIG. 6 is a side view of the driven side rotating member and the driving side rotating member, and a sectional view of the engaged state. In FIG. 5A, a shaft insertion through-hole is provided at the rotation center of the driven side rotation members 52, 53, and 55. A holding shaft 54 for rotatably holding the driven-side rotating member is provided on a casing side plate of the developing device 40 (not shown) so as not to rotate, and is inserted into a through hole of the driven-side rotating member. Since the diameter of the holding shaft 54 is smaller than the diameter of the through hole, the driven-side rotating member is held so as to be movable in a plane direction orthogonal to the rotation axis direction. In addition, although illustration is abbreviate | omitted for convenience in the figure, the end part of the holding shaft 54 is fitted by the donut-shaped metal member with a diameter larger than a through-hole. The metal member is caught on the end surface of the driven side rotating member, thereby preventing the driven side rotating member from falling off the holding shaft 54.
The driving side engaging portion 62 shown in FIG. 5B is moved in a plane perpendicular to the axial direction because the shaft 61 is rotatably supported by a rolling bearing of a side plate (not shown) of the image forming apparatus main body. Can not do it. However, the driven-side rotating members 52, 53, and 55 shown in FIG. 5A can move in any direction within a plane orthogonal to the axial direction as described above. The convex part 55 provided in the driven side engaging part is provided with a taper that tapers from the first gear 52 side toward the end face side. Due to this taper, the diameter of the tip of the concave portion 55 is considerably smaller than the inner diameter of the cup portion 65 of the driving side engaging portion 62. For this reason, when the developing device 40 is mounted, even if the engaging portions are not completely on the same axis, the developing device 40 is gradually mounted on the image forming apparatus main body. The tip of the convex portion 55 of the driven side engaging portion enters the cup portion 65 of the driving side engaging portion 62. When the developing device 40 is further pushed toward the main body of the image forming apparatus so that the developing device 40 is completely set, the concave portion 55 enters the cup portion 65 while abutting the taper at the tip thereof against the inner wall of the cup portion 65. By this, it moves in the direction approaching the axis in a plane orthogonal to the axis direction. As a result, at the stage where the developing device 40 is completely set, the axes of the two engaging portions are completely aligned. In addition to the movement in the plane orthogonal to the axial direction, the backlash caused by the crossing of the parts of the casing side plate of the developing device 40 and the driven side rotating member is set by the reaction of the pushing force when the developing device 40 is set. It is also expected that the driven side rotating member moves in the axial direction by the gap. However, such movement in the axial direction does not affect the operational effects in the present invention, and the movement component in the plane orthogonal to the axis when the movement of the driven side rotating member is decomposed into components is effective. Keep it.

As described above, in the image forming apparatus, the driven side engaging portion of the developing device 40 is not fixed to the shaft as in the prior art, but can be moved in a plane perpendicular to the axial direction by the holding shaft 54. By being held in this position, the developing device 40 can be moved in a very small area. And when engaging the driven side engaging part which can move in this way with the driving side engaging part 62, by moving the rotation center to the place where it matches the rotation axis of the driving side engaging part 62, Position correction of the driven side engaging portion is performed to eliminate axial misalignment of both engaging portions. Therefore, the rotational speed fluctuation of the developing sleeve 42 due to the axial misalignment does not occur, and the fluctuation of the toner amount per unit time conveyed to the developing position which is the position where the photosensitive member 2 and the developing sleeve 42 are opposed is reduced. , Uneven development density can be suppressed.
It should be noted that when viewed in a minute dimension order such as nanometer (nm), it is difficult to completely match the axes of both engaging portions. However, from the viewpoint of mechanical design of the drive transmission system using gears, it is safe to assume that the axial misalignment is in the range of 0.01 to 0.1 mm. In the present invention, “rotate on the same axis” is a concept including this degree of axial misalignment.
The driving side rotating member 60 is a member that is rotationally driven at a position on the driving side of the developing device 40 with respect to a driving motor (not shown) as a driving source.

The diameters of the through holes of the driven side rotating members 52, 53, and 55 are made larger than the diameter of the holding shaft 54 so as to absorb axial misalignment of up to 0.15 mm. By doing in this way, a clearance gap can be formed between the through-hole of a driving | operation side engaging part, and the holding shaft 54 inserted in this. By this gap, the driven-side rotating member can be idled in a direction orthogonal to the rotational axis direction of the driving-side rotating member 60 on the image forming apparatus main body side. Here, even in the conventional gear, the diameter of the through opening is rotated in order to avoid a situation in which a rotating shaft member such as a shaft cannot be inserted into the through opening provided in the gear member due to the dimensional error of the parts. It was slightly larger than the diameter of the shaft member. However, this difference in diameter is at most several tens of μm, which is much smaller than the difference in diameter between the through hole of the driven side rotation member and the holding shaft 54 in this image forming apparatus. The difference in diameter between the through hole and the holding shaft 54 in this image forming apparatus is much larger than the difference in diameter between the through opening and the rotary shaft member in the conventional gear. Due to such a large difference in diameter, the driven-side rotating member can be freely moved in the surface direction orthogonal to the rotation axis direction.
As for the combination of the driven side engaging portion and the driven side engaging portion, as shown in FIG. 6, the claw 53 of the driven side engaging portion and the cup portion 65 of the driven side engaging portion 62 are engaged. It may be. However, as shown in FIG. 5A, it is more reliable to provide a tapered convex portion 55 at the distal end of the driven side engaging portion and to engage the cup portion 65 with this. Is obtained.

  In the image forming apparatus of the present invention, by aligning the axes of the driving side engaging portion 62 and the driven side engaging portions 52, 53, and 55, it is possible to prevent pitch unevenness due to the eccentricity between the engaging portions. However, even if the center distance between the first gear 52 of the driven side engaging portion and the downstream gear (the roller gear 51 in the image forming apparatus) is set to the center distance of the standard gear, the above-mentioned eccentricity The distance between the axes varies due to the correction effect. In addition, there are concerns about problems in each of cases where the distance between the shafts is narrow and wide. Specifically, when the distance between the axes is too small, an impact due to the interference between the tooth tip and the tooth bottom may cause a speed fluctuation, and a toner image with uneven density may be formed on the photoreceptor 2. . In the image forming apparatus, in order to suppress the occurrence of such density unevenness, the first gear 52 and the roller gear 51 which is a gear meshing with the first gear 52 are negatively displaced by a length of 0.1 mm or more. Such negative dislocation can widen the pocket space of the tooth bottom and prevent the above-described interference. However, when a resin gear made of a material such as polyacetal or polycarbonate is used at a setting of about 0.6 to 1.0, if the amount of negative dislocation is larger than 0.3 mm, the tooth root becomes too thin, and development is performed. It has been confirmed that tooth damage occurs at an early stage under the driving load of the sleeve 42. Therefore, in this image forming apparatus, the amount of negative dislocation is set to an amount between 0.1 and 0.3 mm. In the case of using a glass fiber-containing resin gear or metal gear in order to increase the gear strength, it is possible to negatively displace larger than 0.3 mm.

If the distance between the axes is too wide, the teeth may not be engaged, but it can be adjusted to some extent by increasing the number of modules and teeth. Therefore, the situation of not meshing does not occur if a normal design is used. However, the movement distance when the gear teeth move from the currently engaged tooth to the next tooth becomes longer, and the impact increases and the impact increases. There is a risk of growing. In this image forming apparatus, the number of moving teeth of the first gear 52 and the roller gear 51 during the surface movement of the photoconductor 2 by 1 mm is set to 0.72 or more, respectively, in order to suppress the occurrence of such density unevenness, as will be described later. It is set.
The negative shift means a process of cutting gears by setting the reference pitch line of the rack tool for gear cutting when processing the gear to the inner side as viewed from the gear center than the reference pitch line of the gear. The negative transition amount is the difference between the pitch circle of the standard gear and the reference pitch line of the rack tool. As a result of the deep dislocation of the tooth root due to the negative dislocation, the root of the tooth root becomes wide and interference between the tooth tip and the tooth bottom can be suppressed.

  In each of the image forming units 1Y, 1M, 1C, and 1K, the developing interval between the photosensitive member 2 and the developing roller 42 is preferably narrowed from the viewpoint of improving the developing ability, and the developing interval is 0.45 mm or less. It is desirable that the thickness be 0.4 mm or less. In particular, in an image forming apparatus equipped with a DC bias application type developing device, which will be described later, the effect of improving the developing ability becomes more remarkable. When the development gap is narrowed as in these numerical values, the granularity of the developed toner image is greatly improved and a high-quality image can be obtained as compared with the case where the development interval is wider than those. However, when the development interval is narrowed in this way, even if the axial misalignment between the two engaging portions is eliminated, uneven development density due to subtle rotational speed fluctuations of the developing sleeve 42 may be noticeable. is there. In the past, the development interval was set to be larger than 0.4 mm, but such development density unevenness was not so noticeable. However, when the development interval was set to 0.4 mm or less, it became conspicuous. This uneven development density is caused by the contact of teeth of various gears that transmit driving to the developing sleeve 42.

The development density unevenness caused by the impact when the gear teeth come into contact with each other can be suppressed by increasing the number of moving teeth on the rotation path of the gear as much as possible while the photoreceptor 2 moves on the surface by 1 mm. This is because as the number of moving teeth increases, the impact at the time of contact per tooth is reduced. Therefore, the present inventors conducted an experiment to confirm how much the number of moving teeth of the gear should be increased.
Specifically, first, a plurality of gears having a module of 0.8 or 0.6 were prepared. For each gear, the image frequency, which is the number of movements of the gear teeth while the photosensitive member 2 moves 1 mm, is changed within a range of 0 to 3 teeth / mm, and is called a banding chart at each image frequency. A strip image was output. Next, after reading these banding charts with a scanner and converting them into image data, the brightness amplitude in each image data is analyzed with image analysis software (Labview manufactured by Solution Systems Co., Ltd.), and the brightness amplitude and the image frequency are analyzed. The relationship was graphed. FIG. 7 shows the relationship between the brightness amplitude and the image frequency when a gear whose module is 0.8 is used. FIG. 8 shows the relationship between the brightness amplitude and the image frequency when a gear whose module is 0.6 is used. The lightness amplitude is an index indicating the degree of density unevenness. The smaller the value, the less the density unevenness. In FIG. 7, it can be seen that the brightness amplitude is limited to 0.08 or less, which is an allowable range of density unevenness, when the image frequency is set to about 0.70 teeth / mm or more. Considering measurement errors and the like, it is considered that the image frequency needs to be set to 0.72 teeth / mm or more in order to ensure that the density unevenness is within the allowable range with the gear of the module 0.8. On the other hand, in FIG. 8, it is understood that the brightness amplitude is kept below 0.08, which is the allowable range of density unevenness, when the image frequency is set to 0.20 teeth / mm or more. Therefore, if the image frequency is set to 0.20 or more, the density unevenness can be kept within the allowable range by the gear of the module 0.6.

