JP2005352359A - Developing device, image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device which suppresses unevenness in an amount of a developer passing through a gap between a developing roller and a doctor, and to provide an image forming apparatus with the developing device and a process cartridge. <P>SOLUTION: The difference between maximum and minimum values of normal magnetic flux density in a range of turn of ≥±5° from a middle position of the doctor on the basis of the center of the developing roller is set to ≥10 [mT]. Since variation in normal magnetic flux density near the doctor is thus made small, even if a central part of the doctor sags and becomes different in level from ends, the difference in magnetic field between the central part and ends of the doctor can be made small. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developing device, an image forming apparatus, and a process cartridge.

  Conventionally, as shown in FIG. 13, a two-component developer composed of a magnetic carrier and toner is carried on the surface of a developing roller 201 and conveyed to a developing region facing a photoreceptor 210 as a latent image carrier. A device using a developing device for developing the above electrostatic latent image is known. A developing roller 201 includes a magnet roller 202 having a plurality of magnets 203. A magnetic field having a normal direction magnetic flux density distribution such as a dotted line in the figure is formed on the surface of the developing roller from these magnets 203. Then, the magnetic force of these magnets 203 causes the developer to rise on the surface in a brush shape. The developer roller 201 moves relative to these magnets, so that the developer (hereinafter referred to as a magnetic brush) spiked on the surface of the developer roller 201 is conveyed along with the surface movement of the developer roller 201. . In a region where the normal direction magnetic flux density distribution is high as shown in FIG. On the other hand, a portion having a low normal direction magnetic flux density distribution is conveyed in a state of falling over the developing roller.

  Further, in the developing device of FIG. 13, a doctor 206 is provided as a developer amount regulating member in order to adjust the developer pumping amount on the developing roller 201 to a desired value. When the developer passes through the gap between the doctor 206 and the developing roller 201 (hereinafter referred to as doctor gap), the magnetic brush is cut into the doctor 206. As a result, the amount of developer conveyed to the development area is adjusted, and a stable conveyance amount is ensured.

  In order to make the developer conveyed to the developing area constant in the axial direction, the doctor 206 is provided so that the doctor gap is constant in the axial direction. However, in reality, the doctor 145 is deflected and deformed by the developer pressure that the doctor dams up, as shown in FIG. DG2) will spread. As a result, the amount of developer passing through the center of the doctor gap is larger than the amount of developer passing through the end. Therefore, the developer conveyed to the development area cannot be made constant in the axial direction, causing image density unevenness and the like. Therefore, Patent Document 1 and Patent Document 2 describe ones in which the developing roller is stopped and the doctor gap is narrowed toward the center in the axial direction.

JP 2003-122113 A JP 2000-98738 A

  However, even if the doctor gap is kept constant in the axial direction when the center part of the doctor is bent as in Patent Documents 1 and 2, there are cases where the transport amount of the developer differs between the center part and the end part. Further, even when the amount of deflection at the center of the doctor is slight and the spread of the gap due to the deflection is negligible, the amount of development may differ between the center and the end. This is because there is a difference in the normal magnetic flux density between the center and the end of the doctor due to the deflection, and this difference in the normal magnetic flux density allows development that passes through the doctor gap even if there is almost no gap expansion due to the deflection. It was found that a difference was caused in the dosage.

  That is, at a position where the normal direction magnetic flux density is high, the magnetic brush on the developing roller passes through the doctor gap in a state of being raised, so that the amount of cutting by the doctor increases and the amount of developer passing therethrough decreases. . On the other hand, at the position where the normal direction magnetic flux density is low, the magnetic brush on the developing roller passes through the doctor gap in a fallen state, so that the amount of cutting by the doctor decreases and the amount of developer passing therethrough increases. As described above, the normal magnetic flux density at the center position of the doctor is different from the normal magnetic flux density at the position of the doctor end. As a result, the development that passes though the change in the doctor gap is in a negligible range. It was found that the amount of the agent was different in the axial direction.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device that suppresses variation in the amount of developer passing through the gap between the developing roller and the doctor, and image formation including the developing device. An apparatus and a process cartridge are provided.

In order to achieve the above object, the invention of claim 1 comprises a developer containing portion for containing a magnetic developer, and a rotatable nonmagnetic sleeve containing a plurality of magnetic field generating means. A developing roller that carries the magnetic developer in the developer accommodating portion on the surface and conveys it to a developing area facing the image carrier, and forms a gap with the developing roller, and the developer on the developer roller is formed in the gap In a developing device including a doctor that regulates the layer thickness of the developer on the developing roller, in a virtual plane perpendicular to the rotation axis of the developing roller, An imaginary line connecting the position closest to the upstream side in the rotation direction of the developing roller and the center of the developing roller is used as a reference line, and rotated from the reference line by ± 5 ° or more with respect to the center of the developing roller. In range The difference between the maximum value of the normal direction magnetic flux density on the surface of the developing roller and the minimum value of the normal direction magnetic flux density is 10 [mT] or less.
According to a second aspect of the present invention, in the developing device of the first aspect, one of the magnetic field generating means is provided at a position facing the doctor, and the magnetic flux generated from the magnetic field generating means at the position facing the doctor. However, on the virtual plane perpendicular to the rotation axis of the developing roller, the center position of the virtual line segment connecting the two half-value points of the maximum normal direction magnetic flux density on the surface of the developing roller is connected to the center of the developing roller. The maximum value of the normal direction magnetic flux density on the surface of the developing roller and the normal direction magnetic flux density in a range rotated by ± 15 ° or more from the reference line with the center of the developing roller as a reference from the reference line. The difference from the minimum value is 5 [mT] or less.
Further, the invention of claim 3 is the developing device according to claim 1 or 2, wherein the surface of the developing roller has a plurality of grooves extending in the longitudinal direction, and the depth of the grooves is 0.05 mm or more. It is 0.15 [mm] or less.
According to a fourth aspect of the present invention, in the developing device of the first, second, or third aspect, a two-component developer composed of toner and magnetic particles is used as the developer, and the particle size of the magnetic particles is 20 [μm. ] 50 [μm] or less.
According to a fifth aspect of the present invention, there is provided the developing device according to the fourth aspect, wherein the magnetic particles are obtained by coating a core material of a magnetic material with a resin coat film, wherein the resin coat film comprises a thermoplastic resin and a melanin. What contains the resin component which bridge | crosslinked resin and the charge control agent is used, It is characterized by the above-mentioned.
According to a sixth aspect of the present invention, in the developing device of the first, second, third, fourth, or fifth aspect, the toner contained in the developer includes at least a prepolymer, a colorant, and a release agent. A composition obtained by dispersing a composition in an aqueous medium in the presence of resin fine particles and subjecting the toner composition to a polyaddition reaction is used.
The invention of claim 7 is the developing device of claim 1, 2, 3, 4, 5 or 6, wherein the toner contained in the developer has a volume average particle size of 3 [μm] or more and 8 [μm]. In the following, the ratio of the number average particle diameter to the volume average particle diameter is 1.00 or more and 1.40 or less.
The invention of claim 8 is the developing device of claim 1, 2, 3, 4, 5, 6 or 7, wherein the toner contained in the developer has a shape factor SF-1 of 100 or more and 180 or less, In addition, a material having a shape factor SF-2 of 100 or more and 180 or less is used.
According to a ninth aspect of the present invention, in the developing device of the first, second, third, fourth, fifth, sixth, seventh, or eighth aspect, the toner has a substantially spherical shape, the shape of which is a major axis r1 and a minor axis. r2 and thickness r3 (where r1 ≧ r2 ≧ r3), the ratio of the major axis r1 to the minor axis r2 (r2 / r1) is in the range of 0.5 to 1.0, and the thickness The ratio (r3 / r2) between the length r3 and the minor axis r2 is in the range of 0.7 to 1.0.
According to a tenth aspect of the present invention, the toner contained in the developer is attached to the electrostatic latent image formed on the surface of the latent image carrier by the developing device to form a toner image. In an image forming apparatus for transferring an image onto a recording material to form an image, the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9 is used as the developing device. Is.
The invention according to claim 11 is the image forming apparatus according to claim 10, wherein the developing gap that minimizes the distance between the surface of the developing roller of the developing device and the surface of the latent image carrier is 0.1 [ mm] or more and 0.4 [mm] or less.
According to the invention of claim 12, the toner contained in the developer is attached to the electrostatic latent image formed on the surface of the latent image carrier by the developing device to form a toner image, and the toner image is finally obtained. The toner image is transferred onto a recording material to form an image, and the toner image is transferred from the surface of the latent image carrier. In a process cartridge that integrally supports at least the developing device and the latent image carrier among the devices or members arranged around the image carrier, the developing device is defined as any of claims 1, 2, 3, 4, 5, A developing device of 6, 7, 8 or 9 is used.

