Image forming apparatus

Abstract

The invention discloses an image forming apparatus. The electrophotographic photoreceptor includes an electrophotographic photoreceptor, a charging device that charges a surface of the electrophotographic photoreceptor, and an electrostatic charge image forming device that forms an electrostatic charge image on the surface of the charged electrophotographic photoreceptor. A developer that accommodates and supplies a developer containing toner and develops an electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image; a transfer device that transfers the toner image formed on the surface of the electrophotographic photoreceptor to the surface of a recording medium; a fixing device that fixes the toner image to the surface of the recording medium; and a control device that acquires image information of the toner image and controls at least one of the first power supply and the second power supply in accordance with the image information such that a frequency of an AC voltage of a developing voltage applied to the second developing member is smaller than a frequency of an AC voltage of a developing voltage applied to the first developing member. The developing machine includes a first developing member, a second developing member, a first power source, and a second power source.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus. Background Art

[0002] The formation of an image based on the electrophotographic method is performed, for example, as follows: after charging the surface of a photoreceptor, an electrostatic charge image is formed on the surface of the photoreceptor according to image information. Then, the electrostatic charge image is developed with a developer containing toner to form a toner image, and the toner image is transferred and fixed onto the surface of a recording medium.

[0003] Here, Japanese Patent Application Laid-Open No. 2000-172043 discloses "a color image forming apparatus that forms toner images of a plurality of colors on a latent image carrier by a plurality of developing units and then transfers them together onto a transfer material. The plurality of developing units each have the latent image carrier that bears a latent image and a plurality of developer carriers that bear and convey a developer. The color image forming apparatus is characterized in that the plurality of developing units each have a bias applying unit that applies a DC bias voltage with an AC bias voltage superimposed thereon to each of the developer carriers, the AC bias voltage has a constant frequency, and the peak value of the AC bias voltage of the developer carrier disposed on the upstream side with respect to the rotation direction of the latent image carrier is set higher than the peak value of the AC bias voltage of the developer carrier disposed on the downstream side."

[0004] Japanese Patent Application Laid-Open No. 2011-257534 discloses "a developing machine including: a plurality of toner carriers that bear toner on their outer peripheral surfaces and are disposed non-contactly with respect to an image carrier along its rotation direction; and a developer carrier that bears a developer composed of toner and a carrier and supplies toner to the plurality of toner carriers. Toner is attached to an electrostatic latent image by an electric field formed between the voltage of the electrostatic latent image formed on the image carrier and the AC bias voltage applied to the toner carrier. The developing machine is characterized in that the developing duty ratio of the AC bias voltage applied to a first toner carrier disposed on the upstream side in the rotation direction of the image carrier is greater than the developing duty ratio of the AC bias voltage applied to a second toner carrier disposed on the downstream side in the rotation direction." Summary of the Invention

[0005] As an image forming apparatus using an electrophotographic method, there is known "an image forming apparatus (hereinafter also referred to as a 'specific image forming apparatus') including: an electrophotographic photosensitive member; a charging device that charges the surface of the electrophotographic photosensitive member; a static charge image forming device that forms a static charge image on the surface of the charged electrophotographic photosensitive member; a developing machine that houses a developer containing toner, supplies the developer, and develops the static charge image formed on the surface of the electrophotographic photosensitive member as a toner image, the developing machine having: a first developing member that is disposed opposite to the electrophotographic photosensitive member, holds the developer, and transfers it to a developing area; a second developing member that is disposed opposite to the electrophotographic photosensitive member on the downstream side in the rotational direction of the electrophotographic photosensitive member with respect to the first developing member, holds the developer, and transfers it to the developing area; a first power supply that applies a developing voltage obtained by overlapping an alternating voltage on a direct current voltage to the first developing member; and a second power supply that applies a developing voltage obtained by overlapping an alternating voltage on a direct current voltage to the second developing member; a transfer device that transfers the toner image formed on the surface of the electrophotographic photosensitive member to the surface of a recording medium; and a fixing device that fixes the toner image to the surface of the recording medium" (for example, Japanese Patent Application Laid-Open No. 2000-172043 and Japanese Patent Application Laid-Open No. 2011-257534, etc.).

[0006] However, for example, when the image density of the toner image is low and 40% or less, the reproducibility of thin lines sometimes deteriorates.

[0007] Accordingly, an object of the present invention is to provide an image forming apparatus in which deterioration of thin line reproducibility is suppressed as compared with a case where the frequencies of the alternating voltages of the developing voltages applied to the first developing member and the second developing member are the same when the image density of the toner image is low in a specific image forming apparatus, etc.

[0008] According to a first aspect of the present invention, there is provided an image forming apparatus including: an electrophotographic photosensitive member; a charging device that charges a surface of the electrophotographic photosensitive member; a static charge image forming device that forms a static charge image on the charged surface of the electrophotographic photosensitive member; a developing machine that houses a developer containing toner, supplies the developer, and develops the static charge image formed on the surface of the electrophotographic photosensitive member as a toner image, the developing machine having: a first developing member that is disposed opposite to the electrophotographic photosensitive member, holds the developer, and conveys it to a developing area; a second developing member that is disposed opposite to the electrophotographic photosensitive member on a downstream side in a rotational direction of the electrophotographic photosensitive member with respect to the first developing member, holds the developer, and conveys it to the developing area; a first power source that applies a developing voltage in which an alternating voltage is superimposed on a direct current voltage to the first developing member; and a second power source that applies a developing voltage in which an alternating voltage is superimposed on a direct current voltage to the second developing member; a transfer device that transfers the toner image formed on the surface of the electrophotographic photosensitive member to a surface of a recording medium; a fixing device that fixes the toner image to the surface of the recording medium; and a control device that acquires image information of the toner image and controls at least one of the first power source and the second power source based on the image information so that a frequency of the alternating voltage of the developing voltage applied to the second developing member is lower than a frequency of the alternating voltage of the developing voltage applied to the first developing member.

[0009] According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the control device controls the second power source to reduce the frequency of the alternating voltage of the developing voltage applied to the second developing member so that the frequency of the alternating voltage of the developing voltage applied to the second developing member is lower than the frequency of the alternating voltage of the developing voltage applied to the first developing member.

[0010] According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the control device controls at least one of the first power source and the second power source so that a ratio (Fd / Fu) of a frequency Fd of the alternating voltage of the developing voltage applied to the first developing member to a frequency Fu of the alternating voltage of the developing voltage applied to the second developing member is 2.0 or more and 9.0 or less.

[0011] According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the control device acquires an image density of the toner image and controls at least one of the first power source and the second power source.

[0012] According to the fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the adhesion of the toner is 5 MPa or more and 15 MPa or less.

[0013] According to the sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, the toner has toner particles including a binder resin and resin particles.

[0014] According to the seventh aspect of the present invention, in the image forming apparatus according to the sixth aspect, the content of the resin particles is 3% by mass or more and 25% by mass or less with respect to the toner particles.

[0015] According to the eighth aspect of the present invention, in the image forming apparatus according to the sixth or seventh aspect, the resin particles are styrene (meth) acrylic resins.

[0016] According to the ninth aspect of the present invention, in the image forming apparatus according to any one of the sixth to eighth aspects, the average primary particle diameter of the resin particles is 20 nm or more and 300 nm or less.

[0017] (Effect)

[0018] According to the first aspect, there is provided an image forming apparatus in which deterioration of thin line reproducibility is suppressed as compared with a case where the frequency of the AC voltage of the developing voltage applied to the first developing member is the same as the frequency of the AC voltage of the developing voltage applied to the second developing member when the image density of the toner image is low or the like in a specific image forming apparatus.

[0019] According to the second aspect, there is provided an image forming apparatus in which deterioration of thin line reproducibility is suppressed as compared with a case where the control device controls the first power supply to increase the frequency of the AC voltage of the developing voltage applied to the first developing member so that the frequency of the AC voltage of the developing voltage applied to the second developing member is less than the frequency of the AC voltage of the developing voltage applied to the first developing member.

[0020] According to the third aspect, there is provided an image forming apparatus in which deterioration of thin line reproducibility is suppressed as compared with a case where (Fd / Fu) is less than 1.7 or more than 10.0.

[0021] According to the fourth aspect, there is provided an image forming apparatus in which deterioration of thin line reproducibility is suppressed as compared with a case where the frequency of the AC voltage of the developing voltage applied to the first developing member is the same as the frequency of the AC voltage of the developing voltage applied to the second developing member when the image density of the toner image is low in a specific image forming apparatus.

[0022] According to the fifth, sixth, seventh, eighth or ninth aspect, there is provided an image forming apparatus. Compared with a case where, in a specific image forming apparatus, when the image density of a toner image is 40% or less, the frequency of the alternating current voltage of the developing voltage applied to the first developing member is the same as the frequency of the alternating current voltage of the developing voltage applied to the second developing member, even when the adhesion of the toner is 5 MPa or more and 15 MPa or less, deterioration of thin line reproducibility is suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic configuration diagram showing an example of the image forming apparatus of the present embodiment;

[0024] Figure 2 is a schematic configuration diagram showing an example of the control system of the image forming apparatus of the present embodiment;

[0025] Figure 3 is a schematic configuration diagram showing an example of the developing machine of the image forming apparatus of the present embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Hereinafter, an embodiment as an example of the present invention will be described in detail.

[0027] <IMAGE FORMING APPARATUS>

[0028] The image forming apparatus of the present embodiment includes:

[0029] an electrophotographic photosensitive member;

[0030] a charging device that charges the surface of the electrophotographic photosensitive member;

[0031] a static charge image forming device that forms a static charge image on the surface of the charged electrophotographic photosensitive member;

[0032] a developing machine that houses a developer containing toner, supplies the developer, and develops the static charge image formed on the surface of the electrophotographic photosensitive member as a toner image. The developing machine includes: a first developing member that is disposed opposite to the electrophotographic photosensitive member, holds the developer, and conveys it to a developing area; a second developing member that is disposed opposite to the electrophotographic photosensitive member on the downstream side in the rotational direction of the electrophotographic photosensitive member with respect to the first developing member, holds the developer, and conveys it to the developing area; a first power source that applies a developing voltage in which an alternating current voltage is superimposed on a direct current voltage to the first developing member; and a second power source that applies a developing voltage in which an alternating current voltage is superimposed on a direct current voltage to the second developing member;

[0033] a transfer device that transfers the toner image formed on the surface of the electrophotographic photosensitive member to the surface of a recording medium;

[0034] A fixing device that fixes a toner image onto the surface of a recording medium; and

[0035] A control device that acquires image information of the toner image and controls at least one of a first power supply and a second power supply according to the image information, so that the frequency of the alternating voltage of the developing voltage applied to a second developing member is lower than the frequency of the alternating voltage of the developing voltage applied to a first developing member.

[0036] The image forming apparatus according to the present embodiment suppresses deterioration of thin line reproducibility with the above structure. The reason is presumed as follows.

[0037] Conventionally, an image forming apparatus is known that includes a developing machine having a plurality of developing members (Patent Documents 1 and 2, etc.). This image forming apparatus can ensure developability during high-speed printing. However, when forming an image with a low image density of 40% or less, etc., sometimes thin lines are missing and the thin line reproducibility deteriorates. This is because when the frequencies of the alternating voltages applied to a first developing member and a second developing member that is disposed opposite the photoreceptor on the downstream side in the rotational direction of the photoreceptor with respect to the first developing member are the same, the toner developed by the first developing member returns to the second developing member due to the cohesion of the toner. In particular, when the toner returns to the second developing member and toner shortage occurs, the thin line identifies the toner shortage due to the small amount of toner, and the thin line reproducibility deteriorates.

