JP2014010215A - Image forming unit and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent decrease in image qualities even when an image formation speed is increased.SOLUTION: An image forming unit includes an image carrier, a developer carrier, a developer supply roller, and a developer layer regulating member having a bend 27a. The developer is controlled to have a circularity of 0.97 or more and a volume average particle diameter of 3.5 [μm] or more and 6.5 [μm] or less. The curvature of radius of the bend 27a of the developer layer regulating member is controlled to 0.20 [mm] or more and 0.35 [mm] or less. Thereby, even when an image formation speed is increased, an appropriate density of an image is obtained without increase in the graininess of the image, and the image has no contamination. Therefore, decrease in image qualities is prevented.

Description

  The present invention relates to an image forming unit and an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a printer, a copier, a facsimile machine, a multifunction machine, for example, a printer has an image forming unit, and the surface of the photosensitive drum is charged by a charging roller in the image forming unit. Is exposed to form an electrostatic latent image, and toner on the developing roller is attached to the electrostatic latent image to form a toner image. Then, the toner image is transferred onto a sheet by a transfer roller and fixed by a fixing device.

  A developing blade is brought into contact with the developing roller, and the toner on the developing roller is thinned by the developing blade, and a predetermined frictional force is applied and charged (see, for example, Patent Document 1). .

JP 2010-2613 A

  However, in the conventional printer, when the image forming speed, that is, the image forming speed is increased, the graininess (graininess) of the image is increased and the image quality is deteriorated.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the conventional printer and to provide an image forming unit and an image forming apparatus in which image quality does not deteriorate even when the image forming speed is increased.

  Therefore, in the image forming unit of the present invention, an image carrier on which an electrostatic latent image is formed on the surface, a developer carrier that performs development by attaching a developer to the electrostatic latent image, and the development A developer supply roller for supplying the developer to the developer carrying member, and a bent portion, the bent portion being disposed in contact with the developer carrying member, and the developer on the developer carrying member being a thin layer And a developer layer regulating member.

  The circularity of the developer is set to 0.97 or more, and the volume average particle size is set to 3.5 [μm] or more and 6.5 [μm] or less.

  The curvature radius of the bent portion of the developer layer regulating member is set to 0.20 [mm] or more and 0.35 [mm] or less.

  According to the present invention, in the image forming unit, an image carrier on which an electrostatic latent image is formed on the surface, a developer carrier that performs development by attaching a developer to the electrostatic latent image, and the development A developer supply roller for supplying the developer to the developer carrying member, and a bent portion, the bent portion being disposed in contact with the developer carrying member, and the developer on the developer carrying member being a thin layer And a developer layer regulating member.

  The circularity of the developer is set to 0.97 or more, and the volume average particle size is set to 3.5 [μm] or more and 6.5 [μm] or less.

  The curvature radius of the bent portion of the developer layer regulating member is set to 0.20 [mm] or more and 0.35 [mm] or less.

  In this case, the circularity of the developer is 0.97 or more, the volume average particle diameter is 3.5 [μm] or more and 6.5 [μm] or less, and the bent portion of the developer layer regulating member Is set to 0.20 [mm] or more and 0.35 [mm] or less, so even if the image forming speed is increased, the graininess of the image does not increase and the density of the image is increased. It becomes appropriate, and the image is not smudged. Therefore, the image quality does not deteriorate.

1 is a schematic diagram of an image forming unit according to a first embodiment of the present invention. 1 is a schematic diagram of a printer according to a first embodiment of the present invention. FIG. 5 is a diagram illustrating image quality when the volume average particle diameter and the circularity of the toner in the first exemplary embodiment of the present invention are changed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a one-component electrophotographic printer as an image forming apparatus will be described.

  FIG. 2 is a schematic view of the printer according to the first embodiment of the present invention.

  As shown in the figure, the printer 10 includes a main body of the printer 10, that is, an apparatus main body Bd, and an image forming unit 20 that is detachably attached to the apparatus main body Bd. A photosensitive drum 21 as an image carrier is disposed on the surface. In the present embodiment, only one image forming unit 20 for forming a black image is provided. However, in order to form a color image, black, yellow, magenta, and cyan are used. The image forming units for the respective colors can be arranged.

  In the apparatus main body Bd, a transfer roller 17 serving as a transfer member is disposed below the photoconductive drum 21 in contact with the photoconductive drum 21, and the photoconductive drum is disposed above the photoconductive drum 21. An LED head 23 serving as an exposure apparatus is disposed so as to face 21. The image forming unit 20, the transfer roller 17 and the LED head 23 constitute an image forming unit.

  The LED head 23 exposes the surface of the photosensitive drum 21 to form an electrostatic latent image as a latent image.

  Further, the transfer roller 17 is formed of a material having a conductive surface, in this embodiment rubber or the like, and a toner image as a developer image formed on the surface of the photosensitive drum 21 is used as a medium. Transfer to paper P.

  Below the image forming unit 20 in the apparatus main body Bd, a paper cassette 11 as a medium storage unit is disposed, and a plurality of papers P are stored in the paper cassette 11. A hopping roller 12 as a medium supply member and as a feeding member is disposed at the front end of the paper cassette 11, and the paper P is separated one by one by the hopping roller 12 and fed to the transport path Rt. . A first conveying roller pair composed of a pinch roller 13 and a conveying roller 15 is provided downstream of the hopping roller 12 in the conveying direction of the paper P, and a pinch roller 14 and a resist are provided downstream of the first conveying roller pair. A second conveyance roller pair composed of the rollers 16 is disposed. The paper P is sent to the second conveyance roller pair in the first conveyance roller pair as the pinch roller 13 and the conveyance roller 15 rotate. In the second conveyance roller pair, the pinch roller 14 and the registration roller are fed. Then, the skew is corrected by being pinched by the roller 16 and then sent between the photosensitive drum 21 and the transfer roller 17 in the image forming unit as the pinch roller 14 and the registration roller 16 rotate. The hopping roller 12, the transport roller 15, and the registration roller 16 are rotated by transmission of rotation from a first drive source (not shown) via a gear (not shown).