  According to the first to eleventh aspects of the present invention, the difference between the maximum value and the minimum value of the normal direction magnetic flux density in a range rotated by ± 5 ° or more with respect to the center of the developing roller from the center position of the doctor is obtained. 10 [mT] or less. In this way, fluctuations in the normal direction magnetic flux density near the doctor are reduced, so even if the center of the doctor bends and the position of the end differs, the difference in magnetic field between the center and end of the doctor is reduced. can do. Thereby, the variation in the amount of developer in the axial direction due to the difference in the normal direction magnetic flux density between the center and the end of the doctor can be suppressed. As a result, the image density can be kept uniform and a good image can be obtained.

Hereinafter, an embodiment of a tandem color laser printer (hereinafter referred to as “laser printer”) will be described as an image forming apparatus to which the present invention is applied.
First, the basic configuration of the laser printer will be described.
[overall structure]
FIG. 1 is a schematic configuration diagram of a laser printer according to the present embodiment. This laser printer includes four sets of process cartridges 1Y, M, C, and K for forming images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K). Needless to say, Y, M, C, and K appended to the numbers of the respective symbols indicate members for yellow, magenta, cyan, and black (the same applies hereinafter). In addition to the process cartridges 1Y, 1M, 1C, and 1K, an optical writing unit 10, a transfer unit 11, a registration roller pair 19, three paper feed cassettes 20, a fixing unit 21, and the like are disposed.

[Optical writing unit]
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.

[Process cartridge]
FIG. 2 is an enlarged view showing a schematic configuration of the yellow process cartridge 1Y among the process cartridges 1Y, 1M, 1C, and 1K. Since the other process cartridges 1M, 1C, and 1K have the same configuration, their descriptions are omitted. In FIG. 2, the process cartridge 1Y includes a drum-shaped photoconductor 2Y, a charging device 30Y, a static eliminator 31Y, a developing device 40Y, a drum cleaning device 48Y, and the like.

  The charging device 30Y uniformly charges the drum surface by sliding a charging roller to which an AC voltage is applied against the photoreceptor 2Y. The surface of the photoreceptor 2Y 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 40Y to become a Y toner image.

  The developing device 40Y has a developing roller 42Y disposed so as to be partially exposed from the opening of the casing. Further, it also includes a first transport screw 43Y, a second transport screw 44Y, a doctor 45Y, a toner concentration sensor (hereinafter referred to as a T sensor) 46Y, and the like.

  A two-component developer containing a magnetic carrier and negatively chargeable Y toner is accommodated in the casing. The two-component developer is frictionally charged while being agitated and conveyed by the first conveying screw 43Y and the second conveying screw 44Y, and then carried on the surface of the developing roller 42Y. Then, after the layer thickness is regulated by the doctor 45Y, it is transported to the developing area facing the photoreceptor 2Y, where Y toner is attached to the electrostatic latent image on the photoreceptor 2Y. This adhesion forms a Y toner image on the photoreceptor 2Y. The two-component developer that has consumed Y toner by development is returned to the casing as the developing roller 42Y rotates.

  A partition wall 47Y is provided between the first transport screw 43Y and the second transport screw 44Y. The partition wall 47Y separates the first supply unit that accommodates the developing roller 42Y, the first conveyance screw 43Y, and the like and the second supply unit that accommodates the second conveyance screw 44Y in the casing. The first conveying screw 43Y is rotationally driven by a driving unit (not shown), and supplies the two-component developer in the first supply unit to the developing roller 42Y while conveying the two-component developer from the front side to the back side in the drawing. The two-component developer conveyed to the vicinity of the end of the first supply unit by the first conveyance screw 43Y enters the second supply unit through an opening (not shown) provided in the partition wall 47Y. In the second supply unit, the second transport screw 44Y is driven to rotate by a driving unit (not shown), and transports the two-component developer sent from the first supply unit in the direction opposite to that of the first transport screw 43Y. . The two-component developer transported to the vicinity of the end of the second supply unit by the second transport screw 44Y returns to the first supply unit through the other opening (not shown) provided in the partition wall 47Y. .

  The T sensor 46Y including a magnetic permeability sensor is provided on the bottom wall near the center of the second supply unit, 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 has a certain degree of correlation with the toner density, the T sensor 46Y outputs a voltage having a value corresponding to the Y toner density. This output voltage value is sent to a control unit (not shown). This control unit includes a RAM, in which Y Vtref, which is a target value of the output voltage from the T sensor 46Y, is stored. 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 in another developing device, are also stored. The Y Vtref is used for driving control of a Y toner conveying device (not shown). Specifically, the control unit drives and controls a Y toner conveying device (not shown) so that the value of the output voltage from the T sensor 46Y is close to the Y Vtref, and replenishes Y toner into the second supply unit. By this replenishment, the Y toner concentration of the two-component developer in the developing device 40Y is maintained within a predetermined range. Similar toner replenishment control is performed for the developing devices of the other process cartridges.

