Developing device

Abstract

The present invention is a developing device capable of suppressing the generation of aggregated toner. The developing device includes a cylindrical developing roller, a regulating member, a magnetic body, and a synthetic resin member. The developing roller has a built-in magnetic field generating member and rotates. The regulating member has a first facing surface facing the outer peripheral surface of the developing roller. The magnetic body is disposed on an upstream side surface of the regulating member in a rotation direction of the developing roller. The synthetic resin member is disposed on a side surface of the magnetic body on an upstream side in a rotation direction of the developing roller. The regulating member regulates the layer thickness of the magnetic toner on the outer peripheral surface of the developing roller by using the first opposing surface. The synthetic resin member has a second facing surface facing the outer peripheral surface of the developing roller. The second opposing surface is away from the outer peripheral surface of the developing roller toward the upstream side in the rotational direction of the developing roller at an inclination of 40 DEG to 60 DEG with respect to the first opposing surface. The solubility parameter of the material of the synthetic resin member is 23 (J / cm3) 1 / 2 or more. The magnetic toner includes a toner and resin particles.

Description

Technical Field

[0001] The invention relates to a developing device. Background Art

[0002] The conventional developing device includes a developing roller and a limiting scraper. The limiting scraper limits the amount of toner held on the developing roller. The toner is likely to accumulate in a space (upstream space) upstream of the limiting scraper in the rotation direction of the developing roller.

[0003] In the prior art, there is a scheme of disposing an elastic member in the upstream space where toner is easily retained. The elastic member is disposed so as to occupy the upstream space in a state of being closely attached to the upstream surface of the limiting scraper in the rotation direction of the developing roller. The upstream space is occupied by the elastic member, thereby suppressing the retention of toner.

[0004] In addition, the elastic member has a conveying amount limiting surface facing the peripheral surface of the developing roller. The conveying amount limiting surface is set to gradually move away from the developing roller as it moves toward the upstream side in the rotation direction of the developing roller. Therefore, the toner attached to the peripheral surface of the developing roller from the developer storage portion moves forward in the upstream space due to the rotation of the developing roller, and is gradually pushed back to the developer storage portion by the conveying amount limiting surface as it moves forward. This prevents a large amount of toner from being retained on the upstream side of the limiting scraper in the rotation direction of the developing roller. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] However, there is a problem that the toner is adsorbed on the conveying amount limiting surface of the elastic member. The adsorbed toner is difficult to separate from the elastic member and gathers around the conveying amount limiting surface to form aggregated toner. The aggregated toner causes clogging and image contamination.

[0007] In view of the above-mentioned problems, an object of the present invention is to provide a developing device capable of suppressing the generation of aggregated toner.

[0008] (II) Technical solution

[0009] The developing device of the present invention comprises: a cylindrical developing roller, a limiting component, a magnetic body, and a synthetic resin component. The developing roller has a built-in magnetic field generating component and rotates. The limiting component has a first opposing surface that is opposite to the outer peripheral surface of the developing roller. The magnetic body is arranged on the side surface of the limiting component on the upstream side of the rotation direction of the developing roller. The synthetic resin component is arranged on the side surface of the magnetic body on the upstream side of the rotation direction of the developing roller. The limiting component uses the first opposing surface to limit the layer thickness of the magnetic colorant on the outer peripheral surface of the developing roller. The synthetic resin component has a second opposing surface that is opposite to the outer peripheral surface of the developing roller. The second opposing surface is away from the outer peripheral surface of the developing roller toward the upstream side of the rotation direction of the developing roller at an inclination of more than 40° and less than 60° relative to the first opposing surface. The solubility parameter of the material of the synthetic resin component is 23 (J / cm 3 ) 1 / 2 The magnetic toner comprises toner and resin particles.

[0010] (III) Beneficial effects

[0011] According to the developing device of the present invention, it is possible to suppress the generation of aggregated toner.

[0012] Still other objects of the present invention and specific advantages obtainable by the present invention will become more apparent from the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a diagram showing the structure of an image forming apparatus according to an embodiment of the present invention.