Next, each of the printout papers on which a plurality of banding charts were printed was compared with the density unevenness stage sample with the naked eye to identify which value of each density unevenness corresponds to the density unevenness stage sample. This identification was performed by one or two image evaluators. As a result of the comparison, it was found that the density unevenness of the banding chart of the printout paper has the same degree as the unevenness tolerance limit value of the density unevenness stage sample when the brightness amplitude is 0.08. Therefore, if the brightness amplitude is suppressed to 0.08 or less, the uneven development density can be kept within the allowable range. For reference, the comparison results of density unevenness are shown in Table 1 below.

In the image forming apparatus, the first gear 52 and the roller gear 51 are moved during the surface movement of the photosensitive member 2 by 1 mm in order to keep the uneven development density within an allowable range regardless of which gear of the modules 0.6 and 0.8 is used. The number of moving teeth on the rotating track is set to 0.72 or more.
The image frequency can be obtained by the relational expression “image frequency teeth / mm = 1 / image pitch = (linear velocity ratio × number of teeth) / 2πr” (where π is the circumferential ratio, and r is the developing sleeve). 42 radii). Further, the image pitch can be obtained by the relational expression “image pitch mm = 2πr / (linear velocity ratio × number of teeth)”.

The smaller the gear module is, the smaller the image frequency can be. However, if the module is made too small, the durability of the gear tooth base and the tooth surface is lowered and the life of the gear is shortened. However, since the life of the gear is influenced by the material of the gear in addition to the size of the module, the lower limit of the module is set according to the material. As a method of increasing the image frequency, it is conceivable to increase the linear velocity ratio or increase the number of gear teeth. In order to increase the linear velocity ratio, the process linear velocity is decreased or the developing linear velocity is increased. However, considering the recent increase in the image forming velocity, it is appropriate to increase the developing linear velocity. For example, a speed as high as a linear speed ratio of 3 is not desirable from the viewpoint of toner scattering, an increase in internal pressure in the unit, and developer life. In the image forming apparatus, the number of gear teeth is increased by setting the gear module to 0.6 or 0.8. Increasing the number of gear teeth also increases the meshing rate and enables smooth transfer between gears. Further, the durability of the gear is improved by increasing the number of teeth.
Therefore, in the image forming apparatus, the image frequency of each gear of the developing device 40 is set to 0.72 teeth or more. Therefore, it is possible to suppress fluctuations in the rotation speed of the developing sleeve 42 due to the contact of the teeth of each gear, and to keep the development density unevenness invisible. Since the linear speed and pitch of the first gear 52 and the roller gear 51 are the same, the image frequencies of these gears are the same.

In the image forming apparatus of the present invention, a DC voltage application method may be used as a voltage application method to the developing sleeve 42. The DC voltage power source does not use the AC voltage power source, which leads to cost reduction. In addition, since the developing ability is reduced by the AC voltage superimposing method, the reduced amount is compensated for by other developing conditions, and a high-quality image can be obtained because there is no ground cover.
As the development bias, a DC voltage application method is adopted, and development conditions described below are preferable. In particular, the linear velocity ratio Vs / Vp between the linear velocity Vp of the photosensitive member 2 and the linear velocity Vs of the developing sleeve 42 is preferably 1.7 to 2.0. Increasing the linear velocity Vs of the developing sleeve 42 increases the frequency with which the spikes on the developing sleeve 42 come into contact with the electrostatic latent image on the photoreceptor 2. In general, the developing ability can be improved as the contact frequency increases. Therefore, in the DC voltage application method, when the linear velocity ratio Vs / Vp is less than 1.7, the developing ability is low, the toner adhesion amount cannot be increased, and only an image with a low image density can be obtained. Further, in a full-color image, the reproducibility of intermediate colors is lowered, so that the image quality is lowered. On the other hand, when the linear velocity ratio Vs / Vp exceeds 2.0, the scraping force becomes strong, and in solid images and halftone images, scratches on the streaks appear or white spots appear at the rear end. Image quality is reduced. In addition, the reproduction widths of the vertical thin line and the horizontal thin line are different, the vertical line is thick and the horizontal line is thin, and the image reproducibility is lowered.
Further, the development interval Gp between the photosensitive member 2 and the developing sleeve 42 is set to a range of 0.1 to 0.45 mm. Preferably, it is in the range of 0.25 to 0.40 mm. It was found that the developing ability is improved as the developing interval is narrow, but the developing ability tends to be saturated at a certain distance. Furthermore, compared with the case where the development interval Gp is made wider than this, the granularity of the developed toner image can be greatly improved, and a high-quality image can be obtained. However, when the development interval Gp is narrowed in this way, even if the axial misalignment between the two engaging portions is eliminated, the uneven development density due to the subtle fluctuations in the rotational speed of the developing sleeve 42 will be noticeable. There is. In the past, where the development interval was set larger than 0.45 mm, such uneven development density was not so noticeable, but it became noticeable when the development interval was 0.45 mm or less. Furthermore, 0.40 mm or less is preferable in order to obtain a high-quality image excellent in fine line reproducibility, full-color intermediate color reproducibility, etc. without forming an abnormal image such as white spots.
This uneven development density is caused by the contact of teeth of various gears that transmit driving to the developing sleeve 42. However, in the image forming apparatus of the present invention, since the contact of the teeth of each gear is improved, even if the development interval Gp is reduced, vibration is reduced and development density unevenness is reduced. However, if the development interval Gp is less than 0.1 mm, there is a possibility that toner adheres to the photoreceptor 2. Further, since the surfaces of the developer carrying member and the photosensitive member 2 are not necessarily smooth, it is difficult to maintain a predetermined developing ability. Further, in order to obtain a stable image forming apparatus in consideration of manufacturing stability and practical accuracy of machines and devices, 0.25 mm or more is preferable.

FIG. 9 is a configuration diagram showing an internal configuration of the developing device. Since the developing devices 40Y, 40M, 40C, and 40K have the same configuration except for different toner colors, the configuration of one developing device 40 will be described in detail from the internal structure. An angle formed by a line L1 connecting the center of the half-value width of the magnetic field by the main magnetic pole and the rotation center of the developer carrier with respect to a line L2 connecting the rotation center of the image carrier and the rotation center of the developer carrier. R is in the range of 2 ° to 8.5 °. As shown in FIG. 9, the developing device 40 includes a developing sleeve 42. The developing sleeve 42 includes a magnet roller 42b fixedly disposed in a rotating developing sleeve 42 made of aluminum having a diameter of 18 mm. The surface of the developing sleeve 42 is provided with a groove or roughened by sandblasting, processing, or the like in order to enhance the developer conveying capability.
FIG. 10 is a waveform diagram of the magnetic flux density distribution of the magnet roller. Note that the magnetic pole arrangement in FIG. 10 is a configuration example, and the number and arrangement of magnetic poles other than the main magnetic pole for development are not limited to this. As shown in FIG. 10, the magnet roller 42 b includes magnetic poles S <b> 1, N <b> 1, S <b> 2, S <b> 3, and N <b> 2 in the rotation direction of the developing sleeve 42 from the position of the developing area that is the area facing the photoreceptor 2. Among these, the development main magnetic pole S1 is disposed so that the center line L1 of the half width L3 of the magnetic pole is at a position upstream of the line L2 connecting the centers of the developing sleeve 42 and the photoreceptor 2 in the rotation direction. Exhibits the strongest magnetic force among the five magnetic poles. The two-component developer on the developing sleeve 42 is caused to rise in the developing region and forms a magnetic brush. The magnetic brush formed on the developing sleeve 42 by the magnetic force of the developing main magnetic pole S1 passes through the developing area while sliding the tip of the magnetic brush against the photosensitive member 2.

  The movement of the developer in the developing device 40 having such a configuration will be described. As the two-component developer in the developing container is circulated and conveyed by the first conveying screw 43 and the second conveying screw 44, the toner and the carrier are frictionally charged by stirring. The first developer conveying screw 17 supplies a part of the developer to the developing sleeve 42, and the developing sleeve 42 conveys the developer magnetically by the magnetic pole N2. The developer on the developing sleeve 42 is formed such that the layer thickness (supported amount) is regulated by the developer regulating member 45 and is in contact with the photoreceptor 2. The magnetic pole N2 is a pole that combines the developer pumping action and the layer thickness regulating action. In the two-component developer in which the layer thickness is regulated while being attracted to the surface of the developing sleeve 42 by the magnetic pole N2, the frictional charging of the toner is promoted. A developing bias is applied to the developing sleeve 42 by a power source (not shown). The developer transported to the developing area is spiked on the developing sleeve 42 by the magnetic force of the main magnetic pole S1 for development, and the electrostatic latent image on the photosensitive member 2 is rubbed against the photosensitive member 2. The toner is supplied to the toner and passes through the development area. The developer that has passed through the developing region with the rotation of the developing sleeve 42 moves while being constrained on the developing sleeve 42 by the magnetic force of the magnetic pole N <b> 1 while lying down with the drop of the magnetic force. . Then, in the region where the normal magnetic field between the magnetic pole S3 and the magnetic pole N2 is restricted, it is separated from the surface of the developing sleeve 42 and returned to the developing container. The developer returned into the developing container is again conveyed by the first conveying screw 43 and again conveyed by the second conveying screw 44 through the partition wall. When it is detected by the T sensor 46 that the toner concentration of the developer in the developing container has become a predetermined concentration or less, the toner is supplied from the toner replenishing port and is mixed with the developer by stirring by the second conveying screw 44. . The developer adjusted to a predetermined density is again carried on the developing sleeve 42, passes through the developer regulating member 45, is thinned, and the above cycle is repeated.