[0038] Therefore, in the image forming apparatus according to the present embodiment, the control device acquires the image information of the toner image and controls at least one of the first power supply and the second power supply according to the image information, so that the frequency of the alternating voltage of the developing voltage applied to the second developing member is lower than the frequency of the alternating voltage of the developing voltage applied to the first developing member.

[0039] Thereby, the developability is ensured by the first developing member, the developability in the second developing member is reduced, and the return of the toner to the second developing member is suppressed.

[0040] Therefore, toner shortage in the thin line is suppressed, and deterioration of thin line reproducibility is suppressed.

[0041] It is presumed from the above that the image forming apparatus according to the embodiment suppresses deterioration of thin line reproducibility with the above structure.

[0042] Regarding the image forming apparatus of the present embodiment, known image forming apparatuses such as a direct transfer type apparatus that directly transfers a toner image formed on the surface of a photoreceptor to a recording medium, an intermediate transfer type apparatus that first transfers a toner image formed on the surface of a photoreceptor to the surface of an intermediate transfer member and then secondarily transfers the toner image transferred to the surface of the intermediate transfer member to the surface of a recording medium, and an apparatus having a static eliminator that irradiates static elimination light to the surface of the photoreceptor for static elimination after transferring the toner image and before charging can be applied.

[0043] In the case of an intermediate transfer type apparatus, the transfer apparatus may have, for example, a structure including an intermediate transfer member on which a toner image is transferred, a primary transfer apparatus that first transfers a toner image formed on the surface of a photoreceptor to the surface of the intermediate transfer member, and a secondary transfer apparatus that secondarily transfers the toner image transferred to the surface of the intermediate transfer member to the surface of a recording medium.

[0044] In addition, in the image forming apparatus of the present embodiment, at least a part including the photoreceptor constitutes a unit for the image forming apparatus, and it may be a cartridge structure (i.e., a processing cartridge) that can be attached to and detached from the image forming apparatus.

[0045] For example, a unit for the image forming apparatus may include a unit having a photoreceptor and a developing device.

[0046] Next, an example of the structure of the image forming apparatus of the present embodiment will be described in detail.

[0047] Hereinafter, an example of the image forming apparatus of the present embodiment is shown, but it is not limited thereto. In addition, the main parts shown in the figure will be described, and the description of other parts will be omitted.

[0048] Figure 1 It is a schematic configuration diagram showing an example of the image forming apparatus of the present embodiment.

[0049] As Figure 1 shown, in the image forming apparatus 10 of the present embodiment, for example, a photoreceptor 12 is provided. The photoreceptor 12 is cylindrical and is connected to a drive unit 27 such as a motor via a driving force transmission member (not shown) such as a gear, and is driven to rotate by the drive unit 27 around the rotation axis indicated by a black dot. In Figure 1 the example shown, it is driven to rotate in the direction of arrow A.

[0050] Around the photoreceptor 12, a charging device 15 (an example of a charging device), an electrostatic latent image forming device 16 (an example of an electrostatic latent image forming device), a developing machine 18 (an example of a developing machine), a transfer device 31 (an example of a transfer device), a cleaning device 22 (an example of a cleaning device), and an electrostatic eliminator 24 are arranged in sequence along the rotation direction of the photoreceptor 12. Moreover, in the image forming apparatus 10, a fixing device 26 having a fixing member 26A and a pressing member 26B arranged in contact with the fixing member 26A is also provided. In addition, the image forming apparatus 10 has a control device 36 that controls the operations of the respective devices (portions). Further, a unit including the photoreceptor 12, the charging device 15, the electrostatic latent image forming device 16, the developing machine 18, the transfer device 31, and the cleaning device 22 corresponds to an image forming unit.

[0051] In the image forming apparatus 10, as a processing cartridge integrated with other devices, at least the photoreceptor 12 may be provided.

[0052] Details of the respective devices (portions) of the image forming apparatus 10 will be described below.

[0053] [Electrophotographic photoreceptor]

[0054] The photoreceptor 12 has, for example, a conductive substrate, an undercoat layer formed on the conductive substrate, and a photosensitive layer formed on the undercoat layer. The photosensitive layer may also be a two-layer structure of a charge generation layer and a charge transport layer. The photosensitive layer may be an organic photosensitive layer or an inorganic photosensitive layer. The photoreceptor 12 may also have a structure in which a protective layer is provided on the photosensitive layer.

[0055] [Charging device]

[0056] The charging device 15 charges the surface of the photoreceptor 12. The charging device 15 includes, for example, a charging member 14 that is provided in contact with or non-contact with the surface of the photoreceptor 12 and charges the surface of the photoreceptor 12, and a power supply 28 (an example of a voltage application unit for the charging member) that applies a charging voltage to the charging member 14. The power supply 28 is electrically connected to the charging member 14.

[0057] As the charging member 14 of the charging device 15, for example, a contact type charger using a conductive charging roller, charging brush, charging film, charging rubber blade, charging tube, etc. can be cited. In addition, as the charging member 14, for example, a non-contact type roller charger, a grid charger or a corona charger using corona discharge, etc., which are well-known chargers themselves, can also be cited.

[0058] In addition, particularly in the case where the charging device includes a charging member that charges the photoreceptor non-contact, contamination of the surface of the charging member does not occur due to lubricant, so it is preferable.

[0059] [Electrostatic charge image forming device]

[0060] The electrostatic charge image forming device 16 forms an electrostatic charge image on the surface of the charged photoreceptor 12. Specifically, for example, the electrostatic charge image forming device 16 irradiates the surface of the photoreceptor 12 charged by the charging member 14 with the light L modulated based on the image information of the image to be formed, and forms an electrostatic charge image corresponding to the image of the image information on the photoreceptor 12.

[0061] As the electrostatic charge image forming device 16, for example, an optical system device having a light source that exposes light such as a semiconductor laser beam, LED light, or liquid crystal shutter light in an image shape can be cited.

[0062] [Developing machine]

[0063] The developing machine 18 is provided, for example, on the downstream side in the rotation direction of the photoreceptor 12 with respect to the irradiation position of the light L by the electrostatic charge image forming device 16. A storage section for storing the developer is provided in the developing machine 18. A toner-containing electrostatic charge image developer is stored in the storage section. The toner is stored in the developing machine 18 in a charged state, for example.

[0064] The developing machine 18 has, for example, a first developing member 18A that is disposed opposite to the photoreceptor 12, holds the developer, and conveys it to the developing area, and a second developing member 18B that is disposed opposite to the photoreceptor 12 on the downstream side in the rotation direction of the photoreceptor 12 with respect to the first developing member 18A, holds the developer, and conveys it to the developing area (see Figure 3 ).

[0065] The developing machine 18 has a first power source 32A that applies a developing voltage obtained by superimposing an alternating voltage on a direct current voltage to the first developing member 18A, and a second power source 32B that applies a developing voltage obtained by superimposing an alternating voltage on a direct current voltage to the second developing member 18B (see Figure 3 ).

[0066] In the developing machine 18, on the right side in the drawing of the first developing member 18A, a supply screw roller 19A of the developer is disposed such that its axis is at the vertex of a triangle, and on the right side in the drawing of the second developing member 18B, supply screw rollers 19B and 19C of the developer are disposed such that their respective axes are at the vertices of a triangle (see Figure 3 ).

[0067] In addition, each screw roller is disposed on the supply conveyance path of the developer separated by a separating member.

[0068] The first developing member 18A and the second developing member 18B are respectively connected to the first power source 32A and the second power source 32B.

[0069] As the first developing member 18A and the second developing member 18B, for example, a developing roller having a developing sleeve with a built-in magnet can be cited.

[0070] The developing device 18 (including the first power supply 32A and the second power supply 32B) is electrically connected to, for example, a control device 36 provided on the image forming apparatus 10, and the first power supply 32A and the second power supply 32B are driven and controlled by the control device 36 to apply a developing voltage to the first developing member 18A and the second developing member 18B. The first developing member 18A and the second developing member 18B to which the developing voltage is applied are charged to a developing potential corresponding to the developing voltage. Moreover, the first developing member 18A and the second developing member 18B charged to the developing potential hold, for example, a developer accommodated in the developing device 18 on the surface, and supply the toner contained in the developer from the inside of the developing device 18 to the surface of the photoreceptor 12. On the surface of the photoreceptor 12 to which the toner is supplied, the formed electrostatic latent image is developed into a toner image.

[0071] Here, in the developing device 18, the DC voltage applied to the first developing member 18A and the second developing member 18B is preferably in the range of 10 V or more and 800 V or less, more preferably in the range of 20 V or more and 650 V or less.

[0072] The AC voltage superimposed on the DC voltage is preferably in the range of 200 V or more and 2000 V or less in peak-to-peak voltage, more preferably in the range of 300 V or more and 1500 V or less.

[0073] The frequency of the AC voltage superimposed on the DC voltage is preferably in the range of 2 kHz or more and 20 kHz or less, more preferably in the range of 3 kHz or more and 18 kHz or less.

[0074] [Transfer device]

[0075] The transfer device 31 is provided, for example, on the downstream side in the rotation direction of the photoreceptor 12 with respect to the arrangement position of the developing device 18. The transfer device 31 includes, for example, a transfer member 20 that transfers the toner image formed on the surface of the photoreceptor 12 to the recording medium 30A and a power supply 30 that applies a transfer voltage to the transfer member 20. The transfer member 20 is, for example, cylindrical and is conveyed with the recording medium 30A interposed therebetween with respect to the photoreceptor 12. The transfer member 20 is electrically connected to the power supply 30, for example.

[0076] As the transfer member 20, for example, a contact type transfer charger using a belt, a roller, a film, a rubber cleaning blade, etc., a grid transfer charger using corona discharge, a corona transfer charger, or other known non-contact type transfer chargers can be cited.

[0077] The transfer device 31 (including the power supply 30) is electrically connected to, for example, the control device 36 provided on the image forming apparatus 10, and is driven and controlled by the control device 36 to apply a transfer voltage to the transfer member 20. The transfer member 20 to which the transfer voltage is applied is charged to a transfer potential corresponding to the transfer voltage.

[0078] When a transfer voltage having a polarity opposite to that of the toner constituting the toner image formed on the photoreceptor 12 is applied to the transfer member 20 from the power supply 30 of the transfer member 20, for example, in the region where the photoreceptor 12 and the transfer member 20 face each other (refer to Figure 1 the transfer region 31A in), a transfer electric field having an electric field strength that causes each toner constituting the toner image on the photoreceptor 12 to move from the photoreceptor 12 to the transfer member 20 side by electrostatic force is formed.

[0079] The recording medium 30A is housed in a housing portion (not shown), for example, and is conveyed from the housing portion to the region where the photoreceptor 12 and the transfer member 20 face each other, that is, the transfer region 31A, by a plurality of conveying members (not shown) along the conveying path 34. In Figure 1 the example shown, it is conveyed in the direction of arrow B. The recording medium 30A that has reached the transfer region 31A transfers the toner image on the photoreceptor 12 by the transfer electric field formed in this region by applying a transfer voltage to the transfer member 20. That is, for example, by the movement of the toner from the surface of the photoreceptor 12 to the recording medium 30A, the toner image is transferred onto the recording medium 30A. Then, the toner image on the photoreceptor 12 is transferred onto the recording medium 30A by the transfer electric field.