  The Y toner image formed on the Y photoconductor 2Y is transferred onto a transfer sheet that is transported to a paper transport belt described later. The surface of the photoreceptor 2Y after the transfer is discharged by the charge eliminator 31Y after the transfer residual toner is cleaned by the drum cleaning device 48Y. Then, it is uniformly charged by the charging device 30Y and prepared for the next image formation. The same applies to other process cartridges. Each process cartridge can be attached to and detached from the printer body, and is replaced when the end of its service life is reached.

[Transfer unit]
In FIG. 1 described above, the transfer unit 11 includes a paper conveying belt 12, a driving roller 13, a stretching roller 14, four transfer bias rollers 17Y, M, C, and K. The paper conveying belt 12 is endlessly moved counterclockwise in the figure by a driving roller 13 rotated by a driving system (not shown) while being tensioned by a driving roller 13 and a stretching roller 14. A transfer bias is applied to each of the four transfer bias rollers 17Y, 17M, 17C, and 17K from a power source (not shown). Then, the paper conveying belt 12 is pressed from the back surface toward the photoreceptors 2Y, 2M, 2C, and 2K to form transfer nips. At each transfer nip, a transfer electric field is formed between the photoconductor and the transfer bias roller due to the influence of the transfer bias. The above-mentioned Y toner image formed on the Y photoconductor 2Y 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 Y 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 transported on the paper transport belt 12.

[Paper cassette]
Below the transfer unit 11, three paper feed cassettes 20 for accommodating a plurality of transfer papers P in a stacked manner are arranged in multiple stages, and each cassette is provided with a paper feed roller on the top transfer paper P. Is pressed. 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.

[Registration roller pair]
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 unit 21.

[Fixing unit]
The fixing unit 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 paper P that has passed through the fixing unit 21 is discharged out of the apparatus through a pair of paper discharge rollers (not shown).

Next, the developing roller will be described. The developing roller 42Y is manufactured as follows. First, aluminum is extruded hot to form a cylindrical shape. As a material for the developing roller, brass, stainless steel, conductive resin, etc. can be used in addition to aluminum, but aluminum is often used from the viewpoint of cost and accuracy.
Next, a groove extending in the axial direction is formed on the outer periphery of the sleeve by cold-drawing cylindrical aluminum from the inner peripheral surface of the die having V-shaped convex portions formed on the inner peripheral surface. Here, the inner diameter of the die may be slightly smaller than the outer diameter of the sleeve, and processing for increasing the deflection accuracy of the sleeve may be performed simultaneously with the processing of the groove. The number of sleeves is about 50 to 100. The groove may be formed at the time of hot extrusion production of aluminum.

  As shown in FIG. 3, the groove depth H of the developing roller 42Y of this embodiment is set to 0.05 to 0.15 [mm]. If the groove depth is 0.15 [mm] or more, unevenness of the groove pitch occurs, and the conveying force becomes insufficient at 0.05 [mm]. Further, when there is a groove depth deviation, sleeve circumferential pitch unevenness due to the deviation occurs, so the groove depth deviation is set to 30% or less. By suppressing the groove depth deviation to 30% or less, it is possible to obtain a good image in which pitch unevenness due to the groove depth deviation is suppressed.

  Conventionally, the surface of the developing roller is sandblasted to moderately roughen the surface of the developing roller to assist the developer conveying force. However, in the sleeve subjected to the sandblasting process, the protrusions roughened by the wear disappear at the time of diameter, and the conveying ability is reduced at the time of diameter. For this reason, the developer pumping amount cannot be secured at the time of diameter. However, in this embodiment, since the groove is provided on the surface of the developing roller, the conveyance capability due to wear does not deteriorate. For this reason, a stable pumping amount can be ensured over time. in this way. Since the pumping amount over time can be secured, it is possible to suppress the decrease in image density, roughness, and increase in toner density due to the decrease in developing ability over time, and provide high-quality images over time. It can be set as a developing device.

  In this printer, as shown in FIG. 3, the developing gap G between the photosensitive member 2Y and the developing roller 42Y is set to 0.4 mm or less. Thus, by narrowing the gap G, the granularity of the developed toner image can be greatly improved, and a high-quality image can be obtained. Note that if the development gap G is too smaller than 0.1 mm, the toner is liable to adhere to the developing roller 42Y.

  Further, as shown in FIG. 4, the developing roller 42Y of the present embodiment has a magnet roller 53 provided with five magnets 50a, 50b, 50c, 50d, and 50e. The doctor magnet 50b of the mag roller 53 is disposed at a position facing the doctor 45Y. A magnetic flux density distribution as shown by a solid line in FIG. 4 is formed from each magnet of the mag roller 53. The doctor 45 is configured such that the developing gap is uniform in the axial direction in a stationary state. The developing roller 42Y of this embodiment magnetizes the doctor magnet 50b closest to the doctor 45Y so that the normal direction magnetic flux density distribution near the doctor 45Y is substantially flat. Specifically, from a position A at the center of a line (hereinafter referred to as half width) connecting two half-value points B and C of the peak value of the normal direction magnetic flux density generated from the doctor magnet 50b closest to the doctor 45Y. The doctor magnet 50b is magnetized so that the difference between the maximum value and the minimum value of the normal direction magnetic flux density in the range of ± 15 ° with respect to the center of the developing roller 42Y is 5 [mT] or less. The dotted line shown in FIG. 4 indicates the normal direction magnetic flux density distribution of the conventional developing roller.

  FIG. 5 is a graph showing the magnetic flux density at each angle with reference to a line segment connecting the center position of the half-value width in the magnetic flux density of the doctor magnet 50b at the position facing the doctor and the center of the developing roller as a reference (0 °). It is. The dotted line in the figure indicates the magnetic flux density of the conventional developing roller, and the solid line in the figure indicates the magnetic flux density of the developing roller 45Y of this embodiment. As can be seen from FIG. 5, in the developing roller 45Y of this embodiment, the magnetic flux density in the range from −15 ° to 15 ° is set to 5 [mT] or less, so the magnetic flux density near the peak value is substantially flat. Yes. On the other hand, in the conventional developing roller, the magnetic flux density in the range from −15 ° to 15 ° is 5 [mT] or more, and it can be seen that the normal direction magnetic flux density near the peak value increases or decreases.