FIG. 11 is a schematic view showing another configuration of the image forming apparatus of the present invention. FIG. 12 is a schematic diagram showing the configuration of an enlarged image forming unit as another configuration of the image forming apparatus of the present invention. FIG. 13 is a schematic diagram showing the relationship between an enlarged image forming unit and a photoconductor in another configuration of the image forming apparatus of the invention. As shown in FIG. 11, an apparatus main body that is fixed in position for storing each component as an image forming unit and a paper feed cassette 20 that can store transfer paper P are provided. At the center of the apparatus main body, there are provided image forming units 1Y, 1C, 1M and 1K for forming toner images of respective colors. In addition, as shown in FIG. 12, the image forming units 1Y, 1C, 1M, and 1K include drum-shaped photoreceptors 2Y, 2C, 2M, and 2K that rotate in the direction of arrow A in the drawing. The photosensitive member 2 is cleaned around the charging device for charging the photosensitive member 2, developing devices 40Y, 40C, 40M, and 40K for developing a latent image formed on the photosensitive member 2, and residual toner on the photosensitive member 2. A cleaning device is provided. Below each image forming unit 1, an optical unit is provided as exposure means capable of irradiating the photosensitive member 2 with the laser light L. Above each image forming unit 1, an intermediate transfer unit including a transfer belt 12b to which a toner image formed by each image forming unit 1 is transferred is provided. Further, a fixing unit 21 for fixing the toner image transferred to the transfer belt 12b to the transfer paper P is provided. The transfer belt 12b of the intermediate transfer unit includes primary transfer rollers 17Y, 17C, 17M, and 17K that transfer the toner image formed on the photoconductor 2 to the transfer belt 12b at a predetermined timing. The intermediate transfer unit includes a secondary transfer roller 18 that transfers the toner image transferred onto the transfer belt 12b to the transfer paper P, and a belt cleaning that cleans transfer residual toner on the transfer belt 12b that has not been transferred onto the transfer paper P. Equipped with equipment.
Next, a process of obtaining a color image in the image forming apparatus having the above configuration will be described. First, in the image forming units 1Y, 1C, 1M, and 1K, the photoreceptors 2Y, 2C, 2M, and 2K are uniformly charged by the charging device. Thereafter, the laser light L is scanned and exposed by the optical unit based on the image information, and latent images are formed on the surfaces of the photoreceptors 2Y, 2C, 2M, and 2K. The latent images on the photoreceptors 2Y, 2C, 2M, and 2K are developed by the toners of the respective colors carried on the developing sleeves 42Y, 42C, 42M, and 42K of the developing device 12 to be visualized as toner images. The toner images on the photoreceptors 2Y, 2C, 2M, and 2K are sequentially superimposed and transferred onto the transfer belt 12b that is rotated counterclockwise by the action of the primary transfer rollers 17Y, 17C, 17M, and 17K. The image forming operation for each color at this time is executed while shifting the timing from the upstream side toward the downstream side in the moving direction of the transfer belt 12b so that the toner image is transferred to the same position on the transfer belt 12b. The The surfaces of the photoreceptors 2Y, 2C, 2M, and 2K after the completion of the primary transfer are cleaned by a cleaning device and are prepared for the next image formation. A predetermined amount of toner filled in the toner bottle is supplied to the developing devices 40Y, 40C, 40M, and 40K through a conveyance path (not shown) as necessary.
On the other hand, the transfer paper P in the paper feed cassette 2 is transported by a paper feed roller disposed in the vicinity of the paper feed cassette 20 and is transported to a secondary transfer section by a registration roller pair 19 at a predetermined timing. . Then, the toner image formed on the transfer belt 12b is transferred to the transfer paper P in the secondary transfer portion. The transfer paper P onto which the toner image has been transferred passes through the fixing device 21 to be fixed, and is discharged by a discharge roller. Similar to the photoconductor 2, the transfer residual toner remaining on the transfer belt 12b is cleaned by a belt cleaning device in contact with the transfer belt 12b.

In the image forming apparatus of the present invention, the transfer belt 12 as a transfer member may be disposed above the photosensitive member 2 and the developing sleeve 42. Therefore, when the developer on the developing sleeve 42 passes through the developer regulating member 45 or the developing region, even if the developer detached from the developing sleeve 42 falls, it does not adhere to the transfer belt 12. Further, as shown in FIG. 11, the development main magnetic pole S1 has a half-width center line L1 of the magnetic field generated by the development main magnetic pole S1 below the line segment L2 connecting the center of the photosensitive member 2 and the center of the developing sleeve 42. Arranged. The developer held by the main magnetic pole S1 for development is held most densely on the half width center line L1. For this reason, the distance between the photosensitive member 2 and the developing sleeve 42 at the position where the developer is held closest is wider than the developing interval where the distance between the photosensitive member 2 and the developing sleeve 42 is the narrowest. Therefore, the collision between the photoreceptor 2 and the developer spike on the half-value width center line L1 of the magnetic field generated by the developing main magnetic pole S1 is alleviated, and the amount of developer scattered away from the restriction from the magnetic field is reduced. Even if the developer is released from the restraint and separated from the developing sleeve 42, the distance between the photosensitive member 2 and the developing sleeve 42 becomes narrower as it goes upward, so that the upward movement of the developer is prevented and scattering becomes difficult. Further, in the developing region where the space between the photosensitive member 2 and the developing sleeve 42 is the narrowest, the magnetic force acts so that the angle of the rising of the developer that contacts the photosensitive member 2 falls, so that the photosensitive member 2 and the developing sleeve 42 are developed. Collisions with the agent ears are alleviated and less developer is scattered. In the development area, the angle of the ear of the developer that contacts the photoconductor 2 falls, so the toner scraping ability of the developer ear is also reduced, and the occurrence of white spots is reduced. Further, in the development area, the angle of the spike of the developer that contacts the photoconductor 2 falls, and the contact area per unit time of the spike of the developer that contacts the photoconductor 2 increases. Therefore, it is possible to develop well even in a region where the development potential is lowered due to the edge effect.
The developing main magnetic pole S1 has an angle (the center line L1 of the half-value width L3 of the magnetic field generated by the developing main magnetic pole S1 forms a line segment L2 connecting the rotation center of the photosensitive member 2 and the rotation center of the developing sleeve 42). (Hereinafter referred to as the main magnetic pole angle for development) R is arranged so as to be 2 ° to 8.5 °. When the main magnetic pole angle R of this development is smaller than 2 °, the above-described effect of suppressing the developer scattering upward is small. For this reason, the scattered carrier adheres to the photoconductor 2, and the carrier adhering to the photoconductor 2 is carried to the transfer nip, so that the photoconductor 2 is damaged or a blank image is generated due to the carrier adhesion. . On the other hand, when the main magnetic pole angle R of the development is smaller than 2 °, the toner scraping power of the developer ears is large, and a blank image is generated. On the other hand, when the main magnetic pole angle R for development exceeds 9 °, image density unevenness occurs due to a decrease in developing ability. For the above reasons, the main magnetic pole angle R for development is preferably 2 to 8.5 °, more preferably around 6 °.

In the image forming apparatus of the present invention, the developer used is a two-component developer. As the magnetic carrier to be mixed with the two-component developer, the following is used. In this case, the carrier to toner content ratio in the developer is preferably 1 to 10 parts by weight of toner with respect to 100 parts by weight of carrier. The magnetic carrier has a volume average particle size of 30 to 80 μm and an electric resistance of 6 to 10 Log (Ω · cm).
Moreover, it is desirable to use a magnetic carrier having a volume average particle diameter of 30 to 80 μm. By setting the volume average particle size to 80 μm or less, the thickness of the developer spike (carrier chain) at the time of image formation can be uniformly thinned, and more precise toner can be delivered. In addition, since the density of developer spikes per unit area on the developing sleeve 42 is increased, it is possible to transfer toner to the latent image on the photosensitive member 2 without any gap. Thereby, an image with more excellent dot reproducibility can be formed. When the weight average particle diameter exceeds 80 μm, the total surface area of the magnetic carrier is reduced and the amount of toner held is reduced when compared with the same carrier amount. If the rotation speed of the developing sleeve 42 is increased in order to prevent a decrease in toner density due to this, image contamination due to toner scattering is likely to occur. On the other hand, when the volume average particle size is less than 30 μm, the magnetic force holding force by the magnet roller fixed in the developing sleeve 42 becomes small and carrier scattering is likely to occur. Therefore, the image forming apparatus designates the user to use a magnetic carrier having a volume average particle size of 30 to 80 μm by a designation method described later.
In addition, the electric resistance of the magnetic carrier is in the range of 6 to 10 Log (Ω · cm). The electric resistance affects the electric field applied to the carrier itself in the development area. If the electric resistance is less than 6 Log, the electric field in the development area cannot be increased and the developing ability is low. If the electric resistance is more than 10 Log, the electric field in the developing area is increased to increase the developing ability. Furthermore, carrier adhesion increases. Accordingly, the development capacity, ground cover, and white spot are set in the range of 6 to 10 Log (Ω · cm).
Specifically, resin coating is performed on the particle surfaces of Cu—Zn ferrite, Mn—Zn ferrite, Fe ₂ O ₃ hematite, Fe ₃ O ₄ magnetite and the like. Alternatively, a resin-dispersed carrier in which these are dispersed in a resin can be used. Ferrite has a specific gravity of about 5, and the specific gravity can be increased by increasing the amount of Fe and decreasing O oxygen. However, if the specific gravity exceeds 5.5 and a metal-based magnetic material is used, the stress on the toner increases during transportation and mixing, and the chargeability of the carrier decreases due to spent. On the other hand, when the specific gravity is less than 2.6, the mixing property with the toner is lowered and the amount of the reversely charged toner is increased.
Examples of the carrier coating material include amino resins such as urea-formaldehyde resin, melamine resin, benzoguanamine resin, urea resin, polyamide resin, and epoxy resin. Polyvinyl and polyvinylidene resins such as acrylic resins, polymethyl methacrylate resins, polyacrylonitrile resins, polyvinyl acetate resins, polyvinyl alcohol resins, polyvinyl butyral resins, polystyrene resins and styrene acrylic copolymer resins, Halogenated olefin resins such as vinyl, polyester resins such as polyethylene terephthalate resin and polybutylene terephthalate resin, polycarbonate resins, polyethylene resins, polyvinyl fluoride resins, polyvinylidene fluoride resins, polytrifluoroethylene resins, polyhexafluoro Propylene resin, copolymer of vinylidene fluoride and acrylic monomer, copolymer of vinylidene fluoride and vinyl fluoride, tetrafluoroethylene and vinylidene fluoride and non- Monomers including a fluoro terpolymers such, and silicone resins. Moreover, you may contain electrically conductive powder etc. in coating resin as needed. As the conductive powder, metal powder, carbon black, titanium oxide, tin oxide, zinc oxide or the like can be used. These conductive powders preferably have an average particle diameter of 1 μm or less. When the average particle diameter is larger than 1 μm, it becomes difficult to control electric resistance.