[0080] [Cleaning device]

[0081] The cleaning device 22 is provided on the downstream side of the transfer region 31A in the rotation direction of the photoreceptor 12. After transferring the toner image to the recording medium 30A, the cleaning device 22 cleans (sweeps) the residual toner adhering to the photoreceptor 12. In the cleaning device 22, in addition to the residual toner, attachments such as paper powder are also cleaned.

[0082] The cleaning device 22 has a cleaning blade 22A, and the front end of the cleaning blade 22A is brought into contact with the photoreceptor 12 in a direction opposite to the rotation direction of the photoreceptor 12 to remove the attachments on the surface of the photoreceptor 12.

[0083] [Electrostatic eliminator]

[0084] The static eliminator 24 is disposed, for example, on the downstream side of the cleaning device 22 in the rotation direction of the photoreceptor 12. After the toner image is transferred, the surface of the photoreceptor 12 is exposed by the static eliminator 24 to eliminate static electricity. Specifically, for example, the static eliminator 24 is electrically connected to the control device 36 provided on the image forming apparatus 10, and is driven and controlled by the control device 36 to expose the entire surface of the photoreceptor 12 (specifically, for example, the entire surface of the image forming area) to eliminate static electricity.

[0085] As the static eliminator 24, for example, a device having a light source such as a tungsten filament lamp that irradiates white light or a light emitting diode (LED) that irradiates red light can be cited.

[0086] [Fixing device]

[0087] The fixing device 26 is disposed, for example, on the downstream side of the transfer area 31A in the conveyance direction of the conveyance path 34 of the recording medium 30A. The fixing device 26 has a fixing member 26A and a pressing member 26B that is disposed in contact with the fixing member 26A, and fixes the toner image transferred onto the recording medium 30A by the contact portion of the fixing member 26A and the pressing member 26B. Specifically, for example, the fixing device 26 is electrically connected to the control device 36 provided on the image forming apparatus 10, and is driven and controlled by the control device 36 to fix the toner image transferred onto the recording medium 30A onto the recording medium 30A by heat and pressure.

[0088] As the fixing device 26, a known fixing device such as a heat roller fixing device or a baking fixing device can be cited.

[0089] Specifically, for example, for the fixing device 26, a well-known fixing device including a fixing roller or a fixing belt as the fixing member 26A and a pressing roller or a pressing belt as the pressing member 26B is applied.

[0090] Here, the recording medium 30A onto which the toner image is transferred by being conveyed along the conveyance path 34 and passing through the area where the photoreceptor 12 and the transfer member 20 face each other (transfer area 31A) is further conveyed to the installation position of the fixing device 26 along the conveyance path 34 by a conveyance member (not shown) to fix the toner image on the recording medium 30A.

[0091] The recording medium 30A on which the image is formed by fixing the toner image is discharged to the outside of the image forming apparatus 10 by a plurality of conveyance members (not shown). In addition, after the static electricity of the photoreceptor 12 is eliminated by the static eliminator 24, it is charged again to the charging potential by the charging device 15.

[0092] [Control device]

[0093] Next, useFigure 2 An example of the structure of the control system of the image forming apparatus 10 will be described.

[0094] The image forming apparatus 10 includes a control device 36 that controls the operations of various devices (each part).

[0095] The control device 36 is configured as a computer that performs overall control of the apparatus and various operations. Specifically, as Figure 2 shown, the control device 36 includes a CPU (Central Processing Unit) 400A, a ROM (Read Only Memory) 400B that stores various programs, a RAM (Random Access Memory) 400C that is used as a work area when executing programs, a non-volatile memory 400D that stores various information, and an input / output interface (I / O) 400E. The CPU 400A, ROM 400B, RAM 400C, non-volatile memory 400D, and I / O 400E are each connected via a bus 400F.

[0096] In addition, the image forming apparatus 10 includes, in addition to the control device 36, an operation display unit 402, an image processing unit 404, an image memory 406, an image forming unit 408, a storage unit 410, and a communication unit 412. Each part of the operation display unit 402, image processing unit 404, image memory 406, image forming unit 408, storage unit 410, and communication unit 412 is connected to the I / O 400E of the control device 36. The control device 36 exchanges information with each part of the operation display unit 402, image processing unit 404, image memory 406, image forming unit 408, storage unit 410, and communication unit 412, and controls each part.

[0097] The operation display unit 402 includes various buttons such as a start button and numeric keys, and a touch panel for displaying various screens such as a warning screen or a setting screen. The operation display unit 402 receives operations from the user through the above structure and displays various information to the user.

[0098] The image processing unit 404 performs predetermined image processing on the image information acquired from the external device 414 via the communication unit 412, and generates image information for output to the image forming unit 408. For example, it performs a rendering process on PDL data described in a page description language and converts it into raster data (RGB data) expanded into RGB colors, performs a color conversion process on the RGB data, and generates YMCK data represented by the colors reproduced by the image forming apparatus. It may also further perform screen processing or gamma correction processing, etc.

[0099] The image memory 406 stores various image information acquired by the image forming apparatus 10, such as image information acquired from the external device 414 and image information generated by the image processing unit 404. The image memory 406 stores, for example, at least the image information after image processing by the image processing unit 404, that is, the image information for output to the image forming unit 408.

[0100] The image forming unit 408 is the part described as the main structure of the image forming apparatus 10. The image forming unit 408 is, for example, a photoreceptor 12 (its driving unit (not shown)), a charging device 15, an electrostatic latent image forming device 16, a developing machine 18, a transfer device 31, an electrostatic eliminating device 24, a fixing device 26, etc. These respective parts are connected to the control device 36. Information is exchanged between the control device 36 and these respective parts to control the respective parts, etc.

[0101] The storage unit 410 includes a storage device such as a hard disk. Various data such as logarithmic data and various programs are stored in the storage unit 410.

[0102] The communication unit 412 is an interface for communicating with the external device 414 via a wired or wireless communication line. For example, the communication unit 412 acquires an image formation instruction or image information of an electronic document, and image formation information from the external device 414. The image formation information includes parameters indicating attributes such as the type (size, etc.) of the recording paper P, the feeding direction of the recording paper P, the number of copies, and the color mode.

[0103] In addition, various drives may also be connected to the control device 36. The various drives are devices that read data from or write data to a computer-readable portable recording medium such as a flexible disk, an optical disk, a CD-ROM, a DVD-ROM, a USB memory, etc. In the case of having various drives, a control program may also be pre-recorded in the portable recording medium, and the corresponding drive reads and executes the control program.

[0104] [Operation of the Image Forming Apparatus]

[0105] An example of the operation of the image forming apparatus 10 of the present embodiment will be described. In addition, various operations of the image forming apparatus 10 are performed by a control program executed in the control device 36.

[0106] Here, in the image forming apparatus 10, for example, control programs for "image formation processing" and "developing condition change processing" are pre-stored in the ROM 400B. The pre-stored control program is read out by the CPU 400A and executed using the RAM 400C as a work area. In addition, in the image forming apparatus 10, for example, various data such as "image formation conditions (various process control values)" are pre-stored in the non-volatile memory 400D.

[0107] These control programs and various data can also be stored in other storage devices such as ROM 400B, non-volatile memory 400D, or storage unit 410, or can be obtained from the outside via communication unit 412.

[0108] The image forming operation of image forming apparatus 10 will be described.

[0109] First, the surface of photoreceptor 12 is charged by charging device 15. The charged surface of photoreceptor 12 is exposed by static charge image forming device 16 based on the image information. Thus, a static charge image corresponding to the image information is formed on photoreceptor 12. In developing unit 18, the static charge image formed on the surface of photoreceptor 12 is developed with a developer containing toner. Thus, a toner image is formed on the surface of photoreceptor 12.

[0110] In transfer device 31, the toner image formed on the surface of photoreceptor 12 is transferred onto recording medium 30A. The toner image transferred onto recording medium 30A is fixed by fixing device 26.

[0111] On the other hand, the surface of photoreceptor 12 after transferring the toner image is cleaned (scraped) by cleaning blade 22A in cleaning device 22, and then, static electricity is removed by static eliminator 24.

[0112] On the other hand, in image forming apparatus 10, when it is determined by control device 36 that an image has poor image reproducibility of the toner image during the execution of the image forming operation, control for changing the developing conditions of developing unit 18 is executed.

[0113] The operation of changing the developing conditions of developing unit 18 will be described. The operation of changing the developing conditions of developing unit 18 is performed by the control program of "developing condition change process" executed in control device 36. The control program of "developing condition change process" starts, for example, when an image forming instruction or the like is received from operation display unit 402 or from external device 414 via communication unit 412.

[0114] First, in the developing condition change process, the image information of the toner image is acquired.

[0115] The method of acquiring the image information is not particularly limited. For example, there are methods such as reading the toner image formed on recording paper P by a reading device (not shown), and acquiring the image information of the image to be formed.

[0116] As image information for determining an image with poor image reproducibility of a toner image, information on image density is preferable. Further, the image density refers to the area ratio of the formed image with respect to the area of the surface (image forming surface) of the recording paper P (an example of a recording medium).

[0117] Next, in the developing condition changing process, it is determined whether the image is an image with poor image reproducibility based on the acquired toner image information.

[0118] For example, in an image with an image density of 40% or less, when the image reproducibility of thin lines deteriorates, in the developing condition changing process, when it is determined that the image density of the acquired toner image is 40% or less, at least one of the first power supply 32A and the second power supply 32B is controlled from a state where the frequencies of the alternating voltages applied to the first developing member 18A and the second developing member 18B are the same, so that the frequency of the alternating voltage of the developing voltage applied to the second developing member is less than the frequency of the alternating voltage of the developing voltage applied to the first developing member.

[0119] The specific manner of the frequency change based on the control device 36 is as follows.

[0120] Method 1: Control the second power supply 32B to lower the frequency of the alternating voltage of the developing voltage applied to the second developing member 18B so that the frequency of the alternating voltage of the developing voltage applied to the second developing member 18B is less than the frequency of the alternating voltage of the developing voltage applied to the first developing member 18A.

[0121] Method 2: Control the second power supply 32B to increase the frequency of the alternating voltage of the developing voltage applied to the first developing member 18A so that the frequency of the alternating voltage of the developing voltage applied to the second developing member 18B is less than the frequency of the alternating voltage of the developing voltage applied to the first developing member 18A.

[0122] Method 3: A method combining Method 1 and Method 2.

[0123] However, from the viewpoint of suppressing the deterioration of thin line reproducibility while maintaining developability, Method 1 is preferable.

[0124] Here, the ratio (Fd / Fu) of the frequency Fd of the alternating voltage of the developing voltage applied to the first developing member 18A to the frequency Fu of the alternating voltage of the developing voltage applied to the second developing member 18B is set to, for example, 1.7 or more and 10.0 or less (preferably 2.0 or more and 9.0 or less, more preferably 3.0 or more and 6 or less).

[0125] By setting the ratio (Fd / Fu) within the above range, it is easy to suppress the deterioration of thin line reproducibility while maintaining developability.

[0126] In addition, in the developing condition change process, when it is determined that the obtained toner image is not an image with deteriorated image reproducibility, the developing conditions are returned to the initial settings (i.e., the case where the frequencies of the alternating current voltages of the developing voltages applied to the first developing member and the second developing member are the same, etc.).