FIG. 6 is a diagram showing the relationship between the fluctuation due to the deflection of the doctor 45Y due to the developer pressure during development and the normal direction magnetic flux density. The central portion of the doctor 45Y is bent by the pressure of the developing agent during development, and moves from the static position indicated by the dotted line in FIG. 5 to the dynamic position indicated by the solid line. Then, in the conventional developing roller, it can be seen that when the doctor 45Y moves to the solid line, the normal direction magnetic flux density decreases (point D → point D ′). On the other hand, in the developing roller 42Y of the present embodiment, it can be seen that the normal direction magnetic flux density shows almost the same value even if the doctor moves (point E → point E ′). Compared with the developer that has passed through the doctor gap of the conventional developing roller and the amount of developer that has passed through the doctor gap of the developing roller 42Y of the present embodiment, the developing roller 42Y of the present embodiment is more current than the conventional developing roller. The agent was axially uniform. This is because, in the conventional developing roller, the normal direction magnetic flux density is different between the doctor end portion and the bent central portion, so the normal direction magnetic flux density at the bent central portion position is the normal direction at the end position. It is smaller than the magnetic flux density. For this reason, the magnetic brush in the vicinity of the center part falls more than the magnetic brush at the end part and passes through the doctor gap. Therefore, the amount of ear cutting by the doctor 45Y increases at the end portion, and the amount of ear cutting by the doctor 45Y decreases at the center portion. As a result, in the conventional developing roller, the amount of developer that has passed through the doctor gap becomes non-uniform in the axial direction, resulting in density unevenness.
On the other hand, in the developing roller 45Y of this embodiment, there is almost no difference between the normal direction magnetic flux density at the position of the end portion of the doctor 45Y and the normal direction magnetic flux density at the bent central portion. For this reason, the amount of spikes of the magnetic brush that passes through the doctor gap can be made the same, and the amount of the developer that passes through the doctor gap can be made substantially the same at the end portion and the bent central portion. Therefore, in the developing roller 45Y of this embodiment, a high-quality image can be obtained in which the amount of developer that has passed through the doctor gap can be made uniform in the axial direction.

Further, as shown in FIG. 5, the conventional developing roller has a flat magnetic flux density distribution only in a small region near the peak value. For this reason, in the conventional developing roller, the peak value of the magnetic flux density cannot be arranged at the position facing the doctor due to the mounting error of the mag roller, and the magnetic force acting on the doctor gap may be different for each developing device. there were. Even if the mag roller is attached with high precision, the peak value of the magnetic flux density is not arranged at the position facing the doctor due to variations in the mag roller itself, and the magnetic force acting on the doctor gap may be different for each developing device. . As a result, the amount of developer passing through the doctor gap may differ from device to device, and the amount of developer conveyed to the development region may vary from device to device.
On the other hand, the magnetic flux density distribution of the developing roller of the present embodiment has a sufficiently flat region of the peak value. Therefore, even if there is a slight mag roller mounting error or a mag roller manufacturing error, the magnetic flux density at the position facing the doctor is somewhat small. Peak values can be arranged. Thereby, it is suppressed that the magnetic force which acts on a doctor gap differs for every developing apparatus, and it is suppressed that the quantity of a developer differs for every apparatus between doctor gaps. As a result, it is possible to suppress the amount of developer conveyed to the development area from being different for each apparatus.

  Further, in the developing roller of this embodiment, the difference between the maximum value and the minimum value of the normal direction magnetic flux density in the range rotated ± 15 ° is 5 [mT], but in the range rotated ± 15 ° or more. The difference between the maximum value and the minimum value of the normal direction magnetic flux density may be 5 [mT]. By setting the difference between the maximum value and the minimum value of the normal direction magnetic flux density in the range rotated by ± 15 ° or more to 5 [mT], the peak value can be made flatter. Further, since the flat area of the peak value increases, an error in the amount of the developer conveyed to the developing area for each developing device can be eliminated.

Further, as shown in FIG. 7, when the doctor 450Y is arranged at a position greatly deviating from the peak value of the normal direction magnetic flux density of the magnet in the vicinity of the doctor 450Y, the above-mentioned severe conditions may not be required. As shown in FIG. 4, when the doctor 45Y is arranged near the peak value of the magnetic flux density in the normal direction of the magnet 50b, the magnetic brush near the doctor 45Y is in the most prominent state and the amount of developer to be cut off There are many. For this reason, even if the magnetic flux density in the normal direction is low even slightly, even if the magnetic brush falls slightly, the amount of developer cut off by the doctor varies. Therefore, if there is even a slight difference in the normal direction magnetic flux density between the position of the bent central portion and the position of the end portion, the difference in the amount of developer passing through the doctor gap will cause density unevenness. . For this reason, in FIG. 4, it is necessary to define the normal direction magnetic flux density under severe conditions.
On the other hand, as shown in FIG. 7, when the doctor 450Y is arranged at a position greatly deviating from the peak value of the normal direction magnetic flux density of the magnet, the normal direction magnetic flux density is low, so that the magnetic brush has fallen. Because it passes through the doctor gap, the amount of ear cutting by the doctor is small. For this reason, even if the amount of spike fall of the magnetic brush is slightly different, the amount of ear cut by the doctor does not change significantly. For this reason, even if the normal magnetic flux density is slightly different between the position of the bent central portion and the position of the end portion, the difference in the developer amount passing through the doctor gap can be kept within an allowable range. Specifically, the normal direction magnetic flux in the range of ± 5 ° with respect to the center of the developing roller 420Y from the position (gap position) closest to the developing roller surface of the doctor 450Y and the most upstream position (gap position) in the rotating direction of the developing roller. The difference between the maximum value and the minimum value of the density is 10 [mT] or less. If the difference between the maximum value and the minimum value of the normal direction magnetic flux density is 10 [mT] or less within a range of ± 5 ° from the gap position of the doctor 450Y, the doctor gap passes through the doctor gap at the center and the end of the doctor. The difference in developer amount can be kept within an allowable range.

Next, the developer used in this embodiment will be described.
As the carrier for the two-component developer, it is desirable to use a coat film having elasticity and strong adhesive force and coated with a coat film containing particles having a diameter larger than the film thickness on the surface. FIG. 8 is an explanatory diagram of the carrier 500. Ferrite 501 is used as the core material of the carrier 500. The surface of the ferrite 501 is coated with a coating film 502 containing a charge adjusting agent in a resin component obtained by crosslinking a thermoplastic resin such as acrylic and a melamine resin. The coat film 502 has elasticity and strong adhesive force. Further, particles having a diameter larger than the film thickness of the coat film 502, for example, alumina particles 503 are dispersed on the surface. The alumina particles 503 are held with a strong adhesive force of the coating film 502. Whereas the conventional carrier is configured on the basis of the idea of obtaining a long life while gradually scraping off the hard coat film, the carrier 500 shown in the figure absorbs the impact by the elasticity of the coat film 502 and absorbs the impact. Suppress cutting. Further, by dispersing alumina particles 503 having a diameter larger than the film thickness on the surface of the carrier 501, it is possible to prevent the impact on the coat film 502 and to clean the spent material. As described above, since the coating film can be prevented from being scraped and spent, it is possible to achieve a longer life than conventional carriers. Accordingly, it is possible to expect stabilization of the toner pumping amount, that is, stabilization of quality over a long period of time.