  In particular, it is preferable to coat a surface layer containing a thermoplastic resin, a melanin resin, and a charge adjusting agent on the surface of the particles serving as the core material. This is a surface layer in which a charge adjusting agent is contained in a resin component obtained by crosslinking a thermoplastic resin such as acrylic and a melamine resin. The conventional magnetic carrier is configured to obtain a long life while gradually scraping a hard coat film, whereas this magnetic carrier absorbs an impact and suppresses the film scraping because the coat film has elasticity. . Therefore, the lifetime can be further extended as compared with the conventional carrier. Thereby, it is possible to expect stabilization of the toner pumping amount, that is, stabilization of quality over a long period of time. Therefore, in this image forming apparatus, the user is designated to use such a magnetic carrier by a designation method described later.

  FIG. 12 is an enlarged schematic view showing a magnetic carrier. In the figure, as a core material of the magnetic carrier 500, a ferrite 501 which is a magnetic material is used. The surface of the ferrite 501 is covered with a surface layer 502 in which a charge adjusting agent is contained in a resin component obtained by crosslinking a thermoplastic resin such as acrylic and a melamine resin. The surface layer 502 has both elasticity and strong adhesive force. In the surface layer 502, particles having a diameter larger than the film thickness, for example, alumina particles 503 are dispersed. The conventional magnetic carrier was constructed based on the idea of obtaining a long life while gradually scraping the hard surface layer, whereas the illustrated magnetic carrier 500 absorbs the impact by the surface layer 502 exhibiting elasticity. To do. Thereby, film abrasion of the photoreceptor 2 can be suppressed. Further, since the alumina particles 503 having a diameter larger than the film thickness are dispersed in the surface layer 502, it is possible to enhance the surface scraping effect between the carriers and suppress the adhesion of the toner to the magnetic carrier. In this way, by suppressing surface layer 502 film scraping and toner adhesion to the surface, it is possible to extend the life.

  The volume average particle diameter can be measured as follows. That is, it can be measured by a measuring device using a Coulter counter method, for example, Coulter counter TA-II or Coulter Multisizer II (both manufactured by Coulter). Specifically, first, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution. As the electrolytic aqueous solution, approximately 1% NaCl aqueous solution is prepared using primary sodium chloride, and for example, ISOTON-II (manufactured by Coulter) can be used. Further, 2 to 20 mg of a measurement sample is added to the obtained solution. Then, the solution is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number of particles (toner and magnetic carrier) are measured with the above-described measuring apparatus using a 100 μm aperture as the aperture. Calculate distribution and number distribution. From the obtained distribution, the volume average particle diameter Dm and the number average particle diameter Dn can be obtained. In addition, as a channel, it is less than 2.00-2.52 micrometer; 2.52-3.17 micrometer; 3.17-4.00 micrometer; 4.00-5.04 micrometer; 5.04-6.35 micrometer 6.35 to less than 8.00 μm; 8.00 to less than 10.08 μm; 10.08 to less than 12.70 μm; 12.70 to less than 16.00 μm; 16.00 to less than 20.20 μm; Use 13 channels less than 25.40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm. Dm and Dn are both average values per 10,000 pieces.

Next, the toner 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. FIG. 13 is a diagram schematically showing the shape of the toner for explaining the shape factor SF-1 and the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). ((A)) A value obtained by dividing the square of the maximum length MXLNG of a shape formed by projecting toner onto a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
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 (2). ((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 100 / 4π.
SF-2 = {(PERI) ² / AREA} × (100 / 4π) (2)
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 photosensitive member 2 becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity becomes high. The attracting force with the body 2 is also weakened, and the transfer rate is increased. 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 includes a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent are dispersed in an organic solvent. A toner obtained by crosslinking and / or elongation reaction in an aqueous 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 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. As trihydric or higher polyhydric alcohol (TO), 3 to 8 or higher polyhydric aliphatic alcohol (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 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 polyvalent carboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polycarboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the above-mentioned acid anhydride or lower alkyl ester (Methyl ester, ethyl ester, isopropyl ester, etc.).

The ratio of the polyhydric alcohol (PO) to the polyvalent carboxylic acid (PC) is usually 2/1 to 1/1, preferably 1.5 / 1 to 1, as the equivalent ratio OH / COOH of the hydroxyl group OH and the carboxyl group COOH. / 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.

The polyester preferably contains a urea-modified polyester in addition to the unmodified polyester obtained by the polycondensation reaction. The urea-modified polyester is obtained by reacting the terminal carboxyl group or hydroxyl group of the polyester obtained by the 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 amide 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 (R, R, R ′, R′-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 4/1 to 1.2 / as the equivalent ratio NCO / OH of the isocyanate group NCO and the hydroxyl group OH of the polyester having a hydroxyl group. 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 becomes low and the hot offset resistance deteriorates.
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 will be low, and the hot offset resistance will deteriorate.

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 the amines (B) is usually 1/2 to 2 as an equivalent ratio NCO / NHx of the isocyanate group NCO in the polyester prepolymer (A) having an isocyanate group and the amino group NHx in the amine (B). / 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 gloss when used in the full-color image forming apparatus 100 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 Carmin Min BS, 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 with respect to 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 attraction force with the developing sleeve 42 is increased, the flowability of the developer is reduced, and the image density is reduced. Incurs a decline.

(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, and 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, and of course, they may be added when dissolved and dispersed in the 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 nm to 2 μm, and particularly preferably 5 nm to 0.5 μm. 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 50 nm or less, electrostatic force and van der Waals force with the toner are remarkably improved, so that a desired charge level is obtained. Also by the stirring and mixing inside the developing device 40, the fluidity imparting agent is not detached from the toner, and good image quality free from firefly and the like can be obtained, and the residual toner can be further reduced.
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, R-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 fluoroalkylcarboxylic acids having 2 to 10 carbon atoms and metal salts thereof, disodium perfluorooctanesulfonyl glutamate, 3-ω-fluoroalkyl (C6 to C11). Sodium oxy-1-alkyl (C3-C4) sulfonate, sodium 3-ω-fluoroalkanoyl (C6-C8) -N-ethylamino-1-propanesulfonate, fluoroalkyl (C11-C20) carboxylic acid and metal salts Perfluoroalkylcarboxylic acid (C7 to C13) and its metal salt, perfluoroalkyl (C4 to C12) sulfonic acid and its metal salt, perfluorooctanesulfonic acid diethanolamide, N-propyl-N- (2-hydroxyethyl) ) Perfluorooct Examples thereof include tansulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, and the like. It is done.
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, as the cationic surfactant, aliphatic quaternary ammonium such as aliphatic primary, secondary or secondary amic acid, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt which has a fluoroalkyl group on the right is used. Salt, benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (Asahi Glass Co., Ltd.), Florard FC-135 (Sumitomo 3M Co., Ltd.), Unidyne DS-202 (Daikin Industries) Smoke), MegaFuck F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products), Footage 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), SGP (manufactured by Soken), 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, R-cyanoacrylic acid, R-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups 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-containing compounds such as imidazole and ethyleneimine, or homopolymers or copolymers such as those having a heterocyclic ring thereof, polyoxyethylene, polyethylene Oxypropylene, 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, a high-speed shearing type 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, the solvent base is removed to produce spindle-shaped toner base particles. . 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 toner according to the present invention has a substantially spherical shape and can be represented by the following shape rule.
FIG. 14 is a diagram schematically showing the shape of the toner of the present invention. In FIG. 14, when a substantially spherical toner is defined by a major axis r1, a minor axis r2, and a thickness r3 (where r1 ≧ r2 ≧ r3), the toner of the present invention has a major axis and a minor axis. Ratio (r2 / r1) (see (b)) is 0.5 to 1.0, and ratio of thickness to minor axis (r3 / r2) (see (c)) is 0.7 to 1.0. It is preferable to be in the range. When the ratio of the major axis to the minor axis (r2 / r1) 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 of the thickness to the short axis (r3 / r2) 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 minor axis (r3 / r2) is 1.0, the rotating body has a major axis as a rotation axis, and the fluidity of the toner can be improved.
Note that r1, r2, and r3 were measured with a scanning electron microscope (SEM) while changing the angle of field of view and taking pictures.

Next, modifications of the image forming apparatus according to the embodiment will be described.
(First modification)
The configuration of the first modification is the same as that of the image forming apparatus according to the embodiment unless otherwise specified. 15 and 16 are enlarged configuration diagrams showing the driven side rotating member and the driving side rotating member in the first modification. A holding portion 241 a is formed on the side surface of the casing 241 of the developing device 40 to hold the driven side rotation member so as to be movable in a surface direction orthogonal to the axial direction. The holding portion 241 has a cylindrical shape, and an end portion on the opening side protrudes toward the circular opening. A driven side rotating member is accommodated in the cylindrical holding portion 241. Since the diameter of the cylindrical space of the holding portion 241 is larger than the diameter of the driven side rotating member, the driven side rotating member is allowed to idle in the plane direction perpendicular to the rotation axis direction in the holding portion 241. ing.
In this image forming apparatus, a holding shaft having a smaller diameter is inserted into a through hole provided in the central portion of the driven side rotating member, and the driven side rotating member is moved in a direction perpendicular to the rotation axis direction. It was. On the other hand, in the first modified example, such a holding shaft is not provided. Instead, a through hole 256 is provided at the center of the driven side rotating member for insertion into the drive output shaft portion 261 of the driving side rotating member 60 for engagement. The drive output shaft 261 is provided with a taper as shown in FIG. 15 at the tip of the engaging side so as to smoothly engage with the through hole 256 of the driven side rotation member, and from the root side toward the tip side. Tapered. Further, in the first modification, a pin 263 penetrating and fixed to the drive output shaft 261 is provided instead of the claw in the driving side rotation member 60 of the image forming apparatus according to the embodiment.
When the developing device 40 is mounted on the image forming apparatus, the through hole 256 of the driven side rotating member and the tip of the drive output shaft portion 261 of the driving side rotating member 60 are engaged as shown in FIG. At the same time, the two claws 253 of the driven side rotation member and the pin 263 penetrating and fixed to the drive output shaft 261 are hooked to connect the both engaging portions. The end joint structure of the first gear 252 of the driven side rotating member and the drive output shaft 261 of the driving side rotating member 60 constitute a shaft coupling. By this shaft coupling, the rotational driving force of the drive output shaft 261 is connected to the first gear 252. Then, the rotational driving force is transmitted to a roller gear (not shown) meshed with the first gear 252 and the developing sleeve 42 rotates.