[0127] In addition, various processors other than the CPU can also execute the respective processes in which the CPU reads and executes software (i.e., programs) in the above-described respective embodiments. As the processor in this case, examples include PLDs (Programmable Logic Devices) such as FPGAs (Field-Programmable Gate Arrays) whose circuit structures can be changed after manufacturing, and dedicated circuits such as ASICs (Application Specific Integrated Circuits) having circuit structures specifically designed for executing specific processes. In addition, each process can be executed by one of these various processors, or can be executed by a combination of two or more processors of the same type or different types (e.g., multiple FPGAs, and combinations of a CPU and an FPGA, etc.). More specifically, the hardware structures of these various processors are circuits formed by combining circuit elements such as semiconductor elements.

[0128] In addition, although the method in which each program is pre-stored (i.e., installed) in the ROM or non-volatile memory has been described, it is not limited thereto. The program can also be provided in a manner recorded on recording media such as CD-ROMs (Compact Disk Read Only Memories), DVD-ROMs (Digital Versatile Disk Read Only Memories), and USB (Universal Serial Bus) memories. In addition, the program can also be configured to be downloaded from an external device via a network.

[0129] In addition, the method of obtaining the image density as image information in the above-described developing condition change process has been described. However, the developing condition change process can also be a method of obtaining the thickness of a fine line image as image information.

[0130] That is, it can also be a method of executing the above-described developing condition change process based on the thickness of the fine line image (e.g., when image information in which the thickness of the obtained fine line image is 2 dots or less and 1 dot or more is obtained).

[0131] 〔Electrostatic charge image developer〕

[0132] Next, the electrostatic latent image developer housed in the developing machine in the image forming apparatus of the present embodiment (hereinafter also referred to as "the electrostatic latent image developer of the present embodiment") will be described.

[0133] The electrostatic latent image developer of the present embodiment contains at least toner.

[0134] The electrostatic latent image developer of the present embodiment may be a one-component developer containing only toner, or may be a two-component developer containing toner and a carrier.

[0135] The toner contains toner particles. The toner may contain toner particles and external additives.

[0136] The adhesion of the toner may be set to 5 MPa or more and 15 MPa or less.

[0137] When the adhesion of the toner is as high as the above range, it is difficult to separate from the carrier or the photoreceptor, so the developability is likely to decrease. Therefore, when forming a toner image with an image density of 40% or less, the reproducibility of fine lines is likely to deteriorate. In particular, since the cohesion between toners becomes high, in an image forming apparatus equipped with a developing machine having a plurality of developing units, the phenomenon that the toner returns to the second developing unit is likely to occur, and the deterioration of the reproducibility of fine lines is likely to be caused.

[0138] However, in the image forming apparatus of the present embodiment, even when the above toner with high adhesion is applied, the deterioration of the reproducibility of fine lines is suppressed.

[0139] The adhesion of the toner is a value measured as follows.

[0140] After printing a horizontal strip chart image with an image density of 5% on 500 sheets of A4 paper using a Docu Centre Color450 (manufactured by Fujifilm Business Innovation Corporation) copier, a 10 mm × 100 mm patch image is applied to the photoreceptor for development at a developing toner dose of 4.0 g / m 2 in such a manner. Image formation is performed in an environment of a temperature of 25°C and a humidity of 50%.

[0141] Next, an air ejection nozzle with an opening diameter of 0.5 mm is set at a position 10 mm above the photoreceptor, and while increasing the air pressure at a rate of 0.1 Pa / s, it is perpendicularly ejected onto the above patch image. The air pressure at the moment when the image is peeled off and the surface of the photoreceptor is seen is defined as the adhesion.

[0142] Regarding the air pressure, it is measured by setting an AP-V80 (manufactured by Keyence Corporation) in the flow path at a position 10 cm upstream from the front end of the ejection nozzle.

[0143] In addition, when the adhesion of the toner is high, the toner will not peel off unless it is ejected with a strong wind pressure due to poor peelability. However, when the adhesion is weak, the toner will peel off even under a weak wind pressure.

[0144] The method for the adhesion of the toner to be as high as the above range is as described below.

[0145] Method 1: A method in which the toner has toner particles containing a binder resin and resin particles

[0146] Method 2: A method in which the content of the resin particles is 3% by mass or more and 25% by mass or less with respect to the toner particles

[0147] Method 3: A method in which the resin particles are styrene (meth)acrylate resins

[0148] Method 4: A method in which the average primary particle diameter of the resin particles is 20 nm or more and 300 nm or less

[0149] The toner will be described in detail below.

[0150] (Toner particles)

[0151] The toner particles contain, for example, a binder resin. The toner particles may also contain a colorant, a release agent, resin particles, and other additives.

[0152] -Binder resin-

[0153] Examples of the binder resin include vinyl resins composed of homopolymers of monomers such as styrenes (e.g., styrene, p-chlorostyrene, α-methylstyrene, etc.), (meth)acrylates (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), olefins (e.g., ethylene, propylene, butadiene, etc.), or copolymers obtained by combining two or more of these monomers.

[0154] Examples of the binder resin also include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, modified rosin, mixtures of them and the above vinyl resins, or graft polymers obtained by polymerizing vinyl monomers in their coexistence.

[0155] These adhesive resins can be used individually or in combination of two or more.

[0156] As the adhesive resin, a polyester resin is preferred.

[0157] As the polyester resin, for example, known amorphous polyester resins can be cited. The polyester resin can also be a combination of an amorphous polyester resin and a crystalline polyester resin. Among them, the crystalline polyester resin can be used in the range of 2% by mass or more and 40% by mass or less (preferably 2% by mass or more and 20% by mass or less) based on the total adhesive resin.

[0158] In addition, the "crystallinity" of the resin means that in differential scanning calorimetry (DSC), instead of a stepped heat absorption change, there is a distinct endothermic peak. Specifically, it means that the half-width of the endothermic peak measured at a heating rate of 10 (°C / min) is within 10 °C.

[0159] On the other hand, the "amorphousness" of the resin means that the half-width exceeds 10 °C, showing a stepped heat absorption change, or no distinct endothermic peak is confirmed.

[0160] · Amorphous polyester resin

[0161] As the amorphous polyester resin, for example, condensates of polycarboxylic acids and polyols can be cited. In addition, as the amorphous polyester resin, commercially available products or synthetic products can be used.

[0162] As the polycarboxylic acid, for example, aliphatic dicarboxylic acids (such as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, pentenedioic acid, succinic acid, alkenyl succinic acid, adipic acid, sebacic acid, etc.), alicyclic dicarboxylic acids (such as cyclohexanedicarboxylic acid, etc.), aromatic dicarboxylic acids (such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc.), their anhydrides, or their lower (e.g., having 1 to 5 carbon atoms) alkyl esters can be cited. Among them, as the polycarboxylic acid, for example, aromatic dicarboxylic acids are preferred.

[0163] The polycarboxylic acid can also be a combination of a dicarboxylic acid and a carboxylic acid having a crosslinked structure or a branched structure with three or more carboxylic acid groups. As the carboxylic acid having three or more carboxylic acid groups, for example, trimellitic acid, pyromellitic acid, their anhydrides, or their lower (e.g., having 1 to 5 carbon atoms) alkyl esters, etc. can be cited.

[0164] The polycarboxylic acid can be used individually or in combination of two or more.

[0165] As the polyol, for example, aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, hexylene glycol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, etc.) can be cited. Among them, as the polyol, for example, aromatic diols and alicyclic diols are preferred, and aromatic diols are more preferred.

[0166] As the polyol, a diol and a polyol having a crosslinked structure or a branched structure with three or more hydroxyl groups can also be used in combination. As the polyol having three or more hydroxyl groups, for example, glycerol, trimethylolpropane, and pentaerythritol can be cited.

[0167] The polyol can be used alone or in combination of two or more.

[0168] The glass transition temperature (Tg) of the amorphous polyester resin is preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower.

[0169] In addition, the glass transition temperature is determined from the DSC curve obtained by differential scanning calorimetry (DSC). More specifically, it is determined from the "extrapolated glass transition start temperature" described in the method for determining the glass transition temperature in JIS K 7121-1987 "Method for Measuring the Transition Temperature of Plastics".

[0170] The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 5000 or higher and 1000000 or lower, and more preferably 7000 or higher and 500000 or lower.

[0171] The number average molecular weight (Mn) of the amorphous polyester resin is preferably 2000 or higher and 100000 or lower.

[0172] The molecular weight distribution Mw / Mn of the amorphous polyester resin is preferably 1.5 or higher and 100 or lower, and more preferably 2 or higher and 60 or lower.

[0173] In addition, the weight average molecular weight and the number average molecular weight are measured by gel permeation chromatography (GPC). The molecular weight measurement based on GPC is performed using Tosoh GPC·HLC-8120GPC as the measurement device, using Tosoh chromatographic column·TSKgelSuperHM-M (15 cm) and THF solvent. The weight average molecular weight and the number average molecular weight are calculated using the molecular weight calibration curve prepared from the monodisperse polystyrene standard sample based on the measurement results.

[0174] The amorphous polyester resin is obtained by a well-known production method. Specifically, for example, the amorphous polyester resin is obtained by setting the polymerization temperature to 180° C. to 230° C., reducing the pressure in the reaction system as necessary, and reacting while removing water or ethanol generated during condensation.

[0175] In addition, when the monomer of the raw material is insoluble or incompatible at the reaction temperature, a solvent with a high boiling point may be added as a cosolvent to dissolve it. In this case, the polycondensation reaction is carried out while the cosolvent is evaporated and removed. In the case of the presence of monomers with poor compatibility, the monomers with poor compatibility may be condensed in advance with an acid or ethanol to be polycondensed with the monomers, and then polycondensed with the main component.

[0176] Crystalline polyester resin

[0177] Examples of the crystalline polyester resin include polycondensates of polycarboxylic acids and polyols. In addition, as the crystalline polyester resin, a commercially available product may be used, or a synthesized product may be used.

[0178] Here, in the case of the crystalline polyester resin, it is more preferable to use a polycondensate of a polymerizable monomer having a linear aliphatic group rather than a polymerizable monomer having an aromatic group in order to easily form a crystalline structure.

[0179] Examples of the polycarboxylic acid include aliphatic dicarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid and other dibasic acids, etc.), anhydrous products thereof, or lower (e.g., carbon number of 1 to 5) alkyl esters thereof.

[0180] The polycarboxylic acid may also be used in combination with a dicarboxylic acid and a tricarboxylic acid or higher having a cross-linked structure or a branched structure. Examples of the tricarboxylic acid include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), their anhydrous substances, or their lower (e.g., carbon number of 1 to 5) alkyl esters.

[0181] As the polycarboxylic acid, these dicarboxylic acids may be used in combination with dicarboxylic acids having a sulfonic acid group or dicarboxylic acids having an ethylenic double bond.

[0182] The polyvalent carboxylic acid may be used alone or in combination of two or more.

[0183] As the polyol, for example, aliphatic diols (for example, linear aliphatic diols having 7 or more and 20 or less carbon atoms in the main chain portion) can be mentioned. As the aliphatic diol, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,14-eicosanediol, etc. can be mentioned. Among them, as the aliphatic diol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferred.

[0184] The polyol may also be a mixture of a diol and a trihydric or higher alcohol having a crosslinked structure or a branched structure. As the trihydric or higher alcohol, for example, glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, etc. can be mentioned.

[0185] The polyol may be used alone or in combination of two or more.

[0186] Here, the content of the aliphatic diol in the polyol may be 80 mol% or more, preferably 90 mol% or more.

[0187] The melting temperature of the crystalline polyester resin is preferably 50°C or higher and 100°C or lower, more preferably 55°C or higher and 90°C or lower, and still more preferably 60°C or higher and 85°C or lower.