  A fixing device 31 as a fixing device is disposed downstream of the image forming unit 20 in the transport direction of the paper P. The fixing device 31 is a first rotating body and a heat roller 32 as a heating member, and a second rotating body disposed in pressure contact with the heat roller 32 below the heat roller 32. In addition, a backup roller (pressure roller) 33 as a pressure member is provided, and the toner image on the paper P is heated and pressed by the heat roller 32 and the backup roller 33 to be fixed.

  The heat roller 32 is formed of a cylindrical body, and includes an aluminum element tube and a surface layer formed on the aluminum element tube and made of a fluororesin such as PFA or PTFE, and a halogen lamp 34 serving as a heat source is disposed therein. Is done. The backup roller 33 is a cylindrical body formed of an elastic body.

  Further, a first discharge roller pair composed of a pinch roller 35 and a discharge roller 36 is provided downstream of the fixing device 31 in the conveyance direction of the paper P, and a pinch roller 37 is provided downstream of the first discharge roller pair. And the 2nd discharge roller pair which consists of discharge roller 38 is arranged. The paper P is sent to the second discharge roller pair in the first discharge roller pair as the pinch roller 35 and the discharge roller 36 rotate. In the second discharge roller pair, the pinch roller 37 and the discharge roller are fed. The paper is discharged to the stacker unit 39 as 38 rotates. The heat roller 32, the discharge rollers 36, 38 and the like are rotated by transmission of rotation from a second drive source (not shown) via a gear (not shown).

  Next, the image forming unit 20 will be described.

  FIG. 1 is a schematic diagram of an image forming unit according to the first embodiment of the present invention.

  As shown in the figure, the image forming unit 20 is a main body of the image forming unit 20, that is, an image forming unit main body 20a and a developer container that is detachably attached to the image forming unit main body 20a. The toner cartridge 26 is provided as a developer cartridge, and a toner storage chamber 52 as a developer storage chamber for storing toner T as a developer is formed in the toner cartridge 26. In the present embodiment, the toner cartridge 26 is detachably disposed with respect to the image forming unit main body 20a. However, the image forming unit main body 20a and the toner cartridge 26 can be integrally formed. In the present embodiment, as the toner T, a suspension polymerization toner having a high degree of circularity is used so that the granularity of the image does not increase and the image quality does not deteriorate.

  The image forming unit main body 20a is provided with the photosensitive drum 21 and a charging roller 22 as a charging device that is disposed in contact with the photosensitive drum 21 and uniformly charges the surface of the photosensitive drum 21. Development as a developer carrying member which is disposed in contact with the photosensitive drum 21 and forms a toner image (development) by attaching toner T to the electrostatic latent image on the surface of the photosensitive drum 21. A toner supply roller 25 comprising a roller 24 and a sponge roller, arranged in contact with the developing roller 24, as a developer supplying member for supplying the toner T to the developing roller 24, and as a developer supplying roller; A developer layer rule is disposed so that the bent portion 27a is in contact with the developing roller 24, and the toner T on the surface of the developing roller 24 is thinned to form a toner layer as a developer layer having a predetermined thickness. A developing blade 27 as a member is disposed in contact with the photosensitive drum 21, and a cleaning roller as a cleaning member that scrapes off the toner T remaining on the photosensitive drum 21 after the toner image is transferred to the paper P. 28 etc. are arranged.

  The photosensitive drum 21 is composed of an organic photosensitive drum, and includes a base roller made of a conductive material such as aluminum, and an organic photosensitive layer having a three-layer structure formed on the base roller. The organic photosensitive layer is an undercoat layer (UCL) formed by applying a material in which a filler is mixed in a binder resin, and a material in which a charge generator is mixed in the binder resin is applied on the undercoat layer. And a charge transport layer (CTL) formed by applying a material mixed with a charge transport agent in a binder resin on the charge generation layer.

  The charging roller 22 includes a conductive shaft and a conductive elastic layer formed on the shaft. The conductive elastic layer is an ion conductive material mainly composed of epichlorohydrin rubber (ECO). Made of rubber. In this case, surface treatment is performed by infiltrating the surface treatment liquid containing an isocyanate (HDI) component into the conductive elastic layer, the surface is cured, and the releasability is enhanced. Accordingly, it is possible to prevent the toner T, the external additive, and the like from adhering to the surface of the charging roller 22 and to prevent the photosensitive drum 21 from being soiled.

  The hardness of the charging roller 22 is measured by an Asker C hardness meter (manufactured by Kobunshi Keiki Co., Ltd.), and the Asker C hardness is set to 73 °. Further, the resistance value of the charging roller 22 is set to 6.3 [logΩ]. The resistance value of the charging roller 22 has the same outer diameter, surface roughness, and conductivity as those of the photosensitive drum 21 under environmental conditions where the temperature is 20 [° C.] and the relative humidity is 50 [%]. It is a resistance value measured by applying a DC voltage of 500 [V] between the shaft of the charging roller 22 and the metal drum while being pressed against the metal drum at the same pressure as when assembled in the image forming unit 20.

  The developing roller 24 is a conductive shaft, an elastic layer made of semiconductive silicone rubber formed on the shaft and subjected to UV treatment, and a urethane resin is applied to the surface of the elastic layer. A surface coating layer (coat layer) formed by the above-described method is provided, and a surface treatment is performed on the surface of the surface coating layer with a silane coupling agent to form a silane coupling agent layer. The thickness of the surface coating layer is 7 [μm] or more and 13 [μm] or less. Further, the urethane resin of the surface coating layer is mixed with silica particles so that the surface roughness Rz is 6 [μm] or more and 12 [μm] or less (according to JIS B0601-1994). Is done. In order to secure the printing density, it is preferable to increase the surface roughness Rz as much as possible.

  The hardness of the developing roller 24 is measured by a JIS-A standard measuring method and is set to 42 [°] ± 5 [°]. The resistance value of the developing roller 24 is set to 100 [MΩ] or more and 5000 [MΩ] or less. The resistance value is determined by pressing a stainless steel ball bearing having a width of 2.0 [mm] and a diameter of 6.0 [mm] against the developing roller 24 with a force of 20 [gf]. Resistance value measured by applying a DC voltage of 100 [V] between

  The toner supply roller 25 includes a conductive shaft and an elastic layer formed on the shaft and having semi-conductivity and made of foamed silicone rubber, and polishing the surface of the elastic layer. It has a predetermined outer diameter.