FIG. 17 is an enlarged configuration diagram illustrating the drive output shaft and the driven side rotation member before engagement in the first modified example together with the side plate of the developing device 40. FIG. 18 is an enlarged configuration diagram showing the drive output shaft and the driven side rotating member after engagement together with the side plate of the developing device 40. FIG. 19 is a cross-sectional view showing the holding part of the side plate and the driven side rotating member. The driven side rotation member is fixed by being engaged with the drive output shaft 261, and fine position correction is performed.
In the first modification, the above-described holding portion 241a protruding from the side surface is formed on the side plate 241 of the developing device 40. The holding portion 241a has a cylindrical structure and has a cylindrical space therein. The diameter of this cylindrical space is larger than the diameter of the rotating outer periphery of the driven side rotating member. The driven-side rotating member is held in the cylindrical space of the holding portion 241a and engages with the drive output shaft 261 of the driving-side rotating member 60 that is inserted into the through hole 256 that penetrates in the rotation direction. In addition, the protrusion part A which protrudes in a ring shape toward the inside of a cylinder is provided in the edge part of the cylindrical axial direction of the holding | maintenance part 241a. The protrusion A has an inner diameter smaller than the diameter of the outer periphery of the driven-side rotating member, and plays a role in preventing the driven-side rotating member in the cylindrical space from dropping out of the cylindrical space. Even if the driven-side rotating member freely moves in the cylindrical axis direction in the cylindrical space of the holding portion 241a, the driven-side rotating member is prevented from falling out of the cylindrical space by abutting against the protruding portion A of the holding portion 241a.

As shown in FIG. 19, the driven gear 252 holds the driven gear 252 so as to be movable at least in a plane orthogonal to the rotational axis direction by a gap between the rotation outer peripheral surface and the cylindrical space. . Then, in association with the engagement with the drive output shaft 261, it moves toward the rotational axis of the drive output shaft 261, and position correction is performed. By configuring in this way, subtle axial misalignment that occurs between the driven side rotating member and the driving side rotating member 60 due to parts and design accuracy problems, etc. is absorbed by the movement of the driven side rotating member. be able to. The first gear 252 on the developing device 40 side can always be rotated by the rotation center of the drive output shaft 261.
About the diameter of the cylindrical space of the holding | maintenance part 241a, it is 0.5-1.0 mm larger than the diameter of the rotation outer periphery of a driven side rotation member. Accordingly, a clearance is formed between the inner wall of the cylindrical space of the holding portion 241a and the driven side rotating member held therein, and the rotation axis of the driven side rotating member accompanying the engagement with the drive output shaft 261 is formed. It is possible to move in the direction orthogonal to the direction.
The driven rotary member shown in FIGS. 17, 18 and 19 has a cylindrical member whose diameter does not change from the shaft inlet side to the outlet side as the through hole 256 opening. Instead of such an opening, a taper having a smaller diameter toward the outlet side may be employed. In such an opening, even if the center of the through hole 256 of the driven-side rotating member before the engagement and the center of the drive output shaft 261 are greatly deviated, the drive output shaft 261 has a wide inlet at the through hole 256. The driving output shaft 261 can smoothly enter the through hole 256 by applying the tip.

(Second modification)
The configuration of the second modification is the same as that of the image forming apparatus according to the embodiment unless otherwise specified below. In the second modification, the image forming units 1Y, 1M, 1C, and 1K are process units 301Y, 301M, 3C, and 1K that can be integrally attached to and detached from the image forming apparatus main body, respectively. Each process unit 301Y, M, C, K is replaced when the life is reached.
FIG. 20 is an enlarged configuration diagram showing a process unit of the second modified example. As shown in the drawing, the process unit 301 includes a developing device 340, a charging device 330, a drum cleaning device 348, and the like around a drum-shaped photoconductor 302. These are supported by a casing as a common support, and are integrally attached to and detached from the image forming apparatus main body as one unit.
FIG. 21 is a plan sectional view showing the process unit and the image forming apparatus main body side plate. A shaft hole for inserting a drum drive shaft 371 rotatably supported by the image forming apparatus main body side plate 370 is provided at the center of the drum of the photosensitive member 302 of the process unit 301. The drum drive shaft 371 has a pin 371 a that protrudes from the rotational peripheral surface of the root side portion that is not inserted into the shaft hole of the photoconductor 302, and rotates while being hooked on the protrusion 302 a of the photoconductor 302. The photosensitive member 302 rotational driving force is transmitted.
A drum drive gear 372 is fixed to the rear end portion of the drum drive shaft 371, and a relay gear 373 and a second drive output gear 374 are engaged with this. In addition to the drum drive gear 372, the relay gear 373 is engaged with a drive gear 369, and this drive gear 369 is further engaged with the first drive output gear 366.
The drive gear 369 is the most upstream gear that is rotationally driven by a motor (not shown), and this transmits rotational driving force to various gears. On the right side of the drive gear 369 in the drawing, a driving side rotation member 60 is rotatably disposed, and the first drive output gear 366 is engaged with the drive gear 369. The drive output gear 366 is fixed to the rear end portion of the first drive output shaft, and the driving side engaging portion 362 is fixed to the front end of the first drive output shaft 360.

The driving side engaging portion 362 is for sending rotational driving force to the two screws 343 and 344 and the developing sleeve 342 of the developing device 340. The developing device 340 includes a driven side rotating member that engages with the driving side engaging portion 362 of the driving side rotating member. Each of the driving side rotating member and the driven side rotating member has the same configuration as that of the image forming apparatus according to the embodiment. This is a mechanism in which the axial misalignment of the driven side rotating member is eliminated by correcting the position of the driven side rotating member with the engagement of the driving side script member.
A first screw gear 375 and a second screw gear 376 are engaged with the first gear 352 of the driven side rotating member. The first screw gear 375 and the second screw gear 376 are fixed to the ends of the first conveying screw 343 and the second conveying screw 344. The rotational driving force from the driving side rotating member is transmitted to the first screw gear 375 and the second screw gear 376 via the first gear 352, whereby the first conveying screw 343 and the second conveying screw 344 rotate. To do. A roller gear 351 is further engaged with the first screw gear 375, and the developing sleeve 342 is rotated by transmitting a rotational driving force thereto.
The rotational driving force of the most upstream driving gear 396 is sequentially transmitted to the relay gear 373, the drum driving gear 372, and the second driving output gear 374 of the second driving side rotating member. The second drive output gear 374 is fixed to the rear end portion of the second drive output shaft 377, and the driving side rotation engagement portion 378 is fixed to the tip of the second drive output shaft 377.
The second engagement portion 378 of the second driving side rotating member is for sending a rotational driving force to the recovery screw 378 of the drum cleaning device 348. The developing device 340 also includes a second driven side rotation member that engages with the second engagement portion 378, and a third gear 380 is formed on the second driven side rotation member. The second driving side rotating member and the second driven side rotating member have the same configurations as the driving side rotating member and the driven side rotating member of the image forming apparatus according to the embodiment, respectively. The second driven-side rotating member is corrected in position with the engagement with the second driving-side rotating member, so that the axial misalignment between them is eliminated.

  In the image forming apparatus having the above-described configuration, in addition to the rotational speed fluctuation of the developing sleeve 342 caused by the axial misalignment between the first driving side rotating member and the first driven side rotating member, the following speed fluctuation is also present. Can be resolved. That is, the rotational speed fluctuations of the first transport screw 343 and the second transport screw 344 caused by this axial misalignment. Furthermore, fluctuations in the rotational speed of the recovery screw 379 due to axial misalignment between the second driving side rotating member and the second driven side rotating member can be eliminated.

(Third Modification)
FIG. 22 is a schematic configuration diagram showing a photoreceptor and a revolver developing unit in a third modification. A revolver developing unit 600 disposed on the left side of the photoconductor 602 in the drawing has four developing devices 600 for Y, M, C, and K on a support that rotates clockwise around the rotation axis in the drawing. , M, C, K. The developing device 600Y, M, C, and K revolves around the rotation axis when the support rotates around the rotation axis in the clockwise direction in the figure. The developing devices 600M, C, K, and Y are set at the developing positions facing the photoconductor 602 every rotation of 90 °, 180 °, 270 °, and 360 °. An electrostatic latent image for Y, M, C, and K is sequentially formed on the photoconductor 602, and these are sequentially developed into Y, M, C, and K toner images by the developing devices 600Y, M, C, and K. . The developed Y, M, C, and K toner images are sequentially superimposed and transferred onto an intermediate transfer belt (not shown). The four-color toner images formed on the intermediate transfer belt by this superimposing transfer are collectively transferred onto the transfer paper P in a region not shown.
When the four developing devices 600Y, 600M, 600C, and 600K move to the developing position, the drive receiving gear (not shown) meshes with a drive output gear that is rotatably fixed to the image forming apparatus main body. As a result, drive transmission to the developing sleeve and the stirring member is performed. The drive receiving gears of the developing devices 600Y, M, C, and K are configured to supply the shaft on which the developing gear is fixed to the developing sleeve. In the third modification, the image frequency of the drive receiving gear is set to 0.72 teeth or more. Therefore, it is possible to suppress fluctuations in the rotation speed of the developing sleeve due to the contact between the teeth of the drive output gear and the drive receiving gear, and to keep the development density unevenness invisible.