[0188] In addition, the melting temperature is obtained from the DSC curve obtained by differential scanning calorimetry (DSC) according to the method for determining the melting temperature described in JIS K7121-1987 "Method for Measuring the Transition Temperature of Plastics" as the "melting peak temperature".

[0189] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0190] The crystalline polyester resin is obtained, for example, in the same manner as the amorphous polyester by a well-known production method.

[0191] As the content of the binder resin, for example, it is preferably 40% by mass or more and 95% by mass or less, more preferably 50% by mass or more and 90% by mass or less, and still more preferably 60% by mass or more and 85% by mass or less with respect to the whole toner particles.

[0192] -Colorant-

[0193] Examples of colorants include various pigments such as carbon black, chrome yellow, Hansa yellow, benzidine yellow, Vat yellow, quinoline yellow, pigment yellow, Permanent Orange GTR, pyrazolone orange, Vulcan Orange, brilliant red, fast red, brilliant carmine 3B, brilliant carmine 6B, DuPont oil-soluble red, pyrazolone red, Lithol red, rhodamine B lake, lake red C, pigment red, Bengal rose, aniline blue, ultramarine blue, Calco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, malachite green oxalate, etc., or various dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, methylimine-based, indigo-based, phthalocyanine-based, aniline black-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, thiazole-based dyes, etc.

[0194] One kind of colorant may be used alone, or two or more kinds may be used in combination.

[0195] As needed, a surface-treated colorant may be used, or it may be used in combination with a dispersant. In addition, multiple kinds of colorants may be used in combination.

[0196] As the content of the colorant, for example, relative to the whole toner particles, it is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 15% by mass or less.

[0197] - Release agent -

[0198] Examples of release agents include hydrocarbon waxes, palm wax, rice bran wax, candelilla wax and other natural waxes, synthetic or mineral·petroleum waxes such as montan wax, fatty acid esters, ester waxes such as montanic acid esters, etc. The release agent is not limited thereto.

[0199] The melting temperature of the release agent is preferably 50°C or more and 110°C or less, more preferably 60°C or more and 100°C or less.

[0200] In addition, the melting temperature is obtained based on the DSC curve obtained by differential scanning calorimetry (DSC) according to the "melting peak temperature" described in the method for determining the melting temperature in JIS K7121-1987 "Method for Measuring the Transition Temperature of Plastics".

[0201] As the content of the release agent, for example, relative to the whole toner particles, it is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass or less.

[0202] - Resin particles -

[0203] Examples of the resin particles include polyolefin resins (such as polyethylene and polypropylene), styrene resins (such as polystyrene and α-methylstyrene), (meth)acrylic resins (such as polymethyl methacrylate and polyacrylonitrile), epoxy resins, polyurethane resins, polyurea resins, polyamide resins, polycarbonate resins, polyether resins, polyester resins, and copolymer resins thereof.

[0204] As the resin particles, styrene-(meth)acrylic copolymer resin particles are preferred.

[0205] Examples of the styrene-(meth)acrylic copolymer resin particles include resin particles obtained by polymerizing a styrene-based monomer and a (meth)acrylic-based monomer by radical polymerization.

[0206] Examples of the styrene-based monomer include styrene, α-methylstyrene, vinylnaphthalene, or alkyl-substituted styrenes having an alkyl chain such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, and 4-ethylstyrene, halogen-substituted styrenes such as 2-chlorostyrene, 3-chlorostyrene, and 4-chlorostyrene, and fluorine-substituted styrenes such as 4-fluorostyrene and 2,5-difluorostyrene. Among them, as the styrene-based monomer, styrene and α-methylstyrene are preferred.

[0207] Examples of the (meth)acrylic monomer include (meth)acrylic acid, n-methyl (meth)acrylate, n-ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, pentyl (meth)acrylate, neopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, phenyl (meth)acrylate, biphenyl (meth)acrylate, diphenylethyl (meth)acrylate, tert-butylphenyl (meth)acrylate, terphenyl (meth)acrylate, cyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, β-carboxyethyl (meth)acrylate, (meth)acrylonitrile, (meth)acrylamide, etc. Among them, as the (meth)acrylic monomer, n-butyl (meth)acrylate and β-carboxyethyl (meth)acrylate are preferred.

[0208] The resin particles are preferably crosslinked resin particles. Among the crosslinked resin particles, examples of the crosslinking agent for crosslinking the resin include aromatic polyvinyl compounds such as divinylbenzene and divinylnaphthalene; polyvinyl esters of aromatic polycarboxylic acids such as divinyl phthalate, divinyl isophthalate, divinyl terephthalate, divinyl terephthalate, divinyl trimellitate, trivinyl trimellitate, divinyl naphthalene dicarboxylate, and divinyl biphenylcarboxylate; divinyl esters of nitrogen-containing aromatic compounds such as divinyl pyridine dicarboxylate; vinyl esters of unsaturated heterocyclic carboxylic acids such as vinyl furoate, vinyl furancarboxylate, vinyl pyrrole-2-carboxylate, and vinyl thiophenecarboxylate; (meth)acrylates of linear polyols such as butanediol methacrylate, hexanediol acrylate, octanediol methacrylate, decanediol acrylate, and dodecanediol methacrylate; (meth)acrylates of branched and substituted polyols such as neopentyl glycol dimethacrylate and 2-hydroxy-1,3-diacryloxypropane; poly(ethylene glycol) di(meth)acrylate and poly(propylene glycol) di(meth)acrylate; polyvinyl esters of polycarboxylic acids such as divinyl succinate, divinyl fumarate, vinyl maleate, divinyl maleate, divinyl glycolate, vinyl itaconate, divinyl itaconate, divinyl acetonedicarboxylate, divinyl glutarate, divinyl 3,3'-thiodipropionate, divinyl trans-aconitate, trivinyl trans-aconitate, divinyl adipate, divinyl pimelate, divinyl suberate, divinyl azelate, divinyl sebacate, divinyl dodecanedioate, and divinyl tridecanedioate. The crosslinking agent can be used alone or in combination of two or more.

[0209] Here, examples of the resin particles that are likely to improve the adhesion of the toner include (meth)acrylic resin particles.

[0210] Examples of the (meth)acrylic resin particles include homopolymer resin particles of only (meth)acrylic monomers and copolymer resin particles of styrene monomers and (meth)acrylic monomers.

[0211] Examples of the homopolymer resin particles of only (meth)acrylic monomers include homopolymer particles of monomers such as polymethyl methacrylate and polyethyl acrylate.

[0212] As copolymer resin particles of a styrene-based monomer and a (meth)acrylic acid-based monomer, for example, there are copolymer resin particles in which the styrene-based monomer is styrene, the (meth)acrylic acid-based monomer is n-butyl acrylate, and the mass ratio of the styrene-based monomer to the (meth)acrylic acid-based monomer (styrene-based monomer and (meth)acrylic acid-based monomer) is 70 / 30 or more and 10 / 90 or less (preferably 65 / 35 or more and 20 / 80 or less).

[0213] In addition, in the case where the (meth)acrylic acid-based resin particles are crosslinked resin particles using a crosslinking agent, as the crosslinking agent, a bifunctional alkyl acrylate having an alkylene chain with 6 or more and 12 or less carbon atoms is preferred. Regarding the content of the crosslinking agent, for example, relative to 100 parts by mass in total of the styrene-based monomer, the (meth)acrylic acid-based monomer, and the crosslinking agent, it is preferably 0.3 parts by mass or more and 5.0 parts by mass or less, more preferably 0.5 parts by mass or more and 2.5 parts by mass or less, and further preferably 1.0 parts by mass or more and 2.0 parts by mass or less.

[0214] Even when using a toner containing such resin particles and having high adhesion, in the image forming apparatus of the present embodiment, the deterioration of fine line reproducibility is suppressed.

[0215] The average primary particle diameter of the resin particles is preferably 50 nm or more and 500 nm or less, more preferably 20 nm or more and 300 nm or less, and further preferably 30 nm or more and 250 nm or less.

[0216] The average primary particle diameter of the resin particles is a value measured using a transmission electron microscope (TEM).

[0217] As the transmission electron microscope, for example, JEM-2100plus manufactured by JEOL Ltd. can be used.

[0218] Specifically, the method for measuring the average primary particle diameter of the resin particles is as follows.

[0219] The toner particles are sliced into a thickness of about 0.1 μm with a microtome. A 10,000-fold magnification photograph of the cross-section of the toner particles is taken with a transmission electron microscope, and the equivalent circle diameter of 100 resin particles dispersed in the toner particles is calculated based on each cross-sectional area, and the value obtained by arithmetic averaging of the equivalent circle diameters is set as the average primary particle diameter.

[0220] The content of the resin particles is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 25% by mass or less, and further preferably 5% by mass or more and 20% by mass or less, relative to the toner particles.

[0221] - Other Additives -

[0222] As other additives, for example, well-known additives such as magnets, charge control agents, and inorganic powders can be cited. These additives are included in the toner particles as internal additives.

[0223] -Properties of toner particles, etc.-

[0224] The toner particles can be toner particles with a single-layer structure or so-called core-shell structure toner particles composed of a core (nuclear particles) and a coating layer (shell layer) covering the core.

[0225] Here, the core-shell structure toner particles can be composed of, for example, a core containing a binder resin and other additives such as a colorant and a release agent as needed, and a coating layer containing a binder resin.

[0226] As the volume average particle diameter (D50v) of the toner particles, it is preferably 2 μm or more and 10 μm or less, more preferably 4 μm or more and 8 μm or less.

[0227] In addition, various average particle diameters and various particle size distribution indexes of the toner particles are measured using a Coulter Particle Counter II (manufactured by Beckman Coulter), and the electrolyte used is ISOTON-II (manufactured by Beckman Coulter).

[0228] At the time of measurement, as a dispersant, 0.5 mg or more and 50 mg or less of the measurement sample is added to a 5% aqueous solution of 2 ml of a surfactant (preferably sodium alkylbenzene sulfonate). It is added to 100 ml or more and 150 ml or less of the electrolyte.

[0229] The electrolyte in which the sample is suspended is subjected to a 1-minute dispersion treatment using an ultrasonic disperser, and the particle size distribution of particles with a particle diameter in the range of 2 μm or more and 60 μm or less is measured using a Coulter Particle Counter II with a 100 μm aperture. In addition, the number of sampled particles is 50,000.

[0230] For the particle size ranges (channels) divided based on the measured particle size distribution, the cumulative distributions of volume and number are plotted from the small diameter side, and the particle diameter at which the cumulative is 16% is defined as the volume particle diameter D16v and the number particle diameter D16p, the particle diameter at which the cumulative is 50% is defined as the volume average particle diameter D50v and the cumulative number average particle diameter D50p, and the particle diameter at which the cumulative is 84% is defined as the volume particle diameter D84v and the number particle diameter D84p.

[0231] Using them, the volume particle size distribution index (GSDv) is calculated as (D84v / D16v) 1 / 2 , and the number particle size distribution index (GSDp) is calculated as (D84p / D16p) 1 / 2 .

[0232] The average circularity of the toner particles is preferably 0.90 or more and 1.00 or less, more preferably 0.92 or more and 0.98 or less.

[0233] The average circularity of the toner particles is obtained by (equivalent circle circumference) / (circumference) [(circumference of a circle having the same projected area as the particle image) / (circumference of the particle projection image)]. Specifically, it is the value measured by the following method.