  Silicone rubber compound for forming the elastic layer includes various raw rubbers such as dimethyl silicone raw rubber and methylphenyl silicone raw rubber, a filler made of silica as a reinforcing material, a vulcanizing agent necessary for vulcanization and curing, and a foaming agent. Etc. are added. As the foaming agent, an inorganic foaming agent such as sodium bicarbonate or an organic foaming agent such as ADCA is used.

  The hardness of the toner supply roller 25 is measured by an Asker F hardness meter (manufactured by Kobunshi Keiki Co., Ltd.), and the Asker F hardness is set to 41 °. The hardness is 45 mm from the both ends of the toner supply roller 25 and the center when the Asker F hardness tester is dropped on the toner supply roller 25 at a height of 10 mm to 3 seconds. Is the average of the values at the three points. In the image forming unit main body 20a, the toner supply roller 25 is pressed against the developing roller 24 by a pressing amount of 1.0 [mm] ± 0.15 [mm].

  The resistance value of the toner supply roller 25 is set to 1 [MΩ] or more and 100 [MΩ] or less. The resistance value is obtained by pressing the same ball bearing as that for measuring the resistance value of the developing roller 24 against the toner supply roller 25 with a force of 20 [gf], and a DC voltage of 300 [V] between the shaft and the ball bearing. Is a resistance value measured by applying.

  The developing blade 27 is made of stainless steel (SUS) and has a thickness of 0.08 [mm]. The bent portion 27a is formed by bending the contact portion with the developing roller 24. Is done. In the present embodiment, the bending angle of the bent portion 27a is 90 °, the angle formed between the tangent line of the developing roller 24 and the line extending in the longitudinal direction of the developing blade 27 is 15 ° or more, and 20 [°] or less.

  Note that the radius of curvature R of the bent portion 27a is obtained by using SEF 3500 (manufactured by Kosaka Laboratory Ltd.) and scanning the contour shape of the bent portion 27a of the developing blade 27 at a scanning speed of 0.02 [mm / s]. Measured by. Further, the surface roughness Rz of the developing blade 27 is a ten-point average surface roughness and is set to 0.6 [μm]. Further, the linear pressure for pressing the developing blade 27 against the developing roller 24 is 50 [g / cm], preferably 40 [g / cm] or more and 70 [g / cm] or less.

  The cleaning roller 28 is formed by adhering a metal cored bar having a diameter of 6 [mm] and EPDM (ethylene-propylene-diene rubber) as a main material via a primer on the cored bar. A conductive foam layer is provided. The average foam cell diameter of the conductive foam layer is measured using a stereomicroscope, and is 100 [μm] or more and 300 [μm] or less.

  The hardness of the cleaning roller 28 is measured by an Asker C hardness meter with a load of 4.9 [N] applied, and the Asker C hardness is set to 35 [°] or more and 45 [°] or less. .

  Note that springs (not shown) as urging members are disposed at both ends of the cleaning roller 28, and the cleaning roller 28 is pressed against the photosensitive drum 21 by the urging force of each spring.

The resistance value (entire surface resistance) of the cleaning roller 28 is set to 2.0 × 10 ⁶ [Ω] or more and 2.0 × 10 ⁷ [Ω] or less. The resistance value is 400 between the cleaning roller 28 and the photosensitive drum 21 by rotating the cleaning roller 28 against the photosensitive drum 21 having a diameter of 30 [mm] by pressing the cleaning roller 28 by a pressing amount of 0.25 [mm]. It is a resistance value measured by applying a DC voltage of [V].

  The photosensitive drum 21, the developing roller 24, the toner supply roller 25, the charging roller 22, the cleaning roller 28, and the transfer roller 17 are transmitted with rotation from a third drive source (not shown), respectively, in the direction of arrow a and arrow, respectively. It is rotated in the b direction, the arrow c direction, the arrow d direction, the arrow e direction, and the arrow f direction. Therefore, a transfer gear (not shown) on the transfer roller 17, a drum gear (not shown) on the photosensitive drum 21, a charge gear (not shown) on the charging roller 22, and a development gear (not shown) on the developing roller 24 are not shown on the toner supply roller 25. A toner supply gear and a cleaning gear (not shown) are fixed to the cleaning roller 28 by press-fitting or other methods. An idle gear (not shown) is disposed between the developing gear and the toner supply gear.

  To charge the charging roller 22 to the surface of the photosensitive drum 21, the developing roller 24 supplies the toner T to the electrostatic latent image, and the toner supply roller 25 supplies the toner T to the developing roller 24. For this purpose, a predetermined voltage is applied to the transfer roller 17 in order to transfer the toner image on the photosensitive drum 21 onto the paper P. For this purpose, a power supply device (not shown) is provided, and the applied voltage is controlled by a control unit (not shown).

  Next, the operation of the image forming unit 20 having the above configuration will be described.

  First, when a printing instruction is generated in the control unit, the third driving source is driven, rotation is transmitted to the drum gear through several gears (not shown), and the photosensitive drum 21 is moved in the direction of arrow a. Rotated. Then, the rotation is transmitted from the drum gear to the developing gear, the developing roller 24 is rotated in the direction of arrow b, the rotation is transmitted from the developing gear to the toner supply gear via the idle gear, and the toner supply roller 25 is moved to the arrow c. Rotated in the direction. Further, rotation is transmitted from the drum gear to the charge gear, the charging roller 22 is rotated in the direction of the arrow d, rotation is transmitted from the drum gear to the cleaning gear, and the cleaning roller 28 is rotated in the direction of the arrow e, and transferred from the drum gear. The rotation is transmitted to the gear, and the transfer roller 17 is rotated in the direction of arrow f.