(Fourth modification)
FIG. 23 is a plan sectional view showing the transfer device and the image forming apparatus main body side plate in the fourth modified example. This transfer device 411 supports various rollers rotatably by a support 418 and is configured to be detachable from the image forming apparatus main body. A driving roller 413 that supports a paper carrier belt 412 together with two stretching rollers (not shown) while being rotatably supported by the support 418 is rotationally driven by a drive transmission system, which will be described later. The paper transport belt 412 is moved endlessly.
One end side of the shaft member 413a of the driving roller 413 protrudes greatly from the support body 418, and the driving roller gear 481 is fixed to the protruding portion. Further, the tip of the protruding portion is inserted into a positioning bearing provided on the image forming apparatus main body side plate 470. As a result, the transfer device 411 is positioned with respect to the image forming apparatus main body and the respective photosensitive members based on the drive roller 413.
The drive roller gear 481 meshes with a transfer engagement gear 482 which is a driven side rotation engagement portion held by a support body 418. The transfer engagement gear 482 is engaged with a drive-side transfer rotation engagement portion 483 protruding from the image forming apparatus main body side plate 470. The transfer rotation engagement portion 483 and the transfer engagement gear 482 have the same configurations as the driving side rotation member 62 and the driven side rotation members 52, 53, and 55 of the image forming apparatus according to the embodiment, respectively. The position of the transfer engagement gear 482 is corrected as the transfer engagement gear 483 is fitted to the transfer rotation engagement portion 483, thereby eliminating the misalignment between the axes.
The transfer engagement gear 482 is fixed to one end portion of the drive output shaft 485, and the drive output gear 484 is fixed to the other end portion of the drive output shaft 485. The drive output gear 484 meshes with the most upstream drive gear 486, so that the rotational drive force of the drive gear 486 causes the drive output gear 484, transfer rotation engagement portion 483, transfer engagement gear 482, drive roller gear 481, drive It is sequentially transmitted to the rollers 413.

In the fourth modified example having such a configuration, the transfer engagement gear 484 moves in a direction perpendicular to the rotation axis direction in accordance with the fitting with the transfer rotation engagement portion 483, thereby correcting the position of both axes. The rotational speed fluctuation of the driving roller 413 due to the deviation is eliminated. As a result, it is possible to suppress a toner image transfer position shift caused by the endless movement speed fluctuation of the paper conveying belt 412 due to the fluctuation of the rotation speed of the driving roller 413.
In the fourth modification, there is a risk of developing density unevenness as follows. That is, first, in the transfer device 411 serving as transfer means, vibration is generated due to the engagement between the drive roller gear 481 and the transfer engagement gear 481. This vibration is sequentially transmitted to the developing sleeve via the shaft member 413a, the image forming apparatus main body side plate 470, the developing sleeve shaft (not shown), or is transmitted from the driving roller 413 to the photosensitive member 2 via the paper conveying belt 412. Uneven development density is caused.
Therefore, the number of moving teeth on the rotation trajectory of the drive roller gear 481 and the transfer engagement gear 481 in the drive transmission gear train of the transfer device 411 during the surface movement of the photosensitive member 2 by 1 mm is set to 0.72 or more. ing. With this setting, it is possible to effectively suppress development density unevenness caused by propagation of vibration generated by the engagement of both gears to the photosensitive member.

(5th modification)
FIG. 24 is a schematic diagram showing a drive transmission gear train in the developing device of the fifth modification. The drive transmission gear train includes a first gear 552 of a driven-side rotating member that is movably held in a plane orthogonal to the rotational axis direction by a holding shaft (not shown), and a roller gear 551 that is fixed to a developing sleeve shaft (not shown). In between, the relay gear unit 556 is interposed. The relay gear unit 556 is a two-stage gear in which a small-diameter gear 557 that meshes with the roller gear 551 and a large-diameter gear 558 having a larger diameter are integrally formed so as to rotate on the same rotational axis. . The rotational driving force received by the first gear 552 is sequentially transmitted to the large-diameter gear 558, the small-diameter gear 557, and the roller gear 551 to rotate a developing sleeve (not shown). The large-diameter gear 558, the small-diameter gear 557, and the roller gear 551 each function as a downstream gear that transmits drive on the downstream side in the drive transmission direction with respect to the first gear 552.
In the fifth modified example having such a configuration, the number of moving teeth on the gear rotation track during the surface movement of the photosensitive member 2 by 1 mm is set to 0 for each of the first gear 552, the large diameter gear 558, the small diameter gear 557, and the roller gear 551. .72 teeth or more are set.

  Note that the image forming apparatus described in the embodiment and each modification is an example of an apparatus to which the present invention can be applied, and the image forming apparatus according to the present invention is not limited to these. In the embodiment and each modification, a gear having a module of 0.8 or 0.6 is used.

As described above, in the image forming apparatus according to the embodiment, since the developing device is detachably supported as a process unit on the main body of the image forming device, the developing device can be easily replaced. Moreover, it has the driven side engaging part which rotates by abutting and engaging with the driving | running | working side engaging part 62 formed in the one end part of the rotating shaft direction of the driving | running | working side rotating member in the rotating shaft direction. Yes. In such a configuration, the driving side rotating member and the driven side rotating member can be arranged on substantially the same axis and the drive can be transmitted between them. Further, of the gears in the drive transmission gear train, the first gear 52 to which the rotational driving force from the drive motor as the drive source is first transmitted is formed integrally with the convex portion 55 as the driven engagement portion. It is designed to rotate around the same axis of rotation. In such a configuration, the developing sleeve is rotated on an axis different from the rotation axis of the first gear 52 by transmitting drive from the first gear 52 to the roller gear 51 which is a downstream gear downstream of the first gear 52. Can do.
In the image forming apparatus according to the embodiment, the developing device holds the driven side engaging portions 53 and 55 and the first gear 52 at least in a plane perpendicular to the rotation axis direction so as to be movable. 54, the driven side engaging portion and the first gear 52 bring their own rotational axis closer to the rotational axis of the driving side rotating member as the driven side engaging portion and the driving side engaging portion engage with each other. To move. As a result, it is possible to eliminate fluctuations in the rotation speed of the developing sleeve due to axial misalignment between the driving side rotating member and the driven side rotating member.
In the image forming apparatus according to the embodiment, the first gear 52 and the roller gear 51 that is a downstream gear meshing with the first gear 52 are negatively displaced. In such a configuration, for the reason described above, as a result of the first gear 52 moving closer to the axis on the driving side when the developing device is mounted, the inter-axis distance between the first gear 52 and the roller gear 51 becomes narrower than the set value. Even so, it is possible to eliminate a large speed fluctuation of the developing sleeve due to contact between the bottoms of the two gears.
In the image forming apparatus according to the embodiment, the photoconductor as the image carrier and the developing sleeve are disposed so as to face each other with a development interval of 0.1 to 0.4 mm. In such a configuration, for the reasons described above, it is possible to form an image having no rough feeling and excellent dot reproducibility.

An experiment was conducted using an image forming apparatus having a photosensitive member and carrying and developing a two-component developer by a developing sleeve containing a fixed magnet roller.
The experimental conditions are as shown in Table 2 below.

The development conditions and the two-component developer included in the image forming apparatus of the present invention were evaluated for the background fog of the image from the above conditions. When a developing bias with respect to the photosensitive member potential was applied, the number of toners that became background stains as background portions was observed.
FIG. 25 is a graph showing the relationship between the developing bias and the number of adhered toner.
From Examples 1 to 4 and Comparative Examples 1 and 2, the AC superposition application method has a lower toner concentration than the DC voltage application method to reduce the total amount of background toner. Is much more. This is because the DC voltage application method moves from the developing sleeve to the image carrier in one direction and adheres, whereas the AC superimposition application method depends on the AC frequency between the developing sleeve and the photosensitive member 2. As the movement is repeated, the amount of background contamination is increased by scattering to the non-image area. Example 1 has particularly good soiling, which is presumed to be because the carrier particle size is smaller than that of the other examples and the triboelectric charging ability to the toner is higher than that of the carrier having a large particle size. The smaller the carrier particle size, the greater the surface area of the carrier at the same weight, resulting in a higher probability of contact of the toner with the carrier. The

Next, the developing ability when the toner density is unified to 7%. In the evaluation of the development characteristics of the developer, the toner concentration is a very important factor, so the toner concentration is adjusted. Here, the toner density at the time of the experiment is set in advance in the forced replenishment mode in the experimental image forming apparatus, and after the developer is adjusted to the toner density, the developing ability is evaluated at the toner density.
FIG. 26 is a graph showing the relationship between the toner adhesion amount and the developing bias, which is the developing ability evaluation result. The amount of adhesion on the vertical axis may be determined by collecting the development toner per unit area from the photosensitive member with a suction jig and measuring the weight with an electronic balance. The output voltage, which is a measured value of the density of the toner adhering to the photoconductor, may be converted by a sensor using corresponding toner amount correlation data.
As is clear from FIG. 26, the toner adhesion amount per unit area in Examples 1 to 4 is the same as the development potential (= latent image exposure portion potential−DC bias potential) as compared with the comparative example using only DC. The development capability is approaching that of AC + DC development.

Furthermore, the above experimental results were verified on the basis of 5% having a lower toner concentration. However, since the triboelectric charging performance with respect to the toner differs depending on the carrier particle diameter, the toner concentration is set to 7% only for the 35 μm carrier so that the charge amount is the same regardless of the carrier particle diameter.
FIG. 27 is a graph showing the relationship between the toner adhesion amount and the developing bias, which is the developing ability evaluation result.
The development potential at which the development amount is close to the limit and the adhesion amount reaches 0.45 mg / cm ² needs to be slightly higher than that when the toner concentration is 7%. The condition No. 4 can exhibit the developing ability substantially equivalent to AC + DC development.
Further, as is apparent from FIG. 27, the toner adhesion amount per unit area, which is an index of the developing ability, becomes close to the limit beyond a certain development potential, and therefore does not adhere. Under the condition where the toner concentration is 5%, the linear speed ratios of 1.9 and 2.0 are almost the same, and although not described, there was no improvement even under the condition of 2.1. On the other hand, the higher the linear velocity ratio, the greater the number of times the magnetic brush is rubbed against the photoconductor, leading to white spots due to scavenging action. Therefore, the linear speed ratio is set to 2.0 or less.