[0014] Figure 2 It is an enlarged view of the developing device according to this embodiment. DETAILED DESCRIPTION

[0015] The embodiments of the present invention are described below with reference to the accompanying drawings. In addition, the same reference numerals are used for the same or equivalent parts in the drawings, and the description is not repeated. In the present embodiment, the X-axis, the Y-axis, and the Z-axis are orthogonal to each other, the X-axis and the Y-axis are parallel to the horizontal plane, and the Z-axis is parallel to the plumb line.

[0016] First, refer to Figure 1 , the structure of the image forming apparatus 1 according to the first embodiment will be described. Figure 1 2 is a diagram showing a configuration of an image forming apparatus 1. The image forming apparatus 1 is, for example, a monochrome printer.

[0017] like Figure 1 As shown, the image forming apparatus 1 includes an image forming section 4 , a fixing section 5 , a paper discharge tray 12 , a conveyance path 6 , a manual insertion tray 3 , a paper feed cassette 7 , and an operation section (not shown).

[0018] The paper feed cassette 7 stores paper P. The paper P is, for example, plain paper, copy paper, recycled paper, thin paper, thick paper, glossy paper, or an OHP (Overhead Projector) sheet. The paper P is discharged to the paper discharge tray 12 .

[0019] The transport path 6 transports the paper P from the paper feed cassette 7 to the paper discharge tray 12 via the image forming unit 4 and the fixing unit 5 .

[0020] The manual insertion tray 3 is provided on the image forming apparatus 1. Figure 1 Right side shown.

[0021] The operation unit is provided with a plurality of menu setting keys for setting various menus.

[0022] The image forming unit 4 forms a toner image on a paper (sheet) P based on image data from an external device (e.g., a personal computer (PC)). Specifically, the image forming unit 4 includes a photosensitive drum (image carrier) 10, a charger 42, an exposure device 43, a developing device 44, a toner cartridge 45, a transfer roller (transfer member) 46, and a toner remover 47. Figure 1 The charger 42, the developing device 44, the transfer roller 46, and the toner remover 47 are sequentially arranged along the circumferential direction of the photosensitive drum 10 (in the clockwise direction). The exposure device 43 is arranged above the charger 42.

[0023] The photosensitive drum 10 is, for example, a drum having a photosensitive body in which an amorphous silicon layer, which is a positively charged photoconductor, is deposited on the surface of an aluminum cylinder. The thickness of the amorphous silicon layer and the linear speed of the photosensitive drum 10 are appropriately set.

[0024] The charger 42 performs charging processing on the photosensitive drum 10. Specifically, the charger 42 includes, for example, a charging roller 50. The charging roller 50 is composed of a core member and an epichlorohydrin rubber layer covering the core member. In addition, the charging roller 50 is a contact charging method in which the peripheral surface of the charging roller 50 is in approximately point contact with the drum surface of the photosensitive drum 10, and a predetermined reference charging voltage (reference charging bias) composed of a superposition of a DC voltage and an AC voltage is applied to the drum surface, thereby charging the drum surface to a uniform surface potential.

[0025] The exposure device 43 irradiates the charged photosensitive drum 10 with laser light L to form an electrostatic latent image. Specifically, the exposure device 43 has a polygon mirror (not shown) that guides the laser light L based on image data input from an external PC (personal computer) etc. to the drum surface of the photosensitive drum 10. The polygon mirror is rotated by a predetermined driving source, and the laser light L is scanned on the drum surface of the photosensitive drum 10 to form an electrostatic latent image on the drum surface.

[0026] The developing device 44 causes toner to be electrostatically attached to the electrostatic latent image formed on the photosensitive drum 10 , thereby developing the toner image. The toner cartridge 45 supplies the toner filled therein to the developing device 44 .

[0027] The transfer roller 46 transfers the developed toner image onto the paper P. Specifically, the transfer roller 46 is pressed against the drum surface of the photosensitive drum 10 on the conveying path 6, and a nip portion N is formed between the transfer roller 46 and the drum surface. Since a voltage having a polarity opposite to the surface potential of the drum surface is applied to the transfer roller 46, the toner image on the drum surface is transferred onto the paper P when the paper P passes through the nip portion N. The paper P that has passed through the nip portion N is conveyed to the fixing unit 5 through the conveying path 6.