  By applying a voltage to the charging roller 22, the surface of the photosensitive drum 21 is uniformly charged, and the surface potential is set to 600 [V], for example. When the charged portion on the surface of the photosensitive drum 21 reaches the portion facing the LED head 23 with the rotation, the LED head 23 is operated based on the image data sent from the control unit. Then, the photosensitive drum 21 is exposed to form an electrostatic latent image on the photosensitive drum 21. At this time, for example, a bias voltage of −300 [V] is applied to the toner supply roller 25, and a bias voltage of −200 [V] is applied to the developing roller 24, for example.

  Subsequently, when the portion where the electrostatic latent image is formed on the surface of the photosensitive drum 21 reaches the position facing the developing roller 24 with rotation, the potential of the portion where the electrostatic latent image is formed (for example, , −20 [V]) and the developing roller 24, the toner T on the developing roller 24 thinned by the developing blade 27 moves onto the photosensitive drum 21 and is attached to the electrostatic latent image. A toner image is formed.

  When the portion where the toner image is formed on the surface of the photosensitive drum 21 reaches the portion facing the transfer roller 17, the toner image is transferred onto the paper P by the transfer roller 17 and remains on the surface of the photosensitive drum 21. The toner T is scraped off by the cleaning roller 28, and is collected according to the sequence set by the control unit after the printing operation is completed.

  Subsequently, when the paper P is sent to the fixing device 31, the toner image is heated by the heat from the heat roller 32 heated by the halogen lamp 34, melted, pressurized by the backup roller 33, and applied to the paper P. It is fixed. In this way, an image is formed on the paper P.

  Next, a method for producing the suspension polymerization toner used in the printer 10 in the present embodiment will be described.

  First, styrene 77.5 [parts by weight] and acrylic acid-n-butyl 22.5 [parts by weight] low molecular weight polyethylene 2 [parts by weight] as an anti-offset agent, and “Eisenspiron Black TRH” as a charge control agent (Hodogaya Chemical Co., Ltd.) 1 [parts by weight], carbon black (printex L Degussa Co., Ltd.) 6 [parts by weight] and 2,2′-azobisisobutyronitrile 1 [parts by weight] were added. -01SC "(manufactured by Mitsui Miike Chemical Co., Ltd.) and dispersed at 15 [° C] for 10 [hours] to prepare a polymerizable composition. Then, distilled water 600 [parts by weight] is added to ethanol 180 [parts by weight] in which polyacrylic acid 8 [parts by weight] and divinylbenzene 0.35 [parts by weight] are dissolved to prepare a dispersion medium for polymerization. The polymerizable composition is added to the dispersion medium and dispersed for 10 minutes under conditions of 15 ° C. and 8000 rpm by a TK homomixer “M type” (manufactured by Tokushu Kika Kogyo Co., Ltd.). The dispersion solution prepared in this manner is transferred into a 1 liter separable flask, and the separable flask is rotated at 100 [rpm] under a nitrogen stream and reacted at 85 [° C.] for 12 [hours] with stirring. At this point, the dispersoid obtained by the first stage polymerization reaction of the polymerizable composition is used as intermediate particles.

  Next, the intermediate particles were methyl methacrylate 9.25 [parts by weight], acrylic acid-n-butyl 0.75 [parts by weight], and 2,2′-azobisisobutyronitrile 0.5 [parts by weight]. , Put into an aqueous suspension composed of sodium lauryl sulfate 0.1 [parts by weight] and water 80 [parts by weight], and vibrated with an ultrasonic oscillator US-150 (manufactured by Nippon Seiki Seisakusho Co., Ltd.). The aqueous emulsion LA9 [parts by weight] is dropped on the intermediate particles to swell the intermediate particles to prepare a dispersion medium. In addition, immediately after the dropping, observation with an optical microscope was performed, and no emulsion droplets were observed, and it was confirmed that the swelling was completed within an extremely short time. Therefore, the second stage polymerization reaction is performed at a predetermined temperature for a predetermined time while continuing stirring under nitrogen, and after cooling the dispersion medium, it is dissolved with a 0.5N hydrochloric acid aqueous solution until the pH reaches a predetermined value, After filtering and washing with water, drying with wind, drying at 40 [° C.] for 10 [hours] and 10 [mmHg] under reduced pressure, classifying with an air classifier, and a toner base to which no external additive is added Create particles.

  Subsequently, an external additive is added to the toner base particles to prepare toner T.

  Here, a manufacturing method of each toner T used in a printing experiment for preventing the image quality from being deteriorated in the present embodiment will be described. For each toner T, various toner base particles having different volume average particle diameter and circularity are prepared by changing the conditions of the second-stage polymerization reaction and the conditions for dissolving the dispersion medium. It is created by adding an external additive to.

  The volume average particle diameter of the toner T is calculated by measuring 30000 counts using a cell counting analyzer “Coulter Multi-Riser 3” (manufactured by Beckman Coulter) with an aperture diameter of 100 [μm]. The circularity of the toner T is measured using a flow type particle image analyzer “FPIA-2100” (manufactured by Sysmex Corporation). The circularity of the toner T is expressed by Expression (1) based on the circumference L1 of the circle having the same area as the area of the particle projection image and the circumference L2 of the particle projection image.

Circularity = L1 / L2 (1)
If the circularity is 1.00, it is a true sphere, and the particle shape becomes indefinite as the circularity becomes smaller than 1.00.

  Then, in the second-stage polymerization reaction, the toner mother particles when the water emulsion LA was reacted at 85 [° C.] for 5.0 [hours] was A, and the dispersion medium was dissolved in 0.5N hydrochloric acid aqueous solution. The toner base particles A1 to A5 are prepared by changing the pH to 4.5, 4.3, 4.1, 3.9, and 3.7, and external additives are added to the toner base particles A1 to A5. Thus, toners A-1 to A-5 are prepared.

  The volume average particle diameter of each of the toners A-1 to A-5 is 3.0 [μm], the circularity of the toner A-1 is 0.96, the circularity of the toner A-2 is 0.97, The circularity of toner A-3 is 0.98, the circularity of toner A-4 is 0.99, and the circularity of toner A-5 is 1.00.