  Furthermore, the carrier particle size can be reduced to form an image with more excellent dot reproducibility. Specifically, the carrier particle size is desirably 20 μm or more and 50 μm or less. By setting the carrier particle size smaller than before and further setting the particle size in such a range, it becomes possible to uniformly reduce the thickness of the magnetic brush at the time of image formation. Therefore, it is possible to deliver a more precise toner. In addition, since the density of the magnetic brush per unit area on the developing roller is increased, toner can be delivered to the latent image on the photoreceptor without any gap. Thereby, an image with more excellent dot reproducibility can be formed. If the carrier particle diameter is too larger than 50 μm, the total surface area of the carrier is reduced and the amount of toner held is reduced when compared with the same carrier amount. For this reason, the toner density is lowered. Although it is possible to increase the pumping amount to maintain the developing ability, toner sticking is likely to occur. On the other hand, if the carrier particle diameter is too smaller than 20 μm, the magnetic force holding force by the mag roller is reduced, causing carrier scattering and increasing carrier adhesion to the photosensitive member.

  For the toner, 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 is crosslinked and / or in an aqueous solvent. A toner obtained by an extension reaction. Hereinafter, the constituent material and the manufacturing method of the toner will be described.

(polyester)
The polyester is obtained by a polycondensation reaction between a polyhydric alcohol compound and a polycarboxylic acid compound.
Examples of the polyhydric alcohol compound (PO) include dihydric alcohol (DIO) and trihydric or higher polyhydric alcohol (TO). (DIO) alone or a mixture of (DIO) and a small amount of (TO) preferable. Examples of the dihydric alcohol (DIO) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (diethylene glycol) , Triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); bisphenols (bisphenol A, bisphenol) F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol; Alkylene oxide bisphenol (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among them, preferred are alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms. It is a combined use. The trihydric or higher polyhydric alcohol (TO) includes 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); trihydric or higher phenols (Trisphenol PA, phenol novolak, cresol novolak, etc.); and alkylene oxide adducts of the above trivalent or higher polyphenols.
Examples of the polyvalent carboxylic acid (PC) include divalent carboxylic acid (DIC) and trivalent or higher polyvalent carboxylic acid (TC). (DIC) alone and (DIC) with a small amount of (TC) Mixtures are preferred. Divalent carboxylic acids (DIC) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid) And naphthalenedicarboxylic acid). Of these, preferred are alkenylene dicarboxylic acids having 4 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms. Examples of the trivalent or higher polyvalent carboxylic acid (TC) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polyhydric carboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the above-mentioned acid anhydride or lower alkyl ester (Methyl ester, ethyl ester, isopropyl ester, etc.).
The ratio of the polyhydric alcohol (PO) to the polycarboxylic acid (PC) is usually 2/1 to 1/1, preferably as the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. Is 1.5 / 1 to 1/1, more preferably 1.3 / 1 to 1.02 / 1.

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

In addition to the unmodified polyester obtained by the above polycondensation reaction, the polyester preferably contains a urea-modified polyester. The urea-modified polyester is obtained by reacting a terminal carboxyl group or hydroxyl group of the polyester obtained by the above polycondensation reaction with a polyvalent isocyanate compound (PIC) to obtain a polyester prepolymer (A) having an isocyanate group. It is obtained by cross-linking and / or extending the molecular chain by the reaction of the amine with amines.
Examples of the polyvalent isocyanate compound (PIC) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) ); Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; Those blocked with caprolactam or the like; and combinations of two or more of these.

The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably as an equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 4/1 to 1.2 / 1, more preferably 2.5 / 1 to 1.5 / 1. When [NCO] / [OH] exceeds 5, low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1, when a urea-modified polyester is used, the urea content in the ester is lowered and hot offset resistance is deteriorated.
The content of the polyvalent isocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40 wt%, preferably 1 to 30 wt%, more preferably 2 to 20 wt%. . If it is less than 0.5 wt%, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. On the other hand, if it exceeds 40 wt%, the low-temperature fixability deteriorates.
The number of isocyanate groups contained per molecule in the polyester prepolymer (A) having an isocyanate group is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2 on average. Five. If it is less than 1 per molecule, the molecular weight of the urea-modified polyester 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 B1 to B5 blocked amino groups (B6) include ketimine compounds and oxazolidine compounds obtained from the amines of B1 to B5 and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.
The ratio of amines (B) is equivalent to the equivalent ratio [NCO] / [NHx] of isocyanate groups [NCO] in the polyester prepolymer (A) having isocyanate groups and amino groups [NHx] in amines (B). Is usually 1/2 to 2/1, preferably 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2. When [NCO] / [NHx] is more than 2 or less than 1/2, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance is deteriorated.

  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 a master batch or a master batch, a polymer of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyl toluene, or a substituted product thereof, 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 with the developing roller is increased, the developer fluidity is lowered, and the image density is lowered. Invite.

(Release agent)
As a release agent, a low melting point wax having a melting point of 50 to 120 ° C. works more effectively as a release agent in the dispersion with the binder resin between the fixing roller and the toner interface. The effect on high temperature offset is exhibited without applying a release agent such as oil. Examples of such a wax component include the following. Examples of waxes and waxes include plant waxes such as carnauba wax, cotton wax, wood wax, 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 masterbatch and the binder resin, or may be added when dissolved and dispersed in an organic solvent.

(External additive)
Inorganic fine particles are preferably used as an external additive for assisting the fluidity, developability and chargeability of the toner particles. The primary particle diameter of the inorganic fine particles is preferably 5 × 10 −3 to 2 μm, and particularly preferably 5 × 10 −3 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 particles having an average particle size of 5 × 10-2 μm or less, the electrostatic force and van der Waals force with the toner are remarkably improved. Even when stirring and mixing inside the developing device is performed, a fluidity-imparting agent is not detached from the toner, a good image quality that does not cause fireflies and the like is obtained, and a reduction in residual toner is further achieved. .

  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 with respect 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 toner material liquid is poorly dispersed, and toner particles having a predetermined particle diameter cannot be obtained. If it exceeds 20000 parts by weight, it is not economical.