[0028] The toner remover 47 removes and recovers the toner remaining on the drum surface of the photosensitive drum 10 .

[0029] The fixing unit 5 heats the toner image formed on the paper P and fixes it on the paper P. After the toner image on the paper P is heated and fixed on the paper P in the fixing unit 5 , the paper P is transported to the paper discharge tray 12 through the transport path 6 .

[0030] Reference Figure 1 and Figure 2 The structure of the developing device 44 will be described. Figure 2 4 is an enlarged view of the developing device 44. Figure 2 As shown, the developing device 44 develops the electrostatic latent image on the photosensitive drum 10 using a magnetic single-component developer (magnetic toner).

[0031] The magnetic single-component developer (magnetic toner) includes: a toner, a magnetic powder, and resin particles. The resin particles include, for example, particles of styrene acrylic resin. Examples of styrene acrylic resins include: copolymers of styrene, methyl methacrylate, and divinylbenzene; copolymers of styrene, methyl methacrylate, and ethylene glycol methacrylate. The average primary particle size of the styrene acrylic resin particles is, for example, greater than 30 nm and less than 150 nm, preferably greater than 35 nm and less than 125 nm. The solubility parameter of the resin particles is, for example, preferably 18.4 (J / cm 3 ) 1 / 2 Above and 19.6 (J / cm 3 ) 1 / 2 In addition, the magnetic single-component developer (magnetic toner) may contain silica particles, a binder resin, a charge control agent, and a release agent.

[0032] The developing device 44 includes a developing container (housing) 21, a developer storage portion 11, a developing roller 22, a restricting member 30, and a magnet 60. The developing container 21 defines an internal space of the developing device 44. The magnet 60 is an example of a “magnetic body”.

[0033] The developer storage portion 11 is formed on the bottom wall of the developer container 21. Specifically, the developer storage portion 11 is formed by Figure 1 The developer storage chambers 14 and 15 are formed by two adjacent developer storage chambers 14 and 15 extending in a direction perpendicular to the paper surface. The developer storage chambers 14 and 15 are separated from each other in the longitudinal direction by a partition plate 17 made of metal such as aluminum, for example, and the two ends in the longitudinal direction are connected to each other.

[0034] Screw feeders 18 and 19 are rotatably mounted in the developer storage chambers 14 and 15, and the screw feeders 18 and 19 stir and convey the magnetic toner by rotating. Since the conveying directions of the screw feeders 18 and 19 are set to be opposite to each other, the magnetic toner is stirred and conveyed between the developer storage chamber 14 and the developer storage chamber 15. The developer storage section 11 receives toner from the toner cartridge 45 via a replenishment port (not shown).

[0035] The developing roller 22 is disposed in the developing opening 23 of the developing container 21. The developing roller 22 is made of a non-magnetic material such as aluminum, and is a roller member including a cylindrical developing sleeve 24 extending in the longitudinal direction of the developing device 44 (i.e., in the axial direction of the photosensitive drum 10), and a roller member that allows the developing sleeve 24 to be rotated as shown in FIG. Figure 2 The rotation axis (not shown) rotates counterclockwise as shown.

[0036] The developing sleeve 24 is arranged opposite to the photosensitive drum 10 in the following state: a gap of 0.2 mm to 0.4 mm is formed between the outer peripheral surface 26 of the developing sleeve 24 and the drum surface of the photosensitive drum 10. The developing sleeve 24 has a built-in magnetic field generating component. The magnetic field generating component is configured such that the opposing pole opposite to the limiting component 30 is the S pole (S2), and the N pole (N1), S pole (S1), N pole (N2), S pole (S3), and N pole (N3) are arranged in order along the circumferential direction of the developing sleeve 24 on the downstream side of the S pole (S2).