  Then, in the second stage polymerization reaction, the toner mother particles when the water emulsion LA is reacted at 85 [° C.] for 5.5 [hours] is B, and the pH is changed as described above to change the toner. Base particles B1 to B5 are prepared, and external additives are added to the toner base particles B1 to B5 to prepare toners B-1 to B-5. The volume average particle diameter of each of the toners B-1 to B-5 is 3.5 [μm], the circularity of the toner B-1 is 0.96, and the circularity of the toner B-2 is 0.97. The circularity of toner B-3 is 0.98, the circularity of toner B-4 is 0.99, and the circularity of toner B-5 is 1.00.

  In the second stage polymerization reaction, the toner base particles when the water emulsion LA is reacted at 85 [° C.] for 6.0 [hours] is C, and the pH is changed as described above to change the toner. Base particles C1 to C5 are prepared, and external additives are added to the toner base particles C1 to C5 to prepare toners C-1 to C-5. The volume average particle diameter of each of the toners C-1 to C-5 is 4.0 [μm], the circularity of the toner C-1 is 0.96, the circularity of the toner C-2 is 0.97, The circularity of toner C-3 is 0.98, the circularity of toner C-4 is 0.99, and the circularity of toner C-5 is 1.00.

  Further, in the second stage polymerization reaction, the toner base particles when the water emulsion LA is reacted at 85 [° C.] for 7.0 [hours] is D, and the pH is changed as described above to change the toner. Base particles D1 to D5 are prepared, and external additives are added to the toner base particles D1 to D5 to prepare toners D-1 to D-5. The volume average particle diameter of each of the toners D-1 to D-5 is 5.0 [μm], the circularity of the toner D-1 is 0.96, the circularity of the toner D-2 is 0.97, The circularity of the toner D-3 is 0.98, the circularity of the toner D-4 is 0.99, and the circularity of the toner D-5 is 1.00.

  In the second stage polymerization reaction, the toner mother particles when the water emulsion LA is reacted at 85 [° C.] for 8.0 [hours] is E, and the pH is changed as described above to change the toner. Base particles E1 to E5 are prepared, and external additives are added to the toner base particles E1 to E5 to prepare toners E-1 to E-5. The volume average particle diameter of each of the toners E-1 to E-5 is 6.0 [μm], the circularity of the toner E-1 is 0.96, the circularity of the toner E-2 is 0.97, The circularity of toner E-3 is 0.98, the circularity of toner E-4 is 0.99, and the circularity of toner E-5 is 1.00.

  Further, in the second stage polymerization reaction, the toner base particles obtained when the water emulsion LA is reacted at 85 [° C.] for 9.0 [hours] are defined as F, and the pH is changed as described above to change the toner. Base particles F1 to F5 are prepared, and external additives are added to the toner base particles F1 to F5 to prepare toners F-1 to F-5. The volume average particle diameter of each of the toners F-1 to F-5 is 6.5 [μm], the circularity of the toner F-1 is 0.96, and the circularity of the toner F-2 is 0.97. The circularity of the toner F-3 is 0.98, the circularity of the toner F-4 is 0.99, and the circularity of the toner F-5 is 1.00.

  Further, in the second stage polymerization reaction, the toner base particles when the water emulsion LA is reacted at 85 [° C.] for 10.0 [hours] is G, and the pH is changed as described above to change the toner. Base particles G1 to G5 are prepared, and external additives are added to the toner base particles G1 to G5 to prepare toners G-1 to G-5. The volume average particle diameter of each of the toners G-1 to G-5 is 7.0 [μm], the circularity of the toner G-1 is 0.96, the circularity of the toner G-2 is 0.97, The circularity of the toner G-3 is 0.98, the circularity of the toner G-4 is 0.99, and the circularity of the toner G-5 is 1.00.

  Since it is difficult to actually create a true toner T having a circularity of 1.00, the toners A-5, B-5, C-5, D-5, E-5, and F-5 are used. , G-5 has a circularity of 0.995 or more and 0.998 or less, but rounded off to 1.00.

  In the present embodiment, “Aerosil RX 50” (manufactured by Nippon Aerosil Co., Ltd.) as an external additive is added to 100 [parts by weight] of toner base particles and mixed for 25 [minutes]. Toners A-1 to A-5, B-1 to B-5, C-1 to C-5, D-1 to D-5, E-1 to E-5, F-1 to F-5. , G-1 to G-5 are created.

  Next, each of the toners A-1 to A-5, B-1 to B-5, C-1 to C-5, D-1 to D-5, E having different volume average particle diameters and circularity degrees. -1 to E-5, F-1 to F-5, G-1 to G-5, and developing blades 27 having different curvature radii R of the bent portions 27a are used to increase the image forming speed. The printing experiment conducted will be described.

  In this case, the developing blade α-1 in which the radius of curvature R of the bent portion 27a is 0.18 [mm], the developing blade α-2 in which the radius of curvature R of the bent portion 27a is 0.20 [mm], and the bent portion 27a. The developing blade α-3 having a curvature radius R of 0.25 mm, the developing blade α-4 having a curvature radius R of the bent portion 27a of 0.30 [mm], and the curvature radius R of the bent portion 27a being 0. A developing blade α-5 having a thickness of 35 mm and a developing blade α-6 having a curvature radius R of the bent portion 27a of 0.38 mm were prepared.

  Then, a determination is made as to whether or not the formed image has high graininess (feels rough) (hereinafter referred to as “graininess determination”), a determination as to whether the density is appropriate (hereinafter referred to as “density determination”), A determination was made as to whether the image is dirty (hereinafter referred to as “dirt determination”) and a determination as to whether the image quality is comprehensively high (hereinafter referred to as “total determination”).

  In the printing experiment, the linear speed representing the peripheral speed of the photosensitive drum 21 was set to 246 [mm / s], and the printing environment was set to a normal temperature and humidity environment (22 [° C.] and 55 [%]). . Further, the developing blade α-4 was used as the developing blade 27, and the surface roughness Rz of the developing roller 24 was set to 9 [μm].