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

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

  Moreover, as the cationic surfactant, aliphatic quaternary ammonium such as aliphatic primary, secondary or secondary amic acid, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt which has a right fluoroalkyl group 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), Megafac 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 above resin fine particles and inorganic compound dispersant, the dispersed droplets may be stabilized by a polymer protective colloid. For example, acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups 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-loro-2-hydroxypropyl, methacrylic acid-3-chloro-2-hydroxypropyl, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate Of acid ester, 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 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 imidazole , Nitrogen-containing compounds such as ethyleneimine, or homopolymers or copolymers such as those having a heterocyclic ring thereof, polyoxyethylene, Cypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxy Polyoxyethylenes such as ethylene nonylphenyl ester, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.

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

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

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

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

  Furthermore, it is important that the toner has a specific shape and shape distribution. The shape of the toner can be defined by circularity. Specifically, the average circularity of the toner is desirably 0.95 or more and 0.99 or less. More preferably, particles having an average circularity of 0.96 or more and 0.99 or less and a circularity of less than 0.95 are 10% or less. According to experiments, when the average circularity is less than 0.95, particularly less than 0.93, the toner becomes irregularly shaped away from the sphere, and a high-quality image without satisfactory transferability and dust cannot be obtained. On the other hand, when the average circularity is larger than 0.99, in a system employing blade cleaning or the like, a cleaning failure occurs on the photosensitive member or the transfer belt, causing stains on the image. When outputting an image with a low image area ratio, there is little transfer residual toner, and there is no problem with poor cleaning. However, for example, when an image with a high image area ratio such as a color photographic image is output, or when an untransferred image remains on the photoconductor due to a paper feed failure or the like, a cleaning failure is likely to occur. . If such cleaning defects occur frequently, further, the charging roller that contacts and charges the photoreceptor is contaminated, and the original charging ability cannot be exhibited. Therefore, when the average circularity of the toner is 0.95 or more and 0.99 or less, a high-definition image having a reproducibility with an appropriate density can be formed without causing a cleaning defect.

As a method for measuring the shape of the toner, an optical detection band method is suitable in which a suspension containing particles is passed through an imaging unit detection band on a flat plate, and a particle image is optically detected and analyzed by a CCD camera. It is. A value obtained by dividing the perimeter of an equivalent circle having the same projected area obtained by this method by the perimeter of the actual particle is defined as the average circularity.
The average circularity of the toner can be measured by a flow type particle image analyzer FPIA-2100 (manufactured by Toa Medical Electronics Co., Ltd.). As a specific measuring method, 0.1 to 0.5 ml of a surfactant, preferably alkylbenzene sulfonate is added as a dispersant to 100 to 150 ml of water from which impure solids have been removed in advance, and further measurement is performed. Add about 0.1-0.5g of sample. The suspension in which the sample is dispersed is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the shape and distribution of the toner are measured with the above flow type particle image analyzer with a dispersion concentration of 3000 to 10,000 / μl. It is obtained by doing.

Furthermore, it is desirable to define the toner shape factors SF-1 and SF-2. FIG. 9 is an explanatory diagram of the shape factor SF-1, and FIG. 10 is an explanatory diagram of the shape factor SF-2.
First, the shape factor SF-1 will be described. The shape factor SF-1 is a value indicating the ratio of the roundness of the shape of the spherical material, and the square of the maximum length MXLNG of the elliptical shape formed by projecting the spherical material on a two-dimensional plane is divided by the graphic area AREA. And expressed by a value obtained by multiplying by 100π / 4. That is, the shape factor SF-1 is defined by the following equation (1).
<Equation 1>
SF-1 = {(MXLNG) ² / AREA} × (100π / 4)

  When the value of the shape factor SF-1 is 100, the shape of the substance becomes a true sphere, and the larger the value of SF-1, the more irregular the shape of the substance.

On the other hand, as shown in FIG. 10, the shape factor SF-2 is a numerical value indicating the proportion of unevenness of the shape of the substance. The value is obtained by dividing the square of the perimeter PERI of the figure formed by projecting the substance on the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π. That is, the shape factor SF-2 is defined by the following equation (2).
<Equation 2>
SF-2 = {(PERI) ² / AREA} × (100 / 4π)

  When the SF-2 value is 100, there is no unevenness on the surface of the substance, and as the SF-2 value increases, the unevenness on the surface of the substance becomes more prominent.

  The shape factor was determined by randomly sampling a toner image 100 times using an FE-SEM (S-800) manufactured by Hitachi, Ltd., and introducing the image information into an image analyzer (LUSEX 3) manufactured by Nireco. Analysis was performed and the above formula was used for calculation.

According to the study by the present inventors, it has been found that when the shape factors SF-1 and SF-2 both approach 100 and the shape of the toner approaches a spherical shape as much as possible, the transfer efficiency increases. This results in point contact between the toner particles and those that come into contact with the toner particles (toner particles, photoconductor, etc.) due to the shape effect. As a result, it is considered that the toner fluidity is increased or the attracting force (mirroring force) to the image carrier or the like is weakened so that the toner is easily influenced by the transfer electric field.
According to experiments, in order to satisfy both the transfer property and the cleaning property, it is desirable that either the shape factor SF-1 or the shape factor SF-2 is 180 or less.

Furthermore, it is desirable to define the ratio of the number average particle diameter to the volume average particle diameter of the toner. Specifically, the volume average particle diameter (Dv) of the toner is 3 to 8 μm, and the ratio (Dv / Dn) to the number average particle diameter (Dn) is 1.00 or more and 1.40 or less. desirable. More preferably, Dv / Dn is desirably 1.10 or less as the particle size distribution after completion of the polymerization. As a result, the dry toner has a narrow particle size distribution of the toner, resulting in the following advantages. On the other hand, when the particle size distribution is broad, the particles are colored unevenly.
Since the toner particle size distribution becomes narrower in terms of toner particle size, it becomes difficult to generate selective development in which toner particles having a (suitable) toner particle size corresponding to the image pattern are selectively developed, and always stable. Images can be formed.
In addition, when a conventional toner recycling system is installed, a small amount of small-sized toner particles that are difficult to be transferred are recycled in a large quantity. However, since this toner originally has a narrow toner particle size distribution, it is not easily affected by the selective development described above, and a stable image can always be formed.
In addition, in a two-component developer, even if the toner balance for a long time is performed, fluctuations in the toner particle diameter in the developer are reduced, and good and stable developability can be obtained even with long-term stirring in the developing device. It is done.
Even when used as a one-component developer, even if the balance of the toner is performed, the fluctuation of the toner particle diameter is reduced, and the toner filming on the developing roller and the toner layer are made thin. There is no fusion of toner to members such as blades. As a result, good and stable developability and images can be obtained even during long-term use (stirring) of the developing device.
Here, the volume average particle diameter and the number average particle diameter are the values when the aperture current of 100 μm is used in Coulter Multisizer (manufactured by Coulter Electronics Co., Ltd.), and the setting of the aperture current etc. is (30,000) It is a particle size).