[0234] First, the toner particles to be measured are sampled by attraction to form a flat flow, and a particle image is obtained as a still image by instantaneous stroboscopic illumination. The average circularity is obtained by a flow particle image analysis device (FPIA-3000 manufactured by Sysmex Corporation) that analyzes this particle image. Then, the number of samplings when obtaining the average circularity is set to 3500.

[0235] In addition, when the toner has an external additive, the toner (developer) to be measured is dispersed in water containing a surfactant, and then ultrasonic treatment is performed to obtain toner particles from which the external additive has been removed.

[0236] (External additive)

[0237] Examples of the external additive include inorganic particles. Examples of the inorganic particles include SiO 2 , TiO 2 , Al 2 O 3 , SrTiO 3 , CuO, ZnO, SnO 2 , CeO 2 , Fe 2 O 3 , MgO, BaO, CaO, K 2 O, Na 2 O, ZrO 2 , CaO·SiO 2 , K 2 O·(TiO 2 )n, Al 2 O 3 ·2SiO 2 , CaCO 3 , MgCO 3 , BaSO 4 , MgSO 4 and so on.

[0238] The surface of the inorganic particles as an external additive can be subjected to a hydrophobization treatment. The hydrophobization treatment is carried out, for example, by impregnating the inorganic particles in a hydrophobization treatment agent. The hydrophobization treatment agent is not particularly limited, and examples thereof include silane coupling agents, silicone oils, titanate coupling agents, and aluminum coupling agents. They can be used alone or in combination of two or more.

[0239] As the amount of the hydrophobization treatment agent, usually, for example, it is 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the inorganic particles.

[0240] As the external additive, resin particles (such as resin particles of polystyrene, polymethyl methacrylate (PMMA), melamine resin, etc.), cleaning agents (for example, metal salts of higher fatty acids represented by zinc stearate, particles of fluorine-based high molecular weight substances), etc. can also be cited.

[0241] As the external addition amount of the external additive, for example, it is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.01% by mass or more and 6.0% by mass or less with respect to the toner particles.

[0242] (Method for manufacturing toner)

[0243] Next, the method for manufacturing the toner of the present embodiment will be described.

[0244] The toner of the present embodiment is obtained by externally adding an external additive to the toner particles after manufacturing the toner particles.

[0245] The toner particles can also be manufactured by any one of a dry method (such as a kneading and pulverizing method, etc.) and a wet method (such as a coagulation and coalescence method, a suspension polymerization method, a dissolution and suspension method, etc.). The method for manufacturing the toner particles is not particularly limited among these methods, and well-known methods can be adopted.

[0246] Among them, it is preferable to obtain the toner particles by the coagulation and coalescence method.

[0247] Specifically, for example, in the case of manufacturing the toner particles by the coagulation and coalescence method, for example, the toner particles are manufactured through the following steps:

[0248] A step of mixing a first resin particle dispersion liquid in which first resin particles serving as a binder resin are dispersed, a colorant dispersion liquid in which a colorant is dispersed, and a release agent particle dispersion liquid in which particles of a release agent (hereinafter also referred to as "release agent particles") are dispersed, and causing the respective particles and the colorant to coagulate in the obtained dispersion liquid to form first coagulated particles (first coagulated particle formation step);

[0249] After obtaining a first coagulated particle dispersion liquid in which first coagulated particles are dispersed, a second resin particle that will become a binder resin is added to the first coagulated particle dispersion liquid, and the second resin particles are coagulated on the surface of the first coagulated particles to form a second coagulated particle (second coagulated particle forming step); and

[0250] A step of heating the second coagulated particle dispersion liquid in which the second coagulated particles are dispersed to fuse and coalesce the second coagulated particles to form toner particles (fusing and coalescing step).

[0251] In addition, although the present coagulation and coalescence method will be described as a method for producing toner particles containing a binder resin, a colorant, and a release agent, the colorant and the release agent are components contained in the toner particles as needed.

[0252] Details of each step will be described below.

[0253] - Each dispersion liquid preparation step -

[0254] First, each dispersion liquid used in the coagulation and coalescence method is prepared. Specifically, a first resin particle dispersion liquid in which first resin particles that will become a binder resin are dispersed, a colorant dispersion liquid in which a colorant is dispersed, a second resin particle dispersion liquid in which second resin particles that will become a binder resin are dispersed, and a release agent particle dispersion liquid in which release agent particles are dispersed are prepared.

[0255] In addition, in each dispersion liquid preparation step, the first resin particles and the second resin particles will be described as "resin particles".

[0256] Here, the resin particle dispersion liquid is prepared, for example, by dispersing resin particles into a dispersion medium using a surfactant.

[0257] Examples of the dispersion medium used in the resin particle dispersion liquid include aqueous media.

[0258] Examples of the aqueous medium include water such as distilled water and ion-exchanged water, and ethanol-based substances. They can be used alone or in combination of two or more.

[0259] Examples of the surfactant include anionic surfactants such as sulfate ester salts, sulfonate salts, phosphate esters, and soaps, cationic surfactants such as amine salts and quaternary ammonium salts, and nonionic surfactants such as polyethylene glycol-based, alkylphenol ethylene oxide adduct-based, and polyol-based surfactants. Among them, anionic surfactants and cationic surfactants are particularly mentioned. The nonionic surfactant can also be used in combination with anionic surfactants or cationic surfactants.

[0260] The surfactant can be used alone or in combination of two or more.

[0261] As a method for dispersing resin particles in a dispersion medium in a resin particle dispersion liquid, for example, general dispersion methods such as a rotary shear type homogenizer, or a ball mill, a sand mill, a Dyno mill, etc. having a medium can be cited. In addition, depending on the type of resin particles, for example, the phase inversion emulsification method can also be used to disperse the resin particles in the resin particle dispersion liquid.

[0262] In addition, the phase inversion emulsification method is a method in which the resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, an alkali is added to the organic continuous phase (O phase) and neutralized, and then, by introducing an aqueous medium (W phase), the resin is converted from W / O to O / W (so-called phase inversion) to become discontinuous, and the resin is dispersed in the aqueous medium in a particulate form.

[0263] As the volume average particle diameter of the resin particles dispersed in the resin particle dispersion liquid, for example, it is preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and still more preferably 0.1 μm or more and 0.6 μm or less.

[0264] In addition, regarding the volume average particle diameter of the resin particles, using the particle size distribution obtained by measurement with a laser diffraction type particle size distribution measuring device (for example, LA-700 manufactured by Horiba, Ltd.), with respect to the divided particle size range (channel), the cumulative distribution is subtracted from the small particle size side in terms of volume, and the particle diameter at which the cumulative value with respect to all particles is 50% is measured as the volume average particle diameter D50v. In addition, the volume average particle diameter of the particles in other dispersion liquids is also measured in the same manner.

[0265] As the content of the resin particles contained in the resin particle dispersion liquid, for example, it is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 40% by mass or less.

[0266] In addition, for example, a colorant dispersion liquid and a release agent particle dispersion liquid are also prepared in the same manner as the resin particle dispersion liquid. That is, regarding the volume average particle diameter of the particles, the dispersion medium, the dispersion method, and the content of the particles in the resin particle dispersion liquid, the colorant dispersed in the colorant dispersion liquid and the release agent particles dispersed in the release agent particle dispersion liquid are the same.

[0267] -First Agglomerated Particle Formation Step-

[0268] Next, the first resin particle dispersion liquid, the colorant dispersion liquid, and the release agent particle dispersion liquid are mixed.

[0269] Then, in this mixed dispersion liquid, the first resin particles, the colorant, and the release agent particles are hetero-aggregated to form first agglomerated particles containing the first resin particles, the colorant, and the release agent particles.

[0270] Specifically, for example, a flocculant is added to a dispersion obtained by mixing a first resin particle dispersion, a colorant dispersion, and a mold release agent particle dispersion, and the pH of the mixed dispersion is adjusted to be acidic (for example, the pH is 2 or more and 5 or less). After adding a dispersion stabilizer as needed, the temperature is set in the range of 20°C or more and 50°C or less to cause the particles dispersed in the mixed dispersion to aggregate, thereby forming first aggregated particles.

[0271] In the first aggregated particle formation step, for example, the mixed dispersion may be stirred using a rotary shear type homogenizer, and the above-mentioned flocculant may be added at room temperature (for example, 25°C). The pH of the mixed dispersion is adjusted to be acidic (for example, the pH is 2 or more and 5 or less). After adding a dispersion stabilizer as needed, the above-mentioned heating is performed.

[0272] Examples of the flocculant include surfactants having a polarity opposite to that of the surfactant used as the dispersant added to the mixed dispersion, inorganic metal salts, and metal complexes having two or more components. In particular, when a metal complex is used as the flocculant, the amount of the surfactant used is reduced and the charging characteristics are improved.

[0273] An additive that forms a complex or a similar bond with the metal ion of the flocculant may also be used as needed. As this additive, a chelating agent is preferably used.

[0274] Examples of the inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, and inorganic metal salt polymers such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide.

[0275] As the chelating agent, a water-soluble chelating agent may also be used. Examples of the chelating agent include hydroxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid, iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA).

[0276] As the addition amount of the chelating agent, for example, it is preferably 0.01 part by mass or more and 5.0 parts by mass or less, more preferably 0.1 part by mass or more and less than 3.0 parts by mass, relative to 100 parts by mass of the first resin particles.

[0277] -Second Aggregated Particle Formation Step-

[0278] Next, after obtaining the first aggregated particle dispersion in which the first aggregated particles are dispersed, a second resin particle dispersion in which the second resin particles are dispersed is added to the first aggregated particle dispersion.

[0279] In addition, the second resin particles may be the same as or different from the first resin particles.

[0280] Then, in the dispersion liquid of the first aggregated particles and the second resin particles, the second resin particles are aggregated onto the surface of the first aggregated particles. At this time, a release agent particle dispersion liquid may also be added so that the second resin particles and the release agent particles are aggregated onto the surface of the first aggregated particles. Specifically, for example, in the first aggregated particle forming step, when the first aggregated particles reach the target particle size, the second resin particle dispersion liquid is added to the first aggregated particle dispersion liquid, and heating is performed below the glass transition temperature of the second resin particles.

[0281] Then, by making the pH of the dispersion liquid fall within a range of, for example, about 6.5 or more and 8.5 or less, the aggregation is stopped.

[0282] Thereby, second aggregated particles are obtained in which the second resin particles are attached to the surface of the first aggregated particles and aggregated.

[0283] -Fusion / Coalescence Step-

[0284] Next, the dispersion liquid of the second aggregated particles in which the second aggregated particles are dispersed is heated, for example, to a temperature above the glass transition temperatures of the first and second resin particles (for example, a temperature 10 to 30 °C higher than the glass transition temperatures of the first, second, and resin particles), so that the second aggregated particles are fused / coalesced to form toner particles.

[0285] Through the above steps, toner particles can be obtained.

[0286] In addition, in the aggregation / coalescence method described above, the first aggregated particles may be fused / coalesced to form toner particles without performing the second aggregated particle forming step. Alternatively, the second aggregated particle forming step may be repeated multiple times.

[0287] Here, after the fusion / coalescence step, toner particles in a state where the toner particles formed in the solution are dried through a known washing step, solid-liquid separation step, and drying step are obtained.