  Then, letter-size high-quality paper (whiteness is 92 and weighing is 20 [Lb] paper) is used as the paper P, and the paper is fed in the vertical direction (paper feed in which two short sides out of the four sides are the front end and the rear end). 2 x 2 images (2 [dots] x 2 [dots] in a print pattern consisting of a print pattern that repeats printing and blanking, 25% print image) and black solid image (print part 100%) Image).

  Table 1 shows the determination results in Experiments 1-1 to 1-35 performed under the above conditions. In Table 1, the volume average particle diameter is simply expressed as particle diameter.

  The graininess determination was performed by observing the granularity of the image with a loupe for a 2 × 2 image. In Table 1, ◎ indicates that the dot is close to a perfect circle and the graininess of the image is low, ○ indicates that the dot has a circular shape and the graininess of the image is within an allowable range, and × indicates that it is fine The dots are white and the toner is scattered from the dots, indicating that the image has high graininess.

  The density determination was performed by measuring the density of the solid portion of each image using a 500 Series Spectrodensitometer (X-Rite, manufactured by Ink). ◎ is appropriate when the density is 1.35 or more and 1.50 or less, and the image is clear but not too dark, ◯ is the density is 1.51 or more and 1.55 or less, or 1.30 or more and less than 1.35 is appropriate and the image is clear, but the 2 × 2 image is dark, x is not appropriate when the density is 1.56 or more or less than 1.30, Indicates that the 2 × 2 image is too dark and uneven, or the image is not clear.

  The smudge judgment was performed by visually observing the non-printed part. ○ indicates that no toner is attached to the non-printing area, and a 2 × 2 image is uniformly formed. × indicates that toner is attached to the non-printing area and the 2 × 2 image is uneven. Represents. The smear is caused by the toner adhering to the non-printing portion. For example, when the toner charge amount is large and the potential of the toner on the developing roller 24 is higher on the minus side than the photosensitive drum 21, The toner moves from the developing roller 24 to the photosensitive drum 21 and adheres to the non-printing portion.

  As can be seen from Table 1, when a toner having a volume average particle size of 6.0 [μm] or less and a small volume average particle size is used, the granularity of the image is low, and the graininess determination is ◎ or ○. In addition, when a toner having a high degree of circularity is used, the graininess of the image is low, and when a toner having a volume average particle size of 6.5 [μm] or less and a circularity of 0.97 or more is used, the graininess determination is performed. It became ◎ or ○.

  When a toner having a volume average particle size of 7.0 [μm] or more and a circularity of 0.99 or more is used, the density determination is x. This is because the toner has a large volume average particle diameter, and charging due to friction, that is, the number of times that triboelectric charging is performed is reduced, and because the circularity of the toner is high, the toners are slippery and frictional charging is sufficiently performed. This is thought to be because there is not.

  When a toner having a volume average particle size of 3.0 [μm] or less is used, the stain determination is x. This is considered to be because when the volume average particle diameter of the toner is small, the number of times that the frictional charging is performed increases, and the charge amount of the toner increases.

  Even with toner having a circularity of 0.96, there were some cases where the stain determination was x. This is presumably because the toner is excessively triboelectrically charged due to its low circularity, and the toner charge amount increases.

  Further, when a toner having a volume average particle diameter of 4.0 [μm] or more and 6.0 [μm] or less and a circularity of 0.97 or more is used, the graininess determination and the density determination are ◎, Dirt judgment became ○. This is considered to be because the volume average particle diameter and the circularity are within appropriate ranges, and the charge amount between the toners is optimized.

  In the comprehensive judgment, when a toner having a volume average particle size of 3.5 [μm] or more and 6.5 [μm] or less and a circularity of 0.97 or more is used, the granularity of the image is low. As a result, the density of the image became appropriate and the image was not smudged. Preferably, when a toner having a volume average particle size of 4.0 [μm] or more and 6.0 [μm] or less and a circularity of 0.97 or more is used, the image density when visually observed is It becomes even more appropriate.

  Next, in the experiments 1-1 to 1-35, the toners B-2, B-5, F-2, F-5 in which the graininess determination, the density determination, and the stain determination are ◎ or ◯, and the graininess determination and A printing experiment performed using the toners C-2, C-5, E-2, E-5, and the developing blades α-1 to α-6, in which the density determination is ◎, will be described. The method of the experiment is the same as the method of Experiments 1-1 to 1-35, and a 2 × 2 image and a solid black image were printed.

  Table 2 shows the determination results in Experiments 2-1 to 2-28.

  When the toner having a circularity of 0.97 [μm] and the developing blade α-1 having the curvature radius R of the bent portion 27a of 0.18 [mm] are used, the graininess determination is x. This is because not only the radius of curvature R of the bent portion 27a of the developing blade α-1 is too small, the amount of toner on the developing roller 24 is small and the toner layer becomes thin, but also the circularity of the toner is low. This is probably because it is difficult to form.

  Further, when the developing blade α-1 having the curvature radius R of the bent portion 27a of 0.18 [mm] was used, the density was lower than 1.30, and the density judgment was x. This is considered to be because the radius of curvature R of the bent portion 27a of the developing blade α-1 is too small, the amount of toner on the developing roller 24 is small, and the image density cannot be made appropriate.

  When the developing blade α-6 having the curvature radius R of the bent portion 27a of 0.38 [mm] was used, the image was smudged and the smudge judgment was x. This is presumably because the radius of curvature R of the bent portion 27a of the developing blade α-6 is too large, the amount of toner on the developing roller 24 increases, and the toner adheres to the non-printed portion. The range of the radius of curvature R in which the soil determination is “good” was 0.20 [mm] or more and 0.35 [mm] or less.

  Further, when the developing blade α-3 having a curvature radius R of the bent portion 27a of 0.25 [mm] and the developing blade α-4 having a curvature radius R of the bent portion 27a of 0.30 [mm] are used, the graininess is used. Judgment and concentration range became ◎. Further, when a toner having a volume average particle size of 4.0 [μm] or more and 6.0 [μm] or less and a circularity of 0.97 or more is used, the graininess determination and the density determination are ◎. . This is presumably because the volume average particle diameter and circularity of the toner and the radius of curvature R of the bent portion 27a of the developing blade 27 are optimal, and the charged state of the toner and the thickness of the toner layer are appropriate.