Further, the shape of the toner of the present embodiment is a substantially spherical shape, and can be expressed by the following shape rule.
FIG. 11 is a diagram schematically illustrating the shape of the toner of the present embodiment. In FIG. 11, 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 has a ratio of the major axis to the minor axis. (R2 / r1) (see FIG. 11B) is 0.5 to 1.0, and the ratio of thickness to minor axis (r3 / r2) (see FIG. 11C) is 0.7 to 1. It is preferably in the range of 0. 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 being away from the true spherical shape, and high-quality image quality cannot be obtained. On the other hand, if the ratio of thickness to minor axis (r3 / r2) is less than 0.7, the shape is 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.
In addition, r1, r2, r3 can be measured by the following method, for example. That is, the toner is uniformly dispersed and adhered on a smooth measurement surface, and 100 particles of the toner are magnified 500 times by a color laser microscope “VK-8500” (manufactured by Keyence Corporation). The major axis r1 (μm), the minor axis r2 (μm), and the thickness r3 (μm) of the particles can be measured and obtained from their arithmetic average values.

  In this embodiment, an example in which the present invention is applied to a tandem type color printer has been described. However, as shown in FIG. 12, the present invention can be applied to a color printer including a revolver type developing device 600 including four sets of developing units. Of course. The developing units constituting the revolver type developing device 600 of this color printer have different color toners. Then, by rotating the revolver type developing device 600, the developing rollers 601a to 601d of each developing device are sequentially moved to a developing position facing the photoreceptor 2 with a predetermined developing gap G. Thereby, a toner image of each color can be formed on the photoreceptor 2.

(1)
As described above, according to the developing device of the present embodiment, fluctuations in the normal direction magnetic flux density in the vicinity of the doctor are reduced. Therefore, even if the central portion of the doctor is bent, the development between the end portion passing through the doctor gap and the central portion is performed. The difference in the amount of the agent can be reduced. Thereby, the variation in the axial direction of the developer amount passing through the doctor gap due to the fluctuation of the normal direction magnetic flux density can be suppressed, and the density unevenness of the image can be suppressed.
(2)
Further, according to the developing device of the present embodiment, the line segment connecting the center position of the half-value width in the normal direction magnetic flux density of the magnet at the position facing the doctor and the center of the developing roller as a reference (0 °), The difference between the maximum value and the minimum value of the normal direction magnetic flux density in the range rotated by 15 ° or more is 5 [mT]. Thereby, the normal direction magnetic flux density near the peak value can be made substantially flat. As a result, even if the center part of the doctor is bent and the position is different from the end part, the normal direction magnetic flux density of the end part and the center part can be made substantially the same. Therefore, the amount of developer passing through the doctor gap can be made substantially the same at the end and the center.
In addition, since there is enough flat area of the peak value, even if there is a mounting error of the mag roller or a manufacturing error of the mag roller itself, the peak value of the normal direction magnetic flux density easily comes to the position facing the doctor. Can be arranged. Thereby, the variation in the amount of the developer conveyed to the developing area for each developing device is suppressed.
(3)
Further, the depth of the plurality of grooves extending in the longitudinal direction of the surface of the developer carrying member is set to 0.05 mm or more and 0.15 mm or less, and the groove depth deviation is set to 30% or less, thereby generating pitch unevenness. The developer conveying performance can be maintained while preventing the above.
(4)
In this embodiment, a two-component developer composed of a toner and a magnetic carrier is used as the developer, and the particle size of the magnetic carrier is set to 20 [μm] or more and 50 [μm] or less. As a result, 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. Further, since the density of developer spikes per unit area on the developing roller 42 is increased, toner can be delivered to the latent image on the photoreceptor 2 without any gap. Thereby, an image with more excellent dot reproducibility can be formed. Note that if the carrier particle size is too smaller than 20 [μm], the carrier adhesion to the photosensitive member 2 increases, so 20 μm or more is desirable.
(5)
Further, in the present embodiment, as the magnetic carrier, a magnetic core material is coated with a resin coat film, and the resin coat film includes a resin component obtained by crosslinking a thermoplastic resin and a melanin resin, The thing containing a regulator was used. The conventional carrier is configured to obtain a long life while gradually scraping a hard coat film, whereas this 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. Accordingly, it is possible to expect stabilization of the toner pumping amount, that is, stabilization of quality over a long period of time.
(6)
In this embodiment, as a toner, a toner composition comprising at least a prepolymer, a colorant, and a release agent is dispersed in an aqueous medium in the presence of resin fine particles, and the toner composition is polyadded. What was obtained by making it react was used. As a result, a sharp particle size distribution and charge distribution can be obtained, and the toner characteristics can be made uniform.
(7)
In this embodiment, the toner used has a ratio (Dv / Dn) of the number average particle diameter (Dn) to the volume average particle diameter (Dv) of 1.00 to 1.40. According to experiments, when Dv / Dn is within this range, the toner particle size distribution becomes narrow, and therefore, selective development in which toner particles having a (suitable) toner particle size corresponding to the image pattern are selectively developed. There was no outbreak. Further, even with long-term agitation in the developing device, there was no filming of toner on the developing roller and no toner fusion to a member such as a blade for thinning the toner. By these things, the stable image was always able to be formed.
(8)
In this embodiment, toner having a shape factor SF-1 of 100 to 180 and a shape factor SF-2 of 100 to 180 is used. According to experiments, it has been found that when the shape factor SF-1 is 180 or less and the shape factor SF-2 is 180 or less, the transfer efficiency increases as the value approaches 100.
(9)
In this embodiment, 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 ratio of the major axis to the minor axis ( r2 / r1) is in the range of 0.5 to 1.0, and the ratio of thickness to minor axis (r3 / r2) is in the range of 0.7 to 1.0. 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 being away from the true spherical shape, and high-quality image quality cannot be obtained. On the other hand, if the ratio of thickness to minor axis (r3 / r2) is less than 0.7, the shape is 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.
(10)
In the image forming apparatus of the present embodiment, the toner contained in the developer is attached to the electrostatic latent images formed on the surfaces of the photoreceptors 2Y, 2M, 2C, and 2K, which are latent image carriers, by the developing device. The image is formed into a toner image, and the toner image is finally transferred onto a transfer sheet as a recording material to form an image. The developing device described above is used as the developing device. By using this developing device, it is possible to obtain a good image with reduced image density unevenness.
(11)
Further, by setting the development gap G to 0.1 [mm] to 0.4 [mm], it is possible to obtain an image with good image granularity and high quality. Further, the toner does not adhere to the developing roller 42.
(12)
Further, the process cartridge according to the present embodiment forms a toner image by attaching toner contained in a developer to the electrostatic latent images formed on the surfaces of the photoreceptors 2Y, 2M, 2C, and 2K using a developing device. The toner image is finally transferred onto a transfer sheet to form an image, and the toner image is transferred from the surface of the photoconductor to be removed from the main body of the printer for cleaning the remaining toner. Among the devices or members arranged around 2M, 2C, and 2K, at least the developing device and the photosensitive members 2Y, 2M, 2C, and 2K are integrally supported, and the above-described developing device is used as the developing device. . By using this developing device, it is possible to obtain a good image with reduced image density unevenness. Furthermore, maintenance and replacement of the image forming means including the photosensitive member and the developing device are facilitated.