[0037] The limiting component 30 is as follows Figure 2The limiting member 30 is a member made of a plate-shaped magnetic material extending in the axial direction of the developing sleeve 24 and arranged above the developing roller 22. The limiting member 30 has a front end portion 31 extending toward the outer peripheral surface 26 of the developing sleeve 24. The front end portion 31 has a first facing surface 32 facing the outer peripheral surface 26. A gap of a predetermined size is set between the first facing surface 32 and the outer peripheral surface 26 of the developing sleeve 24. The limiting member 30 limits the layer thickness of the magnetic toner on the outer peripheral surface 26 of the developing sleeve 24 by using the first facing surface 32.

[0038] The magnet 60 is arranged on the side surface of the limiting member 30 on the upstream side in the rotation direction of the developing sleeve 24. In addition, the magnet 60 is attached to the side surface of the limiting member 30 by an adhesive in a state where the opposing pole of the magnet 60 facing the developing sleeve 24 is the S pole and the end of the magnet 60 on the developing sleeve 24 side does not protrude more than the end of the limiting member 30 on the developing sleeve 24 side. The magnet 60 assists the limiting member 30 in limiting the layer thickness of the magnetic toner on the outer peripheral surface 26. The layer thickness of the magnetic toner on the outer peripheral surface 26 is limited by the physical limitation of the limiting member 30 and the magnetic limitation of the magnet 60.

[0039] As the developing sleeve 24 rotates, the magnetic toner on the outer peripheral surface 26 of the developing sleeve 24 is transported toward the drum surface of the photosensitive drum 10, and adheres to the electrostatic latent image on the drum surface of the photosensitive drum 10 by the potential difference between the developing bias applied to the developing sleeve 24 and the drum bias applied to the photosensitive drum 10. Thus, a toner image is formed on the drum surface.

[0040] The developing device 44 further includes a synthetic resin member 70. The synthetic resin member 70 is disposed on the side surface of the magnet 60 on the upstream side in the rotation direction of the developing sleeve 24. In addition, the synthetic resin member 70 extends in the axial direction of the developing sleeve 24. Specifically, the synthetic resin member 70 has a second facing surface 71 facing the outer peripheral surface 26 of the developing sleeve 24.

[0041] The second facing surface 71 is set to be located on the upstream side of the first facing surface 32 of the limiting member 30 as viewed in the rotation direction of the developing sleeve 24, and gradually moves away from the developing sleeve 24 as it moves toward the upstream side in the rotation direction. In other words, the second facing surface 71 is set so that the gap between the second facing surface 71 and the outer peripheral surface 26 of the developing sleeve 24 gradually increases as it moves from the first facing surface 32 toward the upstream side in the rotation direction of the developing sleeve 24. A part of the conveyed magnetic toner is gradually pushed back by the second facing surface 71 in the direction opposite to the rotation direction of the developing sleeve 24. In this way, the amount of magnetic toner conveyed to the first facing surface 32 is limited by the second facing surface 71. This suppresses the accumulation of a large amount of magnetic toner on the upstream side in the rotation direction in the gap between the first facing surface 32 and the outer peripheral surface 26.

[0042] The second opposing surface 71 has an inclination of 40° or more and 60° or less relative to the first opposing surface 32. When the angle is smaller than 40°, the pressure on the magnetic toner in the limiting component 30 is too large, and the charge amount of the magnetic toner is reduced, which will cause the image density on the sheet to decrease. In particular, the degree of reduction in image density is greater in a high temperature environment. On the other hand, when the angle is larger than 60°, the magnetic toner around the limiting component 30 will be retained, resulting in aggregation, and the limiting force on the magnetic toner in the aggregation area will be weakened, which will cause the conveying amount of the magnetic toner to increase and the charge amount to be insufficient, resulting in toner stripes (vertical stripes) on the sheet.

[0043] In addition, the solubility parameter of the material of the synthetic resin member 70 is 23 (J / cm 3 ) 1 / 2 As the material of the synthetic resin member 70, for example, ABS resin, polyamide resin, etc. can be cited. In addition, it is preferred that the difference between the solubility parameter of the material of the synthetic resin member 70 and the solubility parameter of the resin particles is 5 (J / cm 3 ) 1 / 2 above.