[0288] In the washing step, displacement washing based on ion-exchanged water can be sufficiently performed from the viewpoint of chargeability. In addition, the solid-liquid separation step is not particularly limited, and suction filtration, pressure filtration, etc. can be performed from the viewpoint of productivity. In addition, the method in the drying step is not particularly limited, and freeze drying, fluidized bed drying, flow drying, vibration type fluidized bed drying, etc. can be performed from the viewpoint of productivity.

[0289] Moreover, the toner of the present embodiment is manufactured, for example, by adding an external additive to the obtained dried toner particles and mixing them. The mixing can be performed, for example, by a V blender, a Henschel mixer, a Lodige mixer, etc. Moreover, if necessary, a vibration sieve, an air classifier, etc. can also be used to remove the coarse particles of the toner.

[0290] <Electrostatic charge image developer>

[0291] The electrostatic charge image developer of this embodiment contains at least the toner of this embodiment.

[0292] The electrostatic charge image developer of this embodiment may be a one-component developer containing only the toner of this embodiment, or a two-component developer formed by mixing the toner and a carrier.

[0293] There is no particular limitation on the carrier, and known carriers can be cited. As the carrier, for example, a coated carrier in which a core material composed of magnetic powder is coated with a coating resin, a magnetic powder-dispersed carrier in which magnetic powder is dispersed and incorporated in a matrix resin, a resin-impregnated carrier in which resin is impregnated in porous magnetic powder, etc. can be cited.

[0294] In addition, the magnetic powder-dispersed carrier and the resin-impregnated carrier may also be carriers in which the constituent particles of the carrier are used as the core material and coated with a coating resin.

[0295] As the magnetic powder, for example, magnetic metals such as iron, nickel, and cobalt, magnetic oxides such as ferrite and magnetite, etc. can be cited.

[0296] As the coating resin and the matrix resin, for example, styrene-(meth)acrylic resin, polyolefin resins such as polyethylene resin and polypropylene resin, polyethylene-based or polyvinylidene-based resins such as polystyrene, (meth)acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, linear silicone resin composed of organosiloxane bonds or its modified products, fluororesins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polytrifluorochloroethylene, polyester, polyurethane, polycarbonate, amino resins such as urea-formaldehyde resin, epoxy resin, etc. can be cited.

[0297] The coating resin and the matrix resin preferably contain (meth)acrylic resin, more preferably contain 50% by mass or more of (meth)acrylic resin based on the total mass of the resin, and further preferably contain 80% by mass or more of (meth)acrylic resin based on the total mass of the resin.

[0298] In particular, the coating resin and the matrix resin preferably contain alicyclic (meth)acrylic resin as the (meth)acrylic resin.

[0299] In addition, the coating resin and the matrix resin may also contain other additives such as conductive particles.

[0300] As the conductive particles, particles such as metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate can be cited.

[0301] Here, when coating the surface of the core material with a coating resin, methods such as coating with a coating resin and a coating layer-forming solution obtained by dissolving various additives in an appropriate solvent as needed can be cited. The solvent is not particularly limited and can be selected in consideration of the coating resin used, coating adaptability, etc.

[0302] As specific resin coating methods, an impregnation method of immersing the core material in the coating layer-forming solution, a spraying method of spraying the coating layer-forming solution onto the surface of the core material, a fluidized bed method of spraying the coating layer-forming solution in a state where the core material is floated by fluid air, a kneading coating method of mixing the core material of the carrier and the coating layer-forming solution in a kneading coater and removing the solvent, etc. can be cited.

[0303] The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer is preferably toner:carrier = 1:100 to 30:100, and more preferably 3:100 to 20:100.

[0304] [Examples]

[0305] Hereinafter, examples and comparative examples are given to illustrate the present invention more specifically and in detail, but the present invention is not limited to these examples.

[0306] <Preparation of Amorphous Resin Particle Dispersion Liquid 1>

[0307] · Terephthalic acid: 98 mol parts

[0308] · Trimellitic anhydride: 2 mol parts

[0309] · Bisphenol A ethylene oxide 2 mol adduct: 20 mol parts

[0310] · Bisphenol A propylene oxide 2 mol adduct: 80 mol parts

[0311] The above materials are filled into a reaction vessel equipped with a stirring device, a nitrogen introduction tube, a temperature sensor, and a rectification column, and the temperature is raised to 190 °C over 1 hour. 1.2 parts of dibutyltin oxide are added to 100 parts of the above materials. While distilling off the generated water, the temperature is raised to 240 °C over 6 hours, and after maintaining 240 °C for 3 hours for the dehydration condensation reaction, the reaction product is cooled.

[0312] The reaction product is fed to Cavitron CD1010 (manufactured by Eurotec) at a rate of 100 g per minute in a molten state. At the same time, separately prepared ammonia water with a concentration of 0.37 mass% is heated to 120 °C with a heat exchanger and fed to Cavitron CD1010 at a rate of 0.1 liter per minute. At a rotor rotation speed of 60 Hz and a pressure of 5 kg / cm 2Cavitron CD1010 was operated under the conditions of , to obtain a resin particle dispersion in which resin particles having a volume average particle size of 160 nm were dispersed. Ion exchange water was added to the resin particle dispersion to adjust the solid content to 20% by mass to prepare an amorphous resin particle dispersion 1.

[0313] <Preparation of Crystalline Resin Particle Dispersion>

[0314] Sebacic acid: 202 parts by mass

[0315] Ethylene glycol: 62 parts by mass

[0316] The above materials were added to a reaction vessel equipped with a stirring device, a nitrogen introduction tube, a temperature sensor and a distillation tower, and the temperature was raised to 160°C over 1 hour, and 0.8 parts by mass of dibutyltin oxide was added. While distilling off the generated water, the temperature was raised to 180°C over 6 hours, and maintained at 180°C for 5 hours for dehydration condensation reaction. After that, the temperature was gradually raised to 230°C under reduced pressure, and maintained at 230°C for 2 hours of stirring. After that, the reactant was cooled. After cooling, solid-liquid separation was performed, and the solid was dried to obtain a crystalline polyester resin.

[0317] Crystalline polyester resin: 100 parts

[0318] Methyl ethyl ketone: 40 parts

[0319] Isopropyl ethanol: 30 parts

[0320] 10% ammonia solution: 6 parts

[0321] The above materials were added to a 3-liter jacketed reaction tank (BJ-30N manufactured by Tokyo Rikakki Co., Ltd.) equipped with a capacitor, a thermometer, a water dripping device, and an anchor wing, and the resin was dissolved while being stirred and mixed at 100 rpm while being maintained at 80°C in a water circulation thermostatic bath. Thereafter, the water circulation thermostatic bath was set to 50°C, and 400 parts of ion exchange water kept at 50°C were dripped at a rate of 7 parts by mass / minute to invert the phase, thereby obtaining an emulsion. 576 parts by mass of the obtained emulsion and 500 parts by mass of ion exchange water were placed in a 2-liter eggplant-shaped bottle, and placed in an evaporator (manufactured by Tokyo Rikakki Co., Ltd.) equipped with a vacuum control unit via a collecting ball. While rotating the eggplant-shaped bottle, it was heated in a water bath at 60°C, and the pressure was reduced to 7 kPa while paying attention to bumping, and the solvent was removed. Thereafter, ion exchange water was added to obtain a crystalline resin particle dispersion having a solid content concentration of 20% by mass.

[0322] <Preparation of Styrene (Meth) Acrylic Resin Particle Dispersion 1>

[0323] (Preparation of Emulsion A)

[0324] · Styrene: 45 parts

[0325] · n-Butyl acrylate: 53 parts

[0326] · Divinylbenzene: 2 parts

[0327] Put the above materials into a mixing container equipped with a stirring device and stir. Add a mixed solution of 1.5 parts of an anionic surfactant (SS-H manufactured by Kao Corporation) and 98.5 parts of ion-exchanged water to the mixing container and stir to prepare emulsion A.

[0328] (Preparation of emulsion B)

[0329] · Styrene: 45 parts

[0330] · n-Butyl acrylate: 54 parts

[0331] · Divinylbenzene: 1 part

[0332] Put the above materials into a mixing container equipped with a stirring device and stir. Add a mixed solution of 1.5 parts of an anionic surfactant (SS-H manufactured by Kao Corporation) and 98.5 parts of ion-exchanged water to the mixing container and stir to prepare emulsion B.

[0333] (Preparation of styrene (meth)acrylate resin particle dispersion 1)

[0334] Add 2.0 parts of an anionic surfactant (SS-H manufactured by Kao Corporation) and 300 parts of ion-exchanged water to a reaction container equipped with a stirring device and a nitrogen inlet tube, and stir. Add 50 parts of emulsion A. Replace the air in the reaction container with nitrogen, heat the reaction solution with an oil bath while stirring to make the temperature of the reaction solution 75°C. Then add 10 parts of ammonium persulfate with a concentration of 10% by mass and hold for 30 minutes.

[0335] After that, while maintaining the temperature of the reaction solution at 75°C, gradually drop 150 parts of emulsion A into the reaction container over 60 minutes (the "dropping time A" described later). After the dropping is completed, change the temperature of the reaction solution to 70°C, hold for 15 minutes, and then while maintaining the temperature of the reaction solution (the "polymerization temperature B" described later) at 70°C, drop 200 parts of emulsion B into the reaction container over 120 minutes (the "dropping time B" described later). After the dropping is completed, add 3 parts of ammonium persulfate with a concentration of 10% by mass, hold for 2 hours, and then cool to room temperature. Add ion-exchanged water to make the solid content concentration 20% to prepare styrene (meth)acrylate resin particle dispersion 1.

[0336] (Preparation of colorant dispersion)

[0337] · Carbon black (Cabot Corporation, Regal 330): 50 parts

[0338] · Anionic surfactant NEOGEN RK (Daiichi Kogyo Seiyaku): 5 parts

[0339] · Ion-exchanged water: 192.9 parts

[0340] Mix the above components and treat them with Altimizer (manufactured by Sugino Machine) at 240 MPa for 10 minutes to prepare a colorant dispersion (solid content: 20%).

[0341] <Preparation of Release Agent Dispersion 1>

[0342] · Fischer-Tropsch synthesis wax (FNP0090 manufactured by Nippon Seiro Co., Ltd., melting temperature Tw: 90 °C): 50 parts

[0343] · Anionic surfactant (NEOGEN RK manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 1 part

[0344] · Ion-exchanged water: 200 parts

[0345] Mix the above materials and heat them to 130 °C. After dispersing them using a homogenizer (ULTRA-TURRAX T50 manufactured by IKA), perform dispersion treatment using a Manton-Gaulin high-pressure homogenizer (manufactured by Gaulin) to obtain a release agent dispersion in which release agent particles are dispersed (solid content 20% by mass). The volume average particle diameter of the release agent particles is 180 nm.

[0346] <Preparation of Developers 1 to 3>

[0347] · Amorphous resin particle dispersion 1: 225 parts

[0348] · Crystalline resin particle dispersion: 25 parts

[0349] · Styrene(meth)acrylate resin particle dispersion 1: 60 parts

[0350] · Colorant dispersion: 30 parts

[0351] · Release agent dispersion 1: 30 parts

[0352] · Ion-exchanged water: 100 parts

[0353] The above materials are placed in a reaction container equipped with a thermometer, a pH meter and a stirrer, heated from the outside to a temperature of 30°C with a hood heater, and kept for 30 minutes while stirring at a speed of 150 rpm. Next, after adding a 0.3N nitric acid aqueous solution and adjusting the pH to 3.0, a 3% polyaluminum chloride aqueous solution is added while being dispersed with a homogenizer (ULTRA-TURRAX T50 manufactured by IKA). Next, the temperature is raised to 50°C and kept for 30 minutes while stirring. Next, 130 parts of amorphous resin particle dispersion 1 are added and kept for 1 hour, and after adding a 0.1N sodium hydroxide aqueous solution and adjusting the pH to 8.5, the mixture is heated to 85°C while continuing to stir and kept for 5 hours. Next, cooling, solid-liquid separation, washing and drying of the solids are carried out in sequence to obtain a toner particle 1 having a volume average particle size of 4.8μm and a shape factor of 0.969.