FIG. 3 is an explanatory diagram of a main part of the image forming apparatus according to the embodiment. FIG. 3 is an enlarged configuration diagram illustrating a process cartridge for Y of the image forming apparatus according to the embodiment. FIG. 3 is an enlarged configuration diagram illustrating an enlarged photoconductor and a developing roll in the image forming apparatus according to the embodiment. Explanatory drawing of the principal part of a developing roller. It is a figure which shows normal direction magnetic flux density distribution. The figure which shows the normal direction magnetic flux density distribution and the fluctuation | variation of a doctor. The figure which shows the image development apparatus arrange | positioned in the position where a doctor magnet does not oppose a doctor. Schematic diagram of the carrier. Explanatory drawing of shape factor SF-1. Explanatory drawing of shape factor SF-2. FIG. 3 is a diagram schematically illustrating a toner shape. 1 is a schematic configuration diagram of a color printer including a revolver type developing device. Explanatory drawing of the principal part of the conventional developing roller. Schematic explaining the state which the doctor bent.

Explanation of symbols

1Y, M, C, K Process cartridge 2Y, M, C, K Photosensitive member (image carrier)
40Y developing device 42Y developing roller (developer carrier, rotating body)
45Y Doctor 500 Carrier 600 Revolver type developing device

Claims (12)

It comprises a developer accommodating portion for accommodating a magnetic developer and a rotatable nonmagnetic sleeve containing a plurality of magnetic field generating means. The magnetic developer in the developer accommodating portion is carried on the surface by the magnetic field generating means. A developing roller that conveys to a developing area facing the image carrier, and a developer layer on the developing roller by forming a gap with the developing roller and allowing the developer on the developer roller to pass through the gap. In a developing device including a doctor for regulating the thickness,
A virtual line that is closest to the surface of the developing roller of the doctor on the virtual plane orthogonal to the rotation axis of the developing roller and connects the center of the developing roller with the position upstream of the developing roller in the rotation direction is used as a reference. The difference between the maximum value of the normal magnetic flux density on the surface of the developing roller and the minimum value of the normal magnetic flux density in a range rotated by ± 5 ° or more from the reference line with respect to the center of the developing roller as a line. A developing device characterized by being 10 [mT] or less.   2. The developing device according to claim 1, wherein one of the magnetic field generating means is provided at a position facing the doctor, and a magnetic flux generated from the magnetic field generating means at a position facing the doctor is applied to the rotation shaft of the developing roller. A virtual line connecting the center position of the imaginary line segment connecting the two half-value points of the maximum normal direction magnetic flux density on the surface of the developing roller on the orthogonal virtual plane is used as a reference line, and the reference line The difference between the maximum value of the normal magnetic flux density on the surface of the developing roller and the minimum value of the normal magnetic flux density in the range rotated by ± 15 ° or more with respect to the center of the developing roller from the line is 5 [mT A developing device characterized by the following.   3. The developing device according to claim 1, wherein the surface of the developing roller has a plurality of grooves extending in a longitudinal direction, and the depth of the grooves is 0.05 [mm] or more and 0.15 [mm] or less. A developing device.   4. The developing device according to claim 1, wherein a two-component developer composed of toner and magnetic particles is used as the developer, and the particle size of the magnetic particles is set to 20 [μm] or more and 50 [μm] or less. A developing device.   5. The developing device according to claim 4, wherein the magnetic particles include a magnetic core material coated with a resin coat film, and the resin coat film includes a resin component obtained by crosslinking a thermoplastic resin and a melanin resin. And a developing device containing a charge control agent.   6. The developing device according to claim 1, wherein a toner composition comprising at least a prepolymer, a colorant, and a release agent is used as a toner contained in the developer in an aqueous medium. A developing device characterized by using a product obtained by dispersing in the presence of fine particles and subjecting the toner composition to a polyaddition reaction.   7. The developing device according to claim 1, wherein the toner contained in the developer has a volume average particle diameter of 3 [μm] or more and 8 [μm] or less, and the number relative to the volume average particle diameter. A developing device having an average particle size ratio of 1.00 to 1.40.   8. The developing device according to claim 1, wherein the toner contained in the developer has a shape factor SF-1 of 100 or more and 180 or less and a shape factor SF-2 of 100. A developing device characterized in that a developing device having 180 or less is used.   5. The developing device according to claim 1, wherein the toner has a substantially spherical shape, and the shape is defined by a major axis r1, a minor axis r2, and a thickness r3 ( However, r1 ≧ r2 ≧ r3.) The ratio of the major axis r1 to the minor axis r2 (r2 / r1) is in the range of 0.5 to 1.0, and the ratio of the thickness r3 to the minor axis r2. (R3 / r2) is in the range of 0.7 to 1.0.   The toner contained in the developer is attached to the electrostatic latent image formed on the surface of the latent image carrier by a developing device to form a toner image, and the toner image is finally transferred onto a recording material to form an image. 10. An image forming apparatus according to claim 1, wherein the developing device is the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9.   11. The image forming apparatus according to claim 10, wherein a development gap that minimizes a gap between the surface of the developing roller included in the developing device and the surface of the latent image carrier is 0.1 [mm] or more and 0.4 [mm]. An image forming apparatus having the following settings.   The toner contained in the developer is attached to the electrostatic latent image formed on the surface of the latent image carrier by a developing device to form a toner image, and the toner image is finally transferred onto a recording material to form an image. It is detachable from the main body of the image forming apparatus for forming and cleaning the toner remaining after transferring the toner image from the surface of the latent image carrier, and is disposed around the latent image carrier. In the process cartridge that integrally supports at least the developing device and the latent image carrier among the devices or members, the developing device according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9 A process cartridge using an apparatus.

Images