[0044] Above, as reference Figure 1 and Figure 2 As described above, the second facing surface 71 of the synthetic resin member 70 has an inclination of 40° or more and 60° or less with respect to the first facing surface 32, and the solubility parameter of the material of the synthetic resin member 70 is 23 (J / cm 3 ) 1 / 2 As described above, since the magnetic toner contains the resin particles, it is possible to suppress the magnetic toner from being adsorbed to the second opposing surface 71 of the synthetic resin member 70 .

[0045] As a result, the generation of aggregated toner can be suppressed.

[0046] (Example)

[0047] The present invention will be described in more detail below using Examples (and Comparative Examples). However, the present invention is not limited to the scope of Examples.

[0048] (Making silica particles)

[0049] First, 30 g of dimethylpolysiloxane and 15 g of 3-aminopropyltrimethoxysilane (both products of Shin-Etsu Chemical Co., Ltd.) were dissolved in 200 g of toluene and diluted 10 times. Next, 200 g of pyrogenic silica particles ("AEROSIL (registered trademark) 130" produced by Aerosil Japan Co., Ltd.) were stirred while the obtained diluted solution was gradually dripped, and ultrasonic irradiation and stirring were performed for 30 minutes to obtain a mixture. The mixture was heated in a thermostatic bath at 150°C, and then toluene was distilled off using a rotary evaporator, and the obtained solid was dried in a vacuum dryer at a set temperature of 50°C until the weight no longer decreased. Then, an electric furnace was used to heat the mixture at 200°C for 3 hours under a nitrogen flow. The obtained powder was crushed using a jet mill and captured using a bag filter to obtain silica particles.

[0050] (Making resin pellets)

[0051] (Making resin pellets A)

[0052] In a 500ml flask equipped with a dropping funnel, a stirrer, a nitrogen inlet tube, a thermometer and a reflux cooling tube, 200g of ion exchange water and 3g of sodium dodecyl sulfate were added. While heating to 80°C under a nitrogen atmosphere, 1g of ammonium persulfate was added, and after 1 hour, a monomer mixture consisting of 42g of styrene, 40g of methyl methacrylate and 26g of divinylbenzene was dropped and stirred for another hour. After the obtained reaction solution was cooled to room temperature, it was filtered using a 300-mesh sieve to obtain an emulsion. The obtained emulsion was dried to obtain an average particle size of 80nm and a solubility parameter (SP value) of 18.4 (J / cm 3 ) 1 / 2 Resin particles A.

[0053] (Making resin pellets B)

[0054] The same method as resin particles A was used except that 1 g of sodium dodecyl sulfate was added instead of 3 g. The obtained particles had an average particle size of 125 nm and a solubility parameter of 18.4 (J / cm 3 ) 1 / 2 Resin particles B.

[0055] (Making resin pellets C)

[0056] The same method as resin particles A was used except that 10 g of sodium dodecyl sulfate was added instead of 3 g. The average particle size was 35 nm and the solubility parameter was 18.4 (J / cm 3 ) 1 / 2 Resin particles C.

[0057] (Making resin pellets D)

[0058] The same as the resin particles A except that 42 g of styrene was changed to 31 g, 40 g of methyl methacrylate was changed to 30 g, and 26 g of divinylbenzene was changed to 79 g of ethylene glycol dimethacrylate, the average particle size was 80 nm, the solubility parameter was 19.6 (J / cm 3 ) 1 / 2 Resin particles D.

[0059] (Example 1)

[0060] The magnetic toner of Example 1 was prepared as follows. The following were mixed at 2000 rpm for 5 minutes using a mixer (FM-20B, a product of Nippon Coke Co., Ltd.): 1100 g of a polyester binder resin (a product of Kao Corporation, Mw: 6500, acid value: 8.2 mgKOH / g, Tm: 96.3°C, Tg: 54.4°C); 1090 g of a binder resin (a product of Kao Corporation, acid value: 11.8 mgKOH / g, Tm: 118.5°C, Tg: 59.6°C, gel content 36%); 1450 g of magnetic powder X (2×105 Ω·cm, a product of Toda Industries, Ltd., MRO-15A); 200 g of a charge control agent (FCA-482PLV, a product of Fujikura Chemicals Co., Ltd.); and 160 g of a release agent (a product of Kato Yoko Co., Ltd., Carnauba Wax Characteristic No. 1).