  As described above, in this exemplary embodiment, the volume average particle diameter of the toner T is 3.5 [μm] or more and 6.5 [μm] or less, and the circularity of the toner T is 0.97 or more. By setting the curvature radius R of the bent portion 27a of the developing blade 27 to 0.20 [mm] or more and 0.35 [mm] or less, the linear velocity of the photosensitive drum 21 is set to 246 [mm / s]. Even if the image forming speed is increased, the graininess of the image does not increase, the density of the image becomes appropriate, and the image is not smudged. Therefore, the image quality does not deteriorate.

  Preferably, the volume average particle diameter of the toner T is 4.0 [μm] or more and 6.0 [μm] or less, the circularity is 0.97 or more, and the radius of curvature R of the bent portion 27a of the developing blade 27 is set. By setting the value to 0.25 [mm] or more and 0.30 [mm] or less, the image quality is not further deteriorated.

  FIG. 3 is a diagram showing the image quality when the volume average particle diameter and the circularity of the toner in the first embodiment of the present invention are changed. In the figure, the horizontal axis represents the volume average particle diameter, and the vertical axis represents the circularity. And ◆ indicates that the image quality is high, and x indicates that the image quality is low.

  Next, in the experiments 1-1 to 1-35, the toners B-2, B-5, F-2, F-5 in which the graininess determination, the density determination, and the stain determination are ◎ or ◯, and the graininess determination and Using toners C-2, C-5, E-2, E-5, and developing blades [alpha] -2 to [alpha] -5, for which the density judgment is ◎, the linear velocity of the photosensitive drum 21 is 223 [mm]. / S] or 264 [mm / s] and a printing experiment performed at a high image forming speed will be described. The printing experiment method is the same as the experiment methods 1-1 to 1-35 and 2-1 to 2-28, and a 2 × 2 image and a solid image are printed.

  Table 3 shows each determination result in Experiments 3-1 to 3-24.

  As can be seen from Table 3, when the linear velocity of the photosensitive drum 21 is set to 223 [mm / s] or 264 [mm / s] and the image forming speed is increased, the graininess determination and the density determination are ○ or ◎. The dirt judgment became “good”.

  Generally, when the linear velocity of the photosensitive drum 21 is lowered, the density is increased, and when the linear velocity is increased, the density is lowered. This is because, when the linear velocity of the photosensitive drum 21 is low, the time for which frictional charging is performed before the toner image is formed on the photosensitive drum 21 is long, the amount of toner charge increases, and the linearity of the photosensitive drum 21 increases. If the speed is high, it is considered that the time during which frictional charging is performed before the toner image is formed on the photosensitive drum 21 is shortened, and the charge amount of the toner is decreased. When the linear velocity of the photosensitive drum 21 is 246 [mm / s], the density determination in Table 3 and the density determination in Tables 1 and 2 are substantially the same.

  As described above, in this embodiment, the volume average particle size of the toner T is 3.5 [μm] or more and 6.5 [μm] or less, the circularity is 0.97 or more, and the developing blade 27 By setting the curvature radius R of the bent portion 27a to 0.20 [mm] or more and 0.35 [mm] or less, the linear velocity of the photosensitive drum 21 is 223 [mm / s] or more and 264. Even when the image forming speed is increased to [mm / s] or less, the granularity of the image does not increase, the density of the image becomes appropriate, and the image is not smudged. Therefore, the image quality does not deteriorate.

  By the way, when the same printing experiment was performed by using the toner of Experiments 3-1 to 3-24 and setting the linear velocity of the photosensitive drum 21 to 323 [mm / s], the density became lower than 1.30. Oops. This is because the image forming speed increases as the linear velocity of the photosensitive drum 21 increases, and the speed at which the toner passes through the developing blade 27 on the developing roller 24 increases, so that the toner adhering to the developing roller 24 is increased. This is thought to be due to the decrease in the amount of

  Therefore, even if the image forming speed is increased, the image graininess is not increased, the image density is appropriate, the image is not smudged, and the image quality is not deteriorated. A second embodiment of the invention will be described. In addition, about the thing which has the same structure as 1st Embodiment, the same code | symbol is provided and the effect of the same embodiment is used about the effect of the invention by having the same structure.

  In this embodiment, in the experiments 1-1 to 1-35, the toners B-2, B-5, F-2, F-5 in which the graininess determination, the density determination, and the stain determination are ◎ or ◯, In addition, the toners C-2, C-5, E-2, and E-5, the developer blades α-2 to α-3, and the surface roughness Rz that are different from each other in the graininess determination and the density determination are ◎. Printing experiments were conducted using the developing roller 24 as a carrier and the linear speed of the photosensitive drum 21 as an image carrier being 323 [mm / s]. The method of the experiment is the same as the method of Experiments 1-1 to 1-35, Experiments 2-1 to 2-28, and Experiments 3-1 to 3-24, and a 2 × 2 image and a solid image were printed. . Each developing roller 24 was formed with different surface roughness Rz by changing the time for polishing the surface coating layer.

  Tables 4 and 5 show the determination results in Experiments 4-1 to 4-52.

  As can be seen from Tables 4 and 5, when the developing roller 24 having a surface roughness Rz of 13 [μm] or more and 26 [μm] or less is used, the linear velocity of the photosensitive drum 21 is 323 [mm / s]. Even so, the graininess determination, the density determination, and the stain determination were ◎ or ◯.

  This is because when the linear velocity of the photosensitive drum 21 is increased, the time for which the triboelectric charging is performed until the toner image as the developer image is formed on the photosensitive drum 21 is shortened. However, since the surface roughness Rz of the developing roller 24 is high, the charge amount of the toner can be increased and the toner adheres to the developing roller 24. This is considered to be because the amount of toner can be optimized.