FIG. 28 is a graph showing the relationship between the developing main magnetic pole angle R and the whiteout amount, which is the development performance evaluation result. As can be seen from the results of FIG. 28, the developing ability is generally decreased by tilting the angle R of the main magnetic pole of development to 0 °, 2 °, and 6 °, but the white spot amount is good. It became. By setting the angle R of the main magnetic pole for development to 2 ° or more, the whiteout amount satisfies the target value of 5 or less at a toner concentration of 5 to 7.5 wt%, and an effect of improving whiteout was obtained. In particular, when the main magnetic pole for development was around 6 °, the effect of improving the whiteout amount was noticeable in the toner concentration range of 5 to 9 wt%.
Usually, the main magnetic pole angle R for development is often set to 0 ° in order to ensure the maximum development capability. For this reason, the main magnetic pole angle for development is not so inclined with respect to the photoreceptor. However, according to the result of this experiment, the decrease in the developing ability due to the inclination of the main magnetic pole angle R by 6 ° was not so much, and it did not affect the image. On the contrary, the white spot improvement effect was noticeable. It is considered that the scavenging force for physically scraping off the already developed toner on the photoconductor is reduced because the angle of the ear of the developer contacting the photoconductor falls in the development gap. In addition, since the angle of the spike of the developer that contacts the photoconductor goes down and the area per unit time of the spike that contacts the photoconductor increases, it is also good in a region where the development potential is lowered due to the edge effect. This is thought to be because development is now possible. On the other hand, when the main magnetic pole angle R for development was set to 9 °, a similar experiment was conducted. As a result, the ear of the head was too slanted in the development gap, resulting in insufficient contact with the photoconductor, resulting in poor development.
Considering the yield at the time of mass production at the factory, it is necessary to allow the angle tolerance of the angle R of the main pole of the development to be about ± 2 °. From this point of view, another verification experiment was conducted. The magnetic brush has a high rubbing force, and the photosensitive member and the developing sleeve, which are considered to be easily exposed to white, have a linear velocity ratio of 2.0, 0 °, 3.5 °, 6 °, 8.5 °, and 9 °. Experiments were performed at 5 levels. FIG. 29 shows the verification result. As a result, when R is in the range of 3.5 °, 6 °, and 8.5 °, the amount of white spots due to the edge effect falls within a slightly worse level of 7, even when the toner density increases. Accordingly, it is determined that white spots are acceptable if image formation is performed in a range of 6 ° ± 2.5 °, which is a variation of mass-produced products. Note that plotting is not performed at 9 ° because development failure has occurred, and when R is 0 °, white spots due to edge effects are unacceptable depending on the toner density, and at the time of transfer due to carrier scattering on the photoreceptor. White spots were also occurring.
The whiteout amount is measured by the following method. The measuring instrument used is NEXCAN F5100 manufactured by HEIDERBERG. The capturing condition is set at a resolution of 1200 dpi. As the sample, a whiteout amount measurement chart in which the image density is varied in one sheet is used. The measurement condition is that the solid part ID is about 1.5 and the halftone part ID is about 0.5. In some cases, the development potential is changed to obtain a desired image density. The transfer paper is not specified. The amount of white spots obtained is an integral value of the area where white spots are generated. Since the white spot which is a problem in the present invention is conspicuous at the front end portion of the image, the white spot amount at the front end portion of the image is compared. The target value of whiteout amount is set to 5 or less based on the ability of the competitor's aircraft. If the amount of white spots is 5 or less, white spots can be visually confirmed, but the level is not so problematic. The relationship between the whiteout amount and the visual evaluation is as follows. White spot amount 1 or less: White spot cannot be confirmed. White spot amount 1 to 5: Level that does not cause a problem as long as white spots are found. White spot amount 5 or more and 8 or less: White spot level is about 0.5 mm, which is a little bad level. White spot amount 8 or more: White spot 0.5 mm or more, very bad level.

FIG. 32 is a graph showing the results of measuring the developing ability with respect to the developing interval and the linear speed ratio between the photosensitive member and the developing roller. The developing ability is measured as follows. In general, the developing ability is often expressed by the inclination of the developing adhesion amount on the photosensitive member with respect to the developing bias, so-called development γ. Using a chart in which solid patches of about 5 cm ² are scattered in the image, the photosensitive member is forcibly stopped at the timing when the toner is developed on the photosensitive member, and the solid portion remaining on the photosensitive member is sucked by the sack-in method. Measure the weight. The horizontal axis represents the development bias, the vertical axis represents the amount of adhesion of the photosensitive member per unit area (unit: mg / cm ² ), and the inclination is called development γ. A larger development γ indicates a higher development ability. There is no particular threshold value for the number of development γ, but if it falls below 1.5, the development capability cannot be compensated for even by changing the development conditions such as increasing the toner density or increasing the linear speed ratio. The developing ability is lowered. Therefore, it is recommended that the development γ is 1.5 or more.
From the results in FIG. 32, it can be seen that the development γ increases as the development interval Gp decreases. When the development gap is 0.50 mm, development γ1.5 cannot be achieved even if the linear velocity ratio is increased to 2.0. Therefore, in order to obtain a development γ of 1.5 or more, the development interval Gp is preferably 0.45 mm or less. However, when the development interval Gp is narrowed, the hitting of the development head to the photoconductor becomes stronger, leading to deterioration of photoconductor filming. In addition, it is necessary to reduce the tolerance fluctuation width at the time of assembly. However, since the manufacturing cost increases as the assembly tolerance of the development interval Gp decreases, it is recognized that the actual lower limit is about 0.20 mm. Yes. Further, it can be seen from the results of FIG. 8 that the development γ increases as the linear velocity ratio increases. Therefore, in order to achieve development γ1.5 or more with a development interval Gp of 0.45 mm or less, the linear speed ratio is 1.7 or more, and 1.8 or more is more preferable in consideration of the variation margin for mass production. However, as the linear speed ratio increases, rear end fading and vertical / horizontal line ratio deterioration occur due to side effects, so the linear speed ratio 2.0 is the upper limit as a practical problem. On the contrary, if the development interval Gp is narrow, the development γ becomes larger than the linear speed ratio, and it is possible to obtain the development γ1.5 without increasing the linear speed ratio.

The linear velocity ratio of 1 was also obtained from the results of setting the linear velocity of the photosensitive member to 150 mm / sec and 205 mm / sec and changing the linear velocity ratio between the photosensitive member and the developing roller to 1.5, 1.8, and 2.0. It was confirmed that 7 or more is preferable. In addition, when a linear velocity ratio fluctuation experiment was performed under the same development conditions by the development method using the AC bias development method, it was confirmed that a high development capability was obtained at a linear velocity ratio of 1.5 to 2.0 because the development capability was high. It was. As described above, in the image forming apparatus of the present invention, the half-width center line L1 of the magnetic field generated by the developing magnetic pole S1 is below the line segment L2 connecting the rotation center of the photosensitive member and the rotation center of the developing sleeve. Therefore, it is possible to reduce the occurrence of abnormal images such as developer scattering and white spots. Even when the DC bias developing method is employed, it is possible to reduce the developer scattering and the white spots due to the edge effect, which occur as a side effect under the developing conditions for improving the developing ability.
In the image forming apparatus of the present invention, the developing magnetic pole angle R formed by the half-width center line L1 of the magnetic field generated by the developing magnetic pole S1 and the line segment l2 connecting the rotational center of the photosensitive member 10 and the rotational center of the developing sleeve is 2 ° to 2 °. 8.5 °. When the developing magnetic pole angle R is smaller than 2 °, the effect of suppressing the scattering of the developer is small, and the toner scraping ability of the developer ears in the developing gap is strong, and a white-out image is generated. When the developing magnetic pole angle R exceeds 8.5 °, the development becomes defective and image density unevenness occurs.
In the image forming apparatus of the present invention, since the entrance seal 30 is provided as a developer receiving member, the inside of the apparatus main body 1 is not contaminated even if the developer detached from the developing sleeve falls downward. In the image forming apparatus of the present invention, since a polymerized toner having a uniform particle size is used, it is possible to achieve high image quality. The printer according to the present embodiment can obtain a high-quality image even if a low-cost DC bias application method is installed, based on a combination of development conditions listed below. The development gap is preferably 0.25 to 0.45 mm. The ratio (Vs / Vp) between the linear velocity Vp of the photoreceptor 10 and the linear velocity Vs of the developing sleeve is preferably 1.7 to 2.0. Further, in the image forming apparatus of the present invention, by using the toner shown under the following conditions, it is possible to obtain a toner having a small particle size, a sharp particle size distribution, and a substantially spherical shape, thereby improving image quality. And the margin of occurrence of abnormal images can be improved. The volume average particle diameter is 3 μm or more and 8 μm or less, and the ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is preferably 1.00 to 1.40. The shape factor SF-1 is in the range of 100 to 180, and the shape factor SF-2 is preferably 100 to 180. In addition, the toner is obtained by crosslinking and / or extending in a water-based medium a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent are dispersed in an organic solvent. A toner obtained by reaction is preferable. The shape of the toner is defined by a major axis r1, a minor axis r2, and a thickness r3. The ratio (r2 / r1) of the major axis r1 to the minor axis r2 is 0.5 to 1.0, and the thickness r3 is short. The ratio (r3 / r2) to the axis r2 is preferably 0.7 to 1.0.

1 is a schematic diagram illustrating a configuration of an image forming apparatus of the present invention. It is an enlarged view showing a schematic configuration of an image forming unit. FIG. 3 is an enlarged configuration diagram showing the developing device and the side plate of the main body in the image forming apparatus of the present invention. FIG. 3 is an enlarged configuration diagram illustrating a developing device being mounted on the image forming apparatus of the present invention and a side plate of the image forming apparatus main body. (A) is an expansion perspective view which shows a driven side rotation member, (b) is an expansion perspective view which shows the drive side engaging part of a drive side rotation member. It is a side view of a driven side rotation member and a driving side rotation member, and sectional drawing of the state which meshed this. It is a graph which shows the relationship between a brightness amplitude and an image frequency. It is a graph which shows the relationship between a brightness amplitude and an image frequency. It is a block diagram which shows the internal structure of a developing device. It is a wave form diagram of magnetic flux density distribution of a magnet roller. It is the schematic which shows the other structure of the image forming apparatus of this invention. FIG. 6 is a schematic diagram illustrating a configuration of an enlarged image forming unit in another configuration of the image forming apparatus of the present invention. It is the schematic which shows the relationship between the enlarged image forming part and the photoconductor with the other structure of the image forming apparatus of invention. It is an expansion schematic diagram which shows a magnetic carrier. FIG. 6 is a diagram schematically illustrating the shape of a toner in order to explain shape factor SF-1 and shape factor SF-2. It is a figure which shows typically the shape of the toner of this invention. It is an expanded block diagram which shows the driven side rotation member and driving | operation side rotation member in a 1st modification. It is an enlarged block diagram which shows the drive output shaft and the driven side rotation member before engagement in a 1st modification with the side plate of a developing device. It is an enlarged block diagram which shows the drive output shaft and the driven side rotation member before engagement in a 1st modification with the side plate of a developing device. It is an enlarged block diagram which shows the drive output shaft and driven side rotation member after engagement with the side plate of a developing device. It is a cross-sectional view which shows the holding | maintenance part of a side plate, and a driven side rotation member. It is an enlarged block diagram which shows the process unit of a 2nd modification. 3 is a plan sectional view showing a process unit and an image forming apparatus main body side plate. FIG. It is a schematic block diagram which shows the photoreceptor and the revolver developing unit in the 3rd modification. FIG. 10 is a plan sectional view showing a transfer device and an image forming apparatus main body side plate in a fourth modification. It is a schematic diagram which shows the drive transmission gear train in the developing device of the 5th modification. 6 is a graph showing the relationship between a developing bias and the number of toner deposits. 7 is a graph showing a relationship between a toner adhesion amount and a developing bias, which is a developing ability evaluation result. 7 is a graph showing a relationship between a toner adhesion amount and a developing bias, which is a developing ability evaluation result. It is a graph which shows the relationship between the angle R of the main magnetic pole of development which is a developing performance evaluation result, and the amount of white spots. It is a graph which shows the relationship between the angle R of the main magnetic pole of development which is a developing performance evaluation result, and the amount of white spots. It is a graph which shows the result of having measured the development capability with respect to the development space | interval and the linear speed ratio of a photoreceptor and a developing roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image formation part 2 Photoconductor (image carrier)
40 Developing Device 41 Casing (Housing)
42 Development sleeve (developer carrier)
51 Roller gear (second gear)
52 1st gear (part of driven side rotating member)
53 Recessed part (a part of the driven side rotating member or the driven side engaging part)
55 Claw (part of driven side rotating member and driven side engaging part)
60, 160 Driving side rotating member 62 Driving side engaging portion 301 Process unit