[0061] The obtained mixture was melt-kneaded using a two-screw extruder (TEM-26SS, a product of Toshiba Machine Co., Ltd.) under the following conditions: cylinder temperature of 120°C, shaft speed of 100 rpm, 75 g / min. After the obtained kneaded product was cooled, it was coarsely pulverized using a pulverizer (Rotoplex 16 / 8, a product of Hosokawa Micron Co., Ltd.). The obtained coarsely pulverized product was finely pulverized using a powder turbine grinder TA (a product of Freund Turbine Co., Ltd.). Then, it was put into a jet mill (MJT-1, a product of Hosokawa Micron Co., Ltd.) for fine pulverization and classification to obtain the toner mother particle Tn1.

[0062] 1 kg of the obtained toner mother particles were mixed with 12 g of the silica particles obtained by the above method and 1 g of the resin particles A as external additives using a mixer (FM-10C, a product of Nippon Coke Industry) at 3200 rpm for 5 minutes to adhere. After that, the mixture was sieved with a 100-mesh (mesh size: 150 μm) sieve to obtain the magnetic toner of Example 1.

[0063] In addition, using the solubility parameter of 23.7 (J / cm 3 ) 1 / 2A synthetic resin member (fixed scraper) was made of ABS resin and arranged in the developing device in such a manner that the second opposing surface had an inclination of 50° with respect to the first opposing surface. As a result, a developing device of Example 1 was obtained. In addition, in Tables 1, 2, and 3 described later, "EX1" represents Example 1.

[0064] (Example 2)

[0065] Example 2 is the same as Example 1 except that resin particles B are used in the toner instead of resin particles A. In addition, "EX2" represents Example 2 in Table 1, Table 2, and Table 3 described below.

[0066] (Example 3)

[0067] Example 3 is the same as Example 1 except that resin particles C are used in the toner instead of resin particles A. In addition, "EX3" represents Example 3 in Table 1, Table 2, and Table 3 described below.

[0068] (Example 4)

[0069] Example 4 is the same as Example 1 except that resin particles D are used in the toner instead of resin particles A. In addition, "EX4" means Example 4 in Table 1, Table 2, and Table 3 described below.

[0070] (Example 5)

[0071] In Example 5, the developer was replaced with a synthetic resin member made of ABS resin and a synthetic resin member having a solubility parameter of 27.8 (J / cm 3 ) 1 / 2 The same as in Example 1 except that the synthetic resin member was made of polyamide resin. In Table 1, Table 2, and Table 3 described later, "EX5" means Example 5.

[0072] (Comparative Example 1)

[0073] Comparative Example 1 is the same as Example 1 except that no synthetic resin member is used in the developing device. In Table 1, Table 2, and Table 3 described below, "CEX1" indicates Comparative Example 1.

[0074] (Comparative Example 2)

[0075] In Comparative Example 2, the developer was replaced with a synthetic resin member made of ABS resin and a synthetic resin member having a solubility parameter of 18.4 (J / cm 3 ) 1 / 2 The same procedures as in Example 1 were performed except that the synthetic resin member was made of a high-density polystyrene resin. In Tables 1, 2, and 3 described below, "CEX2" indicates Comparative Example 2.

[0076] (Comparative Example 3)

[0077] Comparative Example 3 is the same as Example 1 except that the second facing surface is arranged at an inclination of 35° with respect to the first facing surface in the developing device. In Tables 1, 2, and 3 described below, "CEX3" indicates Comparative Example 3.

[0078] (Comparative Example 4)

[0079] Comparative Example 4 is the same as Example 1 except that the second facing surface is arranged at an inclination of 65° with respect to the first facing surface in the developing device. In Tables 1, 2, and 3 described below, "CEX4" indicates Comparative Example 4.

[0080] (Comparative Example 5)

[0081] Comparative Example 5 is the same as Example 1 except that the resin particles A are not used in the toner. In Table 1, Table 2, and Table 3 described below, "CEX5" indicates Comparative Example 5.