[0354] Similarly, the mixture was heated to 85° C. and maintained for 4 hours to obtain toner particles 2 having a volume average particle size of 4.5 μm and a shape factor of 0.958.

[0355] Similarly, the mixture was heated to 85° C. and maintained at that temperature for 6.5 hours to obtain toner particles 3 having a volume average particle size of 5.0 μm and a shape factor of 0.975.

[0356] Using each of the obtained toner particles 1 to 3, 100 parts of the toner particles and 0.7 parts of dimethyl silicone oil-treated silica particles (RY200 manufactured by Nippon Aerosil Co., Ltd.) were mixed with a Henschel mixer to obtain a toner.

[0357] Then, 8 parts of the obtained toner and 100 parts of the following carrier were mixed to obtain a developer 1.

[0358] -Carrier production-

[0359] ·100 parts of ferrite particles (average particle size 35 μm)

[0360] ·Toluene 14 parts

[0361] · 3 parts of styrene / methyl methacrylate copolymer (copolymer ratio 15 / 85)

[0362] · Carbon black 0.2 parts

[0363] The above components except the ferrite particles are dispersed in a sand mill to prepare a dispersion, and the dispersion is put into a vacuum degassing kneader together with the ferrite particles, and dried under reduced pressure while stirring to obtain a carrier.

[0364] <Examples 1 to 7, Comparative Example 1>

[0365] The developer shown in Table 1 is housed in the developing machine of a modified machine of the image forming apparatus "Color1000iPress (manufactured by Fujifilm Business Innovation Corporation)".

[0366] The developing machine is made to have the same structure as that Figure 3 shown, and is modified to be able to independently control the frequency of the alternating current voltage applied to the two developing members (i.e., developing sleeves).

[0367] In this image forming apparatus, the developing conditions (direct current voltage, and alternating current voltage and its frequency superimposed on the direct current voltage) when the image density of the toner image is 40% or less are set as shown in Table 1, and image forming apparatuses of each example are produced.

[0368] In addition, except for Comparative Example 1, when the image density of the toner image is 40% or less, the developing conditions are set such that when the image density of the toner image exceeds 40%, the frequency of the alternating current voltage of the developing voltage applied to the second developing roller is reduced from the state where the developing conditions of the first developing roller and the second developing roller are the same, and the frequency of the alternating current voltage of the developing voltage applied to the second developing roller is made less than the frequency of the alternating current voltage of the developing voltage applied to the first developing roller.

[0369] <Evaluation>

[0370] (Fine line reproducibility)

[0371] Using the image forming apparatuses of each example whose developing conditions are set as shown in Table 1, after playing 1000 charts with an image density of 1% in an environment of a temperature of 30°C and a relative humidity of 88%, a 1on1off image (an image with an image density of 5% in which 1 dot lines are arranged side by side at 1 dot intervals) at a resolution of 2,400 dpi (dots per inch: number of dots per 2.54 cm) is output as a 5 cm × 5 cm chart. Then, evaluation is carried out according to the following criteria.

[0372] A: There is no missing or blurred line at all

[0373] B: The missing or blurred lines that can be recognized are slight and do not affect practical use

[0374] C: Missing or blurred lines can be recognized and it is not suitable for practical use

[0375] [Table 1]

[0376]

[0377] From the above results, it can be seen that compared with the comparative examples, the deterioration of the fine line reproducibility is suppressed in the present embodiment.

[0378] (Postscript) (((1)))

[0380] An image forming apparatus, comprising:

[0381] An electrophotographic photoreceptor;

[0382] A charging device that charges the surface of the electrophotographic photoreceptor;

[0383] A static charge image forming device that forms a static charge image on the surface of the charged electrophotographic photoreceptor;

[0384] A developing machine that houses a developer containing toner, supplies the developer, and develops the static charge image formed on the surface of the electrophotographic photoreceptor as a toner image. The developing machine has: a first developing member that is disposed opposite to the electrophotographic photoreceptor, holds the developer, and conveys it to a developing area; a second developing member that is disposed opposite to the electrophotographic photoreceptor on the downstream side in the rotation direction of the electrophotographic photoreceptor with respect to the first developing member, holds the developer, and conveys it to the developing area; a first power source that applies a developing voltage in which an alternating voltage is superimposed on a direct current voltage to the first developing member; and a second power source that applies a developing voltage in which an alternating voltage is superimposed on a direct current voltage to the second developing member;

[0385] A transfer device that transfers the toner image formed on the surface of the electrophotographic photoreceptor to the surface of a recording medium;

[0386] A fixing device that fixes the toner image to the surface of the recording medium; and

[0387] A control device that acquires image information of the toner image and controls at least one of the first power source and the second power source according to the image information so that the frequency of the alternating voltage of the developing voltage applied to the second developing member is less than the frequency of the alternating voltage of the developing voltage applied to the first developing member. (((2)))

[0389] The image forming apparatus according to (((1))), wherein

[0390] The control device controls the second power source to reduce the frequency of the alternating voltage of the developing voltage applied to the second developing member so that the frequency of the alternating voltage of the developing voltage applied to the second developing member is less than the frequency of the alternating voltage of the developing voltage applied to the first developing member. (((3)))

[0392] The image forming apparatus according to (((1))) or (((2))), wherein

[0393] The control device controls at least one of the first power supply and the second power supply, and sets the ratio (Fd / Fu) of the frequency Fd of the alternating current voltage of the developing voltage applied to the first developing member to the frequency Fu of the alternating current voltage of the developing voltage applied to the second developing member to be 2.0 or more and 9.0 or less. (((4)))

[0395] The image forming apparatus according to any one of (((1))) to (((3))), wherein

[0396] The control device acquires the image density of the toner image and controls at least one of the first power supply and the second power supply. (((5)))

[0398] The image forming apparatus according to any one of (((1))) to (((4))), wherein

[0399] The adhesion of the toner is 5 MPa or more and 15 MPa or less. (((6)))

[0401] The image forming apparatus according to (((5))), wherein

[0402] The toner has toner particles including a binder resin and resin particles. (((7)))

[0404] The image forming apparatus according to (((6))), wherein

[0405] The content of the resin particles is 3% by mass or more and 25% by mass or less with respect to the toner particles. (((8)))

[0407] The image forming apparatus according to (((6))) or (((7))), wherein

[0408] The resin particles are styrene (meth) acrylic resin. (((9)))

[0410] The image forming apparatus according to any one of (((6))) to (((8))), wherein

[0411] The average primary particle diameter of the resin particles is 20 nm or more and 300 nm or less.

[0412] The effects of the above method are as follows.

[0413] According to (((1))), an image forming apparatus is provided, in which deterioration of thin line reproducibility is suppressed as compared with a case where the frequency of the AC voltage of the developing voltage applied to the first developing member is the same as the frequency of the AC voltage of the developing voltage applied to the second developing member when the image density of the toner image is low or the like in a specific image forming apparatus.

[0414] According to (((2))), an image forming apparatus is provided, in which deterioration of thin line reproducibility is suppressed as compared with a case where the control device controls the first power supply to increase the frequency of the AC voltage of the developing voltage applied to the first developing member so that the frequency of the AC voltage of the developing voltage applied to the second developing member is less than the frequency of the AC voltage of the developing voltage applied to the first developing member.

[0415] According to (((3))), an image forming apparatus is provided, in which deterioration of thin line reproducibility is suppressed as compared with a case where (Fd / Fu) is less than 1.7 or more than 10.0.

[0416] According to (((4))), an image forming apparatus is provided, in which deterioration of thin line reproducibility is suppressed as compared with a case where the frequency of the AC voltage of the developing voltage applied to the first developing member is the same as the frequency of the AC voltage of the developing voltage applied to the second developing member when the image density of the toner image is low in a specific image forming apparatus.

[0417] According to (((5))), (((6))), (((7))), (((8))) or (((9))), an image forming apparatus is provided, in which deterioration of thin line reproducibility is suppressed even when the adhesion of the toner is 5 MPa or more and 15 MPa or less as compared with a case where the frequency of the AC voltage of the developing voltage applied to the first developing member is the same as the frequency of the AC voltage of the developing voltage applied to the second developing member when the image density of the toner image is 40% or less in a specific image forming apparatus.

Claims

1. An image forming device, characterized in that: have: Electrophotographic photoreceptor; a charging device for charging the surface of the electrophotographic photoreceptor; an electrostatic charge image forming device for forming an electrostatic charge image on the surface of the charged electrophotographic photoreceptor; a developing machine that contains a developer containing a toner, supplies the developer, and develops the electrostatic charge image formed on the surface of the electrophotographic photoreceptor as a toner image, the developing machine comprising: a first developing member that is arranged opposite to the electrophotographic photoreceptor, holds the developer and conveys it to a developing area; a second developing member disposed opposite to the electrophotographic photoreceptor at a downstream side of the first developing member in the rotation direction of the electrophotographic photoreceptor, and holding the developer and conveying it to a developing area; a first power source for applying a developing voltage obtained by superimposing an alternating voltage on a direct voltage to the first developing component; and a second power source for applying a developing voltage obtained by superimposing an AC voltage on a DC voltage to the second developing member; a transfer device that transfers the toner image formed on the surface of the electrophotographic photoreceptor to the surface of a recording medium; a fixing device that fixes the toner image to a surface of a recording medium; as well as A control device, wherein the control device obtains image information of the colorant image and controls at least one of the first power supply and the second power supply according to the image information so that the frequency of the AC voltage of the development voltage applied to the second developing component is lower than the frequency of the AC voltage of the development voltage applied to the first developing component.

2. The image forming apparatus according to claim 1, wherein: The control device controls the second power supply to reduce the frequency of the AC voltage of the developing voltage applied to the second developing component so that the frequency of the AC voltage of the developing voltage applied to the second developing component is lower than the frequency of the AC voltage of the developing voltage applied to the first developing component.

3. The image forming apparatus according to claim 1 or 2, wherein: The control device controls at least one of the first power supply and the second power supply to set the ratio (Fd / Fu) of the frequency (Fd) of the AC voltage of the development voltage applied to the first developing component and the frequency (Fu) of the AC voltage of the development voltage applied to the second developing component to be greater than 2.0 and less than 9.

0.

4. The image forming apparatus according to any one of claims 1 to 3, wherein: The control device acquires the image density of the toner image and controls at least one of the first power source and the second power source.

5. The image forming apparatus according to any one of claims 1 to 4, wherein: The toner has an adhesion force of 5 MPa or more and 15 MPa or less.

6. The image forming apparatus according to claim 5, wherein: The toner has toner particles including a binder resin and resin particles.

7. The image forming apparatus according to claim 6, wherein: The content of the resin particles is 3% by mass or more and 25% by mass or less relative to the toner particles.

8. The image forming apparatus according to claim 6 or 7, wherein: The resin particles are styrene (meth) acrylic resin.

9. The image forming apparatus according to any one of claims 6 to 8, wherein: The average primary particle size of the resin particles is 20 nm or more and 300 nm or less.

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