Claims (24)

At least an image carrier carrying a latent image on the surface;
A developing device for developing a latent image on the image carrier with a developer carried on a moving surface of the developer carrier;
A drive transmission gear train including a plurality of gears that relays a rotational driving force transmitted from a driving source provided in the image forming apparatus main body and transmits the rotation driving force to the developer carrier, and is detachable from the main body. In the process unit
The process unit characterized in that the number of moving teeth on the rotation trajectory of each of the gears constituting the drive transmission gear train during the surface movement of 1 mm is 0.72 or more. The process unit according to claim 1, wherein
An end in the rotational axis direction of a driving side rotating member disposed in the image forming apparatus main body so as to transmit a rotational driving force from the driving source to the driving transmission gear train at a position closer to the driving side than the drive transmission gear train. A driven-side engaging portion that rotates by being abutted and engaged in the rotational axis direction with respect to the driving-side engaging portion formed in the portion;
Of each gear in the drive transmission gear train, a first gear to which a rotational driving force from the drive source is first transmitted is formed integrally with the driven side engaging portion, and the driven side engagement A process unit that rotates on the same rotation axis as the unit. The process unit according to claim 2, wherein
A holding body that holds the driven side engaging portion and the first gear at least within a plane orthogonal to the rotational axis direction thereof, and the driven side engaging portion and the first gear include the driven side engaging portion; The process unit is configured to move so that its own rotation axis approaches the rotation axis of the driving side rotating member in accordance with the engagement between the driving portion and the driving side engaging portion. The process unit according to claim 3,
A process unit, wherein at least the first gear and a downstream gear meshing with the first gear are negatively displaced. At least an image carrier that carries a latent image on a moving surface;
A developing device for developing a latent image on the image carrier with a developer carried on a moving surface of the developer carrier;
In an image forming apparatus having a drive source for rotationally driving the developer carrier,
The developing device has a drive transmission gear train composed of a plurality of gears that relay the rotational driving force transmitted from the driving source and transmit the rotational driving force to the developer carrier.
The image forming apparatus, wherein the number of moving teeth on the rotation trajectory of each gear in the drive transmission gear train during the surface movement of the image carrier by 1 mm is 0.72 or more. The image forming apparatus according to claim 5.
The driving-side rotation member disposed in the image forming apparatus main body so as to transmit the rotational driving force from the driving source to the driving transmission gear train at a position closer to the driving side than the drive transmission gear train;
A developing device that is detachably supported by the image forming apparatus main body is abutted in the rotational axis direction and engaged with the driving side engaging portion formed at an end portion in the rotational axis direction of the driving side rotating member. A driven side engaging portion that rotates by
Of each gear in the drive transmission gear train, a first gear to which a rotational driving force from the drive source is first transmitted is formed integrally with the driven side engaging portion, and the driven side engagement An image forming apparatus, wherein the image forming apparatus rotates on the same rotation axis as the image forming unit. The image forming apparatus according to claim 6.
The developing device includes a holding body that holds the driven side engaging portion and the first gear so as to be movable at least in a plane orthogonal to the rotation axis direction thereof.
The driven-side engaging portion and the first gear bring their own rotation axis closer to the rotation axis of the driving-side rotating member as the driven-side engaging portion and the driving-side engaging portion are engaged. An image forming apparatus that moves. The image forming apparatus according to claim 7.
An image forming apparatus, wherein at least the first gear and the downstream gear meshing with the first gear are negatively shifted. At least an image carrier that carries a latent image on a moving surface;
A developing device for developing a latent image on the image carrier with a developer carried on a moving surface of the developer carrier;
A transfer device that transfers a visible image on the image carrier to a surface moving member that moves on the surface at a position facing the image carrier or a recording member held on the surface of the surface moving member;
In an image forming apparatus comprising a driving source for applying a driving force to the surface moving body,
The transfer device has a drive transmission gear train composed of a plurality of gears that relay the rotational driving force transmitted from the drive source disposed in the image forming apparatus main body and transmit it to the surface moving body;
The image forming apparatus, wherein the number of moving teeth on the rotation trajectory of each gear in the drive transmission gear train is 0.72 or more while the image carrier moves on the surface by 1 mm. The image forming apparatus according to claim 9.
The driving-side rotation member disposed in the image forming apparatus main body so as to transmit the rotational driving force from the driving source to the driving transmission gear train at a position closer to the driving side than the drive transmission gear train;
A transfer device that is detachably supported by the image forming apparatus main body is abutted and engaged in the rotation axis direction with the driving side engaging portion formed at the end portion in the rotation axis direction of the driving side rotation member. A driven side engaging portion that rotates by
Of each gear in the drive transmission gear train, a first gear to which a rotational driving force from the drive source is first transmitted is formed integrally with the driven side engaging portion, and the driven side engagement An image forming apparatus, wherein the image forming apparatus rotates on the same rotation axis as the image forming unit. The image forming apparatus according to claim 10.
The transfer device has a holding body that holds the driven side engaging portion and the first gear so as to be movable at least in a plane orthogonal to the rotation axis direction thereof,
The driven-side engaging portion and the first gear bring their own rotation axis closer to the rotation axis of the driving-side rotating member as the driven-side engaging portion and the driving-side engaging portion are engaged. An image forming apparatus that moves. The image forming apparatus according to claim 11.
An image forming apparatus, wherein at least the first gear and a downstream gear meshing with the first gear are negatively shifted. An image carrier carrying a latent image on a moving surface;
In an image forming apparatus having a developing device that develops a latent image on the image carrier with a developer carried on a moving surface of the developer carrier.
The developing bias applied to the developer carrying member is a direct current voltage (DC voltage),
A linear velocity ratio Vs / Vp between a linear velocity Vp of the image carrier and a linear velocity Vs of the developer carrier is in a range of 1.7 to 2.0;
The image forming apparatus, wherein a development interval Gp between the image carrier and the developer carrier is in a range of 0.1 to 0.45 mm. An image carrier carrying a latent image on a moving surface;
In an image forming apparatus having a developing device that develops a latent image on the image carrier with a developer carried on a moving surface of the developer carrier.
The developer carrier includes a magnet roller having a plurality of magnetic poles;
The magnet roller includes a main magnetic pole that forms a magnetic brush for sliding the developer on the image carrier,
A line connecting the half-value width center of the magnetic field by the main magnetic pole and the rotation center of the developer carrier is formed with respect to a line connecting the rotation center of the image carrier and the rotation center of the developer carrier. The image forming apparatus is characterized in that an angle R of the developer is in a range of 2 ° to 8.5 ° with respect to an upstream direction in which the developer carrying member rotates. The image forming apparatus according to claim 1, wherein:
The developing bias applied to the developer carrying member is a direct current voltage (DC voltage),
A linear velocity ratio Vs / Vp between a linear velocity Vp of the image carrier and a linear velocity Vs of the developer carrier is in a range of 1.7 to 2.0;
The image forming apparatus, wherein a development interval Gp between the image carrier and the developer carrier is in a range of 0.1 to 0.45 mm. The image forming apparatus according to claim 13 or 15,
The developer carrier includes a magnet roller having a plurality of magnetic poles;
The magnet roller includes a main magnetic pole that forms a magnetic brush for sliding the developer on the image carrier,
A line connecting the half-value width center of the magnetic field by the main magnetic pole and the rotation center of the developer carrier is formed with respect to a line connecting the rotation center of the image carrier and the rotation center of the developer carrier. The image forming apparatus is characterized in that an angle R of the developer is in a range of 2 ° to 8.5 ° with respect to an upstream direction in which the developer carrying member rotates. The image forming apparatus according to claim 15 or 16,
An image forming apparatus comprising: a two-component developer that mixes a carrier and a toner. The image forming apparatus according to claim 17.
The toner has a volume average particle diameter of 3 to 8 μm, and a ratio (Dv / Dn) of volume average particle diameter (Dv) to number average particle diameter (Dn) is in the range of 1.00 to 1.40. An image forming apparatus. The image forming apparatus according to claim 18.
The image forming apparatus, wherein the toner used in the developing device has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180. The image forming apparatus according to claim 18 or 19,
The toner used in the developing device is obtained by crosslinking a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent is dispersed in an organic solvent in an aqueous medium. And / or a toner obtained by an extension reaction. The image forming apparatus according to claim 20, wherein
The toner used in the developing device has a substantially spherical shape. The image forming apparatus according to claim 21, wherein
The shape of the toner is defined by a major axis r1, a minor axis r2, and a thickness r3 (where r1 ≧ r2 ≧ r3), and a ratio (r2 / r1) between the major axis r1 and the minor axis r2 is set. An image forming apparatus, characterized in that it is in the range of 0.5 to 1.0, and the ratio (r3 / r2) of the thickness r3 to the minor axis r2 is in the range of 0.7 to 1.0. The image forming apparatus according to claim 17.
The image forming apparatus, wherein the carrier has a magnetic particle surface coated with a resin and has a volume average particle size in a range of 30 to 80 μm. The image forming apparatus according to claim 23.
The image forming apparatus, wherein the carrier has an electric resistance in a range of 6 to 10 LogΩ · cm.

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