[0082] Table 1 shows the structures of the toners of Examples 1 to 5 and Comparative Examples 1 to 5. In addition, "St" represents styrene, "MMA" represents methyl methacrylate, "DVB" represents divinylbenzene, and "EGDM" represents ethylene glycol dimethacrylate.

[0083] (Table 1)

[0084]

[0085] Table 2 shows the synthetic resin members (fixed blades) of the developing devices of Examples 1 to 5 and Comparative Examples 1 to 5. In addition, "ABS" represents ABS resin, "PA" represents polyamide resin, and "HIPS" represents high-density polystyrene resin.

[0086] (Table 2)

[0087]

[0088] (Evaluation of the durability of actual printing)

[0089] Using the toners and developing devices of Examples 1 to 5 and Comparative Examples 1 to 5, and using a monochrome printer ECOSYS (registered trademark) P2040dw manufactured by Kyocera Document Systems Co., Ltd., 100,000 and 5,000 copies of an image manuscript with a printing rate of 2% were output in an environment of temperature 23°C and humidity 65% ​​and in an environment of temperature 28°C and humidity 80% respectively by an intermittent output method of two copies. The image density in each of the following cases was evaluated: the initial image density; the image density after outputting 100,000 copies in an environment of temperature 23°C and humidity 65%; and the image density after outputting 5,000 copies in an environment of temperature 28°C and humidity 80%, and the presence or absence of vertical streaks when outputting 100,000 copies in an environment of temperature 23°C and humidity 65% ​​was evaluated.

[0090] ○: No vertical streaks (white streaks and black streaks) were observed in 100,000 prints.

[0091] ×: Vertical streaks (white and black) were seen in 100,000 output sheets.

[0092] Table 3 shows the results.

[0093] (Table 3)

[0094]

[0095] As can be seen from the above, in Comparative Examples 1 to 3 and Comparative Example 5, magnetic toner was retained around the limiting member, resulting in aggregation. The limiting force on the magnetic toner in the aggregation area was weakened, resulting in an increase in the conveying amount of the magnetic toner and insufficient charge, resulting in toner streaks (vertical streaks) on the sheet. In addition, in Comparative Example 4, the pressure on the magnetic toner in the limiting member was too large, the charge amount of the magnetic toner was reduced, resulting in a decrease in the image density on the sheet. In particular, the degree of decrease in image density was large under high temperature conditions.

[0096] On the other hand, in Examples 1 to 5, no toner streaks (vertical streaks) were generated on the sheet, and a decrease in image density was suppressed even in a high-temperature environment.

[0097] The developing device of the present invention can be applied to an image forming apparatus.

Claims

1. A developing device comprising: A cylindrical developing roller having a built-in magnetic field generating component and rotating; a limiting member having a first facing surface facing the outer peripheral surface of the developing roller; a magnetic body disposed on a side surface of the restricting member on an upstream side in a rotation direction of the developing roller; and a synthetic resin member disposed on a side surface of the magnetic body on the upstream side of the developing roller in the rotation direction, The limiting member limits the layer thickness of the magnetic toner on the outer peripheral surface of the developing roller by using the first facing surface. The synthetic resin member has a second facing surface facing the outer peripheral surface of the developing roller, The second facing surface is inclined at an angle of 40° or more and 60° or less with respect to the first facing surface, away from the outer peripheral surface of the developing roller toward the upstream side in the rotation direction of the developing roller. The solubility parameter of the material of the synthetic resin component is 23 (J / cm 3 ) 1 / 2 above, The magnetic toner includes toner and resin particles.

2. The developing device according to claim 1, characterized in that: The resin particles include particles of styrene acrylic resin, The particles of the styrene acrylic resin have an average primary particle size of 30 nm or more and 150 nm or less.

3. The developing device according to claim 1, characterized in that: The difference between the solubility parameter of the resin particles and the solubility parameter of the material of the synthetic resin component is 5 (J / cm 3 ) 1 / 2 above.

4. The developing device according to claim 1, characterized in that: The material of the synthetic resin member is ABS resin or polyamide resin.

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