  As described above, in this embodiment, the volume average particle size of the toner T is 3.5 [μm] or more and 6.5 [μm] or less, the circularity is 0.97 or more, and the developing blade 27 The radius of curvature R of the bent portion 27a is 0.20 [mm] or more and 0.35 [mm] or less, and the surface roughness Rz of the developing roller 24 is 13 [μm] or more and 26 [μm] or less. Thus, even if the linear velocity is set to 323 [mm / s] and the image forming speed is increased, the granularity of the image does not increase, the density of the image becomes appropriate, and the image is stained. There is nothing. Therefore, the image quality does not deteriorate.

  Preferably, by setting the surface roughness Rz of the developing roller 24 to 17 [μm] or more and 23 [μm] or less, even when the image forming speed is increased, the graininess of the image is not increased. The density of the image becomes appropriate, the image is not smudged, and the image quality is not further deteriorated.

  Next, in the above 1-1 to 1-35, the toners B-2, B-5, F-2, F-5 in which the graininess determination, the density determination, and the stain determination are ◎ or ◯, and the graininess determination and density The developing rollers 24 formed with different toners C-2, C-5, E-2, E-5, the developing blades α-2 to α-5, and the surface roughness Rz that are judged as ◎. A printing experiment will be described which was used and the linear velocity of the photosensitive drum 21 was 293 [mm / s] or 352 [mm / s]. The method of the experiment is the same as the methods of Experiments 1-1 to 1-35, Experiments 2-1 to 2-28, Experiments 3-1 to 3-24, and Experiments 4-1 to 4-52. A x2 image and a solid black image were printed. Further, each developing roller 24 was formed with different surface roughness Rz by changing the time for polishing the surface coating layer.

  Table 6 shows each determination result in Experiments 5-1 to 5-40.

  As can be seen from Table 6, when the developing roller 24 having a surface roughness Rz of 13 [μm] or more and 26 [μm] or less is used, the linear velocity of the photosensitive drum 21 is 293 [mm / s] or 352 Even in the case of [mm / s], the graininess determination, the density determination, and the stain determination were “◎” or “◯” as in the case where the linear velocity of the photosensitive drum 21 was 323 [mm / s].

  As described above, in this embodiment, the volume average particle size of the toner T is 3.5 [μm] or more and 6.5 [μm] or less, the circularity is 0.97 or more, and the developing blade 27 The radius of curvature R of the bent portion 27a is 0.20 [mm] or more and 0.35 [mm] or less, and the surface roughness Rz of the developing roller 24 is 13 [μm] or more and 26 [μm] or less. Thus, even if the linear velocity of the photosensitive drum 21 is set to 293 [mm / s] or more and 352 [mm / s] or less to increase the image forming speed, the graininess of the image may be increased. Therefore, the density of the image becomes appropriate and the image is not smudged. Therefore, the image quality does not deteriorate.

  Preferably, the volume average particle diameter of the toner T is 4.0 [μm] or more and 6.0 [μm] or less, the circularity is 0.97 or more, and the radius of curvature R of the bent portion 27a of the developing blade 27 is set. Is 0.25 [mm] or more and 0.30 [mm] or less, and the surface roughness Rz of the developing roller 24 is 17 [μm] or more and 23 [μm] or less, the photosensitive drum 21 Even if the linear velocity is set to 293 [mm / s] or more and 352 [mm / s] or less to increase the image forming speed, the granularity of the image does not increase, and the image density becomes appropriate. Since the image is not smudged, the image quality is not further deteriorated.

  In each of the above embodiments, the one-component electrophotographic printer 10 is described. However, the present invention can be applied to an image forming apparatus using a developing blade having a bent portion.

  The present invention is not limited to the above embodiments, and various modifications can be made based on the gist of the present invention, and they are not excluded from the scope of the present invention.

20 Image forming unit 21 Photosensitive drum 24 Developing roller 25 Toner supply roller 27 Developing blade 27a Bending portion

Claims (6)

(A) an image carrier on which an electrostatic latent image is formed on the surface;
(B) a developer carrier for developing the developer by attaching the developer to the electrostatic latent image;
(C) a developer supply roller for supplying a developer to the developer carrying member;
(D) a bent portion, a developer layer regulating member that is disposed in contact with the developer carrying member, and that thins the developer on the developer carrying member.
(E) the circularity of the developer is 0.97 or more, the volume average particle size is 3.5 [μm] or more and 6.5 [μm] or less,
(F) An image forming unit, wherein a curvature radius of a bent portion of the developer layer regulating member is 0.20 [mm] or more and 0.35 [mm] or less. (A) The developer has a circularity of 0.97 or more and a volume average particle size of 4.0 [μm] or more and 6.0 [μm] or less,
(B) The image forming unit according to claim 1, wherein a radius of curvature of the bent portion is set to 0.25 mm or more and 0.30 mm or less. (A) The linear velocity of the image carrier is 223 [mm / s] or more and 264 [mm / s] or less,
(B) The image forming unit according to claim 1, wherein the developer carrying member has a surface roughness of 9 μm. (A) The linear velocity of the image carrier is 293 [mm / s] or more and 352 [mm / s] or less,
(B) The image forming unit according to claim 1 or 2, wherein the developer carrying member has a surface roughness of 13 [μm] or more and 26 [μm] or less. (A) The linear velocity of the image carrier is 293 [mm / s] or more and 352 [mm / s] or less,
(B) The image forming unit according to claim 1 or 2, wherein the developer carrying member has a surface roughness of 17 [μm] or more and 23 [μm] or less. (A) an image carrier;
(B) an exposure device that forms an electrostatic latent image on the surface of the image carrier;
(C) a developer carrying member that forms a developer image by developing a developer on the electrostatic latent image; and
(D) a developer supply roller for supplying a developer to the developer carrying member;
(E) a developer layer regulating member that includes a bent portion, and is disposed so that the bent portion is in contact with the developer carrier, and the developer on the developer carrier is thinned;
(F) a transfer member for transferring the developer image to the medium;
(G) a fixing device for fixing the developer image transferred to the medium;
(H) The developer has a circularity of 0.97 or more and a volume average particle size of 3.5 [μm] or more and 6.5 [μm] or less,
(I) An image forming apparatus, wherein a curvature radius of a bent portion of the developer layer regulating member is 0.20 [mm] or more and 0.35 [mm] or less.

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